JP2003171517A - Thermoplastic resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoplastic resin composition which excels in balance of properties of impact strength and transparency, and furthermore reduces staining of a sheet on sheet processing. <P>SOLUTION: The thermoplastic resin composition comprises (X) a copolymer composed of a styrenic monomer unit and a (meth)acrylate-based monomer unit and (Y) a rubber-like substance, and the copolymer (X) forms a continuous phase and the rubber-like substance (Y) forms a dispersion phase in the form of particles, and the dispersion particles are composed of dispersion particles (I) having a number average particle diameter of 1.0-2.0 μm and dispersion particles (II) having a number average particle diameter of 0.1-0.5 μm, and the amount of the rubber component present in the dispersion particles (I) is 0.2-3.5 mass% and the amount of the rubber component present in the dispersion particles (II) is 4-20 mass% and, simultaneously, the thermoplastic resin composition is constituted by comprising 0.05-2 pts.mass phenolic processing stabilizer based on 100 pts.mass thermoplastic resin composition having a ratio of the weight average molecular weight of the thermoplastic resin composition to its number average molecular weight of ≤2.5. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic resin composition which is excellent in impact strength and transparency and has little sheet contamination during sheet processing.

[0002]

2. Description of the Related Art Conventionally, by mixing a copolymer obtained by grafting styrene, methyl methacrylate and alkyl acrylate onto rubber particles having an average particle diameter of 0.1 to 0.5 μm and a copolymer of methyl methacrylate and styrene, It is known that a thermoplastic resin excellent in impact resistance and transparency can be obtained (Japanese Patent Publication No. 63-47745). However, when it is attempted to use these thermoplastic resins for optical applications such as lenses, both impact strength and transparency are not satisfied at the same time. Furthermore, a rubber-modified styrene resin composition is known in which a copolymer of a styrene monomer and a (meth) acrylic acid ester monomer is used as a continuous phase and rubber particles having bimodal properties are used as a dispersed phase. (Japanese Patent Laid-Open No. 8-269142). However, when these resin compositions are used for optical applications such as lenses,
Although the impact strength was sufficient, the haze was high and the transparency was not always satisfactory. Further, when these resin compositions are processed into a sheet by an extruder, the resin attached to the inside of the cylinder of the extruder or the die (discharge port) receives a heat history, and the sheet discolors or the surface of the sheet is contaminated. There was a problem that reduced the value. Further, in order to solve this problem, it is necessary to appropriately clean the inside of the cylinder and the die, which has a drawback that productivity is remarkably reduced and economical efficiency is poor.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a styrene- (meth) acrylic acid ester-based copolymer in which both impact strength and transparency are well balanced and the sheet is less contaminated during sheet processing. It is intended to provide a thermoplastic resin composition containing:

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a copolymer consisting of a styrene monomer unit and a (meth) acrylic acid ester monomer unit is used. A thermoplastic resin composition containing a rubber-like substance, wherein the rubber-like substance forms a particulate dispersed phase in the continuous phase of the copolymer, and the particulate dispersed phase has two types This problem is a thermoplastic resin composition containing a specific amount of a rubber component, a specific amount of a rubber component, the ratio of the weight average molecular weight and the number average molecular weight of the specified thermoplastic resin and a phenolic processing stabilizer The inventors have found that it is suitable and have completed the present invention.

That is, the present invention relates to (1) a copolymer (X) comprising a styrene-based monomer unit and a (meth) acrylic acid ester-based monomer unit, a rubber-like substance (Y), and a phenol-based processing stability. A thermoplastic resin composition containing an agent, wherein the copolymer (X) forms a continuous phase and the rubber-like substance (Y) forms a particulate dispersed phase, and the dispersed particles are number average particles. Dispersed particles (I) having a diameter of 1.0 to 2.0 μm, and dispersed particles (II) having a number average particle diameter of 0.1 to 0.5 μm.
And the amount of the rubber component contained in the dispersed particles (I) is 0.
2 to 3.5% by mass, the amount of the rubber component contained in the dispersed particles (II) is 4 to 20% by mass, and the ratio of the weight average molecular weight to the number average molecular weight is 2.5 or less. The thermoplastic resin composition containing 0.05 to 2 parts by mass of the phenol-based processing stabilizer, and (2) the phenol-based processing stabilizer are 2- [1- (2-hydroxy-
3,5-Di-t-pentylphenyl) ethyl] -4,6
-Di-t-pentylphenyl acrylate and / or
The thermoplastic resin composition according to (1), which is octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
Examples of the styrene-based monomer used in the present invention include styrene, α-methylstyrene, p-methylstyrene, pt
-Butylstyrene and the like can be mentioned, but styrene is preferable. These may be used alone or in combination of two or more.

Examples of the (meth) acrylic acid ester-based monomer used in the present invention include methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-methylhexyl acrylate, 2-ethylhexyl acrylate and octyl. Acrylate etc. are mentioned. These may be used alone or in combination of two or more. Preferably, methyl methacrylate, ethyl acrylate, n-
Butyl acrylate or mixtures thereof.

If desired, other copolymerizable monomers such as acrylonitrile may be used.

As the rubber-like substance forming the dispersed phase, polybutadiene, styrene-butadiene random copolymer, styrene-butadiene block copolymer and the like can be used. A styrene-butadiene random copolymer and a styrene-butadiene block copolymer can be preferably used in the sense that the refractive index is easily matched with that of the continuous phase copolymer. These may be used alone or in combination of two or more.

The dispersed particles contained in the thermoplastic resin composition of the present invention include dispersed particles (I) having a number average particle diameter of 1.0 to 2.0 μm and number average particle diameters of 0.1 to 0. 5 μm
And dispersed particles (II)

The number average particle diameter of the dispersed particles (I) is 1.0 to
It is 2.0 μm. It is preferably 1.2 to 1.8 μm. If it is less than 1.0 μm, the impact strength is lowered. 2.0
When it exceeds μm, the transparency decreases.

The number average particle diameter of the dispersed particles (II) is 0.1.
Is 0.5 μm. Preferably 0.15-0.45μ
m. If it is less than 0.1 μm, the impact strength is lowered.
If it exceeds 0.5 μm, the transparency decreases.

The amount of the rubber component contained in the dispersed particles (I) in the thermoplastic resin composition of the present invention is 0.2 to 3.5% by mass. It is preferably 0.3 to 3 mass%. 0.2
If it is less than mass%, the impact strength will decrease. If it exceeds 3.5% by mass, the transparency will decrease.

The amount of the rubber component contained in the dispersed particles (II) in the thermoplastic resin composition of the present invention is 4 to 20% by mass. It is preferably 6 to 18% by mass. If it is less than 4% by mass, the impact strength will decrease. If it exceeds 18% by mass, the transparency will decrease.

The number average particle diameter is a value measured by a Coulter counter. The rubber component amount indicates the amount of polybutadiene measured by the halogen addition method.

The ratio (Mw / M) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the thermoplastic resin composition of the present invention.
n) needs to be 2.5 or less. If it exceeds 2.5, the impact strength is lowered and the balance between impact strength and transparency is lost. Both the weight average molecular weight and the number average molecular weight are measured as polystyrene conversion values by the gel permeation chromatography (GPC) method.

The phenolic processing stabilizer used in the present invention is triethylene glycol-bis [3- (3
-T-butyl-5-methyl-4-hydroxyphenyl)
Propionate], 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2- [1- (2-hydroxy-3,5-di-t] -Pentylphenyl) ethyl] -4,
6-di-t-pentylphenyl acrylate, octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl) -4-Hydroxyphenyl) propionate], 2-t-butyl-6-
Examples thereof include (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, and particularly 2- [1- (2-hydroxy-3,5-di-
t-pentylphenyl) ethyl] -4,6-di-t-pentylphenyl acrylate, octadecyl-3-
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate can be preferably used. These may be used alone or in combination of two or more.

The amount of the phenolic processing stabilizer used in the present invention is 0.05 to 2 parts by mass with respect to 100 parts by mass of the thermoplastic resin. Preferably 0.1-1.5
Parts by mass. If the amount is less than 0.05 parts by mass, the sheet is likely to be discolored or the surface of the sheet is easily contaminated during processing. If it exceeds 2 parts by mass, the transparency of the thermoplastic resin composition will decrease.

The method for producing the thermoplastic resin composition of the present invention is not particularly limited, but the styrene monomer unit and the (meth)
A copolymer composed of an acrylic acid ester-based monomer unit that does not contain dispersed particles [hereinafter referred to as a copolymer (A)], a styrene-based monomer unit and a (meth) acrylic acid ester-based monomer A copolymer composed of units and containing dispersed particles (I) having a number average particle diameter of 1.0 to 2.0 μm [hereinafter referred to as a copolymer (B)], a styrene-based monomer unit, and Copolymer consisting of (meth) acrylic acid ester-based monomer units having a number average particle diameter of 0.1 to 0.5 μm
A method of separately producing m-dispersed particles (II) [hereinafter referred to as a copolymer (C)] and mixing them to obtain a thermoplastic resin is advantageous in that dispersed particles are easily uniformly distributed. Is a preferable manufacturing method.

The method of blending the phenolic processing stabilizer is not particularly limited, and the copolymer (A), the copolymer (B),
Examples thereof include a method of blending the copolymer (C) before, during, and after the polymerization, a method of blending the copolymer (A), the copolymer (B), and the copolymer (C) at the time of mixing. .

Each of the continuous phases of the copolymer (A), the copolymer (B) and the copolymer (C), the rubber-like substance forming the dispersed particles (I), and the rubber-like substance forming the dispersed particles (II). It is preferable that the respective refractive indices of the substances are close to each other, and the difference between the respective refractive indices is preferably within 0.02 from the viewpoint of transparency.

The method for producing the copolymer (A), the copolymer (B), and the copolymer (C) is not particularly limited, but the copolymer (A) can be produced by the bulk polymerization method or suspension weight method. Suitable methods are a solid-state method and a solution polymerization method, a bulk polymerization method, a bulk-suspension polymerization method, and a solution polymerization method are suitably used for producing the copolymer (B), and an emulsion polymerization method is suitably used for producing the copolymer (C). it can.

The method of mixing the copolymer (A), the copolymer (B), the copolymer (C), and the phenol-based processing stabilizer is not particularly limited, and examples thereof include a Henschel mixer and a tumbler mixer. After premixing with a known mixing device, melt mixing is performed using an extruder such as a single-screw extruder or a twin-screw extruder, whereby uniform mixing can be achieved.

Additives can be added to the thermoplastic resin composition of the present invention as needed. For example, a plasticizer, a lubricant, silicone oil, or the like can be added to improve fluidity and releasability. In addition, an antistatic agent can be blended to prevent dust in the molded product. Further, glass beads can be added in order to impart light diffusing property. Further, in order to impart light resistance, a light stabilizer or an ultraviolet absorber can be blended, but if an ultraviolet curing agent is applied to the surface of a molded article to cure it with ultraviolet light, it will affect the curing, so be careful. is necessary. In addition, a colorant or the like can be added.

[0025]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. All parts and% in the examples are expressed on a mass basis.

Production of Copolymer (A) 42.5 parts of styrene and 57.5 parts of methyl methacrylate (MMA) were placed in an autoclave equipped with a stirrer, 0.2 part of benzoyl peroxide as a polymerization initiator, and t- as a molecular weight modifier. 0.1 parts of dodecyl mercaptan, sodium dodecylbenzenesulfonate as a suspension stabilizer 0.
001 parts and 0.5 parts of tricalcium phosphate, pure water 20
0 parts were charged, the temperature was 95 ° C for 6 hours, and the temperature was 13
Polymerization was carried out at 0 ° C for 2 hours. After completion of the reaction, washing, dehydration and drying were performed to obtain a bead-shaped copolymer (A1). The polystyrene reduced weight average molecular weight of the copolymer (A1) measured by the GPC method was 145,000. The composition was styrene / MMA = 43.0 / 57.0.

A copolymer (A2) was obtained by carrying out the polymerization in the same manner except that the copolymer (A1) was prepared and the molecular weight modifier was not used. The weight average molecular weight of the copolymer (A2) was 167,000.

Production of Copolymer (B) 42.5 parts of styrene and 57.5 parts of methyl methacrylate, styrene-butadiene copolymer rubber (styrene content 25%, "Tafden 2000" manufactured by Asahi Kasei Co., Ltd. (product Name)) 5 parts were charged, and after stirring at room temperature for 3 hours, 0.04 part of benzoyl peroxide as a polymerization initiator and 0.2 part of t-dodecyl mercaptan as a molecular weight modifier were added, and the mixture was stirred at 200 rpm. Meanwhile, bulk polymerization was performed at a temperature of 90 ° C. until the polymerization conversion rate was 30%. Then, 0.2 part of dicumyl peroxide as a polymerization initiator, 0.001 part of sodium dodecylbenzenesulfonate as a suspension stabilizer, 0.5 part of tribasic calcium phosphate, and 200 parts of pure water were added, and the mixture was added at a temperature of 100 ° C. for 2 minutes. Polymerization was performed at 115 ° C. for 1.5 hours and at 130 ° C. for 2.5 hours. After completion of the reaction, washing, dehydration and drying were performed to obtain a bead-shaped copolymer (B1). The rubber component amount of the copolymer (B1) was 3.7%. The rubber-like substance forms a particulate dispersed phase, and the dispersed particles have a number average particle diameter of 1.4.
was μm. The weight average molecular weight is 129000.
Met.

In the same manner as in the production of the copolymer (B1), by changing only the stirring number during bulk polymerization,
A copolymer (B2) having dispersed particles having a number average particle diameter of 0.8 μm and a copolymer (B3) having dispersed particles having a number average particle diameter of 2.5 μm were obtained.

Polymerization was carried out by the same method except that the copolymer (B1) was prepared and 0.3 part of t-dodecyl mercaptan was added as a molecular weight modifier to obtain a copolymer (B4). The weight average molecular weight of the copolymer (B4) is 103,0.
It was 00. The number average particle diameter of the dispersed particles was 1.4 μm.

Production of Copolymer (C) In an autoclave equipped with a stirrer, 49 parts of butadiene, 16 parts of styrene, 150 parts of pure water, 0.5 part of potassium oleate.
Part, t-butyl hydroperoxide 0.13 part, Rongalit 0.03 part, ferrous sulfate 0.002 part, ethylenediaminetetraacetic acid sodium salt 0.003 part, sodium pyrophosphate 0.1 part, t-dodecyl mercaptan 1.0 part was charged and the polymerization was carried out at a temperature of 45 ° C. for 17 hours. The number average particle size of the obtained styrene-butadiene rubber latex was 0.08 μm. The latex was stabilized by adding 0.005 parts of sodium sulfosuccinate. An aqueous solution of hydrogen chloride was added to this latex under stirring to cause the latex particles to coagulate and enlarge, and a rubber latex having a number average particle diameter of 0.2 μm was obtained. 16 parts of styrene, 17 parts of MMA,
2 parts of n-butyl acrylate, 0.0 of divinylbenzene
4 parts and 0.08 part of t-butyl hydroperoxide were added, and polymerization was carried out at a temperature of 60 ° C. for 6 hours. After adding 0.5 part of t-butylphenol and 0.5 part of dilauryl thiopropionate to this latex, the copolymer is precipitated with hydrochloric acid, neutralized, washed and dehydrated and dried to obtain a powdery copolymer. (C1) was obtained. The amount of rubber component of this copolymer (C1) was 48.0%.

In the same manner as in the production of the copolymer (C1), by changing only the aggregation conditions of the rubber latex, the copolymer (C2) and 0 having dispersed particles having a number average particle diameter of 0.08 μm are obtained. A copolymer (C3) having dispersed particles of 0.6 μm was obtained.

Examples 1 to 9 and Comparative Examples 1 to 11 Copolymers (A), (B), (C), and a phenolic processing stabilizer were mixed at the compounding ratios shown in Table 1 and Table 2, 40
With a single-screw extruder having a diameter of mm, the mixture was kneaded at a temperature of 240 ° C. and a screw rotation speed of 100 rpm to be pelletized to obtain pellets. The GPC of the composition was measured using this pellet. Further, 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, the pellets were heated in a single screw extruder having a diameter of 40 mm at a temperature of 240 ° C. and a screw rotation speed of 10
Sheet processing with a thickness of 1 mm is continuously performed at 0 rpm,
The time when the sheet stain started was measured. The results are shown in Tables 1 and 2. The phenolic processing stabilizer is
(A) 2- [1- (2-hydroxy-3,5-di-t-
Pentylphenyl) ethyl] -4,6-di-t-pentylphenyl acrylate, (b) octadecyl-3-
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate was used.

[0034]

[Table 1]

[0035]

[Table 2]

The measuring method of each physical property value is as follows. (1) Haze: Using a test piece having a thickness of 2 mm, ASTM D
It was measured according to -1003. (2) Charpy impact strength: Measured according to ISO179-2 using a notched test piece having a thickness of 4 mm.

The contamination start time during sheet processing in Tables 1 and 2 refers to the time when sheet contamination begins during sheet processing. For example, the contamination start time during sheet processing in Example 1 in Table 1 is 8 hours, which means that it is 8 after the sheet processing is started.
It means that the contamination of the sheet starts after a lapse of time. Contamination of the sheet, when the resin composition is processed into a sheet by an extruder as described above, the resin attached to the inside of the cylinder of the extruder or the die (discharge port) receives a heat history, and the sheet is discolored, It means polluting the surface of the sheet and reducing the commercial value of the sheet.

Industrial Applicability According to the present invention, a thermoplastic resin composition having an unprecedented balance of impact strength and transparency, which is excellent in physical properties, and having little sheet contamination during sheet processing can be provided extremely advantageously industrially. . Since the thermoplastic resin composition of the present invention is excellent in impact strength and transparency, it can be suitably used for optical applications such as Fresnel lenses and lenticular lenses.

Continued front page    F-term (reference) 4J002 AC032 AC082 BC071 BG041                       BG051 BP012 EJ036 EJ066                       FD036

Claims (2)

[Claims] 1. A thermoplastic resin composition comprising a copolymer (X) comprising a styrene monomer unit and a (meth) acrylic acid ester monomer unit and a rubber-like substance (Y). The copolymer (X) is a continuous phase, and the rubber-like substance (Y)
Form a particulate dispersed phase, and the particulate dispersed phase [hereinafter referred to as dispersed particles] has a number average particle diameter of 1.0 to
Dispersed particles (I) having a size of 2.0 μm and dispersed particles (II) having a number average particle size of 0.1 to 0.5 μm,
The amount of the rubber component contained in the dispersed particles (I) is 0.2 to 3.5.
% By mass, the amount of rubber component contained in the dispersed particles (II) is 4 to
Phenol-based processing stabilizer 0.05 to 50 parts by mass with respect to 100 parts by mass of the thermoplastic resin having a ratio of the weight average molecular weight to the number average molecular weight of the thermoplastic resin composition of 2.5% or less. A thermoplastic resin composition containing 2 parts by mass. 2. The phenolic processing stabilizer is 2- [1-
(2-Hydroxy-3,5-di-t-pentylphenyl) ethyl] -4,6-di-t-pentylphenyl acrylate and / or octadecyl-3- (3,5-di-t-butyl-4) -Hydroxyphenyl) propionate, The thermoplastic resin composition according to claim 1.