JP3162498B2 - Foam resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foamed resin composition which is excellent in flexibility and texture and has good moldability.

[0002]

2. Description of the Related Art Recently, foam molded products have been widely demanded for interior materials such as automobiles, parts for information equipment and home electric appliances, and cushioning materials for measures against vibration and noise. Attention has been paid to thermoplastic elastomer foam moldings that meet this purpose. As a thermoplastic elastomer suitable for such use, a polystyrene-based thermoplastic elastomer can be particularly mentioned. However, these polystyrene-based elastomers have difficulty in moldability, and it is necessary to add a moldability modifier to solve this problem. However, a molding modifier usually decreases the flexibility, so that a rubber softener (plasticizer) must be added. Such a technique is disclosed in, for example, JP-A-2-120334.
The foamed molded product according to the invention is excellent in flexibility and texture and improved in the stickiness of the surface as compared with previously known techniques, but the softening agent is still used even though the amount is small. Since it is used, bleed-out of the softener when used for a long period of time is unavoidable, and the usable applications are limited. Moreover, since the expansion ratio was as low as 1.35 times or less, the foam was a molded article having insufficient flexibility. Therefore, in recent years, these techniques cannot cope with the use of a foam molded article requiring more flexibility and durability, and a further improved technique has been demanded. The present invention
An object of the present invention is to provide a foamed resin composition excellent in moldability, in which a foamed resin molded article having a high expansion ratio can be obtained without using any softener which has alleviated the above disadvantages.

[0003]

That is, the present invention provides a resin composition comprising 20 to 80% by weight of a styrene-based thermoplastic block copolymer, 5 to 60% by weight of a polyoctenamer, and 0 to 80% by weight of a polyolefin-based elastomer.
It is a foamed resin composition comprising 0.1 to 10 parts by weight of a chemical blowing agent with respect to parts by weight.

According to the present invention, a high-foamed material which is not present in conventional thermoplastic elastomers can be obtained without adding a low-molecular weight softening agent, so that the softening agent has no stickiness on the surface due to bleed-out and has an excellent feeling. And a flexible foam.

[0005] The styrene-based thermoplastic block copolymer in the present invention refers to a binary or ternary block copolymer containing styrene as one component, and is represented by AB or ABA, B-B. It is an AB type block copolymer. Here, A represents polystyrene, and B represents a block forming a rubber phase. Among them, ABA type triblock copolymers are particularly suitable for the present invention, for example, styrene-butadiene-styrene (SB
S), styrene-isoprene-styrene (SIS), styrene-ethylenebutylene-styrene (SEBS), and styrene-ethylenepropylene-styrene (SEPS) block copolymer. Among them, SBS and SIS are particularly suitable for the present invention. The weight average molecular weight of the block copolymer used in the present invention is 25,000 to
220,000 and the styrene content is 10-4.
0% by weight is desirable. Such a triblock copolymer takes a two-phase form in terms of microstructure, in which styrene is a hard segment and a rubber phase is a soft segment, exhibiting the properties of an elastomer. In the present invention, styrene block copolymers having different types and different segment lengths may be mixed and used according to the purpose. In order to reduce the hardness of the generally obtained foam, SIS
It is recommended to use

In the present invention, the styrenic block copolymer accounts for 20 to 80% by weight of the whole composition;
Within this range, the composition can be changed by the texture, flexibility and molding method according to the purpose. In general, when the content is 60% by weight or more, the foaming property decreases, and when the content is 80% or more, the mechanical strength slightly decreases. On the other hand, if the amount is less than 20% by weight, the foam lacks flexibility and a hard foam is obtained.

The polyoctenamer used in the present invention is
It is a polyolefin having a structure in which double bonds are regularly present in the molecule, one for every eight carbon atoms, and can be obtained, for example, by subjecting cyclooctene to metathesis polymerization. This regularly existing double bond has two types of configuration, cis and trans, and the crystallinity, melting point, and the like change depending on the ratio of these. Polyoctenamers suitable for the present invention have a trans content of 60-85% and a number average molecular weight of 10,000-300,000. When the trans content is less than 60%, the melting point is remarkably reduced, and the heat resistance of the foam molded article is remarkably reduced.

[0008] Polyoctenamers suitable for use in the present invention include, for example, the trade names "Vestenamer 8012" (trans content 80%) and "Vestenamer 6213" (trans content about 60%) marketed by Huls.
These are suitable for use in the present invention alone or as a mixture. The amount of polyoctenamer used in the composition of the present invention is suitably in the range of 5 to 60% by weight, and varies depending on the type and amount of other components. In the present invention, polyoctenamer plays a role of dispersing a different kind of polymer moderately, and if it is less than 5% by weight, a sufficient dispersing effect cannot be obtained. Conversely, if it is used in excess of 60% by weight, heat resistance can be significantly impaired, so it is desirable to use it at 60% by weight or less.

Next, the polyolefin elastomer used in the present invention refers to an olefin elastomer having a high degree of saturation. For example, EP rubber, EPB rubber, EPDM rubber, butyl rubber, polyisobutylene, nitrile rubber and the like can be mentioned as examples. These polyolefin elastomers are added mainly for the purpose of improving physical properties such as increasing the strength of the composition. Therefore, when the two components of the styrene-based copolymer and polyoctenamer have the desired strength, there is no need to add them.
In addition, since it also has the effect of improving dispersibility, different types of polyolefin elastomers may be used in combination,
It should not exceed 80% by weight in the composition. 80% by weight
It is not preferable if the ratio exceeds the value, since foaming becomes difficult.

The chemical foaming agent used in the present invention may be of any type, such as an inorganic decomposition type or an organic decomposition type, as long as it decomposes by heat to generate an inert gas. Well-known compounds include sodium bicarbonate, ammonium carbonate, ammonium nitrite, azide compounds such as azodicarbonamide, azobisformamide, isobutyronitrile, diazoaminobenzene, and N, N-dinitrosopentamethylenetetramine. and so on. It is common practice to mix and use different types of blowing agents. Further, a foaming aid for adjusting the decomposition temperature, a dispersant for uniformly dispersing the foaming agent, a nucleating agent, and the like may be mixed and used. The amount of the chemical foaming agent used is 0.1 to 10 parts by weight based on 100 parts by weight of the resin, and the amount of the foaming agent is appropriately adjusted within this range according to the state, texture and flexibility of the molded product. Can be used.

The foamed resin composition of the present invention can be made into a foam by any molding method such as injection molding and extrusion molding, including the pressure foaming method. When using an injection molding machine or an extrusion molding machine to make a foam, each resin may be added as it is together with a foaming agent, or only the resin is kneaded in advance with an extruder, a Banbury mixer or a kneader, and pelletized. Foaming may be performed by adding a foaming agent to the resin. The foaming agent may be a material which has been kneaded in advance with a low melting point resin such as polyoctenamer, or may be dry-blended as powder.

In addition to the resin component and the chemical foaming agent, various resin additives such as an antioxidant, an ultraviolet absorber, a coloring agent, an antistatic agent, a lubricant and the like may be added according to the intended use. . Further, a crosslinking agent may be added at the time of molding, and crosslinking may be performed simultaneously with molding to obtain a crosslinked foam.

[0013]

The present invention will be described in more detail with reference to the following examples, which should not be construed as limiting the invention.

Example 1 60 parts by weight of a styrene-isoprene-styrene triblock copolymer (manufactured by Exxon Corporation, 4111D),
15 parts by weight of propylene-diene rubber (Victrex 3708P, manufactured by Exxon) and 25 parts by weight of polyoctenama (Vestenamer 8012, manufactured by Huls) were kneaded and extruded into pellets by a conventional method using a twin-screw extruder.
Azobiscarbonamide (Cermic CAP5 manufactured by Sankyo Kasei Co., Ltd.) was used as a chemical foaming agent for 100 parts by weight of this resin.
00) was dry blended and injection molded using an injection molding machine having a shut-off nozzle. The obtained foam had uniform fine cells and had the physical properties shown in Table 1.

Example 2 Using the same resin as in Example 1, a resin composition having the composition shown in Table 1 was prepared. Injection molding was performed in the same manner as in Example 1 to obtain a foam molded product. Table 1 shows the physical properties of the obtained foam.

Examples 3 and 4 The same resin composition as in Example 1 was extruded and foamed at 200 ° C. using a single-screw extruder using a chemical foaming agent (Neocellbon N5000S manufactured by Eiwa Chemical Co., Ltd.). A foam having uniform fine cells could be continuously obtained. Table 1 shows the physical properties of the obtained foam.

Example 5 100 parts by weight of styrene-isoprene-styrene triblock copolymer (4111D manufactured by Exxon), 60 parts by weight of polyisobutylene (MML-80 manufactured by Exxon) and 40 parts of butyl rubber (268 manufactured by Exxon) Parts by weight, EPDM (JSR181SP manufactured by Nippon Synthetic Rubber Co., Ltd.)
60 parts by weight and 40 parts by weight of polyoctenamer (Vestenamer 8012 manufactured by Huls Co.) were kneaded, and 1 part by weight of a chemical foaming agent was dry-blended and extruded in the same manner as in Example 3. A flexible and well-textured foam having fine cells was obtained. Table 1 shows the physical properties of the obtained foam.
It was shown to.

Comparative Example 1 Example 3 was repeated using only a styrene-isoprene-styrene triblock copolymer (4111D manufactured by Exxon).
The foam extrusion was performed under the same conditions as described above. As shown in Table 1, only a foam having a low expansion ratio was obtained.

[0019]

[0020]

[0021]

EFFECTS OF THE INVENTION The foamable resin composition of the present invention has a feeling, a good touch and a flexibility which are not present in conventional foamed products. Moreover, since no low molecular weight softener is used, the bleeding of the softener is carried out. There is no out and can be used for a wide range of applications. In addition, since a high foam is obtained, the amount of resin used is small and it is economical. In addition, since it is lightweight, it is advantageous from the viewpoint of energy saving. In addition, since it is suitable for general molding methods such as injection molding and extrusion molding, continuous production is possible, and a foamed resin composition suitable for industrial use for mass-produced products such as automobile interior parts and information equipment. It is.

[0022]

[Table 1]

Claims (2)

(57) [Claims] 1. A styrenic thermoplastic block copolymer 2.
0 to 80% by weight, 5 to 60% by weight of polyoctenamer and 0 to 80% by weight of polyolefin elastomer, 100 parts by weight of a resin composition,
A foamed resin composition containing 10 parts by weight. 2. The foamed resin composition according to claim 1, wherein the styrene-based thermoplastic block copolymer is a triblock copolymer having polystyrene blocks at both ends.