JPH0543742B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a food package or container that is resistant to radiation and is made of a large crystalline propylene polymer resin composition containing a specific stabilizer. <Prior Art> Radiation can be used for purposes such as sterilization, insecticide, germination control, adjustment of fruit ripeness, and food modification, since it is possible to treat food while it is fresh. That is, because of its strong penetrating power, it has the advantage of being able to exert the effect of irradiation on food products as they are packaged, and is therefore a preferable treatment method from a sanitary perspective. Conventionally, the packaging or container used in this case is
wooden box, cardboard box, polyethylene film,
A plastic tray or the like may be used, but one made of plastic is preferred for reasons such as light weight, sealability, and hygiene. Among them, crystalline propylene polymer resin (hereinafter simply referred to as polypropylene)
is suitable for food packaging or containers due to its advantages in formability, material mechanical properties, transparency, appearance, etc., and is ideal for such packaging or containers because it does not undergo crosslinking due to radiation irradiation. It is. <Problems to be solved by the invention> However, when polypropylene is irradiated with radiation, it becomes discolored, its impact strength and product life are reduced due to molecular breakage, and furthermore, deterioration products and additives bleed out. When transferred to foods, they change the taste and odor of foods, and problems with stability remain, resulting in various drawbacks that need to be improved. Regarding polypropylene materials having radiation resistance, for example, those containing a general hindered amine (Japanese Unexamined Patent Application Publication No. 1982-19199), and those containing symmetrical triarylphosphite alone or in combination with hindered phenolic antioxidants, etc. A combination formulation (Japanese Unexamined Patent Publication No. 57-179234) has been investigated for medical use and other purposes, but the above-mentioned drawbacks have not yet been sufficiently improved. <Means for Solving the Problems> The present invention solves the above-mentioned drawbacks as a food package or container that is resistant to radiation when a specific hindered amine and a phosphite antioxidant are combined together. This was done after discovering that it would solve the problem. That is, the present invention provides ``100 parts by weight of a crystalline propylene polymer resin, (1) 0.01 to 1 part by weight of a hindered amine compound represented by the following formula [], and (2)
A radiation-resistant food package or container formed by molding a composition containing 0.01 to 1 part by weight of a phosphite antioxidant represented by the following formula [] or [] by a conventional method. In the formula, Aromatic or alkylated aromatic, n is 2-
is an integer of 100, and R ₁ , R ₂ , and R ₃ are alkyl groups each having 3 to 8 carbon atoms, 1 to 18 carbon atoms, and 8 to 30 carbon atoms, and Z
is an alkylene group having 1 to 8 carbon atoms which may be substituted with 1 to 3 of the following groups. It is. <Function> In addition to propylene homopolymer, the polypropylene (crystalline propylene polymer resin) used in the present invention includes propylene in the majority weight and ethylene, butene, pentene, hexene, 4-methylpentene,
It includes random and block copolymers with other α-olefins such as heptene and octene, and specifically includes propylene-ethylene random or block copolymers, propylene-ethylene-
These include butene copolymers, propylene-hexene copolymers, propylene-hexene-butene copolymers, and the like. These polypropylenes are produced through a process in which they are polymerized using a Ziegler-Natsuta type catalyst in the gas phase, liquid phase, or in a solvent such as hexane or heptane, and then deactivated using a catalyst decomposer such as alcohol or an epoxy compound. However, polymers produced by processes in which these steps are simplified or eliminated may also be used. Regarding the catalyst used, a type of catalyst in which catalyst components are supported on a carrier such as magnesium chloride has been developed, and polypropylene produced using such a catalyst may also be used. Among these, especially those with MFR of 1 to 100g/10
Preferably. Further, if necessary, other polyolefins may be mixed with the polypropylene. Polyolefins that can be mixed include α-
There are homopolymers and copolymers of olefins. In the case of copolymers, those containing less than half the weight of propylene and unsaturated monomers other than α-olefins, such as vinyl acetate and vinyl butyrate, etc. It may also be a copolymer containing a small amount of a vinyl ester, an unsaturated organic acid such as acrylic acid or maleic anhydride, or an unsaturated organic acid ester such as ethyl acrylate or methyl methacrylate. For example, high-pressure polyethylene, low-pressure high-density polyethylene, low-pressure low-density polyethylene-peropylene copolymer rubber, ethylene-butene-1 copolymer, propylene-butyne-1
Examples include copolymers, ethylene-vinyl acetate, and the like. Further, in the hindered amine compound represented by the above formula [] used in the present invention, for example, X is hexamethylene and Y is and n is 5 to 10, or X is hexamethylene and Y is However, A is and a compound where n is 3 to 4, or a compound where X and Y are both hexamethylene and n is 5 to 10,
Alternatively, a compound in which X is hexamethylene, Y is ethylene, and n is 3 to 5 is preferable. Further, the phosphite antioxidant represented by the above formula [] used in the present invention is, for example, 4,
4'-methylenebis(3-methyl-6-t-butylphenyl-di-tridecyl) phosphorite,
4,4'-butylidene bis(3-methyl-6-t-
Butylphenyl-di-tridecyl) phosphorite, 1,1,3-tris(2-methyl-4-di-
Tridecyl phosphite-5-t-butylphenyl)butane and the like are preferred. Further, the phosphite antioxidant represented by the above formula [] used in the present invention is, for example, bis-(2,4-di-t-butylphenyl)pentaerythritol-diheosphite, bis-(2
-t-butyl-4-methylphenyl)pentaerythritol diphosphite and the like are preferred. The blending ratio of these ingredients is 100% polypropylene
Based on the weight part, the hindered amine is 0.01 to 1 part by weight, preferably 0.03 to 0.2 part by weight, and the phosphite antioxidant is 0.01 to 1 part by weight, preferably 0.03 to 0.3 part by weight. If the amount added is larger than this, problems such as bleeding and coloring after irradiation will occur, which is not preferable, and it is also not economically preferable. If the amount added is less than this,
The effects of the invention are not fully demonstrated. Other additional components can be added to the composition used in the present invention, if necessary. Additional components include various antioxidants such as phenol, thioether, and phosphorus, various light stabilizers such as other hindered amine, nickel, and benzoate, and various ultraviolet absorbers such as benzophenone and triazole. Clarifying agents such as sorbito, nucleating agents, lubricants, antistatic agents, anti-blocking agents, anti-drop agents, pigments, dispersants, neutralizing agents, molecular weight regulators for organic peroxides, as well as talc and sulfuric acid. barium,
There are fillers such as calcium carbonate and glass fiber.
These can be added within a range that does not significantly impair the effects of the present invention. These components are formed into pellets using a general kneading machine and then subjected to molding, but the composition can also be molded directly without pelletizing. Molding is done by a conventional method. That is, through processes such as injection molding, blow molding, extrusion molding (vacuum, pressure molding), and film molding, the desired packaging or container is made, and after food is placed in it, it is sterilized, insecticided, germinated, controlled, etc. The required amount of radiation is irradiated depending on the purpose, such as adjusting the ripeness of fruits or improving food quality. The radiation used is gamma rays, X-rays, and electron beams, but gamma rays are often used because of their strong penetrating power. <Example> Various additives used in the example are as follows. (Hindered amine compound) A: In the above formula [], X is hexamethylene and Y is and a mixed compound in which n is 5 to 10. B: bis(2,2,6,6-tetramethyl-4
-piperidyl) sebacate. C: Succinic acid and N-(2-hydroxyethyl)-
Condensate of 2,2,6,6-tetramethyl-4-hydroxy-piperidine. (Phosphite ester compound) D: 4,4'-butylidene bis(3-methyl-6
-t-butylphenyl-di-tridecyl)fesuphite. E: 1,1,3-tris(2-methyl-4-di-tridecylphosphite-5-t-butylphenyl)butane. F: bis-(2,4-di-t-butylphenyl)
Pentaerythritol diphosphite. G: Tris-(2,4-di-t-butyl-phenyl) phosphorite. H: Distearylpentaerythritol-diphosphite. (Other antioxidants and neutralizing agents) I: Tetrakis[methylene-3-(3',5'-di-t-butyl-4-hydroxyphenyl)propionate]methane. J: Calcium stearate. K: 2,6-di-t-butyl-4-methylphenol. L: 2,5-dimethyl-2,5-di-(t-butylphenoxy)hexyne-3. Examples 1 to 4 and Comparative Examples 1 to 8 100 parts by weight of a powdered propylene homopolymer with an MFR of 8 g/10 minutes, a hindered amine listed in the table below,
Phosphite ester compounds and other additives are the first
They were added in the proportions (parts by weight) shown in the table and melt-kneaded using a 30 mm diameter extruder (set at 210°C). The obtained pellets were molded into an injection molding machine (set at 240°C) to a size of 100 x 100.
A sheet with a thickness of 1 mm was molded. This injection molded product was irradiated with gamma rays using a cobalt-60 radiation source at the amount shown in Table 1 (dose rate: 0.1 megarad/hour) to prepare a sample. For the obtained sample, the decrease in molecular weight was determined by MFR (ASTM-D-1238,
It was confirmed by the change in temperature (230℃, 2.16Kg load). Also,
The embrittlement time was measured with the gear open at 120°C and used as a measure of product life. Furthermore, samples heat-treated for 7 days while the gear was open at 80°C were evaluated for the degree of coloration and the degree of bleeding of additives and degraded substances, which was used as a guide for marketability and changes in taste due to adhesion to food. The evaluation results are shown in Table 1.

[Table] Examples 5, 6 and Comparative Examples 9 to 13 Polypropylene with an ethylene content of 3% by weight,
Evaluation was performed in the same manner as in Example 1, except that the propylene-ethylene random copolymer with MFR of 5 g/10 min was replaced with the formulation shown in Table 2. The results are shown in Table 2.

[Table] Example 7 and Comparative Example 14 Powdered propylene homopolymer (MFR2.3
g/10 minutes, II96%) were blended with the compounds shown in Table 3 (parts by weight) in a super mixer, and then pelletized in an extruder. The obtained pellets were melt extruded at 240℃,
Solidify into a sheet on a cooling roll with a surface temperature of 40°C, then heat to 115°C using the difference in circumferential speed of the rolls.
The film was stretched 5 times in the transverse direction. Subsequently, after stretching 10 times in the transverse direction in a tenter oven at 160℃,
After heat setting at ℃, one side of the film was subjected to corona discharge treatment to obtain a biaxially stretched polypropylene film with a thickness of 25 μm. Using this film, the film was made into a bag with a melt-cut seal, irradiated with gamma rays using a cobalt-60 radiation source, and the degree of coloring and odor at the time of opening the bag were measured.

[Table] Example 8 and Comparative Example 15 Powdered MFR 10 g/10 minutes, 100 parts by weight of propylene-ethylene random copolymer with an ethylene content of 4% by weight, no antioxidant added, melt index 5 g/10 minutes, density 5 parts by weight of high-pressure polyethylene of 0.924 g/cm ³ , melt index 4 g/10 min without the addition of antioxidants, propylene content
5 parts by weight of 22% by weight ethylene-propylene copolymer rubber (EPR) and the additives (parts by weight) shown in Table 4 were added and mixed in a Henschel mixer, and the L/D was 25 and the diameter was 40 mm. A pelletized composition was obtained by melt-kneading in an extruder with a screw (set at 250°C). These compositions were applied to the 25μ biaxially stretched polypropylene film obtained in Example 7 using an extrusion coating device set so that the temperature of the resin extruded from the die was 280°C so that the coating thickness was 30μ. An extruded coating film was obtained by extrusion. These extruded coating films were irradiated with gamma rays from a cobalt-60 radiation source at the amounts shown in Table 4. The decrease in molecular weight of the obtained sample was confirmed by the change in MFR (measured by peeling off only the extrusion coated film from an extrusion coated film sample) as a measure of the impact strength of the product. Furthermore, the degree of coloring of the sample was visually determined and used as a measure of marketability. The results are shown in Table 4.

[Table] Examples 9, 10 and Comparative Example 16 Powdered propylene-ethylene random copolymer (ethylene content 4.5% by weight, MFR 6.0g/
10 minutes) or propylene-ethylene-butene-1 random copolymer (ethylene content 1.7 wt%, butene-1 content 12.0 wt%, MFR 5.5 g/10 min)
The compounds shown in Table 5 were added to 100 parts by weight (parts by weight), mixed in a super mixer, and then pelletized in an extruder. The obtained pellets were extruded at 230°C from an extruder equipped with a T-shaped die, cooled at 25°C, and one side of the film was subjected to corona discharge treatment to obtain an unstretched film with a thickness of 25μ. The obtained unstretched film and the biaxially stretched film obtained in Example 7 were dry laminated using a urethane adhesive, bag-formed using a heat sealer, and then irradiated with gamma rays using a cobalt-60 heat source. The degree of coloring and odor upon opening the bag were measured.

[Table] Example 11 and Comparative Example 17 Powdered propylene homopolymer 65% by weight
(MFR0.8g/10min), 15% by weight of pelleted high-pressure low-density polyethylene without additives
(MFR 0.7 g/10 minutes, density 0.924 g/cm ³ ) was blended with 100 parts by weight of the resin composition shown in Table 6 (parts by weight), mixed in a super mixer, and then extruded in an extruder. Turned into pellets. The obtained pellets were cooled to 60°C using an extruder with a T-shaped die at 250°C to produce a sheet with a thickness of 0.3 mm, and then heated to a hot plate temperature of 150°C using a hot plate pressure forming machine manufactured by Asano Laboratory. ℃ directly heated for 3 seconds, and compressed air pressure of 2 kg /
After molding in cm ² and solidifying by cooling, it was taken out. The molded product is a bridge-shaped thin-walled container with a length of 190 mm, a width of 100 mm, and a depth of 15 mm. Cobalt-60 for these thin-walled containers
The degree of coloring and low-temperature impact strength were measured by irradiating gamma rays with a heat source. The low-temperature impact strength was measured in an atmosphere of 5℃ using a steel ball with a diameter of 1.5 inches and a weight of 200g at a height of 55cm.
The presence or absence of breakage was examined by dropping it on the corner of the molded product. The results are shown in Table 6.

[Table] <Effects of the Invention> The packaging or container of the present invention has almost no concerns about discoloration due to radiation irradiation, reduction in impact strength or product life, or bleeding of deteriorating substances or additives, and reduces food taste and odor. It has an excellent effect that no change occurs.

Claims (1)

[Claims] 1. 100 parts by weight of crystalline propylene polymer resin,
(1) Hindered amine compound represented by the formula []
0.01 to 1 part by weight, and (2) a phosphite ester antioxidant represented by the following formula [] or []
A radiation-resistant food package or container, characterized in that it is formed by molding a composition containing 0.01 to 1 part by weight by a conventional method. In the formula, Aromatic or alkylated aromatic, n is 2-
is an integer of 100, and R ₁ , R ₂ , and R ₃ are alkyl groups each having 3 to 8 carbon atoms, 1 to 18 carbon atoms, and 8 to 30 carbon atoms, and Z
is an alkylene group having 1 to 8 carbon atoms which may be substituted with 1 to 3 of the following groups.