CA2039087A1 - Method for treating the surface of an absorbent resin - Google Patents
Method for treating the surface of an absorbent resinInfo
- Publication number
- CA2039087A1 CA2039087A1 CA002039087A CA2039087A CA2039087A1 CA 2039087 A1 CA2039087 A1 CA 2039087A1 CA 002039087 A CA002039087 A CA 002039087A CA 2039087 A CA2039087 A CA 2039087A CA 2039087 A1 CA2039087 A1 CA 2039087A1
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- Prior art keywords
- parts
- weight
- absorbent resin
- water
- resin powder
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/12—Powdering or granulating
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
- A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
- A61L15/42—Use of materials characterised by their function or physical properties
- A61L15/60—Liquid-swellable gel-forming materials, e.g. super-absorbents
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F8/00—Chemical modification by after-treatment
- C08F8/14—Esterification
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/24—Crosslinking, e.g. vulcanising, of macromolecules
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L101/00—Compositions of unspecified macromolecular compounds
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F2810/00—Chemical modification of a polymer
- C08F2810/20—Chemical modification of a polymer leading to a crosslinking, either explicitly or inherently
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2300/00—Characterised by the use of unspecified polymers
- C08J2300/14—Water soluble or water swellable polymers, e.g. aqueous gels
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- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Epidemiology (AREA)
- General Chemical & Material Sciences (AREA)
- Animal Behavior & Ethology (AREA)
- General Health & Medical Sciences (AREA)
- Public Health (AREA)
- Veterinary Medicine (AREA)
- Dispersion Chemistry (AREA)
- Hematology (AREA)
- Processes Of Treating Macromolecular Substances (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Treatments Of Macromolecular Shaped Articles (AREA)
- Absorbent Articles And Supports Therefor (AREA)
- Application Of Or Painting With Fluid Materials (AREA)
- Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
- Developing Agents For Electrophotography (AREA)
- Materials For Medical Uses (AREA)
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method for treating the surface of an absorbent resin which comprises mixing (I) 100 parts by weight of an absorbent resin powder having a carboxyl group, (II) 0.01 to 30 parts by weight of a polyhydric alcohol, (m) 0 to 50 parts by weight of water and (IV) 0 to 60 parts by weight of a hydrophilic organic solvent, and heat-treating at a temperature in the range of 90 to 250°C to treat the surface of said absorbent resin powder (I) until the reaction of said absorbent resin powder (I) with said polyhydric alcohol (II) is completed, wherein the time for completion of the reaction is the time that satisfies the following equation (a-1):
A method for treating the surface of an absorbent resin which comprises mixing (I) 100 parts by weight of an absorbent resin powder having a carboxyl group, (II) 0.01 to 30 parts by weight of a polyhydric alcohol, (m) 0 to 50 parts by weight of water and (IV) 0 to 60 parts by weight of a hydrophilic organic solvent, and heat-treating at a temperature in the range of 90 to 250°C to treat the surface of said absorbent resin powder (I) until the reaction of said absorbent resin powder (I) with said polyhydric alcohol (II) is completed, wherein the time for completion of the reaction is the time that satisfies the following equation (a-1):
Description
2~3~ ~r7 METHOD FOR TREATING THE SURFAGE OF AN ABSORBENT RESIN
BACKGROUND OF THE INVENTION
Field of the Invention:
The present invention relates to a method for Sreating the surface o~ an absorbent resin~ More particularly, it relates to a method for treating the sur~ace o~ the absorbent resin by crosslinking the surface region of the absorbent resin using a crosslinking agent to obtain an absorbent excellent in absorption rate under pressure, water-retaining property under pressure and liquid permeability under pressure.
Description of the Prior Art:
Attempts have been made heretofore to use an absorbent resin as one of the component materials for such sanitary articles as sanitary napkins and disposahle diapers which function to absorb body fluid Absorbent resins of this nature heretofore known to the art include a hydrolyzed starch-acrylonitrile graft polymer (U.S. Patent No.
BACKGROUND OF THE INVENTION
Field of the Invention:
The present invention relates to a method for Sreating the surface o~ an absorbent resin~ More particularly, it relates to a method for treating the sur~ace o~ the absorbent resin by crosslinking the surface region of the absorbent resin using a crosslinking agent to obtain an absorbent excellent in absorption rate under pressure, water-retaining property under pressure and liquid permeability under pressure.
Description of the Prior Art:
Attempts have been made heretofore to use an absorbent resin as one of the component materials for such sanitary articles as sanitary napkins and disposahle diapers which function to absorb body fluid Absorbent resins of this nature heretofore known to the art include a hydrolyzed starch-acrylonitrile graft polymer (U.S. Patent No.
3,661,815), a neutralized starch-acrylic acid graft polymer (U.S. Patent No. 4,076,663)3 a saponified vinyl acetate-acrylic ester copolymer (Japanese Patent Laid-Open SHO
52(1977~-14,689), a hydrolyzed acrylonitrile copolymer or acrylamide copolymer (Japanese Patent Publication SHO
53(1978)-15,959),cross-linked products thereof, a partially neutralized polyacrylic acid, and a partially neutralized cross-linked polyacrylic acid (Japanese Patent Laid-Open SHO
57(1982)-34,101)~
Characteristic properties expected in absorbent resins include high absorption capacity, high absorption rate, liquid permeability, and large gel strength. These characteristic properties, however, do not always show a posltive correlation.
For example, an absorbent resin having a high absorption capacity generally posses~e~ a low gel strength, 2 0 ~ 7 forms what resembles "wetted clusters of flour" on contact with an aqueous liquid, suffers from impairment of liquid permeability, prevents the aqueous liquid to be dispersed throughout the entire volume of the particles of the absorbent resin, and has extremely low absorption rate. As a means of remedying these drawbacks, a method which ¢omprises coating the surface of the particles of the absorbent resin with a surfactant or an involatile hydrocarbon has been introduced to the art. Though this method i~ indeed capable of improving the initial dispersibility of the aqueous liquid in the particles of the absorbe~t resin, it produces virtually no discernible ef~ect in the improvement of the absorption rate of the individual particle3.
Further, a method which comprises causing a specific cross-linking agent to react on the surface of the absorbent resin thereby heightening the cross-link density in the surface region of the absorbent resin has been known to the art (U.S. Patent No. 4,666,983 and U.S. Patent No.
52(1977~-14,689), a hydrolyzed acrylonitrile copolymer or acrylamide copolymer (Japanese Patent Publication SHO
53(1978)-15,959),cross-linked products thereof, a partially neutralized polyacrylic acid, and a partially neutralized cross-linked polyacrylic acid (Japanese Patent Laid-Open SHO
57(1982)-34,101)~
Characteristic properties expected in absorbent resins include high absorption capacity, high absorption rate, liquid permeability, and large gel strength. These characteristic properties, however, do not always show a posltive correlation.
For example, an absorbent resin having a high absorption capacity generally posses~e~ a low gel strength, 2 0 ~ 7 forms what resembles "wetted clusters of flour" on contact with an aqueous liquid, suffers from impairment of liquid permeability, prevents the aqueous liquid to be dispersed throughout the entire volume of the particles of the absorbent resin, and has extremely low absorption rate. As a means of remedying these drawbacks, a method which ¢omprises coating the surface of the particles of the absorbent resin with a surfactant or an involatile hydrocarbon has been introduced to the art. Though this method i~ indeed capable of improving the initial dispersibility of the aqueous liquid in the particles of the absorbe~t resin, it produces virtually no discernible ef~ect in the improvement of the absorption rate of the individual particle3.
Further, a method which comprises causing a specific cross-linking agent to react on the surface of the absorbent resin thereby heightening the cross-link density in the surface region of the absorbent resin has been known to the art (U.S. Patent No. 4,666,983 and U.S. Patent No.
4,734,478). When this method is used, the absorbent resin does not easily form wetted clusters on contact with an aqueous liquid and the aqueous liquid is easily dispersed throughout the entire particles of the absorbent resin.
Thu~, this method serves the purpose of improving the absorption rate of the absorbent resin to some extent. In recent years, the growing trend of absorbent articles particularly for sanitary applications toward better performance and better quality have been urging the absorbents used in such ab~orbent articles to offer higher quality of absorption rate. However, an actual absorbent article for sanitary use should absorb body fluids under pressure, so it has been clarified that the absorption property under pressure is important. For ab~orbent re~in-q u3ed as constituent materials for a sanitary material which absorbs body fluid, not only absorption rate, liquid permeability, and absorption capacity under no pre~sure, but 2 ~
also absorption rat;e, liquid permeability and absorption capacity under pressure are important, and high absorption rate under pressure, high liquid permeability under pressure, and high water-retaining property under pressure have been required. None of the prior art satisfies such requirements.
An object of the present invention is, accordingly, to provide a method for treating the ~urface of an absorbent resin.
Another object of the pre~ent invention is to provide an effective method for treating the surface of absorbent resin ~or obtaining an absorbent havir.g high absorption rate under pres3ure, high liquid permeability under pressure, and high water-retaining property under pressure.
Still another object of the present invention is to provide an effective method for treatin~ the surface of absorbent resin fQr obtaining an absorbent which can be dispersed between pulp ~ibers, has high absorption capacity even iP it is contacted with an aqueous liquid under pressure, and ha~ high liquid permeability without closing capillaries between the pulp fibers.
SUMMARY OF THE INVENTION
These objects are accomplished by a method for treating the surface of an absorbent resin which comprises mixing (I) 100 parts by weight of an absorbent resin powder having a carboxyl group, (~) 0.01 to 30 parts by weight of a polyhydria alcohol, ( m ) O to 50 parts by weight of water and (~) O to 60 parts by weight of a hydrophilic organic solvent, and heat-treating at a temperature in the range of 90 to 250C to treat the surface of said absorbent resin powder (I) until the reaction of said absorbent resin powder (I) with said polyhydric alcohol (~) is completed~
wherein the time for completion of the reaction is the time that satisfies the following equation (a~
30 ~ (100 + C) B/A ~ 80 (a~1) 2~ Q8~
wherein A is absorption capacity of said absorbent resin powder (I) for physiolagical saline solution, B is the absorption capacity of the resultant treated absorbent resin for physiological saline solution, and C is parts by weight of said polyhydric alcohol (~) used per 100 parts by weight o~ said absorbent resin powder (I)~
According to the present invention, an absorbent having high absorption rate under pressure, liquid permeability under pressure~ and water-retaining property under pressure is obtained by reacting the sur~ace region of an absorbent resin powder ( r ) having a carboxyl group with a polyhydric alcohol (~) and completing the reaction o~ the surface treatment when the above-mentioned formula (a-1) is satisfied.
Further 7 the absorbent thus obtained shows high absorption rate and absorption capacity even if it is contacted with an aqueous solution under pressure when dispersed between pulp fibers, and has high liquid permeability without closing capillaries between pulp fibers, so if for example, it is used in a disposable diaper, a diaper having less leakage can be obtainedO
The absorbent thus obtained may be used for sanitary field such as dispo~able diapars, sanitary napkins and disposable tow~els, for civil engineering field ~uch as water sealing agents, dewproofing agents and sludge coagulating agents, for architectural ~ield such as humidity controlling agents, for agricultural and horticultural field such as qeed and seedling preserving sheets, for foodstuff packaging field such as freshness preserving materials, dehydrating agents and desiccants, for medical field such as blood absorbents and surgical sponges, for electrical field such as water sealant for cables and humidity sensors, and other oil-water separating agents~ sweat absorbents, water swellable toys9 ion exchanging resins, and they can absorb aqueous liquids such as water, urine, blood, c~team, meat 2 ~ 3 ~
juices, ion-containing water including sea water, aqueous solutions dispersing organics, etc.
BRIEF DESCRIPTION OF THE DRAWING
Fig. 1 is a sectional view of an apparatus for measuring water-retaining property under pressure, and Figo 2 is a sectional view of an apparatus for measuring liquid permeability under pressure.
EXPLANATION OF THE PREFERRED EMBODIMENT
For use in this invention~ it is preferable that the absorbent resin powder (I) po~sesse~ a carboxyl group. The heretofore known carboxyl group-containing absorbent resins include a hydrolyzed starch acrylonitrile graft polymer, a neutralized starch-acryllc acid graft polymer, saponified vinyl acetate-acrylic ester copolymers, hydrolyzed acrylonitrile or acrylamide copolymers, cross-linked products of such copolymers, a partially neutralized polyacrylic acid, and a partially neutralized cros~-linked polyacrylic acid, invariably available in the form of powder 9 for example. These absorbent resin powders may be used either singly or in varying combinations o~ two or more members. The absorbent reqin powder ~ preferable, but not always required9 to possesq a cross-linked structure.
Though the amount of the carboxyl group to be possessed by the absorbent resin powder (I) is not specifically limited, it is preferable to be not less than 0.01 equivalent weight based on 100 g of the absorbent resin powder (I~. In the case of the partially neutralized polyacrylie acid, for example7 the proportion of the unneutralized portion thereof is preferable to be in the range of 1 to 50 mol%, preferably 5 to 40 mol%.
The form in which the absorbent resin powder (I) is used in the present invention is not specifically limited.
It may be in the form of spheres obtained by reverse-phase suspension polymerization7 in the fcrm of flakes obtained by drum drying 7 or in the form of irregular particles obtained by crushing resin lumps, for example. Preferably7 the 2 ~
absorbent resin powder is in the form of flakes or irregular particlesO
The polyhydric alcohol ~) to be u~ed in this invention has at leaqt two hydroxyl groups per molecular unit. It is preferable to use, among polyhydric alcohols answering the description, one member or a varying combination of two or more members selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerol, polyglycero1, propylene glycol, diethanolamine, triethanol-amine, polyoxypropylene, oxyethylene-oxypropyle block copolymer, sorbitan fatty acid esters, polyoxyethy1ene sorbitan ~atty acid esters, trimethylolpropane~
pentaerythritol, 1,3-propanediol, and sorbitol.
The amount of the polyhydric alcohol (~) to be used in the present invention is to be in the range of 0.01 to 30 parts by weight~ preferably 0.1 to 10 parts by weight based on 100 parts by weight of the ab~orbent resln powder (I).
If this amount is less than 0.01 part by weight, even if it is heated for a long time, an increase of absorption rate under pressure, liquid permeability under pressure, and water-retaining property under pressure, cannot be recognized. Gonversely, if the amount exceeds 30 parts by weight, it is difficult to obtain an effect corresponding to the increase of the amount, and the unreacted polyhydric alcohol (~) remains, so that it becomes not only a reason of various trouble~, but also uneconomical.
For the purpose of ensuring the homogeneous mixing of the polyhydric alcohol (~) and the absorbent resin powder (I), the present invention use3 water (m) 0 to 50 parts by weight and a hydrophilic organic solvent (~) 0 to 60 parts by weight based on 100 parts by weight of the absorbent resin powder (I).
The water (m) is effective in promoting the permeation of the polyhydric alcohol (~) into the qurface region of the absorbent resin powder (I~. The water (m~ is preferable to be used in an amount in the range of 0 to 50 parts by weight, pre~erably 0.1 to 50 parts by wei.ght, more preferably Oo1 to 2~ parts by weight, based on 100 parts by weight of the absorbent resin powder (I). If the amount is less than 0~1 part by weight, the effect of the addition is difficult to be recognized, and i~ the amount exceeds 50 parts by weight, the mixing of the water with the absorbent resin powder may possibly necessitate a power~ul mixing device.
The hydrophilic organic solvent (~) is only required to be capable of being uni~ormly mixed with the polyhydric alcohol (~) and refraining ~rom producing any adverse effect on the performance of the absorbent resin powder (I). The hydrophilic organic solvents which fulfill this requirement include lower alcohols such as methanol, ethanol, n-propanol~ isopropanol, n-butanol, isobutanol, sec-butanol, and t-butanol; ketones such as acetone, methylethyl ketone, and methylisobutyl ketone; ethers such as dioxane, tetrahydrofuran, and diethyl ether; amides such as N,N-dimethyl formamide and N,N-diethyl formamide; and sulfoxides such as dimethyl sulfoxide, for example.
The hydrophilic organic solvent (~) is effective in uniformly dispersing the polyhydric alcohol (~) on the surface o.~ the absorbent resin powder (I). The amount of this solvent desirable ~or the manifestation of this effect is in the range of 0 to 60 parts by weight, preferably 0.1 to 60 parts by weight based on 100 parts by weight o~ the absorbent resin powder (I). If this amount exceeds 60 parts by weight, the heat treatment consumes an unduly long time.
In the pre~ent invention, the mixture of the absorbent resin powder possessing a carboxyl group ~I) with the polyhydric alcohol (~, is generally accomplished by spraying or dropping the polyhydric alcohol (~) or the mixture of the polyhydric alcohol (~) with water ( m ) and/or the hydrophilic organic solvent (~) onto the absorbent resin powder (I) and mixing them.
The preferred mixing devices to be used ~or thi~
mixin~ need to produce a large mixing ~orce to ensure uniform rnixingO Mixing machines and kneading machines may be e~fectively used. The mixing devices which are us~ble herein include cylindrlcal mixers9 double-walled cone mixers, V-shaped mixers, ribbon type mixers, screw type mixers, fluidizing type mixers, rotary disc type mixers, gas-current type mixers, twin-arm type kneaders, internal mixers, muller type kneaders, roll mixers, and screw type extruders, for example.
The method of treating the surface of an ~bsorbent resin in accordance with the present invention can be attained by mixing the absorbent re~in powder (I) and the polyhydric alcohol (~) or by mixing the absorbent resin powder (I~, the polyhydric alcohol (~), water (m), and the hydrophilic organic solvent (~) and heating them. Heat treatment can be carried out during mixing the components (I) through (~) or after mixing. Heat treatment can be carried out using a conventional drier or oven. For example, there are groove type mixing driers, rotary driers, disc driers, kneading driers, fluidized-bed type driers, gas flow type driers, and infrared ray driers. When the mixing of the components (1) through ~) and heat treatment are carried out al; the same time 7 a heat mixing type drier is used.
The temperature of the heat treatment is in the range of 90 to 250C~ preferably 120 to 220C. If the temperature is lower than 90C, the heat treatment proves to be uneconomical because it consumes an unduly long time.
Conversely, if this temperature exceeds ~50C, the heat treatment demands careful attention because some, if not all, of the absorbent resins are liable to undergo thermal deterioration. So long as the temperature of the heat treatment is confined ln this range of 90 to 25GC 9 the cross-linking reaction 9 proYiding for the fu]l manifestation of the effect of this invention, can be accompll~hed in a short span of time without entailing the possibility o~
deteriorating or coloring the absorbent resin.
The invention resides in the method herein (I) 100 parts by weight of an absorbent resin powder possessing a carboxyl group i3 mixed with (~) 0.01 to 30 parts by weight of a polyhydric alcohol~ ~ m ) O to 50 parts by weight of water and (~) O to 60 parts by weight of a hydrophilic organic solvent, and the reactisn of the ab30rbent resin powder (I) with the polyhydric alcohol (~) is completed at a temperature of 90 to 250C to treat the surface of the absorbent resin powder, the time for completion of the reaction of the surface treatment being the time that satisfies the above equation (a-1), preferably the following equation (a-2):
40 ~ (100 ~ C) B/A ~ 70 (a-2) If the (100 + C) B/A in the equation (a-1) is (100 + C) B/A
> 80 5 only the cross-linking den~ity at the region of the surface of the absorbent resin powder (I) increases, and although the increase of absorption rate corresponding to the increase of the croqs~linking density is recognized, the increase o~ absorption rate under pressure and liquid permeability under pressure cannot be recognized. Further, the absorbent having high water-retainirlg property under pressure cannot be obtained. On the contrary, if the (100 + C) B/A in the e~uation (a-1) is 30 ~ (100 + C) B/A, increase of the absorption rate under pressure and liquid permeability under pressure corresponding to the promotion of the reaction cannot be recognized, and it is not preferable, because the ab~orption capacity of the absorbent thus obtained decrease~ remarkably compared to that of the starting absorbent resin powder (I) and original properties o~ the absorbent resin is damaged.
According to the preferred embodiment of the present invention, the object of the present invention can be accomplished by a method for the surface treating of an ab30rbent resin in the presence of 0.01 to 10 parts by g weight of a water insoluble fine powder (V) until the reaction of said absorbent resin ~I) with said polyhydric alcohol (~) is oompleted, wherein the time for completion of the reaction is the time that satisfies the following equation (b-1), 30 ~ (100 + C~ D) B/A ~ 80 (b-1) preferably the following equation (b-2):
40 ~ (100 ~ C ~ D) B/A ~ 70 (b-2) wherein A is the absorption capacity of said absorbent resin powder (I) for a physiological sallne solution, B is the absorption capacity of the resultant treated absorbent resin for physiological saline solution, and C is parts by weight of said polyhydric alcohol (~) u~ed per 100 parts by weight of said ab~orbent re~in powder (I), and D is part3 by weight of said water-insoluble fine powder (V) used per 100 parts by weight o~ the absorbent resin powder (I).
The water-insoluble fine powders (V) which are usable in the pre~erred embodiment of this invention include inorganic powders of silicon dioxide, titanium dioxide, aluminum oxicle, magnesium oxide, zinc oxide, calcium pho~phate, barium pho~phate, diatomaceous earth, talc, æeolite, bentonite, kaolin, hydrotalcite, activated carbon, activated clay, and clayish minerals and organic powders such as cellulose powder, pulp powder, rayon, polyesters, polyethylene, polypropylene, polyvinyl chloride, polystyrene, and nylons, for example. Among other water-insoluble fine powders mentioned above 9 water-insoluble inorganic powders prove to be particularly desirable. The water-insoluble fine inorganic powders which are advantageously usable herein include silicon dioxide, titanium dioxids, aluminum oxide, magnesium oxide, zeolite, bentonite7 kaolin, and hydrotalcite, for example.
The amount of the water insoluble fine powder ~V~
to be u~ed in the preferred embodiment is in the range of 0.01 to 10 parts by weight, preferably 0.01 to 5 parts by weight, based on 100 parts by weight of the absorbent resin powder (I).
The particle size of the water~insoluble fine powder (V) is preferably to be not more than 1,000 ~m, more preferably not more than 50 ~m.
In the preferred embodiment of this invention, the timing of the ~ddition of the water-insoluble fine powder (V~ to the reaction mixture may be fixed to suit any of the following procedures.
(i) The absorbent resin powder (I) is mixed with the water-insoluble fine powder (V) before it is mixed with the polyhydric alcohol (~), water (m) and the hydrophilic organic solYent ( rv ) .
(ii) The absorbent resin powder (I) is mixed with the water-insoluble fine powder (V) at the same time when it is mixed with the polyhydric alcohol (~), water ( m ) and the hydrophilic organic ~olvent (~).
(iii~ The water~insoluble fine powder (V) is mixed with the product of the mixture o~ the ab~orbent resin powder (I3 with the polyhydric alcohol (~), water (m) and the hydrophilic organic solvent (~).
The timing of the procedure (i) in which the water-insoluble fine powd0r (V) is added in advance to the absorbent reqin powder (I) or of the procedure (ii) in which the water-insoluble fine powder (V) is added at the same time that the absorbent resin powder (I) is mixed with the polyhydric alcohol ~), water (m) and the hydrophilic organic solvent (IVj is preferable.
As described above9 by the method of mixing 100 parts by weight of the absorbent resin powder (I), 0.01 to 30 parts by weight of a polyhydric alcohol (~), 0 to 5Q
parts by weight of water (~), and 0 to 60 parts by weight of a hydrophilic organic solvent (~), and heat-treating the surface region of said absorbent resin powder (I) at a temperature of 90C to 250Cs wherein the time for complet,ion ~ ~6?,~ 8 r~
of the reaction is the time that satisfies the above~
mentioned equation (a 1), and further by the method of mixing 100 parts by weight of an absorbent resin (I) 0.01 to 30 parts by weight of a polyhydric alcohol (~), 0 to 50 parts by weight of water and (~) 0 to 60 parts by weight of a hydrophilic organic solvent, and heat-treatirlg the surface region of said absorbent resin powder (I) at a temperature of 90C to 250C in the presence of a water-in~oluble fine powder (V), wherein the time for completion of the reaction is She time that ~atisfies the above-mentioned equation (b-1), this invention produces an absorbent which ha~ not only a high absorption rate, but also a high absorption rate under pressure and high liquid permeability under pressure as well as a high water-retaining property under pressure.
Further, the absorbent obtained by the present invention having the above-mentioned features, are useful as one o~ the component materials Qf such sanitary articles as sanitary napkins and disposable diapers and ~s a coagulant for sludge, as a dew-drop proofing agent for building materials, as a water-retaining agent for agriculture and horticulture, and as dryer.
Now, the present invention will be described more specifically below with reference to working examples. It should be noted 9 however, that the scope of this invention is not limited to these examples.
Example 1 A jacketed twin arm type kneader of stainless steel measuring 10 liters in inner volume9 220 mm X 240 mm in the opening, and 240 mm in depth and provided with two Sigma type blades possessing a rotational diameter of 120 mm was stoppered with a lid. Into this kneader, a monomer component containing 5,500 g of an aqueous, solution of sodium acrylate posse~ing a neutralization ratio of 75 mol%
and 1.7 g of trimethylo~. propane triacrylate (0O025 molZ
based on sodium acrylate posse~3lng a neutralization ratio of 75 mol%) ~the monomer concentration 37 % by weight in the f~ $ ~
aqueous solution) was introduced and nitrogen gas was blown to displace the air entrapped in~ide the reaction system.
Then, the two Sigma type blades were set rotating at rates of 46 rpm and, at the ~me time, the Jacket was heated by passage of hot water at 35C. As a polymerization initiator, 2.8 g of sodium persulfate and 0.14 g of L-ascorbic acid were added. Polymerization started four minutes after the addition of the polymerization initiator.
The peak temperature inside the reaction system reached 82C
after the elapse of 15 minutes following the addition of the polymerization initiator. The hydrated gel polymer had been divided into minute particles about 5 mm in size. The stirring was further continued. The lid was removed from the kneader 60 minutes after the start of the polymerization and the gel was removed ~rom the knead~r.
The minute particles of hydrated gel polymer thus obtained were spread on a 50-mesh metal gauze and dried with hot air at 150C ~or 90 minutes. The dried minute particles were pulverized with a ha~mer type crusher and sifted with a 20-mesh metal gauze to obtain a 20-mesh pass portion [absorbent resin powder (A-1)].
A liquid mixture containing 0.75 parts o~ glycerol, 3 parts of water and 12 parts of isopropanol was mixed with 100 parts of the absorbent resin powder (A-1).
The resultant mixture was charged into a bowl dipped in an oil bath (195C) and was subjected to heat treatment for 45 minute~ under ~tirring to obtain an absorbent (l).
The ab~orbent resin powder (A-1~ and the absorbent (1) obtained as de~cribed above were tested for (i) absorption capacity, (ii) water-retaining property under pre~sure 10 min and 30 min, (iii) Liquid Permeability under pressure as follows;
(i) Absorption capacity: A pouch (40 mm X 150 mm) made of non-woven fabric a~ter the fashion of a tea bag and filled evenly with about 0.2 g of a sample of absorbent resin powder (A-1) or absorbent (1) was immersed in an 2 ~
aqueous 0.9 % NaCl solution for 60 min removed from the solution, left draining for 5 sec, removing water on 24 folded toilet paper having 60 cm Por 10 second~, and weighed.
Absorption Weight after absorption (g)-Blank(g) capacity (g/g) - -Weight of absorbent resin (g) (ii) Water-retaining property under pressure: The test for the water-retaining property under pressure wa3 oarried out by the u~e of an apparatus configured as shown in Fig.
1. The upper end 22 of a buret 21 was stoppered with a plug 23 and a mea~uring stand 24 was set flush with an air inlet 25~ On a gla~s filter (No. 1) 26 70 mm in diameter placed in the measuring stand 24, a filter paper, 0.20 g of a sample of absorbent re~in powder (A-1) or absorbent (1), and a filter paper 27 were superpo~ed and a weight of 0.2 psi was mounted thereon. The sample as ~andwiched between the filter papers was left to ab~orbing synthetic urine (containing 1.9% of urea, 0.8% of Nacl, 0.1% of CaC12, and 0.1% of MgS04) for 10 or 30 minutes. At the end of the absorption 7 the volume (A ml) of the synthetic urine abqorhed was mleasured.
Water-retaining property = A (ml)/0~20 (g) under pressure (m~/g) (i~i) Liquid permeability under pre~sure: The te~t for liquid permeability was carried out by the use of an apparatus configured as shown in Fig. 2. A model diaper was prepared by uniformly ~cattering 4.0 g of a sample of absorbent resin powder (A-1) or absorbent (1) 34 on a bed of 12 g CL pulp 33 140 mm X 250 mm in area, superposing 12 g of pulp 33a on the scattered sample, and pre~sing the superposed layers under a load of 2 kg/cm2. A weight 32 of 0.2 p~i mea~uring 150 ~m X 250 mm in area and provided at the center thereof with a synthetic urine inlet (31) wa3 ~ ~ ~eJ~
mounted on the model diaper. Then 100 ml o~ the synthetic urine was poured into the model diaper. After standing for 30 minutes, ~urther when 150 ml of synthetic urine is added, the time wnich elapsed before the synthetic urine disappeared from the inlet was clocked.
(iv) Calculated value of formula: Water content (105C-3 hours) of the ab~orbent resin powder (A-1) was 2% (wet basis), the formula ~a~1) substituted by P/o.98 = P' to calculate the value o~ formula. Further water content of the absorbent (1) was 0%.
Control 1 A similar procedure to Example l was repeated to obtain a control absorbent I, except that the heat treatment waQ carried out for 10 minutes. The tests described in Example 1 were carried out by a similar method to Example 1 and the results are shown in Table 1.
Example 2 A pulverized hydrated gel was obtained by the procedure o~ Example l, except that 1.36 g of trimethylol propane triacrylate (0.020 mol% based on qodium acrylate possessing a neutralization ratio of 75 mol~) was u~ed. The gel was dried and pulverized by a similar method as in Example 1, to obtain a powder that pa~sed through a 20-mesh metal gauze [absorbent resin powder (A-2)].
A liquid mixture containing, l part of glycerol, 3 parts of water and 8 parts of ethanol was mixed with lO0 parts o~ the absorbent resin powder (A 2).
The resultant mixture was charged into a bowl dipped in an oil bath (195C) and wa~ subjected to heat~treatment for 30 minute~ under stirring to obtain an absorbent (2).
The absorbent 12) thus obtained was subjected to the tests of Example l and the results are shown in Table lo Examples 3 and 4 and Control 2 A similar procedure to Example 2 wa carried out to obtain absorbents (3) and (4) and control absorbent (2), except that the surface treatment liquids9 compo~ition, and 2 ~ ~ f~
heating conditions are as shown in Table 1. The performances of these samples are shown in Table 1n Example 5 100 parts by weight of the absorbent resin powder (A-2) and 1 part by weight; of water-insoluble fine silica ("Aerosil 200" a trade name for a produet of Aerosil Co., Ltd.) was mixed by a V-type mixture to obtain ab~orbent resin powder B.
A liquid mixture containing 1 part of 17 3-propanediol, 15 parts of water and 15 parts of isopropanol was mixed with 101 parts o~ the absorbent resin powder B.
The resultant mixture was charged into a bowl dipped in an oil bath (210C) and was subjected to heat-treatment for 40 minutes under stirring to obtain an absorbent (5).
The absorbent (5) thu~ obtained was tested by a similar method to Example 1 and the results are shown in Table 1.
Example 6 100 parts by weight of a commercially available starch-acrylic acid graft polymer (Sanwet IM-1000, manu~actured by Sanyo Kasei Kogyo K~Ko ) and a liquid containing 1 part o~ glycerol and 8 parts of isopropanol were mixed. The resultant mixture was charged into a bowl dipped in an oil bath (210C) and was subjected to heat-treatment for 40 minutes under stirring to obtain an absorbent (6), The absorbent (6) thus obtained was tested by a ~imilar method to Example 1, and the results are shown in Table 1.
. _ ~ __ ~ __ ., . _ ¢ O U '- O 00 CO~ ~ 00 ~ C~ O
~ --- ~ ~-- -----~--_O S ~O ~D t-- O N
1~1 . _ . __ ., . _ O N N O tO o~ ~ iD 10 --10 _ _ __ _. _ __ _ __ S C l ~ O ~ ~ ,1 0N ~ ~D N O ~D
~ _ __ __ _ ~--_ _.
_ C ~ oO ~ 10 ~ O ~r ~o~n oo r-~ _ . __. _ _ __ aN N ~ ~ o ~ C~ C~ 10 ~D
__, _ ____ . ___ _ _ _ -1 P.¢ ~ C~ ~ ~ C`lN~ CJ~ ~_ ~C¢ ___ __ _ . _ P~ ~ eD ~D O ~O O
- - - - ~ - - - - - -h ¢ ~ _~ " to ~ r1 ~ o lo U~ ~o ~ ~o _'- ._ _o _ _ , , ~ ¢ ~ cO~ C~a~ ~ ~r ~o", ~ r-a S ~ ~ _ _ ~ __ .C~'X~ ~ ~ Cl~ ~ .
__ _ _.. . . _ _ _ _ __ _ _ V S ~b ~ t~ _ G !~
_ ~ ' 1~ ê ~ Q~ c A S
Thu~, this method serves the purpose of improving the absorption rate of the absorbent resin to some extent. In recent years, the growing trend of absorbent articles particularly for sanitary applications toward better performance and better quality have been urging the absorbents used in such ab~orbent articles to offer higher quality of absorption rate. However, an actual absorbent article for sanitary use should absorb body fluids under pressure, so it has been clarified that the absorption property under pressure is important. For ab~orbent re~in-q u3ed as constituent materials for a sanitary material which absorbs body fluid, not only absorption rate, liquid permeability, and absorption capacity under no pre~sure, but 2 ~
also absorption rat;e, liquid permeability and absorption capacity under pressure are important, and high absorption rate under pressure, high liquid permeability under pressure, and high water-retaining property under pressure have been required. None of the prior art satisfies such requirements.
An object of the present invention is, accordingly, to provide a method for treating the ~urface of an absorbent resin.
Another object of the pre~ent invention is to provide an effective method for treating the surface of absorbent resin ~or obtaining an absorbent havir.g high absorption rate under pres3ure, high liquid permeability under pressure, and high water-retaining property under pressure.
Still another object of the present invention is to provide an effective method for treatin~ the surface of absorbent resin fQr obtaining an absorbent which can be dispersed between pulp ~ibers, has high absorption capacity even iP it is contacted with an aqueous liquid under pressure, and ha~ high liquid permeability without closing capillaries between the pulp fibers.
SUMMARY OF THE INVENTION
These objects are accomplished by a method for treating the surface of an absorbent resin which comprises mixing (I) 100 parts by weight of an absorbent resin powder having a carboxyl group, (~) 0.01 to 30 parts by weight of a polyhydria alcohol, ( m ) O to 50 parts by weight of water and (~) O to 60 parts by weight of a hydrophilic organic solvent, and heat-treating at a temperature in the range of 90 to 250C to treat the surface of said absorbent resin powder (I) until the reaction of said absorbent resin powder (I) with said polyhydric alcohol (~) is completed~
wherein the time for completion of the reaction is the time that satisfies the following equation (a~
30 ~ (100 + C) B/A ~ 80 (a~1) 2~ Q8~
wherein A is absorption capacity of said absorbent resin powder (I) for physiolagical saline solution, B is the absorption capacity of the resultant treated absorbent resin for physiological saline solution, and C is parts by weight of said polyhydric alcohol (~) used per 100 parts by weight o~ said absorbent resin powder (I)~
According to the present invention, an absorbent having high absorption rate under pressure, liquid permeability under pressure~ and water-retaining property under pressure is obtained by reacting the sur~ace region of an absorbent resin powder ( r ) having a carboxyl group with a polyhydric alcohol (~) and completing the reaction o~ the surface treatment when the above-mentioned formula (a-1) is satisfied.
Further 7 the absorbent thus obtained shows high absorption rate and absorption capacity even if it is contacted with an aqueous solution under pressure when dispersed between pulp fibers, and has high liquid permeability without closing capillaries between pulp fibers, so if for example, it is used in a disposable diaper, a diaper having less leakage can be obtainedO
The absorbent thus obtained may be used for sanitary field such as dispo~able diapars, sanitary napkins and disposable tow~els, for civil engineering field ~uch as water sealing agents, dewproofing agents and sludge coagulating agents, for architectural ~ield such as humidity controlling agents, for agricultural and horticultural field such as qeed and seedling preserving sheets, for foodstuff packaging field such as freshness preserving materials, dehydrating agents and desiccants, for medical field such as blood absorbents and surgical sponges, for electrical field such as water sealant for cables and humidity sensors, and other oil-water separating agents~ sweat absorbents, water swellable toys9 ion exchanging resins, and they can absorb aqueous liquids such as water, urine, blood, c~team, meat 2 ~ 3 ~
juices, ion-containing water including sea water, aqueous solutions dispersing organics, etc.
BRIEF DESCRIPTION OF THE DRAWING
Fig. 1 is a sectional view of an apparatus for measuring water-retaining property under pressure, and Figo 2 is a sectional view of an apparatus for measuring liquid permeability under pressure.
EXPLANATION OF THE PREFERRED EMBODIMENT
For use in this invention~ it is preferable that the absorbent resin powder (I) po~sesse~ a carboxyl group. The heretofore known carboxyl group-containing absorbent resins include a hydrolyzed starch acrylonitrile graft polymer, a neutralized starch-acryllc acid graft polymer, saponified vinyl acetate-acrylic ester copolymers, hydrolyzed acrylonitrile or acrylamide copolymers, cross-linked products of such copolymers, a partially neutralized polyacrylic acid, and a partially neutralized cros~-linked polyacrylic acid, invariably available in the form of powder 9 for example. These absorbent resin powders may be used either singly or in varying combinations o~ two or more members. The absorbent reqin powder ~ preferable, but not always required9 to possesq a cross-linked structure.
Though the amount of the carboxyl group to be possessed by the absorbent resin powder (I) is not specifically limited, it is preferable to be not less than 0.01 equivalent weight based on 100 g of the absorbent resin powder (I~. In the case of the partially neutralized polyacrylie acid, for example7 the proportion of the unneutralized portion thereof is preferable to be in the range of 1 to 50 mol%, preferably 5 to 40 mol%.
The form in which the absorbent resin powder (I) is used in the present invention is not specifically limited.
It may be in the form of spheres obtained by reverse-phase suspension polymerization7 in the fcrm of flakes obtained by drum drying 7 or in the form of irregular particles obtained by crushing resin lumps, for example. Preferably7 the 2 ~
absorbent resin powder is in the form of flakes or irregular particlesO
The polyhydric alcohol ~) to be u~ed in this invention has at leaqt two hydroxyl groups per molecular unit. It is preferable to use, among polyhydric alcohols answering the description, one member or a varying combination of two or more members selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerol, polyglycero1, propylene glycol, diethanolamine, triethanol-amine, polyoxypropylene, oxyethylene-oxypropyle block copolymer, sorbitan fatty acid esters, polyoxyethy1ene sorbitan ~atty acid esters, trimethylolpropane~
pentaerythritol, 1,3-propanediol, and sorbitol.
The amount of the polyhydric alcohol (~) to be used in the present invention is to be in the range of 0.01 to 30 parts by weight~ preferably 0.1 to 10 parts by weight based on 100 parts by weight of the ab~orbent resln powder (I).
If this amount is less than 0.01 part by weight, even if it is heated for a long time, an increase of absorption rate under pressure, liquid permeability under pressure, and water-retaining property under pressure, cannot be recognized. Gonversely, if the amount exceeds 30 parts by weight, it is difficult to obtain an effect corresponding to the increase of the amount, and the unreacted polyhydric alcohol (~) remains, so that it becomes not only a reason of various trouble~, but also uneconomical.
For the purpose of ensuring the homogeneous mixing of the polyhydric alcohol (~) and the absorbent resin powder (I), the present invention use3 water (m) 0 to 50 parts by weight and a hydrophilic organic solvent (~) 0 to 60 parts by weight based on 100 parts by weight of the absorbent resin powder (I).
The water (m) is effective in promoting the permeation of the polyhydric alcohol (~) into the qurface region of the absorbent resin powder (I~. The water (m~ is preferable to be used in an amount in the range of 0 to 50 parts by weight, pre~erably 0.1 to 50 parts by wei.ght, more preferably Oo1 to 2~ parts by weight, based on 100 parts by weight of the absorbent resin powder (I). If the amount is less than 0~1 part by weight, the effect of the addition is difficult to be recognized, and i~ the amount exceeds 50 parts by weight, the mixing of the water with the absorbent resin powder may possibly necessitate a power~ul mixing device.
The hydrophilic organic solvent (~) is only required to be capable of being uni~ormly mixed with the polyhydric alcohol (~) and refraining ~rom producing any adverse effect on the performance of the absorbent resin powder (I). The hydrophilic organic solvents which fulfill this requirement include lower alcohols such as methanol, ethanol, n-propanol~ isopropanol, n-butanol, isobutanol, sec-butanol, and t-butanol; ketones such as acetone, methylethyl ketone, and methylisobutyl ketone; ethers such as dioxane, tetrahydrofuran, and diethyl ether; amides such as N,N-dimethyl formamide and N,N-diethyl formamide; and sulfoxides such as dimethyl sulfoxide, for example.
The hydrophilic organic solvent (~) is effective in uniformly dispersing the polyhydric alcohol (~) on the surface o.~ the absorbent resin powder (I). The amount of this solvent desirable ~or the manifestation of this effect is in the range of 0 to 60 parts by weight, preferably 0.1 to 60 parts by weight based on 100 parts by weight o~ the absorbent resin powder (I). If this amount exceeds 60 parts by weight, the heat treatment consumes an unduly long time.
In the pre~ent invention, the mixture of the absorbent resin powder possessing a carboxyl group ~I) with the polyhydric alcohol (~, is generally accomplished by spraying or dropping the polyhydric alcohol (~) or the mixture of the polyhydric alcohol (~) with water ( m ) and/or the hydrophilic organic solvent (~) onto the absorbent resin powder (I) and mixing them.
The preferred mixing devices to be used ~or thi~
mixin~ need to produce a large mixing ~orce to ensure uniform rnixingO Mixing machines and kneading machines may be e~fectively used. The mixing devices which are us~ble herein include cylindrlcal mixers9 double-walled cone mixers, V-shaped mixers, ribbon type mixers, screw type mixers, fluidizing type mixers, rotary disc type mixers, gas-current type mixers, twin-arm type kneaders, internal mixers, muller type kneaders, roll mixers, and screw type extruders, for example.
The method of treating the surface of an ~bsorbent resin in accordance with the present invention can be attained by mixing the absorbent re~in powder (I) and the polyhydric alcohol (~) or by mixing the absorbent resin powder (I~, the polyhydric alcohol (~), water (m), and the hydrophilic organic solvent (~) and heating them. Heat treatment can be carried out during mixing the components (I) through (~) or after mixing. Heat treatment can be carried out using a conventional drier or oven. For example, there are groove type mixing driers, rotary driers, disc driers, kneading driers, fluidized-bed type driers, gas flow type driers, and infrared ray driers. When the mixing of the components (1) through ~) and heat treatment are carried out al; the same time 7 a heat mixing type drier is used.
The temperature of the heat treatment is in the range of 90 to 250C~ preferably 120 to 220C. If the temperature is lower than 90C, the heat treatment proves to be uneconomical because it consumes an unduly long time.
Conversely, if this temperature exceeds ~50C, the heat treatment demands careful attention because some, if not all, of the absorbent resins are liable to undergo thermal deterioration. So long as the temperature of the heat treatment is confined ln this range of 90 to 25GC 9 the cross-linking reaction 9 proYiding for the fu]l manifestation of the effect of this invention, can be accompll~hed in a short span of time without entailing the possibility o~
deteriorating or coloring the absorbent resin.
The invention resides in the method herein (I) 100 parts by weight of an absorbent resin powder possessing a carboxyl group i3 mixed with (~) 0.01 to 30 parts by weight of a polyhydric alcohol~ ~ m ) O to 50 parts by weight of water and (~) O to 60 parts by weight of a hydrophilic organic solvent, and the reactisn of the ab30rbent resin powder (I) with the polyhydric alcohol (~) is completed at a temperature of 90 to 250C to treat the surface of the absorbent resin powder, the time for completion of the reaction of the surface treatment being the time that satisfies the above equation (a-1), preferably the following equation (a-2):
40 ~ (100 ~ C) B/A ~ 70 (a-2) If the (100 + C) B/A in the equation (a-1) is (100 + C) B/A
> 80 5 only the cross-linking den~ity at the region of the surface of the absorbent resin powder (I) increases, and although the increase of absorption rate corresponding to the increase of the croqs~linking density is recognized, the increase o~ absorption rate under pressure and liquid permeability under pressure cannot be recognized. Further, the absorbent having high water-retainirlg property under pressure cannot be obtained. On the contrary, if the (100 + C) B/A in the e~uation (a-1) is 30 ~ (100 + C) B/A, increase of the absorption rate under pressure and liquid permeability under pressure corresponding to the promotion of the reaction cannot be recognized, and it is not preferable, because the ab~orption capacity of the absorbent thus obtained decrease~ remarkably compared to that of the starting absorbent resin powder (I) and original properties o~ the absorbent resin is damaged.
According to the preferred embodiment of the present invention, the object of the present invention can be accomplished by a method for the surface treating of an ab30rbent resin in the presence of 0.01 to 10 parts by g weight of a water insoluble fine powder (V) until the reaction of said absorbent resin ~I) with said polyhydric alcohol (~) is oompleted, wherein the time for completion of the reaction is the time that satisfies the following equation (b-1), 30 ~ (100 + C~ D) B/A ~ 80 (b-1) preferably the following equation (b-2):
40 ~ (100 ~ C ~ D) B/A ~ 70 (b-2) wherein A is the absorption capacity of said absorbent resin powder (I) for a physiological sallne solution, B is the absorption capacity of the resultant treated absorbent resin for physiological saline solution, and C is parts by weight of said polyhydric alcohol (~) u~ed per 100 parts by weight of said ab~orbent re~in powder (I), and D is part3 by weight of said water-insoluble fine powder (V) used per 100 parts by weight o~ the absorbent resin powder (I).
The water-insoluble fine powders (V) which are usable in the pre~erred embodiment of this invention include inorganic powders of silicon dioxide, titanium dioxide, aluminum oxicle, magnesium oxide, zinc oxide, calcium pho~phate, barium pho~phate, diatomaceous earth, talc, æeolite, bentonite, kaolin, hydrotalcite, activated carbon, activated clay, and clayish minerals and organic powders such as cellulose powder, pulp powder, rayon, polyesters, polyethylene, polypropylene, polyvinyl chloride, polystyrene, and nylons, for example. Among other water-insoluble fine powders mentioned above 9 water-insoluble inorganic powders prove to be particularly desirable. The water-insoluble fine inorganic powders which are advantageously usable herein include silicon dioxide, titanium dioxids, aluminum oxide, magnesium oxide, zeolite, bentonite7 kaolin, and hydrotalcite, for example.
The amount of the water insoluble fine powder ~V~
to be u~ed in the preferred embodiment is in the range of 0.01 to 10 parts by weight, preferably 0.01 to 5 parts by weight, based on 100 parts by weight of the absorbent resin powder (I).
The particle size of the water~insoluble fine powder (V) is preferably to be not more than 1,000 ~m, more preferably not more than 50 ~m.
In the preferred embodiment of this invention, the timing of the ~ddition of the water-insoluble fine powder (V~ to the reaction mixture may be fixed to suit any of the following procedures.
(i) The absorbent resin powder (I) is mixed with the water-insoluble fine powder (V) before it is mixed with the polyhydric alcohol (~), water (m) and the hydrophilic organic solYent ( rv ) .
(ii) The absorbent resin powder (I) is mixed with the water-insoluble fine powder (V) at the same time when it is mixed with the polyhydric alcohol (~), water ( m ) and the hydrophilic organic ~olvent (~).
(iii~ The water~insoluble fine powder (V) is mixed with the product of the mixture o~ the ab~orbent resin powder (I3 with the polyhydric alcohol (~), water (m) and the hydrophilic organic solvent (~).
The timing of the procedure (i) in which the water-insoluble fine powd0r (V) is added in advance to the absorbent reqin powder (I) or of the procedure (ii) in which the water-insoluble fine powder (V) is added at the same time that the absorbent resin powder (I) is mixed with the polyhydric alcohol ~), water (m) and the hydrophilic organic solvent (IVj is preferable.
As described above9 by the method of mixing 100 parts by weight of the absorbent resin powder (I), 0.01 to 30 parts by weight of a polyhydric alcohol (~), 0 to 5Q
parts by weight of water (~), and 0 to 60 parts by weight of a hydrophilic organic solvent (~), and heat-treating the surface region of said absorbent resin powder (I) at a temperature of 90C to 250Cs wherein the time for complet,ion ~ ~6?,~ 8 r~
of the reaction is the time that satisfies the above~
mentioned equation (a 1), and further by the method of mixing 100 parts by weight of an absorbent resin (I) 0.01 to 30 parts by weight of a polyhydric alcohol (~), 0 to 50 parts by weight of water and (~) 0 to 60 parts by weight of a hydrophilic organic solvent, and heat-treatirlg the surface region of said absorbent resin powder (I) at a temperature of 90C to 250C in the presence of a water-in~oluble fine powder (V), wherein the time for completion of the reaction is She time that ~atisfies the above-mentioned equation (b-1), this invention produces an absorbent which ha~ not only a high absorption rate, but also a high absorption rate under pressure and high liquid permeability under pressure as well as a high water-retaining property under pressure.
Further, the absorbent obtained by the present invention having the above-mentioned features, are useful as one o~ the component materials Qf such sanitary articles as sanitary napkins and disposable diapers and ~s a coagulant for sludge, as a dew-drop proofing agent for building materials, as a water-retaining agent for agriculture and horticulture, and as dryer.
Now, the present invention will be described more specifically below with reference to working examples. It should be noted 9 however, that the scope of this invention is not limited to these examples.
Example 1 A jacketed twin arm type kneader of stainless steel measuring 10 liters in inner volume9 220 mm X 240 mm in the opening, and 240 mm in depth and provided with two Sigma type blades possessing a rotational diameter of 120 mm was stoppered with a lid. Into this kneader, a monomer component containing 5,500 g of an aqueous, solution of sodium acrylate posse~ing a neutralization ratio of 75 mol%
and 1.7 g of trimethylo~. propane triacrylate (0O025 molZ
based on sodium acrylate posse~3lng a neutralization ratio of 75 mol%) ~the monomer concentration 37 % by weight in the f~ $ ~
aqueous solution) was introduced and nitrogen gas was blown to displace the air entrapped in~ide the reaction system.
Then, the two Sigma type blades were set rotating at rates of 46 rpm and, at the ~me time, the Jacket was heated by passage of hot water at 35C. As a polymerization initiator, 2.8 g of sodium persulfate and 0.14 g of L-ascorbic acid were added. Polymerization started four minutes after the addition of the polymerization initiator.
The peak temperature inside the reaction system reached 82C
after the elapse of 15 minutes following the addition of the polymerization initiator. The hydrated gel polymer had been divided into minute particles about 5 mm in size. The stirring was further continued. The lid was removed from the kneader 60 minutes after the start of the polymerization and the gel was removed ~rom the knead~r.
The minute particles of hydrated gel polymer thus obtained were spread on a 50-mesh metal gauze and dried with hot air at 150C ~or 90 minutes. The dried minute particles were pulverized with a ha~mer type crusher and sifted with a 20-mesh metal gauze to obtain a 20-mesh pass portion [absorbent resin powder (A-1)].
A liquid mixture containing 0.75 parts o~ glycerol, 3 parts of water and 12 parts of isopropanol was mixed with 100 parts of the absorbent resin powder (A-1).
The resultant mixture was charged into a bowl dipped in an oil bath (195C) and was subjected to heat treatment for 45 minute~ under ~tirring to obtain an absorbent (l).
The ab~orbent resin powder (A-1~ and the absorbent (1) obtained as de~cribed above were tested for (i) absorption capacity, (ii) water-retaining property under pre~sure 10 min and 30 min, (iii) Liquid Permeability under pressure as follows;
(i) Absorption capacity: A pouch (40 mm X 150 mm) made of non-woven fabric a~ter the fashion of a tea bag and filled evenly with about 0.2 g of a sample of absorbent resin powder (A-1) or absorbent (1) was immersed in an 2 ~
aqueous 0.9 % NaCl solution for 60 min removed from the solution, left draining for 5 sec, removing water on 24 folded toilet paper having 60 cm Por 10 second~, and weighed.
Absorption Weight after absorption (g)-Blank(g) capacity (g/g) - -Weight of absorbent resin (g) (ii) Water-retaining property under pressure: The test for the water-retaining property under pressure wa3 oarried out by the u~e of an apparatus configured as shown in Fig.
1. The upper end 22 of a buret 21 was stoppered with a plug 23 and a mea~uring stand 24 was set flush with an air inlet 25~ On a gla~s filter (No. 1) 26 70 mm in diameter placed in the measuring stand 24, a filter paper, 0.20 g of a sample of absorbent re~in powder (A-1) or absorbent (1), and a filter paper 27 were superpo~ed and a weight of 0.2 psi was mounted thereon. The sample as ~andwiched between the filter papers was left to ab~orbing synthetic urine (containing 1.9% of urea, 0.8% of Nacl, 0.1% of CaC12, and 0.1% of MgS04) for 10 or 30 minutes. At the end of the absorption 7 the volume (A ml) of the synthetic urine abqorhed was mleasured.
Water-retaining property = A (ml)/0~20 (g) under pressure (m~/g) (i~i) Liquid permeability under pre~sure: The te~t for liquid permeability was carried out by the use of an apparatus configured as shown in Fig. 2. A model diaper was prepared by uniformly ~cattering 4.0 g of a sample of absorbent resin powder (A-1) or absorbent (1) 34 on a bed of 12 g CL pulp 33 140 mm X 250 mm in area, superposing 12 g of pulp 33a on the scattered sample, and pre~sing the superposed layers under a load of 2 kg/cm2. A weight 32 of 0.2 p~i mea~uring 150 ~m X 250 mm in area and provided at the center thereof with a synthetic urine inlet (31) wa3 ~ ~ ~eJ~
mounted on the model diaper. Then 100 ml o~ the synthetic urine was poured into the model diaper. After standing for 30 minutes, ~urther when 150 ml of synthetic urine is added, the time wnich elapsed before the synthetic urine disappeared from the inlet was clocked.
(iv) Calculated value of formula: Water content (105C-3 hours) of the ab~orbent resin powder (A-1) was 2% (wet basis), the formula ~a~1) substituted by P/o.98 = P' to calculate the value o~ formula. Further water content of the absorbent (1) was 0%.
Control 1 A similar procedure to Example l was repeated to obtain a control absorbent I, except that the heat treatment waQ carried out for 10 minutes. The tests described in Example 1 were carried out by a similar method to Example 1 and the results are shown in Table 1.
Example 2 A pulverized hydrated gel was obtained by the procedure o~ Example l, except that 1.36 g of trimethylol propane triacrylate (0.020 mol% based on qodium acrylate possessing a neutralization ratio of 75 mol~) was u~ed. The gel was dried and pulverized by a similar method as in Example 1, to obtain a powder that pa~sed through a 20-mesh metal gauze [absorbent resin powder (A-2)].
A liquid mixture containing, l part of glycerol, 3 parts of water and 8 parts of ethanol was mixed with lO0 parts o~ the absorbent resin powder (A 2).
The resultant mixture was charged into a bowl dipped in an oil bath (195C) and wa~ subjected to heat~treatment for 30 minute~ under stirring to obtain an absorbent (2).
The absorbent 12) thus obtained was subjected to the tests of Example l and the results are shown in Table lo Examples 3 and 4 and Control 2 A similar procedure to Example 2 wa carried out to obtain absorbents (3) and (4) and control absorbent (2), except that the surface treatment liquids9 compo~ition, and 2 ~ ~ f~
heating conditions are as shown in Table 1. The performances of these samples are shown in Table 1n Example 5 100 parts by weight of the absorbent resin powder (A-2) and 1 part by weight; of water-insoluble fine silica ("Aerosil 200" a trade name for a produet of Aerosil Co., Ltd.) was mixed by a V-type mixture to obtain ab~orbent resin powder B.
A liquid mixture containing 1 part of 17 3-propanediol, 15 parts of water and 15 parts of isopropanol was mixed with 101 parts o~ the absorbent resin powder B.
The resultant mixture was charged into a bowl dipped in an oil bath (210C) and was subjected to heat-treatment for 40 minutes under stirring to obtain an absorbent (5).
The absorbent (5) thu~ obtained was tested by a similar method to Example 1 and the results are shown in Table 1.
Example 6 100 parts by weight of a commercially available starch-acrylic acid graft polymer (Sanwet IM-1000, manu~actured by Sanyo Kasei Kogyo K~Ko ) and a liquid containing 1 part o~ glycerol and 8 parts of isopropanol were mixed. The resultant mixture was charged into a bowl dipped in an oil bath (210C) and was subjected to heat-treatment for 40 minutes under stirring to obtain an absorbent (6), The absorbent (6) thus obtained was tested by a ~imilar method to Example 1, and the results are shown in Table 1.
. _ ~ __ ~ __ ., . _ ¢ O U '- O 00 CO~ ~ 00 ~ C~ O
~ --- ~ ~-- -----~--_O S ~O ~D t-- O N
1~1 . _ . __ ., . _ O N N O tO o~ ~ iD 10 --10 _ _ __ _. _ __ _ __ S C l ~ O ~ ~ ,1 0N ~ ~D N O ~D
~ _ __ __ _ ~--_ _.
_ C ~ oO ~ 10 ~ O ~r ~o~n oo r-~ _ . __. _ _ __ aN N ~ ~ o ~ C~ C~ 10 ~D
__, _ ____ . ___ _ _ _ -1 P.¢ ~ C~ ~ ~ C`lN~ CJ~ ~_ ~C¢ ___ __ _ . _ P~ ~ eD ~D O ~O O
- - - - ~ - - - - - -h ¢ ~ _~ " to ~ r1 ~ o lo U~ ~o ~ ~o _'- ._ _o _ _ , , ~ ¢ ~ cO~ C~a~ ~ ~r ~o", ~ r-a S ~ ~ _ _ ~ __ .C~'X~ ~ ~ Cl~ ~ .
__ _ _.. . . _ _ _ _ __ _ _ V S ~b ~ t~ _ G !~
_ ~ ' 1~ ê ~ Q~ c A S
Claims (20)
1. A method for treating the surface of an absorbent resin which comprises mixing (I) 100 parts by weight of an absorbent resin powder having a carboxyl group, (II) 0.01 to 30 parts by weight of a polyhydric alcohol, (III) o to 50 parts by weight of water and (IV) 0 to 60 parts by weight of a hydrophilic organic solvent, and heat-treating at a temperature in the range of 90 to 250°C to treat the surface of said absorbent resin powder (I) until the reaction o.
said absorbent resin powder (I) with said polyhydric alcohol (II) is completed, wherein the time for completion of the reaction is the time that satisfies the following equation (a-1):
(a-1) wherein A is absorption capacity of said absorbent resin powder (I) for physiological saline solution, B is the absorption capacity of the resultant treated absorbent resin for physiological saline solution, and C is parts by weight of said polyhydric alcohol (II) used per 100 parts by weight of said absorbent resin powder (I).
said absorbent resin powder (I) with said polyhydric alcohol (II) is completed, wherein the time for completion of the reaction is the time that satisfies the following equation (a-1):
(a-1) wherein A is absorption capacity of said absorbent resin powder (I) for physiological saline solution, B is the absorption capacity of the resultant treated absorbent resin for physiological saline solution, and C is parts by weight of said polyhydric alcohol (II) used per 100 parts by weight of said absorbent resin powder (I).
2. A method according to Claim 1, wherein the amount of said polyhydric alcohol (II) is 0.1 to 10 parts by weight per 100 parts by weight of said absorbent resin powder (I).
3. A method according to Claim 1, wherein the amount of water (III) is 0.1 to 20 parts by weight per 100 parts by weight of said absorbent resin powder (I).
4. A method according to Claim 1 7 wherein the amount of said hydrophilic organic solvent (IV) is 0.1 to 20 parts by weight per 100 parts by weight of said absorbent resin powder (I).
5. A method according to Claim 1, wherein the amount of water (III) is 0.1 to 20 parts by weight and the amount of said hydrophilic organic solvent (IV) is 0.1 to 20 parts by weight per 100 parts by weight of said absorbent resin powder (I).
6. A method according to Claim 1, wherein the time for completion of the reaction is the time that satisfies the following equation (a-2):
(a-2)
(a-2)
7. Substantially water insoluble, absorbent, hydrogel-forming, polymer composition produced according to the method of Claims 1, 2, 3, 5 or 6.
8. A method according to Claim 1, wherein heat-treating is carried out in the presence of 0.01 to 10 parts by weight of a water-insoluble fine powder (V) until the reaction of said absorbent resin powder (I) with said polyhydric alcohol (II) is completed, wherein the time for completion of the reaction is the time that satisfies the following equation (b-1):
(b-1) wherein A is the absorption capacity of said absorbent resin powder (I) for a physiological saline solution, B is the absorption capacity of the resultant treated absorbent resin for physiological saline solution, and C is parts by weight of said polyhydric alcohol (II) used per 100 parts by weight of said absorbent resin powder (I), and D is parts by weight of said water-insoluble fine powder (V) used per 100 parts by weight of the absorbent resin powder (I).
(b-1) wherein A is the absorption capacity of said absorbent resin powder (I) for a physiological saline solution, B is the absorption capacity of the resultant treated absorbent resin for physiological saline solution, and C is parts by weight of said polyhydric alcohol (II) used per 100 parts by weight of said absorbent resin powder (I), and D is parts by weight of said water-insoluble fine powder (V) used per 100 parts by weight of the absorbent resin powder (I).
9. A method according to Claim 8, wherein the amount of said water-insoluble fine powder (V) is 0.01 to 5 parts by weight per 100 parts by weight of the absorbent resin powder (I).
10. A method according to Claim 8, wherein the particle size of said water-insoluble fine powder (V) is less than about 50 µm.
11. A method according to Claim 8, wherein said water-insoluble fine powder (V) is a water-insoluble inorganic fine powder.
12. A method according to Claim 11, wherein said water-insoluble inorganic fine powder is at least one member selected from the group consisting of silicon dioxide, titanium dioxide, aluminum oxide, zealite, kaolin, and hydrotalcite.
13. A method according to Claim 8 7 wherein said water-insoluble fine powder (V) is mixed before heat-treating is carried out.
14. A method according to Claim 13, wherein said mixing is carried out in the presence of water-insoluble fine powder (V).
15. A method according to Claim 8, wherein the amount of said polyhydric alcohol (II) is 0.1 to 10 parts by weight per 100 parts by weight of said absorbent resin powder (I).
16. A method according to Claim 8, wherein the amount of water (III) is 0.1 to 20 parts by weight per 100 parts by weight of said absorbent resin powder (I).
17. A method according to Claim 8, wherein the amount of said hydrophilic organic solvent (IV) is 0.1 to 20 parts by weight per 100 parts by weight of said absorbent resin powder (I).
18. A method according to Claim 8, wherein the amount of water (III) is 0.1 to 20 parts by weight and the amount of said hydrophilic organic solvent (IV) is 0.1 to 20 parts by weight per 100 parts by weight of said absorbent resin powder (I).
19. A method according to Claim 8, wherein the time for completion of the reaction is the time that satisfies the following equation (b-2):
(b-2)
(b-2)
20. Substantially water-Insoluble, absorbent, hydrogel-forming, polymer composition produced according to the method of Claims 8, 11, 15, 16, 18 or 19.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/502,735 US5164459A (en) | 1990-04-02 | 1990-04-02 | Method for treating the surface of an absorbent resin |
| US502,735 | 1990-04-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2039087A1 true CA2039087A1 (en) | 1991-10-03 |
Family
ID=23999166
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002039087A Abandoned CA2039087A1 (en) | 1990-04-02 | 1991-03-27 | Method for treating the surface of an absorbent resin |
Country Status (19)
| Country | Link |
|---|---|
| US (1) | US5164459A (en) |
| EP (1) | EP0450924B1 (en) |
| JP (1) | JP2539958B2 (en) |
| KR (1) | KR0143403B1 (en) |
| CN (1) | CN1029125C (en) |
| AT (1) | ATE144152T1 (en) |
| AU (1) | AU634642B2 (en) |
| BR (1) | BR9101310A (en) |
| CA (1) | CA2039087A1 (en) |
| CS (1) | CS86291A2 (en) |
| DE (1) | DE69122643T2 (en) |
| ES (1) | ES2092546T3 (en) |
| FI (1) | FI911524A (en) |
| HU (1) | HUT60303A (en) |
| IE (1) | IE911073A1 (en) |
| MA (1) | MA22107A1 (en) |
| PL (1) | PL289710A1 (en) |
| PT (1) | PT97231A (en) |
| TW (1) | TW215098B (en) |
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| BR112012027406B1 (en) | 2010-04-26 | 2021-02-09 | Nippon Shokubai Co., Ltd. | water-absorbing resin like polyacrylic acid (salt), sanitary material and method for producing said resin |
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| PL2505719T3 (en) | 2011-03-31 | 2016-10-31 | Self healing salt water barrier | |
| CN102558574B (en) * | 2012-01-04 | 2014-12-10 | 江苏博特新材料有限公司 | Surface modification method of carboxyl-containing high-water-absorbability resin |
| US9092585B2 (en) | 2013-01-22 | 2015-07-28 | The Procter & Gamble Company | Computer based models for absorbent articles |
| JP6313280B2 (en) | 2013-03-27 | 2018-04-18 | 住友精化株式会社 | Method for producing water absorbent resin composition |
| KR101719352B1 (en) * | 2013-12-13 | 2017-04-04 | 주식회사 엘지화학 | Super absorbent polymer composition |
| EP3165542B1 (en) | 2014-10-08 | 2020-12-02 | LG Chem, Ltd. | Method of preparing superabsorbent polymer |
| KR102025892B1 (en) | 2016-02-17 | 2019-09-26 | 주식회사 엘지화학 | A method of preparing superabsorbent polymers with improved anti-caking property |
| KR101959547B1 (en) | 2016-03-25 | 2019-03-18 | 주식회사 엘지화학 | Preparation method for super absorbent polymer |
| KR101953764B1 (en) | 2016-11-04 | 2019-03-04 | 주식회사 엘지화학 | Super absorbent polymer and preparation method thereof |
| EP4228577A1 (en) | 2020-10-16 | 2023-08-23 | The Procter & Gamble Company | Absorbent hygiene product comprising superabsorbent polymer partly derived from a recycled resource and methods of producing said product |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3661815A (en) * | 1970-05-18 | 1972-05-09 | Grain Processing Corp | Water-absorbing alkali metal carboxylate salts of starch-polyacrylonitrile graft copolymers |
| JPS51125468A (en) * | 1975-03-27 | 1976-11-01 | Sanyo Chem Ind Ltd | Method of preparing resins of high water absorbency |
| JPS58180233A (en) * | 1982-04-19 | 1983-10-21 | Nippon Shokubai Kagaku Kogyo Co Ltd | Absorbing agent |
| GB2126591B (en) * | 1982-09-02 | 1986-07-30 | Kao Corp | Process for producing highly water absorptive polymer |
| JPS60163956A (en) * | 1984-02-04 | 1985-08-26 | Arakawa Chem Ind Co Ltd | Production of water-absorptive resin |
| US4734478A (en) * | 1984-07-02 | 1988-03-29 | Nippon Shokubai Kagaku Kogyo Co., Ltd. | Water absorbing agent |
| JPH0643500B2 (en) * | 1985-12-04 | 1994-06-08 | 住友精化株式会社 | Granulation method of water absorbent resin |
| DE3878533T2 (en) * | 1987-10-29 | 1993-06-03 | Nippon Catalytic Chem Ind | METHOD FOR TREATING THE SURFACE OF A WATER-ABSORBENT RESIN. |
| DE3741158A1 (en) * | 1987-12-04 | 1989-06-15 | Stockhausen Chem Fab Gmbh | POLYMERISATES WITH HIGH ABSORPTION SPEED FOR WATER AND AQUEOUS LIQUIDS, METHOD FOR THE PRODUCTION THEREOF AND USE AS ABSORBENTS |
-
1990
- 1990-04-02 US US07/502,735 patent/US5164459A/en not_active Expired - Lifetime
-
1991
- 1991-03-27 CA CA002039087A patent/CA2039087A1/en not_active Abandoned
- 1991-03-27 AU AU73889/91A patent/AU634642B2/en not_active Expired - Fee Related
- 1991-03-28 IE IE107391A patent/IE911073A1/en unknown
- 1991-03-28 HU HU911029A patent/HUT60303A/en unknown
- 1991-03-28 FI FI911524A patent/FI911524A/en not_active Application Discontinuation
- 1991-03-28 CS CS91862A patent/CS86291A2/en unknown
- 1991-04-01 JP JP3068450A patent/JP2539958B2/en not_active Expired - Lifetime
- 1991-04-01 MA MA22376A patent/MA22107A1/en unknown
- 1991-04-02 DE DE69122643T patent/DE69122643T2/en not_active Expired - Lifetime
- 1991-04-02 AT AT91302896T patent/ATE144152T1/en not_active IP Right Cessation
- 1991-04-02 ES ES91302896T patent/ES2092546T3/en not_active Expired - Lifetime
- 1991-04-02 KR KR1019910005281A patent/KR0143403B1/en not_active IP Right Cessation
- 1991-04-02 CN CN91102561A patent/CN1029125C/en not_active Expired - Lifetime
- 1991-04-02 BR BR919101310A patent/BR9101310A/en unknown
- 1991-04-02 PL PL28971091A patent/PL289710A1/en unknown
- 1991-04-02 TW TW080102532A patent/TW215098B/zh not_active IP Right Cessation
- 1991-04-02 PT PT97231A patent/PT97231A/en not_active Application Discontinuation
- 1991-04-02 EP EP91302896A patent/EP0450924B1/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| ES2092546T3 (en) | 1996-12-01 |
| EP0450924A2 (en) | 1991-10-09 |
| PL289710A1 (en) | 1991-12-16 |
| CN1056110A (en) | 1991-11-13 |
| AU7388991A (en) | 1991-10-03 |
| AU634642B2 (en) | 1993-02-25 |
| CN1029125C (en) | 1995-06-28 |
| US5164459A (en) | 1992-11-17 |
| BR9101310A (en) | 1991-11-26 |
| PT97231A (en) | 1991-12-31 |
| MA22107A1 (en) | 1991-12-31 |
| EP0450924B1 (en) | 1996-10-16 |
| HU911029D0 (en) | 1991-10-28 |
| IE911073A1 (en) | 1991-10-09 |
| JP2539958B2 (en) | 1996-10-02 |
| ATE144152T1 (en) | 1996-11-15 |
| CS86291A2 (en) | 1991-11-12 |
| DE69122643D1 (en) | 1996-11-21 |
| HUT60303A (en) | 1992-08-28 |
| FI911524A (en) | 1991-10-03 |
| EP0450924A3 (en) | 1992-06-03 |
| JPH04214735A (en) | 1992-08-05 |
| KR0143403B1 (en) | 1998-07-15 |
| KR910018431A (en) | 1991-11-30 |
| DE69122643T2 (en) | 1997-02-20 |
| TW215098B (en) | 1993-10-21 |
| FI911524A0 (en) | 1991-03-28 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |