JPS626583B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a resin composition for heat-shrinkable film,
Specifically, the present invention relates to a resin composition for heat-shrinkable films having good physical properties, which is based on a polyolefin resin, to which an inorganic substance subjected to a specific surface treatment and a chemically modified polyolefin are added. Heat-shrinkable films made mainly of high-density polyethylene, low-density polyethylene, etc. have traditionally been used for packaging various products, but because of their low mechanical strength, they tend to be particularly heavy or angular. In some cases, the film was easily torn and there was a risk of damaging or damaging the contents. In addition, this film is not suitable for secondary processing such as printing and painting, so no aesthetic effect can be expected from packaging, and the surface of the film is smooth.
When the packaged products were stacked on top of each other, there was a risk of them falling off. Therefore, the present inventors have conducted extensive research in order to overcome the drawbacks of the conventional heat-shrinkable films and develop a heat-shrinkable film with excellent physical properties. As a result, it was discovered that a material obtained by adding an inorganic substance subjected to a specific surface treatment and a special chemically modified polyolefin to a polyolefin resin is suitable as a material for a heat-shrinkable film having the desired physical properties, and the present invention was completed. I came to the conclusion. That is, the present invention comprises (A) polyolefin resin, (B)
Provided is a resin composition for a heat-shrinkable film comprising an inorganic substance surface-treated with an unsaturated carboxylic acid or its derivative and a chemically modified polyolefin obtained by modifying (C) a polyolefin resin with a liquid rubber and an unsaturated carboxylic acid or its derivative. It is. As the component (A), which is the base of the resin composition of the present invention, that is, a polyolefin resin, various types can be used, but preferably high-density polyethylene, medium-density polyethylene, low-density polyethylene, etc. or stereoregular polypropylene are used. , atactic polypropylene, ethylene-propylene copolymer, etc. are used. In addition, various types of inorganic substances surface-treated with the unsaturated carboxylic acid or its derivative, which is the component (B) of the resin composition of the present invention, can be considered, and there are various manufacturing methods. Inorganic substances that can be used here include carbonates such as calcium carbonate and barium carbonate, silicates such as sodium silicate and aluminum silicate, sulfates such as calcium sulfate and barium sulfate, titanium oxide, aluminum oxide, etc. In addition, talc, clay, etc. can be mentioned. In the resin composition of the present invention, these inorganic substances surface-treated with an unsaturated carboxylic acid or its derivative are used as component (B), but the unsaturated carboxylic acid as the treatment agent is Although there are various types, they are generally unsaturated carboxylic acids having 10 or less carbon atoms and having a hydrocarbon moiety having one or more ethylenic double bonds and one or more carboxyl groups, and in particular,
Acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, sorbic acid, maleic acid, maleic anhydride,
Itaconic acid, glutaconic acid, vinyl acetic acid and the like are preferably used alone or in combination. Further, examples of derivatives of unsaturated carboxylic acids include metal salts, amides, imides, esters, etc. of the above-mentioned unsaturated carboxylic acids. When treating the inorganic substance with the unsaturated carboxylic acid or its derivative, it is usually sufficient to simply mix the inorganic substance and the unsaturated carboxylic acid or its derivative at a temperature of 15 to 40°C. The surface of inorganic substances subjected to such treatment becomes coated with chemically active unsaturated carboxylic acids or derivatives thereof,
Further, the inorganic substance and the unsaturated carboxylic acid or its derivative are strongly bonded chemically or physically. Instead of adding an inorganic substance treated with an unsaturated carboxylic acid or its derivative, even if the inorganic substance and the unsaturated carboxylic acid or its derivative are added to the resin separately, the surface of the inorganic substance will not be coated with the unsaturated carboxylic acid or its derivative. First, the unsaturated carboxylic acid or its derivative acts only as a lubricant, and the effects of the present invention cannot be obtained. Furthermore, the chemically modified polyolefin, which is component (C) of the resin composition of the present invention, contributes to improving the surface properties of the film formed from the composition, and improves the printability and paintability of the film. A polyolefin resin chemically modified with a liquid rubber and an unsaturated carboxylic acid (including anhydride) or a derivative thereof is preferably used. As the liquid rubber, terminal hydroxylated polybutadiene is suitable. In producing this chemically modified polyolefin, radicals such as benzoyl peroxide are generated by heating a polyolefin such as polypropylene, liquid rubber, and an unsaturated carboxylic acid or its derivative in a solvent such as xylene, toluene, heptane, or monochlorobenzene. The reaction may be carried out using an agent. Details of the method for producing this chemically modified polyolefin are disclosed in JP-A-54-124049. The resin composition of the present invention basically comprises the above (A) and (B).
and (C), and is usually prepared by heating and melting and mixing these components. In the resin composition of the present invention, the blending ratio of each component (A), (B), and (C) cannot be unambiguously determined depending on various conditions, but usually polyolefin resin 40
It is preferable to mix 1 to 5 parts by weight of chemically modified polyolefin to 100 parts by weight of a compound consisting of ~80% by weight and 60 to 20% by weight of an inorganic substance surface-treated with an unsaturated carboxylic acid or its derivative. . If the blending ratio of the chemically modified polyolefin and the inorganic substance to the polyolefin resin is outside the above range, the strength, printability, etc. of the film obtained from the composition will be insufficient, and this cannot be said to be preferable. In the resin composition of the present invention, the above (A), (B),
In addition to component (C), it is also effective to add various additives such as lubricants, stabilizers, antistatic agents, and pigments as necessary. If the thus obtained resin composition of the present invention is used as a raw material and molded into a film by a molding method such as inflation molding, the molded film has heat-shrinkable properties, so that products can be manufactured using this film. After packaging, heat-sealing allows for so-called shrink packaging that tightly adheres to the product.
Moreover, this film has significantly improved mechanical strength compared to conventional heat-shrinkable films, reducing problems such as film tearing. Furthermore, this film has good printability, allowing various patterns to be applied to the surface, and has a large coefficient of static friction, so there is no risk of the packaged products slipping off when stacked on top of each other. Furthermore, since this film has a paper-like feel, it can be effectively used as decorative paper. Therefore, the resin composition of the present invention is widely used as a material for heat-shrinkable films suitable for packaging foods, books, stationery, and general gift packaging. Next, the present invention will be explained in more detail with reference to Examples. Examples 1 to 15, Reference Examples 1 to 5, and Comparative Examples 1 to 6 (1) Production of an inorganic substance surface-treated with an unsaturated carboxylic acid. 10 kg of a specified inorganic substance and 100 g of a specified unsaturated carboxylic acid kept at 40-50℃ in advance are mixed in a stainless steel container at a temperature of 30-40℃ for 1 hour, and the resulting suspension is washed with methanol. The mixture was further dried at 80° C. to obtain an inorganic material whose surface was treated with an unsaturated carboxylic acid, component (B) of the present invention (hereinafter referred to as "treated inorganic material"). (2) Production of chemically modified polyolefin. 100 parts by weight of polypropylene (melt index 8 g/10 minutes, density 0.91 g/cm ³ , trade name: J700G, manufactured by Idemitsu Petrochemical Co., Ltd.) was placed in a three-neck separable flask with an internal volume of 5 and equipped with a stirring blade and a reflux device. 1,4-polybutadiene with terminal hydroxylation (number average molecular weight 3000, product name: Poly bd
R45HT, manufactured by ARCO chem.Div.), 20 parts by weight of maleic anhydride, 1.72 parts by weight of dicumyl peroxide, and 600 parts by weight of xylene.
The mixture was heated in an oil bath using an immersion heater, and reacted with stirring at 120°C for 1 hour, and then continued at 140°C for 3 hours. After the reaction is completed, cool
The mixture was precipitated into a large excess of acetone, filtered under suction, and dried (at 70°C for 50 hours) to obtain a white powder. Subsequently, this powder was placed in a Soxhlet extractor and extracted with acetone for 16 hours to remove unreacted polybutadiene and maleic anhydride to obtain a chemically modified polyolefin, which is component (C) of the present invention. (3) Manufacture of resin composition. High-density polyethylene (density 0.955 g/cm ³ , melt index 0.05, product name: 640UF, manufactured by Idemitsu Petrochemical Co., Ltd.), the treated inorganic material obtained in (1) above and the treated inorganic substance obtained in (2) above. A predetermined amount of chemically modified polyolefin was heated and kneaded using a Banbury mixer at a resin temperature of 150 to 170°C for 10 to 20 minutes to obtain a resin composition. (4) Film forming. Using the resin composition obtained in (3) above as a material, use an inflation molding machine (Modern Machinery, EW50L, die diameter 100 mm) to
170-190℃, blow-up ratio 2.2, folding width 350
A cylindrical film with a thickness of 40 μm and a thickness of 40 μm was molded. (5) Sylink packaging. The cylindrical film obtained in (4) above is cut open to make a sheet-like film, and a pattern is printed on this film by gravure offset using vinyl chloride ink (MX type, manufactured by Showa Ink Co., Ltd.), and then This patterned film is 260mm x
Pack a 360mm x 40mm box, then heat seal the opening at 220℃ for 1.5 seconds.
Furthermore, it was passed through a shrink tunnel at 130°C for 20 seconds to be shrink wrapped. (6) Measurement of physical properties of film and Shrink packaging products. Various mechanical strengths and printing strengths of the film obtained in (4) above were measured by the following methods. In addition, the slip resistance of the shrink-wrapped product obtained in (5) above was measured by the following method. These results are shown in the table. () Tensile breaking strength: Based on JIS K-6781 () Elmendorf tearing strength: JIS Z-1702
() Impact strength: Compliant with JIS P-8134 () Printing strength: Print a pattern on the film with gravure ink for vinyl chloride (MX type, manufactured by Showa Ink Co., Ltd.), and perform a peeling test with cellophane tape after 48 hours. It was measured by performing the following.
Peeling off the cellophane tape was performed by making 100 goblets lightly with a knife on the printed surface and peeling them off with cellophane tape. In the table, X in X/100 indicates the number of goblets remaining after peeling off the cellophane tape. () Slip resistance: Shrink packaging product (300mm x 200mm x 30mm, content weight approximately 1Kg)
This was done by examining the degree of slippage in a stacked state.

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Claims (1)

[Claims] 1 (A) polyolefin resin, (B) an inorganic substance surface-treated with unsaturated carboxylic acid or its derivative, and (C) polyolefin resin chemically modified with liquid rubber and unsaturated carboxylic acid or its derivative. A resin composition for heat-shrinkable films made of chemically modified polyolefin. 2. Add (C) polyolefin resin to 100 parts by weight of a blend consisting of (A) 40-80% by weight of polyolefin resin and (B) 60-20% by weight of an inorganic substance surface-treated with unsaturated carboxylic acid or its derivative. 2. The composition according to claim 1, comprising a mixture of liquid rubber and 1 to 5 parts by weight of a chemically modified polyolefin chemically modified with an unsaturated carboxylic acid or a derivative thereof.