JPH0224657B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a novel packaging material that can be firmly attached to a packaged product by heating after packaging, can be printed in multiple colors on its surface, and has complete light-shielding properties. Conventional Technology Up until now, materials that need to be protected from heat and light, such as heat-sensitive recording paper and photosensitive paper, have been packaged manually using black cardboard and plastic, or a laminate thereof. , a method is used in which labels are pasted manually as needed. However, this method has extremely low work efficiency and is prone to problems such as the packaging's appearance becoming dirty and display errors.Recently, attempts have been made to automate this process, but it is difficult to wrap the packaging in a sealed state. This has not been achieved to date because it has not been possible to solve the problems of the difficulty of packaging and the deterioration of the contents due to heating during packaging. On the other hand, packaging using foamed stretched film has been proposed for the purpose of preventing damage to glass bottles and fruit etc.
(Japanese Patent Publication No. 52-22021), although this foamed stretched film provides packaging with improved insulation and cushioning properties, it does not have light-shielding properties, so it is not suitable for packaging heat-sensitive recording paper or photosensitive paper. Appropriate. Problems to be Solved by the Invention An object of the present invention is to provide a package that has sufficient heat insulation and cushioning properties, as well as complete light-shielding properties, and that is in close contact with the packaged product. An object of the present invention is to provide a new packaging material that can be printed with. Means for Solving the Problems In order to achieve the above object, the present inventors have conducted various studies and found that the surface that contacts the packaged product is a colored foam layer, and the surface on the opposite side is a colored foam layer. It has been discovered that a desired packaging material can be obtained by stretching a composite film having a white non-foamed layer, and based on this knowledge, the present invention has been completed. That is, the present invention provides a light-shielding packaging material comprising a stretched composite film of an olefinic or styrene resin foamed film colored with a dark coloring agent and a white non-foamed film, and a method for producing the same. be. As the material for the colored foam film in the present invention, a thermoplastic resin selected from olefin resins and styrene resins mixed with a foaming agent and a foaming aid is used. The olefin-based resin or styrene-based resin referred to here does not only refer to resins consisting solely of olefin or styrene;
It mainly consists of olefin and styrene, and includes copolymers of these and other copolymerizable monomers, or mixtures thereof. Examples of this olefin resin include high density polyethylene, low density polyethylene, ethylene homopolymers such as linear low density polyethylene, propylene such as polypropylene and polybutylene,
In addition to a butylene homopolymer, copolymers consisting of two or more monomers selected from ethylene, propylene, butylene, and other copolymerizable monomers can be mentioned. Examples of styrene resins include homopolymers of aromatic vinyl monomers such as styrene, methylstyrene, ethylstyrene, isopropylstyrene, dimethylstyrene, vinyltoluene, vinylxylene, and chlorostyrene, and copolymers thereof. Alternatively, copolymers of these aromatic vinyl monomers and other copolymerizable monomers may be mentioned. Next, the blowing agent added to these thermoplastic resins may be either a thermally decomposable type or a low boiling point volatile type; examples of the former include ammonium carbonate, sodium bicarbonate, sodium nitrite, and chloride. Inorganic blowing agents such as in combination with ammonium, dinitrosopentamethylenetetramine, N,
Nitroso blowing agents such as N'-dimethyl-N,N'-dinitrosoterephthalamide, sulfonyl hydrazides such as benzenesulfonyl hydrazide, p-totoluenesulfonyl hydrazide, and P,P'-oxybis(benzenesulfonylhydrazide) Foaming agent, azobisisobutyronitrile, azodicarboxylic acid amide, barium azodicarboxylate,
Azo blowing agents such as diethyl azodicarboxylate, and alkanes such as pentane, hexane, heptane, methyl chloride, methylene chloride, trichloroethane, dichloroethane, dichlorotetrafluoroethane, trichlorofluoromethane, examples of the latter , trichlorotrifluoroethane, and halogenated alkanes such as dichlorodifluoromethane. In addition, foaming aids used in combination with these foaming agents include oxalic acid, lactic acid, citric acid, succinic acid,
Malic acid, salicylic acid, phthalic acid, benzoic acid, phosphoric acid, boric acid, toluenesulfonic acid, borax, boron trifluoride, ethanolamine, guanidine carbonate, dimethylformamide, anhydrous potassium carbonate,
These include titanium oxide, zinc oxide, magnesium oxide, cadmium oxide, zinc chloride, magnesium carbonate, zinc nitrate, zinc powder, zinc acetate, zinc laurate, barium stearate, calcium stearate, and aluminum stearate. The blending amount of these blowing agents and foaming aids is 0.1 to 1.0 parts by weight of the blowing agent per 100 parts by weight of the thermoplastic resin.
Finally, within the range of 0.1 to 1.0 parts by weight of the foaming aid,
The foam is selected to produce a foam with closed cells with an expansion ratio of 1.2 to 3.0 times. It is necessary to mix a dark coloring agent into the material used to form this foamable film in order to impart light-shielding properties. Dyes and pigments that exhibit deep colors, such as dyes and pigments, or various metal powders are used. Particularly suitable are black pigments such as carbon black and metal powders such as aluminum powder. These colorants are usually blended in an amount of 5 to 50 parts by weight, preferably 10 to 30 parts by weight, per 100 parts by weight of the thermoplastic resin. The material of this colored foamable film may contain any
If desired, additives commonly used in ordinary thermoplastic resin films, such as ultraviolet absorbers, antioxidants, flame retardants, antistatic agents, antiblocking agents, and inorganic fillers, can be added. On the other hand, the material for the white non-foamed film that forms the other layer of the composite film of the present invention is not particularly limited as long as it can be formed into a film, but for example, it may be the same material as the colored foamed film described above. Thermoplastic resins such as the following can be used. This material does not necessarily have to have the same composition as the material of the colored foam film. By using thermoplastic resins with the same or similar compositions, the processability, physical properties, etc. will be the same and it will be easier to handle, but by using a different composition within the range that does not impair the composite with the colored foam layer, new processing will be possible. It is useful because it can impart properties, physical properties, etc. This non-foaming film needs to be blended with a light-colored, particularly white, colorant in order to provide a surface on which arbitrary printing can be applied. As such a coloring agent, for example, titanium oxide, zinc oxide, cadmium oxide, calcium carbonate, etc. are used, and titanium oxide is particularly preferred. This white colorant is
It is blended in an amount of 5 to 50 parts by weight, preferably 15 to 25 parts by weight, per 100 parts by weight of the thermoplastic resin. If desired, conventional additives can be added to this white non-foamed film material, as in the case of the colored foamed film described above. In the present invention, the colored foamed film and the white non-foamed film can be formed according to a conventional method, for example, by extrusion molding. In addition, to combine a colored foamed film and a white non-foamed film, each film formed in advance may be bonded using an adhesive, but coextrusion molding,
It is advantageous to use an extrusion lamination method, a heat lamination method, or the like to combine the materials by fusing them simultaneously with film formation or after film formation, without using an adhesive. The thus obtained composite film is then uniaxially stretched in the machine direction or the transverse direction, or biaxially stretched in the machine and transverse directions in order to impart heat shrinkability. The stretching ratio at this time is usually 3 times or more in terms of area ratio, preferably 5 times or more. The ratio of the thicknesses of the non-foamed film and the foamed film in the composite film of the present invention is preferably selected such that the latter is 1 to 2.5 times that of the former. Further, the appropriate thickness of the composite film is in the range of 0.3 to 2.0 mm. To package an article with the packaging material of the present invention,
After packaging the product with the colored foam film layer on the side that contacts the packaged product, the product is heated. This heat treatment causes the entire package to shrink and form a compact package. Effects of the Invention The packaging material of the present invention includes a foam layer, which exhibits a heat insulating effect. Therefore, it is safe to package articles that are likely to be thermally denatured, such as heat-sensitive recording paper, using conventional heat-shrinkable films. In addition, this foam layer also acts as a cushioning material, protecting the packaged items from impact and friction during transportation or storage, and preventing deterioration due to transmitted light during long-term storage. It has the advantage of being preventable. In addition, the surface that comes into contact with the atmosphere is made of a non-foamed film layer, which blocks moisture from the atmosphere.
In addition to preventing deterioration of the packaged product due to moisture, this non-foaming film layer has the advantage that multi-color printing can be performed directly on it because it is white. Therefore, the packaging material of the present invention is suitable for packaging glass containers that are easily damaged, and for packaging foods, pharmaceuticals, photosensitive materials, etc. that are susceptible to deterioration due to heat, light, and moisture. Examples Next, the present invention will be explained in more detail with reference to Examples. Example 1 Polypropylene (B-230 manufactured by Mitsui Petrochemicals)
50 parts by weight of ethylene-vinyl acetate copolymer (DQDJ-1830, manufactured by Nippon Unica Co., Ltd.) and carbon black master pellets (PO manufactured by Nihon Vicks Co., Ltd.).
-0840 black, polyethylene resin-based pellets with a carbon concentration of 50%) 20 parts by weight and blowing agent master pellets (Cellmic MB manufactured by Sankyo Kasei Co., Ltd.)
3013, polyethylene resin-based azodicarboxylic acid amide concentration 10% and foaming aid-containing pellets) 3
After heating and kneading, a black foamed film with a thickness of 0.6 mm and an expansion ratio of 1.8 times was formed by T-die extrusion, and then 50 parts by weight of the above polypropylene and 50 parts by weight of ethylene-vinyl acetate copolymer were added. white pigment master pellets (manufactured by Nihonbix Co., Ltd.)
0961c white, polyethylene resin-based titanium oxide concentration 50% master pellet) A resin composition with 30 parts by weight added to the thickness on one side of a black foam film
A 0.3 mm white non-foamed film was laminated and integrated by extrusion lamination to form a 0.9 mm thick composite sheet. The composite sheet thus obtained was heated and stretched at 100 to 110° C. three times in the longitudinal direction and twice in the transverse direction to obtain a light-shielding packaging material with a thickness of 0.15 mm.
This product had a low heat transfer coefficient of 5.0 Kcal/m ² Hr°C, and when it was immersed in a glycerin bath maintained at a predetermined temperature for 30 seconds and its shrinkage rate was measured, the results shown in Table 1 were obtained.

[Table] Reference example Thermal recording paper for facsimile (manufactured by Jujo Paper KK,
TP50KH-F5) was wrapped with the packaging material obtained in Example 1 so that the black foam film layer was on the inside, and heated with an infrared heater for 5 seconds to bring the surface temperature of the packaging material to 110°C, causing heat shrinkage. As a result, the thermal paper could be tightly packaged without developing color. Regarding light shielding properties, diazo photosensitive paper (for medium-speed Ricopy) was partially masked with the packaging material, wrapped with the black foam film layer on the inside, and exposed to fluorescent light and direct sunlight. The areas that were not masked were completely exposed to light after 2 hours and lost their performance as photosensitive paper, but the areas covered with the packaging material remained unchanged even after 15 days had passed. Since thermal paper is less sensitive to light than diazo-sensitive paper, it has been found that the packaging material can completely protect the printability by applying corona discharge treatment to the surface of the white non-foamed (skin layer) of the packaging material. As with white paper, normal multicolor printing was possible without being affected by the black foam layer, resulting in a photographic print finish with vivid colors. Example 2 Using the same polypropylene, ethylene-vinyl acetate copolymer, carbon black master pellets, white pigment master pellets, and blowing agent master pellets as in Example 1, 50 parts by weight of polypropylene and ethylene-vinyl acetate copolymer were used. A resin composition for a colored foamed film layer comprising 50 parts by weight of carbon black master pellets, 2 parts by weight of white pigment master pellets, and 3 parts by weight of blowing agent master pellets, 50 parts by weight of polypropylene, and ethylene.
Using a resin composition for a white non-foamed film layer containing 50 parts by weight of vinyl acetate copolymer and 40 parts by weight of white pigment master pellets, a composite sheet is formed by a coextrusion method using separate extruders. Then, in the same manner as in Example 1, the material was subjected to longitudinal and lateral biaxial stretching to obtain a packaging material. The packaging material had the same heat shrinkability and heat insulation properties as Example 1, but the whiteness of the surface of the non-foamed film layer was lower than that of Example 1 despite the increased carbon content of the foamed film layer. It was also found that the light-shielding property was higher than that of Example 1 and could be used for photographic paper, which is more photosensitive. Example 3 Using the same polypropylene-vinyl acetate copolymer, blowing agent master pellets, and white pigment master pellets as in Example 1, 10 parts by weight of aluminum powder was added to 50 parts by weight of polypropylene and 50 parts by weight of ethylene-vinyl acetate copolymer. The mixture was heated, kneaded, and extruded to prepare an aluminum powder-containing resin.
A resin composition for a colored foamed film layer was prepared by adding 3 parts by weight of blowing agent master pellets, 50 parts by weight of polypropylene, 50 parts by weight of ethylene-vinyl acetate copolymer, and 20 parts by weight of white pigment master pellets. Using a resin composition for a non-foamed film layer,
A packaging material was prepared in the same manner as in Example 2. As a result of the same performance confirmation test as in Example 1, it was found that the heat shrinkage, buffering properties, light shielding properties, printing suitability, etc. were the same as in Example 1, but the thermal conductivity was 4.3 Kcal. / ^m2・Hr・℃, which was even lower. Comparative Examples 1 to 3 Packaging materials were prepared in the same manner as in Example 1 using resin compositions having the compositions shown in Table 2 (each component was the same as in Example 1). These were satisfactory in terms of heat shrinkability, heat insulation, cushioning properties, printability, and moisture impermeability, but as shown in Comparative Example 3, the amount of titanium oxide added was changed between the foamed film layer and the non-foamed film layer. If both increase, the concealing property will improve, but the light-shielding property will not be obtained, and as in Example 1, thermal paper for printers (Mitsubishi Thermal Paper PM-200M) was shrink-wrapped using the packaging material and exposed to light for 50 minutes under fluorescent lamp illumination. When left for a day, the surface of the thermal paper for printers turned yellow and the quality of the thermal paper deteriorated.

[Table] Example 4 Using the same polypropylene, ethylene-vinyl acetate copolymer, carbon black master pellets, white pigment master pellets, and blowing agent master pellets as in Example 1, 50 parts by weight of polypropylene and ethylene vinyl acetate 30 parts by weight of carbon black master pellets, 4 parts by weight of white pigment master pellets, and 3 parts by weight of blowing agent master pellets are added to 50 parts by weight of the copolymer to prepare a resin composition for a colored foamed film layer. A resin composition for a white non-foamed film layer was prepared by adding 40 parts by weight of white pigment master pellets to 50 parts by weight of polystyrene (Estyrene G-32 manufactured by Nippon Steel Chemical Industry Co., Ltd.). These resin compositions were molded into composite sheets by co-extrusion using separate extruders, and then stretched in the transverse uniaxial direction to obtain packaging materials. The thermal conductivity of this material is
The heating shrinkage rate was measured in the same manner as in Example ¹ , and the results shown in Table 3 were obtained.

[Table] Packaging materials made from combinations of these resin compositions had the same properties as Examples 1 to 3 in terms of heat insulation, cushioning, and light shielding properties, but the film hardness (strength) increased;
It has improved secondary processability such as printability and machine mountability on automatic packaging machines, and has a pearlescent luster on the surface, making it possible to create a packaging material with a unique appearance.

Claims (1)

[Scope of Claims] 1. A light-shielding packaging material comprising a stretched composite film of a foamed film of olefin or styrene resin colored with a dark coloring agent and a white non-foamed film. 2. At the same time or after forming a colored foam film by extrusion molding an olefinic or styrene resin containing a deep coloring agent and a blowing agent,
A method for producing a light-shielding packaging material, which comprises laminating a white non-foamed film on one side of the colored foamed film by fusing or adhesion, and then stretching the laminated film.