JPS63205308A - Lowly water-absorptive plastic - Google Patents

Abstract

PURPOSE:To provide a lowly water-absorptive plastic superior in heat resistance, mechanical strength, and transparency, which comprises a copolymer of methyl methacrylate with two specific monomers. CONSTITUTION:20-70wt.% methyl methacrylate, 10-30wt.% monomer (e.g., trifluoroethyl methacrylate) of formula I (wherein A is a fluorinated 1-20 C alkyl) and 10-60wt.% monomer (e.g., tricyclo[5,2,1,0<2>,<6>] deca-8-yl methacrylate) of formula II are copolymerized in the presence of 0.1-2.0wt.% polymerization initiator [e.g., 2,2'-azobis(butyronitrile)], 0.1wt.% ore more chain transfer agent (e.g., tert-butylthiol) and if desired, an antistatic agent, a colorant, a filler, an ultraviolet absorber, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to plastic optical parts, and particularly to a low water absorption plastic that absorbs little water and has excellent properties in heat resistance and mechanical strength.

[Conventional technology]

Traditionally, various types of glass have been used for optical components, but
Plastics are now being used in many products due to their light weight and ease of production and processing. Among these plastic materials, methyl methacrylate has a good balance of optical properties, heat resistance, and mechanical strength, and is most widely used in various fields. However, methyl methacrylate has a drawback in that it has a higher water absorption rate than polystyrene and polycarbonate. The effect of this water absorption depends on the shape of the molded product, but if the water absorption rate exceeds 1.5%, the molded product will change in size, warp, become distorted, or become cloudy. Also, it absorbs water due to changes in the environment.

Repeated drying may cause cracks.

In this way, water absorption increases the aging deterioration of the molded product.

That is, in order to prevent plastic molded products from deforming, materials with low water absorption are required.

Transparent plastic material with low water absorption is disclosed in JP-A-58-136.
There are disclosures in Japanese Patent Application Laid-open No. 52 and Japanese Patent Application Laid-Open No. 61-73705. The former uses cyclohexyl methacrylate as a component to reduce water absorption, and copolymerizes this with methyl methacrylate. However, because a relatively large amount of cyclohexyl methacrylate is required,
There was a problem in that the heat resistance of this copolymer was reduced. The latter uses tricyclo[5゜2.1.02.6]dec-8-yl methacrylate as a component to reduce water absorption, which improves low water absorption and heat resistance, but the tricyclodecanyl group Because it has a large molecular volume and is rigid, it reduces mechanical strength.

[Problem that the invention seeks to solve]

The present inventors have arrived at the present invention based on the results of studying methacrylate plastics from the viewpoint of their molecular structure in order to improve the current situation.

An object of the present invention is to provide a new low-water-absorbing transparent plastic that has low water-absorption, excellent heat resistance, and mechanical strength, and has a good balance of these properties.

[Means for solving problems]

The following method is well known for obtaining transparent plastics with low water absorption. This is the introduction of a compound with a hydrophobic group. When a hydrophobic group is introduced, the proportion of weakly hydrophilic carboxyl groups in the structural units of methacrylate decreases, resulting in a decrease in water absorption.

On the other hand, in order to improve heat resistance as well as water absorption, a method of introducing a group with a large molecular volume is well known. but,
Hydrophobic groups with large molecular volumes, such as alicyclic hydrocarbon groups with 7 or more carbon atoms, have low water absorption and improve heat resistance, but mechanical strength tends to decrease. It was difficult.

In order to solve the above-mentioned problems, the present invention has developed a hydrophobic fluorine-containing methacrylate monomer with a relatively small atomic radius, a methacrylate monomer containing a tricyclodecanyl group with a large molecular volume, and a methyl methacrylate monomer containing a tricyclodecanyl group with a large molecular volume. The aim is to solve this problem by copolymerizing the problem with ester.

[Effect]

In order to maintain the excellent low water absorption, mechanical strength, and heat resistance of the methacrylate copolymer in the copolymer of the present invention, the copolymer composition ranges from 20 to 70 wt% methacrylate;
Preferably 30-50 wt%, fluorinated methacrylate compound 10-40 wt%, preferably 15-30
wt%, tricyclodecanyl methacrylate is 10-6
0 wt%, preferably 20 to 40 wt%. The unit amount of fluorinated methacrylate compound in the copolymer is 30
If it exceeds wt%, the copolymerization temperature limit will decrease significantly, and if it is less than 10wt%, it will not contribute to a substantial decrease in water absorption. On the other hand, if the unit amount of the tricyclodecanyl group-containing compound exceeds 60 wt%, it is difficult to maintain mechanical strength, and if it is less than 10 wt%, no effect of lowering the water absorption rate can be obtained.

The method for producing the optical plastic material of the present invention includes bulk polymerization,
This can be achieved by well-known polymerization methods such as solution polymerization, suspension polymerization, and emulsion polymerization. Bulk polymerization using the casting method is used to obtain film and sheet materials, and suspension polymerization is used to obtain molding materials that can be injection molded.
Emulsion polymerization is preferred in terms of work efficiency. In either case, it is preferable that the copolymer is free of foreign substances, so the polymerization is carried out after removing foreign substances by filtration, distillation, etc.

In the case of suspension polymerization or emulsion polymerization, a polymerization initiator and a chain transfer agent for molecular weight adjustment are added to water in which a suspension dispersant or emulsifier is dissolved to disperse the monomer mixture, and then polymerization is carried out. It is well known to do this.

In the case of bulk polymerization using the casting method, first, a polymer that has been copolymerized to some extent or an unpolymerized monomer mixture is designed from an arbitrary monomer mixture according to the intended use of glass, metal, plastic, etc. The mixture is poured into molds, etc., and thermal polymerization is performed.

In the case of bulk polymerization by casting, a crosslinking agent may be added to three-dimensionally crosslink the copolymer. Three-dimensionally crosslinked copolymers are currently used in the production of eyeglass lenses because of their improved solvent resistance, surface strength, and processability. Examples of crosslinking agents include polyfunctional methacrylates, polyfunctional acrylates, and aromatic divinyl compounds. However, aromatic divinyl compounds are not preferred because they have a problem with light emitting properties because they have many double bonds. Polyfunctional methacrylates and polyfunctional acrylates are preferred. Specific examples include ethylene glycol, diethylene glycol, diacrylate, dimethacrylate, propylene glycol diacrylate, propylene glycol dimethacrylate, trimethylolpropane dimethacrylate, trimethylolpropane diacrylate, and trimethylolpropane triacrylate.

Examples include trimethylolpropane triacrylate.

On the other hand, the polymerization initiators include 2,2'-azobis(isobutyronitrile), 1,1'-azobis(cyclohexanecarbonitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and azobis(isobutyronitrile). azo compounds such as bisisobutanol diacetate; Examples include organic peroxides such as myristyl peroxydicarbonate.

The blending amount of these polymerization initiators is 0.1 to 2.0% by weight based on the various mixed methacrylate monomers. In addition, the chain transfer agent that has the function of adjusting the molecular weight of the copolymer is te.
Examples include rt-butylthiol, n-butylthiol, n- and tert-dodecylthiol, and the like. The blending amount of these chain transfer agents is 1.0% by weight or less based on the various mixed methacrylate monomers.

The produced copolymer is used as an antistatic agent.

Colorants, fillers, ultraviolet absorbers, heat stabilizers, antioxidants, etc. may be added. The obtained copolymer can be subjected to post-treatment such as annealing in order to remove distortions incorporated during copolymerization or molding.

〔Example〕

Next, the present invention will be explained in more detail by way of examples. However, the present invention is not limited thereby.

In the measurements of physical properties in the following examples, the total light transmittance was ASTM D1003 and the heat distortion temperature was ASTM D6.
48. Impact strength, which is a factor of mechanical strength, is determined by JIS,
-7110, and the water absorption rate was determined from the change in weight after being left in water at 7.0°C for 20 days.

<Example 1> 40 g of methyl methacrylate, aog of trifluoroethyl methacrylate, tricyclo[:5,2゜1,O
2.6] 30 g of dec-8-yl methacrylate was mixed, 3 g of uroyl peroxide (0.3 gwn-butylthiol C) was added thereto, and bulk polymerization was carried out in a glass ampoule purged with nitrogen.

The polymerization temperature was 70°C for 5 hours, and the working time was 105°C. The copolymer thus obtained exhibited the following physical properties.

Total light transmittance 91%, heat distortion temperature 110℃, impact strength 1
-8 (kg-an/an) water absorption rate 0.49%.

<Example 2> 40 g of methyl methacrylate + 20 g of pentafluorobutyl methacrylate, tricyclo(5,2°1.02.
B] Mix 40 g of dec-8-yl methacrylate, and add 0-3 g s n- of lauroyl peroxide.
Add 0.3 g of butylthiol and place it in a glass ampoule purged with nitrogen.

Bulk polymerization was performed. Polymerization temperature: 70°C, standing time: 10
The working time is 5℃. The obtained copolymer is colorless and transparent.
The physical properties are as follows.

Water absorption rate 0.5%, total light transmittance 9.

<Example 3> Methyl methacrylate 40 gy Trifluoroethyl methacrylate 30 g* Tricyclo(5,2.

1,02・B] Mix 30 g of dec-8-yl methacrylate, and add 5 g of trimethylolpropane trimethacrylate.
g v 0.3 g of lauroyl peroxide was added and block molding was performed in a glass ampoule purged with nitrogen. Polymerization was carried out at a temperature of 70°C for an incubation time and at 105°C for a working time. The properties of the colorless and transparent three-dimensional crosslinked product thus obtained are as follows.

Water absorption rate 0.5%, total light transmittance 9% (Example 4)
゛1.0 g of hydroxycellulose as a suspending agent in the reaction vessel
and 0.3 g of sodium polymethacrylate, and 0.3 g of sodium acid dihydrogen as an anti-emulsifying agent and lβ of water.
Put in. Furthermore, 40 g of methyl methacrylate, 30 g of trifluoroethyl methacrylate, tricyclo[5,
2,1,02-8]dec-8-yl methacrylate ao
gt 0.4 g of n-butyl mercaptan and 0.7 g of lauroyl peroxide are added after dissolution. The reaction vessel was kept at 70°C and the incubation period was continued with stirring. The obtained bead-like polymer was washed with water and heated under reduced pressure at 90° C. for a period of time to remove water and low-boiling substances. The obtained bead-like copolymer was shaped into pellets using an extruder and injection molded at a cylinder temperature of 230°C and a metal temperature of 70°C. Each physical property is as follows.

Water absorption rate 0.6%, total light transmittance 9 degrees Celsius 18°C, impact strength 1.6 kg-al/a11.

Comparative Example 1> 0.5 g of uraloyl peroxide and 0.3 g of n-butylthiol were added to 100 g of methyl methacrylate, and these were placed in a glass ampoule purged with nitrogen to perform bulk polymerization. The polymerization temperature was 70°C, the standing time was 1.
The working time is 05°C. The obtained copolymer was colorless and transparent, and its physical properties were as follows.

Water absorption rate 0.5%, total light transmittance 92%, heat distortion temperature 10
The impact strength was 1.5 kg-■/3 at 1°C.

〔Effect of the invention〕

According to the present invention, a well-balanced copolymer with low water absorption and excellent transparency, heat resistance, and mechanical strength can be obtained.

Claims (1)

[Claims] 1. Methyl methacrylate has a monomer represented by the following formula (I) ▲ Numerical formula, chemical formula, table, etc. ▼ (I) (In the formula, A is a fluorine-substituted carbon number of 1 to 1) 20 alkyl group), and a monomer represented by the following formula (II) ▲ Numerical formula, chemical formula, table, etc. ▼ (II) (wherein B is H or CH_3) Water-absorbing plastic. 2. The low water absorption plastic according to claim 1, containing 20 to 70 wt% of methyl methacrylate. 3. The monomer represented by the above formula (I) is 10 to 30w
t%, and the monomer represented by the formula (II) is 10 to 6
The low water absorption plastic according to claim 1 or 2, which is a copolymer consisting of 0 wt%. 4. In the above formula (I), the monomer containing a fluorine-substituted alkyl group having 1 to 20 carbon atoms is one of trifluoroethyl methacrylate, pentafluoropropyl methacrylate, and trifluoroisopropyl methacrylate. A low water absorption plastic according to claim 1. 5. The monomer represented by the formula (II) is tricyclo[5,2,1,0^2^. ^6] Daka-8-yl methacrylate, tricyclo[5,2,1,0^2^. ^6〕
The low water absorption plastic according to claim 1, characterized in that it is dec-8-yl acrylate.