JPH0420933B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a method of adhering a synthetic resin molded product and a porous core material. BACKGROUND OF THE INVENTION Conventionally, in the field of wood industry, decorative boards made by laminating sheets or film materials such as natural wood, printed paper, and resin films on wood materials such as plywood are used as surface materials, and are assembled and processed into furniture and household appliances. It was common to produce building materials, etc. However, since these decorative laminates are flat, they are monotonous and lack a sense of three-dimensionality or weight, and their design is inevitably limited. Therefore, we added a sense of three-dimensionality and weight,
As a means to obtain a variety of designs, a three-dimensional resin molded product that has been molded in advance can be used as the surface material, and a porous core material that corresponds to the shape can be fitted in to create a product with a high degree of design. We can provide furniture, household appliances, and building materials to the world. The synthetic resin molded product referred to here is arbitrarily selected from a wide range of synthetic resins such as thermoplastic resins such as polyvinyl chloride, thermosetting resins such as melamine resin, etc., and the surface is printed with wood grain or other patterns as necessary. It means a material that has been decorated with. In addition, porous core materials include wood materials such as plywood, raw wood, laminated wood, chipboard, fiberboard, organic materials such as paper materials such as cardboard, gypsum board, calcium silicate board,
It means a porous substance that is an inorganic material such as a slate board. If such a porous core material is used, there is an advantage that a water-dispersed adhesive called an emulsion type can be used, which is easy to handle, highly safe, and easy to bond. For these types of bonding, a method can be used to apply an adhesive to one or both of the adherends and press them. Water, which is the main volatile component of the adhesive, is absorbed and diffused into the porous core material. , a dry and solidified adhesive layer is formed. However, when producing a synthetic resin molded product (hereinafter simply referred to as a molded article) and a porous core material having a corresponding shape (hereinafter simply referred to as a core material), the molded article may have a concave shape, a convex shape, or a concave shape. Based on the various shapes such as a flat plate shape or a combination of these shapes, the processing conditions of the molded product, the processing accuracy and processing limits when cutting the core material,
When the two are integrated, a gap or a cavity is usually created. The void here means a gap of about 1 mm or less, which is caused by misalignment caused by the dimensional accuracy of the shapes of the two or by unevenness on the surface of the core material. Further, a cavity is a gap between the core material and the core material that exists from the time of design due to processing limitations of the core material or when the molded product has a complicated shape. Ordinary water-dispersed adhesives used for these adhesives contain about half or more of water as a volatile component, causing volumetric shrinkage after drying, so they are not suitable for adhesives that require filling adhesives. It was causing a lot of trouble. That is, as mentioned above, if there is a gap between the molded product and the core material, it will naturally impede adhesion in that area, and the adhesive as a whole tends to exhibit a poor bonding area. In addition, if there is a hollow part, adhesive is applied to the back side of the molded product or the surface of the core material to form an adhesive film to increase the thickness and reinforce the material of the molded product, but the volume after drying Since the film formed by shrinkage is thin and these adhesive films are flexible, it is difficult to say that a sufficient reinforcing effect can be obtained. Therefore, when a molded product made using these adhesives and a core material are used as furniture parts such as the front door of a Japanese-Western chest of drawers or a drawer, the filling adhesiveness is insufficient, so it is difficult to use with fingers or hands. It produces an unpleasant squeak when pressed, and because the hollow part is not sufficiently reinforced, it lacks strength and easily dents. In such a state, the solid feeling and high-class image originally required of furniture will be wiped out, and the decline in quality value will be fatal. Furthermore, if there are spots that are not filled and bonded, the unbonded areas will swell or deform due to direct sunlight or the heat history of a heater such as a stove. It is no exaggeration to say that this is a fatal flaw. In order to overcome these difficulties, we have improved the adhesive properties of water-dispersed adhesives by adding inorganic fillers mainly composed of calcium carbonate and alumina, and organic fillers such as cellulose powder and wheat flour. However, due to the influence of the incorporation of fillers, the ratio of the adhesive component, which is an effective adhesive component, is relatively reduced, resulting in the disadvantage that the originally necessary adhesive strength is significantly reduced, and it is not effective at all. It was not a solution. In view of the above-mentioned current situation, the present inventor sought to establish an adhesion method that enables both strong adhesion and filling adhesion when adhering a molded product and a core material, and also enables reinforcement by increasing the thickness of the cavity. I have done extensive research on this purpose. As a result, a resin aqueous dispersion containing urethane polymers and vinyl polymers as main components contained 50% silica.
When using an adhesive containing silica filler in an amount of % or more by weight, there is almost no volumetric shrinkage of the adhesive layer after drying, and although the adhesive active ingredient is relatively reduced, Surprisingly, we discovered that the adhesive force (peel strength) was improved compared to when using the resin water dispersion alone, and that the reinforcing effect was improved when reinforcing the hollow part by thickening it. The invention was completed. What is particularly noteworthy is that in the adhesive used in the present invention, it is clear that the adhesive layer is hardened in view of the improvement in the reinforcing effect described above, but according to general adhesive theory, The peel strength decreases, and the softer the adhesive layer, the higher the peel strength), but the adhesive strength improves. Structure of the Invention The present invention provides an aqueous resin dispersion containing a urethane polymer and a vinyl polymer as main components to an adhesive part having voids or cavities when integrating a synthetic resin molded product and a porous core material. Silica content: 50% by weight
The present invention relates to a method of adhering a synthetic resin molded product and a porous core material, characterized in that the adhesive is bonded using an adhesive containing the above-described silica-based filler. Examples of the urethane polymer used in the present invention include Japanese Patent Publication No. 42-24192 and Japanese Patent Publication No. 42-19278.
Those shown in Japanese Patent Publication No. 53-38760 and Japanese Patent Publication No. 40-27349 can be used. Specifically, it is a urethane resin obtained by subjecting an aromatic or aliphatic isocyanate compound and a polyester or polyether compound to a urethane reaction. The manufacturing method is not limited, but those containing acid groups such as carboxyl groups and sulfonic acid groups in the molecule are preferred because they can be crosslinked with a crosslinking agent. In other words, when the type of resin used in the molded product or the moisture content of the core material is high, blistering or deformation is expected to occur due to the influence of heat history such as direct sunlight. By applying a crosslinking agent, heat resistance and water resistance are improved, and it is effective in preventing blistering and deformation. Preferred among the urethane polymers are polyester urethane polymers that exhibit a wide range of adhesive properties to various synthetic resins, and particularly preferred are these polymers containing carboxyl groups. Vinyl polymer has the general formula

[Formula] [In the formula, X represents a hydrogen atom, a halogen atom, or a lower alkyl group. Y is a hydrogen atom, a halogen atom,
It represents a cyano group, a -OCOR group (R represents a lower alkyl group), a -COOR' group (R' represents an alkyl group having 1 to 8 carbon atoms), or a phenyl group. ] Refers to a polymer of a compound represented by Specifically, it is one obtained by polymerizing at least one of vinyl monomers including acrylic esters, methacrylic esters, and acrylonitrile, such as ethylene, vinyl chloride, vinyl acetate, vinyl propionate, and styrene. When these monomers are resinized to form an aqueous dispersion, the manufacturing method is not limited, but usually at least one vinyl monomer is emulsion polymerized in the presence of an emulsifier and/or a protective colloid such as polyvinyl alcohol. Get this. Among these vinyl polymer aqueous dispersions, preferred are resin aqueous dispersions obtained by polymerizing at least one monomer selected from vinyl acetate, ethylene, and acrylic esters, and specifically, Aqueous dispersions of polyvinyl acetate, vinyl acetate-ethylene copolymer, vinyl acetate-acrylic copolymer, vinyl acetate-ethylene-acrylic multi-component copolymer, etc. exhibit good adhesion to various resin molded products. A point is fine. Vinyl polymers can optionally contain functional monomers such as carboxyl groups, glycidyl groups, and methylol groups, and if a crosslinking agent is applied to these, heat resistance and water resistance improve, resulting in blistering. and deformation can be prevented. In the present invention, these aqueous dispersions of urethane-based polymers and vinyl-based polymers have improved adhesive strength and adhesion performance by incorporating a predetermined silica filler, and have expanded the range of adhesion with various resin molded products. Therefore, it is necessary to use both together. The blending ratio of the two is not particularly limited, but it is usually good to set the resin content to about 10 to 1000 parts by weight of the latter to 100 parts by weight of the former. Examples of crosslinking agents that act on functional groups, typically acid groups, in urethane polymers and vinyl polymers include epoxy compounds such as glycerin diglycidyl ether and vinylphenol type epoxy resins;
Melamine compounds such as di- or trimethylolmelamine and its etherified products, isocyanate compounds such as diphenylmethane diisocyanate,
Examples include aziridine ring compounds such as 4,4-bis(ethyleneiminocarbonylamino)diphenylmethane and 2,2-bishydroxymethylbutanol-tris-[3-(1-aziridinyl)propionate]. The amount of the crosslinking agent to be blended is preferably about 0.5 to 40 parts by weight per 100 parts by weight of the resin content of the aqueous resin dispersion. A silica-based filler is an inorganic substance whose main component is silica (SiO ₂ ), and is a powder used in ceramic raw materials, clay, essential pigments for rubber, plastics, and the like. Specifically, zeolite, diatomaceous earth, sericite, silica sand, ziecrite (a mixed mineral of sericite and kaolinite), kaolinite such as kaolin clay, whitebait, talc, talc, white carbon, anhydrous silica, etc. can be exemplified. In the present invention, the silica content of the silica-based filler must be 50% by weight or more in order to obtain the effect of improving adhesive strength retention. In order to further improve adhesive strength, the silica content is preferably 70% by weight or more, particularly preferably 90% by weight or more. If the silica content is less than 50% by weight, the adhesive strength will not improve. Also,
From the viewpoint of workability, etc., it is preferable to use adhesives with low water absorption and little increase in adhesive viscosity. The method of blending a silica-based filler into an aqueous resin dispersion is usually to mix the silica-based filler in the form of a powder into an aqueous dispersion, and then stir the mixture using an appropriate stirring device to avoid creating foreign matter such as lumps. Mix it homogeneously. The reason why the adhesive compounded with the filler used in the present invention has less volumetric shrinkage and can achieve a filling adhesive effect higher than the concentration of the adhesive active ingredient is because the air contained in the filler is encapsulated during mixing and becomes fine bubbles, resulting in an adhesive bond. It is recognized that this is due to the effect that the bubbles remain when the layer is formed and the apparent volumetric shrinkage is reduced.
Therefore, in order to obtain this effect, it is better to mix so that bubbles remain naturally. The blending amount of the silica filler is preferably about 10 to 500 parts by weight per 100 parts by weight of the resin content of the aqueous resin dispersion. If it is less than 10 parts by weight, the filling adhesive effect will be reduced, and if it exceeds 500 parts by weight, the viscosity of the adhesive will increase too much, resulting in poor workability. Particularly preferably 50 to 300 parts by weight. On the other hand, the concentration of the compound (nonvolatile content or evaporation residue) is preferably 50% by weight or more, since it contributes to the filling adhesion effect and also influences the initial adhesion speed. especially,
A content of 60 to 80% by weight is preferable because filling adhesion is good and the initial adhesion speed is fast. Next, the bonding process of the present invention will be described. still,
Adhesion in the present invention includes ordinary adhesion and filling adhesion. The method of bonding the molded product and the core material includes an adhesive coating step and a pressure bonding step. The coating step also includes a thickening step when there is a hollow portion between the molded product and the core material.
Adhesive is applied to one or both of the molded product and the core material. As the coating method, conventional methods such as spray coating, roll coater coating, nozzle coating, brush coating, etc. can be used depending on the viscosity of the adhesive, the shape of the adherend, etc. The amount of application, the concentration of adhesive, and the amount of filler to be mixed may be determined each time depending on the condition of the gap, the width of the gap, etc. The range of gaps that are usually filled and bonded is 1
Approximately 80 to 1200 g/m ² of coating is applied. If the gap exceeds 1mm, it is better to coat both the core material and the molded product and press them together. If the gap is wider and it is difficult to fill and bond, apply a highly concentrated filler containing a large amount of filler to one or both of the molded product and core material in advance and let it dry to thicken it. Just do it. In addition, even if there is a cavity, a highly concentrated filler with a large amount is usually applied to the back of the molded product or the surface of the core material at an amount of 200 to 1500 g/m2 ^.
If you apply a certain amount with a spray or brush and let it dry to reinforce (thicken) it, it will not easily dent even if you press it by hand after adhesion. After applying the adhesive, the crimping operation is usually performed while the adhesive is still wet. However, if the gap is wide and the amount of coating is increased, or if both sides are coated, open time may be taken until the coating is half dry. As for the crimping method, any crimping method can be used, such as fitting it into a molding press and applying pressure from above, crimping it from each direction with a cylinder press, or pressing the entire body from both sides with a vacuum press. The pressing pressure is about 0.5 to 5 kg/cm ² , the pressing temperature is about 10 to 70° C., and the pressing time is determined depending on conditions such as adhesive concentration, temperature, pressure, etc., but at least 1 minute is required. Effects of the Invention According to the present invention, the following remarkable effects can be obtained. (1) The adhesive used in the present invention has improved adhesive strength in peel tests despite the fact that the active adhesive component is reduced due to the combination of silica filler, which is a non-adhesive component. . (2) By adding a silica filler, the volume shrinkage of the adhesive itself is reduced, and at the same time, the air contained in the filler is encapsulated in the adhesive, forming a dry film with air bubbles, resulting in an increase in apparent volume. The additive effect of alleviating shrinkage results in a good filling and adhesion state. (3) By adding a crosslinking agent to the adhesive used in the present invention, even if the molded product is thin or easily deformed by heat, it can prevent blistering or deformation due to thermal history such as direct sunlight. (4) The adhesive used in the present invention has a reduced water content due to the combination of silica-based filler and has a high initial adhesion speed, so the pressing time is short and productivity is excellent. (5) Even if the gap between the molded product and the core material is wide, if the adhesive of the present invention is applied and dried in advance, it can be filled and bonded by increasing the thickness. (6) Even if there is a cavity between the molded product and the core material, the effect of reinforcing the material can be obtained by applying the adhesive of the present invention to the back surface of the molded product or the surface of the core material and drying it in advance. Therefore, in furniture, household appliances, building materials, etc. that use molded products and core materials using the bonding method based on the present invention, the voids are sufficiently filled and bonded, and even if there are voids, the material is reinforced. Since the adhesive used in the present invention has strong and sufficient adhesive strength, it does not make unpleasant squeaking noises or easily dent when pressed with fingers or hands, and the quality of the product is stable, making it suitable for furniture, etc. It provides an inherently important sense of solidity, and also creates quality value that matches the high-class image. In addition, the problems of filling adhesion and material reinforcement are resolved, so even if a molded product has a complex shape due to the need for a three-dimensional effect or design, and there are many voids and cavities that the core material cannot accommodate, it is possible to It can be put to practical use as a product such as furniture. Furthermore, for molding or economic reasons,
Even if you choose a thin or easily deformable resin for the molded product, if you use a polymer with a functional group in the adhesive and add a crosslinking agent, the problems of blistering and deformation due to heat history etc. can be solved, so the molded product Needless to say, a wide range of resins can be selected. Examples Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 Vinyl acetate containing polyvinyl alcohol
Acrylic copolymer aqueous dispersion (monomer weight ratio,
Vinyl acetate: butyl acrylate: ethyl acrylate: acrylonitrile = 30:40:20:10, evaporation residue 45% by weight, viscosity 10000 ops) 40 parts by weight and carboxyl group-containing polyester-type aromatic isocyanate-based polyurethane aqueous dispersion (evaporation residue Adhesive paste A (evaporation residue 43% by weight, viscosity
1200cps). Per 100 parts by weight of this adhesive paste A, 45 parts by weight of various silica-based fillers with different SiO ₂ contents were stirred and mixed using a homomixer (product name "TK Auto Homomixer", manufactured by Tokushu Kiki Kogyo) to form each adhesive. (evaporation residue 61% by weight). The silica fillers used are listed in Table 1. still,
"Talc SS" and "ASP170" in Table 1 have a silica content of less than 50% by weight and were used for comparison.

[Table] The viscosity of each adhesive containing these fillers was measured using polyvinyl chloride sheet (thickness 0.4 mm, plasticizer 23 PHR, wettability index 36 dyne/cm).
and lauan plywood (thickness 5.5 mm, type, 3-ply) were bonded together by cold-press green bonding method under the following conditions. Application method: Apply to the base plate surface using a roll coater. Working temperature: 20℃, 60%RH. Coating amount: 150g/m ² . Deaeration: 1 pass with rubber roll. Deposition: within 20 minutes. Pressure tightening: 1.0Kg/cm ² x 40 minutes x 20℃. Curing: 5 days at 20℃ and 60%RH. Place each of these laminates parallel to the plywood fiber direction.
Adhesive strength was measured by a 180 degree peel test. The width of the test piece was 25 mm. Measurement temperature: 20℃, 60%RH. Tensile speed: 200mm/min. Number of pieces measured: 5 test pieces each. Measuring equipment: Autograph DSS5000 (manufactured by Shimadzu Corporation). Table 2 lists the viscosity and adhesive strength when each filler was blended.

[Table] As is clear from the test results in Table 2, SiO ₂ minutes
At 50% by weight or more, an effect of improving adhesive strength was observed.
In particular, the improvement effect of formulations containing 70% by weight or more of SiO ₂ was remarkable. Furthermore, Zeeklite GSM containing 92% by weight of _SiO2 did not increase the viscosity of the compound, was easy to apply, and had the best adhesive strength. Example 2 Carboxyl group-containing polyester-type aromatic isocyanate-based polyurethane aqueous dispersion (evaporation residue: 45
Vinyl acetate-ethylene copolymer aqueous dispersion containing 55 parts by weight (weight%, viscosity 400cps) and polyvinyl alcohol (monomer weight ratio, vinyl acetate:ethylene = 82:18, evaporation residue 55% by weight, viscosity 2000cps)
40 parts by weight, 3 parts by weight of toluene, 2 parts by weight as a crosslinking agent,
2-bishydroxymethylbutanol-tris-
Adhesive base B (evaporation residue: 49% by weight, viscosity: 800 cps) was obtained by blending 2 parts by weight of [3-(1-aziridinyl)propionate]. For this adhesive paste B, Sieglite GSM (SiO ₂ :92% by weight, average particle diameter of about 10 μm) was mixed in different amounts according to Table 3.

[Table] The evaporation residue and viscosity of the adhesives (B) to (F) were measured, and the polyvinyl chloride sheet and plywood were laminated under the same conditions as in Example 1, and various adhesion tests shown below were conducted. Ta. (1) Normal adhesive strength test: Same as the adhesive test method of Example 1 (number of test pieces: 5). (2) Water-resistant adhesive strength test: After immersing the specimen in water at 20°C for 24 hours, a 180 degree peel test is conducted while it is still wet according to the adhesion test method of Example 1 (the number of test sides is 5). (3) Heat resistant creep test... test piece at 60℃, 90℃
A static load of 500g per 25mm width is applied in the diagonal state, left for 1 hour, and the creep length is measured (3 test pieces). (4) According to the JAS Special Plywood Test Standards Class 1 Immersion Peeling Test (Boiling Water Test) method (the number of test pieces is 4
Individual). (5) Conforms to the JAS Special Plywood Test Standard Water Resistance A Test (Side Seal Water Resistance Test) method (number of test pieces is 4). (6) JAS special plywood test standard cold and hot cyclic A test (5
cycle) method (number of test pieces is 4). The test results are shown in Table 4. Note that all results are shown as average values.

[Table] (Note) Laminated products using adhesives (A) to (F) are
F○, and each corresponds to the other.
Judging from the test results, the laminates of blended products (b) to (f) ○B to ○F have improved effects on various adhesion performances compared to the laminate of non-blended product (a) ○B. . In particular, the effect of improving adhesive performance in (b) to (d) was remarkable, and the increase in viscosity was small, making the application process easier. Comparative Example 1 In Example 1, the amount of vinyl acetate-acrylic copolymer aqueous dispersion containing polyvinyl alcohol was 100 parts by weight, and the carboxyl group-containing polyester-type aromatic isocyanate-based polyurethane aqueous dispersion was not used. Adhesive base C (evaporation residue 43% by weight, viscosity
11000cps). Per 100 parts by weight of this adhesive base C, 45 parts by weight of various silica-based fillers shown in Table 1 were stirred and mixed in the same manner as in Example 1 to obtain each comparative adhesive. Using each of the obtained comparative adhesives, Example 1
The viscosity and adhesive strength were measured in the same manner as above. The results are shown in Table 5.

[Table] From the test results in Table 5, it can be seen that the adhesive strength of the comparative adhesive that does not contain urethane polymer is significantly lower than that of the adhesive used in the present invention in Table 2. it is obvious. Also,
The effect of improving adhesive strength by adding a certain silica-based filler was only a slight increase, up to 1.25 times (in the case of Zeeklite GSM). On the other hand, as shown in Table 2, the effect of improving the adhesive strength of the adhesive used in the present invention due to the filler is a maximum of 2.04 times (in the case of Zeeklite GSM formulation), showing a significant increase in strength. Comparative Example 2 In Example 2, the amount of the vinyl acetate-ethylene copolymer aqueous dispersion containing polyvinyl alcohol was 100 parts by weight, and the carboxyl group-containing polyester-type aromatic isocyanate-based polyurethane aqueous dispersion was not used. Adhesive base D (evaporation residue 54% by weight, viscosity
3200cps). For this adhesive base D,
By blending Sieglite GSM based on Table 3,
Each comparative adhesive was obtained. Using each of the obtained comparative adhesives, Example 2
The evaporation residue and viscosity were measured in the same manner as above, and various adhesion tests were conducted. The results are shown in Table 6. In addition, in Table 6, laminates ○I to ○ are shown in Table 3.
Corresponds to formulations (a) to (f) in the table.

[Table] From the test results in Table 6, the adhesive strength of the comparative adhesives that do not contain urethane polymers is significantly lower than that of the adhesives used in the present invention in Table 4. It is clear that the water resistance and heat resistance are inferior. In addition, laminates ○B to ○F of compounded products (B) to (F) containing a specified silica-based filler have better water resistance and The heat resistance was rather reduced, and the heat resistance of Example 2 (4th
As shown in Table 1, there was no significant improvement in adhesive performance due to the formulation. Furthermore, compared to Example 2, the viscosity increased due to the addition of fillers and was difficult to apply.

Claims (1)

[Scope of Claims] 1. A resin aqueous dispersion containing a urethane polymer and a vinyl polymer as main components is applied to an adhesive part having voids or cavities when integrating a synthetic resin molded product and a porous core material. A method of bonding a synthetic resin molded product and a porous core material, the method comprising bonding a synthetic resin molded product and a porous core material using an adhesive containing a silica filler containing 50% by weight or more of silica. 2. The aqueous resin dispersion contains a polyester urethane polymer containing an acid group and at least one selected from vinyl acetate, ethylene, and acrylic ester.
The adhesive method according to claim 1, which is a mixture with a vinyl polymer obtained by polymerizing seeds. 3. The adhesive contains 10 to 500 parts by weight of a silica filler per 100 parts by weight of the resin content of the aqueous resin dispersion,
The bonding method according to claim 1 or 2, wherein the nonvolatile content is 50% by weight or more. 4. Any one of claims 1 to 3, wherein the adhesive further contains at least one crosslinking agent selected from epoxy compounds, melamine compounds, isocyanate compounds, and aziridine ring compounds. Adhesion method described in Crab.