JPH0892385A - Method for producing styrene resin molded product - Google Patents

Abstract

(57) [Summary] [Object] To provide a method for producing a molded article having excellent chemical resistance, heat resistance and transparency without impairing the excellent characteristics of syndiotactic polystyrene and atactic polystyrene. [Structure] Production of a styrene resin molded product obtained by heating and melting a styrene resin composition composed of syndiotactic polystyrene and atactic polystyrene in a range of 270 to 370 ° C. and molding at a mold temperature of 100 ° C. or less. Method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a styrene resin molded product. More specifically, the present invention relates to a method for producing a styrene resin molded article having excellent chemical resistance, heat resistance and transparency.

[0002]

2. Description of the Related Art Conventionally, a styrene polymer produced by a radical polymerization method has a defect that it is an amorphous resin because of its atactic three-dimensional structure and is inferior in chemical resistance and heat resistance. In order to overcome this drawback, a styrene-based polymer having stereoregular syndiotacticity has been developed, and a composition in which other components have been added to the styrene-based polymer has been proposed (JP-A-62-104818). JP, 62-257948, A and 62-25795.
No. 0).

These styrene-based polymers or compositions thereof were excellent in heat resistance as compared with the styrene-based polymers having atactic structure or compositions thereof, but were not sufficient in chemical resistance. Moreover, the result is that the excellent transparency originally possessed by the styrene polymer having an atactic structure or the composition thereof is impaired.

[0004]

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a styrene polymer having an atactic structure or a composition thereof without impairing the excellent transparency. It is to develop a method for producing a styrene resin molded product having excellent chemical resistance and heat resistance.

[0005]

As a result of repeated research to solve this problem, the present inventor has found that a composition comprising a syndiotactic polystyrene and an atactic polystyrene is molded under a specific condition by a manufacturing method. It came to solving the problem. That is, the present invention comprises (A) 90 to 10% by weight of a styrene polymer having a high degree of syndiotactic stereoregularity, and (B) 10 to 90% by weight of a styrene polymer having an atactic stereostructure. The styrenic resin composition
The present invention relates to a method for producing a styrene-based resin molded article, which comprises heating and melting in the range of ° C and molding at a mold temperature of 100 ° C or less.

The styrene-based polymer (A) having a high degree of syndiotactic stereoregularity (hereinafter referred to as syndiotactic polystyrene) used in the present invention is
It has a steric structure in which phenyl groups or substituted phenyl groups are alternately located in opposite directions with respect to the main chain formed from carbon-carbon bonds, and its tacticity is determined by a nuclear magnetic resonance method ( ¹³ C -NMR method). ^The tacticity measured by the ¹³ C-NMR method can be indicated by the abundance ratio of a plurality of continuous constitutional units, for example, diad in the case of 2 units, triad in the case of 3 units, and pentad in the case of 5 units. .

The syndiotactic polystyrene referred to in the present invention means that the syndiotacticity of the racemic pentad is generally 50% or more, preferably 80% or more, more preferably 90% or more. Formula (I)

[0008]

[Chemical 1]

(In the formula, R represents a hydrogen atom, a halogen atom or a substituent containing at least one of carbon atom, oxygen atom, nitrogen atom, sulfur atom, phosphorus atom, selenium atom, silicon atom and tin atom. , M is an integer of 1 to 3. However, when m is a plurality, each R may be the same or different. It is a combined hydrogenated polymer.

Preferred aromatic vinyl compounds used herein are styrene, α-methylstyrene, methylstyrene, ethylstyrene, isopropylstyrene, tertiary butylstyrene, phenylstyrene, vinylstyrene, chlorostyrene, bromostyrene, fluoro. Styrene, chloromethylstyrene, methoxystyrene,
There are ethoxystyrene and the like, and these are used alone or in combination of two or more. Among these, more preferable aromatic vinyl compounds include styrene, p-methylstyrene,
These are m-methylstyrene, p-tertiarybutylstyrene, p-chlorostyrene, m-chlorostyrene and p-fluorostyrene.

The thermal properties of this syndiotactic polystyrene have a melting peak temperature (T _pm ) of 220 to 280 measured by differential scanning calorimetry (DSC) at a temperature change rate of 20 ° C./min according to JIS K7121.
C., the crystallization peak temperature (T _pc ) is in the range of 150 to 250 ° C., the enthalpy of fusion (ΔH _m ) and the enthalpy of crystallization (ΔH _m ) measured by a DSC according to JIS K7122 at a temperature change rate of 20 ° C./min. Each absolute value of ΔH _c ) is 15 J / g or more.

This syndiotactic polystyrene is not particularly limited in its molecular weight, but in general,
The weight average molecular weight is 10,000 or more, preferably 50,000 or more. Here, if the weight average molecular weight is less than 10,000, the thermal properties and mechanical properties of the obtained molded article are deteriorated, which is not preferable. Furthermore, the molecular weight distribution is not limited to a wide or narrow range, and various kinds can be applied.

In this syndiotactic polystyrene, the insoluble component in boiling methyl ethyl ketone, that is, the residue after Soxhlet extraction using methyl ethyl ketone as a solvent is usually 70% by weight or more, preferably 80% by weight.
As described above, the content is more preferably 90% by weight or more, and the syndiotacticity of the insoluble component is usually 50% or more, preferably 80% or more, more preferably 90% or more in racemic pentad. When the amount of the component (A) insoluble in boiling methyl ethyl ketone is less than 70% by weight, a molded article having good transparency can be obtained.
The balance between the chemical resistance and the heat resistance is practically no problem, but slightly deteriorated. Further, even if the insoluble component with respect to boiling methyl ethyl ketone is 70% by weight or more, if the insoluble component has a syndiotacticity of less than 50%, a molded article having a good transparency can be similarly obtained. The balance between the chemical resistance and the heat resistance is practically no problem, but slightly deteriorated.

Such syndiotactic polystyrene can be produced, for example, by referring to the technique disclosed in JP-A-63-268709.
That is, it can be produced by polymerizing a styrenic monomer in an inert hydrocarbon solvent or in the absence of a solvent, using a titanium compound and alumoxane, which is a condensation compound of water and a trialkylaluminum, as a catalyst. .

The styrene polymer (B) having an atactic three-dimensional structure (hereinafter referred to as atactic polystyrene) used in the present invention is a polymerization such as liquid polymerization, bulk polymerization, suspension polymerization and bulk-suspension polymerization. The following general formula (II) obtained by the method

[0016]

[Chemical 2]

(Wherein R represents a hydrogen atom, a halogen atom or a substituent containing at least one of a carbon atom, an oxygen atom, a nitrogen atom, a sulfur atom, a phosphorus atom, a selenium atom, a silicon atom and a tin atom. , M is an integer of 1 to 3, provided that when m is plural, each R may be the same or different.), The polymer comprising one or more aromatic vinyl compounds. Or a copolymer of at least one other vinyl monomer copolymerizable with at least one aromatic vinyl compound, a hydrogenated polymer of these polymers, and a mixture thereof.

Preferred aromatic vinyl compounds used herein are styrene, α-methylstyrene, methylstyrene, ethylstyrene, isopropylstyrene, tertiary butylstyrene, phenylstyrene, vinylstyrene, chlorostyrene, bromostyrene, fluoro. Styrene, chloromethylstyrene, methoxystyrene,
There are ethoxystyrene and the like, and these are used alone or in combination of two or more. Among these, more preferable aromatic vinyl compounds include styrene, p-methylstyrene,
These are m-methylstyrene, p-tertiarybutylstyrene, p-chlorostyrene, m-chlorostyrene and p-fluorostyrene.

Other copolymerizable vinyl monomers include:
Vinyl cyanide compounds such as acrylonitrile and methacrylonitrile, methyl acrylate, ethyl acrylate,
Propyl acrylate, butyl acrylate, amyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, dodecyl acrylate, octadecyl acrylate, phenyl acrylate, alkyl acrylates such as benzyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, Amyl methacrylate, hexyl methacrylate,
Octyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, phenyl methacrylate, alkyl methacrylates such as benzyl methacrylate, maleimide, N-methyl maleimide, N-ethyl maleimide, N-butyl maleimide, N
There are maleimide compounds such as -laurylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide and N- (p-bromophenyl) maleimide.

The molecular weight of this atactic polystyrene is not particularly limited, but the weight average molecular weight is generally 10,000 or more, preferably 50,000 or more. Here, if the weight average molecular weight is less than 10,000, the thermal properties and mechanical properties of the obtained molded article are deteriorated, which is not preferable. Furthermore, there is no limitation on the molecular weight distribution,
Various things can be applied.

In the present invention, the relationship between the weight molecular weights of the components (A) and (B) or the melt viscosities is such that the weight molecular weights are Mw _A and Mw _B , respectively, and the melt measured at 300 ° C. and a shear rate of 1000 sec ^−1. If the viscosity is η _{A and} η _B , 0.5 ≦ Mw _A / Mw _B ≦ 1.5 or 0.5
≦ η _A / η _B ≦ 5, preferably 0.7 ≦ Mw _A / Mw _B ≦
1.3 or 0.7 ≦ η _A / η _B ≦ 3, more preferably 0.85 ≦ Mw _A / Mw _B ≦ 1.15 or 0.85
It is desirable that the relationship of ≦ η _A / η _B ≦ 1.5 is satisfied. (A)
When the weight molecular weight ratio and the melt viscosity ratio of the component (B) deviate from this range, the balance of chemical resistance, heat resistance and transparency is practically no problem, but slightly deteriorates.

The styrenic polymer composition used in the present invention is based on the total weight of the components (A) and (B).
The component (A) content is 90 to 10% by weight, preferably 2
0 to 80% by weight, and the blending amount of component (B) is 10 to 9
It is 0% by weight, preferably 80 to 20% by weight. (A)
If the content of the components exceeds 90% by weight, it is no longer possible to obtain a molded article excellent in transparency, and if it is less than 10% by weight, a molded article excellent in chemical resistance and heat resistance cannot be obtained.

The styrene polymer composition used in the present invention can be obtained by melt-kneading the components (A) and (B). A known melt-kneading device such as a single-screw extruder or a twin-screw extruder can be used for the melt-kneading, but a vented twin-screw extruder is preferable. The melt-kneading temperature at the time of melt-kneading each component is usually set in the range of 270 to 370 ° C, preferably 280 to 330 ° C. If the melt-kneading temperature is lower than 270 ° C., the melting of the raw materials will be insufficient and a uniform composition cannot be obtained. When the melt-kneading temperature is higher than 370 ° C., decomposition of the raw material occurs, which is not preferable.

The composition of the present invention comprises (A) component and (B)
When the components are melt-kneaded, the chemical resistance of the final molded product, heat resistance, within the range of not impairing transparency, other components, heat stabilizers, antioxidants, weathering agents, nucleating agents, lubricants, antistatic agents,
A rubber-like polymer or the like can be added as an impact resistance modifier. The styrenic resin molded article obtained by the production method of the present invention contains the styrenic resin composition thus obtained in the range of 270 to 370 ° C., preferably 280 to 3 ° C.
It is obtained by heating and melting in the range of 30 ° C. and molding at a mold temperature of 100 ° C. or lower, preferably 90 ° C. or lower. When the heating and melting temperature is lower than 270 ° C., the composition is not sufficiently melted, so that a molded product having uniform physical properties cannot be obtained. When the heating and melting temperature is higher than 370 ° C., decomposition of the composition occurs, which is not preferable. Mold temperature is 100 ℃
Molding as described above makes it impossible to obtain a molded article having excellent transparency. The molding method may be appropriately selected according to the molded product to be manufactured, but various molding methods such as thermoforming method used in the conventional molding of atactic polystyrene, specifically, press molding. Techniques such as molding, blow molding, injection molding, extrusion molding, vacuum molding, injection molding, cast molding, uniaxial stretching, biaxial stretching and the like may be used, among which press molding, blow molding and injection molding are particularly preferable.

[0025]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded. Various physical properties used in Examples and Comparative Examples of the present invention were measured based on the following test methods. (1) Chemical resistance The appearance change of the test piece after being left in methyl ethyl ketone at 23 ° C. for 5 hours was visually judged according to the following criteria.

⊚: No change before and after the test ◯: A slight change can be seen before and after the test, but it can be used. ×: The change was drastic before and after the test, or it was completely dissolved,
Unavailable. (2) Heat resistance A test piece was cut into a size of 5 mm x 5 mm x 2 mm, and the softening temperature was measured according to JIS K7196. (3) Transparency The transparency of the test piece after molding was visually judged according to the following criteria.

◯: The test piece is transparent. Δ: The test piece is slightly opaque. X: The test piece is opaque. Further, (A) used in Examples and Comparative Examples of the present invention,
The following components were used as the components of (B). (A) syndiotactic polystyrene A-1: 1,2,4-trichlorobenzene as a solvent,
Weight average molecular weight measured by gel permeation chromatography at 130 ° C. is 310,000, weight average molecular weight / number average molecular weight is 2.6, boiling methyl ethyl ketone insoluble component is 96% by weight, ¹³ C-NMR analysis of insoluble component is racemic. 9 syndiotacticity in the pentad
7%, melt viscosity (300 ° C, shear rate 1200se
Syndiotactic polystyrene having a c- ¹ ) of 1120 poise.

A-2: 1,2,4-trichlorobenzene as a solvent, the weight average molecular weight measured by gel permeation chromatography at 130 ° C. is 520,000, the weight average molecular weight / number average molecular weight is 2.6, boiling Methyl ethyl ketone insoluble component 94% by weight, insoluble component ¹³ C-NM
Syndiotacticity in racemic pentad by R analysis is 97%, melt viscosity (300 ° C, shear rate 12
Syndiotactic polystyrene in which 00 sec ⁻¹ ) is 1570 poise. (B) Atactic polystyrene B-1: Chloroform as a solvent, the weight average molecular weight measured by gel permeation chromatography at 40 ° C. is 270,000, and the weight average molecular weight / number average molecular weight is 2.
2. Melt viscosity (300 ℃, shear rate 1200sec ^-1 )
Is 730 poise, and is a homopolystyrene polymerized by thermal polymerization.

B-2: Chloroform as a solvent, 40 ° C.
Weight average molecular weight measured by gel permeation chromatography at 360,000, weight average molecular weight / number average molecular weight 2.3, melt viscosity (300 ° C, shear rate 120
Homopolystyrene polymerized with 1,1-bis (t-butylperoxy) trimethylcyclohexane as an initiator, wherein ⁰ sec ⁻¹ ) is 850 poise.

[0030]

Example 1 Components (A) and (B) were mixed in the predetermined amounts shown in Table 1.
The ingredients were dry-blended and adjusted. This is a co-rotating twin-screw extruder with a vent (inner diameter 40 mm, L / D = 4
6) was used and melt-kneaded at a barrel setting temperature of 300 ° C. to prepare pellets. During the melt-kneading, 0.1 part by weight of (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite as an antioxidant and tetrakis [methylene-3- (3 ', 5'-the-
0.1-t-butyl-4′-hydroxyphenyl)] and 0.1% by weight of sodium methylenebis (2,4-di-t-butylphenol) acid phosphate as a nucleating agent.
5 parts by weight was added.

The pellets thus obtained were molded at a molding temperature of 300 ° C.
Injection molding at mold temperature 50 ℃, 100mm × 100mm
A test piece of × 2 mm was obtained.

[0032]

[Comparative Example 1] The same as Example 1 except that the mold temperature was 120 ° C.

[0033]

Example 2 Except that the composition is as shown in Table 1,
This is the same as in the first embodiment.

[0034]

[Comparative Example 2] The same as Example 2 except that the mold temperature was 120 ° C.

[0035]

[Example 3] The composition was as shown in Table 1, and the obtained pellets were press-molded at a melting temperature of 300 ° C and a mold temperature of 50 ° C to obtain a test piece of 100 mm x 100 mm x 2 mm. The same as 1.

[0036]

Comparative Example 3 The same as Example 3 except that the mold temperature is 120 ° C.

[0037]

Examples 4 to 7 The same as Example 1 except that the composition is shown in Table 1.

[0038]

Comparative Examples 4 to 7 The same as Comparative Example 2 except that the composition is shown in Table 1.

[0039]

Comparative Examples 8 to 9 The same as Example 1 except that the composition is shown in Table 1.

[0040]

[Table 1]

[0041]

As described above, according to the molded article and the molding method of the present invention, chemical resistance, heat resistance and transparency can be obtained without impairing the excellent properties of syndiotactic polystyrene and atactic polystyrene. A molded article having excellent properties can be obtained.

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Claims (1)

[Claims] 1. (A) 90 to 10% by weight of a styrene-based polymer having a high degree of syndiotactic stereoregularity,
And (B) a styrene-based resin composition containing 10 to 90% by weight of a styrene-based polymer having an atactic three-dimensional structure, heated and melted in the range of 270 to 370 ° C.
A method for producing a styrene resin molded article, which comprises molding at a mold temperature of ℃ or less.