JPH0233490B2 - METAKURIRUJUSHIBANNOSEIZOHO - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a methacrylic resin board with improved solvent resistance. The methacrylic resin plate obtained by polymerizing methyl methacrylate monomer or a polymerizable unsaturated monomer mainly composed of methyl methacrylate between two molds has excellent transparency, It is used in many fields due to its gloss and weather resistance. Tempered glass plates have traditionally been used as molds for manufacturing, but in recent years, a continuous plate-making method using mirror-polished stainless steel plates as molds has been adopted industrially to improve productivity. It started to be done. Cast-in methacrylic resin sheets made using mirror-polished stainless steel sheets as molds are comparable in appearance and workability to those made from tempered glass sheets in terms of appearance and workability, but they cannot be used under harsh conditions. Under such processing conditions and usage conditions, defects may occur on the surface of the resin plate in some cases, and a solution was urgently required. This defect on the resin plate surface is a decrease in solvent resistance, and the decrease in solvent resistance is the occurrence of cloudiness on the resin plate surface when it comes into contact with the vapor of a good solvent. For example, when bonding resin plates together with solvent,
If cloudiness occurs near the bonded area due to contact with solvent vapor, the excellent transparency and gloss that characterize methacrylic resin plates will be lost, and the commercial value will be significantly reduced. Although there are many unknowns about the formation mechanism of methacrylic resin plates that cause surface defects during processing, the mold surface of the stainless steel plate acts on the polymerization system during casting, resulting in specificity on the resin plate surface. It is estimated that this is due to The inventors of the present invention have conducted extensive research on a method for manufacturing a resin plate that has excellent solvent resistance by suppressing the decrease in solvent resistance of a methacrylic resin plate that is thought to be caused by the effect of the surface of a stainless steel mold. We have discovered that a methacrylic resin plate with excellent solvent resistance can be obtained by electrolytically treating a stainless steel plate used as a mold using the method shown below.
The invention has been completed. That is, the present invention uses a stainless steel plate as a mold to polymerize a methyl methacrylate monomer or a polymerizable unsaturated monomer mixture containing methyl methacrylate as a main component, or a partial polymer thereof, to produce a polymer sheet. 1.0V/as a mold.
This is a method for producing a methacrylic acid resin plate characterized by using a stainless steel plate that has been subjected to anodic electrolysis treatment under an electric field strength of cm or more and a medium containing 20% or more water. Power sources used for electrolysis of the stainless steel plate used as the mold used in the present invention include commonly used DC power sources (including batteries) and low-frequency AC power sources. Specific examples of the medium containing 20% or more of water include water, agar-like material, water-containing cloth, water-containing sponge, etc., but any medium that allows current to easily flow between the electrodes may be used. If the moisture content of the medium is below 20%, the conductivity will drop significantly and the electrolytic treatment will be required for a long time, resulting in a decrease in workability. For the electrolytic strength during electrolytic treatment to be effective in improving solvent resistance, it is necessary to apply a voltage of 1.0 V/cm or more. electric field strength
If it is less than 1.0V/cm, the treatment effect will not be sufficiently achieved. Specific examples of monomers copolymerizable with methyl methacrylate and its partial polymer used in the present invention include esters of alcohols having 1 to 18 carbon atoms and acrylic acid, acrylic acid, methacrylic acid, acrylonitrile, Examples include methacrylonitrile, acrylamide and its derivatives, methacrylamide and its derivatives, styrene, α-methylstyrene, and the like. The amount of these monomers added to methyl methacrylate and its partial polymer is within the range normally used, that is, 40% by weight or less, preferably 20% by weight or less, based on methyl methacrylate and its partial polymer. More preferably, the amount is 10% by weight or less. In the present invention, when a partial polymer of a polymerizable unsaturated monomer containing methyl methacrylate as a main component is used, the concentration of the polymer is within the normal range, that is, 30% by weight or less of the total syrup. is preferred. Various additives used in producing ordinary methacrylic resin plates or modified products thereof can also be added to these polymerizable unsaturated monomers or their partial polymers. The additives mentioned here include dyes, pigments or antioxidants used for coloring, stabilizers such as ultraviolet absorbers, or flame retardants,
These include plasticizers, release agents that facilitate the release of the resin plate from the mold, chain transfer agents, and crosslinking agents. Specific examples of the polymerization initiator used in the present invention include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4 -dimethylvaleronitrile, 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), etc. and organic peroxides such as benzoyl peroxide and lauroyl peroxide, or redox-based polymerization initiators, such as organic peroxides, such as benzoyl peroxide and lauroyl peroxide, etc. Examples include combinations of peroxides and amines.The amount of these initiators added is in the range of 0.001 to 0.5 parts by weight per 100 parts by weight of the polymerizable unsaturated monomer or its partial polymer. Polymerization of a polymerizable unsaturated monomer containing methyl methacrylate as a main component or a partial polymer thereof is carried out by heating, and the polymerization temperature varies depending on the type of radical polymerization initiator used. , generally 40-140
°C, the first stage is 40 to 90 °C, the second stage is 100 °C
Preferably, the polymerization is carried out at a two-step polymerization temperature of ~140°C. The material of the stainless steel mold used in the present invention is not particularly limited, and includes austenitic steel,
A resin plate obtained by subjecting any of ferritic steel, martensitic steel, and austenitic-martensitic dual-phase steel in which a martensitic phase has been generated through processing transformation, etc., to anodic electrolysis treatment when used as a mold. Improvement in solvent resistance was observed. The phenomenon in which the solvent resistance of synthetic resin plates is improved by anodic electrolysis treatment of stainless steel plates used as molds is due to the fact that a mixture of polymerizable unsaturated monomers containing methacrylic acid monomer or methyl methacrylate as the main component Alternatively, this is a phenomenon generally observed in methacrylic resin plates obtained by casting and polymerizing a partially polymerized product using a stainless steel plate as a mold. The method of the present invention is particularly effective in a continuous plate making method using two stainless steel endless belts running opposite each other at a certain interval, but it is particularly effective in a batch type plate making method using stainless steel plates as molds. This method can also be applied, and by employing this method, the effect of significantly improving solvent resistance can be obtained. The surface of the stainless steel plate used as the mold is preferably mirror-polished, as long as the surface smoothness of the resulting resin plate is acceptable as a product, and only one side, which will be the inner surface of the mold, is used. It only needs to be mirror polished. Hereinafter, the present invention will be explained in more detail with reference to Examples. In addition, in the examples, parts represent parts by weight,
The evaluation of the solvent resistance of the resin plate was conducted at 23°C with an inner diameter of 45 mm.
Pour 5 ml of dichloromethane into a glass tray with a height of 18 m/m and place a resin plate on top of it, seal it, and bring the surface of the resin plate into contact with the dichloromethane vapor for 4 minutes. It was expressed as the ratio of gloss after and before contact with steam, that is, gloss retention. The glossiness was measured using a Tokyo Denshoku gloss meter at an incident angle of 60°. Example 1 As shown in FIG. 1, a stainless steel plate 2 with a nonwoven fabric 1 pasted on one side is connected to the cathode of a DC power source 5 whose anode is grounded, and the thickness is such that it is grounded at 9 and tension is applied by the main pulley 4. length 1.5mm, width 1200mm
The non-woven fabric 1 is sandwiched between the stainless steel endless belt 3 and the non-woven fabric 1 absorbs enough water to avoid air bubbles, and the length is 10 cm across the entire width between the non-woven fabric 1 and the stainless steel endless belt 3. Form an aqueous layer over a period of time. A voltage with an electric field strength of 10 V/cm is applied through this water-containing layer,
The electrolytic treatment was carried out while moving on an endless stainless steel belt at a speed of 2 m/min at a current density of 10 mA/cm ² . This stainless steel endless belt and a pair of continuous soft vinyl chloride gaskets running at the same speed as both endless belts on both sides constitute a molding space, and the thickness of the final cast-polymerized sheet is Polymerization rate after adjusting the interval to 4 mm and degassing from the upstream end.
100 parts of 21.2% methyl methacrylate partial polymer;
Tinuvin-P (UV absorber manufactured by Ciba Geigy)
0.01 part, Aerosol-OT (removal agent manufactured by American Cyanamid) 0.001 part, 2,2'-Azobis (2,
After continuously injecting 0.057 parts of 4-dimethylvaleronitrile into the composition and passing through the first polymerization zone at 80°C for 28 minutes, the second polymerization zone and slow cooling zone are heated to a maximum temperature of 135°C. was passed for 14 minutes, and a colorless and transparent methacrylic resin plate with a thickness of 4 mm was obtained continuously from the downstream side. When the solvent resistance of this methacrylic resin plate was measured by the method described above, the gloss retention rate was 98%. Example 2 Length mirror polished on one side as shown in Figure 2
10 stainless steel plates of 320 mm and 320 mm width and 1 tap water
1 is immersed in a heated water tank 12, and the other stainless steel plate 13 is used as a counter electrode to measure the electric field strength.
A DC voltage of 2 V/cm was applied and the mirror surface was subjected to anodic electrolysis treatment for 10 seconds. The current density at this time is 3mA/
It was warm in ^cm2 . These two anodic electrolyzed stainless steel plates are surrounded by a soft vinyl chloride gasket so that the mirror surface becomes the inner wall, and the thickness is 4 mm and the length is 30 mm.
mm, a space with a width of 300 mm was formed. In this space, 100 parts of methyl methacrylate partial polymer with a polymerization rate of 6.6%, which has been degassed in advance, and silicone oil KF96
(Removal agent manufactured by Shin-Etsu Chemical Co., Ltd.) 0.0005 parts, 2,2'-
Azobis(2,4-dimethylvaleronitrile)
After injecting a composition consisting of 0.012 parts and adjusting the interval between the upper and lower stainless steel plates to 3 mm, it was immersed in a 65°C water bath for 5 hours, and then heated in an air heating oven at 120°C for 2 hours to complete polymerization. After cooling to room temperature,
A colorless and transparent methacrylic resin plate was obtained by peeling from the stainless steel cell. This resin plate had excellent solvent resistance, with a gloss retention rate of 98% after contact with dichloromethane vapor by the method described above. Examples 3 to 10, Comparative Examples 1 to 2 Polymerization was carried out in the same manner as in Example 2 except that the electrolytic treatment conditions of the stainless steel plate used as the mold were changed, and the solvent resistance properties of the obtained methacrylic resin plate were measured. did. The results are shown in Table 1.

[Table] Examples 11 to 13, Comparative Examples 3 to 4 An aluminum plate with a sponge pasted on one side was connected to the cathode of a DC power source whose anode was grounded, and the sponge was placed on a grounded stainless steel plate with a mirror-polished surface on one side. The sponge was set so as to be sandwiched between the sponges, the moisture content of the sponge was varied, and a DC voltage with an electric field strength of 10 V/cm was applied to perform anodic electrolysis on the mirror surface. Using this stainless steel plate, a methacrylic resin plate was produced in the same manner as in Example 2, the gloss retention rate was measured, and the solvent resistance was evaluated. The results are shown in Table 2.

【table】 [Brief explanation of drawings]

FIG. 1 is a diagram showing an example of an electrolytic treatment method for a stainless steel endless belt. FIG. 2 is a diagram showing an example of an apparatus for electrolytic treatment of stainless steel sheets. In the figure, 5...DC power supply, 6...Voltmeter,
7... Ammeter, 8, 9... Indicates earth.

Claims (1)

[Claims] 1. A polymer sheet is produced by polymerizing methyl methacrylate monomer, a polymerizable unsaturated monomer mixture containing methyl methacrylate as a main component, or a partial polymer thereof using a stainless steel plate as a mold. A method for producing a methacrylic resin plate, characterized in that a stainless steel plate that has been subjected to anodic electrolysis treatment under an electric field strength of 1.0 V/cm or more and a medium containing 20% or more moisture is used as a mold. 2. The method for manufacturing a methacrylic resin plate according to claim 1, wherein the stainless steel plates are two endless belts running opposite each other with a certain interval. 3. The method for manufacturing a methacrylic resin plate according to claim 1, wherein the stainless steel plates are two plates having at least one side mirror-polished.