JPS5911611B2 - polyolefin resin foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to obtain a polyolefin resin foam containing a large amount of solid non-resin material and having a high expansion ratio.

Closed-cell foams made of conventional polyolefin resin compositions usually have a relatively uniform structure without containing foreign substances.

However, although it is possible to obtain a polyolefin foam from a polyolefin resin composition containing a non-resin substance, in this case, the foam is limited to a relatively low ratio, and it is difficult to obtain a high ratio foam. Not 10. In the case of high-density foams, there are increasing demands for flame retardancy, heat aging resistance, or incorporation of inorganic fillers to reduce combustion heat and make smokeless. It has become necessary to mix non-resin substances such as fuel, various anti-deterioration agents, and fillers. However, when these non-resin substances are mixed into a polyolefin foaming composition and foamed, most of the non-resin substances are present in the cell membranes, destroying the cell structure and reducing the foaming rate. It was quite difficult to achieve the desired purpose as it caused the bubbles to become continuous. In particular, as the amount of the non-resin substance increases, adverse effects such as the formation of open cells increase. Therefore, the inclusion of a large amount of non-resinous substances in the foam composition has been avoided as much as possible since it significantly deteriorates the quality of the closed cell foam. Therefore, for example, in resins with poor long-term stability such as polypropylene,
Although it has extremely excellent other properties, it is not possible to obtain a high-performance foam with performance that can withstand practical use because it requires the inclusion of a relatively large amount of non-resinous material. Ta. The present invention has been made as a result of extensive research aimed at improving these drawbacks, and as a result has arrived at a highly foamed product having a novel structure containing a large amount of non-resinous material.

35 That is, the present invention provides a solid non-resin material (
However, in polyolefin resin extruded foams containing 5 parts by weight or more of non-resin substances (excluding flame retardants), substantially most of the non-resin substances are attached to the membrane surface of the cells, and the polyolefin foams are composed of closed cells with an expansion ratio of 5 times or more. It is the body.

The present invention will be explained in detail based on the drawings.

FIG. 1 is a schematic cross-sectional view of a cell membrane in the foam of the present invention, in which 1 shows the membrane of the foam cell, and 2 shows the granules of the non-resin material.

FIG. 1A is a state diagram in which particles 2 of a non-resin material are attached to the bubble membrane 1, FIG. C indicates that there are some particles of non-resin material inside the bubble membrane 1. This is a state diagram in which a large amount of grains are present on the film surface, but a large amount of grains are also present on the film surface. In both of these phase diagrams, when observed in the direction perpendicular to the cut plane, that is, the surface of the membrane, the non-resinous substance is simply attached to the bubble membrane, as shown in the electron micrographs shown in the reference materials. It can be easily confirmed. In the present invention, adhering to the surface of the bubbles means that the particles and resin are adhered to each other, that the particles are attached to the membrane surface, or that the particle surface is covered with a thin polymer membrane. There are
It includes all of these.

Therefore, in the present invention, since non-dendritic substances may be present in the membrane, it is stated that substantially most of them are attached to the membrane surface.

In order to obtain the polyolefin foam of the present invention, for example, a predetermined amount of various stabilizers is mixed into the polyolefin in advance, and while this composition is fed from the hopper of the extruder, hydrocarbons etc. are added from the barrel portion of the extruder. A so-called volatile foaming agent is supplied in a constant quantity, kneaded, and foamed while being discharged into the atmosphere from the die of an extruder. In this case, in extrusion foaming, the type and particle size of the additive must be selected appropriately. The non-resin material has a high melting point that can maintain a solid state inside the extruder, and most of the particles have a particle size of 0.5μ to 0.111μ.
belongs to.

Preferably, the diameter is 5μ or more, and it is even better to use a needle-like or flattened one. Another method is to knead a non-resin material with a resin that is incompatible with polyolefin, such as polystyrene, at a high concentration, grind it, mix it with the desired polyolefin, and extrude and foam as described above. It is obtained by In the present invention, the non-resin substance is
Antioxidants, metal deactivators, ultraviolet absorbers, extenders,
These include fibrous reinforcing agents, coloring agents, and bubble nucleating agents.

These non-resin substances may be inorganic or organic, but solid non-resin substances are contained in a ratio of 5 to 50 parts by weight, preferably 7 to 30 parts by weight, per 100 parts by weight of polyolefin. This is what is being done.

Furthermore, although a non-resin substance that is liquid at room temperature may be contained, the content thereof is not greater than that of a solid non-resin substance. Note that if the non-resin substance is less than 5 parts by weight, the foam can be obtained even if it is dispersed in the cell membrane of the foam. Next, specific examples of non-resin substances include antioxidants such as 1, 3, 5
-trimethyl-2,4,6-tris(3,5-ditertiarybutyl4-hydroxybenzyl)benzene, 4,
4″-thiobis(6-tertiarybutyl-3-methylenol).

Examples of the metal deactivator include those that act as a copper damage inhibitor, such as 3-(N-salicyloyl)amino-1,2,4-triazole.

Also, an inorganic filler such as calcium carbonate can serve as a filler, a reinforcing agent, and a cell nucleating agent, and the pigment is, for example, carbon black.

In addition, the present invention is a foam that does not destroy closed cell foam, and closed cell foam is defined by JIS K67.
When measured according to the water absorption rate test method of polyethylene foam No. 67, it shows a water absorption of 1.0 η/Cd or less, and its expansion ratio is expressed as a ratio of .

The bulk density of the foam composition is the value obtained by treating the foam by hot press molding or the like to eliminate the bubbles. In the present invention, a closed cell body having a foaming ratio of 5 times or more, preferably 15 times or more is obtained. Further, the polyolefin in the present invention includes olefin polymers such as polyethylene and polypropylene, copolymers such as ethylene monovinyl acetate, and also polymer blends containing polyolefin as a main component.

This polyolefin may be non-crosslinked or crosslinked, but a highly crystalline resin is preferred, and a polymer containing propylene as a component is desirable. The reason for this is that non-resin substances tend to adhere to the membrane surface due to its high crystallinity, and it also has excellent mechanical properties such as heat resistance and rigidity, and the effects of various additives are effective. This is because it is demonstrated. Next, examples of the present invention will be described. Example 1 To 100 parts by weight of polypropylene resin, 3 parts by weight of calcium carbonate, 1,3,5-trimethyl-2,4,6-tris(3,5-ditertiarybutyl-4-hydroxy) as an antioxidant benzyl) benzene (melting point 242℃
) and 2 parts by weight of 3-(N-salicyloyl)amino-1,2,4-triazole (melting point: approximately 30'C) as a metal deactivator was added to the hopper of an extruder. While feeding from one side, the other extruder barrel (temperature approx.
Volatile liquid trichlorotrichloroethane was injected from a die (set at about 140°C) and extruded to obtain a foam.

The density of the obtained foam was 0.04 g/CrA, and the water absorption rate was 0.
．． 7η/Cd, and when the state of the additive was observed using a scanning electron microscope, it was found that many solid particles were attached to the bubble film. Comparative Example 1 For comparison, in Example 1, pentaerythrityl-tetrakis [3-(3,5-jeta-yacerybutyl-4), which has a low melting point and becomes liquid in an extruder, was used as an antioxidant.
-Hydroxyphenyl)propionate (melting point 11
0-125 DEG C.) and the ultraviolet absorber 2-hydroxy-4-n-octoxybenzophenone (melting point 48 DEG-49 DEG C.) was used in place of the metal deactivator.

The resulting foam has a density of 0.099/Cd and a water absorption rate of 2.
3 mg/Cd, and when observed using a scanning electron microscope in the same manner as in Example 1, many of the bubble membranes were broken and became open cells, and the broken bubble membranes had many solid particles sticking out, and the bubble membranes were removed from the broken portions. It was torn.

As detailed above, the foam of the present invention contains a large amount of additives and has a high expansion ratio, so it has excellent durability when an antioxidant is used as an additive. It becomes a closed cell foam.

In particular, foams mainly composed of high-density polyethylene or polypropylene have excellent heat resistance and are therefore extremely useful for various heat insulating materials and construction materials.

[Brief explanation of the drawing]

The drawing is a schematic diagram of a cross section of a cell membrane in the foam of the present invention. 1... Membrane of foam cell, 2... Granules of non-resin material.

Claims (1)

[Claims] 1. Does not melt in the extrusion process and has an average particle size of 0.5 μ to 0.1 per 100 parts by weight of polyolefin resin
5 mm of solid non-resin substances (excluding flame retardants)
A polyolefin resin extruded foam containing at least part by weight of a polyolefin resin, in which a substantial majority of the non-resinous substance is attached to the membrane surface of the cells, and the polyolefin resin foam is composed of closed cells having an expansion ratio of 5 times or more.