JPS6234933A - Radiation-resistant polyolefin composition - Google Patents

Abstract

PURPOSE:To obtain a polyolefin composition having excellent radiation resistance and suitable for radiation sterilization, by compouding a polyolefin with a heterocy clic hindered amine stabilizer, a specific antioxidant and a crosslinking assistant. CONSTITUTION:The objective composition can be produced by compounding (A) 100pts.(wt.) of a polyolefin with (B) 0.01-1pt., preferably 0.03-0.5pts. of a heterocyclic hindered amine stabilizer, e.g. the compound of formula I (M is methyl), etc., having a molecular weight of preferably >=500, (B) 0.01-1pt., preferably 0.03-0.5pts. of an aromatic phosphorus acid ester or aromatic phosphonite antioxidant, preferably the compound of formula II (tBu is t-butyl), etc., and (C) 0.0-2pts., preferably 0.03-0.7pts. of a crosslinking assistant such as triallyl isocyanurate, diallyl phthalate, etc.

Description

[Detailed description of the invention] [Industrial application field] Regarding suitable polyolefin compositions.

[Conventional technology]

Traditionally, methods using ethylene oxide gas and high-temperature sterilization using steam have been routinely used to sterilize medical instruments, etc., but there are problems with ethylene oxide gas adsorption remaining on the product surface and the inability to sterilize small details. Due to problems such as complete irradiation, methods using radiation such as gamma rays are becoming popular.

[Problem that the invention seeks to solve]

However, when polyolefin products are irradiated with radiation, the resin deteriorates, resulting in various problems such as a decrease in molecular weight, a decrease in impact strength, coloring, and an increase in eluates, making it impractical for practical use. Various improvement methods have been tried to solve this problem, such as the method of adding hindered amine (Japanese Patent Application Laid-Open No. 55-1999).
19199), a method of adding a specific phosphite (Japanese Patent Application Laid-open No. 179234/1983), etc. have been proposed. However, although these methods showed some improvement, they were insufficient to meet the requirements for practical products.

[Failure to solve the problem]

The present invention was developed as a result of intensive studies aimed at solving these problems, that is, providing a radiation-resistant polyolefin product with sufficient practicality. This was accomplished based on the discovery that polyolefin compositions having excellent and well-balanced physical properties can be obtained by suppressing the effects extremely effectively.

That is, the present invention provides polyolefin 100i! Radiation-resistant polyolefin composition (A) 0.01 to 1 part by weight of heterocyclic hindered amine stabilizer (Bl aromatic 0.01 to 1 part by weight of surface phosphate ester or aromatic phosphonite antioxidant (C) 0.01 to 2 parts by weight of crosslinking aid.

〔Effect of the invention〕

The composition of the present invention suppresses discoloration, molecular weight decrease (MFR increase), decrease in heat aging resistance, etc. due to radiation irradiation, and has excellent physical property retention, so it can be used for physical and chemical and medical instruments that are sterilized by radiation. Suitable for food or drug containers to be sterilized, as well as instruments, supplies, clothing, rugs, footwear, etc. used in radiation or nuclear facilities, and also for containers made of non-woven fabrics or fibers used in hospitals, food factories, etc. There are also filters, membranes, clothing, etc.

[For production]

The polyolefin used in the present invention is a homopolymer or a copolymer of α-olefins such as ethylene, propylene, butene, 4-methylpentene, hexene, or these α-olefins.
Random, block or graft copolymers of olefins and less than fresh weight of other vinyl monomers (vinyl acetate, acrylic acid, maleic anhydride, styrene, etc.);
So-called olefin polymers such as oxidized, chlorinated, etc. treated products of these alone or copolymers can be used. Specifically, for example, low, medium, and high density polyethylene, ethylene, butene, hexene, etc. Polymerized linear low density polyethylene, polypropylene (homopolymer), globylene-ethylene block or random copolymer,
Propylene-ethylene-butene copolymer, polybutene,
Poly-4-methylpentene, ethylene-butene copolymer, etc. are suitable, and particularly preferred polyolefins are polypropylene, propylene-ethylene random or block copolymer, and propylene-ethylene-butene copolymer. These may be used in combination.

Specific examples of the heterocyclic hindered amine stabilizer used in the present invention include (hereinafter referred to as blank space) 61. In the above formula, M represents a methyl group.

Among these, those having a molecular weight of 500 or more, ie, the compounds of the above formulas (2) to (A), (7) and (9) to (a), are preferred from the viewpoint of bleeding.

The compounding amount of this compound is 0.01 to 1 part by weight, preferably 0.03 to 0.1 part by weight, per 100 parts by weight of polyolefin.
5 parts by weight. If the amount is too small, there will be no effect, and if the amount is too large, problems such as bleeding, coloring, and uneconomical effects will occur.

Further, specific examples of the aromatic phosphite-based or aromatic phosphonite-based antioxidant used in the present invention include H3tBu (hereinafter referred to as a blank). In the above formula, tBu represents a t-butyl group.

Among these, compounds of formula (2), a, (g) and (e) are particularly preferred.

The compounding amount of this compound is 0.01 to 1 part by weight, preferably 0.03 to 0.1 part by weight, per 100 parts by weight of polyolefin.
5 parts by weight. If it deviates from this range, problems similar to those of the hindered amine stabilizers described above will occur, which is not preferable.

Further, specific examples of the crosslinking aid used in the present invention include, for example,
Examples include triallyl isocyanurate, triallyl cyanurate, ethylene glycol dimethyl acrylate, diallyl phthalate, trimethylenepropane trimethacrylate, divinylbenzene, pentaerythritol-tetraacrylic acid ester, and the like. The blending amount is 01 to 2 parts by weight, preferably 0.03 to 0.7 parts by weight, per 100 parts by weight of the polyolefin. If it is too little, it will not be effective, and if it is too much, the quality will deteriorate.

In addition to these essential components, the composition of the present invention also contains stabilizers such as phenol-based, sulfur-based, and phosphorus-based stabilizers other than those listed above, metal soaps, nucleating agents, pigments, lubricants, antistatic agents, and anti-blocking agents. Additional components such as a UV absorber, a light stabilizer, a dispersant, a crosslinking agent, a molecular weight regulator, a filler, etc. may be added within a range that does not significantly impair the effects of the present invention.

The composition of the present invention is manufactured by a conventional resin cross-wiring method or molding method. For example, powdered or pelleted polyolefin is blended with each essential component and desired additional components, mixed in a Henschel mixer, etc., and then melt-mixed in a -screw or twin-screw extruder to form a pelletized composition. . The compounding components may be added to the polyolefin during mixing, or may be added by a masterbatch method.

The obtained pellets are subjected to injection molding, extrusion molding, blow molding,
The molded product is subjected to various molding processes such as air pressure molding, film molding, hot pressure molding, and spinning, and is further subjected to secondary processing as necessary to obtain a molded product.

The radiation irradiated to such products is well known to include α, β, γ, X-rays, etc., and γ-rays are particularly convenient in terms of penetrating power and uniformity of dose. The irradiation dose is generally 1.5 to 5 Mrad for medical instrument sterilization, and 2 Mrad for food and feed sterilization.
Selected within a range of about Mrad.

〔Example〕

100 parts by weight of a propylene-ethylene random copolymer with an MFR of sy/1o and an ethylene content of 4 parts by weight were blended with each component listed in Table 1 and 0.05 weight i of calcium stearate using a Henschel mixer. rear,
The mixture was melt-kneaded using a 30-diameter screw extruder to form pellets. This pellet was molded with an injection molding machine (240°C) and
Prepare a specimen of XBOx26 cod, and add 2.4 to 2.6
Gamma irradiation was performed with a Mrad cobalt-60 source.

Regarding the specimen after irradiation, MFR, hue (b value) by color machine, embrittlement time in open at 140°C, and 8
The specimens were heat-treated at 0°C for one week and evaluated for cracks and cracks when bent with fingers. The results are shown in Table 1.

In Table 1, components (A) and (C) indicate compounds corresponding to each number formula in the above explanation, and 'rAIC of component (C) is triallylisocyanurate, PTAE. indicates pentaerythritol-tetraacrylic acid ester. Other ingredients, RItolo, indicate tetrakis(2,5-di-t-butyl-4-hydroxyphenylpropionate)methane.

Claims (1)

[Scope of Claims] A radiation-resistant polyolefin composition characterized in that each of the following components (A) to (C) is blended with 100 parts by weight of polyolefin. (A) Heterocyclic hindered amine stabilizer 0.01 to 1 part by weight (B) Aromatic phosphite or aromatic phosphonite antioxidant 0.01 to 1 part by weight (C) Crosslinking aid 0 .01-2 parts by weight