JPH09202804A - Methacrylic molding compound and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a methacrylic molding compound excellent in handleability and hardly causing mixing of foam in moldings after forming. SOLUTION: Syrup containing 1-30 pts.wt. isotactic methyl methacrylatebased polymer, 0.01-1.9 pts.wt. syndiotactic methyl methacrylatebased polymer, 98.99-68.1 pts.wt. methyl methacrylate based-monomer, a radical initiator and 0-300 pts.wt. inorganic filler, based on 100 pts.wt. total of the polymer and the monomer, is poured into a cell and polymerization is carried out until a residual amount of the methyl methacrylate-based monomer becomes a range of 3 to 29 pts.wt. to provide the objective methacrylic molding compound excellent in handleability and hardly causing mixing of foam in moldings after forming.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a methacrylic molding compound and a method for producing the same.

[0002]

2. Description of the Related Art Unsaturated polyester sheet molding compounds are well known as materials that are used in press molding by adding various fillers to unsaturated polyester and thickening them with magnesium oxide or the like. There is. Although this material is used in various fields such as bathtubs due to its good moldability and productivity, it has problems in chemical stability and durability because it uses unsaturated polyester as a resin.

On the other hand, a methacrylic resin obtained from a methyl methacrylate-based monomer represented by methyl methacrylate is a material excellent in chemical stability and durability. In order to make the best use of this excellent characteristic, methacrylic artificial marble is produced by a cast polymerization method using a filler such as aluminum hydroxide in methyl methacrylate.

Therefore, in order to achieve both good moldability and productivity of the unsaturated polyester molding compound and excellent chemical stability and durability of the methacrylic resin, the methacrylic monomer is mainly used. Several methods have been proposed for producing a methacrylic molding compound as a monomer component.

For example, JP-A-63-68655 discloses a polymerizable composition comprising a monomer mixture containing alkyl methacrylate as a main component and a cross-linking agent having at least two or more (meth) acryloyl groups in the molecule. A methacrylic resin molding material obtained by adding a specific organic acid and aluminum hydroxide powder to a partially crosslinked gel polymer obtained by polymerizing a mixture to a specific polymerization rate has been proposed. In this proposal, a method of increasing the viscosity of the composition is used by utilizing the phenomenon that gelation occurs even at a low polymerization rate by adding a crosslinking agent.

Further, JP-A-5-32720 discloses that an acrylic resin premix having a composition in which resin particles having a specific degree of swelling are added to a monomer containing methyl methacrylate as a main component and an inorganic powder, and A method for producing an acrylic artificial marble using this premix has been proposed.
In this proposal, by adding specific resin fine particles,
Techniques have been taken to increase the viscosity of the mixture.

On the other hand, it is well known that an isotactic methyl methacrylate polymer and a syndiotactic methyl methacrylate polymer form a stereocomplex methyl methacrylate polymer in a methyl methacrylate monomer. The methyl methacrylate monomer solution of this stereocomplex methyl methacrylate polymer exhibits a gel at room temperature.

As a method of utilizing the gelation by this stereocomplex, JP-A-6-287394 discloses that acrylic syrup is composed of 25 to 65% by weight and inorganic powder is 75 to 35% by weight, and the acrylic syrup is the total amount of syrup. The unsaturated monomer component containing methyl methacrylate as a main component is 90 to 30% by weight, and the weight ratio is 1:99 to 99: 1 to the isotactic methyl methacrylate polymer and the syndiotactic methacrylic acid. An acrylic premix has been proposed which uses a solution containing 10 to 70% by weight of a polymer component composed of a methyl polymer. In this proposal, the isotactic methyl methacrylate polymer and the syndiotactic methyl methacrylate polymer prepared in advance were dissolved in the monomer so that both polymers formed a stereocomplex in the obtained syrup. Then, the method of utilizing the phenomenon of thickening is taken.

[0009]

Among the above methods for obtaining a methacrylic molding compound by using various thickening methods, the thickening method using a stereo complex is a molding and curing method as compared with a gelling method using a crosslinking agent. Excellent in fluidity at the time of However,
The method disclosed in JP-A-6-287394, that is, the isotactic methyl methacrylate polymer and the syndiotactic methyl methacrylate polymer are added in a total amount of 10 to 70.
In the method using a syrup in which a part by weight of methyl methacrylate is dissolved and contained, 30 to 90 parts by weight of an unsaturated monomer containing methyl methacrylate as a main component is present in the obtained acrylic premix. . Therefore, in the case of molding under the next heating, especially at 80 ° C. or higher, innumerable bubbles are generated with the progress of polymerization of the remaining monomer, and bubbles are likely to remain in the material shaped in the molding process. There was a flaw.

In view of such circumstances, the present inventor diligently studied a methacrylic molding compound which is excellent in handleability and in which air bubbles are not easily mixed in a molded article after shaping, and as a result, a specific amount of isotactic methyl methacrylate-based compound was obtained. Polymer, syndiotactic methyl methacrylate-based polymer, methyl methacrylate-based monomer, radical polymerization initiator and syrup containing inorganic filler were injected into the cell, and the residual amount of methyl methacrylate-based monomer Is 3 to 2
It was found that a methacrylic molding compound which is excellent in handleability and in which air bubbles are not easily mixed in a molded product after molding is obtained by carrying out polymerization until the content is within a range of 9 parts by weight, thereby completing the present invention. It was

[0011]

That is, the present invention is as follows. (1) Isotactic methyl methacrylate-based polymer 0.1.
01 to 30 parts by weight, syndiotactic methyl methacrylate-based polymer 41 to 96.99 parts by weight, methyl methacrylate-based monomer 3 to 29 parts by weight, radical polymerization initiator and inorganic filler 0 to 300 parts by weight. A methacrylic molding compound containing. (2) Isotactic methyl methacrylate-based polymer 1 to 1 based on 100 parts by weight of the total of the polymer and the monomer.
30 parts by weight, syndiotactic methyl methacrylate polymer 0.01 to 1.9 parts by weight, methyl methacrylate monomer 99.99 to 68.1 parts by weight, radical polymerization initiator and inorganic filler 0 to A syrup containing 300 parts by weight is injected into the cell, and the polymerization is carried out until the residual amount of the methyl methacrylate-based monomer falls within the range of 3 to 29 parts by weight. -Based molding compound manufacturing method. Hereinafter, the present invention will be described in detail.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The isotactic methyl methacrylate polymer in the present invention is a polymer having a methyl methacrylate unit as a main component, and the isotacticity of the methyl methacrylate unit chain is represented by a triad.
It means 0% or more, and includes a copolymer with another monomer which can be copolymerized if necessary.

Other copolymerizable monomers are known. For example, methacrylic acid esters such as ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, acrylic Acrylic acid esters such as 2-ethylhexyl acid and 2-hydroxyethyl acrylate, unsaturated acids such as methacrylic acid and acrylic acid, and monofunctional monomers such as acrylonitrile, methacrylonitrile and styrene. Furthermore, (poly) alkylene glycol di (meth) acrylic acid ester, allyl (meth) acrylic acid ester, trimethylolpropane tri (meth) acrylic acid ester, divinylbenzene, etc., having two or more unsaturated double bonds in the molecule. It is a polyfunctional monomer contained.

The ratio of each monomer unit in the isotactic methyl methacrylate copolymer is 50 to 100 parts by weight of methyl methacrylate, preferably 90 to 100 parts by weight,
0 to 50 parts by weight, preferably 0 to 50 parts by weight of another copolymerizable monomer
To 10 parts by weight. This is because if the amount of the other copolymerizable monomer exceeds 50 parts by weight, it will be difficult to dissolve in the methyl methacrylate monomer. In particular, a monomer having two or more of these copolymerizable functional groups gives a crosslinked product at the time of copolymerization,
Since the obtained polymer becomes insoluble in the solvent, it should be 1 part by weight or less with respect to 1000 parts by weight of the monofunctional monomer.

The isotactic methyl methacrylate polymer can be produced by a conventionally known method, but is obtained by anionic polymerization using a Grignard reagent as a polymerization initiator (JP-A-61-17).
9210, JP-A-61-176617).

The syndiotactic methyl methacrylate polymer in the present invention is a polymer having a methyl methacrylate unit as a main component, and the syndiotacticity of the methyl methacrylate unit chain is 50% or more in triad display. Means a copolymer with the above-mentioned other copolymerizable monomer, if necessary.

The proportion of each monomer unit in the syndiotactic methyl methacrylate copolymer is 50 to 100 parts by weight, preferably 90 to 100 parts by weight of methyl methacrylate, and other copolymerizable monomers. It is 0 to 50 parts by weight, preferably 0 to 10 parts by weight. 5 other copolymerizable monomers
This is because if it exceeds 0 parts by weight, it becomes difficult to dissolve in the methyl methacrylate-based monomer. In particular, these monomers having two or more functional groups capable of copolymerization give a crosslinked product at the time of copolymerization, and the obtained polymer becomes insoluble in a solvent. It should be 1 part by weight or less.

The syndiotactic methyl methacrylate polymer can be produced by a conventionally known method. As the polymerization initiator, those known for the polymerization of monomers containing methyl methacrylate as a main component are used. For example, organic peroxide-based initiators such as benzoyl peroxide, di-t-butyl peroxide, t-butyl peroxy 2-ethylhexaate; 2,2′-azobisisobutyronitrile, 2,2 ′ -Azobis (2, 4
Azo initiators such as dimethylvaleronitrile); known redox initiators in which a peroxide initiator is combined with a reducing compound such as an amine or mercaptan as a main component; and benzoin, benzoin ether , A 1-hydrohexyl phenyl ketone, a benzyl dimethyl ketal, an acyl phosphenoxide, a benzophenone, a Michler's ketone, a thioxanthone, and the like, and a photopolymerization initiator system, if necessary. It can also be obtained by anion polymerization using a complex compound of an organic aluminum compound and an organic phosphorus compound or an organic lanthanide complex (Japanese Patent Publication No. 6-89054 and Japanese Patent Laid-Open No. 263412).

The monomer containing methyl methacrylate as the main component in the present invention is a monomer mixture containing 50% or more of methyl methacrylate and optionally the above-mentioned other copolymerizable monomer. .

The radical polymerization initiator in the present invention means
A conventionally known radical polymerization initiator may be used for the polymerization of the monomer containing methyl methacrylate as a main component. For example, benzoyl peroxide, di-t-butyl peroxide,
Organic peroxide initiators such as t-butylperoxy 2-ethylhexaate; azo such as 2,2′-azobisisobutyronitrile and 2,2′-azobis (2,4-dimethylvaleronitrile) System initiator; a known redox system initiator in which a peroxide initiator and a reducing compound such as amines and mercaptans are combined as a main component;
A photopolymerization initiator system or the like in which a photosensitizer is optionally used in combination with benzoin, benzoin ethers, 1-hydrohexyl phenyl ketone, benzyl dimethyl ketal, acylphosphenoxide, benzophenone, Michler's ketone, thioxanthone and the like.

The inorganic filler referred to in the present invention is not particularly limited as long as it is insoluble in the methyl methacrylate monomer and does not inhibit the polymerization and curing thereof. Examples thereof include powders of aluminum hydroxide, aluminum oxide, calcium carbonate, calcium silicate, calcium aluminate, calcium sulfate, magnesium hydroxide, silica, talc, clay, etc., but are not limited thereto. Of these, aluminum hydroxide, magnesium hydroxide and silica are particularly preferable. The particle size of the inorganic powder is usually 0.1-10.
Those having a thickness of 0 μm, preferably 0.1 to 75 μm are used.

The method for obtaining a syrup by mixing an isotactic methyl methacrylate polymer, a syndiotactic methyl methacrylate polymer, a methyl methacrylate monomer and the like may be a conventionally known method. For example, the isotactic methyl methacrylate-based polymer and the syndiotactic methyl methacrylate-based polymer are simultaneously dissolved in the monomer, or one of them is first dissolved and the other is then dissolved, and then a radical polymerization initiator is added. , Add inorganic filler if necessary,
You may mix. Also, after partially polymerizing the monomer by prepolymerization, the isotactic methyl methacrylate monomer is added and dissolved by heating, and then a radical polymerization initiator and, if necessary, an inorganic filler. May be added and mixed.

The amount of isotactic methyl methacrylate polymer, syndiotactic methyl methacrylate weight product, and methyl methacrylate monomer in the syrup is 100 parts by weight in total of the polymer and the monomer. As a reference, 1 to 30 parts by weight, 0.01 to 1.9 parts by weight, and 98.
99-68.1 parts by weight, preferably 1-
8 parts by weight, 0.01 to 1.9 parts by weight, 99.99 to 9 parts
0.1 parts by weight.

When the amount of the isotactic methyl methacrylate polymer is less than 1 part by weight, the inorganic filler cannot be prevented from settling in the syrup. On the other hand, if the amount exceeds 30 parts by weight, the viscosity of the syrup is too high and air bubbles may be entrained during dissolution with stirring, and further it becomes difficult to inject the solution into the cell. Further, if the amount of the syndiotactic methyl methacrylate polymer is less than 0.01 part by weight, the inorganic filler cannot be prevented from settling in the syrup. On the other hand, if it exceeds 1.9 parts by weight, the viscosity of the syrup is too high, air bubbles may be entrained during stirring and dissolution, and it becomes difficult to inject the solution into the cell.

When the amount of the isotactic methyl methacrylate-based polymer and the syndiotactic methyl methacrylate-based polymer in the syrup is the above amount, the syrup has an apparent appearance under high shear in the range of 0 to 40 ° C. The viscosity is lower than the apparent viscosity under low shear. That is, the thixotropy property in which the apparent viscosity of the solution decreases with the stirring speed is obtained.

In the syrup having thixotropic properties,
The dispersed inorganic filler can be prevented from settling, and liquid can be easily injected into the cell. When the inorganic filler settles in the syrup, unevenness in the concentration of the inorganic filler occurs in the obtained molding compound, and unevenness in the concentration of the inorganic filler occurs in the molded product obtained after heat molding, which impairs the appearance.

When it is difficult to inject the liquid because of its high viscosity, heating it to a temperature at which the radical polymerization initiator does not decompose,
The viscosity drops sharply and it becomes possible to inject liquid.

When the radical polymerization initiator and the inorganic filler are dissolved and dispersed in the solution of the above-mentioned polymer and monomer, the apparent viscosity is lowered by increasing the stirring speed, so that a uniform slurry can be easily formed. Can be obtained. When the viscosity is high and stirring is difficult, the viscosity is rapidly reduced by heating, and a uniform slurry can be obtained. The temperature at which the formed stereo complex gel is sol.
It may be higher than the gel transition temperature. Generally, it may be heated to 40 to 80 ° C, preferably 40 to 70 ° C.

The radical polymerization initiator is used in an optimum amount depending on its type, molding and curing conditions, or desired curing temperature and time. The total amount of the polymer and the monomer is 100 parts by weight. On the other hand, it is 0.001 to 4 parts by weight. It is preferably 0.001 to 0.4 part by weight.

The inorganic filler is optionally added in accordance with the performance required for the obtained methacrylic molding compound and the molded product obtained by heating and curing the methacrylic molding compound. It is added when the molding obtained by using the methacrylic molding compound has a marble appearance, and the addition amount is 1 to 100 parts by weight of the total amount of the polymer and the monomer in the syrup. It is 300 parts by weight. If the amount of the inorganic filler is less than 1 part by weight, the required performance is not satisfied, and if it exceeds 300 parts by weight, the dispersion in the syrup becomes difficult.

If necessary, an antioxidant, an ultraviolet absorber, a chain transfer agent, a dye or a pigment can be added to the syrup.

The above syrup was poured into a cell, and the residual amount of the methyl methacrylate-based monomer was in the range of 3 to 29 parts by weight, based on the total 100 parts by weight of the polymer and the monomer in the syrup. Polymerize until complete.

The structure of the cell is not particularly limited. For example, 2 made of glass, stainless steel, etc.
It is composed of a single plate and a sealing material such as soft vinyl chloride, and the batch type is fixed by a clamp. A continuous cell can also be used. In addition, it is preferable to stick a film made of a material which is hard to be exposed to the monomer such as polyester, polyethylene, or polypropylene on the inner surface of the cell, because release becomes easy at the time of release. Further, it is also possible to apply various release agents to the inner surface of the cell to perform release treatment.

After pouring into the cell, polymerization is carried out by heating or irradiation with light. As a heating method, a known method, for example, hot air, hot water, or a heat source such as an infrared heater is used. As the light irradiation method, visible light, ultraviolet light, or the like may be irradiated with a high-pressure mercury lamp, a metal halide lamp, a low-wavelength UV lamp, a xenon lamp, a Kuptarc lamp, or the like. These methods, the type of polymerization initiator used,
A suitable one may be used depending on the amount and the like, and is not particularly limited.

By carrying out the polymerization until the residual amount of the monomer falls within the range of 3 to 29 parts by weight, it is possible to obtain a molding compound having no stickiness and having excellent handleability. When the residual amount of the monomer is less than 3 parts by weight, the obtained polymer becomes hard and brittle, and the fluidity at the molding temperature and the moldability, which should be provided as a molding compound, are insufficient, which is not preferable. When the residual amount of the monomer exceeds 29 parts by weight, the obtained molding compound is
Bubbles are generated during heat molding, which causes defects in the molded product.

In order to set the residual amount of the monomer within the range of 3 to 29 parts by weight, the radical polymerization initiator to be used is polymerized for a suitable polymerization time at a 10-hour half-life temperature or 10 to 50 ° C. lower. You can control it by doing. In selecting the temperature and time, the conditions can be determined by several trials. As a method for obtaining the residual amount of the monomer, there are known methods such as gas chromatography and titration method.

Polymerization was carried out until the residual amount of the monomer was within the range of 3 to 29 parts by weight based on 100 parts by weight of the total amount of the polymer and the monomer, and then the cell was opened. Obtain a methacrylic molding compound.

[0038]

EFFECTS OF THE INVENTION The methacrylic molding compound of the present invention is excellent in handleability, and a molded body in which air bubbles are not easily mixed even after shaping is obtained.

[0039]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. In the examples, the relationship between the viscosity and the stirring speed was obtained from the viscosities at 6 rpm and 60 rpm with a B-type viscometer (DVM-B2 manufactured by Tokimec Co., Ltd.). The amount of residual monomer is
After extraction with acetone, gas chromatography based on methyl isobutyl ketone (Shimadzu Corporation, G
C-14A).

Example 1 Isotopic methyl methacrylate syndiotactic methyl methacrylate polymer (number average molecular weight 32,900, isotacticity) obtained by anionic polymerization was added to 93.8 parts by weight of a methyl methacrylate monomer. 99%)
5 parts by weight and syndiotactic methyl methacrylate resin obtained by radical polymerization (methyl methacrylate unit 98% by weight, methyl acrylate unit 2% by weight, number average molecular weight 80,000, syndiotacticity 58%) 1 .2
Part by weight was heated to 60 ° C. and dissolved with stirring. The viscosity of the obtained solution was measured with a B-type viscometer.

To 100 parts by weight of the obtained solution, 2,2'-
Azobis (2,4-dimethylvaleronitrile) 0.25
By weight, 150 parts by weight of aluminum hydroxide having a particle diameter of 8 μm was added and dissolved and dispersed so as to be uniform. After deaeration of the obtained syrup, it was poured into a cell constituted by two glass plates and a vinyl chloride resin gasket so that the gap between the glass plates was 3 mm, and the polymerization was carried out at 30 ° C. for 8 hours. ,
It was cooled and the polymer was taken out.

The obtained molding compound was cut with a cutter and the cross section was observed. Further, the amount of residual methyl methacrylate monomer was quantified by gas chromatography. The obtained molding compound is 70
A pressure of kgf / cm ² was applied, and at 90 ° C., it was molded into a boat shape. The appearance of the obtained molded product was observed. Table 1 shows the results
Shown in

Example 2 The same procedure as in Example 1 was carried out except that the polymerization time was 16 hours and the molding was carried out at 140 ° C. into a boat shape. The results are shown in Table 1.

Comparative Example 1 The procedure of Example 1 was repeated except that the polymerization time was 4 hours. The results are shown in Table 1.

Comparative Example 2 Except that a syrup in which 5 parts by weight of isotactic methyl methacrylate polymer was dissolved was used without adding syndiotactic methyl methacrylate polymer to 95 parts by weight of methyl methacrylate monomer. The same procedure as in Example 1 was performed. The results are shown in Table 1.

[0046]

[Table 1] *: Dispersibility of aluminum hydroxide in the compound

Claims (3)

[Claims] 1. An isotactic methyl methacrylate-based polymer of 0.01 to 30 parts by weight and a syndiotactic methyl methacrylate-based polymer of 41 to 96. based on 100 parts by weight of the total of the polymer and the monomer. A methacrylic molding compound containing 99 parts by weight, a methyl methacrylate monomer 3 to 29 parts by weight, a radical polymerization initiator and an inorganic filler 0 to 300 parts by weight. 2. Isotactic methyl methacrylate-based polymer 1 to 30 parts by weight, syndiotactic methyl methacrylate-based polymer 0.01 to 1. Based on 100 parts by weight of the total of the polymer and the monomer. A syrup containing 9 parts by weight, 99.99 to 68.1 parts by weight of a methyl methacrylate monomer, 0 to 300 parts by weight of a radical polymerization initiator and an inorganic filler was injected into a cell to prepare a methyl methacrylate monomer. The method for producing a methacrylic molding compound according to claim 1, wherein the polymerization is carried out until the remaining amount of the monomer is in the range of 3 to 29 parts by weight. 3. The isotactic methyl methacrylate-based polymer is 1 to 8 parts by weight and the syndiotactic methyl methacrylate-based polymer is 0.01, based on 100 parts by weight of the total of the polymer and the monomer component. 3. The production according to claim 2, wherein a syrup containing 1 to 1.9 parts by weight, methyl methacrylate monomer 99.99 to 90.1 parts by weight, a radical polymerization initiator and an inorganic filler 0 to 300 parts by weight is used. Method.