JPH04227649A - Rubber-modified heat-resistant styrenic resin composition excellent in appearance and impact properties - Google Patents

Abstract

PURPOSE:To obtain the title composition which is improved in the balance among appearance, impact strength and heat resistance by mixing a styrene-alpha- methylstyrene copolymer optionally containing polystyrene as a continuous phase with specified rubber-like elastomer particles as a dispersed phase. CONSTITUTION:The title composition is prepared by polymerizing styrene and alpha-methylstyrene in the presence of 3 to 15wt.% rubber-like elastomer particles to obtain a continuous phase comprising a styrene-alpha-methylstyrene copolymer containing 10 to 40wt.% alpha-methylstyrene and optionally containing polystyrene, and incorporating therein the rubber-like elastomer having such a continuous particle diameter distribution that 25 to 70wt.% of the particles have a particle diameter of less than 7500Angstrom , 25wt.% or more of the particles have a particle diameter of 7500 to 21,500Angstrom and 18wt.% or less of the particles have a particle diameter of 21,500Angstrom or above as a dispersed phase.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber-modified heat-resistant styrenic resin composition having excellent appearance and impact resistance.

0002

BACKGROUND OF THE INVENTION Conventionally, rubber-modified styrene resins have been used in household electrical appliances, audio equipment, automobile parts, and the like. Recently, there has been a demand for heat resistance and appearance characteristics to be imparted to rubber-modified styrenic resins for these uses. Although the balance between appearance characteristics and impact strength of conventional rubber-modified styrenic resins has been improved by controlling the average particle diameter of the rubber-like elastomer, this has not yet fully satisfied market demands. In addition, the heat resistance is 83% at the heating deformation temperature even if unreacted monomers, oligomers, etc. are removed as much as possible.
~84°C is the limit, and the market requirement of 87~90°C cannot be achieved.

0003

[Problems to be Solved by the Invention] The present invention provides a rubber-modified heat-resistant styrenic resin composition that incorporates α-methylstyrene and improves the balance of appearance characteristics, impact strength, and heat resistance to the level required in the market. The purpose is to

0004

[Means for Solving the Problems] In order to achieve this object, the present inventors have developed a rubber-modified heat-resistant styrenic resin composition into which α-methylstyrene has been introduced, in which the particle size of dispersed particles made of a rubber-like elastic body is It has been found that if the distribution is studied in detail and the particle size distribution is appropriately adjusted, an excellent rubber-modified heat-resistant styrenic resin composition with an improved balance between the above-mentioned appearance characteristics and impact strength can be obtained.

That is, in a rubber-modified heat-resistant styrenic resin composition containing a rubber-like elastomer as dispersed particles, a styrene-α-methylstyrene copolymer or a mixture of this and polystyrene is used, and the α-methylstyrene content is 10 to 40% by weight of a polymer or polymer mixture as a continuous phase, 25% or more but less than 70% of particles having a particle size of less than 7500 Å, and a particle size of 7500 Å or more and 2150 Å or more
25% or more of the particles are less than 0 Å, and the particle size is 21
A rubber-modified heat-resistant styrenic resin with excellent appearance and impact resistance, characterized in that the dispersed phase is composed of dispersed particles of a rubber-like elastic material having a continuous particle size distribution, in which 18% or less of dispersed particles are 500 Å or more. It is a composition.

[0006] In the present invention, if the content of α-methylstyrene is less than 10% by weight, heat resistance decreases. or,
When it exceeds 40% by weight, productivity decreases and the molecular weight does not increase, and impact strength does not improve even if the method of the present invention is used. If the proportion of dispersed particles having a particle diameter of less than 7500 Å exceeds 70%, the impact strength will decrease, and if it is less than 25%, the appearance characteristics will decrease. In addition, if the particle size is 7500 Å or more2
If the proportion of dispersed particles less than 1500 Å is less than 25%, the impact strength decreases. If the proportion of dispersed particles with a particle diameter of 21,500 Å or more exceeds 18%, the appearance characteristics will deteriorate.

[0007] The particle diameter of the dispersed particles in the present invention refers to the diameter of the dispersed particles of about 800 mm in a transmission electron micrograph taken at a magnification of 10,000 using an ultra-thin section method of the resin.
It was determined by measuring the number of ~2000 particles. At the time of measurement, the particles are classified as shown in Table 1, and the proportion of dispersed particles having a particle size within a certain range is determined by the following formula. Percentage of dispersed particles (%) = 100 NiDi/
ΣNiDiNi is the number of dispersed particles having the particle diameter Di.

Furthermore, since the dispersed particles seen in the electron micrograph are not perfectly circular, the particle diameter can be calculated using the following equation using the measured values of the actual lengths of the longest axis (a) and the shortest axis (b) of the particle. Calculated by Particle size=(a+b)/2 The rubber-modified heat-resistant styrenic resin of the present invention consists of a rubber-like elastic body constituting a dispersed phase and a continuous phase. The continuous phase is a copolymer of styrene and α-methylstyrene or a mixture of a styrene homopolymer and a styrene-α-methylstyrene copolymer.

The rubber-like elastic material used in the present invention may be any material as long as it exhibits rubber-like properties at room temperature, such as polybutadienes, styrene-butadiene copolymers, blocked styrene-butadiene copolymers, and ethylene. - One or more types of propylene copolymers, ethylene-propylene-nonconjugated diene terpolymers, isoprene polymers, styrene-isoprene copolymers, silicone rubbers, etc. are used. Further, the molecular weight and degree of branching of the rubber-like elastic body are not limited.

[0010] The amount of rubbery elastic material in the rubber-modified styrenic resin composition of the present invention is not particularly limited;
Preferably it is 15% by weight. In the present invention, stearic acid metal salts such as zinc, calcium, and magnesium, and ethylene bisstearamide may be added as additives. The rubber-modified heat-resistant styrenic resin composition of the present invention is produced by known methods such as bulk polymerization, bulk-suspension polymerization, solution polymerization, and emulsion polymerization.

The content of α-methylstyrene can be adjusted by controlling the amount charged during polymerization and the polymerization rate. Also, α
- It can be adjusted by mixing two or more rubber-modified heat-resistant styrene resins or styrene resins with different methylstyrene contents. The particle size of the dispersed particles made of rubbery elastic material can be determined using known methods such as stirring intensity, molecular weight of the produced styrenic polymer, amount of molecular weight modifier, amount of solvent, molecular weight of the rubbery polymer used, and polymerization initiator. It is adjusted by changing the type, amount, etc. It can also be adjusted by mixing two or more types of rubber-modified styrenic resins whose dispersed particles have different particle sizes.

The rubber-modified heat-resistant styrenic resin composition of the present invention contains hindered phenols, hindered bisphenols, hindered trisphenols, etc. as antioxidants, such as 2,6-di-t-butyl-4 -methylphenol, stearyl-β-(3,5-di-t-butyl-
4-hydroxyphenyl) propionate, triethylene glycol-bis-3-(3-t-butyl-4-hydroxy-5-methylphenyl) propionate, etc.; phosphorus compounds such as tri(2,4-di-t-butylphenyl) ) Phosphite, 4,4-butylidene-bis-(3
-methyl-6-t-butylphenyl-di-tridecyl)
Phosphite, etc. can be added.

Furthermore, the rubber-modified heat-resistant styrenic resin composition of the present invention may be used in combination with other polymers.

[0014]

[Examples] The present invention will be specifically explained below with reference to Examples. In addition, unless otherwise specified, "parts" in the examples represent parts by weight.

[0015]

[Example 1] Polybutadiene rubber-like elastic material (NF-3
5) Part 12
Len
79.2 parts α-methylstyrene
8.8 parts Organic peroxide (A)
Prepare 4 kg of 0.10 part mixture, 1
Polymerization was carried out at 00°C for 5 hours. The solid content concentration was 32%. (Polymerization solution-1) Then styrene

60 parts α-methylstyrene

40 parts Organic peroxide (A)
0.
10 parts Perbutyl IF (manufactured by NOF)
0.03 part mixture 4
kg was added to polymerization solution-1, and polymerization was carried out at 130°C for 5 hours. The solid content concentration was 65%. The polymerization solution was placed in a dryer, and unreacted monomers were removed under conditions of 200° C. and 5 mmHg for 30 minutes to obtain Polymer-A.

[0016] Here, what is organic peroxide (A)?

001
7]

[Chemical formula 1]

It has the structural formula: molecular weight 2380, temperature showing a 10-hour half-life of 64.4°C, and active oxygen content 95.2.
g/1 mole of organic peroxide. Polymer-A was pelletized using an extruder. Table 3 shows the properties, physical property values, etc.

[0019]

[Example 2] Add styrene to 4 kg of polymerization solution 1 of Example 1.
50 copies
α-methylstyrene
50 copies
Organic peroxide (A)
0.10 parts
Perbutyl IF (manufactured by NOF)
4 kg of a 0.03 part mixture was added, and polymerization was carried out under the same conditions as in Example 1. The solid content concentration was 63%. Polymer-B was obtained by carrying out the same treatment as in Example 1. Pelletization was performed in the same manner as in Example 1. Table 3 shows the properties.
Indicates physical property values, etc.

[0020]

[Example 3] Polymerization was carried out under the same conditions and operations as in Example 1, except that the stirring rotation speed was different, to obtain a polymerization solution-1. To this polymerization solution-1, 0.1 part of organic peroxide (A) and 0.03 part of Perbutyl IF (manufactured by Nippon Jushi) dissolved in a small amount of styrene were added, and polymerization was carried out at 130°C for 4 hours. . The solid content concentration was 66%. The same treatment as in Example 1 was carried out to obtain Polymer-D. Polymers-E and F were obtained under the same conditions and operations except for changing the stirring rotation speed. Table 2 shows the properties.
Shown below.

Next, styrene was added to a similar device.

55 parts α-methylstyrene

45 parts Organic peroxide (A)

Add 4 kg of 0.2 part mixture and heat at 80℃ for 2 hours at 100℃.
Polymerization was carried out at 125° C. for 3 hours and 5 hours at 125° C., and the same treatment as in Example 1 was performed to obtain Polymer-G. Polymer-
The properties of D, E, and F are shown in Table 2.

25 parts of Polymer-D, 20 parts of Polymer-E, 5 parts of Polymer-F, and 50 parts of Polymer-G were pelletized in the same manner as in the Example. Table 3 shows the properties, physical property values, etc.

[0023]

[Comparative Examples 1 and 2] Pelletization was carried out in the same manner as in Example 1 except that the stirring rotation speed was different. Table 4 shows the properties, physical property values, etc.

[0024]

[Comparative Example 3] 4 kg of polymerization solution-1 Organic peroxide (A)
0.10 parts
Perbutyl IF (manufactured by NOF)
0.03 parts
Chilean
100 parts mixture 4k
g was added thereto, and polymerization was carried out at 130°C for 4 hours. Solid concentration is 6
It was 5%. The same operation as in Example 1 was performed to pelletize. Table 4 shows the properties, physical property values, etc.

[0025]

[Comparative Example 4] 50 parts of Polymer-E and 50 parts of Polymer-G were pelletized in the same manner as in Example 1. Table 4 shows the properties, physical property values, etc.

[0026]

[Comparative Example 5] 40 parts of Polymer-D, 10 parts of Polymer-E, and 50 parts of Polymer-G were pelletized in the same manner as in Example 1. Table 5 shows the properties, physical property values, etc.

[0027]

[Comparative Example 6] 25 parts of Polymer-D, 25 parts of Polymer-F, and 50 parts of Polymer-G were pelletized in the same manner as in Example 1. Table 5 shows the properties, physical property values, etc. (Note-1) The α-methylstyrene content in the rubber-modified heat-resistant styrene resin composition is determined by measuring the α-methylstyrene in the unreacted monomer at the end of polymerization using gas chromatography, and calculating the α-methylstyrene content from the charging composition. Find it by converting it.

(Note 2) The solid content concentration is determined by converting the weight of the polymerization solution after removing unreacted monomers under conditions of 200° C. and 5 mmHg. (Note-3) Heating deformation temperature: In accordance with ASTM D648 Izod impact strength: In accordance with ASTM D256 Gloss: A dumbbell test piece was molded at a molding temperature of 220°C and a mold temperature of 50°C. JIS
Measured according to Z8741

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

[Table 4]

[0033]

[Table 5]

[0034]

[Effect of the invention] As can be seen from the examples and comparative examples,
By meeting all the constituent requirements of the present invention, a rubber-modified heat-resistant styrenic resin composition having excellent heat resistance, appearance characteristics, and impact strength can be obtained.

Claims (1)

[Claims] Claim 1: A polymer or a polymer mixture, which is a styrene-α-methylstyrene copolymer or a mixture of this and polystyrene and has an α-methylstyrene content of 10 to 40% by weight, is used as a continuous phase. and the particle size is 7500 Å
25% or more and less than 70% of particles with a particle diameter of 7500
A rubber characterized by having, as a dispersed phase, dispersed particles of a rubber-like elastic body having a continuous particle size distribution, in which 25% or more of particles have a diameter of Å or more and less than 21,500 Å, and 18% or less of particles have a particle size of 21,500 Å or more. Modified heat-resistant styrene resin composition.