JPS6173711A - Polypropylene composition - Google Patents

Abstract

PURPOSE:A PP composition excellent in radiation resistance, prepared by mixing PP or an ethylene/propylene random copolymer with an organic peroxide and a specified modifier. CONSTITUTION:100pts.wt. PP or ethylene/propylene random copolymer (A) of a melt index of 1-50 is mixed with 0.005-0.2pts.wt. organic peroxide (B) having a decomposition rate in terms of a half-life period at the m.p. of compo nent A >=1sec and one at 300 deg.C <=10min and 0.01-0.5wt% triallyl (iso)cyanurate or diallyl (iso)phthalate (C) as a modifier.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to polypropylene compositions, and more particularly:
The present invention relates to a polypropylene composition having radiation resistance.

BACKGROUND ART When polypropylene molded products are used as medical devices, they are sometimes irradiated with radiation such as gamma rays for the purpose of sterilization.

At that time, the molded product itself deteriorates due to the radiation, and the tensile elongation of the molded product decreases, resulting in a significant drop in impact resistance. Furthermore, there was a problem that deterioration progressed over time after irradiation, and the molded product became extremely brittle.

In conventional polypropylene compositions, the ratio is 2.5 to 5. OMr.
Deterioration progresses due to ad cobalt 60 irradiation, and elongation after irradiation decreases significantly. As a method for preventing the deterioration of polyolefins due to such radiation irradiation, Japanese Patent Application Laid-Open No. 55-1
As shown in Japanese Patent Application Laid-open No. 9199, Japanese Patent Application Laid-open No. 58-42638, and Japanese Patent Application Laid-open No. 58-49737, methods of adding hindered amine thread compounds or phenolic compounds to resins are known. However, the effect of imparting radiation resistance by such additives is still not sufficient, and there is also the problem that the commercial value of the molded article is often impaired due to the coloring of the additives.

The present inventor previously demonstrated in Japanese Patent Application No. 163200/1983 that an ethylene-propylene random copolymer containing 2.8 to 7.0% by weight of ethylene has excellent radiation resistance. As the ethylene content increased, a decrease in rigidity was observed, and there was a limit to the products that could be used. Furthermore, the present inventor has filed Japanese Patent Application No. 58-164137 and Japanese Patent Application No. 58
In application No. 174372, 100 parts by weight of polypropylene or ethylene-propylene copolymer was added
0.05 to 1 part by weight of iso)cyanurate or diallyl(
It has been shown that the radiation resistance of the polymer composition can be improved by incorporating 0.05 to 2 parts by weight of iso)phthalate. Although this composition was found to be effective in maintaining physical properties immediately after irradiation, it was still not perfect in preventing deterioration of physical properties over time after irradiation.

SUMMARY OF THE INVENTION Accordingly, the present invention aims to further improve the radiation resistance of the conventional polypropylene or ethylene-propylene copolymer compositions described above.

Means and action for solving the problem According to the present invention, the problem is solved by adding 100 parts by weight of polypropylene or ethylene-propylene random copolymer to
By a radiation-resistant polypropylene resin composition comprising 0.005 to 0.2 parts by weight of an organic peroxide and 0.01 to 0.5 parts by weight of triallyl(iso)cyanurate or diazyl(iso)phthalate. resolved.

The ethylene-propylene copolymers used in the present invention include random copolymers and block copolymers. Copolymers are preferred. The melting index (MF1, JIS K 675B) of these resins
Therefore, the load was 2.16 kg and the temperature was 230°C. same as below.

) is not particularly limited, and the preferred range varies depending on the molding method, but in the case of injection molding, MFr = 1 to
The range is 50.

The organic peroxide used in the present invention can be any general-purpose organic peroxide, such as polypropylene or ethylene-
The propylene copolymer is selected from those whose decomposition rate at the melting point is longer than 1 second in half-life and whose decomposition rate at 300°C is shorter than 10 minutes in half-life. Examples of preferred organic peroxides include organic peroxides such as hydroperoxides, alkyl peroxides, acyl peroxides, ketone peroxides, alkyl peresters, peroxydicarbonates, and silicon peroxides. Among the substances, those with the above decomposition rate are typically t-butyl hydroperoxide, dicumyl peroxide, and 1,3-bis(1-butylperoxyisopropyl).
Examples include benzene, benzoyl peroxide, methyl isobutyl ketone peroxide, t-butyl perbenzoate, diisoisopropyl peroxydicarbonate, vinyltris(t-butylperoxy)silane, and the like.

These organic peroxides can be used alone or in any mixture. The amount of organic peroxide used is 5 to 0.2 parts by weight, preferably O,'0, per 100 parts by weight of polypropylene or ethylene-propylene copolymer.
05 to 0.1 part by weight. The organic peroxide is thought to be useful in advance to crush the parts that are likely to generate carps, such as double bonds, that exist in the molecular chain of polypropylene or ethylene-propylene copolymer, but if the amount of the organic peroxide is 0. If the amount exceeds .2 parts by weight, severe molecular cleavage will occur, making it impossible to obtain a polypropylene or ethylene-propylene copolymer having a molecule i that can be put to practical use. If the amount of organic peroxide is too small, the desired radiation resistance
This is particularly undesirable since it becomes impossible to prevent the physical properties of the molded article from deteriorating over time after irradiation with radiation.

Modifiers used in combination with organic peroxides in the present invention include triallyl cyanurate (TAC),
Realyl isocyanurate (TA■C), diallyl phthalate (DAP) and diallyl isophthalate (DA
One or more compounds selected from IP) are used.

These modifiers are blended in an amount of 0.01 to 0.5 parts by weight, preferably 0.05 to 0.25 parts by weight, per 100 parts by weight of polypropylene or ethylene-propylene copolymer.

If the amount is less than 0.01 part by weight, the effect will be poor and the resin will deteriorate after radiation irradiation, resulting in a decrease in tensile elongation, which is undesirable.On the other hand, if it exceeds 0.5 part by weight, the radiation crosslinked portion will increase and the tensile elongation will increase. This is not preferable because it tends to reduce elongation.

The composition of the present invention may be blended with ethylene-propylene rubber, etc. to impart cold resistance, or may be blended with sodium benzoate, dibenzylidene sorbitol, bis(P-methylbenzylidene) sorbitol, etc. to impart transparency. Adding clarifying agents and nucleating agents, or depending on other purposes, antioxidants, ultraviolet absorbers, lubricants, antistatic agents,
Anti-blocking agents, dispersants, neutralizing agents, etc. can be added.

The composition of the present invention may be formed into any molded product, but
Generally, powdered polypropylene or ethylene-
A predetermined amount of organic peroxide and a modifier, and if necessary, the various blends or additives mentioned above are added to the propylene copolymer, mixed appropriately, and then melt-kneaded in an extruder to form pellets. is made into a molded product by injection molding or the like.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but it goes without saying that the scope of the present invention is not limited to these Examples. In addition, in the following examples, "%" and "parts" respectively indicate "% by weight" and "parts by weight" unless otherwise specified.

J Noze 111-4 and Comparative Examples 1-5 Polypropylene or ethylene-propylene copolymer compositions in which the organic peroxide and modifier shown in Table 1 are blended with 100 parts by weight of polypropylene or ethylene-propylene copolymer. and 0.05 part of tetrakis[methylene (3,5-di-t-7'' thyl-hydroxyphenyl)propionate cometaf, 0.05 part of calcium stearate, and 0.05 part of dibenzylidene sorbitol] as additives.
35 parts were added and thoroughly mixed. After mixing, 40++uaφ
It was extruded at 220°C using an extruder and pelletized. Using this pellet, a 10 oz.
A flat plate of cm×12 cm was obtained.

The radiation resistance of the flat plate was evaluated by irradiating 3 Mrad of T-rays with this flat cobalt 60 radiation source. The obtained results are the first
Shown in the table.

(Left below) [Footnotes] *1 If machine peroxide A: 2.5-dimethyl-2゜5-
Di(t-butylperoxy)hexane *2 Organic peroxide B dibutyl peroxide *3 Organic peroxide C: 1,3-bis(t-butylperoxyisopropyl)benzene *4 Tensile strength: J T S By K6758*
5 Tensile elongation rate: According to JIS K675B *6 Impact strength after falling weight: Using the above-mentioned injection molded 2 mm thick flat plate, drop the weight from a certain height and calculate the energy value (kg cm) until it breaks. ).

As in Comparative Examples 1.2 and 4, the tensile elongation rate and impact of the molded product after radiation irradiation are The strength decreases rapidly.

In Comparative Example 3, even if the amount of organic peroxide is appropriate, if the modifier is as high as 0.75%, crosslinking continues even after radiation irradiation, and the tensile elongation rate and impact strength decrease with time.

In Comparative Example 5, even if the modifying agent was used in an appropriate amount, when the organic peroxide was used in an excessive amount, the molecular cleavage was large, and the elongation rate decreased sharply even in the non-irradiated state, even though it was a random copolymer. Impact strength is low.

Furthermore, it becomes extremely brittle due to radiation exposure.

From the results of Examples 1 to 4, it was found that a composition with good radiation resistance can be created by combining an appropriate amount of an organic peroxide and a modifier regardless of whether it is a homopolymer or a random copolymer, and radiation sterilization is not necessary. It is clear that it can be used for medical equipment, food packaging materials, nuclear power related materials, etc.

(Margin below)

Claims (1)

[Claims] 1. 0.005 to 0.00 parts by weight of an organic peroxide to 100 parts by weight of polypropylene or ethylene-propylene random copolymer.
2 parts by weight and 0.01 to 0.5 parts by weight of triallyl(iso)cyanurate or diallyl(iso)phthalate.