JPS60108414A - Manufacture of polyurethane elastomer - Google Patents

Abstract

PURPOSE:To obtain the titled elastomer of improve self-releasability, by incorporating specific polysiloxane compound in a reactive mixture made up of active hydrogen-contg. compound and polyisocyanate one followed by performing reacton injection molding. CONSTITUTION:The objective non-porous or microcellular elastomer can be obtained by incorporating (A) a reactive mixture made up of (i) active hydrogen- contg. compound consisting mainly of a) high-molecular weight active hydrogen- contg. compound (pref. polyoxyalkylene polyol) and b) chain extender (pref. ethylene glycol) and ii) polyisocyanate compound (pref. 4,4-diphenylmethane diisocyanate) with (B) a polysiloxane compond of a molecular weight 30,000- 150,000, virtually free from active hydrogen-contg. functional group reactive to isocyanate group (pref. polydimethylsiloxane) followed by performing reaction injection molding. EFFECT:Capable of giving molded articles with no problems in terms of adhesivity in coating operation and discoloration. USE:Outer skin for automabile bumper, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a self-releasing polyurethane elastomer by reaction injection molding, and is particularly characterized by using a specific polysiloxane compound as an internal mold release agent. The present invention relates to a method for producing a 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 incyanate 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 using components 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 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. Furthermore, it is also known to divide the active hydrogen-containing compound component into two or more parts and perform reaction injection molding 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 incyanate component, is reacted and cured in a mold, and is demolded after being cured to an extent that it can withstand demolding. 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 that is applied to the inner surface of the mold (hereinafter referred to as an external mold release agent) is a major obstacle to shortening molding time. In injection molding, the use of external mold release agents is not necessary, or even if necessary, the mold 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 for applying the external mold release agent to the average molding time per molded product is extremely large, and unless the time required for applying 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. 5B-81174 describes the use of a specific polysiloxane compound as an external mold release agent and an internal mold release agent, and Japanese Patent Publication No. 55-1178 describes the use of a specific polysiloxane compound as an external mold release agent and an internal mold release agent. An internal mold release agent consisting of a polysiloxane compound is described. but,
These internal mold release agents are not yet fully effective and are also inconvenient to handle. For example, the carboxylic acid group-containing polysiloxane compounds described in the above-mentioned 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. This method is difficult to apply to reaction injection molding equipment that uses two-component raw materials that are currently widely used.

Furthermore, in addition to the above-mentioned polysiloxane compounds containing carboxylic acids, polysiloxane compounds containing active hydrogen-containing functional groups that can react with incyanate groups such as hydroxyl groups, amino 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.
One is that it 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 the polysiloxane compound containing an active hydrogen-containing functional group reacts with the incyanate group and is fixed to the polyurethane, thereby preventing this leaching. However, on the other hand, considering its performance as a mold release agent, it is thought that it is more effective for the internal mold release agent to exist on the wood surface in contact with the mold during molding, rather than inside it. Suppression of the movement of is considered undesirable from the viewpoint of exhibiting mold releasability.

The present inventor conducted various studies on internal mold release agents that are effective in the production of polyurethane elastomers by reaction injection molding, etc., and as a result, discovered that certain polysiloxane compounds are particularly effective. 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. Furthermore, this compound has an excellent long-lasting mold release effect, and it is possible to produce molded products with no problems with adhesion or discoloration during painting. The present invention provides a polyurethane elastomer characterized in that a polysiloxane compound having a molecular weight of about 30,000 to 150,000 and which does not substantially contain active hydrogen-containing functional groups capable of reacting with the incyanate group is used as an internal mold release agent. The present invention relates to a method for producing a non-containing compound using a reaction injection molding method in which a reactive mixture of a high molecular weight active hydrogen-containing compound, an active hydrogen-containing compound containing a chain extender, and a polyincyanate compound is cured in a mold. In the method for producing a foamy or microcellular polyurethane elastomer, a polysiloxane compound having a molecular weight of about 30,000 to 150,000 that does not substantially contain active hydrogen-containing functional groups that can react with incyanate groups in the reactive mixture. A method for producing a polyurethane elastomer with excellent internal mold releasability, characterized by incorporating the following.

The polysiloxane compound that is the internal mold release agent in the present invention is +Si+R) 2-0% (R: lower alkyl group having 1 to 4 carbon atoms or aryl group such as phenyl group, however, two R may be different) n: an integer) as its main chain, and most preferably a compound whose main chain is polydimethylsiloxane in which both of the two R's are methyl groups. This main chain contains random or block-like i: (-St(R)(X)-0+ (X: monovalent organic groups other than R, but does not substantially have active hydrogen-containing functional groups). Furthermore, the main chain is usually linear, but it may partially have short or relatively long chain branches.

Further, at the end of the main chain, there is usually a group represented by -8i+R)s, but some of these three H's may be X. The most common and widely used polysiloxane compound is (CHa)a! 3i0 (-8i (C)Ia)2
-0)sSi((l)Ia)a, and this polydimethylsiloxane is also preferred as the polysiloxane compound in the present invention. It is necessary that the molecular weight of the polysiloxane compound used in the present invention is about 30,000 to 150,000. Paintability tends to decrease as the molecular weight of the polysiloxane compound decreases. Therefore, the lower limit of the molecular weight is more preferably about 50,000, and even more preferably about 80,000. On the other hand, as the molecular weight increases, the viscosity increases rapidly, and a polysiloxane compound with an excessively high viscosity is difficult to handle, and the preferable upper limit of the molecular weight 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 parts by weight, based on 100 parts by weight of the high molecular weight active hydrogen compound. ~5 parts by weight is preferred. The polysiloxane compound in the present invention does not contain an active hydrogen-containing functional group that can react with incyanate groups as described above.

Therefore, there is no problem even if the polysiloxane compound is mixed in advance with a compound having an incyanate group such as a polyisocyanate compound. However, it is usually preferable to use it by blending it in advance with a component containing an active hydrogen-containing compound described below. Of course, depending on the method for producing the polyurethane elastomer, it can be added to both the polyisocyanate compound and the active hydrogen-containing compound.

The polyurethane elastomer of the present invention is produced by a reaction injection molding method. That is, at least two components ejected at relatively high pressure are collided and mixed in a mixing chamber to form a reactive mixture;
This is a method in which this is immediately injected into a mold and the reactive mixture is cured in a short time in the mold to form a polyurethane elastomer. The reactive mixture may be remixed by an after-mixing mechanism provided downstream of the mixing chamber or part of the runner. An external mold release agent is usually applied to the inside surface of the mold. The combined use of an internal mold release agent and an external mold release agent in the present invention further improves mold releasability and significantly extends the life of the external mold release agent. Various types of external mold release agents can be used, including polysiloxane compounds similar to the internal mold release agent used in the present invention or other polysiloxane compounds, such as wax-based external mold release agents, silicone-based external mold release agents,
Fluorine compound external mold release agents and the like may also be used.

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,
It is a mixture of two components: a component usually called system liquid, which is a mixture of active hydrogen-containing compounds and all raw materials other than polyisocyanate compounds, and a component containing polyisocyanate compounds, and is mixed by a mixing injection device called a high-pressure foamer. It is a reactive mixture that is then injected.

In the reactive mixture, some or all of the components that are non-reactive with the incyanate group, such as reinforcing fibers and powder fillers, may be used in combination with the incyanate 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 carry out reaction injection molding using two or more active hydrogen-containing compound components or polyisocyanate compound-containing components, a total of three or more components.

t 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, a similar 7-minated polyether can be used as part or all of the high molecular weight active hydrogen-containing compound. The 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/(when used alone or in combination with a high molecular weight polyol). Expressed in tens of total hydroxyl groups to total amine groups, approximately (80% or less) is suitable.

In the present invention, high molecular weight polyol refers to an average molecular weight per hydroxyl group of about 800 to 4,000, particularly about 2,1000 to 2,500.The average number of hydroxyl groups per molecule is 1.8.
High molecular weight polyols having a molecular weight of 1 to 8.0, particularly 2.0 to 3.5, or a mixture of two or more, are 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.

In addition to polyoxyalkylene polyols, hydroxyl hydrocarbon polymers such as polybutadiene glycol,
Examples include polyester polyols, polyether ester polyols, polycarbonate polyols, etc., and although these can be used alone, they are preferably used in combination with polyoxyalkylene polyols. When polyoxyalkylene polyols and other high molecular weight polyols are used together, at least 60% by weight, in particular at least 80% by weight of polyoxyalkylene polyols, based on the mixture of both.
The other high molecular weight polyol used in combination is particularly preferably a butadiene homopolymer or copolymer having at least two hydroxyl groups.

Suitable polyoxyalkylene polyols include polyoxyalkylene polyols obtained 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 polyhydric initiators include polyhydric alcohols, polyhydric phenols, alkanolamines, mono- and polyamines, and polyhydric alcohols are particularly preferred. As the epoxide, fullkylene oxide having 2 to 4 carbon atoms is most preferred, but halogen-containing alkylene oxide, styrene oxide, glycidyl ether, and other epoxides can be used in combination therewith. The most preferred polyoxyalkylene polyol 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 fullkylene 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, it is 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 number of hydroxyl groups in the polyoxyalkylene polyol is about 2.1 to 3.0.

This polyoxyalkylene polyol consists of a poly 5 oxyalkylene triol or a mixture of a polyoxyalkylene diol and a trivalent or higher polyoxyalkylene polyol. A mixture of polyoxyalkylene polyols may be produced by mixing separately produced polyoxyalkylene polyols, or by adding an alkylene oxide or the like to a mixture of two or more types of polyvalent initiators. Examples of multivalent initiators include, but are not limited to, the following compounds.

Polyhydric alcohols; polyethylene glycols such as ethylene glycol, propylene glycol, l,4-butanediol, diethylene glycol, polypropylene glycols such as dipropylene glycol, glycerin trimethylolpropane, santriol, pentaerythritol, diglycerin, dextrose, alpha-methyl glycoside, sorbitol, sucrose.

Polyhydric phenol; bisphenol A, bis 6 phenol S, catechol, phenol formaldehyde initial condensate.

Alkanolamine; monoethanolamine, jetanolamine, triethanolamine, diisopropanolamine, N-methyljetanolamine.

Mono- or polyamines; ethylenediamine, diethylenetriamine, diaminodiphenylmethane, aniline.

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. Suitable polyamines are aromatic diamines having alkylene substituents and/or halogens. Preferred specific chain extenders include ethylene glycol, 1,
4-butanediol, propylene glycol, diethylene gelcol, dipropylene glycol, glycerin,
These include trimethylolpropane, jetanolamine, triethanolamine, etc., and ethylene glycol and 1,4-butanediol are particularly preferred. Preferred examples of the aromatic diamine include diethyltoluene diamine, monochloroparaphenylene diamine, and tetramethylmethylene dianiline.

The amount used is 5 to 50% based on the total amount of high molecular weight polyol.
40% by weight, especially 10-30% by weight, is suitable.

The polyincyanate compound includes aromatic, alicyclic, aliphatic, and other polyisocyanate compounds having at least two incyanate groups, and modified products thereof. For example, 2.4-)lylene diisocyanate, 2.8-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, polymethylene polyphenylisocyanate, xylylene diisocyanate, inphorone diisocyanate, methylene-bis(cyclohexyl isocyanate), hexamethylene incyanate, etc. 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 amount of polyisocyanate compound used is 80 to 120 expressed as incyanate index,
In particular, 85 to +10 is suitable.

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, trichlorofluorometa, dichlorofluorometa, 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, and flame retardants. In particular, blending reinforcing fibers or flexible reinforcing agents is effective in reducing 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 glass 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 incyanate groups can also be added to the incyanate 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, 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.

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 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 the polyol component side tank of a high-pressure foaming machine, while a polyisocyanate compound was charged into the incyanate component side tank. . The discharge pressure of the high-pressure foaming machine is 150 kg/am', the discharge amount is 80 to 120 kg/min,
Reaction injection molding was performed while adjusting the liquid temperature of each component to 3G to 40°C. I & shape size is 140mm x 120mm
An iron mold for molding the outer shell of an automobile bumper having a diameter of 1400 mm and an inner thickness of 3 cm was used, and the mold temperature was adjusted to 80 to 70 DEG C. for molding. Furthermore, during molding, a wax-based 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 are shown in Table 1.

a-115 polyol component High molecular weight polyol 84 parts by weight (polyoxypropyleneoxyethylene triol with molecular weight of about fl15Go and oxyethylene group content of about 15% by weight) Chain extender: 16 parts by weight of ethylene glycol Catalyst: ( (Dibutyltin dilaurate Q, 08//) Blowing agent: Freon 11 5 3 Internal mold release agent [below] [Description] Incyanate component carbodiimide-modified diphenylmethane diisocyanate (Neo content 28%) [The amount used is the amount that gives an index of 105] External mold release agent A: Wax having a melting point of about 110°C is dissolved and dispersed in an organic solvent.

B: Wax having a melting point of about 80° C. is dissolved and dispersed in an organic solvent.

The following polydimethylsiloxane which does not substantially contain active hydrogen-containing functional groups that can react with the internal mold release agent incyanate group Molecular weight Viscosity (25°C, ask) A: 30,000 10,000 B: IQ 300,000 300,000 C: 150,000 2,000,000 4 D: 10,300 E: 1,000 lO Paintability Test Painting: 1.1.1) After steam cleaning the molded product with lychloroethane, painting was performed as follows.

1. Undercoat: polyurethane primer baked at 100℃ for 30 minutes, film thickness 20cm 2. Topcoat: polyurethane top coat at 120℃, 40℃
Separation baking, coating film thickness 35 l Evaluation: Adhesion test/JIS 00202 Base grain test 1st
seed

Claims (1)

[Claims] 1. A non-foamed or microcellular shape produced by a reaction injection molding method in which a reactive mixture of a polyisocyanate compound and a high molecular weight active hydrogen-containing compound and a chain extender are indispensable. A method for producing a polyurethane elastomer, characterized in that a polysiloxane compound having a molecular weight of about 30,000 to 150,000 that does not substantially contain active hydrogen-containing functional groups that can react with incyanate groups is blended into the reactive mixture. A method for producing a polyurethane elastomer having internal mold releasability.