JPS62184032A - Polyolefin resin foam improved in yellowing resistance - Google Patents

Abstract

PURPOSE:To obtain the titled foam having excellent cushioning quality, heat resistance and heat insulating property, remarkably low yellowness and a high commercial value, by using a polyolefin resin composition formed by mixing a polyolefin resin with a titanium compound and ultramarine blue. CONSTITUTION:A polyolefin resin composition is obtained by mixing 100pts.wt. polyolefin resin such as PE, PP or an ethylene/propylene copolymer with 0.1-10 pts,.wt. titanium compound such as TiO, Ti2O3 or TiO2 and 0.001-5pts.wt. ultramarine blue represented by a silicic acid of the formula. This composition is mixed with a heat-decomposable blowing agent (e.g., azodicarbonamide) and, optionally, a crosslinking agent which can generate radicals when heated, and the resulting mixture is molded into, e.g., a sheet at a temperature at which neither the blowing agent nor the crosslinking agent is decomposed. The obtained sheet is crosslinked to a gel fraction of 15-45% by an ionizing radiation crosslinking process, a chemical crosslinking process or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a polyolefin resin foam with little yellow coloration and high product value.

[Conventional technology]

Traditionally, polyolefin resin foams, represented by polyethylene, have been used in many applications, including automobile interior materials, due to their excellent heat insulation and cushioning properties, but recently they have been used in cosmetics. Patsukin,
There has been an extremely strong demand for foams that are used in packaging for alcoholic beverages, Western liquors, and health drinks, and have a minimal yellow appearance.

In general, the above polyolefin resin foam is colored yellow due to the foaming mechanism such as decomposition of the blowing agent by heating and crosslinking of the crosslinking agent during its manufacture, and the surface of the foam is particularly colored compared to the inside of the foam. However, it is said that preventing this coloration without sacrificing the industrial productivity of the foam is accompanied by great technical difficulties. For example, as a means to prevent such coloring of foam, it is known to add a decomposition accelerator for the foaming agent, such as zinc oxide or metal soap, to the foam, but this method When a polyolefin resin composition is molded into a sheet or the like by extrusion molding, the foaming agent tends to undergo initial decomposition, making the cell structure of the resulting foam uneven, creating coarse voids, and damaging the foam. There is a problem that performance and quality are impaired.

[Problem that the invention seeks to solve]

An object of the present invention is to prevent coloring of the foam in the above-mentioned polyolefin resin foam production process and to provide a polyolefin resin foam with a small amount of yellowing, which is required for the foam product.

[Means to solve problems]

The purpose of the present invention is to provide polyolefin resin 10
This is achieved by a polyolefin resin foam with improved yellowness, which is made of a polyolefin resin composition containing 0.1 to 10 parts by weight of a titanium compound and 0.001 to 5 parts by weight of ultramarine. I can do it.

The polyolefin resin constituting the foam of the present invention is not particularly limited, and there are various types of polyolefins used in the production of known foams, specifically polyethylene, polypropylene, ethylene, etc. - Propylene copolymers and blend polymers containing at least two or more thereof can be exemplified.

The present invention is characterized in that a titanium compound and ultramarine blue are blended in order to prevent the foam made of such a polyolefin resin from yellowing.

Here, as the titanium compound, Tl0I T1zOs
+TiO□, TiO□・HgO, TIO,・2H30
and so on.

Also, Gunjo refers to the second edition of the reduced edition dated January 31, 1966,
“Chemistry Dictionary 1” published by Kyoritsu Shuppan Co., Ltd., page 811, “
It refers to a silicate expressed by the general formula % formula % listed in the section ``Ultramarine''.

In the present invention, in order to improve the yellow coloration of the foam, it is necessary to blend both the titanium compound and ultramarine into the polyolefin resin, and even if only one of them is blended, the effect of preventing yellow coloration is still high. is virtually unacceptable.

However, the amount of the titanium compound blended is preferably in the range of 0.1 to 10 parts by weight, preferably 1 to 3 parts by weight, per 100 parts by weight of the polyolefin resin, and this amount is less than 0.1 part by weight. If the amount is too low, the effect of preventing yellowing of the foam will not be sufficient, and if it exceeds 10 parts, the cell structure of the foam will become non-uniform, which is not preferable.

On the other hand, the blending ratio of ultramarine is 100% polyolefin resin.
0.001 to 5 parts by weight, preferably 0.03 parts by weight
The amount of ultramarine blue is preferably in the range of ~1.0 part by weight; if the amount of ultramarine is less than 0.001 part, it will not be sufficiently effective in preventing coloration of the foam, and if it exceeds 5 parts, it will cause whiteness. This is not desirable because it produces a more ultramarine (blueish) color.

The method and means for blending the titanium compound and ultramarine blue into the polyolefin resin are not particularly limited, and may be blended using, for example, a Henschel mixer, a kneader, an extruder, or the like.

The polyolefin resin composition containing the titanium compound and ultramarine is made into a foam by a known foam manufacturing method. That is, 0.1 to 10 parts by weight of titanium compound and 0.1 to 10 parts by weight per 100 parts by weight of the polyolefin resin
．． 001 to 5 parts by weight of ultramarine is mixed with a known thermally decomposable blowing agent, such as azodicarbonamide, dinitrosopentamethylenetetramine, etc., and, if necessary, a crosslinking agent that generates radicals when heated. Then, it is held at a temperature at which the foaming agent and crosslinking agent described above do not decompose and is molded, for example, into a sheet shape.

This formed sheet material is cross-linked by applying any known method such as ionizing radiation cross-linking method or chemical cross-linking method so that the gel fraction becomes 15 to 45%, preferably 20 to 40%. do.

More specifically, in the case of the ionizing radiation crosslinking method, α, β, γ, X-rays, electron beams, neutron beams, etc. are used as high-energy rays, and a high-energy electron beam irradiation machine is usually used. Crosslinking is achieved by irradiating the sheet with an electron beam at a dose of ~50 Mrad. In this case, electron beam crosslinking may be performed by adding 1 to 10 parts by weight of various known crosslinking aids such as divinylbenzene, diallyl phthalate, trimethylolpropane triacrylate, etc. to the blend polymer of the present invention. good.

Instead of this radiation irradiation, it is also possible to add an ultraviolet sensitizer such as benzophenone and crosslink by irradiating ultraviolet rays.

In addition, in the case of chemical crosslinking method, dicumyl peroxide,
A cross-linking method using an organic peroxide such as ditertiary-butyl peroxide, and a silane cross-linking method in which a vinyl silane such as vinyltrimethoxysilane is kneaded with these cross-linking agents to form a graft, and then cross-linked by a siloxane condensation reaction are used as appropriate. Can be applied.

The molded product thus obtained is heated in a hot air atmosphere or on a melt bath to rapidly decompose the foaming agent contained within the molded product, thereby converting it into a foam.

In addition, to the extent that the object of the present invention is not impaired, the composition used for producing the foam of the present invention may include lubricants, antioxidants,
Ultraviolet absorbers, colorants, antistatic agents, flame retardants, and other various additives can be blended within the range that can achieve the desired purpose.

Furthermore, the polyolefin resin foam of the present invention is
It is possible to improve workability by applying an adhesive to at least one surface of the material through corona discharge treatment, coating, etc., and laminating it, or by laminating plastic films, sheets, other foam sheets, or metal foils. , .

Soup with a composite structure created by extrusion lamination, etc.
That is, various processing techniques can be applied.

〔Effect of the invention〕

The thus obtained polyolefin resin foam of the present invention has significantly less yellow coloring, so it can be used as packaging for cosmetics, packaging for alcohol, Western liquor, health drinks, etc., as well as existing applications such as automobile interior parts and other applications. products, such as various packing materials, adhesive tape bases, cloak base materials, insulation materials, cushioning materials, and many other applications such as clothing, building materials, and medical applications, by utilizing the cushioning, heat resistance, and insulation properties of foam. It can be used for various purposes.

The effects of the present invention will be explained in more detail below based on Examples.

In addition, in this invention, yellowness is the value calculated|required by the following measuring method and conditions.

Physical properties such as melting point (Tm), drawing ratio (K), gel fraction, and surface roughness are values measured by the following methods.

Tm: DSC method molding drawing ratio: Vacuum forming using the female cup method with a diameter of 50 m,
Displayed in (depth/diameter).

Gel fraction: Extracted with hot tetralin at 135°C and expressed as [(weight after extraction g)/(sample amount g)) x 100.

Surface roughness: Measured using a surface roughness meter using the stylus method.

Yellowness: L-a-b with Suga Test Instruments digital yellowness meter
Calculated using the method, with the b value on the horizontal axis and the yellowness on the vertical axis.

Example 1 4.4 parts by weight of blowing agent azodicarbonamide, 1 part by weight of titanium oxide, and 0.03 parts by weight of ultramarine based on 100 parts by weight of polyethylene having a melt index of 3.7 and a density of 0.923.
After blending parts by weight and mixing uniformly, a sheet with a thickness of about 800 μm was formed using an extruder, and after irradiating this sheet with an electron beam of 4 Mrad, it was placed on a salt bath heated to 230°C. I let it sit and foam.

The resulting foam has a thickness of 1 cm and an apparent density of 0.125 g7
cc: The foam had a uniform cell structure with no voids. When we measured the yellowness of this foam, we found that
It showed a small value of 0.030, and almost no yellow coloration was observed in appearance.

On the other hand, as a result of measuring the yellowness of the polyethylene foam to which the ultramarine blue coloring inhibitor was not added, it showed a value of 0.12. Therefore, it can be seen that the foam of the present invention exhibits extremely less yellowing than commercially available polyethylene foams.

Examples 2 to 4, Comparative Examples 1 to 2 The amount of the blowing agent azodicarbonamide and the amount of titanium oxide and ultramarine blue were varied with respect to 100 parts by weight of polyethylene with a melt index of 7.0 and a density of 0.921.
After uniformly mixing, the mixture was formed into a sheet, and then cross-linked to the sheet, which was then heated to 220 to 240°C to foam. The resulting foam had a uniform cell structure and a low degree of yellowness, and was excellent in terms of practical use, such as a packing material.

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Claims (1)

[Claims] A polyolefin resin foam with improved yellowness, comprising a polyolefin resin composition containing 0.1 to 10 parts by weight of a titanium compound and 0.001 to 5 parts by weight of ultramarine blue per 100 parts by weight of the polyolefin resin.