JPS58141274A - Adhesive composition - Google Patents

Abstract

PURPOSE:To provide an adhesive compsn. excellent in resistance to water and viscosity stability with time during storage, consisting mainly of (A) aqueous emulsion of a copolymer of partly saponified polyvinyl acetate having a specified saponification degree and olefin and (B) isocyanate compd. CONSTITUTION:An aqueous emulsion of polyvinyl acetate/olefin copolymer is prepared by emulsion polymerization in an aqueous medium of (a) 40-90mol% vinyl acetate monomer and (b) 10-60mol% olefin of the formula (where R is 1-4C alkyl or halogenated alkyl or halogen). The emulsion is saponified to the saponification degree of 1-40mol%. The titled adhesive compsn. consists mainly of (A) the above partly saponified aqueous emulsion and (B) a compd. which has at least two isocyanate groups in the molecule or liberates isocyanate groups by heating (B) is used in an amount of 1-10% based on the weight of solids in (A).

Description

Detailed Description of the Invention [Detailed Description of the Invention] Regarding acids, more specifically, adhesives mainly composed of an aqueous emulgene of a partially saponified polyvinyl acetate-φ→olefin copolymer having a specific saponification degree range and an isocyanate-based compound. The present invention relates to a drug composition.

It is already known that an adhesive mainly composed of an aqueous emulgene of polyvinyl alcohol and an isocyanate compound has excellent properties as a water-resistant adhesive.

However, as described in JP-A No. 50-69140, with this type of water-based emulsilone-isocyanate adhesive, when it is applied to an adherend and left for several minutes before being bonded, The adhesive force is significantly reduced, and as stated in Japanese Patent Publication No. 51-16080, when an incyanate compound is added to an aqueous polyvinyl alcohol solution, the reaction between isocyanate and water causes a It has drawbacks such as significant foaming and increased viscosity within 3 hours, as well as a sudden drop in water resistance.

In addition, from the viewpoint of water resistance, the raccoon polyvinyl alcohol-isocyanate adhesive preferably has a degree of saponification and a degree of polymerization of the polyvinyl alcohol of 80 to 100 mol% and 300 to 4000, respectively. As described in JP-A No. 50-69140, in order to obtain sufficient water resistance, the degree of polymerization must be too high,
It is necessary that the saponification degree is 98 mol% or more and the polymer concentration in the polyvinyl alcohol aqueous solution is 10% by weight or more.

At this time, as the concentration of polyvinyl alcohol increases, the viscosity of the aqueous solution increases, so the concentration of this practical aqueous solution is limited to a low concentration of about 10 to 20% by weight, and in the end, the proportion of water is high. Therefore, there is a drawback that the range of use is limited. For example, as an example,
When veneers having a moisture content of 15 to 25% by weight, which is common in the production of plywood, are bonded under heat and pressure, there is a risk of punctures.

Furthermore, when using an adhesive such as that disclosed in JP-A-50-69140, the adhesive itself is soft immediately after the hot-pressure bonding is released, so thickness unevenness tends to occur on the adherend.
In particular, hard materials such as oak, birch, Japanese maple, etc. have the disadvantage that they tend to peel off and cause poor adhesion.

Furthermore, the viscosity changes greatly during storage, and (at low temperatures (0)
It also has the disadvantage that it becomes thixotropic at temperatures of up to 15°C) and becomes insular, which seriously hinders bonding work.

However, the present inventors found that vinyl acetate 7mer 40-90
The polyvinyl acetate-olefin copolymer was copolymerized by emulsion copolymerizing 10 to 60 mol% of the olefins represented by the above general formula in an aqueous medium, and partially saponifying the resulting aqueous emulsion in finished water. Although the polymer Emulgene itself has a high degree of polymerization and high resin solid content, it has a low viscosity and is stable during storage. The inventors have discovered that even when adhesive is applied to an adherend and left for several minutes before adhesion, there is no decrease in adhesive strength and the adhesive has sufficient water resistance, leading to the completion of the present invention. .

That is, the present invention provides (A) vinyl acetate monomer 40-9
0 mol% and 1110 to 60 mol% of an olefin represented by the general formula CH2-CHR (R: an alkyl group having a carbon number of Cm to C4, a halogenated alkyl group, a halogen) are emulsion-polymerized in an aqueous medium to produce polyacetic acid. A partially saponified aqueous emulsion obtained by preparing an aqueous emulsion of a vinyl-olefin copolymer and then saponifying this to a saponification rate of 1 to 40 mol%, and (B) containing an isocyanate compound as the main component. The present invention provides an adhesive composition comprising:

Here, the polyvinyl acetate-olefin copolymer emulgene used to obtain the aqueous emulgene (A) of the above-mentioned partially saponified polyvinyl acetate-olefin copolymer, which is a component of the composition of the present invention, includes: There is no particular restriction as long as it is obtained by emulsion polymerization of vinyl acetate monomer and olefin monomer in an aqueous medium by a known and commonly used method, but polyvinyl alcohol (
It is generally emulsion polymerized in an aqueous medium in the presence of an emulsifier (generally called a colloid) and/or an emulsifier.

Next, the saponification method to be carried out to obtain this partially saponified polyvinyl acetate-olefin copolymer aqueous emulgene (A) is not particularly limited,
Although any known and commonly used method may be used, saponification is generally carried out using an alkali catalyst during ice dispersion.

As the alkali catalyst, any catalyst can be used as long as it has saponification ability; for example, hydroxides of alkali metals or alkaline earth metals are preferred, and the saponification ratio is suitably in the range of 1 to 40 mol%. If the saponified content exceeds 40 mol%, the viscosity will change greatly during storage, and if it is less than 1 mol%, it may be necessary to wait several tens of minutes after applying it to the adherend before adhering. If this is the case, the adhesive strength will decrease, which is not preferable.

Further, the isocyanate compound 1), which is another component constituting the composition of the present invention, refers to a compound having at least two isocyanate groups in the molecule, or a compound that releases incyanate groups by a short action. Among them, representative examples are 4.
4'-diphenylmethane diisocyanate (MDI),
) lylene diisocyanate (TDI), xylene diisocyanate, hydrogenated MDi, hydrogenated TDI, or 4
．． Incyanate compounds such as 4'-dicyclohexylmethane diisocyanate; trimethylolpropane (TM
P) -Incyanate modified products such as TDI7 duct or water-hexamethylene diisocyanate addition mixture;
Mixing method of polyisocyanate and polyol, that is, one obtained by adding an excess of polyisocyanate to a polyol such as a hydrous acid group polyester and/or polyether and reacting it; or isocyanate-based polymers obtained by adding an excess of polyisocyanate to a hydroxyl-terminated prepolymer that has been polymerized with an excess of polyol, or the various isocyanate compounds described above. or by blocking the free isocyanate groups contained in those responsible substances or polymers with a so-called blocking agent such as methanol, ethanol, isopropanol, butanol, ethyl lactate or S-caprolactam, etc., by thermal action. It is a compound that releases isocyanate groups.

The blending ratio of the incyanate compound (B) is usually 1% based on the solid content of the partially saponified polyvinyl acetate-olefin copolymer emulsilone (A).
-100% by weight is suitable, and when used as a plywood adhesive, a range of 10-50% by weight is preferred.

An aqueous solvent or surfactant may be added to these above-mentioned isocyanate compounds (B).

When using the composition of the present invention thus obtained, it is of course possible to further incorporate an extender or filler into the composition, and typical examples of such extenders and fillers include: Wheat flour, wood flour, walnut flour, starches, II
They are organic substances such as bean flour and fat fat powder, and inorganic substances such as clay, kaolin, talc, and calcium carbonate, and these can be used alone or in a mixture of two or more types. In addition, known and commonly used dispersants such as sodium birophosphate or ethylene glycol, thickeners, softeners, antifoaming agents, preservatives, or surfactants may be appropriately added to the mm product of the present invention. Of course, it is possible to do so.

The blending ratio of the above-mentioned various additives varies depending on the purpose of use as an adhesive, but is usually 0 to 300% by weight based on the partially saponified polyvinyl acetate-olefin copolymer emulgene (solid material), especially When used as a plywood adhesive, a range of 20 to 200% overlap is appropriate.

Furthermore, when the composition of the present invention is used as an adhesive, it is possible to achieve sufficient adhesion by normal adhesion (coldplex) alone, but water resistance and adhesive strength can be improved by further applying heat and pressure to the composition.

Furthermore, the composition of the present invention may be used by adjusting it to a desired viscosity using a known and commonly used thickening agent such as polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, sodium alginate, or sodium polyacrylate. .

Since the composition of the present invention has a high resin solid content, the water content is 15 to 15.
Even when bonding veneers of 25% overlap, there are extremely few punctures, and the adhesive strength is excellent immediately after the pressure is released from heat-pressure bonding, making it extremely unlikely that adhesive failures such as peeling will occur even with hard materials. In addition, despite its high polymerization degree and high resin solid content, it has a low viscosity and is not only viscosity stable during storage, but also lasts for several tens of minutes after being applied to an adherend. Even if the adhesive is left to stand for a minute before adhesion is performed, the adhesive strength does not decrease (and even in such a case, sufficient water resistance can be obtained).

Furthermore, since component (A) of the composition of the present invention is an emulsion of partially saponified polyacetic acid and a nyl-olefin copolymer, plastic films and sheets, specifically polyvinyl chloride films and/or sheets, can be used. , polyethylene film and/or sheet, polyvinylidene chloride film and sheet as one adherend, it exhibits excellent adhesion and water resistance.

Because it has these various features, the composition of the present invention has a wide range of uses as an adhesive, and can be used not only as an adhesive for plywood, but also for woodworking, particle board, hardboard, corrugated board, etc. For paper, Ichikawa, for non-woven fabric processing, for fiber addition, for L; for ceramics, for inorganic boards such as asbestos slate boards, pulp/cement boards or concrete boards, for mineral materials such as asbestos or rock wool or glass wool, asphalt tiles. It can also be used as an adhesive for plastic sheets such as polyvinyl chloride tiles. In particular, the composition of the present invention is suitable as an adhesive for plywood. In addition, the composition of the present invention can also be used as a coating agent for paints.

Next, the present invention will be specifically explained according to examples.

Hereinafter, all parts and percentages are based on weight unless otherwise specified.

Example Polyvinyl acetate-ethylene copolymer emulgene (Ebadi, EP-1i solid content 50%, ethylene content 20
%), 5 parts of a 49% aqueous sodium hydroxide solution was added to the solution, the pH drop was measured while stirring uniformly, and after confirming the completion of saponification, the pH was adjusted to 4 to 5 with formic acid. (Saponification rate of copolymer: 5 mol%).

Next, 10 parts of Crude MDI (manufactured by Kasei Upgene Co., Ltd., PAP1135) was thoroughly mixed with the mixture, and 30 parts of calcium carbonate were further added and mixed to obtain the desired composition. Thereafter, plywood was produced using this composition as an adhesive, and an adhesive force test of JAS standard Type I was conducted.

The adhesion conditions at that time were as follows, and the test results are shown in Table 1.

Single board composition 0.7 ■ Cover + 2.8 Theory Lauan + 0.7
■Force-adhesive eyelid placement 30 g/900cj Table 1 shows the relationship between the adhesive force and the darkening (depositional darkening) left until cold pressure after applying the adhesive to the adherend. .

Table III

Claims (1)

[Scope of Claims] (A) Il [vinyl monomer 40 to 90 mol% and represented by the general formula CH2-CHR (R: alkyl group or halogenated alkyl group having a carbon number of Ct to C4, halogen)] Partially saponified aqueous emulgene obtained by emulsion polymerizing ~60 mol% of the olefin s+io in an aqueous medium to form an aqueous emulsion, and then saponifying this to a saponification rate of 1 to 40 mol% and (B) incyanate system An adhesive composition comprising a compound.