DE1694277A1 - Polyurethane reaction mixture, process for its preparation and use thereof - Google Patents

Description

THE GOODYEAR TIRE AND RUBBER COMPANY, Akron, Ohio, 44316 ,. United States

Polyurethane implementation, process for its production

and application of the same

The invention relates to a process for producing polyurethanes with improved resistance to discoloration after 100 hours in a weathering device.

Although polyurethanes have been known for at least two decades and it was known from the first work that polyurethane films can be produced, these films have, however, no commercial significance or at least achieved sales success on a large scale due to the tendency of the polyurethanes to discolour upon exposure to sunlight and eventually dark brown to black. This is a disadvantage particularly for industrial development, where the aim white or light colored sheets or other objects ausPolyurethan '.

One of the tasks underlying the invention is thus to provide a process for making polyurethanes which have improved resistance to discoloration.

According to the invention, one can proceed in such a way that a polyurethane reactant mixture it is prepared that (1) a product having active hydrogen atoms and having a molecular weight is at least about 500 and not more than about 6000, (2) an organic polyisocyanate in which all isocyanate groups are linked to non-benzoid carbon atoms, as well as (3) contains a non-aromatic primary diamine, the polyisocyanate and diamine being selected to cause the reaction between them in boiling methylene chloride at 0.2 to 0.5 molar concentration takes place, causing a turbidity within

009039/2182 - 2 ~

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of 30 seconds results. So that these polyurethane reaction mixtures are editable, it is useful that the same a suitable contain inert diluent. These reprocessable polyurethane reaction mixtures can be brushed, dipped, sprayed, or otherwise onto suitably shaped surfaces Manner can be applied to form a film, while still being shaped objects and deformed accordingly Polyurethane is obtained, which has an improved resistance to discoloration after 100 hours in the weathering device as determined by ASTM Method E-42-57 and ASTM D-1499-59T.

The availability of this polyurethane reaction mixture will be on best achieved where the reaction mixture (1) has an active hydrogen atom containing product with a molecular weight of about 900 to 3000, (3) a non-aromatic, organic polyisocyanate, (3) a non-aromatic primary amine; and (4) sufficient amount of inert solvent to contain the mixture to make it expandable.

Preferred results are obtained when the active hydrogen atoms containing product is first made to react with an organic polyisocyanate in which all isocyanate groups are linked to non-benzenoid carbon atoms and then the non-aromatic primary diamine is added to the reaction product obtained. As the non aromatic organic Polyisocyanates and non-aromatic primary amines such as those here are used, a turbidity according to the Muller hot methylene chloride test, as described in US Pat. No. 2,620,516, it has been found to be a particularly suitable mode of operation to improve or reduce the spreadability of the polyurethane The reaction mixture consists of organic diamine with a ketone selected from the class consisting of acetone and methyl ethyl ketone. Thus, these Ketones are used as part or as the total amount of the solvent to form the polyurethane reaction mixtures, which remain spreadable over a longer period of time.

009 839/21 3.2

The active hydrogen-containing products useful in the present invention have a molecular weight of at least about 500 and no more than about 6000. Wherever elastomers are sought, the molecular weight should be around 1000 and preferably no greater than about 3,000.

Characteristic classes of having active hydrogen atoms Products are the polyester polyols, polyether polyols, polyether polyester polyols, polyester amides, castor oil, polycarbonate polyols and polydiene polyols and the hydrogenated polydiene polyols.

Typical examples of these active hydrogen-containing products can be found in U.S. patents U.S. Patent Applications Ser.No. 274,280, 310 910 and 410003. Eini. ge specific polyester diols are the alkylene adipates, where the Alkylene radicals ethylene, propylene, butylene, amylene and hexylene or represent mixtures thereof. The corresponding alkylene azelates are useful where low temperature properties are required. The (polyalkylether) glycols or triols are preferred where the alkyl radical is propyl and butyl.

Characteristic for organic polyisocyanates in which all isocyanate groups are linked to non-benzoid carbon atoms are, and which are useful according to the invention are m-xylylene diisocyanate, 4,4'-Methlenbis (cpclohexynisocyanat), p-Mehthandiisocyanat, bis (2-IsocyanatoäthyDfumarat, bis (2-IsocyanatäthyDcarbonat, bis (2-Isocyanatoäthyli-4-cyclohexene-1 , 2-dicarboxylate and hexamethylene diisocyanate, l-methylcyclohexyl-2,4-diisocyanate, l-methylcyclohexyr-2,6-diisocyanate and mixtures of i-methylcyclohexyl-2,4-diisocyanate and l-methylcyclohexyl-Zie diisocyanate.

Characteristic for the non-aromatic primary diamines are 1,4-cyclohexane bis (methylamine), p-menthediamine, 1,6-hexamethylene diamine, tear-1,2-cyclobutane bis (methylamine), 1-methylcyclohexyl-2,4-diamine, diaminocyclopentane and ethylene diamine.

Even if the polyurethane reaction mixture by means of simultaneous mixing of the active hydrogen atoms Product, the organic polyisocyanate and the diamine, it is preferred that the active

Product containing hydrogen atoms and the organic poly-

009839/2182 ~ 4 -

ORIGINAL INSPECTED

isocyanate are first reacted to form a prepolymer and then the diamine is added. It has also been found that about 1.3 to 3 hole organic polyisocyanate can be used per mole of active hydrogen product, although slightly lower or higher ratios can be used. It has been found, however, that the mechanical properties achieved in the cured product are not as satisfactory as those obtained under the above-mentioned ratios. The amount of diamines employed should be about 0.5 to 1 mole per mole of free isocyanate present. This is particularly true where the final curing and shaping of the reaction mixture is to be carried out at room temperature, although it has been found that from 0.7 to about 1.2 moles of diamine per mole of free isocyanate can be used. It is understood that the application will influence of catalysts, such as the well-known Zinhkatalysators, the ratio and the final physical properties of the present where the! Reaction is carried out at room temperature or temperatures up to about 150 ⁰ C. It should be emphasized that the use of catalysts, such as the organic tin catalysts, tends to influence the aging properties of the polyurethanes obtained. Other catalysts, such as the well-known tertiary amines, can also be used.

It should be emphasized that where the amount of diamine used is substantially equivalent to the free isocyanate, the physical properties of the cured product usually contribute about 280 kg / cm tensile strength or more, while in the extreme ranges of amounts of diamine versus free Isocyanate, as stated above, the tensile strengths

2
cannot be higher than about 84 kg / cm.

The polyurethane reaction mixtures used according to the invention practically do not discolor after being left in a weathering device for 100 hours are. In particular, valuable results are obtained there, where the polyurethane reaction mixture contains various pigments, usually in a ratio of 5 to 100 Parts per 100 parts of the reaction mixture · * «Usually will

009839/2182 - 5 -

about 5 to 20 parts of pigment will be sufficient to achieve the desired to achieve aesthetic effect. It should be emphasized that the general known inorganic pigments such as titanium dioxide, lead sulfate, chrome yellow, chrome red and other pigments of the inorganic Type according to the invention can be applied. In a similar way organic pigments such as resorcinol, indigo, turkish red, Triphenylmethane dyes, xanthene dyes, the stilbenes and other dyes, as they are in the book νώη William T. Caldwell, Organic Chemistry, Copyrigth 1943, Riverside Press, beginning on page 702 to page 725 are given, use.

The invention is exemplified below with reference to a Series of exemplary embodiments explained:

example 1

A prepolymer of 8000 parts of an 80:20 ethylene: propylene adipate with a reaction number of 62 and 2352 parts of 4.4 ^I- diisocyanate di-cyclohexyl methane is prepared in the following manner.

The polyester wifd an hour degassed under vacuum at 76-100 ⁰ C. The molten diisocyanate (mixture of cis and trans forms) is then added and the mixture is left to react at 90 ° -114 ° C. for one hour. A vacuum is then slowly applied (to prevent excessive foaming) over the course of an hour. The prepolymer then had an isocyanate content of 3.5%.

The prepolymer is diluted in the following way:

Prepolymer 100 parts Methyl ethyl ketone 30 ■ toluene 30 « Cellulose acetate butyrate
Solution (10% in CellosoIv-
Acetate) 5 " 165 parts

The diluted prepolymer has an isocyanate content of 2.0% (% NCO). The diluted prepolymers are referred to as component A below.

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15 parts of p-xylene are added to 40 parts of component A. A hardening solution A is prepared by adding 1.5 parts of 1,4-cyclohexane bis (methylamine), 2 parts of N, N'-dimethylformamide and 3 parts of methyl ethyl ketone are heated. The hardening solution is added to the diluted prepolymer and coated applied from strips of imitation gold braid, as it is used for Kriegsmarine officer's uniforms. It will be as well Applied polyethylene foils and allowed to cure at room temperature.

The transparent film has a tear strength of

2
22.4 kg / cm and 620% elongation when cured at room temperature. The clear, transparent film (0.356 mm) shows negligible discoloration after 100 hours in the weathering device.

It becomes a white, dilute prepolymer of 168 parts of component A and 15 parts of titanium dioxide. The mixture is milled for 20 hours in the KugelmMhüe.

40 parts of this white dilute prepolymer become 4.8 parts of hardening solution B and 10 parts with thorough mixing Methyl ethyl ketone added. The hardening solution B is prepared by adding 100 parts of 1,4-cyclohexane bis (methylamine) and 400 parts of methyl ethyl ketone are heated. White foils are produced by means of spraying. The film shows a tear strength of 147 kg / cm and 590% elongation at room temperature curing. After 100 hours in the weathering device, there is negligible discoloration.

Example 2

It becomes a prepolymer of 400 parts of 80:20 ethylene / propylene adipate with a reaction number of 62 and 85 parts of m-xylylene diisocyanate manufactured in the following way:

The polyester degassed for 30 minutes under vacuum at a temperature of 95-110 ⁰ C and then 0.2 parts of magnesium oxide was added. Degassing continues for an additional 25 minutes. It is the m-xylylene diisocyanate were added and placed for 45 minutes at 90-10O ⁰ C for reaction. A vacuum is then applied and the mixture is degassed for 15 minutes. The VorpoiyKierle & t has an isocyanate content of 3.1%.

009839/2182. ₇ _

150 Parts 45 η 45 η 8th JL 30th η

- 7 The same is diluted in the following catfish:

Pre-polymer methyl ethyl ketone celloiol acetate

Cellulose acetate butyrate solution
(10% in cellosolve acetate)

Titanium dioxide

and then ground for 16 hours in a ball mill, whereby a dilute white prepolymer C is obtained.

A solution is added to 25 parts of dilute, white prepolymer C from 0.5 parts of 1,4-cyclohexane bis (methylamine) in 5 parts of methyl ethyl ketone added. The mixture hardens quickly and is spread on a polyethylene sheet. 3 days later puts the same thing represents a solid white rubber. It shows negligible discoloration after 100 hours in a weathering device.

Example 3

There are 50 parts of clear, thinned prepolymer prepared according to the procedure of Example 1 and with a Solution of 1.0 part of trans-cyclobutane-l ^ -blsimethylamine) in 10 parts of methyl ethyl ketone are added. There is sufficient time to apply two films to one sheet of polyethylene. The film becomes tack-free in 25 minutes at room temperature and can be withdrawn within an hour.

The clear, transparent film has a tensile strength of 147 kg / cm ² and an elongation of 560%. After 100 hours in the weathering device, the clear, transparent film shows negligible discoloration.

Example 4

To 50 parts of the clear, thinned prepolymer according to example 1 10 parts of a white batch A are added, which has been made from 60Θ parts of titanium dioxide and 40 parts of polyester according to Example 1 «The diluted» white Prepolymer is a mixture of 1.0 telene trans-cyclobutane-1,2-bis (methylamine) methyl ethyl ketone in 10 parts added * After thorough stirring, a white film is applied to a polyethylene sheet. The foil is not at tree temperature in 10 minutes

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more sticky and may come off the polyethylene film after 20 minutes subtracted from. There is negligible discoloration after 100 hours in the weathering device.

Example 5

A prepolymer of 1 mol of ethylene adipate (1000 molecular weight) and 2 moles of 4,4'-diisocyanatodicyclohexyl methane. The same thing has an isocyanate content of 5.1% (% NCO).

The prepojbyraerisat is diluted as follows: Vorpoibymerisat 100 parts

Methyl ethyl ketone 30 "

Toluene 30 "

Cellulose acetate butyrate solution

(10% in caliosolv acetate) 5 "

3u 55 parts of the dilute prepolymer, 8 parts of white batch A are added. Then 11 parts of the hardening Solution B added. Films are applied after mixing well and allowed to cure at room temperature. The sample shows negligible discoloration after 100 hours in the Weathering device.

Example 5

The following examinations serve to determine the resistance compared to discoloration of the following polyurethane reaction mixtures.

(1) are polyurethane acrylics made from polyol, aromatic diisocyanate and aromatic diarain

(S) sin Polyurathanaystsm from Polyoi, nichtaromatischeaa Diisocy «Ώα aromatic diamine

(?) aia Pclyursthanaystsm from Folyol, non-aromatic diisocyanate xmä nichtaroauatiacha »diamine.

After «insta check In sinar Bawittarungsvorrichtung IGO for hours saigan wsiäa Ma ^ a ^ n from <D) ^ in @ brown discoloration, wsiäe Maas an from (E) a-aigor, sin« b * ige '/ ar staining, veläi Maaaan from (F / ssigsn vsrsiachlässigbaaa discoloration ”, the procedure summed up by Haratsllan d“ r mixtures (D) , (S) and (F) is indicated as follows.

ORIGINAL BATHROOM

■ ■ ■ - 9 - ■
(D) Aromatic diisocyanate-aromatic diaraine

A prepolymer of 1 mol of tetramethylene adipate is used a reaction number of 60, 2 moles of 80:20 ethylene / propylene adipate with a reaction number of 60 and 6 moles of one 80:20 mixture made of 2,4- and 2,6-tolylene diisocyanate. The prepolymer is diluted in the following manner.

Prepolymer 1000 parts Methyl ethyl ketone 300 *

Toluene 300 "

Cellulose acetate butyrate solution

(10% GAB in Cellosolve Acetate) 50 "

all in all. 1650.

There are 75 parts to 500 parts of the diluted prepolymer Titanium dioxide added. This product will stay in the overnight Grind the ball mill to produce a white, diluted prepolymer.

A film made from the following ingredients is sprayed. 100 parts of white, dilute prepolymer

4.6 parts of 4,4'-methylenebis (2-chloroaniline) dissolved in 20 parts Methyl ethyl ketone.

The cured film shows a tensile strength of 392 kg / cm and 520% elongation.

This white mass shows a strong discoloration in the weathering device. After 100 hours in the weathering device, the film shows a brownish discoloration, the same makes unsuitable for many purposes.

(E) non-aromatic diisocyanate-aromatic diaain - -.

The component λ of Example 1 (500 parts) is 75 parts Titanium dioxide was added and placed in the ball mill for 16 hours Manufacture a white, diluted prepolymer grind. Its mass is sprayed on 100 parts of this, dilute prepolymer and 3 parts of 4,4'-methylenedianiline in 20 parts of methyl ethyl ketone prepared. The sprayed film

has a tensile strength of 147 kg / am and 100% elongation at room temperature curing.

009839/2182 - io -

169A277

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After 100 hours in the weathering device, the white one shows Mass a beige discoloration. This can hardly be regarded as a borderline case with regard to discoloration resistance.

(F) non-aromatic diisocyanate-non-aromatic diamine

Component A (100 parts) is admixed with a hardening solution which has been prepared by heating 2.2 parts of 1,4-cyclohexanebismethy1-amine and 20 parts of methyl ethyl ketone. It a film is sprayed on, which has a tensile strength of

400 kg / am and 630% elongation.

The white film is kept in the weathering device for 100 hours. There is negligible discoloration. Hiker by doing the same is suitable there where the discoloration occurs Problem. It should also be noted that the tensile strength is the same as that of the strongly discoloring polyurethanes according to the composition (E).

Example 7

A prepolymer is prepared by reacting 500 parts of polytetramethylene ether glycol with a molecular weight of about 1340 with 204 parts of 4.4 ^I- diisocyanatdiyclohexylmethane until the product obtained has an isocyanate content of 4.51.

The solution of the above prepolymer is prepared by 100 parts of the prepolymer in a mixture of 20 parts Toluene and 20 parts of methyl ethyl ketone dissolved verden. These Solution of the prepolymer (50 parts) is 11.5 parts, • Mixed in hardening agent and then made from a polyethylene foil film. You leave the same on the Air dry at a temperature of around 22-28 ° C. The clear, transparent foil obtained in this way has a negligible Discoloration after 100 hours in the weathering device (fadeometer).

The · hardening agent ·! will mediate heating a mixture of 20 parts of 1,4-cyclohexane ("* thyl"! nin) and 80 parts of methyl ethyl ketone prepared at 72 ° C for 10 minutes, If the hardening agent is not heated, the processing

008838/2112 " ^u "

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The processing time is very short and a two-component system should be used will. However, if the curing agent is heated to the methyl ethyl ketone, the life is about 8 minutes.

Example 8

It is a mixture of ethylene glycol and propylene glycol with Adipic acid reacted to form a polyester which Contains 80% ethylene adipate and 20% propylene adipate, as well as a reaction number of 62 and an acid number of less than about 5 owns.

To this anhydrous adipate (SOO parts) 90 parts Hexamethylendiisocyana't be zugestst and after IO minutes, the temperature on IIS 1st risen ⁰ C. It can be wnsetzen additional 90 minutes at about 105 ⁰ C to give a prepolymer, this mixture having 3.8% free isocyanate groups ©.

This prepolymer (100 parts) is mixed with 30 parts of methyl ethyl ketone, 30 parts of toluene and 5 parts of a 10% solution of Ceilulose acetate butyrate diluted in C @ ll © soiv & eetat.

The diluted pre-pool polymer (30 parts) is mixed with 3.9 parts of a curing agent which has been prepared by heating 20 parts of 1,4-cyclohexane bismethylamine with 80 parts of methyl ethyl ketone. A film is applied to a polyethylene sheet and allowed to cure by holding it at about 20 ° C. for 36 hours. The film obtained in this way shows negligible discoloration after IOP hours in the weathering device. The foil
on"

The film has an excellent tensile strength of 300 kg / cm ² and an elongation of 630%

■■■ '- Example 9 "■"'

eira eärtungectittsl vexmlttels heating a mixture a «i £ 10 parts anhydrous © 3.-» i-Hexylenäiaiain -and 160 parts

under back conditions for 20 to 30 minutes.

b®4 iS ° €

Härus «imitt« il (7 parts) is diluted with 50 parts of the

m & ch EXAMPLE 1 misses nnü seä & nn two foils

on? olyitiiflQaf © Ii @ a goieen and

on öio fCw-HrsoÄta Bi © feQ fo® £ OsateEg <gg © § © a v & is & o Di © Woltern

00Si3S / 21S2 - '"12 ·

ORIGINAL

- 12 - V ■ - ■

are tack free after holding at about 20 ° C for 25 minutes. The film is clear and shows negligible discoloration after exposure in a weathering device for 100 hours. The hardened polyurethane we
660% elongation.

te polyurethane has a tensile strength of 250 kg / cm and

Example 10

A prepolymer is prepared by converting 500 parts of poly (eetramethylene ether) glycol and 204 parts of methylenebis-4,4 ¹ -cyclohexyl isocyanate to form a prepolymer with 4.5% free isocyanate groups. The prepolymer (100 parts) is diluted with 20 parts of methyl ethyl ketone and 20 parts of toluene to form a dilute prepolymer. A curing agent is prepared by heating the mixture of 20 parts of bls-1,4-methylaminocyclohexane in 80 parts of methyl ethyl ketone at 70 ° C. while holding it for 10 minutes. The curing agent (11.5 parts7 is then mixed with 50 parts of the diluted prepolymer to give a spreadable polyurethane reaction mixture which is used immediately to draw films onto a polyethylene sheet. The clear sheets show negligible discoloration after the same 100 hours the weathering device have been held.

Example 11 .

A commercially available hydrogenated polybutadiene polyol having a molecular weight of about 3400 (17.1 parts) is dissolved ia 15 parts of p-xylene and then 2.9 parts of 4,4 ^r -MethylenbisCcyclohexyllsocyanat) dissolved added in 2.0 parts of p-xylene. The mixture is left to react for 1 hour at 75 ° C. with the formation of a prepolymer. The prepolymer is dissolved in a mixture of methyl ethyl ketone and toluene to form a dilute prepolymer. 4.3 parts of the hardening solution according to Example 10 are then added to the total amount of the diluted prepolymer. Ee a film is drawn on a polyethylene foil and ^{cured in the air at 20 0} C,

■ '-.-' ■ "- 13 -. 00S839 / 2182,

ORIGINAL

The clear, transparent film is then cured for 2 hours additionally at 80 ⁰ C and then held for 100 hours in the weatherometer. There is negligible discoloration.

Similarly, a commercially available polybutadiene polyol may be used in place of the hydrogenated polybutadiene polyol except that it will require 1 to 5% of one non-discoloring antioxidantζ apply to the application together with polyisoprene rubbers with a high cis content is suitable in order to stabilize the ethylene double bonds.

Furthermore, the polycarbonate polyols, such as the reaction product of a phosgenated ethylene glycol with an excess of propylene glycol, can be used instead of the polyester polyols or the polyether polyols.

example 12th

E * 50 parts of the dilute prepolymer according to Example 1 are mixed with 3.3 parts of a curing agent which is prepared by mixing 20 parts of ethylenediamine with 80 parts of methyl ethyl ketone and allowing it to stand for 16 hours at room temperature. The mixture obtained in this way is then used to pull a film onto a polyethylene sheet. Nan lets the films stand overnight at room temperature and then subjects them to exposure in a weathering device for 100 hours. There is only a negligible discoloration.

Example 13

The reaction mixture according to Example 1 is prepared by the diluted prepolymer and the hardening agent are mixed and then immediately the mixture obtained from an extrusion head downwards to form a continuous thread is pressed as the solvent evaporates.

Optionally, continuous threads can be produced, by cutting the thread from a large piece of foil.

009839/2182

-, - 14 - ■, - - - ■■■ - = ■ "■■ ..

There can be more allphatic diamines, such as those that Have 3 to 20 carbon atoms instead of ethylenediamine may be used, however, it should be borne in mind that some of the lower diamines i.e. those of 4 to 5 carbon atoms, have objectionable odor.

It is also possible to use other inert solvents than the hydrocarbons boiling below 260 ° C, e.g. the other solvents that can normally be used for the production of paints, such as nitropropane,
Ethyl formate, alkyl formate, alkyl acetate, ethyl acetate, ketones with the exception of those mentioned above, as well as the chlorinated hydrocarbons that boil below about 260 ° C. Usually the solvent is used in amounts as low as 5 to 20
Parts up to 70 to 100 parts per 100 parts of prepolymer are used.

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Claims (8)

Claims 1 «Process for the production of polyurethanes / characterized by that a compound having active hydrogen atoms having a molecular weight of at least about 500 and no more than about 6000, which is selected from the class consisting of polyester polyols, Pdlyether polyols, polyether polyester polyols, Polyester amides, castor oil, polycarbonate polyols and polydiene polyols and hydrogenated polydiene polyols with an organic polyisocyanate in which all isocyanate groups are linked to non-benzenoid carbon atoms, as well as with a non-aromatic primary amine with a sufficient Amount of solvent is brought to react to the mixture to make it expandable, the polyisocyanate and the diamine are selected so that the reaction between them in boiling methylene chloride in 0.2 to 0.5 molar concentration within of 30 seconds leads to turbidity. 2. The method according to claim 1, characterized in that at least part of the solvent used Ketone is that from the class consisting of acetone and methyl ethyl ketone is selected, as well as the diamine together with the ketone prior to its addition to the containing active hydrogen atoms Compound and the organic polyisocyanate is used. 3, method according to spoke!, Characterized in that the compound having active hydrogen atoms and the organic Polyisocyanate with one another before adding to the diamine mixed and brought to implementation. 839/2182 ORIGINAL INSPECTED It 4. The method according to any one of the preceding claims, characterized in that 5 to 100 parts of pigment are added. 5. The method according to any one of the preceding claims, characterized in that at least 1.3 to 3.0 moles of polyisocyanate per mole of the compound having active hydrogen atoms. 6. The method according to any one of the preceding claims, characterized in that at least 0.5 to 1.2 moles of diamine per Mol free isocyanate groups present are used. 7. The method according to any one of the preceding claims, characterized in that hardening at a temperature of about is carried out until about 150 ° C. 8. Applying a mixture that is created by implementing an active A compound containing hydrogen atoms and having a molecular weight of at least about 500 and not more than about 6,000 those from the class consisting of polyester polyols, polyether polyols, polyether polyester polyols, polyester amides, castor oil, polycarbonate polyols and polydiene polyols and hydrogenated Polydiene polyols are selected with an organic polyisocyanate in which all isocyanate groups are linked to non-benzenoid carbon atoms, as well as with a non-aromatic one primary amine with a sufficient amount of solvent to make the mixture spreadable, the The polyisocyanate and the diamine are selected so that the reaction between them in boiling methylene chloride in 0.2 to 0.5 molar concentration leads to turbidity within 30 seconds, the diamine in an amount less than that of the free Isocyanate equivalent amount used and the DLamin un / das Pre-polymer should be avoided immediately before its application, for Manufacture of malleable polyurethanes with high / resistance to discoloration. 009839/2182 ORIGINAL! K