Solvent-free adhesives, laminates, and packaging

Abstract

To provide a solventless type adhesive which has a fast rise in adhesive strength and heat seal strength even in a low-humidity environment and has a good pot life and excellent handling properties and to provide a laminate and a package prepared using the adhesive.SOLUTION: There is provided a solventless type adhesive which comprises a polyol (A) and a polyisocyanate (B) and satisfies the following (1) and (2). (1) The polyol (A) includes a polyester polyol (a1), the content ratio of the polyester polyol (a1) is 30 mass% or more and 70 mass% or less based on the total mass of the polyol (A). (2) The polyol (A) contains castor oil or a castor oil derivative (a2) and the content ratio of the castor oil or the castor oil derivative (a2) is 30 mass% or more and 70 mass% or less based on the total mass of the polyol (A).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a solventless adhesive suitable for laminating various plastic films and metal vapor deposition films, and a laminate using the same. Further, the present invention relates to a package using the laminate, which is used for foods, pharmaceuticals, cosmetics, detergents, sundries, and the like.

Background Art

[0002] In recent years, due to the strengthening of regulations and consideration for environmental protection or safety, there has been an increasing demand for solventless laminating adhesives used in packaging materials. Also, amid the growing global movement to reduce greenhouse gas emissions, biomass adhesives using biomass-derived raw materials are in demand. In response to the above situation, for example, Patent Document 1 discloses a solventless adhesive that is a reaction product of a specific polyol and polyisocyanate and contains a polyurethane polyisocyanate component using a bio-based polyol such as castor oil, and is excellent in bonding strength and chemical resistance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0004] Solventless adhesives are generally designed to have a low molecular weight of the resin contained in the adhesive from the viewpoint of handling properties, and have a problem that the rise of cohesive force is slow. Especially in an aging environment with low humidity such as in winter, the rise of cohesive force becomes even slower, resulting in a significant decrease in production efficiency. However, the solvent-free adhesive described in Patent Document 1 specifies a polyisocyanate component and uses only at least one polyol selected from the group consisting of polyester polyols, polyether polyols, and combinations thereof as the polyol component. It does not select and combine polyester polyol with cinnamon oil or cinnamon oil derivatives as the polyol component. Therefore, it has not been able to solve the problem of slow physical property development in low humidity environments. [Overview of the project] [Problems that the invention aims to solve]

[0005] Therefore, the object of the present invention is to provide a solvent-free adhesive that exhibits rapid rise in adhesive strength and heat seal strength even in low humidity environments, has good pot life and excellent handling properties, and laminates and packaging materials made using the adhesive. [Means for solving the problem]

[0006] As a result of diligent research to solve the above problems, we have found that the above problems can be solved by the embodiments shown below, and have completed the present invention.

[0007] A solvent-free adhesive according to one aspect of the present invention comprises a polyol (A) and a polyisocyanate (B), and is characterized by satisfying the following conditions (1) and (2). (1) Polyol (A) contains polyester polyol (a1), and the content of polyester polyol (a1) is 30% by mass or more and 70% by mass or less, based on the total mass of polyol (A). (2) The polyol (A) contains cinnamon oil or a cinnamon oil derivative (a2), and the content of the cinnamon oil or cinnamon oil derivative (a2) is 30% by mass or more and 70% by mass or less, based on the total mass of the polyol (A).

[0008] A solvent-free adhesive according to one aspect of the present invention is characterized in that the number average molecular weight of the polyester polyol (a1) is 500 or more and 3,000 or less.

[0009] A solvent-free adhesive according to one aspect of the present invention is characterized in that the polyester polyol (a1) contains an aliphatic polyester polyol.

[0010] A solvent-free adhesive according to one aspect of the present invention is further characterized in that it satisfies the following (3). (3) The polyol (A) contains a polyol (a3) ​​with three or more functional properties, and the content of the polyol (a3) ​​is 5% by mass or more and 30% by mass or less, based on the total mass of the polyol (A).

[0011] A solvent-free adhesive according to one aspect of the present invention is characterized in that the polyisocyanate (B) contains a reaction product of a polyol and a polyisocyanate.

[0012] A solvent-free adhesive according to one aspect of the present invention is characterized in that the ratio (NCO / OH) of the total number of isocyanate groups in the polyisocyanate to the total number of hydroxyl groups in the polyol is 2.5 to 4.5.

[0013] A solvent-free adhesive according to one aspect of the present invention is characterized in that the polyol comprises at least one selected from the group consisting of polyester polyols and polyether polyols.

[0014] A solvent-free adhesive according to one aspect of the present invention is characterized in that the polyisocyanate includes an aromatic polyisocyanate.

[0015] A cured product according to one aspect of the present invention is characterized by being obtained by curing the above-mentioned solvent-free adhesive.

[0016] A laminate according to one aspect of the present invention is characterized in that the above-mentioned solvent-free adhesive is used as the adhesive layer.

[0017] The laminate according to one aspect of the present invention is characterized by having an ink layer in contact with the adhesive layer.

[0018] The laminate according to one aspect of the present invention is characterized in that the ink layer is a layer formed using aqueous ink.

[0019] The package according to one aspect of the present invention is characterized by using the above laminate.

Effects of the Invention

[0020] According to the present invention, it is possible to provide a solvent-free adhesive having a fast rise in adhesive strength and heat seal strength even in a low humidity environment, a good pot life, and excellent handling properties, as well as a laminate and a packaging bag produced using the adhesive.

Embodiments for Carrying Out the Invention

[0021] 〔Solvent-Free Adhesive Composition〕 The solvent-free adhesive of the present invention contains a polyol (A) and a polyisocyanate (B), and is characterized by satisfying the following (1) and (2). (1) The polyol (A) contains a polyester polyol (a1), and the content of the polyester polyol (a1) is 30% by mass or more and 70% by mass or less based on the total mass of the polyol (A). (2) The polyol (A) contains castor oil or a castor oil derivative (a2), and the content of the castor oil or the castor oil derivative (a2) is 30% by mass or more and 70% by mass or less based on the total mass of the polyol (A).

[0022] By containing a polyester polyol (a1) in a predetermined amount, the solvent-free adhesive of the present invention can impart toughness to the coating film, thereby accelerating the rise of the adhesive strength. In addition, by containing castor oil or a castor oil derivative (a2) in a predetermined amount, the multi-branched hydroxyl groups contained in the castor oil or the castor oil derivative (a2) improve the rise of the heat seal strength. Furthermore, by including a predetermined amount of cinnamon seed oil or a cinnamon seed oil derivative (a2), the viscosity of the solvent-free adhesive can be kept low. In addition, since the hydroxyl groups in polyester polyol (a1) and the hydroxyl groups in cinnamon seed oil or a cinnamon oil derivative (a2) have different reactivity with polyisocyanate (B), the reaction after compounding becomes slower, and excessive thickening can be suppressed. This improves handling properties.

[0023] As described above, the solvent-free adhesive of the present invention, as well as laminates and packaging materials using the adhesive, can be used as packaging materials for various applications such as food, pharmaceuticals, cosmetics, detergents, and general merchandise. Furthermore, they are particularly suitable for use as refillable packaging materials. The present invention will be described in detail below.

[0024] <Polyol (A)> The polyol (A) used in the present invention is characterized in that it comprises polyester polyol (a1) and cinnamon oil or cinnamon oil derivative (a2) as essential components, and the content of (a1) and (a2) is 30% by mass or more and 70% by mass or less, based on the total mass of polyol (A). By using polyester polyol (a1) and cinnamon oil or cinnamon oil derivative (a2) in combination, the rise in adhesive strength and heat seal strength can be accelerated.

[0025] [Polyester polyol (a1)] Polyester polyols (a1) are compounds having two or more hydroxyl groups and two or more ester bonds in their molecule, with ester bonds forming repeating units. Examples of such polyester polyols (a1) 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 known, and monofunctional carboxylic acids or polycarboxylic acids can be used. Examples of such carboxyl group components include monofunctional carboxylic acids having aromatic rings 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 dicarboxylic acids; and polybasic acids such as p-hydroxybenzoic acid, p-(2-hydroxyethoxy)benzoic acid, ester-forming derivatives of these dihydroxycarboxylic acids, and dimer acids.

[0026] In particular, from the viewpoint of adhesive performance and heat resistance, the carboxyl group component is preferably an acyclic aliphatic dicarboxylic acid or an aromatic dicarboxylic acid, and more preferably an acyclic aliphatic dicarboxylic acid. The acyclic aliphatic dicarboxylic acid is preferably adipic acid, and the aromatic dicarboxylic acid is preferably at least one selected from the group consisting of isophthalic acid and terephthalic acid. Aliphatic carboxyl group components, such as acyclic aliphatic dicarboxylic acids, are preferred because they make the coating film more flexible and improve adhesive strength. Furthermore, aliphatic carboxyl group components are preferred because they reduce viscosity and improve pot life.

[0027] The above hydroxyl group component is not particularly limited as long as it is known, but examples include diols and polyols with three or more functions, and is preferably a diol. Diols are preferred because they suppress excessive crosslinking when mixed with polyisocyanate, thereby improving pot life. Examples of the diols 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)cyclohesane; ether glycols such as polytetramethylene ether glycol and polyoxyethylene glycol; modified polyetherdiols obtained by ring-opening polymerization of the aliphatic diol with various cyclic ether bond-containing compounds such as ethylene oxide and tetrahydrofuran; lactone-based polyester polyols obtained by polycondensation reactions of the aliphatic diol with various lactones such as lactanoides 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. The diol is preferably an aliphatic diol, and more preferably at least one selected from the group consisting of ethylene glycol, neopentyl glycol, and 1,6-hexanediol.

[0028] Examples of the three- or more functional polyols include aliphatic polyols such as trimethylolethane, trimethylolpropane, glycerin, hexanetriol, and pentaerythritol; modified polyether polyols obtained by ring-opening polymerization of the aliphatic polyol 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 reaction of the aliphatic polyol with various lactones such as ε-caprolactone. The three- or more functional polyol is preferably an aliphatic polyol, and more preferably trimethylolpropane.

[0029] In other words, the polyester polyol (a1) preferably contains an aliphatic polyester polyol. This means that both the carboxyl group component and the hydroxyl group component constituting the polyester polyol are the aliphatic components described above. Including such an aliphatic polyester polyol is preferable because it reduces viscosity and improves handling properties.

[0030] It is important that the polyester polyol (a1) content is 30 to 70% by mass, preferably 40 to 60% by mass, based on the total mass of polyol (A). If it is 30% by mass or more, the cohesive strength of the coating film is improved and the rise in adhesive strength under low humidity conditions is accelerated. If it is 70% by mass or less, the viscosity when compounded with polyisocyanate (B) decreases, and the subsequent increase in viscosity becomes more gradual.

[0031] From the viewpoint of achieving both good physical properties and good handling, the polyester polyol (a1) preferably has a number average molecular weight of 500 to 3,000. More preferably, it has a number average molecular weight of 1,000 to 2,000. A number average molecular weight of 500 or more is preferable because it improves the cohesive force of the polyester polyol (a1) and accelerates the rise in adhesive strength under low humidity conditions. A number average molecular weight of 3,000 or less is preferable because it slows down the increase in viscosity after mixing with polyisocyanate (B) and suppresses the deterioration of coating properties over time.

[0032] The ratio (OH / COOH) of the number of hydroxyl groups in the hydroxyl group component to the number of carboxyl groups in the carboxyl group component used in the synthesis of the polyester polyol (a1) is preferably 1.2 to 2.0, and more preferably 1.2 to 1.5. A ratio of 1.2 or higher is preferable because it improves the cohesive force of the polyester polyol (a1) and allows for a faster rise in adhesive strength even under low humidity conditions. A ratio of 2.0 or lower is preferable because it slows down the increase in viscosity after mixing with polyisocyanate (B) and suppresses the deterioration of coating properties over time.

[0033] The hydroxyl value of the polyester polyol (a1) is preferably 40 to 150 mgKOH / g, and more preferably 60 to 150 mgKOH / g. A value of 40 mgKOH / g or higher is preferable because it reduces the viscosity of the polyester polyol (a1), slows the increase in viscosity after mixing with polyisocyanate (B), and suppresses the deterioration of coating properties over time. A value of 150 mgKOH / g or lower is preferable because it improves the cohesive force of the polyester polyol (a1) and speeds up the rise of adhesive strength under low humidity conditions.

[0034] The polyester polyol (a1) may be a polyol obtained by reacting a diisocyanate with some of the hydroxyl groups to introduce a urethane bond (hereinafter sometimes abbreviated as polyester polyurethane polyol). 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. Furthermore, the polyester polyol (a1) may be a polyol obtained by reacting some of the hydroxyl groups with an acid anhydride to introduce carboxyl groups (hereinafter sometimes abbreviated as acid modification). Examples of the acid anhydride include pyromellitic anhydride, mellitic anhydride, trimellitic anhydride, and trimellitic anhydride esters. Examples of trimellitic anhydrides include ester compounds obtained by esterifying alkylene glycols or alkanetriols having 2 to 30 carbon atoms with trimellitic anhydride, and specifically, ethylene glycol bisanehydrotrimellitate, propylene glycol bisanehydrotrimellitate, etc. can be used.

[0035] [Central hemp oil or hemp seed oil derivative (a2)] Commercially available canister oil can be used. An example of such a commercially available product is Industrial Grade No. 1 Canister Oil (manufactured by Toyokuni Oil Co., Ltd.). Furthermore, the catechu seed oil derivatives are those having hydroxyl groups, and examples include catechu seed oil urethane polyols obtained by urethaneizing catechu seed oil, catechu seed oil ester polyols obtained by esterifying catechu seed oil, dehydrated catechu seed oil, hydrogenated catechu seed oil (a hydrogenated product of catechu seed oil), catechu seed oil fatty acids, dehydrated catechu seed oil fatty acids, catechu seed oil fatty acid condensates, ethylene oxide adducts of catechu seed oil (5-50 molars), or catechu seed oil-based polyols. Commercially available catechu seed oil derivatives may be used. Examples of such commercially available products include CO-FA (cantaloupe seed oil fatty acid, manufactured by Toyokuni Oil Co., Ltd.), HS 2G-120 (cantaloupe seed oil-based polyol, manufactured by Toyokuni Oil Co., Ltd.), HS 2G-160R (cantaloupe seed oil-based polyol, manufactured by Toyokuni Oil Co., Ltd.), and HS 2G-270B (cantaloupe seed oil-based polyol, manufactured by Toyokuni Oil Co., Ltd.). Among these, Cinnamomum erythrorhizon oil is preferred from the viewpoint of improving leveling properties and reducing viscosity.

[0036] It is important that the amount of cinnamon seed oil or cinnamon seed oil derivative (a2) is 30 to 70% by mass, preferably 40 to 60% by mass, based on the total mass of polyol (A). If the amount is 30% by mass or more, a three-dimensional structure is preferentially constructed, and the rise in heat seal strength under low humidity conditions is accelerated. If the amount is 70% by mass or less, the cohesive force of the coating film is improved, and the rise in adhesive strength can be accelerated. In addition, the increase in viscosity after mixing with polyisocyanate (B) becomes gradual, and the deterioration of coating properties over time can be suppressed.

[0037] [Polyols with three or more functions (a3)] The polyol (A) preferably further contains a polyol (a3) ​​with three or more functionalities. The combination of (a1) and (a2) described above with a polyol (a3) ​​with three or more functionalities is preferable because it preferentially forms a three-dimensional structure even under low humidity conditions, improving cohesive strength and accelerating the rise of adhesive strength and heat seal strength.

[0038] Polyols with three or more functions (a3) ​​are compounds with three or more hydroxyl groups in one molecule, excluding (a1) and (a2) described above, and the description of polyols with three or more functions in the section on (polyester polyols (a1)) can be applied. The number of terminal hydroxyl groups in the trifunctional or more polyol (a3) ​​is preferably 3 to 5, more preferably 3 to 4, and particularly preferably 3. A number of 5 or less is preferable because it prevents the overall hydroxyl value of the polyol (A) from becoming too high, resulting in a gradual increase in viscosity after mixing with polyisocyanate (B) and suppressing a decrease in coating properties over time.

[0039] The number-average molecular weight of the trifunctional or more functional polyol (a3) ​​is preferably 100 to 1,000, and more preferably 200 to 500. A number-average molecular weight of 100 or more is preferable because it prevents the overall hydroxyl value of the polyol (A) from becoming too high, resulting in a gradual increase in viscosity after mixing with polyisocyanate (B) and suppressing a decrease in coating properties over time. A number-average molecular weight of 1,000 or less is preferable because it improves the reactivity of the hydroxyl groups of the trifunctional or more functional polyol (a3), allowing for preferential construction of a three-dimensional structure and resulting in a faster rise in adhesive strength and heat seal strength. The polyol (a3) ​​with three or more functions is preferably an adduct (triol) obtained by adding polypropylene glycol to glycerin, and more preferably a triol with a number average molecular weight of 300 to 5000, from the viewpoint of improving the initial rise of adhesive strength and heat seal strength and improving pot life.

[0040] The polyol (A) preferably contains 5 to 30% by mass of a trifunctional or higher polyol (a3) ​​based on the total mass of polyol (A). More preferably, it is 5 to 15% by mass. If it is 5% by mass or more, a three-dimensional structure is preferentially constructed, increasing the cohesive force of the adhesive coating and accelerating the rise in adhesive strength and heat seal strength. If it is 30% by mass or less, the increase in viscosity after mixing with polyisocyanate (B) becomes gradual, which is preferable because it suppresses the deterioration of coating properties over time.

[0041] Polyol (A) may further contain other polyols, provided that the effects of the present invention are not impaired. Examples of these other polyols include polycarbonate polyols, polycaprolactone polyols, polyether polyols, polyolefin polyols, acrylic polyols, silicone polyols, and fluorinated polyols. These other polyols may be those in which urethane bonds are introduced by reacting some of the hydroxyl groups with diisocyanates (for example, polyether urethane polyols), or they may be those in which carboxyl groups are introduced by reacting some of the hydroxyl groups with acid anhydrides. The diisocyanate and acid anhydride can be described by referring to the section on (polyester polyol (a1)) described above.

[0042] <Polyisocyanate (B)> The polyisocyanate (B) constituting the solvent-free adhesive of the present invention is not particularly limited and includes, for example, aromatic polyisocyanates, aromatic aliphatic polyisocyanates, aliphatic polyisocyanates, alicyclic polyisocyanates, or modified versions thereof. These polyisocyanates may be used individually or in combination of two or more.

[0043] Examples of aromatic polyisocyanates include aromatic diisocyanates such as diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, phenylene diisocyanate, tolylene diisocyanate, and naphthalene diisocyanate; and aromatic polyisocyanates such as polymethylene polyphenyl polyisocyanate. Examples of aromatic aliphatic polyisocyanates include 1,3- or 1,4-xylylene diisocyanate or mixtures thereof, ω,ω′-diisocyanate-1,4-diethylbenzene, 1,3- or 1,4-bis(1-isocyanate-1-methylethyl)benzene or mixtures thereof, and other aromatic aliphatic diisocyanates. Examples of aliphatic polyisocyanates include 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(isocyanate methyl)cyclohexane, 1,3-bis(isocyanate methyl)cyclohexane, and norbornene diisocyanate.

[0044] Examples of modified polyisocyanates include allophanate-type modified polyisocyanates, isocyanurate-type modified polyisocyanates, biuret-type modified polyisocyanates, and adduct-type modified polyisocyanates. Alternatively, a polyisocyanate having a urethane bond, which is a reaction product of polyisocyanate and polyol, may be used as a modified polyisocyanate. The polyols that form the modified polyisocyanates mentioned above are not particularly limited, and examples include polyester polyols, polyether polyols, polycarbonate polyols, polycaprolactone polyols, polyolefin polyols, acrylic polyols, silicone polyols, castor oil-based polyols, and fluorine-based polyols.

[0045] [Polyisocyanates containing urethane bonds] Polyisocyanate (B) preferably comprises a polyisocyanate having a urethane bond, and more preferably comprises a reaction product of a polyol and a polyisocyanate. As the polyol mentioned above, at least one selected from the group consisting of polyester polyols and polyether polyols is preferably used, and more preferably contains a polyester polyol. Particularly preferably contains both a polyester polyol and a polyether polyol. By using polyester polyol and polyether polyol in combination, it is possible to achieve both cohesive strength and flexibility in the adhesive layer. This is preferable because it allows for a faster rise in adhesive strength and heat seal strength. In this specification, the reaction product of a polyester polyol and a polyisocyanate may be abbreviated as polyester polyurethane polyisocyanate. Similarly, the reaction product of a polyether polyol and a polyisocyanate may be abbreviated as polyether polyurethane polyisocyanate.

[0046] Polyisocyanates having urethane bonds can be obtained by reacting a polyol with a polyisocyanate under conditions where the isocyanate group is in excess. As described above, the polyol is preferably a polyester polyol or a polyether polyol.

[0047] (Polyester polyol) The above-mentioned polyester polyol can be any compound having two or more hydroxyl groups and two or more ester bonds in its molecule, and those described in the above-mentioned section [Polyester Polyol (a1)] can be used. In particular, it is preferable to include an aliphatic polyester polyol. This means that both the carboxyl group component and the hydroxyl group component constituting the polyester polyol are the aliphatic components described above. Including such an aliphatic polyester polyol is preferable because it reduces viscosity and improves handling properties.

[0048] The above polyester polyol preferably has a number average molecular weight of 500 to 3,000, more preferably 1,000 to 2,000, from the viewpoint of achieving both good initial physical properties and good handling. A number average molecular weight of 500 or more is preferable because it improves the cohesive force of the polyester polyol and accelerates the rise of adhesive strength under low humidity conditions. A number average molecular weight of 3,000 or less is preferable because it slows down the increase in viscosity after mixing with polyol (A) and suppresses the deterioration of coating properties over time.

[0049] The ratio (OH / COOH) of the number of hydroxyl groups in the hydroxyl group component to the number of carboxyl groups in the carboxyl group component used in the synthesis of the above polyester polyol is preferably 1.2 to 2.0, and more preferably 1.2 to 1.5. A ratio of 1.2 or higher is preferable because it improves the cohesive force of the polyester polyol, resulting in a faster rise in adhesive strength even under low humidity conditions. A ratio of 1.5 or lower is preferable because it slows down the increase in viscosity after mixing with polyol (A), suppressing the deterioration of coating properties over time.

[0050] The hydroxyl value of the polyester polyol is preferably 40 to 150 mgKOH / g, and more preferably 60 to 150 mgKOH / g. A value of 40 mgKOH / g or higher is preferable because it reduces the viscosity of the polyester polyol, slows the increase in viscosity after mixing with polyol (A), and suppresses the deterioration of coating properties over time. A value of 150 mgKOH / g or lower is preferable because it improves the cohesive force of polyisocyanate (B) and speeds up the rise of adhesive strength under low humidity conditions.

[0051] The above-mentioned polyester polyol may be one in which a urethane bond is introduced by reacting a diisocyanate with some of the hydroxyl groups, or it may be one in which a carboxyl group is introduced by reacting an acid anhydride with some of the hydroxyl groups.

[0052] (Polyether polyol) The above-mentioned polyether polyols may be any compound having two or more hydroxyl groups and two or more ether bonds in their molecule, and may be either a difunctional polyether polyol or a trifunctional polyether polyol. These polyether polyols may be used individually or in combination of two or more. Examples of bifunctional polyether polyols 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 initiator such as water, ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, or suocrose may be used as the polyether polyol. Examples of such addition polymers include propylene glycol propylene oxide adducts, glycerol propylene oxide adducts, sorbitol-based propylene oxide adducts, and suocrose-based propylene oxide adducts.

[0053] Examples of polyether polyols with three or more functions include aliphatic polyols such as trimethylolethane, trimethylolpropane, glycerin, hexanetriol, and pentaerythritol; modified polyether polyols obtained by ring-opening polymerization of the aliphatic polyol 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 reactions of the aliphatic polyol with various lactones such as ε-caprolactone.

[0054] From the viewpoint of coating film flexibility and resin compatibility, the number-average molecular weight of the polyether polyol is preferably 400 to 2,000. A number-average molecular weight of 400 or more is preferable because it increases the flexibility of the polymer chain in the adhesive. A number-average molecular weight of 2,000 or less is preferable because it improves compatibility with the isocyanate component and facilitates the urethane formation reaction.

[0055] (Polyisocyanate) Examples of polyisocyanates that form polyisocyanates having urethane bonds include aromatic polyisocyanates, aromatic aliphatic polyisocyanates, aliphatic polyisocyanates, alicyclic polyisocyanates, or modified versions thereof. These polyisocyanates may be used individually or in combination of two or more. The above-mentioned aromatic polyisocyanates, aromatic aliphatic polyisocyanates, aliphatic polyisocyanates, alicyclic polyisocyanates, or modified versions thereof can be described by reference to the section <Polyisocyanates (B)> above.

[0056] The above polyisocyanate preferably includes an aromatic polyisocyanate, and more preferably includes diphenylmethane diisocyanate, from the viewpoint of improving the cohesive strength of the adhesive coating film. The diphenylmethane diisocyanate may be either 4,4'-diphenylmethane diisocyanate or 2,4-diphenylmethane diisocyanate.

[0057] The molar ratio (NCO moles / OH moles) of the total isocyanate groups of the polyisocyanate to the total hydroxyl groups of the polyol that form the reaction product of the polyol and polyisocyanate is preferably 2.5 to 4.5, and more preferably 3.0 to 4.0. A molar equivalent ratio of 2.5 or higher is preferable because it suppresses thickening and improves pot life. A molar equivalent ratio of 4.5 or lower is preferable because it increases the molecular weight of the resulting polyisocyanate, leading to a faster rise in adhesive strength and heat seal strength.

[0058] The polyisocyanate group content of polyisocyanate (B) is preferably in the range of 8.0% to 16.0% by mass, and more preferably in the range of 9.0% to 14.5% by mass. This range is preferable because it optimizes the crosslinking density and improves the adhesive strength.

[0059] <Other ingredients> The solvent-free adhesive of the present invention may contain components other than polyol (A) and polyisocyanate (B) to satisfy various performance requirements. Such other components may be blended with either polyol (A) or polyisocyanate (B), or they may be blended when mixing polyol (A) and polyisocyanate (B). The other components may be used individually or in combination of two or more.

[0060] (Silane coupling agent) The solvent-free adhesive of the present invention may contain a silane coupling agent from the viewpoint of improving the adhesive strength to metallic materials such as metal foils and metal vapor-deposited layers. Examples of silane coupling agents include trialksoxysilanes having vinyl groups, such as vinyltriethoxysilane; trialksoxysilanes having amino groups, such as 3-aminopropyltriethoxysilane and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane; and trialksoxysilanes having glycidyl groups, such as 3-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane. The silane coupling agent content is preferably 0.1 to 5% by mass, and more preferably 0.2 to 3% by mass, based on the total mass of the total polyol (A). This range is preferable because it can improve the adhesive strength to the metal foil.

[0061] (Phosphoric acid or phosphoric acid derivatives) The solvent-free adhesive of the present invention may contain phosphoric acid or a phosphoric acid derivative from the viewpoint of improving the adhesive strength to metallic materials such as metal foil and metal vapor-deposited layers. The phosphoric acid mentioned above can be any phosphoric acid having at least one free oxygen acid, and examples include phosphoric acids such as hypophosphorous acid, phosphorous acid, orthophosphoric acid, and subphosphoric acid; and condensed phosphoric acids such as metaphosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, polyphosphoric acid, and ultraphosphoric acid. Furthermore, examples of phosphoric acid derivatives include those obtained by partially esterifying the above-mentioned phosphoric acid with alcohols while retaining 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 phloroglycinol. The content of phosphoric acid or its derivative is preferably 0.01 to 10% by mass, more preferably 0.05 to 5% by mass, and particularly preferably 0.05 to 1% by mass, based on the mass of the solvent-free adhesive.

[0062] (Leveling agent or defoaming agent) The solvent-free adhesive of the present invention may 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-containing polydimethylsiloxane, polyether ester-modified hydroxyl-containing polydimethylsiloxane, acrylic copolymers, methacrylic copolymers, polyether-modified polymethylalkylsiloxane, alkyl acrylate copolymers, alkyl methacrylate copolymers, and lecithin. Examples of antifoaming agents include silicone resins, silicone solutions, and copolymers of alkyl vinyl ethers, alkyl acrylates, and alkyl methacrylates.

[0063] (Reaction accelerator) The solvent-free adhesive of the present invention may contain a reaction accelerator to promote the curing reaction. Examples of reaction accelerators include metal catalysts such as dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate, and dibutyltin dimalate; tertiary amines such as 1,8-diazabicyclo(5,4,0)undecene-7, 1,5-diazabicyclo(4,3,0)nonene-5, and 6-dibutylamino-1,8-diazabicyclo(5,4,0)undecene-7; and reactive tertiary amines such as triethanolamine.

[0064] (Additives) The solvent-free adhesive of the present invention may contain various additives, as long as they do 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.

[0065] <Cured product, laminate> The solvent-free adhesive of the present invention becomes a cured product of the present invention when the substrates described later are bonded together and then cured under conditions such as 20 to 60°C. The laminate of the present invention is obtained by laminating an adhesive layer made of the above-described solvent-free adhesive between at least two sheet-like substrates. As an example, the solvent-free adhesive can be applied to a first sheet-like substrate, a second sheet-like substrate can be laminated onto the applied surface, and the adhesive layer located between the two sheet-like substrates can be cured. The amount of solvent-free adhesive applied is preferably 1.0 to 5.0 g / m². 2 More preferably 1.5 to 4.5 g / m 2 The thickness of the laminate is preferably 10 μm or more.

[0066] [Sheet-like substrate] The sheet-like substrate is not particularly limited and can be, for example, conventionally known plastic films, paper, or metal foils such as aluminum foil. The two sheet-like substrates may be of the same type or different types. As the plastic film, a thermoplastic resin or thermosetting resin film can be used, and a thermoplastic resin film is preferred. Examples of thermoplastic resins include polyolefins, polyesters, polyamides, polystyrenes, vinyl chloride resins, vinyl acetate resins, ABS resins, acrylic resins, acetal resins, polycarbonate resins, and cellulose-based plastics. The sheet-like substrate may have a barrier layer consisting of a metal or metal oxide vapor-deposited layer, and examples of such barrier layers include vapor-deposited layers of aluminum (AL), silica, alumina, etc.

[0067] The first sheet-like substrate is preferably a plastic film. Examples of plastic films commonly used in packaging materials include 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 (NY) 6 and poly-p-xylylene adipamide (MXD6 nylon); polycarbonate resin films; polyacrylonitrile resin films; polyimide resin films; and composites of these (e.g., nylon 6 / MXD6 / nylon 6, nylon 6 / ethylene-vinyl alcohol copolymer / nylon 6) or mixtures thereof. Among these, those with mechanical strength and dimensional stability are preferred. The plastic film preferably has a thickness of 5 to 50 μm, more preferably 10 to 30 μm.

[0068] When the second sheet-like substrate becomes the outermost layer of the laminate, it is preferable that the second sheet-like substrate is a sealant substrate. Examples of sealant substrates include polyethylene such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE), acid-modified polyethylene, polypropylene (PP), acid-modified polypropylene, copolymerized polypropylene, 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, but considering processability and heat-sealability for packaging materials, it is preferably 10 to 150 μm, and more preferably 20 to 70 μm. Furthermore, by providing the sealant substrate with bumps and dips with height differences of several μm, slipperiness and tearability of the packaging material can be imparted. When the second sheet-like substrate becomes an intermediate layer of the laminate, the aforementioned plastic film, paper, metal foil, etc., can be suitably used as the second sheet-like substrate.

[0069] [Ink layer] The sheet-like substrate may have an ink layer on the substrate, and the ink layer may be in contact with the adhesive layer. The ink layer is a layer that forms any desired printed pattern such as letters, numbers, pictures, figures, symbols, or designs for decoration, indication of contents, indication of expiration date, indication of manufacturer, seller, etc., and to add aesthetic appeal, and may be a solid print layer that is printed across the entire surface. Generally, the ink layer is formed using printing ink containing colorants such as pigments and dyes. Examples of printing inks include oil-based inks, water-based inks, and UV inks. Examples of printing methods include gravure coating, flexo coating, roll coating, bar coating, die coating, curtain coating, spin coating, and inkjet printing. In the printing process, blowing air, heating, vacuum drying, and UV irradiation may be performed as needed. The ink layer preferably has a thickness of 0.1 to 10 μm, more preferably 1 to 5 μm, and even more preferably 1 to 3 μm.

[0070] When the laminate of the present invention has an ink layer in contact with the adhesive layer, the ink forming the ink layer is not particularly limited. However, even when the ink layer of the laminate of the present invention is formed using an aqueous ink, the physical properties such as adhesive strength and heat seal strength can be rapidly developed, even in harsh low-humidity environments. Generally, water-based ink layers tend to retain more hydroxyl groups than oil-based ink layers. Therefore, when an adhesive is applied to a water-based ink layer, the residual hydroxyl groups consume the isocyanates in the adhesive, inhibiting the urethane reaction that increases the molecular weight of the adhesive. This reduces the cohesive force of the adhesive layer, leading to a slower onset of physical properties such as adhesive strength and heat seal strength. However, by having the adhesive layer using the solvent-free adhesive of the present invention adjacent to the aqueous ink layer, the cohesive force of the adhesive layer can be maintained, and the rise of physical properties such as adhesive strength and heat seal strength can be accelerated even in harsh low-humidity environments.

[0071] As the resin contained in the water-based ink layer, for example, at least one selected from the group consisting of natural resins or synthetic resins of the dissolving type, hydrosol type, or emulsion type, and modified resins thereof, can be used. Examples of the above resins include polyarylamide resins, poly(meth)acrylic acid resins, polyvinyl chloride resins, polyvinyl acetate resins, polyethylene oxide resins, poly-N-vinylpyrrolidone resins, polyurethane resins (two-component curing polyurethane resins), polyurethane urea resins (two-component curing polyurethane urea resins), polyester resins, polyamide resins, amino resins, phenolic resins, synthetic rubber and other synthetic resins; and natural polymers such as polynucleotides, polypeptides, polysaccharides, and natural rubber. One type may be used alone, or two or more types may be used in combination. The above poly(meth)acrylic acid resin includes, for example, at least one of the following: (meth)acrylic monomers such as acrylic acid esters, methacrylic acid esters, hydroxylethyl acrylate, and hydroxylethyl methacrylate; nitrile monomers such as acrylonitrile and methacrylnitrile; amide monomers such as acrylamide and methacrylamide; N-alkoxy-substituted and N-methylol-substituted derivatives of the amide monomers; styrene monomers such as styrene, vinyltoluene, α-methylstyrene, and divinylbenzene; allyl monomers such as diallyl phthalate, allyl glycidyl ether, and triallyl isocyanurate; and monomers having polymerizable double bonds such as vinyl acetate and N-vinylpyrrolidone. Copolymers of carboxyl group-containing compounds or acid anhydrides such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, and itaconic acid can be used.

[0072] Examples of the laminates of the present invention are given below, but are not limited to these. If the laminate comprises multiple adhesive layers, at least one of the adhesive layers may be formed from the solvent-free adhesive of the present invention. In the following, transparent deposition means a silica or alumina deposition layer. OPP / Ink layer / Adhesive layer / CPP, Ink layer / OPP / Adhesive layer / CPP, OPP / Ink layer / Adhesive layer / AL vapor-deposited CPP, Ink layer / OPP / Adhesive layer / AL vapor-deposited CPP, OPP / Ink layer / Adhesive layer / AL vapor-deposited PET, Ink layer / OPP / Adhesive layer / AL vapor-deposited PET, OPP / Ink layer / Adhesive layer / PE, Ink layer / OPP / Adhesive layer / PE, PET / ink layer / adhesive layer / CPP, Ink layer / PET / Adhesive layer / CPP, PET / ink layer / adhesive layer / AL vapor-deposited CPP, Ink layer / PET / Adhesive layer / AL vapor-deposited CPP, PET / ink layer / adhesive layer / AL vapor-deposited PET, Ink layer / PET / Adhesive layer / AL vapor-deposited PET, PET / ink layer / adhesive layer / PE, Ink layer / PET / Adhesive layer / PE, NY / Ink layer / Adhesive layer / CPP, Ink layer / NY / Adhesive layer / CPP, NY / Ink layer / Adhesive layer / AL vapor deposition CPP, Ink layer / NY / Adhesive layer / AL vapor deposition CPP, NY / Ink layer / Adhesive layer / AL vapor-deposited PET, Ink layer / NY / Adhesive layer / AL vapor-deposited PET, NY / Ink layer / Adhesive layer / PE, Ink layer / NY / Adhesive layer / PE, PET / ink layer / adhesive layer / NY / adhesive layer / CPP, PET / ink layer / adhesive layer / NY / adhesive layer / PE, Transparent vapor-deposited PET / ink layer / adhesive layer / NY / adhesive layer / CPP, Transparent vapor-deposited PET / ink layer / adhesive layer / NY / adhesive layer / PE, PET / ink layer / adhesive layer / AL vapor-deposited PET / adhesive layer / CPP, PET / ink layer / adhesive layer / AL vapor-deposited PET / adhesive layer / PE, NY / Ink layer / Adhesive layer / AL vapor-deposited PET / Adhesive layer / CPP, NY / Ink layer / Adhesive layer / AL vapor-deposited PET / Adhesive layer / PE, PET / ink layer / adhesive layer / AL vapor-deposited PET / adhesive layer / NY / adhesive layer / CPP, PET / ink layer / adhesive layer / AL vapor-deposited PET / adhesive layer / NY / adhesive layer / PE, PET / ink layer / adhesive layer / AL / adhesive layer / CPP, PET / ink layer / adhesive layer / AL / adhesive layer / PE, PET / ink layer / adhesive layer / NY / adhesive layer / AL / adhesive layer / CPP, PET / ink layer / adhesive layer / NY / adhesive layer / AL / adhesive layer / PE, PET / ink layer / adhesive layer / AL / adhesive layer / NY / adhesive layer / CPP, PET / Ink layer / Adhesive layer / AL / Adhesive layer / NY / Adhesive layer / PE

[0073] <Package> The packaging of the present invention may be any product using the above-mentioned laminate, and examples include two-sided bags, three-sided bags, three-sided bags with zippers, gusseted bags, bottom gusseted bags, stand-up pouches, stand-up zippered bags, two-sided bags, four-sided column flat-bottom gusseted bags, side-sealed bags, and bottom-sealed bags. In particular, packaging using the solvent-free adhesive of the present invention is suitable for packaging bags that require molding or heat sealing because it exhibits excellent adhesive strength and rapid heat seal strength development under low humidity conditions. Furthermore, packaging using the solvent-free adhesive of the present invention is suitable for packaging bags that are distributed in winter or in low-humidity environments. [Examples]

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

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

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

[0077] [Method for measuring NCO content (mass %)] Approximately 1 g of the sample was weighed into a 200 mL Erlenmeyer flask, and 10 mL of 0.5 N di-n-butylamine solution in toluene and 10 mL of toluene were added to dissolve it. Next, phenolphthalein reagent was added as an indicator, and after holding for 30 seconds, the solution was titrated with 0.25 N hydrochloric acid solution until it turned pale pink. The NCO content (mass%) was determined by the following formula (Equation 3). (Formula 3): NCO (mass%)={(ba)×4.202×F×0.25} / S However, S: Sample volume (g) a: Amount of 0.25N hydrochloric acid solution consumed (ml) b: Amount of 0.25N hydrochloric acid solution consumed in the blank experiment (ml) F: Titer of 0.25N hydrochloric acid solution

[0078] [Method for measuring ICI viscosity] Viscosity was measured using a Toa Kogyo Co., Ltd. "CV-1S" cone plate viscometer. The displayed value at the point when the reading stabilized was defined as the ICI viscosity.

[0079] <Production of polyol (A)> (Synthesis of polyester polyol (a1-1)) In a reaction vessel equipped with a stirrer, temperature gauge, reflux condenser, dropping tank, and nitrogen gas inlet, 402.3 parts of adipic acid, 186.3 parts of neopentyl glycol, and 211.4 parts of 1,6-hexanediol were charged, and the mixture was heated to 240°C while stirring under a nitrogen atmosphere. The reaction was continued until the acid value was 5 mg KOH / g or less, after which the pressure was gradually reduced and the reaction was continued at 1 mmHg to remove excess alcohol and obtain polyester polyol (a1-1).

[0080] (Synthesis of polyester polyols (a1-2~a1-7)) Except for changing the raw materials to the formulation (parts by mass) listed in Table 1, the esterification reaction was carried out in the same manner as in (a1-1) to obtain polyester polyols (a1-2 to a1-7).

[0081] [Table 1]

[0082] <Synthesis of Centella asiatica seed oil derivatives> In a reaction vessel equipped with a stirrer, temperature gauge, reflux condenser, dropping tank, and nitrogen gas inlet, 746.7 parts of cinnamon seed oil and 53.3 parts of a mixture of 2,4-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate (mass ratio 50:50) were charged. The mixture was heated at 80°C to 90°C for 3 hours while stirring under a nitrogen gas stream to carry out the urethane reaction, thereby obtaining a cinnamon seed oil derivative containing urethane bonds.

[0083] <Production of polyisocyanate (B)> (Synthesis of polyisocyanate (B-1)) In a reaction vessel equipped with a stirrer, temperature gauge, reflux condenser, dropping tank, and nitrogen gas inlet tube, 54.7 parts of polypropylene glycol with a number average molecular weight of 400, 100.1 parts of polytetramethylene glycol with a number average molecular weight of 1,000, 198.8 parts of polypropylene glycol with a number average molecular weight of 2,000, and 286.4 parts of 4,4'-diphenylmethane diisocyanate were charged. The mixture was then heated at 80°C to 90°C for 3 hours while stirring under a nitrogen gas stream to carry out the urethane reaction, thereby obtaining a polyisocyanate containing urethane bonds. Next, 160.0 parts of polymeric diphenylmethane diisocyanate were added and mixed with stirring at 70°C for 30 minutes to obtain polyisocyanate (B-1) with an isocyanate group content of 14.6% by mass.

[0084] (Synthesis of polyisocyanate (B-2)) In a reaction vessel equipped with a stirrer, temperature gauge, reflux condenser, dropping tank, and nitrogen gas inlet, 54.6 parts of polypropylene glycol with a number average molecular weight of 400, 88.9 parts of polytetramethylene glycol with a number average molecular weight of 1,000, 176.5 parts of polypropylene glycol with a number average molecular weight of 2,000, 35.8 parts of triol with a number average molecular weight of 400 obtained by adding polypropylene glycol to glycerin, 5.8 parts of trimethylolpropane, and 438.4 parts of a mixture of 2,4-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate (mass ratio 50:50) were charged. The mixture was heated at 80°C to 90°C for 3 hours while stirring under a nitrogen gas stream to carry out the urethane reaction, yielding polyisocyanate (B-2) having urethane bonds and an isocyanate group content of 13.2% by mass.

[0085] (Synthesis of polyisocyanate (B-3)) Except for changing the raw materials to the formulation (parts by mass) shown in Table 2, the urethane reaction was carried out in the same manner as in (B-2) to obtain polyisocyanate (B-3) having urethane bonds and an isocyanate group content of 12.0% by mass.

[0086] (Synthesis of polyisocyanate (B-4)) Except for changing the raw materials to the formulation (parts by mass) shown in Table 2, the urethane reaction was carried out in the same manner as in (B-1) to obtain polyisocyanate (B-4) having urethane bonds and an isocyanate group content of 14.3% by mass.

[0087] (Synthesis of polyisocyanate (B-5)) Except for changing the raw materials to the formulation (parts by mass) shown in Table 2, the urethane reaction was carried out in the same manner as in (B-2) to obtain polyisocyanate (B-5) having urethane bonds and an isocyanate group content of 13.9% by mass.

[0088] (Synthesis of polyisocyanate (B-6)) Except for changing the raw materials to the formulation (parts by mass) shown in Table 2, the urethane reaction was carried out in the same manner as in (B-2) to obtain polyisocyanate (B-6) having urethane bonds and an isocyanate group content of 11.8% by mass.

[0089] (Synthesis of polyisocyanate (B-7)) Except for changing the raw materials to the formulation (parts by mass) shown in Table 2, the urethane reaction was carried out in the same manner as in (B-1) to obtain polyisocyanate (B-7) having urethane bonds and an isocyanate group content of 13.1% by mass.

[0090] (Synthesis of polyisocyanate (B-8)) Except for changing the raw materials to the formulation (parts by mass) shown in Table 2, the urethane reaction was carried out in the same manner as in (B-1) to obtain polyisocyanate (B-8) with an isocyanate group content of 9.5% by mass.

[0091] [Table 2]

[0092] The abbreviations used in Table 2 are shown below. P-400: Polypropylene glycol with a number-average molecular weight of 400 PTMG-1000: Polytetramethylene glycol with a number-average molecular weight of 1,000. P-2000: Polypropylene glycol with a number-average molecular weight of 2,000 Glycerin PPG adduct: A triol with a number average molecular weight of 400 obtained by adding polypropylene glycol to glycerin. 4,4'-MDI: 4,4'-diphenylmethane diisocyanate A mixture of 2,4'-MDI and 4,4'-MDI: a mixture of 2,4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate in a 50 / 50 mass ratio. HDI biuret: Trimer of biuret-type polyisocyanate and 1,6-hexamethylene diisocyanate

[0093] <Manufacturing of solvent-free adhesives> [Examples 1-23, Comparative Examples 1-2] Solvent-free adhesives C-1-C-25 Polyol (A) and polyisocyanate (B) were mixed according to the formulations shown in Table 3 to obtain solvent-free adhesives 1 to 25.

[0094] <Evaluation of solvent-free adhesives> Laminates 1-4 were prepared using the obtained solvent-free adhesive as described below, and adhesive strength and heat seal peel tests were conducted. Pot life evaluation of the solvent-free adhesive was also performed. The results are shown in Tables 3 and 4.

[0095] (Fabrication of laminate 1: OPP / oil-based ink layer / adhesive layer / VM-PET) Oil-based ink (Toyo Ink Co., Ltd., Rio Alpha R631 White) was diluted with ethyl acetate / IPA mixed solvent (mass ratio 70 / 30) to a viscosity of 16 seconds (25°C, Zahn Cup No. 3). The diluted ink was printed onto a 20 μm thick OPP film (Toyobo Co., Ltd., "P2161") using a gravure proofing machine equipped with a solid plate depth of 35 μm at a printing speed of 50 m / min, and then dried at 50°C. The thickness of the ink layer was within the range of 0.5 to 1 μm. Next, at room temperature, the ink side of the printed material obtained above and the vapor-deposited side of a 12 μm thick aluminum-deposited polyethylene terephthalate (VM-PET) film (Reikosha's "DiaLuster H27") were bonded together using a laminator with the obtained solvent-free adhesive. The lamination speed was 150 m / min, and the coating amount was 2.0 g / m². 2 That's what I decided. The bonded laminates were stored for 24 hours in a low-humidity environment of 40°C and 20%RH to obtain laminate 1, which has the composition of "OPP / oil-based ink layer / adhesive layer / VM-PET".

[0096] (Fabrication of Laminate 2: OPP / Water-based ink layer / Adhesive layer / VM-PET) Water-based ink (Toyo Ink Co., Ltd., Aquaecol R631 white) was diluted with a water / n-propanol mixed solvent (mass ratio 50 / 50) to a viscosity of 16 seconds (25°C, Zahn cup No. 3). The diluted ink was printed onto a 20 μm thick OPP film (Toyobo Co., Ltd., "P2161") using a gravure proofing machine equipped with a solid plate with a plate depth of 35 μm at a printing speed of 50 m / min, and then dried at 60°C. The thickness of the ink layer was within the range of 0.5 to 1 μm. Next, lamination and aging were performed in the same manner as (fabrication of laminate 1), except that the obtained printed material was used, to obtain laminate 2, which has the structure of "OPP / water-based ink layer / adhesive layer / VM-PET".

[0097] (Fabrication of Laminate 3: NY / Oil-based ink layer / Adhesive layer / LLDPE) Using the same method as described in (Preparation of Laminate 1), an oil-based ink (Toyo Ink Co., Ltd., Rio Alpha R631 white) was printed on a 15 μm thick NY film (Unitika Corporation's "Emblem ON-RT") to a thickness of 0.5 to 1 μm. Next, at room temperature, the ink side of the printed material obtained above was laminated to a 50 μm thick LLDPE film (TUX-FCD, manufactured by Mitsui Chemicals Tohcello Co., Ltd.) using the solvent-free adhesive obtained. The lamination speed was 150 m / min, and the application rate was 2.0 g / m². 2 That's what I decided. The bonded laminates were stored for 24 hours in a low-humidity environment of 40°C and 20%RH to obtain laminate 3, which has the composition of "NY / oil-based ink layer / adhesive layer / LLDPE".

[0098] (Fabrication of Laminate 4: NY / Water-based ink layer / Adhesive layer / LLDPE) Using the same method as described in (Preparation of Laminate 2), a water-based ink (Toyo Ink Co., Ltd., Aquaecol R631 white) was printed on a 15 μm thick NY film (Unitika Corporation's "Emblem ON-RT") to a thickness of 0.5 to 1 μm. Next, a laminate 4 was obtained with the configuration of "NY / water-based ink layer / adhesive layer / LLDPE" in the same manner as (fabrication of laminate 3), except that the obtained printed material was used.

[0099] [Adhesive Strength] OPP / Oil-based or water-based ink layer / Adhesive layer / VM-PET Laminate 1 and Laminate 2 were cut into pieces 15 mm wide and 300 mm long to serve as test specimens. Based on JIS K6854, an Instron-type tensile testing machine was used to measure the T-type peel strength [N / 15 mm] between OPP and VM-PET at a peel rate of 300 mm / min under conditions of 20°C and 65% relative humidity. Five measurements were performed, and the average value was used for evaluation according to the following criteria. A: 2.0 [N / 15mm] or better (Very good) B: 1.5 [N / 15mm] or higher, less than 2.0 [N / 15mm] (Good) C: 1.0 [N / 15mm] or higher, less than 1.5 [N / 15mm] (usable) D: Less than 1.0 [N / 15mm] (Not usable)

[0100] [Heat seal peel test] NY / Oil-based or water-based ink layer / Adhesive layer / LLDPE Laminates 3 and 4 were cut into 15 mm wide and 300 mm long test pieces, folded so that the sealant surfaces overlapped, and heat-sealed at 180°C, 2 kg, and 1 second. Then, in accordance with JIS K6854, an Instron type tensile testing machine was used to test the samples at a peeling rate of 300 mm / min in an environment of 20°C and 65% relative humidity until the tensile strength decreased due to film breakage, failure of the heat-sealed portion, etc. Next, the samples after the test were observed and evaluated according to the following criteria based on their morphology. The test was performed five times, and the most common morphology was adopted. A: The laminating film tore, but the heat-sealed portion remained unchanged (very good). B: The laminate film did not break, only the LLDPE film broke (good). C: The laminate film did not break, but the NY / LLDPE layer at the heat-sealed portion began to peel, followed by the LLDPE film breaking (still usable). D: No film breakage occurred, but the NY / LLDPE layer at the heat-sealed portion peeled off (unusable).

[0101] [Pot Life Rating] The solvent-free adhesive, immediately after manufacturing, was poured into glass bottles, sealed, and left to stand in a 40°C warm bath for 30 minutes. The ICI viscosity at 40°C was then measured. A: Less than 3,000 [mPa·s] (Very good) B: 3,000 [mPa·s] or higher, less than 4,000 [mPa·s] (Good) C: 4,000 [mPa·s] or more, less than 5,000 [mPa·s] (usable) D: 5,000 [mPa·s] or more (unusable)

[0102] [Table 3]

[0103] [Table 4]

[0104] The abbreviations used in Tables 3 and 4 are shown below. Cantaloupe seed oil: Industrial grade No. 1 cantaloupe seed oil (manufactured by Toyokuni Oil Co., Ltd.) Glycerin PPG adduct: A triol with a number-average molecular weight of 400 (3 functional groups) obtained by adding polypropylene glycol to glycerin. Trimethylolpropane: 3 functional groups, molecular weight 134 Pentaerythritol: 4 functional groups, molecular weight 136

[0105] According to the evaluation results, the solvent-free adhesive of the present invention showed good adhesive strength and heat seal strength after 24 hours of aging in a low humidity environment of 40°C and 20%RH, confirming its rapid start-up. In particular, Example C-4, which used polyester polyol (a1) in the range of 40-60% by mass and senna seed oil in the range of 40-60% by mass, achieved a better balance between the cohesive force of the adhesive coating and the construction of a three-dimensional structure than Example C-2, which used polyester polyol (a1) in the range of 35% by mass and senna seed oil in the range of 65% by mass, and Example C-3, which used polyester polyol (a1) in the range of 65% by mass and senna seed oil in the range of 35% by mass. It also exhibited faster and superior rise in adhesive strength and heat seal strength. Furthermore, Example C-4, in which the number-average molecular weight of the polyester polyol (a1) was in the range of 1,000 to 2,000, showed superior cohesive strength of the adhesive coating and faster rise in adhesive strength compared to Examples C-8 and C-9, in which the number-average molecular weight was less than 1,000. In addition, Example C-4 showed slower thickening after mixing with polyisocyanate (B) and superior pot life compared to Examples C-10 and C-11, in which the number-average molecular weight was greater than 2,000. Furthermore, Example C-4, in which polyester polyol (a1) is an aliphatic polyester polyol, showed slower thickening after mixing with polyisocyanate (B) and superior pot life compared to Example C-6, in which polyester polyol (a1) is an aromatic polyester polyol. Furthermore, Example C-4, in which the polyester polyol (a1) is formed from a bifunctional polybasic acid and a bifunctional polyhydric alcohol, exhibited slower thickening after mixing with polyisocyanate (B) and superior pot life compared to Example C-7, which is a polyester polyol formed using a trifunctional polyhydric alcohol. Furthermore, Example C-4, which contains a trifunctional or higher polyol (a3) ​​in polyol (A), showed faster crosslinking after mixing with polyisocyanate (B), and faster rise in adhesive strength and heat seal strength compared to Example C-1, which does not contain a trifunctional or higher polyol (a3) ​​in polyol (A). Furthermore, Example C-4, which used a trifunctional or higher polyol (a3) ​​in an amount of 5 to 15% by mass relative to the total amount of polyol (A), showed slower thickening after mixing with polyisocyanate (B) and superior pot life compared to Example C-12, which used the same component at 20% by mass, and Example C-13, which used the same component at 40% by mass. Furthermore, Example C-4, in which the molecular weight of the trifunctional or more polyol (a3) ​​is in the range of 200 to 500, showed slower thickening after mixing with polyisocyanate (B) and superior pot life compared to Example C-14, in which the molecular weight is less than 200. Furthermore, Example C-4, in which the polyol (a3) ​​with three or more hydroxyl groups had three hydroxyl groups, showed slower thickening after mixing with polyisocyanate (B) and superior pot life compared to Example C-15, in which the polyol had four hydroxyl groups.

Claims

1. A solvent-free adhesive comprising a polyol (A) and a polyisocyanate (B), characterized in that it satisfies the following conditions (1), (2), and (3). (1) Polyol (A) contains polyester polyol (a1) (excluding cinnamon seed oil or cinnamon seed oil derivative (a2)), wherein the content of polyester polyol (a1) is 30% by mass or more and 70% by mass or less based on the total mass of polyol (A), and the number average molecular weight of polyester polyol (a1) is 400 or more and 3,400 or less. (2) The polyol (A) contains cinnamon oil or a cinnamon oil derivative (a2), and the content of the cinnamon oil or cinnamon oil derivative (a2) is 30% by mass or more and 70% by mass or less, based on the total mass of the polyol (A). (3) The polyisocyanate (B) includes a reaction product of a polyol and a polyisocyanate, and the ratio of the total number of isocyanate groups in the polyisocyanate to the total number of hydroxyl groups in the polyol (NCO / OH) is 2.5 to 4.

5.

2. The solvent-free adhesive according to claim 1, wherein the number average molecular weight of the polyester polyol (a1) is 500 or more and 3,000 or less.

3. The solvent-free adhesive according to claim 1 or 2, wherein the polyester polyol (a1) contains an aliphatic polyester polyol.

4. Furthermore, the solvent-free adhesive according to any one of claims 1 to 3, which satisfies (4) below. (4) The polyol (A) contains a polyol (a3) ​​with three or more functional properties, and the content of the polyol (a3) ​​is 5% by mass or more and 30% by mass or less, based on the total mass of the polyol (A).

5. The solvent-free adhesive according to any one of claims 1 to 4, wherein the polyol comprises at least one selected from the group consisting of polyester polyols and polyether polyols.

6. The solvent-free adhesive according to any one of claims 1 to 5, wherein the polyisocyanate comprises an aromatic polyisocyanate.

7. A cured product obtained by curing a solvent-free adhesive according to any one of claims 1 to 6.

8. A laminate in which a solvent-free adhesive according to any one of claims 1 to 6 is used as the adhesive layer.

9. The laminate according to claim 8, having an ink layer in contact with the adhesive layer.

10. The laminate according to claim 9, wherein the ink layer is a layer formed using water-based ink.

11. A packaging body using the laminate described in any one of claims 8 to 10.

Images