JP7728860B2 - Reactive adhesives, laminating films, and packaging materials - Google Patents

Description

The present invention relates to a reactive adhesive for laminated films suitable for recycled plastics, and to laminated films and packaging materials using the same.

Conventionally, laminated films manufactured by a lamination method using an adhesive have been developed and evolved not only for packaging purposes but also for laminating films of different resins to meet the demand for a single packaging material that has various high functions such as barrier properties, moisture resistance, and retort resistance (see, for example, Patent Document 1).
However, in recent years, there have been voices saying that these laminated films of different resins degrade the quality of recycled plastics, and there is a demand for packaging materials that are both highly functional and recyclable.

As a way to improve the quality of recycled plastics without compromising the functionality of packaging materials, there is a movement toward "composing packaging materials from as single a raw material as possible" (sometimes referred to as "mono-materialization"). Proposals have begun to use laminated films (sometimes referred to as "mono-material films") composed solely of polyolefin films, such as polyethylene film, as the primary plastic material (see, for example, Patent Document 1). As a global trend, the guidelines of the CEFLEX (Circular Economy for Flexible Packaging) consortium, which promotes the realization of a circular economy in the European flexible packaging sector, stipulate that mono-material films must contain less than 5% impurities, such as adhesives. As described below, even if the amount of adhesive impurities is less than 5%, it affects the recyclability of mono-material films. Therefore, it is necessary to consider developing adhesives that do not affect the recyclability of mono-material films.

In addition to the method of laminating laminated films in which each layer is formed by co-extrusion, as described in paragraph 0070 of Patent Document 1, there is also a method of bonding each film together with an adhesive. In particular, laminated films laminated using a thermosetting reactive adhesive formed by the reaction of an isocyanate compound and a polyol compound exhibit strong lamination adhesive strength due to the crosslinked adhesive layer after the reaction, and are excellent in heat resistance, chemical resistance, and oil resistance. For example, they are used as packaging materials for retort-packaged foods, which require retort resistance (see, for example, Patent Document 2). However, laminated flexible films composed solely of polyolefin films and a thermosetting reactive adhesive formed by the reaction of an isocyanate compound and a polyol compound often fail to achieve the strength, particularly tensile elongation, of recycled plastics after recycling.

Japanese Patent Application Laid-Open No. 2020-55176 Japanese Patent Application Laid-Open No. 2001-335771

The objective of the present invention is to provide a reactive adhesive that can be applied to laminated flexible films composed only of polyolefin film and that can maintain the strength, particularly tensile elongation, of recycled plastics.

That is, the present invention provides a reactive adhesive that satisfies (1) and (2).
(1) The polyolefin resin and the reactive adhesive are blended in a ratio of 96:4, and the particle size of the adhesive after melt-kneading at 240°C for 3 minutes is 20 μm or less.
(2) The reactive adhesive has been cured at 40°C for 72 hours, and the cured coating film has an E' at 200°C of 1.0 x 10 ⁵ to 3.0 x 10 ⁶ .

The present invention also provides a laminated film in which substrate films made of multiple olefin-based resins are laminated with a reactive adhesive, wherein the reactive adhesive is the reactive adhesive described above.

The present invention also provides a packaging material made from the laminated film described above.

The present invention can be applied to laminated flexible films made only of polyolefin film, while maintaining the strength of recycled plastic, particularly its tensile elongation.

(reactive adhesive)
The reactive adhesive of the present invention is characterized by satisfying (1) and (2).
(1) The polyolefin resin and the reactive adhesive are blended in a ratio of 96:4, and the particle size of the adhesive after melt-kneading at 240°C for 3 minutes is 20 μm or less.
(2) The reactive adhesive has been cured at 40°C for 72 hours, and the cured coating film has an E' at 200°C of 1.0 x 10 ⁵ to 3.0 x 10 ⁶ .

Currently, the most common method for recycling waste plastics is to manually sort the collected waste plastics into various types, and then turn them into recycled plastics through processes such as crushing, washing, melting, and extrusion.
In this case, laminated films made using thermosetting reactive adhesives, which are produced by the reaction of an isocyanate compound with a polyol compound, have such strong laminating adhesive strength that they cannot be manually separated into the adhesive and film. Therefore, the reactive adhesive and the plastic resin (often a polyolefin resin) that is the material for the laminated film are mixed together and undergo processes such as crushing, washing, melting, and extrusion.

(1) in this invention simulates the "melting" process in this process. The inventors have discovered that even if an adhesive is mixed into the polyolefin resin, which is the material for the laminated film, during the melting process, the strength of the recycled plastic, particularly its tensile elongation, can be maintained if (1) in this invention is used, i.e., if the polyolefin resin and reactive adhesive are blended in a ratio of 96:4 and the adhesive particle size is 20 μm or less after melt-kneading at 230°C for 3 minutes.

On the other hand, (2) in the present invention simulates the "crushing" process in this process. Even if an adhesive is mixed in the polyolefin resin, which is the material of the laminated film, in the crushing process, (2) in the present invention, i.e., an adhesive in which the E' at 200°C of the cured coating film of the reactive adhesive cured at 40°C for 72 hours is in the range of 1.0 x 10 ⁵ to 3.0 x 10 ⁶ , makes it easier to crush the adhesive during melt-kneading, making it possible to further reduce the adhesive particle size in the melting process following the crushing process, making it even easier to achieve the adhesive particle size of 20 μm or less as described in (1) above. As a result, it is estimated that the tensile elongation of the resulting recycled plastic can be maintained.

The above (1) will be explained.
The above (1) is a mixture of a polyolefin resin and a reactive adhesive in a ratio of 96:4, and after melt-kneading at 240° C. for 3 minutes, the particle size of the adhesive is 20 μm or less.
As used herein, polyolefin resin refers to the raw material of polyolefin resin films, which are often used in laminate films produced by lamination, which are highly recyclable. Specific films often used in these laminate films include polyolefin films such as polyethylene films (LLDPE: linear low-density polyethylene film, LDPE: low-density polyethylene film, MDOPE: machine-direction oriented polyethylene film, BOPE: biaxially oriented polyethylene film, HDPE: high-density polyethylene film) and polypropylene films (CPP: unoriented polypropylene film, OPP: biaxially oriented polypropylene film). Furthermore, the raw materials for these films, ethylene and propylene, are available in both petroleum-derived and bio-derived forms.

The polyolefin resin and reactive adhesive are blended in a mass ratio of 96:4. The reactive adhesive may contain an organic solvent, as described below, but in this invention, this is considered to be the solid content.

In the above (1), the melt-kneading conditions were as follows:
The adhesive coating solution is applied to a 20 μm OPP film (biaxially oriented polypropylene film) or a 30 μm CPP film (unoriented polypropylene film) using a bar coater so that the solid weight of the adhesive is approximately 2.0 g/ ^m2. After the solvent is evaporated, the film is laminated to a 30 μm CPP film using a desktop calendar roll. The film is aged at 40°C for 72 hours to produce a laminated film.
In the obtained laminated film, the ratio of "sum of weight of OPP film and weight of CPP film" to "solid content weight of adhesive" was 96:4.
The laminated film was cut into strips with a width of 10 mm and a length of 300 mm, and melt-kneaded for 3 minutes at 240°C and 100 rpm using a twin-screw kneading extruder (ULTnano15TW, manufactured by Technovel Co., Ltd.). The particle size of the adhesive after such melt-kneading conditions was measured.

The particle size of the adhesive was measured by the following method.
The laminated film obtained under the same conditions as the melt-kneading was cut into strips 10 mm wide and 300 mm long. The strips were melt-kneaded at 240 ° C, 100 rpm, and 3 minutes using a twin-screw kneading extrusion device (ULTnano15TW, manufactured by Technovel Co., Ltd.), extruded from the nozzle, and immediately cooled with tap water to obtain a strand-shaped resin. The resulting strands were randomly cut out at 10 locations using a microtome, and each cross section was observed using a SEM backscattered electron image at 15 KV and 150x magnification to obtain an image with a field of view of 400 μm x 600 μm. The adhesive particles were extracted from the obtained image using the image processing and analysis software ImageJ. In this process, 2 × 2 pixels or less were considered noise, and the diameter was calculated from the area assuming the particles to be circles, and a histogram was created. From the obtained histogram, the maximum value of the area accounting for 90% of the total was taken as the adhesive particle size.

In the present invention, the adhesive particle size is preferably 20 μm or less, more preferably 10 μm or less. On the other hand, the lower limit is preferably 1 μm or more, and most preferably 3 μm or more.

The above (2) will now be explained.
The above (2) indicates that the E' at 200°C of the cured coating film of the reactive adhesive cured at 40°C for 72 hours is in the range of 1.0 x 10 ⁵ to 3.0 x 10 ⁶ .
In the present invention, E', E" and tan δ peaks are values obtained by measurement according to the following method.
Using a dynamic viscoelasticity measuring device (RSA G2 manufactured by TA Instruments), a test piece for viscoelasticity measurement is measured under the following conditions to determine E' (storage modulus), E" (loss modulus), and tan δ (loss tangent). The conditions are as follows:
Sample: length 20 mm (excluding gripping margin) x width 5 mm x thickness 0.3 mm
Measurement temperature range: -50 to 200°C
Frequency: 1.0 Hz
Temperature rise rate 5°C/min

The range of E' is preferably 2.0×10 ⁵ to 2.0×10 ⁶ , and more preferably 3.0×10 ⁵ to 1.0×10 ⁶ .

In the present invention, the reactive adhesive used preferably has a tan δ peak after heating at 240° C. of 0° C. or more and 40° C. or less. If the tan δ peak is in this range, the tensile elongation can be further maintained.
The tan δ peak is preferably in the range of 2°C to 36°C, more preferably in the range of 2°C to 25°C.

(reactive adhesive)
The adhesive used in the present invention is a reactive adhesive, which contains a polyisocyanate composition (A) containing an isocyanate compound and a polyol composition (B) containing a polyol compound, which are often used in laminated films produced by a lamination method for which recycling is highly desired.

(Polyisocyanate composition (A))
The polyisocyanate composition (A) contains a polyisocyanate compound (A1). There are no particular limitations on the polyisocyanate compound (A1), and known compounds can be used. Examples include polyisocyanates having an aromatic structure in their molecular structure, such as tolylene diisocyanate, diphenylmethane diisocyanate, polymeric diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate, and xylylene diisocyanate, and compounds in which part of the isocyanate groups (sometimes abbreviated as NCO groups) of these polyisocyanates have been modified with carbodiimide;

Examples include polyisocyanates with an alicyclic structure within their molecular structure, such as isophorone diisocyanate, 4,4'-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; compounds in which some of the NCO groups of these polyisocyanates have been modified with carbodiimide; isocyanurates of these polyisocyanates; allophanates of these polyisocyanates; biuret forms of these polyisocyanates; adducts of these polyisocyanates modified with trimethylolpropane; and polyurethane polyisocyanates, which are reaction products of these polyisocyanates and polyols.

When a polyurethane polyisocyanate is used as the polyisocyanate compound (A1), in terms of the balance between the cohesive strength and flexibility of the adhesive coating film, it is preferable to use one obtained by reacting the above-mentioned polyisocyanate with a polyol in a ratio such that the equivalent ratio of isocyanate groups to hydroxyl groups [NCO]/[OH] is 0.5 to 5.0.

Examples of polyols that are reactive components of polyurethane polyisocyanates include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, methylpentanediol, dimethylbutanediol, butylethylpropanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, and bishydroxyethoxybenzene;

Alicyclic glycols such as 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol; heterocyclic glycols such as tris(2-hydroxyethyl) isocyanurate; trifunctional or tetrafunctional aliphatic alcohols such as glycerin, trimethylolpropane, and pentaerythritol; bisphenols such as bisphenol A, bisphenol F, hydrogenated bisphenol A, and hydrogenated bisphenol F; dimer diol;

Polyether polyols obtained by addition polymerization of alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide, epichlorohydrin, tetrahydrofuran, and cyclohexylene in the presence of a polymerization initiator such as the glycol or a trifunctional or tetrafunctional aliphatic alcohol;

polyester polyols (1) which are reaction products of polyesters obtained by ring-opening polymerization of cyclic ester compounds such as propiolactone, butyrolactone, ε-caprolactone, σ-valerolactone, and β-methyl-σ-valerolactone with the glycols or trifunctional or tetrafunctional aliphatic alcohols;
(2) a polyester polyol obtained by reacting a polyol such as the chain aliphatic glycol, alicyclic glycol, dimer diol, bisphenol, or the polyether polyol with a polycarboxylic acid;

(3) a polyester polyol obtained by reacting the trifunctional or tetrafunctional aliphatic alcohol with a polycarboxylic acid;
(4) a polyester polyol obtained by reacting a difunctional polyol with the trifunctional or tetrafunctional aliphatic alcohol and a polycarboxylic acid;
Polyester polyols (5), which are polymers of hydroxyl acids such as dimethylolpropionic acid and castor oil fatty acid;

a mixture of the polyester polyols (1), (2), (3), (4), and (5) with a polyether polyol;
Examples include castor oil, hydrogenated castor oil which is a hydrogenated castor oil, and castor oil-based polyols such as castor oil alkylene oxide 5 to 50 mole adducts, and these may be used alone or in combination.
Examples of polyvalent carboxylic acids that are reaction components of the polyester polyols (2) to (5) include aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, maleic anhydride, fumaric acid, 1,3-cyclopentanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, and 1,2-bis(phenoxy)ethane-p,p'-dicarboxylic acid; and anhydrides or ester-forming derivatives of these aliphatic or dicarboxylic acids; p-hydroxybenzoic acid, p-(2-hydroxyethoxy)benzoic acid, and ester-forming derivatives of these dihydroxycarboxylic acids; and polybasic acids such as dimer acid.

As the polyisocyanate compound (A1), isocyanurates, allophanates, biuret compounds, and adducts of polyisocyanates having an aromatic structure within their molecular structure, compounds in which some of the NCO groups of polyisocyanates having an aromatic structure within their molecular structure have been modified with carbodiimide, and polyisocyanates having an alicyclic structure within their molecular structure are preferred, and isocyanurates, allophanates, biuret compounds, and adducts of tolylene diisocyanate, 1,6-hexamethylene diisocyanate, xylylene diisocyanate, and isophorone diisocyanate are preferred.

(Polyol composition (B))
The polyol composition (B) used in the present invention is a composition containing a polyol compound (B1) as a main component. The polyol compound (B1) can be used alone or in combination.
Specifically, the various polyols exemplified as reaction components when polyurethane polyisocyanate is used as the polyisocyanate compound (A1) can be used.
For example, chain aliphatic glycols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, methylpentanediol, dimethylbutanediol, butylethylpropanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, and bishydroxyethoxybenzene;

Alicyclic glycols such as 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol;
Trifunctional or tetrafunctional aliphatic alcohols such as glycerin, trimethylolpropane, and pentaerythritol;
bisphenols such as bisphenol A, bisphenol F, hydrogenated bisphenol A, and hydrogenated bisphenol F;
Dimer diol;

Polyether polyols obtained by addition polymerization of alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide, epichlorohydrin, tetrahydrofuran, and cyclohexylene in the presence of a polymerization initiator such as the glycol or a trifunctional or tetrafunctional aliphatic alcohol;

polyester polyols (1) which are reaction products of polyesters obtained by ring-opening polymerization of cyclic ester compounds such as propiolactone, butyrolactone, ε-caprolactone, σ-valerolactone, and β-methyl-σ-valerolactone with the glycols or trifunctional or tetrafunctional aliphatic alcohols;
(2) a polyester polyol obtained by reacting a polyol such as the chain aliphatic glycol, alicyclic glycol, dimer diol, bisphenol, or the polyether polyol with a polycarboxylic acid;

(3) a polyester polyol obtained by reacting the trifunctional or tetrafunctional aliphatic alcohol with a polycarboxylic acid;
(4) a polyester polyol obtained by reacting a difunctional polyol with the trifunctional or tetrafunctional aliphatic alcohol and a polycarboxylic acid;
Polyester polyols (5), which are polymers of hydroxyl acids such as dimethylolpropionic acid and castor oil fatty acid;

a mixture of the polyester polyols (1), (2), (3), (4), and (5) with a polyether polyol;
Examples include castor oil, hydrogenated castor oil which is a hydrogenated castor oil, and castor oil-based polyols such as castor oil alkylene oxide 5 to 50 mole adducts, and these may be used alone or in combination.
Examples of polyvalent carboxylic acids that are reaction components of the polyester polyols (2) to (5) include aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, maleic anhydride, fumaric acid, 1,3-cyclopentanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, and 1,2-bis(phenoxy)ethane-p,p'-dicarboxylic acid; and anhydrides or ester-forming derivatives of these aliphatic or dicarboxylic acids; p-hydroxybenzoic acid, p-(2-hydroxyethoxy)benzoic acid, and ester-forming derivatives of these dihydroxycarboxylic acids; and polybasic acids such as dimer acid.

(Other components of adhesive)
The reactive adhesive of the present invention may contain components other than those described above. These components may be contained in either or both of the polyisocyanate composition (A) and the polyol composition (B), or may be prepared separately and mixed with the polyisocyanate composition (A) and the polyol composition (B) immediately before application of the adhesive. Each component will be described below.

(organic solvent)
The reactive adhesive of the present invention may be either a solvent-based or solventless type. The "solvent-based" adhesive of the present invention refers to a type used in a so-called dry lamination method, in which the adhesive is applied to a substrate, heated in an oven or the like to volatilize the organic solvent in the coating, and then bonded to another substrate. Either the polyisocyanate composition (A) or the polyol composition (B), or both, contain an organic solvent capable of dissolving (diluting) the components of the polyisocyanate composition (A) and the polyol composition (B) used in the present invention.

Examples of organic solvents include esters such as ethyl acetate, butyl acetate, and cellosolve acetate; ketones such as acetone, methyl ethyl ketone, isobutyl ketone, and cyclohexanone; ethers such as tetrahydrofuran and dioxane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride; dimethyl sulfoxide; and dimethyl sulfamide. The organic solvent used as a reaction medium during the production of the components of polyisocyanate composition (A) or polyol composition (B) may also be used as a diluent during application.

As used herein, the term "solventless" refers to an adhesive that is substantially free of the highly soluble organic solvents, particularly ethyl acetate or methyl ethyl ketone, described above, in polyisocyanate composition (A) and polyol composition (B). The adhesive is applied to a substrate and then bonded to another substrate without undergoing a process of heating in an oven or other heating device to volatilize the solvent. This is known as the "non-solvent lamination" method. This definition is also considered to be "substantially free of organic solvents" when trace amounts of organic solvent remain in polyisocyanate composition (A) or polyol composition (B) due to incomplete removal of the organic solvents used as reaction media in the production of the polyisocyanate composition (A) or polyol composition (B) or their raw materials. Furthermore, if polyisocyanate composition (A) contains a low-molecular-weight alcohol, the low-molecular-weight alcohol reacts with polyol composition (B) to become part of the coating film, and therefore does not need to be volatilized after application. Therefore, this type of adhesive is also considered a solventless adhesive, and the low-molecular-weight alcohol is not considered an organic solvent.

(catalyst)
The curing reaction of the reactive adhesive of the present invention can be accelerated by using a catalyst as needed. The catalyst is not particularly limited as long as it accelerates the urethane reaction of the polyisocyanate composition (A) and the polyol composition (B), and examples thereof include metal catalysts, amine catalysts, aliphatic cyclic amide compounds, and titanium chelate complexes.

Examples of metal catalysts include metal complex catalysts, inorganic metal catalysts, and organic metal catalysts. Examples of metal complex catalysts include acetylacetonate salts of metals selected from the group consisting of Fe (iron), Mn (manganese), Cu (copper), Zr (zirconium), Th (thorium), Ti (titanium), Al (aluminum), and Co (cobalt), such as iron acetylacetonate, manganese acetylacetonate, copper acetylacetonate, and zirconia acetylacetonate. From the viewpoints of toxicity and catalytic activity, iron acetylacetonate (Fe(acac) ₃ ) or manganese acetylacetonate (Mn(acac) ₂ ) is preferred.

Inorganic metal catalysts include those selected from Sn, Fe, Mn, Cu, Zr, Th, Ti, Al, Co, etc.

Organometallic catalysts include organic zinc compounds such as zinc octoate, zinc neodecanoate, and zinc naphthenate; organic tin compounds such as stannous diacetate, stannous dioctoate, stannous dioleate, stannous dilaurate, dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin oxide, and dibutyltin dichloride; organic nickel compounds such as nickel octoate and nickel naphthenate; organic cobalt compounds such as cobalt octoate and cobalt naphthenate; organic bismuth compounds such as bismuth octoate, bismuth neodecanoate, and bismuth naphthenate; and titanium compounds such as tetraisopropyloxytitanate, dibutyltitanium dichloride, tetrabutyltitanate, and butoxytitanium trichloride.

Amine catalysts include triethylenediamine, 2-methyltriethylenediamine, quinuclidine, 2-methylquinuclidine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethylpropylenediamine, N,N,N',N",N"-pentamethyldiethylenetriamine, N,N,N',N",N"-pentamethyl-(3-aminopropyl)ethylenediamine, N,N,N',N",N"-pentamethyldipropylenetriamine, N,N,N',N'-tetramethylhexamethylenediamine, bis(2-dimethylaminoethyl)ether, dimethylethanolamine, dimethylisopropanolamine, dimethylaminoethoxyethanol, N,N-dimethyl-N'-(2-hydroxyethyl)ethylenediamine, N,N-dimethyl-N'-(2-hydroxyethyl)propanediamine, bis(dimethylaminopropyl)amine, bis(dimethylaminopropyl)isopropyl Propanolamine, 3-quinuclidinol, N,N,N',N'-tetramethylguanidine, 1,3,5-tris(N,N-dimethylaminopropyl)hexahydro-S-triazine, 1,8-diazabicyclo[5.4.0]undecene-7, N-methyl-N'-(2-dimethylaminoethyl)piperazine, N,N'-dimethylpiperazine, dimethylcyclohexylamine, N-methylmorpholine, N-ethylmorpholine, 1-methylimidazole, 1 , 2-dimethylimidazole, 1-isobutyl-2-methylimidazole, 1-dimethylaminopropylimidazole, N,N-dimethylhexanolamine, N-methyl-N'-(2-hydroxyethyl)piperazine, 1-(2-hydroxyethyl)imidazole, 1-(2-hydroxypropyl)imidazole, 1-(2-hydroxyethyl)-2-methylimidazole, 1-(2-hydroxypropyl)-2-methylimidazole, and the like.

Examples of aliphatic cyclic amide compounds include δ-valerolactam, ε-caprolactam, ω-enantholactam, η-capryllactam, and β-propiolactam. Of these, ε-caprolactam is more effective in promoting curing.

Titanium chelate complexes are compounds whose catalytic activity is enhanced by ultraviolet irradiation, and titanium chelate complexes with an aliphatic or aromatic diketone as a ligand are preferred because of their excellent cure-accelerating effect. Furthermore, in the present invention, those with an alcohol having 2 to 10 carbon atoms as a ligand in addition to an aromatic or aliphatic diketone are preferred because the effects of the present invention are more pronounced.

These catalysts can be used alone or in combination of two or more. The amount of catalyst blended is preferably 0.001 to 3 parts by mass, and more preferably 0.01 to 2 parts by mass, per 100 parts by mass of the total solids content of the polyisocyanate composition (A) and the polyol composition (B).

(Pigment)
The reactive adhesive of the present invention may contain a pigment as needed. The pigment to be used is not particularly limited, and examples thereof include organic pigments and inorganic pigments such as extender pigments, white pigments, black pigments, gray pigments, red pigments, brown pigments, green pigments, blue pigments, metal powder pigments, luminescent pigments, and pearlescent pigments listed in the 1970 edition of the Paint Raw Materials Handbook (compiled by the Japan Paint Manufacturers Association), as well as plastic pigments.

Examples of extender pigments include precipitated barium sulfate, powdered gourd, precipitated calcium carbonate, calcium bicarbonate, kansui stone, alumina white, silica, hydrous fine powdered silica (white carbon), ultrafine powdered anhydrous silica (aerosil), silica sand, talc, precipitated magnesium carbonate, bentonite, clay, kaolin, and yellow ochre.

Specific examples of organic pigments include various insoluble azo pigments such as Benzidine Yellow, Hansa Yellow, and Lake 4R; soluble azo pigments such as Lake C, Carmine 6B, and Bordeaux 10; various (copper) phthalocyanine pigments such as Phthalocyanine Blue and Phthalocyanine Green; various chlorine dye lakes such as Rhodamine Lake and Methyl Violet Lake; various mordant dye pigments such as Quinoline Lake and Fast Sky Blue; various vat dye pigments such as Anthraquinone pigments, Thioindigo pigments, and Perinone pigments; various quinacridone pigments such as Synchasia Red B; various dioxazine pigments such as Dioxazine Violet; various condensed azo pigments such as Chromophtal; and aniline black.

Inorganic pigments include various chromates such as yellow lead, zinc chromate, and molybdate orange; various ferrocyanide compounds such as Prussian blue; various metal oxides such as titanium oxide, zinc white, Mapico yellow, iron oxide, red iron oxide, chrome oxide green, and zirconium oxide; various sulfides or selenides such as cadmium yellow, cadmium red, and mercury sulfide; various sulfates such as barium sulfate and lead sulfate; various silicates such as calcium silicate and ultramarine; various carbonates such as calcium carbonate and magnesium carbonate; various phosphates such as cobalt violet and manganese violet; various metal powder pigments such as aluminum powder, gold powder, silver powder, copper powder, bronze powder, and brass powder; flake pigments of these metals, mica flake pigments; metallic pigments and pearl pigments such as mica flake pigments coated with metal oxides and micaceous iron oxide pigments; graphite, carbon black, etc.

Examples of plastic pigments include "Grandol PP-1000" and "PP-2000S" manufactured by DIC Corporation.

The pigments used may be selected appropriately depending on the purpose, but for example, inorganic oxides such as titanium oxide and zinc oxide are preferred as white pigments due to their excellent durability, weather resistance, and design properties, and carbon black is preferred as a black pigment.

The amount of pigment to be added is, for example, 1 to 400 parts by mass per 100 parts by mass of the total solid content of the polyisocyanate composition (A) and the polyol composition (B), and it is more preferable to add 10 to 300 parts by mass to improve adhesion.

(Adhesion promoter)
The reactive adhesive of the present invention may contain an adhesion promoter. Examples of the adhesion promoter include coupling agents such as silane coupling agents, titanate coupling agents, and aluminum coupling agents, and epoxy resins.

Examples of silane coupling agents include aminosilanes such as γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethyldimethoxysilane, and N-phenyl-γ-aminopropyltrimethoxysilane; epoxysilanes such as β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-glycidoxypropyltriethoxysilane; vinylsilanes such as vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, vinyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane; hexamethyldisilazane, γ-mercaptopropyltrimethoxysilane, etc.

Examples of titanate coupling agents include tetraisopropoxytitanium, tetra-n-butoxytitanium, butyl titanate dimer, tetrastearyl titanate, titanium acetylacetonate, titanium lactate, tetraoctylene glycol titanate, titanium lactate, and tetrastearoxytitanium.

Examples of aluminum-based coupling agents include acetoalkoxyaluminum diisopropylate.

Examples of epoxy resins include various types of epoxy resins commonly available on the market, such as epibis-type, novolac-type, β-methylepicro-type, cyclic oxirane-type, glycidyl ether-type, glycidyl ester-type, polyglycol ether-type, glycol ether-type, epoxidized fatty acid ester-type, polycarboxylic acid ester-type, aminoglycidyl-type, and resorcinol-type, as well as compounds such as triglycidyl tris(2-hydroxyethyl)isocyanurate, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, acrylic glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, phenol glycidyl ether, p-t-butylphenyl glycidyl ether, adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester, glycidyl methacrylate, and butyl glycidyl ether.

(antioxidant)
The reactive adhesive of the present invention may contain an antioxidant. As the antioxidant, a phosphorus-based antioxidant or a binder phenol-based antioxidant is particularly preferred. Examples of phosphorus-based antioxidants include triphenyl phosphite (JP-360, Johoku Chemical Industry Co., Ltd.), trisnonylphenyl phosphite, tricresyl phosphite, triethyl phosphite, trioleyl phosphite, diphenyl mono(2-ethylhexyl) phosphite, tetraphenyl dipropylene glycol diphosphite, tetra(C12 to C15 alkyl)-4,4'-isopropylidene diphenyl diphosphite, bis(decyl)pentaerythritol diphosphite, and tristearyl phosphite. Examples of bound phenol-based antioxidants include pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (BASF Japan Ltd., Irganox 1010), thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-hydroxyphenyl)propionate, and benzyl acetic acid 3,5-bis(1,1-dimethylethyl)-4-hydroxy-C7-C9 branched alkyl ester.
The amount of the phosphorus-based antioxidant added is most preferably 0.1 to 1.0 mass %, and the amount of the bound phenol-based antioxidant added is most preferably 0.1 to 5.0 mass %. The phosphorus-based antioxidant or the bound phenol-based antioxidant may be used alone or in combination.

(Other additives)
In addition to the above-mentioned components, the reactive adhesive of the present invention may contain leveling agents, inorganic microparticles such as colloidal silica and alumina sol, polymethyl methacrylate-based organic microparticles, defoamers, anti-sagging agents, wetting and dispersing agents, viscosity modifiers, UV absorbers, metal deactivators, peroxide decomposers, flame retardants, reinforcing agents, plasticizers, lubricants, rust inhibitors, fluorescent brighteners, inorganic heat absorbers, flame retardants, antistatic agents, dehydrating agents, known and commonly used thermoplastic elastomers, tackifiers, phosphate compounds, melamine resins, reactive elastomers, etc. The amounts of these additives added are adjusted as appropriate within a range that does not impair the desired properties of the reactive adhesive of the present invention.

(Laminated film)
The reactive adhesive of the present invention is particularly useful as a reactive adhesive for laminated films obtained by laminating substrate films made of multiple olefin-based resins with the reactive adhesive. In laminated films of this configuration, the effect of the present invention, particularly the maintenance of tensile elongation of recycled plastics, can be maximized.

Specific examples of olefin-based resins include, but are not limited to, polyolefin films such as polyethylene film (LLDPE: linear low-density polyethylene film, LDPE: low-density polyethylene film, MDOPE: machine-direction oriented polyethylene film, BOPE: biaxially oriented polyethylene film, HDPE: high-density polyethylene film) and polypropylene film (CPP: unoriented polypropylene film, OPP: biaxially oriented polypropylene film). Furthermore, the raw materials for these films, ethylene and propylene, may be derived from either petroleum or bio-based sources, and there are no particular restrictions. Any commercially available olefin-based resin film can be used. These films can be obtained by laminating them using the dry lamination method or the non-solvent lamination method.

The film may be stretched. Stretching methods typically involve melt-extruding the resin into a sheet using an extrusion film-making method, followed by simultaneous biaxial stretching or sequential biaxial stretching. In the case of sequential biaxial stretching, it is common to first stretch the film longitudinally, then stretch it transversely. Specifically, a commonly used method combines longitudinal stretching, which utilizes the speed difference between rolls, with transverse stretching using a tenter.

More specifically, the laminated film has the following structure:
Examples include, but are not limited to, (1) base film 1/adhesive layer 1/sealant film, (2) base film 1/adhesive layer 1/unstretched film, (3) base film 1/adhesive layer 1/stretched film, (4) transparent vapor-deposited stretched film/adhesive layer 1/sealant film, (5) base film 1/adhesive layer 1/base film 2/adhesive layer 2/sealant film, and (6) base film 1/adhesive layer 1/stretched film/adhesive layer 2/sealant film. The sealant film, unstretched film, and stretched film may be subjected to metal vapor deposition, transparent vapor deposition, etc.

The base film 1 used in structure (1) may be an OPP film. The base film 1 may also be coated to improve gas barrier properties or ink receptivity when a printing layer (described below) is provided. A-OPP film is an example of a commercially available coated base film 1. The adhesive layer 1 is a cured coating of the reactive adhesive of the present invention. Examples of sealant films include CPP film and LLDPE film. A printing layer may be provided on the adhesive layer 1 side of the base film 1 (or, when a coated base film 1 is used, on the adhesive layer 1 side of the coating layer). The printing layer is formed using various printing inks, such as gravure ink, flexographic ink, offset ink, stencil ink, and inkjet ink, using a common printing method conventionally used for printing on polymer films.

An example of the base film 1 used in structures (2) and (3) is an OPP film. The adhesive layer 1 is a cured coating of the reactive adhesive of the present invention. An example of an unstretched film is a CPP film, but a VM-CPP film that has been vapor-deposited with aluminum or the like can also be used. An example of a stretched film is an OPP film, but a VM-OPP film that has been vapor-deposited with aluminum or the like can also be used. As with structure (1), a printed layer may be provided on the surface of the base film 1 that faces the adhesive layer 1.

An example of a transparent vapor-deposited stretched film used in structure (4) is a film obtained by vapor-depositing silica or alumina onto an OPP film. A film with a coating applied to the vapor-deposited inorganic layer of silica or alumina may also be used for the purpose of protecting the vapor-deposited inorganic layer. Adhesive layer 1 is a cured coating of the reactive adhesive of the present invention. Examples of sealant films include those similar to those in structure (1). A printed layer may be provided on the adhesive layer 1 side of the transparent vapor-deposited stretched film (when a coating is applied to the inorganic vapor-deposited layer, the adhesive layer 1 side of the coating layer). The method of forming the printed layer is the same as in structure (1).

Examples of the base film 1 used in structure (5) include OPP film, etc. Examples of the base film 2 include OPP film, etc. Adhesive layer 1 and adhesive layer 2 are cured coating films of the reactive adhesive of the present invention. Examples of the sealant film include those similar to those in structure (1). As in structure (1), a printed layer may be provided on the surface of base film 1 facing adhesive layer 1.

Examples of the base film 1 in structure (6) include those similar to those in structures (2) and (3). Examples of stretched films include OPP films, VM-OPP films vapor-deposited with metals such as aluminum, and films vapor-deposited with silica, alumina, etc. At least one of adhesive layer 1 and adhesive layer 2 is a cured coating film of the reactive adhesive of the present invention. Examples of the sealant film include those similar to those in structure (1). As in structure (1), a printed layer may be provided on the surface of base film 1 facing adhesive layer 1.

Of course, the reactive adhesive of the present invention can also be applied to general-purpose films other than the olefin film. For example, for food packaging, polyethylene terephthalate (PET) film, polystyrene film, polyamide film, polyacrylonitrile film, polyvinyl alcohol film, ethylene-vinyl alcohol copolymer film, etc.

Alternatively, a film laminated with a vapor-deposited layer of a metal such as aluminum or a metal oxide such as silica or alumina, or a barrier film containing a gas barrier layer such as polyvinyl alcohol, ethylene-vinyl alcohol copolymer, or vinylidene chloride, may be used in combination. Using such a film can result in a laminated film with barrier properties against water vapor, oxygen, alcohol, inert gases, volatile organic compounds (fragrances), etc.

More specifically, the laminated film has the following structure:
(1) Base film 1/adhesive layer 1/sealant film (2) Base film 1/adhesive layer 1/metal-deposited unstretched film (3) Base film 1/adhesive layer 1/metal-deposited stretched film (4) Transparent vapor-deposited stretched film/adhesive layer 1/sealant film (5) Base film 1/adhesive layer 1/base film 2/adhesive layer 2/sealant film (6) Base film 1/adhesive layer 1/metal-deposited stretched film/adhesive layer 2/sealant film (7) Base film 1/adhesive layer 1/transparent vapor-deposited stretched film/adhesive layer 2/sealant film (8) Base film 1/adhesive layer 1/metal layer/adhesive layer 2/sealant film (9) Base film 1/adhesive layer 1/base film 2/adhesive layer 2/metal layer/adhesive layer 3/sealant film (10) Base film 1/adhesive layer 1/metal layer/adhesive layer 2/base film 2/adhesive layer 3/sealant film, etc., but are not limited to these.

Examples of the substrate film 1 used in structure (1) include OPP film, PET film, and nylon film (hereinafter also referred to as Ny film). The substrate film 1 may also be coated to improve gas barrier properties or ink receptivity when a printing layer (described below) is applied. A-OPP film is an example of a commercially available coated substrate film 1. The adhesive layer 1 is a cured coating of the reactive adhesive of the present invention. Examples of sealant films include CPP film and LLDPE film. A printing layer may be applied to the surface of the substrate film 1 facing the adhesive layer 1 (or, when a coated substrate film 1 is used, the surface of the coating layer facing the adhesive layer 1). The printing layer is formed using various printing inks, such as gravure ink, flexographic ink, offset ink, stencil ink, and inkjet ink, using a common printing method conventionally used for printing on polymer films.

Examples of the base film 1 used in structures (2) and (3) include OPP film and PET film. The adhesive layer 1 is a cured coating of the reactive adhesive of the present invention. The metal-vapor-deposited unstretched film can be a VM-CPP film, which is a CPP film that has been vapor-deposited with a metal such as aluminum, and the metal-vapor-deposited stretched film can be a VM-OPP film, which is an OPP film that has been vapor-deposited with a metal such as aluminum. As with structure (1), a printed layer can be provided on the surface of the base film 1 that faces the adhesive layer 1.

Examples of transparent vapor-deposited stretched films used in structure (4) include films obtained by vapor-depositing silica or alumina onto OPP film, PET film, nylon film, etc. A film with a coating applied to the vapor-deposited inorganic layer of silica or alumina may also be used for the purpose of protecting the vapor-deposited inorganic layer. Adhesive layer 1 is a cured coating of the reactive adhesive of the present invention. Examples of sealant films include those similar to those in structure (1). A printed layer may be provided on the surface of the transparent vapor-deposited stretched film facing adhesive layer 1 (when a film with a coating applied to the inorganic vapor-deposited layer is used, the surface of the coating layer facing adhesive layer 1). The method of forming the printed layer is the same as in structure (1).

Examples of the base film 1 used in structure (5) include PET film, etc. Examples of the base film 2 include nylon film, etc. At least one of adhesive layer 1 and adhesive layer 2 is a cured coating film of the reactive adhesive of the present invention. Examples of the sealant film include those similar to those in structure (1). As in structure (1), a printed layer may be provided on the surface of base film 1 facing adhesive layer 1.

Examples of the base film 1 in structure (6) include those similar to those in structures (2) and (3). Examples of metal-vapor-deposited stretched films include VM-OPP film and VM-PET film, which are OPP film or PET film on which a metal such as aluminum has been vapor-deposited. At least one of adhesive layer 1 and adhesive layer 2 is a cured coating film of the reactive adhesive of the present invention. Examples of the sealant film include those similar to those in structure (1). As in structure (1), a printed layer may be provided on the surface of base film 1 facing adhesive layer 1.

Examples of the base film 1 in structure (7) include PET film, etc. Examples of transparent vapor-deposited stretched films include those similar to those in structure (4). At least one of the adhesive layers 1 and 2 is a cured coating film of the reactive adhesive of the present invention. Examples of the sealant film include those similar to those in structure (1). As in structure (1), a printed layer may be provided on the surface of the base film 1 facing the adhesive layer 1.

Examples of the base film 1 in structure (8) include PET film, etc. Examples of the metal layer include aluminum foil, etc. At least one of the adhesive layers 1 and 2 is a cured coating film of the reactive adhesive of the present invention. Examples of the sealant film include those similar to those in structure (1). As in structure (1), a printed layer may be provided on the surface of the base film 1 facing the adhesive layer 1.

In structures (9) and (10), examples of the base film 1 include a PET film. Examples of the base film 2 include a nylon film. Examples of the metal layer include aluminum foil. At least one of the adhesive layers 1, 2, and 3 is a cured coating film of the reactive adhesive of the present invention. Examples of the sealant film include those similar to those in structure (1). As in structure (1), a printed layer may be provided on the surface of the base film 1 facing the adhesive layer 1.

When the laminated film of the present invention contains at least one of a metal vapor deposition film, a transparent vapor deposition film, and a metal layer, it is preferable that the adhesive layer in contact with the metal vapor deposition layer, the transparent vapor deposition layer, and the metal layer is a cured coating film of the reactive adhesive of the present invention.

When the reactive adhesive of the present invention is solvent-based, the reactive adhesive of the present invention is applied to the film material that will serve as the substrate using a roll such as a gravure roll, and the organic solvent is evaporated by heating in an oven or the like, and then the other substrate is laminated to obtain the laminated film of the present invention. After lamination, it is preferable to perform an aging treatment. The aging temperature is preferably room temperature to 80°C, and the aging time is preferably 12 to 240 hours.

When the reactive adhesive of the present invention is a solventless type, the reactive adhesive of the present invention, which has been preheated to approximately 40°C to 100°C, is applied to the film material that will serve as the substrate using a roll such as a gravure roll, and then the other substrate is immediately laminated to obtain the laminated film of the present invention. After lamination, it is preferable to perform an aging treatment. The aging temperature is preferably room temperature to 70°C, and the aging time is preferably 6 to 240 hours.

When the reactive adhesive of the present invention is used as an adhesive aid, the adhesive aid of the present invention is applied to the base film material using a roll such as a gravure roll, the organic solvent is evaporated by heating in an oven or the like, and then a molten polymer material is laminated using an extruder to obtain the laminated film of the present invention.

The amount of adhesive to be applied is adjusted as appropriate. In the case of a solvent-based adhesive, for example, the amount of solids is adjusted to 1 g/m2 or ^more and 10 g/m2 or ^less , preferably 2 g/m2 or ^more and 5 g/ ^m2 or less. In the case of a solventless adhesive, for example, the amount of adhesive to be applied is adjusted to 1 g/m2 or ^more and 5 g/m2 or ^less , preferably 1 g/m2 or ^more and 3 g/ ^m2 or less.

When the reactive adhesive of the present invention is used as an adhesion promoter, the amount of application is, for example, 0.1 g/m ² or more and 2 g/m ² or less (solid content).

In addition to the above-described components (1) to (10), the laminated film of the present invention may further include other films or substrates. In addition to the above-described stretched films, unstretched films, and transparent vapor-deposited films, other substrates may also include porous substrates such as paper, wood, and leather, as described below. These can be removed as foreign matter using a mesh filter during melt-kneading in the recycling process, making separation easier than separating different plastics. The adhesive used to bond the other substrates may or may not be the reactive adhesive of the present invention.

The paper can be made from any known paper base material without any particular limitations. Specifically, it is produced using natural fibers for papermaking, such as wood pulp, on a known papermaking machine, but the papermaking conditions are not particularly regulated. Examples of natural fibers for papermaking include wood pulp, such as softwood pulp and hardwood pulp; non-wood pulp, such as Manila hemp pulp, sisal hemp pulp, and flax pulp; and chemically modified versions of these pulps. Examples of pulp that can be used include chemical pulp produced by sulfate cooking, acidic, neutral, or alkaline sulfite cooking, and soda cooking, as well as ground pulp, chemi-ground pulp, and thermomechanical pulp.

Various commercially available high-quality papers, coated papers, lined papers, impregnated papers, cardboard, and paperboard can also be used. If necessary, a printed layer can be provided on the outer or inner surface of the paper layer.

The "other layers" may contain known additives and stabilizers, such as antistatic agents, adhesion-enhancing coating agents, plasticizers, lubricants, and antioxidants. Furthermore, the "other layers" may be pre-treated with corona treatment, plasma treatment, ozone treatment, chemical treatment, solvent treatment, etc., to improve adhesion when laminated with other materials.

The laminated film of the present invention can be suitably used for a variety of applications, such as packaging materials for food, medicines, and household goods; lid materials; paper tableware such as paper straws, paper napkins, paper spoons, paper plates, and paper cups; barrier materials; roofing materials; solar panel materials; battery packaging materials; window materials; outdoor flooring materials; lighting protection materials; automotive components; signs; stickers; and other outdoor industrial applications; decorative sheets used in simultaneous injection molding decoration methods; and packaging materials for liquid laundry detergents, liquid kitchen detergents, liquid bath detergents, liquid bath soaps, liquid shampoos, liquid conditioners, and the like.

<Packaging material>
The laminated film of the present invention can be used as a multilayer packaging material for protecting foods, medicines, etc. When used as a multilayer packaging material, the layer structure can be changed depending on the contents, usage environment, and usage form. In addition, the package of the present invention may be appropriately provided with an easy-open treatment or a resealable means.

The packaging material of the present invention is obtained by overlapping the laminate film of the present invention with the sealant film surfaces facing each other and then heat-sealing the peripheral edges to form a bag. Examples of bag-making methods include folding or overlapping the laminate film of the present invention with the inner layer surfaces (sealant film surfaces) facing each other, and heat-sealing the peripheral edges using, for example, a side seal, two-sided seal, three-sided seal, four-sided seal, envelope seal, flared seal, flat-bottom seal, square-bottom seal, gusset seal, or other heat seal methods. The packaging material of the present invention can be in a variety of forms depending on the contents, usage environment, and usage pattern. Self-standing packaging materials (standing pouches) are also possible. Heat sealing can be performed using known methods such as bar seal, rotary roll seal, belt seal, impulse seal, high-frequency seal, and ultrasonic seal.

The packaging material of the present invention is filled with contents through its opening, and the opening is then heat-sealed to produce a product using the packaging material of the present invention. Examples of contents that can be filled include food products such as rice crackers, bean snacks, nuts, biscuits, cookies, wafers, marshmallows, pies, semi-dried cakes, candy, and snacks; bread, snack noodles, instant noodles, dried noodles, pasta, aseptically packaged cooked rice, porridge, porridge, packaged rice cakes, and cereal foods; pickles, boiled beans, natto, miso, frozen tofu, tofu, nametake mushrooms, konjac, processed wild vegetables, jams, peanut cream, salads, frozen vegetables, and processed potatoes; livestock products such as ham, bacon, sausages, processed chicken, and corned beef; and fish ham and other processed foods. Examples of such foods include processed seafood products such as sausages, fish paste products, kamaboko, nori seaweed, tsukudani (simmered foods in soy sauce), bonito flakes, salted fish, smoked salmon, and spicy mentaiko; fruit pulp such as peaches, mandarin oranges, pineapples, apples, pears, and cherries; vegetables such as corn, asparagus, mushrooms, onions, carrots, radishes, and potatoes; cooked foods such as frozen and chilled prepared dishes, including hamburgers, meatballs, fried seafood, gyoza, and croquettes; dairy products such as butter, margarine, cheese, cream, instant creamy powder, and infant formula; liquid seasonings, retort curry, and pet food.

It can also be used as a packaging material for a variety of non-food items, including cigarettes, disposable hand warmers, medicines such as infusion packs, liquid laundry detergent, liquid kitchen detergent, liquid bath detergent, liquid bath soap, liquid shampoo, liquid conditioner, cosmetics such as lotion and emulsion, vacuum insulation materials, batteries, etc.

(recycled plastic)
The laminated film, particularly a laminated film in which substrate films made of a plurality of olefin-based resins are laminated with the reactive adhesive of the present invention, can be reused as a recycled plastic that maintains its tensile elongation.
Here, an example of a method for processing a laminated film into recycled plastic will be described, but the present invention is not limited to this, and various known methods for processing recycled plastics can be applied.

The laminated film is crushed by a crusher etc. The crusher is not particularly limited and any known crusher may be used.
The pulverized film pieces are physically blended using melt kneading, solvent cast blending, latex blending, polymer complexing, etc. Melt kneading is particularly common. Examples of kneading devices include tumblers, Henschel mixers, rotary mixers, super mixers, ribbon tumblers, and V-blenders. The film pieces are melt-kneaded using such kneading devices and then pelletized. Single- or multi-screw extruders are generally used for melt kneading and pelletizing. In addition to these extruders, Banbury mixers, rollers, co-kneaders, blast mills, Prabender blauthographs, etc. can also be used, and these can be operated batchwise or continuously. Alternatively, the film pieces may be used as a molding resin without being melt-kneaded, and melt-kneaded in the heating barrel of a molding machine.

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

(Synthesis of Polyol)
(Polyol B1)
A polyester reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, rectification tube, etc. was charged with 640 parts of isophthalic acid, 670 parts of sebacic acid, 350 parts of ethylene glycol, 700 parts of diethylene glycol, and 2.1 parts of dibutyltin dilaurate, and the esterification reaction was carried out at an internal temperature of 250 ° C. After the dehydration reaction, an intermediate polyester polyol with an acid value of 1 mg KOH / g was obtained. This was dissolved and diluted with ethyl acetate to form a 60 mass % nonvolatile solution, and a polyester polyol with a hydroxyl value of 7 mg KOH / g was obtained. The number average molecular weight of this polyester polyol was approximately 9,500.

(Synthesis of Polyol)
(Polyol B2)
A polyester reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, and rectification tube was charged with 800 parts of isophthalic acid, 700 parts of sebacic acid, 150 parts of ethylene glycol, 700 parts of neopentyl glycol, and 0.3 parts of dioctyltin dilaurate, and the mixture was subjected to an esterification reaction at an internal temperature of 250°C. After the dehydration reaction, an intermediate polyester polyol with an acid value of 1 mgKOH/g was obtained. This was dissolved and diluted with ethyl acetate to obtain a solution with a nonvolatile content of 60% by mass. Furthermore, 4 parts of isophorone diisocyanate were added to 100 parts of the solid content of the obtained intermediate polyester polyol, and the mixture was heated to 80°C and subjected to a urethane reaction until free NCO groups were substantially eliminated, yielding a polyester urethane polyol with a hydroxyl value of 7 mgKOH/g. The number average molecular weight of this polyester urethane polyol was approximately 9,000.

(Synthesis of Polyol)
(Polyol B3)
A polyester reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, and rectification tube was charged with 600 parts of isophthalic acid, 300 parts of phthalic anhydride, 325 parts of sebacic acid, 1275 parts of neopentyl glycol, and 2.1 parts of dibutyltin dilaurate, and the esterification reaction was carried out at an internal temperature of 250 ° C. After the dehydration reaction, an intermediate polyester polyol with an acid value of 1 mg KOH / g was obtained. This was dissolved and diluted with ethyl acetate to form a solution with a nonvolatile content of 57% by mass, and a polyester polyol with a hydroxyl value of 12 mg KOH / g was obtained. The number average molecular weight of this polyester polyol was approximately 5,500.

(Synthesis of Polyol)
(Polyol B4)
A polyester reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, and rectification tube was charged with 425 parts of terephthalic acid, 250 parts of isophthalic acid, 525 parts of adipic acid, 925 parts of ethylene glycol, 400 parts of bisphenol A propylene oxide (2 moles) adduct, and 2.1 parts of dibutyltin dilaurate, and the esterification reaction was carried out at an internal temperature of 260 ° C. After the dehydration reaction, an intermediate polyester polyol with an acid value of 1 mg KOH / g was obtained. This was dissolved and diluted with ethyl acetate to form a solution with a non-volatile content of 51% by mass, and a polyester polyol with a hydroxyl value of 9 mg KOH / g was obtained. The number average molecular weight of this polyester polyol was approximately 7500.

(Synthesis of Polyol)
(Polyol B5)
A polyester reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, and rectification tube was charged with 900 parts of isophthalic acid, 689 parts of 1,4-cyclohexanedicarboxylic acid, 525 parts of adipic acid, 1596 parts of ethylene glycol, 749 parts of neopentyl glycol, and 0.35 parts of dioctyltin dilaurate, and the mixture was subjected to an esterification reaction at an internal temperature of 260°C. After the dehydration reaction, an intermediate polyester polyol with an acid value of 1 mgKOH/g was obtained. This was dissolved and diluted with ethyl acetate to prepare a solution with a nonvolatile content of 60% by mass, yielding a polyester polyol with a hydroxyl value of 8 mgKOH/g. The number average molecular weight of this polyester polyol was approximately 8,300.

(Synthesis of Polyol)
(Polyol B6)
A polyester reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, rectification tube, etc. was charged with 666 parts of succinic acid, 361 parts of ethylene glycol, and 1,474 parts of tris(2-hydroxyethyl) isocyanurate, and an esterification reaction was carried out at an internal temperature of 220°C. After the dehydration reaction, an intermediate polyester polyol with an acid value of 1 mgKOH/g was obtained. 0.2 parts of phosphoric acid was added to this to obtain a polyester polyol with a hydroxyl value of 410 mgKOH/g. The number average molecular weight of this polyester polyol was approximately 420.

(Preparation of Polyisocyanate)
(Polyisocyanate A1)
A flask equipped with a stirrer, a thermometer, and a nitrogen gas inlet tube was charged with 90 parts of Desmodur N3210A (hexamethylene diisocyanate biuret structure, manufactured by COVESTRO) and 10 parts of ethyl acetate to prepare a solution with a nonvolatile content of 90% by mass. The isocyanate (hereinafter sometimes referred to as NCO) content was 20.7% by mass.

(Preparation of Polyisocyanate)
(Polyisocyanate A2)
A flask equipped with a stirrer, a thermometer, and a nitrogen gas inlet tube was charged with 1,260 parts of xylylene diisocyanate, which was then heated to 70°C while stirring, and 750 parts of Polyol B6 was added dropwise using a dropping funnel over 2 hours, followed by stirring for a further 4 hours to obtain a polyisocyanate having an NCO content of 15.7%.

(Preparation of adhesive coating liquid)
Example 1
An adhesive coating liquid of Example 1 was prepared by blending 10 parts of polyol B1 and 0.8 parts of polyisocyanate A1, and adjusting the solid content to 30% with ethyl acetate.

(Examples 2) to (Examples 5)
Adhesive coating solutions of Examples 2 to 5 were prepared in the same manner as in Example 1, except that the formulations of Polyol B and Polyisocyanate A used were changed to those shown in Table 1.

(Comparative Example 1) to (Comparative Example 2)
Adhesive coating solutions of Comparative Examples 1 and 2 were prepared in the same manner as in Example 1, except that the formulations of Polyol B and Polyisocyanate A used were changed to those shown in Table 1.

(evaluation)
(Viscoelasticity measurement of cured coating film)
The adhesive coating liquid was dropped onto a petri dish so as to give a film thickness of 2 mm, and after the ethyl acetate was evaporated at room temperature, the coating was aged at 40° C. for 72 hours.
Using a dynamic viscoelasticity measuring device (RSA G2 manufactured by TA Instruments), the cured coating film for viscoelasticity measurement was measured under the following conditions to determine E' at 200°C.
Cured coating film: length 20 mm (excluding gripping margin) x width 5 mm x thickness 0.3 mm
Measurement temperature range: -50 to 200°C
Frequency: 1.0 Hz
Temperature rise rate 5°C/min

(Viscoelasticity measurement after heating the cured coating film to 240°C)
The adhesive coating solution was dropped onto a petri dish to a film thickness of 2 mm, and after the ethyl acetate was evaporated at room temperature, aging was carried out for 72 hours at 40° C. The resulting cured coating film was heated in an electric oven for 45 minutes to 230° C., and then held for 15 minutes after reaching 240° C.
Using a dynamic viscoelasticity measuring device (RSA G2 manufactured by TA Instruments), the cured coating film for viscoelasticity measurement was measured under the following conditions to determine the tan δ peak temperature.
Cured coating film: length 20 mm (excluding gripping margin) x width 5 mm x thickness 0.3 mm
Measurement temperature range: -50 to 200°C
Frequency: 1.0 Hz
Temperature rise rate 5°C/min

(Adhesive particle diameter after melt-kneading)
The adhesive coating solution was applied to a 30 μm CPP film using a bar coater so that the solid weight of the adhesive was approximately 2.0 g/ ^m2 . After the solvent was evaporated, the film was laminated to a 30 μm CPP film using a desktop calendar roll. Aging was carried out at 40°C for 72 hours to produce a laminated film.
In the obtained laminated film, the ratio of "sum of weight of OPP film and weight of CPP film" to "solid content weight of adhesive" was 96:4.
The laminated film was cut into strips with a width of 10 mm and a length of 300 mm, and the strips were melt-kneaded at 240°C, 100 rpm, and 3 minutes using a twin-screw kneading extrusion device (ULTnano15TW, manufactured by Technovel Co., Ltd.), and then extruded from a nozzle and immediately cooled with tap water to obtain a strand-shaped resin.
The resulting strand was cut out at random in 10 places using a microtome, and each cross section was observed with a SEM backscattered electron image at 15 KV and 150 magnification to obtain an image of a field of view of 400 μm×600 μm.
The obtained images were used with the image processing and analysis software ImageJ to extract adhesive particles. In this process, 2 x 2 pixels or less were judged to be noise, and the particles were assumed to be circular, and the diameter was calculated from the area to create a histogram. The maximum value of the area that accounted for 90% of the total from the obtained histogram was taken as the adhesive particle size. The following CPP film was used.
CPP film: Pylen P1128 30 μm, manufactured by Toyobo Co., Ltd.
The evaluation was as follows:
○: adhesive particle size ≦20 μm
×: adhesive particle size > 20 μm

(Tensile elongation of recycled plastic)
The adhesive coating solution was applied to a 30 μm CPP film using a bar coater so that the solid weight of the adhesive was approximately 2.0 g/ ^m2 . After the solvent was evaporated, the film was laminated to a 30 μm CPP film using a desktop calendar roll. Aging was carried out at 40°C for 72 hours to produce a laminated film.
The laminated film was cut into strips with a width of 10 mm and a length of 300 mm, which were melt-kneaded at 240°C, 100 rpm, and 3 minutes using a twin-screw kneading extrusion device (ULTnano15TW, manufactured by Technovel Co., Ltd.), and then extruded from a nozzle and immediately cooled with tap water to obtain strand-shaped resin, which was then cut to obtain re-pellet samples.
9 g of the pellet sample was placed in a stainless steel press frame mold (inner dimensions 100 mm square, thickness 1 mm), sandwiched between stainless steel plates (thickness 2 mm), and compression molded at 210°C, 30 MPa, and 3 minutes to produce a 1 mm thick plastic plate. A 1/3 size test piece according to JIS K6251-5 was punched out using a Super Dumbbell Cutter SDK500 1/3 manufactured by Dumbbell Co., Ltd., and used for a tensile test. The tensile test was carried out at 50 mm/min with a chuck distance of 30 mm, and the tensile elongation was measured.

The results of the examples are shown in Table 1, and the results of the comparative examples are shown in Table 2. Blank spaces indicate no formulation.

Claims (2)

It is a laminated film in which a plurality of base films made of olefin-based resins are laminated with a reactive adhesive,
A packaging material comprising a laminated film, wherein the reactive adhesive satisfies (1) and (2) and contains (3) .
(1) A polyolefin resin and a reactive adhesive are blended in a ratio of 96:4, and the particle size of the adhesive is measured after the following melt-kneading conditions, and the particle size of the adhesive is 20 μm or less.
The adhesive coating solution is applied to a 20 μm OPP film (biaxially oriented polypropylene film) or a 30 μm CPP film (unoriented polypropylene film) using a bar coater so that the solid weight of the adhesive is approximately 2.0 g/ ^m2. After the solvent is evaporated, the film is laminated to a 30 μm CPP film using a desktop calendar roll. The film is aged at 40°C for 72 hours to produce a laminated film.
In the obtained laminated film, the ratio of "sum of weight of OPP film and weight of CPP film" to "solid content weight of adhesive" was 96:4.
The laminated film is cut into strips 10 mm wide and 300 mm long, and melt-kneaded using a twin-screw kneading extruder (manufactured by Technovel Co., Ltd., ULTnano15TW) at 240° C., 100 rpm, and for 3 minutes.
(2) The storage modulus E' at 200°C of the cured coating film of the reactive adhesive cured at 40°C for 72 hours is in the range of 1.0 x 10 ⁵ to 3.0 x 10 ⁶ .
(3) A polyol composition (B) which is a polyester polyol that is a reaction product of a polyisocyanate composition (A) having a hexamethylene diisocyanate biuret structure, at least one polycarboxylic acid selected from the group consisting of isophthalic acid, sebacic acid, adipic acid, 1,4-cyclohexanedicarboxylic acid, and succinic acid, and at least one polyol selected from the group consisting of ethylene glycol, diethylene glycol, neopentyl glycol, and bisphenol A propylene oxide. Recycled plastic processed from the laminated film described in claim 1.