Polyester adhesive and method for producing the same, and block copolymer and method for producing 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, as well as 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 the biomass-based production of various polymer materials and the imparting of biodegradability have become important. Adhesive products are also required to be converted to biomass-based production or to impart biodegradability, and various studies are underway (see, for example, Non-Patent Document 1). Non-Patent Document 1 discloses the production of a triblock-type polyester by a two-step synthesis process using biodegradable monomers, and the acquisition of a polyester pressure-sensitive adhesive (PSA) using this polyester. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Angew.Chem,Int.Ed., 2020, No. 59, p.23450-23455 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In polyester adhesives using block copolymers, precise molecular design of the block copolymer is necessary for the adhesive performance to be realized. Therefore, as described in Non-Patent Document 1, the synthesis of block copolymers requires a multi-step process and complicated operations. In such cases, there are concerns that it may lead to increased manufacturing time and costs in adhesive production, as well as the large-scale consumption of organic solvents.

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

[0006] The present inventors have found that the above problems can be solved by polymerizing a monomer mixture, which is a combination of specific monomers, in the presence of a polymerization initiator and a specific catalyst. Specifically, the present invention provides the following polyester adhesive and a method for producing the same, as well as a block copolymer and a method for producing the same.

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

[10] The method for producing a block copolymer according to [8] or [9], which comprises polymerizing a monomer composition containing a cyclic 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. [Effect of the Invention]

[0008] The polyester-based adhesive and the block copolymer of the present invention exhibit excellent adhesive performance and can be obtained by a simple synthesis operation. [Embodiments for Carrying Out the Invention]

[0009] Hereinafter, matters related to the present invention will be described in detail. In this specification, the numerical range indicated by "~" includes the numerical values described before and after it as the upper limit value and the lower limit value.

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

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

[0012] (Polymer block A) · Structural unit (U1) In 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)-) within the molecule. Examples of cyclic acid anhydrides include monocyclic cyclic acid anhydrides and fused cyclic cyclic acid anhydrides. Furthermore, the cyclic acid anhydride may have substituents bonded to the ring. Examples of substituents include monovalent linear hydrocarbon groups having 1 to 20 carbon atoms, monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms, monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, hydroxyl groups, carboxyl groups, nitro groups, halogen atoms (fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, etc.), and monovalent heterocyclic groups.

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

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

[0015] The number of carbon atoms in the cyclic acid anhydride is preferably 5 or more, as this allows the molecular weight of the block copolymer (P) to be sufficiently large, thereby obtaining a block copolymer (P) with superior adhesive performance. From a similar viewpoint, at least one selected from the group consisting of cyclic acid anhydrides with 6 or more ring members and cyclic acid anhydrides having a condensed ring structure can be preferably used as the cyclic acid anhydride.

[0016] Specific examples of cyclic acid anhydrides that constitute structural unit (U1) include, for example, the compound represented by the following formula. Note that polymer block A may contain only one type of structural unit (U1), or it may contain two or more types. [ka]

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

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

[0019] In the above formula (1), the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by R 1 or R 2 includes 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 thereof include the same groups as those exemplified as the substituent that the cyclic anhydride may have. When R 1 or R 2 is a substituted monovalent hydrocarbon group having 1 to 20 carbon atoms, examples of the substituent include a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), a nitro group, and the like.)

[0020] R 1 and R 2 combine to form a ring, examples of the ring include a cyclohexane ring, a cyclohexene ring, and the like. These rings may have a substituent.) From the viewpoint of the reactivity of the compound represented by the above formula (1), it is preferable that at least one of R 1 and R 2 is a hydrogen atom.)

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

Chemical formula

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

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

[0024] (Polymer Block B) In polymer block B, cyclic esters 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. Lactides include glycolides obtained by the dehydration condensation of two glycolic acid molecules, dilactiides (L-lactide, D-lactide, Meso-lactide) obtained by the dehydration condensation of two lactic acid molecules, and tetramethylglycolide. Carbonates include trimethylene carbonate.

[0025] In terms of being a biomass raw material obtainable from natural products, being biodegradable, and readily available, the cyclic ester constituting the structural unit (U3) is preferably a dilactide, and more preferably L-lactide and / or D-lactide. When using L-lactide and / or D-lactide in the synthesis of 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 being easy to control the adhesion of the block copolymer (P) and being easy to design the block copolymer (P), it is preferable to use L-lactide alone as the dilactide.

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

[0027] From the viewpoint of obtaining a block copolymer (P) with excellent adhesive performance, the proportion of structural units (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, relative to the total structural units constituting the block copolymer (P). Furthermore, the upper limit of the proportion of structural units (U3) is preferably 95% by mass or less, and more preferably 90% by mass or less, relative to the total structural units constituting the block copolymer (P).

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

[0029] When the block copolymer (P) is a linear polymer, examples of block copolymers (P) include AB-type diblock polymers, ABA-type triblock polymers, BAB-type triblock polymers, ABABA-type pentablock polymers, BABAB-type pentablock polymers, and the like. Of these, triblock polymers are preferred because polymers with excellent adhesive properties can be obtained through simpler operations, and BAB-type triblock polymers are more preferred.

[0030] When the block copolymer (P) is a branched polymer, examples of the block copolymer (P) include star-type block polymers and core-shell-type block polymers having three or more AB-type arm structures. In these branched polymers, from the viewpoint of improving adhesive performance, it is preferable that polymer blocks B, which can become hard segments, are located at the molecular ends (more specifically, at the ends opposite to the branched or core parts). In star-type block polymers, the number of arm structures within one molecule is preferably 3 to 10, and 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 polymer blocks B, which can act as hard segments, located at the end of the polymer chain within a single polymer molecule. In terms of being able to obtain a polymer exhibiting high adhesive performance through a simple synthesis operation, it is particularly preferable that the block copolymer (P) is a BAB-type triblock polymer or a star-type block polymer having three or more AB-type arm structures with polymer blocks B located at the molecular ends. It is believed that block copolymers (P) with polymer blocks B located at the molecular ends exhibit excellent adhesive performance because a pseudo-crosslinked structure is formed by the polymer blocks B, which can act as hard segments.

[0032] The block copolymer (P) may further contain polymer blocks different from polymer block A and polymer block B (hereinafter also referred to as "other polymer blocks"). Examples of other polymer blocks include polyalkylene oxy structures (e.g., polyethylene oxy structures, polypropylene oxy structures). These other polymer blocks can be introduced into the block copolymer (P) by polymerization using a compound having a structure corresponding to the other polymer block as a polymerization initiator (e.g., polyalkylene glycol).

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

[0034] (Physical properties of block copolymer (P)) Regarding the molecular weight characteristics of Book copolymer (P), 1 The number-average molecular weight (Mn) is measured by H-NMR. NMRThe 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, from the viewpoint of obtaining a polymer that exhibits good adhesion. NMR Regarding the upper limit, from the viewpoint of improving the handling properties of the polymer, it is preferable to have a number average molecular weight of 120,000 or less, and more preferably 100,000 or less. NMR teeth, 1 This value is determined by 1H-NMR measurement.

[0035] Furthermore, the number average molecular weight (Mn) calculated by the following formula (I) is also used. theo 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, from the viewpoint of obtaining a polymer that exhibits good adhesion. theo Regarding the upper limit, from the viewpoint of improving the handling properties of the polymer, a value of 120,000 or less is preferred, and a value of 100,000 or less is more preferred. Mn theo =Mi+(Xm1 / Xi)×(Mm1+Mm2)×Rm1+(Xm3 / Xi)×Mm3×Rm3 …(I) Mi: Molecular weight of polymerization initiator Xi: Amount of polymerization initiator to be added Xm1: Amount of cyclic acid anhydride added Xm2: Amount of cyclic ether to be charged Xm3: Amount of cyclic ester used Rm1: Reaction rate of cyclic acid anhydrides Rm3: Reaction rate of cyclic esters Mm1: Molecular weight of cyclic acid anhydride Mm2: Molecular weight of cyclic ethers Mm3: Amount of cyclic ester added The reaction rates of cyclic acid anhydrides and cyclic esters are as follows: 1 This value is determined by 1H-NMR measurement. For details, 1 This value is calculated from the ratio of the integral values ​​of the monomer and the resulting polymer, which are determined by 1H-NMR measurement.

[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, from the viewpoint of obtaining a polymer with superior adhesive performance. Furthermore, from the viewpoint of meltability during heat bonding, the glass transition temperature of the block copolymer (P) is preferably 100°C or lower, more preferably 80°C or lower, and more preferably 50°C or lower. In this specification, the glass transition point of the polymer is the value measured by differential scanning calorimetry (DSC). Details of the measurement method are as 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 order to obtain a polymer with excellent heat resistance. Details of the method for measuring the 5% weight loss temperature of the polymer are as described in the examples below.

[0038] <Method for manufacturing block copolymers> The method for synthesizing block copolymers (P) is not particularly limited as long as block copolymers (P) can be obtained. It is preferable to produce block copolymers (P) by 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, as this allows for the acquisition of precisely controlled block copolymers in a simple one-step synthesis. This polymerization method is significant because it allows for precise polymerization using a simple catalyst such as an alkali metal carboxylate, without the need for highly designed catalysts such as organometallic catalysts or organic ultrabase catalysts. Furthermore, it is significant because polymerization can be carried out under solvent-free conditions, contributing to a reduction in environmental impact.

[0039] (Polymerization initiator) As polymerization initiators, alcohols or carboxylic acids can be preferably used because they allow for the easy acquisition of the desired polymer. Examples of alcohols include monoalcohols and polyhydric alcohols. Examples of monoalcohols 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, octantriol, 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. Examples of carboxylic acids include aromatic carboxylic acids such as benzoic acid, phthalic acid, and terephthalic acid.

[0040] In the production of block copolymer (P), the amount of polymerization initiator used is, for example, 0.01 to 15 moles, preferably 0.05 to 10 moles, and more preferably 0.1 to 5 moles, per 100 moles of the total amount of monomer used for polymerization.

[0041] (Alkali metal carboxylates) Examples of alkali metal carboxylates include lithium salts, sodium salts, potassium salts, and cesium salts of carboxylic acids. Examples of carboxylic acids that yield alkali metal carboxylates include aliphatic carboxylic acids such as acetic acid, ethaneic 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. Among these, cesium salts of carboxylic acids are preferred as alkali metal carboxylates, and aliphatic monocarboxylic acid cesium salts can be preferably used.

[0042] In the production of the block copolymer (P), the amount of alkali metal carboxylate used is, for example, 0.01 to 15 moles, preferably 0.05 to 10 moles, and more preferably 0.1 to 5 moles, per 100 moles of the total amount of monomer used for polymerization.

[0043] The polymerization temperature and polymerization time are not particularly limited and can be set as appropriate. From the viewpoint of promoting the polymerization reaction, it is preferable to carry out the polymerization of monomers while heating. From the viewpoint of increasing the reaction rate while suppressing side reactions, the polymerization temperature is, for example, in the range of 30°C to 150°C, preferably in the range of 40°C to 130°C, and more preferably in the 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 should be a pressure that can maintain the polymerization temperature. Furthermore, 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 lower), or under dry nitrogen or dry argon. The polymerization reaction may be carried out while stirring in the reactor.

[0044] One example of a polymerization method involves charging cyclic acid anhydrides, cyclic ethers, and cyclic esters as monomers into a reaction vessel. Before, after, or simultaneously with the charging of the monomers, a polymerization initiator and an alkali metal carboxylate as a catalyst are added to the reaction vessel, and the polymerization reaction is initiated by heating. By employing this polymerization method, block copolymers (P) can be obtained through a simple one-step synthesis. By using monofunctional or bifunctional compounds (monoalcohols, dialcohols, etc.) as polymerization initiators, linear polymers can be obtained as block copolymers (P). Furthermore, by using trifunctional or more functional compounds (trialcohols, polyalcohols, etc.) as polymerization initiators, branched polymers can be obtained as block copolymers (P).

[0045] <Other ingredients> The polyester adhesive of the present invention may consist of a block copolymer (P). It may also contain, together with the block copolymer (P), other components different from the block copolymer (P) (referred to as "other components"). Examples of other components include plasticizers, particles, colorants, fragrances, solvents, and strength enhancers. The content of these other components can be appropriately set according to the application of the adhesive, etc., as long as it does not impair the effects of the present invention.

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

[0047] The adherends to which the polyester adhesive of the present invention can be applied are not particularly limited, and adherends of various materials can be used. Examples of adherends include substrates formed from resin, metal, ceramic, rubber, glass, wood, cloth, porcelain, leather, or combinations of two or more of these. Furthermore, the adherend may further contain reinforcing materials such as carbon fibers or glass fibers, or colorants.

[0048] Examples of resins among those listed above 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 (acrylonitrile-butadiene-styrene copolymer), acrylic resin, polymethyl methacrylate resin, polyester resin, polyamide resin, polybutylene terephthalate resin, polycarbonate resin, polyphenylene sulfide (PPS) resin, and polyetheretherketone (PEEK) resin.

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

[0050] Block copolymer The present invention provides the block copolymer (P) described above. Because the block copolymer (P) exhibits excellent adhesive properties, it is suitable as a polymer component in adhesives (including pressure-sensitive adhesives (PSA)). Furthermore, numerous 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 readily available. Moreover, because the main chain of the block copolymer (P) is polyester, its decomposition in the environment can be expected depending on the selection of the monomer structure. Such a block copolymer (P) is also significant from the perspective of realizing a sustainable society in recent years. [Examples]

[0051] The present invention will be described in detail below based on the following 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] <Analysis of the polymer> The details of the polymer analysis method are as follows: (Number average molecular weight Mn calculated based on molecular weight) theo ) The number-average molecular weight Mn is calculated using the above formula (I). theo They sought it.

[0053] (Number-average molecular weight Mn by NMR analysis) NMR ) Number average molecular weight Mn NMR teeth, 1 The results were obtained using a 1H-NMR spectrometer (400MHz). (Glass transition temperature Tg) The glass transition temperature (Tg) of the polymer was measured using a suggestive scanning calorimetry system (DSC7000X, Hitachi High-Tech Science Corporation) under a nitrogen atmosphere. The conditions were as follows: the first heating process involved heating to 180°C at a rate of 10°C / min, holding at isothermal for 5 minutes, then cooling to -100°C at a rate of 10°C / min, holding at isothermal for 5 minutes, and finally, the second heating process involved heating to 180°C at a rate of 10°C / min. The second heating process was recorded. (5% weight loss temperature Td 5% ) Temperature (Td) of polymer at which 5% weight loss occurs. 5% The temperature was measured using a thermogravimetric analyzer (STA200RU, manufactured by Hitachi High-Tech Science Corporation) under a nitrogen atmosphere, with 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 the total structural units of the polymer (unit: mass%), referred to as the "LLA ratio," is: 1The values ​​were obtained by converting the molar percentages measured using a 400 MHz H-NMR spectrometer to mass percentages.

[0055] <Synthesis of block copolymer (P)> [Example 1] Block copolymer P1 was synthesized according to Scheme 1 below. [ka]

[0056] In a glove box, 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) were added to a flask equipped with a needle valve. The flask was sealed with the needle valve under an argon atmosphere, removed from the glove box, and polymerization was carried out in an oil bath at 100°C. After 5.5 hours, polymerization was stopped by diluting the reaction solution with dichloromethane, and the solution was reprecipitation in cooled methanol to obtain poly(L-lactide)-block-poly(glutaric anhydride-alternating-butylene oxide)-block-poly(L-lactide) (PLLA-b-poly(GA-alt-BO)-b-PLLA) as a colorless, viscous solid. This was designated as block copolymer P1. Furthermore, the physical properties of the obtained block copolymer P1 are shown in Table 1.

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

[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 anhydride GA: Glutaric anhydride PA: Phthalic anhydride • Cyclic ether BO: Butylene oxide PO: Propylene oxide EGE: Ethyl glycidyl ether EHGE: Ethylhexylglycidyl ether AGE: Allyl glycidyl ether • Cyclic ester LLA: L-lactide

[0060] [Comparative Synthesis Example 3] Poly-L-lactide (PLLA) was synthesized according to Scheme 2 below. [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 the needle valve under an argon atmosphere, removed from the glove box, and polymerization was carried out in an oil bath at 100°C. After 1.5 hours, polymerization was stopped by diluting the reaction solution with dichloromethane, and the solution was reprecipitation in cooled methanol to obtain PLLA (denoted as PLLA-1) as a colorless, viscous solid. The yield was 4.46 g, with a yield of 92.6%. PLLA-1 has a number-average molecular weight of Mn NMR The result was 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 under an argon atmosphere, removed from the glove box, and polymerization was carried out in an oil bath at 100°C. After 10 hours, polymerization was stopped by diluting the reaction solution with dichloromethane, and the solution was reprecipitation in cooled methanol to obtain PLLA (denoted as PLLA-2) as a colorless, viscous solid. The yield was 4.06 g, with a yield of 80.8%. PLLA-2 has a number-average molecular weight of Mn NMR The result was 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 the needle valve under an argon atmosphere, removed from the glove box, and polymerization was carried out in an oil bath at 100°C. After 19 hours, polymerization was stopped by diluting the reaction solution with dichloromethane, and the solution was reprecipitation in cooled methanol to obtain a colorless, viscous liquid glutaric anhydride / butylene oxide copolymer (denoted as PGABO-1). The yield was 1.06 g, with a yield of 55.1%. The number average molecular weight of PGABO-1 is Mn NMR The result was 4,640.

[0064] <Evaluation of tensile shear bond strength> [Examples 22-27, Comparative Examples 1-5] Each polymer shown in Table 2 was molded into a film measuring 25 mm wide × 12.5 mm long × 300 μm thick to obtain a film body. Two pieces of wood (beech wood, 25 mm wide × 50 mm long × 2 mm thick) were used as substrates. The film body was sandwiched between the substrates and bonded together at 100°C and 1 MPa, then cured at 23°C for 24 hours. The tensile shear adhesive strength was measured at a tensile speed of 10 mm / min in accordance with JIS K 6850-1999 (Test 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 adhesive strength was evaluated in the same manner as in Examples 22-27 and Comparative Examples 1-5. 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 20:80 (mass ratio) was used as an adhesive, and the tensile shear adhesive strength was evaluated in the same manner as in Examples 22-27 and Comparative Examples 1-5. The evaluation results are shown in Table 2.

[0066] [Table 2]

[0067] As shown in Table 2, the adhesives of Examples 22-27 showed 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 (mixing ratio: 33 / 67), had films that were too brittle, making it impossible to conduct tensile shear adhesive strength tests (indicated as "unmeasurable" in the table). Furthermore, the adhesive of Comparative Example 7, which used a blend of glutaric anhydride / butylene oxide copolymer and PLLA (mixing ratio: 20 / 80), had a low adhesive strength of 1.23 MPa, which was inferior to that of Examples 22-27.

[0068] [Examples 28-33, Comparative Examples 8-13] The tensile shear adhesive strength was evaluated in the same manner as in Examples 22-27 and Comparative Examples 1-5, except that polyethylene terephthalate (PET) film (25 mm wide x 100 mm long x 0.1 mm thick) was used as the base material instead of wood. The evaluation results are shown in Table 3.

[0069] [Table 3]

[0070] As shown in Table 3, the adhesives of Examples 28-33 showed 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 the Comparative Example using 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 (mixing ratio: 33 / 67), were too brittle, making it impossible to conduct tensile shear adhesive strength tests.

Claims

1. A method for producing a polyester adhesive containing a block copolymer having polymer block A and polymer block B, The polymer block A comprises structural units derived from cyclic acid anhydrides and structural units derived from cyclic ethers. The polymer block B includes structural units derived from cyclic esters, The proportion of structural units derived from the cyclic ester is 55% by mass or more and 97% by mass or less relative to the total structural units constituting the block copolymer. The cyclic ether is an epoxide, The cyclic ester is a dilactide, A method for producing a polyester adhesive, comprising polymerizing a monomer composition containing the cyclic acid anhydride, the cyclic ether, and the cyclic ester in the presence of a polymerization initiator and an alkali metal carboxylate to obtain the block copolymer.

2. The method for producing a polyester adhesive according to claim 1, wherein the polymerization initiator is an alcohol or a carboxylic acid.

3. A method for producing a polyester adhesive according to claim 1, wherein polymerization is carried out under solvent-free conditions.

4. A method for producing a block copolymer having polymer block A and polymer block B, The polymer block A comprises structural units derived from cyclic acid anhydrides and structural units derived from cyclic ethers. The polymer block B includes structural units derived from cyclic esters, The proportion of structural units derived from the cyclic ester is 55% by mass or more and 97% by mass or less. The cyclic ether is an epoxide, The cyclic ester is a dilactide, A method for producing a block copolymer, comprising polymerizing a monomer composition containing the cyclic acid anhydride, the cyclic ether, and the cyclic ester in the presence of a polymerization initiator and an alkali metal carboxylate.

5. The method for producing a block copolymer according to claim 4, wherein the polymerization initiator is an alcohol or a carboxylic acid.

6. A method for producing a block copolymer according to claim 4, wherein polymerization is carried out under solvent-free conditions.

Images