JP7488676B2 - Adhesive film and its manufacturing method - Google Patents

Description

The present invention relates to a water-absorbent adhesive film and a method for producing the same.

In environments where humidity control is required, a solid or sheet-like desiccant is generally used to absorb moisture from the air. For example, adhesive films are widely used to protect the surfaces of synthetic resin boards, decorative plywood, metal plates, etc., to prevent scratches and dirt during production, processing, and transportation. As a humidity control measure for such adhesive films (adhesive films), Patent Document 1 describes a method in which at least one sheet-like desiccant is layered on at least one adhesive film with a support.

JP 2015-178250 A

Here, if a solid or sheet-like desiccant could be used by fixing it, the applications of the desiccant would be greatly expanded. However, since solid or sheet-like desiccant has no adhesiveness, it has been necessary to use a separate adhesive tape or the like to fix the desiccant to the adherend. Patent Document 1 describes laminating a sheet-like desiccant on one or both sides of an adhesive film with a support, but does not describe at all how to adhere the sheet-like desiccant to the support when laminating it on the support side, and when the sheet-like desiccant is laminated on the adhesive layer side, the adhesive layer is no longer exposed, so it has been necessary to use a separate adhesive tape or the like to fix it to the adherend.

The present invention aims to provide a water-absorbent adhesive film and a method for producing the same.

The present invention relates to a substrate layer made of a resin composition A containing a thermoplastic resin,
A pressure-sensitive adhesive film having an adhesive layer formed on one surface of the base layer and made of a resin composition B containing a thermoplastic elastomer and a tackifier resin ,
The resin composition A contains a desiccant ,
The thermoplastic elastomer is a styrene-based block copolymer or a copolymer obtained by hydrogenating the styrene-based block copolymer.
It is an adhesive film.

The present invention provides a method for producing the pressure-sensitive adhesive film, comprising the steps of:
This is a method for manufacturing an adhesive film by co-extrusion of the resin materials that form each layer.

The present invention provides a water-absorbent adhesive film and a method for producing the same.

1 is a cross-sectional view showing an example of the configuration of an adhesive film according to the present invention.

As shown in FIG. 1, the adhesive film according to the present invention has a base layer 1 and an adhesive layer 2 formed on one surface of the base layer 1. It is preferable that the adhesive film further has a back layer 3 formed on the other surface of the base layer 1.

The substrate layer 1 is formed of a resin composition A containing a thermoplastic resin. As the thermoplastic resin, a polyolefin-based resin is preferable because it does not generate toxic gases even when incinerated after use and there are few problems in terms of post-processing. Examples of polyolefin-based resins include polyethylene, ethylene-α-olefin copolymer, propylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, ethylene-n-butyl acrylate copolymer, polypropylene, etc. One type of thermoplastic resin may be used alone, or two or more types may be used in combination.

The resin composition A forming the base layer 1 contains a desiccant in addition to the thermoplastic resin. This can impart water absorption (hygroscopicity) to the adhesive film. Examples of desiccants include oxides such as calcium oxide (quicklime), silicon dioxide (silica), aluminum oxide (alumina), phosphorus oxide, and magnesium oxide; chlorides such as calcium chloride and zinc chloride; hydroxides such as potassium hydroxide and sodium hydroxide; sulfates such as magnesium sulfate, calcium sulfate, and sodium sulfate; carbonates such as potassium carbonate; and perchlorates such as magnesium perchlorate. The desiccant may be a hydrate, but is preferably an anhydride that is not hydrated (anhydrous). As the desiccant, sulfates are preferred, magnesium sulfate is more preferred, and anhydrous magnesium sulfate is even more preferred. The desiccant may be used alone or in combination of two or more types.

The desiccant content in the resin composition A that forms the base layer 1 is preferably 3 to 30% by weight. By making the desiccant content 3% by weight or more, the desired water absorbency can be imparted to the adhesive film. By making the desiccant content 30% by weight or less, it becomes easier to form the base layer 1 of the adhesive film. It is more preferable that the desiccant content in the resin composition A is 5 to 20% by weight.

The resin composition A that forms the base layer 1 may contain, in addition to the above-mentioned thermoplastic resin and desiccant, light stabilizers, UV absorbers, antioxidants, fillers, lubricants, etc., as necessary.

The adhesive layer 2 is formed on one surface of the base layer 1, and is a layer for attaching the adhesive film to the adherend. There may be other layers between the adhesive layer 2 and the base layer 1, but from the viewpoint of reducing the weight of the adhesive film, it is preferable that the adhesive layer 2 is formed so as to be in contact with one surface of the base layer 1. Since the adhesive layer 2 is a layer for attaching the adhesive film to the adherend, it is preferable that it is the outermost layer. Since the adhesive layer 2 has little anchoring force with the base layer 1 and leaves little adhesive residue, it is preferable that the adhesive layer 2 is formed from a resin composition B containing a thermoplastic elastomer and a tackifier resin.

As the thermoplastic elastomer, a styrene-based block copolymer or a copolymer obtained by hydrogenating the same can be used. The styrene-based block copolymer is generally a block copolymer represented by A-B-A, or a mixture of a block copolymer represented by A-B-A and a block copolymer represented by A-B, where A is a styrene polymer block and B is another polymer block. Examples of the other polymer blocks include olefin-based polymer blocks such as an ethylene polymer block, a propylene polymer block, and a butylene polymer block; diene-based polymer blocks such as a butadiene polymer block and an isoprene polymer block; and hydrogenated blocks obtained by hydrogenating at least a part of a diene-based polymer block. The weight ratio of A to B is A/B=5/95 to 50/50. The thermoplastic elastomer may be used alone or in combination of two or more types.

Examples of styrene-based block copolymers include styrene-butadiene copolymers (styrene-butadiene rubber, SBR), hydrogenated styrene-butadiene copolymers (hydrogenated styrene-butadiene rubber, HSBR), styrene-ethylene/butylene-styrene type block copolymers (SEBS), styrene-ethylene/propylene-styrene type block copolymers (SEPS), styrene-butadiene-styrene type block copolymers (SBS), styrene-isoprene-styrene type block copolymers (SIS), and styrene-isobutylene-styrene type block copolymers (SIBS). Examples of styrene-based block copolymers include styrene-butadiene copolymers and hydrogenated styrene-butadiene copolymers, and more preferably hydrogenated styrene-butadiene copolymers.

The tackifier resin may be any resin capable of imparting tackiness to the adhesive layer 2, and examples thereof include rosin-based resins, terpene-based resins, aliphatic petroleum-based resins, alicyclic petroleum-based resins, and aromatic resins. As the tackifier resin, aliphatic petroleum-based resins and alicyclic petroleum-based resins are preferred, and alicyclic petroleum-based resins are more preferred. The tackifier resin may be used alone or in combination of two or more types. The amount of the tackifier resin may be appropriately set in consideration of the adhesive performance of the surface protective film, but the amount of the tackifier resin to be blended relative to 100 parts by weight of the thermoplastic elastomer contained in the resin composition B is preferably 1 to 50 parts by weight, more preferably 1 to 30 parts by weight, and even more preferably 1 to 20 parts by weight.

In addition to the above-mentioned thermoplastic elastomer and tackifier resin, resin composition B may also contain additives such as light stabilizers, ultraviolet inhibitors, antioxidants, fillers, and lubricants, as necessary.

The back layer 3 is formed on the other surface of the base layer 1 (the surface on which the adhesive layer 1 is not formed), and is a protective layer for preventing the desiccant contained in the base layer 1 from coming into contact with the hands when handling the adhesive sheet. Other layers may be present between the back layer 3 and the base layer 1, but from the viewpoint of reducing the weight of the adhesive film, it is preferable that the back layer 3 is formed so as to be in contact with the other surface of the base layer 1. The back layer 3 is preferably formed using a polyolefin-based resin, since it does not generate toxic gases even when incinerated after use and there are few problems in terms of post-processing. As the polyolefin-based resin, the same resins as those described above can be used.

The back layer 3 may consist only of polyolefin resin, or may contain, in addition to polyolefin resin, light stabilizers, UV absorbers, antioxidants, fillers, lubricants, etc., as necessary.

The adhesive film according to the present invention may have other layers in addition to the base layer 1, the adhesive layer 2, and the back layer 3. However, as described above, it is preferable that there are no other layers between the base layer 1 and the adhesive layer 2, on the outside of the adhesive layer 2, and between the base layer 1 and the back layer 3, and therefore it is preferable that the other layers are disposed on the outside of the back layer 3. For example, after the adhesive film is stored and transported in a rolled state, a release layer can be disposed on the outside of the back layer 3 to make it easier to unfold the adhesive film. In addition, the back layer 3 can be given releasability to serve as a release layer.

The adhesive film according to the present invention can be formed by co-extruding the resin materials forming each layer. For example, an adhesive film consisting of a base layer 1 and an adhesive layer 2 can be formed by co-extruding a resin composition A forming the base layer 1 and a resin composition B forming the adhesive layer 2. Specifically, the adhesive film is obtained by integrally molding the two materials from two extruders through one die using a two-layer co-extrusion method, whereby an adhesive film having an adhesive layer 2 formed on one surface of the base layer 1 is obtained. When forming an adhesive film having a back layer 3 in addition to the base layer 1 and the adhesive layer 2, the material forming the back layer 3 may also be co-extruded. Specifically, the adhesive film is obtained by integrally molding the three materials from three extruders through one die using a three-layer co-extrusion method, whereby an adhesive film having an adhesive layer 2 formed on one surface of the base layer 1 and a back layer 3 formed on the other surface of the base layer 1 is obtained.

The thickness of the base layer 1 in the adhesive film of the present invention is preferably 20 to 100 μm, more preferably 30 to 80 μm, and even more preferably 40 to 60 μm. The thickness of the adhesive layer 2 in the adhesive film of the present invention is preferably 2 to 50 μm, more preferably 3 to 25 μm, and even more preferably 4 to 10 μm. The thickness of the back layer 3 in the adhesive film of the present invention is preferably 2 to 50 μm, more preferably 3 to 25 μm, and even more preferably 4 to 10 μm.

The adhesive film of the present invention as described above maintains adhesion (suppressing peeling due to increased adhesion or decreased adhesive strength) and has water absorption properties, making it suitable for applications such as preventing internal condensation in ceiling lights.

Example 1
A resin composition A for forming a base layer was obtained by mixing a thermoplastic resin polyethylene (manufactured by Japan Polyethylene Co., Ltd., product name: LF580) and a desiccant anhydrous magnesium sulfate (manufactured by Tomita Pharmaceutical Co., Ltd., product name: Anhydrous Magnesium Sulfate A) in a blending ratio of 95:5 (weight ratio). On the other hand, a resin composition B for forming an adhesive layer was obtained by mixing a thermoplastic elastomer hydrogenated styrene-butadiene rubber (HSBR, manufactured by JSR Co., Ltd., product name: Dynaron 1321P) and a tackifier resin alicyclic petroleum-based resin (manufactured by Arakawa Chemical Industries Co., Ltd., product name: Alcon P140) in a blending ratio of 85:15 (weight ratio).

Resin composition A forming the base layer, resin composition B forming the adhesive layer, and polyethylene (manufactured by Nippon Polyethylene, product name: LF580) forming the back layer were formed by the T-die method at a die temperature of 220°C to obtain an adhesive film (base layer: 54 μm, adhesive layer: 6 μm, back layer: 6 μm) having the layer structure shown in Figure 1. The adhesive strength, contamination, and water absorption of the obtained adhesive film were evaluated according to the methods shown in Evaluations 1 to 3 below. The results are shown in Table 1.

Example 2
An adhesive film (substrate layer: 54 μm, adhesive layer: 6 μm, back layer: 6 μm) was obtained in the same manner as in Example 1, except that the blending ratio of polyethylene and anhydrous magnesium sulfate in the resin composition A was 90:10 (weight ratio). The adhesive strength, contamination, and water absorption of the obtained adhesive film were evaluated by the methods shown in the following Evaluations 1 to 3. The results are shown in Table 1.

Example 3
An adhesive film (substrate layer: 54 μm, adhesive layer: 6 μm, back layer: 6 μm) was obtained in the same manner as in Example 1, except that the blending ratio of polyethylene and anhydrous magnesium sulfate in the resin composition A was 80:20 (weight ratio). The adhesive strength, contamination, and water absorption of the obtained adhesive film were evaluated by the methods shown in the following Evaluations 1 to 3. The results are shown in Table 1.

<Comparative Example 1>
Except for not blending anhydrous magnesium sulfate into resin composition A and not forming a back layer, an adhesive film (substrate layer: 54 μm, adhesive layer: 6 μm) was obtained in the same manner as in Example 1. The adhesive strength, staining, and water absorption of the obtained adhesive film were evaluated by the methods shown in Evaluations 1 to 3 below. The results are shown in Table 1.

<Evaluation 1: Adhesive strength>
The surface of a SUS plate (SUS304HL) for evaluation was polished with #280 abrasive paper, and a 25 mm wide adhesive film was attached thereon with a 2 kg roller to obtain a sample, which was then stored under a specified condition. The storage conditions were 23°C, 60% RH x 1 day or 40°C, 90% RH x 7 days. The adhesive strength (peeling strength) of the adhesive film of the sample after storage was measured at 180° peeling using a Tensilon tester at a peeling speed of 0.3 m/min.

<Rating 2: Contamination>
In the evaluation of adhesive strength, the surface of the SUS plate after the adhesive film was peeled off from the SUS plate was visually observed to check for the presence or absence of contamination.

<Evaluation 3: Water absorption>
Ten sheets of 100 mm x 100 mm adhesive films were laminated and stored for 7 days in an environment of 40°C and 90% RH. The change in weight of the adhesive film before and after storage was measured, and the amount of water absorption was calculated.

The above results show that in Examples 1 to 3, which contain a desiccant (anhydrous magnesium sulfate) in the base layer, the desired water absorbency is exhibited and the adhesive strength is maintained when stored under high humidity conditions of 40°C and 90% RH for 7 days, compared to Comparative Example 1, which does not contain a desiccant (anhydrous magnesium sulfate) in the base layer. In other words, it is clear that by including a desiccant in the base layer, as in the present invention, it is possible to impart water absorbency to the adhesive film.

1 Base layer 2 Adhesive layer 3 Back layer

Claims (7)

A base layer made of a resin composition A containing a thermoplastic resin;
A pressure-sensitive adhesive film having an adhesive layer formed on one surface of the base layer and made of a resin composition B containing a thermoplastic elastomer and a tackifier resin ,
The resin composition A contains a desiccant ,
The thermoplastic elastomer is a styrene-based block copolymer or a copolymer obtained by hydrogenating the styrene-based block copolymer.
Adhesive film. The pressure-sensitive adhesive film according to claim 1 , wherein the desiccant is magnesium sulfate. The pressure-sensitive adhesive film according to claim 1 or 2, wherein the content of the desiccant in the resin composition A is 3 to 30% by weight. The pressure-sensitive adhesive film according to any one of claims 1 to 3, wherein the thermoplastic resin contained in the resin composition A is a polyolefin resin. The pressure-sensitive adhesive film according to any one of claims 1 to 4 , further comprising a back layer formed on the other surface of the base layer. The pressure-sensitive adhesive film according to claim 5 , wherein the back layer contains a polyolefin. A method for producing the adhesive film according to any one of claims 1 to 6 ,
A method for manufacturing an adhesive film in which the resin materials that form each layer are co-extruded.

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