TWI818131B - Heat sealing film - Google Patents

Abstract

We provide heat sealing films that do not impair productivity and do not discolor the sealing part due to heat sealing. The heat sealing film of the present invention has a heat sealing layer 10 for thermal fusion by heating and a thermosensitive layer 40 for color development by heating. The heat sealing temperature of the heat sealing layer 10 is lower than the color development temperature of the heat sensitive layer 40 .

Description

Heat sealing film

The present invention relates to a film for heat sealing.

A method has been proposed to "use a heat-sealing film containing a heat-sealing layer for thermal fusion by heating and a heat-sensitive layer for color development by heating, and perform packaging material bag making by heat sealing." According to this method, packaging of goods and the like can be facilitated. However, the heat-sensitive layer of the sealing part may develop color due to heat sealing (HS1 shown in Figure 3). The color development of the sealing part impairs the appearance of the packaging material. By heat sealing at low temperature, discoloration of the sealing portion can be prevented. However, heat sealing at low temperatures takes time, and the productivity of products etc. decreases.

"Patent documents" "Patent Document 1": Japanese Patent Publication No. 2016-093961

The present invention was completed in order to solve the above-mentioned conventional problems, and its main object is to provide a heat-sealing film in which productivity is not impaired and the sealing portion does not develop color due to heat sealing.

The heat sealing film of the present invention has a heat sealing layer for thermal fusion by heating, and a heat sensitive layer for color development by heating. The heat sealing temperature of the heat sealing layer is lower than the color development temperature of the heat sensitive layer. .

In one embodiment, the heat sealing temperature of the heat sealing layer is lower than the color development temperature of the heat sensitive layer by more than 5°C.

In one embodiment, the heat sealing temperature of the heat sealing layer is below 115°C, and the color development temperature of the heat sensitive layer is above 120°C.

In one embodiment, the heat-sensitive layer includes a lubricant with a melting point of 50° C. or higher.

According to the present invention, it is possible to provide a film for heat sealing in which the sealing portion does not develop color due to heat sealing without impairing productivity.

Although embodiments of the present invention are described below, the present invention is not limited to these embodiments.

(Film for heat sealing)

FIG. 1 is a schematic cross-sectional view of a heat sealing film according to an embodiment of the present invention. The illustrated heat sealing film 100 has a heat sealing layer 10 and a heat sensitive layer 40 . The heat sealing film 100 may also have a base material layer 20, a bottom layer 30, an intermediate layer 50, a top layer 60 and a printing layer 70 as required. In the embodiment of the present invention, the heat sealing temperature of the heat sealing layer 10 is lower than the color development temperature of the heat sensitive layer 40 .

In the embodiment of the present invention, as mentioned above, the heat sealing temperature of the heat sealing layer 10 is lower than the color temperature of the heat sensitive layer 40, preferably by more than 5°C. Specifically, the heat sealing temperature of the heat sealing layer 10 is preferably 115°C or lower, preferably 95°C to 115°C, and more preferably 105°C to 115°C. The color development temperature of the thermosensitive layer 40 is preferably 120°C or above, more preferably 120°C to 140°C, and more preferably 120°C to 130°C. With this structure, the heat-sealing film 100 in which "the sealing portion HS2 does not develop color as shown in Fig. 2" can be obtained.

(Heat sealing layer)

The heat sealing layers 10 can be fused by heating in a state where the heat sealing layers 10 are in close contact with each other. In this specification, the temperature at which the heat sealing layer is in a fused state is defined as the heat sealing temperature. Utilizing this property, the packaging sheet formed into a bag shape can be sealed by heating in the same state, that is, heat sealing.

The heat sealing layer 10 is typically made of a material with heat sealability. In the present invention, the heat sealing layer 10 is composed of a material whose "heat sealing temperature is preferably 115°C or lower, preferably 95°C to 115°C, and more preferably 105°C to 115°C." Examples of substances constituting the heat sealing layer 10 include: LDPE (low density polyethylene), HDPE (high density polyethylene), CPP (non-stretched polypropylene), OPP (biaxially stretched polypropylene), polyolefin resin (polyolefin resin) Propylene, polybutylene, etc.), olefin-vinyl acetate copolymer (ethylene-vinyl acetate copolymer, etc.), olefin-(meth)acrylic acid copolymer (ethylene-(meth)acrylic acid copolymer or its metal cross-linked things, etc.).

The heat sealing layer 10 can be formed by stacking a film made of the above-mentioned resin material on the base material layer 20 , or can be formed on the base material layer 20 by co-extruding the above-mentioned resin material together with the resin constituting the base material layer 20 superior. Moreover, it can also be formed by coating the material constituting the heat sealing layer 10 on the base material layer 20 .

When formed by stacking or co-extrusion, the thickness of the heat sealing layer 10 is preferably 1 μm to 100 μm, and preferably 10 μm to 30 μm. When formed by coating, 0.1 μm to 10 μm is preferred, and 0.5 μm to 3.0 μm is preferred.

(Substrate layer)

The base material layer 20 has the function of ensuring the strength of the heat sealing film 100 . Various materials can be used for the base material layer 20 as long as it has transparency and can obtain packaging strength. Examples of materials constituting the base layer 20 include biaxially stretched polypropylene films (OPP films), polyolefin resins such as polyethylene and polypropylene, styrene resins such as polystyrene, and polyethylene terephthalate. Carbonate resins such as polyester resin and polycarbonate. One type of these resins may be used alone, or two or more types may be used in combination. The base material layer 20 may be an unstretched film or a stretched film. The stretched film may be either a uniaxially stretched film or a biaxially stretched film. The base material layer 20 can be a single-layer film or a multi-layer film. Furthermore, the base material layer 20 may be colorless and transparent, or may be colored and transparent. In addition, the details of the base material layer 20 are described in Japanese Patent Publication No. 2016-093961, and the description of this publication can be used as a reference in this specification.

(ground floor)

The bottom layer 30 is provided to improve the adhesion between the base material layer 20 and the heat-sensitive layer 40 . The bottom layer 30 is formed with a binding agent as the main component, and a filler may be used as needed. As the binder and filler, those exemplified as the binder and filler of the heat-sensitive layer 40 described later can be used.

(heat sensitive layer)

The heat-sensitive layer 40 includes a color-developing material that generates color through heating, whereby heat-sensitive printing can be performed on the heat-sensitive layer 40 . The color-developing material is not particularly limited as long as it can develop color by heating. A dye that can develop color by itself can be used, or a transparent or light-colored dye (typically a colorless dye) and a dye that can develop color by heating can be used. Use a combination of color developers. The color-developing material that combines a colorless dye and a developer can also be used on general thermal recording paper, etc. It is easy to obtain and has high versatility. The thermosensitive layer 40 is typically arranged on the upper side of the bottom layer 30 as shown in FIG. 1 . In addition, in this specification, when "printing" is mentioned, it means direct coloring/graphic drawing/text printing, etc. using ink or dye on the top layer, etc., and when "printing" is mentioned, it means causing the heat-sensitive layer to develop color. And perform coloring/graphic drawing/text printing, etc.

As the leuco dye, well-known ones can be used, and examples thereof include: triphenylmethane phthalolactone series, triarylmethane series, fluorescein series, phenanthrene series, thiofluorescein series, fluorescein series, indigo Phthalone (indolephthale, indophthalyl) series, spiropyran series, azophthalide series, 𠳭lopyrazole series, methine series, rose red anilinyl lactone series, rose red lactone series, quinine series Various colorless dyes such as oxazoline series, diazoline series, dilactone series, etc. Although one type of leuco dye can be used alone, two or more types can be used in combination to achieve printing of a desired color.

As the developer, electron acceptors such as acidic substances can be used. The developer can be appropriately selected according to the type of the leuco dye, and a well-known developer can be used. As color developers, in addition to acidic inorganic substances (bentonite, zeolite, silica gel, etc.), carboxylic acids (aliphatic monocarboxylic acids such as stearic acid; polycarboxylic acids such as oxalic acid and maleic acid; tartaric acid, citric acid, amber In addition to aliphatic hydroxycarboxylic acids such as acids; aromatic carboxylic acids such as benzoic acid, etc.), compounds having a phenolic hydroxyl group can also be exemplified. These color developers can be used individually by 1 type or in combination of 2 or more types.

In an embodiment of the present invention, the heat-sensitive layer 40 includes a lubricant. The melting point of the lubricant is preferably above 50°C, and preferably between 50°C and 120°C. With this structure, the color temperature of the thermosensitive layer 40 becomes high. As a result, the difference between the heat sealing temperature and the heat sealing layer becomes large, and a heat sealing film in which the sealing portion does not develop color is obtained. Examples of lubricants include waxes (ester waxes such as paraffin wax and palm wax, polyolefin waxes such as polyethylene wax, etc.), oils and fats (high fatty acids such as oleic acid, high fatty acid salts (metallic soaps such as zinc stearate, etc.) , whale oil and other animal oils, vegetable oils, etc.) and silicone oil, etc. You can also use a lubricant with a melting point above 50°C and a lubricant with a melting point below 50°C.

Generally speaking, as for the lubricant used in the heat-sensitive layer 40, by using a lubricant with a relatively low melting point, since the lubricant is easily melted by heating, it can be easily colored at a low temperature. Moreover, by using a material with a relatively low melting point as the material of the heat sealing layer 10, it is easy to melt by heating, so it can be easily fused at a low temperature. However, when the color development temperature of the heat-sensitive layer 40 is the same as the heat sealing temperature of the heat sealing layer 10, there is a problem that the heat sealing portion develops color during heat sealing. According to the embodiment of the present invention, by using a lubricant with a relatively high melting point as the lubricant used in the heat-sensitive layer 40, since the lubricant is not easy to melt during heat sealing, it can be achieved that the heat-sealed portion does not melt during heat sealing. The heat-sealing film that develops color can also effectively develop the color of the heat-sensitive layer 40 within the heating temperature range of a heating device such as a thermal head. That is to say, as mentioned above, it is possible to achieve "the color development of the heat-sealing part can be suppressed and heat-sealing is reliable when heat-sealing at a low temperature, and the heat-sensitive layer 40 can be effectively colored at a high temperature, and characters, numbers, patterns, and barcodes can be The effect of packaging materials such as "excellent readability" is an unexpected and excellent effect. In addition, the deliberate use of a high-melting-point lubricant that generally deteriorates color development in the heat-sensitive layer 40 as described above is based on a technical thought that is contrary to the technical common sense in the industry.

In addition, the heat-sensitive layer 40 may include fillers and binders as needed. Examples of fillers include inorganic fillers (silica, etc.), organic fillers (styrene resins such as polystyrene (PS), olefin resins such as polyethylene (PE), polymethyl methacrylate (PMMA), etc. Various resin particles such as acrylic resin, urea resin, etc.), etc. As the binding agent, resins and polymers (synthetic polymers, natural polymers, etc.) can be used, and hydrophilic or water-soluble binding agents and water-dispersible binding agents are preferred. In addition, details about fillers and binders are described in Japanese Patent Publication No. 2016-093961, and the description in this publication can be used as a reference in this specification.

The heat-sensitive layer 40 can be formed, for example, by dispersing the above-mentioned materials in a dispersion medium to prepare a coating liquid, applying it on the surface of the base material layer 20 and drying the coating film. When dispersing the constituent materials of the heat-sensitive layer 40 in the dispersion medium, in addition to the well-known mixers, well-known pulverizers such as sand mills and bead mills can also be used. As the dispersion medium, organic solvents such as alcohols, ketones, and nitriles can also be used, and water is preferably used.

The heat-sensitive layer 40 can be formed on the entire surface of the base layer 30 as shown in FIG. 1 . If the portion to be printed is a limited area of the heat-sealing film, it can also be formed on only this area.

(middle layer)

The intermediate layer 50 has barrier properties against water or oil. The intermediate layer 50 is composed of resin. Examples of the resin constituting the intermediate layer 50 include an acrylic resin emulsion, a water-soluble resin such as polyvinyl alcohol (PVA) resin, and a styrene-butadiene rubber (SBR) resin. The intermediate layer 50 is typically disposed above the heat-sensitive layer 40 as shown in FIG. 1 . In addition, details about the intermediate layer are described in Japanese Patent Publication No. 2016-093950, and the description in this publication can be used as a reference in this specification.

(top level)

The top layer 60 ensures printing suitability and printing suitability, and can be the printing surface of the printing layer 70 . It can be used when lubricants, cross-linking agents, fillers, etc. are added to the binding agent. The top layer 60 is typically disposed above the middle layer 50 as shown in FIG. 1 . In addition, details about the top layer are described in Japanese Patent Publication No. 2016-093950, and the description in this publication can be used as a reference in this specification.

As a binding agent, resins and polymers (synthetic polymers, natural polymers, etc.) can be used. Examples of the resin serving as a binder include acrylic resin and the like. Furthermore, hydrophilic or water-soluble binding agents and water-dispersible binding agents are preferred.

Examples of lubricants include polyethylene, waxes (ester waxes such as paraffin wax and palm wax, polyolefin waxes such as polyethylene wax, etc.), oils and fats (high fatty acids such as oleic acid, high fatty acid salts (metallic compounds such as zinc stearate), etc. Soap, etc.), whale oil and other animal oils, vegetable oils, etc.) and silicone oil, etc.

As the cross-linking agent, for example, well-known ones such as ammonium zirconium carbonate can be used depending on the type of functional groups the matrix resin has.

Examples of fillers include inorganic fillers, organic fillers (styrene resins such as polystyrene (PS), olefin resins such as polyethylene (PE), acrylic resins such as polymethyl methacrylate (PMMA), and urea resins). Various resin particles, etc.) etc.

(printing layer)

The printing layer 70 may be provided to display specified information or design in parts other than the printing part. For example, when the printed part will prompt individual product information, the printing layer can prompt overall information (such as the product's manufacturer's logo). Furthermore, excellent design can be added to products (essentially packaging materials). Examples of the material constituting the printing layer include a coating liquid containing, for example, dyes, pigments, metals, materials that are adhesive components, solvents, and other components. Furthermore, the above-mentioned materials also include metals. The type of metal is not particularly limited, and examples thereof include aluminum, aluminum alloys, copper, copper alloys (copper-nickel alloys, copper-zinc alloys, etc.), silver, and silver alloys. The metal may also be in any form such as metal powder, metal sheet, metal fiber, etc. Printed layers containing these metals have excellent design properties and excellent light-shielding properties. The printing layer 70 is typically disposed above the top layer 60 as shown in FIG. 1 . Furthermore, as another example, the printing layer 70 may be disposed between the heat sealing layer 10 and the base material layer 20 , or the printing layer 70 may be disposed on the surface of the heat sealing layer 10 opposite to the base material layer 20 .

The method of printing the above materials can be any appropriate method depending on the compatibility with the printing surface. Examples include: rotogravure printing, offset printing, letterpress rotary printing, UV printing, screen printing, etc. . In the case where the dispersion medium of the heat-sensitive layer 40 is an organic solvent, if it can be formed by printing, the printing layer 70 can be formed simultaneously with the heat-sensitive layer 40 .

(Packaging materials)

By heat-sealing the above-mentioned heat-sealing film, a packaging material can be produced. According to the embodiment of the present invention, as described above, it is possible to produce a packaging material that does not cause the sealing portion to develop color.

"Example"

The present invention is specifically described below through examples, but the present invention is not limited to these examples.

[Example 1]

The bottom layer 30 is formed on the surface opposite to the heat sealing surface of P3162 (manufactured by Toyobo Co., Ltd.) which is HS-OPP (heat-sealing biaxially stretched polypropylene). Subsequently, 3-dibutylamino-6-methyl-7-anilino fluorescent yellow matrix was used as the dye, 4-hydroxy-4'-n-propoxydiphenyl sulfate was used as the color developer, and the lubricant was used Q340 (melting point: 110°C, manufactured by Chukyo Oil & Fat Co., Ltd.) was dispersed in a dispersion medium to prepare a coating liquid, which was applied to the surface of the base layer 30 opposite to the base material layer 20 and dried to form the heat-sensitive layer 40 . Subsequently, the acrylic resin emulsion is coated on the heat-sensitive layer 40 and dried to form the intermediate layer 50 . Subsequently, a coating liquid is prepared in which polyethylene as a lubricant, zirconium carbonate as a cross-linking agent, and silica gel as a filler are added to acrylic resin as a binding agent, and the middle layer 50 is coated and dried to form the top layer 60 . Subsequently, printing layer 70 is formed by rotogravure printing on a portion of top layer 60 . Proceed in this manner to prepare a film for heat sealing. The obtained heat-sealing film was heat-sealed at 115° C. for 1 second, and the presence or absence of color development in the sealed portion was visually evaluated. The results are revealed in Table 1.

[Example 2]

A heat sealing film was produced as in Example 1, except that L-700 (melting point: 75°C, manufactured by Chukyo Oils and Fats Co., Ltd.) was used as the lubricant contained in the heat-sensitive layer. The obtained heat-sealing film was heat-sealed and evaluated with reference to Example 1. The results are revealed in Table 1.

[Example 3]

A heat-sealing film was produced as in Example 1 except that PF60 (melting point: 66°C, manufactured by Chukyo Oil & Fat Co., Ltd.) was used as the lubricant contained in the heat-sensitive layer. The obtained heat-sealing film was heat-sealed and evaluated with reference to Example 1. The results are revealed in Table 1.

[Example 4]

A heat sealing film was produced as in Example 1, except that O-128 (melting point: 120°C, manufactured by Chukyo Oils and Fats Co., Ltd.) was used as the lubricant contained in the heat-sensitive layer. The obtained heat-sealing film was heat-sealed and evaluated with reference to Example 1. The results are revealed in Table 1.

[Comparative example 1]

A heat sealing film was produced as in Example 1, except that R-232 (melting point: 46°C, manufactured by Chukyo Oils and Fats Co., Ltd.) was used as the lubricant contained in the heat-sensitive layer. The obtained heat-sealing film was heat-sealed and evaluated with reference to Example 1. The results are revealed in Table 1.

"Table 1" lubricant Melting point(℃) Whether there is hair color Heat sealability Example 1 Q340 110 without good Example 2 L-700 75 without good Example 3 PF60 66 without good Example 4 O-128 120 without good Comparative example 1 R232 46 have good

The color development temperature of the thermosensitive layer in the above-mentioned Examples 1 to 4 is 120°C. On the other hand, the color development temperature of the thermosensitive layer in Comparative Example 1 was 115°C.

In the heat-sealing film according to the example of the present invention, no color development of the sealing portion after heat-sealing was observed, but the heat-sealing properties were good. On the other hand, in the heat sealing film of the comparative example, although the heat sealability after heat sealing was good, color development of the sealing portion was observed. From the above evaluation results, it can be seen that by using a lubricant with a high melting point for the heat-sensitive layer, a heat-sealing film in which the sealing portion does not develop color during heat-sealing can be obtained.

The heat sealing film of the present invention can be suitably used for packaging of food and the like.

10:Heat sealing layer 20:Substrate layer 30: Bottom floor 40: Heat sensitive layer 50:Middle layer 60:Top 70: Printing layer 100: Film for heat sealing

<Fig. 1> is a schematic cross-sectional view of a heat sealing film according to one embodiment of the present invention. <Fig. 2> is a schematic plan view of a heat sealing film according to one embodiment of the present invention. <Figure 3> is a schematic top view of a heat sealing film having a conventional structure.

10:Heat sealing layer

20:Substrate layer

30: Bottom floor

40: Heat sensitive layer

50:Middle layer

60:Top

70: Printing layer

100: Film for heat sealing

Claims (3)

A heat-sealing film, which has: a heat-sealing layer for thermal fusion through heating, and a heat-sensitive layer for color development through heating, wherein the heat-sealing temperature of the heat-sealing layer is higher than the color-development temperature of the heat-sensitive layer It is still low, and the heat-sensitive layer contains a lubricant with a melting point of 110°C or above. The heat sealing film according to claim 1, wherein the heat sealing temperature of the heat sealing layer is lower than the color development temperature of the heat sensitive layer by more than 5°C. The heat sealing film according to claim 2, wherein the heat sealing temperature of the heat sealing layer is 115°C or lower, and the color development temperature of the heat sensitive layer is 120°C or higher.

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