Copolymers, adhesive compositions, adhesive tapes, and methods of making copolymers

Abstract

A copolymer, an adhesive composition and an adhesive tape using the copolymer, and a manufacturing method of the copolymer, the copolymer being a copolymer obtained by emulsion polymerization, having a first structural unit derived from an alkyl (meth)acrylate and a second structural unit derived from an olefinically unsaturated compound having at least one selected from a carboxyl group and a carboxylate group, the copolymer containing biomass carbon atoms.

Description

Technical Field

[0001] This disclosure relates to copolymers, adhesive compositions, adhesive tapes, and methods for manufacturing copolymers. Background Technology

[0002] Most of the raw materials used to manufacture synthetic resins are compounds derived from fossil fuels such as petroleum, coal, and natural gas. Fossil fuels contain carbon that has been locked underground for a long time. Therefore, the biodegradation or incineration of synthetic resins, releasing carbon dioxide into the atmosphere, will release carbon that is deeply locked underground and does not exist in the atmosphere as carbon dioxide, potentially contributing to global warming.

[0003] Plants are considered carbon sources because they absorb carbon dioxide circulating in the Earth's environment, perform photosynthesis using carbon dioxide and water as raw materials, and act as organisms that assimilate or immobilize carbon dioxide. If plant-derived materials are used as raw materials for synthetic resins, even if they are biodegraded or incinerated to produce carbon dioxide, it is still part of the existing carbon dioxide cycle in the Earth's environment, so the total amount of carbon constituting that carbon dioxide remains unchanged.

[0004] Another representative use of synthetic resins is in adhesives. Adhesives are processed, for example, into adhesive tapes that form a layer containing the adhesive on a substrate, i.e., an adhesive layer, and are then glued to various items for repair or to fix items together.

[0005] Adhesives containing natural rubber are known to be used in applications that utilize biomass-derived materials. However, adhesives containing natural rubber suffer from poor heat resistance and other properties, resulting in insufficient reliability in applications such as electronic components, vehicles, housing, and building materials.

[0006] Adhesive tapes with excellent heat resistance and other properties are widely used, particularly those containing a (meth)acrylic adhesive layer. In such tapes, rosin, terpenes, and other biomass-derived materials can also be used as tackifiers. However, by simply deriving additives from biomass, it is difficult to simultaneously achieve excellent adhesion, holding power, and other properties while increasing the overall carbon content derived from biomass in the adhesive tape.

[0007] Patent Document 1 describes an adhesive tape having an adhesive layer containing a (meth)acrylic copolymer, wherein the (meth)acrylic copolymer comprises structural units derived from (meth)acrylic monomers containing carbon derived from biological sources.

[0008] Patent document 2 describes an adhesive comprising at least a portion of a reaction product of at least one polymerizable monomer derived from a non-petroleum source, a reaction initiator, and a stabilizer.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Application Publication No. 2019-218458

[0012] Patent Document 2: Japanese Patent Application Publication No. 2014-077141 Summary of the Invention

[0013] The problem that the invention aims to solve

[0014] Both the adhesive tape in Patent Document 1 and the particulate adhesive in Patent Document 2 exhibit good adhesion at room temperature, but there is room for improvement in adhesion at high and low temperatures, as well as in retention at high temperatures. Furthermore, the use of organic solvents in the liquid medium may contribute to environmental pollution.

[0015] The purpose of this disclosure is to provide a copolymer comprising biomass carbon atoms, an adhesive composition and adhesive tape using the copolymer, and a method for manufacturing the copolymer, wherein the copolymer has low environmental impact during manufacturing and can form an adhesive layer that exhibits strong adhesion over a wide temperature range from low to high temperatures and excellent retention at high temperatures.

[0016] Methods for solving problems

[0017] [1] A copolymer, obtained by emulsion polymerization, having: The first structural unit derived from alkyl (meth)acrylates; and It originates from the second structural unit of an olefinic unsaturated compound having at least one selected from carboxyl and carboxyl groups. The copolymers described above contain biomass carbon atoms.

[0018] [2] The copolymer described in [1] above has a biomass carbon content of more than 10% as determined by method B in ASTM D6866-22.

[0019] [3] According to the copolymer described in [1] or [2] above, at least one of the structural units included as the first structural unit has an alkyl group containing a carbon atom of biomass.

[0020] [4] According to the copolymer described in [3] above, the carbon atom of the alkyl group comprising the first structural unit described above, which is derived from the alkyl ester of (meth)acrylate, is set as a carbon atom (C). 1A In the case of ), the carbon atoms (C) contained in the above copolymer 1A The total number of biomass carbon contents determined by Method B in ASTM D6866-22 is 20% or more.

[0021] [5] The copolymer according to any one of [1] to [4] above has a glass transition temperature Tg of -80 to 30°C.

[0022] [6] The copolymer according to any one of [1] to [5] above, wherein the first structural unit comprises at least one selected from structural units derived from n-butyl methacrylate, structural units derived from isoamyl methacrylate, structural units derived from n-octyl methacrylate, structural units derived from 2-octyl methacrylate, and structural units derived from lauryl methacrylate.

[0023] [7] The copolymer according to any one of [1] to [6] above further has structural units derived from vinyl ester compounds.

[0024] [8] An adhesive composition comprising the copolymer described in any one of [1] to [7] above and an aqueous medium.

[0025] [9] According to the adhesive composition described in [8] above, the copolymer is dispersed as particles in the aqueous medium to form an emulsion.

[0026]

[10] An adhesive tape comprising a substrate and an adhesive layer formed on the surface of the substrate, The adhesive layer described above is formed using the adhesive composition described in [8] or [9].

[0027]

[11] A method for manufacturing a copolymer, comprising the steps of emulsion polymerization of a monomer comprising an alkyl (meth)acrylate and an olefinically unsaturated compound having at least one selected from carboxyl and carboxyl groups, wherein the copolymer is manufactured by any one of the following methods: At least one of the aforementioned monomers contains biomass carbon atoms.

[0028]

[12] According to the method for manufacturing the copolymer described in

[11] above, the monomer contains an alkyl (meth)acrylate comprising biomass carbon atoms.

[0029]

[13] According to the method for manufacturing the copolymer described in

[12] above, the above-mentioned alkyl methacrylate containing biomass carbon atoms contains biomass carbon atoms in the alkyl group that is combined with (meth)acryloyloxy group.

[0030] The effects of the invention

[0031] According to this disclosure, a copolymer comprising biomass carbon atoms, an adhesive composition using the copolymer and an adhesive tape, and a method for manufacturing the copolymer can be provided, wherein the copolymer has low environmental impact during manufacturing and can form an adhesive layer that exhibits strong adhesion over a wide temperature range from low to high temperatures and excellent retention at high temperatures. Detailed Implementation

[0032] In the following explanation, unless otherwise specified, "surface" refers to "surface (ひょうめん)".

[0033] The term "(meth)acrylic acid system" is a general term for acrylic acid system and methacrylic acid system, and the term "(meth)acrylate" is a general term for acrylic acid ester and methacrylate ester.

[0034] The term "olefin unsaturated compound" refers to a compound containing olefin unsaturated bonds. Unless otherwise specified, "olefin unsaturated bond" refers to an olefin unsaturated bond capable of free radical polymerization.

[0035] In polymers of olefinically unsaturated compounds, structural units derived from a particular olefinically unsaturated compound have the following correspondence: the chemical structure of the portion of the olefinically unsaturated compound other than the olefinically unsaturated bond is identical to the chemical structure of the portion of the polymer other than the portion corresponding to the olefinically unsaturated bond of that structural unit. For example, structural units derived from acrylic acid have the structure shown as -CH2CH(COOH)- in the polymer.

[0036] In the following description, the compound that becomes the source of a structural unit refers to a compound that is in the relationship described above with that structural unit, and does not need to be the same as the compound used in the actual manufacturing process. If, after polymerization, the portion other than the chain corresponding to the olefinic unsaturated bond undergoes a chemical reaction, and the chemical structure of the monomer does not correspond to the chemical structure of the polymer, the chemical structure after polymerization shall be used as the reference. For example, if vinyl acetate is polymerized and then saponified, the chemical structure of the polymer shall be considered as the reference, and the structural unit of the polymer is not derived from the structural unit of vinyl acetate, but from the structural unit of vinyl alcohol.

[0037] Regarding structural units with ionic functional groups such as carboxyl groups, unless otherwise specified, a portion of such a functional group, whether or not it undergoes ion exchange, is a structural unit derived from the same ionic compound. For example, the structural unit represented by -CH2C(CH3)(COONa)-, unless otherwise specified, is a structural unit derived from methacrylic acid.

[0038] The term "carboxylate group" refers to a structure in which the carboxyl group forms a salt, such as -COONa, -COOK, and -COONH4.

[0039] A "dispersion" is a solid-liquid mixture in which a solid that does not dissolve in the liquid but is dispersed as particles in the liquid is present.

[0040] The term "slurry" refers to a fluid in which solid particles such as clay and pigments are suspended in a liquid.

[0041] In the following description, "adhesive force" refers to the force required to peel the adhesive surface from the adhered object. Furthermore, in the following description, "holding force" refers to the force that, for adhesive tapes, etc., resists displacement of the adhesive layer constituting the adhesive surface under a static load in a direction parallel to the adhesive surface.

[0042] The term "biomass" refers to organic resources derived from living organisms, excluding fossil resources.

[0043] The term "biomass compound" refers to compounds derived from biomass.

[0044] The term "biomass carbon atoms" refers to carbon atoms derived from biomass.

[0045] <1. Copolymer>

[0046] The copolymer of this embodiment (hereinafter also referred to as "copolymer (A)") is obtained by emulsion polymerization. Copolymer (A) has a first structural unit derived from an alkyl methacrylate and a second structural unit derived from an olefinic unsaturated compound having at least one selected from carboxyl and carboxyl groups, and contains biomass carbon atoms.

[0047] In addition to the first and second structural units, copolymer (A) may also have other structures that are not equivalent to either the first or second structural unit. Details of these other structures are described below.

[0048] (1-1. Biomass carbon content of copolymer (A))

[0049] The biomass carbon content [%] of copolymer (A) is a value determined by method B in ASTM D6866-22 (hereinafter, sometimes simply referred to as the "ASTM method").

[0050] In Method B of ASTM D6866-22, the biomass carbon content of the analyte is obtained by correcting the modern carbon percentage (pMC, persent of modern carbon) of the analyte, determined by accelerator mass spectrometry (AMS), with the atmospheric correction factor (REF value) described in section 9.4 of the standard.

[0051] Here, the biomass carbon content of copolymer (A) determined by method B in ASTM D6866-22 is defined as "biomass carbon content B". (A) ".

[0052] If the monomers i (i = 1, 2, 3, ...) used for the synthesis of copolymer (A) are... Let the mol fraction of ) be R. i [0 < R] i <1] Let the number of carbon atoms in the molecule of monomer i be C. i Let C be the number of carbon atoms derived from biomass compounds contained in the molecule of monomer i, as determined by the ASTM method described above. Bi These values ​​are related to the above-mentioned biomass carbon content B. (A) Between these points, the following equation (1) holds true.

[0053] B (A) =100×Σ(R) i ×C Bi ) / Σ(R i ×C i (1)

[0054] As biomass carbon content B (A) The copolymer (A) itself can be used as the analytical object of the above ASTM method, or it can be calculated using the above formula (1).

[0055] That is, R is the molar fraction of each monomer used to synthesize copolymer (A). i The number of carbon atoms C contained in each monomer i The number of carbon atoms (C) derived from biomass compounds in each monomer molecule. Bi The calculated biomass carbon content is the same as the biomass carbon content calculated for copolymer (A) using the ASTM method. (A) .

[0056] Biomass carbon content of copolymer (A) B (A) Preferably, it is 10% or more, more preferably 20% or more, even more preferably 30% or more, and even more preferably 40% or more. The above-mentioned biomass carbon content B of copolymer (A) (A) It can be 100%, it can be below 100%, it can be below 80%, or it can be below 60%.

[0057] The above-mentioned biomass carbon content B of copolymer (A) (A) It can be 10-100%, 20-80%, 30-60%, or 40-60%.

[0058] (1-2. Glass transition temperature of copolymer (A))

[0059] The glass transition temperature Tg of copolymer (A) is calculated using the Fox formula based on the glass transition temperatures of the homopolymers of the structural units contained in copolymer (A). Specifically, the glass transition temperature Tg of copolymer (A) is calculated using the Fox formula 1 / Tg = Σ(Xi / Tgi) based on the glass transition temperature Tgi of the homopolymer of each structural unit Mi (i = 1, 2, 3, ...,) and the mass fraction Xi of structural unit Mi in copolymer (A) (ΣXi(all structural units) = 1).

[0060] In the Fox formula, both Tg and Tgi are calculated as values ​​of absolute temperature (K). Here, by converting to 0℃ = 273.15K, the glass transition temperature Tg of copolymer (A) can be obtained as a Celsius temperature.

[0061] The glass transition temperature (Tg) of each homopolymer is the value recorded in the literature "Polymer Handbook (3rd edition, John Wiley & Sons, Inc., 1989)". The glass transition temperature (Tg) of the homopolymer not recorded in this literature is the peak temperature of the DDSC plot obtained by DSC measurement using a differential scanning calorimetry (DSC) apparatus (Hitachi Hightech Siemens EXSTAR DSC / SS7020) at a heating rate of 10 °C / min under a nitrogen atmosphere, as the temperature derivative of the DSC.

[0062] The glass transition temperature (Tg) of copolymer (A) is preferably -80°C or higher, more preferably -65°C or higher, and even more preferably -55°C or higher. This is because it can improve the cohesive strength of the adhesive formed using copolymer (A) and impart better high-temperature retention to the adhesive layer.

[0063] The glass transition temperature (Tg) of copolymer (A) is preferably below 30°C, more preferably below 0°C, further preferably below -20°C, and even more preferably below -35°C. This is because it improves the wettability of the adhesive composition formed using copolymer (A), thereby improving the adhesion of the adhesive layer to the substrate. Furthermore, it improves the flexibility of the adhesive layer formed using copolymer (A), thus increasing the tackiness of the adhesive layer during dry use.

[0064] The glass transition temperature (Tg) of copolymer (A) can be -80 to 30℃, -65 to 0℃, -55 to -20℃, or -55 to -35℃.

[0065] (1-3. First Structural Unit)

[0066] The first structural unit is derived from a (meth)acrylate alkyl ester. Here, the structure of the alkyl group contained in the first structural unit is the same as that of the alkyl group bonded to (meth)acryloyloxy group contained in the (meth)acrylate alkyl ester from which the first structural unit is derived. That is, the alkyl group contained in the first structural unit refers to an alkyl group bonded to an oxygen atom of -COO- directly bonded to the main chain of the copolymer (A).

[0067] The structure of the first structural unit is preferably designed based on the glass transition temperature Tg of the copolymer (A), but is not limited thereto. The alkyl groups contained in the first structural unit may have a straight-chain structure or a branched-chain structure.

[0068] The alkyl group contained in the first structural unit may have 1 or more carbon atoms, or 2 or more carbon atoms, or 4 or more carbon atoms, or 6 or more carbon atoms. Furthermore, the alkyl group contained in the first structural unit may have 20 or fewer carbon atoms, or 15 or fewer carbon atoms, or 10 or fewer carbon atoms.

[0069] The number of carbon atoms in the alkyl group contained in the first structural unit can be 1 to 20, 2 to 15, 4 to 10, or 6 to 10.

[0070] The content of alkyl structural units having 2 to 15 carbon atoms among the structural units included as the first structural unit is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. The content of alkyl structural units having 2 to 15 carbon atoms among the structural units included as the first structural unit may be 100% by mass or less.

[0071] The content of alkyl structural units having 4 to 10 carbon atoms among the structural units included as the first structural unit is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. The content of alkyl structural units having 4 to 10 carbon atoms among the structural units included as the first structural unit may be 100% by mass or less.

[0072] Preferably, at least one of the structural units included as the first structural unit has an alkyl group containing a carbon atom of biomass.

[0073] Here, the carbon atom of the alkyl group derived from (meth)acrylate contained in the first structural unit is set as a carbon atom (C). 1A In the case of ), the carbon atoms (C) contained in copolymer (A) 1A The percentage of biomass carbon content determined by Method B in ASTM D6866-22 out of the total number of biomass is defined as "Biomass Carbon Content B". (1A) ".

[0074] If the monomer Ai (i = 1, 2, 3, ...) corresponding to the first structural unit is used for the synthesis of copolymer (A) Let the mol fraction of ) be R. Ai [0 < R] Ai <1], let the number of carbon atoms contained in the alkyl group of monomer Ai be C Ai Let the number of carbon atoms derived from biomass compounds contained in the alkyl group of monomer Ai, determined by the above ASTM method, be C. BAi Then these values ​​are related to the above biomass carbon content B. (1A) Between [%], the following formula (2) holds true.

[0075] B (1A) =100×Σ(R) Ai ×C BAi ) / Σ(R Ai ×C Ai (2)

[0076] Biomass carbon content B (1A) The alkyl alcohols obtained by saponification of copolymer (A) can be determined by analysis using the aforementioned ASTM method. Alternatively, the number of carbon atoms (C) of the biomass compound-derived portion of the alkyl group in monomer Ai can be determined by analyzing the alkyl alcohols obtained by saponification of monomer using the aforementioned ASTM method. BAi , which is calculated using the above formula (2).

[0077] The above biomass carbon content B (1A)Preferably, it is 20% or more, more preferably 30% or more, even more preferably 40% or more, even more preferably 50% or more, and particularly preferably 65% ​​or more.

[0078] The above biomass carbon content B (1A) It can be 100%, it can be below 100%, it can be below 90%, or it can be below 65%.

[0079] The above biomass carbon content B (1A) It can be 20-100%, 30-90%, 40-65%, 50-65%, or 65-90%.

[0080] The alkyl group containing biomass carbon atoms may have 1 or more carbon atoms, 2 or more carbon atoms, 4 or more carbon atoms, or 6 or more carbon atoms. Furthermore, the alkyl group containing biomass carbon atoms may have 20 or fewer carbon atoms, 15 or fewer carbon atoms, or 10 or fewer carbon atoms.

[0081] The number of carbon atoms in the alkyl group containing biomass carbon atoms can be 1–20, 2–15, 4–10, or 6–10.

[0082] The alkyl group containing biomass carbon atoms preferably contains only biomass carbon atoms.

[0083] Examples of compounds that serve as the source of the first structural unit include methyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, isoamyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, 2-octyl methacrylate, lauryl methacrylate, tridecyl methacrylate, and stearyl methacrylate. The compound serving as the source of the first structural unit can be one or more compounds.

[0084] The first structural unit preferably comprises at least one structural unit selected from methyl methacrylate, n-butyl methacrylate, isoamyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, 2-octyl methacrylate, and lauryl methacrylate. More preferably, it comprises at least one structural unit selected from n-butyl methacrylate, isoamyl methacrylate, n-octyl methacrylate, 2-octyl methacrylate, and lauryl methacrylate. More preferably, it comprises at least one structural unit selected from n-butyl methacrylate and 2-octyl methacrylate.

[0085] (1-4. Structural Unit 2)

[0086] The second structural unit is derived from a structural unit of an olefinic unsaturated compound having at least one selected from carboxyl and carboxyl groups. The number of carboxyl or carboxyl groups contained in the second structural unit is not particularly limited; it can be one or two.

[0087] Examples of compounds that can serve as the source of the second structural unit include (meth)acrylic acid, 2-carboxyethyl (meth)acrylate, itaconic acid, and maleic acid. There can be one or more compounds that serve as the source of the second structural unit.

[0088] The second structural unit may or may not contain biomass carbon atoms.

[0089] The second structural unit preferably comprises a structural unit derived from a compound having at least one of a carboxyl group and a carboxyl group and an acryloyl group, and more preferably comprises a structural unit derived from (meth)acrylic acid.

[0090] The content of structural units derived from (meth)acrylic acid among the structural units included as the second structural unit is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. The content of structural units derived from (meth)acrylic acid among the structural units included as the second structural unit may be 100% by mass or less.

[0091] (1-5. Other structures)

[0092] Other structures that copolymer (A) can have include structural units that are not equivalent to either the first structural unit or the second structural unit (hereinafter also referred to as "other structural units"); terminal structures derived from polymerization initiators, chain transfer agents, etc.; etc.

[0093] [Other structural units]

[0094] Compounds that can serve as sources of other structural units are not particularly limited, but examples include vinyl esters such as vinyl acetate, vinyl formate, vinyl propionate, and branched alkane vinyl versatate; conjugated diene compounds such as butadiene, isoprene, and chloroprene; vinyl compounds containing aminoimide groups such as 1,1,1-trimethylamine methacrylamide; (meth)acrylamide compounds such as (meth)acrylamide, N-methyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, and N,N-dimethylaminopropyl(meth)acrylamide; 3-methacryloyloxypropylmethyldimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, and vinyl... Vinyl compounds containing alkoxysilanes, such as tris(β-methoxyethoxy)silane; vinyl compounds containing epoxy groups, such as glycidyl acrylate, glycidyl vinyl ether, and glycidyl (meth)allyl ether; olefinic unsaturated compounds with carbonyl groups, such as diacetone acrylamide, methyl vinyl ketone, phenyl vinyl ketone, ethyl vinyl ketone, n-propyl vinyl ketone, isopropyl vinyl ketone, n-butyl vinyl ketone, and tert-butyl vinyl ketone; light stabilizers with free radical polymerization properties, such as 1,2,2,6,6-pentamethyl-4-piperidinyl methacrylate; polymerizable surfactants; etc. The compound that serves as the source of other structural units can be one or more.

[0095] When the copolymer (A) has the other structural units mentioned above, it is preferable to have structural units derived from vinyl ester compounds, and more preferably structural units derived from ethyl acetate.

[0096] When the copolymer (A) has structural units derived from vinyl ester compounds, the content of these structural units in the copolymer (A) is preferably 1.0% by mass or more, more preferably 2.5% by mass or more, and even more preferably 4.0% by mass or more. This is because the adhesive containing the copolymer (A) exhibits increased adhesion at room temperature.

[0097] When the copolymer (A) has structural units derived from vinyl ester compounds, the content of these structural units in the copolymer (A) is preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 8.0% by mass or less. This is because the adhesive containing the copolymer (A) exhibits increased adhesion at room temperature.

[0098] When the copolymer (A) has structural units derived from vinyl ester compounds, the content of structural units derived from vinyl ester compounds in the copolymer (A) can be 1.0 to 15% by mass, 2.5 to 10% by mass, or 4.0 to 8.0% by mass.

[0099] Polymerizable surfactants that serve as a source of other structural units are compounds that have olefinically unsaturated bonds and also function as surfactants. Polymerizable surfactants can be nonionic, anionic, or cationic, but are preferably anionic. Examples of anionic polymerizable surfactants include ether sulfate (salt) types, ether sulfate ammonium salts, and phosphate ester types, among which ether sulfate ammonium salts are preferred.

[0100] When the copolymer (A) has structural units derived from the polymerizable surfactant, the content of the structural units derived from the polymerizable surfactant in the copolymer (A) is preferably 0.10% by mass or more, more preferably 0.30% by mass or more, and even more preferably 0.60% by mass or more. This is because it improves the dispersion stability of the copolymer (A).

[0101] When the copolymer (A) has structural units derived from the polymerizable surfactant, the content of the structural units derived from the polymerizable surfactant in the copolymer (A) is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and even more preferably 1.5% by mass or less. This is because the target function of the copolymer (A) is obtained more effectively.

[0102] When the copolymer (A) has structural units derived from polymerizable surfactants, the content of structural units derived from polymerizable surfactants in the copolymer (A) can be 0.10 to 5.0% by mass, 0.30 to 3.0% by mass, or 0.60 to 1.5% by mass.

[0103] The copolymer (A) may further have structural units other than those illustrated above.

[0104] [End structure]

[0105] The copolymer (A) may have end structures derived from polymerization initiators, chain transfer agents, etc.

[0106] The content of the terminal structure in the copolymer (A) is preferably 0.50 parts by mass or less relative to the total mass of 100 parts by mass of the structural units contained in the copolymer (A). When the content of the terminal structure in the copolymer (A) is 0.50 parts by mass or less relative to the total mass of 100 parts by mass of the structural units contained in the copolymer (A), the presence of the terminal structure can be ignored when calculating the content of each structural unit and the carbon content of various biomass.

[0107] Details about the polymerization initiators and chain transfer agents that become the source of the terminal structures are described below.

[0108] (1-6. Content of each structural unit in copolymer (A))

[0109] The content of the first structural unit in copolymer (A) is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. This is because it can suppress the rise in the glass transition temperature of copolymer (A), thereby improving the adhesion, wettability, and bonding strength of the adhesive layer.

[0110] The content of the first structural unit in copolymer (A) is preferably 98% by mass or less, more preferably 95% by mass or less, and even more preferably 93% by mass or less. This is because the polarity of copolymer (A) and the cohesive force of adhesive layer are moderately maintained, thereby obtaining an adhesive layer with high adhesion not only at room temperature but also at high and low temperatures.

[0111] The content of the first structural unit in copolymer (A) can be 60-98% by mass, 70-95% by mass, or 80-93% by mass.

[0112] The content of the second structural unit in copolymer (A) is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, and even more preferably 3.0% by mass or more. This is because it can improve the cohesive strength of the adhesive layer containing copolymer (A) and enhance its holding power at high temperatures.

[0113] The content of the second structural unit in copolymer (A) is preferably 12% by mass or less, more preferably 9.0% by mass or less, and even more preferably 6.0% by mass or less. This is because it can suppress the rise in the glass transition temperature of copolymer (A), thereby improving the adhesion, wettability, and bonding strength of the adhesive layer.

[0114] The content of the second structural unit in copolymer (A) can be 1.0 to 12% by mass, 2.0 to 9.0% by mass, or 3.0 to 6.0% by mass.

[0115] The total content of the first and second structural units in copolymer (A) is preferably 65% ​​by mass or more, more preferably 75% by mass or more, even more preferably 85% by mass or more, and can be 90% by mass or more. This is because it can suppress the rise in the glass transition temperature of copolymer (A), thereby improving the adhesion, wettability, and bonding strength of the adhesive layer. The total content of the first and second structural units in copolymer (A) can be 100% by mass or less.

[0116] <2. Methods for manufacturing copolymers>

[0117] The method for manufacturing copolymer (A) according to this embodiment is a method for manufacturing copolymer, which includes a step of emulsion polymerization of a monomer (hereinafter also referred to as "raw material monomer of copolymer (A)") comprising an alkyl methacrylate and an olefinic unsaturated compound having at least one selected from carboxyl and carboxylate groups, wherein at least one of the monomers comprises biomass carbon atoms.

[0118] By manufacturing copolymer (A) using emulsion polymerization, a high molecular weight copolymer (A) can be obtained. This high molecular weight copolymer (A) can improve the cohesive force of the adhesive and impart superior high-temperature retention to the adhesive layer. Furthermore, as described later, emulsion polymerization can be carried out in an aqueous medium, thus reducing the environmental impact during manufacturing.

[0119] (2-1: Monomer)

[0120] At least one of the raw material monomers of copolymer (A) contains biomass carbon atoms.

[0121] Here, the biomass carbon content of the entire raw material monomers of copolymer (A) obtained by method B in ASTM D6866-22 is defined as "biomass carbon content B". (M) ".

[0122] If the raw material monomers i (i = 1, 2, 3, ...) of copolymer (A) are... Let the mol fraction of ) be R. i [0 < R] i <1] Let the number of carbon atoms in the molecule of monomer i be C. i Let C be the number of carbon atoms derived from biomass compounds contained in the molecule of monomer i, as determined by the ASTM method described above. Bi Then, these values ​​are related to the overall biomass carbon content B of the raw material monomers of copolymer (A). (M) Between these points, the following equation (3) holds true.

[0123] B (M) =100×Σ(R) i ×CBi ) / Σ(R i ×C i (3)

[0124] Biomass carbon content B (M) Alternatively, the raw material monomers of copolymer (A) can be used as the analytical object in Method B of ASTM D6866-22 to determine the composition, or it can be calculated using the above formula (3).

[0125] The above biomass carbon content B (M) Preferably, it is 10% or more, more preferably 20% or more, even more preferably 30% or more, and even more preferably 40% or more.

[0126] The above biomass carbon content B (M) It can be 100%, it can be below 100%, it can be below 80%, or it can be below 60%.

[0127] The above biomass carbon content B (M) It can be 10-100%, 20-80%, 30-60%, or 40-60%.

[0128] The monomers of copolymer (A) preferably contain alkyl (meth)acrylates comprising biomass carbon atoms. More preferably, the alkyl (meth)acrylates comprising biomass carbon atoms contain biomass carbon atoms in the alkyl group bonded to (meth)acryloyloxy group.

[0129] Here, the carbon atom contained in the alkyl group of the (meth)acrylate contained in the raw material monomer of copolymer (A) is designated as C. (1M) In the case of copolymer (A), the C contained in the raw material monomers is... (1M) The biomass carbon content determined by Method B in ASTM D6866-22 out of the total is defined as "Biomass Carbon Content B". (1M) ".

[0130] If the alkyl methacrylate Ai (i = 1, 2, 3, ...) contained in the raw material monomers of copolymer (A) Let the mol fraction of ) be R. Ai [0 < R] Ai <1], let the number of carbon atoms contained in the alkyl group of (meth)acrylate Ai be C. Ai Let the number of carbon atoms derived from biomass compounds contained in the alkyl group of monomer Ai be C. BAi Then these values ​​are related to the above biomass carbon content B. (1M) Between [%], the following equation (4) holds true.

[0131] B(1M) =100×Σ(R) Ai ×C BAi ) / Σ(R Ai ×C Ai (4)

[0132] Biomass carbon content B (1M) The alkyl alcohol obtained by saponifying the monomers of copolymer (A) can be determined by analysis using Method B in ASTM D6866-22. Alternatively, the number of carbon atoms C in the alkyl group of the aforementioned "(meth)acrylate alkyl ester Ai" can be determined by analyzing the alkyl alcohol obtained by saponifying the monomers using Method B in ASTM D6866-22. Ai ”, which is calculated using the above formula (4).

[0133] Biomass carbon content B (1M) Preferably, it is 20% or more, more preferably 30% or more, even more preferably 40% or more, even more preferably 50% or more, and particularly preferably 65% ​​or more.

[0134] Biomass carbon content B (1M) It can be 100%, it can be below 100%, it can be below 90%, or it can be below 65%.

[0135] Biomass carbon content B (1M) It can be 20-100%, 30-90%, 40-65%, 50-65%, or 65-90%.

[0136] The (meth)acrylate alkyl ester and the olefin unsaturated compound having at least one selected from carboxyl and carboxyl groups included as raw material monomers of copolymer (A) are described in the same manner as the (meth)acrylate alkyl ester that serves as the source of the first structural unit and the olefin unsaturated compound having at least one selected from carboxyl and carboxyl groups that serves as the source of the second structural unit in copolymer (A) of this embodiment described above, and suitable schemes are also the same.

[0137] (2-2: The process of emulsion polymerization)

[0138] The manufacturing method of this embodiment includes a step of emulsion polymerization of a monomer comprising an alkyl methacrylate and an olefinic unsaturated compound having at least one selected from carboxyl and carboxylate groups.

[0139] The content of alkyl (meth)acrylate in the total amount (100% by mass) of the raw material monomers of copolymer (A) is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. This is because it can suppress the rise in the glass transition temperature of the obtained copolymer (A), thereby improving the adhesion, wettability, and bonding strength of the adhesive layer.

[0140] The content of alkyl (meth)acrylate in the total amount (100% by mass) of the raw material monomers of copolymer (A) is preferably 98% by mass or less, more preferably 95% by mass or less, and even more preferably 93% by mass or less. The reason is that the polarity of the obtained copolymer (A) and the cohesive force of the adhesive layer are moderately maintained, so as to obtain an adhesive layer with high adhesion not only at room temperature but also at high and low temperatures.

[0141] The content of alkyl methacrylate in the total amount (100% by mass) of the raw material monomers of copolymer (A) can be 60-98% by mass, 70-95% by mass, or 80-93% by mass.

[0142] The content of an olefinic unsaturated compound having at least one selected from carboxyl and carboxyl groups in the total amount (100% by mass) of the raw material monomers of copolymer (A) is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, and even more preferably 3.0% by mass or more. This is because it can improve the cohesive strength of the adhesive layer containing the resulting copolymer (A) and enhance its holding power at high temperatures.

[0143] The content of an olefinic unsaturated compound having at least one selected from carboxyl and carboxyl groups in the total amount (100% by mass) of the raw material monomers of copolymer (A) is preferably 12% by mass or less, more preferably 9.0% by mass or less, and even more preferably 6.0% by mass or less. This is because it can suppress the rise in the glass transition temperature of copolymer (A), thereby improving the adhesion, wettability, and bonding strength of the adhesive layer.

[0144] The content of an olefinic unsaturated compound having at least one selected from carboxyl and carboxylate groups in the total amount (100% by mass) of the raw material monomers of copolymer (A) can be 1.0 to 12% by mass, 2.0 to 9.0% by mass, or 3.0 to 6.0% by mass.

[0145] The total content of alkyl (meth)acrylate and olefinic unsaturated compounds having at least one selected from carboxyl and carboxyl groups in the total amount (100% by mass) of the raw material monomers of copolymer (A) is preferably 65% ​​by mass or more, more preferably 75% by mass or more, and even more preferably 85% by mass or more. This can suppress the rise in the glass transition temperature of the obtained copolymer (A), thereby improving the tack, wettability, and adhesion of the adhesive layer.

[0146] The total content of alkyl methacrylate and olefinic unsaturated compounds having at least one selected from carboxyl and carboxylate groups in the total amount (100% by mass) of the raw material monomers of copolymer (A) can be more than 90% by mass, more than 100% by mass, or less than 100% by mass.

[0147] In emulsion polymerization, polymerization initiators can be used to promote the polymerization reaction, chain transfer agents can be used to control the molecular weight and molecular weight distribution of the copolymer (A) within an appropriate range, and emulsifiers can be used to emulsify the monomers.

[0148] The raw material monomers for copolymer (A) can be added in full to the reactor beforehand, and polymerization can be carried out while they are being supplied continuously or intermittently, from the viewpoint of obtaining uniform particles. The raw material monomers supplied continuously or intermittently can be a portion or all of the raw material monomers for copolymer (A). The polymerization temperature is not particularly limited, but is preferably 5 to 100°C, more preferably 50 to 90°C.

[0149] In the manufacturing method of this embodiment, the emulsion polymerization of the monomer is preferably carried out in an aqueous medium. This yields a copolymer-containing liquid (copolymer dispersion), i.e., an emulsion, in which the copolymer (A) is dispersed as emulsion particles in an aqueous medium.

[0150] The aqueous medium is water, a hydrophilic organic solvent, or a mixture thereof. Examples of hydrophilic organic solvents include methanol, ethanol, isopropanol, and N-methylpyrrolidone. From the viewpoint of polymerization stability, water is preferred as the aqueous medium. Alternatively, a mixture of water and a hydrophilic solvent can be used as the aqueous medium, provided that polymerization stability is not compromised.

[0151] Examples of polymerization initiators include persulfate-based initiators such as potassium persulfate and ammonium persulfate; water-soluble azo-based initiators such as 2,2'-azobis(2-methylpropanediamine) dihydrochloride; organic peroxides such as tert-butyl hydroperoxide and cumene hydroperoxide; and hydrogen peroxide. Only one type of polymerization initiator may be used, or two or more types may be used. The amount of polymerization initiator used is not particularly limited, but is preferably 0.1 to 2.0 parts by mass relative to 100 parts by mass of the raw material monomers of copolymer (A).

[0152] Furthermore, reducing agents can be used in conjunction with polymerization initiators as needed. Examples of such reducing agents include reducing organic compounds such as ascorbic acid, tartaric acid, citric acid, glucose, and formaldehyde sulfoxylate; reducing inorganic compounds such as sodium thiosulfate, sodium sulfite, sodium bisulfite, and sodium metabisulfite; etc. Only one reducing agent may be used, or two or more may be used.

[0153] Examples of chain transfer agents include n-dodecyl mercaptan, tert-dodecyl mercaptan, n-butyl mercaptan, 2-ethylhexyl mercaptoacetic acid, 2-mercaptoethanol, β-mercaptopropionic acid, methanol, n-propanol, isopropanol, tert-butanol, and benzyl alcohol. One or more chain transfer agents may be used.

[0154] The amount of chain transfer agent used is preferably 5.0 parts by mass or less, more preferably 2.0 parts by mass or less, even more preferably 0.50 parts by mass or less, and even more preferably 0.30 parts by mass or less, relative to 100 parts by mass of the raw material monomers of copolymer (A). This is because the increased cohesive force of the adhesive can improve the retention force of the adhesive layer at high temperatures.

[0155] The amount of chain transfer agent used relative to 100 parts by mass of the total monomer can be more than 0.01 parts by mass or more than 0.05 parts by mass. This is because it can improve the adhesion of the adhesive layer.

[0156] Examples of emulsifiers include anionic surfactants such as sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and sodium polyoxyethylene alkyl ether sulfate; nonionic surfactants such as polyoxyethylene alkyl ethers and polyoxyethylene nonylphenyl ethers; and cetyltrimethylammonium bromide and laurylpyridine. Cationic surfactants such as chlorides; amphoteric surfactants such as lauryl betaine; the aforementioned polymeric surfactants; etc. One or more of these surfactants may be used.

[0157] There is no particular limitation on the amount of emulsifier used, but it is preferably 0.1 to 6.0 parts by mass relative to 100 parts by mass of the total monomer, and more preferably 1.0 to 4.0 parts by mass.

[0158] Furthermore, when calculating the content of each structural unit of copolymer (A) and the content of various biomass carbons, polymerizable surfactants are classified as monomers of copolymer (A) and their presence is taken into account. On the other hand, emulsifiers other than polymerizable surfactants are not classified as monomers of copolymer (A) and their presence is ignored.

[0159] <3. Adhesive Composition>

[0160] The adhesive composition involved in this embodiment includes the copolymer (A) of this embodiment and an aqueous medium (hereinafter also referred to as "aqueous medium (B)").

[0161] The adhesive composition described in this embodiment may contain other additives.

[0162] Examples of adhesive compositions in this embodiment include solutions, dispersions (e.g., emulsions), slurries, etc., but are not limited to these.

[0163] In the adhesive composition, the copolymer (A) is preferably dispersed as particles in an aqueous medium to form an emulsion.

[0164] (3-1. Aqueous medium (B))

[0165] The aqueous medium (B) is water, a hydrophilic organic solvent, or a mixture thereof. Examples of hydrophilic organic solvents include methanol, ethanol, isopropanol, and N-methylpyrrolidone. Among these, water is preferred as the aqueous medium (B). The aqueous medium used for the polymerization of the aqueous medium (B) and the copolymer (A) can have the same composition or different compositions. Only one type of aqueous medium (B) may be used, or two or more types may be used.

[0166] (3-2. Other additives)

[0167] Other additives that can be used appropriately include, for example, pH adjusters, thickeners, plasticizers, antioxidants, fillers, pigments, colorants, wetting agents, defoamers, thickeners, and crosslinking agents. Only one type of these additives may be used, or two or more may be used.

[0168] Examples of tackifiers include rosin resin, rosin ester resin, hydrogenated rosin resin, polymerized rosin resin, α-pinene resin, β-pinene resin, terpene phenol resin, C5 fraction petroleum resin, C9 fraction petroleum resin, C5 / C9 fraction petroleum resin, dicyclopentadiene petroleum resin, alkylphenol resin, xylene resin, coumarone resin, and coumarone-indene resin. One type of tackifier may be used, or two or more may be used.

[0169] (3-3. Concentration of non-volatile components in the adhesive composition, etc.)

[0170] The concentration of non-volatile components in the adhesive composition is preferably 20% by mass or more, more preferably 40% by mass or more, and even more preferably 60% by mass or more. This is because more adhesive layers can be formed with a smaller coating amount of the adhesive composition. Furthermore, the drying time of the coated adhesive composition is shortened, thus improving productivity.

[0171] Furthermore, the "non-volatile component" of the adhesive composition is the residue remaining after weighing 1g of the adhesive composition in a 5cm diameter aluminum dish and drying it at 105°C for 1 hour under air circulation in a desiccator at 1 atmosphere (1013hPa). In addition, the so-called "non-volatile component concentration" of the adhesive composition is the ratio (mass%) of the mass of the non-volatile component after drying under the above conditions to the mass (1g) of the adhesive composition before drying.

[0172] The concentration of the non-volatile component in the adhesive composition is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 75% by mass or less. This is because it can more effectively suppress the gelation of the copolymer (A) in the adhesive composition.

[0173] The concentration of non-volatile components in the adhesive composition can be 20–90% by mass, 40–80% by mass, or 60–75% by mass.

[0174] The content of copolymer (A) in the non-volatile component of the adhesive composition is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more. This is because the adhesive layer containing copolymer (A) has improved adhesion and holding power, especially holding power at high temperatures.

[0175] The content of copolymer (A) in the non-volatile component of the adhesive composition is preferably 95% by mass or less, more preferably 92% by mass or less. This is because the adhesive layer containing copolymer (A) has improved adhesion and holding power, especially adhesion at room temperature and high temperature.

[0176] The content of copolymer (A) in the non-volatile component of the adhesive composition can be 50-95% by mass, 60-92% by mass, or 70-92% by mass.

[0177] (3-4. Method for manufacturing adhesive composition)

[0178] The method for manufacturing the adhesive composition of this embodiment is not particularly limited. For example, a method of mixing an emulsion containing emulsified particles comprising copolymer (A) and water with the other additives described above, which may be used as needed, is also possible. The timing of adding the other additives is not particularly limited.

[0179] (3-5. Application of adhesive compositions in products)

[0180] The adhesive composition of this embodiment is not particularly limited and can be used, for example, for adhesive tape, adhesive sheet, adhesive label, self-adhesive label, liquid adhesive, etc.

[0181] <4. Adhesive Layer and Adhesive Tape>

[0182] The adhesive layer in this embodiment is an adhesive layer formed using the adhesive composition of this embodiment.

[0183] The adhesive layer of this embodiment is formed on the substrate, for example, by applying the adhesive composition of this embodiment to the substrate, drying it, and performing a crosslinking reaction as needed.

[0184] The drying conditions after applying the adhesive composition of this embodiment to the substrate are not particularly limited. For example, drying at 80 to 110°C for 1 to 5 minutes is preferred. Alternatively, the substrate can be left to stand at 20 to 50°C for more than one day after drying, if necessary.

[0185] The concentration of non-volatile components in the adhesive layer is preferably 95% by mass or more, more preferably 97% by mass or more, even more preferably 99% by mass or more, and can be 100% by mass or less.

[0186] The thickness of the adhesive layer is not particularly limited; it can be 5–200 μm, 10–100 μm, or 20–50 μm.

[0187] The adhesive tape of this embodiment includes a substrate and an adhesive layer formed on the surface of the substrate, wherein the adhesive layer is formed using the adhesive composition of this embodiment.

[0188] The adhesive layer can be formed on only one side of the substrate or on both sides.

[0189] As a substrate, there are no particular limitations; examples include resin films such as polyethylene terephthalate (PET) films; fabrics; non-woven fabrics; metal foils; etc.

[0190] In addition to the substrate and adhesive layer, the adhesive tape may have other layers (e.g., intermediate layer, primer layer, etc.) without impairing the effect of the invention. Furthermore, the adhesive layer of the adhesive tape can be protected by known release liner such as release paper or release PET.

[0191] The adhesive tape of this embodiment is described in the same manner as the adhesive layer of this embodiment described above.

[0192] <5. Uses of adhesive compositions, adhesive layers and adhesive tapes>

[0193] The adhesive composition, adhesive layer, and adhesive tape of this embodiment can be used in various applications and fields such as packaging, joining, fixing, protecting, decorating, and transporting various articles. Furthermore, there are no particular limitations on the material of the object to which the adhesive composition, adhesive layer, and adhesive tape of this embodiment are applied (the adhered object), and examples include plastics, metals, glass, wood, ceramics, paper, and cloth, enabling its wide application.

[0194] Example

[0195] Hereinafter, embodiments and comparative examples of this implementation will be described. However, this implementation is not limited to this embodiment.

[0196] <1. Preparation of copolymer and adhesive compositions>

[0197] (Example 1)

[0198] In a polymerization apparatus equipped with a stirrer, thermometer, and reflux condenser, 23 parts by mass of ion-exchanged water were heated to 80°C under a nitrogen atmosphere. While stirring, the ion-exchanged water in the polymerization apparatus was kept at 80°C, and 2.0 parts by mass of a 5.0% by mass potassium persulfate aqueous solution was added as a polymerization initiator, resulting in a mixture containing the polymerization initiator.

[0199] A monomer emulsion (1), comprising 20 parts by mass of ion-exchanged water, and the amounts of "Adekalase SR-10" (trade name, manufactured by ADEKA Co., Ltd., an ether sulfate type ammonium salt, a polymerizable surfactant) and "Ratimul E-118B" (trade name, manufactured by Kao Corporation, a polyoxyethylene alkyl ether sulfate sodium sulfate) shown in the first stage of Table 1, and monomers and chain transfer agents of the types and amounts shown in the first stage of Table 1, was added dropwise over 4 hours to a mixture containing a polymerization initiator in the polymerization apparatus. Simultaneously with the start of the addition of the monomer emulsion (1), 20 parts by mass of a 2.5% potassium persulfate aqueous solution was added dropwise over 4 hours. In addition, during the addition of the monomer emulsion (1), the mixture in the polymerization apparatus was stirred at 120 revolutions per minute, and the liquid temperature was maintained at 80°C. After the addition was completed, the reaction was carried out at 80°C for 1 hour with continued stirring. This process is designated as the first stage of polymerization.

[0200] Then, monomer emulsion (2), containing the types and amounts of monomers and chain transfer agents shown in Table 1 for Stage 2, was added dropwise over 2 hours. Simultaneously with the start of the addition of monomer emulsion (2), 20 parts by mass of a 2.5% potassium persulfate aqueous solution were added dropwise over 2 hours. Furthermore, during the addition of monomer emulsion (2), the mixture in the polymerization apparatus was stirred at 120 rpm, and the liquid temperature was maintained at 80°C. After the addition was completed, the reaction was continued at 80°C for 1 hour with stirring. This process is designated as Stage 2 polymerization.

[0201] The mixture in the polymerization apparatus was then cooled to 25°C. Ammonia was added as a neutralizing agent to adjust the pH to 6.0, resulting in an emulsion containing emulsified particles of copolymer (A) and water.

[0202] To 100 parts by weight of the obtained emulsion, 7.5 parts by weight of "Hariestar SK-70D" (trade name, manufactured by Harima Chemical Group Co., Ltd., a rosin ester resin) as a tackifier and 2.0 parts by weight of "Adekano UH-420" (trade name, manufactured by ADEKA Co., Ltd., a nonionic thickener) as a thickener were added to obtain an adhesive composition.

[0203] (Examples 2-5 and Examples 7-9)

[0204] The monomers and chain transfer agents were mixed as described in Table 1, and otherwise operated in the same manner as in Example 1, to obtain the copolymer and adhesive compositions of Examples 2-5 and Examples 7-9.

[0205] (Example 6)

[0206] Regarding the first stage of polymerization, the monomer and chain transfer agent were mixed as described in Table 1. Otherwise, the process was the same as in Example 1, without performing the second stage of polymerization. The subsequent steps were the same as in Example 1, resulting in the copolymer and adhesive composition of Example 6.

[0207] (Comparative Examples 1-2)

[0208] The monomer and chain transfer agent were mixed as described in Table 1, and otherwise operated in the same manner as in Example 1, to obtain the copolymer and adhesive compositions of Comparative Examples 1-2.

[0209] (Comparative Example 3)

[0210] In Comparative Example 3, a copolymer was prepared in toluene via solution polymerization. Specifically, a mixed solution containing 120 parts by mass of toluene and monomers and chain transfer agents of the types and amounts shown in Stage 1 of Table 1 was heated to 70°C under a nitrogen atmosphere in a polymerization apparatus equipped with a stirrer, thermometer, and reflux condenser. While stirring the mixed solution in the polymerization apparatus and maintaining it at 70°C, 1.0 part by mass of 2,2'-azobisisobutyronitrile (2,2'-Azobisisobutyronitrile) was added as a polymerization initiator. After reacting the mixed solution at 70°C for 5 hours with stirring, the mixed solution in the polymerization apparatus was cooled to 25°C to obtain the copolymer. Furthermore, in the above reaction, and after the reaction, the monomers and the polymer as the product were uniformly dissolved in the solvent.

[0211] The subsequent procedures were performed in the same manner as in Example 1 to obtain the adhesive composition of Comparative Example 3.

[0212] (Comparative Example 4)

[0213] The monomer and chain transfer agent were mixed as described in Table 1. Otherwise, the same procedure as in Comparative Example 3 was followed to obtain the copolymer and adhesive composition of Comparative Example 4.

[0214] (Comparative Example 5)

[0215] In Comparative Example 5, a copolymer was prepared in water using a suspension polymerization process. Specifically, in a polymerization apparatus equipped with a stirrer, thermometer, and reflux condenser, a mixed solution containing 80 parts by mass of ion-exchanged water, 100 parts by mass of "Adekalase SR-10" (trade name, manufactured by ADEKA Co., Ltd., an ether sulfate type ammonium salt, a polymerizable surfactant) and "Ratimul E-118B" (trade name, manufactured by Kao Corporation, a polyoxyethylene alkyl ether sulfate sodium sulfate) as emulsifiers (shown in Stage 1 of Table 1), and a total of 100 parts by mass of the mixed monomers and chain transfer agents listed in Table 1 were mixed at 350 rpm for 30 minutes to obtain monomer droplets with a diameter of approximately 50 μm. The temperature was raised to 70°C under a nitrogen atmosphere, and the mixed solution in the polymerization apparatus was maintained at 70°C while stirring. 0.2 parts by mass of 2,2'-azobisisobutyronitrile (2,2'-azobisisobutyronitrile) as a polymerization initiator was added. Then, agglomerates are formed during the reaction, and the adhesive composition of Comparative Example 5 is not obtained.

[0216] <2. Biomass carbon content>

[0217] (Biomass carbon content of the copolymer)

[0218] The biomass carbon content of the copolymers (A) obtained in Examples 1 to 9 in Table 1 was obtained by using the formula on the right side of the above formula (1). In addition, the biomass carbon content of the copolymers obtained in Comparative Examples 1 to 5 was obtained by replacing "monomer i used to synthesize copolymer (A)" with "monomer i used to synthesize copolymers of Comparative Examples 1 to 5" in the above formula (1).

[0219] (Biomass carbon content of alkyl groups in the first structural unit)

[0220] The biomass carbon content of the alkyl group in the first structural unit in Table 1 was obtained by using the formula on the right side of the above formula (2). Furthermore, the biomass carbon content of the alkyl group in the first structural unit of the copolymers obtained in Comparative Examples 1-5 was obtained by replacing "the monomer Ai corresponding to the first structural unit used in the synthesis of copolymer (A)" with "the monomer Ai corresponding to the first structural unit used in the synthesis of the copolymers of Comparative Examples 1-5".

[0221] (Biomass carbon content of individual units)

[0222] The biomass carbon content of the monomers that are the source of the first and second structural units listed in Table 1, determined by method B in ASTM D6866-22, is as follows.

[0223] n-Butyl acrylate: Biomass carbon content 57.1% (n-butyl group is derived from biomass).

[0224] 2-Octyl acrylate: 72.7% biomass carbon content (2-octyl is derived from biomass).

[0225] Isoamyl acrylate: Biomass carbon content 62.5% (isoamyl group is derived from biomass).

[0226] Octyl acrylate: 72.7% biomass carbon content (octyl group is derived from biomass).

[0227] Lauryl acrylate: Biomass carbon content 80.0% (Lauryl is derived from biomass.)

[0228] 2-Ethylhexyl acrylate: Biomass carbon content 0%

[0229] Methyl methacrylate: 0% biomass carbon content

[0230] Methacrylic acid: 0% biomass carbon content

[0231] <3. Determination of the concentration of non-volatile components in adhesive compositions>

[0232] 1 g of adhesive composition was weighed into an aluminum dish with a diameter of 5 cm. It was dried in a desiccator at 105 °C for 1 hour under air circulation at 1 atm (1013 hPa). The mass of the remaining non-volatile components was then measured. The concentration (%) of the non-volatile components in the adhesive composition was determined by the ratio of the mass of the non-volatile components after drying to the mass (1 g) of the adhesive composition before drying.

[0233] <4. Making Adhesive Tape>

[0234] The adhesive compositions obtained in Examples 1-9 and Comparative Examples 1-4 were coated onto a PET film (A4 size, 50 μm thick). A doctor blade with a coating width of 15 cm was used as the coater. The coated adhesive composition was dried at 100°C for 2 minutes to remove the aqueous medium from the adhesive composition, forming an adhesive layer with a thickness of 30 μm on the PET film. After attaching the release surface (silicone coated surface) of the release paper to the adhesive layer on the PET film, it was cured at 23°C for 1 day to obtain a substrate and an adhesive layer formed on the substrate, with an adhesive tape of the release paper attached to the adhesive layer.

[0235] <5. Evaluation of Adhesive Tape>

[0236] The following evaluations were made regarding the adhesive tapes produced in the various embodiments and comparative examples 1 to 4.

[0237] In addition, in the following description, the operations in each embodiment and comparative example are common unless otherwise specified.

[0238] [5-1. Evaluation 1: Determination of adhesion at room temperature (room temperature adhesion)]

[0239] Cut the adhesive tape to a width of 25mm and a length of 100mm. Peel off half of the release paper along the length and cut it. Attach the release paper to the SUS#304 board to make an evaluation sample.

[0240] Bonding was achieved by reciprocating a 2kg roller once at 23°C. The atmosphere temperature during bonding when the evaluation sample was made will be referred to as the bonding temperature. (Bonding temperature in Evaluation 1: 23°C)

[0241] In the evaluation sample, the portion of the adhesive tape that adhered to the SUS#304 board was a rectangle measuring 25mm × 50mm. The ends of the adhesive tape did not coincide with the ends of the SUS#304 board. That is, in this state, half of one end of the adhesive tape along its length was adhered to the SUS#304 board, and the other half was adhered to the release paper.

[0242] After preparing the evaluation samples, they were left to stand for 30 minutes in an atmosphere at 23°C. The atmosphere temperature during the standing period after sample preparation will be referred to as the standing temperature. (Standing temperature in Evaluation 1: 23°C)

[0243] Then, the following measurements were performed in an atmosphere at 23°C. The measurement temperature of the sample used for evaluation will be referred to as the measurement temperature below. (Measurement temperature in Evaluation 1: 23°C)

[0244] The test was a so-called 180° peel test. The adhesive tape of the evaluation sample was folded 180° back along the boundary between the portion adhered to the SUS#304 board and the unattached portion, using the fold line as the folding line. The unattached end of the adhesive tape (the folded-back portion) was then tested using a testing machine (Tensilon RTG-1210). アンド The upper chuck of the (made by Dayi) is used for clamping. One end of the SUS#304 plate, which is opposite the upper chuck across the fold line, is clamped with the lower chuck.

[0245] In this state, the adhesive tape was peeled off from the SUS#304 board at a speed of 300 mm / min, and a graph of peel length (mm) versus peel force (N) was obtained. The average peel force (N) within the peel length range of 25–50 mm was calculated from the obtained graph (the value obtained by dividing the area of ​​the graph within the peel length range of 25–50 mm by the peel length), and this value was set as the room temperature adhesive force (N / 25 mm).

[0246] [5-2. Evaluation 2: Determination of adhesion under high temperature conditions (high temperature adhesion)]

[0247] The static temperature was set to 70°C, and the measurement temperature was set to 70°C. Otherwise, the adhesion (N / 25mm) under high temperature conditions was measured using the same procedure as in "Evaluation 1" above.

[0248] [5-3. Evaluation 3: Determination of adhesion at low temperatures (low-temperature adhesion)]

[0249] The bonding temperature was set to -20°C, the standing temperature was set to -20°C, and the measurement temperature was set to -20°C. Otherwise, the adhesion (N / 25mm) under low temperature conditions was measured using the same steps as in "Evaluation 1" above.

[0250] [5-4. Evaluation 4: Determination of High Temperature Holding Power]

[0251] The adhesive tape was cut to a width of 25mm and a length of 100mm. 25mm of release paper was peeled off from one end along the length, and the tape was then bonded to the SUS board (SUS#304) to completely cover the portion where the release paper had been peeled off, thus creating an evaluation sample. Specifically, in the evaluation sample, the area where the adhesive tape and SUS board were bonded formed a 25mm x 25mm square. Bonding was performed by reciprocating once with a 2kg roller at 23°C. Furthermore, the portion of the SUS board that was not bonded to the adhesive tape, extending from the end of the adhesive tape bonded to the SUS board, was designated as the SUS board side clamp portion.

[0252] The evaluation sample was placed in a constant temperature bath at 80°C for 30 minutes. Then, the SUS plate side clamp of the evaluation sample was held in the constant temperature bath at 80°C with a clamp, and a 1 kg weight was suspended from the end of the adhesive tape not attached to the SUS plate along its length. The time (h) until the weight fell was measured. The test was conducted until 24 hours later, and cases where the weight did not fall after 24 hours were recorded in Table 1 as "24 <".

[0253] <6. Evaluation Results>

[0254] The evaluation results for ratings 1 through 4 are shown in Table 1.

[0255]

[0256] As shown in Table 1, the adhesive tapes of Examples 1 to 9, which use the copolymer (A) containing biomass carbon atoms of this embodiment, are formed with strong adhesive force not only at room temperature but also at high and low temperatures, and further have high holding power at high temperatures.

[0257] On the other hand, for the adhesive tapes involved in Comparative Examples 1 and 2, which were made from adhesive compositions using copolymers that do not contain biomass carbon atoms, at least one of the adhesion and high-temperature holding power was insufficient. In Comparative Example 2, although the amount of vinyl acetate and methyl methacrylate mixed in the copolymer was increased, no improvement in adhesion was achieved.

[0258] Based on these circumstances, it is clear that the objective of this embodiment cannot be achieved in copolymers that do not contain biomass carbon atoms.

[0259] Furthermore, for the adhesive tapes of Comparative Examples 3 and 4, which were made using an adhesive composition of a copolymer produced by solution polymerization, at least one of the high-temperature adhesion, low-temperature adhesion, and high-temperature holding power was insufficient.

[0260] Based on these circumstances, it is clear that the objective of this embodiment cannot be achieved in the form of copolymers produced by methods other than emulsion polymerization.

[0261] As described above, according to this embodiment, copolymers, adhesive compositions and related technologies capable of forming adhesive layers can be provided, wherein even if carbon dioxide is generated during incineration, the amount of carbon dioxide present in the Earth's environment does not increase or increases only slightly.

[0262] Furthermore, according to this embodiment, a copolymer and adhesive composition can be provided that can form an adhesive layer that exhibits strong adhesion not only at room temperature but also at high and low temperatures, and further has high holding power at high temperatures.

[0263] Furthermore, according to this embodiment, an adhesive layer that exhibits strong adhesion not only at room temperature but also at high and low temperatures, and an adhesive tape having the adhesive layer, can be provided.

Claims

1. A copolymer, obtained by emulsion polymerization, having the following characteristics: The first structural unit derived from alkyl (meth)acrylates; and It originates from the second structural unit of an olefinic unsaturated compound having at least one selected from carboxyl and carboxyl groups. The copolymer contains biomass carbon atoms.

2. The copolymer according to claim 1, wherein the biomass carbon content determined by method B in ASTM D6866-22 is 10% or more.

3. The copolymer according to claim 1, wherein at least one of the structural units included as the first structural unit has an alkyl group comprising a carbon atom of biomass.

4. The copolymer according to claim 3, wherein the carbon atom of the alkyl group comprising the first structural unit, which is derived from an alkyl (meth)acrylate, is set to carbon atom C. 1A In the case of the copolymer containing carbon atoms C 1A The total number of biomass carbon contents determined by Method B in ASTM D6866-22 is 20% or more.

5. The copolymer according to claim 1, wherein the glass transition temperature Tg is -80 to 30°C.

6. The copolymer according to claim 1, wherein the first structural unit comprises at least one selected from structural units derived from n-butyl methacrylate, structural units derived from isoamyl methacrylate, structural units derived from n-octyl methacrylate, structural units derived from 2-octyl methacrylate, and structural units derived from lauryl methacrylate.

7. The copolymer according to claim 1, further comprising structural units derived from vinyl ester compounds.

8. An adhesive composition comprising the copolymer of any one of claims 1 to 7 and an aqueous medium.

9. The adhesive composition according to claim 8, wherein the copolymer is dispersed as particles in the aqueous medium to form an emulsion.

10. An adhesive tape comprising a substrate and an adhesive layer formed on the surface of the substrate, The adhesive layer is formed using the adhesive composition of claim 8.

11. A method for manufacturing a copolymer, comprising the steps of emulsion polymerization of a monomer comprising an alkyl (meth)acrylate and an olefinically unsaturated compound having at least one selected from carboxyl and carboxyl groups. At least one of the monomers contains biomass carbon atoms.

12. The method for manufacturing the copolymer according to claim 11, wherein the monomer contains an alkyl (meth)acrylate comprising biomass carbon atoms.

13. The method for manufacturing the copolymer according to claim 12, wherein the alkyl (meth)acrylate containing biomass carbon atoms contains biomass carbon atoms in the alkyl group bound to (meth)acryloyloxy group.

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