JP4610881B2 - Styrenic resin composition and molded body thereof - Google Patents

Description

  The present invention relates to a resin composition excellent in light diffusibility used as a transmissive screen for a screen of a projection television or the like and a diffusion plate for a liquid crystal TV, and a molded product thereof.

  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. The light projecting material used for these screen lenses has been widely used methacrylic resin, which is excellent in transparency, light resistance, scratch resistance, etc., and has excellent molding processability. It has been carried out by extrusion molding, cast molding, injection molding and the like.

  Since the methacrylic resin used as a base material for such a screen lens molded body has a high water absorption rate, the dimensional change of the screen lens molded body occurs, the screen warps and floats, and the optical properties are impaired. There has been a problem that the screen lens is detached from the frame.

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, this technique is insufficient to obtain a molded article for a screen lens having excellent light diffusibility.
In addition, since the methacrylic resin used as the base material of the diffusion plate of the liquid crystal TV has a high water absorption, the dimensional change of the diffusion plate molding occurs, the diffusion plate warps, and the optical properties are impaired. It was.

Japanese Patent Laid-Open No. 5-341101

The subject of this invention is providing the styrene-type resin composition excellent in light diffusibility, and its molded object.

As a result of intensive studies to solve the above-mentioned problems in the styrene resin, the present inventors have included a specific amount of fused silica in a specific styrene copolymer, thereby providing a styrene resin composition having excellent light diffusibility. The present invention has been found and the present invention has been achieved.

That is, the present invention comprises (1) 20 to 80% by mass of a styrene monomer unit and 80 to 20% by mass of a (meth) acrylic acid ester monomer unit. The average molecular weight ratio is 2. A styrene resin composition comprising 0.1 to 20 parts by mass of fused silica having an average particle diameter of 1 to 20 μm with respect to 100 parts by mass of a styrene copolymer resin of 0 or less, (2) (1) A sheet comprising the styrene resin composition according to the description, and an injection molded article comprising the styrene resin composition according to (3) (1).

  According to the present invention, an unprecedented styrenic resin composition excellent in light diffusibility can be provided industrially very advantageously. Since the styrene resin composition of the present invention is excellent in light diffusibility, it can be suitably used for optical applications such as Fresnel lenses, lenticular lenses, and diffusion plates.

Hereinafter, the present invention will be described in detail.
Examples of the styrenic monomer used in the present invention include styrene, α-methylstyrene, p-methylstyrene, pt-butylstyrene, and the like, and styrene is preferable. These may be used alone or in combination of two or more.

  Examples of the (meth) acrylic acid ester monomer used in the present invention include methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-methylhexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, and the like. Is mentioned. These may be used alone or in combination of two or more. Preferably, it is methyl methacrylate, ethyl acrylate, n-butyl acrylate or a mixture thereof.

  Further, if necessary, other copolymerizable monomers such as acrylonitrile can also be used.

The styrene monomer unit constituting the styrene resin of the present invention is 20 to 80% by mass, and the (meth) acrylic acid ester monomer unit is 80 to 20% by mass.
If it is out of this range, the transparency of the resulting styrenic resin is undesirably lowered.

The ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the styrene resin of the present invention needs to be 2.5 or less. If it exceeds 2.5, the strength is undesirably lowered. Both the weight average molecular weight Mw and the number average molecular weight Mn were measured by the gel permeation chromatography (GPC) method described below.
Device name: SYSTEM-21 Shodex (manufactured by Showa Denko)
Column: 3 PL gel MIXED-B in series Temperature: 40 ° C
Detection: Differential refractive index Solvent: THF (tetrahydrofuran)
Concentration: 2% by mass
Calibration curve: Prepared using standard polystyrene (PS) (manufactured by PL), and the weight average molecular weight Mw and number average molecular weight Mn were expressed in terms of PS.

The silica used in the present invention is preferably fused silica.
The silica used in the present invention preferably has an average particle size of 1 to 20 μm.
When the average particle size is reduced, the haze is reduced and the light diffusibility tends to be lowered. When the average particle size is increased, the total light transmittance is lowered and the light diffusibility is lowered. Silica may be pulverized or spherical.
The average particle diameter of silica was measured using a Coulter Multisizer (manufactured by Beckman Coulter).

  As for content of the silica used by this invention, 0.1-20 mass parts is preferable with respect to 100 mass parts of thermoplastic resins. When the amount is less than 0.1 parts by mass, the haze is reduced and the light diffusibility is lowered. When the amount exceeds 20 parts by mass, the total light transmittance is lowered and the light diffusibility is lowered.

  Although there is no restriction | limiting in particular in the manufacturing method of the styrene-type copolymer of this invention, The block polymerization method, suspension polymerization method, solution polymerization method, and emulsion polymerization method can be employ | adopted suitably.

There are various methods for producing silica, for example, there are various methods for producing fused silica. For example, high-purity silica stone, silica sand, crystal, etc., or a powder obtained by pyrolysis from a silicon halide compound is melted. The agglomerated material, adjusted to the target particle size by grinding or grinding, is a fused silica pulverized product, and the fused agglomerated material is sprayed and spheronized with a flame such as propane / oxygen flame, and further the spherical shape. A fused silica sphere is prepared by sufficiently stirring and dispersing the body in water and performing wet classification to adjust the particle size to the target.
There is no restriction | limiting in particular in the compounding method of a silica, The method of mix | blending before the superposition | polymerization of a styrene-type copolymer, the superposition | polymerization, after superposition | polymerization, the method of mix | blending by mixing with a styrene-type copolymer, etc. are mentioned.

The method for mixing silica with the styrene copolymer is not particularly limited. For example, after premixing with a known mixing apparatus such as a Henschel mixer or a tumbler mixer, the extrusion is performed using a single screw extruder or a twin screw extruder. Uniform mixing can be achieved by melt-kneading using a machine.
For example, a high-concentration mixture of fused silica may be prepared by the above-described method, and the high-concentration mixture and a styrene copolymer may be dry blended at the time of sheet molding or injection molding.

An additive can be mix | blended with the styrene resin composition of this invention as needed. For example, a plasticizer, a lubricant, silicone oil or the like can be blended in order to improve fluidity and releasability. An antistatic agent can be blended for dust prevention of the molded product.
In order to impart heat resistance, a heat stabilizer can be blended. To impart light resistance, light stabilizers and UV absorbers can be added. However, when UV curing is applied to the surface of the molded product and UV curing is performed, care must be taken because it affects curing. is there. In addition, a coloring agent or the like can be blended. As the light diffusing material, resin beads such as inorganic beads such as glass beads, polystyrene cross-linked beads, polymethyl methacrylate cross-linked beads, polymethacryl styrene cross-linked beads, polyorganosiloxane cross-linked beads may be used in combination.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples. In addition, both the part and% in an Example were represented on the basis of mass.

Production of styrene resin (A) In an autoclave equipped with a stirrer, 42.5 parts of styrene and 57.5 parts of methyl methacrylate (MMA), as a polymerization initiator, 0.2 part of benzoyl peroxide, 0.1 part of t-dodecyl mercaptan, As a suspension stabilizer, 0.001 part of sodium dodecylbenzenesulfonate, 0.5 part of tribasic calcium phosphate and 200 parts of pure water were charged and polymerized at a temperature of 95 ° C. for 6 hours and further at a temperature of 130 ° C. for 2 hours. After completion of the reaction, washing, dehydration and drying were performed to obtain a bead-like styrene resin (A1). It was Mw / Mn = 2.0 in terms of polystyrene measured by the GPC method of the styrene resin (A1). The composition was styrene / MMA = 43.0 / 57.0.

  In an autoclave with a stirrer, 42.5 parts of styrene and 57.5 parts of methyl methacrylate (MMA), 0.2 parts of benzoyl peroxide as a polymerization initiator, 0.5 part of t-dodecyl mercaptan, dodecylbenzenesulfone as a suspension stabilizer 0.001 part of sodium phosphate, 0.5 part of tribasic calcium phosphate and 200 parts of pure water were added, and after 4 hours at a temperature of 95 ° C., 0.5 part of t-dodecyl mercaptan was further added, Polymerization was performed for a period of time, and further polymerization was performed at a temperature of 130 ° C. for 2 hours. After completion of the reaction, washing, dehydration and drying were performed to obtain a bead-like styrene resin (A2). It was Mw / Mn = 2.6 in terms of polystyrene measured by the GPC method of the styrene-based resin (A2). The composition was styrene / MMA = 43.1 / 56.9.

  In an autoclave with a stirrer, 22.5 parts of styrene and 77.5 parts of methyl methacrylate (MMA), 0.2 parts of benzoyl peroxide as a polymerization initiator, 0.1 part of t-dodecyl mercaptan as a compound having a mercapto group, suspended As stabilizers, 0.001 part of sodium dodecylbenzenesulfonate, 0.5 part of tribasic calcium phosphate and 200 parts of pure water were charged, and polymerization was carried out at a temperature of 95 ° C. for 6 hours and further at a temperature of 130 ° C. for 2 hours. After completion of the reaction, washing, dehydration and drying were performed to obtain a bead-like styrene resin (A3). It was Mw / Mn = 2.0 in terms of polystyrene measured by the GPC method of the styrene resin (A3). The composition was styrene / MMA = 22.4 / 77.6.

  In an autoclave with a stirrer, 77.5 parts of styrene and 22.5 parts of methyl methacrylate (MMA), 0.2 parts of benzoyl peroxide as a polymerization initiator, 0.1 part of t-dodecyl mercaptan, dodecylbenzenesulfone as a suspension stabilizer 0.001 part of sodium acid, 0.5 part of tribasic calcium phosphate, and 200 parts of pure water were charged and polymerized at a temperature of 95 ° C. for 6 hours and further at a temperature of 130 ° C. for 2 hours. After completion of the reaction, washing, dehydration and drying were performed to obtain a bead-like styrene resin (A4). It was Mw / Mn = 2.0 in terms of polystyrene measured by the GPC method of the styrene resin (A4). The composition was styrene / MMA = 77.4 / 22.6.

  15.5 parts of styrene and 84.5 parts of methyl methacrylate (MMA) in an autoclave equipped with a stirrer, 0.2 part of benzoyl peroxide as a polymerization initiator, 0.1 part of t-dodecyl mercaptan, dodecylbenzenesulfone as a suspension stabilizer 0.001 part of sodium acid, 0.5 part of tribasic calcium phosphate, and 200 parts of pure water were charged and polymerized at a temperature of 95 ° C. for 6 hours and further at a temperature of 130 ° C. for 2 hours. After completion of the reaction, washing, dehydration and drying were performed to obtain a bead-like styrene resin (A5). It was Mw / Mn = 2.0 in terms of polystyrene measured by the GPC method of the styrene resin (A5). The composition was styrene / MMA = 15.4 / 84.6.

  In an autoclave equipped with a stirrer, 84.5 parts of styrene and 15.5 parts of methyl methacrylate (MMA), 0.2 part of benzoyl peroxide as a polymerization initiator, 0.1 part of t-dodecyl mercaptan as a compound having a mercapto group, suspended As stabilizers, 0.001 part of sodium dodecylbenzenesulfonate, 0.5 part of tribasic calcium phosphate and 200 parts of pure water were charged, and polymerization was carried out at a temperature of 95 ° C. for 6 hours and further at a temperature of 130 ° C. for 2 hours. After completion of the reaction, washing, dehydration and drying were performed to obtain a bead-like styrene resin (A6). It was Mw / Mn = 2.0 in terms of polystyrene measured by the GPC method of the styrene resin (A6). The composition was styrene / MMA = 84.6 / 15.4.

Production of fused silica (B) High-purity quartz powder obtained by pulverizing high-purity quartz through a jaw crusher, a W roll crusher, and a ball mill so that the cumulative particle size of 149 μm or less is about 100% by weight is propane / oxygen = 1/5. The mixture was put into a flame of about 2000 ° C. maintained at a ratio of 6, and melt spheroidized. At this time, fused silica spheres having a maximum particle diameter of 24 μm or less collected by a cyclone classified in the furnace or a bag filter were collected. After sufficiently stirring and dispersing in water, ultrafine powder is classified and removed with a hydrocyclone, fused silica spheres B-1 having an average particle size of 0.5 μm, fused silica spheres B-2 having an average particle size of 2 μm, average Fused silica spheres B-3 having a particle diameter of 5 μm, fused silica spheres B-4 having an average particle diameter of 18 μm, and fused silica granules B-5 having an average particle diameter of 22 μm were obtained.
After pulverizing a high-purity quartz fused ingot through a jaw crusher and a W roll crusher, classification is performed, a fused silica pulverized product B-6 having an average particle size of 0.5 μm, a fused silica pulverized product B-7 having an average particle size of 2 μm, an average A fused silica pulverized product B-8 having a particle size of 5 μm, a fused silica pulverized product B-9 having an average particle size of 18 μm, and a fused silica pulverized product B-10 having an average particle size of 22 μm were obtained.

Examples 1-10, Comparative Examples 1-9
The styrenic resins (A1) to (A6) were each kneaded with a 40 mm diameter single screw extruder at a temperature of 240 ° C. and a screw rotation speed of 100 rpm, and pelletized to obtain pellets.
Using this pellet, GPC of the composition was measured and shown in Table 1.
Moreover, this styrene-type copolymer and fused silica B-1 to B-10 were mixed at the compounding ratio shown in Table 2, and the temperature was 240 ° C. and the screw rotation speed was 100 rpm with a 40 mm diameter single screw extruder. It knead | mixed and pelletized and the pellet of the styrene-type resin composition was obtained.
The pellets were injection molded at a temperature of 220 ° C. to obtain test pieces. Various physical properties were measured using this test piece.
Further, a sheet was formed at a cylinder temperature of 230 ° C. by a T-die type extruder. The measured physical properties are shown in Table 2. The physical properties and transparency of the obtained sheet are shown in Table 2.

The measuring method of each physical property value is as follows.
(1) Total light transmittance, haze Ri index: shows the injection molding articles of Table 2, using an injection molding machine (manufactured by Toshiba Machine Co., Ltd. IS-50EPN), a thickness of 1mm at a cylinder temperature of 220 ° C., A 3 mm plate with 2 mm and 3 mm was formed. It measured using the HAZE meter (Nippon Denshoku Industries Co., Ltd. NDH-1001DP) according to ASTMD-1003 using the 2 mm thickness part of this 3 step | paragraph plate.
Moreover, what was shown to the physical property of the sheet molded article of Table 2 was measured using the obtained sheet | seat using HAZE meter (Nippon Denshoku Industries Co., Ltd. NDH-1001DP) according to ASTM D-1003.

  Since the styrene resin composition of the present invention is excellent in light diffusibility, it can be suitably used for optical applications such as Fresnel lenses, lenticular lenses, and diffusion plates.

Claims (3)

It consists of 20 to 80% by mass of styrene monomer units and 80 to 20% by mass of (meth) acrylate monomer units, and the ratio of the weight average molecular weight to the number average molecular weight of the THF-soluble component is 2. A styrene resin composition comprising 0.1 to 20 parts by mass of fused silica having an average particle diameter of 1 to 20 μm with respect to 100 parts by mass of styrene copolymer resin of 0 or less. A sheet comprising the styrenic resin composition according to claim 1. An injection-molded article comprising the styrenic resin composition according to claim 1.