JPH0229408A - Lowly water-absorbing and transparent plastic - Google Patents

Abstract

PURPOSE:To obtain a transparent plastic having low water absorption properties and excellent heat resistance and mechanical strengths by compounding two specified methacrylate compd. and methyl methacrylate. CONSTITUTION:A transparent plastic having low water absorption properties is obtd. by compounding a compd. of formula I, a compd. of formula II and methyl methacrylate. In the formulas, A is a 3-20C alkyl wherein part or the whole of H atoms are substd. with F; Z is a 10C alicyclic hydrocarbon group. Said plastic is a copolymer consisting of 5-70wt.% compd. of formula I, 5-60wt.% compd. of formula II and 20-70wt.% methyl methacrylate and exhibits a saturation water absorption ratio of 0.7% or less and excellent heat resistance and mechanical strengths. As the compd. of formula I, 2,2,3,3-tetrafluoropropyl methacrylate, fluorodecyl methacrylate etc. are cited. As the compd. of formula II, tricyclo[5,2,1,0<2>,<6>]decyl methacrylate is cited.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a transparent plastic and a method for manufacturing the same, and particularly relates to a transparent plastic with low water absorption and excellent heat resistance and mechanical strength. Regarding plastic.

[Conventional technology]

Traditionally, various types of glass have been used for optical components, but
Recently, plastics are being applied to many products such as lenses, optical disks, and optical fibers, taking advantage of their characteristics such as light weight, impact resistance, and ease of production. Among these plastic materials, polymethyl methacrylate-1 (hereinafter referred to as P M
Acrylic resin whose main component is M (abbreviated as "A") has excellent optical properties and is well-balanced in heat resistance and mechanical strength, and is widely used in various fields.

However, acrylic resins have a drawback in that they have a higher water absorption rate than polystyrene resins and polycarbonate resins.

The effect of this water absorption depends on the shape of the molded product, but it is 0.2%
When water is absorbed, the molded product may change dimensions, warp, become distorted, or become cloudy. Furthermore, due to changes in the environment, repeated water absorption and drying may cause cracks. In this way, the molded product changes significantly over time due to water absorption. That is, in order to prevent plastic molded products from deforming, materials with low water absorption are required.

On the other hand, polystyrene resins and polycarbonate resins have no problem in terms of water absorption, but they have a problem in that they have high birefringence, which is an important optical property in the fields of lenses, optical disks, and the like.

By the way, transparent plastic materials made of acrylic resin and having low water absorption are disclosed in JP-A-58-13652 and JP-A-61-7.
This is disclosed in Publication No. 3705, etc. The former uses cyclohexyl methacrylate as a component to reduce water absorption, and copolymerizes cyclohexyl methacrylate with methyl methacrylate (hereinafter referred to as MMA). However, since a relatively large amount of cyclohexyl methacrylate is required, there is a problem in that the heat resistance and mechanical strength of this copolymer are reduced. The latter uses tricyclo I:5.2.1.02'')-decyl-methacrylate as the component amount to reduce water absorption, so low water absorption and heat resistance are improved. , 1,0''G)-decyl group has a larger molecular volume than a cyclohexyl group and is also more rigid, so it greatly reduces mechanical strength.

[Problem to be solved by the invention]

The present inventors have arrived at the present invention based on the results of studying plastics from the viewpoint of their molecular structure in order to improve the current situation. The purpose of the present invention is to have low water absorption and heat resistance.

Our objective is to provide a new low water absorption transparent plastic with excellent mechanical strength.

[Means to solve the problem]

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.

For example, in the case of acrylic resin whose main component is PMMA,
When copolymerized with a compound in which a hydrophobic group is introduced into a carboxyl group, the proportion of weakly hydrophilic carboxyl groups in the structural units of MMA decreases, resulting in a lower water absorption rate. On the other hand, in order to improve the water absorption rate and heat resistance, a rigid group with a large molecular volume is introduced. However, a hydrophobic group with a large molecular volume, such as an alicyclic hydrocarbon group having 5 or more carbon atoms, improves water absorption and heat resistance, but tends to become brittle and decreases mechanical strength.

Two methods are well known for improving mechanical strength, particularly impact strength. ■ Addition of rubber components, ■
This is due to high molecular weight. ■In the case of acrylic resin, PMMA
Rubber components such as butyl acrylate are added to. but,
In this method, the rubber component has a microphase-separated structure in the form of islands, and the size of the dispersed rubber component must be about 1 to 10 μm. #The impact strength does not improve. That is, since particles larger than the wavelength of visible light are dispersed, there is a problem in terms of transparency. Furthermore, since the rubber component was added, the heat resistance temperature also tended to decrease. Regarding (2), since molecular weight and impact strength are in a highly proportional relationship, impact strength improves as the molecular weight increases. However, due to the high molecular weight, the viscosity increases when heated and melted, resulting in moldability problems. As described above, with conventional techniques, it has been impossible to create low water absorption transparent plastics with a good balance of mechanical strength, heat resistance, and moldability.

The present invention attempts to solve these problems by providing a new low water absorption transparent plastic.

That is, the structure of the low water absorbency transparent plastic of the present invention is a compound represented by the general formula (I), (wherein 5A is a compound having 3 to 20 carbon atoms in which some or all of the hydrogen atoms have been replaced with fluorine atoms. ), and general formula (II)
It is a copolymer containing three essential components: a compound represented by (in the formula, 2 represents an alicyclic hydrocarbon group having 10 carbon atoms) and methyl methacrylate.

The low water absorption transparent plastic of the present invention has general formula (I) of 5
~70 wt%, general formula (If) is 5 to 60 wt%,
It is a copolymer containing 20 to 70% by weight of methyl methacrylate. In addition, plastic has a saturated water absorption rate of 0.7% or less and exhibits excellent heat resistance and mechanical strength.

[Effect]

In order to maintain excellent low water absorption, transparency, and heat resistance 2 and mechanical strength in the low water absorption transparent plastic of the present invention, the range of the copolymerization composition is 5 to 7.
0 wt%, preferably 10 to 60 wt%, formula (II)
The amount of the compound containing an alicyclic hydrocarbon group is 5 to 60 wt%, preferably 7 to 50 wt%. Methyl methacrylate is 20-70 wt% preferably 25-6'Ow
t%. If the unit amount of the fluorinated compound in the copolymer exceeds 70 wt%, the heat resistance temperature will decrease significantly.
If it is less than t%, it will not contribute to improving mechanical strength or substantially reducing water absorption. On the other hand, if the unit amount of a compound containing an alicyclic hydrocarbon group exceeds 60 wt%, it is difficult to maintain mechanical strength, and if it is less than 7 wt%, the effect of lowering the water absorption rate and increasing the heat resistance temperature cannot be obtained.

The low water absorption transparent plastic material of the present invention can be produced by known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Bulk polymerization by casting is preferred for obtaining film or sheet materials, and suspension polymerization and emulsion polymerization for injection moldable materials are preferred from the viewpoint of work efficiency. In either case, it is preferable that the copolymer is free of foreign substances, so copolymerization 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, and the monomer mixture is dispersed, 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 prepared from an arbitrary monomer mixture to form glass or metal.

After pouring into a mold made of plastic or the like designed according to the intended use, thermal polymerization is performed.

In the case of bulk polymerization by injection method, 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, two-surface strength, and production processability. Examples of crosslinking agents include polyfunctional methacrylates, polyfunctional acrylates, and aromatic divinyl compounds. However, aromatic divinyl compounds have a large number of double bonds and therefore have a problem with light resistance, which is not preferable. 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, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, etc. There is.

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 acetate and lauroyl peroxide,
Di-tert-butyl peroxide, Methyl ethyl ketone peroxide, Di-tert-butyl perphthalate, Di-tert-butyl peracetate, Di-tert
Examples include organic peroxides such as t-amyl peroxide and similystyl peroxydicarbonate.

The blending amount of these polymerization initiators is 0.05 to 2.5 wt% based on the total amount of various compounds blended.

In addition, chain transfer agents that have the function of adjusting the molecular weight of the copolymer include tert-butanethiol, n-butanethiol,
tart-octanethiol, n-octanethiol,
Examples include n-dodecanethiol and tert-dodecanethiol. What are the amounts of these chain transfer agents?

It is 1.0 wt% or less based on the total amount of various compounds blended.

Antistatic agent depending on the use of the produced copolymer.

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 with reference to Examples. However, the present invention is not limited thereto.

The physical properties in the following examples were measured at a nozzle temperature of 230°C.
The tests were carried out using specimens of each shape molded using an injection molding machine. The total light transmittance was determined according to JIS-6717, the heat distortion temperature was determined according to A method of JIS-7207, and the impact strength, which is a factor of mechanical strength, was determined according to JIS-7110 (However, in order to clarify the difference, (Measurement was made without making a notch in the specimen).

To determine the saturated water absorption rate, first, test the specimen at 70°C/0, 1 rt.
Dry for 10 hours or more at mHg or less and measure the initial weight,
Next, the weight of the test piece after being left in water at 70°C for 20 days was measured, and the weight was calculated according to the JIS-7209 calculation formula (when calculated from the ratio of the original weight of the test piece to the increase in weight after water absorption). A
I asked for it from the law.

The dimensional change rate is 50X30X5t obtained by injection molding (unit:
The sample obtained in 1) was left in a temperature of 40° C./95% RH, and the change in length was measured using a micrometer and calculated from the following equation.

Dimensional change rate = ((Length after moisture absorption - Initial length) / Initial length) The length after moisture absorption is the length after being left in 40° C./95% RH.

The warpage test was performed by injection molding at a nozzle temperature of 250°C and using a 300na+φ, 1.2t thick product with information markings on one side.
Obtain ya optical disk base. Furthermore, aluminum was vapor-deposited using a vapor deposition apparatus under a vacuum of 10 mHg. Thereafter, a SiN protective film was coated using a conventional method, and the two substrates were bonded together using an adhesive. This is 60℃/95
%RH atmosphere for two weeks, and a warping test of the optical disk substrate was conducted.

To measure warpage, measure the distance between the center of the optical disk substrate and a plane passing through at least two points on the outer periphery of the disk substrate using a three-dimensional measuring device (AF-121, Sankai Seisakusho II), and calculate the amount of warpage. Shown as warpage.

<Example 1> In a 4Q flask equipped with a stirrer and a condenser, 40 g of a 10 wt% aqueous solution of basic calcium phosphate, 0.002 g of sodium dodecylbenzenesulfonate, and 0.5 g of sodium sulfate were added as a dispersant to 2200 g of ion-exchanged water.
and keep the stirring speed at 25 rpm. Add the following composition to this.

Polymerization was carried out at 65° C. for an incubation time under a nitrogen atmosphere, followed by 2 hours at 97° C.

Methyl methacrylate 480g tricyclo[5.2,1,0”6) 380g-decyl methacrylate 2.2,3.3-tetrafluoropro 340g pyrumethacrylate lauroyl peroxide 4.2 gl-octanethiol 1.44gn-octadecyl-3 -(4'Hydroxy-3',5'-di-tert-butylphenyl)propionate 4g Stearyl alcohol 2g The produced copolymer particles were washed with water, dehydrated, and then dried to obtain a low water absorption transparent plastic. Its properties are shown in Table 1.

No. table [Examples 2 to 9 and Comparative Example 1. ~3] The copolymer composition is shown in Table 2.

A low water absorption transparent plastic was obtained in the same manner as in Example 1, except that the polymerization conditions were 65°C for 3 to 6 hours and 97°C for 2 to 6 hours. Their properties are also listed in Table 1.

The dimensional change rate of the low water absorption transparent plastics obtained in Examples 1 to 9 and Comparative Examples 1 to 3 in Table 2 was measured in an atmosphere of 40° C./95% RH.

As a representative example, Example 1. The measurement results of Comparative Examples 1 and 2 are shown in FIG. Next, Examples 1 to 3. Example 5. Warpage of optical disk substrates obtained from the low water absorption transparent plastics of Comparative Examples 1 and 2 was measured.

The measurement results are shown in Table 3.

Table 3 In addition, the saturated water absorption rate, which is closely related to warpage, is also listed in the table.

As is clear from the above Examples and Comparative Examples, in the case of acrylic resin, the saturated water absorption rate of PMMA (polymethyl methacrylate) of Comparative Example 1 is 2.2%, while in all Examples the saturated water absorption rate is 0. It is low at less than 7%. The heat distortion temperature of the example is also higher than that of the comparative example.

PM has the best total light transmittance in all examples.
Shows a high value equivalent to MA. That is, it is clear that all of the examples have low water absorption, and exhibit well-balanced values for transparency, heat resistance, and mechanical strength. Furthermore, as is clear from FIG. 1 and Table 3, the low water absorption transparent plastic according to the present invention is stable against water absorption even in applications such as optical disk substrates.

〔Effect of the invention〕

The low water absorption transparent plastic of the present invention is resistant to water absorption.

Heat resistance 2: Excellent mechanical strength and transparency.

[Brief explanation of the drawing]

FIG. 1 is a graph of the dimensional change rate due to water absorption of one embodiment of the present invention over time.

Claims (1)

[Claims] 1. A compound represented by the general formula (I) ▲ There are mathematical formulas, chemical formulas, tables, etc. (represents an alkyl group having 3 to 20 carbon atoms) and compounds represented by the general formula (II) ▲ Numerical formulas, chemical formulas, tables, etc. A low water absorption transparent plastic characterized by having three essential components: cyclic hydrocarbon group) and methyl methacrylate. 2. The compound represented by the general formula (I) is 5 to 70
wt% and the compound represented by the general formula (II) is 5
~60wt% and 20~70w methyl methacrylate
The low water absorption transparent plastic according to claim 1, wherein the copolymer has a blending amount of t%. 3. The low water absorption transparent plastic according to claim 1 or 2, which has a saturated water absorption of 0.7% or less. 4. In the general formula (I), the compound containing a fluorinated substituted alkyl group having 3 to 20 carbon atoms is 2,2,3
, 3-tetrafluoropropyl methacrylate, 1H,
1H,5H-octafluoropentyl methacrylate,
1H,1H,2H,2H-heptadecafluorodecyl methacrylate, 1H-hexafluoroisopropyl methacrylate, perfluoro-tert-butyl methacrylate, 1H,1H,2H,2H-heptadecafluorodecyl methacrylate, 1H,1H,2H,2H -tridecafluorooctamethacrylate, 1H, 1H, 2H
, 2H-heneicosafluorododecyl methacrylate, and 1H, 1H, 2H, 2H-pentacosafluorotetradecyl methacrylate. Low water absorption transparent plastic as described. 5. Compound represented by general formula (II) Gatricyclo[5.2.1.0^2^,^6]-decyl methacrylate, tricyclo[3.3.1.1^3^,^7]-
The low water absorption transparent plastic according to claim 1, 2 or 3, which is decyl methacrylate.