JP2017087664A - Method for producing methacrylic resin sheet, and the methacrylic resin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a methacrylic resin sheet by a cast sheet making method preferably applicable in the case where a mold is arranged in a substantially horizontal direction, even if a plasticizer is eluted from a gasket into a polymerizable raw material, by which the reduction of the ultraviolet permeability by the plasticizer of a methacrylic resin sheet is suppressed, and capable of producing a methacrylic resin sheet excellent in transparency, particularly, in ultraviolet permeability.SOLUTION: Provided is a method for producing a methacrylic resin sheet where a polymerizable raw material comprising at least one kind of polymer including methyl methacrylate by 60-90 pts.mass and at least one kind of methacrylic polymer including a monomer unit derived from methyl methacrylate by 40-10 pts.mass, not including ultraviolet absorbers, and whose viscosity at 25°C is 0.1-10 Pa s is prepared, the polymerizable raw material is injected into the internal space part of a die made of a pair of die plates and a gasket, and is subjected to polymerization curing, and thereafter, a planar polymer is peeled and taken out from the die.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a methacrylic resin plate and a methacrylic resin plate.

  Methacrylic resin plates are excellent in light resistance, transparency, and the like, and thus are used in various applications. A methacrylic resin plate is generally added with an ultraviolet absorber to improve light resistance. However, methacrylic resin plates used in some fields, such as agricultural greenhouses and optical equipment, do not contain ultraviolet absorbers and may require transparency including the ultraviolet region.

  As a method for producing a methacrylic resin plate, a mold composed of a gasket and a pair of mold plates opposed to each other with a predetermined interval therebetween is prepared, and methyl methacrylate (hereinafter, “ In some cases, it is abbreviated as “MMA”.) A cast raw material method (also called “casting polymerization method”) in which a polymerizable raw material containing at least one monomer and a polymerization initiator is injected and polymerized and cured by heating. .)It has been known. Since the methacrylic resin plate by this method does not go through the melt extrusion step, the molecular weight and the plate thickness can be increased.

  As a material for the gasket, a soft vinyl chloride resin is widely used. The soft vinyl chloride resin usually contains a phthalate such as dioctyl phthalate (DOP) and dibutyl phthalate (DBP) as a plasticizer for softening the resin. Such a phthalate ester contains an aromatic ring and has ultraviolet absorption.

  In the cast plate method, the plasticizer elutes from the soft vinyl chloride resin gasket into the polymerizable raw material during the polymerization and curing, and the transparency of the resulting methacrylic resin plate, in particular, the UV transmittance is reduced. There is a fear.

Patent Document 1 discloses a gasket made of a vinyl chloride resin containing a plasticizer having a density of 0.94 g / cm ³ or less (Claim 1).
Patent Document 1 also discloses a method for producing a methacrylic resin plate in which a mold is arranged in the vertical direction (Claim 3). In this method, the polymerizable raw material convects in the mold by heating, and a low-density plasticizer gathers at the upper end of the mold (this part is finally cut off), and the plasticizer is actually applied to the part that becomes the product. There is hardly any remaining.
In Patent Document 1, examples of the polymerizable material include a monomer liquid containing 70% by mass or more of MMA and no polymer, and syrup containing a monomer such as MMA and a polymer such as PMMA. (Paragraph 0017).

JP 2002-179867 A

When the method described in Patent Document 1 is applied to a method in which a mold is arranged in a substantially horizontal direction, the plasticizer eluted from the gasket diffuses from the vicinity of the gasket toward the surface of the template due to convection of the polymerizable raw material by heating. End up. Therefore, a lot of plasticizer remains in the part that is actually a product, and there is a risk that the ultraviolet transmittance of the resulting methacrylic resin plate is lowered.
In particular, when a monomer liquid is used as the polymerizable raw material, since the viscosity of the polymerizable raw material is low, convective diffusion of the polymerizable raw material occurs in a wide range, and the ultraviolet transmittance of the resulting methacrylic resin plate tends to decrease. It is not preferable in terms of productivity to excise a part where a large amount of the plasticizer remains.
Even when syrup is used as the polymerizable raw material, the same problem may occur depending on the viscosity.

  The present invention has been made in view of the above circumstances, and can be preferably applied when the mold is arranged in a substantially horizontal direction. Even if the plasticizer is eluted from the gasket into the polymerizable raw material, the plasticizer for the methacrylic resin plate An object of the present invention is to provide a method for producing a methacrylic resin plate by a cast plate method capable of producing a methacrylic resin plate excellent in transparency, in particular, ultraviolet ray transparency, in which a decrease in ultraviolet transmittance due to is suppressed. And

  The present invention provides the following methacrylic resin plate production method [1] to [4] and [5] methacrylic resin plate.

[1] 60 to 90 parts by mass of at least one monomer containing methyl methacrylate (MMA) and 40 to 10 mass of at least one methacrylic polymer containing monomer units derived from methyl methacrylate (MMA) A polymerizable raw material having a viscosity at 25 ° C. of 0.1 to 10 Pa · s.
Injecting the polymerizable raw material into the inner space of a mold composed of a pair of mold plates and a gasket and polymerizing and curing, and then removing the plate-like polymer from the mold and taking it out.
A method for producing a methacrylic resin plate.

[2] The gasket is made of a soft vinyl chloride resin.
The method for producing a methacrylic resin plate according to [1].

[3] While the polymerizable raw material is polymerized and cured, the mold is arranged in a substantially horizontal direction.
The method for producing a methacrylic resin plate according to [1] or [2].

[4] As the polymerizable raw material, 60 to 90 parts by mass of at least one monomer containing methyl methacrylate, and 40 to 10 masses of at least one methacrylic polymer containing a monomer unit derived from methyl methacrylate. Part, a polymerization initiator, and a chain transfer agent are used.
The method for producing a methacrylic resin plate according to any one of [1] to [3].

[5] Obtained by the production method according to any one of [1] to [4], wherein the ultraviolet ray absorbing substance derived from the gasket is 0.2% by mass or less.
Methacrylic resin plate.

  In this specification, unless otherwise specified, “dispose the mold in a substantially horizontal direction” means that the template surface of the mold is disposed in a direction within a range of ± 5 ° from the complete horizontal direction.

In the present specification, unless otherwise specified, the viscosity of the polymerizable raw material at 25 ° C. is measured by the following method using a Brookfield rotary viscometer in accordance with JIS K7117.
A BL type viscometer manufactured by Toki Sangyo Co., Ltd. is used as the viscometer.
First, after the rotor of the viscometer is immersed in 100 cc of syrup kept at 25 ° C., the viscosity is measured. Viscosity is measured under the condition that the rotor speed is 30 rpm.

  In the present specification, unless otherwise specified, “viscosity average molecular weight” is measured at 25 ° C. in accordance with JIS K7367 by dissolving 0.02 g of a sample in 25 ml of chloroform.

  According to the present invention, it can be preferably applied when the mold is arranged in a substantially horizontal direction, and even if the plasticizer is eluted from the gasket into the polymerizable raw material, the decrease in ultraviolet transmittance due to the plasticizer of the methacrylic resin plate is suppressed. Thus, it is possible to provide a method for producing a methacrylic resin plate by a cast plate method, which is capable of producing a methacrylic resin plate excellent in transparency, particularly ultraviolet ray permeability.

2 is a spectral transmittance curve of a methacrylic resin plate obtained in each example of Example 1 and Comparative Example 1.

"Production method of methacrylic resin plate"
The present invention relates to a method for producing a methacrylic resin plate by a cast plate method.
The present invention can be preferably applied when the mold is arranged in a substantially horizontal direction, and even if the plasticizer is eluted from the gasket into the polymerizable raw material, a decrease in ultraviolet transmittance due to the plasticizer of the methacrylic resin plate is suppressed, An object of the present invention is to provide a method for producing a methacrylic resin plate by a cast plate method, which is capable of producing a methacrylic resin plate excellent in transparency, in particular, ultraviolet ray transparency.

  In the cast plate method, a polymerizable raw material is injected into an inner space portion of a mold made up of a pair of mold plates and a gasket, polymerized and cured, and then the plate polymer is peeled off from the mold and taken out.

The pair of mold plates is not particularly limited, and is preferably a glass plate, a chrome plated plate, a stainless steel plate, or the like, and more preferably a glass plate because of high surface smoothness and good releasability.
A pair of endless belts that run opposite each other at a predetermined interval can also be used as a pair of templates. In this case, a mold can be constituted by the pair of endless belts and the pair of gaskets that travel following the traveling of the pair of endless belts.

  The cross-sectional shape of the gasket is not particularly limited, and examples thereof include a circular shape and a hollow circular shape. Since the gasket itself is easily crushed and the sealing property between the pair of templates is good, the cross-sectional shape of the gasket is preferably a hollow circular shape.

The material of the gasket is not particularly limited.
In the cast plate method, a soft vinyl chloride resin is widely used as a gasket material. The soft vinyl chloride resin usually contains phthalic acid esters such as dioctyl phthalate (DOP, specific gravity 0.986) and dibutyl phthalate (DBP, specific gravity 0.986) as plasticizers for softening the resin. Such a phthalate ester contains an aromatic ring and has ultraviolet absorption. Dioctyl phthalate (DOP) generally absorbs ultraviolet light of 390 nm or less. Dibutyl phthalate (DBP) generally absorbs ultraviolet light of 310 nm or less.
The content of the plasticizer in the soft vinyl chloride resin is preferably 15 to 50% by mass, more preferably 30 to 40% by mass, since it can exhibit flexibility suitable as a gasket.

The present invention can be preferably applied when the gasket is made of a soft vinyl chloride resin containing a plasticizer having ultraviolet absorptivity.
Even in the case where the gasket is made of a soft vinyl chloride resin containing a plasticizer having ultraviolet absorptivity, according to the production method of the present invention, a decrease in ultraviolet transmittance due to the plasticizer of the methacrylic resin plate is suppressed, and the transparent It is possible to produce a methacrylic resin plate having excellent properties, in particular, ultraviolet transparency.

  In the present invention, at least one monomer (M) containing methyl methacrylate (MMA) and at least one methacrylic polymer (P) containing a monomer unit derived from methyl methacrylate (MMA) A polymerizable raw material containing no ultraviolet absorber is used.

  As the monomer (M), at least one alkyl methacrylate can be used. As the monomer (M), at least one alkyl methacrylate and another copolymerizable unsaturated monomer can be used in combination.

Examples of the alkyl methacrylate used as the monomer (M) include methyl methacrylate (MMA), ethyl methacrylate (EMA), n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, and 2-ethylhexyl methacrylate. , Lauryl methacrylate, cyclohexyl methacrylate, and the like.
These can be used alone or in combination of two or more.
In the present invention, at least methyl methacrylate (MMA) is used as the monomer (M).

As the monomer (M), other copolymerizable unsaturated monomers that can be used in combination with alkyl methacrylate,
Alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, and cyclohexyl acrylate;
Hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxy-3-chloropropyl (meth) acrylate;
(Meth) acrylic acid;
and,
Examples include (meth) acrylic acid metal salts.

The amount of MMA in the entire monomer used for the polymerizable raw material is not particularly limited.
Since a methacrylic resin plate having high surface hardness, good impact resistance, and good transparency can be obtained, the amount of MMA in the entire monomer used for the polymerizable raw material is preferably 90% by mass or more. Preferably it is 95 mass% or more, More preferably, it is 98 mass% or more, Especially preferably, it is 99 mass% or more, Most preferably, it is 100 mass%.

The methacrylic polymer (P) can contain monomer units derived from alkyl methacrylate.
The methacrylic polymer (P) may be a homopolymer or copolymer of at least one alkyl methacrylate, or at least one alkyl methacrylate and at least one other copolymerizable unsaturated monomer. A copolymer may be used.

Examples of the alkyl methacrylate as a raw material for the methacrylic polymer (P) include methyl methacrylate (MMA), ethyl methacrylate (EMA), n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, 2-ethylhexyl. Examples include methacrylate, lauryl methacrylate, and cyclohexyl methacrylate.
These can be used alone or in combination of two or more.
At least methyl methacrylate (MMA) is used as a raw material for the methacrylic polymer (P).

As a raw material of the methacrylic polymer (P), as other copolymerizable unsaturated monomer that can be used in combination with alkyl methacrylate,
Alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, and cyclohexyl acrylate;
Hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxy-3-chloropropyl (meth) acrylate;
(Meth) acrylic acid;
and,
Examples include (meth) acrylic acid metal salts.

  The viscosity average molecular weight of the methacrylic polymer (P) is not particularly limited, and is preferably 100,000 to 6,000,000, more preferably 200,000 to 4,000,000.

The content of the monomer unit derived from MMA in the methacrylic polymer (P) is not particularly limited.
The content of the monomer unit derived from MMA in the methacrylic polymer (P) is preferably from a methacrylic resin plate having high surface hardness, good impact resistance, and good transparency. It is 90 mass% or more, More preferably, it is 95 mass% or more, More preferably, it is 98 mass% or more.
As the methacrylic polymer (P), polymethyl methacrylate (MMA homopolymer, PMMA) is particularly preferable.

The compounding ratio of the monomer (M) and the methacrylic polymer (P) in the polymerizable raw material is as follows.
For a total amount of 100 parts by mass of the monomer (M) and the methacrylic polymer (P),
The amount of the monomer (M) is 60 to 90 parts by mass, and the amount of the methacrylic polymer (P) is 40 to 10 parts by mass.

When the amount of the monomer (M) is less than 60 parts by mass (the amount of the methacrylic polymer (P) exceeds 40 parts by mass), the viscosity of the polymerizable raw material becomes too high, and the handling property at the time of injection into the mold, etc. Decreases.
When the amount of the monomer (M) exceeds 90 parts by mass (the amount of the methacrylic polymer (P) is less than 10 parts by mass), the viscosity of the polymerizable raw material becomes too low, and the plasticizer is eluted from the gasket during polymerization curing. In addition, convection of the polymerizable raw material is likely to occur during polymerization and curing, and the eluted plasticizer is likely to diffuse widely.
If the amount of the monomer (M) is 60 to 90 parts by mass (the amount of the methacrylic polymer (P) is 40 to 10 parts by mass), the viscosity of the polymerizable raw material is suitable and the handleability is good. Excess plasticizer elution and diffusion from the gasket during polymerization and curing are suppressed.
The amount of the monomer (M) is 70 to 95 parts by mass with respect to 100 parts by mass of the total amount of the monomer (M) and the methacrylic polymer (P), and the methacrylic polymer (P) The amount is preferably 30 to 5 parts by mass, more preferably 80 to 92 parts by mass of the monomer (M), and 20 to 8 parts by mass of the methacrylic polymer (P).

The polymerization initiator is not particularly limited,
Azobisisobutyronitrile, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), acetylcyclohexylsulfonyl peroxide, Isobutyryl peroxide, cumylperoxyneodecanoate, diisopropylperoxydicarbonate, di-n-propylperoxydicarbonate, dimyristylperoxycarbonate, di- (2-ethoxyethyl) peroxydicarbonate, di- (Methoxyisopropyl) peroxydicarbonate, di- (2-ethylhexyl) peroxydicarbonate, and the like.
These can be used alone or in combination of two or more.

  The amount of the polymerization initiator in the polymerizable raw material is not particularly limited, and is preferably 0.018 to 0.05 g / kg because the polymerization reaction proceeds suitably.

The polymerizable raw material can contain a chain transfer agent as required.
The chain transfer agent is not particularly limited,
Styrene dimers such as α-methyl-styrene dimer;
mercaptans such as n-octyl mercaptan, n-dodecyl mercaptan, and hyophenol;
Thioglycolic acid or esters thereof such as thioglycolic acid, ethyl thioglycolate, and butyl thioglycolate;
β-mercaptopropionic acid and esters thereof such as β-mercaptopropionic acid, methyl β-mercaptopropionate, and octyl β-mercaptopropionate;
and,
Examples include terpinolene.
These can be used alone or in combination of two or more.

  The amount of the chain transfer agent in the polymerizable raw material is not particularly limited, and is preferably 0.015 to 0.03 g / kg because the polymerization reaction proceeds suitably.

The polymerizable raw material is composed of 60 to 90 parts by mass of at least one monomer containing methyl methacrylate, 40 to 10 parts by mass of at least one methacrylic polymer containing a monomer unit derived from methyl methacrylate, and polymerization. It can contain only an initiator and a chain transfer agent.
However, the polymerizable raw material can contain one or more other additives as required.
Other additives are not particularly limited as long as they do not absorb ultraviolet rays, and include antioxidants, colorants such as pigments and dyes, and release agents.

Since the polymerizable raw material used in the production method of the present invention contains a monomer and a polymer, it has a higher viscosity than a monomer liquid that does not contain a polymer.
In the present invention, the viscosity of the polymerizable raw material at 25 ° C. is set in the range of 0.1 to 10 Pa · s.
If the viscosity of the polymerizable raw material at 25 ° C. is less than 0.1 Pa · s, convection is likely to occur during polymerization and curing, and the eluted plasticizer is likely to diffuse widely.
When the viscosity of the polymerizable raw material at 25 ° C. is more than 10 Pa · s, the handleability at the time of pouring into the mold is lowered.
If the viscosity of the polymerizable raw material at 25 ° C. is in the range of 0.1 to 10 Pa · s, the handleability of the polymerizable raw material at the time of injection into the mold is good, and the convection of the polymerizable raw material at the time of polymerization and curing is good. It is suppressed and diffusion of the eluted plasticizer is suppressed. Thus, in the production method of the present invention, a methacrylic resin plate having an ultraviolet absorbing material such as a plasticizer derived from a gasket of 0.2% by mass or less, preferably 0.15% by mass or less can be obtained. In addition, the spectral transmittance at 350 nm of the methacrylic resin plate can be set to 85% or more.
The viscosity of the polymerizable raw material at 25 ° C. is more preferably 0.7 to 3 Pa · s.

In the production method of the present invention, the polymerizable raw material is derived from MMA and at least one unreacted monomer containing MMA obtained by prepolymerizing at least one monomer containing MMA. A prepolymerized syrup containing at least one methacrylic polymer containing monomer units can be used.
The polymerization rate in the preliminary polymerization is not particularly limited, and is preferably 5 to 40%, more preferably 5 to 30%.
In the present specification, the “polymerization rate” is the ratio of the methacrylic polymer mass to the total mass of the polymerizable raw material.

As the polymerizable raw material, syrup obtained by adding at least one monomer containing MMA to the prepolymerized syrup can be used (see Example 1 described later).
As the polymerizable raw material, it is possible to use a dissolved syrup obtained by dissolving at least one methacrylic polymer containing a monomer unit derived from MMA separately polymerized in at least one monomer containing MMA. it can.

The polymerization curing of the polymerizable raw material can be carried out by a known method.
When the distance between the pair of molds is less than 15 mm, the temperature is changed in two stages, and when the distance between the molds is 15 mm or more, the temperature is changed and the polymerizable material is preferably polymerized and cured in three stages or more.

Hereinafter, the two-stage polymerization method will be described.
The polymerizable raw material is first immersed in a water bath whose temperature is adjusted to about 55 to 85 ° C., and the first stage pre-polymerization is performed for about 1 to 20 hours. It is preferable to do so. By this prepolymerization, the polymerization rate can be increased to about 80% to cause gelation, and the elution of the plasticizer can be suppressed.
Next, the mold is placed in a hot stove, and preferably heated at a temperature of about 80 ° C. for about 2 to 15 hours, and then preferably post-heated at a temperature of about 130 ° C. for about 3 to 15 hours. It is preferable to drive in.
If the polymerization temperature or the polymerization time is insufficient throughout the prepolymerization and postpolymerization, the polymerization reaction may not proceed well.
If the polymerization temperature or polymerization time is excessive during pre-polymerization and post-polymerization, the elution and diffusion of the plasticizer from the gasket may increase.
When the two-stage polymerization is performed at the above polymerization temperature and polymerization time, the polymerization reaction proceeds well, and excessive elution and diffusion of the plasticizer from the gasket is suppressed.

The arrangement direction of the mold during the polymerization and curing of the polymerizable raw material is not particularly limited.
The production method of the present invention can be preferably applied to the case where the mold is disposed in a substantially horizontal direction while the polymerizable raw material is polymerized and cured.
When the method described in Patent Document 1 listed in the “Background Art” section is applied to a method in which a mold is arranged in a substantially horizontal direction, the plasticizer eluted from the gasket by the convection of the polymerizable raw material by heating is near the gasket. May diffuse in the surface direction of the template, and the ultraviolet transmittance of the resulting methacrylic resin plate may be reduced.
In the production method of the present invention, a polymerizable raw material containing a monomer and a polymer is used, and the viscosity is regulated within a range of 0.1 to 10 Pa · s, whereby the diffusion range of the plasticizer eluted from the gasket. Can be kept within a narrow range, for example, about 5 mm from the gasket. Therefore, the outer peripheral part of the methacrylic resin plate taken out from the mold (this part is also a part cut by the conventional manufacturing method), for example, the outer peripheral part from the gasket to the inner side of about 5 mm is obtained as a product. A methacrylic resin plate containing almost no plasticizer can be obtained.
Therefore, in the production method of the present invention, it can be preferably applied when the mold is arranged in a substantially horizontal direction. Even if the plasticizer is eluted from the gasket into the polymerizable raw material, the UV transmissive property of the plasticizer of the methacrylic resin plate can be reduced. It is possible to stably suppress the decrease.

The viscosity average molecular weight of the entire methacrylic resin plate is not particularly limited, and is preferably 200,000 or more, more preferably 200,000 to 6,000,000, particularly preferably 200,000 to 4,000,000.
If the viscosity average molecular weight is less than 200,000, durability such as chemical resistance may be lowered.
If the viscosity average molecular weight exceeds 6 million, secondary processing of the methacrylic resin plate may be difficult.

The thickness of the methacrylic resin plate is not particularly limited, and is preferably 1 to 100 mm, more preferably 5 to 100 mm.
If the thickness of the methacrylic resin plate is less than 1 mm, it is difficult to produce the resin plate.
When the thickness of the methacrylic resin plate is more than 100 mm, it is difficult to carry out polymerization uniformly throughout.

  As described above, according to the present invention, the present invention can be preferably applied when the mold is arranged in a substantially horizontal direction, and even if the plasticizer is eluted from the gasket into the polymerizable raw material, the ultraviolet rays by the plasticizer of the methacrylic resin plate are used. It is possible to provide a method for producing a methacrylic resin plate by a cast plate method, which is capable of producing a methacrylic resin plate excellent in transparency, particularly ultraviolet ray permeability, in which a decrease in permeability is suppressed.

  In addition, with respect to the methacrylic resin plate obtained by the production method of the present invention, secondary processing such as bending and cutting can be performed by a known method as necessary.

  Examples and comparative examples according to the present invention will be described.

[Example 1]
(Preparation of polymerizable raw material)
500 g of methyl methacrylate (MMA) was placed in a 2 L reaction vessel and heated by a known method. When the temperature reached 130 ° C., 0.015% by mass of azobisisobutyronitrile (AIBN) as a polymerization initiator was added and mixed with stirring. Polymerization of MMA was carried out by continuing stirring and mixing at 130 ° C. for 40 minutes. The polymerization rate was 20%. Thereafter, 500 g of normal temperature (20 to 25 ° C.) MMA was added and stirred and mixed. By adding MMA at room temperature, the temperature of the reaction solution was lowered to about 50 ° C. to stop the reaction.
Furthermore, 0.012 g / kg of 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator and 0.018 g of terpinolene as a chain transfer agent were added and mixed with stirring.
As described above, syrup having 90 parts by mass of MMA and 10 parts by mass of PMMA as main components and a viscosity at 25 ° C. of 0.7 Pa · s was obtained as a polymerizable raw material.

(Preparation of mold)
A glass cell was prepared as a mold.
A commercially available soft vinyl chloride resin gasket containing dioctyl phthalate (DOP) as a plasticizer is sandwiched between two glass plates (vertical 20 cm, width 25 cm, thickness 5 mm). After that, these were fixed using a plurality of clamps. The distance between the two glass plates was 15 mm.

(Molding)
The polymerizable raw material (syrup) was injected into the internal space of the mold (glass cell) by a known method.
Next, the mold in which the polymerizable raw material was injected into the internal space was placed in a vacuum dryer, and the pressure was reduced to 1 kPa and held for 5 minutes.
Next, the mold was taken out from the vacuum dryer and immersed in a water bath adjusted to 60 ° C. for 15 hours (prepolymerization).
Next, the mold was placed in a hot stove, heated at 80 ° C. for 3 hours, heated from 80 ° C. to 130 ° C. over 1 hour, and heated at 130 ° C. for 3.5 hours (post-polymerization).
During the prepolymerization and postpolymerization, the mold was placed in a completely horizontal direction.
After completion of post-polymerization, the mold was removed from the hot stove and allowed to cool naturally to room temperature (20-25 ° C.). After the mold cooled, the methacrylic resin plate molded from the mold was peeled off and taken out.
As a result of measuring the viscosity average molecular weight of the obtained methacrylic resin using “capillary type automatic viscosity measuring device SS4-02-L1” manufactured by Shibayama Scientific Instruments, it was 3 million.
The outer peripheral part of the methacrylic resin plate taken out (outer peripheral end to 5 mm inner area from the gasket) was cut off.
As described above, a methacrylic resin plate having a length of 15 cm, a width of 20 cm, and a thickness of 13 mm was obtained.

[Comparative Example 1]
AIBN of 0.03 g / kg and terpinolene of 0.018 g were added to MMA and mixed by stirring to obtain a polymerizable raw material (monomer liquid) free from a methacrylic polymer.
A comparative methacrylic resin plate was obtained in the same manner as in Example 1 except that this polymerizable material was used.

[Evaluation]
(DOP amount)
The resin at a position of 5 mm from the gasket in the methacrylic resin plate obtained in each example of Example 1 and Comparative Example 1 was dissolved in chloroform, and the amount of DOP was measured by gas chromatography.
As shown in Table 1, in Example 1, a methacrylic resin plate containing almost no plasticizer was obtained.
The results are shown in Table 1.

(Measurement of spectral transmittance curve)
A sample plate of 5 cm square was cut out from the methacrylic resin plate obtained in each example of Example 1 and Comparative Example 1, and a spectrophotometer “UV-VIS-NIR Spectro Photometer UV-3600 manufactured by Shimadzu Corporation” was obtained. Was used to measure the spectral transmittance curve (change in transmittance with respect to wavelength).

  The spectral transmittance curves of the methacrylic resin plates obtained in each example of Example 1 and Comparative Example 1 are shown in FIG.

As shown in FIG. 1, in Comparative Example 1 using a monomer liquid as the polymerizable raw material, the plasticizer diffuses widely in the surface direction of the template due to the convection of the polymerizable raw material by heating, and in the part that actually becomes the product. However, a lot of plasticizer remained, and the UV transmittance of the methacrylic resin plate was lowered.
In Example 1 using 90 parts by weight of monomer (MMA) and 10 parts by weight of polymer (PMMA) as a polymerizable raw material, and using syrup having a viscosity of 0.1 to 10 Pa · s at 25 ° C. As a result, the convection diffusion of the plasticizer to the actual product portion was suppressed, and a methacrylic resin plate excellent in ultraviolet transmittance could be obtained. The spectral transmittance at 350 nm of the methacrylic resin plate obtained in Example 1 was 85% or more.

  The present invention is not limited to the above-described embodiments and examples, and can be appropriately modified without departing from the spirit of the present invention.

Claims (5)

60 to 90 parts by mass of at least one monomer containing methyl methacrylate and 40 to 10 parts by mass of at least one methacrylic polymer containing a monomer unit derived from methyl methacrylate, Without preparing a polymerizable raw material having a viscosity at 25 ° C. of 0.1 to 10 Pa · s,
Injecting the polymerizable raw material into the inner space of a mold composed of a pair of mold plates and a gasket and polymerizing and curing, and then removing the plate-like polymer from the mold and taking it out.
A method for producing a methacrylic resin plate. The gasket is made of a soft vinyl chloride resin,
The method for producing a methacrylic resin plate according to claim 1. While the polymerizable material is polymerized and cured, the mold is arranged in a substantially horizontal direction.
The manufacturing method of the methacrylic resin board of Claim 1 or 2. As the polymerizable raw material, 60 to 90 parts by mass of at least one monomer containing methyl methacrylate, 40 to 10 parts by mass of at least one methacrylic polymer containing a monomer unit derived from methyl methacrylate, Use only a polymerization initiator and a chain transfer agent.
The manufacturing method of the methacrylic resin board in any one of Claims 1-3. It is obtained by the manufacturing method according to any one of claims 1 to 4, and the ultraviolet ray absorbing substance derived from the gasket is 0.2% by mass or less.
Methacrylic resin plate.