Crystalline polyester resin

Abstract

Provided is a crystalline polyester-based resin providing good retort resistance of a coating film and having excellent compatibility with a (meth)acrylic monomer mixture. The present invention is a crystalline polyester resin containing a polycarboxylic acid component and a polyhydric alcohol component, containing 5-40 mol% of a 2,6-naphthalenedicarboxylic acid component in 100 mol% of the polycarboxylic acid component, containing 40-75 mol% of a terephthalic acid component in 100 mol% of the polycarboxylic acid component, containing 60 mol% or more of a 1,4-butanediol component in 100 mol% of the polyhydric alcohol component, and having a melting point of 130°C-160°C.

Description

crystalline polyester resin

[0001] The present invention relates to a crystalline polyester resin, and more particularly to a crystalline polyester resin suitable for coating metal plates, metal cans, or electric wires.

[0002] Metal cans, such as beverage cans and food cans, are coated with organic resins to prevent corrosion of the metal by food (corrosion resistance) and to preserve the flavor and taste of the contents (flavoring). This coating film undergoes demanding processes, such as necking and threading, during the molding process for the neck of a bottle can. Therefore, the coating film must be durable enough to withstand such post-processing (processability). Furthermore, it must also have adhesion to the metal substrate and hardenability. Depending on the application, the can may be subjected to high-temperature, high-humidity conditions, such as retort sterilization. Even in such cases, the coating film must maintain adhesion to the metal substrate and not whiten (retort resistance).

[0003] Conventionally, epoxy-based paints such as epoxy-phenolic paints, epoxy-amino paints, and epoxy-acrylic paints, polyester-based paints such as polyester-phenolic paints, polyester-amino paints, and polyester-isocyanate paints, and vinyl chloride-based paints have been widely used as paints that offer the aforementioned corrosion resistance, flavor, and durability for can molding. However, recent research has reported that bisphenol A, a raw material for epoxy resins, may have estrogenic effects and may affect the brains of fetuses and infants. Furthermore, vinyl chloride-based paints have issues with stabilizers and the generation of dioxins during incineration. Formaldehyde, which is used as a raw material for phenolic resins and amino resins, and remains in paints, is known to be harmful to the human body, including being carcinogenic, and to adversely affect the flavor of the contents. Similarly, isocyanate resins are known to be harmful to the human body, including being carcinogenic.

[0004] Due to concerns about these various adverse effects on the human body, there is a demand in the market for paints that do not use these raw materials, but the reality is that they do not provide satisfactory performance for can applications.

[0005] From this viewpoint, for example, Patent Document 1 proposes a resin composition for can coating that does not require a curing agent by using a crystalline polyester. Also, Patent Document 2 discloses a water dispersion obtained by acrylic acid-modifying a crystalline polyester resin with a copolymer of acrylic acid, butyl acrylate, and styrene.

[0006] JP 2001-234115 A JP 2018-123249 A

[0007] However, the coating film made from the resin composition for can coatings described in Patent Document 1 contains a large amount of amorphous polyester resin along with crystalline polyester resin. This is to compensate for the low solvent solubility of the crystalline polyester resin, but it has been found that this also reduces retort resistance. It has been found that the crystalline polyester resins described in Patent Document 2 all have low melting points, resulting in poor retort resistance. Furthermore, it has been found that increasing the melting point of the crystalline polyester resin to improve retort resistance tends to worsen compatibility with a monomer mixture containing a (meth)acrylic monomer for (meth)acrylic acid modification (e.g., a mixture of (meth)acrylic acid, butyl acrylate, and styrene; hereinafter, sometimes referred to as an "acrylic monomer mixture"), making it difficult to achieve both retort resistance and (meth)acrylic modification.

[0008] The present invention aims to provide a crystalline polyester resin capable of forming a coating film with excellent retort resistance and excellent compatibility with an acrylic monomer mixture, as well as an aqueous dispersion and coating composition containing the same, a coating film, a metal plate, a metal can, and an electric wire. Another object of the present invention is to provide a coating film that does not contain a curing agent and is therefore free of harmful substances such as bisphenol A and formaldehyde.

[0009] Therefore, an object of the present invention is to provide a crystalline polyester resin which gives a coating film with good retort resistance and has excellent compatibility with an acrylic monomer mixture.

[0010] The present invention achieves the above-mentioned object as follows: [1] A crystalline polyester resin containing a polycarboxylic acid component and a polyhydric alcohol component, wherein the 2,6-naphthalenedicarboxylic acid component accounts for 5 to 40 mol% of the 100 mol% of the polycarboxylic acid component, the terephthalic acid component accounts for 40 to 75 mol% of the 100 mol% of the polycarboxylic acid component, and the 1,4-butanediol component accounts for 60 mol% or more of the 100 mol% of the polyhydric alcohol component, and the crystalline polyester resin has a melting point of 130 to 160°C. [2] The crystalline polyester resin according to [1], wherein the polycarboxylic acid component further contains an isophthalic acid component, and the content of the isophthalic acid component in 100 mol% of the polycarboxylic acid component is 30 mol% or less. [3] The crystalline polyester resin according to [1] or [2], wherein the polyhydric alcohol component does not contain an ethylene glycol component or contains less than 35 mol% of the ethylene glycol component in 100 mol% of the polyhydric alcohol component. [4] The crystalline polyester resin according to any one of [1] to [3], wherein the polyhydric alcohol component further comprises a 1,4-cyclohexanedimethanol component and / or a tricyclodecane dimethanol component. [5] The crystalline polyester resin according to any one of [1] to [4], wherein the crystalline polyester resin further comprises a trifunctional or higher polycarboxylic acid component and / or a trifunctional or higher polyhydric alcohol component, and the amount of the trifunctional or higher polycarboxylic acid component and the trifunctional or higher polyhydric alcohol component is 0.1 to 5 mol % when the total amount of all components constituting the molecular chain of the crystalline polyester resin is 100 mol %. [6] The crystalline polyester resin according to any one of [1] to [5], wherein the acid value is 100 eq / ton or more. [7] The crystalline polyester resin according to any one of [1] to [6], wherein the glass transition temperature is 30 to 55°C. [8] A coating composition comprising the crystalline polyester resin according to any one of [1] to [7]. [9] A crystalline polyester resin aqueous dispersion containing the crystalline polyester resin according to any one of [1] to [7].

[10] A coating film obtained from the coating composition according to [8].

[11] A metal plate having the coating film according to

[10] .

[12] A metal can having the coating film according to

[10] .

[13] An electric wire whose surface is coated with the coating film according to

[10] .

[0011] According to the present invention, a crystalline polyester resin can be provided that exhibits excellent retort resistance of the coating film and compatibility with an acrylic monomer mixture. Furthermore, in addition to the above-described effects, the crystalline polyester resin of the present invention can preferably exhibit at least one of good processability and good solvent solubility. Therefore, a coating composition containing the crystalline polyester of the present invention is preferably used for coating metal plates, metal cans, etc.

[0012] <Crystalline polyester resin> The crystalline polyester resin of the present invention contains a polycarboxylic acid component and a polyhydric alcohol component, and has a chemical structure that can be obtained by polycondensation of a polycarboxylic acid and a polyhydric alcohol. In this specification, the polycarboxylic acid component of the crystalline polyester does not include polycarboxylic acids derived from compounds having a polycarboxylic anhydride group in the molecule that are introduced into the end of the polyester resin after the polycondensation reaction is completed in order to adjust the acid value of the polyester resin. The ratio of the polycarboxylic acid component and the polyhydric alcohol component contained in the polyester resin can be determined, for example, by the amounts of these components charged, １ H-NMR analysis, １３ It is identified by various analyses such as C-NMR analysis.

[0013] In the present invention, the polycarboxylic acid component contains 2,6-naphthalenedicarboxylic acid and terephthalic acid. 2,6-Naphthalenedicarboxylic acid and terephthalic acid are polycarboxylic acid components that can increase the crystallinity of the polyester resin and improve the retort resistance of the coating film obtained from the crystalline polyester resin. Furthermore, by including 2,6-naphthalenedicarboxylic acid as the polycarboxylic acid component, the crystallinity can be appropriately disrupted due to the steric hindrance of the polycyclic skeleton, thereby improving compatibility with the acrylic monomer mixture.

[0014] The compatibility with the acrylic monomer mixture can be evaluated by the solubility of the crystalline polyester resin in a monomer mixture of (meth)acrylic acid and an aromatic monomer. As the aromatic monomer, a styrene-based monomer such as styrene or α-methylstyrene can be used. The monomer mixture contains, in addition to (meth)acrylic acid and the aromatic monomer, (meth)acrylic acid C １－５The acrylic monomer mixture preferably contains 300 to 350 parts by mass of an aromatic monomer per 100 parts by mass of (meth)acrylic acid. １－５ When an alkyl is contained, the amount thereof is preferably 90 to 130 parts by mass relative to 100 parts by mass of (meth)acrylic acid. １－５ The total alkyl content is preferably 90 to 100 mass%, more preferably 95 to 100 mass%, and even more preferably 100 mass%. The amount of the crystalline polyester resin mixed per 100 mass parts of the monomer mixture is preferably 60 to 70 mass parts.

[0015] The content of the 2,6-naphthalenedicarboxylic acid component is 5 to 40 mol% out of 100 mol% of the polycarboxylic acid component. By having the content of the 2,6-naphthalenedicarboxylic acid component be 5 mol% or more, the compatibility between the crystalline polyester resin and the acrylic monomer mixture can be improved. On the other hand, by having the content of the 2,6-naphthalenedicarboxylic acid component be 40 mol% or less, it becomes easy to adjust the melting point (Tm) of the crystalline polyester resin within an appropriate range, resulting in good retort resistance. Furthermore, by having the content of the 2,6-naphthalenedicarboxylic acid component be 40 mol% or less, it becomes possible to further adjust the glass transition temperature (Tg) within an appropriate range, thereby improving processability. The content of the 2,6-naphthalenedicarboxylic acid component is preferably 10 to 35 mol%, and more preferably 15 to 30 mol%.

[0016] The content of the terephthalic acid component is 40 to 75 mol% out of 100 mol% of the polycarboxylic acid component. By having a terephthalic acid component content of 40 mol% or more, the melting point Tm of the crystalline polyester resin can be increased, and preferably processability can be improved. Furthermore, by having a terephthalic acid component content of 75 mol% or less, the solvent solubility of the crystalline polyester resin is improved, which is preferable, and aggregation of the crystalline polyester resin in a solvent dispersion or aqueous dispersion can be prevented. The content of the terephthalic acid component is preferably 45 to 70 mol%, more preferably 50 to 65 mol%.

[0017] The polycarboxylic acid component preferably further contains an isophthalic acid component, which further improves the compatibility between the crystalline polyester resin and the acrylic monomer mixture and also contributes to improving the solvent solubility of the crystalline polyester resin.

[0018] The isophthalic acid component is preferably 30 mol% or less of the polycarboxylic acid component (100 mol%), and by setting it in this range, the retort resistance of the coating film obtained from the crystalline polyester resin can be improved. The content of the isophthalic acid component is more preferably 5 to 30 mol%, and even more preferably 10 to 25 mol%.

[0019] From the viewpoint of compatibility with the acrylic monomer mixture, it is preferable that the polycarboxylic acid component does not contain an orthophthalic acid component.

[0020] The polycarboxylic acid component may also contain other polycarboxylic acid components (a1) other than 2,6-naphthalenedicarboxylic acid and terephthalic acid, and the isophthalic acid component contained as needed. Examples of other polycarboxylic acid components (a1) include 1,2-naphthalenedicarboxylic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 1,7-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalate, 2,5-furandicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and hexahydrophthalic acid; aliphatic polycarboxylic acids such as fumaric acid, adipic acid, sebacic acid, malonic acid, and succinic acid; alicyclic polycarboxylic acids other than those mentioned above; and tri- or higher functional aromatic polycarboxylic acids. In 100 mol% of the polycarboxylic acid component, the total amount of the other polycarboxylic acid component (a1) is preferably 20 mol% or less, more preferably 10 mol% or less, even more preferably 5 mol% or less, and most preferably 0 mol%.

[0021] The total content of the 2,6-naphthalenedicarboxylic acid component and the terephthalic acid component in 100 mol % of the polycarboxylic acid component is preferably 65 to 100 mol %, more preferably 75 to 99 mol %, and even more preferably 80 to 99 mol %. When the polycarboxylic acid component further contains an isophthalic acid component, the total content of the 2,6-naphthalenedicarboxylic acid component, the terephthalic acid component, and the isophthalic acid component in 100 mol % of the polycarboxylic acid component is preferably 75 to 100 mol %, more preferably 85 to 99 mol %, and even more preferably 95 to 99 mol %.

[0022] In the present invention, the polyhydric alcohol component includes a 1,4-butanediol component. The linear structure and alkyl chain length of 1,4-butanediol impart crystallinity to the polyester resin that satisfies retort resistance, enabling the polyester resin to exhibit a high melting point and, preferably, improving processability and solvent solubility.

[0023] In 100 mol % of the polyhydric alcohol component, the content of the 1,4-butanediol component is 60 mol % or more, preferably 60 to 95 mol %, more preferably 75 to 95 mol %, and even more preferably 80 to 95 mol %.

[0024] The polyhydric alcohol component preferably further contains a 1,4-cyclohexanedimethanol component and / or a tricyclodecane dimethanol component. 1,4-Cyclohexanedimethanol and / or tricyclodecane dimethanol suppress the glass transition temperature of the crystalline polyester resin from increasing too much, thereby preventing deterioration of processability. The content of the 1,4-cyclohexanedimethanol component and / or tricyclodecane dimethanol component in 100 mol% of the polyhydric alcohol component is preferably 15 mol% or less, more preferably 3 to 15 mol%, and even more preferably 5 to 10 mol%.

[0025] The polyhydric alcohol component may or may not contain an ethylene glycol component, and preferably contains less than 35 mol% of the ethylene glycol component or no ethylene glycol component (i.e., 0 mol%), based on 100 mol% of the polyhydric alcohol component. By containing a predetermined amount or less of the ethylene glycol component or no ethylene glycol component, it is possible to prevent the glass transition temperature from increasing too much and to prevent deterioration of processability. The amount of the ethylene glycol component is preferably 0 to 30 mol%, more preferably 0 to 20 mol%, and may be 0 mol% (i.e., no ethylene glycol component).

[0026] The polyhydric alcohol component may contain a polyhydric alcohol component (b1) other than a 1,4-butanediol component, a 1,4-cyclohexanedimethanol component, a tricyclodecanedimethanol component, and an ethylene glycol component, for example, Polyhydric alcohols having a side chain, such as 1,2-propylene glycol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-methyl-1,3-hexanediol, 2-methyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2-n-propyl-1,3-propanediol, 2,2-di-n-propyl-1,3-propanediol, 2-n-butyl-2-ethyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, mannitol, sorbitol, dimer diol, polypropylene glycol, and pentaerythritol; Examples include polyhydric alcohols with a straight chain structure such as 1,3-propylene glycol, 1,5-pentanediol, 1,6-hexanediol, and 1,8-octanediol; and polyhydric alcohols with an aromatic or alicyclic skeleton such as hydroquinone, catechol, and resorcinol.

[0027] In 100 mol % of the polyhydric alcohol component, the total amount of the other polyhydric alcohol component (b1) is preferably 10 mol % or less, more preferably 5 mol % or less, and even more preferably 0 mol %.

[0028] With respect to the 1,4-butanediol component, and the 1,4-cyclohexanedimethanol component, tricyclodecanedimethanol component, and ethylene glycol component which may be further contained as necessary, the total content thereof is preferably 80 to 100 mol %, more preferably 85 to 100 mol %, still more preferably 90 to 100 mol %, and most preferably 100 mol %, based on 100 mol % of the polyhydric alcohol component.

[0029] The polycarboxylic acid component and polyhydric alcohol component constituting the crystalline polyester resin of the present invention can be derived from biomass resources. Biomass resources include the stored materials obtained by converting solar energy into starch, cellulose, etc. through photosynthesis in plants, the bodies of animals that grow by eating plants, and products made by processing plants or animals. Among these, plant resources are more preferred, including wood, rice straw, rice husks, rice bran, used rice, corn, sugarcane, cassava, sago palm, soybean pulp, corn cob, tapioca dregs, bagasse, vegetable oil cake, potato, buckwheat, soybean, oils and fats, waste paper, papermaking residues, seafood residues, livestock excrement, sewage sludge, and food waste. Corn, sugarcane, cassava, and sago palm are even more preferred.

[0030] Specific examples of polycarboxylic acid raw materials derived from biomass resources include adipic acid, sebacic acid, fumaric acid, itaconic acid, terephthalic acid, and 2,5-furandicarboxylic acid. These may be used alone or in combination.

[0031] Specific examples of polyhydric alcohol raw materials derived from biomass resources include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, neopentyl glycol, 1,4-butanediol, and 1,4-cyclohexanedimethanol, which may be used alone or in combination of two or more.

[0032] The crystalline polyester resin in the present invention preferably has a branched structure. In this specification, the term "branched structure" refers to a branched structure in a polymer chain, specifically a structure in which three or more branches (molecular chains) extend from one structural unit constituting the molecular chain of the polyester resin. In other words, a polyester resin having a branched structure means, for example, that the polymer molecular chain of the polyester resin has a triester structure, a tetraester structure, or a pentaester structure.

[0033] To introduce a branched structure into a polyester, for example, a method of copolymerizing a trifunctional or higher functional component as part of a polycarboxylic acid component and / or a polyhydric alcohol component in a polyester polycondensation reaction is exemplified, and it is preferable to use a trifunctional or higher functional polycarboxylic acid component. As the trifunctional or higher functional polycarboxylic acid component, the following polycarboxylic acids or their esters and polycarboxylic acid anhydrides can be used. Specific examples include trimellitic acid, trimellitic anhydride, pyromellitic acid, and benzophenone tetracarboxylic acid, and one or more of these can be used. As the trifunctional or higher functional polyhydric alcohol component, glycerin, trimethylolethane, trimethylolpropane, mannitol, sorbitol, pentaerythritol, and the like can be used, and one or more of these can be used. When the crystalline polyester resin has a branched structure, the processability of the resulting coating film is improved.

[0034] The tri- or higher functional polycarboxylic acid component and / or tri- or higher functional polyhydric alcohol is preferably 0.1 to 5 mol %, more preferably 0.3 to 3 mol %, even more preferably 0.5 to 2 mol %, and particularly preferably 0.5 to 1.5 mol %, when the total of all components constituting the molecular chain of the crystalline polyester resin is taken as 100 mol %. If the amount exceeds the above range, the crystallinity of the crystalline polyester resin may decrease, the retort resistance may deteriorate, or gelation may occur during polyester polymerization.

[0035] The melting point (Tm) of the crystalline polyester resin in the present invention is the temperature at the apex of the endothermic peak with the largest heat of fusion during the temperature rise process, measured using a differential scanning calorimeter (DSC) after aging the polyester resin at 100°C for 30 hours and then raising the temperature from -50 to 200°C at 20°C / min. The melting point (Tm) of the crystalline polyester resin in the present invention is in the range of 130 to 160°C, preferably 135 to 155°C, and more preferably 140 to 150°C. By setting the melting point to 130°C or higher, good crystallinity can be achieved and excellent retort resistance can be exhibited. Furthermore, by setting the melting point to 160°C or lower, good compatibility with the monomer mixture can be achieved, and preferably excellent processability and solvent solubility can be exhibited.

[0036] In the present invention, the term "crystalline" refers to the melting point (Tm) exhibited by the polyester resin when measured under the above-mentioned conditions. Furthermore, "high crystallinity" means that the polyester resin has a high melting point.

[0037] The glass transition temperature (Tg) of the crystalline polyester resin is, for example, 30 to 55°C, preferably 35 to 50°C, and more preferably 40 to 45°C. When the Tg is 30°C or higher, retort resistance can be further improved. Furthermore, when the Tg is 55°C or lower, the processability of the coating film can be improved.

[0038] The reduced viscosity of the crystalline polyester resin is preferably 0.2 to 0.8 dl / g, more preferably 0.4 to 0.8 dl / g, and even more preferably 0.6 to 0.8 dl / g. When the reduced viscosity is 0.2 dl / g or more, the toughness and processability of the coating film are improved. On the other hand, when the reduced viscosity is 0.8 dl / g or less, the solvent solubility is improved.

[0039] The crystalline polyester resin can be given an acid value by any method. The method of giving an acid value includes a method of adding a compound having a polycarboxylic anhydride group in the molecule at the later stage of polycondensation, a method of increasing the acid value at the stage of prepolymer (oligomer) and then polycondensing it to obtain a polyester resin having an acid value, etc. However, the former method of adding reaction is preferred because of ease of operation and ease of obtaining the target acid value.

[0040] The acid value of the crystalline polyester resin is preferably 100 eq / ton or more. By setting the acid value in this range, it becomes easier to obtain an aqueous dispersion of the crystalline polyester resin. The acid value is more preferably 100 to 220 eq / ton, even more preferably 105 to 200 eq / ton, and even more preferably 110 to 180 eq / ton. The crystalline polyester resin of the present invention has good compatibility with the acrylic monomer mixture, and can be favorably modified with acrylic acid. Since the effect of the aqueous dispersion due to the acrylic acid modification can be obtained, an acid value within the above range makes it possible to sufficiently prepare an aqueous dispersion.

[0041] Among compounds having a polyvalent carboxylic acid anhydride group in the molecule for imparting an acid value to the crystalline polyester resin, examples of carboxylic acid monoanhydrides include phthalic anhydride, succinic anhydride, maleic anhydride, trimellitic anhydride, itaconic anhydride, citraconic anhydride, etc., and one or more of these can be selected and used. Among these, trimellitic anhydride is preferred from the viewpoints of versatility and economy.

[0042] Among the compounds having a polyvalent carboxylic acid anhydride group in the molecule for imparting an acid value to the crystalline polyester resin of the present invention, examples of carboxylic acid polyanhydrides include pyromellitic anhydride, 1,2,3,4-butanetetracarboxylic acid dianhydride, 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride, 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, ethylene glycol bistrimellitate dianhydride, and 2,2',3,3'-biphenyltetracarboxylic acid dianhydride, and one or more of these can be selected and used. Among these, ethylene glycol bistrimellitate dianhydride is preferred from the standpoints of versatility and economy.

[0043] The carboxylic acid monoanhydrides and carboxylic acid polyanhydrides may each be used alone or in combination of two or more.

[0044] <Method for Producing Crystalline Polyester Resin> Next, the method for producing the crystalline polyester resin of the present invention will be described. In the esterification / exchange reaction, all monomer components and / or oligomers thereof are heated, melted, and reacted. The esterification / exchange reaction temperature is preferably 180 to 250°C, more preferably 200 to 250°C. The reaction time is preferably 1.5 to 10 hours, more preferably 3 to 6 hours. The reaction time is the time from when the desired reaction temperature is reached until the subsequent polycondensation reaction begins. In the polycondensation reaction, the polyhydric alcohol component is distilled off from the esterified product obtained in the esterification reaction under reduced pressure at a temperature of 220 to 280°C, and the polycondensation reaction is continued until the desired molecular weight is reached. The reaction temperature for polycondensation is preferably 220 to 280°C, more preferably 240 to 275°C. The degree of vacuum is preferably 150 Pa or less. An insufficient degree of vacuum tends to prolong the polycondensation time, which is undesirable. The time required for reducing the pressure from atmospheric pressure to 150 Pa or less is preferably 30 to 180 minutes.

[0045] In the esterification / exchange reaction and polycondensation reaction, polymerization is carried out, if necessary, using an organic titanate compound such as tetrabutyl titanate, or an organic tin compound such as germanium dioxide, antimony oxide, or tin octoate. From the viewpoint of reactivity, organic titanate compounds are preferred, and from the viewpoint of resin coloration, germanium dioxide is preferred.

[0046] The crystalline polyester resin of the present invention can provide a coating film with excellent retort resistance and further excellent processability. Furthermore, since the crystalline polyester resin has excellent compatibility with acrylic monomer mixtures, it can be suitably used after being acrylic-modified. The acrylic-modified crystalline polyester resin has a carbon-carbon bond structure, resulting in excellent hydrolysis resistance. Furthermore, the crystalline polyester resin of the present invention may be epoxy-modified, isocyanate-modified, or acid anhydride-modified.

[0047] <Water Dispersion / Coating Composition> The water dispersion and coating composition of the present invention contain the crystalline polyester resin of the present invention. In the water dispersion and coating composition, the crystalline polyester resin is contained as a main component. In the water dispersion, the main component is defined as the component with the highest content (mass percentage) among non-volatile components excluding water and volatile substances such as organic solvents contained as needed. In the coating composition, the main component is defined as the component with the highest content (mass percentage) among the solid components (non-volatile components excluding volatile substances such as water and organic solvents) that form the coating film in the coating composition.

[0048] The coating composition of the present invention may contain any other additives. Examples of such additives include known inorganic pigments such as titanium oxide and silica, phosphoric acid and its esters, surface smoothing agents, antifoaming agents, dispersants, lubricants, crystal nucleating agents, and plasticizers. Lubricants are particularly important for imparting the lubricity of the coating film required when molding DI cans, DR (or DRD) cans, etc. Suitable examples of lubricants include fatty acid ester waxes, which are esters of polyol compounds and fatty acids, silicone waxes, fluorine-based waxes, polyolefin waxes such as polyethylene, lanolin waxes, montan waxes, and microcrystalline waxes. Lubricants can be used alone or in combination.

[0049] The dispersion medium of the coating composition of the present invention may be an organic solvent or water. In particular, water is preferred as the dispersion medium in view of the effects on environmental pollution and the working environment. When the dispersion medium of the coating composition contains water (i.e., an aqueous coating composition), the coating composition of the present invention is preferably an aqueous dispersion in which an acrylic-modified polyester resin is dispersed in water. In the acrylic-modified polyester resin, (meth)acrylic acid is bonded to the alcohol terminal of the crystalline polyester resin of the present invention.

[0050] The modified polyester resin of the present invention, in which (meth)acrylic acid is bonded to the alcohol terminal of the crystalline polyester resin, can be prepared by, for example, dissolving the crystalline polyester resin in an organic solvent capable of dissolving the crystalline polyester resin at 80 to 130°C, adding a radical polymerization initiator, and then dissolving the crystalline polyester resin in an organic solvent capable of dissolving the crystalline polyester resin at 80 to 130°C. The resulting polyester resin contains (meth)acrylic acid and an aromatic monomer, and if necessary, further contains (meth)acrylic acid C. １－５ The copolymer can be prepared by adding a mixture of alkyl-containing monomers dropwise over 1 to 5 hours and reacting them.

[0051] The aqueous dispersion of the crystalline polyester resin of the present invention can be prepared by, for example, (i) dissolving the crystalline polyester resin of the present invention in a water-soluble organic solvent and, if necessary, sequentially adding a basic compound and water to disperse the resin, or (ii) adding the crystalline polyester resin to water, a water-soluble organic solvent, and, if necessary, a basic compound, and then heating and dispersing the resulting mixture. Furthermore, if it is desired to reduce the amount of organic solvent or to completely remove the organic solvent to prepare an aqueous dispersion, it is also possible to dissolve and disperse the resin in an organic solvent having a boiling point of 100°C or less, and then remove the solvent by heating or under reduced pressure. From the viewpoint of film-forming properties, the aqueous dispersion is preferably prepared by the former method (i).

[0052] In this case, the temperature at which the crystalline polyester resin is dissolved is preferably 40 to 160°C, more preferably 50 to 140°C, even more preferably 60 to 130°C, and most preferably 70 to 100°C. At 40°C or higher, the crystalline polyester resin dissolves sufficiently, making it possible to prevent entanglement of molecular chains, while at 160°C or lower, thermal degradation of the crystalline polyester resin can be suppressed. Examples of organic solvents that can dissolve the crystalline polyester resin by heating in the temperature range of 40 to 160°C include methyl ethyl ketone, cyclohexanone, dimethylacetamide, dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, 1,4-dioxane, 1,3-dioxane, 1,3-dioxolane, 1,2-hexanediol, methyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, propylene glycol monomethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, and triethylene glycol monobutyl ether. Of these, methyl ethyl ketone, butyl cellosolve, propylene glycol monopropyl ether, propylene glycol monobutyl ether, etc. are preferred.

[0053] When dissolving the crystalline polyester resin in an organic solvent, it is preferable to also mix a crystal nucleating agent, which can further improve the crystallinity of the resulting coating film. Therefore, the crystalline polyester resin of the present invention can be used together with the crystal nucleating agent to form a resin composition, and this resin composition usually contains an organic solvent. The content of the crystal nucleating agent in 100% by mass of the resin composition is, for example, 5 to 40% by mass. Furthermore, the amount of the crystal nucleating agent per 100 parts by mass of the crystalline polyester resin is, for example, 0.1 to 5 parts by mass.

[0054] When the crystalline polyester resin is dissolved at 100°C or higher, it is preferable to obtain an aqueous dispersion by cooling the temperature of the crystalline polyester resin solution to 100°C or lower, and then gradually adding water and, if necessary, a basic compound while stirring the resin solution to cause phase inversion.

[0055] The crystalline polyester resin aqueous dispersion of the present invention is prepared so that the organic solvent content is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 13% by mass or less, based on 100 parts by mass of the aqueous dispersion. When the organic solvent content is 20% by mass or less, the occurrence of a flash point due to the organic solvent can be prevented.

[0056] The basic compound used when dispersing the crystalline polyester resin of the present invention in water is preferably a compound that volatilizes during the drying or baking process during coating film formation, such as ammonia and / or an organic amine compound having a boiling point of 250°C or less. Preferred examples include triethylamine, N,N-diethylethanolamine, N,N-dimethylethanolamine, aminoethanolamine, N-methyl-N,N-diethanolamine, isopropylamine, iminobispropylamine, ethylamine, diethylamine, 3-ethoxypropylamine, 3-diethylaminopropylamine, sec-butylamine, propylamine, methylaminopropylamine, dimethylaminopropylamine, methyliminobispropylamine, 3-methoxypropylamine, monoethanolamine, diethanolamine, triethanolamine, morpholine, N-methylmorpholine, and N-ethylmorpholine. These basic compounds must be present in an amount sufficient to at least partially neutralize the carboxyl groups of the crystalline polyester resin; specifically, it is desirable to add 0.5 to 1.5 equivalents per carboxyl group equivalent.

[0057] The aqueous dispersion of the crystalline polyester resin of the present invention is preferably prepared with a resin solids concentration of 10 to 45% by mass. It is more preferably 15 to 40% by mass, and even more preferably 20 to 35% by mass. When the resin solids concentration is 45% by mass or less, the viscosity of the aqueous dispersion is appropriate and aggregation between resin particles can be prevented, resulting in good dispersion stability. Furthermore, when the resin solids concentration is 10% by mass or more, practical application becomes easier in terms of both production and application.

[0058] The above-mentioned aqueous coating composition can form a coating film by using only the crystalline polyester resin aqueous dispersion without adding a curing agent.Therefore, it is preferable that the above-mentioned aqueous coating composition does not substantially contain a curing agent, that is, the curing agent content is preferably less than 1 mass part (solid content equivalent) for 100 mass parts (solid content equivalent) of the crystalline polyester resin of the aqueous coating composition, and it is most preferable that the curing agent is not contained.When the content of the curing agent is less than the above range, it is economically advantageous, and it prevents the deterioration of processability due to the self-condensation reaction between curing agents, the volatilization of blocking agents, and the generation of harmful outgassing such as formaldehyde, and it also has excellent long-term storage stability.

[0059] Here, the curing agent refers to a known curing agent that reacts with a polyester resin to form a crosslinked structure, and the form of the crosslinked structure can be, for example, a reaction in which unsaturated double bonds in the polyester resin are reacted by a radical addition reaction, a cation addition reaction, an anion addition reaction, etc. to form an intermolecular carbon-carbon bond, or the formation of an intermolecular bond by a condensation reaction with a polycarboxylic acid group or a polyhydric alcohol group in the polyester resin, a polyaddition reaction, an ester exchange reaction, etc. Examples of the curing agent include phenolic resins, amino resins, isocyanate compounds, epoxy compounds, β-hydroxylamide compounds, and unsaturated bond-containing resins.

[0060] The aqueous coating composition described above is ideal for coatings for food and beverage cans, etc. In order to make it into a coating for food and beverage cans, etc., various additives may be blended depending on the purpose. Plasticizers for improving solubility in organic solvents, leveling agents and surfactants for improving coatability, smoothness and appearance of the coating film, lubricants for preventing scratches on the coating film, coloring pigments, and in some cases polyester resins other than the crystalline polyester resin of the present invention, resins other than polyester resins, such as acrylic resin emulsions and polyurethane resin emulsions, may be blended within a range that does not impair the object of the present invention, such as food hygiene and flavor properties.

[0061] The above-mentioned aqueous coating composition can be blended with other resins for the purpose of improving the properties of the coating film, such as imparting flexibility, adhesion, etc. Examples of other resins include amorphous polyesters, crystalline polyesters, ethylene-polymerizable unsaturated carboxylic acid copolymers, and ethylene-polymerizable carboxylic acid copolymer ionomers, and blending at least one resin selected from these may impart flexibility and / or adhesion to the coating film.

[0062] The coating composition of the present invention can be applied to metal substrates for cans, such as aluminum or steel, or to metal substrates for other uses (such as electric wires), using a gravure roll coater, comma coater, or spray method. There are no particular limitations on the coating thickness, but a dry film thickness of 3 to 18 μm is generally preferred, with a range of 5 to 15 μm being preferred. The coating is typically baked at a temperature in the range of about 180 to 260°C for about 20 seconds to 1 hour, preferably at a temperature in the range of about 200 to 240°C for about 30 seconds to 10 minutes.

[0063] It is preferable that the coating film made of the above-mentioned coating composition is baked within the above range and then subjected to an aging treatment, which further promotes crystallization in the coating film and improves retort resistance.

[0064] <Coating Film> The coating film of the present invention is a substrate coated with a crystalline polyester resin (two layers: substrate / crystalline polyester resin). It may also be configured such that a layer made of another resin is superimposed on either the top or bottom of the crystalline polyester resin layer. In this case, the layer made of another resin is referred to as a coating layer. The coating film of the present invention can be obtained by laminating the crystalline polyester resin of the present invention on various substrates according to a conventional method, and further laminating another resin layer thereon. The coating film of the present invention can coat the surface of metal plates, metal cans, electric wires, etc.

[0065] <Metal Plate, Metal Can, and Electric Wire> The metal plate, metal can, and electric wire of the present invention preferably have the coating film, and their surfaces are preferably coated with the coating film. The metal can may be coated on either the inner or outer surface of the can, and on either the inner or outer surface, a portion or the entire surface may be coated. The metal plate may also be coated on either the main surface or the side surface, and either a portion or the entire surface may be coated. Examples of metal plates include steels such as tinplate, tin-free steel, and chrome-free steel, as well as aluminum, copper, titanium, nickel, and zinc. Metal cans can be obtained by coating one or both sides, and, if necessary, the end surfaces, of a metal plate made of a metal material that can be used for, for example, beverage cans, canned food cans, their lids, and caps. Examples of metal materials for the metal can include the aforementioned metal plates, such as tinplate, tin-free steel, chrome-free steel, and aluminum. Metal plates made of these metal materials may be subjected to a surface treatment such as phosphate treatment, chromate chromate treatment, chromate phosphate treatment, or other anticorrosion treatment using an antirust treatment agent, or a treatment to improve the adhesion of a coating film.Cu, Al, or alloys thereof may be used as the electric wire.

[0066] The crystalline polyester resin of the present invention can be used for purposes other than coating compositions, such as adhesive compositions and adhesive sheets.

[0067] <Adhesive composition> The adhesive composition contains at least the above-mentioned crystalline polyester resin and an organic solvent and / or water. The organic solvent can be the same as the organic solvent preferably used in the above-mentioned aqueous coating composition. When the dispersion is an aqueous coating composition in which the dispersion medium is water, all of the preferred embodiments for the above-mentioned aqueous coating composition can be referenced. Furthermore, the adhesive composition contains the crystalline polyester resin as the main component (the component with the largest mass proportion among the solid components forming the adhesive layer in the adhesive composition).

[0068] The adhesive composition may further contain other components as needed, such as a flame retardant, a tackifier, a filler, and a silane coupling agent.

[0069] (Flame Retardant) The adhesive composition may contain a flame retardant as needed. Examples of flame retardants include bromine-based, phosphorus-based, nitrogen-based, and metal hydroxide compounds. Phosphorus-based flame retardants are preferred, and known phosphorus-based flame retardants such as phosphate esters (e.g., trimethyl phosphate, triphenyl phosphate, tricresyl phosphate), phosphate salts (e.g., aluminum phosphinate), and phosphazenes can be used. These flame retardants may be used alone or in any combination of two or more. When a flame retardant is included, it is preferably included in an amount of 1 to 200 parts by mass, more preferably 5 to 150 parts by mass, and most preferably 10 to 100 parts by mass, per 100 parts by mass of the polyester and curing agent components combined. By keeping the amount within this range, flame retardancy can be achieved while maintaining adhesion, solder heat resistance, and electrical properties.

[0070] (Tackifier) ​​A tackifier may be blended into the adhesive composition as needed. Examples of tackifiers include polyterpene resins, rosin-based resins, aliphatic petroleum resins, alicyclic petroleum resins, copolymerized petroleum resins, styrene resins, and hydrogenated petroleum resins, and are used to improve adhesive strength. These may be used alone or in any combination of two or more. When a tackifier is included, it is preferably included in an amount of 1 to 200 parts by mass, more preferably 5 to 150 parts by mass, and most preferably 10 to 100 parts by mass, per 100 parts by mass of the polyester and curing agent components combined. By keeping the amount within this range, the effects of the tackifier can be exhibited while maintaining adhesion, solder heat resistance, and electrical properties.

[0071] (Filler) The adhesive composition may contain a filler as needed. Examples of organic fillers include powders of heat-resistant resins such as polyimide and polyamideimide. Examples of inorganic fillers include silica (SiO ２ ), alumina (Al２ O ３ ), titania (TiO ２ ), tantalum oxide (Ta ２ O ５ ), zirconia (ZrO ２ ), silicon nitride (Si ３ N ４ ), boron nitride (BN), calcium carbonate (CaCO ３ ), calcium sulfate (CaSO ４ ), zinc oxide (ZnO), magnesium titanate (MgO.TiO ２ ), barium sulfate (BaSO ４ ), organic bentonite, clay, mica, aluminum hydroxide, magnesium hydroxide, etc.

[0072] (Silane Coupling Agent) A silane coupling agent may be blended into the adhesive composition as needed. The incorporation of a silane coupling agent is highly preferred because it improves adhesion to metals and heat resistance. The silane coupling agent is not particularly limited, but examples include those having an unsaturated group, an epoxy group, and an amino group. Of these, from the perspective of heat resistance, silane coupling agents having an epoxy group, such as γ-glycidoxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltriethoxysilane, are more preferred.

[0073] <Adhesive Sheet> An adhesive sheet can be obtained by applying the adhesive composition to various substrates or various laminates and drying it according to a conventional method, or by melting the crystalline polyester resin of the present invention. Furthermore, if a release substrate is attached to the adhesive layer after drying, the adhesive layer is protected, resulting in excellent storage stability and ease of use. Furthermore, if the adhesive composition is applied to a release substrate and dried, and then a separate release substrate is attached as needed, the adhesive layer itself can be transferred to another substrate.

[0074] The adhesive sheet can be suitably used for each adhesive layer of a laminate film for decorating three-dimensional molded products. A laminate film for decorating three-dimensional molded products is a film used in the decorative molding of three-dimensional molded products. That is, a decorative film is adhered to various molded bodies to impart design features and surface protection functions to the molded bodies. In this process, the film is deformed to conform to the surface of the three-dimensional shape and adheres tightly. In particular, the adhesive sheet has high adhesion to conventional resin substrates such as soft vinyl chloride film, polycarbonate film, polyester film, and ABS that constitute laminate films for decorating three-dimensional molded products, and also has excellent sheet life. Therefore, the adhesive sheet is suitable for use in laminate films for decorating three-dimensional molded products in automotive exterior components such as side underskirts, side garnishes, and door mirrors, automotive interior components such as instrument panels and door switch panels, and housings of home appliances such as refrigerators, mobile phones, and lighting fixtures.

[0075] The adhesive sheet can also be used as each adhesive layer of a film for laminating metal cans or as a film for laminating metal cans. In particular, the adhesive sheet has high adhesion to conventional polyester films that constitute films for laminating metal cans and to metal substrates such as tinplate, tin-free steel, and aluminum that constitute metal cans, and also has excellent pot life. Therefore, the adhesive sheet is suitable as an adhesive sheet for each adhesive layer of a film for laminating metal cans or as an adhesive sheet for use in a film for laminating metal cans.

[0076] This application claims the benefit of priority based on Japanese Patent Application No. 2024-065170, filed on April 15, 2024. The entire contents of the specification of Japanese Patent Application No. 2024-065170, filed on April 15, 2024, are incorporated herein by reference.

[0077] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples, and can of course be practiced with appropriate modifications within the scope of the above and below-described aims, all of which are included in the technical scope of the present invention.

[0078] <Crystalline Polyester Resin> (1) Measurement of Resin Composition A crystalline polyester resin sample was dissolved in deuterated chloroform, and the composition was measured using a nuclear magnetic resonance (NMR) apparatus AVANCE-NEO600 manufactured by BRUKER. １ H-NMR analysis or １３ C-NMR analysis was carried out, and the molar ratio was calculated from the ratio of the integral values.

[0079] (2) Measurement of reduced viscosity (unit: dl / g) 0.1 g of a crystalline polyester resin sample was dissolved in 25 cc of a mixed solvent of phenol / tetrachloroethane (mass ratio 6 / 4), and the reduced viscosity was measured at 30°C using an Ubbelohde viscometer.

[0080] (3) Measurement of Melting Point (Tm) and Glass Transition Temperature (Tg) The melting point (Tm) and glass transition temperature (Tg) were measured using a differential scanning calorimeter (DSC) DSC-220 manufactured by Seiko Instruments Inc. The aging treatment of the crystalline polyester resin was performed under the aging treatment conditions of 100°C x 30 hours, and 5 mg of the treated crystalline polyester resin sample was placed in an aluminum clamp-lid type container and sealed. Nitrogen gas was flowed at 30 ml / min to create a nitrogen atmosphere, and then the sample was cooled to -50°C using liquid nitrogen and then heated to 200°C at 20°C / min. The temperature at the apex of the maximum peak of the heat of fusion obtained during this process was determined as the melting point (Tm, unit: °C). Furthermore, using the above-mentioned measuring device, the sample was heated to 200°C under the same conditions, then rapidly cooled to -50°C, and again heated to 200°C at 20°C / min. In the endothermic curve obtained in this process, the temperature at the intersection of the baseline before the endothermic peak and the tangent line to the endothermic peak was taken as the glass transition temperature (Tg, unit: ° C.).

[0081] (4) Measurement of Acid Value 0.2 g of a crystalline polyester resin sample was dissolved in 40 ml of chloroform, and titrated with a 0.01 N potassium hydroxide ethanol solution to obtain 10% of the polyester resin. ６ The equivalent weight per gram (eq / ton) was calculated. Phenolphthalein was used as an indicator.

[0082] (5) Solvent Solubility Evaluation The crystalline polyester resin was dissolved according to the following procedure. 160 parts by mass of cyclohexanone and 40 parts by mass of crystalline polyester resin were charged into a 500 mL four-neck flask equipped with a stirrer, a condenser, a thermometer, and a mantle heater. A rubber stopper was attached to the charge port, and the temperature was gradually increased to 130°C over 1 hour at a stirring speed of 200 rpm. The temperature was then decreased to 120°C over 1 hour. After the temperature decrease, the stirring speed was changed to 50 rpm, and the state of dissolution of the crystalline polyester resin was visually evaluated as follows: (Evaluation) A: No undissolved resin and no cloudiness. B: No undissolved resin, but cloudiness. C: Undissolved resin was present.

[0083] (6) Evaluation of Compatibility with Monomer Mixture The crystalline polyester resin was dissolved according to the following procedure. 72 parts by mass of styrene, 26 parts by mass of n-butyl acrylate, 22 parts by mass of acrylic acid, and 80 parts by mass of crystalline polyester resin were charged into a 500 mL four-neck flask equipped with a stirrer, a condenser, a thermometer, and a mantle heater. A rubber stopper was attached to the charge port, and the temperature was gradually increased to 130°C over 1 hour at a stirring speed of 200 rpm. The temperature was then decreased to 120°C over 1 hour. After the temperature decrease, the stirring speed was changed to 50 rpm, and the state of dissolution of the crystalline polyester resin was visually evaluated as follows: (Evaluation) A: No undissolved resin and no cloudiness. B: No undissolved resin, but cloudiness. C: Some undissolved resin was present.

[0084] <Preparation of Crystalline Polyester Resin Coating Composition> 100 parts by mass (solid content) of crystalline polyester resin was dissolved in cyclohexanone to obtain a crystalline polyester resin coating composition (solid content: approximately 10% by mass).

[0085] <Preparation of test piece> The crystalline polyester resin coating composition was applied to one side of a tinplate (JIS G 3303 (2008) SPTE, 70 mm × 150 mm × 0.3 mm) using a bar coater so that the film thickness after drying would be 10 ± 2 μm, and the coating was baked under baking conditions of 200°C × 30 seconds to prepare a test piece (hereinafter referred to as test piece).

[0086] (7) Evaluation of Workability The obtained test specimen was bent 180° so that the coating film was facing outward, and the cracks in the coating film occurring at the bend were evaluated by measuring the current value. The bending was performed without any interposition (so-called 0T). An aluminum plate electrode (width 20 mm, depth 50 mm, thickness 0.5 mm) was prepared, on which a sponge (width 20 mm, depth 50 mm, thickness 10 mm) soaked in 1% NaCl aqueous solution was placed. The test specimen was brought into contact with the sponge near the center of the bent portion so that it was parallel to the 20 mm side of the sponge. A DC voltage of 5.0 V was applied between the aluminum plate electrode and the uncoated portion on the back of the test specimen, and the current value was measured. A smaller current value indicates better bending properties. (Judgment) A: Less than 0.5 mA B: 0.5 mA or more but less than 1.0 mA C: 1.0 mA or more but less than 2.0 mA D: 2.0 mA or more

[0087] (8) Evaluation of retort resistance A test specimen was placed upright in a stainless steel cup, and ion-exchanged water was poured into it up to half the height of the test specimen. This was then placed in the pressure cooker of a retort testing machine (ES-315, manufactured by Tomy Kogyo Co., Ltd.) and subjected to retort treatment at 125°C for 30 minutes. Evaluation after treatment was carried out at the steam-contacting portion, which is generally considered to be subjected to more severe conditions for the coating film, and the state of whitening and blistering of the coating film was visually judged as follows: (Judgment) A: Good (no whitening or blisters). B: Slight whitening but no blisters. C: Slight whitening and / or slight blisters. D: Significant whitening and / or significant blisters.

[0088] <Preparation of crystalline polyester resin> Synthesis example (a) 495 parts by mass of terephthalic acid, 135 parts by mass of isophthalic acid, 105 parts by mass of dimethyl 2,6-naphthalenedicarboxylate, 8 parts by mass of trimellitic anhydride, 730 parts by mass of 1,4-butanediol, 60 parts by mass of 1,4-cyclohexanedimethanol, 0.4 parts by mass of tetra-n-butyl titanate (hereinafter sometimes abbreviated as TBT) as a catalyst were charged into a 3 L four-neck flask, and the temperature was gradually raised to 240 ° C. over 3 hours, while carrying out an esterification reaction and a transesterification reaction. After completion of the esterification reaction, the pressure in the system was gradually reduced, and the temperature was raised to 250 ° C. and subjected to reduced pressure polymerization to 10 mmHg over 1 hour, and further subjected to post-polymerization for 120 minutes under a vacuum of 1 mmHg or less. After the polycondensation reaction was completed, the mixture was cooled to 220°C under a nitrogen atmosphere. A predetermined amount of trimellitic anhydride was then added, and stirring was continued for 30 minutes at 220°C under a nitrogen atmosphere. After the reaction was completed, the mixture was removed to obtain a crystalline polyester resin (Synthesis Example (a)). The resulting crystalline polyester resin had a reduced viscosity of 0.65 dl / g, a glass transition temperature (Tg) of 35°C, a crystalline melting point (Tm) of 155°C, and an acid value of 180 eq / t.

[0089] Synthesis Examples (b) to (l) In Synthesis Examples (b) to (i) and (l), polyester resins having the resin compositions shown in Table 1 were produced in the same manner as in Synthesis Example (a), except that the feed compositions were changed. In Synthesis Examples (j) and (k) other than the above, polyester resins having the resin compositions shown in Table 1 were produced by a direct polymerization method (the transesterification reaction step in Synthesis Example (a) was omitted).

[0090]

[0091] Table 1 shows that the crystalline polyester resins of Examples 1 to 9, which contained predetermined amounts of 2,6-naphthalenedicarboxylic acid and terephthalic acid as polycarboxylic acid components, contained predetermined amounts of 1,4-butanediol as polyhydric alcohol component, and had melting points of 130 to 160° C., exhibited good retort resistance and compatibility with the monomer mixture. In contrast, Comparative Examples 1 and 2, which did not contain 2,6-naphthalenedicarboxylic acid, exhibited poor compatibility with the monomer mixture, and Comparative Example 3, which contained a small amount of 1,4-butanediol, exhibited poor retort resistance.

[0092] The present invention relates to a crystalline polyester resin having excellent retort resistance and compatibility with a monomer mixture containing an acrylic monomer, and a resin composition containing the crystalline polyester resin of the present invention can be used in a variety of applications. In particular, the crystalline polyester resin of the present invention can be effectively used in the form of a coating composition and is preferably used as a base agent for coating metal cans, metal plates, electric wires, etc., that contain beverages or foods. The crystalline polyester resin of the present invention can also be effectively used in the form of an adhesive composition and is preferably used for laminating metal cans, decorating three-dimensional molded products, etc.

Claims

1. A crystalline polyester resin containing a polycarboxylic acid component and a polyhydric alcohol component, which contains 5 to 40 mol% of a 2,6-naphthalenedicarboxylic acid component out of 100 mol% of the polycarboxylic acid component, 40 to 75 mol% of a terephthalic acid component out of 100 mol% of the polycarboxylic acid component, and 60 mol% or more of a 1,4-butanediol component out of 100 mol% of the polyhydric alcohol component, and has a melting point of 130 to 160°C.

2. The crystalline polyester resin according to claim 1, wherein the polycarboxylic acid component further contains an isophthalic acid component, and the content of the isophthalic acid component in 100 mol % of the polycarboxylic acid component is 30 mol % or less.

3. The crystalline polyester resin according to claim 1, wherein the polyhydric alcohol component does not contain an ethylene glycol component or contains less than 35 mol % of an ethylene glycol component per 100 mol % of the polyhydric alcohol component.

4. The crystalline polyester resin according to claim 1, wherein the polyhydric alcohol component further contains a 1,4-cyclohexanedimethanol component and / or a tricyclodecanedimethanol component.

5. The crystalline polyester resin according to claim 1, further comprising a tri- or higher functional polycarboxylic acid component and / or a tri- or higher functional polyhydric alcohol component, and when the total components constituting the molecular chain of the crystalline polyester resin are taken as 100 mol %, the amount of the tri- or higher functional polycarboxylic acid component and the tri- or higher functional polyhydric alcohol component is 0.1 to 5 mol %.

6. The crystalline polyester resin according to claim 1, which has an acid value of 100 eq / ton or more.

7. The crystalline polyester resin according to claim 1, which has a glass transition temperature of 30 to 55°C.

8. A coating composition containing the crystalline polyester resin according to any one of claims 1 to 7.

9. A crystalline polyester resin water dispersion containing the crystalline polyester resin according to any one of claims 1 to 7.

10. A coating film obtained from the coating composition according to claim 8.

11. A metal sheet having the coating film according to claim 10.

12. A metal can having the coating film of claim 10.

13. An electric wire whose surface is coated with the coating film according to claim 10.

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