JPS6053521A - Preparation of polyurethane elastomer - Google Patents

Abstract

PURPOSE:To obtain the titled elastomer having improved dimensional stability of water absorption, by subjecting a polyol prepared by blending a high-molecular- weight polyol and a chain extender with an organic phosphorus compound, and an isocyanate component consisting of a polyisocyante compound to reactive injection molding. CONSTITUTION:(A) A polyol component obtained by reacting a high-molecular- weight polyol(preferably polyoxyalkylene polyol) and an chain extender (preferably ethylene glyocol, 1,4-butanediol with an organic phosphorus compound, and (B) an isocyanate component (preferably 4,4'-diphenylmethane diisocyanate) as essential components are subjected to reactive injecting molding, to give the desired elastomer. A (halo)alkyl group-, or (halo)aryl group-containing phosphate, or phosphonate is preferable as the organic phosphorus compound, and an amount of it blended is preferably 0.5-15pts.wt. based on 100pts.wt. high polymer polyol.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a polyurethane elastomer or polyurethane urea elastomer produced by reaction injection molding.

The present invention relates to a method for producing a polyurethane elastomer such as tomer, and particularly to a method for producing a polyurethane elastomer with improved water absorption dimensional stability.

Methods for producing molded articles of polyurethane, polyurethane urea, and other synthetic resins by reaction injection molding are known. Reaction injection molding is a method in which at least two components that react rapidly when mixed with each other are rapidly mixed by collision mixing, the mixture is filled into a mold, and the mixture is reacted and cured. The two mutually reactive components are usually liquids, but in some cases they may be slurry-like liquids containing insoluble components such as fillers.

Polyurethane, polyurethane urea, etc. have one component mainly composed of a polyisocyanate compound and the other component mainly composed of an active hydrogen compound having at least two active hydrogen-containing groups. Both are obtained using two components. In reaction injection molding, non-foamed elastomers and microcellular elastomers such as polyurethane and polyurethane urea (hereinafter both referred to as polyurethane elastomers) are usually produced using active hydrogen compounds that are a combination of high molecular weight polyols and low molecular weight polyols or polyamines. Obtained by reacting with an isocyanate compound. Low molecular weight polyols and polyamines are sometimes called crosslinking agents (especially in the case of trifunctional or higher functional compounds), but in the present invention, bifunctional and trifunctional or higher functional compounds are also referred to as chain extenders.

In addition, the polyurethane elastomer in the present invention, including microcellular elastomers, has a density of about 0.8 g/cd or more, particularly 0.9 g/c1 or more, and when it does not contain a filler. The upper limit is about 1-2g/cr
1, especially about], 15 g/cut. This microcellular elastomer is usually obtained using small amounts of blowing agents. The amount of blowing agent used is usually about 15 parts by weight or less, particularly 10 parts by weight or less, per 100 parts by weight of the high molecular weight active hydrogen compound. Furthermore, the difference between a microcellular elastomer and a normal flexible polyurethane foam lies in the difference in expansion ratio, and the expansion ratio of a microcellular elastomer is usually 2 or less.

The production of polyurethane elastomers by reaction injection molding is currently used for molded products in automobile-related fields, including the outer shell of automobile bumpers. Also, car fenders and door panels.

Adoption is also being considered for front panels and other exterior parts. These exterior members for automobiles, including the outer shell of the bumper, are required to have greater water resistance than interior members. However, the polyurethane elastomers conventionally used for bumper outer shells had problems with poor water resistance.The most problematic aspect of conventional polyurethane elastomers was dimensional changes due to water absorption. That is, the polyurethane-based nidistomer easily absorbs water, and the dimensions change due to water absorption, which tends to cause deformation of the molded product. Conventionally,
In order to avoid dimensional changes due to water absorption, the wall thickness of molded products has been increased. However, it is extremely uneconomical to increase the wall thickness of a molded product solely to cope with dimensional changes due to water absorption. In addition, being limited to thick walls means that the degree of freedom regarding the shape and physical properties of the molded product is reduced. Therefore, in order to essentially solve this problem, it is considered necessary to lower the water absorption of polyurethane elastomers.

When the water absorbency Ijχ of polyurethane elastomers was investigated, it was found that it was due to the hydrophilicity of the oxyethylene groups in the high molecular weight polyoxyalkylene polyol that was the raw material.

It is believed that the problem of water absorption can be solved if a polyoxyalkylene polyol containing no oxyethylene group can be used. However, on the other hand, the presence of an oxyethylene group is essential for a polyoxyalkylene polyol that can be applied to reaction injection molding. That is, the polyoxyalkylene polyol used in reaction injection molding must have high reactivity, and therefore the polyol must have a high proportion of primary hydroxyl groups. It is necessary that the terminal oxyalkylene group of the polyol is an oxyethylene group.

Typical polyoxyalkylene polyols include substantially only oxypropylene groups as oxyalkylene groups, or polyoxyalkylene polyols with oxyethylene groups at the terminals obtained by adding ethylene oxide to polyoxyalkylene polyols that have oxypropylene groups and oxybutylene groups. It is a polyoxyalkylene polyol having a proportion of primary hydroxyl groups. Therefore, there is a need for a technique that can produce polyurethane elastomers with excellent water absorption dimensional stability even when polyoxyalkylene polyols containing some oxyethylene groups are used.

The present inventor investigated various compounds as water absorption improvers that can be used by adding them to a polyol component containing a high molecular weight polyol such as a polyoxyalkylene polyol and a chain extender. As a result, it was found that organic phosphorus compounds are particularly effective. Particularly preferred organic phosphorus compounds are organic phosphates or phosne 1- and derivatives thereof. The gist of the present invention is to use at least two components: a polyol component containing a high molecular weight polyol and a chain extender as essential components, and an incyane 1 component containing a polyisocyanate compound as an essential component. A method for producing a polyurethane elastomer by a reaction injection molding method, which is characterized in that an organic phosphorus compound is blended into the polyol component.

Organic phosphorus compounds include organic phosphoric acid esters, phosphonic acid esters, and phosphorous acid esters.

Thiophosphoric acid ester, thiophosphonic acid ester.

Thiophosphite and other organic phosphoric acid ester compounds are suitable. As the organic group, an alkyl group, a haloalkyl group, an aryl group, and a haloaryl group are preferable, and a (halo)alkyl group or (halo)aryl group having 1 to 8 carbon atoms is particularly preferable. Particularly preferred organic phosphorus compounds are phosphates and phosphonates having an organic group described in 1. For example, trialkyl phosphate,
These include trihaloalkyl phosphates, triarylphosphate-1-2 and 1-lihaloaryl phosphates, and dialkylalkylphosphonates, dihaloalkylalkylphosphonates, and dihaloalkylhaloalkylphosphonates. Specifically, for example, triethyl phosphate, tributyl phosphate, tris(β-chloroethyl)phosphate 2-tris(β-chloroisopropyl)phosphate-1-.

Tris(dichloropropyl)phosphate-1-, l-lis(2,3-dibromopropyl)phosphate-1-.

Tribuenyl phosphate, tricresyl phosphate, dimethylmethylphosphonate-1-.

Di(β-chloroethyl)ethylphosphone-1, di(β-chloroethyl)ethylphosphone-1.
-chloroethyl) β-chloroethylphosphonate, and the like. The amount of these organic phosphorus compounds to be blended is not particularly limited, but it is suitably 1 to 10 parts by weight per 100 parts by weight of high molecular weight polyol.
It is. In addition, it is preferable that the organic phosphorus compound does not deactivate a catalyst such as an organic tin compound or a secondary amine that is usually added to the polyol component. For this reason,
It is preferable that the organic phosphorus compound is not strongly acidic.

In the present invention, high molecular weight polyol means an average molecular weight per hydroxyl group of about 800 to 4000, particularly about 1000 to 25
High molecular weight polyols having an average number of hydroxyl groups per molecule of about 1.8 to 6.0, particularly about 2.0 to 3.5, or a mixture of five or more of +t' 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. Other than polyoxyalkylene polyols, there are hydroxyl group-containing hydrocarbon polymers such as polybutadiene glycol, polyester polyols, polyether ester polyols, polycarbonate polyols, etc., and these can be used alone, but It is preferably used in combination with polyoxyalkylene polyol. When using polyoxyalkylene polyols and other high molecular weight polyols together.

It is preferred that the polyoxyalkylene polyol accounts for at least 60% by weight, in particular 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 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- or polyamines, and polyhydric alcohols are particularly preferred. As the epoxide, alkylene 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 dipolyvalent 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, it is about 8% by weight or more. As the proportion of all oxyethylene groups in the polyoxyalkylene polyol increases, the water absorption dimensional stability tends to decrease as described above. Therefore, the upper limit of the proportion of total oxyethylene groups is 3
It is preferably 5% by weight or less, particularly 20% by weight or less.

Therefore, since the terminal oxyethylene group is necessary to ensure reactivity, it is preferable that substantially all of the oxyethylene groups in the polyoxyalkylene polyol be present at the terminal portions of the oxyalkylene chains. Accordingly, the most preferred high molecular weight polyol in the present invention is a polyoxypropylene/oxyethylene polyol having an oxyethylene group content of 5 to 20% by weight, substantially all of which is present at the terminal portion of the oxyalkylene chain.

A more preferable average number of hydroxyl groups in the polyoxyalkylene polyol is about 2.1 to 3.0.

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

Polyhydric alcohol: polyethylene glycol such as ethylene glycol, propylene glycol, 1,4-butanediol, diethylene glycol.

Polypropylene glycol such as dipropylene glycol, glycerin, trimethylolpropane, hexanetriol, pentaerythritol, diglycerin, dextrose, α-methylcricoside, sorbitol, sucrose polyhydric phenols: bisphenol A, bisphenol S
, catechol, phenol-formaldehyde precondensate. 5 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. As a polyamine.

Aromatic diamines with alkyl substituents and/or halogens are suitable. Preferred specific chain extenders are:
Ethylene glycol, 1,4-butanediol, propylene glycol, diethylene glycol, dipropylene glycol.

These include glycerin, trimethylolpropane, jetanolamine, triethanolamine, etc., and ethylene glycol and 1,4-butanediol are particularly preferred. As the aromatic diamine, -C is preferably, for example, diethyltoluene diamine, monochloroparaphenylene diamine, tetramethylmethylene dianiline, or the like. The amount used is 5 to 40% by weight and 10 to 30% by weight based on the total amount with the high molecular weight polyol.

It has been found that the use of a chain extender having an oxyethylene group such as ethylene glycol does not have any adverse effect on the water absorption dimensional change of the polyurethane elastomer. The reason is that the chain extender reacts with the polyisocyanate compound to form a hard block of the polyurethane elastomer, and this hard block has low water absorption even if oxyethylene groups are present therein, and even if it does not absorb water, Since Moso-Ku is hard, it is thought that it will not cause deformation1.

On the other hand, the oxyethylene group present at the end of the molecular chain of high molecular weight polyol is thought to exist adjacent to this hard block, but unlike the case where it exists within the hard block, this group belonging to rough 1 to block It is thought that the presence of oxyethylene groups in the moiety has a large influence on the water absorption dimensional change.

The polyisocyanate compounds include aromatic, alicyclic, aliphatic, and other polyisocyanate compounds having at least two incyanate groups, and modified products thereof. For example, 2,1I-1-lylene diisocyanate, 2,6-lylene diisocyanate, 4,4'-diphenylmethane diisocyanate, polymethylene polyphenylisocyanate 1-. Xylylene diisosiapho 1~. Examples include inphorone diisocyanate-1-, methylene-bis(cyclohexylisocyanate-1-), and hexamethylene diisocyanate. Also, it is a modified form.

Now, dimers, trikeids, and prepolymer-type modified products.

There are carbodiimide denatured products, urea denatured products, and other types. Two or more of these polyisocyanate-1 compounds may be used in combination. Particularly preferred polyisocyanate compounds are 4,4'-diphenylmethane diisocyanate-1 and its carbodiimide-modified and prepolymer-type modified products. The amount of polyisocyanate compound used is -r)
90 to +20, particularly 95 to 110, expressed as an 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. Extomer is obtained.

However, it is preferable to use a foaming agent with a small amount of foam for reasons such as improving moldability. As the blowing agent, air, water, etc. can be used, but halogenated hydrocarbons with a low boiling point are preferably used. Specifically, 1-lichlorofluoromethane, dichlorodifluoromethane, methylene chloride, etc. are suitable.

The amount thereof is preferably 15 parts by weight or more, 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, flame retardants, and internal mold release agents. In particular, blending reinforcing fibers or flake-like reinforcing agents has the effect of lowering the rate of dimensional change after water absorption. This seems to be to increase the rigidity and strength of the polyurethane elastomer to -42. Suitable reinforcing fibers include milled glass fibers, cut fibers, and wollastonite.

Further, as the flake reinforcing agent, mica, glass flakes, etc. can be used. The phosphor has a sufficient effect at a content of about 20% by weight or less based on the entire polyurethane elastomer. 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 that are inert to isocyanate groups can also be added to the isocyanate component.

The reaction injection molding method is usually carried out by rapidly mixing the polyol component and the isocyanate component, immediately injecting the mixture into a mold, reacting the mixture in the mold, and taking out the molded product after curing. In some cases, three or more components may be used by dividing the polyol component or incyanate 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 structure may be provided in a part of the runner 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 molded products and other uses that require water resistance.

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

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

Reaction injection molding was performed by adjusting the discharge pressure of the high-pressure foaming machine to 150 to 4H/ciτ, the discharge pressure to 60 to 120 kg/min, and the liquid temperature of each component to 30 to 40°C.The mold size was 140 UN.
Used for a mold for molding the outer shell of an automobile bumper with dimensions of 120mm x 1400axn and an inner thickness of 3 strokes.
Molding was carried out at a temperature of -70°C. A sample for measuring physical properties was cut out from the obtained molded article, and the physical properties listed in Table 1 were measured, including the water absorption dimensional change rate llff1.

The physical properties 81 listed in Table 1 were determined by the following method.

Density: method by water or alcohol displacement.

(ASTM-D79'2) Water absorption dimensional change rate: Molded product sample (100X150X3
m) at 80°C x 6111-Bost cured, the length in the long side direction is 1. .

If this is immersed in 40℃ hot water for 2401 minutes and the length is t, then the water absorption normalization rate ΔL is expressed as q by the following formula.
Well, IL.

Flexural modulus: Based on ASTM-D790 method.

Tensile strength: JIs-630] - Based on dumbbell No. 2.

Elongation: According to J Is-630 L dumbbell No. 2.

The raw materials used were as follows.

(2) Polyoxyalkylene polyol The following polyols A to G are polyoxypropylene/oxyethylene polyols having an oxyethylene group at the end, and the number of hydroxyl groups, oxyethylene group content, and hydroxyl value are as follows.

Polyo-hydroxyl Oxyethylene Name of hydroxyl Radix Number of groups Containing type Base value polyol A 3. 8'gX amount% 26JT B 3
20n 28 1' C320n 56 n D 2 20 JJ 2.8 II E 2 23n 28 n F 2 30n 37 R: Trisdibumopropyl phosphate ■, polyisocyanate compound [In the case of use, the incyanate index is 105
] Polyisocyanate A: Carbodiimide-modified diphenyl meta>' diisocyanate (NGO-containing
28.5%) Polyisocyanate B: Brepolymer type modified diphenylmethane diisocyanate-1- (NCO content 26%) ■, Other raw materials EG: Ethylene glycol catalyst A nitriethylenediamine solution (trade name: DABCO 33 LV)

Claims (1)

[Scope of Claims] (1) A polyurethane elastomer produced by reaction injection molding using at least two components: a polyol component containing a high molecular weight polyol and a chain extender as essential components, and an isocyanate component containing a polyisocyanate compound as an essential component. 1. A method for producing a polyurethane elastomer, which comprises blending an organic phosphorus compound into the polyol component. 2. The amount of organic phosphorus compound is 100% of the polymer polyol.
The method according to claim 1, characterized in that the amount is 0.5 to 15 parts by weight. 3. The method according to claim 1, wherein the organic phosphorus compound is a phosphate or phosphonate having a (halo)alkyl group or a (halo)aryl group.