JPS58201812A - Transparent plastic - Google Patents

Abstract

PURPOSE:A transparent plastic having high refractive index, improved chemical resistance, water and solvent resistance, and mechanical processing properties, etc., obtained by polymerizing a mixed monomer system consisting of a monofunctional monomer, a polyfunctional monomer and a dimer of alpha-methylstyrene. CONSTITUTION:A polymerization initiator (e.g., azobisisobutyronitrile, etc.) is added to a mixed monomer system consisting of 70-95wt% one or more monomers such as vinyl acetate, vinyl chloride, vinylidene chloride, etc., 5-30wt% one or more monomers such as ethylene glycol, dimethacrylate, triethylene glycol, etc., and 0.1-2wt% dimer of alpha-methylstyrene, the mixed monomer system is previously polymerized to give syrup, which is polymerized to give the desired plastic having >=70% light transmittance in a visible range.

Description

Detailed Description of the Invention The present invention provides a hard transparent glass material that can be used for optical purposes, and in particular has excellent physical properties such as transparency, chemical resistance, water resistance, solvent resistance, heat resistance, and machinability. It concerns transparent plastic.

Conventionally, hard transparent F3JJv is used to make optical lenses and prisms by injection molding! The 4-fat raw materials include polymethyl methacrylate (PMMA), polycarbonate (PC), polystyrene (Ps), acrylonitrile-styrene copolymer resin (A/8), and methacrylic acid-styrene copolymer resin (VIJ). MA8), styrene, butadiene copolymer resin, polymethylpentene (TPX)
etc. Among these resins, PMMA is the most commonly used (used for optical purposes).The reason is that PMMA has relatively good optical properties such as low transparency and low birefringence. .PC,PS,As%MA
Grade 8 has a high refractive index among plastics and is optically attractive, but it has strong birefringence (and is slightly less transparent than PMMA, and the resin is not hard enough and is easily scratched). As and PS have many problems in terms of weather resistance, heat resistance, etc.As TPX is a crystalline resin, it generates strong birefringence just like PC.Also, these resins can be injection molded. = 3-, it is difficult to avoid the occurrence of molecular orientation that has a strong influence on birefringence.In other words, resins used for optical applications must have excellent transparency, refractive index, high stability in terms of dispersion, etc. Because of the necessity, it is undesirable to treat the resins with various modifiers, so that the selection range of resins for optical applications is becoming increasingly narrow.

Diethylene glycol bisallyl carbonate, known as CI (-39), is a thermosetting resin whose molecular structure has a three-dimensional three-dimensional network structure.

For this reason, CR-39 is inferior in chemical resistance, water resistance, solvent resistance, heat resistance, machinability, etc., compared to other resins. However, the monomer of CR-39 is difficult to synthesize and the cost of raw materials is high. In addition, molded products of CR-39 are obtained by cast polymerization using a glass mold, but the polymerization pressure is not required for a long time because the reactivity of the 7-mer is low and the volumetric shrinkage during conversion from monomer to polymer is large. (for example, several days). Even after it becomes a polymer, unreacted portions of about 10% to 20% remain, so deformation and shrinkage are likely to occur when heat treatment is applied. Due to these various circumstances, CR-394- is polished or cut after casting to obtain the final shape.
Even if the price per weight is high, it is acceptable and is only used in fields such as eyelid lenses.

Recent advances in numerical control using computers, linear motors as drive mechanisms, encoders for precision position detection of air bearings, and development of interferometric measurement methods using infrared laser light.
Development of diamond tools Various machine tools for ultra-precision machining have been developed from isobaric machines. People are beginning to think of using such ultra-precision machine tools to make aspheric lenses, prisms, reflectors, etc. from plastic. Generally, glass is hard and brittle, so it is extremely difficult to process it with ultra-precision machine tools. On the other hand, thermoprintable plastics are easily thermally fused, and phenomena such as sticky deformation occur, so machining is almost impossible.

The object of the present invention is that the refractive index is at least higher than that of PMMA;
The object of the present invention is to provide a transparent plastic that is transparent, has excellent chemical resistance, water resistance, solvent resistance, heat resistance, and excellent machinability.

The present inventors have carried out research on the idea that a cast molding resin obtained by copolymerization and crosslinking polymerization may be optimal in meeting these requirements, and as a result, they have achieved the present invention.

That is, the transparent plastic of the present invention has the following first weight ratio:
At least 70% by weight of one type of first monomer as shown in the table (9)
Less than 5% by weight and less than 1 type of secondary
Obtained by polymerizing a mixed monomer system mainly consisting of 5% Ik% or more and less than 30% by weight of monomers and 0.1 to 2% by weight of α-methylstyrene dimer in the presence of a radical polymerization initiator, 70 % or more visible area (380-800 n
It has a light transmittance of I+# length).

Table 1 Furthermore, the transparent plastic of the present invention is thermosetting and does not exhibit phenomena such as stickiness, melting, or deformation due to generated heat. Therefore, this transparent plastic is extremely suitable for manufacturing aspherical lenses, prisms, and reflective mirrors by machining. 'In addition, the transparent glass of the present invention can be easily made into large plate-like products, so it can be used as window glass materials, lighting covers for solar water heaters, protective covers for solar cells, transparent covers for various meters, etc. You can also use it.

Furthermore, according to the present invention, it is also possible to produce transparent plastics with various refractive indexes, which are products with high optical utility value, in small-scale production quantities.

The present invention will be explained in detail below.

In general, the polymerization reaction of monomers is an exothermic reaction, so once the polymerization reaction starts, the heat generated causes the reaction to progress, and beyond a certain point, an explosive reaction occurs, a so-called runaway reaction. Easy to foam.

Furthermore, as the monomer state becomes a polymer, the distance between molecules becomes smaller, so it is inevitable that volumetric shrinkage will occur during polymerization. For this reason, in normal cast polymerization, a method is adopted in which the amount of catalyst (or amount of initiator) is reduced and the reaction is carried out slowly at low temperature for a long time. The heat of polymerization of various types of hexamers is shown in Table 3 below.

Table 3 In addition, the following Table 4 shows the polymerization volumetric shrinkage rates of various monomers.

Table 4 In the course of the research, the inventors focused on the following points and continued experiments.

1) Even in cross-linking polymerization, if prepolymerization is performed before main polymerization in the mold, most of the volume shrinkage will be completed at the prepolymerization stage, and therefore the amount of heat generated will be less during main polymerization. Therefore, runaway reactions can be prevented and the reaction time can be shortened.

2) In order to obtain a hard resin, it is not just a matter of mixing monomers appropriately, but there may be a certain range of types and amounts of monomers to be combined.

The present inventors paid attention to the following documents and facts regarding the above l). Namely, "Polymer Chemistry", Chapter 2, by P. J. Flory, co-translated by Koten Oka and Kyo Kanamaru, (Maruzen) and CsH,
According to "Chemistry of Polymers" Chapters 1 to 3 (Gihodo), co-translated by E-Bawnii, Hisao Sato, and Yuya Yamashita, in the cross-linked polymerization or reaction process of polymers having a network structure,
The product in its early stages is soluble in solvents and is therefore considered to be a linear polymer.

In addition, according to Naoki Yoshimi, "Diallyl phthalate resin," Plastic Materials Course 3, pages 12-14, (Nikkan Kogyo Shimbun), diallyl phthalate monomer becomes a β-polymer in the first stage reaction, and this material is melted. It is a softening thermoplastic resin and is said to be soluble in solvents.

-12- The diallyl phthalate resin is either a β-polymer further polymerized in the second stage reaction to become a γ-polymer, or this resin is infusible and insoluble.

In short, even if the thermosetting resin has a tertiary steric network structure, it is presumed that a linear polymer is formed in the initial stage of the polymerization reaction.

On the other hand, the molecular structure of the enthusiasm W resin is linear, and it is generally believed that the length of this molecular chain determines the basic physical properties of the resin. A molecular weight regulator is used to determine the length of the molecular chain. This is also called a chain transfer agent, PS
, PMMA, AS, etc., n-butyl mercaptan, n-dodecyl mercaptan, etc. are used. These also help shorten the polymerization reaction time.

The present inventors have discovered that even in the case of cross-linking polymerization, by using an appropriate molecular weight regulator at the initial stage of the reaction, the number of linear polymers can be dramatically increased, and most of the seven polymers in the system can be It was speculated that - could be converted into a polymer. The initial stage of the reaction is called prepolymerization, and the resulting liquid (actually, it is a viscous liquid with various viscosities)
When we refer to syrup as syrup, we speculate that by first prepolymerizing the raw monomers to make syrup, most of the volume shrinkage and reaction heat generated during the entire reaction process are generated during the prepolymerization process.

Mercaptans as molecular weight modifiers are toxic and have a strong odor (and are inconvenient to handle in small-scale equipment. Therefore, the inventors set the following conditions when selecting a molecular weight modifier. did.

l The preparation itself must be transparent. Also, it must not color the polymer.

■) High refractive index.

l) It is a type that has a weak effect and is used in relatively large amounts.

It must be easy and safe to handle.

As a regulator that satisfies the above conditions, the 2tR form of α-methylstyrene c2-4 “phenyl-4-methyl-1
-Pentene, nD = 1.536) Y selected.

The dimer of α-methylstyrene is expressed by the following formula It is said that molecular radicals are stabilized by oxidation.

The effect of the α-methylstyrene dimer as a molecular weight regulator varies depending on the monomers to be mixed, but it is said to have an effect of 14 to 4) when compared to mercaptans. The crosslinking reaction takes place at a certain temperature or higher after the monomers start polymerization, so if the monomer is converted into a polymer before the crosslinking reaction, almost only the crosslinking reaction will occur during the main polymerization. Become. In order to smoothly perform the conversion to the polymer before this crosslinking reaction and to shift the crosslinking reaction as far back as possible, the α-methylstyrene dimer was converted into a mixed monomer system of S : Less than double t% -15
It was found that adding it at - is effective. If the amount added exceeds 2% by weight, the initial growth of molecular chains will be suppressed and the polymerization reaction will be extremely slow or polymerization will not occur. In this way, a prepolymerization rate of up to 30% can be achieved, and the remaining volumetric shrinkage is only a few percent in the case of
It is. Even if the prepolymerization rate is 15 to 20%, the residual volumetric shrinkage during conversion from syrup to polymer is almost 7% or less, making it possible to carry out cast polymerization very easily.

In the cast polymerization method, which involves injecting syrup into a glass mold,
Since the main reaction is a crosslinking reaction rather than a mere polymerization of mixed monomers, the reaction temperature can be set high from the beginning, making it possible to significantly shorten the main polymerization time.

Moreover, since the α-methylstyrene dimer itself has a high refractive index, it also contributes to improving the refractive index of the resulting polymer.

The first monomer shown in Table 1 is a monofunctional monomer, and the polymer obtained from it is almost transparent and forms a -16-linear polymer.

Although this homopolymer is well known, it has problems with solvent resistance and heat resistance, so it has not been widely used in optical applications such as lenses.

The second monomer shown in Table 2 is a polyfunctional monomer,
It is mainly used as a crosslinking agent or modifier, or as a base monomer for thermosetting resins. The homopolymer is rarely used. The reason for this is that the polymerization reaction is difficult to occur and crosslinking occurs at an extremely low degree of polymerization, so that a portion of unreacted monomers is incorporated into the polymer. As a result, only polymers with many defects such as difficulty in becoming hard or extremely brittle polymers even after hardness can be obtained.

As a result of various experiments +'Y, N%, the present inventors found that
When the properties of the first monomer and its polymerization properties shown in Table 1 are combined with the properties of the second monomer and its polymerization properties shown in Table 2, a polymer having the desired physical properties can be obtained. I have come to the conclusion that I may be able to obtain it.

As a result of experiments, the reactivity of each of the first monomers shown in Table 1, except for styrene, α-methylstyrene, ethyl crotonate, etc., was improved by adding a small amount of the crosslinked second monomer shown in Table 2. , was found to be about the same as y. The same tendency is observed in the case of a mixture of two or more types of additives, but when styrene, α-methylstyrene, or ethyl crotonate is used, the reactivity becomes much worse, requiring a higher reaction temperature and longer reaction time. Vinyl chloride monomer shows a somewhat similar trend.

It has also been found that it is easier to control the reaction when the second monomer shown in Table 2 is used in a smaller amount than the first monomer shown in Table 1. The second monomers listed in Table 2 are generally less reactive than the nine first monomers listed in Table 1.

Therefore, if a large amount of the 27th monomer shown in Table 2 is used, the polymerization reaction proceeds faster than the 1st monomer shown in Table 1, causing gelation of the entire system and fluidization of the monomer system. After the properties are lost, the second monomer shown in Table 2 is activated, so the unreacted portion of the second monomer remains in the polymer, which improves the physical properties of the resulting polymer, especially heat resistance. It turned out that it was either bad or bad.

Based on the above, the present inventors divided the monomer composition of the reaction system into three parts and polymerized them as a mixed monomer system with determined composition ratios, thereby obtaining the desired transparent glasstic with excellent physical properties. I discovered that.

The first monomer has a monomer composition shown in Table m1 or a mixture of two or more thereof, and the amount used is 70% by weight or more and less than 95% by weight. When mixing two or more types,
The mixing ratio is preferably 90 M% or more for one side.

The second monomer is one of the monomers shown in Table 2 or a mixture of two, and the amount used is 5% by weight or more and 30% by weight.
less than % precious. When two or more kinds are mixed, one of them is preferably ethylene glycol dimethacrylate.

In this case as well, the mixing ratio is preferably 85% or more for one side.

Prepolymerization is carried out as follows. That is, the first mode 19
- A mixed monomer system is prepared by weighing predetermined amounts of the monomer, the second monomer, and the dimer of α-methylstyrene as the third monomer. A predetermined amount of a reaction initiator is added to this system, and the temperature of the system is gradually raised while stirring slowly to carry out polymerization. Polymerization started at around 60℃, generating 5 polymerization heat (
Ru. Therefore, raise the temperature more slowly. Prepolymerization is usually 8
The prepolymerization proceeds at a temperature of 5° C. to 95° C., or if the main component of the first monomer is styrene or α-methylstyrene, the prepolymerization proceeds at a higher temperature. Since no crosslinking reaction occurs during prepolymerization, the reaction is usually stopped before the gelation point. Once gelation begins, the cross-linking reaction proceeds all at once, forming monomers or complete polymers, making it impossible to control the reaction. The method for stopping the reaction in prepolymerization is to stop heating the system before the gelation point, cool the system quickly while stirring slowly, and raise the monomer temperature to a maximum of 10°C, preferably 2 to 5°C. Cool to ℃. If the refractive index is higher than the original value, prepolymerization has taken place and the resulting monomer becomes a syrup. This Shiroto 20-P can be used at temperatures below 10°C if it is kept from contact with air.
No deterioration occurs within 4 hours.

Gas in the syrup is removed while stirring using an exhaust bell or the like. At this time, it is preferable that the degree of vacuum is 15 to H9 or less, and the exhaust is performed for 15 to 20 minutes. After the degassed syrup is injected into a cell such as a glass type through a gasket made of vinyl chloride or the like around it, the air in the cell is evacuated at the joint to perform main polymerization. FIG. 1 shows a flat glass cell assembly used to carry out the main polymerization, and FIG. 2 shows the polymer obtained therefrom.

In Figure 1, 1 is a glass plate, 2 is a vinyl chloride gasket, 3 is a clamp with a spring, and 4 is a glass plate 1.
This is the syrup injected into the cell defined by the gasket 2 and the gasket 2. In FIG. 2, reference numeral 5 denotes a polymer obtained by polymerization in the glass cell assembly of FIG. 1 and held by a gasket 2, that is, transparent glass.

The main polymerization is carried out by pressurizing the cell in a hot air circulation furnace or hot water bath.
Finally, it is cured at high temperature to form a polymer.

The transparent plastic obtained by the present invention has good transparency, is hard, and has a refractive index of almost nD = 1.5 or more. Birefringence is almost unnoticeable unless the amount of styrene or α-methylstyrene is increased, and the optical properties are stable. The heat resistance was found to be sufficient as the rubber hardness measured after heat treating the resin at 120° C. for 2 hours was 95 or more for Shore 8 type, and there was no deformation. In addition, the solvent and water resistance of this plastic is poor, and P
Unlike boards made of C or PMMA, it does not expand due to moisture absorption and warp.

FIG. 3 shows an example of an aspherical lens 6 obtained by processing the transparent glass obtained according to the present invention using an ultra-precision machine tool. One side of the aspherical lens 6 is a flat surface, and the aspherical surface has an axial direction of Z, an incident height of H1, and a Nikkei of R (in this example, 24 degrees).
Then, it can be expressed by the following formula.

The present invention will be explained below with reference to examples.

Example 1 Methyl methacrylate (MMA) 8:1 styrene (SM) 4 g diallyl terephthalate (DATP) 79 ethylene glycol dimethacrylate (EGDMA) 5 g α-methylstyrene dimer (α-MSD) A syrup was prepared by adding 0.2 g of azobisisobutyronitrile as a polymerization initiator to the mixed monomer system consisting of 19.

After the produced syrup was vacuum degassed, it was placed in a glass cell as shown in FIG. 1 and main polymerization was carried out to obtain a transparent glasstic resin with a thickness of 5 cm. Main polymerization conditions were 75°C x 2hr, 1
It was carried out in three stages: 15°C x lhr and 130°C x 0.5hr.

The resulting resin was transparent and had a refractive index of nD = 1.5050. This resin was heat treated at 120°C for 2 hours and the hardness of the resin at high temperature was measured, and it was found to be 95 on Shore A rubber hardness.・No deformation or discoloration after heat treatment was observed.

In addition, even when this resin was cut with a lathe, it did not melt or stick (it had excellent machinability). Observe the appearance by immersing it in solvents such as acetone alcohol, methylene dichloride, xylene, toluene, MMA and DATP,
After the solvent was volatilized, the weight was measured and it was found that there was no change in appearance and the weight change was about 3 to 5%. This is in sharp contrast to the fact that, for example, PMMA cutting waste easily dissolves in Narene dichloride or acetone, swells and significantly increases in weight, and proves that the resin of the present invention has good solvent resistance. I can say that.

Example 2 MMA339, α-methylstyrene (α-MS) 79r
, DATP4gr, EGDMA59r, a-M
0.1 of dicumyl peroxide (PCD) and t-
A syrup was made by adding 0.6 g of butylperoxyisopropyl car-24 (FBI). After the produced syrup was degassed under vacuum, main polymerization was carried out in the glass cell assembly shown in FIG. 1 to obtain a transparent plastic resin having a thickness of 5 layers. Main polymerization conditions were 80°C x 3 hr, 90
M? : XI hr, 120CX 0.5 hr.

The refractive index of the obtained resin was nD = 1°5063.

The rubber hardness at high temperature after heat treatment at 120°C x 2 hrO is Shore A and is 100 or more, with no deformation or discoloration.
It showed the same results as Example 1 in both machinability and IA resistance. No birefringence was observed when observed using a polarizing film.

Example 3 A syrup was prepared by adding 0.22 g of azobisisobutyronitrile as a polymerization initiator to the same mixed monomer system as described in Example 2. After vacuum degassing, this syrup was heated at 80°C for 3 hours in a glass cell through a 5-fin thick gasket.
115℃×1hr.

A polymer was obtained by performing main polymerization in three stages at 130° C. for 1 hr.

The conobolimano refractive index is nD = 1.5054.12
After heat treatment at 0°C for 2 hours, the rubber hardness at high temperature was 95 to 99 Shore A, and no thermal deformation or discoloration was observed. Cutting resistance and solvent resistance were the same as in Example 1. The results were shown.

Example 4 MMA 86g, α-MS 4g, DATP! Ml, E.G.
A mixed monomer system consisting of 3 g of DMA, 2 g of α-MS D, and 95 g of PCDO and PBIo as a reaction initiator.

6g was added to obtain syrup.

After vacuum degassing, this syrup was injected into a glass cell through a 5-wall thick gasket and heated at 60°C x 1 hr and at 80°C x 2.
A polymer was obtained by carrying out main polymerization in four stages: 2 hours at 90°C and xx hours at 110°C. The light transmittance of the obtained polymer was 94%, and the refractive index was nD == 1.5068.
Shore A rubber hardness at high temperature after heat treatment at 120° C. for 2 hours was 95 to 96, with no thermal deformation or discoloration.

The machinability and solvent resistance were the same as in Example 1.

Example 5 MMA83g, a-MS 49, DATP7g, E
From QDMA 59, α-MSDI g, P B I O, 69 and Z-t were added to the mixed monomer system as a reaction initiator.
- Add 0.2 g of butyl peroxide to create wrinkles, inject this into a glass cell through a 109 thick gasket, heat at 80°C x 2° for 5 hr, and at 95°C x 1 hr.
Polymerization was carried out in three stages at 125° C. for 1 hr to obtain a polymer.

YN! J W-(D'fr index D = 1.505
3. Shore A rubber hardness at high temperature after heat treatment at 120°C for 2 hours is 95-100. No deformation or discoloration was observed. The results were the same as in Example 1 regarding machinability and solvent resistance.

Example 6 MMA 82 g, triallyl in cyanurate 5],
A syrup was prepared by adding 0.2 g of benzoyl peroxide as a reaction initiator to a mixed monomer system consisting of 7 g of DATP, 5 g of lyethylene glycol dimethacrylate, and 1 p of α-MSD. During vacuum degassing of the syrup, 0.4 g of methyl ethyl ketone peroxide was further added, and this was injected into a glass cell through a 101111 thick gasket and heated at 75°C x 2.
Polymerization was carried out in three stages: 1 hr at 115°C and 1 hr at 140°C to obtain a polymer.

The refractive index of the polymer was nD = 1.5114, and the light transmittance was 91%. After heat treatment at 120°C for 2 hours, the Shore A rubber hardness at high temperature was 95, and no deformation or discoloration was observed. Both machinability and solvent resistance are from Example 1.
showed the same result.

[Brief explanation of drawings]

Figure 1 is an elevational view of a flat glass cell assembly used in the present invention! FIG. 2 is a plan view of the obtained flat polymer, and FIG. 3 is a diagram showing an example of a lens made from the transparent plastic of the present invention. 1...Glass plate, 2...Gasket, 3...Clamp with spring, 4...Syrup, 5. Clear plastic, 6...Lens. Patent Applicant Olympus Optical Industry Co., Ltd. No. 1-1, -28- Figure 1 Figure 2 Figure 3 Procedural amendment (voluntary) Commissioner of the Japan Patent Office Kazuo Wakasugi 1, Indication of the case 1982 Patent Application No. 84525 No. 2, Title of the invention: Transparent plastic 3, Relationship with the person making the amendment: Patent applicant: 2-43-2 Hatagaya, Shihetaya-ku, Tokyo Name (Name> (037) Olympus Optical Industry) Shigeo Kitamura, President and CEO of Co., Ltd. 4, Agent 6, Number of inventions to be increased by amendment (1) The scope of claims will be amended as shown in the attached sheet. (2) 1 on page 6, line 2 of the specification (4) The statement "Alylidene diacrylate" on page 8, line 12 of the specification shall be amended to "Alylidene diacrylate". (5) The statement in the first line of page 9 of the specification is amended to 2- (6) The statement in lines 11 and 12 of page 17 of the specification is amended as follows. In contrast to cast polymerization of monomers, the cast polymerization method in which prepolymerized syrup is injected into a glass mold, etc., results in crosslinking.''(7) Specification, page 18, lines 16-17 and line 18 The “polymerization characteristics” described in “
"Polymer properties". 9. List of attached documents (1) Attachment 1 copy 2. Claims (1) Vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, ethyl methacrylate,
70% by weight or more of at least one first monomer selected from methyl methacrylate, methyl acrylate, ethyl acrylate, styrene, α-methylstyrene, methacrylic acid and ethyl crotonate 95:t:! and at least 1 m selected from ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, allyl acrylate, allylidene acrylate, vinyl methacrylate, allyl methacrylate, diallyl isophthalate, diallyl terephthalate, and triallyl isocyanurate. Visible region of 70 inches or more (380 to Transparent plastic with -)lit transmission of 800 nm wavelength). (2) the first monomer is methyl methacrylate;
2. The transparent plastic according to claim 1, wherein α-methylstyrene, dihistyrene, and the 27th polymer are diallyl terephthalate and ethylene glycol dimethacrylate. (3) The transparent plastic according to claim 1, wherein the first monomer comprises methyl methacrylate and α-methylstyrene, and the second monomer comprises diallyl terephthalate and ethylene glycol dimethacrylate. (4) The transparent plastic according to claim 1, wherein the mixed monomer system contains dicumyl peroxide and t-butylperoxyisopropyl carbonate as reaction initiators. (5) The transparent plastic according to claim 1, wherein the mixed additive system comprises syrup to which azobisisobutyronitrile is added as a polymerization initiator. (6) The transparent plastic according to claim 1, wherein the mixed monomer system comprises a syrup to which dicumyl peroxide and di-t-butyl peroxide are added as reaction initiators. (Force) The transparent plastic according to claim 1, wherein the first monomer comprises methyl methacrylate, triallyl isocyanurate, and diallyl terephthalate, and the second monomer comprises triethylene glycol dimethacrylate. (8) The mixed monomer 2. A transparent plastic according to claim 1, wherein the system comprises a syrup to which benzoyl peroxide is added as a reaction initiator.

Claims (1)

[Scope of Claims] (1) A first monomer of 1'P1 selected from vinyl acetate, vinyl chloride, vinyl chloride, styrene, α-methylstyrene, methacrylic acid and ethyl crotonate in weight ratio. 70% by weight or more and less than 95% by weight, ethylene glycol dimethacrylate, triethylene glycol;
-rudimethacrylate, allyl acrylate, allylidene acrylate, vinyl methacrylate. 5 weight t% or more of a second monomer selected from acrylic methacrylate, diallyl isophthalate, diallyl terephthalate and triallyl isocyanurate3
Less than 0 wt% and α-methylstyrene dimer 0.1~
70 obtained by polymerizing a mixed monomer system consisting of 2 i%
% or more of light transmittance in the visible region (380-800 nm wavelength). A transparent plastic according to claim 1, comprising luterephthalate and ethylene glycol dimethacrylate. (3; The transparent plastic according to claim 1, wherein the first monomer is methyl methacrylate, styrene, α-methylstyrene, and the second monomer is diallyl terephthalate and ethylene glycol dimethacrylate. (4) The mixed monomer system The transparent plastic according to claim 1, wherein the mixed monomer system contains dicumyl peroxide and t-butylbaroxyisofurovir carbonate as a reaction initiator. The transparent plastic according to claim 1, which comprises a syrup containing azobisin butyronitrile. (6) The above-mentioned mixed additives contain dicumyl peroxide and di-t-butyl peroxide as reaction initiators. The transparent plastic according to claim 1, comprising a syrup to which an oxide is added. (7) The first monomer is methyl methacrylate, triallyl isocyanurate and diallyl terephthalate, and the second monomer is triethylene glycol dimethacrylate. The transparent plastic according to claim 1. (8) The transparent plastic according to claim 1, wherein the mixed monomer system comprises syrup to which benzoyl peroxide is added as a reaction initiator.