JPS6322215B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a self-releasing polyurethane elastomer by reaction injection molding, etc., and particularly relates to the use of a specific nonionic surfactant as an internal mold release agent. The present invention relates to a method for producing a characteristic polyurethane elastomer. At least two components: an active hydrogen-containing compound component that essentially includes a high-molecular-weight active hydrogen-containing compound such as a relatively high-molecular-weight polyol, a chain extender, and optionally a catalyst and a blowing agent, and an isocyanate component that essentially includes a polyisocyanate compound. A method for producing polyurethane elastomers such as polyurethane elastomers and polyurethane urea elastomers by reaction injection molding is known. A typical example of a high molecular weight active hydrogen-containing compound is the above-mentioned relatively high molecular weight polyol, which will be described below as a high molecular weight polyol unless otherwise specified. 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, but it can also be added to the isocyanate component.
Using a small amount of a halogenated hydrocarbon blowing agent or the like to produce a microcellular polyurethane elastomer is a commonly used means for improving moldability. Furthermore, it is also known to divide the active hydrogen-containing compound component into two or more components and perform reaction injection molding using three or more components in total, including the isocyanate component. In the method for producing polyurethane elastomers by component 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 cured in a mold, cured to an extent that can withstand demolding, and then demolded. 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 the injection molding of ordinary synthetic resins with low adhesion, the use of an external mold release agent is not necessary, or even if it is necessary, its life is sufficiently long, that is, a single application of an external mold release agent is sufficient. A large number of molded products can be formed by using the same method. However, in component 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 for applying the external mold release agent occupies an extremely large proportion of the average molding time per molded product, and unless the time required for applying the external mold release agent is shortened, the molding time cannot be shortened. is 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. In other words, an internal mold release agent is blended into the reactive mixture to reduce the adhesion of the resulting polyurethane elastomer. It becomes possible to significantly extend the lifespan. For example, Japanese Patent Publication No. 58-8974 describes an example in which a specific organosilicon compound is used both as an external mold release agent and as an internal mold release agent.
Further, specific internal mold release agents are described in Japanese Patent Publication No. 55-1176 and Japanese Patent Publication No. 51-12898. 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 organosilicon compounds described in the first two of the three publications mentioned above tend to deactivate the catalyst necessary for the production of polyurethane elastomers, so they cannot be used at a stage before they are made into a reactive mixture. The two cannot coexist. 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. This is difficult to apply to reaction injection molding equipment that uses two-component raw materials, which are currently widely used. The present inventors have studied internal mold release agents that can be applied to the production of polyurethane elastomers by reaction injection molding. The internal mold release agent does not simply have to be non-stick itself. For example, the internal mold release agent needs to have a high affinity with the components containing it, otherwise it will be easily separated from other components and it will be difficult to obtain a polyurethane elastomer with a uniform composition. In addition, compatibility with the polyurethane elastomer is also necessary; for example, low molecular weight compounds that are not chemically bonded to the polyurethane elastomer may leach onto the surface of the polyurethane elastomer and reduce its paintability. be. That is, if a large amount of the non-adhesive internal mold release agent leaches onto the surface of the polyurethane elastomer, the paint will easily peel off in the case of a painted polyurethane elastomer. The present inventor conducted various research studies on effective internal mold release agents in the production of polyurethane elastomers by reaction injection molding, etc., and as a result, discovered that certain nonionic surfactants are particularly effective. This nonionic surfactant is a monoepoxide adduct of amines having long-chain aliphatic hydrocarbon groups, mainly ethylene oxide.
Compounds with an HLB value of approximately 18 or less. The present invention relates to a method for producing a polyurethane elastomer characterized by using this specific nonionic surfactant as an internal mold release agent, that is, a polyurethane elastomer containing a high molecular weight active hydrogen-containing compound and a chain extender. In a method for producing a non-foamed or microcellular polyurethane elastomer by curing a reactive mixture of an active hydrogen-containing compound and a polyisocyanate compound in a mold, long-chain aliphatic carbonization is added to the reactive mixture. It is a monoepoxide adduct mainly containing ethylene oxide of amines or alkanolamines having hydrogen groups.
A method for producing a polyurethane elastomer with excellent internal mold releasability, characterized by blending a nonionic surfactant with an HLB value of about 18 or less. In the nonionic surfactant that is the internal mold release agent in the present invention, the starting materials are aliphatic monoamine,
aliphatic polyamine, aliphatic alkanolamine,
Consists of etc. They have at least one long-chain aliphatic hydrocarbon group, preferably only one long-chain aliphatic hydrocarbon group. These starting materials require a hydrogen atom or at least one hydroxyalkyl group bonded to at least one nitrogen atom to which the monoepoxide can be attached.
Preferred amines are aliphatic mono- or diamines represented by R ¹ (R ² )NH (R ¹ : long-chain aliphatic hydrocarbon group, R ² : hydrogen atom, lower aminoalkyl group, or lower alkyl group); R ¹ (R ³ )NR-
OH (R ³ : lower alkyl group, or hydroxyalkyl group that is the same as or different from -R ⁴ -OH, R ⁴ :
It is an aliphatic alkanolamine represented by a lower alkylene group), and an aliphatic monoamine represented by R ¹ -NH ₂ is particularly preferred. The long chain aliphatic hydrocarbon group is preferably a saturated or unsaturated long chain aliphatic hydrocarbon group having 8 to 30 carbon atoms, preferably 12 to 24 carbon atoms, particularly preferably 14 to 20 carbon atoms. The lower alkyl group represented by R ² and R ³ above has 1 to 6 carbon atoms,
The number of carbon atoms in the lower alkylene group represented by R ⁴ is 2
~6 is appropriate. The monoepoxide added to the above-mentioned amines is mainly composed of ethylene oxide, and it is particularly preferable that the monoepoxide is substantially composed only of ethylene oxide. Other epoxides include alkylene oxides such as propylene oxide, halogen-containing alkylene oxides such as epichlorohydrin, and styrene oxide. These monoepoxides other than ethylene oxide may be used in small amounts relative to ethylene oxide, and in that case, they can be added in a mixture with other than ethylene oxide, or they can be added sequentially with ethylene oxide. The amount of ethylene oxide added is related to the HLB value described below; for example, taking the aliphatic monoamine represented by R ¹ -NH ₂ above as an example, if R ¹ remains unchanged, the HLB value increases as the amount of ethylene oxide added increases. Also, if the amount of ethylene oxide added is the same,
Generally, the HLB value decreases as the number of R ¹ carbons increases. Therefore, the amount of ethylene oxide added is determined by the HLB value of the compound obtained. In addition,
When using other epoxides in combination, especially alkylene oxides other than ethylene oxide, the HLB value generally decreases as the proportion increases. For example, in the monoepoxide adduct of the present invention obtained by adding only ethylene oxide, that is, the nonionic surfactant, the hydrogen atom of the hydroxyl group of the hydroxyalkyl group bonded to the nitrogen atom is -(C ₂ H ₄ O) It is a compound substituted with n-H, for example, in the case of R ¹ -NH ₂ , R ¹ -[(C ₂ H ₄ O)k-H] [(C ₂ H ₄ O) l-
HLB of the nonionic surfactant in the present invention, which is a compound represented by [H] (n, k, l: integers, but the average value is not necessarily an integer)
The value should be about 18 or less. The HLB value of nonionic surfactants is a well-known concept that indicates the balance between lipophilicity and hydrophilicity of the surfactant. A small HLB value indicates high lipophilicity, and a large HLB value indicates high hydrophilicity. When lipophilicity and hydrophilicity are almost balanced, the HLB value is approximately in the range of 12 to 14. When a nonionic surfactant has only long-chain alkyl groups and polyoxyethylene groups, the HLB value is said to be proportional to (number of added moles of oxyethylene groups)/number of carbon atoms in long-chain alkyl groups). . However, in the case of other lipophilic or hydrophilic groups, the value expressed by this formula and the HLB value are not necessarily in a proportional relationship, and even in the case of the nonionic surfactant containing nitrogen atoms in the present invention, The same is true. However, in the present invention as well, the HLB value and the value expressed by the above formula are in a largely proportional relationship. The HLB value of the nonionic surfactant in the present invention is about 18 or less, preferably about 17 or less, and the lower limit is preferably about 6. HLB of the nonionic surfactant in the present invention
The amount of compounding is not particularly limited, but it is 0.1 parts by weight per 100 parts by weight of the high molecular weight active hydrogen-containing compound.
~10 parts by weight is suitable, particularly preferably 0.5 to 5 parts by weight. As is clear from its structure, the nonionic surfactant in the present invention has at least one active hydrogen, particularly at least one hydroxyl group. Therefore, it is reactive with isocyanate groups,
It is difficult to use it by mixing it with a polyisocyanate compound in advance. Therefore, it is preferable to use this nonionic surfactant in combination with an active hydrogen-containing compound. High molecular weight polyols are suitable as active hydrogen-containing compounds. In reaction injection molding, it can also be directly blended into the active hydrogen-containing compound-containing component described below. The most preferred method for producing the polyurethane elastomer of the present invention is reaction injection molding, but it is not limited thereto. Other one-shot methods,
It can be applied to methods for producing polyurethane elastomers using prepolymer methods, quasi-prepolymer methods, etc. However, the problem of mold releasability is a problem specific to molding methods that use molds, and is not related to manufacturing methods that do not use molds. Further, the present invention does not include application to a method of molding a pre-produced polyurethane elastomer by injection molding or the like. This is because the above-mentioned nonionic surfactant reacts with isocyanate groups and is chemically bonded to the polyurethane elastomer, which is thought to be important in preventing it from leaching to the surface. In this respect, it is considered that blending into a pre-manufactured polyurethane elastomer that does not contain isocyanate groups is not effective. Therefore, the present invention requires the presence of the nonionic surfactant in a reactive mixture in which free isocyanate groups are present in reaction injection molding or other processes. Further, the use of an internal mold release agent in the present invention does not obviate the need for the combined use of an external mold release agent. It is necessary to use an external mold release agent, and good mold release properties are not achieved using molds that are not coated with an external mold release agent. Various types of external mold release agents can be used, such as wax-based external mold release agents, silicone-based external mold release agents, and fluorine compound external mold release agents. In the present invention, the reactive mixture is a mixture of at least two components, an active hydrogen-containing compound and a polyisocyanate compound, and usually further contains a catalyst. Furthermore, it is usually a mixture containing all raw materials for the polyurethane elastomer, including a blowing agent. In reaction injection molding, two components are used: a component usually called system liquid, which is a mixture of an active hydrogen-containing compound and all raw material components other than the polyisocyanate compound, and a component containing the polyisocyanate compound.
It is a mixture of components, and is a reactive mixture that is mixed and injected by a mixing and injection device called a high-pressure foamer. In the reactive mixture, some or all of the components that are non-reactive with isocyanate groups, such as reinforcing fibers and powder fillers, may be used in combination with the isocyanate compound.
Further, it may be used as part or all of a polyisocyanate compound obtained by reacting a part of a high molecular weight polyol with a polyisocyanate compound in advance. It is also possible to perform reaction injection molding using two or more active hydrogen-containing compound components or polyisocyanate compound-containing components, and using a total of three or more components. In the present invention, the high molecular weight active hydrogen-containing compound is preferably a high molecular weight polyol, particularly a polyoxyalkylene polyol, but is not limited thereto. For example, it is known to produce a polyurethane elastomer by reaction injection molding using an aminated polyether in which some or all of the hydroxyl groups of a high molecular weight polyoxyalkylene polyol are replaced with amine groups.
In the present invention, similar aminated polyethers can be used as part or all of the high molecular weight active hydrogen-containing compound. This aminated polyol preferably has a molecular weight in the same range as the high molecular weight polyol described below, and the amination rate is the number of total amino groups / in the case of using it as a monogroup or in combination with a high molecular weight polyol. Expressed as (total number of amino groups + total number of hydroxyl groups), approximately (80% or less is suitable.) In the present invention, high molecular weight polyol is defined as an average molecular weight per hydroxyl group of approximately 800 to 4000, particularly approximately 1000 to 4000.
2500, a high molecular weight polyol consisting of one type or a mixture of two or more types having an average number of hydroxyl groups per molecule of 1.8 to 6.0, particularly about 2.0 to 3.5, is suitable. The high molecular weight polyol is particularly preferably a polyoxyalkylene polyol or a high molecular weight polyol mixture containing it as a main component. Other than polyoxyalkylene polyols, there are hydroxyl hydrocarbon polymers such as polybutadiene glycol, polyester polyols, polyether ester polyols, polycarbonate polyols, etc. These can be used alone, but they can also be used in combination with polyoxyalkylene polyols. preferable. When a polyoxyalkylene polyol and another high molecular weight polyol are used in combination, it is preferred that the polyoxyalkylene polyol accounts for at least 60% by weight, particularly at least 80% by weight of the mixture of both. As the other high molecular weight polyol used in combination, butadiene homopolymers and copolymers having at least two hydroxyl groups are particularly preferred. Suitable examples of the polyoxyalkylene polyol include polyoxyalkylene polyols selected by adding a large number of epoxides such as alkylene oxides to a polyvalent initiator, and ring-opening polymers of cyclic ethers having four or more membered rings such as tetrahydrofuran. Suitable polyvalent initiators include polyhydric alcohols, polyphenols, alkanolamines, mono- and polyamines, and polyhydric alcohols are particularly preferred. As an epoxide,
Alkylene oxides having 2 to 4 carbon atoms are most preferred, but also halogen-containing alkylene oxides, styrene oxides, glycidyl ethers,
Other epoxides can be used in combination. The most preferred polyoxyalkylene polyol is
It is a polyoxyalkylene polyol obtained by adding propylene oxide or butylene oxide, particularly preferably propylene oxide and ethylene oxide, to a polyvalent initiator. Ethylene oxide is preferably reacted in the last step of the addition reaction in order to cause an oxyethylene group to be present at the end of the oxyalkylene chain of the polyoxyalkylene polyol. In some cases,
Ethylene oxide and other alkylene oxides may be mixed or reacted sequentially to form an oxyethylene group at the non-terminal portion of the oxyalkylene chain. Preferably, the proportion of oxyethylene groups present at the terminal parts of the oxyalkylene chains is at least 5% by weight. More preferably about 8
% by weight or more. Further, the upper limit of the proportion of all oxyethylene groups is preferably 35% by weight or less. In particular, since terminal oxyethylene groups are necessary to ensure reactivity, it is preferable that substantially all of the oxyethylene groups in the polyoxyalkylene polyol are present at the terminal portions of the oxyalkylene chains. A more preferable average hydroxyl group of the polyoxyalkylene polyol is about 2.1 to 3.0. This polyoxyalkylene polyol consists of a polyoxyalkylene triol or a mixture of a polyoxyalkylene diol and a trivalent or lower polyoxyalkylene polyol. The mixture of polyoxyalkylene polyols may be obtained by mixing separately produced polyoxyalkylene polyols, or by adding an alkylenoxide or the like to a mixture of two or more types of polyvalent initiators and reacting them. Examples of polyvalent initiators include, but are not limited to, the following compounds. Polyhydric alcohols: polyethylene glycols such as ethylene glycol, propylene glycol, 1,4-butanediol, diethylene glycol, polypropylene glycols such as dipropylene glycol, glycerin, trimethylolpropane, hexanetriol, pentaerythritol, diglycerin, dextrose,
α-Methylglyloside, sorbitol, sucrose. Polyhydric phenol; bisphenol A, bisphenol S, catechol, phenol formaldehyde initial condensate. alkanolamine; monoethanolamine;
diethanolamine, triethanolamine,
Diisopanolamine, N-methyldiethanolamine. Mono- or polyamine; ethylenediamine,
Diethylenetriamine, diaminodiphenylmethane, aniline. The chain extender consists of a low molecular weight polyol and/or polyamine compound with a molecular weight of 400 or less. In particular, low molecular weight polyols having a molecular weight of 200 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 alkylenoxide to the above-mentioned polyvalent initiators. Particularly preferred low molecular weight polyols are dihydric alcohols having 2 to 4 carbon atoms. Suitable polyamines are aromatic diamines having alkylene substituents and/or halogens. Preferred specific chain extenders are ethylene glycol, 1,4-butanediol, propylene glycol, diethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, diethanolamine, triethanolamine, etc., especially ethylene glycol and 1,4-butanediol. 4-butanediol is preferred. As the aromatic diamine, for example, diethyltoluene diamine, monochloroparaphenylene diamine, tetramethylmethylene dianiline, etc. are preferable. The amount used is 5% based on the total amount of high molecular weight polyol.
~40% by weight, especially 10-30% by weight are suitable. The polyisocyanate compound includes aromatic, alicyclic, aliphatic, and other polyisocyanate compounds having at least two isocyanate groups, and modified products thereof. For example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, polymethylene polyphenyl isocyanate,
xylylene diisocyanate, isophorone diisocyanate, methylene bis(cyclohexyl isocyanate, hexamethylene isocyanate,
and so on. Examples of modified products include dimers, trimers, prepolymer modified products, 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 and prepolymer-type modified products. The appropriate amount of the polyisocyanate compound to be used is 90 to 120, particularly 95 to 110, expressed as an isocyanate index. 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; even without using a blowing 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. An elastomer is 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 halogen hydrocarbons with a low boiling point are preferably used. Specifically, trichlorofluoromethane, dichlorofluoromethane, methylene chloride, etc. are suitable. The amount is 15 parts by weight or less, especially 2 to 10 parts by weight, based on 100 parts by weight of the high molecular weight polyol and chain extender.
Parts by weight are appropriate. 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. In particular, blending reinforcing fibers or flexible reinforcing agents 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 glass fibers such as milled 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 containing the high molecular weight polyol and chain extender. However, additives which are inert towards isocyanate groups can also be added to the isocyanate component. The reaction injection molding method usually involves rapidly mixing the above polyol component and isocyanate component to form a reactive mixture, which is immediately injected into a mold, allowing the reactive mixture to react in the mold, and taking it out as a molded product after curing. It is carried out by. 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 third component. Rapid mixing is usually achieved by collisional mixing of each component, and an after-mixing mechanism may be provided in the runner section to perform remixing. 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 other automobile parts, molded products for housings, and 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 A mixture of a high molecular weight polyol containing the internal mold release agent of the present invention, a chain extender, etc. was charged into a tank on the polyol component side of a high-pressure foaming machine, and a polyisocyanate compound was charged into a tank on the isocyanate component side. Reaction injection molding was carried out by adjusting the discharge pressure of the high-pressure foaming machine to 150 kg/cm ² , the discharge rate to 60 to 120 kg/min, and the liquid temperature of each component to 30 to 40°C. The size of the mold
A 140 mm x 120 mm x 1400 mm, 3 mm inner thickness iron mold for forming the outer shell of an automobile bumper was used, and the mold temperature was adjusted to 60 to 70°C. Furthermore, during molding, a wax-based mold release agent was first applied to the mold, and then the number of times the molding force could be measured without application was measured. The results are shown in Table 1. Raw material polyol component High molecular weight polyol or high molecular weight polyol
100 parts by weight High molecular weight polyol A: Polyoxypropylenoxyethylene diol with a molecular weight of about 4000 and an oxyethylene group content of about 20% by weight. High molecular weight polyol B: polyoxypropylenoxyethylene triol with a molecular weight of about 6500 and an oxyethylene group content of about 15% by weight. Chain extender: ethylene glycol 16 parts by weight Catalyst: 0.5 〃 Internal mold release agent (shown in Table 1) 1.0 〃 [In the table, (EO) is an oxyethylene group,
(C ₂ H ₄ O)] Isocyanate component carbodiimide-modified diphenylmethane diisocyanate (NCO content 28%) [Amount used is the amount that makes the index 105] External mold release agent (wax type) B-263D (Chukyo Yushi ( Co., Ltd.): Examples 1 to 4, and Comparative Example D-186 ( ): Examples 5 to 6 [Table]

Claims (1)

[Claims] 1. A reactive mixture of a high molecular weight active hydrogen-containing compound and a polyisocyanate compound, which includes an active hydrogen-containing compound and a chain extender, is cured in a mold to form a non-foamed or microcellular product. In the method for producing a polyurethane elastomer with a HLB value of about 18 or less, the reactive mixture consists of a monoepoxide adduct of amines or alkanolamines having a long-chain aliphatic hydrocarbon group, mainly containing ethylene oxide. A method for producing a polyurethane elastomer having internal mold releasability, which comprises blending an ionic surfactant. 2. The method according to claim 1, characterized in that a nonionic surfactant is mixed in advance with the active hydrogen-containing compound. 3. The method according to claim 1, wherein the amine having a long-chain aliphatic hydrocarbon group is an aliphatic monoamine having 12 to 24 carbon atoms. 4. The method according to claim 1, wherein the method for manufacturing the polyurethane elastomer is a reaction injection molding method.