JP7156176B2 - LAMINATE ADHESIVE HAVING RELEABILITY FROM COMPOSITE FILM, LAMINATE, AND METHOD FOR RECYCLING SHEET SUBSTRATE - Google Patents

Description

TECHNICAL FIELD The present invention relates to a releasable laminating adhesive from a composite film, a laminate, and a method for recycling a sheet-like substrate.

In recent years, minute plastic particles present in the environment are called microplastics, and have become an extremely serious problem especially in the marine environment. There is concern that marine organisms will ingest microplastics and harmful substances attached to them, and bioaccumulation will affect the health of seabirds and humans. Various efforts have been started to reduce the generation of microplastics.

As a method to reduce the generation of microplastics, methods of replacing conventional plastic materials with recyclable "paper" using wood, which is a renewable resource, as raw materials are being considered.
Various coating agents have been investigated, and technologies are being developed to compensate for the weak points of paper such as gas barrier properties and water resistance. It is difficult to convert all plastic packaging materials into paper.

In addition, plastic materials such as polyethylene terephthalate (PET), nylon (NY), unstretched polypropylene (CPP), aluminum vapor deposition film, etc. have been used in the past. Attempts are also being made to recycle plastic films, and technologies are being developed to cover the weaknesses of polyolefin with functional coating agents such as barrier coating agents. It is difficult to convert all plastic packaging materials into polyolefins because they are inferior in terms of performance. Furthermore, in the case of a laminate structure, there is also a problem that the ink, functional coating agent, adhesive, etc. laminated between the polyolefin films become impurities when recycling the plastic film.

On the other hand, in Patent Document 1, an adhesive used for affixed items such as labels, which contains a copolymer containing a lower alkyl ester unit of acrylic acid and/or maleic acid, is detachable with alkaline water. Something is disclosed.
Further, Patent Document 2 discloses an adhesive tape having excellent alkali peelability, which contains natural rubber and a high acid value tackifier in the adhesive used for the adhesive tape.

JP-A-11-323280 JP 2017-145327 A

However, in a two-liquid curing type urethane-based lamination adhesive containing polyol and polyisocyanate, the composite film (hereinafter referred to as "laminate (also called body) adhesive for detachment has not been realized.
Therefore, the object of the present invention is to remove the adhesive and the printed layer from the plastic film with an alkaline aqueous solution in a composite film structure such as OPP and CPP, and to remove from the composite film that exhibits good retortability. An object of the present invention is to provide a laminating adhesive having releasability, a laminate using the adhesive, and a recycling method for sheet-like substrates.

As a result of intensive studies on the above problems, the inventors of the present invention have found that the above problems can be solved by using the lamination adhesive described below, and have completed the present invention.
The present invention relates to the following inventions [1] to [7].

[1] A laminate adhesive that contains a polyol and a polyisocyanate and has releasability from a composite film,
an acid value of 5.0 mgKOH/g or more,
The polyol comprises a polyester polyol component (A),
The polyisocyanate contains a polyisocyanate component (B),
A laminate having releasability from a composite film, wherein the polyisocyanate component (B) has a viscosity of 1,000 mPa s or more and 20,000 mPa s or less, as measured by a Brookfield viscometer at 25°C and 12 rpm. glue.

[2] The laminate adhesive releasable from the composite film of [1], wherein the polyester polyol component (A) has an acid value of 8.0 mgKOH/g or more.

[3] The laminate adhesive having releasability from the composite film according to [1] or [2], wherein the isocyanate component (B) is an aliphatic polyisocyanate derivative.

[4] A laminate in which an adhesive layer composed of a lamination adhesive having releasability from the composite film according to any one of [1] to [3] is laminated between at least two sheet-like substrates. body.

[5] The laminate according to [4], wherein at least one of the sheet-like substrates is a polypropylene substrate.

[6] The laminate according to [4] or [5], which is for recycling sheet-like substrates.

[7] Recycling of a sheet-like substrate, wherein the adhesive layer is removed from the laminate according to any one of [4] to [6] with an alkaline aqueous solution, and the sheet-like substrate is separated. Method.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a laminate adhesive for peeling off a composite film, and a laminate, in which the adhesive and the printed layer can be removed from the plastic film with an alkaline aqueous solution in the structure of the composite film such as OPP and CPP.

Embodiments of the present invention will be described in detail below, but the description of the constituent elements described below is an example of embodiments of the present invention, and the present invention is not limited to these contents as long as it does not exceed the gist of the present invention. .

The laminate adhesive having releasability from the composite film of the present invention contains a polyol and a polyisocyanate, the polyol contains a polyester polyol component (A),
The polyisocyanate contains a polyisocyanate component (B), and has a viscosity of 1,000 mPa s or more, measured at 25° C. and a rotation speed of 12 rpm, with the solid content concentration of the polyisocyanate component (B) being 100% by mass, It is characterized by being 20,000 mPa·s or less.
By including a polyisocyanate component (B) having a high viscosity of 1,000 mPa·s or more and 20,000 mPa·s or less as the polyisocyanate constituting the adhesive, the polyisocyanate component (B) permeates into the printed layer. This prevents the printed layer from excessively hardening, and has the effect of achieving both the alkali-releasing property of the adhesive layer and the alkali-releasing property of the printed layer.
As a result, it is possible to manufacture a laminate suitable for recycling of plastic films such as base materials and sealant base materials constituting the laminate, preferably polypropylene, etc., and remove the printed layer from the laminate in an alkaline aqueous solution. The plastic base material such as olefin can be recovered by washing with water and drying, and the recovered olefin can be recycled into pellets by an extruder for use.
The present invention will be described in detail below.

<Polyester polyol component (A)>
The polyester polyol component (A) can be selected from conventionally known polyester polyols, and may be used alone or in combination of two or more.
Examples of polyester polyol component (A) include, but are not limited to, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, phthalic anhydride, adipic acid, azelaic acid, sebacic acid, succinic acid, glutaric acid, anhydride dibasic acids such as tetrahydrophthalic acid, hexahydrophthalic anhydride, maleic anhydride, and itaconic anhydride, dialkyl esters thereof, or mixtures thereof (hereinafter also referred to as a carboxyl group component);
For example, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, butylene glycol, neopentyl glycol, dineopentyl glycol, trimethylolpropane, glycerin, 1,6-hexanediol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, 3,3′-dimethylolheptane, 1,9-nonanediol, polyoxyethylene glycol, polyoxypropylene glycol, polytetramethylene ether glycol , polyether polyols, polycarbonate polyols, polyolefin polyols, acrylic polyols, diols such as polyurethane polyols, or mixtures thereof (hereinafter also referred to as hydroxyl group components);
or polyester polyols obtained by ring-opening polymerization of lactones such as polycaprolactone, polyvalerolactone and poly(β-methyl-γ-valerolactone).
Two or more of the carboxyl group component and the hydroxyl group component may be used in combination.

The polyester polyol component (A) may be a polyester polyurethane polyol reacted with a diisocyanate, or may be reacted with an acid anhydride.
Diisocyanates include, for example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, hexamethylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and the like. can be mentioned.
Examples of acid anhydrides include trimellitic anhydride and trimellitic ester anhydride. Examples of trimellitic ester anhydrides include ethylene glycol anhydro trimellitate and the like.

Since the adhesive of the present invention has an acid value of 5.0 mgKOH/g or more as described above, it is preferable that the polyester polyol component (A) has an acid value. is preferably 8.0 mgKOH/g or more, more preferably 10.0 mgKOH/g or more. Moreover, the acid value of the polyester polyol component (A) is preferably 40.0 mgKOH/g or less. By having the above acid value, a laminate (hereinafter also referred to as a composite film) in which an adhesive layer composed of the laminating adhesive of the present invention is laminated between two sheet-like substrates is brought into contact with an aqueous alkaline solution. At the time of application, the alkaline aqueous solution permeates and decomposes, exhibiting excellent composite film releasability.

When the adhesive contains a plurality of polyester polyol components, the acid value of the polyester polyol component (A) can be determined from the acid value of each polyester polyol component and its mass ratio.

The polyester polyol component (A) preferably has a number average molecular weight (Mn) of 3,000 to 20,000, more preferably 5,000, more preferably 5,000, more preferably 5,000, more preferably 3,000 to 20,000. 000 to 10,000 polyester polyols.
When the number average molecular weight (Mn) of the polyester polyol component (A) is 3,000 or more, not only coatability but also sufficient retort suitability can be exhibited, and when it is 20,000 or less, only coatability is improved. However, it is preferable because the alkali elimination property is improved.

The number average molecular weight in the present specification is a value converted to standard polystyrene using GPC (gel permeation chromatography) “Shodex GPCS System-21” manufactured by Showa Denko KK and using tetrahydrofuran as a solvent.

Moreover, the polyester polyol component (A) may be used in combination with a plurality of polyester polyol components in order to satisfy various physical properties required for packaging materials. For example, it is preferable to contain a small amount of a polyester polyol component having an Mn of less than 3,000 in order to improve adhesion to the substrate.

The polyester polyol component (A) used in the present application preferably contains the following three types of polyol components from the viewpoint of suitability for retort and releasability in an alkaline aqueous solution.
First polyol component: polyester polyol with an acid value of 10.0 mg/KOH or more Second polyol component: polyester polyol with a number average molecular weight of less than 3,000 Third polyol component: polyester polyol with a number average molecular weight of 5,000 or more ( However, except when the second polyol component and the third polyol component are the first polyol component)

The first polyol component has a role of imparting alkali releasability, and the second polyol component improves adhesion to substrates and contributes to improvement of coatability. Furthermore, the third polyol component has a role of improving retortability.
The content of the first polyol component is preferably 50% by mass or more relative to the total amount of the polyester polyol component (A) from the viewpoint of maintaining sufficient alkali-releasing properties.

The first polyol component is preferably a polyester polyurethane polyol modified with an acid anhydride, and more preferably has a number average molecular weight of 5,000 or more and less than 10,000, and an acid value of 15.0 mgKOH. /g or more and 40 mgKOH/g or less.
The second polyol component preferably has an acid number of less than 5.0 mg KOH/g, more preferably less than 1.0 mg KOH/g.
The third polyol component is preferably a polyester polyurethane polyol modified with an acid anhydride, and more preferably has a number average molecular weight of 5,000 or more and less than 10,000 and an acid value of 5.0 mgKOH/g. is less than

[Other polyols]
Moreover, the adhesive of the present invention may contain other polyols than the polyester polyol component (A).
Polyol components that may be contained in addition to the polyester polyol component (A) are not particularly limited, and examples include polycarbonate polyols, polycaprolactone polyols, polyether polyols, polyolefin polyols, acrylic polyols, silicone polyols, and castor oil. Polyols such as fluorine-based polyols and fluorine-based polyols may be used alone, or two or more of them may be used in combination.

<Polyisocyanate component (B)>
The polyisocyanate component (B) has a viscosity of 1,000 mPa s or more and 20,000 mPa s or less, measured with a Brookfield viscometer at 25 ° C. and a rotation speed of 12 rpm with a solid content concentration of 100% by mass. It can be selected, and two or more kinds may be used in combination.
Examples of the polyisocyanate (B) satisfying the above viscosity include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3 -aliphatic diisocyanates such as butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, 2,6-diisocyanatomethylcaproate; 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate , 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, 4,4′-methylenebis(cyclohexyl isocyanate), methyl 2,4-cyclohexane diisocyanate, methyl 2,6-cyclohexane diisocyanate, 1,4-bis(isocyanate Alicyclic diisocyanates such as methyl)cyclohexane and 1,3-bis(isocyanatomethyl)cyclohexane; - aromatic diisocyanates such as diphenylmethane diisocyanate, 2,4- or 2,6-tolylene diisocyanate or mixtures thereof, 4,4'-toluidine diisocyanate, dianisidine diisocyanate, 4,4'-diphenylether diisocyanate; 1,3- or 1,4-xylylene diisocyanate or mixtures thereof, ω,ω′-diisocyanate-1,4-diethylbenzene, 1,3- or 1,4-bis(1-isocyanate-1-methylethyl)benzene or mixtures thereof, etc. araliphatic diisocyanates; organic triisocyanates such as triphenylmethane-4,4′,4″-triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene; 4,4′- organic tetraisocyanates such as diphenyldimethylmethane-2,2'-5,5'-tetraisocyanate; polyisocyanates such as dimers, trimers, nurates, biurets or allophanates derived from isocyanate monomers such as; A polyisocyanate derived from a monomer or the above isocyanate monomer, and polyethylene glycol and adducts of hydroxyl group components such as polyether polyol or polyester polyol. These can be suitably used as polyisocyanate derivatives.
Among them, aliphatic polyisocyanate derivatives derived from aliphatic isocyanates are preferred as the polyisocyanate component (B). Examples of such commercially available products include Coronate 2785 and Coronate HX manufactured by Tosoh Corporation.

The viscosity of the polyisocyanate component (B) measured under the above conditions is preferably 1,500 mPa s or more and 15,000 mPa s or less, more preferably 2,000 mPa s or more and 10,000 mPa s or less. be. When the viscosity is 1,500 mPa·s or more, the permeation of the polyisocyanate component into the printed layer is suppressed, and the alkaline desorption property of the printed layer is improved, which is preferable. When it is 15,000 mPa·s or less, the wettability at the time of coating is improved, and uniform deinking property can be developed, which is preferable.
The viscosity herein was measured using a Brookfield viscometer in accordance with JIS K6833-1 at 25° C. and 12 rpm. As the B-type viscometer, a rotor No. manufactured by Tokyo Keiki Co., Ltd. was used. 3 was used.

[Other polyisocyanate components]
Moreover, the adhesive of the present invention may contain other polyisocyanates other than the polyisocyanate component (B).
The polyisocyanate component that may be contained in addition to the polyisocyanate component (B) is not particularly limited, and includes aliphatic diisocyanates, alicyclic diisocyanates, aromatic Examples include isocyanate monomers such as diisocyanates, araliphatic diisocyanates, organic triisocyanates, and organic tetraisocyanates.

<Laminate adhesive having releasability from composite film>
The adhesive of the present invention may contain components other than the aforementioned polyol component and polyisocyanate component. The other components may be blended with either the polyol component or the polyisocyanate component, or may be added when blending the polyol component and the polyisocyanate component.

[Other ingredients]
(Silane coupling agent)
The adhesive of the present invention can further contain a silane coupling agent in order to improve hot water resistance. Examples of the silane coupling agent include trialkoxysilanes having a vinyl group such as vinyltrimethoxysilane and vinyltriethoxysilane, 3-aminopropyltriethoxysilane, and N-(2-aminoethyl)3-aminopropyltrimethoxysilane. Trialkoxysilane having an amino group such as, 3-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane having a glycidyl group trialkoxysilane and the like. The amount of the silane coupling agent added is preferably 0.1 to 5% by mass, more preferably 0.5 to 3% by mass, based on the solid content of the adhesive.

(Phosphorus oxyacid or derivative thereof)
The adhesive of the present invention may further contain an oxyacid of phosphorus or a derivative thereof to enhance acid resistance. Of the phosphorus oxyacids or derivatives thereof, the phosphorus oxyacids may be those having at least one free oxyacid, such as hypophosphorous acid, phosphorous acid, orthophosphoric acid, Phosphoric acids such as phosphoric acid, and condensed phosphoric acids such as metaphosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, polyphosphoric acid and ultraphosphoric acid can be mentioned. Examples of the phosphorus oxyacid derivative include those obtained by partially esterifying the above phosphorus oxyacid with alcohols while leaving at least one free oxyacid. These alcohols include aliphatic alcohols such as methanol, ethanol, ethylene glycol and glycerin, and aromatic alcohols such as phenol, xylenol, hydroquinone, catechol and phloroglycinol. Two or more of the phosphorus oxyacids or derivatives thereof may be used in combination. The amount of phosphorus oxyacid or derivative thereof added is preferably 0.01 to 10% by mass, more preferably 0.05 to 5% by mass, more preferably 0.1% by mass, based on the solid content of the adhesive. ~1% by mass is particularly preferred.

The adhesive of the present invention further contains additives such as antioxidants, ultraviolet absorbers, hydrolysis inhibitors, antifungal agents, thickeners, plasticizers, pigments, fillers, etc., as necessary. be able to. In addition, known catalysts, additives and the like can be contained in order to adjust the curing reaction.

The adhesive of the present invention can be used as a solventless type when its viscosity is normal temperature to 150° C., preferably 100 to 10,000 mPa s, preferably 100 to 5,000 mPa s at normal temperature to 100° C. . If the viscosity of the adhesive is higher than the above range, it may be diluted with an organic solvent. As the organic solvent, for example, esters such as ethyl acetate, ketones such as methyl ethyl ketone, and aromatic hydrocarbons such as toluene and xylene, which are inert to the polyisocyanate component, are preferably used, and are appropriately selected. can be used as

As described above, the adhesive of the present invention is a two-liquid curing type urethane-based laminate adhesive containing polyol and polyisocyanate. It is 7.0 mgKOH/g or more, and particularly preferably 10.0 mgKOH/g or more. Further, the acid value of the adhesive of the present invention immediately after blending is preferably 40.0 mgKOH/g or less.

As an example of a specific formulation using the adhesive of the present invention, a polyol and a polyisocyanate are mixed so that the equivalent ratio of the isocyanate group of the polyisocyanate to the hydroxyl group in the polyol is 0.3 to 1. Then, the adhesive is applied to the surface of the sheet-like substrate with a solvent-type or solvent-free laminator. In the case of a solvent-type, the solvent is volatilized. Alternatively, a method of curing under heating may be used.

<Laminate>
The laminate of the present invention is obtained by laminating, between at least two sheet-like substrates, an adhesive layer composed of a laminating adhesive having releasability from the composite film described above. The laminate of the present invention may be hereinafter referred to as a composite film. In the composite film of the present invention, the adhesive exhibits excellent detachability with an alkaline aqueous solution, and the adhesive layer can be detached from the sheet-like substrate.
The laminate of the present invention may further have a printed layer, and the printed layer is preferably adjacent to the adhesive layer. Since the printed layer and the adhesive layer are adjacent to each other, the polyisocyanate component (B) having a viscosity of 1,000 mPa·s or more and 20,000 mPa·s or less contained in the adhesive layer penetrates into the printed layer. It is preferable because it is inhibited, prevents the printed layer from excessive hardening, and exhibits the effect of achieving both the alkali-releasing property of the adhesive layer and the alkali-releasing property of the printed layer.
The alkaline aqueous solution is not particularly limited, but a 2% by mass sodium hydroxide aqueous solution at 70° C. is preferably used.
In addition, since the laminate of the present invention has retort suitability, it can be suitably used for pouches for packaging foods, as well as pouches for refilling detergents, medicines, and the like.

[Sheet-like base material]
Examples of sheet-like substrates include gas barrier substrates such as plastic films, papers and metal foils, and sealants, which are generally used for packaging laminates.
Examples of plastic films include polyester resin films such as polyethylene terephthalate, polyethylene naphthalate (PEN) and polylactic acid (PLA); polyolefin resin films such as polyethylene (PE) and polypropylene (PP); polystyrene resin films; Polyamide resin films such as poly-p-xylylene adipamide (MXD6 nylon); polycarbonate resin films; polyacrylonitrile resin films; polyimide resin films; 6/ethylene-vinyl alcohol copolymer/nylon 6) and mixtures thereof are used. Among them, those having mechanical strength and dimensional stability are preferable.
Examples of paper include natural paper and synthetic paper.
As the gas barrier substrate, in addition to aluminum foil, a plastic film having a deposited layer of aluminum, silica, alumina, or the like is preferable. For example, in the case of aluminum foil, the thickness is preferably in the range of 3 to 50 μm from an economical point of view.

Examples of sealants include polyethylene such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE), acid-modified polyethylene, polypropylene (PP), acid-modified polypropylene, copolymerized polypropylene, Polyolefin resins such as ethylene-vinyl acetate copolymers, ethylene-(meth)acrylic acid ester copolymers, ethylene-(meth)acrylic acid copolymers, ionomers and the like can be mentioned. Among them, from the viewpoint of heat resistance during retorting, polypropylene-based resins are preferable, and from the viewpoint of heat-sealing properties, unstretched polypropylene is particularly preferable.
Although the thickness of the sealant is not particularly limited, it is preferably in the range of 10 to 60 μm, more preferably in the range of 15 to 40 μm, in consideration of processability to packaging materials, heat sealability, and the like. In addition, by providing the sealant with unevenness having a height difference of 5 to 20 μm, it is possible to provide the sealant with slipperiness and tearability of the packaging material.
In addition, the method of laminating the sealant is not particularly limited. For example, a method of laminating an adhesive layer and a sealant film with heat (heat lamination, dry lamination), a method of melting a sealant resin and extruding it onto the adhesive layer, cooling and solidifying it, and laminating (extrusion lamination method) ) and the like.

[Adhesive layer]
The adhesive layer is a coating film obtained with the adhesive of the present invention. Generally, the adhesive is applied to one surface of the first sheet-like substrate, and dried if necessary. Later, it can be formed by bonding to one surface of the second sheet-like base material.
Although the amount of the adhesive layer is arbitrary, it is preferably in the range of 0.001 to 6 g/m ² with respect to the area of the adhesive surface, 1 to 2 g/m ² in the non-solvent type, and 1 in the solvent type. It is preferably in the range of ~6 g/m ² .

[Print layer]
The laminate of the present invention preferably has a printed layer.
The printed layer is a layer that forms an arbitrary printed pattern for the purpose of decoration, imparting aesthetics, content, expiration date, manufacturer's or seller's indication, and the like. The printed layer can be provided, for example, between the first sheet-like substrate and the adhesive layer, and may be provided over the entire surface of the first sheet-like substrate, or may be provided partially. The printed layer can be formed using conventionally known pigments and dyes, and may be formed using printing inks containing pigments and dyes, and the formation method is not particularly limited. The printed layer may be formed from a single layer or multiple layers.
The thickness of the printed layer is preferably 0.1 μm or more and 10 μm or less, more preferably 1 μm or more and 5 μm or less, and still more preferably 1 μm or more and 3 μm or less.

Examples of printing inks for forming the printing layer include printing inks containing media such as pigments, binders, solvents, and water. Examples of the binder include fibrous materials such as nitrocellulose, cellulose acetate and propionate, chlorinated polypropylene, vinyl chloride-vinyl acetate copolymer, polyester, acrylic, polyurethane and acrylic urethane, polyamide, Polybutyral-based, cyclized rubber-based, chlorinated rubber-based binders, or a combination of these binders can be used.

[Primer layer]
In addition, a primer layer may be formed between the base material and the printed layer, if necessary, in order to satisfy various performance requirements for the packaging material such as adhesion to the base material. As the primer layer, conventionally known ones can be used, and either water-based or oil-based primer layer can be preferably used.
Examples of compositions that form such a primer layer include water-based primer compositions that satisfy the following (1) to (3) described in JP-A-2017-114930.
(1) The aqueous primer composition contains a polyurethane resin (A) having a carboxyl group.
(2) At least part of the carboxyl groups of the polyurethane resin (A) are neutralized with the amine compound (a-1).
(3) The acid value of the polyurethane resin (A) before neutralization is 25-45 mgKOH/g.

[Laminate structure]
Although the structure of the laminate is not particularly limited, it preferably has a structure in which at least one layer of plastic film or gas barrier base material and a sealant are laminated via an adhesive layer. More preferably, it has a printed layer adjacent to the adhesive layer.
Specific laminate structures include biaxially oriented polypropylene (OPP)/printing layer/adhesive layer/CPP, OPP/printing layer/adhesive layer/AL deposition CPP, OPP/printing layer/adhesive layer/PE, NY/printing layer/adhesive layer/PE, NY/printing layer/adhesive layer/CPP, PET/printing layer/adhesive layer/NY/adhesive layer/CPP, transparent vapor deposition PET/printing layer/adhesive layer/ NY/adhesive layer/CPP, PET/printing layer/adhesive layer/AL/adhesive layer/CPP, PET/printing layer/adhesive layer/AL/adhesive layer/PE, PET/printing layer/adhesive layer /NY/adhesive layer/AL/adhesive layer/CPP, PET/printing layer/adhesive layer/AL/adhesive layer/NY/adhesive layer/CPP and the like.
These laminates may have a primer layer, a top coat layer, etc., if necessary. When having a primer layer, OPP/primer layer/printing layer/adhesive layer/CPP, OPP/primer layer/printing layer/adhesive layer/PE, PET/primer layer/printing layer/adhesive layer/NY /adhesive layer/CPP and the like.

EXAMPLES The present invention will now be described more specifically with reference to examples and comparative examples. "Parts" and "%" in Examples and Comparative Examples mean "mass parts" and "mass%" unless otherwise specified.

<Measurement of acid value>
Approximately 1 g of the sample (polyester polyol solution) was accurately weighed into a stoppered Erlenmeyer flask, dissolved by adding 100 ml of toluene/ethanol (volume ratio: toluene/ethanol = 2/1) mixture, and phenolphthalein test solution was used as an indicator. and hold for 30 seconds. Thereafter, the solution was titrated with a 0.1N alcoholic potassium hydroxide solution until it turned pale pink, and the acid value was determined by the following formula.
Acid value (mgKOH/g) = (5.611 x a x F)/S
S: Sample collection amount (g)
a: consumption of 0.1N alcoholic potassium hydroxide solution (ml)
F: Factor of 0.1N alcoholic potassium hydroxide solution

<Number average molecular weight (Mn)>
The number average molecular weight (Mn) was measured using Showa Denko GPC (gel permeation chromatography) "Shodex GPCS System-21". In the measurement, tetrahydrofuran was used as a solvent, and a value converted to standard polystyrene was obtained.

<Measurement of viscosity>
The viscosity was measured using a Brookfield viscometer in accordance with JIS K6833-1 at 25° C. and 12 rpm. As the B-type viscometer, a rotor No. manufactured by Tokyo Keiki Co., Ltd. was used. 3 was used.

<Production of aqueous primer composition>
(Primer composition 1)
Aqueous primer composition S15 described in JP-A-2017-114930 was used as primer composition 1.
Specifically, poly(3-methyl-1,5- 100 parts of poly(3-methyl-1,5-pentaneadipate)diol (hereinafter “PMPA”) having a number average molecular weight of 1,000, 40 parts of poly(3-methyl-1,5-pentaneadipate)diol (hereinafter “PMPA”) having a number average molecular weight of 2,000 35 parts of polyethylene glycol (hereinafter "PEG"), 30 parts of 2,2-dimethylolpropionic acid (hereinafter "DMPA") and 109.6 parts of isophorone diisocyanate (hereinafter "IPDI") are mixed with methyl ethyl ketone (hereinafter "MEK")77. Reflux reaction was carried out in 4 parts at 80° C. for 6 hours to form an isocyanate-terminated prepolymer, which was then cooled to 40° C. to obtain a solvent solution of the isocyanate-terminated prepolymer. Next, 14 parts of isophoronediamine (hereinafter “IPDA”), 8.6 parts of 2-hydroxyethylethylenediamine (hereinafter “AEA”), 1.0 part of dibutylamine (hereinafter “DBA”) and 699.9 parts of acetone are mixed. The resulting isocyanate-terminated prepolymer solution was gradually added to the mixture at room temperature and allowed to react at 80° C. for 1 hour to obtain a solvent-type polyurethane resin solution. Next, 13.6 parts of 28% aqueous ammonia and 777.3 parts of ion-exchanged water were gradually added to the above solvent-type polyurethane resin solution to neutralize it, and then the total amount of MEK and acetone was added under azeotropic conditions. was distilled off, water was added to adjust the solid content, and a polyurethane resin having an acid value of 37.7 mgKOH/g, a solid content concentration of 30% and a weight average molecular weight of 30,000 was obtained.
65 parts of the obtained polyurethane resin, 2 parts of a styrene-maleic acid resin derivative ("SMA1440H" manufactured by Sartomer, solid content 30% aqueous solution, ammonia-neutralized product of alcohol-modified styrene-maleic acid), vinyl chloride emulsion ( Nisshin Chemical Industry Co., Ltd. "Vinyblan 700", solid content 30% aqueous solution, copolymer of vinyl chloride and other double bond monomers) 4 parts, water 24 parts, isopropanol (hereinafter "IPA") Five parts were mixed and stirred for 30 minutes using a disper to obtain a water-based primer composition 1.
Primer composition 1 corresponds to a water-based primer composition that satisfies (1) to (3) above.

<Production of polyol>
(Production Example 1) Polyester polyol (P-1)
A four-necked separable flask was charged with 472 parts of isophthalic acid, 528 parts of adipic acid, 263 parts of ethylene glycol and 937 parts of neopentyl glycol, and an esterification reaction was carried out at 220-260°C. After distilling out a predetermined amount of water, the pressure was gradually reduced and deglycol reaction was carried out at 240 to 260° C. for 5 hours under 1 mmHg or less. 700 and an acid value of 0.5 mgKOH/g, a polyester polyol (P-1) solution was obtained.

(Production Example 2) Polyester polyol (P-2)
82 parts of terephthalic acid, 682 parts of isophthalic acid, 236 parts of adipic acid, 236 parts of ethylene glycol, 525 parts of neopentyl glycol, and 405 parts of 1,6-hexanediol are charged in a four-necked separable flask and esterified at 220 to 260°C. reaction was carried out. After a predetermined amount of water was distilled off, the pressure was gradually reduced and deglycolization was carried out at 240 to 260° C. for 5 hours under 1 mmHg or less. After that, 2 parts of isophorone diisocyanate was gradually added, and reaction was carried out at 150° C. for about 2 hours to obtain a polyester polyurethane polyol. 2.83 parts of trimellitic anhydride was added to 100 parts of this polyester polyurethane polyol, reacted at 180° C. for about 2 hours, and then diluted with ethyl acetate until the non-volatile content reached 50%, resulting in a number average molecular weight of 6,000. , to obtain a partially acid-modified polyester polyol (P-2) solution having an acid value of 16.5 mgKOH/g.

(Production Example 3) Polyester polyol (P-3)
A four-neck separable flask was charged with 262 parts of terephthalic acid, 393 parts of isophthalic acid, 345 parts of adipic acid, 253 parts of ethylene glycol, 662 parts of 2-methyl-1,3-propanediol, and 153 parts of 1,6-hexanediol. , 220-260°C. After a predetermined amount of water was distilled off, the pressure was gradually reduced and deglycolization was carried out at 240 to 260° C. for 5 hours under 1 mmHg or less. After that, 2 parts of isophorone diisocyanate was gradually added, and reaction was carried out at 150° C. for about 2 hours to obtain a polyester polyurethane polyol. 0.62 parts of trimellitic anhydride was added to 100 parts of this polyester polyurethane polyol, reacted at 180° C. for about 2 hours, and then diluted with ethyl acetate until the non-volatile content reached 50%, resulting in a number average molecular weight of 7,000. , to obtain a partially acid-modified polyester polyol (P-3) solution having an acid value of 3.6 mgKOH/g.

(Production Example 4) Polyester polyol (P-4)
682 parts of isophthalic acid, 274 parts of sebacic acid, 72 parts of adipic acid, 202 parts of ethylene glycol, 506 parts of neopentyl glycol, and 493 parts of 1,6-hexanediol are charged in a four-necked separable flask and esterified at 220 to 260°C. reaction was carried out. After a predetermined amount of water was distilled off, the pressure was gradually reduced and deglycolization was carried out at 240 to 260° C. for 5 hours under 1 mmHg or less. After that, 95 parts of isophorone diisocyanate was gradually added and reacted at 150° C. for about 2 hours to obtain a polyester polyurethane polyol. 2.41 parts of ethylene glycol anhydrotrimellitate was added to 100 parts of this polyester polyurethane polyol, reacted at 180° C. for about 2 hours, and then diluted with ethyl acetate until the nonvolatile content reached 50%. A partially acid-modified polyester polyol (P-4) solution having an acid value of 7,000 and an acid value of 8.5 mgKOH/g was obtained.

(Production Example 5) Polyether polyol (P-5)
P-2000 (trade name, manufactured by ADEKA Corporation, bifunctional polyoxypropylene glycol, hydroxyl value 56.1) 81.95 parts, P-400 (trade name, manufactured by ADEKA Corporation, bifunctional polyoxypropylene glycol, hydroxyl value 265.9) 382.3 parts, T-400 (trade name, manufactured by Mitsui Chemicals, Inc., trifunctional polyoxypropylene glycol, hydroxyl value 404) 81.95 parts, dimethylolpropionic acid 19 parts, acetic acid 132.91 parts of ethyl, 95.53 parts of tolylene diisocyanate, 121 parts of 4,4-diphenylmethane diisocyanate, and 0.22 parts of dibutyltin laurate were charged, heated to 90° C., and isocyanate was detected by infrared absorption spectrum. The reaction was run until the group peak disappeared. Then, by diluting with ethyl acetate so that the non-volatile content becomes 50%, a partially acid-modified polyether polyol (P-5) solution having a number average molecular weight of 9,000 and an acid value of 10.4 mgKOH/g was obtained.

<Production of polyisocyanate>
(Production Example 6) Aliphatic polyisocyanate (CAT-1)
26.6 parts of polypropylene glycol having a number average molecular weight of 400, 1.7 parts of dipropylene glycol, 2.4 parts of tripropylene glycol, and 41.3 parts of isophorone diisocyanate were charged into a reaction vessel, and the NCO/OH molar ratio was 2.1. The mixture was heated at 70° C. to 80° C. for 8 hours while being stirred under a nitrogen gas stream to carry out a urethanization reaction to obtain a polyether polyurethane having an isocyanate group. The obtained polyether polyurethane having isocyanate groups was an aliphatic polyisocyanate with a solid content concentration of 100% by mass and a viscosity of 12,000 mPa·s.

(Production Example 7) Aromatic polyisocyanate (CAT-2)
2.2 parts of neopentyl glycol, 17.8 parts of polypropylene glycol having a number average molecular weight of about 400, 1.7 parts of dipropylene glycol, 2.5 parts of tripropylene glycol, and 47.7 parts of 4,4'-diphenylmethane diisocyanate are reacted. The mixture was charged into a container and heated at 70° C. to 80° C. for 8 hours while being stirred under a nitrogen gas stream under conditions of an NCO/OH molar ratio of 2.1 to carry out a urethanization reaction to obtain a polyether polyurethane having an isocyanate group. . The resulting polyether polyurethane having isocyanate groups was an aromatic polyisocyanate with a solid content concentration of 100% by mass and a viscosity of 17,000 mPa·s.

<Manufacture of lamination adhesive>
[Examples 1 to 9, Comparative Examples 1 to 3]
A polyol and a polyisocyanate were blended at the ratio (mass ratio) shown in Table 2, and ethyl acetate was added to prepare an adhesive solution having a non-volatile content of 30% by mass.

<Evaluation of lamination adhesive>
Using the obtained adhesive solution, a laminate (composite film) was produced by the following method. The obtained laminate was subjected to a laminate strength test and an alkali desorption test as described below. Table 2 shows the results.

(Preparation of configuration A laminate (OPP/printing layer/adhesive layer/LLDPE))
The aforementioned primer composition 1 and printing ink (Rio Alpha R631 White, manufactured by Toyo Ink Co., Ltd.) were each mixed with an ethyl acetate/IPA mixed solvent (mass ratio: 70/30) to give a viscosity of 16 seconds (25°C, Zahn Dilute to cup No. 3).
For a corona-treated OPP film (20 μm thick), diluted primer composition 1 and diluted printing ink are applied in this order at a printing speed of 50 m / min on a gravure proofreading two-color machine equipped with a solid plate with a plate depth of 35 μm. After printing, each unit was dried at 50° C. to obtain a laminate of OPP/primer layer/printing layer.
Next, the adhesive solutions obtained in Examples and Comparative Examples are applied onto the printed layer of the resulting laminate using a laminator so that the amount of adhesive is 3.0 g/m ² at room temperature. After volatilizing the solvent, the adhesive-coated surface and a corona-treated LLDPE film (40 μm thick) were laminated using a laminator to obtain a laminate.
The resulting laminate was kept at 40° C. for 4 days to obtain a composite film having a configuration of OPP/primer layer/printing layer/adhesive layer/LLDPE (hereinafter referred to as configuration A).

(Production of configuration B laminate (PET/printing layer/adhesive layer/NY/adhesive layer/CPP))
A printing ink (Rio Alpha R631 White, manufactured by Toyo Ink Co., Ltd.) is added to a mixed solvent of ethyl acetate/IPA (mass ratio 70/30) to give a viscosity of 16 seconds (25°C, Zahn Cup No. 3). diluted as
After printing the diluted printing ink on a PET film (thickness 12 μm) with a gravure proofing machine equipped with a solid plate with a plate depth of 35 μm, it was dried at 50° C. to obtain a PET/printing layer laminate. .
Next, on the printed layer of the obtained PET/printed layer, the adhesive solutions obtained in Examples and Comparative Examples were applied using a laminator so that the adhesive amount was 3.0 g/m ² at room temperature. After the solvent was volatilized, the adhesive-applied surface was laminated with a NY film (thickness: 15 μm) to obtain a laminate.
Next, on the NY film of the obtained laminate, an adhesive solution was applied in the same manner as before, and after the solvent was volatilized, the adhesive-coated surface was laminated with a corona-treated CPP film (thickness 70 μm). to obtain a laminate.
The resulting laminate was kept at 40° C. for 4 days to obtain a composite film having a structure of PET/printing layer/adhesive layer/NY/adhesive layer/CPP (hereinafter referred to as structure B).

(Removability test)
A 0.2 cm x 1.5 cm test piece was cut from the resulting composite film of configuration A and immersed in 50 g of a 2% aqueous sodium hydroxide (NaOH) solution at 70°C for 20 minutes, 1 hour, and 12 hours. After immersion and agitation were performed under conditions of time, water washing and drying were performed. Detachability of the adhesive and the printed layer from the composite film was visually observed and evaluated according to the following criteria.
◎: All the adhesive and the printed layer were removed within 20 minutes (very good)
○: All the adhesive and the printed layer were detached within 1 hour over 20 minutes (good)
△: All the adhesive and printing layer were removed within 12 hours exceeding 1 hour (usable)
×: Within 12 hours, the adhesive and the printed layer did not all come off (cannot be used)

(Laminate strength test (before retort))
A test piece having a size of 15 mm × 300 mm was cut out from the obtained composite film of configuration B, and a tensile tester was used to perform T-type peeling at a temperature of 20 ° C. and a relative humidity of 65% at a peel speed of 30 cm / In minutes, the laminate strength (N/15 mm) between PET film/NY film and between NY film/CPP film was measured.

(Laminate strength test (after retort))
A pouch having a size of 21 cm x 30 cm was prepared using the obtained composite film of configuration B, and the sauce containing salad oil, ketchup, and 4.2% vinegar at a mass ratio of 1:1:1 as the contents. was vacuum filled. The resulting pouch was subjected to 10 r.p.m. p. m. , 120° C., 30 minutes, hot water sterilization under pressure of 3 MPa.
A test piece with a size of 15 mm × 300 mm was prepared from the pouch after retort treatment, and the laminate strength between PET film / NY film and between NY film / CPP film (N / 15 mm) was performed in the same manner as in the pre-retort laminate strength test. was measured.

Abbreviations in Table 2 are shown below.
CAT-3: HDI isocyanurate derivative (Coronate HK: Tosoh Co., Ltd., aliphatic polyisocyanate derivative), viscosity at 25 ° C. 6300 mPa s
CAT-4: Allophanate derivative of HDI (Coronate 2785: manufactured by Tosoh Corporation, aliphatic polyisocyanate derivative), viscosity at 25 ° C. 2100 mPa s
CAT-5: HDI monomer (aliphatic diisocyanate monomer manufactured by Tokyo Chemical Industry Co., Ltd.) Viscosity at 25 ° C. 3 mPa s

Based on the results in Table 2, the viscosity measured at 25° C. and a rotational speed of 12 rpm with the polyester polyol component (A) and the polyisocyanate component (B) included and the solid content concentration of the polyisocyanate component (B) being 100% by mass. However, the adhesive of the present invention, which has a high viscosity of 1,000 mPa·s or more and 20,000 mPa·s or less, exhibits not only the alkali releasability of the adhesive layer but also excellent alkali releasability of the printed layer. rice field.
Moreover, all of the adhesives of the present invention had retort suitability. Among them, Examples 3 and 4 using three specific polyester polyols showed good lamination strength.

Claims (6)

A lamination adhesive for plastic film recycling that contains a polyol and a polyisocyanate and has releasability from a composite film,
an acid value of 5.0 mgKOH/g or more,
The polyol comprises a polyester polyol component (A),
The polyisocyanate contains a polyisocyanate component (B),
The polyester polyol component (A) contains a polyester polyol having a number average molecular weight of 3,000 to 20,000,
The polyisocyanate component (B) has a viscosity of 1,000 mPa s or more and 20,000 mPa s or less, as measured by a Brookfield viscometer at 25°C and 12 rpm, and is releasable from the composite film. Laminating adhesive for film recycling. 2. The laminating adhesive for plastic film recycling having releasability from the composite film according to claim 1, wherein said polyester polyol component (A) has an acid value of 8.0 mgKOH/g or more. 3. The laminating adhesive for plastic film recycling having releasability from the composite film according to claim 1 or 2, wherein the isocyanate component (B) is an aliphatic polyisocyanate derivative. A laminate in which an adhesive layer made of a laminating adhesive having releasability from a composite film is laminated between at least two sheet-like substrates,
The laminate is for sheet-like substrate recycling,
The laminate adhesive having releasability from the composite film contains a polyol and a polyisocyanate and has an acid value of 5.0 mgKOH/g or more,
The polyol comprises a polyester polyol component (A),
The polyisocyanate contains a polyisocyanate component (B),
The polyester polyol component (A) contains a polyester polyol having a number average molecular weight of 3,000 to 20,000,
A laminate in which the polyisocyanate component (B) has a viscosity of 1,000 mPa·s or more and 20,000 mPa·s or less as measured with a Brookfield viscometer at 25° C. and a number of revolutions of 12 rpm. 5. The laminate according to claim 4, wherein at least one of said sheet-like substrates is a polypropylene substrate. A method for recycling a sheet-like substrate, characterized by detaching the adhesive layer from the laminate and separating the sheet-like substrate with an alkaline aqueous solution,
The laminate is a laminate in which an adhesive layer made of a laminating adhesive having releasability from the composite film is laminated between at least two sheet-like substrates,
The laminate adhesive having releasability from the composite film contains a polyol and a polyisocyanate and has an acid value of 5.0 mgKOH/g or more,
The polyol comprises a polyester polyol component (A),
The polyisocyanate contains a polyisocyanate component (B),
The polyester polyol component (A) contains a polyester polyol having a number average molecular weight of 3,000 to 20,000,
The polyisocyanate component (B) has a viscosity of 1,000 mPa s or more and 20,000 mPa s or less, measured with a Brookfield viscometer at 25° C. and a rotation speed of 12 rpm.
A method for recycling a sheet-shaped base material.