JP4528181B2 - Colored resin composition and molded body thereof - Google Patents

Description

  In the field of packaging of foods and the like, for example, when heating is performed in a microwave oven or the like, the present invention generates odor due to volatilization of a low molecular weight component of a polypropylene resin contained in a trace amount in a container, and the scent of the contents More particularly, the present invention relates to a colored resin composition excellent in low odor, in which titanium dioxide, tocopherol and a phosphorus-based antioxidant are blended with a polypropylene resin. Moreover, it is related with the molded object excellent in the low odor property containing the said colored resin composition.

  The polypropylene resin is molded and used at a processing temperature of 170 to 300 ° C., but the polypropylene resin may be oxidatively decomposed during processing to generate low molecular weight propylene and its oxide. If these are attached to the surface of a molded product that has been molded, the low molecular weight polypropylene or its oxide may be felt as an odor when the molded product is heated by a microwave oven or the like.

  The odor due to the decomposition product of the polypropylene-based resin during the molding process may be felt more strongly when the molded product is a container and the container is filled with the contents and sealed. Occurrence of odor due to the decomposition product of such a polyprolene resin has been a problem because it is promoted particularly when titanium dioxide is blended as a colorant for polypropylene resin.

  It is well known that such problems can be improved by blending an antioxidant in the polypropylene resin. For example, methods using various antioxidants have been proposed to suppress oxidative degradation of polypropylene resins and as a result prevent odors.

  The invention of “Propylene resin composition and food container using the same” described in Patent Document 1 includes a resin composition in which a phosphorus-based antioxidant, a phenol-based antioxidant, and a calcium salt of a higher fatty acid are blended with a polypropylene-based resin It is disclosed that the generation of odor in food containers made of food and the resin composition is suppressed.

  However, when the composition is used in a colored composition containing titanium dioxide, when the colored resin composition is molded at a processing temperature of 220 ° C. or lower, the odor is satisfactorily suppressed, but at a temperature of 220 ° C. or higher. When the molding process is performed, there is a problem that an odor of the antioxidant itself is generated due to the sublimation property of the antioxidant itself blended in the resin composition.

Patent Document 2 discloses an invention relating to “a propylene resin composition and a food container using the same”, and the invention relates to a polypropylene resin and a calcium salt of a tocopherol and a higher fatty acid, or a tocopherol and a phenol-based oxidation. A resin composition containing an inhibitor and a calcium salt of a higher fatty acid is disclosed. Since the composition contains tocopherol, the sublimation of the antioxidant at 220 ° C. or higher is suppressed, but when titanium dioxide is added, the deterioration odor of the polypropylene resin due to titanium dioxide is suppressed. It was not reached.
JP-A-11-172058 JP-A-11-302469

  Accordingly, an object of the present invention is to provide a colored resin composition in which the generation of odor is well suppressed in the polypropylene colored resin composition containing titanium dioxide as described above when heated at the time of molding and after molding. Is to provide.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have used a specific surface-treated titanium dioxide with less odor generation as a colorant for the polypropylene resin, It has been found that the above problem can be solved by blending a tocopherol, which is an antioxidant suitable for preventing oxidative degradation, and a phosphorus-based antioxidant, and the present invention has been completed.

  That is, in the present invention, 0.1 to 200 parts by mass of titanium dioxide, 0.0005 to 5 parts by mass of tocopherol, and 0.0005 to 5 parts by mass of a phosphorus-based antioxidant as a color pigment with respect to 100 parts by mass of the polypropylene resin. A colored resin composition characterized by comprising:

  In the present invention, the polypropylene resin is a homopolymer of propylene, an ethylene-propylene block copolymer or an ethylene-propylene random copolymer; the polypropylene resin has an MFR of 0.1 to 100 g / 10 min. Propylene homopolymer, ethylene-propylene block copolymer or ethylene-propylene random copolymer; and oxidation of Al, Si, Zr, Sb, Sn and Zn with respect to the total mass of titanium dioxide. It is preferably coated with a metal oxide selected from a group of materials alone or in combination.

  Further, the present invention provides a synthetic resin container lid comprising a base resin containing a polypropylene resin and the colored resin composition of any of the present invention; and a base resin containing a polypropylene resin; A synthetic resin liner for a container lid, comprising the colored resin composition according to any one of the present invention.

  The resin composition according to the present invention generates little odor due to titanium dioxide at the time of molding and use of the molded product, and when the molded product is a container, the odor transfer from the container to the contents in the container is prevented. Excellent in properties.

Next, the present invention will be described in more detail with reference to the best mode for carrying out the invention.
The components of the colored resin composition of the present invention are a polypropylene resin, titanium dioxide as a color pigment, tocopherol as an antioxidant and a phosphorus antioxidant.

  The polypropylene resin used in the present invention is a normal polypropylene resin, and examples thereof include a propylene homopolymer, an ethylene-propylene block copolymer, and an ethylene-propylene random copolymer.

  The polypropylene resin is preferably a propylene homopolymer, an ethylene-propylene block copolymer or an ethylene-propylene random copolymer having an MFR of 0.1 to 100 g / 10 min. A more preferable MFR is 1 to 50 g / 10 min.

  When the above MFR is less than 0.1 g / 10 min, the polypropylene resin at the time of melting has a high viscosity, so heat is generated during the molding process of the polypropylene resin, and the thermal discoloration inherent to tocopherol increases, It is insufficient in that the appearance of the molded product is impaired. On the other hand, when the above MFR exceeds 100 g / 10 min, in the process of dispersing titanium dioxide in the polypropylene resin, for example, when a kneading facility such as an extruder is used, if the melt viscosity becomes low, the shearing force due to kneading is reduced. It is insufficient in that it is lowered and titanium dioxide cannot be sufficiently dispersed.

  The titanium dioxide used in the present invention is coated with at least one metal oxide selected from the group consisting of oxides of Al, Si, Zr, Sb, Sn and Zn with respect to the total mass of titanium dioxide. preferable.

  The coating amount of the metal oxide is preferably 2 to 10% by mass of titanium dioxide. When the coating amount is less than 2% by mass, the effect of suppressing the catalytic activity of titanium dioxide is insufficient, and it is insufficient for suppressing the oxidation of the polypropylene resin. On the other hand, when the coating amount exceeds 10% by mass, the coated titanium dioxide easily absorbs water, and the foaming phenomenon occurs in the molded product during the molding process from the volatilization of moisture during the processing of the resin composition. The workability of the object is reduced. Preferably, the coating amount is 5 to 9 parts by mass, and the resin composition of the present invention having better low odor and workability in this range is obtained.

  The coating of the titanium dioxide particles with the metal oxide suppresses the catalytic activity of titanium dioxide. The coating of titanium dioxide with the above metal oxide is performed by uniformly mixing titanium dioxide with a desired amount of an aqueous salt solution selected from the group consisting of Al, Si, Zr, Sb, Sn and Zn, alone or in combination. It is carried out by adding an acid or alkali to the liquid and precipitating the metal salt as an oxide on the surface of the titanium dioxide particles. In particular, coating with a combination of an oxide of silicon and an oxide of aluminum is preferable.

  The tocopherol used in the present invention is known as vitamin E. Tocopherol includes α-tocopherol (5,7,8-trimethyltocol), β-tocopherol (5,8-dimethyltocol), γ-tocopherol (7,8-dimethyltocol), δ-topherol (8-methyltocol). Α-tocopherol has the highest antioxidant effect and is most desirable in the present invention.

  Examples of the phosphorus antioxidant used in the present invention include tris (2,4-di-tert-butylphenyl) phosphite and tetrakis (2,4-di-tert-butylphenyl) [1,1-biphenyl. It is preferable to use at least one selected from the group consisting of -4,4'-diylbisphosphite and bis (2,4-di-tert-butylphenyl) pentaerythritol diphosphite. More preferably, tris (2,4-di-tert-butylphenyl) phosphite is highly effective when used in combination with tocophenol.

  The said covering titanium dioxide is used in the ratio of 0.1-200 mass parts with respect to 100 mass parts of polypropylene resins. More preferably, it is 0.5-30 mass parts. If the amount of titanium dioxide used is less than 0.1 parts by mass, the problem of odor does not occur, but coloring and concealment by titanium dioxide are insufficient. On the other hand, when the amount of titanium dioxide used exceeds 200 parts by mass, the density of the titanium dioxide particles scattered in the polypropylene resin increases, and when the particles are close to each other and interact with each other, a dispersion failure called aggregation occurs. Inadequate in terms of When the colored composition of the present invention is a colored resin composition that is molded as it is, the coated titanium dioxide is preferably used at a ratio of 0.5 to 30 parts by mass with respect to 100 parts by mass of the polypropylene resin. . When the amount of titanium dioxide used is high, the coloring composition is used as a masterbatch (concentrate). A masterbatch is a compound in which pigments, additives, and the like are blended in an amount of 1 or more times the predetermined amount in a molding-like resin composition, and the masterbatch is diluted with a natural resin at the time of molding. In addition, additives and the like are at a predetermined concentration.

  The tocopherol is used at a ratio of 0.0005 to 5 parts by mass with respect to 100 parts by mass of the polypropylene resin. More preferably, it is 0.001-1 mass part. If the amount of tocopherol used is less than 0.0005 parts by mass, it is insufficient in that a sufficient odor reduction effect cannot be obtained. On the other hand, when the amount of tocopherol used exceeds 5 parts by mass, the thermal discoloration inherent to tocopherol tends to be conspicuous, and the odor reduction effect reaches a saturation amount, which is insufficient. When the colored composition of the present invention is a colored resin composition molded as it is, the tocopherol may be used in a proportion of 0.001 to 0.2 parts by mass with respect to 100 parts by mass of the polypropylene resin. preferable.

  The phosphorus antioxidant is used in a proportion of 0.0005 to 5 parts by mass with respect to 100 parts by mass of the polypropylene resin. More preferably, it is 0.001-1 mass part. If the amount of the phosphorus-based antioxidant used is less than 0.0005 parts by mass, it is insufficient in that it is difficult to obtain an odor reducing effect. On the other hand, when the usage-amount of phosphorus antioxidant exceeds 5 mass parts, an odor reduction effect will reach a saturation amount and is economically disadvantageous. When the colored composition of the present invention is a colored resin composition that is molded as it is, the phosphorus antioxidant is in a proportion of 0.001 to 0.2 parts by mass with respect to 100 parts by mass of the polypropylene resin. It is preferable to use it. In addition, it is preferable to add 0.01-10 mass parts of tocopherol and phosphorus antioxidant with respect to 100 mass parts of polypropylene resin.

  The resin composition of the present invention comprises the above components as essential components and other additives used as additives for polypropylene resins, such as pigments other than titanium dioxide, ultraviolet absorbers, lubricants, plasticizers, antistatic agents. Further, a nucleating agent, a filler, a pigment dispersing agent, and the like can be used as long as the object of the present invention is not prevented. In particular, as the dispersant for the polypropylene resin, it is preferable to use a low odor dispersant such as a fatty acid metal salt, a fatty acid ester, a fatty acid amide, or a low molecular weight polyethylene.

  The colored composition of the present invention can be produced by a method of simply mixing the above essential components and optional components, and the above essential components and optional components are melted and kneaded with an extruder, kneader, roll, etc. into pellets or flakes. May be. When the ratio of titanium dioxide to be used is large, for example, it is in the state of a masterbatch (concentrated material), and when it is in the state of the masterbatch, it is diluted to an appropriate concentration with a natural polypropylene resin during molding. And use it. Moreover, when the density | concentration of titanium dioxide is a density | concentration requested | required of a desired molded article, for example, it uses for a shaping | molding as it is.

  The colored composition of the present invention is useful as a raw material for various resin molded products, and is particularly useful as a raw material for forming synthetic resin container lids and synthetic resin liners for container lids. Examples of the synthetic resin container lid include the container lid described in JP-A-2002-173157, and the manufacturing method thereof includes, for example, melting the colored resin composition of the present invention in a base polypropylene resin. Examples thereof include a method of kneading and extruding the mixed resin extruded by an extruder into a mold with a cutter and compression molding in the mold, but the production method is not limited to the above method. The container lid manufactured in this way can effectively suppress the generation of odor components during melt kneading at a high temperature during molding. In addition, since the container lid is wrapped around a container filled with 80-90 ° C. content at a high temperature, the inner surface of the container lid is heated, but the generation of odor components is suppressed, so that the odor component inside the container head space The intention of odor is effectively prevented.

  The synthetic resin liner is produced by, for example, melting and kneading the colored resin composition of the present invention in a base polypropylene resin, and mixing the extruded resin with an extruder into a synthetic resin or metal container lid shell. The container lid with a synthetic resin liner can be molded by supplying to the mold and stamping, but the production method is not limited to the above method. According to the present invention, generation of an odor component at the time of melt kneading at a high temperature during liner molding can be effectively suppressed. In addition, since the container lid is wrapped around a container filled with 80-90 ° C. content at a high temperature, the inner surface of the container lid is heated, but the generation of odor components is suppressed. The intention of odor is effectively prevented.

Next, the present invention will be described more specifically with reference to examples and comparative examples. In the text, “part” or “%” is based on mass unless otherwise specified.
[Comparative Examples 1-5]
20 parts of titanium dioxide E (surface treatment: 2% silica, 4% alumina) and 0.2 parts of various antioxidants are mixed with 100 parts of polypropylene resin (MFR = 10, J700GP made by Idemitsu Chemical Co., Ltd.) and set to 170 ° C. Dispersion treatment was carried out using a twin screw extruder (TEX30α manufactured by JSW) to obtain a colored composition. 10 g of the obtained colored composition was put into a 50 ml glass bottle which had been washed and dried, and sealed, and heated in a gear oven at 80 ° C. for 100 hours. The heated glass bottle is allowed to stand at room temperature for 1 hour to smell the odor after opening. As a standard for odor evaluation, “mostly no odor” was level 1, and the odor of polypropylene that was oxidized and deteriorated by heating at 250 ° C. for 1 hour was level 5. Odor evaluation criteria are listed in Table 1. Table 2 shows the evaluation results of the antioxidant alone.

[Comparative Examples 6 to 11]
20 parts of titanium dioxide E (surface treatment: 2% silica, 4% alumina) and 0.05 to 0.2 parts of α- or β-tocopherol are mixed with 100 parts of polypropylene resin (MFR = 10, J700GP manufactured by Idemitsu Chemical Co., Ltd.). Then, dispersion treatment was performed with a twin screw extruder (TEX30α manufactured by JSW) set at 170 ° C. to obtain a colored composition. About the coloring composition, the odor evaluation described in the said Comparative Examples 1-5 was performed. Table 3 shows the evaluation results of tocopherol alone.

[Comparative Examples 12 to 13]
20 parts titanium dioxide E (surface treatment: 2% silica, 4% alumina), 0.1 part α-tocopherol and 0.1 part phenolic antioxidant to 100 parts polypropylene resin (MFR = 10, J700GP manufactured by Idemitsu Chemical Co., Ltd.) The mixture was mixed and dispersed in a twin-screw extruder (TEX30α manufactured by JSW) set at 170 ° C. to obtain a colored composition. About the coloring composition, the odor evaluation described in the said Comparative Examples 1-5 was performed. Table 4 shows the evaluation results of combinations of tocopherol and phenolic antioxidant.

[Examples 1 to 5]
20 parts of titanium dioxide having a different surface treatment amount relative to 100 parts of polypropylene resin (MFR = 10, J700GP manufactured by Idemitsu Chemical Co., Ltd.), 0.1 part of α-tocopherol and phosphorus antioxidant (Tris (2,4-di-tert -Butylphenyl) phosphite) 0.1 part was mixed, and the dispersion process was performed with the twin-screw extruder (TEX30 (alpha) made from JSW) set to 170 degreeC, and the coloring composition was obtained. About the coloring composition, the odor evaluation described in the said Comparative Examples 1-5 was performed. Table 5 shows the results of odor improvement by the surface treatment of titanium dioxide.

[Examples 6 to 10]
20 parts of titanium dioxide E (surface treatment: silica 2%, alumina 4%), α-tocopherol 0.05 to 0.1 part and phosphorus antioxidant for 100 parts of polypropylene resin (MFR = 10, J700GP manufactured by Idemitsu Chemical Co., Ltd.) 0.05 to 0.1 part of the agent was mixed and subjected to dispersion treatment with a twin screw extruder (TEX30α manufactured by JSW) set at 170 ° C. to obtain a colored composition. About the coloring composition, the odor evaluation described in the said Comparative Examples 1-5 was performed. Table 6 shows the results of odor improvement by the combination of tocopherol and phosphorus antioxidant.

[Examples 11 to 13]
0.5 to 40 parts of titanium dioxide E (surface treatment: 2% of silica, 4% of alumina), 0.004 to 0.1 part of α-tocopherol and 100 parts of polypropylene resin (MFR = 10, J700GP manufactured by Idemitsu Chemical Co., Ltd.) Phosphorous antioxidant (Tris (2,4-di-tert-butylphenyl) phosphite) 0.004 to 0.1 part was mixed and set at 170 ° C. with a twin screw extruder (JSW TEX30α). Dispersion treatment was performed to obtain a colored composition. About the coloring composition, the odor evaluation described in the said Comparative Examples 1-5 was performed. Table 7 shows the odor improvement results when the titanium dioxide concentration was changed.

[Example 14]
100 parts of polypropylene resin (MFR = 10, J700GP manufactured by Idemitsu Chemical Co., Ltd.) 0.5 parts of titanium dioxide E (surface treatment: 2% silica, 4% alumina), 0.005 part α-tocopherol and phosphorus antioxidant ( 0.005 part of tris (2,4-di-tert-butylphenyl) phosphite) was mixed and subjected to dispersion treatment with a twin-screw extruder (TEX30α manufactured by JSW) set at 170 ° C. to obtain a colored composition. . 10 parts of the colored composition and 100 parts of polypropylene resin (MFR = 10, J700GP manufactured by Idemitsu Chemical Co., Ltd.) were mixed, and the container lid was molded using an injection molding machine (manufactured by Sumitomo Heavy Industries, Ltd., SE350S). As molding conditions, the resin temperature was set to 220 ° C., and molding was performed at an injection pressure of 150 MPa. The container lid has an outer diameter of 30 mm, an inner diameter of 26 mm, and a height of 26 mm. Ten container lids thus obtained were sealed in a glass bottle and heated in a gear oven at 80 ° C. for 100 hours. The heated glass bottle was allowed to stand at room temperature for 1 hour, and after opening, the odor was evaluated. The evaluation results are shown in Table 8.

[Example 15]
100 parts of polypropylene resin (MFR = 10, J700GP manufactured by Idemitsu Chemical Co., Ltd.) 0.5 parts of titanium dioxide E (surface treatment: 2% silica, 4% alumina), 0.005 parts α-tocopherol and phosphorus antioxidant ( 0.005 part of tris (2,4-di-tert-butylphenyl) phosphite) was mixed, and dispersion treatment was performed with a twin screw extruder (TEX30α manufactured by JSW) set at 170 ° C. to obtain a colored composition. . 10 parts of the colored composition and 100 parts of polypropylene resin (MFR = 10, J700GP manufactured by Idemitsu Chemical Co., Ltd.) are mixed, and a container lid liner is molded using an injection molding machine (SE350S manufactured by Sumitomo Heavy Industries, Ltd.). As molding conditions, the resin temperature was set to 220 ° C., and molding was performed at an injection pressure of 150 MPa. The container lid liner has dimensions of an outer diameter of 30 mm, an inner diameter of 26 mm, and a height of 3 mm. Ten container lid liners thus obtained were sealed in a glass bottle and heated in a gear oven at 80 ° C. for 100 hours. The heated glass bottle was allowed to stand at room temperature for 1 hour, and after opening, the odor was evaluated. The evaluation results are shown in Table 8.

  ADVANTAGE OF THE INVENTION According to this invention, in the polypropylene coloring resin composition containing titanium dioxide, the coloring resin composition by which generation | occurrence | production of the odor was suppressed favorably at the time of the shaping | molding process and when it heats after shaping | molding can be provided. .

Claims (6)

  To 100 parts by mass of polypropylene resin, 0.1 to 200 parts by mass of titanium dioxide, 0.0005 to 5 parts by mass of tocopherol and 0.0005 to 5 parts by mass of phosphorous antioxidant are added as coloring pigments. A colored resin composition characterized by the above.   The colored resin composition according to claim 1, wherein the polypropylene resin is a homopolymer of propylene, an ethylene-propylene block copolymer, or an ethylene-propylene random copolymer.   The colored resin composition according to claim 1, wherein the polypropylene resin is a propylene homopolymer, an ethylene-propylene block copolymer, or an ethylene-propylene random copolymer having an MFR of 0.1 to 100 g / 10 min.   The coloring according to claim 1, wherein the titanium dioxide is coated with a metal oxide selected from the group consisting of oxides of Al, Si, Zr, Sb, Sn and Zn with respect to the total mass of titanium dioxide. Resin composition.   A synthetic resin container lid comprising a base resin containing a polypropylene resin and the colored resin composition according to any one of claims 1 to 4. A synthetic resin liner for a container lid, comprising a base resin containing a polypropylene resin and the colored resin composition according to any one of claims 1 to 4.