JPH01198651A - Rubber-modified styrene resin composition - Google Patents

Abstract

PURPOSE:To obtain the above composition having remarkably improved impact strength and suitable as a substitute for ABS resin for housing of electric appliance, etc., by specifying the content of a rubbery elastomer and the particle diameter, particle diameter distribution, etc., of a soft component containing the rubbery elastomer. CONSTITUTION:The objective composition contains a matrix-forming styrene resin and a rubber elastomer. The soft component of the composition has particle form having an average particle diameter of 0.2-2.6mum, preferably 0.4-2.3mum and a particle diameter distribution characterized by two peaks in <0.8mum and >=0.8, respectively. The soft component is dispersed at a ratio to give a rubbery elastomer content of 5-10wt.%. The ratio of the swelling index [SI] of the soft component particle in toluene to the intrinsic viscosity [eta]of the resin matrix [SI]/[eta] is 17-23.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention relates to a rubber-modified styrenic resin composition with improved impact strength.

More specifically, the content of the rubber-like elastic body used as a toughening agent, the particle size, particle size distribution, degree of swelling of the soft component containing the rubber-like elastic body (hereinafter referred to as the soft component), and the resin matrix) The present invention relates to a rubber-modified styrenic resin composition that has an IJ sock viscosity within a specific range and has significantly improved impact strength.

<Prior art> In order to improve the impact strength of hard and brittle styrene resin,
Blending rubber-like elastic material and styrene polymer,
Obtaining a rubber-modified styrenic resin composition by polymerizing a styrenic monomer in the presence of a rubbery elastomer,
well known.

However, impact strength is still low compared to ABS resin, and in response to recent market demands for cost reduction and thinner walls, the development of rubber-modified styrene resin compositions with impact strength comparable to ABS resin is underway. Highly desired.

Methods for improving the impact strength of rubber-modified styrene resin compositions include, for example, JP-A-57-172948, JP-A-57-187345, and JP-A-57-18734.
No. 6, JP-A No. 60-166338, and JP-A No. 61-85461, etc., all of which include the addition of organic polysiloxane or two types of styrene-based impact strength modifiers. It is a copolymerization of monomers, and the disadvantage of such impact strength improvement methods is that it costs money to purchase additives, install supply equipment, and store and blend the two types of styrenic monomers. Furthermore, the degree of improvement in impact strength cannot be said to be sufficient.

<Problems to be Solved by the Invention> The present inventors aimed to solve this problem and significantly improve the impact strength of a rubber-modified styrenic resin composition without adding an impact strength improver to 1. As a result of intensive research, we found that by specifying the content of the rubber-like elastic body, the particle size of the soft component, the particle size distribution, the degree of swelling, and the intrinsic viscosity of the resin matrix, a significant improvement in impact strength was observed. The present invention has now been completed.

<Means for Solving the Problems> That is, the present invention provides a rubber-modified styrenic resin composition in which a styrene resin forms a matrix and a soft component containing a rubber-like elastic body is dispersed in the form of particles. , (A) the average particle diameter of the soft component particles dispersed in the composition is 0.2 to 2.6 μ; (B) the particle size distribution of the soft component is in a range of less than 0.8 μ; each has a maximum value within the above range, (C) the content of the rubbery elastic body is 5.0 wt% or more and 10.0 wt% or less of the resin composition, and (D) the soft component particles are contained in toluene. The ratio [SI]/[η] between the degree of swelling [SI] and the intrinsic viscosity [η] of the resin matrix is 17 to
The present invention relates to a rubber-modified styrenic resin composition characterized in that the rubber-modified styrenic resin composition is within the range of No. 23.

In order to achieve the object of the present invention, as described above, the content of the rubber-like elastic body, the average particle diameter of the soft component, the particle diameter distribution, the ratio of the swelling degree and the IJ Fuchs intrinsic viscosity of the resin material are respectively specified. It is necessary.

This will be explained in more detail below.

The rubber-modified styrenic resin used in the present invention can be produced by a bulk polymerization method in which an aromatic monovinyl monomer is polymerized in the presence of a rubber-like elastomer, or a two-stage bulk-suspension polymerization method. .

Styrene is common as an aromatic monovinyl monomer, but 0-methylstyrene, m-methylstyrene,
Alkyl substituted styrenes such as p-methylstyrene can also be used.

Examples of rubber-like elastic bodies include polybutadiene, styrene-butadiene copolymers, ethylene-propylene copolymers, ethylene-propylene-nonconjugated diene terpolymers, isoprene polymers, and styrene-isoprene copolymers. Copolymers are used, among which polybutadiene is most preferably used. As the polybutadiene, both high-cis polybutadiene with a high cis content and low-cis polybutadiene with a low cis content can be used.

In the rubber-modified styrenic resin composition of the present invention, the soft component is dispersed in the form of particles, and the average particle size of the soft component is in the range of 0.2 to 2.6μ, preferably 0.4 to 2.6μ.
It is necessary that it be in the range of 3μ. The average particle diameter is 0
．． Even if it is smaller than 2μ or larger than 2.6μ, the impact strength improvement effect decreases.

The average particle diameter referred to here is calculated by taking a transmission electron microscope photograph of an ultra-thin section of rubber-modified styrene resin, measuring the particle diameter of 500 soft component particles in the photograph, and using the following formula. be.

Here, n+ is the number of soft component particles having a particle diameter DI.

In addition, in the present invention, the particle size distribution of the soft component particles (B) has separate maxima in a range of less than 0.8μ and a range of 048μ or more, preferably a range of 0.5μ or less and a range of 3.0μ or more. It is necessary to have a value. If the particle size distribution has only one maximum value or if the maximum value is only within one of the above ranges, the effect of improving the impact strength will not be recognized or will be small.

The particle size distribution referred to here is n110 at the time of average particle size measurement.
Although this is a distribution obtained from the i value, it is also possible to use a special analytical device that measures the distribution of fine particles, such as a Coulter counter, taking into account the difference from the measured value from an electron micrograph. good.

The average particle size and particle size distribution of the soft component specified in the present invention can be determined by changing the stirring intensity in the polymerization process, the polymerization temperature, the amount of the polymerization initiator and chain transfer agent, or by changing the polymerization solution in which polymerization has progressed. It can be adjusted by feeding back a part of the amount to the monomer, or by providing two polymerization tanks, taking out a predetermined amount of polymerization liquids with different degrees of polymerization, mixing them, and then completing the polymerization.

Furthermore, by mixing a predetermined amount of two or more types of rubber-modified styrenic resins having different average particle diameters and particle diameter distributions of the soft components, it is also possible to obtain the above-mentioned specific average particle diameter and particle diameter distribution.

In addition, the amount of rubber-like elastic body contained in the resin composition is
5. Qwt% or more and 10.3wt% or less, preferably,
5. It must be adjusted to between Qwt% and 9.3wt%. Rubber-like elastic material content is 5. In the case of Qwt% non-vortex, the effect of improving impact strength becomes small or does not appear.

When the rubber-like elastic body content exceeds 10.9 wt%, the heat resistance and rigidity of the resin composition decrease, and as a functional material,
It becomes difficult to use.

Furthermore, the degree of swelling of the soft component particles in toluene [S'l
: ] and the resin mass from which the rubber-like elastic body has been removed) and the IJ Fuchs intrinsic viscosity [η] [:SI'] / (η) is 17
-23, preferably 19-22. Even if C3I3/[η] is smaller than 17,
Even if it is larger than 23, the effect of improving impact strength will not be recognized or will be small.

The degree of swelling [:Sr1] referred to in the present invention is measured by the following method. That is, 1.0 gr of the resin composition is dissolved in 50 ml of toluene at room temperature, and the undissolved gel content is precipitated and collected by centrifugation. The gel fraction is then isolated by decanting the solution and weighed wet. Then dry and reweigh.

Wet weight of soft component is W, (gel content), dry weight is L
The degree of swelling [SI] is defined by the following formula.

1!12 Swelling degree C3I: ] is considered to be such that the larger the value, the smaller the degree of crosslinking of the soft component, and the softer the material.

In addition, the intrinsic viscosity [η] of the resin matrix is determined by mixing 0.5 gr of the resin component with methyl ethyl ketone/methanol = 10
/1 solution 50ml! After dissolving the undissolved gel in a solution and centrifuging to precipitate the undissolved gel, the supernatant is transferred to methanol 1β and the resin component is reprecipitated. After filtration, 100 mg of the dried precipitate was accurately weighed, dissolved in 30 rnl of toluene,
This value was measured using an Ubbelohde capillary viscometer at a temperature of 30°C. It is thought that the larger the value of the intrinsic viscosity [η], the thicker the molecular weight of the resin matrix.

Examples are shown below, but the present invention is not limited only to the examples.

<Example> The Izod impact strength shown in the example and comparative example is J
Measured based on IS K7110.

Example-1 Rubber-modified polystyrene (hereinafter abbreviated as PS) with an average particle diameter of 0.2 μ as a soft component and 11 with an average particle diameter of 4.9 μ
After PS was mixed 90/10, injection molding was performed. The ratio of the degree of swelling of this sample to the viscosity of the resin matrix (hereinafter [:S
r1/Cη] was 20.7, and the Izod impact strength was as high as 11.4 kg-cm/c+n.

Example-2 Old PS with average particle size of soft component 0.2μ and average particle size 4
．． After mixing 9μ of old PS in a ratio of 75/25, injection molding was performed. The [SI]/[η] of this sample was 19.5, and the Izod impact strength was as high as 11.3 kg-Cm/Cm.

Example-3 Old PS with average particle size of soft component of 0.2μ and average particle size of 4
．． After mixing 2μ of old PS with 50150, injection molding was performed. The C3l)/Cη] of this sample was 20.3, and the Izot impact strength was as high as 11.1 kg-cm 7 cm.

Comparative Example-1 Old PS with average particle size of soft component 0.2μ and average particle size 4
．． After mixing 2μ of old PS at 5/95, injection molding was performed. The average particle size of this sample was 4.0μ, [SI:]
/Cη] was 19.2, the Izot impact strength was as low as 8.1 kg-cm/cm.

Comparative Example-2 Old PS with a soft component having an average particle diameter of 1.6 μm was injection molded. Although the [SI] / Cη] of the sample after molding is 20.6, the Izod impact strength is as low as 7.3 kg-cm/cm because the particle size distribution has only one maximum value. Became.

Comparative Example-3 Old PS with average particle size of soft component 1.0μ and average particle size 1
．． After mixing 6μ of old PS at 25/75, injection molding was performed.

The average particle diameter of this sample is 1.5 μ, [Sl:] / [
η] was 19.4, the maximum value of the particle size distribution was only in the range of 0.8μ or more, so the Izot impact strength was as low as 7.4 kg-cm/cm.

Comparative Example 4 After mixing the soft component of old PS with an average particle size of 0.2 μm and an average particle size of 1.0 μm in a ratio of 10/90, injection molding was performed.

The average particle size of this sample was 0.9μ, and although the maximum value of the particle size distribution was divided into the ranges of less than 0.8μ and 0.8μ or more, [SI]/[η] was 16.5 Because of its small size, the Izot impact strength showed a low value of 7.0 kg-cm/cm.

Table 1 summarizes the Examples and Comparative Examples.

Examples 4 to 5, Comparative Examples 5 to 6 The old PS used in Example 1 with an average particle size of 0°2μ as a soft component and the old PS with an average particle size of 4.9μ were mixed in a ratio of 90/10. Polystyrene resin (hereinafter referred to as GPPS) that does not contain a rubber-like elastic body and has the same intrinsic viscosity as the resin composition
) were mixed in a ratio of 90/10 to 50,150, and then injection molded. (Sl) of these samples
/Cη], Izod impact strength measurement results are shown in Table-2.
Shown below.

<Effects of the Invention> The resin composition of the present invention has extremely high impact strength,
It can be used as a substitute for ABS resin in the housings of electrical equipment and various containers where ABS resin has been used up until now, and the economic value associated with cost reduction can be said to be extremely large.

Claims (1)

[Scope of Claims] A rubber-modified styrenic resin composition in which a styrene resin forms a matrix and a soft component containing a rubber-like elastic body is dispersed in the form of particles; The average particle size of the dispersed soft component particles is 0.2 to 2.6μ, and (B) the particle size distribution of the soft component has maximum values in a range of less than 0.8μ and a range of 0.8μ or more, respectively. (C) The content of the rubber-like elastic body is 5.0 wt% or more of the resin composition.
0.0 wt% or less, and (D) the ratio [SI]/[η] of the swelling degree [SI] of the soft component particles in toluene to the intrinsic viscosity [η] of the resin matrix is 17 to 2.
3. A rubber-modified styrenic resin composition characterized by being in the range of 3.