US3519477A - Sizing cellulosic and acrylic staple fiber yarns with acrylonitrile/acrylic acid copolymer - Google Patents

Description

United States Patent 3,519,477 SIZING CELLULOSIC AND ACRYLIC STAPLE FIBER YARNS WITH ACRYLONITRILE/ ACRYLIC ACID COPOLYMER Hans Wolf, Ludwigshafen (Rhine), Herbert Spoor, Mutterstadt, Pfalz, and Wilhelm Ruemens and Heinz Pohlemann, Limburgerhof, Pfalz, Germany, assignors to Badische Anilin- & Soda-Fabrik Aktiengesellschaft, Ludwigshafen (Rhine), Germany No Drawing. Filed Jan. 31, 1967, Ser. No. 612,811 Claims priority, application Germany, Feb. 1, 1966, 1,594,905 Int. Cl. D02g 3/40; B32b 27/08, 27/12 US. Cl. 117-1395 8 Claims ABSTRACT OF THE DISCLOSURE Sizing materials for stable yarns consisting of, or containing, a water-soluble polymer which contains copolymerized units of (a) acrylonitrile and (b) acrylic I acid and its sodium or ammonium salt in the molar ratio of (a):(b)=l:l.5 to 1:7.

In the textile industry it is customary to treat yarns, especially warp yarns containing cotton or staple yarns containing other cellusoic fibers, with hot, that is, almost boiling, aqueous preparations of corn (maize) or potato starch prior to weaving. This pretreatment of the yarns, known in the trade as sizing, serves to secure cohesion of the spun fibers and to improve their mechanical strength so that they can stand up better to the stresses arising during the weaving process than they would in the raw and untreated state. In addition to natural vegetable starches, chemically modified starch products are employed for sizing cotton, these being easier to remove than normal starches and producing liquors of comparatively low viscosity. Lubricants, such as tallow, are frequently added to sizing liquors containing mainly starches. The fatty substance is added to improve the slip of the threads and to prevent them becoming too brittle. Usually, the sizing agent has to be removed from the woven material prior to further treatment, and this is achieved to a more or less satisfactory extent only by subjecting it to the action of enzymes for several hours.

In some cases, cotton or other cellusoic yarns are sized with substances that have been produced by the chemical modification of cellulose. Such substances include cellulose ethers, for example carboxymethylcellulose or methylcellulose. These are commonly marketed in the form of powders which can be made up as collodial aqueous solutions only by prolonged standing in water, by vigorous stirring or kneading, or by heating. In general, their solutions are not homogeneous, but turbid and comparatively highly viscous. Frequently, the powders, owing on the chemical modification of the cellulose, contain large quantites of common salt. It is well known, however, that common salt is the sizing liquor readily causes corrosion of the weaving equipment; Even carboxymethylcellulose type products usually have to be applied to the yarns from a hot liquor, and this not only requires a considerable amount of steam, but also impairs the yarn to some extent, for instance, by causing a reduction in extensibility. Sizing with cellulose ethers produces only comparatively Weak sizing efiects on cellulosic yarns, so that improvement in the mechanical propreties of the yarn is only slight, and the effect of such sizes is to produce a yarn that is too soft.

Attempts have already been made to employ synthetic polymers as sizing agents for staple yarns of cellulosic fibers or acrylic fibers, or yarns containing these. Thusv 3,519,477 Patented July 7, 1970 in US. Pat. 2,819,189 it is proposed to size continuous filament of staple yarns of a great variety of types by employing copolymers which contain carboxyl and nitrile groups in a molar ratio of 0.3:1 to 0.75:1 either free or combined with sodium potassium or ammonium in a 5 percent aqueous solution at 60 C. at a pH value of between 5 and 9 and with a viscosity of between 5 and 200 cp. However these synthetic sizing agents still leave much to be desired. The sizing efiects attainable are not always adequate, and it is expressly emphasized in US. Pat. 2,819,189 that it is important to remain within the molar ratios indicated in order to obtain good results. This is denoted as being particularly important because the sizing action of the polymers falls olf markedly even near the limits of the molar ratios defined in the specification. A further significant disadvantage of these essentially neutral polymers is the fact that they are only partially soluble in water. Some of these polymers, particularly those with a high nitrile content, are only collodially soluble, or even entirely insoluble, in water and these are therefore supplied as aqueous dispersions. Such dispersions are sometimes so unstable that they often coagulate even as they are manufactured, so that they become unusable. Sizing agents of this type, that are not completely soluble in Water, are not readily scoured off the fabric.

It is an object of the present invention to provide sizing agents for staple yarns which consist of or contain at least 30 percent by weight of cellulose and/or acrylic fibers and which are more effective than the sizing agents hitherto employed for such yarns.

Another object of the invention is to provide sizing agents for the type of yarns mentioned which are particularly readily soluble in Water.

Still another object of the invention is to provide sizing agents for the type of fibers mentioned which are chemically and mechanically very stable in the treatment liquors.

A further object of this invention is to provide sizing agents for the type of yarns mentioned which can be removed from the yarns particularly easily.

A still further object of the invention is to provide an improved process for sizing the type of yarns mentioned which, compared with processes employed hitherto, effects savings in energy and personnel costs and an increase in productivity when processing the sized yarns, and which also ensures more satisfactory and easier desizing.

Other objects will be apparent from the following detailed description.

These objects are achieved by the present invention which is based on the surprising discovery that polymers which are of a very similar composition to those in US. Pat. 2,819,189 produce markedly superior results, not only as regards water solubility, but also with respect to their sizing effects, when the componentsof the polymers are used in different molar ratios and the polymers are applied in acidic form.

It has been found that staple yarns consisting of or containing cellulosic fibers and/or acrylic fibers in an amount of at least 30' percent by weight can be sized better than hitherto by applying to the yarn an aqueous solution of a polymer containing copolymerized units of (a) acrylonitrile and (b) acrylic acid and its sodium or ammonium salt in the molar ratio of (a) (b) of 1:15 to 1:7, preferably from 1:2 to 1:6, its 10 percent by Weight aqueous solution at 20 C. having a viscosity of 20 to 2000 cp. and a pH value of 2.5 to 6.5, preferably 3 to 5.5, and drying the yarn thus treated.

Staple yarns that can be sized according to the invention include, for example, those of natural and/or regenerated cellulose such as cotton, rayon staple, linen and their blends with one another and with other staple fibers such as polyester and acrylic fibers and their blends with other staple fibers. Our acrylic fibers are understood both fibers prepared from acrylonitrile homopolymers and those of copolymers of acrylonitrile with up to approximately 20 percent by weight of other monomers, e.g., methyl acrylate, vinyl acetate and vinyl pyridine.

The polymers used in the form of their solutions in accordance with the invention can, in addition to the monomers described under (a) and -(b) above, incorporate up to 20 percent by weight of coplymerized units of other, at least partially water-soluble, monomers, such as acrylamide, methacrylamide, methyl acrylate, methacrylic acid or its alkali or ammonium salts, maleic acid or its salts or semiesters, methacrylonitrile and vinyl pyrrolidone. They can be prepared by conventional processes, preferably by the copolymerization of acrylic acid with acrylonitrile and, if desired, other monomers in aqueous solution, and by subsequent partial neutralization of the carboxyl groups contained in the polymers by means of an alkali or ammonium hydroxide to set up the molar ratio between the free acrylic acid groups and the sodium or ammonium carboxylate groups which produces the required pH value of the polymer solution. A further method of preparation consists in copolymerizing mixtures which already contain acrylic acid, sodium or ammonium acrylate and acrylonitrile in the desired molar proportions. In general, the polymers to be used in accordance with the invention contain carboxylic acid groups and sodium or ammonium carboxylate groups in the molar ratio of approximately 1:03 to 1:3, preferably from 1:0.8 to 1:2. The polymers can be applied as sizing agents either in the form obtained in manufacture or after dilution. However, they can also be dried to a powder and dissolved in water before use.

As a 10 percent aqueous solution at 20 C. the polymers should have a viscosity of from 20 to 2000 cp., polymers having a viscosity of from 250 to 2000 cp. under the said conditions being preferred. The viscosity is expediently determined with a Hoppler falling sphere viscometer according to German standard specification DIN 53,015.

The solutions employed in accordance with the invention preferably contain 0.5 to 20 percent by weight of polymer. The following concentrations have proved particularly satisfactory: 0.5 to for rayon staple and linen, 3 to for cotton, and 5 to percent by weight for acrylic staple fiber. The size solutions have pH values ranging from approximately 2.5 to 6.5, preferably from approximately 3 to 5.5, depending on the molar ratio of free carboxylic acid groups to sodium or ammonium carboxylate groups present in the polymer.

In addition to the polymers mentioned, the solutions according to the invention can contain conventional sizing agents and/or sizing auxiliaries, e.g., chemically moditied starches, carboxymethylcellulose, methylcellulose, polyvinyl alcohol and emulsified fats; such additives, however, should not constitute more than 50 percent by weight of the solids content of the sizing liquors, and preferably not more than percent by weight.

The polymer solution employed for sizing in accordance with the invention can be brought on to the yarn at temperatures of between 0 and 100 C. In many cases, however, it is particularly advantageous to employ the liquor at a temperature of between 10 and C., that is, at approximately room temperature. Nevertheless, the polymer solution can also be used at higher temperatures, in which case the associated fall in viscosity permits working at a higher concentration resulting in a considerable increase in the output of the sizing machine since less water has to be evaporated from more concentrated solutions on drying.

The application of the size to the yarn is carried out in the usual manner, that is, mainly on machines well known in the open width sizing of warps. However, it may also be applied to the individual yarn, for instance, on a cross-Wound package. It is also possible to apply the size to bobbins or warp beams by means of appropriate dyeing machinery. It is preferable to apply the sizing agent in such an amount that the treated yarn carries 0.5 to 10 percent of polymer, referred to the weight of the untreated, dry yarn.

The present invention possesses a number of important technical advantages:

The polymers of the invention are particularly readily soluble in water. A consequence of this is that the sizing liquors can be prepared with cold water and require only moderate stirring, particularly when the polymer is in the form of an aqueous solution. In the process of the invention, the use of pressure boilers and steam or other thermal energy for preparing the sizing liquors, such as is necessary with most of the existing sizing agents and especially with starch products, can be dispensed with. Labor costs can be saved as a result of the considerably simpler and more rapid preparation of the liquor, and the danger of personnel being scalded is reduced.

No evaporation losses occur during application at normal temperature, an it is particularly easy to keep the temperature and concentration of the sizing baths constant. Furthermore, it must be pointed out that the polymers of the invention produce sizing effects equivalent or even superior to those of conventional sizes, even at considerably lower rates of application.

The fact that smaller amounts of sizing agent are required also means that more yarn can be wound onto a warp beam than is the case with conventional sizing agents, so that weaving capacity is increased and savings are effected in ancillary machinery.

Another important advantage is the stability of the sizing liquors which can, if necessary, be stored for weeks without undergoing change. Sizing liquors based on starch, on the other hand, lose considerably in efficiency even on storing for only a few hours, so that they have to be discarded in the evening or at the end of the week. Thus, compared with prior processes, the new process offers the possibility of savings in the cost of materials. A considerable reduction in the number of broken ends on the loom can be achieved as a result of the invention. This also means that the productivity of the loom is increased. Warps sized in accordance with the invention does considerably less than warps sized by conventional processes.

Yarns sized in accordance with the invention are more resistant to abrasion than yarns treated with starch products, cellulose ethers, or in accordance with the invention described in U.S. Pat. 2,819,189. Furthermore, the yarns can be desized more easily, since simple scouring or rinsing is all that is required. Faulty dyeings and difiiculties in finishing, so very often attributable to inadequate desizing, are largely elminated by the process of the invention.

From the point of view of river pollution the low biochemical oxygen demand for the sizing agents of the invention is particularly advantageous as compared with that of the most commonly used starch sizes. The high biochemical oxygen demand of saccharification products of starch often leads to a considerable disturbance of the biological equilibrium in the rivers into which the effluents run, and may result in anaerobic fermentation and odor nuisance. The superiority of the polymers of the invention over those described in U.S. Pat. 2,819,189 can be seen principally in the fact that, as homogeneous solutions, they are much easier to use than dispersions which are very unstable in some cases. Whereas such dispersions and colloidal solutions exhibit a marked tendency to tures or subjected to repeated freezing and thawing. It is well known that good transport and storage stability is of importance in practice. The invention is further illustrated by, but not limited to, the following examples in which the parts and percentages specified are by weight.

Testing of the yarns was carried out under standard conditions, namely, at 20 C. and 65 percent relative humidity. The mechanical values given in the stables constitute the mean values of or individual determinations, as the case may be. The abrasion number is the average number of abrasions up to breakage of the yarn, and has been measured on the apparatus described by E. Kenk in Textil-Praxis, 7, 9, 6 98 (1952).

EXAMPLE 1 A cotton yarn, of Nm. 34/ 1 count, was treated with two different sizing liquors on a laboratory sizing machine consisting of one pair of squeeze rollers with a sizing trough capable of being heated, a drying tube heated with hot air, and a wind-on device operating at constant tension; the conditions were otherwise identical in both cases.

Liquor 1(a) Parts Potato starch 77 Degraded starch 16 Bone glue 6 Emulsified fat 1 4 the liquor being made up to 900 parts with water.

This mixture, which has a formulation well tried in practice, was boiled up for minutes and then applied at 85-90 C.

Liquor 1(b) This comprised a 15 percent aqueous solution of a polymer which was made up, on the one hand, with acrylic acid and sodium acrylate and, on the other, acrylonitrile, the two groups of components being in the molar ratio of 2:1. When diluted to 10 percent, the solution had a viscosity of 315 cp. at 20 C. and a pH value of 4.5. The liquor contained no other additives and was applied at 20 C.

On comparing untreated Nm. 34/1 cotton yarn with the two yarns sized in liquors 1(a) and 1(b) respectively, after conditioning for 24 hours at 20 C. and 65 percent relative humidity, the values presented in the following table are obtained:

Coating Elongaweight Breaking tion at (weight Abrasion ad break percent) number (g.) (percent) Untreated 105 316 8. 4 Treated with liquor 1(a 19. 8 1517 599 4. 3 Treated with liquor It can be seen from these figures that the cotton sized according to the invention with formulation 1(b) at room temperature has a greater extensibility, a larger abrasion number, and about the same breaking load as thattreated sizing machine described in Example 1 with three different sizing liquors at a bath temperature of 20 C. The composition andpreparation of the sizing liquors were as follows:

6 Liquor 2(a) 120 parts of a commercial carboxymethylcellulose powder recommended for sizing cotton, and 880 parts water.

This size powder was slowly stirred into hot water at C., allowed to swell overnight, and then vigorously stirred once more on the following day. In spite of this, the liquor was not homogeneous and entirely clear, but turbid and with swollen particles distributed throughout it.

Liquor 2 (b) 400 parts of a 25 percent aqueous solution of a polymer made up of acrylic acid, ammonium acrylate and acrylonitrile in molar proportions of 1:0.8:0.5 (corresponding to a molar ratio of acrylate to acrylonitrile, (a):(b) =1:3.6), whose 10 percent solution at 20 C. has a viscosity of 635 cp. and a pH value of 4.3, were diluted with 600 parts of water by simple stirring.

The liquor 2(b) obtained in this manner is color less, clear, and homogeneous.

Liquor 2(c) Coating Elongaweight Breaking tion at (weight Abrasion load brealr percent) number (g.) (percent) Untreated 206 5. 2 Treated with liquor 2 a 9. 2 234 4. 9 Treated with 1 nor 2(b 8. 9 486 289 4. 0 Treated with liquor In spite of the low liquor concentration and in spite of the small amount applied, the superiority of the size applied in accordance with formulation 2(b) of the invention is made evident by the resultant higher breaking load and considerably higher number of abrasion cycles required to effect rupture of the fiber.

EXAMPLE 3 Two 10,000 m. long warps containing 4,600 cotton threads (Nm. 68/ 1) were sized for comparison purposes in different liquors on an open-width sizing machine equipped with a cylinder dryer. Liquor 3(a) was prepared by submitting a suspension of 35 parts of potato starch and 35 parts of a commercial esterified starch ether sizing agent in 430 parts of water to boiling for about 40 minutes while stirring. Liquor 3(b) was prepared by stirring parts of a 25 percent solution of a polymer of acrylic acid, ammonium acrylate and acrylonitrile in the molar proportions 1:1:0.6 (COIICSpOITCElg to the molar ratio of acrylate to acrylonitrile, (a):(b)=1:3.33) into 375 parts of water at room temperature. A 10 percent solution of this polymerhad a viscosity of 288 cp. and a pH value of 4.5.

Whereas liquor 3(a) had to be applied to the warp at 85 to 90 C. inorder to prevent gelling of the starch paste, liquor 3(b) could be applied at room temperature. Both warps were subsequently lubricated on the sizing machine with a molten commercial grease.

The above two warps were then woven on similar looms and under the same conditions. The warp sized with liquor 3(a) had an average of 47 broken ends per 100,000 picks, while the warp sized according to the invention with liquor 3(b) had an average of only 1.6 broken ends per 100,000 picks. Each of these constitutes the mean values of observations made over approximately 500,000 picks.

made from the (b) warp presented a very much more even appearance than that produced with the 5(a) warp.

EXAMPLE 6 Each of two warps containing 787 linen threads (Nm.

To remove the size from the loom-state cloth, the goods 5 f r wels was sized in one of two difl'erent sized with liquor 3(a) had to be subjected to a desizing l q n an pp machlue q pp W 1th a Y process lasting several hours in the presence of enzymatic l der dryer. L1quor 6(a) compnsed a suspension of desizing agents, this being followed by open-width scour- Parts Of a com crclal starch der1vat1ve and 1.5 parts of ing, whereas the goods sized with liquor 3(b) simply r 10 an emuls1fiable fat 1n 490 parts of water, whlch had been quired a cold cour to remove the size boiled up for 10 minutes WhllC being Slill'ffid and then applied at 60 C. EXAMPLE 4 Liquor 6(b) comprised a solution of 5 parts of a lymer of acrylic acid ammonium acrylate and acrylo- A red-d ed 800 m.1on acr l1c fiber war Nm. 40/1) a containing/3,600 ends i a};veaving f 120 n1tr1le 1n molar proportions of 1:1.5 :1 (corresponding to was sized with two different sizing liquors on an openi of (a):(b)=1:2'5) 2 parts of Water width machine equipped with an air dryer. Liquor 4(a) 1e r0021 e e 10 percent was prepared by boiling and stirring a suspension of 40 t g a vlseoslty of 1130 and a parts of potato starch and 25 parts of a chemically modi- P Va ue 0 fied starch with 335 parts of water for 1 hour. Liquor ,T warps Slzed Wlth the orespeetlve hquors were 9 4(b) consisted of an 8 percent aqueous solution of the P F for 24 hours at 20 65 percent relatlve polymer described in Example 3. Liquor 4( a) was applied hemldlty whereupon they were mvestlgated and eompared to the yam at c and liquor 4(b) at C an other with untreated yarn. The values 1n the followlng table conditions being identical. Investigation of the yarns in were obtamed: comparison with untreated yarn gave the values presented 25 in the fOllOWiHg table: Coating Elongaweight Breaking tion at (weight; Abrasion load break Coating Elon percent) number (g.) (percent) h B k t" t $3511? Abrasion 132 b'ie k gfiggg g m g 662 11732 percent) number (g.) cent) T g H t}; 1 0 1' 144 1 595 2 o a 1 I101 gg g 116 489 2 eliv 0. e 1, 554 1, 689 2. e

4(a) 12. 3 736 530 19. 2 T- t d t 1 nor f i) l.. 8 564 In spite of the considerably smaller amount of S126 applied, warp 6(b), which had been sized in accordance In assessing the weaving behavior of the two warps with the invention with a cold liquor, behaved better on practically no difference can be established without the WeaYmg than warp as shown by betterfiheddmg, less statistical determination of the number of broken ends, dustlng, and fewer k n ends. An ther important adand this despite the fact that the amount of sizing agent Vantage was the ease of Washlng out 5126 applied in accordance with the invention was not even 2311f EXAMPLE 7 as great as that applied by t e convent1ona process. e warp sized with formulation 4(b) in accordance with the .Stap 1e rayon (polynoslc 48/1) W i slzed invention was virtually non-dusting, whereas the warp i the hquors on the laboratory 512mg sized with formulation 4( a) produced an extremely large 0 me descnbed m Example amount of dust. To this must be added the fact that the Liquor 7(a) loom-state cloth sized with formulation 4(a) has to be This consi o sted of a hot (85 C.) aqueous preparation of i ig g fg i g gg gi gg 55 52 g i g g ggi g 30 parts of carboxymethylcellulose, 30 parts sodium polyf0 methacrylate solut1on (30 percent in water), 2 parts of open'wl or m rope mineral oil emulsion and 938 parts of water.

EXAMPLE 5 Liquor 7(b) The F liquors descfibed Example 4 were dilufed This consisted of a hot (85 C.) aqueous preparation y One-fluid 0f Volume wlthhot Water (formula?!on of 30 parts of a polymer of acrylic acid, sodium acrylate and cold Water (formulatlon and 100 55 and acrylonitrile in the molar ratio of 1:2:0.6 (correlengths of a warp containing 2,400 pale blue rayon staple/ sponding to the molar ratio of (a) (b)=1;5; a 10 f 'yl fiber blend y z Slzfid cent aqueous solution of this polymer had a viscosity of 1H elfllel The Values p m 011 lllvestlgatlng the 1880 cp. and a pH value of 5.3), 10 parts of a commercial two f P In COmPaHSOII Wlth untreated Y are p water-soluble starch ether and 940 parts of water. Sentfid In the followlng table? The following data were obtained on testing the fibers:

6 ti El wogigrlllf r ing tioei e t @3 11? Breaking gii a t (weight Abrasion 108 break (weight Abrasion load break percent) numb er (g.) (percent) 6 5 percent) numb (percent) --1 257 279 1 Untreated T 83 348 11. 4 233 i 11. 5 686 294 10.2 r l wlthhqum 7 3 374 345 6 3 Treated 'w'itli use; Tre ted with lidiffz to be expficted from these Valli-{65, p The warp sized with liquor 7(b) in accordance with sized With the 5(b) 11ql10r 1n accorda ce with t e ln the invention had better weaving characteristics than that tion behaved similarly on the loom to the warp treated of 7(a) because of its very high abrasion rating obtained with the 5(a) liquor. The 5(b) warp, however, produced in spite of the considerably smaller amount of sizing agent very much less dust than the 5(a) warp, and the material applied.

9 EXAMPLE 8 A polyester fiber/cotton blend (67/33) yarn (Nm. 69/1) was sized with two different liquors on the lab oratory sizing machine described in Example 1. Liquor 8(a) was obtained by boiling up a suspension of 230 parts of a commercial starch derivative and 16 parts of a commercial emulsified fat in 850 parts of water until the viscosity became approximately constant, this taking about 45 minutes. This liquor, which is representative of a commercially employed formulation, was applied at 90 C.

Liquor 8(b) was obtained by stirring 300 parts of an aqueous 30 percent solution of a copolymer of acrylic acid, sodium acrylate and acrylonitrile in the molar ratio of 1:2:1 (corresponding to the molar ratio of (a) :(b): 1:3) into 700 parts of water at room temperature; a percent solution of the polymer had a viscosity of 420 cp. and a pH value of 5.2. The liquor was applied to the yarn at room temperature.

Investigation of these two sized yarns and untreated yarn gave the following values which demonstrate the superiority of sizing liquor 8(b) prepared and applied in accordance with the invention.

Coating Elongaweight Breaking tion at (weight Abrasion load break percent) number (g.) (percent) Untreated 195 279 13. 1 Treated with liquor 8(a 22. 7 502 286 9. 6 Treated with liquor monium salt in the molar ratio of (a) (b) of from 1:15 to 127, a 10 percent by weight aqueous solution of said polymer at 20 C. having a viscosity of 20 to 2000 cp. and a pH value of 2.5 to 6.5, in order to deposit on said yarn at least about 0.5% by weight of said polymer with reference to the weight of the untreated dry yarn; and drying the yarn thus treated.

2. A process as claimed in claim 1, in which the poly mer is applied in an amount of 0.5 to 10 percent, referred to the weight of the untreated dry yarn.

3. A process as claimed in claim 1, in which the molar ratio of (a):(b) in the polymer is from 1:2 to 1:6.

4. A process as claimed in claim 1, in which a 10 percent by Weight aqueous solution of the polymer at 20 C. has a viscosity of 250 to 2000 cp.

5. A process as claimed in claim 1, in which a 10 percent by Weight aqueous solution of the polymer at 20 C. has a pH value of 3 to 5.5.

6. A process as claimed in claim 1, in which an aqueous solution containing 0.5 to 20 percent by weight of polymer is applied to the yarn.

7. A process as claimed in claim 1, in which the aqueous solution of the polymer is applied to the yarn at a temperature of between 10 and 30 C.

8. A process as claimed in claim 1, in which the poly mer contains carboxylic acid groups and sodium or ammonium carboxylate groups in the molar ratio of from 1:0.8 to 1:2.

References Cited UNITED STATES PATENTS 2,819,189 1/1958 Suen et a1. 117139.5

WILLIAM D. MARTIN, Primary Examiner T. G. DAVIS, Assistant Examiner US. Cl. X.R.

ll7l38.8, 161, 143,