JPS59187019A - Manufacture of polyurethane elastomer - Google Patents

Abstract

PURPOSE:To obtain titled elastomer having moderate water resistance, also with improved moldability, by the use of a high-molecular weight polyol consisting mainly of polyoxyalkylenediol with reduced unsaturated group-contg. mono-ol content. CONSTITUTION:The objective elastomer can be obtained by carrying out a reactive injection molding using (A) a high-molecular weight polyol consisting of (i) 51-100wt% of a polyoxyalkylenediol with a hydroxyl value 15-60, average unsaturated group-contg. mono-ol (hereafter referring as mono-ol) content <=0.08meg/g, etc., and (ii) 0-49wt% of a tri- or more hydric polyoxyalkylene polyol (POAP), (B) a polyol component consisting essentially of chain extender, and (C) a polyisocyanate. The component (A) has the following characteristics; (1) average oxyethylene group content... <21wt%, >=5wt% of which being at the oxyalkylene group terminal. (2) POAP with a mono-ol content <=0.07meg/g, etc.... >=80wt%.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a polyurethane elastomer by a reaction injection molding method, and particularly to a method for producing a polyurethane elastomer using raw materials with excellent moldability.

It is known to produce polyurethane didistomers such as microcellular didistomers or non-foamed elastomers by reaction injection molding using high molecular weight polyols, chain extenders, and organic polyisocyanates as main raw materials. The production of polyurethane-based nidistomers by reaction injection molding is currently being used for molded products in automobile-related fields, including the outer shell of automobile bumpers.

It is also being considered for use in automobile fenders, door panels, front panels, and other exterior panels. The exterior parts of these automobiles, including the outer shell of the bumper, are required to have greater water resistance than interior parts. However, the polyurethane-based nidistomer conventionally used for bumper outer shells has a problem of poor water resistance.

As a result of studying methods for improving the water resistance of polyurethane elastomers in a method for producing polyurethane elastomers using a reaction injection molding method, the present inventors have determined that they can reduce the content of oxyethylene groups in high molecular weight polyols and improve the water resistance of polyurethane elastomers. He discovered that the objective could be achieved by reducing the amount of the unsaturated group-containing monol component, and filed a patent application (Japanese Patent Application No. 57-22
5784). The purpose of this invention was to improve the water resistance of polyurethane elastomers, but subsequent studies revealed that the moldability was not sufficient, except for shortening demolding time. Moldability includes shortening of demolding time, filling properties into molds, surface properties, etc. Improving water resistance and moldability are important improvement goals, but in some cases it is often necessary to improve moldability even at the expense of some water resistance. In particular, in applications other than the above-mentioned automotive exterior members, a certain degree of water resistance is required, but at the same time, excellent moldability is often required.

One factor in improving moldability is the reactivity of raw materials, especially high molecular weight polyols. In order for the reactivity of the high molecular weight polyol to provide sufficient filling properties into the mold, it is necessary that the increase in viscosity at the initial stage of the reaction be small and allow a long flow time, and at the same time, the viscosity of the raw material polyol itself must be low. is preferred. On the other hand, as the number of hydroxyl groups (number of functional groups) in a polymeric polyol increases from 2 to 2, the initial viscosity increases rapidly, and the molecular weight at the same equivalent (molecular needle per hydroxyl group) becomes 2 or more.

That is, the viscosity becomes high. Therefore, as high molecular weight polyols, divalent polyols having 4 moles and polyoxyalkylene diols are most preferable.

However, the use of polyols with a low number of hydroxyl groups has the problem that demolding time becomes long. This is because crosslinking does not occur with divalent polyols, so it takes a relatively long time for the polyol to have a high molecular weight and harden to the extent that it can be demolded.

Of course, the demolding time is also related to the reactivity of the polyol, and the more reactive the polyol, the shorter the demolding time. In order to improve the reactivity of polyoxyalkylene polyols, it is necessary to increase the amount of oxyethylene groups at the terminal end to increase the content of primary hydroxyl groups, but when water resistance is taken into account, the cause of the decrease in water resistance is polyoxyethylene. Hydrophilic oxyethylene group (7) in oxyalkylene polyol Since VC is closely related, there is a limit to shortening demolding time across the entire reactivity of polyoxyfluquinone polyol.

As a result of studying a method for producing a polyurethane elastomer with improved moldability using a polyoxyalkylene polyol containing polyoxyalkylene diol as the main component while ensuring a certain degree of water resistance, the inventor found that polyoxyalkylene polyol In particular, we have found that demolding time can be shortened by reducing the content of unsaturated group-containing monool in polyoxyalkylene diol, which is the main component. There are two effects by reducing the content of the unsaturated group-containing monol. One is that the reactivity can be ensured while reducing the oxyethine group content of the polyoxoalkynone polyol, and the other is that the curability of the reactive mixture is increased. All of these methods are effective in shortening demolding time. The latter (is a force that is thought to inhibit curing by lowering the average functional number of the reaction system by the unsaturated group-containing monool).The fact that this is small means that the curing reaction between the polyoxyalkylene polyol and the incyanate group progresses more easily. It is thought that it will happen.

The present invention relates to a method for producing a polyurethane elastomer by reaction injection molding using a polyoxyalkynone polyol containing the above-mentioned polyoxyalkylene diol as a main component, that is, a high molecular weight polyol and a chain extender are essential components. Reaction injection molding (reaction injection molding to produce non-foamed or microcellular polyurethane elastomer molded products using at least two components: a polyol component and a polyincyanate component having a polyincyanate compound as an essential component. In a method for producing a polyurethane elastomer by a reaction injection molding method, a polyoxyalkylene polyol containing substantially the entire amount of a polymeric polyol or at least 80% polyoxyalkylene diol as a main component, the polyoxyalkylene The polyol consists of a polyoxyalkylene diol of 51 to 100% by weight and a polyoxyalkylene polyol having a valence of 6 or more and a weight range of 0 to 49%, with an average number of hydroxyl groups of 2.0 to 249, and an average hydroxyl value of 15 to 60.Average oxy A polyoxyalkylene having an ethylene group content of less than 21 meq/kg and at least 5 weight groups of the ethylene group being present at the terminal portion of the oxyalkylene group, and an average unsaturated group-containing monool component content of 0.07 meq/? a polyol, the polyoxyalkylene diol has an average hydroxyl value of 15 to 10, an average oxyethylene group content of less than 21%, and at least 8% by weight of the polyoxyalkylene diol is present at the terminal portion of the oxyalkylene group; This is a method for producing a polyurethane elastomer, characterized in that it is prepared using a polyoxyalkylene diol having an average unsaturated group-containing monool component content 'K of 0.08 rneq/f' or less.

The reason for the presence of unsaturated group-rich monool components in polyoxyalkynone polyols is thought to be due to side reactions in the production of oxypropylene groups by propylene-oxygen, yodo-addition in the presence of catalysts such as caustic alkali. is considered to be as follows.

Therefore, in polyoxyalkylene polyol, 0H2
It contains =OH-OH20H or an unsaturated group-containing monool component (hereinafter simply referred to as monool) produced by adding alkylene oxide to the hydroxyl group. This monool has a relatively low molecular weight and is present in polyoxyalkylene polyol in a small amount in terms of equivalent weight, but in a relatively large amount in terms of molar amount. It is believed that ethylene oxide has a high tendency to react selectively to monool during addition. Therefore, it seems that much of the oxyethylene group was allocated to the hamonol, which was conventionally necessary to increase the proportion of primary hydroxyl groups, and was not sufficiently allocated to the polyoxyalkynone polyol. Therefore, the high proportion of primary hydroxyl groups in conventional polyoxyalkylene polyols takes into account the primary hydroxyl groups of this monol, and the proportion of primary hydroxyl groups in polyoxyalkylene polyols excluding monools is actually It is estimated that the ratio was lower than its apparent appearance. Therefore, it is considered that if the amount of monool is reduced, the reaction activity equivalent to that of conventional polyoxyalkylene polyols can be maintained even if the proportion of the 1st m water group in the polyoxyalkylene polyol is lower than that of conventional polyoxyalkylene polyols.

In addition, when considering the molding time, i.e., the time until demolding becomes possible, the molding time is theoretically in a parallel relationship with the time required to reach the stage once the molecular weight of polyurethane has increased beyond a certain level. It is believed that there is. However, as mentioned above, the hydroxyl groups of monools have a high proportion of primary hydroxyl groups, and because the proportion of primary hydroxyl groups of polyokine alkylene polyols is relatively low in practice, the monools react with low molecular weight. Due to its high activity, it can be assumed that the reaction between the hydroxyl group and isocyanate group of the monool precedes the reaction between the hydroxyl group and incyanate group of conventional polyoxyalkylene polyols. On the other hand, in the reaction between a monool and a polyisocyanate compound, polymerization does not proceed, so in the case of conventional polyoxyalkynone polyols containing a large number of monools, their reactivity is apparently sufficiently high to increase the reaction rate. It is believed that a higher proportion of primary hydroxyl groups was considered necessary. Therefore, if the monool content is reduced, the reaction between the polyoxyalkylene polyol and the polyisocyanate compound will proceed more quickly, increasing the molecular weight.
It is thought that even if the proportion of class hydroxyl groups is low, it is possible to achieve a molding time equal to or longer than that of the conventional method.

In addition, the small amount of monool allows the polyurethane elastomer to achieve a higher molecular weight within the molding time, and if after-cure is required, it can be completed in a shorter time. can. Moreover, the physical properties of the resulting polyurethane elastomer are much better than those obtained using a polyoxyalkylene polyol containing a large amount of monool.

Therefore, a feature of the present invention is that in order to improve the moldability such as the filling property of a reactive mixture containing a high molecular weight polyol, the main component of the polyoxyalkylene polyol is a polyoxyalkylene diol having a relatively low viscosity. In order to shorten the demolding time, which is a problem when using polyoxyalkylene diols, the content of unsaturated group-containing monool components is reduced to accelerate the increase in molecular weight during reaction, and the oxyethylene group of all polyoxyalkylene polyols is reduced. The content is 21-? The problem of demolding time was solved by combining these two factors by increasing the oxyethylene group content at the end of the oxyalkylene chain as much as possible while ensuring water resistance by setting the Z value to be less than Z.

In the present invention, the high molecular weight polyol consists essentially of a polyoxyalkynone polyol whose main component is at least 80% by weight polyoxyalkylene diol. This polyoxyalkynone polyol is composed of 51 to 100% by weight of polyoxyalkylene diol and 0 to 49% by weight of polyoxyalkylene polyol having a valence of 3 or more, especially the former 65 to 98% by weight.
I'm curious about the weight of 35 weight. The average number of hydroxyl groups is 2.0-2
．． 49, especially 2.1 to 2.4. The average hydroxyl value is preferably 15 to 60, particularly about 20 to 40.

The oxyethylene group content is less than 21 parts by weight and at least 5 parts by weight are at the end of the oxyalkylene chain. In particular, in terms of ensuring reactivity, the average oxyethylene group content is more than 14% by weight, more preferably less than 21% by weight on a 15% weight plate, and most of it is present at the terminal portion of the oxyalkylene chain. It is appropriate to do so. That is, in fields where water resistance is not so required, the oxyethylene group content may exceed 14 weight by weight, and particularly may exceed 15 weight by weight. It is preferred that substantially all of the oxyethylene groups be present at the terminal portions of the oxyalkylene chains in order to ensure reactivity. When ethylene glycol or polyoxyethylene glycol is used as an initiator, if this part is considered as an oxyethylene group, it will be located in the center of the oxyalkylene chain, but even if the oxyethylene group in this initiator is taken into account. Even so, the total oxyethylene group content must be less than 21 by weight. Further, "substantially all of the oxyethylene groups are located at the ends of the oxyalkylene chain" means that all of the oxyethylene groups except for the oxyethylene groups of this initiator portion are located at the ends of the oxyalkylene chain.

The average unsaturated group-containing monool component content of the polyoxyalkynone polyol is preferably 0.07 meq/V or less, particularly preferably 0.065 mθq/liter or less.

The polyoxyalkylene diol, which is the main component of the above polyoxyalkylene polyol, has an average hydroxyl value of 15 to 60.
, an average oxyethynyl group content of less than 21 meq/f, at least 8 of which are present at the terminal portion of the oxyalkylene chain, and an average unsaturated group-containing monool component content of 0.08 meq/f or less. It is an oxyalkylene diol. Particularly preferred hydroxyl value is 20-4
It is 0. In order to ensure reactivity, the particularly preferred average oxyethylene group content is preferably more than 12% by weight, more preferably 15% by weight. In the same sense as above, at least 8%, preferably most, of the oxyethylene groups are present in the terminal portions of the oxyalkylene chains, and in particular, substantially all of the oxyethylene groups are present in the terminal portions of the oxyalkylene chains. Preferably, it exists in Unsaturated group-containing monool component content fi 0
．． 065 meq/? The following is preferable, especially 0.0
．． 6 meq/? It is preferable to keep it below. This polyoxyalkylene diol may be a mixture of two or more types, in which case these values are the average values.

As the trivalent or higher polyoxyalkylene polyol that can be used in combination with the polyoxyalkylene diol, the mixture with the polyoxyalkylene diol has the average number of hydroxyl groups, average hydroxyl value, average oxyethylene group content, and Various polyoxyalkylene polyols having a valence of 3 or more may be used within the range of the average unsaturated group-containing monool content. The preferred number of hydroxyl groups is 3 to 8, especially 3 to 6, and the preferred average hydroxyl value is 15 to 120, especially 20 to 60. The preferred range of oxyethylene group content is 5 to 35% by weight, especially 5 to 25% by weight. It is preferred that the oxyethylene groups are predominantly, in particular substantially all, located at the terminal portions of the oxyalkylene chains. In some cases, especially when the amount thereof is small, the terminal portion of the oxyalkylene chain may not contain substantially any oxyethylene group, but may contain only oxypropylene groups. It's okay. The content of the unsaturated group-containing monool component varies depending on the oxyethylene group-containing part, and the upper limit is not limited to 0.10 mfllq.
/ f or less, particularly preferably 0.085 or less. In the present invention, two or more polyoxyalkylene polyols having a valence of 3 or more may be used. The average number of hydroxyl groups, etc. is preferably within the above range.

In the present invention, polyoxyalkylene diol is dihydric alcohol, dihydric phenol, dihydric alkanol i
Polyoxyalkylene diol obtained by adding an alkylene oxide to a divalent amine, divalent amine, or other divalent initiator. Similarly, a polyoxyalkylene polyol having a valence of 3 or more can be obtained by adding an alkylene oxide to an initiator having a valence of 6 or more. Preferred dihydric initiators are dihydric alcohols and dihydric phenols, and particularly preferred are dihydric initiators. As the initiator having a valence of 3 or more, polyhydric alcohols having a valence of 3 or more are particularly suitable. Two or more of these initiators can be used in combination, and in particular, by adding alkylene oxide to a mixture of a divalent initiator and a hexavalent or higher initiator, polyoxyalkylene diol and trivalent polyoxyalkylene Mixtures with polyols can be prepared. Examples of initiators include, but are not limited to, the following compounds.

Bivalent initiators: proviV glycol, sifurobylene glycol, to! /Flopylene gelicol and other polypropylene gelylcols, ethylene glycol,
Diethylene glycol, triethylene glycol and other polyethylene glycols, 1,4-butanediol, 1.2-7"tanediol, 1゜6-hexane diol, cyclohexene-1,4-diol, etc. dihydric alcohols, bisphenol A1 bisphenol s1 bis(hydroxyphenyl)methane, and other dihydric phenols.

Trivalent or higher initiator: glycerin, trimethylolpropane, pentaerythritol, diglycerin, sorbitol, sucrose, other polyhydric alcohols, resol, novolac, other polyhydric phenols, triethanolamine, jetanolamine, other alkanols Amines, ethylenediamine and other polyamines.

The alkylene oxide added to the initiator is preferably ethylene oxide and propylene oxide, or a combination of ethylene oxide, propylene oxide, and butylene oxide. Depending on the case,
Small amounts of other epoxides, such as rogen-containing alkylene oxides and styrene oxides, may be used together with these. Particularly preferred alkylene oxides consist essentially of only two types: ethylene oxide and propylene oxide. The most preferred polyoxyalkylene diol is polyoxypropylene oxyethylene diol, which is produced by adding propylene oxide and ethylene oxide in this order to a divalent initiator. Similarly 3
As the polyoxyalkylene polyol having a value higher than 3
The most preferred is a polyoxypropylene oxyethylene polyol produced by adding propylene oxide and ethylene oxide in this order to an initiator having a higher valence or higher. However, in some cases, especially in the case of trivalent or higher polyoxyalkylene polyols, small amounts of oxyethylene groups may be introduced randomly or in blocks at the non-terminal portions of the oxyalkylene chains. Further, as described above, a small amount of polyoxyalkylene polyol in which an alkylene oxide other than ethylene oxide is added to the trivalent or higher initiator can be used. Furthermore, as described above, a mixed initiator such as polyoxypropylene/oxyethylene polyol obtained by adding propylene oxytoethylene oxide to a mixture of a divalent initiator and a trivalent or higher valent initiator in this order is used. It can also be used to produce various polyoxyalkylene polyols.

The production of a polyoxyalkylene polyol with a small amount of unsaturation-containing monool components in the present invention involves the selection of catalyst components in the production of ordinary polyoxyalkylene polyols,
This can be carried out by changing the reaction conditions, removing the monol component, or by other methods. For example, JP-A-54-30110, JP-A-54-44720, JP-A-56-38322, JP-A-56-4
No. 3322, U.S. Patent No. 3,427,256,
U.S. Patent No. 3,427,334, M.A.I., U.S. Patent No. 34
No. 27335, US Pat. No. 3,393,243 and the like describe methods for producing polyoxyalkylene polyols containing a small amount of unsaturated group-containing monool components.

Particularly useful is the selection of catalyst components and the production of polyoxyalkylene polyols under milder reaction conditions than conventional ones. Measurement of unsaturated group-containing monool components J Engineering SK 1
557 (1970) '6' of "total unsaturation degree -" described in "Polyether test method for polyurethane"
4] This is done by the j-determination. In the present invention, the unsaturated group-containing monool component content is used in the same meaning as the total unsaturation. In addition, in general, in polyoxypropylene/oxyethylene diol of the same molecular weight, the higher the oxypropylene group content (i.e.,
As the number of oxyethylene group-containing eggplants decreases, the content of unsaturated group-containing monool components increases. .07 meq
/ f, 0.10 meq 7' with about 20 weights? ,
Approximately 1010 and 0.12 meq/? That's about it.

In the present invention, the high molecular weight polyol may consist essentially only of the above-mentioned polyoxyalkylene polyol, but it may also contain other high molecular weight polyols of up to 20*%. Examples of other high molecular weight polyols include high molecular weight polyols other than the above-mentioned polyoxyalkylene polyols, such as fd' polyester polyols, polyester ether polyols, and polyoxytetramethylene polyols produced by methods other than alkylene oxide addition reactions. Examples include ether polyols and hydroxyl group-containing hydrocarbon polymers such as hydroxyl group-containing polybutadiene. In particular, it is effective to use a hydrocarbon-based polymer containing a hydroxyl group, which is a hydrophobic polyol, in order to reduce the dimensional change rate of a polyurethane-based elastomer upon water absorption. Suitable examples of the hydroxyl group-containing hydrocarbon polymer include a butadiene homopolymer having hydroxyl groups at both ends, and a butadiene copolymer consisting of a copolymer of butadiene with acrylonitrile, styrene, or other vinyl mono-7-. Furthermore, a high molecular weight polyol obtained by adding a small amount of alkylene oxide to this hydroxyl group-containing hydrocarbon polymer may also be used.

The chain extender consists of a low molecular weight polyol and/or polyamine compound having a molecular weight of #400 or less. Especially molecular weight 20
Low molecular weight polyols of 0 or less are preferred. Low molecular weight polyols include polyhydric alcohols and divalent to trivalent alkanolamines having 2 or more hydroxyl groups, especially 2 to 4 hydroxyl groups, and polyols obtained by adding a small amount of alkylene oxide to the above-mentioned polyvalent initiators. Appropriate. Particularly preferred low molecular weight polyols are dihydric alcohols having 2 to 4 carbon atoms, and trivalent low molecular weight polyols such as these and trialkanolamines. Suitable polyamines are aromatic diamines having alkyl substituents and/or nitrogen. Preferred specific chain extenders include ethylene glycol, 1.4-butanediol, fluoropylene gellicol, di-engineered FV glycol, cyclopyrene glycol, glycerin, trimethylolpropane, jetanolamine, triethanolamine, triisoglobulin. Banolamine, etc., and combinations of ethylene glycol and 1,4-butanediol, or their combination with triethanolamine are particularly clever. The amount used is 5 to 40% of the combined amount with high molecular weight polyol.
A weight ratio of 1θ to 30 is appropriate.

It has been found that the use of a chain extender containing an oxyethylene group such as ethylene glycol as a chain extender does not have any adverse effect on the water absorption dimensional change of polyurethane-based nidistomers. reacts with the polyurethane elastomer to form a hard block of polyurethane elastomer, and this hard block has low water absorption even if oxyethylene groups are present, and even if it absorbs water, it is hard and causes deformation. It is thought that this will not happen.

On the other hand, the oxyethylene group present at the end of the molecular chain of high molecular weight polyol is thought to exist adjacent to this hard block, but if it is within the hard block, it is different, and the oxyethylene group in this part belonging to the soft block It is thought that the presence of groups has a large influence on the change in water absorption dimensions.

The polyisocyanate compounds include aromatic, alicyclic, aliphatic, and other polyisocyanate compounds having at least two incyanate groups, and modified products thereof. For example, 2.4-) lylene diisocyanate, 2.6-tolylene isocyanate, 4.4'-diphenylmethane diisocyanate, polymethylene polyphenylisocyanate, xylylene diisocyanate, isophorone diisocyanate, methylene-bis(cyclohexyl isocyanate), hexamethylene Diisocyanates, etc. Examples of modified products include dimers, trimers, prepolymer-type modified products, carbodiimide modified products, urea modified products, and others. These polyisocyanate compounds are 2
More than one species may be used in combination. Particularly preferred polyincyanate compounds are 4,4'-diphenylmethane diisocyanate and its carbodiimide-modified and grebolymer-type modified products. Use of polyisocyanate compounds fit
90-12o expressed in l isocyanate index
1, especially 95 to 11Q are suitable.

In the production of polyurethane elastomers using the reaction injection molding method, it is essential to use a catalyst in addition to the above-mentioned main raw materials, and it is also preferable to use a blowing agent. Catalysts include various tertiary amine catalysts and organometallic compounds such as organotin compounds, and both may be used alone or in combination. In the present invention, the blowing agent is not necessarily essential.
Even without using a foaming agent, a slightly foamed elastomer can be obtained due to the presence of air and water dissolved in the raw materials, and by sufficiently removing these, a non-foamed elastomer can be obtained.

However, it is preferable to use a small amount of blowing agent for reasons such as improving moldability. Air, water, etc. can be used as the blowing agent, but halogenated hydrocarbons with a low boiling point are preferably used.

Specifically, trichlorofluoromethane, dichlorodifluoromethane, methylene chloride, etc. are suitable. The amount thereof is preferably 15 parts by weight or less, particularly 2 to 10 parts by weight, based on 100 parts by weight of the high molecular weight polyol and chain extender.

Furthermore, various additives may be added as optional additive components. Examples include reinforcing fibers, fillers, colorants, ultraviolet absorbers, antioxidants, retardants, and internal mold release agents. In particular, blending reinforcing fibers has the effect of lowering the water absorption dimensional change rate.

This seems to be to improve the rigidity and strength of the polyurethane elastomer. Suitable reinforcing fibers include milled glass fibers, cut fibers, and wollastonite. The amount thereof is about 30 wt-t'% or less based on the entire polyurethane elastomer, particularly about 20 layers or less to have a sufficient effect. These additives, including the catalysts and blowing agents mentioned above, are usually added to the polyol component, which includes a low molecular weight polyol and a chain extender.

However, additives which are inert toward inocyanate groups can also be added to the isocyanate component.

The reaction injection molding method is usually carried out by rapidly mixing the polyol component and the incyanate component, immediately injecting the mixture into a mold, allowing the mixture to react in the mold, and taking out the molded product after curing. In some cases, three or more components may be used by dividing the polyol component or isocyanate component into two or more, or by using a sixth component. Rapid mixing is usually achieved by impingement mixing of each component, and an after-mixing mechanism may be provided in a portion of the runner to perform remixing. In the present invention, it is considered that the practical upper limit of demolding time is about 120 seconds or less as measured by the method of the Examples. Preferably 1
It is considered that 00 seconds or less is required.

The density of the polyurethane elastomer is suitably 0.9 to 1152/3 if it does not contain reinforcing fibers or fillers. The present invention is used for molding exterior parts of automobiles, especially bumper shells. However, the present invention is not limited to this use, and can also be applied to automobile exterior parts and other uses that require a certain degree of water resistance.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to these Examples.

Examples 1 to 6, Comparative Examples 1 to 4 A mixture of high molecular weight polyols, chain extenders, etc. listed in Table 1 below was charged into a tank on the polyol component side of a high-pressure foaming machine.
On the other hand, a polyisocyanate compound was charged into the isocyanate component side tank.

High-pressure foaming machine
) discharge pressure to 150/crn2, discharge-density 60~
Reaction injection molding was carried out by adjusting the liquid flow rate of each component to 120 kg/min and 30 to 40 c. The size of the mold is 140 x 120
A mold for molding the outer shell of an automobile bumper with an inner thickness of 1,400 mm and an inner thickness of 3 mm was used, and the mold temperature was adjusted to 60 to 70° C. for molding. A sample for measuring physical properties was cut out from the obtained molded product, and the physical properties listed in Table 3 including the water absorption dimensional change rate were measured. The demolding time and physical properties described in Table 3 were measured by the following methods.

Demolding time: The time from the completion of injection until the mold can be demolded (the molded product can be demolded without cracking, etc.).

Density: method by water or alcohol displacement.

(ASTM-D792) Water absorption dimensional change rate: Molded product sample (100X200X3
+mm) at 100°C for 3 hr The length in the long side direction is t.

If this is immersed in warm water at 40° C. for 240 hr and the length is t, then the water absorption dimensional change rate ΔL is given by the following equation.

△ L = −X 1 0 0 t.

Flexural modulus: Based on ASTM-D790 method.

Tensile strength: Based on J-tech 8-630 dumbbell No. 2.

Elongation: By 6301 dumbbell No. 2 on J Engineering S-.

Minimum filling density: Density at the minimum filling amount required to fill the mold by 100%.

The raw materials used were as follows.

③ Polyoxyalkynon polyol The following polyols A to H are polyoxypropylene/oxyethylene polyols having an oxyethylene group at the end obtained by adding propynon oxide to an initiator and then adding ethylene oxide, and the hydroxyl group The number, oxyethylene group content, unsaturated monol content, and hydroxyl value are as shown in Table 1 below.

Table 1 Polyol A 2 15 Weight 4 0.058
mθ now 29tt B 2 20 //
0.045 tt 28tt O213t
t 0.040 // 28tt D
2 20 tt O,090tt 29tt
E 2 25 tt 0.076 //
26tt F 2 3On O,034
tt 38n G 3 20 // 0
．． 082 // 28// H320tt
O,025tt 56 The mixed polyoxyalkylene polyol used in Examples and Comparative Examples is a mixture of the above polyols, and its composition ratio (weight) and average number of hydroxyl groups, etc., are shown in Table 2 below.

(2) Chain extender ga, /'rEA: A mixture of ethyl glycol and triethanolamine at a weight ratio of 15/1.However, in Comparative Example 4, only ethylene glycol (EG) was used.

■, Polyincyanate compound [Use 1. is the amount at which the isocyanate index is 105] Polyisocyanate A dicarbodiimide-modified diphenylmethane diisocyanate (NCo content 285%) Polyisocyanate B: prepolymer type modified diphenylmethane diisocyanate (NCo content 260%) ■, Other raw material catalyst A nitriethylene diamine solution ( Product name: DAPCO 33LV) Catalyst B Nidibutyltin dilaurate R-11:) Lichlorofluoromethane M F B : Milled glass fiber with an average length of about 015ffi+++/ Example 7 Bumper using the high pressure foaming machine of Examples 1 to 6 7 Asia was molded. The molding conditions are as follows.7 Raw materials: Same mold as in Example 6: 1600L, steel fascia mold, cavity volume 4.6 t, average thickness 5.6 knots Molding conditions: Liquid part 40°C , mold temperature 70℃, discharge pressure 150℃
K17cm2, discharge speed 12oK9/min, mold clamping time 40
As a result of molding under the above conditions, a molded product with a good appearance and no defects such as blisters and sink marks was obtained with a weight of 4.3 K9~
5. It was obtained within the range of I Kp and had sufficient green strength. In addition, the physical properties of the obtained molded product are as follows: average density to4r/α3, bending elastic modulus 2250
K9/crtt2, water absorption dimensional change rate was 0.75.

161-

Claims (1)

[Scope of Claims] 1. A polyol component board containing a high molecular weight polyol and a chain extender as essential components and at least two polyisocyanate components containing a polyisocyanate compound as an essential component are used to form a non-foamed product by reaction injection molding. In a method for producing a polyurethane diystomer by a reaction injection molding method for producing molded articles of a polyurethane diystomer in the form of polyurethane or microcellular polyurethanes, substantially the entire amount or at least 80% by weight of the high molecular weight polyol is mainly composed of polyoxyalkylene diol. The polyoxyalkylene polyol is composed of 51 to 100% by weight of polyoxyalkylene diol and 0 to 49% by weight of trivalent or higher polyoxyalkylene polyol.
The average number of hydroxyl groups is 2.0 to 2.49, the average hydroxyl value is 15 to 60, and the average oxyethylene group content is 21% by weight.
and at least 5% by weight thereof is present in the terminal portion of the oxyalkylene group, and the average unsaturated group-containing monool component content ft 0.0? A polyoxyalkylene polyol having a meq/y or less, the polyoxyalkylene diol has an average hydroxyl value of 15 to 60, an average oxyethylene group content of less than 21, and at least 8 hydroxyl groups of 71-oxyalkylene groups. 1. A method for producing a polyurethane elastomer, characterized in that the polyoxyalkylene diol is present at the terminal end of the polyoxyalkylene diol and has an average unsaturated group-containing child nol content of 0.08 meq/r or less. 2. The method according to claim 1, characterized in that the amount of oxyethylene fund M in the polyoxyalkylene diol exceeds 12% by weight, and most of it is present at the terminal portion of the oxyalkylene chain. 3. The method according to claim 1, wherein the content of the unsaturated group-containing monool component of the polyoxyalkylene diol is 0.070 meq/f or less. 4. The method according to claim 1, wherein the average oxyethylene group content of the polyoxyalkylene polyol is 15% by weight or more, and most of the oxyethylene group content is present at the terminal portion of the oxyalkylene chain. 5. The method according to claim 1, wherein the average unsaturated group-containing monool component content of the polyoxyalkylene polyol is 0,065 meq/r or less. 6. The method according to claim 1, wherein the polyoxyalkylene polyol consists of 65 to 98% by weight of polyoxyalkylene diol and 2 to 35% by weight of polyoxypropylene/oxyethylene triol.