Method for improving dispersibility of crystalline resin having hydrophilic group into neutral water

Abstract

The present invention provides a method for improving the dispersibility of a crystalline resin having a hydrophilic group into neutral water, the method comprising an amorphization step in which a crystalline resin having a hydrophilic group is amorphized. The present invention is able to provide a method which improves the dispersibility of a water-soluble resin having excellent moisture resistance into neutral water.

Description

Method for improving dispersibility of crystalline resin having hydrophilic groups in neutral water

[0001] The present invention relates to a method for improving the dispersibility of a crystalline resin having a hydrophilic group in neutral water.

[0002] In some applications of resins, it is sometimes necessary to quickly remove the resin after it has completed its function. One possible method for removing the resin is to dissolve it in a solvent or an alkaline aqueous solution (see, for example, JP 2001-131484 A).

[0003] The present invention provides a method for improving the dispersibility of a crystalline resin having a hydrophilic group in neutral water, which method comprises an amorphization step of amorphizing the crystalline resin having a hydrophilic group. Detailed Description of the Invention

[0004] Removing resin using an alkaline aqueous solution is undesirable from the viewpoint of the working environment and safety. One possible solution to this problem is to use a water-soluble resin such as polyvinyl alcohol that dissolves in neutral water. However, conventional water-soluble resins have poor moisture resistance, and when used in a relatively humid environment, they may be damaged by the moisture in the environment and no longer be able to perform their intended function.

[0005] To address the above-mentioned issues, it is conceivable to use a water-soluble resin that has excellent moisture resistance and is less likely to break even when used in a high-humidity environment. However, in order to remove such a water-soluble resin with neutral water, the temperature of the neutral water must often be raised, which poses issues from the standpoints of safety and energy conservation.

[0006] The present invention provides a method for improving the dispersibility of a water-soluble resin having excellent moisture resistance in neutral water.

[0007] The present invention provides a method for improving the dispersibility of a crystalline resin having a hydrophilic group in neutral water, which method comprises an amorphization step of amorphizing the crystalline resin having a hydrophilic group.

[0008] According to the present invention, a method for improving the dispersibility of a water-soluble resin having excellent moisture resistance in neutral water can be provided.

[0009] An embodiment of the present invention will be described below.

[0010] <Method for Improving the Dispersibility of a Crystalline Resin Having Hydrophilic Groups in Neutral Water> The method for improving the dispersibility of a crystalline resin having hydrophilic groups in neutral water (hereinafter also referred to simply as the water-dispersibility improving method) of this embodiment includes an amorphization step of amorphizing the crystalline resin having hydrophilic groups. In this specification, "dispersion of a crystalline resin having hydrophilic groups in neutral water" refers to dissolving the crystalline resin having hydrophilic groups in neutral water, or dispersing the crystalline resin having hydrophilic groups in neutral water due to the disintegration of a molded body of the crystalline resin having hydrophilic groups in neutral water. Furthermore, "dispersibility of a crystalline resin having hydrophilic groups in neutral water" refers to the ease of dissolving the crystalline resin having hydrophilic groups in neutral water, or the ease of dispersing the crystalline resin having hydrophilic groups in neutral water due to the disintegration of a molded body of the crystalline resin having hydrophilic groups in neutral water. According to the water-dispersibility improving method of this embodiment, the dispersibility of a water-soluble resin with excellent moisture resistance in neutral water can be improved. The reason why the water-dispersibility improving method exhibits such an effect is unclear, but is thought to be as follows.

[0011] It is thought that crystalline resins having hydrophilic groups have high moisture resistance due to aggregation and crystallization of the hydrophilic groups immediately after melt synthesis, but when a crystalline resin having hydrophilic groups is heated above its melting point after molding, the crystals melt, molecular mobility increases, and the hydrophilic groups re-aggregate, resulting in the loss of crystals due to the hydrophobic parts, which is thought to improve dispersibility in neutral water.

[0012] [Amorphization Step] The amorphization step is a step of amorphizing the crystalline resin.

[0013] The crystalline resin having a hydrophilic group is not particularly limited as long as it is a resin that has crystallinity and dispersibility in neutral water. Examples of the crystalline resin having a hydrophilic group include a crystalline water-soluble resin having a monomer unit A having a hydrophilic group other than the hydrophilic group (hereinafter also simply referred to as a hydrophilic group) constituting the polymerization for producing the crystalline resin having a hydrophilic group, and a monomer unit B having no hydrophilic group.

[0014] The neutral water may be water or an aqueous solution having a pH of 6 to 8 at 25°C, preferably 6.5 to 7.5. Specific examples of the neutral water include deionized water, pure water, tap water, and industrial water. Deionized water or tap water is preferred due to its availability. The neutral water may also contain other components such as a water-soluble organic solvent and a surfactant. Examples of the water-soluble organic solvent include lower alcohols such as methanol, ethanol, and 2-propanol; glycol ethers such as propylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monotertiary butyl ether, and diethylene glycol monobutyl ether; and ketones such as acetone and methyl ethyl ketone. Examples of the surfactant include anionic surfactants such as alkyl sulfates, alkyl ether sulfates, olefin sulfonates, and alkyl ether carboxylates; cationic surfactants such as alkyltrimethylammonium salts; and nonionic surfactants such as polyoxyethylene alkyl ethers and alkyl glycosides.

[0015] Examples of the crystalline resin having a hydrophilic group include water-soluble polyester resins, water-soluble polyamide resins, water-soluble polyimide resins, water-soluble acrylic resins, water-soluble polyurethane resins, water-soluble polyallylamine resins, water-soluble phenolic resins, water-soluble epoxy resins, water-soluble phenoxy resins, water-soluble urea resins, water-soluble melamine resins, and polyvinyl alcohol resins, as well as modified products of these resins. These can be used alone or in combination of two or more. Among these, from the viewpoint of achieving the effects of the present invention, one or more selected from the group consisting of water-soluble polyester resins, water-soluble polyamide resins, and water-soluble acrylic resins are preferred, and water-soluble polyester resins are more preferred.

[0016] [Monomer Unit A] The monomer unit A has a hydrophilic group. The monomer from which the monomer unit A is derived is referred to as "monomer A."

[0017] The hydrophilic group may be one or more selected from the group consisting of cationic groups, neutral groups, and anionic groups, which provide dispersibility in neutral water. Among these, from the viewpoint of providing dispersibility in neutral water, one or more selected from the group consisting of anionic groups is preferred, and sulfonate groups are more preferred.

[0018] The sulfonate group is —SO ３ M ３ (However, M ３ represents a counter ion of the sulfonic acid group constituting the sulfonate group, and from the viewpoint of imparting dispersibility in neutral water, is preferably one or more ions selected from the group consisting of metal ions and ammonium ions, more preferably one or more ions selected from the group consisting of metal ions, even more preferably one or more ions selected from the group consisting of alkali metal ions and alkaline earth metal ions, even more preferably one or more ions selected from the group consisting of alkali metal ions, even more preferably one or two ions selected from the group consisting of sodium ions and potassium ions, and even more preferably sodium ions.

[0019] The monomer unit A is not particularly limited as long as it is a monomer unit having the hydrophilic group. However, from the viewpoint of imparting dispersibility in neutral water and improving moisture resistance, a dicarboxylic acid monomer unit having the hydrophilic group is preferred.

[0020] From the viewpoints of imparting dispersibility in neutral water, improving moisture resistance, and facilitating the polymerization reaction during production of a crystalline resin having a hydrophilic group, the monomer A is preferably one or more selected from the group consisting of carboxylic acids, amines, amino acids, and salts thereof having a hydrophilic group, and more preferably the carboxylic acids or salts thereof having a hydrophilic group. Among the carboxylic acids or salts thereof, from the same viewpoints, aromatic carboxylic acids or salts thereof having a hydrophilic group are preferred, and one or more selected from the group consisting of sulfonate group-containing aromatic dicarboxylic acids and salts thereof are more preferred. Among these, from the same viewpoints, one or more selected from the group consisting of sulfophthalic acid, sulfonaphthalenedicarboxylic acid, and salts thereof are preferred, and one or more selected from the group consisting of sulfophthalic acid and salts thereof are even more preferred, and one or more selected from the group consisting of sulfoisophthalic acid, sulfoterephthalic acid, and salts thereof are even more preferred, and 5-sulfoisophthalic acid or a salt thereof is even more preferred.

[0021] The content of the hydrophilic group in the crystalline resin having the hydrophilic group is preferably 0.4 mmol / g or more, more preferably 0.6 mmol / g or more, and even more preferably 0.7 mmol / g or more, from the viewpoint of imparting dispersibility in neutral water, and is preferably 3.0 mmol / g or less, more preferably 2.0 mmol / g or less, even more preferably 1.5 mmol / g or less, and even more preferably 1.0 mmol / g or less, from the viewpoint of improving moisture resistance.

[0022] The ratio of the amount of substance of the monomer unit A to the total amount of substance of all monomer units of the crystalline resin having a hydrophilic group is preferably 5 mol% or more, more preferably 7 mol% or more, and even more preferably 10 mol% or more, from the viewpoint of imparting dispersibility in neutral water, and is preferably 35 mol% or less, more preferably 30 mol% or less, even more preferably 20 mol% or less, and even more preferably 15 mol% or less, from the viewpoint of improving moisture resistance.

[0023] [Monomer Unit B] The monomer unit B does not have a hydrophilic group. A monomer for deriving the monomer unit B is referred to as monomer B. From the viewpoint of improving moisture resistance, the monomer unit B is preferably a dicarboxylic acid monomer unit (hereinafter also referred to as dicarboxylic acid monomer unit B) that does not have a hydrophilic group.

[0024] From the viewpoint of improving moisture resistance and facilitating the polymerization reaction during production of a crystalline resin having a hydrophilic group, the dicarboxylic acid from which the dicarboxylic acid monomer unit B is derived is preferably one or more selected from the group consisting of aromatic dicarboxylic acids having no hydrophilic group and aliphatic dicarboxylic acids having no hydrophilic group, and more preferably one or more selected from the group consisting of aromatic dicarboxylic acids having no hydrophilic group.

[0025] Examples of the aromatic dicarboxylic acid having no hydrophilic group include one or more selected from the group consisting of benzenedicarboxylic acid, furandicarboxylic acid, and naphthalenedicarboxylic acid. Among these, from the viewpoint of improving moisture resistance, one or more selected from the group consisting of terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid are preferred.

[0026] Examples of the aliphatic dicarboxylic acid having no hydrophilic group include one or more selected from the group consisting of malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, and 1,3-adamantanedicarboxylic acid. Among these, adipic acid is preferred from the viewpoint of improving moisture resistance.

[0027] From the viewpoint of improving moisture resistance, the ratio of the monomer units derived from the aromatic dicarboxylic acid having no hydrophilic group to the total of the dicarboxylic acid monomer units B is preferably 20 mol % or more, more preferably 30 mol % or more, and even more preferably 40 mol % or more.

[0028] Furthermore, from the viewpoint of imparting dispersibility in neutral water, the ratio of the monomer units derived from the aromatic dicarboxylic acid having no hydrophilic group to the total of the dicarboxylic acid monomer units B is preferably 100 mol % or less, more preferably 80 mol % or less, and even more preferably 60 mol % or less.

[0029] The ratio of the amount of the monomer unit B to the total amount of all monomer units in the crystalline resin having a hydrophilic group is preferably 15 mol% or more, more preferably 25 mol% or more, even more preferably 30 mol% or more, and even more preferably 35 mol% or more from the viewpoint of improving moisture resistance, and is preferably 45 mol% or less, more preferably 42 mol% or less, and even more preferably 40 mol% or less from the viewpoint of imparting dispersibility in neutral water. Note that in this specification, the composition of the crystalline resin is measured by the method described in the Examples.

[0030] The molar ratio of the monomer unit A to the monomer unit B in the crystalline resin having a hydrophilic group (the monomer unit A / the monomer unit B) is preferably 10 / 90 or more, more preferably 15 / 85 or more, and even more preferably 20 / 80 or more, from the viewpoint of imparting dispersibility in neutral water, and is preferably 70 / 30 or less, more preferably 60 / 40 or less, even more preferably 40 / 60 or less, and even more preferably 30 / 70 or less, from the viewpoint of improving moisture resistance.

[0031] The melting point Tm of the crystalline resin having a hydrophilic group is preferably 70° C. or higher, more preferably 80° C. or higher, and even more preferably 90° C. or higher from the viewpoint of improving heat resistance during use, and is preferably 200° C. or lower, more preferably 160° C. or lower, and even more preferably 150° C. or lower from the viewpoint of imparting dispersibility in neutral water. In this specification, the melting point Tm of the crystalline resin is measured by the method described in the examples.

[0032] The glass transition temperature of the crystalline resin having a hydrophilic group is preferably −10° C. or higher, more preferably −5° C. or higher, and even more preferably 0° C. or higher, from the viewpoint of improving heat resistance during use, and is preferably 180° C. or lower, more preferably 100° C. or lower, even more preferably 60° C. or lower, and even more preferably 50° C. or lower, from the viewpoint of imparting dispersibility in neutral water. In this specification, the glass transition temperature of the crystalline resin is measured by the method described in the examples.

[0033] The weight average molecular weight of the crystalline resin having a hydrophilic group is preferably 1,000 or more, more preferably 3,000 or more, and even more preferably 4,000 or more from the viewpoint of improving moisture resistance, and is preferably 80,000 or less, more preferably 50,000 or less, and even more preferably 30,000 or less from the viewpoint of imparting dispersibility in neutral water. In this specification, the weight average molecular weight is measured by the method described in the examples.

[0034] (Diol Monomer Unit C) When the crystalline resin having a hydrophilic group is a water-soluble polyester resin, it has a diol monomer unit C other than the monomer unit A and the monomer unit B. The diol from which the diol monomer unit C is derived is also referred to as diol C.

[0035] As the diol C, an aliphatic diol, an aromatic diol, or the like can be used, but an aliphatic diol is preferred from the viewpoint of easy availability of raw materials for the water-soluble polyester resin.

[0036] The number of carbon atoms in the diol C is preferably 2 or more from the viewpoint of imparting dispersibility in neutral water, and is preferably 31 or less, more preferably 25 or less, even more preferably 20 or less, and still more preferably 15 or less from the viewpoint of improving moisture resistance.

[0037] The aliphatic diol may be one or more selected from the group consisting of chain diols and cyclic diols. From the viewpoint of easy availability of raw materials, chain diols are preferred, and from the viewpoint of improving water resistance, cyclic diols are preferred.

[0038] The proportion of the monomer units derived from a cyclic diol to the total of the diol monomer units C is preferably 40 mol% or more, more preferably 50 mol% or more, and even more preferably 60 mol% or more, from the viewpoint of imparting dispersibility in neutral water, and is preferably 90 mol% or less, more preferably 85 mol% or less, and even more preferably 80 mol% or less, from the viewpoint of easy availability of raw materials.

[0039] The number of carbon atoms in the chain diol is preferably 2 or more from the viewpoint of improving moisture resistance, and is preferably 20 or less, more preferably 15 or less, and even more preferably 6 or less from the viewpoint of imparting dispersibility in neutral water.

[0040] From the viewpoint of improving moisture resistance and imparting dispersibility in neutral water, the chain diol is preferably an alkanediol, more preferably one or more selected from the group consisting of ethylene glycol, propanediol, butanediol, neopentyl glycol, pentanediol, hexanediol, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, and polypropylene glycol, still more preferably one or more selected from the group consisting of ethylene glycol, 1,2-propanediol, 1,3-propanediol, and triethylene glycol, and still more preferably 1,3-propanediol or ethylene glycol.

[0041] The number of carbon atoms in the cyclic diol is preferably 3 or more, more preferably 4 or more, and even more preferably 6 or more from the viewpoint of improving moisture resistance, and is preferably 31 or less, more preferably 20 or less, and even more preferably 15 or less from the viewpoint of imparting dispersibility in neutral water.

[0042] From the viewpoint of improving moisture resistance and imparting dispersibility in neutral water, the cyclic diol is preferably one or more selected from the group consisting of cyclohexanedimethanol, hydrogenated bisphenol A, isosorbide, bisphenoxyethanolfluorene, bisphenolfluorene, biscresoxyethanolfluorene, and biscresolfluorene, and more preferably 1,4-cyclohexanedimethanol.

[0043] The water-soluble polyester resin may contain a monomer unit other than the dicarboxylic acid monomer unit A, the dicarboxylic acid monomer unit B, and the diol monomer unit C, as long as the effect of this embodiment is not impaired.

[0044] The method for producing the water-soluble polyester resin is not particularly limited, and any conventionally known method for producing a polyester resin can be used.

[0045] In the amorphization step, a method of amorphizing the crystalline resin having a hydrophilic group is preferably a method of heat-treating the crystalline resin having a hydrophilic group, i.e., the amorphization step preferably includes a heat treatment step of heat-treating the crystalline resin having a hydrophilic group.

[0046] The heat treatment temperature of the crystalline resin having a hydrophilic group in the heat treatment step is, from the viewpoint of efficiently amorphizing the crystalline resin having a hydrophilic group, preferably Tm+10°C or higher, more preferably Tm+20°C or higher, and even more preferably Tm+30°C or higher, relative to the melting point Tm of the crystalline resin having a hydrophilic group; from the viewpoint of energy saving, it is preferably Tm+70°C or lower, more preferably Tm+60°C or lower, and even more preferably Tm+50°C or lower.

[0047] The heat treatment temperature of the crystalline resin having a hydrophilic group in the heat treatment step is preferably 110°C or higher, more preferably 120°C or higher, and even more preferably 140°C or higher, from the viewpoint of efficiently amorphizing the crystalline resin having a hydrophilic group; and from the viewpoint of energy saving, it is preferably 220°C or lower, more preferably 190°C or lower, and even more preferably 160°C or lower.

[0048] The heat treatment time of the crystalline resin having a hydrophilic group in the heat treatment step is preferably 10 seconds or more, more preferably 30 seconds or more, and even more preferably 45 seconds or more, from the viewpoint of efficiently amorphizing the crystalline resin having a hydrophilic group; from the same viewpoint, it is preferably 15 minutes or less, more preferably 10 minutes or less, even more preferably less than 3 minutes, and even more preferably 2 minutes or less.

[0049] In the heat treatment step, the shear rate during the heat treatment of the crystalline resin having a hydrophilic group is preferably 1 cycle / second or less, more preferably 0.1 cycle / second or less, and even more preferably 0.01 cycle / second or less, from the viewpoint of efficiently amorphizing the crystalline resin having a hydrophilic group.

[0050] In the heat treatment step, the extrusion speed when centrifuging the crystalline resin having hydrophilic groups while heating is preferably 100 m / min or less, more preferably 10 m / min or less, even more preferably 1 m / min or less, and even more preferably 0.1 m / min or less, from the viewpoint of efficiently amorphizing the crystalline resin having hydrophilic groups.

[0051] In the heat treatment step, the heat treatment of the crystalline resin having hydrophilic groups is preferably carried out under non-shear conditions in which no shear is applied to the crystalline resin having hydrophilic groups, from the viewpoint of efficiently amorphizing the crystalline resin having hydrophilic groups.

[0052] The heat treatment method in the heat treatment step is not particularly limited, and any known heat treatment method can be used.

[0053] <Method for dispersing a crystalline resin having hydrophilic groups in neutral water> The method for dispersing a crystalline resin having hydrophilic groups in neutral water of this embodiment (hereinafter also referred to simply as the dispersion method) is a method in which the water solubility of the crystalline resin having hydrophilic groups is improved by the water dispersibility improvement method, and then the crystalline resin having hydrophilic groups is dispersed in neutral water.

[0054] The dispersion method may be a method in which the crystalline resin having a hydrophilic group is brought into contact with the neutral water.

[0055] In the dispersion method, the amount of neutral water used is preferably 10 times by mass or more, more preferably 20 times by mass or more, relative to the amount of the crystalline resin having a hydrophilic group, from the viewpoint of dispersing the crystalline resin having a hydrophilic group; and from the viewpoint of reducing the environmental load, the amount of neutral water used is preferably 10,000 times by mass or less, more preferably 5,000 times by mass or less, even more preferably 1,000 times by mass or less, and even more preferably 100 times by mass or less, relative to the amount of the crystalline resin having a hydrophilic group.

[0056] In the dispersion method, the time for contacting the crystalline resin having hydrophilic groups with water is preferably 5 minutes or more from the viewpoint of dispersing the crystalline resin having hydrophilic groups, and is preferably 30 minutes or less from the viewpoint of energy saving, more preferably 20 minutes or less, and even more preferably 10 minutes or less.

[0057] In the dispersion method, the temperature of the neutral water is preferably 30°C or higher, more preferably 40°C or higher, from the viewpoint of dispersing the crystalline resin having a hydrophilic group, and is preferably 70°C or lower, more preferably 60°C or lower, from the viewpoint of reducing the environmental load.

[0058] The crystalline resin having a hydrophilic group may be a used resin. When the crystalline resin having a hydrophilic group is contained in a printed matter, an adhesive, a pressure-sensitive adhesive, or a coating, the printed matter, the adhesive, the pressure-sensitive adhesive, or the coating containing the crystalline resin having a hydrophilic group can be removed by the method for improving water dispersibility or the dispersion method.

[0059] <Printed matter removal method> The printed matter removal method of this embodiment includes a method of improving the dispersibility of the crystalline resin having a hydrophilic group in neutral water, or a method of dispersing the crystalline resin having a hydrophilic group in neutral water.

[0060] <Method for Removing Adhesive> The method for removing adhesive of the present embodiment includes a method for improving the dispersibility of the crystalline resin having a hydrophilic group in neutral water, or a method for dispersing the crystalline resin having a hydrophilic group in neutral water.

[0061] <Adhesive Removal Method> The adhesive removal method of this embodiment includes a method of improving the dispersibility of the crystalline resin having a hydrophilic group in neutral water, or a method of dispersing the crystalline resin having a hydrophilic group in neutral water.

[0062] <Coating Removal Method> The coating removal method of this embodiment includes a method of improving the dispersibility of the crystalline resin having a hydrophilic group in neutral water, or a method of dispersing the crystalline resin having a hydrophilic group in neutral water.

[0063] The present specification further discloses the following embodiments.

[0064] <1> A method for improving the dispersibility of a crystalline resin having a hydrophilic group in neutral water, comprising an amorphization step of amorphizing the crystalline resin having a hydrophilic group. <2> The method according to <1>, wherein the melting point (Tm) of the crystalline resin having a hydrophilic group is preferably 70°C or higher, more preferably 80°C or higher, and even more preferably 90°C or higher. <3> The method according to <1> or <2>, wherein the melting point (Tm) of the crystalline resin having a hydrophilic group is preferably 200°C or lower, more preferably 160°C or lower, and even more preferably 150°C or lower. <4> The method according to any one of <1> to <3>, wherein the glass transition temperature of the crystalline resin having a hydrophilic group is preferably -10°C or higher, more preferably -5°C or higher, and even more preferably 0°C or higher. <5> The method according to any one of <1> to <4>, wherein the glass transition temperature of the crystalline resin having a hydrophilic group is preferably 100°C or lower, more preferably 60°C or lower, and even more preferably 50°C or lower. <6> The method according to any one of <1> to <5>, wherein the content of the hydrophilic group in the crystalline resin having a hydrophilic group is preferably 0.4 mmol / g or more, more preferably 0.6 mmol / g or more, and even more preferably 0.7 mmol / g or more. <7> The method according to any one of <1> to <6>, wherein the content of the hydrophilic group in the crystalline resin having a hydrophilic group is preferably 3.0 mmol / g or less, more preferably 2.0 mmol / g or less, even more preferably 1.5 mmol / g or less, and even more preferably 1.0 mmol / g or less. <8> The method according to any one of <1> to <7>, wherein the crystalline resin having a hydrophilic group is a crystalline water-soluble resin having a monomer unit A having a hydrophilic group and a monomer unit B not having a hydrophilic group. <9> The method according to any one of <1> to <8>, wherein the molar ratio of the monomer unit A to the monomer unit B (the monomer unit A / the monomer unit B) in the crystalline resin having a hydrophilic group is preferably 10 / 90 or more, more preferably 15 / 85 or more, and even more preferably 20 / 80 or more.<10> The method according to any one of <1> to <9>, wherein the molar ratio of the monomer unit A to the monomer unit B (the monomer unit A / the monomer unit B) in the crystalline resin having a hydrophilic group is preferably 70 / 30 or less, more preferably 60 / 40 or less, even more preferably 40 / 60 or less, and even more preferably 30 / 70 or less. <11> The method according to any one of <1> to <10>, wherein the weight-average molecular weight of the crystalline resin having a hydrophilic group is preferably 1,000 or more, more preferably 3,000 or more, and even more preferably 4,000 or more. <12> The method according to any one of <1> to <11>, wherein the weight-average molecular weight of the crystalline resin having a hydrophilic group is preferably 80,000 or less, more preferably 50,000 or less, and even more preferably 30,000 or less. <13> The method according to any one of <1> to <12>, wherein the amorphization step includes a heat treatment step of heat-treating the crystalline resin having a hydrophilic group. <14> The method according to <13>, wherein the heat treatment of the crystalline resin having a hydrophilic group in the heat treatment step is carried out under non-shear conditions. <15> The method according to <13> or <14>, wherein the heat treatment temperature of the crystalline resin having a hydrophilic group in the heat treatment step is preferably Tm + 10°C or higher, more preferably Tm + 20°C or higher, and even more preferably Tm + 30°C or higher, relative to the melting point Tm of the crystalline resin having a hydrophilic group. <16> The method according to any of <13> to <15>, wherein the heat treatment temperature of the crystalline resin having a hydrophilic group in the heat treatment step is preferably Tm + 70°C or lower, more preferably Tm + 60°C or lower, and even more preferably Tm + 50°C or lower, relative to the melting point Tm of the crystalline resin having a hydrophilic group. <17> The method according to any one of <13> to <16>, wherein the heat treatment temperature of the crystalline resin having a hydrophilic group in the heat treatment step is preferably 110° C. or higher, more preferably 120° C. or higher, and even more preferably 140° C. or higher. <18> The method according to any one of <13> to <17>, wherein the heat treatment temperature of the crystalline resin having a hydrophilic group in the heat treatment step is preferably 220° C. or lower, more preferably 190° C. or lower, and even more preferably 160° C. or lower.<19> The method according to any one of <1> to <18>, wherein the hydrophilic group is preferably one or more types selected from the group consisting of anionic groups, and more preferably a sulfonate group. <20> The method according to any one of <1> to <19>, wherein the crystalline resin having a hydrophilic group is a water-soluble polyester resin. <21> A method for producing a crystalline resin having a hydrophilic group, comprising: an amorphization step of amorphizing a crystalline resin having a hydrophilic group; wherein the melting point Tm of the crystalline resin having a hydrophilic group is 70°C or more and 200°C or less; the glass transition temperature of the crystalline resin having a hydrophilic group is -10°C or more and 100°C or less; the content of the hydrophilic group in the crystalline resin having a hydrophilic group is 0.4 mmol / g or more and 3.0 mmol / g or less; the crystalline resin having a hydrophilic group is a crystalline water-soluble resin having a monomer unit A having a hydrophilic group and a monomer unit B not having the hydrophilic group; the molar ratio of the monomer unit A to the monomer unit B in the crystalline resin having a hydrophilic group (the monomer unit A / the monomer unit B) is 10 / 90 or more and 70 / 30 or less; and the weight average molecular weight of the crystalline resin having a hydrophilic group is 1,000 or more and 80,000 or less; and the amorphization step comprises a heat treatment step of heat treating the crystalline resin having a hydrophilic group; A method for improving the dispersibility of a crystalline resin having a hydrophilic group in neutral water, wherein the heat treatment step is performed under non-shear conditions, the heat treatment temperature of the crystalline resin having a hydrophilic group in the heat treatment step is from Tm + 10°C to Tm + 70°C, where Tm is the melting point of the crystalline resin having a hydrophilic group, the hydrophilic group being a sulfonate group, and the crystalline resin having a hydrophilic group being a water-soluble polyester. <22> The method according to any one of <1> to <21>, wherein the crystalline resin having a hydrophilic group is a used resin. <23> The method according to any one of <1> to <22>, wherein the crystalline resin having a hydrophilic group is contained in a printed matter, an adhesive, a pressure-sensitive adhesive, or a coating. <24> A method for improving the dispersibility of a crystalline resin having a hydrophilic group in neutral water by the method according to any one of <1> to <23>, and then dispersing the crystalline resin having a hydrophilic group in neutral water. <25> A method for removing a coating, comprising the method according to any one of <1> to <24>.

[0065] Pressure is expressed as absolute pressure. "Normal pressure" refers to 101.3 kPa.

[0066] Synthesis Example of Crystalline Resin Having Hydrophilic Groups Synthesis Example of Crystalline Resin 1 Having Hydrophilic Groups A 2 L stainless steel flask equipped with a separable lid was charged with 120.00 g of dimethyl terephthalic acid (manufactured by SK Yuka Co., Ltd.), 107.64 g of dimethyl adipic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), 109.83 g of 5-dimethyl sodium sulfoisophthalate (manufactured by Sanyo Chemical Industries, Ltd.), 174.66 g of 1,4-cyclohexanedimethanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 124.13 g of 1,3-propanediol (manufactured by Tokyo Chemical Industry Co., Ltd.), 252.4 mg of tetrabutyl orthotitanate (manufactured by Tokyo Chemical Industry Co., Ltd.), and 675.7 mg of sodium acetate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and the flask was then fitted with a nitrogen inlet tube, an anchor-type stirring blade, a Dean-Stark tube, and a Liebig condenser, and placed in a mantle heater. The flask was heated with stirring at a nitrogen flow rate of 0.5 L / min under normal pressure until the wall temperature reached 160 ° C. The temperature was then raised to 220 ° C. over 25 minutes, and the resulting distillate was removed from the Dean-Stark apparatus while reacting for 6.5 hours under normal pressure. The temperature was then raised to 240 ° C. over 20 minutes, and the pressure was reduced to 1.5 kPa, after which the resulting distillate was removed while reacting for 6.5 hours. The mixture was allowed to cool to room temperature, yielding 438.68 g of crystalline resin 1 having hydrophilic groups.

[0067] [Synthesis example of crystalline resin 2 having hydrophilic groups] The reaction was carried out under the same conditions as in the synthesis example of crystalline resin 1, except that the raw materials listed in Table 1 were used and, after reducing the pressure to 1.5 kPa, the reaction was carried out for 5.5 hours while removing the resulting distillate, and 396.39 g of crystalline resin 2 having hydrophilic groups was obtained.

[0068] [Synthesis example of crystalline resin 3 having hydrophilic groups] The reaction was carried out under the same conditions as in the synthesis example of crystalline resin 1, except that the raw materials listed in Table 1 were used and that after reducing the pressure to 1.5 kPa, the reaction was carried out for 6 hours while removing the resulting distillate, and 378.84 g of crystalline resin 3 having hydrophilic groups was obtained.

[0069] [Synthesis example of crystalline resin 4 having hydrophilic groups] The reaction was carried out under the same conditions as in the synthesis example of crystalline resin 1, except that the raw materials listed in Table 1 were used and, after reducing the pressure to 1.5 kPa, the reaction was carried out for 8.5 hours while removing the resulting distillate, and 400.06 g of crystalline resin 4 having hydrophilic groups was obtained.

[0070] [Synthesis example of crystalline resin 5 having hydrophilic groups] The reaction was carried out under the same conditions as in the synthesis example of crystalline resin 1, except that the raw materials listed in Table 1 were used and that after reducing the pressure to 1.5 kPa, the reaction was carried out for 6.5 hours while removing the resulting distillate, and 412.94 g of crystalline resin 5 having hydrophilic groups was obtained.

[0071] [Synthesis example of crystalline resin 6 having hydrophilic groups] The reaction was carried out under the same conditions as in the synthesis example of crystalline resin 1, except that the raw materials listed in Table 1 were used and that after reducing the pressure to 1.5 kPa, the reaction was carried out for 3 hours while removing the resulting distillate, and 286.81 g of crystalline resin 6 having hydrophilic groups was obtained.

[0072] [Synthesis example of crystalline resin 7 having hydrophilic groups] The reaction was carried out under the same conditions as in the synthesis example of crystalline resin 1, except that the raw materials listed in Table 1 were used and, after reducing the pressure to 1.5 kPa, the reaction was carried out for 15.5 hours while removing the resulting distillate, and 274.41 g of crystalline resin 7 having hydrophilic groups was obtained.

[0073] [Synthesis example of crystalline resin 8 having hydrophilic groups] The reaction was carried out under the same conditions as in the synthesis example of crystalline resin 1, except that the raw materials listed in Table 1 were used and that after reducing the pressure to 1.5 kPa, the reaction was carried out for 8 hours while removing the resulting distillate, and 321.71 g of crystalline resin 8 having hydrophilic groups was obtained.

[0074] [Synthesis example of crystalline resin 9 having hydrophilic groups] The reaction was carried out under the same conditions as in the synthesis example of crystalline resin 1, except that the raw materials listed in Table 1 were used and, after reducing the pressure to 1.5 kPa, the reaction was carried out for 7 hours while removing the resulting distillate, and 362.20 g of crystalline resin 9 having hydrophilic groups was obtained.

[0075]

[0076] The symbols in Table 1 mean the following: DMT: dimethyl terephthalate (manufactured by SK Yuka Co., Ltd.) NDCM: dimethyl 2,6-naphthalenedicarboxylate (manufactured by Indorama Corporation) DMA: dimethyl adipate (manufactured by Tokyo Chemical Industry Co., Ltd.) DMSeb: dimethyl sebacate (manufactured by Tokyo Chemical Industry Co., Ltd.) DMSuc: dimethyl succinate (manufactured by Tokyo Chemical Industry Co., Ltd.) SID: sodium dimethyl 5-sulfoisophthalate (manufactured by Sanyo Chemical Industries, Ltd.) EG: ethylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 1,3-PD: 1,3-propanediol (manufactured by Tokyo Chemical Industry Co., Ltd.) 1,4-CHDM: 1,4-cyclohexanedimethanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) AcONa: sodium acetate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Ti(OBu) ４ : Tetrabutyl orthotitanate (Tokyo Chemical Industry Co., Ltd.)

[0077] <Evaluation Method> [Proportion of the amount of substance of the monomer unit (monomer unit A) derived from 5-dimethyl sodium sulfoisophthalate to the total amount of substance of all monomer units in the crystalline resin having a hydrophilic group] 10 mg of the crystalline resin having a hydrophilic group was dissolved in a solvent prepared by mixing deuterated chloroform and deuterated trifluoroacetic acid in a mass ratio of 3:2, and proton NMR was measured using an NMR MR400 manufactured by Agilent Corporation. The amount of substance A was calculated by dividing the integral value A of the peak derived from a proton directly bonded to an aromatic ring in a monomer unit (monomer unit A) derived from sodium 5-sulfoisophthalate by the number of protons directly bonded to the aromatic ring present in monomer unit A; the amount of substance B1 was calculated by dividing the integral value B1 of the peak derived from a proton directly bonded to an aromatic ring in a monomer unit (monomer unit B1) derived from the dimethyl aromatic dicarboxylate having no hydrophilic group by the number of protons directly bonded to the aromatic ring present in monomer unit B1; and the amount of substance B2 was calculated by dividing the integral value B2 of the peak derived from a proton directly bonded to the alpha position of an ester in a monomer unit (monomer unit B2) derived from the dimethyl aliphatic dicarboxylate having no hydrophilic group by the number of protons directly bonded to the alpha position present in monomer unit B2. The amount of substance A was divided by twice the sum of the amount of substance A, amount of substance B1, and amount of substance B2, and the value obtained was expressed as a percentage (100 × amount of substance A / (2 × (amount of substance A + amount of substance B1 + amount of substance B2))), which was taken as the ratio of the amount of substance of monomer unit A to the total amount of substance of all monomer units in the crystalline resin having a hydrophilic group. The results are shown in Table 1.

[0078] [Measurement of Weight-Average Molecular Weight] A crystalline resin having hydrophilic groups was dissolved in dimethylformamide to a concentration of 0.1% by mass, and a calibration curve was created from standard polystyrene using gel permeation chromatography (GPC) under the following conditions to determine the weight-average molecular weight (Mw). The results are shown in Table 1. [Measurement Conditions] Apparatus: HLC-8320GPC (manufactured by Tosoh Corporation, detector integrated) Column: α-M x 2 (manufactured by Tosoh Corporation, 7.8 mm I.D. x 30 cm) Eluent: 60 mmol / L phosphoric acid + 50 mmol / L lithium bromide dimethylformamide mixed solution Flow rate: 1.0 mL / min Column temperature: 40°C Detector: RI detector Standard material: polystyrene

[0079] [Sample Preparation Method for DSC and Wide-Angle X-ray Measurement] A 10% by mass crystalline resin dispersion having hydrophilic groups was heated and dried on a hot plate (Digital Hotplate NINOS ND-1, manufactured by AS ONE Corporation) heated to 70°C, and then dried under reduced pressure at 70°C using a vacuum dryer (VACUUM OVEN VOS-451SD, manufactured by Tokyo Rikakikai Co., Ltd.). The obtained resin was pulverized to obtain a crystallized crystalline resin powder. The obtained crystalline resin powder was heated on a hot plate at 150°C for 10 minutes to obtain a resin powder after an amorphization treatment.

[0080] [Glass Transition Temperature] 5 to 10 mg of sample was precisely weighed and sealed in an aluminum pan. Using a DSC device (DSC7020 manufactured by Seiko Instruments Inc.), the sample was heated from 30°C to 230°C at a rate of 10°C / min, and then cooled to 30°C at a cooling rate of 150°C / min. The sample was again heated to 230°C at a rate of 10°C / min, and the glass transition temperature (°C) was determined from the resulting DSC curve. The results are shown in Table 1.

[0081] [Measurement of melting point of crystalline resin having hydrophilic groups (DSC)] 5 mg of crystalline resin powder was placed in an aluminum pan (Hitachi High-Tech Science Corporation GAA-0065, GAA-0064), and the temperature was changed from -60 ° C to 230 ° C, -30 ° C, and 230 ° C at a scanning rate of 10 ° C / min using a differential scanning calorimeter (Hitachi High-Tech Science Corporation DSC7020), and the temperature of the peak top of the melting point occurring in the first run was taken as the melting point of the crystalline resin having hydrophilic groups. The results are shown in Table 1.

[0082] [Confirmation of Crystallinity (Wide-Angle X-Ray Measurement)] Each crystalline resin powder, or a resin powder obtained by amorphizing each crystalline resin at the temperature and time shown in Tables 2, 4, or 5, was placed on a glass plate and placed in a wide-angle X-ray measurement device Mini Flex II (manufactured by Rigaku Corporation) and measured at 32 kV, 15 mA, and a scanning speed of 1° / min. The presence or absence of crystals in the resins according to Examples 1 to 18 and Comparative Examples 1 to 9 was confirmed based on the presence or absence of peaks at diffraction angles 2θ of approximately 17° and 23°. The measurement results are shown in Tables 2 to 5.

[0083] [Evaluation of Solubility of Crystalline Resin Having Hydrophilic Groups] [Preparation of Evaluation Sample] 4.0 g of crystalline resin having hydrophilic groups was added to 16 g of deionized water heated to 70 ° C. using a hot stirrer (manufactured by AS ONE, HS-7BHSD), and the mixture was stirred until all solids were dispersed. Heating was then stopped and the mixture was allowed to cool to room temperature to prepare a 20% by mass dispersion of crystalline resin having hydrophilic groups. The prepared crystalline resin dispersion having hydrophilic groups was applied to the corona-treated surface of a PET film (manufactured by Futamura Chemical Co., Ltd., FE2001 #25) that had been corona-treated on one side by gravure solid printing using a desktop gravure printing machine (manufactured by Matsuo Sangyo Co., Ltd., K Printing Proofer). The dispersion was then heated to 90°C on a hotplate (Digital Hotplate NINOS ND-1, manufactured by AS ONE Corporation) and held there for 5 minutes for drying to obtain a PET film having a coating containing a crystalline resin having hydrophilic groups. Note that for crystalline resin 10, the prepared dispersion was allowed to stand for 24 hours, and the resulting small amount of insoluble matter was removed, and the supernatant was then coated onto a PET film.

[0084] [Amorphization Treatment] A PET film having a coating containing a crystalline resin having a hydrophilic group was placed on a hot plate heated to a temperature shown in Table 2, 4, or 5, and heated for a time shown in Table 2, 4, or 5 to amorphize the crystalline resins 1 to 10, thereby obtaining evaluation samples according to Examples 1 to 18.

[0085] [pH of Neutral Water] Tap water was used as the neutral water used in the evaluation of removability described below. Tap water (neutral water) was collected in a beaker, and the pH was measured using a glass electrode under the following conditions. The pH was 7.44. Tap water (neutral water) temperature: 23°C Glass electrode: 9615S-10D (manufactured by HORIBA) pH meter: F-72 (manufactured by HORIBA) The above operation was performed after calibrating the pH and glass electrode using a standard buffer solution (phthalate pH buffer) pH 4.01 (25°C) (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), a standard buffer solution (neutral phosphate pH buffer) pH 6.86 (25°C) (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), and a standard buffer solution (borate pH buffer) pH: 9.18 (25°C) (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.).

[0086] [Evaluation of Removability with Neutral Water] (Examples 1 to 17, Comparative Examples 1 to 9) Evaluation samples (2 cm x 2 cm) according to Examples 1 to 17 and Comparative Examples 1 to 9 were attached to a glass slide (S2112, 76 mm x 26 mm, manufactured by Matsunami Glass Industrial Co., Ltd.) using double-sided tape. The glass slide was suspended by clips at its edges and placed in a 500 mL beaker containing 400 mL of tap water (neutral water) at the temperatures listed in Tables 2 to 4, which was being stirred with a magnetic stirrer, so that the PET film was completely submerged in water. The deinking time was defined as the time until the coating containing the crystalline resin having hydrophilic groups on the film was completely removed. If the coating was not removed even after 120 minutes of placement in water, the sample was evaluated as "no removal." The evaluation results are shown in Tables 2 to 4.

[0087]

[0088]

[0089]

[0090] (Example 18, Comparative Example 10) In the same manner as in Example 1, the PET film was placed so that it was completely submerged in water at 70°C. After 120 minutes had passed, the coating had not been removed from any of the evaluation samples. The evaluation samples were removed, and the ink releasability was evaluated by rubbing the surface with a rubber glove. The evaluation results are shown in Table 5.

[0091]

Claims

1. A method for improving the dispersibility of a crystalline resin having a hydrophilic group in neutral water, comprising an amorphization step of amorphizing the crystalline resin having a hydrophilic group.

2. The method according to claim 1 , wherein the melting point Tm of the crystalline resin having a hydrophilic group is 70° C. or more and 200° C. or less.

3. The method according to claim 1, wherein the glass transition temperature of the crystalline resin having a hydrophilic group is from -10°C to 180°C.

4. The method according to claim 1 , wherein the content of the hydrophilic group in the crystalline resin having a hydrophilic group is 0.4 mmol / g or more and 3.0 mmol / g or less.

5. The method according to claim 1 , wherein the crystalline resin having a hydrophilic group is a crystalline water-soluble resin having a monomer unit A having a hydrophilic group and a monomer unit B not having a hydrophilic group.

6. The method according to claim 1 , wherein the molar ratio of the monomer unit A to the monomer unit B in the crystalline resin having a hydrophilic group (monomer unit A / monomer unit B) is 10 / 90 or more and 70 / 30 or less.

7. The method according to claim 1 , wherein the weight average molecular weight of the crystalline resin having a hydrophilic group is 1,000 or more and 80,000 or less.

8. The method according to claim 1 , wherein the amorphization step comprises a heat treatment step of heat treating the crystalline resin having a hydrophilic group.

9. The method according to claim 8, wherein in the heat treatment step, the heat treatment of the crystalline resin having a hydrophilic group is carried out under non-shear conditions.

10. The method according to claim 8, wherein the heat treatment temperature of the crystalline resin having a hydrophilic group in the heat treatment step is Tm+10°C or higher and Tm+70°C or lower, where Tm is the melting point of the crystalline resin having a hydrophilic group.

11. The method according to claim 8, wherein the heat treatment temperature of the crystalline resin having a hydrophilic group in the heat treatment step is 110°C or higher and 220°C or lower.

12. The method according to claim 1 , wherein the hydrophilic group is one or more types selected from the group consisting of anionic groups.

13. The method according to claim 1 , wherein the crystalline resin having a hydrophilic group is a water-soluble polyester resin.

14. The method of claim 1 , wherein the crystalline resin having hydrophilic groups is a used resin.

15. The method according to claim 1 , wherein the crystalline resin having a hydrophilic group is contained in a printed matter, an adhesive, a pressure-sensitive adhesive, or a coating.

16. A method for improving the dispersibility of a crystalline resin having a hydrophilic group in neutral water by the method according to any one of claims 1 to 15, and then dispersing the crystalline resin having a hydrophilic group in neutral water.

17. A coating removal method comprising the method according to any one of claims 1 to 15.