JP3568295B2 - Method for producing plate polymer - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a platy polymer.
[0002]
[Prior art]
As a method for producing a plate-like polymer by casting polymerization, a polymerizable compound or a partially polymerized syrup is molded into a mold (cell) composed of a pair of inorganic glass or metal plates, four sides of which are sealed with a gasket such as polyvinyl chloride. Is injected and polymerized in a mold to obtain a plate-like polymer, and two endless metal rotating belts arranged so as to face each other up and down and sandwiched between the belts on both sides. A continuous plate manufacturing method in which a syrup of a polymerizable compound is continuously injected into a mold constituted by sealing with a gasket and polymerized to obtain a plate-like polymer (for example, Japanese Patent Publication Nos. 46-41602 and 47-33495). Gazettes, JP-B-47-33497, and JP-B-47-34815).
[0003]
By the way, when a plate-like polymer is produced by a radical polymerization method using a mold composed of a metal plate, a large amount of monomer radicals, polymer radicals, and initiator radicals are used as a support for the polymer. Activates surface ions (especially transition metals such as iron ions), and the metal ions cause a redox reaction (catalysis) with the polymerization system, adversely affecting the physical properties of the polymer (with contamination of the metal ions) Fine polymerization spots occur in the polymer, and the degree of polymerization and the molecular weight change locally). That is, contamination by a small amount of metal ions occurs from the surface layer of the metal plate, and non-uniform polymerization is induced in the surface layer of the polymer in contact with the metal plate. The residual stress is frozen as a residual stress, and when the obtained plate-like polymer is heated and molded later, the residual stress that is unevenly frozen on the surface layer is released, so that the surface layer of the plate-like polymer is released. There is a disadvantage that fine deformation is caused on the surface and wrinkles (wrinkles) are generated.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to prevent contamination by metal ions from a metal plate surface layer in a polymerization stage, to prevent generation of wrinkles due to fine deformation of a plate-shaped polymer surface layer even in a heat molding process, to achieve stable and high quality. An object of the present invention is to provide a method for producing an excellent plate polymer.
[0005]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that the above object can be achieved by using a metal plate constituting a mold that has been heat-treated under specific conditions. Invented the invention. That is, in the present invention, in a method of injecting a polymerization raw material into a mold composed of a metal plate and polymerizing to produce a plate-like polymer, the metal plate constituting the mold was heat-treated at a temperature of 300 ° C. or more. A method for producing a plate-like polymer, characterized by using a polymer.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Examples of the metal plate used in the present invention include steel and stainless steel (stainless steel), but stainless steel is preferably used. The thickness of the metal plate cannot be unequivocally determined because it varies depending on the production method of the plate polymer, but is generally in the range of 0.5 to 10 mm.
[0007]
As the heat treatment means for the metal plate, for example, there are various methods such as a method using a heating resistor, a method using a high-frequency electromagnetic field, and a method using a high-power laser. However, in order to avoid thermal deformation of the entire metal plate, it is desirable to heat-treat only the extremely surface portion (about 10 nm) where the metal plate is in contact with the polymer in a short time.
[0008]
The heat treatment temperature of the metal plate is preferably 300 ° C. or higher, more preferably 400 ° C. or higher and 600 ° C. or lower. If the heat treatment temperature is lower than 300 ° C., the desired effects of the present invention cannot be obtained. On the other hand, if the heat treatment temperature is higher than 600 ° C., the effect can be expected, but it causes deterioration of the metal and causes thermal deformation of the metal plate. Is not preferred.
[0009]
The heat treatment atmosphere is not particularly limited, and the heat treatment can be performed in an atmosphere such as air, nitrogen, or argon.
The heating time is not particularly limited, but is usually in the range of 1 to 120 minutes.
[0010]
In the method of the present invention, as the gasket used to construct the mold, a string made of plastic is used, but when a monomer having a low viscosity is used as a polymerization raw material, the cross section is square or It is preferable to use a rectangular gasket to prevent liquid leakage. When a partially polymerized syrup is used, a hollow pipe-shaped gasket can be used because of its high viscosity. Examples of the material of the gasket include plastics such as soft polyvinyl chloride and polyethylene, and it is preferable to use soft polyvinyl chloride having excellent flexibility.
[0011]
The plate-like polymer of the present invention is obtained by using two sheets of the above-mentioned heat-treated metal plate, injecting a polymerization raw material into a mold formed by sealing the periphery thereof with a gasket, and performing polymerization.
[0012]
Examples of the polymerizable compound used as a polymerization raw material in the method of the present invention include one or a mixture of two or more selected from a monoethylenically unsaturated compound and a polyfunctional polymerizable compound. These polymerizable compounds can also be used as a monomer-polymer mixture (syrup) obtained by dissolving or partially polymerizing a polymer in these monomers as long as the polymerization raw material does not lose fluidity.
[0013]
As the monoethylenically unsaturated compound, for example, methyl methacrylate, methacrylates such as ethyl methacrylate, styrene, aromatic vinyls such as α-methylstyrene and the like are used, or the main component amount of these compounds and methyl acrylate, ethyl Mixtures with alkyl acrylates such as acrylates and acrylonitrile are also used.
[0014]
Examples of the polyfunctional polymerizable compound include ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, diallyl methacrylate, diallyl phthalate, and diethylene glycol bisallyl carbonate. The present invention is particularly advantageous for obtaining a plate-like polymer of methyl methacrylate and a plate-like copolymer of methyl methacrylate of a main component amount and a copolymerizable comonomer.
[0015]
A polymerization initiator is mixed with the polymerization raw material. As the polymerization initiator, for example, a polymerization initiator that generates free radicals such as azobisisobutyronitrile, azobisdimethylvaleronitrile, benzoyl peroxide, and lauroyl peroxide can be used. Further, a redox polymerization initiator, for example, a combination of a peroxide and an amine can be used.
[0016]
Further, various additives that do not inhibit the polymerization, such as stabilizers, plasticizers, polymerization regulators, fillers, dyes, pigments, release agents, and the like, can also be added to the polymerization raw material.
[0017]
The polymerization temperature for obtaining the plate-like polymer is not unequivocally determined by the type of polymerization initiator used, but is preferably in the range of 50 to 150 ° C.
[0018]
The heating method of the polymerization is not particularly limited, and can be performed by a known method, for example, water bath heating, infrared heating, hot air heating, or a combination thereof.
[0019]
The thickness of the plate-like polymer obtained by the present invention is not particularly limited, and one having a thickness of 0.5 to 20 mm can be obtained.
[0020]
Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.
[0021]
【Example】
A pair of two single-side polished stainless steel plates (hereinafter abbreviated as SUS plates) (dimensions: 15 cm × 15 cm × 2 mm (thickness)) are placed in a closed heating furnace, and the temperature is set to 200 ° C. to 600 ° C. Heat treatment was performed for 30 minutes at a temperature of ° C.
[0022]
Then, using the heat-treated SUS plate as a template, the polished surface is opposed to the inner surface, and the periphery thereof is sealed with a gasket (a soft polyvinyl chloride hollow body having an outer diameter of 5 mmφ) to mold a mold. Formed. Then, into the mold, a polymerization raw material obtained by dissolving 100 ppm of azobisdimethylvaleronitrile in 100 g of a partial polymer of methyl methacrylate (polymerization ratio: about 20%, viscosity: 1000 centipoise at 20 ° C.) was injected. Polymerization was performed in a water bath for 90 minutes to obtain a methacrylic resin plate having a thickness of 3 mm. Next, the deframed heat-treated SUS plate was repeatedly used as a template to produce a methacrylic resin plate having a thickness of 3 mm.
[0023]
FIG. 2 shows the relationship between the haze value of the solvent haze of the obtained methacrylic resin plate and the number of times of repetitive forming, with respect to the heat treatment temperature of each SUS plate. The hatched area in FIG. 2 shows the distribution of the haze value when the untreated SUS plate was used, and the test result of the solvent cloudiness of the test piece obtained using the heat-treated SUS plate was within this range. If it does, it was determined that the effect of the heat treatment could hardly be expected.
[0024]
As is clear from FIG. 2, the effect of the present invention cannot be obtained by heating the SUS plate at about 200 ° C. On the other hand, in the treatment at 300 ° C. and 350 ° C., the effect is recognized in the early stage of repeated plate making, but the effect tends to gradually decrease. In the SUS plate subjected to the heat treatment at 400 ° C. or higher, the occurrence of solvent clouding is almost completely suppressed. Although not shown, the SUS plate heat-treated at a temperature of 400 ° C. or more retained excellent effects even in repeated plate making more than 30 times.
[0025]
The fine wrinkles generated in the methacrylic resin plate were measured using a test method as shown in FIG. That is, the surface layer of a test piece prepared by cutting a methacrylic resin plate was exposed to the vapor of dichloromethane for about 2 minutes, and fine wrinkles (solvent fogging) generated on the surface layer of the test piece were measured with a haze meter (Suga Test Machine Co., Ltd.) ) SGM-2DP). The greater the non-uniformity of polymerization due to metal ions in the surface layer of the test piece, the greater the opacity of the plate and the greater the haze value. On the other hand, the haze value when there is no contamination by metal ions is displayed as zero.
[0026]
【The invention's effect】
According to the method of the present invention, contamination by a trace amount of metal ions from a metal plate can be prevented, and uniform polymerization can be performed on the surface layer of the plate-shaped polymer. For this reason, even in the heat molding of the obtained platy polymer, a stable and excellent quality platy polymer can be obtained without generating wrinkles due to fine deformation in the surface layer.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a method for testing the cloudiness of a platy polymer in a solvent.
FIG. 2 is a graph showing the relationship between the haze value of solvent clouding and the number of times of repeated heat treatment of a SUS plate.

Claims (1)

A method for injecting a polymerization raw material into a mold composed of a metal plate and polymerizing to produce a plate-like polymer, characterized in that a metal plate constituting the mold is heated at a temperature of 300 ° C. or more. A method for producing a plate polymer.

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