JP2008208147A - Styrenic resin and optical resin molded article comprising the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a styrenic resin exhibiting low water absorption property and containing reduced amount of foreign matter, and an optical resin molded article comprising the same. <P>SOLUTION: The styrenic resin is produced by polymerizing 5-100 mass% of a styrenic monomer and 95-0 mass% of a (meth)acrylate based monomer, wherein the styrenic resin contains foreign matter insoluble in methyl ethyl ketone and having a particle diameter of ≥100 μm in an amount of ≤1 piece/g and foreign matter having a particle diameter of ≥10 μm in an amount of ≤1,000 pieces/g. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a styrenic resin with little foreign matter and an optical resin molded body made of the same. Specifically, the present invention relates to a styrene resin having a low water absorption and a small amount of foreign matter, and an optical resin molded body made of the same.

PMMA has been used in optical products because of its excellent optical performance such as transparency. However, since PMMA has a problem that dimensional change and warpage are likely to occur due to moisture absorption, styrenic resins such as MS resin and GPPS have been studied.
On the other hand, styrene-based resins are excellent in water absorption resistance and molding processability, but have more foreign matters than optical PMMA resins, and have limited optical applications. On the other hand, Patent Document 1 proposes a method of reducing foreign matter by using a fully mixed reaction vessel and a bulk liquid in a heat-insulating state with a full liquid substance having no gas phase portion, but it is not sufficient.
JP 2001-342263 A

  The inventors of the present invention provide a styrene-based resin having excellent water absorption resistance and from which foreign substances having a specific particle diameter have been removed, and an optical resin molded article comprising the same.

That is, the present invention is (1) a styrene resin obtained by polymerizing 5 to 100% by mass of a styrene monomer and 95 to 0% by mass of a (meth) acrylic acid ester monomer. 1 type / g or less of foreign matter having a particle diameter of 100 μm or more and 1000 pieces / g or less of foreign matter having a particle size of 10 μm or more, which is insoluble in methyl ethyl ketone, and (2) a styrene monomer ( (1) Styrenic resin described in (1) obtained by bulk continuous polymerization containing a solvent of less than 20 parts by mass with respect to a total of 100 parts by mass of the (meth) acrylic acid ester monomer, (3) 1) and 2 below 3) The styrenic resin according to claim 1 or 2 obtained by one or more methods selected from 3).
1) After polymerization, after removing the residual monomer and solvent, extrude into a strand in a molten state from the die, and after cooling with cooling water or cutting the strand while cooling to use as a resin pellet The cooling water to be used is water filtered through a filter having an opening of 5 μm or less.
2) The cut resin pellets are dried using clean air having a cleanness class of 10,000 or less that has passed through a HEPA (High-Efficiency Particulate Air) filter.
3) Package the resin pellets in a clean room with a cleanliness class of 10,000 or less and avoid contact with outside air exceeding the class 10,000.
(4) An optical resin molding comprising the styrene resin according to any one of (1) to (3).

The styrenic resin of the present invention and an optical resin molded body comprising the same are excellent in water absorption resistance, have few foreign matters, are suitable for optical applications, and are useful.

The present invention is described in detail below.
The styrene resin is obtained by polymerizing a styrene monomer and / or a (meth) acrylic acid ester monomer.

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

  The (meth) acrylic acid ester monomer used is methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-methylhexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate , 2-methylhexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, and the like, preferably methyl methacrylate and n-butyl acrylate. These (meth) acrylic acid ester monomers may be used alone or in combination of two or more.

The ratio of the styrene monomer and the (meth) acrylate monomer is styrene monomer: (meth) acrylate monomer = 5 to 100% by mass: 95 to 0% by mass. Preferably, it is 31-100 mass%: 69-0 mass%, More preferably, it is 51-100 mass%: 49-0 mass%. If the proportion of the (meth) acrylic acid ester monomer is increased, water absorption and molding processability may be deteriorated, which may not be preferable.

At the time of polymerization, other monomers that can be copolymerized with styrene monomers and (meth) acrylic acid ester monomers, for example, acrylonitrile, methacrylic acid, maleic anhydride, etc. can be used as necessary. . The addition ratio of other monomers copolymerizable with the styrene monomer and the (meth) acrylate monomer is 100 in total of the styrene monomer and the (meth) acrylate monomer. It is less than 50 parts by mass with respect to parts by mass.
Further, polybutadiene, styrene butadiene copolymer rubber, or the like can be dissolved in a styrene monomer or a (meth) acrylic acid ester monomer and polymerized. The addition ratio of polybutadiene, styrene butadiene copolymer rubber or the like is less than 50 parts by mass with respect to 100 parts by mass in total of the styrene monomer and the (meth) acrylic acid ester monomer.

The polymerization is preferably bulk continuous polymerization including a solvent of less than 20 parts by mass with respect to a total of 100 parts by mass of the styrene monomer and the (meth) acrylic acid ester monomer. As the solvent, known solvents can be used, and ethylbenzene, toluene and cyclohexane are preferred. In addition, suspension polymerization and emulsion polymerization are not suitable for optical applications because the suspension dispersant or emulsion dispersant remains in the styrene resin and foreign matter increases or transparency decreases.
Furthermore, styrene monomers, (meth) acrylate monomers, styrene monomers, other monomers copolymerizable with (meth) acrylate monomers, and solvents are: It is preferable to use after filtering with a filter having an opening of 5 μm or less.

During the polymerization, a known polymerization initiator or chain transfer agent can be added. The polymerization temperature and polymerization time are not particularly limited and can be carried out under known conditions.

The polymerization is preferably carried out to a resin rate of 70 to 95% by mass, more preferably to a resin rate of 75 to 85% by mass, and then led to a step of removing residual monomers and solvents. When the resin ratio is less than 70%, the production efficiency is poor, and when it is 95% or more, the viscosity of the polymerization solution is high and transportation is difficult.

  After the polymerization, a step of removing the residual monomer and solvent is preferably extruded from the die into a strand in a molten state, and after cooling with cooling water or with cooling, the strand is cut into resin pellets. Further, the cooling water used here is preferably water filtered using a filter having an opening of 5 μm or less.

  The cut resin pellets are preferably dried using clean air having a cleanliness class of 10,000 or less that has passed through a HEPA (High-Efficiency Particulate Air) filter or the like. Furthermore, it is preferable to package in a clean room having a cleanliness class of 10,000 or less and avoid contact with outside air exceeding 10,000 classes.

The styrenic resin has 1 / g or less foreign matter having a particle diameter of 100 μm or more and 1000 / g or less foreign matter having a particle diameter of 10 μm or more, which is insoluble in methyl ethyl ketone. If the number of foreign matters having a particle diameter of 100 μm or more exceeds 1 / g or the number of foreign matters having a particle diameter of 10 μm or more exceeds 1000 / g, it is difficult to use for optical purposes. The reduction of foreign matter can be controlled by the opening of the filter, the degree of clean air, and the like.
In order to measure foreign matter, the resin was dissolved in methyl ethyl ketone that had been filtered through a 0.5 μm filter in advance, and this sample was passed through a liquid particle counter (HIAC, manufactured by ROYCO) using a light scattering / light blocking method using laser light. The number of foreign substances contained in the resin was measured.
The cleanness was measured using a light scattering type particle counter KC-03 (manufactured by Rion Co., Ltd.) according to JIS B 9920.

  The styrene resin preferably has a saturated water absorption rate of less than 1.5%, and more preferably less than 1%. When the saturated water absorption is 1% or more, the dimensional change and warpage increase, and it may be difficult to use for optical applications.

The styrene resin has a melt mass flow rate (MFR) measured at a temperature of 200 ° C. and a load of 49 N based on JIS K7210, preferably 1 g / 10 min or more, and more preferably 2 g / 10 min or more. If the MFR is less than 1 g / 10 minutes, the molding processability is inferior, and there are cases where problems such as a large molded product not being obtained or molding time taking.

  Additives such as antioxidants, weathering agents, lubricants, plasticizers, colorants, antistatic agents, mineral oils, flame retardants, etc. can be added to the styrenic resin at any stage during production. Can be blended.

  Styrenic resin with few foreign substances is processed into various molded articles by known methods such as injection molding, extrusion molding, compression molding, and vacuum molding. The processed optical resin molded body is used for optical applications such as a light guide plate, an optical disk, a screen lens, an antireflection film, a base film for an optical film such as a diffusion film, and the like.

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

Example 1
A devolatilizing tank in which a first reactor which is a fully mixed stirring tank having a capacity of about 20 L and a second reactor which is a tower-type plug flow reactor with a stirring capacity of about 40 L are connected in series, and a preheater is further attached. Two units were connected in series. 15 parts by mass of ethylbenzene, 0.01 parts by mass of t-butylperoxyisopropyl monocarbonate, 85 parts by mass of monomer solution composed of 52% by mass of styrene and 48% by mass of methyl methacrylate (hereinafter abbreviated as MMA), n -0.01 parts by mass of dodecyl mercaptan (hereinafter abbreviated as n-DDM) and 0.05 parts by mass of octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate were mixed to obtain a raw material solution. .
This raw material solution was filtered through a filter having an opening of 5 μm, and then fed to a first reactor controlled at 127 ° C. at 6.2 kg per hour. The conversion rate at the outlet of the first reactor was 34% by mass. The reaction solution exiting from the first reactor was introduced into a second reactor adjusted to have a gradient of 127 ° C. to 155 ° C. from the inlet toward the flow direction. The conversion rate at the outlet of the second reactor was 85% by mass. 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. Monomers and solvents were removed. This was extruded in the form of a strand from the die in a molten state, cooled with cooling water filtered using a filter having an opening of 5 μm, and then the strand was cut into resin pellets. The cut resin pellets were dried using clean air having a cleanliness class of 10,000 or less passed through a HEPA filter to obtain a styrene resin with few foreign matters. The obtained resin was tested in a clean room with a cleanliness class of 10,000 or less, and the obtained results are shown in Table 1.

Example 2
The resin obtained in Example 1 was carried out in the same manner as in Example 1 except that the test was performed after leaving the resin in a clean room with a cleanliness class of 10,000 or less for 1 day. The results are shown in Table 1.

Example 3
The same procedure as in Example 1 was performed except that the raw material solution was not filtered with a filter having an opening of 5 μm. The results are shown in Table 1.

Example 4
The same procedure as in Example 3 was performed except that the clean air passed through the HEPA filter was not used, and the air was dried using air having a cleanliness class exceeding 10,000. The results are shown in Table 1.

Example 5
The monomer solution was implemented in the same manner as in Example 1 except that MMA was not used and 100% by mass of styrene was used. The results are shown in Table 1.

Comparative Example 1
The resin obtained in Example 1 was carried out in the same manner as in Example 1 except that the resin was not placed in a clean room but left in the outside air exceeding the cleanliness class 10,000 for 1 day and then tested. The results are shown in Table 1.

Comparative Example 2
The same operation as in Example 4 was performed except that the cooling water was used without being filtered. The results are shown in Table 1.

Comparative Example 3
The monomer solution was carried out in the same manner as in Example 1 except that styrene was not used and the MMA was composed of 100% by mass. The results are shown in Table 1.

The evaluation was based on the following method.
(1) Measurement of foreign matter in the molded body Using the injection molding machine manufactured by Toshiba Machine Co., Ltd., the obtained resin pellets were molded at a molding temperature of 230 ° C, a mold temperature of 40 ° C, and a 210 mm long, 210 mm wide, 3 mm thick plate. Molded. Check the number of foreign matter contained in the compact by visual inspection using a distortion inspection machine, and measure the size of the foreign matter with an optical microscope with a magnification of 20 times. ) Was used to determine the number of foreign matters having a size of 0.01 mm ² or more. The number of molded product foreign bodies was less than 4 as acceptable.
(2) Measurement of saturated water absorption rate A plate having a thickness of 3 mm was cut into a length of 100 mm and a width of 50 mm to obtain a test piece. After measuring the weight of the test piece, it was immersed in pure water at 23 ° C. After saturating the water, the weight of the test piece was measured to determine the saturated water absorption. A saturated water absorption of less than 1.5% was considered acceptable.
(3) Measurement of warpage (4) Measurement of melt mass flow rate (MFR) 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.
(4) Measurement of melt mass flow rate (MFR) Based on JIS K7210, it measured using resin pellets at a temperature of 200 ° C. and a load of 49 N (unit: g / 10 minutes). The measuring machine used was a Toyo Seiki Seisakusho melt indexer (F-F01). MFR passed 1 g / 10 min or more.

Examples relating to the styrenic resin of the present invention and the optical resin molded body comprising the same have less foreign matter in the molded body and less water absorption.

Claims (4)

  It is a styrene resin obtained by polymerizing 5 to 100% by mass of a styrene monomer and 95 to 0% by mass of a (meth) acrylic acid ester monomer, and is insoluble in methyl ethyl ketone in the styrene resin. A styrenic resin having 1 / g or less foreign matter having a particle size of 100 μm or more and 1000 / g or less foreign matter having a particle size of 10 μm or more. The styrene resin according to claim 1, which is obtained by bulk continuous polymerization containing a solvent of less than 20 parts by mass with respect to a total of 100 parts by mass of the styrene monomer and the (meth) acrylic acid ester monomer. The styrenic resin according to claim 1 or 2 obtained by one or more methods selected from the following 1), 2) and 3).
1) After polymerization, after removing the residual monomer and solvent, extrude into a strand in a molten state from the die, and after cooling with cooling water or cutting the strand while cooling to use as a resin pellet The cooling water to be used is water filtered through a filter having an opening of 5 μm or less.
2) The cut resin pellets are dried using clean air having a cleanness class of 10,000 or less that has passed through a HEPA (High-Efficiency Particulate Air) filter.
3) Package the resin pellets in a clean room with a cleanliness class of 10,000 or less and avoid contact with outside air exceeding the class 10,000.   The optical resin molding which consists of a styrene-type resin in any one of Claims 1-3.