NO137161B - PROCEDURES FOR PROCESSING CELLULOSE FIBER TEXTILE MATERIALS - Google Patents

Description

The present invention relates to a method for treating cellulose fiber-containing fabrics to improve their creasing resistance and their uniform drying properties with a minimal loss of physical properties.

There is an ever-increasing demand for easy-care garments with permanent press, i.e. for garments that have folds and pleats permanently pressed into them, and which remain wrinkle-free with normal use, so to speak, and which can be worn after washing without requiring much, if any , pressing.

It is well known to give cellulosic textiles such as cotton permanent resistance to curling by impregnation by an aqueous solution of a suitable heat-setting resinous precondensate or cellulose cross-linking agent, usually with a suitable catalyst, and eventual curing of the impregnated textile].

Such treatment has been effective in the development of shape-retaining properties in cotton textiles and has resulted in a greatly increased demand for iron-free cotton textiles because these combine the natural fiber's traditional comfort, washability and economy with the easy-care properties required in today's textile market.

Particularly good shape-retaining properties were achieved if the curing of such resin-treated textiles was postponed until after the treated textiles had been cut and sewn to make the desired finished garment and after such garments had been given the desired shape by pressing.

A particularly promising approach to the production of easy-care garments with permanent press comprises wet fixing of resin or polymer-forming anti-crease agents such as formaldehyde-melamine precondensates, as mentioned, e.g. in the U.S. patent No. 3138,802. In this type of method, a fiber system such as a cotton textile is protected against excessive strength loss and made susceptible in advance to permanent press treatment by fixing a suitable polymer former and anti-crease agent in the fibers while they are wet and swollen, but without greatly changing the curl recovery angle in the dry state or the permanent press properties of the fiber system. The latter properties are only given to the desired extent by a subsequent dry curing. According to this, such a method allows finished folding or other special shaping of the fiber system during fabric production or the like, after the wet-fixing step and for the exposed dry curing. However, wet-fixing methods heretofore known have typically required neutralization and rewashing of the strongly acidic wet-fixing catalyst after the wet-fixing step, followed by drying and then re-catalyzing and drying again for the actual curing, which required a lot of manufacturing time and effort.

Another promising approach to the production of easy-care garments with permanent press has been to expose conditioned cotton textiles to a reactive atmosphere of formaldehyde and sulfur dioxide in gaseous form, as mentioned e.g. in Canadian Patent No. 856,132. However, this method directly results in a

hardened textile and is therefore not suitable for a method with

set hardening. In addition to this, textiles treated by such a method tend to suffer from a permanent loss of strength.

According to this, the primary object of the present invention is to produce a method for increasing the creasing resistance and the even drying properties of cellulose fiber-containing fabrics, where said method essentially avoids or reduces the problems from the prior art, which are discussed above.

Another object of the present invention is to produce a method for achieving a favorable balance between easy-care and physical properties in cellulose fiber-containing substances, where said method allows the use of both delayed curing and pre-curing methods.

Another object of the present invention is

to produce a method for improving the creasing resistance in cellulose fiber-containing substances, where said method allows simplification of production by minimizing the production time.

These and other objects of the present invention will appear more clearly from the following description.

In accordance with this, the present invention provides a method for giving a cellulose fiber-containing textile material the ability to resist curling and to give it advantageous properties with the aim of even drying and lasting pressure, by supplying to the material an aqueous solution comprising at least one water-soluble polymer-forming precondensate with reactive N-methylol groups and polymerization of said precondensate in said material, in the presence of an acidic catalyst while the cellulose fibers are swollen due to moisture, thereby forming a substantially water-insoluble polymer in the swollen fibers, which can then be cross-linked by curing for to achieve the desired properties, and the method is characterized in that the material with the applied water-soluble polymer-forming N-methylol precondensate and in a water-swollen state in a steam treatment zone at a temperature of between 80 and 180°C, preferably between 120 and 170°C, is exposed to a reactive atmosphere, including vapors of formaldehyde etc g vapors of a volatile acid with a boiling point below 120°C

1 a period of between 10 sec. and 15 min., preferably 30 sec. to

2 min., and sufficient to fix in the cellulose fibers from 3 to 12% polymer and formaldehyde in an essentially water-insoluble form, and that the material is then partially dried to a moisture content of not less than 6%, while residues of volatile acid catalyst are driven by in preparation for making a garment which can be given "permanent pressure" properties by curing in a substantially dry condition in the presence of a latent acid solid catalyst.

The permanent press article can be made by first making a garment with heat-pressed pleats from the uncured fabric and then curing the garment (delayed curing), or by first curing the fabric and then making the garment from the cured fabric (pre-curing).

The essential aspect of the present invention is the discovery that N-methylol compounds can be made insoluble or polymerized in moisture-swollen cellulose fibers, i.e. fixed in the substance of water-insoluble products or resins by exposure to a reactive atmosphere containing formaldehyde and a gaseous acid catalyst, thereby simultaneously effectively controlling and limiting the weakening effect otherwise obtained if a textile, such as cotton, is dry-cured, and to produce a textile that can finally be dry-cured without requiring any further application of cross-linking agent or catalyst after the fixing step. By controlling the amounts and the relative time sequences where the gaseous acid catalyst and the formaldehyde vapor are introduced into the process, particularly good process control can be achieved.

It has been proposed that the gaseous acid, which quickly enters the system, promotes the fixation of the methylolated melamine or similar pre-condensate at the reactive sites in the cellulose fibers in the cotton, which, according to the nature of the matter, can also react with a cross-linker, such as formaldehyde. By exposing the cellulose material in the process chamber to formaldehyde only after a preparatory exposure to the acidic catalyst, the degree of direct cross-linking of the cellulose fibers with formaldehyde can be reduced and in that way the strength of the cotton is better kept the same.

In this way, a balance is achieved between the physical and the easy-care properties, but no neutralization or washing off of the catalyst is necessary, and the resulting material is suitable either for delayed curing or for pre-curing treatment.

According to the precisely preferred design of the present invention, the cellulose material is first impregnated with an aqueous dipping solution containing one or more polymerisable N-methylol compounds and a water-soluble salt that serves as

a latent curing catalyst, and then the impregnated fabric containing an appropriate amount of moisture is heated and exposed to a reactive atmosphere of gaseous sulfur dioxide and formaldehyde vapor at a temperature of at least 100°C, in order to

by enabling the N-methylol compound to be fixed in the fabric and for the formaldehyde to bind to it so that it can then cause the desired cross-linking in the final curing step.

In another embodiment of the present invention, the impregnated fabric is first exposed to a warm gaseous atmosphere under conditions of relatively high humidity to heat the fabric and to optimize the distribution and/or fixation or polymerization of the N-methylol compound in the fiber system in the absolute absence of extraneous formaldehyde to cause heating and to insolubilize the resin in a single step or in a sequence of steps, and then expose the heated and preconditioned fabric to another atmosphere at a lower humidity in a later step to optimize fixation of formaldehyde in the system for the final curing.

These and other views, advantages and designs of the present invention will appear more clearly from the following more detailed description.

The present invention is suitable for treating different natural or artificial cellulose fibers alone or as mixtures with each other in different ratios or as mixtures with other fibers. They include natural cellulosic fibers such as cotton, linen and hemp, as well as regenerated or artificial cellulosic fibers such as viscose rayon and copper ammonium rayon. Other fibers that can be used in mixtures with one or more of the above-mentioned cellulose fibers are e.g. cellulose acetate, polyamides (ie nylon), polyesters (ie polyethylene terephthalate), acrylics, polyolefins (ie polypropylene), polyvinyl chloride, polyvinylidene chloride and polyvinyl alcohol fibers. Such mixtures preferably contain at least 20% by weight, most preferably at least 40% by weight, of cotton or natural or regenerated cellulose.

The fabric can be a knitted, woven, non-woven or

otherwise constructed textile, or the present invention can be used on fibers or yarns because they are transferred to more complex structures. The fabric may be flat, folded, pleated, draped, or in fact formed into any shape after contact with the formaldehyde-containing atmosphere. After finishing the treatment, the formed wrinkle-free textile will retain the desired shape so to speak for the life of the article, i.e. a textile with permanent pressure will be produced which will retain the desired shape again through numerous "wash-wash-dry" periods, and only requires little or no pressing.

The application of the present invention typically includes the use of at least one water-soluble polymer-forming compound with reactive N-methylol groups, formaldehyde as a cross-linking agent and a latent solid curing catalyst. On the one hand, on exposure to a hot, moist, acidic steam atmosphere, the polymer-forming compound is polymerized on the inside of the cotton fibers while the latter are wet and swollen, so that the polymeric substance thus formed is fixed inside the fibers and protects them from undue loss of strength which is normally caused by regular anti-aging treatment; and, on the other hand, the fixed polymeric substance cross-linking agent eventually participates in the cross-linking of the cellulose when cured in the dry state in the presence of the latent curing catalyst.

The currently preferred polymer-forming N-methylol compounds include melamine-formaldehyde and phenol-formaldehyde precondensates, although other N-methylol-containing polymer-forming compounds such as urea-formaldehyde precondensates are also usable.

Polymer formers suitable for this include particularly easily hardenable precondensates which are completely water-soluble and which are obtained by condensing formaldehyde with a compound such as melamine

or a lower alkyl-substituted melamine, a urea or a hydroxybenzene such as phenol or resorcinol. The resulting methylol-containing compound or precondensate can further be etherified by reaction with a lower alkanol such as methanol or butanol. As is well known in the textile processing industry, these pre-condensates can be applied to the cellulose material from an aqueous solution, and they can be quickly wet-fixed or rendered insoluble therein as described, e.g. in the U.S. patent No. 3-138,802. Triazines obtained by condensation of methyl or other lower alkyl substituted melamines and formaldehyde

are further examples of such precondensates.

Good results are achieved e.g. by precondensates obtained by condensation of 1 mol of melamine or an alkyl-substituted melamine with from 2 to 6 mol of formaldehyde, i.e. using di-, tri-, tetra-, penta- or hexamethylol melamine. Such products are well suited as polymer formers that can quickly be wet-fixed in the fabric by heating or steaming as described herein.

Commercially available products of this type include "Aerotex 23", an alkylated melamine-formaldehyde precondensate; "Aerotex M-3", a dimethoxymethylhydroxymethylmelamine; "Aerotex P-225",

a hexakis(methoxymethyl)melamine; and "Aerotexl9", which is a less complex fractional modification of "Aerotex P-225". These products are supplied in the form of aqueous solutions.

The application of the present invention also includes the use of an aqueous latent curing catalyst. E.g. one can use a water-soluble salt of a strong acid with a weak base such as ammonium salts of hydrochloric acid, sulfuric acid, nitric acid, oxalic acid, lactic acid or other inorganic or organic acids, various amine hydrochlorides, as well as acid-reactive salts of metals such as zinc or magnesium, e.g. zinc nitrate or magnesium chloride or a mixed catalyst such as MgC^/ZnC^, MgC^/citric acid or Zn(NO^/tartaric acid. Zinc nitrate, zinc chloride, magnesium chloride and ammonium chloride represent latent hardening catalysts whose use is particularly preferred in connection with the present invention.

In order to treat cellulosic fabrics in accordance with the present invention, it is most convenient to apply the desired N-methylol polymer-forming compound such as a methylolated melamine or a mixture of such compounds and a latent curing catalyst to the fabric initially from an ordinary aqueous solution. or an impregnation bath. However, the curing catalyst can be omitted from this initial step and applied at a later stage in the process, as its presence is only required in the final curing step.

E.g. using conventional impregnation in use

of ordinary equipment, or by spraying or other known methods,

the polymerizable N-methylol compound or precondensate can be dissolved in water to form a solution containing from om-

3 to 25 percent, preferably from 5 to 15 percent, of the N-methylolfo compound. To enable its final curing in the cellulosic material, a curing catalyst may be included in this same solution, or in a separate solution, in an amount of about 1 to 10 µl, preferably between 4 and 6 µl, based on the weight of the N-methylol compound. The optimum concentration depends somewhat on the particular catalyst and particular N-methylol compound used, and can be determined in advance by routine investigations.

Depending on the requirements of the final fabric or textile, the impregnation is carried out in such a way that the applied N-methylol compound deposited on the fabric is between 3 and 12%, preferably between 6 and 8 tfo, calculated as dry, solid deposition based on the weight of tort fiber material ("owf"). The impregnation usually takes place at ambient temperature, i.e. between approximately 10° and 30°C.

An essential feature of this part of the present method is that the deposited N-methylol compound is fixed in the fibrous material together with a cross-linking agent while the fibers are stretched or swollen with water, so that the compound or precondensate is rendered insoluble in the fibrous cellulose material without reforming the latter to a design with a curl-resistant shape at this stage, i.e. without changing the curl recovery angle in the dry state of the fiber system to such an extent that it makes folding or other special shaping of such a fiber system difficult during the subsequent production of garments or other products. Without wishing to be bound by any particular theory, it is believed that a possible explanation may be that such fixation achieves this result because the water-swollen state of the fibers either prevents extensive cross-linking of the cellulose by any cross-linking agent present or, although such cross-linking occurs, that the fibers are very stretched when they are treated and that therefore the treated structure still maintains a high degree of mobility when it is used.

The aqueous impregnation bath can also contain other conventional treatment agents for textiles, e.g. wetting agents and softeners for textiles, i.e. polymers that can form a soft film on the fabric or textile. E.g. "suitable textile softeners contain a latex or a fine aqueous dispersion of polyethylene, various alkyl acrylate polymers, acrylonitrile-butadiene copolymers, deacetylated tylene-vinyl acetate copolymers, polyurethanes and the like. Polymer additives suitable for such general use are otherwise well known in the art and are in most cases commercially available in the form of a concentrated aqueous latex.For use in the present invention, such a dispersion is preferably diluted to obtain about 0.1 to 4 1° plasticizer based on the weight of the fabric ("owf").

After the cellulosic fabric has been impregnated with an N-methylol compound or otherwise applied, the fabric is heated while its moisture content is between about 15 and about 90°F, preferably between 30 and 70°F ("owf"), in the presence of a gaseous, acidic catalyst, so that the N-methylol compound is fixed in the substance.

It is important to maintain an appropriate amount of moisture

in the textile, within the limits mentioned, as it is subjected to exposure to the hot steam atmosphere or atmospheres. In the absence of sufficient moisture, it turns out that not enough polymer is fixed inside the fibers at an early stage of steaming to stretch the fibers and protect them from excessive cross-linking by formaldehyde during the later stages of steaming or during final curing. As a result, the final product in such a case tends to suffer from a rapid loss of strength analogous to that suffered by the usual "impregnate-dry-cure" method.

On the other hand, if too much moisture is present, and especially if water vapor present in the reactive vapor phase condenses on the fabric as a liquid, this is found to unnecessarily dilute the acid migrating from the vapor phase to the fabric. As a result, the polymer-forming compound is left insufficiently catalyzed to produce the desired degree of polymerization or amount of fixed polymer in the fibers. Consequently, much of the potential advantage that can arise from the use of the present invention can be lost either due to too much or too little moisture in the system. However, the humidity conditions leading to the production of optimum results are quickly determined from prior empirical trials.

In order to achieve optimal process flexibility or process control, it can be advantageous to divide the process into several more or less specific steps, either by using separate chambers for each such step or by supplying the different treatment liquids in a spatial or chronological sequence along the path where the textile moves. For example, after the textile has been impregnated in the liquid bath containing the polymer former, it may be useful to line it between press rollers where excess liquid is pressed out in preparation for the steam treatment which represents the essential part of the present invention.

The pressed impregnated textiles are then fed into a first step in a reaction chamber where they are heated to the desired reaction temperature, i.e. at least 80°C, but preferably between approximately 100 and 170°C, in a steam atmosphere where the humidity in the textile is achieved or adjusted to the desired level. The hot textile is then fed over rollers to another stage in the chamber where an acidic gas, i.e. SO^ or formic acid, is fed in so that it stbter on the textile while the latter is kept at a predetermined temperature and degree of humidity. This causes the polymer former to be fixed firmly on the inside of the fibres. One can assume that this keeps the reactive sites in the cellulose from eventually reacting with an excess of the active cross-linker, i.e. formaldehyde.

From the initial polymerization step, the textile is lined

to a third step where formaldehyde is fed in so that it hits the textile while maintaining appropriate controlled conditions in terms of temperature, humidity and acidity, which may be the same or different from the corresponding conditions maintained in previous steps. For example, after the polymer former is sufficiently fixed in the fibers by passing through the second stage, it is permissible and may be advantageous to maintain a somewhat lower degree of moisture in the third stage than in the previous stages. Such a lower degree of moisture in the third step can not only allow the further polymerization of the polymer former in the fibers,

but also the fixation of formaldehyde in the system more easily.

By dividing the treatment into such separate steps, suitable adjustments can be made in reaction temperature, humidity level, acidity and formaldehyde fixation. is used most appropriately as it is needed or desired. Dividing the process into stages can be satisfactorily accomplished by passing the textile through a single reaction chamber over a series of rollers arranged along a path shaped like an inverted V. Steam is produced from the remaining moisture in the textile after the textile enters the heated chamber.

SOg or other acid vapor is fed in and hits the textile near the entrance to the chamber. Formaldehyde in reactive form is introduced near the top of the inverted V and sticks to the heated textile. The up-

IO I J Ul

heated textile with the polymer former at least partially polymerized in it is then fed along the downward leg of the inverted V towards the exit of the chamber.

Alternatively, the various phases of the process can be carried out by passing the textile through a series of completely separate successive chambers, or the entire steam treatment can be carried out by passing the impregnated textile straight through a single stage containing a mixed atmosphere of water vapour, gaseous acid catalyst and formaldehyde. However, it is advantageous even in the latter design to have at least a spatial separation between the sites of introduction of acid vapor and of the reactive formaldehyde, to allow at least some protective polymer to be fixed within the moisture-swollen fibers of the textile. exposed to somewhat higher concentrations of formaldehyde.

While the moisture content of the textile to be treated is important, the concentrations of water, acid and formaldehyde in the treating atmosphere or gas phase can be varied within wide limits and are not particularly important in and of themselves. In order to achieve optimal results for a particular case, they can be easily coordinated with other factors such as the nature and quantity of the applied polymer former, type of acid vapor used, reaction temperature and exposure time for the textile on the basis of previous trials and textile development. Generally speaking, the amount of acid vapor and formaldehyde present in the vapor phase or phases that fill the treatment chambers is well in excess of the small amounts of such chemicals that are actually "needed" to complete the desired chemical reactions in the textile being treated.

Sulfur dioxide has been found to give particularly good results and

is the most preferred gaseous acid catalyst according to the present invention, because it is particularly suitable for forming a strong acid in the presence of formaldehyde, probably in the form of a sulphonic acid, and yet it is easily removed from the textile by washing after the steam treatment. However, other acids that have a boiling point may

below 120°C, i.e. formic or acetic acid, is used instead of SC^. Hydrochloric acid is likewise usable, although it may cause greater darkening of the fabric if left in the fabric without any counteractive acid acceptor for an extended period of time for the final curing and washing.

In the preferred method, the wet cotton textile is fed continuously through one or more zones containing the reactive acid and formaldehyde vapor and which are maintained at a temperature of at least 80°C, preferably from 100 to 170°C. The textile is fed through such a chamber or several such chambers or reaction stages at such a rate that a total exposure time of from about 10 seconds to about 15 minutes, preferably 30 seconds to 2 minutes, is achieved. Typical of a multi-step process as described earlier herein is a textile exposure time of about 1 minute at 102°C to an atmosphere of water vapor and SO 2 in the first step(s) and from about an additional 30 seconds to 1 minute in a subsequent formaldehyde-containing step at the same temperature, which should be considered representative of satisfactory operating conditions.

The optimum vapor phase reaction time is one just long enough to cause the desired degree of fixation of the N-methylol compound (ie 3 to 12 * ?<> polymer intended for the textile) and active formaldehyde crosslinker (ie 0.2 to 5.0 fo calculated on the textile), without overexposure of the textile to the reactive atmosphere. In addition to formaldehyde vapor and gaseous acid catalyst, the reactive vapor phase can also contain inert gases such as air, nitrogen, carbon dioxide, helium and the like. Of course, steam is present in the hot vapor phase at least as a result of evaporation of water from the passing impregnated textile, or it may be intentionally supplied as such to the treatment chamber as a means of heating the impregnated textile to the desired temperature or as a means to maintain the moisture level in the textile at the desired level or levels while it is being processed. However, instead of using steam to achieve the desired reaction temperature, other heat sources such as infrared lamps can be used.

The formaldehyde may be provided for the process in any convenient manner, such as heating a suspension of paraformaldehyde in mineral oil to provide formaldehyde gas, or by passing air through an aqueous formaldehyde solution and dosing the resulting formaldehyde vapor or vapor mixture in suitable portions to the reaction zone. If a highly methylated melamine is used as the polymer former, such a compound can itself also provide some active formaldehyde crosslinker if exposed to high temperature in the final dry curing step.

After exposure to the reactive atmosphere, the cellulosic fabric is dried directly, if the original impregnation bath contained a latent curing catalyst, in preparation for the production of permanent press articles. No other rinsing or treatment is necessary in such a case. Only if the latent catalyst was not contained in the original impregnation bath is it necessary, after the steam treatment and before the drying step, to pass the textile through a second impregnation bath containing an aqueous solution of a suitable latent curing catalyst, whereby the textile is catalyzed for the final dry curing . The drying conditions are not particularly critical, but drying should be limited so that the moisture content of the textile does not fall below 6 to 10 $ and so that accidental hardening is avoided. E.g. the treated cellulose material can be dried at temperatures between approx. 20 and 60°C for a suitable period of time.

The permanent press articles can be made by first making a garment with heat-pressed pleats from the dry, uncured fabric, ("delayed cure''), or by first curing the fabric in a flat state and then making a final product from the cured fabric (" hardening").

The curing or the final treatment to make the treated textiles wrinkle-free can be carried out by dry curing in a hot air oven at temperatures between 100°C and the charring temperature of the textile, preferably at temperatures of approx. 120 to 180°C, or in any other suitable heating equipment. Curing can also e.g. is carried out in equipment such as a toy press which is equipped with suitable heating and residence time control means. A residence time of about 5 minutes in an air oven at 160°C provides satisfactory curing in most cases, although curing times in the range of about 2 to 10 minutes can usually be used.

It will of course be understood that the cellulose material according to the present invention can be treated with other conventional textile treatment agents such as water-repellent agents, antimicrobial agents, flame-retardant agents, dirt-removing agents, anti-stain agents and the like which are otherwise well known in the art.

The present invention is additionally illustrated by the following examples. All parts and percentages are by weight in the examples as well as in other parts of the specification and requirements, unless otherwise noted.

All examples were carried out in accordance with the present invention, using 100% cotton cyper textile with a

2

weight of 257.7 g per m and a thread density of 166 x 52.

Examples 1-4

The examples were carried out using the preferred simple foulard method.

Samples of the cotton cypress textile, approximately 4.6 meters long

and 43 cm wide, weight approx. 500 g, was fed from a preroll and impregnated to about 70 µl wet absorption in an aqueous bath maintained at room temperature (about 22°C) and containing various amounts of hexakis (methoxymethyl) melamine precondensate ("Aerotex P- 225") or dimethoxymethylhydroxymethylmelamine precondensate ("Aerotex M-3"), 0.5 f° zinc nitrate hexahydrate, 0.5 1° "Triton X-100" nonionic wetting agent, and 1.0 $> finely divided polyethylene textile softener ("Velvamine 732"), as further shown in Table I.

After lightly squeezing out excess liquid by feeding through a pair of press rollers, each of these samples was quickly passed over three transport rollers through a treatment chamber with a volume of approx. 0.085 m^ (approx. 45.7 cm width, 30.5 cm length and 61 cm height), where one of said rollers was placed close to the textile intake gap on one side of the base of the chamber, the other roller placed near the top of the chamber on a line between the two side walls of the chamber and the third roller placed near the textile outlet gap at the bottom surface of the chamber opposite the intake gap whereby the textile is fed through the chamber along an inverted V-shaped path with approx. 1.22 m length.

Formaldehyde was obtained by heating a paraformaldehyde-mineral oil mixture in a stainless steel tank. The heated steam was carried by a metered amount of compressed air through heated manifolds and one of many gas inlet tubes into the reaction chamber. Sulfur dioxide was taken from a tank and dosed through the same or similar supply lines. In some experiments, both sulfur dioxide and formaldehyde gas were introduced into the chamber through a branch tube placed near the textile inlet, but in the preferred embodiment only SOg was introduced near the textile inlet. at the bottom while the formaldehyde was introduced into the interior of the chamber near the top roll. Steam introduction could also be carried out and was used in some cases, but was usually found unnecessary in this equipment for small scale because a suitable moisture content was easily achieved in the impregnated textile without steam introduction. However, in commercial-scale equipment, steam injection can provide increased humidity control for optimal resin fixation.

By varying the textile speed, the residence time of the textile in the chamber could be varied from 30 seconds to 3 minutes as desired.

At the beginning of each trial, the formaldehyde generator was filled with 200 g of paraformaldehyde. The air flow into the generator was usually 0.14 m^/hour while sulfur dioxide was supplied at 0.11 m^/hour, measured at approx. 22°C and approx. 1 atmosphere. The formaldehyde generator temperature was between 120 and 140°C, and the treatment chamber was in most cases kept either at approx. 102°C or approx. 118°C, depending on the desired reaction conditions.

In typical tests, approximately 100 g of SO2 and 50 g of formaldehyde quickly entered the treatment chamber when treating a cotton textile sample of approx. 500 g of 4.6 meter length. However, lay

these steam quantities several times above the minimum requirements. In a chamber of commercial steel with much larger volume and proportionally less gas leakage, satisfactory results should be obtained by introducing as little as 3 to 5 g of SC^ and 2 to 3 g of formaldehyde per 100 g of cotton textile in such a chamber.

After the steam treatment, the textile was dried in an air oven at 52°C for approx. 20 minutes and, after pressing, air cured at 160°C

for 5 minutes, washed (AATCC 124-1967 III B), and assessed for appearance and other properties after a round of washing and drumming (1 L+D). In addition, in some cases the textile was also dyed before curing, after steam treatment and washing. In addition to this, some of the treated, hardened samples were washed for curing and their properties were measured.

For comparison, a sample on the same cotton wick was also treated by a previously used "steam-wet fixing" method, similar to that described in Swedish patent no. 364320.

More specifically, the textile in this trial was impregnated

to 60 io wet absorption in a bath containing 29 i° "Aerotex 19", methylolated melamine (65 1° active compound), 38 $ "Fixapret PCL", methylolated melamine (50 <f° active compound), 0.1 <fo "Triton X-100" wetting agent, the bath was adjusted to a pH of 2 by adding a suitable amount of sulfuric acid.

After impregnation, this sample was steamed in the steam chamber at 102°C for 45 seconds, neutralized in 0.5 µg sodium carbonate solution, rinsed, washed and dried. It was then catalyzed by impregnation to 60 µg wet absorption in a solution containing 0, 8 fo ZnN0^.6H20 and 2% polyethylene plasticizers. After drying, the sample was dried, pressed and air-cured at 160°C for 10 minutes, the same as all other samples, and its appearance and other physical properties were determined.

Data in connection with the number of trials which are representative of the present invention, as well as trials where the trial was treated according to the previous "steam-wet fixation" method, are listed in table I.

As can be seen from Table I, textiles treated in accordance with the present invention achieve a desired balance between easy-care properties (lasting pressure, crease retention, folding recovery) and physical properties (break and tear resistance, "Stoll flex abrasion"), together with the commercially important advantage of short production time (no necessary washing-off and only 1-2 minute reaction time). A comparison between example 5 and examples 1 - 4 points to the fact that injecting SO 2 and formaldehyde one after the other rather than simultaneously results in better iron retention.

In all cases, the fold recovery ability of the uncured textile was low enough for delayed curing treatment. Furthermore, when compared to the same cotton cypress fabric treated by the conventional steam-wet fixing method, the cured fabrics treated according to the present invention generally had better easy care properties with comparable physical properties.

Example 2/ l - 2/ 4

In another series of tests, samples of cotton cypertek^ styles were impregnated to about $70 wet absorption in an aqueous bath containing $10 "Aerotex P-225" precondensate or "Aerotex M-3" precondensate, 0.5 1» ( "owf") zinc nitrate, 0.5 1° "Triton X-100" nonionic wetting agent, and 1.0 <fo ("owf") finely divided polyethylene fabric softener ("Velvamine 732"), and then continuously treated in two different vapor atmospheres as mentioned. Data from these trials are listed in Table II.

In the first steam treatment, the sample was exposed to an atmosphere consisting of saturated water vapor, or an atmosphere containing gaseous sulfur dioxide and saturated water vapor, at about 102°C for either 1 or 3 minutes to attach or fix the precondensate to the interior of the fibers, which shown in Table II.

In the second steam treatment, the sample was exposed to an atmosphere containing a mixture of formaldehyde vapour, air and gaseous sulfur dioxide at 102°C for 3 minutes in tests 2/1, 2/2 and 2/3, and at 115°C for 1 minute in attempt 2/4.

The samples treated in this way were then air-dried at approximately 50°C.

Some of the fabric samples were washed and their textile properties measured as was done in examples 1-5.

The remaining samples were folded by pressing with a hot iron, air cured at about 160°C for 5 minutes, washed, and their textile properties measured as was done in Examples 1-5.

As can be seen from Table II, fabrics treated according to this aspect of the present invention also have a usable level of ease of care and physical properties. In general, however, they show no important advantage compared to the textiles from examples 1-5 which were treated by the faster and somewhat simpler method, without any addition of steam.

Example 3/ 1

In order to visualize the effectiveness of the vapor phase treatment when fixing a polymer former in cellulose fibres, a couple of comparison tests were carried out, one of which included a vapor treatment according to the present invention, while the other did not.

More specifically, the two samples of cotton cypress fabric, as described earlier herein, were impregnated in a bath containing 4% "M-3" methylated melamine plus 4% "P-225" methylolated melamine,

and 0.8 io Zn(NO 2 ) 6 H 2 O. After such impregnation, one of these samples was subjected to a vapor phase fixation treatment with SO^ and formaldehyde analogous to that described previously for example 1-4 (table i) after which it was washed, recatalyzed by impregnation in a solution containing 0.8 in Zn(N0 ^)2« åRgO, dried, cured for 5 minutes at 160°C, and washed and dried again, while the other sample was washed, catalyzed, dried, cured, washed and dried again in a similar manner, but without any intervening vapor phase fixation step.

The results are summarized in table III.

As is clearly evident from Table III, the steam treatment according to the present invention transforms the aminoplast precondensate into an insoluble form which resists washing and which, by re-catalysing the textile, can serve to promote the permanent press properties of the textile when it is cured. In contrast, most of the pre-condensate remains water-soluble if a steam treatment is missing, so that it is removed by washing, and is not able to provide satisfactory lasting pressing properties by a subsequent curing.

The difference in addition determined on the basis of the finally cured samples further confirms the effectiveness of the present invention in fixing the aminoplast in a so-called non-absorbable form in the textile, while only a small fraction of the originally applied aminoplast remains on the textile after washing if such a steam treatment missing.

'One should note that in comparison with the procedure

in example 3/1-A with the method used in all previous examples, a washing step and a recatalysis step were inserted between steam

the treatment step and the dry curing step. This method allows the development of the efficiency of the resin fixation that was achieved by steam treatment, but is not necessary for some practical reasons. As shown in Table III, the easy care properties of the fabric in Example J>/l-B are not developed because there is insufficient resin fixation when the steam treatment is lacking.

The aforementioned specifications describe the general principles and features as well as preferred embodiments and modifications of the present invention.

Claims (5)

1. Method for giving a cellulose fiber-containing textile material the ability to resist curling and to give it advantageous • properties with a view to uniform drying and lasting pressure, by adding to the material an aqueous solution comprising at least one water-soluble polymer-forming precondensate with reactive N- methylol groups and polymerization of said precondensate in said material, in the presence of an acidic catalyst while the cellulosic fibers are swollen due to moisture, thereby forming a substantially water-insoluble polymer in the swollen fibers which can then be cross-linked by curing to achieve the desired properties, characterized in that the material with the applied water-soluble polymer-forming N-methylol precondensate and in a water-swollen state in a steam treatment zone at a temperature of between 80°C and 180°C, preferably between 120°C and 170°C, is exposed to a reactive atmosphere , comprising vapors of formaldehyde and vapors of a volatile acid with a boiling point below 120°C for a period of time m in between 10 sec. and 15 min., preferably 30 sec. to 2 min., and sufficient to fix in the cellulose fibers from 3 to 1258 polymer and formaldehyde in an essentially water-insoluble form, and that the material is then partially dried to a moisture content of not less than 6%, while residues of volatile acid catalyst are driven of as preparation for the manufacture of a garment which can be given "durable-press" properties by curing in a substantially dry state in the presence of a latent acid solid catalyst. 2. Method according to claim 1, characterized in that sulfur dioxide, formic acid or acetic acid are used as acidic vapors. 3. Method according to claim log2, characterized in that the material with the applied N-methylol compound is precondensed by heating to a temperature of between 100°C and 180°C, while the moisture content in the material is kept to between 15 and 90, preferably 30 to 70 by weight %, for the thus swollen material is exposed to the reactive vapors of formaldehyde and sulfur dioxide. 4. Method according to any one of the preceding claims, characterized in that the material is treated in the steam treatment zone in a number of successive steps, where sulfur dioxide is supplied in a first step, while formaldehyde is supplied in a subsequent step. 5. Method according to any one of the preceding claims, characterized in that the latent acid solid catalyst which is necessary for the final dry curing is supplied to the material from the same aqueous solution as the polymer-formed precondensate.