Transparentizing agent, manufacturing method thereof, transparent paper, and manufacturing method thereof

Abstract

To provide a transparentizing agent that can be used to obtain a transparent paper having excellent transparency and temporal stability using a bio-derived raw material.SOLUTION: A transparentizing agent contains polyester resin components comprising reaction products of raw material components including (A) rosins, (B) polyvalent carboxylic acids, (C) polyols, and (D) aliphatic monocarboxylic acids, wherein the acid value of the polyester resin component is 100 mgKOH / g or under, the weight-average molecular weight of the polyester resin component is 1,000,000 or under, and the refractive index of the polyester resin component is 1.40 or over and 1.60 or under.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a clarifying agent, a method for producing the same, and transparent paper and a method for producing the same. [Background technology]

[0002] Common methods for producing paper with high transparency include, for example, making paper using pulp fibers with a high degree of beating, and impregnating the spaces between the fibers of the made base paper with a resin or the like. The method of making paper using pulp fibers with a high degree of beating is used to manufacture glassine paper, tracing paper, etc. Paper made using pulp fibers with a high degree of beating is used as packaging paper for windows in envelopes, etc. However, such paper is generally difficult to apply to applications requiring strength, such as packaging bags, because the pulp fibers are crushed and cut by the high beating.

[0003] On the other hand, a method of impregnating the spaces between fibers of a paper-made base paper with a resin or the like is used in the manufacture of oil paper, wax paper, etc. For example, Patent Document 1 proposes obtaining transparent paper by thermally melting and coating or impregnating a transparent agent containing a resin and paraffin wax on a base paper. Patent Document 2 proposes obtaining transparent paper by coating or impregnating a paper with a composition containing a liquid diene polymer and irradiating it with ultraviolet light. Patent Document 3 proposes coating a rosin-based aqueous transparent agent on a part of the base paper and heating it to obtain a windowed packaging bag. Patent Document 4 proposes printing and impregnating a transparent agent mainly composed of vegetable oil on a specific surface of a part of an opaque paper, and forming an oil layer protective film on both sides to make the opaque paper transparent. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Unexamined Patent Publication No. 132698 / 1983 [Patent Document 2] Japanese Patent Publication No. 132699 / 1983 [Patent Document 3] JP 2011-63286 A [Patent Document 4] Japanese Patent Application Publication No. 15395 / 1983 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, the replacement of plastic films with paper has been considered as a transition to sustainable and recyclable materials. For example, the replacement of packaging materials with paper is also progressing. If the transparency of plastic films could be imparted to paper, it is expected that its applications will expand even further.

[0006] In the techniques of Patent Documents 1 to 4, the transparency of the translucent regions impregnated with the clarifying agent can be increased by impregnating the voids between the cellulose fibers of the paper with the clarifying agent. However, the paraffin wax used in Patent Document 1 is a mixture of solid hydrocarbons made from petroleum, and is not a bio-derived raw material. The liquid diene polymer used in Patent Document 2 is also a petroleum-derived resin and does not use a bio-derived raw material.

[0007] The rosin-based aqueous clarifying agent used in Patent Document 3 is unable to achieve sufficient transparency. In Patent Document 4, an oil layer protection layer was required to prevent the impregnated vegetable oil from leaking out. If an oil layer protection layer is not provided, the vegetable oil will leak out and dry over time, causing the paper to become cloudy.

[0008] The present invention aims to provide a clarifying agent using bio-derived raw materials that can give transparent paper that is excellent in transparency and stability over time, and a manufacturing method thereof, as well as transparent paper that is excellent in transparency and stability over time and uses a clarifying agent using bio-derived raw materials, and a manufacturing method thereof. [Means for solving the problem]

[0009] The inventors have investigated a clarifying agent that uses a combination of rosins and aliphatic carboxylic acids. Although rosins and aliphatic carboxylic acids are substances that each exhibit a refractive index close to that of cellulose pulp, by using them in combination, the refractive index approaches that of cellulose pulp more than that of each other. However, as in Patent Document 4, if used as is, the aliphatic carboxylic acid will leach out or dry, causing the paper to become cloudy. After further investigation, the inventors have found that the above problem can be solved by introducing rosins and aliphatic carboxylic acids into polyester resins, and have completed the present invention.

[0010] The present invention has the following aspects. [1] A clarifying agent comprising a polyester resin component which is a reaction product of raw material components including (A) a rosin, (B) a polycarboxylic acid, (C) a polyol, and (D) an aliphatic monocarboxylic acid, wherein the polyester resin component has an acid value of 100 mgKOH / g or less, a weight average molecular weight of 1,000,000 or less, and a refractive index of 1.40 or more and 1.60 or less. [2] The clarifying agent according to [1], wherein the iodine value of the polyester resin component is 10 g / 100 g or more and 140 g / 100 g or less. [3] A method for producing a clarifying agent, comprising reacting raw material components including (A) a rosin, (B) a polycarboxylic acid, (C) a polyol, and (D) an aliphatic monocarboxylic acid, to obtain a polyester resin component having an acid value of 100 mgKOH / g or less, a weight-average molecular weight of 1,000,000 or less, and a refractive index of 1.40 or more and 1.60 or less. [4] The method for producing a clarifying agent according to [3], wherein the iodine value of the polyester resin component is 10 g / 100 g or more and 140 g / 100 g or less. [5] The (B) polyvalent carboxylic acid includes an α,β-unsaturated dicarboxylic acid, The method for producing a clarifying agent according to [3] or [4], wherein, when obtaining the polyester resin component, the (A) rosin is reacted with the α,β-unsaturated dicarboxylic acid to obtain a first product, and the first product is reacted with the (C) polyol and the (D) aliphatic monocarboxylic acid. [6] The (B) polyvalent carboxylic acid includes an α,β-unsaturated dicarboxylic acid, The method for producing a clarifying agent according to [3] or [4], wherein, when obtaining the polyester resin component, the (A) rosin is reacted with the α,β-unsaturated dicarboxylic acid to obtain a first product, the (C) polyol is modified with the (D) oil or fat having an aliphatic monocarboxylic acid as a constituent fatty acid to obtain a modified product, and the first product is reacted with the modified product. [7] A transparent agent is contained at least inside the paper base material, The clarifying agent comprises a polyester resin component which is a reaction product of raw material components including (A) rosins, (B) polycarboxylic acids, (C) polyols, and (D) aliphatic monocarboxylic acids, the polyester resin component having an acid value of 100 mgKOH / g or less, a weight average molecular weight of 1,000,000 or less, and a refractive index of 1.40 or more and 1.60 or less. [8] The transparent paper according to [7], wherein the iodine value of the polyester resin component is 10 g / 100 g or more and 140 g / 100 g or less. [9] The transparent paper according to [7] or [8], wherein the paper base material contains softwood chemical pulp and hardwood chemical pulp.

[10] A method for producing transparent paper by applying or impregnating a liquid composition containing a transparentizing agent and a liquid medium onto or onto a paper substrate, and drying the composition, The method for producing transparent paper, wherein the clarifying agent contains a polyester resin component which is a reaction product of raw material components including (A) rosins, (B) polycarboxylic acids, (C) polyols, and (D) aliphatic monocarboxylic acids, the polyester resin component having an acid value of 100 mgKOH / g or less, a weight average molecular weight of 1,000,000 or less, and a refractive index of 1.40 or more and 1.60 or less.

[11] The method for producing transparent paper according to

[10] , wherein the iodine value of the polyester resin component is 10 g / 100 g or more and 140 g / 100 g or less.

[12] The method for producing transparent paper according to

[10] or

[11] , wherein the paper base material contains softwood chemical pulp and hardwood chemical pulp. Effect of the Invention

[0011] According to the present invention, it is possible to provide a clarifying agent using bio-derived raw materials that can give transparent paper that is excellent in transparency and stability over time, and a method for producing the same, as well as transparent paper that is excellent in transparency and stability over time and uses a clarifying agent using bio-derived raw materials, and a method for producing the same. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] In this specification, the use of "to" indicating a range of values ​​means that the values ​​before and after it are included as the lower limit and upper limit. The lower and upper limits of the numerical ranges disclosed in this specification can be combined in any manner to create new numerical ranges.

[0013] "Clarifying agent" The clarifying agent of the present invention contains a polyester resin component which is a reaction product of raw material components including (A) rosins, (B) polycarboxylic acids, (C) polyols, and (D) aliphatic monocarboxylic acids. The acid value of the polyester resin component is 100 mgKOH / g or less, the weight average molecular weight is 1,000,000 or less, and the refractive index is 1.40 or more and 1.60 or less. The raw material components will be described in detail later.

[0014] The acid value of the polyester resin component is 100 mgKOH / g or less, and thus the transparency characteristics are excellent. The acid value of the polyester resin component is preferably 70 mgKOH / g or less, more preferably 60 mgKOH / g or less, and even more preferably 50 mgKOH / g or less. From the viewpoint of transparency suitability, the acid value of the polyester resin component is, for example, 0 mgKOH / g or more, preferably 5 mgKOH / g or more, more preferably 10 mgKOH / g or more, and even more preferably 20 mgKOH / g or more. The acid value is measured in accordance with JIS K 5601-2-1 (1999).

[0015] The weight average molecular weight (Mw) of the polyester resin component is 1,000,000 or less, and thus the transparency property is excellent. The weight average molecular weight of the polyester resin component is preferably 900,000 or less, and more preferably 800,000 or less. The lower limit of the weight average molecular weight of the polyester resin component is not particularly limited, and is, for example, preferably 5,000 or more, and more preferably 10,000 or more. The weight average molecular weight of the polyester resin component is a value calculated as standard polystyrene, measured by gel permeation chromatography (GPC).

[0016] When the refractive index of the polyester resin component is 1.40 or more and 1.60 or less, the clarifying agent has an excellent effect of clarifying a sheet mainly composed of cellulose, such as paper. This is because the refractive index of cellulose fibers is generally within the range of 1.4 to 1.6. By making the refractive index of the polyester resin component close to the refractive index of the cellulose fibers, the refraction of light at the interface between the clarifying agent and the pulp fibers in the paper base material can be reduced. The refractive index of the polyester resin component is preferably 1.45 or more and 1.58 or less, more preferably 1.47 or more and 1.57 or less, and even more preferably 1.48 or more and 1.56 or less. The refractive index is measured in accordance with JIS K 7142 (2014).

[0017] The iodine value of the polyester resin component is, from the viewpoint of drying property, for example, 5 g / 100 g or more, preferably 10 g / 100 g or more, more preferably 20 g / 100 g or more, and even more preferably 40 g / 100 g or more. Also, from the viewpoint of transparency suitability, the iodine value of the polyester resin component is, for example, 160 g / 100 g or less, preferably 140 g / 100 g or less, more preferably 120 g / 100 g or less, and even more preferably 100 g / 100 g or less. The iodine value is measured in accordance with JIS K 0070 (1992).

[0018] The softening point of the polyester resin component is, from the viewpoints of film-forming ability and tack resistance, for example, 70° C. or more, preferably 75° C. or more, and more preferably 80° C. or more. Also, the softening point of the polyester resin component is, from the viewpoints of film-forming ability and tack resistance, for example, 150° C. or less, preferably 130° C. or less, and more preferably 120° C. or less. The softening point is measured by the Mettler method.

[0019] (Raw material for polyester resin) (A) rosins are plant-derived components. Therefore, the polyester resin component can contribute to carbon neutrality. More specifically, (A) rosins are compounds derived from pine. There are no particular limitations on the pine, and examples of pine include Merkusian pine, slash pine, and Masson pine. These can be used alone or in combination of two or more types.

[0020] (A) Rosins are not particularly limited, and include known unmodified rosins and derivatives thereof. Examples of unmodified rosins include crude rosin and refined rosin. Examples of crude rosins include gum rosin, tall rosin, and wood rosin. Examples of refined rosins include refined products of crude rosin. Examples of rosin derivatives include hydrogenated rosin, disproportionated rosin, and polymerized rosin. These can be used alone or in combination of two or more types. The origin of rosin is not particularly limited, and examples include China, Vietnam, Indonesia, and Brazil. These can be used alone or in combination of two or more types. As the (A) rosin, from the viewpoints of film-forming ability and water resistance, unmodified rosin is preferred, and gum rosin is more preferred.

[0021] The content ratio of the (A) rosins relative to the total amount of the raw material components is not particularly limited as long as the refractive index of the resulting polyester resin component is 1.40 or more and 1.60 or less. The content ratio of the (A) rosins relative to the total amount of the raw material components is, for example, 10% by mass or more, preferably 15% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more, from the viewpoints of the suitability for clarifying, film-forming properties, water resistance, and tack resistance. The content ratio of the (A) rosins relative to the total amount of the raw material components is, for example, 80% by mass or less, preferably 70% by mass or less, more preferably 65% ​​by mass or less, and even more preferably 60% by mass or less, from the viewpoints of the film-forming properties, water resistance, and tack resistance.

[0022] The polycarboxylic acid (B) refers to a compound having two or more carboxy groups and anhydrides thereof. The polycarboxylic acid (B) is a component that adjusts the molecular weight of the polyester resin component. (B) Examples of polyvalent carboxylic acids include oxalic acid, malonic acid, succinic acid, fumaric acid, maleic acid, itaconic acid, citraconic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, oxaloacetic acid, methylmalonic acid, dimethylmalonic acid, methylsuccinic acid, 2,2-dimethylsuccinic acid, methylglutaric acid, dimethylglutaric acid, diglycolic acid, 1 ,3-acetonedicarboxylic acid, ketoglutaric acid, cyclopropane-1,1-dicarboxylic acid, cyclobutane-1,1-dicarboxylic acid, cyclohexane-1,1-dicarboxylic acid, 2-oxoadipic acid, 4-oxoheptanedioic acid, 5-oxoazelaic acid, phenylenedioxydiacetic acid, indan-2,2-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, cyclohexanedicarboxylic acid, ethylenediaminetetraacetic acid, and anhydrides thereof. These may be used alone or in combination of two or more. As the (B) polyvalent carboxylic acid, a dicarboxylic acid is preferred from the viewpoint of adjusting the molecular weight.

[0023] The polycarboxylic acid (B) preferably contains an α,β-unsaturated dicarboxylic acid. Since the α,β-unsaturated dicarboxylic acid reacts with the rosin (A), the polycarboxylic acid (B) containing an α,β-unsaturated dicarboxylic acid improves the suitability for clarifying. Examples of α,β-unsaturated dicarboxylic acids include fumaric acid, maleic acid, itaconic acid, citraconic acid, and their anhydrides. Examples of anhydrides include maleic anhydride, itaconic anhydride, and citraconic anhydride. These can be used alone or in combination of two or more. In addition, α,β-unsaturated dicarboxylic acids can be used in combination with other dicarboxylic acids.

[0024] From the viewpoint of adjusting the molecular weight, the (B) polyvalent carboxylic acid preferably contains at least one selected from the group consisting of succinic acid, fumaric acid, maleic anhydride, and adipic acid, and more preferably contains fumaric acid.

[0025] The content ratio of the polyvalent carboxylic acid (B) relative to the total amount of the raw material components is, from the viewpoint of the molecular weight of the polyester resin component, for example, 3 mass% or more, preferably 5 mass% or more, more preferably 10 mass% or more, and even more preferably 12 mass% or more. Also, the content ratio of the polyvalent carboxylic acid (B) relative to the total amount of the raw material components is, from the viewpoint of the molecular weight of the polyester resin, for example, 40 mass% or less, preferably 30 mass% or less, more preferably 25 mass% or less, and even more preferably 20 mass% or less. The content ratio of the (B) polyvalent carboxylic acid relative to 100 moles of the (A) rosins is, from the viewpoint of the molecular weight of the polyester resin component, for example, 20 moles or more, preferably 30 moles or more, more preferably 35 moles or more, and even more preferably 40 moles or more. The content ratio of the (B) polyvalent carboxylic acid relative to 100 moles of the (A) rosins is, for example, 150 moles or less, preferably 120 moles or less, more preferably 110 moles or less, and even more preferably 100 moles or less. When the content of the polycarboxylic acid (B) is equal to or higher than the lower limit of the above range, the amount of unreacted rosins (A) is relatively small, and the molecular weight of the polyester resin component can be increased. When the content of the polycarboxylic acid (B) is equal to or lower than the upper limit of the above range, the amount of unreacted polycarboxylic acid (B) is relatively small, and the molecular weight of the polyester resin component can be easily adjusted, and as a result, gelation is less likely to occur.

[0026] (C) Examples of polyols include dihydric alcohols, trihydric alcohols, and tetrahydric or higher alcohols. Examples of dihydric alcohols include linear alkyl diols, branched alkyl diols, and ether diols. Examples of linear alkyl diols include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. Examples of branched alkyl diols include propylene glycol, 1,3-butanediol, 1,2-butanediol, 3-methyl-1,5-pentanediol, and 2,6-dimethyl-1-octene-3,8-diol. Examples of ether diols include diethylene glycol, triethylene glycol, and dipropylene glycol. Examples of dihydric alcohols include 1,4-dihydroxy-2-butene, isosorbide, cyclohexanedimethanol, cyclohexanediol, tricyclodecanedimethylol, bisphenol A, hydrogenated bisphenol A, hydrogenated bisphenol F, hydrogenated bisphenol S, hydrogenated catechol, hydrogenated resorcinol, hydrogenated hydroquinone, and dicyclopentadiene diallyl alcohol copolymer. Examples of trihydric alcohols include glycerin, trimethylolethane, trimethylolpropane, trimethylolhexane, and trimethyloloctane. Examples of the tetrahydric or higher alcohol include tetrahydric to octahydric alcohols, such as pentaerythritol, diglycerin, ditrimethylolpropane, sorbitan, sorbitol, dipentaerythritol, inositol, and tripentaerythritol. These can be used alone or in combination of two or more kinds.

[0027] From the viewpoint of adjusting the molecular weight of the polyester resin component, the (C) polyol preferably contains at least one selected from the group consisting of trihydric alcohols and tetrahydric or higher alcohols, more preferably contains a trihydric alcohol, even more preferably contains at least one selected from the group consisting of trimethylolpropane, glycerin, and pentaerythritol, and particularly preferably contains glycerin.

[0028] The number of carbon atoms in the (C) polyol is, for example, 2 or more, preferably 3 or more. The number of carbon atoms in the (C) polyol is, for example, 30 or less, preferably 20 or less, more preferably 10 or less, and still more preferably 8 or less.

[0029] The content ratio of the polyol (C) relative to the total amount of the raw material components is, from the viewpoint of the molecular weight of the polyester resin component, for example, 5% by mass or more, preferably 8% by mass or more, more preferably 12% by mass or more, even more preferably 13% by mass or more, and particularly preferably 15% by mass or more. The content ratio of the polyol (C) relative to the total amount of the raw material components is, from the viewpoint of the molecular weight of the polyester resin, for example, 40% by mass or less, preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less.

[0030] (D) Examples of the aliphatic monocarboxylic acids include formic acid, acetic acid, trifluoroacetic acid, propionic acid, acrylic acid, methacrylic acid, pivalic acid, mercaptoacetic acid, and sorbic acid. Further, the fatty acid derived from fats and oils can be exemplified as the (D) aliphatic monocarboxylic acid. More specifically, linseed oil fatty acid, yuzu oil fatty acid, pistachio oil fatty acid, rice oil fatty acid, safflower oil fatty acid, apricot oil fatty acid, cottonseed oil fatty acid, sesame oil fatty acid, corn oil fatty acid, watermelon oil fatty acid, soybean oil fatty acid, poppy seed oil fatty acid, apple oil fatty acid, sunflower oil fatty acid, cactus oil fatty acid, tall oil fatty acid, walnut oil fatty acid, paulownia oil fatty acid, clove oil fatty acid and castor oil fatty acid can be exemplified. These can be used alone or in combination of two or more kinds.

[0031] The refractive index of the (D) aliphatic monocarboxylic acid is, for example, 1.35 to 1.65, or preferably 1.40 to 1.60.

[0032] From the viewpoint of suitability for clarifying, the aliphatic monocarboxylic acid (D) preferably has a predetermined iodine value. From the viewpoint of suitability for clarifying, the iodine value of the aliphatic monocarboxylic acid (D) is, for example, 0 mg / 100 mg or more, preferably 70 mg / 100 mg or more, and more preferably 100 mg / 100 mg or more.

[0033] From the viewpoint of the suitability for clarifying, the (D) aliphatic monocarboxylic acid preferably contains an aliphatic monocarboxylic acid having an iodine value of 20 g / 100 g or more as a main component. The main component indicates 80% by mass or more, preferably 90% by mass or more, and more preferably 95% by mass or more. That is, the content ratio of the aliphatic monocarboxylic acid having an iodine value of 20 g / 100 g or more relative to the total amount of the (D) aliphatic monocarboxylic acid is, for example, 80% by mass or more, preferably 90% by mass or more, and more preferably 95% by mass or more. Particularly preferably, the (D) aliphatic monocarboxylic acid is composed of an aliphatic monocarboxylic acid having an iodine value of 20 g / 100 g or more.

[0034] Examples of aliphatic monocarboxylic acids with an iodine value of 20 g / 100 g or more include linseed oil fatty acids, yuzu oil fatty acids, pistachio oil fatty acids, rice oil fatty acids, safflower oil fatty acids, apricot oil fatty acids, cottonseed oil fatty acids, sesame oil fatty acids, corn oil fatty acids, watermelon oil fatty acids, soybean oil fatty acids, poppy seed oil fatty acids, apple oil fatty acids, sunflower oil fatty acids, cactus oil fatty acids, tall oil fatty acids, walnut oil fatty acids, paulownia oil fatty acids, clove oil fatty acids, and castor oil fatty acids.

[0035] The content ratio of the (D) aliphatic monocarboxylic acid (when used in combination, the total amount of them) relative to the total amount of the raw material components is not particularly limited as long as the refractive index of the resulting polyester resin component satisfies 1.40 or more and 1.60 or less. The content ratio of the (D) aliphatic monocarboxylic acid relative to the total amount of the raw material components is, for example, 5% by mass or more, preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and particularly preferably 25% by mass or more, from the viewpoints of the suitability for making transparent, flexibility, water resistance, and the like. In addition, the content ratio of the (D) aliphatic monocarboxylic acid relative to the total amount of the raw material components is, for example, 60% by mass or less, preferably 55% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less, from the viewpoints of the suitability for making transparent, flexibility, water resistance, and the like.

[0036] (Production of polyester resin component) The polyester resin component can be produced by reacting the above-mentioned raw material components. In order to adjust the acid value and molecular weight of the polyester resin component to fall within the above ranges, for example, the blending amounts of the raw material components are adjusted to the above preferred ratios, and the reaction temperature and reaction time are also adjusted. In order to adjust the refractive index of the polyester resin component to fall within the above range, for example, the content ratio of (A) the rosin and (D) the aliphatic monocarboxylic acid is adjusted. In order to adjust the iodine value of the polyester resin component to fall within the above range, for example, the iodine value and content of the (D) aliphatic monocarboxylic acid are adjusted.

[0037] When reacting the raw material components, the raw material components may be reacted all at once, or the raw material components may be reacted in multiple stages. In the batch reaction, the polyester resin component can be produced by a known dehydration condensation reaction between an acid and an alcohol. Suitable conditions for the dehydration condensation reaction are about 150 to 300° C. and a reaction time of about 2 to 20 hours.

[0038] When the (B) polyvalent carboxylic acid contains an α,β-unsaturated dicarboxylic acid, a multi-stage reaction is preferred. Specifically, first, (A) rosin is reacted with α,β-unsaturated dicarboxylic acid to obtain a first product, and then (C) the first product is reacted with (D) aliphatic monocarboxylic acid to obtain a second product containing a polyester resin component.

[0039] In the step of obtaining the first product, (A) an unsaturated bond contained in the rosin is subjected to an addition reaction with an unsaturated bond contained in the α,β-unsaturated dicarboxylic acid. The reaction temperature in the step of obtaining the first product is, from the viewpoint of adjusting the acid value and molecular weight of the polyester resin component, for example, 150° C. or more, preferably 170° C. or more, and more preferably 180° C. or more. In addition, the reaction temperature in the step of obtaining the first product is, from the viewpoint of adjusting the acid value and molecular weight of the polyester resin component, for example, 230° C. or less, preferably 220° C. or less, and more preferably 200° C. or less. The reaction time in the step of obtaining the first product is, for example, 0.1 hours or more, preferably 0.5 hours or more, from the viewpoint of adjusting the acid value and molecular weight of the polyester resin component. The reaction time in the step of obtaining the first product is, for example, 5 hours or less, preferably 3 hours or less, from the viewpoint of adjusting the acid value and molecular weight of the polyester resin component. In the step of obtaining the first component, a known reaction catalyst can be added in an appropriate ratio as necessary. In the step of obtaining the first product, the raw material components may be reacted in the absence of a solvent or in the presence of a known solvent.

[0040] In the step of obtaining the second product, the first product or a carboxy group of the aliphatic monocarboxylic acid (D) is esterified with a hydroxyl group of the polyol (C). The first product, the polyol (C), and the aliphatic monocarboxylic acid (D) may be reacted in one step or in multiple steps. The reaction temperature in the step of obtaining the second product is, from the viewpoint of adjusting the acid value and hydroxyl value of the polyester resin component, for example, 150° C. or more, preferably 160° C. or more, more preferably 170° C. or more, and even more preferably 180° C. or more. In addition, the reaction temperature in the step of obtaining the second product is, from the viewpoint of adjusting the acid value and molecular weight of the polyester resin component, for example, 230° C. or less, preferably 220° C. or less, more preferably 210° C. or less, and even more preferably 200° C. or less. The reaction time in the step of obtaining the second product is, for example, 1 hour or more, preferably 3 hours or more, from the viewpoint of adjusting the acid value and molecular weight of the polyester resin component. The reaction time in the step of obtaining the second product is, for example, 48 hours or less, preferably 24 hours or less, from the viewpoint of adjusting the acid value and molecular weight of the polyester resin component. In this reaction, condensation water generated by the esterification reaction can be distilled off by a known method, if necessary. In the step of obtaining the second product, a known reaction catalyst can be added in an appropriate ratio as necessary. In the step of obtaining the second product, the raw material components may be reacted in the absence of a solvent or in the presence of a known solvent.

[0041] When the (D) aliphatic monocarboxylic acid contains a fatty acid derived from a fat or oil, the (C) polyol can be modified with a fat or oil having the (D) aliphatic monocarboxylic acid as a constituent fatty acid before obtaining the second product. When the (C) polyol is modified with the oil, a modified product containing an ester (fatty acid ester) of the (C) polyol and a fatty acid derived from the (C) polyol and the oil is obtained by transesterification. The fatty acid ester is hydrolyzed to produce the (C) polyol and a fatty acid. Therefore, the modified product can be used in place of the (C) polyol and the (D) aliphatic monocarboxylic acid. Specifically, as described above, (A) rosins and α,β-unsaturated dicarboxylic acids are reacted to obtain a first product. Separately, (C) polyol is modified with (D) oils and fats having an aliphatic monocarboxylic acid as a constituent fatty acid to obtain a modified product. Next, the first product is reacted with the modified product to obtain a second product containing a polyester resin component. In the step of obtaining the second component, the first product and the modified product undergo an esterification reaction, thereby obtaining the second product.

[0042] (D) Examples of fats and oils having an aliphatic monocarboxylic acid as a constituent fatty acid include linseed oil, yuzu oil, pistachio oil, rice oil, safflower oil, apricot oil, cottonseed oil, sesame oil, corn oil, watermelon oil, soybean oil, poppy seed oil, apple oil, sunflower oil, cactus oil, tall oil, walnut oil, paulownia oil, clove oil, and castor oil.

[0043] The blending ratio in the step of obtaining the modified product is appropriately set, but for example, the amount of hydroxyl groups in the (C) polyol per 1 mole of the oil or fat is, for example, 3 moles or more, preferably 10 moles or more, and for example, 50 moles or less, preferably 40 moles or less.

[0044] The reaction temperature in the step of obtaining the modified product is, from the viewpoint of film-forming properties, for example, 230°C or higher, preferably 240°C or higher, more preferably 250°C or higher. In addition, the reaction temperature in the step of obtaining the modified product is, from the viewpoint of film-forming properties, for example, 300°C or lower, preferably 280°C or lower, more preferably 270°C or lower. If the reaction temperature is too low, the reaction in the step of obtaining the modified product does not proceed, and (D) the aliphatic monocarboxylic acid may not be incorporated into the polyester resin. Therefore, the film-forming properties may be reduced. In addition, if the reaction temperature is too high, a decomposition reaction may occur, causing an increase in low molecular weight components. Therefore, the film-forming properties may be reduced. The reaction time in the step of obtaining the modified product is, from the viewpoint of film-forming property, for example, 0.5 hours or more, preferably 1 hour or more, and, from the viewpoint of film-forming property, for example, 20 hours or less, preferably 10 hours or less. In the step of obtaining the modified product, a known reaction catalyst can be added in an appropriate ratio as necessary. In the step of obtaining the modified product, the raw material components may be reacted in the absence of a solvent or in the presence of a known solvent.

[0045] The second product thus obtained is a resin composition containing (A) a rosin and (D) a polyester resin modified with an aliphatic monocarboxylic acid (hereinafter also referred to as a rosin-modified polyester resin). The second product can be used as a polyester resin component of a clarifying agent. The second product may contain unreacted raw material components in addition to the rosin-modified polyester resin. Examples of the unreacted raw material components include unreacted (A) rosins, unreacted (B) polydicarboxylic acids, unreacted (C) polyols, and unreacted (D) aliphatic monocarboxylic acids. The unreacted raw material components are removed from the second product as necessary.

[0046] The content of the rosin-modified polyester resin relative to the total amount of the polyester resin components is, for example, 25% by mass or more, or preferably 30% by mass or more, and, for example, 100% by mass or less, or preferably 90% by mass or less, relative to the total amount of the polyester resin components.

[0047] (Other ingredients) The clarifying agent may further contain other components in addition to the above polyester resin component, if necessary.

[0048] For example, the clarifying agent can include a liquid medium. Examples of the liquid medium include organic solvents, water, and mixtures thereof. The liquid medium is preferably one capable of dissolving or dispersing the polyester resin component. As the liquid medium, an organic solvent is preferred from the viewpoints of excellent permeability into the paper base material, no lumpyness that occurs when water is used, and excellent drying properties.

[0049] Examples of the organic solvent include alcohols, ethers, esters, and non-polar solvents. Examples of the alcohols include alcohols having 1 to 6 carbon atoms, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, n-pentanol, and n-hexanol.

[0050] Examples of the ethers include ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol monoethyl ether, ethylene glycol monopropyl ether, diethylene glycol monopropyl ether, triethylene glycol monopropyl ether, tetraethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monoisopropyl ether, triethylene glycol monoisopropyl ether, tetraethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, diethylene glycol monoisobutyl ether, triethylene glycol monoisobutyl ether, tetraethylene glycol monoisobutyl ether, ethylene glycol monotert-butyl ether, diethylene glycol monotert-butyl ether, triethylene glycol monotert-butyl ether, tetraethylene glycol monotert-butyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monoethyl ether, tetrapropylene glycol monoethyl ether, propylene glycol monopropyl ether, dipropylene glycol monopropyl ether, tripropylene glycol monopropyl ether, propylene glycol monoisopropyl ether, dipropylene glycol monoisopropyl ether, tripropylene glycol monoisopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monobutyl ether, propylene glycol monoisobutyl ether,Examples of glycol ethers include dipropylene glycol monoisobutyl ether, tripropylene glycol monoisobutyl ether, propylene glycol monotertiary butyl ether, dipropylene glycol monotertiary butyl ether, and tripropylene glycol monotertiary butyl ether.

[0051] Examples of the esters include diethylene glycol monoethyl ether acetate and diethylene glycol monobutyl ether acetate. Examples of non-polar solvents include paraffinic hydrocarbons such as pentane, hexane, heptane, octane, nonane, decane, and dodecane; isoparaffinic hydrocarbons such as isohexane, isooctane, and isododecane; alkylnaphthenic hydrocarbons such as liquid paraffin; aromatic hydrocarbons such as benzene, toluene, xylene, alkylbenzene, and solvent naphtha; and silicone oil.

[0052] The content of the liquid medium is appropriately set according to the purpose and application. For example, the liquid medium is, for example, 5% by mass or more, preferably 10% by mass or more, based on the total amount of the liquid medium and the polyester resin component. Also, the liquid medium is, for example, 80% by mass or less, preferably 70% by mass or less, based on the total amount of the liquid medium and the polyester resin component. Also, the polyester resin component is, for example, 20% by mass or more, preferably 30% by mass or more, based on the total amount of the liquid medium and the polyester resin component. Also, the polyester resin component is, for example, 95% by mass or less, preferably 90% by mass or less, based on the total amount of the liquid medium and the polyester resin component. If the ratio of the liquid medium to the polyester resin component is within the above range, a sudden increase in viscosity can be suppressed, and the productivity, coatability and drying property of the clarifying agent can be improved.

[0053] The clarifying agent may contain other resins. The other resins are resins other than the above polyester resin component. Examples of other resins include acrylic resins, styrene-modified acrylic resins, silicone acrylic resins, modified silicone acrylic resins, rosin phenolic resins, rosin ester resins, terpene phenolic resins, coumarone-indene resins, petroleum resins, epoxy resins, modified epoxy resins, polyester resins, vinyl acetate resins, ethylene-vinyl acetate resins, urethane resins, urea resins, melamine resins, and cellulose resins. These can be used alone or in combination of two or more.

[0054] The clarifying agent may contain a wax, which can suppress blocking when used on a paper substrate. Examples of the wax include fatty acid amide wax, carnauba wax, rice wax, polyolefin wax, paraffin wax, Fischer-Tropsch wax, beeswax, microcrystalline wax, oxidized polyethylene wax, and amide wax. These may be used alone or in combination of two or more kinds. As the wax, preferably, fatty acid amide wax, carnauba wax, polyolefin wax, paraffin wax and microcrystalline wax are used, and more preferably, carnauba wax, polyolefin wax and paraffin wax are used.

[0055] More specifically, the fatty acid amide wax may include, for example, pelargonic acid amide, capric acid amide, undecylic acid amide, lauric acid amide, tridecylic acid amide, myristic acid amide, pentadecylic acid amide, palmitic acid amide, heptadecylic acid amide, stearic acid amide, nonadecanoic acid amide, arachidic acid amide, behenic acid amide, lignoceric acid amide, oleic acid amide, cetoleic acid amide, linoleic acid amide, linolenic acid amide, and mixtures thereof.Further, the fatty acid amide wax may include animal and vegetable oil fatty acid amides.These may be used alone or in combination of two or more kinds.

[0056] More specifically, examples of carnauba wax include MICROKLEAR 418 (manufactured by Micro Powders, Inc.) and Refined Carnauba Wax Powder No. 1 (manufactured by Nippon Wax Co., Ltd.). These may be used alone or in combination of two or more kinds. More specifically, examples of olefin waxes include polyethylene wax, polypropylene wax, MPP-635VF (Micro Powders, Inc.), and MP-620VF XF (Micro Powders, Inc.). These may be used alone or in combination of two or more kinds. More specifically, examples of paraffin wax include MP-28C, MP-22XF, and MP-28C (all from Micro Powders, Inc.). These may be used alone or in combination of two or more kinds.

[0057] The melting point of the wax is, for example, 60° C. or higher and, for example, 130° C. or lower from the viewpoint of heat resistance.

[0058] The wax content in the clarifying agent is appropriately set according to the purpose and use.For example, the wax content is, for example, 0 parts by mass or more, preferably 1 part by mass or more, more preferably 3 parts by mass or more, per 100 parts by mass of the polyester resin component.Furthermore, the wax content is, for example, 50 parts by mass or less, preferably 30 parts by mass or less, per 100 parts by mass of the polyester resin component.

[0059] The clarifying agent can contain additives in an appropriate ratio. Examples of additives include fillers, thickeners, foaming agents, antioxidants, light stabilizers, heat stabilizers, flame retardants, color tone adjusters, and drying accelerators such as cobalt octylate and cobalt naphthenate. These can be used alone or in combination of two or more types.

[0060] The clarifying agent can be produced by producing the polyester resin component as described above and, if necessary, mixing other components.

[0061] The clarifying agent of the present invention uses bio-derived raw materials ((A) rosins, (D) aliphatic monocarboxylic acids, etc.) and yet can provide transparent paper with excellent transparency and stability over time. The polyester resin component in the clarifying agent has a refractive index close to that of pulp (cellulose), the main component of the paper base material, so that the polyester resin component fills the voids inside the paper base material, thereby reducing the refraction of light inside the paper base material and providing excellent transparency. In addition, the clarifying agent of the present invention is also excellent in recyclability because transparency can be ensured by single-sided coating. The clarifying agent of the present invention is not limited to paper substrates, but can also be applied to substrates made of materials having a refractive index equivalent to that of cellulose, such as woven fabric, nonwoven fabric, film, synthetic paper, and the like.

[0062] "Transparent paper" The transparent paper of the present invention contains a transparent agent at least inside the paper base material. The transparent agent contains a polyester resin component which is a reaction product of raw material components including (A) rosins, (B) polycarboxylic acids, (C) polyols, and (D) aliphatic monocarboxylic acids. The acid value of the polyester resin component is 100 mgKOH / g or less, the weight average molecular weight is 1,000,000 or less, and the refractive index is 1.40 or more and 1.60 or less.

[0063] (Clarifying agent) As the clarifying agent, the above-mentioned clarifying agents can be used.

[0064] (Paper base material) The paper substrate comprises pulp. Examples of the pulp constituting the paper base material include chemical pulp, mechanical pulp, recycled paper pulp, non-wood pulp, etc. These pulps may be used alone or in combination of two or more. Among them, chemical pulp is preferred.

[0065] Chemical pulp includes softwood chemical pulp and hardwood chemical pulp, and it is preferable that the paper base material contains both softwood chemical pulp and hardwood chemical pulp. Hardwood chemical pulp has a shorter and thinner fiber structure than softwood chemical pulp. When hardwood chemical pulp is used, the paper base material has a better texture because of the short and thin fiber structure. If the paper base material has a poor texture, the transparent agent may not penetrate evenly due to the non-uniformity caused by the texture, even if the paper base material is impregnated with a transparent agent, and the transparency may be impaired. In order to obtain a good transparent paper, it is preferable that the paper base material has a good texture. However, hardwood chemical pulp, which has a thin and short fiber structure, has a good texture, but the gaps and voids are small, and it is easy to generate parts into which the transparent agent does not penetrate. In addition, since there are many interfaces, there is a tendency that the transmitted light is refracted and attenuated, and the transparency is reduced. Furthermore, since it is easily covered with the transparent agent, the defibration property when recycled as waste paper tends to be inferior to that of softwood chemical pulp. For this reason, by using hardwood chemical pulp and softwood chemical pulp in combination as the paper base material, it is possible to achieve both the transparency and recyclability of the transparent paper.

[0066] Examples of softwood chemical pulp include unbleached softwood kraft pulp (NUKP), bleached softwood kraft pulp (NBKP), semi-bleached softwood kraft pulp (NSBKP), softwood sulfite pulp (NSP), etc. Among them, from the viewpoint of achieving both transparency and strength of the transparent paper, bleached softwood kraft pulp (NBKP) and softwood sulfite pulp (NSP) are preferred.

[0067] The Canadian Standard Freeness (CSF) of the softwood chemical pulp is preferably 400 to 700 mL, more preferably 420 to 650 mL, and even more preferably 450 to 600 mL. When the CSF of the softwood chemical pulp is equal to or greater than the lower limit of the above range, the voids in the paper base material can be maintained, resulting in excellent impregnation of the transparent material. When the CSF of the softwood chemical pulp is equal to or less than the upper limit of the above range, the texture of the paper base material can be improved, and transparent paper having a transparent region with excellent transparency and visibility can be easily obtained.

[0068] Examples of hardwood chemical pulp include hardwood unbleached kraft pulp (LUKP), hardwood bleached kraft pulp (LBKP), hardwood semi-bleached kraft pulp (LSBKP), hardwood sulfite pulp (LSP), etc. Among them, from the viewpoint of achieving both transparency and strength of the transparent paper, hardwood bleached kraft pulp (LBKP) and hardwood sulfite pulp (LSP) are preferred.

[0069] The Canadian Standard Freeness (CSF) of the hardwood chemical pulp is preferably 350 to 650 mL, more preferably 370 to 630 mL, and even more preferably 400 to 600 mL. When the CSF of the hardwood chemical pulp is equal to or greater than the lower limit of the above range, the strength of the paper base material can be increased. When the CSF of the hardwood chemical pulp is equal to or less than the upper limit of the above range, the texture of the paper base material can be improved, and transparent paper having a transparent region with excellent transparency and visibility can be easily obtained.

[0070] The mass ratio of softwood chemical pulp to hardwood chemical pulp (softwood chemical pulp:hardwood chemical pulp) is preferably 80:20 to 20:80, more preferably 75:25 to 25:75, and even more preferably 70:30 to 30:70.

[0071] When the paper base material contains softwood chemical pulp and hardwood chemical pulp, the paper base material may contain, in addition to these chemical pulps, other pulps such as mechanical pulp, recycled paper pulp, and non-wood pulp. Examples of mechanical pulp include stone ground pulp (SGP), pressed stone ground pulp (PGW), refiner ground pulp (RGP), thermo ground pulp (TGP), chemi-ground pulp (CGP), groundwood pulp (GP), and thermomechanical pulp (TMP). Examples of waste paper pulp include disintegrated waste paper pulp, disintegrated and deinked waste paper pulp, and disintegrated, deinked and bleached waste paper pulp. Examples of waste paper that can be used as a raw material for waste paper pulp include brown waste paper, kraft envelope waste paper, magazine waste paper, newspaper waste paper, flyer waste paper, office waste paper, cardboard waste paper, white waste paper, Kent waste paper, imitation waste paper, and land certificate waste paper. Non-wood pulps include various pulps such as pulps produced chemically or mechanically from non-wood fibers such as kenaf, cotton, hemp, and reed. These pulps may be used alone or in combination of two or more kinds.

[0072] When recycled paper pulp is used as the pulp, the recycled paper pulp content is preferably 10% by mass or less, more preferably 5% by mass or less, based on the total mass of the pulp constituting the paper base material. When the recycled paper pulp content is equal to or less than the upper limit, the transparent paper can be suitably used as a packaging material for food and beverages. The lower limit of the recycled paper pulp content is 0% by mass.

[0073] The opacity of the paper base material is, for example, 45 to 95%. The opacity is measured in accordance with JIS P 8149 (2000).

[0074] The paper base material has a basis weight of 35 to 150 g / m 2 is preferable, and 40 to 100 g / m 2 More preferably, 43 to 80 g / m 2 When the basis weight is equal to or more than the lower limit of the above range, the strength of the paper is obtained, and the transparent paper is suitable for applications such as packaging paper, printing paper, etc. When the basis weight is equal to or less than the upper limit of the above range, the transparency of the transparent paper can be increased. The basis weight is measured in accordance with JIS P8124.

[0075] The air permeability of the paper base material is preferably 10 to 40 seconds, more preferably 12 to 35 seconds, and even more preferably 15 to 33 seconds. When the air permeability is equal to or greater than the lower limit of the above range, the paper has sufficient strength, and the transparent paper is suitable for applications such as packaging paper and printing paper. When the air permeability is equal to or less than the upper limit of the above range, the permeability of the transparentizing agent is excellent, and the transparency of the transparent paper can be increased. The air permeability is the Oken air permeability measured in accordance with J.TAPPI-5-2:2000.

[0076] The density of the paper base material is 0.5 to 0.90 g / cm 3 is preferable, and 0.6 to 0.8 g / cm3 When the density is equal to or greater than the lower limit of the above range, the strength of the paper is sufficient, and the transparent paper is suitable for applications such as packaging paper, printing paper, etc. When the density is equal to or less than the upper limit of the above range, the permeability of the transparent material is excellent, and the transparency of the transparent paper can be increased. The density is measured in accordance with JIS P8118.

[0077] The porosity of the paper substrate is preferably 30 to 80%, more preferably 40 to 70%, and even more preferably 50 to 70%. When the porosity of the paper substrate is equal to or higher than the lower limit of the above range, the transparency of the transparent region is easily increased. When the porosity of the paper substrate is equal to or lower than the upper limit of the above range, the physical strength of the sheet is less likely to decrease. The porosity of the paper base material is the density measured in accordance with JIS P8118 divided by the true density of cellulose, 1.50.

[0078] The Parker Print Surf smoothness of at least one surface of the paper substrate is preferably 7 μm or less, more preferably 5 μm or less. There is no particular limit to the lower limit. The smaller the value, the smoother the surface. The Parker Print Surf smoothness can be evaluated for the smoothness of fine details, and the smaller this value, the more the light scattering on the paper surface can be reduced, thereby improving visibility through the transparent parts. Parker Print Surf smoothness is determined in accordance with ISO 8791-4:1992 (soft backing / clamping pressure 500 kPa).

[0079] In addition to pulp, the paper base material may contain known papermaking auxiliaries such as paper strength agents, sizing agents, fillers, and colorants. The incorporation of fillers such as talc and calcium carbonate improves the smoothness and whiteness of the paper base material, but also acts to increase the hiding power of the paper, making it difficult to impart transparency. Therefore, it is preferable to keep the content of the filler in the paper base material within a range that does not impair transparency and visibility, and it is more preferable that the paper base material does not contain any filler.

[0080] The method for producing the paper base material is not particularly limited, and may include, for example, a method including a step of beating pulp, which is a raw material for the paper base material, a step of making a pulp slurry containing the beaten pulp, and a step of drying the wet sheet obtained by papermaking.

[0081] In the beating step, it is preferable to beat the raw pulp so as to have the above-mentioned Canadian standard freeness. The beating machine is not particularly limited. For example, a known beating machine such as a double disc refiner can be used. There are no particular limitations on the papermaking machine used for papermaking, and examples thereof include a Fourdrinier papermaking machine, a short wire papermaking machine, and a cylinder papermaking machine. The drying step is not particularly limited, and for example, a dryer attached to a papermaking machine can be used.

[0082] The paper base material may be subjected to a smoothing treatment, which can reduce light scattering on the paper surface and improve visibility through the transparent parts. Examples of smoothing treatments include tension presses, machine calendars, gloss calendars, soft nip calendars, and super calendars. However, these devices increase the density of the paper, so care must be taken to reduce the linear pressure so that the density does not become too high. On the other hand, the transfer method, in which the paper is attached to a smooth surface while still wet and then dried to transfer the smooth surface, is preferred because it does not increase the density of the paper. For example, techniques such as Yankee cylinders, cast drums, and film transfers can be used. Among these, Yankee dryers using Yankee cylinders are preferred because they are attached to papermaking machines and have excellent productivity.

[0083] As the paper substrate, commercially available papers such as kraft paper, one-sided gloss kraft paper, fine paper, electrophotographic paper, inkjet recording paper, thermal recording paper, laser thermal paper, thermal transfer recording paper, art paper, coated paper, cast coated paper, white paperboard, colored paperboard, cardboard liners, glassine paper, rice paper, India paper, Japanese paper, etc. Among them, fine paper, electrophotographic paper, kraft paper, and one-sided gloss kraft paper, which have a low pigment content, are preferred because they provide excellent visibility of the transparent area due to the transparentizing agent.

[0084] (transparent paper) By including a clarifying agent at least inside the paper base material, transparency is increased compared to when no clarifying agent is included. The area of ​​the paper base material that is made transparent by the transparentizing agent (transparent area) may be the entire surface or a part of the paper base material in a plan view. The opacity of the transparent region is preferably 30% or less, more preferably 20% or less, and even more preferably 16% or less. The lower the opacity, the better the transparency.

[0085] As a method for incorporating the clarifying agent at least inside the paper base material, it is possible to add the agent when making the paper, but when productivity is important, it is preferable to coat or impregnate the paper base material with the clarifying agent, as shown in the manufacturing method described below.

[0086] In transparent paper, it is not necessary that all of the clarifying agent be present within the paper substrate. When a part of the clarifying agent covers the surface of the paper base material, it is possible to suppress diffuse reflection of light by the surface of the paper base material, and to further increase transparency. In addition, since the coating film of the clarifying agent on the surface of the paper base material has heat sealability, it can also be used as a sealant layer.

[0087] The content of the transparentizing agent depends on the type of paper substrate used (void volume, etc.), but it is generally 10 to 80 g / m2 in terms of the solid content of the polyester resin component per unit area of ​​the transparent region. 2 is preferable, and 20 to 70 g / m 2 More preferably, 30 to 60 g / m 2When the content of the clarifying agent is equal to or more than the lower limit of the above range, the transparency of the transparent region is easily increased. When the content of the clarifying agent is equal to or less than the upper limit of the above range, the recyclability can be increased.

[0088] As described above, the transparent paper of the present invention has excellent transparency because the voids inside the paper base are filled with a transparentizing agent containing a polyester resin component having a refractive index close to that of the pulp, which is the main component of the paper base, thereby reducing the refraction of light inside the paper base. In addition, the transparent paper has excellent stability over time and recyclability.

[0089] The transparent paper of the present invention can be used as a packaging paper having a transparent region, for applications such as boxes, bags, envelopes, clear files, etc. In addition, since it can achieve unprecedented transparency and visibility, it can be used not only for packaging paper, but also for various applications such as printing paper, book paper, copying paper, information paper, label paper, and household paper, in which an image (characters, symbols, pictures, objects, etc.) on the opposite side of the paper can be visually recognized through the paper base material.

[0090] "How to make transparent paper" The method for producing transparent paper of the present invention is a method for producing transparent paper by coating or impregnating a paper substrate with a liquid composition containing a transparentizing agent and a liquid medium, and drying the liquid composition. The transparentizing agent contains a polyester resin component which is a reaction product of raw material components containing (A) rosins, (B) polycarboxylic acids, (C) polyols, and (D) aliphatic monocarboxylic acids. The acid value of the polyester resin component is 100 mgKOH / g or less, the weight average molecular weight is 1,000,000 or less, and the refractive index is 1.40 or more and 1.60 or less.

[0091] (Liquid composition) As the clarifying agent, the above-mentioned clarifying agents can be used.

[0092] The liquid medium may be any medium capable of dissolving or dispersing the clarifying agent. The liquid medium may be the same as the liquid medium in the clarifying agent, and an organic solvent is preferable. The use of an organic solvent has the advantages of allowing the clarifying agent to penetrate quickly into the paper substrate, preventing the paper substrate from becoming lumpy, and allowing the drying to be performed quickly. The liquid medium may be used alone or in combination of two or more kinds.

[0093] The content of the liquid medium can be appropriately set taking into consideration the ease of application or impregnation to the paper base material, and is, for example, 30 to 50% by mass relative to the total mass of the liquid composition.

[0094] The viscosity of the liquid composition is preferably 50 to 5000 mPa·s, more preferably 50 to 4000 mPa·s, and even more preferably 50 to 3000 mPa·s. When the viscosity is equal to or less than the upper limit of the above range, the liquid composition easily penetrates into the paper substrate, and the transparency of the transparent region is easily increased. When the viscosity is equal to or more than the lower limit of the above range, when a part of the paper substrate is made into a transparent region, the boundary between the transparent region and the other region becomes clear. The viscosity is measured using a Brookfield type viscometer at 30° C. and 60 rpm.

[0095] (Paper base material) As the paper substrate, the above-mentioned paper substrates can be used.

[0096] The application or impregnation of the liquid composition can be carried out by a known method, for example, a coating method, an impregnation method, or a printing method such as flexographic printing, inkjet printing, gravure printing, offset printing, gravure offset printing, silk screen printing, spray coater, roll coater, gravure coater, bar coater, blade coater, curtain coater, flow coater, comma coater, brush coating, or dipping.

[0097] The liquid composition may be applied to or impregnated over the entire surface of the paper substrate, or may be applied partially to the entire surface of the paper substrate. In addition, when the liquid composition is applied to or impregnated over the paper substrate, a part in which the clarifying agent does not reach a part of the surface opposite to the impregnated surface may be formed in the cross section of the paper substrate. The liquid composition may be applied to or impregnated onto only one side of the paper substrate, or the liquid composition may be applied to or impregnated onto both one side and the other side of the paper substrate. The application or impregnation of the liquid composition may be carried out in one step or in multiple steps. When the application or impregnation is carried out in multiple steps, the components and composition of the clarifying material used in each step may be the same or different from each other.

[0098] The amount of the liquid composition to be applied or impregnated depends on the type of paper substrate used (void volume, etc.), but is generally 10 to 80 g / m2 in terms of the mass of the polyester resin component in the transparentizing agent in terms of solid content per unit area of ​​the region to be applied or impregnated with the liquid composition (transparentized region). 2 is preferable, and 20 to 70 g / m 2 More preferably, 30 to 60 g / m 2 When the amount of coating or impregnation is equal to or greater than the lower limit of the above range, the transparency of the transparent region is easily increased, whereas when the amount of coating or impregnation is equal to or less than the upper limit of the above range, the recyclability can be increased.

[0099] By drying the paper substrate coated or impregnated with the liquid composition, the liquid medium is removed and transparent paper containing the transparentizing agent at least inside the paper substrate is obtained. Drying after coating or impregnation can be carried out by a known method. The drying conditions may be natural drying at room temperature or drying by heating. Drying by heating is preferred. The drying temperature in drying by heating is, for example, 40° C. or higher, preferably 50° C. or higher. The drying temperature is, for example, 150° C. or lower, preferably 130° C. or lower. The drying time is, for example, 1 second or longer, preferably 5 seconds or longer. The drying time is, for example, 600 seconds or shorter, preferably 500 seconds or shorter. After drying, humidity control may be performed to adjust the moisture content, for example, at a temperature of 23° C. and a relative humidity of 50%. EXAMPLES

[0100] Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited to the following examples. "Parts" and "%" are by mass unless otherwise specified. In addition, specific numerical values ​​such as blending ratios (content ratios), physical property values, parameters, etc. used in the following description can be replaced with the upper limit values ​​(numerical values ​​defined as "equal to or less than") or lower limit values ​​(numerical values ​​defined as "equal to or more than" or "exceeding") of the corresponding blending ratios (content ratios), physical property values, parameters, etc. described in the above "Form for implementing the invention."

[0101] <Measurement method> (1) Acid value The acid value of the polyester resin component was measured in accordance with JIS K 5601-2-1 (1999).

[0102] (2) Iodine value The iodine value of the polyester resin component was measured in accordance with JIS K 0070 (1992).

[0103] (3)Molecular weight The polyester resin component was dissolved in tetrahydrofuran to obtain a 1.0 g / L sample. The sample was then measured using a gel permeation chromatograph (GPC) equipped with a refractive index detector (RID), and the weight average molecular weight (Mw) of the sample was calculated from the obtained chromatogram (chart). The measurement device and measurement conditions are shown below. Equipment: Shodex GPC-101 (Showa Denko) Detector: RI detector Column used: Shodex Column GPC KF-802, 803, 804, 806 (Shoko Science Co., Ltd.) Eluent:THF Column speed: 1.0mL / min. Measurement temperature: 40℃ Molecular weight marker: Standard polystyrene (Agilent EasiCal Polystyren Standards PS-1)

[0104] (4) Refractive index The refractive index was measured using a multi-wavelength Abbe refractometer DR-M4 (manufactured by Atago Co., Ltd.) in accordance with JIS K 7142 (2014).

[0105] <Production Example 1> 27.8 parts of gum rosin was placed in a four-neck flask equipped with a stirrer, a reflux condenser with a water separator, and a thermometer while blowing in nitrogen gas, and the temperature was raised to 210° C. Then, 9.8 parts of fumaric acid was added thereto, and the mixture was stirred at 210° C. for about 90 minutes. This produced a first product. Into another four-neck flask equipped with a reflux condenser with a water separator and a thermometer, 73.4 parts of linseed oil and 15.5 parts of glycerin were added and stirred at 250°C for about 90 minutes. Next, the first product was mixed therein, and after mixing, it was cooled to 190°C. After that, a dehydration condensation reaction was carried out at 190°C for 8 hours to obtain a polyester resin component (resin 1) which was the second product. The acid value of this resin 1 was 10 mgKOH / g, the iodine value was 109 g / 100 g, the weight average molecular weight was 82000, and the refractive index was 1.49. The refractive index of linseed oil fatty acid was 1.49.

[0106] <Manufacturing Examples 2, 3, 5, 8, 10> Polyester resin components (resins 2, 3, 5, 8, and 10) were obtained in the same manner as in Production Example 1, except that the ratio of the raw material components was changed to the ratio shown in Table 1. The physical properties of each resin are shown in Table 1.

[0107] <Production Example 4> 46.9 parts of gum rosin was placed in a four-neck flask equipped with a stirrer, a reflux condenser with a water separator, and a thermometer while blowing in nitrogen gas, and the temperature was raised to 210° C. Then, 16.5 parts of fumaric acid was added thereto, and the mixture was stirred at 210° C. for about 90 minutes. This produced a first product. Into another four-neck flask equipped with a reflux condenser with a water separator and a thermometer, 56.8 parts of linseed oil and 25 parts of pentaerythritol were added and stirred at 250°C for about 90 minutes. Next, the first product was mixed therein, and after mixing, the mixture was cooled to 190°C. Thereafter, a dehydration condensation reaction was carried out at 190°C for 7 hours to obtain a polyester resin component (resin 4). The acid value of this resin 4 was 8 mgKOH / g, the iodine value was 74 g / 100 g, the weight average molecular weight was 618,000, and the refractive index was 1.50.

[0108] <Production Example 6> A polyester resin component (Resin 6) was obtained in the same manner as in Production Example 1, except that linseed oil was replaced with tung oil. The acid value of this Resin 6 was 8 mg KOH / g, the iodine value was 98 g / 100 g, the weight average molecular weight was 98,000, and the refractive index was 1.56. The refractive index of tung oil fatty acid was 1.52.

[0109] <Production Example 7> In a four-neck flask equipped with a stirrer, a reflux condenser with a water separator, and a thermometer, 18.5 parts of gum rosin were placed while blowing in nitrogen gas, and the temperature was raised to 210°C. Then, 6.5 parts of fumaric acid were added thereto, and the mixture was stirred at 210°C for about 90 minutes. After the reaction, the mixture was cooled to 190°C, and 25.0 parts of glycerin and 77.9 parts of oleic acid were added, and a dehydration condensation reaction was carried out at 190°C for 10 hours to obtain a polyester resin component (resin 7). The acid value of this resin 7 was 10 mgKOH / g, the iodine value was 55 g / 100 g, the weight average molecular weight was 122,000, and the refractive index was 1.40. The refractive index of oleic acid was 1.37.

[0110] <Production Example 9> 27.8 parts of gum rosin was placed in a four-neck flask equipped with a stirrer, a reflux condenser with a water separator, and a thermometer while blowing in nitrogen gas, and the temperature was raised to 210° C. Then, 9.8 parts of fumaric acid was added thereto, and the mixture was stirred at 210° C. for about 90 minutes. This produced a first product. Into another four-neck flask equipped with a reflux condenser with a water separator and a thermometer, 73.4 parts of coconut oil and 15.5 parts of glycerin were added and stirred at 250°C for about 90 minutes. Next, the first product was mixed therein, and after mixing, the mixture was cooled to 190°C. Thereafter, a dehydration condensation reaction was carried out at 190°C for 8 hours to obtain a polyester resin component (resin 9). The acid value of this resin 9 was 8 mgKOH / g, the iodine value was 9 g / 100 g, the weight average molecular weight was 86,000, and the refractive index was 1.47. The refractive index of coconut oil fatty acid was 1.45.

[0111] <Production Example 11> A polyester resin component (Resin 11) was obtained in the same manner as in Production Example 1, except that the time for the dehydration condensation reaction to obtain the second product was extended to 12 hours. The acid value of this Resin 11 was 2 mgKOH / g, the iodine value was 109 g / 100 g, the weight average molecular weight was 11,000,000, and the refractive index was 1.49.

[0112] <Production Example 12> 35.2 parts of gum rosin was placed in a four-neck flask equipped with a stirrer, a reflux condenser with a water separator, and a thermometer while blowing in nitrogen gas, and the temperature was raised to 210° C. Then, 12.4 parts of fumaric acid was added thereto, and the mixture was stirred at 210° C. for about 90 minutes. This produced a first product. Into another four-neck flask equipped with a reflux condenser with a water separator and a thermometer, 64.3 parts of clove oil and 19.1 parts of glycerin were added and stirred at 250°C for about 90 minutes. Next, the first product was mixed therein, and after mixing, the mixture was cooled to 190°C. After that, a dehydration condensation reaction was carried out at 190°C for 8 hours to obtain a polyester resin component (resin 12) which was the second product. The acid value of this resin 12 was 9 mgKOH / g, the iodine value was 45 g / 100 g, the weight average molecular weight was 72000, and the refractive index was 1.61. The refractive index of clove oil fatty acid was 1.56.

[0113] <Production Example 13> 13.7 parts of gum rosin was placed in a four-neck flask equipped with a stirrer, a reflux condenser with a water separator, and a thermometer, and heated to 210°C while blowing in nitrogen gas. Then, 4.7 parts of fumaric acid was added thereto, and the mixture was stirred at 210°C for about 90 minutes. After the reaction, the mixture was cooled to 190°C, and 18.2 parts of glycerin and 75.6 parts of oleic acid were added, and a dehydration condensation reaction was carried out at 190°C for 10 hours to obtain a polyester resin component (resin 13). The acid value of this resin 13 was 10 mgKOH / g, the iodine value was 61 g / 100 g, the weight average molecular weight was 102000, and the refractive index was 1.38. The refractive index of oleic acid was 1.37.

[0114] <Examples 1 to 9 and Comparative Examples 1 to 4> (Preparation of Liquid Composition) Into a Erlenmeyer flask equipped with a reflux condenser, 50 parts of a polyester resin component shown in Table 2 and 50 parts of isopropyl alcohol were placed and stirred at 50° C. for about 1 hour. As a result, a liquid composition was obtained.

[0115] (Preparation and evaluation of transparent paper) Paper base material, basis weight 50g / m 2 The pulp constituting this one-sided gloss kraft paper was 40% bleached hardwood kraft pulp and 60% bleached softwood kraft pulp, and the opacity of this one-sided gloss kraft paper was 68.5% and the density was 0.72 g / cm 3 and the thickness was 70 μm. The liquid composition adjusted to 25°C was applied to the non-glossy side of the paper substrate using a wire-wound bar coater No. 36 to obtain coated paper. The amount of the liquid composition applied was 30 g / m2 in terms of resin solids. 2 The obtained coated paper was then dried at 120°C for 2 minutes. After drying, the paper was conditioned in a constant temperature and humidity environment (23°C, relative humidity 50%) for 12 hours. This resulted in a transparent paper.

[0116] <Comparative Example 5> 50 parts of gum rosin and 50 parts of isopropyl alcohol were mixed to obtain a gum rosin solution. 50 parts of linseed oil and 50 parts of isopropyl alcohol were mixed to obtain a linseed oil solution. Next, 90 parts of the rosin solution and 10 parts of the linseed oil solution were mixed. This resulted in the liquid composition of Comparative Example 7.

[0117] <Comparative Example 6> 50 parts of gum rosin and 50 parts of isopropyl alcohol were mixed to obtain a rosin solution. 50 parts of linseed oil and 50 parts of isopropyl alcohol were mixed to obtain a linseed oil solution. Next, 44 parts of the rosin solution and 56 parts of the linseed oil solution were mixed. This resulted in the liquid composition of Comparative Example 8.

[0118] <Comparative Example 7> 50 parts of gum rosin and 50 parts of isopropyl alcohol were mixed to obtain a rosin solution. 50 parts of linseed oil and 50 parts of isopropyl alcohol were mixed to obtain a linseed oil solution. Next, 20 parts of the rosin solution and 80 parts of the linseed oil solution were mixed. This resulted in the liquid composition of Comparative Example 9.

[0119] <Evaluation> The obtained transparent paper was subjected to the following evaluations, and the results are shown in Table 2.

[0120] (transparency) The opacity of the transparent paper immediately after humidity conditioning was measured in accordance with JIS P 8149 (2000). Opacity of 16% or less was evaluated as ◎, opacity of more than 16% to 20% or less was evaluated as ○, opacity of more than 20% to 30% was evaluated as △, and opacity of more than 30% was evaluated as ×.

[0121] (Total light transmittance) The total light transmittance of the transparent paper immediately after humidity adjustment (total light transmittance immediately after) was measured. The transparent paper was then left to stand for 7 days in an environment of 22°C and 50% relative humidity, and the total light transmittance was measured again (total light transmittance after 7 days). The total light transmittance was measured using a haze meter NDH5000 (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K 7361-1 (1997). However, in Comparative Example 4, the viscosity of the liquid composition exceeded 10,000 mPa·s, making it difficult to apply or impregnate the paper substrate, and therefore, no transparent paper was produced or evaluated.

[0122] [Table 1]

[0123] [Table 2]

[0124] As shown in the above results, the transparent papers of Examples 1 to 9 were transparent papers with excellent stability over time, with small differences in total light transmittance immediately after application and after 7 days. Among them, the transparent papers of Examples 1 to 7 had excellent transparency, with total light transmittances immediately after application and after 7 days both being 58% or more. Furthermore, the transparent papers of Examples 1 to 5 had the same total light transmittance immediately after application and after 7 days, with particularly excellent stability of transparency over time. On the other hand, Comparative Example 1, in which the acid value exceeded 100 mgKOH / g, was poor in transparency. Comparative Example 2, in which the weight-average molecular weight exceeded 1 million, was thickened, and production of the transparent paper was discontinued. The transparent papers of Comparative Examples 3 and 4, in which a polyester resin component with a refractive index not satisfying the range of 1.40 to 1.60 was used, were poor in transparency. Comparative Examples 5 to 7, in which a mixture of rosin and linseed oil was used instead of the polyester resin component, were poor in stability over time, such as the total light transmittance after 7 days being lower than the total light transmittance immediately after the preparation and the paper turning white over time.

Claims

1. A clarifying agent comprising a polyester resin component which is a reaction product of raw material components including (A) a rosin, (B) a polyvalent carboxylic acid, (C) a polyol, and (D) an aliphatic monocarboxylic acid, wherein the polyester resin component has an acid value of 100 mgKOH / g or less, a weight average molecular weight of 1,000,000 or less, and a refractive index of 1.40 or more and 1.60 or less.

2. The clarifying agent according to claim 1 , wherein the polyester resin component has an iodine value of 10 g / 100 g or more and 140 g / 100 g or less.

3. A method for producing a clarifying agent, comprising reacting raw material components including (A) a rosin, (B) a polyvalent carboxylic acid, (C) a polyol, and (D) an aliphatic monocarboxylic acid, to obtain a polyester resin component having an acid value of 100 mgKOH / g or less, a weight average molecular weight of 1,000,000 or less, and a refractive index of 1.40 or more and 1.60 or less.

4. The method for producing a clarifying agent according to claim 3, wherein the polyester resin component has an iodine value of 10 g / 100 g or more and 140 g / 100 g or less.

5. The polyvalent carboxylic acid (B) contains an α,β-unsaturated dicarboxylic acid, 5. The method for producing a clarifying agent according to claim 3, wherein, in obtaining the polyester resin component, the rosin (A) is reacted with the α,β-unsaturated dicarboxylic acid to obtain a first product, and the first product is reacted with the polyol (C) and the aliphatic monocarboxylic acid (D).

6. The polyvalent carboxylic acid (B) contains an α,β-unsaturated dicarboxylic acid, 5. The method for producing a clarifying agent according to claim 3 or 4, wherein, in obtaining the polyester resin component, the rosin (A) is reacted with the α,β-unsaturated dicarboxylic acid to obtain a first product, the polyol (C) is modified with the oil or fat (D) having an aliphatic monocarboxylic acid as a constituent fatty acid to obtain a modified product, and the first product is reacted with the modified product.

7. A transparent agent is contained at least inside the paper substrate, The transparent paper, wherein the clarifying agent contains a polyester resin component which is a reaction product of raw material components including (A) rosins, (B) polycarboxylic acids, (C) polyols, and (D) aliphatic monocarboxylic acids, the polyester resin component having an acid value of 100 mgKOH / g or less, a weight average molecular weight of 1,000,000 or less, and a refractive index of 1.40 or more and 1.60 or less.

8. The transparent paper according to claim 7 , wherein the iodine value of the polyester resin component is from 10 g / 100 g to 140 g / 100 g.

9. The transparent paper according to claim 7 or 8, wherein the paper base material comprises softwood chemical pulp and hardwood chemical pulp.

10. A method for producing transparent paper by coating or impregnating a paper substrate with a liquid composition containing a transparentizing agent and a liquid medium, and drying the composition, The method for producing transparent paper, wherein the clarifying agent comprises a polyester resin component which is a reaction product of raw material components including (A) a rosin, (B) a polyvalent carboxylic acid, (C) a polyol, and (D) an aliphatic monocarboxylic acid, the polyester resin component having an acid value of 100 mg KOH / g or less, a weight average molecular weight of 1,000,000 or less, and a refractive index of 1.40 or more and 1.60 or less.

11. The method for producing transparent paper according to claim 10, wherein the iodine value of the polyester resin component is 10 g / 100 g or more and 140 g / 100 g or less.

12. The method for producing transparent paper according to claim 10 or 11, wherein the paper base material contains softwood chemical pulp and hardwood chemical pulp.

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