JP7700521B2 - Polyester resin composition, pressure-sensitive adhesive composition, pressure-sensitive adhesive, pressure-sensitive adhesive sheet, and double-sided pressure-sensitive adhesive sheet - Google Patents

Description

The present invention relates to a polyester resin composition that contains structural units derived from a polyvalent carboxylic acid having a furan skeleton, and that, when used as an adhesive, has excellent adhesive properties such as adhesive strength and holding power, and to an adhesive composition, adhesive, adhesive sheet, and double-sided adhesive sheet that contain the polyester resin composition.

In recent years, pressure sensitive adhesives have come to be used to join parts together in order to make products smaller and lighter. Instead of the commonly used acrylic resins, pressure sensitive adhesives using polyester resins, which have superior adhesive strength, are being considered.

On the other hand, in recent years, as part of measures to combat the depletion of fossil resources and global warming, the use of plant-derived raw materials, which are renewable resources, has been recommended, and there is a demand for adhesives with a high biomass content that use plant-derived raw materials that are environmentally friendly. In particular, adhesives that use polycarboxylic acids with a furan skeleton, which are aromatic plant-derived compounds, have attracted attention.

As an example of a polyester resin using a polyvalent carboxylic acid having such a furan skeleton, Patent Document 1 proposes a copolymer polyester resin containing 10 mol % or more of a furandicarboxylic acid component as a dicarboxylic acid component, and 25 mol % or more of one or more selected from the group consisting of linear aliphatic dicarboxylic acids having 5 to 12 carbon atoms and linear aliphatic glycols having 5 to 12 carbon atoms. The same document also proposes a copolymer polyester resin containing 80 mol % or more of a furandicarboxylic acid component, 30 mol % or more of an aliphatic glycol having 4 to 9 carbon atoms and having a side chain, and 25 mol % or less of one or more selected from the group consisting of linear aliphatic dicarboxylic acids having 5 to 12 carbon atoms and linear aliphatic glycols having 5 to 12 carbon atoms.
These copolymer polyester resins are considered to be useful as copolymer polyester resins that exhibit excellent solvent solubility and adhesive properties, and as adhesives using the same.
Furthermore, Patent Document 2 proposes an aqueous polyester dispersion containing a polyester copolymerized with 25 to 100 mol % of 2,5-furandicarboxylic acid, 0 mol % to 75 mol % of an aliphatic dicarboxylic acid having 4 to 36 carbon atoms, and 1 mol % to 10 mol % of a sulfonate group-containing compound.

International Publication No. 2015/108026 Special Publication No. 2020-502355

However, the technology disclosed in Patent Document 1 enhances the adhesiveness as an adhesive by incorporating a certain amount of furandicarboxylic acid and setting the glass transition temperature to near room temperature, and thus has the problem that the adhesive properties are insufficient when used as a pressure-sensitive adhesive.
In addition, the technology disclosed in the above-mentioned Patent Document 2 also enhances water dispersibility by containing a certain amount of furandicarboxylic acid and a sulfonate group-containing compound, and the composition is not suitable for use as a pressure-sensitive adhesive.

In light of this background, the present invention aims to provide a polyester resin composition that has good adhesive properties for various adherends and has excellent adhesive properties such as adhesive strength and holding power, even when polyvalent carboxylic acids having a furan skeleton are used, and a pressure-sensitive adhesive composition, pressure-sensitive adhesive, pressure-sensitive adhesive sheet, and double-sided pressure-sensitive adhesive sheet that contain the same.

However, the present inventors have discovered that, in a polyester resin composition, the polyvalent carboxylic acids and polyols constituting the polyester resin include at least one compound selected from aliphatic and/or alicyclic polyvalent carboxylic acids having 10 or more carbon atoms, and aliphatic and/or alicyclic polyols having 10 or more carbon atoms, and polyvalent carboxylic acids having a furan skeleton, and that by setting the amount of the aliphatic and/or alicyclic polyvalent carboxylic acids having 10 or more carbon atoms, and at least one compound selected from aliphatic and/or alicyclic polyols having 10 or more carbon atoms in the polyester resin to the amount of the polyvalent carboxylic acids having a furan skeleton in a molar concentration ratio of 0.6 or more, it is possible to obtain an adhesive that is environmentally friendly, has good adhesive properties for various adherends, and has excellent adhesive strength and retention, and thus completed the present invention.

That is, the present invention has the following aspects [1] to [14].
[1] A polyester-based resin composition containing a polyester-based resin (A),
a polyester-based resin composition, wherein the polyester-based resin (A) contains structural units derived from at least one compound (a1) selected from aliphatic and/or alicyclic polycarboxylic acids having 10 or more carbon atoms and aliphatic and/or alicyclic polyols having 10 or more carbon atoms, and further contains structural units derived from polycarboxylic acids (a2) having a furan skeleton, and the ratio (X1/X2) of the molar concentration (X1) of the structural units derived from the compound (a1) to the molar concentration (X2) of the structural units derived from the polycarboxylic acids (a2) in the polyester-based resin (A) is 0.6 or more.
[2] The polyester resin composition according to [1], wherein the compound (a1) is a plant-derived raw material.
[3] The polyester resin composition according to [1] or [2], wherein the compound (a1) is a dimer acid and/or a dimer diol.
[4] The polyester resin composition according to any one of [1] to [3], wherein the polyvalent carboxylic acid (a2) is a 2,5-furan dicarboxylic acid.
[5] The polyester-based resin composition according to any one of [1] to [4], wherein the polyester-based resin (A) has a number average molecular weight of 3,000 or more.
[6] The polyester-based resin composition according to any one of [1] to [5], wherein the polyester-based resin (A) has a weight average molecular weight of 10,000 or more.
[7] The polyester-based resin composition according to any one of [1] to [6], wherein the glass transition temperature of the polyester-based resin (A) is −10° C. or lower.
[8] The polyester-based resin composition according to any one of [1] to [7], wherein the polyester-based resin (A) has a biomass degree of 50% or more.
[9] The polyester resin composition according to any one of [1] to [8], further comprising a polyisocyanate compound (B).
[10] The polyester resin composition according to any one of [1] to [9], further comprising a hydrolysis inhibitor (C).
[11] A pressure-sensitive adhesive composition comprising the polyester resin composition according to any one of [1] to [10].
[12] A pressure-sensitive adhesive obtained by crosslinking the pressure-sensitive adhesive composition according to [11].
[13] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive according to [12].
[14] A double-sided pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive according to [12].

The polyester resin composition of the present invention is a polyester resin composition that has a high biomass content and is environmentally friendly, and at the same time, when used as an adhesive, it has excellent adhesive strength and holding power.
Therefore, it can be effectively used as a single-sided or double-sided pressure-sensitive adhesive sheet for use in laminating optical members, or as a single-sided or double-sided pressure-sensitive adhesive sheet for fixing members of portable electronic devices or electronic members.

The configuration of the present invention will be described in detail below, but these are merely examples of preferred embodiments.
In the present invention, the term "carboxylic acids" includes not only carboxylic acids but also carboxylic acid derivatives such as carboxylic acid salts, carboxylic acid anhydrides, carboxylic acid halides, and carboxylic acid esters.
In the present invention, the term "α and/or β (α and β are optional structures or components)" means three combinations, namely, α only, β only, and α and β.

The polyester resin composition according to one embodiment of the present invention (hereinafter referred to as "the polyester resin composition") contains structural units derived from at least one compound (a1) [hereinafter referred to as "compound (a1)"] of aliphatic and/or alicyclic polycarboxylic acids having 10 or more carbon atoms and aliphatic and/or alicyclic polyols having 10 or more carbon atoms, and structural units derived from polycarboxylic acids (a2) having a furan skeleton, and contains a polyester resin (A) in which the ratio (X1/X2) of the molar concentration (X1) of the structural units derived from the compound (a1) to the molar concentration (X2) of the structural units derived from the polycarboxylic acids (a2) in the polyester resin (A) is 0.6 or more. The polyester resin (A) will be described in detail below.

<Polyester Resin (A)>
The polyester resin has, as its resin structure, a structural unit derived from a polyvalent carboxylic acid and a structural unit derived from a polyol, and is usually obtained by polymerizing polymerization components including a polyvalent carboxylic acid and a polyol.

The polyester resin (A) used in the polyester resin composition contains structural units derived from compound (a1) and structural units derived from polyvalent carboxylic acids (a2) having a furan skeleton. Such polyester resin (A) is obtained by polymerizing a polymerization component containing compound (a1) and polyvalent carboxylic acids (a2) having a furan skeleton.

[Compound (a1)]
As described above, the compound (a1) is an aliphatic and/or alicyclic polycarboxylic acid having 10 or more carbon atoms, or an aliphatic and/or alicyclic polyol having 10 or more carbon atoms. The compound (a1) will be specifically described below.

[Aliphatic and/or alicyclic polycarboxylic acids having 10 or more carbon atoms]
Examples of the aliphatic and/or alicyclic polycarboxylic acids having 10 or more carbon atoms include sebacic acids, undecanedioic acids, dodecanedioic acids, brassylic acids, dimer acids, etc. Among these, sebacic acids or dimer acids are preferred, and dimer acids are more preferred, in view of the plant-derived raw materials, ease of availability, and adhesive properties.

The dimer acids are mainly composed of unsaturated fatty acid dimers having an average carbon number of 10 to 26, preferably unsaturated fatty acid dimers having an average carbon number of 12 to 24, and more preferably unsaturated fatty acid dimers having an average carbon number of 14 to 22. Specific examples include dicarboxylic acids derived from unsaturated fatty acids such as oleic acids, linoleic acids, linolenic acids, and erucic acids. These may be used alone or in combination of two or more kinds.
The term "main component" as used herein refers to a component whose content is 90% by weight or more, preferably 95% by weight or more, and more preferably 98% by weight or more of the total.

Examples of the dimer acids include dimer acids derived from the unsaturated fatty acids (mainly those with 36 or 44 carbon atoms) and hydrogenated dimer acids. Among these, hydrogenated dimer acids are preferred because they are easier to prevent crystallization.

As the raw material for the dimer acids, plants, beef tallow, etc. are usually used. In the present invention, dimer acids derived from any raw material can be used, but it is preferable to use raw materials derived from plants, which are environmentally friendly. By using raw materials derived from plants, the biomass content of the polyester resin (A) described later can be increased.

When the aliphatic and/or alicyclic polycarboxylic acids having 10 or more carbon atoms are used as the copolymerization component of the polyester resin (A), the content is preferably 10 to 100 mol % based on the total polycarboxylic acids, particularly preferably 20 to 99 mol %, further preferably 35 to 90 mol %, and especially preferably 51 to 80 mol %. If the content is too low, the polyester resin (A) tends to become too hard and the adhesive strength tends to decrease. If the content is too high, it tends to become too soft and the adhesive properties tend to decrease slightly.

[Aliphatic and/or alicyclic polyols having 10 or more carbon atoms]
Examples of the aliphatic and/or alicyclic polyol having 10 or more carbon atoms include 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, dimer diol, etc. These may be used alone or in combination of two or more. Among these, 1,10-decanediol or dimer diol is preferred, and dimer diol is more preferred, in terms of being a plant-derived raw material and being easily available.

The dimer diol is generally a diol derived from the dimer acids. In the present invention, the dimer diol is preferably a plant-derived raw material, like the dimer acids.

When the aliphatic and/or alicyclic polyol having 10 or more carbon atoms is used as a copolymerization component of polyester resin (A), the content is preferably 10 to 100 mol % relative to the total polyol, particularly preferably 20 to 99 mol %, further preferably 35 to 90 mol %, and especially preferably 51 to 80 mol %. If the content is too low, the adhesive properties tend to decrease. If the content is too high, the material tends to become too soft, resulting in a slight decrease in adhesive properties.

[Polyvalent carboxylic acids (a2) having a furan skeleton]
The polyvalent carboxylic acid (a2) having a furan skeleton may be any polyvalent carboxylic acid having a furan skeleton in the structure of the compound, and examples thereof include 2,5-furan dicarboxylic acids, etc. These may be used alone or in combination of two or more kinds.

The polyester resin (A) used in the present invention may contain, as a copolymerization component, an aliphatic compound (a3) having 9 or less carbon atoms or an aromatic compound (a4) in addition to the above compound (a1) and polyvalent carboxylic acid having a furan skeleton (a2).

[Aliphatic compound (a3) having 9 or less carbon atoms]
Examples of the aliphatic compound (a3) having 9 or less carbon atoms include aliphatic polyvalent carboxylic acids having 9 or less carbon atoms and aliphatic polyols having 9 or less carbon atoms.

(Aliphatic polycarboxylic acids having 9 or less carbon atoms)
Examples of the aliphatic polycarboxylic acids having 9 or less carbon atoms include divalent aliphatic dicarboxylic acids and trivalent or higher polyvalent carboxylic acids.
Examples of the aliphatic dicarboxylic acids include linear alkyl dicarboxylic acids such as malonic acids, dimethylmalonic acids, succinic acids, glutaric acids, adipic acids, trimethyladipic acids, pimelic acids, 2,2-dimethylglutaric acids, and azelaic acids; non-cyclic aliphatic dicarboxylic acids such as fumaric acids, maleic acids, itaconic acids, thiodipropionic acids, and diglycolic acids;
Examples of the dicarboxylic acid include alicyclic dicarboxylic acids such as 1,3-cyclopentanedicarboxylic acids, 1,2-cyclohexanedicarboxylic acids, 1,3-cyclohexanedicarboxylic acids, and 1,4-cyclohexanedicarboxylic acids.
These aliphatic polyvalent carboxylic acids having 9 or less carbon atoms may be used alone or in combination of two or more kinds.

In addition, it is preferable to use, as the aliphatic polycarboxylic acids having 9 or less carbon atoms, a plant-derived aliphatic polycarboxylic acid in order to increase the biomass degree.
Examples of the plant-derived aliphatic polycarboxylic acids include succinic acids derived from corn.

(Aliphatic polyols having 9 or less carbon atoms)
Examples of the aliphatic polyol having 9 or less carbon atoms include dihydric aliphatic diols and trihydric or higher aliphatic polyhydric alcohols.
Examples of the divalent aliphatic diol include acyclic aliphatic diols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 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, and 2,2,4-trimethyl-1,6-hexanediol;
Examples of the diol include alicyclic diols such as 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, isosorbide, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol.
Examples of the trihydric or higher aliphatic polyhydric alcohol include pentaerythritol, glycerin, trimethylolpropane, trimethylolethane, 1,2,4-butanetriol, 1,2,5-pentanetriol, and 1,3,6-hexanetriol.
These aliphatic polyols having 9 or less carbon atoms may be used alone or in combination of two or more kinds.

Among these, it is preferable to have the polyol contain an acyclic aliphatic diol having 9 or less carbon atoms, from the viewpoint of lowering the glass transition temperature (Tg) of the polyester resin (A) and improving the initial adhesive strength, and more preferably an acyclic aliphatic diol having 2 to 9 carbon atoms, and particularly preferably ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, or 1,6-hexanediol. Among these, ethylene glycol is particularly preferable, since it can lower the glass transition temperature (Tg) of the polyester resin (A) and improve the adhesiveness.

The content of the acyclic aliphatic diol having 9 or less carbon atoms is preferably 10 to 100 mol % relative to the total polyol, more preferably 20 to 99 mol %, even more preferably 30 to 95 mol %, and particularly preferably 40 to 90 mol %. If the content is too low, it tends to be difficult to obtain stable resin formation.

The aliphatic polyol having 9 or less carbon atoms is preferably a plant-derived polyol in order to increase the biomass content.
Examples of the plant-derived polyol include isosorbide, fatty acid ester diol derived from castor oil, bioethylene glycol, bio-1,3-propane glycol, biobutylene glycol, etc. Among these, bioethylene glycol is preferred.

In addition, polyethylene terephthalate may be used as the acyclic aliphatic diol having 9 or less carbon atoms. The polyethylene terephthalate is a polyester resin obtained by polymerizing terephthalic acids and ethylene glycol. Therefore, by using polyethylene terephthalate, the polyester resin (A) has a structural unit derived from ethylene glycol derived from polyethylene terephthalate as a structural unit derived from the acyclic aliphatic diol having 9 or less carbon atoms. In addition, the polyethylene terephthalate may be a virgin product or a recycled product, but it is preferable to use a recycled product from the viewpoint of the global environment.

Furthermore, in order to form reaction sites with the polyisocyanate compound (B) described below in the polyester resin (A) and increase the cohesive strength, it is preferable to use an aliphatic polyol having a carbon number of 9 or less, which is a trivalent or higher aliphatic polyol. For example, trimethylolpropane, trimethylolethane, glycerin, pentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, and 1,2,6-hexanetriol can be used. Among these, it is particularly preferable to use trimethylolpropane, which is relatively unlikely to cause gelation.

The content of such trihydric or higher aliphatic polyhydric alcohol is preferably 20 mol% or less, more preferably 0.1 to 10 mol%, and particularly preferably 0.5 to 5 mol%, based on the total polyol. If the content of such trihydric or higher aliphatic polyhydric alcohol is too high, it tends to be difficult to produce the polyester resin (A).

It is preferable to use an aliphatic polyol having 9 or less carbon atoms that is derived from a plant, but if the biomass degree of polyvalent carboxylic acids is high, an aliphatic polyol that is not derived from a plant may be used in terms of ease of polycondensation. However, even in this case, in order to increase the biomass degree, it is preferable to use an acyclic aliphatic diol having a straight chain structure with 4 or less carbon atoms, and in particular, it is preferable to use an acyclic aliphatic diol having a straight chain structure with 2 to 3 carbon atoms. Examples of acyclic aliphatic diols having a straight chain structure with 4 or less carbon atoms include ethylene glycol, 1,3-propanediol, and 1,4-butanediol. In other words, when an aliphatic polyol having 9 or less carbon atoms with a small carbon number of 4 or less is used, the weight ratio of carboxylic acids having a high biomass degree as the polyester resin (A) increases, and the biomass degree can be increased.

[Aromatic compound (a4)]
Examples of the aromatic compound (a4) include aromatic polyvalent carboxylic acids and aromatic polyols. These may be used alone or in combination of two or more. Among them, it is preferable to use aromatic polyvalent carboxylic acids as the aromatic compound (a4) because they have excellent adhesive strength and holding power.

(Aromatic polycarboxylic acids)
Examples of the aromatic polyvalent carboxylic acids include divalent aromatic dicarboxylic acids and trivalent or higher aromatic polyvalent carboxylic acids, with aromatic dicarboxylic acids being preferred since they allow the polyester resin to be stably obtained.

Examples of the aromatic dicarboxylic acids include benzene-based aromatic dicarboxylic acids such as phthalic acids, terephthalic acids, isophthalic acids, benzylmalonic acids, diphenic acids, 4,4'-oxydibenzoic acids, naphthalene dicarboxylic acids such as 1,8-naphthalene dicarboxylic acids, 2,3-naphthalene dicarboxylic acids, and 2,7-naphthalene dicarboxylic acids; and heterocyclic dicarboxylic acids such as thiophenedicarboxylic acids (pyrrole, pyrazole, imidazole, pyridine, pyridazine, pyrimidine, pyrazine, etc.). These may be used alone or in combination of two or more. Of these, terephthalic acids and isophthalic acids are preferred because of their ease of availability.

Examples of the aromatic polyvalent carboxylic acids having a valence of three or more include trimellitic acids, pyromellitic acids, trimesic acids, etc. These may be used alone or in combination of two or more.

It is also preferable to use polyethylene terephthalate as the aromatic polycarboxylic acid. As described above, polyethylene terephthalate is a polyester resin obtained by polymerizing terephthalic acid and ethylene glycol. By using the polyethylene terephthalate, the polyester resin (A) has a structural unit derived from terephthalic acid derived from polyethylene terephthalate as a structural unit derived from aromatic polycarboxylic acid.
The polyethylene terephthalate may be modified, if necessary, with a substance such as isophthalic acids, phthalic anhydrides, adipic acids, cyclohexanedicarboxylic acids, sebacic acids, 1,3-butanediol, 1,4-butanediol, cyclohexanedimethanol, etc. The polyethylene terephthalate may be a virgin product or a recycled product, but it is preferable to use a recycled product from the viewpoint of the global environment.

(Aromatic polyol)
The aromatic polyol includes a divalent aromatic diol.
Examples of the divalent aromatic diol include bisphenol A, 4,4'-thiodiphenol, 4,4'-methylenediphenol, 4,4'-dihydroxybiphenyl, o-, m-, and p-dihydroxybenzene, 2,5-naphthalenediol, p-xylenediol, and ethylene oxide adducts and propylene oxide adducts thereof. These may be used alone or in combination of two or more kinds.

[Production of polyester resin (A)]
In the present invention, the polyester resin (A) can be produced by polycondensation reaction of polyvalent carboxylic acids and polyol in the presence of a catalyst by a known method, and in the polycondensation reaction, an esterification reaction or an ester exchange reaction is carried out first, and then the polycondensation reaction is carried out. When it is not necessary to obtain a high molecular weight, the polyester resin (A) may be produced by only the esterification reaction or the ester exchange reaction.

In such an esterification reaction or transesterification reaction, a catalyst is used, and 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, and one or more of these are used. Among these, antimony trioxide, tetrabutyl titanate, germanium dioxide, and zinc acetate are preferred from the perspective of the balance between high catalytic activity and the hue of the resulting reaction product.

The amount of the catalyst is preferably 1 to 10,000 ppm based on the total copolymerization components (by weight), more preferably 10 to 5,000 ppm, and even more preferably 20 to 3,000 ppm. If the amount is too small, the polymerization reaction tends not to proceed sufficiently, and if the amount is too large, there is no advantage to shortening the reaction time, and side reactions tend to occur easily.

The reaction temperature during the esterification reaction is preferably 200 to 300°C, particularly preferably 210 to 280°C, and even more preferably 220 to 260°C. If the reaction temperature is too low, the reaction tends not to proceed sufficiently, and if it is too high, side reactions such as decomposition tend to occur easily. The pressure during the reaction is usually normal pressure.

The reaction conditions for the polycondensation reaction carried out after the above esterification reaction or transesterification reaction are as follows: the same amount of catalyst as that used in the above esterification reaction or transesterification reaction is further compounded, the reaction temperature is preferably 200 to 280°C, and particularly preferably 210 to 270°C, and the reaction system is gradually decompressed until the reaction is finally carried out at 5 hPa or less. If the reaction temperature is too low, the reaction tends not to proceed sufficiently, and if it is too high, side reactions such as decomposition tend to occur easily.

Thus, a polyester resin (A) is obtained that contains structural units derived from compound (a1) and structural units derived from polyvalent carboxylic acid (a2) having a furan skeleton.

In the polyester resin (A), in order to obtain excellent adhesive strength and holding power, the ratio (X1/X2) of the molar concentration (X1) of the structural unit derived from compound (a1) to the molar concentration (X2) of the structural unit derived from polyvalent carboxylic acids (a2) having a furan skeleton in the polyester resin (A) must be 0.6 or more. It is preferably 1.0 or more, more preferably 1.5 or more, even more preferably 2.0 or more, and particularly preferably 2.5 or more. If (X1/X2) is less than the above numerical value, the adhesive strength and holding power are reduced. The upper limit of (X1/X2) is usually 20, preferably 10, more preferably 6.0, even more preferably 5.0, particularly preferably 4.0, and especially preferably 3.5.

The number average molecular weight of the polyester resin (A) is preferably 3,000 or more, more preferably 3,500 to 50,000, even more preferably 4,000 to 40,000, particularly preferably 5,000 to 30,000, especially preferably 6,000 to 20,000, and most preferably 7,000 to 15,000. If the number average molecular weight is too large, the handling properties decrease, requiring a large amount of solvent and tending to increase the environmental load, whereas if the number average molecular weight is too small, the adhesive properties tend to decrease.

The weight average molecular weight of the polyester resin (A) is preferably 10,000 or more, more preferably 10,000 to 500,000, even more preferably 20,000 to 300,000, particularly preferably 30,000 to 250,000, especially preferably 40,000 to 200,000, and most preferably 50,000 to 150,000. If the weight average molecular weight is too small, the adhesive properties tend to decrease. If the weight average molecular weight is too large, the handling properties decrease, a large amount of solvent is required, and the environmental load tends to increase.

The number average molecular weight and weight average molecular weight are number average molecular weight and weight average molecular weight converted into standard polystyrene molecular weight, and are measured using a high performance liquid chromatograph (manufactured by Tosoh Corporation, "HLC-8320GPC") equipped with two columns: TSKgel SuperMultipore HZ-M (exclusion limit molecular weight: 2 × 10 ⁶ , theoretical plate number: 16,000 plates/column, packing material: styrene-divinylbenzene copolymer, packing particle size: 4 μm) arranged in series.

The biomass degree of the polyester resin (A) is preferably 50% or more, more preferably 60% or more, even more preferably 70% or more, particularly preferably 80% or more, especially preferably 85% or more, and most preferably 90% or more. The upper limit is 100%. If the biomass degree is low, the reduction of the environmental load tends to be insufficient.

Here, the biomass degree of the polyester resin (A) refers to the weight ratio of the portion of the resin in which the plant-derived raw materials used in producing the polyester resin (A) are incorporated relative to the total weight of the polyester resin (A), and is calculated as follows.
The biomass degree of the polyvalent carboxylic acids and the polyol is determined from the weighted average of the respective biomass degrees.
In addition, it is sufficient if the value obtained by any of the following calculation methods falls within the above range.

(Calculation method)
<When polycondensation reaction is involved>
Biomass ratio (%)=[(number of moles of carbon of plant-derived monomer calculated from the molar ratio of polyvalent carboxylic acids and polyol in polyester resin (A))/(number of moles of carbon of all constituent monomers in polyester resin (A)]×100

<When no polycondensation reaction is involved>
Biomass ratio (%)=[(number of moles of carbon of plant-derived monomer in polyester resin (A))/(number of moles of carbon of all constituent monomers in polyester resin (A)]×100

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

The biomass content can also be measured by the method described in "Technology for determining the origin of biofuels using natural radioactive carbon C-14" in the Tokyo Metropolitan Industrial Technology Research Center Research Report, No. 4, 2009.

Methods for adjusting the biomass degree to within a predetermined range include using mainly plant-derived polycarboxylic acids or plant-derived polyols, but it is particularly preferable to use plant-derived polycarboxylic acids, as this allows for an efficient increase in the biomass degree.

The glass transition temperature (Tg) of the polyester resin (A) is preferably -10°C or lower, more preferably -90 to -10°C, particularly preferably -60 to -20°C, even more preferably -50 to -30°C, and especially preferably -45 to -35°C. If the glass transition temperature (Tg) is too high, the adhesive properties when used as an adhesive tend to decrease, and if it is too low, the heat resistance and cohesive strength tend to decrease.

The glass transition temperature (Tg) is measured using a differential scanning calorimeter DSC Q20 manufactured by TA Instruments. The measurement temperature range is -90 to 100°C, and the temperature rise rate is 10°C/min.

The ester group concentration of the polyester resin (A) is usually 2 mmol/g or more, preferably 3 to 10 mmol/g, more preferably 3.6 to 6 mmol/g, and particularly preferably 4.2 to 5 mmol/g. If the ester group concentration is too low, the polyester resin (A) becomes soft, and if it is too soft, the adhesive properties tend to decrease.

The ester group concentration (mmol/g) refers to the number of moles of ester bonds in 1 g of polyester resin (A), and is calculated from the amounts charged, for example. The calculation method is to divide the number of moles of the carboxylic acid or polyol, whichever is charged in smaller amounts, by the total weight, and an example of the calculation formula is shown below.
When the polyvalent carboxylic acid and the polyol are charged in equal molar amounts, either of the following calculation formulas may be used.
Furthermore, when a monomer having both a carboxyl group and a hydroxyl group is used, or when polyester is produced from caprolactone or the like, the calculation method will be changed appropriately.

<When polycarboxylic acids are scarce>
Ester group concentration (mmol/g)=[(X1/x1×m1+X2/x2×m2+X3/x3×m3...)/Z]×1000
X1, X2, X3...: Amount of polyvalent carboxylic acid (g)
x1, x2, x3...: molecular weight of polycarboxylic acid m1, m2, m3...: number of carboxyl groups per molecule of polycarboxylic acid Z: finished weight (g)
<When there is a small amount of polyol>
Ester group concentration (mmol/g)=[(Y1/y1×n1+Y2/y2×n2+Y3/y3×n3...)/Z]×1000
Y1, Y2, Y3...: Amount of polyol charged (g)
y1, y2, y3...: molecular weight of polyol n1, n2, n3...: number of hydroxyl groups per molecule of polyol Z: finished weight (g)

The ester group concentration can also be measured by a known method using NMR or the like.
For example, the ester group concentration of the polyester resin (A) can be measured by ¹ H-NMR measurement (proton type nuclear magnetic resonance spectroscopy) or ¹³ C-NMR measurement (carbon type nuclear magnetic resonance spectroscopy) at a resonance frequency of 400 MHz.

Methods for adjusting the ester group concentration include, for example, selecting a polyol having 4 or less carbon atoms as the polyol, increasing the content of linear carboxylic acids as the polyvalent carboxylic acids, or combining both of these methods.

The heat of crystalline fusion of the polyester resin (A) measured by a differential scanning calorimeter is usually 10 J/g or less, preferably 5 J/g or less, more preferably 2 J/g or less, and particularly preferably no heat of crystalline fusion occurs. If the heat of crystalline fusion is too large, crystallinity occurs, and the storage stability of the resin solution decreases, and the stability and adhesive properties at low temperatures when made into an adhesive sheet tend to decrease.
The heat of fusion of crystals refers to the energy consumed when a crystallized substance is heated and melted, and can be measured by a differential scanning calorimeter (DSC).

Methods for adjusting the heat of crystalline fusion include, for example, appropriately using polycarboxylic acids having an alkyl group on the side chain or polyols having an alkyl group on the side chain, and using three or more copolymerizable monomer components, preferably four or more components.

The acid value of the polyester resin (A) is preferably 10 mgKOH/g or less in terms of preventing hydrolysis and increasing durability, more preferably 5 mgKOH/g or less, and particularly preferably 2 mgKOH/g or less. If the acid value is too high, durability tends to decrease.
The acid value can be adjusted, for example, by increasing the ratio of polyol during the esterification reaction or transesterification reaction, or by adjusting the reaction conditions. The lower limit of the acid value is usually 0 mgKOH/g.

The acid value of the polyester resin (A) is determined by neutralization titration in accordance with JIS K0070.
In the present invention, the acid value means the content of carboxy groups in the polyester resin (A). The carboxy groups include those in a carboxylate ion state in which the carboxy groups are neutralized with a basic compound.

In terms of adhesive properties, the content of polyester resin (A) in this polyester resin composition is usually 70% by weight or more, preferably 80% by weight or more, and particularly preferably 90% by weight or more.

In addition to the polyester resin (A), the polyester resin composition preferably contains a polyisocyanate compound (B), a hydrolysis inhibitor (C), and, if necessary, a tackifier (D), a urethane catalyst (E), an antioxidant (F), etc.

<Polyisocyanate Compound (B)>
It is preferable that the polyester resin composition further contains a polyisocyanate compound (B) as a crosslinking agent. By containing the polyisocyanate compound (B), the polyester resin (A) is crosslinked with the polyisocyanate compound (B) to have excellent cohesive strength, thereby improving the performance as a pressure-sensitive adhesive.

Examples of such polyisocyanate-based compounds (B) include aromatic isocyanate-based crosslinking agents such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, etc., xylylene diisocyanate-based crosslinking agents such as 1,3-xylylene diisocyanate, diphenylmethane-4,4-diisocyanate, etc., and naphthalene diisocyanate-based crosslinking agents such as 1,5-naphthalene diisocyanate, etc.; isophorone diisocyanate, 1,4-cyclohexane diisocyanate, 4,4'-dicyclohexyl methyl ether, etc. Alicyclic isocyanate crosslinking agents such as hexane diisocyanate, methylcyclohexane diisocyanate, isopropylidenedicyclohexyl-4,4'-diisocyanate, 1,3-diisocyanatomethylcyclohexane, and norbornane diisocyanate; aliphatic isocyanate crosslinking agents such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; and adducts of the above isocyanate compounds with polyol compounds such as trimethylolpropane, biuret compounds, and isocyanurates of these isocyanate compounds. The polyisocyanate compound (B) may be one in which the isocyanate portion is blocked with phenol, lactam, or the like. These polyisocyanate compounds (B) may be used alone or in combination of two or more.

When such a polyisocyanate compound (B) is used, its content can be appropriately selected depending on the molecular weight of the polyester resin (A) and the intended use. In general, the polyisocyanate compound (B) is preferably contained in a ratio such that the reactive group contained in the polyisocyanate compound (B) is 0.2 to 10 equivalents per equivalent of at least one of the hydroxyl group and the carboxy group contained in the polyester resin (A), more preferably 0.5 to 5 equivalents, and even more preferably 0.5 to 3 equivalents. If the equivalent number of the reactive group contained in the polyisocyanate compound (B) is too small, the cohesive strength tends to decrease, and if it is too large, the flexibility tends to decrease.

In addition, in the reaction between the polyester resin (A) and the polyisocyanate compound (B), organic solvents that do not have functional groups that react with the polyester resin (A) and the polyisocyanate compound (B) components can be used, such as 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. These can be used alone or in combination of two or more.

<Hydrolysis Inhibitor (C)>
The hydrolysis inhibitor (C) is contained as necessary in order to ensure the long-term durability of the polyester resin composition.
As the hydrolysis inhibitor (C), a conventionally known one can be used, and for example, a compound that reacts with the carboxyl group terminal of the polyester resin (A) and bonds thereto can be mentioned.Specific examples include compounds that contain functional groups such as carbodiimide groups, epoxy groups, and oxazoline groups.Among these, carbodiimide group-containing compounds are preferred because they have a high effect of eliminating the catalytic activity of the protons derived from the carboxyl group terminal.

As the carbodiimide group-containing compound, a known carbodiimide having one or more carbodiimide groups (-N=C=N-) in the molecule may be used, but in order to increase durability under high temperature and high humidity, a compound having two or more carbodiimide groups in the molecule, i.e., a polyvalent carbodiimide compound, is preferred, and in particular, a compound having three or more, further five or more, and especially seven or more carbodiimide groups in the molecule is preferred. The number of carbodiimide groups in the molecule is usually 50 or less, and if there are too many carbodiimide groups, the molecular structure becomes too large, and compatibility tends to decrease. It is also preferred to use a high molecular weight polycarbodiimide produced by decarboxylation condensation reaction of diisocyanate in the presence of a carbodiimide catalyst.

Furthermore, in terms of storage stability, it is preferable that the terminal isocyanate groups of the high molecular weight polycarbodiimide are blocked with a blocking agent. Examples of blocking agents include compounds having active hydrogen that reacts with isocyanate groups, or compounds having isocyanate groups. Examples include monoalcohols, monocarboxylic acids, monoamines, and monoisocyanates having one substituent selected from a carboxy group, an amino group, and an isocyanate group.

Examples of such high molecular weight polycarbodiimides include those obtained by subjecting the following diisocyanates to a decarboxylation condensation reaction.

Examples of such diisocyanates include 4,4'-diphenylmethane diisocyanate, 3,3'-dimethoxy-4,4'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 4,4'-diphenylether diisocyanate, 3,3'-dimethyl-4,4'-diphenylether diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, tetramethylxylylene diisocyanate, and the like. These can be used alone or in combination of two or more. Such high molecular weight polycarbodiimides can be synthesized or commercially available products can be used.

Commercially available products of the above carbodiimide group-containing compounds include, for example, the Carbodilite (registered trademark) series manufactured by Nisshinbo Chemical Co., Ltd. Among these, Carbodilite (registered trademark) "V-01", "V-02B", "V-03", "V-04K", "V-04PF", "V-05", "V-07", "V-09", and "V-09GB" are preferred because of their excellent compatibility with organic solvents.

As the epoxy group-containing compound, for example, a glycidyl ester compound or a glycidyl ether compound is preferred.

Specific examples of the above glycidyl ester compounds include benzoic acid glycidyl ester, t-butylbenzoic acid glycidyl ester, p-toluic acid glycidyl ester, cyclohexane carboxylic acid glycidyl ester, pelargonic acid glycidyl ester, stearic acid glycyl ester, lauric acid glycidyl ester, palmitic acid glycidyl ester, behenic acid glycidyl ester, versatic acid glycidyl ester, oleic acid glycidyl ester, linoleic acid glycidyl ester, linolenic acid glycidyl ester, behenolic acid glycidyl ester, stearolic acid glycidyl ester, terephthalic acid diglycidyl ester, and isophthalic acid. Examples of such glycidyl esters include diglycidyl esters of phthalic acid, diglycidyl esters of naphthalenedicarboxylic acid, diglycidyl esters of methyl terephthalic acid, diglycidyl esters of hexahydrophthalic acid, diglycidyl esters of tetrahydrophthalic acid, diglycidyl esters of cyclohexanedicarboxylic acid, diglycidyl esters of adipic acid, diglycidyl esters of succinic acid, diglycidyl esters of sebacic acid, diglycidyl esters of dodecanedioic acid, diglycidyl esters of octadecanedicarboxylic acid, triglycidyl esters of trimellitic acid, and tetraglycidyl esters of pyromellitic acid. These glycidyl esters may be used alone or in combination of two or more kinds.

Specific examples of the glycidyl ether compound include phenyl glycidyl ether, o-phenyl glycidyl ether, 1,4-bis(β,γ-epoxypropoxy)butane, 1,6-bis(β,γ-epoxypropoxy)hexane, 1,4-bis(β,γ-epoxypropoxy)benzene, 1-(β,γ-epoxypropoxy)-2-ethoxyethane, 1-(β,γ-epoxypropoxy)-2-benzyloxyethane, 2,2-bis-[р-(β,γ-epoxypropoxy)phenyl]propane, and bisglycidyl polyethers obtained by reacting bisphenols such as 2,2-bis-(4-hydroxyphenyl)propane and 2,2-bis-(4-hydroxyphenyl)methane with epichlorohydrin, and these can be used alone or in combination of two or more kinds.

As the oxazoline group-containing compound, a bisoxazoline compound is preferable. 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'-ethylene Examples include 2,2'-tetramethylenebis(4,4-dimethyl-2-oxazoline), 2,2'-9,9'-diphenoxyethanebis(2-oxazoline), 2,2'-cyclohexylenebis(2-oxazoline), and 2,2'-diphenylenebis(2-oxazoline). Among these, 2,2'-bis(2-oxazoline) is most preferred in terms of reactivity with the polyester resin (A). These can be used alone or in combination of two or more.

The hydrolysis inhibitor (C) preferably has low volatility, and therefore it is preferable to use one having a high number average molecular weight, which is usually 300 to 10,000, preferably 1,000 to 5,000.
From the viewpoint of hydrolysis resistance, it is preferable to use a hydrolysis inhibitor (C) having a high weight average molecular weight. The weight average molecular weight of the hydrolysis inhibitor (C) is preferably 500 or more, more preferably 1000 or more, even more preferably 2000 or more, and particularly preferably 3000 or more. The upper limit of the weight average molecular weight is usually 50,000.
If the molecular weight of the hydrolysis inhibitor (C) is too small, the hydrolysis resistance tends to decrease.
If the molecular weight is too large, the compatibility with the polyester resin (A) tends to decrease.

Among the hydrolysis inhibitors (C), it is preferable to use a carbodiimide group-containing compound, and in this case, the carbodiimide equivalent is preferably 50 to 10,000, particularly 100 to 1,000, and more preferably 150 to 500. The carbodiimide equivalent indicates the chemical formula weight per one carbodiimide group.

When the hydrolysis inhibitor (C) is used, its content is preferably 0.01 to 10 parts by weight, particularly preferably 0.1 to 5 parts by weight, and even more preferably 0.2 to 3 parts by weight, per 100 parts by weight of the polyester resin (A). If the content is too high, turbidity tends to occur due to poor compatibility with the polyester resin (A), and if the content is too low, sufficient durability tends to be difficult to obtain.

The content of the hydrolysis inhibitor (C) is preferably optimized depending on the acid value of the polyester resin (A), and the molar ratio [(y)/(x)] of the total number of moles (y) of functional groups of the hydrolysis inhibitor (C) in the polyester resin composition to the total number of moles (x) of acidic functional groups of the polyester resin (A) in the polyester resin composition is preferably 0.5≦(y)/(x), particularly preferably 1≦(y)/(x)≦1000, and further preferably 1.5≦(y)/(x)≦100.
If the molar ratio of (y) to (x) is too low, the moist heat resistance tends to decrease, whereas if the molar ratio of (y) to (x) is too high, the compatibility with the polyester resin (A) tends to decrease, and the adhesive strength, cohesive strength, and durability tend to decrease.

<Tackifier (D)>
In the present polyester resin composition, it is preferable to contain a tackifier (D) in order to improve the adhesive properties.

The tackifier (D) is not particularly limited, and conventionally known tackifiers can be used. Examples of the tackifier (D) include hydrocarbon tackifier resins, terpene resins, phenolic resins, rosin resins, xylene resins, epoxy resins, polyamide resins, ketone resins, and elastomer resins. These may be used alone or in combination of two or more. Among these, hydrocarbon tackifier resins and terpene resins are preferred. It is particularly preferred that the tackifier (D) contains at least one hydrocarbon tackifier resin, and the hydrocarbon tackifier resin is preferably 30% by weight or more of the total tackifier, preferably 50% by weight or more, and more preferably 70% by weight or more.

Examples of the above-mentioned hydrocarbon-based tackifying resins include various hydrocarbon-based resins such as aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic and aromatic petroleum resins (such as styrene-olefin copolymers), aliphatic and alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, and coumarone-indene resins. Commercially available products include, for example, "FTR6100", "FTR6110", "FTR6125", "FTR8100", "FTR8120", and "FMR0150" manufactured by Mitsui Chemicals, Inc.

Examples of the terpene resin include terpene resin, terpene phenol resin, and aromatic modified terpene resin. Specifically, α-pinene polymer, β-pinene polymer, dipentene polymer, and terpene resins obtained by modifying these with phenol, aromatic, hydrogenation, or hydrocarbon can be used. Commercially available products include "YS Polystar S145", "YS Resin PX1000", "YS Resin PX1250", "YS Polystar T160", "YS Polystar T145", "YS Polystar T130", "YS Resin TO115", "YS Polystar G150", "YS Polystar G125", "YS Polystar U130", and "Clearon P125" manufactured by Yasuhara Chemical Co., Ltd. Terpene resins are preferred because of their good adhesion to non-polar substrates such as polypropylene.

As the phenol-based resin, for example, a condensation product of various phenols such as phenol, m-cresol, 3,5-xylenol, p-alkylphenol, and resorcin with formaldehyde can be used. In addition, resol obtained by addition reaction of the phenols with formaldehyde under an alkali catalyst, novolak obtained by condensation reaction of the phenols with formaldehyde under an acid catalyst, and rosin-modified phenolic resin obtained by adding phenol to rosins such as unmodified or modified rosin or derivatives thereof under an acid catalyst and thermally polymerizing the rosin can be used.

Examples of the rosin-based resin include rosin resin, polymerized rosin resin, hydrogenated rosin resin, rosin ester resin, hydrogenated rosin ester resin, rosin phenol resin, polymerized rosin ester, etc. Specifically, unmodified rosin (raw rosin) such as gum rosin, wood rosin, tall oil rosin, etc., modified rosins that have been hydrogenated, disproportionated, polymerized, or otherwise chemically modified, and derivatives of these can be used. Commercially available products include, for example, Hariestar TF, Haritac 8LJA, Haritac PH, Haritac FK100, Haritac PCJ, etc., manufactured by Harima Chemicals.

The tackifier (D) preferably has an acid value of 30 mgKOH/g or less, particularly preferably 10 mgKOH/g or less, further preferably 6 mgKOH/g or less, and especially preferably 3 mgKOH/g or less. When multiple types of tackifiers (D) are used in combination, it is preferable that the average is within the above range.

The softening point of the tackifier (D) (measured, for example, by the ring and ball method) is preferably 80 to 170°C, particularly 90 to 160°C, more preferably 100 to 155°C, even more preferably 120 to 155°C, and particularly preferably 135 to 150°C. If the softening point is within the above range, the adhesive properties (adhesive strength, cohesive strength) can be improved, which is preferable.

In the present polyester resin composition, the tackifier (D) is preferably plant-derived in order to maintain a high biomass content in the entire polyester resin composition. Examples of plant-derived tackifiers include terpene resins and rosin resins.

The tackifier (D) preferably contains an aromatic structural unit from the viewpoints of improving cohesive strength and compatibility. Examples of tackifiers containing aromatic structural units include aromatic hydrocarbon resins, aliphatic and aromatic petroleum resins (styrene-olefin copolymers, etc.), coumarone resins, coumarone-indene resins, terpene phenol resins, and aromatic modified terpene resins.

When a tackifier (D) is used, its content is preferably 2 to 200 parts by weight, more preferably 5 to 150 parts by weight, even more preferably 8 to 100 parts by weight, particularly preferably 10 to 80 parts by weight, and most preferably 20 to 50 parts by weight, per 100 parts by weight of the polyester resin (A). If the content is within the above range, there is a tendency for the adhesive properties (adhesive strength, cohesive strength) to be improved.

<Urethanization catalyst (E)>
From the viewpoint of reaction rate, the present pressure-sensitive adhesive composition more preferably contains a urethanization catalyst (E).

Examples of the urethane catalyst (E) include organometallic compounds and tertiary amine compounds. These can be used alone or in combination of two or more.

Examples of the organometallic compounds include zirconium-based compounds, iron-based compounds, tin-based compounds, titanium-based compounds, lead-based compounds, cobalt-based compounds, and zinc-based compounds.

Examples of the zirconium compound include zirconium naphthenate and zirconium acetylacetonate.
Examples of the iron-based compound include iron acetylacetonate and iron 2-ethylhexanoate.
Examples of the tin compounds include dibutyltin dichloride, dibutyltin oxide, and dibutyltin dilaurate.
Examples of the titanium-based compound include dibutyltitanium dichloride, tetrabutyltitanium, and butoxytitanium trichloride.
Examples of the lead-based compounds include lead oleate, lead 2-ethylhexanoate, lead benzoate, and lead naphthenate.
Examples of the cobalt-based compound include cobalt 2-ethylhexanoate and cobalt benzoate.
Examples of the zinc-based compound include zinc naphthenate and zinc 2-ethylhexanoate.

Examples of the tertiary amine compounds include triethylamine, triethylenediamine, and 1,8-diazabicyclo-(5,4,0)-undecene-7.

Among these urethane-forming catalysts (E), organometallic compounds are preferred in terms of reaction speed and pot life of the adhesive layer, and zirconium compounds are particularly preferred. Furthermore, it is preferable to use acetylacetone in combination with the urethane-forming catalyst (E) as a catalytic action inhibitor. The inclusion of acetylacetone is preferable in that it inhibits catalytic action at low temperatures and extends the pot life.

When the urethane catalyst (E) is used, its content is preferably 0.0001 to 1 part by weight, more preferably 0.001 to 0.1 parts by weight, and even more preferably 0.01 to 0.05 parts by weight, per 100 parts by weight of the polyester resin (A). If the content is too low, the aging time until the crosslinking reaction is complete tends to be long, and if the content is too high, the adhesive properties tend to decrease.

<Antioxidant (F)>
The polyester resin composition preferably contains an antioxidant (F) in order to improve the stability of the resin.

Examples of the antioxidant (F) include hindered phenol-based antioxidants, amine-based antioxidants, sulfur-based antioxidants, and phosphoric acid-based antioxidants. These may be used alone or in combination of two or more. Among them, at least one selected from the group consisting of hindered phenol-based antioxidants, amine-based antioxidants, and phosphoric acid-based antioxidants is preferred, and an antioxidant consisting of a hindered phenol-based compound is particularly preferred.
Examples of the hindered phenol-based antioxidants include antioxidants having a hindered phenol structure in which a group with large steric hindrance, such as a tertiary butyl group, is bonded to at least one of the carbon atoms adjacent to the carbon atom on the aromatic ring to which the phenolic hydroxyl group is bonded.

When the antioxidant (F) is used, the content thereof is preferably 0.01 to 10 parts by weight, more preferably 0.03 to 8 parts by weight, and even more preferably 0.05 to 5 parts by weight, based on 100 parts by weight of the polyester resin (A).
If the content is too low, adhesive residue on the adherend tends to be more likely to occur, whereas if the content is too high, the adhesive properties tend to decrease.

In addition to the polyester resin (A), polyisocyanate compound (B), hydrolysis inhibitor (C), tackifier (D), urethanization catalyst (E), and antioxidant (F), additives such as softeners, UV absorbers, stabilizers, and antistatic agents, as well as inorganic or organic fillers, powders such as metal powders, pigments, and other particulate additives, may be blended in the present polyester resin composition within the range that does not impair the effects of the present invention. Furthermore, the composition may contain small amounts of impurities contained in the manufacturing raw materials of the components of the polyester pressure-sensitive adhesive composition.
These may be used alone or in combination of two or more.

This polyester resin composition can be obtained, for example, by preparing the polyester resin (A) and optional components as necessary, and mixing and dispersing them during the production of the polyester resin (A), or by mixing them in a solution of the polyester resin (A) dissolved in an organic solvent and dispersing them using a mixing roller.

From the viewpoint of reducing the environmental load, the present polyester resin composition preferably has a biomass degree of 50% or more, more preferably 60% or more, even more preferably 70% or more, particularly preferably 80% or more, especially preferably 85% or more, and most preferably 90% or more. The biomass degree of the pressure-sensitive adhesive can be adjusted by adjusting the types and amounts of the polyester resin (A) and other blending components.
The biomass degree of the polyester resin composition is the ratio of the weight of plant-derived raw materials used in producing the polyester resin composition to the total weight of the polyester resin composition, and can be calculated, for example, by the following formula.
Biomass ratio (%)=[(biomass ratio of each plant-derived raw material used in producing the polyester-based resin composition)×(weight of each plant-derived raw material used in producing the polyester-based resin composition)]/(total weight of the polyester-based resin composition)

The biomass degree of the polyester resin composition can also be measured by the above-mentioned NMR method or the method using natural radioactive carbon C-14. It is sufficient that the value obtained by any of the above calculation methods falls within the above range.

An adhesive composition according to one embodiment of the present invention (hereinafter referred to as "the adhesive composition") contains the polyester-based resin composition, and preferably consists of the polyester-based resin composition.
Moreover, a pressure-sensitive adhesive according to one embodiment of the present invention (hereinafter referred to as "the pressure-sensitive adhesive") is obtained by crosslinking the pressure-sensitive adhesive composition.

The adhesive sheet of one embodiment of the present invention (hereinafter referred to as "the adhesive sheet") has an adhesive layer containing the above-mentioned adhesive of the present invention, and it is preferable that such an adhesive layer is formed on one or both sides of a supporting substrate.
In the present invention, the term "sheet" is used to include the meanings of "film" and "tape."

<Adhesive sheet>
The pressure-sensitive adhesive sheet can be produced, for example, as follows.
The present pressure-sensitive adhesive sheet can be manufactured according to a known general method for manufacturing pressure-sensitive adhesive sheets. For example, the present pressure-sensitive adhesive composition is applied to a substrate, dried, and a release sheet is attached to the opposite surface of the pressure-sensitive adhesive layer, followed by curing as necessary to obtain the present pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing a pressure-sensitive adhesive on a substrate.

The adhesive sheet can also be obtained by coating the adhesive composition on a release sheet, drying it, attaching a substrate to the adhesive layer on the opposite side, and curing if necessary.

In addition, a substrate-less double-sided adhesive sheet can be produced by forming an adhesive layer on a release sheet and laminating a release sheet to the opposite side of the adhesive layer.

When using the resulting adhesive sheet or substrate-less double-sided adhesive sheet, the release sheet is peeled off from the adhesive layer and the adhesive layer is bonded to the adherend.

Examples of the substrate include polyester resins such as polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate, and polyethylene terephthalate/isophthalate copolymer; polyolefin resins such as polyethylene, polypropylene, and polymethylpentene; polyethylene fluoride resins such as polyvinyl fluoride, polyvinylidene fluoride, and polyethylene fluoride; 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; and sheets made of at least one synthetic resin selected from the group consisting of cycloolefin polymers; metal foils of aluminum, copper, and iron; paper such as fine paper and glassine paper; and woven and nonwoven fabrics made of glass fiber, natural fibers, synthetic fibers, and the like. These substrates can be used as single-layer bodies or as multi-layer bodies in which two or more types are laminated.

Among these, substrates made of polyethylene terephthalate and polyimide are particularly preferred, with polyethylene terephthalate being particularly preferred due to its excellent adhesion to pressure-sensitive adhesives.

The substrate may be a foam substrate, for example a foam sheet made of a synthetic resin foam such as polyurethane foam, polyethylene foam, or polyacrylate foam. Among these, polyethylene foam and polyacrylate foam are preferred because they have an excellent balance between conformability to the adherend and adhesive strength.

The thickness of the substrate is preferably, for example, 1 to 1000 μm, particularly preferably 2 to 500 μm, and even more preferably 3 to 300 μm.

As the release sheet, for example, a sheet made of the various synthetic resins exemplified above as the base material, paper, cloth, nonwoven fabric, etc., which has been subjected to a release treatment can be used. As the release sheet, it is preferable to use a silicone-based release sheet.

The adhesive composition may be applied using, for example, a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, spray coater, comma coater, etc.

The conditions for the above curing treatment are usually a temperature of room temperature (23°C) to 70°C, and a time of 1 to 30 days. Specifically, the treatment may be performed under conditions such as 23°C for 1 to 20 days, preferably 23°C for 3 to 14 days, or 40°C for 1 to 10 days.

As for drying conditions, the drying temperature is preferably 60 to 140°C, and particularly preferably 80 to 120°C, and the drying time is preferably 0.5 to 30 minutes, and particularly preferably 1 to 5 minutes.

The thickness of the adhesive layer of the above-mentioned adhesive sheet and substrate-less double-sided adhesive sheet is preferably 2 to 500 μm, particularly preferably 5 to 200 μm, and even more preferably 10 to 100 μm. If the thickness of such an adhesive layer is too thin, the adhesive strength tends to decrease, while if it is too thick, it becomes difficult to apply uniformly and problems such as air bubbles entering the coating tend to occur. When considering impact absorption properties, it is preferable to make the thickness 50 μm or more.

The thickness of the adhesive layer is determined by subtracting the measured thickness of the components other than the adhesive layer from the measured thickness of the entire adhesive sheet using a Mitutoyo ID-C112B.

The gel fraction of the adhesive layer of the adhesive sheet is preferably 10% by weight or more from the viewpoint of durability and adhesive strength, and is particularly preferably 20 to 80% by weight, and further preferably 30 to 70% by weight. If the gel fraction is too low, the cohesive strength tends to decrease, resulting in a decrease in holding power. However, if the gel fraction is too high, the adhesive strength tends to decrease, resulting in an increase in cohesive strength.

The gel fraction is an indication of the degree of crosslinking, and is calculated, for example, by the following method. That is, an adhesive sheet (without a release sheet) consisting of an adhesive layer formed on a polymer sheet (e.g., a PET film, etc.) that serves as a substrate is wrapped in a 200-mesh SUS wire mesh and immersed in toluene at 23°C for 24 hours, and the gel fraction is the weight percentage of the insoluble adhesive component remaining in the wire mesh after immersion relative to the weight of the adhesive component before immersion. However, the weight of the substrate is subtracted.

Furthermore, such an adhesive sheet may be protected by providing a release sheet on the outside of the adhesive layer, if necessary. In an adhesive sheet in which the adhesive layer is formed on one side of a substrate, it is also possible to apply a release treatment to the side of the substrate opposite the adhesive layer, thereby using the release-treated surface to protect the adhesive layer.

This adhesive can be used to bond various components, particularly as a single-sided or double-sided adhesive sheet for bonding optical components, for fixing components of portable electronic devices, and for fixing electronic components.

The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not exceed the gist of the invention. In the examples, "parts" and "%" are by weight.

In the following examples, the biomass degree of the polyester resin, the recycled carbon usage rate, the weight average molecular weight, the glass transition temperature, and the gel fraction of the adhesive layer, the biomass degree of the polyester resin composition, and the recycled carbon usage rate were measured according to the methods described above.

Polyester resin was produced by the following method (see Table 1).

[Examples 1 to 5, Comparative Examples 1 to 3]
[Production of Polyester Resins (A) [A-1 to A-5] and (A') [A'-1 to A'-3]]
In a reactor equipped with a thermometer, a stirrer, a distillation column, a nitrogen inlet tube, and a vacuum device, polycarboxylic acids and polyols were mixed as shown in Table 1 below, tetrabutyl titanate was charged as a catalyst in an amount of 0.2 mmol/mol relative to the polycarboxylic acids, and the internal temperature was gradually increased to 240 to 250° C., and an esterification reaction was carried out over 4 hours. Thereafter, the internal temperature was increased to 260° C., tetrabutyl titanate was charged as a catalyst in an amount of 0.2 mmol/mol relative to the polycarboxylic acids, the pressure was reduced to 1.33 to 2.66 hPa, and a polymerization reaction was carried out over 2 to 3 hours to produce polyester resin (A) or (A').
The composition ratio and various physical properties of the resulting polyester resin (A) or (A') are shown in Table 2 below.
In the above production, the raw materials derived from plants were hydrodistilled dimer acid, 2,5-furandicarboxylic acid, and sebacic acid.

Next, prior to preparing the polyester resin composition (adhesive composition), the following components were prepared:

[Polyisocyanate Compound (B)]
Polyisocyanate compound (B-1): "Coronate L55E, solid content concentration 55%" (manufactured by Tosoh Corporation)

[Hydrolysis Inhibitor (C)]
Carbodiimide compound (C-1): "Carbodilite V-09GB, solid content concentration 70%" (manufactured by Nisshinbo Chemical Inc.)

[Examples 1-1 to 5-1, Comparative Examples 1-1 to 3-1]
Using the above polyester resin, crosslinking agent, and hydrolysis inhibitor, polyester resin compositions (adhesive compositions) were prepared as described below in the formulation shown in Table 3 below, and adhesive sheets were produced.

The polyester resin (A) or (A') obtained above was diluted with ethyl acetate to a solid content concentration of 50%, and a polyisocyanate compound (B-1) and a carbodiimide compound (C-1) were blended in the blending ratios (solid content ratios) shown in Table 3. 0.02 parts (solid content) of a zirconium compound ("Orgatics ZC-150" manufactured by Matsumoto Fine Chemical Co., Ltd.) diluted with acetylacetone to a solid content concentration of 1% was further added as a urethanization catalyst, followed by stirring and mixing to obtain a polyester resin composition (adhesive composition).
The obtained adhesive composition was applied to a polyethylene terephthalate (PET) film (thickness: 38 μm) so that the thickness after drying would be about 25 μm, and then dried for 3 minutes at 100° C. to form an adhesive layer. Thereafter, a release-treated PET film (release film) was attached to the adhesive layer to protect its surface, and the layer was aged in an atmosphere at a temperature of 40° C. for 10 days to obtain an adhesive sheet.

The adhesive sheets obtained in the examples and comparative examples were evaluated as follows. The evaluation results are shown in Table 3 below.

<Initial adhesive strength (peel strength) (to SUS-BA)>
A SUS-BA plate was prepared as an adherend. The pressure-sensitive adhesive sheet obtained above was cut to 25 mm x 200 mm in an environment of 23 ° C. and 50% RH, and then the release film was peeled off, the pressure-sensitive adhesive layer side was brought into contact with a SUS-BA plate, and a 2 kg roller was reciprocated to pressurize and attach it. Then, after leaving it for 30 minutes in the same atmosphere, the 180-degree peel strength (N/25 mm) was measured at a peel speed of 300 mm/min using an autograph (Shimadzu Corporation, Autograph AGS-H 500N), and the peeling state was visually observed.

<Adhesive strength (peel strength) after 72 hours (to SUS)>
A SUS-BA plate was prepared as an adherend. The pressure-sensitive adhesive sheet obtained above was cut to 25 mm x 200 mm in an environment of 23 ° C. and 50% RH, and then the release film was peeled off, the pressure-sensitive adhesive layer side was brought into contact with a SUS-BA plate, and a 2 kg roller was reciprocated to pressurize and attach the sheet. After leaving the sheet to stand for 72 hours in the same atmosphere, the 180° peel strength (N/25 mm) was measured at a peel speed of 300 mm/min using an autograph (Shimadzu Corporation, Autograph AGS-H 500N), and the peeling state was visually observed.

<Initial adhesive strength (peel strength) (against PP)>
A PP plate was prepared as an adherend. The pressure-sensitive adhesive sheet obtained above was cut to 25 mm x 200 mm in an environment of 23 ° C. and 50% RH, and then the release film was peeled off, the pressure-sensitive adhesive layer side was brought into contact with a PP plate, and a 2 kg roller was reciprocated to pressurize and attach it. Then, after leaving it for 30 minutes in the same atmosphere, the 180 degree peel strength (N/25 mm) was measured at a peel speed of 300 mm/min using an autograph (Shimadzu Corporation, Autograph AGS-H 500N), and the peeling state was visually observed.

<Holding force (cohesive force)>
The pressure-sensitive adhesive sheet obtained above was attached to a substrate of SUS304 in accordance with JIS Z-0237 with an area of 25 mm × 25 mm, and then allowed to stand at 80°C for 20 minutes. A load of 1 kg was applied to the sheet, and the displacement after 24 hours was measured.

From the results in Table 3 above, the pressure-sensitive adhesive sheets of Examples 1-1 to 5-1 prepared using the polyester resin compositions (pressure-sensitive adhesive compositions) of Examples 1 to 5 had excellent adhesion to metal adherends both initially and after aging, and further had the desired adhesion even to difficult-to-adhere adherends such as polyolefin resins, and had an excellent balance of adhesive strength and holding power.
In addition, the adhesive sheets of Comparative Examples 1-1 and 2-1, which were prepared using the polyester resin compositions (adhesive compositions) of Comparative Examples 1 and 2, which did not contain structural units derived from polyvalent carboxylic acid (a2) having a furan skeleton and only had structural units derived from compound (a1), had particularly low adhesive strength over time. Furthermore, the adhesive sheet of Comparative Example 3-1, which was prepared using the polyester resin composition (adhesive composition) of Comparative Example 3, which contained structural units derived from polyvalent carboxylic acid (a2) having a furan skeleton but had too few structural units derived from compound (a1) relative to the content of structural units derived from polyvalent carboxylic acid (a2) having a furan skeleton, had poor adhesive properties both initially and after aging to a metal adherend, and did not fully satisfy the effects of the present invention.

The polyester resin composition of the present invention, the adhesive composition containing the same, and the adhesive have excellent adhesive properties for various adherends such as metals, even when a polyester resin with a high biomass content is used, and are used as single-sided or double-sided adhesive sheets for laminating optical components, single-sided or double-sided adhesive sheets for fixing components of portable electronic devices, single-sided or double-sided adhesive sheets for fixing electronic components, etc.

Claims (12)

A pressure- sensitive adhesive composition comprising a polyester-based resin composition containing a polyester-based resin (A),
the polyester resin (A) contains a structural unit derived from at least one compound (a1) selected from an aliphatic and/or alicyclic polycarboxylic acid having 10 or more carbon atoms and an aliphatic and/or alicyclic polyol having 10 or more carbon atoms, and further contains a structural unit derived from a polycarboxylic acid (a2) having a furan skeleton;
The compound (a1) is a dimer acid and/or a dimer diol,
A pressure-sensitive adhesive composition, characterized in that the ratio (X1/X2) of the molar concentration (X1) of the structural unit derived from the compound (a1) to the molar concentration (X2) of the structural unit derived from the polyvalent carboxylic acid (a2) in the polyester-based resin (A) is 0.6 or more. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the compound (a1) is a plant-derived raw material. 3. The pressure-sensitive adhesive composition according to claim 1 , wherein the polyvalent carboxylic acid (a2) is a 2,5-furan dicarboxylic acid. 4. The pressure-sensitive adhesive composition according to claim 1 , wherein the polyester resin (A) has a number average molecular weight of 3,000 or more. 5. The pressure-sensitive adhesive composition according to claim 1 , wherein the polyester resin (A) has a weight average molecular weight of 10,000 or more. 6. The pressure-sensitive adhesive composition according to claim 1 , wherein the polyester resin (A) has a glass transition temperature of −10° C. or lower. The pressure-sensitive adhesive composition according to any one of claims 1 to 6 , wherein the polyester resin (A) has a biomass ratio of 50% or more. The pressure-sensitive adhesive composition according to any one of claims 1 to 7 , further comprising a polyisocyanate compound (B). The pressure-sensitive adhesive composition according to any one of claims 1 to 8 , further comprising a hydrolysis inhibitor (C). A pressure-sensitive adhesive, characterized in that the pressure-sensitive adhesive composition according to any one of claims 1 to 9 is crosslinked. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive according to claim 10 . A double-sided pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive according to claim 10 .