Resin particle dispersion for paper coating

Abstract

To provide a resin particle dispersion for paper coating capable of obtaining coated paper having excellent water repellency and water resistance, a coating liquid for paper containing the resin particle dispersion, coated paper using the coating liquid for paper, and a manufacturing method of the coated paper.SOLUTION: Disclosed are: a resin particle dispersion for paper coating, a coating liquid for paper containing the resin particle dispersion, coated paper using the coating liquid for paper, and a manufacturing method of the coated paper, wherein the resin particle dispersion includes a polyester-based resin X, the polyester-based resin X includes an amorphous polyester-based resin A and a crystalline polyester-based resin C, and a mass ratio of the amorphous polyester-based resin A to the crystalline polyester-based resin C in the polyester-based resin X, (amorphous polyester-based resin A / crystalline polyester-based resin C) is 5 / 95 or more and 94 / 6 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin particle dispersion for paper coating, a paper coating solution containing the resin particle dispersion, coated paper using the paper coating solution, and a method for manufacturing the coated paper. [Background technology]

[0002] Traditionally, paper materials used for paper labels, packaging, and containers requiring water resistance have been paper laminated with plastic films such as polyethylene or polypropylene to provide water resistance and water repellency. However, paper laminated with plastic films is difficult to recycle. Therefore, with the growing environmental awareness in recent years, there has been a demand for and investigation of alternative technologies to lamination that can provide water resistance and water repellency.

[0003] For example, Patent Document 1 describes a paper coating agent that can be used for food packaging paper and has hydrolyzable and biodegradable properties, and contains an aliphatic polyester as an active ingredient, which has a structural unit consisting of one unit selected from the group consisting of oxyacid units, diol units, dicarboxylic acid units and cyclic ester units, and a polyvalent cyanate unit, and a laminated paper made of the aliphatic polyester and paper. Patent Document 2 describes a paper coating agent comprising a water-soluble polyester and a pigment, which has excellent coating properties and, when applied to paper, provides coated paper with excellent water resistance and other properties. Patent Document 3 provides a moisture-proof laminate that is completely wax-free, yet possesses high moisture resistance and can be recovered as recycled paper. In this moisture-proof paper, a moisture-proof composition layer is formed on at least one side of a paper support, consisting of a flat pigment with an aspect ratio of 5 or more and an average particle size of 5 to 50 μm and a synthetic resin, wherein 0.1 to 10 g / m² of pigment is applied to the moisture-proof composition layer. 2 A moisture-proof laminate having a coating layer made of a cross-linked water-soluble resin is described. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2001-62977 [Patent Document 2] Japanese Patent Application Publication No. 3-279495 [Patent Document 3] Japanese Patent Application Publication No. 9-268494 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, the technologies described in Patent Documents 1 to 3 could not achieve sufficient water repellency and water resistance. The object of the present invention is to provide a resin particle dispersion for paper coating that can produce coated paper with excellent water repellency and water resistance, a paper coating solution containing the resin particle dispersion, coated paper using the paper coating solution, and a method for manufacturing the coated paper. [Means for solving the problem]

[0006] The inventors focused on providing a coating layer that suppresses contact between paper and water, similar to paper laminated with a plastic film, and found that the aforementioned problem can be solved by using a resin particle dispersion liquid containing a polyester resin as the resin particle dispersion liquid for forming the coating layer, and by including a specific amorphous polyester resin and a specific crystalline polyester resin in the polyester resin.

[0007] In other words, the present invention provides the following [1] to [4]. [1] A resin particle dispersion containing polyester resin X, The polyester resin X comprises amorphous polyester resin A and crystalline polyester resin C. The mass ratio of amorphous polyester resin A to crystalline polyester resin C in polyester resin X (amorphous polyester resin A / crystalline polyester resin C) is 5 / 95 or more and 94 / 6 or less. Resin particle dispersion for paper coating. [2] A coating liquid for paper containing the resin particle dispersion described in [1] above. [3] Coated paper having a coating layer obtained by coating at least one side of a paper substrate with the paper coating liquid described in [2] above. [4] A method for manufacturing coated paper, comprising: step 1 of applying the paper coating liquid described in [2] above to at least one side of a paper substrate; and step 2 of drying the paper coating liquid on the paper substrate coated in step 1. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a resin particle dispersion for paper coating that can produce coated paper with excellent water repellency and water resistance, a paper coating solution containing the resin particle dispersion, coated paper using the paper coating solution, and a method for producing the coated paper. [Modes for carrying out the invention]

[0009] [Resin particle dispersion for paper coating] The resin particle dispersion for paper coating of the present invention (hereinafter also simply referred to as "resin particle dispersion") is a resin particle dispersion containing a polyester resin X, wherein the polyester resin X includes amorphous polyester resin A and crystalline polyester resin C, and the mass ratio of amorphous polyester resin A to crystalline polyester resin C in the polyester resin X (amorphous polyester resin A / crystalline polyester resin C) is 5 / 95 or more and 94 / 6 or less.

[0010] The resin particle dispersion of the present invention is preferably one in which resin particles are dispersed in an aqueous medium. Here, "water system" means that water makes up the largest proportion in the medium. Deionized water, ion-exchanged water, or distilled water are preferably used as the water in the aqueous medium. The aqueous medium may further contain an organic solvent. Examples of the organic solvent include water-soluble organic solvents that are soluble in water, such as aliphatic alcohols having 1 to 4 carbon atoms like methanol, ethanol, 2-propanol; ketones having 3 to 8 carbon atoms like acetone, methyl ethyl ketone; and ethers like diethyl ether, tetrahydrofuran. From the perspective of environmental impact, the water content in the aqueous medium is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, even more preferably 95% by mass or more, and preferably 100% by mass or less, and even more preferably 100% by mass.

[0011] The definitions of various terms in this specification are shown below. The crystallinity of the resin is represented by the crystallinity index defined as the ratio of the softening point to the maximum peak temperature of endothermic by a differential scanning calorimeter (DSC), that is, "softening point (°C) / maximum peak temperature of endothermic (°C)". The "crystalline resin" refers to a resin having a crystallinity index of 0.6 or more and 1.4 or less. The "amorphous resin" refers to a resin in which no endothermic peak is observed by a differential scanning calorimeter (DSC), or if an endothermic peak is observed, the crystallinity index is less than 0.6 or more than 1.4. The maximum peak temperature of endothermic refers to the temperature of the peak with the largest peak area among the endothermic peaks observed under the conditions of the measurement method described in the examples. The crystallinity of the resin can be adjusted by the type and ratio of the raw material monomers, and manufacturing conditions (for example, reaction temperature, reaction time, cooling rate), etc. The "carboxylic acid component" includes not only carboxylic acids but also their anhydrides and their alkyl esters having 1 to 3 carbon atoms, etc. That is, in this specification, when only the name of the carboxylic acid is described, it is assumed that the anhydride of the carboxylic acid and its alkyl esters having 1 to 3 carbon atoms, etc. are also included.

[0012] According to the present invention, it is possible to provide a resin particle dispersion that can impart water resistance and water repellency to paper when coated with it. The detailed mechanism by which the resin particle dispersion of the present invention can impart water repellency and water resistance to paper is not clear, but it is thought to be as follows. Generally, in dispersions of resin particles dispersed in an aqueous medium, the resin component of the resin particles is known to be a non-crystalline resin such as acrylic resin or polyurethane resin. However, because these resins are relatively polar and hydrophilic in order to obtain dispersibility in aqueous mediums, coating paper with a dispersion of resin particles using such resins does not impart good water repellency. Therefore, dispersions of hydrophobic materials such as paraffin wax and synthetic wax have been used as paper coatings to impart water repellency to paper. Because these materials are crystalline, when applied to paper, they can impart water repellency due to their hydrophobicity and crystallinity. However, these hydrophobic materials do not contain ester bonds, hydroxyl groups, or carboxyl groups, or contain only small amounts. Perhaps due to the low affinity between the hydrophobic material and paper, they have poor water resistance. Furthermore, when the crystals melt due to the heat generated during drying after application to the paper, they penetrate into the paper, resulting in the need for a large amount of processing to obtain sufficient water repellency and water resistance. As a result, further improvements have been sought. On the other hand, in the present invention, the polyester resin X contained in the resin particles dispersed in the resin particle dispersion contains amorphous polyester resin A and crystalline polyester resin C. When a coating layer is formed on a paper substrate using the resin particle dispersion, the crystalline polyester resin C crystallizes in the coating layer, which is thought to impart high water repellency to the coated paper. In addition, since amorphous polyester resin A and crystalline polyester resin C are both polyesters, they have high affinity, and their compatibility in the coating layer results in a smooth surface and an improved uniformity of the coating layer. Furthermore, due to their high affinity for each other, even if the crystalline polyester crystals melt due to the heat of the drying process after coating, the amorphous polyester resin suppresses penetration into the paper, thus forming a good coating layer on the paper surface. Therefore, it is thought that high water repellency and water resistance can be imparted to the coated paper. In addition, the presence of ester bond sites and terminal hydroxyl and carboxyl groups in the polyester resin skeleton contained in the polyester resin X contained in the resin particles has a high affinity with cellulose, the main component of paper. This is thought to improve the adhesion between the formed coating layer and the paper substrate, thereby imparting high water repellency and water resistance to the coated paper.

[0013] <Polyester resin X> In the present invention, the polyester resin X contained in the resin particles includes amorphous polyester resin A (hereinafter also referred to as "resin A") and crystalline polyester resin C (hereinafter also referred to as "resin C"). The polyester resin X may contain resin A and resin C in the same resin particle, or resin A and resin C may be contained in separate resin particles.

[0014] [Amorphous polyester resin A] Resin A contains a polycondensate of a diol-containing alcohol component (A-al) (hereinafter also simply referred to as "alcohol component (A-al)") and a divalent or higher carboxylic acid component (A-ac) (hereinafter also simply referred to as "carboxylic acid component (A-ac)"), from the viewpoint of improving the water repellency and water resistance of the resulting coated paper. Resin A is not particularly limited as long as it contains a polycondensate of an alcohol component (A-al) and a carboxylic acid component (A-ac). Examples include polyester resins made from polycondensates and modified polyester resins. Examples of modified polyester resins include composite resins containing polyester resin segments and addition polymerization resin segments, urethane-modified polyester resins, and epoxy-modified polyester resins. Among these, resin A is preferably an amorphous polyester resin which is a polycondensate of an alcohol component (A-al) and a carboxylic acid component (A-ac).

[0015] (Alcohol content (A-al)) The alcohol component (A-al) constituting resin A contains linear or branched aliphatic diols, aromatic diols, and alicyclic diols, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper. The alcohol component (A-al) may be used individually or in combination of two or more types.

[0016] Examples of linear or branched aliphatic diols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 2,4-pentanediol, 1,2-hexanediol, 1,5-hexanediol, and 2,5-hexanediol. Examples include linear or branched aliphatic diols such as ol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, 1,14-tetradecanediol, 1,16-hexadecanediol, 3,3-dimethyl-1,2-butanediol, and 2,2-dimethyl-1,3-propanediol, with aliphatic diols having 2 to 10 carbon atoms being preferred.

[0017] Examples of aromatic diols include alkylene oxide adducts of bisphenol A. The alkylene oxide adduct of bisphenol A is preferably a compound represented by the following general formula (I).

[0018] [ka]

[0019] In general formula (I), OR 1 , and R 2 Each of the O groups is an alkylene oxy group, preferably an alkylene oxy group having 1 to 4 carbon atoms independently, more preferably an ethylene oxy group or a propylene oxy group, and even more preferably a propylene oxy group. x and y correspond to the number of moles of alkylene oxide added. The average value of the sum of x and y is preferably 2 or more, preferably 7 or less, more preferably 5 or less, and even more preferably 3 or less. x pieces OR 1 and y R 2 O may be the same or different in each case, but it is preferable that they be the same from the viewpoint of improving the adhesion of the formed coating layer to the paper substrate.

[0020] The alkylene oxide adduct of bisphenol A may be used individually or in combination of two or more types. The alkylene oxide adduct of bisphenol A is preferably one or more selected from propylene oxide adduct of bisphenol A and ethylene oxide adduct of bisphenol A, and more preferably a combination of propylene oxide adduct of bisphenol A and ethylene oxide adduct of bisphenol A.

[0021] Examples of alicyclic diols include cyclohexanediol, cyclohexanedimethanol, and hydrogenated bisphenol A.

[0022] The above-mentioned diols can be used individually or in combination of two or more types. Among these, the alcohol component (A-al) preferably contains one or more selected from linear or branched aliphatic diols having 2 to 10 carbon atoms and alkylene oxide adducts of bisphenol A, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper; more preferably contains one or more selected from ethylene glycol, branched aliphatic diols, and alkylene oxide adducts of bisphenol A; even more preferably contains one or more selected from ethylene glycol, 1,2-propanediol, 2,3-butanediol, ethylene oxide adducts of bisphenol A, and propylene oxide adducts of bisphenol A; and even more preferably contains one or more selected from ethylene glycol, 1,2-propanediol, and 2,3-butanediol.

[0023] The alcohol component (A-al) may contain other alcohols besides the aforementioned diol, as long as it does not impair the effects of the present invention. Examples of other alcohols include polyhydric alcohols of trihydric or higher hydricity. Examples of polyhydric alcohols with a valency of 3 or higher include glycerin, pentaerythritol, trimethylolpropane, sorbitol, and sorbitan. Other alcohols may be used individually or in combination of two or more.

[0024] The content of diol in the alcohol component (A-al) is preferably 60 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and preferably 100 mol% or less, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper.

[0025] (Carboxylic acid component (A-ac)) The carboxylic acid component (A-ac) constituting resin A can be an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, a trivalent or higher aromatic polycarboxylic acid, a trivalent or higher aliphatic polycarboxylic acid, etc. The carboxylic acid component (A-ac) may be used individually or in combination of two or more types. Examples of aromatic dicarboxylic acids include phthalic acid, isophthalic acid, and terephthalic acid. Among these, isophthalic acid, terephthalic acid, and more preferably terephthalic acid are preferred from the viewpoint of improving the water repellency and water resistance of the resulting coated paper. Examples of aliphatic dicarboxylic acids include straight-chain, branched-chain, or alicyclic aliphatic dicarboxylic acids such as fumaric acid, adipic acid, sebacic acid, maleic acid, azelaic acid, succinic acid, succinic acid substituted with hydrocarbon groups having 1 to 20 carbon atoms, and cyclohexanedicarboxylic acid. Specific examples of succinic acid substituted with hydrocarbon groups having 1 to 20 carbon atoms include dodecyl succinic acid, dodecenyl succinic acid, and octenyl succinic acid. Among these, fumaric acid is preferred as the aliphatic dicarboxylic acid from the viewpoint of improving the water repellency and water resistance of the resulting coated paper. Examples of aromatic polycarboxylic acids with a valency of 3 or higher include trimellitic acid, 2,5,7-naphthalentricarboxylic acid, and pyromellitic acid. Examples of aliphatic polycarboxylic acids with a valency of three or more include aconitic acid. Among these, the carboxylic acid component (A-ac) preferably includes one or more selected from aromatic dicarboxylic acids and aliphatic dicarboxylic acids, more preferably includes an aromatic dicarboxylic acid, and even more preferably includes both aromatic dicarboxylic acids and aliphatic dicarboxylic acids, from the viewpoint of improving the water repellency and water resistance of the coated paper.

[0026] The total content of aromatic dicarboxylic acids and aliphatic dicarboxylic acids in the carboxylic acid component (A-ac) is preferably 60 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, and preferably 100 mol% or less, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper.

[0027] The content of aromatic dicarboxylic acid in the carboxylic acid component (A-ac) is preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 65 mol% or more, and preferably 100 mol% or less, more preferably 95 mol% or less, and even more preferably 90 mol% or less, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper.

[0028] When the carboxylic acid component (A-ac) contains a trivalent or higher aromatic polycarboxylic acid, the content of the trivalent or higher aromatic polycarboxylic acid is preferably 3 mol% or more, more preferably 5 mol% or more, even more preferably 7 mol% or more, even more preferably 10 mol% or more, and preferably 35 mol% or less, more preferably 25 mol% or less, even more preferably 20 mol% or less, and even more preferably 15 mol% or less.

[0029] The equivalent ratio (COOH group / OH group) of the carboxyl group (COOH group) of the carboxylic acid component (A-ac) to the hydroxyl group (OH group) of the alcohol component (A-al) constituting resin A is preferably 0.90 or higher, more preferably 0.95 or higher, and preferably 1.10 or lower, more preferably 1.05 or lower.

[0030] The content of the polycondensate of the alcohol component (A-al) and the carboxylic acid component (A-ac) in resin A is preferably 90% by mass or more, more preferably 95% by mass or more, and preferably 100% by mass or less, more preferably 100% by mass, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper.

[0031] (Method for producing amorphous polyester resin A) Resin A may be produced, for example, by polycondensation of an alcohol component (A-al) and a carboxylic acid component (A-ac).

[0032] The polycondensation of an alcohol component (A-al) and a carboxylic acid component (A-ac) can be produced, for example, by polycondensing the alcohol component (A-al) and the carboxylic acid component (A-ac) in an inert gas atmosphere at a temperature of 120°C to 250°C, using the following esterification catalysts, esterification co-catalysts, and radical polymerization inhibitors as needed.

[0033] Examples of esterification catalysts include tin compounds such as dibutyltin oxide and tin(II) di(2-ethylhexanoate), and titanium compounds such as titanium diisopropoxybis(triethanolamine). Examples of esterification co-catalysts that can be used together with the esterification catalyst include gallic acid. The amount of esterification catalyst used is preferably 0.01 parts by mass or more and 10 parts by mass or less, based on 100 parts by mass of the total amount of the alcohol component (A-al) and carboxylic acid component (A-ac), which are raw material monomers of resin A. The amount of esterification co-catalyst used is preferably 0.001 parts by mass or more and 1 part by mass or less, based on 100 parts by mass of the total amount of the alcohol component (A-al) and the carboxylic acid component (A-ac). Examples of polymerization inhibitors include radical polymerization inhibitors such as 4-tert-butylcatechol. When a polymerization inhibitor is used, the amount of polymerization inhibitor used is preferably 0.001 parts by mass or more and 1 part by mass or less per 100 parts by mass of the total amount of the alcohol component (A-al) and the carboxylic acid component (A-ac).

[0034] (Physical properties of amorphous polyester resin A) The softening point of resin A is preferably 80°C or higher, more preferably 90°C or higher, even more preferably 100°C or higher, and preferably 140°C or lower, more preferably 130°C or lower, and even more preferably 120°C or lower, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper. The aforementioned softening point is measured by the method described in the examples.

[0035] The glass transition temperature of resin A is preferably 35°C or higher, more preferably 40°C or higher, even more preferably 45°C or higher, and even more preferably 50°C or higher, and preferably 85°C or lower, more preferably 80°C or lower, even more preferably 75°C or lower, and even more preferably 70°C or lower, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper. The glass transition temperature is measured using a differential scanning calorimeter, specifically by the method described in the examples.

[0036] The acid value of resin A is preferably 3 mg KOH / g or more, more preferably 5 mg KOH / g or more, even more preferably 10 mg KOH / g or more, and preferably 40 mg KOH / g or less, more preferably 30 mg KOH / g or less, and even more preferably 25 mg KOH / g or less, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper. The acid value is measured by the method described in the examples.

[0037] Resin A may be used individually or in combination of two or more types. The softening point, glass transition temperature, and acid value of resin A can be appropriately adjusted depending on the type and amount of raw material monomer used, as well as manufacturing conditions such as reaction temperature, reaction time, and cooling rate. These values ​​can be determined by the method described in the examples. Furthermore, when using two or more types of resin A in combination, it is preferable that the softening point, glass transition temperature, and acid value obtained from the mixture thereof are all within the aforementioned ranges.

[0038] The content of resin A in the total amount of polyester resin X is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and preferably 94% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper.

[0039] [Crystalline polyester resin C] Resin C contains a polycondensate of an alcohol component (C-al) containing an aliphatic diol (hereinafter also simply referred to as "alcohol component (C-al)") and a divalent or higher carboxylic acid component (C-ac) (hereinafter also simply referred to as "carboxylic acid component (C-ac)"). Examples of resin C include crystalline polyester resins composed of polycondensates and modified crystalline polyester resins. Examples of modified crystalline polyester resins include crystalline composite resins containing polyester resin segments and addition polymerization resin segments, urethane-modified crystalline polyester resins, and epoxy-modified crystalline polyester resins. Among these, resin C is preferably a crystalline polyester resin which is a polycondensate of an alcohol component (C-al) and a carboxylic acid component (C-ac).

[0040] (Alcohol content (C-al)) The alcohol component (C-al) constituting resin C contains an aliphatic diol, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper. The alcohol component (C-al) may be used alone or in combination of two or more types. From the same viewpoint as above, the aliphatic diol is preferably an α,ω-aliphatic diol. Examples of α,ω-aliphatic diols include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, and 1,16-hexadecanediol. The number of carbon atoms in the α,ω-aliphatic diol is preferably 2 or more, preferably 6 or less, more preferably 5 or less, and even more preferably 4 or less. Among these, the α,ω-aliphatic diol is preferably one or more selected from ethylene glycol, 1,3-propanediol, and 1,4-butanediol, more preferably ethylene glycol and 1,4-butanediol.

[0041] The alcohol component (C-al) may contain alcohols other than α,ω-aliphatic diols. Examples of other alcohols include aliphatic diols other than α,ω-aliphatic diols such as 1,2-propanediol and neopentyl glycol; aromatic diols such as alkylene oxide adducts of bisphenol A; and trivalent or higher alcohols such as glycerin, pentaerythritol, and trimethylolpropane. These alcohol components may be used individually or in combination of two or more.

[0042] The content of α,ω-aliphatic diol in the alcohol component (C-al) constituting resin C is preferably 80 mol% or more, more preferably 85 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and preferably 100 mol% or less, and more preferably 100 mol%, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper.

[0043] When the alcohol component (A-al) constituting resin A is a linear or branched aliphatic diol with 2 to 10 carbon atoms, the difference between the number of carbon atoms in the linear or branched aliphatic diol constituting resin A and the number of carbon atoms in the aliphatic diol constituting resin C is preferably 0 to 2. By designing the molecules in this way, the affinity between resin A and resin C is further increased, resulting in a smoother surface and improved uniformity of the coating layer formed on a paper substrate using the resin particle dispersion, thus enabling the production of coated paper with superior water repellency and water resistance. When the alcohol component (A-al) contains two or more linear or branched aliphatic diols with 2 to 10 carbon atoms and / or when the alcohol component (C-al) contains two or more aliphatic diols, the difference between the number of carbon atoms of the linear or branched aliphatic diols with 2 to 10 carbon atoms constituting resin A and the number of carbon atoms of the aliphatic diols constituting resin C shall be the difference in the number of carbon atoms of the linear or branched aliphatic diol / aliphatic diol with 2 to 10 carbon atoms that has the highest molar ratio (mol%) in the alcohol component constituting each resin. Furthermore, if two or more linear or branched aliphatic diols with 2 to 10 carbon atoms that have the highest molar ratio are included in the same ratio, a coated paper with superior water repellency and water resistance can be obtained if the difference in the number of carbon atoms of at least one of the two or more linear or branched aliphatic diols / aliphatic diols constituting each resin is 0 or more and 2 or less. The number of carbon atoms in the straight-chain or branched aliphatic diol with 2 to 10 carbon atoms that constitutes resin A, and the number of carbon atoms in the aliphatic diol that constitutes resin C, may be greater in either case.

[0044] When the alcohol component (A-al) constituting resin A is an aromatic diol, particularly an alkylene oxide adduct of bisphenol A, it is preferable that the aliphatic diol constituting resin C has 2 to 5 carbon atoms. By designing the molecules in this way, the affinity between resin A and resin C is further increased, resulting in a smoother surface and improved uniformity of the coating layer formed on a paper substrate using a resin particle dispersion, thus enabling the production of coated paper with superior water repellency and water resistance. If the alcohol component (C-al) contains two or more aliphatic diols, the number of carbon atoms in the aliphatic diol constituting resin C shall be the number of carbon atoms of the aliphatic diol with the highest molar ratio (mol%) in the alcohol component constituting resin C. If two or more aliphatic diols with the highest molar ratio are present in the same proportion, it is sufficient that at least one of the two aliphatic diols has a carbon number between 2 and 5.

[0045] (Carboxylic acid component (C-ac)) The carboxylic acid component (C-ac) constituting resin C preferably includes an aliphatic dicarboxylic acid, and more preferably a linear aliphatic dicarboxylic acid, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper. The carboxylic acid component (C-ac) may be used alone or in combination of two or more types. The number of carbon atoms in the aliphatic dicarboxylic acid is preferably 4 or more, more preferably 8 or more, even more preferably 10 or more, and preferably 14 or less. Examples of aliphatic dicarboxylic acids include sebacic acid, octanodioic acid, dodecanedioic acid, tetradecanedioic acid, fumaric acid, and succinic acid. Among these, sebacic acid, dodecanedioic acid, and tetradecanedioic acid are preferred, with sebacic acid and tetradecanedioic acid being more preferred.

[0046] The carboxylic acid component (C-ac) constituting resin C may contain carboxylic acids other than aliphatic dicarboxylic acids. Examples of other carboxylic acids include monocarboxylic acids such as benzoic acid and stearic acid, aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, and polycarboxylic acids with a valency of three or more. These carboxylic acid components may be used individually or in combination of two or more.

[0047] The content of aliphatic dicarboxylic acid in the carboxylic acid component (C-ac) constituting resin C is preferably 80 mol% or more, more preferably 85 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and preferably 100 mol% or less, and even more preferably 100 mol%.

[0048] The equivalent ratio [COOH group / OH group] of the carboxyl group of the carboxylic acid component (C-ac) to the hydroxyl group of the alcohol component (C-al) is preferably 0.8 or higher, more preferably 0.9 or higher, and preferably 1.2 or lower, more preferably 1.1 or lower.

[0049] The content of the polycondensate of the alcohol component (C-al) and the carboxylic acid component (C-ac) in resin C is preferably 90% by mass or more, more preferably 95% by mass or more, and preferably 100% by mass or less, more preferably 100% by mass, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper.

[0050] A method for manufacturing resin C can be, for example, the same method as described above for resin A.

[0051] (Physical properties of crystalline polyester resin C) The softening point of resin C is preferably 40°C or higher, more preferably 50°C or higher, even more preferably 60°C or higher, and preferably 120°C or lower, more preferably 110°C or lower, and even more preferably 100°C or lower, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper. The melting point of resin C is preferably 40°C or higher, more preferably 50°C or higher, even more preferably 60°C or higher, and preferably 120°C or lower, more preferably 110°C or lower, and even more preferably 100°C or lower, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper. The acid value of resin C is preferably 5 mg KOH / g or more, more preferably 10 mg KOH / g or more, even more preferably 15 mg KOH / g or more, and preferably 40 mg KOH / g or less, more preferably 35 mg KOH / g or less, and even more preferably 30 mg KOH / g or less. The softening point, melting point, and acid value of resin C can be appropriately adjusted depending on the type and amount of raw material monomer used, as well as manufacturing conditions such as reaction temperature, reaction time, and cooling rate, and can be determined by the method described in the examples below. When two or more types of resin C are used in combination, it is preferable that the softening point, melting point, and acid value obtained as a mixture thereof are within the aforementioned ranges.

[0052] The content of resin C in the total amount of polyester resin X is preferably 6% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper.

[0053] The mass ratio of resin A to resin C in the polyester resin X (resin A / resin C) is 5 / 95 or more, preferably 10 / 90 or more, more preferably 15 / 85 or more, and 94 / 6 or less, preferably 90 / 10 or less, more preferably 85 / 15 or less, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper. When the alcohol component (A-al) constituting resin A is a linear or branched aliphatic diol and / or alicyclic diol, the mass ratio of resin A to resin C in the polyester resin X (resin A / resin C) is 5 / 95 or more, preferably 10 / 90 or more, more preferably 15 / 85 or more, and 94 / 6 or less, preferably 90 / 10 or less, more preferably 85 / 15 or less. When the alcohol component (A-al) constituting resin A is an aromatic diol, the mass ratio of resin A to resin C in polyester resin X (resin A / resin C) is 5 / 95 or more, preferably 10 / 90 or more, more preferably 15 / 85 or more, and preferably 65 / 35 or less, more preferably 60 / 40 or less, and even more preferably 55 / 45 or less.

[0054] In the present invention, resins A and C are preferably substantially water-insoluble from the viewpoint of improving the water repellency and water resistance of the resulting coated paper. Because resins A and C are water-insoluble, the polyester resin X becomes water-insoluble, and the coating layer formed by coating the paper substrate with a resin particle dispersion becomes water-insoluble, thereby improving the water repellency and water resistance of the coated paper. Here, "substantially water-insoluble" means that when resin A or resin C, which has been vacuum-dried at 40°C for 12 hours and reached a constant weight, is dissolved in 100g of water at 25°C until saturated, the amount dissolved is 1g or less. If resins A and C contain acidic groups, the amount dissolved is the amount dissolved after neutralizing the acidic groups of resins A and C with 100 mol% sodium hydroxide.

[0055] In the present invention, if the polyester resin X contains an acidic group, it is preferable that the polyester resin X is a neutralized product of a basic compound from the viewpoint of improving the dispersion stability of resin particles in an aqueous medium. Basic compounds include metallic basic compounds and non-metallic basic compounds. Basic compounds may be used individually or in combination of two or more. Examples of metal-based compounds include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide. Examples of nonmetallic basic compounds include nitrogen-containing basic substances such as ammonia, trimethylamine, and diethanolamine.

[0056] The equivalent amount of basic compound used is preferably 50 mol% or more, more preferably 55 mol% or more, even more preferably 60 mol% or more, and preferably 100 mol% or less. The equivalent amount of basic compound used can be determined by the following formula (1). If the equivalent amount of basic compound used is 100 mol% or less, it is equivalent to the degree of neutralization. If the equivalent amount of basic compound used exceeds 100 mol% in the following formula, it means that the basic compound is in excess of the acidic groups of polyester resin X, and in this case, the degree of neutralization of polyester resin X is considered to be 100 mol%. Equivalent amount of basic compound used (mol%) = {[Mass of basic compound added (g) / Equivalent amount of basic compound (g / mol)] / [[Acid value of polyester resin X (mgKOH / g) × Mass of polyester resin X (g)] / (56.1 × 1000 (mgKOH / mol))]} × 100 (1)

[0057] Furthermore, the resin particles according to the present invention may also contain resins other than polyester resin X, such as acrylic resins like styrene-acrylic copolymers or polyurethane resins, to the extent that they do not impair the effects of the present invention. Furthermore, the resin particles according to the present invention may contain reinforcing fillers such as fibrous materials, additives such as antioxidants, etc., as optional components, to the extent that they do not impair the effects of the present invention. The content of polyester resin X in the resin particles according to the present invention is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and preferably 100% by mass or less, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper.

[0058] (Manufacturing of resin particle dispersion) The resin particle dispersion of the present invention is preferably produced by a method of dispersing a resin containing polyester resin X in an aqueous medium. Methods for dispersing a resin containing polyester resin X in an aqueous medium include (i) a method of dispersing resin particles containing polyester resin X that pre-contain resin A and resin C in an aqueous medium, and (ii) a method of mixing separately obtained aqueous dispersions of resin particles containing resin A and aqueous dispersions of resin particles containing resin C. Of these, method (i) of dispersing resin particles containing polyester resin X that pre-contain resin A and resin C in an aqueous medium is more preferable. The following explanation will describe method (i) described above.

[0059] Methods for obtaining a resin particle dispersion include adding a resin containing polyester resin X to an aqueous medium and performing dispersion treatment using a disperser or the like, and gradually adding an aqueous medium to a solution of resin containing polyester resin X to perform phase inversion emulsification. Among these, the phase inversion emulsification method is preferred from the viewpoint of improving the water repellency and water resistance of the resulting coated paper.

[0060] In phase inversion emulsification, it is preferable to first dissolve a resin containing polyester resin X in an organic solvent to obtain a resin solution, then add an aqueous medium to the solution to perform phase inversion, and then remove the organic solvent. Organic solvents for dissolving the resin containing polyester resin X include ketone solvents such as acetone and dialkylketones having an alkyl group with 1 to 3 carbon atoms, such as methyl ethyl ketone; ether solvents such as dibutyl ether and tetrahydrofuran; ester solvents such as ethyl acetate and isopropyl acetate; and alkyl halide solvents such as dichloromethane and chloroform. Among these, from the viewpoint of dissolving the resin containing resin A and resin C and easily removing it from the emulsion, dialkylketones having an alkyl group with 1 to 3 carbon atoms, such as acetone and methyl ethyl ketone, are preferred, and methyl ethyl ketone is more preferred. The resins A and C contained in the polyester resin X may be dissolved in an organic solvent after being mixed beforehand, or dissolved in an organic solvent after being mixed with other resins, or dissolved simultaneously by adding resins A and C to an organic solvent, or a mixture of solutions obtained by dissolving each of resins A and C in an organic solvent. The mass ratio of the organic solvent to the resin containing the polyester resin X [organic solvent / resin] is preferably 50 / 100 or more, more preferably 70 / 100 or more, even more preferably 100 / 100 or more, and preferably 500 / 100 or less, more preferably 400 / 100 or less, and even more preferably 300 / 100 or less. If the polyester resin X is a neutralized product of a basic compound, it is preferable to obtain a solution of the resin containing the polyester resin X, and then further neutralize it by adding an aqueous solution of the aforementioned basic compound. The dissolution of the polyester resin X in an organic solvent, and the subsequent addition of an aqueous solution of a basic compound, are usually carried out at a temperature below the boiling point of the organic solvent.

[0061] The temperature at which an aqueous medium is added to a resin solution containing polyester resin X is preferably 10°C or higher, more preferably 20°C or higher, even more preferably 25°C or higher, and preferably 80°C or lower, more preferably 75°C or lower, from the viewpoint of improving the dispersion stability of the resin particle dispersion. From the viewpoint of improving the dispersion stability of the resin particle dispersion, the addition rate of the aqueous medium is preferably 0.5 parts by mass / min or more, more preferably 1 part by mass / min or more, even more preferably 3 parts by mass / min or more, and preferably 100 parts by mass / min or less, more preferably 50 parts by mass / min or less, and even more preferably 30 parts by mass / min or less, per 100 parts by mass of the resin component constituting the resin particles, until the phase inversion is completed. After the phase inversion, there are no restrictions on the addition rate of the aqueous medium after the resin particles have been obtained. From the viewpoint of improving the productivity of the resin particle dispersion, the amount of aqueous medium added is preferably 50 parts by mass or more, more preferably 100 parts by mass or more, even more preferably 200 parts by mass or more, and preferably 900 parts by mass or less, more preferably 500 parts by mass or less, and even more preferably 400 parts by mass or less, per 100 parts by mass of the resin component constituting the resin particles.

[0062] After phase inversion emulsification, it is preferable to remove the organic solvent from the dispersion obtained by phase inversion emulsification in order to improve the dispersion stability of the resin particle dispersion. The removal of organic solvents is not particularly limited, and any method can be used. The resulting resin particle dispersion is preferably filtered through a wire mesh or the like to remove coarse particles. Furthermore, if the organic solvent is removed, water is also reduced by azeotropic formation along with the organic solvent; therefore, it is preferable to add water to adjust the solid content concentration.

[0063] The solid content concentration of the resin particle dispersion of the present invention is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, and preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper. The solid content concentration of the dispersion is measured by the method described in the examples.

[0064] The volume-average particle size Dv of the resin particles in the resin particle dispersion of the present invention is preferably 20 nm or more, more preferably 40 nm or more, even more preferably 60 nm or more, and even more preferably 70 nm or more, and preferably 500 nm or less, more preferably 400 nm or less, even more preferably 300 nm or less, and even more preferably 220 nm or less, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper. The volume-average particle size Dv is measured by the method described in the examples. Both the aqueous dispersion of resin particles containing resin A and the aqueous dispersion of resin particles containing resin C used in method (ii) above can be manufactured in accordance with the method described above. The preferred range for the volume-average particle size Dv of the resin particles containing resin A and the resin particles containing resin C is the same as the range described above.

[0065] The resin particle dispersion of the present invention may optionally contain various additives such as organic solvents, humectants, wetting agents, penetrating agents, viscosity modifiers, defoaming agents, preservatives, fungicides, rust inhibitors, pH adjusters, antioxidants, and ultraviolet absorbers. Furthermore, because surfactants have a very high affinity for water, their presence in the resin particle dispersion will result in them being present in the coating layer formed when the dispersion is applied to a paper substrate, leading to a decrease in the water repellency and water resistance of the coated paper. Therefore, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper, it is preferable that the resin particle dispersion of the present invention substantially does not contain surfactants. Here, "substantially contained" means that surfactants are not intentionally added, and does not exclude the possibility of small amounts of surfactants being present as impurities. In addition, in the present invention, when producing the resin particle dispersion liquid, a method of adding a resin containing the above-mentioned polyester resin X to an aqueous medium and performing a dispersion treatment with a disperser or the like, or a method of gradually adding an aqueous medium to a solution of the resin containing the polyester resin X to perform phase inversion emulsification is used. As a result, resin particles can be dispersed in the aqueous medium without using a surfactant, and a resin particle dispersion liquid substantially free of a surfactant can be obtained.

[0066] [Coating liquid for paper] The resin particle dispersion liquid can be used as it is as a coating liquid for paper, but various additives used in the coating liquid for paper can also be added and mixed into the resin particle dispersion liquid as needed and then used. That is, the coating liquid for paper of the present invention (hereinafter, also simply referred to as "coating liquid") preferably contains the resin particle dispersion liquid. Since the surfactant has a very high affinity with water as described above, when the surfactant is present in the coating liquid, it will also be contained in the coating layer for paper formed when coating the paper substrate. This will cause a decrease in the water repellency and water resistance of the coated paper for paper. Therefore, from the perspective of improving the water repellency and water resistance of the obtained coated paper, it is also preferable that the coating liquid of the present invention is substantially free of a surfactant.

[0067] [Coated paper] The coated paper of the present invention has a coating layer formed by coating a coating liquid for paper on at least one side of a paper substrate. Examples of the paper substrate include uncoated papers such as high-quality paper, medium-quality paper, and recycled paper; coated papers such as art paper, coated paper, and matte coated paper; information papers such as PPC paper; packaging papers such as kraft paper; the base paper of cardboard; and paperboard such as paperboard for paper containers. The basis weight of the paper substrate is not particularly limited. However, from the viewpoints of the handling property of the coated paper and the ease of coating the coating liquid on the paper substrate, it is preferably 10 g / m 2 or more, more preferably 30 g / m 2 or more, still more preferably 50 g / m 2 or more, and preferably 200 g / m 2 or less, more preferably 150 g / m 2 or less, still more preferably 120 g / m2 The following applies:

[0068] [Manufacturing method for coated paper] From the viewpoint of obtaining coated paper with excellent water repellency and water resistance, the method for manufacturing coated paper of the present invention preferably includes step 1 of applying the coating liquid to at least one side of a paper substrate. This makes it possible to obtain coated paper having a coated layer formed by applying the coating liquid to at least one side of a paper substrate. Examples of paper substrates include the aforementioned paper substrates.

[0069] From the viewpoint of obtaining coated paper with excellent water repellency and water resistance, the amount of coating liquid applied in step 1 is preferably 1 g / m² in terms of solid content. 2 Above, a comfortable 3g / m 2 More preferably 5 g / m 2 More preferably 10 g / m 2 The above applies, and preferably 25 g / m². 2 More preferably 20 g / m 2 More preferably 15 g / m 2 The following applies: The method for applying the coating liquid to the paper substrate in step 1 is not particularly limited, and examples include using a roll coater, gravure coater, die coater, curtain coater, spray coater, blade coater, wire bar coater, bar coater, rod bar coater, impregnation coater, cast coater, air knife coater, reverse coater, lip coater, kiss coater, etc.

[0070] In the present invention, from the viewpoint of obtaining coated paper with excellent water repellency and water resistance, it is preferable to further include step 2 of drying the coating liquid on the paper substrate coated in step 1. Examples of drying methods in step 2 include static drying, forced-air drying, heat drying, vacuum drying, and infrared drying. One or more drying methods may be used. Among these, from the viewpoint of ease of operation, at least one selected from forced-air drying and heat drying is preferred, and heat drying is more preferred. Examples of heating and drying methods include heating by applying hot air to the surface of the coating liquid on the paper substrate, heating by bringing a heater close to the surface of the coating liquid on the paper substrate, heating by bringing a heater into contact with the surface of the paper substrate opposite to the surface to which the coating liquid is applied, and heating by steam curing using high-temperature steam at normal or high pressure. The drying temperature is preferably 30°C or higher, more preferably 40°C or higher, even more preferably 50°C or higher, even more preferably 60°C or higher, and even more preferably 70°C or higher, from the viewpoint of obtaining coated paper with excellent water repellency and water resistance, and preferably 200°C or lower, more preferably 150°C or lower, and even more preferably 120°C or lower, from the viewpoint of suppressing deformation of the paper substrate due to heat and reducing energy. The drying time is preferably 3 minutes or more from the viewpoint of obtaining coated paper with excellent water repellency and water resistance, and preferably 15 minutes or less, more preferably 10 minutes or less, from the viewpoint of suppressing deformation of the paper substrate due to heat and reducing energy. [Examples]

[0071] The present invention will be described in more detail below with reference to examples. In the following examples, each physical property was measured by the following method.

[0072] [Measurement method] The properties of polyester resin, resin particles, etc., were measured and evaluated using the following method.

[0073] [Softening point of resin] Using a flow tester "CFT-500EX" (manufactured by Shimadzu Corporation), 1 g of sample was heated at a heating rate of 6°C / min while a load of 1.96 MPa was applied by a plunger, and the sample was extruded from a nozzle with a diameter of 1 mm and a length of 1 mm. The amount of plunger descent of the flow tester was plotted against temperature, and the temperature at which half of the sample flowed out was defined as the softening point.

[0074] [Glass transition temperature and melting point of resins] Using a differential scanning calorimeter "Q-20" (manufactured by T.A. Instruments Japan Co., Ltd.), 0.01 to 0.02 g of the sample was weighed into an aluminum pan, heated to 200°C, and then cooled to 0°C at a rate of 10°C / min to prepare the sample for measurement. Subsequently, the temperature was increased at a rate of 10°C / min and the heat quantity was measured. Among the observed endothermic peaks, the peak temperature with the largest peak area was defined as the maximum endothermic peak temperature. In the case of crystalline resins, this peak temperature was defined as the melting point. In the case of amorphous resins, the temperature at the intersection of the extension of the baseline below the maximum endothermic peak temperature and the tangent line showing the maximum slope from the rising part of the peak to the peak apex was defined as the glass transition temperature.

[0075] [Crystallization index of resins] Using a differential scanning calorimeter "Q-20" (manufactured by T.A. Instruments Japan Co., Ltd.), 0.01 to 0.02 g of the sample was weighed into an aluminum pan and cooled to 0°C at a cooling rate of 10°C / min. The sample was then left to stand still for 1 minute, and then heated to 180°C at a heating rate of 10°C / min, and the amount of heat was measured. Among the observed endothermic peaks, the temperature of the peak with the largest peak area was defined as the maximum endothermic peak temperature, and the crystallinity index was determined by the formula (softening point (°C)) / (maximum endothermic peak temperature (°C)).

[0076] [Acid value of resins] Measurements were performed in accordance with JIS K0070. However, the measurement solvent was a mixed solvent of acetone and toluene [acetone:toluene = 1:1 (volume ratio)].

[0077] [Volume-average particle size (Dv) of resin particles] The volume-average particle size Dv was measured using the following measuring device and conditions. Measurement device: Zeta potential and particle size measurement system "ELSZ-2" (manufactured by Otsuka Electronics Co., Ltd.) Measurement conditions: Cumulant analysis method. The concentration of the particles to be measured is approximately 5 × 10⁻⁶. -3 A dispersion diluted with water to a mass percent was placed in a measurement cell at a temperature of 25°C, with 100 cumulative measurements. The refractive index of the dispersion solvent was set to the refractive index of water (1.333).

[0078] [Solid content concentration of aqueous dispersion of polyester resin particles] Using a heat-drying type moisture meter "MX-50" (manufactured by A&D Co., Ltd.), 5 g of the sample was dried at a drying temperature of 150°C, in standard measurement mode, standard heating pattern, and with ACCURACY:LO, and the moisture content (mass%) of the aqueous dispersion was measured. The solid content concentration was calculated according to the following formula. Solid concentration (mass%) = 100-moisture (mass%)

[0079] [Resin manufacturing] Manufacturing Example A1 (Manufacturing of Amorphous Polyester Resin A-1) A 10 L four-necked flask equipped with a nitrogen inlet tube, dehydration tube, stirrer, and thermocouple was purged with nitrogen. 2344 g of 1,2-propanediol, 3583 g of terephthalic acid, 35 g of tin(II) di(2-ethylhexanoate), and 0.7 g of gallic acid were added. Under a nitrogen atmosphere, the mixture was heated to 180°C with stirring and held for 1 hour, then heated to 210°C over 6 hours. After holding at 210°C for 1 hour, the pressure inside the flask was further reduced to 8.3 kPa and held for 1 hour. After returning to atmospheric pressure, the mixture was cooled to 180°C, 1073g of fumaric acid and 3.5g of 4-tert-butylcatechol were added, and the temperature was raised to 210°C over 3 hours. After holding at 210°C for 1 hour, the pressure in the flask was further reduced and held at 8.3kPa until the softening point reached the temperature shown in Table 1, thereby obtaining amorphous polyester resin A-1. The various physical properties of the resin are shown in Table 1.

[0080] Manufacturing Example A2 (Manufacturing of Amorphous Polyester Resin A-2) A 10L four-necked flask equipped with a nitrogen inlet tube, dehydration tube, stirrer, and thermocouple was purged with nitrogen. 1053g of ethylene glycol, 1056g of 1,2-propanediol, 4355g of terephthalic acid, 35g of tin(II) di(2-ethylhexanoate), and 0.7g of gallic acid were added. Under a nitrogen atmosphere, the mixture was heated to 180°C with stirring and held for 1 hour, then heated to 210°C over 6 hours. After holding at 210°C for 1 hour, the pressure inside the flask was further reduced to 8.3kPa and held for 1 hour. After returning to atmospheric pressure, the mixture was cooled to 180°C, 537g of fumaric acid and 3.5g of 4-tert-butylcatechol were added, and the temperature was raised to 210°C over 3 hours. After holding at 210°C for 1 hour, the pressure in the flask was further reduced and held at 8.3kPa until the softening point reached the temperature shown in Table 1, thereby obtaining amorphous polyester resin A-2. The various physical properties of the resin are shown in Table 1.

[0081] Manufacturing Example A3 (Manufacturing of Amorphous Polyester Resin A-3) A 10 L four-necked flask equipped with a nitrogen inlet tube, dehydration tube, stirrer, and thermocouple was purged with nitrogen. 2614 g of 2,3-butanediol, 3375 g of terephthalic acid, 35 g of tin(II) di(2-ethylhexanoate), and 0.7 g of gallic acid were added. Under a nitrogen atmosphere, the mixture was heated to 180°C with stirring and held for 1 hour, then heated to 210°C over 6 hours. After holding at 210°C for 1 hour, the pressure inside the flask was further reduced to 8.3 kPa and held for 1 hour. After returning to atmospheric pressure, the mixture was cooled to 180°C, 1011g of fumaric acid and 3.5g of 4-tert-butylcatechol were added, and the temperature was raised to 210°C over 3 hours. After holding at 210°C for 1 hour, the pressure in the flask was further reduced and held at 8.3kPa until the softening point reached the temperature shown in Table 1, thereby obtaining amorphous polyester resin A-3. The various physical properties of the resin are shown in Table 1.

[0082] Manufacturing Example A4 (Manufacturing of Amorphous Polyester Resin A-4) A 10 L four-necked flask equipped with a nitrogen inlet tube, dehydration tube, stirrer, and thermocouple was purged with nitrogen. 3475 g of bisphenol A propylene oxide (2.2) adduct, 1383 g of bisphenol A ethylene oxide (2.2) adduct, 1648 g of terephthalic acid, 35 g of tin(II) di(2-ethylhexanoate), and 0.7 g of gallic acid were added. Under a nitrogen atmosphere, the mixture was heated to 235°C with stirring and held for 6 hours. After that, the pressure inside the flask was reduced and held at 8.3 kPa for 1 hour. After returning to atmospheric pressure, the mixture was cooled to 190°C, 494g of fumaric acid and 3.5g of tert-butylcatechol were added, and the temperature was raised to 210°C over 2 hours. After holding at 210°C for 1 hour, the pressure in the flask was further reduced and held at 8.3kPa until the softening point reached the temperature shown in Table 1, thereby obtaining amorphous polyester resin A-4. The various physical properties of the resin are shown in Table 1.

[0083] [Table 1]

[0084] Manufacturing Example C1 (Manufacturing of Crystalline Polyester Resin C-1) A 10 L four-necked flask equipped with a nitrogen inlet tube, dehydration tube, stirrer, and thermocouple was purged with nitrogen, and 1607 g of ethylene glycol and 5393 g of sebacic acid were added. While stirring, the temperature was raised to 135°C and held at 135°C for 3 hours, then the temperature was raised from 135°C to 200°C over 10 hours. Subsequently, 28 g of tin(II) di(2-ethylhexanoate) was added, and the temperature was further raised to 200°C for 1 hour. After that, the pressure inside the flask was reduced and held at 8.3 kPa for 2 hours to obtain crystalline polyester resin C-1. The various physical properties of the resin are shown in Table 2.

[0085] Manufacturing Example C2 (Manufacturing of Crystalline Polyester Resin C-2) A 10 L four-necked flask equipped with a nitrogen inlet tube, dehydration tube, stirrer, and thermocouple was purged with nitrogen, and 1771 g of 1,4-butanediol and 5229 g of tetradecanediol were added. While stirring, the temperature was raised to 135°C and held at 135°C for 3 hours, then the temperature was raised from 135°C to 200°C over 10 hours. Subsequently, 28 g of tin(II) di(2-ethylhexanoate) was added, and the flask was held at 200°C for another hour. The pressure inside the flask was then reduced and held at 8.3 kPa for 2 hours to obtain crystalline polyester resin C-2. The various physical properties of the resin are shown in Table 2.

[0086] Manufacturing Example C3 (Manufacturing of Crystalline Polyester Resin C-3) A 10 L four-necked flask equipped with a nitrogen inlet tube, dehydration tube, stirrer, and thermocouple was purged with nitrogen, and 1314 g of ethylene glycol and 5686 g of tetradecanedioic acid were added. While stirring, the temperature was raised to 135°C and held at 135°C for 3 hours, then the temperature was raised from 135°C to 200°C over 10 hours. Subsequently, 28 g of tin(II) di(2-ethylhexanoate) was added, and the temperature was further raised to 200°C for 1 hour. After that, the pressure inside the flask was reduced and held at 8.3 kPa for 1 hour to obtain crystalline polyester resin C-3. The various physical properties of the resin are shown in Table 2.

[0087] [Table 2]

[0088] Manufacturing Example E1 (Manufacturing of Resin Particle Dispersion E-1) In a 2L four-necked flask equipped with a reflux condenser, a stirrer "Three One Motor BL300" (manufactured by Shinto Kagaku Co., Ltd.), and a thermocouple, 140g of amorphous polyester resin A-1 as resin A and 60g of crystalline polyester resin C-1 as resin C were placed and mixed with 400g of methyl ethyl ketone (hereinafter referred to as "MEK") at 65°C to dissolve the resins. Next, a 5% by mass aqueous solution of sodium hydroxide was added so that the amount of sodium hydroxide used was 100 mol% relative to the sum of the acid values ​​of amorphous polyester resin A-1 and crystalline polyester resin C-1, and the mixture was stirred for 60 minutes. Next, 600 g of deionized water was added dropwise at a rate of 10 mL / min at 65°C with stirring to induce phase inversion emulsification. Then, while maintaining the temperature at 65°C, MEK was removed by distillation while gradually reducing the pressure from 80 kPa to 30 kPa, and some of the water was further removed by distillation. After cooling to room temperature, the mixture was filtered through a 150-mesh wire mesh, and the solid content concentration was adjusted to 30% by mass with deionized water to obtain resin particle dispersion E-1. The volume-average particle size Dv of the resin particles in the obtained dispersion is shown in Table 3-1.

[0089] Manufacturing Examples E2-E5 and E8-E10 (Manufacturing of resin particle dispersions E-2-E-5 and E-8-E-10) In manufacturing example E1, resin A and / or resin C were changed to those shown in Tables 3-1 and 3-2, and their quantities were changed to those shown in Tables 3-1 and 3-2. Except for these changes, the process was carried out in the same manner as in manufacturing example E1 to obtain resin particle dispersions E-2 to E-5 and resin particle dispersions E-8 to E-10. The volume-average particle size Dv of the resin particles in the obtained dispersions is shown in Tables 3-1 and 3-2.

[0090] Manufacturing Example E6 (Manufacturing of Resin Particle Dispersion E-6) In a 2L four-necked flask equipped with a reflux condenser, a stirrer "Three One Motor BL300" (manufactured by Shinto Kagaku Co., Ltd.), and a thermocouple, 200g of amorphous polyester resin A-1 was placed and mixed with 400g of methyl ethyl ketone (hereinafter referred to as "MEK") at 30°C to dissolve the resin. Next, a 5% by mass aqueous solution of sodium hydroxide was added so that the amount of sodium hydroxide used was 65 mol% relative to the acid value of amorphous polyester resin A-1, and the mixture was stirred for 60 minutes. Next, the temperature was raised to 65°C and maintained at 65°C while stirring, 600 g of deionized water was added dropwise at a rate of 10 mL / min to induce phase inversion emulsification. Then, while maintaining 65°C, the MEK was removed by distillation while gradually reducing the pressure from 80 kPa to 30 kPa, and some of the water was further removed by distillation. After cooling to room temperature, the mixture was filtered through a 150-mesh wire mesh, and the solid content concentration was adjusted to 30% by mass with deionized water to obtain resin particle dispersion E-6. The volume-average particle size Dv of the resin particles in the obtained dispersion is shown in Table 3-1.

[0091] Manufacturing Example E7 (Manufacturing of Resin Particle Dispersion E-7) In a 2L four-necked flask equipped with a reflux condenser, a stirrer "Three One Motor BL300" (manufactured by Shinto Kagaku Co., Ltd.), and a thermocouple, 200g of crystalline polyester resin C-1 was placed and mixed with 400g of MEK at 65°C to dissolve the resin. Next, a 5% by mass aqueous sodium hydroxide solution was added so that the amount of sodium hydroxide used was 75 mol% relative to the acid value of crystalline polyester resin C-1, and the mixture was stirred for 60 minutes. Next, 600 g of deionized water was added dropwise at a rate of 10 mL / min while stirring at 65°C to emulsify the mixture through phase inversion. Then, while maintaining the temperature at 65°C, MEK was removed by distillation while gradually reducing the pressure from 80 kPa to 30 kPa, and some of the water was further removed by distillation. After cooling to room temperature, the mixture was filtered through a 150-mesh wire mesh, and the solid content concentration was adjusted to 30% by mass with deionized water to obtain resin particle dispersion E-7. The volume-average particle size Dv of the resin particles in the obtained dispersion is shown in Table 3-1.

[0092] [Table 3-1] [Table 3-2]

[0093] Examples 1-9 and Comparative Examples 1 and 2 (Process 1) In Examples 1-5, Examples 7-9, and Comparative Examples 1 and 2, the resin particle dispersions shown in Table 4 were used as the coating liquid as is. In Example 6, a mixture of resin particle dispersions E-6 and E-7 in a 1:1 mass ratio was used as the coating liquid. The paper substrate used was PPC paper "J paper" (basis weight 82 g / m²). 2 Each coating solution was applied to one side of a paper substrate (manufactured by Fujifilm Business Innovation Co., Ltd.) using a bar coater (No. 20). The coating amount for the paper substrate was 14 g / m² in solid content. 2 It was done in such a way. (Process 2) Next, the aqueous dispersion of resin particles on the paper substrate was dried in an 80°C dryer for 5 minutes to obtain coated paper having a coating layer on the paper substrate. For each of the obtained coated papers, the water repellency and water resistance were evaluated on the surface with the coating layer.

[0094] [Evaluation of water repellency] Water repellency was evaluated in accordance with JAPAN TAPPI Paper and Pulp Test Method No. 68:2000. At room temperature, coated paper was tilted at a 45° angle, and droplets of deionized water were dropped onto the surface with the coating from 10 mm above the paper. The degree of water repellency was determined by observing the state of the water droplets after they passed over the coated paper, according to the following criteria. R10 was the highest evaluation of water repellency, and R0 was the lowest evaluation of water repellency. (Water repellency) R0: A continuous trace showing a uniform width. R2: A continuous trace that is slightly narrower than a water droplet. R4: A continuous pattern, but broken in places, clearly narrower than a water droplet. R6: The mark is half wet. R7: One-quarter of the trace is wet with elongated water droplets. R8: More than a quarter of the traces consist of scattered spherical droplets. R9: A substance with small, spherical droplets scattered throughout. R10: Something that rolls down completely

[0095] [Evaluation of water resistance] Coated paper was placed on a horizontal surface with the coated side facing up, and droplets of deionized water were dropped onto the paper from 10 mm above and left to stand for 1 minute. Next, the water droplets on the coated paper were wiped off, and the condition of the paper after wiping was examined. The water resistance was evaluated according to the following criteria. L5 had the highest water resistance, and L1 had the lowest water resistance. (Judgment criteria) L5: No water stains are visible on the paper. L4: Slight water stains are visible. L3: Water stains are visible, but the stains are smaller than water droplets. L2: A stain the same size as a water droplet is visible. L1: A stain larger than a water droplet is visible.

[0096] [Table 4]

[0097] Table 4 shows that the resin particle dispersion containing polyester resin X, which includes resins A and C used in Examples 1 to 9, can produce coated paper with superior water repellency and water resistance compared to the resin particle dispersion containing only resin A used in Comparative Example 1, and the resin particle dispersion containing only resin C used in Comparative Example 2. Furthermore, the results from Examples 1-5, 7-9, and 6 show that resin particle dispersions obtained by dispersing resin particles containing resin A and resin C in an aqueous medium, and resin particle dispersions obtained by mixing an aqueous dispersion of resin particles containing resin A with an aqueous dispersion of resin particles containing resin C, can both yield coated paper with excellent water repellency and water resistance. [Industrial applicability]

[0098] According to the present invention, coated paper having a coating layer with excellent water repellency and water resistance can be obtained, and can be used for paper labels, packaging paper, paper containers, etc., where water resistance is required.

Claims

1. A resin particle dispersion containing a polyester resin X, wherein the polyester resin X contains an amorphous polyester resin A and a crystalline polyester resin C, and the mass ratio of the amorphous polyester resin A to the crystalline polyester resin C in the polyester resin X (amorphous polyester resin A / crystalline polyester resin C) is 5 / 95 or more and 94 / 6 or less, A resin particle dispersion for paper coating.

2. The resin particle dispersion for paper coating according to claim 1, wherein the glass transition temperature of the amorphous polyester resin A is 35°C or higher and 85°C or lower.

3. The resin particle dispersion for paper coating according to claim 1, which substantially does not contain a surfactant.

4. The resin particle dispersion for paper coating according to claim 1, wherein the amorphous polyester resin A and the crystalline polyester resin C are substantially water-insoluble.

5. The amorphous polyester resin A contains a polycondensate of an alcohol component (A-al) containing a diol and a dicarboxylic acid component (A-ac) having two or more valences, and the diol is an aliphatic diol having 2 to 10 carbon atoms, The resin particle dispersion for paper coating according to claim 1, wherein the crystalline polyester resin C contains a polycondensate of an alcohol component (C-al) containing an aliphatic diol and a dicarboxylic acid component (C-ac) having two or more valences.

6. The resin particle dispersion for paper coating according to claim 5, wherein the difference between the number of carbon atoms of the aliphatic diol constituting the amorphous polyester resin A and the number of carbon atoms of the aliphatic diol constituting the crystalline polyester resin C is 0 or more and 2 or less.

7. The amorphous polyester resin A contains a polycondensate of an alcohol component (A-al) containing a diol and a dicarboxylic acid component (A-ac) having two or more valences, and the diol is an alkylene oxide adduct of bisphenol A, The crystalline polyester resin C contains a polycondensate of an alcohol component (C-al) containing an aliphatic diol and a dicarboxylic acid component (C-ac) having two or more valences, The resin particle dispersion for paper coating according to claim 1, wherein the mass ratio of the amorphous polyester resin A to the crystalline polyester resin C (amorphous polyester resin A / crystalline polyester resin C) is 5 / 95 or more and 65 / 35 or less.

8. A paper coating liquid containing the resin particle dispersion according to any one of claims 1 to 7.

9. A coated paper having a coating layer formed by coating the paper coating liquid according to claim 8 on at least one side of a paper substrate.

10. A method for manufacturing a coated paper, comprising: step 1 of coating the paper coating liquid according to claim 8 on at least one side of a paper substrate; and step 2 of drying the paper coating liquid on the paper substrate coated in step 1.