Solvent-free polyurethane adhesive composition for lamination with excellent resistance to contents.

Abstract

This invention provides a solvent-free adhesive composition for lamination that suppresses the decrease in the lamination strength of laminated films during filling and storage due to permeable and volatile contents, and exhibits excellent resistance to contents. [Solution] The polyester polyol component (A) contains at least three components: a polycarboxylic acid component (a-1), a monofunctional fatty acid component (a-2), and a polyhydric alcohol component (a-3). The content of sebacic acid in the total of the polycarboxylic acid component (a-1) and the monofunctional fatty acid component (a-2) is 20 mol% or more and 60 mol% or less. The elastic modulus of the cured film of the adhesive composition is 3.5 MPa or more and 10.0 MPa or less. This provides a "soft" cured adhesive film, the opposite of the conventional "hard" designs.

Description

Technical Field

[0001] The present invention relates to an adhesive composition that is excellent in resistance to contents, suppressing a decrease in the laminate strength of a laminated film during filling and storage due to permeable and volatile contents, such as in the field of toiletries typified by refill containers for liquid detergents, shampoos, body soaps, cosmetics, etc. (hereinafter, these product groups may be abbreviated as "detergents, etc."). Further, the present invention relates to an adhesive composition that is suitable for use as a solvent-free adhesive, has good handling of a first liquid containing a polyester polyol component and a second liquid containing a polyisocyanate component, and has an excellent pot life after blending the adhesive. Furthermore, the present invention relates to an adhesive composition that can suppress the transfer of a deposited material to the non-deposited film side when a deposited film and a non-deposited film are laminated.

Background Art

[0002] In recent years, from the perspective of global environmental protection including measures against marine plastics, reduction of waste has been demanded. Flexible packaging materials do not take up much space compared to conventional bottle-type containers and can contribute to volume reduction of waste, so they are widely used in the fields of retort foods, pharmaceuticals, and toiletries. Such flexible packaging materials generally use a laminated film in which a polyolefin-based resin film is laminated via an adhesive on a barrier layer such as an aluminum foil. By laminating a plurality of films, the contents can be protected from external light, moisture, oxygen, etc., and functions such as heat resistance, chemical resistance, and printability of the surface layer can be imparted.

[0003] However, depending on the nature of the contents, there are also factors that affect from the inside of the flexible packaging material. For example, like in the field of toiletries typified by refill containers for detergents, etc., the laminate strength of the laminated film may decrease during filling and storage due to permeable and volatile contents.

[0004] On the other hand, there is a demand for solvent-free adhesives that do not use solvents in order to respond to stricter regulations, reduction of environmental impact, and improvement of the working environment. However, from the standpoint of handling, solvent-free adhesives need to be designed with a lower molecular weight of resin compared to conventional dry laminating adhesives. As a result, the initial cohesive force is weaker, making it easier for winding misalignment to occur when winding the laminate film, and a phenomenon called tunneling, in which streaks of lifting or peeling occur between the films, is more likely to occur.

[0005] Patent Document 1 discusses the estimated mechanism for the "decrease in laminate strength after filling with contents," suggesting that it is caused by components in the contents permeating from the inner film side and attacking the adhesive layer. It then speculates that the adhesive layer "swells" or "decomposes" due to the attack, and that the degree of this depends on the permeating components. It also indicates that if there are non-uniform parts in the components or film thickness of the adhesive layer, for example, parts with thin film thickness or parts with insufficient cross-linking hardening, the laminate strength during storage is more likely to decrease due to the attack of components in the contents.

[0006] On the other hand, the paper addresses the problem of poor appearance, insufficient laminate strength, and poor impact resistance resulting from poor wetting of the substrate when solvent-free polyester adhesives are applied at high speed. Regarding the mechanism of "poor wetting" when the adhesive is applied at high speed, especially when the amount applied is large, the paper suggests that if the adhesive viscosity is too high, the transfer of the adhesive to the outer film, inner film, and ink layer tends to be uneven, resulting in partial "repellency," and the film thickness becomes thinner in the "repellent" areas. Although the degree of poor wetting improves somewhat with subsequent aging, the difference in film thickness is likely to cause a decrease in laminate strength after filling with contents.

[0007] Therefore, firstly, it is disclosed that the viscosity of the main component at 70°C is specified to be within a specific range, thereby balancing the wettability during adhesive application with the impact resistance of the adhesive layer. Secondly, it is specified that the curing agent be a combination of 1,6-hexamethylene diisocyanate (HDI) and 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI). By using these in combination, the viscosity of the curing agent at 70°C can be adjusted to be within a specific range, thereby reducing the viscosity difference with the main component and balancing the laminate strength and impact resistance.

[0008] Patent Document 2 discloses a solvent-free adhesive with excellent internal material resistance, comprising a polyol composition (X) and a polyisocyanate composition (Y). Here, the polyol composition (X) is characterized by comprising a polyol (A), which is a tetrafunctional or higher sugar alcohol derivative having a number average molecular weight of 450 to 1000, and a polyester polyol (B), which is a reaction product of a composition containing a polyhydric alcohol and a polyhydric carboxylic acid. Furthermore, the amount of polyol (A) in relation to the total amount of polyol (A) and polyester polyol (B) is 5% to 30% by mass, and the amount of aromatic polycarboxylic acid in relation to the polyhydric carboxylic acid is 25% to 50% by mass. In addition, the amount of diethylene glycol in relation to the polyhydric alcohol is 50% or more by mass.

[0009] Furthermore, it is considered that by using the aforementioned polyol (A), the crosslinking density of the cured adhesive coating is increased, thereby improving its resistance to internal materials. Furthermore, it is considered that by including the polyester polyol (B) together with the polyol (A), an adhesive with excellent resistance to contents can be made. In particular, it is preferable to include an aromatic polycarboxylic acid as the polycarboxylic acid because it improves the resistance to contents, and it is preferable that the amount of aromatic polycarboxylic acid in the polycarboxylic acid is 25% by mass or more and 50% by mass or less. It is also stated that the resistance to contents is not impaired even if the amount of diethylene glycol in the polyhydric alcohol is 50% by mass or more.

[0010] As described above, for permeable and volatile contents, such as those found in toiletries like refillable detergent containers, it is standard practice to design with a high crosslink density. However, in Patent Documents 1 and 2, the crosslink density of the adhesive cured film tends to be high (i.e., the adhesive cured film tends to become "hard"), and there is a risk that the vapor-deposited material will transfer to the non-vapor-deposited film when the vapor-deposited film and non-vapor-deposited film are laminated together. Here, "transfer of vapor-deposited material" refers to the transfer of vapor-deposited aluminum onto the nylon film when the laminate film is peeled off, using a laminate film in which a nylon film and an aluminum vapor-deposited film are laminated together with an adhesive as an example. When such transfer of vapor-deposited material occurs, it can be said that when the laminate film is used as a packaging material, the vapor-deposited layer is prone to collapse due to external stress. Therefore, the barrier properties obtained by the vapor-deposited layer are easily impaired, which can be said to be one of the causes of a decrease in the resistance of contents.

[0011] Incidentally, while there are prior art documents that state that monofunctional fatty acids may be included in adhesives used for packaging laminate films, there are few documents that explicitly state their usefulness. Patent Document 3 discloses a solvent-based two-component curing adhesive that can be applied with a non-volatile content of 40% or more, has high initial adhesive strength immediately after lamination, high adhesive strength under normal conditions, and excellent boil resistance. Specifically, it discloses a two-component curing adhesive using a polyol mixture in which 0.5 to 3% by weight of the polyol component is a polyhydric alcohol having 3 or more hydroxyl groups and 30% by weight or more of the remaining polyol component is a glycol having a side-chain alkyl group, and a polyester polyol with a number average molecular weight of 5,000 to 10,000 obtained by reacting a mixture of a monofunctional fatty acid containing a hydrocarbon group having a straight or branched chain of 8 or more carbon atoms as an acid component with a dibasic acid, and a polyisocyanate as a curing agent. The document states that this design allows for balancing physical properties that could not be achieved simply by reducing the number-average molecular weight of conventional polyols, which is around tens of thousands. In particular, it states that by adjusting the number of hydroxyl groups per molecule of polyester polyol to an average of 1.9 to 2.1, the crosslinking density can be adjusted, and thus the adhesion can be controlled, with the addition of monofunctional fatty acids contributing to this. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Publication No. 2010-023379 [Patent Document 2] Patent No. 7193045 [Patent Document 3] Japanese Patent Publication No. 2008-156502 [Overview of the project] [Problems that the invention aims to solve]

[0013] The present invention provides a solvent-free polyurethane adhesive composition for lamination that addresses the above-mentioned problems. More specifically, it provides an adhesive composition that suppresses the decrease in the lamination strength of laminated films during filling and storage due to permeable or volatile contents, such as in the field of toiletries represented by refillable containers for detergents, and has excellent resistance to contents. Furthermore, the present invention provides an adhesive composition that is suitable for use as a solvent-free adhesive, exhibits good handling of the first liquid polyester polyol component and the second liquid polyisocyanate component, and has excellent pot life after adhesive compounding. Furthermore, the present invention provides an adhesive composition that can suppress the transfer of vapor-deposited material to the non-vapor-deposited film when a vapor-deposited film and a non-vapor-deposited film are laminated together. [Means for solving the problem]

[0014] The inventors of the present invention conducted extensive research to solve the aforementioned problems and found that an adhesive cured film with a lower crosslinking density and a relatively "softer" structure than conventional designs is effective. Specifically, the inventors investigated increasing the crosslinking density in accordance with suggestions from Patent Documents 1 and 2 and common technical knowledge regarding adhesive cured films in order to improve the resistance to the contents, but this left challenges in adjusting the pot life after adhesive compounding. Therefore, they investigated an adhesive cured film that was the opposite of what they had been aiming for, a "softer" adhesive cured film, and surprisingly found that it had excellent resistance to the contents, solved the problems related to pot life, and was also advantageous in suppressing the risk of transfer of deposited material, leading to the completion of the present invention. More specifically, the present invention relates to a solvent-free polyurethane adhesive composition for lamination comprising at least a polyester polyol component (A) and a polyisocyanate component (B). Herein, the polyester polyol component (A) comprises at least three components: a polycarboxylic acid component (a-1), a monofunctional fatty acid component (a-2), and a polyhydric alcohol component (a-3), and the content of sebacic acid in the total of the polycarboxylic acid component (a-1) and the monofunctional fatty acid component (a-2) is 20 mol% or more and 60 mol% or less. Furthermore, the polyisocyanate component (B) comprises at least two components: a polyol component (b-1) and an aromatic isocyanate component (b-2). In addition, the elastic modulus of the single cured film of the solvent-free polyurethane adhesive composition for lamination is 3.5 MPa or more and 10.0 MPa or less.

[0015] The elastic modulus of the single-layer cured film of the solvent-free polyurethane adhesive composition for lamination can be calculated as the stress gradient in the stress-strain curve obtained by a tensile test, in the range where the strain is 0.05 to 0.25%. In other words, it can be considered a measure of how stress is applied when a small strain occurs in the single-layer cured film of the adhesive composition. It is thought that the higher the elastic modulus, the more likely surface fracture of highly crystalline films and transfer of deposited material from vapor-deposited films are to occur. On the other hand, if the elastic modulus is too low, sufficient cohesive force cannot be exerted. Therefore, it is important to design the adhesive composition so that the elastic modulus of the single-layer cured film is within a predetermined range. [Effects of the Invention]

[0016] Because it contains a lower proportion of aromatic polycarboxylic acids than conventional designs, it is easier to adjust the viscosity of the polyester polyol contained in the first solution, and thus easier to adjust the pot life of the adhesive. Furthermore, since the relatively "soft" adhesive cured film of the present invention tends to stretch easily, it is expected to work advantageously in the drop test method for packaged goods specified in JIS Z 0202. [Modes for carrying out the invention]

[0017] Regarding the solventless polyurethane adhesive composition for lamination of the present invention, in consideration of the handling properties as a solventless adhesive, it is preferable to prepare a first liquid and a second liquid and mix them immediately before coating. Hereinafter, regarding the first liquid containing the polyester polyol component (A) and the second liquid containing the polyisocyanate component (B) used in the present invention, details regarding each component constituting them will be described. Note that the raw materials exemplified in the following description do not limit the configuration of the present invention, and modifications may be made without departing from the spirit of the present invention.

[0018] <Polyester polyol component (A)> The polyester polyol component (A) contained in the first liquid of the present invention can be produced by a method known in this industry using at least a polyvalent carboxylic acid component (a-1), a monofunctional fatty acid component (a-2), and a polyhydric alcohol component (a-3). Specifically, a dehydration condensation reaction, an ester exchange reaction, or a ring-opening reaction can be utilized. In addition to the above three components, a monofunctional alcohol component (a-4) can be included. Furthermore, if necessary, a polyisocyanate component (a-5) may be used to extend the chain length.

[0019] <Polyvalent carboxylic acid component (a-1)> As the polyvalent carboxylic acid component (a-1), an aliphatic polyvalent carboxylic acid, an alicyclic polyvalent carboxylic acid, or an aromatic polyvalent carboxylic acid can be used. An acid anhydride can also be used. These can be used alone or in combination of two or more. Examples of the aliphatic polyvalent carboxylic acid include succinic acid, adipic acid, sebacic acid, maleic acid, fumaric acid, itaconic acid, and the like. Examples of the alicyclic polyvalent carboxylic acid include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2,3-norbornenedicarboxylic acid, and the like. Examples of aromatic polycarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, trimellitic acid, and pyromellitic acid. Examples of acid anhydrides include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, tetrabromophthalic anhydride, tetrachlorophthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, hettic anhydride, and hymic anhydride.

[0020] Since the cured adhesive film tends to become "hard" when aromatic polycarboxylic acids are used, it is preferable to use aliphatic polycarboxylic acids from the viewpoint of flexibility of the cured adhesive film. However, aromatic polycarboxylic acids may be used as long as they do not depart from the spirit of the present invention. When using aromatic polycarboxylic acids, it is preferable that the amount in the polycarboxylic acid component (a-1) be 20 mol% or less, and more preferably 10 mol% or less.

[0021] Furthermore, from the viewpoint of the flexibility of the adhesive cured film, it is preferable to use adipic acid or sebacic acid as the aliphatic polycarboxylic acid or alicyclic polycarboxylic acid, and more preferable to use sebacic acid. It is preferable that the amount of sebacic acid in the polycarboxylic acid component (a-1) be 20 mol% or more and 60 mol% or less, and more preferable to be 30 mol% or more and 50 mol% or less. If it is less than 20 mol%, the adhesive cured film tends to become "hard". If it exceeds 60 mol%, the elastic modulus of the adhesive cured film is low and the cohesive force is insufficient, which may cause winding misalignment when winding the laminate film.

[0022] <Monofunctional fatty acid components (a-2)> The aforementioned monofunctional fatty acid component (a-2) contributes to reducing the viscosity of the polyester polyol component (A). It also contributes to adjusting the crosslinking density of the cured adhesive film. Furthermore, it contributes to adhesive strength, and in particular, to adhesive strength after the content resistance test. Although the mechanism by which the aforementioned monofunctional fatty acid component (a-2) contributes to adhesive strength is not clear, it is thought that its hydrophobicity suppresses the penetration of moisture between films, that it relaxes the crosslinking density of the adhesive-cured film, thereby allowing it to follow the deformation of the film, and that it functions as a tackifier.

[0023] The monofunctional fatty acid component (a-2) may contain a hydrocarbon group having eight or more carbon atoms in a straight or branched chain. Examples include caprylic acid, octic acid, capric acid, lauric acid, palmitic acid, and stearic acid. Unsaturated fatty acids such as linoleic acid and oleic acid may also be used, as may soybean oil or rice oil containing a mixture of multiple fatty acids. One or more of these may be used.

[0024] From the viewpoint of the flexibility of the adhesive curing film, it is preferable to use saturated fatty acids with 8 or more carbon atoms. The amount of monofunctional fatty acid component (a-2) is preferably 0.5 mol% to 3.0 mol%, and more preferably 1.0 mol% to 2.0 mol%, relative to the total acid component with the polycarboxylic acid component (a-1). If the amount is less than 0.5 mol%, the resistance to contents may be insufficient. This is thought to be because if the amount of monofunctional fatty acid component (a-2) added is too small, the effect of suppressing the penetration of moisture into the film is insufficient. On the other hand, if the amount exceeds 3.0 mol%, the resistance to contents when using detergents, etc., may also be insufficient. This is thought to be because if the amount of monofunctional fatty acid component (a-2) added is too large, the crosslinking density is relaxed too much, making it easier for detergents, etc., to penetrate into the laminate film.

[0025] <Polyhydric alcohol component (a-3)> As the polyhydric alcohol component (a-3), an aliphatic diol, a glycol ether, or a trihydric or higher alcohol can be used. One or more of these can be used. Examples of aliphatic diols include ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,4-bis(hydroxymethyl)cyclohesane, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, and hydrogenated bisphenol A. Examples of glycol ethers include diethylene glycol, dipropylenediol, triethylene glycol, tripropylene glycol, tetraethylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol. Examples of alcohols with a hydride of 3 or higher include glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, and dipentaerythritol.

[0026] From the viewpoint of the flexibility of the adhesive cured film, it is preferable to use triethylene glycol. It is preferable that the amount of triethylene glycol in the polyhydric alcohol component (a-3) be 10 mol% to 50 mol%, and more preferably 20 mol% to 40 mol%. If it is less than 10 mol% or more than 50 mol%, it becomes difficult to adjust the balance of physical properties.

[0027] <Monofunctional alcohol component (a-4)> The aforementioned monofunctional alcohol component (a-4) can be used to adjust the hydroxyl value of the polyester polyol component (A) and contribute to adjusting the crosslinking density of the adhesive cured film. In particular, it is preferable to use one with 8 or more carbon atoms. Furthermore, the monofunctional alcohol component (a-4) can be used without being incorporated into the polyester polyol component (A). In this case, it acts as a reactive diluent before the adhesive is formulated, and can adjust the viscosity of the adhesive. On the other hand, after the adhesive is formulated, it contributes to adjusting the crosslinking density of the cured adhesive film. However, it is important to note that it may also react with the polyisocyanate component (B) after the adhesive is formulated.

[0028] Examples of the monofunctional alcohol component (a-4) include octyl alcohol, decyl alcohol, lauryl alcohol, stearyl alcohol, isostearyl alcohol, etc. One or more of these can be used.

[0029] It is preferable to use stearyl alcohol from the viewpoint of the flexibility of the cured adhesive film. The monofunctional alcohol component (a-4) is preferably 3.0 mol% or less, and more preferably 2.0 mol% or less, relative to the total alcohol component with the polyhydric alcohol component (a-3). If it exceeds 3.0 mol%, the resistance to the contents may be insufficient.

[0030] The polyisocyanate component (a-5) can be used to lengthen the urethane chains in the backbone of the polyester polyol component (A). Lengthening the urethane chains can impart flexibility, chemical resistance, and other properties to the cured adhesive film.

[0031] The polyisocyanate component (a-5) is not particularly limited, and aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, and biuret, isocyanurate, adduct, allophanate, and uretdione-modified forms of these diisocyanates can be used. One or more of these can be used. However, polyisocyanates diluted with organic solvents must have the organic solvent removed beforehand.

[0032] Examples of aromatic diisocyanates include tolylene diisocyanate (sometimes abbreviated as TDI), diphenylmethane diisocyanate (sometimes abbreviated as MDI), 1,5-naphthalene diisocyanate, 1,3-phenylene diisocyanate, and 1,4-phenylene diisocyanate.

[0033] Examples of aliphatic diisocyanates include hexamethylene diisocyanate (sometimes abbreviated as HDI), isophorone diisocyanate (sometimes abbreviated as IPDI), m-xylylene diisocyanate (sometimes abbreviated as XDI), α,α,α',α'-tetramethyl-m-xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, and 1,3-bis(isocyanatomethyl)cyclohexane.

[0034] The number-average molecular weight of the polyester polyol component (A) can be adjusted to achieve a viscosity suitable for handling, and is preferably 500 to 5,000, and more preferably 800 to 3,000.

[0035] In this invention, the number-average molecular weight is the polystyrene-converted value obtained by GPC. For example, the measurement conditions in the example were: column temperature (Showa Denko K.K. KF-805L x 2) at 35°C, tetrahydrofuran (THF) as the eluent, flow rate at 1.0 mL / min, detection performed with an RI detector (differential refractometer), and sample concentration at 0.3 mass%.

[0036] The viscosity of the polyester polyol component (A) is preferably 3,000 mPa·s or less at 60°C, and more preferably 1,500 mPa·s or less. If the viscosity at 60°C exceeds 3,000 mPa·s, handling performance deteriorates.

[0037] <Polyisocyanate component (B)> The polyisocyanate component (B) contained in the second liquid of the present invention can be produced by a method known in the industry using a polyol component (b-1) and an aromatic isocyanate component (b-2). In addition to the above two components, a polyfunctional aliphatic isocyanate component (b-3) may also be included.

[0038] <Polyol component (b-1)> Examples of the polyol component (b-1) include polyhydric alcohols, polyolefin polyols, polyether polyols, polyester polyols, polyester polyether polyols, polyurethane polyols, polyether polyurethane polyols, polyester polyurethane polyols, polyester polyether polyurethane polyols, polycarbonate polyols, acrylic polyols, phenoxy resins, and the like. Among these, polyester polyol, polyester polyether polyol, polyester polyurethane polyol, and polyester polyether polyurethane polyol are preferred from the viewpoint of flexibility and adhesive strength. The aforementioned polyester polyol component (A) can also be used.

[0039] The number-average molecular weight of the polyol component (b-1) can be adjusted to achieve a viscosity suitable for handling, preferably between 500 and 5,000, and more preferably between 800 and 3,000.

[0040] The viscosity of the polyol component (b-1) is preferably 3,000 mPa·s or less, and more preferably 1,500 mPa·s or less, at 60°C. If the viscosity at 60°C exceeds 3,000 mPa·s, handling performance deteriorates.

[0041] <Aromatic isocyanate component (b-2)> Examples of the aromatic isocyanate component (b-2) include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), 1,5-naphthalene diisocyanate, 1,3-phenylene diisocyanate, and 1,4-phenylene diisocyanate. One or more of these can be used. However, polymeric compounds of these are not included. From the viewpoint of the flexibility of the adhesive curing film, it is preferable to use MDI.

[0042] <Polyfunctional aliphatic isocyanate component (b-3)> Examples of the polyfunctional aliphatic isocyanate component (b-3) include hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), m-xylylene diisocyanate (XDI), α,α,α',α'-tetramethyl-m-xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, and biuret derivatives, isocyanurates, adducts, allophanates, and uretdione-modified derivatives of these diisocyanates. One or more of these can be used. From the viewpoint of the crosslinking density of the adhesive cured film, it is preferable to use aliphatic isocyanate components with three or more functions, and more preferable to use isocyanurate derivatives of HDI.

[0043] The polyisocyanate component (B) is obtained by reacting at least the polyol component (b-1) and the aromatic isocyanate component (b-2), but the polyfunctional aliphatic isocyanate component (b-3) may also be reacted and used. Alternatively, the polyfunctional aliphatic isocyanate component (b-3) may be used as a third liquid without reacting it with the reaction product of the polyol component (b-1) and the aromatic isocyanate component (b-2). From the viewpoint of storage stability of the adhesive, the former embodiment, in which the polyfunctional aliphatic isocyanate component (b-3) is also included in the reaction, is preferred. On the other hand, in the latter embodiment, in which it is used as a mixture, the viscosity of the polyisocyanate component (B) can be reduced.

[0044] The number-average molecular weight of the polyisocyanate component (B) can be adjusted to achieve a viscosity suitable for handling, and is preferably 400 to 2,000, and more preferably 600 to 1,500.

[0045] The viscosity of the polyisocyanate component (B) is preferably 3,000 mPa·s or less at 60°C, and more preferably 1,500 mPa·s or less. If the viscosity at 60°C exceeds 3,000 mPa·s, handling performance deteriorates.

[0046] <Other ingredients> Furthermore, as necessary, other components such as silane coupling agents, phosphoric acids, tackifiers, reaction accelerators, leveling agents, defoamers, antioxidants, and pigments may be appropriately added to the first and / or second liquids, provided that they do not impair the performance of the other components.

[0047] Examples of silane coupling agents include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, and their ethoxy derivatives. One or more of these can be used.

[0048] Examples of phosphoric acids include orthophosphoric acid, metaphosphoric acid, polyphosphoric acid, and their ester derivatives. One or more of these can be used.

[0049] Examples of tackifiers include rosin-based, terpene-based, and petroleum-based types. One or more of these can be used.

[0050] Examples of reaction accelerators include metal complex catalysts such as dibutyl acetate, dibutyl laurate, dioctyl laurate, and dibutyl malate of tin, zinc, aluminum, titanium, zirconium, and cobalt; and tertiary amines such as 1,8-diazabicyclo[5,4,0]-7-undecene and 1,5-diazabicyclo[4,3,0]-5-nonene, as well as reactive tertiary amines such as triethanolamine. One or more of these can be used.

[0051] Examples of leveling agents include acrylic polymer-based, modified silicone-based, and acetylenediol-based agents. One or more of these can be used.

[0052] Examples of defoaming agents include surfactants and polyether-modified silicones. One or more of these can be used.

[0053] Examples of antioxidants include phenols, lactones, thioethers, gallic acids, ascorbic acid, erythorbic acid, catechins, dibutylhydroxytoluene, tocopherol, citric acid, butylhydroxyanisole, phosphites, hindered amines, and aromatic amines. One or more of these can be used.

[0054] Examples of pigments include organic coloring pigments such as anthraquinone, diketopyrrolopyrrole, perylene maroon, carbon black, dioxazine, perylene, benzimidazolon, isoindolinone, isoindoline, phthalocyanines, and indanthrene; inorganic coloring pigments such as yellow iron oxide, red iron oxide, azomethine copper complex, titanium dioxide, and silicon dioxide; and extender pigments such as barium sulfate, calcium carbonate, barium carbonate, calcium carbonate, magnesium oxide, magnesium carbonate, magnesium hydroxide, barium titanate, calcium hydroxide, calcium sulfite, calcium sulfate, calcium oxide, calcium silicate, titanium dioxide, silica, zeolite, and talc. One or more of these can be used.

[0055] <Adhesive> The solvent-free polyurethane adhesive composition for lamination of the present invention is obtained by blending a first liquid containing the polyester polyol component (A), a second liquid containing the polyisocyanate component (B), and, if necessary, a third liquid. The first and second liquids are preferably blended immediately before coating. It is also preferable to use the mixture after heating.

[0056] Regarding the mixing ratio of the first liquid and the second liquid, considering the supply by the mixing machine, it is preferable that the second liquid be 30 to 300% by weight, and more preferably 50 to 200% by weight, relative to the first liquid, so that it can be handled by either a dynamic or static method. Furthermore, the equivalent ratio of isocyanate groups to hydroxyl groups (NCO / OH) is preferably 1.0 to 4.0, and more preferably 1.0 to 3.0. Setting it within this range results in an appropriate viscosity when the adhesive is compounded, which is preferable from the viewpoint of coating workability.

[0057] The application temperature for the compounded adhesive is preferably 50 to 100°C, and more preferably 60 to 80°C. Furthermore, the viscosity of the adhesive immediately after compounding is preferably 3,000 mPa·s or less, and more preferably 1,500 mPa·s or less. If the viscosity of the adhesive immediately after compounding exceeds 3,000 mPa·s, the coating stability will deteriorate, potentially leading to defects such as poor appearance and insufficient strength.

[0058] <Lamination Method> The amount of adhesive to apply is 0.5 to 5 g / m². 2 It is preferable that the concentration be around 1.5 to 3.5 g / m². 2 A degree of 0.5 g / m² is more preferable. 2 If the amount is less than 5g / m², the adhesive performance may not be fully realized, or cosmetic defects such as streaking may occur. 2 If it exceeds this, it becomes economically disadvantageous. Generally, laminated films require curing for 2 to 5 days at room temperature to 50°C.

[0059] <Film and Laminate Structure> The solvent-free polyurethane adhesive for lamination of the present invention can be used for laminating various plastic films, metal foils, and vapor-deposited films. Examples of plastic films include polyester resin films such as polyethylene terephthalate (PET), polyamide resin films such as biaxially oriented nylon (ONY), and polyolefin resin films such as linear low-density polyethylene (LLDPE), unoriented polypropylene (CPP), and biaxially oriented polypropylene (OPP). Examples of metal foils include aluminum foil (ALM), copper foil, and stainless steel foil. Examples of vapor-deposited films include PET films (VMPET) on which metals such as aluminum are vapor-deposited; and films on which inorganic oxides such as silica, alumina, indium tin oxide, zinc oxide, tin oxide, titanium oxide, zirconium oxide, vanadium oxide, barium oxide, and chromium oxide are vapor-deposited.

[0060] The configuration of the laminated film is not particularly limited, but for example, it can be a configuration such as PET / / LLDPE, ONY / / VMPET, ONY / / LLDPE, ONY / / VMPET / / LLDPE, etc. [Examples]

[0061] The following are examples of the present invention, but the present invention is not limited to these examples.

[0062] (Example of synthesis of polyester polyol component (A-1)) In a flask equipped with a nitrogen inlet tube, stirrer, rectification column, and condenser, adipic acid (310.0 parts by weight), sebacic acid (236.0 parts by weight), stearic acid (14.0 parts by weight), 1,4-butanediol (50.0 parts by weight), diethylene glycol (232.0 parts by weight), and triethylene glycol (158.0 parts by weight) were added, and dehydration condensation was carried out at an internal temperature of 180-200°C while stirring. After confirming that the acid value reached 15 mg KOH / g, the dehydration reaction was further carried out at 200-240°C while blowing in nitrogen, and the reaction was terminated after confirming that the acid value was 1 mg KOH / g or less, yielding polyester polyol component (A-1). The number average molecular weight was 2,800, and the viscosity at 60°C was 900 mPa·s. Here, the proportions of sebacic acid, aromatic polycarboxylic acid, and monofunctional fatty acid component (a-2) in the total acid component of the polycarboxylic acid component (a-1) and monofunctional fatty acid component (a-2) are 35 mol%, 0 mol%, and 1.5 mol%, respectively. In addition, the proportion of triethylene glycol in the polyhydric alcohol component (a-3) is 30 mol%.

[0063] (Example of synthesis of polyisocyanate component (B-1)) In a flask equipped with a nitrogen inlet tube, a stirrer, and a condenser, the polyester polyol component (A-1) (236.8 parts by weight) and myrionate MT (Tosoh Corporation, diphenylmethane diisocyanate) (513.2 parts by weight) were added, and the reaction was carried out for 4 hours at a liquid temperature of 80-90°C while stirring. After cooling, duranate TPA-100 (Asahi Kasei Corporation, isocyanurate of hexamethylene diisocyanate) (250.0 parts by weight) was added, and the reaction was carried out for 2 hours. The polyisocyanate component obtained in this way was designated as polyisocyanate component (B-1). The isocyanate group content was 21.8%. The viscosity at 60°C was 300 mPa·s. Please note that "Millionate" and "Duranate" are registered trademarks.

[0064] (Measurement of elastic modulus) The polyester polyol component (A-1) and the polyisocyanate component (B-1) were mixed so that the equivalent ratio of isocyanate groups to hydroxyl groups (NCO / OH) was 1.5. The mixture was placed in a PP mold container and cured in a 60°C oven for 6 days to obtain a single-component cured adhesive film. The amount of adhesive mixture placed in the mold container was adjusted so that the thickness of the single-component cured adhesive film after curing was 1 mm. The single-component cured adhesive film after curing was cut to prepare a test piece measuring 10 mm wide x 40 mm long. A tensile test was performed in the long-side direction at a speed of 200 mm / min in a 25°C atmosphere using a tensile testing machine (AandD, Tensilon RTG-1210). In the stress-strain curve obtained from the tensile test, the stress gradient in the section where the strain was 0.05 to 0.25% was calculated as the elastic modulus (unit: MPa).

[0065] (Measurement of laminate strength (initial strength)) An adhesive containing a polyester polyol component (A-1) and a polyisocyanate component (B-1) is formulated so that the equivalent ratio of isocyanate groups to hydroxyl groups (NCO / OH) is 1.5, applied at a rate of 1.5 g / m². 2A PET film (Toyobo Co., Ltd., E5102, thickness: 12 μm) was coated using a bar coater in the manner described above, and an LLDPE film (Mitsui Chemicals, Inc., TUX-FCS (TUX is a registered trademark), thickness: 70 μm) was laminated to obtain a laminate film (hereinafter, this laminate film configuration will be referred to as "Configuration 1"). The obtained laminate film was cured in a 40°C oven for 4 days. A 15 mm wide test piece was prepared from the cured laminate film, and the laminate strength was measured using a tensile tester (AandD, Tensilon RTG-1210) at a tensile speed of 50 mm / min in a 25°C atmosphere by peeling at 180°, and this was defined as the initial strength (unit: N / 15 mm). The following criteria were used for evaluation, and a score of ○ or higher was considered acceptable. <Evaluation Criteria> ◎: 5N / 15mm or more ○: 3N / 15mm or more, less than 5N / 15mm ×: 3N / less than 15mm

[0066] (Preliminary considerations for content resistance testing) The laminate film of the above-mentioned configuration 1 was cut to 3.0 cm x 3.0 cm. The cut laminate film was immersed in the detergent shown in Table 1, left at 60°C for one week, and then removed. After rinsing with water and evaluating the appearance, the laminate strength was measured in the same manner as above. The evaluation was performed according to the following criteria, and a score of ○ or higher was considered acceptable. <Evaluation Criteria> ◎: No delamination, and the laminate strength after testing is 3N / 15mm or higher. ○: No delamination, and the laminate strength after testing is 2N / 15mm or higher, and less than 3N / 15mm. ×: Delamination present

[0067] In this immersion test, the detergent or other substance comes into direct contact with the edges of the film on all four sides, allowing for easy penetration and clearly demonstrating the differences. When the film was not immersed in detergent or other substance, no significant change occurred in the laminate strength (Example 1). On the other hand, when the film was immersed in detergent or other substance, a decrease in laminate strength was observed (Examples 2-7). In particular, when the laminate strength after the test fell below 3N / 15mm, delamination was likely to occur, and the decrease in laminate strength was especially pronounced when using the fabric softener in Example 2 (Molto Parfum+Protect, manufactured by Unilever).

[0068] [Table 1]

[0069] (Contents resistance test) Based on the results of the preliminary study, it was decided to use the fabric softener from Study Example 2 (Molto Parfum+Protect, manufactured by Unilever). Using the laminate film from Configuration 1, a 7.0cm x 15cm rectangle was cut, folded in half, and the long and short sides were heat-sealed so that the LLDPE film was on the inside to create a 7.0cm x 7.5cm bag. 12.0g of the fabric softener from Study Example 2 (Molto Parfum+Protect, manufactured by Unilever) was filled into the bag, and the remaining short side was heat-sealed. After being left at 60°C for one week, the bag was removed. After opening and rinsing with water, the appearance was evaluated, and the laminate strength was measured as described above. The evaluation was performed according to the following criteria, and a score of ○ or higher was considered acceptable. <Evaluation Criteria> ◎: No delamination, and the laminate strength after testing is 3N / 15mm or higher. ○: No delamination, and the laminate strength after testing is 2N / 15mm or higher, and less than 3N / 15mm. △: No delamination, and the laminate strength after testing is less than 2N / 15mm. ×: Delamination present

[0070] (Examples of synthesis of polyester polyol components (A-2) to (A-11) and (A-EX1) to (A-EX9)) Except for the changes in composition shown in Tables 2-4, the polyester polyol components (A-2) to (A-11) and (A-EX1) to (A-EX9) were reacted in the same manner as polyester polyol component (A-1) unless otherwise specified.

[0071] (Examples of synthesis of polyisocyanate components (B-2) to (B-6) and (B-EX1)) Except for the changes in composition shown in Table 4, the polyisocyanate components (B-2) to (B-6) and (B-EX1) were reacted in the same manner as polyisocyanate component (B-1) unless otherwise specified.

[0072] For adhesives formulated by combining polyester polyol components (A-1) to (A-11), (A-EX1) to (A-EX9) and polyisocyanate components (B-1) to (B-6), (B-EX1), the elastic modulus, laminate strength (initial strength), and content resistance were evaluated as shown in Tables 2 to 4. In addition, the viscosity was measured and the pot life was evaluated for polyester polyol component (A), polyisocyanate component (B), and the adhesive immediately after formulation. Furthermore, a transfer test of the deposited material was conducted.

[0073] (Viscosity measurement) Using the EMS-1000S (manufactured by Kyoto Electronics Manufacturing Co., Ltd.), the viscosity of the polyester polyol component (A), the polyisocyanate component (B), and the adhesive immediately after compounding were measured at 60°C. The following criteria were used for evaluation, with a score of ○ or higher considered acceptable. <Evaluation Criteria> ◎: 1,500mPa·s or less ○: Above 1,500 mPa·s and 3,000 mPa·s or less ×: Exceeding 3,000 mPa·s

[0074] (Pot life evaluation) The viscosity of the adhesive was measured using the EMS-1000S (manufactured by Kyoto Electronics Manufacturing Co., Ltd.) after mixing and leaving it at 60°C for 30 minutes. The following criteria were used for evaluation, with ○ indicating a pass. <Evaluation Criteria> ○: 5,000mPa·s or less ×: Exceeding 5,000 mPa·s

[0075] (Transfer test of deposited material) A laminate film was obtained by coating an ONY film (manufactured by Unitika Ltd., Emblem ONBC-RT (Emblem is a registered trademark), thickness: 15 μm) with VMPET film (manufactured by Toray Film Processing Co., Ltd., VM-PET 1310, thickness: 12 μm) and laminating it (hereinafter, this laminate film configuration will be referred to as "Configuration 2"). Using the laminate film of Configuration 2, a tensile test was performed in the same manner as the measurement of laminate strength (initial strength), and the presence or absence of transfer of the vapor-deposited material (aluminum) to the non-vapor-deposited film, ONY film, was confirmed by visual inspection of the peel surface. The following criteria were used for evaluation, and ○ was considered a pass. <Evaluation Criteria> ○: No transfer of deposited material. ×: Transfer of vapor-deposited material present.

[0076] [Table 2]

[0077] [Table 3]

[0078] [Table 4]

[0079] (Examples 1-4, Comparative Examples 1-3) Based on Example 1, the first liquid: polyester polyol component (A) was investigated by changing the content ratio of sebacin contained in the acid component. As the content ratio of sebacin increased, the elastic modulus of the cured adhesive film decreased. In addition, a decrease in laminate strength and deterioration of the content resistance were observed. On the other hand, as the proportion of sebacic acid decreased, the elastic modulus of the cured adhesive film increased, but in configurations including a vapor-deposited film, transfer of the vapor-deposited material was observed. In addition, the pot life decreased, and the balance of the adhesive's physical properties was disrupted.

[0080] (Examples 5-6, Comparative Examples 4-5) Based on Example 1, the first liquid: polyester polyol component (A) was investigated by changing the content ratio of aromatic polycarboxylic acid contained in the acid component. As the content ratio of aromatic polycarboxylic acid increased, the elastic modulus of the adhesive cured film increased, but in configurations including a vapor-deposited film, transfer of the vapor-deposited material was observed. In addition, a decrease in laminate strength and deterioration of pot life were observed.

[0081] (Examples 7-9, Comparative Examples 6-7) Based on Example 1, the first liquid: polyester polyol component (A) was investigated by changing the content ratio of monofunctional fatty acids contained in the acid component. No significant change was observed in the elastic modulus of the cured adhesive film. However, when monofunctional fatty acids were not included, the resistance to contents deteriorated. Furthermore, the resistance to contents deteriorated as the content ratio of monofunctional fatty acids increased.

[0082] (Examples 10-11, Comparative Examples 8-9) Based on Example 1, the first liquid: polyester polyol component (A) was investigated by changing the content ratio of triethylene glycol contained in the alcohol component. No significant change was observed in the elastic modulus of the cured adhesive film. However, when triethylene glycol was not included, the resistance to contents deteriorated. Furthermore, the resistance to contents deteriorated as the content ratio of triethylene glycol increased.

[0083] (Examples 12-14) In Example 12, the composition of the third solution was modified to include a polyfunctional aliphatic isocyanate component (b-3) based on Example 1. In Example 13, the composition of the second solution was modified based on Example 12. In all compositions, a balance of each physical property was achieved. In Example 14, the polyol component (b-1) was changed to polyester polyol (A-EX6) based on Example 12. Although the elastic modulus of the cured adhesive film decreased, the balance of each physical property was maintained.

[0084] (Example 15) In Example 15, based on Example 1, the polyol component (b-1) was changed to a polyester polyol component (X) synthesized by the method shown below, and a balance of each physical property was achieved. <Method for synthesizing polyester polyol component (X)> In a flask equipped with a nitrogen inlet tube, stirrer, rectification column, and condenser, adipic acid (582.0 parts by weight), neopentyl glycol (236.0 parts by weight), and 1,4-butanediol (182.0 parts by weight) were added, and dehydration condensation was carried out at an internal temperature of 180-200°C while stirring. After confirming that the acid value reached 15 mg KOH / g, the dehydration reaction was further carried out at 200-240°C while blowing in nitrogen, and the reaction was terminated after confirming that the acid value was 1 mg KOH / g or less, yielding polyester polyol (X). The number average molecular weight was 6,300, and the viscosity at 60°C was 12,000 mPa·s. Here, the content of sebacic acid, aromatic polycarboxylic acid, and monofunctional fatty acid component (a-2) in the total acid component of the polycarboxylic acid component (a-1) and monofunctional fatty acid component (a-2) is 0 mol%. Also, the content of triethylene glycol in the polyhydric alcohol component (a-3) is 0 mol%. (Example 16, Comparative Example 10) In Example 16, the aromatic isocyanate component (b-2) was changed from MDI to TDI, based on Example 1. Although the viscosity tended to be slightly higher when compounded with the adhesive, the balance of each physical property was maintained. In Comparative Example 10, the composition of the second liquid was changed from Example 1 to the composition described in Example 1 of WO2018 / 186383. The elastic modulus of the cured adhesive film decreased. In addition, a decrease in laminate strength and deterioration of the content resistance were observed.

[0085] As described above, by using the adhesive composition of the present invention to produce a laminated film containing permeable and volatile contents, it is possible to suppress the decrease in laminate strength over time and ensure the resistance to contents. Furthermore, the adhesive composition of the present invention is suitable for use as a solvent-free adhesive, has good handling properties for the first liquid containing a polyester polyol component and the second liquid containing a polyisocyanate component, and exhibits excellent pot life after adhesive compounding. Furthermore, when laminating a vapor-deposited film with a non-vapor-deposited film, it is possible to suppress the transfer of vapor-deposited material to the non-vapor-deposited film side.

Claims

1. A solvent-free polyurethane adhesive composition for lamination comprising at least a polyester polyol component (A) and a polyisocyanate component (B), The aforementioned polyester polyol component (A) It is synthesized from at least three components: a polycarboxylic acid component (a-1), a monofunctional fatty acid component (a-2), and a polyhydric alcohol component (a-3). The content of sebacic acid in the total of the polycarboxylic acid component (a-1) and the monofunctional fatty acid component (a-2) is 20 mol% or more and 60 mol% or less. The monofunctional fatty acid component (a-2) has 8 or more carbon atoms. The content ratio of the monofunctional fatty acid component (a-2) in the total of the polycarboxylic acid component (a-1) and the monofunctional fatty acid component (a-2) is 0.5 mol% or more and 3.0 mol% or less. The content of triethylene glycol contained in the aforementioned polyhydric alcohol component (a-3) is 10 mol% or more and 50 mol% or less. The aforementioned polyisocyanate component (B) It is synthesized from at least two components: a polyol component (b-1) and an aromatic isocyanate component (b-2). The elastic modulus of the individual cured film of the adhesive composition is 3.5 MPa or more and 10.0 MPa or less. The elastic modulus is calculated for a single-component cured adhesive obtained by blending the polyester polyol component (A) and the polyisocyanate component (B) such that the equivalent ratio of isocyanate groups to hydroxyl groups (NCO / OH) is 1.5, placing the mixture in a PP mold container so that the thickness of the single-component cured adhesive film after curing is 1 mm, and curing it at 60°C for 6 days. The elastic modulus is characterized by being obtained by cutting a material to a width of 10 mm and a length of 40 mm, performing a tensile test in the long-side direction at a speed of 200 mm / min in a 25°C atmosphere, and calculating the stress gradient in the section where the strain is 0.05 to 0.25% in the resulting stress-strain curve. Solvent-free polyurethane adhesive composition for lamination.

2. The content of aromatic polycarboxylic acid in the total of the polycarboxylic acid component (a-1) and the monofunctional fatty acid component (a-2) is 20 mol% or less. The solvent-free polyurethane adhesive composition for lamination according to claim 1.

3. The aforementioned polyol component (b-1) is A material characterized by containing at least the polyester polyol component (A), The solvent-free polyurethane adhesive composition for lamination according to claim 1.

4. The aforementioned aromatic isocyanate component (b-2) Characterized by being diphenylmethane diisocyanate and / or tolylene diisocyanate, The solvent-free polyurethane adhesive composition for lamination according to claim 1.

5. The aforementioned polyisocyanate component (B) It is synthesized from at least three components: a polyol component (b-1), an aromatic isocyanate component (b-2), and a polyfunctional aliphatic isocyanate component (b-3). The polyfunctional aliphatic isocyanate component (b-3) is characterized in that it is an aliphatic isocyanurate. The solvent-free polyurethane adhesive composition for lamination according to claim 1.

6. A laminated film characterized by being used in a film containing a vapor-deposited film layer, The solvent-free polyurethane adhesive composition for lamination according to claim 1.

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