JPS63297481A - Adhesive composition - Google Patents

Abstract

PURPOSE:To provide an aqueous one-pack adhesive composition of good workability, satisfiable in terms of both heat and low-temperature resistances, for use in polyvinyl chloride sheets, comprising an ethylene-vinyl acetate copolymer aqueous emulsion and aziridinyl group-contg. polyvalent aziridine compound. CONSTITUTION:The objective adhesive composition comprising (A) an aqueous emulsion of a copolymer consisting of 8-40wt.% of ethylene and 92-60wt.% of vinyl acetate and (B) a polyvalent aziridine compound having in the molecule at least 1.5 (pref. three or more) aziridinyl groups on an average (pref. group of formula I or II) [e.g., 2,2-bishydroxymethylbutanol-tris(3-(1-aziridinyl) propionate) etc.].

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is an ethylene-based material for decorative plywood and boards using polyvinyl chloride sheets (hereinafter referred to as PVC sheets) as decorative materials.
This invention relates to a vinyl acetate copolymer emulsion adhesive.

<Prior art and problems> Traditionally, ethylene-vinyl acetate copolymerization has been used to bond PVC sheets to plywood and boards in terms of adhesion and workability.
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It is widely used for furniture, interior of transport aircraft, ceilings, wall coverings, etc. In order to meet the respective performance requirements, such as heat resistance, cold resistance, and water resistance, for example, for heat-resistant creep, adhesives with reduced ethylene content and amounts of plasticizers such as DBP and DOP are used. However, in winter, adhesion at low temperatures decreased, and the cold resistance of the adherend itself decreased, resulting in poor adhesion. On the other hand, if mechanical processing such as cutting or drilling is performed in an atmosphere below the glass transition point (0 to -3°C) of the adhesive film, such as -5 to -20°C, the adhesive layer film becomes hard and brittle. In order to solve this problem, the above-mentioned plasticizers may be added, or various alkyl acrylates may be used as copolymerization monomers to prepare multi-component copolymer emulsions. However, the heat resistance creep decreased.

<Object of the invention> The present invention provides a water-based, one-component type adhesive for PVC sheets that has good workability and can satisfy heat resistance and cold resistance.
be.

<Disclosure of the Invention> The present invention comprises 8 to 40% by weight of captive ethylene and 92% by weight of vinyl acetate.
~60% by weight copolymer aqueous emulsion, and (B)
This is an adhesive composition containing a polyvalent aziridine compound having an average of 1.5 or more aziridinyl groups in the molecule.

Here, the copolymer aqueous emulsion will be described in detail.

The reason why the amount of ethylene copolymerized was limited to 8 to 40 by weight was because
If it is less than 8 inches, sufficient adhesion to the PVC sheet cannot be obtained, and if it exceeds 40 inches, no further effect on adhesion can be obtained. Note that the aqueous copolymer emulsion (4) does not have to consist only of vinyl acetate and ethylene monomers, but also methyl (meth)acrylate, butyl (meth)acrylate, octyl (meth)acrylate, and (meth)acrylate. Various (meth)acrylic acid esters such as acid glycidyl, various unsaturated acids such as acrylic acid, itaconic acid, maleic acid, (meth)acrylamide, vinyl sulfonic acid (!!
2-hydroxyethyl (meth)acrylamide, diallyl esters of areic acid, adipic acid, phthalic acid, triallyl ester of benzenetricarboxylic acid, triallyl isocyanurate, etc., as appropriate. It may be polymerized. Moreover, restrictions on the manufacturing method are particularly dangerous. Emulsifiers include, for example, completely or partially saponified polyvinyl alcohol, fibrous derivatives such as methyl cellulose and hydroxyethyl cellulose, various water-soluble polymers such as ammonium salts of α-olefin-maleic anhydride, polyoxyethylene alkylphenyl ether, polyoxy Various nonionic surfactants such as ethylene alkylphenyl ether, polyoxyethylene polyoxypropylene block copolymer, polyoxyethylene sorbitan fatty acid ester,
Lauric acid ester sodium salt, dialkyl succinate,
Anionic surfactants such as alkylbenzene sulfonates are exemplified, and these may be used alone or as a mixture. As the polymerization initiator, a redox initiator is preferable. Examples of the oxidizing agent include ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, and various organic peroxides. Note that persulfates are particularly preferably used because they and their decomposition products act as crosslinking catalysts. Examples of the reducing agent include formaldehyde sodium sulfoxylate, a reaction substance of glyoxal and a salt of a reducing sulfur oxide, and the like. Additionally, additives such as pH adjusters and electrolytes can also be used using known emulsion polymerization techniques. There are no particular restrictions on polymerization conditions such as polymerization pressure and temperature, but generally the polymerization temperature is between 0 and 1.
It is practical to maintain the temperature in the range 00°C, preferably between 30 and 80°C. The polymerization pressure is arbitrarily adjusted depending on the desired amount of ethylene in the copolymer, and in order to obtain an ethylene copolymer having a weight ratio of 8 to 40, a polymerization pressure of 5 to 100/d is used. The solid content concentration in the emulsion can be adjusted by adjusting the amount of copolymerized hexamer and water, but it is 40~
A solid content concentration of about 65% by weight/f1% is appropriate from the viewpoint of industrial use.

Regarding the polyvalent aziridine compound (B) having an average of 1.5 or more aziridine groups in the molecule, those having 2 or more groups in the molecule can be widely used. Preferably, those having three or more such groups in the molecule are more preferable.

Specifically, those that are commercially available are 2゜2-bishydroxymethylbutanol-tris(3-(1-aziridinyl)propionate), diphenylmethane-bis-4,
Either 4'-N or N'-diethynurea may be used, but the former, which is a triaziridinyl compound, is more practical in terms of effectiveness.

There is no particular restriction on the mixing ratio of the copolymer aqueous emulsion = 17 and the polyhydric acylidine compound (4), but the solid content weight ratio is preferably 100:0.05-20. That is, if the amount (based on 100 parts by weight) is less than 0.05 parts by weight, it is difficult to achieve the object of the present invention;
If it exceeds parts by weight, the purpose of the present invention, that is, heat resistance,
The cold resistance and adhesion have reached a plateau, and a large amount of the polyvalent aziridine compound described in (1) must be used unnecessarily.Furthermore, depending on the type of PVC sheet, especially in the case of a thin sheet, discoloration may occur. Note that there are no particular restrictions on the mixing method of (4) and a3). That is, it may be added to the aqueous emulsifier solution for polymerization of ethylene and vinyl acetate monomers (4) before polymerization, during polymerization, or after completion of polymerization. In some cases, the ingredients may be mixed and stirred immediately before use.

In addition to the above, known foaming agents, antifoaming agents, dispersion stabilizers, thickeners, solvents, plasticizers, inorganic or organic extender fillers, and other emulsions and latexes may also be used. You may do so.

There are no restrictions on the method of manufacturing PVC plywood and PVC boards using the adhesive according to the present invention. After applying the adhesive, it may be wet-attached, semi-dry-attached using pre-drying, or dry-attached for heat recovery. Continuous roll compaction, cold pressure, and hot pressure are all possible.

Next, the present invention will be explained in more detail with reference to comparative examples and examples, but the present invention is not limited thereto.

Comparative Example 1 In an autoclave equipped with a stirrer, 5 parts of polyvinyl alcohol with a degree of polymerization of 1700 and a degree of saponification of 88 molt (parts by weight, the same applies hereinafter), 2 parts of polyoxyethylene nonylphenol ether with an HLB of 14, and 100 parts of ion-exchanged water were added. The mixture was charged and heated and stirred at about 90° C. for 2 hours to completely dissolve. After cooling this solution to 60° C., an aqueous solution of 0.3 parts of sodium carbonate dissolved in 5 parts of water was added, and the air in the autoclave was replaced with ethylene. Next, 0.4 parts of ammonium persulfate dissolved in 5 parts of vinyl acetate and 10 parts of water was added to initiate polymerization. From the time the polymerization was started, 95 parts of vinyl acetate was added dropwise at a constant rate over 4 hours. During this time, ethylene was kept constant at 40 ky7 cxt and was press-injected to carry out polymerization. The polymerization temperature was about 70°C. After the vinyl acetate dropwise addition was completed, the mixture was kept at about 70° C. for 5 hours and then cooled to complete the polymerization. The product has an ethylene content of 18%, a vinyl acetate content of 82%, and a solids content of 52%. C)% aqueous emulsion was obtained. This was used as the adhesive of Comparative Example 1.

Comparative Example 2 Polymerization was carried out in the same manner as in Comparative Example 1, except that a copolymerization monomer mixture in which 2 parts of acrylic acid had been mixed in advance was continuously added dropwise to 95 parts of vinyl acetate monomer that was continuously added dropwise over 4 hours. The composition ratio of the obtained polymer was such that the contents of ethylene, acrylic acid, and vinyl acetate were 17, 1.5, and 1.5, respectively.
It was an aqueous emulsion with a weight of 81.5% by weight and a solids content of 52.2%. With respect to 100 parts of the solid content of this aqueous emulsion, 8 parts of DBP as a plasticizer was mixed and stirred to adjust the total solid content to 53.9%, and the adhesive of Comparative Example 2 was prepared.0 Example 1 Comparative Example 1 The adhesive composition of Example 1 was prepared by mixing and stirring 2 parts of 2,2-bishydro-tetraoxymethylbutanol tris(3-(1-aziridinyl)gropionate) with 100 parts of the adhesive.

Example 2゜Diphenylmethane was added to 100 parts of the adhesive of Comparative Example 2.
25-bis-4,4'-N,N'-diethylene urea
The adhesive composition of Example 2 was prepared by mixing and stirring 10 parts of the % aqueous dispersion.

Example 8 To confirm that the adhesive composition of Example 1 was a one-component product rather than a two-component product that was mixed immediately before use, the adhesive composition of Example 1 was placed in a sealed polyethylene container and heated for 40 minutes. ℃×
The adhesive composition of Example 3 was obtained after being left to stand for 3 months.

No change in viscosity was observed even after being left at 40°C for 3 months.

Using the adhesives and adhesive compositions of Comparative Examples 1 and 2 and Examples 1, 2, and 3, a PVC sheet and plywood were bonded as shown below, and an adhesive strength test was conducted.

Adhering conditions> Adherent material: 0.2m thick semi-rigid PVC sheet and 311oI thick lauan plywood Coating site: 150 f/W1 coating on one side on the plywood Closed deposition time: Within 5 minutes Pressing: 1 course f/d, 20 ℃, 1 hour compression curing: 20℃,
Test items for 3 days> Peel adhesion strength test = 25B width, 90 degree angle, 180 degree angle,
Pull speed 200 fl/min.

Heat resistant creep: Measure the peeling length of the cod after 1 hour by applying a load of 0.5 kgf per 25 cod width at a 90 degree angle in a 60° C. constant temperature chamber.

Cold Resistance The test pieces were left in thermostats at 5° C. and -20° C. for one day each, and the state of forced peeling was observed.

(Evaluation) ○: Plywood broken, PVC broken ×: PVC interface peeling The results of these measurements are shown in Table 1.

Table 1

Claims (1)

[Claims] (A) ethylene 8-40% by weight, vinyl acetate 92-60%
% by weight of an aqueous copolymer emulsion, and (B) a polyvalent aziridine compound having an average of 1.5 or more aziridinyl groups in the molecule.