JP3274491B2 - High gloss rubber modified styrenic resin composition and method for producing the same - Google Patents

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 balance between appearance and impact resistance of a molded article and having high gloss, 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 product and impact strength, and is widely used in household electric appliances, electronic equipment and the like. Recently, the cost reduction trend 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 large and more complex molded products with thinner walls. It became so. Under such circumstances, a rubber-modified styrene-based resin having good gloss, excellent moldability and high impact strength has been required.

[0003] The rubber-modified styrene-based resin is obtained by dispersing rubber particles in a styrene-based resin, and the particle size of the dispersed rubber particles has an important effect on product performance. The smaller, the better the gloss of the molded article. Usually, the rubber particle diameter (average particle diameter, the same applies hereinafter) in the rubber-modified styrenic resin is about 1.0 to 5.0 μm.
Resins in which rubber particles of m or less are dispersed have also been developed.
However, when the rubber particle diameter of the rubber-modified styrenic resin is 1.0 μm or less, the impact strength is usually significantly reduced, and there is a limit to improving the gloss while maintaining the impact strength of the molded product. In order to solve these problems, a method of blending a rubber-modified styrenic resin in which rubber particles of 1.0 μm or less is dispersed with a rubber-modified styrene resin in which particles of 1.0 μm or more are dispersed is disclosed in
6-41467, JP-A-59-1519, JP-A-63-15
241053 and U.S. Pat. No. 4,146,589. However, these methods have problems such as insufficient gloss and poor balance between impact strength and gloss.

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 having a single occlusion structure of 0.5 μm or less are dispersed in polystyrene. It is well known that they are formed in an inclined state (eg, Angew. Makromol. Chem. 58 /
59P175-198 (1977)). A method for producing a rubber-modified styrenic resin having an extremely excellent gloss and transparency of a molded product by utilizing this is disclosed in JP-B-48-1859.
4, JP-A-61-500977, 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 certainly remarkably improved as compared with the conventional rubber-modified styrene resin. However, although the impact strength has been improved, it has not been sufficient. Further, a rubber-modified styrene resin in which rubber particles having a single occlusion structure formed 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. Improve impact resistance while maintaining the gloss of molded products at a high level by blending resin-based resin and making the particle size distribution curve of the dispersed rubber particles into a two-peak shape (distribution curve having two maximum values). No. 4,493,922, JP-A-63-112646.
And so on. In these methods, although the impact strength is certainly improved, there are still problems such as insufficient gloss and the need to add polydimethylsiloxane or the like to the resin because the impact strength is insufficient. there were.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rubber-modified styrenic resin which has a significantly improved appearance and a superior impact strength as compared with conventional rubber-modified styrenic resins, and its production. It is to provide a method.

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

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the importance of the above object, and have found that, in a rubber-modified styrenic resin composition, (1) a rubber particle having a salami structure has a small particle size; (2) The rubber particles having a single occlusion structure are made into a dispersed state, the particle size distribution is made into a single mountain shape, and the volume average diameter is set to 0.1.
(3) The particle size distribution is wider than before, and the 5% value of the new 5% value of the volume-based cumulative distribution of rubber-like polymer particles, which is completely different from the conventional knowledge, is 95%. By finding a special index called the value of the ratio of the% value and controlling this, when this rubber-modified styrenic resin is used for a molded product, the appearance of the molded product,
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 styrenic resin composition obtained by dispersing rubbery polymer particles in a homopolymer or copolymer of a styrenic monomer. Particles have salami structure and single occluder
Particles having a salami structure, including particles having a John structure
The volume average diameter of the
The volume average diameter of the particles having a lution structure is 0.1 to
1.0 μm and has a single occlusion structure
The ratio of the number of particles to the total number of particles is 30 to 99%
And the ratio of the number of particles having a salami structure is 70 to 1%.
There, the volume average diameter of (b) the rubber-like polymer particles 0.2-0.8
( c ) the shape of the volume-based particle size distribution curve of the rubber-like polymer particles is composed of one peak, and ( d ) the cumulative distribution of the volume-based particle size of the rubber-like polymer particles is 5 ( E ) a 5% by weight styrene solution having a viscosity of 20 to 50 centipoise and a styrene-butadiene block having a styrene content of 25 to 50% by weight. A highly glossy rubber-modified styrenic resin composition characterized by using a rubbery polymer as a polymer as a raw material for forming rubbery polymer particles .

The present invention also provides a rubber-modified styrenic resin composition according to claim 1 which is obtained by polymerizing a solution obtained by dissolving the rubbery polymer according to claim 1 in a styrene monomer or a mixture thereof. In the production method, the amount of the styrenic polymer in the reaction vessel for converting the rubbery polymer into particles 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. Wherein the conversion of the styrene monomer or a mixture thereof is controlled 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 styrenic resin composition, wherein an organic peroxide is dissolved in an amount of from 0.0005 to 0. 0
07 parts by weight.

The styrenic monomer referred to in the present invention includes side chain alkyl-substituted styrene such as styrene, α-methylstyrene and α-ethylstyrene, vinyltoluene, vinylxylene, ot-butylstyrene, p- Examples thereof include nucleated alkyl-substituted styrenes such as t-butylstyrene and p-methylstyrene, halogenated styrenes such as monochlorostyrene, dichlorostyrene, tribromostyrene, and tetrahydrostyrene, p-hydroxystyrene, and o-methoxystyrene. , Particularly preferably, styrene,
α-methylstyrene and p-methylstyrene.
Styrene monomers can be used alone or in combination of two or more.

The rubber-like polymer particles are obtained by polymerizing a rubber-like polymer described later, that is, the above-mentioned styrene 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 dispersing in a styrene-based polymer. Here, the rubbery 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 described later are not formed, and the gloss becomes low. When the styrene content exceeds 50% by weight, the impact strength becomes low.

Further, regarding the viscosity, if the viscosity is less than 20 centipoise, the impact strength is low, and if it exceeds 50 centipoise, the gloss is reduced.

In the present invention, the rubber-like polymer particles formed as described above have a volume average particle size of 0.2 to 0.1.
It needs to be 8 μm. Here, the volume average particle diameter is measured as follows. That is, an electron micrograph of the resin was taken by an ultra-thin section method, the short diameter and the long diameter of 500 to 700 rubber particles in the photograph were measured, the average was determined as the particle diameter, and the average was obtained by the following equation. is there.

Volume average particle size = ΣnD ⁴ / ΣnD ³ (where n is the number of rubber particles having a particle size of D μm.) When the volume average particle size is less than 0.2 μm, the obtained rubber modified The impact strength of styrene resin is low,
If it exceeds 8 μm, the appearance of the molded product, especially the surface gloss, is undesirably reduced.

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

The fact that the shape of the distribution curve of the rubbery polymer particles according to the present invention consists of one peak means that the horizontal axis represents 0.1%.
When plotting the volume average particle size in μm units and the frequency on the vertical axis, the mode diameter (maximum frequency diameter) monotonically increases and the inflection point of the distribution curve is one point or less, and the mode curve diameter monotonically decreases above the mode diameter. A distribution in which the inflection point of the distribution curve is one point or less.

When the shape of the distribution curve is two peaks, the effect of improving the impact strength is obtained, but the appearance of the molded product is inferior, and the gloss gradient is particularly large. The shape of the distribution curve of the polymer particles is adjusted by the molecular weight distribution of the rubbery polymer used, the ratio of the rubbery 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 an injection-molded product, a portion in which the wall thickness changes, or a portion in which the flow state greatly changes during injection molding such as a corner-shaped portion. Indicates the difference in gloss from a standard part.

Further, in the present invention, the number of the rubber-like polymer particles is counted from the larger volume-based particle of the rubber-like polymer particles, and the number is counted, and each of them corresponds to 5% and 95% of the cumulative distribution. Particle size ratio value, ie 5% of cumulative distribution
The value of the ratio of the value to the 95% value (hereinafter referred to as the distribution coefficient) is
It must be in the range of 45. Preferably 3.5 to 40
And particularly preferably in the range of 4 to 35. If it is less than 3, the effect of improving the impact strength is low, and if it exceeds 45, the appearance of the molded product is inferior, and particularly the gloss gradient becomes large. The amount is adjusted according to the molecular weight distribution of the rubbery polymer to be used, the quantitative ratio of the rubbery polymer to be mixed, the stirring intensity during 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 term "salami structure" as used in the present invention refers to a structure of particles having a plurality of occlusions in one rubber particle when an electron micrograph is taken and observed by an ultra-thin section method of a resin. The single occlusion structure refers to a structure of particles having only one occlusion in one rubber particle.

In the present invention, among the rubber-like polymer particles, the particles having a salami structure have a volume average diameter of 0.3 to 2.0.
In the range of 0 μm, the volume average diameter of the particles having a single occlusion structure is in the range of 0.1 to 1.0 μm, and the ratio of the particles having the single occlusion structure to the total number of particles is in the 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 rubbery polymer particles is 0.2
Care must be taken to be in the range 〜0.8 μm.

If the volume average diameter of the particles having a salami structure is larger than 2.0 μm, the appearance of the molded product is inferior, and particularly the gloss gradient becomes large, and if it is less than 0.3 μm, the impact strength becomes low. On the other hand, if the volume average diameter 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%,
Gloss decreases or gloss gradient increases. If it is more than 99%, the impact strength decreases.

As a method for producing the rubber-modified styrenic resin composition of the present invention, a solution obtained by dissolving a rubbery polymer in a styrenic monomer is polymerized by bulk polymerization or bulk-suspension two-stage polymerization. In any case, the amount of the styrene-based polymer in the reaction vessel for granulating the rubber-like polymer is X% by weight, the total amount of the rubber-like polymer is Y% by weight, Assuming that the styrene content is Z% by weight, it is necessary to adjust the conversion 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) Although particles can be formed outside this range, abnormal particles are generated. When the particle size is less than 42, rubber particles appearing as rods are formed when an electron microscope photograph of the obtained product is observed,
Gloss and impact strength are reduced. On the other hand, when it exceeds 52, giant particles are generated and the gloss is reduced. Making the above formula (II) a predetermined value specifically means that the amount of the rubbery polymer in the reaction tank for granulating the rubbery polymer is large or the styrene content of the rubbery polymer is reduced. If the amount is large, the conversion of the styrene-based monomer is adjusted so that the amount of the styrene-based polymer in the reaction tank for converting the rubber-like polymer into particles increases. This means that the conversion of the styrene monomer is adjusted so that the amount of the styrene polymer in the reaction vessel to be converted is reduced.

In the present invention, the conversion of the styrene monomer is controlled by a known method, for example, the polymerization temperature, the type and concentration of the polymerization initiator used, the polymerization time, and the residence time in the case of the continuous polymerization method. Is done.

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

[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: FIG.
(A) A falling weight impact strength test was performed on three portions of the molded article 1 having the shape shown in FIG. 1 (b), that is, the portion (1), the portion (2), and the portion (3). Tip of falling weight R =
It was 6.4 m / m, and the inside diameter of the carrier was 25 m / m. The part (1) is a part where the thickness changes, the part (2) is a part near the corner, and the part (3) is a standard part. (3) Gloss: A molded product having the shape shown in FIGS. 1A and 1B according to JIS 8741 (incident angle 60 °).
(1), (2), (3)
Was measured. Example 1 A rubber-modified styrene-based resin was produced using a continuous mass polymerization apparatus in which a preheater was connected to the outlets of three reactors each having a stirrer and a vacuum tank was connected. In a first reaction vessel equipped with a stirrer, 6 parts by weight of a styrene-butadiene block copolymer having a styrene content of 38% and a 5% styrene solution viscosity of 37 centipoise as a rubbery polymer, 15 parts by weight of ethylbenzene, and 79 parts by weight of styrene 1,1- as an organic peroxide
A raw material liquid consisting of 0.005 parts by weight of bis (t-butylperoxy) 3,3,5-trimethylcyclohexane was continuously supplied. Stirring of the first stirrer is 300 rpm
m, the reaction temperature was 146 ° C., and the residence time was 1 hour. The second unit is that the reaction temperature is 145 ° C. and the residence time is 2 hours.
The third unit was 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 Example 2 was performed under the same conditions as in Example 1 except that the first stirring was performed at 200 rpm. Example 3 Example 3 was performed under the same conditions as in Example 1 except that the first stirring was performed at 400 rpm. Comparative Example 1 The same operation as in Example 1 was performed except that the first stirring was performed at 100 rpm. The average particle size of the rubbery polymer particles in the obtained product was as large as 0.90 μm, and the gloss was low. Comparative Example 2 The same operation as in Example 1 was performed except that the first stirring was performed at 550 rpm. The average particle size of the rubber-like polymer particles in the obtained product was as small as 0.10 μm, and the impact strength was low. Comparative Example 3 In Example 1, the reaction temperature of the first base was 143 ° C., the residence time was 2 hours, and a 5% styrene solution having a viscosity of 32 centipoise and a styrene-butadiene block copolymer having a styrene content of 42% was used as the rubbery polymer. Other than using coalescing,
Under the same conditions as in Example 1, a rubber-modified styrene resin (A) having a small particle diameter and a single occlusion structure having an average particle diameter of 0.30 μm of rubber-like polymer particles was produced. Separately, a rubbery polymer particle having an average particle diameter of 1.15 μm was prepared under the same conditions as in Example 1 except that 6 parts by weight of a 5% styrene solution polybutadiene having a viscosity of 50 centipoise was used as the rubbery polymer in Example 1. A rubber-modified styrene resin (B) having a large particle size having a structure was produced. The rubber-modified styrenic resin (A) and (B) are mixed at a ratio of 85/15,
The product was obtained by melt-kneading with an extruder. The particle size distribution of the rubbery polymer was two peaks, and the gloss gradient of the molded product was large. Comparative Example 4 Example 1 was carried out under the same conditions as in Example 1 except that the first residence time was 45 minutes. The obtained product 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 was performed under the same conditions as in Example 1 except that the first residence time was 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 directly molded and evaluated for physical properties. The gloss was high, but the impact strength was low. Comparative Example 7 In Example 1, the styrene content was 2 as the rubbery polymer.
A 0%, 5% styrene solution was prepared in the same manner 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 In Example 1, the styrene content was 5 as the rubbery polymer.
A 5% and 5% styrene solution was prepared under the same conditions 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 4 was performed under the same conditions as in Example 1 except that the reaction temperature was changed to 138 ° C. Example 5 Example 5 was carried out under the same conditions as in Example 1 except that the reaction temperature was changed to 148 ° C. 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 A reaction was performed under the same conditions as in Example 1 except that the reaction temperature was changed to 136 ° C. The conversion of the first styrene monomer was 35.5%. When the product was observed with an electron micrograph, rod-like particles were observed, and gloss and impact strength were low. Comparative Example 10 A reaction was performed under the same conditions as in Example 1 except that the reaction temperature was changed to 154 ° C. The conversion of the first styrene monomer was 53%. When the product was observed with an electron micrograph, large particles were present and the gloss was low. Comparative Example 11 Example 1 was carried out under the same conditions as in Example 1 except that the reaction temperature was 139 ° C and 0.01 parts by weight of the organic peroxide was used. The conversion of the first styrene monomer is 45%.
Met. When the product was observed with an electron micrograph, large particles were present 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 material for parts of household electric appliances and electronic equipment. The industrial use value is great in the use of the above.

[Brief description of the 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 molding

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kozo Ichikawa 1-6-6 Takasago, Takaishi City, Osaka Prefecture Inside Mitsui Toatsu Chemicals Co., Ltd. (72) Inventor Akihiko Nakajima 1-6-6 Takasago, Takaishi City, Osaka Prefecture Mitsui Toatsu Within Chemical Co., Ltd. (72) Inventor Masato Takaku 1-6-6 Takasago, Takaishi City, Osaka Prefecture Mitsui East Pressure Chemical Co., Ltd. (56) References JP-A-3-68612 (JP, A) (58) Fields investigated ( Int.Cl. ⁷ , DB name) C08F 287/00 C08F 279/02 C08L 51/04 C08L 55/02

Claims (3)

(57) [Claims] 1. A high gloss rubber-modified styrenic resin composition obtained by dispersing rubbery polymer particles in a homopolymer or copolymer of a styrenic monomer, wherein (a) the rubbery polymer particles are salami Structure and single occluder
Particles having a salami structure, including particles having a John structure
The volume average diameter of the
The volume average diameter of the particles having a lution structure is 0.1 to
1.0 μm and has a single occlusion structure
The ratio of the number of particles to the total number of particles is 30 to 99%
And the ratio of the number of particles having a salami structure is 70 to 1%.
There, the volume average diameter of (b) the rubber-like polymer particles 0.2-0.8
( c ) the shape of the volume-based particle size distribution curve of the rubber-like polymer particles is composed of one peak, and ( d ) the cumulative distribution of the volume-based particle size of the rubber-like polymer particles is 5 ( E ) a 5% by weight styrene solution having a viscosity of 20 to 50 centipoise and a styrene-butadiene block having a styrene content of 25 to 50% by weight. A high-gloss rubber-modified styrenic resin composition using a rubber-like polymer as a polymer as a raw material for forming rubber-like polymer particles. 2. The process for producing a rubber-modified styrenic resin composition according to claim 1, wherein a solution obtained by dissolving the rubbery polymer according to claim 1 in a styrenic monomer or a mixture thereof is polymerized. The amount of the styrene-based polymer in the reaction vessel for converting the rubbery polymer into particles is represented by X% by weight, the total amount of the rubbery polymer is represented by Y% by weight, and the styrene content of the rubbery polymer is represented by Z% by weight. High gloss, wherein the conversion of the system monomer or a mixture thereof is controlled in a range satisfying the following formula (I): 42 ≦ X + 2.33 × Y + (Z−40) ≦ 52 (I) A method for producing a rubber-modified styrene resin composition. 3. The rubber according to claim 2, wherein when the rubbery polymer is formed into particles, 0.0005 to 0.007 parts by weight of an organic peroxide is added to 100 parts by weight of the solution in which the rubbery polymer is dissolved. A method for producing a modified styrene resin composition.