US3572988A - Fabrics of crosslinked cellulose acrylates and methacrylates crosslinked with nitrate catalysts - Google Patents

Abstract

ALPHA,BETA UNSATURATED CARBOXYLIC ACID ESTERS OF CELLULOSE IN FIBER FORM ARE TREATED WITH ZINC, ALUMINUM OR CADMIUM NITRATE AND HEATED TO FORM CELLULOSE CROSSLINKAGES.

Description

United States Patent FABRICS 0F CROSSLINKED CELLULOSE ACRY- LATES AND METHACRYLATES CROSSLINKED WITH NITRATE CATALYSTS Gene Surnrell, New Orleans, and Matthew F. Margavio and Clark M. Welch, Metairie, La., assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Filed Dec. 30, 1969, Ser. No. 889,322

Int. Cl. C08b 11/12, 13/00; D06m 13/10 US. Cl. 8-120 8 Claims ABSTRACT OF THE DISCLOSURE Alpha,beta unsaturated carboxylic acid esters of cellulose in fiber form are treated with zinc, aluminum or cadmium nitrate and heated to form cellulose crosslinkages.

A non-exclusive, irrevocable, royalty free license in the invention herein described, throughout the world for all purposes of the United States Government, with the. power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to an improved process for the wrinkleproofing and permanent creasing of cellulosic fabrics. In particular it is applicable to the preparation of cotton and rayon garments possessing wrinkle resistance, smooth drying qualities, resistance to shrinking, and permanent creases or pleats formed after garment fabrication. Many processes have previously been described for the impregnation of cellulosic fabrics with chemicals and catalysts which are intended to remain inactive in the fabric at room temperature, but which will, at elevated temperatures, impart wrinkle resistance to fabric and render creases durable to mechanical deformation or to laundering. The fabrics thus impregnated and dried can be fabricated into garments; the desired creases, pleats, roundness, or folds can be pressed or molded into the garment, and on heat-curing, the garment acquires wrinkle resistance and permanence of shape.

A nearly universal problem with these so-called delayed curing processes, particularly when utilizing N-methylolureas, N-methylolamides or related formaldehyde derivatives in the presence of acidic catalysts, is that even at room temperature, an appreciable degree of reaction of the wrinkleproofing agent with the cellulosic fabric occurs on continued fabric storage. The cellulose becomes crosslinked permanently, before the fabric or garment is to be creased or otherwise shaped, and heat cured. It is then found to be diflicult or impossible to obtain creases of the desired sharpness and permanence in the already crosslinked fabric.

A second disadvantage of many such processes is that on long storage in moist air, the wrinkleproofing agent may undergo dissociation to liberate free formaldehyde objectionable both as to odor and toxicity. Because of the loss of active wrinkleproofing agent during storage, the degree of wrinkle resistance finally obtained on heatcuring is also found to diminish as the storage time prior to curing is increased.

A third disadvantage of processes in which fabric is merely impregnated with the wrinkleproofing agent and catalyst, dried, and subsequently heat-cured, is that the accidental contact of impregnated, dried fabric with water or droplets of condensed moisture during storage prior to curing renders the fabric unusable because of leaching or uneven migration of wrinkleproofing agent and catalyst. The only remedy is to wash the fabric, which entails the loss of expensive wrinkleproofing agent, and again impregnate with agent and catalyst. Moreover such processes automatically fix the ratio of catalyst to wrinkleproofing agent, and this ratio cannot subsequently be altered without washing both components from the fabric and starting over. This limits usage of the impregnated fabric. For example a low ratio of catalyst to wrinkleproofing agent may be required for treating sheeting, in which a medium level of wrinkle resistance together with a high level of tensile strength relative to the light-weight fabric construction used, is required. On the other hand, a high ratio of catalyst to wrinkleproofing agent may be needed for treating trouser material in which a very high level of wrinkle resistance is required in a fabric construction sufliciently heavy to compensate for increased tensile strength losses.

A further disadvantage of nearly all nitrogenous wrinkleproofing agents previously described is the fabric tendering and discoloration they induce when the wrinkleproofed cloth is treated with chlorine or sodium hypochlorite bleaches, and then is washed and dried at elevated temperatures. This effect is due to chlorine retention by the nitrogenous wash-wear resin, leading to formation of hydrogen chloride and N-chloroamides, which degrade and discolor the fabric at elevated temperatures.

The above disadvantages of previous delayed curing processes are largely eliminated in the present invention, as will be seen from the objects and description which follow.

The main object of the present invention is to provide a method of imparting wrinkle resistance and permanent creases to cellulosic fabrics.

A second object is to provide a means of preparing cellulosic fabrics which can be stored at room temperature, sewn into garments, and at a later date can be rendered wrinkle resistant and permanently creased by application of heat.

A third object is to provide a means of preparing cellulosic fabrics which can be washed with water, and on impregnation with an inexpensive catalyst, can subse quently be heated to impart wrinkle resistance and permanent creases.

A fourth object is to provide a means of imparting wrinkle resistance and permanent creases to cellulosic fabrics without the use of nitrogenous wrinkleproofing agents. Other objects will be apparent from the description of the invention.

The present invention arises from the unexpected observation that alpha,beta-unsaturated carboxylic esters of cellulose become molecularly crosslinked when heated with certain metal nitrate salts as catalysts. When the unsaturated carboxylic ester is in the form of a woven fabric, the crosslinking that occurs imparts to the fabric a high degree of wrinkle resistance and smooth-drying qualities, and renders fabric creases durable to laundering and mechanical deformation. While alpha,beta-unsaturated carboxylic esters of cellulose might be expected to undergo crosslinking if heated with sodium hydroxide, which can, according to Frick, Reeves, and Guthrie (Textile Res. J. 27 92-99 (1957)) catalyze the addition of acrylate esters to cotton cellulose, the catalysts suitable for the present crosslinking reactions unexpectedly are certain mild Lewis acids. The efficiency of sodium hydroxide as a catalyst for the addition of acrylate esters to cotton is poor, being impaired by the tendency of the base to saponify the ester. The present catalysts do not cause ester hydrolysis and thus have the advantage of leaving ester groups in cellulose acrylate intact.

The alpha,beta-unsaturated carboxylic esters of cellulose which are effective in the present process are esters prepared in fabric form, said esters having the molecular structure wherein radical R is selected from the class consisting of methyl and hydrogen radicals, and cell denotes a portion of a cellulose chain, the ratio of said unsaturated ester groups to anhydroglucose units in the cellulose being about from 0.10 to 0.50. Such esterification ratios correspond to a fabric weight gain of from 3.3% to 17% in preparing the acrylate ester of cellulose, and to a weight gain of from 4% to 20% in preparing the methacrylate ester of cellulose.

At lower degrees of cellulose esterification, the wrinkle resistance imparted by the present process is too low to be of practical value, while at higher degrees of esterification than those specified, the time required for cellulose esterification and the degree of swelling of the fibers of esterified cellulose become excessive. The aforesaid alpha,beta-unsaturated carboxylic esters of cellulose in fabric form are known materials (Dorset, Textile Mfr. 83 34-8 (1957)) and can be prepared by esterification of native or regenerated cellulose in fabric form by reaction of the cellulosic fabric with the corresponding alpha,betaunsaturated carboxylic acid, anhydride or halide by known esterification procedures. When acryloyl chloride or methacryloyl chloride is employed as the esterifying agent, the desired degree of esterification of cellulosic fabric may be achieved by use of the procedure of McKelvey, Benerito, and Berni (Textile Research J. 35, 365-376 (1965)) wherein pyridine is the acid scavenger used to remove hydrogen chloride formed by the esterification reaction, and N,N-dimethylformamide (hereinafter called dimethylformamide) is the diluent and reaction medium. If desired, finely divided calcium carbonate may be used in place of pyridine as the acid scavenger in this procedure. Calcium carbonate has the advantage of showing no tendency to form an insoluble complex at low temperature with acryloyl chloride, and also is less costly than pyridine. A great variety of other acid scavengers may be used however.

N,N-dimethylaniline or other tertiary amines of basicity comparable to N,N-dimethylaniline may be employed. As already stated, the introduction of from 0.10 to 0.50 acryloyl or methacrylol groups per anhydroglucose unit of the cellulosic fabric furnishes a fabric suitable for crosslinking.

The process of the present invention comprises the following steps:

(a) conversion of cellulosic fabric to an alpha,betaunsaturated carboxylic ester of cellulose in fabric form, said ester having the molecular structure wherein R is a radical selected from the class consisting of methyl and hydrogen radicals and cell denotes a portion of a cellulose chain, the ratio of said unsaturated ester groups to anhydroglucose units in the cellulose being about from 0.10 to 0.50,

(b) impregnating the fabric with an aqueous solution containing about from 1% to 8% by weight of a crosslinking catalyst selected from the group consisting of zinc nitrate, aluminum nitrate, and cadmium nitrate,

(c) drying the fabric at about from 60 C. to 110 C.

for about from 2 minutes to 10 minutes, and

(d) curing the fabric at about from 140 C. to 170 C. for from 1 minute to 10 minutes.

As already indicated, the metal salts suitable as crosslinking catalysts for step (b) of the present process are unexpectedly certain metal nitrates. Salts containing other anions such as chloride, sulfate, fiuoborate or perchlorate are ineffective. The catalytic activity of the metal nitrate is also highly dependent on the particular metal ion present in the salt. The nitrates of Group II metals of the Mendeleelf periodic table are particularly effective, with zinc nitrate having high catalytic activity and cadmium nitrate possessing a moderate degree of activity. Among the nitrates of Group III metals, aluminum nitrate shows moderate effectiveness. Nitrates of certain transition metals such as iron, cobalt and copper are unsuitable as catalysts since they cause discoloration of cellulosic fabrics. It is particularly noteworthy that nitric acid, in spite of its extremely high acidity, is less effective catalytically than zinc nitrate, indicating the effectiveness of a given catalyst in the present process is not predictable from the acidity of the catalyst or the possibility of forming free nitric acid by hydrolysis of the metal nitrate. Of the nitrate salts found to be catalytically active, the most effective are zinc nitrate, cadmium nitrate and aluminum nihate; and of these three salts zinc nitrate is the most effective and suitable.

If it is desired to prepare fabric for storage and later use in fabricating garments subsequently to be given a delayed cure, the fabric is esterified, impregnated With catalyst and dried in accordance with steps (a), (b), and (0) above. It may then be stored and at a later date subjected to curing step (d). At any time in this storage period prior to the curing step, the fabric may be creased or pleated by conventional ironing or by steam pressing. The creases and pleats so formed become permanently fixed in the fabric during the subsequent curing step (d).

Fabrics treated 'by the present process may be given a subsequent washing and drying, but this is not essential to the process inasmuch as the treated fabric does not contain chemicals injurious or irritating to the skin at this stage. The aqueous catalyst solution applied in step (b) above may contain wetting agents, inert softeners and the usual textile auxiliary agents.

Temperatures suitable for the drying step (c) above are 60 C. to 110 C. as already indicated, with temperatures of C. to C. preferred. Drying is slow at very low temperatures. At temperatures higher than C. there is some danger of premature crosslinking of the alpha, beta-unsaturated cellulose ester fabric prior to its being fabricated into garments later to be creased or pleated. If it is desired to impart wrinkle resistance to flat sheets or other yard goods without any delay prior to curing step (d), the drying step (c) is optional and may be omitted, since drying can be accomplished during the high temperature curing step (d).

Temperatures suitable for the curing step (d), which imparts molecular crosslinking to the fabric, are C. to 170 C. as already specified, with temperatures of C. to C. preferred. At low temperatures, inadequate wrinkle resistance is imparted, but at temperatures above C., excessive yellowing and tendering of the fabrics may occur.

As stated previously, the curing step (d) produces molecular crosslinking in the alpha,beta-unsaturated ester of cellulose of which the fabric is composed. This is shown by the behavior of fibers of the fabric in aqueous 1 molar cupriethylenediamine, hereafter called cuene. Prior to the curing step (d), the fibers are generally either soluble in cuene or are greatly swollen by this agent, particularly if the degree of cellulose esterification is less than one ester group for every three anhydroglucose units. During the curing step (d) the fibers are rendered insoluble and immune to swelling in cuene, indicating they are now crosslinked.

The following examples illustrate the practice of this invention without limiting the scope thereof. Wrinkle resistance of treated fabrics was measured by the Monsanto crease angle method.

EXAMPLE 1 6 cotton print cloth weighing 3.2 oz./yd. which had been dried for one hour at 60 C., were immersed in the dimethylformamide-acryloyl chloride solution at room temperature. After the fabric was in place, finely powdered free-flowing calcium carbonate was poured into the liquid phase, the amount of calcium carbonate added being 10 g. for each 100 ml. of dimethylformamide used. A steady ebullition of carbon dioxide commenced when the mixture was warmed to the desired reaction temperature, and this ebullition continued during the reaction, serving to provide an effective stirring action in the liquid phase. The mixture was kept at constant temperature for TABLE II.ACRYLATE ESTERS OF CELLULOSE PREPARED IN FABRIC FORM IN THE PRESENCE OF CALCIUM CARBONATE Coneen- Crease angles,

trate, Reaction Percent W+F acid 'me, weight Sample chloride hours gain Behavior in 1M cuene Dry Wet 1 8. 3 0. 6 4. 9 Slowly soluble 205 201 2,. 8. 3 0. 75 6. 2 Mostly soluble 215 189 3.- 8. 3 1. 25 8. 3 swelled, partly insoluble 217 191 4 5 1 5. 8 Slowly soluble 206 183 5. 5 3 6. 5 6 5 5 6. 8 7 7. 5 1 6.8 8.. 7. 5 2 9. 6 9.. 7. 5 3 10. 0 10 7. 5 2 12. 5 11 7. 5 4 14. 3 12 7. 5 5 15. 3 1 7.5 6 14.6 14 1 15 1. 5 13. 9 15 2 15 3 15. 9 16 l5 4. 5 17. 3 Control Solubl 1 Concentration in parts by volume of acid chloride to 100 parts by volume of dimethyformamide, measured at C.

2 Reaction temperature was 90 C.

60 C. and kept at this temperature for varying periods of time, with the reaction vessel covered to exclude moisture. After the desired reaction time had elapsed, the fabric was removed and washed with warm methanol and then with Warm water, and air-dried at room temperature. This procedure was used with several different concentrations of acryloyl chloride and pyridine, and with several different reaction temperatures. The procedure was also used with methacryloyl chloride in place the desired reaction time. At the end of this time, the fabric was removed and washed with warm methanol and then with warm water, and was air-dried at room temperature. This procedure was used with several different concentrations of acryloyl chloride. Except where otherwise stated, the reaction temperature was 100 C. The results are listed in Table 11. As with the ester fabrics of Example 1, the esterification of the cellulose produced little enhancement of crease angles.

TABLE I.-ACRYLATE AND METHACRYLATE ESTERS OF CELLULOSE PREPARED IN FABRIC FORM IN THE PRESENCE OF PYRIDINE Monsanto Parts by volume 2 crease angles,

Reaction Percent W+F Cellulose ester Acid Dimethyltime, weight Behavior in prepared 1 chloride Pyridine formamide hours gain Dry Wet 1M euene A 5 5 200 1. 5 2. 7 184 200 Very soluble. A..- 5 5. 5 200 3.5 3.0 167 0 Do. A 5 5. 5 200 6. O 6. 1 168 206 Do. A- 15 4. 0 200 6. 0 8. 4 221 181 Do. A 15 15 200 6. 0 11. 6 237 220 Do. A 30 8 200 6. 0 10. 6 237 221 Do. A. 30 30 200 6. 0 12. 3 226 224 Do. A 60 200 6. 0 14. 7 233 220 Do. 5 5 5 200 3. 5 2. 7 168 179 Do. M- 5 5 200 6.0 6. 4 198 203 SloWl) soluble. M--. 15 4 200 6. 0 6. 2 108 203 Do. M 15 15 200 6. 0 11. 9 188 186 Swelled. M 30 30 200 6. 0 14. 2 193 195 Do. Untreated fabric 176 156 Very soluble.

t =Acrylate ester prepared using acryloyl chloride; M=Methacrylate ester prepared using methacryloyl chloride.

2 Parts by volume measured at 25 C.

of acryloyl chloride. The results are listed in Table I in the order of increasing fabric weight gains obtained.

The results show that the esterified cotton fabrics possessed only a little higher wrinkle resistance than untreated fabric, and fibers of the treated fabrics were greatly affected by cuene, indicating an absence of molecular crosslinking in the cellulose ester fabric.

EXAMPLE 2 Conversion of cotton fabric to acrylate esters of cellulose in fabric form, using calcium carbonate as acid scavenger To dimethylformamide in a cylindrical reaction vessel was added acryloyl chloride followed by mixing of the EXAMPLE 3 Zinc nitrate-catalyzed crosslinking of acrylate esters of cellulose in fabric form solution. Samples of 86 x 76 desized, scoured and bleached prepared were immersed in an aqueous solution containing 4% by weight of zinc nitrate hexahydrate. The pH of this solution was found to be 4.2. The fabrics were drained free of excess solution and were then oven-dried at 85 C. for 4 minutes, followed by oven curing at 150 C. for 4 minutes. The samples were then rinsed in 7 changes of warm tap water, blotted free of excess water and air-dried. The properties of the crosslinked fabrics appear in Table III.

reaction temperature, and this ebullition continued during the reaction, serving to provide an effective stirring action in the liquid phase. The mixture was kept at 80 C. for 1 /2 hours. At the end of this time the fabrics were removed and washed with warm methanol and then with warm water, and were air-dried at room temperature. This procedure was used in runs made at two different concentrations of acryloyl chloride, as indicated in Table TABLE I1I.ZINC NITRATE-CATALYZED CROSSLINKING OF ACRY- LAIE ESTERS OF CELLULOSE IN FABRIC FORM A, acrylate ester Control (Zn) 4 Acid scavenger on this run was 4 ml. of pyridine instead of calcium carbonate (procedure of Example 1). I

2 Sample 4 cured at 150 C. for 4 minutes in absence of zinc nitrate.

3 Sample 5 cured at 150 C. for 4 minutes with 4% zine nitrate-1% hydroquinone.

4 Untreated fabric cured with 4% zinc nitrate.

Fibers of the fabrics cured with zinc nitrate were found to be insoluble and unswollen in cuene, indicating they had been highly crosslinked. This is also indicated by the large increase in dry crease angles produced by the zinc nitrate treatment.

EXAMPLE 4 Zinc nitrate-catalyzed crosslinking of methacrylate esters of cellulose in fabric form Samples of 86 x 76 desized, scoured and bleached cotton printcloth Weighing 3.2 oZ./yd. were dried for 1% hours at 60 C. and were then converted to methacrylate esters of cellulose in fabric form by the following procedure: the fabrics were immersed in a mixture of dimethylformamide and methacryloyl chloride in a cylindrical reaction vessel at room temperature. After the fabrics were in place, finely powdered free-flowing calcium carbonate was poured into the liquid phase, the amount of calcium carbonate added being g. for each 100 ml. of dimethylformamide used. A steady ebullition of carbon dioxide commenced when the mixture was warmed to the desired TABLE IV.ZINC NITRATE-CATALYZED CROSS-LINK- ING OF HETHACRYLATE ESTERS OF CELLULOSE IN FABRIC FORM A, methacrylate ester prep- 1 Ester prepared in presence of 10 g. of CaCOa for each 100 ml. of dimethyltormamide used.

2 Concentration in parts by volume of methacryloyl chloride to 100 parts by volume of dimethylformamide, measured at C.

IV. Subsequently, the esterified fabrics were immersed in an aqueous solution containing 4% 'by weight of zinc nitrate hexahydrate. The fabrics were drained free of excess solution and were oven-dried at C. for 4 minutes, followed by oven-curing at C. for 4 minutes. The samples were then washed in hot running tap water followed by oven-drying at 85 C. for 15 minutes. The properties of the treated fabrics are shown in Table IV.

The results show that curing the cellulose methacrylate fabric with zinc nitrate imparted wrinkle resistance to the fabric. The crease angles obtained were greater at the higher degree of cellulose esterification used. A degree of esterification corresponding to a weight gain even as low as 3.9% was sufficient to raise the crease angles by 50 above those of the untreated fabric.

EXAMPLE 5 Aluminum nitrate-catalyzed crosslinking of an acrylate ester of cellulose in fabric form A sample of 86 x 76 desized, scoured and bleached cotton printcloth weighing 3.2 oz./yd. was converted to an acrylate ester of cellulose in fabric form. It is shown above in Table II as sample 10. This esterified fabric was immersed in an aqueous solution containing 4% by weight of aluminum nitrate nonahydrate and 0.4% by weight of a nonionic wetting agent. The fabric, containing its maximum wet pickup of solution, was oven-dried at 85 C. for 4 minutes followed by oven curing at 150 C. for 4 minutes. The sample was washed in hot running tap water, and oven-dried at 85 C. for 15 minutes. The properties of the crosslinked fabric appear in Table V below. Fibers of the fabric cured with aluminum nitrate were found to be insoluble in cuene, indicating the cellulose acrylate had been highly crosslinked. The occurrence of molecular crosslinking is also indicated by the large increase in dry crease angle produced by the aluminum nitrate treatment.

TABLE V.ALUMINUM NITRAIE-CAIALYZED CROSSLINKING OF AN ACRYLAIE ESTER OF CELLULOSE IN FABRIC FORM A, acrylate ester preparation B, aluminum nitrate Goncen- Crease treatment crease trate Percent angles, angles, W+F acryloyl weight W+F chloride 2 gain dry Dry Wet Sample:

Treated 7. 12. 5 203 244 220 Control, untreated 176 156 1 Reaction time was 2 hours at 100 C.

2 Concentration in parts by volume of acryloyl chloride to 100 parts by volume of dimcthylformamide in the presence of g. or 08.0 ()3 for each 100 ml. of dimethylformamide used.

The results show that aluminum nitrate, although fairly EXAMPLE 7 active as a crosslinking catalyst, is much less effective in this respect than zinc nitrate.

The latter imparted 277288 dry crease angles to fabric esterified to weight gains of 7.0%13.5%, as shown in Table III of Example 3. Aluminum nitrate imparted a dry crease angle of only 244, even on a fabric esterified to a weight gain of 12.5%. The pH of the aluminum nitrate solution was 3.1, as compared to a pH of 4.2 for the zinc nitrate solution, showing aluminum nitrate is more acidic than zinc nitrate. Thus the catalytic effectiveness of a given metal nitrate cannot be attributed to its acidity in aqueous solution.

EXAMPLE 6 Cadmium nitrate-catalyzed crosslinking of an acrylate ester of cellulose in fabric form A sample of 86 x 76 desized, scoured and bleached cotton printcloth weighing 3.2 oz./yd. was converted to an acrylate ester of cellulose in fabric form by the method of Example 2 and is shown above as sample 11 in Table II. This sample was treated with an aqueous solution containing 4% by weight of cadmium nitrate tetrahydrate and 0.4% by weight of a nonionic wetting agent. The fabric while containing its maximum pickup of solution was placed in an oven and dried at 85 C. for 4 minutes, followed by oven curing at'150 C. for 4 minutes. The sample was washed in hot running water and oven-dried at 85 C. for 15 minutes. The properties of the crosslinked fabric appear in Table VI below. Fibers of the esterifled cellulosic fabric cured with cadmium nitrate were found to be insoluble in cuene, indicating they had been highly crosslinked. This is also indicated by the large increase in dry-crease angle produced by the cadmium nitrate treatment.

Zinc nitrate-catalyzed permanent creasing and crosslinkmg of an acrylate ester of cellulose in fabric form A sample of 86 x 76 desized, scoured and bleached cotton printcloth weighing 3.2 oz./yd. was converted to an acrylate ester of cellulose in fabric form by the method of Example 2 and is shown above in Table 2 as sample 9. This esterified fabric along with a portion of the unesterified fabric were immersed in an aqueous solution containing 4% by weight of zinc nitrate hexahydrate and 3 drops of liquid nonionic wetting agent per 50 grams of solution. The fabrics were placed in an oven, and ovendried at C. for 4 minutes. The samples were removed from the oven and pressed flat with a steam iron containing water and adjusted to the temperature of the steamwool setting. Then each fabric was folded in two and again pressed to introduce a sharp crease into the fabrics typical of creases normally applied to trousers. The creased fabrics were then oven-cured for 4 minutes at 150 C. The samples were washed in hot running tap water and oven-dried at 85 C. for 10 minutes. As a result the creased, esterified, crosslinked fabric retained a very sharp crease which could not be removed by hot ironing over the crease either when the fabric was dry or when first wetted with water. The unesterified fabric did not retain a crease, and it was diflicult to recognize the area where the crease had originally been introduced. The results show that a permanent crease durable to washing, drying, and even ironing was imparted to the zinc nitrate-catalyzed crosslinked acrylate cellulose ester in fabric form.

EXAMPLE 8 Comparison of various catalysts for the crosslinking of acrylate esters of cellulose in fabric form TABLE VI.CADMIUM NITRATE-CA'IALYZED CROSSLINKING OF AN ACRYLATE ESTER OF CELLULOSE IN FABRIC FORM A, acrylate ester preparation 1 B, cadmium nitrate Concon- Crease treatment crease trate Percent angles, angles, W+F acryloyl weight W-i-F", chloride 1 gain dry Dry Wet Sample Treated 7. 5 l4. 3 191 250 249 Control, untreated 176 156 1 Reaction time was 4 hours at C.

2 Concentration was in parts by volume of acryloyl chloride to 100 parts by volume of dimethyliormamide in the presence oi 10 g. of CaOOa per 100 ml. of dimethyltcrmamide.

The results show that cadmium nitrate was slightly more effective than aluminum nitrate, but much less effective than zinc nitrate, as a crosslinking and wrinkleproofing catalyst for the cellulose acrylate fabric. The pH of the cadmium nitrate solution used was 3.3, or less than for the zinc nitrate solution used in Example 3, but greater than for the aluminum nitrate solution of Example 5. Thus the order of catalytic effectiveness of these three metal nitrates cannot be attributed to their acidity or to the presence of free nitric acid in their aqueous solutions. 75 C. for

1 1 changes of hot tap water, blotted free of excess water and air-dried. The properties of the crosslinked fabrics appear in Table VII which follows.

TABLE VII.COMPARISON OF CATALYSTS FOR THE CROSS- LINKING OF ACRYLATE ES- lonlc wetting agent present.

The results show that of the various zinc salts tried, only zinc nitrate was an effective catalyst for the crosslinking of cellulose acrylate fabric to impart enhanced wrinkle resistance. The failure of zinc perchlorate to catalyze crosslinking demonstrates that the catalytic activity of the zinc salt of a given acid cannot be predicted from the strength of that acid as an oxidizing agent. The results also show nitric acid to be less etfective than zinc nitrate as a crosslinking catalyst for the present process. The failure of zinc chloride and zinc fiuoborate to catalyze the crosslinking reaction shows that the effectiveness of a given metal salt as catalyst for the present process cannot be predicted from the effectiveness of that metal salt as a Friedel-Crafts catalyst.

We claim:

1. A process for imparting wrinkle resistance to cellulosic fabrics comprising:

(a) conversion of a cellulosic fabric to an alpha,betaunsaturated carboxylic ester of cellulose in fabric form, said ester having the molecular structure wherein R is a radical selected from the class consisting of methyl and hydrogen radicals, and cell denotes a portion of a cellulose chain, the ratio of said unsaturated ester groups to anhydroglucose units in the cellulose being about from 0.10 to 0.50,

(b) impregnating the fabric with an aqueous solution containing about from 1% to 8% by weight of a catalyst selected from the group consisting of zinc nitrate, aluminum nitrate and cadmium nitrate,

12 (c) drying the fabric at about from C. to C.

for about from 2 minutes to 10 minutes, and (d) curing the fabric at about from C. to C.

for from 1 minute to 10 minutes. 2. The process of claim 1 wherein R is hydrogen and the catalyst is zinc nitrate.

3. The process of claim 1 wherein R is hydrogen and the catalyst is aluminum nitrate.

4. The process of claim 1 wherein R is hydrogen and the catalyst is cadmium nitrate.

5. The process of claim 1 wherein R is methyl and the catalyst is zinc nitrate.

6. A process for imparting Wrinkle resistance and permanent creases to cellulosic fabrics comprising:

(a) conversion of a cellulosic fabric to an alpha,betaunsaturated carboxylic ester of cellulose in fabric form, said ester having the molecular structure wherein R is a radical selected from the class consisting of methyl and hydrogen radicals, and cell denotes a portion of a cellulose chain, the ratio of said unsaturated ester groups to anhydroglucose units in the cellulose being about from 0.10 to 0.50,

(b) impregnating the fabric with an aqueous solution containing about from 1% to 8% by weight of a catalyst selected from the group consisting of zinc nitrate, aluminum nitrate and cadmium nitrate,

(c) drying the fabric at about from 60 C. to 110 C.

for about from 2 minutes to 10 minutes, and

(d) creasing the fabric, and

(e) curing the fabric at about from 140 C. to 170 C.

for from 1 minute to 10 minutes.

7. The Wrinkle-resistant fabric prepared by the process of claim 1.

8. The wrinkle resistant and permanently creased fabric prepared by the process of claim 6.

References Cited Frick et al.: Textile Research Journal, vol. 27, pp. 92- 99 (1957).

GEORGE F. LESMES, Primary Examiner J. CANNON, Assistant Examiner U.S. Cl. X.R.