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Publication numberUS2769711 A
Publication typeGrant
Publication dateNov 6, 1956
Filing dateMay 14, 1952
Priority dateMay 14, 1952
Publication numberUS 2769711 A, US 2769711A, US-A-2769711, US2769711 A, US2769711A
InventorsLucius H Wilson
Original AssigneeAmerican Cyanamid Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Deposition of tacky impregnating agents on cellulosic fibers
US 2769711 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

with a cationic hydrophilic resin.

nite A The invention relates to the deposition of coating or impregnating materials to cellulosic fibers, to the coated or impregnated fibers obtained thereby, and to the manufacture of useful articles from the thus coated fibers. More specifically, the present invention relates to the deposition of tacky or sticky impregnating agents from aqueous dispersions or emulsions thereof on cellulosic fibers in aqueous suspension which have been treated More specifically still, the present invention relates to a method for preventing the formation of fibrous resin-bonded balls, clots, or aggregates during deposition of the impregnating agent as described.

The coating or impregnating of cellulosic fibers with insoluble organic, hydrophobic impregnating agents has been performed in the past by forming an aqueous stock or suspension of cellulosic fibers, adding to the stock an aqueous solution or dispersion of a cationic hydrophilic resin, and then adding the impregnating agent in the form of an aqueous emulsion or dispersion. The cationic resin causes a very uniform deposition or flocculation of the particles of the impregnating agent diectly on the fibers, while preserving the drainage qualities and the felting properties of the fibers. By means of this process it has been found readily feasible to produce cellulosic felted bodies, including paper, which contain 100% and even more of the impregnating agent, based on the weight of the fibers. The felted bodies obtained are characterized by the uniformity of their content of impregnating agent, and in this process only a negligible proportion of the impregnant is lost in the white water.

'In this process it is frequently desirable to allow the suspension of cellulosic fibers to stand or age for a period of time immediately subsequent to the addition of the cationic resin, and to defer addition of the emulsion or dispersion of the impregnating agent until adsorption of the cationic agent by the fibers has become substantially complete. This is particularly desirable in cases where large amounts of impregnating agent are deposited in comparison with the weight of the fibers. Ordinarily, during this aging the fibrous cellulosic suspension is allowed to stand for at least about 15 minutes, and longer periods have been employed to advantage.

The reason for the success of the above-described process in causing deposition of the impregnating agent while maintaining the freeness of the fibers has not been fully understood. it is believed, however, that the chief effects produced by the several steps involved are these. The cationic resin, which is always added first, is positively charged and converts the normally negatively charged fibers to a more positively charged state. The dispersion of impregnating agent, which preferably contains an anionic or a non-ionic emulsifying agent, is fioccu'lated in the immediate presence of the more positively charged fibers causing uniform and substantially complete deposition of the impregnating agent directly on the surface of the fibers. That other mechanisms exist is demonstrated by the fact that excellent deposition of the resin occurs in numerous instances when the emulsion or dispersion of the impregnating agent is added before more than a negligible amount of the ts i a 2,769,711 Patented Nov. 6, 1956 cationic resin has been adsorbed by the fibers, that is, when the step of aging referred to above is omitted.

in applying the above-described process to the deposition of large amounts, that is, about 25% to 100% base-d on the weight of the fibers, of sticky or tacky impregnating agents, it has been found that after deposition of the dispersed particles of impregnant on the resintreated fibers is substantially complete, and while the fibers are still in aqueous suspension, the fibers tend to form balls or clots rendering the fibers unsuitable for paper making purposes. Typically, these clots are of about the size of grains of rice and have a similar appearance.

in some instances, only a portion of the fibers in the stock clot, whereas in other instances,.substantially the whole of the fibrous suspension may form itself into aggregates of this type. When clotting is extensive or complete, the value of the stock for papermaking purposes is destroyed, as it is not possible to felt a substantially clotted stock into a coherent sheet. When clot formation is slight or partial, it is sometimes possible to form a paper, but the sheets thus made are mottled and lumpy, unattractive in appearance, and of low tensile and bursting strengths.

it is a striking fact that in these clots the cellulosic fibers are almost perfectly aligned in parallel, in which position the distance between the fibers is at a minimum. It is believed that in the clotting of these fibers the im pregnating agent acts as an adhesive for the fibers, bonding them together.

Despite numerous attempts, it has not been found practical to defiocculate these clots so as to regenerate a useful paper stock. Even where clotting is only partial, it has not been found practical to remove the clots so as to permit the unclotted portion of the stock to be processedin the normal manner. Up to the present, therefore, once any noticeable clotting has taken place in the stock, it has been necessary to discard the stock completely.

The emulsions of impregnating agents which so far have caused the most severe clotting are those which are formed by emulsifying a polymerizable, organic hydrophobic impregnating agent in the soft tacky stage by the use of a water-soluble soap, that is, an alkali metal, an amine, or an ammonium salt of a saturated or unsaturated fatty acid. Among these, the soaps most Widely used on a commercial scale are sodium stearate, sodium oleate, and sodium palmitate, the sodium soaps of cocoa nut fatty acids, sodium rosinate, the soaps of other rosin acids, and the sodium soap of disproportionated rosm.

Typical impregnants which are usually sufiiciently tacky to cause clotting in this manner are the polymers of butadiene and styrene, styrene and ethyl acrylate, butadicne and acrylonitrile, vinyl acetate and ethyl acrylate, and esters of acrylic acid and isobutylene. These include the commercially important synthetic rubbers known as GR-S, Buna-N, Buns-S, Hycar, GR-N- and Ameripol. Polymers which contain more than 50% butadiene or ethyl acrylate are particularly disadvantageous in this respect. In addition, clotting has been observed when emulsions comprising homopolymerized isobutylene in the tacky stage are employed, as well as the tacky asphalts and tars.

in general, the emulsions which are most frequently responsible for the formation of clots are those which, when dried on a glass plate at room temperature, yield I films which are tacky to the touch. However, clotting stabilize the emulsion to alum, the mixture comprising a non-ionic dispersing agent and an anionic dispersing agent selected from the group consisting of the alumstable sulfate and the alum-stable sulfonate dispersing agents. In the second step the thus stabilized emulsions or dISPCISlOHS are deflocculated and deposited on the catiomc resin bearing cellulosic fibers in the presence of ,ralfum, all as will be more particularly described hereina ter.

V In one embodiment of the invention the alum is added to the dispersion of impregnating agent subsequent to the addition of the stabilizing mixture, and the stabilized alum-containing emulsion is added to the cellulosic suspension previously treated with the hydrophilic cationic resin. In another embodiment the stabilizing mixture of dispersing agents is added to the dispersion of impregnating agent, the alum is added to the suspension of cellulose fibers bearing the hydrophilic cationic resin, and the stabilized emulsion is then added to the cellulosic fibrous suspension containing the alum.

I In the first embodiment it is important that the stabilizlng mixture of dispersing agents be added to the emulsion first, and that the alum be added only after the stabilizing agent has been uniformly distributed through the emulsion. In the second embodiment it is important that the alum be substantially uniformly distributed through the treated cellulosic suspension before the emulsioncontaining the stabilizing mixture is added. If these requirements are not met, unsatisfactory deposition of the resin or the formation of clots may be expected to occur.

The effect of the stabilizing mixture and of the alum on the emulsion and on the mechanism whereby the emulsified imprenating agent is deposited on the fibers, and the reason why clots do not form in the process of the present invention are not understood, and the invention should not be limited by any particular theory.

In addition to overcoming the problem of clotting, the

F process of the present invention has numerous distinct advantages. In the first place, the soap-containing emulsions used in the present invention are extraordinarily stable. Ordinarily, emulsions containing soap are readily flocculated by acid and electrolytes. The stabilized emulsions of the present invention, 'however, are acidinsensitive and fail to coagulate even when their pH is reduced to 2. Nevertheless, they display the unexpected property of flocculating in the presence of alum at that or higher pH values in the presence of the cationic resin bearing fibers, and of depositing their content of impregnating agent thereon in a uniform and most satisfactory manner. Since the pH of the cellulosic stocks upon addition of the cationic hydrophilic, resin typically ranges from 3 to 5, this means that it now becomes unnecessary to adjust the pH of the stock to about neutrality prior to the addition of dispersion or emulsion as was heretofore thought necessary. Furthermore, acidic stabilizing gums may be incorporated such as alginic acid, polyacrylic acid, and carboxymethyl cellulose. Moreover, the emulsions are extremely alkali resistant. As a result, they may be :added successfully when the stock has any pH up to' about 12.

It is a further advantage of the present invention that the use of the stabilizing mixture of dispersing agents and alum, as described, provides a means for retarding the about 6% of the weight of the fibers.

rate at which the emulsion flocculates and the particles of impregnant are deposited on the fibers. The importance of this is discussed as follows.

In the ordinary case, Where neither the stabilizing mixture nor alum is present, flocculation and deposition of the impregnant may take place practically instantaneously upon addition of the emulsion to the suspension of cellulosic fibers bearing the cationic, hydrophilic resin. One effect of this extremely rapid deposition is to cause a somewhat non-uniform distribution of the deposited impregnating agent throughout the stock, as the bulk of the impregnating agent is often deposited before .the emulsion or dispersion can be evenly distributed throughout the fibrous suspension.

When the stabilizing mixture is employed but no alum is present either in the emulsion or in the stock, deposition of the impregnating agent on the fibers is almost always incomplete. In a few instances, substantially complete deposition of the impregnant on the fibers has taken place under these conditions, but in those instances the time required for the complete deposition has been unduly long, making the process impractical for commercial application.

When, however, alum is present either in the emulsion or'in the stock, as described, deposition of the impregnating agent takes place not instantly, but expeditiously over a period of some minutes, without formation of clots and without deposition of flocs of the impregnant on the sides and bottom of the vessel. Thus the rate of deposition is retarded for a sufficient period of time to permit the dispersion or emulsion to be distributed in very uniform fashion throughout the stock While obviating the objectionable formation of clots.

More in detail, the process in its preferred embodiment is performed as follows. First a stock of papermakers cellulosic fibers is formed at any ordinary consistency, for example, 0.5% to 5%. To this is added a predetermined amount of a cellulose-substantive, cationic,'hydrophilic resin at least sufficient to cause deposition of the impregnating agent from the subsequently added emulsion. The stock is allowed to stand or age until adsorption of the resin by the fibers is substantially complete. Usually at least 15 minutes is necessary, and a much longer time may be allowed.

As cationic hydrophilic resin may be employed the cationic hydrophilic acid colloids formed by reacting melamine or melamine-urea with formaldehyde under acid conditions, as shown in U. S. Patents Wohnsiedler et' al. No.'2,345,543 and Wilson et al. No. 2,563,897; the cationic hydrophilic resins prepared by reacting poly- 'alkylenep'olyamines with epichlorohydrin according to copending Daniel et al. application Serial No. 695,292, filed September'6, 1946, now U. S. Patent No. 2,601,579; the resins formed by reacting ammonium hydroxide with epichlorohydrin according to Daniel et al. copending application Serial No. 277,742, filed March 20, 1952; and the more complex resins disclosed in Daniel et al. application Serial No. 794,116, now U. S. Patent No. 2,601,598. In general, any resin possessing the same cellulose-substantive, cationic and hydrophilic characteristics of the above resins may also be employed. At least about /4% of the cationic resin, based on the weight of the fibers, but not more than necessary to saturate the adsorptive capacity of the cellulosic fibers therefor, is then added to the stock. In practice, this maximum is The suspension is then aged until adsorption of the resin is substantially complete, that is, for at least about 15 minutes and preferably 34 hours. s

The emulsion selected for use is modified by first adding thereto a stabilizing mixture consisting of a nonionic dispersing agent and an alum-stable anionic dispersing agent of the sulfate or sulfonate type, the ratio of two dispersing agents to' each other being between about one to five parts by weight of the non-ionic agent to one part of the anionic agent. The intermediate ratio of about 2.5:1 is preferred.

The amount of the stabilizing mixture which must be added to the emulsion depends on many variables, chief among which are the type and amount of soap used in the preparation of the emulsion, the tackiness of impregnating agent in the emulsion, the effectiveness of the dispersing agents of which the stabilizing mixture is composed, and the strength of the positive charges on the fibers. As a result, no exact numerical ratio has been found for correlating the amount of stabilizing mixture necessary in each instance with the above-mentioned variables. It has been found, however, that a correct amount can readily be ascertained by adding to the emulsion at least sufficient of the stabilizing mixture to stabilize the emulsion to alum. According to this method, a small amount of the stabilizing mixture is added to an aliquot of the emulsion or dispersion diluted to about 20% solids with water, followed by the addition of of alum as a dilute, for example, 3% aqueous solution thereof, the percentage of alum so added being based on the weight of elastomer or impregnant in the emulsion or dispersion. If flocculation of the emulsion occurs, the test is repeated upon a fresh aliquot of the emulsion or dispersion using an increased amount of the stabilizing mixture. The end point of the test occurs when the emulsion remains stable in the presence of 5% alum, based on the weight of the elastomer or impregnant in the emulsion. If desired, there is then incorporated in the emulsion at least mol of aluminum sulfate per mol of the soap employed in emulsifying or dispersing the impregnating agent. The emulsion is then ready for use. Alternately, the alum may be added to the cellulosic stock after adsorption of the hydrophilic resin is substantially complete.

Ordinarily, commercial emulsions are supplied at a solids content of 30% to 60%. Since the process requires a uniform distribution of the emulsion in the cellulosic suspension, it is advantageous to dilute these emulsions to roughly 20%-10% solids content or lower with water. The emulsion is added to the stock of cellulosic fibers at any appropriate location as is customary and is distributed uniformly therethrough with the least amount of agitation possible.

The impregnated stock may be formed into useful products by any means known in the art. Preferably it will be shee't'ed as in thesame manner as ordinary paper-. making fibers. The water-laid sheets thus formed are then or RCOO(CH2CH20)nC2H4OH. In addition there may be employed the condensates formed by reacting ethylene oxide or propylene oxide with a mono or polycarboxylic acid' glycol or" polyglycol esters. Thus mannitol or sor- 1 bitol may be mono esterified with a fatty acid, and the product reacted with 6 to 50 mols of ethylene oxide. Moreover, the condensation products of aryl, alkaryl, cycloaliphatic and aryl-cycloaliphatic alcohols and thioalcohols with 6 to 50 mols of ethylene oxide or propylene oxide to form dispersing agents may likewise be used. Such agent may have the formula or RCHZS(CHZCH2 O)11CH2CH2OH. In addition, the polyethyleneglycol-substituted maleic esters of the formula HO(CH20)1LCH2OCH(COOR)CHZCOOR may be used.

condensed with Sodium alkylsulfobenzoate condensed with formaldehyde Purified sulfolignin Sodium alkyl phenylene sulfonate Sodium alkyl (ca. C11) sulfonate Sodium octyl sulfate Sodium aryl alkyl polyether sulfonate Sodium aryl alkyl ether sulfate Sodium alkylbenzene mono-sulfonates Sodium salt of N-oleyl-N-methyltaurine Sodium salt formaldehyde condensate of benzyl naphthalene sulfonic acid Sodium dodecyl phenyl poly (3) glycol ether sulfonate Sodium alkylanilinesulfonate Mixtures of the two or more nonionic dispersing agents and mixtures of two or more anionic dispersing agents of the above types may also be used.

In the specification and claims the word alum is used to designate papermakers alum, that is, aluminum sulfate tetradecylhydrate.

The following specific examples represent preferred embodiments of the invention, which has been disclosed above, and are not in limitation thereof. Parts are by weight unless otherwise stated.

Example 1 Bleached kraft pulp was beaten to a Green freeness of approximately 500 c. at 2.93% consistency. An aqueous dispersion of a melamine-formaldehyde colloid was prepared by dissolving l2 parts of spray-dried melamineformaldehyde condensate (1:3 molar ratio) in 88 parts of water at 20 C. containing 0.8 mol of HCl per mol of melamine equivalent in the condensate, and aging the dispersion over night. An amount of this colloidal dispersion, containing 4% of colloid based on the weight of the fibers was stirred into the stock. The stock was then adjusted to pH 4.5 and allowed to stand for one hour.

Test emulsions were prepared from commercial GR-S type VI latex, an aqueous emulsion of the oil-in-water type having a pH of 10.0 formed by emulsifying 60 parts of a 55% butadiene-45% styrene mixture with 40 parts of water in the presence of synthetic emulsifiers and rosin soaps, and stripping off unreacted monomer. The solids content of this emulsion was about 62%. When this latex was evaporated on a glass plate, a distinctly tacky film developed. One aliquot of the latex was diluted to 10% solids with water and used as the control emulsion. The remaining aliquots were diluted to 20% solids, treated with the additives shown in the table below, and then likewise diluted with water to 10% solids.

In tests 5, 6, and 7, where alum and one or two dispersing agents were added, the dispersing agents were first thoroughly mixed with the emulsion and the alum then added as a 3% aqueous solution. The amount of alum added in each instance was equivalent to 5% of alum on the weight of copolymer in the emulsion.

The several emulsions were then added with gentle stirring to the aliquots of stock at room temperature, and the stock observed for formation of clots and rate of deposition of the copolymer on the fibers in the stock. The amounts of emulsion added in each instance conshown in the table below. The stability of the emulsions in the presence of this alum was noted. The emulsions which remained stable were then further tested for stability by diluting 1 part of the emulsion with 100 parts of water. Results are shown in the table below. GR-S Emulsion Additives Extent of Test Stability on Dilution Name Type Percent 1 Clotting Latex Ppn.

1 Control..- Stable... Severe- Instantaneous and complete. 2 Alum 5 p 3 Note A.... Non-ionic.-- 5 Very slow and incomplete. 4 Note B Anionic 3 Incomplete.

Very slow and incomplete. 5 6 {Note A Non-ionic... 5 Slow but complete.

Note Anionic..." 5 Alum 5 7 Note A... Non-ionic. 5 .do do. Rapid and complete. Note 13..-. Anionic... 3 a

1 Based on the polymer content of the emulsion.

Note A. Condensation product of t-octylphenol with 10 mols of ethylene oxide. Note B. Sodium alkylnaphthyl sulfonate condensed with formaldehyde.

Tests 1 through 4 show that the emulsions which contained only one or two of the three additives employed in tests 5 and 6 resulted in premature flocculation of the emulsion, severe fiber clotting, or incomplete deposition of the copolymer on the fibers. Test 6 shows that no fiber clotting coupled with good precipitation of the copolymer took place when the weight ratio of the components of the stabilizing mixture was at the lowest preferred ratio of 1:1.

In test 7, when the weight ratio of the components was Well within the referred range, precipitation was not instantaneous, but was rapid and complete. In this example the speed of precipitation was slower than in the case of test 1, resulting in more even distribution of the impregnant throughout the cellulosic fiber suspension.

type II latex is a water emulsion having a pH of about 9.0 and a solids content of 26%-28% containing a 76.5% butadiene-23.5% styrene copolymer, prepared by the use of a sodium soap of a fatty acid as emulsifying agent. GR-S type III latex is a water emulsion having a pH of about 10.5 and a solids content of 37%-39% containing a 52% butadiene-48% styrene copolymer, prepared by the use of a rosin soap as emulsifying agent. The polyethyl acrylate emulsion was prepared by adding over 3 hours parts of ethyl acrylate to parts of agitated water at pH 8.5 at about 82 C. The water contained 5% sodium ol'eate as the emulsifying agent and 0.25% ammonium persulfate as catalyst on the weight of ethyl acrylate. The reaction was stopped 15 minutes after all the ethyl acrylate had been entered, and unreacted monomer was stripped off.

Percent Stability on Stabiliz- Percent Dilutlonwith Test Latex in g Mix- Alum Stability on Addition of Alum 100 Parts of ture Added 1 7 Water Added 1 1. GR-S type II 6. Coagulated do 7. Floceulated; s1. coagulation 8. Slight flocculation 9. do Flocculated. l0. Stable.

1 Based on the weight 01 elastomer in the emulsion.

Example 2 A series of concentrated commercial emulsions .oi elastomers, prepared by the use of a soap as emulsifying agent, all of which gave sticky films when evaporated on a glass plate, were diluted with water to about 20% elastomer content. To each of these was added. the amount of a stabilizing mixture shown in the table below. The stabilizing mixture consisted of'70 parts of the nonionic dispersing agent formed by reaction of t-octylphenol with 10 mols of ethylene oxide, and 30 parts of the anionic dispersing agent known as Accocel 740 formed by condensing sodium alkyl naphthalene sulfonate with formaldehyde. Aliquots of these emulsions were taken,

and to each was added alum as a 5% aqueous solution thereof, the amount of alum added in each instance being do GRHS type III.

Unstable. Stable.

' r sees w-s pt This table shows that the amount of stabilizing. agent needed to stabilize the respective emulsions to 5% alum necessary in the case of GR-S type; VI and polyethyl acrylate' respectively. This table further indicates that when just 'sufficient of the stabilizing mixture has been "added to'stabilize GR-Stype III latex to 2% of alum, the

emulsion is thereby rendered stable to 5% of alum.

j "Example 3' stabilized alum-containing emulsions of tests 5, 10, 14, 17, and 24 of Example 3 diluted to 1% elastomer content with Water were divided into two portions. One set of emulsions was acidified to pH 2 with dilute hydroehloric acid. The second set of emulsions was made alkaline to pH 12 with dilute sodium hydroxide. All emulsions remained stable under these conditions.

Example 4 Unbleached northern kraft pulp was beaten, treated wi h melamine-formaldehyde colloid, and aged, as de- 10 Example A commercial GR-S type III latex, reduced to 15% solids with water, was blended with of the stabilizing mixture of Example 4, and 3% alum added as a 5% aqueous solution thereof. The quantities of stabilizing mixture and alum added were based on the weight of the latex solids. A stock of melamine resin treated fibers was prepared according to the procedure of Example 1 scribed in Example 1, the proportions of colloid added, 10 using unbeaten Stem 32 bleached kraft pulp but the PH however, being as shown in the table below, and the step of adjusting the pH of the treated stock was omitted.

Emulsions of commercial elastomeric impregnating agents, having the composition set forth in Examples 1 of the stock was not adjusted from the value of 3.2 which it reached after incorporation of the melamine colloid. The emulsion was then reduced to 10% solids with water and. added to the stock with gentle stirring, the amount a and) 2 were first diluted to 20% elastomer content, and of elastomer m the emulsion bemg equal to of the then stabilized to alum by the addition of a stabilizing mixture formed by mixing 70 parts of the condensation product of t-octylphenol with 10 mols of ethylene oxide and 30 parts of the condensation product of sodium alkyl naphthalene sulfonate with formaldehyde. solution containing 5% of alum as Al2(SO)3.l8H2O based on the weight of the elastomer in the emulsions, was then added. The amounts of stabilizing mixture and alum added in each instance are shown in the table An aqueous weight of the fibers. Deposition of the impregnating agent was substantially complete in 15 minutes. No clot formation occurred, and the fibers were sheeted on a handsheet machine of the type of the Noble Wood machine without adhesion to the wire or felt. The paper thus obtained was free from the effects of clots.

I claim:

1. In a method for making an impregnated cellulos'ic product wherein an aqueous suspension of fibrous cellub 610w. losic material is prepared, a hydrophilic cationic resin is The resulting emulsions were then gently stirred into aliquots of the colloid-treated cellulosic stock. The pH of the stock was determined as soon as deposition of the impregnating agents had substantially ceased. Handsheets were prepared on a Nash handsheet machine.

vulcanizing agent based on the weight of elastomer was added to the stock suspension after the elastomer had been deposited on the fibers. The vulcanizing agent consisted of 12.5% 0RD sulfur, 12.5% butyl zimate, 18.75% ZnO, 6.25% of the antioxidant (2,2-methylene added to said suspension, said suspension is aged until adsorption of said resin by said fibers is substantially complete, an aqueous dispersion of a water-insoluble hydrophobic organic impregnating agent in a tacky stage containing a water-soluble soap as principal dispersing agent is added to said suspension, the weight of impregnating agent in said dispersion being 25% to 100% of the weight of said fibrous material, and particles of said impregnating agent are deposited from said dispersion uniformly on said fibers by the action of said adsorbed cationic resin: the steps of adding to said dispersion of said impregnating agent sufficient of a stabilizing mixture containing about 55% to 80% by weight of a non-ionic dispersing agent and 20% to 45% by weight bis 4 methyl 6 t butylphenol) and 50% water. of an anionic dispersing agent selected from the group Precipitation of the emulsified impregnating agent in each instance was substantially complete, and no evidence: of the formation of clots was observed in the stock.

The handsheets were excellent in appearance and texture, being soft, pliable and completely homogeneous. The impregnating agents were completely deposited on the fibers in uniform condition and no balls or fiocs were. observed in the sheets.

consisting of the alum-stable sulfonate and the alumstable sulfate dispersing agents to render said emulsion stable in the presence of about 5% of alum, based on the weight of impregnant in said dispersion, and then depositing particles of said impregnating agent on said fibers in the presence of at least about mol of alum based on the mols of the soap in said dispersion.

2. A method according to claim 1 wherein the alum is Mela- Emulsion Added 2 Tensile Percent mine Stabil Percent Drain. Strength 5 Elong. Test Colloid Mixture Alum Emul. Fiber Time Basis Burst Added, Added, Added; Ppn. Clotting (See) Wt. 4 Percent 1 Type Per- Percent 3 Dry Wet Dry Wet cent 1 0. 0 None 7 198 77. 6 3. 2 5. 2 3. 5 205 0. 5 None 8 202 83. 4 8. 8 5. 2 4. 4 233 1.0 None 8.0 205 101.0 17. 4 6.0 6.0 272 1. 5 None 8 205 109. 4 23. 8 6. 5 7. 0 238 3.0 None 8 205 115.2 36. 2 7.1 8. 4 271 5.0 do None 8. 5 203 108. 8 37. 6 7.1 8. 7 274 0.5 GRS Type II 5 10. 0 5. 0 Comp. None 8 206. 5 62. 4 8. 4 4. 8 4. 5 173 1. 0 do 10 10.0 5.0 Comp. None 8 220. 5 58. 4 13. 6 5. 7 6.8 165 0. 5 GRS Type III 5 10.0 5.0 Comp. None 8. 5 207 72. 6 9. 4 3. 4 5.1 189 1. 0 -do 10 10.0 5. 0 Comp. None 8 216 69. 6 14. 6 6.1 6.8 195 5.0 10.0 5.0 Comp. None 9 289 69. 0 18.4 9. 4 9. 6 222 0. 5 5 5. 0 5.0 Comp. None 8 206. 5 74. 6 9.2 5. 2 4. 6 188 l. 0 1O 5. 0 5. 0 Comp. None 8 211 67. 4 12. 2 6. 1 6. 4 203 1. 5 25 5. 0 5. 0 Comp. None 10 235 76. 2 16. 2 6. 8 7. 5 205 3. 0 50 5.0 5.0 Comp. None 20 293 70.0 19. 8 9.0 9. 5 227 3. 0 50 6. 0 6. 0 Comp. None 13 300 67. 8 21. 8 7. 7 10.0 221 5. 0 5. 0 5. 0 Comp. None 28 379 69. 0 24.0 9. 4 11. 7 227 0. 5 5 7. 0 5. 0 Comp None 10 209 80. 0 10.0 5. 6 5. 0 225 1. 0 10 7. 0 5. 0 Comp. None 10 222 74. 6 12. 6 6. 0 6. 6 236 1. 5 25 7.0 5.0 Comp None 10 250 77.0 16.0 6. 8 10. 7 251 3.0 50 7.0 5.0 Comp. None 11. 5 286 69. 8 20.0 26. 2 17.0 260 5. 0 100 7. 0 5.0 Comp. None 7 384 40.0 14. 2 22. 9 34. 9 226 1 Based on the weight of the fibers.

2 All emulsions were prepared by the use of a soap as dlspersmg agent. 3 Based on the weight of elastomer in the emulsion.

4 Lb. per ream 25" x 40]500.

5 Lb. per inch.

6 Lb.lin. by Mullen test.

7 Polyethyl acrylate.

11 mixed with the stabilized dispersion of the impregnating agent, and the mixture is added to the aged suspension of fibrous cellulosic material.

3. A method according to claim 1 wherein the alum is added to the aged suspension of fibrous cellulosic material and the stabilized dispersion of impregnating agent is added to the fibrous suspension containing said alum.

4. A method according to claim 1 wherein the stabilizing mixture contains about 70% by weight of the nonionic dispersing agent and about 30% by weight of the anionic dispersing agent.

5. A method according to claim 4 wherein the anionic dispersing agent is the condensation product of a sodium naphthylsulfonate with formaldehyde.

6. A method according to claim 1 wherein the impregnating agent is a copolymer containing more than 50% butadiene.

7. A method according to claim 1 wherein the impregnating agent is a copolymer containing more than 50% ethyl acrylate.

8. A method according to claim 1 wherein the soap is a soap of a rosin acid.

9. A method according to claim 1 wherein the cationic resin is a melamine-formaldehyde acid colloid. V

10. A method according toclaim 1 wherein the pH of the suspension of fibrous cellulosic material on addition of the stabilized dispersion of impregnating agent is 3.0 to 5.0. i

11. A method according to claim 1 wherein the anionic dispersing agent is a sulfate dispersing agent.

12. A method according to claim 1 wherein the anionic dispersing agent is a sulfonate dispersingagent.

References Cited in the file of this patent UNITED STATES PATENTS Mead Dec. 8, 1953

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U.S. Classification162/166, 525/163, 162/169, 525/164, 516/41, 162/168.7, 516/DIG.400, 162/182, 516/58, 260/DIG.220, 162/168.1
International ClassificationD21H17/66, D21H23/76, D21H17/09, D21H17/53, D21H17/14, D21H17/06
Cooperative ClassificationY10S260/22, D21H17/14, D21H17/09, D21H17/66, D21H23/765, D21H17/53, D21H17/06, Y10S516/04
European ClassificationD21H17/14, D21H17/09, D21H17/66, D21H23/76B, D21H17/53, D21H17/06