CA1037191A - Polyurethane adhesive and a method for heat sealing textiles - Google Patents

Abstract

Abstract of the Disclosure A solvent-free polyurethane adhesive for heat seal-ing textiles which is resistant to solvents and detergents used in dry cleaning processes which is prepared from a) about 55 to about 95% by weight, based on the whole polyurethane mass, of at least one compound which contains at least two aliphatic hydroxyl groups and has a molecular weight of from about 1000 to about 2500 and a melting point of from about 25° to about 130°C, b) at least one organic polyisocyanate, prefer-ably present in about 5 to about 45% by weight, and c) 0 to about 15% by weight, based on the whole polyurethane mass, of at least one aliphatic polyol and/or polyamine, using an equivalent ratio of

Description

Mo-1452-H
LeA 15,196 ~0~
POLYURETHANE ADHESIVE AND A METHOD
FOR HEAT SEALING TEXTILES

This invention relates generally to textiles and more particularly to a process for heat sealing textile sheets or sheet-like structures with polyurethanes or poly-urethane ureas.

It is known that thermoplastic synthetic resins may be used to heat seal textile sheets. The thermoplasts may be applied to the textile surface as solids, e.g in the form of powders (with certain particle sizes), fibers, woven fabrics or non-woven webs. Alternatively, the thermoplasts may be applied as viscous aqueous suspensions or dispersions.
The thermoplasts may also be dissolved in suitable solvents to form viscous pastes which are applied to the textile surface and then heated to dryness before the textile is sealed by further heating. A further layer of fabric may be applied to a surface which has been prepared in this way.

In the field of heat sealing textile sheets it is advantageous to utilize heat sealing compounds which develop the strongest possible bond and can still be ironed, at a low temperature and pressure, within a short time. There is, therefore, a commercial demand for products which can be sealed at temperatures below 150C in less than 10 seconds.

In the past, heat sealing adhesives prepared from polyethylene, polyvinyl chloride, polyamides or polyvinyl acetate-polyethylene copolymers have been preferred. The adhesives have melting points of from 100 to 120C and their - melt viscosity may be adjusted to provide sufficient elasticity and adhesive power, even at ironing temperatures above 120C, enabling ironing of the treated textile to be LeA 15,196 10;~7~91 carried out over a wide range of temperatures using a short operating cycle.

The main disadvantage of these heat sealing adhesives lies in their low resistance to detergents and dry cleaning solvents. Polyurethanes, however, are much more resistant to detergents and dry cleaning solvents and there have, therefore, been attempts to utilize polyurethanes in place of the well-known heat sealing adhesives. The poly-urethane heat sealing adhesives used in the past have all suffered from unsatisfactory melting properties. Thus, for example, the heat sealable polyurethanes described in German Offenlegungsschriften Nos. 1,915,803, 1,930,340 and 1,769,482 are not suitable as quick-setting heat sealing adhesives because, their melting points being above 120C, they muqt be ironed at temperatures of above 150C, at a pressure of from 0.5 to 0.7 kg/cm2 for a period of more than 10 seconds.

In the past, several attempts have been made to overcome this difficulty, e.g by adding plasticizers to the heat sealing compounds or by incorporating other additives to lower the softening and glueing point of the polyurethanes.
All of these substances share the same disadvantage, namely, ~ that they are removed by normal dry cleaning and washing ; procedures; furthermore, once removed, they contaminate the washing liquor or cleaning bath. In addition, these known substances may sometimes have a noxious odor and be liable to ` migrate. For example, when interlinings are used, these substances are liable to have a deleterious effect on the cohesion of the synthetic resin used for bonding the fleece.
Migration of these substances may also spoil the appearance of the textile on the side remote from the layer of adhesive, in other words, the outside of the article, which is exposed , -LeA 15,196 -2-.. . .

to view. 1037~
The use of soft linear polyurethanes, having low softening point and heat sealing temperatures, for heat sealing textiles has been described in DOS No. 1j619,019.
Although these heat sealing compounds melt at from 100C to 120C, their melt viscosities being too low and their poor flow properties, when melted render them unsuitable. The heat sealing compounds described in DOS No. 1,619,019 melt within a narrow temperature range and, due to their low melt viscosity, they rapidly migrate into the textile substrate.
The textile is thereby hardened. The bonding strength thus obtained is only moderate, and in many cases it is found to be insufficient. Because of these poor flow properties, the products are difficult to handle, e.g. even slight deviations from the correct sintering and ironing temperatures will impair the bond strength of the sealed textile sheet.

It is therefore an object of this invention to provide an adhesive for heat sealing textile sheets together which is devoid of the foregoing disadvantages. Another object of the invention is to provide a polyurethane adapted to be used as a heat sealing adhesive for textile sheets.
Another object of the invention is to provide a polyurethane or polyurethaneurea adhesive having a melting point below 150C. which is resistant to dry cleaning solvents and detergents. Still another object of the invention is to provide a process for heat sealing textile sheets together.

The foregoing objects and others are accomplished in accordance with this invention, generally speaking, by providing a process for heat sealing textile sheets wherein at least one surface of a textile sheet is treated with a **DOS stands for German Offenlegungsschrift.

LeA 15,196-Ca _3_ 103719~
solvent-free polyurethane and/or polyurethane urea which has been prepared from a) about 55 to about 95% by weight, based on the whole polyurethane mass, of at least one com-pound which contains at least two aliphatic hydroxyl groups and has a molecular weight of from about 1000 to about 2500 and a melting point of from about 25 to about 130C, b) at least one organic polyisocyanate, prefer-ably present in about 5 to about 45% by weight, and c) 0 to about 15% by weight, based on the whole polyurethane mass, of at least one aliphatic polyol and/or polyamine, using an equivalent ratio of a+c = 0 9 to 1.05 wherein said solvent-free polyurethane and/or polyurethane urea has a melting range within the range of 100 to 120C
and a melt index, according to ASTM 1238 - 62 T, of 10 + 5 under condition B, 30 + 10 under condition C and 150 + 50 under condition E.

The present invention further relates to a solvent-free polyurethane adhesive prepared from a) about 55 to about 95% by weight, based on the whole polyurethane mass, of a compound which contains at least two aliphatic hydroxyl groups and has a molecular weight of between about 1000 and about 2500 and a melting point between about 25 and about 130C, b) an organic polyisocyanate, preferably present in about 5 to about 45% by weight, and _.~ LeA 15,196-Ca ~ -4-~037191 c) 0 to about 15% by weight, based on the whole polyurethane mass, of an aliphatic polyol and/or a polyamine at an equivalent ratio abc of between about 0.9 and about 1.05 S wherein said polyurethane adhesive has a melting range of from about 100C to about 120C and a melt index according to ASTM 1238-62T condition B of 10 ~ 5, condition C of 30 + 10 and condition E of 150 + 50.

Polymers of this kind can be prepared by reacting 10 high molecular weight compounds, having a molecular weight of 1000 to 2500 and a melting point of from 25 to 130C, which preferably contain two, but optionally more, aliphatic hydroxyl groups, with polyisocyanates, and optionally aliphatic polyols and/or polyamines which have a molecular weight of up 15 to 400. The quantity of the high molecular weight polyhydroxyl compound used is from 55% to 95% by weight, preferably from 75% to 90% by weight, based on the polyaddition product; the quantity of the lower molecular weight chain lengthening agent LeA 15,196-Ca -4A-,.. ~

103ql9~
used is from 0 to 15% by weight and the ratio of NCO/(OH+NH2) is from 0.9 to 1.05, preferably from 0.95 to 0.99.

The high molecular weight polyhydroxyl compounds (a) used for the preparation of the polyurethanes or polyurethane ureas may be prepared by polycondensation or polymerization.
Suitable high molecular weight polyhydroxyl compounds for this purpose are, for example, the known polyesters, poly-acetals, polyethers, polyamides, polyester amides, polycar-bonates and polylactones and are described for example, in the boo~ entitled "Polyurethanes: Chemistry and Technology" by Saunders and Frisch published by Interscience Publishers.

The polycondensates which may be prepared from polybasic, preferably dibasic, saturated and/or unsaturated carboxylic acids and polyvalent, preferably divalent, saturated and/or unsaturated alcohols, aminoalcohols, diamines, polyamines and mixtures thereof, are to be included in the scope of the terms polyester, polyester amide and polyamide ; ~ as used herein. Suitable polyacetals are, for example, the compounds which can be prepared from hexane-1,6-diol and i 20 formaIdehyde.

Any suitable polyether may be used in the process of the present invention, including the polymerization products of alkylene oxides such as, ethylene oxide, propylene oxide, tetrahydrofuran and butylene oxide, as well as their copoly-merization or graft polymerization products, and also the polyethers which can be obtained by condensation of polyvalent alcohols, amines, polyamines and amino alcohols Any suitable polylactone may be used, including .1 the polyesters which can be prepared by polymerizing lactones, in particular ~-caprolactone.
LeA 15,196 -5-10~7191 Any suitable polycarbonate may be used including those prepared, for example, by a process of ester interchange from glycols and polyols, such as hexanediol or trimethylol-propane, and diphenylcarbonate.

Any suitable polyol which contains aliphatic hydroxyl groups and has a molecular weight of up to about 400 may be used such as, for example, ethylene glycol, propylene-1,3-glycol, butane-1,4-diol, pentane-1,5-diol, hexane-1,6-diol, methy~hexane-1,6-diol, trimethyl-hexanediol, neopentyl glycol, 1,4-bis-hydroxymethyl-cyclohexane, diethylene glycol, thio-diglycol, methyldiethanolamine, xylylene glycol, hexane-1,2,6-triol and also the ethoxylation products of divalent phenols and glycols, e.g. bis-hydroxyethyl-hydroquinone and hydroxy-ethyl-hexane-1,6-diol and the like may be used.

Any suitable aliphatic polyamine which has a molecular weight of up to about 400 may be used, such as, for example, ethylene diamine, diethylenetriamine, 1,2-diaminopropane, 1,4-diaminobutane, 1,3-diaminobutane, hexamethylenediamine, N,N'-diethyl-1,3-propanediamine, N,N'-dibutyl-1,6-hexanediamine, ; 20 diamino-cyclohexane, hydrazine, 4,4'-diamino-dicyclohexyl-methane, l-amino-3,3,5-trimethyl-5-aminomethyl-cyclohexane or the like may be used.

"
The polyols and polyamines with a molecular weight of up to 400 may be used in a quantity of from 0 to about 15%
by weight, based on the whole polyurethane or polyurethane ` urea mass.

The starting materials used for preparing the polyurethanes and polyurethane ureas which are to be used according to the process of the present invention also include aliphatic, cycloaliphatic, araliphatic, aromatic or hetero-LeA 15,196 -6-103719~
cyclic polyisocyanates. The equivalent ratio of polyisocyanates to the other components used is from 0.9 to 1,05, preferably from O.9S to 0.99.

Aliphatic polyisocyanates including cycloaliphatic S polyisocyanates are particularly preferred, for example, butane-1,4-diisocyanate, hexane-1,6-diisocyanate, 2,2,4-tri-methyl-hexane-1,6-diisocyanate, xylylene diisocyanate, methyl cyclohexane diisocyanate, cyclohexane diisocyanate and diisocyanatocarboxylic acid esters (such as those described e.g. in U.K. Patent Nos. 1,072,956 and 965,474), l-isocyanato-3,3,S-trimethyl-S-isocyanatomethyl cyclohexane and biuret triisocyanates. Biuret triisocyanates may be prepared by a reaction between aliphatic diisocyanates and water accompanied by the formation of urea and biuret groups; for example, the biuret triisocyanate OCN-(CH2)6-NH-CO-N-(CH2)6-NCO
CO
NH
(CH2)6 which can be prepared from hexane-1,6-diisocyanate. Also addition products obtained by reacting aliphatic diisocyanates with polyols, which contain at least 3 hydroxyl groups, and reaction products which are obtained by an addition reaction of acrylonitrile with polyols followed by hydrogenation and phosgenation may be used.
. .
In addition to the starting materials mentioned above, minor quantities of compounds such as those described in e.g. U. S. Patent 3,756,992 may also be included. These compounds modify the polyurethanes cationically or anionically without greatly affecting the properties which are desirable in this instance.
~eA 15,196 _7_ `~10371~1 Compounds of this kind include chain lengthening .~cnt~ which contain basic nitrog~n atoms, e.g. N-methyl-dicth~nolamine, N- ~-hydroxyethylpiperazine or 2,6-diamino-pyridine; cllain lengthening agents which contain halogen atoms cap~blc of quaternization e.g. glycerol-~-chlorohydrin, or R-SO2o ~roups, e.g. glycerol monotosylate; and compounds which contain at least one hydrogen atom capable of reacting with isocyanate groups and at least one salt-type group capable of anionic salt formation e~g. lactic acid, uric acid, glycine, arignine, thiodiglycollic acid, nitrolotriacetic acid, 2-hydroxyethane sulphonic acid, hydroxylamine mono-sulphonic acid, bis-propylene glycol ester of phosphoric acid, hydrazine dicarboxylic acids, or polyesters which contain carboxyl groups.

lS The compounds which are suitable for ionic modifica-tion are mixed with the other components either before or during the formation of the polyurethane or polyurethane urea.
A process in which prepolymers of the polyisocyanates and poly-hydroxyl compounds, so-called NCO prepolymers, are cationically or anionically modified by reacting them with the above-' mentioned compounds, is particularly preferred.

Preparation of the polyurethanes and polyurethane ureas which are to be used as heat sealing adhesives according to the process of the present invention, may be carried out ` 25 by heating the solvent-free starting components to 40 to 200C, I but the components may also be reacted in solution, using j solvents which are inert towards the polyisocyanates, polyols, polyamines, and high molecular weight polyhydroxyl compounds, for example, acetone, tetrahydrofuran, dioxane, methyl ethyl ketone, benzene, toluene, xylene, methyl acetate, butyl acetate, chloroform, carbon tetrachloride, tetrachloroethylene, LeA 15,196 -8-trichloroethane, chlorobenzene, formamide, dimethylformamide, aimethylacetamide and dimethylsulphoxide. Preparation of the polyurethanes and polyurethane ureas may be carried out, for example, by dissolving the reactants in the chosen solvent.
The reaction is carried out by conventional methods at temperatures of from 40 to 200C, optionally under pressure (e.g. 1 to 10 atmospheres) and with the addition of catalysts such as tertiary amines or organometallic compounds. If the reaction product is insoluble in the solvent used, it may be isolated by suction filtration and subsequently dried. If, on the other hand, the polyurethane remains partly or completely in solution it may be isolated either by distilling off the solvent or by precipitating it by the addition of water or other solvents, in which the product is insoluble, which are readily, or at least partly, miscible with the reaction solvent, traces of the solvent are then removed by drying, optionally under vacuum and optionally at an elevated tem-perature.

If desired, however, the high molecular weight poly-hydroxyl compound, with a molecular weight of 1000 to 2500 and a melting point of above 25C may first be reacted with the aliphatic polyisocyanates and the reaction may then be completed by adding the polyols or polyamines, which have a lecular weight of up to about 400, either with or without a solvent present.

If desired, the polyurethane or polyurethane urea may be isolated from a solution by a process of spray ` drying in which the solutions are atomized under pressure through nozzles into a drying chamber at elevated temperature.

The crude product may also be granulated or broken down by grinding in a mill. The particles of the required LeA 15,196 -9-1037~9~
size for use in conventional application machines are isolated by fractional sieving.

The average particle size of the powders generally varies between 0.01 and 0.5 mm according to the purpose for which the heat sealing compounds are required and the form in which they are to be used, for example, particles of between 0.001 and 0.08 mm are used for viscous pastes, particles of O.08 to 0.2 mm for the powder point process and particles of O.2-0.5 mm for the powder scattering process.

The fact that the polyurethanes and polyurethane ureas, which are to be used according to the process of the present invention, can be used in the form of fibers, woven fabrics or non-woven webs enables them to be distributed uniformly as required, without any waste and without using any special apparatus for dist,ributing the sealing compound.
Waste of the sealing material such as may occasionally occur, e.g. when the material is sprayed in the form of a powder, is thus avoided.

The bonding strength and other properties which can be achieved, according to the present invention, allow for wide and varied use of the heat sealing compounds for heat sealing woven and knitted fabrics, felts and non-woven webs of natural and synthetic fibers, particularly cotton, rayon, wool, horse hair and polyacrylonitrile, polyamide and polyester fibers.

The bond in the textile material is resistant to washing and dry cleaning.

Heat sealing is carried out by applying the poly-urethanes and polyurethane ureas in the form of powders or LeA 15,196 -10-103719i threads, woven or non-woven webs or pastes to the textile surface and then sintering them by means of a source of heat.
The amount of heat required depends on the structure of the lining material which is to be treated, the quantity applied and the application technique.

Powder with a particle size of 0.2 to 0.5 mm is applied by uniformly spraying or scattering a sufficient quantity of it over the surface of the substrate such as a woven or non-woven fabric, for example, in a quantity of from about 6 to about 30 g/m . The substrate, covered with powder, is then exposed to an infrared radiant heater for about 10 to 20 seconds. By the action of heat the substance becomes permanently bonded to the surface of the substrate.
The material is then removed from the heating zone, cooled and, at a later date, joined to another web of material, for example, a cotton poplin or woolen top cloth, to form a composite material. This is carried out by placing the treated substrate and the above-mentioned second layer of material together in such a way that the heat sealing adhesive forms the middle layer between them. The materials are then bonded together by subjecting them to a sudden application of heat for approximately 10 seconds at a pressure of 0.3 to 0.4 kg/cm2, e.g. in an electric ironing press at a temperature o~ 145C.
During this short period of time, the adhesive becomes plastic and permanently bonds the substrate to the second layer.
The composite material is then removed from the ironing press and is immediately ready for use when cool.

Powders with a particle size of from 0.08 to 0.2 mm are applied by processes known in the industry as powder point processes. The amount applied may vary from 15 to 30 g/m according to the substrate and is preferably LeA 15,196 : 103~
approximately 20 g/m2. The substrate is then sealed to the top cloth in an electrically heated ironing press under the conditions mentioned above.

Heat sealing with the polyurethanes or polyurethane ureas in the form of paste is generally carried out as follows: by mixing 1 part by weight of a powder which has a particle size of 0.001 to 0.08 mm with 1 part by weight of water, which contains a thickener, for example, one based on polymethacrylate; stirring the mixture, adjusting the pH to 7.5 with ammonia; then uniformly imprinting the paste on the substrate, preferably pointwise, using a stencil or sieve drum and applying a quantity of from 10 to 30 g/m2, preferably approximately 20 g/m2. The substrate, for example, a woven fabric or non-woven web, to which the paste has been applied, is then dried in a drying chamber at temperatures of up to 160C. The polyurethane particles are thereby so firmly bonded to the support material that the textile webs can easily be rolled up. Another textile, e.g. a woven or knitted fabric or non-woven web, may then be applied to that side of the support on which the synthetic resin has been printed and the two layers are then bonded together by sudden application of heat under pressure, for example, in an electric ironing press as described above. The composite material is then removed from the press and can be used as soon as it has cooled. The laminates produced in this way have a pleasant, soft handle due to the uniform distribution of the bonding agent.

Fibers or sheets may also be produced in a similar manner by the application of polyurethanes and polyurethane ureas according to the process of the present invention.
When used in this way fibers are drawn from the melt in known LeA 15,196 -12-~03719~ ~
manner, e.g, at temperatures of from 100 to 200C in the absence of air, and are then stretched and cut up into staple fibers. These fibers can be made up into non-woven webs or spun to form threads and then made up into woven or knitted fabrics or layers of random threads in known manner.
Alternatively, filaments, which have been drawn from the melt and stretched, can be directly deposited as spinning fleeces in ~nown manner. When used for heat sealing textiles, these sheets are applied to the substrate and then either sintered, if they are subsequently to be bonded in ironing presses, or directly bonded to a second material by sudden application of heat and pressure, e.g. a woven or knitted fabric or non-woven web made of a material which is not thermoplastic at the operating temperatures employed. ~oth ironing presses and calendars are suitable for this purpose. This process again results in soft composite materials which are distinguished by their high resistance to water and solvents.

! Examples I

Polyurethane A) Formulation: 86.3 parts by weight of a polyester from adipic acid and butane-1,4-diol, OH number 50 (molecular weight 2240),

2.6 parts by weight of butane-1,4-diol and 11.1 parts by weight of hexane-1,6-diisocyanate a) Preparation in solution A polyester from adipic acid and butane-1,4-diol, which has been dried in vacuo at 120C for 30 minutes, is dissolved in tetrachloroethylene. Hexane-1,6-diisocyanate is added at a temperature of 100C, followed by butane-1,4-diol.
The components are heated under reflux for 5 hours.

~eA 15/196 .13-103P7~9~
When the reacted mixture of polyurethane and solvent is cooled with vigorous stirring by a high speed laboratory stirrer, the polyurethane is obtained as a moist powder. After removal of the solvent, the reaction product is dried and sieved to remove coarse particles. Melting point: 110-112C, Melt index according to ASTM 1238 - 62 T Condition B: 12.0 Melt index according to ASTM 1238 - 62 T Condition C: 33.6 Melt index according to ASTM 1238 - 62 T Condition E: 168 b) Preparation in the melt Hexane-1,6-diisocyanate and butane-1,4-diol are added, with stirring, at 100C, to a polyester which has been dried in vacuo at 120C for 30 minutes. The reaction mixture is kept at 100C for 20 hours. When the resulting polyurethane has cooled, it is ground up and sieved. Melting range:
110-114C.

Melt index according to ASTM 1238 - 62 T Condition B: 7.3 Melt index according to ASTM 1238 - 62 T Condition C: 49.2 Melt index according to ASTM 1238 - 62 T Condition E: 182 Polyurethane urea B
Formulation: 85.0 parts by weight of a hexanediol polycarbo-nate with molecular weight 1870 13.5 parts by weight of hexamethylene diiso-cyanate 0.75 parts by weight of N-methyl-diethanolamine 0.75 parts by weight of dimethylsulphate and 100 parts by weight of acetone.

The polycarbonate is dried in vacuo at 120C for 30 minutes,and hexamethylene diisocyanate is added at 105C.

~eA 15,196 -14-The mixture is kept at 100C for one hour and N-methyl-di-ethanolamine in 1/11 of the total quantity of acetone is added after the mixture has been cooled to 60C. The resulting mixture is then kept at 60C for 3 hours and a further 2/11 of the acetone are added~ The product is then quaternized with a solution of dimethylsulphate in the remaining quantity of acetone (8/11). A 50% acetonic NCO prepolymer solution which is slightly cationically modifed is obtained. It has an NCO
content of 1.20~ and a viscosity of n25 = 179 cP.

When this prepolymer solution and equal parts of water containing, in solution, 85~ of the theoretical quantity of propylene-1,2-diamine, based on the NCO content of the pre-polymer, are mixed with vigorous stirring, for example, by a rapidly rotating laboratory stirrer, a suspension which lS has a tendency to sediment is obtained. The aqueous acetone ~, i8 decanted off and the powder obtained is dried. Melting point: 104-108C.

Melt index according to ASTM 1238 - 62 T Condition B: 5.4 Melt index according to ASTM 1238 - 62 T Condition C: 34.7 Melt index according to ASTM 1238 - 62 T Condition E: 197.3 Example 1 The polyurethane powder A prepared in solution i according to method (a) is fractionated by sieving. The fraction isolated within the sieve limits of 0.2 to 0.3 mm is uniformly sprinkled over an undyed cotton twill fabric weighing 200 g/m2, the amount applied being 25 g/m2. It is then exposed for 20 seconds to a 1500 watt infrared radiant heater which has a surface area of 300 cm2, the heater being held at a distance of 20 cm. The powder is thereby softened ; 30 and adheres to the fabric. When cool, it is firmly bonded ~eA 15,196 -15-~1037191 to the fabric. A cotton tricot fabric is then placed on the surface to which the powder has been applied, and the two fabrics are pressed together under an ironing press (manu-factured by Ducker) at a temperature of 170C and pressure of 400 g/cm2 for 10 seconds. The resistances to separation of the resulting laminate after it has been cooled and aired are as follows:
Without treatment 0.7-1.0 kg/2.5 cm After machine washing (60C) 0.6-0.8 kg/2.5 cm After dry cleaning (in perchloroethylene) 0.5-0.7 kg/2.5 cm.

Example 2 Polyurethane A obtained from the melt by method (b) is ground and sieved. The fraction of particles measuring 0.08 to 0.2 mm i8 isolated and applied to an interlining fabric weighing 180 g/m2 by means of an 11 mesh applicator roller in a powder point machine (made by Saladin of Sirnach/Switzerland).
After passing through a cooling zone, the fabric is rolled up.
After this fabric, to which 20 g/m2 of powder has been applied by point application, has been sealed it is bonded to a second fabric (wool top cloth) by pressing the two fabrics under an ironing press as described iD Example 1 at a temperature of 170 and pressure of 400 g/m2 for 15 seconds.
The resulting composite material has the following resis-tances to separation after cooling and airing.
Without treatment 0.8-1.1 kgj2.5 cm After machine washing (60C) 0.7-0.9 kg/2,5 cm After dry cleaning (in perchloroethylene) 0.6-0.8 kg/2.5 cm Comparison Example 3 The polyurethane urea B (Powder I) described above and a polyurethane (Powder II) prepared according to Example 1 LeA 15,196 -16-~037~ 9~
of DOS No. **1,930,340 (U. S. Patent No. 3,684,639), which con-sist of particles smaller than 0.08 mm are each made up into an aqueous paste and then uniformly applied pointwise to a cotton fabric weighing 80 g/m2 by means of a screen printing stencil and finally dried. The paste has the following constituents:
500 g of the polyurethane powder, 750 g of water, 40 g of glycerol 65 g of emulsifier (*) 2 g of silicone defoaming agent.

After drying, the pretreated cotton fabrics are bonded to a cotton tricot layer by ironing using a laboratory press (manufactured by Kannegiesser) under the conditions indicated in the following table. The heating of the poly-urethane was accomplished using a thermoelectric element.From the table, it is clear to one skilled in the art that powder I has distinct sealing properties having been sub-jected to temperatures of from 125C,a sealing time of 10 seconds and a pressure of 300 p/cm2 and can be sealed sufficiently firmly by application of a pressure of 400 g/cm2 for 5 seconds. If a pressure of 400 g/cm2 is applied for a longer time, then overfixing results. Powder II, on the other hand, does not fix sufficiently under the given con-ditions. To obtain a satisfactory bond by ironing, it is necessary to apply a higher pressure at a higher temperature for a longer sealing time, as can be seen from Example 1 of ; DOS **No. 1,930,340 (U. S. Patent No. 3,684,639).

(*) Reaction product of polyethylene oxide and stearylisocyanate, ** DOS stands for German Offenlegungsschrift.

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TABLE
(Continuation) Rolle~ Temperature 160C
Press~re Pressing T. Powder I) Powder II) g/cm time C
seconds. _ . .
200 5 100 0.05 0 ~ 10 . 115 0.15 0.1 ; 15 120 0.15-0.2 0.15 300 5 100 0.05-0.15 0 . 10 120 0.4 -0,65 0.2-0.4 , 15 125 0.4 -0.7 0.2-0.4 400 5 110 0.5 -0.7 0.05-0.1 . 10 125 0.7 -1.0 0.25-0.4 .l 15 _ 135 0.8 -1.1 0.25-0.45 T. : = temperature in the gap (measured on the fabric) Any of the other polyurethanes and polyurethane ureas indicated as suitable herein can be substituted for those of the foregoing examples.

Although the invention has been described in detail for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without dèparting from the spirit and scope of the invention except as it may be limited by the claims.

LeA 15,196 -19-

Claims (5)

The embodiments of the invention in which exclusive property or privilege is claimed are defined as follows:

1. A method for heat sealing textile sheets which comprises treating at least one sheet with a solvent-free polyurethane which has been prepared from a) about 55 to about 95% by weight, based on the whole polyurethane mass, of a compound which contains at least two aliphatic hydroxyl groups and has a molecular weight of between about 1000 and about 2500 and a melting point between about 25° and about 130°C, b) an organic polyisocyanate, and c) 0 to about 15% by weight, based on the whole polyurethane mass, of at least one of an aliphatic polyol or polyamine at an equivalent ratio of between about 0.9 and about 1.05 wherein said polyurethane has a melting range of from about 100°C to about 120°C and a melt index according to ASTM
1238-62T condition B of 10 + 5, condition C of 30 + 10 and condition E of 150 + 50 and sealing the textile sheets with heat.

2. The process of Claim 1 wherein the polyurethane is a polyurethane urea.

3. A solvent-free polyurethane adhesive prepared from a) about 55 to about 95% by weight, based on the whole polyurethane mass, of a compound which contains at least two aliphatic hydroxyl groups and has a molecular weight of between about 1000 and about 2500 and a melting point between about 25° and about 130°C, b) an organic polyisocyanate and, c) 0 to about 15% by weight, based on the whole polyurethane mass, of at least one of an ali-phatic polyol or a polyamine at an equivalent ratio of between about 0.9 and about 1.05 wherein said polyurethane adhesive has a melting range of from about 100°C to about 120°C and a melt index according to ASTM 1238-62T condition B of 10 + 5, condition C of 30 + 10 and condition E of 150 + 50.

4. The adhesive of Claim 3 wherein the polyurethane is a polyurethane urea.

5. A method for heat sealing textile sheets which comprises treating at least one sheet with a solvent-free polyurethane which has been prepared from a) about 55 to about 95% by weight, based on the whole polyurethane mass, of a compound which contains at least two aliphatic hydroxyl groups and has a molecular weight of between about 1000 and about 2500 and a melting point between about 25° and about 130°C, b) an organic polyisocyanate, and c) 0 to about 15% by weight, based on the whole polyurethane mass, of at least one of an aliphatic polyol or polyamine at an equivalent ratio of between about 0.9 and about 1.05 wherein said polyurethane has a melting range of from 104°C
to about 114°C and a melt index according to ASTM 1268-62T

condition B of from about 5.4 to 12, condition C of from about 33.6 to 49.2 and condition E of from about 168 to 197.3, and sealing the textile sheets with heat.