JP2003268165A - Polyolefin molded product for radiation sterilization - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyolefin molded product for radiation sterilization which has good thermal stability on processing, and controls the generation of discoloration and an odor with sterilization treatment by irradiation with radiation to a low level. <P>SOLUTION: The polyolefin molded product for radiation sterilization comprises (A) 100 pts.wt. polyolefin resin and (B) 0.001-1 pt.wt. antioxidant composed of a phosphorous acid ester. The above polyolefin molded product for radiation sterilization has an ethylene-α-olefin copolymer as the polyolefin resin (A). Further, the above polyolefin molded product for radiation sterilization is a film as the polyolefin molded product. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyolefin molding for radiation sterilization. For more details,
TECHNICAL FIELD The present invention relates to a polyolefin molded product for radiation sterilization, which has good thermal stability during processing and in which the generation of coloring and odor associated with radiation irradiation sterilization treatment is suppressed to an extremely low level.

[0002]

2. Description of the Related Art Polyolefin resins such as polyethylene and polypropylene have excellent mechanical properties, thermal properties, moldability, etc., and are lightweight and relatively inexpensive, so they are used as various molded products, films, fibers, etc. ing.

Since polyolefin resins are excellent in hygiene, they are widely used in applications such as food containers and medical instruments. Many food containers, medical instruments and the like need to be sterilized before use, and the sterilization method by irradiation with radiation is widely used as an efficient sterilization method.

On the other hand, the polyolefin-based resin sometimes deteriorates in physical properties or is colored due to thermal oxidative deterioration during processing. Therefore, in order to suppress thermal oxidative deterioration during the processing, a phenol-based or phosphorus-based antioxidant is generally added to the polyolefin-based resin.

As described above, in general, when a molded product made of a polyolefin resin to which a phenol-based or phosphorus-based antioxidant is added is irradiated with radiation, the molded product is colored or odor is generated. I have something to do.

[0006] As a method for preventing coloring of a molded product and generation of an odor that occur when a molded product made of a polyolefin resin is irradiated with radiation, for example, JP-A-5-3394 is used.
No. 31, gazette describes a method for improving the color stability of a polyolefin composition against sterilizing radiation,
Further, Japanese Patent Laid-Open No. 11-255824 describes a food container for radiation irradiation, which has improved coloring and generation of odor. However, further improvements have been desired in terms of thermal stability and suppression of coloration and odor generation associated with radiation irradiation sterilization treatment.

[0007]

The object of the present invention is to provide a polyolefin for radiation sterilization, which has good thermal stability during processing and in which the generation of coloring and odor associated with radiation irradiation sterilization treatment is suppressed to an extremely low level. It is to provide a molded body.

[0008]

DISCLOSURE OF THE INVENTION In view of such circumstances, the inventors of the present invention have made earnest studies, and as a result, have found that phosphorus-containing phosphorus having a specific structure in which the weight is within a certain range with respect to a certain weight of the polyolefin resin. We have found that a polyolefin molded article for radiation sterilization containing an antioxidant consisting of acid esters solves the above problems, and completed the present invention.

That is, the present invention is based on 100 parts by weight of the polyolefin resin (A), an antioxidant (B) comprising a phosphite represented by the following general formula (I).
The present invention relates to a polyolefin molded product for radiation sterilization containing 0.001 to 1 part by weight. (In the formula, R ¹ , R ² , R ⁴ and R ⁵ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, an alkylcycloalkyl having 6 to 12 carbon atoms. Group, an aralkyl group having 7 to 12 carbon atoms or a phenyl group, R ³ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, X represents a sulfur atom or a —CHR ⁶ — group (R ⁶ represents a hydrogen atom,
An alkyl group having 1 to 8 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms is shown. ), And n is 0 or 1. A is an alkylene group having 2 to 8 carbon atoms * -CO (R ⁷⁾ m-
A group (R ⁷ represents an alkylene group having 1 to 8 carbon atoms, * represents a binding site with an oxygen atom, and m is 0 or 1). One of Y and Z has a hydroxyl group, an alkoxy group having 1 to 8 carbon atoms, or a carbon atom having 7 to 7 carbon atoms.
12 represents an aralkyloxy group, and the other represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. )

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The polyolefin resin used in the present invention is obtained by an ionic polymerization method or a radical polymerization method. For example, homopolymers such as polyethylene, polypropylene, polybutene-1, poly-4-methyl-pentene-1, and ethylene-propylene copolymers, ethylene-butene-1 copolymers, ethylene-4.
-Methylpentene-1 copolymer, ethylene-hexene-
1 copolymer, ethylene-octene-1 copolymer, ethylene-decene-1 copolymer, propylene-4-methylpentene-1 copolymer, propylene-butene-1 copolymer,
Examples are ethylene / α-olefin copolymers such as ethylene-propylene-butene-1 copolymer. Further α-
Copolymers with olefins and polyunsaturated compounds such as conjugated dienes and non-conjugated dienes are also included. In addition to the ethylene-α-olefin copolymer, a copolymer of ethylene and an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, and maleic acid and its esterified product or acid anhydride, ethylene and vinyl acetate, etc. Examples thereof include copolymers with vinyl esters. It can be applied to a propylene-based copolymer as well as an ethylene-based polymer. These polyolefin resins may be used alone,
You may use it in mixture of 2 or more types. Above all, ethylene / α
-Olefin copolymers are preferred, most preferably ethylene-hexene-1 copolymers.

The density of the polyolefin resin used in the present invention is usually in the range of 880 to 970 Kg / m ³ , and preferably 890 to 940 Kg / m from the viewpoint of tackiness, handleability or impact strength of the molded product. ³
It is a range.

The melt flow rate of the polyolefin resin used in the present invention measured at 190 ° C. is
It is usually in the range of 0.1 to 50 g / 10 minutes, preferably 0.2 to 20 g / 10 minutes from the viewpoint of moldability and strength.

Examples of the method for producing the polyolefin used in the present invention include a known polymerization method using a known radical polymerization catalyst or ionic polymerization catalyst. Known catalysts include, for example, peroxide catalysts, Ziegler-Natta catalysts, metallocene catalysts, and the like, and known polymerization methods include, for example, solution polymerization method, slurry polymerization method, high pressure ionic polymerization method, high pressure. A radical polymerization method, a gas phase polymerization method and the like can be mentioned. Of these, ethylene / α-olefin copolymers produced by a gas phase polymerization method using a metallocene catalyst are preferable.

The antioxidant (B) comprising phosphite ester used in the present invention is phosphite ester represented by the following general formula (I). (In the formula, R ¹ , R ² , R ⁴ and R ⁵ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, an alkylcycloalkyl having 6 to 12 carbon atoms. Group, an aralkyl group having 7 to 12 carbon atoms or a phenyl group, R ³ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, X represents a sulfur atom or a —CHR ⁶ — group (R ⁶ represents a hydrogen atom,
An alkyl group having 1 to 8 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms is shown. ), And n is 0 or 1. A is an alkylene group having 2 to 8 carbon atoms * -CO (R ⁷⁾ m-
A group (R ⁷ represents an alkylene group having 1 to 8 carbon atoms, * represents a binding site with an oxygen atom, and m is 0 or 1). One of Y and Z has a hydroxyl group, an alkoxy group having 1 to 8 carbon atoms, or a carbon atom having 7 to 7 carbon atoms.
12 represents an aralkyloxy group, and the other represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. )

In the antioxidant (B) composed of the phosphite represented by the general formula (I), the substituent R ¹ ,
R ² , R ⁴ and R ⁵ are each independently a hydrogen atom and a carbon number of 1
~ 8 alkyl group, C5-8 cycloalkyl group,
Alkylcycloalkyl group having 6 to 12 carbon atoms, 7 carbon atoms
~ 12 represents an aralkyl group or a phenyl group.

Examples of the alkyl group having 1 to 8 carbon atoms include methyl group, ethyl group, n-propyl group, i-
Examples include propyl group, n-butyl group, i-butyl group, sec-butyl group, t-butyl group, t-pentyl group, i-octyl group, t-octyl group, 2-ethylhexyl group, and the like, having 5 carbon atoms. Examples of the cycloalkyl group having 8 to 8 include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group and a cyclooctyl group, and examples of the alkylcycloalkyl group having 6 to 12 carbon atoms include a 1-methylcyclopentyl group and 1- Methylcyclohexyl group, 1-
Examples thereof include a methyl-4-i-propylcyclohexyl group, and examples of the aralkyl group having 7 to 12 carbon atoms include a benzyl group, an α-methylbenzyl group, an α, α-dimethylbenzyl group and the like.

R ¹ , R ² , and R ⁴ are preferably an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, and an alkylcycloalkyl group having 6 to 12 carbon atoms. Among them, R ¹ and R ⁴ are more preferably a t-alkyl group such as a t-butyl group, a t-pentyl group and a t-octyl group, a cyclohexyl group and a 1-methylcyclohexyl group.

More preferably, R ² is methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butyl group, t-butyl group,
an alkyl group having 1 to 5 carbon atoms such as t-pentyl group,
More preferred are methyl group, t-butyl group and t-pentyl group.

R ⁵ is preferably a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms, and more preferably a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, i-propyl group, n-butyl group,
i-butyl group, sec-butyl group, t-butyl group, t-
It is an alkyl group having 1 to 5 carbon atoms such as a pentyl group.

The substituent R ³ is a hydrogen atom or has 1 to 8 carbon atoms.
The alkyl group having 1 to 8 carbon atoms includes, for example, the same alkyl groups as described above. Preferably a hydrogen atom or an alkyl group having 1 to 5 carbon atoms,
More preferably, it is a hydrogen atom or a methyl group.

Further, when n is 0, the substituent X has two
Groups having a phenoxy group skeleton are directly bonded
When n is 1, a sulfur atom or -CHR⁶−
Group (R ⁶Is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or carbon
The cycloalkyl groups of the numbers 5 to 8 are shown. ) Is represented. -CH
R⁶-Group is a methylene group, an alkyl group having 1 to 8 carbon atoms, or
Is a methyl substituted with a cycloalkyl group having 5 to 8 carbon atoms.
Represents a len group, wherein the substituent R⁶1 to 8 carbon atoms
As an alkyl group of 5 to 8 carbon atoms
Are the same alkyl groups and cycloalkyl groups as described above.
Groups. As the substituent X, preferably n is 0 and
A group having two phenoxy group skeletons is directly bonded
Or n is 1 and a methylene group or a group
Chill group, ethyl group, n-propyl group, i-propyl group,
n-butyl group, i-butyl group, t-butyl group, etc. are substituted
It is a methylene group.

The substituent A is an alkylene group having 2 to 8 carbon atoms or a * -CO (R ⁷ ) m-group (R ⁷ is an alkylene group having 1 to 8 carbon atoms, * is a bonding site with an oxygen atom. And m is 0 or 1.).

Examples of the alkylene group having 2 to 8 carbon atoms include ethylene group, propylene group, butylene group,
Examples thereof include a pentamethylene group, a hexamethylene group, an octamethylene group, and a 2,2-dimethyl-1,3-propylene group, and a propylene group is preferable. Also * -COR
The * in the ⁷ -group indicates that the carbonyl group is the part that bonds to the oxygen atom of the phosphite group. Examples of the alkylene group having 1 to 8 carbon atoms in R ⁷ include methylene group, ethylene group, propylene group, butylene group, pentamethylene group, hexamethylene group, octamethylene group,
2,2-dimethyl-1,3-propylene group and the like can be mentioned. * -CO (R ⁷⁾ as preferably m- group, m is 0
In a * -CO- group or,, m is 1 as R ⁷ is ethylene _{* -CO (CH 2 CH 2)} - a group.

One of Y and Z has a hydroxyl group, an alkoxy group having 1 to 8 carbon atoms, or a carbon atom having 7 to 1 carbon atoms.
2 represents an aralkyloxy group, and the other represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.

Here, examples of the alkyl group having 1 to 8 carbon atoms include the same alkyl groups as described above, and examples of the alkoxy group having 1 to 8 carbon atoms include, for example, an alkyl portion having 1 to 8 carbon atoms as described above. Examples of the aralkyloxy group having 7 to 12 carbon atoms include an alkoxy group which is the same alkyl as the alkyl of, and examples thereof include an aralkyloxy group having an aralkyl moiety which is the same aralkyl as the aralkyl having 7 to 12 carbon atoms. .

As the antioxidant (B) composed of phosphite ester used in the present invention, the following compound 1 is preferable. The structure of Compound 1 is shown in Formula (Formula 1). Compound 1: 2,4,8,10-tetra-t-butyl-6- [3-
(3-Methyl-4-hydroxy-5-t-butylphenyl) propoxy] dibenzo [d, f] [1,3,2] dioxaphosphepine (trade name Sumilizer GP, manufactured by Sumitomo Chemical Co., Ltd.)

[Chemical 1]

The content of the antioxidant (B) composed of phosphite ester used in the present invention is 0.001 to 1 part by weight, preferably 100 parts by weight of the polyolefin resin (A). Is 0.01 to 0.3 parts by weight.
Most preferably, it is 0.05 to 0.2 parts by weight. If the content is less than 0.001 part by weight, the effect as an antioxidant is insufficient, and if it exceeds 1 part by weight, the antioxidant effect on the polyolefin resin is saturated, which is uneconomical. Is.

Antioxidant (B) comprising polyolefin resin (A) and phosphite ester used in the present invention
As a method for mixing the above, known methods can be mentioned, and a method for dry blending, a method for melt blending and the like can be mentioned. Various blenders such as a Henschel mixer and a tumbler mixer are used in the dry blend, and various mixers such as a single-screw extruder, a twin-screw extruder, a Banbury mixer, and a heat roll are used in the melt blend. Further, an antioxidant (B) composed of phosphite ester was melt-blended in advance at a high concentration of 1 to 10% by weight to prepare a master batch, and finally the master batch was blended so as to have a desired concentration. It can also be used.

If desired, a phenol type antioxidant or a phosphorus type antioxidant other than the antioxidant (B) composed of phosphite ester may be added to the polyolefin molded product for radiation sterilization of the present invention. May be. As antioxidants other than the antioxidant (B) composed of phosphite,
For example, examples of phenolic antioxidants include 2,6-di-t-butyl-4-methylphenol (BHT), n-
Octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (trade name Irgan
ox1076, manufactured by Ciba Specialty Chemicals), pentaerythrityl-tetrakis [3- (3,5-di-t-
Butyl-4-hydroxyphenyl) propionate]
(Product name Irganox 1010, manufactured by Ciba Specialty Chemicals), 1,3,5-tris (3,5-di-te)
rt-Butyl-4-hydroxybenzyl) isocyanurate (trade name Irganox 3114, manufactured by Ciba Specialty Chemicals), 1,3,5-trimethyl-2,4.
6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, 3,9-bis [2- {3- (3-
t-butyl-4-hydroxy-5-methylphenyl) propionyloxy} -1,1-dimethylethyl] -2,
4,8,10-tetraoxaspiro [5.5] undecane (trade name Sumilizer GA80, manufactured by Sumitomo Chemical Co., Ltd.) and the like can be mentioned.

Examples of phosphorus antioxidants include distearyl pentaerythritol diphosphite, tris (2,4-di-t-butylphenyl) phosphite (trade name Irgafos168, manufactured by Ciba Specialty Chemicals), Bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite, tetrakis (2,4-di-t-butylphenyl) 4,4 ′
-Biphenylene Phosphonite (trade name Sando
stab P-EPQ, Clariant Chapan Co., Ltd., screw (2
-T-butyl-4-methylphenyl) pentaerythritol diphosphite and the like.

The polyolefin molding for radiation sterilization of the present invention may optionally contain an anti-blocking agent, a lubricant,
Additives such as pigments, antistatic agents and processability improvers may be added. These additives may be used alone or in combination. Examples of the anti-blocking agent include an inorganic anti-blocking agent and an organic anti-blocking agent.Examples of the inorganic anti-blocking agent include silica, diatomaceous earth, talc, aluminosilicate, kaolin, hydrotalcite and calcium carbide. As the organic anti-blocking agent, for example, Eposta-
MA (manufactured by Nippon Shokubai Co., Ltd.). Examples of the lubricant include higher fatty acid amides and higher fatty acid esters. Examples of pigments include white pigments and carbon black. Examples of the antistatic agent include glycerin esters and sorbitan acid esters of fatty acids having 8 to 22 carbon atoms, alkyldialkanolamides of fatty acids having 8 to 22 carbon atoms, polyethylene glycol esters, alkyldiethanolamine, and the like.
Examples of the processability improver include a fatty acid metal salt such as calcium stearate and a fluorine-based processing aid.

If necessary, other resin may be added to the polyolefin molded product for radiation sterilization of the present invention. The other resin is a resin other than the polyethylene resin (A) used in the present invention, and examples thereof include a low density elastomer used for improving impact strength. These other resins may be used alone or in combination.

The polyolefin molded product for radiation sterilization of the present invention is irradiated with radiation such as γ-rays and electron beams for the purpose of sterilization, and its application is not particularly limited as long as it is used for radiation sterilization. It is not something that is
It is mainly used for food packaging containers and films, medical instruments and their packaging containers and films. Among them, it is suitable for a film for radiation sterilization.

[0034]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The following polyolefin-based resins and antioxidants were used in the examples or comparative examples. 1. Polyolefin resin (A) PO-1: Sumikasen E FV403 (Japan Evolution
Co., Ltd., Sumitomo Chemical Co., Ltd. sales), ethylene-hexene-1 copolymer produced by metallocene catalyst, MFR
= 4 g / 10 min, density = 919 Kg / m ³ PO-2: Sumikasen L FS150 (Sumitomo Chemical Industries, Ltd.
(Manufactured by K.K.) containing no antioxidant, ethylene-butene-1 copolymer produced by Ziegler-Natta catalyst, MFR = 1 g / 10 min, density = 921 Kg / m ³ 2. Antioxidant (B) AO-1: Sumitomo Chemical Co., Ltd., trade name Sumilizer G
PAO-2: Ciba Specialty Chemicals, trade name
Irganox 1076 AO-3: Clariant Japan KK, trade name Sand
ostab P-EPQ

The film was evaluated according to the following method. (1) Yellowness index (YI value) The YI value was measured using a color computer SM-5-CH (Suga Test Instruments). The lower this value is, the better the coloration is suppressed.

(2) Odor The samples of Examples and Comparative Examples were roughly classified into the following two ranks by a sensory test. A: A weak odor is felt. B: A strong pungent odor is felt.

(3) Thermal stability Using a Labo Plastomill device manufactured by Toyo Seiki Co., Ltd., a temperature of 220
While kneading at a temperature of 150 ° C. and a rotor speed of 150 rpm, the torque (resistance force) applied to the rotor was detected, and the change with time was examined. In the case of polyethylene, the cross-linking proceeds due to heat deterioration, so that the torque increases with time and then decreases due to decomposition. In the obtained time-torque curve, the time (Tp) at the torque peak was determined. The longer this time, the better the thermal stability.

Examples 1 to 4 PO-1 (ethylene / hexene-1 copolymer, MFR =
4g / 10min, density = 919Kg / m ³⁾ or P
O-2 (ethylene / butene-1 copolymer, MFR = 1 g
/ 10 min, density = 921 Kg / m ³ ) powder, Sumilyzer GP as an antioxidant (B) consisting of phosphite ester was added at a ratio shown in Table 1, and after mixing with a Henschel mixer, The mixture was melt-kneaded and granulated with a 40 mmφ single screw extruder. The obtained pellets are 150 mm in length and 180 m in width at 150 ° C using a heat press machine.
A test piece having m and a thickness of 2 mm was molded. This test piece was gamma-rayed at a dose of 20 kilogray using a cobalt 60 source.
The line was irradiated. Table 1 shows the results of evaluation of the degree of coloring and odor of the test pieces after irradiation.

Comparative Examples 1 and 2 Carried out in the same manner as in Examples 1 to 4 except that an antioxidant different from the phosphite ester which is a requirement of the present invention was used and added at the ratio shown in Table 2. did. The results are shown in Table 2.

Examples 5 and 6, Comparative Example 3 PO-2 was mixed with an antioxidant in the composition and proportion shown in Table 3 using a Henschel mixer, and then melt-kneaded with a 40 mmφ single screw extruder to granulate. did. The thermal stability of the obtained pellet was evaluated. The results are shown in Table 3.

Examples 1 to 6 satisfying the requirements of the present invention are
It can be seen that the thermal stability is excellent, the coloration after γ-ray irradiation is suppressed, and the generation of odor is suppressed to an extremely low level.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

As described in detail above, according to the present invention, for radiation sterilization, which has good thermal stability during processing and in which the generation of coloring and odor associated with radiation irradiation sterilization treatment is suppressed to an extremely low level. A polyolefin molded product can be obtained.

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Claims (3)

[Claims] 1. An amount of 0.001 to 1 part by weight of an antioxidant (B) composed of a phosphite represented by the following general formula (I) relative to 100 parts by weight of a polyolefin resin (A). A polyolefin molded body for radiation sterilization, which is characterized in that: (In the formula, R ¹ , R ² , R ⁴ and R ⁵ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, an alkylcycloalkyl having 6 to 12 carbon atoms. Group, an aralkyl group having 7 to 12 carbon atoms or a phenyl group, R ³ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, X represents a sulfur atom or a —CHR ⁶ — group (R ⁶ represents a hydrogen atom,
An alkyl group having 1 to 8 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms is shown. ), And n is 0 or 1. A is an alkylene group having 2 to 8 carbon atoms * -CO (R ⁷⁾ m-
A group (R ⁷ represents an alkylene group having 1 to 8 carbon atoms, * represents a binding site with an oxygen atom, and m is 0 or 1). One of Y and Z has a hydroxyl group, an alkoxy group having 1 to 8 carbon atoms, or a carbon atom having 7 to 7 carbon atoms.
12 represents an aralkyloxy group, and the other represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. ) 2. The polyolefin resin (A) is ethylene-
The polyolefin molded article for radiation sterilization according to claim 1, which is an α-olefin copolymer. 3. The polyolefin molded product for radiation sterilization according to claim 1, wherein the polyolefin molded product is a film.