Adhesive tape

Abstract

The present invention provides an adhesive tape having a high bio-based carbon content and having an excellent shear retention force at a high temperature. The present invention is an adhesive tape having an adhesive layer containing an acrylic copolymer, wherein: the acrylic copolymer contains a constituent unit derived from alkyl (meth)acrylate containing bio-based carbon; and the total content of a compound having a structure represented by general formula (A) and a compound having a structure represented by general formula (B) in the adhesive layer is at most 2 wt%. In general formulae (A) and (B), R1 and R2 each represent a C4-C12 alkyl group.

Description

[Technical Field]

[0001] This invention relates to adhesive tape. [Background technology]

[0002] Conventionally, adhesive tapes having an adhesive layer containing an adhesive have been widely used to fix components in electronic components, vehicles, housing, and building materials (for example, Patent Documents 1 to 3). Specifically, for example, adhesive tapes are used to adhere a cover panel for protecting the surface of a portable electronic device to a touch panel module or display panel module, or to adhere a touch panel module to a display panel module. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2015-052050 [Patent Document 2] Japanese Patent Publication No. 2015-021067 [Patent Document 3] Japanese Patent Publication No. 2015-120876 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In recent years, the depletion of petroleum resources and the emission of carbon dioxide from the combustion of petroleum-derived products have become serious concerns. Therefore, attempts are being made, particularly in the medical and packaging materials sectors, to conserve petroleum resources by using bio-derived materials instead of petroleum-derived materials. These efforts are spreading to all sectors, and the use of bio-derived materials is now being demanded in the adhesives and adhesive tapes sectors as well.

[0005] The present invention aims to provide an adhesive tape with a high content of bio-derived carbon and excellent shear holding power at high temperatures.

Means for Solving the Problem

[0006] The present disclosure 1 is an adhesive tape having an adhesive layer containing an acrylic copolymer, wherein the acrylic copolymer contains a structural unit derived from an alkyl (meth)acrylate containing carbon derived from a biological source, and the total content of the compound having a structure represented by the following general formula (A) and the compound having a structure represented by the following general formula (B) in the adhesive layer is 2% by weight or less.

[0007]

Chemical Formula

[0008] In the general formulas (A) and (B), R 1 and R 2 represent an alkyl group having 4 to 12 carbon atoms.

[0009] The present disclosure 2 is the adhesive tape of the present disclosure 1, wherein the total content of the compound having a structure represented by the general formula (A), the compound having a structure represented by the general formula (B), and the compound having a structure represented by the following general formula (C) in the adhesive layer is 2% by weight or less.

[0010]

Chemical Formula

[0011] In the general formula (C), R 1 and R 2 represent an alkyl group having 4 to 12 carbon atoms.

[0012] The present disclosure 3 is the adhesive tape of the present disclosure 1 or 2, wherein the content of the compound having a structure represented by the general formula (A) in the adhesive layer is less than 1% by weight. The present disclosure 4 is the adhesive tape of the present disclosure 1, 2 or 3, wherein the compound having a structure represented by the general formula (A) is a compound having a structure represented by the following formula (a1).

[0013] [ka]

[0014] Disclosure 5 is an adhesive tape according to Disclosure 1, 2, 3, or 4, wherein the adhesive layer contains less than 1% by weight of a compound having the structure represented by the general formula (B). Disclosure 6 is an adhesive tape according to Disclosure 2, 3, 4, or 5, wherein the adhesive layer contains less than 1% by weight of a compound having the structure represented by the general formula (C). Disclosure 7 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, or 6, wherein the compound having the structure represented by the general formula (B) is a compound having the structure represented by the following formula (b1).

[0015] [ka]

[0016] Disclosure 8 is an adhesive tape according to Disclosures 2, 3, 4, 5, 6, or 7, wherein the compound having the structure represented by the general formula (C) is a compound having the structure represented by the following formula (c1).

[0017] [ka]

[0018] Disclosure 9 is an adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, or 8, wherein the bio-derived carbon-containing alkyl (meth)acrylate contains n-heptyl (meth)acrylate. Disclosure 10 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, or 9, wherein the acrylic copolymer contains 85% by weight or more of constituent units derived from the bio-derived carbon-containing alkyl (meth)acrylate. Disclosure 11 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, wherein the adhesive layer further contains a tackifying resin. Disclosure 12 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, wherein the adhesive layer has a bio-derived carbon content of 10% by weight or more. Disclosure 13 is an adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 used for fixing electronic equipment components or automotive components.

[0019] In this specification, (meth)acrylate means acrylate or methacrylate, and (meth)acrylic means acrylic or methacrylic. Acrylic copolymer may also be methacrylic copolymer. The present invention will be described in detail below.

[0020] The present inventors investigated using an alkyl (meth)acrylate containing bio-derived carbon as the acrylic monomer constituting the acrylic copolymer in an adhesive tape having an adhesive layer containing an acrylic copolymer. However, when using an alkyl (meth)acrylate containing bio-derived carbon, sufficient adhesive strength could not be obtained, and for example, the shear holding strength at high temperatures sometimes decreased.

[0021] The inventors investigated the reason why sufficient adhesive strength could not be obtained and found that the alkyl (meth)acrylate containing bio-derived carbon contained impurities because it was of bio-derived origin. In particular, when an alkyl (meth)acrylate containing bio-derived carbon is used, and that has a relatively large number of C1 alkyl groups, the glass transition temperature (Tg) of the acrylic copolymer becomes sufficiently low, and excellent adhesive strength can be expected. However, (meth)acrylates containing bio-derived carbon and that have a relatively large number of C1 alkyl groups contain dialkyl ethers and ether esters having a relatively large number of C1 alkyl groups as impurities. The inventors have found that since these impurities remain in the adhesive layer, when exposed to high temperatures, for example, the impurities may bleed out, reducing the cohesive force and leading to a decrease in adhesive strength. In response to this, the present inventors have discovered that by adjusting the total content of specific compounds corresponding to impurities in the alkyl (meth)acrylate containing bio-derived carbon in the adhesive layer to a certain value or less, an adhesive tape with excellent shear holding power at high temperatures can be obtained, thus completing the present invention.

[0022] The adhesive tape of the present invention has an adhesive layer containing an acrylic copolymer. The above acrylic copolymer contains constituent units derived from alkyl (meth)acrylate containing bio-derived carbon. As a result, the adhesive tape of the present invention has a high content of bio-derived carbon, exhibits excellent adhesive strength, and is an adhesive tape with excellent shear holding power at high temperatures.

[0023] The above-mentioned alkyl (meth)acrylate containing bio-derived carbon is not particularly limited, but (meth)acrylate having an alkyl group with 7 to 12 carbon atoms is preferred because it lowers the glass transition temperature (Tg) of the acrylic copolymer sufficiently and increases the adhesive strength of the adhesive layer. Examples of the above-mentioned (meth)acrylates having an alkyl group with 7 to 12 carbon atoms include n-heptyl(meth)acrylate, n-octyl(meth)acrylate, n-decyl(meth)acrylate, and lauryl(meth)acrylate. These alkyl(meth)acrylates containing bio-derived carbon may be used alone or in combination of two or more. Among these, n-heptyl(meth)acrylate, n-octyl(meth)acrylate, and lauryl(meth)acrylate are preferred, and n-heptyl(meth)acrylate is more preferred, as they result in higher adhesive strength of the adhesive layer.

[0024] The alkyl (meth)acrylate containing bio-derived carbon described above is not particularly limited as long as it contains bio-derived carbon, but it is preferable that it be synthesized by esterification of a bio-derived alcohol with (meth)acrylic acid, or by a transesterification reaction of a bio-derived alcohol with a (meth)acrylic acid ester. For example, n-heptyl alcohol, a bio-derived material, can be obtained inexpensively and easily by cracking materials extracted from plants and animals (e.g., ricinoleic acid derived from castor oil). Similarly, n-octyl alcohol, also a bio-derived material, can be easily and readily obtained by reducing materials extracted from plants and animals (e.g., caprylic acid derived from coconut oil). Furthermore, lauryl alcohol, also a bio-derived material, can be easily and readily obtained by reducing materials extracted from plants and animals (e.g., lauric acid derived from palm oil or palm kernel oil).

[0025] The content of the constituent units derived from the alkyl (meth)acrylate containing the above-mentioned bio-derived carbon in the above-mentioned acrylic copolymer is not particularly limited, but is preferably greater than 50% by weight, more preferably 60% by weight, even more preferably 70% by weight, and most preferably 85% by weight. If the content of the above-mentioned constituent units is 85% by weight or more, the content of bio-derived carbon in the entire adhesive tape will be higher, the adhesive strength of the adhesive layer will be higher, and the shear holding force of the adhesive tape at high temperatures will be higher. The most preferred lower limit for the content of the above-mentioned constituent units is 90% by weight. The upper limit for the content of the constituent units derived from the alkyl (meth)acrylate containing the above-mentioned bio-derived carbon is not particularly limited, but from the viewpoint of adjusting the gel fraction of the adhesive layer, the preferred upper limit is 99% by weight and the more preferred upper limit is 97% by weight. In particular, the adhesive strength of the adhesive layer is increased when the content of constituent units derived from the n-heptyl(meth)acrylate in the acrylic copolymer is more than 50% by weight, more preferably 60% by weight, even more preferably 70% by weight, and especially preferably 85% by weight or more.

[0026] The content of constituent units derived from the above-mentioned bio-derived carbon-containing alkyl (meth)acrylate in the above-mentioned acrylic copolymer is determined by mass spectrometry of the above-mentioned acrylic copolymer and 1 This can be calculated by performing 1H-NMR measurements and analyzing the integral intensity ratio of the hydrogen peaks originating from each monomer.

[0027] The above acrylic copolymer preferably further contains constituent units derived from monomers having crosslinkable functional groups. The presence of structural units derived from monomers having the above-mentioned crosslinkable functional groups in the above-mentioned acrylic copolymer increases the cohesive force of the adhesive layer, resulting in higher adhesive strength.

[0028] The monomers having the above-mentioned crosslinkable functional group are not particularly limited, and examples include monomers having a hydroxyl group, monomers having a carboxyl group, monomers having a glycidyl group, monomers having an amide group, monomers having a nitrile group, etc. These monomers having crosslinkable functional groups may be used alone or in combination of two or more. Among these, monomers having a hydroxyl group and monomers having a carboxyl group are preferred, and monomers having a hydroxyl group are more preferred, as they allow for easy adjustment of the gel fraction of the adhesive layer.

[0029] Examples of monomers having a hydroxyl group include acrylic monomers having a hydroxyl group, such as 4-hydroxybutyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate. Examples of monomers having a carboxyl group include acrylic monomers having a carboxyl group, such as (meth)acrylic acid. Examples of monomers having a glycidyl group include acrylic monomers having a glycidyl group, such as glycidyl (meth)acrylate. Examples of monomers having the above-mentioned amide group include acrylic monomers having an amide group such as (meth)acrylamide, dimethyl(meth)acrylamide, diethyl(meth)acrylamide, isopropyl(meth)acrylamide, t-butyl(meth)acrylamide, methoxymethyl(meth)acrylamide, and butoxymethyl(meth)acrylamide. Examples of monomers having a nitrile group include acrylic monomers having a nitrile group, such as (meth)acrylonitrile.

[0030] The content of structural units derived from the monomer having the crosslinkable functional group in the above acrylic copolymer is not particularly limited, but a preferred lower limit is 0.01% by weight and a preferred upper limit is 15% by weight. If the content of structural units derived from the monomer having the crosslinkable functional group is within the above range, the cohesive force of the adhesive layer will increase further, and the adhesive force will be even higher. A more preferred lower limit for the content of structural units derived from the monomer having the crosslinkable functional group is 0.1% by weight, a more preferred upper limit is 10% by weight, an even more preferred lower limit is 0.5% by weight, and an even more preferred upper limit is 5% by weight.

[0031] The content of the constituent units derived from the monomer having the crosslinkable functional group in the above acrylic copolymer is determined by mass spectrometry of the above acrylic copolymer and 1 This can be calculated by performing 1H-NMR measurements and analyzing the integral intensity ratio of the hydrogen peaks originating from each monomer.

[0032] The above acrylic copolymer may have structural units derived from monomers other than the above-mentioned alkyl (meth)acrylate containing carbon of biological origin and the structural units derived from the above-mentioned monomer having a crosslinkable functional group. The other monomers mentioned above are not particularly limited and include, for example, (meth)acrylates (petroleum-derived monomers) and alkyl (meth)acrylates having an alkyl group with 7 to 12 carbon atoms that do not contain bio-derived carbon. Examples of the alkyl (meth)acrylate esters mentioned above include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, myristyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, esters of 5,7,7-trimethyl-2-(1,3,3-trimethylbutyl)octanol-1 with (meth)acrylic acid, esters of (meth)acrylic acid with an alcohol having 1 or 2 methyl groups in a linear main chain and a total of 18 carbon atoms, behenyl (meth)acrylate, arachidyl (meth)acrylate, and the like. These alkyl (meth)acrylate esters may be used alone or in combination of two or more.

[0033] Other monomers include, for example, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, and polypropylene glycol mono(meth)acrylate. From the viewpoint of excellent rebound resistance, isobornyl (meth)acrylate is preferred. Furthermore, other monomers such as vinyl carboxylates like vinyl acetate and various monomers commonly used in acrylic polymers like styrene can also be used. When producing the acrylic copolymer by UV polymerization, polyfunctional monomers such as 1,6-hexanediol di(meth)acrylate can also be used as other monomers. These other monomers may be used individually or in combination of two or more.

[0034] The content of constituent units derived from the other monomers in the above acrylic copolymer is determined by mass spectrometry of the above acrylic copolymer and 1 This can be calculated by performing 1H-NMR measurements and analyzing the integral intensity ratio of the hydrogen peaks originating from each monomer.

[0035] The monomers having the above-mentioned crosslinkable functional group, and the other monomers, preferably contain bio-derived carbon, but may also consist only of petroleum-derived materials without containing bio-derived carbon. Theoretically, it is also possible to make all of the acrylic monomers constituting the above-mentioned acrylic copolymer monomers containing bio-derived carbon. From the viewpoint of cost and productivity of adhesive tape, it is also possible to use monomers containing bio-derived carbon, which are relatively inexpensive and readily available, and combine them with monomers consisting only of petroleum-derived materials.

[0036] The glass transition temperature (Tg) of the above acrylic copolymer is not particularly limited, but is preferably -20°C or lower. If the glass transition temperature (Tg) of the above acrylic copolymer is -20°C or lower, the adhesion of the adhesive layer to the adherend is improved, and the adhesive strength becomes higher. The glass transition temperature (Tg) of the above acrylic copolymer is more preferably -30°C or lower, even more preferably -40°C or lower, and even more preferably -50°C or lower. The lower limit of the glass transition temperature (Tg) of the above acrylic copolymer is not particularly limited, but is usually -90°C or higher, and is preferably -80°C or higher. The glass transition temperature (Tg) of the above acrylic copolymer can be determined, for example, by differential scanning calorimetry.

[0037] The weight-average molecular weight (Mw) of the above acrylic copolymer is not particularly limited, but a preferred lower limit is 200,000 and a preferred upper limit is 2,000,000. If the weight-average molecular weight of the above acrylic copolymer is within the above range, the adhesive strength of the adhesive layer will be higher. A more preferred lower limit for the weight-average molecular weight of the above acrylic copolymer is 400,000, a more preferred upper limit is 1,800,000, an even more preferred lower limit is 500,000, and an even more preferred upper limit is 1,500,000. The weight-average molecular weight (Mw) is the weight-average molecular weight on a standard polystyrene basis, measured by GPC (Gel Permeation Chromatography). Specifically, the 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 (Waters, product name "2690 Separations Module" or equivalent) 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 of the acrylic copolymer is measured, and this value is taken as the weight-average molecular weight of the acrylic copolymer.

[0038] The above-mentioned acrylic copolymer can be obtained by subjecting a mixture of raw material monomers to a radical reaction in the presence of a radical polymerization initiator. The method of radical reaction is not particularly limited, and examples include living radical polymerization and free radical polymerization. Living radical polymerization yields copolymers with more uniform molecular weight and composition compared to free radical polymerization, and the generation of low molecular weight components can be suppressed, thereby increasing the cohesive force of the adhesive layer and resulting in higher adhesive strength. The polymerization method is not particularly limited, and conventionally known methods can be used. Examples of polymerization methods include solution polymerization (boiling point polymerization or constant temperature polymerization), UV polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. Among these, solution polymerization and UV polymerization are preferred because they result in higher adhesive strength of the adhesive layer. Furthermore, solution polymerization is more preferred because it facilitates mixing of the tackifying resin with the obtained acrylic copolymer and further increases the adhesive strength of the adhesive layer.

[0039] When solution polymerization is used as the polymerization method, examples of reaction solvents include ethyl acetate, toluene, methyl ethyl ketone, dimethyl sulfoxide, ethanol, acetone, and diethyl ether. These reaction solvents may be used individually or in combination of two or more.

[0040] The radical polymerization initiators mentioned above are not particularly limited and include, for example, organic peroxides and azo compounds. Examples of organic peroxides include 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, and t-butylperoxylaurate. Examples of azo compounds include azobisisobutyronitrile and azobiscyclohexanecarbonilonitrile. These radical polymerization initiators may be used individually or in combination of two or more. Furthermore, in the case of living radical polymerization, examples of radical polymerization initiators include organic tellurium polymerization initiators. The organic tellurium polymerization initiator is not particularly limited as long as it is commonly used in living radical polymerization, and examples include organic tellurium compounds and organic telluride compounds. In addition to the organic tellurium polymerization initiator, an azo compound may also be used as a radical polymerization initiator in living radical polymerization to accelerate the polymerization rate.

[0041] The adhesive layer described above preferably does not contain a surfactant. The absence of surfactants in the adhesive layer enhances the adhesive strength of the tape, particularly at high temperatures. Note that the absence of surfactants in the adhesive layer means that the surfactant content in the adhesive layer is 3% by weight or less, preferably 1% by weight or less. In order for the above adhesive layer to not contain a surfactant, it is preferable not to use a surfactant when obtaining the above acrylic copolymer. To achieve this, for example, solution polymerization, UV polymerization, etc., may be used as the polymerization method when obtaining the above acrylic copolymer. The content of the above-mentioned surfactant can be determined, for example, by measuring the adhesive layer using a liquid chromatography-mass spectrometer (e.g., NEXCERA from Shimadzu Corporation, Exactive from Thermo Fisher Scientific, etc.). More specifically, the ethyl acetate solution of the adhesive layer is filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm). Approximately 10 μL of the obtained filtrate is injected into a liquid chromatography-mass spectrometer and analyzed under the following conditions. The content of the surfactant can be determined from the area ratio of the peaks corresponding to the surfactant in the adhesive layer. It is preferable to prepare samples with known surfactant content in the adhesive layer for each surfactant type, create a calibration curve showing the relationship between surfactant content and peak area ratio, and analyze it. Column: Thermo Fisher Scientific, Hypersil GOLD (2.1 x 150 mm) Mobile phase: acetonitrile Column temperature: 40°C Flow rate 1.0mL / min Ionization method ESI Capillary temperature 350℃

[0042] From the viewpoint of being able to appropriately adjust the gel fraction, it is preferable that the above adhesive layer further contains a crosslinking agent. The above crosslinking agent is not particularly limited and examples include isocyanate-based crosslinking agents, aziridine-based crosslinking agents, epoxy-based crosslinking agents, and metal chelate-type crosslinking agents. Among these, isocyanate-based crosslinking agents are preferred because the adhesive layer exhibits excellent adhesion to the adherend. The molecular weight of the crosslinking agent is not particularly limited, but from a manufacturing standpoint, a molecular weight of less than 2000 is preferred, and 100 or more is preferred.

[0043] The content of the crosslinking agent in the adhesive layer is not particularly limited, but a preferred lower limit is 0.05 parts by weight and a preferred upper limit is 7 parts by weight per 100 parts by weight of the acrylic copolymer. If the content of the crosslinking agent is within the above range, the gel fraction of the adhesive layer is appropriately adjusted, and the adhesive strength is increased. A more preferred lower limit for the content of the crosslinking agent is 0.1 parts by weight and a more preferred upper limit is 5 parts by weight. The above-mentioned crosslinking agent content indicates the amount of solids contained in the crosslinking agent.

[0044] Preferably, the adhesive layer further contains a tackifying resin. This increases the adhesive strength of the adhesive layer and the shear holding power of the adhesive tape at high temperatures. Examples of the tackifying resins mentioned above include rosin ester tackifying resins, terpene tackifying resins, coumarone indene tackifying resins, alicyclic saturated hydrocarbon tackifying resins, C5 petroleum tackifying resins, C9 petroleum tackifying resins, and C5-C9 copolymer petroleum tackifying resins. These tackifying resins may be used individually or in combination of two or more. Among these, at least one selected from the group consisting of rosin ester tackifying resins and terpene tackifying resins is preferred.

[0045] Examples of the rosin ester-based tackifying resins mentioned above include polymerized rosin ester resins and hydrogenated rosin ester resins. Examples of the terpene-based tackifying resins mentioned above include terpene resins and terpene phenol resins. The rosin ester-based tackifying resin and the terpene-based tackifying resin described above are preferably of biological origin. Examples of biologically derived rosin ester-based tackifying resins include rosin ester-based tackifying resins derived from natural resins such as pine resin. Examples of biologically derived terpene-based tackifying resins include terpene-based tackifying resins derived from plant essential oils, etc.

[0046] The content of the tackifier resin in the adhesive layer is not particularly limited, but the preferable lower limit with respect to 100 parts by weight of the acrylic copolymer is 10 parts by weight, and the preferable upper limit is 60 parts by weight. If the content of the tackifier resin is within the above range, the adhesive strength of the adhesive layer becomes higher, and the shear holding force of the adhesive tape at high temperature becomes higher. The more preferable lower limit of the content of the tackifier resin is 15 parts by weight, the more preferable upper limit is 50 parts by weight, and the further preferable upper limit is 35 parts by weight.

[0047] The adhesive layer may contain additives such as silane coupling agents, plasticizers, softeners, fillers, pigments, dyes, etc. as necessary.

[0048] The adhesive layer has a total content of a compound having a structure represented by the following general formula (A) and a compound having a structure represented by the following general formula (B) of 2% by weight or less.

[0049]

Chemical formula

[0050] In general formulas (A) and (B), R 1 and R 2 represent an alkyl group having 4 to 12 carbon atoms.

[0051] It is preferable that the adhesive layer has a total content of a compound having a structure represented by the general formula (A), a compound having a structure represented by the general formula (B), and a compound having a structure represented by the following general formula (C) of 2% by weight or less.

[0052]

Chemical formula

[0053] In general formula (C), R 1 and R 2 represent an alkyl group having 4 to 12 carbon atoms.

[0054] The compounds having the structure represented by the above general formula (A) and the compounds having the structure represented by the above general formula (B) are compounds that correspond to impurities in the above bio-derived carbon-containing alkyl (meth)acrylate. Therefore, the alkyl(R) of the compounds having the structure represented by the above general formula (A) and the compounds having the structure represented by the above general formula (B) 1 and R 2 ) is preferably the same as the alkyl group of the above-mentioned organism-derived alkyl (meth)acrylate. However, the above-mentioned alkyl group (R 1 and R 2 ) may be different from the alkyl group of the alkyl (meth)acrylate containing carbon of the above-mentioned biological origin. The compound having the structure represented by the above general formula (C) is a compound that corresponds to an impurity in the above bio-derived carbon-containing alkyl (meth)acrylate. Therefore, the alkyl group (R) of the compound having the structure represented by the above general formula (C) 1 and R 2 ) is preferably the same as the alkyl group of the above-mentioned organism-derived alkyl (meth)acrylate. However, the above-mentioned alkyl group (R 1 and R 2 ) may be different from the alkyl group of the alkyl (meth)acrylate containing carbon of the above-mentioned biological origin. The above alkyl group (R 1 and R 2 The alkyl group (R) is not particularly limited as long as it is an alkyl group having 4 to 12 carbon atoms, but it is preferably an alkyl group having 7 to 12 carbon atoms. 1 and R 2 Specifically, examples of these include n-heptyl group, n-octyl group, n-decyl group, lauryl group, etc. In the above general formula (A) and the above general formula (B), R 1 and R 2 They may be the same or different, but it is preferable that they be the same. In the above general formulas (A) to (C), R 1 and R 2 They may be the same or different, but it is preferable that they be the same.

[0055] The compound having the structure represented by the general formula (A) above may consist of only one compound having the structure represented by the general formula (A), or it may consist of multiple compounds having the structure represented by the general formula (A) in combination. Similarly, the compound having the structure represented by the general formula (B) above may consist of only one compound having the structure represented by the general formula (B), or it may consist of multiple compounds having the structure represented by the general formula (B) in combination. Similarly, the compound having the structure represented by the general formula (C) above may consist of only one compound having the structure represented by the general formula (C), or it may consist of multiple compounds having the structure represented by the general formula (C) in combination.

[0056] The compound having the structure represented by the above general formula (A) is more specifically preferably a compound having the structure represented by the following formula (a1).

[0057] [ka]

[0058] The compound having the structure represented by the above general formula (B) is more specifically preferably a compound having the structure represented by the following formula (b1).

[0059] [ka]

[0060] The compound having the structure represented by the above general formula (C) is more specifically preferably a compound having the structure represented by the following formula (c1).

[0061] [ka]

[0062] If the total content of the compound having the structure represented by the above general formula (A) and the compound having the structure represented by the above general formula (B) is 2% by weight or less, the decrease in adhesive strength due to bleed-out of these compounds can be suppressed, and the shear holding strength of the adhesive tape at high temperatures can be increased. Preferably, the total content of the compound having the structure represented by the above general formula (A) and the compound having the structure represented by the above general formula (B) is 1% by weight or less, and more preferably 0.1% by weight or less. The lower limit of the total content of the compound having the structure represented by the above general formula (A) and the compound having the structure represented by the above general formula (B) is not particularly limited, and is preferably as close to 0% by weight as possible, and may be 0% by weight. In other words, the adhesive layer does not have to contain the compound having the structure represented by the above general formula (A) and the compound having the structure represented by the above general formula (B).

[0063] The total content of the compound having the structure represented by the above general formula (A), the compound having the structure represented by the above general formula (B), and the compound having the structure represented by the above general formula (C) is preferably 2% by weight or less. If it is below the above upper limit, the decrease in adhesive strength due to bleed-out of these compounds can be suppressed more effectively, and the shear holding strength of the adhesive tape at high temperatures will be increased. The total content of the compound having the structure represented by the above general formula (A), the compound having the structure represented by the above general formula (B), and the compound having the structure represented by the above general formula (C) is more preferably 1% by weight or less, and even more preferably 0.1% by weight or less. The lower limit of the total content of the compound having the structure represented by the above general formula (A), the compound having the structure represented by the above general formula (B), and the compound having the structure represented by the above general formula (C) is not particularly limited, and is preferably as close to 0% by weight as possible, and may be 0% by weight. In other words, the adhesive layer does not have to contain the compound having the structure represented by the above general formula (A), the compound having the structure represented by the above general formula (B), and the compound having the structure represented by the above general formula (C).

[0064] The total content of compounds having the structure represented by the above general formula (A) and compounds having the structure represented by the above general formula (B), or the total content of compounds having the structure represented by the above general formula (A), compounds having the structure represented by the above general formula (B), and compounds having the structure represented by the above general formula (C), is calculated as follows. The sol component of the adhesive layer in the adhesive tape is extracted using toluene and dried. The obtained sol component is dissolved in deuterated chloroform. 1 H-NMR measurement and 13 By performing 1C-NMR measurements, the content of compounds having the structure represented by the above general formula (A) and compounds having the structure represented by the above general formula (B) can be calculated. By summing these, the total content can be calculated.

[0065] As a method for adjusting the total content of the compound having the structure represented by the above general formula (A) and the compound having the structure represented by the above general formula (B) to the above range, for example, the following method can be used. That is, when using an alkyl (meth)acrylate containing carbon of a specific biological origin as the acrylic monomer constituting the above acrylic copolymer, the content of the above compound contained as an impurity can be reduced by purifying the alkyl (meth)acrylate containing carbon of a specific biological origin. Alternatively, the content of the above compound contained as an impurity can be reduced by purifying the obtained acrylic copolymer, or the content of the above compound can be reduced by adjusting the heating and drying conditions when manufacturing the adhesive tape (for example, when forming the adhesive layer). Among these, it is preferable to purify the alkyl (meth)acrylate containing carbon of a specific biological origin. The method for purifying the alkyl (meth)acrylate and acrylic copolymer described above is not particularly limited, and conventionally known methods can be used, such as distillation, reprecipitation, preparative liquid chromatography, and column chromatography. For the purification of alkyl (meth)acrylates, distillation, preparative liquid chromatography, and column chromatography are preferred, and for the purification of acrylic copolymers, reprecipitation, preparative liquid chromatography, and column chromatography are preferred.

[0066] The content of the compound having the structure represented by the general formula (A) in the adhesive layer is not particularly limited as long as the total content can be adjusted to the above range, but it is preferably less than 1% by weight. If the content of the compound having the structure represented by the general formula (A) is less than 1% by weight, the shear holding force of the adhesive tape at high temperatures will be higher. The lower limit of the content of the compound having the structure represented by the general formula (A) is not particularly limited, and it is preferable to be as close to 0% by weight as possible, and may even be 0% by weight.

[0067] The content of the compound having the structure represented by the general formula (B) in the adhesive layer is not particularly limited as long as the total content can be adjusted to the above range, but it is preferably less than 1% by weight, and more preferably 0.01% by weight or less. If the content of the compound having the structure represented by the general formula (B) is within the above range, the shear holding force of the adhesive tape at high temperatures will be higher. The lower limit of the content of the compound having the structure represented by the general formula (B) is not particularly limited, and it is preferable to be as close to 0% by weight as possible, and may even be 0% by weight.

[0068] The gel fraction of the adhesive layer described above is not particularly limited, but a preferred lower limit is 10% by weight and a preferred upper limit is 70% by weight. If the gel fraction of the adhesive layer is within the above range, the adhesive strength of the adhesive layer will be higher. A more preferred lower limit for the gel fraction of the adhesive layer is 20% by weight and a more preferred upper limit is 50% by weight. The gel fraction of the adhesive layer described above is measured as follows. First, a test specimen is prepared by cutting the adhesive tape into a 20mm x 40mm rectangular shape. The test specimen is then immersed in ethyl acetate at 23°C for 24 hours, removed from the ethyl acetate, and dried at 110°C for 1 hour. The weight of the dried test specimen is measured, and the gel fraction is calculated using the following formula (1). Note that the test specimen does not have a release film laminated on it to protect the adhesive layer. Gel fraction (weight %) = 100 × (W2 - W0) / (W1 - W0) (1) (W0: Weight of the substrate, W1: Weight of the test specimen before immersion, W2: Weight of the test specimen after immersion and drying)

[0069] The method for adjusting the gel fraction of the adhesive layer to the above range is not particularly limited, but it is preferable to adjust the composition and weight-average molecular weight of the acrylic copolymer, as well as the type and amount of the crosslinking agent, as described above.

[0070] The adhesive layer described above preferably contains 10% by weight or more of bio-derived carbon. A bio-derived carbon content of 10% by weight or more is an indicator that a product is "bio-based." A bio-derived carbon content of 10% by weight or more is preferable from the viewpoint of conserving petroleum resources and reducing carbon dioxide emissions. A more preferable lower limit for the bio-derived carbon content is 30% by weight, and an even more preferable lower limit is 60% by weight. The upper limit for the bio-derived carbon content is not particularly limited and may be 100% by weight. Furthermore, while bio-derived carbon contains a certain percentage of the radioactive isotope C-14, petroleum-derived carbon contains almost no C-14. Therefore, the content of bio-derived carbon can be calculated by measuring the concentration of C-14 contained in the adhesive layer. Specifically, this can be measured in accordance with ASTM D6866-20, a standard widely used in the bioplastics industry.

[0071] The thickness of the adhesive layer described above is not particularly limited, but a preferred lower limit is 3 μm and a preferred upper limit is 300 μm. If the thickness of the adhesive layer is within the above range, the adhesive strength of the adhesive layer will be higher. A more preferred lower limit for the thickness of the adhesive layer is 5 μm, and an even more preferred lower limit is 10 μm. A more preferred upper limit for the thickness of the adhesive layer is 200 μm, and an even more preferred upper limit is 100 μm.

[0072] The adhesive tape of the present invention may be a non-support tape without a base material, a single-sided adhesive tape having an adhesive layer on one side of the base material, or a double-sided adhesive tape having adhesive layers on both sides of the base material. The above-mentioned substrate is not particularly limited, and conventionally known substrates can be used, however, in order to increase the content of bio-derived carbon in the adhesive tape as a whole, it is preferable to use a bio-derived substrate. Examples of the above-mentioned bio-derived substrates include films and nonwoven fabrics made from plant-derived polyesters (PES) such as polyethylene terephthalate (PET), polyethylene furanoate (PEF), polylactic acid (PLA), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), and polybutylene succinate (PBS). Also included are films and nonwoven fabrics made from plant-derived polyethylene (PE), polypropylene (PP), polyurethane (PU), triacetylcellulose (TAC), cellulose, and polyamide (PA).

[0073] From the viewpoint of substrate strength, the above-mentioned substrate is preferably a film made of PES or a film made of PA. Furthermore, from the viewpoint of heat resistance and oil resistance, a film made of PA is preferred. Examples of materials that make up a film made of the above-mentioned PA include nylon 11, nylon 1010, nylon 610, nylon 510, nylon 410, etc., which are made from castor oil, and nylon 56, etc., which are made from cellulose.

[0074] Furthermore, from the perspective of reducing environmental impact by decreasing the use of new petroleum resources and suppressing carbon dioxide emissions, base materials made from recycled resources may be used. Methods for recycling resources include, for example, recovering waste from packaging containers, home appliances, automobiles, construction materials, food, etc., or waste generated in the manufacturing process, and using the extracted materials again as raw materials by washing, decontamination, or decomposition by heating or fermentation. Examples of base materials using recycled resources include films and nonwoven fabrics made from PET, PBT, PE, PP, PA, etc., using recovered plastics that have been re-resinated as raw materials. Alternatively, recovered waste may be burned and used as thermal energy for the manufacture of base materials and their raw materials, or the oils and fats contained in the recovered waste may be mixed with petroleum, fractionated, and refined to be used as raw materials.

[0075] The above-mentioned substrate may be a foam substrate from the viewpoint of improving compression characteristics. The foam substrate described above is preferably made of PE, PP, and / or PU, and is more preferably made of PE from the viewpoint of achieving a high degree of both flexibility and strength. Examples of components of the foam substrate made of PE include PE derived from sugarcane.

[0076] The method for producing the foamed substrate described above is not particularly limited, but for example, it is preferable to prepare a foamed resin composition containing a PE resin containing PE made from sugarcane and a foaming agent, and to foam the foaming agent when extruding the foamed resin composition into a sheet using an extruder, and to crosslink the obtained polyolefin foam as needed.

[0077] The thickness of the foam substrate described above is not particularly limited, but a preferred lower limit is 50 μm and a preferred upper limit is 5000 μm. When the thickness of the foam substrate is within this range, it can exhibit high impact resistance while also exhibiting high flexibility that allows it to adhere closely to the shape of the substrate. A more preferred upper limit for the thickness of the foam substrate is 1000 μm, and an even more preferred upper limit is 300 μm.

[0078] The adhesive tape of the present invention has a preferred lower limit for the total thickness of the adhesive tape (sum of the thickness of the base material and the adhesive layer) of 3 μm and a preferred upper limit of 6000 μm. If the total thickness of the adhesive tape is within the above range, the adhesive strength will be higher. A more preferred upper limit for the total thickness of the adhesive tape is 1200 μm, and an even more preferred upper limit is 500 μm.

[0079] 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 method can be used. First, a solution of adhesive A is prepared by adding a solvent to an acrylic copolymer, a radical scavenger, and, if necessary, a crosslinking agent or tackifying resin. This solution of adhesive A is then applied to the surface of the substrate, and the solvent in the solution is completely dried and removed to form adhesive layer A. Next, a release film is placed on top of the formed adhesive layer A with its release-treated surface facing the adhesive layer A. Next, a separate release film is prepared, and a solution of adhesive B, prepared in the same manner as above, is applied to the release surface of this release film. By completely drying and removing the solvent in the solution, a laminated film is created in which adhesive layer B is formed on the surface of the release film. The obtained laminated film is then placed on the back surface of a substrate on which adhesive layer A is formed, with adhesive layer B facing the back surface of the substrate, to create a laminate. Then, by pressing 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 substrate, and the surface of the adhesive layer is covered with a release film.

[0080] Alternatively, two sets of laminated films may be prepared in the same manner, and these laminated films may be superimposed on each of the two sides of a substrate with the adhesive layer of the laminated film facing the substrate to create a laminate. This laminate may then be pressed with a rubber roller or the like to obtain a double-sided adhesive tape having adhesive layers on both sides of the substrate, with the surface of the adhesive layer covered with a release film.

[0081] The applications of the adhesive tape of the present invention are not particularly limited, but because it has a high content of bio-derived carbon and excellent shear holding power at high temperatures, it is preferably used for fixing electronic equipment components or automotive components. Specifically, the adhesive tape of the present invention can be suitably used for adhesive fixing of electronic equipment components in large portable electronic devices, and for adhesive fixing of automotive components (e.g., automotive panels). [Effects of the Invention]

[0082] According to the present invention, it is possible to provide an adhesive tape with a high content of bio-derived carbon and excellent shear holding power at high temperatures. [Modes for carrying out the invention]

[0083] 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.

[0084] <Lauryl acrylate containing bio-derived carbon> Lauryl acrylate was prepared by esterifying lauryl alcohol (manufactured by Kao Corporation), which contains bio-derived carbon, with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.).

[0085] <n-octyl acrylate containing bio-derived carbon> n-octyl acrylate was prepared by esterifying n-octyl alcohol (manufactured by Kao Corporation), which contains bio-derived carbon, with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.).

[0086] <n-heptyl acrylate containing bio-derived carbon> Ricinoleic acid derived from castor oil was cracked to obtain a mixture containing undecylenic acid and heptyl alcohol. Then, by distillation, the undecylenic acid was separated to obtain n-heptyl alcohol containing bio-derived carbon. n-heptyl acrylate was prepared by esterifying the n-heptyl alcohol containing bio-derived carbon with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.). Furthermore, the impurity content was reduced by distilling the n-heptyl acrylate at this stage.

[0087] <Other acrylic monomers> • 2-Ethylhexyl acrylate (manufactured by Mitsubishi Chemical Corporation) • Acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) • 2-hydroxyethyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.)

[0088] <Crosslinking agent> • Isocyanate-based crosslinking agent (Tosoh Corporation, Coronate L-45)

[0089] <Adhesive-granting resin> • Terpene phenol (Terpene phenol G-150, manufactured by Yasuhara Chemical Co., Ltd.)

[0090] (Example 1) (1) Production of acrylic copolymers (solution polymerization) Ethyl acetate was added to the reaction vessel as the polymerization solvent, and after bubbling with nitrogen, the reaction vessel was heated while introducing nitrogen to initiate reflux. Subsequently, a radical polymerization initiator solution, prepared by diluting 0.1 parts by weight of azobisisobutyronitrile 10-fold with ethyl acetate, was added to the reaction vessel, and predetermined amounts of n-heptyl acrylate, acrylic acid, and 2-hydroxyethyl acrylate were added dropwise over 2 hours. After the dropwise addition was complete, the radical polymerization initiator solution, prepared by diluting 0.1 parts by weight of azobisisobutyronitrile 10-fold with ethyl acetate, was added again to the reaction vessel, and the polymerization reaction was carried out for 4 hours to obtain an acrylic copolymer-containing solution.

[0091] Mass spectrometry of the obtained acrylic copolymer and 1 1H-NMR measurements were performed, and the content of constituent units derived from each monomer was calculated from the integral intensity ratio of the hydrogen peaks derived from each monomer.

[0092] The obtained acrylic copolymer was diluted 50-fold with tetrahydrofuran (THF), and the resulting dilution was filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm) to prepare the measurement sample. This measurement sample was supplied to a gel permission chromatograph (Waters, 2690 Separations Module), and GPC measurement was performed under conditions of sample flow rate of 1 mL / min and column temperature of 40°C. The polystyrene-equivalent molecular weight of the acrylic copolymer was measured, and the weight-average molecular weight was determined.

[0093] Furthermore, the glass transition temperature (Tg) of the obtained acrylic copolymer was determined by differential scanning calorimeter (DSC7000X, Hitachi High-Tech Science Corporation) measurement. Specifically, approximately 2 mg of the acrylic copolymer was weighed into an aluminum pan, and the measurement was performed under a nitrogen atmosphere with a heating rate of 10°C / min. The resulting chart was read to determine the glass transition point.

[0094] (2) Manufacturing of adhesive tape To the obtained acrylic copolymer-containing solution, an adhesive solution was prepared by adding an isocyanate-based crosslinking agent (Tosoh Corporation, Coronate L-45) in a solid content of 0.5 parts by weight per 100 parts by weight of the acrylic copolymer. This adhesive solution was applied to the release-treated surface of a 75 μm thick release-treated PET film so that the thickness of the adhesive layer after drying was 50 μm, and then dried at 110°C for 5 minutes. This adhesive layer was then placed on top of the release-treated surface of a 75 μm thick release-treated PET film and cured at 40°C for 48 hours to obtain an adhesive tape (non-support type).

[0095] (3) Total content of compounds having the structure represented by general formula (A) and compounds having the structure represented by general formula (B) The sol component of the adhesive layer in the adhesive tape was extracted using toluene and dried. The obtained sol component was dissolved in deuterated chloroform. 1 H-NMR measurement and 13By performing 1C-NMR measurements, the total content of compounds having the structure represented by general formula (A) and compounds having the structure represented by general formula (B) was calculated. Note that in Tables 1-2, compound a1 is a compound having a structure represented by general formula (A) (R 1 and R 2 (where is an n-heptyl group), and compound a2 is a compound having a structure represented by general formula (A) (R 1 and R 2 (where is an n-octyl group), and compound a3 is a compound having a structure represented by general formula (A) (R 1 and R 2 Compound b1 is a compound having a structure represented by general formula (B) (R 1 and R 2 (where is an n-heptyl group), and compound b2 is a compound having a structure represented by general formula (B) (R 1 and R 2 (where is an n-octyl group), and compound b3 is a compound having a structure represented by general formula (B) (R 1 and R 2 (This is the lauryl group.)

[0096] (4) Total content of compounds having the structure represented by general formula (A), compounds having the structure represented by general formula (B), and compounds having the structure represented by general formula (C) The sol component of the adhesive layer in the adhesive tape was extracted using toluene and dried. The obtained sol component was dissolved in deuterated chloroform. 1 H-NMR measurement and 13 By performing 1C-NMR measurements, the total content of compounds with the structure represented by general formula (A), compounds with the structure represented by general formula (B), and compounds with general formula (C) was calculated. Note that in Tables 1-2, compound c1 is a compound having a structure represented by general formula (C) (R 1 and R 2 (where is an n-heptyl group), and compound c2 is a compound having a structure represented by general formula (C) (R 1 and R 2 (where is an n-octyl group), and compound c3 is a compound having a structure represented by general formula (C) (R1 and R 2 (This is the lauryl group.)

[0097] (5) Measurement of gel fraction The release film was peeled off one side of the adhesive tape and bonded to a 23 μm thick PET film (Futamura Chemical Co., Ltd., FE2002). The tape was then cut into a 20 mm x 40 mm rectangular shape. The release film was then peeled off the other side of the adhesive tape to prepare a test specimen, and its weight was measured. The test specimen was immersed in ethyl acetate at 23°C for 24 hours, then removed from the ethyl acetate and dried at 110°C for 1 hour. The weight of the dried test specimen was measured, and the gel fraction was calculated using (1) below. Gel fraction (weight %) = 100 × (W2 - W0) / (W1 - W0) (1) (W0: Weight of the substrate (PET film), W1: Weight of the test specimen before immersion, W2: Weight of the test specimen after immersion and drying)

[0098] (Examples 2-15, Comparative Examples 1-4) An adhesive tape was obtained in the same manner as in Example 1, except that the type and amount of acrylic monomers constituting the acrylic copolymer, the weight-average molecular weight of the acrylic copolymer, the amount of tackifying resin, and the amount of crosslinking agent were changed as shown in Tables 1 and 2, and the method for manufacturing the adhesive tape was changed as shown below.

[0099] In Examples 3-10 and 15, the alkyl (meth)acrylate containing bio-derived carbon was not purified by distillation to reduce the impurity content. Instead, the resulting acrylic copolymer was reprecipitation by adding an ethyl acetate solution to methanol dropwise. Subsequently, adhesive tape was manufactured using the reprecipitation acrylic copolymer.

[0100] In Example 11, after applying the adhesive solution to the release-treated surface of the PET film, it was dried at 110°C for 20 minutes instead of drying at 110°C for 5 minutes. In Example 12, after applying the adhesive solution to the release-treated surface of the PET film, it was dried at 110°C for 10 minutes instead of drying at 110°C for 5 minutes. In Example 13, n-heptyl acrylate was not distilled after synthesis, but rather a portion of the fraction containing compound a1 was removed using a preparative HPLC (liquid chromatography) apparatus (GL Sciences, Inertsil SIL-150A). In Example 14, n-heptyl acrylate was not distilled after synthesis, but a portion of the fraction containing compound b1 was removed using a preparative HPLC (liquid chromatography) apparatus (GL Sciences, Inertsil SIL-150A) and used.

[0101] In Comparative Examples 1 and 2, neither distillation nor purification using a preparative HPLC system was performed to reduce the content of the alkyl (meth)acrylate impurities containing bio-derived carbon, nor was the resulting acrylic copolymer reprecipitated. In Comparative Example 3, a portion of the fraction containing compound a3 was removed and used. In Comparative Example 4, a portion of the fraction containing compound b1 was removed and used.

[0102] <Rating> The adhesive tapes obtained in the examples and comparative examples were evaluated using the following method. The results are shown in Tables 1 and 2.

[0103] (1) Shear holding force at high temperature (85°C) Adhesive tape was cut to a width of 25 mm and a length of 100 mm. In accordance with JIS Z-1528, one side of the adhesive tape was bonded to a cold-rolled stainless steel plate (SUS304 plate) with a thickness of 1.5 mm, a width of 25 mm, and a length of 100 mm at 23°C. At this time, the bonded length of the adhesive tape was 25 mm, and the adhesive tape was bonded with a vertical offset so that a 75 mm portion of the adhesive tape protruded from the edge of the SUS304 plate. After backing the other side of the adhesive tape with PET film, a 2 kg rubber roller was passed back and forth once to press and create an adhesion test piece. The adhesive test specimens were left in an atmosphere of 23°C and 50% humidity for 20 minutes. Under conditions of 85°C, a 1 kg weight was attached to the protruding portion of the adhesive tape so that a shear load was applied to the obtained adhesive test specimens. If the time from the application of the load until the adhesive tape peeled off and fell was 24 hours or more, it was marked with ◎; if it was 1 hour or more but less than 24 hours, it was marked with ○; and if it was less than 1 hour, it was marked with ×.

[0104] (2) Content of bio-derived carbon The bio-derived carbon content of the adhesive tape was measured in accordance with ASTM D6866-20.

[0105] [Table 1]

[0106] [Table 2] [Industrial applicability]

[0107] According to the present invention, it is possible to provide an adhesive tape with a high content of bio-derived carbon and excellent shear holding power at high temperatures.

Claims

1. An adhesive tape having an adhesive layer containing an acrylic copolymer, The acrylic copolymer contains constituent units derived from alkyl (meth)acrylate containing bio-derived carbon, The adhesive layer has a total content of a compound having the structure represented by the following general formula (A) and a compound having the structure represented by the following general formula (B) that is greater than 0% by weight and less than or equal to 2% by weight. An adhesive tape characterized by the following features. 【Chemistry 1】 In general formulas (A) and (B), R １ and R ２ This represents an alkyl group with 4 to 12 carbon atoms.

2. The adhesive tape according to claim 1, characterized in that the total content of the compound having the structure represented by the general formula (A), the compound having the structure represented by the general formula (B), and the compound having the structure represented by the general formula (C) below exceeds 0% by weight and is 2% by weight or less. 【Chemistry 2】 In general formula (C), R １ and R ２ This represents an alkyl group with 4 to 12 carbon atoms.

3. The adhesive tape according to claim 1 or 2, characterized in that the adhesive layer contains less than 1% by weight of a compound having the structure represented by the general formula (A).

4. The adhesive tape according to claim 1 or 2, characterized in that the compound having the structure represented by the general formula (A) is a compound having the structure represented by the following formula (a1). 【Transformation 3】

5. The adhesive tape according to claim 1 or 2, characterized in that the adhesive layer contains less than 1% by weight of a compound having the structure represented by the general formula (B).

6. The adhesive tape according to claim 2, characterized in that the adhesive layer contains less than 1% by weight of a compound having the structure represented by the general formula (C).

7. The adhesive tape according to claim 1, 2, or 6, characterized in that the compound having the structure represented by the general formula (B) is a compound having the structure represented by the following formula (b1). 【Chemistry 4】

8. The adhesive tape according to claim 2 or 6, characterized in that the compound having the structure represented by the general formula (C) is a compound having the structure represented by the following formula (c1). 【Transformation 5】

9. The adhesive tape according to claim 1, 2, or 6, characterized in that the alkyl (meth)acrylate containing carbon of biological origin contains n-heptyl (meth)acrylate.

10. The adhesive tape according to claim 1, 2, or 6, characterized in that the acrylic copolymer contains 85% by weight or more of constituent units derived from the bio-derived alkyl (meth)acrylate.

11. The adhesive tape according to claim 1, 2, or 6, characterized in that the adhesive layer further contains a tackifying resin.

12. The adhesive tape according to claim 1, 2, or 6, characterized in that the adhesive layer has a bio-derived carbon content of 10% by weight or more.

13. The adhesive tape according to claim 1, 2, or 6, characterized in that it is used for fixing electronic equipment components or in-vehicle components.

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