JPH0347670B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention fixes poor substrates by simple preparation of the substrate, such as metal surfaces, concrete floors, walls, etc. that have been contaminated with oil, moisture, rust, etc., and provides long-term coating. This relates to paints for inferior quality surfaces that protect objects. [Prior Art] Conventionally, the most widely used method for long-term corrosion protection of steel structures has been painting, which uses epoxy resins, urethane resins, vinyl chloride resins, chlorinated rubber resins, etc., bituminous substances, and Products containing various pigments as main ingredients are widely used. However, in order to demonstrate excellent anticorrosion performance using these paints, it is necessary to prepare the substrate in advance, such as by sandblasting, and if this prescribed treatment is not sufficiently performed, various anticorrosion paints and metal substrates will not work properly. This results in poor adhesion and a marked decline in anticorrosion performance. Furthermore, when oil or water is present on the substrate surface, even more perfect preparation of the substrate is required, which often poses technical and economical problems. In particular, most of the repainting of existing steel structures is carried out on-site, which poses pollution and hygiene issues due to the generation of dust and noise, as well as restrictions on construction conditions. In many cases, it is impossible to apply such paints, and there has been a long-standing social demand for the development of paints for poor quality surfaces that can be painted without these treatments. Conventionally, it has been used as a paint for inferior substrates or as a method for coating inferior substrates (Japanese Patent Publication No. 58-46275).
(Japanese Patent Publication No. 1983-222176)
37148) etc., but the rust surface,
It is not suitable for surfaces to be coated that have the three major disadvantages of oil and wet surfaces, and both are inadequate for on-site construction. In addition, if a material that is adapted to the rust layer is used, the moisture contained in the rust layer will be sealed under the paint film and remain as it is, causing rust to grow and progress under the paint film. However, there was a drawback that the occurrence of spot rust was unavoidable. [Problems to be Solved by the Invention] The paint for poor quality surfaces of the present invention requires only a light degreasing of the oil-contaminated surface, and a light cleaning of the water-wet surface with a cloth. A corrosion-resistant coating equivalent to high-grade sandblasting can be applied to rusted metal surfaces by simply wiping it off with a sandblast, or by simply adjusting the surface using power tools such as a disk sander or power brush, or hand tools such as a pitting hammer or scaler. It is possible to provide a paint for poor quality surfaces that can form a film and exhibit excellent anticorrosion effects over a long period of time. [Structure of the invention] Rust is an oxide that contains condensed water, and this condensed water becomes an electrolyte and oxidation progresses further through the supply and diffusion of oxygen in the air, so it is applicable to rusted surfaces. It is important that the paint has the ability to remove moisture from the surface of the object to be coated or from the rust layer. The paint of the present invention can be applied directly to rusted surfaces because it uses a polyisocyanate mixture that has moisture curing properties.
It penetrates into the minute spaces on the rust surface and reacts with the moisture inside the rust, the hydrated iron oxide in the red rust, and the moisture in the air to form a hardened coating, converting the rust layer into an inert fixed layer. This is because it made it possible. Furthermore, the synthetic fluorine phlogopite and flaky iron oxide in the paint of the present invention overlap in the form of scales in the cured coating film, blocking the coated object from corrosion factors such as moisture and oxygen over a long period of time, and exhibiting a corrosion-preventing effect. Forms a base for painting. In addition, since it has excellent solvent resistance, it has become possible to coat it with epoxy resin paints, which are conventionally commonly used anticorrosion paints, and further increase the anticorrosion effect. Further, the attached oil is dispersed and diluted in the composition by the solvent 1.1.1-trichloroethane in the composition and incorporated into the cured coating film. The polyisocyanate compound in the paint of the present invention has an isocyanate group at the end of the molecule that is highly reactive with water molecules, so it is also suitable for wet surfaces. In addition, the objects to be coated to which the paint of the present invention is suitably applied are:
It is usually a metal surface, and steel is the most common, but it can also be applied to non-ferrous metals, and can also be applied to concrete surfaces when applied to oily and wet surfaces. The paint of the present invention will be explained below. The raw material polyisocyanate for the resin in the composition of the present invention includes tolylene diisocyanate (TDI),
Crude tolylene diisocyanate, diphenylmethane diisocyanate, crude diphenylmethane diisocyanate (C-MDI), hexamethylene diisocyanate (HMDI), and 3-mole tolylene diisocyanate adduct of trimethylolpropane, and high molecular weight products obtained therefrom. Polyisocyanates (prepolymers) and the like are used, and two or more of these are preferably used by appropriately blending and mixing them. In the present invention, mainly considering economic efficiency and safety and health aspects, crude diphenylmethane diisocyanate (C
-MDI) and tolylene diisocyanate (TDI)
It was adopted. Furthermore, by appropriately distributing hexamethylene diisocyanate (HMDI), premature reactivity can be suppressed without changing the performance of the cured coating, improving penetration into rusted surfaces and adjusting the desired curing time required for reaction. I planned to do this. This also provides the effect of imparting appropriate flexibility to the cured coating film. The specific blending amount of each polyisocyanate is not particularly limited in terms of coating film performance, and may be mixed as appropriate from the viewpoints of economy, safety and hygiene, and workability. It is as follows. C-MDI 30 to 70 parts (preferably 40 to 60 parts) TDI 20 to 60 parts (〃 30 to 50 parts) HMDI 5 to 30 parts (〃 8 to 15 parts) Add an appropriate methyl ethyl ketone solvent to the above and leave at room temperature. Then, mix in a system that blocks moisture to create a blended isocyanate solution. The effective NCO content in 100 parts by weight of the mixture obtained is 10-30% by weight, preferably 15-25% by weight. The weight part of the polyisocyanate mixture thus obtained is 15 to 40 parts, preferably 20 to 40 parts per 100 parts of the paint.
Mix 30 parts. If the amount is less than 15 parts, coating film performance with sufficient hardness will not be obtained, and physical properties will also deteriorate.
Moreover, if the amount exceeds 40 parts, an abnormal coating film due to foaming tends to occur, and the desired effective cured coating film cannot be obtained. In addition, the paint of the present invention contains synthetic fluorophlogopite (mica), which has the same crystal structure as naturally occurring phlogopite, but has water of crystallization (OH) replaced with fluorine (F), so it has anticorrosion properties as well. , heat resistance, and chemical resistance can be improved. The amount of these ingredients is 100% of the paint.
It is 10 to 25 parts by weight, preferably 15 to 20 parts.
If it is less than 10 parts, the desired effect cannot be obtained, and if it is more than 26 parts, the viscosity increases too much and workability decreases, making it impossible to obtain an effective coating film. Furthermore, the paint of the present invention contains 8 to 20 parts of scaly iron oxide (MIO), preferably 10 to 20 parts, as an essential component.
Contains 15 parts. If the amount is less than 7 parts, a sufficient effect will not be obtained, and if it is more than 21 parts, the specific gravity will be heavy and will tend to settle during work, making it difficult to form a cured coating film with the desired effect. In addition to the above, Bengara is added as a coloring pigment to the paint, but if necessary, extender pigments, anti-sagging agents, anti-settling agents, etc. can be mixed as appropriate. In addition, the polyisocyanate in the paint of the present invention reacts with moisture on the surface of the object to be coated and humidity in the atmosphere, generating carbon dioxide gas, so if it is applied too thickly at once, it will foam in the cured coating and form pinholes. In addition, it may react with compounded pigments and trace amounts of water in the solvent, reducing the storage stability of the paint, and the terminal isocyanate reactive groups may already be in the paint. If moisture is consumed and a cured coating film is used, it may not be possible to obtain the desired performance, but synthetic zeolite, synthetic silica, calcined gypsum, methyl orthoformate, etc. can be used as foaming inhibitors and paint stabilizers. The above problem can be solved by appropriately adding a removing agent alone or in combination of two or more. The paint obtained as described above can be used with the addition of a solvent, but in this case, the selected solvents include methyl ethyl ketone, ethyl acetate, toluene, 1.1.1-trichloroethane, xylene, etc., containing as much water as possible. I have to use what I don't have. In the present invention, 1.1.1-trichloroethane is mainly used to improve the oil surface adaptability and flame retardancy of the composition. The method of coating the composition thus obtained is as follows:
This can be done by already known means such as brush coating, roller coating, spray coating, etc. Oily surfaces need to be lightly cleaned with a degreaser, wet surfaces need to be wiped off with a rag, and then applied by brushing, rubbing the product into the substrate with a stiff brush. In addition, it is necessary to remove floating rust on the metal surface. If floating rust is removed and cleaning is not done, the adhesion of the paint film may deteriorate. Although the coating amount is not particularly limited, it is generally 40 to 200 μm in dry film thickness, preferably 50 to 150 μm. Next, Table 1 shows examples of the compounding ratios of the components of the paint of the present invention, but the scope of the present invention is not limited to these examples. In addition, all parts in the examples mean parts by weight.

【table】

[Table] Effective NCO in paints obtained in Examples
The content was about 4% by weight, about 5.5% by weight for Examples, and about 6% by weight for Examples. Test-1 The paint film performance on rusted surfaces was evaluated in the following manner for the paints obtained in the above examples and the comparative examples shown in Table 2 below. (1) Creation of test steel plate Cold rolled steel plate (JIS G-3141, SPCC-D)
The material was degreased with a solvent and exposed outdoors for six months to allow natural rust to develop.Then, the rust was removed using skin scraping and sandpaper and the condition was adjusted to SIS St-2 (Class 3 Ceramic). Next, the paint of each Example A was applied twice with a brush (Dry 120 to 150 μ) to the treated board, and the paint of each Example B was applied three times to the same treated board (Dry 50 to 70 μ).
This was left to cure indoors for 7 days and was used as a test plate. (2) Evaluation method Γ Paint film appearance Visually inspect the paint film for blisters, cracks,
Determine whether there are any abnormalities such as rust. Γ Adhesion Cut the base lines at 2 mm intervals with a cutter knife, peel off rapidly with adhesive tape, and count the number of remaining sections. ΓBending resistance: Bend 180° along a 1-inch diameter rod and check for cracks, peeling, etc. Γ Impact resistance Dupont impact tester 500g x 150
Apply impact with a 1/2 inch punch and check for peeling of the paint film. Γ Salt water resistance After soaking in 3% saline solution at room temperature for 3 months, examine the appearance and adhesion of the coating film. Γ Sulfuric acid resistance Examine the appearance and adhesion of the coating after immersing it in a 10% aqueous solution at room temperature for 30 days. Γ Hydrochloric acid resistance Examine the appearance and adhesion of the paint film after immersing it in a 10% aqueous solution at room temperature for 30 days. Γ Caustic Soda Resistance Examine the appearance and adhesion of the paint film after immersing it in a 10% aqueous solution at room temperature for 30 days. ΓSalt spray resistance JIS Z 2371 Examine the appearance and adhesion of the paint film after 2000 hours. (3) Evaluation criteria Γ Paint film appearance ◎ No abnormalities at all ○ Several blister points △ Full-face blisters and blisters × Full peeling Γ Flex resistance, impact resistance ◎ No abnormalities at all ○ No practical problems × Rejected Γ Adhesion ◎ No abnormalities at all (100/100) ○ No practical problems (95-99/100) △ Fail (90/100 or less) × Unmeasurable

[Table] The evaluation results from the above test are as shown in Table 2 above, and in each item, the best results were shown by the coating coated with the paint according to the present invention. That is, the paint coated with the paint for coating on inferior substrates according to the present invention has no abnormalities in terms of water resistance and salt water resistance, both in terms of film appearance and adhesion, as indicated by marks ◎, and also in sulfuric acid resistance and adhesion. Regarding hydrochloric acid resistance and caustic soda resistance, the appearance of the paint film was marked ◎ and showed no abnormality at all, and some of the adhesion properties were marked ○ (no practical problem), but in both cases, other companies' products (comparative examples and) It can be seen that the results were much better than those that were applied. Test-2 Tests on oil and wet surfaces were conducted and evaluated in the following manner. Creation and evaluation method of test plates The concrete slab for the sidewalk and the rust-treated steel plate were immersed in tap water for 3 days, then pulled out, left at room temperature (around 18°C) for 30 minutes, and then soaked in Ciel's diesel engine oil Rotella SX. It was immersed in water for 7 days and then pulled out. Next, lightly remove the surface of each board with a rag, moisten it with a damp cloth,
The paints of Examples-A, -A, and -A were applied by rubbing with a stiff brush. At room temperature (18-20℃,
Examples -A, -A, which appear to have been semi-cured after about 1 hour using a humidity of 68% (JIS Z 8806 psychrometer)
- Apply a solvent-free epoxy resin adhesive (base material: ADEKA EP4100/curing agent: ADEKA EP306, manufactured by Asahi Denka Co., Ltd.) on top of A, and after curing at room temperature for 7 days, the adhesive strength was determined using the Kenken adhesive strength test method. was measured.

【table】

Claims (1)

[Claims] 1 Crude diphenylmethane diisocyanate (C
- MDI), 20 to 60 parts by weight of tolylene diisocyanate (TDI) and 5 to 30 parts by weight of hexamethylene diisocyanate (HMDI). , 1.1.1- A poor quality surface paint characterized by containing trichloroethane.