Durable Press Process For Treating Cellulosic Material With Methylolamides And Acetic Acid Or Formic Acid Vapors

Abstract

The dimensional stability, wrinkle resistance, smooth drying characteristics and total shape retentivity of cellulosic materials such as cotton fabrics are improved by treatment with acetic acid or formic acid vapors after impregnation of the materials with an aqueous solution of a water-soluble crease-proofing agent containing reactive N-methylol groups such as trimethylolmelamine or DHDMEU, whereby the cellulosic fibers become crosslinked.

Parent Case Text

CROSS-REFERENCE

This application is a continuation-in-part of Ser. No. 762,119, which was filed Sept. 24, 1968 and is now U.S. Pat. No. 3,653,805.

Description

BACKGROUND OF THE INVENTION

In recent years various methods have been devised for treating cellulosic fiber-containing products, such as cloth made of cotton or cotton blends, in order to impart durable crease resistance and smooth drying characteristics thereto. For example, cellulosic materials have been crosslinked with formaldehyde, giving durable crosslinks having good resistance to repeated laundering and also to various acids and alkalis, and chlorine bleaches. These formaldehyde treated cellulosic materials have certain advantageous features. For example, they are resistant to discoloration and yellowing.

However, while formaldehyde has made a significant contribution to the cotton finishing art, the results have been far from perfect. For instance, in some cases the formaldehyde crosslinking treatment has tended to lack reproducibility, since control of the formaldehyde crosslinking reaction heretofore has been difficult. When high curing temperatures were used with an acid or potential acid catalyst, overreaction and degradation of the cotton often happened which considerably impaired its strength. On the other hand, when attempts were made to achieve reproducibility at temperatures of 50.degree.C. or less, much longer reaction or finishing times were usually required, rendering the process economically relatively unattractive. See for example, British Patent 980,980. In other cases, formaldehyde crosslinking has not been able to meet commercial standards with respect to dry wrinkle recovery. For these and similar reasons, efforts have been continuing to develop new and better cellulosic and cotton finishing processes.

The use of an atmosphere containing hydrochloric acid to catalyze crosslinking between a crease-proofing agent and a cellulosic fabric material in which the agent is impregnated has been suggested in the prior art. Control of such a reaction is difficult but important since the strong mineral acid catalyst may degrade the fabric itself. Hydrochloric acid-catalyzed fabric materials also have been found to have low tensile strength properties, particularly if the crosslinked fabric is post-heated.

SUMMARY OF THE INVENTION

Accordingly, a primary object of the present invention is to provide a practical process for treating cellulosic materials with a suitable crease-proofing agent which process substantially prevents or alleviates the problems mentioned above.

A more specific object has been to develop a process for crosslinking cotton with the aid of a water-soluble crease-proofing agent containing reactive N-methylol groups, using an acid catalyst used in the vapor phase, so as to keep fiber injury to a minimum.

Another more specific object is to provide a process for crease-proofing cotton or other cellulosic materials using a water-soluble crease-proofing agent containing reactive N-methylol groups which permits the cure of the treated material to be safely delayed for long or indefinite periods until after completion of desired articles therefrom including, for instance, the cutting, sewing and pressing of garments.

Another specific object is to provide a crease-proofing process for use with cellulosic materials which produces good wrinkle recovery and smooth drying characteristics, keeps loss of tensile strength and abrasion resistance to a minimum, gives good laundering life and chlorine resistance, employs simple reactants and, if desired, can produce a pre-treated fabric which is relatively insensitive to surrounding conditions and has virtually infinite shelf life prior to final cure.

It is further an object of this invention to provide a process for treating cellulosic materials with an acidic catalyst in the vapor phase without the degrading characteristics of strong mineral acids such as hydrochloric acid.

These and other objects, as well as the scope, nature, and utilization of the invention will become more clearly apparent from the following more detailed description. Unless otherwise indicated, all proportions and percentages of materials or compounds are expressed on a weight basis throughout this specification and appended claims.

In accordance with the present invention, a process is provided for improving the dimensional stability, wrinkle resistance, smooth drying characteristics and total shape retentivity of a cellulosic fiber-containing fabric which comprises: (a) applying to the fabric an aqueous solution of a water-soluble crease-proofing agent containing reactive N-methylol groups; and (b) heating the impregnated fabric containing the water-soluble crease-proofing agent containing reactive N-methylol groups in a non-reactive vapor atmosphere containing a catalyst selected from the group consisting of formic acid and acetic acid to a temperature between above 80.degree.C. up to about 160.degree.C. for a time of between about 10 seconds and 2 hours until the cellulose fibers become effectively crosslinked.

The process requires relatively short reaction times and gives high wrinkle recoveries while at the same time producing satisfactory tensile and tear strengths.

The process of the present invention has substantial advantages of use as compared with typical prior art processes such as hydrochloric acid vapor-catalyzed durable press systems. For example, the process of the present invention prevents excessive degradation of cellulosic fibers and does not require neutralization of the fabric after treatment. Also, there is no need for an afterwash of the fiber. Reproducibility of the reaction is substantially improved and special controls and equipment for handling the highly toxic and corrosive hydrochloric acid is not necessary.

DESCRIPTION OF PREFERRED EMBODIMENTS

In the embodiment disclosed and claimed herein, the cotton or cellulose-containing fabric is impregnated with an aqueous solution containing about 1 to about 40 percent, preferably from about 2 to about 20 percent, most preferably from about 5 to 15 percent, of a water-soluble crease-proofing agent containing reactive N-methylol groups to give a wet pick-up of between about 50 and about 100 percent, preferably from about 60 to about 90 percent, most preferably from about 65 to 85 percent, based on dry fabric weight.

The present invention is useful for treating various natural or artificial cellulosic fibers alone or as mixtures with each other in various proportions or as mixtures with other fibers. Such natural cellulosic fibers include cotton, linen and hemp, and regenerated or artificial cellulosic fibers useful herein include, for example, viscose rayon and cuprammonium rayon. Other fibers which may be used in blends with one or more of the above-mentioned cellulosic fibers are, for example, cellulose acetate, polyamides, polyesters, polyacrylonitrite, polyolefins, polyvinyl chloride, polyvinylidine chloride and polyvinyl alcohol fibers. Such blends preferably include at least about 20 percent by weight and most preferably at least about 40 percent by weight, of cotton or other cellulosic fibers.

The fabric may be knit, woven or non-woven, or be any otherwise constructed fabric. The fabric may be flat, creased, pleated, hemmed or sewn or otherwise formed to produce an article such as a garment of any desired shape prior to contact with the acetic acid or formic acid catalyst-containing atmosphere. After processing, the formed crosslinked fabric will maintain substantially the original configuration for the life of the article, that is, a wash-wear or durable press fabric will be produced.

The crease-proofing agents useful herein include particularly the easily hardenable precondensates which are substantially water soluble and are obtained by condensation of formaldehyde with a compound such as a lower alkyl substituted melamine, a urea, or a phenol such as resorcinol. As is well known in the resin treating art, these precondensates are capable of being applied to the cellulosic material from an aqueous solution. Triazines obtained by condensing a lower alkyl substituted melamine and formaldehyde are examples of such precondensates. Good results are obtained, for instance, using precondensates obtained by condensing 1 mole of melamine or an alkyl substituted melamine with 2 to 6 moles of formaldehyde, i.e., using di-, tri- or hexamethylol melamine. Commercially available products of this kind include Aerotex 23, a triazine-formaldehyde precondensate; Aerotex M--3, a melamine-formaldehyde condensate; Aerotex P-225, hexakis-(methoxymethyl) melamine; and Aerotex 19, which is a less completely fractionated modification of Aerotex P-225. These products are supplied in the form of aqueous solutions by American Cyanamid Company.

Other suitable crease-proofing agents include products such as dihydroxydimethylolethyleneurea, DHDMEU, available as Permafresh 183 or in a somewhat modified, less reactive form as Permafresh 113B from Sun Chemical Company, as well as modified propylene urea compounds such as Fixapret PCL, available from Badische Anilin und Soda-Fabrik. Compounds having at least 11/2 moles of formaldehyde combined as methylol formaldehyde with a cyclic urea or cyclic propylene urea are suitable and the dimethylol derivatives are preferred. However, it is similarly feasible to use other known crease-proofing agents such as N-methylol carbamates and methylol urea compounds.

Pretreatment of the cloth, prior to the vapor phase catalytic treatment, with polymeric resinous additives that form soft films, such as conventional dispersions or latexes, can result in an unusually great incremental improvement in wrinkle recovery of the treated fabric. Polymer additives can also improve the flex abrasion resistance and tear strength, or alter the ratio of dry wrinkle recovery to wet wrinkle recovery, or in some instances shorten the reaction time needed to produce an acceptable durable press fabric. Polymeric additives suitable for such purposes are, in most cases, available commercially in concentrated aqueous latex form, and it is desirable to dilute these to a concentration of 1 to 10 percent polymer before padding onto the fabric. Suitable polymeric additives include solid resinous or rubbery acrylonitrile-butadiene copolymers and mixtures containing the same with various vinyl resins; polyethylene; deacetylated copolymers of ethylene and vinyl acetate; polyurethanes and various polymers of alkyl acrylates, other polyesters and polyamides.

The impregnated fabric may be dried or conditioned to a moisture content of from about 2 up to about 100, preferably from about 3 to about 65 percent by weight of the dry cellulosic fabric material. The impregnated fabric may thus be catalyzed in a condition ranging from about essentially dry to about essentially wet condition.

The fabric is then passed into a non-reactive, catalyzing atmosphere containing a catalytically effective amount of formic acid or acetic acid which may be obtained from any convenient source. In addition to the catalyst, the treating atmosphere may contain inert gases such as air, nitrogen, carbon dioxide, helium, steam and the like. The treating atmosphere is "non-reactive" in that it contains the gaseous catalyst and an inert gas. Gaseous materials or monomers that could react, condense or polymerize with the fabric or methylolamide crease-proofing agent should not be present in the treating atmosphere.

The non-reactive atmosphere can contain up to about 100, often from about 5 to 90 volume percent acetic acid or formic acid, balance, (if any) inert gas.

Contact of the conditioned fabric with the non-reactive atmosphere is performed at a temperature of from about 80.degree. and 160.degree.C., preferably from about 100.degree.C. to about 140.degree.C. most preferably from about 110.degree.C. to about 125.degree.C., for a time of between about 10 seconds and 2 hours, preferably from about 1 to about 20 minutes, most preferably from about 2 to about 15 minutes.

Any suitable means to contact the fabric with the gaseous acetic acid or formic acid catalyst may be employed. For example, a batch system utilizing a closed vessel or tube containing the gaseous catalyst may be used into which the conditioned, crease-proofing agent-containing fabric may be placed and there exposed to the treating atmosphere for the appropriate time. In the alternative, a dynamic or continuous system can be used such as one wherein a gas stream containing acetic acid or formic acid catalyst, is passed through a closed elongated chamber through which the impregnated fabric or articles are also passed at an appropriate rate, either concurrently or countercurrently relative to the gas. It is also possible to use combinations of the above, that is, such as by passing a stream of the catalyst-containing atmosphere over a stationary fabric.

The crosslinked fabric is thereafter desirably heated to a temperature above about 100.degree.C., e.g., in the range of from about 100.degree. to 180.degree.C., preferably from about 140.degree.C. to about 160.degree.C., to volatilize and remove water vapor, residual catalyst and any unbound, volatile, crease-proofing agent. In addition, this heating step further cures the crosslinked fabric thus improving its durability to laundering as well as improving the duration press characteristics of the treated fabric. This heating and curing step may also allow a reduction in the time of exposure to the gaseous catalyst-containing atmosphere without sacrificing durable press performance.

Heating the crosslinked fabric may advantageously be performed in any suitable fabric heating chamber.

The temperature of the post-heating step can be reduced or the post-heating step entirely eliminated without impairing wash-wear performance by using crease-proofing agents more reactive than dihydroxydimethylolethyleneurea. These fabrics containing the more reactive crease-proofing agents may be neutralized with a slightly alkaline solution (such as a 1 percent solution of sodium carbonate) and washed to remove all traces of catalyst or unbound crease-proofing agent.

The invention is additionally illustrated in connection with the following examples which are to be considered as illustrative of the present invention. It should be understood, however, that the invention is not limited to the specific details of the Examples.

EXAMPLES

The reactor used in this work was a cylindrical vessel having a capacity of about 71 liters, constructed of 1/8-inch aluminum (42 cm. inside diameter and 57 cm. high). The walls of this reactor are heated with band heaters equipped with a three-way switch which permits operation at 600, 1,200 or 2,400 watts. The reactor wall temperature is controlled by an adjustable bimetallic thermostat, and the reactor is surrounded by an insulating blanket. The gas content of the reactor is recirculated through an external recycle line by an aluminum pressure blower equipped with a heat slinger and high-temperature, lubricated sealed bearings. An adjustable damper in the recycle line permits some control of the pressure within the reactor, but during normal operation nearly atmospheric reactor pressure is preferred.

This reactor was fitted with aluminum tubing through which a solution containing 85 percent by weight of formic acid is poured to fall onto an evaporating dish in the bottom of the reactor. Substantially all of the vapors in the reactor are in each of the following Examples formic acid vapors evaporated from the evaporating dish. Some water vapor is also present. The acetic acid and hydrochloric acid atmospheres in the Examples are provided in the same manner.

EXAMPLE I

Cotton twill fabric samples and trouser cuffs were padded to 70 percent wet pickup with aqueous solutions containing the amounts of crease-proofing agent and polymeric additive shown in Table I. Crease-proofing agents included trimethylolmelamine (Resloom HP, Monsanto Chemical Co.), methylated methylolmelamine (Resloom M-75, Monsanto Chemical Co.), a mixed amide product including a methylolmelamine (Aerotex 23, American Cyanamid Co.) and dimethylol dihydroxyethylene urea (Permafresh 183, Sun Chemical Co.). Polymeric additives included polyethylene (Mykon SF), and an acrylic resin (Rhoplex K-87). After impregnation, fabric samples were dried to moisture content of about 7-10 percent, exposed to formic acid vapor in the reaction chamber described above at about 115.degree.C. for various reaction times, washed, dried, and tested.

The tabulated data show that high levels of wrinkle recovery were achieved in all cases. Generally, shorter reaction times were necessary and higher tensile strength retentions recorded, when the melamine derivatives were used, which are more polymerizable than the dihydroxyethylene urea derivative.

TABLE I-A __________________________________________________________________________ Stoll HCO.sub.2 H Wrinkle Recovery Angle Tearing Flex Exposure Total (degrees) Strength Abrasion, Run Pad Bath Composition Time Add-On Warp Fill (grams) Warp No. Methylol Softener (min) (%) Dry Wet Dry Wet Warp Fill (cycles) Compound __________________________________________________________________________ 15% 1 Resloom M-75 2% Mykon SF 5 2.4% 146 139 117 110 2420 1580 550 2 4 2.7 154 142 120 111 2090 1660 445 3 3 2.8 146 139 126 119 2620 1670 670 4 2 3.0 131 124 124 111 2820 1880 660 10% 5 Aerotex 23 3% Rhoplex K-87 4 7.6 149 148 128 136 1740 1020 580 6 3 7.9 148 147 126 132 1810 1100 560 7 2 8.7 148 150 132 136 1740 1080 460 8 11/2 8.6 142 142 122 125 2120 1180 520 9% 9 Permafresh 183 2% Mykon SF 5 -- 146 136 118 129 2860 1660 1550 10 10 -- 144 140 114 122 2620 1780 1180 11 121/2 -- 144 140 119 132 2600 1570 730 12 15 -- 148 139 126 128 2440 1620 680 13 n.a. n.a. n.a. n.a. 90 88 84 82 4240 2780 620 __________________________________________________________________________ n.a. = not applicable. a. methylated methylolmelamine b. a misture of dimethylolurea and trimethylolmelamine c. dihydroxydimethylolethyleneurea

Tensile Properties Warp Fill Wash-Wear Work to Extension Tensile Work to Extension Tensile Rating Rupture at Break Strength Rupture at Break Strength Tumble Line Run No. (in.-lb) (%) (lb) (in.-lb) (%) (lb) Dried Dried __________________________________________________________________________ 1 20.0 12.9 141 5.9 15.4 52 31/2 3 2 17.0 12.3 126 5.8 14.8 50 4 3 3 20.0 13.0 137 6.3 16.6 51 4 3 4 21.1 13.4 144 6.2 15.8 51 31/2 3 5 14.4 11.0 125 4.7 13.8 45 31/2 3 6 14.9 11.2 127 5.7 15.2 50 4 3 7 15.8 11.4 130 5.8 15.0 50 4 3 8 17.8 12.4 136 6.6 16.2 51 31/2 3 9 13.7 12.4 114 5.1 16.7 44 31/2 3 10 13.9 12.7 114 4.6 15.8 42 4 3 11 13.0 12.4 110 4.5 16.8 41 4 31/2 12 13.1 12.3 110 4.8 16.0 44 4 4 13 28.3 12.6 174 11.2 19.9 70 -- -- __________________________________________________________________________

TABLE I-B __________________________________________________________________________ Stoll Wrinkle Recovery Tearing Flex Exposure Total Angle (degrees) Strength Abrasion, Run Pad Bath Composition Time.sup.a Add-On Warp Fill (grams) Warp No Methylol Compound Softener (min) (%) Dry Wet Dry Wet Warp Fill (cycles) __________________________________________________________________________ 1 15%.sup.b TMM 3%.sup.b Rhoplex K-87 1 6.3 124 114 112 102 2380 2480 1300 2 2 8.5 152 136 135 118 1850 1670 560 3 4 8.8 158 140 136 126 1710 1440 410 4 5 8.8 158 146 140 130 1620 1390 450 5 9%.sup.b Permafresh 183 5 7.9 134 140 104 123 1990 1870 700 6 71/2 8.6 151 142 134 139 1530 1450 850 7 10 8.3 152 145 124 131 1570 1680 840 8 n.a. n.a. n.a. n.a. 93 89 85 84 3100 2940 670 (Untreated control) __________________________________________________________________________ n.a. = not applicable a. Time exposed to formic acid at 120.degree.C. b. Percentage solids c. Trimethylolmelamine d. Dihydroxydimethylolethylene urea

Damage by Tensile Properties Retained Run No. Warp Fill Chlorine Work to Extension Tensile Work to Extension Tensile (% loss in Rupture at Break Strength Rupture at Break Strength tensile (in.-lb) (%) (lb) (in.-lb) (%) (lb) strength) __________________________________________________________________________ 1 26.9 18.8 133 17.5 20.0 90 -- 2 19.0 15.2 126 8.7 15.2 65 -- 3 16.1 13.8 114 8.4 15.5 59 -- 4 15.4 14.9 107 6.9 14.8 55 -- 5 19.9 14.6 124 9.0 14.9 64 70 6 14.1 12.4 105 7.6 16.7 56 17 7 14.5 12.6 108 9.2 18.6 60 31 8 29.5 13.7 156 16.1 19.9 86 n.a. __________________________________________________________________________

TABLE I-C __________________________________________________________________________ Stoll Wrinkle Recovery Tearing Flex Exposure Angle (degrees) Strength Abrasion, Pad Bath Time.sup.a Warp Fill (grams) Warp Run No. Composition (min) Dry Wet Dry Wet Warp Fill (cycles) __________________________________________________________________________ 1 15% TMM 2 138 134 113 110 2360 2280 1420 2 3 149 138 136 120 2320 1970 2010 3 4 150 145 136 127 1970 1600 740 4 5 152 144 140 124 2080 1660 870 5 2 133 116 94 116 2280 2160 840 6 3 140 120 110 110 2140 2220 1120 7 4 148 130 122 115 1920 1600 1280 8 5 141 130 120 124 2100 1920 680 9 n.a. n.a. 93 89 85 84 3100 2940 670 (Untreated control) __________________________________________________________________________ n.a. = Not applicable a. Time exposed to formic acid at 110.degree.C. b. Trimethylolmelamine Tensile Properties Wash-Wear Warp Fill Ratings Number of Work to Extension Tensile Work to Extension Tensile Tumble Dried Line Dried Wash-Dry Run Rupture at Break Strength Rupture at Break Strength Wash- Crease Wash- Crease Cycles No. (in.-lb) (%) (lb) (in.-lb) (%) (lb) Wear Retention Wear Retention to __________________________________________________________________________ Holes Properties After 1 Washing 1 21.4 14.8 148 13.2 19.0 88 31/2 41/2 31/2 4 -- 2 21.0 14.0 151 10.9 17.1 82 4 5 4 4 -- 3 16.2 12.4 135 7.7 16.2 66 4 5 31/2 4 -- 4 16.5 12.2 136 8.9 16.8 72 4 5 4 4 -- Properties After 20 Washings 5 23.7 16.6 141 12.5 18.0 82 31/2 31/2 3 3 >20 6 22.1 15.2 138 11.3 16.4 79 31/2 4 31/2 4 18,20 7 17.5 13.4 128 9.8 16.0 72 4 4 4 4 10,12 8 19.4 13.7 132 7.5 15.4 61 4 4 4 4 11,14 9 29.5 13.7 156 16.1 19.9 86 n.a. n.a. n.a. n.a. n.a. __________________________________________________________________________

EXAMPLE II

Cotton twill fabric samples ("Twist twill", J. P. Stevens & Co.) were padded with 70 percent wet pickup with an aqueous solution containing 10 percent (solids) of various water-soluble crease-proofing agents having reactive N-methylol groups and 2.5 percent (solids) of urethane Latex E-502, (Wyandotte Chemical Co.), and, without prior drying, were exposed to formic acid vapor in the reaction chamber described above for 2 minutes at 115.degree.C., and then heated in air for 5 minutes at 160.degree.C. Fabric samples were then washed, dried and tested. Results are shown in Table II.

The tabulated results show that a high degree of useful reaction could be achieved with all crease-proofing agents used. Similarly, good results are achieved using 10 percent (solids) solutions of hexamethoxymethylmelamine, trimethylolmelamine and trimethylolmelaminedimethylolurea.

TABLE II __________________________________________________________________________ Wrinkle Recovery Angle Tearing Stoll Flex Tensile (degrees) Strength Abrasion, Strength Dry Wet (grams) Warp (lb) Methylolamide Warp Fill Warp Fill Warp Fill (cycles) Warp Fill __________________________________________________________________________ Properties After 1 Washing Dimethylol- 154 134 162 139 (a) 1060 550 100 30 propyleneurea Dimethyloluron 161 134 158 144 (a) 890 190 98 27 Dimethylol- Carbamate 131 110 147 130 2390 1520 960 110 46 Trimethylol- Melamine 164 142 154 146 (a) 940 200 105 33 Properties After 10 Washings Dimethylol- 158 130 154 140 2000 1190 480 98 36 propyleneurea Dimethyloluron 160 131 158 144 (a) 930 180 93 30 Dimethylol- carbamate 120 109 141 123 2590 1590 940 124 49 Trimethylol- melamine 155 138 158 133 (a) 970 230 104 30 Untreated (unwashed) 78 71 74 78 3800 2060 640 175 66 Untreated (Washed) 70 68 69 72 2840 1630 670 161 74 __________________________________________________________________________ n.a. = not applicable (a) Fabric specimens tore across filling yarns only.

EXAMPLE III

Samples of the same twill fabric as used in Example II were impregnated with an aqueous solution containing 9 percent (solids) of Permafresh 113B (dimethylol dihydroxyethylene urea) and 2.5 percent (solids) urethane Latex E-502 to 50 percent wet pickup, and, without prior drying, were exposed to formic acid or acetic acid for different times, and then post-heated for different times and at different temperatures as shown in Table III. The samples were then washed, dried and tested. Results are shown in Table III.

TABLE III __________________________________________________________________________ Exposure Heating Time Wrinkle Recovery Angle Tearing Stoll Flex Tensile Time and and (degrees) Strength Abrasion, Strength Gaseous Temperature Temperature Dry Wet (grams) Warp (lb) Catalyst (min/.degree.C) (min/.degree.C) Warp Fill Warp Fill Warp Fill (cycles) Warp Fill __________________________________________________________________________ HCOOH 3/115 5/160 158 136 152 142 1990 1160 690 105 35 do. 2/115 5/160 150 132 151 134 2050 1270 530 110 40 do. 1.5/115 5/160 154 129 148 134 2150 1250 560 109 34 do. 1/115 5/160 154 128 148 136 2140 1340 570 112 39 do. 2/115 5/150 148 128 136 124 1900 1130 400 118 42 do. 2/115 5/140 146 130 131 122 2030 1200 510 119 45 do. 2/115 5/130 130 120 123 118 2280 1440 700 126 51 CH.sub.3 COOH 3/115 5/160 131 122 140 130 2440 1430 720 129 44 do. 2/115 5/160 132 124 137 128 2190 1280 670 111 43 do. 1.5/115 5/160 138 122 138 128 2430 1450 660 121 46 do. 1/115 5/160 140 123 138 128 2410 1350 650 127 43 Untreated -- 78 71 74 78 3800 2060 640 175 66 (unwashed) Untreated -- 70 68 69 72 2840 1630 670 161 74 (washed) __________________________________________________________________________

These tabulated results show that a short exposure to acetic acid, as well as to formic acid, is sufficient to allow a high level of wrinkle recovery to be achieved after a subsequent heat treatment. The balance of wrinkle recovery gained to strength and abrasion resistance lost is about the same for each catalyst, and comparable with a conventional pad/dry/cure system using the same crease-proofing agent.

EXAMPLE IV

The twill samples of Example II are impregnated with an aqueous solution containing 20 percent dimethylolurea (Permafresh 477) and 10 percent urethane Latex (E-502) and dried to various add-ons as shown in Table IV-A. These impregnated twill samples were exposed to formic or hydrochloric acid vapors at temperatures between 60.degree. and 120.degree.C. and either post-heated in air for 5 minutes at 150.degree.C. or neutralized and washed. Conditions and results are shown in Table IV-A.

These results show the advantages of the present invention as compared with hydrochloric acid systems.

TABLE IV-A __________________________________________________________________________ Exposure Postheated Wrinkle Recovery Angle, Tensile Strength Wash- Temp. at 150.degree.C Add-on W + F (degrees) (% retention) Wear Catalyst (.degree.C) for 5 min (%) Dry Wet Warp Fill Ratings __________________________________________________________________________ HCOOH 60 No.sup.(b) 2.6 146 208 82 97 2.7 do. 80 do. 3.4 150 210 79 98 3.0 do. 100 do. 5.1 223 257 65 77 3.0 do. 120 do. 5.7 286 270 61 69 4.2 do. 60 Yes 5.2 293 292 56 60 4.4 do. 80 do. 5.4 289 295 53 51 4.4 do. 100 do. 5.4 306 307 54 55 4.3 do. 120 do. 5.5 308 306 52 53 3.9 HCl 60 No.sup.(b) -- 258 254 51 62 3.0 do. 80 do. -- 282 284 37 63 3.0 do. 100 do. -- 286 290 34 32 3.6 do. 120 do. -- 305 304 27 16 4.0 do. 60 Yes -- a a a a a do. 80 do. -- a a a a a do. 100 do. -- a a a a a do. 120 do. -- a a a a a 100 100 -- Untreated -- -- -- 152 160 (186 lb) (74 lb) Control __________________________________________________________________________ .sup.a Fabrics too weak to test. .sup.b Neutralized with a 1 percent sodium carbonate solution and washed

Prior to the post-heating step, fabrics treated with the hydrochloric acid system showed good degrees of wrinkle recovery angles, but rather low tensile strength retentions. The post-heating step, however, proved to be highly detrimental to the strength of these HCl-system fabrics. As in the case of the Permafresh 113B-treated fabrics, the acid degradation was such that it was imposible to measure any of their physical properties.

To show that post-heating at lower temperatures could yield fabrics with acceptable degrees of strength retention for formic acid but not hydrochloric acid systems, further runs were conducted in which fabrics impregnated with dimethylolurea (Permafresh 477) and urethane Latex-502 were exposed to formic or hydrochloric acid vapors for 5 min. at 120.degree. or 60.degree.C., respectively, and then post-heated at 100.degree.-140.degree.C. The resulting fabric properties are listed in Table IV-B.

TABLE IV-B __________________________________________________________________________ Exposure Postheating Wrinkle Recovery Angle Tensile Strength Wash-Wear Time/Temp Time/Temp W + F (degrees) (% retention) Ratings Catalyst (min/.degree.C) (min/.degree.C) Dry Wet Warp Fill __________________________________________________________________________ HCOOH 5/120 5/100 296 284 66 61 4.2 do. do. 5/120 288 281 68 60 4.2 do. do. 5/130 302 297 66 65 4.2 do. do. 5/140 309 294 66 61 4.2 HCl 5/60 5/100 290 296 35 31 3.8 do. do. 5/120 275 304 17 4 3.7 do. do. 5/130 297 309 10 6 4.0 do. do. 5/140 294 304 10 8 3.5 Untreated -- -- 152 160 100 100 -- Control (186 lb) (74 lb) __________________________________________________________________________

EXAMPLE V

Cotton twill fabric (7.8 oz./sq. yd., J. P. Stevens twist twill having 112/50 threads per inch) was treated with a 20 percent solution of dihydroxydimethylolethyleneurea (Permafresh 113B, Sun Chemicals Corporation) to 65 percent wet pickup. The solution also contained 5 percent (solids) of an acrylic emulsion (Rhoplex K-14, Rohm and Haas Co.). The impregnated fabric samples were dried, exposed to a formic acid or hydrochloric acid atmosphere at varying temperatures and times.

TABLE V-A __________________________________________________________________________ HCOOH Warp Exposure Wrinkle Recovery Angle, Tearing Strength Tensile Strength Stoll Wash- Add-on Time/Temp. W +F, (degrees) (% retention) (% retention) Abrasion(% Wear (%) (min/.degree.C) Dry Wet Warp Fill Warp Fill retention) Ratings __________________________________________________________________________ Properties Prior to Post-heating 2.2 1/120 236(207).sup.a 218(201).sup.a 155 144 71 82 308 2.0 4.0 5/120 274(224) 264(254) 105 118 68 77 272 2.2 5.0 10/120 276(260) 285(270) 98 91 60 63 306 3.0 5.0 15/120 281(262) 280(272) 96 99 62 66 253 2.8 4.9 20/120 302(271) 284(282) 91 95 63 65 279 2.4 1.6 1/100 190(179) 214(198) 106 114 92 82 185 2.0 2.5 5/100 225(217) 260(255) 80 96 74 83 162 2.6 5.2 10/100 268(260) 286(278) 76 77 68 67 153 3.2 6.2 15/100 274(264) 295(288) 73 79 65 71 151 3.4 6.2 20/100 268(260) 280(278) 73 75 65 65 156 3.3 2.6 1/80 177(179) 202(194) 104 123 90 95 179 2.0 3.4 5/80 199(180) 204(202) 100 113 89 94 169 2.0 5.1 10.80 206(179) 249(219) 89 101 77 91 157 2.4 5.4 15/80 221(196) 243(246) 85 99 82 86 174 2.3 3.7 20/80 226(212) 250(252) 83 94 79 85 188 2.4 2.8 1/60 178(183) 187(184) 110 121 87 100 193 2.0 3.1 5/60 193(178) 200(186) 116 125 96 110 191 2.0 3.7 10/60 211(193) 201(200) 112 125 94 104 180 2.1 3.7 15/60 197(185) 194(200) 120 124 92 103 177 2.0 4.2 20/60 200(189) 207(192) 117 120 92 102 219 2.0 Properties After Post-Heating 5.0 1/120 248(212) 250(231) 127 132 72 69 394 3.0 4.8 5/120 286(275) 272(272) 97 93 60 56 312 3.6 5.4 10/120 296(285) 296(282) 80 84 58 56 151 3.8 5.5 15/120 290(282) 279(285) 93 98 66 60 283 4.0 6.0 20/120 310(285) 285(292) 78 80 60 61 220 3.6 5.6 1/100 241(234) 270(267) 76 84 69 72 168 3.2 6.3 5/100 272(263) 267(274) 69 70 65 61 165 3.4 6.4 10/100 296(281) 301(288) 64 62 58 59 144 4.0 6.3 15/100 291(288) 289(287) 66 61 58 58 133 3.8 6.6 20/100 295(288) 296(291) 64 62 56 57 136 3.6 6.5 1/80 274(251) 289(274) 59 68 64 69 153 3.6 6.8 5/80 268(273) 276(272) 60 64 61 65 148 3.6 7.0 10/80 289(276) 289(276) 59 65 61 62 107 3.5 6.8 15/80 289(276) 286(278) 55 69 62 64 105 3.8 6.2 20/80 290(282) 286(280) 57 59 58 63 123 3.8 4.6 1/60 274(238) 246(242) 90 104 81 88 202 3.1 6.6 5/60 270(265) 270(242) 70 84 73 79 180 3.7 6.6 10/60 257(252) 262(255) 66 82 69 72 192 3.8 6.8 15/60 276(268) 277(261) 68 74 72 69 170 3.7 7.0 20/60 284(272) 277(279) 63 73 70 75 208 4.4 Control -- -- 152 160 100 100 100 100 100 (3024 g) (1827 g) (186 lb) (74 lb) (602 cycles) __________________________________________________________________________ a. WRAs determined after 10 launderings

TABLE V-B __________________________________________________________________________ HCl Warp Exposure Wrinkle Recovery Angle, Tearing Strength Tensile Strength Stoll Wash- Add-on Time/Temp. W + F, (degrees) (% retention) (% retention) Abrasion Wear (%) (min/.degree.C) Dry Wet Warp Fill Warp Fill (% retention) Ratings __________________________________________________________________________ 5.5 1/120 309(302).sup.b 308(305).sup.b 66 74 51 54 89 3.0 4.8 2/120 314(305) 304(303) 44 75 23 17 59 3.4 5.0 3/120 322(a) 320(a) 31 11 24 16 21 4.3 4.8 4/120 312(a) 297(a) a 31 a a a a a 5/120 a a a a a a a a a 10/120 a a a a a a a a 6.4 1/100 275(267) 299(285) 77 93 51 53 128 3.5 6.2 2/100 310(284) 312(289) 26 31 45 34 15 3.6 5.9 3/100 310(293) 304(299) 17 18 47 14 12 3.8 -- 4/100 312(a) 314(a) 2 13 30 9 3 3.8 a 5/100 a a 2 a a a a a a 10/100 a a 2 a a a a a 5.8 1/80 280(266) 295(252) 68 89 52 63 175 3.5 6.1 2/80 286(288) 308(280) 67 82 51 60 158 3.6 5.9 3/80 307(291) 303(290) 32 27 33 37 52 3.8 4.7 4/80 293(290) 316(301) 26 28 27 34 22 3.7 5.2 5/80 304(294) 312(293) a 23 16 16 12 4.0 a 10/80 a a a a a a a a 4.8 1/60 286(260) 279(270) 87 94 67 72 166 3.6 5.5 2/60 299(262) 292(282) 53 78 59 55 98 4.3 6.1 3/60 303(291) 304(296) 46 38 40 49 68 4.0 5.9 4/60 302(296) 316(298) a 31 35 35 50 4.2 5.7 5/60 306(291) 307(301) a 21 26 29 16 3.6 a 10/60 a a a a a a a a Control -- -- 152 160 100 100 100 100 100 -- (3024 g) (1827 g) (186 lb) (74 lb) (602 cycles) __________________________________________________________________________ a. Too weak to test b. WRAs determined after 10 launderings

With respect to the formic acid system, it is evident from these data that the degree of crosslinking of fabrics as measured by the development of WRA's (wrinkle recovery angles) increased as the length of exposure time or reaction temperature increased. Conversely, the strength retention of these fabrics diminished somewhat as the reaction temperature increased. However, strength losses exhibited by the postheated fabrics were considerably smaller than those shown by the control fabrics. Reaction time, on the other hand, had a less pronounced effect on strength retention. Fabrics exposed for 5 to 20 minutes exhibited similar degrees of strength retentions.

Thus, these results indicate that the process of this invention can be operated within a wide range of reaction times without significantly adversely affecting the strength retention of the treated fabrics. The use of temperatures above 80.degree.C. (100.degree. or 120.degree.C.) is preferred in order to obtain high levels of crosslinking when using Permafresh 113B. The use of other crosslinking agents such as methylated methylolmelamine (Resloom M-75, Monsanto), methylolmelamine (Resloom HP, Monsanto), and a triazineformaldehyde condensate (Aerotex special resin 23, American Cyanamid) reduce the reaction time considerably.

As shown in Table V-B, fabrics treated with the Permafresh 113B-hydrochloric acid system developed high levels of WRAs in very short lengths of time. Fabrics treated for 1 or 2 minutes exhibited significant strength losses comparable to those obtained with the conventional pad-dry-cure process particularly at the lowest reaction temperatures. Samples treated for 3 to 5 minutes were extremely weak and those treated for longer than 5 minutes were too weak to be tested.

Due to the extreme acid degradation exhibited by all hydrochloric acid-catalyzed samples after the post-heating step, it was impossible to measure any of their physical properties.

From the above observations, it can be concluded that some of the basic differences between the hydrochloric and formic acid or acetic acid catalyzed systems using fabrics impregnated with methylolamides are: (1) the range of reaction times and temperatures uder which both systems operate, (2) the method of removing the volatile residues (i.e., by washing or heat soaking), and (3) the possibility of treating garments rather than flat goods due to the omission of the neutralizing and washing steps in the formic acid- or acetic acid-catalyzed process.

Some of the disadvantages of the hydrochloric acid-catalyzed system are: (1) excessive degradation of the cotton fibers, (2) the need for neutralization of the fabric after treatment, (3) the need for afterwash, (4) lack of reproducibility due to the narrow range of reaction times and temperatures under which the process operates, and (5) the need for special controls and equipment for handling the highly corrosive and toxid hydrochloric acid.

EXAMPLE VI

The twill samples of Example V were treated with an aqueous solution containing 20 percent dimethylolethyleneurea (Rhonite R-1, Rohm and Haas Co.) and 10 percent Rhoplex K-14, dried and exposed to gaseous formic acid for 5 minutes at 120.degree.C. Conditions and results are shown in Table VI.

TABLE VI __________________________________________________________________________ Warp Wash- Postheating Wrinkle Recovery Angles, Tearing Strength Tensile Strength Stoll Wear Add-on Time & Temp W + F, (degrees) (% retention) (% retention) Abrasion Ratings (%) (min/.degree.C) Dry Wet Warp Fill Warp Fill (%retention) __________________________________________________________________________ 6.7 0 302 284 88 92 69 63 262 3.6 7.4 5/130 299 287 72 77 58 56 204 3.7 7.6 5/140 308 294 68 76 56 60 174 3.5 7.4 5/150 313 294 67 70 58 56 168 3.7 -- 152 160 100 100 100 100 100 -- (3024 g) (1827 g) (186 lb) (74 lb) (602 cycles) __________________________________________________________________________

These data show that the post-heating temperature can be reduced or the post-heating step entirely eliminated without diminishing the degree of wash-wear performance by using methylolamides that are more reactive than dihydroxydimethylolethyleneurea. The results shown in Table VI indicate that the WRAs and wash-wear ratings of fabrics treated with dimethylolethyleneurea were not affected by reducing the temperature of or omitting the post-heating step.

EXAMPLE VII

Cotton twill fabrics (7.8 oz/sq yd NCC standard twill) were padded to 70 percent wet pickup with an aqueous solution containing 15 percent trimethylolmelamine (Resloom HP, Monsanto) and either 2.5 percent (solids) Urethane Latex E-502 (Wyandotte Chem. Corp.), 2.0 percent (solids) high density polyethylene or 3.2 percent (solids) Rhoplex K-87, dried, and then exposed to acetic acid vapor at 115.degree.C. Conditions and results are shown in Table VII. ##SPC1##

It is evident from Table VII that acetic acid is capable of producing samples with wrinkle recovery and tensile strengths retention comparable to those obtained with formic acid vapor.

The principles, preferred embodiments and modes of operation of the present invention have been described in the foregoing specification. The invention which is intended to be protected herein, however, is not to be construed as limited to the particular forms disclosed, since these are to be regarded as illustrative rather than restrictive. Variations and changes may be made by those skilled in the art without departing from the spirit of the invention.

Claims

What is claimed:

1. A process for improving the dimensional stability, wrinkle resistance, smooth drying characteristics and total shape retentivity of a cellulose fiber-containing fabric which process consists essentially of:

a. applying to the fabric an aqueous solution of a water-soluble crease-proofing agent containing reactive N-methylol groups;

b. heating the impregnated fabric containing the said crease-proofing agent in a non-reactive vapor atmosphere containing a catalyst selected from the group consisting of formic acid and acetic acid vapor as essentially the only reactive component to a temperature between above 80.degree.C. and up to about 160.degree.C. for a time of between about 1 to about 20 minutes to crosslink the cellulose fibers to a first level of crosslinking; and

c. heating the said crosslinked fabric in an inert atmosphere in the absence of additional catalyst to a temperature of above about 100.degree.C. to further cure the said crosslinked fabric to a second level of cross-linking having increased Wrinkle Recovery Angles and Wash-Wear Ratings while dissipating residual reagents.

2. A process according to claim 1 wherein said aqueous solution contains from about 1 to about 40 percent of the said crease-proofing agent.

3. A process for improving the dimensional stability, crease resistance, smooth drying characteristics and total shape retentivity of cotton-containing fabrics which comprises in sequence the steps of:

a. applying to the fabric an aqueous solution consisting essentially of about 5 to about 15 percent by weight of a water-soluble, crease-proofing agent containing reactive N-methylol groups;

b. conditioning or drying the fabric to give the cotton a moisture content of between about 2 to about 100 percent based on dry weight of the fabric;

c. exposing the conditioned fabric to a non-reactive vapor phase consisting essentially of a catalytically effective amount of formic acid or acetic acid as essentially the only reactive component in a reaction zone maintained at a temperature between about 100.degree.C. and about 140.degree.C. for a time of between about 1 and 20 minutes to crosslink the cotton fibers to a first level of crosslinking;

d. at the end of said crosslinking step (c) heating said fabric in an inert gaseous atmosphere in the absence of additional catalyst at a temperature of from about 100.degree.C. to about 180.degree.C., to further cure the fabric to a second, higher level of crosslinking while dissipating residual reagents thereby directly producing a dry, crosslinked, essentially neutral fabric.

4. A process according to claim 3 wherein said non-reactive vapor phase consists essentially of formic acid.

5. A process according to claim 3 wherein said non-reactive vapor phase consists essentially of acetic acid.

6. A process for improving the dimensional stability, wrinkle resistance, smooth drying characteristics and total shape retentivity of cotton-containing fabrics which consists of the sequential steps of:

a. impregnating the fabric with an aqueous solution containing about 5 to 15 percent trimethylolmelamine or dihydroxydimethylolethyleneurea to give a wet pick-up between about 65 and 85 percent based on dry cotton weight;

b. drying and conditioning the impregnated fabric to a moisture content of between about 3 to about 65 percent;

c. exposing the fabric to a non-reactive gaseous atmosphere consisting of from about 20 to 50 volume percent of a catalytic material taken from the group consisting of formic acid and acetic acid, balance inert gaseous material, at a temperature between 110.degree. and 125.degree.C. for a time of about 2 to about 15 minutes, thereby effecting a first level of crosslinking;

d. removing said fabric from said atmosphere; and

e. postheating the said fabric at a temperature of from about 140.degree.C. to about 160.degree.C. to further cure the fabric to a second level of crosslinking while dissipating residual reagents.

7. A process according to claim 6 wherein the fabric is introduced into the process as a flat fabric, and prior to step (c) is formed into a garment.

8. A process according to claim 6 which process is continuous and in which the fabric being treated is flat fabric.

9. A process according to claim 6 which process is continuous and in which the fabric being treated is a garment.