US3357954A - Synthetic elastomeric filaments from (a) polyester diols, (b) aliphatic or cycloaliphatic diols and (c) aliphatic or cycloaliphatic diisocyanates - Google Patents

Description

United States Patent- Ofilice 3,357,954 Patented Dec. 12, 1967 ABSTRACT OF THE DISCLOSURE A process for the manufacture of synthetic polyesterurethane elastomers capable of being melt-spun into filaments, comprising bringing about by the application of heat an interaction between (1) a diol whch is a hydroxylterminated linear copolyester derivable from one or more aliphatic or cycloaliphatic glycols having from 2 to 20 carbon atoms, and adipic acid optionally together with one or more other dibasic acids selected from the group consisting of saturated aliphatic dibasic acids and aromatic dibasic acids, and has a number average molecular weight of between 1500 and 3500, (2) from 2 to 20 moles, per mole of the aforesaid polyester diol of an aliphatic diol Opt al y w tain ng a vlen gr p or a y pha ic diol, which diol has not more than 20 carbon atoms and (3) from 96 to 100 moles, per 100 moles of the total weight of the foregoing diols, of an aliphatic or cycloaliphatic diisocyanate having from 4to 24 carbon atoms, which may optionally contain aromatic nuclei provided the latter are separated from the isocyanate groups by at least one methylene group. I

This invention relates to the manufacture of novel synthetic elastomers, and more particularly to such elastome'rs as consist of segmented polyester-urethanes with aliphatic urethane segments and are capable of being melt-spun into filaments.

For many years synthetic rubbers have been manufactured including polyester-urethane elastomers but it is difficult or impossible to dissolve these elas tomers, which are cross-linked (cured), without degradation, and such solutions as are obtainable cannot be solution spun into filaments. Nor can filaments be made by melt-spinning the elastomers. Elastic filaments could only be formed therefrom by mechanically cutting up thin sheets into narrow strips, but such a process has drawbacks; in particular it is not possible to produce filaments of low denier, i.e. much below 500.

In the last decade much research has been carried out on the development of synthetic elastome rs capable of being solution spun into elastic filaments possessing desirable textile properties. Such elastic filaments possess an extensibility of over 100%, a low initial modulus and a high percentage elastic recovery. The terms extensibility, initial modulus and elastic recovery are defined below. Some of the aforesaid research had been directed to the improvement of elastornerswhich are polyester-urethanes. U.S. patent specification 3,097,- 192, for example, describes 'malr in g polyester-urethaneureas from a polyester, a molar excess of an aromatic diisocyanate and a diamine; the polyester-urethane-ureas can be solution spun into elastic filaments by means of Wet or dry spinning. Such elastic polymers comprise segments consisting of a low molecular weight polymer which if fully polymerised so as to constitute a fibre-forming homopolymer would possess a relatively high melting point, together with segments which can similarly be regarded as derived from a fully polymerised homopolymer of relatively low melting point! The former segments are frequently called hard segments and the latter soft segments, as, for example, in the article by W. H. Charch and I. C. Shivers entitled Elastomeric Condensation Block Copolymers and to be found in the Textile Research Journal for July 19.59. i

Attempts have also been made to produce synthetic elastomers which can be elt-sputum textile filaments for the process' of melt-spinning is well known to possess nurnerous advantages over that ofsolution spinning. Thus Belgian patent specification No. 619,994 it proposed to make melt-spinnable polyurethanes by the reaction of a hydroxyl-terminated polyester or copolyester (i.e. a'diol) having an average molecular weight not exceeding 1400 with an organic diisocyanate and 'a 'chain extender, preferably a dihyd ric alcohol elg. butanediol-IA the molar excess of diisocyanate to total diol, ranging from 1.1451 to 1.02: 1. TheBelgian specification mentions alicyclic and aliphatic diisocyanates such as tetramethylene diisocyanate or hexamethylene diisocyanate but gives no examplesof the use thereof. In fact processes are described wherein a molar excess of diisocyanate isheated with a hydroxylte i ed P l ster and uc ocesse ould be l 9 m With. an. p ati d s pyana e beaus nde these ,wnq i n ell n oc rs.- N ike new be n oun at no e mel -sn nna e po y- =st 1 1 a es mp ove r pe ti s can he. made f om a y oisy etm a d opo st r o mo ecu ar weigh greater than 1500, a dihydric alcohol and an aliphatic or cycloaliphatic diisocyanate provided the diisocyanate is neither employed in molar excess nor allowed to be present molar excess at any time during the reaction; A1 though the "above Belgian specification states that the. use or polyestersofhigher molecuiar weight yields filaments of iiife'rior properties, applicants have found that by raising the 'molecular weight of the polyester better values for work recovery and stress decay (as defined below) are obtained."Moreover the elastic filamentsof polyesterurethanes derived from aliphatic diisocyanates are distinguished from the elastic filaments of those based on aromatic "diisocyanatesby possessing advantageous properties. Thus the former polyester-urethane filaments re} tain their elastic properties and whiteness to a greater extent when exposed to lig ht than do the latter; moreover the latter became yellow when submitted to bleaching by hot aqueous sodium chlorite and also on ageing, whereas the former do not. The degree of resistance to'light and bleaching is determined by means of tests which maybe defined in the following manner.

Light resistance test The filaments are, Wound on a frame and exposed to light fram a Xenon Arc for 300 hours. The elastic properties and colour of the filaments are determined before and after the exposure.

Bleaching resistance test The filaments are immersed for a period of 45 minutes in an aqueous solution containing 0.1% by weight of sodium chlorite and 0.5 cc. per litre of glacial acetic acid maintainedat C. is W V The colour of the filaments is determined before and after the bleaching treatment. a I

With regard to the polyester-urethanes of Belgian patent specification No. 619,994 therefore, not only do the present polyesterurethanes differ in respect of the molecular Weight of the polyester used and the proportion and chemical constitution of the diisocyanate employed, but the elastic filaments made'by' mel pinning the present polyester-urethanes possess superior textile properties. A

Definitions of properties of filaments.Extensibility By extensibility of the filaments is meant the length by which they can be extended before they break expressed as a percentage of their original length.

Tenacity The breaking load of the filaments expressed in grams per denier.

Initial modulus By initial modulus of the filaments is meant the quotient obtained by dividing the specific stress by the strain, when the strain is an extension of 1 percent of the original length. (Specific stress is defined at page 138 of the Textile Terms and Definitions, 4th edition, published by the Textile Institute, Manchester, and may be expressed in grams per denier.)

Elastic recovery The elastic recovery of the filaments is expressed by the fraction obtained by dividing the length by which the filaments are extended on the application of a stress thereto, into the length by which they contract on removal of the stress therefrom. The fraction is commonly expressed as a percentage.

Work recovery The work recovery of the filaments is expressed by the fraction obtained by dividing the energy or work expended in stretching the said filaments by applying a stress thereto into the energy or work recovered when the said filaments retract to their original dimensions on release of the stress. The fraction is commonly expressed as a percentage.

Stress decay The stress decay of the filaments is expressed by the fraction obtained by dividing the stress necessary to extend the filaments by a selected percentage of their original length, into the stress required to produce the same extension at the end of a selected time, the said extension being maintained constant during the Wholeof the time. The fraction is commonly expressed as a percentage.

Stick temperature The lowest temperature at which the filaments adhere to a hot smooth surface when brought into contact therewith.

Inherent viscosity The inherent viscosity is defined as being twice the natural logarithm of the viscosity at 25 C. of a solution of /2 weight by volume of the polyester-urethane dissolved in meta-cresol, divided by the viscosity of the metacresol at the same temperature.

Vicat softening point The Vicat Softening Points alluded to have been determined by a penetrometer similar to the apparatus described by Edgar and Ellery at page 2638 of Journal of the Chemical Society 1952.

Accordingly the invention consists of a process for the manufacture of synthetic polyester-urethane elastomers capable of being melt-spun into filaments, comprising bringing about by the application of heat an interaction between (1) a diol which is a hydroxyl-terminated linear copolyester derivable from one or more aliphatic or cycloaliphatic glycols having from 2 to 20 carbon atoms, and adipic acid optionally together with one or more other dibasic acids selected from the group consisting of satugoing diols, of an aliphatic or cycloaliphatic diisocyanate having from 4 to 24 carbon atoms, which may optionally contain aromatic nuclei provided the latter are separated from the isocyanate groups by at least one methylene group.

Examples of the reagents which may be employed in the present process are as follows:

Hydroxyl-terminated linear copolyesters copolyesters derived from the subjoined glycols and dibasic acids in the ratios by Weight quoted and having the molecular Weights (M.W.) stated.

Glycols Ratio Dlbaslc acids Ratio M.W.

Ethylene glycol, pro- 7:3 Adlplc 1, 640

pylene glycol. Ethylene glycol, 2,3- 7:3 .do 1, 550

butanediol. Ethylene glycol, 1,3- 7:3 .....(10 1, 550

butanediol. Ethylene glycol, 1,3- 7:3 do 1, 540

dihydroxy-2,2-dimethylpropane. Ethylene glycol Adiplc, succlnic..- 3:1 1, 560 Ethylene glycol Adipic, phthalic. 8:1 1, 550 Ethylene glycol, 13- 7:3 Adlpic 1, 650

dihydroxy-2,2-diethylpropane. Ethylene glycol, 1,4- 7:3 dc 1, 600

butanediol. Ethylene glycol, 2,5- 7:3 .-do 1, 550

hexanediol. Ethylene glycol, 1,3-di- 7:3 do 2, 490

hydroxy-2,2,4-trlmethylpentaue. Ethylene glycol, pro- 7:3 Glutaric 1, 650

py ene glycol.

Do 7:3 Sebaclc 1, 550 Ethylene glycol, trl- 7:3 Adiplc 1,630

methylene glycol.

The hydroxyl-terminated linear copolyester may be prepared from the required glycol and dibasic acid by conventional methods, i.e. by the use of a moderate excess, eg. 10 molar percent of the glycol. In place of the acid the acid chloride may be employed. It is also possible to use the methyl ester of the dibasic acid, that is, to make the polyester by a process of ester interchange but this method requires the use of a catalyst and it is preferred that no catalyst shall have been employed in making the copolyesters used as reagents in the present invention. This is because the presence of even small quantities of catalysts, which are difiicult or impossible to remove, causes discoloration of the polyester-urethane finally obtained. Such discoloration is unacceptable in commercial textile filaments, unless the latter are required to be deeply coloured. It is therefore normally essential to use polyesters in the manufacture of which no catalyst has been employed.

Aliphatic dials optionally containing arylene groups and cycloaliphatic dials 1,4-butanediol 1,6-hexanediol di 2-hydroxyethy1) -terephthalate di (4-hydroxy-n-butyl) -terephthalate trans-l,4-dihydroxycyclohexane cis-l,4-dihydroxycyclohexane 2,2,4,4-tetramethyl-cyclobutane-1,4-diol 1,4-di(hydroxymethyl)benzene l,4-di(2-hydroxy-n-propyl)-benzene trans-2,5-di(hydroxymethyl)-1,4-dioxan cis-l,4-di(hydroxymethyl)cyclohexane transl ,4-di (hydroxymethyl) cyclohexane l,4-di-beta-hydroxyethoxybenzene 2,2-bis-4-beta-hydroxyethoxyphenylpropane Aliphatic and cycloaliphatic diisocyanates hexamethylene diisocyanate trans-1,4-di-isocyanate-cyclohexane tetramethylene diisocyanate meta-xylylene diisocyanate para-xylylene diisocyanate pentamethylene diisocyanate trans-l,4-bis-isocyanate-methyl-cyclohexane decamethylene diisocyanate 2,2-di(4'-isocyanato-cyclohexyl)-propane di-(4-isocyanato-cyclohexyl) -methane In the manufacture of the present synthetic elastomers the diols and diisocyanate may be brought together in any convenient manner provided that no molar excess of diisocyanate over the total weight of diols present occurs under reaction conditions, that is to say, for example, at a temperature high enough for reaction to take Place. One method of proceeding is to mix the copolyester diol with the low molecular weight diol, heat the mixture up to, say, 100 C. and add the diisocyanate, whilst the temperature is raised further so that the polyester-urethane formed does not solidify. The reaction is preferably carried out under an inert atmosphere, e.g. nitrogen, to prevent oxidation of the polymer occurring. Eificient mechanical mixing of the reagents is highly desirable. Another method of proceeding is to add part of the diisocyamate to the copolyester diol. The diisocyanate may amount to half or two thirds mole per mole of the copolyester, for instance. The low molecular weight diol is then added followed by the remainder of the diisocyanate.

The low molecular weight diol which provides the hard segment in the present polyester-urethanes is employed, as already stated, in a molar excess over the copolyester diol which provides the soft segment, the molar ratio of the two diols ranging from 2:1 to 20:1. The filaments spun from the polyester-urethanes possess the most desirable textile properties, however, when the aforesaid molar ratio is from 3:1 to 9:1.

Catalyst such as the following may, if desired, be included in the reaction mixture to further the reaction of the diisocyanate.

dibutyl stannic dilaurate dimethylcyclohexylamine sodium ethoxide sodium phenate ferric acetylacetonate Moreover the manufacture of the polyester-urethane can be carried out in solution. Suitable solvents for this purpose'are:

N,N-dimethylacetamide pyridine dimethylsulphoxide mixed with an equal volume of methyl isobutyl ketone N,N-dimethylformamide hexamethylphosphoramide tetramethylene sulphone The present polyester-urethanes can be manufactured in solution and the latter directly spun into filaments by conventional dry or wet spinning methods. The solutions of the polyester-urethanes can also be cast into films. As

already indicated the textile filaments are, however, preferably made by melt-spinning in which case no solvent is required. The filaments can be drawn in the solid state (a process often termed cold drawing) although this is not essential and if the maximum extensibility is required no drawing should be carried out.

Among the reagents employed in making the present polyesterurethanes there may be included pigments, plasticisers, delustrants or stabilisers.

The polyester-urethanes of this invention preferably possess a molecular weight corresponding to an inherent viscosity of from 0.5 to 1.5.

The invention includes melt-spinning the above novel synthetic polyester-urethanes into filaments and the filaments so-obtained. The latter possess excellent elasticity, and do not discolour when exposed to a Xenon are or bleached with sodium chlorite in accordance with the Light Resistance and Bleaching Resistance Tests hereinbefore defined. The filaments likewise possess good elastic recovery and good work recovery, frequently exhibiting an Elastic Recovery from 50% extension of at least and a Work Recovery from 50% extension of at least 75%. The filaments are usually submitted to a hot wet treatment, e.g. with boiling water during dyeing or scouring before commercial use and have therefore in the following examples been given a treatment with boiling water before the physical properties were determined in order to obtain more comparable results.

The present polyester-urethanes are advantageously distinguished from other synthetic elastomers by the ease with which they can be melt-spun into filaments which exhibit no tendency to stick together and consequently do not need dusting with talcum powder. Furthermore these novel polyester-urethane filaments are superior to known elastomeric filaments having similar physical properties in that they do not discolour when submitted to the Light and Bleaching Resistance Tests hereinbefore defined. The filaments are suitable for so-called foundation garments such as corsets, in elastic outerwear, for instance sweaters, ski-trousers, also in surgical elastic hosiery and bandages. Other uses comprise woven or knitted swimwear, hosiery, brassieres, and pyjamas. The present filaments are likewise adapted for similar widespread application in the form of staple fibres, especially when blended with e.g. wool, cotton, polyhexamethylene adipamide. The novel polyester-urethane filaments of this invention may be fabricated into composite elastic yarns by introducing them as continuous filaments together with one or more rovings of staple fibres e.g. polyethylene terephthalate, wool or cotton fibres, into a conventional spinning or drafting frame. In the form of fibres the present polyesterurethanes can be used in making non-woven fabrics or, blended with wool, for weaving cloth suitable for mens suits.

In the following examples which are for the purpose of illustrating, not limiting, the invention, the parts are parts by weight.

Example 1 54.7 parts of a hydroxy-terminated copolyester derived from ethylene and propylene glycols in a molar ratio of 7:3 and adipic acid and having a molecular weight of 1640, are mixed with 14.0 parts of 1,4-butanediol. The mixture is heated for 30 minutes at C. in an atmosphere of nitrogen with continuous stirring.

To the above mixture of diols there are added with stirring during 5 minutes 15.7 parts of hexamethylene diisocyanate. A further addition of 15.7 parts of hexamethylene diisocyanate is then made during 70 minutes whilst the temperature is gradually raised at 200 C., the reac tion mixture being constantly stirred. The mixture is stirred at the same temperature for 25 minutes longer and then cooled under the atmosphere of nitrogen.

The resulting polyester-urethane has an inherent viscosity of 0.59 and a Vicat softening point of C.

The polyester-urethane is melt-spun at a temperature of -195 C. into 10 filaments of total denier 319. The lO-filament yarn after treatment with boiling water has the following properties:

Tenacity gram/den 0.43

Initial modulus gram/den 0.24 Stress decay at 25% extension:

15 minutes percent 25.2

16 hours do 37.6

Elastic recovery from 50% extension d0 98 Work recovery from 50% extension do 75 Example 2 The manufacture of polyester-urethane described in Example 1 is repeated except that the 58.8 parts of copolyester there employed are replaced by 58.8 parts of a hydroxyl-terminated copolyester derived from ethylene glycol and 1,4-butanediol in a molar ratio of 7:3 and adipic acid and having a molecular weight of 1600, the

7 weight of 1,4-butanediol is reduced from 14.0 to 12.2 parts and the total Weight of hexamethylene diisocyanate used is 28.3 instead of 31.4 parts.

The properties of the polyester-urethane obtained are:

Inherent viscosity 0.88 Vicat softening point C 164 The yarn melt-spun therefrom and cold drawn (at C.) to three times its original length; it is then treated with boiling water and has the properties listed below:

Stress decay at 25% extension:

15 minutes percent 22.2

16 hours do 34.5

Elastic recovery from 50% extension do 98 Work recovery from 50% extension do.. 94

Example 3 Example 1 is repeated except that the reagents therein employed are replaced by the following:

The copolyester is derived from ethylene glycol together with adipic and succinic acids in a molar proportion of 3 to 1 and has a molecular weight of 1560, 58.7 parts are taken and mixed with 12.2 parts of 1,4-butanediol, 291 parts of hexamethylene diisocyanate are employed (in two equal portions).

The properties of the resulting polyester-urethane are:

Inherent viscosity 1.14 Vicat softening point C-.. 160

The yarn melt-spun therefrom has after treatment with boiling Water the following properties:

Stress decay at 25% extension:

15 minutes percent 23.4

16 hours do 37.4

Elastic recovery from 50% extension do 94 Work recovery from 50% extension do 93 Example 4 Example 3 is repeated except that the copolyester is replaced by 58.4 parts of one derived from ethylene glycol and 1,3-dihydroxy-2,2-dimethylpropane in the molar pro portion of 7 to 3 and adipic acid and has a molecular weight of 1540.

The properties of the polyester-urethane are:

Inherent viscosity 0.60 Vicat softening point C 165 The polyester-urethane is melt-spun in the manner described in Example 1 and the resulting filaments drawn to four times their original length and treated with boiling water.

They are found to possess the following properties:

A polyester-urethane elastomer possessing greater extensibility can be obtained by increasing the molecular weight of the copolyester and altering the quantities of reagents as follows:

Parts Copolyester 84.0 Butane diol 12.9 Diisocyanate 32.2

The resulting polyester-urethane has an inherent viscosity of 0.85 and a Vicat softening point of 140 C. Its extensibility is 460%.

Example 5 A polyester-urethane is made in the manner described in Example 1, except that the copolyester is replaced by 58.9 parts of a copolyester derived from ethylene glycol and trimethylene glycol in a molar proportion of 7:3 and adipic acid, and having a molecular weight of 1631. 29.7 parts of hexamethylene diisocyanate are employed. The polyester-urethane has an inherent viscosity of 1.03 and a Vicat softening point of 159 C. The polymer is melt-spun into filaments and the latter drawn to three times their original length. The filaments on being extended by 50% exhibit an Elastic Recovery of 99% and a work recovery of 79%.

Example 6 57.6 parts of the copolyester used in Example 2 are heated to 100 C. under an atmosphere of nitrogen, and 2.6 parts of hexamethylene diisocyanate added during 15 minutes. Efficient stirring is maintained continuously during the manufacture of the polyester-urethane. The reaction mixture is heated to C. and maintained thereat for 30 minutes. The temperature is then lowered to 60 C. and 12.2 parts of 1,4-butanediol are added during 10 minutes. The mixture is heated to 100 C. during 15 minutes and 25.2 parts of hexamethylene diisocyanate are gradually added during 60 minutes while the temperature is further raised to C. so that the reaction mixture remains molten. The temperature is kept at 180 C. for 30 minutes and the polyester-urethane then cooled. Ithas an inherent viscosity of 0.65 and a Vicat softening point of 171.

The polymer is melt-spun at 169 C. yielding filaments which after drawing to three timestheir original length and boiling in water possess the following properties Stress decay at 25 extension:

15 minutes percent.... 25.0

16 hours o 36.2

Elastic recovery from 50% extension do 99 Work recovery from 50% extension do 80 Example 7 Example 8 57 parts of a hydroxyl-terminated polyester derived from ethylene glycol and 1,3-dihydroxy-2,2-dimethyl propane in the molar ratio of 7 to 3 and adipic acid and having a molecular weight of 1540, are mixed with 18.95 parts of 1,4-di(fl-hydroxyethoxy) benzene at 110 in an atmosphere of nitrogen and stirred for 30 minutes.

To the above mixture of diols there are added with stirring 15 parts hexamethylene diisocyanate during 15 minutes while the temperature is raised to 180. A further 8.18 parts of hexamethylene diisocyanate are added during 60 minutes while the temperature is gradually raised to 200. The mixture is stirred at the same temperature for 40 minutes longer and then cooled under the atmosphere of nitrogen.

The resulting polyester-urethane has an inherent viscosity of 0.86 and a Vicat softening point of 179.

The polyester-urethane is melt-spun at 215 and after treatment with boiling water the yarn has the following properties:

Percent Stress decay at 25% after 15 minutes 47 Elastic recovery from 100% extension 95 Work recovery from 100% extension 75 Example 60 parts of a hydroxyl-terminated polyester derived from ethylene glycol and 1,3-dihydroxy-2,2-dimethylpropane in the molar proportion 7 to 3 and adipic acid and having a molecular weight of 1656 are mixed with 15.3 parts p-xylylene glycol at 110 in an atmosphere of nitrogen and stirred continuously for 30 minutes.

To the above mixture of diols there are added with stirring 12 parts of hexamethylene diisocyanate over minutes while the temperature is raised to 180. A further 11.7 parts hexamethylene diisocyanate is added over 60 minutes while the temperature is raised to 200. The mixture is stirred at the same temperature for 30 minutes longer and then cooled under the atmosphere of nitrogen.

The resulting polyester-urethane has an inherent viscosity of 0.56 and a Vicat softening point of 180. The polymer is melt-spun at 203 to give yarn which after treatment with boiling water has the following properties.

Percent Stress decay at extension (after 15 minutes) 31 Elastic recovery from 100% extension 87 Work recovery from 100% extension 50 Example 11 The p-xylylene glycol of Example 10 is replaced by 15.7 parts of cis/trans-1,4-di(hydroxymethyl) cyclohexane. The resulting polyester-urethane has an inherent viscosity of 0.59 and a Vicat softening point of 151. It is melt-spun at 182 C. into yarn having good elastic properties.

Example 12 36 parts of a hydroxyl-terminated polyester derived from ethylene glycol and 1,3-dihydroxy-2,2-dimethylpropane in the molar proportion of 7 to 3 and adipic acid and having a molecular weight of 2028 are mixed with 4.95 parts of butane-1,4-diol at 110 C. in an atmosphere of nitrogen and stirred together for minutes.

To the above mixture of diols there are added with stirring 19.05 parts of trans, trans-di(4-isocyanatocyclohexyl) methane during 75 minutes While the temperature is gradually raised to 200 C. The mixture is stirred at 200 C. for a further 40 minutes and then cooled.

The resulting polyester-urethane has an inherent viscosity of 0.96 and a Vicat softening point of 193 C.

Example 13 The proportions of the reagents employed in Example 12 are altered to the following:

Di(isocyanatocyclohexyl)methane 12.32

10 'A polyester-urethane having an inherent viscosity of 0.64 and a Vicat softening point of 172 C. is obtained. It is melt-spun at 205 to give yarn having the following properties.

Percent Elastic recovery from 100% extension 96 Work recovery from 100% extension 78 Example 14 35 parts of a hydroxyl-terminated polyester derived from ethylene glycol and 1,3-dihydroxy-2,Z-dimethylpropane in the molar proportion of 7 to 3 and adipic acid and having a molecular weight of 2028 are mixed with 4.95 parts of butane-1,4-diol at 110C. in an atmosphere of nitrogen and stirred together for 30 minutes.

To the above mixture of diols there are added with stirring 19.05 parts of di(4-isocyanato-cyclohexyl)rnethane (a mixture of the steric isomers) during 75 minutes while the temperature is gradually raised to 200 C. The mixture is stirred at this temperature for a further 40 minutes and then cooled.

The resulting polyester-urethane has an inherent viscosity of 0.50 and a Vicat softening point of 141 C.

The polymer is melt-spun at 188 C. giving yarn with the following properties:

Percent Elastic recovery from 100% extension 89 Work recovery from 100% extension 56 Example 15 Percent Elastic recovery from 100% extension 90 Work recovery from extension 55 Example 16 Example 15 is repeated except that the 17.3 parts of di(4-isocyanato-cyclohexyl)-methane (mixed steric isomers) are replaced by the same quantity of m-Xylylene diisocyanate. The resulting polyester-urethane has an inherent viscosity of 0.66 an a Vicat softening point of 127 C.

Example 17 Example 14 is repeated except that the quantity of butane-1,4-diol is reduced from 4.95 to 3.8 parts and the di(isocyanato-cyclohexyl) methane replaced by 11.2 parts of p-xylylene diisocyanate. The resulting polyester-urethane has an inherent viscosity of 0.44 and a Vicat softening point of 174 C.

What I claim is:

An elastomeric filament consisting of a polyester-urethane obtainable by heating together (1) a diol being a hydroxyl-terminated linear copolyester with a number average molecular weight between 1500 and 3500 and being a reaction product of aliphatic and cycloaliphatic glycols having from 2 to 20 carbon atoms and adipic acid optionally together with other dibasic acids selected from the group consisting of saturated aliphatic dibasic acids and aromatic dibasic acids, .(2) from 2 to 20 moles, per mole of the aforesaid polyester diol, of a diol having not more than 20 carbon atoms and selected from the group consisting of aliphatic diols optionally containing arylene groups and cycloaliphatic diols and (3) from 96 to 100 moles, per 100 moles of the total weight of the foregoing diols, of a diisocyanate having from 4 to 24 carbon atoms, selected from the group consisting of aliphatic and cyclo- 1 1 aliphatic diisocyanates and optionally containing aromatic nuclei provided the latter are separated from the isocyanato groups by at least one methylene group, which filament has an Elastic Recovery from 50% extension of at least 95%, a work recovery from 50% extension of at least 75% and does not discolour when exposed to a Xenon Arc or bleached with sodium chlorite in accordance with the light resistance and bleaching resistance tests in which the filaments are immersed for a period of 45 minutes in an aqueous solution containing 0.1% by weight of sodium chlorite and 0.5 c.c. per litre of glacial acetic 12 acid maintained at 85 C. and the colour of the filaments is determined before and after the bleaching treatment.

References Cited UNITED STATES PATENTS 2,871,218 1/ 1959 Schollenberger 26075 3,174,949 2/ 1965 Harper 2607S 3,233,025 2/1966 Frye et a1 26075 10 DONALD E. CZAJA, Primary Examiner.

G. W. RAUCHFUSS, 111., Assistant Examiner.