JP2005290285A - Adhesive for dry laminate for metal film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an adhesive for dry laminate, which is obtained by using an aqueous urethane resin and exhibits excellent adhesiveness to metal films and various films and coating appearance and has retort resistance. <P>SOLUTION: The dry laminate adhesive composition for a metal film comprises an aqueous polyurethane resin as a main component that is obtained by reacting a polyester polyol (A) with a polyisocyanate and a compound containing a functional group to be reacted with an isocyanate group and a hydrophilic group to give a polyurethane resin containing a hydroxy group on the terminal and a hydrophilic group and emulsifying the polyurethane resin. The acid value of the polyurethane resin is 3-15 mg KOH/g, the polyester polyol (A) comprises a condensation structure of a polycarboxylic acid and a polyol and the polycarboxylic acid comprises >60 wt.% and ≤80 wt.% based on the whole polycarboxylic acid of an aromatic polycarboxylic acid. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an adhesive for dry lamination for metal films using an aqueous urethane resin. The adhesive exhibits excellent adhesion and coating appearance to metal films and various films, and further has retort resistance.

  In recent years, in the food packaging field, foods to be packaged have been diversified by improving eating habits and changing distribution structures. The sterilization method also tends to be hotter to boil, retort, and high retort, and accordingly, the performance improvement of the adhesive is required. On the other hand, due to the recent increase in awareness of the environment, regulations on organic solvents released into the atmosphere have advanced, and in the printing processing industry, installation of equipment for removing solvent vaporized in a drying furnace or use of organic solvents has been used. Consideration is being made for alternatives that do not.

  As an alternative that does not use an organic solvent, for example, there is a method of synthesizing a resin having a relatively low molecular weight without solvent and heating and melting it at the time of coating. However, since this method requires a special coater for coating, examples of introduction in Japan are very limited, as is the case with solvent removal equipment. In this respect, the water-based adhesive as another alternative has an advantage that the existing coating equipment can be used as it is. However, water-based adhesives have problems such as adhesive strength and heat resistance, which are inferior to solvent-based adhesives in terms of performance, and use applications are limited.

  What has been confirmed up to now as retort resistance as an aqueous dry laminate adhesive, Japanese Patent Application Laid-Open No. 06-80948 using a self-emulsifying polyisocyanate curing agent, or adding a silane coupling agent to polyurethane resin particles Japanese Patent Application Laid-Open No. 07-063220 for cross-linking within a particle and Japanese Patent No. 3471058 for improving film adhesion by having a hydrazine residue in the molecule of an aqueous urethane resin, refer to a structure including a metal film. Absent.

Regarding an aqueous adhesive for a laminate having adhesiveness to a metal film such as an aluminum film, an acrylic resin-based patent No. 2945526 containing a glycidyl group, a phosphate group, and a 1,1-dialkylsemicarbazide group, phosphoric acid Japanese Patent Application Laid-Open No. 10-077455, which is a hydrazine cross-link of an aqueous acrylic resin containing a group, and an amphoteric polyurethane resin increase acid-base interaction with the metal surface, and after drying, intramolecular and intermolecular ionic bonds There is an increasing Japanese Patent Laid-Open No. 11-181394.
However, the former two did not disclose the adhesive strength after boiling, and the latter had lower adhesive strength due to boiling, and neither of them had sufficient adhesive strength to the aluminum film.

  Further, in JP-A-2004-43519 in which the adhesive strength before and after boiling is measured with a nylon / polyethylene film configuration, aromatic dicarboxylic acid and alicyclic dicarboxylic acid among the acid components of the polyester polyol are total 10 wt% to 60 wt%. The aqueous urethane adhesive is characterized in that the proportion of branched glycol in the glycol component is adjusted to 30 to 100% by weight and the acid value is 6 to 31 [mg KOH / g]. However, there was no description regarding the adhesive strength to the aluminum film, and in fact, the appearance and adhesive strength after retorting to the aluminum film was still insufficient.

A water-based dry laminate adhesive for metal films that has resistance to retort has not been known so far.
Japanese Patent Laid-Open No. 06-80948 Japanese Patent Laid-Open No. 07-063220 Japanese Patent No. 3471058 Patent No. 2945526 Japanese Patent Application Laid-Open No. 10-077455 Japanese Patent Laid-Open No. 11-181394 2004-43519

  That is, an object of the present invention is to provide an adhesive for dry laminating using a water-based urethane resin that exhibits excellent adhesion and coating appearance to metal films and various films, and further has retort resistance.

  As a result of intensive studies to achieve the above object, the present inventor has found that an adhesive using the aqueous urethane resin of the present invention is suitable for achieving the above object, and completed the present invention.

That is, in the present invention, the end of the polyester polyol (A), the polyisocyanate (B), and the compound (C) having a functional group capable of reacting with an isocyanate group and a hydrophilic group (C) is a hydroxyl group. A dry laminate adhesive composition for a metal film having a polyurethane resin having a hydrophilic group as a main component, emulsified aqueous polyurethane resin as a main agent, and a curing agent as an auxiliary agent,
The polyurethane resin has an acid value of 3 to 15 [mg KOH / g], and
The polyester polyol (A) includes an aromatic polycarboxylic acid containing a condensation structure of a polycarboxylic acid and a polyol, and the polycarboxylic acid is more than 60% by weight and not more than 80% by weight based on the whole polycarboxylic acid. The present invention relates to a dry laminate adhesive composition for metal films.

  Moreover, this invention relates to the laminated body laminated | stacked in order of a metal film, the said dry laminate adhesive for metal films, and a film.

  By this invention, the water-based urethane adhesive which has favorable adhesiveness with respect to various film base materials and retort resistance was obtained.

  The polyester polyol (A) used in the present invention has a terminal hydroxyl group and includes a condensation structure of a polycarboxylic acid and a polyol.

Examples of the polycarboxylic acid include succinic acid, malonic acid, tartaric acid, oxalic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, alkyl succinic acid, linolenic acid, maleic acid, fumaric acid. Aliphatic polycarboxylic acids such as mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, 1,10-decanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,20-eicosanedicarboxylic acid,
Cycloaliphatic polycarboxylic acids such as cyclopropanedicarboxylic acid, cyclobutanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, cyclohexanetricarboxylic acid,
Phthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, tetrahydrophthalic acid, 1,2-bis ( Aromatic polycarboxylic acids such as phenoxy) ethane-p, p′-dicarboxylic acid, trimellitic acid and pyromellitic acid.
The present invention is characterized in that aromatic polycarboxylic acid is more than 60% by weight and 80% by weight of the total polycarboxylic acid. Aromatic polycarboxylic acids are suspected to have sufficient cohesive strength and heat resistance and suppress hydrolysis of ester bonds. As a result, adhesion strength, retort resistance, and storage stability of aquatic adhesives are greatly increased. It was possible to improve.

  Examples of the above polyols include ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6. -Hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl 1,3 -Polymers of aliphatic diols such as propanediol, alicyclic diols such as 1,4-cyclohexanedimethanol and hydrogenated bisphenol A, bisphenol A, hydroquinone, bishydroxyethoxybenzene and their alkylene oxide adducts. Examples of polyols and polyols such as glycerin, trimethylolpropane and pentaerythritol are given as polyfunctional components.

The polyester polyol (A) used in the present invention can be obtained by an esterification reaction of the polycarboxylic acid and the polyol. Polycarboxylic acids and polyols may be esterified at the time of reaction, and may be reacted from derivatives of carboxylic acid anhydrides or esters. Moreover, 2 or more types may be sufficient as polycarboxylic acid and a polyol, and also other components, such as hydroxycarboxylic acid, may be added as needed. For the esterification reaction, known esterification techniques can be used.
The polyester polyol (A) used in the present invention preferably has a number average molecular weight of 2,000 to 8,000.
The polyester polyol (A) used in the present invention has a hydroxyl group at the terminal. There may be more than two ends that diverge. Moreover, not all terminals need necessarily be hydroxyl groups.
In order to make the terminal a hydroxyl group, the ratio between the carboxyl group value of the raw material and the hydroxyl value of the raw material is preferably 1: 1.1 to 1.4.

  As the polyisocyanate (B) used in the present invention, any conventionally known polyisocyanate (B) can be used. However, from the regulations of FDA (Food and Drug Administration) § 175.105 and § 177.1390, aliphatic or alicyclic The use of group diisocyanate compounds is desirable.

In the present invention, the hydrophilic group refers to a functional group that can be emulsified by forming a salt alone or using a neutralizing agent, and specifically includes a carboxylic acid group, a sulfonic acid group, and a tertiary amino acid. Groups, carboxylic acid salts, sulfonic acid salts, quaternary amino groups, polyalkyleneoxy groups, hydroxyl groups and the like.
Examples of the functional group capable of reacting with an isocyanate group in the present invention include an amino group, a hydroxyl group, and a carboxyl group.

The compound (C) having a functional group and a hydrophilic group capable of reacting with the isocyanate group used in the present invention reacts with the polyisocyanate (B) to become a part of the urethane resin, and the urethane resin has a hydrophilic group. Used to give. Examples of such compounds (C) include 2,2'-dimethylolpropionic acid, 2,2'-dimethylolbutanoic acid, 2,2'-dimethylolbutyric acid, 2,2'-dimethylolvaleric acid, dioxymalein. Carboxylic acid-containing compounds such as acids, 2,6-dioxybenzoic acid, 3,4-diaminobenzoic acid and derivatives thereof,
2-oxyethanesulfonic acid, phenolsulfonic acid, sulfobenzoic acid, sulfosuccinic acid, 5-sulfoisophthalic acid, sulfanilic acid, 1,3-phenylenediamine-4,6-disulfonic acid, 2,4-diaminotoluene-5 Examples include sulfonic acid-containing compounds such as sulfonic acid and derivatives thereof.

The polyurethane resin used in this invention can obtain the said polyester polyol (A), polyisocyanate (B), and the compound (C) which has a hydrophilic group and an isocyanate group by well-known urethanation reaction. A known urethanization technique can be used for the urethanization reaction.
As the urethane resin used in the present invention, those having a number average molecular weight of 5,000 to 60,000 are preferably used.

  In the present invention, a hydrophilic group is necessary for dispersing the polyurethane resin in water. As the hydrophilic group, in addition to a substance derived from the compound (C) having a hydrophilic group and an isocyanate group, a polyester polyol (A) or polyisocyanate (B) having a hydrophilic group may be used. . For example, the polyester polyol (A) having a hydrophilic group can be obtained by having a hydrophilic group in all or part of the polycarboxylic acid, polyol, and other components that are raw materials.

The acid value of the polyurethane resin is preferably 3 to 15 [mg KOH / g]. If it is less than 3 [mg KOH / g], it may be unfavorable because the aquatic ability is too low for stable self-emulsification.
On the other hand, if it exceeds 15 [mg KOH / g], the resin layer may become too hard and the adhesive strength may be lowered.

  Since the polyurethane resin used in the present invention has a hydrophilic group, it can be made aqueous. When the hydrophilic group is a functional group capable of forming a salt, if necessary, some or all of the hydrophilic groups are salted and neutralized with a neutralizing agent. As the neutralizing agent, inorganic bases such as sodium hydroxide and potassium hydroxide, organic tertiary amines such as ammonia, trimethylamine and triethylamine are used. The neutralizing agent is preferably added so that 40 to 100% of the hydrophilic group is neutralized.

  The dry laminate adhesive for metal films of the present invention is mainly composed of the above polyurethane resin emulsified after neutralization or in the presence of a neutralizing agent as required. General methods for emulsifying a polyurethane resin include the following. If necessary, an emulsifier is used, and a known one can be used as the emulsifier.

In this method, a urethane prepolymer is synthesized using a polyester polyol and a polyisocyanate, and this is dispersed in an aqueous medium using an emulsifier. When this prepolymer and compound (C) are further reacted, the prepolymer is mixed with an aqueous medium. The dispersion and the aqueous solution or dispersion of compound (C) may be reacted before or after being dispersed therein.
Alternatively, a urethane prepolymer having a hydrophilic group is synthesized using a polyol, a polyisocyanate and a compound (C), and this is dissolved or dispersed in an aqueous medium. The hydrophilic group is a polyol and a compound (C The urethane prepolymer may be directly dissolved or dispersed in an aqueous medium, or the organic solvent may be removed after reacting the organic solvent solution or organic solvent dispersion with the aqueous medium.

  A water-dispersible polyvalent isocyanate is used as a curing agent which is an auxiliary agent used in the present invention. Such water-dispersible polyvalent isocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4 ′. -Diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 3,3'dimethoxy-4,4'-biphenylene diisocyanate, 3,3'-dichloro-4, 4-biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate, tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, dodecamethylene diisocyanate Nate, trimethylhexamethylene diisocyanate, 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, xylene diisocyanate, tetramethylxylylene diisocyanate, hydrogenated xylylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, 4,4'- Polyisocyanate compounds such as dicyclohexylmethane diisocyanate, 3,3-dimethyl-4,4′-dicyclohexylmethane diisocyanate, tetramethylxylene diisocyanate, or their isocyanurate type or burette type trifunctional polyisocyanates or polyols having two or more functions The terminal isocyanate group containing prepolymer etc. which are obtained by reaction with a compound can be mentioned.Commercially available self-emulsifiable polyisocyanate compounds include EL436 manufactured by Nippon Soda Co., Ltd., Aquanate AQ-100, AQ-200, AQ-210 manufactured by Nippon Polyurethane Co., Ltd., and Chitabond T- manufactured by Nippon Soda Co., Ltd. 15W, Sumitomo Bayer Urethane Co., Ltd. Despacor 0772 etc. can be mentioned. As the mixing ratio of the water-dispersible resin main agent and the water-dispersible polyvalent isocyanate curing agent, the water-dispersible polyvalent isocyanate curing is performed with respect to an equivalent of 100 functional groups capable of reacting with the isocyanate group contained in the water-dispersible resin main agent. The amount of the isocyanate group equivalent of the agent can be an amount corresponding to an equivalent of 100 to 1200, preferably 400 to 800.

  The target film to which the laminate adhesive composition of the present invention is applied is, for example, a plastic film such as a polyester film, a nylon film, and a polyolefin film, and on these plastic films, aluminum, gold, silver, copper, nickel, chromium, etc. Examples thereof include a deposited film obtained by depositing a metal and a metal film such as an aluminum foil.

In the present invention, as a method of laminating, an extrusion laminating method in which the aqueous laminating adhesive of the present invention is applied to the above various films and a molten resin is back-phased, and an aqueous laminating adhesive of the present invention is applied to the above various films. Any of the dry laminating methods in which a plastic film is applied and the plastic film is laminated can be used, but the aqueous laminating adhesive of the present invention is particularly suitable for the dry laminating method.
In the case of a laminate in which the metal film, the dry laminate adhesive for metal film of the present invention and the film are laminated in this order, the adhesive of the present invention is laminated on the metal film and then another film is laminated. Alternatively, after laminating the adhesive of the present invention on a film, a metal film may be laminated. Moreover, the laminated body of the same kind or different kind of metal films may be sufficient. Moreover, it may be a laminate including two or more adhesive layers.

  Next, the present invention will be described specifically by way of examples. In the examples, “parts” and “%” are all based on weight unless otherwise specified.

Polyester polyols (A) to (D) were prepared according to the formulation shown in Table 1.
Polyester polyol (A)
Terephthalic acid dimethyl ester 206.7 parts, ethylene glycol 48.4 parts, neopentyl glycol 48.7 parts, 1,6-hexanediol 165.9 parts, diethylene glycol 49.7 parts, and zinc acetate 0 as catalyst 0.032 part was charged, and the esterification reaction was carried out while distilling off the methanol produced at 160 to 210 ° C. while substituting with dry nitrogen under normal pressure. After confirming that the amount of methanol distilled out was 95% or more of the calculated value, 176.8 parts of isophthalic acid and 103.7 parts of adipic acid were charged into the reaction vessel, and further esterification was performed at 170 to 230 ° C. It was. When the acid value of the polyester became 20 mgKOH / g or less, 0.32 parts of a 1% solution of titanium tetrabutoxide in ethylene glycol was charged as a catalyst, and then the reaction was completed by gradually increasing the degree of vacuum with a vacuum pump. It was. The obtained polyester polyol (hereinafter referred to as polyester polyol A) had an acid value of 1.9 mgKOH / g and a number average molecular weight of 6,200.

Polyester polyol (B)-(D)
Based on the formulation shown in Table 1, polyester polyols (B) to (D) were obtained by the same procedure as the polyester polyol (A).

Synthesis of Aqueous Polyurethane Resin Next, using the polyester polyols A to D synthesized above, the aqueous polyurethane resins of Synthesis Examples 1 to 3 and Comparative Synthesis Examples 1 to 6 were synthesized according to the formulation shown in Table 2.

(Synthesis Example 1)
A 1000 ml four-necked flask equipped with a thermometer, stirrer, nitrogen inlet tube, and condenser tube was charged with 164.5 parts of polyester polyol A and 3.9 parts of dimethylolbutanoic acid, and the temperature was raised to 90 ° C. while replacing with dry nitrogen. Warmed to clear. Next, 11.6 parts of isophorone diisocyanate was added dropwise over 30 minutes with stirring, and the mixture was further reacted for 3 hours to obtain a polyurethane having a number average molecular weight of about 30,000. After completion of the reaction, the mixture was cooled to 85 ° C., and diluted with 370 parts of methyl ethyl ketone and 90 parts of isopropyl alcohol over 15 to 20 minutes. Further, the mixture was cooled to 75 ° C., and 360 parts of distilled water containing 1.8 parts of 25% ammonia water corresponding to an equimolar amount to the carboxyl group was added over 1 hour to carry out a neutralization reaction. After aging at 65 ° C. for 1 hour, the solvent was removed under reduced pressure at 85 ° C. to obtain an aqueous urethane resin emulsion (A) having a solid content of about 30% by weight.

(Synthesis Examples 2-3, Comparative Synthesis Examples 1-6)
Based on the formulation shown in Table 2, aqueous polyurethane resins of Synthesis Examples 2 to 4 and Comparative Synthesis Examples 1 to 6h were obtained by the same procedure as in Synthesis Example 1.

Preparation of Laminate Adhesive Using Aqueous Polyurethane Resin Next, to the aqueous polyurethane resin synthesized above, a curing agent was added as shown below in the blending amounts shown in Tables 3 and 5, and Examples 1-3 The laminate adhesives of Comparative Examples 1 to 6 were obtained.

  The amount of EL436B (made by Nippon Soda Co., Ltd.), an aqueous isocyanate, was mixed as an adhesive curing agent in 100 parts of the adhesive main agent adjusted to a solid content of 30% by weight immediately before use. To obtain an adhesive. Immediately after mixing, the adhesive thus obtained was subjected to dry lamination on the following films to obtain composite films.

(Laminate film configuration)
PET film 12μm / New fine // Aluminum film 9μm
Aluminum film 9μm // CPP (unstretched polypropylene) film 60μm
NY film 15μm / New fine // CPP film 60μm
New Fine: Solvent-based ink (R39 eye / R630 white) manufactured by Toyo Morton Co., Ltd. Solid color: no ink, white: white ink, overlay: white ink and indigo ink

(Lamination)
An adhesive was applied to each of the PET film, aluminum film, and nylon film at a solid content conversion of 3.5 g / m ² and dried at 80 ° C. for 30 seconds. After drying, an aluminum film or a CPP film was laminated thereon at 50 ° C. and 5 kgf / cm ² . 4 at 40 ° C
Cured for 8 hours.

(Evaluation methods)
For normal strength, the adhesive strength after curing was measured. The retort test was immersed in hot water of about 120 ° C. for 30 minutes, and the subsequent adhesive strength was measured. The adhesive strength was measured by a T peel test according to JIS-Z1701 (food packaging plastic film). The measuring device was a Tensilon type tensile tester, and the test piece width was 15 mm and the tensile speed was 300 mm / min. Tables 4 and 6 show the adhesion performance evaluation test results of this laminate film.

PETf, Nyf: PET film, nylon film break ○: No change in film appearance.
Δ: A small part of the film is delaminated.
X: A part of film is delaminated.

From the above results, the laminate adhesives of Examples 1 to 3 using polyester polyols A to C showed higher adhesion and retort resistance than the adhesives of Comparative Examples 1 to 6.
In the formulation disclosed in JP-A-2004-43519, the total of aromatic dicarboxylic acid and alicyclic dicarboxylic acid is in the range of 10% to 60% by weight of the acid component, and the branched glycol is 30 to 100 of the glycol component. It may be desirable to be in the weight percent range. Comparative Example 6 corresponds to Synthesis Example 2 of Japanese Patent Application Laid-Open No. 2004-43519, but is inferior in terms of adhesive strength and retort resistance as is apparent from Examples 1-3.

  Although the water-based adhesive of the present invention can be dissolved or dispersed in water, it can form a resin layer excellent in water resistance, acid resistance and adhesion, so that it is not limited to water-based adhesives, water-based paints, water-based inks, etc. Can be expected.

Claims (2)

Polyurethane having a terminal hydroxyl group and a hydrophilic group obtained by reacting a polyester polyol (A), a polyisocyanate (B), and a compound (C) having a functional group capable of reacting with an isocyanate group and a hydrophilic group. Based on an aqueous polyurethane resin emulsified resin,
A dry laminate adhesive composition for metal film with a curing agent as an auxiliary agent,
The polyurethane resin has an acid value of 3 to 15 [mg KOH / g], and
The polyester polyol (A) includes an aromatic polycarboxylic acid containing a condensation structure of a polycarboxylic acid and a polyol, and the polycarboxylic acid is more than 60% by weight and not more than 80% by weight based on the whole polycarboxylic acid. A dry laminate adhesive composition for a metal film, comprising: The laminated body formed by laminating | stacking in order of a metal film, the dry-laminate adhesive for metal films of Claim 1, and a film.