JPH06322352A - Aqueous adhesive composition - Google Patents

Abstract

PURPOSE:To provide an aqueous adhesive composition which comprises a specific urethane polymer and a tackifier and can be used as an adhesive for materials of low heat resistance because it shows satisfactory adhesion, even when the temperature is low on thermocompression bonding, and high water resistance. CONSTITUTION:The adhesive composition comprises 100 pts.wt. (on the solid basis) of a urethane polymer self-dispersible in water which is obtained by reaction of the following essential components: (A) one or more compounds bearing active hydrogen atoms reactive with isocyanate groups in its molecule, (B) aliphatic or aromatic polyisocyanate and (C) compounds bearing one or more ionic or latently ionic functional groups or nonionic and hydrophilic functional groups in its molecule, and further having functional groups containing active hydrogen atoms reactive with isocyanate groups, and preferably 5 to 200 pts.wt. of a tackifier such as gum rosin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a urethane-based water-based adhesive composition which is excellent in normal state adhesiveness and water-resistant adhesiveness, and can obtain sufficient adhesive force even at low temperature during thermocompression bonding. is there.

[0002]

2. Description of the Related Art Urethane-based adhesives have excellent adhesiveness to a wide range of adherends, have characteristics such as flexibility, and are widely used because they are suitable for many purposes. . On the other hand, from the viewpoints of air pollution due to volatilization of organic solvent, deterioration of working environment, risk of fire occurrence, etc., in the field of urethane-based adhesives, development in consideration of conversion to water-based adhesives has been actively conducted in recent years.

However, in the water-based urethane adhesive, generally, when the urethane polymer is water-dispersed with an emulsifier, the emulsifier remains in the dried film to deteriorate the water resistance of the film. Therefore, when bonding is performed using such an adhesive composition, there is a problem in that the cohesive force of the adhesive layer is reduced due to water absorption and the water resistance thereof is significantly deteriorated.

To solve this problem, for example, as described in JP-A-3-21626, an isocyanate compound, a polyol having a carboxyl group and / or
Alternatively, by reacting an amino acid and a urethane group-containing prepolymer containing a carboxyl group with a basic organic compound and an extender in the presence of a solvent and water, a carboxyl group is introduced into the polyurethane chain to improve the water resistance of the film. A method for producing an improved quick-drying aqueous resin solution has been proposed.

By the way, as a bonding method using such an adhesive, there is often adopted a method in which the adhesive is coated on both sides of the adherends to be bonded and then dried, and the surfaces of the adhesives are thermocompression bonded. The temperature at this time must be equal to or higher than the lowest temperature (heat activation temperature) at which the adhesive layer can exhibit a sufficient adhesive force. This is because if pressure bonding is performed at a temperature that does not reach the heat activation temperature, the fluidity of the adhesive layer is small, so that a sufficient effective bonding area cannot be obtained and the adhesive force after pressure bonding is also reduced.

However, the adhesive having a carboxyl group introduced into the polyurethane chain as described above has a high heat activation temperature. It is considered that this is because the polymer introduced with a carboxyl group generally contains a large number of highly polar functional groups, the interaction between the polymers is large, and the elastic modulus of the film is high. In order to perform thermocompression bonding with an adhesive having such a high thermal activation temperature, it is necessary to increase the pressure bonding temperature. However, when the pressure bonding temperature is increased, it is attempted to bond the adherends having low heat resistance. Various problems such as deformation and deterioration of the adherend occur.

Further, as described in JP-A-59-51253, an ethylene oxide unit for the purpose of introducing a nonionic hydrophilic group in combination with an ionic functional group in the molecule is used. Aqueous dispersions of polyurethane-urea containing hydrophilic side and / or terminal chains have been proposed. By using this aqueous dispersion, the increase in elastic modulus as described above can be suppressed. However, the nonionic hydrophilic group needs to be used in a large amount in order to obtain good dispersion stability, and if a large amount of the hydrophilic group remains in the film, it does not lead to improvement in water resistance of the film.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides a urethane-based water-based adhesive which has excellent adhesiveness and water-resistant adhesiveness under normal conditions, and which can provide sufficient adhesiveness even when the temperature during thermocompression bonding is relatively low. It was made for the purpose of providing a composition.

[0009]

Means for Solving the Problems The present invention comprises (a) at least one compound having an active hydrogen atom capable of reacting with an isocyanate group in the molecule, and (b) an aliphatic or aromatic organic poly An isocyanate compound and (c) a molecule having at least one functional group of an ionic or potentially ionic functional group or a nonionic hydrophilic group,
Further, an adhesive comprising a compound having a functional group containing an active hydrogen atom capable of reacting with an isocyanate group as an essential component, a urethane polymer self-dispersible in water obtained by the reaction of these compounds, and a tackifier. It is a composition.

In the present invention, the compound (a) having an active hydrogen atom capable of reacting with an isocyanate group in the molecule includes polyols having two or more hydroxyl groups in the molecule and two or more primary groups in the molecule. Alternatively, polyamines having a secondary amino group and the like are used, and among them, polyols are preferably used.

Examples of polyols include polyhydric alcohols such as ethylene glycol, diethylene glycol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane and glycerin, and polyether polyols such as polyethylene glycol and polypropylene glycol. , Adipic acid, sebacic acid, itaconic acid,
Obtained from dicarboxylic acids such as maleic anhydride, terephthalic acid and isophthalic acid and glycols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, 1,6-hexanediol, tripropylene glycol and neopentyl glycol Examples thereof include polyester polyols, polycaprolactone polyols, polytetramethylene ether glycols, polybutadiene polyols, hydrogenated polybutadiene polyols, polycarbonate polyols, polythioether polyols and polyacrylic ester polyols.

These polyols may be used singly or in a mixture of two or more kinds, and may be properly selected according to the purpose and application, and required physical properties such as hardness and adhesiveness. Can be designed arbitrarily.

In the present invention, as the aliphatic or aromatic organic polyisocyanate compound (b), an organic polyisocyanate compound containing two or more isocyanate groups in the molecule is used.

Examples of such organic polyisocyanate compounds include 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate,
2,4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, dicyclohexylmethane-4,4'-diisocyanate, methylcyclohexyl- Aliphatic diisocyanates such as 2,4-diisocyanate, methylcyclohexyl-2,6-diisocyanate, xylylene diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, tetramethylxylylene diisocyanate, transcyclohexane-1,4-diisocyanate , 2,4-toluylene diisocyanate, 2,6-toluylene diisocyanate, diphenylmethane-4,4'-diisocyanate,
Aromatic diisocyanates such as 1,5-naphthene diisocyanate, tolidine diisocyanate, tetraalkyldiphenylmethane diisocyanate and paraphenylene diisocyanate, lysine diisocyanate, lysine ester triisocyanate, triphenylmethane triisocyanate, 1,6,11-undecane triisocyanate, 1 , 8-diisocyanate-4-isocyanate, methyloctane, 1,3,6-hexamethylene triisocyanate, bicycloheptane triisocyanate, and other triisocyanates. These organic polyisocyanate compounds may be used alone or 2
You may use it in mixture of 2 or more types.

In the present invention, the compound (c) is
Having one or more ionic or potentially ionic functional groups or at least one functional group of nonionic hydrophilic groups in the molecule, and further containing an active hydrogen atom capable of reacting with an isocyanate group A compound having a functional group is used.

The functional group containing an active hydrogen atom capable of reacting with an isocyanate group contained in the compound (c) is preferably a hydroxyl group or a primary or secondary amino group, and the compound (c)
Must contain one or more of these functional groups.

Examples of the ionic functional group contained in the compound (c) include anionic functional groups such as a sulfonate group and a carboxylate group, and cationic functional groups such as an ammonium group. Examples of the latent ionic functional group include a latent anionic functional group such as a sulfonic acid group and a carboxylic acid group, and a latent cationic functional group such as a tertiary amino group.

Of these ionic or latent ionic functional groups, anionic or latent anionic functional groups are preferred. Here, the latent ionic functional group means a functional group which can be converted into an ionic group by adding an appropriate compound, that is, the latent ionic functional group is a functional group before the dispersion operation. After that, the compound can be completely or partially converted into an ionic functional group by adding an appropriate compound such as an ionizing agent later.

The compound having a latent anionic functional group and a functional group capable of further reacting with an isocyanate group is, for example, dimethylol lactic acid, dimethylol propionic acid or dimethylol butyric acid, and a compound having a carboxyl group and 2 Compounds having two hydroxyl groups are preferred.

A latent anionic urethane polymer obtained by using such a compound having a latent anionic functional group can be prepared by using an ionizing agent called a so-called neutralizing agent. The groups can be converted wholly or partially into anionic groups.

As the neutralizing agent used for this purpose, ammonia or a volatile tertiary amine such as trimethylamine or triethylamine is preferably used. This is because these neutralizing agents can be removed by evaporating during drying, so that the water resistance of the film does not decrease.

Alkali metal salts and non-volatile amines can also be used as the neutralizing agent, but when these are used as the neutralizing agent, the neutralizing agent cannot be evaporated and removed during drying, and the film It is not preferable because the water resistance of is decreased.

Examples of the functional group having a latent cationic property include a tertiary amino group, and such a tertiary amino group can be converted to a quaternary amino group (ammonium group) by a suitable quaternizing agent. Is converted into a cationic group.

Examples of the nonionic hydrophilic group include ether groups. Specifically, a segment containing a large number of highly hydrophilic ether bonds such as a polyethylene oxide chain is preferable. However, such a nonionic hydrophilic group remains in the dry film and deteriorates the water resistance of the film, and therefore it is not preferable to use a large amount.

Polymerization of the urethane polymer proceeds by a reaction between an isocyanate group and a functional group having an active hydrogen atom. Regarding the polymer polymerization in the present invention, the ratio of the isocyanate group to the functional group having an active hydrogen atom is preferably in the range of 0.5 to 2.3 (mol / mol), and 1.1 to 2 (mol / mol). More preferably, it is within the range.

These polymerization reactions are carried out within the temperature range of 50 to 150 ° C. The polymerization reaction method may be bulk polymerization or solution polymerization. The solvent used in the case of solution polymerization is preferably one that is inert to isocyanate groups such as acetone, methyl ethyl ketone, tetrahydrofuran, and methyl acetate, has high miscibility with water, and has a boiling point of 100 ° C. or lower. 100
This is because when a solvent having a boiling point higher than 0 ° C. is used, it is difficult to remove only the solvent from the obtained dispersion to the outside of the system in the step after water dispersion.

In the present invention, when the urethane polymer contains an isocyanate group as a starting point for chain extension, the chain can be extended by using any chain extender.
The compound used as the chain extender is a compound having two or more active hydrogen atoms capable of reacting with an isocyanate group in the molecule, and specifically, polyamine and polyols are preferable.

Examples of polyamines and polyols include ethylenediamine, 1,4-diaminobutane, 1,6-hexamethylenediamine, piperazine and 3-aminomethyl-.
A low molecular weight diamino compound such as 3,5,5-trimethylcyclohexylamine and glycols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol and polyethylene glycol are preferably used. Add the chain extender before water dispersion,
It may be carried out at the same time as the water dispersion or at any time after the water dispersion.

The urethane polymer or the organic solvent solution of the urethane polymer obtained as described above is dispersed in water by a known means to be converted into an aqueous dispersion. That is, while adding mechanical shearing force with a high speed disperser such as a homomixer or a disper, water is added to the organic phase containing the urethane polymer to disperse it, or the organic phase containing the urethane polymer is added to the aqueous phase. The method of doing is applied. Further, an organic solvent may be added for the purpose of adjusting the viscosity of the organic phase at the time of water dispersion to an appropriate level. As the organic solvent at this time, solvents such as acetone, methyl ethyl ketone, tetrahydrofuran and methyl acetate are preferably used for the same reason as the selection of the solvent at the time of polymerization.

The tackifier used in the present invention includes:
Gum rosin, tall oil rosin, wood rosin, polymerized rosin, hydrogenated rosin, disproportionated rosin, rosin ester such as rosin ester, hydrogenated rosin ester, disproportionated rosin ester, rosin modified phenolic resin, terpene resin, terpene phenol resin , Terpene resin such as aromatic modified terpene resin, aliphatic petroleum resin, aromatic petroleum resin, petroleum resin such as alicyclic petroleum resin, coumarone resin, styrene resin, alkylphenol resin, xylene resin, ketone Resin etc. are mentioned.

This tackifier may be used alone,
You may use it in mixture of 2 or more types. The amount used is the solid content of the tackifier, and the solid content of the urethane polymer is 10
It is preferably 5 to 200 parts by weight with respect to 0 parts by weight. The softening point of the tackifier used is 60 to 1
It is preferably 60 ° C.

As a mixture of such a tackifier and a urethane polymer self-dispersible in water, dispersed particles of the urethane polymer self-dispersible in water and dispersed particles of the tackifier are independent. Examples thereof include existing forms, or forms in which the respective components are present in the same particle in a uniform or non-uniform mixture. As a method for obtaining a mixed dispersion of independent particles, an aqueous dispersion of a tackifier in which a tackifier is dispersed in water by the addition of a so-called external emulsifier is self-dispersed in water obtained by the above method. There is a method of simply mixing with a water dispersion of a water-soluble urethane polymer.

As a method for obtaining a dispersion of particles in which the respective components are mixed in the same particle, a tackifier is added to the urethane polymer before being converted into an aqueous dispersion or a solution of the urethane polymer in an organic solvent. After forming a mixture, there is a method of dispersing this in water.

In the present invention, since the urethane polymer self-dispersing in water is used, the water resistance of the film is remarkably lowered even if an appropriate amount of external emulsifier is used for the purpose of dispersing the tackifier. There is no such thing. However, the amount of external emulsifier used should be limited to the extent that it does not reduce the water resistance of the film, and for that purpose, a dispersion of a urethane polymer self-dispersing in water and a dispersion of a tackifier are simply mixed. The latter method is preferable to the former method.

The volatile organic solvent added to the system during polymerization, mixing of the tackifier, or dispersion in water can be removed from the system by means such as heating or decompression after the dispersion in water. . If a large amount of these solvents remains in the dispersion, the solvent resistance and heat resistance of the dry film are deteriorated and the working environment is deteriorated, which is not preferable.

The urethane-based water-based adhesive composition containing the tackifier obtained as described above is adjusted to have an appropriate viscosity and concentration and applied to various adherends by a method such as coating, spraying or impregnation. It can be used for bonding.

[0037]

The water-based adhesive composition of the present invention is excellent in adhesiveness in a normal state because it comprises a urethane polymer self-dispersible in water and a tackifier, and it is necessary to use an external emulsifier almost. Since it is not present, the dry film has excellent water resistance and water-resistant adhesiveness, and further, since thermocompression bonding can be performed at a relatively low pressure bonding temperature, it is possible to bond materials having low heat resistance.

[0038]

Example 1 Polycaprolactone diol (OH value = 90, manufactured by Daicel Chemical Industries, Ltd., trade name “PLACCEL, L212AL”) 100 in a separable flask equipped with a cooling tube and stirring blades.
g, 71.1 g of isophorone diisocyanate, 10.6 g of dimethylolpropionic acid, and 45.4 g of methyl ethyl ketone as a diluting solvent were further charged, and polymerization was carried out at the boiling point while stirring the mixed solution until the isocyanate content was 6% by weight or less. It was After the polymerization liquid was cooled to room temperature, 8.00 g of triethylamine was added to neutralize it.

Next, at room temperature, ethylenediamine 8.2
While stirring 300 g of an aqueous solution in which 9 g was dissolved, 200 g of the above mixture was added dropwise over 20 minutes to disperse, and at the same time, chain extension was carried out. Finally, the pressure was reduced with an aspirator under stirring at 40 ° C. for solvent removal for 1 hour.

The nonvolatile content of the urethane polymer aqueous dispersion thus obtained was 40% by weight. This water dispersion 4
An aqueous dispersion of a rosin ester-based tackifier (Arakawa Chemical Co., Ltd., trade name "Super Ester E-740", non-volatile content 50%, softening point 100 ° C) 96 g was added to 00 g to prepare a mixed dispersion (non-volatile content 42%). And

Example 2 Polymerization was carried out at the boiling point with the same composition and scale as in Example 1. After cooling to room temperature, 8.00 g of triethylamine was added to the obtained polymerization solution for neutralization, and a rosin ester-based tackifier (manufactured by Arakawa Chemical Co., Ltd., trade name "Super Ester S-100", softening point 100 ° C). 54.5 g were mixed.

Next, at room temperature, ethylenediamine 8.33 is added.
While stirring 340 g of an aqueous solution in which g was dissolved, 250 g of the above mixture was added dropwise over 25 minutes to disperse, and at the same time, chain extension was performed. Finally, the pressure was reduced with an aspirator under stirring at 40 ° C. for solvent removal for 1 hour. The nonvolatile content of the water dispersion of the urethane polymer and tackifier mixture thus obtained was 4
It was 2% by weight.

Example 3 Instead of the rosin ester-based tackifier used in Example 2, an alkylphenol-based tackifier (manufactured by Hitachi Chemical Co., Ltd.,
Product name “Hitanol # 1501, softening point 90 ° C.) 54.
An aqueous dispersion of the mixture was obtained in the same manner as in Example 2, except that 5 was used.

Comparative Example 1 Polycaprolactone diol (OH value = 90, trade name "PLACCEL: L212AL" manufactured by Daicel Chemical Industries, Ltd.) 100 was placed in a separable flask equipped with a cooling tube and a stirring blade.
g, isophorone diisocyanate 70.2 g, 1,4-
A mixed solution of 6.94 g of butanediol and 44.3 g of methyl ethyl ketone as a diluting solvent was subjected to boiling point polymerization with stirring until the isocyanate content was 6% by weight or less.

The mixture was cooled to room temperature, and 8.59 g of ethylenediamine and 5.06 g of a nonionic emulsifier (manufactured by Nippon Emulsifier Co., Ltd., trade name "Newcol 210") were dissolved in 310 g of an aqueous solution, and 200 g of the above mixture was vigorously stirred. At room temperature, the solution was added dropwise over about 20 minutes to disperse and chain extension was carried out at the same time. Finally, the solvent was removed by stirring at 40 ° C. and reducing the pressure. A 400 g aqueous dispersion of the urethane polymer thus obtained (40% non-volatile content) was added to an aqueous dispersion of a rosin ester tackifier (Arakawa Chemical Co., Ltd., trade name "Super Ester E-740, non-volatile content 50%, softened. 96 g (point 100 ° C.) was added and mixed dispersion (nonvolatile content 42
%) Was obtained.

Comparative Example 2 An aqueous dispersion of a urethane polymer self-dispersing in water used in Example 1 was used to obtain a dispersion without addition of an aqueous dispersion of a tackifier.

Comparative Example 3 Using the aqueous dispersion of the urethane polymer used in Comparative Example 1 dispersed with an external emulsifier, a dispersion without the addition of the tackifier water dispersion was obtained.

The aqueous dispersions obtained by the methods shown in Examples 1 to 3 and Comparative Examples 1 to 3 were evaluated by the evaluation methods shown below. The results are shown in Tables 1 and 2. (1) Normal-state adhesive strength Using a brush, the obtained water dispersion was used to print a canvas and a rigid polyvinyl chloride resin plate (width 25 mm, length 125 mm, thickness 2).
mm) (the coating amount is against cloth: solid content 10 g / m
² , Against rigid PVC: same 4 g / m ² ], after drying for 10 minutes in a blast drying oven at 60 ° C., the respective adhesive-coated surfaces are overlaid and pressed by pressure (pressure 10 kg / c
m ² for 5 minutes) to prepare a test piece (the temperature during pressing is 60 ° C. or 100 ° C.). 2 pieces of the test piece thus obtained
9 at a pulling speed of 50 mm / min under the condition of 3 ° C
A 0 degree peel test was performed.

(2) Water resistant adhesive strength A canvas-rigid vinyl chloride resin test plate prepared in the same manner as the adhesiveness evaluation test piece (temperature at the time of pressure bonding is 60 ° C.) was immersed in water at 23 ° C. for 12 hours, and then, The test piece obtained by wiping with water was subjected to a 90 ° peel test at a pulling speed of 50 mm / min under the condition of 23 ° C.

[0050]

[Table 1]

[0051]

[Table 2]

As is clear from the comparison of Tables 1 and 2, in each of Examples 1 to 3 of the present invention, good normal-state adhesiveness was exhibited even when thermocompression bonding was performed at a relatively low temperature, and ,
While water-resistant adhesion is also excellent, in each of Comparative Examples 1 to 3, at least one of the normal-state adhesion and the water-resistant adhesion is inferior.

[0053]

EFFECTS OF THE INVENTION The water-based adhesive composition of the present invention, having the above-mentioned constitution, has excellent adhesiveness and water-resistant adhesiveness in the normal state, and the temperature during thermocompression bonding is sufficiently low. It can be used as an adhesive for an adherend, which has a strong adhesive force and is difficult to be thermocompression-bonded at high temperature due to deformation or deterioration.

Claims (1)

[Claims] 1. (a) At least one compound having an active hydrogen atom capable of reacting with an isocyanate group in the molecule, (b) an aliphatic or aromatic organic polyisocyanate compound, and (c) a molecule. A compound having at least one functional group of an ionic or potentially ionic functional group or a nonionic hydrophilic group, and further having a functional group containing an active hydrogen atom capable of reacting with an isocyanate group A water-based adhesive composition comprising, as an essential component, a urethane polymer self-dispersible in water obtained by the reaction of these compounds, and a tackifier.