JPS5947711B2 - water-based adhesive composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vinyl acetate-ethylene copolymer emulsion adhesive composition.

More specifically, the present invention relates to a vinyl acetate-ethylene copolymer emulsion adhesive composition that has excellent water-resistant adhesive properties and excellent heat-resistant creep properties. Vinyl acetate-ethylene copolymer emulsions have conventionally been used as adhesives in a wide range of applications, including PVC plywood, PVC building materials, board plywood, flexible ports, fibers, and paper building materials.

However, the above-mentioned vinyl acetate-ethylene copolymer emulsion adhesive does not have any drawbacks, and has the disadvantage of poor adhesion to polyolefin resins.
For example, when used as an adhesive between a polyolefin resin sheet and plywood, it does not exhibit sufficient adhesive strength. Furthermore, when used as an adhesive between vinyl chloride sheets and plywood, it has poor heat resistance and creep resistance when used under harsh conditions, particularly at high temperatures. In order to improve these drawbacks, attempts have been made to mix epoxy compounds with vinyl acetate-ethylene copolymer emulsion and use a suitable amine curing agent in combination.For example, Airco Chemicals and Plastics' adhesive Technical Service Report 4-3 (August 15, 1968) for Pharmaceutical Applications, or JP-A-49-128980 and JP-A-50-58132.

However, although adhesive compositions using the above methods can be effective in terms of adhesion under normal usage conditions, they can be used under harsh conditions, such as water-resistant adhesion in humid conditions and high-temperature conditions. In terms of heat resistance and creep resistance, it is not possible to achieve a sufficiently satisfactory effect.

In view of these circumstances, the inventors of the present invention set out to provide a vinyl acetate-ethylene copolymer emulsion adhesive composition that has adhesion to polyolefin resins, particularly water-resistant adhesion, and also has excellent heat-resistant creep properties. As a result of various studies, we found that an epoxy compound with an epoxy equivalent of 250 or less was added to a ternary copolymer emulsion in which vinyl acetate, ethylene, and unsaturated glycidyl monomers were polymerized using a dispersant mainly consisting of partially saponified polyvinyl alcohol during emulsion polymerization. or an emulsion composition obtained by copolymerizing vinyl acetate in which the epoxy compound is pre-dissolved with ethylene and unsaturated glycidyl monomers, and an amine curing agent added to the water-based adhesive composition. The adhesive composition improves the adhesive strength under normal conditions compared to the above-mentioned improved method, and is particularly superior in water-resistant adhesive strength, and also exhibits remarkable superiority when such an adhesive composition is used as an adhesive between a vinyl chloride sheet and plywood. The present invention was based on the discovery that it has a high heat-resistant creep property.

That is, the present invention emulsion polymerizes A ethylene, B vinyl acetate, and C unsaturated glycidyl monomers in the presence of a dispersant mainly composed of partially saponified polyvinyl alcohol while maintaining the pH during polymerization in the range of 3 to 7. The composition (polymerization ratio) of the copolymer is A:B:C=5~40:94.9~55:
95 of a terpolymer emulsion having a molecular weight of 0.1 to 5.
This is a water-based adhesive composition prepared by blending an amine curing agent into an emulsion composition consisting of ~99.5 parts by weight and 5 to 0.5 parts by weight of an epoxy compound having an epoxy equivalent of 250 or less. According to the method of the present invention, such an emulsion composition contains a dispersant mainly composed of partially saponified polyvinyl alcohol, an epoxy compound having an epoxy equivalent of 250 or less, and a vinyl acetate-ethylene copolymer having an epoxy group.
By maintaining the pH of the reaction system in a thin range of 3 to 7, the ring-opening of the epoxy group during polymerization is suppressed, and it has excellent adhesive strength, and also has an epoxy group. When vinyl acetate-ethylene copolymer and epoxy compound undergo a curing reaction with an amine curing agent, vinyl acetate-ethylene copolymer
A curing reaction occurs between the epoxy groups of the ethylene copolymer and the epoxy groups of the epoxy compound, and a curing reaction occurs between the epoxy groups of the co-Iζ vinyl acetate-ethylene copolymer and the epoxy groups of the epoxy compound, resulting in higher density curing. It is thought that the reaction results in a product having not only adhesive strength but also extremely excellent heat creep resistance.

In the method of the present invention, there is no significant difference in performance, which is the objective of the present invention, whether the epoxy compound is used during emulsion polymerization or added to the emulsion after emulsion polymerization.
Although both methods exhibit excellent performance, the former method is advantageous in terms of production because the epoxy compound is produced all at once in one reaction.

In the present invention, partially saponified polyvinyl alcohol as a dispersant is essential for achieving the above-mentioned purpose. When a polyester polymer is used as a protective colloid, it does not exhibit sufficient adhesive strength to polyolefin resins. The partially saponified polyvinyl alcohol used in the present invention preferably has an average degree of saponification of 60 to 97 mol% and an average degree of polymerization of 300 to 2,700 from the viewpoint of suitable emulsion viscosity and stability.

Fully saponified polyvinyl alcohol can also be used, but even in that case, it is necessary to use partially saponified polyvinyl alcohol in combination so that the average degree of saponification of both is 97 mol% or less in order to obtain a stable emulsion. The amount of partially saponified polyvinyl alcohol used is generally 1.0 to 10% by weight based on the resin solid content. More preferably, it is used in an amount of 2 to 6% by weight. Furthermore, in the present invention, a dispersant other than partially saponified polyvinyl alcohol is used to adjust the particle size.
There is no problem in using it as an auxiliary means to increase emulsifying power. In the present invention, the content of the unsaturated glycidyl monomer component in the terpolymer emulsion consisting of vinyl acetate, ethylene, and unsaturated glycidyl monomer is 0.
．． 1 to 5% by weight is suitable.

Preferably it is 0.2 to 3% by weight. That is, in the present invention, the unsaturated glycidyl monomer component greatly contributes to increasing the density of the curing reaction as well as the adhesive strength as described above, and the content of the unsaturated glycidyl monomer component is 0.1.
If the amount is less than % by weight, extremely excellent heat creep resistance cannot be obtained. Moreover, if it exceeds 5% by weight, the heat-resistant creep property and the water-resistant adhesive strength tend to decrease, which is not preferable. The unsaturated glycidyl monomer used in the present invention is a monomer having one or more copolymerizable unsaturated bonds and one or more epoxy groups in one molecule, such as glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, Examples include glycidyl vinyl ether, itaconic acid diglycidyl ether, and their analogs.

In the present invention, the ethylene content of the terpolymer emulsion is suitably 5 to 40% by weight.

If the ethylene content is less than 5% by weight, the water-resistant adhesive strength will be poor, and if it is 40% by weight, the heat-resistant creep property will be poor, so 10 to 30% by weight is generally preferred. The content of the epoxy compound in the emulsion composition obtained according to the present invention is 0.5 to 5% by weight based on the resin solid content. is appropriate.

When the content of the epoxy compound is less than 0.5% by weight, the adhesive strength targeted by the present invention cannot be sufficiently obtained. 5 weight? Even if a larger amount is used, practically sufficient adhesive strength is exhibited, but this is economically disadvantageous and the heat creep resistance tends to decrease.

The epoxy compound used in the present invention has an epoxy equivalent (
The epoxy equivalent referred to here is the number of grams of an epoxy compound containing 1 gram equivalent of epoxy group), which has a low molecular weight of 250 or less, such as bisphenol A-epichlorohydrin type epoxy compounds with an epoxy equivalent of 250 or less, Examples include alkylene ether type epoxy compounds, side chain type epoxy compounds, alicyclic epoxy compounds, polymerized fatty acid ester type epoxy compounds, glyceryl triepoxide, alkylphenol type epoxy compounds, novolak type epoxy compounds, and the like.

When a high molecular weight epoxy compound having an epoxy equivalent exceeding 250 is used, sufficient adhesive strength cannot be obtained with the content of the epoxy compound of the present invention, and the amount used must be increased, which is disadvantageous. In addition, in the present invention, as mentioned above, in order to suppress the ring opening of the epoxy group and prevent the hydrolysis of vinyl acetate, the pH of the emulsification system is adjusted to 3 to 7.
It is necessary to maintain P within the range of
H modifiers can also be used.

The amount of the pH adjuster is the amount necessary to adjust the pH of the polymerization system to a desired value, and examples of such pH adjusters include ammonium bicarbonate and sodium, 2-sodium phosphate, sodium acetate, and ammonia. Examples include hydroacetic acid and hydrochloric acid, which may be used alone or in combination of two or more. Examples of the amine curing agent used in the present invention include diethylenetriamine, triethylenetetramine or their monos, aliphatic polyamines such as diepoxide adducts and adducts thereof, heterocyclic amines and adducts thereof, aliphatic polyamines of dimer acids, etc. Polyamines and their adducts, heterocyclic amines and their adducts, polyamides of dimer acids with aliphatic amines, diphenyldiaminomethane or its monomers, aromatic polyamines and their adducts such as adducts with diepoxides, polysulfides, benzyldimethyl Examples include tertiary amines such as amines, initial condensates such as melamine formaldehyde, and phenol formaldehyde.

The appropriate amount of the amine curing agent used is 1 to 20 parts by weight based on the solid content of the emulsion composition.

To specifically explain the method for producing the emulsion composition of the present invention, a dispersion solution in which a dispersant mainly composed of partially saponified polyvinyl alcohol as described above and a PH adjuster are added to water, and vinyl acetate (an epoxy compound) are prepared by emulsion polymerization. When used in a reactor, the whole amount or a part of the unsaturated glycidyl monomer (vinyl acetate in which one or more epoxy compounds are dissolved) is introduced into a reactor and stirred and dispersed, and then ethylene is added to the reactor. The radical polymerization catalyst, remaining vinyl acetate, and unsaturated glycidyl monomer are added under constant pressure of ethylene, and if necessary, ethylene and P are added.
A method is used in which emulsion polymerization is carried out while adding an H regulator or the like.
Further, if the epoxy compound is not added during emulsion polymerization, it is added afterwards to the produced emulsion. In emulsion polymerization, the polymerization temperature is usually selected to be in the range of 30 to 90°C. The polymerization pressure can be arbitrarily adjusted depending on the desired ethylene content. In order to obtain an ethylene content of 5 to 40% by weight, it is effective to maintain the ethylene content in the range of 3 to 100 kg/CwL. The radical polymerization catalyst is not particularly limited, and various free radical-forming catalysts commonly used in emulsion polymerization, such as peroxides, can be used. Particularly preferred catalysts are so-called free radical-forming catalysts that are composed of a combination of a reducing agent and an oxidizing agent. Examples include redox catalysts. Suitable oxidizing agents include, for example, hydrogen peroxide, organic peroxides such as lauryl peroxide, t-butylhydroberoxide, salts such as ammonium persulfate, potassium persulfate, sodium persulfate, and persulfate. Examples of the reducing agent include compounds having reducing properties such as bisulfite, sodium formaldehyde sulfoxylate, and ferrous salts. Generally, the appropriate amount of the oxidizing agent to be used is in the range of 0.1 to 2% by weight based on the vinyl acetate, and the amount of the reducing agent to be used is 25 to 10% by weight based on the oxidizing agent.
0% by weight is suitable. The solid content of the emulsion composition of the present invention can be changed as appropriate depending on the amount of water used during emulsion polymerization, but in general, 40 to 60% by weight is appropriate depending on the intended use.

This will be explained in detail below using examples.

Note that "parts" in the descriptions in the examples indicate parts by weight. Example 1 3.5 parts of partially saponified polyvinyl alcohol with an average polymerization degree of 500 and a saponification degree of 90 mol% and 1.5 parts of partially saponified polyvinyl alcohol with a number average molecular weight of 1700 and a saponification degree of 86 mol% in 90 parts of water. A dispersion containing 0.01 part of sodium acetate and 80 parts of vinyl acetate monomer were charged into an autoclave, and the temperature was raised to 60°C while stirring and dispersing.
Ethylene was forced into the tank until it reached 5 kg/Cfil.

Then 10% Rongarit aqueous solution and 0.0% sodium acetate solution.
A 6% aqueous solution of ammonium persulfate containing 5% was continuously added to initiate polymerization, and 20 parts of vinyl acetate monomer and 1.6 parts of glycidyl methacrylate were continuously added over 4 hours. The pH of the reaction system during polymerization was maintained at 5-6. Five hours after the start of polymerization, it was confirmed that the amount of unreacted vinyl acetate monomer was 0.5 weight or less, and the polymerization was completed by cooling. The solid content of the emulsion obtained was 55
．． The ethylene content in the terpolymer at 2% by weight is 17
% by weight, and the glycidyl methacrylate content was 1% by weight (calculated from the balance of raw materials used).

1.7 parts of bisphenol A-epichlorohydrin polymer having an epoxy equivalent weight of 186 was mixed with 100 parts of this emulsion to obtain an emulsion composition containing 3% by weight of the epoxy compound.

Example 2 Emulsion polymerization was carried out in the same manner as in Example 1, except that 4 parts of the bisphenol A-epichlorohydrin polymer having an epoxy equivalent of 186 was dissolved in 80 parts of the vinyl acetate of Reference Example 1 to obtain an emulsion composition.

The content of the epoxy compound in the solid content was 3% by weight, the ethylene content in the terpolymer was 16.9% by weight, and the content of glycidyl methacrylate was 1% by weight (calculated from the balance of raw materials used). ). Example 3 As a dispersant, 3.0 parts of partially saponified polyvinyl alcohol with a number average molecular weight of 1700 and a degree of saponification of 89 mol%, H. L
．． 1.5 parts of polyoxyethylene nonylphenol ether with Bl8.5, H. L. Using 1.5 parts of polyoxyethylene nonyl phenol ether with a Bl of 4.3, 6.2 parts of an epoxy compound was added to 80 parts of the vinyl acetate monomer in Example 1, and 0.8 parts of glycidyl methacrylate to be added later. Emulsion polymerization was carried out in the same manner as in Example 1 to obtain an emulsion composition.

The content of the epoxy compound in the solid content was 4% by weight, the content of ethylene in the terpolymer was 17% by weight, and the content of glycidyl methacrylate was 0.5% by weight (calculated from the balance of raw materials used). ). The epoxy equivalents in the solid content of the aqueous dispersions of Examples 1 to 3 were determined using the hydrochloric acid monodioxane method described on page 856 of the Polymer Analysis Handbook (published by Asakura Shoten, 4th edition, August 15, 1970). As a result, it was found that the epoxy equivalents were in agreement with the epoxy equivalent calculated from the raw materials, and it was found that the ring opening of the epoxy group during polymerization was suppressed in both cases.

Comparative Example 1 In place of the dispersant used in Example 1, hydroxylethylcellulose 2 with an added mole of ethylene oxide of about 2.5 was added.
, 0 parts, H. L. 2.0 parts of polyoxyethylene nonylphenol ether with Bl8.5, H. L. Emulsion polymerization was carried out in the same manner as in Example 1, except that 2.0 parts of polyoxyethylene nonylphenol ether having a Bl of 4.3 was used to obtain a terpolymer emulsion.

An epoxy compound was mixed into this emulsion in the same manner as in Example 1 to obtain an emulsion composition. Comparative Example 2 Emulsion polymerization was carried out in the same manner as in Example 1 except that the amount of glycidyl methacrylate in Example 1 was changed to 6 parts. A terpolymer emulsion of (calculation) was obtained.

Comparative Example 3 Emulsion polymerization was carried out in the same manner as in Example 2 except that 5.5 parts of the epoxy compound was used instead of using glycidyl methacrylate, and an emulsion containing 4% by weight of the epoxy compound based on the solid content was prepared. A composition was obtained.

Comparative Example 4 In Example 1, the emulsion polymerization of Example 1 was carried out without using glycidyl methacrylate, and the ethylene content was 17.2.
weight? A vinyl acetate-ethylene copolymer emulsion was obtained.

Example 4 Emulsion composition 10 of Examples 1 to 3 and Comparative Examples 1 to 3
0 parts and 5 parts of xylene diamine as a curing agent were added to prepare an adhesive composition.

Claims (1)

[Claims] 1 A: ethylene, B: vinyl acetate, C: unsaturated glycidyl monomers, in the presence of a dispersant mainly composed of partially saponified polyvinyl alcohol, while maintaining the pH in the range of 3 to 7 during polymerization. Obtained by emulsion polymerization, the composition (weight ratio) of the copolymer is A
:B:C=5-40:94.9-55:95-99.5 parts by weight of a terpolymer emulsion having 0.1-5 and 5-0.5 parts by weight of an epoxy compound having an epoxy equivalent of 250 or less.
A water-based adhesive composition comprising an emulsion composition containing 5 parts by weight and an amine curing agent. 2. The water-based adhesive composition according to claim 1, wherein the emulsion composition is a mixture of a terpolymer emulsion and an epoxy compound having an epoxy equivalent of 250 or less. 3. A patent claim in which the emulsion composition is a terpolymer emulsion containing an epoxy compound obtained by emulsion polymerization of vinyl acetate in which an epoxy compound having an epoxy equivalent of 250 or less is pre-dissolved, and ethylene and unsaturated glycidyl monomers. The water-based adhesive composition according to item 1. 4 Partially saponified polyvinyl alcohol has an average saponification degree of 6
The water-based adhesive composition according to claim 1, which has an average polymerization degree of 0 to 97 mol% and an average degree of polymerization of 300 to 2,700. 5. The aqueous adhesive composition according to claim 1, wherein the amount of partially saponified polyvinyl alcohol used is 1.0 to 10% by weight based on the solid content in the emulsion composition. 6. The aqueous adhesive composition according to claim 1, wherein the unsaturated glycidyl monomer is a monomer having one or more copolymerizable unsaturated bonds and one or more epoxy groups in one molecule. 7. The water-based adhesive composition according to claim 1, wherein the unsaturated glycidyl monomer is glycidyl methacrylate. 8. The water-based adhesive composition according to claim 1, wherein the epoxy compound has an epoxy equivalent of 250 or less. 9. The water-based adhesive composition according to claim 1, wherein the epoxy compound is a bisphenol A-epichlorohydrin type epoxy compound having an epoxy equivalent of 250 or less. 10. The aqueous adhesive composition according to claim 1, wherein the amount of the amine curing agent used is 1 to 20 parts by weight based on the solid content of the emulsion composition.