JPH0739527B2 - Methacrylic resin molding material and molding method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a methacrylic resin molding material and a molding method thereof. More specifically, the present invention relates to a methacrylic resin molding material that gives a molded article that is substantially free from coloration during high temperature polymerization and has excellent heat resistance, and a method for manufacturing the same, such as a method for manufacturing artificial marble.

(Prior Art) A polymer molded product whose main component is methyl methacrylate filled with aluminum hydroxide powder has a beautiful surface with a sense of depth, excellent mechanical strength, excellent weather resistance, and corrosion resistance. Since it has excellent properties such as excellent properties and excellent flame retardancy, it is used as an artificial marble product for various top plates, countertops, vanities, sinks, bathtubs, shower trays, waterproof pans, flooring materials, wall materials, Widely used for partition boards and arts and crafts.

The method for producing such a methacrylic resin molded article is roughly classified into two. One of them is to melt-mix a thermoplastic methacrylic resin and a filler to form a molded product by extrusion molding or injection molding.Since the methacrylic resin of the matrix is thermoplastic, heat resistance and It has the disadvantage of poor chemical resistance. The other is a method of injecting a slurry in which a methylmethacrylate-based syrup and a filler are mixed into a mold and curing it, that is, casting molding, in which heat resistance and heat resistance are improved by increasing the degree of polymerization or adding a crosslinking agent. Although chemical resistance is improved, molding time is long, the slurry is sticky, and it is difficult to handle and the workability is poor. Also, if the slurry is stored, the filler will settle and harden, so it will be strong every time it is used. Must be stirred. Furthermore, since methyl methacrylate has a high polymerization shrinkage rate, surface defects such as sink marks are likely to occur in the molded product, which limits the shape of the molded product and requires special casting equipment. is there. When the amount of the polymerization initiator is increased or the polymerization temperature is increased to shorten the molding time, bubbles or cracks are generated in the molded product. As a method of preventing defects due to polymerization shrinkage,
Although it has been proposed to increase the filler filling amount and the polymer concentration in the syrup, all of them are not practical because they increase the slurry viscosity and make injection difficult.

On the other hand, since the inorganic filler and the organic resin are remarkably different in properties from each other, and the interface affinity such as compatibility and adhesiveness is poor, the conventionally used inorganic filler is the mechanical property of artificial marble. In order to improve the drawback that it often fails to exhibit sufficient improvement in bending strength and impact strength, a specific (a) carboxylic acid monomer or (b) sulfonic acid monomer or sulfonate is used. Monomer,
A composition for artificial marble comprising an organic bond filler and a vinyl compound obtained by polymerizing at least one radically polymerizable vinyl monomer in a polymerization system in which an inorganic compound is dispersed, and the composition is cured. A method for producing an artificial marble consisting of the above is proposed (Japanese Patent Laid-Open Nos. 61-57,601, 61-60,716 and 61-60,702).
issue). However, the artificial marble obtained by such a composition or method has a drawback that heat resistance and solvent resistance are still insufficient.

In general, methacrylic resin containing methyl methacrylate as a main component is used in various fields such as lighting covers, automobile parts, signboards, ornaments, and sundries due to its excellent weather resistance and excellent transparency, Since the methacrylic resin is a linear polymer, it has a drawback that heat resistance, solvent resistance, impact resistance and surface hardness are insufficient. For example, the heat resistance is limited to about 100 ° C., and it is the current situation that the demands from each field requiring heat resistance cannot be sufficiently met.

(Problems to be Solved by the Invention) In order to solve the various drawbacks of the methacrylic resin, the present inventors have previously proposed a methacrylic resin molding material composed of a partially crosslinked gel polymer. (Japanese Patent Laid-Open No. 60
-202,128). Then, the compound obtained by mixing and kneading the methacrylic resin molding material and aluminum hydroxide is heated and pressure-polymerized in a press die to be molded, whereby a white and transparent composite material molded article is obtained. This method
Compared to the conventional mold method, (a) molding time is short (high temperature molding and high temperature extraction possible), (b) molding shrinkage is small, dimensional stability is good, and (c) sink marks etc. It is difficult to use and (d) has good manufacturing characteristics such as good releasability from the mold, and because it is a high-density cross-link, it has high heat distortion temperature and excellent solvent resistance. There is.

However, the molding temperature needs to be sufficiently high (to accelerate the molding cycle and to increase the degree of polymerization completion at the end of molding) in order to exert the characteristics of the above method, but unfortunately the molding temperature is high. And the molded product turns yellow. The higher the molding temperature, the greater the degree of coloration, and post-polymerization (heat treatment, heat treatment,
For example, at 130 ° C. for 4 hours, the coloration is further increased. Further, there is a drawback in that even a product which is not colored after molding is colored in the post-polymerization stage, and a substantially white or colorless molded product cannot be obtained.

Therefore, an object of the present invention is to provide a novel methacrylic resin molding material and a method for producing the same. Another object of the present invention is to provide a methacrylic resin molding material which is excellent in physical properties such as heat resistance, solvent resistance, mechanical strength and the like and which can give a molded product without coloring, and a method for producing the same.

(Means for Solving Problems) These various purposes are (A) (a) an alkyl methacrylate monomer, α containing alkyl methacrylate as a main component,
A resin raw material selected from the group consisting of syrup containing a β-ethylenically unsaturated monomer mixture and a polymer thereof, and (b) at least two in a molecule of 2 to 250 parts by weight per 100 parts by weight of the resin raw material. The mixture of the cross-linking agent having a (meth) acryloyl group is partially polymerized so that the content of the polymer is higher than the content of the polymer in the mixture as long as the total polymer content does not exceed 80% by weight. 20 to 80% by weight of partially crosslinked gel polymer increased by 4 to 65% by weight, 0.15 to 1.5 parts by weight of formic acid, oxalic acid and chloroacetic acid per 100 parts by weight of (c), (a) and (b) in total. A methacrylic system consisting of an acid selected from the group consisting of malonic acid, citraconic acid, phthalic anhydride, succinic anhydride, fumaric acid, phthalic acid, malic acid and phosphoric acid, and 80 to 20% by weight of (B) aluminum hydroxide powder. Achieved by resin molding material .

Further, these various objects are selected from the group consisting of (A) (a) an alkyl methacrylate monomer, an α, β-ethylenically unsaturated monomer mixture containing alkyl methacrylate as a main component, and a syrup containing the polymer. Total weight by partially polymerizing a mixture of the selected resin raw material and (b) a crosslinking agent having at least two (meth) acryloyl groups in the molecule in an amount of 2 to 250 parts by weight per 100 parts by weight of the resin raw material. 20-80% by weight of a partially crosslinked gel polymer in which the content of the polymer is increased by 4 to 65% by weight relative to the content of the polymer in the mixture within a range in which the content of the polymer does not exceed 80% by weight, (c ) (A)
0.1 to 1.5 parts by weight of formic acid per 100 parts by weight of (b),
An acid selected from the group consisting of oxalic acid, chloroacetic acid, malonic acid, citraconic acid, phthalic anhydride, succinic anhydride, fumaric acid, phthalic acid, malic acid and phosphoric acid, and (B)
It is also achieved by a method for producing a molded article, which comprises curing a methacrylic resin molding material containing 80 to 20% by weight of aluminum hydroxide powder.

According to the knowledge of the present inventors, as a cause of coloring, a coloring substance or a precursor thereof is generated by the interaction between impurities in the filler aluminum hydroxide and the alkyl methacrylate monomer during high temperature polymerization. It is estimated that this is the case. The reason for this is that (1) casting polymerization (low-temperature long-time polymerization) causes almost no coloration and no coloration occurs even after post-polymerization, (2) the degree of coloration varies depending on the type of filler, and high-purity filler is used. For example, there is less coloring after molding and after polymerization than in the case of using a normal filler. However, the molding material according to the present invention is characterized in that it is pressurized at a high temperature (the molded product is temporarily raised to a temperature of several tens of degrees higher than the set temperature due to the heat of polymerization), so the low-temperature polymerization loses its characteristics. Nau. Further, even if a high-purity filler is used, coloring is unavoidable, and the cost becomes high, which poses a problem for industrial use.

Therefore, a selective search was made for the coloring-causing substance in the filler to change it to a non-coloring substance, or a search was made for an additive that would not cause coloring. The present invention has been completed by finding that coloring can be suppressed by adding a trace amount of a specific acid to the composition or to the partially cross-linked gel polymer.

(Function) Examples of the monomer used as the resin raw material (a) in the present invention include alkyl methacrylate alone or a mixture of alkyl methacrylate and an α, β-ethylenically unsaturated monomer copolymerizable therewith. . In the case of such a monomer mixture, the alkyl methacrylate content is preferably 50 mol% or more, and more preferably 60 mol% or more. As alkyl methacrylate,
Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate,
Although there are n-butyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, etc., methyl methacrylate is particularly preferable.

As the copolymerizable monomer, an alkyl methacrylate other than the alkyl methacrylate used as the main component (for example, methyl methacrylate) (for example, the above-mentioned alkyl methacrylate or 2-ethylhexyl methacrylate,
Lauryl methacrylate, cyclohexyl methacrylate, etc.), methyl acrylate, ethyl acrylate, n
-Propyl acrylate, isopropyl acrylate,
Alkyl acrylates such as n-butyl acrylate, 2-ethylhexyl acrylate and lauryl acrylate, cyclohexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxy-3-. Hydroxyalkyl acrylate such as chloropropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, hydroxyalkyl methacrylate such as 2-hydromy-3-chloropropyl methacrylate, acrylic acid , Methacrylic acid, neodymium acrylate, lead acrylate, boron acrylate, etc. Crylates, methacrylic acid salts such as neodymium methacrylate, lead methacrylate, boron methacrylate, vinyl chloride, vinyl acetate, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, styrene, α-methylstyrene, vinyltoluene, anhydrous Maleic acid etc.

In addition, the syrup containing the polymer of the alkyl methacrylate or the monomer mixture containing alkyl methacrylate as a main component generally has a viscosity of 0.05 to 1,000 poise at 25 ° C., and 3 to 40% by weight, preferably 6 to 20
It is a monomer solution containing wt% polymer.

The crosslinking agent (b) used in the present invention has at least two (meth) acryloyl groups in the molecule, and the main chain carbon atoms existing between the (meth) acryloyl groups are 10 carbon atoms. a monomer or less, preferably the following formula (1) ~ (3) MA -O- (CH 2) n-O-MA ...... (1) [where n is an integer of 3-6 , MA represents a methacryloyl group. ] (Wherein R ¹ is a group of H, CH ₃ , C ₂ H ₅ or CH ₂ OH, and R ² is H, C
H ₃ , (R ⁴ represents a group of H, CH ₃ ) or a group of CH ₂ OH, and R ³ is
H and CH ₃ groups are respectively represented, R ¹ , R ² and R ³ are not hydrogen at the same time, and (M) A represents a methacryloyl group or an acryloyl group. ] [Wherein R ⁵ is H or CH ₃ and n is 1 or 2
Is. ] It is a monomer represented by.

Specific examples of these monomers include propylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,3-butylene glycol dimethacrylate, and dimethylolethane dimethacrylate. , 1,
1-dimethylolpropane dimethacrylate, 2,2-dimethylolpropane dimethacrylate, trimethylolethane tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolmethane dimethacrylate , Ethylene glycol di (meth) acrylate and diethylene glycol di (meth) acrylate.

The amount of the cross-linking agent (b) used is the same as that of the resin raw material (a).
2 to 250 parts by weight, preferably 4 to 150 parts by weight per 100 parts by weight
Parts by weight. That is, when the amount is less than 2 parts by weight, the heat resistance of the finally obtained molded product is not improved, and
If the amount is more than parts by weight, the molded product finally obtained is brittle and cannot be put to practical use.

The acid used in the present invention is selected from the group consisting of formic acid, oxalic acid, chloroacetic acid, malonic acid, citraconic acid, phthalic anhydride, succinic anhydride, fumaric acid, phthalic acid, malic acid and phosphoric acid. It is a thing. The amount used is a mixture 100 of the resin raw material (a) and the cross-linking agent (b).
The amount is 0.15 to 1.5 parts by weight, preferably 0.25 to 1.5 parts by weight. The acids from formic acid to phosphoric acid exhibit the most excellent effect as compared with other acids. These acids can be added before or after the formation of the partially crosslinked gel polymer.

The methacrylic resin molding material according to the present invention is polymerized by heating a mixture of the resin raw material (a) and the cross-linking agent (b) in the presence of a polymerization initiator, and the monomer present in the mixture is It is composed of a gel-like partial polymer obtained by stopping the reaction at the stage where a part of the reaction has occurred without reacting the whole amount.

In this case, the content of the polymer present in the methacrylic resin molding material, which is a partially crosslinked gel polymer, is (a) an alkyl methacrylate monomer and an α, β-ethylenically unsaturated compound containing alkyl methacrylate as a main component. 4 more than the polymer content in the mixture of the resin raw material selected from the group consisting of the monomer mixture and these partial polymers and (b) the cross-linking agent.
Up to 65% by weight and not exceeding 80% by weight, preferably 10 to 65% by weight and not exceeding 80% by weight, most preferably 20 to 65% by weight and It does not exceed 80% by weight. If the content of the polymer is less than 4% by weight, the product does not show a gel and is inconvenient to handle, and if the value increased by 65% by weight or the upper limit of 80% by weight is exceeded, it may occur during molding. Does not show good flow,
Both do not meet the purpose of the present invention.

The polymer content of the partially crosslinked gel polymer can be determined by the extraction method.

As the polymerization initiator, various ones can be used, but if a low temperature active polymerization initiator and a high temperature active polymerization initiator are used in combination,
When the formation reaction of the gelled partial polymer is carried out by the action of a low temperature active polymerization initiator, and then the gelled molding material thus obtained is further heated to form a desired article, the high temperature active polymerization initiation It can be performed by the action of an agent. However, it is also possible to use only one of the high-temperature activated initiator and the low-temperature activated initiator.

As the low temperature active polymerization initiator, for example, a peroxide having a decomposition temperature of 50 ° C. or lower for obtaining a 10-hour half-life and an azo compound radical polymerization initiator are preferable. In order to increase the storage stability of this molding material, the low temperature active polymerization initiator is preferably eliminated as much as possible in the polymerization process for obtaining the molding material, so the decomposition temperature is preferably 26 to 45 ° C., particularly 26 to 45 ° C. 41
C is preferred. The amount of the low temperature active polymerization initiator used is based on the total amount of the resin raw material (a) and the crosslinking agent (b).
It is used in an amount of 0.001 to 1% by weight, preferably 0.002 to 0.1% by weight.

Examples of such a low temperature active polymerization initiator include (I)
Acetyl cyclohexyl sulfonyl peroxide, isobutyryl peroxide, cumyl peroxy neodecanoate, diisopropyl peroxydicarbonate,
Di-n-propyl peroxydicarbonate, dimyristyl peroxydicarbonate, 2,2'-azobis (4
-Methoxy-2,4-dimethylvaleronitrile), (II)
Di- (2-ethoxyethyl) peroxydicarbonate, di- (methoxyisopropyl) peroxydicarbonate, di- (2-ethylhexyl) peroxydicarbonate, (III) di- (3-methyl-3-methoxybutyl) ) Peroxydicarbonate, t-butylperoxyneodecanoate, 2,2'-azobis (2,4-dimethylvaleronitrile), etc., among which, preferably, the groups of (I) and (II) Is a compound belonging to
Particularly preferred are compounds belonging to the group (I).

As the high-temperature active polymerization initiator, a polymerization initiator such as a peroxide having a decomposition temperature of 60 to 220 ° C. for obtaining a 10-hour half-life is preferable, and it is 90 in order to improve the molding cycle and keep the storage safety. A polymerization initiator having a decomposition temperature of ˜170 ° C., more preferably 120˜170 ° C. The amount of the high temperature active polymerization initiator used is 0.02 to 2.0% by weight, preferably 0.05 to 2.0% by weight based on the total amount of the resin raw material (a) and the crosslinking agent (b).
Used by weight percent.

Examples of such a high temperature active polymerization initiator include (IV)
t-butyl cumyl peroxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, p-menthane hydroperoxide, 2,5-
Dimethyl-2,5-di- (t-butylperoxy) hexyne-3,1,1,3,3-tetramethylbutyl hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, Cumene hydroperoxide, t-butyl hydroperoxide, 1,1,2,2-tetraphenyl-1,2-ethanediol, (V) 1,1-bis (t-butylperoxy) -3,3, 5-trimethylcyclohexane,
1,1-bis (t-butylperoxy) cyclohexane,
t-butylperoxymaleic acid, t-butylperoxylaurate, t-butylperoxy-3,5,5
-Trimethylhexanoate, cyclohexanone peroxide, t-butylperoxyisopropyl carbonate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,2-bis (t-butylperoxy) octane, t-butylperoxyacetate, 2,2-bis (t-butylperoxy) butane, t-butylperoxybenzoate, n-butyl-4,4-bis (t-butylperoxy) valerate, di-t- Butyl diperoxyisophthalate, methyl ethyl ketone peroxide,
α, α-bis (t-butylperoxyisopropyl) benzene, dicumyl peroxide, 2,5-dimethyl-2,5
-Di (t-butylperoxy) hexane, (VI) m-toluoyl peroxide, benzoyl peroxide,
t-butylperoxyisobutyrate, di-t-butylperoxy-hexahydroterephthalate, 2,3-dimethyl-2,3-diphenylbutane, octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, stearoyl peroxide There are oxides, propionyl peroxide, succinic acid peroxide, acetyl peroxide, 1,1′-azobis (cyclohexane-1-carbonitrile), etc., and among these, preferably (IV) and (V) groups The compound belongs to the group, and particularly preferably the compound belonging to the group (IV).

As described above, the methacrylic resin molding material according to the present invention comprises a mixture of the resin raw material (a) and the crosslinking agent (b) in the presence or absence of the acid (c) and in the presence of the polymer initiator. A partially crosslinked gel polymer (A) is obtained by heating and polymerizing. The polymerization reaction is carried out at a temperature of 10 to 80 ° C, preferably 35 to 65 ° C for 10 to 300 minutes, preferably 2 to 180 minutes. However, when both low-temperature active and high-temperature active polymerization initiators are used in combination, the low-temperature active polymerization initiator is consumed almost entirely, but the high-temperature active polymerization initiator remains as it is without being decomposed at the reaction temperature. Therefore, it is consumed during the molding reaction using the molding material.

According to the present invention, a partially crosslinked gel polymer having a desired polymerization rate can be obtained by stopping the polymerization reaction by quenching or the like. Further, according to the present invention, the resin raw material (a) is used.
When a mixture of the polymer and a crosslinking agent (b) is heated and polymerized in the presence of the above-mentioned polymerization initiator, a gelling polymer having a desired polymerization rate can be obtained more easily by adding a specific amount of a specific regulator. A methacrylic resin molding material can be obtained. Such specific regulators include 1,4 (8) -p-menthadiene, 2,6-dimethyl-2,4,6-octatriene, 1,4
There are -p-menthadiene, 1,4-cyclohexadiene, and α-methylstyrene dimer.

Such regulators include the resin raw material (a) and the crosslinking agent (b).
And 0.0001 to 0.5% by weight, preferably 0.0
It can be used in the range of 01 to 0.2% by weight, most preferably 0.005 to 0.1% by weight. When the added amount of the regulator is less than 0.0001% by weight, the regulating effect of the present invention is not exhibited,
If the amount added exceeds 0.5% by weight, the desired polymerization rate cannot be reached.

Originally, an acrylic resin is a resin that is hardly deteriorated by sunlight or the like, but it is common to add a small amount of an ultraviolet absorber in order to further improve durability against light deterioration. As such an ultraviolet absorber, there are benzotriazole type, benzophenone type, and salicylic acid type, all of which are effective. The addition amount thereof may be 0.002 to 1% by weight, preferably 0.005 to 0.5% by weight, based on the total amount of the resin raw material (a) and the crosslinking agent (b). If the added amount of the ultraviolet absorber is less than 0.002% by weight, the effect of preventing photodegradation is not exerted, and even if the added amount exceeds 1% by weight, no further effect can be expected.

According to the method of the present invention, the desired degree of polymerization is the amount of the regulator,
It can be adjusted by selecting the amount of the low temperature active radical polymerization initiator and the polymerization temperature. That is, as the amount of the low temperature active polymerization initiator is reduced, the polymerization rate becomes remarkably slow at low polymerization rates. In addition, the larger the amount of the regulator, the slower the polymerization rate at a lower polymerization rate and the longer the time required to reach it, as compared with the case where the regulator is not used. Also, the lower the polymerization temperature, the lower the polymerization rate and the slower the polymerization rate in the same formulation.

According to the method of the present invention, a gelled polymer having a desired polymerization rate can be obtained by stopping the polymerization reaction by quenching during the polymerization or slowing the polymerization rate by decreasing the polymerization initiator. According to the method (2), a partially crosslinked gel polymer having a desired polymerization rate can be obtained with good reproducibility by a simpler operation, and a partially crosslinked gel polymer having good storage stability can be obtained. .

Incidentally, in the raw material mixture before the formation of the partially crosslinked gel polymer or in the partially crosslinked gel polymer, if necessary, an additive such as a chain transfer agent, a colorant, a filler, or another resin is blended. be able to. For example, as a chain transfer agent,
Examples thereof include alkyl n-alkyl and t-alkyl mercaptan having 6 to 12 carbon atoms, thioglycolic acid, and alkyl thioglycolic acid alkyl ester having 11 to 8 carbon atoms. Further, as the colorant, any ordinary dye or pigment can be used. Further, as the filler, there are glass fiber, calcium carbonate, titanium oxide, particulate carbon, carbon fiber, mica flakes, calcium phosphate, barium sulfate, magnesium oxide, magnesium hydroxide, tin oxide and the like. Further, in order to maintain the storage stability of the partially crosslinked gel-like polymer, a polymerization initiator that could not be added during the production of the partially crosslinked gel-like polymer was molded into the partially crosslinked gel-like polymer. It is also possible to add and knead into the partially crosslinked gel polymer immediately before the reaction. As the polymerization initiator, there are the above-mentioned ones.

The aluminum hydroxide powder used in the present invention is not particularly limited, but the particle size is 200 μm or less, preferably 1
It is at most 00 μm, more preferably at most 50 μm. The amount of aluminum hydroxide powder added to the resin phase is naturally determined by the depth feeling, specific gravity, hardness, strength, heat resistance, price, etc. of the target artificial marble product, but usually based on the total amount of both. 20-80% by weight, preferably 40
~ 75% by weight. The amount of aluminum hydroxide powder added
If it exceeds 80% by weight, the artificial marble product loses the feeling of depth and the properties such as strength are deteriorated, which is not preferable. The amount added
If it is less than 20% by weight, properties such as hardness, heat resistance and flame retardancy are deteriorated, which is not preferable.

There is no particular limitation on the mixing and kneading of the partially crosslinked gelled polymer and the acid or aluminum hydroxide powder, but the mixing and kneading can be performed using, for example, a pressure kneader or a twin screw extruder. In that use, in order to avoid polymerization of the partially crosslinked gel polymer, it is desirable to mix and knead at a temperature as low as possible while cooling.

The methacrylic resin molding material according to the present invention is not sticky,
Since it has shape retention, it can be handled in any shape such as a sheet, rod, block, or pellet.
Furthermore, since it flows by applying a shear stress at room temperature or at an elevated temperature, it is possible to obtain a product having a complicated shape that cannot be achieved by casting polymerization. In particular, when the methacrylic resin molding material is crushed to an average particle size of 5 mm or less, preferably 2 mm or less, only a slight shearing stress is applied when molding is performed by an injection molding method, a compression molding method, or the like. Shows extremely stable fluidity, and can flow into a predetermined shape to obtain a molded product as a mold.

As the injection molding method, the compression molding method, or the transfer molding method applied to the present invention, a known device for each purpose can be applied. Depending on the mold shape of the article to be molded and the physical properties of the molding material used, the operating conditions are 90 to 180 ° C,
Preferably at a temperature of 100-150 ℃, molding pressure is 20-500kg / cm
² , preferably ²⁰ to 250 kg / cm ² , the molding time is 1 to 30 minutes,
Preferably, it can be selected within a range of 2 to 20 minutes.
Since the molding material used in the present invention decreases in volume with polymerization, it is preferable that the mold used has a structure capable of decreasing the volume of the cavity in the thickness direction as the volume shrinks.

(Examples) Next, the present invention will be described in more detail with reference to Examples.

In the examples, the polymer content of the partially crosslinked gel polymer was measured by the following method.

To the Soxhlet extractor, add 1,000 ppm of hydroquinone monomethyl ether and dissolve 150 ml of dichloromethane, and in a cylindrical filter paper for extraction, put 15 g of the gel-like polymer into strips and keep it at 50 ° C. Perform reflux extraction for 20 hours in a water bath, after extraction, put the extract in 1,200 ml of methanol, separate the polymer, combined with the polymer content in the paper, dried under reduced pressure at 55 ℃ until a constant weight, Determine the weight of the polymer.

Further, parts in the examples are parts by weight, and the abbreviations used in the examples are as follows.

V-70 2,2'-Azobis (4-methoxy-2,4-dimethylvaleronitrile), PBD di-t-butyl peroxide, PH-22 2,2-bis (t-butylperoxy) butane, Kaya Ester HTP-65W Di-t-butylperoxy-hexahydroterephthalate, Tinuvin P2- (2'-hydroxy-5'-methyl-phenyl) benzotriazole.

Examples 1 to 6 and Comparative Examples 1 to 20 Polymethylmethacrylate (PMMA) having an average degree of polymerization of 11500
Methyl methacrylate monomer (M
MA) 80 parts and neopentyl glycol dimethacrylate (NPGDM) 20 parts are mixed, and V-7 as a polymerization initiator is mixed with this.
0 0.003 part, PBD 0.3 part, PH-22 0.1 part, Kayaester HTP-65W 0.05 part, 1,4 (8) -p as polymerization regulator
-Mentadiene (0.01 part) and tinuvin P (0.01 part) as an ultraviolet absorber were added and dissolved to prepare a preparation liquid (A). A cell assembled by adding 1 part of an acid of the type shown in Table 1 to 100 parts of the total amount of the components of MMA and NPGDM in this preparation liquid (A) and assembling them with a distance of 10 mm between two glass plates. Inject into 50
Polymerization was carried out at 2.5 ° C. for 2.5 hours to obtain a partially crosslinked gel polymer having a polymer content shown in Table 1. A pressure type kneader D1 was prepared by adding aluminum hydroxide powder in the ratio shown in Table 1 to the total amount of MMA and NPGDM components in this partially crosslinked gel polymer.
-5 (manufactured by Moriyama Seisakusho) was mixed and kneaded at room temperature for 30 minutes to obtain a filler-filled compound. This compound is used in a mold to obtain a plate-shaped molded product with a mold temperature of 130 ° C and an initial pressure of 20 kg / cm.
After pressurizing at ² for 0.5 minutes, increase the pressure to 150 kg / cm ² and carry out 14.5
Press molding was carried out for a minute to obtain a methacrylic composite material molded product having a plate thickness of 5 mm. This molded product was heated in air at 130 ° C for 4 hours, and then measured for colorimetric value (b value), deflection temperature under load, bending strength, and weight increase rate in acetone (23 ° C, 72 hours). The results in the table were obtained.

The colorimetric value (b value) is the b value of the Hunter color system, and the deflection temperature under load is JIS K 7207 (bending stress 18.6 kg / c
m ² ).

Example 7 and Comparative Examples 21 to 22 The preparation liquid (A) obtained in the same manner as in Example 1 was poured into a cell assembled with two glass plates at an interval of 10 mm, and the mixture was heated at 50 ° C. for 2.5 hours. Polymerization was performed to obtain a partially crosslinked gel polymer having a polymer content shown in Table 1. After adding 1 part of an acid of the type shown in Table 1 to 100 parts of the total amount of components of MMA and NPGDM in this partially crosslinked gel-like polymer and thoroughly mixing them in the same kneader as in Example 1, Further, aluminum hydroxide powder in a ratio shown in Table 1 was added to the total amount of MMA and NPGDM components of this partially crosslinked gel polymer, and the mixture was kneaded at room temperature for 30 minutes in the same kneading machine as in Example 1 to obtain a filler. A filling compound was obtained. This compound was press-molded in the same manner as in Example 1 to obtain a methacrylic composite material molded product having a plate thickness of 5 mm. This molded product was heated in air at 130 ° C. for 4 hours and then subjected to the same test as in Example 1,
The results shown in Table 1 were obtained.

Comparative Examples 23 to 28 MMA and N in the prepared liquid (A) obtained in the same manner as in Example 1
100 parts of the total amount of PGDM components was added with 1 part of acid of the type shown in Table 2 or without addition, and injected into a cell assembled with two glass plates with a distance of 10 mm. Polymerization was carried out at 50 ° C. for 2.5 hours to obtain a partially crosslinked gel polymer having a polymer content shown in Table 2. Aluminum hydroxide powder in the ratio shown in Table 2 was added to the total amount of MMA and NPGDM components of this partially crosslinked gel polymer, and the mixture was mixed and kneaded at room temperature for 30 minutes in the same kneading machine as in Example 1 to fill the filler. I got a compound. This compound was press-molded in the same manner as in Example 1 to obtain a methacrylic composite material molded product having a plate thickness of 5 mm. This molded product was heated in air at 130 ° C. for 4 hours and then tested in the same manner as in Example 1, and the results shown in Table 2 were obtained.

Examples 8-12 and Comparative Examples 29-46 MMA monomer containing 17% by weight of PMMA having an average degree of polymerization of 1300 8
0 parts and 20 parts of NPGDM were mixed, and V was added to this as a polymerization initiator.
-70 0.003 parts, PBD 0.3 parts, PH-22 0.1 parts, Kayaester HTP-65W 0.05 parts, 1,4 (8)-as a polymerization regulator
0.01 parts of p-menthadiene and 0.01 parts of tinuvin P as an ultraviolet absorber were added and dissolved to prepare a preparation liquid (B). A cell assembled by adding two kinds of glass plates with an interval of 10 mm by adding the acid of the type and amount shown in Table 3 to 100 parts of the total amount of MMA and NPGDM components in this preparation liquid (B). Injected into
Polymerization was carried out at 50 ° C. for 2.5 hours to obtain a partially crosslinked gel polymer having a polymer content shown in Table 3. With the same kneading machine as in Example 1, 65 parts of aluminum hydroxide powder was added to 35 parts of the total amount of MMA and NPGDM components in this partially crosslinked gel polymer.
The mixture was mixed and kneaded at room temperature for 30 minutes to obtain a filler-filled compound. This compound was press-molded in the same manner as in Example 1 to obtain a methacrylic composite material molded product having a plate thickness of 5 mm. When this molded product was heated in air at 130 ° C. for 4 hours and then tested in the same manner as in Example 1, the results shown in Table 3 were obtained.

Examples 13 to 14 and Comparative Example 47 The preparation liquid (B) obtained in the same manner as in Example 8 was poured into a cell assembled with two glass plates at a distance of 10 mm, and the mixture was heated at 50 ° C. for 2.5 hours. Polymerization was carried out to obtain a partially crosslinked gel polymer having a polymer content shown in Table 3. After adding 1 part of an acid of the type shown in Table 3 to 100 parts of the total amount of components of MMA and NPGDM in this partially crosslinked gel-like polymer and thoroughly kneading with the same kneader as in Example 1, Further, 65 parts of aluminum hydroxide powder was added to 35 parts of the total amount of components of MMA and NPGDM in this partially crosslinked gel polymer, and the same kneader as in Example 1 was used.
The mixture was mixed and kneaded at room temperature for 30 minutes to obtain a filler-filled compound. This compound was press-molded in the same manner as in Example 1 to obtain a methacrylic composite material molded product having a plate thickness of 5 mm. When this molded product was heated in air at 130 ° C. for 4 hours and then tested in the same manner as in Example 1, the results shown in Table 3 were obtained.

Comparative Examples 48 to 52 MMA and N in the preparation liquid (B) obtained in the same manner as in Example 8
One part of the acid of the kind shown in Table 4 was added to 100 parts of the total amount of PGDM component, or no addition was added to a cell assembled with two glass plates with a gap of 10 mm. Polymerization was carried out at 50 ° C. for 2.5 hours to obtain a partially crosslinked gel polymer having a polymer content shown in Table 4. 65 parts of aluminum hydroxide powder was added to 35 parts of the total amount of MMA and NPGDM components of this partially crosslinked gel polymer, and the mixture was kneaded for 30 minutes at room temperature in the same kneader as in Example 1 to obtain a filler-filled compound. It was This compound was press-molded in the same manner as in Example 1 to obtain a methacrylic composite material molded product having a plate thickness of 5 mm. When this molded product was heated in air at 130 ° C. for 4 hours and then tested in the same manner as in Example 1, the results shown in Table 4 were obtained.

Comparative Example 53 When a commercially available artificial marble was tested in the same manner as in Example 1, the results shown in Table 4 were obtained.

(Effects of the Invention) As described above, the present invention provides (A) (a) an alkyl methacrylate monomer and an α, β-ethylenically unsaturated monomer mixture containing an alkyl methacrylate as a main component as a polymer thereof. A resin raw material selected from the group consisting of syrup containing (b) 2 to 250 parts by weight of a crosslinking agent per 100 parts by weight of the resin raw material, (c) 0.1 per 100 parts by weight of a mixture of (a) and (b).
A mixture of 5 to 1.5 parts by weight of an acid selected from the group consisting of formic acid, oxalic acid, chloroacetic acid, malonic acid, citraconic acid, phthalic anhydride, succinic anhydride, fumaric acid, phthalic acid, malic acid and phosphoric acid. Is partially polymerized to increase the content of the polymer by 4 to 65% by weight from the content of the polymer in the mixture within the range in which the total polymer content does not exceed 80% by weight. A compound or a mixture of (c) and a partially crosslinked gel polymer consisting of (a) and (b) 20
-80% by weight and (B) aluminum hydroxide powder 80-20
Since it is a methacrylic resin molding material consisting of wt%,
In addition to being able to obtain a product of any shape in a relatively short time by heating and pressurizing at a relatively high temperature, such as injection molding and compression molding, molding obtained even when heated to a high temperature There is no concern that the article will be colored, and it will not be colored even after post-polymerization. Further, the molding material is not sticky and can be molded into any shape because it has shape-retaining property, and since it crosslinks when molding by the molding method, the heat resistance and solvent resistance of the resulting molded article are obtained. It has high mechanical properties and high mechanical strength.
Therefore, the molded article exhibits excellent effects when used as artificial marble.

Claims (4)

[Claims] 1. A selected from the group consisting of (A) (a) an alkyl methacrylate monomer, an α, β-ethylenically unsaturated monomer mixture containing alkyl methacrylate as a main component, and a syrup containing the polymer. Containing a whole polymer by partially polymerizing a mixture of a resin raw material (b) and (b) a crosslinking agent having at least two (meth) acryloyl groups in the molecule in an amount of 2 to 250 parts by weight per 100 parts by weight of the resin raw material. 20-80% by weight of the partially crosslinked gel polymer in which the content of the polymer is increased by 4 to 65% by weight relative to the content of the polymer in the mixture within the range of not exceeding 80% by weight, (c) ( 0.15 to 1.5 parts by weight of formic acid, oxalic acid, chloroacetic acid, malonic acid, citraconic acid, phthalic anhydride, succinic anhydride, fumaric acid, phthalic acid, malic acid and phosphorus per 100 parts by weight of the total of a) and (b). Selected from the group consisting of acids A methacrylic resin molding material comprising 80 to 20% by weight of an acid and (B) aluminum hydroxide powder. 2. A selected from the group consisting of (A) (a) an alkyl methacrylate monomer, an α, β-ethylenically unsaturated monomer mixture containing alkyl methacrylate as a main component, and a syrup containing the polymer. Containing a whole polymer by partially polymerizing a mixture of a resin raw material (b) and (b) a crosslinking agent having at least two (meth) acryloyl groups in the molecule in an amount of 2 to 250 parts by weight per 100 parts by weight of the resin raw material. 20-80% by weight of the partially crosslinked gel polymer in which the content of the polymer is increased by 4 to 65% by weight relative to the content of the polymer in the mixture within the range of not exceeding 80% by weight, (c) ( 0.15 to 1.5 parts by weight of formic acid, oxalic acid, chloroacetic acid, malonic acid, citraconic acid, phthalic anhydride, succinic anhydride, fumaric acid, phthalic acid, malic acid and phosphorus per 100 parts by weight of the total of a) and (b). Selected from the group consisting of acids A method for producing a molded article, which comprises curing a methacrylic resin molding material comprising 80 to 20% by weight of an acid and (B) aluminum hydroxide powder. 3. The method according to claim ² , wherein the curing is carried out at a temperature of 90 to 180 ° C. and a pressure of 20 to 500 kg / cm ² . 4. The method according to claim 2 or 3, wherein the shaped article is artificial marble.