JPH10218914A - Production of resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition desirable for artificial marble having good falling ball impact strength, not undergoing discoloration and having beautiful appearance and good heat resistance, chemical resistance and weatherability by forming a mixture obtained by mixing a monomer based on a methacrylic ester with a methacrylic ester polymer and an inorganic filler into a clayish or solid matter and kneading the matter at a specified temperature. SOLUTION: The monomer based on a methacrylic ester means methacrylic ester itself or a mixture comprising a methacrylic ester and other unsaturated monomers copolymerizable therewith and having a methacrylic ester content of 70wt.% or above. A 5-18C methacrylic ester is used for this purpose. The other unsaturated monomers include acrylic esters, aromatic vinyl compounds, polyfunctional unsaturated monomers, etc. The methacrylic ester polymer is obtained by polymerizing a monomer based on a methacrylic ester. The inorganic filler used is aluminum hydroxide. The clayish matter is kneaded at 65-120 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a resin composition, and more particularly, to a method for producing an acrylic resin composition containing an inorganic filler, which is useful as a molding material for artificial marble and the like.

[0002]

2. Description of the Related Art Acrylic artificial marble in which an acrylic resin is filled with an inorganic filler is used for kitchen tops, various counter tops, vanities, shower trays, flooring materials, wall materials, and the like, utilizing its beautiful appearance and excellent characteristics. Widely used for partition boards. As a method for producing an acrylic artificial marble, for example, a casting method proposed in Japanese Patent Publication No. 50-22586 is known. Generally, the casting method uses 10 to 30% of methacrylates.
After preliminarily polymerizing, or blending and mixing an inorganic filler in a so-called syrup in which a methacrylic acid ester polymer is dissolved in methacrylic esters, and then injecting the mixture into a gap in a mold, the mixture is mixed. Is cured under normal pressure to obtain an artificial marble product. However, this casting method requires a long curing time and is low in productivity, and in addition to having a large amount of monomer components, giving off a monomer odor, and inconvenient handling due to stickiness caused by syrup at the time of injection. It is difficult to maintain a good working environment because it is easy to occur.

As one method for avoiding such a problem, for example, a press molding method as proposed in Japanese Patent Publication No. 5-13899 has been studied. In this method, a monomer containing 20% by weight or more of a polyfunctional (meth) acrylate as an essential component, a methacrylic resin powder, a curing agent, an inorganic filler, and the like are kneaded at room temperature or at a temperature lower than the curing temperature. The molding material obtained by aging is molded and cured by heating under pressure. However, according to this method, although a considerable improvement in productivity is achieved as compared with the conventional casting method or press molding method, mixing can be performed only at room temperature or at a temperature lower than the curing temperature because the curing agent is added and kneaded. In addition, since the aging process is required, the productivity is still low, and if the productivity is to be improved, the components cannot be sufficiently mixed, and the falling strength of the molded product is low. Then, there was a problem that the resin composition was colored.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an acrylic artificial marble having good falling ball impact strength, no discoloration, good beauty, heat resistance, chemical resistance and weather resistance. An object of the present invention is to provide a method for producing a resin composition suitable for a press molding method or the like.

[0005]

According to the present invention, there is provided a first step of mixing a monomer mainly composed of methacrylic acid ester, a methacrylic acid ester-based polymer and an inorganic filler. A method for producing a resin composition mainly comprising a second step of converting the mixture obtained in step 2 into a clay-like or solid state, and a third step of kneading the clay-like or solid state obtained in the second step at 65 to 120 ° C. Achieved by

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The methacrylate-based monomer used in the present invention refers to a methacrylate alone or a monomer mixture of methacrylate-based monomer and another unsaturated monomer copolymerizable therewith. It is desirable that the content of methacrylic acid ester is 50% by weight or more, preferably 70% by weight or more.

[0007] Methacrylic acid esters include those having 5 carbon atoms.
Methacrylates of about 18 to 18 are preferably used, and specific examples include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, lauryl methacrylate, and the like. . These are used alone or in combination of two or more. Among them, methyl methacrylate is particularly preferably used.

The other unsaturated monomer copolymerizable with the methacrylic acid ester is not particularly limited.
For example, acrylic esters such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, and lauryl acrylate; aromatic vinyl compounds such as styrene and α-methylstyrene; acrylonitrile, methacrylonitrile And unsaturated monomers such as acrylamide, vinyl acetate, vinyl chloride, acrylic acid, and methacrylic acid; and various monomers such as ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, neopentyl glycol dimethacrylate, and trimethylolpropane trimethacrylate. Functional unsaturated monomers and the like. One or more of these monomers may be used.

As the methacrylate polymer used in the present invention, any methacrylate polymer which can be dissolved in the above-mentioned methacrylate-based monomer can be used without particular limitation. Preferred examples include those obtained by polymerizing the above-mentioned methacrylate-based monomers, or those obtained by polymerizing one or more of these monomers and other polymerizable monomers. Can be.

As the methacrylic acid ester-based polymer, a polymer obtained by polymerizing the above-mentioned monomer mainly composed of methacrylic acid ester by an emulsion polymerization method, a suspension polymerization method, a bulk polymerization method or the like is usually used. The methacrylic acid ester-based polymer obtained by such a polymerization method is preferably in the form of particles from the viewpoint of mixing solubility with the monomer, and the particle diameter is large enough to be used for mixing and kneading described below. Although it is not particularly limited as long as it is as small as possible, it is usually 5 mm or less, more preferably about 0.1 to 2 mm. The methacrylic acid ester is usually in the form of beads, pellets, pulverized powder, or the like, and is preferably in the form of beads from the viewpoint of solubility, handleability, and the like. The weight average molecular weight of the methacrylate polymer is such that it can be dissolved in the monomer, and is usually 50,000 to 600,000, preferably 7 to 30.
And more preferably in the range of 100,000 to 200,000. Also,
The blending ratio of the methacrylate polymer is usually 50 to 400 parts by weight, preferably 80 to 300 parts by weight, based on 100 parts by weight of the monomer mainly composed of methacrylate.
Parts by weight. Further, a part of the methacrylate polymer can be used in place of, for example, an acrylic partially crosslinked gel polymer whose production method is described in JP-A-60-202128.

Examples of the inorganic filler used in the present invention include aluminum hydroxide, magnesium hydroxide, alumina, magnesium oxide, calcium carbonate, silica, mica, glass beads and the like. There is no particular limitation unless it impairs. Among these inorganic fillers, aluminum hydroxide, magnesium hydroxide, silica, and glass beads are preferred, and aluminum hydroxide is particularly preferably used, from the viewpoint of high-grade feeling, stain resistance, and processing performance of acrylic artificial marble. . The particle size of the inorganic filler is usually 0.1 to 100.
μm is used, more preferably 1 to 30 μm.
Inorganic fillers that have been surface-treated, such as silane treatment, are also preferably used. The mixing ratio of the inorganic filler is usually 50 parts by weight based on 100 parts by weight of the monomer mainly composed of methacrylic acid ester.
To 500 parts by weight, preferably 100 to 400 parts by weight.

In the present invention, first, in a first step, a monomer mainly composed of methacrylate, a methacrylate polymer and an inorganic filler are mixed.
The method of mixing is not particularly limited, and a method such as stirring in a mixing tank at room temperature or mixing in a kneader having an improved mixing function is preferably employed. The mixing time varies depending on the method and conditions, but usually 1 minute or more is employed. The mixing usually results in a slurry-like form, but if the mixing time is long, it changes to a clay-like state, so that the first step and the second step can be performed continuously.

Next, in a second step, the usually slurry mixture obtained in the first step is made into a clay or solid. Clay or solid method, the temperature is 120 ℃
There is no particular limitation except that it is not set higher, and for example, it can be achieved by continuing stirring and mixing after the first step or leaving the mixture to stand still. The time required for making the clay or solid varies depending on the conditions of the second step, but is generally about 4 minutes to 1 day. In this step, the methacrylate polymer is not completely dissolved in the monomer, but is partially dissolved.

In the third step, the clay-like or solid composition obtained in the second step is kneaded at 65 to 120 ° C., preferably 70 to 100 ° C., thereby dissolving the methacrylate polymer. Is efficiently completed.
If the temperature is lower than 65 ° C., the polymer may remain without being completely dissolved, and if the kneading temperature is low and the kneading time is long, the kneaded material may be colored, and the molded product such as artificial marble obtained by molding may be beautiful. Tends to be inferior. On the other hand, kneading at a temperature higher than 120 ° C. is not preferable because polymerization of a monomer mainly composed of methacrylic acid ester or decomposition of the polymer tend to occur. In order to knead at the above temperature, the kneading machine usually has a temperature adjusting portion such as a jacket portion, and the kneading portion is heated to a predetermined temperature by using an electric heater, steam, hot or cooling water, oil for adjusting temperature, or the like. Preferably, it can be adjusted as follows.

The kneading method is not particularly limited as long as the effects of the present invention can be realized. As the kneading machine, a batch type twin screw kneader, a continuous type twin screw kneader or the like is preferably used.

As a batch type twin-screw kneader, for example, two mixing blades such as a Z type, an H type, a finish tail type and a dispersion type placed in parallel in a trough rotate in opposite directions to each other. A double-arm kneader for shearing, compressing, stretching and kneading the mixture; a double-arm kneader provided with a mechanical pressure cover, and the pressure cover is compressed by air pressure, liquid pressure, etc., so that the kneaded material and the trough wall surface are compressed. Or, a kneader in which a strong shear force is generated between kneaded materials to enhance kneading; a raw material is charged into a closed mixing chamber, and two rotors incorporated in the mixing chamber rotate in opposite directions to each other to form a chamber. An internal mixer or the like is used in which a strong shearing force is applied between the wall surface and the rotor or between the rotors to perform kneading.

As a continuous twin-screw kneader, raw materials are continuously fed into a kneading section by a feed screw section arranged in a raw material supply section, and are kneaded in a kneading section in which a rotor or a kneading desk is arranged. Is continuously discharged, and a twin-screw kneader, a container kneader or the like is preferably employed.

The kneading time in the third step varies depending on the type of kneader, the number of revolutions and the kneading temperature, but is generally from 2 minutes to 1 minute.
Zero minutes is employed. As the kneader, a continuous twin-screw kneader is particularly preferably used in terms of mass productivity.

According to the present invention, a colorless, clay-like resin composition having substantially no change in viscosity can be produced in a short time. The phrase "substantially no change in viscosity" means that there is no change in viscosity within 24 hours, or even if there is no change in viscosity within 5%, it is evaluated by pressure spreadability. The change in viscosity occurs, for example, when the methacrylate polymer remains undissolved.
If there is a change in the viscosity, the suitable molding conditions are not constant, and the molded product tends to have poor appearance, which is not preferable.

In the method of the present invention, the second step of converting the slurry into a clay-like or solid state is necessary for improving the kneading efficiency of the third step. Is reduced.

A curing agent is usually added to the resin composition produced by the method of the present invention for thermosetting.
Generally, the resin composition is charged into the resin composition after cooling or during the cooling process. The curing agent is not particularly limited, and is usually benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide, bis (4-t-butylcyclohexyl) dicarbonate, 1,1-di-t-butyl which is generally used for radical polymerization. Organic peroxides such as peroxy-3,3,5-trimethylcyclohexane; azo compounds such as azobisisobutyronitrile and 2,2-azobis (2,4-dimethylvaleronitrile) are used. These curing agents are used alone or in combination of two or more. The mixing ratio of the curing agent is usually 1 to 10 parts by weight, preferably 3 to 7 parts by weight, based on 100 parts by weight of the monomer mainly composed of methacrylic acid ester. When the curing agent is a solid, it is preferable to dissolve it in a small amount of monomer and to add it easily, because uniform mixing can be easily achieved.

In the method of the present invention, fiber materials such as glass fibers, aramid fibers, carbon fibers, etc., various patterning materials, coloring Agents, coupling agents, light stabilizers,
Additives such as antioxidants, release agents, polymerization regulators, and defoamers can be used in combination.

The resin composition obtained by the method of the present invention can be shaped and cured by a method such as compression molding, injection molding, or extrusion molding to obtain a molded product, particularly a marble-like product. As the molding conditions of the compression molding, usually, the molding pressure is 10 to 200 kg / cm ² and the molding temperature is 80 to 180.
℃, molding time is about 10 minutes.

[0024]

The present invention will be described below in more detail with reference to examples. The examples show one embodiment of the present invention, and the present invention is not limited to these examples. In addition, the pressure spreadability and falling ball impact strength were measured and measured by the following methods.
evaluated.

(Measurement of Extensibility under Pressure)
0 g is weighed and heated by a press machine heated to a hot platen temperature of 50 ° C.
Upper heating plate / 50 μm thick nylon film / resin composition /
A 50 μm-thick nylon film / lower heating plate is applied and a total load of 3 tons is applied for 60 seconds, and the spread area of the resin composition is measured with an area meter [Hayashi Electric Co., Ltd .: Automatic area meter AAM-
No. 8].

(Evaluation of pressurization spreadability) According to the above method, pressurization immediately after kneading of the resin composition and after leaving the resin composition in a nylon film bag having a thickness of 50 μm for about 1 day at room temperature. Measure the spread area by heating (press ductility),
The obtained resin composition was evaluated for any change in viscosity due to standing at room temperature for one day (if no change was observed, it was evaluated that aging was not necessary). Further, the film-shaped resin composition stretched between the nylon films was visually observed, and the presence or absence of the undissolved polymer was examined.

(Measurement of impact strength of falling ball) JIS K72
The 50% breaking energy was determined by the method of No. 11, and this was defined as falling ball impact strength. Falling ball impact test equipment is JIS K
The steel ball used was JIS ball type 2 (1 ± 0.05 kg, diameter of about 63 mm). The test piece size is a square of 150 ± 1 mm on one side.

Example 1 1.425 parts by weight of methyl methacrylate, 1.075 parts by weight of neopentyl glycol dimethacrylate, 6.85 of silane-treated aluminum hydroxide having an average particle size of 8 μm
Parts by weight and methacrylic resin beads [a copolymer of 98% by weight of methyl methacrylate and 2% by weight of methyl acrylate,
Weight average molecular weight 110000, average particle diameter 0.3 mm]
2.625 parts by weight were put into a stirring tank equipped with stirring blades,
Stirred at room temperature for 5 minutes. The obtained slurry was allowed to stand at room temperature for one day to solidify (sticky solid). After making this into a small lump, this was heated in a jacket with a heating medium of 90 ° C. and a continuous twin-screw kneader [Kurimoto Iron Works Ltd .: S4 type KRC kneader, caliber 100φ, L / L
D = 10, rotation speed 100 rpm], and kneaded. As a result, a clay-like resin composition having a production rate of 200 kg / hour and a temperature of 81 ° C. was obtained. After cooling the resin composition to 50 ° C., 13 kg of the resin composition and 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane 5
0g is a roll type pressure kneader [Moriyama Seisakusho Co., Ltd., D
-10-20 type, mixing volume 10 liter]
Mix for minutes. The pressure spreadability is 295 cm ² , 24
There was no change over time.

860 g of the obtained resin composition was placed in a 250 mm
× 200 mm into a flat mold, molding temperature 130
C., pressurized resin pressure 100 kgf / cm ² , pressurized time 12 min.
A flat plate of acrylic artificial marble of 0 mm × 10 mm was obtained.
The obtained molded article had no molding defects such as cracks, no discoloration, and had an extremely beautiful surface. 150mm
When a sample of 150 mm square was cut out and the falling ball impact strength was measured, it had a high falling ball impact strength of 3.7 J.
It was a highly practical molded product.

Comparative Example 1 1.425 kg of methyl methacrylate, 1.075 kg of neopentyl glycol dimethacrylate, average particle size of 8
6.85 kg of silane-treated aluminum hydroxide
And 2.62 methacrylic resin beads similar to those in Example 1.
5 kg was placed in a stirring tank equipped with stirring blades and stirred at room temperature for 5 minutes. The obtained slurry was allowed to stand at room temperature for one day to solidify (sticky solid). 13 kg of this solid and 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane 50
g into a roll type pressure kneader [Moriyama Seisakusho Co., Ltd., D-
10-20 type, mixing volume 10 liter]
Mix for 3 minutes at ° C. 860 g of the obtained resin composition was added to 2
It is put into a 50 mm × 200 mm flat plate mold, and is subjected to pressure molding under a molding temperature of 130 ° C., a pressure resin pressure of 100 kgf / cm ² , and a pressure time of 12 minutes, and 250 m
An acrylic artificial marble flat plate of mx 200 mm x 10 mm was obtained. The resulting molded article had undissolved resin and was inferior in appearance. Although no discoloration was observed in the obtained molded product, a 150 mm × 150 mm square sample was cut out, and the falling ball impact strength was measured to be as low as 1.4 J.

Comparative Example 2 In Example 1, methyl methacrylate, neopentyl glycol dimethacrylate, silane-treated aluminum hydroxide having an average particle diameter of 8 μm and methacrylic resin beads were directly supplied to a continuous twin-screw kneader. When kneading, the production amount of 100 kg / hour was the limit. In the case of supplying more than this, only a discharged material containing a part of the methacrylic resin beads in an undissolved state was obtained.

[0032]

The method of the present invention is a method in which a monomer component, a polymer component, and an inorganic filler are mixed and solidified and kneaded under heating. This significantly improves the productivity of the kneading equipment. It is suitable as a method for producing a molding material for artificial marble and the like, since it is possible and the strength of the molded product of the produced resin composition is high.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C08L 33/06 C08L 33/06 // (C04B 26/06 14:36 16:04) 111: 54 (72) Inventor Kazuhiko Ma 2-28 Kurashiki-cho, Nakajo-cho, Kitakanbara-gun, Niigata Prefecture Kuraray Co., Ltd.

Claims (1)

[Claims] 1. A first step of mixing a monomer mainly composed of methacrylic acid ester, a methacrylic acid ester-based polymer and an inorganic filler, and a second step of converting the mixture obtained in the first step into a clay-like or solid form. A method for producing a resin composition, which mainly comprises a third step of kneading the clay-like or solid substance obtained in the step and the second step at 65 to 120 ° C.