Solvent-free adhesives, laminates and packaging

Abstract

To provide: a solvent-free adhesive which materializes superior adhesive strength and heat seal strength (heat resistance) of a metal deposition layer interface and is excellent in coating performance; and a laminate and a package which are excellent in adhesive strength and heat seal strength of the interface, and excellent in appearance.SOLUTION: A solvent-free adhesive is provided, including: polyol compound; and a polyisocyanate compound including polyisocyanate (b1) satisfying the following conditions (1) to (4): (1) polyisocyanate (b1) is a product of reaction between polyether polyol and isocyanate compound; (2) polyether polyol includes 95 mol% or more of the hydroxyl group derived from difunctional polyether polyol; (3) isocyanate compound includes 90 mol% or more of the isocyanate group derived from aromatic diisocyanate compound; and (4) the ICI viscosity at 90°C of polyisocyanate (b1) is 600 [mPa-s] or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a solventless adhesive suitable for laminating various plastic films and metal-deposited films, and a laminate using the same. The present invention also relates to packaging using the laminate for food, medicine, cosmetics, detergents, miscellaneous goods, etc. [Background technology]

[0002] In recent years, due to stricter legal regulations and considerations of environmental conservation and safety, there has been an increasing demand for solvent-free laminating adhesives used in packaging materials. In particular, packaging materials for refills of detergents, fabric softeners, etc., are often composed of three or more laminate films including a metal-deposited film and a thick sealant film, and solvent-free adhesives that can achieve both laminate strength at the interface of the metal-deposited layer, good appearance, and heat seal strength are desired. However, solvent-free adhesives are generally designed to contain resins with low molecular weights for ease of handling, which poses the problem of reduced lamination strength and heat seal strength. On the other hand, increasing the molecular weight of the resin to address this issue results in increased viscosity and a poorer appearance. Therefore, conventional solvent-free adhesives have a trade-off between the above performances, making them difficult to replace solvent-based adhesives.

[0003] To address the above-mentioned issues, Patent Document 1 describes a hot-type solventless adhesive that uses a high-molecular-weight resin in anticipation of high-temperature coating, and describes that by incorporating nurate-type or biuret-type isocyanates, crosslink density is improved, and initial adhesive strength and heat resistance are also improved. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-67319 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the solvent-free adhesive described in Patent Document 1 is designed to have a high crosslink density to compensate for heat resistance. Therefore, when rigid substrates containing metallized films are bonded together to form a laminated film, there is a problem of reduced adhesive strength at the interface of the metallized layer (for example, between nylon and aluminum-vapor-deposited PET in a nylon (NY) / adhesive layer / aluminum-vapor-deposited PET structure, or between PET and aluminum-vapor-deposited PET in a PET / adhesive layer / aluminum-vapor-deposited PET structure). Furthermore, thick sealants are required to be heat-sealed at high temperatures, so heat resistance is required. However, introducing a rigid skeleton to improve heat resistance often results in a trade-off with the aforementioned adhesive strength. Therefore, an object of the present invention is to provide a solventless adhesive that has excellent adhesive strength at the interface of the metal vapor deposition layer, excellent heat seal strength (heat resistance), and excellent coatability.Another object of the present invention is to provide a laminate and a package that have excellent adhesive strength at the interface of the metal vapor deposition layer, heat seal strength (heat resistance), and appearance. [Means for solving the problem]

[0006] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by the following embodiments, and have thus completed the present invention.

[0007] A solventless adhesive according to one embodiment of the present invention comprises a polyol compound (A) and a polyisocyanate compound (B), wherein the polyisocyanate compound (B) contains a first polyisocyanate (b1) that satisfies the following (1) to (4): (1) The polyisocyanate (b1) is a reaction product of a polyether polyol and an isocyanate compound. (2) The polyether polyol contains a bifunctional polyether polyol, and the proportion of the total number of moles of hydroxyl groups contained in the bifunctional polyether polyol is 95 mol% or more based on the total number of moles of hydroxyl groups contained in the polyether polyol. (3) The isocyanate compound contains an aromatic diisocyanate compound, and the proportion of the total number of moles of isocyanate groups contained in the aromatic diisocyanate compound is 90 mol% or more based on the total number of moles of isocyanate groups contained in the isocyanate compound. (4) The polyisocyanate (b1) has an ICI viscosity at 90°C of 600 [mPa·s] or more.

[0008] A solventless adhesive according to another embodiment of the present invention is characterized in that the polyisocyanate compound (B) further contains a second polyisocyanate (b2), and the second polyisocyanate (b2) is contained in an amount of 5 mass % or more and 15 mass % or less, based on the mass of the polyisocyanate compound (B) (however, the second polyisocyanate (b2) excludes the first polyisocyanate (b1)).

[0009] A solventless adhesive according to another embodiment of the present invention is characterized in that the second polyisocyanate (b2) contains 4,4'-diphenylmethane diisocyanate.

[0010] A solventless adhesive according to another aspect of the present invention is characterized by further containing a resin obtained by copolymerizing a (meth)acrylic acid ester and maleic anhydride.

[0011] A solventless adhesive according to another embodiment of the present invention is characterized in that it contains the resin obtained by copolymerizing the (meth)acrylic acid ester and maleic anhydride in an amount of 0.1 mass % or more and 2.0 mass % or less, based on the mass of the polyisocyanate compound (B).

[0012] The solventless adhesive according to another embodiment of the present invention is further characterized by containing a filler having a pH value measured in accordance with JIS K 5101 of more than 7.0.

[0013] A solventless adhesive according to another embodiment of the present invention is characterized in that the filler is contained in an amount of 0.1 mass % or more and 2.0 mass % or less, based on the mass of the polyisocyanate compound (B).

[0014] A solventless adhesive according to another aspect of the present invention is characterized in that the polyol compound (A) contains a polyester polyol.

[0015] A solventless adhesive according to another embodiment of the present invention is characterized in that the polyester polyol is a reaction product of a hydroxyl group component and a carboxyl group component, and satisfies all of the following (5) to (7): (5) The hydroxyl group component contains a diol, the carboxyl group component contains a dicarboxylic acid, and the ratio of the total number of moles of hydroxyl groups and carboxyl groups contained in the diol and the dicarboxylic acid is 85 mol% or more based on the total number of moles of hydroxyl groups and carboxyl groups contained in the hydroxyl group component and the carboxyl group component. (6) The molar equivalent ratio (OH / COOH) of the hydroxyl groups of the hydroxyl group component to the carboxyl groups of the carboxyl group component is 1.1 or more and 1.5 or less. (7) The carboxyl group component contains 25 mol % or more and 60 mol % or less of aromatic carboxyl group components based on the total number of moles of the carboxyl group components.

[0016] A laminate according to another embodiment of the present invention is characterized in that an adhesive layer formed using the solventless adhesive is laminated between at least two sheet-like substrates.

[0017] A laminate according to another embodiment of the present invention is characterized in that at least one of the at least two sheet-like substrates is a metal vapor deposition film, and the metal vapor deposition layer of the metal vapor deposition film is in contact with the adhesive layer.

[0018] A package according to another aspect of the present invention is characterized by using the above-mentioned laminate. [Effects of the Invention]

[0019] The present invention provides a solventless adhesive that has excellent adhesive strength at the interface of the metal vapor deposition layer, excellent heat seal strength (heat resistance), and excellent coatability.The present invention also provides a laminate and a package that have excellent adhesive strength at the interface of the metal vapor deposition layer, heat seal strength (heat resistance), and appearance. DETAILED DESCRIPTION OF THE INVENTION

[0020] [Solvent-free adhesive composition] The solventless adhesive of the present invention comprises a polyol compound (A) and a polyisocyanate compound (B), wherein the polyisocyanate compound (B) contains a first polyisocyanate (b1) that satisfies the following (1) to (4): (1) The polyisocyanate (b1) is a reaction product of a polyether polyol and an isocyanate compound. (2) The polyether polyol contains a bifunctional polyether polyol, and the proportion of the total number of moles of hydroxyl groups contained in the bifunctional polyether polyol is 95 mol% or more based on the total number of moles of hydroxyl groups contained in the polyether polyol. (3) The isocyanate compound contains an aromatic diisocyanate compound, and the proportion of the total number of moles of isocyanate groups contained in the aromatic diisocyanate compound is 90 mol% or more based on the total number of moles of isocyanate groups contained in the isocyanate compound. (4) The polyisocyanate (b1) has an ICI viscosity at 90°C of 600 [mPa·s] or more.

[0021] The polyisocyanate (b1) is a highly flexible and viscous polyether urethane polyisocyanate containing a high proportion of bifunctional polyether polyol. Therefore, it can exhibit high lamination strength even between rigid substrates such as NY / aluminum-deposited PET or PET / aluminum-deposited PET. Furthermore, the polyisocyanate (b1) has an ICI viscosity of 600 mPa·s or more at 90°C. Furthermore, because it contains a high proportion of rigid aromatic diisocyanate compounds, it has high heat resistance and exhibits excellent heat seal strength. Furthermore, because the solventless adhesive of the present invention possesses the aforementioned flexibility and rigidity, it also exhibits excellent coatability and a good coating appearance.

[0022] More specifically, it is presumed that the polyisocyanate compound (B) used in the solventless adhesive of the present invention exhibits the above-mentioned excellent effects because it has an optimal balance of the following items (i) to (iii): (i) Stress relaxation ability (flexibility) due to the flexible polyether polyurethane chain, which is low in branching due to the use of a high proportion of bifunctional polyether polyol and has a high molecular weight due to the presence of polyisocyanate with a high ICI viscosity. (ii) Polymer elasticity due to entanglement of polymer chains. (iii) Interfacial cohesion (rigidity) due to the use of a high proportion of aromatic diisocyanate compounds, which have a rigid skeleton with low degrees of freedom.

[0023] As a result, the solvent-free adhesive of the present invention, as well as laminates and packages using the adhesive, can be used as packaging materials for a variety of applications, such as food, pharmaceuticals, cosmetics, detergents, and miscellaneous goods, and can be particularly suitably used as refill packaging materials. The present invention will be described in detail below.

[0024] <Polyol compound (A)> The polyol compound (A) used in the present invention may be any compound having two or more hydroxyl groups and may be selected from known polyols. The polyol compound (A) may be a single polyol or a combination of two or more polyols. Examples of the polyol include polyester polyol, polycarbonate polyol, polycaprolactone polyol, polyether polyol, polyolefin polyol, acrylic polyol, silicone polyol, castor oil polyol, and fluorine-based polyol.

[0025] These polyols may be those in which urethane bonds have been introduced by reacting some of the hydroxyl groups with diisocyanate (for example, polyether urethane polyol, polyester urethane polyol), or those in which carboxyl groups have been introduced by reacting some of the hydroxyl groups with acid anhydride. Examples of the diisocyanate include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, hexamethylene diisocyanate, and hydrogenated diphenylmethane diisocyanate. Examples of the acid anhydride include pyromellitic anhydride, mellitic anhydride, trimellitic anhydride, and trimellitic ester anhydride. Examples of the trimellitic ester anhydride include ester compounds obtained by esterifying alkylene glycol or alkanetriol having 2 to 30 carbon atoms with trimellitic anhydride, and specific examples of the acid anhydride include ethylene glycol bisanhydrotrimellitate and propylene glycol bisanhydrotrimellitate.

[0026] From the viewpoint of leveling ability and adhesive performance to a substrate, the polyol compound (A) preferably contains a polyether polyol or a polyester polyol, and from the viewpoint of improving heat resistance and metal adhesion, it is more preferable that the polyol compound (A) contains a polyester polyol.

[0027] (Polyether polyol) The polyether polyol may be any compound having two or more hydroxyl groups and two or more ether bonds in the molecule, and these polyether polyols may be used alone or in combination of two or more. Examples of the polyether polyol include polyalkylene glycols such as polyethylene glycol, polytrimethylene glycol, polypropylene glycol, polytetramethylene glycol, and polybutylene glycol; polyethylene glycol / polypropylene glycol block copolymers; and propylene oxide / ethylene oxide random polyethers. Alternatively, an addition polymer obtained by addition polymerization of an oxirane compound such as ethylene oxide, propylene oxide, butylene oxide, or tetrahydrofuran to a low molecular weight polyol such as water, ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, or sucrose may be used as the polyether polyol. Examples of the addition polymer include propylene glycol propylene oxide adducts, glycerin propylene oxide adducts, sorbitol-based propylene oxide adducts, and sucrose-based propylene oxide adducts. The number average molecular weight of the polyether polyol is preferably 400 or more and 4,000 or less, and more preferably 400 or more and 2,000 or less.

[0028] (polyester polyol) Examples of polyester polyols include polyester polyols obtained by reacting a carboxyl group component with a hydroxyl group component; and polyester polyols obtained by ring-opening polymerization of lactones such as polycaprolactone, polyvalerolactone, and poly(β-methyl-γ-valerolactone). The carboxyl group component is not particularly limited as long as it is a known component, and a monofunctional carboxylic acid or a polyvalent carboxylic acid can be used. Examples of such carboxy group components include monofunctional carboxylic acids having an aromatic ring, such as benzoic acid, phenylacetic acid, and 3-phenylpropionic acid; acyclic aliphatic dicarboxylic acids, such as succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, maleic anhydride, and fumaric acid; alicyclic dicarboxylic acids, such as 1,3-cyclopentanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid; aromatic dicarboxylic acids, such as terephthalic acid, isophthalic acid, phthalic 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; anhydrides or ester-forming derivatives of these aliphatic or aromatic dicarboxylic acids; and polybasic acids, such as p-hydroxybenzoic acid, p-(2-hydroxyethoxy)benzoic acid, and ester-forming derivatives of these dihydroxycarboxylic acids, and dimer acids. Preferably, it is at least one selected from the group consisting of benzoic acid, adipic acid, sebacic acid, isophthalic acid and terephthalic acid.

[0029] Among these, from the viewpoints of adhesive performance and heat resistance, the carboxyl group component preferably contains an aromatic carboxyl group component, which includes a monofunctional aromatic carboxylic acid, a difunctional aromatic dicarboxylic acid, and a trifunctional or higher aromatic polycarboxylic acid. Based on the total number of moles of carboxyl group components used in the synthesis of polyester polyol, the aromatic carboxyl group component is preferably 25 mol% or more and 60 mol% or less. It is particularly preferably 35 mol% or more and 45 mol% or less. A content of 25 mol% or more is preferred because the difference between flexibility and rigidity becomes significant, forming a sea-island structure and improving adhesion and heat resistance. A content of 60 mol% or less is preferred because the viscosity is reduced, improving appearance and pot life.

[0030] The hydroxyl group component is not particularly limited as long as it is a known component, and examples thereof include diols and tri- or higher functional polyols. Examples of the diol include aliphatic diols such as ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3,3'-dimethylolheptane, and 1,4-bis(hydroxymethyl)cyclohexane; ether glycols such as polytetramethylene ether glycol and polyoxyethylene glycol; modified polyether diols obtained by ring-opening polymerization of the aliphatic diols with various cyclic ether bond-containing compounds such as ethylene oxide and tetrahydrofuran; lactone-based polyester polyols obtained by polycondensation of the aliphatic diols with various lactones such as lactanoids and ε-caprolactone; and alkylene oxide adducts of bisphenols obtained by adding ethylene oxide or the like to bisphenols such as bisphenol A and bisphenol F. Preferably, the diol is at least one selected from the group consisting of ethylene glycol, diethylene glycol, and neopentyl glycol.

[0031] Examples of the tri- or higher functional polyols include aliphatic polyols such as trimethylolethane, trimethylolpropane, glycerin, hexanetriol, and pentaerythritol; modified polyether polyols obtained by ring-opening polymerization of the aliphatic polyols with various cyclic ether bond-containing compounds such as ethylene oxide, propylene oxide, tetrahydrofuran, ethyl glycidyl ether, propyl glycidyl ether, butyl glycidyl ether, phenyl glycidyl ether, and allyl glycidyl ether; and lactone-based polyester polyols obtained by polycondensation of the aliphatic polyols with various lactones such as ε-caprolactone. Trimethylolpropane is preferred.

[0032] From the viewpoint of imparting flexibility, the polyester polyol is preferably a polyester polyol using a bifunctional carboxyl group component and / or a bifunctional hydroxyl group component, such as a dicarboxylic acid or a diol, i.e., a reaction product of a hydroxyl group component containing a diol and a carboxyl group component containing a dicarboxylic acid. The ratio of the total number of moles of hydroxyl groups and carboxyl groups contained in the diol and dicarboxylic acid is preferably 85 mol% or more, based on the total number of moles of hydroxyl groups and carboxyl groups contained in the hydroxyl group component and carboxyl group component. It is particularly preferably 90 mol% or more. A ratio of 85 mol% or more is preferable because it suppresses an excessive increase in crosslink density, prevents a decrease in the degree of freedom of the polymer chain, and exhibits excellent flexibility.

[0033] The ratio of the total number of moles of hydroxyl groups and carboxy groups contained in the bifunctional raw materials (bifunctional carboxy group components and bifunctional hydroxy group components) can be determined by first determining the number of moles of carboxy groups or hydroxyl groups contained in each raw material, then determining the total number of moles of carboxy groups and hydroxyl groups contained in all raw materials, and then determining the ratio of the total number of moles of carboxy groups or hydroxyl groups contained in the bifunctional raw materials from among the obtained moles. The number of moles of carboxyl groups or hydroxyl groups contained in each raw material can be calculated by the following formula. [Number of moles of each ingredient] = [Amount of each raw material charged (g)] × [Number of functional groups in each raw material] / [Molecular weight of each raw material]

[0034] The reaction equivalent ratio (OH / COOH) between the hydroxyl groups of the hydroxyl group component and the carboxyl groups of the carboxyl group component used in the synthesis of the polyester polyol is preferably 1.1 or more and 1.5 or less. It is particularly preferably 1.2 or more and 1.4 or less. A ratio of 1.1 or more is preferable because the cohesive force of the polyester polyol increases, resulting in superior adhesive strength. A ratio of 1.5 or less is preferable because the viscosity increase after mixing with the polyisocyanate compound (B) is gradual, preventing deterioration of coatability over time.

[0035] <Polyisocyanate compound (B)> The polyisocyanate compound (B) used in the present invention contains a first polyisocyanate (b1), which is a polyetherurethane polyol that satisfies the above-mentioned (1) to (4). The polyetherurethane as the main skeleton improves the degree of freedom of the polymer chain, resulting in an adhesive layer with excellent flexibility after curing. This allows a laminate laminated between hard substrates to exhibit high adhesive strength that cannot be achieved with conventional solventless adhesives.

[0036] [Polyisocyanate (b1)] The polyisocyanate (b1) in the present invention is a reaction product of a polyether polyol in which the proportion of the total number of moles of hydroxyl groups contained in the bifunctional polyether polyol is 95 mol % or more, based on the total number of moles of hydroxyl groups contained in the polyether polyol, and an isocyanate compound in which the proportion of the total number of moles of isocyanate groups contained in the aromatic diisocyanate compound is 90 mol % or more, based on the total number of moles of isocyanate groups contained in the isocyanate compound, and the polyisocyanate (b1) has an ICI viscosity at 90°C of 600 mPa s or more.

[0037] (Polyether polyol) It is important that the polyether polyol contains a bifunctional polyether polyol, and that the ratio of the total number of moles of hydroxyl groups contained in the bifunctional polyether polyol is 95 mol% or more based on the total number of moles of hydroxyl groups contained in the polyether polyol. By containing a high ratio of 95 mol% or more of hydroxyl groups derived from the bifunctional polyether polyol, the degree of freedom of the polymer chain increases, the flexibility of the adhesive layer after curing increases, and high adhesive strength can be achieved between hard substrates. The bifunctional polyether polyol is not particularly limited, and for example, bifunctional polyether polyols among the polyols described in the section on polyol compound (A) can be appropriately used. Preferred bifunctional polyether polyols are (poly)alkylene glycols such as dipropylene glycol, tripropylene glycol, and polypropylene glycol, and more preferably (poly)propylene glycol. From the viewpoints of flexibility and resin compatibility, the molecular weight of the bifunctional polyether polyol is preferably 400 to 2,000. A molecular weight of 400 or more is preferable because excellent cohesive strength can be obtained during adhesion. A molecular weight of 2,000 or less is preferable because compatibility with the isocyanate compound described below increases and the reactivity between the polyether polyol and the isocyanate compound improves.

[0038] The proportion of the total number of moles of hydroxyl groups contained in the bifunctional polyether polyol can be determined by first determining the number of moles of hydroxyl groups contained in each polyether polyol, then determining the total number of moles of hydroxyl groups contained in all polyether polyols, and then determining the proportion of the total number of moles of hydroxyl groups contained in the bifunctional polyether polyol from among the determined number of moles. The number of moles of hydroxyl groups contained in each polyether polyol can be calculated by the following formula. [Number of moles of hydroxyl groups contained in each polyether polyol] = ([Amount of each polyether polyol charged (g)] × [Hydroxyl value of each polyether polyol (mgKOH / g)]) / ([Number of functional groups of each polyether polyol] × 56100

[0039] The above polyether polyol may be used in combination with a polyether polyol other than a bifunctional polyether polyol, as long as the effects of the present invention are not impaired.

[0040] (Isocyanate compounds) It is important that the isocyanate compound contains an aromatic diisocyanate compound, and that the proportion of the total number of moles of isocyanate groups contained in the aromatic diisocyanate compound is 90 mol% or more based on the total number of moles of isocyanate groups contained in the isocyanate compound. By using an aromatic diisocyanate compound at a high proportion of 90 mol% or more, not only is heat resistance improved, but also adhesive strength is improved due to the rigidity of the aromatic ring and the flexibility of the polyether urethane chain described above.

[0041] Examples of aromatic diisocyanate compounds include diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, phenylene diisocyanate, tolylene diisocyanate, and naphthalene diisocyanate. The aromatic diisocyanate compound is preferably diphenylmethane diisocyanate.

[0042] The proportion of the total number of moles of isocyanate groups contained in the aromatic diisocyanate compounds can be determined by determining the number of moles of isocyanate groups contained in each of all isocyanate compounds used as the isocyanate compounds, then determining the total number of moles of isocyanate groups contained in all the isocyanate compounds, and then determining the proportion of the total number of moles of isocyanate groups contained in the aromatic diisocyanate compounds from the determined number of moles. The number of moles of isocyanate groups contained in each isocyanate compound can be calculated by the following formula. [Number of moles of each isocyanate compound] = ([Amount of each isocyanate compound charged (g)] × [NCO% of each isocyanate compound]) / ([Number of functional groups of each isocyanate compound] × 42 × 100)

[0043] The isocyanate compound may be used in combination with an isocyanate compound other than an aromatic diisocyanate compound, as long as the effects of the present invention are not impaired. Examples of the isocyanate compound that may be used in combination include tri- or higher functional aromatic polyisocyanates, or modified aromatic polyisocyanates. Examples of the isocyanate compound that may be used in combination include araliphatic polyisocyanates, aliphatic polyisocyanates, alicyclic polyisocyanates, or modified products thereof.

[0044] An example of the tri- or higher functional aromatic polyisocyanate is polymethylene polyphenyl polyisocyanate. Examples of modified aromatic polyisocyanates include allophanate-type modified products, isocyanurate-type modified products, biuret-type modified products, and adduct-type modified products, as well as reaction products having an isocyanate group and a urethane bond, which are obtained by reacting the aromatic polyisocyanate with a polyol under conditions of excess isocyanate groups. The polyol that forms the modified polyisocyanate is not particularly limited and can be selected from known polyols, such as polyester polyols, polyester urethane polyols, polycarbonate polyols, polycaprolactone polyols, polyether polyols, polyether urethane polyols, polyolefin polyols, acrylic polyols, silicone polyols, castor oil-based polyols, and fluorine-based polyols.

[0045] Examples of the araliphatic polyisocyanate include araliphatic diisocyanates such as 1,3- or 1,4-xylylene diisocyanate or a mixture thereof, ω,ω′-diisocyanato-1,4-diethylbenzene, 1,3- or 1,4-bis(1-isocyanato-1-methylethyl)benzene or a mixture thereof. Examples of the aliphatic polyisocyanate include aliphatic diisocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, 2,6-diisocyanate methyl caproate, lysine diisocyanate, and dimer acid diisocyanate. Examples of alicyclic polyisocyanates include alicyclic diisocyanates such as 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, isophorone diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), methyl 2,4-cyclohexane diisocyanate, methyl 2,6-cyclohexane diisocyanate, 1,4-bis(isocyanatemethyl)cyclohexane, 1,3-bis(isocyanatemethyl)cyclohexane, and norbornene diisocyanate.

[0046] The above description of the modified aromatic polyisocyanate can be applied to the modified polyisocyanate.

[0047] It is also important that the polyisocyanate (b1) has an ICI viscosity of 600 mPa·s or more at 90°C. ICI viscosity refers to the viscosity measured using an ICI viscometer (cone-plate type). An ICI viscosity of 600 mPa·s or more at 90°C increases the adhesive's cohesive strength, resulting in excellent adhesive strength and heat resistance. Furthermore, it can improve appearance defects such as orange peel and tunneling. The ICI viscosity is preferably 800 mPa·s or more, more preferably 900 mPa·s or more, from the viewpoint of improving cohesive strength, and is preferably 1200 mPa·s or less, more preferably 1100 mPa·s or less, from the viewpoint of handling during coating.

[0048] [Polyisocyanate (b2)] The polyisocyanate compound (B) may further contain a polyisocyanate (b2) other than the polyisocyanate (b1) for the purposes of imparting cohesive strength and reducing viscosity. By adding such a second polyisocyanate (b2) to impart cohesive strength, a sea-island structure is formed in contrast to the flexibility of the polyisocyanate (b1), thereby improving adhesive strength and heat resistance. Furthermore, the reduced viscosity of the polyisocyanate compound (B) can improve appearance performance.

[0049] The amount of polyisocyanate (b2) added is preferably 5% by mass or more and 15% by mass or less, based on the mass of the polyisocyanate compound (B). A content of 5% by mass or more is preferable because sufficient heat resistance can be imparted. A content of 15% by mass or less is preferable because a good balance between cohesive strength and flexibility is achieved, thereby achieving both adhesive strength and heat resistance.

[0050] The polyisocyanate (b2) preferably contains 4,4'-diphenylmethane diisocyanate, which is preferred because the use of 4,4'-diphenylmethane diisocyanate increases the density of aromatic rings and urethane bonds, thereby efficiently imparting cohesive strength.

[0051] <Resin obtained by copolymerizing (meth)acrylic acid ester and maleic anhydride> From the viewpoint of improving compatibility and adhesive strength, the solventless adhesive of the present invention preferably contains a resin obtained by copolymerizing a (meth)acrylic acid ester and maleic anhydride. The resin is not particularly limited as long as it is a copolymer of a known (meth)acrylic acid ester and maleic anhydride, and can be selected from conventionally known resins. One type may be used alone, or two or more types may be used in combination.

[0052] The (meth)acrylic acid ester represents a methacrylic acid ester or an acrylic acid ester, and examples thereof include methyl methacrylate, ethyl methacrylate, propyl methacrylate, i-propyl methacrylate, butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, decyl methacrylate, heptyl methacrylate, cyclohexyl octylate methacrylate, and phenyl methacrylate. Among these, methyl methacrylate is preferred from the viewpoint of copolymerizability with maleic anhydride.

[0053] The copolymerization method of (meth)acrylic acid ester and maleic anhydride includes radical copolymerization, and can be appropriately selected from, for example, solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, etc. The resin preferably contains 5 to 50 mass% of structural units derived from maleic anhydride, more preferably 30 to 50 mass%, based on the total mass of all structural units, including (meth)acrylic acid ester and maleic anhydride. A content of structural units derived from maleic anhydride of 5 mass% or more is preferred because it prevents a decrease in adhesive strength during long-term storage of the laminated body. A content of 50 mass% or less is preferred because it facilitates the synthesis of a copolymer of (meth)acrylic acid ester and maleic anhydride.

[0054] The acid value of the resin obtained by copolymerizing a (meth)acrylic acid ester and maleic anhydride is preferably 250 mgKOH / g or more, more preferably 300 mgKOH / g or more, and even more preferably 350 mgKOH / g or more. An acid value of 250 mgKOH / g is preferable because it increases the cohesive force at the metal interface. The acid value of the resin obtained by copolymerizing a (meth)acrylic acid ester and maleic anhydride is preferably 1000 mgKOH / g or less.

[0055] The weight average molecular weight (Mw) of the resin obtained by copolymerizing a (meth)acrylic acid ester and maleic anhydride is preferably from 1,000 to 5,000, more preferably from 1,500 to 3,000. When the weight average molecular weight is 1,000 or more, it is preferable because the decrease in adhesive strength when the laminate after lamination is stored for a long time is suppressed. When it is 5,000 or less, it is preferable because it has excellent compatibility with the solvent-free adhesive and excellent coating appearance.

[0056] The weight average molecular weight described in this specification is a value in terms of standard polystyrene using GPC (gel permeation chromatography) "Shodex GPC System-21" manufactured by Showa Denko KK and using tetrahydrofuran as a solvent. When the copolymer of a (meth)acrylic acid ester and maleic anhydride contains a plurality of copolymers, its weight average molecular weight can be determined from the weight average molecular weight of each copolymer and its mass ratio.

[0057] The solvent-free adhesive of the present invention preferably contains a resin obtained by copolymerizing a (meth)acrylic acid ester and maleic anhydride in a range of 0.1% by mass or more and 2.0% by mass or less based on the total mass of the polyisocyanate compound (B). When it is 0.1% by mass or more, the cohesive force at the metal interface increases, and it is preferable because of excellent adhesive strength and heat seal strength. When it is 2.0% by mass or less, the increase in viscosity after blending the adhesive becomes moderate, and it is preferable because the appearance performance is improved.

[0058] <Filler with a pH value exceeding 7.0> The solvent-free adhesive of the present invention preferably contains a filler having a pH value exceeding 7.0 measured in accordance with JIS K 5101. By blending such a filler, the cohesive force of the adhesive after lamination is improved, and the appearance performance is improved, which is preferable. In particular, by coexisting with an acid component such as the resin obtained by copolymerizing the above-mentioned (meth)acrylic acid ester and maleic anhydride, the filler and the acid component interact electrically, and the dispersibility of the filler is improved. As a result, the sedimentation of the filler is suppressed, and the appearance defect can be further reduced.

[0059] Examples of fillers having a pH value exceeding 7.0 include aluminosilicates (e.g., Shilton JC-20 manufactured by Mizusawa Industrial Chemicals), magnesium oxide, silica, etc. Aluminosilicates are preferred from the viewpoint of improving dispersibility and imparting cohesive strength through interaction with acid components. The average particle size of fillers with a pH value above 7.0 is usually 1×10 -5 ~0.2 mm, preferably 1 × 10 -4 When the average particle size is 0.2 mm or less, the appearance of the coating film after coating is excellent. -5 When the particle size is 1 / 2 mm or more, the adhesive has excellent flow characteristics and the coating appearance has excellent transparency, which is preferable. The average particle size in this specification is the average volume diameter, and is a value determined by a laser light scattering method.

[0060] The solventless adhesive of the present invention preferably contains a filler having a pH value exceeding 7.0 in an amount of 0.1% by mass or more and 2.0% by mass or less, based on the total mass of the polyisocyanate compound (B). A content of 0.1% by mass or more is preferred because it improves the cohesive strength of the adhesive after lamination and reduces appearance defects such as orange peel and tunneling. A content of 2.0% by mass or less is preferred because it maintains adhesive strength and heat resistance.

[0061] <Other ingredients> In order to satisfy various performance requirements, the solventless adhesive of the present invention may contain components other than the polyol compound (A), the polyisocyanate compound (B), the resin obtained by copolymerizing a (meth)acrylic acid ester and maleic anhydride, and the filler having a pH value of more than 7.0 measured in accordance with JIS K 5101. Such other components may be blended with either the polyol compound (A) or the polyisocyanate compound (B), or may be blended when the polyol compound (A) and the polyisocyanate compound (B) are mixed. One type of other component may be used alone, or two or more types may be used in combination.

[0062] (Silane coupling agent) The solventless adhesive of the present invention can contain a silane coupling agent from the viewpoint of improving adhesive strength to metal materials such as metal foils and metal vapor deposition layers. Examples of silane coupling agents include trialkoxysilanes having a vinyl group, such as vinyltriethoxysilane and vinyltriethoxysilane; trialkoxysilanes having an amino group, such as 3-aminopropyltriethoxysilane and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane; and trialkoxysilanes having a glycidyl group, such as 3-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane. The content of the silane coupling agent is preferably 0.1 to 5 mass %, more preferably 0.2 to 3 mass %, based on the total amount of polyol compounds. By setting the content within this range, the adhesive strength to the metal foil can be improved, which is preferable.

[0063] (phosphoric acid or phosphoric acid derivatives) The solventless adhesive of the present invention may contain phosphoric acid or a phosphoric acid derivative from the viewpoint of improving adhesive strength to metal materials such as metal foils and metal vapor deposition layers. The phosphoric acid may be any phosphoric acid having at least one free oxygen acid, such as hypophosphorous acid, phosphorous acid, orthophosphoric acid, or hypophosphoric acid; or condensed phosphoric acids such as metaphosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, polyphosphoric acid, or ultraphosphoric acid. Phosphoric acid derivatives include, for example, phosphoric acids partially esterified with alcohols, while leaving at least one free oxygen acid. Examples of such alcohols include aliphatic alcohols such as methanol, ethanol, ethylene glycol, and glycerin; and aromatic alcohols such as phenol, xylenol, hydroquinone, catechol, and phloroglucinol. The content of phosphoric acid or a derivative thereof is preferably 0.01 to 10 mass %, more preferably 0.05 to 5 mass %, and particularly preferably 0.05 to 1 mass %, based on the mass of the solvent-free adhesive.

[0064] (Leveling agent or defoaming agent) The solventless adhesive of the present invention can contain a leveling agent and / or an antifoaming agent to improve the appearance of the laminate. Examples of leveling agents include polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, aralkyl-modified polymethylalkylsiloxane, polyester-modified hydroxyl group-containing polydimethylsiloxane, polyetherester-modified hydroxyl group-containing polydimethylsiloxane, acrylic copolymer, methacrylic copolymer, polyether-modified polymethylalkylsiloxane, acrylic acid alkyl ester copolymer, methacrylic acid alkyl ester copolymer, and lecithin. Examples of the antifoaming agent include silicone resin, silicone solution, and copolymers of alkyl vinyl ether, alkyl acrylate, and alkyl methacrylate.

[0065] (Reaction accelerator) The solventless adhesive of the present invention can contain a reaction accelerator to accelerate the curing reaction. Examples of reaction accelerators include metal catalysts such as dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate, and dibutyltin dimaleate; tertiary amines such as 1,8-diaza-bicyclo(5,4,0)undecene-7 and 1,5-diazabicyclo(4,3,0)nonene-5,6-dibutylamino-1,8-diazabicyclo(5,4,0)undecene-7; and reactive tertiary amines such as triethanolamine.

[0066] (additives) The solventless adhesive of the present invention may contain various additives within the range that does not impair the effects of the present invention. Examples of additives include inorganic fillers such as alumina, mica, talc, aluminum flakes, and glass flakes, layered inorganic compounds, stabilizers (antioxidants, heat stabilizers, UV absorbers, hydrolysis inhibitors, etc.), rust inhibitors, thickeners, plasticizers, antistatic agents, lubricants, antiblocking agents, colorants, fillers, nucleating agents, and catalysts for adjusting the curing reaction.

[0067] <Laminate> The laminate of the present invention is one in which an adhesive layer made of the above-mentioned solvent-free adhesive is laminated between at least two sheet-like substrates. One example is one in which the solvent-free adhesive is applied to a first sheet-like substrate to form an adhesive layer, a second sheet-like substrate is superimposed on the adhesive layer, and the adhesive layer located between the two sheet-like substrates is cured.

[0068] [Sheet substrate] The sheet-like substrate is not particularly limited, and examples thereof include conventionally known plastic films, paper, metal foils, etc., and the two sheet-like substrates may be of the same type or different types. The plastic film may be a film of a thermoplastic resin or a thermosetting resin, preferably a film of a thermoplastic resin, such as polyolefin, polyester, polyamide, polystyrene, vinyl chloride resin, vinyl acetate resin, ABS resin, acrylic resin, acetal resin, polycarbonate resin, or cellulose-based plastic. The sheet-like substrate may have a barrier layer made of a vapor-deposited layer of a metal or metal oxide, and examples of such a barrier layer include vapor-deposited layers of aluminum, silica, alumina, and the like.

[0069] The first sheet-like substrate is preferably a plastic film. Examples of plastic films include those commonly used in packaging materials, such as polyester resin films such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polylactic acid (PLA); polyolefin resin films such as polyethylene (PE) and polypropylene (PP); polystyrene resin films; polyamide resin films such as nylon 6 and poly-p-xylylene adipamide (MXD6 nylon); polycarbonate resin films; polyacrylonitrile resin films; polyimide resin films; and multilayers thereof (e.g., nylon 6 / MXD6 / nylon 6, nylon 6 / ethylene-vinyl alcohol copolymer / nylon 6) or mixtures thereof. Among these, those having mechanical strength and dimensional stability are preferred. The plastic film preferably has a thickness of 5 μm or more and 50 μm or less, more preferably 10 μm or more and 30 μm or less.

[0070] When the second sheet-like substrate is the outermost layer of the laminate, the second sheet-like substrate is preferably a sealant substrate. Examples of sealant base materials include polyethylenes such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE), acid-modified polyethylene, polypropylene (PP), acid-modified polypropylene, copolymerized polypropylene, ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid ester copolymer, ethylene-(meth)acrylic acid copolymer, and ionomer. The thickness of the sealant substrate is not particularly limited, and is preferably 10 to 150 μm, more preferably 20 to 70 μm, taking into consideration processability into packaging materials, heat sealing properties, etc. Furthermore, by providing the sealant substrate with unevenness having a height difference of about several μm, it is possible to impart slip properties and tearability to the packaging material. When the second sheet-like substrate is to be an intermediate layer of the laminate, the above-mentioned plastic film, paper, metal foil, etc. can be suitably used as the second sheet-like substrate.

[0071] The sheet-like substrate may have a printed layer on the substrate. The printed layer is a layer on which any desired printed pattern such as letters, numbers, pictures, figures, symbols, designs, etc. is formed for the purpose of decoration, indication of contents, indication of expiration date, indication of manufacturer, seller, etc., or for imparting aesthetic appeal, and includes solid printed layers. The printed layer can be formed using conventionally known pigments or dyes, and the method for forming the printed layer is not particularly limited. Generally, the printed layer is formed using a printing ink containing a colorant such as a pigment or dye. The method for applying the printing ink is not particularly limited, and the printing ink can be applied by methods such as gravure coating, flexo coating, roll coating, bar coating, die coating, curtain coating, spin coating, and inkjet coating. The printed layer can be formed by leaving the ink to stand, or, if necessary, subjecting the ink to air blowing, heating, drying under reduced pressure, or ultraviolet irradiation. The printing layer preferably has a thickness of 0.1 μm or more and 10 μm or less, more preferably 1 μm or more and 5 μm or less, and even more preferably 1 μm or more and 3 μm or less.

[0072] The laminate can be produced by a conventional method, for example, by applying a solvent-free adhesive to one surface of one sheet-like substrate using a laminator to form an uncured adhesive layer, then laminating the coated surface to the other sheet-like substrate, and then curing the adhesive layer at room temperature or under heating. The amount of the solvent-free adhesive applied is preferably 1.0 to 5.0 g / m 2 , more preferably 1.5 to 4.5 g / m 2 The thickness of the laminate is preferably 10 μm or more.

[0073] Examples of the structure of the laminate of the present invention are given below, but are not limited to these. When the laminate has multiple adhesive layers, at least one of the adhesive layers should be an adhesive layer formed from the solventless adhesive of the present invention. In the following, transparent vapor deposition refers to a vapor-deposited layer of silica or alumina. Biaxially oriented polypropylene (OPP) / printing layer / adhesive layer / non-oriented polypropylene (CPP), OPP / printing layer / adhesive layer / AL vapor deposition CPP, OPP / printing layer / adhesive layer / PE, Printing layer / OPP / adhesive layer / CPP, NY / printing layer / adhesive layer / PE, Printing layer / NY / Adhesive layer / CPP NY / printing layer / adhesive layer / CPP, PET / printing layer / adhesive layer / CPP, Printing layer / PET / adhesive layer / CPP, PET / printing layer / adhesive layer / NY / adhesive layer / CPP, PET / printing layer / adhesive layer / NY / adhesive layer / PE, Transparent vapor-deposited PET / printed layer / adhesive layer / NY / adhesive layer / CPP, PET / printed layer / adhesive layer / AL vapor-deposited PET / adhesive layer / PE, NY / printing layer / adhesive layer / AL vapor-deposited PET / adhesive layer / PE, PET / printed layer / adhesive layer / AL vapor-deposited PET / adhesive layer / NY / adhesive layer / PE, PET / printing layer / adhesive layer / AL / adhesive layer / CPP, PET / printing layer / adhesive layer / AL / adhesive layer / PE, PET / printing layer / adhesive layer / NY / adhesive layer / AL / adhesive layer / CPP, PET / printing layer / adhesive layer / AL / adhesive layer / NY / adhesive layer / CPP [Example]

[0074] The present invention will be specifically described below with reference to examples and comparative examples. In the examples and comparative examples, "parts" and "%" mean "parts by mass" and "% by mass" unless otherwise specified.

[0075] [Method for measuring weight average molecular weight (Mw) and number average molecular weight (Mn)] The weight-average molecular weight and number-average molecular weight were measured using a GPC (gel permeation chromatography) "Shodex GPC System-21" manufactured by Showa Denko Co., Ltd. GPC is a liquid chromatography that separates and quantifies substances dissolved in a solvent based on differences in their molecular size. Tetrahydrofuran was used as the solvent, and the molecular weight was determined in terms of polystyrene.

[0076] [Method for measuring hydroxyl value (OHV)] Approximately 1 g of sample was precisely weighed into a stoppered Erlenmeyer flask and dissolved in 100 mL of a toluene / ethanol mixture (volume ratio: toluene / ethanol = 2 / 1). Exactly 5 mL of an acetylating agent (25 g of acetic anhydride dissolved in pyridine to a volume of 100 mL) was then added and stirred for approximately 1 hour. Phenolphthalein test solution was added as an indicator and the mixture was stirred for 30 seconds. The solution was then titrated with 0.1 N alcoholic potassium hydroxide solution until it turned a pale pink color. The hydroxyl value was calculated using the following formula (2). The hydroxyl value was the value for the resin in its dry state. (Equation 2) Hydroxyl value (mgKOH / g) = [{(ba) × F × 28.25} / S] / (non-volatile content / 100) + D S: Amount of sample collected (g) a: Amount of 0.1N alcoholic potassium hydroxide solution consumed (mL) b: Amount of 0.1N alcoholic potassium hydroxide solution consumed in the blank experiment (mL) F: Potency of 0.1N alcoholic potassium hydroxide solution D: Acid value (mgKOH / g)

[0077] [Method for measuring NCO content (mass%)] Approximately 1 g of sample was weighed into a 200 mL Erlenmeyer flask and dissolved in 10 mL of 0.5 N di-n-butylamine toluene solution and 10 mL of toluene. Next, phenolphthalein test solution was added as an indicator, and after 30 seconds, the solution was titrated with 0.25 N hydrochloric acid until it turned pale pink. The NCO content (mass%) was calculated using the following formula (3). (Formula 3):NCO(mass%)={(ba)×4.202×F×0.25} / S Where S: sample amount (g) a: Consumption of 0.25N hydrochloric acid solution (ml) b: Amount of 0.25N hydrochloric acid solution consumed in the blank experiment (ml) F: Potency of 0.25N hydrochloric acid solution

[0078] [ICI viscosity measurement method] The viscosity was measured at 90°C using a cone and plate viscometer "CV-1S" manufactured by Toa Kogyo Co., Ltd. The value displayed when the value stabilized was taken as the ICI viscosity.

[0079] <Production of Polyol Compound (A)> (Synthesis of Polyether Polyol (A-1)) A reaction vessel equipped with a stirrer, a temperature control system, a reflux condenser, a dropping tank, and a nitrogen gas inlet tube was charged with 520.1 parts of polypropylene glycol having a number average molecular weight of 2,000, 218.4 parts of polypropylene glycol having a number average molecular weight of 400, 16.6 parts of dipropylene glycol, and 45.0 parts of tolylene diisocyanate. The mixture was heated at 80°C to 90°C for 3 hours while stirring under a nitrogen gas stream to carry out a urethane reaction, thereby obtaining a polyether polyol (A-1) having a urethane bond introduced therein.

[0080] (Synthesis of Polyether Polyols (A-2 to A-5)) A urethane reaction was carried out in the same manner as in (A-1), except that the raw materials were changed to the formulation (parts by mass) shown in Table 1, to obtain polyether polyols (A-2 to A-5) into which urethane bonds had been introduced.

[0081] The polyether polyols (A-1 to A-5) are shown in Table 1. The values ​​in Table 1 are parts by mass.

[0082] [Table 1]

[0083] (Synthesis of polyester polyol (A-6)) A reaction vessel equipped with a stirrer, a temperature control system, a reflux condenser, a dropping tank, and a nitrogen gas inlet tube was charged with 322.7 parts of adipic acid, 226.7 parts of isophthalic acid, 74.7 parts of ethylene glycol, and 375.9 parts of neopentyl glycol, and the mixture was heated to 240°C with stirring under a nitrogen stream. After the reaction was continued until the acid value reached 5 or less, the pressure was gradually reduced and the reaction was continued at 1 mmHg. Excess alcohol was removed to obtain polyester polyol (A-6).

[0084] (Synthesis of polyester polyol (A-8)) A reaction vessel equipped with a stirrer, temperature control system, reflux condenser, dropping tank, and nitrogen gas inlet tube was charged with 321.1 parts of adipic acid, 176.4 parts of isophthalic acid, 49.2 parts of benzoic acid, 74.3 parts of ethylene glycol, and 374.0 parts of neopentyl glycol, and the mixture was heated to 240 ° C. while stirring under a nitrogen stream. After the reaction was continued until the acid value reached 5 or less, the pressure was gradually reduced and the reaction was continued at 1 mmHg to remove excess alcohol. Then, 5.0 parts of ethylene glycol bisanhydrotrimellitate was added to the resulting resin, and the mixture was reacted at 120 ° C. for 1 hour to obtain a polyester polyol (A-8) with a carboxyl group introduced by reacting with the acid anhydride.

[0085] (Synthesis of polyester polyols (A-7, A-9 to A-16)) The esterification reaction was carried out in the same manner as in (A-6), except that the raw materials were changed to the compositions (parts by mass) shown in Table 1, to obtain polyester polyols (A-7, A-9 to A-16).

[0086] The polyester polyols (A-6 to A-16) are shown in Table 2. The values ​​in Table 2 are parts by mass.

[0087] [Table 2]

[0088] <Production of polyisocyanate (b1)> (Synthesis of polyisocyanate (b1-1)) A reaction vessel equipped with a stirrer, temperature control system, reflux condenser, dropping tank, and nitrogen gas inlet tube was charged with 103.9 parts of polypropylene glycol having a number average molecular weight of 400, 518.3 parts of polypropylene glycol having a number average molecular weight of 2,000, 13.1 parts of dipropylene glycol, 18.7 parts of tripropylene glycol, and 346.0 parts of a mixture of 2,4-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate (mass ratio 50:50). The mixture was heated at 80-90°C for 3 hours while stirring under a nitrogen gas stream to carry out a urethane reaction, resulting in a polyisocyanate (b1-1) with an isocyanate group content of 5.4% by mass and an ICI viscosity at 90°C of 1000 [mPa / s].

[0089] (Synthesis of polyisocyanates (b1-2 to b1-10)) A urethane reaction was carried out in the same manner as in (b1-1), except that the raw materials were changed to the compositions (parts by mass) shown in Table 1, to obtain polyisocyanates (b1-2 to b1-10).

[0090] (Synthesis of polyisocyanate (b1-11)) A reaction vessel equipped with a stirrer, a temperature control system, a reflux condenser, a dropping tank, and a nitrogen gas inlet tube was charged with 599.4 parts of polyester polyol (A-7) and 400.6 parts of a mixture of 2,4-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate, and the mixture was heated at 80-90°C for 3 hours while stirring under a nitrogen gas stream to carry out a urethane reaction, thereby obtaining polyisocyanate (b1-11) with an isocyanate group content of 10.1% by mass and an ICI viscosity at 90°C of 1000 [mPa / s].

[0091] The polyisocyanates (b1-1 to b1-11) are shown in Table 3. The values ​​in Table 3 are parts by mass.

[0092] [Table 3]

[0093] The abbreviations in Table 3 are as follows: 4,4'-MDI: 4,4'-diphenylmethane diisocyanate 2,4'-MDI: 2,4'-diphenylmethane diisocyanate HDI Biuret: Biuret type polyisocyanate, trimer of 1,6-hexamethylene diisocyanate

[0094] <Production of Resin Obtained by Copolymerizing (Meth)acrylic Acid Ester and Maleic Anhydride> (Synthesis of Resin-1) A reaction vessel equipped with a stirrer, temperature control system, reflux condenser, dropping tank, and nitrogen gas inlet tube was charged with 200 parts of toluene, and the temperature was raised to 110 ° C. while stirring and introducing nitrogen gas. Next, 90 parts of methyl methacrylate, 70 parts of butyl acrylate, 40 parts of maleic anhydride, and 50 parts of toluene were charged into dropping tank 1, and a solution of 9 parts of benzoyl peroxide in 50 parts of toluene was charged into dropping tank 2. Each was simultaneously added dropwise over 2 hours with stirring while maintaining the temperature in the reaction vessel at 110 ° C. After the reaction was completed, the mixture was cooled to room temperature, and the polymer was precipitated with a large amount of methanol, filtered, and dried at 120 ° C. for 6 hours to obtain Resin-1, a copolymer of (meth)acrylic acid ester and maleic anhydride with a weight average molecular weight of 1,000 and an acid value of 170 mg KOH / g.

[0095] (Synthesis of Resin-2) A reaction vessel equipped with a stirrer, temperature control system, reflux condenser, dropping tank, and nitrogen gas inlet tube was charged with 200 parts of toluene, and the temperature was raised to 110 ° C. while stirring and introducing nitrogen gas. Next, 90 parts of methyl methacrylate, 50 parts of butyl acrylate, 80 parts of maleic anhydride, and 50 parts of toluene were charged into dropping tank 1, and a solution of 9 parts of benzoyl peroxide in 50 parts of toluene was charged into dropping tank 2. Each was simultaneously added dropwise over 2 hours with stirring while maintaining the temperature in the reaction vessel at 110 ° C. After the reaction was completed, the mixture was cooled to room temperature, and the polymer was precipitated with a large amount of methanol, filtered, and dried at 120 ° C. for 6 hours to obtain Resin-2, which was a copolymer of (meth)acrylic acid ester and maleic anhydride with a weight average molecular weight of 1,600 and an acid value of 340 mg KOH / g.

[0096] (Synthesis of Resin-3) A reaction vessel equipped with a stirrer, temperature control system, reflux condenser, dropping tank, and nitrogen gas inlet tube was charged with 200 parts of toluene, and the temperature was raised to 110 ° C. while stirring and introducing nitrogen gas. Next, 80 parts of methyl methacrylate, 50 parts of butyl acrylate, 100 parts of maleic anhydride, and 50 parts of toluene were charged into dropping tank 1, and a solution of 9 parts of benzoyl peroxide in 50 parts of toluene was charged into dropping tank 2. Each was added dropwise over 2 hours with stirring while maintaining the temperature in the reaction vessel at 110 ° C. After the reaction was completed, the mixture was cooled to room temperature, and the polymer was precipitated with a large amount of methanol, filtered, and dried at 120 ° C. for 6 hours to obtain Resin-3, which was a copolymer of (meth)acrylic acid ester and maleic anhydride with a weight average molecular weight of 2,300 and an acid value of 460 mg KOH / g.

[0097] <Manufacturing of solvent-free adhesives> [Examples 1 to 37, Comparative Examples 1 to 4] Solvent-free Adhesives 1 to 41 According to the formulations in Table 4, the polyol compound (A), the polyisocyanate compound (B), and other components were mixed to obtain solventless adhesives 1 to 41.

[0098] <Evaluation of solvent-free adhesives> The solvent-free adhesives obtained were evaluated as follows, and the results are shown in Tables 4 and 5.

[0099] [Preparation of Laminate] Printing ink (Toyo Ink Co., Ltd., Rio Alpha R631 White) was diluted with an ethyl acetate / IPA mixed solvent (70 / 30 by mass) to a viscosity of 16 seconds (25°C, Zahn cup No. 3). The diluted printing ink was printed onto a 15 μm thick nylon film (Unitika Ltd., "Emblem ON-RT," hereafter referred to as NY) at a printing speed of 50 m / min using a gravure proofing machine equipped with a solid plate with a plate depth of 35 μm, and then dried at 50°C. The thickness of the printed layer was in the range of 0.5 to 1 μm. Next, using a laminator at room temperature, the ink surface of the printed matter obtained above was bonded to the aluminum-deposited surface of a 12 μm-thick aluminum-deposited polyethylene terephthalate film ("Dialastar H27" manufactured by Reiko Co., Ltd., hereafter referred to as VM-PET) using the solvent-free adhesive obtained. The lamination speed was 150 m / min, and the coating amount was 2.0 g / m. 2 After bonding, the adhesive was allowed to harden to some extent by keeping it at 40°C for 6 hours. Next, using a laminator in a room temperature environment, a 100 μm thick linear low-density polyethylene film ("TUX-FCD" manufactured by Mitsui Tocello Co., Ltd., hereinafter referred to as LLDPE) that had been subjected to surface corona discharge treatment was laminated to the PET surface of the laminated film having the "NY / printed layer / adhesive layer / VM-PET" structure obtained above, using the obtained solvent-free adhesive at a speed of 150 [m / min] and a coating amount of 2.0 [g / m]. 2 ] and then the adhesive was completely hardened by keeping it at 40°C for 3 days to obtain a laminate with the structure "NY / printed layer / adhesive layer / VM-PET / adhesive layer / LLDPE."

[0100] [Adhesive strength] The resulting laminate was cut into a 15 mm wide, 300 mm long test piece. Based on JIS K6854, the T-peel strength [N / 15 mm] between the NY and VM-PET films was measured at a peel rate of 300 mm / min using an Instron tensile tester under conditions of 20°C and 65% relative humidity. Five measurements were taken, and the average value was used to evaluate the results according to the following criteria. A: 4.5 [N / 15mm] or more (very good) B: 3.5 [N / 15mm] or more, less than 4.5 [N / 15mm] (good) C: 2.5 [N / 15mm] or more, less than 3.5 [N / 15mm] (usable) D: Less than 2.5 [N / 15mm] (unusable)

[0101] [Heat seal peel test] The resulting laminate was cut into 15 mm wide and 300 mm long test pieces, folded so that the sealant faces overlapped, and heat-sealed at 180°C for 1 second under 2 kg. The test was then conducted in accordance with JIS K6854 using an Instron tensile tester at a temperature of 20°C and a relative humidity of 65% at a peel rate of 300 mm / min until the film broke or the heat-sealed area broke, resulting in a decrease in tensile strength. The samples were then observed and evaluated according to their shape using the following criteria. Measurements were conducted five times, and the most common shape was selected. A: The laminate film is torn, but the heat seal is intact (very good). B: The laminate film did not break, and only the LLDPE film broke (good). C: The laminate film did not break, but the VM-PET / LLDPE in the heat-sealed area began to peel, and the LLDPE film itself broke (usable). D: The film did not break at all, and only the VM-PET / LLDPE in the heat-sealed area peeled off (unusable).

[0102] [Coatability and appearance] The obtained laminate was rewound, and the number of meters at which all appearance defects such as orange peel, tunneling, air bubbles, and adhesive peeling disappeared between the NY-VMPET and VM-PET / LLDPE were measured, and the laminate was evaluated according to the following criteria. The smaller the number of meters, the shorter the time from the start of lamination until appearance defects disappeared, and the better the coatability. A: The appearance defect disappeared when the number of meters was 0m or more and less than 3m (very good) B: The appearance defect disappeared within 3 meters or more and less than 10 meters (good) C: The appearance defect has disappeared within 10 meters and less than 15 meters (usable). D: The appearance defect has disappeared after 15 meters or more, or the appearance defect has not disappeared (cannot be used)

[0103] [Table 4]

[0104] [Table 5]

[0105] The abbreviations and details in Tables 4 and 5 are shown below. Lupranate M-20S: BASF, a mixture of polymeric diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate (mass ratio 60:40) Mixture of 2,4'-MDI and 4,4'-MDI: Mixture of 2,4-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate (mass ratio 50:50) HDI Biuret: Biuret type polyisocyanate, trimer of 1,6-hexamethylene diisocyanate Shilton JC-20: Mizusawa Industrial Chemicals, aluminosilicate (pH: 11.0), average particle size 2.0 × 10 -3 mm Kyowamag MF30: Kyowa Chemical Industry Co., Ltd., magnesium oxide filler (pH: 10.3), average particle size 5.4 × 10 -4 mm Mizukasil P-707: Mizusawa Industrial Chemicals, Ltd., silica filler (pH: 9.5), average particle size 4.0 × 10 -3 mm

[0106] The evaluation results showed that the solvent-free adhesive of the present invention had excellent adhesive strength when used with hard substrates, such as NY-VMPET, including metal-deposited interfaces. It also showed good heat seal peelability test results and excellent heat resistance. Furthermore, appearance defects disappeared immediately after lamination began, demonstrating excellent coatability. In particular, Example 3, which contained 10% by mass of polyisocyanate (b2) in the polyisocyanate compound (B), had a better balance of flexibility and rigidity than Example 35, which contained 5% by mass of polyisocyanate (b2), Example 36, which did not contain polyisocyanate (b2), and Example 37, which contained 20% by mass of the second polyisocyanate (b2), and exhibited good adhesive strength and good results in the heat seal peel test. Example 3, in which the polyisocyanate (b2) contained 4,4'-diphenylmethane diisocyanate, had higher rigidity than Example 15, in which the polyisocyanate (b2) contained HDI biuret, which is an aliphatic compound, and showed good results in the heat seal peel test. Example 3, which contains 0.45 mass % of a resin obtained by copolymerizing a (meth)acrylic acid ester and maleic anhydride based on the total mass of the polyisocyanate compound (B), has better resin compatibility and is superior in coatability and appearance performance than Example 7, which contains 2.2 mass % of said resin, and also has higher metal adhesion and superior adhesive strength than Examples 12 and 13, which do not contain said resin. Example 3, which contained 0.9% by mass of a filler having a pH value of more than 7.0 measured in accordance with JIS K 5101, based on the total mass of the polyisocyanate compound (B), had higher resin-to-substrate adhesion and better adhesive strength and heat seal peel test results than Example 10, which contained 2.2% by mass of the filler. Example 3 also had better coatability and appearance performance than Examples 11 and 13, which did not contain the filler, due to its higher cohesive strength after lamination, resulting in less bubble accumulation. Example 3, which contained a polyester polyol in the polyol compound (A), had higher metal adhesion and rigidity than Examples 30, 31, 32, 33, and 34, which contained a polyether polyol in the polyol compound (A), and was excellent in adhesive strength and heat seal peel test. Example 3, in which the polyol compound (A) contained a polyester polyol synthesized such that the total number of moles of bifunctional hydroxyl group components and bifunctional carboxyl group components was 100 mol %, had a higher degree of freedom in the polymer chain and a higher stress relaxation property than Examples 18 and 19, which used trifunctional raw materials, and therefore had superior adhesive strength. Example 3, which contained a polyester polyol synthesized in a polyol compound (A) with a molar equivalent ratio (OH / COOH) of difunctional hydroxyl group components to difunctional carboxyl group components of 1.3, had a lower viscosity than Example 22, which contained a polyester polyol synthesized with a molar equivalent ratio of 1.1, and therefore had high substrate leveling properties and excellent coatability and appearance performance. Furthermore, it had higher substrate adhesion and rigidity than Example 23, which contained a polyester polyol synthesized with a molar equivalent ratio of 1.5, and exhibited good adhesive strength and heat seal peel test results. Example 3, in which polyol compound (A) was synthesized from a bifunctional hydroxyl group component and a bifunctional carboxy group component, and the bifunctional carboxy group component contained 40 mol% or less of an aromatic carboxy group component based on the total moles of the bifunctional carboxy group component, had higher rigidity and better heat seal peel test results than Example 20, which contained 31 mol% or less of an aromatic carboxy group component. Furthermore, Example 3 had a lower viscosity than Example 21, which contained 51 mol% or less of an aromatic carboxy group component, and therefore had high substrate leveling properties, excellent coatability, and excellent appearance performance.

Claims

1. Contains a polyol compound (A) and a polyisocyanate compound (B), the polyol compound (A) contains a polyester polyol and / or a polyether polyol, A solvent-free adhesive, wherein the polyisocyanate compound (B) contains a first polyisocyanate (b1) and a second polyisocyanate (b2) that satisfy the following (1) to (4), and the content of the second polyisocyanate (b2) is 5 mass% or more and 15 mass% or less, based on the mass of the polyisocyanate compound (B) (however, the second polyisocyanate (b2) excludes the first polyisocyanate (b1)): (1) The polyisocyanate (b1) is a reaction product of a polyether polyol and an isocyanate compound. (2) The polyether polyol contains a bifunctional polyether polyol, and the proportion of the total number of moles of hydroxyl groups contained in the bifunctional polyether polyol is 95 mol% or more based on the total number of moles of hydroxyl groups contained in the polyether polyol. (3) The isocyanate compound contains an aromatic diisocyanate compound, and the proportion of the total number of moles of isocyanate groups contained in the aromatic diisocyanate compound is 90 mol% or more based on the total number of moles of isocyanate groups contained in the isocyanate compound. (4) The polyisocyanate (b1) has an ICI viscosity at 90°C of 600 mPa·s or more.

2. The solventless adhesive of claim 1, wherein the second polyisocyanate (b2) comprises 4,4'-diphenylmethane diisocyanate.

3. 3. The solventless adhesive composition according to claim 1, further comprising a resin obtained by copolymerizing a (meth)acrylic acid ester with maleic anhydride.

4. 4. The solventless adhesive composition according to claim 3, wherein the resin obtained by copolymerizing the (meth)acrylic acid ester and maleic anhydride is contained in an amount of 0.1 mass % or more and 2.0 mass % or less, based on the mass of the polyisocyanate compound (B).

5. The solventless adhesive according to any one of claims 1 to 4, further comprising a filler having a pH value of greater than 7.0 as measured in accordance with JIS K 5101.

6. The solvent-free adhesive according to claim 5 , wherein the filler is contained in an amount of 0.1 mass % or more and 2.0 mass % or less, based on the mass of the polyisocyanate compound (B).

7. The solventless adhesive according to any one of claims 1 to 6, wherein the polyol compound (A) comprises a polyester polyol.

8. The solventless adhesive according to any one of claims 1 to 7, wherein the polyester polyol is a reaction product of a hydroxyl group component and a carboxyl group component, and satisfies all of the following (5) to (7): (5) The hydroxyl group component contains a diol, the carboxyl group component contains a dicarboxylic acid, and the ratio of the total number of moles of hydroxyl groups and carboxyl groups contained in the diol and the dicarboxylic acid is 85 mol % or more based on the total number of moles of hydroxyl groups and carboxyl groups contained in the hydroxyl group component and the carboxyl group component. (6) The molar equivalent ratio (OH / COOH) of the hydroxyl groups of the hydroxyl group component to the carboxyl groups of the carboxyl group component is 1.1 or more and 1.5 or less. (7) The carboxyl group component contains 25 mol % or more and 65 mol % or less of aromatic carboxyl group components based on the total number of moles of the carboxyl group components.

9. A laminate comprising an adhesive layer formed using the solventless adhesive according to any one of claims 1 to 8 and laminated between at least two sheet-like substrates.

10. The laminate according to claim 9 , wherein at least one of the at least two sheet-like substrates is a metallized film, and a metallized layer of the metallized film is in contact with the adhesive layer.

11. A package using the laminate according to claim 9 or 10.

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