JPH05279427A - Rubber-modified styrenic resin composition having high luster and its production - Google Patents

Abstract

PURPOSE:To obtain a rubber-modified styrenic resin composition having extremely improved appearance of molded article, especially luster and excellent impact strength. CONSTITUTION:In dispersed rubber particles of rubber modified styrenic resin composition, particles of one rubbery polymer having a salami structure are made into particles having small particle diameter and blended with particles having a single occlusion structure. A particle diameter distribution has one peak and the average particle diameter is 0.2-0.8mum. Further the particle diameter distribution is wider than a conventional one and the ratio of 5% value and 95% value of cumulative distribution of particle diameter of volume standard of rubbery polymer particles is 3-45.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber-modified styrenic resin composition having a high gloss, which is excellent in the balance between the appearance of molded articles and impact resistance, and a method for producing the same.

[0002]

2. Description of the Related Art ABS resin is a resin having a good balance between the appearance of a molded article and impact strength, and is widely used in household electric appliances, electronic devices and the like. Recently, the trend toward cost reduction of these products has increased, the use of rubber-modified styrenic resins in place of ABS resins has increased, and they are also used for molded products having large and more complicated shapes and thin thickness. It became so. Under such circumstances, there has been a demand for a rubber-modified styrenic resin having good gloss, excellent moldability, and high impact strength.

The rubber-modified styrenic resin is obtained by dispersing rubber particles in a styrene-based resin, and the particle size of the dispersed rubber particles has an important influence on the product performance. The smaller the size, the better the gloss of the molded product. Usually, the rubber particle size (average particle size, the same applies hereinafter) in the rubber-modified styrene-based resin is about 1.0 to 5.0 μm, but recently, in order to improve the gloss of the molded product, it is 1.0 μm.
Resins in which rubber particles of m or less are dispersed have also been developed.
However, in the rubber-modified styrenic resin, when the rubber particle diameter is 1.0 μm or less, the impact strength is usually remarkably lowered, and therefore there is a limit to improving the gloss while maintaining the impact strength of the molded product. In order to improve these problems, a method of blending a rubber-modified styrene resin in which rubber particles of 1.0 μm or less are dispersed with a rubber-modified styrene resin in which particles of 1.0 μm or more are dispersed is disclosed in JP-B-4.
6-41467, JP-A-59-1519, JP-A-63-
241053, U.S. Pat. No. 4,146,589, and the like. However, these methods have problems that the gloss is not yet sufficient and that the balance between impact strength and gloss is not good.

On the other hand, when a styrene monomer in which a styrene-butadiene block copolymer having a high styrene content is dissolved as a rubber component is polymerized, rubber particles of 0.5 μm or less having a single occlusion structure are dispersed in polystyrene. It is well known that they are formed in the state (eg Angew. Makromol. Chem. 58 /
59P175-198 (1977)). Utilizing this, a method for producing a rubber-modified styrenic resin excellent in gloss and transparency of a molded article is disclosed in JP-B-48-1859.
4, JP-A-61-500497, JP-A-63-4831
7, proposed in JP-A-64-74209. According to these methods, the surface gloss and the transparency of the molded product are remarkably improved as compared with the conventional rubber-modified styrene resin. However, although improvements in impact strength have been attempted, they have not been sufficient. Further, a rubber-modified styrene resin in which rubber particles having a single occlusion structure formed by using the styrene-butadiene copolymer rubber are dispersed, and a normal rubber-modified styrene in which a small amount of rubber particles having a salami structure are dispersed. By blending a series of resins and making the particle size distribution curve of the dispersed rubber particles into a bimodal shape (distribution curve having two maximum values), try to improve impact resistance while maintaining the gloss of the molded product at a high level. Attempts to achieve the above are disclosed in US Pat. No. 4,493,922 and JP-A-63-112646.
Etc. In these methods, although the impact strength is certainly improved, the gloss is still insufficient, and the impact strength is insufficient, so that it is necessary to add polydimethylsiloxane or the like to the resin. there were.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rubber-modified styrene-based resin which has a markedly improved appearance of a molded article and is excellent in impact strength as compared with conventional rubber-modified styrene-based resins, and the production thereof. To provide a method.

Another object of the present invention is a rubber-modified styrene resin, which is suitable as a resin material for a large-sized, thin-walled and complex-shaped molded product molded by, for example, an injection molding method, and It is to provide a manufacturing method.

[0007]

Means for Solving the Problems The inventors of the present invention have made extensive studies in view of the importance of the above object, and as a result, in a rubber-modified styrene-based resin composition, (1) a rubber particle having a salami structure having a small particle size. (2) The rubber particles having a single occlusion structure are made into a dispersed state, and the particle size distribution is made into a mountain shape so that the volume average diameter is 0.
The range is from 2 to 0.8 μm, and (3) the particle size distribution is made wider than before, which is completely different from the conventional knowledge, and is 5% of the cumulative distribution of the volume-based particle size of rubber-like polymer particles and 95%. By finding a special index called the value of the ratio of% value and controlling it, when this rubber-modified styrene resin is used in a molded article, the appearance of the molded article,
In particular, they have found that the gloss is remarkably improved and the impact strength is also excellent, and the present invention has been completed.

That is, the present invention relates to a high-gloss rubber-modified styrene-based resin composition obtained by dispersing rubber-like polymer particles in a homopolymer or copolymer of a styrene-based monomer, wherein (a)
The volume average diameter of the rubber-like polymer particles is in the range of 0.2 to 0.8 μm, (b) the volume-based particle size distribution curve of the rubber-like polymer particles has a single peak, and (c) The value of the ratio of the 5% value and the 95% value of the cumulative distribution of the volume-based particle size of the rubber-like polymer particles is in the range of 3 to 45, and (d) the 5 wt% styrene solution viscosity is 20 to 50 centipoise. A high-gloss rubber-modified styrenic resin composition, characterized in that a rubber-like polymer which is a styrene-butadiene block copolymer having a styrene content of 25% by weight to 50% by weight is used as a raw material for forming rubber-like polymer particles. And the rubber-like polymer particles include particles having a salami structure and a single occlusion structure, and the volume average diameter of the particles having a salami structure is from 03 to 2.
0 μm, the volume average diameter of particles having a single occlusion structure is 0.1 to 1.0 μm, and the ratio of the number of particles having a single occlusion structure to the total number of particles is 30 to 99%, The ratio of the number of particles having a salami structure is 70 to 1%.

The present invention also provides a rubber-modified styrenic resin composition according to claim 1 or 2 by polymerizing a solution in which the rubbery polymer according to claim 1 is dissolved in a styrenic monomer or a mixture thereof. In the method for producing a product, the amount of the styrenic polymer in the reaction vessel for granulating the rubber-like polymer is X.
%, The total amount of the rubbery polymer is Y% by weight, and the styrene content of the rubbery polymer is Z% by weight, and the conversion rate of the styrene-based monomer or a mixture thereof is represented by the following formula (I) 42 ≦ X + 2. 33 × Y + (Z-40) ≦ 52 ... (I) A method for producing a high-gloss rubber-modified styrene-based resin composition, which comprises controlling to a range satisfying the formula (I) when granulating a rubber-like polymer. 0.0005 to 0.0 with respect to 100 parts by weight of a solution obtained by dissolving an organic peroxide in a rubbery polymer.
Including addition of 07 parts by weight.

The styrene-based monomer as used in the present invention is a side chain alkyl-substituted styrene such as styrene, α-methylstyrene and α-ethylstyrene, vinyltoluene, vinylxylene, ot-butylstyrene, p-styrene. Nuclear alkyl-substituted styrenes such as t-butylstyrene and p-methylstyrene, halogenated styrenes such as monochlorostyrene, dichlorostyrene, tribromostyrene and tetrahydrostyrene, and p-hydroxystyrene, o-methoxystyrene and the like. , Particularly preferably styrene,
α-methylstyrene and p-methylstyrene.
The styrene-based monomer may be used alone or in combination of two or more.

The rubber-like polymer particles are obtained by polymerizing the rubber-like polymer described below, that is, the styrene-based monomer or a mixture of the above-mentioned monomers to which a predetermined amount of a styrene-butadiene block copolymer is added. It is formed by being dispersed in a styrene polymer. Here, the rubber-like polymer, that is, the styrene-butadiene block copolymer has a styrene content of 25 to 50% by weight and a 5% by weight styrene solution viscosity of 20 to 50 centipoise.

When the styrene content is less than 25%, particles having a single occlusion structure, which will be described later, are not formed and the gloss becomes low, and when it exceeds 50% by weight, the impact strength becomes low.

Further, regarding the viscosity, when the viscosity is less than 20 centipoise, the impact strength becomes low, and when it exceeds 50 centipoise, the gloss decreases.

In the present invention, the rubber-like polymer particles formed as described above have a volume average particle size of 0.2 to 0.
It must be 8 μm. The volume average particle diameter here is measured as follows. That is, an electron micrograph of a resin by an ultra-thin section method is taken, and the minor and major diameters of 500 to 700 rubber particles in the photograph are measured, and the average is defined as the particle diameter, which is averaged by the following formula. is there.

Volume average particle diameter = ΣnD ⁴ / ΣnD ³ (where n is the number of rubber particles having a particle diameter D μm). When the volume average particle diameter is less than 0.2 μm, the obtained rubber modification The impact strength of styrene resin is low, and
If it exceeds 8 μm, the appearance of the molded article, especially the surface gloss, is deteriorated, which is not preferable.

In the present invention, the shape of the distribution curve of the rubber-like polymer particles needs to be a single peak.

In the present invention, the fact that the shape of the distribution curve of the rubber-like polymer particles is composed of one peak means that the horizontal axis is 0.1.
When the particle size based on volume average is plotted in μm and the frequency is plotted on the vertical axis, it increases monotonically up to the mode diameter (maximum frequency diameter) and the inflection point of the distribution curve is 1 point or less, and monotonically decreases above the mode diameter. The distribution curve has an inflection point of 1 or less.

When the shape of the distribution curve is two peaks, the impact strength can be improved, but the appearance of the molded article is inferior and the gloss gradient is particularly large. The shape of the distribution curve of the polymer particles is adjusted according to the molecular weight distribution of the rubber-like polymer to be used, the amount ratio of the rubber-like polymer to be mixed and the like. In the present invention, the gloss gradient means a difference in gloss due to a difference in distance from a gate in a molded article for injection molding, a site where the wall thickness changes, or a site where a fluid state greatly changes during injection molding such as a corner-shaped site. Indicates the difference in gloss from the standard area.

Further, in the present invention, the number is cumulatively counted from particles having a larger volume-based particle diameter of the rubber-like polymer particles, and the cumulative distributions are respectively 5% and 95%. Value of ratio of particle size, ie 5% of cumulative distribution
Value to 95% value (hereinafter referred to as distribution coefficient)
It must be in the range of 45. Preferably 3.5-40
The range of 4 to 35 is particularly preferable. When it is less than 3, the effect of improving the impact strength is low, and when it exceeds 45, the appearance of the molded product is inferior and particularly the gloss gradient becomes large. The amount is adjusted by the molecular weight distribution of the rubber-like polymer used, the amount ratio of the rubber-like polymer to be mixed, the stirring strength during the polymerization, the residence time and the like.

The present invention includes the case where the rubber-like polymer particles are particles having a salami structure and a single occlusion structure.

The salami structure referred to in the present invention means a structure of particles having a plurality of occlusions in one rubber particle when an electron micrograph of a resin by an ultrathin section method is taken and observed. Further, the single occlusion structure means a structure of particles having only one occlusion in one rubber particle.

In the present invention, among the rubber-like polymer particles, particles having a salami structure have a volume average diameter of 0.3 to 2.
In the range of 0 μm, the volume average diameter of the particles having a single occlusion structure is set to a range of 0.1 to 1.0 μm, and the ratio of the particles having a single occlusion structure to the total number of particles is set to a range of 30 to 99%. The ratio of the number of particles having a salami structure is preferably in the range of 70 to 1%. In this case, the volume average diameter of the rubber-like polymer particles is 0.2
Care must be taken to be in the range of ~ 0.8 μm.

If the volume average particle diameter of the particles having a salami structure is larger than 2.0 μm, the appearance of the molded product is inferior and the gloss gradient is particularly large, and if it is less than 0.3 μm, the impact strength is low. On the other hand, when the volume average particle size of the particles having a single occlusion structure is larger than 1.0 μm, the gloss becomes low,
If it is less than 0.1 μm, the impact strength will be low. When the number of particles having a single occlusion structure is less than 30%,
The gloss decreases and the gloss gradient increases. If it exceeds 99%, the impact strength will decrease.

As the method for producing the rubber-modified styrenic resin composition of the present invention, a solution obtained by dissolving a rubber-like polymer in a styrenic monomer is polymerized by bulk polymerization or bulk-suspension two-stage polymerization method. In any case, the amount of the styrenic polymer in the reaction vessel for granulating the rubbery polymer is X% by weight, the total amount of the rubbery polymer is Y% by weight, and the amount of the rubbery polymer is When the styrene content is Z% by weight, it is necessary to adjust the conversion rate of the styrene monomer so that the value of the following formula (II) falls within the range of 42 to 52.

X + 2.33 × Y + (Z-40) (II) Particles can be formed outside this range, but in that case abnormal particles occur. When it is less than 42, rubber particles that look like rods are formed when the obtained product is observed with an electron microscope.
The gloss and impact strength are low. On the other hand, when it exceeds 52, huge particles are generated and the gloss is lowered. Setting the above formula (II) to a predetermined value specifically means that when the amount of the rubber-like polymer in the reaction tank for granulating the rubber-like polymer is large or the styrene content of the rubber-like polymer is If the amount is large, the conversion rate of the styrene-based monomer is adjusted so that the amount of the styrene-based polymer in the reaction tank for particleizing the rubber-like polymer is increased. It means adjusting the conversion rate of the styrene-based monomer so that the amount of the styrene-based polymer in the reaction tank to be converted becomes smaller.

In the present invention, the conversion of the styrenic monomer is adjusted by a known method, for example, the polymerization temperature, the type and concentration of the polymerization initiator to be used, the polymerization time, and the residence time in the case of the continuous polymerization method. To be done.

In the present invention, it is not necessary to use a polymerization initiator when the rubber-like polymer is made into particles, but a solution 1 in which an organic peroxide is dissolved in the rubber-like polymer as a polymerization initiator.
It is preferable to use 0.0005 to 0.007 parts by weight with respect to 00 parts by weight. If it is used in an amount of more than 0.007 parts by weight, a large amount of giant particles may be generated, which may reduce the gloss. The rubber-modified styrenic resin of the present invention may optionally contain a hindered phenolic antioxidant, a phosphorus antioxidant, an antioxidant such as a sulfur antioxidant, a fluidity improver such as mineral oil, and stearic acid. A release agent such as zinc stearate or organic polysiloxane may be added to the raw material solution or during the polymerization or at the time when the polymerization is completed.

[0028]

EXAMPLES The present invention will be specifically described below with reference to examples, but these do not limit the scope of the present invention. Evaluation of physical properties (1) Izod impact strength: measured according to JIS K-6871 (2) Evaluation of practical impact strength: Figure 1 by injection molding
A falling weight impact strength test was conducted on three parts of the molded article 1 having the shape shown in (a) and FIG. 1 (b), that is, part (1), part (2), and part (3). Tip of falling weight R =
The inner diameter of the carrier was 6.4 m / m, and the inner diameter was 25 m / m. The part (1) is a part whose thickness changes, the part (2) is a part near the corner, and the part (3) is a standard part. (3) Gloss: According to JIS 8741 (incident angle 60 °), the molded article 3 having the shape shown in FIGS. 1 (a) and 1 (b)
Sites, ie site (1), site (2), site (3)
Was measured. Example 1 A rubber-modified styrenic resin was produced using a continuous bulk polymerization apparatus in which a preheater was connected to the outlets of three reactors equipped with a stirrer in series, and then a vacuum tank was connected. 6 parts by weight of a styrene-butadiene block copolymer having a styrene content of 38%, a 5% styrene solution viscosity of 37 centipoise as a rubber-like polymer in a first reaction vessel equipped with a stirrer, 15 parts by weight of ethylbenzene, and 79 parts by weight of styrene. , 1,1-as organic peroxide
A raw material liquid consisting of 0.005 parts by weight of bis (t-butylperoxy) 3,3,5-trimethylcyclohexane was continuously supplied. The stirring of the first stirrer is 300 rp
m, the reaction temperature was 146 ° C., and the residence time was 1 hour. The second group has a reaction temperature of 145 ° C. and a residence time of 2 hours,
The third group had a reaction temperature of 145 ° C. and a residence time of 3 hours. The temperature of the preheater was maintained at 210 to 240 ° C., and the degree of vacuum in the vacuum chamber was 40 Torr. The results are shown in Tables 1 and 2. Example 2 It carried out on the same conditions as Example 1 except having set the 1st stirring to 200 rpm. Example 3 The conditions were the same as in Example 1 except that the first stirring was 400 rpm. Comparative Example 1 The conditions were the same as in Example 1 except that the first stirring was 100 rpm. The rubber-like polymer particles in the obtained product had a large average particle size of 0.90 μm and had low gloss. Comparative Example 2 The same conditions as in Example 1 were carried out except that the first stirring was 550 rpm. The rubber-like polymer particles in the obtained product had a small average particle size of 0.10 μm and had a low impact strength. Comparative Example 3 In Example 1, the reaction temperature of the first group was 143 ° C., the residence time was 2 hours, the viscosity of the rubbery polymer was 5% styrene solution viscosity 32 centipoise, and the styrene content was 42%. Except for using coalescing
Under the same conditions as in Example 1, a rubber-modified styrene-based resin (A) having a small particle size and a single occlusion structure having an average particle size of rubber-like polymer particles of 0.30 μm was produced. Separately in Example 1, except that 6 parts by weight of polybutadiene having a 5% styrene solution viscosity of 50 centipoise was used as the rubber-like polymer, the salami having an average particle diameter of 1.15 μm of the rubber-like polymer particles was prepared under the same conditions as in Example 1. A rubber-modified styrenic resin (B) having a structure and having a large particle size was produced. Rubber-modified styrenic resins (A) and (B) were mixed in a ratio of 85/15,
The product was obtained by melt-kneading with an extruder. The particle size distribution of the rubber-like polymer had two peaks, and the gloss gradient of the molded product was large. Comparative Example 4 The conditions were the same as those in Example 1 except that the residence time of the first base was changed to 45 minutes in Example 1. The product obtained is
The distribution coefficient was as large as 47.5, and the gloss gradient of the molded product was large. Comparative Example 5 The procedure of Example 1 was repeated except that the residence time of the first base was changed to 3 hours. The obtained product had a small distribution coefficient of 2.0 and low impact strength. Comparative Example 6 The rubber-modified styrenic resin (A) produced in Comparative Example 3 was molded as it was and the physical properties were evaluated. High gloss, but low impact strength. Comparative Example 7 Styrene content 2 as the rubber-like polymer in Example 1
A 0%, 5% styrene solution was used under the same conditions as in Example 1 except that a styrene-butadiene block copolymer having a viscosity of 40 centipoise was used. The resulting product did not have a single occlusion structure and had low gloss. Comparative Example 8 Styrene content of 5 as rubbery polymer in Example 1
5%, 5% styrene solution The conditions were the same as in Example 1 except that a styrene-butadiene block copolymer having a viscosity of 38 centipoise was used. The resulting product had low impact strength. Example 4 Example 1 was repeated except that the reaction temperature was 138 ° C. Example 5 It carried out on the conditions similar to Example 1 except having set the reaction temperature to 148 degreeC in Example 1. Example 6 Example 6 was carried out under the same conditions as in Example 1 except that the reaction temperature was 148 ° C. and no organic peroxide was used. Comparative Example 9 The conditions were the same as in Example 1 except that the reaction temperature in Example 1 was 136 ° C. The conversion rate of the first styrene monomer was 35.5%. Electron micrograph observation of the product revealed rod-shaped particles with low gloss and impact strength. Comparative Example 10 The procedure of Example 1 was repeated except that the reaction temperature was changed to 154 ° C. The conversion rate of the first styrene monomer was 53%. Electron micrograph observation of the product revealed that there were large particles and the gloss was low. Comparative Example 11 The conditions were the same as those in Example 1 except that the reaction temperature was 139 ° C. and 0.01 parts by weight of the organic peroxide was used. Conversion rate of the first styrene monomer is 45%
Met. Electron micrograph observation of the product revealed that there were large particles and the gloss was low.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

As described above, the rubber-modified styrenic resin obtained by the method of the present invention has an excellent balance of impact strength and appearance, particularly gloss, and is a component material for household electric appliances, electronic devices and the like. The industrial utility value is great in the use of.

[Brief description of drawings]

FIG. 1 is a plan view (a) and a sectional view (b) of an injection-molded test piece used for evaluation of practical impact strength and gloss.

[Explanation of symbols]

 1 molded product

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kozo Ichikawa 1-6 Takasago, Takaishi-shi, Osaka Mitsui Toatsu Chemical Co., Ltd. (72) Inventor Akihiko Nakajima 1-6 Takasago, Takaishi-shi, Osaka Mitsui Toatsu Inside the Chemical Co., Ltd. (72) Masato Takahisa 1-6 Takasago, Takaishi City, Osaka Prefecture Mitsui Toatsu Chemical Co., Ltd.

Claims (4)

[Claims] 1. A high-gloss rubber-modified styrene-based resin composition obtained by dispersing rubber-like polymer particles in a homopolymer or copolymer of a styrene-based monomer, wherein (a) the volume of rubber-like polymer particles. The average diameter is in the range of 0.2 to 0.8 μm,
(B) The shape of the volume-based particle size distribution curve of the rubber-like polymer particles is composed of one mountain, and (c) 5% value and 95% value of the cumulative distribution of the volume-based particle diameter of the rubber-like polymer particles. The ratio value of is 3
In the range of (d) 5% by weight styrene solution viscosity is 20 to 50 centipoise and the styrene content is 25% by weight.
A high-gloss rubber-modified styrene-based resin composition, wherein a rubber-like polymer, which is a styrene-butadiene block copolymer, is used as a raw material for forming rubber-like polymer particles in an amount of ˜50 wt%. 2. The rubber-like polymer particles include particles having a salami structure and a single occlusion structure, and the volume average diameter of the particles having a salami structure is 0.3 to 2.0 μm.
The volume average diameter of particles having a single occlusion structure is 0.1 to 1.0 μm, and the ratio of the number of particles having a single occlusion structure to the total number of particles is 30 to
99%, the ratio of the number of particles having a salami structure is 70-
The rubber-modified styrene resin composition according to claim 1, which is 1%. 3. A rubber-modified styrenic resin composition according to claim 1, which is obtained by polymerizing a solution of the rubber-like polymer according to claim 1 dissolved in a styrenic monomer or a mixture thereof. In the method, the amount of the styrenic polymer in the reaction vessel for granulating the rubbery polymer is X% by weight, the total amount of the rubbery polymer is Y% by weight, and the styrene content of the rubbery polymer is Z% by weight. The styrene-based monomer or the mixture thereof is controlled to have a conversion rate within a range satisfying the following formula (I) 42 ≦ X + 2.33 × Y + (Z-40) ≦ 52 (I). A method for producing a high-gloss rubber-modified styrene resin composition. 4. The rubber according to claim 3, wherein 0.0005 to 0.007 parts by weight of an organic peroxide is added to 100 parts by weight of a solution in which the rubbery polymer is dissolved when the rubbery polymer is made into particles. A method for producing a modified styrene resin composition.