Method for dismantling multilayer films, adhesive tapes, and laminates.

Abstract

The present invention provides a multilayer film that can be easily disassembled by leaving it in a high-temperature, high-humidity environment. It also provides an adhesive tape having the multilayer film. Furthermore, it provides a method for disassembling a laminate to which the adhesive tape is attached. [Solution] The material has an intermediate layer and an outermost layer on both sides of the intermediate layer, the outermost layer contains a resin (A) with a biodegradability of less than 60%, the intermediate layer contains a resin (B) with a biodegradability of 60% or more, and the outermost layer (A) has a water vapor transmission rate (WVTR) of 15 g / (m²) in an environment of 40°C and 90% RH. 2 Multilayer film with a lifespan of 1 day or more.

Description

[Technical Field]

[0001] This invention relates to multilayer films. Furthermore, this invention relates to adhesive tapes. Moreover, this invention relates to a method for dismantling laminates. [Background technology]

[0002] Polyester film is used as a base material for adhesive tape, a release film to protect the adhesive layer of adhesive tape, and a release film to protect objects in the manufacturing process, among other applications.

[0003] For example, Patent Document 1 discloses a release film having a release layer formed on at least one side of a polyester film, which, when used in the manufacture of electrical and electronic components, does not cause silicone transfer to the electrical and electronic component material, has release properties comparable to those of a silicone release layer, has excellent processability, and also has good release properties. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2003-148781 [Overview of the project] [Problems that the invention aims to solve]

[0005] In recent years, from an environmental perspective, there has been a growing demand for adhesive tapes that are easy to disassemble, for the purpose of reusing and recycling electrical and electronic components that are bonded together. However, with conventional adhesive tapes that use polyester film as a base material, the robustness of the polyester film base makes it difficult to disassemble the adhesive tape, and thus it is difficult to disassemble the laminated structure to which the adhesive tape is bonded and reuse the electrical and electronic components.

[0006] The present invention aims to provide a multilayer film that can be easily disassembled by leaving it in a high-temperature, high-humidity environment. Furthermore, the present invention aims to provide an adhesive tape having the multilayer film. Moreover, the present invention aims to provide a method for disassembling a laminate to which the adhesive tape is attached. [Means for solving the problem]

[0007] Disclosure 1 comprises an intermediate layer and an outermost layer on both sides of the intermediate layer, wherein the outermost layer contains a resin (A) with a biodegradability of less than 60%, the intermediate layer contains a resin (B) with a biodegradability of 60% or more, and the outermost layer has a water vapor transmission rate (WVTR) of 15 g / (m²) in an environment of 40°C and 90% RH. 2 It is a multilayer film with a lifespan of at least one day. Disclosure 2 is a multilayer film of Disclosure 1, wherein the resin (A) is a resin having a melting point of 100°C or higher. Disclosure 3 is a multilayer film of Disclosure 1 or 2 in which the resin (A) comprises a polyester resin. Disclosure 4 is a multilayer film of Disclosure 3 in which the resin (A) comprises a resin having a polybutylene terephthalate skeleton. Disclosure 5 is a multilayer film of Disclosure 1, 2, 3, or 4, wherein the outermost layer is 50 μm or less in thickness. Disclosure 6 states that the resin (B) is a multilayer film of Disclosure 1, 2, 3, 4, or 5, which includes a polyester resin. Disclosure 7 is a multilayer film of Disclosure 6 in which the resin (B) comprises a resin having a skeleton selected from the group consisting of polylactic acid, polybutylene succinate, polyglycolic acid, polycaprolactone, poly-3-hydroxybutyrate-co-hydroxyhexanoate, and polybutylene adipate terephthalate. Disclosure 8 is a multilayer film of Disclosure 1, 2, 3, 4, 5, 6, or 7, wherein the content ratio of resin (B) to the total resin contained in the intermediate layer is 50% by mass or more. Disclosure 9 is a multilayer film of Disclosure 1, 2, 3, 4, 5, 6, 7, or 8, wherein the intermediate layer has a thickness of 30 μm or more and 200 μm or less. Disclosure 10 is a multilayer film according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, or 9, wherein the multilayer film has a total thickness of 300 μm or less. Disclosure 11 is an adhesive tape having a multilayer film according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, and an adhesive layer on at least one surface of the multilayer film. Disclosure 12 is an adhesive tape according to Disclosure 11, wherein the adhesive layer contains at least one selected from the group consisting of urethane resin and (meth)acrylic copolymer. Disclosure 13 is an adhesive tape according to Disclosure 11 or 12, wherein the adhesive layer has a thickness of 75 μm or less. Disclosure 14 is a method for dismantling a laminate, which includes the step of leaving the laminate, to which the adhesive tape of Disclosure 11, 12, or 13 is attached to a component, to stand for 6 hours or more in an environment of 85°C or higher and 85%RH or higher. The present invention will be described in detail below.

[0008] The inventors focused on the resin contained in the layers that make up the film used as a base material and investigated how to make the resin contained in the film layers a resin whose biodegradability meets a specific range. As a result, they found that when the biodegradability of the resin is set above a specific value, the layer containing the resin exhibits decomposition triggered by high temperature and high humidity. Furthermore, by creating a multilayer film in which the layer having decomposition triggered by high temperature and high humidity is used as an intermediate layer, and the layer containing a resin with a biodegradability below a specific value is used as the outermost layer, it becomes possible to easily peel the film between the outermost and intermediate layers after leaving it in a high temperature and high humidity environment. As a result, it becomes easy to dismantle adhesive tape using this multilayer film as a base material, and we have found that the laminate to which the adhesive tape is attached can be easily dismantled and the electrical and electronic components can be reused. Based on the above findings, we discovered that it is possible to obtain a multilayer film that can be easily disassembled by leaving it in a high-temperature, high-humidity environment, and thus completed the present invention.

[0009] The multilayer film of the present invention has an intermediate layer and an outermost layer on both sides of the intermediate layer. While the intermediate layer is decomposable in response to high temperature and humidity, the outermost layer does not decompose even in high temperature and humidity environments, and its performance does not deteriorate. Therefore, when the multilayer film of the present invention is left undisturbed in a high temperature and humidity environment, it becomes possible to easily peel it apart between the outermost layer and the intermediate layer. As a result, the multilayer film of the present invention can be easily disassembled in a high temperature and humidity environment (it has easy disassembly properties). Although the multilayer film of the present invention can be easily disassembled in a high temperature and humidity environment, it has adequate strength and can be used without problems in normal usage environments. Furthermore, the multilayer film of the present invention may have other layers between the intermediate layer and the outermost layer, as long as the effects of the present invention are not impaired.

[0010] The outermost layer described above has a lower limit of water vapor transmission rate (WVTR) of 15 g / m² under conditions of 40°C and 90% RH. 2 The water vapor permeability of the outermost layer under conditions of 40°C and 90%RH is 15 g / (m²). 2 By having a minimum of (1 / 2 days), water vapor can be transferred to the intermediate layer, which is decomposable in response to high temperature and high humidity. Therefore, the multilayer film of the present invention can be easily dismantled in a high temperature and high humidity environment (it has easy dismantling properties). The preferred lower limit of water vapor transmission of the outermost layer in an environment of 40°C and 90%RH is 20 g / (m²). 2 •day), a more preferable lower limit is 30g / (m 2 It is a day. Furthermore, while there is no particular upper limit to the water vapor transmission rate of the outermost layer under the conditions of 40°C and 90%RH, the practical upper limit is 1000 g / (m³). 2 It is a day. Furthermore, the water vapor transmission rate of the outermost layer at 40°C and 90%RH can be measured in accordance with JIS K 7129-2, using a sample of the outermost layer alone, by a water vapor transmission humidity test using the MOCON method under the conditions of 40°C and 90%RH.

[0011] Methods for adjusting the water vapor permeability of the outermost layer at 40°C and 90%RH include, for example, reducing the thickness of the outermost layer (for example, reducing the thickness of the outermost layer can increase the water vapor permeability of the outermost layer at 40°C and 90%RH), and adjusting the blending ratio of resins with high water vapor permeability (for example, increasing the blending ratio of resins with high water vapor permeability in the outermost layer can increase the water vapor permeability of the outermost layer at 40°C and 90%RH).

[0012] The outermost layer contains resin (A), which has a biodegradability of less than 60%. Because the outermost layer contains resin (A), decomposition and deterioration of the outermost layer in a high-temperature, high-humidity environment can be suppressed. Therefore, when the multilayer film of the present invention is left standing in a high-temperature, high-humidity environment, the decomposition of the intermediate layer progresses, and it becomes possible to easily peel off the layers between the outermost layer and the intermediate layer. In this specification, "biodegradability" means the degree of degradation at 28 days in the OECD 301C biodegradability test, or the degree of degradation at 6 months in at least one biodegradability test selected from the group consisting of JIS K 6950, JIS K 6951, JIS K 6953-1, JIS K 6953-2, and JIS K 6955. In other words, a biodegradability of less than 60% means that the degree of degradation at 28 days in the OECD 301C biodegradability test, or less than 60% in any one method selected from the group consisting of JIS K 6950, JIS K 6951, JIS K 6953-1, JIS K 6953-2, and JIS K 6955.

[0013] The above resin (A) preferably contains a resin having a melting point of 100°C or higher. By the above resin (A) containing a resin having a melting point of 100°C or higher, the heat resistance of the outermost layer is further improved, and it will not melt or soften in a high temperature and high humidity environment, and can continue to exhibit the function as an adhesive tape base material. Also, since the tensile strength of the outermost layer is further improved, the multilayer film of the present invention has more excellent strength. The above resin (A) more preferably contains a resin having a melting point of 110°C or higher, still more preferably contains a resin having a melting point of 150°C or higher, and still more preferably contains a resin having a melting point of 200°C or higher. Also, from the viewpoint of moldability, the above resin (A) preferably contains a resin having a melting point of 350°C or lower, and more preferably contains a resin having a melting point of 300°C or lower. In the present specification, the "melting point" means the temperature at which the crystalline part of the resin starts to flow and becomes liquid, and can be determined by a method in accordance with JIS K7121 using differential scanning calorimetry (DSC).

[0014] The above resin (A) is not particularly limited, and examples thereof include polyester resins, polyethylene resins, polypropylene resins, etc. Also, ethylene-acrylic monomer copolymers such as ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, etc. are also included. Among them, from the viewpoint that the outermost layer has more excellent strength, the above resin (A) preferably contains a polyester resin.

[0015] The polyester resin included as resin (A) is not particularly limited, but examples include resins having a polyethylene terephthalate skeleton, resins having a polybutylene terephthalate skeleton, resins having a polytrimethylene terephthalate skeleton, resins having a polyethylene naphthalate skeleton, resins having a polybutylene naphthalate skeleton, resins having a benzoic acid skeleton, and butanediol terephthalate polytetramethylene glycol copolymer. Among these, resins having a polybutylene terephthalate skeleton are preferred from the viewpoint of having a better balance of heat resistance and strength of the outermost layer. These polyester resins may be used individually or in combination of two or more. Furthermore, a mixed resin of a resin having a polybutylene terephthalate skeleton and a block copolymer of polybutylene terephthalate and an aliphatic polyether is also preferred. The aliphatic polyether is not particularly limited and examples include polyethylene glycol, polydiethylene glycol, polypropylene glycol, and polytetramethylene glycol.

[0016] Among the polyester resins included as resin (A) above, commercially available examples include "Perprene P70-B" (manufactured by Toyobo Co., Ltd., melting point 200℃), "Novaduran 5026" (manufactured by Mitsubishi Chemical Corporation, melting point 224℃), "TRN-RTJC" (manufactured by Teijin Corporation, melting point 260℃), and "Sorona" (manufactured by Huafeng Group, melting point 228℃).

[0017] The proportion of the polyester resin in the total resin contained in the outermost layer is not particularly limited, but a preferred lower limit is 15% by mass. A polyester resin content of 15% by mass or more further improves the heat resistance and strength of the outermost layer. A more preferred lower limit for the polyester resin content in the total resin contained in the outermost layer is 30% by mass, and an even more preferred lower limit is 50% by mass. The upper limit of the polyester resin content in the total resin contained in the outermost layer is 100% by mass; that is, the outermost layer may be composed solely of the polyester resin. In this specification, the "resin content ratio" of the layers constituting the multilayer film of the present invention can be obtained from the amount added to the resin composition used to produce the layers constituting the multilayer film. Furthermore, when measuring the resin content ratio using a finished product or a commercially available film, after separating each layer of the film, NMR measurement is performed on the layer to be measured, and the result is obtained. 1 It can also be calculated from the H-NMR spectrum. NMR measurements performed to determine the resin content may include, for example, measurements using an NMR spectrometer (Bruker AVANCE 400, manufactured by Bruker Corporation), a frequency of 400 MHz, a solvent of HFIP-d7 / CDCl3 = 3 / 7, a temperature of 25°C, and a sample concentration of approximately 1 wt / vol%.

[0018] The polyethylene resin included as resin (A) is not particularly limited, but examples include high-density polyethylene (HDPE) resin and low-density polyethylene (LDPE) resin. Among these, low-density polyethylene resin is preferred from the viewpoint of moldability.

[0019] Examples of the high-density polyethylene resin mentioned above include "HF335" (manufactured by Nippon Polyethylene Co., Ltd., melting point 130°C). Examples of the low-density polyethylene resin mentioned above include "LF640MA" (manufactured by Nippon Polyethylene Co., Ltd., melting point 113°C).

[0020] The proportion of resin (A) in the total resin contained in the outermost layer is not particularly limited, but a preferred lower limit is 60% by mass. By having a resin (A) content of 60% by mass or more, the decomposition and deterioration of the outermost layer in a high-temperature, high-humidity environment can be further suppressed, so that when the multilayer film of the present invention is left standing in a high-temperature, high-humidity environment, it becomes easier to peel it off between the outermost layer and the intermediate layer. A more preferable lower limit for the content of resin (A) in the total resin contained in the outermost layer is 70% by mass, and an even more preferable lower limit is 90% by mass. Furthermore, the upper limit of the proportion of resin (A) in the total resin contained in the outermost layer is 100% by mass, meaning the outermost layer may be composed solely of resin (A).

[0021] The outermost layer may contain a rubber component. The inclusion of a rubber component in the outermost layer improves the conformability of the multilayer film of the present invention. The above rubber components are not particularly limited and include, for example, natural rubber, styrene-butadiene copolymer, polybutadiene, polyisoprene, acrylonitrile-butadiene copolymer, ethylene-propylene copolymer (EPM, EPDM), polychloroprene, butyl rubber, acrylic rubber, silicone rubber, urethane rubber, etc. Furthermore, examples of the above rubber components include olefin-based thermoplastic elastomers, styrene-based thermoplastic elastomers, PVC-based thermoplastic elastomers, ester-based thermoplastic elastomers, amide-based thermoplastic elastomers, etc.

[0022] The outermost layer may contain a stabilizer. The above-mentioned stabilizers are not particularly limited and include, for example, hindered phenol antioxidants and heat stabilizers. The above-mentioned hindered phenol antioxidants are not particularly limited, and examples include 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene and 3,9-bis{2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)-propionyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5,5]undecane. The above-mentioned heat stabilizers are not particularly limited, and examples include tris(2,4-di-t-butylphenyl) phosphite, trilauryl phosphite, 2-t-butyl-α-(3-t-butyl-4-hydroxyphenyl)-p-cumenylbis(p-nonylphenyl) phosphite, dimyristyl 3,3'-thiodipropionate, distearyl 3,3'-thiodipropionate, pentaerythryltetrakis(3-laurylthiopropionate), ditridecyl 3,3'-thiodipropionate, and the like.

[0023] The outermost layer described above may further contain conventionally known additives such as fibers, inorganic fillers, flame retardants, ultraviolet absorbers, antistatic agents, inorganic substances, and higher fatty acid salts.

[0024] The thickness of the outermost layer described above has a preferred upper limit of 50 μm. Having an outermost layer thickness of 50 μm or less makes it easier to adjust the water vapor transmission rate (WVTR) under the aforementioned 40°C, 90% RH environment to within the range described above, thereby further improving the ease of disassembly of the multilayer film of the present invention. A more preferred upper limit for the thickness of the outermost layer is 30 μm, and an even more preferred upper limit is 20 μm. Furthermore, while the lower limit of the thickness of the outermost layer is not particularly limited, from the viewpoint of further improving the strength of the multilayer film of the present invention, a preferred lower limit is 5 μm, and a more preferred lower limit is 10 μm.

[0025] The multilayer film of the present invention has an intermediate layer. Since the intermediate layer is decomposable when exposed to high temperature and high humidity, the multilayer film of the present invention can be easily disassembled when left undisturbed in a high temperature and high humidity environment.

[0026] The above-mentioned intermediate layer contains resin (B) which has a biodegradability of 60% or more. Because the above-mentioned intermediate layer contains resin (B), the intermediate layer becomes biodegradable in high temperature and high humidity environments, and therefore the multilayer film of the present invention has excellent ease of dismantling.

[0027] The above resin (B) preferably contains a resin having a melting point of 90°C or more and 200°C or less. By including a resin having a melting point of 90°C or more and 200°C or less in the above resin (B), a good balance is achieved between the decomposition properties of the intermediate layer in a high-temperature, high-humidity environment and the strength of the intermediate layer. The above resin (B) more preferably contains a resin having a melting point of 95°C or more and 180°C or less, and even more preferably contains a resin having a melting point of 100°C or more and 170°C or less.

[0028] The above resin (B) is not particularly limited, but examples include polyester resin and cellulose resin. In particular, from the viewpoint of further improving the strength of the intermediate layer, it is preferable that the above resin (B) contains polyester resin.

[0029] The polyester resin included as resin (B) is not particularly limited, but examples include resins having a polylactic acid (PLA) skeleton, resins having a polybutylene succinate (PBS) skeleton, resins having a polyglycolic acid (PGA) skeleton, resins having a polycaprolactone (PCL) skeleton, resins having a poly-3-hydroxybutyrate-co-hydroxyhexanoate (PHBH) skeleton, and resins having a polybutylene adipate terephthalate (PBAT) skeleton. In particular, from the viewpoint of moldability, it is preferable to include a resin having at least one skeleton selected from the group consisting of polylactic acid, polybutylene succinate, polyglycolic acid, polycaprolactone, poly-3-hydroxybutyrate-co-hydroxyhexanoate, and polybutylene adipate terephthalate. Furthermore, from the viewpoint of compatibility with polyester resins such as polyethylene terephthalate resin and polybutylene terephthalate resin, it is even more preferable to include a resin having at least one skeleton selected from the group consisting of polybutylene succinate and polybutylene adipate terephthalate. These polyester resins may be used individually or in combination of two or more types.

[0030] Examples of commercially available polyester resins included as resin (B) above include BioPBS FZ91PB (manufactured by Mitsubishi Chemical Corporation, melting point 115°C), ecoflex C1200 (manufactured by BASF, melting point 115°C), Luminy LX575 (manufactured by Total Corbion, melting point 165°C), and Green Planet X331N (manufactured by Kaneka Corporation, melting point 100°C).

[0031] The content ratio of the polyester resin in the resin contained in the intermediate layer is not particularly limited, but a preferred lower limit is 15% by mass. The strength of the intermediate layer is further improved when the content ratio of the polyester resin in the resin contained in the intermediate layer is 15% by mass or more. A more preferred lower limit for the content ratio of the polyester resin in the resin contained in the intermediate layer is 30% by mass, and an even more preferred lower limit is 50% by mass. Furthermore, the upper limit of the polyester resin content in the total resin contained in the intermediate layer is 100% by mass, meaning the intermediate layer may be composed solely of the polyester resin.

[0032] The proportion of resin (B) in the total resin contained in the intermediate layer is not particularly limited, but a preferred lower limit is 50% by mass. A resin (B) content of 50% by mass or more allows the intermediate layer to exhibit excellent decomposition properties in high-temperature, high-humidity environments. A more preferred lower limit for the proportion of resin (B) in the total resin contained in the outermost layer is 70% by mass, and an even more preferred lower limit is 80% by mass. Furthermore, the upper limit of the proportion of resin (B) in the total resin contained in the intermediate layer is 100% by mass, meaning the intermediate layer may be composed solely of resin (B).

[0033] The above-mentioned intermediate layer may further contain additives such as fibers, inorganic fillers, flame retardants, ultraviolet absorbers, antistatic agents, inorganic substances, and higher fatty acid salts.

[0034] The above-mentioned intermediate layer may be a single-layer structure consisting of one layer, or a multilayer structure consisting of a laminate of multiple layers. If the intermediate layer is a multilayer structure, the multiple layers may be laminated and integrated via an adhesive layer.

[0035] The thickness of the intermediate layer is not particularly limited, but a preferred lower limit is 30 μm and a preferred upper limit is 200 μm. A thickness of 30 μm or more of the intermediate layer improves the strength of the intermediate layer. A thickness of 200 μm or less of the intermediate layer improves the moldability of the multilayer film of the present invention. A more preferred lower limit for the thickness of the intermediate layer is 45 μm, a more preferred upper limit is 175 μm, an even more preferred lower limit is 60 μm, and an even more preferred upper limit is 150 μm.

[0036] The multilayer film of the present invention has a preferred upper limit of 300 μm in total thickness. Having a total thickness of 300 μm or less improves the moldability of the multilayer film of the present invention. The preferred upper limit of the total thickness of the multilayer film of the present invention is 250 μm, and a more preferred upper limit is 200 μm. Furthermore, from the viewpoint of strength as an adhesive tape substrate, the multilayer film of the present invention has a preferred lower limit of 50 μm in total thickness, and a more preferred lower limit of 75 μm.

[0037] The method for producing the multilayer film of the present invention is not particularly limited, and examples include a method of forming a film by co-extrusion T-die, a water-cooled or air-cooled co-extrusion inflation method, a solvent casting method, a hot press molding method, etc. Among these, the method of forming a film by co-extrusion T-die is preferred because it offers excellent control over the thickness of each layer.

[0038] The applications of the multilayer film of the present invention are not particularly limited, but for example, it can be used as a base material in adhesive tapes. Furthermore, the multilayer film of the present invention has excellent ease of disassembly because the intermediate layer can be decomposed in high temperature and high humidity environments. Therefore, when the multilayer film of the present invention is used as a base material in adhesive tapes, it is useful in that it facilitates the reuse and recycling of parts fixed with the adhesive tape.

[0039] An adhesive tape having a multilayer film and an adhesive layer on at least one surface of the multilayer film is also one aspect of the present invention. In the adhesive tape of the present invention, the multilayer film serves as the base material. Because the multilayer film used as the base material of the adhesive tape of the present invention is easily disassembled in high temperature and high humidity environments, it is possible to easily reuse or recycle parts fixed with the adhesive tape of the present invention.

[0040] The adhesive tape of the present invention has an adhesive layer on at least one side of the multilayer film. That is, the adhesive tape of the present invention may be a single-sided adhesive tape having an adhesive layer on only one side of the multilayer film, or it may be a double-sided adhesive tape having adhesive layers on both sides of the multilayer film.

[0041] The adhesive layer preferably contains at least one selected from the group consisting of urethane resin and (meth)acrylic copolymer. Since urethane resin and (meth)acrylic copolymer have relatively high polarity, the water vapor permeability (WVTR) of the adhesive layer at 40°C and 90% RH is increased, and the adhesive tape of the present invention has superior ease of dismantling in high temperature and high humidity environments. In this specification, "(meth)acrylic" means acrylic or methacrylic.

[0042] The above-mentioned urethane resin is not particularly limited, and conventionally known urethane resins can be used. The weight-average molecular weight of the above urethane resin has a preferred lower limit of 10,000 and a preferred upper limit of 300,000. A weight-average molecular weight within this range allows the urethane resin to exhibit high adhesive strength. A more preferred lower limit for the weight-average molecular weight of the above urethane resin is 30,000, and a more preferred upper limit is 250,000. In this specification, the weight-average molecular weight is the weight-average molecular weight on a standard polystyrene basis, measured by GPC (Gel Permeation Chromatography). Specifically, a (meth)acrylic copolymer is diluted 50-fold with tetrahydrofuran (THF), and the resulting dilution is filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm) to prepare the measurement sample. Next, this measurement sample is supplied to a gel permeation chromatograph, and GPC measurement is performed under conditions of a sample flow rate of 1 mL / min and a column temperature of 40°C. The polystyrene-based molecular weight is measured, and this value is taken as the weight-average molecular weight. Examples of the gel permeation chromatograph include the 2690 Separations Module (manufactured by Waters).

[0043] The (meth)acrylic copolymer mentioned above is not particularly limited, and conventionally known (meth)acrylic copolymers can be used. From the viewpoint of improving the polarity of the (meth)acrylic copolymer, it is preferable that the (meth)acrylic copolymer has constituent units derived from a monomer containing a polar functional group. Examples of constituent units derived from the above polar functional group-containing monomers include constituent units derived from carboxyl group-containing monomers, constituent units derived from hydroxyl group-containing monomers, constituent units derived from glycidyl group-containing monomers, constituent units derived from amide group-containing monomers, and constituent units derived from nitrile group-containing monomers.

[0044] The weight-average molecular weight of the above (meth)acrylic copolymer has a preferred lower limit of 400,000 and a preferred upper limit of 1,500,000. A weight-average molecular weight within this range allows for high adhesive strength. A more preferred lower limit for the weight-average molecular weight of the above (meth)acrylic copolymer is 500,000, and a more preferred upper limit is 1,400,000.

[0045] The above adhesive layer has a preferred lower limit of 50 g / m² for water vapor transmission rate (WVTR) at 40°C and 90% RH.2 · day). When the water vapor permeability of the adhesive layer at 40°C and 90% RH is 50 g / (m 2 · day) or more, the adhesive tape of the present invention becomes excellent in the ease of disintegration in a high-temperature and high-humidity environment. A more preferable lower limit of the water vapor permeability of the adhesive layer at 40°C and 90% RH is 60 g / (m 2 · day), and a further preferable lower limit is 70 g / (m 2 · day). Also, there is no particular upper limit to the water vapor permeability of the adhesive layer at 40°C and 90% RH, but 1000 g / (m 2 · day) is a substantial upper limit.

[0046] As a method for adjusting the water vapor permeability of the adhesive layer at 40°C and 90% RH, for example, a method of changing the composition of the adhesive layer (for example, a method of containing a (meth)acrylic copolymer or a urethane resin), a method of reducing the thickness of the adhesive layer (for example, by reducing the thickness of the adhesive layer, the water vapor permeability of the adhesive layer at 40°C and 90% RH can be increased), etc. can be mentioned.

[0047] The upper limit of the thickness of the adhesive layer is preferably 75 μm. When the thickness of the adhesive layer is 75 μm or less, the water vapor permeability of the adhesive layer at 40°C and 90% RH becomes larger, and the adhesive tape of the present invention becomes excellent in the ease of disintegration in a high-temperature and high-humidity environment. The more preferable upper limit of the thickness of the adhesive layer is 60 μm, and the further preferable upper limit is 50 μm. Also, the lower limit of the adhesive layer is not particularly limited, but from the viewpoint of enabling the adhesive layer to exhibit sufficient adhesive force, the preferable lower limit is 10 μm, and the more preferable lower limit is 20 μm.

[0048] The adhesive tape of the present invention has a preferred lower limit of 100 μm and a preferred upper limit of 400 μm in total thickness. A total thickness of 100 μm or more allows the adhesive tape to exhibit sufficient adhesive strength and provides excellent handling. A total thickness of 400 μm or less facilitates the transfer of water vapor to the intermediate layer of the multilayer film used as the base material for the adhesive tape, resulting in superior ease of disassembly in high-temperature and high-humidity environments. A more preferred lower limit of 150 μm and a more preferred upper limit of 250 μm in total thickness for the adhesive tape of the present invention.

[0049] The method for manufacturing the adhesive tape of the present invention is not particularly limited and can be manufactured by conventionally known manufacturing methods. For example, in the case of double-sided adhesive tape, the following methods can be used. First, an adhesive composition is prepared by adding urethane resin, (meth)acrylic copolymer, and additives such as tackifying resin, crosslinking agent, and solvent. Next, the obtained adhesive composition is applied to one surface of a multilayer film manufactured by the method described above, and the solvent in the adhesive composition is completely dried and removed by heating to form an adhesive layer. Then, a release film is placed on top of the formed adhesive layer with its release treated surface facing the adhesive layer. Furthermore, a separate release film is prepared from the release film described above, and an adhesive composition prepared in the same manner as described above is applied to the release surface of this release film. By completely drying and removing the solvent in the adhesive composition, a laminated film is produced in which an adhesive layer is formed on the surface of the release film. The obtained laminated film is then placed on the back surface of a multilayer film in which the adhesive layer is formed, with the adhesive layer facing the back surface of the multilayer film, to create a laminate. Then, by applying pressure to the laminate with a rubber roller or the like, a double-sided adhesive tape is obtained in which adhesive layers are present on both sides of the multilayer film, and the surface of the adhesive layer is covered with a release film.

[0050] The applications of the adhesive tape of the present invention are not particularly limited, but as described above, since the adhesive tape of the present invention is easily disassembled in high temperature and high humidity environments, it is preferable to use it to fix parts to be reused or recycled. When a member fixed using the adhesive tape of the present invention is left to stand in a high temperature and high humidity environment, the components constituting the member can be easily separated by peeling between the layers of the multilayer film used as the base material of the adhesive tape. While there are no particular limitations on the types of parts that can be reused or recycled, examples include parts for electronic devices such as smartphones, tablets, and personal computers, and parts for display devices such as televisions and monitors.

[0051] A method for dismantling a laminate, which includes the step of leaving the laminate, to which the adhesive tape of the present invention is attached, to a component for at least 6 hours in an environment of 85°C or higher and 85% RH or higher, is also one of the present inventions. The present invention provides a method for dismantling laminates, which facilitates the dismantling of laminates by triggering the release of adhesive tape in a high-temperature, high-humidity environment. Therefore, it is useful in that it makes it easier to separate the components constituting the laminate that were fixed by the adhesive tape, thus facilitating the reuse and recycling of the components.

[0052] The above-mentioned laminate is not particularly limited as long as it is constructed by applying the adhesive tape of the present invention to the members, but examples include those in which members are bonded together with the adhesive tape of the present invention.

[0053] Examples of the above-mentioned components include the casings of electronic devices such as smartphones, tablets, and personal computers.

[0054] The present invention's method for dismantling a laminate includes a step of standing it for 6 hours or more in an environment of 85°C or higher and 85%RH or higher (hereinafter sometimes referred to as "step (I)"). By including step (I) in the present invention's method for dismantling a laminate, the adhesive tape in the laminate can be dismantled.

[0055] In step (I) above, the temperature at which the material is left to stand is not particularly limited as long as it is 85°C or higher, but from the viewpoint of ease of water vapor permeation, the preferred lower limit is 90°C. Furthermore, from the viewpoint of the melting point of the film constituent resin, the preferred upper limit of the temperature at which the film is left to stand is 100°C, and the more preferred upper limit is 95°C.

[0056] In step (I) above, the humidity at which the material is left to stand is not particularly limited as long as it is 85% RH or higher, but from the viewpoint of ease of water vapor permeation, the preferred lower limit is 90% RH. Furthermore, while there are no particular limitations on the maximum humidity level for stationary storage, the practical upper limit is 100%RH.

[0057] In step (I) above, the standing time is not particularly limited as long as it is 6 hours or more, but from the viewpoint of ensuring that the adhesive tape can be removed more reliably, the preferred lower limit is 12 hours. Furthermore, from the standpoint of speeding up the dismantling process, the preferred upper limit for the above-mentioned standing time is 120 hours, and the more preferred upper limit is 72 hours.

[0058] Specific methods for carrying out the above process (I) include setting the laminated material in a high-temperature, high-humidity oven (such as the "SH-242" manufactured by ESPEC Corporation) set to 85°C and 85%RH and leaving it to stand.

[0059] In the present invention's method for dismantling a laminate, a step of dismantling the adhesive tape is performed after the above step (I). Specifically, the adhesive tape is dismantled by peeling the interlayer between the outermost layer and the intermediate layer of the substrate. Methods for peeling the interlayer between the outermost layer and the intermediate layer of the substrate include peeling by hand and peeling the laminate with a suction cup. By performing the above-mentioned process of dismantling the adhesive tape, the laminate is dismantled between the base materials of the adhesive tape that make up the laminate, making it easier to separate and reuse the components that make up the laminate. [Effects of the Invention]

[0060] According to the present invention, it is possible to provide a multilayer film that can be easily disassembled by leaving it in a high-temperature, high-humidity environment. Furthermore, according to the present invention, it is possible to provide an adhesive tape having the multilayer film. Moreover, according to the present invention, it is possible to provide a method for disassembling a laminate to which the adhesive tape is attached. [Modes for carrying out the invention]

[0061] The embodiments of the present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0062] (Preparation of acrylic adhesive) (1) Synthesis of (meth)acrylic copolymer 52 parts by mass of ethyl acetate were placed in a reactor equipped with a thermometer, stirrer, and condenser, and after purging with nitrogen, the reactor was heated and reflux was started. Thirty minutes after the ethyl acetate boiled, 0.08 parts by mass of azobisisobutyronitrile was added as a polymerization initiator. A monomer mixture consisting of 70 parts by mass of n-butyl acrylate, 27 parts by mass of 2-ethylhexyl acrylate, 3 parts by mass of acrylic acid, and 0.2 parts by mass of 2-hydroxyethyl acrylate was added dropwise and evenly over 1 hour and 30 minutes to allow the reaction to proceed. Thirty minutes after the end of the dropwise addition, 0.1 parts by mass of azobisisobutyronitrile was added, and the polymerization reaction was continued for a further 5 hours. By adding ethyl acetate to the reactor and cooling while diluting, a solution of (meth)acrylic copolymer with a solid content of 40% by mass was obtained. The weight-average molecular weight of the obtained (meth)acrylic copolymer was measured by GPC using a Waters 2690 Separations Module as the column, and was found to be 710,000.

[0063] (2) Preparation of adhesive To 100 parts by mass of the solid content of the obtained (meth)acrylic copolymer, 15 parts by mass of polymerized rosin ester with a softening point of 150°C, 10 parts by mass of terpene phenol with a softening point of 145°C, and 10 parts by mass of rosin ester with a softening point of 70°C were added. Furthermore, 30 parts by mass of ethyl acetate and 1.8 parts by mass of a crosslinking agent (Desmodule L75, manufactured by Covestro) were added, and the mixture was stirred to obtain an adhesive solution.

[0064] (Preparation of urethane-based adhesive) (1) Synthesis of urethane resin In a four-necked flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel, 112 g of polyoxypropylene diol polyol (hydroxyl value 56.1 mg KOH / g), prepared by reacting propylene oxide with propylene glycol as an initiator and a KOH catalyst, 14.5 g of 2,4-toluene diisocyanate (Mitsui Chemicals Fine, "Cosmonate T-100"), and dibutyltin dilaurate (DBTDL) as a urethane catalyst were added in an amount equivalent to 20 ppm relative to the total amount of polyoxypropylene diol polyol and 2,4-toluene diisocyanate. The temperature was then gradually increased to 80°C, and the reaction was carried out for 2 hours to obtain a solution containing the prepolymer (NCO% was 1.80% by mass). The solution was then cooled to 60°C, and 85 g of ethyl acetate and 125 g of methyl ethyl ketone (MEK) were added to the solution containing the prepolymer. Subsequently, 1.52 g of N-(2-hydroxypropyl)ethanolamine and 1.14 g of 14-butanediol were added as chain extenders, and the reaction was carried out. The reaction was continued at 60°C, and when the NCO% fell below 0.10% by mass, 0.29 g of monoisopropanolamine (MIPA), a terminal termination agent, was added to terminate the reaction. The resulting polyurethane resin solution was colorless and transparent with a solid content of 42% by mass. Furthermore, the weight-average molecular weight (Mw) of the obtained polyurethane resin was measured by GPC using a Waters "2690 Separations Module" column, and it was found to be 80,000.

[0065] (2) Preparation of adhesive 80 parts by mass of the solid content of the obtained urethane resin solution, 20 parts by mass of terpene phenol resin (Yasuhara Chemical Co., Ltd., "YS Polystar T-145") as a tackifying resin, and 1.2 parts by mass of crosslinking agent (Covestro Co., Ltd., "Desmodule L75") were added, and the mixture was stirred to obtain an adhesive solution.

[0066] (Example 1) (1) Fabrication of multilayer films 100 parts by mass of polybutylene terephthalate (PBT, Novaduran 5026 (manufactured by Mitsubishi Chemical Corporation)) was used as the outermost layer resin. 100 parts by mass of polybutylene succinate (PBS, BioPBS FZ91PB (manufactured by Mitsubishi Chemical Corporation)) was used as the intermediate layer resin.

[0067] The outermost layer resin and the intermediate layer resin were co-extruded in three layers using an extruder (GM30-28, manufactured by GM Engineering Co., Ltd. (screw diameter 30 mm, L / D 28)) at a molding temperature of 250°C and a T-die width of 400 mm. The extruded molten resin was cooled using a cooling roll (temperature 90°C, surface arithmetic mean roughness Ra 0.1 μm). This resulted in a 1700 mm wide multilayer film with a three-layer structure having the outermost layer on both sides of the intermediate layer. The thickness of both outermost layers was 25 μm, the thickness of the intermediate layer was 50 μm, and the total thickness of the multilayer film was 100 μm. During cooling, the contact time between the molten resin and the cooling roll was 1.0 second, and the tensile stress when cooling the molten resin with the cooling roll was 450 kPa.

[0068] (2) Measurement of water vapor transmission rate (WVTR) of the outermost layer under conditions of 40°C and 90% RH In accordance with JIS K 7129-2, a water vapor transmission humidity test was performed using the MOCON method with a single sample of the outermost layer at 40°C and 90%RH, and the water vapor transmission rate (g / m³) of the outermost layer under the conditions of 40°C and 90%RH was measured. 2 The day's energy was measured. The results are shown in Table 1.

[0069] (Examples 2-17, Comparative Examples 1-4) (1) Fabrication of multilayer films A three-layer multilayer film was obtained in the same manner as in Example 1, except that the compositions of the outermost layer resin and the intermediate layer resin, and the thicknesses of the outermost layer and the intermediate layer were as shown in Tables 1 to 3.

[0070] (2) Measurement of water vapor transmission rate (WVTR) of the outermost layer under conditions of 40°C and 90% RH In the same manner as in Example 1, the water vapor transmission rate (g / m³) of the outermost layer under conditions of 40°C and 90% RH was measured. 2 The day's energy was measured. The results are shown in Tables 1-3.

[0071] (3) Preparation of adhesive tape The adhesives shown in Tables 1-3 were applied to the release-treated surface of a 75 μm thick release PET film so that the thickness of the adhesive layer after drying was as shown in Tables 1-3, and the resulting adhesive layer was formed by drying at 110°C for 5 minutes. This adhesive layer was then laminated to one side of the prepared multilayer film. Furthermore, an adhesive layer with the same composition and thickness was formed on the release-treated surface of another 75 μm thick release PET film and laminated to the other side of the multilayer film. The film was then cured at 40°C for 48 hours to obtain an adhesive tape having adhesive layers on both sides of the multilayer film.

[0072] The types of resins used for the outermost layer and the intermediate layer in Tables 1-3 are as follows: PBT: Polybutylene terephthalate • PET: Polyethylene terephthalate • PE: Polyethylene • EMMA: Ethylene-methyl methacrylate copolymer • PBS: Polybutylene succinate PBAT: Polybutylene adipate terephthalate • PLA: Polylactic acid PHBH: Poly-3-hydroxybutyrate-co-hydroxyhexanoate • PP: Polypropylene In Tables 1-3, "biodegradability" is indicated as "○" if the degree of biodegradation was 60% or higher, and "×" if it was less than 60%.

[0073] The multilayer films and adhesive tapes obtained in the examples and comparative examples were evaluated using the following methods. The results are shown in Tables 1 to 3.

[0074] <Difficulty in disassembling after being left undisturbed for 72 hours in an environment of 23°C and 50%RH> (1) Test method (Example 1) A test specimen was prepared by cutting the multilayer film of Example 1 to a size of 25 mm in width and 50 mm in length, and the prepared test specimen was left to stand for 72 hours in an environment of 23°C and 50% RH. After leaving the test specimen to stand for 72 hours in an environment of 23°C and 50% RH, the interlayer between the middle layer and the outermost layer of the test specimen was peeled off by hand.

[0075] (Examples 2-17, Comparative Examples 1-4) Test specimens were prepared by cutting the adhesive tapes of Examples 2-17 and Comparative Examples 1-4 to a size of 25 mm in width and 50 mm in length. The prepared test specimens were left to stand for 72 hours in an environment of 23°C and 50% RH. After leaving the test specimens to stand for 72 hours in an environment of 23°C and 50% RH, the interlayer between the intermediate layer and the outermost layer of the multilayer film of the test specimen was peeled off by hand.

[0076] (2) Evaluation The evaluation was conducted by marking "○" if the intermediate layer and outermost layer of the multilayer film could not be separated by hand, and "×" if the intermediate layer and outermost layer of the multilayer film could be separated by hand. If the evaluation is "○", then the multilayer film of the present invention can be used without disassembling it during normal use.

[0077] <Easy dismantling in high-temperature, high-humidity environments> (1) Ease of disassembly after standing for 6 hours in an environment of 85°C and 85%RH (1-1) Test Method (Example 1) Test specimens were prepared by cutting the multilayer film of Example 1 to a size of 25 mm in width and 50 mm in length. The prepared test specimens were placed in a high-temperature, high-humidity oven (ESPEC Corporation, "SH-242") set to 85°C and 85% RH, and left to stand for 6 hours in an environment of 85°C and 85% RH. After the test specimens were removed from the oven and left to stand for 15 minutes in an environment of 23°C and 50% RH, the interlayer between the middle layer and the outermost layer of the test specimen was peeled off by hand.

[0078] (Examples 2-17, Comparative Examples 1-4) Test specimens were prepared by cutting the adhesive tapes of Examples 2-17 and Comparative Examples 1-4 to a size of 25 mm in width and 50 mm in length. The prepared test specimens were placed in a high-temperature, high-humidity oven (ESPEC Corporation, "SH-242") set to 85°C and 85% RH, and left to stand for 6 hours in an environment of 85°C and 85% RH. After the test specimens were removed from the oven and left to stand for 15 minutes in an environment of 23°C and 50% RH, the interlayer between the intermediate layer and the outermost layer of the multilayer film of the test specimen was peeled off by hand. In Example 2, although signs of resin softening were observed on the outermost layer of the multilayer film, the intermediate and outermost layers of the multilayer film could be peeled off by hand.

[0079] (1-2) Evaluation The evaluation was based on whether the intermediate and outermost layers of the multilayer film could be separated by hand ("○") and whether they could not be separated by hand ("×").

[0080] (2) Ease of disassembly after standing for 72 hours in an environment of 85°C and 85%RH Except for leaving the test specimens standing for 72 hours at 85°C and 85%RH, the ease of disassembly was evaluated using the same test method and evaluation criteria as described above for "(1) Ease of disassembly when left standing for 6 hours at 85°C and 85%RH". Similar to the evaluation described above for "(1) Ease of disassembly when left standing for 6 hours at 85°C and 85%RH", a multilayer film was used for the evaluation in Example 1, while adhesive tape was used for the evaluation in Examples 2-17 and Comparative Examples 1-4.

[0081] (3) Overall evaluation Using the results of the above-mentioned "(1) ease of disassembly after standing for 6 hours in an environment of 85°C and 85%RH" and "(1) ease of disassembly after standing for 72 hours in an environment of 85°C and 85%RH", the ease of disassembly of the obtained multilayer films and adhesive tapes in high-temperature and high-humidity environments was evaluated according to the following criteria. • ◎: In all evaluations, if the interlayer and outermost layer of the multilayer film can be peeled off by hand (in all evaluations, "○") • ○: When left standing for 6 hours, the interlayer and outermost layer of the multilayer film could not be separated by hand (evaluation "×"), but when left standing for 72 hours, the interlayer and outermost layer of the multilayer film could be separated by hand (evaluation "○"). • ×: In any evaluation, if the interlayer and outermost layer of the multilayer film could not be separated by hand (in any evaluation, the result is "×")

[0082] [Table 1]

[0083] [Table 2]

[0084] [Table 3] [Industrial applicability]

[0085] According to the present invention, it is possible to provide a multilayer film that can be easily disassembled by leaving it in a high-temperature, high-humidity environment. Furthermore, according to the present invention, it is possible to provide an adhesive tape having the multilayer film. Moreover, according to the present invention, it is possible to provide a method for disassembling a laminate to which the adhesive tape is attached.

Claims

1. An intermediate layer, and an outermost layer on both sides of the intermediate layer, The outermost layer contains resin (A) with a biodegradability of less than 60%, The aforementioned intermediate layer contains a resin (B) with a biodegradability of 60% or more. The outermost layer has a water vapor transmission rate (WVTR) of 15 g / m² under conditions of 40°C and 90% RH. ２ - day) or more A multilayer film characterized by the following features.

2. The multilayer film according to claim 1, wherein the resin (A) comprises a resin having a melting point of 100°C or higher.

3. The multilayer film according to claim 1 or 2, wherein the resin (A) comprises a polyester resin.

4. The multilayer film according to claim 3, wherein the resin (A) comprises a resin having a polybutylene terephthalate skeleton.

5. The multilayer film according to claim 1 or 2, wherein the outermost layer has a thickness of 50 μm or less.

6. The multilayer film according to claim 1 or 2, wherein the resin (B) comprises a polyester resin.

7. The multilayer film according to claim 6, wherein the resin (B) comprises a resin having a skeleton selected from the group consisting of polylactic acid, polybutylene succinate, polyglycolic acid, polycaprolactone, poly-3-hydroxybutyrate-co-hydroxyhexanoate, and polybutylene adipate terephthalate.

8. The multilayer film according to claim 1 or 2, wherein the content ratio of the resin (B) to the total resin contained in the intermediate layer is 50% by mass or more.

9. The multilayer film according to claim 1 or 2, wherein the intermediate layer has a thickness of 30 μm or more and 200 μm or less.

10. The multilayer film according to claim 1 or 2, wherein the multilayer film has a total thickness of 300 μm or less.

11. A multilayer film according to claim 1 or 2, An adhesive layer is provided on at least one surface of the multilayer film. Adhesive tape.

12. The adhesive tape according to claim 11, wherein the adhesive layer contains at least one selected from the group consisting of urethane resin and (meth)acrylic copolymer.

13. The adhesive tape according to claim 11, wherein the adhesive layer has a thickness of 75 μm or less.

14. A laminate formed by attaching the adhesive tape described in claim 11 to a member, This process includes leaving the area standing for 6 hours or more in an environment with a temperature of 85°C or higher and a humidity of 85% or higher. Method for dismantling a laminated structure.

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