JP4846228B2 - Styrenic resin composition and molded article thereof - Google Patents

Description

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

  A screen lens such as a transmission screen is widely used to administer an image of a projection television and realize a target display. The screen lens is generally configured by combining lens molded bodies such as a lenticular lens and a Fresnel lens so that the observer can observe a bright image and have a wide viewing angle. 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 article has a high water absorption rate, the dimensional change of the screen lens molded article occurs, the screen warps or floats, and the optical properties are impaired. There has been a problem that the screen lens is detached from the frame. Further, there has been a problem that the screen lens is deformed when the temperature at the time of transportation or the use environment temperature is high.

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 warping of the diffusion plate occurs, and the optical characteristics are impaired. It was. Further, there is a problem of deformation when the use environment temperature is high.

Japanese Patent Laid-Open No. 5-341101

  An object of the present invention is to provide a styrenic resin composition used for a molded article for a screen lens or a molded article for a diffusion plate, which has excellent dimensional stability, a high heat distortion temperature, and excellent light diffusibility. is there.

  As a result of intensive studies to solve the above problems in the styrene-based resin, the inventors have included a specific amount of an unmelted compound in a specific styrene-based polymer, thereby providing excellent step stability and a heat distortion temperature. The present inventors have found a styrenic resin composition having a high diffusivity and excellent light diffusivity, and have reached the present invention.

That is, the present invention comprises (1) 80 to 99% by mass of styrene monomer units, 20 to 1% by mass of methacrylic acid monomer units, and 0 to 10% by mass of copolymerizable vinyl compound monomer units. 0.1 to 35 parts by mass of fused silica having a refractive index of 1.52 or less and an average particle diameter of 1 to 20 μm is contained with respect to 100 parts by mass of the styrene copolymer. An injection-molded product obtained by molding a styrene-based resin composition described in ( 2 ) (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 and heat resistance, it can be suitably used particularly for optical applications such as Fresnel lenses, lenticular lenses, and diffusion plates.

Hereinafter, the present invention will be described in detail.
(Styrene polymer A)
Examples of the styrene monomer used in the present invention include styrene, α-methyl styrene, p-methyl styrene, pt-butyl styrene, and the like, preferably styrene.

  Examples of the vinyl monomer copolymerizable with the styrene monomer and methacrylic acid in the present invention include (meth) acrylic acid ester monomers such as methyl methacrylate and n-butyl acrylate, acrylonitrile and methacrylo Vinyl cyanide monomers such as nitrile, unsaturated carboxylic acid monomers other than methacrylic acid such as maleic anhydride, maleic acid, itaconic acid, itaconic anhydride, maleimide, N-methylmaleimide, N-phenylmaleimide, etc. And maleimide monomers. These may be used alone or in combination of two or more.

The styrene copolymer A used in the present invention is 80 to 99% by mass, preferably 85 to 98% by mass, and 20 to 1% by mass, preferably 15 to 15% by mass, of methacrylic acid monomer units. It consists of 2% by mass and 0-10% by mass of copolymerizable vinyl compound monomer units, preferably 0-5% by mass. If the styrenic monomer unit exceeds 99% by mass, the heat resistance is low, and if it is less than 80 parts by mass, the heat resistance is too high and the flowability of the resin is lowered, and a molded product may not be obtained. .

(Unmelted compound)
The unmelted compound used in the present invention is a compound having a melting point or softening point at 200 ° C. or higher in an atmosphere of 101.3 kPa (1 atm). When the melting point and softening point are less than 200 ° C., the compound is easily melted at the time of melt-kneading with a styrene-based polymer, or at the time of forming a sheet of a styrene-based resin composition or at the time of injection molding, and can retain excellent optical properties. Can not.

The refractive index of the unmelted compound used in the present invention is 1.52 or less, preferably 1.49 or less. When the refractive index exceeds 1.52, the haze is reduced and the light diffusibility is lowered.

The unmelted compound preferably has an average particle size of 1 to 20 μm, more preferably 1.5 to 19. When the average particle size is less than 1 μm, the haze is reduced and the light diffusibility is lowered. The average particle size of the unmelted compound was measured using a Coulter Multisizer (manufactured by Beckman Coulter).

As for content of the unmelted compound used for this invention, 0.1-35 mass parts is preferable with respect to 100 mass parts of styrene-type copolymers, and also 0.1-20 mass parts is more preferable. When the amount is less than 0.1 parts by mass, the haze is reduced and the light diffusibility is reduced.

Examples of the unmelted compound used in the present invention include silica such as fused silica, and crosslinked polyorganosiloxane such as polyorganosiloxane crosslinked beads. These may be used alone or in combination. May be. As fused silica, high-purity silica stone, quartz sand, crystal, etc., or a powder obtained by thermal decomposition from a halogenated silicon compound, adjusted to the target particle size by grinding or grinding Is a pulverized fused silica product, which is melted and agglomerated with a flame such as propane / oxygen flame, and spheronized and spheroidized, and the spheroids are thoroughly stirred and dispersed in water to obtain a desired particle size. Examples include adjusted fused silica spheres.

(Production method)
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 is no restriction | limiting in particular in the mixing | blending method of an unmelted compound, The method of mix | blending by the mixing with a styrene-type copolymer etc., the method of mix | blending before superposition | polymerization of a styrene-type copolymer, the middle of superposition | polymerization, etc. are mentioned.

Although there is no particular limitation on the method of mixing the unmelted material with the styrene copolymer, for example, after premixing in a known mixing device such as a Henschel mixer or a tumbler mixer, a single screw extruder or a twin screw extruder, etc. By performing melt kneading using an extruder of No. 5, uniform mixing is possible.
Alternatively, a high-concentration mixture of unmelted compounds may be prepared by the above-described method, and the high-concentration mixture and styrene copolymer may be dry blended during sheet molding or injection molding.

(Additive)
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. Moreover, an antistatic agent can be mix | blended for the dust prevention of a molded article. Moreover, in order to provide heat resistance, a heat stabilizer can be mix | blended. In addition, in order to impart light resistance, a light stabilizer or UV absorber can be blended. However, if UV curing is applied to the surface of the molded product and UV curing is performed, care should be taken as this will affect curing. is necessary. In addition, a coloring agent or the like can be blended. Further, inorganic beads such as glass beads, resin beads such as polystyrene cross-linked beads, polymethyl methacrylate cross-linked beads, and polymethacryl styrene cross-linked beads can be used in combination as the light diffusing material.

The molded body of the present invention is a sheet or an injection molded body formed by molding the styrene resin composition. Specifically, it is a molded product for optical use such as a transmission screen of a projection television or the like, a diffusion plate of a liquid crystal TV, a lenticular lens or a Fresnel lens.

  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 mass basis.

(Production of styrene copolymer A)
A first complete mixing tank with a capacity of about 5 liters and a second complete mixing tank with about 15 liters are connected in series, and two first and second devolatilization tanks with preheaters are connected in series. Configured.
15 parts by mass of ethylbenzene with respect to 100 parts by mass of a monomer solution composed of 95% by mass of styrene containing 0.1 ppm of 4-t-butylcatechol and 5% by mass of methacrylic acid (hereinafter referred to as “MAA”), t -0.01 part by mass of butyl peroxyisopropyl monocarbonate and 0.2 part by mass of 2,4-diphenyl-4-methyl-1-pentene were mixed to obtain a raw material solution.
This raw material solution was supplied to the first complete mixing tank controlled at 135 ° C. at 6.0 kg / hour. The conversion rate at the outlet of the first complete mixing tank was 28% by mass. Next, it extracted continuously from the 1st complete mixing tank, and supplied to the 2nd complete mixing tank controlled to 135 degreeC. The conversion rate at the second complete mixing vessel outlet was 63% by mass. Next, it extracted continuously from the 2nd complete mixing tank, heated with the preheater, and introduce | transduced into the 1st devolatilization tank controlled to 67 kPa and 160 degreeC. Furthermore, it extracted continuously from the 1st devolatilization tank, heated with the preheater, and introduce | transduced into the 2nd devolatilization tank controlled to 1.3 kPa and 230 degreeC, and the monomer was removed. This was extruded and cut into strands to obtain pellet-shaped styrenic copolymer A-1.

Except having used the monomer solution comprised by 90 mass% of styrene and 10 mass% of MAA, it implemented similarly to the styrene copolymer A-1, and obtained the styrene copolymer A-2.

Except having used the monomer solution comprised by styrene 85 mass% and MAA 15 mass%, it implemented similarly to the styrene copolymer A-1, and obtained the styrene copolymer A-3.

A styrene copolymer A-4 is obtained in the same manner as the styrene copolymer A-1, except that a monomer solution composed of 85% by mass of styrene, 10% by mass of MAA, and 5% by mass of methyl methacrylate is used. It was.

Except having used the monomer solution comprised by 100 mass% of styrene, it implemented similarly to the styrene-type copolymer A-1, and obtained the styrene-type copolymer A-5.

Except having used the monomer solution comprised by styrene 75 mass% and MAA 25 mass%, it implemented similarly to the styrene copolymer A-1, and obtained the styrene copolymer A-6.

The value obtained by subtracting the measured value of the methacrylic acid monomer unit and the residual methacrylic acid in the styrene copolymer from the measurement of the total amount of the methacrylic acid monomer unit and the residual methacrylic acid in the obtained styrene copolymer. Was determined as the amount of methacrylic acid monomer units in the styrene copolymer and shown in Table 1. Further, Table 1 shows the composition of the obtained styrene copolymer.

(Production of fused silica B)
High-purity quartz powder pulverized so that the cumulative particle size of 149 μm or less through the jaw crusher, W roll crusher, and ball mill is about 100% by weight was maintained at a ratio of propane / oxygen = 1 / 5.6. It was put into a flame of about 2000 ° C. 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 was classified and removed with a liquid cyclone to obtain fused silica spheres B-1 to B-5 shown in Table 2.
Moreover, after pulverizing the high purity quartz fused ingot through a jaw crusher and a W roll crusher, classification was performed, and fused silica pulverized products B-6 to B-10 shown in Table 2 were obtained.

(Polyorganosiloxane cross-linked beads C)
As polyorganosiloxane cross-linked beads, C-1: KMP590 manufactured by Shin-Etsu Chemical Co., Ltd., C-2: X-52-1032 manufactured by Heishinetsu Chemical Co., Ltd., and C-3: X-52-854 manufactured by Shin-Etsu Chemical Co., Ltd. were used. These average particle diameters and refractive indexes are shown in Table 2.

(Polystyrene cross-linked beads D)
In an autoclave with a stirrer, 100 parts of styrene, 5 parts of divinylbenzene as a crosslinking agent, 0.2 part of benzoyl peroxide, 0.1 part of t-dodecyl mercaptan as a polymerization initiator, and sodium dodecylbenzenesulfonate as a suspension stabilizer 001 parts, 0.5 part of tribasic calcium phosphate and 200 parts of pure water were charged and polymerized at 95 ° C. for 6 hours and further at 130 ° C. for 2 hours. After completion of the reaction, washing, dehydration and drying were performed to obtain polystyrene cross-linked beads D shown in Table 2.

Examples 1-12, Comparative Examples 1-11
Styrene copolymers A-1 to A-6, fused silica B-1 to B-10, and polyorganosiloxane crosslinked beads C-1 to C-3 were mixed at a blending ratio shown in Tables 3 and 4, and 40 mm. In a single screw extruder, the mixture was kneaded at a temperature of 240 ° C. and a screw rotation speed of 100 rpm, and pelletized to obtain pellets of a styrene resin composition.
The pellets were injection molded at a temperature of 230 ° C. to obtain test pieces. Further, a sheet was formed at a cylinder temperature of 240 ° C. by a T-die type extruder.
The physical properties were evaluated using these test pieces and sheets. The results are shown in Tables 3 and 4.
In addition, about transparency, it is required in order to express the outstanding light diffusibility that haze degree is 80% or more and total light transmittance is 50% or more.

  In addition, the measuring method of each physical property value is as follows.

(1) Measurement of methacrylic acid monomer unit content in styrene copolymer:
I. Measurement of total amount of methacrylic acid monomer unit and residual methacrylic acid a) 100 ml of a chloroform: ethanol mixed solution (2: 1) is added to 2 g of styrene copolymer and dissolved. b) Add 0.5% phenolphthalein / ethanol solution as an indicator, and titrate with 0.1N potassium hydroxide / ethanol solution. The end point was when the color of the indicator did not disappear for 30 seconds. c) As a blank test, 100 ml of a chloroform: ethanol mixed solution (2: 1) was taken and the same operation as b) was performed. d) The methacrylic acid content in the styrene copolymer was determined from the following formula.
Methacrylic acid content (%) = [{(A−Bt) × M} / (S × 1000)] × 100
A: Titration required for a) (ml)
B: Enemy determination required for c) (ml)
S: Mass of styrene copolymer (g)
M: Mass of methacrylic acid equivalent to 1 ml of 0.1N potassium hydroxide / ethanol solution (8.6 (mg))

II. Measurement of amount of residual methacrylic acid 0.5 g of styrene copolymer was dissolved in 10 ml of chloroform and measured using N, N-dimethylformamide as an internal standard, and measured under the following GC measurement conditions.
Device name: GC14B FID detector column manufactured by Shimadzu Corporation: Glass column φ3mm × 3m
Filler: Diethylene glycol succinate Carrier: Nitrogen temperature: Column 110 ° C, inlet 180 ° C
Sample 0.5g

III. The value obtained by subtracting the amount of residual methacrylic acid in the styrene copolymer measured in II from the total amount of methacrylic acid monomer units and residual methacrylic acid in the styrene copolymer measured in I is the styrene copolymer weight. It calculated | required as methacrylic acid monomer unit content in a coalescence. However, for those having a measured value of residual methacrylic acid in the styrene copolymer of less than 0.1% by mass,
The residual methacrylic acid amount was 0% by mass, and the methacrylic acid monomer unit content in the styrene copolymer was determined.

(2) Measurement of methyl methacrylate monomer content in styrene copolymer 2% solution prepared by dissolving styrene copolymer in deuterated chloroform was used as a measurement sample, and FT-NMR (FX manufactured by JEOL Ltd.) -90Q type) was measured using C13 and calculated from the peak areas of styrene and methyl methacrylate.

(3) Refractive index The refractive index of the unmelted compound was measured with an Abbe refractometer in an atmosphere having a wavelength of 589 nm and 23 ° C.

(4) Heat deformation temperature A test piece having a thickness of 12.7 mm, a width of 3.2 mm, and a length of 57.1 mm was molded at a cylinder temperature of 220 ° C. using an injection molding machine (IS-50EPN) manufactured by Toshiba Machine. The test piece was measured at a load of 18.6 kg in accordance with ASTM D-648 in the direction of 12.7 mm thickness.

(5) Total light transmittance, haze a) Properties of injection molded product Using an injection molding machine (IS-50EPN) manufactured by Toshiba Machine Co., Ltd., molding a three-stage plate with a thickness of 1 mm, 2 mm and 3 mm at a cylinder temperature of 220 ° C. did. Using a 2 mm thickness of the three-stage plate, measurement was performed using a Nippon Denshoku Industries HAZE meter (NDH-1001DP) in accordance with ASTM D-1003.
b) Physical Properties of Sheet Molded Products The obtained sheets were measured using a HAZE meter (NDH-1001DP) manufactured by Nippon Denshoku Industries Co., Ltd. according to ASTM D-1003.

Claims (2)

100 parts by mass of a styrene copolymer comprising 80 to 99% by mass of styrene monomer units, 20 to 1% by mass of methacrylic acid monomer units, and 0 to 10% by mass of a copolymerizable vinyl compound monomer unit. On the other hand, 0.1 to 35 parts by mass of fused silica having a refractive index of 1.52 or less and an average particle diameter of 1 to 20 μm is contained. An injection-molded article obtained by molding the styrenic resin composition according to claim 1.