Method for recycling layered product, recycled pellet, and molded article

Abstract

Provided is a method for obtaining a high quality recycled plastic having little discoloration.　A method for recycling a layered product includes melting and kneading a layered product, which has a first base material, a second base material and an adhesive layer that bonds the first base material to the second base material, in a state in which the first base material and the second base material are bonded by the adhesive layer. The adhesive layer is a cured coating film of a two-pack curable adhesive containing a polyol composition (X) and a polyisocyanate composition (Y). When a coating film, which is obtained by mixing so that the ratio of the number of moles of isocyanate groups [NCO] contained in the polyisocyanate composition and the number of moles of hydroxyl groups [OH] contained in the polyol composition ([NCO] / [OH]) is 0.5-5.0 and coating at a quantity of 10 g / m2, is heated for 30 minutes at 225ºC, the value of Δb＊ is 15.0 or less.

Description

Recycling method for laminates, recycled pellets, molded products

[0001] The present invention relates to a method for recycling a laminate, recycled pellets produced by the recycling method, and molded articles produced using the recycled pellets.

[0002] In recent years, environmental pollution caused by the disposal and dumping of plastic products has become a problem, leading to an increasing demand for the recycling of plastic products. Among plastic products, plastic film packaging materials generally have a multilayer structure to meet the different performance requirements for each application. For example, food packaging is composed of a laminated laminate formed by bonding a printed layer formed by printing ink on a first substrate to a second substrate, optionally via an adhesive layer. This laminate is cut and heat-sealed to form the package shape. Laminated laminates, such as those used in food packaging, use various plastic substrates as film substrates, including polyester, nylon, polypropylene, and polyethylene. Therefore, there is a demand for material recycling of laminated laminates.

[0003] In order to meet such demands, studies are being conducted on material recycling of laminated bodies such as food packaging. For example, Patent Document 1 discloses a method in which impurities contained in the package are removed, the package is crushed, and if necessary, alkali treatment or the like is performed, followed by separation, and then the raw materials separated and recovered according to specific gravity are melted and formed into pellets. Patent Document 2 discloses a method for producing recycled plastics in which a laminate is melt-kneaded without performing a step of separating or removing layers other than the plastic substrate, such as an adhesive layer.

[0004] JP 2014-019003 A Japanese Patent No. 7425948 A

[0005] As a result of extensive research, the inventors have found that when a laminate is melt-kneaded without a step of separating or removing the adhesive layer, the resulting recycled plastic may discolor to a yellow to brown color. Discolored recycled plastic is unsuitable for reuse.

[0006] The present invention has been made in view of the above circumstances, and has as its object to provide a high-quality recycled plastic that is less susceptible to discoloration, and a method for obtaining said recycled plastic.

[0007] The present invention provides a method for recycling a laminate, which comprises melting and kneading a laminate having a first substrate, a second substrate, and an adhesive layer bonding the first substrate and the second substrate together, in a state in which the first substrate and the second substrate are bonded together by the adhesive layer, the adhesive layer being a cured coating film of a two-component curing adhesive containing a polyol composition (X) and a polyisocyanate composition (Y), and the polyol composition and the polyisocyanate composition are mixed so that the ratio [NCO] / [OH] of the number of moles of isocyanate groups contained in the polyisocyanate composition to the number of moles of hydroxyl groups contained in the polyol composition is 0.5 to 5.0, and the polyisocyanate composition is mixed at a concentration of 10 g / m ２ Δb when the coating film applied at 225°C was heated for 30 minutes ＊ The present invention relates to a method for recycling a laminate, wherein the value of the thickness of the laminate is 15.0 or less.

[0008] According to the present invention, high-quality recycled plastics with little discoloration can be obtained.

[0009] <Recycling method> The recycling method of the present invention involves melting and kneading a laminate including a first substrate, a second substrate, and an adhesive layer bonding the first substrate and the second substrate together, or a packaging material made of the laminate, in a state in which the first substrate and the second substrate are bonded together by the adhesive layer. The recycling method of the present invention will be described in detail below.

[0010] (First substrate) The first substrate can be any film or sheet (unless otherwise specified below, film is a general term for film and sheet) that has excellent chemical and physical strength. Examples of the first substrate include polyethylene terephthalate (PET) film, polystyrene film, polyamide film, polyacrylonitrile film, polyethylene film (LLDPE: low-density polyethylene film, HDPE: high-density polyethylene film, MDOPE: uniaxially oriented polyethylene film, OPE: biaxially oriented polyethylene film), polypropylene film (CPP: unstretched polypropylene film, OPP: biaxially oriented polypropylene film), ethylene-vinyl alcohol copolymer, polyolefin film such as a gas barrier film having an olefin-based heat-sealable resin layer on one or both sides of a resin having gas barrier properties such as polyvinyl alcohol, polyvinyl alcohol film, ethylene-vinyl alcohol copolymer film, etc.

[0011] It is also preferable to use a film made of a material containing biomass-derived components. Biomass films are commercially available from various companies, and for example, sheets such as those listed in the list of biomass-certified products listed by the Japan Organics Recycling Association can be used.

[0012] Specifically, well-known films are made from biomass-derived ethylene glycol. Biomass-derived ethylene glycol is made from ethanol (biomass ethanol) produced from biomass as a raw material. For example, biomass-derived ethylene glycol can be obtained by converting biomass ethanol into ethylene oxide by a conventionally known method to produce ethylene glycol. Alternatively, commercially available biomass ethylene glycol may be used; for example, biomass ethylene glycol commercially available from India Glycoal Limited can be suitably used.

[0013] Alternatively, products using biomass raw materials classified by the biomass plastic content specified in ISO 16620 or ASTM D6866 are also on the market. Radioactive carbon-14C exists in the atmosphere at a rate of 1 in 1012 particles, and this rate is the same for atmospheric carbon dioxide, so this rate remains the same even in plants that fix this carbon dioxide through photosynthesis. Therefore, the carbon in plant-derived resins contains radioactive carbon-14C. In contrast, the carbon in fossil fuel-derived resins contains almost no radioactive carbon-14C. Therefore, by measuring the concentration of radioactive carbon-14C in the resin using an accelerator mass spectrometer, the plant-derived resin content in the resin, i.e., the biomass plastic content, can be determined. Examples of plant-derived low-density polyethylene, which is a biomass plastic having a biomass plastic content of 80% or more, preferably 90% or more as specified by ISO 16620 or ASTM D6866, include products manufactured by Braskem under the trade names "SBC818," "SPB608," "SBF0323HC," "STN7006," "SEB853," and "SPB681," and films using these as raw materials can be suitably used.

[0014] The film may be one that has been subjected to a stretching treatment. A typical stretching method involves melt-extruding a resin into a sheet using an extrusion film-forming method or the like, followed by simultaneous biaxial stretching or sequential biaxial stretching. In the case of sequential biaxial stretching, it is common to first perform longitudinal stretching and then transverse stretching. Specifically, a method that combines longitudinal stretching utilizing the speed difference between rolls and transverse stretching using a tenter is often used.

[0015] The film surface may be subjected to various surface treatments such as flame treatment and corona discharge treatment as necessary so that an adhesive layer without defects such as film breakage or repellency is formed.

[0016] Alternatively, inorganic vapor-deposited films such as metal vapor-deposited films on which a metal layer such as aluminum is vapor-deposited, transparent vapor-deposited films on which a vapor-deposited layer of a metal oxide such as silica or alumina is laminated, or barrier films containing a gas barrier layer of polyvinyl alcohol, ethylene-vinyl alcohol copolymer, vinylidene chloride, etc. When a barrier film is used, it is preferable to use a transparent vapor-deposited film on which a vapor-deposited layer of a metal oxide such as silica or alumina is laminated, or a barrier film containing a gas barrier layer of polyvinyl alcohol or an ethylene-vinyl alcohol copolymer.

[0017] The thickness of the first substrate is not particularly limited, and may be appropriately selected in the range of 1 to 300 μm, preferably 1 to 100 μm, from the viewpoints of formability and transparency.

[0018] (Second substrate) The second substrate can be the same as the first substrate. In one embodiment of the present invention, the second substrate is a film (sealant film) having heat-sealability that can be melted by heat and fused to each other, and the first substrate is a substrate that is not expected to function as a sealant film. In another embodiment of the present invention, the second substrate is a film in which a film without heat-sealability and a resin layer (heat-seal layer) having heat-sealability are laminated, and the first substrate is a substrate that is not expected to function as a sealant film.

[0019] Examples of heat-sealable resins include polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ionomer resin, ethylene-(meth)acrylic acid copolymer, ethylene-ethyl(meth)acrylate copolymer, ethylene-propylene copolymer, methylpentene polymer, modified olefin resins such as polyethylene or polypropylene modified with acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, or other unsaturated carboxylic acids, ethylene-(meth)acrylic acid ester-unsaturated carboxylic acid terpolymers, cyclic polyolefins, cyclic olefin copolymers, polyethylene terephthalate (PET), polyacrylonitrile (PAN), ethylene-vinyl alcohol copolymers, polyvinyl alcohol, and other gas-barrier resins, and gas-sealable heat-sealable films having an olefin-based heat-sealable resin layer on one or both sides thereof. Films, sheets, and other coating films made of one or more of these resins can be used as sealant films.

[0020] As the sealant film, any of unstretched, uniaxially stretched and biaxially stretched films can be used.

[0021] A biaxially stretched film can be obtained by, for example, longitudinally stretching the film to 2 to 4 times its original size using a roll stretching machine at 50 to 100° C., then transversely stretching the film to 3 to 5 times its original size using a tenter stretching machine in an atmosphere at 90 to 150° C., and subsequently heat-treating the film using the tenter stretching machine in an atmosphere at 100 to 240° C. Alternatively, a film that has been subjected to simultaneous biaxial stretching or sequential biaxial stretching may also be used.

[0022] An easily peelable sealant film (easy peel film) may be used as the sealant film. Any of the interfacial peeling type, cohesive peeling type, and interlayer peeling type sealant films can be used, and can be appropriately selected depending on the type and required properties of the packaging material described below. The index of easy peelability is appropriately set depending on the type and required properties of the packaging material, and an example is a seal strength of 2 to 20 N / 15 mm. For example, easy peelability can be achieved by a phase-separated polymer blend that combines polypropylene with high-density polyethylene, low-density polyethylene, ethylene-vinyl acetate copolymer, or the like.

[0023] When the second substrate is a film in which a film without heat sealing properties and a resin layer (heat sealing layer) with heat sealing properties are laminated, the second substrate can be, for example, a film without heat sealing properties coated with a heat sealing agent containing a resin with heat sealing properties.

[0024] Examples of heat-sealable resins include thermoplastic resins such as shellacs, rosins, rosin-modified maleic acid resins, rosin-modified phenolic resins, nitrocellulose, cellulose acetate, cellulose acetyl propionate, cellulose acetyl butyrate, chlorinated rubber, cyclized rubber, vinyl chloride, vinylidene chloride, polyamide resins, vinyl chloride-vinyl acetate copolymers, polyester resins, ketone resins, butyral resins, chlorinated polypropylene resins, chlorinated polyethylene resins, chlorinated ethylene vinyl acetate resins, ethylene vinyl acetate resins, acrylic resins, urethane resins, ethylene-vinyl alcohol resins, styrene-maleic acid resins, casein, and alkyd resins, which may be used singly or in combination. In the present invention, it is preferable not to use chlorine-containing resins such as vinyl chloride-vinyl acetate copolymers or resins containing nitro groups such as nitrocellulose.

[0025] The heat sealing agent may be in any form, such as a type in which these resins are dissolved in an organic solvent, a type in which these resins are dissolved in water or an aqueous organic solvent, or an emulsion type in which an acrylic emulsion, a urethane emulsion, a polyvinyl alcohol resin, an ethylene-vinyl alcohol emulsion, an ethylene-methacrylic acid emulsion, a polyolefin emulsion, an ethylene vinyl acetate emulsion, or the like is dispersed in water or an aqueous organic solvent.

[0026] The organic solvent is not particularly limited, and examples thereof include various organic solvents such as aromatic hydrocarbons such as toluene, xylene, Solvesso #100, and Solvesso #150; aliphatic hydrocarbons such as hexane, heptane, octane, and decane; and esters such as methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate, amyl acetate, ethyl formate, and butyl propionate.

[0027] Examples of aqueous organic solvents include alcohols such as methanol, ethanol, propanol, and butanol; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; and glycol ethers such as ethylene glycol (mono, di)methyl ether, ethylene glycol (mono, di)ethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, monobutyl ether, diethylene glycol (mono, di)methyl ether, diethylene glycol (mono, di)ethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, triethylene glycol (mono, di)methyl ether, propylene glycol (mono, di)methyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, and dipropylene glycol (mono, di)methyl ether.

[0028] The heat-sealing agent may contain components other than the heat-sealable resin and solvent, such as wax, filler, antifoaming agent, viscosity modifier, leveling agent, tackifier, preservative, antibacterial agent, rust inhibitor, antioxidant, etc.

[0029] The heat sealing agent can be applied by any known method, such as a roll coater, gravure coater, flexo coater, air doctor coater, blade coater, air knife coater, squeeze coater, impregnation coater, transfer roll coater, kiss coater, curtain coater, cast coater, spray coater, die coater, offset printing machine, screen printing machine, etc. After coating, a drying step in an oven or the like can be performed.

[0030] The thickness of the heat seal layer (the amount of heat sealant applied (solid content)) may be any value. For example, it is 0.5 g / m ２ ~5g / m ２ is.

[0031] The thickness of the second substrate can be selected arbitrarily, but when applied to a packaging material as described below, it is selected in the range of 5 to 500 μm, more preferably 10 to 250 μm, and even more preferably 15 to 100 μm.

[0032] The second substrate may be an inorganic vapor-deposited film such as a metal vapor-deposited film on which a metal layer such as aluminum is vapor-deposited, a transparent vapor-deposited film on which a vapor-deposited layer of a metal oxide such as silica or alumina is laminated, or a barrier film containing a gas barrier layer of polyvinyl alcohol, an ethylene-vinyl alcohol copolymer, vinylidene chloride, etc. When a barrier film is used as the second substrate, it is preferable to use a transparent vapor-deposited film on which a vapor-deposited layer of a metal oxide such as silica or alumina is laminated, or a barrier film containing a gas barrier layer of polyvinyl alcohol or an ethylene-vinyl alcohol copolymer.

[0033] The second substrate preferably contains the same type of resin as the first substrate. This allows for a laminate with excellent recyclability. Both the first substrate and the second substrate preferably contain a polyester resin or an olefin resin, and more preferably an olefin resin. When both the first substrate and the second substrate contain a polyester resin, the first substrate is, for example, a PET film, and the second substrate is a PET film having heat-sealability. When both the first substrate and the second substrate contain an olefin resin, the first substrate is, for example, selected from biaxially oriented polypropylene film (OPP), biaxially oriented polyethylene film (OPE), uniaxially oriented polyethylene film (MDOPE), and high-density polyethylene film (HDPE), and the second substrate is selected from unstretched polypropylene film (CPP) and low-density polyethylene film (LLDPE).

[0034] (Adhesive Layer) The adhesive layer is formed from a two-component curing adhesive containing a polyol composition and a polyisocyanate composition, and is a layer that bonds the first substrate and the second substrate together directly or via an optional layer that is formed as needed.

[0035] The polyol composition contains polyols such as polyester polyols, polyether polyols, vegetable oil polyols, polyurethane polyols, sugar alcohols, etc. These polyols may be used in combination of two or more kinds.

[0036] Examples of polyester polyols include polyester polyols which are reaction products of polyhydric alcohols and polycarboxylic acids, and lactone-based polyester polyols obtained by polycondensation reaction of aliphatic polyols with various lactones such as ε-caprolactone. It is preferable to use polyester polyols which are reaction products of polyhydric alcohols and polycarboxylic acids.

[0037] Examples of polyhydric alcohols include aliphatic diols such as ethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, 1,2,2-trimethyl-1,3-propanediol, 2,2-dimethyl-3-isopropyl-1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 3-methyl-1,3-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,4-bis(hydroxymethyl)cyclohexane, and 2,2,4-trimethyl-1,3-pentanediol;

[0038] aliphatic polyols having three or more functional groups, such as trimethylolethane, trimethylolpropane, glycerin, hexanetriol, and pentaerythritol;

[0039] Bisphenols such as bisphenol A and bisphenol F; alkylene oxide adducts of bisphenols obtained by adding ethylene oxide, propylene oxide, or the like to bisphenols such as bisphenol A and bisphenol F;

[0040] Examples of such polyether polyols include polyether polyols obtained by ring-opening polymerization of an aliphatic diol or polyol with various cyclic ether bond-containing compounds such as ethylene oxide, propylene oxide, tetrahydrofuran, ethyl glycidyl ether, propyl glycidyl ether, butyl glycidyl ether, phenyl glycidyl ether, and allyl glycidyl ether. These polyether polyols may be used alone or in combination of two or more.

[0041] Examples of polyvalent carboxylic acids include aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, maleic acid, fumaric acid, 1,3-cyclopentanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid; aromatic dicarboxylic acids such as orthophthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, and 1,2-bis(phenoxy)ethane-p,p'-dicarboxylic acid; and anhydrides or ester-forming derivatives of these aliphatic or dicarboxylic acids; and polybasic acids such as p-hydroxybenzoic acid, p-(2-hydroxyethoxy)benzoic acid, and ester-forming derivatives of these dihydroxycarboxylic acids, and dimer acids, and these may be used alone or in combination of two or more.

[0042] The molecular weight of the polyester polyol is not particularly limited, but is, for example, 250 g / mol to 20,000 g / mol. The hydroxyl value of the polyester polyol is not particularly limited, but is, for example, 5 mgKOH / g to 500 mgKOH / g.

[0043] Examples of polyether polyols include those obtained by addition polymerization of alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide, epichlorohydrin, tetrahydrofuran, and cyclohexylene in the presence of a polymerization initiator.

[0044] Examples of the polymerization initiator include glycols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, methylpentanediol, dimethylbutanediol, butylethylpropanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, bishydroxyethoxybenzene, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and triethylene glycol;

[0045] trifunctional or tetrafunctional aliphatic alcohols such as glycerin, trimethylolpropane, pentaerythritol, and triols of polypropylene glycol;

[0046] Examples thereof include primary or secondary alkylamines such as ethylamine and diethylamine, amine compounds having a plurality of amino groups such as methylenediamine and ethylenediamine, and amine compounds having an active hydrogen group such as primary or secondary alkanolamines such as monoethanolamine and diethanolamine.

[0047] The molecular weight of the polyether polyol can be adjusted appropriately, but is, for example, 100 g / mol to 8000 g / mol. The hydroxyl value of the polyether polyol can be adjusted appropriately, but is, for example, 10 mgKOH / g to 1200 mgKOH / g.

[0048] Examples of the vegetable oil polyol include castor oil, dehydrated castor oil, hardened castor oil which is a hydrogenated castor oil, and an alkylene oxide 5 to 50 mole adduct of castor oil.

[0049] Polyurethane polyol is a reaction product of a low-molecular-weight or high-molecular-weight polyol and a polyisocyanate compound. The low-molecular-weight or high-molecular-weight polyol may be the same as the polyhydric alcohol exemplified as the raw material for polyester polyol. The polyisocyanate compound may be the same as the polyisocyanate that can be contained in the isocyanate composition described below.

[0050] Examples of sugar alcohols include pentaerythritol, sucrose, xylitol, sorbitol, isomalt, lactitol, maltitol, and mannitol.

[0051] The polyisocyanate composition contains a polyisocyanate compound having multiple isocyanate groups. The polyisocyanate compound is not particularly limited, and examples thereof include aromatic diisocyanates, araliphatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, and biuret, nurate, adduct, allophanate, carbodiimide-modified, and uretdione-modified products of these diisocyanates, as well as urethane prepolymers obtained by reacting these polyisocyanates with polyols, and these can be used alone or in combination.

[0052] Examples of aromatic diisocyanates include, but are not limited to, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate (also referred to as polymeric MDI or crude MDI), 1,3-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, and 4,4',4"-triphenylmethane triisocyanate.

[0053] The araliphatic diisocyanate means an aliphatic isocyanate having one or more aromatic rings in the molecule, and examples thereof include, but are not limited to, m- or p-xylylene diisocyanate (also known as XDI), α,α,α',α'-tetramethylxylylene diisocyanate (also known as TMXDI), and the like.

[0054] Examples of aliphatic diisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (also known as HDI), pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate, but are not limited to these.

[0055] Examples of alicyclic diisocyanates include 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, isophorone diisocyanate (also known as IPDI), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), and 1,4-bis(isocyanatomethyl)cyclohexane, but are not limited to these.

[0056] The polyol used in the synthesis of the urethane prepolymer may be the same as the polyhydric alcohols exemplified as raw materials for the polyester polyols described above, and may be used alone or in combination of two or more. It is preferable to use at least one polyalkylene glycol or polyester polyol having a molecular weight of 200 to 3000 g / mol.

[0057] The adhesive may be solvent-based or solventless. In this specification, a solvent-based adhesive refers to a polyol composition and a polyisocyanate composition containing esters such as ethyl acetate, butyl acetate, and cellosolve acetate; ketones such as acetone, methyl ethyl ketone, isobutyl ketone, and cyclohexanone; ethers such as tetrahydrofuran and dioxane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride; and highly soluble organic solvents such as dimethyl sulfoxide and dimethyl sulfamide. A solventless adhesive refers to a composition that is substantially free of these organic solvents. When the organic solvents used as reaction media in the production of the components of the polyol composition and polyisocyanate composition or their raw materials are not completely removed, leaving trace amounts of organic solvent remaining in the polyol composition and polyisocyanate composition, the adhesive is considered to be substantially free of organic solvent. Furthermore, when the polyol composition contains a low-molecular-weight alcohol, the low-molecular-weight alcohol reacts with the polyisocyanate composition to become part of the coating film, and therefore does not need to be volatilized after coating. Therefore, such a form is also treated as a solventless adhesive, and the low molecular weight alcohol is not considered an organic solvent.

[0058] The adhesive may contain components other than the above-mentioned components, such as a urethanization catalyst, an acid anhydride, a coupling agent, a pigment, a plasticizer, a phosphoric acid derivative, etc. These components may be contained in either or both of the polyol composition and the polyisocyanate composition, or may be prepared separately from these and then mixed with the polyol composition and the polyisocyanate composition immediately before application of the adhesive.

[0059] The adhesive may or may not contain an antioxidant. Examples of the antioxidant include phosphoric acid-based antioxidants such as triphenyl phosphite, trisnonylphenyl phosphite, tricresyl phosphite, triethyl phosphite, trioleyl phosphite, diphenyl mono(2-ethylhexyl) phosphite, tetraphenyl dipropylene glycol diphosphite, tetra(C12 to C15 alkyl)-4,4'-isopropylidene diphenyl diphosphite, bis(decyl)pentaerythritol diphosphite, and tristearyl phosphite. and hindered phenol-based antioxidants such as pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-hydroxyphenyl)propionate, and benzyl acetic acid 3,5-bis(1,1-dimethylethyl)-4-hydroxy-C7-C9 branched alkyl ester. These may be used alone or in combination of two or more.

[0060] When the adhesive contains an antioxidant, the content thereof is, for example, 0.1 mass % or more and 5.0 mass % or less.

[0061] The adhesive is preferably used by blending so that the excess ratio of the number of moles [NCO] of isocyanate groups contained in the polyisocyanate composition relative to the number of moles [OH] of hydroxyl groups contained in the polyol composition ([NCO] / [OH], hereinafter also referred to as the isocyanate excess ratio) is 0.5 to 5.0. The isocyanate excess ratio is, for example, 4.5 or less, another example, 4.0 or less, and another example, 3.5 or less.

[0062] The adhesive layer is formed by applying an adhesive to either the first substrate or the second substrate directly or via a first resin layer or any other layer that is optionally provided, and then bonding the substrate to the other substrate and performing an aging treatment. For example, the aging temperature is room temperature to 70°C, and the aging time is 6 to 240 hours. The amount of adhesive applied is adjusted as appropriate, but for example, it is 1 g / m２ 5g / m or more ２ The following is the result.

[0063] The adhesive is mixed so that the excess isocyanate ratio is 0.5 to 5.0, and the adhesive is mixed at 10 g / m ２ Δb when the coating film applied at 225°C was heated for 30 minutes ＊ (In the following, the adhesive's Δb ＊ This allows for the production of recycled plastic with extremely little coloring. ＊ is more preferably 6.5 or less, and even more preferably 4.5 or less. Virgin plastics are often used in the production of recycled plastics, but by using a laminate produced using such an adhesive as a raw material, high-quality recycled plastics can be obtained even with a small amount of virgin plastic used in combination. As an example, Δb ＊ When Δb is 6.5 or less, the laminate bonded using the above adhesive can be used to make up to 50% by mass of the raw material of recycled plastics. ＊ When the value is 4.5 or less, even if up to 75 mass % of the recycled raw material is used, it is expected that the recycled plastic will have little yellowing and will be of high quality.

[0064] Note that Δb ＊ is the L standardized by the International Commission on Illumination in 1976. ＊ a ＊ b ＊ b is a value that indicates the color of yellow and blue in the color system. ＊ The change in the coating film after heating ＊ -b of the coating film before heating ＊ ) b ＊ can be measured using a spectrophotometer or a color difference meter.

[0065] Δb of the adhesive under the above conditions ＊ For example, Δb can be adjusted by the compounds contained in the polyol composition or the polyisocyanate composition. By avoiding the use of aromatic diisocyanates or polyisocyanates derived from aromatic diisocyanates, Δb ＊Alternatively, it is possible to prevent the increase of Δb by avoiding the use of polypropylene glycol as a raw material for synthesizing the polyisocyanate compound or as a polyol in the polyol composition. ＊ It is presumed that it becomes difficult to increase Δb. It is also possible to avoid the use of polyols having alkyl side chains, or polyester polyols or polyurethane polyols made from polyols having alkyl side chains as raw materials for synthesizing polyisocyanate compounds or polyols for polyol compositions. ＊ It is expected that it will be difficult to increase

[0066] The amount of aromatic diisocyanate or polyisocyanate derived from aromatic diisocyanate used can be adjusted as appropriate, but is, for example, less than 40 mass% of the raw materials for synthesizing the polyisocyanate compound, less than 30 mass%, less than 20 mass%, or less than 10 mass%. The raw materials for synthesizing the polyisocyanate compound do not necessarily need to contain aromatic diisocyanate or polyisocyanate derived from aromatic diisocyanate.

[0067] The amount of polypropylene glycol used can be adjusted as appropriate, but is, for example, less than 40% by mass of the total amount of the polyol raw material and the polyisocyanate compound raw material, for example, 30% by mass or less, for example, 20% by mass or less, for example, 10% by mass or less. The polyol raw material and the polyisocyanate compound raw material do not necessarily need to contain polypropylene glycol.

[0068] The amount of polyol having an alkyl side chain used can be adjusted as appropriate, but is, for example, less than 20 mass% of the total amount of the raw materials for the polyol and the raw materials for the polyisocyanate compound, and is, for example, less than 10 mass%. The raw materials for the polyol and the raw materials for the polyisocyanate compound do not necessarily need to contain polyol having an alkyl side chain.

[0069] Alternatively, if the molecular motion of the adhesive is suppressed, Δb ＊It is presumed that it is difficult to increase Δb under the above conditions. Examples of such adhesives include adhesives in which a structure is incorporated in which at least one polycarboxylic acid selected from ortho-oriented aromatic polycarboxylic acids and cis-type polycarboxylic acids is linked by a glycol with a short alkyl chain into a polyol or polyisocyanate compound. By incorporating such a structure, molecular motion (rotation of molecular chains) is suppressed, and as a result, Δb ＊ Methods for incorporating such a structure into an adhesive include a method using, as a polyol, a polyester polyol derived from a polycarboxylic acid containing at least one selected from ortho-oriented aromatic polycarboxylic acids and cis-type polycarboxylic acids, and at least one polyhydric alcohol selected from the group consisting of ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, and cyclohexanedimethanol, and a method using, as a polyisocyanate compound, a polyurethane polyisocyanate derived from such a polyester polyol and a polyisocyanate.

[0070] It is also preferable to use an adhesive having a structure derived from an isocyanuric ring. Methods for introducing a structure derived from an isocyanuric ring into an adhesive include using a compound having an isocyanuric ring as a component of the adhesive or as a raw material for the adhesive component, and using a compound synthesized using a compound having an isocyanuric ring as a raw material for the adhesive component or as a raw material for the adhesive component. Examples of compounds having an isocyanuric ring include alkylene oxide adducts of isocyanuric acid such as 1,3,5-tris(2-hydroxyethyl)isocyanuric acid and 1,3,5-tris(2-hydroxypropyl)isocyanuric acid. Examples of compounds synthesized using a compound having an isocyanuric ring as a raw material include polyester polyol and polyester polyurethane polyisocyanate in which an isocyanate group is introduced at the terminal of a polyester polyol.

[0071] When a polyester polyol is used as the polyol or when a polyester polyol is used as a raw material for a polyisocyanate compound, it is preferable that the polycarboxylic acid used as the raw material for the polyester polyol contains an aromatic polycarboxylic acid. The proportion of aromatic polycarboxylic acid in the polycarboxylic acid used as the raw material for the polyester polyol is, for example, 10% by mass or more, as another example, 20% by mass or more, as another example, 30% by mass or more, as another example, 40% by mass or more, as another example, 40% by mass or more, as another example, 50% by mass or more. The total amount of the polycarboxylic acid used as the raw material for the polyester polyol may be aromatic polycarboxylic acid.

[0072] (Printed Layer) The laminate used in the recycling method of the present invention may have a layer other than the first substrate, the second substrate, and the adhesive layer. An example of such a layer is a printed layer. The printed layer is a layer printed with printing ink between the first substrate and the adhesive layer or on the surface of the first substrate opposite the adhesive layer, and examples of the printed layer include letters, figures, symbols, and other desired patterns or information.

[0073] The printing method and printing ink are not particularly limited, and known printing methods and printing inks can be used. Printing inks using methods such as gravure printing, flexographic printing, lithographic offset printing, and inkjet recording printing are often used for the films used as the substrate. Printing inks that combine these printing methods with methods of curing using active energy rays such as ultraviolet (UV), LED, and electron beam (EB), or methods of curing using heat, are also used. Depending on the solvent used, inks may be referred to as aqueous inks or organic solvent-based inks.

[0074] Specific examples include gravure printing ink, flexographic printing ink (in some industries, gravure printing ink and flexographic printing ink are sometimes called liquid ink), ultraviolet-curable ink for lithographic offset printing, electron beam-curable ink for lithographic offset printing, ultraviolet-curable ink for inkjet recording and printing, electron beam-curable ink for inkjet recording and printing, etc. Biomass inks made from biomass raw materials are also used as appropriate.

[0075] The printing ink may contain a resin, a colorant, and a solvent as essential components, or may be a so-called clear ink that contains a resin and a solvent but does not substantially contain a colorant. The printing layer may be provided on the entire surface of the first substrate, or may be provided only on a part of the surface.

[0076] Taking the case where the printing ink is a gravure printing ink or a flexographic printing ink as an example, the resin used in the printing ink is not particularly limited, and examples thereof include acrylic resin, polyester resin, styrene resin, styrene-maleic acid resin, maleic acid resin, polyamide resin, polyurethane resin, vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-acrylic copolymer resin, ethylene-vinyl acetate copolymer resin, vinyl acetate resin, polyvinyl acetal obtained by reacting vinyl acetate resin with an aldehyde such as butyl aldehyde under acidic conditions, polyvinyl chloride resin, chlorinated polypropylene resin, cellulose-based resin, epoxy resin, alkyd resin, rosin-based resin, rosin-modified maleic acid resin, ketone resin, cyclized rubber, chlorinated rubber, butyral, petroleum resin, etc., and one or more of these can be used in combination. Preferably, at least one or two or more selected from polyurethane resin and polyvinyl acetal are used. Furthermore, the resins used in the printing ink preferably contain 0.8 mass % or less of chlorine-containing resins such as vinyl chloride-vinyl acetate copolymer resins and resins having nitro groups such as nitrocellulose resins.It is also preferable that the printing ink does not contain chlorine-containing resins such as vinyl chloride-vinyl acetate copolymer resins or resins having nitro groups such as nitrocellulose resins.

[0077] When the printing ink contains a urethane resin, it is preferable to avoid as much as possible the use of aromatic diisocyanates and their derivatives, polypropylene glycol, polyols with alkyl side chains, and polyester polyols and polyurethane polyols derived from polyols with side chains as raw materials, which can more effectively suppress yellowing of the recycled pellets obtained by the recycling method of the present invention, particularly when the printed layer is formed from clear ink.

[0078] Colorants used in printing inks include inorganic pigments such as titanium oxide, red iron oxide, antimony red, cadmium red, cadmium yellow, cobalt blue, Prussian blue, ultramarine, carbon black, and graphite; organic pigments such as soluble azo pigments, insoluble azo pigments, azo lake pigments, condensed azo pigments, copper phthalocyanine pigments, and condensed polycyclic pigments; and extender pigments such as calcium carbonate, kaolin clay, barium sulfate, aluminum hydroxide, and talc.

[0079] The organic solvent used in the printing ink preferably does not contain an aromatic hydrocarbon organic solvent. More specific examples include alcohol organic solvents such as methanol, ethanol, n-propanol, isopropanol, and butanol, ketone organic solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, ester organic solvents such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate, aliphatic hydrocarbon organic solvents such as n-hexane, n-heptane, and n-octane, and alicyclic hydrocarbon organic solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, cycloheptane, and cyclooctane, and these can be used alone or in combination of two or more.

[0080] In consideration of the establishment of a recycling-oriented society that should continue to develop (sustainability), it is also preferable that the liquid printing ink used in the present invention is a gravure printing ink or a flexographic printing ink that uses plant-derived raw materials.

[0081] Examples of plant-derived raw materials include cellulose resins such as cellulose acetate propionate resin and nitrocellulose; polyamide resins using dimer acids or polymerized fatty acids derived from natural oils such as soybean oil, palm oil, and rice bran oil; biomass polyurethanes synthesized from plant-derived raw materials such as polycarboxylic acids such as succinic acid, succinic anhydride, adipic acid, azelaic acid, sebacic acid, dimer acid, glutaric acid, and malic acid; polyols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, pentylene glycol, 1,10-dodecanediol, dimer diol, and isosorbide; and polyisocyanates such as 1,5-pentamethylene diisocyanate and dimer diisocyanate; and rosin resins.

[0082] As the biomass gravure printing ink or flexographic printing ink, commercially available products listed by the Japan Organics Recycling Association can also be used.

[0083] The area of ​​the printed layer occupies preferably 50% or less of the area of ​​the laminate or packaging material. The printed layer is preferably provided so as to have a light color. Specifically, the density measured using a densitometer with ISO status T, a viewing angle of 2°, and a light source D50 as the density standard is preferably 0.8 or less, more preferably 0.5 or less. For example, an eXactAdvance manufactured by X-rite Corporation can be used as the densitometer.

[0084] (Third substrate) The laminate of the present invention may include a third substrate in addition to the first substrate and the second substrate. The third substrate can be the same as the first substrate. In one embodiment of the present invention, the second substrate is a film (sealant film) having heat sealability that can be melted by heat and fused to each other, and the first substrate and the third substrate are substrates that are not expected to function as sealant films. In another embodiment of the present invention, all of the first substrate, the second substrate, and the third substrate are substrates that are not expected to function as sealant films.

[0085] When the laminate of the present invention includes a third substrate, the third substrate is disposed between the first substrate and the second substrate, and the first substrate and the third substrate, and the third substrate and the second substrate are bonded together directly or via a first resin layer or other layers provided as necessary, using the same adhesive as described above. The adhesive layer disposed between the first substrate and the third substrate and the adhesive layer disposed between the third substrate and the second substrate may be formed with the same adhesive, or may be formed with different adhesives. The adhesive for both the adhesive layer disposed between the first substrate and the third substrate and the adhesive layer disposed between the third substrate and the second substrate is a mixture of a polyol composition and a polyisocyanate composition with an isocyanate excess ratio of 0.5 to 5.0, and a thickness of 10 g / m ２ Δb when the coating film applied at 225°C was heated for 30 minutes ＊ It is preferable to use one having a ρ of 15.0 or less, more preferably one having a ρ of 6.5 or less, and even more preferably one having a ρ of 4.5 or less.

[0086] The third substrate preferably contains the same type of resin as the first substrate and the second substrate. This allows for a laminate with excellent recyclability. The first substrate, the second substrate, and the third substrate preferably all contain a polyester resin or an olefin resin, and more preferably an olefin resin. When the first substrate, the second substrate, and the third substrate all contain a polyester resin, the first substrate and the third substrate are, for example, PET films, and the second substrate is a PET film having heat-sealability. When the first substrate, the second substrate, and the third substrate all contain an olefin resin, the first substrate and the third substrate are, for example, selected from biaxially oriented polypropylene film (OPP), biaxially oriented polyethylene film (OPE), uniaxially oriented polyethylene film (MDOPE), and high-density polyethylene film (HDPE), and the second substrate is selected from unstretched polypropylene film (CPP) and low-density polyethylene film (LLDPE).

[0087] (Barrier Coat Layer) The laminate of the present invention may include layers other than those described above. An example of such a layer is a barrier coat layer. The barrier coat layer is a layer that prevents the permeation of oxygen and water vapor, and can be provided at any position of the laminate of the present invention by applying and drying a barrier coating agent.

[0088] An example of the barrier coating agent is a barrier coating agent (1) containing a vinyl alcohol polymer and an aqueous solvent.

[0089] Specific examples of vinyl alcohol polymers include polyvinyl alcohol, ethylene vinyl alcohol, polyvinyl butyral, etc. The vinyl alcohol polymer may have a reactive functional group other than a hydroxyl group, such as an acetoacetyl group, a carboxyl group, an anionic carboxyl group, a sulfonic acid group, or an anionic sulfonic acid group. These may be used alone or in combination of two or more.

[0090] Examples of aqueous solvents include water, glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, polyethylene glycol, and polypropylene glycol; diols such as butanediol, pentanediol, and hexanediol; glycol esters such as propylene glycol laurate; diethylene glycol ethers such as diethylene glycol monoethyl, diethylene glycol monobutyl, diethylene glycol monohexyl, and carbitol; glycol ethers such as propylene glycol ether, dipropylene glycol ether, and cellosolve containing triethylene glycol ether; alcohols such as methanol, ethanol, isopropyl alcohol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, butyl alcohol, and pentyl alcohol; lactones such as sulfolane, esters, ketones, and γ-butyrolactone; lactams such as N-(2-hydroxyethyl)pyrrolidone; and glycerin and its polyalkylene oxide adducts. The aqueous solvents can be used alone or in combination of two or more.

[0091] The barrier coating agent (1) may further contain additives such as a layered inorganic compound, a crosslinking agent capable of reacting with a functional group possessed by the vinyl alcohol polymer, an adhesion improver, an inorganic filler, an antifoaming agent, a stabilizer (antioxidant, heat stabilizer, ultraviolet absorber, etc.), a plasticizer, an antistatic agent, a lubricant, an antiblocking agent, a colorant, and a leveling agent.

[0092] Commercially available barrier coating agents (1) can also be used, and examples thereof include EXEVIA (registered trademark) manufactured by Sumitomo Chemical Co., Ltd., SunBar (registered trademark) series manufactured by Sun Chemical Co., Ltd., Takelac WPB (registered trademark) series manufactured by Mitsui Chemicals, Inc., and LG-OX manufactured by Tokyo Ink Co., Ltd.

[0093] The barrier coating agent is a water-soluble polymer having a hydroxyl group and Si(OR １ ) ４ , or R ２ Si(OR ３ ) ３ (However, OR １ and OR ３ represents a hydrolyzable group, R ２ represents an organic functional group), or one or more hydrolyzates of the silicon compounds.

[0094] Examples of water-soluble polymers having a hydroxyl group include vinyl alcohol polymers, polyvinylpyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, and sodium alginate.

[0095] Examples of silicon compounds or hydrolyzates of silicon compounds include tetraethyl silicate (Si(OC ２ H ５ ) ４) (hereinafter sometimes referred to as TEOS), tetraalkoxysilanes such as tetramethyl silicate; trialkoxysilanes such as trimethoxymethylsilane, triethoxymethylsilane, trimethoxyvinylsilane; dialkoxysilanes such as dimethoxydimethylsilane, diethoxydimethylsilane; monoalkoxysilanes such as methoxytrimethylsilane, ethoxytrimethylsilane, or hydrolysates or partial hydrolysates thereof.

[0096] TEOS is preferred because it is relatively stable in an aqueous solvent after hydrolysis. ２ Si(OR ３ ) ３ Contains R ２ is preferably a vinyl group, an epoxy group, an acryloyl group, a methacryloxy group, a ureido group, or an isocyanate group.

[0097] The barrier coating agent (2) may contain components other than those described above. Such components include other water-soluble polymers (e.g., sodium polyacrylate, polyethylene oxide, polyvinylpyrrolidone, dextrin, chitosan, chitin, methylcellulose, hydroxyethyl cellulose, etc.), fragrances, rust inhibitors, colorants, extenders, antifoaming agents, ultraviolet absorbers, fluorescent brighteners, liquid paraffins, bitter components (e.g., denatonium benzoate, etc.), etc. The barrier coating agent (2) can use the same aqueous solvent as the gas barrier coating agent (1).

[0098] An example of the barrier coating agent is a barrier coating agent (3) containing a polyester polyol, which is a reaction product of an acid component essentially containing an ortho-orienting polycarboxylic acid or a meta-orienting polycarboxylic acid and a polyol component, and an isocyanate compound.

[0099] Examples of ortho-orienting polycarboxylic acids include orthophthalic acid or its anhydride, naphthalene 2,3-dicarboxylic acid or its anhydride, naphthalene 1,2-dicarboxylic acid or its anhydride, anthraquinone 2,3-dicarboxylic acid or its anhydride, and 2,3-anthracene carboxylic acid or its anhydride. These compounds may have a substituent on any carbon atom of the aromatic ring. Examples of the substituent include a chloro group, a bromo group, a methyl group, an ethyl group, an i-propyl group, a hydroxyl group, a methoxy group, an ethoxy group, a phenoxy group, a methylthio group, a phenylthio group, a cyano group, a nitro group, an amino group, a phthalimido group, a carboxyl group, a carbamoyl group, an N-ethylcarbamoyl group, a phenyl group, and a naphthyl group.

[0100] Examples of meta-oriented polycarboxylic acids include isophthalic acid, 1,3-naphthalenedicarboxylic acid, etc. These compounds may have the same substituents as those exemplified in the description of ortho-oriented polycarboxylic acids on any carbon atom of the aromatic ring.

[0101] The polycarboxylic acid used in the synthesis of the polyester polyol may contain a polycarboxylic acid other than an ortho-oriented polycarboxylic acid or a meta-oriented polycarboxylic acid. Examples of such a polycarboxylic acid include aliphatic polycarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid; unsaturated bond-containing polycarboxylic acids such as maleic anhydride, maleic acid, and fumaric acid; alicyclic polycarboxylic acids such as 1,3-cyclopentanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid; terephthalic acid, pyromellitic acid, trimellitic acid, 1,4-naphthalenedicarboxylic acid, 1,5-anthracenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid, and 1,4-anthracenedicarboxylic acid. Examples of aromatic polycarboxylic acids include helical dicarboxylic acids, 2,6-anthracene dicarboxylic acid, 2,7-anthracene dicarboxylic acid, 1,8-anthracene dicarboxylic acid, 9,10-anthracene dicarboxylic acid, biphenyl dicarboxylic acid, 1,2-bis(phenoxy)ethane-p,p'-dicarboxylic acid, and acid anhydrides or ester-forming derivatives of these dicarboxylic acids, p-hydroxybenzoic acid, p-(2-hydroxyethoxy)benzoic acid, and ester-forming derivatives of these dihydroxycarboxylic acids, and these can be used alone or in combination of two or more. Among these, succinic acid, 1,3-cyclopentane dicarboxylic acid, and acid anhydrides thereof are preferred.

[0102] When the polycarboxylic acid contains a polycarboxylic acid other than an ortho-oriented polycarboxylic acid or a meta-oriented polycarboxylic acid, the proportion of the ortho-oriented polycarboxylic acid or the meta-oriented polycarboxylic acid in the total amount of the polycarboxylic acid is preferably 40 to 100 mass%.

[0103] The polyhydric alcohol used in the synthesis of polyester polyol preferably contains a dihydric alcohol such as ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, or cyclohexanedimethanol, or a trihydric alcohol such as glycerol, trimethylolethane, or trimethylolpropane. Among these, it is more preferable to contain ethylene glycol or glycerol. It is particularly preferable to contain glycerol. The polyhydric alcohol preferably contains 10 to 100% by mass of glycerol.

[0104] Polyhydric alcohols other than those mentioned above may be used in combination, and examples thereof include aliphatic diols such as 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, methylpentanediol, dimethylbutanediol, butylethylpropanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol; trihydric or higher polyhydric alcohols such as glycerin, trimethylolpropane, trimethylolethane, tris(2-hydroxyethyl)isocyanurate, 1,2,4-butanetriol, pentaerythritol, and dipentaerythritol; hydroquinone, resorcinol, catechol, naphthalenediol, biphenol, bisphenol A, bisphenol F, and tetramethylbiphenol; ethylene oxide-extended products thereof; and aromatic polyhydric phenols such as hydrogenated alicyclic alcohols.

[0105] When the polyester polyol has three or more hydroxyl groups, some of the hydroxyl groups may be modified with a polycarboxylic acid or its acid anhydride. The proportion of hydroxyl groups modified with the polycarboxylic acid is preferably ⅓ or less of the hydroxyl groups of the polyester polyol. Examples of polycarboxylic acids used for modification include, but are not limited to, succinic anhydride, maleic acid, fumaric acid, 1,2-cyclohexanedicarboxylic anhydride, 4-cyclohexene-1,2-dicarboxylic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, phthalic anhydride, 2,3-naphthalenedicarboxylic anhydride, trimellitic anhydride, oleic acid, and sorbic acid.

[0106] The polyester polyol may be a polyester polyurethane polyol having a number average molecular weight of 1,000 to 15,000 obtained by urethane elongation through a reaction with a diisocyanate compound. The urethane-elongated polyester polyol contains components with molecular weights equal to or greater than a certain level and urethane bonds, and therefore has excellent gas barrier properties and initial cohesive strength.

[0107] The isocyanate compound used in the barrier coating agent (3) may be the same as the polyisocyanate compound used in the adhesive (1), and is preferably one having an aromatic ring or an aliphatic ring. Examples of isocyanate compounds having an aromatic ring or an aliphatic ring include toluene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, or trimers of these isocyanate compounds, and adducts obtained by reacting an excess amount of these isocyanate compounds with low-molecular-weight active hydrogen compounds such as ethylene glycol, propylene glycol, meta-xylylene alcohol, 1,3-bishydroxyethylbenzene, 1,4-bishydroxyethylbenzene, trimethylolpropane, glycerol, pentaerythritol, erythritol, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine, and meta-xylylenediamine, and alkylene oxide adducts thereof, various polyester resins, polyether polyols, and high-molecular-weight active hydrogen compounds such as polyamides. The isocyanate compounds may be used alone or in combination.

[0108] It is also preferable to use a compound having an active hydrogen group in combination with the barrier coating agent (3). Examples of the active hydrogen group in the compound having active hydrogen include a hydroxyl group, an amino group, an imino group, a carboxylic acid, a urea group, and an SH group. Among these, a hydroxyl group, an amino group, and an SH group are preferred.

[0109] When the solubility parameter of the compound having active hydrogen is 29.5 or less, the compatibility between the polyester polyol and the isocyanate compound is improved, the compound having active hydrogen is uniformly present in the barrier coat layer, and the effect of improving gas barrier properties can be expected. Note that in this specification, the solubility parameter refers to the δT value listed in the Hansen Solubility Parameter Calculation Software (HSPiP) or the δT value calculated using the SMILES notation.

[0110] Examples of compounds having a hydroxyl group as an active hydrogen group include alkanols such as octanol and decanol, aliphatic diols such as 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2,2,2-trimethylpentanediol, 3,3-dimethylolheptane, octanediol, and decanediol, alicyclic alcohols such as 1,3- or 1,4-cyclohexanedimethanol and 1,3- or 1,4-cyclohexanediol, aromatic alcohols such as salicylic alcohol and vanillyl alcohol, hydrogenated bisphenol A, 1,4-dihydroxy-2-butene, 2,6- Examples of the alcohol include dihydric alcohols such as dimethyl-1-octene-3,8-diol, bisphenol A, diethylene glycol, triethylene glycol, and dipropylene glycol; trihydric alcohols such as glycerin, trimethylolpropane, and triisopropanolamine; tetrahydric alcohols such as tetramethylolmethane (pentaerythritol) and diglycerin; pentahydric alcohols such as xylitol; hexahydric alcohols such as sorbitol, mannitol, allitol, iditol, dulcitol, altritol, inositol, and dipentaerythritol; and heptahydric alcohols such as perseitol.

[0111] Examples of compounds having an amino group as an active hydrogen group include aliphatic amines such as octylamine, decaneamine, 1,8-diaminooctane, and 1,10-diaminodecane; alicyclic amines such as isophoronediamine, norbornenediamine, bis(aminomethyl)cyclohexane, cyclohexanediamine, diaminodicyclohexylmethane, and methylenebis(methylcyclohexaneamine); and aromatic amines such as 1-xylylenediamine, N-benzylethylenediamine, phenylenediamine, diaminodiphenylmethane, diaminodiphenyl ether, 1,3-bis(3-aminophenoxy)benzene, toluenediamine, and diethyltoluenediamine.

[0112] Examples of compounds having an SH group as an active hydrogen group include hexyl mercaptan, heptyl mercaptan, octyl mercaptan, nonyl mercaptan, decyl mercaptan, undecyl mercaptan, and dodecyl mercaptan. , tridecyl mercaptan, tetradecyl mercaptan, pentadecyl mercaptan, mercaptophenol, mercaptopropionic acid, mercaptobutyric acid, 1,4-butanedithiol, 2-mercaptobenzothiazole, 3-mercapto-1,2-propanediol, mercaptomethylbutanol, 3-mercapto-2-methylpentanol, 3-mercapto-3-methylbutanol, 4-ethoxy-2-methyl-2-butanethiol, hexanethiol, dimethylthiophenol, 1,4-bis(3-mercaptobutyryloxy)butane, trimethylolpropane tris(3-mercaptobutyrate), pentaerythritol tetrakis(3-mercaptobutyrate), and the like.

[0113] The compound having active hydrogen may be used alone or in combination of two or more kinds. Isosorbide, tris(2-hydroxyethyl) isocyanurate, trimethylolpropane, dipentaerythritol, and 1,4-cyclohexanedimethanol are preferred.

[0114] The amount of the compound having active hydrogen is preferably 0.5% by mass or more and 20% by mass or less based on the solid content of the barrier coating agent (3).

[0115] The barrier coating agent (3) may further contain a layered inorganic compound, an acid anhydride, an oxygen scavenger, an inorganic filler, and when an inorganic material is used, a dispersant, a stabilizer (antioxidant, heat stabilizer, ultraviolet absorber, etc.), a plasticizer, an antistatic agent, a lubricant, an antiblocking agent, a colorant, a leveling agent, a slip improver, etc.

[0116] The barrier coating agent (3) may be diluted with an organic solvent, such as ester solvents like ethyl acetate, propyl acetate, and butyl acetate, ketone solvents like acetone and 2-butanone, ether solvents like tetrahydrofuran, aliphatic solvents like hexane and cyclohexane, and aromatic solvents like toluene.

[0117] (Heat-resistant coating layer) The laminate of the present invention may include layers other than those described above. An example of such a layer is a heat-resistant coating layer. The heat-resistant coating layer is a layer having a function of improving the heat resistance of the laminate of the present invention, and can be provided at any position on the laminate of the present invention by applying and drying a heat-resistant coating agent.

[0118] Taking the case where the laminate of the present invention is used as a component of a packaging material for packaging contents as an example, if a bag is made and filled with contents, and the outermost substrate is a film with low heat resistance such as a polyethylene film or a polypropylene film, there is a risk that the laminate will shrink due to heat when the bag is made by heat sealing. Such a problem can be prevented by providing a heat-resistant coating layer.

[0119] The heat-resistant coating layer is preferably disposed outside the substrate that is positioned outermost from the contents when the bag is made from the substrates constituting the laminate. For example, when the first substrate is the outermost substrate among the substrates constituting the laminate of the present invention and the printed layer is disposed between the first substrate and the adhesive layer, the heat-resistant coating layer is preferably disposed on the surface of the first substrate opposite the adhesive layer. Alternatively, when the first substrate is the outermost substrate among the substrates constituting the laminate of the present invention and the printed layer is disposed on the surface of the first substrate opposite the adhesive layer, the heat-resistant coating layer may be disposed between the printed layer and the first substrate, or the printed layer may be disposed between the heat-resistant coating layer and the first substrate.

[0120] Examples of heat-resistant coating agents include coating agents containing compounds having a cellulose skeleton, a benzene ring skeleton, an isocyanuric ring skeleton, or an alicyclic skeleton, whose homopolymer glass transition temperature (hereinafter sometimes referred to as Tg) is 100° C. or higher. Specific examples of such compounds include cellulose derivatives such as cellulose acetate, cellulose propionate, and cellulose butyrate; polyester resins having a benzene ring such as phthalic acid, naphthalenedicarboxylic acid, and an ethylene oxide (hereinafter sometimes referred to as EO) adduct of bisphenol A, and / or an alicyclic skeleton such as cyclopentanediol and dimethyloltricyclodecane; and urethane resins obtained by combining aromatic isocyanates such as diphenylmethane diisocyanate, toluene diisocyanate, xylene diisocyanate, and naphthalene diisocyanate; alicyclic isocyanates such as isophorone diisocyanate and norbornene diisocyanate; and / or isocyanuric triisocyanate with a polyol and / or tris(2-hydroxyethyl)isocyanurate. Polyisocyanates using the aforementioned isocyanates may also be used as curing agents. Furthermore, compounds having a benzene ring and an unsaturated double bond, such as styrene and phenoxydiethylene glycol acrylate, and / or compounds having an alicyclic structure and an unsaturated double bond, such as isobornyl acrylate and dicyclopentanyl acrylate, and radical copolymers such as (meth)acrylates are also preferably used. Furthermore, in consideration of adhesion to olefin films, a resin with a low Tg may be mixed and used.

[0121] The heat-resistant coating agent preferably uses inorganic fine particles such as alumina, magnesia, titania, zirconia, and silica (quartz, fumed silica, precipitated silica, silicic anhydride, fused silica, crystalline silica, and ultrafine amorphous silica) as aggregates because they have excellent heat resistance. Alternatively, boron nitride, aluminum nitride, alumina oxide, titanium oxide, magnesium oxide, zinc oxide, and silicon oxide are preferred because they have excellent thermal conductivity. The inorganic fine particles may be used alone or in combination.

[0122] The shape of the silica fine particles is not particularly limited, and spherical, hollow, porous, rod-like, plate-like, fibrous, or irregularly shaped particles can be used. For example, commercially available hollow silica fine particles such as Silinax manufactured by Nittetsu Mining Co., Ltd. can be used.

[0123] The primary particle diameter of the inorganic fine particles is preferably in the range of 5 nm to 200 nm, and more preferably 10 nm to 100 nm. The inorganic fine particles can be blended in a proportion of 5 to 90 wt % based on the total solid content of the heat-resistant coating agent and the inorganic fine particles, and the blending amount can be changed as needed depending on the purpose. In particular, a proportion of 20 mass % or more is preferred.

[0124] The heat-resistant coating agent may be colored. The colorant is not particularly limited, and examples thereof include inorganic pigments, organic pigments, and dyes used in general inks, paints, and recording agents, such as those used in the printing layer described below.

[0125] The heat-resistant coating agent may contain wax, silicon additives, or organic beads, such as amide wax, polypropylene wax, polyethylene wax, paraffin wax, carnauba wax, or rice wax, an ethylene oxide (EO) adduct of dimethylsiloxane, a silicon additive such as a silicon-modified product, or organic beads made of acrylic, nylon, urethane, or epoxy.

[0126] The solvent used in the heat-resistant coating agent is not particularly limited, but examples thereof include water, aromatic hydrocarbon organic solvents such as toluene, xylene, Solvesso #100, Solvesso #150, etc.; aliphatic hydrocarbon organic solvents such as hexane, methylcyclohexane, heptane, octane, decane, etc.; and various ester organic solvents such as methyl acetate, ethyl acetate, isopropyl acetate, normal propyl acetate, butyl acetate, amyl acetate, ethyl formate, butyl propionate, etc. Examples of water-miscible organic solvents include alcohols such as methanol, ethanol, propanol, butanol, and isopropyl alcohol; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; and glycol ethers such as ethylene glycol (mono- and di-)methyl ether, ethylene glycol (mono- and di-)ethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, monobutyl ether, diethylene glycol (mono- and di-)methyl ether, diethylene glycol (mono- and di-)ethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, triethylene glycol (mono- and di-)methyl ether, propylene glycol (mono- and di-)methyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, and dipropylene glycol (mono- and di-)methyl ether. These can be used alone or in combination of two or more. Furthermore, to more effectively carry out coating, an antifoaming agent or a leveling agent can be used.

[0127] Commercially available heat-resistant coating agents can also be used, examples of which include SUNSYS FS241 manufactured by Sun Chemical Co., DH-S004 / DH-HARDENER P-60 manufactured by DIC Corporation, and ThermaGloss 463 manufactured by Michelman.

[0128] (Packaging Material) The packaging material used in the recycling method of the present invention is made of the above-mentioned laminate. One example is a bag made from the laminate, but the layer structure can be changed depending on the contents, the environment in which it is used, and the form of use.

[0129] When the packaging material used in the recycling method of the present invention is a bag made from the above-mentioned laminate, it can be obtained, for example, by overlapping the heat-sealable layers of the laminate so that they face each other and then heat-sealing the peripheral edges. Examples of bag-making methods include folding or overlapping the laminate of the present invention so that the inner layer surfaces (the surfaces of the sealant film) face each other, and heat-sealing the peripheral edges using, for example, a side seal type, a two-sided seal type, a three-sided seal type, a four-sided seal type, an envelope seal type, a flared seal type, a flat-bottom seal type, a square-bottom seal type, a gusset seal type, or other heat seal type. The packaging material of the present invention can take various forms depending on the contents, usage environment, and usage form. Self-standing packaging materials (standing pouches) are also possible. Heat-sealing methods can be known, such as bar seal, rotary roll seal, belt seal, impulse seal, high-frequency seal, and ultrasonic seal.

[0130] The uses of the packaging material are not particularly limited. Examples of contents that can be filled include confectioneries such as rice crackers, bean snacks, nuts, biscuits, cookies, wafer snacks, marshmallows, pies, semi-dried cakes, candy, and snacks, staple foods such as bread, snack noodles, instant noodles, dried noodles, pasta, aseptically packaged cooked rice, porridge, rice porridge, packaged rice cakes, and cereal foods, pickles, boiled beans, natto, miso, frozen tofu, tofu, nametake mushrooms, konjac, processed wild vegetables, jams, peanut cream, salads, frozen vegetables, and processed potato products, processed livestock products such as ham, bacon, sausages, processed chicken products, and corned beef, and fish ham and sausages. Examples of suitable packaging materials include processed seafood products such as fish paste products, kamaboko (fish paste), nori (seaweed paste), tsukudani (simmered foods in soy sauce), dried bonito flakes, salted fish, smoked salmon, and spicy cod roe, fruit pulp such as peaches, mandarin oranges, pineapples, apples, pears, and cherries, vegetables such as corn, asparagus, mushrooms, onions, carrots, radishes, and potatoes, prepared foods such as frozen and chilled prepared foods, including hamburger steaks, meatballs, fried seafood, gyoza (dumplings), and croquettes, dairy products such as butter, margarine, cheese, cream, instant creamy powder, and infant formula, liquid seasonings, retort curry, and pet food. They can also be used as packaging materials for cigarettes, disposable body warmers, infusion packs, and other pharmaceuticals, cosmetics, and vacuum insulation materials.

[0131] (Apparatus) In the recycling method of the present invention, a laminate or packaging material is melted and kneaded in a state in which a first substrate and a second substrate are bonded together by an adhesive layer. The extrusion device used in the recycling method of the present invention may be any device capable of melting and kneading a general thermoplastic resin and then extruding it. The extrusion device has a supply port for supplying a material such as a thermoplastic resin, a melt-kneading section for melting and kneading the material supplied from the supply port, and a discharge section for discharging the material melted and kneaded in the melt-kneading section. The extrusion device may be equipped with a pelletizer for shredding the material discharged from the discharge section to a predetermined length. It may also be equipped with a cooling section for cooling.

[0132] The melt-kneading section includes, for example, a cylinder with a screw disposed therein and a heat source such as an electric heater. A discharge section is provided at the tip of the cylinder. The cylinder may be provided with a supply port such as a hopper for supplying materials. In addition, to prevent foreign matter from being mixed into the pellets described below, a screen mesh is preferably provided inside the cylinder closer to the tip than the screw.

[0133] In the melt-kneading section, shearing action caused by the rotation of the screw arranged inside the cylinder and heating by an electric heater or the like generates shear heat from the material itself, melting and kneading the material. The material melted and kneaded in the melt-kneading section passes through a screen mesh that is installed as needed and is discharged from the discharge section. The discharge section may be provided with a die having a predetermined shape. The material discharged from the discharge section solidifies or loses its fluidity by cooling, becoming recycled plastic.

[0134] The screw configuration is not particularly limited. For example, it may have a known structure such as a single-screw extruder, a twin-screw extruder, or a rotor-type twin-screw kneader. In one embodiment, the screw diameter is 25 to 400 mm, preferably 50 to 300 mm, and more preferably 100 to 250 mm. In one embodiment, the screw effective length (L / D) is 15 to 45, preferably 20 to 40, and more preferably 25 to 35. In the screw effective length (L / D), L represents the screw length, and D represents the screw diameter.

[0135] The cylinder diameter is larger than the screw diameter, and there is usually a gap between them. In one embodiment, the size of the gap is 0.01 to 1 mm, preferably 0.05 to 0.7 mm, and more preferably 0.1 to 0.5 mm.

[0136] In one embodiment, the screw compression ratio is 2 to 5, preferably 2.5 to 4.5, and more preferably 3.4 to 3.7. The screw compression ratio refers to the ratio (V1 / V2) of the volume per pitch of the screw groove near the supply portion of the recycled plastic material (V1) to the volume per pitch of the screw groove near the discharge portion (V2).

[0137] The material constituting the screw is not particularly limited, and known materials can be used. From the viewpoint of preventing the inclusion of foreign matter due to wear, the screw is preferably made of stainless steel. The surface of the screw can be subjected to various treatments. Examples include nitriding, quenching, and powder metal quenching. From the viewpoint of wear prevention, it is preferable to apply powder metal quenching. As a combination of the constituting material and surface treatment of the screw, a form in which stainless steel is subjected to powder metal quenching is more preferable.

[0138] Examples of the screen mesh include plain weave, twill weave, plain tatami weave, and twill tatami weave, as well as punched metal types. Considering the pressure and clogging of the discharge port, the screen mesh size is preferably 40 mesh or larger, more preferably 80 mesh or larger, and even more preferably 120 mesh or larger. In one embodiment, the screen mesh size is 250 mesh or smaller, preferably 200 mesh or smaller.

[0139] (Melting and Kneading Process) In the method for producing recycled plastics of the present invention, the laminate or packaging material is heated and melted, and then further kneaded. The melting temperature can be adjusted taking into consideration the glass transition temperature and melting temperature of the resin, the shape during pelletization, the pressure applied during the molding process, and the like. For example, it is 120°C to 280°C, preferably 160 to 250°C. For example, the screw rotation speed during kneading is 50 rpm to 900 rpm, preferably 80 rpm to 800 rpm, and more preferably 100 to 500 rpm. For example, the shear rate of the screw is 200 to 4000 / sec, preferably 300 to 3500 / sec, and more preferably 400 to 3000 / sec.

[0140] The filling rate of the laminate and packaging material in the extrusion device is, for example, 50 to 100% by volume, preferably 65 to 95% by volume, and more preferably 80 to 90% by volume, relative to the void volume in the extrusion device. The void volume in the extrusion device refers to the cylinder volume minus the screw volume.

[0141] (Pelletization) The melt-kneaded laminate or packaging material is extruded from an extruder, cooled, and shredded to form pellets of the recycled plastic of the present invention. The discharge rate of the extruder can be appropriately adjusted depending on the size of the extruder, the production volume, etc.

[0142] The resin pressure at the tip discharge section of the extrusion device (hereinafter also referred to as discharge pressure) is preferably 18 MPa or less, more preferably 15 MPa or less, even more preferably 10 MPa or less, and particularly preferably 8 MPa or less. In one embodiment, the resin discharge pressure at the tip discharge section is 0.1 MPa or more, preferably 1 MPa or more, and more preferably 2 MPa or more.

[0143] Examples of pelletizing methods include, but are not limited to, hot cutting and strand cutting. Examples of cooling methods include air cooling, wind cooling, and water cooling. In the present invention, it is preferable to include a water cooling step. For example, cooling to 20°C to 80°C is preferable, and cooling to 30°C to 60°C is more preferable.

[0144] (Additives, etc.) The recycled plastic obtained by the recycling method of the present invention may contain known additives. Such additives include at least one antioxidant selected from the group consisting of phenolic and phosphorus-based additives; at least one lubricant selected from the group consisting of fatty acid amides, alkylene fatty acid amides, metal soaps, and esters; hindered amine weathering stabilizers; waxes having an acid value of 5 mg KOH / g or less; and at least one antistatic agent selected from the group consisting of fatty acid sulfonates and fatty acid esters.

[0145] The recycled plastic of the present invention may contain virgin plastic as a raw material in addition to the laminate and packaging material described above. The virgin plastic to be added is of the same resin type as that of the first substrate and the second substrate. The virgin plastic may be added when pelletizing the laminate and packaging material, or when molding the pelletized recycled plastic of the present invention. The virgin plastic may be added both when pelletizing and when molding the recycled plastic. The amount of virgin plastic used in combination when pelletizing the laminate and packaging material is, for example, in a laminate / packaging material:virgin plastic ratio range of 100:0 to 25:75 (mass ratio). The amount of virgin plastic used when molding the pelletized recycled plastic of the present invention is, for example, in a recycled plastic:virgin plastic ratio range of 100:0 to 25:75 (mass ratio).

[0146] (Crushing Step) Prior to the melt-kneading step, a crushing step of the laminate and packaging material may be provided. In the crushing step, the laminate is crushed (including cutting) into small rectangular pieces with sides of about 1 to 50 mm, preferably 3 to 30 mm, and more preferably 3 to 15 mm. The crushing method may be so-called wet crushing, in which crushing is performed in water or a cleaning solution, or dry crushing, in which crushing is performed in an air atmosphere in the absence of a liquid such as a solvent.

[0147] The wet crusher is not particularly limited, but is preferably a wet crusher that can crush, disperse, mix, and pump solids in a liquid simultaneously. Specifically, it is preferably a crusher that has a mechanism for crushing solids in a liquid by shear force and / or friction force, and also has a mechanism for crushing and pumping plastic films. Examples of such wet crushers include a wet crushing pump, a colloid mill, and an attritor.

[0148] The dry crusher is not particularly limited, but examples of the dry crusher that can be used include a mycoloider, a mass colloider, a ball mill, a power mill, a pin mill, an airflow crusher (jet mill), a shear friction crusher, a cutter crusher, an impact crusher (hammer mill, ball mill), a roll crusher, a homogenizer, and an ultrasonic crusher.

[0149] (Washing Process) The crushed laminate pieces and packaging material pieces are preferably subjected to a washing process before being sent to the melt-kneading process. In the washing process, the pieces are placed in a washing container storing a washing liquid such as water or an aqueous detergent solution, and stirred in the washing container to wash away organic matter (food residue, oil stains, etc.) and inorganic matter (sand, dust, etc.) adhering to the laminate. Next, the laminate pieces are transferred to a rinsing container storing rinsing water and rinsed, followed by dehydration and drying.

[0150] Dehydration methods include centrifugal dehydration. Drying methods include hot air drying. Dehydration and drying can adjust the moisture content of the laminate to be subjected to the melt-kneading process. This can prevent foaming during the production of recycled plastic. If bubbles are generated during pellet production, the pressure in the cylinder changes, causing the extrusion volume and extrusion pressure to fluctuate, which can lead to irregular pellet shapes and dimensions. Furthermore, when using the produced pellets to perform secondary molding to produce molded products, unevenness is likely to occur on the surface, which can deteriorate the surface condition of the molded product.

[0151] In one embodiment, dehydration and drying are carried out until the moisture content of the laminate to be used in the production of recycled plastic is 3% by mass or less, preferably 2% by mass or less, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less, based on the total mass of the laminate.

[0152] <Molded Products> The recycled plastic of the present invention can be used as a raw material for various plastic products. Examples of plastic products include, but are not limited to, automobile parts such as bumpers and interior materials, components for home appliances, transportation pallets and containers, containers such as bottles, hangers, stationery, pots and cups, disposable cutlery, and play equipment. The recycled plastic can also be recycled as a film, or the recycled film can be molded and used as, for example, a cushioning material for transporting fruit, but this is not limited to this. Methods for converting the recycled plastic of the present invention into a film and producing a recycled film include known methods such as T-die molding, inflation molding, solution casting molding, and calendar molding. Methods for molding the recycled film include known methods such as vacuum molding and hot press molding.

[0153] The present invention will be described in more detail below with reference to specific synthesis examples and examples, but the present invention is not limited to these examples. In the following examples, "parts" and "%" represent "parts by mass" and "% by mass", respectively, unless otherwise specified.

[0154] <Preparation of Adhesives> (Preparation of Adhesive 1) (Synthesis of Polyol Composition 1) A polyester reaction vessel equipped with a stirrer, a nitrogen gas inlet tube, a Snyder tube, and a condenser was charged with 20.98 parts of ethylene glycol, 0.12 parts of glycerin, 50.94 parts of 1,3,5-tris(2-hydroxyethyl)isocyanuric acid, and 50.41 parts of phthalic anhydride, and the mixture was gradually heated so that the temperature at the top of the distillation tube did not exceed 100°C, and the internal temperature was maintained at 220°C. When the acid value reached 1 mgKOH / g or less, the esterification reaction was terminated, yielding a polyester polyol having a number average molecular weight of 670. The hydroxyl value was 230.2 mgKOH / g. This was used as Polyol Composition 1.

[0155] (Synthesis of Polyisocyanate Composition 1) 56.53 parts of ethylene glycol, 79.48 parts of phthalic anhydride, and 0.007 parts of titanium tetraisopropoxide were charged into a polyester reaction vessel equipped with a stirrer, a nitrogen gas inlet tube, a Snyder tube, and a condenser, and the mixture was gradually heated so that the temperature at the top of the distillation tube did not exceed 100°C, and the internal temperature was maintained at 220°C. When the acid value reached 1 mgKOH / g or less, the esterification reaction was terminated, and 0.01 parts of phosphoric acid was added to obtain a polyester polyol having a number average molecular weight of 400. The hydroxyl value was 280.0 mgKOH / g.

[0156] 136.00 parts of xylylene diisocyanate was placed in a reaction vessel equipped with a stirrer, a nitrogen gas inlet tube, a Snyder tube, a cooling condenser, and a dropping funnel, and the mixture was stirred while heated to 70°C, to which 99.50 parts of the polyester polyol synthesized above was added dropwise using the dropping funnel over 2 hours, followed by stirring for a further 4 hours to obtain Polyisocyanate Composition 1. The NCO% measured in accordance with JIS-K1603 was 16.0%.

[0157] (Preparation of Adhesive 1) Polyol composition 1 and polyisocyanate composition 1 were mixed in a mass ratio of 25:100 to prepare adhesive 1. Adhesive 1 was prepared by mixing polyol composition 1 and polyisocyanate composition 1 at an isocyanate excess ratio of 3.0±0.5, and applying 10 g / m ２ Δb when the coating film applied at 225°C was heated for 30 minutes ＊ The b of the coating film was 1.5. ＊ was measured using a spectrophotometer (SE7700 manufactured by Nippon Denshoku Industries Co., Ltd., using optical fiber) under the conditions of a viewing angle of 10° and a light source D65. ＊ From b of the coating film before heating ＊ Subtract Δb of the coating film ＊ was calculated.

[0158] (Preparation of Adhesive 2) (Synthesis of Polyol Composition 2) 319 parts by mass of diethylene glycol, 121 parts by mass of 2-methyl-propanediol, and 55 parts by mass of trimethylolpropane were charged into a reaction vessel and dissolved by heating to 80°C while stirring under a nitrogen gas stream. Furthermore, 504 parts by mass of adipic acid was charged into the reaction vessel while stirring and heated to 150°C to 240°C to carry out an esterification reaction. When the acid value reached 5 mgKOH / g or less, the pressure in the reaction vessel was gradually reduced, and the reaction was carried out at 1 mmHg or less and 200 to 220°C for 1 hour to obtain a polyester polyol resin having an acid value of 0.8 mgKOH / g and a molecular weight of approximately 660 and hydroxyl groups at both ends. This was used as polyol composition 2.

[0159] (Synthesis of Polyisocyanate Composition 2) A flask equipped with a stirrer, a thermometer, and a nitrogen gas inlet tube was charged with 36 parts of 4,4'-diphenylmethane diisocyanate and 19 parts of 2,4'-diphenylmethane diisocyanate, and heated to 60°C with stirring under a nitrogen gas atmosphere. 11 parts of polypropylene glycol having a number average molecular weight of 400, 22 parts of polypropylene glycol having a number average molecular weight of 1000, and 11 parts of polypropylene glycol having a number average molecular weight of 2000 were added dropwise in several portions, and the mixture was stirred for 5 to 6 hours to complete the urethanization reaction. Polyisocyanate Composition 2 having an NCO group content of 13.5% was obtained.

[0160] (Preparation of Adhesive 2) Polyol composition 2 and polyisocyanate composition 2 were mixed in a mass ratio of 60:100 to prepare adhesive 2. Adhesive 2 was prepared by mixing polyol composition 2 and polyisocyanate composition 2 at an isocyanate excess ratio of 3.2±0.5, and applying a 10 g / m ２ Δb when the coating film applied at 225°C was heated for 30 minutes ＊ (Measurement conditions were the same as for Adhesive 1) was 10.2.

[0161] (Preparation of Adhesive 3) (Synthesis of Polyol Composition 3) A flask equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a rectifying tube, a water separator, etc. was charged with 13.3 parts of ethylene glycol, 28.5 parts of diethylene glycol, and 3.0 parts of trimethylolpropane in a reaction vessel, and the mixture was stirred under nitrogen gas introduction and heated to 100° C. At 100-110° C., 35.7 parts of adipic acid and 19.1 parts of isophthalic acid were added, and the mixture was gradually heated so that the temperature at the top of the rectifying tube did not exceed 100° C. The internal temperature was maintained at 240° C. and stirred for 8 hours to obtain a polyester polyol.

[0162] Polyol composition 3 was prepared by mixing 41.83 parts of the polyester polyol synthesized above, 8.00 parts of polyoxypropylene sorbitol ether (Sanyo Chemical Industries, Ltd., Sannix SP-750), and 0.17 parts of dimethylolpropionic acid.

[0163] (Synthesis of Polyisocyanate Composition 3) 7 parts of ethylene glycol and 35 parts of diethylene glycol were charged into a flask equipped with a stirrer, thermometer, nitrogen gas inlet tube, rectification tube, water separator, etc., and heated to 80°C while stirring under a nitrogen gas stream. 36 parts of adipic acid and 22 parts of isophthalic acid were further charged into a reaction vessel while stirring, and the reaction vessel was gradually heated so that the temperature at the top of the rectification tube did not exceed 100°C, and the internal temperature was maintained at 250°C, and an esterification reaction was carried out. When the acid value reached 12.0 mgKOH / g or less, the temperature was increased to 240°C, and the pressure inside the reaction vessel was gradually reduced, and the reaction was carried out at 40 Torr or less, to obtain a polyester polyol having an acid value of 1.0 mgKOH / g and a hydroxyl value of 84 mgKOH / g and having hydroxyl groups at both ends.

[0164] A flask equipped with a stirrer, a thermometer, and a nitrogen gas inlet tube was charged with 54 parts of a mixture of 2,2-diphenylmethane diisocyanate, 2,4-diphenylmethane diisocyanate, and 4,4'-diphenylmethane diisocyanate, and the mixture was heated to 60°C while stirring under a nitrogen gas stream. 23 parts of the polyester polyol synthesized above and 23 parts of polypropylene glycol having a number average molecular weight of 1,000 were added dropwise in several portions, and the mixture was further heated and maintained at an internal temperature of 70°C for 4 hours to carry out a urethanization reaction, yielding Polyisocyanate Composition 3 having an NCO group content of 14.7%.

[0165] (Preparation of Adhesive 3) Polyol Composition 3 and Polyisocyanate Composition 3 were mixed in a mass ratio of 50:100 to prepare Adhesive 3. Adhesive 3 was prepared by mixing Polyol Composition 3 and Polyisocyanate Composition 3 at an isocyanate excess ratio of 1.9±0.5, and applying a 10 g / m ２ Δb when the coating film applied at 225°C was heated for 30 minutes ＊ (Measurement conditions were the same as for Adhesive 1) was 26.9.

[0166] <Production of Laminate> (Example 1) Adhesive 1 was applied at 3.5 g / m to an MDOPE film (PE3K-BT) having a thickness of 25 μm. ２ (solid content), and then laminated to a 60 μm-thick LLDPE film (TUX-MC-S). After aging at 40° C. for 4 days, a laminate for Example 1 was obtained.

[0167] (Example 2) Adhesive 2 was applied at 2.0 g / m to an MDOPE film (PE3K-BT) with a thickness of 25 μm. ２ (solid content) and then laminated to a 60 μm-thick LLDPE film (TUX-MC-S). Aging was performed at 40° C. for 2 days to obtain a laminate for Example 2. (Comparative Example 1) A laminate for Comparative Example 2 was obtained in the same manner as Example 2, except that adhesive 3 was used instead of adhesive 2.

[0168] <Evaluation> (Examples, Comparative Examples) The laminates of the Examples and Comparative Examples were each pulverized in a pulverizer (DAS-20, manufactured by Daiko Seiki Co., Ltd.) to obtain pulverized laminates. In addition, a mixture of a 25 μm-thick MDOPE film (PE3K-BT) and a 60 μm-thick LLDPE film (TUX-MC-S) in a mass ratio of 30:70 was also pulverized in the pulverizer to obtain a pulverized mixture of virgin films.

[0169] The crushed laminate and the crushed virgin film mixture were mixed at a mass ratio of 50:50 and fed into the melt-kneading section of a twin-screw extruder (Kobe Steel, Ltd., Twin-screw Extruder KTX-30). The molten and kneaded resin was extruded through a 100 μm filter, cooled by immersion in cold water, and then cut with a petalizer to obtain recycled plastic pellets for the Examples and Comparative Examples. The extruder's set screw rotation speed was 300 rpm, the set temperature was 230°C, the set output was 8 kg / h, and the pressure at the output section immediately after the start of extrusion was 1.3 to 2.0 MPa.

[0170] (Reference Example) Plastic pellets were obtained in the same manner as above, except that only the virgin film crushed mixture was used.

[0171] Using a spectrophotometer (CM-5 manufactured by Konica Minolta, Inc.), the b of the pellets of the Examples, Comparative Examples, and Reference Examples was measured under the conditions of a viewing angle of 10° and a light source of D65. ＊ The b of the pellets of the reference example was measured. ＊ Based on the standard, the pellets of the examples and comparative examples were compared. ＊ Difference from: Δb ＊ The results are summarized in Table 1. ＊ For example, it is preferably 7 or less, and more preferably 5 or less.

[0172]

Claims

1. A method for recycling a laminate, comprising: melting and kneading a laminate having a first substrate, a second substrate, and an adhesive layer bonding the first substrate and the second substrate together in a state in which the first substrate and the second substrate are bonded together by the adhesive layer; wherein the adhesive layer is a cured coating film of a two-component curing adhesive containing a polyol composition (X) and a polyisocyanate composition (Y); the polyol composition and the polyisocyanate composition are mixed so that the ratio [NCO] / [OH] of the number of moles of isocyanate groups contained in the polyisocyanate composition to the number of moles of hydroxyl groups contained in the polyol composition is 0.5 to 5.0; and the polyisocyanate composition is mixed at a rate of 10 g / m ２ Δb when the coating film applied at 225°C was heated for 30 minutes ＊ A method for recycling a laminate, wherein the value of the thickness of the laminate is 15.0 or less.

2. The method for recycling a laminate according to claim 1, wherein the first substrate and the second substrate contain the same type of resin.

3. A method for recycling a laminate according to claim 1, wherein the laminate and virgin plastic made of the same resin type as the first substrate and the second substrate are melted and kneaded.

4. The method for recycling a laminate according to claim 1, wherein the Δb* is 6.5 or less.

5. The method for recycling a laminate according to claim 1, wherein the laminate includes a printed layer.

6. The method for recycling a laminate according to claim 1, wherein the melting and kneading are carried out in an extrusion device.

7. The method for recycling a laminate according to claim 1, wherein the laminate is pulverized using a wet pulverizer or a dry pulverizer.

8. Recycled plastic obtained by the method for recycling the laminate according to claim 1.

9. A plastic product molded from the recycled plastic according to claim 8.

10. A plastic product made from the recycled plastic according to claim 8 and virgin plastic of the same type of resin as said recycled plastic.

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