JP6881547B2 - Solvent-free adhesive composition and laminate - Google Patents

Description

INDUSTRIAL APPLICABILITY The present invention has an excellent adhesive function, which is suitably used when a plurality of various plastic films and metal vapor-deposited films or metal foils are laminated to produce a laminate for packaging of foods, medical products, cosmetics, etc. The present invention relates to a solvent-based adhesive composition. Furthermore, the present invention relates to a laminate used for packaging foods, medical products, cosmetics and the like.

In recent years, as a packaging material for foods, medical products, cosmetics, etc., a composite of a metal foil such as aluminum foil or a metal-deposited film and a plastic film such as polyethylene, polypropylene, vinyl chloride, polyester, nylon, etc. has been used in multiple layers. Has been done. As an adhesive for laminating these plastic films with a metal foil or a metal vapor-deposited film, those composed of a polymer polyol and an organic isocyanate compound obtained by reacting an aromatic polyvalent carboxylic acid anhydride are known.

Further, conventionally, as a solvent-type laminate adhesive used for a laminate composite film containing such a metal foil, a two-component adhesive containing a polyol compound as a main agent and a polyisocyanate compound as a curing agent is preferably used. In addition, for the purpose of imparting content resistance (acid resistance) to metal foils, there are a wide range of methods such as introducing an acid group into the molecular end of a polyol compound or using phosphoric acid and a silane coupling agent as additives. It is known (for example, Patent Document 1 or 2).
Further, in Patent Document 3, by using a resin obtained by copolymerizing (meth) acrylic acid ester and maleic anhydride, solvent-based adhesion having excellent heat resistance and acid resistance and suppressing deterioration of adhesiveness with time is suppressed. The agent composition is disclosed.

On the other hand, in recent years, there has been an increasing demand for solvent-free adhesives due to the tightening of laws and regulations and consideration for environmental protection or safety, and there is no laminate adhesive used for bonding between metal foil and various plastic films. Solventification is being considered.

However, the solvent-free adhesive has a much faster curing reaction rate than the solvent-based adhesive. Therefore, for example, when an acid group is introduced into the main agent for the purpose of imparting acid resistance to a metal foil, the acid group is introduced. Due to the urethanization catalytic effect of the above, curing is further promoted, the viscosity increases sharply after the main agent and the curing agent are mixed, and there is a problem that workability is poor.

Special Fair 7-94654 Gazette Japanese Unexamined Patent Publication No. 2-84482 Japanese Unexamined Patent Publication No. 2012-184283

The present invention provides a solvent-free adhesive composition that suppresses an increase in viscosity after blending, has excellent workability, is suitable for acid-resistant contents, and does not easily deteriorate over time, and a laminate using the composition. The purpose is to do.

That is, the present invention relates to the following [1] to [7].

[1] None containing a resin (A) obtained by copolymerizing a (meth) acrylic acid ester and maleic anhydride, a polyol (B) having a secondary hydroxyl group at the terminal, and an aromatic polyisocyanate (C). Solvent-type adhesive composition.

[2] The solvent-free adhesive composition according to [1], wherein the content of the resin (A) is 0.1 to 10% by mass with respect to the polyol (B).

[3] The solvent-free adhesive composition according to [1] or [2], wherein the polyol (B) is a polyester polyol.

[4] The solvent-free adhesive according to any one of [1] to [3], wherein the content of the polyol (B) is 50% by mass or more and 100% by mass or less in 100% by mass of the total polyol component. Agent composition.

[5] The solvent-free adhesive composition according to any one of [1] to [4], wherein the acid value of the resin (A) is 250 mgKOH / g or more.

[6] The solvent-free adhesive composition according to any one of [1] to [5], further containing 0.1 to 10% by mass of a silane coupling agent with respect to the polyol (B).

[7] A laminate in which an adhesive layer composed of the solvent-free adhesive composition according to any one of [1] to [6] is laminated between at least two or more sheet-like substrates.

INDUSTRIAL APPLICABILITY According to the present invention, a solvent-free adhesive composition that suppresses an increase in viscosity after blending, has excellent workability, is suitable for acid-resistant contents, and does not easily deteriorate over time, and a laminate using the composition are provided. can do.
More specifically, the adhesive strength between the plastic film of the laminated laminate or the metal leaf when the content is strongly acidic such as vinegar, ketchup, chili sauce, etc. does not change even after long-term storage, and good solvent-free adhesion. It is possible to provide an agent composition and a laminate using the composition.

<Solvent-free adhesive composition>
The solvent-free adhesive composition of the present invention comprises a resin (A) obtained by copolymerizing a (meth) acrylic acid ester and maleic anhydride, a polyol (B) having a secondary hydroxyl group at the terminal, and an aromatic poly. It is characterized by containing isocyanate (C).
By combining a resin (A) obtained by copolymerizing these (meth) acrylic acid esters and maleic anhydride, a polyol (B) having a secondary hydroxyl group at the terminal, and an aromatic polyisocyanate (C), no solvent is used. Even when it is molded, it has the effect of suppressing the increase in viscosity after blending and prolonging the pot life, improving workability.
Hereinafter, the present invention will be described in detail.

<Resin (A) obtained by copolymerizing (meth) acrylic acid ester and maleic anhydride>
The resin (A) obtained by copolymerizing the (meth) acrylic acid ester and maleic anhydride used in the present invention is particularly limited as long as it is a copolymer of a known (meth) acrylic acid ester and maleic anhydride. Instead, it can be selected from conventionally known resins, and can be used alone or in combination of two or more.

Examples of the (meth) acrylic acid ester monomer include methyl methacrylate, ethyl methacrylate, propyl methacrylate, -i-propyl methacrylate, butyl methacrylate, -i-butyl methacrylate, -t-butyl methacrylate and methacrylic acid. Examples thereof include pentyl acid acid, decyl methacrylate, heptyl methacrylate, cyclohexyl methacrylate octylate, and phenyl methacrylate. Of these, methyl methacrylate is preferable from the viewpoint of copolymerizability with maleic anhydride.
A radical copolymerization method is used as a method for synthesizing the resin (A) obtained by copolymerizing a (meth) acrylic acid ester and maleic anhydride. For example, it is appropriately selected from solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization and the like.

When copolymerizing the resin (A), the amount of (meth) acrylic acid ester and maleic anhydride is the content of (meth) acrylic acid ester with respect to the total amount of (meth) acrylic acid ester and maleic anhydride. The amount is preferably 50 to 95% by mass, more preferably 50 to 70% by mass. The content of maleic anhydride is preferably 5 to 50% by mass, more preferably 30 to 50% by mass. When the content of maleic anhydride is 5% by mass or more, the adhesive strength during long-term storage does not deteriorate, which is preferable. Further, when it is 50% by mass or less, it is preferable because it is easy to synthesize a copolymer of (meth) acrylic acid ester and maleic anhydride.

The acid value of the resin (A) is preferably 250 mgKOH / g or more, more preferably 300 mgKOH / g or more, and particularly preferably 350 mgKOH / g or more. An acid value of 250 mgKOH / g is preferable because there is no decrease in adhesive strength during long-term storage.

The number average molecular weight (Mn) of the resin (A) is preferably 1,000 to 50,000, more preferably 10,000 to 12,000. When the number average molecular weight is 1,000 or more, the adhesive strength does not deteriorate during long-term storage, and when it is 50,000 or less, the compatibility of the adhesive composition is good and the coating appearance of the adhesive composition is good. Is preferable because it is excellent.

The content of the resin (A) is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, and particularly preferably 0.5% by mass, based on the polyol (B) having a secondary hydroxyl group at the terminal. It is 0.5 to 3% by mass. When it is 0.1% by mass or more, the adhesive strength can be maintained for a long period of time, and when it is 10% by mass or less, the compatibility of the adhesive composition is good and the coating appearance of the adhesive is excellent, which is preferable.

<Polyol (B) having a secondary hydroxyl group at the end>
The solvent-free adhesive composition of the present invention contains a polyol (B) having a secondary hydroxyl group at the terminal from the viewpoint of pot life. The polyol (B) is not particularly limited as long as it has a secondary hydroxyl group at the terminal, and for example, a polyester polyol, a polyether polyol, a polyether ester polyol, a polyesteramide polyol, an acrylic polyol, a polycarbonate polyol, a polyhydroxylalkane, and the like. Examples include polyurethane polyols, castor oil or mixtures thereof. Of these, polyester polyols are preferable from the viewpoint of deterioration of adhesive performance over time.

Examples of the polyester polyol having a secondary hydroxyl group at the terminal include dibasic acids such as terephthalic acid, isophthalic acid, adipate azelaic acid, and sebatic acid, dialkyl esters thereof, or mixtures thereof, and at least one of them is a secondary terminal. Polyhydric alcohols with hydroxyl groups, preferably glycols with at least one secondary terminal hydroxyl group, such as propylene glycol, 1,3-butylene glycol, 2,2,4-trimethyl-1,3-pendandiol, 2,4 Polyester polyol or polycaprolactone, polyvalerolactone, poly (β-methyl-Υ) obtained by reacting glycols such as -pentanediol, 2,5-hexanediol, 1,2,6-hexanetriol or mixtures thereof. -Examples include polyester polyols obtained by ring-opening polymerization of lactones such as valerolactone). Then, while the primary hydroxyl group having a high reaction rate reacts preferentially with the dibasic acid or its dialkyl ester, the secondary hydroxyl group having a slower reaction rate tends to remain, and as a result, the terminal hydroxyl group in the molecule is likely to remain. As a result, the secondary terminal hydroxyl group remains preferentially over the primary terminal hydroxyl group.

A polyester polyol having a secondary hydroxyl group at the terminal may have a carboxyl group inside the molecule or at the end of the molecule. The above carboxyl group can be introduced by reacting a polyester polyol with a polybasic acid or an anhydride thereof.
The polyester polyol has a number average molecular weight of preferably 1,000 to 100,000, more preferably 1,000 to 10,000, and particularly preferably 1,000 to 6,000. When the number average molecular weight is 1,000 or more, the cohesive force is sufficient, and when it is 100,000 or less, a polybasic acid or an anhydride thereof can be easily reacted at the terminal in synthesis, and the viscosity is increased. And gelation can be suppressed.

<Other polyol components>
Further, the solvent-free adhesive composition of the present invention may contain other polyol components other than the polyol (B) having a secondary hydroxyl group at the terminal as long as the effects of the present invention are not impaired.
The other polyol may be a polyol having no secondary hydroxyl group at the terminal, for example, a polyester polyol having a primary hydroxyl group at the terminal, a polycarbonate polyol, a polycaprolactone polyol, a polyether polyol, a polyolefin polyol, an acrylic polyol, or a silicone. Polyols, castor oil-based polyols, fluorine-based polyols and the like can be used alone, or two or more of them can be used in combination.

Examples of the polyvalent carboxylic acid component constituting the polyester polyol having a primary hydroxyl group at the terminal and no secondary hydroxyl group include maleic acid, fumaric acid, succinic acid, isophthalic acid, terephthalic acid, adipic acid, and azelaic acid. , Sevacinic acid, orthophthalic acid and their dialkyl esters or acid anhydrides and other single or mixed components. Examples of polyhydric alcohol components include ethylene glycol, neopentyl glycol, diethylene glycol, 1,6. Examples thereof include a single component or a mixed component of a polyhydric alcohol having no secondary terminal hydroxyl group such as hexanediol.

From the viewpoint of improving the pot life, the polyol (B) having a secondary hydroxyl group at the terminal is preferably 50% by mass or more and 100% by mass or less based on 100% by mass of all the polyol components.

<Aromatic polyisocyanate (C)>
The solvent-free adhesive composition of the present invention contains an aromatic polyisocyanate (C).
Examples of the aromatic polyisocyanate (C) include m-phenylenediocyanate, p-phenylenediocyanate, 4,4'-diphenyldiisocyanate, 1,5-naphthalenediocyanate, 2,4-tolylene diisocyanate or 2,6-tolylene diisocyanate. Or a mixture thereof, 4,4'-toluene diisocyanate, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 1, 3-Xylylene diisocyanate or 1,4-xylylene diisocyanate or a mixture thereof, ω, ω'-diisocyanate-1,4-
Aromatic diisocyanates such as diethylbenzene, 1,3-bis (1-isocyanate-1-methylethyl) benzene or 1,4-bis (1-isocyanate-1-methylethyl) benzene or a mixture thereof; triphenylmethane-4, Aromatic triisocyanates such as 4', 4''-triisocyanate, 1,3,5-triisocyanatebenzene, 2,4,6-triisocyanate toluene; 4,4'-diphenyldimethylmethane-2,2'- Aromatic polyisocyanates such as 5,5'-tetraisocyanate; and the like.

Further, the aromatic polyisocyanate compound (C) may be an aromatic isocyanate group-containing compound derived from the above aromatic polyisocyanate compound. Examples of such an aromatic isocyanate group-containing compound include polyurethane polyisocyanate, which is a reaction product of the above-mentioned known aromatic polyisocyanate compound and a known polyol component.

Known polyol components include, for example, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-5-pentanediol, 1,6-hexane. Glycols such as diols, neopentyl glycols, methylpentane glycols, triethylene glycols, tetraethylene glycols, dipropylene glycols, bishydroxyethoxybenzenes, 1,4-cyclohexanediols, 1,4-cyclohexanedimethanol, triethylene glycols; Polyols such as polypropylene glycol, polyester polyol, polyether ester polyol, polyesteramide polyol, polycaprolactone polyol, polyvalerolactone polyol, acrylic polyol, polycarbonate polyol, polyhydroxyalkane, castor oil, polyurethane polyol, etc. having an average molecular weight of 200 to 3,000; Trifunctional or tetrafunctional aliphatic alcohols such as glycerin, trimethylolpropane, and pentaerythritol; polyols obtained by adding the above glycol or polyol to the above trifunctional or tetrafunctional aliphatic alcohol can be used.

Among them, the aromatic polyisocyanate compound (C) preferably contains a polyisocyanate compound having a structure derived from polypropylene glycol in the molecule.
As the polyisocyanate compound having a structure derived from polypropylene glycol in the molecule, a reaction product of a known aromatic polyisocyanate compound and polypropylene glycol is preferably used. The reaction ratio of the aromatic polyisocyanate compound to polypropylene glycol is preferably an NCO / OH ratio of 2 or more, and the number average molecular weight of polypropylene glycol is preferably 200 to 3,000. Further, in the above reaction, in addition to polypropylene glycol, a known polyol may be used in combination.

From the viewpoint of adhesive performance, the content of the aromatic polyisocyanate (C) is preferably 50 to 150% by mass, more preferably 100 to 140% with respect to the polyol (B) having a secondary hydroxyl group at the terminal. It is mass%.
Further, the aromatic polyisocyanate compound (C) can be used alone or in combination of two or more.

<Other polyisocyanates>
In addition, the solvent-free adhesive composition of the present invention may contain other polyisocyanate components other than the aromatic polyisocyanate (C) as long as the effects of the present invention are not impaired.
The polyisocyanate component that may be contained in addition to the aromatic polyisocyanate (C) is not particularly limited, and is a well-known aliphatic diisocyanate, an alicyclic diisocyanate, or an allophanate type, a nurate type, or a biuret type derived from them. , Adduct-type derivatives, or complexes thereof, etc. can be used.

<Silane coupling agent>
The solvent-free adhesive composition of the present invention preferably further contains a silane coupling agent in order to enhance the adhesion to the metal foil. Examples of the silane coupling agent include trialkoxysilanes having vinyl such as vinyltrimethoxysilane and vinyltriethoxysilane, 3-aminopropyltriethoxysilane, and N- (2-aminoethyl) 3-glycidoxypropyltri. Trialkoxysilane having a glycidyl group such as methoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltriequitosisilane, 3-isocyanatepropyltrimethoxysilane, 3-isocyanatepropyltri Examples thereof include a trialkoxysilane having an isocyanate group such as ethoxysilane, an alkoxysilane having a mercapto group such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and an organosilane. The silane coupling agent may be used alone or in combination of two.
The content of the silane coupling agent is preferably 0.1 to 10% by mass, more preferably 0.1 to 5% by mass, and particularly preferably 0.% by mass, based on the solid content of the polyol (B). It is 5 to 5% by mass.

<Inorganic acid>
The solvent-free adhesive composition of the present invention preferably further contains an inorganic acid in order to enhance the adhesion to the metal foil. Examples of the inorganic acid include hydrochloric acid, sulfuric acid, phosphoric acid, boric acid, nitric acid and the like, and phosphoric acid is preferable. Phosphoric acid also includes diphosphoric acid, metaphosphoric acid, polyphosphoric acid and the like.
The content of the inorganic acid is preferably 0.01 to 0.5% by mass, more preferably 0.02 to 0.25% by mass, and particularly preferably 0.02 to 0.25% by mass with respect to the solid content of the polyol (B). It is 0.05 to 0.10% by mass.

<Other additives>
The adhesive composition of the present invention may contain various additives as long as the pot life property is not impaired. Examples of the additive include inorganic fillers such as silica, alumina, mica, talc, aluminum flakes, and glass flakes, layered inorganic compounds, stabilizers (antioxidants, heat stabilizers, ultraviolet absorbers, hydrolysis inhibitors, etc.). ), Anticorrosive agents, thickeners, plasticizers, antistatic agents, lubricants, antiblocking agents, colorants, fillers, crystal nucleating agents, catalysts for adjusting the curing reaction, and the like.

The solvent-free adhesive composition of the present invention comprises a resin (A) obtained by copolymerizing a (meth) acrylic acid ester and maleic anhydride, a polyol (B) having a secondary hydroxyl group at the terminal, and an aromatic poly. It contains isocyanate (C) and has a viscosity of 100 to 10,000 mPa · s, more preferably 1,000 to 5,000 mPa · s at room temperature (25 ° C.) to 120 ° C., preferably room temperature to 80 ° C. When it is 100 mPa · s or more, the initial cohesive force of the adhesive is excellent. When it is 10,000 mPa · s or less, the coating appearance is excellent.

<Laminated body>
The laminated body of the present invention is obtained by laminating an adhesive layer made of the above-mentioned solvent-free adhesive composition between at least two sheet-like substrates. Specifically, the solvent-free adhesive composition of the present invention is applied to a first sheet-like base material to form an adhesive layer, and a second sheet-like base material is superposed on the adhesive layer to form both sheets. The adhesive layer located between the shaped substrates is cured.
The sheet-shaped base material is not particularly limited, and examples thereof include conventionally known plastic films, papers, metal foils, and the like, and the two sheet-shaped base materials may be of the same type or different types.
As the plastic film, a film made of a thermoplastic resin or a thermosetting resin can be used, but a film made of a thermoplastic resin is preferable. Examples of the thermoplastic resin include polyolefins, polyesters, polyamides, polystyrenes, vinyl chloride resins, vinyl acetate resins, ABS resins, acrylic resins, acetal resins, polycarbonate resins, fibrous plastics and the like.
Further, as the sheet-like base material, a printing ink may be gravure-printed or flexographically printed on the base material to provide a printing ink layer, and the printing ink can be used without limitation. A water-based type or active energy ray-curable ink can be used.

The thickness of the laminate is usually 10 μm or more. To prepare a laminate using the solvent-free adhesive composition of the present invention, an adhesive is applied to one side of one sheet-like substrate by a commonly used method, for example, a laminator, and the other. It may be bonded to a sheet-like substrate and cured at room temperature or under heating. The amount of adhesive applied to the surface of the sheet-like substrate ^{is preferably about 1 to 4 g / m 2} , and the laminate of the present invention is preferably used for packaging.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. Parts and% in Examples and Comparative Examples mean parts by mass and% by mass unless otherwise specified.

<Measurement method of number average molecular weight (Mn)>
The number average molecular weight (Mn) was measured by using GPC (gel permeation chromatography) "Shodex GPC System-21" manufactured by Showa Denko KK. GPC is a liquid chromatography in which a substance dissolved in a solvent is separated and quantified by the difference in its molecular size. The solvent is tetrohydrofuran, and the molecular weight is determined in terms of polystyrene.

<Measurement method of acid value>
Approximately 1 g of the sample was precisely weighed in an Erlenmeyer flask with a stopper, and 100 ml of a toluene / ethanol (volume ratio: toluene / ethanol = 2/1) mixed solution was added and dissolved. Phenolphthalein test solution was added to this as an indicator and lasted for 30 seconds. Then, it was titrated with 0.1N alcoholic potassium hydroxide solution until the solution became pink.
The acid value was determined by the following (Equation 1). (Unit: mgKOH / g).
(Equation 1) Acid value (mgKOH / g) = [{(ba) × F × 28.25} / S]
However, S: sample collection amount (g)
a: Consumption of 0.1N alcoholic potassium hydroxide solution (ml)
b: Consumption (ml) of 0.1N alcoholic potassium hydroxide solution in the blank experiment
F: Titer of 0.1N alcoholic potassium hydroxide solution

<Measurement method of hydroxyl value>
Approximately 1 g of the sample was precisely weighed in an Erlenmeyer flask with a stopper, and 100 ml of a toluene / ethanol (volume ratio: toluene / ethanol = 2/1) mixed solution was added and dissolved. Further, exactly 5 ml of an acetylating agent (a solution in which 25 g of acetic anhydride was dissolved in pyridine to make a volume of 100 ml) was added, and the mixture was stirred for about 1 hour. Phenolphthalein TS is added as an indicator to this and lasts for 30 seconds. Then, it was titrated with 0.1N alcoholic potassium hydroxide solution until the solution became pink.
The hydroxyl value was determined by the following (Equation 2). The hydroxyl value was taken as the value of the dry state of the resin (unit: mgKOH / g).
(Equation 2) Hydroxy group value (mgKOH / g) = [{(ba) × F × 28.25} / S] / (nonvolatile content concentration / 100) + D
However, S: sample collection amount (g)
a: Consumption of 0.1N alcoholic potassium hydroxide solution (ml)
b: Consumption (ml) of 0.1N alcoholic potassium hydroxide solution in the blank experiment
F: Titer of 0.1N alcoholic potassium hydroxide solution
D: Acid value (mgKOH / g)

<Measuring method of NCO content (mass%)>
About 1 g of the sample was weighed in a 200 mL Erlenmeyer flask, and 10 mL of a toluene solution of 0.5 N-n-butylamine and 10 mL of toluene were added and dissolved. Next, a phenolphthalein test solution was added as an indicator, held for 30 seconds, and then titrated with a 0.25N hydrochloric acid solution until the solution turned pink. The NCO content (mass%) was determined by the following (Equation 3).
(Equation 3): NCO (mass%) = {(ba) × 4.202 × F × 0.25} / S
However, S: sample collection amount (g)
a: Consumption of 0.25N hydrochloric acid solution (ml)
b: Consumption of 0.25N hydrochloric acid solution in blank experiment (ml)
F: Titer of 0.25N hydrochloric acid solution

<Synthesis of resin (A)>
(Synthesis Example 1) (Meta) Acrylic Acid Ester-Maleic anhydride copolymer (A-1)
200 parts of toluene was charged into a reaction vessel equipped with a stirrer, a temperature system, a reflux condenser, a dropping tank and a nitrogen gas introduction tube, and the temperature was raised to 110 ° C. while stirring while introducing nitrogen gas. Next, 80 parts of methyl methacrylate, 50 parts of butyl acrylate, 100 parts of maleic anhydride, and 50 parts of toluene were charged in the dropping tank 1, and 9 parts of benzoyl peroxide dissolved in 50 parts of toluene were charged in the dropping tank 2. Each of them was added dropwise under stirring while maintaining the temperature in the reaction vessel at 110 ° C. for 2 hours at the same time. After completion of the reaction, the polymer was cooled to room temperature, the polymer was precipitated with a large amount of methanol, filtered, and dried at 120 ° C. for 6 hours. A polymer (A-1) was obtained.

(Synthesis Example 2) (Meta) Acrylic Acid Ester-Maleic anhydride copolymer (A-2)
200 parts of toluene was charged into a reaction vessel equipped with a stirrer, a temperature system, a reflux condenser, a dropping tank and a nitrogen gas introduction tube, and the temperature was raised to 110 ° C. while stirring while introducing nitrogen gas. Next, 90 parts of methyl methacrylate, 50 parts of butyl acrylate, 80 parts of maleic anhydride, and 50 parts of toluene were charged in the dropping tank 1, and 9 parts of benzoyl peroxide dissolved in 50 parts of toluene were charged in the dropping tank 2. Each of them was added dropwise under stirring while maintaining the temperature in the reaction vessel at 110 ° C. for 2 hours at the same time. After completion of the reaction, the polymer was cooled to room temperature, the polymer was precipitated with a large amount of methanol, filtered, and dried at 120 ° C. for 6 hours. A polymer (A-2) was obtained.

(Synthesis Example 3) (Meta) Acrylic Acid Ester-Maleic anhydride copolymer (A-3)
200 parts of toluene was charged into a reaction vessel equipped with a stirrer, a temperature system, a reflux condenser, a dropping tank and a nitrogen gas introduction tube, and the temperature was raised to 110 ° C. while stirring while introducing nitrogen gas. Next, 90 parts of methyl methacrylate, 70 parts of butyl acrylate, 40 parts of maleic anhydride, and 50 parts of toluene were charged in the dropping tank 1, and 9 parts of benzoyl peroxide dissolved in 50 parts of toluene were charged in the dropping tank 2. Each of them was added dropwise under stirring while maintaining the temperature in the reaction vessel at 110 ° C. for 2 hours at the same time. After completion of the reaction, the polymer was cooled to room temperature, the polymer was precipitated with a large amount of methanol, filtered, and dried at 120 ° C. for 6 hours. A polymer (A-3) was obtained.

<Synthesis of polyol (B) having a secondary hydroxyl group at the end>
(Synthesis Example 4) Polyester Polyol (B-1)
110 parts of terephthalic acid, 250 parts of adipic acid, 200 parts of diethylene glycol (hereinafter referred to as DEG), 75 parts of neopentyl glycol and 200 parts of propylene glycol were charged into a reaction vessel, and the temperature was adjusted to 150 ° C. to 240 ° C. while stirring under a nitrogen gas stream. The esterification reaction was carried out by heating. When the acid value becomes 10.0 mgKOH / g or less, the reaction temperature is set to 200 ° C., the inside of the reaction vessel is gradually depressurized, and the reaction is carried out at 1.3 kPa or less. The acid value is 0.4 mgKOH / g and the hydroxyl value is 120 mgKOH / g. , A polyester polyol (B-1) which is a polyester diol resin having a secondary hydroxyl group at the terminal and having a number average molecular weight of about 5,800 was obtained.

(Synthesis Example 5) Polyester Polyol (B-2)
100 parts of terephthalic acid, 200 parts of adipic acid, 250 parts of diethylene glycol (hereinafter referred to as DEG), 50 parts of neopentyl glycol and 300 parts of propylene glycol are charged in a reaction vessel, and the temperature is adjusted to 150 ° C. to 240 ° C. while stirring under a nitrogen gas stream. The esterification reaction was carried out by heating. When the acid value becomes 10.0 mgKOH / g or less, the reaction temperature is set to 200 ° C., the inside of the reaction vessel is gradually depressurized, and the reaction is carried out at 1.3 kPa or less. The acid value is 0.4 mgKOH / g and the hydroxyl value is 150 mgKOH / g. , A polyester polyol (B-2), which is a polyester diol resin having a secondary hydroxyl group at the terminal and having a number average molecular weight of about 4,200, was obtained.

(Synthesis Example 6) Polyether polyol (B-3)
300 parts of polypropylene glycol with a number average molecular weight of about 400, 200 parts of polypropylene glycol with a number average molecular weight of about 2000, 300 parts of triol with a number average molecular weight of about 400 added with polypropylene glycol, 4,4'-diphenylmethane diisocyanate (4,4'-diphenylmethane diisocyanate ( 150 parts (hereinafter referred to as 4,4'-MDI) are charged in a reaction vessel and heated at 80 ° C. to 90 ° C. for 3 hours while stirring under a nitrogen gas stream to carry out a urethanization reaction. After confirming the disappearance, a polyether polyol (B-3), which is a polyether polyurethane resin having a secondary hydroxyl group at the terminal, was obtained.

<Synthesis of other resins>
(Styrene-maleic anhydride copolymer)
200 parts of toluene was charged into a reaction vessel equipped with a stirrer, a temperature system, a reflux condenser, a dropping tank and a nitrogen gas introduction tube, and the temperature was raised to 110 ° C. while stirring while introducing nitrogen gas. Next, 150 parts of styrene, 150 parts of maleic anhydride, and 50 parts of toluene were charged in the dropping tank 1, and 9 parts of benzoyl peroxide dissolved in 50 parts of toluene were charged in the dropping tank 2, and each of them took 2 hours at the same time in the reaction vessel. The mixture was added dropwise with stirring while maintaining the temperature inside at 110 ° C. After completion of the reaction, the polymer was cooled to room temperature, the polymer was precipitated with a large amount of methanol, filtered, and dried at 120 ° C. for 6 hours to obtain a styrene-maleic anhydride copolymer having a number average molecular weight of 2,800 and an acid value of 400. ..

<Manufacturing of other polyols>
(Polyester polyol having a primary hydroxyl group at the end)
60 parts of ethylene glycol, 400 parts of neopentyl glycol, 120 parts of isophthalic acid, and 300 parts of adipic acid were charged, and the temperature was raised to 260 ° C. while stirring under a nitrogen stream. After continuing the reaction until the acid value became 5 or less, the pressure was gradually reduced, the reaction was continued at 1 mmHg, excess alcohol was removed, the hydroxyl value was 57 mgKOH / g, and the number average molecular weight was about 2,000. , A polyester polyol having a primary hydroxyl group at the terminal and no secondary hydroxyl group was obtained.

<Manufacturing of aromatic polyisocyanate (C)>
(Aromatic polyisocyanate (C-1))
120 parts of polypropylene glycol having a number average molecular weight of about 400, 30 parts of triol having a number average molecular weight of about 400 obtained by adding polypropylene glycol to glycerin, and 350 parts of 4,4'-diphenylmethane diisocyanate were charged into a reaction vessel and stirred under a nitrogen gas stream. While heating at 80 ° C. to 90 ° C. for 3 hours, the urethanization reaction was carried out, and isocyanate groups were added to both ends with an isocyanate group content of 12.4% and a 4,4'-diphenylmethane diisocyanate content of 20.9%. An aromatic polyisocyanate (C-1), which is a polyurethane polyisocyanate resin composition having a substance, was obtained.

(Aromatic polyisocyanate (C-2))
100 parts of polypropylene glycol having a number average molecular weight of about 400, 45 parts of triol having a number average molecular weight of about 400 obtained by adding polypropylene glycol to glycerin, and 400 parts of 4,4'-diphenylmethane diisocyanate were charged into a reaction vessel and stirred under a nitrogen gas stream. The urethanization reaction was carried out by heating at 80 ° C. to 90 ° C. for 3 hours, and isocyanate groups were added to both ends with an isocyanate group content of 12.4% and a 4,4'-diphenylmethane diisocyanate content of 22.5%. An aromatic polyisocyanate (C-2), which is a polyurethane polyisocyanate resin composition having a substance, was obtained.

<Manufacturing of solvent-free adhesive composition>
[Example 1]
(Solvent-free adhesive composition (D-1))
The (meth) acrylic acid ester-maleic anhydride copolymer (A-1) obtained in Synthesis Example 1 was placed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping tank and a nitrogen gas introduction tube. 0 parts, 98.0 parts of the polyester polyol (B-1) obtained in Synthesis Example 4 were charged, the temperature was raised to 120 ° C. with stirring while introducing nitrogen gas, and the mixture was held for 1 hour. After cooling to 70 ° C., 1.0 part of a silane coupling agent (3-glycidoxypropyltriechitosisilane) was mixed.
Next, 120.0 parts of aromatic polyisocyanate (C-1) was mixed to obtain a solvent-free adhesive composition (D-1).

[Examples 2 to 15, Comparative Examples 1 to 2, 4]
(Solvent-free adhesive composition (D-2 to 17, 19))
Solvent-free adhesive compositions (D-2 to 17, 19) were obtained by the same operations as in Example 1 except that the materials and blending amounts shown in Table 1 were used.

[Comparative Example 3]
(Solvent-free adhesive composition (D-18)
98.0 parts of the polyester polyol (B-1) obtained in Synthesis Example 4 was charged into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping tank and a nitrogen gas introduction tube, and nitrogen gas was introduced. The temperature was raised to 150 ° C. with stirring, 1.0 part of trimellitic acid was charged, and the mixture was held for 1 hour. After cooling to 70 ° C., 1.0 part of a silane coupling agent (3-glycidoxypropyltriechitosisilane) was mixed.
Next, 120.0 parts of aromatic polyisocyanate (C-1) was mixed to obtain a solvent-free adhesive composition (D-18).

<Evaluation of solvent-free adhesive composition>
The obtained solvent-free adhesive composition was evaluated as follows. The results are shown in Table 1.

(Preparation of laminate)
Using a solvent-free test coater, the obtained solvent-free adhesive composition was applied to a polyethylene terephthalate film (Toyo Boseki ester film E5102, hereinafter referred to as PET film) having a thickness of 12 μm at a temperature of 80 ° C. and a coating speed of 200 m / min. The solid content was applied at a coating amount of 2.0 g / m ² , and the film was laminated with a 9 μm-thick aluminum foil (hereinafter referred to as AL foil) in a normal temperature environment using a laminator. Next, the solvent-free adhesive composition was applied onto the Al foil surface of the obtained laminate in the same manner as before, and the coated surface was subjected to surface corona discharge having a thickness of 100 μm in a normal temperature environment using a laminator. After laminating with a treated linear low-density polyethylene film (Mitsui Tohcello TUX-FCD, hereinafter referred to as LLDPE), it is kept warm at 40 ° C. for 2 days, and then PET film / adhesive layer / AL foil / adhesive layer / LLDPE. A laminate, which is the composition of the film, was obtained.

(Laminate strength)
Using the laminated body, a packaging bag having a size of 9 cm × 12 cm was produced. The packaging bag was filled with 30 ml of HEINZ ketchup and stored in an environment of 40 ° C. and 60% RH for 1 week, 2 weeks and 4 weeks, respectively. The packaging bag after storage was cut into a width of 15 mm and a length of 300 mm to form a test piece. Based on JIS K 6854, using an Instron type tensile tester, pulling at a peeling speed of 300 mm / min under an environment of temperature 20 ° C. and relative humidity 65%, between PET / AL foils and between AL foils / LLDPE. The T-type peel strength (N / 15 mm) between them was measured. The measurement was performed 5 times, and the average value was used.

(Heat seal strength)
A test piece having a width of 15 mm and a length of 300 mm was prepared in the same manner as the lamination strength, the LLDPEs of the two test pieces were overlapped with each other, and heat-sealed at 190 ° C., 2 kg, and 1 second to obtain a test piece. .. The T-type peel strength (N / 15 mm) between LLDPE / LLDPE was measured in the same manner as the laminate strength. The measurement was performed 5 times, and the average value was used.

(Pot life)
The viscosity of the solvent-free adhesive composition immediately after compounding and after storage at 40 ° C. for 30 minutes after compounding was measured using a cone plate viscometer CV-1 manufactured by Toa Kogyo Co., Ltd. at a measurement temperature of 40 ° C. It was measured. Evaluation was performed according to the following criteria based on the change in viscosity before and after storage.
S: The viscosity after storage is less than twice the viscosity immediately after compounding (very good).
A: The viscosity after storage is 2 times or more and less than 3 times the viscosity immediately after compounding (good).
B: The viscosity after storage is 3 times or more and less than 4 times the viscosity immediately after compounding (usable).
C: The viscosity after storage is 4 times or more and less than 5 times the viscosity immediately after compounding (cannot be used).
D: The viscosity after storage is 5 times or more the viscosity immediately after compounding (defective).

The abbreviations in Table 1 are shown below.
PPG-400: Polypropylene glycol (number average molecular weight about 400)
MPO: 2-methyl-1,3-propanediol

From the results in Table 1, a resin (A) obtained by copolymerizing a (meth) acrylic acid ester and maleic anhydride, a polyol (B) having a secondary hydroxyl group at the terminal, and an aromatic polyisocyanate (C) were obtained. The solvent-free adhesive composition of the present invention contained therein has excellent pot life by suppressing an increase in viscosity after being blended, and further has acid resistance content suitability (lamination strength, heat seal strength) and is less likely to deteriorate over time. It has been shown that packaging materials can be formed.
Examples 1 to 9 and 11 to 15 containing the silane coupling agent showed excellent lamination strength even after a lapse of time because they had excellent adhesion to the aluminum foil. Among them, Examples 14 and 15 containing a silane coupling agent and phosphoric acid as an inorganic acid showed particularly high lamination strength.

Claims (7)

A solvent-free adhesive containing a resin (A) obtained by copolymerizing (meth) acrylic acid ester and maleic anhydride, a polyol (B) having a secondary hydroxyl group at the terminal, and an aromatic polyisocyanate (C). Composition. The solvent-free adhesive composition according to claim 1, wherein the content of the resin (A) is 0.1 to 10% by mass with respect to the polyol (B). The solvent-free adhesive composition according to claim 1 or 2, wherein the polyol (B) is a polyester polyol. The solvent-free adhesive composition according to any one of claims 1 to 3, wherein the content of the polyol (B) is 50% by mass or more and 100% by mass or less in 100% by mass of the total polyol component. The solvent-free adhesive composition according to any one of claims 1 to 4, wherein the acid value of the resin (A) is 250 mgKOH / g or more. The solvent-free adhesive composition according to any one of claims 1 to 5, further comprising 0.1 to 10% by mass of a silane coupling agent with respect to the polyol (B). A laminate in which an adhesive layer composed of the solvent-free adhesive composition according to any one of claims 1 to 6 is laminated between at least two or more sheet-like substrates.