Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
  • B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
  • B29B17/02—Separating plastics from other materials
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D175/00—Coating compositions based on polyureas or polyurethanes; Coating compositions based on derivatives of such polymers
  • C09D175/04—Polyurethanes
  • C09D175/06—Polyurethanes from polyesters
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J5/00—Adhesive processes in general; Adhesive processes not provided for elsewhere, e.g. relating to primers

Definitions

• the present invention relates to a release agent suitable for separating laminates bonded together with an adhesive, and a method for separating laminates using the release agent.
• plastic waste including food packaging
• plastic waste including food packaging
• plastic waste including food packaging
• plastic waste including food packaging
• plastic waste including those made from synthetic resins such as polyethylene, polypropylene, polystyrene (styrofoam), polyethylene terephthalate, and polyvinyl chloride, as well as many laminated films made by layering these synthetic resin films with metal foils such as aluminum foil and then printing them with product names or other marks or decorations, and these types are all mixed together when they are collected as garbage.
• waste plastics that contain a mixture of thermoplastic and thermosetting resins can be recycled by separating them based on their specific gravity, but the ease of recovery varies depending on the resin.
• Many food packaging uses different synthetic resins bonded together with adhesives, making separation using this method difficult.
• Thermosetting resins are also generally considered difficult to recycle because they are difficult to thermally decompose. Laminated films that have been decorated with printing ink to display product names and other marks may not completely separate from the printing ink during the recycling process, and recycled products may be discolored or may still have printed patterns.
• Patent Document 1 discloses a method for separating and recovering composite plastic waste, which comprises the steps of using triethylene glycol as a separation solvent, adding an alkali metal hydroxide as a catalyst, heating the triethylene glycol to 250-280°C, which is close to the boiling point of 200°C or more, and melting component P1 that can melt in triethylene glycol, dissolving or depolymerizing component P2 that is difficult to melt under stirring in triethylene glycol heated to 250-280°C and discharging it together with the solvent, recovering the remaining meltable component P1 and reinforcing fiber F or metal component M, recovering non-melted component P2 and separation solvent, distilling the separation solvent under reduced pressure to separate it from non-melted component P2, and purifying and reusing it.
• the present invention aims to provide a release agent and a method for separating laminates that can easily separate adhesively laminated laminates present in plastic composite waste into single-layer films even under mild conditions.
• the present invention relates to a stripping agent that contains water (A), a basic compound (B), and a hydrophilic alcohol (C), in which the content of the basic compound (B) is 0.01% by mass or more and 5% by mass or less, and the content of the hydrophilic alcohol (C) is 1% by mass or more and less than 60% by mass.
• laminated bodies that are mixed in with plastic composite waste and are bonded with an adhesive can be easily separated into single-layer films even under mild conditions.
• the stripping agent of the present invention contains water (A), a basic compound (B), and a hydrophilic alcohol (C).
• the stripping agent of the present invention will be described in detail below.
• Water (A) As the water (A) used in the stripping agent of the present invention, pure water such as tap water, ion-exchanged water, ultrafiltered water, reverse osmosis water, distilled water, or ultrapure water can be used. From the viewpoint of long-term storage, it is preferable to use water sterilized by ultraviolet irradiation or addition of hydrogen peroxide, etc., since this can prevent the growth of mold or bacteria. In addition, it is preferable to use water with a hardness of 120 ppm or less, and more preferable to use water with a hardness of 80 ppm or less.
• the content of water (A) used in the stripping agent of the present invention can be adjusted as appropriate, but as an example, it is preferably 35% by mass or more and 90% by mass or less.
• Basic Compound (B) examples include sodium hydroxide, potassium hydroxide, sodium carbonate, calcium hydroxide, etc.
• concentration of the basic compound (B) is 0.01% by mass or more and 5% by mass or less.
• the basic compound (B) is adjusted so that the pH of the stripping agent of the present invention is about 10 to 14.
• the hydrophilic alcohol used in the stripping agent of the present invention is an aliphatic alcohol that can be mixed with water at any ratio.
• examples of the hydrophilic alcohol (C) include methanol, ethanol, 1-propanol, 2-propanol, ethylene glycol, and glycerin. These can be used alone or in combination of two or more kinds, and it is preferable to use ethanol.
• the content of hydrophilic alcohol (C) is 1% by mass or more and less than 60% by mass of the release agent. If the content of hydrophilic alcohol (C) is less than 1% by mass, it may take a long time to peel off the laminate. If the content of hydrophilic alcohol (C) exceeds 60% by mass, the ability to peel off the laminate gradually decreases.
• the content of hydrophilic alcohol (C) is more preferably 5% by mass or more and less than 60% by mass of the release agent, more preferably 10% by mass or more and less than 60% by mass, and even more preferably 25% by mass or more and less than 60% by mass.
• the release agent of the present invention preferably contains a terpene compound (D).
• a terpene compound (D) a conventionally known compound can be used, and examples of such compounds include monoterpenes such as ⁇ -pinene, ⁇ -pinene, limonene, ⁇ -phellandrene, ⁇ -terpinene, ⁇ -terpinene, aucimene, myrcene, camphene, terpinolene, sylvestrene, sabinene, carene, tricyclene, and fentchene, sesquiterpenes such as longifolene, caryophyllene, bisabolene, santalene, zingiberene, curcumene, cadinene, sesquibenihene, and cedrene, and diterpenes such as camp
• Monoterpene alcohols such as ⁇ -citronellol, geraniol, nerol, linalool, terpineol, carpeol, thuyl alcohol, pinocampheol, and fenchyl alcohol; sesquiterpene alcohols such as farnesol, nerolidol, casinol, eudesmol, guayol, baturyl alcohol, carotol, lanceol, and kessoglycol; terpene alcohols such as diterpene alcohols such as phytol, sclareol, manol, hinokitiol, ferruginol, and totarol;
• Terpene aldehydes such as citronellal, citral, cyclocitral, safranal, ferrandolal, and perillaldehyde,
• monoterpene ketones such as dagetone, ionone, irone, carbomentone, carbotanacetone, piperitenone, thujone, and calone; sesquiterpene ketones such as cyperone, eremophilone, and zerumbone; and terpene ketones such as sugiol and ketomanoyl oxide.
• terpene hydrocarbons and it is more preferable to use limonene.
• the content of the terpene compound (D) can be adjusted as appropriate, but as an example, it is 0.1% by mass or more and 90% by mass or less of the stripping agent.
• the content of the terpene compound (D) is more preferably 1% by mass or more of the stripping agent, and more preferably 5% by mass or more. Also, the content of the terpene compound (D) is more preferably 50% by mass or less of the stripping agent.
• the stripping agent of the present invention may contain compounds other than those mentioned above, for example, surfactants.
• surfactants include anionic surfactants such as alkylbenzenesulfonates, alkylphenylsulfonates, alkylnaphthalenesulfonates, higher fatty acid salts, sulfate ester salts of higher fatty acid esters, sulfonates of higher fatty acid esters, sulfate ester salts and sulfonates of higher alcohol ethers, higher alkyl sulfosuccinates, polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfates, alkyl phosphates, and polyoxyethylene alkyl ether phosphates;
• Nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyglycerin fatty acid esters, sucrose fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene fatty acid amides, fatty acid alkylol amides, alkyl alkanol amides, acetylene glycol, oxyethylene adducts of acetylene glycol, and polyethylene glycol polypropylene glycol block copolymers,
• silicone surfactants such as polysiloxane oxyethylene adducts
• fluorosurfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and oxyethylene perfluoroalkyl ethers
• biosurfactants such as spiculisporic acid, rhamnolipids, and lysolecithin.
• surfactants can be used alone or in combination of two or more.
• the amount added is preferably in the range of 0.001 to 2 mass % of the total amount of the stripping agent, more preferably 0.001 to 1.5 mass %, and even more preferably 0.01 to 1 mass %.
• the method for separating the laminate of the present invention includes a step of immersing the laminate in the release agent of the present invention (hereinafter also referred to as an immersion step).
• an immersion step By immersing in the release agent of the present invention for a certain period of time, the adhesive or printing ink is peeled off from the laminate, and the laminate can be separated into a single layer film.
• the immersion time is not particularly limited, but is, for example, 10 minutes or more and less than 5 hours.
• This step may be performed only once or multiple times.
• the stripping agents used may be the same or different.
• a stripping agent containing water (A), a basic compound (B), and a hydrophilic alcohol (C) but not a terpene compound (D) may be used
• a stripping agent containing water (A), a basic compound (B), a hydrophilic alcohol (C), and a terpene compound (D) may be used.
• the stripping agent used in the first immersion step and the stripping agent used in the second immersion step may differ in the compounds used in any one or more of the water (A), basic compound (B), hydrophilic alcohol (C), and terpene compound (D), or the amount of any one or more of these compounds may be different.
• the release agent is preferably heated to a temperature range of 20° C. to 90° C., more preferably 40° C. to 90° C. This can shorten the separation time of the laminate.
• the heating method There is no particular limitation on the heating method, and known heating methods using heat rays, infrared rays, microwaves, etc. can be used.
• the treatment tank used in the immersion step is preferably provided with a reflux condenser for refluxing the heated and evaporated stripping agent.
• the release agent is preferably stirred when the laminate is immersed.
• Stirring methods include, for example, mechanical stirring of the dispersion of the laminate film contained in the treatment tank using a stirring blade, water flow stirring using a water flow pump, and bubbling with an inert gas such as nitrogen gas. Several methods may be used in combination. This allows the laminate to be separated more efficiently.
• ultrasonic vibrations may be applied to the stripping solution.
• an ultrasonic vibrator may be attached to the treatment tank to apply ultrasonic vibrations.
• a crushing step of the laminate Prior to the step of immersing the laminate in the release agent, a crushing step of the laminate may be provided. This allows the end surface of the laminate in contact with the release agent to be increased, and the peeling time of the laminate to be shortened.
• the separated laminate may be subsequently separated by gravity sorting or the like, and in this case, it is preferable that the film pieces are not too small. Taking these into consideration, it is preferable that in the crushing step, the laminate is crushed (including cutting) into small rectangular pieces with one side of about 5 to 60 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 liquid such as a solvent.
• wet crusher While there is no particular limitation on the wet crusher, a wet crusher that can simultaneously crush, disperse, mix, and pump solids in a liquid is preferred. Specifically, a crusher having a mechanism for crushing solids in a liquid using shear force and/or friction force is preferred, and a crusher having a mechanism for crushing and pumping plastic films is also preferred. Examples of such wet crushers include wet crushing pumps, colloid mills, and grinders.
• dry crusher there are no particular limitations on the dry crusher, but examples that can be used include mycoloiders, mass colloiders, ball mills, power mills, pin mills, airflow crushers (jet mills), shear friction crushers, cutter crushers, impact crushers (hammer mills, ball mills), roll crushers, homogenizers, ultrasonic crushers, etc.
• the crushed laminate pieces are preferably subjected to a washing step before being sent to the immersion step.
• the pieces are placed in a washing vessel storing a washing liquid such as water or an aqueous detergent solution, and stirred in the washing vessel to wash away organic matter (food residue, oily stains, etc.) and inorganic matter (sand, dust, etc.) adhering to the laminate.
• the laminate pieces are transferred to a rinsing vessel storing rinsing water to be rinsed, and then drained.
• the release agent that has been through the immersion process contains floating or dissolved adhesive and printing ink that have been peeled off from the laminate, film pieces that have become a single layer when the laminate has been separated by peeling off the adhesive, and metal pieces (if the laminate contains a metal layer or a metal vapor deposition layer). In the separation and recovery process, these are removed from the release agent and separated and recovered.
• floatation separation is used to separate plastics with light specific gravity such as polyolefins such as polypropylene and polyethylene (floating matter) from heavy materials such as condensed synthetic films such as polyester and nylon, which have a higher specific gravity than polyolefins, or metal foil, and the heavy materials are removed.
• the recovered plastics are then washed and dehydrated, and plastics with different specific gravities are separated by centrifugation.
• plastic isolates containing vinyl chloride resins and polyethylene terephthalate with a specific gravity of 1 or more that sink in water can be separated from plastic isolates containing olefin-based resins such as polyethylene and polypropylene that do not contain vinyl chloride resin.
• the laminate separation method of the present invention may include a step other than those described above.
• polystyrene dissolves in an organic solvent such as limonene, and a step of removing a resin that dissolves in a specific organic solvent in advance may be provided.
• Laminate Various resin films are used in the manufacture of laminates used for packaging food and daily necessities, but the method for separating a laminate of the present invention is effective for all laminates for packaging food and daily necessities.
• resin films used in the manufacture of such laminates include polyethylene terephthalate (PET) films, polystyrene films, polyamide films, polyacrylonitrile films, polyethylene films (LLDPE: low density polyethylene film, HDPE: high density polyethylene film, MDOPE: uniaxially oriented polyethylene film, OPE: biaxially oriented polyethylene film), polypropylene films (CPP: non-oriented polypropylene film, OPP: biaxially oriented polypropylene film), polyolefin films such as gas barrier films in which an olefin-based heat-sealable resin layer is provided on one or both sides of a resin having gas barrier properties such as ethylene-vinyl alcohol copolymers and polyvinyl alcohol, polyvinyl alcohol films, and ethylene-vinyl
• Biomass films are sold by various companies, and for example, sheets such as those listed in the list of biomass certified products listed by the Japan Organics Resources Association can be used.
• biomass films include those that use biomass-derived ethylene glycol as a raw material.
• Biomass-derived ethylene glycol is made from ethanol (biomass ethanol) produced from biomass as a raw material.
• biomass-derived ethylene glycol can be obtained by converting biomass ethanol into ethylene oxide using a conventionally known method to produce ethylene glycol.
• Commercially available biomass ethylene glycol may also be used; for example, biomass ethylene glycol available from India Glycoal Limited can be suitably used.
• films containing biomass polyester, biomass polyethylene terephthalate, etc. in which biomass-derived ethylene glycol is used as the diol unit and fossil fuel-derived dicarboxylic acid is used as the dicarboxylic acid unit, are known.
• the dicarboxylic acid unit of the biomass polyester uses a dicarboxylic acid derived from a fossil fuel.
• a dicarboxylic acid an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, and a derivative thereof can be used without limitation.
• the copolymer polyester may be a copolymer polyester containing a copolymer component as a third component, such as a bifunctional oxycarboxylic acid or at least one polyfunctional compound selected from the group consisting of a trifunctional or higher functional polyhydric alcohol, a trifunctional or higher functional polycarboxylic acid and/or anhydride thereof, and a trifunctional or higher functional oxycarboxylic acid, in order to form a crosslinked structure.
• a copolymer component as a third component, such as a bifunctional oxycarboxylic acid or at least one polyfunctional compound selected from the group consisting of a trifunctional or higher functional polyhydric alcohol, a trifunctional or higher functional polycarboxylic acid and/or anhydride thereof, and a trifunctional or higher functional oxycarboxylic acid, in order to form a crosslinked structure.
• biomass polyolefin films such as biomass polyethylene films containing polyethylene resins made from biomass-derived ethylene glycol and biomass polyethylene-polypropylene films are also known.
• the polyethylene-based resin is not particularly limited except that ethylene glycol derived from biomass is used as a part of the raw material.
• examples of the polyethylene-based resin include an ethylene homopolymer and a copolymer of ethylene and an ⁇ -olefin containing ethylene as a main component (ethylene- ⁇ -olefin copolymer containing 90% by mass or more of ethylene units), and these can be used alone or in combination of two or more.
• the ⁇ -olefin constituting the copolymer of ethylene and ⁇ -olefin is not particularly limited, and examples thereof include ⁇ -olefins having 4 to 8 carbon atoms, such as 1-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene.
• Known polyethylene resins such as low-density polyethylene resins, medium-density polyethylene resins, and linear low-density polyethylene resins, can be used.
• linear low-density polyethylene resins (LLDPE) (copolymers of ethylene and 1-hexene, or copolymers of ethylene and 1-octene) are preferred, and linear low-density polyethylene resins having a density of 0.910 to 0.925 g/cm 3 are more preferred.
• Biomass films that use biomass raw materials and are classified according to the biomass plastic degree specified by ISO 16620 or ASTM D6866 are also on the market.
• Radioactive carbon-14C exists in the atmosphere at a ratio of 1 in 1012 particles, and this ratio is the same for atmospheric carbon dioxide, so this ratio remains the same even in plants that fix this carbon dioxide through photosynthesis.
• the carbon in plant-derived resins contains radioactive carbon-14C.
• 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 with an accelerator mass spectrometer, the proportion of plant-derived resin in the resin, i.e., the biomass plastic degree, can be determined.
• plant-derived low-density polyethylene which is a biomass plastic with a biomass plastic content of 80% or more, preferably 90% or more as specified by ISO16620 or ASTM D6866
• examples of plant-derived low-density polyethylene 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.
• films and sheets containing starch, a biomass raw material, and polylactic acid are also known. These can be selected and used as appropriate depending on the application.
• the biomass film may be a laminate of multiple biomass films, or a laminate of a conventional petroleum-based film and a biomass film. These biomass films may be unstretched or stretched films, and there are no limitations on the manufacturing method.
• the film may be one that has been stretched.
• a typical stretching method involves melt-extruding a resin into a sheet using an extrusion film-making method or the like, followed by simultaneous biaxial stretching or sequential biaxial stretching.
• sequential biaxial stretching it is common to first perform longitudinal stretching, and then transverse stretching. Specifically, a method that combines longitudinal stretching using the speed difference between rolls and transverse stretching using a tenter is often used.
• the film surface may be subjected to various surface treatments such as flame treatment or corona discharge treatment to ensure that an adhesive layer is formed that is free of defects such as film breaks or repellency.
• inorganic vapor deposition films such as metal vapor deposition films with a vapor deposition layer of a metal such as aluminum, transparent vapor deposition films with a vapor deposition layer of a metal oxide such as silica or alumina, and barrier films containing a gas barrier layer such as polyvinyl alcohol, ethylene-vinyl alcohol copolymer, vinylidene chloride, etc. may be used.
• the vapor deposition layer is dissolved by the basic compound (C) contained in the release agent, making it easier to peel the printing layer and adhesive from the resin film.
• the present invention can also be applied to a laminate in which a resin film and paper are bonded together.
• the paper can be any known paper base material without any particular limitations. Specifically, the paper is manufactured using natural fibers for papermaking such as wood pulp in a known papermaking machine, but the papermaking conditions are not particularly regulated. Examples of natural fibers for papermaking include wood pulp such as softwood pulp and hardwood pulp, non-wood pulp such as Manila hemp pulp, sisal hemp pulp, and flax pulp, and pulps obtained by chemically modifying these pulps. Types of pulp that can be used include chemical pulp produced by sulfate cooking, acidic/neutral/alkaline sulfite cooking, soda salt cooking, etc., ground pulp, chemi-ground pulp, thermomechanical pulp, etc. In addition, various commercially available fine papers, coated papers, backing papers, impregnated papers, cardboard, and paperboard can also be used.
• adhesives used in the manufacture of laminates for packaging food and daily necessities are two-component curing urethane adhesives containing a polyol composition and a polyisocyanate composition.
• the release agent of the present invention not only effectively removes such adhesives under mild conditions, but also effectively separates laminates that have been bonded together using adhesives with a different curing system than urethane adhesives, such as a two-component curing adhesive consisting of a resin with an acid anhydride group and a curing agent with an active hydrogen group such as an amino group or a hydroxyl group.
• a so-called one-component curing adhesive in which an isocyanate group is introduced at the end of the polyol and the adhesive cures due to moisture in the air.
• the cured coating of the adhesive prefferably has an acid value, as this makes it easier to peel off the laminate.
• the adhesive used to manufacture the laminate is a urethane-based two-component curing adhesive
• the cured coating of the adhesive can be made to have an acid value by a method of acid-modifying at least a portion of the terminals of the polyol compound contained in the polyol composition, or by a method of adding a compound having an acid value to the adhesive.
• the printed layer is formed by a general printing method that has been used for printing on polymer films using various printing inks such as gravure ink, flexographic ink, offset ink, stencil ink, and inkjet ink.
• the release agent of the present invention and the method for separating a laminate using the release agent can satisfactorily separate a printed layer using various inks from the laminate.
• the printed layer is formed using a deinking ink (a printing ink designed to be easily peeled from a resin film by immersion in a basic solution), since this makes it easier to peel from the laminate in a shorter time.
• the laminate has a primer layer between the resin film and the printed layer.
• a primer layer By providing a primer layer, the adhesion between the printed layer and the resin film can be improved.
• the primer layer is formed from a composition designed to be easily peeled off from the resin film by immersion in a basic solution, it is preferable because it can be easily peeled off from the laminate in a shorter time.
• Such compositions include, but are not limited to, compositions containing a resin having an acidic group and compositions containing an additive having an acidic group.
• a composition designed to be easily peeled off from the resin film by immersion in a basic solution hereinafter also referred to as a removable primer
• a removable primer is one that contains a urethane resin and an aqueous medium.
• the urethane resin used in such a removable primer is a reaction product of a composition containing a polyester polyol and a polyisocyanate, which contains an aromatic dicarboxylic acid as a raw monomer for the polyester polyol, has an aromatic ring concentration of 1 mmol/g or more derived from the aromatic dicarboxylic acid (a raw material for the polyester polyol), has an ester bond concentration of 1 mmol/g or more, and has an acid value of 8 to 45 mg KOH/g.
• Aromatic dicarboxylic acids used as raw material monomers for polyester polyols include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, 1,2-bis(phenoxy)ethane-P,P'-dicarboxylic acid, and their acid anhydrides or ester-forming derivatives, aromatic hydroxycarboxylic acids such as p-hydroxybenzoic acid and their ester-forming derivatives, and sulfonic acid group-containing aromatic dicarboxylic acids such as 5-sulfoisophthalic acid and their ester-forming derivatives.
• aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, 1,4-naphthalenedicarboxylic acid, 2,
• the raw material monomers for polyester polyol may contain aliphatic carboxylic acids or alicyclic carboxylic acids.
• carboxylic acids include aliphatic dicarboxylic acids such as succinic acid, succinic anhydride, adipic acid, suberic acid, azelaic acid, sebacic acid, dimer acid, maleic anhydride, and fumaric acid, and alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, as well as their anhydrides or ester-forming derivatives. These may be used alone or in combination of two or more.
• Polyols used as raw material monomers for polyester polyols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 1,2-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,5-hexanediol, 2,5-hexanediol, 1,6-hexanediol, 1,7-heptanediol, and neopentyl glycol.
• Polyester polyols are obtained by reacting these raw material monomers at 100°C to 300°C under normal or reduced pressure conditions in a reaction vessel purged with an inert gas such as nitrogen.
• catalysts such as acetates of alkali metals or alkaline earth metals, or compounds containing zinc, manganese, cobalt, antimony, germanium, titanium, tin, zirconium, etc. can be used. It is preferable to use tetraalkyl titanates or tin oxalate, which are effective in transesterification reactions and polycondensation reactions.
• the urethane resin used in the removable primer is obtained by reacting a composition containing the polyester polyol obtained as described above and a polyisocyanate in the absence of a solvent or in the presence of an organic solvent.
• the organic solvent is removed as necessary when dispersing the urethane resin in an aqueous medium.
• the method for removing the organic solvent is a method by distillation.
• the polyisocyanate used in the synthesis of the urethane resin may be an aromatic diisocyanate such as phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, or naphthalene diisocyanate, or an aliphatic or alicyclic structure-containing diisocyanate such as hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate, or tetramethylxylylene diisocyanate, either alone or in combination of two or more.
• aromatic diisocyanate such as phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, or naphthalene diisocyanate
• polyester polyols When synthesizing the urethane resin, other polyols may be used in addition to the polyester polyol.
• the polyols that can be used in combination with the polyester polyol include the same polyols as those exemplified as raw material monomers for the polyester polyol.
• a chain extender When synthesizing the urethane resin, a chain extender may be used in combination.
• the chain extender include diamines such as ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, piperazine, 2,5-dimethylpiperazine, isophoronediamine, 4,4'-dicyclohexylmethanediamine, 3,3'-dimethyl-4,4'-dicyclohexylmethanediamine, and 1,4-cyclohexanediamine; N-hydroxymethylaminoethylamine, N-hydroxyethylaminoethylamine, N-hydroxypropylaminopropylamine, N-ethylaminoethylamine, N-methylaminopropylamine; Diethylenetriamine, dipropylenetriamine, triethylenetetramine; Hydrazine, N,N'-dimethylhydrazine, 1,6-hexamethylenebishydrazine; Su
• Glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, hexamethylene glycol, neopentyl glycol, sucrose, methylene glycol, glycerin, and sorbitol; Phenols such as bisphenol A, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, hydrogenated bisphenol A, and hydroquinone; and water.
• the chain extender may be used when reacting the polyester polyol with the polyisocyanate, or may be used after the polyester polyol and the polyisocyanate have reacted. It may also be used when dispersing the urethane resin in an aqueous medium.
• the aromatic ring concentration of the urethane resin derived from aromatic dicarboxylic acid is calculated from the number of moles of aromatic rings derived from aromatic dicarboxylic acid contained in 1 g of the urethane resin.
• the aromatic ring concentration of the urethane resin is preferably 1.5 mmol/g or more, and more preferably 2 mmol/g or more.
• it is preferably 6 mmol/g or less, and more preferably 5 mmol/g or less.
• the ester bond concentration of the urethane resin is calculated from the number of moles of ester bonds contained in 1 g of the urethane resin. From the viewpoint of improving the adhesion to the substrate and releasability of the primer layer, it is preferably 2 mmol/g or more, and more preferably 4 mmol/g or more. From the viewpoint of blocking resistance of the primer layer, it is preferably 9 mmol/g or less, and more preferably 7 mmol/g or less.
• the acid value of a urethane resin is the amount of acid in 1 g of resin calculated by titrating the acid with an alkali, converted into mg of potassium hydroxide, and can be measured by the method described in JIS K0070. If the acid value is 8 mgKOH/g or more, the water dispersion stability can be improved, and 15 mgKOH/g or more is preferable, and 20 mgKOH/g or more is more preferable. If the acid value is 45 mgKOH/g or less, good adhesion to the substrate can be ensured, and 40 mgKOH/g or less is preferable, and 30 mgKOH/g or less is more preferable.
• the value obtained by dividing the mass of the raw material monomer of the polyisocyanate contained in 1 g of the urethane resin by the NCO equivalent weight of the raw material monomer of the polyisocyanate (a2) is preferably 1.0 to 6.0 mmol/g.
• the content is preferably 1.5 mmol/g or more, and more preferably 1.8 mmol/g or more.
• the content is preferably 5.0 mmol/g or less, and more preferably 4.0 mmol/g or less.
• the weight average molecular weight of the urethane resin is preferably 10,000 to 100,000. From the viewpoints of blocking resistance to the substrate and hydrolysis stability of the resin, it is preferably 20,000 or more, and more preferably 30,000 or more. Also, from the viewpoints of low viscosity when dispersed in an aqueous medium and productivity, it is preferably 80,000 or less, and more preferably 60,000 or less.
• the weight average molecular weight of the urethane resin is a value measured by gel permeation chromatography (GPC) under the following conditions.
• Measurement apparatus high-speed GPC apparatus ("HLC-8220GPC” manufactured by Tosoh Corporation) Column: The following columns manufactured by Tosoh Corporation were used, connected in series.
• “TSKgel G5000” (7.8mm I.D. x 30cm) x 1 "TSKgel G4000" (7.8mm I.D. x 30cm) x 1 "TSKgel G3000” (7.8mm I.D. x 30cm) x 1 "TSKgel G2000" (7.8mm I.D.
• the glass transition temperature of the urethane resin is preferably 0 to 110°C.
• Aqueous media include water, water-miscible organic solvents, and mixtures thereof.
• organic solvents that are miscible with water include alcohols such as methanol, ethanol, n- and isopropanol; ketones such as acetone and methyl ethyl ketone; polyalkylene glycols such as ethylene glycol, diethylene glycol, and propylene glycol; alkyl ethers of polyalkylene glycol; and N-methyl-2-pyrrolidone.
• water alone or a mixture of water and an organic solvent miscible with water is preferred, and water alone is particularly preferred.
• the urethane resin is dispersed in the aqueous medium by a known method. If necessary, a machine such as a homogenizer can be used.
• the removable primer preferably contains a urethane resin in the range of 5% by mass to 50% by mass, and more preferably in the range of 10% by mass to 25% by mass.
• the removable primer preferably contains an aqueous medium in the range of 50% by mass to 95% by mass, and more preferably contains an aqueous medium in the range of 75% by mass to 90% by mass.
• the removable primer may contain various additives, such as a film-forming assistant, a crosslinking agent, a curing accelerator, a plasticizer, an antistatic agent, a wax, a light stabilizer, a flow adjuster, a dye, a leveling agent, a rheology control agent, an ultraviolet absorber, an antioxidant, a photocatalytic compound, an inorganic pigment, an organic pigment, and an extender pigment, as necessary.
• a film-forming assistant such as a crosslinking agent, a curing accelerator, a plasticizer, an antistatic agent, a wax, a light stabilizer, a flow adjuster, a dye, a leveling agent, a rheology control agent, an ultraviolet absorber, an antioxidant, a photocatalytic compound, an inorganic pigment, an organic pigment, and an extender pigment, as necessary.
• a film-forming assistant such as a film-forming assistant, a crosslinking agent, a curing accelerator, a plasticizer, an antistatic agent,
• the removable primer can also be used in combination with various crosslinking agents to form a layer with superior durability.
• the crosslinking agent include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an amino-based crosslinking agent, an aziridine-based crosslinking agent, a silane coupling agent-based crosslinking agent, a carbodiimide-based crosslinking agent, and an oxazolidine-based crosslinking agent.
• the crosslinking agent is preferably used in an amount of 30% by mass or less, and more preferably 20% by mass or less, based on the total amount of the urethane resin, from the viewpoints of improving adhesion to the substrate and improving deinking properties, etc.
• the crosslinking agent is preferably mixed and used immediately before coating the removable primer.
• Stripping solutions of the examples and comparative examples were prepared according to the compositions shown in Tables 1 and 2 using ion-exchanged water as the water (A), sodium hydroxide as the basic compound (B), ethanol as the hydrophilic alcohol (C), and limonene as the terpene compound (D).
• polyester polyol 740 parts of polyester polyol, 200 parts of isophorone diisocyanate, and 60 parts of 2,2'-dimethylolpropionic acid were charged into a four-neck flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, and reacted at 75°C for 8 hours under a nitrogen stream to obtain a urethane resin.
• the urethane resin had an aromatic ring concentration derived from the aromatic dicarboxylic acid raw material monomer of 2.8 mmol/g, an ester bond group concentration of 6.6 mmol/g, and an acid value of 25 mg KOH/g.
• Ammonia was used as a neutralizing agent, and neutralization was performed to a neutralizing agent/acid equivalent ratio of 1.05, followed by dilution with water to obtain an aqueous dispersion of the urethane resin.
• a removable primer was obtained by mixing 100 parts of urethane resin with 3 parts of "Bayhydur Ultra BU3100” manufactured by Covestro, and further diluting the mixture with isopropyl alcohol (IPA) to a solid content of 10%.
• IPA isopropyl alcohol
• a urethane-based laminating ink (DIC Corporation, Finart R794 white) was adjusted to 15 seconds (25°C) using a Rigo Zahn Cup #3, and a gravure printing machine equipped with a gravure plate with a plate depth of 43 ⁇ m was used to print the OPP film. (P2161, manufactured by Toyobo Co., Ltd.) was printed in a solid form and dried and cured by passing through an oven at 70° C. to form a printed layer. Next, a urethane-based two-component curing type laminating adhesive was applied onto the printed layer.
• the laminate was then laminated with a CPP film (P1128, manufactured by Toyobo Co., Ltd.) and aged at 40° C. for 3 days to obtain a laminate of OPP/printed layer (white)/adhesive layer/CPP.
• a CPP film P1128, manufactured by Toyobo Co., Ltd.
• OPP/printing layer (indigo)/adhesive layer/CPP A laminate of OPP/printed layer (blue)/adhesive layer was prepared in the same manner as the laminate of OPP/printed layer (white)/adhesive layer/CPP, except that a urethane-based laminating ink (Finart R507 blue, manufactured by DIC Corporation) was used. A laminate of 100% polyester/CPP was obtained.
• a urethane laminating ink (DIC Corporation, Finart R507 indigo) was adjusted to 15 seconds (25°C) using a Rigo Zahn Cup #3, and a gravure printing machine equipped with a gravure plate with a plate depth of 43 ⁇ m was used to print the OPP film.
• the printing was performed on a paper (P2161, manufactured by Toyobo Co., Ltd.) and the paper was passed through an oven at 70° C. to dry and harden the paper, forming a printed layer (indigo blue).
• the mixture was adjusted to 15 seconds (25°C) using a Zahn Cup #3 manufactured by Rigo Co., Ltd., printed on a printing layer (indigo blue) using a gravure printing machine equipped with a gravure plate having a plate depth of 43 ⁇ m, and passed through an oven at 70°C. This allowed it to dry and harden, forming a printed layer (white).
• a urethane-based two-liquid curing type laminating adhesive was applied onto the printed layer (white), and then it was laminated with a CPP film (P1128, manufactured by Toyobo Co., Ltd.). It was aged at 40°C for 3 days to obtain an OPP/printed layer (indigo)/ A laminate of printing layer (white)/adhesive layer/CPP was obtained.
• OPP/(printing layer)/adhesive layer/VMCPP A laminate of OPP/(printing layer)/adhesive layer/VMCPP was obtained in the same manner as the corresponding laminate described above, except that a VMCPP film (2203, manufactured by Toray Film Processing Co., Ltd.) was used instead of the CPP film. .
• OPP/primer layer/adhesive layer/CPP The removable primer was applied solidly to an OPP film (P2161, manufactured by Toyobo Co., Ltd.) using a gravure printing machine equipped with a gravure plate with a plate depth of 22 ⁇ m, dried for 10 minutes at 100° C., and then left at room temperature for one day to form a primer layer.
• a urethane-based two-component curing lamination adhesive was applied onto the primer layer, which was then bonded to a CPP film (P1128, manufactured by Toyobo Co., Ltd.) and aged for three days at 40° C. to obtain a laminate of OPP/primer layer/adhesive layer/CPP.
• OPP/primer layer/printing layer/adhesive layer/CPP A laminate of OPP/primer layer/printing layer/adhesive layer/CPP was obtained in the same manner as the corresponding laminate described above, except that a primer layer was provided.
• the following urethane-based two-liquid curing type laminating adhesive was used: (5210A/520B) A mixture of 10 parts of DICDRY (registered trademark) NS-5210A and 7 parts of HA-520B, both manufactured by DIC Corporation, was used. The coating amount was 2 g/ m2 .

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