JP2007031560A - Molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molded product suitable for use in a thin/highly precise optical lens by using a rubber modified styrene resin composition having good dimensional stability, impact resistance, high index of refraction and moldability, and moderate transparency. <P>SOLUTION: This molded product is made from the rubber modified styrene resin composition, wherein the rubber modified styrene resin is produced by graft polymerizing a styrene monomer in the presence of a styrene-butadiene copolymer including a 20-50 mass% styrene monomer unit, the rubbery polymer particle of ≥80 volume% that forms a discontinuous phase of the resin has a core/shell structure, and the rubber modified styrene resin composition comprises a 45-100 mass% rubber modified styrene resin (A) with a 0.3-2.0 μm volume median particle diameter (dv) of a rubbery polymer particle, and a 0-55 mass% styrene-(meth)acrylate copolymer resin (B) obtained by copolymerizing a styrene monomer with a (meth)acrylate monomer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a molded article made of a specific rubber-modified styrene resin composition. In particular, the present invention relates to an optical lens molded body used for a screen lens used as a transmission type screen of a projection television screen.

  A screen lens such as a transmission screen is widely used to administer an image of a projection television and realize a target display. This screen lens is generally configured by combining lens moldings such as a lenticule lens and a Fresnel lens so that it is bright when an observer observes and the viewing angle is enlarged. As the light projecting material used for these screen lenses, methacrylic resins having excellent transparency have been widely used, and screen lens processing methods have been performed by press molding, extrusion molding, cast molding, injection molding, and the like. .

  The methacrylic resin used as a base material for such a screen lens molded body has a high water absorption rate, so that the dimensional change of the screen lens molded body is likely to occur, the optical characteristics are impaired, and the screen lens from the frame body is damaged. It had the problem of dropping out. In addition, methacrylic resin is inferior in impact resistance, and cracks and the like may occur during manufacture, transportation, and assembly of screen lenses, resulting in defective products.

In order to solve these problems, a styrene-diene copolymer is dissolved in an aromatic vinyl monomer, a (meth) acrylic acid ester monomer, and a polyfunctional unsaturated monomer mixture. A method for obtaining a Fresnel lens is disclosed (see Patent Document 1). However, it is not sufficient for recent demands for thinning and high definition, and further cost reduction, and a resin with high refractive index and good moldability is required. There is a demand for an optical lens molded body formed by injection molding or extrusion molding.
Japanese Patent Laid-Open No. 5-341101

  The present invention provides a thin-walled, high-definition optical lens application by using a rubber-modified styrene resin composition having good dimensional stability, impact resistance, high refractive index, good moldability, and appropriate transparency. The molded object suitable for is provided.

  As a result of intensive studies to solve the above problems, the present inventors have found that a specific rubber-modified styrene-based resin composition has good dimensional stability, impact resistance, high refractive index, moldability, and is practical. The present inventors have found that a molded article having such transparency and comprising this specific rubber-modified styrenic resin composition is suitable for use in a thin-walled, high-definition optical lens.

  That is, the present invention relates to (1) a rubber-modified styrene obtained by graft polymerization of a styrene monomer in the presence of a styrene-butadiene copolymer having a styrene monomer unit content of 20 to 50% by mass. 80% by volume or more of the rubber-like polymer particles forming the dispersed phase of the resin have a core / shell structure, and the volume-median particle diameter (dv) of the rubber-like polymer particles is 0.00. Styrene- (meth) acryl obtained by copolymerizing 45 to 100% by mass of a rubber-modified styrene resin (A) 3 to 2.0 μm, a styrene monomer and a (meth) acrylic acid ester monomer A molded article comprising a rubber-modified styrene resin composition containing 0 to 55% by mass of an acid ester copolymer resin (B), (2) the molded article according to (1), wherein the molded article is an extrusion molded article or an injection molded article (3) The molded body is an optical lens molded body. There (1) or (2) molding according a molded body according to any one of (4) molded article is a screen lens (1) to (3).

  According to the present invention, by using a rubber-modified styrenic resin composition having good dimensional stability, impact resistance, high refractive index, good moldability and practical transparency, it is thin and high-definition. A molded article suitable for optical lens applications can be obtained.

Hereinafter, the present invention will be described in detail.
The rubber-modified styrene resin (A) constituting the present invention is obtained by graft polymerization of a styrene monomer in the presence of a styrene-butadiene copolymer.

Examples of the styrene monomer include styrene, α-methyl styrene, p-methyl styrene, pt-butyl styrene, and the like, and styrene is preferable. These styrene monomers may be used alone or in combination of two or more.
Monomers other than styrenic monomers, such as (meth) acrylic acid ester monomers, acrylonitrile, maleic anhydride, methacrylic acid, etc. may be less than 10 parts by mass with respect to 100 parts by mass of styrene monomers. Can be used.

The styrene-butadiene copolymer has a styrene monomer unit content of 20 to 50% by mass, preferably 30 to 45% by mass. When a styrene-butadiene copolymer or polybutadiene having a styrene monomer unit content of less than 20% by mass is used, the transparency is low. When a styrene-butadiene copolymer exceeding 50% by mass is used, Impact resistance is low.
As the structure of the styrene-butadiene copolymer, a known structure such as random, block or taper can be adopted. Moreover, a styrene-butadiene copolymer may be used independently and may use 2 or more types together. Further, a rubbery polymer other than the styrene-butadiene copolymer used in the present invention, such as a styrene-butadiene copolymer having a content of polybutadiene or a styrene monomer unit of less than 20% by mass, is used in the present invention. The styrene-butadiene copolymer can be mixed and used, but when mixed, the content of the styrene monomer unit in the whole mixture is 20 to 50% by mass, preferably 30 to 45%. % By mass.

  The ratio of the styrene-butadiene copolymer is preferably 3 to 30 parts by mass with respect to 100 parts by mass of the styrene monomer. When the styrene-butadiene copolymer is less than 3 parts by mass, impact resistance and the like are low, and when it exceeds 30 parts by mass, the transparency is low and the purpose may not be achieved.

As a polymerization method of the rubber-modified styrene resin (A), a known method can be used, but a bulk polymerization method and a solution polymerization method are preferable.
Then, a rubber-modified styrenic resin (A) satisfying the conditions of the present invention can be obtained by a known technique such as adjustment of the stirring speed and temperature during the polymerization reaction, addition of a polymerization initiator, a chain transfer agent, and the like. it can. As the polymerization initiator, benzoyl peroxide, azobisisobutyronitrile, t-butylperoxybenzoate, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, t-butyl Peroxyisopropyl carbonate, dicumyl peroxide, t-butyl peroxyacetate, t-butylperoxy-2-ethylhexanoate, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane , Ethyl-3,3-di (t-butylperoxy) butyrate, t-butylperoxyisobutyrate and the like. Examples of the chain transfer agent include t-dodecyl mercaptan, n-dodecyl mercaptan, α-methylstyrene dimer and the like.

The rubber-modified styrene resin (A) is composed of rubber-like polymer particles that form a dispersed phase with a styrene resin as a matrix. The ratio of the core / shell structure in the rubber-like polymer particles is 80% by volume or more, preferably 85% by volume or more. When the core / shell structure is less than 80% by volume, the transparency, particularly the parallel line transmittance, which is practical transparency, is inferior.
In the present invention, the content ratio of the core / shell structure rubber-like polymer particles in the rubber-like polymer particles is obtained by staining a rubber-modified styrene resin with osmium tetroxide, forming a sample by an ultrathin section method, and using an electron microscope. A photograph magnified 10,000 times is taken, the shape of 1000 or more dispersed rubber particles in the magnified photograph is measured, and the following formula is obtained.
Content ratio (volume%) of core / shell structure rubbery polymer particles = ΣmiDi ³ / ΣniDi ³
(In the formula, ni represents the number of rubber-like polymer particles having a particle diameter Di, and mi represents the number of core / shell structure rubber-like polymer particles having a particle diameter Di.)
The structure of the rubber-like polymer particles can be controlled by the polymerization initiator, the number of stirring, the rubber-like polymer, and the like.

The volume median particle diameter (dv) of the rubber-like polymer particles in the rubber-modified styrenic resin (A) is 0.3 to 2.0 μm, preferably 0.3 to 1.0 μm. When the volume median particle diameter (dv) is less than 0.3 μm, the impact resistance of the resulting rubber-modified styrenic resin composition is significantly reduced, and the core / shell structure rubbery polymer exceeds 2.0 μm. The rubber-modified styrene resin having particles has low transparency.
The volume median particle diameter (dv) can be controlled by an initiator, the number of stirring, a rubbery polymer, and the like at the time of polymerization.

  In the present invention, the volume-median particle diameter (dv) is obtained by dissolving the rubber-modified styrene resin (A) in dimethylformamide and using a laser diffraction particle size distribution analyzer (Laser diffraction particle analyzer LS-230 manufactured by Coulter). Measure and use the median particle size of the volume-based particle size distribution curve as the volume median particle size (dv).

  The styrene- (meth) acrylic acid ester copolymer resin (B) is obtained by copolymerizing a styrene monomer and a (meth) acrylic acid ester monomer. Here, examples of the (meth) acrylic acid ester monomer include methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, and n-butyl acrylate. Preferably, methacrylic acid is used. Methyl. As the polymerization method, conventionally known methods can be employed, but a bulk polymerization method and a solution polymerization method are preferable. And the styrene- (meth) acrylic acid ester copolymer resin (B) satisfying the conditions of the present invention by adjusting the temperature during polymerization reaction, adding a polymerization initiator, a chain transfer agent, etc. Obtainable.

  The content of the (meth) acrylic acid ester monomer unit in the styrene- (meth) acrylic acid ester copolymer resin (B) is preferably 0 to 80% by mass, more preferably 5 to 25% by mass. . When the content is 80% by mass or more, transparency and impact resistance are lowered.

  The rubber-modified styrene resin composition is composed of a rubber-modified styrene resin (A) and a styrene- (meth) acrylic ester copolymer resin (B). The ratio of the rubber-modified styrene resin (A) and the styrene- (meth) acrylic ester copolymer resin (B) is (A) :( B) = 45 to 100% by mass: 55 to 0% by mass, preferably (A) :( B) = 55-100% by mass: 45-0% by mass. When the rubber-modified styrenic resin (A) is less than 45% by mass, the impact resistance is low.

The melt mass flow rate (MFR) measured based on JIS K7210 of the rubber-modified styrene resin composition is preferably 1 to 15 g / 10 min. If it is out of the range, transparency and workability may be deteriorated.
The matrix refractive index of the rubber-modified styrenic resin composition is preferably 1.585 or more. If the refractive index is low, there is a limitation for thin-walled, high-definition optical lens applications.

  The rubber-modified styrenic resin composition constituting the present invention includes known plasticizers, lubricants, antioxidants, colorants, anti-glare agents, antistatic agents, flame retardants, sliding materials used for styrene resins depending on the purpose. Agents, pigments, etc., known glass beads and crosslinked resin particles used for screen lenses can be added. These may be added at any step during production. For example, when the rubber-modified styrene resin (A) or styrene- (meth) acrylate copolymer resin (B) is polymerized or rubber-modified. Examples include the melt-kneading extrusion of the styrene resin (A) and the styrene- (meth) acrylic ester copolymer resin (B).

  The optical lens molded body can be obtained by a known method, but extrusion molding and injection molding are preferable. A known shape can also be adopted, and a screen lens in which a lenticular lens and / or a Fresnel lens is provided on at least one surface is a preferable example.

   EXAMPLES Next, although an Example is given and this invention is demonstrated in detail, this invention is not limited by these examples.

Reference Example 1 Polymerization of rubber-modified styrenic resin ((A) -1) A first fully mixed reactor having a volume of about 5 L with a stirrer and a second completely mixed reactor having a volume of about 15 L with a stirrer A tower type plug flow reactor having a volume of about 40 L and a devolatilization tank equipped with a preheater were connected in series. Asaprene 670A manufactured by Asahi Kasei Chemicals Co., Ltd. as a styrene-butadiene copolymer (15 parts by mass) is dissolved in a mixed solution composed of 100 parts by mass of styrene and 15 parts by mass of ethylbenzene. 0.03 part by mass of 1,1-bis (t-butylperoxy) -cyclohexane and 0.05 part by mass of octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate were mixed. A raw material solution was obtained. This raw material solution was introduced into a first complete mixing reactor controlled at a temperature of 115 ° C. at 7 kg / hour. The reaction solution was continuously withdrawn from the first complete mixing reactor, and 3.0 g of n-dodecyl mercaptan was added to the reaction solution per hour, and then introduced into the second complete mixing reactor controlled at a temperature of 130 ° C. The number of stirrings in the second complete mixing reactor was 150 rpm. Next, the reaction solution is continuously withdrawn from the second complete mixing reactor, and 4.0 g of n-dodecyl mercaptan is added to the reaction solution per hour, and then a gradient of 130 ° C. to 150 ° C. is formed in the flow direction. It was introduced into a tower-type plug flow reactor adjusted as described above. While this reaction solution was heated by a preheater, it was introduced into a devolatilization tank controlled at a temperature of 230 ° C. and a pressure of 1.3 kPa to remove volatile components such as unreacted monomers. This resin liquid was extracted with a gear pump, and extruded into a strand shape and cut to obtain a pellet-shaped rubber-modified styrene resin.

Reference Example 2 Polymerization of rubber-modified styrenic resin ((A) -2) The same procedure as in Reference Example 1 was conducted except that the stirring rate of the second complete mixing reactor was 220 rpm.

Reference Example 3 Polymerization of Rubber-Modified Styrene Resin ((A) -3) 10.5 parts by mass of Asaprene 670A (styrene monomer unit: 40% by mass) manufactured by Asahi Kasei Chemicals Corporation as a styrene-butadiene copolymer, and Asahi Kasei The same procedure as in Reference Example 2 was performed except that 4.5 parts by mass of Toughden 2000A (styrene monomer unit: 25% by mass) manufactured by Chemicals Co. was used.

Reference Example 4 Polymerization of Rubber-Modified Styrene Resin ((A) -4) As a styrene-butadiene copolymer, 15 parts by mass of Toughden 2000A (styrene content: 25% by mass) manufactured by Asahi Kasei Chemicals Co., Ltd. was used. t-butylperoxy) -cyclohexane 0.06 parts by mass, octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate 0.10 parts by mass, and a second complete mixing type reactor This was carried out in the same manner as in Example 1 except that the stirring number was set at 220 rpm.

Reference Example 5 Polymerization of rubber-modified styrenic resin ((A) -5) The same procedure as in Reference Example 1 was conducted except that the stirring rate of the second complete mixing reactor was 120 rpm.

Reference Example 6 Polymerization of Rubber-Modified Styrene Resin ((A) -6) The same procedure as in Reference Example 1 was conducted except that the stirring rate of the second complete mixing reactor was 20 rpm.

Reference Example 7 Polymerization of Rubber-Modified Styrene Resin ((A) -7) In an autoclave with a stirrer of 50 L internal volume, with a stirrer, 30 kg of styrene, Asaprene 670A (styrene-based) made as a styrene-butadiene copolymer (Monomer unit content: 40% by mass) 4.5 kg was dissolved to obtain a raw material solution. To this raw material liquid, 48 g of t-dodecyl mercaptan was added, and after substituting with nitrogen, it was sealed and bulk polymerized at 115 ° C. for 6 hours with stirring at 157 rpm to obtain a prepolymerized liquid. Next, 40 kg of pure water, 140 g of tribasic calcium phosphate and 0.2 g of sodium dodecylbenzenesulfonate were added to an autoclave with a stirrer having an internal volume of 100 L and stirred, and 35 kg of the prepolymerized solution and 61 g of azobisisobutyronitrile, ethyl After adding 5 g of -3,3-di (t-butylperoxy) butyrate and replacing with nitrogen, it was sealed and polymerized at a temperature of 80 ° C. for 5 hours and at 132 ° C. for 4 hours to complete the polymerization. The obtained beads were washed, dehydrated and dried, and then extruded at 230 ° C. using a single screw extruder to obtain a pellet-shaped rubber-modified styrene resin ((A) -7).

Reference Example 8 Polymerization of rubber-modified styrene resin ((A) -8) Instead of styrene-butadiene copolymer, 15 parts by mass of diene 35A (styrene content: 0% by mass) manufactured by Asahi Kasei Chemicals Co., Ltd. was used. Bis (t-butylperoxy) -cyclohexane 0.06 parts by mass, octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate 0.10 parts by mass, second complete mixed reaction The same procedure as in Reference Example 1 was performed except that the stirring number of the vessel was changed to 350 rpm.

Reference Example 9 Polymerization of rubber-modified styrenic resin ((A) -9) 1,3-bis (t-butylperoxy) -cyclohexane 0.03 parts by mass, octadecyl-3- (3,5-di-t- The same procedure as in Reference Example 4 was carried out except that 0.05 part by mass of butyl-4-hydroxyphenyl) propionate was changed to 250 rpm.

Reference Example 10 Polymerization of Rubber-Modified Styrene Resin ((A) -10) 9.4 parts by mass of Asaprene 670A (styrene monomer unit: 40% by mass) manufactured by Asahi Kasei Chemicals Corporation as a styrene-butadiene copolymer, and polybutadiene As in Reference Example 6, except that 5.6 parts by mass of diene 35A (styrene monomer unit: 0% by mass) manufactured by Asahi Kasei Chemicals Corporation was used.

Reference Example 11 Polymerization of Rubber-Modified Styrene Resin ((A) -11) The same procedure as in Reference Example 1 was conducted except that the stirring rate of the second complete mixing reactor was 350 rpm.

Reference Example 12 Polymerization of Styrene- (Meth) Acrylate Ester Copolymer Resin ((B) -1) First Reactor as a Completely Mixing Stirring Tank with a Volume of about 20 L and Tower Type Plug Flow with a Stirrer of about 40 L A second reactor, which is a type reactor, was connected in series, and two devolatilization tanks equipped with a preheater were connected in series. 15 parts by mass of ethylbenzene, 0.01 parts by mass of t-butylperoxyisopropyl monocarbonate, n-dodecyl with respect to 100 parts by mass of a monomer solution composed of 83% by mass of styrene and 17% by mass of methyl methacrylate (hereinafter referred to as MMA) Mercaptan (hereinafter n-DDM) 0.1 part by mass and octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate 0.03 part by mass were mixed to obtain a raw material solution. This raw material solution was fed to the first reactor controlled at 127 ° C. at 6.0 kg / hour. The reaction liquid was continuously withdrawn from the second reactor of the first reactor and introduced into the second reactor adjusted to have a gradient from 127 ° C to 155 ° C. Next, after heating to 160 ° C. with a preheater, it was introduced into the first devolatilization tank reduced to 67 kPa, and further heated to 230 ° C. with a preheater and then introduced into the second devolatilization tank reduced to 1.3 kPa. The monomer was removed. This was extruded and cut into strands to obtain pellet-shaped styrene- (meth) acrylic ester copolymer resin.

Reference Example 13 Polymerization of styrene- (meth) acrylic ester copolymer resin ((B) -2) Reference except that the monomer solution was composed of 70% by mass of styrene and 30% by mass of methyl methacrylate (hereinafter referred to as MMA). Performed as in Example 12. .

Reference Example 14 Polymerization of Styrene- (Meth) acrylate Copolymer ((B) -3) Reference except that the monomer solution was composed of 60% by mass of styrene and 40% by mass of methyl methacrylate (hereinafter referred to as MMA). Performed as in Example 12.

Examples 1-7, Comparative Examples 1-4
Tables 1 and 2 show the physical property evaluation results of (A) -1 to (A) -11 obtained by the above method.

Examples 8-11, Comparative Example 5
A rubber-modified styrene resin (A) and a styrene- (meth) acrylic ester copolymer resin (B) are extruded into strands at a temperature of 230 ° C. using a 40 mm single screw extruder, and cut into pellets by a pelletizer. A rubber-modified copolymer resin composition was obtained. The physical property evaluation results are shown in Table 3.

The evaluation was based on the following method.
(1) Dimensional stability Using a T-die type sheet extruder, a 2 mm thick sheet was obtained at a cylinder temperature of 230 ° C. A test piece of 18 cm × 18 cm was cut out from this sheet, sandwiched between steel plates larger than the test piece, heated at 90 ° C. for 5 hours, and then allowed to cool for 24 hours. After removing the test piece and placing it flat in a 30 cm × 23 cm container, pure water was poured into the container so that only one side of the test piece was immersed in water. After leaving at room temperature for 24 hours, the amount of warping (mm) at the four corners of the test piece was measured, and the average value of these was taken as the amount of warpage. A warpage amount of 0.4 mm or less was regarded as acceptable.
(2) Transparency Using an injection molding machine (IS-50EPN manufactured by Toshiba Machine Co., Ltd.), a three-stage plate having a thickness of 1 mm, 2 mm, and 3 mm was molded at a cylinder temperature of 200 ° C. Using a 2 mm portion of this three-stage plate, in accordance with ASTM D1003, a haze meter (NDH-1001DP type manufactured by Nippon Denshoku Industries Co., Ltd.) was used to measure haze, and parallel transmittance was measured as practical transparency. (unit:%). A haze of 30% or less and a parallel line transmittance of 60% or more were considered acceptable.
(3) Impact resistance Based on JIS K7111, a type 1 test piece having a notch type A was used, and the impact direction was measured by employing edgewise and the Charpy impact strength was measured (unit: kJ / m ² ).
The measuring machine used was a digital impact tester manufactured by Toyo Seiki Seisakusho. A Charpy impact strength of 4 kJ / m ² or more was accepted.
(4) Melt mass flow rate (MFR) was measured using resin pellets at a temperature of 200 ° C. and a load of 49 N based on JIS K7210 (unit: g / 10 minutes). The measuring machine used was a melt indexer (F-F01) manufactured by Toyo Seiki Seisakusho.

(5) Refractive index of matrix 3.5 g of sample was dissolved in 350 ml of toluene at a temperature of 25 ° C. for 24 hours, then transferred to a 500 ml centrifuge tube, and centrifuged at a temperature of 10 ° C. or lower and 14000 rpm for 40 minutes. . After separating the precipitate, the supernatant was concentrated with a rotary evaporator and dried in a vacuum dryer at a temperature of 70 ° C. for 24 hours. The dried product was pressed and measured with an ATAGO precision Abbe refractometer type III (manufactured by Atago Co., Ltd.).

Claims (4)

  A rubber-modified styrene resin obtained by graft polymerization of a styrene monomer in the presence of a styrene-butadiene copolymer having a styrene monomer unit content of 20 to 50% by mass, comprising: 80% by volume or more of the rubber-like polymer particles forming the dispersed phase have a core / shell structure, and the volume-median particle diameter (dv) of the rubber-like polymer particles is 0.3 to 2.0 μm. Styrene- (meth) acrylic ester copolymer resin (B) obtained by copolymerizing 45-100% by mass of styrene resin (A), styrene monomer and (meth) acrylic acid ester monomer A molded article comprising a rubber-modified styrenic resin composition containing 0 to 55% by mass.   The molded body according to claim 1, wherein the molded body is an extrusion molded body or an injection molded body.   The molded body according to claim 1 or 2, wherein the molded body is an optical lens molded body.   The molded body according to any one of claims 1 to 3, wherein the molded body is a screen lens.