DE2261482C2 - Process for the production of a polyether urethane elastomer with improved cut growth and better resistance to bending cracks - Google Patents

Description

Many attempts have been made to improve the cut growth and flex crack resistance of To improve polyether urethane elastomers. Examples of this are changes in type or quantity the hardening agent or the increase in molecular weight of the polyether, which is used as the raw material is used. However, no satisfactory products have yet been obtained. For example the cut growth and flex crack resistance of a polyether urethane elastomer up to can be improved to some extent by considering the number average molecular weight of the as Polyether used as the starting material. However, this polyether urethane elastomer cannot can be used for practical purposes because the modulus and tensile strength at break are extremely high are low.

According to GB-PS 1Ö44Ö4Ö, polyurethane elastomers are obtained with improved low-temperature crystallization by using polyoxypropylene glycols a molecular weight between 900 and 4000 with polyoxytetramethylene glycols having a molecular weight between 1800 and 3000 in a ratio of 15 to 50 to 50% by weight. The average molecular weight of these polyether blends is in the range between 1350 and 3500,

Based on investigations, it has now been found that the cut growth and flex crack resistance improve and at the same time a sufficient tensile strength at break and good castability before crosslinking in the case of polyether urethane elastomers can be achieved if one is involved in a process according to the preamble of claim 1 the ίο molecular weights of the polyether mixtures in certain Way.

The invention is based on the object of a process for the production of polyether-urethane elastomers with improved incision growth and ι> improved resistance to bending, while at the same time a there is sufficient tensile strength at break and good castability prior to crosslinking To make available.

This object is achieved by the method according to claim 1.

The invention is explained in more detail with reference to the drawings.

The F i g. 1 shows the relationship between viscosity and number average molecular weight of polyoxytetramethylene glycol. The critical molecular weight of the polyoxytetramethylene glycol is derived from the breakpoint determined as 4500. The abscissa and ordinate are on a logarithmic scale.

The viscosity of the polyether is measured using a capillary rheometer with a constant shear rate and measured at constant temperature.

The weight average molecular weight of the polyether is indicated by the number of the molecular weight distribution curve determines which is measured by gel permeation chromatography (GPC).

F i g. 2 shows the relationship between the GPC number and the number average molecular weight The relationship is established by the osmometric vapor pressure method and measured using the osmometric mem-ίο bran method.

F i g. 3 shows a molecular weight distribution curve according to Example 4 and Comparative Examples 4 and 5.

The term "peak" is intended not only to indicate an obvious maximum peak, but also one Designate shoulder in the molecular weight distribution.

The term polyether of the »DHDM type« used denotes a polyether with a double or polygonal or multi-hilly distribution of the molecular weight,

The critical molecular weight is a specific property of polyethers. This value can be due to the relationship between the viscosity and the number average molecular weight of the polyether be determined.

The critical molecular weight of the polyether can be found from the above relationship.

The polyethers used are those which have at least one terminal functional group which contains active hydrogen which can react with isocyanate groups. The functional group can be a hydroxyl group, a thiol group, an amino group and / or a carboxyl group.
Examples of polyethers which can be used according to the invention are polyoxyethylene glycol, polyoxypropylene glycol and polyoxyethylene glycol.

The polyether mixtures used according to the invention

See can easily be produced by at least one polyether, the peak of which is the molecular weight distribution curve in a higher molecular weight Range as the critical rheological molecular weight (hereinafter referred to as critical molecular weight denotes) of the polyether, with at least one polyether whose peak of the molecular weight distribution curve is in a region of the lower molecular weight than the critical molecular weight of the Polyether lies, is mixed. It extends the weight average molecular weight of the mixture is essentially from 4,500 to 20,000.

A mixture of two or more different types of polyethers can be used whose critical molecular weights are different from each other. An example of this is a Mixture of polyoxypropylene glycol and polyoxytetramethylene glycol. In this case it is essential that at least 1 peak is in the region of lower molecular weight than the lowest critical molecular weight of the polyether and that at least 1 peak is in the region of higher molecular weight than the highest critical molecular weight of the poly others and that the weight average molecular weight of the mixture is between 4,500 to 20,000

It is an essential factor of this invention to use a DHDM type polyether. Otherwise namely, as will be shown in the comparative examples, the objects of the invention are not achieved, if only polyethers are used, they only have a single peak on the molecular weight distribution curve or where all of the peaks of the molecular weight distribution curve are in the region of the molecular weight lower than the critical molecular weight of the polyether. In these cases the cut growth and the elastic crack resistance of the elastomer are not improved

Elastomers obtained by using a polyether in which all peaks in the region of a higher molecular weight than the critical molecular weight of the ο polyether are obtained very low tensile strength at break. Therefore, it can be made into an elastomer with excellent Cut growth and flex crack resistance and tensile strength at break cannot be obtained.

It is another essential factor of this invention that the weight average molecular weight of the polyether or polyethers be within the range Located range from 4500 to 20,000

Satisfactory results cannot be obtained using polyethers whose weight average molecular weight below 4500 or above 20,000 For example, an elastomer made using a polymer having a weight average molecular weight of less than 4500 shows none improved cut growth and flex crack resistance regardless of the molecular weight distribution curve. The one using a polyether with Elastomers made with a weight average molecular weight of 20,000 do not show good ones Tensile strength at break and are difficult to process before crosslinking.

The production of the polyether urethane elastomers according to the invention can be carried out in one or two stages take place.

The isocyanates and the usual chain extenders are used

The invention is illustrated in the examples. The cut growth and flex crack resistance were determined using a De Mattia fatigue tester. In the De Mattia fatigue tester, a 50% constant tensile stress repeated on the test specimen (50 mm 25 mm 1 mm), which has a 2 mm wide cut in its center, applied at 300 cycles per minute until the pattern is broken. The number of cycles is determined

ίο The tensile strength is done using a Instron universal tester, the pulling speed was 50 mm / min. A sample according to D (N 3 used

Examples 1 to 2 and Comparative Examples 1 to 3

The relationship between viscosity and number average molecular weight was measured to find the critical molecular weight of To determine polytetrarethylene glycol. The results are in Fig. 1 shown

The critical molecular weight of polytetramethylene glycol corresponding to that shown in FIG. 1 shown Break point was about 4500.

Polyoxytetramethylene glycol with a number average molecular weight of 9500 and polyoxytetramethylene glycol with a number average molecular weight of 1900 were used in the in Table I specified various weight ratios

jo mixed The molecular weight distribution curve each mixture was made by the GPC method certainly. It was confirmed that all mixtures

DHDM-type polyethers included. A molar equivalent of this mixture was 2 mol

2,4-tolylene diisocyanate reacted for 8 hours at 80 ⁰ C whereby a prepolymer having terminal isocyanate groups was obtained. For the comparative examples, the same procedures were used for polyoxytetramethylene glycol with a number-average mol Applied weight of 9500 and 1900 respectively.

Methylene-bis-ortho-chloroaniline was added to the prepolymer in the equivalent ratio (—NH2 / NCO) of 0.9 mixed in. The mixture was poured into a stick mold and cured at 100 ° C for 4 hours.

A test for cut growth and flex crack resistance was carried out on the obtained test specimen. The results are in Table I along with the results of the measurement of the tensile strength at break and the cast workability.

From the results it can be seen that the elastomer according to Examples 1 and 2 improves the Cut growth and flex crack resistance and a high tensile strength at break and a good one Forgetting processability resulted.

From Comparative Examples 1 and 3 it can be seen that the elastomers, produced with a polyether, which has only one peak of the molecular weight distribution curve in terms of the section growth and the Flex crack resistance were poor.

The comparison? Example 2 shows the result of a Elastomers obtained using a polyoxytetramethylene glycol having two peaks in the molecular weight distribution curve and one ?! lower weight average molecular weight than 4500

(> 5 was obtained. The result shows that the elastomer des Comparative Example 2 ζν, -ar has good cast processability, but not good cutting growth and has no resistance to bending cracks.

Table I. Counting- Mixed üewichls- Cut wax Casting tensile strenght Example no. church section relationship average- tum and processing at break Molecular weight l / ll lichos mole Flex crack barkcit (kg / cm ² ) of the polyether (W / w) gross weight permanentkcil after this (Cycles) (IN THE) Mix 9 500 1 900 75/25 8O0O no easy 180 Example 1 Damage after 200,000 cycles 9 500 I 900 50/50 6 020 4,200 easy 322 Example 2 9 500 - 9,990 2000 difficult 80 Comparison example I. 9 500 I 900 25/75 4030 I 000 easy 390 Comparison example 2 I 900 _ 1 040 350 easy 472 Wrplpirhs-

example 3

Examples 3 to 5 and
Comparative Examples 4 and 5

Following the procedure of Example I. but using a polyoxytetramethylene glycol with a number average Molecular weight of 11,500 and a number average polyoxytetramethylene glycol Molecular weight of 1900 in various mixing ratios were used, the obtained mixtures shown in Table II.

The molecular weight distribution curve of the example 4. of Comparative Examples 4 and 5., measured by the GPC method, are shown in FIG. 3 compiled.

The test samples were prepared by mixing the mixture of polyoxytetramethylene glycol with a paying '.'- average molecular weight of 11,500 and 1900 or any individual polyoxytetramethylene glycol having a number average molecular weight from 11 500 or 1900 with 2,4-tolylene diisocyanate and methylene-bis-ortho-chloranüin reacted and in a rod shape was cast.

Table Il Counting- Uli Mixed (iewichls- Cut wax Pour Tension wedge Example no. _ relationship average- iiim and vera rbcit- at break l / ll Lich MoIc- Hot crack barkcil ikg / enr ι averagecs 1 900 after this l / yklcn) Molecular weight Mix _ 12 400 2,500 extreme 6 (1 Comparison ti) 1 900 difficult example 4 II 500 75/25 9810 no some 170 Example 3 Damage after difficult 11 500 I 900 200,000 cycles I 900 50/50 7 220 no easy 250 Example 4 Damage after 11 500 200,000 cycles 25/75 4 630 4000 easy 380 Example 5 - 2,040 350 easy 475 Comparative II 500 _

example 5

Examples 6 and 7 and
Comparative Examples 6 to 8

Following the procedure of Example I. but using a polyoxytetramethylene glycol with a number average Molecular weight of 9500 and a

Polyoxy tetramethylene glycol with a number average Molecular weights of 850 in various weight ratios have been used the mixtures shown in Table III prepared and Test pattern examined from it.

7th Counting- Mixed 22 61 482 Cut wax 8th tensile strenght y average relationship tum and at break % Table III Molecular weight ! / Il Flex crack Pour (kg / cm ² ) i Example no. of the polyether (Gcw./Ciew.) Weight resistance processed ? average (Cycles) availability (I) (II) liches mole 1 9 500 _ gross weight 2,000 80 i after this 9 500 850 75/25 Mix 25,000 difficult 210 Comparison 9 500 850 50/50 9,990 4,200 350 example 6 9 500 850 25/75 300 easy 457 Example 6 7 730 easy Example 7 850 - 5 460 10 easy 580 Comparative 3,200 example 7 easy Comparative 930 example 8

Comparative example and 10

In Comparative Example 9, a polyoxytetramethylene glycol having a number average 1900 molecular weight and a number average molecular weight polyoxytetramethylene glycol of 850 in a mixing ratio of 50'30. as shown in Table IV.

In Comparative Example 10, a polyoxytetramethylene glycol having a number average Molecular weight of 11,500 and a number average molecular weight polyoxytetramethylene glycol of 7200 with a mixing ratio of 25/75. as shown in Table IV.

Mixing and testing of the mixtures was carried out as in Example 1. The results are shown in the table IV compiled.

Table IV / iihlen- Mixed Gettichtv Schniltwachv- Gicß tensile strenght Example no. average relationship average- turn and impoverishment at break Molecular weight l / ll liches mule- BendcriU- availability (kg / cnr) des l'olyiilhcrs (W / w) k u large w i! hesitation after this I cycles ι (I) IMl Mix I 900 850 50/50 I 490 200 easy 525 Comparison example 9 I I 500 7 200 25/75 8 480 1,500 some 60 Comparative difficult Iicispici iw

In Comparative Example 9, both were peaks of the molecular weight distribution curve of polytetramethylene glycol located in a lower molecular weight range than the critical molecular weight > "and the weight average molecular weight of the mixture was less than 4,500.

In Comparative Example 10, both peaks were Molecular weight distribution curve in the higher molecular weight range than the critical molecule larweight.

In both cases, the cut growth and flex crack resistance properties and the tensile strength at breakage of the elastomer does not improve. en

Example 8

Hexamethylene diisocyanate became a polyoxy tetramethylene glycol with a number average molecular weight of 1900 in the equivalent ratio (-NCO / -OH) of 0.88. It was 16 hours heated to 80 ° C with a prepolymer a molecular weight of 11,500.

Then there were 2.0 molar equivalents of tolylene diisocyanate added to 1.0 molar equivalent of the pre-stretched polyol, using a prepolymer π .it terminal Isocyanate groups received.

On the other hand, 2.0 molar equivalents of tolylene diisoeyanate became to 1.0 molar equivalent of polyoxymethylene glycol with a number average molecular weight from 1900, whereby a prepolymer with terminal isocyanate groups was obtained.

Both prepolymers were mixed in a mixing ratio of 50/50, whereby a mixture was obtained, which had a weight average molecular weight of 7,700. Further processing was carried out as in Example 1 carried out.

The test showed that no defects occurred after stretching for 200,000 cycles. The tensile strength was 280 kg / cm ² .

Example 9

40 parts of the prepolymer according to the example! 8 with a number average molecular weight of

. IW 741 / ITB

11,500 and 60 parts of polyoxytetramethylene glycol with 1900 number average molecular weight became a mixture with weight average molecular weight Blended molecular weight of 8800. )

To the mixture was added 2.0 molar equivalents of 4,4'-diphenylmethun diisocyanate and 8 hours reacted at 60 ° C, whereby a prepolymer with terminal isocyanate groups was obtained.

Methylene-bis-ortho-chloroaniline was added to the mixture of the prepolymer in an equivalent ratio (-NCO / -OH) of 0.9.

The test specimens were prepared by curing the mixture for 3 hours at 100 ° C. The examination of the cut growth and bending cracks was carried out as follows. The results showed that the specimen broke after an elongation load of about 10,000 cycles. The tensile strength at break was 345 kg / cm ² .

Example 10

50 parts of polyoxypropylene glycol with a number average Molecular weight of 9340 and 50 parts of polyoxytetramethylene glycol with a number average Molecular weight of 1900 became a mixture with a weight average Molecular weight of 5900 blended.

To the mixture was added 4,4'-diphenylmethane diisocyanate in an equivalent ratio (-NCO / -OH) optionally from 2.0 and reacted for 8 hours at 80 ⁰ C to give a prepolymer having terminal diisocyanate groups was obtained.

Methylene-bis-orthochloroaniline was added to the prepolymer in an equivalent ratio (- NHj / NCO) of 0.9. The mixture was cast into test samples and cured for 4 hours at ^r IOO C. It was found that the specimen broke after dehydrating 4800 cycles. The tensile strength at break was 350 kg / cm- '.

llicr / u } watts /.c

Claims (3)

Claims; U Process for the production of a polyether urethane elastomer with improved cut growth and better resistance to bending cracks, through Implementation of a mixture of polyethers with terminal hydroxyl, amino, carboxy and / or thiol groups with an aromatic or aliphatic diisocyanate or triisocyanate and treating the product with a polyamine, polyol or their derivatives as a chain extender in the equivalent ratio of active hydrogen to isocyanate groups of 0.7 to 1.2, thereby characterized in that the weight average molecular weight of the used Polyether mixture is between 4,500 and 20,000 and by mixing at least one polyether, at which a peak in the molecular weight distribution curve in the lower, below the critical molecular weight of the polyether Range of molecular weight is, with at least one other polyether in which the Peak of the molecular weight distribution curve in a higher than critical molecular weight of the polyether is within the molecular weight range 2. The method according to claim 1, characterized in that the polyether polyoxyethylene glycol, Polyoxypropylene glycol, polyoxytetramethylene glycol and / or mixtures thereof are used. 3. The method according to claim 1, characterized in that instead of the mixture of polyethylene Mixtures of separately prepared propolymers made of polyethylene and diisocyanates will.