JPH0318646B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a monovinyl aromatic resin composition, and more particularly to a monovinyl aromatic resin composition that has high impact strength and excellent gloss and appearance. Conventionally, a composition obtained by polymerizing styrene in the presence of polybutadiene with a high content of 1,4-cis bonds has been known as a polystyrene resin composition with excellent gloss and impact resistance (Japanese Unexamined Patent Application Publication No. 1989-1992). −86444
issue). However, this composition has the drawback of exhibiting a pearl-like appearance and also has insufficient impact strength. In addition, as a polystyrene resin composition with excellent appearance without pearl patterns etc., it is a low cis type and 1,2-
A composition has been proposed in which styrene is polymerized in the presence of polybutadiene rubber with a high vinyl bond content, and the particle diameter of the soft component particles produced at that time is specified (Japanese Patent Application Laid-open No. 72010/1989), but It was inferior in sex. The present inventors have conducted extensive research in order to eliminate the above-mentioned conventional drawbacks. As a result, the present inventors found that when low-cis polybutadiene rubber is melt-polymerized, by adjusting the area average diameter of the soft component particles produced, as well as the grafting ratio and degree of crosslinking, to a specific range, excellent gloss and appearance can be obtained. The present inventors have discovered that a polystyrene resin composition having excellent impact resistance can be obtained, and have completed the present invention. That is, the present invention provides monovinyl aromatic monomer 88
~98% by weight, 1 to 30 mol% of 1,2-vinyl bonds, 30 to 42 mol% of 1,4-cis bonds, 1,4-
In a resin composition obtained by dissolving and polymerizing 12 to 2% by weight of a low cis polybutadiene rubber containing 40 to 57 mol% of trans bonds, the low cis polybutadiene rubber contains the monovinyl aromatic monomer in the resin composition. Rubber-like soft component particles produced by graft polymerization with the polymer are dispersed, and the soft component particles have an area average diameter of 0.5 to 1.5 μ, a grafting rate of 30% or more, and a degree of crosslinking of 55% or less. The present invention provides a monovinyl aromatic resin composition having the following characteristics. The monovinyl aromatic monomer used in the present invention includes not only styrene alone but also a mixture of styrene and other vinyl monomers that can be copolymerized with styrene. Examples of other vinyl monomers that can be copolymerized with styrene include acrylonitrile, methyl methacrylate, α-methylstyrene, and nuclear-substituted monobromstyrene.
The mixing ratio of these vinyl monomers is usually 30% by weight or less, preferably 10% by weight or less of the total monomers. Next, low-cis polybutadiene rubber can be produced by polymerizing 1,3-butadiene using an organolithium catalyst using a known method, for example, as described in JP-A-53-130793. Here, the low-cis polybutadiene rubber contains 1,2-vinyl bonds, 1,4-cis bonds, and 1,4-trans bonds, and the content of 1,2-vinyl bonds is usually 1 to 30 mol. %, preferably 5-20
It is mole%. The content of 1,2-vinyl bonds is 1
If it is less than mol%, the appearance of the resulting resin composition will deteriorate, which is not preferable. Moreover, if the content of 1,2-vinyl bonds exceeds 30 mol%, the impact strength of the resulting resin composition will decrease, which is not preferable. Next, the content of 1,4-cis bonds is usually 30
~42 mol%, preferably 35-40 mol%. Here, if the content of 1,4-cis bonds is less than 30 mol%, the impact strength of the resulting resin composition decreases, which is not preferable. Moreover, if the content of 1,4-cis bonds exceeds 42 mol%, the appearance of the resulting resin composition will deteriorate, which is not preferable. 1,4-
The content of trans bonds is usually 40 to 57 mol%, preferably 45 to 55 mol%. The microstructure of this low-cis polybutadiene rubber can be determined by measuring its infrared absorption spectrum and using the Morello method or the like. In addition, the solution viscosity of this low-cis polybutadiene rubber is usually 30 to 150cst,
Preferably 50 to 100 cst. The amount of the above monovinyl aromatic monomer and low cis polybutadiene rubber is usually 88 to 98% by weight, preferably 90 to 96% by weight, and the latter is usually 88 to 98% by weight, preferably 90 to 96% by weight.
12-2% by weight, preferably 10-5% by weight.
If the latter content is less than 2% by weight, the impact strength of the resulting resin composition will decrease, and if it exceeds 12% by weight, it will be difficult to uniformly disperse the soft component particles using the solution polymerization method. So I don't like it. The present invention provides a resin composition in which soft component particles obtained by dissolving and polymerizing 12 to 2% by weight of low cis polybutadiene rubber in 88 to 98% by weight of the monovinyl aromatic monomer are dispersed, the area of the soft component particles being It is characterized in that the average diameter, grafting rate, and degree of crosslinking are adjusted to specific ranges. Note that the soft component particles herein refer to rubber particles produced by graft polymerization of polybutadiene rubber with an aromatic monomer. The area average diameter of the soft component particles in the present invention is usually 0.5 to 1.5μ, preferably 0.7 to 1.3μ. If the area average diameter of the soft component particles is less than 0.5 μm, the impact strength of the resulting resin composition will decrease, which is not preferable. Moreover, if it exceeds 1.5μ, the resulting resin composition will have poor gloss, which is not preferable. In addition,
The area average diameter is determined by taking an electron micrograph of the resin using an ultrathin section method, measuring the particle diameters of 200 to 500 soft component particles in the photograph, and averaging the area according to the following formula. Area average diameter (μ) = ΣnD ³ /ΣnD ² (However, n indicates the number of particles of the soft component with particle diameter D.) Next, the grafting rate of the soft component in the present invention is usually 30% or more, preferably It is 33-45%. If the grafting ratio of the soft component is less than 30%, the impact strength of the resulting resin composition decreases, which is not preferable. The grafting rate was determined by measuring solid echo signals using pulsed NMR, and using the signal intensities of butadiene and styrene as their respective contents using the formula below. Grafting rate (%) = Styrene content in graft gel/
(Styrene + butadiene) content in the graft gel x 100 (However, the graft gel contains methyl ethyl ketone/
Acetone = 1/1 solvent insoluble matter. ) Furthermore, the degree of crosslinking of the soft component in the present invention is usually
55% or less, preferably 50-45%. If the degree of crosslinking of the soft component exceeds 55%, it is not preferable because the impact strength of the resulting resin composition decreases. In addition,
The degree of crosslinking was determined from the attenuation rate of the spin echo signal by measuring pulse NMR of the graft gel (methyl ethyl ketone/acetone = 1/1 solvent insoluble portion). The resin composition of the present invention having such characteristics can be produced by applying any known polymerization method as long as the above characteristics are satisfied. Such known polymerization methods include, for example, emulsion polymerization, bulk polymerization, bulk-suspension two-stage polymerization, etc. Among these, bulk polymerization, in which styrene is polymerized in the presence of a rubber-like elastic body, is used. Alternatively, bulk-suspension two-stage polymerization is preferred. below,
An example of manufacturing the resin composition of the present invention by a bulk-suspension two-stage polymerization method will be shown. First, polybutadiene is added to styrene and, if necessary, heated and dissolved. It is preferable to perform this dissolution as uniformly as possible. Next, in the presence of a molecular weight regulator such as alkyl mercaptan and a polymerization catalyst such as diacyl peroxide or dialkyl peroxide used as necessary,
Prepolymerization is carried out by bulk polymerization at 150° C. with stirring until the polymerization rate of styrene reaches 10 to 40%. In this prepolymerization step, the soft component is dispersed into particles by stirring. After completing the above prepolymerization step, suspension polymerization is carried out by suspending in an aqueous phase containing tertiary calcium phosphate, polyvinyl alcohol, etc. as a suspending agent. Usually, polymerization (main polymerization) is carried out until the polymerization rate approaches 100%. Note that, if necessary, heating may be continued after this main polymerization step. Next, the resulting slurry is dehydrated, the beads are separated and dried, and then pelletized by a conventional method to produce a resin composition. In the composition after polymerization, the soft component is dispersed as particles in the hard phase of the styrene polymer. The area average diameter, grafting ratio, and degree of crosslinking of the soft component particles are mainly adjusted in the prepolymerization step, and the relationship between these factors and polymerization conditions is as follows. First, the area average diameter of the soft component particles becomes smaller by increasing the stirring rotation speed or by increasing the amount of catalyst, and becomes larger by increasing the molecular weight regulator. Next, the grafting rate of the soft component particles is decreased by increasing the stirring rotation speed, and increased by increasing the amount of catalyst, molecular weight regulator, or polymerization temperature. Furthermore, the degree of crosslinking of the soft component particles is increased by increasing the amount of catalyst or by increasing the polymerization temperature, and decreased by increasing the molecular weight regulator. Therefore, the soft component particles can be adjusted by operating in consideration of the above relationship. According to the present invention, the area average diameter of the soft component particles,
By adjusting the grafting rate and degree of crosslinking within specific ranges, it is possible to obtain a monovinyl aromatic resin composition with excellent impact resistance, having an Izot impact strength of 11.5 Kg·cm/cm or more. Furthermore, according to the present invention, it is possible to obtain a monovinyl aromatic resin composition that is free from pearl patterns, has an excellent appearance, and has excellent gloss. Next, the present invention will be explained by examples. Examples 1 to 8 and Comparative Examples 1 to 6 A predetermined amount of styrene and low cis polybutadiene rubber as shown in Table 1 were charged into a polymerization tank with an internal volume of 4 and equipped with a stirrer, and n-dodecyl mercaptan and n-dodecyl mercaptan were added as molecular weight regulators. 1,1-di-t as a catalyst
Prepolymerization was carried out using -butylperoxy-3,3,5-trimethylcyclohexane at 100°C for 6 hours under stirring at a rotational speed of 500 rpm until the polymerization rate reached 40%. After the preliminary polymerization was completed, the polymer was added to the aqueous phase of a polymerization tank with an internal volume of 10 and was dispersed. Next, tertiary calcium phosphate and sodium dodecylbenzenesulfonate were added as suspension stabilizers, and 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane and dicumyl peroxide were added as polymerization initiators. 5 at 140℃
Time suspension polymerization (main polymerization) was performed. The obtained granular polymer was filtered and dried to obtain a resin composition. Table 1 shows the measurement results of the physical properties of the obtained resin composition.

【table】

[Table] *1: Catalyst 1...1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane *2: Molecular weight regulator...n-dodecyl mercaptan *3: Catalyst 2...dicumyl peroxide *4: Compliant with JIS K 7110. *5: Compliant with JIS Z 8741.

Claims (1)

[Claims] 1 88 to 98% by weight of monovinyl aromatic monomer,
1 to 30 mol% of 1,2-vinyl bonds, 30 to 42 mol% of 1,4-cis bonds, and 1,4-trans bonds.
Low cis polybutadiene rubber containing 40-57 mol%
In a resin composition obtained by dissolving and polymerizing 12 to 2% by weight, a rubbery soft component produced by graft polymerization of the low cis polybutadiene rubber with the monovinyl aromatic monomer in the resin composition. The particles are dispersed, and the soft component particles are 0.5~
Area average diameter of 1.5μ, grafting rate of more than 30%, 55%
A monovinyl aromatic resin composition having the following degree of crosslinking.