JP2002114959A - Recycle type water-based adhesive composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-based adhesive suitably employable for bonding a plastic sheet to a porous board and permitting recycle by re-release and the like of an adhered product once obtained by adhesion using the same. SOLUTION: The water-based adhesive composition has characteristics such that it exhibits excellent adhesive properties in adhesion of a plastic sheet such as a polyester sheet, a polyolefin sheet and the like to a porous board and that it permits easy release of the adhered product by heating, and comprises (A) a polyvinyl alcohol-containing, ethylene/vinyl acetate/ polyfunctional monomer copolymer emulsion having a toluene insoluble content of at least 70 mass%, (B) a sulfonic acid-modified, anionic polyurethane emulsion and (C) fine heat-expandable hollow particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an aqueous adhesive composition. More specifically, it is used to bond overlay decorative boards such as plastic sheets and porous boards,
The present invention relates to a water-based adhesive having a function of allowing only a plastic sheet to be removed again by leaving it in a high-temperature atmosphere when the decorative board becomes unnecessary.

[0002]

2. Description of the Related Art In the past, overlay decorative boards represented by PVC plywood have been widely used in the fields of building materials, housing equipment, vehicles and the like. These are decorative sheets made of polyester, polyolefin or polyvinyl chloride with woodgrain printing, and decorative boards themselves made by overlaying wooden boards, inorganic boards, etc. with an aqueous adhesive, or assembling them. . In this bonding step, a water-based adhesive is traditionally used. The reason is that there is no more adhesive than water-based adhesive in terms of adhesive line suitability, easy handling, health care of workers, prevention of fire accident, and environmental protection.

[0003] These bondings are carried out on a factory line, but polyvinyl acetate emulsion type adhesives are mainly used because they have suitable line suitability and are excellent in adhesiveness to various plastic materials. This polyvinyl acetate emulsion rarely uses a polyvinyl acetate homopolymer emulsion having poor adhesion to plastics, and a polyvinyl acetate emulsion obtained by copolymerizing an ethylene monomer and an acrylic monomer, and those polyvinyl acetate emulsions An adhesive in which an acrylic emulsion, a urethane emulsion, a polyester emulsion, or the like is blended with the emulsion is used.

In the field of adhesion of these plastic overlay decorative boards, due to social demands for dechlorination, PVC sheets have been replaced with polyester sheets and polyolefin sheets, which are difficult to bond. Various aqueous adhesives have been proposed. ing. However, these are inventions aiming at the performance required for the purpose of bonding and use. Therefore, in an adhesive product once adhered, no adhesive is considered at all, as far as the recycling technology for re-peeling these overlaid plastic sheets is considered.

[0005]

SUMMARY OF THE INVENTION With the aim of developing an adhesive that takes into consideration recycling techniques such as re-peeling, once an adhesive product has been bonded, an aqueous solution suitable for bonding a plastic sheet and a porous board has been developed. To develop an adhesive.

[0006] In bonding the plastic sheet and the porous board, polyester which meets the demand for dechlorination,
Good adhesion must be provided to plastic sheets containing poorly adhesive materials such as polyolefin sheets. And, since these are used for building materials, housing equipment and the like, they must be excellent in water resistance and heat resistance, and must exhibit a performance level that passes an industry quality requirement test such as JAS2 immersion peel test. Furthermore, when used as an adhesive product, while maintaining a sufficient adhesive state and adhesive performance, when recycled, the sheet is easily peeled by hand by heating so that only the sheet is easily peeled by hand. is there.

[0007]

Means for Solving the Problems The present inventors have started research on blending a heat-expandable fine hollow particle, that is, a heat-expandable microcapsule, with an emulsion adhesive. 2. Description of the Related Art In general, a technique of blending a heat-expandable fine hollow body with an adhesive and foaming by heating has been widely proposed for various purposes.

[0008] By the way, when this thermally expandable fine hollow body is blended, there is a problem that the adhesiveness is lowered with respect to a plastic sheet made of a poorly adhesive material such as a polyester or polyolefin sheet. Next, since the compounding of the heat-expandable fine-grained hollow body particularly lowers the water resistance, even if the compounding agent does not contain the adhesive, it has failed even if it passed the quality requirement test in the industry such as the JAS2 immersion peel test. Difficulties were also found. Finally, it was found that there is no correlation between the adhesion under normal conditions and the removability at high temperatures when the film is finally peeled off by heating. After such a discovery, we continued our intensive research with the aim of developing an adhesive that could overcome all of these difficulties, and finally found an adhesive that satisfies all requirements.

Hereinafter, means of the present invention for solving the above-mentioned problems will be specifically described.

According to the first aspect of the present invention, the adhesion between a plastic sheet including a polyester or polyolefin sheet and a porous board is excellent in adhesiveness, water resistance, heat resistance, heat creep resistance and hot water immersion peeling performance. The purpose of the present invention is to provide an aqueous adhesive composition having a property that the adhesive can be easily peeled off by heating, and (A) a polyvinyl alcohol-containing ethylene-vinyl acetate having a toluene insoluble content of 70% by mass or more. Polyfunctional monomer-based copolymer emulsion, (B) sulfonic acid-modified anionic polyurethane emulsion and (C)
An aqueous adhesive composition comprising a thermally expandable fine hollow particle.

According to a second aspect of the present invention, the heat-expandable fine hollow particles have an expansion ratio of 20 to 100 times and an expansion start temperature of 90 to 150 ° C. It is an adhesive composition.

The invention of claim 3 is characterized in that the toluene insoluble content is 70%.
Ethylene-vinyl acetate-polyfunctional monomer-based copolymer emulsion containing 10% by mass or more of polyvinyl alcohol 10
It is characterized by blending 2 to 50 parts by mass (solid content) of a sulfonic acid-modified anionic polyurethane emulsion and 2 to 100 parts by mass of thermally expandable fine hollow particles with respect to 0 parts by mass (solid content). An aqueous adhesive composition according to claim 1 or 2.

[0013] The thermally expandable fine hollow particles in the present invention are:
A component that is blended to re-peel only the plastic sheet by heating. It has a foaming ratio of 20 to 100 times and a foaming start temperature of 90 to 150 ° C. Such a heat-expandable fine hollow body is a microcapsule composed of a plastic sphere having an average particle diameter of 9 to 17 µ formed in a polymer shell containing a liquid gas, and when heated, the gas pressure increases inside the shell. The softening of the thermoplastic shell increases the volume dramatically, resulting in hollow spherical particles. In the thermally expandable fine hollow particles having an expansion ratio of less than 20 times, the re-peeling performance tends to decrease, and in the thermally expandable fine particles having an expansion ratio of more than 100 times, the foaming start temperature exceeds 150 ° C. Due to the tendency, it is necessary to set the heating temperature high and set the time long. The average particle size of the thermally expandable fine hollow particles is very important. If the average particle size is less than 9 μm, the removability and the dispersibility during mixing may be reduced. If it exceeds 17μ, the tendency to generate elementary particles during mixing increases, and
There is a tendency to impair the aesthetics of the overlay veneer. In particular, the present invention can be most effectively implemented by selecting a thermally expandable fine hollow body having an average particle diameter in the range of 10 to 16 μm. Commercially available products can be used as these thermally expandable fine hollow particles. Examples of the commercially available products include EXPANCEL053DU (Ex
Pancel, foaming ratio 35 times, foaming start temperature 10
1 ° C).

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The aqueous adhesive composition of the present invention comprises
Component (A), a polyvinyl alcohol-containing ethylene-vinyl acetate-polyfunctional monomer copolymer emulsion containing 70% by mass or more of toluene insoluble matter, component (B), a sulfonic acid-modified anionic polyurethane emulsion, and (C) ) It is composed of a heat-expandable fine-grained hollow body as a component.

The polyvinyl alcohol-containing ethylene-vinyl acetate-polyfunctional monomer copolymer emulsion having a toluene insoluble content of 70% by mass or more is disclosed in JP-A-9-19.
No. 4811, it is a component that can be obtained by using the production method and is used for securing the adhesiveness to the plastic sheet surface, and enables only the plastic sheet to be removed again by heating. Is an essential condition that the toluene insoluble content is in the range of 70% by mass or more.

This toluene-insoluble matter was obtained by coating 2.0 g of the copolymer film with 200 ml of toluene at 60 ° C.
After the time extraction, measure the mass of the insoluble content recovered,
It is determined by the following equation (1).

[0017]

## EQU1 ## Toluene-insoluble matter (% by mass) = [(residual mass g)
/ (Film mass g)] × 100

The polyfunctional monomer is a monomer capable of supplying two or more ethylenic double bonds as a component of the copolymer, and specific examples thereof include triallyl cyanurate, triallyl isocyanurate, diallyl phthalate and the like. Is mentioned.

The ethylene / vinyl acetate / polyfunctional monomer copolymer emulsion having a toluene insoluble content of 70% by mass or more has a mass ratio of ethylene / vinyl acetate of 5-30 / 95-70. It is preferably from 10 to 30/90 to 70 from the viewpoint of the film forming property of the adhesive, the flexibility of the film, the heat resistance of the adhesive, and the mass ratio of the polyfunctional monomer / vinyl acetate is from 0.05 to 0. .4 / 1
00, more preferably 0.1 to 0.2 / 100. If the content of the polyvinyl alcohol is selected in the range of preferably 1 to 10% by mass, more preferably 3 to 8% by mass based on the whole polymer, the adhesion to various plastics is improved by the interaction with the aqueous polyurethane. Further, the presence of the toluene-insoluble component is a factor for providing excellent heat creep resistance and removability. If the toluene insoluble content is less than 70% by mass, good heat creep resistance and removability cannot be obtained. The proportion of a toluene-insoluble component that provides excellent heat creep resistance and removability is preferably 85 to 100% by mass.

If necessary, other monomers may be copolymerized into the above-mentioned copolymer emulsion of ethylene-vinyl acetate-polyfunctional monomer containing polyvinyl alcohol having a toluene insoluble content of 70% by mass or more. Examples of the other monomers include acrylic acid; methacrylic acid;
Acrylates such as 2-ethylhexyl acrylate, butyl acrylate, and ethyl acrylate; methacrylates such as butyl methacrylate and ethyl methacrylate; sulfonic acid and hydroxyl groups in addition to carboxyl group-containing monomers other than (meth) acrylic acid Various monomers containing a functional group such as an epoxy group, a methylol group, an amino group, and an amide group can be used.

The above-mentioned sulfonic acid-modified anionic polyurethane emulsion is a component used for exhibiting adhesiveness to a plastic sheet, in particular, heat creep resistance. Further, when this polyurethane emulsion is combined with the above-mentioned ethylene-vinyl acetate-polyfunctional monomer copolymer emulsion containing polyvinyl alcohol having a toluene insoluble content of 70% by mass or more, it is caused by blending a heat-expandable fine hollow particle. It is possible to suppress a decrease in water resistance, which is an adverse effect.

The sulfonic acid-modified anionic polyurethane emulsion has high stability even in the acidic pH range, and has a polyvinyl alcohol-containing ethylene-vinyl acetate-polyfunctional monomer copolymer having a toluene insoluble content of 70% by mass or more. It can be easily blended with the emulsion.

When an anionic polyurethane emulsion modified with a carboxylic acid is used, it is stored in a blend with a polyvinyl alcohol-containing ethylene-vinyl acetate-polyfunctional monomer copolymer emulsion having a toluene insoluble content of 70% by mass or more. Not only the stability is impaired, but the gelation can be achieved in a matter of minutes by incorporating the thermally expandable fine hollow particles. Therefore, it is an essential condition that the anionic polyurethane emulsion is modified with sulfonic acid.

The sulfonic acid-modified anionic polyurethane emulsion refers to an emulsion having a sulfonate group in the urethane polymer molecule and usually being a sulfonate salt and being emulsion-stable.

The sulfonic acid-modified anionic polyurethane emulsion has a solid content of 20%.
The content is preferably from 35 to 55% by mass from the viewpoints of workability, mechanical stability and the like.

Preferable specific examples of the sulfonic acid-modified anionic polyurethane emulsion include, for example, Sanyo Kasei Co., Ltd.'s UPUPN UXA-3005, UX-
306, Dainippon Ink and Chemicals, Inc. ECOS-10
00S, ECOS-1000H, and Superflex 410, 700, and 750 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

The above-mentioned thermally expandable fine hollow particles in the present invention are components that are blended to re-peel only the plastic sheet by heating, and have an expansion ratio of 20 to 100.
And the foaming start temperature is 90 to 150 ° C., for example, EXPANCEL053DU (Expancel)
(Expansion ratio 35 times, foaming start temperature 101 ° C.). Selection of this range is a preferable range of the present invention because foaming does not start at daily environmental changes and living environment temperatures, and it is easily peeled off during recycling.

The aqueous adhesive composition of the present invention comprises: (A) an emulsion of a polyvinyl alcohol-containing ethylene-vinyl acetate-polyfunctional monomer copolymer having a toluene insoluble content of 70% by mass or more, and (B) a sulfonic acid-modified emulsion. The preferred range of the mixing ratio of the anionic polyurethane emulsion and (C) the thermally expandable fine hollow particles is (A) Component 1
2 to 50 parts by mass of the component (B), particularly 3 to 40 parts by mass (solids), and 2 to 1 parts of the component (C) based on 00 parts by mass (solids).
It is preferably 00 parts by mass, particularly preferably 5 to 75 parts by mass. If the amount of the component (B) is too small, the heat-resistant creep property is remarkably deteriorated. Also,
If the amount of the component (C) is too small, it is difficult to remove again.

In the practice of the present invention, an aqueous processing kettle is used as a standard, and an ethylene-vinyl acetate-polyfunctional monomer copolymer emulsion containing polyvinyl alcohol having a toluene insoluble content of 70% by mass or more, sulfonic acid The modified anionic polyurethane emulsion and the heat-expandable fine hollow particles are mixed and processed. In this case, the thickener, p
An H adjuster, a filler, an organic solvent such as toluene, xylene, diethylene glycol monobutyl ether acetate, adipic diester, glutaric diester, and succinic diester, a plasticizer, an antifoaming agent, and a fungicide can be compounded.

The aqueous adhesive composition of the present invention is used in a continuous laminator machine, and can be usually applied to a porous board such as plywood or MDF by a roll spreader to bond a plastic sheet.

When the plastic decorative board adhered by the above method is to be peeled off again for the purpose of recycling, the plastic decorative board is left in an atmosphere of 150 ° C. or more for 20 minutes or more, and immediately forcibly peeled off by hand or the like. Thereby, only the plastic sheet can be removed again. Note that 12
When left at 0 ° C. for a long time (about 1 hour), the same effect is observed.

[0032]

The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

(Production of EVA (1)) Ethylene-containing polyvinyl alcohol having a toluene insoluble content of 70% by mass or more.
The vinyl acetate-polyfunctional monomer copolymer emulsion has a mass ratio of ethylene / vinyl acetate of 17/83, using triallyl isocyanurate as the polyfunctional monomer, and the mass ratio of the polyfunctional monomer / vinyl acetate. Is 0.
It was selected and copolymerized to be 1/100, and the polyvinyl alcohol content was set to 5% by mass of the whole polymer, and a polyvinyl alcohol aqueous solution was charged into a pressure polymerization apparatus to meet the design value. After enclosing ethylene gas, a mixed solution of vinyl acetate and a polyfunctional monomer was dropped, and emulsion polymerization was performed at 50 to 70 ° C. under pressure. The toluene insoluble content of this polymer is 9
2.5% by mass, its properties are viscosity 2000mPa · s
/ 25 ° C, solids content 55.3% by mass, pH 4.6. This resin emulsion is referred to as EVA (1).

(Production of EVA (2)) A resin emulsion was obtained in the same manner as in the production of EVA (1) except that the mass ratio of polyfunctional monomer / vinyl acetate was changed to 0.07 / 100. The toluene-insoluble content of this polymer is 75.5% by mass.
The properties were as follows: viscosity: 2200 mPa · s / 25 ° C., solid content: 55.0% by mass, and pH: 4.5. This resin emulsion is referred to as EVA (2).

(Production of EVA (3)) A resin emulsion was obtained in the same manner as in the production of EVA (1) except that the mass ratio of polyfunctional monomer / vinyl acetate was changed to 0.01 / 100. The toluene-insoluble content of this polymer is 65.3% by mass.
The properties were viscosity of 1800 mPa · s / 25 ° C., solid content of 55.4% by mass, and pH of 4.6. This resin emulsion is referred to as EVA (3).

(Example 1) (A) Toluene insoluble content is 70%
EVA (1) was used as an ethylene-vinyl acetate-polyfunctional monomer-based copolymer emulsion containing polyvinyl alcohol containing at least mass%, and the sulfone (B) of the present invention was used for 100 parts by mass (solid content) of the component (A). An acid-modified aromatic anionic urethane emulsion having a polyester skeleton having a sulfonic acid group (hereinafter referred to as “S group-containing PU”) (solid content: 45% by mass, pH: 8)
0 parts by mass (solid content) was added and mixed well. Then
C) EXPANCEL053 as a thermally expandable fine hollow particle
DU (foaming ratio 35 times, foaming start temperature 101 ° C) 40
A part by mass was added and mixed to obtain an aqueous adhesive composition.

(Examples 2 to 4, Comparative Examples 1 to 3) EVA (1), EVA (2) and EVA (3) in the amounts shown in the table
Aqueous adhesion was carried out in the same manner as in Example 1 except that [the component (A)], the S group-containing PU [the component (B)], and the thermally expandable fine hollow particles [the component (C)] were used. Agent composition was obtained.

The aqueous adhesive compositions obtained in the above Examples and Comparative Examples were subjected to the following performance evaluations, and the results are shown in Table 1.

[0039]

[Table 1]

As described above, in the examples, heat creep resistance and hot water immersion performance were excellent, and easiness of re-peeling was recognized under conditions of a short time such as 20 minutes at 150 ° C. Alcohol-containing ethylene-vinyl acetate-
When the toluene-insoluble content of the multifunctional monomer-based copolymer emulsion was 65.3% by mass, even if the thermally expandable fine hollow particles were blended, the peelability was extremely poor.
Unless a sulfonic acid-modified anionic polyurethane emulsion was blended as described above, heat creep resistance and hot water immersion performance were extremely poor.

(Preparation of Plastic Cosmetic Sample) The obtained water-based adhesive composition was uniformly applied to a 3.0 mm thick JAS1 type Rawan plywood using a rubber roll so as to have an application amount of 110 g / m ² . After bonding a decorative sheet made of polyethylene terephthalate having a thickness of 0.08 mm to the surface to which the aqueous adhesive composition has been applied, 0.2 M was applied at 22 ° C.
It pressed at the pressure of Pa for 1 hour. After the pressure was released, it was left to cure for 5 days at the same temperature to prepare a plastic decorative board sample.

(JAS2 Class Immersion Peeling Test) The obtained decorative sheet sample was cut into a 75 mm square, immersed in 70 ° C. hot water for 2 hours, and then dried in a 60 ° C. thermostat for 3 hours. Was measured. The evaluation is
：: no peeling, Δ: peeling within 25 mm per side, ×: peeling 25 mm or more per side.

(Heat-Resistant Creep) The obtained decorative board sample was cut into 25 mm (width) × 200 mm (length), and the decorative sheet made of polyethylene terephthalate was peeled off by 50 mm in the longitudinal direction from the end, then placed horizontally and peeled. After leaving the polyethylene terephthalate decorative sheet hanging in a constant temperature oven at 70 ° C. for one hour, 5 μm was applied to the end of the peeled polyethylene terephthalate decorative sheet.
The peel length after 24 hours under a load of 00 g was measured. In this case, the shorter the peel length, the better the heat-resistant creep property.

(Repeeling test) The obtained decorative board sample was cut into 25 mm (width) x 200 mm (length), and the decorative sheet made of polyethylene terephthalate was peeled 50 mm from the end in the vertical direction. The material was left in a thermostat set at each temperature for 20 minutes, and immediately the material was peeled off by hand to confirm the state of material breakage.

In this case, recycling is possible by peeling off at the interface of the decorative sheet, that is, by peeling off only the decorative sheet.

The evaluation was ○: interface peeling, Δ: mixed interface and wood fracture, ×: wood fracture or cohesive failure. The cohesive failure is a state in which the adhesive adheres to both the plastic sheet side and the porous board side and peels off, and the adhesive adheres to the plastic sheet, so that recycling is extremely difficult.

[0047]

As described above, the water-based adhesive of the present invention is suitable for bonding a plastic sheet containing a poorly adhesive material such as a polyester or polyolefin sheet to a porous board or the like to form an overlay decorative board. A water-based adhesive composition having the property of imparting adhesive properties and being easily peelable by heating the bonded material. The water-based adhesive composition is used for building materials, housing equipment and the like, and is used for water resistance and heat resistance. It has excellent performance in JAS2 immersion peeling test, etc .. When used as an adhesive product, maintain a sufficient adhesive state and adhesive performance, and heat to 150 ° C or higher when recycling. In the past, it was easy to peel off only the sheet by hand, and it was easy to recycle. Having had excellent properties.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J040 DA051 DD022 DE031 EF352 GA02 GA19 GA25 JA03 JA10 KA02 KA05 KA38 LA06 MA01 MA08 MA10 MA11 MB03 MB05 NA13

Claims (3)

[Claims] 1. An emulsion of (A) an ethylene-vinyl acetate-polyfunctional monomer copolymer containing polyvinyl alcohol having a toluene insoluble content of 70% by mass or more, (B) a sulfonic acid-modified anionic polyurethane emulsion, and (C) An aqueous adhesive composition comprising a thermally expandable fine hollow body. 2. The heat-expandable fine-particle hollow body has an expansion ratio of 20.
The aqueous adhesive composition according to claim 1, wherein the foaming start temperature is 90 to 150 ° C. 3. An anionic polyurethane emulsion modified with sulfonic acid with respect to 100 parts by mass (solid content) of a polyvinyl alcohol-containing ethylene-vinyl acetate-polyfunctional monomer copolymer emulsion having a toluene insoluble content of 70% by mass or more. The aqueous adhesive composition according to claim 1, wherein 2 to 50 parts by mass (solid content) and 2 to 100 parts by mass of the thermally expandable fine hollow particles are blended.