JP2005325195A - Manufacturing process of methacrylate resin-made light transmitting body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for manufacturing a methacrylate resin light transmitting body in which the methacrylate resin is not thermally decomposed nor discolored by heating and melting. <P>SOLUTION: The process for manufacturing the methacrylate resin light transmitting body comprises molding a methacrylate resin composition obtained by mixing (1) a disulfide expressed by formula (1): R<SP>1</SP>-S-S-R<SP>2</SP>(1) with a methacrylate resin in a heat-melted state. In the formula, R<SP>1</SP>and R<SP>2</SP>are each independently a 1-12C alkyl group or a 3-12C cycloalkyl group which may be substituted with a 1-12C alkoxy group. The amount of the disulfide mixed is 0.1-5,000 ppm. Injection molding or extrusion molding is employed for the molding. The composition composed of the methacrylate resin mixed with 0.1-5,000 ppm of (1) the disulfide is useful as a methacrylate resin composition for light transmittance. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a method for producing a molded body made of methacrylic resin.

Since the methacrylic resin is excellent in transparency, for example, a plate-like methacrylic compound incorporated in a backlight (2) disposed on the back side of a flat panel display (4) including the color liquid crystal display shown in FIG. Widely used as a resinous light guide (1). The backlight (2) shown in FIG. 1 is a so-called edge light type backlight in which a light source (3) is disposed on an end surface (1a) of a plate-like light guide (1).

By the way, as a method for producing such a methacrylic resin light guide, a method in which a methacrylic resin is molded in a heat-melted state is common, but a methacrylic resin is likely to be thermally decomposed by heat-melting.
Paragraph No. 0017 of JP-A-7-166020

As a method of molding in a heated and melted state without causing thermal decomposition of the acrylic resin, Patent Document 1 (paragraph number 0017 of JP-A-7-166020) discloses a methacrylic resin blended with di-tert-dodecyl disulfide. Although a method using a composition is disclosed, a light guide produced by this method can prevent thermal decomposition due to heating and melting, but produces a slight coloration on a light guide after molding. I found out there was a problem. When the light guide is colored, even if it is slight, the influence of the edge light type backlight for large screens becomes large because the optical path length becomes long.

Therefore, as a result of intensive studies to develop a method capable of producing a light guide made of methacrylic resin without causing thermal decomposition or coloring, the present inventor has obtained a formula (1).
R ¹ —S—S—R ² (1)
Wherein R ¹ and R ² each independently represent a cycloalkyl group having 3 to 12 carbon atoms which may be substituted with an alkyl group or an alkoxy group having 1 to 12 carbon atoms having 1 to 12 carbon atoms. ]
It was found that by blending the disulfides represented by the formula (1), not only the thermal decomposition of the methacrylic resin can be prevented, but also a light guide with less coloring can be obtained, and the present invention has been achieved.

That is, the present invention provides a method for producing a methacrylic resin molded product, characterized in that a methacrylic resin composition comprising a methacrylic resin blended with the disulfide represented by the formula (1) is molded in a heated and melted state. It is to provide.

According to the production method of the present invention, a methacrylic resin light guide can be produced without causing thermal decomposition or coloring of the methacrylic resin during molding.

The methacrylic resin used in the production method of the present invention is a polymer obtained by polymerizing a monomer containing methyl methacrylate as a main component, specifically, a monomer containing 50% by mass or more of methyl methacrylate. Polymethyl methacrylate obtained by polymerizing methyl methacrylate alone, or a copolymer of 50% by mass or more of methyl methacrylate and 50% by mass or less of a monomer copolymerizable therewith. There may be. Examples of the monomer copolymerizable with methyl methacrylate include ethyl methacrylate, propyl methacrylate, butyl methacrylate, benzyl methacrylate, 2-ethylhexyl acrylate, cyclohexyl methacrylate, bornyl methacrylate, adamantyl methacrylate, and methacrylic acid. Methacrylate esters such as cyclopentadienyl acid,
Acrylic esters such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, bornyl acrylate, adamantyl acrylate, and cyclopentadienyl acrylate ,
Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, maleic anhydride, itaconic anhydride and their anhydrides, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxy acrylate Hydroxyl group-containing monomers such as propyl, monoglycerol acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, monoglycerol methacrylate, acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, diacetone acrylamide, methacryl Nitrogen-containing monomers such as dimethylaminoethyl acid, epoxy group-containing monomers such as allyl glycidyl ether, glycidyl acrylate, and glycidyl methacrylate, and styrene and α-methylstyrene. Such as alkylene monomer and the like.

In the disulfides represented by the formula (1), examples of the cycloalkyl group represented by the substituents R ¹ and R ² include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclo A dodecyl group etc. are mentioned, Preferably it is a C3-C8 cycloalkyl group.

Such a cycloalkyl group may be substituted with an alkyl group having 1 to 12 carbon atoms or an alkoxyl group having 1 to 12 carbon atoms. The C1-C12 alkyl group that can be substituted on the cycloalkyl group may be linear or branched. Examples of the linear alkyl group include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, and an n-dodecyl group. Group and the like. Examples of the branched alkyl group include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group and the like.

The alkoxy group having 1 to 12 carbon atoms may be linear or branched. Examples of the linear alkoxyl group include a methoxy group, an ethoxy group, an n-propoxy group, and an n-butoxy group. Examples of the branched alkoxyl group include an isopropoxy group, an isobutoxy group, a sec-butoxy group, and a tert-butoxy group.

Examples of such disulfides (1) include dicyclopropyl disulfide, dicyclobutyl disulfide, dicyclopentyl disulfide, dicyclohexyl disulfide, dicyclooctyl disulfide, dicyclododecyl disulfide, and the like. These disulfides (1) are used alone or in combination of two or more.

The compounding quantity of disulfides (1) is 0.1 ppm-5000 ppm normally with respect to a methacryl resin, Preferably it is 10 ppm-2000 ppm.

Such a methacrylic resin composition can be produced, for example, by a method in which disulfides (1) are blended with a monomer mainly composed of methyl methacrylate or a partial polymer thereof and polymerized. Examples of the polymerization method include usual polymerization methods such as bulk polymerization method (bulk polymerization method), solution polymerization method, emulsion polymerization method and suspension polymerization method, and additives for polymerization such as stabilizers and emulsifiers are added. Bulk polymerization and solution polymerization are preferred in that they can be easily polymerized without using them, and there are few impurities, and an excellent transparent light guide can be easily obtained.

In order to obtain a methacrylic resin composition by a bulk polymerization method or a solution polymerization method, specifically, for example, a disulfide (1) and a polymerization initiator are added to a monomer containing methyl methacrylate as a main component, and bulk polymerization or Solution polymerization is performed to obtain a partial polymer having a polymer content of 40% by mass to 70% by mass, and an unpolymerized monomer is devolatilized from the partial polymer to obtain a polymer. Further, the disulfide (1) may be added to the partially polymerized product after polymerizing the monomer and devolatilized. Furthermore, you may add disulfides (1) to the polymer after devolatilization. You may add a chain transfer agent, a mold release agent, etc. previously to the monomer used for the block polymerization method or the solution polymerization method.

Also, disulfides (1) are added to a powdered or pelleted methacrylic resin obtained by a method such as an emulsion polymerization method or a suspension polymerization method or a pulverized product thereof, and mixed with a mixer such as a Henschel mixer or a V-type blender. You may mix and melt-knead with kneading machines, such as a uniaxial kneader and a biaxial kneader. Mixing with a mixer or melt-kneading with a kneader is preferably performed in an atmosphere of an inert gas such as nitrogen gas or argon gas.

Thus, a composition in which the disulfide (1) is blended with the methacrylic resin is obtained. Such a composition is suitable as a methacrylic resin composition for a light guide for producing a light guide made of methacrylic resin.

As a method for molding the methacrylic resin composition in a heated and melted state, for example, the methacrylic resin composition may be heated and melt-kneaded with a kneader and then molded with a molding machine. Examples of the molding method include an injection molding method in which an injection molding machine is used as a molding machine and injection is performed in a molding die, and an extrusion molding method in which an extrusion molding machine is used as a molding machine to perform extrusion molding from a die. When a methacrylic resin composition is obtained by adding disulfides (1) to a methacrylic resin and kneading and kneading with a kneading machine, the obtained methacrylic resin composition may be sent to a molding machine in a molten state. Good. Although the molding temperature is usually 230 ° C. or higher, for example, the molding can be performed at 260 ° C. or higher, and is usually 290 ° C. or lower.

The production method of the present invention is preferably applied in the case of molding by an injection molding method, and more preferably, a relatively large light guide plate for a screen with a long molding cycle and a long residence time in the extruder and the injection molding machine, Specifically, it is suitable when a light guide plate that is applied to a screen size of 10 cm or more diagonally is formed by an injection molding method.

Since the methacrylic resin light guide (1) thus obtained is not colored, the light guide incorporated in the backlight device (2) disposed on the back of the color flat panel display device (4) as shown in FIG. It is preferably used as (1), and particularly for a relatively large screen having a screen size of 10 cm or more, preferably 15 cm or more, more preferably 20 cm or more on a diagonal line, and a light guide for an edge-light type backlight device (2) ( Suitable as 1).

EXAMPLES Hereinafter, although the Example demonstrates the manufacturing method of this invention in detail, this invention is not limited by these Examples.

In addition, evaluation in each Example was performed with the following method.
(1) Using a heat-stable TG-DTA device (“TG / DTA6300”, manufactured by Seiko Instruments Inc.), the weight loss was measured while raising the pellet from 50 ° C. to 430 ° C. at a rate of temperature rise of 2 ° C./min. The temperature when the weight of the pellet decreased by 2% was read. The higher this temperature is, the better the thermal stability and the harder it is to decompose.
(2) Monomer content 0.1 g of a test piece was taken from each of the pellets and molded bodies obtained in each Example, dissolved in 20 cm ³ of dichloromethane to form a solution, and a gas chromatograph [“GC-14B type” ”, Manufactured by Shimadzu Corporation], and the monomer content (mass%) was measured.
(3) Molding colorability The end face of the test piece obtained in each example was polished with a polishing machine ["Pura Beauty PB-100" manufactured by Asahi Megaro Co., Ltd.], and then a spectrophotometer ["U-4000", Hitachi Manufactured by Seisakusho Co., Ltd.], measuring the 150 mm path transmittance in the wavelength range of 380 to 780 nm, obtaining the XYZ value from the obtained transmittance according to the method described in JIS Z-8722, and determining the yellowness according to the method described in JIS K-7105. Asked. The average value of _yellowness (YI _avr ) obtained for two test pieces was _defined as molding colorability. It shows that there is little coloring at the time of shaping _| molding, so that the average value ( _YIavr ) of _yellowness is small.

Example 1
98.8 parts by weight of methyl methacrylate and 0.8 part by weight of methyl acrylate were mixed, 0.1 part by weight of dicyclohexyl disulfide, 0.17 part by weight of a chain transfer agent [octyl mercaptan] and a release agent [stearyl alcohol] 0 .1 part by mass was added to obtain a monomer mixture. Further, 0.036 parts by mass of a polymerization initiator [1,1-di (t-butylperoxy) 3,3,5-trimethylcyclohexane] was added to 100 parts by mass of methyl methacrylate to obtain an initiator mixed solution. The monomer mixture and the initiator mixture are continuously fed to the fully mixed polymerization reactor so that the flow ratio is 8.8: 1, and the average polymerization rate is 20 minutes at an average residence time of 175 ° C. Polymerization to 54% gave a partially polymerized product. The resulting partially polymerized product is heated to 200 ° C. and led to a vented devolatilizing extruder, and unreacted monomers are devolatilized from the vent at 240 ° C., and the polymer after devolatilization is extruded in a molten state. After cooling with water, it was cut into pellets. The thermal stability and monomer content of this pellet are shown in Table 1.

The pellets obtained above were melted by heating to 280 ° C. and 290 ° C. in an injection molding machine (“M-140SJ type”, manufactured by Meiki Seisakusho), respectively, and injection molded into the mold under the conditions of a molding cycle of 1 minute. Then, it was molded into a flat plate of 150 × 150 × 3 mm to obtain a light guide-shaped molded body. Table 1 shows the monomer content and molding colorability of the molded product.

Using the injection molding machine ["IS130FII" manufactured by Toshiba Machine Co., Ltd.], the pellets obtained above were melted by heating to 240 ° C and 280 ° C, respectively, and repeatedly injected into the mold in a molding cycle of 1 minute. And it shape | molded into the flat plate of 200x120x3 mm, and was set as the molded object. When the molded product of the 11th molding cycle and the molded product of the 12th molding cycle were operated in the same manner as in the evaluation of molding colorability, the 200 mm pass transmittance was determined and the yellowness (YI) was determined. = 4 (molding temperature 240 ° C.) and YI = 7 (molding temperature 280 ° C.).

Example 2
Pellets were obtained in the same manner as in Example 1 except that the amount of methyl methacrylate used in the monomer mixture was 98.7 parts by mass and that of dicyclohexyl disulfide was 0.18 parts by mass. The thermal stability and monomer content of this pellet are shown in Table 1.

A 150 × 150 × 3 mm molded body was obtained in the same manner as in Example 1 except that the pellets obtained above were used instead of the pellets obtained in Example 1. Table 1 shows the monomer content and molding colorability of the molded product.

A 200 × 120 × 3 mm molded body was obtained in the same manner as in Example 1 except that the pellets obtained above were used instead of the pellets obtained in Example 1. When the yellowness was determined for the 11th and 12th moldings in the same manner as in Example 1, the average values were YI = 5 (molding temperature 240 ° C.) and YI = 8 (molding temperature), respectively. 280 ° C.).

Comparative Example 1
A pellet was obtained in the same manner as in Example 1 except that 0.01 part by mass of di-tert-dodecyl disulfide was used instead of dicyclohexyl disulfide. The thermal stability and monomer content of this pellet are shown in Table 1.

A 150 × 150 × 3 mm molded body was obtained in the same manner as in Example 1 except that the pellets obtained above were used instead of the pellets obtained in Example 1. Table 1 shows the monomer content and molding colorability of the molded product.

Comparative Example 2
Pellets were obtained in the same manner as in Example 1 except that dicyclohexyl disulfide was not used. The thermal stability and monomer content of this pellet are shown in Table 1.

A 150 × 150 × 3 mm molded body was obtained in the same manner as in Example 1 except that the pellets obtained above were used instead of the pellets obtained in Example 1. Table 1 shows the monomer content and molding colorability of the molded product.

Table 1
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Pellet compact
Thermal stability Monomer content Monomer content Molding colorability
(° C.) (mass%) (mass%) (YI _avr )
280 ° C 290 ° C 280 ° C 290 ° C
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Example 1 298 0.18 0.51 0.82 7.2-
Example 2 302 0.17-0.73-8.5
Comparative Example 1 297 0.18 0.46 0.73 14.8 17.1
Comparative Example 2 269 0.23 1.54-5.6-
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It is a schematic diagram which shows an example of the backlight apparatus and flat panel display apparatus using a methacrylic resin light guide.

Explanation of symbols

1: Methacrylic resin light guide 1a: End face 2: Backlight 3: Light source 4: Flat panel display

Claims (8)

Formula (1) on methacrylic resin
R ¹ —S—S—R ² (1)
Wherein R ¹ and R ² each independently represent a cycloalkyl group having 3 to 12 carbon atoms which may be substituted with an alkyl group or an alkoxy group having 1 to 12 carbon atoms having 1 to 12 carbon atoms. ]
A method for producing a methacrylic resin light guide, characterized in that a methacrylic resin composition containing a disulfide represented by the formula is molded by heating and melting. The manufacturing method of Claim 1 whose compounding quantity of the disulfide shown by said Formula (1) is 0.1 ppm-5000 ppm with respect to a methacryl resin. The manufacturing method according to claim 1, wherein the molding is performed by an injection molding method or an extrusion molding method. The manufacturing method of Claim 1 shape | molded at 230 degreeC or more. A methacrylic resin composition for a light guide, comprising a methacrylic resin and a disulfide represented by the formula (1). The methacrylic resin composition according to claim 5, wherein the compounding amount of the disulfides represented by the formula (1) is 0.1 ppm to 5000 ppm with respect to the methacrylic resin. A light guide made of methacrylic resin comprising a methacrylic resin composition comprising a methacrylic resin and a disulfide represented by the formula (1). The methacrylic resin light guide according to claim 7, wherein the compounding amount of the disulfides represented by the formula (1) is 0.1 ppm to 5000 ppm with respect to the methacrylic resin.

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