JPS61155435A - Radiation-resistant polyolefin composition - Google Patents

Abstract

PURPOSE:The titled composition exhibiting excellent resistance to degradation, discoloration, etc., caused by irradiation, prepared by mixing a highly crystalline polyolefin with a lowly crystalline olefin copolymer comprising specified 1- olefins. CONSTITUTION:The desired radiation-resistant polyolefin composition is obtained by mixing 20-90pts.wt. highly crystalline polyolefin (A) with 0-10pts.wt. lowly crystalline copolymer (B) comprising a 4C or higher 1-olefin and another 1-olefin or a diolefin (the total of components A and B is 100pts.wt.). It is preferable that said crystalline polyolefin component A is a homopolymer or a copolymer having a crystallinity as determined by X-ray diffractometry >=40% and a propylene unit content >=45mol%, and said lowly crystalline copolymer, component B, is an olefin copolymer having a crystallinity <=40% and a 4C or higher 1-olefin content >=5mol%.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to radiation-resistant polyolefin compositions, and more particularly to radiation-resistant polyolefin compositions that have been exposed to radiation, particularly high-energy radiation such as X-rays, gamma rays, and electron beams. The present invention relates to a polyolefin composition that has excellent resistance to undesirable changes such as deterioration of physical properties and discoloration that occur in some cases.

Background Art and Technical Problems of the Invention Recently, medical instruments made of glass, such as syringe barrels, drip containers, etc., have been replaced by those made of resin. The place is
Disinfection, which is particularly important for medical instruments, remains a problem. Among these, sterilization by γ-ray irradiation is beginning to be adopted in place of ethylene oxide, which has been used in conventional sterilization. Since r-rays are high-energy rays, conventionally used products made of polyvinyl chloride resin tend to break the molecular chains of the resin, greatly reducing the physical properties of the resin and making it difficult to use. .

In order to solve this problem, adding a stabilizer is being considered, but nothing suitable for saving lives has yet been discovered.

In addition, it is possible to use olefin resin as a resin molded product for such radiation sterilization, but the olefin resin that has been irradiated with radiation has a significant decrease in elongation at yield point over time after irradiation, and the above-mentioned This book is not yet satisfactory in terms of applications.0 Purpose of the Invention The present inventors have developed a composition in which a low crystalline olefin copolymer containing a 1-olefin having 4 or more carbon atoms is blended with a high crystalline polyolefin. 1. The material has excellent durability against radiation irradiation such as γ-rays. It has been found that this composition shows almost no deterioration in physical properties such as mechanical properties, not only after irradiation, but also over a long period of time thereafter.

That is, an object of the present invention is to provide an olefin resin composition that has remarkable resistance to physical property deterioration and discoloration caused by radiation irradiation and subsequent aging.

Another object of the present invention is to provide an olefin resin composition that is capable of imparting excellent radiation resistance to propylene resins that are particularly prone to degradation and deterioration due to radiation.

Still another object of the present invention is to provide an olefin resin composition that can be advantageously used in the production of instruments that are subjected to radiation irradiation treatment, particularly sterilization treatment.

Structure of the Invention According to the present invention, it is characterized by comprising a highly crystalline polyolefin (a) and a low crystalline copolymer (b) of a 1-olefin having 4 or more carbon atoms and another 1-olefin or diolefin. A radiation-resistant polyolefin composition is provided.

Effects of the Invention In general, when a polymeric substance is irradiated with ionizing radiation such as R-rays, it undergoes a process of generating primary electrons to generate radicals in the polymer chain, and in an oxygen atmosphere, these radicals combine with oxygen. This generation of polymer chain radicals causes deterioration due to molecular chain scission, or polymer chain radicals recombine [and crosslink the molecular chains].In olefin resins, Polypropylene is a resin with a remarkable tendency to degrade, while polyethylene is a resin with a remarkable tendency to crosslinking. is produced, and this radical is said to recombine due to steric hindrance effect.

Molecular chain scission, or degradation, caused by scavenging radicals (peroxide radicals) is noticeable not only during radiation irradiation, but also over time; for example, in the case of propylene resins, the elongation at break decreases after irradiation Although it was several tens of inches, it decreased to less than a few inches over time.

On the other hand, according to the present invention, by incorporating a copolymer containing a 1-olefin having 4 or more carbon atoms into an olefin resin that has a marked tendency to degrade, radiation irradiation and subsequent The retention rate of elongation at break over time can be maintained at 80% or more.

In addition, the aging acceleration test (temperature 80C) after radiation irradiation used in the examples described below is a severe test in which only 5 days corresponds to one year of normal use, and the composition of the present invention The fact that the physical properties show only a slight decrease even after 4 weeks of the test is a completely unexpected and surprising fact.

This is because, as mentioned above, molecular chain scission, or degradation, is thought to occur preferentially in resins containing 6th-class carbon atoms, such as propylene-based resins.
This is because olefin copolymers are expected to exhibit a similar tendency.

Preferred Embodiments of the Invention The preferred embodiments of the present invention will be explained in detail below.

Highly crystalline polyolefin which is component (a) constituting the composition of the present invention, such as polyethylene, polypropylene, poly-4-methyl-1-pentene, poly-1-hexene, poly-1-octene, poly-1- In addition to 1-olefin homopolymers such as decene, ethylene-propylene copolymers, ethylene-4-methyl-1-pentene copolymers, ethylene-1-octene copolymers, propylene-1
-butene copolymer, propylene-4-methyl-1-pentene copolymer, propylene-1-decene copolymer, 4-
Methyl-1-pentene-1-hexene copolymer, 4-methyl-1-pentene-1-7'ene copolymer, and multicomponent polymers such as propylene-ethylene-1-butene terpolymer. The crystallinity by X-ray diffraction method is usually 40-70.
%, preferably 45 to 60%, MFR (2 OC) usually 0.5 to 100 P/10, preferably 6 to 50 F/
I can list 10 things in order.

Of course, any of the above-mentioned combinations of homopolymers, combinations of multi-component polymers, and combinations of homopolymers and multi-component polymers can be used.

Further, the structure of the polymer is not limited as long as it satisfies the above crystallinity and MFR, and may be a random copolymer or a block copolymer, for example.

Of course, even though it is called a random copolymer, it means that each monomer is randomly introduced into the molecular chain during polymerization. If it is, the properties of a crystalline copolymer will appear. Furthermore, since the block copolymer is obtained by melting the block copolymer and charging each monomer into the polymerization system in a block form, the copolymer is not necessarily composed only of homopolymer blocks. For example, in the case of a block copolymer consisting of propylene and ethylene, even if the monomers are charged in the order of propylene → ethylene, the monomers are added in the following order: propylene homopolymer block → propylene-ethylene random copolymer 7-lock → 6-block ethylene homopolymer block. Usually, a copolymer consisting of ethylene is produced, but depending on the operation at the time of entrainment, it is possible to prevent the formation of ethylene homopolymer blocks or copolymer blocks.

Among these polymers, preferred are Hononoke propylene homopolymers, random copolymers of propylene and ethylene (containing propylene units! 98 to 45 mol%), and ternary random copolymers of propylene-1-butene-ethylene. Copolymer (
propylene unit content: 98 to 55 ruti, 1-butene unit content: t05 to 20 mol%), and a propylene-1-butene copolymer (propylene unit content: 98 to 55 mol%).

In particular, the most important feature of the present invention is that it can significantly suppress the decline in physical properties due to radiation exposure or subsequent aging, compared to propylene resins that have a marked tendency to degrade.

A low-crystalline copolymer or multicomponent polymer of a 1-olefin having 4 or more carbon atoms and another 1-olefin or diolefin, which is the component (b) constituting the composition of the present invention, is melted and determined by X-ray diffraction method. Crystallinity is usually less than 40%, preferably 35% or less, MFR (230r) usually 0.5 to 100,
Good size 3-50? /10m.

Examples of component (b) include ethylene-1-butene copolymer, ethylene-4-methyl-1-pentene copolymer, ethylene-1-hexene copolymer, propylene-1-butene copolymer, propylene -4-methyl-1-pentene copolymer, propylene-1-hexene copolymer, propylene-1-decene copolymer, 4-methyl-1-pentene-
1-octene copolymer and 4-methyl-1-pentene-
Examples include 1-decene copolymer.

The content of the 1-olefin having 4 or more carbon atoms in the copolymer of component (b) may be varied, but it is generally 5 to 98 molty, particularly 10 to 45 molty. is desirable.

The composition of the present invention contains (a) a crystalline polyolefin, usually 20 to 90 parts by weight, preferably 40 to 70 parts by weight; Usually 80 to 10 parts by weight, preferably 60 to 60 parts by weight of a low-crystalline copolymer or multicomponent polymer with diolefin is blended (this is a book consisting of two parts).

Of course, even if component (a) consists of two or more types,
(b) Component may consist of two or more kinds of components O In the present invention, it is possible to use a combination of crystalline polyolefin (a) and low crystallinity copolymer or multicomponent polymer (b). is important. That is, when component (a) is used alone, radiation irradiation causes a significant decrease in various physical properties, especially a significant decrease in elongation at break, and moreover, the toughness of the resin is almost completely lost over time. However, by blending the low crystallinity copolymer or multicomponent polymer (6) such as butene-1 described above, the deterioration of physical properties can be almost suppressed.

The use of crystalline polyolefin (a) also maintains various physical properties such as elastic modulus, yield point stress, stiffness, and impact strength of the article formed from this composition at an excellent level [-and makes this article economical. This is important in order to provide products at low prices.

If the raw materials are in the form of powder or granules, they can be blended using a Henschel mixer, Banbury mixer, VW blender, pellet mill, etc.; however, it is necessary to melt and knead both in an extruder, etc. Depending on the use, the composition of the present invention can be used as an oxidation stabilizer, a heat stabilizer, a weathering stabilizer, a light stabilizer, It may contain antistatic agents, processing aids, various inorganic fillers, carbon black, etc.

When the composition of the present invention is used as a material for medical devices, it is preferable to incorporate tocopherol (vitamin E) as an oxidation and heat stabilizer.
,5-ditcrt-butyl-4-hydroxyphenyl)propionyloxymethylcomethane (trade name Irganox 1010), 1.1.3-trisC3-(3,
Of course, stabilizers containing a large number of sterically hindered phenol nuclei such as 5-di-1trt-)(thyl-4-hydroxyphenylprobionyloxymethyl)propane (trade name Irganox 1076) can also be used.

The composition of the present invention has excellent radiation resistance and has excellent strength and other physical properties even after being exposed to radiation, so it can be used in various applications where it is exposed to radiation, such as It is extremely useful as a resin material constituting medical instruments subjected to radiation sterilization, various containers, and packaging containers.

Examples 1 to 6 The high crystalline polyolefin shown in Table 1 and the low crystalline α-olefin copolymerized polymer shown in Table 1 were blended in various ratios shown in the same table, and the mixture was heated in an extruder at 260C in a nitrogen atmosphere. The mixture was melt-kneaded and the following stabilizer was added in the same amount to form a pellet.

Approximately 482 of these pellets are placed in a frame on a press (150 animals x 15
0III+×2fl), heated to 200C and pressed at 9/-G to a pressure of 100 (7) to form a press sheet with a thickness of 1.

From this press sheet, 1) Punch out a size 53 dumbbell and hang it with one end between the clips.
Perform line irradiation. The irradiation dose was 2.5 Mrad, the temperature of the irradiation system was 23C0K after irradiation, and the dumbbells were heat-treated at 80C.
Thereafter, the elongation at break is measured.

The degree of deterioration of the sample due to irradiation was converted from the elongation at break after heat treatment to the elongation remaining based on the high elongation at break of the unirradiated sample after heat treatment for the same time. According to the same table, it can be seen that the composition of the present invention retains 80% or more of the elongation rate before irradiation after heat treatment for 4 weeks after irradiation. Dumbbell tensile testing machine (
Stabilizers: (1) Tetrakis [methylene (515-tcrt
-Butyl-4-hydroxyphenyl)probionyloxy]methane 0.6 part and (2) dilaurylthiodipropionate 0.3 part Measurement method: Density ASTM D1505 Elongation at break AST・V D 638 Tensile yield at break point stress

Claims (5)

[Claims] (1) A radiation-resistant polyolefin characterized by comprising a highly crystalline polyolefin (a) and a low crystalline copolymer (b) of a 1-olefin having 4 or more carbon atoms and another 1-olefin or diolefin. Composition. (2) Highly crystalline polyolefin (a) is present in an amount of 20 to 90 parts by weight, and low crystalline copolymer (b) is present in an amount of 80 to 10 parts by weight, based on a total amount of both components of 100 parts by weight. A composition according to claim 1, characterized in that: (3) Highly crystalline polyolefin (a) is a homopolymer or copolymer having a crystallinity measured by X-ray diffraction of 40% or more and containing 45 mol% or more of propylene units, as described in claim 1 Composition of. (4) Highly crystalline polyolefin (a) contains 98 to 45 mol% of α-olefin units and 2 to 55 mol% of ethylene units
The composition according to claim 1, which is obtained by random copolymerization of and has a crystallinity of 40% or more as measured by X-ray diffraction. (5) The low-crystalline copolymer (b) is an olefin copolymer with a crystallinity as measured by X-ray diffraction as less than 40% and containing 5 mol% or more of 1-olefin having 4 or more carbon atoms. A composition according to claim 1, characterized in that: