US 3483077 A
Description (OCR text may contain errors)
United States Patent O F Int. Cl. D21h 3/68, 3/36 US. Cl. 162158 6 Claims ABSTRACT OF THE DISCLOSURE In the forming of paper containing water-insoluble additaments the retention of the additaments is improved by adding a cationic thermosetting resin to an aqueous slurry of papermaking fibers and additaments. The cationic resin and additaments may be added to the slurry of fibers in any order with the resin added in amounts from 0.01% to less than 0.1% by weight, based on the dry weight of fibers. The cationic resin is a water-soluble reaction product of epichlorohydrin and a polyamide derived from a polyalkylene polyamine and a C C saturated aliphatic dicarboxylic acid. The additaments may be pigments, clays, waxes or ketene dimers.
This application is a continuation of application Ser. No. 323,152, filed Nov. 12, 1963, now abandoned, which is a continuation-in-part of application Ser. No. 125,928, filed July 24, 1961, now abandoned, which, in turn, is a continuation-in-part of application Ser. No. 694,930, filed Nov. 7, 1957, now abandoned.
The present invention relates to the manufacture of paper and similar products from fibrous cellulosic material and, more particularly, to improvements in the incorporation of certain water-insoluble additives into such products during manufacture thereof.
It is known that many water-insoluble additives can be highly effective for improving various characteristics of paper when they are properly distributed within the fibers forming the sheet. However, when anionic or nonionic aqueous dispersions or emulsions of such materials are added to a paper pulp slurry as in the beater, stock chest or the like of a papermaking system, there is substantially no tendecy for the fibers to adsorb such materials and, hence, they are largely lost in the White Water during the sheeting operation. As a result, it is common practice to add alum to the system to serve as a precipitating agent and/ or retention aid. By this procedure, the materials are precipitated and the resulting flocs are entangled or mixed with the fibrous paper stock and carried into the finished paper.
While this procedure works out all right in some cases, it is subject to disadvantages in others. Thus, in the preparation of paper products where an acidic papermaking system is undesirable or where aluminum and similar polyvalent cations must be kept out of the system, the use of alum is disadvantageous and, in most cases, unsatisfactory.
A principal object of the present invention is the provision of an improved process for the incorporation of certain water-insoluble additives in paper and similar 3,483,077 Patented Dec. 9, 1969 products whereby the above disadvantages are overcome or at least substantially minimized.
Another object of the invention is the provision of a process of the indicated type in which a novel retention aid is employed in conjunction with certain water-insoluble additives to obtain improvements both in retention of such additives and in the characteristics of the resulting products.
In accordance with the invention, the above and other objects are attained by incorporating in an aqueous suspension of papermaking fibers containing, or to which is substantially added, a material selected from the group consisting of pigments, clays, waxes and ketene dimers, from about 0.01% to less than about 0.1% by weight (solids basis), based on the dry weight of fibers, of a cationic thermosetting resin, which is a Water-soluble polymeric reaction product of epichlorohydrin and a polyamide derived from a polyalkylene polyamine and a C -C saturated aliphatic dicarboxylic acid. It has been found that these cationic thermosetting resins substantially improve the absorption and retention of these materials by the fibers. Moreover, in the relatively small amounts required to obtain these improved results, there is no appreciable increase in wet strength of the treated paper. This is an advantage Where wet strength is not desired and, in addition, facilitates the reworking of broke from such treated paper.
In carrying out the process of the invention, the waterinsoluble material, preferably in the form of an aqueous dispersion or emulsion, and the cationic polyamideepichlorohydrin resin, preferably in aqueous solution, are incorporated with an aqueous suspension of paper fibers, as in the beater, fan pump or the like of a papermaking system, and the fibers then formed into sheets or webs and dried in the conventional manner. Optimum results are obtained if the pH of the system is maintained Within the range from about 6 to about 9. However, substantial improvements are obtained if the pH is maintained within the broader range of from about 4 to about 10.
At the relatively low level of resin addition herein described and claimed, optimum results are obtained in the case of some water-insoluble materials when they are added and mixed thoroughly with the paper pulp before the cationic resin is added. In addition, in such cases, optimum results are obtained if sheet formation takes place about 0.5 minutes to about 25 minutes after addition of the resin, though good results can be obtained when the cationic resin is added 2 to 15 seconds before sheet formation, especially if the temperature of the pulp slurry is raised from about 25 C. to about 45 C. These conditions are satisfied in conventional papermaking systems when the water-insoluble material is added batchwise to the beater or continuously or batchwise at some convenient point well before the addition point for the cationic resin. The cationic resin can be added at any convenient point after refining up to the headbox and after the water-insoluble material is well mixed with the pulp.
In the case of other water-insoluble materials, e.g., strongly anionic materials such as Paracol 404R, an anionic wax emulsion manufactured and sold by Hercules Incorporated, optimum results are obtained by premixing the wax emulsion and the cationic resin and then adding the mixture to the paper pulp.
The water-insoluble materials may be added dry or as aqueous dispersions or emulsions and the cationic resin as an aqueous solution. Any convenient concentrations can be utilized. For most machine operation, this will be in the range of 0.1 to 10% for each material.
The amount of water-insoluble additive to be added will depend on a number of factors such as the partioular material used, the results desired and so on. For example, in the case of a sizing material such as a ketene dimer, quite satisfactory results are obtained when the addition is such that from about 0.05% to about 2% of the ketene dimer, based on the dry weight of pulp, is incorporated in the paper. Other materials may have to be incorporated in larger amounts to obtain a desired result. In general, however, it may be stated that from about 0.05% to about 100% of such material, based on the dry weight of fiber, will be adequate in most cases.
The amount of cationic resin to be added will likewise vary with many factors such as the particular resin used,
the results desired and so on. In general, it has been found that amounts less than about 0.1% by weight, based on the dry weight of paper, will give satisfactory retention without appreciable increase in wet strength. Amounts as low as 0.01% give some improvement, though it will usually be desirable to use somewhat more than this.
The cationic thermosetting polyamide-epichlorohydrin resins contemplated for use herein comprise a water-soluble polymeric reaction product of epichlorohydrin and a polyamide derived from a polyalkylene polyamine and a C C saturated aliphatic dicarboxylic acid. It has been found that resins of this type are uniquely effective for the purposes of the present invention.
In the preparation of these cationic thermosetting resins, the dicarboxylic acid is first reacted with the polyalkylene polyamine under conditions such as to produce a water-soluble polyamide containing the recurring groups where n and x are each 2 or more and R is the divalent hydrocarbon radical of the dicarboxylic acid. This watersoluble polyamide is then reacted with epichlorohydrin to form the water-soluble cationic thermosetting resin.
The dicarboxylic acids contemplated for use in preparing these resins are the C -C saturated aliphatic dicarboxylic acids such as succinic, glutaric, adipic and the like. The saturated dicarboxylic acids having from 4 to 8 carbon atoms in the molecule are preferred. Blends of two or more of the saturated dicarboxylic acids may also be used.
A variety of polyalkylene polyamines including polyethylene polyamines, polypropylene polyamines, polybutylene polyamines and so on may be employed of which the polyethylene polyamines represent an economically preferred class. More specifically, the polyalkylene poly amines contemplated for use may be represented as polyamines in which the nitrogen atoms are linked together by groups of the formula C H where n is a small integer greater than unity and the number of such groups in the molecule ranges from two up to about eight. The nitrogen atoms may be attached to adjacent carbon atoms in the group C H or to carbon atoms further part, but not to the same carbon atom. This invention contemplates not only the use of such polyamines as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenetriamine, and the like, which can be obtained in reasonably pure form, but also mixtures and various crude polyamine materials. For example, the mixture of polyethylene polyamines obtained by the reaction of ammonia and ethylene dichloride, refined only to the extent of removal of chlorides, water, excess ammonia and ethylenediamine, is a very satisfactory starting material. The term polyalkylene polyamine employed in the claims, therefore, refers to and includes any of the polyalkylene polyamines referred to above or to a mixture of such polyalkylene polyamines.
It is desirable, in some cases, to increase the spacing of secondary amino groups on the polyamide molecule 4 in order to change the reactivity of the polyamide-epichlorohydrin complex. This can be accomplished by substituting a diamine such as ethylenediamine, propylenediamine, hexamethylenediamine and the like for a portion of the polyalkylene polyamine. For this purpose, up to about of the polyakylene polyamine may be replaced by a molecularly equivalent amount of the diamine. Usually, a replacement of about 50% or less will serve the purpose. 7
The temperatures employed for carrying out the reaction between the dicarboxylic acid and the polyalkylene polyamine may vary from about C. to about 250 C. or higher at atmospheric pressure. For most purposes, however, temperatures between about" C. and 210" C. have been found satisfactory and are preferred. Where reduced pressures are employed, somewhat lower 'temperatures may be utilized. The time of reaction depends on the temperatures and pressures utilized and will ordinarily vary from about /2 to 2 hours, although shorter or longer reaction times may be utilized depending on reaction conditions. In any event, the reaction is desirably continued to substantial completion for best results.
In carrying out the reaction, it is preferred to use an amount of dicarboxylic acid sufficient to react substantially completely with the primary amine groups of the polyalkylene polyamine but insufiicient to react with the secondary amine groups to any substantial extent. Thiswill usually require a mole ratio of polyalkylene polyamine to dicarboxylic acid of from about 0.9:1 to about 1.221. However, mole ratios of from about 0.8:1 to about 1.4:1 may be used with quite satisfactory results. Mole ratios outside of these ranges are generally unsatisfactory. Thus, mole ratios below about 0.821 result in a gelled product or one having a pronounced tendency to gel while mole ratios above 1.411 result in low molecular weight polyamides. Such products, when reacted with epichlorohydrin, do not produce resins having the desired efficiency for use herein.
In converting the polyamide, formed as above described, to a cationic thermosetting resin, it is reacted with epichlorohydrin at a temperature from about 45 C. to about 100 C. and preferably between about 45 C. and 70 C. until the viscosity of a 20% solids solution at 25 C. has reached about C or higher on the Gardner- Holdt scale. This reaction is preferably carried out in aqueous solution to moderate the reaction. pH adjustment is usually not necessary. However, since the pH decreases during the polymerization phase of the reaction, it may be desirable, in some cases, to add alkali to combine with at least some of the acid formed.
When the desired viscosity is reached, sufficient water is then added to adjust the solids content of the resin solution to the desired amount, i.e., about 10% more or less, the product cooled to about 25 C. and then stabil ized by adding sufficient acid to reduce the pH at least to about 6 and preferably to about 5. Any suitable acid such as hydrochloric, sulfuric, nitric, formic, phosphoric and acetic acid may be used to stabilize the product. However, hydrochloric acid is preferred.
In the polyamide-epichlorohydrin reaction, it is preferred to use sufficient epichlorohydrin to convert all sec ondary amine groups to tertiary amine groups. However, more or less may be added to moderate or increase reaction rates. In general, satisfactory results may be obtained utilizing from about 0.5 mole to about 1.8 moles of epichlorohydrin for each secondary amine group of the polyamide. It is preferred to utilize from about 1.0 mole to about 1.5 moles for each secondary amine group of the polyamide.
The process of the invention is particularly useful for improving the retention by paper fibers and/or in paper of ketene dimers. These, in some cases, may be dispersed directly in the aqueous pulp suspension. They also may be utilized in the form of aqueous emulsions such as those disclosed in US. 2,627,477 to William F. Downey or in any other suitable manner such as in the form of aqueous dispersions of ketene dimer compositions comprising ketene dimer supported on particles of a finely divided inorganic material such as clay, silica, and the EXAMPLES 1-4 A ketene dimer emulsion containing 6.0% by weight, based on the weight of emulsion, of an alkylketene dimer prepared from a mixture of palmitic and stearic acids and 3.0% by weight based on the weight of emulsion of cationic starch (Cato 8) as emulsifier was prepared as follows. The starch was cooked at 90 C. for a period of 15 minutes. The temperature was then adjusted to 160 F. and the pH to 6.0 following which the ketene dimer was added and dispersed with high speed mixing. This preblend was then processed in a piston-type homogenizer and immediately cooled to 80-90 F.
A polyamide-epichlorohydrin resin, of the type hereinabove described, was prepared as follows. To 319 g. triethylenetetramine and 100 g. water heated to 123 C. was added 290 g. adipic acid in small portions. When the addition of acid was complete, the mixture was heated to about 190 C. and held at 190-205 C. for about 105 minutes. At the end of this time, the heat was removed and the pressure over the resin reduced as low as possible without excessive foaming for a period of ten minutes. Then 500 ml. water was added to give a fluid solution with 49.8% total solids. Sixty-three grams of this soltuion was diluted with 225 ml. water and heated to 50 C. Heat was removed and the addition of 22 g. epichlorohydrin was started and maintained at a rate which held the temperature of the solution at about 55 C. The addition required three minutes. The mixture was warmed to about 60 C. and held at about 6066 C. for 70 mintues during which time the viscosity of the solution rose to E. At this point, 225 ml. water was added and the pH adjusted to 5 with hydrochloric acid. Final viscosity was about C and total solids was 89.5%.
A sample of Weyerhaeuser bleached sulfite pulp was beaten to a Schopper-Riegler freeness of 750 cc. at a consistency of 2.5% in pH 7.5 water containing 100 ppm. hardness and 50 pm. alkalinity in a Noble and Wood cycle beater. Fifty grams of this pulp (dry basis) was placed in the proportioner of a Noble and Wood handsheet machine and diluted to 0.25%. From the proportioner, portions containing 2.5 g. (dry basis) of pulp were withdrawn and placed in a 2-liter beaker and agitated. Further addition of chemicals was made here. Sufficient dilute ketene dimer emulsion was then added so that 0.0025 g. of ketene dimer was present (0.1% based on dry fibers). The mixture was stirred about ten seconds and a dilute solution of the cationic polyamideepichlorohydrin resin was added. The amount of resin added was 0.00125 g. (0.05% based on dry fibers). The mixture was stirred an additional ten seconds. The pulp was then formed into 8 x 8 inch square sheets which were dried on a rotary drum drier to a moisture content of 5% Sizing in the sheets was measured with the Hercules photometer using Standard Feather Ink. The results re corded were average times in seconds (5 sheets tested in each set) to 85% of original reflectance.
Similar tests were run in which the amounts of ketene dimer were varied. Comparative tests were also run utilizing a cationic starch as retention aid in place of the cationic polyamide-epichlorohydrin resin. Results are listed in Table I below.
TABLE I Percent retention aid Photometer Percent Polyamide, sizing sec.
Ex ketene Cationic ephiehlorostandard N 0. dimer starch hydrin resin feather ink The Cato 8 starch utilized in Examples 1-4 is a cationic starch (modified corn starch having a nitrogen content of about 0.25%) produced and sold by National Starch and Chemical Company.
EXAMPLES 5-8 are set forth in Table II below.
TABLE II Percent retention aid Photometer Percent Polyamide, sizing sec. Ex. ketene Cationic ephichlorostandard N o. dimer starch hydrin resin feather ink EXAMPLES 9 and 10 Tacoma bleached kraft pulp was beaten at 2.5% consistency to 750 cc. Schopper-Riegler freeness in a Valley beater. The pulp was diluted to 0.5% consistency with distilled water and the pH adjusted to 6.5 with 5% sulfuric acid.
Various fillers were added to portions of the pulp as 10% slurries and in amounts such as to provide 10% by weight, based on the dry weight of pulp, of the filler. A 0.005% solution of a polyamide-epichlorohydrin resin, prepared as in Examples l-4, was then added in amounts as to provide 0.05% by weight, based on the dry weight of pulp, of resin solids. Handsheets were formed using a 40-mesh wire on laboratory handsheet apparatus. The sheets were pressed between felts and dried 60 seconds on a steam heated drum drier at 240 F. Sheets were similarly made except that no resin was used. The percent retention was calculated from ash basis weight) kaolin clay was beaten at 2.5% consistency to 750 cc. Schopper-Riegler freeness in the cycle beater. The pulp slurry was adjusted to pH 6.5 with sulfuric acid and diluted to a consistency of 0.5% in a Noble and Wood proportioner. To a 500 ml. aliquot of this slurry a 0.1% or less solution of a polyamideepichlorohydrin resin, prepared as in Examples 1-4, was added in an amount necessary to give the required addon. The pulp was then formed into 8 x 8 inch square handsheets on a Noble and Wood handsheet machine at a basis weight of 40 lb./ream. The sheets were then dried on a rotary drum drier. The filler retention was determined from the ash content of the sheets. Sheets were similarly prepared and tested utilizing TiO instead of clay. Results are set forth in Table IV below in com- 7 8 parison with results obtained on sheets similarly presaid water-insoluble additive from about 0.01 to less than pared but without the polya-midehyepichlorohydrin resin. about 0.1% by weight, basedon the dry weight of fibers,
TABLE IV I 1 Percent retention 12% clay 12% TiOz Ex. N0. Retention aid 0.025 0.050 0.090 0.025 0.050 0.000.
11 None 8 1. 11 12 Polyamide-epichlorohydrin 14 21 20 35 43 I'BSlIl.
EXAMPLE 13 of a cationic thermosetting resin obtained by reacting a polyalkylene polyamine having two primary amine groups and at least one secondary amine group with a 15 C C saturated aliphatic"dicarboxylic acid in a 'mole tio of from about 0.8 to about 1,4 of the former to based on dry pulp and the amount of polyamrde-epichlo- Ta a rohydrin resin increased so as to provide 0.09% resin ggg fi g gggf fii fil zigd tli ri fie ih i z fonds by ba-Sed on the welihtfof dry i 8 g polyamide with epichl'orolfiydriil in a mole ratio of epiute wax emu sion was prepare rom Paraco a commercial product of Hercules Incorporated containgfi gg g g jgffi g 3 3 3 3 2 35 35532; '45 l' i iiil a x T l i e i z iiig b ti ine by il e of l lii fggzig g gi zg of said cat1on1c thermosetting res1n mcorporated 1n the conjunction with the cationic polyamide-epichlorohyd-rin gigg i zig i g g i g g g i 2 2 :3 ff g jgi zgz resm was substantially better than that obtained with the of i Water igsgluble additive retaingd by the Paper wax emulsion alone.
It will thus be apparent that the present invention filprocess ggii to 61.2mm ltwherem wateran of "Jazz; access: an: 0 war r'- certain water-insoluble addItIVCS lnto paper. Improve- 1 e e ments are obtained not only in increased retention of such :3 6 papa a 1 2;? 1S 5 1 h th t additives in Pap r but also in the rate at which water d g ggg iifg g Z iy l f Wa drams from the p H1? Slurry thus permlmng fast-er opera- 5 A rocess accordin to claim 1 wherein the watertion of paper machines. Moreover, the flocculatmg effect g as well as the improved retention improves the efiiicency e g s i z the roduct re fired of the white water systems resulting in clearer plant- 5 p 1 th p P p water eflluent and decreased solids losses. And finally, m accor ance ePrceS0 6 am these improvements are obtainable without acidifying the system or adding a polyvalent cation to the system,
The method of Example was followed except that a dilute wax emulsion was substituted for the ketene dimer emulsion in an amount such as to give 2.0% wax solids References Cited as would be required by the use of alum. UNITED STATES PATENTS What I claim and desire to protect by Letters Patent 40 2,601,597 6/1952 D ni l t a1, 162 164 is: 2,926,116 2/1960v Keim 162-164 1. In a process of making paper wherein a water- 2,969,302 1/1961 Green 162-164 insoluble paper additive selected from the group 0011- 3,049,469 8/1962 Davison 162-164 sisting of pigments, clays, waxes and alkylketene dimers is added to an aqueous suspension of papermaking fibers S. LEON BASHORE, Primary Examiner and the thus-treated fibers formed into a sheet, the im- U.S. C1.X.R. provement which comprises incorporating 1n said aqueous suspension of papermaking fibers in conjunction with 162-164, 183