JPS60245621A - Production of polyurethane elastomer - Google Patents

Abstract

PURPOSE:To produce the titled elastomer of excellent mold release, by reaction- injection-molding a mixture comprising a polyisocyanate compound, a specified high-MW polyol, an internal releasing agent and a chain extender. CONSTITUTION:A noncellular or microcellular polyurethane elastomer is obtained by mixing (A) a polyisocyanate compond of an isocyanate index of 90- 120 with (B) a high-MW polyol containing 5-35wt% polymer obtained by polymerizing a polymerizable monomer in a polyol of a MW of 800-3,000 per OH group and having an average hydroxyl value of 2.1-2.8 and a prim. hydroxyl group content >=75%, (C) 0.1-10pts.wt. per 100pts.wt. component B, internal releasing agent comprising a carboxyl group-free polysiloxane compound (e.g., polydimethylsiloxane) of a MW of 30,000-150,000, (D) a chain extender (e.g., ethylene glycol) and (E) a catalyst (e.g., dibuthyltin dilaurate) and reaction-injection-molding the resulting mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a self-releasing polyurethane elastomer by reaction injection molding, in particular using a specific high molecular weight polyol and a polysiloxane compound as an internal mold release agent. The present invention relates to a method for producing a polyurethane elastomer.

A polyurethane elastomer or a polyurethane elastomer is produced by reaction injection molding using at least two components: a polyol component that essentially includes a relatively high molecular weight polyol and a chain extender, and optionally contains a catalyst and a blowing agent, and an incyanate component that essentially includes a polyisocyanate compound. Methods for producing polyurethane elastomers such as polyurethane urea elastomers are known. Representative examples of high molecular weight polyols are relatively high molecular weight polyether polyols. The chain extender is a relatively low molecular weight polyhydric alcohol or polyamine, which is also a type of active hydrogen-containing compound. The use of a catalyst is usually essential and is usually added to the polyol component, but it can also be added to the incyanate component. Using a small amount of a blowing agent such as a halogenated hydrocarbon blowing agent to produce a microcellular polyurethane elastomer is a commonly used means for improving moldability. The density of the microcellular polyurethane elastomer obtained using this small amount of blowing agent is usually 0.8 g/c-J or more, especially about 0.9 g/cn! This is 2. Unless a particularly large amount of reinforcing #& fiber, flake filler, powder filler, or other filler is added, the upper limit is usually less than 1.2 g/cn, especially about 1.15 g/cn.
c+tl or less. The electrical conductivity of non-foamed polyurethane elastomers is also generally within the above range. It is also known to perform reaction injection molding by dividing the active hydrogen-containing compound component into two or more components and using a total of three or more components including the incyanate component.

In the method for producing polyurethane elastomers by reaction injection molding, it is essential to apply a mold release agent to the inner surface of the mold. The reactive mixture, which is a mixture of a polyol component and an isocyanate component, is reacted and cured in a mold, and is removed after being hardened to an extent that it can be removed from the mold. The polyurethane elastomer obtained at this time easily adheres firmly to the surface of the mold and is extremely difficult to release from the mold without a mold release agent. However, the use of a mold release agent applied to the inner surface of a mold (hereinafter referred to as an external mold release agent) is a major obstacle to shortening molding time. In conventional injection molding of synthetic resins with low adhesion, the use of an external mold release agent is unnecessary or necessary, and its life is sufficiently long. That is, a large number of molded articles can be molded by applying the external mold release agent once. However, in reaction injection molding of polyurethane elastomers, the life of the external mold release agent is extremely short, and it is necessary to repeat the application of the external mold release agent frequently. Moreover, the application process of the external mold release agent is usually complicated and takes a long time. It takes. Therefore, the time required to apply the external mold release agent occupies an extremely large proportion of the average molding time per molded product, and unless the time required to apply the external mold release agent is shortened, the molding time cannot be shortened. We are in an extremely difficult situation.

In order to extend the life of the external mold release agent, attempts are known to improve the mold release properties of the polyurethane elastomer itself. A typical method is the use of internal mold release agents. That is, an internal mold release agent is blended into the reactive mixture to reduce the adhesion of the resulting polyurethane elastomer, and even if this eliminates the need to use an external mold release agent, it may shorten its lifespan. It is possible to extend it significantly. For example, Japanese Patent Publication No. 58-8974 describes the use of a specific polysiloxane compound as an external mold release agent and an internal thinning agent;
No. 5-1178 describes an internal mold release agent made of this specific polysiloxane compound. However, the effects of these internal mold release agents are still not sufficient, and they are also inconvenient to handle. For example, the carboxylic acid group-containing polysiloxane compounds described in the above publication tend to deactivate the catalyst necessary for producing polyurethane elastomers, so it is difficult to coexist the two before forming a reactive mixture. It is something that cannot be done. Therefore, a component containing a catalyst and a component containing the internal mold release agent are required, and since neither can be added to the isocyanate component, it is necessary to perform reaction injection molding using at least three components. It is difficult to find a suitable material for reaction injection molding equipment that uses two different raw materials, which are currently widely used.

On the other hand, in addition to the above-mentioned polysiloxane compounds containing carboxylic acids, polysiloxane compounds containing active hydrogen-containing functional groups that can react with isocyanate groups such as hydroxyl groups, amide groups, and mercapto groups have also been investigated as internal mold release agents. ing. One of the reasons why polysiloxane compounds containing these active hydrogen-containing functional groups are being considered as internal mold release agents is that they can be expected to improve paintability. The problem with common internal mold release agents is that they leach from the interior of the molded product to the surface over time, reducing the adhesion of paint to the surface of the molded product. On the other hand, it is thought that polysiloxane compounds containing active hydrogen-containing functional groups react with incyanate groups and become fixed to polyurethane chains, thereby preventing this leaching. In addition, according to the studies of the wood inventors, specific polysiloxane compounds that do not have active hydrogen-containing functional groups, such as those described in item 1, are also effective and may also solve the problem of paintability. Understood.

However, these internal mold release agents have not yet been able to exhibit sufficient mold release properties to a completely satisfactory degree, and it is desired to improve the mold release properties.

The present inventor also investigated the improvement of mold releasability from the viewpoint of high molecular weight active hydrogen-containing compounds. For example, when a polyether polyol is used as a high molecular weight polyol, it has been found that the higher the activity, the better the mold releasability. Furthermore, it has been found that #-shaped property is improved when inert fine particles are dispersed in the polyether polyol. The reason for the latter is thought to be that the contact area between the polyurethane and the mold decreases to the extent that the fine particles come into contact with the inner surface of the mold, improving mold releasability. So-called polymer polyols are known as polyols in which fine particles are dispersed. Polymer polyol refers to a polyol in which a polymer such as a vinyl monomer is dispersed in a polyol, and is usually produced by polymerizing a vinyl monomer or the like in a polyol.

The reactivity of the polymer polyol depends on the reactivity of the polyol used as a paste. Therefore, it is considered that the two requirements in item 1 can be satisfied by using a reactive crystal obtained by using a highly reactive polyol and a polymer polyol. However, on the other hand, when a highly reactive polyol is used, the fluidity of the reactive mixture decreases, resulting in a decrease in so-called filling properties. That is, because the reactivity is too rapid, the viscosity of the reactive mixture increases before it is sufficiently filled into the mold, resulting in a decrease in fluidity, and there is a risk that the reactive mixture will not be sufficiently distributed throughout the mold. As a result, underfilling and filling defects are likely to occur in the molded product. To improve the filling properties of the reactive mixture, it is advisable to use less reactive polyols or to use non-crosslinking polyols, ie diols. However, the former method is 111iy! X!
The latter method also requires too long demolding times (ie, it takes a long time for the elastomer to cure before it can be demolded).

The present inventor conducted various studies to solve these problems, and found that when producing polyurethane elastomers using polysiloxane internal mold release agents, polymer-containing high molecular weight polyols such as polymer polyols or 3, the polymer content in the high molecular weight polyol is about 5 to 35% by weight, the average number of hydroxyl groups per molecule of high molecular weight polyol is 2.1 to 2.8, and at least about 7
It has been found that all of the above problems can be solved by using a material containing 5% of primary hydroxyl groups. In the present invention, the term "polymer-containing high-molecular-weight polyol" refers to a high-molecular-weight polyol containing a polymer obtained by polymerizing a polymerizable monomer such as a vinyl monomer in a high-molecular-weight polyol, and a high-molecular-weight polyol containing such a polymer and other A mixture (i.e., a diluted product) with a high molecular weight polyol.

The present invention relates to a method for producing a polyurethane elastomer with excellent mold release properties, that is, by a reaction injection molding method using a high molecular weight polyol, a chain extender, an inner BB mold release agent, and a polyinyanate compound as main raw materials. In a method for producing a non-foamed or microcellular polyurethane elastomer, the internal and external molding agents are polysiloxane compounds having no carboxylic acid groups, and the high molecular weight polyol has an average molecular weight per hydroxyl group of about 800 to 3000. Contains a high molecular weight polyol containing a polymer obtained by polymerizing a polymerizable polymer in a polyol, the polymer content is about 5 to 35% by weight, the average number of hydroxyl groups is 2.1 to 2.8, and at least about A method for producing a polyurethane elastomer, characterized in that the polyol is a polymer-containing polyol containing 75% of primary hydroxyl groups.

It is.

The polysiloxane compound that is the internal mold release agent in the present invention is a polysiloxane compound that does not substantially contain carboxylic acid groups. This polysiloxane compound may contain active hydrogen-containing functional groups that are reactive with hydroxyl groups, amine groups, imine groups, thiol groups, and other isocyanate groups, and may substantially contain these active hydrogen-containing functional groups. It may also be a polysiloxane-based compound. As mentioned above, it is believed that the polysiloxane compound containing the active hydrogen-containing functional group reacts with the polyisocyanate compound and becomes fixed to the polyurethane chain. Therefore, it is thought that leaching of the polysiloxane compound onto the surface of the molded product is prevented and the paintability is improved. However, considering its performance as a mold release agent, it is considered more effective to have more internal mold release agent on the surface in contact with the mold than inside the mold during molding, and the migration of the internal mold release agent to the surface is suppressed. I don't like it. on the other hand.

Polysiloxane compounds that do not have active hydrogen-containing functional groups tend to leach onto the surface of molded products and tend to reduce the paintability of molded products. However, from the standpoint of mold releasability, this leaching is considered to be effective. As a result of studying these problems, the present inventors have found that polysiloxane-based compounds that do not substantially contain active hydrogen-containing functional groups and have a high molecular weight are particularly excellent as internal mold release agents in the present invention. . That is, it has been found that even polysiloxane compounds having substantially no active hydrogen-containing functional groups within a certain specific molecular weight range do not significantly reduce paintability.

Its molecular weight ranges from about 30,000 to 150,000. Moreover, this compound has an excellent long-lasting mold release effect, and it is possible to produce molded products without problems with adhesion or discoloration during painting.In the present invention, active hydrogen that can react with this incyanate group Molecular weight approximately 30,000 to 1, substantially containing no functional groups
Particular preference is given to using polysiloxane compounds of 50,000 as internal mold release agents.

The polysiloxane compound which is the internal mold release agent in the present invention is +Si+Rh-0+l (R: a lower alkyl group having 1 to 4 carbon atoms or an aryl group such as a phenyl group, however, the two R's may be different.n: In particular, a compound having a main chain of polydimethylsiloxane in which both R's are methyl groups is most preferable.
-/ Ri-shaped knee (-5i (R) (X) -0+ (X:
The main chain is usually linear. may partially have short chain or relatively long chain branches. Further, at the end of the main chain, there is usually a group represented by -Si+R), but some of these three H's may be X. Examples of X include a group having a polyoxyalkylene button whose terminal end is capped with an alkyl group, alkenyl group, aryl group, or other organic group having no active hydrogen-containing functional group (eg, alkyl etherified). Further, examples of the organic group having an active hydrogen-containing functional group include a group having a polyoxyalkylene chain having a hydroxyl group or an amino group at its terminal, a hydroxyalkyl group, an aminoalkyl group, and the like.

As mentioned above, preferred polysiloxane compounds are those which do not have a siloxy group containing the above-mentioned X or have a siloxy group containing an X but do not have an active hydrogen-containing functional group. Particularly preferred are compounds whose main chain consists of a polydimethylsiloxy group. The most common and widely used polysiloxane compounds are (H*)3siO+S+ (CH3)2-0)-9i
It is polydimethylsiloxane represented by (C[3)3, and this polydimethylsiloxane is also preferred as the preferred polysiloxane compound in the present invention.

The preferred molecular weight of the polysiloxane compound in the present invention needs to be about 30,000 to 150,000. Paintability tends to decrease as the molecular weight of the polysiloxane compound decreases. Therefore, the more preferable lower limit of molecular weight is about 50,000. On the other hand, as the molecular weight increases, the viscosity increases rapidly, and polysiloxane compounds with too high viscosity are difficult to handle, and the preferable molecular weight t limit is about 120,000.

The amount of the polysiloxane compound in the present invention is not particularly limited, but is suitably about 0.1 to 10 parts by weight, particularly about 0.5 to 10 parts by weight, based on 100 parts by weight of the polymer-containing polyol. 5 parts by weight is preferred. Preferred polysiloxane compounds in the present invention do not contain active hydrogen-containing functional groups that can react with incyanate groups as described above. Therefore, there is no problem even if this polysiloxane compound is mixed in advance with a compound having an isocyanate group such as a polyisocyanate compound. However, it is usually preferable to use it by blending it in advance with a component containing a polymer-containing polyol, which will be described later. Of course, depending on the method for producing the polyurethane elastomer, it can also be blended into both the polyisocyanate compound and the polymer-containing polyol.

The polymer-containing polyol in the present invention means a high molecular weight polyol containing a polymer obtained by polymerizing a polymerizable child in a high molecular weight polyol, or a mixture thereof with a high molecular weight polyol. Among them, the high molecular weight polyol that serves as a pace for polymerizing the polymerizable monomer is hereinafter referred to as a "paste polyol", and the high molecular weight polyol that is added after the latter is hereinafter referred to as a "dilution polyol". Coalescence-containing polyols are known, and the polymer-containing polyols used in the present invention refer to those known that have particularly high reactivity as described below. The pace polyol may be a substantially saturated polyol or a polyol having an unsaturated group that can be copolymerized with a polymerizable monomer. Types of base polyols 9. As for types of polymerizable monomers, polymerization methods, etc., known ones can basically be employed, and for example, the following publications are known as known examples.

Special Publication No. 39-24737 Publication No. 53-1784
No. 0 Special Publication Showa 41-34'? Publication No. 3 Special Publication No. 1973-
4400 Publication, Special Publication No. 4a-22108, Publication No. 4758, Special Publication, Publication No. 4408, Publication No. 4B-20508, Publication No. 4400.
Special Publication No. 54-14159 Publication No. 47-47999
Publication No. 57-5835 Special Publication No. 51-37
Publication No. 228 Special Publication Showa 5? -E1471 Publication Special Publication Showa 5
Publication No. 1-40914 Publication of Japanese Patent Publication No. 57-24385 Publication of Publication No. 34311 of 1987 Publication of Japanese Patent Publication No. 59-5608
In the present invention, the polymer-containing polyol must be a highly reactive polyol with a high proportion of primary hydroxyl groups. The primary hydroxyl groups of the polymer-containing polyol are linked to the primary hydroxyl groups of the base polyol and to the diluent polyol, if used, and to the primary hydroxyl groups of the base polyol. That is, for example, if no diluent polyol is used,
The proportion of primary hydroxyl groups in the base polyol and the proportion of primary hydroxyl groups in the resulting polymer-containing polyol are almost the same. When a dilute polyol is used, the average proportion of primary hydroxyl groups between it and the base polyol and the proportion of primary hydroxyl groups in the polymer-containing polyol will be almost the same. Therefore, a polymer-containing polyol with a high proportion of primary hydroxyl groups can be obtained by using a base polyol with a high proportion of primary hydroxyl groups, or a diluted polyol with a high proportion of primary hydroxyl groups. The proportion of primary hydroxyl groups is required to be at least about 75%,
In particular, when the proportion of primary hydroxyl groups in the polymer-containing polyol is low, which is preferably at least about 85%, the resulting polyurethane elastomer tends to have insufficient self-release properties.

The average number of hydroxyl groups in the polymer-containing high molecular weight polyol is approximately 2.
1 to 2.8, the average number of hydroxyl groups in the base polyol, and if a diluted polyol is used, the average number of hydroxyl groups in the combination of the base polyol and diluted polyol must be approximately 2.1 to 2.8. is necessary. Therefore, in any case, the high molecular weight polyol must be a combination of a diol and a trivalent or higher valent polyol. For example, a triol is added as a diluent polyol to a polymer-containing polyol obtained using a diol as a base polyol, a diol is added to a polymer-containing polyol obtained using a triol as a base polyol, A polymer-containing polyol containing a diol and a polyol having a valence of 3 or more and having an average number of hydroxyl groups of about 2.1 to 2.8, such as a polymer-containing polyol obtained using a mixture of a diol and a triol as a base polyol. used. Of course, diols, triols, or mixtures thereof can be added as diluent polyols to polymer-containing polyols obtained using base polyols with an average hydroxyl value of less than about 2.1 or between about 2. Polymer-containing polyols with an average hydroxyl group content of about 2.1 to 2.8 can also be obtained by combining various polyols, such as by adding various similar diluent polyols to polymer-containing polyols obtained using base polyols with an average hydroxyl group content of greater than .8. is obtained. As described above, the combination of diol and trivalent or higher-L polyol in the polymer-containing polyol is not particularly limited as long as the average number of hydroxyl groups is about 2.1 to 2.8. In the present invention, the average number of hydroxyl groups is more preferably about 2.1 to 2.6, particularly about 2.3 to 2.
It is 5. As the trivalent or higher polyol, a combination of triol and tetrol, or a trivalent or higher polyol having an average number of hydroxyl groups of about 4.5 or less is preferred, and triol is particularly preferred.

-.- As the polyol, polyether polyols and modified products thereof are preferred. The most preferred substantially saturated polyol is a polyether polyol. This polyether polyol has 2 carbon atoms as a polyvalent initiator.
Polyether polyols obtained by adding ethylene oxide and propylene oxide are preferred, and polyether polyols obtained by adding ethylene oxide and propylene oxide are particularly preferred. The addition of ethylene oxide produces a primary hydroxyl group,
A secondary hydroxyl group is generated by adding another alkylene oxide such as propylene oxide. Therefore, in order for the polyether polyol to have a high proportion of primary hydroxyl groups, the oxyalkylene group at the end of the polyether chain must have a high proportion of oxyethylene groups. However, if the proportion of oxyethylene groups in the oxyalkylene groups of the entire polyether polyol is too high, problems such as decreased water resistance and excessive flexibility of the resulting polyurethane elastomer arise. Therefore, the oxyethylene group content of the entire polyether polyol is preferably about 40% by weight or less, particularly about 30% by weight or less. On the other hand, if one oxyethylene group exists at the end of a polyether chain, a primary hydroxyl group will be generated.Theoretically, if an equivalent amount of ethylene oxide is added to a polyether polyol having a secondary hydroxyl group, a primary hydroxyl group will be formed. The ratio is thought to be 10 oz, but in reality, due to the probability of addition of ethylene oxide and the fact that primary lactic acid groups easily react with ethylene oxide, polyamides with a sufficiently high ratio of primary hydroxyl groups are added by adding an equivalent amount of ethylene oxide. Ether polyols are not obtained. It is therefore preferred that the proportion of oxyethylene groups in the terminal portion of the polyether polyol is at least about 15% by weight, especially at least about 20% by weight. Although oxyethylene groups may also exist inside the polyether chain, it is preferable that the upper limit of the oxyethylene group content in the entire polyether polyol is limited to the above ratio. Particularly preferred polyether polyols are polyols that are substantially free of internal oxyethylene groups.

The polyether polyols as pace polyols may also be unsaturated polyether polyols having unsaturated groups. For example, there are polyether polyols obtained using unsaturated monoepoxides such as allyl glycidyl ether with alkylene oxides. Moreover, an unsaturated group-containing modified polyether polyol modified for introducing unsaturated groups can also be used as the base polyol. For example, unsaturated poly(or mono)
There are unsaturated polyether ester polyols modified with carboxylic acids or their anhydrides, and urethane-modified unsaturated polyether polyols in which unsaturated poly(or mono)alcohols are bonded to polyether polyols via polyisocyanate compounds. Moreover, a polyether polyol having a radical-generating group can also be used as the base polyol. These polymer-containing polyols whose base polyol is a modified polyether polyol having an unsaturated group are known, and are described, for example, in the cited known examples. Base polyols are these (modified)
The base polyol is not limited to polyether polyols, and known polyols such as polyester polyols and unsaturated polyester polyols can be used.

As the diluted polyol, a substantially saturated polyether polyol is preferred. However, other polyols such as polyester polyols can also be used. When a diluted polyol is used as described above, it is sufficient that the primary hydroxyl group in the polymer-containing polyol to which the diluted polyol is added is within the above range. Therefore, the proportion of primary hydroxyl groups in the diluted polyol does not necessarily need to be about 75% or more. For example, if the amount added is small, it may be less than about 75%. Similarly, in this case, as long as the proportion of primary hydroxyl groups in the diluted polyol is high, the proportion of primary hydroxyl groups in the base polyol does not necessarily need to be about 75% or more.

The average molecular weight of the base polyol is 800 to 800 per hydroxyl group.
It needs to be 3000. The use of polyols outside this range results in polyurethane elastomers with good physical properties.
difficult to manufacture. The average molecular weight per hydroxyl group is more preferably about 1000 to 2500, particularly about 1500 to 250.
It is 0. The diluted polyol also has an average molecular weight of 8 per hydroxyl group.
00-3000, preferably about 1000-2500, especially about 1500-2500. However, as in the case of the primary hydroxyl group, the molecular weight of the diluent polyol is evaluated based on the average value with respect to the base polyol, so as long as the amount used is small, the molecular weight is not necessarily limited to the above range.

As the polymerizable monomer to be polymerized in the pace polyol, compounds containing a polymerizable unsaturated group such as those described in the above-mentioned known examples can be used. Especially the vinyl thousand
is appropriate. Examples of polymerizable materials include acrylonitrile, 2,4-dicyanobutene-1, styrene,
(meth)acrylic liquor ester, (meth)acrylic amide I
-, alkyl vinyl ether, butadiene, isoprene, etc. Especially acrylonitrile.

It is preferable to use 2.4-dicyanobutene-1, styrene, and alkyl (meth)acrylate alone or in combination, or in combination with other monomers mainly containing these. It is preferable that these polymerizable monomers are polymerized in the base polyol in the presence of an Appis compound, a peroxide, or other polymerization initiator. The resulting polymer is usually dispersed in the form of fine particles in the pace polyol and has high dispersion stability. Therefore, it can be diluted with a diluent polyol, and there is almost no decrease in dispersion stability. There is no particular upper limit to the content of the polymer in the base polyol. That is, the content can be reduced by dilution. However, if the content is too high, it is difficult to manufacture due to reasons such as decreased dispersion stability, and the content is usually about 50% by weight or less, particularly about 10% by weight or less. The polymer content of the polymer-containing polyol in the present invention is required to be about 5.-35% by weight; a more preferred polymer content is about IC' to 30% by weight.

The chain extender consists of a low molecular weight polyol and/or a polyamine compound having a molecular weight of 400 or less. Especially molecular weight 20
Low molecular weight polyols of 0 or less are preferred. Suitable low molecular weight polyols include polyhydric alcohols and alkanolamines having 2 or more, especially 2 to 4, hydroxyl groups, and polyols obtained by adding a small amount of alkylene oxide to the above-mentioned polyvalent initiators. Particularly preferred low molecular weight polyols are dihydric alcohols having 2 to 4 carbon atoms. Polyamines include alkylene substituents and/or
Alternatively, aromatic diamines with halokenes are suitable.

Preferred specific chain extenders include ethylene glycol,
1.4-'tanediol, propylene glycol, diethylene gelcol, dipropylene glycol, glycerin, trimethylolpropane, jetanolamine, triethanolamine, and the like. Preferred are dihydric alcohols, especially ethylene glycol and 1,4-butane.

All is preferred. Preferred examples of the aromatic diamine include ethyltoluanediamine, monochloroparaphenylenediamine, and tetramethylmethylenedianiline. The amount used is preferably 5 to 40% by weight, particularly 10 to 30% by weight, based on the total amount with the polymer-containing polyol.

The polyisocyanate compound includes aromatic, alicyclic, aliphatic, and other polyisocyanate compounds having at least two incyanate groups, and modified products thereof. For example, 2. i-) lylene diisocyanate, 2.6-) lylene diisocyanate, 4.4'-diphenylmethane diisocyanate, polymethylene polyphenyl inocyanate, xylylene diisocyanate, inphorone diisocyanate, methylene bis(cyclohexyl isocyanate), hexamethylene isocyanates, etc. Examples of modified products include dimers, dimers, and prepolymer-type modified products.

There are carbodiimide modified products, urea modified products, and others. Two or more of these polyisocyanate compounds may be used in combination. Particularly preferred polyisocyanate compounds are 4
．． 4'-diphenylmethane diisocyanate, and its carbodiimide-modified products and prepolymer-type modified products. The amount of polyisocyanate compound used is f30 to 120, especially 85 to 1, expressed as incyanate index.
10 is appropriate.

In the production of polyurethane elastomers using the reaction injection molding method, it is usually 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, a blowing agent is not necessarily essential, and even without using a blowing agent, a slightly foamed elast can be obtained due to the presence of air and water dissolved in the raw materials, and by sufficiently removing these, non-foaming can be obtained. An elastomer of the form is obtained.

However, it is preferable to use a small amount of blowing agent for reasons such as improving moldability. As the blowing agent, air, water, etc. may be used, but halokene hydrocarbons having a low point are preferably used. Specifically, trichlorofluoromethane, dichlorofluoromethane, 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 polymer-containing polyol and chain extender.

Furthermore, various additives may be added as optional additive components. Examples include reinforcing fibers, fillers, colorants, ultraviolet absorbers, antioxidants, flame retardants, and internal mold release agents other than polysiloxane compounds. In particular, blending reinforcing fibers or flake reinforcing agents not only improves the strength but also reduces the rate of dimensional change after water absorption. This seems to be to improve the rigidity and strength of the polyurethane elastomer. Suitable reinforcing fibers include milled fibers of glass A fibers, cut fibers, and wollastonite. Moreover, mica glass flakes or the like can be used as the flake-like reinforcing agent. The amount thereof is approximately 20% by weight or less based on the entire polyurethane elastomer to have a sufficient effect. These additives, including the catalysts and blowing agents mentioned above, are usually added to the polyol component, which includes the polymer-containing polyol and chain extender. However, additives which are inert towards incyanate groups can also be added to the incyanate component.

In the reaction injection molding method, the polyol component and incyanate component are usually rapidly mixed to form a reactive mixture, which is immediately injected into a mold, the reactive mixture is allowed to react in the mold, and after curing is taken out as a molded product. It is done by

In some cases, a polyol component or an incyanate component may be added.
Three or more components may be used by dividing them into the above components or by using a third 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.

An external mold release agent is usually applied to the inside surface of the mold.

By using an internal mold release agent and an external mold release agent in the present invention, the mold release property is further improved, and the life of the external mold release agent is greatly extended. Various types of external mold release agents can be used, including wax-based external mold release agents, silicone-based external mold release agents, and fluorine compound external mold release agents.

The present invention is used for molding exterior parts of automobiles, especially bumper shells. However, it is not limited to this use, and can be used for other automobile parts, molded products for housing,
It can also be applied to other uses.

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

Examples and Comparative Examples The internal # of the present invention was installed in the polyol component side tank of a high-pressure foaming machine.
A mixture of a polymer-containing polyol containing an L-type agent, a chain extender, etc. was charged, and a polyincyanate compound was charged into an incyanate component side tank.The discharge pressure of the high-pressure foaming machine was set at 150 kg/crn', and the discharge i was 80~ 120
Reaction injection molding was carried out by adjusting the liquid temperature of each component to 3° to 40°C. The size of the mold is 140m+g
Molding was carried out using an iron mold for molding the outer shell of an automobile bumper, measuring 120 mm x 1600 mm and having an inner thickness of 3.5 cm, and adjusting the mold temperature to 70°C. Furthermore, during molding, a wax-based external mold release agent was first applied to the mold, and then the number of times molding could be performed without application was measured. In addition, the paintability of the molded product was tested using the following method. These results and physical properties are shown in Table 3.

84 parts by weight Chain extender: ethylene glycol 16 parts by weight Agent: (Dub: I-33LV O, 4tt) (Dibutyltin dilaurate 0.08//) Foaming agent: Freon 11 5/
/ Internal mold release agent [listed in Table 2] [Description] Incyanate component carbodiimide-modified diphenylmethane diisocyanate (Neo content 28%) [Amount used is the amount that makes the index 105] External mold release agent [Limurikei 13-263DJ Chukyo Yushi Polyoxypropylene oxyethylene similar to the polymer-containing polyol obtained by polymerizing acrylonitrile using a substantially saturated polyoxypropylene oxyethylene polyol having oxyethylene groups only at the end portion as a base polyol. Combination with diluted polyol consisting of polyol. The types of polyols are shown in Table 1, and the combination ratios are shown in Table 3.

Polydimethylsiloxane compounds A-B (listed in Table 2) substantially free of or having active hydrogen-containing functional groups capable of reacting with the internal mold release agent isocyane-1. group.

Table 1 Table 2 Physical property test Mold release property: Maximum number of molds that can be removed from the mold without any additional application of external moldability without mold staining, skin peeling, cracking, etc. Flowability: Minimum packing density The density of the molded product at the minimum filling amount required for filling.゛The lower the density, the better the flowability.

Paintability test painting: 1.1. After steam cleaning the molded product with dichloroethane, it was painted as follows: 1. Undercoat; polyurethane primer 100'C, baked for 30 minutes, coating thickness 20pL2, topcoat;
Polyurethane top coat baked at 120°C for 40 minutes,
Paint film thickness 35-average value: Paint film adhesion test/JIS 00202 Substrate test type 1

Claims (1)

[Claims] 1. A method for producing a non-foamed or microcellular polyurethane elastomer by a reaction injection molding method using a high molecular weight polyol, a chain extender, an internal mold release agent, and a polyisocyanate compound as main raw materials, A polymer obtained by polymerizing a polymerizable monomer in a polyol in which the internal mold release agent is a polysiloxane compound having substantially no carboxylic acid groups, and the high molecular weight polyol has an average molecular weight per hydroxyl group of about 800 to 3000. containing a high molecular weight polyol with a polymer content of about 5-35% by weight,
average hydroxyl number from 2.1 to 2.8, and at least about 75
% of a primary hydroxyl group. 2. The method according to claim 1, wherein the polysiloxane compound is substantially free of active hydrogen-containing functional groups and has a molecular weight of about 30,000 to 150,000. 3. The method of claim 1, wherein the high molecular weight polyol is a polyether polyol containing at least 85% of primary hydroxyl groups.