JP3319038B2 - Polypropylene resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene-based resin composition which exhibits little deterioration in physical properties such as tensile strength even when irradiated with radiation, has little discoloration and odor, and has excellent transparency.

[0002]

2. Description of the Related Art Polypropylene resins are widely used in food containers, medical instruments and the like because of their excellent hygiene properties and rigidity and impact strength. However, in applications such as food containers and medical equipment, it is important to be able to confirm that the contents are free of dust and other foreign matter.
It is also desirable that the true color tone of the contents can be confirmed without being disturbed by the container. For this reason, in the above-mentioned applications, in reality, it is desired to improve the transparency of containers and instruments made of polypropylene resin. In addition, food containers, medical instruments, etc. need to be sterilized before use in view of their applications. Usually, heat sterilization using steam, gas sterilization using ethylene oxide gas with strong sterilizing action, peroxidation Sterilization with hydrogen is performed. 2. Description of the Related Art In recent years, a radiation sterilization method for performing sterilization by irradiating radiation has been developed, and examples of use in sterilization of food containers or medical instruments have increased. Polypropylene resin is stable with respect to heat sterilization and gas sterilization with steam, but has poor stability with respect to radiation sterilization, and has a drawback of causing yellowing, generation of odor, and deterioration of physical properties. In particular, regarding the decrease in physical properties, when a nucleating agent is added to the polypropylene resin to improve transparency, there is a disadvantage that irradiation with radiation significantly reduces mechanical properties such as tensile strength and tensile elongation. Various methods have been proposed in order to prevent yellowing, odor generation, and deterioration in physical properties of the polypropylene resin due to such radiation irradiation (for example, JP-A-58-165858, JP-A-60-112845, 60-2124
42, JP-A-62-235344, JP-A-62-235345, and JP-A-1-38454. However, these known methods are not sufficiently improved.

[0003]

DISCLOSURE OF THE INVENTION The present invention relates to a polypropylene-based resin which is stable to radiation-resistant irradiation, has very little yellowing and odor, has a small decrease in physical properties such as tensile strength, and has excellent transparency. It is an object to obtain a composition.

[0004]

Means for Solving the Problems The present inventors have repeatedly studied the improvement of the transparency of the above-mentioned molded article of a polypropylene resin having excellent radiation resistance, and as a result, it has been found that one or two kinds of α or -It has been found that the above problems can be solved by blending a specific hindered phenolic antioxidant with a polypropylene-based random copolymer containing 2 mol% or more of olefin and a vinylcycloalkane compound, and arrived at the present invention. did.

That is, the present invention relates to (A) 2% by mole or more of α-olefin having 2 to 8 carbon atoms (excluding 3 carbon atoms), Polypropylene random copolymer 100 containing 0.001 to 5.0 mmol% of alkane compound
(B) triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 2,2'-oxamide-bis [ethyl-3- (3 , 5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl-4).
-Hydroxyphenyl) propionate, and 3,9
-Bis [1,1-dimethyl-2- ｛β- (3-tert
-Butyl-4-hydroxy-5-methylphenyl) propionyloxydiethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane and at least one hindered phenolic antioxidant selected from the group consisting of: 0.0
A polypropylene resin composition having good stability to radiation irradiation and excellent transparency, characterized by being blended with 1 to 1.0 part by weight.

[0006] The polypropylene random copolymer in the present invention refers to a random copolymer of propylene with one or two or more α-olefins having 2 to 8 carbon atoms (excluding 3 carbon atoms) and a vinylcycloalkane compound. It is a copolymer. Preferably, a random copolymer of propylene with ethylene and / or butene-1, and further with vinylcyclohexane or vinylcyclopentane, or a random copolymer of propylene with butene-1 and vinylcyclohexane or vinylcyclopentane. The α-olefin content must be at least 2 mol%. 2
If it is less than mol%, degradation due to irradiation is large, and transparency is not good. The content of the vinylcycloalkane compound must be at least 0.001 mmol%.
If it is less than 0.001 mmol%, the effect of improving transparency is small. In addition, the vinylcycloalkane compound is prepared in advance of a high content polypropylene random copolymer,
This may be adjusted to the desired content by dilution (blend). The intrinsic viscosity of the polypropylene random copolymer in the present invention is usually from 1.0 to 3.
5 dl / g, preferably 1.3 to 3.0 dl / g is used.

The hindered phenolic antioxidant triethylene glycol-bis [3-
(3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 2,2′-oxamido-bis [ethyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] Octadecyl-3- (3,5-di-tert-butyl-4-
(Hydroxyphenyl) propionate, and 3,9
-Bis [1,1-dimethyl-2- ｛β- (3-tert
-Butyl-4-hydroxy-5-methylphenyl) propionyloxydiethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane was added in an amount of 0.1 to 100 parts by weight of the polypropylene resin. The amount is from 0.01 to 1.0 part by weight, preferably from 0.03 to 0.3 part by weight. 0.
Addition of less than 01 parts by weight has no remarkable effect on the stability after irradiation, and addition of more than 1.0 part by weight does not only increase the effect significantly,
High price results in economic problems.

In the present invention, sodium benzoate, aluminum p-tert-butyl benzoate,
Sodium bis (4-tert-butylphenyl) phosphate, and general formula (I) (Wherein, R ₁ and R _{2 each} represent a hydrogen atom or an alkyl group having 2 to 8 carbon atoms, an alkoxy group or a hydroxyl group, or a halogen atom, m and n each independently represent an integer of 1 to 3, l is 0 or The sorbitol derivative represented by the formula (1) can be used. In particular, sorbitol derivatives are preferred.

As a specific example of the sorbitol derivative, 1.
3,2,4-dibenzylidene sorbitol, 1,3,2
-4-di (p-ethylbenzylidene) sorbitol, 1
3,2,4-di (p-propylbenzylidene) sorbitol, 1,3,2,4-di (p-butylbenzylidene) sorbitol, 1,3,2,4-di (p-hexylbenzylidene) sorbitol, 1,3,2,4-di (p
-Ethoxybenzylidene) sorbitol, 1.3-p-
Chlorbenzylidene-2,4-p-ethylbenzylidene sorbitol and the like. The addition amount of this compound is
0.01 to 100 parts by weight of polypropylene resin
1.0 parts by weight, preferably 0.05 to 0.7 parts by weight. If it is less than 0.01 part by weight, the transparency is not sufficiently improved,
If the amount exceeds 1.0 part by weight, bleeding is problematic, which is not preferable.

[0010] Other additives such as neutralizing agents, light stabilizers, ultraviolet absorbers, antistatic agents, lubricants, dispersants, pigments and the like are added to the composition of the present invention as long as the properties are not impaired. be able to. Antioxidants other than those used in the composition of the present invention may be added as long as their properties are not impaired.

The composition of the present invention comprises a polypropylene random copolymer, a hindered phenolic antioxidant and a nucleating agent, as well as commonly used additives such as a neutralizing agent such as calcium stearate, a light stabilizer, and an ultraviolet ray. An absorbent, an antistatic agent, a lubricant, a dispersant, a pigment, and the like are mixed and uniformly dispersed in a blender such as a Henschel mixer, and the resulting mixture is melted and pelletized by an extruder.

As described above, the polypropylene resin composition of the present invention has extremely high stability to radiation irradiation and excellent transparency, and is effective for food packaging, medical equipment and other uses by utilizing its properties. It can be used for.

[0013]

The present invention will be described in more detail with reference to the following examples, which do not limit the present invention in any way. In the tensile test, a test piece was prepared with a JIS-K6758-2 type dumbbell and measured at a tensile speed of 50 mm / min to determine the strength at break (kg / cm ² ) and elongation (%). Transparency was measured with a direct-reading haze meter manufactured by Toyo Seiki (ASTM-
D-1003). Yellowness is Yellowness I
ndex (YI) was measured according to ASTM-D1925.

The odor was measured in a 250 ml wide-mouthed reagent bottle.
After adding 0 g and conditioning in an oven at 60 ° C. for 30 minutes, the odor level was determined in the following five steps by seven panelists, and the score given to each step was the average value of seven persons (value The larger the odor, the greater the odor).

Example-1 The intrinsic viscosity measured in tetralin at 135 ° C. is 1.65.
dl / g, 100 parts by weight of a polypropylene random copolymer containing 5.0 mol% of ethylene and 0.05 mmol% of vinylcyclohexane, 0.05 parts by weight of calcium stearate, and as a hindered phenol antioxidant, 3,9-bis [1,1-dimethyl-
2- {β- (3-tert-butyl-4-hydroxy-
5-methylphenyl) propionyloxydiethyl]-
0.2 parts by weight of 2,4,8,10-tetraoxaspiro [5.5] undecane was added, mixed with a Henschel mixer, and extruded under a nitrogen atmosphere at 220 ° C. using a 40 mmφ extruder to form pellets. . The obtained pellets were injected at an injection pressure of 60 kg / cm ² G, a molding temperature of 230 ° C., and a mold temperature of 50.
A flat plate having a thickness of 2 mm was prepared under the injection molding conditions of ° C. The obtained flat plate was irradiated with γ-rays of a cobalt 60 radiation source at 50 KGy (5 Mr).
ad) After irradiation, leave in the air at 60 ° C. for 30 days,
The breaking strength and elongation at break, transparency, yellowing, and odor in tensile tests before and after irradiation were examined. Table 2 shows the results.

Example 2 As a polypropylene random copolymer, the intrinsic viscosity measured in tetralin at 135 ° C. was 1.67 dl / g, 7.5 mol% of butene-1 and 0.05 mmol% of vinylcyclohexane. Was performed in the same manner as in Example 1 except that a polypropylene-based random copolymer containing Table 2 shows the results.

Example 3 An intrinsic viscosity of a polypropylene random copolymer measured in tetralin at 135 ° C. was 1.67 dl / g, ethylene was 4.0 mol%, butene-1 was 2.5 mol%, and The procedure was performed in the same manner as in Example 1 except that a random copolymer of polypropylene containing 0.05 mmol% of vinylcyclohexane was used. Table 2 shows the results.

Example 4 The polypropylene-based random copolymer has an intrinsic viscosity of 1.65 dl / g measured in tetralin at 135 ° C. and contains 5.0 mol% of ethylene and 0.5 mmol% of vinylcyclohexane. Example 1 was repeated except that a polypropylene random copolymer was used.
Table 2 shows the results.

Example 5 As a nucleating agent, 1,3,2,4-
Example 1 was repeated except that 0.3 parts by weight of dibenzylidene sorbitol was added. Table 2 shows the results.

Example-6 As a hindered phenolic antioxidant, 3,9-bis [1,1-dimethyl-2- {β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyl] Oxydiethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane is replaced by triethylene glycol-bis [3- (3-tert-butyl-5).
-Methyl-4-hydroxyphenyl) propionate]
Was carried out in the same manner as in Example 1 except that 0.2 parts by weight was added. Table 2 shows the results.

Example-7 As a hindered phenolic antioxidant, 3,9-bis [1,1-dimethyl-2- {β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyl] is used. Instead of oxydiethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane, 2,2′-oxamido-bis [ethyl-3- (3,5-di-tert)
-Butyl-4-hydroxyphenyl) propionate]
Was carried out in the same manner as in Example 1 except that 0.2 parts by weight was added. Table 2 shows the results.

Example-8 As a hindered phenolic antioxidant, 3,9-bis [1,1-dimethyl-2- {β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyl] is used. Oxydiethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane was replaced with octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate in 0.1%. It carried out like Example 1 except adding 2 weight part. Table 2 shows the results.

Example-9 As a hindered phenolic antioxidant, 3,9-bis [1,1-dimethyl-2- {β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyl] Example 1 was repeated except that the amount of oxydiethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane was reduced to 0.1 part by weight. Table 2 shows the results.

Example 10 As a hindered phenolic antioxidant, triethylene glycol-bis [3- (3-tert-butyl-5)
-Methyl-4-hydroxyphenyl) propionate]
Example 1 except that the amount of added was reduced to 0.1 part by weight.
The same was done. Table 2 shows the results.

Comparative Example 1 The procedure of Example 1 was repeated, except that a propylene homopolymer having an intrinsic viscosity of 1.65 dl measured in tetralin at 135 ° C. was used as the random polypropylene copolymer. Table 2 shows the results. This was remarkably inferior in transparency and physical properties such as tensile strength after γ-ray irradiation.

Comparative Example 2 As a polypropylene random copolymer, a propylene-ethylene random copolymer having an intrinsic viscosity of 1.65 dl / g measured in tetralin at 135 ° C. and containing 5.0 mol% of ethylene is used. Other than that, it carried out similarly to Example 1. Table 2 shows the results. This was markedly inferior in transparency.

Comparative Example 3 As a nucleating agent, 1,3,2,4-
The procedure was performed in the same manner as in Comparative Example 2 except that di (p-ethylbenzylidene) sorbitol was added. Table 2 shows the results. It had good transparency, but had an extremely poor odor.

Comparative Example 4 3,9-bis [1,1-dimethyl-2- {β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyl, a hindered phenolic antioxidant Instead of oxydiethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane, tetrakis [methylene-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] Example 1 was repeated except that 0.2 parts by weight of methane was added. Table 2 shows the results. It had good transparency but poor yellowing.

Comparative Example-5 3,9-bis [1,1-dimethyl-2- {β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyl, a hindered phenolic antioxidant 1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanate in place of oxydiethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane The procedure was performed in the same manner as in Example 1 except that 0.2 part by weight of nurate was added. Table 2 shows the results. This product had good transparency, but was extremely inferior in yellowing. Also, physical properties such as tensile strength after γ-ray irradiation were poor.

Comparative Example-6 3,9-bis [1,1-dimethyl-2- {β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyl, a hindered phenolic antioxidant The procedure was performed in the same manner as in Example 1 except that [oxydiethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane was not used. Table 2 shows the results. This was inferior in physical properties such as tensile strength after γ-ray irradiation.

[0031]

[Table 1]

The contents of the additives indicated by A to H in Table 1 are as follows. (Antioxidant) A: 3,9-bis [1,1-dimethyl-2- {β- (3
-Tert-butyl-4-hydroxy-5-methylphenyl) propionyloxydiethyl] -2,4,8,1
0-tetraoxaspiro [5.5] undecane, (Sumilyzer GA-80 manufactured by Sumitomo Chemical Co., Ltd.) B: triethylene glycol-bis [3- (3-ter
t-butyl-5-methyl-4-hydroxyphenyl) propionate], (Irganox 245 manufactured by Ciba-Geigy) C: 2,2′-oxamide-bis [ethyl-3- (3,3)
5-di-tert-butyl-4-hydroxyphenyl)
Propionate], (Nowguard X, manufactured by Uniroyal)
L-1) D: Octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, (Irganox 1076 manufactured by Ciba-Geigy) E: Tetrakis [methylene-3- (3,5 -Di-ter
t-butyl-4-hydroxyphenyl) propionate] methane, (Irganox 1 manufactured by Ciba-Geigy)
010) F: 1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, (Irganox 3114 manufactured by Ciba-Geigy) (nucleating agent) G: 1.3 , 2,4-dibenzylidene sorbitol,
(EC-1 manufactured by EC Chemical Co., Ltd.) H: 1,3,2,4-di (p-methylbenzylidene) sorbitol, (Gelall MD manufactured by Nippon Rika Co., Ltd.)

[0033]

[Table 2]

[0034]

According to the present invention, it is possible to provide a polypropylene-based resin composition which is less likely to deteriorate in physical properties even when irradiated with radiation, has less discoloration and odor, and is excellent in transparency.

Continuation of front page (56) References JP-A-60-139710 (JP, A) JP-A-62-283142 (JP, A) JP-A-4-359040 (JP, A) JP-A-62-132937 (JP) , A) (58) Fields surveyed (Int. Cl. ⁷ , DB name) C08L 23/00-23/36

Claims (3)

(57) [Claims] (A) 2% by mole or more of (A) one or two or more α-olefins having 2 to 8 carbon atoms (excluding 3 carbon atoms) based on propylene; (B) based on 100 parts by weight of the polypropylene random copolymer containing 001 to 5.0 mmol%
Triethylene glycol-bis [3- (3-tert-
Butyl-5-methyl-4-hydroxyphenyl) propionate], 2,2'-oxamide-bis [ethyl-3
-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,
5-di-tert-butyl-4-hydroxyphenyl)
Propionate and 3,9-bis [1,1-dimethyl-2- {β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy} ethyl] -2,4,8,10- Tetraoxaspiro [5.
5) good stability to radiation irradiation and transparency, characterized by comprising 0.01 to 1.0 part by weight of at least one hindered phenolic antioxidant selected from undecane Excellent polypropylene resin composition. 2. The polypropylene resin composition according to claim 1, wherein the vinylcycloalkane compound is vinylcyclohexane or vinylcyclopentane. 3. A polypropylene resin composition comprising the polypropylene resin composition according to claim 1 and 0.01 to 1.0 parts by weight of a nucleating agent.