CN113348093A

CN113348093A - Recovery method of plastic container and transfer printing film applied to plastic container

Info

Publication number: CN113348093A
Application number: CN202080011145.5A
Authority: CN
Inventors: 石井秀夫; 玉冈贵司; 大原伸一
Original assignee: DIC Corp
Current assignee: DIC Corp
Priority date: 2019-02-15
Filing date: 2020-02-06
Publication date: 2021-09-03
Anticipated expiration: 2040-02-06
Also published as: WO2020166474A1; AU2020223598A1; CN113348093B; JPWO2020166474A1; AU2020223598B2; JP6819828B2

Abstract

A method of recycling plastic containers, comprising: a step (1) of decorating a plastic container with a transfer film; a step (2) of recovering the decorated plastic container; and a step (3) of washing the recovered plastic container with an alkali solution and peeling off the decorative layer; a transfer printing film is applied to a plastic container, and is formed by at least sequentially laminating a decoration layer and a stripping film on a holding layer, wherein the decoration layer is alkali-soluble; a transfer printing film is applied to a plastic container, and is formed by at least sequentially laminating an adhesion layer, a decoration layer and a stripping film on a holding layer, wherein the adhesion layer is alkali-soluble; and a transfer film applied to the plastic container, which is formed by laminating at least an adhesive layer, a decoration layer, a surface protection layer and a peeling film in this order on the holding layer, wherein the adhesive layer and/or the surface protection layer are alkali-soluble.

Description

Recovery method of plastic container and transfer printing film applied to plastic container

Technical Field

The invention relates to a novel plastic container recycling method and a transfer printing film applied to the plastic container.

Background

In recent years, due to the growing awareness of environmental protection, recycling of plastic containers such as PET bottles (also referred to as polyethylene terephthalate bottles, PET and the like), coffee cups (often made of polypropylene or polystyrene) and the like is recommended.

For example, a shrink label formed in a tubular shape and provided with a perforation, a roll label, a single label, an adhesive label, or the like adhered to a bottle using an adhesive or the like is attached to a plastic container such as a PET bottle as a label which is easily peeled and removed for providing display and/or decoration of a product name or the like. For these labels, it is recommended to recycle PET bottles after peeling them off at the time of recycling classification (refer to the PET bottle recycling promotion protocol HP), but these actions are not necessarily completed by entrusting consumers to do so.

In order to improve PET bottle recovery, the following criteria are disclosed in the PET bottle independent design guidelines: the label raw material is desired to be a specific gravity, raw material which has no problem even if mixed at the time of recycling treatment; and/or the label sheet and the adhesive are not left in the bottle, and the label sheet and the adhesive can be easily peeled off by hand by reducing the adhesive coating area and amount of the label attached to the bottle using the adhesive or the like without using the aluminum-laminated label. This is a reference that labels have been required for the purpose of imparting display and/or decorativeness of trade names and the like.

Polypropylene used in coffee cups and yogurt cups has been conventionally collected as a plastic for food packaging, and then classified into polyethylene, polypropylene, polyester, and the like, and pelletized after washing for recycling (refer to japan society for packaging and recycling HP), but printed matters printed for the purpose of display of product names and the like and/or decoration cannot be completely separated, and there is a problem that coloring and the like occur in recycled plastics.

On the other hand, as a method for decorating an article, a transfer method using a transfer film is used, which enables a protective layer to be easily formed on the surface of various transfer substrates such as a synthetic resin base material, a wood base material, an inorganic base material, and a metal base material by a dry processing method. The transfer method refers to a method of: a transfer film is produced by providing a release film made of paper, a thermoplastic resin film, or the like with a pattern layer, an adhesive layer, or the like (hereinafter, these are collectively referred to as a transfer layer together with the above-mentioned protective layer) in a releasable state, and further, if necessary, with a protective layer for the purpose of protecting the transferred pattern layer, and after the transfer layer is bonded to a transfer target substrate by pressing the transfer layer surface of the transfer film against the surface of the substrate (transfer target substrate), the transfer layer is peeled off at the interface between the transfer layer and the release film to remove the release film, thereby producing a decorative article or the like for the purpose of transferring the transfer layer to the transfer target substrate. As the transfer method, a method of performing molding transfer to a three-dimensional shape by applying elongation and deformation to a transfer film at the time of thermal transfer, such as an in-mold molding transfer method of a blow molded article, a decoration injection molding simultaneous transfer method, a vacuum molding simultaneous transfer method, a polishing simultaneous transfer method, and the like, and a transfer method of not applying elongation and deformation to a transfer film, such as a thermal press, are known. (see, for example, patent document 1)

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2004-90313

Disclosure of Invention

Problems to be solved by the invention

The invention provides a method for improving the recovery rate of plastic containers such as PET bottles and a transfer film applicable to the plastic containers used in the method.

Means for solving the problems

The present inventors considered that the recovery rate would be improved without using a label such as a shrink label applied to a plastic container such as a PET bottle, and the like, without causing the action of peeling the label itself which is entrusted to a consumer, and also considered that the recovery rate could be improved by applying decoration based on a transfer film which can be peeled off by an alkaline solution used in the washing process of a PET bottle as it is instead of the label, and thereby enabling the display and/or decoration of a desired product name or the like to be applied to the plastic container, and without performing the action of peeling the label.

That is, the present invention provides a method for recycling a plastic container, comprising: a step (1) of decorating a plastic container with a transfer film; a step (2) of recovering the decorated plastic container; and a step (3) of washing the recovered plastic container with an alkali solution and peeling off the decorative part.

The present invention also provides a transfer film for use in a plastic container, wherein at least a decoration layer and a release film are laminated in this order on a holding layer, and the decoration layer is alkali-soluble.

The present invention also provides a transfer film for use in a plastic container, wherein at least an adhesive layer, a decorative layer, and a release film are sequentially laminated on a holding layer, and the adhesive layer is alkali-soluble.

The present invention also provides a transfer film for use in a plastic container, wherein at least an adhesive layer, a decorative layer, a surface protective layer and a release film are laminated in this order on a holding layer, and the adhesive layer and/or the surface protective layer are alkali-soluble.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, the recovery rate can be improved without peeling off the label while maintaining the display and/or decoration of the product name and the like required for the PET bottle.

Further, this method is a method for improving the recovery rate in the case of directly decorating a plastic container, and therefore, the method is not limited to PET bottles, and can be applied to food packaging plastics such as polypropylene used in coffee cups and yogurt cups.

Description of the drawings

Fig. 1 shows an example of a specific embodiment of the transfer film of the present invention.

Fig. 2 shows an example of a specific embodiment of the transfer film of the present invention.

Fig. 3 shows an example of a specific embodiment of the transfer film of the present invention.

Detailed Description

(Process (1) for decorating Plastic Container with transfer film)

In the present invention, a process of decorating a plastic container with a transfer film will be described with respect to a case where a PET bottle is used as the plastic container.

The transfer film used in the present invention may be a thermal transfer film used in a method of molding and transferring a three-dimensional shape by applying elongation and deformation to the transfer film at the time of thermal transfer, such as an in-mold molding transfer method, a decoration injection molding simultaneous transfer method, a vacuum molding simultaneous transfer method, a polishing simultaneous transfer method, or the like, which are known transfer methods, to a three-dimensional shape by applying elongation and deformation to the transfer film at the time of thermal transfer, a transfer method of applying elongation and deformation to the transfer film by thermal stamping or the like (for example, see patent document 1), or a thermal sublimation transfer method of forming an image by transferring a dye in a sublimation dye layer on a thermal transfer sheet and a transfer target such as a thermal transfer image receiving sheet to the dye using a heating device for controlling heat generation based on image information, using a sublimation dye as a color material (for example, see patent document 2).

Heat transfer film

Specific examples of the heat transfer film applied to, for example, an in-mold transfer method include:

(1) at least a decoration layer and a peeling film are sequentially laminated on the holding layer, and the decoration layer is an alkali-soluble transfer film;

(2) the adhesive layer is an alkali-soluble transfer film, and the adhesive layer, the decorative layer and the release film are laminated on the holding layer in sequence;

(3) and a transfer film or the like in which at least an adhesive layer, a decorative layer, a surface protective layer, and a release film are laminated in this order on the holding layer, and the adhesive layer and/or the surface protective layer are alkali-soluble.

Fig. 1 shows an example of the specific embodiment of the above (3).

Here, the alkali-soluble state means a state in which the layer is not completely dissolved when immersed in an alkali solution, and the layer is partially dissolved or swollen to such an extent that the layer is peeled off from the interface of the PET bottle after transfer. In order to bring the layer into a partially dissolved or swollen state, it is preferable that a reactive group such as a carboxyl group or a hydroxyl group and/or an ester bond capable of reacting with a base is present in the layer.

The presence of an ester bond in this layer includes, specifically, a reactive adhesive containing one or both of a polyol composition having a polyol compound such as a polyester polyol having an ester bond, a polyetherester polyol, a polyester (polyurethane) polyol, and an acrylic polyol, and a polyisocyanate composition having a polyisocyanate compound which is a reaction product of the polyol compound having an ester bond and the various polyisocyanates.

In addition, in addition to the above polyol composition and the above polyisocyanate composition, a reactive adhesive to which a resin having an ester bond and/or a compound having an acid group is added can be preferably used. The compound having an acidic group is not particularly limited as long as it can be easily mixed with the polyol composition and the polyisocyanate composition (in this case, a solvent described later may be used as needed) which are main components of the reactive adhesive, and has an acid value.

Specifically, examples thereof include: resins having an acid value such as a rosin-modified maleic acid resin and a rosin-modified fumaric acid resin; resins as radical copolymers, such as (meth) acrylic resins, styrene-maleic anhydride resins, and terpene-maleic anhydride resins, obtained by copolymerizing polymerizable monomers having a carboxyl group, such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, cinnamic acid, or acid anhydrides thereof, polymerizable monomers having a sulfonic acid group, such as sulfonated styrene, and polymerizable monomers having an acid group, such as polymerizable monomers having a sulfonamide group, such as vinylbenzenesulfonamide; the acid-modified polyolefin resin may be used alone or in combination of two or more.

The acid value of the compound having an acidic group is not particularly limited, but is preferably 150mgKOH/g or more, and more preferably 150 to 500 mgKOH/g.

The molecular weight of the compound having an acidic group is not particularly limited, and for example, the weight average molecular weight (Mw) is preferably in the range of 500 to 20000.

(holding layer)

The holding layer is not particularly limited as long as it is a film that can be provided with a transfer layer such as a decorative layer, does not cause thermal deterioration by coating, drying, dry lamination, or the like, and can be satisfactorily peeled off before thermal transfer processing. Specifically, examples thereof include: polyolefin resins such as polyethylene and polypropylene; olefin copolymer resins such as ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, ethylene- (meth) acrylic acid (ester) copolymers, and ethylene-unsaturated carboxylic acid copolymer metal neutralizers (so-called ionomer resins); acrylic resins such as polyacrylonitrile, polymethyl methacrylate, and polyethyl methacrylate; styrene resins such AS polystyrene, AS resin and ABS resin; polyethylene resins such as polyvinyl acetal, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, and vinyl chloride-vinyl acetate copolymers; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyarylate, and polycarbonate; a film made of a thermoplastic resin such as a fluorine-based resin such as polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene, or an ethylene-tetrafluoroethylene copolymer, or a film obtained by subjecting a release film layer to plasma irradiation and/or surface treatment with a release agent such as a fluorine-based compound or a silicone-based compound in order to enhance or weaken the adhesion between the film and the release film.

The thickness of the holding layer is not particularly limited, and is preferably about 10 to 200 μm in view of good printing suitability and coating suitability. More preferably 20 to 100 μm.

(adhesive layer)

Examples of the adhesive used for the adhesive layer include: examples of the adhesive include acrylic resins, polyurethane-modified polyester resins, epoxy resins, ethylene-vinyl acetate copolymer resins (EVA), vinyl chloride resins, vinyl chloride-vinyl acetate copolymer resins, natural rubbers, SBR, NBR, and synthetic rubbers such as silicone rubbers, and solvent-based, solvent-free, or aqueous emulsion adhesives diluted with organic solvents can be used.

Alternatively, the adhesive may be a reactive adhesive. The reactive adhesive is not particularly limited as long as it is a commercially available reactive adhesive, and among them, a so-called two-pack type of polyisocyanate composition and polyol composition or a one-pack type of polyisocyanate composition is particularly effective and preferable.

(reactive adhesive polyisocyanate composition)

The polyisocyanate composition used in a general reactive adhesive is a composition containing a polyisocyanate compound as a main component, and any composition known as a polyisocyanate compound for a reactive adhesive can be used without particular limitation. Specific examples of the polyisocyanate compound include: polyisocyanates having an aromatic structure in their molecular structure, such as toluene diisocyanate, diphenylmethane diisocyanate, polymeric diphenylmethane diisocyanate, 1, 5-naphthalene diisocyanate, triphenylmethane triisocyanate and xylylene diisocyanate, and compounds obtained by modifying a part of the isocyanate groups (NCO groups) of these polyisocyanates with carbodiimide; polyisocyanates having an alicyclic structure in their molecular structure, such as isophorone diisocyanate, 4' -methylenebis (cyclohexyl isocyanate), and 1, 3- (isocyanatomethyl) cyclohexane; linear aliphatic polyisocyanates such as 1, 6-hexamethylene diisocyanate, 1, 5-pentamethylene diisocyanate, lysine diisocyanate, and trimethylhexamethylene diisocyanate, and compounds obtained by modifying a part of NCO groups of these polyisocyanates with carbodiimide;

isocyanurate bodies of the above-mentioned various polyisocyanates; allophanate bodies derived from the above-mentioned various polyisocyanates; biuret derived from the above-mentioned various polyisocyanates; adducts obtained by modifying the above-mentioned various polyisocyanates with trimethylolpropane; and polyisocyanates which are reaction products of the above-mentioned various polyisocyanates with a polyol component described later.

(reactive adhesive polyol composition)

The polyol composition used in a general reactive adhesive is a composition containing a polyol compound as a main component, and any composition known as a polyol compound for a reactive adhesive can be used without particular limitation. Specific examples of the polyol compound include compounds selected from: 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, dimethylbutylene glycol, butylethylpropanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, bishydroxyethoxybenzene, 1, 4-cyclohexanediol, 1, 4-cyclohexanedimethanol, and triethylene glycol; 3-or 4-functional aliphatic alcohols such as glycerin, trimethylolpropane and pentaerythritol; bisphenols such as bisphenol a, bisphenol F, hydrogenated bisphenol a, and hydrogenated bisphenol F; a dimer diol,

Polyester polyols, polyether polyols, polyurethane polyols, polyetherester polyols, polyester (polyurethane) polyols, polyether (polyurethane) polyols, polyesteramide polyols, acrylic polyols, polycarbonate polyols, polyhydroxyalkanes, castor oil or polymer polyols in mixtures thereof.

Among them, since the reactive adhesive is easily dissolved or hydrolyzed by an alkaline solution, it is preferable that any one of the components of the reactive adhesive has an ester bond and can be easily separated into a single-layer film in a short time.

Any one of the constituent components of the reactive adhesive has an ester bond, and specific examples thereof include: and a reactive adhesive containing either or both of a polyol composition having a polyol compound such as a polyester polyol having an ester bond, a polyether polyol, a polyester (polyurethane) polyol, or an acrylic polyol, and a polyisocyanate composition having a polyisocyanate compound which is a reaction product of the polyol compound having an ester bond and the various polyisocyanates.

In addition, in addition to the above polyol composition and the above polyisocyanate composition, a reactive adhesive to which a resin having an ester bond and/or a compound having an acid group is added can be preferably used. The compound having an acid group is not particularly limited as long as it can be easily mixed with the polyol composition and the polyisocyanate composition (in this case, a solvent described later may be used as needed) which are main components of the reactive adhesive, and has an acid value.

In addition, as the reactive adhesive, additives such as pigments, silane coupling agents, titanate coupling agents, coupling agents of aluminum series and the like, adhesion promoters such as epoxy resins, leveling agents, inorganic fine particles such as colloidal silica and alumina sol, organic fine particles of polymethyl methacrylate series, antifoaming agents, anti-sagging agents, wetting dispersants, viscosity modifiers, ultraviolet absorbers, metal deactivators, peroxide decomposers, flame retardants, reinforcing agents, plasticizers, lubricants, rust inhibitors, fluorescent whitening agents, inorganic heat ray absorbers, flameproofing agents, antistatic agents, dehydrating agents and the like are used in some cases.

The reactive adhesive includes a dry laminating adhesive diluted with a highly soluble organic solvent for dilution, a solventless laminating adhesive containing almost no organic solvent for dilution, an aqueous adhesive containing water as a diluent, and the like, and any of the adhesives can be peeled off by the separation and collection method of the present invention. Specific examples of the highly soluble organic solvent for dilution include: toluene, xylene, dichloromethane, tetrahydrofuran, methyl acetate, ethyl acetate, n-butyl acetate, acetone, Methyl Ethyl Ketone (MEK), cyclohexanone, toluene, xylene, n-hexane, cyclohexane, and the like. Among them, toluene, xylene, methylene chloride, tetrahydrofuran, methyl acetate, ethyl acetate are known as organic solvents having particularly high solubility. The aqueous adhesive may use water or an organic solvent having affinity with water as a diluting solvent.

In the reactive adhesive, if commercially available, the two-component type mixing ratio of the polyisocyanate composition and the polyol composition is a recommended mixing ratio, and usually, the equivalent ratio of the isocyanate groups in the polyisocyanate composition to the hydroxyl groups in the polyol composition (isocyanate groups/hydroxyl groups) is usually in the range of 1.0 to 5.0. Of course, the composition may be used in combination in other ranges.

The one-pack adhesive which is a reactive adhesive can be used as a laminating adhesive by applying the polyisocyanate composition alone to a film and reacting and crosslinking isocyanate groups contained in the polyisocyanate composition as moisture in the air.

Further, as the adhesive, a commercially available adhesive may be used. The binder may be one having a viscosity at a temperature of thermoforming, and examples thereof include: examples of the pressure-sensitive adhesive include solvent-type pressure-sensitive adhesives such as acrylic resins, isobutylene rubber resins, styrene-butadiene rubber resins, isoprene rubber resins, natural rubber resins, and silicone resins, and solvent-free pressure-sensitive adhesives such as acrylic emulsion resins, styrene-butadiene latex resins, natural rubber latex resins, styrene-isoprene copolymer resins, styrene-butadiene copolymer resins, styrene-ethylene-butylene copolymer resins, ethylene-vinyl acetate resins, polyvinyl alcohols, polyacrylamides, and polyvinyl methyl ethers.

(decorative layer)

The decorative layer can be formed using a general-purpose printing ink or paint, and can be formed using gravure printing, flexography, offset printing, screen printing, inkjet printing, thermal transfer printing, or the like. The dry film thickness of the decorative layer is preferably 0.1 to 15 μm, and more preferably 0.1 to 10 μm. The coloring layer having no pattern and the colorless varnish resin layer may be formed by coating.

The print pattern in the case of printing may be any print pattern as long as it can form a plate or a printable pattern or characters. In addition, a solid plate may be used.

Examples of the binder resin include: cellulose resins such as nitrocellulose, polyurethane resins, polyamide resins, vinyl chloride/vinyl acetate copolymers, rosin resins and modified products thereof, ketone resins, cellulose resins, polyester resins, (meth) acrylic resins, and the like, and they may be used in combination as appropriate. Among these, cellulose resins such as nitrocellulose, polyurethane resins, polyamide resins, vinyl chloride/vinyl acetate copolymers, and the like are often used in combination as appropriate.

The colorant may be an organic or inorganic pigment and/or dye used for general inks, paints, recording agents, and the like. Examples of the organic pigment include: pigments such as azo-based, phthalocyanine-based, anthraquinone-based, perylene-based, perinone-based, quinacridone-based, thioindigo-based, dioxazine-based, isoindolinone-based, quinophthalone-based, azomethine azo-based, dicumylpyrrole-based, isoindoline-based, and the like, and as inorganic pigments, there can be mentioned: carbon black, titanium oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silica, red iron oxide, aluminum, mica (mica), and the like. Further, there is exemplified a bright pigment (METASHINE, Japan Board Nitri K.K.) obtained by coating a base material of a glass flake or a bulk flake with a metal or a metal oxide.

Examples of the solvent, if organic, include: aromatic organic solvents, ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone, ester solvents such as ethyl acetate, n-propyl acetate, butyl acetate and propylene glycol monomethyl ether acetate, and alcohol solvents such as n-propanol, propargyl alcohol, n-butanol and propylene glycol monomethyl ether. In addition, the aqueous solvent includes a mixture of water as a main component and a water-soluble alcohol solvent.

Examples of the additives include: extender pigments, pigment dispersants, leveling agents, antifoaming agents, waxes, plasticizers, antiblocking agents, infrared absorbers, ultraviolet absorbers, fragrances, flame retardants, and the like.

In addition, a crosslinking agent and a chelating agent may be further added to crosslink the printing ink layer itself and increase the hardness.

Since the printing ink layer is also easily dissolved or hydrolyzed by an alkaline solution as in the case of the reactive binder, it is preferable that any of the components of the printing ink layer has an ester bond.

Any one of the components of the printing ink has an ester bond, and specific examples of the binder resin include polyester urethane resins, polyester polyamide resins, polyester resins, vinyl chloride/vinyl acetate copolymers, and (meth) acrylic resins having an ester bond.

In addition, a printing ink to which a resin having an ester bond and/or a compound having an acidic group is added may also be preferably used. The compound having an acidic group is not particularly limited as long as it can be easily mixed with the binder resin, the organic solvent, and the like, which are main components of the printing ink, and has an acid value.

(primer layer)

As shown in fig. 1, an example of a specific embodiment of the transfer film of the present invention may be provided with a primer layer before the decorative layer is applied in order to facilitate peeling of the decorative layer. The primer layer is preferably a resin having an ester bond and/or an acid group because it is easily dissolved or hydrolyzed by an alkaline solution, and the laminated film to which an adhesive is applied thereafter can be easily separated into single-layer films. (refer to FIG. 2)

Similarly, the adhesive may be prepared by applying a primer layer to a release layer to such an extent that the adhesion of the decorative layer after transfer to the plastic container is not impaired. (refer to FIG. 3)

For the above primer layer, a compound having an acidic group may be used alone. Examples of the compound having an acidic group which can be preferably used in the primer layer include: resins having an acid value such as a rosin-modified maleic acid resin and a rosin-modified fumaric acid resin; resins as radical copolymers, such as (meth) acrylic resins, styrene-maleic anhydride resins, and terpene-maleic anhydride resins, obtained by copolymerizing polymerizable monomers having a carboxyl group, such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, cinnamic acid, or acid anhydrides thereof, polymerizable monomers having a sulfonic acid group, such as sulfonated styrene, and polymerizable monomers having an acid group, such as polymerizable monomers having a sulfonamide group, such as vinylbenzenesulfonamide; acid-modified polyolefin resins, and the like.

In order to impart film-forming properties to the acidic group compound at the time of application, a resin may be added as appropriate. Examples of the resin include polyester urethane resins, polyester polyamide resins, polyester resins, vinyl chloride/vinyl acetate copolymers, and (meth) acrylic resins having an ester bond.

When the primer layer is applied, it may be diluted with a solvent as appropriate and applied to a substrate. Alternatively, the acidic group may be neutralized with a volatile organic amine such as ammonia, diluted in water, and applied.

In the case of using the primer layer, if the decorative layer design is based on white, almost all of the decorative layer uses white ink, and there is a case where peeling is difficult only with the primer layer. In this case, by further introducing the intermediate layer made of the resin component of the ink, the peelability of the decorative layer can be further improved.

(surface protective layer)

The surface protective layer to be provided as required may be a protective layer mainly composed of a non-reactive resin such as a polyester resin, a polyether ester resin, a polyester urethane resin, or a (meth) acrylic resin having an ester bond to such an extent that peeling is not inhibited.

(Release film)

The release film used in the present invention is not particularly limited as long as it has a suitable adhesive force with the transfer layer before the transfer processing and can be satisfactorily released from the transfer layer after the thermal transfer processing. Specifically, examples thereof include: polyolefin resins such as polyethylene and polypropylene; olefin copolymer resins such as ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, ethylene- (meth) acrylic acid (ester) copolymers, and ethylene-unsaturated carboxylic acid copolymer metal neutralizers (so-called ionomer resins); acrylic resins such as polyacrylonitrile, polymethyl methacrylate, and polyethyl methacrylate; styrene resins such AS polystyrene, AS resin and ABS resin; polyethylene resins such as polyvinyl acetal, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, and vinyl chloride-vinyl acetate copolymers; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyarylate, and polycarbonate; a film made of a thermoplastic resin such as a fluorine-based resin such as polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene, or an ethylene-tetrafluoroethylene copolymer, or a film obtained by subjecting the film to plasma irradiation and/or surface treatment with a release agent such as a fluorine-based compound or a silicone-based compound. Further, polyvinyl alcohol, modified polyvinyl alcohol, and the like described in patent document 2 may also be used.

The thickness of the release film is not particularly limited, but if it is too thin, the film may be broken when peeled after thermal transfer, while if it is too thick, the film may not completely follow the shape of the transfer target substrate, and therefore, the film thickness is preferably about 10 to 200 μm. More preferably 20 to 100 μm.

The surface properties of the transfer layer transferred to the transfer target substrate tend to be reversed in the release film used. Therefore, if a film having a smooth mirror-like surface is used as the release film, the surface of the transferred layer after transfer can be subjected to a smooth mirror finish, and if a film having a matte surface and/or a film having an embossed shape with irregularities is used as the release film, the surface of the transferred layer after transfer can be given these glossy states and/or embossed shapes. These may be appropriately selected depending on the desired design.

(method of manufacturing Heat transfer film)

The heat transfer film is formed by laminating an adhesive layer (if present), a decorative layer, a surface protective layer (if present), and a release film in this order on a holding layer. In addition, an anchor layer or the like may be provided as the case may be.

The step of laminating each layer is not particularly limited, and lamination can be performed by a known printing method or coating method.

For example, the decorative layer can be provided on the holding layer by various general-purpose printing methods such as a gravure printing method, an offset printing method, a gravure offset printing method, a flexographic printing method, and a screen printing method. In addition, when the adhesive layer is provided, the adhesive layer can be provided by using various known coating methods such as a gravure coating method, a microgravure coating method, a roll coating method, a bar coating method, a kiss coating method, a blade coating method, an air knife coating method, a comma coating method, a die coating method, a lip coating method, a flow coating method, a dip coating method, and a spray coating method. The holding layer provided with various layers and the release film may be laminated by a lamination method.

(Process (1) for decorating PET bottle with transfer film)

The method of decorating the PET bottle with the heat transfer film can be performed by a known transfer method. Specifically, a method of molding and transferring a transfer film to a three-dimensional shape by applying elongation and deformation to the transfer film at the time of thermal transfer, such as an in-mold molding transfer method of a blow-molded article, a decoration injection molding simultaneous transfer method, a vacuum molding simultaneous transfer method, a polishing simultaneous transfer method, and the like, and a transfer method of not applying elongation and deformation to a transfer film by thermal pressing, are known, but here, an in-mold molding transfer method of a blow-molded article, which is a preferable embodiment in the present invention, is described as an example.

The heat transfer film is attached to the inside of the mold by vacuum suction, with the holding layer being peeled off in advance from the parting mold surface of the blow mold, and with the decorative layer (adhesive layer in the case where the adhesive layer is present) being provided on the front side so that the decorative layer after molding corresponds to a desired position of the molded article. Next, a molten parison of polyethylene terephthalate was sandwiched between blow molds, and blow molding was performed according to the blow molding temperature and molding pressure of the resin.

The molten parison and the heat transfer film are pressure-bonded according to the molding temperature and molding pressure of the molten parison, the decorative layer (adhesive layer in the case where an adhesive layer is present) is bonded to the surface of the molten parison, and the heat transfer film is bonded to the wall surface of the blow-molded article via the adhesive layer.

After molding, the blow mold is opened to take out the molded article, and the release film is peeled off, whereby the decorative layer and the adhesive layer are transferred to the wall surface of the blow molded article, thereby decorating the article.

(Process (2) for collecting decorated PET bottle)

After the decorated PET bottles are filled with contents such as drinking water and distributed as commodities, the PET bottles are discharged from homes and collected by sorting in urban streets and villages, or collected by sorting from operators who manage discharge places such as vending machines, factories, offices, supermarkets, convenience stores, transportation facilities, and public facilities. These are used flexibly according to the waste treatment method and/or the regulation of the autonomous body.

(Process (3) of washing the recovered PET bottle with an alkaline solution and peeling off the decorative part.)

The alkaline solution for washing the recovered PET bottle is preferably an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide or the like. The aqueous sodium hydroxide solution and the aqueous potassium hydroxide solution are preferably aqueous solutions having a concentration of 0.5 to 10% by mass, and more preferably aqueous solutions having a concentration of 1 to 5% by mass. Alternatively, the pH is 8 or more, preferably 10 or more.

In addition, a water-soluble organic solvent or a water-insoluble organic solvent may be contained in a small amount. Examples of the water-soluble organic solvent include: methanol, ethanol, propanol, isopropanol, ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether (cellosolve), ethylene glycol monobutyl ether (butyl cellosolve), ethylene glycol dibutyl ether, diethylene glycol monomethyl ether (methyl carbitol), diethylene glycol dimethyl ether, diethylene glycol monoethyl ether (carbitol), diethylene glycol diethyl ether (diethyl carbitol), diethylene glycol monobutyl ether (butyl carbitol), diethylene glycol dibutyl ether, triethylene glycol monomethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, methylene dimethyl ether (methylal), propylene glycol monobutyl ether, tetrahydrofuran, acetone, diacetone alcohol, acetonyl acetone, acetylacetone, ethylene glycol monomethyl ether acetate (methyl cellosolve acetate), diethylene glycol monomethyl ether acetate (methyl carbitol acetate), diethylene glycol monoethyl ether acetate (carbitol acetate), Ethyl hydroxyisobutyrate, ethyl lactate, morpholine and the like, and these may be used alone or in combination of 2 or more.

The content of the water-soluble organic solvent in the alkaline solution is preferably 0.1 to 20% by mass, and more preferably 1 to 10% by mass.

The alkali solution may contain a water-insoluble organic solvent. Specific examples of the water-insoluble organic solvent include: alcohol solvents such as n-butanol, 2-butanol, isobutanol, and octanol, aliphatic hydrocarbon solvents such as hexane, heptane, and n-paraffin, aromatic hydrocarbon solvents such as benzene, toluene, xylene, and alkylbenzene, halogenated hydrocarbon solvents such as methylene chloride, 1-chlorobutane, 2-chlorobutane, 3-chlorobutane, and carbon tetrachloride, ester solvents such as methyl acetate, ethyl acetate, and butyl acetate, ketone solvents such as methyl isobutyl ketone, methyl ethyl ketone, and cyclohexanone, and ether solvents such as ether and butyl ether, which may be used alone or in combination of 2 or more.

In addition, the above-mentioned alkali solution may contain a surfactant. Examples of the surfactant include: and various anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, etc., among which anionic surfactants and nonionic surfactants are preferable.

Examples of the anionic surfactant include: alkylbenzenesulfonates, alkylphenylsulfonates, alkylnaphthalenesulfonates, higher fatty acid salts, sulfuric ester salts of higher fatty acid esters, sulfonates of higher fatty acid esters, sulfuric ester salts and sulfonates of higher alcohol ethers, higher alkylsulfosuccinates, polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, and the like, and specific examples thereof include: dodecylbenzene sulfonate, isopropylnaphthalene sulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenylphenol sulfonate, dibutylphenylphenol disulfonate, and the like.

Examples of the nonionic surfactant include: polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester, polyoxyethylene glycerin fatty acid ester, polyglycerin fatty acid ester, sucrose fatty acid ester, polyoxyethylene alkylamine, polyoxyethylene fatty acid amide, fatty acid alkanolamide, alkyl alkanolamide, acetylene glycol, an oxyethylene adduct of acetylene glycol, a polyethylene glycol-polypropylene glycol block copolymer, etc., among them, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, fatty acid alkanolamide, acetylene glycol, etc. are preferable, Ethylene oxide adduct of acetylene glycol, and polyethylene glycol polypropylene glycol block copolymer.

As other surfactants, silicone surfactants such as silicone alkoxyethylene adducts; fluorine-based surfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and oxyethylene perfluoroalkyl ethers; and biosurfactants such as penicillic acid (spiculisporic acid), rhamnolipids, and lysolecithins.

These surfactants may be used alone, or 2 or more of them may be used in combination. When the surfactant is added, the amount of the surfactant added is preferably in the range of 0.001 to 2% by mass, more preferably 0.001 to 1.5% by mass, and still more preferably 0.01 to 1% by mass, based on the total amount of the alkali solution.

In addition, when the PET bottle is washed with the alkali solution, it is preferable to wash the PET bottle in a treatment tank under heating at 20 to 90 ℃ or ultrasonic vibration, for example. The heating method is not particularly limited, and a known heating method using heat rays, infrared rays, microwaves, or the like can be used. The ultrasonic vibration may be, for example, a method of attaching an ultrasonic transducer to the treatment bath and applying ultrasonic vibration to the alkali solution.

In addition, it is preferable to stir the alkali solution at the time of washing. Examples of the stirring method include: a method of mechanically stirring a dispersion of a laminated film contained in a treatment tank with a stirring blade, a method of stirring a water flow with a water flow pump, a bubbling method with an inert gas such as nitrogen gas, and the like may be used in combination in order to efficiently peel off a multilayer film.

The time for immersing the PET bottle in the above-mentioned alkali solution is usually in the range of 2 minutes to 48 hours in most cases. If the dipping time is less than 2 minutes, the transferred decorative layer may not be completely peeled off from the PET bottle and a part may remain.

The number of immersion in the alkali solution may be 1 or several times. In addition, when the dipping is performed a plurality of times, the concentration of the alkali solution may be changed. During this time, it is preferable to appropriately add a known step such as washing with water or drying.

When polyethylene terephthalate is immersed in an alkaline aqueous solution for a long time, hydrolysis of an ester bond may occur, which may impair the quality after recovery. In order to shorten the time for immersion in the alkaline aqueous solution, the ink layer may be removed with a solvent such as morpholine before and after the alkaline solution treatment in the step.

It is presumed that the alkaline solution used in the present recovery method acts on the interface with the adhesive layer to significantly reduce the adhesive strength when the PET bottle is used with the decorative layer and the adhesive layer, and thereby causes interfacial peeling between the PET bottle and the decorative layer and the adhesive layer. In this case, even when a reactive adhesive is used as the adhesive layer, since interfacial peeling occurs instead of dissolution in the present invention, it is presumed that separation and collection can be efficiently performed in a short time.

The decorative layer peeled from the PET bottle is mostly not dissolved in an alkaline solution but becomes a residue in the alkaline solution. That is, the residues of the decorative layer, the adhesive layer, and/or the surface protective layer that have been separated in the alkaline solution are in a floating or dissolved state. They were taken out from the alkali solution and recovered separately.

The recycling method of the present invention can be applied to the PET bottle as described above, and can also be applied to printed matter printed on polypropylene, polyethylene, and/or polystyrene used as plastic for food packaging, such as coffee cups, yogurt cups, and the like.

[ examples ] A method for producing a compound

Hereinafter, the contents and effects of the present invention will be described in more detail by examples.

(polyester polyol A)

Polyol A having a high acid value of 5% was prepared by dissolving 5 parts of "MALKYD # 32" available from Mitsuka chemical industries, Ltd., in 95 parts of "HA 450B" available from DIC, Ltd., at 160 ℃.

(primer A)

50 parts of MALKYD #32 available from Mikan chemical industries, Ltd was dissolved in 50 parts of ethyl acetate at 40 ℃ with stirring to obtain primer A having a solid content of 50%.

(method of manufacturing transfer film)

Transfer films (A-1) and (A-2) were produced in which an adhesive layer, a decorative layer, and a release film were sequentially laminated on a holding layer, and a transfer film (B-1) was produced in which an adhesive layer, a decorative layer, a primer layer (5), and a release film were sequentially laminated on a holding layer.

(transfer sheet (A-1))

The release film used was the release film (a) described below: as the release layer, a release composition prepared by mixing 100 parts of "MC- クリヤ -KAH-011" manufactured by DIC Graphics with 3 parts of "PL curing agent C" manufactured by DIC Graphics was prepared so that the solid content was 1g/m²The release film (A) was formed by coating the film on a polyethylene terephthalate film "E-5101" (50 μm thick) made by Toyobo spinning and baking the film at 180 ℃ for 30 seconds.

On the release film (a), blue and white inks of gravure ink "TRC-ink series" manufactured by DIC Graphics were printed by a gravure coater so that the print layer became 2 μ to produce a decorative layer. On the other hand, 100/60 is used as the adhesive layerAn adhesive composition obtained by mixing NS-4500A and HA-450B manufactured by DIC at a ratio of 2g/m in a non-solvent laminator²The release film having the decorative layer was laminated on the holding layer, and the transfer film (a-1) was obtained by performing an aging reaction at 40 ℃ for 3 days.

(transfer sheet (A-2))

In the transfer film (A-1), as an adhesive layer, an adhesive composition obtained by mixing "NS-4500A" manufactured by DIC and "polyol A" at a ratio of 100/60 was used to form 2g/m in a non-solvent laminator²The release film having the decorative layer was laminated on the holding layer, and the transfer film (a-2) was obtained by performing an aging reaction at 40 ℃ for 3 days.

(transfer sheet (B-1))

In the transfer film (A-1), the solid content of the holding layer is 1g/m²The primer A as a primer layer was applied and dried, and then as an adhesive layer, an adhesive composition obtained by mixing "NS-4500A" and "HA-450B" manufactured by DIC at a ratio of 100/60 was laminated by a non-solvent laminator so that the ratio of the adhesive composition became 2g/m²The transfer film (B-1) was obtained by laminating the release film having the decorative layer on the decorative layer and the adhesive layer and carrying out an aging reaction at 40 ℃ for 3 days.

(Heat transfer printing Process)

On the parting mold surface of the blow mold, an adhesive layer is provided as the front side in a state where the holding layer is peeled off in advance, and the obtained heat transfer film is stuck in the mold by vacuum suction so that the decorative layer after molding corresponds to a desired position of the molded article.

Next, a molten parison of polyethylene terephthalate was sandwiched between blow molds, and blow molding was performed according to the blow molding temperature and molding pressure of the resin, thereby obtaining a decorated PET bottle.

(Process for peeling decorative part)

50 parts of sodium hydroxide was dissolved in 950 parts of ion-exchanged water to prepare a 5% aqueous solution of sodium hydroxide. The 5% aqueous sodium hydroxide solution was sprayed to the printed portion of the PET bottle at 60 ℃ by a sprayer to confirm the peeling state of the printed portion.

The results are shown in Table 1.

TABLE 1

TABLE 1	Example 1	Example 2	Example 3
				Transfer film used	Transfer sheet (A-1)	Transfer sheet (A-2)	Transfer sheet (8-1)
Peelability of	95% peeling	100% peeling	00% peeling

As a result, the decorative layer decorated on the PET bottle can be easily peeled off with an alkali solution.

Description of the reference numerals

1: release film

2: surface protective layer

3: decorative layer

4: adhesive layer

5: holding layer

6: primer layer

Claims

1. A method of recycling a plastic container, comprising:

a step (1) of decorating a plastic container with a transfer film;

a step (2) of recovering the decorated plastic container; and

and (3) cleaning the recovered plastic container with an alkali solution and peeling off the decorative part.

2. The recycling method of plastic containers according to claim 1, wherein the plastic containers are PET bottles.

3. A transfer film, which is applied to a plastic container, is formed by laminating at least a decoration layer and a release film in this order on a holding layer, and the decoration layer is alkali-soluble.

4. A transfer film which is applied to a plastic container and is formed by laminating at least an adhesive layer, a decoration layer and a release film in this order on a holding layer, wherein the adhesive layer is alkali-soluble.

5. A transfer film which is applied to a plastic container and is formed by laminating at least an adhesive layer, a decorative layer, a surface protective layer and a release film in this order on a holding layer, wherein the adhesive layer and/or the surface protective layer are alkali-soluble.

6. A transfer film according to any of claims 3-5, wherein the plastic container is a PET bottle.