Polyester, adhesive composition, adhesive, adhesive tape, and adhesive tape for electronic member

Abstract

The purpose of the present invention is to provide a polyester for use in an adhesive composition having a high environmental load-reducing effect, which has excellent wet-heat peelability, adhesive strength, retention, and solution stability in a film state, and also has excellent biomass degree, reusability, and biodegradability, and is a polyester for use in an adhesive composition having a high environmental load-reducing effect. The polyester resin composition contains a polyester having a structural unit derived from a polycarboxylic acid (a) and a structural unit derived from a polyol (b), the polycarboxylic acid (a) contains an aliphatic polycarboxylic acid (a1) having 4 or less carbon atoms, and the content of the structural unit derived from the aliphatic polycarboxylic acid (a1) is 50 moles or more per 100 moles of the structural unit derived from the polycarboxylic acid (a). The polyester has a crystal melting heat of 30 J / g or less, or a structural unit derived from 1, 4-butanediol is less than 50 moles per 100 moles of the structural unit derived from the polyol (b).

Description

Technical Field

[0001] The present invention relates to polyesters, adhesive compositions containing polyesters, adhesives, adhesive tapes, and adhesive tapes for electronic components, and particularly to thin adhesive tapes and adhesive tapes for electronic components that are suitable for use in housings of portable electronic terminals or in joining portions of components and have a high environmental impact reduction effect. Background Art

[0002] Adhesive tapes, which can bond substrates and components without requiring heat or other energy, offer excellent workability and are used as a highly reliable bonding method for securing components in various industries, including office automation (OA) equipment and home appliances. These OA devices are becoming increasingly miniaturized and thinner, along with their increasing functionality. The demand for miniaturization and thinning is particularly high in portable electronic devices, such as personal computers, digital video cameras, and, increasingly, electronic notebooks, mobile phones, PHSs, smartphones, gaming devices, and e-readers. Along with the thinning of key components in these portable electronic devices, the adhesive tapes used to secure them are also being thinned.

[0003] In addition, adhesive tapes are widely used for fixing and labeling main components (metal, plastic components, etc.) of OA equipment, portable electronic terminals, etc. However, existing adhesive tapes are difficult to peel / disassemble, cannot be graded and reused, and are mostly discarded as incombustibles.

[0004] In view of environmental issues in recent years, there is a demand for adhesive tapes that can be easily disassembled and peeled off when discarded and are suitable for fractional recycling, and adhesives therefor.

[0005] For a double-sided adhesive tape of a transparent film with excellent adhesive strength and high-temperature retention, which is suitable for fixing components of portable electronic terminals such as mobile phones, film displays, etc., or for laminating substrates of optical disks, fixing polarizing plates, etc., for example, Patent Document 1 proposes a double-sided adhesive tape, which has adhesive layers formed from an adhesive composition on both sides of a core material, and the total thickness is 30 μm or less, and the thickness of the adhesive layers on both sides is 2 to 10 μm, respectively. The adhesive composition contains: a specific amount of an acrylic acid ester copolymer containing 90% by mass or more of butyl acrylate units and a weight-average molecular weight of 700,000 or more, and a specific amount of a tackifier.

[0006] In addition, for example, Patent Document 2 proposes an adhesive containing a polyester, wherein the polyester comprises an aromatic dicarboxylic acid and a diol having a hydrocarbon in a side chain, and a trivalent or higher polyol and / or a trivalent or higher polycarboxylic acid as essential components, and is obtained by polycondensing a specific amount of the polyol and / or the polycarboxylic acid. By using this polyester, an adhesive having excellent adhesiveness and heat resistance is obtained, which exhibits sufficient adhesive force with a pressure of the order of finger pressure, has excellent adhesiveness, mechanical strength, and especially excellent heat resistance, and can be expanded to a wide range of uses.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2007-169327

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2007-099879

[0011] Patent Document 3: Japanese Patent Application Laid-Open No. 2022-079443 Summary of the Invention

[0012] Problems to be solved by the invention

[0013] However, the techniques disclosed in Patent Documents 1 and 2 above do not exhibit sufficient adhesive strength to various adherends when in the form of thin films, and further improvement is needed. Furthermore, the acrylic adhesive disclosed in Patent Document 1 generally has a low elastic modulus and low cohesive strength. Therefore, when the adhesive layer is formed into a thin film, adhesive residue is easily left when peeled, and further improvement is needed.

[0014] Polyester-based adhesives have also been studied as adhesives with high elastic modulus and high cohesive strength (resulting in adhesive rupture during peeling and less likely to leave adhesive residue). However, the aforementioned Patent Document 2 discloses no application of polyester-based adhesives in a film state. Furthermore, when formed into films, the adhesive strength is not sufficiently exhibited, requiring further improvement.

[0015] Acrylic adhesives have been widely used, but in recent years, the use of polyester adhesives has also increased. Compared with acrylic adhesives, polyester adhesives have higher heat resistance and are therefore excellent for use in electronic components, etc. In addition, they have good compatibility with ester films such as polyethylene terephthalate (PET). Therefore, polyester adhesives can often be used even in areas where acrylic adhesives are difficult to use. Furthermore, in recent years, the response to environmental load has received increasing attention, but during waste disposal, polyester adhesives can be reduced to oligomers and monomers through depolymerization. When considering reuse, it can be said that they have a smaller environmental load than using acrylic adhesives.

[0016] Therefore, although a film-based PSA sheet using a specific polyester, such as that disclosed in Patent Document 3, has been proposed, there is room for improvement in terms of adhesive strength and holding power. Furthermore, the proposal in Patent Document 3 does not consider the biomass content, biodegradability, or recyclability of the PSA sheet, leaving issues with regard to environmental impact.

[0017] Methods used to solve problems

[0018] When polyester is used in an adhesive composition, it is generally known that increasing the ester bond concentration of the polyester improves adhesion to an adherend and increases adhesive strength.

[0019] However, if the ester bond concentration is too high, there are problems such as the molecular weight between ester bonds becomes too small, the glass transition temperature of the polyester becomes too high, and adhesion is impaired, or crystallinity is developed, which impairs solution stability, biodegradability, and recyclability.

[0020] Therefore, it is difficult to simultaneously lower the glass transition temperature while increasing the ester bond concentration, and it is difficult to obtain a polyester-based adhesive composition that achieves a balance between strong adhesive strength, solution stability, biodegradability, and recyclability.

[0021] Therefore, the present inventors have conducted intensive studies and have found that, by using a polyester for use in a polyester-based adhesive composition, a polyester-based adhesive composition having excellent film-like adhesive strength, holding power, solution stability, and recyclability, and further having excellent biomass content and biodegradability, can be obtained. The polyester contains, in the polycarboxylic acid component, a specific amount or more of an aliphatic polycarboxylic acid (a1) having 4 or fewer carbon atoms and having a crystal fusion heat of 30 J / g or less, or a polyester in which the content of structural units derived from 1,4-butanediol is less than 50 mol per 100 mol of structural units derived from a polyol (b).

[0022] Furthermore, surprisingly, it has been found that, by using, as the polyester used in the polyester-based adhesive composition, a polyester containing a specific amount or more of an aliphatic polycarboxylic acid (a1) having 4 or fewer carbon atoms in the polycarboxylic acid component and having a crystal fusion heat of 30 J / g or less, or a polyester containing less than 50 mol of structural units derived from 1,4-butanediol per 100 mol of structural units derived from the polyol (b), a polyester-based adhesive composition having easy wet heat releasability and excellent recyclability and having a high environmental load reduction effect can be obtained.

[0023] When the present adhesive composition is used to bond components of a product that is made by combining and integrating components made of multiple different materials with the intention of recycling, the components can be easily separated and disassembled and sorted by material simply by heating the bonded parts under high humidity when the product is recycled. This is therefore extremely useful for improving the recycling rate.

[0024] That is, the present invention has the following aspects [1] to

[16] .

[0025] [1] A polyester having a structural unit derived from a polycarboxylic acid (a) and a structural unit derived from a polyol (b),

[0026] The polycarboxylic acid (a) contains an aliphatic polycarboxylic acid (a1) having 4 or less carbon atoms.

[0027] In 100 mol of the structural units derived from the polycarboxylic acid (a), the structural units derived from the aliphatic polycarboxylic acid (a1) having 4 or less carbon atoms account for 50 mol or more.

[0028] The polyester has a crystal melting heat of 30 J / g or less.

[0029] [2] A polyester having a structural unit derived from a polycarboxylic acid (a) and a structural unit derived from a polyol (b),

[0030] The polycarboxylic acid (a) contains an aliphatic polycarboxylic acid (a1) having 4 or less carbon atoms.

[0031] In 100 mol of the structural units derived from the polycarboxylic acid (a), the structural units derived from the aliphatic polycarboxylic acid (a1) having 4 or less carbon atoms account for 50 mol or more.

[0032] The content of the structural unit derived from 1,4-butanediol in 100 mol of the structural unit derived from the polyol (b) is less than 50 mol.

[0033] [3] The polyester according to [1] or [2], wherein the aliphatic polycarboxylic acid (a1) having 4 or less carbon atoms contains a structural unit derived from succinic acid.

[0034] [4] The polyester according to any one of [1] to [3], wherein the polyol (b) contains a linear aliphatic polyol (b1) having an odd number of carbon atoms.

[0035] [5] The polyester according to any one of [1] to [4], wherein the polyol (b) contains a linear aliphatic polyol (b1) composed of an odd number of carbon atoms, and the content of the linear aliphatic polyol (b1) composed of an odd number of carbon atoms is 10 mol or more in 100 mol of the structural units derived from the polyol (b).

[0036] [6] The polyester according to any one of [1] to [5], wherein the polyol (b) contains a linear aliphatic polyol (b1) having an odd number of carbon atoms, and the linear aliphatic polyol (b1) having an odd number of carbon atoms contains a structural unit derived from at least one selected from the group consisting of 1,3-propylene glycol, 1,5-pentanediol, 1,7-heptanediol, and 1,9-nonanediol.

[0037] [7] The polyester according to any one of [1] to [6], wherein the polyol (b) contains a side chain aliphatic diol (b2) having a hydrocarbon group in a side chain.

[0038] [8] The polyester according to any one of [1] to [7], wherein the polyol (b) contains: a linear aliphatic polyol (b1) composed of a polyol having an odd number of carbon atoms, and a side-chain aliphatic diol (b2) having a hydrocarbon group in the side chain, and the molar ratio (b1) / (b2) of the linear aliphatic polyol (b1) composed of a polyol having an odd number of carbon atoms to the side-chain aliphatic diol (b2) having a hydrocarbon group in the side chain is 0.5 to 10.0.

[0039] [9] The polyester according to any one of [1] to [8], wherein the polyester has an ester bond concentration of 11 to 14 mmol / g.

[0040]

[10] The polyester according to any one of [1] to [9], wherein the biomass degree of the polyester is 30% or more.

[0041]

[11] An adhesive composition comprising the polyester described in any one of [1] to

[10] .

[0042]

[12] An adhesive composition, wherein the adhesive composition of

[11] or

[16] comprises a hydrolysis inhibitor, and the hydrolysis inhibitor is a monocarbodiimide compound.

[0043]

[13] An adhesive comprising the adhesive composition of

[11] or

[16] and a crosslinking agent, wherein the adhesive is crosslinked by the crosslinking agent, and the adhesive has a gel fraction of 5 to 60%.

[0044]

[14] An adhesive tape comprising the adhesive according to

[13] .

[0045]

[15] An adhesive tape for electronic components, comprising the adhesive according to

[13] .

[0046]

[16] An adhesive composition comprising a polyester having a structural unit derived from a polycarboxylic acid (a) and a structural unit derived from a polyol (b),

[0047] The polycarboxylic acid (a) contains an aliphatic polycarboxylic acid (a1) having 4 or less carbon atoms.

[0048] The structural unit derived from the aliphatic polycarboxylic acid (a1) having 4 or less carbon atoms accounts for 50 mol or more of 100 mol of the structural unit derived from the polycarboxylic acid (a).

[0049] Effects of the Invention

[0050] The adhesive composition using the polyester of the present invention exhibits excellent wet-heat peelability, adhesive strength, and holding power, particularly excellent adhesive strength when formed into a film. Furthermore, the adhesive composition exhibits excellent biomass content, solution stability, recyclability, and biodegradability.

[0051] Therefore, the adhesive composition of the present invention is suitable for adhesives such as single-sided or double-sided adhesive tapes used for bonding optical components, and single-sided or double-sided adhesive tapes for fixing components of portable electronic terminals and electronic components. DETAILED DESCRIPTION

[0052] Hereinafter, the configuration of the present invention will be described in detail, but these are merely examples of preferred embodiments.

[0053] It should be noted that in this specification, the term "class" following a compound name is a concept that includes not only the compound itself but also its derivatives. For example, "carboxylic acids" refers to carboxylic acid derivatives such as carboxylates, carboxylic anhydrides, carboxylic halides, and carboxylic esters in addition to carboxylic acids.

[0054] Furthermore, “X and / or Y (X and Y are arbitrary configurations)” means at least one of X and Y, and also means three types: X alone, Y alone, and X and Y.

[0055] Furthermore, in this specification, the term "tape" also includes "film" and "sheet".

[0056] The polyester according to one embodiment of the present invention comprises structural units derived from a polycarboxylic acid (a) and structural units derived from a polyol (b), wherein the polycarboxylic acid (a) contains an aliphatic polycarboxylic acid (a1) having 4 or less carbon atoms, and the proportion of structural units derived from the aliphatic polycarboxylic acid (a1) having 4 or less carbon atoms is 50 mol or more per 100 mol of the structural units derived from the polycarboxylic acid (a), and the heat of crystallization fusion of the polyester is 30 J / g or less, or the proportion of structural units derived from 1,4-butanediol is less than 50 mol per 100 mol of the structural units derived from the polyol (b).

[0057] Furthermore, the adhesive according to one embodiment of the present invention is obtained by crosslinking an adhesive composition containing the aforementioned polyester and a crosslinking agent (B), and has a gel fraction of 5 to 60%.

[0058] Hereinafter, each component constituting the polyester and the adhesive composition which is one embodiment of the present invention (hereinafter sometimes referred to as “this embodiment”) will be described in order.

[0059] <Polyester>

[0060] The polyester used in the present embodiment has structural units derived from polycarboxylic acids (a) and structural units derived from polyols (b), and the structural units derived from the polycarboxylic acids (a) contain 50 mol or more, preferably 60 mol or more, more preferably 70 mol or more, particularly preferably 80 mol or more, 85 mol or more, particularly preferably 90 mol or more, and most preferably 95 mol or more of structural units derived from aliphatic polycarboxylic acids having 4 or less carbon atoms, per 100 mol of the structural units derived from the polycarboxylic acids (a).

[0061] It should be noted that the upper limit is usually 100 mol or less. The adhesive layer of this embodiment contains a polyester containing a specific amount of structural units derived from an aliphatic polycarboxylic acid (a1) having 4 or less carbon atoms. Therefore, even in the form of a film, it has excellent adhesion to various adherends and is also excellent in biodegradability and recyclability.

[0062] Furthermore, the polyester used in the present embodiment has a structural unit derived from a polycarboxylic acid (a) and a structural unit derived from a polyol (b).

[0063] [Structural unit derived from polycarboxylic acid (a)]

[0064] The polyester contains, as the structural units derived from the polycarboxylic acid (a), 50 mol or more of structural units derived from an aliphatic dicarboxylic acid (a1) having 4 or less carbon atoms (including carbon atoms in carboxyl groups) per 100 mol of the structural units derived from the polycarboxylic acid (a) in the entire polycarboxylic acid (a).

[0065] (Structural unit derived from aliphatic polycarboxylic acid (a1) having 4 or less carbon atoms)

[0066] As the structural unit derived from the aliphatic polycarboxylic acid (a1) having a carbon number of 4 or less, for example, there can be mentioned: a structural unit derived from a straight-chain aliphatic dicarboxylic acid such as succinic acid, oxalic acid, malonic acid, diglycolic acid, a structural unit derived from aliphatic dicarboxylic acids having an alkyl group in the side chain such as methylmalonic acid, a structural unit derived from aliphatic dicarboxylic acids containing unsaturated groups such as fumaric acid and maleic acid, etc., among which the structural unit derived from a straight-chain aliphatic dicarboxylic acid is preferred. These can be contained alone or in combination of two or more. Among them, the structural unit derived from succinic acid is preferred in terms of excellent adhesion to various adherends, the ability to increase biomass content, biodegradability, and excellent reusability.

[0067] Furthermore, in terms of excellent adhesion to various adherends, biodegradability, and recyclability even in the form of a film, the structural unit derived from the aliphatic polycarboxylic acid having 4 or less carbon atoms (a1) is preferably a structural unit derived from succinic acid.

[0068] The content of the structural unit derived from the aliphatic polycarboxylic acid (a1) having 4 or less carbon atoms is generally 50 mol or more, preferably 60 mol or more, more preferably 70 mol or more, particularly preferably 80 mol or more, more particularly preferably 85 mol or more, especially preferably 90 mol or more, and most preferably 95 mol or more, relative to 100 mol of the structural unit derived from the polycarboxylic acid (a). It should be noted that the upper limit of the content of the structural unit derived from the aliphatic polycarboxylic acid (a1) having 4 or less carbon atoms is generally 100 mol or less. If the content of the structural unit derived from the aliphatic polycarboxylic acid (a1) having 4 or less carbon atoms is above the aforementioned numerical value, there is a tendency for excellent adhesion to various adherends, biodegradability, and excellent reusability.

[0069] (Structural units derived from other polycarboxylic acids)

[0070] As the structural units derived from the polycarboxylic acids (a) possessed by the polyester, in addition to the structural units derived from the aliphatic polycarboxylic acids (a1) having 4 or less carbon atoms, structural units derived from other polycarboxylic acids such as polycarboxylic acids having 5 or more carbon atoms, aromatic dicarboxylic acids, and trivalent or higher polycarboxylic acids may be contained. These may be contained alone or in combination of two or more.

[0071] Examples of the structural units derived from the polycarboxylic acids having 5 or more carbon atoms include: structural units derived from aliphatic dicarboxylic acids such as glutaric acid, adipic acid, trimethyladipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, thiodipropionic acid, and 1,9-nonanedicarboxylic acid; structural units derived from alicyclic dicarboxylic acids such as 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2,5-norbornanedicarboxylic acid, and adamantanedicarboxylic acid; and structural units derived from dimer acids derived by dimerizing unsaturated aliphatic acids such as oleic acid, linoleic acid, linolenic acid, and erucic acid.

[0072] The content of the structural units derived from the polycarboxylic acid having 5 or more carbon atoms is generally 50 mol or less, preferably 40 mol or less, more preferably 30 mol or less, even more preferably 20 mol or less, particularly preferably 10 mol or less, and particularly preferably 5 mol or less, relative to 100 mol of the structural units derived from the polycarboxylic acid (a). The lower limit is generally 0 mol or more. If the content of the structural units derived from the polycarboxylic acid having 5 or more carbon atoms is too high, film adhesion, biodegradability, and recyclability tend to decrease.

[0073] Examples of the structural unit derived from the aromatic dicarboxylic acid include structural units derived from aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, benzylmalonic acid, biphenyl dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, and naphthalene dicarboxylic acid such as 1,8-naphthalene dicarboxylic acid, 2,3-naphthalene dicarboxylic acid, and 2,7-naphthalene dicarboxylic acid.

[0074] Examples of the structural unit derived from trivalent or higher polycarboxylic acids include structural units derived from trimellitic acid, pyromellitic acid, adamantanetricarboxylic acid, and trimesic acid.

[0075] Among the structural units derived from the polycarboxylic acids having 5 or more carbon atoms, structural units derived from aromatic dicarboxylic acids are preferably contained, and structural units derived from asymmetric aromatic dicarboxylic acids are particularly preferably contained, from the viewpoint of reducing the crystallinity of the polyester.

[0076] Examples of the structural unit derived from the asymmetric aromatic dicarboxylic acid include structural units derived from phthalic acid, isophthalic acid, 1,8-naphthalene dicarboxylic acid, and 2,3-naphthalene dicarboxylic acid. Among them, the structural unit derived from isophthalic acid is particularly preferred in terms of reactivity and adhesive strength.

[0077] The content of the structural units derived from aromatic dicarboxylic acids, particularly structural units derived from asymmetric aromatic dicarboxylic acids, is generally 50 mol or less, preferably 40 mol or less, more preferably 30 mol or less, even more preferably 25 mol or less, particularly preferably 20 mol or less, especially preferably 15 mol or less, and most preferably 5 mol or less, per 100 mol of structural units derived from the polycarboxylic acid (a). The lower limit is generally 0 mol. If the content of the structural units derived from aromatic dicarboxylic acids is too high, initial adhesion, tack, film adhesion, biodegradability, and recyclability tend to decrease.

[0078] [Structural unit derived from polyols (b)]

[0079] Examples of the structural units derived from polyols (b) in the polyester include structural units derived from diols and structural units derived from trivalent or higher polyols. These structural units may be present alone or in combination of two or more. In this embodiment, the polyester preferably contains structural units derived from diols having an odd number of carbon atoms. Using polyols having an odd number of carbon atoms rather than an even number of carbon atoms results in a more irregular structure of the polyester, which softens the polyester and reduces its crystallinity, thereby improving its adhesiveness.

[0080] (Structural unit derived from diols)

[0081] Examples of the structural units derived from diols include: structural units derived from aliphatic diols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 2,4-dimethyl-2-ethylhexane-1,3-diol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,6-hexanediol, and dimer diols derived by dimerizing unsaturated aliphatic acids such as oleic acid and erucic acid;

[0082] Structural units derived from alicyclic diols such as 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, spirodiol, tricyclodecanedimethanol, adamantanediol, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol;

[0083] Structural units derived from aromatic diols such as 4,4'-dihydroxydiphenyl sulfide, 4,4'-methylenediphenol, 4,4'-dihydroxybiphenyl, catechol, resorcinol, hydroquinone, 1,3-dihydroxynaphthalene, 1,4-benzenedimethanol, and ethylene oxide adducts and propylene oxide adducts thereof.

[0084] Furthermore, structural units derived from fatty acid esters derived from castor oil, glyceryl monostearate, etc. Among them, structural units derived from glycols having an odd number of carbon atoms are preferably contained.

[0085] Furthermore, the structural units derived from aliphatic diols can be distinguished as structural units derived from aliphatic diols having a linear structure and structural units derived from aliphatic diols having a hydrocarbon group in a side chain.

[0086] In this case, the content of the structural units derived from the linear aliphatic diol is generally 10 to 100 mol, preferably 15 to 98 mol, more preferably 40 to 95 mol, particularly preferably 50 to 90 mol, especially preferably 60 to 85 mol, and most preferably 70 to 80 mol, relative to 100 mol of the structural units derived from the polyol (b). If the above content is too low, the glass transition temperature of the polyester tends to increase, the adhesive strength tends to decrease, and the biodegradability and recyclability tends to decrease. However, if the above content is too high, the polyester tends to crystallize, the adhesive strength of the adhesive tends to decrease, and the solution stability tends to decrease.

[0087] As the structural units derived from linear aliphatic diols, those derived from linear aliphatic diols having 2 to 18 carbon atoms are preferred. Structural units derived from linear aliphatic diols having 4 or fewer carbon atoms are particularly preferred because they increase the ester bond concentration and polarity, resulting in excellent binding strength, and further, excellent biodegradability and recyclability. Specifically, structural units derived from ethylene glycol, 1,3-propylene glycol, and 1,4-butanediol are particularly preferred because they reduce crystallinity, provide excellent binding strength, and can increase biomass content.

[0088] The amount of the structural unit derived from 1,4-butanediol is preferably 50 mol or less, more preferably 30 to 0 mol, particularly preferably 15 to 0 mol, particularly preferably 5 to 0 mol, and most preferably 0 mol, per 100 mol of the structural unit derived from the polyol (b).

[0089] In addition, the polyester contained in the adhesive composition of the present embodiment preferably has the aforementioned structural units derived from the polyols (b), and the structural units derived from 1,4-butanediol are preferably 50 mol or less, more preferably 30 to 0 mol, particularly preferably 15 to 0 mol, especially preferably 5 to 0 mol, and most preferably 0 mol per 100 mol of the aforementioned structural units derived from the polyols (b).

[0090] If the content of the structural unit derived from 1,4-butanediol is too high, the crystallinity increases, and thus the wet heat peelability, adhesive strength, holding power, and solution stability of the film when the polyester adhesive composition is formed tend to deteriorate.

[0091] The content of the structural unit derived from the aliphatic diol (b2) having a hydrocarbon group in the side chain is generally 1 to 100 mol, preferably 2 to 70 mol, more preferably 3 to 60 mol, particularly preferably 5 to 50 mol, particularly preferably 7 to 40 mol, further preferably 10 to 35 mol, and most preferably 20 to 30 mol, relative to 100 mol of the structural unit derived from the polyol (b). If the above content is too low, the polyester tends to crystallize, resulting in a decrease in the adhesive strength of the adhesive. However, if the above content is too high, the ester bond concentration of the polyester tends to decrease, resulting in a decrease in adhesive strength, or poor recyclability and solution stability.

[0092] Examples of the structural unit derived from the aliphatic diol (b2) having a hydrocarbon group in a side chain include dipropylene glycol, 2,4-dimethyl-2-ethylhexane-1,3-diol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2-methyl-2-ethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 1,3-butanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,6-hexanediol, and dimer glycol. Among them, structural units derived from 2,2-dimethyl-1,3-propanediol (neopentyl glycol) and 2-methyl-1,3-propanediol are preferred.

[0093] (Structural unit derived from trivalent or higher polyols)

[0094] In the present embodiment, from the viewpoint of forming a reaction site with a crosslinking agent (B) described later and improving cohesive strength, the structural unit derived from the polyol (b) preferably contains a structural unit derived from a trivalent or higher polyol.

[0095] The content of the structural units derived from the trivalent or higher polyol is generally 20 mol or less, preferably 0.1 to 10 mol, more preferably 0.5 to 5 mol, particularly preferably 0.5 to 3 mol, particularly preferably 0.8 to 2.0 mol, and most preferably 1.0 to 1.5 mol, per 100 mol of the structural units derived from the polyol (b). If the content of the trivalent or higher polyol is too high, the production of the polyester tends to become difficult.

[0096] Examples of structural units derived from trivalent or higher polyols include structural units derived from 2-ethyl-2-hydroxymethyl-1,3-propanediol (trimethylolpropane), trimethylolethane, glycerol, pentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, and 1,2,6-hexanetriol. Among these, structural units derived from trimethylolpropane are particularly preferred because they are less likely to cause gelation.

[0097] In the present embodiment, from the viewpoints of being able to collapse crystallinity while lowering the glass transition temperature, and having excellent adhesive strength to various adherends, biodegradability, and recyclability, it is preferred to select at least one structural unit derived from a linear aliphatic polyol (b1) having an odd number of carbon atoms as the structural unit derived from the polyol (b). As the structural unit of the polyol (b), the structural unit derived from the aliphatic polyol (b1) having an odd number of carbon atoms further preferably includes a structural unit derived from 1,3-propanediol, 1,5-pentanediol, 1,7-heptanediol, or 1,9-nonanediol, and particularly preferably includes a structural unit derived from 1,3-propanediol or 1,5-pentanediol. From the viewpoints of increasing the ester bond concentration, achieving excellent adhesive strength, biodegradability, recyclability, and being able to increase the biomass content, it is particularly preferred to include a structural unit derived from 1,3-propanediol.

[0098] The content of the structural units derived from at least one selected from the aforementioned linear aliphatic polyols (b1) having an odd number of carbon atoms is generally 10 to 100 moles, preferably 20 to 98 moles, more preferably 40 to 95 moles, particularly preferably 50 to 90 moles, particularly preferably 60 to 85 moles, and most preferably 70 to 80 moles, per 100 moles of the structural units derived from the polyol (b). If the content of the linear aliphatic polyol having an odd number of carbon atoms is too low, the glass transition temperature of the polyester tends to increase, resulting in a decrease in the adhesive strength of the adhesive. However, even if the content is too high, the polyester tends to crystallize, resulting in a decrease in the adhesive strength, or poor reusability and solution stability.

[0099] In the present embodiment, in the case of a linear aliphatic polyol (b1) containing a polyol having an odd number of carbon atoms and at least one side-chain aliphatic diol (b2) having a hydrocarbon group in the side chain, the molar ratio (b1) / (b2) of the linear aliphatic polyol (b1) containing a polyol having an odd number of carbon atoms relative to the at least one side-chain aliphatic diol (b2) having a hydrocarbon group in the side chain is preferably 0.5 to 10.0, more preferably 0.6 to 8.0, further preferably 0.8 to 6.0, particularly preferably 1.0 to 5.0, especially preferably 2.0 to 4.5, and most preferably 3.0 to 4.0.

[0100] When the molar ratio (b1) / (b2) is within the above range, it is preferred in terms of excellent solution stability and reusability.

[0101] In this embodiment, the ratio (composition ratio) of the structural units derived from the various components of the polyester can be determined by a known method using NMR, for example, 1H-NMR measurement (proton nuclear magnetic resonance spectroscopy measurement) with a resonance frequency of 400 MHz, 13 The results can be determined by C-NMR measurement (carbon nuclear magnetic resonance spectroscopy) or the like.

[0102] The polyester used in this embodiment may have, in addition to the structural units derived from the polycarboxylic acids (a) and the structural units derived from the polyols (b), structural units derived from compounds having both carboxylic acid and hydroxyl groups in the molecule, within a range that does not impair the effects of this embodiment.

[0103] Examples of structural units derived from compounds having both a carboxylic acid and a hydroxyl group in the molecule include structural units derived from glycolic acid, lactic acid, hydroxybutyric acid, and hydroxycaproic acid. Among these, structural units derived from lactic acid and hydroxybutyric acid are particularly preferred from the perspectives of increasing the ester bond concentration, achieving excellent adhesive strength, biodegradability, and recyclability.

[0104] The content of the structural unit derived from a compound having both a carboxylic acid and a hydroxyl group in the molecule is preferably 100 mol or less, more preferably 80 mol or less, further preferably 60 mol or less, particularly preferably 40 mol or less, especially preferably 20 mol or less, and most preferably 10 mol or less, relative to 100 mol of the structural unit derived from the polycarboxylic acid (a). The lower limit is usually 0 mol or more. If the content of the structural unit derived from a compound having both a carboxylic acid and a hydroxyl group in the molecule is too high, the polyester tends to crystallize, the adhesive strength tends to decrease, or the solution stability tends to deteriorate. If it is too low, the biodegradability tends to deteriorate.

[0105] The polyester used in this embodiment may also contain structural units derived from cyclic esters. Examples of structural units derived from cyclic esters include: structural units derived from aliphatic lactones such as lactide, β-propiolactone, β-butyrolactone, γ-butyrolactone, γ-caprolactone, γ-octalactone, δ-valerolactone, δ-caprolactone, δ-octalactone, ε-caprolactone, δ-dodecalactone, α-methyl-γ-butyrolactone, β-methyl-δ-valerolactone, glycolide, and lactaldehyde. Among them, structural units derived from ε-caprolactone are preferred from the perspectives of lowering the glass transition temperature, excellent adhesion, and further excellent biodegradability. Structural units derived from these cyclic ester monomers may be used in combination of one or more.

[0106] The amount of the structural units derived from the cyclic ester is preferably 100 mol or less, more preferably 80 mol or less, particularly preferably 60 mol or less, further preferably 40 mol or less, particularly preferably 20 mol or less, and most preferably 10 mol or less, relative to 100 mol of the structural units derived from the polycarboxylic acid (a). The lower limit is usually 0 mol or more. If the content of the structural units derived from the cyclic ester is too high, the polyester tends to crystallize, the adhesive strength decreases, or the solution stability becomes poor. If it is too low, the biodegradability tends to be poor.

[0107] [Production of polyester]

[0108] The polyester of this embodiment can be produced by using the polycarboxylic acid (a) and the polyol (b) as raw materials and subjecting them to a polycondensation reaction in the presence of a catalyst according to a known method. Specifically, the polyester is obtained by subjecting the polycarboxylic acid (a) and the polyol (b) to a polycondensation reaction, and thus comprises structural units derived from the polycarboxylic acid (a) and structural units derived from the polyol (b).

[0109] When the polycondensation reaction is carried out, the esterification reaction or transesterification reaction is first carried out, and then the polycondensation reaction is carried out. It should be noted that when it is not necessary to form a high molecular weight, it is sometimes possible to produce it only by the esterification reaction or transesterification reaction.

[0110] The mixing ratio of the polycarboxylic acid (a) to the polyol (b) is preferably 1 to 2 equivalents, particularly preferably 1.1 to 1.7 equivalents, of the polyol (b) per 1 equivalent of the polycarboxylic acid (a). If the mixing ratio of the polyol (b) is too low, the acid value tends to increase, making it difficult to achieve a high molecular weight. If it is too high, the yield tends to decrease.

[0111] 〔Esterification reaction or transesterification reaction〕

[0112] In esterification or transesterification reactions, a catalyst is generally used. Specific examples include titanium-based catalysts such as tetraisopropyl titanate and tetrabutyl titanate, antimony-based catalysts such as antimony trioxide, germanium-based catalysts such as germanium dioxide, and catalysts such as zinc acetate, manganese acetate, and dibutyltin oxide. One or more of these catalysts can be used. Among these, antimony trioxide, tetrabutyl titanate, germanium dioxide, and zinc acetate are preferred from the perspective of balancing catalytic activity with the color tone of the resulting reactant.

[0113] The amount of the catalyst blended is preferably 1 to 10,000 ppm, particularly preferably 10 to 5,000 ppm, and even more preferably 20 to 3,000 ppm relative to the total copolymerization components (by mass). If the blending amount is too small, the polymerization reaction tends to be difficult to proceed sufficiently, while if it is too large, there is no advantage in shortening the reaction time and a tendency to cause side reactions.

[0114] The reaction temperature during the esterification reaction or transesterification reaction is preferably 200-300°C, particularly preferably 210-280°C, and even more preferably 220-260°C. If the reaction temperature is too low, the reaction tends to be less likely to proceed sufficiently, while if it is too high, side reactions such as decomposition tend to occur. The reaction pressure is usually atmospheric pressure.

[0115] The reaction conditions for the polycondensation reaction conducted after the esterification or transesterification reaction are preferably to further add an equivalent amount of the same catalyst used in the esterification or transesterification reaction, set the reaction temperature to preferably 220-280°C, particularly preferably 230-270°C, and gradually reduce the pressure in the reaction system to a final pressure of 5 hPa or less. If the reaction temperature is too low, the reaction tends to be less likely to proceed sufficiently, while if it is too high, side reactions such as decomposition tend to occur.

[0116] The ester bond concentration of the polyester obtained above is preferably 11 to 14 mmol / g, more preferably 11.1 to 13.5 mmol / g, even more preferably 11.2 to 13.0 mmol / g, particularly preferably 11.4 to 12.8 mmol / g, particularly preferably 11.6 to 12.6 mmol / g, and most preferably 12.0 to 12.5 mmol / g. If the ester bond concentration is too low, the polarity of the polyester decreases, resulting in poor adhesion, film adhesion, biodegradability, and recyclability.

[0117] The ester bond concentration (mmol / g) refers to the number of moles of ester bonds per gram of polyester and can be determined, for example, from a calculated value based on the input amount. This calculation method is based on dividing the smaller number of moles of the polycarboxylic acid (a) or the polyol (b) input by the total mass of the final product. An example of the calculation formula is shown below.

[0118] In addition, when each charging amount of polycarboxylic acid (a) and polyol (b) is the same molar amount, any of the following calculation formulas can be used.

[0119] In addition, when a substance having both a carboxylic acid and a hydroxyl group is used as a monomer, or when polyester is produced from caprolactone or the like, the calculation method may be changed as appropriate.

[0120] <When the amount of polycarboxylic acid (a) is small>

[0121] Ester bond concentration (mmol / g) = [(A1 / α1×m1+A2 / α2×m2+A3 / α3×m3…) / Z] × 1000

[0122] A: Amount of polycarboxylic acid (a) (g)

[0123] α: Molecular weight of polycarboxylic acid (a)

[0124] m: the number of carboxyl groups per molecule of the polycarboxylic acid (a)

[0125] Z: mass of the final product (g)

[0126] <When the amount of polyol (b) is small>

[0127] Ester bond concentration (mmol / g) = [(B1 / β1×n1+B2 / β2×n2+B3 / β3×n3…) / Z] × 1000

[0128] B: Amount of polyols (b) added (g)

[0129] β: molecular weight of polyol (b)

[0130] n: Number of hydroxyl groups per molecule of the polyol (b)

[0131] Z: mass of the final product (g)

[0132] The ester bond concentration of the polyester can also be determined by a known method using NMR, for example, 1H-NMR measurement (proton nuclear magnetic resonance spectroscopy) or 13C-NMR measurement (carbon nuclear magnetic resonance spectroscopy) at a resonance frequency of 400 MHz.

[0133] As methods for adjusting the ester bond concentration to a predetermined range, for example, the following methods can be cited: a method of selecting a polyol having 4 or less carbon atoms as the polyol (b); a method of increasing the content of a straight-chain carboxylic acid having 4 or less carbon atoms as the polycarboxylic acid (a); a method of further increasing the content of a dicarboxylic acid having a smaller carbon number; a method of combining the two; a method of reducing the average carbon number of the structural units derived from the polycarboxylic acid and the structural units derived from the polyol to 5 or less; etc.

[0134] The average number of carbon atoms (including carbon atoms in carboxyl groups) in the polyester's polycarboxylic acid-derived structural units and polyol-derived structural units is preferably 5 or less, more preferably 4.8 or less, particularly preferably 4.6 or less, even more preferably 4.4 or less, particularly preferably 4.2 or less, and most preferably 4.0 or less. If the average number of carbon atoms in the polyester's polycarboxylic acid-derived structural units and polyol-derived structural units is too high, the polyester's ester bond concentration tends to decrease, resulting in reduced adhesive strength and poor biodegradability. The lower limit of the average number of carbon atoms in the polyester's polycarboxylic acid-derived structural units and polyol-derived structural units is 2.0.

[0135] The glass transition temperature (Tg) of the polyester is preferably -70 to 20°C, particularly preferably -50 to 10°C, further preferably -40 to 0°C, particularly preferably -35 to -5°C, further preferably -30 to -10°C, and most preferably -25 to -15°C. If the glass transition temperature (Tg) is too high, the adhesive strength in the film state tends to decrease, while if it is too low, the heat resistance and cohesive strength tend to decrease.

[0136] In order to adjust the glass transition temperature, for example, there may be mentioned a method of introducing an aromatic skeleton or a method of changing the alkyl chain length of the polycarboxylic acid (a) or the polyol (b).

[0137] The glass transition temperature (Tg) is a value measured using a differential scanning calorimeter DSCQ20 manufactured by TA Instruments, Inc. The measurement temperature range is -90 to 100°C, and the temperature increase rate is 10°C / min.

[0138] The weight average molecular weight of the polyester is preferably 5,000 to 500,000, more preferably 10,000 to 300,000, particularly preferably 20,000 to 200,000, further preferably 30,000 to 150,000, and particularly preferably 50,000 to 130,000. If the weight average molecular weight is too high, handleability is reduced, requiring a large amount of solvent and tending to increase the environmental load. If the weight average molecular weight is too low, adhesiveness tends to be reduced.

[0139] The weight average molecular weight is the weight average molecular weight calculated based on the molecular weight of standard polystyrene. In a high performance liquid chromatography (HLC-8320GPC manufactured by Tosoh Corporation) using tetrahydrofuran as solvent, two columns were connected in series: TSKgel Super Multipore HZ-M (exclusion limit molecular weight: 2×10 6 , theoretical plate number: 16,000 stages / plate, filler material: styrene-divinylbenzene copolymer, filler particle size: 4 μm) and used for measurement.

[0140] In order to prevent hydrolysis and improve durability, the acid value of the polyester is preferably 10 mgKOH / g or less, more preferably 5 mgKOH / g or less, particularly preferably 2 mgKOH / g or less, even more preferably 1 mgKOH / g or less, and most preferably 0.5 mgKOH / g or less. If the acid value is too high, durability tends to decrease.

[0141] The acid value can be adjusted by, for example, increasing the ratio of the polyol (b) during the esterification reaction or transesterification reaction or adjusting the reaction conditions. The lower limit of the acid value is usually 0 mgKOH / g.

[0142] The acid value of the polyester is a value determined by neutralization titration based on JIS K0070.

[0143] It should be noted that the acid value in this embodiment refers to the carboxyl group content in the polyester. The carboxyl groups mentioned above also include carboxyl groups in the form of carboxylate ions obtained by neutralization with a basic compound.

[0144] The polyester preferably has a heat of crystalline fusion of 30 J / g or less, more preferably 10 J / g or less, even more preferably 5 J / g or less, particularly preferably 2 J / g or less, and particularly preferably no heat of crystalline fusion, as measured by a differential scanning calorimeter (DSC). If the heat of crystalline fusion is too high, crystallinity may develop, leading to poor storage stability of the resin solution, low-temperature stability when formed into an adhesive tape, and poor adhesive strength in a film state.

[0145] As methods for adjusting the aforementioned crystal melting heat to a specified range, for example, the following methods can be cited: a method in which a polycarboxylic acid having an alkyl group in a side chain or a polyol having an alkyl group in a side chain is suitably used; a method in which a straight-chain aliphatic polycarboxylic acid composed of an odd number of carbon atoms is suitably used; a method in which a straight-chain aliphatic polyol composed of an odd number of carbon atoms is suitably used; a method in which a comonomer component of three or more components, preferably four or more components is used; etc.

[0146] The heat of crystal fusion refers to the energy consumed when a crystalline substance is heated and melted, and can be measured by a differential scanning calorimeter (DSC).

[0147] Furthermore, to reduce the impact on the global environment, the polyester is preferably made from plant-derived raw materials and has a biomass content. The biomass content is preferably 30% or higher, more preferably 50% or higher, particularly preferably 60% or higher, even more preferably 70% or higher, and most preferably 80% or higher. The upper limit is generally 100% or lower. A low biomass content tends to be insufficient in reducing the impact on the global environment.

[0148] Here, the biomass content of the polyester refers to the mass ratio of the plant-derived raw materials used in producing the polyester that are incorporated into the resin, relative to the total mass of the polyester. The calculation method is described below. The biomass content of polycarboxylic acids and polyols is calculated by taking the weighted average of their respective biomass contents. The value obtained by any of the following calculation methods may be within the aforementioned range.

[0149] (Calculation method)

[0150] Biomass content (%) = [(the number of moles of carbon in the plant-derived monomer calculated from the molar ratio of the polycarboxylic acid and the polyol in the polyester) / (the number of moles of carbon in all the constituent monomers in the polyester)] × 100

[0151] The biomass degree can also be determined by analyzing the composition ratio using NMR and calculating the number of carbon atoms in the plant-derived monomer / the total number of carbon atoms.

[0152] Furthermore, the biomass content can be measured by the method described in Tokyo Metropolitan Industrial Technology Research Center Research Report No. 4, 2009, "Technology for Identifying the Origin of Biofuels Using Natural Radioactive Carbon C-14."

[0153] <Adhesive Composition>

[0154] The adhesive composition used in this embodiment preferably contains, in addition to the aforementioned polyester, a crosslinking agent (B), a hydrolysis inhibitor (C), a urethanization catalyst (D), and an antioxidant (E).

[0155] [Crosslinking agent (B)]

[0156] The adhesive composition used in this embodiment preferably contains a crosslinking agent (B). By containing the crosslinking agent (B), the crosslinking agent (B) crosslinks the polyester, thereby improving the cohesive force and further improving the performance as an adhesive.

[0157] Examples of the crosslinking agent (B) include isocyanate crosslinking agents and polyepoxy crosslinking agents, which have a functional group that reacts with at least one of the hydroxyl and carboxyl groups contained in the polyester. Furthermore, polyfunctional acrylic monomers and urethane acrylate oligomers, which increase cohesive strength even without reacting with the polyester, can also be used. Among these, isocyanate crosslinking agents are particularly preferred because they can achieve a good balance between initial adhesion, mechanical strength, and heat resistance.

[0158] Examples of the isocyanate crosslinking agent include polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, tetramethylxylylene diisocyanate, 1,5-naphthalene diisocyanate, and triphenylmethane triisocyanate. Examples include adducts of the aforementioned polyisocyanates with polyol compounds such as trimethylolpropane, and biuret and isocyanurate forms of these polyisocyanate compounds. It should be noted that the aforementioned polyisocyanate compounds may also be those in which the isocyanate moiety is blocked with phenol, lactam, or the like. These isocyanate crosslinking agents may be used alone or as a mixture of two or more.

[0159] Among the above-mentioned isocyanate-based crosslinking agents, aromatic polyisocyanate-based compounds are preferred, and trifunctional aromatic isocyanate-based compounds are preferably used because of their good compatibility with polyester.

[0160] The content of the crosslinking agent (B) can be appropriately used depending on the molecular weight of the polyester and the intended use. However, it is generally preferred that the crosslinking agent (B) be contained in a ratio of 0.2 to 10 equivalents of the reactive groups contained in the crosslinking agent (B) per equivalent of at least one of the hydroxyl and carboxyl groups contained in the polyester, particularly preferably 0.3 to 5 equivalents, further preferably 0.5 to 3 equivalents, and particularly preferably 0.6 to 1.5 equivalents. If the equivalent number of reactive groups contained in the crosslinking agent (B) is too small, the cohesive force tends to decrease, while if it is too large, the flexibility tends to decrease.

[0161] The content of the crosslinking agent (B) is preferably 0.01 to 10 parts by mass, particularly preferably 0.1 to 8 parts by mass, further preferably 0.5 to 6 parts by mass, particularly preferably 0.75 to 4 parts by mass, and most preferably 1 to 3 parts by mass, relative to 100 parts by mass of the polyester. If the content of the crosslinking agent is too low, the cohesive force tends to decrease, while if the content is too high, the flexibility tends to decrease, and the desired adhesive strength tends to fail to be obtained.

[0162] In the reaction between the polyester and the crosslinking agent (B), an organic solvent having no functional group reactive with these components, for example, esters such as ethyl acetate and butyl acetate, ketones such as methyl ethyl ketone and methyl isobutyl ketone, and aromatics such as toluene and xylene, can be used. These organic solvents can be used alone or in combination of two or more.

[0163] 〔Hydrolysis inhibitor (C)〕

[0164] The hydrolysis inhibitor (C) is not particularly limited, and conventionally known substances can be used. Examples thereof include compounds that react and bond with the carboxylic acid terminal groups of the polyester. Specifically, compounds having functional groups such as carbodiimide groups, epoxy groups, and oxazoline groups can be mentioned. Among these, compounds containing carbodiimide groups are preferred because they are highly effective in eliminating the catalytic activity of protons derived from the carboxyl terminal groups.

[0165] As the carbodiimide group-containing compound used in this embodiment, generally known carbodiimides having one or more carbodiimide groups (-N=C=N-) in the molecule can be used. Examples include monocarbodiimide compounds having one carbodiimide group in the molecule and polycarbodiimide compounds having two or more carbodiimide groups in the molecule. Among these, monocarbodiimide compounds are preferred due to their high ester bond concentration, excellent compatibility with highly polar polyesters, excellent adhesive strength, and recyclability.

[0166] The carbodiimide group-containing compound used in this embodiment is preferably a monocarbodiimide compound. Examples of the monocarbodiimide compound include diphenylcarbodiimide, bis(methylphenyl)carbodiimide, bis(methoxyphenyl)carbodiimide, bis(nitrophenyl)carbodiimide, bis(dimethylphenyl)carbodiimide, bis(diisopropylphenyl)carbodiimide, bis(di-tert-butylphenyl)carbodiimide, and bis(triphenylsilyl)carbodiimide. Among them, bis(diisopropylphenyl)carbodiimide is preferred due to its compatibility with polyester, excellent adhesive strength, reactivity with carboxyl groups, and excellent wet heat durability.

[0167] As the carbodiimide group-containing compound used in this embodiment, a polycarbodiimide compound may also be used from the viewpoint of hydrolysis resistance. The weight average molecular weight of the polycarbodiimide compound is preferably 1000 or more, more preferably 2000 or more, and even more preferably 3000 or more. It should be noted that the upper limit of the weight average molecular weight is usually 50,000.

[0168] Furthermore, as the polycarbodiimide compound, those with low volatility are preferred. Therefore, those with high number average molecular weight are preferably used, and are usually 300 to 10,000, and preferably 1,000 to 5,000.

[0169] If the molecular weight of the polycarbodiimide compound is too small, hydrolysis resistance tends to decrease. If the molecular weight is too large, compatibility with polyester tends to decrease, resulting in poor adhesive strength.

[0170] The carbodiimide equivalent of the carbodiimide group-containing compound is preferably 50 to 10,000, particularly preferably 100 to 1,000, and further preferably 150 to 500. The carbodiimide equivalent refers to the chemical formula weight per one carbodiimide group.

[0171] Furthermore, as the carbodiimide group-containing compound, a polycarbodiimide compound produced by subjecting diisocyanate to a decarboxylation condensation reaction in the presence of a carbodiimidization catalyst is also preferably used.

[0172] [Polycarbodiimide compounds]

[0173] The polycarbodiimide compound can be obtained by subjecting an organic diisocyanate compound to a condensation reaction.

[0174] Examples of the organic diisocyanate compound include aromatic diisocyanate compounds such as 1,5-naphthalene diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-diphenyldimethylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate, xylylene diisocyanate, and tetramethylxylylene diisocyanate;

[0175] Non-cyclic aliphatic diisocyanates such as hexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, methylcyclohexane diisocyanate, 2,5(2,6)-bis(isocyanatomethyl)bicyclo[2.2.1]heptane, and other cyclic aliphatic diisocyanates. These can be used alone or in combination of two or more.

[0176] Among these, aromatic diisocyanate compounds are preferred, and tetramethylxylylene diisocyanate is more preferred, in that they can form an adhesive composition having excellent moisture and heat resistance.

[0177] The polycarbodiimide compound can be obtained by subjecting the organic diisocyanate compound to a decarboxylation condensation reaction using a known carbodiimidization catalyst according to a conventional method.

[0178] The polycarbodiimide compound is preferably an aromatic polycarbodiimide compound because it exhibits little change in haze even under high-temperature and high-humidity conditions and can form an adhesive having excellent moisture-heat resistance.

[0179] The polycarbodiimide compound used in the present embodiment is more preferably a polycarbodiimide compound in which at least one of the terminal isocyanate groups is substituted with a substituent derived from a hydrophilic organic compound.

[0180] [At least one of the terminal isocyanate groups of the polycarbodiimide compound is substituted with a substituent derived from a hydrophilic organic compound]

[0181] Next, a description will be given of a polycarbodiimide compound in which at least one of the terminal isocyanate groups is substituted with a substituent derived from a hydrophilic organic compound.

[0182] First, the hydrophilic organic compound will be described.

[0183] [Hydrophilic organic compounds]

[0184] The hydrophilic organic compound is a compound having a substituent and one or more heteroatoms in the molecule in addition to the substituent, wherein the substituent has active hydrogen that is reactive with the terminal isocyanate group of the polycarbodiimide compound.

[0185] Examples of the substituent having an active hydrogen group reactive with an isocyanate group include a hydroxyl group, a primary amino group, a secondary amino group, an imino group, an isocyanate group, and a carboxyl group. Among these, a hydroxyl group, a primary amino group, a secondary amino group, and an imino group are preferred. The hydrophilic organic compound may contain these substituents alone or in combination of two or more.

[0186] The number of the substituents having active hydrogen reactive with an isocyanate group in the hydrophilic organic compound is usually 2 or less, and preferably 1. The substituents are preferably present at the terminals of the hydrophilic organic compound.

[0187] Examples of the compound having the aforementioned substituent having active hydrogen reactive with an isocyanate group and having one or more heteroatoms in the molecule in addition to the aforementioned substituent include compounds containing an oxyalkylene structure, compounds containing a hydroxy polyester structure, compounds containing a hydroxy alkyl sulfonic acid structure, compounds containing a dialkylamino alcohol structure, compounds containing a hydroxy carboxylic acid alkyl ester structure, and compounds containing a dialkylaminoalkylamine structure. Among them, compounds containing an oxyalkylene structure are preferred.

[0188] Furthermore, it is preferred that the terminal of the hydrophilic organic compound is capped with an alkoxy group or a phenoxy group.

[0189] Among these, compounds containing an oxyalkylene structure end-capped with an alkoxy group or a phenoxy group are preferred as the hydrophilic organic compound because of their excellent compatibility with polyesters having a high ester bond concentration.

[0190] Examples of the oxyalkylene structure-containing compound whose terminals are capped with an alkoxy group or a phenoxy group include compounds represented by the following formula (1).

[0191] R 1 -O-(CH2-CHR 2 -O)mH…(1)

[0192] In the above formula (1), R 1 represents an alkyl group or a phenyl group having 1 to 4 carbon atoms, R 2 represents a hydrogen atom or a methyl group, and m is an integer of 4 to 100.

[0193] Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, and a tert-butyl group.

[0194] Specific examples of the compound represented by the formula (1) include polyethylene glycol monomethyl ether, polyethylene glycol monoethyl ether, polypropylene glycol monomethyl ether, polypropylene glycol monoethyl ether, polypropylene glycol monophenyl ether, etc. Among them, polyethylene glycol monomethyl ether is preferred.

[0195] The weight-average molecular weight of the hydrophilic organic compound is preferably 200 or greater, more preferably 400 or greater. The upper limit of the weight-average molecular weight is generally 5000 or less, preferably 4000 or less, more preferably 2000 or less, and even more preferably 1000 or less. If the weight-average molecular weight is too low, compatibility with the polyester resin and adhesive strength tend to decrease. However, if the weight-average molecular weight is too high, adhesive strength tends to decrease.

[0196] The polycarbodiimide compound in which at least one of the terminal isocyanate groups is substituted with a substituent derived from a hydrophilic organic compound can be obtained by reacting the polycarbodiimide compound with the hydrophilic organic compound.

[0197] The reaction of the polycarbodiimide compound and the hydrophilic organic compound is carried out by heating the polycarbodiimide compound usually to 50-200°C, preferably to 100-180°C, adding the hydrophilic organic compound, and further reacting at 80-200°C for 0.5-5 hours.

[0198] In this manner, a polycarbodiimide compound can be obtained in which at least one of the terminal isocyanate groups is substituted with a substituent derived from a hydrophilic organic compound.

[0199] Examples of commercially available polycarbodiimide compounds include CARBODILITE (registered trademark) V-09GB, V-02B, V-04K, V-04PF, and V-07 manufactured by Nisshinbo Chemical Inc. and Elastostab H01 manufactured by BASF Corporation. Among them, CARBODILITE V-09GB and V-04K are preferred.

[0200] Preferred examples of the epoxy group-containing compound include glycidyl ester compounds and glycidyl ether compounds.

[0201] Examples of the glycidyl ester compound include glycidyl benzoate, glycidyl tert-butylbenzoate, glycidyl p-toluate, glycidyl cyclohexanecarboxylate, glycidyl pelargonate, glycidyl stearate, glycidyl laurate, glycidyl palmitate, glycidyl behenate, glycidyl versatate, glycidyl oleate, glycidyl linoleate, glycidyl linolenate, glycidyl behenate, glycidyl stearate, diglycidyl terephthalate, diglycidyl isophthalate, and glycidyl oleate. Glycidyl esters, diglycidyl phthalate, diglycidyl naphthalate, diglycidyl methyl terephthalate, diglycidyl hexahydrophthalate, diglycidyl tetrahydrophthalate, diglycidyl cyclohexanedicarboxylate, diglycidyl adipate, diglycidyl succinate, diglycidyl sebacate, diglycidyl dodecanedioate, diglycidyl octadecanedicarboxylate, triglycidyl trimellitate, tetraglycidyl pyromellitate, and the like can be used alone or in combination of two or more.

[0202] Examples of the glycidyl ether compound include phenyl glycidyl ether, o-phenyl glycidyl ether, 1,4-bis(β,γ-glycidyloxy)butane, 1,6-bis(β,γ-glycidyloxy)hexane, 1,4-bis(β,γ-glycidyloxy)benzene, 1-(β,γ-glycidyloxy)-2-ethoxyethane, 1-(β,γ-glycidyloxy)-2-benzyloxyethane, 2,2-bis-[p-(β,γ-glycidyloxy)phenyl]propane, 2,2-bis-(4-hydroxyphenyl)propane, and bisglycidyl polyethers obtained by the reaction of bisphenols with epichlorohydrin, such as 2,2-bis-(4-hydroxyphenyl)methane. These compounds may be used alone or in combination of two or more.

[0203] As the aforementioned oxazoline group-containing compound, a bisoxazoline compound is preferred. Specifically, for example, 2,2'-bis(2-oxazoline), 2,2'-bis(4-methyl-2-oxazoline), 2,2'-bis(4,4-dimethyl-2-oxazoline), 2,2'-bis(4-ethyl-2-oxazoline), 2,2'-bis(4,4'-diethyl-2-oxazoline), 2,2'-bis(4-propyl-2-oxazoline), 2,2'-bis(4-butyl-2-oxazoline), 2,2'- Bis(4-hexyl-2-oxazoline), 2,2'-bis(4-phenyl-2-oxazoline), 2,2'-bis(4-cyclohexyl-2-oxazoline), 2,2'-bis(4-benzyl-2-oxazoline), 2,2'-p-phenylenebis(2-oxazoline), 2,2'-m-phenylenebis(2-oxazoline), 2,2'-o-phenylenebis(2-oxazoline), 2,2'-p-phenylenebis(4-methyl-2-oxazoline), 2,2' -p-phenylenebis(4,4-dimethyl-2-oxazoline), 2,2'-m-phenylenebis(4-methyl-2-oxazoline), 2,2'-m-phenylenebis(4,4-dimethyl-2-oxazoline), 2,2'-ethylenebis(2-oxazoline), 2,2'-tetramethylenebis(2-oxazoline), 2,2'-hexamethylenebis(2-oxazoline), 2,2'-octamethylenebis(2-oxazoline), 2,2'-decamethylenebis( 2-oxazoline), 2,2'-ethylenebis(4-methyl-2-oxazoline), 2,2'-tetramethylenebis(4,4-dimethyl-2-oxazoline), 2,2'-9,9'-diphenoxyethanebis(2-oxazoline), 2,2'-cyclohexylenebis(2-oxazoline), 2,2'-diphenylenebis(2-oxazoline), etc. Among these, 2,2'-bis(2-oxazoline) is most preferred from the viewpoint of reactivity with polyester.

[0204] Furthermore, the bisoxazoline compounds listed above may be used alone or in combination of two or more as long as the purpose of the present embodiment is achieved.

[0205] As these hydrolysis inhibitors (C), those having excellent compatibility with polyester are preferred, and therefore, those having a low molecular weight are preferably used.

[0206] The amount of the hydrolysis inhibitor (C) blended is preferably 0.01 to 10 parts by mass, particularly preferably 0.1 to 5 parts by mass, further preferably 0.2 to 4 parts by mass, particularly preferably 0.3 to 3 parts by mass, and most preferably 0.5 to 2 parts by mass, relative to 100 parts by mass of the polyester. If the blending amount is too large, turbidity tends to be easily generated due to poor compatibility with the polyester, while if it is too small, sufficient durability tends to be difficult to obtain.

[0207] The amount of the hydrolysis inhibitor (C) is preferably optimized according to the acid value of the polyester. The molar ratio ((β) / (α)) of the total amount (β) of the functional groups of the hydrolysis inhibitor (C) in the adhesive composition to the total acid value (α) of the polyester in the adhesive composition is preferably 0.5 ≤ (β) / (α), particularly preferably 1 ≤ (β) / (α) ≤ 1000, further preferably 1.5 ≤ (β) / (α) ≤ 500, 2 ≤ (β) / (α) ≤ 250, 2.5 ≤ (β) / (α) ≤ 100, and 3 ≤ (β) / (α) ≤ 50.

[0208] If the content ratio of (β) to (α) ((β) / (α)) is too high, the compatibility with polyester tends to decrease, or the adhesive force, cohesive force, and durability tend to decrease. If the content ratio of (β) to (α) ((β) / (α)) becomes low, the moisture and heat resistance tends to decrease.

[0209] [Urethanization catalyst (D)]

[0210] From the viewpoint of reaction rate, it is more preferable that the pressure-sensitive adhesive composition used in the present embodiment contains a urethanization catalyst (D).

[0211] Examples of the urethanization catalyst (D) include organometallic compounds and tertiary amine compounds, which can be used alone or in combination of two or more.

[0212] Examples of the organometallic compound include zirconium compounds, iron compounds, tin compounds, titanium compounds, lead compounds, cobalt compounds, and zinc compounds.

[0213] Examples of the zirconium-based compound include zirconium naphthenate and zirconium acetylacetonate.

[0214] Examples of the iron-based compound include iron acetylacetonate and iron 2-ethylhexanoate.

[0215] Examples of the tin compound include dibutyltin dichloride, dibutyltin oxide, and dibutyltin dilaurate.

[0216] Examples of the titanium-based compound include dibutyltitanium dichloride, tetrabutyl titanate, and butoxytitanium trichloride.

[0217] Examples of the lead compound include lead oleate, lead 2-ethylhexanoate, lead benzoate, and lead naphthenate.

[0218] Examples of the cobalt-based compound include cobalt 2-ethylhexanoate and cobalt benzoate.

[0219] Examples of the zinc-based compound include zinc naphthenate and zinc 2-ethylhexanoate.

[0220] Examples of the tertiary amine compound include triethylamine, triethylenediamine, and 1,8-diazabicyclo[5.4.0]undec-7-ene.

[0221] Among these urethanization catalysts (D), organometallic compounds are preferred in terms of reaction rate and pot life of the adhesive layer, with iron compounds, tin compounds, and zirconium compounds being particularly preferred. Furthermore, the urethanization catalyst (D) is preferably used in combination with acetylacetone as a catalyst inhibitor. The inclusion of acetylacetone is preferred in terms of suppressing catalytic activity at low temperatures and extending pot life.

[0222] The content of the urethanization catalyst (D) is preferably 0.0001 to 1 part by mass, particularly preferably 0.001 to 0.1 part by mass, and even more preferably 0.01 to 0.05 part by mass, relative to 100 parts by mass of the polyester. If the content is too low, the aging time until the cross-linking reaction is completed tends to be prolonged, while if it is too high, the adhesiveness tends to be reduced.

[0223] 〔Antioxidant (E)〕

[0224] From the viewpoint of improving the stability of the resin, the adhesive composition used in the present embodiment more preferably contains an antioxidant (E).

[0225] Examples of the antioxidant (E) include hindered phenol-based antioxidants, amine-based antioxidants, sulfur-based antioxidants, and phosphoric acid-based antioxidants. Among these, at least one selected from hindered phenol-based antioxidants, amine-based antioxidants, and phosphoric acid-based antioxidants is preferred, and antioxidants composed of hindered phenol-based compounds are particularly preferred.

[0226] Examples of hindered phenol-based antioxidants include antioxidants having a hindered phenol structure in which a group having a large steric hindrance, such as a tert-butyl group, is bonded to at least one of carbon atoms adjacent to a carbon atom on an aromatic ring to which a phenolic hydroxyl group is bonded.

[0227] The content of the antioxidant (E) is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 8 parts by mass, and even more preferably 0.05 to 5 parts by mass, relative to 100 parts by mass of the polyester. If the content is too low, adhesive residue tends to form on the adherend, while if it is too high, the adhesiveness tends to decrease.

[0228] The adhesive composition of this embodiment may contain, in addition to the aforementioned polyester, crosslinking agent (B), hydrolysis inhibitor (C), urethanization catalyst (D), and antioxidant (E), additives such as tackifying resins, softeners, ultraviolet absorbers, stabilizers, and antistatic agents, as well as inorganic or organic fillers, powders, or granular additives such as metal powder and pigments, within a range that does not impair the effects of this embodiment (e.g., 10% by mass or less of the adhesive composition). These additives may be used alone or in combination of two or more. Furthermore, a small amount of impurities contained in the raw materials used to make the components of the adhesive composition may also be contained.

[0229] The adhesive composition can be obtained, for example, by preparing the aforementioned polyester and any desired components, blending and dispersing them during polyester production, or blending them into the polyester and dispersing them using a mixing roll or the like. In this case, the polyester can be dispersed by forming a solution using a solvent, or dispersion can be performed without a solvent. It should be noted that the polyester is preferably the main component. The main component means a component comprising 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more. A low polyester content tends to result in poor heat resistance.

[0230] <Adhesive>

[0231] The adhesive of this embodiment is formed by crosslinking (curing) the adhesive composition. The adhesive can be formed into an adhesive layer of an adhesive tape by applying the adhesive composition and drying it. The formation method is described in detail in the adhesive tape manufacturing method described below.

[0232] The gel fraction of the adhesive is preferably 3% by mass or greater, particularly preferably 5 to 80% by mass, further preferably 10 to 60% by mass, particularly preferably 15 to 50% by mass, and most preferably 20 to 40% by mass, from the perspectives of durability and adhesive strength. If the gel fraction is too low, cohesion decreases, tending to reduce holding power and durability. However, if the gel fraction is too high, there is a concern that adhesive strength may decrease due to increased cohesion.

[0233] The gel fraction is a target for the degree of crosslinking and is therefore calculated, for example, by the following method: The adhesive layer obtained by coating the adhesive is covered with a 200-mesh SUS metal mesh, and then immersed in toluene at 23°C for 24 hours. The gel fraction is calculated as the mass percentage of the undissolved adhesive component remaining in the metal mesh after immersion relative to the mass of the adhesive component before immersion.

[0234] <Adhesive Layer>

[0235] The thickness of the adhesive layer used in this embodiment is 25 μm or less, preferably 15 μm or less, more preferably 12 μm or less, further preferably 8 μm or less, and particularly preferably 3 μm or less. It should be noted that the lower limit is generally 0.1 μm. Generally, the thicker the adhesive layer, the higher the adhesive strength. However, the adhesive layer used in this embodiment, despite its relatively thin thickness, exhibits excellent adhesive strength to various adherends.

[0236] It should be noted that the thickness of the adhesive layer can be measured using a digital gauge (Mitutoyo Corporation, ID-C112B). In the case of the adhesive tape described later, the thickness can be obtained by subtracting the measured value of the thickness of the constituent members other than the adhesive layer from the measured value of the overall thickness of the adhesive tape.

[0237] <Adhesive Tape>

[0238] The pressure-sensitive adhesive tape of this embodiment includes the pressure-sensitive adhesive layer described above.

[0239] A first aspect of the pressure-sensitive adhesive tape of the present embodiment is a tape comprising the pressure-sensitive adhesive layer and a substrate, wherein the substrate is laminated on one surface of the pressure-sensitive adhesive layer and the other surface is subjected to a release treatment.

[0240] A second aspect of the pressure-sensitive adhesive tape of the present embodiment includes the pressure-sensitive adhesive layer and a release-treated tape, wherein the release-treated tape is laminated on both surfaces of the pressure-sensitive adhesive layer.

[0241] That is, the pressure-sensitive adhesive tape of this embodiment may be a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer on one or both sides of a supporting substrate, or may be a substrate-free double-sided pressure-sensitive adhesive tape having no substrate.

[0242] The manufacturing method of the adhesive tape of the above-mentioned first mode can be manufactured according to a generally known manufacturing method of an adhesive tape, for example, the above-mentioned adhesive composition is applied to one surface of a substrate and dried to form an adhesive layer, a demolded tape is attached to its surface (the opposite side of the surface in contact with the substrate), and it is aged as needed to obtain the adhesive tape.

[0243] Alternatively, the adhesive composition is applied to the release-treated tape and dried to form an adhesive layer, and a substrate is bonded to the surface (opposite to the surface in contact with the release-treated tape) and aged as needed.

[0244] Examples of the substrate include polyester resins such as polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate, polyethylene terephthalate / ethylene isophthalate copolymer, polybutylene succinate, polybutylene adipate / terephthalate copolymer, hydroxybutyrate / hydroxyhexanoate copolymer, and polycaprolactone; polyolefin resins such as polyethylene, polypropylene, and polymethylpentene; and polyvinyl fluoride, polyvinylidene fluoride, and polyvinyl fluoride. Examples include polyvinyl fluoride (PVF), polyamides such as nylon 6 and nylon 6,6, vinyl polymers such as polyvinyl chloride, polyvinyl chloride / vinyl acetate copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyvinyl alcohol, and vinylon, cellulose resins such as cellulose triacetate and cellophane, acrylic resins such as polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, and polybutyl acrylate, polystyrene, polycarbonate, polyarylate, polyimide, synthetic resin tapes made of cycloolefin polymers, and the like, metal foils such as aluminum, copper, and iron, high-quality paper and cellophane, and woven and non-woven fabrics made of glass fiber, natural fiber, and synthetic fiber. Among these, polyester resin tapes and polyimide resin tapes are preferred, and polyethylene terephthalate is more preferred.

[0245] As the release-treated tape, for example, a tape obtained by subjecting the substrate to a release treatment can be used. Among these, a silicone release tape is preferably used.

[0246] The adhesive composition may be applied by, for example, a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, spray coater, or comma coater.

[0247] The drying conditions after applying the adhesive composition are preferably a drying temperature of 60 to 140° C., particularly preferably 80 to 120° C. The drying time is preferably 0.5 to 30 minutes, particularly preferably 1 to 5 minutes.

[0248] The aging treatment is usually carried out at a temperature of room temperature (23°C) to 70°C and for a time of 1 to 30 days. Specifically, the aging treatment can be carried out at 23°C for 1 to 20 days, preferably at 23°C for 3 to 14 days, or at 40°C for 1 to 10 days.

[0249] The method for producing the adhesive tape of the second embodiment can also be produced according to a generally known method for producing adhesive tapes. For example, the adhesive composition is applied to a release-treated tape and dried to form an adhesive layer. A release-treated tape different from the release-treated tape is then attached to the surface of the release-treated tape (the surface opposite to the surface in contact with the release-treated tape), thereby producing the adhesive tape of the second embodiment. It should be noted that the release-treated tape used in the second embodiment can be the same as that exemplified in the first embodiment. Furthermore, the coating method, drying conditions, and aging conditions can also be the same as those of the first embodiment.

[0250] When using the obtained pressure-sensitive adhesive tape or substrate-less double-sided pressure-sensitive adhesive tape, the release-treated tape is peeled off from the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is bonded to an adherend.

[0251] The adhesive tape of this embodiment can be used for laminating various components, and is suitable for use as a single-sided or double-sided adhesive tape for laminating optical components, an adhesive tape for fixing components of portable electronic terminals, or an adhesive tape for electronic components for fixing electronic components. These are suitable for use in any single-sided or double-sided adhesive tape.

[0252] Example

[0253] Hereinafter, the present embodiment will be described in more detail with reference to examples, but the present embodiment is not limited to the following examples unless the gist of the present embodiment is exceeded.

[0254] Polyester was produced by the following method.

[0255] [Example 1: Production of polyester (A-1)]

[0256] In a reactor equipped with a thermometer, a stirrer, a distillation column, a nitrogen inlet, and a vacuum device, 580.26 parts of succinic acid as the polycarboxylic acid (a), 295.42 parts of 1,3-propylene glycol, 117.73 parts of neopentyl glycol, and 6.59 parts of trimethylolpropane as the polyol (b), and 0.050 parts of tetrabutyl titanate as a catalyst were added. The temperature was gradually raised to an internal temperature of 250°C, and an esterification reaction was carried out over 4 hours. Thereafter, the temperature was raised to an internal temperature of 260°C, 0.050 parts of tetrabutyl titanate was added as a catalyst, and the pressure was reduced to 1.33 hPa, and a polymerization reaction was carried out over 3 hours to produce polyester (A-1).

[0257] The composition (molar ratio) of the obtained polyester (A-1) was succinic acid / 1,3-propylene glycol / neopentyl glycol / trimethylolpropane = 100 / 76.7 / 22.3 / 1.0, the ester bond concentration was 12.1 mmol / g, the glass transition temperature (Tg) was -26°C, the weight-average molecular weight was 115,000, the acid value was 0.2 mgKOH / g, and the crystal melting heat was 0 J / g.

[0258] Examples 2 to 4 and Comparative Production Examples 1 to 4 were prepared in the same manner as in Example 1 except that the compositions were as shown in Table 1 below.

[0259] The compositions and physical properties of the prepared polyesters (A-1) to (A-4) and (A'-1) to (A'-4) are shown in Table 1 below.

[0260] The ester bond concentration, glass transition temperature, weight-average molecular weight, acid value, heat of crystallization fusion, and gel fraction of the polyesters in the aforementioned Examples and Comparative Examples were measured according to the aforementioned methods. Furthermore, the biomass content and solution stability were calculated or evaluated as described below. These results are collectively shown in Table 1 below.

[0261] Although not shown in Table 1, the melting point of Comparative Example 3 was 114°C, and the melting point of Comparative Example 4 was 87°C.

[0262] <Biomass Degree>

[0263] The biomass content of polyester was calculated according to the following formula.

[0264] Biomass content (%) = [(the number of moles of carbon atoms in the plant-derived monomer calculated from the molar ratio of the polycarboxylic acid and the polyol in the polyester) / (the number of moles of carbon atoms in all monomers in the polyester)] × 100

[0265] <Solution Stability>

[0266] A solution of polyester diluted with ethyl acetate to a solid content concentration of 50% was prepared. After standing at 0°C for 12 hours, the state of the solution was visually observed and evaluated based on the following criteria.

[0267] (Evaluation Criteria)

[0268] ◎ (Excellent) ...This is a solution with high transparency.

[0269] ○ (very good) ...The solution was foggy.

[0270] △ (good) ...is a solution with precipitate.

[0271] × (poor) ... the solution solidified, or the polyester did not dissolve.

[0272] [Table 1]

[0273]

[0274] Next, the following components were prepared.

[0275] [Crosslinking agent (B)]

[0276] Isocyanate crosslinking agent: "TAKENATE D101E" (manufactured by Mitsui Chemicals, Inc.)

[0277] 〔Hydrolysis inhibitor (C)〕

[0278] Carbodiimide compound (C-1): monocarbodiimide compound, "Stabaxol IPowder" (manufactured by RheinChemie)

[0279] Carbodiimide compound (C-2): polyfunctional carbodiimide compound, "CARBODILITE V-09GB" (manufactured by Nisshinbo Chemical Inc.)

[0280] [Urethanization catalyst (D)]

[0281] Tin compounds: dibutyltin dilaurate

[0282] 〔Antioxidant (E)〕

[0283] Hindered phenol antioxidant: "IRGANOX 1010" (manufactured by BASF Corporation)

[0284] Using the polyesters (A-1) to (A-4) and (A'-1) to (A'-4) obtained above, adhesive compositions of Examples and Comparative Examples were prepared as described below, and adhesive tapes using these compositions in adhesive layers were prepared.

[0285] [Example 5]

[0286] The polyester (A-1) obtained above is diluted with ethyl acetate to a solid content concentration of 50%. With respect to 100 parts of the solid content, 1.4 parts (solid content) of an isocyanate crosslinking agent (B-1), 1.0 part (solid content) of a carbodiimide compound (C-1), 0.005 parts (solid content) of a tin compound (D-1), and 0.1 parts of a hindered phenol antioxidant (E-1) are added, and the mixture is stirred and mixed to obtain an adhesive composition.

[0287] The resulting adhesive composition was applied to a polyethylene terephthalate (PET) film (38 μm thick) to a thickness of approximately 25 μm after drying, and then dried at 120°C for 4 minutes to form an adhesive layer. A release-treated PET tape (release tape) was then attached to the adhesive layer to protect the surface, and the film was aged for 7 days at 40°C to produce an adhesive tape.

[0288] [Examples 6 to 8, Comparative Example 5]

[0289] In Example 5, a pressure-sensitive adhesive composition was prepared in the same manner as described in Table 2 below, and a pressure-sensitive adhesive tape was obtained.

[0290] Using the obtained pressure-sensitive adhesive tapes of Examples and Comparative Examples, adhesive strength, wet heat durability test, wet heat peelability, and holding power were evaluated as shown below. The obtained results are collectively shown in Table 2 below.

[0291] <Adhesion (peel strength) (N / 25mm)>

[0292] A SUS-BA plate was prepared as the adherend. The adhesive tape obtained above was cut into 25 mm x 200 mm pieces under an environment of 23°C and 50% RH. The release film was then removed, and the adhesive layer side was placed against the SUS-BA plate. A 2 kg roller was then used to apply pressure and adhere the tape. The tape was then allowed to stand for 30 minutes in the same atmosphere. The 180-degree peel strength (N / 25 mm) was then measured using a universal tensile tester (Autograph AGS-H 500N, manufactured by Shimadzu Corporation) at a peel rate of 300 mm / min.

[0293] The SUS-BA sheet refers to a sheet obtained by cold-rolling SUS304 and then bright annealing (non-oxidation annealing), or a sheet obtained by temper rolling to improve gloss (the same applies in the present embodiment).

[0294] <Wet heat durability test (N / 25mm)>

[0295] The pressure-sensitive adhesive tapes, which had been pressure-bonded in the same manner as in the above-mentioned adhesive strength (peel strength) measurement, were subjected to the following conditions (X) or (Y), and then their 180-degree peel strength (N / 25 mm) was measured in the same manner as in the above-mentioned adhesive strength (peel strength) measurement.

[0296] Condition (X): Allow to stand at 40°C and 90% RH for 500 hours.

[0297] Condition (Y): Allow to stand at 85°C and 85% RH for 500 hours.

[0298] <Easy to peel off under humidity and heat>

[0299] The 180-degree peel strength (N / 25 mm) value after passing through condition (X) or condition (Y) measured in the wet heat durability test was applied to the following evaluation criteria to evaluate wet heat peelability.

[0300] (Evaluation Criteria)

[0301] ○ (very good) ... the value of condition (X) is >5N / 25mm, and the value of condition (Y) is <5N / 25mm.

[0302] × (difference) ... except when the value of the condition (X) is > 5 N / 25 mm and the value of the condition (Y) is < 5 N / 25 mm.

[0303] <Holding force (cohesion)>

[0304] In accordance with JIS Z-0237, the adhesive tapes of Examples 5 to 8 and Comparative Example 5 obtained above were adhered to SUS304 in a 25 mm × 25 mm adhesive area. The adhesive tapes were then allowed to stand at 80°C for 20 minutes. A load of 1 kg was applied to the resulting material, and the adhesive tapes were observed to see if they fell off during the 24-hour stand. Evaluation was performed based on the following criteria.

[0305] (Evaluation Criteria)

[0306] ○ (very good) ...No falling even after being left to stand for 24 hours.

[0307] × (poor) ... fell during the 24-hour standing period.

[0308] [Table 2]

[0309]

[0310] According to the above results, the adhesive layers (adhesive tapes) of Examples 5 to 8 containing a specific amount or more of structural units derived from aliphatic dicarboxylic acids (a1) having 4 or less carbon atoms as structural units derived from polycarboxylic acids (a) have excellent adhesion to the adherend, easy peelability with moisture and heat, and holding power, and further have a high biomass content, excellent recyclability, and a high environmental load reduction effect.

[0311] On the other hand, the PSA layer (PSA tape) of Comparative Example 5, which did not contain a structural unit derived from an aliphatic dicarboxylic acid having 4 or less carbon atoms (a1), was inferior in wet heat releasability and poor in recyclability compared to the PSA layers of the Examples.

[0312] In addition, since the resin obtained in Comparative Examples 3 and 4 did not dissolve in the solvent, various evaluations as adhesive compositions could not be performed.

[0313] The above embodiments illustrate specific aspects of the present invention, but the above embodiments are merely examples and are not to be construed as limiting. Various modifications obvious to those skilled in the art should be considered to fall within the scope of protection of the present invention.

[0314] Industrial applicability

[0315] The polyester of the present invention is used in an adhesive composition capable of forming an adhesive layer that exhibits excellent adhesion to various adherends, even in the form of a thin film, and further exhibits excellent biomass content, recyclability, and biodegradability, resulting in a high environmental impact reduction effect. The adhesive composition is suitable for use in single-sided or double-sided adhesive tapes used for laminating optical components, adhesive tapes for securing components in portable electronic terminals, and adhesive layers of these single-sided or double-sided adhesive tapes.

Claims

1. A polyester comprising a structural unit derived from a polycarboxylic acid and a structural unit derived from a polyol, The polycarboxylic acid a contains an aliphatic polycarboxylic acid a1 consisting of 4 or less carbon atoms. In 100 mol of the structural units derived from the polycarboxylic acid a, the structural units derived from the aliphatic polycarboxylic acid a1 having 4 or less carbon atoms account for 50 mol or more. The polyester has a crystal melting heat of 30 J / g or less.

2. A polyester comprising a structural unit derived from a polycarboxylic acid and a structural unit derived from a polyol, The polycarboxylic acid a contains an aliphatic polycarboxylic acid a1 consisting of 4 or less carbon atoms. In 100 mol of the structural units derived from the polycarboxylic acid a, the structural units derived from the aliphatic polycarboxylic acid a1 having 4 or less carbon atoms account for 50 mol or more. The content of the structural unit derived from 1,4-butanediol in 100 mol of the structural unit derived from the polyol b is less than 50 mol.

3. The polyester according to claim 1 or 2, wherein The aliphatic polycarboxylic acid a1 having 4 or less carbon atoms contains a structural unit derived from succinic acid.

4. The polyester according to claim 1 or 2, wherein The polyols b include a linear aliphatic polyol b1 having an odd number of carbon atoms.

5. The polyester according to claim 1 or 2, wherein The polyol b contains a linear aliphatic polyol b1 having an odd number of carbon atoms, and the content of the linear aliphatic polyol b1 having an odd number of carbon atoms is 10 mol or more per 100 mol of the structural units derived from the polyol b.

6. The polyester according to claim 1 or 2, wherein The polyol b includes a linear aliphatic polyol b1 having an odd number of carbon atoms, and the linear aliphatic polyol b1 having an odd number of carbon atoms includes a structural unit derived from at least one selected from the group consisting of 1,3-propylene glycol, 1,5-pentanediol, 1,7-heptanediol, and 1,9-nonanediol.

7. The polyester according to claim 1 or 2, wherein The polyols b include side chain aliphatic diols b2 having a hydrocarbon group in the side chain.

8. The polyester according to claim 1 or 2, wherein The polyol b contains: a linear aliphatic polyol b1 of a polyol composed of an odd number of carbon atoms, and a side-chain aliphatic diol b2 having a hydrocarbon group in the side chain, and a molar ratio b1 / b2 of the linear aliphatic polyol b1 of the polyol composed of an odd number of carbon atoms to the side-chain aliphatic diol b2 having a hydrocarbon group in the side chain is 0.5 to 10.

0.

9. The polyester according to claim 1 or 2, wherein The ester bond concentration of the polyester is 11 to 14 mmol / g.

10. The polyester according to claim 1 or 2, wherein The biomass degree of the polyester is greater than 30%.

11. An adhesive composition comprising the polyester according to claim 1 or 2.

12. An adhesive composition, wherein The adhesive composition according to claim 11 comprises a hydrolysis inhibitor which is a monocarbodiimide compound. 13 . An adhesive comprising the adhesive composition according to claim 11 , comprising a crosslinking agent, the adhesive being crosslinked by the crosslinking agent, wherein the adhesive has a gel fraction of 5 to 60%.

14. An adhesive tape comprising the adhesive according to claim 13. 15 . A pressure-sensitive adhesive tape for electronic components, comprising the pressure-sensitive adhesive according to claim 13 .

16. An adhesive composition comprising a polyester having a structural unit derived from a polycarboxylic acid and a structural unit derived from a polyol, The polycarboxylic acid a contains an aliphatic polycarboxylic acid a1 consisting of 4 or less carbon atoms. The structural unit derived from the aliphatic polycarboxylic acid a1 having 4 or less carbon atoms accounts for 50 mol or more of 100 mol of the structural unit derived from the polycarboxylic acid a.

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