US 3776692 A
Cellulosic fabrics are treated with formulations containing methylol crosslinking reagents and polycarboxylic acids having three or more acidic groups per molecule. The treated fabrics are cured in a flat configuration and washed. The fabric is subsequently heated in a folded configuration whereby the folded or creased configuration is permanently imparted to the fabric.
Description (OCR text may contain errors)
United States Patent [1 1 Franklin et al.
I RECURABLE CROSSLINKED CELLULOSIC FABRICS FROM METHYLOL REACENTS AND POLYCARBOXYLIC ACIDS Inventors: William E. Franklin; Stanley P.
Rowland, bothof New Orleans, La.
The United States of America as represented by the Secretary of Agriculture, Washington, DC.
Filed: Apr. 27, 1972 Appl. N0.: 248,200
US. Cl 8/181, 8/182, 8/183, 8/185, 8/184, 8/186, 8/187, 8/1 16.4, 8/120, 8/115.7, 260/231 A, 260/234 R Int. Cl.D06m 15/56, D06m 13/20, D06m 13/14 Field of Search 8/1 16.3, 116.4, 120, 8/181,182,183,184,-186,185,l87
References Cited OTHER PUBLICATIONS Berni et al., Textile Research Journal, 40, 377-385 (1970). Soignet et al., Textile Research Journal 38, 1143 (1968).
3,776,692 Dec 4, 1973 Primary Examiner-George F. Lesines Assistant Examiner-J. Cannon Attorney- M. Howard Silverstein V  ABSTRACT Cellulosic fabrics are treated with formulations containing methylol crosslinking reagents and polycarboxylic acids having three or more acidic groups per molecule. The treated fabrics are cured in a flat configuration and washed. The fabric is subsequently heated in a folded configuration whereby the folded or creased configuration is permanently imparted to the fabric.
22 Claims, No Drawings RECURABLE CROSSLINKED CELLULOSIC FABRICS FROM METHYLOL REAGENTS AND POLYCARBOXYLIC ACIDS A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout all the world for all purposes of the Unites 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 chemical treatment of cellulosic textiles. Specifically,this invention relates to imparting durable configurations to cellulosic textile products. More specifically, this invention relates to the chemical treatment of cellulosic textiles with mixtures containing a methylol crosslinking reagent and a polycarboxylic acid to produce a product consisting of a crosslinked cellulose derivative having acidic, catalytic groups convalently bondedto the cellulose. More specifically yet, this invention relates to the production of cellulosic textiles having the properties of wrinkle resistance and smooth drying, but which can be given a heat treatment subsequent to the cure in order to impart a new durable crease or other configuration to the textile product. By the process of the instant invention, cellulosic textiles, garments, and other products may be treated to give them the properties generally known as durable press, except that the textiles, garments, or other products may be given a heat treatment at any time subsequent to the cure, thereby imparting durable creases, pleats, or other desired configuration to the textile products. This invention constitutes a process which is useful in the preparation of improved cellulosic fabrics or improved blended fabrics.
The main object of this invention is to provide treated textiles or textile products which have smooth drying and wrinkle-resistant properties, but which can be given a heat treatment at any time subsequent to the curing step of the finishing operation in order to impart new, permanent creases, pleats, or other desired configurations to thefabric.
. Another object of this invention is to provide textile treating compositions, formulations, and methods which can be used in conventional textile treating processes to produce wrinkle-resistant cellulosic textile products which can be permanently creased or pleated at any time subsequent to a conventional precure or postcure step by a further heat treatment.
BACKGROUND AND PRIOR ART It is well known to those versed in the art of textile treatment that wrinkle-resistance and smooth-drying properties are imparted to cellulosic or cellulosic blended fabrics by chemical treatments which establish crosslinks between the molecules of the cellulosic fibers. The crosslinks bind the fibers, and therefore the fabric, in the configuration present at the time the crosslinks are established. The covalent nature of the crosslinks makes it impossible to change the configuration of the treated fabric without a chemical reaction which involves breaking crosslinks and reformin them in new positions to bind the fibers, and therefore the fabric in the new configuration. Conventional delayed cure processes are useful for imparting creases or other desired configurations to textile products, but do not solve the problem of unalterability of finished cellulosic textile products.
In examining the prior art for solutions to this problem of unalterability of crosslinked cellulosic textile products, we find several approaches to solutions of this problem. One approach is through the use of thermally reversible crosslinks, that is, crosslinks which break and reform in new positions when heated. Examples of such crosslinks are those containing partial chemical structure such as Diels-Alder adducts, aryl biscarbamates, and partial esters of polycarboxylic acids. Fabrics with crosslinks such as these can be given heat treatments to impart new, durable configurations, but long periods of heat at high temperatures are required to impart sharp, durable creases in these fabrics, and the fabrics do not have the high wrinkle resistance and smooth drying properties required of durable-press fabrics.
Another approach to alterable, crosslinked cellulosic fabrics is through internally catalyzed fabrics, that is, fabrics containing catalytic groups convalently bonded to the cellulose of the fibers, along with conventional crosslinks. An example of such a fabric is one prepared by first reacting a cotton fabric with reagents which bond quaternary ammonium hydroxide groups to the cellulose, then reacting the resulting fabric with divinyl sulfone to introduce crosslinks into the cellulose. Such a fabric has high resilience and can be given new, durable configurations by heat treatments, but the manufacture of such a fabric requires a number of steps and unusual reagents, and therefore is not widely accepted by textile manufacturers on the basis of its high cost.
On further examination of the prior art, one finds that polycarboxylic acids are used as crosslinking reagents in processes for producing wrinkle-resistant cotton textiles. In these processes, polycarboxylic acids are used as a sole crosslinking agent and produce a modified textile fabric having partial ester crosslinks, that is, part of the carboxyl groups of the reagents are in the form of ester groups bonding the reagent and the cellulose molecules, and the remainder of the carboxyl groups are in the form of free acidic groups bonded to the cellulose matrix.
In searching the prior art it is also found that numerous carboxylic acids are used as catalyst for crosslinking reactions of methylol reagents with cellulose. These carboxylic acids are used, either alone or in conjunction with other catalysts, in small, catalytic amounts to promote crosslinking reactions of the methylol re nts ut t,. 's..n the. ractice o mam? a y out the crosslinking reactions in such a manner that large amounts of the carboxylic acids become permanently attached to the cellulose.
It is also found in the prior art that crosslinkedcellulosic fabrics may be given new, durable configurations when a catalyst isapplied to the cured fabric and the fabric is given a heat treatment. In these processes of the prior art, the ability to accept a new, permenent configuration is dependent on the added catalyst, which is not bonded to the fabric but may be washed out of the fabric with water. The reagents employed in this type or recuring process are usually strongcatalysts, and consequently have deleterious effects on the strength of the fabric and the durable press properties of the treated areas of the fabric.
THE NEW INVENTION We have now discovered that cellulosic textile products may be impregnated with aqueous solutions of a conventional methylol crosslinking reagent and a polycarboxylic acid containing three or more carboxyl groups per molecule, dried, and cured, and that the re sulting textile product has high wrinkle resistance and smooth drying properties and may or may not be washed to remove excess reagents and may be given a heat treatment to impart new, permanent creases, pleats, or other desired configurations to thetextile product. The essence of this recovery may be stated as follows: Recurable durable-press fabrics may be produced by reacting cellulosic textile products with combinations of methylol reagents and polycarboxylic acids. in this statement the terms recurability and durable press may be defined as follows: Durable press (as applied to cellulosic fabrics) may be defined as having the properties of high wrinkle resistance, good smooth-drying appearance, and excellent retention of creases imparted to the fabric during the cure. Durable press properties are generally imparted to cellulosic fabrics by reactions which form crosslinks in the cellulose. Recurability may be defined as the property of crosslinked cellulosic fabrics being able to accept new, durable configurations when subjected to a heat treatment, by virtue of a chemical reaction which breaks the crosslinks and reforms them in new positions.
In the process of this invention, the polycarboxylic acid serves two essential functions: (a) by virtue of its acidic nature, the polycarboxylic acid serves as the catalyst for the crosslinking reaction of the methylol reagent with the cellulose of the fibers, and (b) the polycarboxylic acid reacts with the cellulose to form partial ester groups which have free carboxylic acid groups which are able to catalyze the breaking and reformation of the crosslinks from the methylol reagent. The structure of the modified cellulose may be depicted as follows:
In the practice of the invention, substantially any cellulosic textile material may be used, but our preferred materials are textile materials made either entirely of cotton fibers or of cotton fibers blended with other natural or synthetic fibers. The cellulosic textile material is impregneted with an aqueous solution containing from 8 to 40 percent of a methylol crosslinking reagent and from 3 to 12 percent of a polycarboxylic acid. The
solution may also contain other useful textile finishing agents, suchas wetting agents or polymeric softeners. The preferred concentrations of the methylol reagents in the treating solutions are from 8 to l2 percent, depending on the weave of the fabric, and the preferred concentration of the polycarboxylic acid is from 25 to 50 percent of that of the methylol reagent.
The methylol crosslinking reagent may be any of the conventional crosslinking reagents used for finishing cellulosic fabrics. The preferred reagent is dimethyloldihydroxyethyleneurea, but other reagents which also may be used include methylated methylol melamines, methylated ureaformaldehyde reagents, methylolated carbamates, formaldehyde, methylol urons, dimethylolpropyleneurea, methylol triazones, and dimethylolethyleneurea.
The polycarboxylic acid may be any acid organic compound having three or more carboxylic acid groups per molecule and which is soluble in water to the extent required in a treating solution. The preferred polycarboxylic acids are cyclopentanetetracarboxylic acid and tetrahydrofurantetracarboxylic acid. Other carboxylic acids which may be used include melletic acid, nitrilotriacetic acid, (ethylenedinitrilo)tetraacetic acid, pyromellitic acid, tris(carboxyethyl)isocyanurate, naphthalenetetracarboxylic acid, and benzophenonetetracarboxylic acid.
After the cellulosic textile is impregnated, it may be dried immediately or it may be stored in the wet state or subjected to a fixation process before it is dried. The methylol reagentmay also be fixed to the cotton fabric, the fabric washed, and the polycarboxylic acid applied in'a second impregnation step. The impregnated and dried textile may be cured immediately or it may be stored or manufactured into garments or other useful articles before it is cured. The curing step consists of a high temperature treatment carried out in an oven or apparatus such as a hot head press. The curingstep may be carried out at any temperature between C and 205C, and for times varying between 15 seconds and 12 minutes. The preferred curing conditions are eight minutes at C, in either a forced draft oven or a tenter frame. The cured textile may be washed with water containing a non-ionic detergent to remove unreacted reagents, but this washing is not essential. The cured textile, prepared according to the preferred conditions, has a conditioned wrinkle recovery angle of 270 to 295 (W+F) if no softener is used in the treating solution, and 290 to 3l0 (W-l-F) if a softener is used. Textile fabrics prepared according to the preferred conditions of this invention have strength retentions comparable to conventional durable press fabrics.
The cured fabric of this invention is subjected to a heat treatment during which it is constrained in the new desired configuration. The textile may be constrained by folding it in the desired configuration and applying pressure from a hand iron or other heated object. This may also be accomplished with a stream or electrically heated hot-head press. Pressure may be applied in order toproduce sharp creases. The textile may be wet or dry when it is constrained and heated, but of course it becomes dried during the heating. The temperatures of the heat treatment may vary between 130C and 205C, and the time of th heat treatment may vary from 15 seconds to 8 minutes. In the preferred process, the textile is wet, folded at the position of the desired new crease, placed on a preheated surface. and covered with a heated hot iron. The temperature in the textile is maintained at 160C and the textile is held at this temperature for 4 to 5 minutes.
If the cured textile has been washed with an alkaline detergent, it may lose its ability to accept durable creases or other configurations when subjected to a heat treatment. in this case, the recurability of the fabric may be restored by soaking it for a short time in a very dilute solution of an acid, for example a solution of 5 percent or less of acetic acid in water. After this acid treatment, the fabric may be creased by the usual heat treatment as described above.
Fabrics prepared and given heat treatments according to the processes of this invention permanently retain the creases or other configurations imparted by the heat treatments. Thus, textiles prepared by the preferred process and given creases according to the preferred heat treatments retain creases rated at 4.0 or better according to the AATCC cease appearance test after five machine wash and tumble dry cycles.
SUMMARY This invention can be summarized as a new process and cellulosic ether derivatives produced by the new process, the cellulosic derivatives being those resulting from reactions involving polycarboxylic acids and dior poly functional methylol agents.
The process, which imparts to cellulosic textiles high resilience and smooth-drying qualities and the capability of responding to thermal formation and reformation at any time after the cure, comprises:
a. impregnating the cellulosic textile with an aqueous solution containing:
1. a methylol crosslinking agent selected from the group consisting of formaldehyde dimethylolpropyleneurea bis(methoxymethy1)uron tris(methoxymethyl)urea dimethyloltriazone dimethyloldihydroxyethyleneurea highly methylated, fully-methylolated melamine dimethylolethyleneurea dimethylolmethylcarbamate, and partially-methylated trimethylolmelamine; and
2. a polycarboxylic acid having 3 or more carboxylic acid groups to the molecule, said polycarboxylic acid being selected from the group consisting of: melletic acid pyromelletic acid nitrilotriacetic acid cyclopentanetetracarboxylic acid (ethylenedinitrilo)tetracetic acid tetrahydrofurantetracarboxylic acid tris(carboxyethyl)isocyanurate naphthalenetetracarboxylic acid, and benzophenonetetracarboxylic acid;
b. curing the impregnated cellulosic textile for about 2 to 12.5 minutes at temperatures about from 130 to 205C,
c. optionally washing the cured cellulosic textile with a non-ionic detergent and drying-the washed cellulosic textile, and
d. optionally subjecting the cellulosic textile to a hea treatment while constrained with or without pressure for about from 0.25 to 8 minutes at a temperature of about from 130 to 205C.
Note: There are instances where a drying step would be more suitable prior to the curing step of the process.
The following list of examples is presented to illustrate this invention and is not meant to limit its scope in any manner whatever.
EXAMPLE 1 Cotton twill fabric (7.6 oz/yd was impregnated to percent wet pick-up with a solution containing 12% of dimethyloldihydroxyethyleneurea (DMDHEU), 6 percent of cyclopentanetetracarboxylic acid (CPTA), 2 percent of an emulsified polyethylene softener, and 0. 1 percent of a non-ionic wettigg gent. The fabric was dried on a pin frame in a forced draft over for 8 minutes at 70C, then cured in the same equipment for 8 minutes at C. After washing in water with a non-ionic detergent, the fabric had an add-on of 9.1 percent and a conditioned wrinkle recovery angle (WRA) (determined by the procedure of ASTM designation B1295-67) of 306 (W+ F), a wet WRA of276 (W+ F), a Stoll flex abra sio n resistance in the warp direction (determined by the method of ASTM designation D1 -64 T) of 30 percent of that of the unmodified, laundered fabric, and a tearing strength in the fill direction (measured by the Elmendorf method, as described in ASTM Designation D 1424-63) of 50 percent of that of the unmodified control. These physical properties are similar to those of cotton fabrics treated by conventional durable press processes.
A portion of the fabric was analyzed for nitrogen by the Kjeldahl method and for formaldehyde by the chromotropic acid method. The fabric was found to contain 1.29% N and 1.43% formaldehyde. Another portion of the fabric was analyzed for saponification equivalent by a modification Eberstadt method (as described by Tanghe, et al. in Methods of Carbohydrate Chemistry, Vol. 111, R. L. Whistler, Ed, 1963, pp. 201-203) and free carboxyl groups by a titration (as described by Reinhardt, Fenner, and Reid in Textile Research Journal, Vol. 27, p. 873 (1957)). The fabric was found to contain 0.54 meq/g of saponifiable groups (ester and carboxyl) and 0.33 meq/g of free carboxylic acid groups. These analyses indicate that the textile contained crosslinks from the methylol reagent dimethyloldihydroxyethyleneurea (DMDHEU, chemically known as 1,3-bis(hydroxymethyl)-4,5-dihydroxy-2- imidazolidinone) and ester and free carboxylic acid groups from the polycarboxylic acid cyclopentanetetracarboxylic acid. The textile therefore consisted of the cellulosic derivative, the l,3-dimethylene-4,5-dihydroxy-2-imidazolidinone ether of cellulose cyclopentanetetracarboxylate.
EXAMPLE 2 A portion of the textile prepared according to Example 1 was soaked in distilled water, folded so that the warp yarns were bent, and placed on a pre-heated cloth surface. A thermocouple was placed between the sides of the fabric sample and the assembly was covered with a heated hand iron. The temperature of the iron was controlled by an apparatus attached to the thermocouple. The fabric sample was heated at 160C for 5 minutes. After the creasing treatment, the fabric sample was rinsed in hot, running water, then stapled to a towel and subjected to five machine washing and tumble drying cycles. After the last drying cycle, the crease remaining in the fabric sample was evaluated by the AATCC method (AATCC Test Method 88 C-1969) modified as described by Hobart in Textile Research Journal, Vol. 37, p. 380 (1967). The crease retained in this fabric after the laundering cycles was rated at 4.3 on the AATCC scale (running from no crease to excellent). This example indicates that good, very durable creases are imparted to fabrics prepared according to Example 1 and treated according to this Example by a heat treatment. The most reasonable explanation for the formation of durable creases in the heat treatment is that a recure (as defined above) occurred during the heat treatment and was catalyzed by the free acid groups in the fabric.
EXAMPLE 3 Cotton twill fabric was treated according to the process of Example 1 except that it was dried at 70C for 4 minutes in a tenter frame and cured at 160C for 4 minutes in the tenter frame. This fabric had a conditioned WRA of 292 (W+F). Other physical and chemical tests gave results similar to those in Example 1. This fabric was given a heat treatment according to the process of Example 2. After the five laundering cycles the fabric retained a crease with an AATCC crease rating of 5.0
EXAMPLE 4 Cotton twill fabrics were treated according to the process of Example 1 except that the curing times were varied from 30 seconds to 6 minutes. The fabric samples were given heat treatments according to the process of Example 2. The conditioned WRA and the AATCC crease ratings after five launderings are reported in Table I.
TABLE I Cure Time Cond. WRA AATCC Crease (min.) (,W+F) Rating 0.5 260 4.6 1.0 273 5.0 2.0 280 4.9 3.0 279 5.0 4.0 286 4.9 5.0 278 4.6 6.0 287 4.5
EXAMPLE 5 Cotton twill fabric was treated according to Example 1 except that different concentrations of various polycarboxylic acids were used in the treating solutions. These fabrics were creased according to the procedure of Example 2. The conditioned WRA and AATCC crease ratings after five launderings are given along with the name and concentration of the polycarboxylic acids in Table ll Cotton printcloth (3.2 oz/yd) was impregnated with a solution containing 8 percent of DMDHEU, 6.3% of a polycarboxylic acid, and a trace of a non-ionic wetting agent. The impregnated fabric samples were dried and cured according to the procedure of Example I. The cured fabrics were creased according to the procedure of Example 2. The concentration of DMDHEU, the polycarboxylic acid and its concentration are given along with the conditioned WRA and the AATCC rating of the crease remaining after the five laundering cycles are given in Table III.
TABLE II! Polycarboxylic Acid Cond. WRA AATCC Crease (.W+F) Rating Mellitie Acid 283 2.8 Tris(carboxyethyl)isocyanurate 258 2.8 Benzophcnonetetracarboxylic Acid 286 4.2
EXAMPLE 7 Samples of cotton printcloth were impregnated with solutions containing 8 percent of a methylol crosslinking reagent, 4 percent of CPTA, 2 percent of a polyethylene softener, and a trace of a non-ionic wetting agent. The fabric samples were dried and cured according to the process of Example 1 and creased according to the process of Example 2. The methylol crosslinking reagents, conditioned WRA and AATCC crease ratings after five laundering cycles are given in Table IV.
Table IV Methylol Reagent Cond. WRA AATCC Crease W+F) Rating Formaldehyde 309 1.0 Dimethylolpropyleneurea 258 2.3 Bis(mcthoxymethyl)uron 298 3.5 Tris(methoxymethyl)urea 311 4.0 Dimethyloltriazone 296 3.8 Dimethyloldihydroxyethyleneurea 318 4.0 Highly methylated, fully methylolated melamine 298 3.0 Dimethylolethyleneurea 230 2.0 Dimethylolmethylcarhamate 261 0.6 Partially methylated trimethylolmelamine 240 2.1
EXAMPLE 8 Cotton twill fabric was impregnated with a solution containing 20 percent of DMDHEU, 20 percent of a highly methylated fully methylolated melamine, and sufficient hydrochloric acid to lower the pH of the solution to 2.0. The fabric was stored in the wet state for 24 hours, then washed to remove the excess reagents. The fabric was then impregnated with a solution containing 15 percent of mellitic acid, dried for eight minutes at C, and cured for 12.5 minutes at C. The cured fabric had a conditioned WRA of 265 (W+F). This fabric was creased according to the process of Example 2. After five laundering cycles it had an AATCC crease rating of 3.3.
EXAMPLE 9 Cotton twill fabric was impregnated and dried according to the process of Example 3. Portions of this fabric were cured by heating them in an electrically heat hot-head press for 2 minutes at various temperatures between l30 and 205C. These fabric samples all had very good smooth drying appearances and retained creases which were present during the heating process to repeated washing and drying cycles. This demonstrates that at least a fair cure was obtained in all of the samples by heating them in a hot-head press.
EXAMPLE 1O Portions of the fabric prepared and cured in Example 3 were creased according to the process of Example 2, except that a series of different times and temperatures were used for the heat treatments. The times and temperatures of the heat treatments are given along with crease ratings of the fabrics after five washing and drying cycles in Table V.
A portion of the cotton twill fabric treated according to the process of Example 3 was creased according to the process of Example 2. After five laundering cycles it had an AATCC crease rating of 4.0. Another portion of the fabric prepared according to Example 3 was given one washing cycle with an alkaline detergent, followed by tumble drying. This washed fabric was creased according to the process of Example 2. After five machine wash and dry cycles this fabric'retained a crease with an AATCC crease rating of 1.7. A portion of the fabric washed with the alkaline detergent was soaked in a water solution containing 5 percent acetic acid for 30 minutes, then rinsed with distilled water. The acidified fabric was creased according to the process of Example 2. After five washing and drying cycles this fabric retained a crease with an AATCC crease rating of 3.7.
EXAMPLE 12 I method-s given in Example I. The fabric was found to contain 1.14 percent nitrogen, 1.22 percent formaldehyde, 0.33 meq/g of saponifiable groups, and 0.21 meq/g of free carboxyl groups. These analyses indicated that the textile contained crosslinks from the methylol reagent dimethyloldihydroxyethyleneurea (DMDHEU, chemically known as 1,3- bis(hydroxymethyl)-4,5-dihdroxy-2-imidazolidinone) and ester and free carboxylic acid groups from the polycarboxylic acid tetrahydrofurantetracarboxylic acid. The textile therefore consisted of the cellulosic derivative, the l,3-dimethylene-4,5-dihydroxy-2- imidazolidinone ether of cellulose tetrahydrofurantetracarboxylate.
1. A process for imparting to a cellulosic textile high resilience and smooth-drying qualities and capability of responding to thermal formation and re-formation at any time after the cure, the process comprising: a. impregnating the cellulosic textile with an aqueous solution containing:
1. about from 8 to 40 percent of a methylol crosslinking agent selected from the group consisting of: formaldehyde, dimethylolpropyleneurea, bis(methoxymethyl)uron, tris(methyoxymethyl)urea, dimethyloltriazone, dimethyloldihydroxyethyleneurea, highly methylated, fully-methylolated melamine, dimethylolethyleneurea, dimethylolmethylcarbamate, and partially-methylated trimethylolmelamine; and
2. about from 3 to 12 percent of a polycarboxylic acid having 3 or more carboxylic acid groups to the molecule, said polycarboxylic acid being selected from the group consisting of:
melletic acid, pyromelletic acid, nitrilotriacetic acid, cyclopentanetetracarboxylic acid, (ethylenedinitrilo )tetracetic acid, tetrahydrofurantetracarboxylic acid, tris(carboxyethyl)isocyanurate, naphtha]enetetracarboxylic acid, and benzophenonetetracarboxylic acid; and
b. curing the impregnated cellulosic textile for about from 2 to 12.5 minutes at a temperature of about from to 205C.
2. The process of claim 1 wherein the crosslinking agent is formaldehyde.
3. The process of claim 1 wherein the crosslinking agent is dimethylolpropyleneurea.
4. The process of claim 1 wherein the crosslinking agent is bis(methoxymethyl)uron.
5. The process of claim 1 wherein the crosslinking agent is tris(methoxymethyl)urea.
6. The process of claim 1 wherein the crosslinking agent is dimethyloltriazone.
7. The process of claim 1 wherein the crosslinking agent is dimethyloldihydroxyethyleneurea.
8. The process of claim 1 wherein the crosslinking agent is highly methylated, fully-methylolated melamine.
9. The process of claim 1 wherein the crosslinking agent is dimethylolethyleneurea.
10. The process of claim 1 wherein the crosslinking agent is dimethylolmethylcarbamate.
11. The process of claim 1 wherein the crosslinking agent is partially-methylated trimethylolmelamine.
12. The process of claim 1 wherein the polycarboxylic acid is melletic acid.
13. The process of claim 1 wherein the polycarboxylic acid is pyromelletic acid.
14. The process of claim 1 wherein the polycarboxylic acid is nitrilotriacetic acid.
15. The process of claim 1 wherein the polycarboxylic acid is cyclopentanetetracarboxylic acid and the cross-linking agent is dimethyloldihydroxyethyleneurea.
16. The process of claim 1 wherein the polycarboxylic acid is (ethylenedinitrilo)tetraacetic acid.
17. The process of claim 1 wherein the polycarboxylic acid is tetrahydrofurantetracarboxylic acid and the cross-linking agent is dimethyloldihydroxyethyleneurea.
18. The process of claim 1 wherein the polycarbox- 5 ylic acid is tris(carboxyethyl)isocyanurate.
19. The process of claim 1 wherein the polycarboxylic acid is naphthalenetetracarboxylic acid.