JP2698862B2 - Rubber particles containing resin fine particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a so-called occluded polymer (a polymer embodied in a rubber-like polymer) having a high impact resistance reinforcing effect and a high thermal stability. It relates to rubber particles contained in high density.

(Prior art) A so-called graft rubber obtained by graft-polymerizing a monomer onto a rubber-like polymer is a high-impact polystyrene (HIPS).
And ABS resin, which have a high effect of imparting impact resistance, and form a group of resin compositions that are extremely useful in practical use.

It is known that these rubber reinforcing effects are greatly influenced by rubber properties (gel content, swelling index, glass transition temperature), graft ratio, etc., and various efforts have been made to improve impact resistance.

The method for producing these resins is roughly classified into a bulk polymerization method, an emulsion polymerization method, and a suspension polymerization method, and a method in which these are combined is also performed, but the bulk polymerization method and the emulsion polymerization method are industrially used. Widely used.

In the case of the bulk polymerization method, a rubbery polymer is dissolved in a monomer or a hydrocarbon solvent and then polymerized.
A rubbery polymer is produced by grafting a monomer to the polymer, forming particles by utilizing phase separation of the grafted rubbery polymer as the monomer is converted into a polymer, and generating a crosslinked structure at a high temperature. Therefore, the amount of the rubbery polymer in the polymer is at most 20 parts by weight, and the graft polymer and the matrix polymer formed by polymerization are manufactured under the same polymerization conditions. It is a method that can not be done.

On the other hand, in the case of the emulsion polymerization method, it is produced by adding a monomer in the presence of a rubbery polymer latex and performing graft polymerization by the emulsion polymerization method. According to this method, the degree of crosslinking and the degree of swelling of the rubbery polymer used can be arbitrarily changed, and the graft ratio can be relatively easily controlled. Various efforts have been made for improvements.

For example, in JP-A-62-164707, a graft copolymer layer comprising an aromatic vinyl compound and a vinyl cyanide compound is formed on the surface of rubber particles, and the average thickness thereof is controlled to 100 to 200 mm. Describes that the resulting resin composition has excellent surface gloss and impact resistance.

In JP-A-63-69855, a copolymer comprising an aromatic vinyl compound and a vinyl cyanide compound in rubber particles is used in an amount of from 20 to 20% based on the total amount of rubber and the copolymer contained in rubber. A technique is disclosed in which the impact resistance of an ABS resin is improved by using a graft rubber containing 10% or more of a copolymer having a particle diameter of 0.1 μm or more among 50% by weight of a contained copolymer. ing.

However, it is known that the graft copolymer produced by such a method comprises a graft polymer and a free polymer (non-grafted homopolymer) formed at the same time. Therefore, in order to increase the grafting efficiency, the catalyst, rubber concentration, and monomer concentration are industrially optimized, but it is not easy to increase the grafting efficiency. Has become.

(Problems to be Solved by the Invention) In the present invention, rubber particles are filled with resin particles at a very high density, thereby exhibiting an effect of reinforcing impact resistance effectively with a small rubber content and having high thermal stability. It is intended to give rubber particles.

(Means for Solving the Problems) As a result of intensive studies to solve the above problems, the use of rubber particles having a high density occluded structure graft-polymerized by a specific method significantly increases the impact resistance of the matrix resin. And found that they had excellent thermal stability, and reached the present invention.

That is, a large number of resin particles are filled in the rubber independently of each other, and the weight ratio of the rubber to the resin is 8: 2.
~ 2: 8, and the amount of resin extracted when extracted with a solvent that is a good solvent for the resin component and a poor solvent for rubber /
It was found that the impact resistance of the matrix resin was remarkably increased by using rubber particles containing resin fine particles characterized by having a resin amount of 0.3 or less.

As the rubbery polymer used in the present invention, those having a glass transition temperature of 0 ° C. or lower can be used.
Specifically, polybutadiene rubbers such as polybutadiene rubber (PBR), styrene butadiene rubber (SBR), and acrylonitrile-butadiene rubber (NBR); and saturation of ethylene-propylene rubber (EPR) and ethylene-propylene-diene rubber (EPDM) Rubber; acrylic rubber such as butyl acrylate polymer; styrene-butadiene block rubber; block rubber such as hydrogenated styrene-butadiene block rubber; silicon rubber;

The average particle diameter of the rubber particles used in the present invention is in the range of 0.01 to 5.0 μm from the viewpoint of the impact resistance reinforcing effect. Preferably, the average particle size is 0.1 to 2.0
Those having a range of μm are used.

The average particle size of the rubber particles is expressed by taking an image of the dyed rubber particles with an electron microscope, measuring the particle sizes of several hundred particles in one visual field, and performing a number-average measurement.

As the resin used in the present invention, any resin having a glass transition temperature of 0 ° C. or higher can be used. Preferably, the glass transition temperature is 30 ° C. or higher, and specifically, aromatic vinyl polymers such as styrene and α-methylstyrene; acrylonitrile, vinyl cyanide polymers such as methacrylonitrile; methyl methacrylate, An acrylic polymer such as ethyl acrylate is typically used. These can be used in the form of a homopolymer or a copolymer. In the case of a copolymer, it is used if the glass transition temperature of the copolymer is 0 ° C or higher, preferably 30 ° C or higher.

In addition, these polymers (resins) can also contain various polyfunctional monomers as constituent components. Specifically, an epoxy group-containing monomer represented by glycidyl methacrylate; represented by maleic anhydride. And polymer acid anhydrides.

The average particle diameter of the resin fine particles used in the present invention, 1/4 ~ 1 of the average particle diameter of the rubber particles serving as the substrate
It is on the order of / 10.

The average particle diameter of the resin fine particles is obtained by slicing rubber particles dispersed and fixed in gelatin or the like, measuring the diameter of the resin fine particles appearing on the slice surface of the rubber particles under a microscope, and measuring the number of rubber particles. Determined by taking the number average.

As the composition of the rubber and resin constituting the rubber-like particles,
The rubber can be used within a range of not less than 20% and not more than 80% by weight. Preferably, it is used in a range of 40% or more and 80% or less. If the proportion of rubber is less than 20% by weight, the necessary impact strength reinforcing effect cannot be obtained. On the other hand, if the weight exceeds 80%, uniform dispersion in the matrix resin becomes difficult.

(Regulation of Occluded Structure of Resin) The structure of the rubber particles filled with the resin used in the present invention is such that the resin particles are filled in the rubber independently of each other as shown in attached photograph 1. It is necessary that the amount of resin extracted / the amount of resin extracted by using a solvent that is a good solvent for the resin component and a poor solvent for rubber is 0.3 or less. If the ratio of extracted resin / resin exceeds 0.3, the effect of reinforcing impact resistance is not sufficient, and the intended effect cannot be obtained.

The mechanism by which the impact resistance is effectively developed is unknown, but the resin particles are filled into the rubber,
It is presumed that the area of the interface between the rubber and the resin has increased dramatically, and that the rubber reinforcing action relating to the absorption of impact energy has occurred extremely efficiently.

The method of determining the “extracted resin amount / resin amount” is as follows:
25 g of a solvent that is a good solvent for the resin component and a poor solvent for the rubber is added to 1 g of a dry frame of the rubber particles, dissolved in a shaker for 2 hours, centrifuged at 20,000 rpm for 40 minutes with a centrifuge, and the supernatant is removed. Separate the liquid. This operation is performed twice to separate the resin component extracted with the solvent and the insoluble component in the solvent, and measure the weight% of the insoluble component. The amount of extracted resin is represented by the amount obtained by subtracting the weight of the insoluble component from the weight of the rubber particles. The resin amount is represented by the weight of the monomer added during the polymerization, which has been polymerized and converted into a polymer.

Next, an example of producing the rubber particles of the present invention will be described. First, a monomer, a polymerization initiator and, if necessary, other polymerization aids (such as a chain transfer agent) are added to the latex-shaped rubber particles, and the rubber particles are absorbed (impregnated).

Here, the rubber particles in the form of latex may be those obtained by dissolving a veil-like rubber in a solvent and then emulsifying by a mechanical method, in addition to rubber particles produced by ordinary emulsion polymerization.

At the time of absorption, it is necessary to sequentially add the monomers, the polymerization initiators, and the polymerization auxiliaries in ascending order of water solubility. The time required for absorption is longer as the solubility in water is lower, and is about 30 minutes to 3 hours. When the substance to be added is solid, it can be added after dissolving in a solvent. As a solvent for the polymerization, one having water solubility and oil solubility, for example, acetone is typically used.

Any polymerization initiator can be used as long as it is oil-soluble, but one having high reactivity in hydrogen abstraction reaction and high graft activity is particularly preferable.

In addition, a polymerization aid such as a chain transfer agent can be used if necessary. However, if the amount of addition increases, the amount of extracted resin / the amount of resin exceeds 0.3, so the amount of addition is limited to a range not exceeding this value. You.

After all the monomers, the polymerization initiator, and the polymerization aid are added and absorbed, the mixture is heated to a predetermined temperature and a polymerization reaction is performed, whereby rubber particles containing the desired resin fine particles can be obtained.

(Examples) The present invention will be specifically described by way of examples, but the present invention is not limited thereto.

Example 1 After adding 1.4 kg of deionized water to 2.37 kg of polybutadiene rubber latex (average particle size: 3000 mm, UA1001, manufactured by Nippon Zeon Co., 54%), 900 g of styrene was added, and stirring was continued for 1 hour. Impregnated. Next, 5 g of tert-butyl-peroxy-2-ethylhexanate (Perbutyl O manufactured by NOF) is added, and stirring is continued for 30 minutes to sufficiently impregnate the rubber. Further, 350 g of acrylonitrile is added, and stirring is continued for 30 minutes in the same manner to sufficiently impregnate the rubber. Finally, 4.0 kg of deionized water was added, the temperature was raised to 80 ° C. while stirring was continued, and polymerization was carried out for 3 hours to obtain a polymer latex having a polymerization rate of 92%.

The obtained latex polymer was embedded in gelatin, stained with osmium tetroxide, and then observed with an electron micrograph of the ultrathin section. As shown in the photograph of FIG. 1, acrylonitrile-styrene was obtained. It was found that the copolymer (AS resin) particles had a unique occluded structure in which the inside of the rubber was filled with honey, and that the rubber particles had an average particle diameter of 3780 °.

In FIG. 1, a black portion represents a rubber component, and a white portion represents a resin component.

1.0 part of aluminum sulfate was added to 100 parts by weight (solid content) of the obtained polymer latex to carry out salting out, and after dehydration and collection, dried at 100 ° C. for 1 hour to obtain flakes. The flakes were dissolved in acetone, and the amount of the extracted resin / the amount of the resin was measured to be 0.07. The thermal decomposition characteristics of this flake were measured using a thermobalance (under N ₂ atmosphere).
Weight loss temperature is 370 ℃, 10% weight loss temperature is 390 ℃
Met.

(Measurement of physical properties) AS resin (AN content 30%, 10% methyl ethyl ketone solution viscosity 7.7 cps) was blended with this flake so that the rubber content was 18%, and granulated to obtain pellets. A test piece was prepared by the method described above, and the Izod impact strength was measured. As a result, the value was as high as 32 kg cm / cm.

(Comparative Example 1) The same polybutadiene rubber latex as in Example 1. 2.37
After adding 1.4 kg of deionized water to the kg, a mixed solution composed of 900 g of styrene, 5 g of tertiary butyl peroxy-2-ethylhexanate, and 5 g of acrylonitrile is added all at once. Thereafter, 4.0 kg of deionized water was added, the temperature was raised to 80 ° C. while stirring was continued, and polymerization was performed for 3 hours to obtain a polymer latex having a conversion of 89%.

The electron micrograph of the obtained polymer particles was measured by the same method as in Example 1. The result is shown in the photograph of FIG. 2, and the average particle diameter was 3500 ° and the AS contained in the rubber particles was It was found that the ratio of the resin particles was smaller than that in Example 1.

In FIG. 2, a black portion represents a rubber component, and a white portion represents a resin component.

A dried flake was prepared in the same manner as in Example 1, and the amount of extracted resin / the amount of resin was measured using acetone as an extraction solvent. The result was 0.81.

Further, when the thermal decomposition characteristics of the flakes was measured with a thermobalance (N under ₂ atmosphere), a 5% weight loss temperature 360 ° C., 10
The% weight loss temperature was 384 ° C.

When a test piece was prepared in the same manner as in Example 1, and the Izod impact strength was measured, it was as low as 15 kg cm / cm.

(Comparative Example 2) The same polybutadiene rubber latex as in Example 1. 2.37
After adding 1.4 kg of deionized water to each kg, the temperature was raised to 70 ° C. with stirring, and a mixed solution consisting of 900 g of styrene, 350 g of acrylonitrile, 5 g of cumene hydroperoxide, sodium formaldehyde sulfoxylate, ferric sulfate, and EDTA Was added successively over 6 hours to polymerize. After one hour polymerization, the polymerization rate was measured.
%Met.

When the electron micrograph of the obtained polymer particles was measured in the same manner as in Example 1, the average particle diameter was 3200 ° and the ratio of the AS resin particles contained in the rubber particles was as shown in Example 1.
It was found that the number was extremely small compared to.

Dry flakes were prepared in the same manner as in Example 1, and the amount of extracted resin / the amount of resin was measured using acetone as an extraction solvent. The result was 0.40.

The thermal decomposition characteristics of the flakes were measured with a thermobalance (under N ₂ atmosphere). As a result, the 5% weight loss temperature was 358 ° C and the 10% weight loss temperature was 382 ° C.

A test piece was prepared in the same manner as in Example 1, and the Izod impact strength was measured. The result was 20 kg cm / cm.

The results shown in these Examples and Comparative Examples are summarized in Table 1 below.

(Effects of the Invention) In the present invention, the resin particles can be filled and encapsulated in the rubber particles at an extremely high density independently of each other. There is an effect that reinforced rubber particles having stability can be obtained.

[Brief description of the drawings]

FIG. 1 shows an electron micrograph (× 50,000 magnification) of rubber particles containing resin fine particles according to the present invention obtained according to Example 1. FIG. 2 shows an electron micrograph (× 50,000) of the reinforcing rubber particles obtained according to Comparative Example 1 based on the conventional method.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication (C08L 51/04 57:00)

Claims (1)

(57) [Claims] The rubber particles are filled with a large number of resin particles independently of each other, and the weight ratio of rubber to resin is 8: 2.
~ 2: 8, and a resin fine particle characterized in that the amount of resin extracted / the amount of resin when extracted with a solvent that is a good solvent for the resin component and a poor solvent for rubber is 0.3 or less. Rubber particles included.