JPS6011517A - Monovinyl aromatic resin composition - Google Patents

Abstract

PURPOSE:The titled composition excellent in impact resistance and excellent also in gloss and appearance, prepared by dissolving a specified rubber in a monovinyl aromatic monomer and polymerizing the mixture so as to form flexible component particles having a surface mean diameter, a degree of grafting and a degree of crosslinking each in a specified range. CONSTITUTION:High-cis-polybutadiene rubber (e.g., one having a 1,4-cis bond content >=78mol%, a 1,2-vinyl bond content <=20mol%, and a solution viscosity, as measured in a 5% styrene solution at 25 deg.C, of 20-200cSt) is dissolved in 88-98wt% monovinyl aromatic monomer (e.g., styrene), and the mixture is polymerized to form a resin composition in which flexible component particles are dispersed. The polymerization is conducted so that the flexible component particles may have a surface mean diameter of 0.5-1.5mum, a degree of grafting of 24-35%, and a degree of crosslinking of 40-55%. It is possible to obtain the titled composition excellent in impact resistance, gloss and appearance, and free of an iridescent appearance.

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 excellent impact resistance, as well as excellent gloss and appearance.

Conventionally, a composition in which styrene is polymerized in the presence of low-cis polybutadiene rubber has been known as a polystyrene-based resin composition that has no pearl patterns and has an excellent appearance (Japanese Patent Application Laid-open No. 72010/1983). , impact resistance is insufficient.

In addition, a composition in which styrene is polymerized in the presence of high-cis polybutadiene rubber is known as a polystyrene-based resin composition with excellent gloss and impact resistance.
No. -86444, ■No. 54-141838, ■ No. 57
-143313). However, the composition shown in (2) has the drawback of exhibiting a pearl-like appearance, and its impact strength is also insufficient. Furthermore, the compositions shown in (1) and (2) have the disadvantage of poor balance between impact resistance and gloss.

The present inventors have conducted extensive research in order to eliminate the above-mentioned conventional drawbacks. As a result, the present inventors achieved excellent rain resistance by adjusting the grafting ratio and degree of crosslinking to specific ranges in addition to the area average diameter of the particles of the desired component produced when high-cis polybutadiene rubber was dissolved and polymerized. The inventors discovered that it is possible to obtain a monovinyl aromatic resin composition that has hardening properties and hard gloss and appearance.17 This led to the completion of the present invention.

That is, the present invention provides monovinyl aromatic monomer M 88 to 98
In a resin composition in which conductive component particles obtained by dissolving and polymerizing 12 to 2 fl% of high-cis polybutadiene rubber in a maximum weight percent, the soft component particles have a particle size of 065 to 1.5μ
area average diameter, grafting rate of 24-65%, 40-55
% of crosslinking.

The monovinyl aromatic monomer ht 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 tit ht compounds that can be copolymerized with styrene include acrylonitrile, methyl methacrylate, and α-methylstyrene-substituted motsupromustyrene. 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, high-cis polybutadiene rubber can be produced, for example, by polymerizing 1,3-butadiene using a catalyst containing an organoaluminum compound and a cobalt or nickel compound. Here, the high-cis polybutadiene rubber contains at least 1,4-cis bonds and 1,2-vinyl bonds, and the amount of 1,4-cis bonds is usually 78 mol% or more, preferably It is 80-97 mol%.

If the amount of 1.4-cis bond is less than 78 mol%, the impact strength of the resulting resin composition will decrease, which is not preferable.

In addition, the amount of 1,2-vinyl bond is usually 20 mol% or less,
Preferably it is 1 to 10 mol%. Here, if the amount of 1,2-vinyl bond exceeds 20 mol %, the impact strength of the resulting resin composition will decrease, which is not preferable. Furthermore, this high-cis polybutadiene rubber preferably contains a 1.4-trans bond, and the amount of the 1.4-)lance bond is usually 2 mol % or less. The microstructure of this high-cis polybutadiene rubber can be determined by measuring its infrared absorption spectrum and using the Morello method or the like. In addition, this high-cis polybutadiene rubber usually has a solution viscosity of 2 in a 5% styrene solution at 25°C.
0 to 200 centistokes, preferably 30 to 150 centistokes
Centistokes ones are good. If the solution viscosity is less than 20 centistocs, the impact strength of the resulting resin composition is undesirably reduced. Moreover, if it exceeds 200 centistokes, the gloss of the resulting resin composition will decrease, which is not preferable.

The amount of the monovinyl aromatic monomer and high-cis polybutadiene rubber blended is that the former is usually 88 to 98% by weight, preferably 90 to 96% by weight, and the latter is usually 12 to 2% by weight, preferably It is 10-5%. 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 contains 88 to 98% by weight of the above monovinyl aromatic monomer.
In a resin composition in which soft component particles obtained by dissolving and polymerizing 12 to 2% by weight of high-cis polybutadiene rubber are dispersed, the area average diameter, grafting ratio, and degree of crosslinking of the soft component particles are adjusted to a specific range. It is characterized by the fact that Note that the soft component particles herein refer to rubber-like 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
-1.5μ, preferably 0.7-1.5μ.

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 gloss of the resulting resin composition will decrease, which is not preferable.

The area average diameter is determined by taking an electron microscope photograph 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) - ΣnD3/ΣnD2 (where n indicates the number of particles of the soft component in the particle size.) Next, the grafting rate of the soft component in the present invention is usually 24
-35%, preferably 26-64%. If the grafting rate of the soft tt component is less than 24%, the disclosed strength of the resulting resin composition will decrease, which is not preferable. Also, 35
If it exceeds %, the gloss of the resin composition to be decorated will decrease, which is not preferable.

The grafting rate was determined by measuring solid echo signals using pulsed NMR, and using the following formula using the signal intensities of butadiene and styrene as their respective implications.

(However, the graft gel contains methyl ethyl ketone/acetone-1/1 solvent.) In addition, the degree of crosslinking of the soft component in the present invention is usually 40 to 5.
5%, preferably 43-50%.

If the degree of crosslinking of the soft component is less than 40%, the resulting resin composition will have a poor appearance, which is not preferred. Moreover, if the degree of crosslinking of the soft component exceeds 55%, the impact strength of the resulting resin composition will decrease, which is not preferable. In addition, the degree of crosslinking is based on the graft gel (methyl ethyl ketone/acetone-1
/1 solvent-insoluble matter) was measured by pulse NMR and determined from the attenuation rate of the spin echo signal.

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, an emulsion polymerization method, a bulk polymerization method, a bulk-suspension two-stage polymerization method, and among these, a bulk polymerization method in which styrene is polymerized in the presence of a rubber-like elastic body is used. Alternatively, a bulk-suspension two-stage polymerization method is preferred. An example of producing the resin composition of the present invention by the bulk-suspension two-stage polymerization method will be shown below.

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, the polymerization rate of styrene is adjusted to 10 to 40% while stirring at 90 to 150°C. Bulk polymerization and prepolymerization are carried out until the polymerization is completed. In this prepolymerization step, the transmission 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 is close to ioo%. Note that, if necessary, heating may be continued after this main polymerization step.

Next, the obtained slurry is dehydrated, the beads are collected and dried, and then pelletized by a conventional method to produce a resin composition. In addition, when carrying out the polymerization, as mentioned above, commonly used polymerization initiators, molecular weight regulators, antioxidants, and other additives can be used. In the composition after polymerization, styrene polymers may be added. The soft components are dispersed as particles in the hard phase of the coalescence.

The area average diameter, graph 1 ratio, and degree of crosslinking of the soft component particles are mainly adjusted in the prepolymerization step, and the relationship between these factors and the polymerization rate 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 decreases by increasing the stirring rotation speed, and increases by increasing the amount of catalyst, molecular weight regulator, or polymerization temperature.

Furthermore, the degree of crosslinking of the soft component 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 invention, the area average diameter of the soft component particles.

By adjusting the grafting rate and degree of crosslinking within a specific range,
A monovinyl aromatic resin composition having excellent impact resistance with an Izot impact strength of IL 5 kg·cm 10 nm or more can be obtained. Further, according to the present invention, it is possible to obtain a monovinyl aromatic resin composition which has an excellent gloss of 80% or more and an excellent appearance without pearl patterns or the like.

Therefore, the monovinyl aromatic resin composition of the present invention can be used as housings for electrical equipment such as televisions and radios.

It can be effectively used as a molding material for kitchen utensils, various containers, etc.

Next, the present invention will be explained by examples.

Examples 1 to 9 and Comparative Examples 1 to 6 A predetermined amount of styrene and high-cis polybutadiene rubber as shown in Table 1 were charged into a polymerization tank with an internal volume of 4 L equipped with a stirrer, and n-dodecyl mercaptan was added as a molecular weight regulator. , 1,1-di-t-butylperoxy-3 as catalyst
,3,5-)limethylcyclohexane at a rotation speed of 2.
00-800r, p, m, stirring 90-15
Prepolymerization was carried out at 0°C for 4 to 8 hours (polymerization rate 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 tons and was dispersed. Next, tertiary calcium phosphate and sodium dodecylbenzenesulfonate were added as suspension stabilizers, and 1,1-di-
Add t-butylperoxy-3,5,5-trimethylcyclohexane and dicumyl peroxide,
Polymerization was carried out at 0-150°C for 3-12 hours.

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.

Claims (2)

[Claims] (1) In a resin composition in which soft component particles obtained by dissolving and polymerizing 12 to 2% tit of high-cis polybutadiene rubber in 88 to 98% by weight of a monovinyl aromatic monomer are dispersed, the soft component particles A monovinyl aromatic resin composition having an area average diameter of 0.5 to 1.5 μ, a grafting rate of 24 to 35%, and a degree of crosslinking of 40 to 55%. (2) High-cis polybutadiene rubber contains 78 mol% or more of 1,4-cis bonds and 20 mol% of 1,2-vinyl bonds.
2. The monovinyl aromatic resin composition according to claim 1, which has a solution viscosity of 20 to 200 centistokes in a 5% styrene solution at 25°C.