JPH10130615A - Polyurethane adhesive composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyurethane adhesive composition excellent in especially alkali resistance, suitability for dry lamination and adhesiveness to substrates such as plastic films and metal foils. SOLUTION: This composition comprises a polyurethane resin having NH groups and NH2 groups and obtained by reacting an organic polyol compound with an organic polyisocyanate compound and a chain extender and having a number-average molecular weight of 2,000-20,000 and an amine value of 5-30 mgKOH/g and an organic polyisocyanate compound or a modified product thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyurethane adhesive composition, and more particularly to a polyurethane adhesive for producing a laminated composite film such as a plastic film and a metal foil.

[0002]

2. Description of the Related Art There has been a great deal of research on adhesives for dry lamination for food packaging, and various types of adhesives having oil resistance and heat resistance with the diversification of foods, sophistication and spread of retort foods. Agents are being developed.
Examples of such an adhesive include a polyurethane-based adhesive obtained by combining a polyester polyol or a polyether polyol with an organic polyisocyanate compound (for example, JP-A-60-243182) and an adhesive obtained by combining a polyamine compound and an epoxy compound. Agents (for example, JP-A-5-202162) are known,
Laminated products have been obtained using such adhesives.

[0003] On the other hand, the content itself packaged by such a laminated product has been expanded from conventional dry foods and retort pouch foods to other foods and non-foods,
The demand for laminated products that can store their contents stably for a long period of time has increased, and the performance of laminate adhesives that can laminate various plastic films, metal foils, etc. has been required along with the diversification and high functionality of laminated products. ing.

[0004]

Other foods and non-foods that are to be newly packaged with laminates include:
For example, there are oils, alcoholic beverages, bath additives, liquid detergents, liquid waxes, and the like that have been conventionally sealed and stored in containers such as glass bottles, metal cans, and plastic bottles. The demand for products packed in packaging materials is increasing. However, these contents
For example, they often contain alkaline substances, fragrances, surfactants, high-boiling organic solvents, and so on. Diverting a packaging for food packaging that has been laminated using a conventional adhesive as it is, and packaging them as a product Could not.

Specifically, for example, when packaging a highly alkaline content containing an organic alkaline substance, a long-term storage test reduces the adhesive strength between the metal foil and the plastic film or the plastic film constituting the laminate. And in extreme cases, it completely peels off,
The strength as a packaging material also deteriorated, and it could not withstand long-term storage. This is because the adhesive used during lamination does not have alkali resistance, and the conventional adhesive for food packaging can be used as a laminate package for packaging highly alkaline contents. could not.

[0006] Lamination processing by dry lamination is generally produced by applying an adhesive having a solid content of 20 to 40% to a film, drying the solvent, bonding the resultant, and winding the obtained laminated product. 1 to 10 g / m ² (as solid content)
The laminating speed is often 50 to 200 m / min. Therefore, the adhesive for dry lamination is required to be suitable for dry lamination that can be easily used under such laminating film production conditions. The suitability for dry lamination includes, for example, the solid content of the adhesive, the solubility in a solvent, the viscosity of the adhesive, the drying property, the pot life, and the on-machine stability of the adhesive. Among them,
In particular, pot life and on-machine stability are important. After mixing the main agent and the curing agent, those that rapidly react and increase the viscosity cannot be used. It is necessary to have stability.

As described above, in developing an adhesive for dry lamination, both the alkali resistance and the adhesiveness must be taken into consideration, and the suitability for dry lamination must be taken into account, and both must be satisfied at the same time.

Accordingly, the present invention provides a polyurethane adhesive composition having particularly excellent alkali resistance, excellent dry lamination suitability, and a performance capable of satisfying adhesive strength to various plastic films and metal foils. With the goal.

[0009]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, reacted a polyurethane resin having an NH group and an NH ₂ group with an excessive amount of an organic isocyanate compound. As a result, the inventors have found that alkali resistance is improved as compared with known polyurethane adhesives, and reached the present invention.

That is, the alkali-resistant adhesive composition of the present invention comprises an NH group and an NH group obtained by reacting an organic polyol compound, an organic polyisocyanate compound and a chain extender.
It is characterized by blending a polyurethane resin having _two groups with an organic polyisocyanate compound or a modified product thereof.

Further, the adhesive composition of the present invention comprises the above NH
The polyurethane resin having a group and an NH ₂ group has a number average molecular weight of 2,000 to 20,000 and an amine value of 5 to 30 mgKOH / g.

Further, the adhesive composition of the present invention is characterized in that the polyurethane resin and the organic polyisocyanate compound or a modified product thereof are obtained by combining the organic polyisocyanate compound or the organic polyisocyanate compound with the number of active hydrogen-containing groups contained in the polyurethane resin. Is characterized in that it is blended in a ratio of the number of isocyanate groups contained in the modified product of from 1 to 20, and is further characterized by blending a silane coupling agent. Hereinafter, the present invention will be described in detail.

The polyurethane resin containing an NH group or an NH ₂ group used in the present invention is a polyurethane resin obtained by adding an organic polyol, an organic polyisocyanate compound, a chain extender and, if necessary, a terminal terminator and reacting them. Yes, to obtain an adhesive composition having excellent alkali resistance by using the obtained polyurethane resin as a main component, using a polyisocyanate-based compound as a curing agent in place of the epoxy compound conventionally used in this, and blending these. Can be.

As described above, an alkali-resistant adhesive can be obtained by using a polyurethane resin and a polyisocyanate compound. However, the reaction between an NH group or an NH ₂ group and an isocyanate group is extremely fast, and the obtained cured product can be obtained. Has a high crosslinking density. Therefore, when both react rapidly when they are mixed and cured, it becomes inconvenient to use as an adhesive for lamination in various points such as pot life and adhesive properties. Therefore, considering the so-called dry lamination suitability such as suitability for a laminating apparatus when manufacturing a laminate film and the characteristics of the adhesive itself, the molecular weight of the polyurethane resin, NH group or NH
The content of the _two groups is important.

When considering the suitability for lamination, the polyurethane resin used in the present invention has a number average molecular weight of 2,000 to 20,000, more preferably 5,000 to 5,000.
000. When the number average molecular weight is less than 2,000, the initial adhesive strength tends to be low, and the alkali resistance tends to decrease. When the number average molecular weight exceeds 20,000, the solution viscosity increases and the dry lamination suitability, that is, coating The properties and the appearance of the laminate tend to be poor.

The content of NH groups or NH ₂ groups in the polyurethane resin is 5 to 30 mg KOH / g, preferably 5 to 20 mg KOH / g, when this content is represented by an amine value.
It is in the range of KOH / g. Amine value is 30mgKOH /
If it exceeds g, the curing reaction will be accelerated, and the pot life and curing characteristics will be affected on dry lamination suitability. In addition, NH groups or NH in the polyurethane resin
_Two units affect performance such as adhesion and alkali resistance,
From this aspect, the higher the amine value, the better. However, even if a polyurethane resin having an amine value of more than 30 mgKOH / g is used, further improvement in adhesion and alkali resistance cannot be expected, and the amine value is 5 mgKOH / g. If it is less than / g, a sufficient crosslink density cannot be obtained, and the adhesive strength tends to be slightly lowered.

The amine value is defined as polyurethane resin 1
g, the total basic nitrogen contained in g, ie, NH group or NH
_It represents the number of mg of perchloric acid and an equivalent amount of potassium hydroxide required to neutralize the _two groups, and is defined by JIS K7237.
This is determined by titrating a polyurethane resin according to the “Test Method for Total Amine Value of Amine-Based Curing Agent for Epoxy Resin”.

Examples of the organic polyisocyanate compound or a modified product thereof which can be used as a curing agent in the present invention include an isocyanate compound containing two or more isocyanate groups, and adducts, burettes, uretidiones, and isocyanurates of these isocyanate compounds. Body and the like.

Examples of the isocyanate compound include 1,6-hexamethylene diisocyanate (HD
I) aliphatic polyisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate and lysine methyl ester diisocyanate; hydrogenated diphenylmethane diisocyanate, isophorone diisocyanate (IP
DI), alicyclic polyisocyanates such as hydrogenated tolylene diisocyanate; tolylene diisocyanate (TD)
I) and aromatic polyisocyanates such as 4,4'-diphenylmethane diisocyanate (MDI), naphthylene diisocyanate, xylylene diisocyanate (XDI), triphenylmethane triisocyanate, and tris (4-phenyl isocyanate) thiophosphate.

As an adduct body, for example, MD
An adduct obtained by reacting I, TDI, HDI, XDI, IPDI, etc. with a dihydric or trihydric polyhydric alcohol, HD
Examples include burettes such as I and IPDI, uretidiones such as TDI, and isocyanurates such as TDI, HDI and IPDI, and a mixture of two or more of these compounds may be used. Of these, aliphatic polyisocyanates are preferred in terms of pot life.

The polyurethane-based adhesive composition according to the present invention comprises a main component which is a polyurethane resin having the above-mentioned NH group and NH ₂ group and a curing agent component which is a polyisocyanate compound having a terminal NCO group or a modified product thereof. As the main component, an alkali-resistant adhesive can be obtained by mixing the two, but considering the suitability for dry lamination, the mixing ratio of the two is based on the number of the organic polyisocyanate compound or the number of active hydrogen-containing groups contained in the polyurethane resin. The ratio of the number of isocyanate groups contained in the modified products, that is, “(the number of NCO groups in the curing agent) /
(The number of groups having active hydrogen in the main agent) "is 1 to 20, preferably 5 to 10.

The group having an active hydrogen contained in the polyurethane resin refers to a functional group containing a hydrogen capable of reacting with an NCO group.
—HCONH— and —NH generated by reacting with NH ₂ groups such as —OCONH— and polyamine generated by reacting with H group
NH groups such as CONRCONH-, terminal NH ₂ groups and OH groups remaining unreacted, and reaction of NH groups and terminals of -HNCONH- generated by the reaction of alkanolamine used as a terminal terminator with isocyanate groups. Not including OH groups.

It is necessary to adjust the blending ratio of the two to 1 to 20 in order to adjust the degree of crosslinking and also to adjust the curing speed and the physical properties of the cured product. The adhesive for use has a tendency to decrease slightly, and when it exceeds 20, a decrease in adhesion and a tendency to remain unreacted isocyanate are observed.

Further, particularly when laminating a metal foil such as an aluminum foil, when a silane coupling agent is blended with the adhesive composition of the present invention, the adhesion between the aluminum foil and the resin film is further enhanced, and a favorable result is obtained. Can be The silane coupling agent used in the present invention has the following formula

Embedded image (Wherein R represents an organic group having a vinyl group, an epoxy group, an imino group or a mercapto group, R ′ represents a lower alkyl group, and X represents a methoxy group, an ethoxy group or a chlorine atom). For example, chlorosilanes such as vinyltrichlorosilane; n- (dimethoxymethylsilylpropyl) ethylenediamine, n-
(Triethoxysilylpropyl) ethylenediamine, γ
Aminosilanes such as -aminopropyltrimethoxysilane; epoxysilanes such as γ-glycidoxypropyltrimethoxysilane; vinylsilanes such as vinyltriethoxysilane. In addition, these silane coupling agents are usually added to the polyurethane resin component, and a sufficient effect can be obtained at about 1.0% by weight based on the whole adhesive composition.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The NH group or N
The polyurethane resin containing an H ₂ group is the target NH 2
Organic polyol compound, in consideration of the degree of polymerization of the polyurethane resin containing a group or an NH ₂ group, an amine value, and the like.
It is obtained by reacting an organic polyisocyanate compound and a chain extender.First, an organic polyol compound and an organic polyisocyanate compound are reacted to produce a prepolymer having an isocyanate group at a terminal, and then, these prepolymers are produced. By a known method such as a prepolymer method of obtaining a polyurethane by reacting a chain extender with the resin, or a one-shot method of obtaining a polyurethane by reacting an organic polyol compound, an organic polyisocyanate compound and a chain extender in one step. Can be.

As the organic polyol compound used as a raw material for preparing the polyurethane resin used in the present invention, those usually used in the production of polyurethane can be used, such as polyethers, polyesters and polyetheresters. And these can be used alone or as a mixture of two or more.

The polyethers are those obtained by homo- or copolymerizing alkylene oxides, such as polyethylene glycol, polypropylene glycol,
Examples include polyethylene propylene glycol, polytetramethylene ether glycol, and polyhexamethylene ether glycol. Examples of the polyvalent hydroxyl compound include trimethylolpropane, hexanetriol, glycerin, pentaerythritol and the like.

As the polyesters, dibasic acids (for example, succinic acid, glutaric acid, adipic acid, sebacic acid,
Fumaric acid, maleic acid, phthalic acid, etc.) or their anhydrides and glycols (eg, ethylene glycol,
Aliphatic glycols such as diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, butanediol, pentanediol, hexanediol, octanediol and nonanediol; alicyclic glycols such as bishydroxymethylcyclohexane; xylylene glycol Aromatic glycols; alkyl dialkanolamines such as C1 to C18 alkyldiethanolamines) and condensation polymerization polyester polyols such as polyethylene adipate, polybutylene adipate and polyhexamethylene adipate; or Polylactone diol, polycaprolactone diol, polymethyl vale obtained by subjecting lactone to ring-opening polymerization using the above diols and the like as an initiator. Lactone-based polyester diols such as lolactone diol are exemplified.

The polyetherester diols can be obtained by reacting a mixture with an ether group-containing diol or another glycol by reacting the dicarboxylic acid with an anhydride thereof, or by reacting a polyester glycol with an alkylene oxide. Examples thereof include poly (polytetramethylene ether) adipate. In addition, polycarbonate diols can also be used.

The organic polyisocyanate compound used for producing the polyurethane resin in the present invention includes 2,4- or 2,6-tolylene diisocyanate, xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, Methylene diisocyanate, isopropylene diisocyanate, lysine diisocyanate, 2,2,4- or 2,4,4-trimethylhexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate (IPD
I), 4,4'-dicyclohexylmethane diisocyanate, isopropylidene dicyclohexyl-4,4'-
And diisocyanates. These can be used alone or in combination of two or more.

The polyurethane resin can be produced, for example, by using a prepolymer method as follows. That is, first, the above-mentioned organic polyol compound and organic polyisocyanate compound are reacted at a temperature of 10 to 150 ° C. using an inert solvent for an isocyanate group, if necessary, and further using a urethane-forming catalyst if necessary. To produce a prepolymer having terminal isocyanate groups.

In preparing the prepolymer, the amount of the organic polyol compound and the amount of the organic polyisocyanate compound are determined by the NCO / OH ratio, which is the ratio of the equivalent of the isocyanate group of the organic polyisocyanate compound to the equivalent of the hydroxyl group of the organic polyol compound. It is preferable that the ratio be in the range of 1.1 to 3.0. When this ratio is smaller than 1.1, sufficient alkali resistance tends not to be obtained.
When it is larger than 3.0, the solubility of the obtained prepolymer tends to decrease.

The reaction is preferably carried out using a solvent from the viewpoint of controlling the reaction. As the solvent that can be used, those that can dissolve the polyurethane adhesive composition are preferable, and examples thereof include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ethers such as dioxane and tetrahydrofuran;
Aromatic hydrocarbons such as xylene; esters such as ethyl acetate and butyl acetate; halogenated hydrocarbons such as chlorobenzene and perchrene; and the like can be used as a mixed solvent by mixing two or more kinds thereof.

Further, in this urethanization reaction,
A catalyst can also be used. Catalysts that can be used include:
For example, 3 such as triethylamine and dimethylaniline
Secondary amine catalysts; and metal catalysts such as tin and zinc. These catalysts are usually used in the range of 0.001 to 1 mol% based on the polyol compound.

Then, the obtained prepolymer having an isocyanate group at a terminal is reacted with a chain extender such as diol, diamine, or triol at 10 to 80 ° C. to produce a high-molecular-weight polyurethane having an active hydrogen group at a terminal. obtain.

As the chain extender to be used, there may be mentioned a low molecular weight diamine or a low molecular weight diol used in usual production of polyurethane. Examples of the diamine include aliphatic diamines such as ethylenediamine, 1,2-propylenediamine, and hexamethylenediamine; isophoronediamine (IPDA), dicyclohexyl-4,4′-diamine, 1,4-diaminocyclohexane, and 1,3-bis. There are alicyclic diamines such as aminomethylcyclohexane, and these can be used alone or in combination of two or more.

On the other hand, the low molecular diol is preferably a low molecular diol having a molecular weight of less than 500, for example, aliphatic glycols such as ethylene glycol and 1,4-butanediol and aromatic glycols such as xylylene glycol and bishydroxyethoxybenzene. Glycols,
By performing a chain extension reaction using these in combination with a diamine-based chain extender, an NH ₂ group can also be introduced. Among these chain extenders, diamine-based ones can easily increase the molecular weight because of high reactivity.

The chain extender reacts with the isocyanate group of the prepolymer, and connects the prepolymers to each other through the functional group of the chain extender to form a polymer. Gradually increase and become large. However, in consideration of suitability for dry lamination, it is necessary to control the molecular weight and amine value of the polyurethane resin, for example, to obtain an adhesive suitable for coating. In such a case, when a monoalcohol or a monoamine is used as a terminal stopper together with a chain extender, an increase in molecular weight can be suppressed. This is because the terminating agent competes with the chain extender to generate a terminal having no OH group or NH ₂ group, the prepolymer cannot be bonded, and the chain extension reaction does not occur. Can be reduced in molecular weight.

For the terminating agent used, the reactivity between the chain extender and the terminating agent with respect to isocyanate is important, and not only monofunctional compounds such as monoalcohols and monoamines, but also different reactivities with isocyanate. Compounds having two types of functional groups can be used, for example, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol,
monoalcohols such as tert-butyl alcohol; monoamines such as monoethylamine, n-propylamine, diethylamine, di-n-propylamine and di-n-butylamine; alkanolamines such as monoethanolamine and diethanolamine. Among them, alkanolamines are preferable because the reaction can be easily controlled.

When a terminal terminating agent is used, the chain terminating agent may be used together with the chain extender to carry out the chain extension reaction. The terminal termination reaction may be performed by adding alone. On the other hand, the molecular weight can be controlled without using a terminal terminator, but in this case, a method of adding a prepolymer to a solution containing a chain extender is preferable from the viewpoint of reaction control.

The terminating agent is used to control the molecular weight. As the amount used increases, the molecular weight of the obtained polyurethane resin decreases. This degree varies depending on the reactivity of the chain extender and the terminator with the prepolymer, but generally, the ratio of the equivalent of the amino group or hydroxyl group of the chain extender to the equivalent of the amino group or hydroxyl group of the terminator is 0.1. 5
The range of -5.0 is preferable. When this ratio exceeds 5.0, the suitability for dry lamination tends to be deteriorated due to the high molecular weight, and when it is less than 0.5, the molecular weight and the initial adhesive strength tend to decrease.

The ratio of the total equivalent of the amino group and the hydroxyl group of the chain extender and the terminal terminator to the equivalent of the isocyanate group in the prepolymer is 1.1 to 3.0, preferably 1.5 to 2.0. The reaction is carried out so as to be within the range.
When this ratio is large and the amount of the chain extender or terminal terminator used is large, the chain extender or terminal terminator remains unreacted and odor tends to remain.

The polyurethane adhesive composition of the present invention comprises:
A two-pack type adhesive comprising, as a main component, the polyurethane resin having an NH group or an NH ₂ group obtained as described above, and a polyisocyanate compound or a modified product thereof as a curing agent. Groups (eg, NH
Groups, NH ₂ groups or OH groups) in the curing agent
Good adhesiveness is exhibited by mixing both such that the ratio of groups is in the range of 1 to 20. When preparing the adhesive, an appropriate amount of the above-mentioned urethanization catalyst and other additives such as a silane coupling agent and an antioxidant can be added to promote the reaction, if necessary.

The polyurethane-based adhesive of the present invention is particularly preferable as an adhesive for dry lamination. Examples of the laminating substrate include various plastics such as polyethylene film, polypropylene film, nylon film and polyester film and aluminum foil. Such as metal foil and paper.

To bond using the adhesive of the present invention, the adhesive is applied to one surface of one of the laminated substrates by a commonly used method, for example, a dry laminator.
After the solvent is volatilized, it may be bonded to the other laminate substrate and cured at room temperature or under heating. The amount of the adhesive applied to the surface of the laminate substrate is 1 to 10 g / m ^2.
(Solid content).

[0046]

Next, the present invention will be described in more detail by way of examples.

Polyurethane Resin Synthesis Example 1 A four-necked flask equipped with a stirrer, thermometer, reflux condenser and dropping funnel was charged with a number average molecular weight of 1,000 and a hydroxyl value of 11 in a four-necked flask.
700 parts by weight of 0 mg KOH / g polypropylene glycol, number average molecular weight 2000, hydroxyl value 56 mg KOH
/ G of polypropylene glycol, 21.3 parts by weight of dipropylene glycol and 263.7 parts by weight of tolylene diisocyanate, and reacted at 80 ° C. for 6 hours to obtain a prepolymer containing 3.74% by weight of free isocyanate. Was. Then, methyl ethyl ketone 682.
After adding 0 parts by weight and 682.0 parts by weight of ethyl acetate to make a homogeneous solution, 60.1 parts by weight of isophoronediamine, N-
40.1 parts by weight of (β-aminoethyl) ethanolamine was reacted at 30 ° C. for 3 hours while stirring to obtain a polyurethane solution A (nonvolatile content: 50%). About the obtained polyurethane resin, the number average molecular weight was determined by GPC.
When the amine value was determined by neutralization titration using 0.1 N hydrochloric acid according to JIS K7237, the number average molecular weight was 7
000, amine value was 15.0 mgKOH / g.

[0048] As the silane coupling agent to the polyurethane solution A, 100 by weight portion was synthesized in the same manner γ-
0.5 parts by weight of each of aminopropyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane were added, and a polyurethane solution A-1 (non-volatile content: 50%) was added.
%) And A-2 (nonvolatile content 50%).

Polyurethane Resin Synthesis Example 2 In the same apparatus as in Synthesis Example 1, 700 parts by weight of polytetramethylene ether glycol having a number average molecular weight of 1,000, 300 parts by weight of polytetramethylene ether glycol having a number average molecular weight of 2,000, and 21.3 were used. Parts by weight and 263.7 parts by weight of tolylene diisocyanate were charged and reacted at 80 ° C. for 6 hours to obtain a prepolymer having an organic isocyanate content of 3.78% by weight. Then, 698.0 parts by weight of methyl ethyl ketone, 69 ethyl acetate
After adding 8.0 parts by weight to make a uniform solution, 100.5 parts by weight of isophoronediamine was reacted at 30 ° C. for 3 hours while stirring, to obtain a number average molecular weight of 13,000 and an amine value of 5.2 m.
gKOH / g polyurethane solution B (50% non-volatile content)
I got

Further, 0.5 parts by weight of γ-aminopropyltrimethoxysilane as a silane coupling agent was added to 100 parts by weight of the polyurethane solution B to prepare a polyurethane solution B-1 (nonvolatile content: 50%).

Polyurethane Resin Synthesis Example 3 Adipic acid-based polyester polyol having a number average molecular weight of 1000 (product name: Adecan New Ace YG-108, hydroxyl value: 110, manufactured by Asahi Denka Kogyo Co., Ltd.) in the same apparatus as in Synthesis Example 1 Parts, dipropylene glycol 23.7
Parts by weight and 136.8 parts by weight of ethyl acetate to prepare a homogeneous solution, 312.2 parts by weight of tolylene diisocyanate was added, and the mixture was reacted at 80 ° C. for 6 hours to give a prepolymer having a free isocyanate content of 2.64% by weight. Obtained. Next, 712.5 parts by weight of methyl ethyl ketone and 575.7 parts by weight of ethyl acetate were added to form a uniform solution, and 53.4 parts by weight of isophoronediamine and 35.6 parts by weight of N- (β-aminoethyl) ethanolamine were added. 3 with stirring
The mixture was reacted at 0 ° C. for 3 hours to obtain a polyurethane solution C having a number average molecular weight of 6,500 and an amine value of 18.8 mgKOH / g (nonvolatile content: 50%).

To 100 parts by weight of the polyurethane solution C, 0.5 parts by weight of γ-aminopropyltrimethoxysilane was added as a silane coupling agent to prepare a polyurethane solution C-1 (nonvolatile content: 50%).

Synthetic Example 4 of Polyurethane Resin The same apparatus as in Synthetic Example 1 was charged with 1,000 parts by weight of polypropylene glycol having a number average molecular weight of 1,000 and 180.8 parts by weight of tolylene diisocyanate, and reacted at 80 ° C. for 6 hours to obtain a free isocyanate content. 0.42% by weight of the prepolymer was obtained. Then, methyl ethyl ketone 605.
After adding 1 part by weight and 605.1 parts by weight of ethyl acetate to form a uniform solution, 30.1 parts by weight of isophoronediamine was reacted at 30 ° C. for 3 hours while stirring, and the number average molecular weight was 190.
00, a polyurethane solution D having an amine value of 27.4 mgKOH / g (nonvolatile content: 50%).

Further, 0.5 parts by weight of γ-aminopropyltrimethoxysilane as a silane coupling agent was added to 100 parts by weight of the polyurethane solution D to prepare a polyurethane solution D-1 (nonvolatile content: 50%).

Examples 1 to 6 A polyurethane solution obtained by a polyurethane resin synthesis example and a trimethylolpropane adduct of TDI (ethyl acetate 75% by weight solution, isocyanate content 13%, and −TMP ”)
Or a trimethylolpropane adduct of HDI (75% by weight solution of ethyl acetate, isocyanate content 12.
8%, indicated as “HDI-TMP” in Table 1), the components were blended in the number of parts shown in Table 1, and 25 to 30 with ethyl acetate.
% By weight to obtain an adhesive solution. The resulting adhesive was evaluated as a measure of lamination suitability at the time of mixing and 2
The Zahn cup viscosity after 48 hours at 5 ° C. was measured.
The measurement was carried out by measuring the solution outflow time using Zahn Cup # 3.

Table 1 shows the obtained results. The "mixing ratio" in the table indicates the ratio of the number of isocyanate groups contained in the organic polyisocyanate compound or a modified product thereof to the number of groups having active hydrogen contained in the polyurethane resin, and the amount of each component used. Is the value obtained from

[0057]

[Table 1] Next, in order to test the alkali resistance of the adhesive, a laminated product was prepared using each of the obtained adhesive compositions.
% Ethylenediamine aqueous solution was sealed and an alkali resistance test was performed as follows.

(1) Laminating Method Each of the adhesive compositions shown in Table 1 was previously prepared by using a polyester film (PET; thickness, 12 μm) and an aluminum foil (A
L; thickness, 9 μm) was applied by a dry laminator so that the dry coating amount was 3.5 g / m ^2, and the solvent was evaporated. A nylon film (NY; 15 μm in thickness) subjected to corona discharge treatment was bonded. Then, the same adhesive is applied to the NY surface by a dry laminator, and after the solvent is dried, a low-density polyethylene film (LLDPE; thickness: 50 μm) is attached to the adhesive surface, and then aged at 40 ° C. for 4 days. The adhesive was cured to obtain a laminate made of PET / AL / NY / LLDPE.

Similarly, an adhesive was applied to the printing surface of a nylon film print (ink; NEW LP Super (trade name, manufactured by Toyo Ink Mfg. Co., Ltd.)) with a dry laminator (dry coating amount: 3.5 g / m ² ), after the solvent is evaporated, a low-density polyethylene film (LLDPE; thickness 50 μm) is bonded to the adhesive surface,
Aged at 40 ° C for 4 days to cure the adhesive, NY
/ LLDPE was obtained.

(2) Alkali Resistance Test The obtained laminated product was cut into a size of 9 cm × 12 cm, two sheets were overlapped with the LLDPE surface inside, and the ends were heat-sealed (heat-sealing width: 5 mm, heat-sealed). (Seal temperature: 160 ° C.) to produce a bag. Then, a 5% aqueous solution of ethylenediamine (pH, 1
1.9) was filled therein, the opening was heat-sealed and sealed, and then placed in a hot-air circulating oven set at 50 ° C. and stored. After 2 weeks, the condition was visually observed and according to the following criteria. evaluated.

○: no change in appearance.

Δ: Slight pinhole-shaped delamination is observed.

X: Continuous occurrence of delamination is observed.

Table 2 shows the results.

[0065]

[Table 2] Comparative Example 1 As a comparison, a conventional dry laminate adhesive for food was used. That is, a polyester polyol (product name: AD-502, a 50% by weight solution of ethyl acetate, manufactured by Toyo Morton Co., Ltd.) was used as a main agent as a urethane-based adhesive, and a trimethylolpropane adduct of TDI was used as a curing agent in the same manner as in Example. Prepared and evaluated. The results are shown in Tables 1 and 2.

Comparative Example 2 As an example of an epoxy curing agent for a food-grade dry laminating adhesive, an epoxy resin solution (product name: CAT-EP) was added to the polyurethane solution A obtained in polyurethane resin synthesis example 1.
I, 84% by weight of ethyl acetate, manufactured by Toyo Morton Co., Ltd.)
Was prepared and evaluated in the same manner as in the examples. The results are shown in Tables 1 and 2.

According to Tables 1 and 2, the NH group and N
It can be seen that a laminated product prepared using an adhesive comprising a polyurethane resin having an H ₂ group and an isocyanate can store an alkaline substance for a long period of time, and that the adhesive has alkali resistance. this is,
Isocyanate group of curing agent and NH _{2 of} polyurethane resin
The urea bond generated by the reaction of the group has a higher alkali resistance than the urethane bond. Further, the NH group generated by the chain extension reaction or the NH group in the urea bond generated by the reaction with the curing agent further contains isocyanate. It is presumed that it reacts with a group to form a crosslinked structure.

When the adhesive composition of the present invention is used as an adhesive for dry lamination, considering the suitability for dry lamination from the viewpoint of operability during dry lamination, the suitability for dry lamination mainly depends on the polyurethane resin used. It can be seen that favorable results are obtained when the molecular weight is 2,000 to 20,000 in number average molecular weight and the amine content is 5 to 30 mgKOH / g in amine value, affected by the molecular weight and amine content. Also, the mixing ratio of the main agent and the curing agent is
It is thought to affect the curing speed and the properties of the adhesive, but good results are shown within the experimental range.

The system to which the silane coupling agent was added showed better adhesiveness to the base material than the case where no silane coupling agent was added.

[0070]

As described above, the polyurethane adhesive composition of the present invention comprises:
Shows excellent resistance even when filled with highly alkaline contents compared to conventional polyurethane-based adhesives,
It can be stably stored for a long time, and is useful as an adhesive for dry lamination. In addition, it has excellent suitability for dry lamination, and has excellent adhesiveness to various plastic films such as polyolefin films, polyester films, and nylon films.

Claims (4)

[Claims] 1. An alkali-resistant adhesive comprising a polyurethane resin having an NH group and an NH ₂ group obtained by reacting an organic polyol compound, an organic polyisocyanate compound and a chain extender with an organic polyisocyanate compound or a modified product thereof. Composition. _2. A polyurethane resin having an NH group and an NH ₂ group obtained by reacting an organic polyol compound, an organic polyisocyanate compound and a chain extender, wherein the polyurethane resin has a number average molecular weight of 2,000 to 2,000.
In the range of 20,000 and an amine value of 5 to 30 mg KO
An adhesive composition comprising the polyurethane resin in the range of H / g and an organic polyisocyanate compound or a modified product thereof. 3. The mixing ratio of the polyurethane resin and the organic polyisocyanate compound or a modified product thereof is such that the mixing ratio of the organic polyisocyanate compound or the modified product thereof to the number of active hydrogen-containing groups contained in the polyurethane resin. The adhesive composition according to claim 1, wherein the ratio of the number of isocyanate groups contained in the adhesive composition is in the range of 1 to 20. 4. 4. The adhesive composition according to claim 1, further comprising a silane coupling agent.