JPH0329806B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a method for producing a high refractive index transparent resin. In recent years, polymers with particularly high refractive indexes have been proposed as synthetic resins (organic glasses) to replace inorganic glasses. However, in the case of high refractive index organic glasses,
It is a polymer obtained by heating and polymerizing monomers that mostly have aromatic rings. In this case, a pale yellow coloration occurs, although the cause is unknown. Similar to inorganic glass, organic glass is used for optical lenses, prisms,
A wide variety of products including window glass, dustproof glass, and windshield glass. However, the pale yellow coloration greatly reduces the commercial value of organic glass, and is fatal to the field of optical lenses, making it unusable. The present inventors have repeatedly conducted research on preventing coloration of polymers obtained by heating and polymerizing monomers having aromatic rings. As a result, the present inventors discovered that a resin having the desired excellent properties can be obtained by including a specific antioxidant during the thermal polymerization, leading to the completion of the present invention. That is, the present invention provides (a) at least one monomer selected from dimethacrylates and diacrylates having an aromatic ring, (b) a radical polymerization initiator that acts upon heating, and (c) 2,6 - A method for producing a high refractive index transparent resin, which comprises injecting a polymerizable composition containing ditertiarybutyl-4-methylphenol into a mold, heating the polymerizable composition, and performing cast polymerization. Diethylene glycol bis(allyl carbonate), a conventionally known organic glass,
Colorless and transparent polymers have been obtained by heat polymerization using diisopropyl peroxydicarbonate as a polymerization initiator, but as mentioned above, in the case of high refractive index resins with aromatic rings, the unique characteristics of the resins are unknown. A pale yellow coloration occurs. However, by adding 2,6-ditertiarybutyl-4-methylphenol during polymerization, a colorless and transparent high refractive index resin can be obtained. The at least one monomer selected from dimethacrylates having an aromatic ring and diacrylates having an aromatic ring used in the present invention is not particularly limited, and any known monomer can be used, but a particularly high refractive index is required. In this case, it is preferable to use dimethacrylates having a nuclear halogen-substituted aromatic ring or diacrylates having an aromatic ring. Bromine is particularly preferred as the halogen. The number of halogens contained in the aromatic ring is not particularly limited, and is 1
~4 items can be used. Typical examples that are generally preferably used include, for example, 1, 4
-dimethacryloxybenzene, 1,4-dimethacryloxy-2,3,5,6-tetrabromobenzene, 1,4-diacryloxyethoxybenzene,
1,4-dimethacryloxyethoxy-2,3,
5,6-tetrachlorobenzene, dimethacryloxy-di(4-chlorophenyl)methane, di(2-methacryloxyethyl) phthalate, di(2-acryloxyethyl) tetrabromphthalate,
2,2bis(4-methacryloxyphenyl)propane, 2,2bis(4-methacryloxy-3-chlorophenyl)propane, 2,2bis(4-acryloxy-3,5-dichlorophenyl)propane, 2,2bis (4-methacryloxy-3-bromphenyl)propane, 2,2bis(4-methacryloxy-3,5-dibromphenyl)propane, 2,2bis(4-methacryloxy-3-iodophenyl)propane, 2,2bis(4- methacryloxyethoxyphenyl)propane, 2,2bis(4-methacryloxyethoxy-3,5-dibromophenyl)propane, 2,2bis(4-methacryloxypolyethoxyphenyl)propane,
2,2bis(4-methacryloxypolyethoxy-
3,5-dibromphenyl)propane, 1,5-
Dimethacryloxinaphthalene, 1,5-diacryloxy-2,4,6,8-tetrachloronaphthalene, 1,5-dimethacryloxyethoxy-2,
4,6,8-tetrabromnaphthalene, These include 2,2 bis(4-methacryloxyethoxyphenyl) sulfone, 2,2 bis(4-methacryloxyethoxyphenyl)methane, and mixtures thereof. In the present invention, at least one monomer selected from the above-mentioned dimethacrylates having an aromatic ring and diacrylates having an aromatic ring can be used alone, but other monomers capable of radical polymerization can also be used. It is also possible to adopt a mode in which a mixture of these is used. The other radically polymerizable monomers are not particularly limited, and known ones can be used. The monomer used is a bifunctional monomer when mechanical properties and dimensional stability are important, a monomer with an aromatic ring when a high refractive index is required, and a monomer with an aromatic ring when a high refractive index is required. When doing so, the monomer having an epoxy group may be selected as appropriate depending on the intended use of the resulting copolymer. Of course, it is also optional to select and use multiple types of monomers in order to satisfy these multiple properties. Typical monofunctional monomers that are generally preferably used include, for example, styrene, vinyltoluene, methoxystyrene, chlorostyrene, bromustyrene, iodostyrene,
Styrene derivatives such as dichlorostyrene, dibromustyrene, trichlorstyrene, tribromustyrene, P-styryltrimethylsilane, phenyl methacrylate, phenyl acrylate, chlorphenyl acrylate, dichlorophenyl methacrylate, bromphhenyl acrylate, dibrome Phenyl methacrylate, pentabromo phenyl methacrylate, methoxyphenyl acrylate, benzyl methacrylate, chlorobenzyl acrylate, bromobenzyl methacrylate, pentabromobenzyl methacrylate, methyl methacrylate, ethyl methacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, allyl methacrylate, α - Acrylates such as methyl trimethylsilylacrylate, methacryloyloxyethoxytrimethylsilane, methacrylates, 1-vinylnaphthalene, 2-vinylnaphthalene, α-naphthyl methacrylate,
Naphthalene derivatives such as β-naphthyl methacrylate, α-naphthyl acrylate, and vinyl-α-naphthylphenylsilane; other vinyl compounds such as vinyl acetate, acrylonitrile, vinyltriethoxysilane, vinyltrimethylsilane, and vinyltriphenylsilane; polyfunctional Monomers include aliphatic acrylates such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, trimethylolpropane triacrylate, triethylene glycol diacrylate, and tetramethylolpropane trimethacrylate, methacrylates, diallyl phthalate, diallyl isophthalate, These include diallyl compounds such as ethylene glycol bis(allyl carbonate), diallyl tartrate, diallyl epoxysuccinate, diallyldiphenylsilane, and diallyldimethylsilane, and mixtures thereof. The amount of the other monomer capable of radical polymerization to be used may be selected depending on the physical properties such as mechanical properties and refractive index required of the polymer. Generally 10~ of the total amount of monomers
It is preferred that 100% by weight, preferably 20 to 100% by weight, be dimethacrylates having an aromatic ring or diacrylates having an aromatic ring. A typical example of the most preferred embodiment is that the other monomer capable of radical polymerization is 70 to
This is an embodiment in which the content is in the range of 30% by weight. The catalyst used in the present invention is not particularly limited and any known catalyst can be used as long as it is a radical polymerization initiator that acts upon heating. Typical examples include:
Benzoyl peroxide, P-chlorobenzoyl peroxide, decanoyl peroxide,
Raunoyl peroxide, diacyl peroxide such as acetyl peroxide, diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, myristyryl peroxy Percarbonate such as dicarbonate, tertiary butyl peroxybiparate,
These are alkyl peresters such as tert-butylperoxy-2-ethylhexanate, or azo compounds such as azoisobutyronitrile. The antioxidant used in the present invention is 2,6-ditertiarybutyl-P-cresol (hereinafter referred to as
(abbreviated as BHT). If the amount of BHT is too large, polymerization will be prevented, and conversely, there will be disadvantages such as not being able to obtain a highly polymerized product or polymerization being too slow. On the other hand, if the amount added is too small, the effect of preventing coloring will be reduced. Generally, the amount of BHT added is 10 to 2000 PPM based on the total monomer, preferably
It is preferred to use 10-500 PPM. Generally, techniques for adding stabilizers such as antioxidants during polymerization are known. However, in the present invention, stabilizers other than BHT, such as

【formula】

[Formula] These hindered phenols have good solubility in monomers, but are not effective in preventing coloration. Also

【formula】

[Formula] These P-based compounds are difficult to dissolve in monomers and have no coloration prevention effect. The polymerization method in the present invention is a method in which a polymerizable composition containing the monomer, a radical polymerization initiator, and an antioxidant is injected into a mold, and the polymerizable composition is polymerized by heating. For example, a mixture of the polymerization component monomers containing a radical polymerization initiator may be injected into a mold in which the elastomer is held by a skate or a spacer, cured in a heating oven, and then taken out.
Of course, it is also possible to preliminarily polymerize a mixture of copolymerization component monomers in the presence of a polymerization initiator to increase the viscosity of the mixture, and then perform cast polymerization. Among the polymerization conditions, temperature particularly affects the properties of the high refractive index transparent resin obtained. Generally, it is preferable to carry out so-called taper polymerization, in which polymerization is started slowly at a relatively low temperature and then cured at a high temperature when the polymerization is completed. For example, it is preferable to start polymerization slowly at about 20°C to 40°C, gradually raise the temperature, and terminate the polymerization at a high temperature of about 80°C to 120°C. In particular, when the objective is to obtain a thick high refractive index transparent resin, it is preferable to lengthen the polymerization time at a low temperature or to perform the preliminary polymerization described above. However, if the polymerization time is too long, especially at a high temperature, the resin will be colored pale yellow and the effect of the polymerization initiator of the present invention will be lost. is not desirable. Generally, it is preferable to select conditions such that copolymerization is completed in 5 to 30 hours. Since the polymerization time varies depending on various conditions, it is preferable to determine the optimum conditions in advance according to these conditions. Of course, during the polymerization, additives such as release agents, ultraviolet absorbers, other antioxidants, anti-coloring agents, antistatic agents, fluorescent dyes, and various stabilizers may be added as necessary. You can. In order to explain the present invention more specifically, Examples and corresponding comparative examples are shown below. From these results, it can be easily understood that the present invention is a colorless and transparent resin with a high refractive index. Of course, the present invention is not limited to these examples. The physical properties of the high refractive index transparent resins obtained in the examples were measured using the following test methods. (1) Refractive index (N ²⁰ _D ) The refractive index at 20° C. was measured using an Atsube refractometer. Monobromnaphthalene was used as a contact liquid. (2) Transmittance (Tt%) Measured using a fade meter. (3) Pale yellow coloring Using a color difference meter manufactured by Nippon Denshoku Engineering Co., Ltd., a
(hue) and b (chroma) were measured. The larger the a and b values, the greater the yellow coloration. Examples 1 to 6 60 parts by weight of 2,2bis(4-methacryloethoxy-3,5-dibromophenyl)propane was dissolved in 40 parts by weight of styrene. Next, after adding BHT in the composition shown in Table 1, as a polymerization initiator
MSP (myristyryl peroxydicarbonate)
1.0 part by weight of was added and mixed well. This mixed solution was poured into a mold consisting of a glass plate with a diameter of 73 mm and a gasket made of ethylene-vinyl acetate copolymer, and cast polymerization was performed. Polymerization was initially started at 25℃ using an electric heating furnace, and after 18 hours the polymerization was heated to 90℃.
The temperature was gradually increased so that the temperature reached ℃. Further 90℃
After polymerizing for 2 hours at 110°C, the polymer was taken out from the gasket and mold and polymerized for 2 hours at 110°C.
The physical properties of the polymer were measured and shown in Table 1. Comparative Examples 1-2 The same procedure as in Examples 1-6 was carried out except that BHT was not added. From Table 1 it is clear that the addition of the BHT of the invention significantly improves the coloration of the polymer.

[Table] Examples 7 to 10 The same procedure as in Example 2 was carried out except that the polymerization initiator was changed as shown in Table 2. The results are shown in Table 2. Comparative Examples 3 to 6 Examples 7 to 10 were carried out in the same manner as in Examples 7 to 10 except that BHT was not added, and the results are shown in Table 2.

[Table] Example 11 Polymerization was carried out in the presence of BHT using various monomers and polymerization initiators shown in Table 3. The rest was carried out in the same manner as in Examples 1 to 7. The results are shown in Table 3.

[Table] Comparative Examples 7 to 13 In Example 4, various stabilizers shown in Table 1 were used instead of BHT. Everything else was carried out in the same manner as in Example 4. From the results in Table 1 and Example 4, it is clear that, unlike other stabilizers, BHT specifically exhibits the effect of preventing coloration.

【table】

【table】

Claims (1)

[Claims] 1 (a) at least one monomer selected from dimethacrylates having an aromatic ring and diacrylates having an aromatic ring, (b) a radical polymerization initiator that acts upon heating, and (c) 2,6- 1. A method for producing a high refractive index transparent resin, which comprises injecting a polymerizable composition containing ditertiary-butyl-4-methylphenol into a mold, heating the polymerizable composition, and performing cast polymerization.