JPH0794592B2 - Thermoplastic resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a thermoplastic resin composition having an excellent appearance of a molded article and having good impact resistance.

<Prior Art> Generally, in the fields of home appliances housings, automobile parts, etc., a resin that has both impact resistance and a good appearance represented by surface gloss is required. ABS resin (acrylonitrile-butadiene-styrene resin) is often used.

However, in recent years, with the diversification of applications and the complicated shapes of molded products, higher performance such as a better surface gloss in terms of appearance and uniform and evenness over the entire molded product, has been achieved. Is required.

However, the impact resistance and the appearance generally have a contradictory relationship. That is, in order to improve the impact resistance, a method of increasing the content of the rubber-like polymer in the resin and a method of increasing the particle size of the rubber-like polymer are effective. It is known that, as the content of the rubbery polymer in the resin is smaller and the particle size is smaller, the smoothness of the surface of the molded article is maintained and the appearance is improved.

Attempts have been made to improve rubbery polymers and graft copolymers in order to overcome these conflicting conditions and achieve both impact resistance and excellent appearance. For example, a method of combining two or more kinds of rubbery polymers having different particle diameters (JP-A-52-141859, JP-A-54-133588, JP-A-57-2).
3652, JP-A-59-202211) and a method for specifying the gel content and composition of a rubbery polymer (JP-A-53-57293, JP-A-59-184244, JP-A-62-84109). No.) has been proposed, the presence of a rubbery polymer having a relatively large particle size is indispensable, which causes uneven gloss on the surface of the molded product and the effect of improving the appearance is insufficient.

On the other hand, as an example of using a small particle size rubbery polymer, Japanese Patent Laid-Open No.
Proposal on impact-resistant thermoplastic resin composition having good light-transmitting property and plating property by using a graft copolymer having a rubbery copolymer of 0.04 to 0.15 μm as a skeleton, as in No. 62-201959. However, although the appearance is good, the impact resistance is low, and it is not suitable for achieving both the impact resistance and the excellent appearance, which is the object of the present invention.

<Problems to be Solved by the Invention> The inventors of the present invention have surprisingly studied as a result of aiming to achieve both the impact resistance, which is a contradictory condition, and the excellent appearance of a molded product, and surprisingly. There is a good combination in terms of impact resistance between the particle size of the rubbery polymer in the resin and the copolymer composition of aromatic vinyl and vinyl cyanide that form a continuous phase. Is relatively high, and within a specific range, impact resistance is maintained even if the particle size of the rubbery polymer is reduced, and as a result, it is found that both impact resistance and excellent appearance can be achieved. Invented.

<Means for Solving the Problem> That is, the present invention relates to a graft copolymer (A) having a rubber polymer having a specific particle size as a skeleton, and aromatic vinyl and vinyl cyanide having a specific ratio. In the presence of 50 to 80% by weight of a butadiene rubbery polymer (solid content) having a weight average particle diameter of 0.15 to 0.25 μm. Aromatic vinyl 80-70% by weight and vinyl cyanide 20-
A graft copolymer (A) having a graft ratio of 20% or more obtained by graft polymerizing 50 to 20% by weight of a monomer mixture of 30% by weight, 68 to 50% by weight of aromatic vinyl and 32 to 50% of vinyl cyanide. Copolymer (B) consisting of wt% (AS copolymer)
And the content of the butadiene rubbery polymer in the composition is 5 to 30% by weight, and the copolymer of aromatic vinyl and vinyl cyanide in the composition (graft The total ratio of the free copolymer derived from the copolymer (A) and the copolymer (B) is 32 to 45.
It is intended to provide a thermoplastic resin composition having an excellent appearance of a molded product characterized by being in a weight percentage and having good impact resistance.

The first point of the present invention is that the weight average particle diameter of the butadiene-based rubbery polymer as the skeleton is 0.15 to 0.25 μm.

When the particle size is less than 0.15 μm, the appearance is excellent, but the impact resistance is remarkably deteriorated. Even if the AS copolymer (B) having a vinyl cyanide ratio of 32 to 50% by weight is blended in the present invention, the impact resistance is reduced. Is insufficient.

On the other hand, if the particle size exceeds 0.25 μm, the impact resistance is relatively good, but the difference in gloss between the vicinity of the gate and the end of the resin molded product is large, and the appearance is deteriorated such as uneven gloss, which is not preferable.

Here, as the butadiene-based rubbery polymer used in the present invention, those generally used for ABS resin can be applied as they are. That is, polybutadiene, butadiene-styrene copolymer, butadiene-acrylonitrile copolymer and the like are not particularly limited, but those having a butadiene content of 70% by weight or more and a gel content of 50% or more are preferable.

Further, the butadiene rubbery polymer is produced by using a known emulsion polymerization technique, and the production method is not particularly limited.

The graft copolymer (A) according to the present invention contains 80 to 80% by weight of aromatic vinyl in the presence of 50 to 80% by weight of a butadiene rubbery polymer (solid content) having a polymerization average particle size of 0.15 to 0.25 μm.
A graft copolymer having a graft ratio of 20% or more obtained by graft-polymerizing 50 to 20% by weight of a monomer mixture consisting of 70% by weight and vinyl cyanide 20 to 30% by weight.

If the amount of the butadiene rubbery polymer is less than 50% by weight, the amount of the non-grafted free aromatic vinyl and vinyl cyanide copolymer (free AS copolymer), which is a by-product, increases. Is not preferable because the effect of the present invention decreases.
If it exceeds 80% by weight, the impact resistance decreases, which is not preferable. Further, if the graft ratio of the graft copolymer is less than 20%, the impact resistance decreases, which is not preferable.

The graft copolymer (A) obtained by graft polymerization is generally a graft polymer in which aromatic vinyl and vinyl cyanide are chemically bonded to a rubber-like polymer, and without grafting to the rubber-like polymer. It is composed of a free AS copolymer obtained by copolymerizing aromatic vinyl and vinyl cyanide.

These graft products and free AS copolymers can be separated into insoluble parts (grafts) and soluble parts (free AS copolymers) with acetone. The ratio of vinyl cyanide constituting the free AS copolymer can be determined by nitrogen analysis.

The graft ratio is (weight of aromatic vinyl and vinyl cyanide chemically combined on the rubbery polymer) / (weight of the rubbery polymer) x 100 (%), which is generally used for graft polymerization. It can be calculated from the ratio of the raw material (prepared composition), the acetone insoluble portion, and the soluble portion.

Here, examples of the aromatic vinyl used in the graft polymerization include styrene, α-methylstyrene and vinyltoluene, and styrene is preferable. Examples of vinyl cyanide include acrylonitrile and methacrylonitrile, with acrylonitrile being preferred.

The graft copolymer (A) in the present invention can be easily produced by a commonly used emulsion polymerization method. For example,
Examples of the method for adding the monomer mixture include a method of adding all at once during polymerization, a method of continuously adding, or a method of dividing into two or more portions. Further, as an emulsifier, a usual anionic surfactant such as sodium oleate is used. Etc. can be used, and as the polymerization initiator, a usual persulfate, an organic peroxide, and a redox type initiator obtained by combining them with a reducing agent can be used.

Furthermore, if necessary, a molecular weight modifier such as alkyl mercaptans may be used. Incidentally, the graft copolymer in the present invention is a known bulk polymerization other than the emulsion polymerization method,
It can also be produced by suspension polymerization, solution polymerization or the like.

Next, the second important point of the present invention is the composition of the AS copolymer (B) used by being mixed with the graft copolymer (A) to form the continuous phase in the resin composition. The proportion of vinyl cyanide constituting the AS copolymer (B) is 32 to 50% by weight, preferably 35 to 45% by weight. AS copolymer (B)
In the case where the ratio of vinyl cyanide is less than 32% by weight, the impact resistance is deteriorated, and when it exceeds 50% by weight, the resin composition is markedly colored (yellowing during processing), and further, physical properties such as processability are deteriorated. Getting worse. The ratio of vinyl cyanide in the AS copolymer (B) can be determined by a nitrogen analysis method.

As the aromatic vinyl and vinyl cyanide constituting the copolymer (B), the same ones as those described in the graft copolymer (A) can be used, and also in this case, styrene and acrylonitrile are used, respectively. And are preferred.

Further, there is no limitation on the method for producing the copolymer (B), and those produced by ordinary emulsion polymerization, suspension polymerization, bulk polymerization or the like can be used.

The third essential point of the present invention is the content of the butadiene rubbery polymer in the resin composition, which is 5 to 30% by weight. If it is less than 5% by weight, the impact resistance is lowered. On the other hand, if it exceeds 30% by weight, the impact resistance is good but the physical properties such as moldability are deteriorated, which is not preferable. The content of the butadiene rubbery polymer is the amount of butadiene rubber constituting the graft copolymer (A) and / or the graft copolymer (A).
It can be adjusted by changing the compounding ratio of the AS copolymer (B).

Further, the fourth gist of the present invention is to provide a copolymer of aromatic vinyl and vinyl cyanide in the resin composition, that is, a free AS copolymer obtained from the graft copolymer (A).
It is the ratio of vinyl cyanide in the total amount with the AS copolymer (B), and the ratio is 35 to 45% by weight. If it is less than 35% by weight, impact resistance is lowered, while if it exceeds 45% by weight, coloring problems (yellowing during processing) and physical properties such as moldability are deteriorated, which is not preferable in practice.

The ratio of vinyl cyanide in the copolymer of aromatic vinyl and vinyl cyanide in the resin composition is the blending ratio of free AS copolymer and AS copolymer (B) and cyan in each copolymer. It can be calculated from the vinyl chloride ratio. In addition, the resin composition is separated with acetone to
It can also be determined by nitrogen analysis from an acetone-soluble part, which is a mixture of the AS copolymer and the AS copolymer (B).

In the present invention, the graft copolymer (A) and the AS copolymer (B) are mixed mainly after making them solid, but when both are emulsion polymerization products, latex blending is also possible. Is. The emulsion polymerized product is collected and used as a solid (powder) through the usual steps of coagulation, washing with water and drying.

The composition in the present invention is kneaded by an extruder, a Banbury mixer or the like. At this time, normal stabilizers, lubricants,
An antistatic agent or the like can be added as appropriate.

Further, the thermoplastic resin composition of the present invention, a general method,
For example, it can be processed into a molded product by injection molding or the like.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, in the examples, various evaluations were performed by the following methods.

 Weight average particle diameter of butadiene rubber polymer Average value of 200 to 300 particles observed using an electron microscope.

 Impact resistance (Izod impact strength) Measured according to ASTM-D256.

Molding processability Measured with a high-performance flow tester (210 ℃, 30kg load).

Appearance of molded product L-shaped with width 20 mm, thickness 2 mm, length 20 cm in length and width 20 cm in width, and a fixed length of resin (about 30 cm) in a molding die with a gate at the inner end. Each part of the molded product obtained by adjusting the injection pressure so that
B, C, D, at equal intervals from A to the tip of the molded product
The surface gloss of E) was measured according to ASTM-D523.

Production Example A butadiene rubbery polymer latex (a), a graft copolymer (A), and a graft copolymer (A) used in Examples and Comparative Examples described later.
The AS copolymer (B) was produced by the following method.

Production of butadiene-based rubbery polymer latex (a-1) Butadiene 93 parts by weight Styrene 7 〃 Sodium oleate 2.0 〃 Dodecyl mercaptan 0.2 〃 Potassium persulfate 0.3 parts by weight Sodium hydroxide 0.1 〃 Deionized water 150 〃 Stir the above mixture The reaction mixture was placed in a stainless steel reaction vessel equipped with a machine, replaced with nitrogen, and then polymerized at 60 ° C for 18 hours and then at 70 ° C for 7 hours to obtain a rubbery polymer latex (a-1). The polymerization rate was 97%, and the weight average particle diameter was 0.10 μm.

Production of butadiene-based rubbery polymer latex (a-2) The same operation was performed as in Production Example (a-1) except that the amount of sodium oleate was changed to 1.5 parts by weight to obtain a rubbery polymer latex (a- 2) was obtained. The polymerization rate was 98%, and the weight average particle diameter was 0.15 μm.

Production of butadiene rubbery polymer latex (a-3) In Production Example (a-1), the amount of sodium oleate was 0.8 parts by weight, and the amount of potassium persulfate was 0.4 parts by weight, and further at 70 ° C. The same operation was performed except that the polymerization time was 12 hours, to obtain a rubbery copolymer latex (a-3). Polymerization rate is 97%, weight average particle size is 0.24μm
Met.

Production of butadiene rubbery polymer latex (a-4) a-3 (solid content) 15 parts by weight Butadiene 80 〃 Styrene 5 〃 Sodium oleate 0.2 〃 Dodecyl mercaptan 0.2 〃 Potassium persulfate 0.3 〃 Sodium hydroxide 0.05 〃 Desorption Ionized water 100 〃 The above mixture was placed in a stainless steel reaction vessel equipped with a stirrer and, after purging with nitrogen, polymerized at 60 ° C for 30 hours and then at 70 ° C for 30 hours to obtain a rubbery polymer latex (a-4). The polymerization rate was 97%, and the weight average particle diameter was 0.40 μm.

Manufacture of graft copolymer (A-1) a-1 (solid content) 60 parts by weight Potassium persulfate 0.3 〃 deionized water 100 〃 The above mixture was charged into a stainless steel reaction vessel equipped with a stirrer, and after nitrogen substitution, up to 65 ° C The temperature was raised, and from that time point, the following monomer mixture and aqueous emulsifier solution were continuously added over 4 hours for polymerization.

Monomer mixture: Styrene 28 parts by weight: Acrylonitrile 12 〃: tert-dodecyl mercaptan 0.3 〃 Aqueous emulsifier solution: Sodium oleate 1.0 parts by weight: Deionized water 20 〃 After continuous addition, heat to 70 ° C and age for 2 hours The reaction was completed.

An emulsion of an antioxidant was added to this graft copolymer latex and coagulated with an aqueous magnesium sulfate solution to obtain a graft copolymer (A-1).

The graft ratio of the obtained graft copolymer is 41%,
The ratio of acrylonitrile in the ungrafted free AS copolymer was 28.2% as determined by nitrogen analysis.

Production of Graft Copolymer (A-2, A-3, A-4) In the same manner as in the production of graft copolymer (A-1), rubbery polymer latex (a-2), (a -3), (a
-4) was carried out and graft polymerization was carried out to obtain respective graft copolymers (A-2), (A-3) and (A-4).

The graft ratio of the obtained graft copolymer and the ratio of acrylonitrile in the free AS copolymer are shown in Table-1.

Production of Graft Copolymer (A-5, A-6, A-7) In the same manner as in the production of graft copolymer (A-1), (a-3) was used as the rubbery copolymer latex. , The ratio of the rubbery polymer latex and the monomer mixture was changed as shown in Table 2, and the graft copolymers (A-5) and (A-
6) and (A-7) were obtained. The analytical values of the obtained copolymer are shown in Table 2.

Production of AS Copolymer (B-1) After replacing the stainless reactor equipped with a stirrer with nitrogen,
100 parts of deionized water in which 0.3 part of potassium persulfate was dissolved was charged and the temperature was raised to 65 ° C. From that point, the following monomer mixture and aqueous emulsifier solution were continuously added and polymerized for 4 hours.

Monomer mixture: Styrene 75 parts by weight: Acrylonitrile 25 〃: tert-dodecyl mercaptan 0.4 〃 Aqueous solution of emulsifier: Sodium oleate 1.5 parts by weight: Deionized water 20 〃 After continuous addition is completed, the temperature is raised to 70 ° C and aged for 2 hours. The reaction was completed.

This AS copolymer latex was coagulated with an aqueous magnesium sulfate solution to obtain an AS copolymer (B-1).

The ratio of acrylonitrile in the obtained AS copolymer was 24.0% as determined by nitrogen analysis.

Production of AS Copolymers (B-2), (B-3), (B-4) The composition of the monomer mixture was changed as shown in Table 3 in the same manner as in the above (B-1). Polymerized to form AS copolymer (B-
2), (B-3) and (B-4) were obtained.

The ratio of acrylonitrile in the obtained copolymer is shown in Table-3.
It was shown to.

Examples and Comparative Examples The graft copolymer (A) and the AS copolymer (B) were mixed in the proportions shown in Table 4, and 1.0 part of ethylenebisstearoamide and 0.2 part of calcium stearate were added to a Banbury mixer and a pelletizer. Pelletized.

The pellets obtained are injection molded (cylinder temperature 220
C., mold temperature 50.degree. C.), various test pieces were obtained and evaluated under the above measurement conditions.

<Effects of the Invention> Consisting of a graft copolymer having a specific particle diameter as defined in the present invention and an AS copolymer having a specific vinyl cyanide ratio, and having a specific rubber content and a vinyl cyanide ratio. The composition has excellent impact resistance and appearance, and makes it possible to produce molded products with complicated shapes and large-sized molded products that were not possible with conventional ABS resins in terms of uneven gloss and insufficient impact resistance. It is possible to cope with the diversification of ABS resin,
It has high industrial value.

Claims (1)

[Claims] 1. In the presence of 50 to 80% by weight of a butadiene rubbery polymer (solid content) having a weight average particle diameter of 0.15 to 0.25 μm, 80 to 70% by weight of aromatic vinyl and 20% of vinyl cyanide.
A graft copolymer (A) having a graft ratio of 20% or more, which is obtained by graft-polymerizing 50 to 20% by weight of a monomer mixture of 30 to 30% by weight, 68 to 50% by weight of aromatic vinyl, and 32 to 32% of vinyl cyanide. A composition comprising 50% by weight of the copolymer (B), wherein the content of the butadiene rubbery polymer in the composition is 5 to 30% by weight, and the aromatic vinyl in the composition. The ratio of vinyl cyanide in the copolymer of vinyl cyanide with vinyl cyanide (total of free copolymer derived from graft copolymer (A) and copolymer (B)) is 35-
45% by weight of the thermoplastic resin composition.