JPH03199252A - Styrene-based resin composition - Google Patents

Abstract

PURPOSE:To obtain a styrene-based resin composition, excellent in injection moldability and impact strength and suitable as molded products of a complicated shape such as parts of electrical apparatus, etc., by blending a styrene- based polymer regulated to a specific molecular weight and distribution thereof with a specified amount of a higher fatty acid. CONSTITUTION:A styrene-based resin composition obtained by blending (A) 100 pts.wt. styrene-based polymer, prepared by polymerizing a styrene-based monomer alone or further a mixture thereof with a vinyl monomer copolymerizable therewith using one or more polyfunctional organic peroxides (e.g. di-tert-butyl peroxyhexahydroterepthalate) and having 200000-450000 weight- average molecular weight, 2.0-3.0 ratio (Mw/Mn) and <=1.0wt.% oligomer content with (B) 0.01-0.5 pt.wt., preferably 0.02-0.3 pt.wt. higher fatty acid (e.g. behenic acid or erucic acid).

Description

Detailed Description of the Invention [Industrial Application Field] The present invention uses styrenic resin M1 as a polymerization initiator, more specifically, a specific organic peroxide, and adjusts it to a specific molecular weight and molecular weight distribution. This invention relates to a styrenic resin composition that has excellent injection molding and 1i impact strength, in which a styrenic polymer is made to contain a higher fatty acid.

[Prior Art] False coloring is a known method for producing polymers with excellent impact strength by polymerizing styrenic monomers.

For example, there is a method in which a crosslinking agent is present in the polymerization system, but the polymer produced by this method has poor fluidity during processing and is not preferred because flash phenomena and flow mark phenomena occur. Therefore, there are ways to increase the molecular weight to some extent by lowering the polymerization temperature or reducing the amount of polymerization initiator to improve these drawbacks, but the polymerization reaction takes a long time and production efficiency decreases significantly. There are drawbacks such as:

In addition, there is a method of producing a styrene-based high molecular weight polymer using a polymerization initiator with a specific structure, but even if a product with excellent impact strength can be obtained by this method, the moldability during injection molding and mold release It has the disadvantage of poor performance and hinders productivity and workability.

In addition, as a styrenic resin composition that has improved these drawbacks, behenic acid is added to a polymer polymerized with two specific radical polymerization initiators (Japanese Patent Laid-Open No. 56-67).
No. 352), which has excellent mold releasability during injection molding, but its mechanical strength is still not sufficient. Furthermore, as a styrene resin m-acid which has improved this drawback, there is a product in which behenic acid is added to a polymer polymerized using two types of radical polymerization initiators different from those mentioned above (Japanese Patent Publication No. 5B-56576). Although this has an excellent balance of mechanical strength and fluidity, it uses two types of radical polymerization initiators to reduce the amount of residual monomer in the polymer, which increases the viscosity. bulk polymerization,
It is not suitable for solution polymerization.

[Problems to be Solved by the Invention] The present invention aims to provide a styrenic resin composition with excellent injection moldability and impact strength, that is, a well-balanced styrenic resin composition.

[Means for Solving the Problems] The present invention relates to a styrenic resin composition in which a higher fatty acid is contained in a polymer that is polymerized using a specific polymerization initiator and adjusted to have a specific molecular weight and molecular weight distribution.

That is, in the present invention, at least one styrenic monomer or a mixture thereof with a vinyl monomer copolymerizable with the styrenic monomer is used.
Obtained by polymerizing one or more polyfunctional organic peroxides using a radical polymerization initiator, the weight average molecular weight is 200,000 to 450,000, the Mw/Mn is 2.0 to 3.0, and the oligomer content is 1.0%.
This is a styrenic resin composition containing 0.01 to 0.5 parts by weight of a higher fatty acid in 100 parts by weight of the following styrene polymer.

The present invention will be explained in detail below.

Examples of the styrenic monomer used in the present invention include styrene, α-methylstyrene, vinyltoluene, and tertiary styrene.
These styrene monomers may be used alone or in mixtures thereof, such as butylstyrene, or may be a mixture of these styrene monomers with copolymerizable monomers such as acrylonitrile and methyl methacrylate.

The method for producing the styrenic polymer constituting the present invention can utilize known bulk polymerization, solution polymerization, etc., but polymerization is carried out at a point where the residual monomer remains from 10% to 50%, preferably from 20% to 30%. Characterized by stopping the reaction. If the residual monomer content is less than 10%, the viscosity will be high and operation will be difficult, and if it exceeds 50%, the yield will be poor and it will be uneconomical. Further, residual monomers can be removed by devolatilization or the like.

In the present invention, at least one polyfunctional organic peroxide is used as a radical polymerization initiator for styrenic monomers. The polyfunctional organic peroxides used include di-tert-butyl peroxy hexahydroterephthalate, di-tert-butyl peroxy-2,4,
4-trimethyladipate, tertiarybutylperoxy-2,2,4-)limethyladipate, 1,
1-tertasharybutylperoxy-3,3,5
-) Limethylcyclohexane, etc.

The amount of polyfunctional organic peroxide used is 0.01 to 0.5% by weight based on the styrenic monomer, preferably 0.0%.
It is 2 to 0.25%. If it is less than 0.01%, a large amount of oligomers will be generated due to thermal polymerization, and if it exceeds 0.5%, the polymerization rate will be so fast that it will be difficult to control the removal of reaction heat, etc. Further, if at least one type of polyfunctional organic peroxide is used, an initiator such as a monofunctional organic peroxide can also be used in combination.

The polymerization temperature is preferably between the 10-hour half-life temperature and the 30-minute half-life temperature of the polyfunctional organic peroxide;
If the temperature is below the half-life temperature, the yield per unit time will be low, and if the temperature exceeds the half-life temperature of 30 minutes, the reaction rate will be extremely high, making it difficult to control the polymerization smoothly.

The weight average molecular weight of the styrenic polymer used in the present invention is from 200,000 to 450,000, preferably from 250,000 to 400,000.

When the molecular weight is less than 200,000, the moldability is excellent but the impact strength is insufficient. On the other hand, when the molecular weight is over 450,000, the impact strength is excellent but the moldability is insufficient and the balance of physical properties is poor. Further, the molecular weight distribution expressed by Mw/Mn (weight average molecular weight/number average molecular weight) is 2.0 to 3.0, preferably 2.2 to 2.6.

If Mw/Mn is outside this range, the balance between high molecular weight and low molecular weight substances in the polymer will be poor, and the objective cannot be achieved. This molecular weight adjustment can be carried out by adding a chain transfer agent such as mercaptans during polymerization.

The amount of oligomer contained in the styrenic polymer of the present invention is 1.0% or less, preferably 0.8% or less.

If the amount of oligomer exceeds 1.0%, the impact strength will be poor and the objective cannot be achieved. The amount of oligomer can be adjusted by changing the amount of polyfunctional organic peroxide added.

The higher fatty acids to be blended in the present invention include stearic acid, palmitic acid, behenic acid, erucic acid, etc. alone or in combination, but behenic acid and erucic acid are preferred as those that cause less mold staining during molding. Acids alone or in mixtures are preferred.

The amount of higher fatty acids added is 0.00 parts by weight per 100 parts by weight of the styrene polymer. O1 to 0.5 parts by weight, preferably 0.02 to 0
．． It is 3 parts by weight. If it is added in a small amount, there is no effect, and if it is too large, it may cause bleeding into the molded product or mold, which is not preferable. Furthermore, in the present invention, a plasticizer such as mineral oil or polyethylene glycol may be added to improve moldability. Further, these may be added at any step from the time of polymerization to melt granulation.

[Examples] Next, the present invention will be further explained with reference to Examples, but the present invention is not limited to these Examples.

Example 1 A 30 L reactor equipped with a stirring blade was charged with 20 kg of styrene, 5 kg of ethylbenzene, and 10 g of
Polymerization was carried out at 0'C for 3 hours and then at 130C for 3 hours. Thereafter, residual volatile components were removed under reduced pressure at 200°C to obtain 17.5 kg of styrene polymer. Next, 12 g of behenic acid was added to 10 kg of this styrene polymer, mixed, and then formed into pellets (styrene resin m-acid) using an extruder. These physical properties are shown in Table 1.

Example 2 Polymerization was carried out in the same manner as in Example 1, except that 5 g of di-tert-butyl peroxyhexahydroterephthalate and 2 g of cushary butyl peroxybenzoate were used as radical polymerization initiators. After that, the remaining volatile matter was removed under reduced pressure at 200°C, and the styrene polymer 15.3k
I got g. Next, 12 g of behenic acid was added to 10 kg of this styrene polymer, mixed, and then formed into pellets (styrenic resin composition) using an extruder. These physical properties are shown in Table 1.

Example 3 10% n-dodecyl mercaptan as a chain transfer agent
Polymerization was carried out in the same manner as in Example 1, except that g was added to the polymerization. Thereafter, residual volatile components were removed under 200° CX pressure to obtain 17.1 kg of styrene polymer.

Next, add 12g of Behen 9 to 10kg of this styrene polymer.
After addition and mixing, the mixture was formed into pellets (styrenic polymer composition) using an extruder. These physical properties are shown in Table 1.

Example 4 The same procedure as in Example 1 was carried out except that 12 g of erucic acid was added instead of 12 g of behenic acid. These physical properties are shown in Table 1.

Comparative Example 1 20 kg of styrene and 5 kg of ethylbenzene were charged into a 30 L reactor equipped with a stirring blade, and polymerization was carried out at 135°C for 6 hours without adding a radical polymerization initiator.

Thereafter, residual volatile components were removed under reduced pressure at 200'C to obtain 16.5 kg of styrene polymer. Next, 12 g of behenic acid was added to 10 kg of this styrene polymer, mixed, and then formed into pellets (styrenic resin composition) using an extruder.

These physical properties are shown in Table 1.

It can be seen that the polymer obtained here has a larger amount of oligomer than the polymer of Example 2, which has approximately the same molecular weight, and the resin composition has inferior falling weight strength.

Comparative Example 2 Using n-dodecyl mercaptan as a chain transfer agent
The same procedure as in Example 1 was carried out except that the polymerization was carried out with the addition of g.

These physical properties are shown in Table 1.

It can be seen that the resin composition has good fluidity compared to Example 1, but is inferior in falling weight strength and has a poor balance of physical properties.

Comparative Example 3 The same procedure as in Example 1 was carried out except that 5 g of divinylhenzene was added and polymerization was carried out. These physical properties are shown in Table 1.

It can be seen that although the falling weight strength is good compared to the resin Mi acid compound and Example 1, the fluidity is greatly inferior and the physical property balance is poor.

Comparative Example 4 5 kg of the resin composition obtained in Comparative Example 2 and i”
1. After mixing 5 kg of the resin composition in a blender, it is shaped into pellets (styrene resin composition) using an extruder.
And so. These physical properties are shown in Table 1.

It can be seen that the polymer in this dz-combined styrenic resin composition has a larger Mw/Mn than the polymer of Example 1, and the resin composition is inferior in falling weight strength.

Ratio 11.2 Example 5 Same as Example 1 except that tertiary butyl peroxyhenzoate Og was used as a radical polymerization initiator and 5 g of n-dodecyl mercaptan was used as a chain transfer agent, and polymerization was carried out using a 112" C1 trowel for 5 hours. The physical properties are shown in Table 1.

It can be seen that the eye oil composition is inferior to Example 1 in terms of stone drop strength.

Comparative Example 6 The same procedure as Example 1 was carried out except that behenic acid was not added. These physical properties are shown in Table 1.

When this resin Mi product was molded into a bottom shape, the mold releasability was poor.

Comparative Example 7 The same procedure as Example 1 was carried out except that 100 g of behenic acid was added. These physical properties are shown in Mugi 1.

After molding this resin composition (100 mm), stains on the mold were observed.

[Effect of the invention 1 The styrenic resin Mi acid of the present invention has excellent injection moldability and impact strength, has a better balance than conventional products, and has excellent mold releasability, so It is possible to efficiently obtain bottom-shaped crystals with complex tl shapes for parts, audio products, etc.

Claims (1)

[Claims] 1. Weight average obtained by polymerizing a styrenic monomer alone or a mixture of a vinyl monomer copolymerizable with these monomers using at least one polyfunctional organic peroxide as a radical polymerization initiator. Molecular weight is 200,000 to 450,000, @M@w/@
A styrenic resin containing 0.01 to 0.5 parts by weight of a higher fatty acid in 100 parts by weight of a styrenic polymer having an M@n of 2.0 to 3.0 and an oligomer content of 1.0% or less. Composition.