JPS6366253A - Cast methacryl resin plate having excellent antistaticity and production thereof - Google Patents

Abstract

PURPOSE:To obtain a cast plate having high and permanent antistaticity and keeping the original characteristics of methyl methacrylate, by compounding a copolymer of methyl methacrylate and a monomer containing a quaternary ammonium base. CONSTITUTION:(A) 100pts.wt. of methyl methacrylate or a copolymer containing >=50wt% methyl methacrylate is compounded with (B) 0.1-20pts.wt. of a (co)poly mer obtained by polymerizing 20-100wt% monomer having quaternary ammo nium base and expressed by formula (R1 is H or methyl; R2-R4 are H or alkyl which may have 1-9C substituent group; m is 1-10; X<-> is anion of quaternarizing agent) and a monomer copolymerizable therewith. The composi tion can be produced by mixing the component B to a monomer mixture of the component A and polymerizing the mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a methacrylic resin cast plate having good and permanent antistatic properties and a method for producing the same.

Methacrylic resin cast plates are widely used for lighting equipment, signboards, building materials, various nameplates, decorations, etc. due to their excellent transparency, surface gloss, beautiful appearance, and good mechanical properties. ) Due to the high surface resistance value, it is easily charged and attracts dust, clumps, etc., damaging the appearance. P) It causes scratches. There is.

[Conventional technology]

Methods for imparting antistatic properties to Mekkrylic resin cast plates include (1) internal addition of surfactants, (2) surface coating, (3) surface coating of silicon compounds, and (4) surface modification by plasma treatment. It will be done. Among these (
Since both methods 3) and (4) are expensive, methods (1) and (2) are generally used.

The surfactants used include anionic, cationic, and nonionic surfactants, but compounds containing cationic quaternary ammonium salts are particularly known to provide excellent antistatic performance. .

When applying these surfactants to the surface, delicate operations are required to avoid damaging the surface condition of the methacrylic resin cast board, and the methacrylic/L' resin cast board treated in this way has However, there is a problem in that the antistatic agent attached to the surface easily falls off due to washing with water, friction, etc., and the antistatic performance is lost.

The method of internally adding a surfactant simplifies the manufacturing process because the antistatic agent is mixed or dispersed into the resin raw material before polymerization, but in order to obtain sufficient antistatic performance, it is generally necessary to add more. If dusting occurs, the transparency and mechanical properties of the methacrylic resin will be impaired, and the antistatic properties obtained will be easily lost due to washing with water, friction, etc.

In order to overcome the above-mentioned drawbacks of the internal addition method, attempts were made to use polymerizable monomers as antistatic agents (Japanese Patent Publication No. 4B-15471, Japanese Patent Publication No. 23395-1983).
issue). However, this type of product had the disadvantages of insufficient antistatic performance, strong adhesion between the plate obtained by cast polymerization and the mold, and difficulty in stable production.

[Problem to be solved by the invention 0 As described above, a megacrylic resin that does not require any special manufacturing process, permanently exhibits good antistatic performance, and maintains the physical properties inherent to methacrylic resin. Cast boards have not been proposed so far.

[Means for solving problems]

As a result of intensive studies on the above-mentioned problems, the present inventors have discovered that a good and permanent effect can be obtained by adding a small amount of a (co)polymer having a certain type of quaternary ammonium base during cast polymerization of methyl methacrylate. It has excellent antistatic performance,
It has been found that a megcryl resin cast plate that retains the original physical properties of methacrylic resin can be obtained.

That is, the invention of the present application provides a monomer mixture consisting of 50 weight or more of methyl methacrylate or methyμ methacrylate and 50 weight or less of at least one monomer copolymerizable therewith, or a partial polymer thereof (J) With respect to 100 parts by weight, the general formula % formula % (R + is a hydrogen atom or a methyl group, R3-R4 is a hydrogen atom or an alkyl group that may contain a substituent having 1 to 9 carbon atoms, m is 1 to 10, X is an anion of a quaternizing agent) Monomer 20 having a quaternary ammonium base represented by
-100% by weight, preferably 30-90% by weight and 80-0% by weight of at least one monomer copolymerizable therewith
(co)polymer (III) obtained by polymerizing a monomer or monomer mixture, preferably consisting of 70 to 10% by weight.
The present invention relates to a method for producing a methacrylate/I/resin cast plate with excellent antistatic properties, which is characterized by mixing and polymerizing 0.1 to 20 parts by weight, and a cast plate obtained by such a production method.

In the present invention, the copolymerizable monomers used in the methyl methacrylate monomer mixture or their partial polymers include methacrylic acid esters such as ethyl methacrylate, methyl methacrylate, and 2-ethylhexyl methacrylate, methyl acrylate, Acrylic acid esters such as ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid;
Acid anhydrides such as maleic anhydride and itaconic anhydride, N-phenylmaleimide, N-cyclohexylmaleimide, N
- Maleimide derivatives such as t-butylmaleimide, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl acrylate,
-Hydroxy group-containing monomers such as hydroxypropyl methacrylate, acrylamide, methacrylamide, acrylonitrium, methacrylateryl, diacetone acrylamide, dimethylaminoethyl methacrylate, etc., aliμ glycidiμ ether μ , epoxy group-containing monomers such as glycidyl acrylate and glycidyl methacrysate, styrene monomers such as styrene and α-methylstyrene, ethylene glyco! Examples include crosslinking agents such as diacrylate, allyl acrylate, ethylene glycol dimethacrylate, allyl methacrylate, divinylbenzene, and trimethylo-μ propane triacrylate.

The type and amount of the copolymerizable monomer can be appropriately selected depending on the properties of the intended cast plate.

In the present invention, the monomer having a quaternary ammonium base constituting the (co)polymer (II) is represented by the general formula 0 (R1-R4 and m are the same as above), and this can be obtained by quaternizing an acrylate or methacrylate having an amino group using a quaternizing agent. As the methacrylate or acrylate having an amino group, dimethylμ aminoethyl V-methacrylate;
Examples include diethylaminoethyl methacrylate, dimethylaminopropyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dimethylaminobutyl methacrylate, dihydroxyethylaminoethyl methacrylate, dipropylaminoethyl methacrylate, and dibutylaminoethyl methacrylate.

Examples of quaternizing agents include alkyl sulfates such as dimethyl sulfate, diethyl sulfate, and dipropyl sulfate, sulfonic acid esters such as methyl P-toluene sulfonate, and methyl benzenesulfonate, and alkyl phosphoric acids such as trimethyl phosphate. ,
Various halides such as alkyl bendi p chloride, benzyl chlorophyte, alkyl bromide, and alkyl bromide are used, and alkyl sulfates and sulfonic acid esters are particularly preferred from the viewpoint of heat decomposition resistance. m in the general formula is 1 to 1
0, but 2 to 6 are particularly preferred.

As the monomer copolymerizable with the monomer having a quaternary ammonium base, known monomers can be used. For example, methacrylate such as methyl acrylate, ethyl methacrylate, etc.
Acrylic acid esters such as phosphoric acid esters, methyl acrylate and ethyl acrylate, unsaturated carboxylic acids such as acrylic acid and meccrylic acid, acid anhydrides such as maleic anhydride and itaconic anhydride, maleimide derivatives such as N-phenylmaleimide, 2-hydroxyethylacrysate, 2-
Examples include hydroxy group-containing monomers such as hydroxypropyμ methacrylate, nitrogen-containing monomers such as acrylamide and acrylonitrile, and epoxy group-containing monomers such as allyl glycidyl ether and glycidyl acrylic 1/-).

Among these, the following general formula ('R6 is a hydrogen atom or a methyl group, 8 is a hydrogen atom or an Aμ group having 1 to 18 carbon atoms, an Avrv group, an aryl group, an aralkyl group, and A is a C2 to C2 group) 4 alkylene group,
A compound selected from the following (n is 0 to 500) is used.

The preferred composition of the (co)polymer (n) in the present invention is:
30 to 90 monomer components having a quaternary ammonium base
It contains 10 to 70% by weight of a monomer component copolymerizable with polyalkylene glyco-μ component.

If the monomer component having a quaternary ammonium base in (co)polymer 0 is less than 30% by weight, especially less than 20% by weight, it may not be possible to impart good antistatic properties to the resulting methacrylic resin cast plate. , 90% by weight or more, the solubility for the methyl methacrylate monomer (mixture) or its partial polymer CI) tends to be insufficient.

The method for preparing the (co)polymer (I[) is not particularly limited, but techniques such as solution polymerization and bulk polymerization in the presence of a usual radical polymerization initiator and chain transfer agent can be used. In particular, solution polymerization is preferable because polymerization can be carried out in a homogeneous system. In the case of solution polymerization, various addition methods such as bulk addition, divided addition, and dropwise addition of monomers can be employed.

The molecular weight of the (co)polymer (II) in the present invention is 10
It is preferable that it is 00 or more. If it is less than 1,000, good permanent antistatic performance may not be obtained, and the heat resistance inherent to the Shimekuri μ resin tends to be lowered due to the plasticizing effect.

Methyl methacrylate monomer (co)polymer (II) (
The amount added is preferably from 0.1 to 20 parts by weight, particularly preferably from 5 to 10 parts by weight, per 100 parts by weight of the mixture) or its partial polymer (I).

If the amount added is less than 0.1 part by weight, good antistatic performance cannot be imparted, and if it exceeds 20 parts by weight, the inherent physical properties of the methacrylic resin will be greatly impaired and the cost will increase.

The methacrylic resin cast plate with excellent antistatic properties in the present invention is preferably manufactured by a cast polymerization method commonly practiced by those skilled in the art. That is, 50% by weight or more of methyl methacrylate or methyl methacrylate and 50% by weight of at least one type of monomer that can be copolymerized.
Polymer (II) in a predetermined area is added to a monomer mixture consisting of the following or a partial polymer thereof (I) and dissolved uniformly, and a radical polymerization initiator is further added to the resulting mixture. and use it as casting raw material.

The raw materials were placed facing each other with the periphery sealed with a gasket.
A space sealed with a gasket and a 7μ casting method in which it is injected between two inorganic glass plates or metal plates and heated, or with two mirror-polished stainless steel endless belts that move in the same direction and at the same speed. A specific polymerization method is a continuous casting method in which the above-mentioned casting raw material is continuously injected and heated from upstream.

To polymerize the above-mentioned polymerizable raw material (I) of the present invention,
It is preferable to use a radical polymerization initiator such as an azo compound or an organic peroxide.

Specific examples of azo compounds include 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylpanronitrile), 2,2'-azobis(2,4
Specific examples of organic peroxides include benzoyl peroxide, lauroyl peroxide, and the like. In addition, Ndox-based polymerization initiators,
For example, combinations of organic peroxides and amines can also be used.

The polymerization temperature when producing the methacrylic resin cast plate of the present invention by polymerization varies depending on the type of radical polymerization initiator used, but is generally 10 to 150°C.

The thickness of the cast plate obtained by the cast polymerization method is not particularly limited, but it is usually the thickness that is commercially available, that is, 0.2 ~
Preferably, it is within a range of 65 m.

Furthermore, additives such as colorants, ultraviolet absorbers, heat stabilizers, other antistatic agents, lightning protection agents, etc. can be mixed and used in any of the convenient steps of the invention.

Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

The electrical properties of all samples were measured after being conditioned at 23° C. and 65% relative humidity for one day.

For the charge half-life time, use a static one-meter meter (manufactured by Sagetsu Shokai) and apply an applied voltage of 1ooo.

■ Measured under the conditions of sample rotation speed 1300 rpm, application time 30 seconds, measurement humidity 23℃, measurement humidity 65℃, sample voltage at the time of voltage application is initial voltage (V), sample voltage after voltage application is half of the initial voltage The time it takes for the charge to halve (s
ee). The surface resistance value was measured using a super insulation resistance meter (manufactured by TAGADA RIKEN, TR-8601) at a measurement temperature of 23℃ and a measurement humidity of 65%, and after 1 minute at an applied voltage of 500μ ) was measured. Wash at 30℃
Ultrasonic cleaning was performed in warm water for 30 minutes. Regarding heat resistance, the sample was subjected to annealing and HDT (6) was measured according to ASTM D648. ASTM for strength
A tensile test was conducted according to D63B, and the tensile elastic modulus and tensile breaking strength were measured. Regarding transparency, an integrating sphere haze meter (manufactured by Nippon Seimitsu Kogaku, 5EP-a-SS) was used.
) was used to measure the haze value.

Example 1 Into a 3t glass flask equipped with a stirring blade, 374 parts by weight of Jethi μ aminoethyl methacrylate, 4 parts by weight of hydroquinone methyl ether, and 450 parts by weight of Mekno/l' were added, and while stirring, 252 parts by weight of dimethyl sulfate and methanol were added. /l/80 parts by weight of the mixture was added dropwise at a temperature of 30° C. or below, and stirring was continued for 30 minutes after the completion of the addition to obtain a monomer (M-1) solution having a quaternary ammonium base.

To this solution, 6 parts by weight of azobisisobutyronitrile, n
- Octime μcaptan 4 parts by weight, methanol/l/48
0 parts by weight and 620 parts by weight of polyethylene glyco/l/(2!l) monomethacrylate monomethyl ether were added, and the mixture was polymerized at 60°C under a nitrogen atmosphere for 4 hours. After polymerization, the mixture was directly vacuum-dried to obtain a copolymer (P-1). Methyl methacrylate partial polymer (viscosity 100 centipoise,
After dissolving 5 parts by weight of the above copolymer (P-1) in 100 parts by weight (polymerization rate 8%), and 05 parts by weight of 2'-azobisisobutyronitrile Q as a polymerization initiator. , vacuum is applied to remove dissolved air, the gasket and two pieces of tempered glass are formed, and the thickness is 31! Pour into a cell set to II+. Polymerization was carried out at 60°C for 10 hours and at 110°C for 4 hours. This cast plate had a surface resistivity of 2.0×10”Ω, a charge half-life time of 52 seconds, and a haze value of 2.5 inches.

In addition, the obtained board was washed with water and immediately evaluated for antistatic performance, and the surface resistivity was 1.5 x 10110, and the charge was halved in time! It was Lo seconds.

In addition, an HDT specimen was prepared according to ASTM D648, and the HDT was measured after annealing, and it was 100°C.
When a tensile test was conducted according to ASTM D638, the tensile modulus of elasticity was 3 x 10' (kg/2), and the tensile strength at break was 750 (y/α2).

Comparative Example 1 After dissolving 0.05 parts by weight of 2゜2'-azobisisobutyronitrile in 100 parts by weight of methyl methacrylate partial polymer (viscosity 100 centipoise, polymerization rate 8%), the same procedure as in Example 1 was carried out. A cast plate with a thickness of 3 m was obtained by polymerization according to the method. The surface resistivity of this plate is 10160 or more,
The charge half-life time was 120 seconds or more, and the haze value was 1.0 chi.

] (DT is 100℃, tensile modulus is 3
10' (kg/1yn2), tensile breaking strength is 760 (
k! 9/6n2).

Examples 2 to 4 1.0 to 10.0 parts by weight of copolymer P-1 obtained in Example 1 were added and mixed to 100 parts by weight of methyl methacrylate partial polymer (viscosity 100 centipoise, polymerization rate 8%). By the same method as in Example 1, a methacrylic resin cast plate having a thickness of 3tllIH was obtained.

Table 1 shows the evaluation results of antistatic performance and other physical properties after humidity conditioning for one day in an atmosphere of 23° C. and 65° relative humidity.

Examples 5 to 9 Monomer M- containing quaternary ammonium base obtained in Example 1
1 solution, add a monomer mixture having the composition shown in Table 2, and polymerize in the same manner as in Example 1 to obtain a copolymer (P-2~
6) was obtained. Using 2.0 parts by weight of each of these copolymers, a methacrylic resin cast plate having a thickness of 3 cm was obtained in the same manner as in Example 1. Table 3 shows the evaluation results of antistatic performance and other physical properties after humidity conditioning at 23° C. and 65° relative humidity for one day.

Examples 10 to 14 A copolymer having a quaternary ammonium base (
P-7 to P-11) Obtained. 2.0 parts by weight of these were added to 100 parts by weight of methyl methacrylate partial polymer (viscosity 100 centipoise, polymerization rate 8 cm), and Example 1
A methacrylic resin plate with a thickness of 3 sheets was obtained using the same method as above. Table 5 shows the evaluation results of antistatic performance and other physical properties after conditioning the humidity in an atmosphere of 23° C. and 65 relative humidity for one day.

Example 15 To 100 parts by weight of methyl methacrylate partial polymer (viscosity 1000 centipoise, polymerization rate 20%), 20 parts by weight of copolymer P-1 obtained in Example 1, 2.
A mixture of 10.05 parts by weight of 2'-azobisisobutyronitrile/I and sodium dioctyl sulfosuccinate 4 o, o o s as a mold release agent is shown in Japanese Patent Publication No. 52-30985. A methacrylic resin plate having a thickness of 5111I+ was produced by polymerization using a continuous plate making apparatus such as the above. Polymerization was carried out in a warm water atmosphere at 70°C for 60 minutes, and then in an air atmosphere at 130°C for 15 minutes to complete the polymerization. Example 1 The obtained methacrylic resin cast plate
When evaluated in the same manner as above, the surface resistivity was 5.0×10'Ω
The charge half-life time was 1.7 seconds, the haze value was 4.0%, and the surface resistivity after washing with water was 56×1090.

Also, the tensile elastic modulus is l OX 1 o'IKg/crn
”, tensile breaking strength is 740 kg/cm2, HDT is 1
It was 00℃.

Example 16 Example 15 except that P-3 was used instead of copolymer P-1
In the same manner as above, a methacrylic resin cast board with a thickness of 3 days was obtained. The surface resistivity was 2°5×1010Ω, the charge half-life time was 23 seconds, the haze value was 50°, and the surface resistivity after washing with water was ZOX1010Ω.

In addition, the tensile elastic modulus is 5OX 10'kg/lyn",
The tensile strength at break was 740 kg/cm'', and the HDT was 100°C.

Comparative Examples 2 to 4 Monomer M- containing a quaternary ammonium base obtained in Example 1
1 solution, add a monomer mixture with the composition shown in Table 2,
Polymerization was performed in the same manner as in Example 1 to obtain a copolymer (P-12
-14) were obtained.

Using 0.5 parts by weight, 2.0 parts by weight, and 2.0 parts by weight of these copolymers, methacrylic resin cast plates having a thickness of 3 mm were obtained in the same manner as in Example 1. Table 6 shows the performance evaluation results of the obtained cast plate.

Comparative Example 5 5 parts by weight of glycerin monostearate was added and mixed to 100 parts by weight of methyl methacrylate partial polymer (viscosity 1007 inch, polymerization rate 8%), and the same method as in Example 1 was used to prepare a plate with a thickness of 3W11. A methacrylic resin cast plate was obtained. Table 6 shows the performance and evaluation results of this cast board.

Comparative Example 6 Coating type antistatic agent having quaternary ammonium base (Staticide, Analytical Chemical L
A methacrylic resin plate (Acrylite, manufactured by Mitsubishi Rayon) with a thickness of 6 cm was immersed in a 1.5 inch aqueous solution of Aboratories Co., Ltd. for 1 minute, and after air drying, it was evaluated in the same manner as in Example 1. The results are shown in Table 6.

[Efficacy of invention]

The invention of the present application has good and permanent antistatic performance,
The object of the present invention is to provide a methacrylic resin cast plate and a method for manufacturing the same without degrading the original physical properties of the methacrylic resin. This metal-acrylic resin cast plate does not cause problems due to static electricity, so it can be used in industries that require high reliability, such as electronics-related fields.

Table 2 Monomethacrylate monomethyl ether PEG (500
): polyethylene v nguri = ff-fi/(500) monomethacrylate monomethyl ether MMA:
Methyl methacrylate 1 width table 4 7'iJ: l,, DEMA Ni-diethylaminoethyl methacrylate DMMA Ni-dimethylaminoethyl methacrylate DEA Ni-diethylaminoethyl acrylate DES Ni-diethyl sulfate DMS Nidimethyl〃 Ts-OMe: p-toμene methyl phonate
CL: Methyl chloride procedural amendment 1. Description of the case Patent Application No. 211158 of 1985 2 Name of the invention Methacrylic resin cast plate with excellent antistatic properties and its manufacturing method 3 Person making the amendment Relationship to the case Patent applicant 2-3 Kyobashi, Chuo-ku, Tokyo No. 1g (603) Mitsubishi Rayon Co., Ltd. President Akio Kawasaki 4, Agent 5, Date of amendment order (1) Addition of (co)polymer (n) described on page 15, lines 16-17 of the specification "(co)polymer (II) is added and uniformly dissolved or suspended" is corrected to "(co)polymer (II) is added and uniformly dissolved or suspended").

(2) "620 parts by weight of polyethylene glycol (23) monomethacrylate monomethyl ether" described on page 19, lines 7 to 9 of the specification.
) Monomethacrylate monomethyl ether [The number in parentheses is the number of polyethylene glycol units, 1620 parts by weight.”
Correct.

(3) "Comparative Example 2 - Sleeve" described in page 24, line 4 of the specification "Contains" is corrected to "Example 17, Comparative Examples 2-3".

(4) "Comparative Example 5" written on line 14 is corrected to "Comparative Example 4".

(5) "Comparative Example 6" written in the first line of page 25 of the specification is corrected to "Comparative Example 5."

(6) Table 2 on page 27 of the specification and Table 6 on page 31 are corrected as shown in the attached sheet.

Table

Claims (1)

[Claims] 1. Methyl methacrylate or methyl methacrylate 5
100 parts by weight of a (co)polymer consisting of 0% by weight or more and 50% by weight or less of at least one monomer copolymerizable with the polymer, and the general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (R_1 is hydrogen atom or methyl group, R_2 to R_4 are hydrogen atoms or alkyl groups that may contain substituents having 1 to 9 carbon atoms, m is 1 to 10, X^- is an anion of a quaternizing agent) Monomer 20 having a quaternary ammonium base
(Co)polymer (II) 0.1 to 20% by weight obtained by polymerizing a monomer (mixture) consisting of 100% by weight and 80 to 0% by weight of at least one monomer copolymerizable therewith. A methacrylic resin cast plate with excellent antistatic properties. 2. Methyl methacrylate or methyl methacrylate 5
For 100 parts by weight of a monomer mixture consisting of 0% by weight or more and 50% by weight or less of at least one copolymerizable monomer, or a partial polymer thereof (I), the general formula ▲ mathematical formula, chemical formula, There are tables, etc. ▼ (R_1 is a hydrogen atom or a methyl group, R_2 to R_4 are hydrogen atoms or an alkyl group that may contain a substituent having 1 to 9 carbon atoms, m is 1 to 10, and X^- is a Anion of a grading agent) A monomer having a quaternary ammonium base represented by 20~
(Co)polymer (II) obtained by polymerizing a monomer (mixture) consisting of 100% by weight and 80 to 0% by weight of at least one type of monomer copolymerizable with the monomer (co)polymer (II) 0.1 to 20% A method for producing a methacrylic resin cast plate with excellent antistatic properties, which is characterized by mixing and polymerizing parts by weight. 3. 30 to 90% by weight of a monomer having a quaternary ammonium base and at least one monomer copolymerizable with the monomer 70
A method for producing a methacrylic resin cast plate with excellent antistatic properties according to claim 2, which uses a copolymer obtained by polymerizing a monomer mixture consisting of ~10% by weight. 4. Monomers that can be copolymerized with monomers having a quaternary ammonium base include the following general formula ▲ mathematical formula, chemical formula, table, etc. ▼ (R_5 is a hydrogen atom or a methyl group, R_6 is a hydrogen atom or the number of carbon atoms) 1 to 18 alkyl group, allyl group, aryl group, aralkyl group, A is an alkylene group having 2 to 4 carbon atoms, n
0 to 500) A method for manufacturing a methacrylic resin cast plate having excellent antistatic properties according to claim 2, wherein a compound selected from the following is used. 5. The counter anion of the quaternary ammonium base has the general formula R_7SO_3^- or R_7OSO_3^-(R_7
3. The method for producing a methacrylic resin cast plate having excellent antistatic properties according to claim 2, wherein is a hydrogen atom or an alkyl group which may contain a phenyl group having 1 to 20 carbon atoms. 6. A methacrylic resin cast plate with excellent antistatic properties as set forth in claim 2, wherein polymerization during production of the cast plate is carried out in a mold composed of two inorganic glass plates or metal plates and a gasket. manufacturing method. 7. The claim that the polymerization during production of the cast plate is carried out continuously in a mold consisting of two single-sided mirror-polished stainless steel endless belts and gaskets that proceed in the same direction and at the same speed. 2. A method for producing a methacrylic resin cast plate with excellent antistatic properties as described in item 2.