JP7534875B2 - Laminating Adhesive - Google Patents

Description

The present invention relates to a laminating adhesive, and more specifically to a laminating adhesive that has excellent stability and adhesiveness and does not impair the appearance of the films when multiple films are bonded together, and a laminate film using the same.

When manufacturing packaging materials for food, medical products, cosmetics, etc., and substrates such as FPC boards and TAB boards, composite films made by laminating plastic films (e.g., films of polyethylene, polypropylene, nylon, polyester, polyimide, etc.), metallized films, and metal foils (e.g., aluminum, copper, etc. foils) are used. A urethane adhesive that combines an organic polyol and an organic isocyanate is known as an adhesive for bonding these plastic films, metallized films, and metal foils.

In recent years, there has been an increasing demand for solvent-free urethane adhesives, taking into consideration environmental considerations, simple equipment, and cost benefits. Compared to solvent-based adhesives, solvent-free adhesives have the advantage of not using solvents, but they have poor wettability and are prone to air bubbles forming on the film surface when multiple films are bonded together, which can degrade the film's appearance. In particular, aluminum-deposited polyethylene terephthalate films often suffer from poor appearance.

Patent Documents 1 to 3 disclose laminated films laminated with a urethane adhesive.
Patent Document 1 discloses a urethane adhesive composition obtained by mixing a polyisocyanate, a polyol, and an ester that is liquid at 25°C, and a laminate obtained by coating the composition (see [Claims] and [Tables 1] to [Tables 6]).

Patent Document 2 discloses a solventless laminating adhesive containing a polyisocyanate, a polyol, and castor oil (or a castor oil derivative) (see [Claims], [Table 1], and [Table 2]).

Patent document 3 discloses a one-component adhesive having a polyester-based urethane resin, a specific polyol, and a polyisocyanate (see [Claims]). Table 4 of the patent discloses an adhesive having a polyester-based urethane resin, a rosin ester, and diphenylmethane diisocyanate (see [Claim 4] and [Table 4]).

Patent Documents 1 to 3 state that the appearance of the laminated film is improved (see Patent Document 1 [0017], Patent Document 2 [0015], and Patent Document 3 [0005]), but it cannot be said that they fully meet the high demands of users. Furthermore, when considering the work efficiency when manufacturing packaging bags with laminated films, it is desirable for the adhesive to have excellent compatibility of each component and excellent adhesive strength to the film after curing. Furthermore, when considering the work efficiency of workers and the production efficiency of films, it is required that the adhesive has a gradual increase in viscosity (a relatively long pot life).

JP 2018-162420 A International Publication No. 2016/152370 Japanese Patent Application Publication No. 8-048962

The present invention has been made to solve these problems, and aims to provide a laminating adhesive that, when used to produce a laminate film by laminating plastic films, has excellent adhesive strength to the film after curing, has excellent compatibility between the components, does not impair the appearance of the laminate film, has an appropriate pot life, and allows efficient application and film production, as well as a laminate film with excellent appearance that is produced using the laminating adhesive.

The inventors conducted extensive research to solve the above problems, and discovered that a urethane resin composition containing a urethane prepolymer, a polyol, and a specific plasticizer has excellent compatibility between the components, excellent adhesive strength to a film when a plastic film is laminated to produce a laminate film, a gradual increase in viscosity, an appropriate pot life, and does not impair the appearance of the laminate film, which led to the completion of the present invention.

The present specification includes the following aspects.
1. A composition obtained by blending (A) a urethane prepolymer having an isocyanate group at its terminal, (B) a polyol component, (C) a rosin ester, and (D) a castor oil-based compound,
A laminating adhesive comprising 50 to 250 parts by mass of component (C) per 100 parts by mass of component (B).
2. The laminating adhesive according to 1, wherein 100 to 150 parts by mass of component (C) is blended per 100 parts by mass of component (B).
3. The laminating adhesive according to 1 or 2, wherein the polyol (B) comprises a polyether polyol.
4. The laminating adhesive according to any one of 1 to 3, wherein the softening temperature of the rosin ester (C) is 80 to 120°C.
5. A laminate film in which a plurality of films are bonded together via the lamination adhesive according to any one of 1 to 4.

The laminating adhesive of the present invention is obtained by blending (A) a urethane prepolymer having an isocyanate group at its terminal, (B) a polyol component, (C) a rosin ester, and (D) a castor oil-based compound, and contains 50 to 250 parts by mass of component (C) per 100 parts by mass of component (B).

By blending components (A) to (D) in the above composition, the laminating adhesive of the embodiment of the present invention has excellent compatibility, a moderately long pot life, and excellent adhesive strength. When a laminate film is produced by laminating a plastic film with the laminating adhesive of the embodiment of the present invention, the appearance of the laminate film is not impaired.

The laminate film of the embodiment of the present invention is obtained using the above-mentioned laminating adhesive, so it can be quickly bonded, has excellent appearance, and is produced efficiently.

FIG. 1 is a schematic cross-sectional view of a laminate film according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a laminate film according to another embodiment of the present invention.

The laminating adhesive of the embodiment of the present invention is obtained by blending (or mixing) (A) a urethane prepolymer having an isocyanate group at its terminal (hereinafter also referred to as "component (A)"), (B) a polyol component (hereinafter also referred to as "component (B)"), (C) a rosin ester (hereinafter also referred to as "component (C)"), and (D) a castor oil-based compound (hereinafter also referred to as "component (D)"), and contains components (A) to (D).

The adhesive of the embodiment of the present invention is not particularly limited by the order and method of mixing the components (A) to (D) as long as the desired adhesive can be obtained. The adhesive of the embodiment of the present invention can be obtained, for example, by simultaneously mixing four components: (A) urethane prepolymer, (B) polyol component, (C) rosin ester, and (D) castor oil compound, or by mixing any one of the components (A), (C), and (D) with the component (B) in advance and then mixing the remaining components. However, it is more preferable to mix the components (B) to (D) in advance and mix the mixture with the component (A).

The adhesive can be produced by blending (or mixing) components (A) to (D) using known methods. Components (A) to (D) can be blended in a solvent to produce the adhesive, but components (A) to (D) can also be blended without using a solvent for each other.

The adhesive of the embodiment of the present invention may be a two-part adhesive obtained by blending a first liquid containing the (A) component with a second liquid containing the (B), (C) and (D) components, or may be a two-part adhesive obtained by blending a first liquid containing the (A), (C) and (D) components with a second liquid containing the (B) component.

The adhesive of the present invention is preferably a two-liquid adhesive containing a first liquid containing component (A) and a second liquid containing components (B), (C) and (D). The first liquid and the second liquid may each contain various additives as described below.

<(A) Urethane prepolymer having an isocyanate group at its terminal>
In an embodiment of the present invention, the (A) urethane prepolymer is a product obtained by reacting the (a1) polyol with the (a2) isocyanate monomer. The number average molecular weight of the (A) urethane prepolymer is preferably 1500 to 4000. When the number average molecular weight of the (A) urethane prepolymer is within the above range, the laminating adhesive of the embodiment of the present invention has superior adhesiveness.

In this specification, the number average molecular weight (Mn) is a value obtained by measuring using gel permeation chromatography (GPC) and converting using a polystyrene standard. Specifically, the value can be measured and converted using the following GPC device and measurement method. The GPC device used is an HCL-8220GPC manufactured by Tosoh Corporation, and an RI is used as a detector. Two TSKgel SuperMultipore HZM columns manufactured by Tosoh Corporation are used as GPC columns. The sample is dissolved in tetrahydrofuran and passed through the column at a flow rate of 0.35 ml/min and a column temperature of 40°C to obtain a measured value. The measured value is converted using a calibration curve using polystyrene with a monodisperse molecular weight as a standard substance to obtain the desired Mn. The same applies to the Mn of (a1) polyol and (a2) isocyanate monomer, which will be described later.

In this specification, (a1) polyol is a general term for compounds having two or more hydroxyl groups in one molecule, and examples of such compounds include polyether polyols, polyester polyols, acrylic polyols, polycaprolactone polyols, and polycarbonate polyols. As long as the adhesive of the embodiment of the present invention can be obtained, the type of (a1) polyol is not limited.

In an embodiment of the present invention, the number average molecular weight of the (a1) "polyol" is preferably 400 to 1300. When the number average molecular weight of the (a1) polyol is in the above range, the chain length of the (a1) polyol is shortened, and the (a2) polyol is easily crosslinked with the isocyanate monomer. Since there is less unreacted (a2) isocyanate monomer, the laminating adhesive of the embodiment of the present invention contains more (A) urethane prepolymer, resulting in better adhesion.

The (a2) isocyanate monomer in the embodiment of the present invention is not particularly limited as long as the laminating adhesive targeted by the present invention can be obtained, but it is preferable that the isocyanate monomer contains an aromatic isocyanate. When the (a2) isocyanate monomer contains an aromatic isocyanate, the adhesiveness of the laminating adhesive of the embodiment of the present invention is further improved.

The "(a2) isocyanate monomer" in the embodiment of the present invention does not mean that it is composed only of aromatic isocyanate. The (a2) isocyanate monomer may contain aliphatic isocyanate and/or alicyclic isocyanate as long as it does not adversely affect the adhesiveness of the laminating adhesive and the appearance of the film in the embodiment of the present invention.

In this specification, "aliphatic isocyanate" refers to a compound that has a linear hydrocarbon chain and an isocyanate group directly bonded to the hydrocarbon chain, but does not have a cyclic hydrocarbon chain. "Aliphatic isocyanate" may have an aromatic ring, but the aromatic ring and the isocyanate group are not directly bonded to each other.
In this specification, aromatic rings are not included in the cyclic hydrocarbon chain.

"Alicyclic isocyanates" are compounds that have a cyclic hydrocarbon chain and may have a linear hydrocarbon chain. The isocyanate group may be directly bonded to the cyclic hydrocarbon chain or to a linear hydrocarbon chain that may be present. "Alicyclic isocyanates" may have an aromatic ring, but the aromatic ring is not directly bonded to the isocyanate group.

"Aromatic isocyanate" refers to a compound that has an aromatic ring and an isocyanate group that is directly bonded to the aromatic ring. Therefore, even if a compound has an aromatic ring in its molecule, if the isocyanate group is not directly bonded to the aromatic ring, it is classified as either an aliphatic isocyanate or an alicyclic isocyanate.

Therefore, for example, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, and 4,4'-diphenylmethane diisocyanate (OCN-C ₆ H ₄ -CH ₂ -C ₆ H ₄ -NCO) correspond to aromatic isocyanates since the isocyanate group is directly bonded to the aromatic ring.

On the other hand, for example, xylylene diisocyanate (OCN-CH ₂ -C ₆ H ₄ -CH ₂ -NCO) has an aromatic ring, but the isocyanate group is not directly bonded to the aromatic ring but is bonded to a methylene group, and therefore corresponds to an aliphatic isocyanate.
The aromatic ring may be condensed with two or more benzene rings.

Examples of aromatic isocyanates include 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, and 4,4'-diphenylmethane diisocyanate.

Examples of aliphatic isocyanates include 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane (hereinafter referred to as HDI), 1,6-diisocyanato-2,2,4-trimethylhexane, methyl 2,6-diisocyanatohexanoate (lysine diisocyanate), and 1,3-bis(isocyanatomethyl)benzene (xylylene diisocyanate).

Examples of alicyclic isocyanates include 5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane (isophorone diisocyanate: IPDI), 1,3-bis(isocyanatomethyl)cyclohexane (hydrogenated xylylene diisocyanate), bis(4-isocyanatocyclohexyl)methane (hydrogenated diphenylmethane diisocyanate), and 1,4-diisocyanatocyclohexane.

In the embodiment of the present invention, the reaction method of the polyol (a1) and the isocyanate monomer (a2) is not limited as long as the urethane prepolymer (A) of the embodiment of the present invention can be obtained, and a general urethane reaction method can be used. For example, bulk polymerization without using a solvent and solution polymerization using a solvent can be used, and heating and stirring can be performed appropriately, and a catalyst can be used as necessary. Furthermore, various additives can be used during the reaction of the polyol (a1) and the isocyanate monomer (a2).
Incidentally, examples of commercially available urethane prepolymers (A) include the LOCTITE LIOFOL LA series manufactured by Henkel Japan Ltd.

<(B) Polyol Component>
In the embodiment of the present invention, the "polyol component (B)" is not particularly limited as long as it is generally used in laminating adhesives, can produce the desired laminating adhesive of the embodiment of the present invention, and does not adversely affect the production of the adhesive. Examples of the polyol component (B) include polyester polyol, acrylic polyol, polyether polyol, polycaprolactone polyol, polyether polyester polyol, polyester polyurethane polyol, polyether polyurethane polyol, and modified products of these polyols.

The (B) polyol component preferably contains a polyether polyol.
By including polyether polyol, the laminating adhesive according to an embodiment of the present invention is more effectively prevented from increasing in viscosity, has a more appropriate pot life, and is more suitable for application work.

Polyether polyol refers to what is usually understood as polyether polyol, and is not particularly limited as long as the laminating adhesive of the present invention can be obtained. Examples of polyether polyols include polyethylene glycol (PEG), polyoxytetramethylene glycol (PTMG), polypropylene glycol (PPG), etc. Polyether polyols can be used alone or in combination.

Polyether polyols are generally produced by addition polymerization of alkylene oxides, such as propylene oxide and ethylene oxide, with low molecular weight compounds with two or more hydroxyl groups in the molecule, such as propylene glycol, glycerin, sorbitol, and sucrose, and/or polyamines.

The laminating adhesive of the embodiment of the present invention preferably contains polypropylene glycol as the polyether polyol. By containing polypropylene glycol, the laminating adhesive of the embodiment of the present invention is more suppressed from a sudden increase in viscosity, making it more suitable for application to films during the production of laminate films.

<(C) Rosin Ester>
In the embodiment of the present invention, the rosin ester (C) refers to a rosin ester that can be generally used in adhesives, and is not particularly limited as long as the laminating adhesive of the embodiment of the present invention can be obtained. Rosin generally includes natural rosin, modified rosin, hydrogenated rosin, etc., and the rosin ester (C) generally includes esters of natural rosin, modified rosin, and/or hydrogenated rosin, etc. Examples of rosin esters include glycerol esters of natural rosin, glycerol esters of modified rosin, glycerol esters of hydrogenated rosin, pentaerythritol esters of natural rosin, pentaerythritol esters of modified rosin, and pentaerythritol esters of hydrogenated rosin.
The laminating adhesive according to an embodiment of the present invention contains component (C), which improves the compatibility of the respective components and improves the adhesive strength and stability.

In an embodiment of the present invention, component (C) preferably contains a rosin ester having an acid value of 0 to 50 mgKOH/g, more preferably contains a rosin ester having an acid value of 0 to 30 mgKOH/g, and most preferably contains a rosin ester having an acid value of 0 to 10 mgKOH/g. When the acid value of the rosin ester is within this range, the laminating adhesive of the embodiment of the present invention is more inhibited from increasing in viscosity and has higher stability.

In the present invention, the rosin ester (C) preferably has a softening point of 80 to 120°C, more preferably 85 to 110°C, and most preferably 80 to 100°C. By having the softening point of the rosin ester (C) within the above range, the laminating adhesive of the embodiment of the present invention can maintain a more appropriate hardness, has better adhesive strength, and is more effective in preventing the formation of air bubbles when applied to a film, thereby improving the appearance of the film.

(C) As the rosin ester, commercially available products can be used. Examples of such commercially available products include KOMOTAC KB90H (trade name), KOMOTAC KH100 (trade name), KOMOTAC KHR75 (trade name), and KOMOTAC K107 (trade name) manufactured by GUANDONG KOMO Co., Ltd.; Foralyn 5020-F (trade name), Foral AX-E (trade name), and Foral 85E (trade name) manufactured by Eastman Chemical Co., Ltd.

In an embodiment of the present invention, it is preferable to mix 50 to 250 parts by mass of component (C) per 100 parts by mass of component (B), and more preferably mix 100 to 150 parts by mass of component (C). By mixing the two components in the above ratio, the laminating adhesive of the embodiment of the present invention has better compatibility, more suppressed viscosity increase, a more appropriate pot life, and better adhesive strength, and in particular has a more appropriate pot life, which can further improve the ease of application to the adherend. When plastic films are laminated to produce a laminate film, the laminating adhesive of the embodiment of the present invention is applied more uniformly to the film, so the appearance of the laminate film is not impaired.

<(D) Castor oil-based compounds>
The laminating adhesive of the embodiment of the present invention contains a castor oil-based compound (D). By containing the castor oil-based compound (D), the adhesive strength of the laminating adhesive is improved. The castor oil-based compound (D) is not particularly limited as long as the laminating adhesive of the embodiment of the present invention can be obtained, and the type of the castor oil-based compound is not limited, and the compound may be modified or unmodified, and may be hydrogenated or unhydrogenated.

Examples of castor oil-based compounds include castor oil and castor oil derivatives. By including castor oil and/or castor oil derivatives, the laminating adhesive of the embodiment of the present invention has improved compatibility and excellent adhesive strength.

Castor oil is a type of vegetable oil extracted from the seeds of the castor bean plant of the Euphorbiaceae family, and is a glyceride of unsaturated fatty acids (e.g., 87% ricinoleic acid, 7% oleic acid, 3% linoleic acid) and small amounts of saturated fatty acids (e.g., 3% palmitic acid, stearic acid, etc.). Commercially available products can be used as castor oil compounds. Commercially available products can be used as castor oil. Examples of such commercially available products include Industrial No. 1 Castor Oil Compound (product name) manufactured by Toyokuni Oil Mills Co., Ltd. and LAV (product name) manufactured by Ito Oil Mills Co., Ltd.

In the present invention, a castor oil derivative refers to a compound that is based on castor oil, a type of vegetable oil, and has been modified by introducing functional groups, oxidizing, reducing, replacing atoms, etc., to a degree that does not significantly change the structure or properties of the parent castor oil.

Examples of castor oil derivatives include castor oil polyols, castor oil modified polyols, dehydrated castor oil, hardened castor oil, castor oil fatty acid, dehydrated castor oil fatty acid, 12-hydroxystearic acid, and castor oil fatty acid esters.

Commercially available castor oil derivatives can be used. Examples of such commercially available products include Castor Hardened Oil A (trade name), CO-FA (trade name), DCO-FA (trade name), Rickcizer S4 (trade name), Rickcizer C-101 (trade name), and Rickcizer GR-310 (trade name), URIC H52, URIC H52, and URIC H52, all of which are manufactured by Ito Oil Mills. AC-006; BRAUNON BR-410 (trade name), BRAUNON BR-410 (trade name), BRAUNON BR-430 (trade name), BRAUNON BR-450 (trade name), BRAUNON CW-10 (trade name), BRAUNON RCW-20 (trade name), BRAUNON RCW-40 (trade name), BRAUNON RCW-50 (trade name), and BRAUNON RCW-60 (trade name) manufactured by Aoki Oil & Fat Co., Ltd.; and Castor Wax A (trade name), New Cizer 510R (trade name), Sakura Stearic Acid (trade name), Castor Hydrogenated Fatty Acid (trade name), NAA-34 (trade name), NAA-160 (trade name), and NAA-175 (trade name) manufactured by NOF Corporation.
The castor oil based compounds may be used alone or in combination.

The laminating adhesive of the embodiment of the present invention preferably contains 10 to 90 parts by mass of (C) rosin ester per 100 parts by mass of the total of (C) rosin ester and (D) castor oil compound, more preferably 20 to 90 parts by mass, particularly preferably 25 to 70 parts by mass, and most preferably 30 to 60 parts by mass. By blending the (C) and (D) components in the above ratio, the laminating adhesive of the embodiment of the present invention has improved compatibility, superior adhesive strength, and suppressed viscosity increase, making it easier to attach multiple films when producing a laminate film and reducing the generation of air bubbles in the laminate film.

The laminating adhesive of the embodiment of the present invention may contain other components such as various additives, as necessary, in addition to components (A) to (D). The other components are components generally contained in laminating adhesives, and are not particularly limited as long as the laminating adhesive of the embodiment of the present invention can be obtained. Examples of other components include solvents, pigments, plasticizers (excluding the above-mentioned components (C) and (D)), catalysts, and adhesion promoters.

"Pigments" include, for example, nanopigments based on _TiO2 , _SiO2 , _Fe2O3 or similar oxides or _oxyhydrates . These pigments typically have a particle size of preferably less than 500 nm, more preferably less than 100 nm.

Examples of the "plasticizer" include white oil, naphthenic mineral oil, paraffinic hydrocarbon oil, polypropylene oligomer, polybutene oligomer, polyisoprene oligomer, hydrogenated polyisoprene and/or polybutadiene oligomer, phthalate, adipate, benzoate ester, vegetable oil or animal oil, and derivatives thereof.
Vegetable oils, animal oils and their derivatives are generally used in food and are considered to be safer, and therefore are more preferred when considering the use of the laminating adhesive of the embodiment of the present invention in the production of food packaging films.

Examples of "catalysts" include metal catalysts such as tin catalysts (trimethyltin laurate, trimethyltin hydroxide, dibutyltin dilaurate, dibutyltin maleate, etc.), lead-based catalysts (lead oleate, lead naphthenate, lead octenate, etc.), other metal catalysts (metal salts of naphthenic acid such as cobalt naphthenate, etc.), and amine catalysts such as triethylenediamine, tetramethylethylenediamine, tetramethylhexylenediamine, diazabicycloalkenes, dialkylaminoalkylamines, etc.

The "adhesion promoter" includes silane compounds. Known organofunctional silanes, such as (meth)acryloxy-functional, epoxy-functional, amine-functional, and non-reactive substituted silanes, can be used as adhesion promoters. Examples include vinyltrialkoxysilane, alkyltrialkoxysilane, tetraalkoxysilane, 3-acryloxypropyltrialkoxysilane, 3-methacryloxypropyltrialkoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-glycidyloxymethyltrimethoxysilane, 3-glycidyloxymethyltriethoxysilane, 2-glycidyloxyethyltrimethoxysilane, and the like.
As an embodiment of the present invention, it is preferred that the adhesive contains 0.1 to 5 parts by mass of an adhesion promoter per 100 parts by mass (solid content) of the total mass of the adhesive.

The laminating adhesive of the embodiment of the present invention can be produced by mixing the (A), (B), (C) and (D) components as described above. The laminating adhesive of the embodiment of the present invention may be a two-liquid type laminating adhesive containing a first liquid containing the (A) component and a second liquid containing the (B) to (D) components, or a two-liquid type laminating adhesive containing a first liquid containing the (A), (C) and (D) components and a second liquid containing the (B) component, and the two liquids. Other components may be mixed as necessary. The first liquid and the second liquid may each contain other components as appropriate.
The laminating adhesive of the embodiment of the present invention is preferably a two-part laminating adhesive containing a first part containing the component (A) and a second part containing the components (B) to (D).

The mixing method is not particularly limited as long as the laminating adhesive of the present invention can be obtained. The order in which the components are mixed is also not particularly limited. The laminating adhesive of the embodiment of the present invention can be produced without requiring a special mixing method or a special mixing order. The obtained laminating adhesive has a small adhesive strength to the film and a small decrease in adhesive strength over time.

The laminating adhesive of the embodiment of the present invention is usually applied to the film at 15 to 100°C, so it should have a low viscosity in this temperature range. Taking into account the applicability, the viscosity of the adhesive for food packaging films is preferably 300 to 5000 mPas at 40°C and 200 to 4000 mPas at 50°C (using a Brookfield viscometer).

When the viscosity of the laminating adhesive of the embodiment of the present invention is within the above range, the laminating adhesive can be applied more uniformly to the film, which can further improve the adhesive strength and the appearance of the film.

The laminate film of the embodiment of the present invention is a laminate produced using the above-mentioned laminating adhesive. The film used to form the laminate is not particularly limited as long as the laminate of the embodiment of the present invention can be obtained, but examples include a film in which a metal layer is formed on a plastic substrate and a film in which no metal layer is formed.

When preparing a laminate film, the laminating adhesive of the embodiment of the present invention is applied to the film. The application method can be various methods such as gravure coating, wire bar coating, air knife coating, die coating, lip coating, and comma coating.

The laminating adhesive of the embodiment of the present invention can be used to bond multiple films together to produce a laminate film. When applying the laminating adhesive to the film, the amount of application is preferably 0.5 to 10 g/ ^m2 , and more preferably 1 to 5 g/ ^m2 .

The laminate film of the embodiment of the present invention is formed by bonding multiple films together with the adhesive described above. An example of an embodiment of the present invention is shown in Figures 1 and 2, but the present invention is not limited to these forms.

Figure 1 shows a schematic cross-section of a laminate film according to one embodiment of the present invention. The laminate film 10 is formed from two films and a laminate film adhesive 13 between them, and the two films 11 and 12 are bonded together by the laminate film adhesive 13. The films 11 and 12 may be made of the same material or different materials.

In FIG. 1, two films 11 and 12 are bonded together, but three or more films may be bonded together.

A cross section of a laminate film according to another embodiment of the present invention is shown in FIG. 2. In FIG. 2, a thin film 11a is formed between the film 11 and the adhesive 13 for the laminate film. For example, when the film 11 is a plastic film, a form in which a thin metal film 11a is formed on the surface of the film 11 is shown. The thin metal film 11a can be formed on the surface of the plastic film 11 by, for example, vapor deposition, and the film 11 on which the thin metal film 11a is formed and the film 12 can be attached via the adhesive 13 for the laminate film to obtain the laminate film according to FIG. 2.

Examples of metals that can be vapor-deposited on the plastic film include aluminum, steel, and copper. By subjecting the plastic film to vapor deposition processing, it is possible to impart barrier properties to the film. Vapor deposition materials include silicon oxide and aluminum oxide. The plastic film 11 substrate may be transparent or colored, such as white or black.

For example, a plastic film made of polyvinyl chloride, polyester, fluororesin, acrylic resin, etc. is used as film 12, but it is particularly preferable to use a polyethylene terephthalate film or a polybutylene terephthalate film, etc., to impart heat resistance, weather resistance, rigidity, insulation, etc. Films 11 and 12 may be transparent or colored.

The evaporated thin film 11a of film 11 and film 12 are attached using the laminate film adhesive 13 of an embodiment of the present invention, but films 11 and 12 are often laminated by a dry lamination method. Therefore, the laminate film adhesive 13 is required to have excellent initial adhesion to the film during lamination and excellent adhesion to the film after curing.

The laminate films of the embodiments of the present invention are used to manufacture a variety of packaging bags and outdoor materials.
The packaging bag refers to a bag-shaped product obtained by processing a laminate film to contain food, detergent, shampoo, conditioner, etc. The outdoor materials include products used outdoors, such as barrier materials, roofing materials, solar cell modules, window materials, outdoor flooring materials, lighting protection materials, automotive parts, and signs.
These packaging bags and outdoor materials take the form of a laminate film in which multiple films are bonded together.

The present invention will be specifically and in detail explained below with reference to examples and comparative examples. However, these examples are merely one embodiment of the present invention, and the present invention is not limited to these examples in any way.
In the description of the examples, unless otherwise specified, parts by mass and percentages by mass are based on the parts not taking into account the solvent.

<Production of Laminating Adhesive>
The ingredients for making the adhesive are given below.
(A) Urethane prepolymer having an isocyanate group at its terminal (A1) LOCTITE LIOFOL LA7735 (component: polymer of polypropylene glycol and diethylene glycol with isocyanate monomer, NCO mass %: 11.5, Henkel Japan Ltd.)
(A2) LOCTITE LIOFOL LA7715 (component: polymer of polypropylene glycol, polyester polyol and isocyanate monomer, NCO mass%: 13.8%, Henkel Japan Ltd.)

(B) Polyol Component (B1) EXCENOL 1020 (polypropylene glycol, Mn: 1000, hydroxyl value 111 mgKOH/g, AGC Inc.)
(B2) Sannix GP1500 (polypropylene glycol trifunctional, Mn: 1500, hydroxyl value 111 mgKOH/g, Sanyo Chemical Industries, Ltd.)
(B3) PLACCEL 220EB (polycaprolactone polyol, Mn: 2000, hydroxyl value 56 mgKOH/g, manufactured by Mitsubishi Chemical Corporation)
(B4) Sannix GP400 (polypropylene glycol trifunctional, Mn: 400, hydroxyl value 365 mg KOH/g, Sanyo Chemical Industries, Ltd.)
(B5) PEG1000 (polyethylene glycol, Mn: 1000, hydroxyl value 111 mgKOH/g, NOF Corporation)

(C) Rosin ester (C1) KOMOTAC KB90H (unhydrogenated rosin ester, softening point 90°C, acid value 0-10mgKOH/g, GUANDONG KOMO Co., Ltd.)
(C2) KOMOTAC KH100 (hydrogenated rosin ester, softening point 100°C, acid value 0-15mgKOH/g, GUANDONG KOMO Co., Ltd.)
(C3) Foralyn 5020-F (liquid hydrogenated rosin ester, Eastman Chemical Co.)
(C'4) Quintone B170 (unhydrogenated C5 resin, softening point 70°C, Zeon Corporation)
(C'5) ARKON P90 (hydrogenated C9 resin, Arakawa Chemical Industries, Ltd.)

(D) Castor oil (D1) Industrial No. 1 castor oil-based compound (castor oil-based compound, Toyokuni Oil Mill Co., Ltd.)
(D2) URIC H52 (castor oil-based polyol, Ito Oil Mills, Ltd.)
(D'3) Diana Fresia S32 (paraffin oil, Idemitsu Kosan Co., Ltd.)
(D'4) Rice salad oil (rice oil, Boso Oil Co., Ltd.)

As shown in Tables 1 and 2, components (A) to (D) were mixed to produce the laminating adhesives of Examples 1 to 9 and Comparative Examples 1 to 6. Specifically, components (B) to (D) were mixed in the compositions (parts by mass) shown in Tables 1 and 2 and stirred at 120°C for 1 hour. After the mixture was cooled, component (A) was added to the mixture in the amount shown in Tables 1 and 2. The mixture was stirred at 40°C for 5 minutes to prepare the laminating adhesives.

<Production of Laminate Film>
The laminating adhesive of the example was applied to the printed surface of a PET film having a white solid print area and a plain area, so that the solid content mass was 2 g/ ^m2 . Another PET film having an aluminum-deposited surface was laminated on the adhesive-coated surface (printed surface) of the PET film from the deposition surface side. A hand roller was used to press the adhesive and the deposition surface so that as many air bubbles as possible were removed. The laminate film was then aged for 24 hours in an atmosphere of 40°C to obtain a laminate film.

<Evaluation>
1. Initial Viscosity Measurement The initial viscosity of the laminating adhesive was measured using a Brookfield viscometer in accordance with JAI7-1991, Method B. Specifically, the viscosity was measured at 40° C. using a No. 27 rotor at a rotation speed of 1 rpm.
Immediately after preparing the laminating adhesive, the above-mentioned device was set up, and the viscosity 1 minute after the start of measurement (start of rotor rotation) was taken as the initial viscosity (also referred to as "η1").

2. Compatibility Components (B), (C), and (D) were mixed in the ratios shown in Tables 1 and 2, and 50 g of this mixture was added to a 140 ml transparent bottle and allowed to stand in the bottle for 3 hours (40°C), and the presence or absence of separation was visually confirmed. The evaluation criteria are as follows.
○: No separation was observed and the mixture was homogeneous.
×: Separation was observed.

3. Measurement of adhesive strength The laminate film after aging for 24 hours was cut into a 15 mm width in the TD direction, and a peel test was performed using a tensile strength tester (Tensilon RTM-250 (trade name) manufactured by Orientec Co., Ltd.) to measure the adhesive strength.
The peel test was performed by leaving the laminate film at rest for 24 hours or more at room temperature (23°C), and then performing a T-type peel at a pulling speed of 300 mm/min. The evaluation criteria are as follows. The peeled portion was measured on both the solid white printed portion and the plain portion, and the lower of the measured values was used for evaluation. The evaluation criteria are as follows.
○: 1.5N/15mm or more △: 0.8N/15mm or more, less than 1.5N/15mm ×: Less than 0.8N/15mm -: Poor compatibility, making it difficult to measure adhesive strength

4. Stability (pot life)
After preparing the adhesive, the viscosity was measured at 40° C. to evaluate the stability. The measurement conditions (method) were the same as those (method) described in the above-mentioned initial viscosity measurement.
The viscosity (η1) was measured 1 minute after the start of the measurement, and the viscosity (also called "η2") was measured 30 minutes after the η1 measurement. The viscosity after 30 minutes was measured 1 minute after the rotor started to rotate after leaving the sample stationary for 30 minutes at 40°C after the η1 measurement. The viscosity increase rate was calculated to evaluate the stability of the adhesive. The viscosity increase rate here means (η2/η1) x 100. The evaluation criteria are as follows:
○: Viscosity increase rate is less than 300% △: Viscosity increase rate is 300% or more and 400% or less ×: Viscosity increase rate is more than 400% -: Poor compatibility makes it difficult to measure stability

5. Appearance Evaluation The appearance of the laminate film after the above-mentioned 24-hour curing was visually evaluated. The evaluation criteria are as follows.
○: Few dots (air bubbles) △: Dots (air bubbles) are visible but not noticeable ×: Dots (air bubbles) are quite noticeable or adhesive does not work -: Poor compatibility makes it difficult to evaluate appearance

As shown in Table 1, the laminating adhesives of Examples 1 to 9 have excellent compatibility between components (A) to (D), provide a very high level of appearance to the film, and also have excellent adhesion to films having printed portions. Furthermore, the laminating adhesives of Examples 1 to 9 have a low and stable rate of viscosity increase from the initial viscosity, and can be applied uniformly to the film.
The laminating adhesive of the embodiment of the present invention can be fully utilized as a laminating adhesive for food packaging bags, which require an extremely high level of appearance.

In contrast, the laminating adhesives of Comparative Examples 1 and 2, as shown in Table 2, do not contain rosin ester, and therefore have low compatibility and do not function as adhesives.
The laminating adhesives of Comparative Examples 3 and 4 do not contain a castor oil-based compound. The laminating adhesive of Comparative Example 3 has low compatibility and does not function as an adhesive. The laminating adhesive of Comparative Example 4 has no compatibility problems, but has too low adhesive strength.

The laminating adhesives of Comparative Examples 5 and 6 have an inappropriate blend ratio of polyol and rosin ester. The laminating adhesive of Comparative Example 5 is inferior in stability. The laminating adhesive of Comparative Example 6 has noticeable air bubbles in the laminate film, resulting in a poor film appearance.

In this way, it has been demonstrated that the laminating adhesive of the embodiment of the present invention has excellent compatibility, does not deteriorate the appearance of the film, has excellent adhesive strength, is stable, and improves workability.

The laminating adhesive of an embodiment of the present invention does not deteriorate the appearance of the films when bonding multiple films together, has excellent adhesive strength after curing, and is excellent in uniformity and prevention of cloudiness, and can be used for a variety of applications.
It is particularly suitable as an adhesive for laminate films used to package food, detergents, shampoos, conditioners, etc.

REFERENCE SIGNS LIST 10 Laminate film 11 Film 11a Vapor-deposited thin film 12 Film 13 Adhesive layer

Claims (2)

A method for producing a laminating adhesive, comprising blending (A) a urethane prepolymer having an isocyanate group at its terminal, (B) a polyol component, (C) a rosin ester, and (D) a castor oil-based compound,
The method includes blending a first liquid containing the component (A) and a second liquid containing the components (B) to (D),
A method for producing a laminating adhesive, comprising blending 50 to 250 parts by mass of component (C) per 100 parts by mass of component (B). The method for producing a laminating adhesive according to claim 1 , wherein the (B) polyol comprises a polyether polyol.