Coated paper

Abstract

To provide a coated paper containing a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), and having a coated layer having few coating defects.SOLUTION: A coated paper has a coated layer containing a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and an adhesive agent on at least one surface of a paper substrate. The coated paper has a solid content weight ratio of 99.9 / 0.1 to 60.0 / 40.0 between the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) in the coated layer and the adhesive agent, and a basis weight of 150 g / m2 to 600 g / m2 measured in conformity to JIS P 8124.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to coated paper. [Background technology]

[0002] Conventionally, coated paper has been known in which an aqueous dispersion of resin is coated onto a paper substrate (base paper) to impart functions such as water resistance, oil resistance, gas barrier properties, water vapor barrier properties, and heat sealability to paper. For example, Patent Document 1 (JP-A-09-003795) describes water- and oil-resistant paper coated with an aqueous emulsion containing an acrylic emulsion and a wax emulsion, Patent Document 2 (JP-A-2003-119697) describes moisture-proof paper coated with a mixture of a synthetic resin emulsion and a wax emulsion, and Patent Document 3 (JP-A-2004-15978) describes water-resistant and mold-proof paper coated with a water-dispersible mold inhibitor.

[0003] In recent years, efforts have begun to prevent environmental damage caused by plastic waste, and there is a demand to replace disposable plastic products with materials that have a smaller environmental impact. Examples of alternative materials to plastic include biodegradable plastics, wood, and paper. As mentioned above, coated paper can exhibit various functions derived from the resin to which it is coated. However, if the resin used for coating is derived from fossil resources or is not biodegradable, the environmental impact reduction effect achieved by using paper is diminished. Therefore, there is a demand for coated paper in which an aqueous dispersion of biodegradable plastic is coated onto a paper base.

[0004] Aliphatic polyesters such as polylactic acid and polycaprolactone are known as biodegradable plastics. However, aliphatic polyesters have the problem that they take a long time to biodegrade at low temperatures, and their decomposition rate in natural environments such as the ocean is slow. On the one hand, poly(3-hydroxybutyrate) resin is a thermoplastic produced by microorganisms using plant raw materials, which is excellent in degradability under aerobic and anaerobic conditions, and has a remarkable performance of being decomposed by microorganisms in a short period even in water such as in the ocean. Poly(3-hydroxybutyrate) resin is thermoplastic and can be processed by methods such as extrusion molding and injection molding. In addition, a biodegradable polyester aqueous dispersion containing poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (hereinafter also referred to as "P3HB3HH" or "PHBH"), which is a copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate, is known. For example, Patent Document 4 (International Publication No. 2004 / 041936) describes a biodegradable polyester aqueous dispersion that has excellent film-forming properties and, when applied to paints, adhesives, fiber processing, sheet / film processing, paper processing, etc., gives a resin coating film that is flexible, has good elongation, and is strong against bending. However, there is a problem that the coated layer coated with the aqueous dispersion of PHBH is likely to have coating defects such as cracks and pinholes.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide a coated paper containing poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and having a coated layer with few coating defects.

Means for Solving the Problems

[0007] The means for solving the problems of the present invention are as follows. 1. A coated paper having a coating layer containing poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and an adhesive on at least one surface of a paper substrate, wherein the solid content weight ratio of the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) to the adhesive in the coating layer is 99.9 / 0.1 to 60.0 / 40.0, and the basis weight of the paper substrate measured according to JIS P 8124 is 150 g / m 2 or more and 600 g / m 2 or less. The coated paper is characterized by the above. 2. The coated paper according to 1., wherein the coating amount (dry weight) of the coating layer is 1.0 g / m per side 2 or more and 50.0 g / m 2 or less. 3. The coated paper according to 1. or 2., wherein the coating amount (dry weight) of the coating layer is 9.0 g / m per side 2 or more and 50.0 g / m 2 or less. 4. The coated paper according to any one of 1. to 3., wherein the solid content weight ratio of the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) to the adhesive in the coating layer is 90.0 / 10.0 to 75.0 / 25.0. 5. The coated paper according to any one of 1. to 4., wherein the paper substrate has coating layers containing poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and an adhesive on both sides. 6. The coated paper according to any one of 1. to 5., further having a blocking layer between the paper substrate and the coating layer. 7. The coated paper according to 6., wherein the coating amount (dry weight) of the blocking layer is 3.0 g / m per side 2 or more and 15.0 g / m 2 or less. 8. The coated paper according to any one of items 1 to 7, characterized in that the paper substrate has a Wang Ken smoothness of 55 seconds or less in its state before coating. 9. The coated paper according to any one of claims 1 to 8, characterized in that the adhesive contains at least one selected from the group consisting of polyvinyl alcohols, starches, cellulose derivatives, partially saponified ethylene-vinyl acetate copolymers, styrene-butadiene copolymer latex, methyl methacrylate-butadiene copolymer conjugated diene polymer latex, and acrylic polymer latex. 10. The coated paper according to 9, characterized in that the adhesive contains at least one selected from fully saponified polyvinyl alcohol and partially saponified polyvinyl alcohol. 11. The coated paper according to 9, characterized in that the adhesive contains a partially saponified ethylene-vinyl acetate copolymer. 12. The coated paper according to any one of claims 1 to 11, characterized in that the coating layer is a heat-seal layer. 13. The coated paper according to any one of items 1 to 11, characterized in that the coating layer is a water-resistant layer. 14. The coated paper according to any one of items 1 to 11, characterized in that the coating layer is an oil-resistant layer. 15. Coated paper according to any one of items 1 to 14, characterized in that it is for use with paper cups. 16. Coated paper according to any one of items 1 to 14, characterized in that it is for use in paper containers. 17. Coated paper as described in any one of items 1 to 14, characterized in that it is for use in paper boxes. 18. Coated paper according to any one of items 1 to 14, characterized in that it is for use with paper plates. 19. Coated paper according to any one of items 1 to 14, characterized in that it is for use as a paper tray. [Effects of the Invention]

[0008] The coated paper of the present invention has few coating defects in the coating layer and can prevent a decrease in quality due to coating defects. Further, since the coated paper of the present invention can be made biodegradable as a whole, even if it leaks into the environment, it will be rapidly decomposed.

Mode for Carrying Out the Invention

[0009] The present invention relates to a coated paper having a coating layer containing poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and an adhesive on at least one surface of a paper base material, where the solid content weight ratio (PHBH / adhesive) of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and the adhesive in this coating layer is 99.9 / 0.1 to 60.0 / 40.0, and the basis weight of this paper base material measured according to JIS P 8124 is 150 g / m 2 or more and 600 g / m 2 or less. In the present specification, the description “A to B” (A and B are numerical values) means a numerical range including A and B, that is, “not less than A and not more than B”.

[0010] (Paper base material) The paper base material is a sheet mainly made of pulp, and is obtained by papermaking a paper stock containing a filler, various aids, and the like. As pulp, chemical pulps such as bleached hardwood kraft pulp (LBKP), bleached softwood kraft pulp (NBKP), unbleached hardwood kraft pulp (LUKP), unbleached softwood pulp (NUKP), and sulfite pulp can be used, as can mechanical pulps such as stone-ground pulp and thermomechanical pulp, wood fibers such as deinked pulp and recycled paper pulp, and non-wood fibers obtained from kenaf, bamboo, hemp, etc., and can be used in appropriate blends. Among these, chemical pulps and mechanical pulps made from wood fibers are preferred, and chemical pulps are more preferred, for reasons such as being less prone to foreign matter contamination in the paper substrate, being less prone to discoloration over time when recycled as recycled paper raw material, having high whiteness resulting in a good surface texture when printed, and having particularly high value when used as packaging material. Specifically, it is preferable that the proportion of chemical pulp such as LBKP and NBKP relative to the total pulp be 80% or more, and it is particularly preferable that the proportion of chemical pulp be 100%.

[0011] As fillers, known fillers such as talc, kaolin, calcined kaolin, clay, heavy calcium carbonate, light calcium carbonate, white carbon, zeolite, magnesium carbonate, barium carbonate, titanium dioxide, zinc oxide, silicon dioxide, amorphous silica, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, barium sulfate, calcium sulfate, and other inorganic fillers, as well as organic fillers such as urea-formaldehyde resin, polystyrene resin, phenolic resin, and fine hollow particles can be used. Note that fillers are not essential materials and may not be used.

[0012] Examples of various additives include sizing agents such as rosin, alkyl ketene dimer (AKD), and alkenyl succinic anhydride (ASA); dry strength enhancers such as polyacrylamide polymers, polyvinyl alcohol polymers, cationized starch, various modified starches, urea-formaldehyde resins, and melamine-formaldehyde resins; wet strength enhancers; yield enhancers; water drainage enhancers; coagulants; aluminum sulfate; bulk enhancers; dyes; fluorescent whitening agents; pH adjusters; defoamers; UV inhibitors; fade inhibitors; pitch control agents; and slime control agents. These can be selected and used as needed.

[0013] The paper substrate may have its surface treated with various chemicals. Examples of chemicals include oxidized starch, hydroxyethyl etherified starch, enzyme-modified starch, polyacrylamide, polyvinyl alcohol, surface sizing agents, water-resistant agents, water-retaining agents, thickeners, and lubricants, which can be used individually or in combination of two or more. Furthermore, these various chemicals may be used in combination with pigments. Examples of pigments include inorganic pigments such as kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, light calcium carbonate, mica, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicates, colloidal silica, and satin white, as well as organic pigments such as dense, hollow, or core-shell types, which can be used individually or in combination of two or more.

[0014] The basis weight of the paper substrate is 150 g / m². 2 More than 600g / m 2 The following applies. This paper substrate with this basis weight can be suitably used for paper cups, paper containers, paper boxes, paper plates, paper trays, etc. The basis weight of the paper substrate is 150 g / m². 2 More than 300g / m 2 The following are preferred. Furthermore, the density of the paper substrate can be appropriately selected depending on the desired quality and handling requirements, but it is typically 0.5 g / cm³. 3 More than 1.0g / cm 3 The following are preferred.

[0015] The paper substrate preferably has a Wang-Gan smoothness rating of 100 seconds or less, more preferably 70 seconds or less, and even more preferably 55 seconds or less, as measured in accordance with JIS P8155:2010. By using a paper substrate with low smoothness (rough surface), the adhesion between the coating layer and the paper substrate can be improved.

[0016] The method of manufacturing (papermaking) the paper substrate is not particularly limited, and known manufacturing (papermaking) methods and papermaking machines such as long-wire papermaking machines, cylinder papermaking machines, short-wire papermaking machines, gap formers, hybrid formers (on-top formers), and twin-wire papermaking machines can be selected. Furthermore, the pH during papermaking can be in the acidic range (acidic papermaking), pseudo-neutral range (pseudo-neutral papermaking), neutral range (neutral papermaking), or alkaline range (alkaline papermaking), and an alkaline agent may be applied to the surface of the paper layer after papermaking in the acidic range. In addition, the paper substrate may be a single layer or may be composed of two or more layers. Furthermore, when treating the surface of a paper substrate with a chemical, the surface treatment method is not particularly limited, and known coating equipment such as rod metering size presses, pound-type size presses, gate roll coaters, spray coaters, blade coaters, and curtain coaters can be used.

[0017] (Sealing layer) The coated paper of the present invention may have a sealing layer between the paper substrate and the coating layer. The sealing layer prevents the performance of the coating layer from degrading by suppressing the sinking of the coating liquid into the paper substrate. The sealing layer is not particularly limited as long as it can suppress the sinking of the coating liquid into the paper substrate, but it is preferable, for example, to include a pigment and a binder. In addition, the sealing layer may contain sizing agents, water-resistant agents, water-repellent agents, dyes, surfactants, etc., as needed.

[0018] Examples of pigments include inorganic pigments such as light calcium carbonate, heavy calcium carbonate, kaolin, calcined kaolin, engineered kaolin, clay, delaminated clay, talc, silica, colloidal silica, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, calcium silicate, magnesium silicate, aluminum hydroxide, alumina, magnesium carbonate, magnesium hydroxide, kaolinite, antigorite, smectite, vermiculite, and mica; and organic pigments made from resins such as acrylic or methacrylic resins, vinyl chloride resins, vinyl acetate resins, polyester resins, styrene-acrylic resins, styrene-butadiene resins, styrene-isoprene resins, polycarbonate resins, silicone resins, urea resins, melamine resins, epoxy resins, phenolic resins, and diallyl phthalate resins. One or more of these pigments can be used as a mixture.

[0019] As a binder, any type commonly used in the coated paper field can be used as appropriate. For example, polyvinyl alcohols such as fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, olefin-modified polyvinyl alcohol, nitrile-modified polyvinyl alcohol, pyrrolidone-modified polyvinyl alcohol, silicone-modified polyvinyl alcohol, other modified polyvinyl alcohols, ethylene vinyl alcohol copolymers, (meth)acrylic acid, and monomer components copolymerizable with (meth)acrylic acid (excluding olefins). Examples of suitable materials include acrylic resins, ethylene-acrylic resins, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, methylcellulose, ethylcellulose, carboxymethylcellulose, and acetylcellulose, starches such as oxidized starch, etherified starch, and esterified starch, styrene-maleic anhydride copolymers, styrene-butadiene copolymers, casein, gum arabic, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylic acid esters, polyvinyl butyral, polystyrene and their copolymers, polyamide resins, silicone resins, petroleum resins, terpene resins, ketone resins, and coumarone resins. One or more of these can be used as binders. In the present invention, it is preferable to use a biodegradable binder such as polyvinyl alcohols, cellulose derivatives, or starches in the sealing layer, as this can further improve the overall biodegradability of the coated paper.

[0020] By using a binder with high water vapor barrier properties, water vapor barrier properties can be imparted to the sealing layer. When imparting water vapor barrier properties to the sealing layer, it is preferable to use a mixture of one or more binders selected from ethylene vinyl alcohol copolymer, ethylene-acrylic resin, and styrene-butadiene copolymer. The amount of pigment used in the sealing layer is preferably in the range of 1 part by weight or more and 1000 parts by weight or less per 100 parts by weight of binder, and more preferably 10 parts by weight or more and 500 parts by weight or less.

[0021] (Coating layer) The coating layer contains PHBH and adhesive in a solids weight ratio (PHBH / adhesive) within the range of 99.9 / 0.1 to 60.0 / 40.0. <phbh> PHBH is a copolymer of 3-hydroxybutyrate (hereinafter also referred to as 3HB) and 3-hydroxyhexanoate (hereinafter also referred to as 3HH), and is a biodegradable resin known to be produced by microorganisms. In the present invention, PHBH may be derived from microorganisms or from petroleum resources, but it is preferable to use PHBH derived from microorganisms from the viewpoint of reducing environmental impact.

[0022] Microorganisms that produce PHBH are not particularly limited to any microorganism that accumulates PHBH within its cells, but examples include bacteria of the genera Alcaligenes (such as A. lipolytica, A. eutrophus, and A. latus), Pseudomonas, Bacillus, Azotobacter, Nocardia, and Aeromonas. In particular, strains such as Aeromonas caviae are preferred in terms of PHBH productivity, as are Alcaligenes eutrophas AC32 (accession number FERM BP-6038, deposit date August 7, 1997, National Institute of Advanced Industrial Science and Technology, Patent Organism Depositary Center, address: 1-1-1 Higashi, Tsukuba, Ibaraki Prefecture, Japan, Central No. 6) (J. Bacteriol., 179, pp. 4821-4830 (1997)). A method for obtaining PHBH from Aeromonas caviae, a microorganism of the genus Aeromonas, is disclosed, for example, in Japanese Patent Publication No. 05-093049. These microorganisms are cultured under appropriate conditions to accumulate PHBH within the cells before use. The carbon source and culture conditions used for cultivation can be obtained according to the methods described in Japanese Patent Publication No. 05-093049, Japanese Patent Publication No. 2001-340078, etc., but are not limited thereto.

[0023] The composition ratio (mol%) of PHBH is preferably 3HB:3HH = 97:3 to 75:25, and more preferably 95:5 to 85:15. If the 3HH composition is less than 3 mol%, the properties of PHBH become similar to those of the 3HB homopolymer, resulting in a loss of flexibility and an undesirable tendency for the film deposition temperature to become too high. If the 3HH composition exceeds 25 mol%, the crystallization rate becomes too slow, making it unsuitable for film deposition, and the degree of crystallinity decreases, which tends to make the resin more flexible and reduce its flexural modulus. The composition ratio of PHBH can be measured by NMR analysis of the powder obtained by centrifuging an aqueous dispersion and drying it. Microbially produced PHBH is a random copolymer. Methods to adjust the molar ratio of the copolymer include selecting the microbial cells, selecting the carbon source as the raw material, blending with PHBH of different molar ratios, and blending with 3HB homopolymer.

[0024] In one embodiment of the present invention, the weight-average molecular weight of PHBH in the aqueous dispersion is 50,000 to 550,000, preferably 100,000 to 500,000, and more preferably 150,000 to 450,000. Having the weight-average molecular weight of PHBH in the aqueous dispersion within this range allows the aqueous dispersion containing PHBH to form a film at low temperatures, and the resulting coated paper exhibits good heat-sealability. The weight-average molecular weight of PHBH in the aqueous dispersion can be determined by gel permeation chromatography (GPC, such as Showa Denko's "Shodex GPC-101") using a polystyrene gel column (such as Showa Denko's "Shodex K-804") with chloroform as the mobile phase, and expressed as the molecular weight in polystyrene equivalent. For measurement, the sample used is a powder obtained by centrifuging and drying the aqueous dispersion containing PHBH.

[0025] The average particle size of PHBH in the aqueous dispersion of the present invention is preferably 0.1 to 50 μm, and more preferably 0.5 to 10 μm. PHBH with an average particle size of less than 0.1 μm is difficult to achieve by microbial production, and even when obtained by chemical synthesis, a process of micronization is required. If the average particle size exceeds 50 μm, uneven coating may occur on the surface when the aqueous dispersion containing PHBH is applied. The average particle size of PHBH is determined by adjusting the aqueous suspension of PHBH to a predetermined concentration using a general-purpose particle size analyzer such as a Microtrac particle size analyzer (manufactured by Nikkiso, FRA), and the particle size corresponding to the 50% accumulation amount of all particles in a normal distribution. The solid content concentration of PHBH in the aqueous dispersion is preferably 5 to 70% by weight, and more preferably 10 to 50% by weight. If the solid content concentration is less than 5% by weight, the coating film tends not to form properly. If it exceeds 70% by weight, the viscosity of the aqueous dispersion becomes too high, making coating difficult.

[0026] <Adhesive> The adhesive adheres the PHBH in the coating layer to the paper substrate and / or to each other within the coating layer. The coated paper of the present invention, by containing the adhesive in the coating layer, can adhere the PHBH to the paper substrate and obtain a uniform coating layer with suppressed coating defects such as cracks and pinholes. The adhesive can be used without particular limitations, as long as it dissolves or disperses in water and can bond these materials together. Examples include polyvinyl alcohols such as fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, olefin-modified polyvinyl alcohol, nitrile-modified polyvinyl alcohol, pyrrolidone-modified polyvinyl alcohol, silicone-modified polyvinyl alcohol, other modified polyvinyl alcohols, and ethylene vinyl alcohol copolymers; starches such as oxidized starch, etherified starch, and esterified starch; cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, methylcellulose, ethylcellulose, carboxymethylcellulose, acetylcellulose, and nanocellulose; partially saponified ethylene-vinyl acetate copolymers; styrene-butadiene copolymer latex; conjugated diene polymer latex of methyl methacrylate-butadiene copolymer; acrylic polymer latex; styrene-maleic anhydride copolymer latex; polyvinyl chloride latex; and polyvinyl acetate latex. One or more of these can be appropriately selected and used. Among these, it is preferable to include at least one selected from the group consisting of polyvinyl alcohols, starches, cellulose derivatives, partially saponified ethylene-vinyl acetate copolymers, styrene-butadiene copolymer latex, methyl methacrylate-butadiene copolymer conjugated diene polymer latex, and acrylic polymer latex, and more preferably at least one selected from this group. Furthermore, because it is biodegradable, it is more preferable to include at least one selected from the group consisting of polyvinyl alcohols, starches, cellulose derivatives, and partially saponified ethylene-vinyl acetate copolymers, and even more preferable to include at least one selected from the group consisting of fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, and partially saponified ethylene-vinyl acetate copolymer.

[0027] It is preferable to include at least one of fully saponified polyvinyl alcohol and partially saponified polyvinyl alcohol as an adhesive, as this further improves the adhesion between the PHBH in the coating layer and the paper substrate, and / or between the PHBHs in the coating layer themselves. It is even more preferable that the adhesive consists of at least one of fully saponified polyvinyl alcohol and partially saponified polyvinyl alcohol. Furthermore, the inclusion of a partially saponified ethylene-vinyl acetate copolymer as an adhesive is preferable because it further improves the adhesion between the PHBH in the coating layer and the paper substrate, and / or between the PHBHs in the coating layer, as well as improving the water resistance of the coated paper, and is even more preferable to be composed of a partially saponified ethylene-vinyl acetate copolymer.

[0028] The coating layer contains PHBH and adhesive in a solids weight ratio (PHBH / adhesive) within the range of 99.9 / 0.1 to 60.0 / 40.0. If the amount of adhesive is less than this range, coating defects such as cracks and pinholes are more likely to occur in the coating layer, and the surface strength of the coating layer and the adhesion between the coating layer and the paper substrate may decrease. If the amount of adhesive is more than this range, the functionality of PHBH may not be fully exhibited. The solids weight ratio of PHBH to adhesive is preferably 94.0 / 6.0 to 75.0 / 25.0, more preferably 92.0 / 8.0 to 78.0 / 22.0, and even more preferably 90.0 / 10.0 to 80.0 / 20.0. In addition to PHBH and adhesives, the coating layer may, as needed, contain various additives used in coating solutions in the papermaking field, such as dispersants, viscosity modifiers, water-retaining agents, defoamers, water-resistant agents, fluorescent dyes, coloring dyes, coloring pigments, surfactants, pH adjusters, cationic resins, anionic resins, UV absorbers, and metal salts.

[0029] Because the coating layer contains PHBH, it can exhibit the functional properties of PHBH and can be used, for example, as a heat-sealing layer, a water-resistant layer, an oil-resistant layer, etc. The coating layer can be applied to one side or both sides of the paper substrate. A heat-seal layer is a layer that has heat-sealing properties, specifically a layer that can be bonded to an object by heating and pressing it. The water-resistant layer is defined as having a water absorption (Cobb value) of 20 g / m², measured after a contact time of 120 seconds, in accordance with the "Paper and cardboard - Water absorption test method - Cobb method" specified in JIS P 8140:1998. 2 The following layers are present. The water absorption rate is 10 g / m². 2 Preferably, it is 5 g / m 2 The following is more preferable: An oil-resistant layer is defined as a layer in which the lowest value of the kit number measured at any five points on the layer surface, in accordance with the "Paper and cardboard - Oil repellency test method - Kit method" specified in J.TAPPI No.41:2000, is 10 or higher. Preferably, this lowest kit number is 11 or higher, and more preferably 12.

[0030] <Method of manufacturing coated paper> The coated paper of the present invention can be manufactured by coating a paper substrate with a coating liquid for the coating layer and drying it. If a sealing layer is to be provided, the sealing layer is to be applied to the paper substrate before applying the coating liquid for the coating layer, or simultaneously with the application of the coating liquid for the coating layer, so that a sealing layer is provided between the paper substrate and the coating layer.

[0031] The coating method for the sealing layer and the coating layer is not particularly limited and can be performed using known coating equipment and coating systems. For example, coating equipment includes blade coaters, bar coaters, air knife coaters, curtain coaters, spray coaters, roll coaters, reverse roll coaters, size press coaters, gate roll coaters, etc. Coating systems include water-based coating using solvents such as water, and solvent-based coating using solvents such as organic solvents. The coated paper of the present invention has the characteristics that PHBH is biomass-derived and biodegradable, and has a low environmental impact, so it is preferable that the manufacturing process also uses a water-based coating which has a low environmental impact. The viscosity, solid content concentration, etc., of the coating liquid for the sealing layer and the coating liquid for the coating layer can be appropriately adjusted according to the coating equipment, coating system, etc. used.

[0032] Conventional methods such as steam heaters, gas heaters, infrared heaters, electric heaters, hot air heaters, microwaves, and cylinder dryers are used to dry the sealing layer and coating layer. Increasing the drying temperature is preferable because it promotes film formation of PHBH, which tends to improve heat sealability, water resistance, and oil resistance.

[0033] The coating amount (dry weight) of the sealant layer is 3.0 g / m². 2 More than 15.0g / m 2 The following is preferable: Coating amount of 3.0 g / m² 2 If the amount is less than 15.0 g / m², the sealing effect may be insufficient. 2 If the amount is too high, the drying load during coating increases, which is undesirable from both an operational and cost perspective. The sealing layer may be one layer or two or more layers. If there are two or more sealing layers, it is preferable that the total coating amount of all sealing layers is within the range specified above in terms of dry weight.

[0034] The amount of coating layer (dry weight) is not particularly limited as long as it can achieve its performance, but for example, 1.0 g / m² per side. 2 More than 50.0g / m 2 The following is preferable: Coating amount of 1.0 g / m² per side. 2 Below this level, the performance derived from PHBH may not be fully realized. Also, the coating amount should be 50.0 g / m² per side. 2 Beyond this point, further improvement in properties is unlikely, and costs will increase. The coating amount (dry weight) of the coating layer is 5.0 g / m² per side. 2 More than 40.0g / m 2 The following is more preferable: 9.0 g / m 2 More than 30.0g / m 2 The following are even more preferable. The coating layer may be one layer or two or more layers. If there are two or more coating layers, it is preferable that the total coating amount of all layers is within the range specified above in terms of dry weight.

[0035] The coated paper of the present invention can be used for a variety of applications depending on the functions of the coating layer. Furthermore, the coating layer can simultaneously possess the functions of two or more layers selected from a heat-seal layer, a water-resistant layer, an oil-resistant layer, and so on. Coated paper, in which the coating layer is a heat-sealable layer, is easy to mold, maintain its shape, and ensure airtightness, making it suitable for use as paper bags, paper containers, paper boxes, paper cups, packaging materials, lids, and the like. Coated paper with a water-resistant coating layer can be suitably used as wrapping paper, paper bags, paper containers, paper boxes, paper cups, packaging materials, paper plates, paper trays, posters for outdoor use, and the like. Coated paper with an oil-resistant coating layer can be suitably used as packaging material or wrapping paper for oily foods such as hamburgers, hot dogs, french fries, fried chicken, and potato chips, as well as for lining paper for fried foods such as tempura, paper plates, paper trays, and paper cups.

[0036] As described above, the coated paper of the present invention suppresses the deterioration of the coating layer's performance when a sealing layer is present between the paper substrate and the coating layer. In particular, for applications such as paper cups, paper containers, paper boxes, paper plates, and paper trays, the presence of a sealing layer is preferable because it particularly effectively suppresses the deterioration of the coating layer's performance. [Examples]

[0037] The present invention will be specifically described below with reference to examples, but the present invention is of course not limited to these examples. Unless otherwise specified, parts and % in the examples refer to parts by weight and weight %, respectively. The obtained coated paper was tested based on the evaluation method shown below.

[0038] [Example 1] (Preparation of coating solution 1 for the coating layer) A PHBH aqueous dispersion with a solid content of 50% by weight was obtained by the method described in Patent Document 4. Next, this PHBH aqueous dispersion was hydrolyzed at 60°C to adjust the molecular weight, thereby obtaining a PHBH aqueous dispersion with a weight-average molecular weight of 230,000. Next, the aqueous dispersion of PHBH and the adhesive (fully saponified polyvinyl alcohol, manufactured by Kuraray Co., Ltd.: 28-98) were mixed in a solid content weight ratio of 99.9 / 0.1. Water was then added and the mixture was stirred to prepare coating liquid 1 for the coating layer, in which the combined solid content concentration of PHBH and adhesive was 40% by weight.

[0039] (Preparation of coated paper) Paper base material (basis weight 200g / m 2 On one side of the cup base paper (Oken method, smoothness 55 seconds), apply coating liquid 1 for the coating layer by dry weight, with a coating rate of 20.0 g / m². 2 The paper was coated using the barblade method and dried at 160°C to obtain coated paper. In this specification, the Ogakuen-type smoothness of the paper substrate was measured using a digital Ogakuen-type air permeability and smoothness tester (manufactured by Asahi Seiko Co., Ltd.) in accordance with JIS P8155.

[0040] [Example 2] Coated paper was obtained in the same manner as in Example 1, except that the PHBH aqueous dispersion and adhesive in coating solution 1 for the coating layer were changed to a solid content weight ratio of 99.0 / 1.0. [Example 3] Coated paper was obtained in the same manner as in Example 1, except that the PHBH aqueous dispersion and adhesive in coating solution 1 for the coating layer were changed to a solid content weight ratio of 98.0 / 2.0. [Example 4] Coated paper was obtained in the same manner as in Example 1, except that the PHBH aqueous dispersion and adhesive in coating solution 1 for the coating layer were changed to a solid content weight ratio of 90.0 / 10.0. [Example 5] Coated paper was obtained in the same manner as in Example 1, except that the PHBH aqueous dispersion and adhesive in coating solution 1 for the coating layer were changed to a solid content weight ratio of 80.0 / 20.0. [Example 6] Coated paper was obtained in the same manner as in Example 1, except that the PHBH aqueous dispersion and adhesive in coating solution 1 for the coating layer were changed to a solid content weight ratio of 75.0 / 25.0. [Example 7] Coated paper was obtained in the same manner as in Example 1, except that the PHBH aqueous dispersion and adhesive in coating solution 1 for the coating layer were changed to a solid content weight ratio of 70.0 / 30.0. [Example 8] Coated paper was obtained in the same manner as in Example 1, except that the PHBH aqueous dispersion and adhesive in coating solution 1 for the coating layer were changed to a solid content weight ratio of 60.0 / 40.0.

[0041] [Example 9] (Preparation of coating solution 2 for the coating layer) A PHBH aqueous dispersion and an adhesive (partially saponified ethylene-vinyl acetate copolymer, manufactured by Kuraray Co., Ltd.: RS-1713) were mixed in a solids weight ratio of 98.0 / 2.0. Water was then added and the mixture was stirred to prepare coating solution 2 for the coating layer, in which the combined solids concentration of PHBH and adhesive was 40% by weight. (Preparation of coated paper) Coated paper was obtained in the same manner as in Example 1, except that coating liquid 1 for the coating layer was changed to coating liquid 2 for the coating layer.

[0042] [Example 10] (Preparation of coating liquid for sealing layer) Kaolin (manufactured by Imerys Co., Ltd.: KCS) and a binder (fully saponified polyvinyl alcohol, manufactured by Kuraray Co., Ltd.: 28-98) were mixed in a solids weight ratio of 90.0 / 10.0, and water was added and stirred to prepare a coating liquid for sealing layers with a solids concentration of 35% by weight. (Preparation of coated paper) Paper base material (basis weight 200g / m 2 On one side of the cup base paper, apply a sealing layer coating liquid by dry weight at a rate of 10.0 g / m². 2 The paper was coated and dried using the barblade method to obtain a pore-sealing coated paper. On the sealing layer of this sealing layer coated paper, apply coating liquid 2 for the coating layer at a dry weight of 20.0 g / m². 2 The paper was coated using the barblade method and dried at 160°C to obtain coated paper.

[0043] [Example 11] Coated paper was obtained in the same manner as in Example 9, except that the PHBH aqueous dispersion and adhesive in coating liquid 2 for the coating layer were changed to a solid content weight ratio of 90.0 / 10.0.

[0044] [Example 12] (Preparation of coating solution 3 for the coating layer) A PHBH aqueous dispersion and adhesive (oxidized starch, manufactured by Sanwa Starch Industry Co., Ltd.: PLV-500) were mixed in a solid content weight ratio of 90.0 / 10.0, and water was added and stirred to prepare coating liquid 3 for coating layers with a solid content concentration of 40% by weight. (Preparation of coated paper) Coated paper was obtained in the same manner as in Example 1, except that coating liquid 1 for the coating layer was changed to coating liquid 3 for the coating layer.

[0045] [Example 13] Coating layer dry weight: 1.0 g / m² 2 Coated paper was obtained in the same manner as in Example 9, except that the following changes were made. [Example 14] Coating layer dry weight: 5.0 g / m² 2 Coated paper was obtained in the same manner as in Example 9, except that the following changes were made. [Example 15] Coating layer dry weight: 10.0 g / m² 2 Coated paper was obtained in the same manner as in Example 9, except that the following changes were made. [Example 16] The coating layer has a dry weight of 30.0 g / m². 2 Coated paper was obtained in the same manner as in Example 9, except that the following changes were made. [Example 17] Coating layer dry weight: 40.0 g / m² 2 Coated paper was obtained in the same manner as in Example 9, except that the following changes were made. [Example 18] Coating layer dry weight: 50.0 g / m² 2 Coated paper was obtained in the same manner as in Example 9, except that the following changes were made.

[0046] [Example 19] Paper base material (basis weight 200g / m 2 On one side of the cup base paper, apply a sealing layer coating liquid by dry weight at a rate of 10.0 g / m². 2 The paper was coated and dried using the barblade method to obtain a pore-sealing coated paper. On the sealing layer of this sealing layer coated paper, apply coating liquid 2 for the coating layer at a dry weight of 10.0 g / m². 2 The paper was coated using the barblade method and dried at 160°C to obtain coated paper.

[0047] [Comparative Example 1] Coated paper was obtained in the same manner as in Example 1, except that the PHBH aqueous dispersion and adhesive (fully saponified polyvinyl alcohol) in coating solution 1 for the coating layer were changed to 100 / 0 by weight of solids. [Comparative Example 2] Coated paper was obtained in the same manner as in Example 1, except that the PHBH aqueous dispersion and adhesive (fully saponified polyvinyl alcohol) of coating liquid 1 for the coating layer were changed to a solid content weight ratio of 50.0 / 50.0. [Comparative Example 3] Coated paper was obtained in the same manner as in Example 12, except that the PHBH aqueous dispersion and adhesive (oxidized starch) of coating liquid 3 for the coating layer were changed to a solid content weight ratio of 50.0 / 50.0.

[0048] [Example 20] Coated paper was obtained in the same manner as in Example 9, except that the paper substrate was changed to one with a smoothness rating of 10 seconds according to the Wangyan method. [Example 21] Coated paper was obtained in the same manner as in Example 9, except that the paper substrate was changed to one with a smoothness rating of 40 seconds according to the Wangyan method. [Example 22] Coated paper was obtained in the same manner as in Example 9, except that the paper substrate was changed to one with a smoothness rating of 50 seconds according to the Wangyan method.

[0049] [Example 23] Coated paper was obtained in the same manner as in Example 9, except that the paper substrate was changed to one with a smoothness rating of 60 seconds according to the Wangyan method. [Example 24] Coated paper was obtained in the same manner as in Example 9, except that the paper substrate was changed to one with a smoothness rating of 80 seconds according to the Wangyan method. [Example 25] Coated paper was obtained in the same manner as in Example 9, except that the paper substrate was changed to one with a smoothness rating of 90 seconds according to the Wangyan method.

[0050] [Example 26] Coated paper was obtained in the same manner as in Example 25, except that the PHBH aqueous dispersion and adhesive in coating solution 2 for the coating layer were changed to a solid content weight ratio of 95.0 / 5.0. [Example 27] Coated paper was obtained in the same manner as in Example 25, except that the PHBH aqueous dispersion and adhesive in coating solution 2 for the coating layer were changed to a solid content weight ratio of 93.0 / 7.0. [Example 28] Coated paper was obtained in the same manner as in Example 25, except that the PHBH aqueous dispersion and adhesive in coating liquid 2 for the coating layer were changed to a solid content weight ratio of 90.0 / 10.0.

[0051] [Example 29] Coated paper was obtained in the same manner as in Example 25, except that the PHBH aqueous dispersion and adhesive in coating liquid 2 for the coating layer were changed to a solid content weight ratio of 80.0 / 20.0. [Example 30] Coated paper was obtained in the same manner as in Example 25, except that the PHBH aqueous dispersion and adhesive in coating liquid 2 for the coating layer were changed to a solid content weight ratio of 70.0 / 30.0. [Example 31] Coated paper was obtained in the same manner as in Example 25, except that the PHBH aqueous dispersion and adhesive in coating solution 2 for the coating layer were changed to a solid content weight ratio of 60.0 / 40.0.

[0052] [Example 32] Basis weight 200g / m 2 Coated paper was obtained in the same manner as in Example 19, except that the paper substrate was changed to one with a smoothness rating of 90 seconds according to the Wangyan method. [Example 33] Coating layer dry weight: 5.0 g / m² 2 Coated paper was obtained in the same manner as in Example 20, except that the following changes were made.

[0053] (Evaluation method) The coated paper obtained was evaluated as follows. The results are shown in Tables 1 and 2. (1) Coating defects The surface of the coating layer was observed using a scanning electron microscope, and the area within a 1 mm square (area 1 mm) was measured. 2 The presence or absence of coating defects such as cracks and pinholes was checked. Coating defects were evaluated according to the following criteria. [Evaluation Criteria] ○: No coating defects. ×: There is a coating defect.

[0054] (2) Adhesion to paper substrate A 25mm wide piece of cellophane tape was applied to the surface of the coating layer, and a 130mm wide, 1.8kg rubber roller was moved back and forth five times using its own weight to ensure the cellophane tape adhered tightly to the surface of the coating layer. Immediately afterward, the cellophane tape was quickly peeled off, and the ratio of the area where the coating layer adhered to the cellophane tape and peeled away from the surface of the paper substrate (area of ​​interfacial failure), or the ratio of the area where part of the paper substrate adhered to the cellophane tape along with the coating layer and the paper substrate was damaged (area of ​​internal paper substrate failure), was calculated. The adhesion to the paper substrate was evaluated according to the following criteria. An evaluation of ◎〇△ indicates no practical problems. If the evaluation differed between the ratio of the area where the coating layer peeled off and the ratio of the area where the paper substrate was damaged, the more stringent evaluation was adopted. [Evaluation Criteria] ◎: The percentage of the area where the coating layer has peeled off is less than 5%. Alternatively, the area where the paper substrate is destroyed is 95% or more. ○: The percentage of the area where the coating layer has peeled off is 5% or more but less than 10%. Alternatively, the area in which the paper substrate is damaged is between 90% and 95%. △: The percentage of the area where the coating layer has peeled off is 10% or more but less than 30%. Alternatively, the percentage of the paper substrate that has been damaged is between 70% and 90%. ×: The area where the coating layer has peeled off is 30% or more. Alternatively, the percentage of the paper substrate that was damaged was less than 70%.

[0055] (3) Heat seal suitability Two 100mm square test pieces were cut from the obtained coated paper, and the coated layers were brought into contact with each other. The test was then conducted at a pressurized temperature of 160°C and a pressurized pressure of 2 kgf / cm². 2 It was heat-sealed after a pressurizing time of 1 second. The heat-sealed test specimens were peeled off by hand, and the peeled area was visually observed to evaluate the heat-sealability according to the following criteria. A rating of ○ or △ indicates no practical problems. [Evaluation Criteria] ○: Peeling occurs within the paper substrate (the paper substrate is destroyed). △: Most of the material peels off within the paper substrate (the paper substrate is damaged). ×: Peeling occurs between coating layers.

[0056] (4) Water resistance In accordance with JIS P 8140:1998, "Paper and cardboard - Water absorption test method - Cobb method," the water absorption (Cobb value) was measured at two arbitrary points on the surface of the coated layer with a contact time of 120 seconds. The average of the water absorption values ​​(Cobb values) measured at two points was used as the water resistance value, and water resistance was evaluated according to the following criteria. A rating of ◎〇△ indicates that there are no practical problems. [Evaluation Criteria] ◎: Average water absorption (Cobb value) is 5g / m 2 below. ○: Average water absorption (Cobb value) is 5g / m 2 Over 10g / m 2 below. △: Average water absorption (Cobb value) is 10g / m 2 Over 20g / m 2 below. ×: The average water absorption rate (Cobb value) is 20g / m 2 It exceeds.

[0057] (5) Oil resistance In accordance with the "Paper and cardboard - Oil repellency test method - Kit method" specified in JAPAN TAPPI No. 41:2000, the kit number was measured at five arbitrary points on the surface of the coating layer. The average value of the five measured kit numbers was used as the oil resistance value, and water resistance was evaluated according to the following criteria. A rating of ○ or △ indicates that there are no practical problems. [Evaluation Criteria] ○: The average number of kit numbers is 12. △: The average kit number is between 10 and 12. ×: The average number of kits is less than 10.

[0058] [Table 1]

[0059] [Table 2]

[0060] The coated papers of Examples 1 to 33 of the present invention were free of coating defects in the coating layer and were able to exhibit performance derived from the PHBH contained in the coating layer. From Examples 9 and 20 to 25, it was observed that when the paper substrate became smoother (the value of the Wang Ken smoothness scale increased), the adhesion between the paper substrate and the coating layer tended to decrease. However, by increasing the ratio of adhesive in the coating layer, the adhesion to the paper substrate could be improved. In Comparative Example 1, where the coating layer did not contain adhesive, the coated paper showed coating defects in the coating layer and poor adhesion between the coating layer and the paper substrate. In Comparative Examples 2 and 3, the coated papers obtained in the coating layer containing a large amount of adhesive had a coating layer free of coating defects, but they were unable to fully exhibit the performance derived from PHBH.< / phbh>

Claims

1. Coated paper having a coating layer containing poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and an adhesive on at least one surface of a paper substrate, The weight ratio of the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) in the coating layer to the solid content of the adhesive is 99.9 / 0.1 to 60.0 / 40.

0. The basis weight of the aforementioned paper substrate, measured in accordance with JIS P 8124, is 150 g / m². ２ More than 600g / m ２ The following: Coated paper characterized in that the coating amount (dry weight) of the coating layer is 1.0 g / m² or more and 50.0 g / m² or less per side.

2. The coating amount (dry weight) of the aforementioned coating layer is 9.0 g / m² per side. ２ 50.0g / m or more ２ The coated paper according to claim 1, characterized in that it is as follows.

3. The coated paper according to claim 1 or 2, characterized in that the weight ratio of the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) in the coating layer to the adhesive is 90.0 / 10.0 to 75.0 / 25.

0.

4. The coated paper according to any one of claims 1 to 3, characterized in that the paper substrate has a coating layer containing poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and an adhesive on both sides.

5. The coated paper according to any one of claims 1 to 4, further comprising a sealing layer between the paper substrate and the coating layer.

6. The coating amount (dry weight) of the aforementioned sealing layer is 3.0 g / m² per side. ２ 15.0g / m or more ２ The coated paper according to claim 5, characterized in that it is as follows.

7. The coated paper according to any one of claims 1 to 6, characterized in that the paper substrate has a Wangyan smoothness of 55 seconds or less in its state before coating.

8. The coated paper according to any one of claims 1 to 7, characterized in that the adhesive contains at least one selected from the group consisting of polyvinyl alcohols, starches, cellulose derivatives, partially saponified ethylene-vinyl acetate copolymers, styrene-butadiene copolymer latex, methyl methacrylate-butadiene copolymer conjugated diene polymer latex, and acrylic polymer latex.

9. The coated paper according to claim 8, characterized in that the adhesive comprises at least one selected from fully saponified polyvinyl alcohol and partially saponified polyvinyl alcohol.

10. The coated paper according to claim 8, characterized in that the adhesive contains a partially saponified ethylene-vinyl acetate copolymer.

11. The coated paper according to any one of claims 1 to 10, characterized in that the coating layer is a heat-seal layer.

12. The coated paper according to any one of claims 1 to 10, characterized in that the coating layer is a water-resistant layer.

13. The coated paper according to any one of claims 1 to 10, characterized in that the coating layer is an oil-resistant layer.

14. Coated paper according to any one of claims 1 to 13, characterized in that it is for use with paper cups.

15. Coated paper according to any one of claims 1 to 13, characterized in that it is for use in paper containers.

16. Coated paper according to any one of claims 1 to 13, characterized in that it is for use in paper boxes.

17. Coated paper according to any one of claims 1 to 13, characterized in that it is for use with paper plates.

18. Coated paper according to any one of claims 1 to 13, characterized in that it is for use as a paper tray.

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