JPH0632777B2 - Method for forming coating film on railway vehicle roof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a coating film on a roof of a railway vehicle.

[0002]

2. Description of the Related Art A corrugation plate formed by bending a thin high-strength metal plate is used for the purpose of reducing the weight of railway vehicles. It is waterproof, corrosion-resistant, durable, and has a high withstand voltage (dielectric breakdown resistance). Japanese Patent Publication No. 59-8431 discloses a method for uniformly and thinly applying a coating film having voltage characteristics.

This known invention is a prior art film forming method using a non-sag type polyurethane resin for applying a brush or a roller to form a coating film because of mixing of bubbles at the time of stirring two liquids and mixing of poor stirring positions. With uneven thickness,
In addition, there is a limit to the reliability of the vehicle roofing material, such as a decrease in withstand voltage, and since it is necessary to apply multiple coats in order to eliminate these drawbacks, it becomes significantly heavy in weight. It is said that it was made in view of the fact that it is a thing. Specifically, DAM and MOC
Using a two-component room temperature curable polyurethane resin composition prepared by combining two kinds of A aromatic amines of A and composite prepolymer isocyanate (two kinds of TDI and MDI combined) of respective A and B components, In order to prevent the mixture of the two liquids in a low viscosity range with a starting mixer, the controlled chemical reaction of the above components is used to bring about a rapid change in viscosity, and immediately after spraying, a viscosity range in a thixotropic state is passed. It is a method of applying a coating film by spray coating, which is cured so as to prevent sagging by this chemical reaction.

According to the above-mentioned known invention, it takes 20 to 90 seconds at 40 ° C. to 45 ° C. to reach a thixotropic state after mixing the two liquids, and from a thixotropic state to a walkable cured state. It is said that the time is about 12 to 20 hours.

[0005]

However, according to the above-mentioned construction method, in order to prevent the coating film from dripping after the two liquids are mixed, D
A thixotropic state involving a rapid viscosity change in a very short time of 20 to 90 seconds due to a chemical reaction by AM and MOCA, and therefore bubbles entrapped during mixing of two liquids are difficult to escape There was a limit in roof performance. In addition, there is a problem in that the raw materials used are practically expensive. Furthermore, it has been pointed out that aromatic diamines have carcinogenicity.

The present invention, while maintaining the suitability for use as the vehicle roof, enables a coating film to be formed as the sagging prevention means without the above-mentioned chemical changes, thereby improving the work performance and the dielectric breakdown voltage. Another object of the present invention is to provide a method for forming a coating film for a railway vehicle roof, which has a higher insulation resistance value and can be more suitable as a vehicle roof coating film.

[0007]

As a method for forming a coating film on a roof of a railway vehicle for solving the above problems, the present invention is directed to a polyol having two or more hydroxyl groups containing a polyolefin polyol, and an organic and / or inorganic thixotropic agent. A two-component curable polyurethane resin composition having a thixotropic and slow curing rate, which comprises a mixture of an agent (anti-sagging agent) as a main agent and a polyisocyanate having two or more isocyanate groups as a curing agent, The method is characterized in that a coating film is formed by uniformly spray-applying the resin composition onto the roof structure surface of a railway vehicle.

The main component is a mixture of about 50 to 98% by weight of a polyol having two or more hydroxyl groups containing at least 30% by weight of a polyolefin polyol and about 2 to 50% by weight of an organic and / or inorganic thixotropic agent. Is desirable.

The above-mentioned polyolefin polyol has a smaller water absorption rate than the polyoxypropylene polyols disclosed in the above-mentioned publicly known documents, and has the effect of increasing the volume resistivity of the obtained polyurethane resin. obtain.

When the content of the polyolefin polyol is less than 30% by weight, the withstand voltage and the insulation resistance value of the paint become small, and it becomes difficult to sufficiently obtain the reliability of the roof of a railway vehicle or the like. When the polyol content is less than about 50% by weight or when the thixotropic agent content is greater than about 50% by weight, the viscosity of the main agent is so high that spray coating cannot be performed and the polyol content exceeds 98% by weight. If the thixotropic agent is less than about 2%, it becomes difficult to obtain the necessary thixotropy.

The above-mentioned polyol is an essential component of the urethane paint, but the larger the amount of the polyolefin polyol used, the higher the insulation resistance value of the paint can be. The thixotropic agent improves the thixotropy index of the paint.

The main component of the two-component curable polyurethane resin composition according to the present invention has a thixotropy index of 2 to
It is desirable that the range is 5. The thixotropy index here refers to the viscosity ratio at 50 ° C. when the rotation number by the F cone of the E-type viscometer is 1 and 10.

When the thixotropy index is smaller than 2, the coating film is liable to sag, and when it is larger than 5, stirring is difficult and the stirrer is liable to be damaged. The film becomes uneven and it is difficult to obtain a flat and uniform coating film.

Examples of polyolefin polyols include:
There are polybutadiene polyol, polyisoprene polyol, acrylic polyol, hydrogenated polybutadiene polyol, hydrogenated polyisoprene polyol, etc., and an average molecular weight of about 100 to 10,000, preferably about 1,000 to.
5,000 is good.

Examples of polyols other than the polyolefin polyols that can be used in combination include ethylene glycol, propylene glycol, butylene glycol, glycerin,
Low molecular weight polyols such as trimethylolpropane, pentaerythritol and bisphenol A, and polyoxyalkylene polyols obtained by adding alkylene oxides to the above low molecular weight polyols, and further ethanolamine, triisopropanolamine, ethylenediamineaniline, tolylenediamine. Examples thereof include amine polyols obtained by adding alkylene oxides to low molecular weight amines such as castor oil and castor oil modified polyols.

Examples of the organic thixotropic agent include castor oil derivatives, dehydration condensation products of sorbitol and benzaldehyde, polycarboxylic acid derivatives, modified polyolefin waxes, and the like.

Examples of inorganic thixotropic agents include silica, surface-treated calcium carbonate, talc and the like. Further, examples of the isocyanate include diphenylmethane diisocyanate (MDI), liquid MDI, polymethylene polyphenyl polyisocyanate (crude MDI), tolylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, and the above polyisocyanate. Examples thereof include isocyanate-terminated prepolymers obtained by reacting the above-mentioned polyol in the state of excess isocyanate groups.

N of the polyisocyanate used in the present invention
The ratio of CO to OH of the polyol (NCO / OH) is about 0.5 to 1.5, preferably about 0.8 to 1.2.
If it is lower than 0.5, the coating film is hard to cure,
If it is larger than 1.5, foaming is likely to occur, which is not suitable for forming a coating film.

It is needless to say that various inorganic fillers, plasticizers, colorants, catalysts, antifoaming agents, diluting solvents and the like can be used in combination with the two-part curable polyurethane resin composition according to the present invention.

[0020]

As described above, according to the present invention, the main component of the two-component curable polyurethane resin composition has a high thixotropy index and a large thixotropic property, so that the corrugation plate having a vertical surface, a bent portion, etc. Even if it is applied to etc., there is no dripping (no flow), and since the time until it becomes tack-free after application is relatively long, the bubbles entrained during the two-component mixed spray are removed. Since a sufficient time can be maintained, a thin and uniform coating film without bubbles can be formed. Therefore, it is possible to obtain a coating film having a large dielectric breakdown voltage and a large insulation resistance value, at the same time having a small water absorption rate and enhancing anticorrosion properties. Moreover, from the viewpoint of raw materials used, it is not a high-priced product. It is extremely suitable as a waterproof material.

[0021]

EXAMPLES The present invention will be described below with reference to two examples according to the present invention and comparative examples as known examples.

After the temperature of the main agent and the curing agent (units are parts by weight) shown in Table 1 (two examples) and Table 2 (comparative example) was adjusted to the main agent 50 ° C. and the curing agent 20 ° C., two-component airless mixing was performed. Using a spray coating machine (APW5000 type manufactured by Asahi Osumi Sangyo Co., Ltd.), a thickness of 1.
It was applied so as to be 0 mm. The performance of the obtained coating film is
After curing at room temperature of 20 ° C. for 2 to 7 days, it was subjected to a test. The coating performance and properties of the test results are shown in Table 3.

[0023]

[Table 1] "Example" Example 1 Example 2 Main ingredient [polyol] -Polybutadiene polyol 95 65 (OH value 46.5 mgkaf / g) -Polyoxypropylene glycol 520 (430) -castor oil modified polyol (same) 167) -15 [thixotropic agent] -silica 23-surface-treated calcium carbonate 1520 [additives, auxiliaries] -catalyst 0.1 0.1-foaming inhibitor 33 curing agent [polyisocyanate] -crude MDI (F-NCO 31.0%) 33.9- Liquid MDI (F-NCO 29.0%) 29.2

In Table 1, polyoxine propylene glycol is a commercial product, castor oil-modified polyol is a product of Ito Oil Co., silica is Nippon Aerosil Co., Ltd. product "Aerosil", and surface-treated calcium carbonate is Shiraishi Calcium Co. product "Gelton 50". , Respectively.

Each test was based on the following criteria. Hardness: JIS K6301 Tensile strength: JIS K7113 Elongation at break: JIS K7113 Dielectric breakdown voltage: (KV / mm): JIS C2105 Insulation resistance: JIS C2105 Water absorption rate: JIS C2105 Thixotropy index (shaking value): E-type viscosity Total,
Viscosity ratio at 50 ° C at rotations 1 and 10 with F-cone Gelation time: Tack-free state after application (generation of string)
Time to

[0026]

[Table 2] "Comparative example" Main agent -Polyoxypropylene triol (OH number 56.0) 30-Polyoxypropylene glycol (the same) 35-3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA) 35-4 , 4'Diaminodiphenylmethane (DAM) 40-Monophenyldiisopropylphenylphosphate 170-Dipropylene glycol 33% solution of triethylenediamine 2-Dioctylphthalate 140 curing agent -Polyoxypropylenetriol (OH value 56.0) and polyoxypropylene Terminal isocyanate prepolymer (F-NCO 31%) 800-Coronate 1040 (F-NCO 23%) 50 obtained by the reaction of a 1/1 mixture of glycol (the same) and tolylene diisocyanate 50 A product of Nippon Polyurethane Company was used.

[0027]

Table 3 / Examples (Example 1) (Example 2) (Comparative example) Hardness (Shore A) 75 70 55 Tensile strength (kgf / cm ² ) 29 33 31 Elongation at break (%) 75 80 480 Dielectric breakdown voltage (KV / mm) 30 28 23 Volume resistivity (Ωcm) 5 × 10 ¹⁵ Same as the left 4 × 10 ¹² Water absorption rate (50 ° C 7 days immersion,%) 0.7 0.8 1.5 Thixotropy of the main agent Index 3.0 3.8 1.5 Flowability of coating film on vertical iron plate None None None None Gelation time 180 seconds 180 seconds 20 seconds Good coating surface condition Good Good Air bubbles included

As is clear from the above, the coating film according to the present invention is preferable in physical strength as compared with the conventionally known comparative examples, and the elongation at break is also sufficient from the viewpoint of suitability for use, and the dielectric breakdown resistance. The voltage was high, the volume resistivity had a difference of 10 3 and the water absorption rate was halved, and excellent physical properties could be provided. The thixotropy index value of the coating film is about twice that of the comparative example, and the time to reach the tack-free state is maintained for a longer time than the conventionally known comparative example without causing the coating film flow, and the entrained bubbles are surely obtained. It was able to be released, resulting in a thin (light) good coating. Moreover, the cost of applying this coating film was lower than that of the comparative example.

Claims (3)

[Claims] 1. A curing agent containing a polyisocyanate having two or more isocyanate groups as a main component, which is a mixture of a polyol having two or more hydroxyl groups containing a polyolefin polyol and an organic and / or inorganic thixotropic agent, that is, an anti-sagging agent. Which has thixotropy and slow curing rate
A method for forming a coating film on a railway vehicle roof, which comprises preparing a liquid-curable polyurethane resin composition, and spray-coating the resin composition uniformly on the surface of the railway vehicle roof structure to form a coating film. 2. A mixture comprising, as a main component, about 50 to 98% by weight of a polyol having two or more hydroxyl groups containing at least 30% by weight of a polyolefin polyol, and about 2 to 50% by weight of an organic and / or inorganic thixotropic agent. The method for forming a coating film on a railway vehicle roof according to claim 1, which is used. 3. The method for forming a coating film on a railway vehicle roof according to claim 1, wherein the thixotropy index of the main component of the two-component curable polyurethane resin composition is in the range of 2-5.