Adhesive, laminate, packaging material

Abstract

The present invention provides a two-liquid curing adhesive which is less likely to cause appearance defects caused by bubbles or dissolution of a printed layer. A two-liquid curing adhesive comprising: a polyisocyanate composition (A) comprising a urethane prepolymer (A1) which is a reaction product of a polyester polyol (a1) and a polyether polyol (a2) and a polyisocyanate compound (a3); and a polyol composition (B) comprising a polyester polyol (B1), a polyvalent alcohol (a1-2) used in the synthesis of the polyester polyol (a1), and a polyvalent alcohol (b1-2) used in the synthesis of the polyester polyol (B1) each comprising 80% by mass or more of diethylene glycol, the blending amount of the polyester polyol (a1) in the total amount of the polyester polyol (a1) and the polyether polyol (a2) being 50% by mass or more and 90% by mass or less.

Description

Technical Field

[0001] This invention relates to adhesives, laminates obtained using the adhesives, and packaging materials. Background Technology

[0002] The laminates used in various packaging materials and labels are given design, functionality, preservation, convenience and transportability by laminating various plastic films, metal foils, paper and other substrates. In particular, the packaging formed by shaping the laminate into bags is used as packaging for food, medicine, detergents and the like.

[0003] Previously, the mainstream method for lamination used in packaging was to apply an adhesive dissolved in volatile organic solvents (sometimes called solvent-based laminating adhesives) to a substrate, evaporate the organic solvents during the drying process, and then bond the laminations to other substrates using a dry lamination method. However, in recent years, from the perspective of reducing environmental impact and improving the working environment, the demand for reactive two-component laminating adhesives that do not contain volatile organic solvents (hereinafter referred to as solvent-free adhesives) has been increasing (Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2014-159548 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] Solvent-free adhesives offer numerous advantages, including no drying process and no solvent discharge, energy efficiency and low operating costs, and no concerns about solvent residue in laminates formed by bonding plastic films together or laminating plastic films with metal foils or metal vapor-deposited layers. However, they also present the following problems: air bubbles trapped during adhesive mixing and application to the substrate can easily remain in the cured adhesive film. These bubbles can coalesce during aging, leading to poor appearance.

[0009] Furthermore, in laminates used in packaging materials, generally speaking, a printed layer is applied to the back side of the substrate (viewed from the contents) as the outermost layer using printing ink, and the printed layer is bonded to other substrates via an adhesive. On the other hand, the components used in solvent-free adhesives need to be designed with low molecular weights to achieve a coatable viscosity when heated to around 40°C to 100°C. However, low molecular weight polyols can easily cause the printed layer to redissolve, potentially resulting in undesirable appearances such as blackening of the printed layer.

[0010] The present invention was made in view of the following circumstances, and its object is to provide a solvent-free adhesive that is not prone to producing appearance defects caused by bubbles or dissolution of the printed layer, a laminate obtained using the adhesive, and packaging materials.

[0011] Methods for solving problems

[0012] This invention relates to a two-component curing adhesive, comprising: a polyisocyanate composition (A) containing a urethane prepolymer (A1), said urethane prepolymer (A1) being a reaction product of a polyester polyol (a1), a polyether polyol (a2), and a polyisocyanate compound (a3); and a polyol composition (B) containing a polyester polyol (B1), said polyester polyol (B1) being a mixture containing a polycarboxylic acid (b1-1) and a polyvalent alcohol (b1-2). The reaction product of the monomer composition, polyester polyol (a1), is the reaction product of a monomer composition comprising polycarboxylic acid (a1-1) and polyol (a1-2), wherein the polyol (a1-2) comprises more than 80% by mass of diethylene glycol, the amount of polyester polyol (a1) in the total amount of polyester polyol (a1) and polyether polyol (a2) is more than 50% by mass and less than 90% by mass, and the polyol (b1-2) comprises more than 80% by mass of diethylene glycol.

[0013] Furthermore, the present invention relates to a laminate and a packaging material comprising the laminate, the laminate comprising a first substrate, a second substrate, and an adhesive layer for bonding the first substrate and the second substrate, the adhesive layer being a cured coating of the two-component curable adhesive.

[0014] Invention Effects

[0015] The adhesive according to the present invention can provide laminates and packaging materials that suppress appearance defects of laminates caused by bubbles and ink re-dissolution. Detailed Implementation

[0016] <Adhesive>

[0017] The adhesive of the present invention is a two-component curing adhesive comprising a polyisocyanate composition (A) and a polyol composition (B). The adhesive of the present invention will now be described in detail.

[0018] (Polyisocyanate composition (A))

[0019] (Urethane prepolymer (A1))

[0020] The polyisocyanate composition (A) used in the adhesive of the present invention comprises a urethane prepolymer (A1), which is a reaction product of a polyester polyol (a1), a polyether polyol (a2), and a polyisocyanate compound (a3). The polyester polyol (a1) is a reaction product of a monomer composition comprising a polycarboxylic acid (a1-1) and a polyvalent alcohol (a1-2), wherein 80% by mass or more of the polyvalent alcohol (a1-2) is diethylene glycol.

[0021] Examples of polycarboxylic acids (a1-1) used in the synthesis of polyester polyols (a1) include: phthalic acid, terephthalic acid, isophthalic acid, phthalic anhydride, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic anhydride, naphthalenedicarboxylic acid, trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, biphenyl phthalic acid, 1,2-bis(phenoxy)ethane-p,p'-dicarboxylic acid, benzophenone tetracarboxylic acid, benzophenone tetracarboxylic dianhydride, sodium isophthalate-5-sulfonate, tetrachlorophthalic anhydride, tetrabromophthalic anhydride, and other aromatic polycarboxylic acids.

[0022] Methyl esters of aromatic polybasic acids such as dimethyl terephthalic acid and dimethyl 2,6-naphthalenedicarboxylic acid;

[0023] Malic acid, succinic acid, succinic anhydride, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, maleic anhydride, itaconic acid, and other aliphatic polyacids;

[0024] Alkyl esters of aliphatic polyacids such as dimethyl malonate, diethyl malonate, dimethyl succinate, dimethyl glutarate, dimethyl adipate, diethyl heptaate, diethyl sebacate, dimethyl fumarate, diethyl fumarate, dimethyl maleate, and diethyl maleate.

[0025] Alicyclic polyacids such as 1,1-cyclopentanedicarboxylic acid, 1,2-cyclopentanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, tetrahydrophthalic anhydride, 4-methylhexahydrophthalic anhydride, hexahydrophthalic anhydride, cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride, nadic anhydride, and chlorobridged anhydride can be used, either one or two or more in combination.

[0026] From the perspective of effectively reducing the viscosity of the urethane prepolymer (A1) and improving its coating adaptability at low temperatures, it is preferable that the polycarboxylic acid (a1-1) contains adipic acid. The amount of adipic acid can be appropriately adjusted according to factors such as the temperature during coating, and is preferably 80% by mass or more, more preferably 90% by mass or more of the polycarboxylic acid (a1-1). The entire amount of the polycarboxylic acid (a1-1) can be adipic acid.

[0027] There are no particular limitations on the polyvalent alcohols (a1-2) that can be used in combination with diethylene glycol. Examples of difunctional alcohols include: ethylene glycol, propylene glycol, 1,3-propanediol, 1,2,2-trimethyl-1,3-propanediol, 2,2-dimethyl-3-isopropyl-1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 3-methyl-1,3-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, neopentanediol, 1,6-hexanediol, 1,4-bis(hydroxymethyl)cyclohexane, 2,2,4-trimethyl-1,3-pentanediol, and other aliphatic diols.

[0028] Polyoxyethylene glycol, polyoxypropylene glycol and other ether glycols;

[0029] Modified polyether diols are obtained by ring-opening polymerization of aliphatic diols with various compounds containing cyclic ether bonds, such as ethylene oxide, propylene oxide, tetrahydrofuran, ethyl glycidyl ether, propyl glycidyl ether, butyl glycidyl ether, phenyl glycidyl ether, and allyl glycidyl ether.

[0030] Lactone-based polyester polyols are obtained through the polycondensation reaction of aliphatic diols with various lactones such as lactol and ε-caprolactone.

[0031] Bisphenol A, bisphenol F, and other bisphenols;

[0032] Bisphenol alkyl oxide adducts obtained by adding bisphenol A, bisphenol F and other bisphenols to ethylene oxide, propylene oxide and other compounds.

[0033] Examples of polyols with three or more functions include aliphatic polyols such as trimethylolethane, trimethylolpropane, glycerol, hexanetriol, and pentaerythritol.

[0034] Modified polyether polyols are obtained by ring-opening polymerization of aliphatic polyols with various compounds containing cyclic ether bonds, such as ethylene oxide, propylene oxide, tetrahydrofuran, ethyl glycidyl ether, propyl glycidyl ether, butyl glycidyl ether, phenyl glycidyl ether, and allyl glycidyl ether.

[0035] Lactone-based polyester polyols are obtained through the polycondensation reaction of aliphatic polyols with various lactones such as ε-caprolactone.

[0036] From the perspective of minimizing ink redissolution when the adhesive is applied to the printing layer, the proportion of diethylene glycol in the polyvalent alcohol (a1-2) is preferably 90% by mass or more, more preferably 95% by mass or more. The total amount of the polyvalent alcohol (a1-2) can be diethylene glycol.

[0037] The number average molecular weight of the polyester polyol (a1) is not particularly limited. As an example, it is 400 or more and 10,000 or less, more preferably 500 or more and 2,000 or less. It should be noted that the number average molecular weight in this specification is the value measured by gel permeation chromatography (GPC) under the following conditions.

[0038] Measuring device: HLC-8320GPC manufactured by Tosoh Corporation

[0039] Columns: TSKgel 4000HXL, TSKgel 3000HXL, TSKgel2000HXL, TSKgel 1000HXL manufactured by Tosoh Corporation

[0040] Detector: RI (differential refractometer)

[0041] Data processing: MultiStation GPC-8020modelII manufactured by Tosoh Corporation

[0042] Measuring conditions: Column temperature 40°C

[0043] Solvent: Tetrahydrofuran

[0044] Flow rate: 0.35 ml / minute

[0045] Standard: Monodisperse polystyrene

[0046] Sample: A substance (100 μl) obtained by filtering a tetrahydrofuran solution containing 0.2% by mass of resin solid content through a microfilter

[0047] Examples of the polyether polyol (a2) include substances obtained by polymerizing oxirane compounds such as ethylene oxide, propylene oxide, butylene oxide, and tetrahydrofuran using low molecular weight polyols such as water, ethylene glycol, propylene glycol, trimethylolpropane, and glycerol as initiators. One kind or two or more kinds can be used in combination. The number of functional groups of the polyether polyol (a2) is not particularly limited, and polyether polyols having 3 or more functional groups can also be used in addition to those having 2 functional groups. Polypropylene glycol having 2 or 3 functional groups is preferably used.

[0048] The number average molecular weight of the polyether polyol (a2) is not particularly limited. As an example, it is 200 or more and 10,000 or less, more preferably 400 or more and 2,000 or less.

[0049] The blending amount of the polyester polyol (a1) in the total amount of the polyester polyol (a1) and the polyether polyol (a2) is 50% by mass or more and 90% by mass or less.

[0050] As for the polyisocyanate compound (a3), there are no particular limitations. Examples include aromatic diisocyanates, aromatic aliphatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, as well as biuret bodies, isocyanurate bodies, adducts, urea carbamate bodies, carbodiimide-modified bodies, urea diketone-modified bodies, and urethane prepolymers obtained by reacting these polyisocyanates with polyols. They can be used alone or in combination.

[0051] Examples of aromatic diisocyanates include, but are not limited to, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate (also known as polymeric MDI or crude MDI), 1,3-phenyl diisocyanate, 4,4'-diphenyl diisocyanate, 1,4-phenyl diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, bianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, and 4,4',4”-triphenylmethane triisocyanate.

[0052] Aromatic aliphatic diisocyanates refer to aliphatic isocyanates that have one or more aromatic rings in their molecules. Examples include meta- or terephthalic diisocyanate (also known as XDI) and α,α,α',α'-tetramethylphthalic diisocyanate (also known as TMXDI), but are not limited to these.

[0053] Examples of aliphatic diisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (also known as HDI), pentamethylene diisocyanate, 1,2-propylidene diisocyanate, 2,3-butylidene diisocyanate, 1,3-butylidene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate, but these are not the only examples.

[0054] Examples of alicyclic diisocyanates include 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate, isophorone diisocyanate (also known as IPDI), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), and 1,4-bis(isocyanate methyl)cyclohexane, but these are not the only examples.

[0055] Examples of polyols used in the synthesis of urethane prepolymers include: ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, neopentanediol, methylpentanediol, dimethylbutanediol, butyl ethyl propylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanediol, and other alkylene glycols.

[0056] Bisphenol A, bisphenol F, hydrogenated bisphenol A, hydrogenated bisphenol F, and other bisphenols;

[0057] Dimer diol;

[0058] Dihydroxyethoxybenzene;

[0059] Diethylene glycol, triethylene glycol, other polyethylene glycols, polypropylene glycol, polybutylene glycol and other polyalkylene glycols;

[0060] Polyether polyols containing urethane bonds are obtained by further increasing the molecular weight of polyalkylene glycols with aromatic or aliphatic polyisocyanates.

[0061] Polyester polyols are obtained by reacting alkylene glycols or polyalkylene glycols with at least one of the following aliphatic dicarboxylic acids with 2 to 13 carbon atoms: oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid, octanoic acid, azelaic acid, sebacic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, etc., as well as aromatic polycarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, etc.

[0062] Polyester polyols are products of the reaction between polyesters obtained by the ring-opening polymerization of cyclic ester compounds such as proprolactone, butyrolactone, ε-caprolactone, σ-valerolactone, and β-methyl-σ-valerolactone and polyols such as glycols, glycerol, trimethylolpropane, and pentaerythritol.

[0063] From the perspective of initial cohesion and shortening aging time, aromatic diisocyanates and / or their derivatives are preferred.

[0064] The urethane prepolymer (A1) is obtained by reacting the above-mentioned polyester polyol (a1), polyether polyol (a2), and polyisocyanate compound (a3) ​​under conditions of excess isocyanate groups. The ratio of the molar number of isocyanate groups [NCO] to the molar number of hydroxyl groups [OH] [NCO] / [OH] is preferably 1.0 or more and 3.0 or less. More preferably, it is 1.5 to 2.0.

[0065] (Isocyanate compound (A2))

[0066] The polyisocyanate composition (A) may contain an isocyanate compound (A2) other than a urethane prepolymer. As the isocyanate compound (A2), the same substance as the polyisocyanate compound (a3) ​​described above may be used.

[0067] The viscosity of the polyisocyanate composition (A) is adjusted to a range suitable for solventless lamination. For example, the viscosity at 40°C is adjusted to be in the range of 500–5000 mPas, more preferably 500–3000 mPas. For example, the viscosity of the polyisocyanate composition (A) can be adjusted by the amount of urethane prepolymer (A1) and the amount of isocyanate compound (A2).

[0068] (Polyol Composition (B))

[0069] (Polyester polyol (B1))

[0070] The polyol composition (B) used in the adhesive of the present invention comprises a polyester polyol (B1) as a reaction product of a polycarboxylic acid (b1-1) and a polyvalent alcohol (b1-2). Additionally, the polyvalent alcohol (b1-2) comprises at least 80% by mass of diethylene glycol.

[0071] As the polycarboxylic acid (b1-1), the same substance as the polycarboxylic acid (a1-1) can be used. Among these, adipic acid is preferred because it effectively reduces the viscosity of the polyester polyol (B1), improves wettability to the substrate, and enhances coating adaptability at low temperatures. The amount of adipic acid can be adjusted appropriately according to coating conditions, etc. As an example, it is preferably 10% by mass or more and 50% by mass or less of the polycarboxylic acid (b1-1).

[0072] Furthermore, considering the excellent effect of improving the cohesiveness of polyester polyol (B1), suppressing bubble aggregation, and obtaining a laminate with excellent appearance even when the barrier films are laminated together, the polycarboxylic acid (B1-1) preferably includes isophthalic acid. The amount of isophthalic acid is preferably 50% by mass or more and 70% by mass or less of the polycarboxylic acid (B1-1).

[0073] The total amount of adipic acid and isophthalic acid preferably accounts for more than 90% by mass of the polycarboxylic acid (b-1).

[0074] As a polyvalent alcohol (b1-2) that can be used in combination with diethylene glycol, the same substance as polyvalent alcohol (a1-2) can be used. From the perspective of excellent effect in inhibiting ink re-dissolution, the amount of diethylene glycol in the polyvalent alcohol (b1-2) is more preferably 90% by mass or more, and more preferably 95% by mass or more. The total amount of polyvalent alcohol (b1-2) can be diethylene glycol.

[0075] There is no particular limitation on the number average molecular weight of the polyester polyol (B1), but as an example, it is preferred to be 500 or more and 3,000 or less.

[0076] The amount of polyester polyol (B1) incorporated is preferably 50% by mass or more of the polyol composition (B). This results in increased cohesiveness of the adhesive, inhibiting bubble aggregation / growth and improving the appearance of the laminate.

[0077] (Monohydric alcohol compound (B2))

[0078] The polyol composition (B) preferably contains a monohydric alcohol compound (B2). This allows for more effective suppression of poor appearance of the laminate caused by air bubbles. It is presumably because the monohydric alcohol compound (B2) lacks a hydroxyl group at one end, thus easily reducing the viscosity of the polyol composition (B) and suppressing air bubble entrapment during adhesive application. Furthermore, by including the monohydric alcohol compound (B2), the crosslinking density of the adhesive layer is reduced, and the flexibility is increased, thereby improving the adhesion to vapor-deposited metal and metal oxide layers. Improvements in coating adaptability and low-temperature processability are also achieved.

[0079] The main chain of the monohydric alcohol compound (B2) is not particularly limited, and examples include vinyl resins, acrylic resins, polyesters, epoxy resins, and urethane resins having one hydroxyl group. Aliphatic alcohols and alkylalkylene glycols can also be used. The main chain of the monohydric alcohol compound (B2) can be linear or branched. The bonding position of the hydroxyl group is not particularly limited, but it is preferred to be located at the end of the molecular chain.

[0080] Specific examples of such monohydric alcohol compounds (B2) include: methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, lauryl alcohol, myristol, pentadecanol, cetyl alcohol, heptadecanol, stearyl alcohol, nonadecanol, other alkanols (C20-50), oleyl alcohol, and their isomers, etc., all aliphatic monohydric alcohols.

[0081] Cyclohexanol, methylcyclohexanol, 4-butylcyclohexanol, 4-pentylcyclohexanol, 4-hexylcyclohexanol, cyclodecyl alcohol, cyclododecanol, cyclopentadecanol, 4-isopropylcyclohexanol, 3,5,5-trimethylcyclohexanol, menthol, 2-norborneol, borneol, 2-adamantaneol, dicyclohexylmethanol, 6-isopropyl-2-decahydronaphthol (Japanese: デカトール), 2-cyclohexylcyclohexanol, 4-cyclohexylcyclohexanol, 4-(4-propylcyclohexyl)cyclohexanol, 4-(4-pentylcyclohexyl)cyclohexanol, α-ambroxol (Japanese: α-アンブリノール), deoxycorticosterone, 11-Dehydrocorticosterone, cholesterol, β-sitosterol, campesterol, stigmasterol, lanosterol, ergosterol, β-cholesterol, testosterone, estrone, digitalisin, dehydroepiandrosterone, coprosterol, pregnenolone, epicholesterol, 7-dehydrocholesterol, estradiol benzoate, sisal saponin, heco saponin, dehydromethyltestosterone, cortisone acetate, hydroxymethylandrostenone, and their isomers, etc., are alicyclic monohydric alcohols.

[0082] Aromatic aliphatic monohydric alcohols such as benzyl alcohol,

[0083] Polyoxyalkylene monohydric alcohols are obtained by using alkyl compounds containing one active hydrogen atom as initiators to perform ring-opening addition polymerization of ethylene oxide, propylene oxide, butane oxide, tetrahydrofuran, and other epoxides.

[0084] Among them, polyoxyalkylene monohydric alcohols are preferred, and polypropylene glycol monomethyl ether, polypropylene glycol monoethyl ether, and polypropylene monobutyl ether are even more preferred.

[0085] The amount of monohydric alcohol compound (B2) can be appropriately adjusted according to the target properties. For example, to facilitate obtaining the aforementioned effects, it is preferably 1% by mass or more of the total amount of polyester polyol (B1). More preferably, it is 3% by mass or more of the polyol composition (X), and even more preferably 5% by mass or more. Furthermore, to maintain the cohesive strength of the adhesive, it is preferably 30% by mass or less of the total amount of polyester polyol (B1).

[0086] (Polyol (B3))

[0087] The polyol composition (B) may contain a polyol (B3) other than polyester polyol (B1) and monohydric alcohol compound (B2). Examples of such polyols (B3) include: ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, neopentanediol, methylpentanediol, dimethylbutanediol, butyl ethyl propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, dihydroxyethoxybenzene, 1,4-cyclohexanediol, 1,4-cyclohexanediol, triethylene glycol, and other diols.

[0088] Trifunctional or tetrafunctional aliphatic alcohols such as glycerol, trimethylolpropane, and pentaerythritol;

[0089] Bisphenol A, bisphenol F, hydrogenated bisphenol A, hydrogenated bisphenol F, and other bisphenols; dimer diols;

[0090] Polyether polyols are obtained by addition polymerization of ethylene oxide, propylene oxide, butane oxide, styrene oxide, epichlorohydrin, tetrahydrofuran, cyclohexene (Japanese: シクロヘキシレン) and other epoxides in the presence of polymerization initiators such as the above-mentioned diols, trifunctional or tetrafunctional aliphatic alcohols.

[0091] Polyether polyols are further polymerized using the above-mentioned aromatic or aliphatic polyisocyanates to obtain polyether urethane polyols.

[0092] Polyester polyols are products of the reaction of polyesters obtained by the ring-opening polymerization of cyclic ester compounds such as propiolactone, butyrolactone, ε-caprolactone, σ-valerolactone, and β-methyl-σ-valerolactone with polyvalent alcohols such as the above-mentioned diols, glycerol, trimethylolpropane, and pentaerythritol (1).

[0093] Polyester polyol (2) obtained by reacting the above-mentioned diol, dimer diol or the above-mentioned bisphenol and other difunctional polyols with polycarboxylic acids:

[0094] Polyester polyols obtained by reacting trifunctional or tetrafunctional aliphatic alcohols with polycarboxylic acids (3).

[0095] Polyester polyols (4) are obtained by reacting difunctional polyols with the above-mentioned trifunctional or tetrafunctional aliphatic alcohols and polycarboxylic acids.

[0096] Polyester polyols are polymers of hydroxy acids such as dimethylolpropionic acid and castor oil fatty acids (5).

[0097] Polyester polyether polyols (1) to (5) are reacted with the above-mentioned polyether polyols and aromatic or aliphatic polyisocyanates to obtain polyester polyether polyols;

[0098] Polyester polyurethane polyols are obtained by increasing the molecular weight of polyester polyols (1) to (5) using aromatic or aliphatic polyisocyanates.

[0099] Castor oil, dehydrated castor oil, hydrogenated castor oil as a hydrogenated form of castor oil, castor oil-based polyols such as 5-50 molar adducts of castor oil epoxides, and mixtures thereof. As a polycarboxylic acid used in the preparation of polyester polyol (2), examples of polycarboxylic acids that are raw materials for polyester polyol (B1) can be cited.

[0100] The amount of polyol (B3) is not particularly limited, but is preferably limited to less than 50% by mass of the total amount of polyester polyol (B1).

[0101] The viscosity of the polyol composition (B) is adjusted to be suitable for solventless lamination. As an example, the viscosity is adjusted so that it is in the range of 100–5000 mPas, more preferably 100–3000 mPas, at 40°C. As an example, the viscosity of the polyol composition (B) can be adjusted by the backbone of the polyester polyol (B1) and the plasticizer (C5) described later.

[0102] (Other components of the adhesive (C))

[0103] The adhesive of the present invention may contain components other than those described above. Other component (C) may be included in either or both of the polyisocyanate composition (A) or the polyol composition (B), or may be prepared separately beforehand and mixed with the polyisocyanate composition (A) and the polyol composition (B) just before the adhesive is applied. The components are described below.

[0104] (Catalyst (C1))

[0105] Examples of catalysts (C1) include metal catalysts, amine catalysts, and aliphatic cyclic amide compounds.

[0106] Examples of metal-based catalysts (C1) include metal complex-based, inorganic metal-based, and organometallic catalysts. Examples of metal complex-based catalysts include acetylacetone salts of metals selected from Fe (iron), Mn (manganese), Cu (copper), Zr (zirconium), Th (thorium), Ti (titanium), Al (aluminum), and Co (cobalt), such as iron acetylacetone, manganese acetylacetone, copper acetylacetone, and zirconium oxide acetylacetone.

[0107] Examples of inorganic metal catalysts include substances selected from Sn, Fe, Mn, Cu, Zr, Th, Ti, Al, and Co.

[0108] Examples of organometallic catalysts include organozinc compounds such as zinc octanoate, zinc neodecanoate, and zinc naphthenate; organotin compounds such as tin diacetate, tin dioctanoate, tin dioleate, tin dilaurate, dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin oxide, and dibutyltin dichloride; organonitrile compounds such as nickel octanoate and nickel naphthenate; organocobalt compounds such as cobalt octanoate and cobalt naphthenate; organobismuth compounds such as bismuth octanoate, bismuth neodecanoate, and bismuth naphthenate; titanium compounds such as tetraisopropyl titanate, dibutyltitanium dichloride, tetrabutyl titanate, butoxytitanium trichloride, and titanium chelates that use at least one of aliphatic diketones, aromatic diketones, or alcohols with 2 to 10 carbon atoms as ligands.

[0109] Examples of amine catalysts include triethylenediamine, 2-methyltriethylenediamine, quinine ring, 2-methylquinine ring, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethylpropanediamine, 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, and bis(di... Methylaminopropyl)isopropanolamine, 3-quinol, N,N,N',N'-tetramethylguanidine, 1,3,5-tris(N,N-dimethylaminopropyl)hexahydro-triazine, 1,8-diazabicyclo[5.4.0]undecene-7, N-methyl-N'-(2-dimethylaminoethyl)piperazine, N,N'-dimethylpiperazine, dimethylcyclohexylamine, N-methylmorpholine, N-ethylmorpholine, 1-methylimidazolium, 1,2-dimethylimidazolium, 1-isobutyl-2-methylimidazolium, 1-dimethylaminopropylimidazolium, N,N-dimethylhexanolamine, N-methyl-N'-(2-hydroxyethyl)piperazine, 1-(2-hydroxyethyl)imidazolium, 1-(2-hydroxypropyl)imidazolium, 1-(2-hydroxyethyl)imidazolium, 1-(2-hydroxypropyl)imidazolium, 1-(2-hydroxyethyl)-2-methylimidazolium, 1-(2-hydroxypropyl)-2-methylimidazolium, etc.

[0110] Examples of aliphatic cyclic amide compounds include δ-valeramide, ε-caprolactam, ω-heptanolactam, η-octanolactam, and β-propiolactam. Among them, ε-caprolactam is more effective in promoting curing.

[0111] (Acid anhydride (C2))

[0112] As the acid anhydride (C2), cyclic aliphatic acid anhydrides, aromatic acid anhydrides, unsaturated carboxylic acid anhydrides, etc. can be cited, and one kind or two or more kinds in combination can be used. More specifically, for example, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic dianhydride, dodecenyl succinic anhydride, polyadipic anhydride, polynonanoic anhydride, sebacic anhydride, poly(ethyl octadecanedioic) anhydride, poly(phenyl hexadecanedioic) anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, hexahydrophthalic anhydride, methyl humic anhydride, trialkyltetrahydrophthalic anhydride, methylcyclohexene dicarboxylic anhydride, methylcyclohexene tetracarboxylic anhydride, ethylene glycol bis(trimellitate) dianhydride, chlorendic anhydride, nadic anhydride, methyl nadic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalenesuccinic dianhydride, 1-methyl-dicarboxy-1,2,3,4-tetrahydro-1-naphthalenesuccinic dianhydride, etc. can be cited.

[0113] In addition, as the acid anhydride (C), a substance obtained by modifying the above compound with a diol can also be used. As the diol that can be used for modification, alkylene diols such as ethylene glycol, propylene glycol, and neopentyl glycol can be cited; polyether diols such as polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol can be cited, etc. In addition, a copolymer polyether diol of two or more kinds of diols and / or polyether diols among them can also be used.

[0114] (Coupling agent (C3))

[0115] As the coupling agent (C3), silane coupling agents, titanate coupling agents, aluminum coupling agents, etc. can be cited.

[0116] As the silane coupling agent, amino silanes such as γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane can be cited; epoxy silanes such as β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane can be cited; vinyl silanes such as vinyl tris(β-methoxyethoxy)silane, vinyltriethoxysilane, vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane can be cited; hexamethyldisilazane, γ-mercaptopropyltrimethoxysilane, etc.

[0117] As the titanate coupling agent, for example, tetra(isopropoxy)titanium, tetra(n-butoxy)titanium, dibutyl titanate dimer, tetra(stearoyl)titanium, titanium acetylacetonate, titanium lactate, tetra(octylene glycol) titanate, titanium lactate, tetra(stearoxy)titanium, etc. can be cited.

[0118] Examples of aluminum-based coupling agents include aluminum acetylalkoxydiisopropoxide.

[0119] (Pigment (C4))

[0120] As for pigments (C4), there are no particular restrictions. Examples include organic pigments, inorganic pigments, and plastic pigments, such as extender pigments, white pigments, black pigments, gray pigments, red pigments, brown pigments, green pigments, blue pigments, metallic pigments, luminescent pigments, and pearl pigments, as well as pigments listed in the 1970 edition of the Paint Raw Materials Handbook (edited by the Japan Paint Industry Association).

[0121] Examples of pigments that can be categorized as body pigments include: precipitated barium sulfate, lead oxide, precipitated calcium carbonate, calcium bicarbonate, calcite, alumina white, silica, hydrated micronized silica (white carbon), ultrafine anhydrous silica (AEROSIL), silica sand (silica sand), talc, precipitated magnesium carbonate, bentonite, clay, kaolin, loess, etc.

[0122] Specific examples of organic pigments include various insoluble azo pigments such as benzidine yellow, Hansa yellow, and Lake red 4R; soluble azo pigments such as Lake red C, carmine 6B, and maroon 10; various (copper) phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green; various basic dyeing lakes such as rhodamine lake and methyl violet lake; various mordant dyes such as quinoline lake and lapis lazuli; various vat dyes such as anthraquinone, thioindigo, and violet ketone pigments; various quinacridone pigments such as Cinquasia Red B; various dioxazine pigments such as dioxazine violet; various condensed azo pigments such as Gummel; and aniline black.

[0123] As inorganic pigments, examples include various chromates such as chrome yellow, zinc chromate, and molybdenum orange; various ferrocyanide compounds such as Prussian blue; various metal oxides such as titanium dioxide, zinc white, brownish yellow, iron oxide, iron oxide, chromium oxide green, and zirconium oxide; various sulfides or selenides such as cadmium yellow, cadmium red, and mercuric 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, and flake pigments; metal pigments such as mica coated with metal oxides, flake pigments, and mica-like iron oxide pigments; pearl pigments; graphite and carbon black, etc.

[0124] Examples of plastic pigments include DIC Corporation's "GRANDOLL PP-1000" and "PP-2000S".

[0125] Regarding the pigments (C4) used, appropriate selection can be made according to the purpose. For example, in terms of durability, weather resistance, and design excellence, inorganic oxides such as titanium dioxide and zinc white are preferred as white pigments, while carbon black is preferred as a black pigment.

[0126] Regarding the amount of pigment (C4), as an example, it is 1 to 400 parts by mass relative to 100 parts by mass of the total solid components of the polyisocyanate composition (A) and the polyol composition (B). More preferably, it is set to 10 to 300 parts by mass to improve adhesion and anti-blocking properties.

[0127] (Plasticizer (C5))

[0128] Examples of plasticizers include phthalic acid-based plasticizers, fatty acid-based plasticizers, aromatic polycarboxylic acid-based plasticizers, phosphoric acid-based plasticizers, polyol-based plasticizers, epoxy-based plasticizers, polyester-based plasticizers, and carbonate-based plasticizers.

[0129] Examples of phthalic acid-based plasticizers include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diisobutyl phthalate, dihexyl phthalate, diheptyl phthalate, di-(2-ethylhexyl) phthalate, di-n-octyl phthalate, dinonyl phthalate, diisononyl phthalate, didecyl phthalate, diisodecyl phthalate, di(tridecyl) phthalate, di(undecyl) phthalate, and phthalic acid-based plasticizers. Phthalate plasticizers include dilaurate formate, distearate phthalate, diphenyl phthalate, dibenzyl phthalate, butyl benzyl phthalate, dicyclohexyl phthalate, octyl decyl phthalate, dimethyl isophthalate, di-(2-ethylhexyl) isophthalate, and diisooctyl isophthalate; tetrahydrophthalate plasticizers include di-(2-ethylhexyl) tetrahydrophthalate, di-n-octyl tetrahydrophthalate, and diisodecyl tetrahydrophthalate.

[0130] Examples of fatty acid-based plasticizers include di-n-butyl adipate, di-(2-ethylhexyl) adipate, diisodecyl adipate, diisononyl adipate, di(C6-C10) alkyl adipate, and di(butyl diethylene glycol) adipate (Japanese: ジブチルジグリコールアジペート), etc.; and di-n-hexyl azelate, di-(2-ethylhexyl) azelate, etc. Azelaic acid-based plasticizers, such as diisooctyl azelate; sebamic acid-based plasticizers, such as di-n-butyl sebacate, di-(2-ethylhexyl) sebacate, and diisononyl sebacate; maleic acid-based plasticizers, such as dimethyl maleate, diethyl maleate, di-n-butyl maleate, and di-(2-ethylhexyl) maleate; and fumaric acid-based plasticizers, such as di-n-butyl fumarate and di-(2-ethylhexyl) fumarate. Examples of plasticizers include: itaconic acid-based plasticizers such as monomethyl itaconic acid, monobutyl itaconic acid, dimethyl itaconic acid, diethyl itaconic acid, dibutyl itaconic acid, and di-(2-ethylhexyl) itaconic acid; stearic acid-based plasticizers such as n-butyl stearate, glyceryl monostearate, and diethylene glycol distearate; oleic acid-based plasticizers such as butyl oleate, glyceryl monooleate, and diethylene glycol monooleate; citric acid-based plasticizers such as triethyl citrate, tri-n-butyl citrate, acetylated triethyl citrate, acetylated tributyl citrate, and acetylated tri-(2-ethylhexyl) citrate; ricinoleic acid-based plasticizers such as methyl acetylated ricinoleate, acetylated butyl ricinoleate, glyceryl monoricinoleate, and diethylene glycol monoricinoleate; and other fatty acid-based plasticizers such as diethylene glycol monolaurate, diethylene glycol dinonanoate, and pentaerythritol fatty acid esters.

[0131] Examples of aromatic polycarboxylic acid plasticizers include trimellitic acid plasticizers such as tri-n-hexyl trimellitate, tri-(2-ethylhexyl) trimellitate, tri-n-octyl trimellitate, triisooctyl trimellitate, triisononyl trimellitate, tridecyl trimellitate, and triisodecyl trimellitate; and pyromellitic acid plasticizers such as tetra-(2-ethylhexyl) pyromellitic acid and tetra-n-octyl pyromellitic acid.

[0132] Examples of phosphoric acid-based plasticizers include triethyl phosphate, tributyl phosphate, tri-(2-ethylhexyl) phosphate, tri(butoxyethyl) phosphate, triphenyl phosphate, octyl diphenyl phosphate, toluene diphenyl phosphate, toluene phenyl phosphate, tri(toluene) phosphate, tri(xylene) phosphate, tri(chloroethyl) phosphate, tri(chloropropyl) phosphate, tri(dichloropropyl) phosphate, and tri(isopropylphenyl) phosphate.

[0133] Examples of polyol-based plasticizers include diethylene glycol dibenzoate, dipropylene glycol dibenzoate, triethylene glycol dibenzoate, triethylene glycol di-(2-ethylbutyrate), triethylene glycol di-(2-ethylhexanoate), and dibutyl methylene bis(thioglycolic acid) ester; and glycerol-based plasticizers such as glyceryl monoacetate, glyceryl triacetate, and glyceryl tributyrate.

[0134] Examples of epoxy-based plasticizers include epoxidized soybean oil, epoxidized butyl stearate, bis(2-ethylhexyl) epoxidized hexahydrophthalic acid, diisodecyl epoxidized hexahydrophthalic acid, epoxidized triglyceride, epoxidized octyl oleate, and epoxidized decyl oleate.

[0135] Examples of polyester plasticizers include adipic acid-based polyesters, sebacic acid-based polyesters, and phthalic acid-based polyesters.

[0136] Examples of carbonate-based plasticizers include propylene carbonate and ethylene carbonate.

[0137] In addition, other plasticizers include partially hydrogenated terphenyl, adhesive plasticizers, diallyl phthalate, acrylic monomers, oligomers, and other polymeric plasticizers. These plasticizers can be used alone or in combination of two or more.

[0138] (Phosphoric acid compound (C6))

[0139] Examples of phosphoric acid compounds (C6) include phosphoric acid, pyrophosphate, triphosphate, methyl phosphate, ethyl phosphate, butyl phosphate, dibutyl phosphate, 2-ethylhexyl phosphate, bis(2-ethylhexyl) phosphate, isododecyl phosphate, butoxyethyl phosphate, oleic acid phosphate, tetradecyl phosphate, 2-hydroxyethyl methacrylate, polyoxyethylene alkyl ether phosphate, etc.

[0140] (Form of adhesive)

[0141] The adhesive of the present invention can be used in a solvent-free form. It should be noted that, in this specification, "solvent-free" adhesive refers to the form of adhesive used in the following method, namely the so-called solvent-free lamination method: the polyisocyanate composition (A) and the polyol composition (B) are substantially free of esters such as ethyl acetate, butyl acetate, and cellosol 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 dichloromethane and dichloroethane, dimethyl sulfoxide, and dimethyl sulfonamide, especially ethyl acetate or methyl ethyl ketone, and after the adhesive is applied to the substrate, it is bonded to other substrates without a process of heating in an oven or the like to evaporate the solvent. When trace amounts of organic solvents used as reaction media during the manufacture of the components of the polyisocyanate composition (A) and the polyol composition (B) are not completely removed, and thus remain in the polyisocyanate composition (A) and the polyol composition (B), it can be understood that they are substantially free of organic solvents. Furthermore, if the polyol composition (B) contains a low molecular weight alcohol, the low molecular weight alcohol reacts with the polyisocyanate composition (A) to become part of the coating film; therefore, it is not necessary to allow it to evaporate after application. Thus, this form is also treated as a solvent-free adhesive, and the low molecular weight alcohol is not considered an organic solvent.

[0142] The adhesive of the present invention is preferably used in a formulation in which the molar ratio of the isocyanate groups [NCO] contained in the polyisocyanate composition (A) to the molar ratio of the hydroxyl groups [OH] contained in the polyol composition (B) is [NCO] / [OH] of 1.0 to 3.0. This allows for appropriate curing properties regardless of the ambient humidity at the time of application.

[0143] The reason why the adhesive of the present invention excels in suppressing appearance defects caused by bubbles and appearance defects caused by ink re-dissolution is presumably as follows. If the fine bubbles entrained in the adhesive during application remain as they are, they will not be visually perceptible and therefore will not become appearance defects. However, during the aging process, they gradually coagulate and become appearance defects when they reach a size that is visually perceptible. Generally, appearance defects caused by bubbles are less likely to occur when the compounds contained in the polyisocyanate composition (A) and polyol composition (B) have a polyester backbone, but are more likely to occur when they have a polyether backbone. This is believed to be because, in the case of a polyester backbone, the adhesive itself has high cohesiveness, which hinders the coagulation of bubbles.

[0144] On the other hand, appearance defects caused by ink redissolution are less likely to occur when the compounds in the polyisocyanate composition (A) and polyol composition (B) have a polyether backbone, but are more likely to occur when they have a polyester backbone. If the ink redissolves, densely pigmented portions and relatively sparse portions are created in the printed layer. In particular, when a film with a metal vapor-deposited layer such as aluminum is used on one of the substrates to be bonded, the difference between the dense and sparse portions is more visually discernible, and the printed layer appears black when viewed from the surface of the laminate. The less adhesive applied, the more likely appearance defects caused by ink redissolution will occur, and the more adhesive applied, the less likely they will occur. The adhesive of the present invention can highly suppress appearance defects caused by ink redissolution and can provide a laminate with a good appearance even when the amount of adhesive applied is small.

[0145] In the adhesive of the present invention, by selecting diethylene glycol as the compound contained in polyhydric alcohols (a1-2) and (b1-2), and setting the amount of polyester polyol (a1) in the total amount of polyester polyol (a1) and polyester polyol (a2) to be 50% by mass or more and 90% by mass or less, it is possible to suppress appearance defects caused by bubbles without impairing the cohesiveness of the adhesive derived from the polyester skeleton. Furthermore, by setting the amount of diethylene glycol in polyhydric alcohols (a1-2) and (b1-2) to be 80% by mass or more, and setting the amount of polyether polyol (a2) in the total amount of polyester polyol (a1) and polyether polyol (a2) to be 10% by mass or more and 50% by mass or less, it is also possible to suppress ink re-dissolution.

[0146] When the substrates to be bonded are high-barrier substrates (barrier films) such as nylon films or polyester films, or films with vapor-deposited layers of metals such as aluminum or metal oxides such as silicon dioxide or aluminum oxide, appearance defects caused by air bubbles are particularly likely to occur. However, the adhesive of the present invention is excellent at suppressing the occurrence of appearance defects caused by air bubbles even when the barrier films are bonded together.

[0147] In addition, solvent-free adhesives have a relatively lower molecular weight compared to solvent-based adhesives.

[0148] Therefore, the curing shrinkage is large, and when using films with vapor-deposited layers of metals or metal oxides, the adhesive strength sometimes becomes insufficient. However, the adhesive of the present invention exhibits excellent adhesive strength even when using such substrates. This is believed to be due to the high proportion of ester bonds in the adhesive, which maintain adhesive strength through their interaction with the vapor-deposited metal or metal oxide layers.

[0149] <Layered Body>

[0150] The laminate of the present invention is obtained by laminating multiple substrates (films or papers) using the adhesive of the present invention and a solvent-free lamination method. There are no particular limitations on the films used; films appropriate to the intended application can be selected. For example, for food packaging, examples include polyethylene terephthalate (PET) films, polystyrene films, polyamide films, polyacrylonitrile films, polyethylene films (LLDPE: low-density polyethylene film, HDPE: high-density polyethylene film), polypropylene films (CPP: non-stretch polypropylene film, OPP: biaxially oriented polypropylene film), polyolefin films, polyvinyl alcohol films, ethylene-vinyl alcohol copolymer films, etc.

[0151] The film can be a film that has undergone stretching treatment. As a stretching treatment method, resin is typically melted and extruded into a sheet using methods such as extrusion film forming, followed by simultaneous biaxial stretching or successive biaxial stretching. In the case of successive biaxial stretching, longitudinal stretching is usually performed first, followed by transverse stretching. Specifically, a method combining longitudinal stretching utilizing the speed difference between rollers with transverse stretching using a tenter frame is commonly used.

[0152] Various surface treatments, such as flame treatment and corona discharge treatment, can be applied to the membrane surface as needed to form an adhesive layer without defects such as membrane rupture or depression.

[0153] Alternatively, membranes with vapor-deposited layers of metals such as aluminum, silicon dioxide, and alumina, or barrier membranes containing gas barrier layers such as polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and vinylidene chloride can be used. By using such membranes, laminates that provide barrier properties against water vapor, oxygen, alcohols, inactive gases, and volatile organic compounds (fragrances) can be produced.

[0154] There are no particular limitations on the paper itself; any known paper substrate can be used. Specifically, it can be manufactured using natural papermaking fibers such as wood pulp and a known papermaking machine, but the papermaking conditions are not specifically specified. Examples of natural papermaking fibers include wood pulps such as softwood pulp and hardwood pulp, non-wood pulps such as Manila hemp pulp, sisal pulp, and flax pulp, as well as pulps that have undergone chemical modification. As for the type of pulp, chemical pulps based on sulfate hydrolysis, acid / neutral / alkaline sulfite hydrolysis, sodium salt hydrolysis, etc., milled pulps, chemi-milled pulps, thermomechanical pulps, etc., can be used. Additionally, various commercially available high-quality papers, coated papers, lining papers, impregnated papers, corrugated board, and paperboard can also be used.

[0155] The adhesive of the present invention effectively suppresses appearance defects caused by air bubbles, thus exhibiting excellent suppression even when bonding substrates with high gas barrier properties, such as nylon films or polyester films, or films with vapor-deposited layers of metals such as aluminum or metal oxides such as silicon dioxide or aluminum oxide (transparent vapor-deposited films), to each other. Specific examples of such configurations include, but are not limited to, PET film / adhesive layer / aluminum vapor-deposited OPP film, PET film / adhesive layer / aluminum vapor-deposited CP film, PET film / adhesive layer / aluminum vapor-deposited PET film, PET film / adhesive layer / aluminum foil, Ny film / adhesive layer / aluminum vapor-deposited PET film, and PET film / adhesive layer / transparent vapor-deposited PET film. Here, the adhesive layer refers to the cured coating of the adhesive of the present invention.

[0156] The laminate of the present invention may have a printing layer disposed between the adhesive layer and the substrate (usually the outermost substrate relative to the contents). The printing layer is formed using various printing inks such as gravure ink, flexographic ink, offset ink, screen printing ink, and inkjet ink, and by conventional printing methods used for printing on films.

[0157] The adhesive of the present invention, preheated to approximately 40°C to 100°C, is applied to a film or paper material that serves as the substrate using a gravure roller or similar roller coating process. Immediately after application, another substrate is bonded to obtain the laminate of the present invention. After lamination, an aging treatment is preferably performed. The aging temperature is preferably room temperature to 70°C, and the aging time is preferably 6 to 240 hours.

[0158] The amount of adhesive applied should be adjusted appropriately based on the appearance of the laminate (whether there are defects caused by ink redissolution), adhesive properties, etc. For example, it is 1 g / m³. 2 Above and 5g / m 2 The following applies. If the amount of adhesive applied increases, it may become easier for the adhesive to tangle and shift. From a processability point of view, 1 g / m² is preferable. 2 Above and 3g / m 2 the following.

[0159] The lamination speed (the application speed of the adhesive) can be appropriately adjusted based on the appearance of the laminate (whether there are defects caused by air bubbles or ink re-dissolution), productivity, etc. For example, it is 100 to 250 m / min, preferably 150 to 200 m / min. In particular, the faster the lamination speed, the easier it is to entangle air bubbles when applying the adhesive, and the easier it is to produce appearance defects caused by air bubbles. However, according to the adhesive of the present invention, even a lamination speed of about 250 m / min can suppress appearance defects caused by air bubbles and provide a laminate with a good appearance.

[0160] The laminate of the present invention is formed by bonding two substrates together using the adhesive of the present invention, but other substrates may also be included as needed. As a method for laminating other substrates, known methods such as dry lamination, solvent-free lamination, hot lamination, heat sealing, and extrusion lamination can be used. The adhesive used may or may not be the adhesive of the present invention. The same substrates as those described above can be used as other substrates.

[0161] Packaging Materials

[0162] Regarding the packaging material of the present invention, it is manufactured by forming the above-mentioned laminated body into a bag shape and then heat-sealing it. Various packaging materials are available, including three-sided sealed bags, four-sided sealed bags, corner-supported bags, pillow-shaped bags, top-mounted bottomed containers, Tetra Pak cartons, brick-shaped bags, tube containers, paper cups, and lids. Furthermore, the packaging material of the present invention can be appropriately designed with easy-opening and resealing mechanisms.

[0163] The packaging material of this invention can primarily be used industrially as a packaging material for filling food, detergents, and pharmaceuticals. Specific applications include, as detergents and pharmaceuticals, liquid washing detergents, liquid kitchen detergents, liquid bath detergents, liquid bath soaps, liquid shampoos, liquid conditioners, and pharmaceutical tablets. Additionally, it can also be used as a secondary packaging material for packaging the aforementioned containers.

[0164] Example

[0165] The present invention will be described in more detail below with specific examples and embodiments, but the present invention is not limited to these embodiments. It should be noted that, in the following examples, unless otherwise specified, "parts" and "%" represent "parts by mass" and "% by mass", respectively.

[0166] <Polyisocyanate Composition (A)>

[0167] (Synthesis of polyester polyol (a1)-1)

[0168] Seven parts of ethylene glycol and 35 parts of diethylene glycol were added to a flask equipped with a stirrer, thermometer, nitrogen inlet tube, distillation tube, and water separator. The mixture was heated to 80°C under a nitrogen flow while stirring. Further, 36 parts of adipic acid and 22 parts of isophthalic acid were added to a reaction vessel while stirring. The vessel was slowly heated, maintaining the internal temperature at 250°C, with the temperature at the top of the distillation tube not exceeding 100°C, to carry out the esterification reaction. When the acid value became below 12.0 mg KOH / g, the temperature was set to 240°C, and the internal pressure of the reaction vessel was slowly reduced to below 40 Torr, yielding a polyester polyol with hydroxyl groups at both ends, an acid value of 1.0 mg KOH / g, and a hydroxyl value of 84 mg KOH / g. This polyester polyol was designated as (a1)-1.

[0169] (Synthesis of polyester polyols (a1)-2 to (a1)-4)

[0170] By changing the polycarboxylic acid (a1-1) and polyhydric alcohol (a1-2) used to the substances listed in Table 1, and otherwise performing the same operation as polyester polyol (a1)-1, polyester polyols (a1)-2 to (a1)-4 were obtained.

[0171] [Table 1]

[0172]

[0173] (Synthesis of polyisocyanate composition (A)-1)

[0174] A mixture of 2,2-diphenylmethane diisocyanate, 2,4-diphenylmethane diisocyanate, and 4,4'-diphenylmethane diisocyanate (hereinafter referred to as "MDI-50"), comprising 54 parts, was added to a flask equipped with a stirrer, thermometer, and nitrogen inlet tube. The mixture was heated to 60°C under a nitrogen atmosphere with stirring. Then, 23 parts of polyester polyol (a1)-1 and 23 parts of polypropylene glycol (hereinafter referred to as "PPG-1000") with a number average molecular weight of 1000 were added dropwise in several batches. The mixture was further heated to an internal temperature of 70°C for 4 hours to induce a urethane esterification reaction, yielding a urethane prepolymer with isocyanate groups at both ends, containing 14.7% NCO groups. This urethane prepolymer was designated as (A)-1.

[0175] (Synthesis of polyisocyanate compositions (A)-2 to (A)-9)

[0176] By changing the polyester polyol (a1), polyether polyol (a2), and polyisocyanate (a3) ​​used to the substances listed in Tables 2 and 3, and otherwise operating in the same manner as polyisocyanate composition (A)-1, polyester polyols (A)-2 to (A)-9 were obtained.

[0177] [Table 2]

[0178]

[0179] [Table 3]

[0180]

[0181] <Polyol Composition (B)>

[0182] (Synthesis of polyester polyol (B1)-1)

[0183] Nine parts of ethylene glycol and 39 parts of diethylene glycol were added to a flask equipped with a stirrer, thermometer, nitrogen inlet tube, distillation tube, and moisture separator. The mixture was heated to 80°C under a nitrogen flow while stirring. Further, 52 parts of adipic acid were added to the reaction vessel while stirring, and the vessel was slowly heated to maintain an internal temperature of 250°C, ensuring the temperature at the top of the distillation tube did not exceed 100°C, to carry out the esterification reaction. When the acid value fell below 6.0 mg KOH / g, the temperature was set to 240°C, and the pressure inside the reaction vessel was slowly reduced to below 40 Torr, yielding a polyester polyol with hydroxyl groups at both ends, an acid value of 1.0 mg KOH / g, and a hydroxyl value of 203 mg KOH / g. This polyester polyol was designated (B1)-1.

[0184] (Synthesis of polyester polyols (B1)-2 to (B1)-4)

[0185] By changing the polycarboxylic acid (b1-1) and polyhydric alcohol (b1-2) used to the substances listed in Table 4, and otherwise operating in the same manner as polyester polyol (B1)-1, polyester polyols (B1)-2 to (B1)-4 were obtained.

[0186] [Table 4]

[0187]

[0188] (Preparation of polyol composition (B))

[0189] Polyol compositions (B)-1 to (B)-10 were prepared according to the formulations in Tables 5 and 6.

[0190] [Table 5]

[0191]

[0192] [Table 6]

[0193]

[0194] It should be noted that the details of the compounds in Tables 1-6 are as follows.

[0195] AA: Adipic acid

[0196] IPA: Isophthalic acid

[0197] TPA: Terephthalic acid

[0198] SeA: Sebacic acid

[0199] EG: Ethylene glycol

[0200] DEG: Diethylene glycol

[0201] 1,6-HD: 1,6-Hexanediol

[0202] 2MPD: 2-Methylpentanediol

[0203] NPD: Neopentyl Glycol

[0204] MDI-50: A mixture of 2,2-diphenylmethane diisocyanate, 2,4-diphenylmethane diisocyanate, and 4,4-diphenylmethane diisocyanate.

[0205] PPG-1000: Excenol 1020 (manufactured by AGC)

[0206] PPG-400: Excenol 420 (manufactured by AGC)

[0207] Polyalkylene glycol monoalkyl ether: SMACK MP-70 (manufactured by Kao Corporation)

[0208] Polyether polyol (3-functional): Excenol 430 (manufactured by AGC)

[0209] Polyether polyol (6-functional): Excenol 385SO (manufactured by AGC)

[0210] <Preparation of Adhesives>

[0211] The adhesives of Examples 1-6 and Comparative Examples 1-7 were prepared by combining the polyisocyanate composition (A) heated to 40°C and the polyol composition (B) according to Tables 7 and 8.

[0212] <The manufacture of printed materials>

[0213] The urethane-type laminating ink (Finart R794 White G3; manufactured by DIC Corporation) was adjusted to 15 seconds (25°C) using a Zein Cup #3 manufactured by a clutch company. The ink was then printed on a corona-treated PET (polyethylene terephthalate) film (Toyobo ESTER film E5102#12) at a printing speed of 150 m / min using a gravure printing press equipped with a 43 μm deep gravure plate. The film was then dried or cured in an oven at 70°C to form a printed layer on the PET film.

[0214] <Evaluation of the manufacturing of sample 1>

[0215] Using a solvent-free experimental coating machine, the coating amount was set to 2.0 g / m² on the surface of the printed layer printed on the PET film. 2 The prepared adhesive was applied at four speeds: 250 m / min, 200 m / min, 150 m / min, and 100 m / min. An aluminum vapor-deposited unstretched polypropylene film (hereinafter referred to as VMCPP, thickness: 25 μm) was then overlapped and bonded to the coated surface. Next, the adhesive was cured for 24 hours at 40°C and 50% RH, resulting in a laminate consisting of PET / printed layer / adhesive layer / VMCPP, which was used for evaluation as sample 1.

[0216] <Evaluation of the manufacturing of sample 2>

[0217] Using a solvent-free test coating machine, a coating speed of 200 m / min was applied to the surface of the printed layer on the PET film, with a coating concentration of 1.8 g / m. 2 2.1g / m 2 2.3g / m 2 2.5g / m 2 The prepared adhesive was applied in varying amounts, and the vapor-deposited VMCPP surface was overlapped and bonded to the coated surface. Next, the adhesive was cured for 24 hours at 40°C and 50% RH to create a laminate consisting of PET / printed layer / adhesive layer / VMCPP, resulting in evaluation sample 2.

[0218] <Evaluation of the manufacturing of sample 3>

[0219] Using a solvent-free test coating machine, the prepared adhesive was applied to the surface of the printed layer on a PET film at a coating speed of 200 m / min and a coating amount of 2.0 g. The vapor-deposited surface of VMCPP was then overlapped and bonded onto this coated surface. Next, the adhesive was cured for 48 hours at 40°C and 50% RH, thus creating a laminate consisting of PET / printed layer / adhesive layer / VMCPP, resulting in evaluation sample 3.

[0220] <Evaluation>

[0221] (Appearance 1 (bubble))

[0222] The vapor-deposited surface was visually observed through the printed and adhesive layers from the PET side of the evaluation sample 1, and evaluated according to the following criteria.

[0223] 5: Even when the adhesive was applied at a speed of 250 m / min, no air bubbles with a maximum diameter of 0.1 μm or larger were detected.

[0224] 4: Even when the adhesive was applied at a speed of 200 m / min, no air bubbles with a maximum diameter of 0.1 μm or larger were detected.

[0225] 3: Even when the adhesive was applied at a speed of 150 m / min, no air bubbles with a maximum diameter of 0.1 μm or larger were detected.

[0226] 2: Even when the adhesive was applied at a speed of 100 m / min, no air bubbles with a maximum diameter of 0.1 μm or larger were detected.

[0227] 1: Even when the adhesive is applied at a speed of 100 m / min, air bubbles with a maximum diameter of 0.1 μm or more were observed.

[0228] (Appearance 2 (Ink Dissolution))

[0229] The vapor-deposited surface was visually observed through the ink layer and adhesive layer from the PET side of the evaluation sample 2, and evaluated according to the following criteria.

[0230] 5: No blackening areas were detected when the coating amount was 1.8g.

[0231] 4: No blackened areas were detected when the coating amount was 2.1g.

[0232] 3: No blackening areas were detected when the coating amount was 2.3g.

[0233] 2: No blackening areas were detected when the coating amount was 2.5g.

[0234] 1: Blackening was also observed even when the coating amount was 2.5g.

[0235] (Adhesive strength)

[0236] Evaluation sample 3 was cut into pieces 300 mm long and 15 mm wide, and used as test specimens. Using an Instrom tensile testing machine, tensile testing was performed at 25°C and a peel speed of 300 mm / min. The T-peel strength (N) between PET / VMCPP was determined with a width of 15 mm. This test was performed 5 times, and the average value was calculated. Evaluation was then performed according to the following criteria.

[0237] 5: Above 1.0N, and peeling between the aluminum vapor-deposited layer and the CPP or damage and peeling of the aluminum vapor-deposited layer.

[0238] 4: 0.5N or more but less than 1.0N, and peeling between the aluminum vapor-deposited layer and the CPP or damage and peeling of the aluminum vapor-deposited layer.

[0239] 3: 1.0N or more but less than 1.5N, and peeling between the adhesive layer and the aluminum vapor deposition.

[0240] 2: 0.5N or more but less than 1.0N, and peeling between the adhesive layer and the aluminum vapor deposition.

[0241] 1: Below 0.5N, and the peeling between the adhesive and the aluminum vapor deposition.

[0242] [Table 7]

[0243]

[0244] [Table 8]

[0245]

Claims

1. A two-liquid curing type adhesive comprising: a polyisocyanate composition A comprising a urethane prepolymer Al that is a reaction product of a polyester polyol al and a polyether polyol a2 and a polyisocyanate compound a3; and a polyol composition B comprising a polyester polyol Bl that is a reaction product of a monomer composition comprising a polycarboxylic acid bl-1 and a polyvalent alcohol bl-2, the blending amount of the polyester polyol Bl is 50% by mass or more of the polyol composition B, the polyester polyol al is a reaction product of a monomer composition comprising a polycarboxylic acid al-1 and a polyvalent alcohol al-2, the polyvalent alcohol al-2 comprising 80% by mass or more of diethylene glycol, the blending amount of the polyester polyol al in the total amount of the polyester polyol al and the polyether polyol a2 is 50% by mass or more and 90% by mass or less, the polycarboxylic acid al-1 comprises adipic acid, the polycarboxylic acid bl-1 comprises adipic acid, the polyvalent alcohol bl-2 comprises 80% by mass or more of diethylene glycol.

2. The two-liquid curable adhesive according to any one of claims 1, wherein the polycarboxylic acid bl-1 comprises isophthalic acid.

3. The two-part curable adhesive according to claim 1 or 2, wherein the blending amount of the adipic acid in the polycarboxylic acid bl-1 is 10% by mass or more and 50% by mass or less.

4. The two-liquid curable adhesive according to claim 2, wherein the blending amount of the isophthalic acid in the polycarboxylic acid bl-1 is 50% by mass or more and 70% by mass or less.

5. The two-liquid curable adhesive according to claim 1 or 2, wherein the polycarboxylic acid al-1 comprises 80% by mass or more of adipic acid.

6. The two-liquid curable adhesive according to claim 1 or 2, wherein the polyol composition B comprises a monohydric alcohol B2.

7. The two-liquid curable adhesive according to claim 6, wherein the blending amount of the monohydric alcohol B2 in the polyol composition B is 30% by mass or less.

8. The two-liquid curing type adhesive according to claim 1 or 2, comprising a phosphoric acid compound C6.

9. A laminate comprising a first substrate, a second substrate, and an adhesive layer that adheres the first substrate to the second substrate, the adhesive layer being a cured coating film of the two-liquid curing type adhesive according to any one of claims 1 to 8.

10. A packaging material comprising the laminate according to claim 9.

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