Biodegradable resin aqueous dispersion and method for producing the same, and food packaging paper using the biodegradable resin aqueous dispersion

Abstract

The present invention provides a biodegradable resin aqueous dispersion having stable dispersibility, without reducing biodegradability, and capable of improving heat sealability of paper products and the like, and a method for producing the same. The biodegradable resin aqueous dispersion of the present invention is a biodegradable resin aqueous dispersion containing a biodegradable resin and an anionic compound, wherein the anionic compound has a pH of 7 or more in a 1 mass % aqueous solution.

Description

Technical Field

[0001] The present invention relates to a biodegradable resin aqueous dispersion, a method for producing the same, and food packaging paper using the biodegradable resin aqueous dispersion. Background Art

[0002] Food packaging papers having oil resistance and heat sealability are known from prior literature. Specifically, in conventional food packaging papers, for example, oil resistance and heat sealability are imparted to the paper by lamination using polypropylene (PP) or polyethylene (PE).

[0003] On the other hand, in recent years, with the rise of environmental awareness and the problem of marine plastic waste, the demand for plastic alternatives has been increasing. Among them, there is a demand for alternatives in food packaging applications where plastics are used in large proportions, and even in food packaging paper, biodegradable materials that can replace PP and PE are being developed.

[0004] For example, as a biodegradable material, a biodegradable resin aqueous dispersion has been proposed (for example, Patent Documents 1 to 5). In these biodegradable resin aqueous dispersions, an anionic compound having a better electrostatic interaction is used as a dispersant.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 10-101911

[0008] Patent Document 2: Japanese Patent Application Publication No. 2004-035811

[0009] Patent Document 3: Japanese Patent Application Publication No. 2004-168927

[0010] Patent Document 4: Japanese Patent Application Publication No. 2004-323640

[0011] Patent document 5: International Publication No. 2016 / 080530. Summary of the invention

[0012] Problems to be solved by the invention

[0013] However, if an anionic compound in a suitable pH range is not used in the water-based dispersion of the biodegradable resin, the dispersibility of the biodegradable resin deteriorates and the particle size of the biodegradable resin does not decrease. Therefore, when applied to paper products, it is difficult to ensure sufficient heat-sealing properties. In addition, in the conventional water-based dispersion of the biodegradable resin such as Patent Documents 1 to 5, since the pH range of the anionic compound is not taken into consideration and an anionic compound in an inappropriate pH range is used, it is difficult to obtain a stable dispersion, and there is still room for improvement in terms of heat-sealing properties.

[0014] Furthermore, in order to use the biodegradable resin aqueous dispersion for food packaging, it must be a substance that meets the criteria for food, additives, etc. based on the Food Sanitation Law, or is registered in the FDA (U.S. Food and Drug Administration)'s use permission list. Therefore, when developing a new biodegradable resin aqueous dispersion for food packaging, it is also necessary to consider that there will be restrictions on the materials that can be used.

[0015] The present invention is proposed in view of the above situation, and its subject is to provide a biodegradable resin aqueous dispersion having stable dispersibility, not reducing biodegradability, and capable of improving the heat-sealing properties of paper products, etc., and a method for producing the same. In addition, the present invention also provides a food packaging paper having biodegradability and excellent heat-sealing properties.

[0016] Technical solutions to problems

[0017] In order to solve the above problems, the biodegradable resin aqueous dispersion of the present invention is characterized in that:

[0018] The invention is a biodegradable resin aqueous dispersion containing a biodegradable resin and an anionic compound, wherein the anionic compound has a pH of 7 or more in a 1 mass % aqueous solution.

[0019] In the aqueous biodegradable resin dispersion, the anionic compound is preferably at least one selected from a fatty acid salt having 12 to 16 carbon atoms, sodium tetradecene sulfonate, sodium polyphosphate, sodium carboxymethylcellulose, sodium alkylbenzene sulfonate and sodium polyacrylate.

[0020] In the aqueous biodegradable resin dispersion, the anionic compound is preferably at least one selected from a fatty acid salt having 12 to 16 carbon atoms in the fatty acid, sodium tetradecene sulfonate, sodium polyphosphate, sodium carboxymethylcellulose and sodium polyacrylate.

[0021] In the biodegradable resin aqueous dispersion, the anionic compound is preferably at least one selected from the group consisting of a fatty acid salt having 12 to 16 carbon atoms in the fatty acid, sodium tetradecene sulfonate, and sodium polyacrylate.

[0022] In the biodegradable resin aqueous dispersion, the anionic compound is preferably at least one selected from a fatty acid salt having 12 to 16 carbon atoms in a fatty acid and sodium polyacrylate.

[0023] In the biodegradable resin aqueous dispersion, the anionic compound preferably has a weight average molecular weight of 10,000 to 20,000,000.

[0024] In the biodegradable resin aqueous dispersion, it is preferred that:

[0025] The invention comprises: polyvinyl alcohol having a saponification degree of 70 to 90% as a dispersion stabilizer; and at least one selected from guar gum, gum arabic and xanthan gum as a viscosity modifier.

[0026] The mass ratio (A / B) of the polyvinyl alcohol (B) to the anionic compound (A) is in the range of 1 / 2 to 1 / 99,

[0027] The viscosity modifier is added in an amount of 0.05 to 1.0% by mass relative to the biodegradable resin.

[0028] In the biodegradable resin aqueous dispersion, the biodegradable resin is polylactic acid.

[0029] The food packaging paper of the present invention is characterized by using the above-mentioned biodegradable resin aqueous dispersion.

[0030] The method for producing an aqueous biodegradable resin dispersion of the present invention is characterized in that:

[0031] The production method is a method for producing a biodegradable resin aqueous dispersion containing a biodegradable resin and an anionic compound.

[0032] The production method includes a dispersing step of dispersing at least the dissolved biodegradable resin and the anionic compound in a solvent to obtain a dispersion.

[0033] The anionic compound has a pH of 7 or more in a 1 mass % aqueous solution,

[0034] The pH of the dispersion in the dispersing step is 4-9.

[0035] The biodegradable resin aqueous dispersion of the present invention can be obtained by the above-mentioned production method.

[0036] Effects of the Invention

[0037] The biodegradable resin dispersion of the present invention has stable dispersibility, does not reduce biodegradability, and can improve the heat sealability of fiber products or paper products. The method for producing the biodegradable resin dispersion of the present invention can reliably obtain the biodegradable resin dispersion. The food packaging paper of the present invention has biodegradability and excellent heat sealability. DETAILED DESCRIPTION

[0038] Hereinafter, one embodiment of the biodegradable resin aqueous dispersion and its production method, and food packaging paper of the present invention will be described.

[0039] The biodegradable resin aqueous dispersion of the present invention (hereinafter sometimes referred to as “aqueous dispersion”) contains a biodegradable resin and an anionic compound (dispersant).

[0040] The method for producing an aqueous biodegradable resin dispersion of the present invention includes a dispersing step of dispersing at least a dissolved biodegradable resin and an anionic compound in a solvent to obtain a dispersion.

[0041] There is no particular limitation on biodegradable resins, and examples thereof include copolymers of polylactic acid, lactic acid and other hydroxycarboxylic acids; dibasic acid polyesters such as polybutylene succinate, polybutylene succinate-adipate, polyethylene succinate, and polybutylene adipate; polycaprolactone, copolymers of caprolactone and other hydroxycarboxylic acids; polyhydroxybutyrate, copolymers of polyhydroxybutyrate and other hydroxycarboxylic acids; polyhydroxybutyric acid, copolymers of polyhydroxybutyric acid and other hydroxycarboxylic acids, etc. They can be used alone or two or more can be mixed and used. Among them, from the viewpoints of heat resistance, water resistance, solvent resistance, gloss, etc. of the resin, the biodegradable resin is preferably a copolymer of polylactic acid, lactic acid and other hydroxycarboxylic acids; polybutylene succinate, polybutylene succinate-adipate; polycaprolactone, and more preferably polylactic acid.

[0042] The D-lactic acid content of the polylactic acid is preferably 1 to 30 mol %, more preferably 5 to 20 mol %.

[0043] The number average molecular weight of the biodegradable resin is preferably in the range of 5,000 to 1,000,000, more preferably in the range of 10,000 to 300,000.

[0044] Regarding the copolymer of lactic acid and other hydroxycarboxylic acids, other hydroxycarboxylic acids include glycolic acid, 2-hydroxybutyric acid, 2-hydroxyvaleric acid, 2-hydroxyhexanoic acid, 2-hydroxyheptanoic acid, 2-hydroxyoctanoic acid, 2-hydroxy-2-methylpropionic acid, 2-hydroxy-2-methylbutyric acid, 2-hydroxy-2-ethylbutyric acid, 2-hydroxy-2-methylvaleric acid, 2-hydroxy-2-ethylvaleric acid, 2-hydroxy-2-propylvaleric acid, 2-hydroxy-2-butyl ...methylpropionic acid, 2-hydroxy-2-methylbutyric acid, 2-hydroxy-2-ethylbutyric acid, 2-hydroxy-2-methylvaleric acid, 2-hydroxy-2-ethylvaleric acid, 2-hydroxy-2-propylvaleric acid, 2-hydroxy-2-butylvaleric acid, 2-hydroxy-2-propylvaleric acid, 2-hydroxy-2-butylvaleric acid, 2-hydroxy-2-propylvaleric acid, 2-hydroxy-2-butylvaleric acid, 2-hydroxy-2-methylpropionic acid, 2-hydroxy-2-methylbutyric acid, 2-hydroxy-2-ethylbutyric acid, 2-hydroxy-2-methylvaleric acid, 2-hydroxy-2-ethylvaleric acid, 2-hydroxy-2-propylvaleric acid, 2-hydroxy-2- Hydroxy-2-methylhexanoic acid, 2-hydroxy-2-ethylhexanoic acid, 2-hydroxy-2-propylhexanoic acid, 2-hydroxy-2-butylhexanoic acid, 2-hydroxy-2-pentylhexanoic acid, 2-hydroxy-2-methylheptanoic acid, 2-hydroxy-2-ethylheptanoic acid, 2-hydroxy-2-propylheptanoic acid, 2-hydroxy-2-butylheptanoic acid, 2-hydroxy-2-methyloctanoic acid, 3-hydroxypropionic acid, 4-hydroxybutyric acid, 5-hydroxypentanoic acid, 6-hydroxyhexanoic acid, 7-hydroxyheptanoic acid and the like.

[0045] Lactic acid and hydroxycarboxylic acid may be in the form of D-form, L-form, D / L-form or the like, but may be in any form without limitation.

[0046] The pH of the anionic compound in a 1% by mass aqueous solution is 7 or more. Specifically, the pH of the anionic compound in a 1% by mass aqueous solution is preferably 7 to 11, more preferably 8 to 10, and further preferably 9 to 10. If an anionic compound that satisfies this range is selected, the electromotive force can easily become an appropriate value by appropriately adjusting the pH of the dispersion in the dispersion process, and as a result, the dispersion stability can be further improved. Therefore, the water resistance and heat sealing properties of paper products obtained using the biodegradable resin aqueous dispersion can be improved. On the other hand, if the pH of the 1% by mass aqueous solution of the anionic compound is less than 7, the electromotive force deviates from the range of the appropriate value, resulting in a weakened repulsive force between the particles and agglomeration, and the stability of the dispersion is reduced.

[0047] The anionic compound is not particularly limited, and examples thereof include fatty acid salts having 12 to 16 carbon atoms in the fatty acid, sodium tetradecene sulfonate, sodium polyphosphate, sodium carboxymethyl cellulose, sodium alkylbenzene sulfonate, sodium polyacrylate, etc. Among them, sodium tetradecene sulfonate, sodium polyphosphate, sodium carboxymethyl cellulose, sodium alkylbenzene sulfonate, and sodium polyacrylate are preferred from the viewpoint of excellent dispersion stability, and sodium polyacrylate is more preferred.

[0048] From the viewpoint of improving the heat sealability of paper products etc. obtained by using the aqueous dispersion of the biodegradable resin, at least one selected from a fatty acid salt having 12 to 16 carbon atoms in the fatty acid, sodium tetradecene sulfonate, sodium polyphosphate, sodium carboxymethyl cellulose, and sodium polyacrylate is preferred, at least one selected from a fatty acid salt having 12 to 16 carbon atoms in the fatty acid, sodium tetradecene sulfonate, and sodium polyacrylate is more preferred, and at least one selected from a fatty acid salt having 12 to 16 carbon atoms in the fatty acid and sodium polyacrylate is further preferred.

[0049] The weight average molecular weight of the anionic compound can be exemplified as a range of 1 to 25 million, but from the viewpoint of dispersion stability and thickening inhibition of the biodegradable resin aqueous dispersion, it is preferably 10,000 to 20 million, and more preferably 100,000 to 10 million. It should be noted that the weight average molecular weight can be obtained by, for example, gel permeation chromatography (GPC) by comparing the molecular weight with a known standard substance.

[0050] The content of the anionic compound is preferably 0.01 to 5.0% by mass, more preferably 0.01 to 2.0% by mass, further preferably 0.01 to 1.0% by mass, and particularly preferably 0.01 to 0.8% by mass relative to the content of the biodegradable resin. If the content of the anionic compound is 0.01% by mass or more, the effects such as dispersion stability can be further improved, and if the content of the anionic compound is 5.0% by mass or less, the stable viscosity control of the aqueous dispersion becomes easy, and the water resistance and heat sealing properties of paper products etc. obtained using the aqueous dispersion of the biodegradable resin can also be improved.

[0051] If necessary, a surfactant, a plasticizer, a viscosity modifier, etc. other than the above-mentioned anionic compound may be added to the biodegradable resin aqueous dispersion.

[0052] Examples of the surfactant other than the anionic compound include anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants, and polymer surfactants.

[0053] The anionic surfactant is not particularly limited, and examples thereof include fatty acid salts, higher alcohol sulfate ester salts, liquid fatty oil sulfate ester salts, sulfates of aliphatic amines and aliphatic amides, fatty alcohol phosphate ester salts, alkylbenzene sulfonates, aliphatic amide sulfonates, and sulfonates of dibasic fatty acid esters.

[0054] Examples of the cationic surfactant include alkylamine salts, quaternary ammonium salts, alkylpyridinium salts, fatty acid triethanolamine monoester salts, and alkylpolyoxyethyleneamine.

[0055] Examples of the nonionic surfactant include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters, and polyoxyethylene sorbitan alkyl esters.

[0056] As the macromolecular surfactant, anionic macromolecules, cationic macromolecules, nonionic macromolecules, amphoteric macromolecules etc. can be listed. These macromolecular surfactants can be water-soluble, for example, polyacrylate, polymethacrylate, polyacrylamide, acrylic acid-methacrylic acid alkyl ester copolymer, acrylate-acrylamide copolymer, methacrylate-acrylamide copolymer, diisobutylene-maleic acid copolymer, alkyl vinyl ether-maleic acid copolymer, maleated polybutene, maleated polybutadiene, polymethyl vinyl ether, polyvinyl pyrrolidone, polystyrene sulfonate, cationized cellulose, carboxymethyl cellulose, alginate, polyvinyl alcohol etc. can be listed. Among them, from the viewpoint of safety and supply surface, nonionic macromolecules are preferably used.

[0057] The biodegradable resin aqueous dispersion preferably contains polyvinyl alcohol as a nonionic polymer as a dispersion stabilizer. The polyvinyl alcohol preferably has a saponification degree of 70 to 90% and a number average molecular weight of 50,000 to 300,000. The saponification degree of the polyvinyl alcohol can be calculated from the hydroxyl value of the polyvinyl alcohol. By adding the polyvinyl alcohol, the biodegradable resin particles can be stably dispersed in the solvent.

[0058] The mass ratio (A / B) of (A) anionic compound (dispersant) to (B) polyvinyl alcohol (dispersion stabilizer) is preferably in the range of 1 / 2 to 1 / 99, more preferably in the range of 1 / 5 to 1 / 99, and further preferably in the range of 1 / 10 to 1 / 99. When the mass ratio (A / B) is in this range, dispersion becomes easy and the stability after dispersion is improved, so that the water resistance and heat sealability of paper products etc. obtained using the biodegradable resin aqueous dispersion can be improved.

[0059] In addition, the total mass of (A) anionic compound (dispersant) and (B) polyvinyl alcohol (dispersion stabilizer) is preferably in the range of 0.1 to 20 mass %, more preferably in the range of 0.5 to 20 mass %, and further preferably in the range of 1 to 20 mass % relative to the mass of the biodegradable resin. If the total mass of (A) anionic compound and (B) polyvinyl alcohol is 0.1 mass % or more, uniform stirring / dispersion becomes easy, and if the total mass of (A) anionic compound and (B) polyvinyl alcohol is 20 mass % or less, the inefficiency caused by excessive addition of dispersant can be reduced, and the influence on water resistance can be reduced.

[0060] Moreover, the mass ratio of the total mass of (A) anionic compound (dispersant), (B) polyvinyl alcohol (dispersion stabilizer) and biodegradable resin to water is preferably in the range of 2 / 8 to 6 / 4. When the mass ratio is 2 / 8 or more, it is effective because the content of biodegradable resin is high. When the mass ratio is 6 / 4 or less, it becomes easy to stir and disperse uniformly, and the stability of the aqueous dispersion is also improved. Therefore, the water resistance and heat sealing properties of paper products etc. obtained using the aqueous dispersion of biodegradable resin can be improved.

[0061] Examples of the plasticizer include citric acid derivatives such as triethyl citrate, tributyl citrate, acetylcitrate triethyl, and acetylcitrate tributyl; ether ester derivatives such as diethylene glycol diacetate, triethylene glycol diacetate, and triethylene glycol dipropionate; glycerol derivatives such as triacetin, tripropionin, and tributyrin; phthalic acid derivatives such as ethyl phthalyl ethyl glycolate, ethyl phthalylbutyl glycolate, and butyl phthalyl butyl glycolate; adipic acid derivatives such as a mixed ester of adipic acid, 2-(2-ethoxymethoxy)ethanol, and benzyl alcohol; adipic acid derivatives such as a condensate of adipic acid and 1,4-butanediol; polyhydroxycarboxylic acids such as polycaprolactone and polypropiolactone, etc. Among them, adipic acid derivatives and phthalic acid derivatives are particularly preferably used from the viewpoint of a good film-forming property improvement effect. The amount of the plasticizer added is preferably 5 to 40 parts by weight per 100 parts by weight of the biodegradable resin. If the amount of the plasticizer added is 5 parts by weight or more, the plasticizing effect can be further exerted, and if the amount of the plasticizer added is 40 parts by weight or less, the occurrence of plasticizer bleeding can be suppressed.

[0062] As viscosity modifiers, cellulose derivatives such as methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, etc.; starch derivatives such as cationized starch and etherified starch; plant gums such as gum arabic, guar gum, and xanthan gum; animal polymers such as casein, chitosan, and chitin, etc. can be listed. Among them, guar gum, gum arabic, and xanthan gum are preferred. The amount of viscosity modifier added is preferably 0.05 to 1.0% by mass relative to the biodegradable resin. If the amount of viscosity modifier added is 0.05% by mass or more, the viscosity adjustment effect can be improved. If the amount of viscosity modifier added is 1.0% by mass or less, the control of the stable viscosity of the aqueous dispersion becomes easy.

[0063] In a preferred embodiment, the biodegradable resin aqueous dispersion contains: polyvinyl alcohol having a saponification degree of 70 to 90% as a dispersion stabilizer; and at least one selected from guar gum, gum arabic, and xanthan gum as a viscosity modifier, the mass ratio (A / B) of the polyvinyl alcohol (B) to the anionic compound (A) is in the range of 1 / 2 to 1 / 99, and the amount of the viscosity modifier added is 0.05 to 1.0% by mass relative to the biodegradable resin. Preferred examples of the polyvinyl alcohol (B) are as described above.

[0064] The viscosity of the aqueous dispersion of the biodegradable resin is preferably within the range of 0.1 to 10 Pa·s, that is, preferably above 0.1 Pa·s and below 10 Pa·s. For example, when the viscosity of the aqueous dispersion of the biodegradable resin is lower than 0.1 Pa·s, it is difficult to maintain a good dispersion state due to phase separation, inhomogenization or sedimentation of the resin particles, and it may be necessary to use a dispersion device such as a homogenizer or a high-pressure emulsifier to stir vigorously. During this intense stirring, due to the application of strong shear force, the dispersant molecules adsorbed on the dispersed particles are peeled off, resulting in an increase in particle size distribution and the dispersion itself may become difficult. On the other hand, if the viscosity of the aqueous dispersion of the biodegradable resin exceeds 10 Pa·s, the solution viscosity is too high, so it may not be possible to disperse well.

[0065] It should be noted that, in order to improve surface smoothness, water repellency, demoulding properties, etc., the biodegradable resin aqueous dispersion of the present invention may also contain waxes such as natural waxes and synthetic waxes. As natural waxes, for example, plant-based natural waxes such as candelilla wax, carnauba wax, rice bran wax, wood wax, and jojoba solid wax; animal-based natural waxes such as beeswax, lanolin, and spermaceti; mineral-based natural waxes such as montan wax, ozokerite, and ceresin; petroleum-based natural waxes such as paraffin, microcrystalline wax, and petrolatum wax, etc. In addition, as synthetic waxes, synthetic hydrocarbons such as Fischer-Tropsch wax and polyethylene wax; modified waxes such as montan wax derivatives, paraffin derivatives, and microcrystalline wax derivatives; hydrogenated waxes such as solidified castor oil and solidified castor oil derivatives; 12-hydroxystearic acid, stearic acid amide, phthalic anhydride imide, etc. can be listed.

[0066] The biodegradable resin contained in the biodegradable resin aqueous dispersion is in the form of particles, and the average particle size of the particles is preferably in the range of 0.1 to 500 μm, more preferably in the range of 0.5 to 50 μm, and further preferably in the range of 0.5 to 10 μm.

[0067] Next, one embodiment of the method for producing the biodegradable resin aqueous dispersion of the present invention will be described.

[0068] The method for producing an aqueous biodegradable resin dispersion of the present invention comprises a dispersing step of dispersing at least a dissolved biodegradable resin and an anionic compound in a solvent to obtain a dispersion.

[0069] As described above, the pH of the anionic compound in a 1 mass % aqueous solution is 7 or more.

[0070] The dispersion in the dispersing step can be obtained by, for example, simultaneously mixing and stirring a solvent, a biodegradable resin, an anionic compound, and, if necessary, other materials.

[0071] Specifically, the first method includes, for example, a pressure dispersion method in which a biodegradable resin, anionic compound, polyvinyl alcohol, viscosity modifier and water are simultaneously added to a closed tank equipped with a stirring device, and the biodegradable resin is dispersed by applying pressure while heating and stirring.

[0072] Second, there can be exemplified a direct dispersion method in which a melt containing a biodegradable resin, an anionic compound, and, if necessary, polyvinyl alcohol and a viscosity modifier is added to hot water maintained under pressure and stirred to disperse the melt.

[0073] Thirdly, a phase inversion method can be exemplified in which a biodegradable resin is heated and melted, and an aqueous solution containing an anionic compound, and optionally polyvinyl alcohol and a viscosity modifier is added thereto and stirred to disperse the biodegradable resin in water.

[0074] Fourthly, there can be exemplified a method in which an organic solvent, water, a biodegradable resin, an anionic compound, and, if necessary, polyvinyl alcohol and a viscosity modifier are added, stirred and dispersed, and then the organic solvent is removed.

[0075] Fifthly, there can be exemplified a method in which an aqueous solution containing an anionic compound, and optionally polyvinyl alcohol and a viscosity modifier is added to an organic solvent solution of a biodegradable resin, stirred and dispersed, and then the organic solvent is removed.

[0076] Any method other than the first to fifth methods may be appropriately adopted as long as it is a method capable of obtaining an aqueous dispersion of a biodegradable resin.

[0077] More specifically, with regard to the point that it is applicable to a wide variety of biodegradable resins, considering the hydrolysis etc., as a method for obtaining a dispersion liquid, for example, a method is preferably a method in which an organic solvent, water, a biodegradable resin, an anionic compound, polyvinyl alcohol as required, and a viscosity modifier are added to a closed tank equipped with a stirring device, the temperature is raised while stirring, the solid raw material is dissolved and dispersed, the mixture is cooled, and then the organic solvent is removed under reduced pressure.

[0078] In addition, as a method for obtaining a dispersion liquid, a preferred method is to add an organic solvent and a biodegradable resin into a closed tank equipped with a stirring device, stir and heat them to form a dissolved biodegradable resin solution, add water, anionic compounds, polyvinyl alcohol as needed, and an aqueous solution of a viscosity modifier dissolved in another stirring tank to the closed tank and stir, disperse them while heating to a temperature above the resin dissolution temperature, cool them, and then remove the organic solvent under reduced pressure.

[0079] In these methods, the organic solvent includes ester organic solvents such as formate esters such as methyl formate, ethyl formate, propyl formate, and butyl formate; acetate esters such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; chlorine organic solvents such as chloroform and carbon tetrachloride; aromatic hydrocarbons such as benzene, toluene, and xylene, etc., preferably ester organic solvents with good resin solubility, and particularly preferably formate esters and acetates.

[0080] In the method for producing a biodegradable resin aqueous dispersion of the present invention, the pH of the dispersion in the dispersion step is 4 to 9, preferably 4 to 6. By making the pH within this range, the zeta potential is easily formed to an appropriate value, the polymer particles can repel each other appropriately, etc., and as a result, a biodegradable resin aqueous dispersion with stable dispersibility can be obtained. Specifically, the zeta potential of the biodegradable resin aqueous dispersion is preferably below -30 mV, more preferably below -40 mV. Basically, if the zeta potential is below these values, the stability over time will become better. There is no particular limitation on the lower limit of the zeta potential, but in normal preparation, for example, it is above -50 mV. In addition, it is preferred to remove the organic solvent after phase inversion emulsification so that the residual solvent amount is below 1000 ppm.

[0081] The biodegradable resin dispersion of the present invention has stable dispersibility and does not reduce biodegradability, so that when applied to fiber products or paper products, the heat sealability of the paper products can be improved. Therefore, it is very useful in various industrial applications and can be used practically.

[0082] There is no particular limitation on the use of the biodegradable resin dispersion of the present invention, and examples thereof include paper for food packaging. In addition, the biodegradable resin dispersion of the present invention can also be used, for example, as spacers for liquid crystal display devices, additives for toners; toners for electrophotographic development; rheology modifiers / additives for coatings, etc.; mechanical property modifiers for powder coating materials, automotive materials, building materials, etc.; mechanical property modifiers for films, papers, fibers, etc.; raw materials for resin molded bodies such as rapid prototyping and rapid manufacturing, materials for flash molding, paste resins for plastisols, powder plugging materials, and fluidity / smoothness improvers for powders; lubricants; rubber compounding agents; abrasives; thickeners ; filters and filter aids; gelling agents; coagulants; oil absorbents; release agents; slip improvers for plastic films / sheets; anti-adhesion agents; gloss regulators; rough surface finishing agents; light diffusers; surface hardness improvers; toughness improvers; chromatographic fillers; microcapsule additives; medical materials such as drug release systems / diagnostic agents; medical diagnostic test agents; retainers for fragrances / pesticides; catalysts and carriers for chemical reactions; gas adsorbents; ion exchange resins; sintered materials for ceramic processing; standard particles for measurement / analysis and particles for the food industry, etc.

[0083] The aqueous biodegradable resin dispersion and the method for producing the same, and the food packaging paper using the aqueous biodegradable resin dispersion of the present invention are not limited to the above-described embodiments.

[0084] Example

[0085] Hereinafter, the biodegradable resin aqueous dispersion and the like of the present invention will be described in detail together with Examples, but the present invention is not limited to the following Examples.

[0086] 1. Preparation of biodegradable resin dispersion

[0087] In the examples and comparative examples, the following substances were used as a biodegradable resin, an anionic compound having a pH of 7 or higher in a 1 mass % aqueous solution (dispersant (A)), or a surfactant other than the anionic compound (dispersant (A)), polyvinyl alcohol (dispersion stabilizer (B)), and a viscosity modifier.

[0088] (Biodegradable resin)

[0089] Biodegradable resin A: Polylactic acid

[0090] Biodegradable resin B: polybutylene succinate

[0091] Biodegradable resin C: polybutylene succinate-adipate

[0092] Biodegradable resin D: Polycaprolactone

[0093] (Anionic compound having a pH of 7 or more in a 1 mass % aqueous solution)

[0094] Anionic compound A: sodium polyacrylate (weight average molecular weight 500,000)

[0095] Anionic compound B: sodium polyacrylate (weight average molecular weight 3 million to 5 million)

[0096] Anionic compound C: Sodium fatty acid (C12, 14, 16)

[0097] Anionic polymer compound D: Sodium tetradecene sulfonate

[0098] Anionic compound E: Sodium polyphosphate

[0099] Anionic compound F: Sodium carboxymethyl cellulose

[0100] Anionic compound G: Sodium alkylbenzene sulfonate

[0101] [Surfactant other than the above anionic compound (anionic compound)]

[0102] Anionic compound H: polyacrylamide-sodium acrylate (weight average molecular weight 16 million to 17 million)

[0103] Anionic compound I: acrylamide-methacrylic acid copolymer (weight average molecular weight: 20 million)

[0104] Anionic compound J: methacrylic acid-acrylamide (weight average molecular weight: 4 million)

[0105] Anionic compound K: Sodium alginate

[0106] (Polyvinyl alcohol)

[0107] Polyvinyl alcohol A: saponification degree 80%, number average molecular weight 100,000

[0108] Polyvinyl alcohol B: saponification degree 99%, number average molecular weight 90,000

[0109] (Viscosity modifier)

[0110] Viscosity modifier A: xanthan gum (manufactured by DSP Gokyo Food & Chemical Co., Ltd., ECHO GUM)

[0111] Viscosity modifier B: guar gum (manufactured by San-Ei Gen FFI, Inc., VISTOP D20)

[0112] Viscosity modifier C: Gum Arabic (manufactured by Japan Sanei Pharmaceutical Trading Co., Ltd., Arabic KORU SS)

[0113] <Examples 1 to 15, Comparative Examples 1 to 4>

[0114] The components were charged into a closed dispersion tank at the component ratios shown in Tables 1 and 2, heated to 65° C. in the case of using biodegradable resins A, C, and D, and heated to 120° C. in the case of using biodegradable resin B, and dispersed for 1 hour by a dispersion method using a given stirring and dispersing device, and then rapidly cooled to 40° C. Then, ethyl acetate was removed under reduced pressure to obtain a biodegradable resin aqueous dispersion.

[0115] In addition, the viscosity and stability of the aqueous dispersion (after heating and dispersing during mixing and stirring and cooling) and the aqueous dispersion (after removing ethyl acetate) in the preparation of the aqueous dispersion of the biodegradable resin were measured and evaluated by the following method.

[0116] (pH)

[0117] The pH was measured at 25°C using a glass electrode hydrogen concentration meter, pH METER 9615S-10D, manufactured by Horiba, Ltd.

[0118] (Electrode potential (mV))

[0119] The zeta potential of each biodegradable resin aqueous dispersion diluted to 1% by solid content by adding water was measured using a Zetasizer Nano ZS measuring apparatus manufactured by Malvern Instruments Inc. The measurement was performed at 25°C.

[0120] (Average particle size (μm))

[0121] The average particle size of the particles was measured using a laser diffraction particle size distribution analyzer (manufactured by Shimadzu Corporation, SALD-2300 model, refractive index 1.45-0.00i).

[0122] (Centrifugal separation)

[0123] Centrifugal separation was performed at 3500 rpm for 20 minutes using a table centrifuge Model 4000 manufactured by KUBOTA. The separation status of the obtained samples was then evaluated according to the following four levels: ◎: separation less than 10%, ○: separation between 10% and less than 30%, △: separation between 30% and less than 50%, and ×: separation above 50%.

[0124] (Stability test: standing at 25°C)

[0125] Each biodegradable resin aqueous dispersion was added to a 100 ml glass container and stored in a thermostatic chamber at 25° C. The separation state after 14 days of storage was evaluated according to the following four levels: ◎: separation less than 10%, ○: separation between 10% and less than 30%, △: separation between 30% and less than 50%, and ×: 50% or more.

[0126] (Stability test: standing at 40°C)

[0127] Each biodegradable resin aqueous dispersion was added to a 100 ml glass container and stored in a thermostatic chamber at 40° C. The separation state after 14 days of storage was evaluated according to the following four levels: ◎: separation less than 10%, ○: separation between 10% and less than 30%, △: separation between 30% and less than 50%, and ×: more than 50%.

[0128] (Heat sealability: peel strength (N / m))

[0129] The aqueous dispersions of Examples 1 to 15 and Comparative Examples 1 to 4 were coated on kraft paper (basic weight 70 g / m2) cut into small pieces of 25 mm × 200 mm using a rod coater No. 20. 2 ) on a 25 mm × 150 mm portion and dried at 25°C and 40% RH for 24 hours. The two test pieces were sandwiched between iron plates so that the coated surfaces were bonded together and heated at 180°C and 300 g / cm 2 Under the condition of , the test piece was pressed for 3 minutes using a fully automatic transfer press HP-84 manufactured by Hashima Co., Ltd., Japan. After the obtained test piece was left to stand for 1 day, the peel strength (N / m) of each test piece was measured at a tensile speed of 10 mm / min using a tensile tester STROGRAPH E3 manufactured by Toyo Seiki Co., Ltd., Japan, in accordance with JIS K6854-3 standard.

[0130] (Water resistance test)

[0131] The aqueous dispersions of Examples 1 to 15 and Comparative Examples 1 to 4 were coated on kraft paper (weight 70 g / m2) cut into small pieces of 130 mm × 130 mm using a rod coater No. 20. 2 ) and dried at 25°C, 40% RH for 24 hours, and at 180°C, 300g / cm 2 Under the condition of , the test piece was obtained by pressing for 3 minutes using the fully automatic transfer press HP-84 manufactured by Hashima Co., Ltd. of Japan. The water resistance was evaluated according to the JIS-P-8140 standard, with the water absorption (g / m2 ) was judged.

[0132] Evaluation criteria: ◎: 0-5, ○: 5-10, △: 10-20, ×: 20 or more.

[0133] The results are shown in Tables 1A to 1C, Table 2, and Table 3, respectively.

[0134] [Table 1A]

[0135]

[0136] [Table 1B]

[0137]

[0138] [Table 1C]

[0139]

[0140] [Table 2]

[0141]

[0142] [Table 3]

[0143]

[0144] As shown in Table 1A and Table 1B, Examples 1 to 15, which were aqueous biodegradable resin dispersions containing an anionic compound having a pH of 7 or higher in a 1 mass % aqueous solution and in which the pH of the dispersion in the dispersion step was 4 or higher, were confirmed to have excellent stability and heat-sealing properties.

[0145] On the other hand, in Comparative Examples 1 to 4 in which the aqueous biodegradable resin dispersion contained an anionic compound having a pH of less than 7 in a 1 mass % aqueous solution and the pH of the dispersion in the dispersion step was less than 4, it was confirmed that the stability and heat sealing properties were insufficient.

[0146] As shown in Table 3, even in the biodegradable resin aqueous dispersion containing an anionic compound having a pH of 7 or more in a 1 mass % aqueous solution, the water resistance of kraft paper coated with the biodegradable resin aqueous dispersion containing sodium polyacrylate was confirmed to be improved.

Claims

1. A biodegradable resin aqueous dispersion, characterized in that: It is a biodegradable resin aqueous dispersion containing a biodegradable resin and an anionic compound. The anionic compound has a pH of 7 or more in a 1 mass % aqueous solution, The anionic compound is sodium polyacrylate, The content of sodium polyacrylate as the anionic compound is 0.01 to 0.8% by mass relative to the content of the biodegradable resin. The biodegradable resin aqueous dispersion further contains polyvinyl alcohol, and a mass ratio of the sodium polyacrylate as the anionic compound to the polyvinyl alcohol is in a range of 1 / 5 to 1 / 99.

2. The biodegradable resin aqueous dispersion according to claim 1, characterized in that: The weight average molecular weight of the sodium polyacrylate is 10,000 to 20,000,000.

3. The biodegradable resin aqueous dispersion according to claim 1 or 2, characterized in that: The biodegradable resin is polylactic acid.

4. A food packaging paper, wherein: The biodegradable resin aqueous dispersion according to any one of claims 1 to 3 is used.

5. A method for producing a biodegradable resin aqueous dispersion, characterized in that: The production method is a method for producing an aqueous biodegradable resin dispersion according to any one of claims 1 to 3, The production method includes a dispersing step of dispersing at least the dissolved biodegradable resin and sodium polyacrylate as the anionic compound in a solvent to obtain a dispersion. The pH of the dispersion in the dispersing step is 4-9.

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