JPH1143551A - Thermoplastic elastomer foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject foam having a high foaming ratio, easy in the control of the foaming, and useful for thermoplastic resins, etc., by adding a dispersant to a composition comprising an olefinic thermoplastic resin and a rubber component, adding fine plastic spheres encapsulating a foaming agent to the mixture, and subsequently foaming and molding the mixture. SOLUTION: This thermoplastic foam is obtained by adding (C) a dispersant (ethylene vinyl acetate, etc.), in an amount of about 30-70 pts.wt. per 100 pts.wt. of a component D to an olefinic thermoplastic elastomer produced by preliminarily dynamically crosslinking (A) an olefinic thermoplastic resin (polypropylene, etc.), with (B) a rubber component (natural rubber, etc.), in an amount of about 5-80 pts.wt. per 100 pts.wt. of the component A, adding to the mixture (D) foaming agent (butane, etc.,)-encapsulated plastic (vinylidene chloride) fine particles in an amount of about 0.5-10 pts.wt. per 100 pts.wt. of the total amount of the component A and the component B, and subsequently foaming and extruding the mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible thermoplastic elastomer foam having a high expansion ratio, easy foam control, closed cells having a small cell diameter and being uniformly dispersed.

[0002]

2. Description of the Related Art Decomposition type foaming agents such as azodicarbonamide are often used as a foaming method for plastics, but the foaming ratio is small, at most 2 times.
In addition, since the diameter of the cell becomes too large or conversely small, the dispersion of the cell tends to be uneven. A dispersion of hollow plastic or glass microspheres in a plastic hard matrix is known as a syntactic foam (Plastic Foam Handbook, 1973, pp. 212-218, Nikkan Kogyo Shimbun). However, since this syntactic foam is dispersed in a plastic-based hard matrix, the molded product has compression resistance but is inflexible and hard, and whitens (crystallizes) or returns to its original shape when bent. It cannot be used as a door seal material or cushioning material (cushion material) because it has no elastomeric properties.

[0003] In addition, heat-expandable microcapsules containing isobutane are mixed with an elastomer or rubber and injected.
Extrusion can be achieved by polymer digest 199.
6, 7, 106-108. This microcapsule has a particle size after expansion of 50 to 120 μm and is 1 μm.
It is described that it is 00% complete closed cells, and when used for thermoplastic resins, elastomers, and rubbers, it has excellent surface smoothness, has a uniform expansion state, and is easy to form intricately. And heat-expandable microcapsules (balloons) are not evenly dispersed, so that there are places where the strength is extremely weak, and there is a problem in physical properties.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a flexible thermoplastic elastomer foam having a high expansion ratio, easy control of foaming, closed cells, small cell diameter and uniformly dispersed. Is to provide.

[0005]

Means for Solving the Problems A first invention of the present invention is to foam a mixture obtained by adding a dispersant to an olefin-based thermoplastic resin and a rubber component, and adding a plastic microsphere containing a foaming agent thereto. The present invention relates to a thermoplastic elastomer foam obtained by extrusion.

[0006] A second invention of the present invention is to add a dispersing agent to an olefinic thermoplastic elastomer in which an olefinic thermoplastic resin and a rubber component are dynamically crosslinked in advance, and to add plastic microspheres containing a foaming agent to the dispersing agent. The present invention relates to a thermoplastic elastomer foam obtained by foaming and extruding the added mixture.

[0007] A third invention of the present invention is an unfoamed mixture (masterbatch) obtained by previously mixing a dispersant and plastic microspheres encapsulating a foaming agent at a foaming temperature or lower with an olefinic thermoplastic resin and a rubber component. The present invention relates to a thermoplastic elastomer foam obtained by foaming and extruding a mixture to which is added.

In a fourth aspect of the present invention, a dispersing agent and a foaming agent-encapsulated plastic microsphere are preliminarily mixed at a foaming temperature or below with an olefinic thermoplastic resin and an olefinic thermoplastic elastomer in which a rubber component is dynamically crosslinked in advance. The mixture to which the unfoamed mixture (master batch) obtained by adding
The present invention relates to a thermoplastic elastomer foam obtained by extrusion.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The olefinic thermoplastic resin of the present invention includes, for example, polypropylene (PP), polyethylene (PE), polystyrene (PS), ethylene-vinyl acetate copolymer (EVA), ethylene-vinyl alcohol Copolymers (EVOH), polybutylene and the like can be mentioned.

As the rubber component of the present invention, for example, natural rubber (NR), ethylene propylene diene rubber (EPD)
M), ethylene propylene rubber (EPM), isoprene rubber (IR), styrene butadiene rubber (SBR), nitrile butadiene rubber (NBR), polybutadiene rubber (BR), butyl rubber (IIR), halogenated butyl rubber (X-IIR), Chloroprene rubber (CR) and the like can be mentioned, and it is preferable to use about 5 to 80 parts by weight based on 100 parts by weight of the olefin-based thermoplastic resin.

The foaming agent of the plastic microspheres (sometimes called balloons) containing the foaming agent of the present invention includes:
For example, butane, pentane, cyclopentane, trichlorofluoromethane (R11), chlorodifluoroethane (R142b), trichlorotrifluoroethane (R1
13). Examples of the plastic containing the foaming agent include polymers such as vinylidene chloride and acrylonitrile, copolymers of vinylidene chloride and acrylonitrile, and copolymers of methyl methacrylate (MMA) and acrylonitrile. No. As a commercial product,
For example, Expancel 09 of Nippon Ferrite Co., Ltd.
1,461,461DU, 551, Matsumoto Yushi Pharmaceutical Co., Ltd. Matsumoto Microsphere F-30, F-
50, F-80 and the like. These balloons are preferably used in an amount of about 0.5 to 10 parts by weight based on 100 parts by weight of the total amount of the olefin-based thermoplastic resin and the rubber component.

As the dispersant (carrier), for example, a thermoplastic material having a melting point lower than the softening point of the shell of plastic microspheres is preferable. For example, fatty acid or its modified material such as ethylene vinyl acetate (EVA), acrylic acid Wax, vinyl acetate wax, ethylene butadiene acrylonitrile (EBA), PP, PE
And the like. The dispersant is preferably used in an amount of about 30 to 70 parts by weight based on 100 parts by weight of the balloon.

[0013] In the first invention of the present invention, the thermoplastic elastomer foam is obtained, for example, by charging the above-mentioned olefin-based thermoplastic resin, rubber component and dispersant into an extruder, and further forming plastic microspheres containing a foaming agent. It is obtained by charging and foaming and extruding the mixture. The extrusion conditions are preferably, for example, a processing temperature of about 120 to 200 ° C. and an extrusion rate of about 100 to 200 g / min. While taking out the foam obtained by extrusion,
After being formed into a predetermined shape by a sizing die, it is cooled and formed by a immersion method, a shower method, or the like. Then, it is cut into a predetermined length by a cutting machine to obtain a product. The expansion ratio of the foam of the present invention is usually preferably about 2.5 to 3.5 times.

In the present invention, it is particularly preferable to use an olefinic thermoplastic elastomer in which an olefinic thermoplastic resin and a rubber component are dynamically crosslinked in advance. Dynamic Valucanization refers to a process in which rubber is blended in a thermoplastic matrix and kneaded with a crosslinking agent to highly crosslink the rubber and to finely disperse the rubber. For example, an olefin-based thermoplastic resin, a rubber component, zinc white, and stearic acid are kneaded and melted in an extruder at 180 to 190 ° C., and then melted to obtain tetramethylthiuram disulfide and 2-benzothiazyl disulfide (a sulfur accelerator). And further extruding sulfur (crosslinking agent), the rubber is crosslinked at this time. When such dynamic crosslinking is performed, the rubber component is microscopically dispersed in the thermoplastic elastomer, the affinity at the interface between the two is high, and the balloon which is to be foamed at a high magnification is formed into a matrix (the thermoplastic elastomer and the rubber component). The alloy is wrapped without tearing, and the surface cracks appearing during cell roughening and high foaming do not occur, and the mechanical strength is also improved, which is preferable. In addition, because of the dynamic crosslinking, even if the melting temperature of the resin is high and the foaming temperature of the balloon is low, it is possible to perform processing with a good surface condition at a considerably lower temperature than that of a non-crosslinked resin, which is preferable.

In the present invention, if an unfoamed mixture (masterbatch) obtained by mixing the foaming agent-encapsulated plastic microspheres and the dispersant at a foaming temperature or lower is used, the balloon can be highly dispersed and the balloon can be highly dispersed. The amount that can be added increases, and high foaming with an excellent surface state can be achieved, which is preferable. When it is necessary to add and mix a compounding agent and a dispersing agent to the main material, the masterbatch first mixes the compounding agent and the dispersing agent, and then mixes the mixture with the main material. The compounding agent has a good dispersion and can be easily processed. In the present invention, the main material is a thermoplastic elastomer, the compounding agent is a balloon, and the dispersing agent is EVA.

In the second to fourth aspects of the present invention, the extrusion molding method, extrusion conditions, cooling method and the like are the same as those of the first aspect, and the expansion ratio of the foam is usually about 2.5 to 3.5 times. The degree is preferred. For example, in the second invention, a method in which an olefin-based thermoplastic elastomer, a dispersant, and a balloon which have been dynamically crosslinked in advance is charged into an extruder, and in the third invention, an olefin-based thermoplastic resin, a rubber component, and a master batch are simultaneously extruded. In the fourth invention, there can be mentioned, for example, a method in which an olefin-based thermoplastic elastomer dynamically crosslinked in advance and a master batch are simultaneously charged into an extruder.

[0017]

The present invention will be described below with reference to examples and comparative examples.
In addition, "parts or%" means parts by weight or% by weight. Example 1 Polypropylene (PP) [melt flow rate (MFR) for extrusion molding = 2 g / 10 min, 230 ° C.] was charged into an extruder at a blending ratio of 58 parts and 42 parts of ethylene propylene rubber (EPDM), and further as a dispersant. 2.5 parts (2.5%) of ethylene vinyl acetate (EVA) and 5% of thermoplastic resin microspheres (Expancel 91DU manufactured by Nippon Ferrite Co., Ltd.) containing a foaming agent were charged as balloons. Extruded.

The extrusion conditions were as follows.
Using a S40-25 type screw with a diameter of 40 mm, L /
D = 25, full-flight compression ratio 2.5, extruder die diameter 5 mm × 4 strand die, extrusion speed 200 g / min
And Extrusion temperature feed zone 160 ° C, compression zone 180 ° C, metering zone 185
° C, a die portion of 185 ° C, and a screw rotation speed of 50 RPM. As a result, an elastomer foam having the properties shown in Table 1 was obtained.

For the expansion ratio, a high precision electronic hydrometer MD-200S manufactured by Mirage Trading Co., Ltd. was used. The shape of the cell was cut out in a cubic shape, and the shape of the cell in each section was observed. When the shape of all the cells was substantially spherical, ○, when the shape of all the cells was concave, and △ when most of the cells were significantly deformed from the sphere, × was given. The dispersibility of the cells was determined by taking the number of cells per unit area of the cross section of the extrudate for each location and examining the variation. When the variation from the average was 50% or more of the number of cells, ×, when 30% or more, Δ, when 10% or more, 、, and below, ◎. The cell size (μm) was enlarged with a microscope, the diameter of each cell was measured, and the average was taken. Since the balloon is a sphere, it is easy to measure its diameter. In the case of chemical foaming, the cell had a shape close to a cylinder, and the average of the cross-sectional diameters was defined as the cell diameter. The state of the cells was cut out in a cubic shape, and the shape of each cell in each cross section was compared. The amount of water absorption at the time of immersion was determined by immersing a test specimen left in a room for 24 hours in water for 1 minute, compressing and deforming 20 times, taking out excess water on the surface, measuring the weight, and measuring the water absorption. .

Example 2 EPDM, vulcanizing agent, and PP were kneaded and vulcanized by an extruder to obtain an elastomer foam in the same manner as in Example 1 except that a dynamically crosslinked product was used in advance. Table 1 shows the characteristics.
Shown in Example 3 EVA of dispersant and Expancel of balloon 91DU
An elastomer foam was obtained in the same manner as in Example 1, except that a master batch was prepared by heating and mixing at a temperature higher than the melting point of the dispersant and lower than the foaming temperature of the balloon. The characteristics are shown in Table 1.

Example 4 PP and EPDM were dynamically crosslinked in advance as in Example 2, and EVA as a dispersant and Expancel 91DU as a balloon were prepared as a masterbatch in the same manner as in Example 3. Except for using, an elastomer foam was obtained in the same manner as in Example 1. The characteristics are shown in Table 1. Comparative Example 1 An elastomer foam was obtained in the same manner as in Example 1 except that the dispersant EVA was not used. The characteristics are shown in Table 2.

Comparative Example 2 An elastomer foam was obtained in the same manner as in Example 2 except that the dispersant EVA was not used. The characteristics are shown in Table 2. Comparative Example 3 Azodicarbonamide (Seymark M-71, decomposition temperature 190 ° C. or higher) as a decomposable foaming agent instead of a balloon
Was used in the same manner as in Comparative Example 2 to obtain an elastomer foam. The characteristics are shown in Table 2.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

According to the present invention, it has a high expansion ratio,
It is possible to obtain a flexible thermoplastic elastomer foam in which foaming is easily controlled, closed cells having a small cell diameter and uniformly dispersed, and having flexibility.

Claims (4)

[Claims] 1. A thermoplastic elastomer foam obtained by foaming and extruding a mixture obtained by adding a dispersant to an olefin-based thermoplastic resin and a rubber component, and adding a plastic microsphere containing a foaming agent thereto. 2. A mixture obtained by adding a dispersant to an olefin-based thermoplastic elastomer in which an olefin-based thermoplastic resin and a rubber component are previously dynamically crosslinked and adding plastic microspheres containing a foaming agent to the mixture. Thermoplastic elastomer foam obtained by extrusion. 3. A foam obtained by adding an unfoamed mixture (master batch) obtained by previously mixing a dispersant and plastic microspheres containing a foaming agent at a foaming temperature or lower with an olefin-based thermoplastic resin and a rubber component. -A thermoplastic elastomer foam obtained by extrusion. 4. An unfoamed foam obtained by mixing a dispersant and plastic microspheres encapsulating a foaming agent at a foaming temperature or lower with an olefin thermoplastic elastomer in which an olefin thermoplastic resin and a rubber component are dynamically crosslinked in advance. A thermoplastic elastomer foam obtained by foaming and extruding a mixture to which the above-mentioned mixture (master batch) is added.