DE2215736A1 - Soluble Polyurethanes - Google Patents

Description

PATENT LAWYERS

DR.-ING. H. FINCKE DIPL.-ING. H. BOHR DIPL, -ING. S. STAEGER

Remote call: * 2ή όθ 60

8 MUNICH 5, Müllerstrafle 31

30th MAR. 1972

Folder 22844 - Dr. Ca3s Du 23734

Imperial Chemical Industries Ltd. London, UK

Dissolving polyurethanes

Priorities: 30.3.197I and 8 * March 1972 - Great Britain

The invention relates to polyurethanes and in particular on a process for the preparation of soluble polyurethane elastomers.

According to the invention, a process is used for the production of soluble polyurethane elastomers from a highly valuable linear polymer with a molecular weight of over 80O ₅

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22Ί5736

a diol with a * molecular weight of at most 250 and proposed an organic diocyanate, the quantity * » of the latter at most the polymeric polyol and the diol taken together is equivalent. The Ver / ahran thereby becomes carried out that the organic diisocyanate and the polymer Polyol reacted with each other to create an isocyanttabgeschlosaenes Prepare prepolymer, then the Yorpolyoer with the diol converts to an insoluble polyurethane product and finally the insoluble polyurethane product is heated until a soluble product is formed.

It is true that the polyurethane product can become insoluble as a result of the action heat alone converts it into a soluble product but it is preferred to be the insoluble product to work through mechanically at an elevated temperature until the desired solubility is achieved

Examples of polymeric polyols having a molecular weight over 800 are polyether thioethers and polyacetals, but it is preferred to use a polyester or a polyether. These polymers should preferably be linear. But they can also be slightly branched. Finally, they should either be liquid or no longer have a Schmelspunkt of 60 ^0C.

Examples of polyethers that can be used are polymers and copolymers of cyclic oxides, such as 1,2-alkylene oxide, for example ethylene oxide, epichlorohydrin, 1,2-propylene oxide «i _t 2-3utylene oxide and 2,3- Butylene oxide, O.iycyc3.obvit8.ii and su'oßti uuier ^- c <? N0xyc, ycXobutanai as well as tetrahydrofuran, Ls should also be mentioned here and polyethers, as they are, for example, due to the polymerization of an alkylene oxide in Gögcnwa: ot eino.s baischen ^ Glycol oasz eiweu primary Honoan'i.n

2098A2 / 10

will. It can atioh Gemlsclie before, such polyethers used wordeziu DIE bevorssugrt & n P.oly & thor are Folytetrahydrofuranpolyiaere having a molecular weight "wipe 1000 and 25OO, and more particularly polypropylene glycols having a molecular weight s-wipe 1000 and TiJOO * This latter polyether give a Polyurethartprcdukt which _t when it from Solution is applied "has a number of physical and mechanical properties that could not previously be obtained with this class of polyols"

Examples of polyether thioethers that can be used are the products of the coadeneation of thioglycols, such as e.g. * Thiodiglycolj or the condensation of thioglycols with Glyeols *

The polyesters that can be used can be obtained from aliphatic dicarboxylic acids and dihydric alcohols by customary measures. Suitable dicarboxylic acids are berasteinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic acid and mixtures thereof. Small amounts of up to about 20 mol% of phthalic acid, isophthalic acid and terephthalic acid can also be used. Suitable dihydric alcohols are ethylene glycol, 1,2-propylene glycol, diethylene glycol, dipropylene glycol, trimethylene glycol, 1,2-, 1,3'-, 2,3- and 1,4-butylene glycol, neopentyl glycol, pentamethylene glycol and hexamethylene glycol and mixtures thereof. Small amounts of polyols with more than two hydroxyl groups, such as glycerol * trimethylolpropane and pentaerythritol, can also be used. The acid value of the polyester used should be less than 6.0 and preferably less than 3. The preferred polyesters have melting points below GO ⁰ O and are derived from glycols with 2 to 8 carbon

substance atoms off. Particularly suitable are polyesters with a Molecular weight between 1000 and 2500, which is based on such dicarboxylic acids, especially adipic acid, and a glycol or derived from a glycol mixture. Polyesters obtained by polymerizing cyclic lactones or mixtures of cyclic lactones Lactones such as caprolactone and the alkyl substituted ones Derivatives derived therefrom are also suitable.

As examples of polyacetals that can be used, the reaction products of aldehydes such as as.B. Formaldehyde, acetaldehyde and butyraldehyde, with aweiivalentη Alcohols such as propylene glycol, butylene glycol and diethylene glycol can be mentioned.

It is preferred that the organic diisocyanate which is used in the new process is one which has a symmetrical structure, as is the case, for example, with hexamethylene-1,6-diisocyanate, tetiamethylene-1,4-diisocyanate, 4, 4 »-Diphenylmethandiisocyanat, 1 ^ -Phenylendiisocyanat and 1,5-Naphthylezidiisocyanat is the case. Hexamethylene-1,6-di ~ isocyanate and ^, ^ '- Dipnenylmethandiieocyanat are special · suitable.

The diol having a molecular weight of at most 250, which is used in the second stage of the novel traversed is preferably one that can react with an organic diisocyanate as the only other Reaktionsteilnehiier to a crystalline polymer having a melting point of at least 150 ⁰ C. to build. Preferred examples of such diols are ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-bis (β-hydroxyethoxy) benzene and 1, G-cyclohexanediol.

Small amounts of one or more compounds of which are known is that Hie a stabilization of polymers against light or against oxidative or thermal discoloration or

2098A2 / 1094

opposed to degradation effects, such as alkyl-substituted phenolic Compounds can also be added. If necessary, fillers and pigments can also be added will. In order to interfere with the polymer formation reaction of the Keep diisocyanates low, these additives should be dry «

The first stage of the process, namely the reaction of the organic diisocyanate and the polymeric polyol to produce a prepolymer, is preferably carried out under slightly acidic conditions, since the insoluble polyurethane product obtained at the end of the second stage, ie during the reaction of the prepolymer with the diol, then in a more mechanically workable form. The necessary degree of affinity can be achieved by adding a mineral acid, an organic acid or a compound which reacts to form a mineral acid or an organic acid to the polymeric polyol. Examples of acidic or acid-forming compounds which can be used are adipic acid and bensoyl chloride. The amount of acid present should be equivalent to an amount of hydrogen chloride which corresponds to up to 0.02% by weight of the diisocyanate. The lower limit of acidity depends on the individual polymers. However, whether there is sufficient acidity can easily be determined by experiment, and if necessary enough acid can be added to the mixture to bring the acidity to a desired level. If an organic acid is added, then the acid dissociation constant and the possible Reactivity with isocyanates should be taken into account; if necessary, a correspondingly larger amount must then be used. Thus, it is usually appropriate to the polymeric PolyhydrorjcyverMn & tmg before the ⁶ Usasotsung the old "Oiißocyanat about 0.1 * -% adipic add" The organic © diisocyanate may itself have sufficient Aaidltät, 30 that addition of an acidic compound unnecessary.

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is. The acidity of the diisocyanate can be measured by adding a measured weight of the diisocyanate to a large excess of n-propanol , allowing the mixture to stand for about 10 minutes at ordinary temperatures so that the n-propanol and the diisocyanate are completely reacted with one another, and Finally, titrate with a standard solution of potassium in alcohol.

Pie reaction between the diisocyanate and the polymeric PoIyöl is carried out at a temperature not exceeding 10O ⁰ O, and preferably at a temperature of 50 to 100 ⁰ C, "the" wide stage, the traversed between the prepolymer and the DLOL is carried out by reacting the diol mixed with the heated to a temperature of 60 to 150 ⁰ O prepolymer at a temperature of 10 to 150 ° 0, and that mixture keeps 0 ° C to a temperature of 70 to 1? until it solidifies. If necessary, the reaction can be brought to an end by subsequently heating the solid product, for example up to 40 hours to a temperature of up to 120 ^° C. or longer. Camping at lower temperatures.

The second stage of the process is preferably carried out in a continuous manner.

For example, the prepolymer and the diol can be used independently at a temperature within the stated ranges a heated mixing chamber, which contains a device Lura mixing the two reaction participants and which is constructed so that the liquid mixture is fed into or onto a second receiver, e.g. a moving belt that runs over a plate heated to the desired temperature. A particularly suitable one The band consists of a glass cloth made with polytetrafluoroethylene is coated, as the feata polyurethane product does not adhere to such a tape. The plate should be like this be such that a temperature in the mixture of not menr

209842/1094

than 1? 0 ° ö is reached - H & ch solidified in a short time Calibrate the mixture and then go to a final heating stage be subjected, in the form of a plate or in the form of divided strips or granules * Gerneineam customary catalysts can optionally be used with the diol for isocyanate reactions, such as organic and inorganic bases and organometallic compounds " the rate of solidification of the reaction mixture speed up «Antioxidants of the phenol type can also be added« to reduce discoloration.

Bending final hardening stage © is preferred in the absence run of oxygen and moisture, for example in a sealed container, under a nitrogen blanket or in a vacuum oven.

The solid polyurethane product, which at the end of the second Step of the process obtained is in strong solvents, such as E.B «dirnethylsulfoxide, and Dimethylacetaaid Dimethylformamide insoluble

In the final stage of the process, the insoluble one becomes. Polyurethane product, optionally after granulation, heated and preferably also mechanically worked through until a soluble product is obtained. The temperature at which this process is carried out is usually in the range from 180 to 220 ^° C. The mechanical working through can be carried out by the polyurethane product is subjected to an injection molding process, the temperature in this case preferably being 180 to 190 ⁰ O, or that the product is passed through a heated cylinder with the aid of a screw or a helical, axially rotatable cylinder, in which case the temperature is preferred 200 Mp 2'10 ^c 0. En Jr.onaen e.XIe measures wcsrclon .. ^ .- orfiTi which da ν f ^ ate prodi & t at the

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■ * ■ ο ** ·

combined exposure to heat and shear forces. At the preferred temperatures, working through for a time of 1 to 60 minutes is preferred 6 to 12 minutes. After this final stage of the process, the product is easily in strong solvents, like E.B. Dimethylformamide, soluble.

^Ex: findungsgemä8en products are thermoplastic elastomers. They are of particular value as one-pack elaatomers for coating, especially for textiles *

The invention is illustrated in more detail by the following examples, in which the parts and percentages are by weight are expressed.

example 1

237 parts of a polypropylene glycol having a hydroxyl value of 59.3 mg KOBVg du'och were dehydrated with stirring at 110 ⁰ C and at a pressure of 100 mm Hg until the moisture content is less than 0.015%, respectively. The dry Glycol was then cooled under nitrogen to ⁰ G 80 and slowly su a mixture of 177 parts Diphenyluethan <~ 4-, V-dii8ocyan t, 0,051 parts of 2,6-di-tert-butyl-p-oresol and 0.0255 parts Benzoyl chloride at 50 ⁰ C added. The temperature of the mixture was set to 60 ° C. and held at this value for a further 11/2 hours, a pressure of 100 mm Hg being maintained. Another 8 parts uiphenylmethan-4,4'-dii800yanat were added to the prepolymers of the Ieocyanatgehalt set to 12.11% »DAB prepolymer was then cooled under dry nitrogen at a pressure of 100 mm Hg at 70 ⁰ C. The pressure was then brought back to atmospheric pressure with dry nitrogen and the prepolymer

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was prepared using a gear pump through a heat exchanger which raised the temperature to '104 ⁰ G, metered to a mixing head, with a rate of 1.3509 part / min · 1.4> -but & ndiol which eiae temperature of 70 ⁰ O and in a separate container was independently metered to the mixing head at a rate of 0.1806 parts / one. The dwell time in the mixing head was approximately 3 seconds. The mixture which left the head at 112 ° C was applied to a heated glass cloth tape which was coated with polytetrafluoroethylene. The product remained on the tape for approximately 10 minutes. After being removed from the tape, the solid material was granulated and stored in sealed containers for several days. If an attempt was made to dissolve the product in dimethylformamide by rumming and vigorous fishing, it was found that the product was insoluble, although there was an excess of hydroxyl groups over the isocyanate groups.

The insoluble product was then ^{injection molded at 180 to 190 0} O, the curl time in the cylinder of the injection molding machine being approximately 3 minutes. The elastomer obtained was easily soluble in dimethylformamide and gave "ine solution having a viscosity of 20 poise at 25 ⁰ O and a Peatetoffgehalt 20% *

Films were cast from this solution. You owned that following physical properties. You can »it according to the physical properties of the elastomer Injection molding but be compared before casting.

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Tensile strength
speed
(kg / cm ² ) Tear
strain
<%) permanent
Fixation
(%) module 300% 500% poured
apritz-
poured 400
190 55O ^BC
400 110
100 100% 185
168 330 92
144

Example 2

23? Parts of polypropylene glycol having a hydroxyl value of 5913 mg KOH / g were dehydrated by stirring at 110 ⁰ C and at a pressure of 100 mm Hg until the moisture content is less than 0.015%, respectively. The dry Glycol was then cooled under nitrogen to 80 ⁰ C and slowly zn a mixture of 177 parts of 4,4'-Biphenylmethen ~ _f diiaocyanat 0.051 parts of 2,6-di-tert-butyl-p-oresol and 0.0255 parts of benzoyl chloride at 50 ⁰ C issued. The temperature of the mixture was set to 80 ° 0 and held at this value for a further 11/2 hours, a pressure of 100 mm Hg being maintained. A further 8 parts of diphenylmethane-4,4'-diisooyanate were added in order to adjust the isoyanate content of the prepolymer to 12.11%. The prepolymer was then cooled under a Stiokstoff at a pressure of 100 mm Hg at 70 ⁰ C * The pressure was then adjusted again with dry nitrogen to atmospheric pressure, and the prepolymer was applied via a heat exchanger * the temperature which then using a gear pump 104 ⁰ C increased, xu carried out a mixing head, at a speed of 1.3509 parts / min. 1,4-Butanediol, which had a temperature of 70 ^° C. and was in a separate container, was fed independently to the mixing head, at a rate of 0.1766 parts / min.

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The dwell time in the mixing head was approximately 5 seconds * The mixture r left the head with a temperature of 112 ° 0 and became applied to a heated glass cloth tape which was coated with polytetrafluoroethylene. Bas product remained approximately 10 bin on the tape. After being removed from the tape, the solid material was granulated and lasted for several days stored in closed containers. Venn was tried " the product under Romeels and under strong mixing in To dissolve dimethylformamide, it was found that the product was insoluble, although an excess of hydroxyl groups to isocyanate groups was present.

The insoluble polyurethane was then ^{spritegoseen at 180 to 190 0} C, the residence time in the cylinder of the injection molding machine being approximately 3 minutes Viscosity of 40 poise.

From this solution, films were cast showing the following possessed physical properties * You could with the physical properties of the elastomer after the fuel «- but be compared before casting.

Tensile strength
speed
(kg / cm ² ) Tear module 210
168 poured
injection molded 360
190 <*) 10056 450
440 85
144

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Example 3

200 parts of a Polypropylfeuglynole with eintλ hydroxyl value of 59 "3 mg KOH / s were mixed by stirring at 110 ⁰ C and" ine "pressure of 100 to Hg Aehydratio ?. place where the moisture content was less than 0.03%. Dad dry Glycol was then cooled uutfti * ⁶ nitrogen to 80 C and added slowly to a mixture of 101 parts of EEA Dipbenylaethan ~ 4 '4' ~ dii £ 0.03 ooyanat _v '!' Rush 2,6-di-butyl-p TTRT -eresol and 0.015 part of benzoyl chloride fit 50 ⁰ C was added. The temperature of the GemJash was set to 80.degree. C. and kept at this value for 1 1/2 hours, while a pressure of 100 Hg was maintained divide the isocyanate content of the prepolymers to 8 * 73%. The gate polymer was then cooled to 0 ° C under dry nitrogen and at a pressure of 100 mN Hg. The pressure was then adjusted bit trockenom nitrogen to atmospheric pressure, and the prepolymer was cherelnhelt using a gear pump via a Wäraeaustau &, which increased the temperature to 113 ⁰ C, su supplied to a mixing head, and swsr with a Oesohwindigkeit of 1.4846 parts / min. 1, 4-Butt.ndiol was At 70 ⁰ C, which "in a separate container, regardless sum mixing head was supplied, specifically at a rate of 0.1399 part / min. The dwell time in the mixing head was approximately 3 seconds, and the mixture left the head at a temperature of 112 ° C. It was applied to a heated glass cloth tape which was coated with Pclytatrufluoroäthylen * The product remained on the tape for approximately 10 minutes. After the bond was taken, the solid material was granulated and stored in closed containers for several days * When the product was tried auiculöeen with rubbing and vigorous mixing in dimethylformamide, then it was found that it was insoluble.

4 fr ο ft /. 9/4 Λ 6 /.

groups opposite the isocyanate groups was present.

The insoluble polyurethane was then apritz-cast at 160 ble 170 °, the curl in the cylinder of the 3- fuel casting machine being approximately 3 minutes. The elastomer obtained was easily soluble in dimethylformamide and gave a solution which had a viscosity of 45 poise at 25 ° 0 and a content of 30%.

From this solution vuinien pilme poured. They had the following physical properties, soft® with physical properties Properties of the elastomer after injection molding but before casting could be compared.

Zugfeatig-
speed '
(kg / cm ² ) Elongation at break
(3 *) Kodul 300 # 50056 poured
| injection molded 260
144 650
325 100% 95
130 180 34
95

Example 4

258.5 parts of a FolypzOpyleneglycols with a hydroxyl value of 59-3 mg KOH / g were ^{dehydrated by stirring at 110 0} O and at a bridge of 100 mn Hg until the moisture content was less than 0.010%. The dry glycol was then cooled to 80.degree. C. under nitrogen and slowly added a "Ge ei β oh from 195 t5 parts diphenyls" than-4, M- '-diisocyanate _t 0.0577 parts

M Λ Ö I.

2,6-Di-tert ~ butyl-p-cresol and 0.0288 part gr _: Benzoyl chloride added at 50 ⁰ C »The temperature of the mixture was set to 80 ° 0 and kept another 1 1/2 et at the same Were, with the Pressure was 100 mm Hg. A further 8 parts of diphenylmethane-i'-diisocyanate were added in order to increase the isocyanate content of the prepolymer. 12.11% to be paid. The prepolymer was then cooled ^{to 70 c 0 under dry 3t.} The pressure was then brought back to the outer sphere with dry nitrogen, and the prepolyacr- was replaced using a gear pump via a heat exchange unit which kept the temperature at 97 ° C, a mixing head fed, namely -with a first QeriCfcvflacliöfcait of 1.5382 parts / min. 1,4-butanediol, which had eirts temperature of 70 ⁰ G and calibration was in a separate container, was / min zugaführt independently at a rate -vou 0.2037 parts to the mixing head. D10 Verwoilzeit in Mlachkopf was approximately 3 eek * The Gemiacii left the mixing head with einar temperature of 106 ⁰ C and was applied onto a heated QlastuchbaM, which was coated with PoIytetrafluoroäthylen. DaB product * was approximately 10 min on the tape! Πχά times dei * Decrease Baud wutde the solid material is granulated and several To. & S stored in sealed containers. When an attempt was made to dissolve the product in dimethylformamide by rummaging and mixing vigorously, it was found that it was insoluble, although there was a 3: 1 excess of hydroxyl groups over the isocyanate groups.

The insoluble polyurethane was then kept at 21C to 215 ° C extruded, the residence time in the barrel of the extruder being approximately 4 minutes. The elastomer obtained was light soluble in dimethylformamide and gave a solution which was at 25 ° C and a solids content of 20%, a viscosity of 10 poise exhibited.

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Films were cast from Closer's solution. " You owned that the following properties a.

Tensile strength
speed
(kg / cm ² ) Tear
strain permanent: ©
Fixation Hod
100% ul
300% 500% poured 390 560 105 100 175 340

Example 5

β of a polypropylene glycol with a hydroxyl value of 5953 mg KOH / g were dehydrated by stirring at 110 ° C and a pressure of 100 mm Hg until the fissure content was less than 0 * 015%. * The dry glycol became that * under nitrogen to 80 ⁰ C cooled and slowly asu a mixture of 105 parts of diphenylmethane-4 _t 4'-diisocyanate 0.0: 508 ropes of 2,6-di-tert-butyl-p-cresol and 0.0154 parts of benzotrichloride aifc 50 ⁰ G a ^ . egoben the temperature dee mixtures was 3isgeetellt to 8O ⁰ G and additional 1 1/2 et at this value held wobsi the pressure was 100 sam Hg "another 22 ₅ V5 parts Dipkenylmetlian - ^, ^ '- diisocyanate were Bugesetst to the Isocyanstgehalt adjust the Torpolymers to 8.73%. the prepolymer was then cooled under dry nitrogen and at einoa pressure of 100 mm Hg at 70 ⁰ C. the pressure wurda then nit dry nitrogen to atmospheric again ?! push brought UNAE dt \ s Vorpnlymer was xmU-.v using övne: i 'gear pump via a V / heat exchanger, who raised the temperature to 118 ⁰ C, to a Mi; ' ¹ I-VfPf to £ o, iand ζν.χτ? _ri it a speed of

Π Q fi L 7 I 1 ■ ß 9 L

1 * 5235 parts / min, "1,4-butanediol, which had a temperature of 70 ⁰ C and was in a separate container, regardless sum mixing head was supplied, specifically at a rate of 0.1454 part / min. The dwell time la mixing head was approximately 5 seconds. The mixture leaving the top with a (temperature of 140 ⁰ C and was applied onto a heated glass cloth belt, which was coated WLIS polytetrafluoroethylene. The product remained approximately 10 minutes on the tape. After removal from the tape, the solid material was granulated and several days When an attempt was made to dissolve the product in dimethylformamide under Rummein and strong IH, it was found to be insoluble, although there was an excess of hydroxyl groups over the isocyanate groups.

The insoluble polyurethane was extruded at 210 to 215 ° C., the residence time in the barrel of the extruder being approximately 15 minutes. The resulting elastomer was then readily soluble in dimethylformamide and gave a solution which had ^{a viscosity of 5 poise at 25 0} O and a plague content of 20%.

Films were cast from this solution. You owned that the following physical properties, which are related to the physical properties of the elastomer according to the Injection molding but before casting are comparable.

Tensile strength
speed
(kg / cm ² ) Tear module 300% 500% poured
injection
goseen 230
145 (%) 100% 90
110 150
147 670
570 20th
80

209842 / 1G9 *

Claims (1)

Claims Λ / Process for the preparation of soluble polyurethane elastomers from an essentially linear polymeric polyol with a molecular weight of more than 800, an Oiol with a molecular weight of at most 250 and an organic diisocyanate, the latter being used in an amount that does not exceed the polymeric polyol and the diol together taken is equivalent, characterized in that the organic diisocyanate and the polymeric polyol are reacted with one another to produce an isocyanate-terminated prepolymer, then further reacting the prepolymer with the diol to produce an insoluble polyurethane product, and finally heating the insoluble polyurethane product until soluble Product was created. 2. The method according to claim 1, characterized in that the insoluble polyurethane product is worked through mechanically during the heating. 3 · The method according to claim 1 or 2, characterized in that the polymeric polyol is a polypropylene glycol with a Molecular weight between 1000 and 2500 is used. 4 ·. A method according to any one of claims 1 to 3, characterized in that the reaction between the polymer and the diol is carried out by mixing the diol at a temperature of 10 to 150 ° 0 with the prepolymer kept at a temperature of 60 to 150 ° 0, and that the mixture is kept at a temperature of 70 to 170 ⁰ C until ea solidifies. 209842 / 109A 5 * Missing according to any one of claims 1 to 4, characterized in that the reaction between the prepolymer and the diol is carried out continuously by independently feeding the prepolymer and the diol to a heated mixing chamber, the liquid mixture then on a moving belt is applied, which runs over a heated plate, bo that a temperature in the mixture of not more than 170 ⁰ C exists, wherein the mixture solidifies. 6. The method according to any one of claims 1 to 5 *, characterized in that the reaction between the prepolymer and the diol is brought to an end in that the solid product is heated to a temperature of up to 120 ⁰ O for a time of up to 40 st. 7. The method according to any one of claims 1 to 6> characterized in that the insoluble polyurethane product thereby is converted into a soluble product that it is heated to a temperature of 180 to 220 ° 0 for 1 to 60 min. 8. The method according to any one of claims 2 to 7 »characterized * that the mechanical working through of the heated insoluble polyurethane product is carried out in that the product is subjected to a Spjcitzgußvorgang at a temperature of 180 to 190 ⁰ O O. 9 * Method according to one of claims 2 to 7 * thereby characterized in that the mechanical working through of the heated insoluble polyurethane product is thereby carried out is that the product through an axially rotatable worm shaft at a temperature of 200 to 210 ° 0 is carried out through a heated cylinder. ? 098 £ 2 / 109A