JPS6411234B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a urethane resin coating composition, and particularly to a solvent-free urethane resin coating composition that can be coated in thick coats. (Prior art) Steel structures that require high durability, high corrosion resistance, etc.
For example, thick film epoxy resin paints, tar epoxy resin paints, tar urethane resin paints, etc. have been mainly used for coated objects such as cast iron pipes, tanks, bridges, and marine structures. However, these paints dry slowly and usually take one to several days before they can be handled at room temperature, and especially at low temperatures in winter, there is a problem in that they require an even longer period of time. By the way, in the above, if the object to be coated is dried by heating, the drying time can be shortened considerably.
However, when the object to be coated is large, there is a problem in that it is not necessarily easy to implement from the standpoint of accompanying equipment. Therefore, urethane resins made of polyether polyols or polyester polyols and polyisocyanates, which have good drying properties, have been attracting attention in recent years, but they have the same durability and corrosion resistance as conventionally known paints. A solvent-free urethane resin paint that has the same properties and can be spray painted is not yet known. (Problems to be solved by the invention) In view of the above-mentioned current situation, the present inventors have
As a result of extensive research into a solvent-free urethane resin paint that has excellent corrosion resistance, short drying time, and can be spray painted, we have arrived at the present invention. (Means for Solving the Problems) The present invention is a reaction product of (1)(A)(i) castor oil...25 to 80% by weight, (ii) a polyhydric alcohol and an alkylene oxide, Its hydroxyl value is
100 to 600, and a polyol having a number average molecular weight of 1100 or less...15 to 70% by weight; (iii) a smoothing aid...1 to 20% by weight; (B) a curing agent component consisting of a polyisocyanate; and the equivalent ratio of isocyanate groups in the curing agent component (B) to hydroxyl groups in the base component (NCO/OH)
A urethane resin coating composition characterized by being blended in a ratio of (0.6 to 2.0/1.0), and as another embodiment, (2)(A)(a)(i) Castor oil... 25-80% by weight, (ii) polyol, which is a reaction product of polyhydric alcohol and alkylene oxide and has a hydroxyl value of 100-600 and a number average molecular weight of 1100 or less...15-70% by weight, and (iii) 100 parts by weight of a mixture consisting of 1-20% by weight of a smoothing aid; (b) a main component consisting of 10-100 parts by weight of a liquid bituminous substance; (B) a curing agent component consisting of polyisocyanate; Equivalent ratio of isocyanate groups in the curing agent component (B) to hydroxyl groups in the main component (NCO/OH)
It relates to a urethane resin coating composition characterized in that it is blended so that (0.6 to 2.0/1.0). (Specific Description) The castor oil used in the present invention is a non-drying oil usually obtained from castor bean seeds by a pressing method, and contains glyceride of ricinoleic acid as a main component. Usually, those having an average of about 2.5 hydroxyl groups in one molecule and a viscosity of about 6 to 9 stoke poise (at 20° C.) are preferably used.
Note that castor oil modified with polyhydric alcohols such as glycerin, trimethylolpropane, and pentaerythritol can also be used in the present invention, and is naturally included in the present invention. Furthermore, in the present invention, if the polyol component in the main component is castor oil alone, the reaction with the polyisocyanate is extremely slow and the resulting coating film is somewhat sticky. Therefore, in the present invention, a polyol (hereinafter abbreviated as "polyether polyol" as necessary), which is a reaction product of a polyhydric alcohol and an alkylene oxide, is further used as a polyol component. The "polyether polyol" used in the present invention includes diols such as ethylene glycol and propylene glycol; triols such as glycerin, trimethylolethane and trimethylolpropane; tetraols such as diglycerin and pentaerythritol; sorbitol and dipenta Hexaol such as erythritol; is an addition reaction between a polyhydric alcohol such as octaol such as sucrose and an alkylene oxide such as ethylene oxide or propylene oxide at a molar ratio of approximately 1/2 to 1/30. It has a hydroxyl value of about 100 to 600 and a number average molecular weight of about 1100 or less. If the hydroxyl value is less than 100 or the number average molecular weight exceeds 1100, the final coating film will be too soft and will tend to remain sticky. On the other hand, if the hydroxyl value exceeds 600, the resulting coating film becomes brittle. The use of the specified ranges is therefore particularly preferred. In particular, in the present invention, adducts of polyhydric alcohols and propylene oxide, such as glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, or mixtures of two or more thereof, have good coating workability and are advantageous. This is the most preferred because the resulting coating film has excellent mechanical strength. In the present invention, a "smoothness aid" is further blended as a main component. The smoothing aid has the function of adsorbing moisture and reacting with water. Specifically, zeolite, calcined lime, slaked lime, quicklime, etc. can be mentioned. Preferably, the powders have a particle size of less than about 500 microns, especially less than 100 microns. As is well known, urethane resins are obtained by reacting isocyanate groups with hydroxyl groups. No matter what the conditions are, if moisture is present (e.g., in the paint raw material, on the surface of the object to be coated, or in the atmosphere), the moisture will react with the polyisocyanate, producing carbon dioxide gas. Pinholes etc. occur in the coating film, and as a result, it is difficult to obtain a smooth and uniform coating film. Therefore, in the present invention, a smoothing agent that has the effect of adsorbing moisture or reacting with water is blended into the composition, and by removing moisture that reacts with polyisocyanate. , the various problems mentioned above are solved or improved. In particular, zeolite has been found to be suitable for the present invention because it has a fast water adsorption rate. In the present invention, the main ingredient consists of the above-mentioned components. The blending ratio is castor oil 25 to 80% by weight, particularly preferably 30 to 75% by weight, polyether polyol 15 to 70% by weight, particularly preferably 20 to 65% by weight,
Smoothness aid 1-20% by weight, particularly preferably 3-10%
A composition of % by weight is suitable. In the above composition, if the amount of castor oil is less than the above composition range, the fluidity of the paint will be low, resulting in poor painting workability.
The disadvantages are that the miscibility with pigments becomes poor and the resulting coating film has poor flexibility. On the other hand, if the amount of castor oil exceeds the above composition range, the curing speed will be slow and the resulting coating film will remain tacky. Therefore, neither case is preferable. Next, regarding polyether polyol, if it is less than the above composition range, the mechanical strength of the coating film will be insufficient, and conversely, if it is too much, the fluidity of the coating will be reduced, and the smoothness of the resulting coating film will be poor. A problem arises. Therefore, neither case is preferable. Regarding the smoothness aid, if the amount is less than the above-mentioned composition range, no effect will be observed, and if it is too much, the water resistance and chemical resistance of the coating film will decrease. Therefore, it is not desirable in any case. In another embodiment of the present invention shown above, a "liquid bituminous substance" is further used as the base ingredient. The liquid bituminous material further improves corrosion resistance, water resistance, and provides fluidity suitable for thick film coating of the composition. As the liquid bituminous substance, all liquid bituminous substances normally used in tar epoxy resin paints can be used and are easily available on the market.
For example, there are petroleum-based, coal-based, asphalt-based tar components, or their various derivatives.Specifically, coal such as Tarkron No. 230, Tarkron No. 180, Tarklon No. 180-L (product name manufactured by Yoshida Refinery), etc. Examples include tar compounds, tar pitch, coal tar, straight asphalt, blown asphalt, and mixtures of these with process oil. In the present invention, these liquid bituminous substances are blended in an amount of 100 parts by weight or less, preferably 10 to 80 parts by weight, to 100 parts by weight of the mixture consisting of castor oil, polyether polyol, and smoothing aid. . Incidentally, if the liquid bituminous substance is in excess of the above range, the crosslinking density of the resulting coating film will decrease, and the solvent resistance and physical strength will deteriorate, which is not preferable. Next, in the present invention, polyisocyanate is used as the curing agent component (B). Examples of the polyisocyanate include toluylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polyphenylmethane polyisocyanate (crude MDI), modified diphenylmethane polyisocyanate (modified MDI), xylylene diisocyanate (XDI), and hexyl diisocyanate (XDI). Typical examples include methylene diisocyanate (HMDI), trimer compounds of these polyisocyanates, and reaction products of these polyisocyanates and polyols. The polyisocyanate is mixed with the base component (A) immediately before use (painting) to form a paint. The mixing ratio is as follows: the equivalent ratio of isocyanate groups in the curing agent component to hydroxyl groups in the main component (NCO/OH) is
It is used within a range of 0.6 to 2.0/1.0, particularly preferably 0.9 to 1.6/1.0. However, if it deviates from this range, the original performance of the urethane resin will not be exhibited, which is not preferable. In the present invention, organic or inorganic coloring pigments such as yellow lead, zinc white, Bengara, chromium oxide, phthalocyanine blue, carbon black, titanium oxide, etc.; silica, barite, Extender pigments such as calcium carbonate, clay, talc, mica, red lead, calcium leadate, zinc chromate, basic lead chromate, zinc molybdate,
It is also possible to blend various pigments such as antirust pigments such as condensed zinc phosphate. In particular, in the present invention, in order to obtain a thick coating film,
Add 50 parts of this type of pigment to 100 parts by weight of the main component (A).
It is appropriate to mix it in a proportion of ~200 parts by weight. In the present invention, if necessary, the main component may include glass fiber, asbestos, nylon, a range of substances such as carbon, various plasticizers, modifiers such as various synthetic resins, or catalysts such as tertiary amines and organic tin compounds. ,
It is also possible to blend various additives such as ultraviolet absorbers and antioxidants. The method for applying the urethane resin coating composition of the present invention is, for example, by mixing the main component and the curing agent component immediately before use, and then spraying the mixture. Particularly preferred is a method of spray coating using a so-called two-liquid gun, in which only the main component is heated to 50 to 80°C and mixed with the curing agent component in a spray gun. As explained above, the urethane resin coating composition of the present invention can be spray coated and can be applied in one coat.
A thick coating of about 0.3 to 3 mm can be applied, and the drying time required for handling is several tens of minutes to several hours.
That is, compared to conventionally known paints of this type, the time can be significantly reduced. In addition, the resulting coating film has excellent durability and corrosion resistance, and is characterized by being smooth and dense. Furthermore, the present invention has the advantage that it can be applied not only to steel structures such as cast iron pipes and tanks mentioned above, but also to concrete, mortar, slate, wood, and other objects to be coated. Hereinafter, the present invention will be explained in more detail with reference to Examples. In the examples, "parts" and "%" are based on weight. Examples 1 to 11 and Comparative Examples 1 to 5 The main ingredients in the proportions (unit: parts) shown in Table 1 were sufficiently stirred and mixed with a stirrer, then kneaded with a sand mill, and then left in a sealed state for one day. did. This main ingredient heated to 70°C and the polyisocyanate shown in Table 1 are spray-painted onto a sandblasted steel plate using a two-component gun to a dry film thickness of approximately 1 mm, and dried at room temperature (20°C). I let it happen. The resulting coating film was subjected to various tests on curing time, adhesion, flexibility, hardness, water resistance, alkali resistance, acid resistance, salt water resistance, and coating appearance. The results are listed in the lower part of Table 1.

【table】

【table】

[Table] (Effects of the invention) The urethane resin paint of the present invention has a short curing time.
Moreover, the obtained coating film has excellent coating properties. (See Table 1) From a different perspective, when using a paint that does not contain polyether polyol or whose amount is less than the specified range of the present invention, the paint film will remain sticky forever and The membrane performance was also poor. (Comparative Examples 1 and 2) Furthermore, when a paint containing no castor oil or a small amount of castor oil was used, the paint film was very brittle and had poor smoothness.
(Comparative Examples 3 and 4) Furthermore, when a paint containing no smoothing aid was used, foaming remained in the paint film. (Comparative Example 5) It can thus be understood that the specific blended composition of the present invention is extremely excellent.

Claims (1)

[Scope of Claims] 1 (A) (i) Castor oil...25 to 80% by weight, (ii) A reaction product of polyhydric alcohol and alkylene oxide, with a hydroxyl value of 100 to 600 and a number average molecular weight of 1100 or less. A main component consisting of a polyol...15 to 70% by weight and (iii) a smoothing aid...1 to 20% by weight, and (B) a curing agent component consisting of a polyisocyanate, and the isocyanate group of the curing agent component to the main component. The equivalent ratio of hydroxyl groups (NCO/OH) is (0.6 to 2.0/
1.0). 2 The polyol (ii) is a reaction product of a polyhydric alcohol, which is glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, or a mixture of two or more thereof, and propylene oxide. The urethane resin coating composition according to scope 1. 3. The urethane resin coating composition according to claim 1, wherein the smoothness aid (iii) is zeolite powder. 4 (A)(a)(i) Castor oil...25-80% by weight, (ii) A reaction product of polyhydric alcohol and alkylene oxide, hydroxyl value 100-
600, a polyol with a number average molecular weight of 1100 or less...15-70% by weight; (iii) a smoothing aid...1-20% by weight; (b) 10-100 parts by weight of a liquid bituminous substance; and (B) a curing agent component consisting of polyisocyanate, the equivalent ratio of the isocyanate groups of the curing agent component to the hydroxyl groups of the main resin component (NCO/OH) is (0.6 to 2.0/
1.0). 5 Claims characterized in that the polyol (ii) is a reaction product of a polyhydric alcohol, which is glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, or a mixture of two or more thereof, and propylene oxide. The urethane resin coating composition according to item 4. 6. The urethane resin coating composition according to claim 4, wherein the smoothness aid (iii) is zeolite powder.