JPH056593B2 - - Google Patents

Description

[Detailed description of the invention]

OBJECTS The present invention relates to a thick film-forming emulsion coating composition that dries rapidly and does not thermally blister. In more detail, the finished film thickness of several hundred microns on the object to be coated.
Even if the coating is applied to a temperature of more than m and then heated immediately at a high temperature without pre-drying at a temperature below the boiling point of water, there will be no thermal blistering.
The present invention relates to an aqueous emulsion coating composition that does not crack, sag, and has a smooth finish. (Prior Art and Process of Completion of the Present Invention) A coating film formed with a commonly used paint has a thickness of about 50 to 100 μm. On the other hand, a thick coating film of 300 to 1000 μm or more is called a thick film, but there are many problems in forming such a thick film compared to normal coating film formation. On the other hand, the technical fields that utilize thick films cover a wide range of areas, including the formation of surface protection layers, binder layers, and adhesive layers, and one-coat and one-bake methods are strongly desired from the productivity standpoint. It is rare. Conventionally, PVC plastisol-based coating materials have been used to form such thick films, but when the heating temperature reaches 140°C, the dehydrochlorination reaction causes significant deterioration of the coating film and plasticization. The paint film deteriorates due to migration and evaporation of the agent, and attempts have been made to use solvent-based paint as an alternative, but it is not only difficult to form a thick film, but also poses a risk of toxicity and fire due to the solvent. Due to the problem of resource conservation, there has been a desire for a water-based emulsion-based coating material that can form a thick film. However, when a water-based emulsion-based coating material is applied thickly, if it is immediately heated to a high temperature without pre-drying it at a temperature below the boiling point of water, the surface of the coating film dries first, resulting in a water-insoluble film. As the moisture remaining inside evaporates, the film lifts up, causing blisters (thermal blisters), or the film ruptures, causing cracks. Furthermore, since it is a thermoplastic resin, it softens at high temperatures and has the drawback of sagging where the surface to be coated is not horizontal. Therefore, conventional coating lines for solvent-based coating materials cannot be used as they are, and it is necessary to install a pre-drying line at a temperature below the boiling point of water. Further, since the coated surface formed with such a thick film coating material is often coated with a finishing coat, it is also required to be sufficiently smooth. In order to solve such problems, the present inventors conducted various studies. First, various emulsions have a particle size of approximately 200 to 400μ.
Add and mix silica sand to m and finish the film thickness on the iron plate.
When sprayed to a thickness of 500 μm and immediately placed in a drying oven at 150°C, there was significant sagging of the paint on the painted surface of the iron plate placed diagonally, and thermal blisters appeared on the painted surface of the iron plate placed on a horizontal surface. Furthermore, unevenness due to silica sand appeared, making it impossible to obtain a smooth painted surface. In place of silica sand, vermicrite with low specific gravity,
We tested with perlite, talc, and asbestos powder, but the heat blistering of the paint film was significant, and cracking and sagging could not be prevented. Next, in order to change the viscosity, we tested using polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, and sodium polyacrylate as thickeners, but all of them caused heat blister,
It was not possible to prevent it from burning and becoming soggy. The present inventors further continued their research, solved the conventional problems, and completed the present invention. (Structure) That is, the present invention consists of sepiolite and gel content.
A thick film-forming emulsion coating composition containing 20% to 90% synthetic resin emulsion and having a viscosity of about 5,000 to about 100,000 centipoise at 20°C, which does not cause thermal blistering even when rapidly heated and dried. (Description of structure) Sepilite used in the present invention has the general formula:
(OH ₂ ) ₄ (OH) ₄ MgSi ₁₂ O ₃₀・6～8H ₂ O, or
Si ₈ O ₂₀ Mg ₅ (OH) ₂ (OH ₂ ) ₄ 4H ₂ O is a hydrous hydrated magnesium silicate compound, which is made by refining and crushing special needle-shaped clay. (OH) is thought to act as a unique thixotropic agent. Also, it has a chemical composition similar to talc and asbestos, but its crystal structure is brick-like in cross section, with gaps in it, whereas talc is in the form of a plate and asbestos is in the form of a roll. Diameter is 0.1~0.5μ
It shows countless hollow fibers with a length of 8 to 10 μm. Therefore, it does not have the slipperiness of talc or the abrasion resistance of asbestos, but it has unique rheological properties, and these properties provide excellent heat-resistant blister resistance, chipping resistance, and The present inventors believe that this exhibits sagging resistance. The amount of sepiolite used is suitably from 0.3 to 10 parts by weight, preferably from 0.8 to 5 parts by weight, based on 100 parts by weight of the coating composition. If it is less than 0.3 parts by weight, there is no effect of preventing thermal blistering, and if it is added in excess of 10 parts by weight, the viscosity tends to increase and coating properties tend to deteriorate. The thick film-forming emulsion coating composition of the present invention has a viscosity of about 5,000 to about 100,000 centipoise.
10,000 to 50,000 centipoise is appropriate. Approximately 5000
If it is less than centipoise, thermal blistering and sagging cannot be prevented, and if it exceeds about 100,000 centipoise, coating properties tend to deteriorate. As the synthetic resin aqueous emulsion used as a binder for the thick film-forming emulsion coating composition of the present invention, an aqueous emulsion obtained by emulsion polymerization of α,β monoethylenic monomers, which can be used as a binder for general emulsion paints, is suitable. be. Namely, (meth)acrylates such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, 2-ethylhexyl acrylate, and nonyl acrylate; vinyl esters such as vinyl acetate and Beoba (trade name of vinyl ester manufactured by Ciel Chemical); , isoprene, butadiene and other dienes, and optionally ethylene, styrene, vinyl chloride, acrylic acid, methacrylic acid, crotonic acid, acrylonitrile, acrylamide, N-methylolacrylamide, hydroxyalkyl acrylate, glycidyl methacrylate, and divinylbenzene. An emulsion prepared by copolymerizing copolymerizable monomers such as , triallyl isocyanurate, and tetraallyloxyethane is used. The synthetic resin emulsion with a gel content of 20% to 90% used in the present invention is a synthetic resin emulsion with polymerizable unsaturated groups such as divinylbenzene, triallylisocyanurate, and tetraallyloxyethane among the above-mentioned synthetic resin aqueous emulsions. In emulsions that are polymerized by containing monomers having two or more of , or mutually crosslinking monomers such as glycidyl methacrylate and acrylic acid, internal crosslinking occurs during polymerization, resulting in a three-dimensional structure. Polymers are formed and components insoluble in organic solvents are formed. The content of this solvent-insoluble matter is called gel content, and in the present invention, by using an emulsion with a gel content of 20% to 90%, excellent heat-resistant blister properties and cracking resistance are exhibited. Since the gel content shows different values depending on the type of polymer and the type of organic solvent, in this application, the weight (W ₀ ) of the film obtained from the emulsion was determined by drying it at 40°C for 16 hours. was extracted with acetone at reflux temperature for 3 hours, and the remainder was dried under the same conditions as above to determine the weight (W ₁ ), and the gel content was calculated using the following formula. Gel content (%) = W ₁ /W ₀ ×100 When the gel content is less than 20%, there is no significant difference from that without internal crosslinking, but when it exceeds 90%, cracks are more likely to occur. As the polymerization method for the synthetic resin emulsion, known emulsion polymerization methods such as batch polymerization, multistage polymerization, low temperature polymerization, pressure polymerization, monomer drop polymerization, emulsion monomer drop polymerization, etc. are used. (Effects) The thick film-forming emulsion coating composition of the present invention has an excellent property of forming a smooth finished surface without generating thermal blisters, cracks, or sagging even if it is rapidly heated and dried after application. It has an effect. For example, even if the film is coated thickly to a finished film thickness of about 500 to about 1500 μm and rapidly dried in a high-temperature drying oven at temperatures of 120 to 200 degrees Celsius without pre-drying at a temperature below the boiling point of water, thermal blistering will occur. No cracking occurs, no sagging occurs even on vertical or inclined coating surfaces, and the coating surface is extremely smooth after drying. Therefore, it can be very suitably used as an emulsion-based coating material for coating lines that produce thick film coated products using a rapid heating and drying oven. For example, when used as a chipping-resistant coating material for automobiles, which has traditionally been difficult to achieve with water-based coatings, it exhibits superior effects that are incomparable to PVC plastisol-based coating materials or solvent-based coating materials. It can also be suitably applied as a carpet lining agent, which has hitherto had many problems. That is, tufted carpets, which are often used as interior goods, are coated with a coating material called a backing agent in order to prevent the pile from falling off and to provide dimensional stability. Solvent-based coatings have also been used, but water-based emulsion coatings are superior in that they pose no fire hazard and are easy to apply due to their low viscosity even at high concentrations. The disadvantage is that there is a strong tendency for so-called thermal blisters to bleed onto the surface. However, when the thick film-forming emulsion coating composition of the present invention is applied to a carpet backing agent, no thermal blisters occur and it exhibits extremely excellent effects. Next, the present invention will be explained with reference to Examples and Comparative Examples. Production Example 1 Into a polymerization tank equipped with a stirrer, reflux condenser, thermometer, and dropping funnel, add 110 parts of water (parts by weight, same below),
Add and mix 1.5 parts of sodium lauryl sulfate and bring the internal temperature to
The temperature was raised to 80°C, the inside of the tank was replaced with nitrogen gas, and then 100 parts of a mixed monomer of 48 parts of methyl methacrylate, 48 parts of 2-ethylhexyl acrylate, 3 parts of acrylic acid, and 1 part of tetraallyloxyethane was added. 1 part of the 4% potassium persulfate aqueous solution was added to start polymerization, and the remaining mixed monomers and the remaining potassium persulfate aqueous solution were added dropwise over 3.5 hours. After further aging for 1 hour and cooling, the pH was adjusted to 7.5-8 with aqueous ammonia to obtain an emulsion with a gel content of 45% and a concentration of about 45%. Production Example 2 After polymerizing in the same manner as Production Example 1, add 50% water.
and 1.5 parts of polyoxyethylene nonylphenol ether, the internal temperature was set to 50°C, and a mixture of 20 parts of methyl methacrylate, 14 parts of butyl acrylate, and 2 parts of divinylbenzene was added, and after 30 minutes, 5% acidity was added. 5 parts of sodium sulfite aqueous solution and 5 parts of 4% potassium persulfate aqueous solution were added dropwise over 1.5 hours for two-stage polymerization,
After aging for 1 hour, the pH was adjusted to 7.5-8 with aqueous ammonia to obtain an emulsion with a gel content of 75% and a concentration of about 43%. Production Example 3 In Production Example 2, the polymerization in Production Example 1 was not carried out, and a gel content of about 40% was added to the same polymerization tank as in Production Example 1.
%, minimum film forming temperature 0℃, styrene concentration approximately 45%.
222 parts by weight of butadiene synthetic rubber latex was charged in place of the emulsion in Production Example 1, and two-stage polymerization was carried out in the same manner as in Production Example 2. The gel content was approx.
An emulsion with a concentration of 80% and approximately 43% was obtained. Production Example 4 An emulsion having a concentration of about 45% was obtained in the same manner as Production Example 1 except that tetraallyloxyethane was removed from the mixed monomers. Example 1 (Thick film coating material) Each component was uniformly kneaded according to the following recipe to obtain a red thick film coating material. (Formulation) Emulsion obtained in Production Example 1 (concentration approximately 45%)
50 parts by weight 10% sodium tripolyphosphate 10 〃 Aqueous solution (dispersant) Sepiolite (Ade Plus SP) 2 〃 Calcium carbonate (average particle size approximately 5 μm) 90 〃 2% hydroxyethylcellulose 10 〃 Aqueous solution (thickener) Water Appropriate amount Pickled The coating material has a viscosity of approximately 20,000 centipoise, and can be applied in thick films to slate, mortar, rust-proofed metal surfaces, etc., and has excellent general coating properties such as weather resistance, adhesion, and wash resistance. The heat blister resistance was shown to be extremely good, as shown in a separate comparative test along with comparative examples. *Ade Plus SP is a product of Takeda Pharmaceutical Co., Ltd., and is sepiolite that has been treated to be easily dispersed in water. Comparative Example 1 (Thick film coating material) In the formulation of Example 1, "50 parts by weight of the emulsion obtained in Production Example 1 (concentration approximately 45%)" was replaced with "the emulsion obtained in Production Example 4 having a gel content of 0% (concentration approximately 45%)".
A thick film coating material was obtained in the same manner as in Example 1 except that the amount was changed to 50 parts by weight. The resulting coating material has a viscosity of approx.
40000 centipoise, slate, mortar,
Can be coated with a thick film on rust-proofed metal surfaces, etc.
The general coating properties such as weather resistance, adhesion, and washing resistance are also very good, and the heat blister resistance is shown in a separate comparative test, and it was excellent at finished film thicknesses of about 1100 μm or less, but poor at about 1500 μm. Nakatsuta. Example 2 (Thick film coating material) In the formulation of Example 1, "50 parts by weight of the emulsion obtained in Production Example 1 (concentration approximately 45%)" was replaced with "50 parts by weight of the emulsion obtained in Production Example 3 (concentration approximately 43%)". ”
, change "Sepiolite (Ade Plus SP) 2 parts by weight" to "Sepiolite (Atagel) 3 parts by weight"
A thick film coating material was prepared in exactly the same manner as in Example 1, except that the following was changed. The obtained coating material has a viscosity of approximately 30,000 centipoise, and its general coating performance is excellent, as in Example 1 and Comparative Example 1.The heat blister resistance is shown in a separate comparative test along with the comparative example, and is extremely excellent. Ta. **Atagel is the trade name of sepiolite manufactured by Tsuchiya Kaolin Co., Ltd. Example 3 (Carpet lining agent) Each component was uniformly kneaded according to the following recipe to obtain a white carpet lining agent. (Formulation) Emulsion obtained in Production Example 2 (concentration approximately 43%)
200 parts by weight 10% sodium tripolyphosphate 10 〃 Aqueous solution (dispersant) 10% zinc white dispersion 3 〃 Sepiolite (Ade Plus SP) 5 〃 Calcium carbonate (average particle size approximately 5 μm) 300 〃 Titanium oxide 20 〃 2% polyacrylic Acid soda 50 〃 Aqueous solution (thickener) Anti-aging agent 2 〃 The obtained backing agent has a viscosity of 15,000 centipoise, and when it was applied thickly to the back of the carpet and immediately heated and dried, thermal blistering (oozing to the surface) occurred. There wasn't any. Comparative Example 2 A coating material was prepared by changing "2 parts by weight of sepiolite" to "2 parts by weight of talc" in the formulation of Example 1. Comparative Example 3 In the formulation of Comparative Example 1, "2 parts by weight of sepiolite" was replaced with "2 parts by weight of asbestos powder" to create a coating material. Comparative Example 4 A coating material was prepared by changing the formulation of Example 2 from "3 parts by weight of sepiolite" to "2 parts by weight of talc and 1 part by weight of asbestos powder." Comparative test (heat-resistant blister) Examples 1 and 2, Comparative examples 1, 2, 3 and 4
Apply the coating material to a degreased iron plate with an applicator to a thickness of 80 μm, 160 μm, 320 μm, 650 μm, 950 μm,
1450μm, 1800μm, 2500μm (finished film thickness respectively approximately 50μm, 100μm, 200μm, 400μm, 600μm,
900μm, 1100μm, 1500μm) and immediately
After drying in a drying oven at 120-160°C, the coated surface was examined for thermal blisters, cracks, and sagging on vertical surfaces. The test results were as shown in Table 1.

【table】

[Table] 〓×：Yes

Claims (1)

[Claims] 1. A thick film-forming emulsion coating composition that does not cause heat blistering even when rapidly heated and dried, which contains sepiolite and a synthetic resin emulsion with a gel content of 20% to 90%, and has a viscosity of about 5000 to 100000 centipoise at 20°C. thing.