Paper coating agent

Abstract

The present invention provides a paper coating agent that forms a coating layer having excellent water repellency, heat sealability, and blocking resistance, a method for manufacturing the paper coating agent, and coated paper using the paper coating agent. [Solution] A paper coating agent comprising resin particles containing a polyester resin and one or more selected from wax and silicone, wherein the polyester resin is a polycondensate of an alcohol component, a carboxylic acid component, and polyethylene terephthalate, and the amount of polyethylene terephthalate is 5% by mass or more and 50% by mass or less of the total amount of the alcohol component, the carboxylic acid component, and polyethylene terephthalate. Paper coating agent.

Description

[Technical Field]

[0001] The present invention relates to a paper coating agent containing resin particles, a method for producing the paper coating agent, and coated paper using the coating agent. [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 research into alternative technologies to lamination that can provide water resistance and water repellency. While fluorine-based paper coatings are known as an alternative to laminating plastic films onto paper materials to impart water repellency and water resistance, non-fluorine-based paper coatings are needed from the perspective of safety and environmental considerations.

[0003] For example, Patent Document 1 describes a resin particle dispersion for paper coating containing resin particles including a polyester resin X, wherein the resin particles contain a modified silicone oil, and the polyester resin X contains an amorphous polyester resin A which includes an alcohol component containing a divalent or higher alcohol and a carboxylic acid component containing one or more selected from aromatic dicarboxylic acids and aliphatic dicarboxylic acids, and the dispersion medium is water. It states that coated paper having a coating layer obtained by coating at least one side of a paper substrate with the resin particle dispersion for paper coating is excellent in water repellency and oil resistance. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Special Publication No. 2024-6437 [Overview of the project] [Problems that the invention aims to solve]

[0005] Polyester-containing paper coatings are known as non-fluorine-based paper coatings that impart water repellency and water resistance. However, in packaging paper and containers that use coated paper coated with a water-repellent and water-resistant paper coating, it is sometimes required that the coating possess not only water repellency and water resistance but also heat-sealability for use as paper packaging or containers. Furthermore, coated paper coated with a heat-sealing paper coating agent has components on its surface that are easily melted by heating and pressurizing, and that flow easily after melting. As a result, when coated paper coated with a heat-sealing paper coating agent is wound into a roll and stored before processing, blocking occurs during storage, where the coated surface of the paper adheres strongly due to the pressure from winding and the temperature of the storage location. As a paper coating agent containing polyester, methods for achieving heat-sealing properties and suppressing blocking include using polyester with a high glass transition temperature and techniques for making polyester highly viscoelastic. However, when applied to paper, the wetting spread is insufficient, making it impossible to impart water repellency or water resistance. Furthermore, in the conventional technology described in Patent Document 1, there was room for improvement in the heat sealability and blocking resistance of the water-repellent coated paper. The present invention relates to a paper coating agent that forms a coating layer having excellent water repellency, heat sealability, and blocking resistance, a method for producing the paper coating agent, and coated paper using the coating agent. [Means for solving the problem]

[0006] The inventors have found that a paper coating agent containing resin particles containing a polyester resin and one or more selected from wax and silicone, which imparts water resistance by coating on a paper substrate, and the polyester resin is a polycondensate of an alcohol component, a carboxylic acid component, and polyethylene terephthalate, and the amount of polyethylene terephthalate is 5% by mass or more and 50% by mass or less of the total amount of the alcohol component, the carboxylic acid component, and polyethylene terephthalate can solve the above problems.

[0007] That is, the present invention provides the following [1] to [3]. 〔1〕A paper coating agent containing resin particles containing a polyester resin and one or more selected from wax and silicone, where the polyester resin is a polycondensate of an alcohol component, a carboxylic acid component, and polyethylene terephthalate, and the amount of the polyethylene terephthalate is 5% by mass or more and 50% by mass or less of the total amount of the alcohol component, the carboxylic acid component, and polyethylene terephthalate. Paper coating agent. 〔2〕A method for producing the paper coating agent according to [1] above, having the following steps 1 to 5 in this order. Step 1: A step of producing the polyester resin by reacting the alcohol component, the acid component, and the polyethylene terephthalate Step 2: A step of dissolving the polyester resin and one or more selected from the wax and the silicone in an organic solvent Step 3: A step of adding a basic compound to neutralize the polyester resin Step 4: A step of adding an aqueous medium to invert and emulsify the polyester resin and one or more selected from the wax and the silicone Step 5: A step of distilling off the organic solvent 〔3〕A coated paper having a coating layer containing a polyester resin and at least one selected from wax and silicone on at least one side of a paper substrate, The polyester resin contains a structural unit derived from an alcohol component, a structural unit derived from an acid component, and a structural unit derived from polyethylene terephthalate. The structural unit derived from polyethylene terephthalate is 5% by mass or more and 50% by mass or less of the total amount of the structural unit derived from an alcohol component, the structural unit derived from an acid component, and the structural unit derived from polyethylene terephthalate. Coated paper.

Effect of the Invention

[0008] According to the present invention, it is possible to provide a paper coating agent that can impart water repellency by coating a paper substrate, and can achieve both heat sealability and blocking resistance of the coated paper, a method for producing the paper coating agent, and a coated paper using the paper coating agent.

Embodiment for Carrying Out the Invention

[0009] [Paper Coating Agent] The paper coating agent of the present invention contains resin particles containing a polyester resin and one or more selected from wax and silicone. Here, the polyester resin is a polycondensate of an alcohol component, a carboxylic acid component, and polyethylene terephthalate, and the amount of polyethylene terephthalate is 5% by mass or more and 50% by mass or less of the total amount of the alcohol component, the carboxylic acid component, and polyethylene terephthalate.

[0010] According to the present invention, by coating the paper coating agent of the present invention on paper, a coated paper having water repellency and achieving both heat sealability and blocking resistance can be obtained. The reason is not clear, but it is considered as follows. By treating a paper substrate with a paper coating agent containing resin particles containing a polyester resin, a coated paper having water repellency can be obtained. In addition, when the coated paper is used for packaging paper, paper containers, etc., it may be required to have heat sealability. When resin particles containing polyester resin are infused with hydrophobic compounds such as wax and / or silicone, the softening of the wax and silicone due to high-temperature heating during heat sealing contributes to the softening of the polyester resin in the resin particles, thus enabling heat sealing at lower temperatures. However, if the resin particles contain polyester resin and wax and / or silicone, the coated surfaces of the coated paper may stick together even at temperatures lower than those used for heat sealing, causing the stacked coated papers to adhere to each other, i.e., blocking may occur. In response to this, the present inventors have found that coated paper coated with a paper coating agent containing resin particles that include a polyester resin which is a polycondensate of an alcohol component, a carboxylic acid component, and polyethylene terephthalate, and one or more selected from wax and silicone, exhibits water repellency and achieves both heat sealability and blocking resistance. This is because the relatively hydrophilic polyethylene terephthalate-derived repeating units are present in a block-like manner within the polyester resin. As a result, the compatibility between the polyester resin and the relatively hydrophobic wax and / or silicone is reduced. Therefore, at the pressures applied during winding of coated paper and the temperatures during storage, the softening of the wax and silicone does not affect the softening of the polyester resin within the resin particles, thus improving blocking resistance.

[0011] The definitions of various terms used in this specification are shown below. The crystallinity of a resin is expressed by the crystallinity index, which is defined as the ratio of the softening point to the maximum endothermic peak temperature measured by differential scanning calorimeter (DSC), i.e., "softening point (°C) / maximum endothermic peak temperature (°C)". "Crystalline resin" refers to a resin whose crystallinity index is between 0.6 and 1.4. "Amorphous resin" refers to a resin in which no endothermic peak is observed by differential scanning calorimeter (DSC), or, if an endothermic peak is observed, the crystallinity index is less than 0.6 or greater than 1.4. The maximum endothermic peak temperature 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 raw materials, and the manufacturing conditions (e.g., reaction temperature, reaction time, cooling rate). "Bisphenol A alkylene oxide adduct" refers to the entire structure obtained by adding an alkylene oxide to 2,2-bis(4-hydroxyphenyl)propane. The term "carboxylic acid component" includes not only carboxylic acids but also their anhydrides and alkyl esters having 1 to 3 carbon atoms. In other words, in this specification, when only the name of a carboxylic acid is mentioned, it is assumed that the anhydrides and alkyl esters having 1 to 3 carbon atoms of that carboxylic acid are also included. Polyethylene terephthalate is calculated as one mole consisting of one mole of ethylene glycol and one mole of terephthalic acid.

[0012] [Polyester resin] The polyester resin is a polycondensate of an alcohol component, a carboxylic acid component, and polyethylene terephthalate (PET). The polyester resin may be a crystalline polyester resin or an amorphous polyester resin, but an amorphous polyester resin is preferred.

[0013] (Alcohol content) The alcohol component includes alcohols with a hydride of 2 or more. The alcohol component can be used individually or in combination of two or more. Examples of alcohols with a hydride of 2 or more include diols and polyhydric alcohols with a hydride of 3 or more. Examples of diols include aliphatic diols, aromatic diols, and alicyclic diols.

[0014] The aliphatic diol has two or more carbon atoms, preferably 16 or fewer, more preferably 14 or fewer, and even more preferably 10 or fewer. Examples of 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, 2,5- Examples of aliphatic diols include hexanediol, 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, 2,2-dimethyl-1,3-propanediol, and 3-methyl-1,5-pentanediol.

[0015] 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).

[0016] [ka]

[0017] 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 from the standpoint of availability, it is preferable that they be the same.

[0018] 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 adducts of bisphenol A and ethylene oxide adducts of bisphenol A, and more preferably propylene oxide adducts of bisphenol A.

[0019] Examples of alicyclic diols include cyclohexanediol, cyclohexanedimethanol, and hydrogenated bisphenol A. Examples of polyhydric alcohols with a valency of 3 or higher include glycerin, pentaerythritol, trimethylolpropane, sorbitol, and sorbitan.

[0020] Among these, the alcohol component preferably contains one or more selected from aliphatic diols and aromatic diols, from the viewpoint of obtaining a paper coating agent that forms a coating layer having excellent water repellency, heat sealability, and blocking resistance, more preferably contains one or more selected from aliphatic diols having 2 to 16 carbon atoms and alkylene oxide adducts of bisphenol A, and even more preferably contains one or more selected from 1,2-propanediol and propylene oxide adducts of bisphenol A.

[0021] From the viewpoint of obtaining a paper coating agent that forms a coating layer having excellent water repellency, heat sealability, and blocking resistance, the content of diol in the alcohol component is preferably 60 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and even more preferably 95 mol% or more, and preferably 100 mol% or less, more preferably 100 mol%.

[0022] (Carboxylic acid component) Examples of carboxylic acid components include dicarboxylic acids and polycarboxylic acids with three or more valent values. Examples of dicarboxylic acids include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and alicyclic dicarboxylic acids.

[0023] Examples of aromatic dicarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, and 2,6-naphthalenedicarboxylic acid. Among these, from the viewpoint of obtaining a paper coating agent that forms a coating layer with excellent water repellency, heat sealability, and blocking resistance, isophthalic acid, terephthalic acid, and 2,6-naphthalenedicarboxylic acid are preferred, and more preferably terephthalic acid and 2,6-naphthalenedicarboxylic acid. 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, the aliphatic dicarboxylic acid is preferably one or more selected from fumaric acid, dodecenyl succinic acid, and succinic acid, from the viewpoint of obtaining a paper coating agent that forms a coating layer with excellent water repellency, heat sealability, and blocking resistance. Examples of polycarboxylic acids with a valency of 3 or higher include trimellitic acid, 2,5,7-naphthalentricarboxylic acid, pyromellitic acid, and aconitic acid. Among these, trimellitic acid is preferred as the polycarboxylic acid with a valency of 3 or higher from the viewpoint of obtaining a paper coating agent that forms a coating layer with excellent water repellency, heat sealability, and blocking resistance. Among these, the carboxylic acid component preferably includes an aromatic dicarboxylic acid, more preferably one or more selected from aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and trivalent or higher polycarboxylic acids, from the viewpoint of obtaining a paper coating agent that forms a coating layer having excellent water repellency, heat sealability, and blocking resistance.

[0024] From the viewpoint of obtaining a paper coating agent that forms a coating layer having excellent water repellency, heat sealability, and blocking resistance, the content of aromatic dicarboxylic acid in the carboxylic acid component is preferably 30 moles or more, more preferably 35 moles or more, even more preferably 38 moles or more, and preferably 75 moles or less, more preferably 70 moles or less, and even more preferably 65 moles or less. From the viewpoint of obtaining a paper coating agent that forms a coating layer having excellent water repellency, heat sealability, and blocking resistance, the content of aliphatic dicarboxylic acid in the carboxylic acid component is preferably 10 moles or more, more preferably 15 moles or more, even more preferably 20 moles or more, and preferably 80 moles or less, more preferably 70 moles or less. When the carboxylic acid component contains a polycarboxylic acid of trivalent or higher, the content of the polycarboxylic acid of trivalent or higher in the carboxylic acid component is preferably 5 moles or more, more preferably 10 moles or more, even more preferably 12 moles or more, and preferably 25 moles or less, more preferably 22 moles or less, and even more preferably 20 moles or less, from the viewpoint of obtaining a paper coating agent that forms a coating layer having excellent water repellency, heat sealability, and blocking resistance.

[0025] (Polyethylene terephthalate) Polyethylene terephthalate is a polycondensate of ethylene glycol and terephthalic acid. Polyethylene terephthalate can be new polyethylene terephthalate, i.e., "Virgin PET," or recycled polyethylene terephthalate. Recycled polyethylene terephthalate refers to a material obtained by recovering used polyethylene terephthalate, washing it as needed, separating it from other materials, crushing it, depolymerizing the crushed material to monomer units, and then resynthesizing it using these monomers as raw materials. In the present invention, it is preferable that the polyethylene terephthalate is a polyethylene terephthalate having a relatively small intrinsic viscosity (hereinafter also referred to as "IV value") compared to conventionally used polyethylene terephthalate.

[0026] The IV value of polyethylene terephthalate is preferably 0.4 or higher, more preferably 0.45 or higher, even more preferably 0.5 or higher, even more preferably 0.55 or higher, and preferably 0.9 or lower, more preferably 0.75 or lower, and even more preferably 0.7 or lower. The IV value is an indicator of the molecular weight of polyethylene terephthalate, and polyethylene terephthalate with a small IV value is relatively low molecular weight polyethylene terephthalate. The IV value of polyethylene terephthalate can be adjusted by the molar ratio of the raw material monomers, ethylene glycol and terephthalic acid, the polycondensation time, etc.

[0027] Polyethylene terephthalate can be manufactured according to known methods or can be a commercially available product. Examples of commercially available polyethylene terephthalate include "RAMAPET L1" (IV value: 0.60), "RAMAPET BF3067" (IV value: 0.64), "RAMAPET N2G" (IV value: 0.75), "RAMAPET S1" (IV value: 0.84) (manufactured by Indorama Ventures), "TRN-NTJ" (IV value: 0.53), and "TRN-RTJC" (IV value: 0.64) (manufactured by Teijin Limited).

[0028] The content of polyethylene terephthalate with an IV value of 0.4 or more and 0.9 or less is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 98% by mass or more, and 100% by mass or less, of the total amount of polyethylene terephthalate.

[0029] The amount of polyethylene terephthalate relative to the total amount of the alcohol component, carboxylic acid component, and polyethylene terephthalate used as raw materials for the polyester resin is 5% by mass or more, preferably 8% by mass or more, more preferably 10% by mass or more, and 50% by mass or less, preferably 45% by mass or less, more preferably 40% by mass or less, from the viewpoint of obtaining a paper coating agent that forms a coating layer having excellent water repellency, heat sealability, and blocking resistance.

[0030] (Method of manufacturing polyester resins) Polyester resins are produced, for example, by polycondensation of an alcohol component, a carboxylic acid component, and polyethylene terephthalate. In addition to the condensation reaction between the alcohol component and the carboxyl group of polyethylene terephthalate, and the condensation reaction between the carboxylic acid component and the hydroxyl group of polyethylene terephthalate, the "polycondensation" in the present invention also includes a transesterification reaction between the alcohol component and / or the carboxylic acid component and polyethylene terephthalate.

[0031] Polycondensation of an alcohol component, a carboxylic acid component, and polyethylene terephthalate can be produced, for example, by polycondensing the alcohol component, the carboxylic acid component, and polyethylene terephthalate in an inert gas atmosphere at a temperature of 160°C to 250°C, using the esterification catalyst and co-catalyst described below as necessary.

[0032] 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, relative to 100 parts by mass of the total amount of the alcohol component, carboxylic acid component, and polyethylene terephthalate, which are raw materials for the polyester resin. 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, carboxylic acid component, and polyethylene terephthalate, which are raw materials for the polyester resin. Furthermore, when using a carboxylic acid containing multiple bonds, such as fumaric acid, as the carboxylic acid component, a polymerization inhibitor may be used. 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, based on 100 parts by mass of the total amount of the alcohol component, carboxylic acid component, and polyethylene terephthalate, which are raw materials for the polyester resin.

[0033] The alcohol content in the raw material of the polyester resin is preferably 35 moles or more, more preferably 40 moles or more, even more preferably 42 moles or more, and preferably 85 moles or less, more preferably 80 moles or less, and even more preferably 78 moles or less, relative to 100 moles of the total of the alcohol content and ethylene glycol constituting polyethylene terephthalate, from the viewpoint of obtaining a paper coating agent that forms a coating layer with excellent water repellency, heat sealability, and blocking resistance. The content of the carboxylic acid component in the raw material of the polyester resin is preferably 30 moles or more, more preferably 35 moles or more, even more preferably 42 moles or more, and preferably 85 moles or less, more preferably 80 moles or less, and even more preferably 78 moles or less, relative to 100 moles of the total of the alcohol component and ethylene glycol constituting polyethylene terephthalate, from the viewpoint of obtaining a paper coating agent that forms a coating layer with excellent water repellency, heat sealability, and blocking resistance. The polyethylene terephthalate content in the raw material of the polyester resin is preferably 15 moles or more, more preferably 20 moles or more, even more preferably 22 moles or more, and preferably 65 moles or less, more preferably 60 moles or less, and even more preferably 58 moles, relative to 100 moles of the total amount of alcohol component and ethylene glycol constituting polyethylene terephthalate. The polyethylene terephthalate content in the raw materials of the polyester resin is preferably 5 mol% or more, more preferably 10 mol% or more, preferably 50 mol% or less, more preferably 45 mol% or less, and even more preferably 40 mol% or less, relative to the total amount of alcohol component, carboxylic acid component, and polyethylene terephthalate.

[0034] (Physical properties of polyester resins) From the viewpoint of obtaining a paper coating agent that forms a coating layer with excellent blocking resistance, the softening point of the polyester resin is preferably 90°C or higher, more preferably 100°C or higher, and from the viewpoint of obtaining a paper coating agent that forms a coating layer with excellent heat sealing properties, it is preferably 140°C or lower, more preferably 135°C or lower, and even more preferably 130°C or lower.

[0035] The glass transition temperature of the polyester resin is preferably 45°C or higher, more preferably 50°C or higher, and even more preferably 55°C or higher, from the viewpoint of obtaining a paper coating agent that forms a coating layer with excellent blocking resistance, and preferably 80°C or lower, more preferably 78°C or lower, and even more preferably 75°C or lower, from the viewpoint of obtaining a paper coating agent that forms a coating layer with excellent heat sealability.

[0036] From the viewpoint of improving the dispersion stability of resin particles containing the polyester resin in the paper coating agent, the acid value of the polyester resin 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 45 mg KOH / g or less, more preferably 40 mg KOH / g or less, and even more preferably 35 mg KOH / g or less.

[0037] Polyester resins may be used individually or in combination of two or more types. The softening point, glass transition temperature, and acid value of polyester resins can be appropriately adjusted depending on the type and amount of the raw materials (alcohol component, carboxylic acid component, and polyethylene terephthalate), 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 polyester resins in combination, it is preferable that the softening point, glass transition temperature, and acid value obtained from the mixture are all within the aforementioned ranges.

[0038] In the present invention, the polyester resin is preferably substantially water-insoluble from the viewpoint of obtaining a paper coating agent that forms a coating layer having excellent water repellency. When the polyester resin is water-insoluble, the coating layer formed by applying the paper coating agent to a paper substrate becomes water-insoluble, which improves water repellency. Here, "substantially water-insoluble" means that when a polyester resin that 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 that dissolves is 1g or less. If the polyester resin contains acidic groups, the amount that dissolves is the amount that dissolves when the acidic groups of the polyester resin are neutralized by 100 mol% with sodium hydroxide.

[0039] In the present invention, when the polyester resin contains an acidic group, it is preferable that the polyester resin is a neutralized product of a basic compound, from the viewpoint of improving the dispersion stability of the resin particles containing the polyester resin in the paper coating agent. Basic compounds include metallic basic compounds and non-metallic basic compounds. Examples of metal-based compounds include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide. Examples of nonmetallic basic compounds include ammonia and organic amine compounds. Basic compounds can be used individually or in combination of two or more.

[0040] 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, more preferably 90 mol% or less, and even more preferably 80 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 the polyester resin, and in this case, the degree of neutralization of the polyester resin 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 (mgKOH / g) × Mass of polyester resin (g)] / (56.1 × 1,000 (mgKOH / mol))]} × 100 (1)

[0041] From the viewpoint of obtaining a paper coating agent that forms a coating layer having excellent water repellency, heat sealability, and blocking resistance, the content of polyester resin in the paper coating agent is preferably 10% by mass or more, more preferably 14% by mass or more, even more preferably 18% by mass or more, and preferably 30% by mass or less, more preferably 28% by mass or less, and even more preferably 27% by mass or less.

[0042] 〔wax〕 Examples of waxes include petroleum-based waxes, synthetic waxes, fatty acid amides, plant-based waxes, and animal-based waxes.

[0043] Examples of petroleum-based waxes include Montan wax, paraffin wax, and Fischer-Tropsch wax. Examples of synthetic waxes include synthetic ester waxes, polyethylene waxes, polypropylene waxes, polybutene waxes, polyethyleneimide waxes, and other olefin waxes. Examples of fatty acid amides include oleic acid amide and stearic acid amide. Examples of plant-based waxes include carnauba wax, rice wax, and candelilla wax. An example of an animal-derived wax is beeswax.

[0044] Among these, one or more selected from petroleum-based waxes, synthetic waxes, and plant-based waxes are preferred, one or more selected from paraffin wax, Fischer-Tropsch wax, olefin wax, synthetic ester wax, and carnauba wax are more preferred, and one or more selected from paraffin wax, Fischer-Tropsch wax, and synthetic ester wax are even more preferred.

[0045] From the viewpoint of obtaining a paper coating agent that forms a coating layer with excellent heat sealability, the melting point of the wax is preferably less than 100°C, more preferably 95°C or lower, and even more preferably 90°C or lower. Furthermore, from the viewpoint of obtaining a paper coating agent that forms a coating layer with excellent blocking resistance, the melting point is preferably 60°C or higher, more preferably 65°C or higher, and even more preferably 70°C or higher.

[0046] 〔silicone〕 Examples of silicones include general dimethyl silicone, methylphenyl silicone obtained by replacing at least one methyl group in dimethyl silicone with a phenyl group, and modified silicones with introduced reactive functional groups. From the viewpoint of obtaining a paper coating agent that forms a coating layer with excellent water repellency, heat sealability, and blocking resistance, modified silicones are preferred.

[0047] The modified silicone is preferably a modified silicone having one or more groups selected from amino groups, epoxy groups, ester groups, hydroxyl groups, and carboxyl groups in its side chains, one end, or both ends. More preferably, it is a modified silicone having one or more groups selected from amino groups, epoxy groups, ester groups, and hydroxyl groups in its side chains, even more preferably, it is a modified silicone having one or more groups selected from amino groups, hydroxyl groups, and carboxyl groups in its side chains, one end, or both ends, even more preferably, it is a modified silicone having one or more groups selected from amino groups, hydroxyl groups, and carboxyl groups in its side chains, and even more preferably, it is a modified silicone having an amino group in its side chains.

[0048] The modified silicone includes at least one selected from a modified silicone having repeating units represented by formula (1) and formula (2), a modified silicone having repeating units represented by formula (1) and the structure represented by formula (3), and a modified silicone having repeating units represented by formula (1) and formula (4). The modified silicone is a modified silicone having repeating units represented by formula (1) and formula (2), wherein X in formula (2) is preferably a group containing an amino group.

[0049] [ka] [In formula (1), R is independently a hydrocarbon group having 1 to 6 carbon atoms, and * is a bonding site.]

[0050] [ka] [In formula (2), R is independently a hydrocarbon group having 1 to 6 carbon atoms, R' is independently an alkylene group having 1 to 10 carbon atoms, a is 1 or 0, X is independently a group containing an amino group, an epoxy group, an ester group, a hydroxyl group, or a carboxyl group, and * is a bonding site.]

[0051] *-SiR 3-b (R''-X) b (3) [In formula (3), R is independently a hydrocarbon group having 1 to 6 carbon atoms, R'' is independently an alkylene group having 1 to 10 carbon atoms, b is an integer between 1 and 3, X is independently a group containing an amino group, an epoxy group, an ester group, a hydroxyl group, or a carboxyl group, and * is a bonding site to the repeating unit represented by formula (1) and / or formula (2).]

[0052] *-(R'''-O) c -* (4) [In formula (4), each R''' is independently an alkylene group having 2 to 4 carbon atoms, c is an integer between 30 and 60, and * is a bonding site to the repeating unit represented by formula (1) and / or formula (2).]

[0053] The repeating units represented by equation (1), equation (2), and equation (4) may be random or block-based, and are not particularly limited.

[0054] In formulas (1) to (3), the number of carbon atoms in the hydrocarbon group R is 6 or less, preferably 4 or less, more preferably 3 or less, even more preferably 2 or less, and even more preferably 1. Examples of hydrocarbon groups for R include methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, pentyl, and phenyl groups. Among these, the methyl group is preferred.

[0055] In formulas (2) and (3), the number of carbon atoms in the alkylene groups R' and R'' is 10 or less, preferably 8 or less, more preferably 5 or less, even more preferably 4 or less, even more preferably 3 or less, and preferably 1 or more. Examples of alkylene groups for R' and R'' include methanediyl group, ethane-1,2-diyl group, ethane-1,1-diyl group, propane-1,3-diyl group, and propane-1,2-diyl group. Among these, the methanediyl group is preferred.

[0056] In formula (4), examples of the alkylene group R''' include ethane-1,2-diyl group, propane-1,3-diyl group, propane-1,2-diyl group, butane-1,4-diyl group, butane-1,3-diyl group, butane-1,2-diyl group, and butane-2,3-diyl group. Among these, ethane-1,2-diyl group, propane-1,3-diyl group, and propane-1,2-diyl group are preferred.

[0057] Each of X is independently a group containing an amino group, an epoxy group, an ester group, a hydroxyl group, or a carboxyl group. When a is 0, X may have an ether bond. That is, X may be an aliphatic hydrocarbon group which may contain an ether bond and is substituted with one or more amino groups, epoxy groups, ester groups, hydroxyl groups, or carboxyl groups, and the total number of carbon atoms of X is preferably 10 or less, more preferably 9 or less, and preferably 1 or more, more preferably 2 or more. Furthermore, an aliphatic hydrocarbon group containing an ether bond refers to a group that has an ether bond (-O-) between carbon-carbon bonds.

[0058] When the modified silicone is a silicone having an amino group in its side chain, X is a group containing an amino group. In this case, in formula (2) above, a is preferably 1 or 0, and X is preferably independently -NH2 or -R''''-NH-R''''-NH2, and R'''' is preferably independently an alkylene group having 1 to 10 carbon atoms. When a is 1, X is preferably -NH2, and when a is 0, X is preferably -R''''-NH-R''''-NH2. It is even more preferable that a is 1, X is -NH2, and R'''' is an alkylene group having 1 to 10 carbon atoms.

[0059] The modified silicone contains 500 or fewer repeating units represented by formula (1), preferably 450 or fewer, more preferably 400 or fewer, and preferably 10 or more, preferably 30 or more, more preferably 50 or more. Furthermore, the repeating units represented by formula (2) preferably number 40 or less, more preferably 20 or less, even more preferably 10 or less, and preferably 1 or more.

[0060] When the modified silicone has one or more functional groups selected from an amino group, an epoxy group, an ester group, a hydroxy group, or a carboxy group, the functional group equivalent of the modified silicone is preferably 300 g / mol or more, more preferably 500 g / mol or more, still more preferably 1,000 g / mol or more, and still more preferably 2,000 g / mol or more, and is preferably 10,000 g / mol or less, more preferably 8,000 g / mol or less, still more preferably 6,000 g / mol or less. The functional group equivalent means the mass of the modified silicone per mole of the functional group.

[0061] When the modified silicone is liquid at 25°C, from the viewpoint of obtaining a paper coating agent that forms a coating layer having excellent water repellency, heat sealability, and blocking resistance, at 25°C, the kinematic viscosity of the modified silicone is preferably 100 mm 2 / s or more, more preferably 200 mm 2 / s or more, still more preferably 500 mm 2 / s or more, and is preferably 10,000 mm 2 / s or less, more preferably 7,000 mm 2 / s or less, still more preferably 5,000 mm 2 / s or less. The kinematic viscosity of the modified silicone may be an adopted catalog value, and can also be measured using, for example, a fully automatic micro kinematic viscometer (manufactured by Bisco Co., Ltd.).

[0062] Examples of the modified silicones mentioned above include: modified silicones having amino groups in the side chain (commercial products include, for example, "KF-864", "KF-865" (manufactured by Shin-Etsu Chemical Co., Ltd.), "WT-1650", "WT-1270" (manufactured by Asahi Kasei Wacker Silicone Co., Ltd.)); modified silicones having amino groups at both ends (commercial products include, for example, "KF-8008" (manufactured by Shin-Etsu Chemical Co., Ltd.), "DOWSIL BY16-871" (manufactured by Dow Toray Industries, Inc.)); modified silicones having an amino group at one end; and modified silicones having carboxyl groups in the side chain (commercial products include, for example, "X-22-3701E" (manufactured by Shin-Etsu Chemical Co., Ltd.), "DOWSIL BY16-880 (manufactured by Dow Toray Industries, Inc.), modified silicones having epoxy groups in their side chains (commercially available examples include "KF-101", "KF-1001", "X-22-343" (manufactured by Shin-Etsu Chemical Co., Ltd.), "DOWSIL SF8413 (manufactured by Dow Toray Industries, Inc.), modified silicones having epoxy groups at both ends (commercial products include, for example, "KF-105", "X-22-163A", "X-22-163B", "X-22-163C", "X-22-169AS", "X-22-169B" (manufactured by Shin-Etsu Chemical Co., Ltd.)), modified silicones having epoxy groups at one end (commercial products include, for example, "X-22-173BX", "X-22-173DX" (both manufactured by Shin-Etsu Chemical Co., Ltd.)), modified silicones having ester groups in the side chain (commercial products include, for example, "X-22-715" (manufactured by Shin-Etsu Chemical Co., Ltd.), etc.) Modified silicones having ster groups at both ends, modified silicones having an ester group at one end, modified silicones having hydroxyl groups at both ends (commercially available examples include "KF-6003" (manufactured by Shin-Etsu Chemical Co., Ltd.)), modified silicones having a hydroxyl group at one end (commercially available examples include "X-22-170BX" (manufactured by Shin-Etsu Chemical Co., Ltd.)), modified silicones having carboxyl groups at both ends (commercially available examples include "X-22-162C" (manufactured by Shin-Etsu Chemical Co., Ltd.)), and modified silicones having a carboxyl group at one end (commercially available examples include "X-22-3710" (manufactured by Shin-Etsu Chemical Co., Ltd.)).Modified silicones having hydroxyl groups in their side chains (commercially available examples include "X-22-4015" (manufactured by Shin-Etsu Chemical Co., Ltd.)).

[0063] From the viewpoint of obtaining a paper coating agent that forms a coating layer having excellent water repellency and heat sealability, the content of wax and silicone in the paper coating agent is preferably 2% by mass or more, more preferably 3% by mass or more, and even more preferably 4% by mass or more. From the viewpoint of obtaining a paper coating agent that forms a coating layer having excellent blocking resistance, the content is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 12% by mass or less.

[0064] The mass ratio of the total amount of polyester resin to wax and silicone in the paper coating agent (polyester resin / wax and silicone) is preferably 50 / 50 or more, more preferably 55 / 45 or more, even more preferably 60 / 40 or more, and preferably 95 / 5 or less, more preferably 90 / 10 or less, and even more preferably 88 / 12 or less, from the viewpoint of obtaining a paper coating agent that forms a coating layer having excellent water repellency, heat sealability, and blocking resistance.

[0065] From the viewpoint of obtaining a paper coating agent that forms a coating layer having excellent water repellency, heat sealability, and blocking resistance, the content of resin particles in the paper coating agent is preferably 15% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more. From the viewpoint of dispersion stability of the paper coating agent, it is preferably 40% by mass or less, more preferably 38% by mass or less, and even more preferably 36% by mass or less.

[0066] [Other polyester resins] The resin particles may contain polyester resins other than the above-mentioned polyester resins, waxes, and silicones. There are no particular restrictions on the polyester resins other than those mentioned above, as long as they contain a polycondensate of an alcohol component and a carboxylic acid component. Examples include polyester resins made from polycondensates of raw materials that do not contain polyethylene terephthalate, 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. Other preferred polyester resins include those made from polycondensates of raw materials containing an alcohol component and a carboxylic acid component, but without polyethylene terephthalate. Examples of alcohol and carboxylic acid components include those listed above.

[0067] The total content of polyester resin and one or more selected from wax and silicone in the resin particles is preferably 95% by mass or more, more preferably 98% by mass or more, even more preferably 99% by mass or more, and even more preferably 100% by mass, from the viewpoint of obtaining a paper coating agent that forms a coating layer having excellent water repellency, heat sealability, and blocking resistance.

[0068] From the viewpoint of obtaining a paper coating agent that forms a coating layer having excellent water repellency, heat sealability, and blocking resistance, the content of polyester resin in the resin particles is preferably 10% by mass or more, more preferably 14% by mass or more, even more preferably 18% by mass or more, and preferably 30% by mass or less, more preferably 28% by mass or less, and even more preferably 27% by mass or less.

[0069] From the viewpoint of obtaining a paper coating agent that forms a coating layer having excellent water repellency and heat sealability, the content of wax and silicone in the resin particles is preferably 2% by mass or more, more preferably 3% by mass or more, and even more preferably 4% by mass or more. From the viewpoint of obtaining a paper coating agent that forms a coating layer having excellent blocking resistance, the content is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 12% by mass or less.

[0070] The mass ratio of the total amount of polyester resin to wax and silicone in the resin particles (polyester resin / wax and silicone) is preferably 50 / 50 or more, more preferably 55 / 45 or more, even more preferably 60 / 40 or more, and preferably 95 / 5 or less, more preferably 90 / 10 or less, and even more preferably 88 / 12 or less, from the viewpoint of obtaining a paper coating agent that forms a coating layer having excellent water repellency, heat sealability, and blocking resistance.

[0071] The paper coating agent may contain hydrophobic compounds other than the wax and silicone mentioned above, to the extent that it does not impair the effects of the present invention.

[0072] [Manufacturing of paper coating agents] The resin particles contained in the paper coating agent of the present invention are preferably produced by dispersing one or more selected from amorphous polyester resins, waxes, and silicones in an aqueous medium. Methods for obtaining an aqueous dispersion of resin particles include adding one or more selected from amorphous polyester resins, waxes, and silicones to an aqueous medium and performing dispersion treatment using a disperser or the like, and gradually adding an aqueous medium to a solution containing one or more selected from amorphous polyester resins, waxes, and silicones to perform phase inversion emulsification. Among these, the method of performing phase inversion emulsification is preferred. Phase inversion emulsification is preferably performed by first dissolving one or more selected from amorphous polyester resins, waxes, and silicones in an organic solvent to obtain a solution containing one or more selected from polyester resins, waxes, and silicones, then adding an aqueous medium to the solution to perform phase inversion emulsification, and then removing the organic solvent.

[0073] In other words, the method for producing the paper coating agent of the present invention preferably comprises the following steps 1 to 5 in this order. Step 1: A process for producing a polyester resin by reacting an alcohol component, a carboxylic acid component, and polyethylene terephthalate. Step 2: Dissolving a polyester resin and one or more substances selected from wax and silicone in an organic solvent. Step 3: Adding a basic compound to neutralize the polyester resin. Step 4: Add an aqueous medium and perform phase inversion emulsification of the polyester resin with one or more selected from waxes and silicones. Step 5: Step of removing organic solvent by distillation.

[0074] [Process 1] Step 1 is a process for producing a polyester resin by reacting an alcohol component, a carboxylic acid component, and polyethylene terephthalate. An example of a method for producing a polyester resin is the method described in "(Method for producing polyester resin)" above. The alcohol component, carboxylic acid component, and polyethylene terephthalate are the same as those listed above, and the preferred examples are also the same.

[0075] [Process 2] Step 2 is a step of dissolving a polyester resin and one or more substances selected from wax and silicone in an organic solvent. Organic solvents for dissolving polyester resins and one or more selected from waxes and silicones 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 polyester resins and one or more selected from waxes and silicones and being easy to remove 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.

[0076] Polyester resins and waxes and / or silicones may be dissolved in an organic solvent either first or all at the same time. If the polyester resins include multiple types of polyester resins, they may be pre-mixed before dissolving in the organic solvent. Similarly, if the waxes and / or silicones include multiple types of waxes and / or silicones, they may be pre-mixed before dissolving in the organic solvent.

[0077] The mass ratio of the total amount of polyester resin to wax and silicone (polyester resin / wax and silicone) is the same as the mass ratio in the resin particles [amorphous polyester resin / wax and silicone].

[0078] The mass ratio of the organic solvent to the total mass of one or more selected from polyester resins, waxes, and silicones [organic solvent / total mass of one or more selected from polyester resins, waxes, and silicones] is preferably 50 / 100 or more, more preferably 100 / 100 or more, even more preferably 150 / 100 or more, and preferably 500 / 100 or less, more preferably 400 / 100 or less, and even more preferably 300 / 100 or less.

[0079] [Step 3] Step 3 is a process in which a basic compound is added to neutralize the polyester resin. Specifically, in step 2, a solution is obtained of a polyester resin and one or more selected from wax and silicone, after which an aqueous solution of a basic compound is added and neutralized. The addition of the aqueous solution of the basic compound is usually carried out at a temperature below the boiling point of the organic solvent. The basic compounds are the same as those listed in the section above under "[Polyester Resins]" for neutralized polyester resins, and the preferred examples are also the same.

[0080] [Step 4] Step 4 is a step in which an aqueous medium is added and one or more selected from the neutralized polyester resin, wax, and silicone are inverted and emulsified. In this invention, "aqueous system" means that water accounts for the largest proportion in the medium. Deionized water or distilled water is preferably used as the water in the aqueous medium. The aqueous medium may further contain an organic solvent. Examples of such organic solvents include aliphatic alcohols having 1 to 4 carbon atoms, such as methanol, ethanol, and 2-propanol; ketones having 3 to 8 carbon atoms, such as acetone and methyl ethyl ketone; and water-soluble organic solvents such as ethers, such as diethyl ether and tetrahydrofuran. From an environmental standpoint, the water content in the aqueous medium is preferably 60% by mass or more, more preferably 70% 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, and even more preferably 100% by mass.

[0081] When adding an aqueous medium, the temperature of one or more solutions selected from polyester resins, waxes, and silicones is preferably 10°C or higher, more preferably 15°C or higher, even more preferably 20°C or higher, and preferably 40°C or lower, more preferably 35°C or lower, and even more preferably 25°C or lower, from the viewpoint of improving the dispersion stability of resin particles in the aqueous medium. From the viewpoint of improving the dispersion stability of the resin particles in the aqueous medium, 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 20 parts by mass / min or less, more preferably 15 parts by mass / min or less, and even more preferably 10 parts by mass / min or less, based on 100 parts by mass of the total mass of the polyester resin constituting the resin particles and one or more selected from wax and silicone, until the phase inversion is completed. After the phase inversion, there is no restriction on the addition rate of the aqueous medium after the resin particles have been obtained.

[0082] [Step 5] Step 5 is the step of removing the organic solvent by distillation. After performing phase inversion emulsification in step 4, it is preferable to remove the organic solvent from the aqueous dispersion of resin particles obtained by phase inversion emulsification, from the viewpoint of improving the dispersion stability of resin particles in an aqueous medium. The removal of organic solvents is not particularly limited, and any method can be used. The resulting aqueous dispersion of resin particles 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 non-volatile content.

[0083] The non-volatile content of the aqueous dispersion of resin particles of the present invention is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% 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 non-volatile content of the aqueous dispersion is measured by the method described in the examples.

[0084] The volume median particle size (D) of the resin particles in the aqueous dispersion of the resin particles of the present invention 50 The volume median particle size (D) is preferably 0.020 μm or more, more preferably 0.040 μm or more, even more preferably 0.060 μm or more, even more preferably 0.080 μm or more, and preferably 0.50 μm or less, more preferably 0.40 μm or less, even more preferably 0.35 μm or less, and even more preferably 0.30 μm or less, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper. 50 ) is measured by the method described in the examples.

[0085] The aqueous dispersion of the resin particles can be used as is as the paper coating agent of the present invention. That is, the paper coating agent of the present invention may be a paper coating agent in which resin particles are dispersed in an aqueous medium. Various additives used in paper coating agents can also be added to and mixed with the aqueous dispersion as needed. Examples of such additives include organic solvents, humectants, wetting agents, penetrating agents, viscosity modifiers, defoaming agents, preservatives, fungicides, rust inhibitors, pH adjusters, antioxidants, and UV absorbers. Furthermore, the paper coating agent of the present invention may contain hydrophobic substances other than the wax and silicone described above, to an extent that does not impair the effect of the paper coating agent.

[0086] Furthermore, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper, the paper coating agent of the present invention preferably contains substantially no surfactants. When the paper coating agent contains substantially no surfactants, the affinity of the coating layer formed by coating a paper substrate with the paper coating agent to water is reduced, thereby improving water repellency. Here, "substantially absent" means that surfactants are not intentionally added, and does not exclude the presence of small amounts of surfactant as impurities. For example, even if the paper coating agent of the present invention contains surfactants, the amount of surfactant is preferably 0.1% by mass or less, more preferably 0.01% by mass or less, and even more preferably 0.001% by mass or less. Furthermore, in the present invention, when producing an aqueous dispersion of resin particles, by using a method in which the aforementioned polyester resin and wax are added to an aqueous medium and dispersed using a disperser or the like, or by a method in which the aqueous medium is gradually added to a solution of polyester resin and wax and phase inversion emulsification is performed, the wax can be dispersed in an aqueous medium without using a surfactant, and a paper coating agent that is substantially free of surfactants can be obtained.

[0087] [Coated paper] The coated paper of the present invention has a coating layer on at least one side of a paper substrate containing a polyester resin and at least one selected from wax and silicone. Here, the polyester resin is a polycondensate of an alcohol component, a carboxylic acid component, and polyethylene terephthalate, and the amount of polyethylene terephthalate is 5% by mass or more and 50% by mass or less of the total amount of the alcohol component, the carboxylic acid component, and polyethylene terephthalate. Furthermore, it is preferable that the coated paper of the present invention has a coating layer formed by the paper coating agent described above.

[0088] [Paper base material] Examples of paper substrates include uncoated papers such as fine paper, medium-quality paper, and newsprint; coated papers such as art paper, coated paper, and matte coated paper; information paper such as PPC paper; packaging paper such as kraft paper; base paper for corrugated cardboard; and cardboard such as paperboard for paper packaging. The basis weight of the paper substrate is not particularly limited, but from the viewpoint of handling the coated paper and ease of coating the paper substrate, it is preferably 10 g / m². 2 The above applies, and preferably 200 g / m². 2 More preferably, 150 g / m² 2 More preferably 120 g / m² 2 The following applies:

[0089] [Polyester resin] The polyester resin contained in the coating layer can be the polyester resin listed above for paper coating agents, and the preferred examples are also the same.

[0090] 〔wax〕 The waxes included in the coating layer can be those listed above for paper coating agents, and the preferred examples are similar.

[0091] 〔silicone〕 The silicone contained in the coating layer can be the silicone listed above for paper coating agents, and the preferred examples are similar.

[0092] The coating layer may also contain other polyester resins listed above in the paper coating agent section, and the same applies to preferred examples.

[0093] [Manufacturing method for coated paper] The present invention provides a method for manufacturing coated paper, comprising: step I, applying the paper coating agent to at least one side of a paper substrate to form a coating layer; and step II, drying the coating layer on the paper substrate coated in step I. As the paper substrate, the paper substrates listed above for coated paper can be used, and the preferred examples are the same.

[0094] [Process I] Step I is a step of applying a paper coating agent to at least one side of a paper substrate to form a layer of coating liquid. In step I, the amount of paper coating agent applied is preferably 1 g / m² in solid content, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper. 2Above, a comfortable 3g / m 2 More preferably 5 g / m 2 The above is true, and preferably 30 g / m² 2 More preferably 25 g / m 2 More preferably 20 g / m 2 The following applies: There are no particular restrictions on the method of applying the paper coating agent to the paper substrate in step I. 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.

[0095] [Process II] Step II is the process of drying the coating liquid layer on the paper substrate coated in Step I. Examples of drying methods in step II 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. Heat drying methods include applying hot air to the surface of the coating liquid layer on a paper substrate to heat it, bringing a heater close to the surface of the coating liquid layer on a paper substrate to heat it, contacting a heater with the surface of the paper substrate opposite to the surface on which the coating liquid layer is formed to heat it, 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 70°C or higher, and even more preferably 90°C or higher, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper, and preferably 200°C or lower, more preferably 150°C or lower, and even more preferably 130°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, more preferably 5 minutes or more, from the viewpoint of improving the water repellency and water resistance of the resulting coated paper, and preferably 30 minutes or less, more preferably 15 minutes or less, from the viewpoint of suppressing deformation of the paper substrate due to heat and reducing energy. [Examples]

[0096] The present invention will be specifically described below with reference to examples, but the present invention is not limited in any way by these examples. In the examples, room temperature means a temperature of 20°C or higher and 25°C or lower.

[0097] [Measurement method] In the following examples, various physical properties were measured by the following methods.

[0098] [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.

[0099] [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)).

[0100] [Glass transition temperature 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. If a peak was observed, that peak temperature was recorded. If no peak was observed but a step was observed, the temperature at the intersection of the tangent line showing the maximum slope of the curve at the step and the extension of the baseline on the low-temperature side of the step was recorded as the glass transition temperature.

[0101] [Acid value of resins] The measurement was performed according to the neutralization titration method described in JIS K0070:1992. However, in this method, only the measurement solvent was changed from a mixed solvent of ethanol and ether to a mixed solvent of acetone and toluene [acetone:toluene = 1:1 (volume ratio)].

[0102] [Medium particle size (D) of resin particles 50 )〕 The volume median particle size (D) was measured using the following measuring device and conditions. 50 ) was measured. (1) Measuring device: Laser diffraction / scattering particle size distribution analyzer "LA-960V2" (manufactured by Horiba, Ltd.) (2) Measurement conditions: A flow cell is used as the measurement cell, deionized water is used as the dispersion medium, and the sample to be measured is added so that the absorbance is within an appropriate range, and the volume median particle size (D 50 ) was measured.

[0103] [Non-volatile content concentration of aqueous dispersion of resin particles] Using a heat-drying type moisture meter "MX-50" (manufactured by A&D Co., Ltd.), 5g 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 dispersion was measured. The non-volatile content concentration was calculated according to the following formula. Non-volatile content concentration (mass%) = 100 - water content (mass%)

[0104] [Evaluation of water repellency] The 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 a droplet of deionized water was dropped from 10 mm above the coated paper. The water repellency was determined by observing the state of the paper after the droplet passed over it, and then rated on a scale of R0 to R10. (Water repellency) R10: Something that rolls down completely R9: A substance with small, spherical droplets scattered throughout. R8: More than a quarter of the traces consist of scattered spherical droplets. R7: One-quarter of the trace is wet with elongated water droplets. R6: The mark is half wet. R4: A continuous pattern, but broken in places, clearly narrower than a water droplet. R2: A continuous trace that is slightly narrower than a water droplet. R0: A continuous trace showing a uniform width.

[0105] [Evaluation of heat sealability] Prepare two sheets of coated paper to be tested, overlap them so that the coated surfaces are in contact with each other, and apply pressure at a temperature of 120°C and a pressure of 2 kgf / cm². 2 The sheets were heat-sealed using a heat seal tester (manufactured by Tester Sangyo Co., Ltd.) with a pressurization time of 1 second. After standing at room temperature for 1 hour, the condition of the paper and the peeled surface were observed when the two stacked coated papers were separated, and the heat sealability was evaluated according to the following criteria. L5: The papers were stuck together and could not be separated, causing the paper to tear. L4: The glued part of the paper could be peeled off, but the paper also tore at the same time. L3: More than half of the paper was adhered, and traces of adhesion were observed on more than half of the surface of the peeled paper. L2: Part of the paper was adhered, and traces of the adhesive were observed on the surface of the peeled-off paper. L1: The papers were not adhered to each other at all, and there were no traces of adhesion on the surface of the peeled paper.

[0106] [Evaluation of blocking resistance] Two sheets of coated paper to be tested are placed on top of each other so that the coated sides are in contact, and the coating is applied at 2 kg / cm². 2 The samples were left standing for 12 hours in a constant temperature and humidity chamber at 50°C and 75% relative humidity under pressure. After removing them from the chamber and allowing them to return to room temperature, the presence or absence of blocking during the separation of the two stacked coated papers was evaluated according to the following criteria. L5: When separating the two stacked coated papers, they could be peeled off without resistance, and no signs of adhesion between the coated papers were observed. L4: There was resistance when separating the two stacked coated papers, and traces of adhesion between the coated papers were observed in less than 5% of the surface area of ​​the coating layer. However, the papers could be separated without causing damage such as cracking or peeling to the coating layer. L3: When peeling the two stacked coated papers apart, there was resistance, and traces of adhesion between the coated papers were observed in an area of ​​5% to less than 25% of the surface of the coating layer. However, the papers could be peeled apart without causing damage such as cracking or peeling to the coating layer. L2: Resistance was observed when separating the two stacked coated papers, and traces of adhesion between the coated papers were seen in more than 25% of the surface area of ​​the coating layer. Furthermore, cracks and peeling were observed in less than 5% of the surface area of ​​the coating layer. L1: Resistance was observed when separating the two stacked coated papers, and traces of adhesion between the coated papers were seen in more than 25% of the surface area of ​​the coating layer. Furthermore, cracks and peeling were observed in more than 5% of the surface area of ​​the coating layer.

[0107] [Manufacturing of polyester resins] Manufacturing Example A1 (Manufacturing of polyester resin A-1) A four-necked flask equipped with a nitrogen inlet tube, dehydration tube, stirrer, and thermocouple was purged with nitrogen. 4605g of bisphenol A propylene oxide (2.2) adduct, 1176g of terephthalic acid, 1360g of polyethylene terephthalate ("RAMAPET BF3067" (IV value: 0.64) (manufactured by Indorama Ventures)), 40g of tin di(2-ethylhexanoate), and 0.8g of gallic acid were added. Under a nitrogen atmosphere, the mixture was heated to 235°C with stirring and held for 8 hours. After that, the pressure inside the flask was reduced and held at 8.3kPa for 1 hour. After returning to atmospheric pressure, the mixture was cooled to 190°C, and 470g of fumaric acid, 389g of trimellitic anhydride, and 2g of tert-butylcatechol were added. The mixture was then heated to 210°C over 2 hours and held at 210°C for 1 hour. The pressure in the flask was then further reduced and held at 8.3kPa until the softening point reached the temperature shown in Table 1, thereby obtaining polyester resin A-1. The physical properties of the obtained polyester resin A-1 are shown in Table 1.

[0108] Manufacturing Example A2 (Manufacturing of polyester resin A-2) A four-necked flask equipped with a nitrogen inlet tube, dehydration tube, stirrer, and thermocouple was purged with nitrogen. 4975g of bisphenol A propylene oxide (2.2) adduct, 1416g of terephthalic acid, 910g of polyethylene terephthalate ("RAMAPET BF3067" (IV value: 0.64) (manufactured by Indorama Ventures)), 40g of tin di(2-ethylhexanoate), and 0.8g of gallic acid were added. Under a nitrogen atmosphere, the mixture was heated to 235°C with stirring and held for 8 hours. The pressure inside the flask was then reduced and held at 8.3kPa for 1 hour. After returning to atmospheric pressure, the mixture was cooled to 210°C. 336g of succinic acid and 364g of trimellitic anhydride were added. The mixture was held at 210°C for 1 hour. The pressure inside the flask was then further reduced and held at 8.3kPa until the softening point reached the temperature shown in Table 1, thereby obtaining polyester resin A-2. The physical properties of the obtained polyester resin A-2 are shown in Table 1.

[0109] Manufacturing example A3 (Manufacturing of polyester resin A-3) A four-necked flask equipped with a nitrogen inlet tube, dehydration tube, stirrer, and thermocouple was purged with nitrogen. 1745g of 1,2-propanediol, 1905g of terephthalic acid, 2938g of polyethylene terephthalate ("RAMAPET BF3067" (IV value: 0.64) (manufactured by Indorama Ventures)), and 40g of tin(II) di(2-ethylhexanoate) were added. Under a nitrogen atmosphere, the mixture was heated to 180°C with stirring and held for 1 hour, then heated to 220°C over 8 hours. After holding at 220°C for 2 hours, 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 210°C, and 677g of succinic acid and 735g of trimellitic anhydride were added. The mixture was then held at 210°C for 1 hour. The pressure in the flask was then further reduced and maintained at 8.3kPa until the softening point reached the temperature shown in Table 1, thereby obtaining polyester resin A-3. The physical properties of the obtained polyester resin A-3 are shown in Table 1.

[0110] Manufacturing example A4 (Manufacturing of polyester resin A-4) A four-necked flask equipped with a nitrogen inlet tube, dehydration tube, stirrer, and thermocouple was purged with nitrogen. 1062 g of 1,2-propanediol, 1085 g of dimethyl 2,6-naphthalenedicarboxylate, 3414 g of polyethylene terephthalate, and 40 g of tin(II) di(2-ethylhexanoate) were added. Under a nitrogen atmosphere, the mixture was heated to 180°C with stirring and held for 1 hour, then heated to 220°C over 10 hours. After holding at 220°C for 2 hours, the pressure inside the flask was further reduced to 8.3 kPa and held for 1 hour. After returning to atmospheric pressure, 2439 g of dodecenyl succinic anhydride was added, and the mixture was held at 220°C for 1 hour. The pressure inside the flask was further reduced to 8.3 kPa and the reaction was carried out until the softening point reached the temperature shown in Table 1, yielding polyester resin A-4. The physical properties of the obtained polyester resin A-4 are shown in Table 1.

[0111] Manufacturing Example A5 (Manufacturing of polyester resin A-5) A four-necked flask equipped with a nitrogen inlet tube, dehydration tube, stirrer, and thermocouple was purged with nitrogen. 3675g of bisphenol A propylene oxide (2.2) adduct, 697g of terephthalic acid, 2016g of polyethylene terephthalate ("RAMAPET BF3067" (IV value: 0.64) (manufactured by Indorama Ventures)), 40g of tin di(2-ethylhexanoate), and 0.8g of gallic acid were added. Under a nitrogen atmosphere, the mixture was heated to 235°C with stirring and held for 8 hours. The pressure inside the flask was then reduced and held at 8.3kPa for 1 hour. After returning to atmospheric pressure, the mixture was cooled to 220°C, and 1613g of dodecenyl succinic anhydride was added. The mixture was held at 220°C for 2 hours, and the pressure inside the flask was further reduced and held at 8.3kPa until the softening point reached the temperature shown in Table 1, thereby obtaining polyester resin A-5. The physical properties of the obtained polyester resin A-5 are shown in Table 1.

[0112] Comparative manufacturing example A'1 (Manufacturing of polyester resin A-6) A four-necked flask equipped with a nitrogen inlet tube, dehydration tube, stirrer, and thermocouple was purged with nitrogen. 2654 g of 1,2-propanediol, 4058 g of terephthalic acid, and 40 g of tin(II) di(2-ethylhexanoate) were added. Under a nitrogen atmosphere, the mixture was heated to 180°C with stirring and held for 1 hour, then heated to 220°C over 6 hours. After holding at 220°C for 2 hours, 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 210°C, and 618 g of succinic acid and 670 g of trimellitic anhydride were added. The mixture was held at 210°C for 1 hour, then the pressure inside the flask was further reduced to 8.3 kPa and the reaction was carried out until the softening point reached the temperature shown in Table 1, yielding polyester resin A-6. The physical properties of the obtained polyester resin A-6 are shown in Table 1.

[0113] Comparative manufacturing example A'2 (Manufacturing of polyester resin A-7) A four-necked flask equipped with a nitrogen inlet tube, dehydration tube, stirrer, and thermocouple was purged with nitrogen. 983 g of 1,2-propanediol, 1021 g of ethylene glycol, 2733 g of terephthalic acid, 1004 g of dimethyl 2,6-naphthalenedicarboxylate, and 40 g of tin(II) di(2-ethylhexanoate) were added. Under a nitrogen atmosphere, the mixture was heated to 180°C with stirring and held for 1 hour, then heated to 220°C over 6 hours. After holding at 220°C for 2 hours, the pressure inside the flask was further reduced to 8.3 kPa and held for 1 hour. After returning to atmospheric pressure, 2258 g of dodecenyl succinic anhydride was added, and the mixture was held at 220°C for 1 hour. The pressure inside the flask was further reduced to 8.3 kPa and the reaction was carried out until the softening point reached the temperature shown in Table 1, yielding polyester resin A-7. The physical properties of the obtained polyester resin A-7 are shown in Table 1.

[0114] Comparative manufacturing example A'3 (Manufacturing of polyester resin A-8) A four-necked flask equipped with a nitrogen inlet tube, dehydration tube, stirrer, and thermocouple was purged with nitrogen. 2173g of 1,2-propanediol, 2658g of terephthalic acid, 1047g of dimethyl 2,6-naphthalenedicarboxylate, and 40g of tin(II) di(2-ethylhexanoate) were added. Under a nitrogen atmosphere, the mixture was heated to 180°C with stirring and held for 1 hour, then heated to 220°C over 6 hours. After holding at 220°C for 2 hours, the pressure inside the flask was further reduced to 8.3kPa and held for 1 hour. After returning to atmospheric pressure, 2123g of dodecenyl succinic anhydride was added, and the mixture was held at 220°C for 1 hour. The pressure inside the flask was further reduced to 8.3kPa and the reaction was carried out until the softening point reached the temperature shown in Table 1, yielding polyester resin A-8. The physical properties of the obtained polyester resin A-8 are shown in Table 1.

[0115] [Table 1]

[0116] Example 1 (Manufacturing of paper coating agent 1) In a 2L four-necked flask equipped with a reflux condenser, stirrer, and thermocouple, 140g of polyester resin A-1 and 60g of silicone (H1, amino-modified silicone, Shin-Etsu Chemical Co., Ltd. "KF-864") were placed and mixed with 400g of methyl ethyl ketone at room temperature. The mixture was then heated to 65°C and dissolved. Next, it was cooled to room temperature, and a 5% by mass aqueous sodium hydroxide solution was added at room temperature to achieve a degree of neutralization of 65 mol% relative to the acid value of amorphous polyester resin A-1. The mixture was then stirred for 60 minutes. Next, under stirring at room temperature, 600 g of deionized water was added dropwise at a rate of 10 mL / min to emulsify the mixture through phase inversion. Then, the temperature was raised to 65°C, and while maintaining this temperature, the methyl ethyl ketone was removed by 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 paper coating agent 1 as a resin particle dispersion. The median particle size (D) of the resin particles in the obtained paper coating agent X-1 was then measured. 50 ) are shown in Table 2.

[0117] (Manufacturing of coated paper 1) PPC paper "J paper" (basis weight 82g / m²) is used as the paper base material. 2 Paper coating agent 1 was applied to a paper substrate (manufactured by Fujifilm Business Innovation Corporation) using a bar coater (No. 12) to form a coating layer. The coating amount of paper coating agent 1 to the paper substrate was 10 g / m² as non-volatile content. 2 It was done in such a way. Next, the paper coating layer on the paper substrate was dried in a 110°C dryer for 5 minutes to obtain coated paper 1 having a coating layer on the paper substrate. The obtained coated paper 1 was evaluated for the above-mentioned water repellency, heat sealability, and blocking resistance. The results are shown in Table 2.

[0118] Examples 2-5 and Comparative Examples 1 and 2 Paper coating agents 2 to 5, and paper coating agents C1 and C2 were obtained in the same manner as in Example 1, except that the polyester resin and silicone were changed to those shown in Table 2. The median particle size (D) of the resin particles in the obtained paper coating agents was determined. 50) are shown in Table 2. Next, coated papers 2-5 and coated papers C1 and C2 were manufactured in the same manner as in Example 1, and their water repellency, heat sealability, and blocking resistance were evaluated. The results are shown in Table 2.

[0119] In Table 2, Silicone H1 and H2 refer to the following, respectively. H1: KF-864 (amino-modified silicone, viscosity 1700 mm) 2 (Manufactured by Shin-Etsu Chemical Co., Ltd.) H2: KF-861 (amino-modified silicone, viscosity 3500 mm) 2 (Manufactured by Shin-Etsu Chemical Co., Ltd.)

[0120] [Table 2]

[0121] Table 2 shows that coated papers 1-5, coated with paper coating agents 1-5 of Examples 1-5, exhibited excellent water repellency, as well as superior heat sealability and blocking resistance. On the other hand, coated papers C1 and C2, coated with paper coating agents C1 and C2 of Comparative Examples 1 and 2, exhibited excellent water repellency, but inferior heat sealability and blocking resistance.

[0122] Example 6 (Manufacturing of paper coating agent 6) In a 2L four-necked flask equipped with a reflux condenser, stirrer, and thermocouple, 160g of polyester resin A-4 and 40g of wax (H3, ester wax, NOF Corporation "WE-14") were placed and mixed with 400g of methyl ethyl ketone at room temperature. The mixture was then heated to 65°C and dissolved. Next, while maintaining the temperature at 70°C, a 5% by mass aqueous sodium hydroxide solution was added to achieve a degree of neutralization of 65 mol% relative to the acid value of amorphous polyester resin A-4, 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 70°C to emulsify the mixture through phase inversion. Then, while maintaining the temperature at 70°C, the methyl ethyl ketone 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 paper coating agent 6 as a resin particle dispersion. The median particle size (D) of the resin particles in the obtained paper coating agent 6 was measured. 50 ) are shown in Table 3.

[0123] (Manufacturing of coated paper 6) Coated paper 6 was manufactured in the same manner as in Example 1, and its water repellency, heat sealability, and blocking resistance were evaluated. The results are shown in Table 3.

[0124] Examples 7 and 8, and Comparative Examples 3-5 In Example 6, paper coating agents 7 and 8, and paper coating agents C3 to C5 were obtained in the same manner as in Example 6, except that the polyester resin and wax were changed to those shown in Table 3. The median particle size (D) of the resin particles in the obtained paper coating agents was determined. 50 ) are shown in Table 3. Next, coated papers 7 and 8, and coated papers C3 to C5 were manufactured in the same manner as in Example 1, and the water repellency, heat sealability, and blocking resistance of the coated papers were evaluated. The results are shown in Table 3.

[0125] In Table 3, waxes H3 and H4 refer to the following, respectively. H3:WE-14 (ester wax, melting point 78℃, manufactured by NOF Corporation) H4: HNP-9 (Paraffin wax, melting point 75°C, manufactured by Nippon Seiro Co., Ltd.)

[0126] [Table 3]

[0127] Table 3 shows that coated papers 6-8, coated with paper coating agents 6-8 of Examples 6-8, exhibited excellent water repellency, as well as superior heat sealability and blocking resistance. On the other hand, coated papers C3-C5, coated with paper coating agents C3-C5 of Comparative Examples 3-5, showed excellent water repellency, but inferior heat sealability and blocking resistance. [Industrial applicability]

[0128] According to the present invention, coated paper having a coating layer with excellent water repellency, heat sealability, and blocking resistance can be obtained, and can be used for paper labels, packaging paper, paper containers, etc., where water resistance is required.

Claims

1. A paper coating agent comprising resin particles containing a polyester resin and one or more selected from wax and silicone, The polyester resin is a polycondensate of an alcohol component, a carboxylic acid component, and polyethylene terephthalate. The amount of polyethylene terephthalate is 5% by mass or more and 50% by mass or less of the total amount of the alcohol component, carboxylic acid component, and polyethylene terephthalate. Paper coating agent.

2. The paper coating agent according to claim 1, wherein the polyester resin is water-insoluble.

3. The paper coating agent according to claim 1, wherein the mass ratio of the total amount of the polyester resin in the resin particles to the wax and the silicone (polyester resin / wax and silicone) is 50 / 50 or more and 95 / 5 or less.

4. The paper coating agent according to claim 1, wherein the silicone is a modified silicone having one or more selected from an amino group, a hydroxyl group, and a carboxyl group.

5. The paper coating agent according to claim 1, wherein the wax is one or more selected from paraffin wax, Fischer-Tropsch wax, and ester wax.

6. The paper coating agent according to claim 1, wherein the resin particles are dispersed in an aqueous medium.

7. A method for producing a paper coating agent according to any one of claims 1 to 6, comprising the following steps 1 to 5 in this order. Step 1: A step to produce the polyester resin by reacting the alcohol component, the carboxylic acid component, and the polyethylene terephthalate. Step 2: A step of dissolving the polyester resin and one or more selected from the wax and the silicone in an organic solvent. Step 3: Adding a basic compound to neutralize the polyester resin. Step 4: Add an aqueous medium and perform phase inversion emulsification of the polyester resin and one or more selected from the wax and the silicone. Step 5: Step of removing the organic solvent by distillation.

8. The method for producing a paper coating agent according to claim 7, wherein the intrinsic viscosity of the polyethylene terephthalate is 0.4 or more and 0.9 or less.

9. Coated paper having a coating layer on at least one side of a paper substrate containing a polyester resin and at least one selected from wax and silicone, The polyester resin is a polycondensate of an alcohol component, a carboxylic acid component, and polyethylene terephthalate. The amount of polyethylene terephthalate is 5% by mass or more and 50% by mass or less of the total amount of the alcohol component, carboxylic acid component, and polyethylene terephthalate. Coated paper.

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