JP3865554B2 - Method for producing methacrylic resin molded product - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention has excellent transparency, production method methacrylic based resin AburaNaru molded article about no appearance defect.
[0002]
[Prior art]
There are methods for producing methacrylic resin plates, such as a mold plate method and an extrusion plate method, but methacrylic resin plates obtained by mold polymerization have less optical distortion and have a molecular weight than that of melt-molded extruded plates. Since the selection range is wide, chemical resistance, workability, mechanical strength, and the like can be enhanced, and thus it is used in many fields.
[0003]
For the polymerization of conventional methacrylic resin plates, various release agents have been used to improve the release properties. For example, in Japanese Patent No. 2571787, the release property of the resin is improved by adding a monoester of alkyl acid phosphate having 8 to 13 carbon atoms to the methacrylic resin under pressure and heating conditions in the mold. It is disclosed to improve. Further, JP-A-58-84807 discloses that a resin having a mold release property can be obtained by adding a diester of an organic phosphate ester having 8 to 18 carbon atoms to a methacrylic resin during polymerization in a mold made of glass or metal. Is disclosed to improve. Further, in JP-A-2-14207, a mixture of monoester and diester of alkyl acid phosphate having 8 to 13 carbon atoms is added to a methacrylic resin at the time of polymerization in a mold made of glass, metal, ceramic or the like. Thus, it is disclosed that the releasability of the resin at room temperature is improved.
[0004]
However, when these release agents are used, the release effect is excessive or insufficient depending on the type and amount added, resulting in poor release properties at high temperatures, and defects on the resin surface during release at high temperatures. Or the mold release agent component migrates to the surface, contaminating the mold, resulting in a decrease in product yield.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a methacrylic resin that is excellent in high-temperature releasability after polymerization, does not contaminate the mold even when the mold is repeatedly used, has excellent transparency, and has no appearance defects.
[0006]
[Means for Solving the Problems]
As a result of diligent studies, the present inventors have found that a specific acidic alkyl phosphate ester and sulfosuccinate ester are added to a monomer mixture or a partial polymer mixture comprising methyl methacrylate and another copolymerizable vinyl monomer. By adding and mixing together with salt and polymerizing, methacrylic acid can be peeled at high temperature, has no surface defects, and retains the excellent optical and mechanical properties that are characteristic of methacrylic resins, while maintaining good methacrylic yield. The present inventors have found that a system resin plate can be obtained and have completed the present invention.
[0008]
That is, the production method of the present invention comprises a monomer mixture comprising 60 to 100% by mass of methyl methacrylate and 40 to 0% by mass of another copolymerizable vinyl monomer, or the monomer mixture and the monomer. In the presence of a radical polymerization initiator, 100 parts by mass of the mixture with the polymer, 0.001 to 0.05 parts by mass of 2-ethylhexyl acid phosphate and 0.002 to 0.1 parts by mass of sulfosuccinate ester salt A method for producing a methacrylic resin molded product, characterized in that polymerization is carried out in a mold and a polymerized cured product is taken out from the mold at a temperature of 70 to 110 ° C.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The monomer used in the present invention may be a monomer mixture of methyl methacrylate and a vinyl monomer copolymerizable therewith. In the present invention, even a single monomer is referred to as a “monomer mixture” for convenience. Vinyl monomers copolymerized with methyl methacrylate are, for example, ethyl methacrylate, isopropyl methacrylate, t-butyl methacrylate, s-butyl methacrylate, n-butyl methacrylate, amyl methacrylate, octyl methacrylate, methacrylic acid. 2-ethylhexyl, lauryl methacrylate, phenyl methacrylate, cyclohexyl methacrylate, cycloalkyl groups such as benzyl methacrylate, methacrylic esters having 1 to 12 carbon atoms of alkyl group including benzyl group; bornyl methacrylate, isobornyl methacrylate Methacrylic acid ester having an alkyl group having 8 to 20 carbon atoms or an alicyclic hydrocarbon group, such as phentyl methacrylate, 1-menthyl methacrylate, adamantyl methacrylate and dimethyladamantyl methacrylate Methyl acrylate, ethyl acrylate, isopropyl acrylate, butyl acrylate, t-butyl acrylate, amyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, cyclohexyl acrylate, phenyl acrylate Acrylic esters such as benzyl acrylate; vinyl aromatics such as styrene, α-methyl styrene, paramethyl styrene, isopropenyl styrene and vinyl toluene; unsaturated nitriles such as acrylonitrile and methacrylonitrile; methacrylic acid, Unsaturated carboxylic acids such as acrylic acid and maleic anhydride; polyunsaturated compounds such as ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, divinylbenzene, and the like. These can be used alone or in combination of two or more.
[0010]
The composition of the monomer used is usually in the range of 40 to 0 parts by mass of another copolymerizable vinyl monomer with respect to 60 to 100 parts by mass of methyl methacrylate, but can be copolymerized depending on the modification purpose. The amount of the vinyl monomer used is preferably 10 parts by mass or less as the amount used so as not to impair the original physical properties of the methacrylic resin obtained by polymerization.
[0011]
In the present invention, the monomer mixture is subjected to polymerization. A partial polymer (hereinafter referred to as syrup) containing a polymer of the monomer mixture in the monomer mixture is used as a monomer mixture. Instead, it can be used for polymerization.
[0012]
The monomer mixture or syrup can be added with various additives used in the production of ordinary methacrylic resins or modified products thereof. Examples of the additive herein include dyes and pigments used for coloring; stabilizers such as antioxidants and ultraviolet absorbers; flame retardants, chain transfer agents, and crosslinking agents.
[0013]
The 2-ethylhexyl acid phosphate used in the present invention is a monoester represented by C ₈ H ₁₇ OP (O) (OH) ₂ , a diester represented by (C ₈ H ₁₇ ) ₂ OP (O) OH, or these It is a mixture and is preferably a mixture. The mixing ratio of monoester and diester is preferably 1 to 9 to 9 to 1, more preferably 3 to 7 to 7 to 3, and still more preferably 5 to 5. When the alkyl chain has 7 or less carbon atoms, the production mold is contaminated, and when the alkyl chain has 9 or more carbon atoms, the releasability may be deteriorated. Moreover, it is preferable to use the usage-amount of 2-ethylhexyl acid phosphate in the range of 0.001-0.05 mass part with respect to 100 mass parts of monomer mixtures or syrup. If the amount used is less than 0.001 part by mass, the releasability at high temperature peeling from the mold of the resin plate is not sufficient, and if the amount used exceeds 0.05 part by mass, the water absorption of the methacrylic resin plate obtained May increase the rate and adversely affect the resin surface.
[0014]
Examples of the sulfosuccinic acid ester salt used in the present invention include sodium di (2-ethylhexyl) sulfosuccinate, sodium dihexyl sulfosuccinate, and dibutyl sodium sulfosuccinate. The sulfosuccinic acid ester salt is generally a sodium salt, but other than the sodium salt can also be used. The amount of the sulfosuccinic acid ester salt used is preferably in the range of 0.002 to 0.1 parts by mass with respect to 100 parts by mass of the monomer mixture or syrup. If the amount used is less than 0.002 parts by mass, the releasability at high temperature peeling from the mold of the resin plate is not sufficient, and if the amount used exceeds 0.1 parts by mass, the surface of the methacrylic resin plate obtained May be adversely affected.
[0015]
Examples of the radical polymerization initiator used in the present invention include azo polymerization initiators such as azobisisobutyronitrile and 2,2′-azobis- (2,4-dimethylvaleronitrile), benzoyl peroxide, and t-butyl. And organic peroxides such as peroxy 2-ethylhexanoate and t-hexyl peroxypivalate. Examples of the molecular weight regulator used as necessary include alkyl mercaptans such as n-butyl mercaptan, n-dodecyl mercaptan, and octyl mercaptan.
[0016]
Although the polymerization temperature in the present invention varies depending on the type of polymerization initiator used, it is generally 40 to 170 ° C., and the first stage is 40 to 90 ° C. and the second stage is 100 to 140 ° C. Polymerization is preferably carried out at the polymerization temperature.
[0017]
The temperature at which the polymerized cured product is taken out from the mold (hereinafter referred to as the peeling temperature) varies somewhat depending on the composition of the resin composition, but is preferably in the range of 70 to 110 ° C. If the peeling temperature is less than 70 ° C., a small scratch may occur on the resin surface. The peeling temperature is more preferably 75 ° C. or higher, and further preferably 80 ° C. or higher. Moreover, since a streak-like defect will arise on the resin surface when it exceeds 110 degreeC, the outstanding transparency and optical characteristic of a methacryl resin may be lost.
[0018]
The methacrylic resin plate of the present invention is obtained by adding a radical polymerization initiator, an acidic alkyl phosphate ester and a sulfosuccinate ester salt to the above monomer mixture or syrup and then mixing them with a mold such as tempered glass or a chrome plated plate. , Stainless steel plates and soft vinyl chloride gaskets, two endless belts that run in the same direction and at the same speed, and both endless on the opposite side It is composed of a belt and a gasket that travels at the same speed, and can be manufactured by injecting and polymerizing a gap between two endless belts set in advance. The production method of the present invention is highly effective when a metal mold is used, and particularly effective when manufactured by an endless belt device. In the case of manufacturing with an endless belt device, the two endless belts are preferably pressurized at a pressure of normal pressure to 0.1 MPa.
[0019]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these. In addition, the physical property evaluation in an Example was performed based on the following method.
1) High-temperature releasability After polymerizing a methacrylic resin plate, the releasability from the mold when the polymerized cured product was taken out from the mold at the temperature described in each example was evaluated according to the following criteria.
Good: When the resin plate is peeled from the mold, it can be peeled smoothly.
Defect: When the resin plate is peeled from the mold, there is a catch on the way, resulting in surface defects.
2) Mold Contamination Polymerization of the methacrylic resin plate was repeated 20 times with the same mold without washing the mold in the middle, and then the contamination status of the mold surface was observed under illumination in a dark place.
3) Resin plate appearance The appearance of the methacrylic resin plate taken out from the mold was observed under illumination in a dark place.
Example 1
93 parts by mass of methyl methacrylate and 7 parts by mass of butyl acrylate are supplied to a reactor equipped with a condenser, a thermometer and a stirrer, and after adding 630 ppm of n-dodecyl mercaptan as a molecular weight regulator, the mixture is heated with stirring. When the internal temperature reaches 80 ° C., 500 ppm of 2,2′-azobis- (2,4-dimethylvaleronitrile) is added, further heated to an internal temperature of 90 ° C. and held for 13 minutes, then cooled to room temperature. A syrup having a polymerization rate of about 26% and a viscosity of 2 Pa · s at 20 ° C. was obtained.
[0020]
Subsequently, to 100 parts by mass of this syrup, 0.01 parts by mass of n-dodecyl mercaptan, 0.32 parts by mass of t-hexyl peroxypivalate, 2-ethylhexyl acid phosphate (mixing ratio of monoester and diester 5 to 5) ) After adding 0.01 parts by mass and 0.005 parts by mass of di (2-ethylhexyl) sodium sulfosuccinate, the mixture was stirred and passed through two SUS304 plates facing each other at intervals of 3 mm through a polyvinyl chloride gasket. It was poured into the formed mold. After immersing in warm water at 78 ° C for 30 minutes to cure by polymerization, heat treatment in an air heating furnace at 135 ° C for 60 minutes, cooling to 81 ° C, detaching the formwork, and a methacrylic system with a plate thickness of about 3 mm A resin plate was obtained. When the production of this resin plate was repeated 20 times without washing the mold, there was no problem with the high temperature peelability every time, and a resin plate with a good appearance was obtained. There was no contamination of the mold.
[0021]
Example 2
100 parts by mass of methyl methacrylate was supplied to the same reaction apparatus as in Example 1, heated with stirring, and when the internal temperature reached 80 ° C., 2,2′-azobis- (2,4-dimethylvaleronitrile) ) 500 ppm was added, further heated to an internal temperature of 90 ° C. and held for 8 minutes, and then cooled to room temperature to obtain a syrup having a polymerization rate of about 22% and a viscosity at 20 ° C. of 1.5 Pa · s.
[0022]
Next, 100 parts by mass of syrup, 0.083 parts by mass of 2,2′-azobis- (2,4-dimethylvaleronitrile), 2-ethylhexyl acid phosphate (mixing ratio of monoester and diester 5 to 5) After adding 0.005 part by mass and 0.01 part by mass of sodium di (2-ethylhexyl) sulfosuccinate, the mixture was stirred and poured into the mold in the same manner as in Example 1. After polymerization and curing, heat treatment was performed, and after cooling to 100 ° C., the mold was removed to obtain a methacrylic resin plate having a plate thickness of about 3 mm. When this plate making operation was repeated 20 times without washing the mold halfway, a high temperature release property was obtained each time, a resin plate having a good appearance was obtained, and the mold was not contaminated.
[0023]
Example 3
100 parts by mass of syrup as in Example 2, 0.083 parts by mass of 2,2′-azobis- (2,4-dimethylvaleronitrile), 2-ethylhexyl acid phosphate (a ratio of monoester to diester of 5 pairs) 5) After adding 0.005 part by mass and 0.01 part by mass of di (2-ethylhexyl) sodium sulfosuccinate, a mirror surface having a width of 1200 mm and a thickness of 1 mm which is stirred and relatively travels in the same direction at the same speed. It is composed of a finished SUS304 endless belt and a polyvinyl chloride gasket that runs at the same speed as both endless belts at both ends on the opposite surface side, and the gap between the two endless belts is 3 mm thick beforehand. The mold set up as described above was injected at a constant flow rate using a metering pump. Along with the movement of the belt, it was polymerized and cured for 30 minutes in a hot water shower at 78 ° C., then heat-treated at 135 ° C. for 20 minutes with a far-infrared heater, cooled to 100 ° C. by blowing for 10 minutes, and the resin plate was peeled off from the belt Thus, a methacrylic resin plate having a thickness of about 3 mm was obtained. When this plate-making operation was repeated 20 times without cleaning the belt in the middle, there was no problem with high-temperature releasability every time, a resin plate with a good appearance was obtained, and the endless belt was not contaminated.
[0024]
Comparative Example 1
In the same manner as in Example 2, syrup was charged into a mold, polymerized and cured, followed by heat treatment. After cooling to 50 ° C., the resin plate was taken out of the mold. When this plate making operation was repeated 20 times without washing the mold in the middle, the high temperature release property was good each time and the mold was not contaminated. There were fine scratches due to contact with the SUS304 plate.
[0025]
Comparative Example 2
The operation of obtaining a resin plate in the same manner as in Example 3 was repeated except that the peeling temperature in Example 3 was changed to 50 ° C. When this plate-making operation was repeated 20 times without cleaning the belt in the middle, there was no problem with the high temperature releasability every time and there was no contamination of the endless belt, but the resin plate contacted the endless belt during heat shrinkage. Minor scratches were observed.
[0026]
Comparative Example 3
A resin plate production operation was repeated in the same manner as in Example 1 except that 0.01 parts by mass of ethyl acid phosphate was used instead of 2-ethylhexyl acid phosphate. As a result, there was no problem with high-temperature releasability, but after the fifth plate making, the mold was contaminated and needed to be washed, and the surface of the resin plate obtained without washing was whitened and transparent Decreased.
[0027]
Comparative Example 4
A syrup was charged in the mold in the same manner as in Example 1 except that 0.01 parts by mass of octadecyl acid phosphate was used instead of 2-ethylhexyl acid phosphate, and heat treatment was performed after polymerization and curing. After cooling to 81 ° C., the cured product was taken out from the mold. As a result, the resin in the vicinity of the polyvinyl chloride gasket adhered to the SUS304 plate, and the high-temperature releasability was poor. The resulting resin plate was also streaky. It became defective.
[0028]
Comparative Example 5
Except that the sodium sulfosuccinate di (2-ethylhexyl) used in Example 2 was not added, the syrup was charged into the mold in exactly the same manner as in Example 2, followed by heat treatment after polymerization and cooling to 100 ° C. Thereafter, the resin plate was taken out from the mold. As a result, the resulting resin plate had streak defects due to poor high-temperature releasability, and lost the excellent transparency and optical characteristics that are characteristic of methacrylic resins.
[0029]
【The invention's effect】
According to the present invention, a methacrylic resin plate that can be taken out from a mold at a high temperature, is excellent in transparency, and has no appearance defect can be manufactured with high yield. Further, the production mold to be repeatedly used is not contaminated.

Claims (2)

  100 mass% of a monomer mixture comprising 60-100 mass% of methyl methacrylate and 40-0 mass% of other copolymerizable vinyl monomers, or a mixture of the monomer mixture and a polymer of the monomer mixture. Part, 2-ethylhexyl acid phosphate 0.001-0.05 parts by mass and sulfosuccinate ester salt 0.002-0.1 parts by mass in the presence of a radical polymerization initiator in a mold A method for producing a methacrylic resin molded article, wherein a product is taken out from a mold at a temperature of 70 to 110 ° C. The mold is composed of two endless belts that run at the same speed in the same direction relative to each other, and two endless belts that run at the same speed as the endless belt at both ends on the opposite side of the endless belt. The method for producing a methacrylic resin molded article according to claim 1 , wherein the gap of the belt is set in advance.