Polyester adhesive and production method of the same, and block copolymer and production method of the same

Abstract

To provide a polyester adhesive that exhibits excellent adhesive performance, and can be obtained by a simple synthesis operation.SOLUTION: A polyester adhesive contains a block copolymer having a polymer block A and a polymer block B, wherein the polymer block A includes a structural unit derived from a cyclic acid anhydride and a structural unit derived from a cyclic ether, the polymer block B includes a structural unit derived from a cyclic ester, and a ratio of the structural unit derived from the cyclic ester is 55 mass% or more and 97 mass% or less to all structural units that constitute the block copolymer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyester adhesive and a method for producing the same, and to a block copolymer and a method for producing the same. [Background technology]

[0002] In recent years, the importance of biomass raw materials and biodegradable materials has been recognized from the perspective of realizing a sustainable society, and it has become important to use biomass raw materials and impart biodegradability to various polymer materials. There is also a demand for adhesive products to switch to using biomass raw materials and imparting biodegradability, and various studies are underway (see, for example, Non-Patent Document 1). Non-Patent Document 1 discloses the production of a triblock polyester by a two-stage synthesis process using a biodegradable monomer, and the use of this polyester to obtain a polyester pressure-sensitive adhesive (PSA). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Angew.Chem,Int.Ed., 2020, No. 59, p.23450-23455 Summary of the Invention [Problem to be solved by the invention]

[0004] In polyester adhesives using block copolymers, precise molecular design of the block copolymer is required to achieve adhesive performance. Therefore, as shown in Non-Patent Document 1, the synthesis of the block copolymer requires a multi-step process and complicated operations. In such cases, there are concerns that the production time and costs of the adhesive may increase and that this may lead to the consumption of large amounts of organic solvents.

[0005] The present invention has been made in view of the above circumstances, and one object of the present invention is to provide a polyester adhesive that exhibits excellent adhesive performance and can be obtained by a simple synthetic procedure. Another object of the present invention is to provide a block copolymer that exhibits excellent adhesive performance and can be obtained by a simple synthetic procedure. [Means for solving the problem]

[0006] The present inventors have found that the above-mentioned problems can be solved by polymerizing a monomer mixture of specific monomers in the presence of a polymerization initiator and a specific catalyst. Specifically, according to the present invention, the following polyester adhesive and production method therefor, and block copolymer and production method therefor are provided.

[0007] [1] A block copolymer having a polymer block A and a polymer block B, a polyester-based adhesive, wherein the polymer block A contains a structural unit derived from a cyclic acid anhydride and a structural unit derived from a cyclic ether, and the polymer block B contains a structural unit derived from a cyclic ester, and the proportion of the structural unit derived from the cyclic ester is 55% by mass or more and 97% by mass or less of all structural units constituting the block copolymer. [2] The polyester-based adhesive according to [1], wherein the cyclic acid anhydride has 5 or more carbon atoms. [3] The polyester adhesive according to [1] or [2], wherein the block copolymer is a BAB triblock polymer or a star block polymer having three or more AB arm structures, in which the polymer block B is located at the end of the polymer chain. [4] 1 The polyester adhesive according to any one of [1] to [3], which has a number average molecular weight of 15,000 or more as measured by H-NMR. [5] A method for producing a polyester-based adhesive according to any one of [1] to [4], comprising polymerizing a monomer composition containing a cyclic acid anhydride, a cyclic ether, and a cyclic ester in the presence of a polymerization initiator and an alkali metal carboxylate to obtain the block copolymer. [6] The method for producing a polyester adhesive according to [5], wherein the polymerization initiator is an alcohol or a carboxylic acid. [7] A method for producing a polyester adhesive according to [5] or [6], in which polymerization is carried out under solvent-free conditions. [8] A block copolymer comprising a polymer block A and a polymer block B, wherein the polymer block A contains structural units derived from a cyclic acid anhydride and structural units derived from a cyclic ether, and the polymer block B contains structural units derived from a cyclic ester, and the proportion of the structural units derived from the cyclic ester is 55% by mass or more and 97% by mass or less. [9] The block copolymer according to [8], which is a BAB triblock polymer or a star block polymer having three or more AB arm structures, in which the polymer block B is arranged at the end of the polymer chain.

[10] A method for producing the block copolymer according to [8] or [9], comprising polymerizing a monomer composition containing a cyclic acid anhydride, a cyclic ether, and a cyclic ester in the presence of a polymerization initiator and an alkali metal carboxylate.

[11] The method for producing a block copolymer according to

[10] , wherein the polymerization initiator is an alcohol or a carboxylic acid. [Effects of the Invention]

[0008] The polyester adhesive and block copolymer of the present invention exhibit excellent adhesive properties and can be obtained by a simple synthesis procedure. DETAILED DESCRIPTION OF THE INVENTION

[0009] Matters relating to the present invention will be described in detail below. In this specification, a numerical range indicated by "to" includes the numerical values ​​before and after it as the upper and lower limits.

[0010] <Polyester adhesive> The polyester adhesive of the present invention contains a block copolymer (hereinafter also referred to as "block copolymer (P)") having a polymer block A and a polymer block B. In the block copolymer (P), the polymer block A contains a structural unit derived from a cyclic acid anhydride and a structural unit derived from a cyclic ether, and the polymer block B contains a structural unit derived from a cyclic ester. Hereinafter, the structural unit derived from the cyclic acid anhydride will also be referred to as "structural unit (U1)," the structural unit derived from the cyclic ether will also be referred to as "structural unit (U2)," and the structural unit derived from the cyclic ester will also be referred to as "structural unit (U3)." The components contained in the polyester adhesive of the present invention will be described in detail below.

[0011] <Block copolymer (P)> The block copolymer (P) is a polymer having a polyester as its main skeleton. In one embodiment of the block copolymer (P), polymer block A is formed by ring-opening alternating copolymerization of a cyclic acid anhydride and a cyclic ether, and polymer block B is formed by ring-opening polymerization of a cyclic ester, thereby giving the block copolymer (P) a polyester skeleton. In the block copolymer (P) having polymer block A and polymer block B, polymer block A can be a soft segment, and polymer block B can be a hard segment.

[0012] (Polymer block A) Structural unit (U1) In the polymer block A, the cyclic acid anhydride constituting the structural unit (U1) is not particularly limited as long as it has one acid anhydride group (-C(=O)-OC(=O)-) in the molecule. Examples of the cyclic acid anhydride include monocyclic cyclic acid anhydrides and fused ring cyclic acid anhydrides. The cyclic acid anhydride may have a substituent bonded to the ring. Examples of the substituent include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, a hydroxyl group, a carboxyl group, a nitro group, a halogen atom (such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom), and a monovalent heterocyclic group.

[0013] When the cyclic acid anhydride has a chain hydrocarbon group having 1 to 20 carbon atoms as a substituent bonded to the ring, the chain hydrocarbon group having 1 to 20 carbon atoms may be saturated or unsaturated. Specific examples of the chain hydrocarbon group having 1 to 20 carbon atoms include saturated chain hydrocarbon groups such as alkyl groups, methyl groups, ethyl groups, n-propyl groups, isopropyl groups, n-butyl groups, isobutyl groups, sec-butyl groups, tert-butyl groups, n-pentyl groups, isopentyl groups, sec-pentyl groups, 3-pentyl groups, tert-pentyl groups, n-hexyl groups, n-octyl groups, 2-ethylhexyl groups, 2-octyl groups, isononyl groups, isodecyl groups, isotridecyl groups, hexyldecyl groups, and octyldodecyl groups; alkenyl groups, such as ethenyl groups, propenyl groups, butenyl groups, pentenyl groups, and hexenyl groups; and alkynyl groups, such as ethynyl groups, propynyl groups, butynyl groups, pentynyl groups, and hexynyl groups.

[0014] Specific examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include a cyclopentyl group, a cyclohexyl group, etc. Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as a phenyl group, a methylphenyl group, and an ethylphenyl group; and aralkyl groups such as a phenylmethyl group and a phenethyl group.

[0015] The number of carbon atoms of the cyclic acid anhydride is preferably 5 or more, since this allows the molecular weight of the block copolymer (P) to be sufficiently increased, thereby enabling the production of a block copolymer (P) with superior adhesive properties. From the same viewpoint, the cyclic acid anhydride is preferably at least one selected from the group consisting of cyclic acid anhydrides having 6 or more ring members and cyclic acid anhydrides having a condensed ring structure.

[0016] Specific examples of cyclic acid anhydrides constituting the structural unit (U1) include compounds represented by the following formula: The polymer block A may contain only one type of structural unit (U1), or may contain two or more types. [ka]

[0017] The proportion of the structural unit (U1) in the block copolymer (P) is preferably 1% by mass or more and 20% by mass or less, based on all structural units constituting the block copolymer (P). From the viewpoint of improving the adhesive performance of the block copolymer (P), the proportion of the structural unit (U1) is preferably 2% by mass or more, more preferably 5% by mass or more, based on all structural units constituting the block copolymer (P). The upper limit of the proportion of the structural unit (U1) is preferably 15% by mass or less, more preferably 12% by mass or less, based on all structural units constituting the block copolymer (P).

[0018] Structural unit (U2) The cyclic ether constituting the structural unit (U2) is preferably a compound having an oxirane structure or an oxetane structure, because of its high reactivity with cyclic acid anhydrides, and more preferably a compound having an oxirane structure (epoxide). Examples of epoxides include compounds represented by the following formula (1): [ka] (In formula (1), R 1 and R 2are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms, which may contain an oxygen atom between the carbon-carbon bond and may have a substituent; R 1 and R 2 may be bonded to form a ring.

[0019] In the above formula (1), R 1 or R 2 Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms and represented by the formula (I) include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms. Specific examples of these include the same groups as those exemplified as the substituent that the cyclic acid anhydride may have. R 1 or R 2 When is a substituted monovalent hydrocarbon group having 1 to 20 carbon atoms, examples of the substituent include a halogen atom (such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom), a nitro group, and the like.

[0020] R 1 and R 2 When these are bonded to form a ring, examples of the ring include a cyclohexane ring, a cyclohexene ring, etc. These rings may have a substituent. In view of the reactivity of the compound represented by the above formula (1), R 1 and R 2 At least one of these is preferably a hydrogen atom.

[0021] Specific examples of the cyclic ether constituting the structural unit (U2) include compounds represented by the following formula: The polymer block A may contain only one type of structural unit (U2), or may contain two or more types. [ka]

[0022] The proportion of the structural unit (U2) in the block copolymer (P) is preferably 1% by mass or more and 20% by mass or less, based on all structural units constituting the block copolymer (P). From the viewpoint of improving the adhesive performance of the block copolymer (P), the proportion of the structural unit (U2) is preferably 2% by mass or more, more preferably 5% by mass or more, based on all structural units constituting the block copolymer (P). The upper limit of the proportion of the structural unit (U2) is preferably 15% by mass or less, more preferably 12% by mass or less, based on all structural units constituting the block copolymer (P).

[0023] The total proportion of the structural units (U1) and (U2) in the block copolymer (P) is preferably 3% by mass or more and 45% by mass or less, based on all structural units constituting the block copolymer (P). From the viewpoint of improving the adhesive performance of the block copolymer (P), the total proportion of the structural units (U1) and (U2) is preferably 5% by mass or more, more preferably 10% by mass or more, based on all structural units constituting the block copolymer (P). The upper limit of the total proportion of the structural units (U1) and (U2) is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less, based on all structural units constituting the block copolymer (P).

[0024] (Polymer block B) In the polymer block B, examples of the cyclic ester constituting the structural unit (U3) include lactones, lactides, and carbonates. Specific examples of these include lactones such as β-propiolactone, γ-butyrolactone, β-butyrolactone, pivalolactone, δ-valerolactone, ε-caprolactone, and β-methyl-δ-valerolactone. Examples of lactides include glycolide, which is obtained by dehydration condensation of two glycolic acid molecules, dilactide (L-lactide, D-lactide, Meso-lactide), which is obtained by dehydration condensation of two lactic acid molecules, and tetramethyl glycolide. Examples of carbonates include trimethylene carbonate.

[0025] In terms of being a biomass raw material obtainable from natural products, being biodegradable, and being easily available, the cyclic ester constituting the structural unit (U3) is preferably dilactide, and more preferably L-lactide and / or D-lactide. When L-lactide and / or D-lactide are used in synthesizing the block copolymer (P), L-lactide may be used alone, D-lactide may be used alone, or a mixture of L-lactide and D-lactide may be used. In terms of ease of controlling the adhesiveness of the block copolymer (P) and ease of designing the block copolymer (P), it is preferable to use L-lactide alone as the dilactide.

[0026] The proportion of the structural unit (U3) in the block copolymer (P) is 55% by mass or more and 97% by mass or less of all structural units constituting the block copolymer (P). If the proportion of the structural unit (U3) is less than 55% by mass of all structural units constituting the block copolymer (P), the adhesive properties of the block copolymer cannot be sufficiently ensured. In addition, the block copolymer tends to become liquid at room temperature (25°C), which may make it difficult to apply to, for example, hot melt adhesives. On the other hand, if the proportion of the structural unit (U3) exceeds 97% by mass of the total amount of structural units constituting the block copolymer (P), the proportion of polymer block A, which can become a soft segment, is too low, and the block copolymer tends to become hard and brittle, resulting in poor adhesive properties.

[0027] From the viewpoint of obtaining a block copolymer (P) having excellent adhesive properties, the proportion of the structural unit (U3) is preferably 60% by mass or more, more preferably 65% ​​by mass or more, even more preferably 70% by mass or more, and even more preferably 75% by mass or more, based on all structural units constituting the block copolymer (P). The upper limit of the proportion of the structural unit (U3) is preferably 95% by mass or less, more preferably 90% by mass or less, based on all structural units constituting the block copolymer (P).

[0028] (Structure of block copolymer (P)) The block copolymer (P) may be linear or branched. The number of polymer blocks A and B in one molecule of the block copolymer (P) and the arrangement of the polymer blocks are not particularly limited, as long as the block copolymer (P) has at least one polymer block A and one polymer block B in one molecule.

[0029] When the block copolymer (P) is a linear polymer, examples of the block copolymer (P) include AB type diblock polymers, ABA type triblock polymers, BAB type triblock polymers, ABABA type pentablock polymers, BABAB type pentablock polymers, etc. Among these, triblock polymers are preferred, and BAB type triblock polymers are more preferred, in that polymers with excellent adhesive performance can be obtained by simpler operations.

[0030] When the block copolymer (P) is a branched polymer, examples of the block copolymer (P) include star block polymers and core-shell block polymers having three or more AB-type arm structures. In these branched polymers, from the viewpoint of enhancing adhesive performance, it is preferred that the polymer block B, which can become a hard segment, is located at the molecular end (more specifically, the end opposite to the branch site or core site). In the star block polymer, the number of arm structures in one molecule is preferably 3 to 10, more preferably 4 to 8, from the viewpoint of balancing adhesive performance and ease of synthesis.

[0031] In terms of exhibiting higher adhesive performance, it is preferable that the block copolymer (P) has a polymer block B, which can become a hard segment, located at the end of the polymer chain in one polymer molecule. In terms of being able to obtain a polymer exhibiting high adhesive performance through a simple synthesis procedure, it is particularly preferable that the block copolymer (P) is a BAB triblock polymer or a star block polymer having three or more AB arm structures and in which the polymer block B is located at the molecular end. It is believed that the block copolymer (P) in which the polymer block B is located at the molecular end exhibits excellent adhesive performance due to the formation of a pseudo-crosslinked structure by the polymer block B, which can become a hard segment.

[0032] The block copolymer (P) may further have a polymer block (hereinafter also referred to as "another polymer block") different from polymer block A and polymer block B. Examples of the other polymer block include a polyalkyleneoxy structure (e.g., a polyethyleneoxy structure, a polypropyleneoxy structure). The other polymer block can be introduced into the block copolymer (P) by polymerization using, for example, a compound having a structure corresponding to the other polymer block (e.g., a polyalkylene glycol) as a polymerization initiator.

[0033] In the block copolymer (P), the polymer block A may contain the structural unit (U3) of the polymer block B, and the polymer block B may contain the structural unit (U1) and / or the structural unit (U2) of the polymer block A. The incorporation of the structural unit (U3) into the polymer block A and the incorporation of the structural unit (U1) and / or the structural unit (U2) into the polymer block B tend to occur particularly easily at the transition portion between the polymer block A and the polymer block B.

[0034] (Physical properties of block copolymer (P)) Regarding the molecular weight characteristics of the book copolymer (P), 1 The number average molecular weight (Mn) measured by H-NMR NMRFrom the viewpoint of obtaining a polymer that exhibits good adhesiveness, the number average molecular weight Mn is preferably 10,000 or more, more preferably 12,000 or more, even more preferably 15,000 or more, and even more preferably 17,000 or more. NMR The upper limit of the number average molecular weight Mn is preferably 120,000 or less, more preferably 100,000 or less, from the viewpoint of improving the handleability of the polymer. NMR teeth, 1 This is a value determined by H-NMR measurement.

[0035] The number average molecular weight (Mn) calculated by the following formula (I) theo From the viewpoint of obtaining a polymer that exhibits good adhesiveness, the number average molecular weight Mn is preferably 10,000 or more, more preferably 12,000 or more, even more preferably 15,000 or more, and even more preferably 17,000 or more. theo The upper limit of the molecular weight is preferably 120,000 or less, more preferably 100,000 or less, from the viewpoint of improving the handleability of the polymer. Mn theo =Mi+(Xm1 / Xi)×(Mm1+Mm2)×Rm1+(Xm3 / Xi)×Mm3×Rm3 …(I) Mi: Molecular weight of polymerization initiator Xi: Amount of polymerization initiator charged Xm1: Amount of cyclic acid anhydride Xm2: Amount of cyclic ether Xm3: Amount of cyclic ester Rm1: Reaction rate of cyclic acid anhydride Rm3: Reaction rate of cyclic ester Mm1: Molecular weight of cyclic acid anhydride Mm2: Molecular weight of cyclic ether Mm3: Amount of cyclic ester The reaction rate of the cyclic acid anhydride and the cyclic ester is 1 This is a value determined by H-NMR measurement. 1 The integral values ​​of the monomer and the polymer product are determined by H-NMR measurement, and the value is calculated from the ratio of these integral values.

[0036] The glass transition temperature of the block copolymer (P) is preferably 0°C or higher, more preferably 5°C or higher, and even more preferably 10°C or higher, in order to obtain a polymer with superior adhesive performance. Furthermore, the glass transition temperature of the block copolymer (P) is, for example, 100°C or lower, preferably 80°C or lower, and more preferably 50°C or lower, in terms of meltability during heat adhesion. In this specification, the glass transition temperature of the polymer is a value measured by differential scanning calorimetry (DSC). Details of the measurement method follow the procedures described in the Examples below.

[0037] The 5% weight loss temperature of the block copolymer (P) is preferably 150° C. or higher, more preferably 180° C. or higher, and even more preferably 200° C. or higher, in that a polymer with excellent heat resistance can be obtained. Details of the method for measuring the 5% weight loss temperature of the polymer follow the method described in the Examples below.

[0038] <Method of producing block copolymer> The synthesis method for the block copolymer (P) is not particularly limited as long as it can produce the block copolymer (P). It is preferable to produce the block copolymer (P) by a method in which a monomer composition containing a cyclic acid anhydride, a cyclic ether, and a cyclic ester is polymerized in the presence of a polymerization initiator and an alkali metal carboxylate, since this method allows for the production of a block copolymer with a precisely controlled structure through a simple one-step synthesis. This polymerization method is advantageous in that it allows precise polymerization to proceed using a simple catalyst, such as an alkali metal carboxylate, without the need for a highly engineered catalyst, such as an organometallic catalyst or an organic superbase catalyst. It is also advantageous in that it allows polymerization to be carried out under solvent-free conditions, thereby contributing to reducing environmental impact.

[0039] (Polymerization initiator) As the polymerization initiator, alcohols or carboxylic acids are preferably used because they can easily produce the target polymer. Examples of the alcohol include monoalcohols and polyhydric alcohols. Examples of the monoalcohol include methanol, ethanol, propanol, 1-butanol, 2-methyl-1-propanol, 2-butanol, 2-methyl-2-propanol, 1-pentanol, 2-pentanol, 2,2-dimethyl-1-propanol, polyethylene glycol, and polypropylene glycol. Specific examples of polyhydric alcohols include dihydric alcohols such as 1,3-benzenedimethanol and 1,4-benzenedimethanol; trihydric alcohols such as glycerin, trimethylolethane, trimethylolpropane, tris(2-hydroxyethyl)isocyanurate, hexanetriol, octanetriol, and decanetriol; tetrahydric alcohols such as ditrimethylolethane, ditrimethylolpropane, diglycerin, and pentaerythritol; pentahydric alcohols such as tritrimethylolethane, tritrimethylolpropane, and triglycerin; hexahydric or higher alcohols such as polytrimethylolethane, polytrimethylolpropane, polyglycerin, dipentaerythritol, tripentaerythritol, sorbitol, and polypentaerythritol; and alkylene oxide adducts of trihydric or higher alcohols. Specific examples of carboxylic acids include aromatic carboxylic acids such as benzoic acid, phthalic acid, and terephthalic acid.

[0040] In producing the block copolymer (P), the amount of the polymerization initiator used is, for example, 0.01 to 15 parts by mole, preferably 0.05 to 10 parts by mole, and more preferably 0.1 to 5 parts by mole, relative to 100 parts by mole of the total amount of the monomers used in the polymerization.

[0041] (alkali metal carboxylate) Examples of alkali metal carboxylates include lithium carboxylic acid salts, sodium carboxylic acid salts, potassium carboxylic acid salts, and cesium carboxylic acid salts. Carboxylic acids that give alkali metal carboxylates include aliphatic carboxylic acids such as acetic acid, ethanoic acid, propanoic acid, butanoic acid, 2-methylpropionic acid, 2,2-dimethylpropionic acid, pentanoic acid, hexanoic acid, heptanoic acid, dodecanoic acid, and trifluoroacetic acid; and aromatic carboxylic acids such as benzoic acid and phthalic acid. Of these, cesium carboxylic acid salts are preferred as alkali metal carboxylates, and cesium aliphatic monocarboxylic acid salts can be preferably used.

[0042] When producing the block copolymer (P), the amount of the alkali metal carboxylate used is, for example, 0.01 to 15 parts by mole, preferably 0.05 to 10 parts by mole, and more preferably 0.1 to 5 parts by mole, relative to 100 parts by mole of the total amount of the monomers used in the polymerization.

[0043] The polymerization temperature and polymerization time are not particularly limited and may be set appropriately. From the viewpoint of accelerating the polymerization reaction, it is preferable to carry out polymerization of the monomers under heating. From the viewpoint of increasing the reaction rate while suppressing side reactions, the polymerization temperature is, for example, within a temperature range of 30°C to 150°C, preferably within a temperature range of 40°C to 130°C, and more preferably within a temperature range of 50°C to 120°C. The polymerization time is, for example, 1 to 72 hours, preferably 5 to 36 hours. The pressure during polymerization may be any pressure that can maintain the polymerization temperature. From the viewpoint of suppressing a decrease in the degree of polymerization, it is preferable to carry out the reaction under dry air (for example, under conditions where the dew point at atmospheric pressure is −40°C or less), or under dry nitrogen or dry argon. The polymerization reaction may be carried out with stirring in the reactor.

[0044] In one example of the polymerization method, a cyclic acid anhydride, a cyclic ether, and a cyclic ester are charged as monomers into a reaction vessel. A polymerization initiator and an alkali metal carboxylate as a catalyst are added to the reaction vessel before, after, or simultaneously with the addition of the monomers, and the polymerization reaction is then initiated by heating. This polymerization method allows for a simple, one-step synthesis of the block copolymer (P). Linear polymers can be obtained as the block copolymer (P) by using monofunctional or difunctional compounds (e.g., monoalcohols, dialcohols) as the polymerization initiator. Branched polymers can be obtained as the block copolymer (P) by using trifunctional or higher functional compounds (e.g., trialcohols, polyalcohols) as the polymerization initiator.

[0045] <Other ingredients> The polyester adhesive of the present invention may be composed of a block copolymer (P). It may also contain, together with the block copolymer (P), components different from the block copolymer (P) (also referred to as "other components"). Examples of other components include plasticizers, particles, colorants, fragrances, solvents, and strength improvers. The content of these other components can be appropriately determined depending on the application of the adhesive, as long as the effects of the present invention are not impaired.

[0046] <Application> The form of use of the polyester adhesive of the present invention is not particularly limited. The polyester adhesive can be used, for example, in the form of a sheet, film, small piece, rod, etc. The polyester adhesive of the present invention can be solid at room temperature (25°C) and can melt when heated (for example, heated to 70°C or higher), so it can be preferably used as a hot melt adhesive.

[0047] The polyester adhesive of the present invention can be used on any substrate, including, but not limited to, various materials. Examples of the substrate include substrates made of resin, metal, ceramic, rubber, glass, wood, cloth, porcelain, leather, or a combination of two or more of these materials. The substrate may further contain a reinforcing material such as carbon fiber or glass fiber, a colorant, or the like.

[0048] Among the above resins, examples include vinyl chloride resins (polyvinyl chloride, ethylene-vinyl chloride copolymer, polyvinylidene chloride, etc.), polyvinyl acetate resin, polyurethane resin, polystyrene resin, AS resin (acrylonitrile-styrene copolymer), ABS resin (acrylonitrile-butadiene-styrene copolymer), AXS resin (styrene copolymer of a rubber component other than acrylonitrile-butadiene), acrylic resin, polymethyl methacrylate resin, polyester resin, polyamide resin, polybutylene terephthalate resin, polycarbonate resin, polyphenylene sulfide (PPS) resin, polyether ether ketone (PEEK) resin, etc.

[0049] Examples of metals include copper, aluminum, iron, gold, silver, titanium, nickel, zinc, tin, alloy steel (stainless steel, manganese steel, nickel steel, etc.), and composites of two or more of these.

[0050] <Block copolymer> According to the present invention, the above-mentioned block copolymer (P) is provided. Because the block copolymer (P) exhibits excellent adhesive performance, it is suitable as a polymer component contained in adhesives (including pressure-sensitive adhesives (PSA)). Furthermore, many biomass raw materials exist for the cyclic acid anhydrides, cyclic ethers, and cyclic esters used in the synthesis of the block copolymer (P), making them easily available. Furthermore, because the main chain of the block copolymer (P) is polyester, environmental decomposition can be expected by selecting the monomer structure. Such block copolymers (P) are also significant from the perspective of realizing a sustainable society, which has become a trend in recent years. [Example]

[0051] The present invention will be specifically described below based on examples. However, the present invention is not limited to the following examples. In the following, "parts" and "%" mean "parts by mass" and "% by mass", respectively, unless otherwise specified.

[0052] <Polymer analysis> The details of the polymer analysis method are as follows. (Number average molecular weight Mn theo ) The number average molecular weight Mn theo asked for.

[0053] (Number average molecular weight Mn NMR ) Number average molecular weight Mn NMR teeth, 1 The values ​​were determined using a 1 H-NMR device (400 MHz). (glass transition temperature Tg) The glass transition temperature (Tg) of the polymer was measured under a nitrogen atmosphere using a differential scanning calorimeter (DSC7000X, Hitachi High-Tech Science Corp.) under the following conditions: in the first heating step, the sample was heated to 180°C at a heating rate of 10°C / min, held isothermally for 5 minutes, cooled to -100°C at a heating rate of 10°C / min, held isothermally for 5 minutes, and then heated to 180°C at a heating rate of 10°C / min. The second heating step was recorded. (5% weight loss temperature Td 5% ) 5% weight loss temperature (Td 5% ) was measured using a thermogravimetric analyzer (STA200RU, manufactured by Hitachi High-Tech Science Corporation) under conditions of a nitrogen atmosphere, a measurement temperature range of 30-550°C, and a heating rate of 10°C / min.

[0054] (LLA ratio) The ratio of structural units derived from L-lactide to all structural units of the polymer (unit: mass%, referred to as the "LLA ratio") is 1The value (mol %) measured using a H-NMR device (400 MHz) was converted to mass %.

[0055] <Synthesis of Block Copolymer (P)> [Example 1] Block copolymer P1 was synthesized according to the following scheme 1. [ka]

[0056] In a glovebox, a flask equipped with a needle valve was charged with cesium pivalate (70.2 mg, 300 μmol), 1,4-benzenedimethanol (41.4 mg, 300 μmol), glutaric anhydride (685 mg, 6.00 mmol), butylene oxide (1.73 g, 24.0 mmol), and L-lactide (4.76 g, 33 mmol). The flask was sealed with a needle valve under argon and removed from the glovebox. Polymerization was then carried out in an oil bath at 100 °C. After 5.5 h, the reaction mixture was terminated by diluting with dichloromethane. The solution was then reprecipitated into chilled methanol to yield a colorless, viscous solid: poly(L-lactide)-block-poly(glutaric anhydride-alternating-butylene oxide)-block-poly(L-lactide) (PLLA-b-poly(GA-alt-BO)-b-PLLA). This block copolymer was designated P1. The physical properties of the resulting block copolymer P1 are shown in Table 1.

[0057] [Examples 2 to 21 and Comparative Synthesis Examples 1 and 2] Polymerization was carried out in the same manner as in Example 1, except that the types of reagents used were changed to the compounds shown in Table 1 and the polymerization time (unit: hours) was changed as shown in Table 1, to obtain block copolymers P2 to P21, Q1, and Q2. In Example 21, butylene oxide (BO) and allyl glycidyl ether (AGE) were used as the cyclic ethers in a molar ratio of 1:1. The structures and physical properties of the obtained block copolymers P2 to P21, Q1, and Q2 are shown in Table 1. In Table 1, "-" indicates that the data was not measured.

[0058] [Table 1]

[0059] Details of the abbreviations in Table 1 are as follows: Polymerization initiator BDM: 1,4-benzenedimethanol BA: Benzyl alcohol BTM: 1,3,5-benzenetrimethanol PET: Pentaerythritol TMP: Trimethylolpropane ·catalyst CsOPiv: Cesium pivalate Cyclic acid anhydrides GA: Glutaric anhydride PA: Phthalic anhydride Cyclic ethers BO: Butylene oxide PO: Propylene oxide EGE: Ethyl glycidyl ether EHGE: Ethylhexyl glycidyl ether AGE: Allyl glycidyl ether Cyclic esters LLA: L-lactide

[0060] [Comparative Synthesis Example 3] Poly-L-lactide (PLLA) was synthesized according to the following Scheme 2. [ka]

[0061] In a glove box, cesium pivalate (140 mg, 600 μmol), benzyl alcohol (64.9 mg, 600 μmol), and L-lactide (4.76 g, 33 mmol) were added to a flask equipped with a needle valve. The flask was sealed with a needle valve under an argon atmosphere, and after removal from the glove box, polymerization was carried out in an oil bath at 100 °C. After 1.5 hours, the reaction mixture was diluted with dichloromethane to terminate the polymerization. The solution was then reprecipitated in chilled methanol to obtain PLLA (referred to as PLLA-1) as a colorless viscous solid. The yield was 4.46 g, a 92.6% yield. PLLA-1 had a number-average molecular weight of Mn NMR =9,410.

[0062] [Comparative Synthesis Example 4] In a glove box, cesium pivalate (46.8 mg, 200 μmol), 1,4-benzenedimethanol (27.6 mg, 200 μmol), and L-lactide (4.04 g, 28 mmol) were added to a flask equipped with a needle valve. The flask was sealed with the needle valve while maintaining an argon atmosphere, and after removal from the glove box, polymerization was carried out in an oil bath at 100 °C. After 10 hours, the polymerization was terminated by diluting the reaction solution with dichloromethane. The solution was then reprecipitated in chilled methanol to obtain PLLA (referred to as PLLA-2) as a colorless viscous solid. The yield was 4.06 g, a yield of 80.8%, and PLLA-2 had a number-average molecular weight of Mn NMR =16,100.

[0063] [Comparative Synthesis Example 5] In a glove box, cesium pivalate (117 mg, 500 μmol), benzyl alcohol (54.1 mg, 500 μmol), glutaric anhydride (1.14 g, 10.0 mmol), and butylene oxide (2.88 g, 40.0 mmol) were added to a flask equipped with a needle valve. The flask was sealed with a needle valve under argon atmosphere, removed from the glove box, and polymerized in an oil bath at 100 °C. After 19 h, the polymerization was terminated by diluting the reaction solution with dichloromethane. The solution was then reprecipitated in chilled methanol to obtain a colorless, viscous liquid glutaric anhydride / butylene oxide copolymer (PGABO-1). The yield was 1.06 g, a 55.1% yield. PGABO-1 had a number-average molecular weight of Mn NMR =4,640.

[0064] <Evaluation of tensile shear adhesive strength> [Examples 22 to 27, Comparative Examples 1 to 5] Each polymer shown in Table 2 was molded into a film measuring 25 mm wide x 12.5 mm long x 300 μm thick to obtain a film. Two sheets of wood (beech, 25 mm wide x 50 mm long x 2 mm thick) were used as substrates, and the film was sandwiched between the substrates, pressure-bonded at 100°C and 1 MPa, and then aged at 23°C for 24 hours. Tensile shear adhesive strength was measured at a pulling rate of 10 mm / min according to JIS K 6850-1999 (Testing method for tensile shear adhesive strength of rigid adherends). The evaluation results are shown in Table 2.

[0065] Comparative Example 6 A mixture of PGABO-1 from Comparative Synthesis Example 5 and PLLA-1 from Comparative Synthesis Example 3 in a mass ratio of 33:67 was used as an adhesive, and the tensile shear bond strength was evaluated in the same manner as in Examples 22 to 27 and Comparative Examples 1 to 5. The evaluation results are shown in Table 2. Comparative Example 7 A mixture of PGABO-1 from Comparative Synthesis Example 5 and PLLA-1 from Comparative Synthesis Example 3 in a mass ratio of 20:80 was used as an adhesive, and the tensile shear bond strength was evaluated in the same manner as in Examples 22 to 27 and Comparative Examples 1 to 5. The evaluation results are shown in Table 2.

[0066] [Table 2]

[0067] As shown in Table 2, the adhesives of Examples 22 to 27 exhibited high adhesion to wood. In contrast, the adhesives of Comparative Example 1, which used a polymer with an LLA ratio of 25% by mass; Comparative Example 2, which used a polymer with an LLA ratio of 45% by mass; Comparative Examples 3 and 4, which used PLLA; Comparative Example 5, which used a glutaric anhydride / butylene oxide copolymer; and Comparative Example 6, which used a blend of glutaric anhydride / butylene oxide copolymer and PLLA (compounding ratio: 33 / 67), produced films that were too brittle to perform tensile shear bond strength tests (indicated as "not measurable" in the table). Furthermore, the adhesive of Comparative Example 7, which used a blend of glutaric anhydride / butylene oxide copolymer and PLLA (compounding ratio: 20 / 80), had a low bond strength of 1.23 MPa, inferior to Examples 22 to 27.

[0068] [Examples 28 to 33, Comparative Examples 8 to 13] The tensile shear adhesive strength was evaluated in the same manner as in Examples 22 to 27 and Comparative Examples 1 to 5, except that a polyethylene terephthalate (PET) film (width 25 mm × length 100 mm × thickness 0.1 mm) was used instead of wood as the substrate. The evaluation results are shown in Table 3.

[0069] [Table 3]

[0070] As shown in Table 3, the adhesives of Examples 28 to 33 exhibited high adhesion to PET. In contrast, the adhesives of Comparative Example 8, which used a polymer with an LLA ratio of 25% by mass, and the adhesive of Comparative Example 1, which used a polymer with an LLA ratio of 45% by mass, had low adhesive strengths of 0.06 MPa and 0.14 MPa, respectively. Furthermore, the adhesives of Comparative Examples 10 and 11, which used PLLA, Comparative Example 12, which used a glutaric anhydride / butylene oxide copolymer, and Comparative Example 13, which used a blend of glutaric anhydride / butylene oxide copolymer and PLLA (blending ratio: 33 / 67), were too brittle in film form to undergo tensile shear adhesive strength testing.

Claims

1. The polymer composition contains a block copolymer having a polymer block A and a polymer block B, the polymer block A contains a structural unit derived from a cyclic acid anhydride and a structural unit derived from a cyclic ether, the polymer block B contains a structural unit derived from a cyclic ester, A polyester-based adhesive, wherein the proportion of the structural units derived from the cyclic ester is 55% by mass or more and 97% by mass or less based on all structural units constituting the block copolymer.

2. The polyester-based adhesive according to claim 1 , wherein the cyclic acid anhydride has 5 or more carbon atoms.

3. 2. The polyester-based adhesive according to claim 1, wherein the block copolymer is a BAB triblock polymer or a star block polymer having three or more AB arm structures and the polymer block B is located at the end of a polymer chain.

4. １ 2. The polyester-based adhesive according to claim 1, having a number average molecular weight measured by H-NMR of 15,000 or more.

5. A method for producing the polyester adhesive according to any one of claims 1 to 4, comprising: A method for producing a polyester adhesive, comprising polymerizing a monomer composition containing a cyclic acid anhydride, a cyclic ether, and a cyclic ester in the presence of a polymerization initiator and an alkali metal carboxylate to obtain the block copolymer.

6. The method for producing a polyester adhesive according to claim 5 , wherein the polymerization initiator is an alcohol or a carboxylic acid.

7. The method for producing the polyester adhesive according to claim 5 , wherein the polymerization is carried out under solvent-free conditions.

8. having a polymer block A and a polymer block B, the polymer block A contains a structural unit derived from a cyclic acid anhydride and a structural unit derived from a cyclic ether, the polymer block B contains a structural unit derived from a cyclic ester, A block copolymer in which the proportion of structural units derived from the cyclic ester is 55% by mass or more and 97% by mass or less.

9. 9. The block copolymer according to claim 8, which is a BAB triblock polymer or a star block polymer having three or more AB arm structures, in which the polymer block B is arranged at the end of a polymer chain.

10. A method for producing the block copolymer according to claim 8 or 9, A method for producing a block copolymer, comprising polymerizing a monomer composition containing a cyclic acid anhydride, a cyclic ether, and a cyclic ester in the presence of a polymerization initiator and an alkali metal carboxylate.

11. The method for producing a block copolymer according to claim 10 , wherein the polymerization initiator is an alcohol or a carboxylic acid.

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