US3690939A - Process for the coating of textiles - Google Patents

Abstract

PROCESS FOR COATING OF TEXTILE FLAT-SHAPED ARTICLES WHICH COMPRISES IMPREGNATING THE ARTICLES WITH A SOLUTION OR DISPERSION CONTAINING AN EPOXY COMPOUND, A THIO COMPOUND CONTAINING A

-C(=S)-

GROUP BOUND TO AT LEAST ONE NITROGEN ATOM AND A HIGH POLYMERIC MATERIAL. AFTER IMPREGNATION, THE COATING IS AFFIXED TO THE SUBSTRATE EITHER IN WET OR DRY STATE.

Description

Unit

ABSTRACT OF THE DISCLOSURE Process for coating of textile flat-shaped articles which comprises impregnating the articles with a solution or dispersion containing an epoxy compound, a thio compound containing a II C group bound to at least one nitrogen atom and a high polymeric material. After impregnation, the coating is afiixed to the substrate either in wet or dry state.

The present invention relates to a process for the coating of textile fiat-shaped articles by coating with highpolymeric compounds. It is characterised in that the textile material is impregnated with a solution or dispersion containing an epoxy compound, a thio compound containing a group bound to at least one nitrogen atom, as well as a high-polymeric compound differing from those mentioned, and subsequently fixed in the wet or dry state.

Coated textile flat-shaped articles serve the most diverse purposes, and have a continually widening field of application in a growing number of fields.

The coating with high-polymeric compounds can be applied in one stage, e.g. by padding, spreading, knifecoating, or by simple immersion, for the sole purpose of modifying the surface, whereby it is usual and also necessary, in most cases, for so-called adhesion-promoting agents to be added.

The coating can, however, also be applied in two stages, the first stage consisting of the application of a thin coating designed to provide adequate adhesion for the actual final coating applied in the second stage. A small amount of the high polymer to be fixed, or a related substance, is bonded with the adhesion-promoting agent firmly to the textile material, in order to serve as an anchor for the main amount of high polymer subsequently applied. This procedure is essential especially in the case of fibres having a smooth surface, and in the case of heavy coatings such as are usual for rubberised fabric and for tire-cord.

Regarding inert textile fibres such as polyolefin fibres, and particularly carbon and glass fibres, the adhesive layer can be applied also for rendering these fibres accessible to subsequent processing operations, such as dyeing and finishing, using conventional agents and equipment.

Corresponding to these very varied possibilities, the requirements to be satisfied by the properties of the coatings are both numerous and stringent.

A coating should adhere firmly to the textile material; it should be possible for the coating to be fixed in quantitative yield, and the process should involve no expensive aftertreatment operations, or produce any troublesome by-products. Damage to the ground fabric should not occur either in the fixing operation or subsequently in service. Accordingly, the coating should also be fast to water, solvents, washing, rubbing and scouring, and to cracking; it should not unfavourably affect the feel of the fabric, and, in particular, not cause hardening. Furthermore, the preparation to be applied should be so stable that it ensures pot times of sufficient length to render possible the maintenance of a reliable and reproducible working procedure, even under varying climatic conditions.

Numerous suggestions have already been published for the fixing of high polymers on textiles, especially for synthetic fibres and glass fibres. For example, the fixing of chitin derivatives by complex salt formation with heavy metal salts has been suggested (US. Pat. 3,323,- 072). Apart from undesirable discolourations, the adhesiveness of such coatings is not particularly good.

The fixing of epoxy compounds with the aid of thiourea has also already been suggested. As an example can be mentioned the reaction of cotton with epichlorhydrin and thiourea, which 'was, of course, for the purpose of crosslinking and gave poor results (J. Polymer. Sci. 13, 1969, 607-627). Described in the French Pat. 1,502,124 is the fixing of dyestuffs by means of epoxy compounds and thio compounds. The use of thiourea as a hardening accelerator in the polymerisation of epoxy resins is also known (British Pat. 1,153,639). Substituted thioureas have been used with epoxy compounds for copolymerisation (French Pat. 1,478,361 and US. Pat. 3,459,694).

In the case of the present invention, thiourea is only used in order to form from the epoxy derivative the more reactive episulphide which, in its turn, acts as adhesionpromoting agent for the high-polymeric substance also used in the instant invention. The last-mentioned determines essentially the finishing effect to be expected. The process is therefore extremely variable and very economical.

On the basis of the known prior publications regarding the reaction of epoxy compounds with thiourea and its derivatives, it was not to be anticipated that it would be possible therewith to quantitatively fix high polymers by copolymerisation, or by another unknown mechanism, under mild conditions and without catalysts, with the episulphides forming in statu nascendi.

For fixing the adhesive layer for the rubberising of fabrics and cord, resorcin-formaldehyde latex preparations of the most varied compositions and forms are used (Rayon and Synthetic Textiles 31, 79, 1950). Of the many other suggested substances, only polyisocyanates have so far proved effective as an adhesive-promoting agent in practice (Textil Praxis 24, 163-167, 1969). The other suggested substances produce, especially on polyester fibres, undesirable hardening eflfects, while the polyisocyanates have the disadvantage of short pot times which make a rational working procedure very difiicult.

With the coming into use of synthetic fibres in the cord field, the RFL-adhesion-promoting agents have proved, in many respects, to be inadequate. Apart from poor adhesiveness, a further complaint has been that the handle of the cord fabric is too hard, causing great difiiuculties in processing.

Numerous attempts have therefore been made to improve the RFL-adhesion-promoting agents with respect to their behaviour on synthetic fibres.

For example, they were combined with polyisocyanates (US. Pat. 3,433,768, US. Pat. 3,240,649, Swiss Pat. 436,700). The last-named have also been used alone together with a latex emulsion (US. Pat. 3,240,659). There have also been numerous suggestions for combinations of RFL with epoxy compounds (British Pat. 1,181,482, published Japanese applications /259, 70/5,398, German Pats. 1,620,771, and 1,928,475, British Pat. 1,122,117

70 and French Pat. 1,478,501).

In order to overcome the observed disadvantages of RFL on synthetic fibres, it has also been suggested that epoxy compounds be used with the addition of catalysts, in combination with latex and without RFL (U.S. Pats. 2,902,398 and 3,423,230, French Pat. 1,568,059, and Belgian Pat. 645,063).

The disadvantages of the stated processes are essentially the need to use strong catalysts such as, e.g. zinc fluoborate, unstable dispersions, water-insoluble epoxy compounds, and high fixing temperatures leading to damage to the fibres.

In order to avoid difiiculties therefore, it is suggested in French Pat. 1,571,472 that the catalyst, e.g. a strong basic amine, be added to the fibre during the spinning operation, a procedure, however, which introduces other disadvantages.

Compared with this, the process according to the present invention enables, by a simple procedure and under conditions which cause no damage to the fibres, the latex layer to be fixed, without the addition of catalysts, quantitatively and very firmly on a varied range of cord fabrics, thus ensuring very good adhesion of the rubber coating subsequently applied. Particularly remarkable is also the soft and elastic handle of the cord fabric. For the fixing of natural or modified high polymers on synthetic fibres, and particularly on glass fibres, it has been suggested that, in addition to numerous polymerisable substances of the urea resin and melamine resin type, complex salt formation with heavy metal salts also be used, e.g. for chitin derivatives (US. Pat. 3,023,072). Apart from severe discolourations, the adhesion of such coatings is not particularly good.

In quite general terms, it can be said of the hitherto known processes for the coating of textiles, amongst which also figure various epoxy compounds, that they have the disadvantage that strong acids or bases are required as catalysts.

The process according to the present invention has, in various respects, a number of significant and unexpected advantages, especially a very wide field of application, long pot times, good effects with small amounts of the adhesion-promoting agent, and application under mild conditions. Not only does fixation of the various high polymers occur quantitatively on any desired textile substrate, and without catalysts having to be used, but elfects are obtained which are distinguished by good adhesion, and which withstand boiling water as good as they Withstand organic solvents.

The high-polymeric substances can be used in the form of solutions in water, alcohol, or similar, preferably watermiscible solvents, or in the form of fine colloidal disper- SlOIlS.

Of natural high-polymeric compounds, proteins and proteids can be mentioned. For example, albumins such as egg alubumin, globulins such as myosin, prolamines such as zein, skleroproteins, collagens, gelatine, casein; also polysaccharides such as cellulose, starch, chitin deriatives and, finally, the various types of natural rubber.

Suitable chemically modified, natural high polymers are starches and cellulose ethers and -esters, such as, e.g. starch xanthogenate, acetyl cellulose, hydroxypropyl cellulose and cellulose ethyl sulphonate.

Of the suitable fully synthetic high polymers, the following are given as examples: polyvinyl compounds such as polyvinyl chloride, -acetate, -alcohol, -pyrrolidone, polyvinylidene chloride; polyacryl compounds such as polyacrylic acid and polyacrylic acid ester and methacrylic acid ester, as well as polyacrylonitrile; also polyacrolein, polyamides such as Polyamide 6,6 and 6,10 as well as Polyamide 6, polyesters such as ethylene' glycol terephthalate, polycarbonates, polyurethanes, polyaldehydes, polyethers, polysulphides, polysulphones, also mixed polymerisates such as butadiene-styrene, acrylonitrile-styrene and vinylpyridine-butadiene-styrene.

Suitable as rubber emulsions are natural or synthetic latex such as, e.g. butadiene-acrylonitrile and butadienestyrene copolymers, also styrene-butadiene-vinylpyridine capolymers, polybutadiene, polyisoprene, polychloroprene and polysulphide rubber, cross-linked polyurethanes and sulphochlorinated polyethylene.

Suitable epoxy compounds for the present process, on their own or in mixtures of various epoxy compounds, are: glycide, epoxypropionaldehyde, epoxypropionic acid, epoxyamines such as l,2-epoxydiethylaminopropane, allylglycidyl ether, as well as epoxysilanes and -si1oxanes; also very suitable are diepoxy compounds such as diglycidylformal, diglycidyl ether, ethylene glycol diglycidyl ether, vinylcyclohexenediepoxide, 2,3-bis-(epoxypropoxy) 1,4- dioxane, 1,3- and 1,4-butanedioldiglycidyl ether, diepoxytrimethylenetrisulphone and N-bis-(epoxy-2,3 proyl)- aniline.

It is particularly simple to work with water-soluble, polyfunctional heterocyclic epoxy compounds such as diglycidyldimethylhydantoin, diglycidylimidazolidone, triglycidylcyanurate and -isocyanurate, triglycidylmelamine, as well as hexahydro tris (beta-epoxy 2,3 propoxy)- propionyl-triazine. Polyepoxy compounds of this type are described, for example, in the French Pats. 1,267,432 and 1,355,847, as well as in the US. Pats. 2,809,942, 2,741,- 607 and 2,469,683.

Also suitable are compounds which can be converted under the reaction conditions into epoxy compounds, such as sulphuric acid hydrins and halogen hydrins, or their quaternary derivatives.

Of thio compounds containing a S H C group bound to a nitrogen atom, mention is made of Illlu urea and its derivatives, as well as the salts of thiocyanic acid. As in the case of the epoxy compounds, they are applied most advantageously from aqueous solution.

Suitable textile fibres, in addition to natural vegetable and animal fibres such as cotton, linen, jute, wool and silk, are, in particular, chemically modified fibres such as cellulose esterand ether and especially fully synthetic fibres made from polyamides, polyesters, polyolefins, polyvinyl and polyacryl compounds, as well as fibres made from glass, asbestos, carbon and metals.

The concentrations of chemicals to be used depend to a great extent on the desired effect. Whereas for a simple priming (adhesive) layer, 1-5% of the weight of the fibres suffices, the weight increase for the proper coatings can vary within the range of 5-5 0%; indeed, for special cases it can be even greater.

The epoxy compound should constitute approximately 550% of the applied polymer, whilst of the thio compound, half to double the amount, relative to the epoxy compound, is used.

In the case of a squeezing effect of 50%, the amounts used are, e.g. g. of high-polymeric compound per litre, 10 g. of epoxy compound per litre, and 10 g. of thio compound per litre. The fixation time depends on the duration of the process and on the temperature; this can vary from room temperature to about 200 C. For example, the fabric can be rolled up after impregnation and wrapped in a plastic sheet, in order to avoid loss of moisture. Fixing takes at room temperature about 6 to 24 hours. It is also possible to firstly dry and then to fix by means of steam or hot air. At 100-150, fixing takes between 3 minutes and 30 seconds. The milder the fixing conditions, the softer and more supple is the coating. As a rule, however, the chosen conditions have no effect on the fastness to washing and to solvents, and on adhesion in general. The desired optimum between the rate of working and the desired effect can easily be determined, in each case, by preliminary tests.

Depending on the intended use of the material, various other additives may be added to the coatings; dyestuffs can, for example, be incorporated and fixed. Particularly advantageous is the addition of high polymers which contain large proportions of chemically bonded dyestuff molecules, or which have been reacted beforehand with waterinsoluble dyestuffs such as vat dyestuffs. It is also possible, however, to incorporate and fix pigments or delustring agents such as titanium dioxide, melamine resins, or polysulphide and polysulphone resins. The addition of mica in a finely divided flake-like form also produces particularly interesting effects. In addition to optical brighteners and UV-absorbers, a great number of other processing agents may also be added.

The urea formed as the sole by-product during the reaction from the thiourea is harmless and does not need to be washed out, an aspect to be considered as a further significant advantage of the process according to the present invention.

The three components, namely epoxy, thio compound and latex, can be applied together from a single bath to the cord fabric. It is also possible to first apply the epoxy compound, and afterwards the latex emulsion together with the thio compound, whereupon they are jointly fixed. This embodiment does have the disadvantage of being somewhat more complicated. On the other hand, the treatment baths are stable to an unlimited extent, which is not the case in the three-component system. Nevertheless, pot times of 12-24 hours are attainable, which fully ensures a safe working procedure.

Fixing can be performed in the wet or dry state. For example, the impregnated fabric, rolled up and packed in a plastic sheet, can be allowed to stand for 12 to 24 hours at room temperature, and subsequently dried.

Drying may also be carried out immediately by means of hot air, whereupon fixing is subsequently performed likewise in hot air. Temperatures of 100 to 250 correspond to fixing times of 3 minutes to 30 seconds.

The fixing conditions to be applied depend to a great extent on the desired rate of working and on the effect required. The milder the conditions, the softer is the obtained handle.

A special embodiment of the present invention consists in the textile carrier fabric, after coating is completed, being dissolved out or decomposed, so that a flatshaped article remains consisting only of the copolymeric synthetic resin. Such articles are especially suitable for use as filters and catalyst-carriers. Apart from this special form, fabrics coated according to the present process are suitable for the following applications: Feed-belt material, wagon and car covers, inflatable marquees, oil-collecting covers, oil-adsorbing nonwoven textiles, roof-sealing sheets, gas-storage balloons, tent floors, bellows, pneumatic boots, cord fabric for vehicle tires, tent materials and blind materials.

The following examples contain the temperatures expressed in degrees centigrade. Parts denote parts by weight, and percentage figures denote percent by weight, where not otherwise stated.

EXAMPLE 1 1 part of thiourea and 2 parts of triglycidylisocyanurate are dissolved in 75 parts of water, and 25 parts of a 50% emulsion of vinyl-butadiene-styrene are added. A fabric made from polypropylene is impregnated in this emulsion; the fabric is then squeezed out to 50% weight-increase, dried, and fixed for 2 minutes at 100. The fabric can be dyed or printed with dispersion dyestuffs.

EXAMPLE 2 The procedure is used as described in Example 1; the thiourea is replaced, however, by potassium rhodanide and a polyacryl emulsion is used obtainable commercially under the name of Dicrylan C, whereby a similarly good result is obtained.

EXAMPLE 3 4 parts of the triepoxy compound of hexahydrotriacryloyltriazine and 4 parts of thiourea are dissolved in 30 parts of water; 5 parts of a polysulphide produced according to the French Pat. 1,502,124 are introduced, and 20 parts of a 50% vinyl-butadiene-styrene emulsion are also added.

A glass fabric is then impregnated, dried and thermofixed in an infrared oven. The weight increase is 55%. The coating is not affected by boiling in water for half an hour.

If the fabric is placed into a large vessel with water containing small amounts of toluene or mineral oil, and the whole shaken, the fabric absorbs in a short time all the organic substance. The fabric is taken out and re generated with alcohol or by distillation.

EXAMPLE 4 A polyester fabric is impregnated in a solution of 1 part of thiourea, 1 part of triglycidylisocyanurate, 1 part of finely dispersed copper phthalocyanine and 10 parts of a 10% butadiene-styrene emulsion; the fabric is then squeezed out, dried and thermofixed. The fabric is subsequently impregnated with a rubber solution and vulcanised. The coating is distinguished by exceptional adhesiveness, and a soft handle.

EXAMPLE 5 A polyester fabric made from ethylene glycol terephthalate is impregnated in a dispersion of parts of vinyl-butadiene-styrene in the form of a 50% emulsion, 10 parts of thiourea and 20 parts of triglycidylisocyanurate in 1000 parts of water at room temperature; the fabric is then squeezed out and dried. It is afterwards dried and fixed in an infrared field for 30 seconds. The weight increase of the fabric is 15%. The weight increase is unchanged after the fabric has boiled for one hour in 0.2% soap solution.

An identically treated fabric is rolled up and stored for 24 hours wrapped in a plastic sheet. After drying, the fabric has the same weight increase and similar properties.

EXAMPLE 6 A glass fabric is impregnated in a solution of 50 parts of zein, 10 parts of sodium thiocyanate and 10 parts of the epoxy compound stated in Example 3 in 1000 parts of 70% alcohol, and then dried. The fabric is afterwards fixed for 30 seconds at It has a 5% weight increase.

EXAMPLE 7 A fabric made from polypropylene is impregnated with a solution of 40 parts of chitosan, 20 parts of thiourea and 20 parts of the epoxy compound mentioned in Example 3 in 1000 parts of water, and then dried. The fabric is thermo-fixed for two minutes at 100. It can be dyed and printed with reactive and acid dyestuffs.

EXAMPLE 8 Two parts of thiourea and two parts of triglycidylisocyanurate are dissolved in 75 parts of water, and 25 parts of a 50% emulsion of styrene-butadiene-vinylpyridinecopolymer latex are added.

A cord fabric is impregnated in this emulsion, whereby the weight increase is adjusted to 100%. The fabric is dried immediately afterwards and fixed with hot air. The time is 60 seconds at The fabric has a compact, but supple and soft handle.

It is subsequently coated on both sides with vulcanisable rubber, and vulcanised for 30 minutes at 145.

The adhesion of the rubber to the enclosed polyester fibres is very good, as is shown by tensile tests at 120.

If, instead of triglycidylisocyanurate, identical parts of dimethyl-diglycidylhydantoin are used, or identical parts of the triepoxy compound of triacryloylhexahydrotriazine, the procedure otherwise being as described, then similarly good results are obtained.

If, instead of a cord fabric made from polyester fibres, one made from rayon fibres, glass fibres or polyamide fibres is used, then likewise are obtained similarly good adhesive-strength values.

EXAMPLE 9 A cord fabric made from polyester fibres is impregnated in a aqueous solution of triglycidylisocyanurate, and dried at 200. It is then immersed in an aqueous preparation of 30 parts of a 50% emulsion of styrene-butadiene-copolymer latex and 5 parts of thiourea, and again dried for 2 minutes at 200 in hot air, and thermofixed.

The fabric is further treated as described in Example 1. The fabric possesses the same good properties.

If, instead of thiourea, identical parts of sodium thiocyanate are used, or instead of triglycidylisocyanurate, one of the other epoxy compounds mentioned in Example 1, the procedure being otherwise as described, then similarly good results are obtained.

I claim:

1. A process of coating a flat-shaped textile article which comprises impregnating said article with a solution or a dispersion containing an epoxy compound, a thio compound having a s [I C group which is bound to at least one nitrogen atom and a high polymeric material selected from natural and synthetic latex, the weight increase of the textile article due to said epoxy and thio compounds and the high polymeric material combined being from 1 to 50 percent by weight, the epoxy compound constituting from 5 to 50 percent of said polymeric material and the thio compound constituting from one half to twice the amount by weight of the epoxy compound and drying the treated textile.

2. Process according to claim 1, characterized in that the epoxy compound is water soluble.

3. Process according to claim 1, characterized in that the thio compound is thiourea or a salt of thiocyanic acid.

4. Process according to claim 1, wherein said textile article is a cord fabric made from polyamide, polyester, glass or metal, or from mixtures thereof.

5. Process according to claim 1, characterized in that S ll group which is bound to at least one nitrogen atom and a high polymeric material selected from natural and synthetic latex to a solids pick-up of 1 to percent by weight of the textile, the epoxy compound constituting from 5 to 50 percent of said polymeric material and the thio compound constituting from one half to twice the amount by weight of the epoxy compound, said compounds and the polymer having been fixed onto said textile cord by drying and by dry heat treatment.

References Cited UNITED STATES PATENTS 2,795,513 6/1957 Rossin 117-11 3,247,016 4/1966 Zimmerman et a1. 117137 3,310,420 3/1967 Wagner 117-136 3,376,160 4/1968 Blane 117136 3,423,230 1/1969 Georges 117138.8 N 3,475,251 10/1969 Widmer 117-138.8 F

FOREIGN PATENTS 1,502,124 10/ 1967 France.

WILLIAM D. MARTIN, Primary Examiner D. COHEN, Assistant Examiner U.S. Cl. X.R.

117126 GQ, GE, 128.4, 138.8 N, E, F, 161 P, K, UZ, UN, UB, KP, R, UT, UD, 163, 164