Classifications

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  • B32B29/00—Layered products comprising a layer of paper or cardboard
  • B32B29/002—Layered products comprising a layer of paper or cardboard as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B29/005—Layered products comprising a layer of paper or cardboard as the main or only constituent of a layer, which is next to another layer of the same or of a different material next to another layer of paper or cardboard layer
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  • B32B37/12—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by using adhesives
  • B32B37/1284—Application of adhesive
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  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/04—Interconnection of layers
  • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D65/00—Wrappers or flexible covers; Packaging materials of special type or form
  • B65D65/38—Packaging materials of special type or form
  • B65D65/40—Applications of laminates for particular packaging purposes
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  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/02—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques
  • C08J3/03—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in aqueous media
  • C08J3/05—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in aqueous media from solid polymers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/18—Manufacture of films or sheets
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
  • C08J7/04—Coating
  • C08J7/0427—Coating with only one layer of a composition containing a polymer binder
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
  • C08J7/04—Coating
  • C08J7/052—Forming heat-sealable coatings
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D129/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Coating compositions based on hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Coating compositions based on derivatives of such polymers
  • C09D129/02—Homopolymers or copolymers of unsaturated alcohols
  • C09D129/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D167/00—Coating compositions based on polyesters obtained by reactions forming a carboxylic ester link in the main chain; Coating compositions based on derivatives of such polymers
  • C09D167/04—Polyesters derived from hydroxycarboxylic acids, e.g. lactones
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J167/00—Adhesives based on polyesters obtained by reactions forming a carboxylic ester link in the main chain; Adhesives based on derivatives of such polymers
  • C09J167/04—Polyesters derived from hydroxycarboxylic acids, e.g. lactones
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J5/00—Adhesive processes in general; Adhesive processes not provided for elsewhere, e.g. relating to primers
  • C09J5/06—Adhesive processes in general; Adhesive processes not provided for elsewhere, e.g. relating to primers involving heating of the applied adhesive
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
  • B32B37/12—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by using adhesives
  • B32B2037/1276—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by using adhesives water-based adhesive
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B2255/00—Coating on the layer surface
  • B32B2255/12—Coating on the layer surface on paper layer
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2255/00—Coating on the layer surface
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• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2260/00—Layered product comprising an impregnated, embedded, or bonded layer wherein the layer comprises an impregnation, embedding, or binder material
  • B32B2260/02—Composition of the impregnated, bonded or embedded layer
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B2260/00—Layered product comprising an impregnated, embedded, or bonded layer wherein the layer comprises an impregnation, embedding, or binder material
  • B32B2260/04—Impregnation, embedding, or binder material
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/30—Properties of the layers or laminate having particular thermal properties
  • B32B2307/31—Heat sealable
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/70—Other properties
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B2309/00—Parameters for the laminating or treatment process; Apparatus details
  • B32B2309/02—Temperature
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B32B2317/00—Animal or vegetable based
  • B32B2317/12—Paper, e.g. cardboard
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
  • C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
  • C08G63/06—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from hydroxycarboxylic acids
  • C08G63/08—Lactones or lactides
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
  • C08J2367/04—Polyesters derived from hydroxy carboxylic acids, e.g. lactones
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2429/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
  • C08J2429/02—Homopolymers or copolymers of unsaturated alcohols
  • C08J2429/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J2401/00—Presence of cellulose
  • C09J2401/006—Presence of cellulose in the substrate
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J2429/00—Presence of polyvinyl alcohol
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J2467/00—Presence of polyester
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W90/00—Enabling technologies or technologies with a potential or indirect contribution to greenhouse gas [GHG] emissions mitigation
  • Y02W90/10—Bio-packaging, e.g. packing containers made from renewable resources or bio-plastics

Definitions

• the present invention relates to an improvement of an aqueous dispersion containing polylactic acid as a dispersoid.
• a laminate has been proposed in which a biodegradable polylactic acid film is laminated on a sheet (substrate) made of a cellulose material such as paper. By heat-sealing a pair of laminates such that the polylactic acid layers face each other, an excellent heat-sealing property can be provided between the two.
• a technique has been proposed in which an aqueous dispersion of polylactic acid is prepared, applied to the surface of a sheet, and then dried.
• Patent Document 1 An example of such an aqueous dispersion of polylactic acid is described in Patent Document 1.
• a polyvinyl alcohol-based resin is adopted as a dispersant, and its blending ratio to polylactic acid is a specific ratio (the blending ratio of polyvinyl alcohol-based resin to polylactic acid is 99/1 to 30/70 (mass )), the obtained aqueous dispersion of polylactic acid has excellent storage stability, and the film obtained by coating and drying the aqueous dispersion has excellent adhesiveness, film-forming properties and coatability to the substrate. has given to
• a heat-sealing property of 5.0 (N/15 mm) or more is required when thermocompression bonding is performed at 100°C.
• the laminate is required to have water resistance, for example, a Cobb water absorbency of 10 g/m 2 or less.
• the present inventors have made earnest studies to solve the above problems. As a result, it was found that high heat sealability can be obtained by adjusting the degree of saponification of polyvinyl alcohols and the compounding ratio (mass ratio) of polylactic acid and polyvinyl alcohols.
• the aqueous dispersion of the first aspect of the invention is defined as follows.
• a film containing polylactic acid in an amount of 3 g/m 2 (dry weight) or more relative to a substrate, and having a thermal compression bonding of 5.0 (N/15 mm) or more at 100°C (JIS Z 1707, Peeling speed: 300 mm/min) is an aqueous dispersion for forming a film having a heat-sealing property, including polylactic acid, polyvinyl alcohols and water,
• the polyvinyl alcohols have an average degree of saponification of 60.0 to 82.0 mol% and an average degree of polymerization of 200 to 700
• An aqueous dispersion, wherein the compounding ratio (mass ratio) of the polylactic acid and the polyvinyl alcohol is 98/2 to 90/10.
• An aqueous dispersion defined in this manner provides excellent heat sealability and water resistance.
• Polyvinyl alcohol is preferably used as the polyvinyl alcohol (second aspect).
• polyvinyl alcohol is a polymer having a basic skeleton of polyvinyl acetate obtained by polymerizing vinyl acetate.
• polyvinyl alcohol obtained by partially saponifying this polymer was used.
• Polyvinyl alcohols include, in addition to the above polyvinyl alcohol itself, monomers containing sulfonic acid groups, carboxyl groups, amino groups, etc. that can be copolymerized with vinyl acetate, and copolymers with monomers such as ethylene and butanediol. Partially saponified copolymers are used in this invention. Modified products obtained by modifying partially saponified polyvinyl alcohols and copolymers thereof are also included in polyvinyl alcohols. These polyvinyl alcohols function as dispersants for dispersing polylactic acid in water.
• the average degree of polymerization of polyvinyl alcohols is 240-600 (third aspect).
• the average degree of polymerization is 230 to 300 (fourth aspect).
• the average degree of polymerization is 240.
• the average degree of polymerization is 500 to 700 (fifth aspect).
• the average degree of polymerization is 600.
• the average degree of polymerization is 400 to 600 (sixth aspect).
• the average degree of polymerization is 500.
• the average degree of polymerization is 200 to 400 (seventh aspect). More preferably, the average degree of polymerization is 300. When a polyvinyl alcohol having a degree of saponification of 78.5 to 82.0 mol % is employed, the average degree of polymerization is 200 to 600 (eighth aspect). More preferably, the average degree of polymerization is 500.
• a ninth aspect of the present invention is a method for producing a laminate using the aqueous dispersion defined in the first to eighth aspects, which is defined as follows. Namely providing a defined aqueous dispersion in any of aspects 1-8; laminating the aqueous dispersion to the surface of a first substrate made of cellulosic material and to the surface of a second substrate; removing the water from the aqueous dispersion to form a first sealing layer on the surface of the first substrate and forming a second sealing layer on the surface of the second substrate; adhering the first sealing layer and the second sealing layer; A method of manufacturing a laminate comprising
• the first base material constituting the surface of the first base material is paper or nonwoven fabric made of biodegradable cellulose fibers
• the second base material constituting the surface of the second base material is also cellulose paper or nonwoven fabric.
• Non-woven fabric the first base material and the second base material may be continuous bodies or separate bodies.
• the first sealing layer and the second sealing layer may be made of aqueous dispersions of different components.
• the first sealing layer and the second sealing layer are heated. , pressure or vibration such as ultrasound. This allows the gluing step to be performed inexpensively.
• the first sealing layer and the second sealing layer are: A heating condition of 70 to 300° C. and a pressure condition of 0.1 to 1.0 MPa are added for 5 seconds or less. This stabilizes the adhesion between the first seal layer and the second seal layer.
• a twelfth aspect defines laminates obtained using the aqueous dispersions of the first to eighth aspects. That is, the twelfth aspect is defined as follows. a first substrate surface laminated with a first sealing layer formed from the specified water dispersion on any one of aspects 1 to 8; A laminate comprising a second substrate surface laminated with a second sealing layer formed from the specified aqueous dispersion on any one of aspects 1 to 8, The film thickness of the first sealing layer is 3 to 10 g/m 2 and the film thickness of the second sealing layer is 3 to 10 g/m 2 , and both are heat-sealed at 100° C. and 0.2 MPa for 1 second. A laminate having a heat seal strength of 5 N/15 mm or more and less than 10 N/15 mm (JIS Z 1707, peel speed: 300 mm/min, peel condition: 180 degree peel).
• the heat seal strength when the first seal layer and the second seal layer are heat-sealed at 120 ° C. and 0.2 MPa for 1 second is 6 N / 15 mm or more (JIS Z 1707 , test speed: 300 mm/min, peeling conditions: 180 degree peeling) (13th aspect).
• the Cobb water absorbency is set to 10.0 g/m 2 or less as water resistance (fourteenth aspect, fifteenth aspect).
• a sixteenth aspect of the present invention is defined as follows: Use of the aqueous dispersion defined in any one of the first to eighth aspects for the manufacture of a coating agent or binder.
• polylactic acid was selected as the biodegradable resin because it is industrially practically used and is inexpensive compared to other biodegradable resins and is preferable for food packaging.
• the mixing ratio of L-type and D-type polylactic acid is preferably 6:94 to 94:6. Excellent heat-sealability can be obtained within this range.
• Polylactic acid may be a homopolymer of lactic acid as a monomer, or a copolymer with other hydroxycarboxylic acids as long as the biodegradability is not impaired.
• a biodegradable resin other than polylactic acid can be blended as an auxiliary agent added for modifying the polylactic acid.
• biodegradable resins are materials that are completely consumed by microorganisms and produce only natural by-products. Examples of such biodegradable resins include the following.
• Polylactic acids such as copolymers of lactic acid and other hydroxycarboxylic acids, polycaprolactone (PCL), polycaprolactones such as copolymers of caprolactone and hydroxycarboxylic acids, polybutylene succinate (PBS), polybutylene Succinate adipate (PBSA), thermoplastic starch (TPE), polymerate (PMA), polybutylene adipate terephthalate (PBAT), polyethylene terephthalate succinate (PETS), polybutylene terephthalate succinate (PBTS), polyhydroxyalkanoic acids (PHA) , PHB, PHV and PHBH), polyethylene furanoate (PEF), polyglycolic acid (PGA) and the like.
• PBS polybutylene succinate
• PBSA polybutylene Succinate adipate
• TPE thermoplastic starch
• PMA polymerate
• PETS polyethylene terephthalate succinate
• PBTS polybutylene
• the amount of the biodegradable resin to be blended is appropriately selected according to the use of the aqueous dispersion, and can be, for example, 1.0 to 50.0% by mass relative to the polylactic acid.
• the polylactic acid film has excellent water resistance and oil resistance, and can be used as water-resistant paper and oil-resistant paper by laminating it on a paper substrate.
• food packaging materials are required to have high water resistance.
• the Cobb water absorbency is preferably 10 g/m 2 or less.
• any material can be selected for the base material. It is preferably made of material.
• substrates include paper, non-woven fabrics and cloths composed of biodegradable fibers such as cellulose, and biodegradable resin films.
• Polyvinyl alcohols are used as dispersants for dispersing polylactic acid in water, which is a dispersion medium.
• polyvinyl alcohol having a predetermined degree of saponification is used as the polyvinyl alcohol.
• Prior Patent Document 1 proposes polyvinyl alcohols having a degree of saponification of 84 mol % or less and an average degree of polymerization of 700 or less.
• the inventors of the present application have found that the use of polyvinyl alcohols with a degree of saponification of 60 to 82 mol % can ensure excellent heat sealability and water resistance.
• the configuration is as follows, as defined in the first aspect described above.
• the polyvinyl alcohols have an average saponification degree of 60.0 to 82.0 mol%
• aqueous dispersions of Examples and Comparative Examples were coated on one side using a bar coater so that the desired film thickness (dry mass, g/m 2 ) was obtained on a paper substrate (manufactured by Nippon Paper Industries Co., Ltd.: NPI fine quality).
• a heat seal layer was formed on the substrate sheet by processing and drying at 130° C. for 60 seconds.
• the film thickness (g/m 2 ) was calculated by weighing the paper substrate before and after coating.
• Various properties were measured or evaluated by the following methods.
• Heat seal strength evaluation The heat seal layers of the paper substrate were heat sealed with a heat sealer at different heat seal temperatures of 80, 90, 100, 110, and 120°C, and only the heat seal temperature was changed. A sample was made. The press pressure at the time of heat sealing was 0.2 MPa, and the press time was 1 second. The heat-seal strength was measured by a tensile tester according to JIS Z1707 at a tensile speed of 300 mm/min and the heat-seal strength (N/15 mm) when the peeling conditions were 180° peeling. The current market requires a heat seal strength of 5 N/15 mm or more. More preferably, a heat seal strength of 6 N/15 mm or more is required.
• the sealing temperature is more preferably 70 to 300°C, still more preferably 90 to 200°C, and most preferably 100 to 150°C.
• the method of sealing the pair of polylactic acid films is not limited to the above pressure heating (heat sealing). By increasing the heating conditions, it is also possible to omit pressurization and perform sealing. If the pressurization condition is increased, heating can be omitted and sealing can be performed. Furthermore, it is also possible to seal by ultrasonic vibration without heating or pressurization. Of course, any combination of heat, pressure and vibration can be used for sealing.
• Table 1 shows dispersions in the aqueous dispersions of Examples and Comparative Examples.
• the mixing ratio of water, which is the dispersion medium for the dispersion, to the dispersion is arbitrarily selected according to the required viscosity and the like.
• the properties of water itself (hardness, ion concentration, etc.) are also arbitrarily selected according to the use of the water dispersion.
• auxiliaries can be added to the water. Auxiliary agents will be described later.
• Aqueous dispersions of Examples and Comparative Examples were prepared by dispersing by a phase inversion emulsification method.
• the mixing ratio (mass ratio) of polylactic acid and polyvinyl alcohol is 98/2 to 90/10.
• polylactic acid may not be uniformly dispersed in water. If the blending ratio of polyvinyl alcohol exceeds 10% by mass, the heat seal strength and Cobb water absorbency may deteriorate.
• the heat-sealing property and water resistance are mainly borne by polylactic acid, so it is preferable to increase the proportion of polylactic acid. According to studies by the present inventors, it is preferable that the mixing ratio (mass ratio) of the two is 98/2 to 95/5.
• phase inversion emulsification method known mechanical emulsification methods such as colloid mill, homomixer, homogenizer, various extruders, kneader ruder, and triaxial planetary disperser can be employed.
• the particle size of the polylactic acid in the aqueous dispersion is adjusted by controlling the conditions (time, temperature, rotation speed, etc.) of the phase inversion emulsification method.
• Polylactic acid Luminy LX930 (registered trademark) manufactured by Total Corbion Co., Ltd.
• PVA1 partially saponified polyvinyl alcohol with an average degree of saponification of 65 mol% and an average degree of polymerization of 240
• PVA2 partially saponified polyvinyl alcohol with an average degree of saponification of 65 mol% and an average degree of polymerization of 600
• PVA3 an average degree of saponification of 72 mol%
• PVA4 Partially saponified polyvinyl alcohol with a degree of saponification of 80 mol% and an average degree of polymerization of 300
• PVA5 Partially saponified polyvinyl alcohol with a degree of saponification of 80 mol% and an average degree of polymerization of 500
• PVA6 Ken Parti
• the average degree of polymerization of polyvinyl alcohol is preferably 200 to 700.
• Table 1 with the lower limit (200) of the standard width of the polymerization degree of polyvinyl alcohol used in Example 1 and the like and the upper limit (700) of the standard width of the polymerization degree of polyvinyl alcohol used in Example 13 and the like, The average degree of polymerization of polyvinyl alcohol was defined. This is because it can be expected that polyvinyl alcohol having a degree of polymerization within this range will have the same effects as those of the examples in Table 1.
• the degree of polymerization of polyvinyl alcohol can also be defined at its median value. At this time, the lower limit is 240 and the upper limit is 600.
• Example 9 From the results of Example 9 in Table 1, by adopting polyvinyl alcohol having an average degree of saponification of 69.0 to 74.0 mol% and an average degree of polymerization of 400 to 600, suitable heat seal strength and water resistance is obtained.
• the lower limit (69.0) and the upper limit (74.0) of the standard width of the saponification degree of polyvinyl alcohol used in Example 9 are used to define the average degree of saponification of polyvinyl alcohol, and the standard width of the polymerization degree is
• the average degree of polymerization of polyvinyl alcohol was defined by the lower limit (400) and the upper limit (600) of . This is because it can be expected that polyvinyl alcohol having a degree of saponification and a degree of polymerization within such ranges will have the same effect as in Example 9.
• Example 10 From the results of Example 10 in Table 1, by adopting polyvinyl alcohol having an average degree of saponification of 78.5 to 82.0 mol% and an average degree of polymerization of 200 to 400, suitable heat seal strength and water resistance is obtained.
• the lower limit (78.5) and the upper limit (82.0) of the standard width of the saponification degree of polyvinyl alcohol used in Example 10 define the average degree of saponification of polyvinyl alcohol, and the standard width of the degree of polymerization
• the average degree of polymerization of polyvinyl alcohol was defined by the lower limit (200) and the upper limit (400) of . This is because it can be predicted that polyvinyl alcohol having a degree of saponification and a degree of polymerization within these ranges will have the same effect as in Example 10.
• Polyvinyl alcohols used in the examples were commercially available and were all partially saponified polyvinyl alcohols. As long as it is applicable as a dispersion of polylactic acid and the average degree of saponification and the average degree of polymerization are defined as described above, polyvinyl alcohol itself, copolymers thereof, and modified products thereof That is, similar effects can be obtained with polyvinyl alcohols.
• pH adjusters include, but are not limited to, alkali metal hydroxides, alkaline earth metal hydroxides, other inorganic salts, and amines. Specifically, sodium hydroxide, potassium hydroxide, calcium hydroxide, calcium acetate, sodium lactate, calcium lactate, calcium oxalate, magnesium hydroxide, magnesium acetate, magnesium lactate, magnesium oxalate, basic aluminum lactate, base reactive aluminum chloride, ammonia, methylamine, dimethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine and triethanolamine.
• one type of basic compound may be used alone, or two or more types of basic compounds may be used in combination.
• a pH adjuster By using a pH adjuster, it is possible to neutralize residual acid monomers in polylactic acid and acidic decomposition products generated when polylactic acid is hydrolyzed. Since an acidic substance acts as a catalyst for hydrolysis, the pH adjuster is useful for suppressing hydrolysis of polylactic acid.
• the amount of the pH adjuster to be blended is appropriately selected according to the use of the aqueous dispersion, and can be, for example, 0.05 to 2.0% by mass relative to the polylactic acid.
• Styrene-acrylic copolymers starches and waxes can be mentioned as water resistance improving aids.
• the styrene-based monomer of the styrene-acrylic copolymer is not particularly limited, and examples include styrene, ⁇ -methylstyrene, ⁇ -methylstyrene, 2,4-dimethylstyrene, ⁇ -ethylstyrene, ⁇ -butylstyrene, 4 -Methoxystyrene, vinyltoluene, and the like.
• the acrylic monomer is not particularly limited, and examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate and other (meth) acrylic acid esters, 3- (Meth)acrylic acid ester derivatives such as ethoxypropyl acrylate, 3-ethoxybutyl acrylate, and hydroxyethyl methacrylate; acrylic acid aryl esters and acrylic acid aralkyl esters such as phenyl acrylate and benzyl acrylate; diethylene glycol; triethylene glycol and polyhydric alcohol monoacrylates such as glycerin.
• starch examples include modified starch such as corn starch, potato starch, tapioca starch, oxidized starch, phosphated starch, etherified starch, dialdehyde starch, and esterified starch.
• Waxes such as natural waxes and synthetic waxes can be used as waxes.
• Natural waxes include plant-based natural waxes such as candelilla wax, rice wax, Japan wax, and jojoba solid wax, animal-based natural waxes such as beeswax, lanolin, spermaceti, and mineral-based natural waxes such as montan wax, ozokerite, and ceresin. , paraffin wax, microcrystalline wax, and petrolatum wax.
• Synthetic waxes include synthetic hydrocarbons such as Fischer-Tropsch wax and polyethylene wax; modified waxes such as montan wax derivatives, paraffin wax derivatives and microcrystalline wax derivatives; hydrogenated waxes such as hydrogenated castor oil and hydrogenated castor oil derivatives; -Hydroxystearic acid, ester waxes synthesized from higher fatty acids obtained from vegetable oils and animal oils and higher alcohols, stearic acid amides, phthalic anhydride imides, and the like. These can be used singly or in combination of two or more as long as the heat-sealing property is not impaired.
• a dispersing aid one selected from anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, polymer surfactants, cationic polymer compounds, and anionic polymer compounds. Or a mixture of two or more can be used.
• the following thickening agents can be blended.
• thickening agents include cellulose derivatives such as methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, and hydroxypropylcellulose; starch derivatives such as cationic starch and etherified starch; gum arabic, guar gum, xanthan gum, and the like; Animal polymers such as vegetable gums, casein, chitosan and chitin, polyalkoxide polymers such as polyethylene glycol and the like.
• the blending amount of the thickening agent is appropriately selected according to the use of the aqueous dispersion, and is, for example, 0.01 to 2.0% by mass relative to the biodegradable resin aqueous dispersion. can.
• a plasticizer can also be added as an auxiliary agent.
• a plasticizer is an auxiliary agent for softening polylactic acid and a biodegradable resin, and can impart flexibility to a heat seal layer obtained from polylactic acid.
• plasticizers include the following. Citric acid derivatives such as triethyl citrate, tributyl citrate, acetyl triethyl citrate, acetyl tributyl citrate, ether ester derivatives such as diethylene glycol diacetate, triethylene glycol diacetate, triethylene glycol dipropionate, glycerin triacetate, glycerin tripro Pionate, glycerin derivatives such as glycerin tributyrate, phthalic acid derivatives such as ethylphthalylethylglycolate, ethylphthalylbutylglycolate, butylphthalylbutylglycolate, 2-(2-methoxyethoxy)ethanol adip
• the amount of the plasticizer to be blended is appropriately selected according to the use of the aqueous dispersion. ⁇ 5% by weight is most preferred. If the blending amount is less than 1% by mass, the improvement in heat sealing performance is poor and there is little meaning in adding it.
• the dispersoid may contain a carbodiimide compound as an auxiliary agent for improving the stability of the aqueous dispersion over time.
• a carbodiimide compound it is desirable to use a polyvalent carbodiimide compound (compound containing a plurality of carbodiimide groups in one molecule). More preferred examples include carbodiimide-modified isocyanate compounds, derivatives obtained by reacting isocyanate groups of carbodiimide-modified isocyanate compounds with amino groups such as cyclohexylamine, hydroxyl groups such as polyethylene glycol monomethyl ether, and carboxylic acid groups such as cyclohexanecarboxylic acid. .
• the carbodiimide-modified isocyanate is obtained by carbodiimidating a part of the isocyanate compound.
• the carbodiimide-modified isocyanate compound a polymer obtained by carbodiimidating the following isocyanate can be used.
• carbodiimide-modified isocyanates include the following. Phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, dimethylbiphenylene diisocyanate, dimethoxybiphenylene diisocyanate, tetrahydronaphthalene diisocyanate, tolylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexylene diisocyanate, polymethylene polyphenyl polyisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, 4,4′-dimethyldicyclohexylmethane diisocyanate and the like.
• the polyvalent carbodiimide compound can be used singly or in combination of two or more.
• the amount of the polyhydric carbodiimide compound to be blended is appropriately selected according to the use of the aqueous dispersion, and is preferably 0.6 to 5.5% by mass, for example, 0.6 to 5.5% by mass relative to the polylactic acid. 6 to 2.6% by weight is most preferred.
• the mixing ratio of the carbodiimide compound is less than 0.6% by mass relative to the polylactic acid, the polylactic acid may not exhibit sufficient stability over time. On the other hand, even if it exceeds 5.5% by mass, the effect corresponding to the amount used is not obtained, and it is not economical, either.

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