JP6545873B1 - Method of using adhesive composition - Google Patents

Abstract

An adhesive composition which is transparent at the time of bonding and which can be visually judged as to whether or not it is unsealed by utilizing properties of an adhesive itself which is not accompanied by chemical change or breakage of a substrate when peeled off I will provide a. SOLUTION: At least two kinds of thermoplastic resins having compatibility and melting at a predetermined heating temperature and having mutually different refractive indexes, and being incompatible with the thermoplastic resin and having an average particle diameter of 0.3 to 20 μm And a solvent. [Selected figure] Figure 1

Description

The present invention relates to an adhesive composition which melts and softens to exhibit an adhesive function by being sandwiched between base materials to be bonded by thermocompression bonding, and in particular, it is transparent when it is bonded and is peeled off thereafter. its mark is opaque, it relates to the use of the adhesive composition be stripped visually be used to verify possible applications to.

  2. Description of the Related Art Conventionally, various methods have been proposed for easily determining whether or not the container is opened, for example, with respect to intentional or random opening of a container or a packaging film, a sealed letter, a certificate, etc. For example, Japanese Patent Application Laid-Open No. 2017-107001 discloses an example using a heat sensitive microcapsule. The pressure-sensitive adhesive used for sealing has the disadvantage that the adhesive strength is degraded by heating by abuse, and it is opened, so that it is easily discovered by the method in which the microcapsule is broken and the color is developed when it is heated. Although it is a thing, when it uses for the method of sealing by thermocompression bonding, since there exists a possibility that it may color at the time of thermocompression bonding, application is difficult.

  In addition, there is also a seal in which the seal is broken by opening the seal and the seal can be easily determined whether or not the seal is opened. However, it may be necessary to prepare a sealing agent and a sealing seal separately. Alternatively, the adhesive seal needs to be the sealing agent itself. In any case, since the sticking seal is stuck using a pressure sensitive adhesive, the disadvantage that the peel strength is reduced by heating and the package is unsealed can not be avoided.

  Furthermore, Japanese Patent Application Publication No. 5082008 is cited as being accompanied by partial destruction of the substrate by unsealing. Although the direct object of the patent is an easy-open container, since a part of the lid separated by perforation after opening is removed, the appearance changes and visual discrimination is possible. Further, Japanese Patent No. 2936969 discloses a lid material in which a heat seal layer containing a film layer, a base layer and an inorganic powder is sequentially laminated on a base material, and delamination of the base layer and the heat seal layer occurs at the time of opening. It is possible to leave a delaminated heat seal layer as a trace in the unsealing portion. As described above, many devices have been proposed that allow easy visual inspection to determine the presence or absence of the opening, but there is no known device that can determine the presence or absence of the opening visually by the adhesive itself.

JP 2017-107001 A Patent No. 5082008 gazette Patent No. 2936969

The present invention is transparent at the time of adhesion which could not be carried out with the above-mentioned conventional adhesive composition, and visual observation by utilizing the property of the adhesive itself without chemical change or peeling of the substrate when peeled off. It is an object of the present invention to provide a method of using an adhesive composition which can be judged by the

The adhesive composition according to the present invention, which was made to solve the above problems, has at least two types of thermoplastic resins having compatibility and melting at a predetermined heating temperature and having mutually different refractive indices, and the thermoplastic resin It is characterized in that it is composed of fine particles of 0.3 to 20 [mu] m in average particle diameter incompatible with a resin, and a solvent.

In the present invention, the compounding amount of the fine particles is 0 per 100 parts by weight of the thermoplastic resin.
. The content is 5 to 30 parts by weight, and in particular, the fine particles are preferably a rubber composition.

  Furthermore, the method of using the adhesive composition according to the present invention comprises applying the adhesive composition according to the present invention to at least one adhesive surface of the adherend substrates to be adhered to each other and removing the solvent to dry it. The adhesive composition which has been applied and dried is melted and softened in a compatible state by thermocompression bonding of the adhesive surface, and a transparent adhesive layer is formed between the adherend substrate layers to exert an adhesive function. The thermocompression bonding part formed on the transparent adhesive layer when the substrate to be adhered is peeled off forms an irregular reflection surface by the peeling resistance at peeling and the mark is visually confirmed by making the surface opaque. It is characterized in that it made it possible.

  According to the present invention, the adhesive composition in which the solvent sandwiched between the substrates to be adhered has been removed and dried is thermocompression-bonded at a predetermined heating temperature to melt and soften to exhibit a transparent and strong adhesive action. When peeled off, the adhesive surface remaining on the peeled surface becomes opaque and it is possible to visually confirm the trace, and in particular, containers, packaging, etc. which require virginity in food, medical and other fields It can be widely used as an adhesive for the opening of

The photograph which shows the state of the time of adhesion | attachment in Example 1 of this invention, and peeling. The photograph which shows the state of the time of adhesion | attachment in Example 2 of this invention, and peeling. The photograph which shows the state of the time of adhesion | attachment in comparative example 1 of this invention, and the time of peeling. The photograph which shows the state of the time of adhesion | attachment in comparative example 2 of this invention, and the time of peeling.

  The adhesive composition according to the present invention has compatibility and melting at a predetermined heating temperature, and at least two types of thermoplastic resins having different refractive indexes, which are incompatible with the thermoplastic resin and having an average particle size. Is composed of fine particles of 0.3 to 20 μm and a solvent.

The thermoplastic resin is selected according to the type of the base material to be bonded, etc., but when the adhesive is peeled off, the adhesive surface remaining on the peeled surface becomes opaque and both are visually confirmed. Although it is preferable that there is a difference in refractive index, the adhesive composition is applied by sandwiching it between the substrates to be adhered, and it is melted and softened by thermocompression bonding at a predetermined heating temperature to exert a transparent and strong adhesive action For this purpose, it is preferable to use one having a similar refractive index, for example, ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid ester copolymer, maleic anhydride modified product of ethylene-vinyl acetate copolymer, ethylene -(Meth) acrylic acid ester copolymer-maleic anhydride copolymer, ethylene-(meth) acrylic acid copolymer and its metal salt, ethylene-alpha olefin copolymer, etc. Tylene-based (co) polymer, propylene-α-olefin copolymer, and modified unsaturated carboxylic acid thereof, ethylene-vinyl acetate copolymer such as thermoplastic polyurethane, ethylene- (meth) acrylate copolymer, ethylene -Maleic anhydride modified product of vinyl acetate copolymer, ethylene (meth) acrylic acid ester copolymer-maleic anhydride copolymer, ethylene (meth) acrylic acid copolymer and metal salt thereof, ethylene-α At least one selected from olefin polymers such as an olefin copolymer, a propylene-α-olefin copolymer, and a modified product of unsaturated carboxylic acid thereof and at least one selected from a thermoplastic polyurethane and a thermoplastic polyester Can be used.

  The weight ratio of the olefin polymer to the thermoplastic polyurethane and / or the thermoplastic polyester is preferably 80/20 to 20/80.

  Further, the fine particles are preferably those which are incompatible with the thermoplastic resin, and in particular, fine particles whose surface is likely to be irregularly reflected with respect to sunlight are preferable, and for example, fine particles of rubber or silica are preferably used. As for silica, plate-like silica is most preferable in terms of the improvement of the peeling strength or the magnitude of the change in color change before and after the peeling.

Examples of the fine rubber particles include natural rubber, butadiene rubber, isoprene rubber, styrene-butadiene rubber, fluorine rubber, silicone rubber, chlorsulfonated polyethylene and the like, but when heated and pressure-bonded, the particles themselves melt Those tend to be undesirable, and rubber fine particles having a vulcanized and crosslinked structure are particularly preferable. As the silica component, for example, silicon dioxide or a compound containing silicon dioxide as a main component is preferable, and any synthetic or natural product may be used.

The fine particles used in the present invention preferably have an average particle diameter of 0.3 to 20 μm or less. When the average particle size is less than 0.3 microns, the rate of change in color before and after peeling is small, 20
If it is more than μ, it is not smooth between bonded substrates at the time of thermocompression bonding, but it is difficult to distinguish due to small change in color change at the time of peeling depending on the thickness of the adhesive.

  Furthermore, the blending amount of the fine particles is preferably 0.5 to 30 parts by weight per 100 parts by weight of the thermoplastic resin. If it is less than 0.5 parts by weight, it is poor for improvement in peel strength and discoloration, and if it is more than 30 parts by weight, thermocompression-bonding property is deteriorated.

  In addition, the adhesive composition in the present invention can be applied by being dissolved or dispersed in water and / or an organic solvent. In particular, water dispersions are preferred in consideration of environmental health, safety and the like. As components of these adhesive compositions, commercially available products may be appropriately selected or, if necessary, those produced by the method described in JP-A-58-127752 and JP-A-58-118843 may be used. . Of course, it is safe to use hydrophilic solvents such as alcohols, ketones and esters as a small amount of organic solvent.

In addition, as a base material suitable for use of the adhesive composition which is the present invention, for example, a container or a packaging film with a lid, a plastic film used for a sealed letter, a certificate etc., a sheet, a foil, a paper, etc. In particular, films such as polyethylene phthalate, polynaphthalene phthalate, polypropylene, polycarbonate, polystyrene, ethylene-vinyl alcohol copolymer, polyamide, polyvinyl chloride and the like, sheets, metal-deposited materials thereof Inorganic deposit, corona discharge and surface treatment thereof are suitable.

In addition, the plastic film which is the base material to be adhered, the sheet may be stretched in order to improve the transparency, strength, heat resistance and tear resistance, and it has gas barrier properties, tear resistance and thermocompression bondability. Other plastic films may be laminated to improve the homogeneity of the film, the feeling of peeling, and the like.

  In such a base material to be adhered, it is necessary to be transparent enough to allow visual observation of the change in the part to be adhered after peeling, but the other part may be opaque.

  In the present embodiment, the adhesive is formed of at least two different types of thermoplastic resins, but it is extremely transparent by selecting an adhesive which has the property of being compatible with each other at the time of melt bonding and having a similar refractive index to each other. An adhesive surface is formed, so that it is visually observed that the adhesive is adhered through the transparent adherend substrate.

  Next, when the lid, which is the base material to be adhered, is opened and the adhesion state is peeled off, since the surface unevenness, void, and the like change due to peeling resistance at the time of peeling. It is confirmed that the adhesion state is released and the lid is opened by visual observation. In particular, in the present embodiment, since different types of thermoplastic resins are combined as an adhesive, changes in surface irregularities, voids, etc. are easily exposed when peeled off, and further, since fine particles are added in advance, these fine particles are also Exposed to the peeled surface to increase opacity.

  In addition, even if there are some voids or unevenness that irregularly reflects light on the base material to be bonded before bonding, sufficient heat pressure is applied during thermocompression bonding to soften / flow and smooth reflection of smooth light The difference between this structure and the irregular reflection of light due to voids or surface irregularities caused by peeling resistance at peeling becomes remarkable, and peeling can be confirmed visually.

  In addition, it is preferable to select an adhesive having a small difference in refractive index as much as possible. This is because if the adhesive itself is opaque before peeling, it becomes difficult to determine the change in color after peeling. In the case of using one having a large difference in refractive index, it is necessary to make a large difference in the amount used. It is particularly preferable to use the above-mentioned ethylene (co) polymer and thermoplastic polyurethane together as the thermoplastic resin component from the viewpoint of being able to be compounded in a wide range of ratio and capable of expanding the target range of the adherend substrate.

  Next, examples of the present invention will be described.

This example is based on Example 1 to Example 3 in Table 1 which is the present invention, for example, in the case where the cover base and the container body of a transparent 200 μm thick polyethylene terephthalate food container are used as bonding substrates. The adhesive composition according to the present invention was applied to at least one of the adhesive surfaces of the substrates to be adhered according to the adhesive composition of the present invention.
The solution is applied to a film thickness of 22.90 μm and dried with a hand dryer with hot air to evaporate the solvent or moisture obtained for the substrate for thermocompression bonding, and drying it. Then, the adhesive coated surface of the adherend substrate and the adherend substrate to which the adhesive is not applied are superimposed (the container main body is covered) and heated at 120 ° C., 130 ° C., 140 ° C. and 150 ° C. At temperature, a pressure of 0.5 MPa was applied, each was thermocompression-bonded for 2 seconds, and left at room temperature. The refractive index of the ethylene-vinyl acetate copolymer used was 1.4, and that of the polyurethane was 1.5.

After that, the adhesive surface was peeled off by hand, and the condition of the peeled surface was observed through the substrate on which the adhesive was applied. In addition, the peeling state at that time (interface peeling: 90% or more of the adhesive remains on the adhesive coated surface, adhesive peeling: adhesive peeling from the coated substrate, cohesive peeling: adhesive itself breaks) and 15 mm width T peel (peel) strength was measured by a peel strength tester. The composition conditions of Examples and Comparative Examples are shown in Table 1. The unit in the table represents the weight converted to solid (excluding water or solvent). The ethylene-vinyl acetate copolymer used in the examples is the aqueous dispersion "Kemipearl V100 (registered trademark)" of Mitsui Chemicals, Inc., and the polyurethane is the aqueous dispersion "Superflex E 2000 (registered trademark)" manufactured by Daiichi Kogyo Seiyaku Co., Ltd. The rubber particles used were Shin-Etsu Chemical's silicone rubber "KM series", but are not limited thereto. Further, the addition amount of the fine particles described in the table is the addition amount (part by weight) per 100 parts by weight of the thermoplastic resin.

  Next, with respect to the examples and comparative examples, the adhesive surface was peeled off by hand, and the state of the peeled surface was observed through the substrate on which the adhesive was applied. In addition, the peeling state at that time (interface peeling: 90% or more of the adhesive remains on the adhesive coated surface, adhesive peeling: adhesive peeling from the coated substrate, cohesive peeling: adhesive itself breaks) and 15 mm width T peel (peel) strength (N) was measured with a peel strength tester. The results are shown in the drawing.

As shown in FIG. 1 and the figures, in Examples 1 and 2, 120 ° C., 130 ° C., 14
Before peeling off at any heating temperature of 0 ° C. and 150 ° C. (the same for the “right side” and below), it was sufficiently transparent, and after peeling (the same for the “left side” and below) the whitening was remarkable. On the other hand, as shown in FIG. 3, Comparative Example 1 containing no fine particles and Comparative Example 2 exceeding the appropriate weight ratio as shown in FIG. 4 were sufficiently transparent before peeling, but after peeling Did not get whitening.

From these facts, the adhesive composition of the present invention is transparent at the time of adhesion, and when it is peeled off, it is visually opened by utilizing the property of the adhesive itself without causing any chemical change or destruction of the substrate. It has been confirmed to provide an adhesive composition capable of determining the presence or absence.

Claims (3)

Thermoplastic resin having a weight ratio of an olefin-based polymer having a compatibility and melting at a predetermined heating temperature and having a refractive index different from each other and a thermoplastic polyurethane of 80/20 to 20/80, and the thermoplastic resin 100 and rubber particles average grain size of the parts by weight per 0.5 to 30 parts by weight are incompatible with the thermoplastic resin ordinarily from 0.3 to 20 m, and a solvent, the adhesive composition Ru Tona, be bonded to each other The adhesive composition is applied to at least one adhesive surface of the adherend substrate to be adhered, the solvent is removed and dried, and the adhesive composition obtained by applying and drying the adhesive surface is thermally compressed. It melts and softens in a molten state and forms a transparent adhesive layer between the adherend substrate layers to exert an adhesive action and is formed on the adhesive layer which was transparent when the adherend substrate was peeled off heat Using adhesive composition characterized in that it possible to confirm visually the traces by opacifying form a diffuse reflection surface by peeling resistance upon peeling the Chakububun. The method for using an adhesive composition according to claim 1, wherein the olefin polymer forming the thermoplastic resin is a copolymer of ethylene and another vinyl monomer. The method of using an adhesive composition according to claim 2, wherein the copolymer of ethylene and another vinyl monomer is an ethylene-vinyl acetate copolymer.