JPS6128704B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to vehicle compositions, particularly vehicle compositions containing particulate solids, and more particularly single-package zinc-filled vehicle compositions that, when applied to a metal surface, provide galvanizing protection thereto. Regarding. Zinc-filled protective coatings are used to protect metal surfaces, especially iron surfaces, from corrosion. For example, US Pat. No. 3,056,684 discloses a zinc-filled coating that utilizes partially hydrolyzed tetraethylorthosilicate as a vehicle. Another method for making zinc-filled protective coatings is described in U.S. Patent No.
No. 3,730,743, in which zinc powder is incorporated into a vehicle composition obtained from hydrolysis and condensation of an alkyl polysilicate. When these vehicles are mixed with zinc and applied to the surface of an object, the coating hardens or dries after a few hours. However, if zinc is added to the vehicle at the time of packaging, gelation will occur within a few hours due to the reactivity of the zinc with the vehicle resulting in a short "shelf life". This is unacceptable. Many of the single-package zinc-filled protective coatings produced to date have another problem: outgassing. These compositions evolve gas, apparently hydrogen, within the container when stored at room temperature for periods exceeding about two months. One strategy to address the problem of outgassing in single-pack zinc-filled coating compositions is to package the material in a container with a pressure regulating valve to allow hydrogen gas to escape. However, such deviations from standard packaging formats are undesirable because they require specialized containers and complicate the manufacturing process. Moreover, this approach raises safety concerns since the evaporating flammable solvent will also escape through the pressure regulating valve. Other zinc-rich coating compositions containing substantially non-aqueous colloidal silica, zinc chloride and zinc dust suspended in an organic solvent are described in US Pat. No. 3,615,730. It has been found that these coating compositions have disadvantages, for example they are stable for periods of up to one month at most. Thus, it has not heretofore been possible to create a single-pack zinc-filled silicate coating composition that is stable for several months and yet yields a coating of quality comparable to that of the coating of the present invention. Thus, vehicle composition preparation is one object of the invention, and it is another object of the invention to provide a single-pack coating composition containing a metal that serves as a cathode. Another object of the present invention is to provide a single-pack zinc-filled coating composition for use on iron-containing substrates, and yet another object is to provide a single-pack zinc-filled coating composition with substantially no hydrogen evolution. An object of the present invention is to provide a one-pack zinc-filled coating composition. Yet another object of the present invention is 1-24
It is an object of the present invention to provide a single-pack zinc-filled coating composition that provides a hard, wear-resistant coating layer on a ferrous substrate within hours and has a "shelf life" of at least four months. Excellent single-pack protective coating compositions available from 50 to
It has now been found that it can be made from a vehicle containing an alkyl polysilicate, zinc chloride and an organic solvent that has been hydrolyzed to a level of 65%. The vehicle is mixed with the metal serving as the cathode, and optionally filler, and then applied to a ferrous substrate to form a protective coating layer thereon. The alkyl polysilicate useful in the present invention is an alkyl polysilicate, preferably an ethyl polysilicate, specifically an ethyl polysilicate having about 40% available silica and containing an average of about 5 silicon atoms per molecule. It is a mixture. This can be made by controlled hydrolysis of tetraethylsilicate. The formula of ethyl polysilicate can be shown as follows. [Additional information on making the partial hydrolysis products of the monomeric organosilicon compounds described above is provided by HD Hogan and CA Setterstrom in Industrial and Engineering Chemistry Vol. 39, No. 11 (1947), p. 1364. It will be found in the paper entitled "Ethyl Silicate". ] The vehicle composition of the present invention is prepared by combining the ethyl polysilicate with sufficient water and an acid catalyst at about 80°C.
ethyl polysilicate in the presence of an organic solvent with a boiling point ranging from 50 to 65
It is made by hydrolysis to the level of %. It has been found that the level of hydrolysis is of critical importance in providing single package coating compositions with the desired hardness, "shelf life" and "pot life". If the hydrolysis level of the alkyl polysilicate is less than about 50%, the resulting coating layer has a pencil hardness of less than 4B after 1 hour and a pencil hardness of approximately F after 24 hours. When the hydrolysis level of the alkyl polysilicate exceeds about 65%, the pencil hardness of the resulting coating is approximately 3B after 1 hour and approximately 6H after 24 hours, but the "pot" of the coating composition is・Life' is only 2 days, and its ``Sielf life'' is only about 10 days. The term "hydrolysis level" or "degree of hydrolysis" refers to 50
Refers to the amount of water required to hydrolyze up to 65%. That is, when an alkyl polysilicate is used, the amount of water required to achieve a 50 to 65% hydrolysis level ranges from 0.08 to 0.21 moles of water per mole of alkoxy groups on the alkyl polysilicate. be. It is preferred, but not essential, to use a solvent in preparing the vehicle compositions of the present invention. Examples of preferred solvents are relatively high boiling ethers such as monoalkylene glycol monoalkyl ethers, dialkylene glycol monoalkyl ethers, dialkylene glycol dialkyl ethers and monoalkylene glycol dialkyl ethers. Other solvents that can be used are ketones such as acetone; alcohols such as ethanol, isopropanol, butanol, hexanol, diacetone alcohol; glycols such as ethylene glycol and polyalkylene glycols; hydrocarbon solvents such as hexane, heptane, benzene, toluene, xylene. , chlorinated hydrocarbon solvents and mixtures thereof. Drying time, viscosity, etc. can be adjusted by proper selection of the solvent or solvent mixture. The ratio of solvent to alkyl polysilicate varies widely depending on the properties desired for the final binder. Thus, the ratio is from about 0.5:1 to
It can take any value within the range up to 10:1. The amount of acid required to hydrolyze the alkyl polysilicate is not critical, but from about 1.0 to about
PH of 6.5, and more preferably about 1.4 to 5.5
Preferably, sufficient acid is present to produce .
Inorganic acids suitable for use are hydrochloric acid, sulfuric acid and hydrofluoric acid, which acids may be used alone or in combination. Then also monobasic and dibasic organic acids, and metal chlorides, metal nitrates, metal sulphates and metal salts of carboxylic acids, where the metal is selected from the first and third groups of the periodic table, are used. It's fine. Examples of suitable organic acids are acetic acid, butyric acid, caproic acid, capric acid, palmitic acid, oleic acid, oxalic acid, fumaric acid, crotonic acid, acrylic acid, maleic acid, malonic acid, succinic acid, glutaric acid, adipic acid. , suberic acid and sebacic acid. Other organic acids which may be used include benzoic acid, toluenesulfonic acid, alkylphosphoric acids in which the alkyl group contains 1 to 4 carbon atoms and halogenated carboxylic acids. Techniques for making vehicle compositions are known in the art. However, it is preferred that sufficient water, preferably acidified water, be added after the polysilicate has been dissolved in the organic solvent so as to obtain a hydrolysis range of 50 to 65%. The hydrolysis temperature is not critical and ranges from about 25° to about 80°C, more preferably 30°C.
It is sufficient that the temperature is within the range from ゜ to about 50℃. The vehicle composition incorporates zinc chloride into the hydrolyzate in an amount of about 3 to 5.5% by weight, more preferably about 3.5 to 5% by weight, based on the total weight of the hydrolyzate (hydrolyzed silicate ester and organic solvent). prepared by adding The coating composition is prepared by combining the vehicle composition described above with finely divided particulate solids, such as metals serving as cathodes, such as zinc dust, and if desired, fillers, in the presence of an inert atmosphere for at least 0.5 hours. made by stirring. This coating composition is applied onto a metal substrate to provide galvanization protection thereto. Other cathodically active metals that may be used are aluminum and magnesium. Fillers or extenders that can be used in these coating compositions are, for example, metal oxides such as lead oxide, iron oxide, alumina, titanium dioxide, iron monophosphide, and the like. Instead of pure metal powders, it is often desirable to use mixtures of metal powders with suitable fillers, such as calcium and magnesium metasilicates or minerals containing them. Other fillers, especially fibrous mineral fillers such as asbestos, silica, refined clay, fibrous talc, fibrous calcium metasilicate, plaster, etc., are also used in these coating compositions together with metal powders, such as zinc dust. May be mixed. Additional materials that may be included within the coating composition are pigments such as zinc chromate, cadmium sulfide and most of the lithopones. The ratio of vehicle to particulate solid is largely a matter of customer preference or the specification to be followed. Generally, the particulate solids of the vehicle (i.e. cathodically active metals and fillers)
The ratio by weight is in the range of 70:30 to 10:90. However, if fillers such as the calcium and magnesium metasilicates listed above are not incorporated into the composition, the ratio of vehicle to cathodically active metal will be from about 10:90 to about 50:50 on a weight basis. It is preferable that it is up to. Generally, these coatings can be cured within about 1 to 24 hours at ambient temperature. However, if desired, the coating can be heated to temperatures from about 40°C to as high as 500°C.
It may be thermally cured within a temperature range of up to 100 ml. Clearly, at these elevated temperatures the curing time will be substantially reduced. A preferred coating composition according to the invention is about 80〓
(26.7°C) to about 150°C (65.0°C) (tag open cup method) and a pot life that meets the requirements of virtually any field of use. It is often desirable to add additional organic solvents to these coating compositions to form thin film-like coating layers on metal substrates. These diluted compositions are called "shop primers".
It is particularly suitable as a primer. In other words,
They are particularly suitable for use as pre-construction primer materials to protect the steel sheets prior to their incorporation into structures, such as ships.
The finished structure is then coated with the thick coating composition of the present invention. These coating compositions may be applied to a cleaned metal substrate by painting, spraying, or other conventional techniques known in the art. They exhibit excellent adhesion when used, and in some cases can be successfully applied to clean steel surfaces, omitting sandblasting. Good adhesion to wet galvanized surfaces was achieved. These coating compositions do not freeze and are not adversely affected by exposure to bright sunlight at tropical temperatures. They exhibit very good resistance to salt spray, fuels and organic solvents. These coating compositions can be easily pigmented, thereby obviating the use of an overcoat. The coating compositions of the present invention have completely unique properties, i.e. they can be formulated into a single packaging system, can be stored for at least 6 months without gel formation, and yet without gas formation. The present invention will be further illustrated by the following specific examples. "Parts" always mean "parts by weight" unless otherwise specified. Example 1 (a) 1000 parts of ethyl silicate "40", 1177 parts of ethylene glycol monoethyl ether and 3 parts of zinc chloride are added to a reactor with stirring deionized water.
22.5 parts were gradually added, then the reaction mixture was reduced to approx.
The hydrolyzate is prepared by stirring for about 2 hours at a temperature up to 60°C. In the present invention, "ethyl silicate "40"" refers to a mixture of ethyl polysilicate having about 40% effective silica. About 40 parts of zinc chloride was added to about 1000 parts of the hydrolyzate thus prepared, and the mixture was heated at 45°C under stirring.
A vehicle composition is formed by heating at . (b) 241 parts of the vehicle composition prepared above was then mixed with 21 parts of Celite 499, 3 parts of Bentone 27 and granules while stirring in an inert atmosphere for 0.5 hour. A coating composition is made by mixing with 735 parts of zinc dust 2 to 7 microns in diameter and applied onto a lightly sandblasted steel substrate. After drying at 77°C (25°C) at 50% relative humidity, the coatings are tested after 1 hour and again after 24 hours according to standard hardness test methods. In this exam,
Scale 6B, 4B, 3B, F, H, 2H, 3H, 4H, 5H
Pencil leads with various hardnesses are used. These values indicate a sequential increase in hardness. The pencil lead is held at a 45° angle to the zinc coating layer placed on the steel plate, and then moderate force is applied until the coating layer is removed. Properties such as hardness,
"Life" and "Pot Life" are shown in the table below. "Shelf life" and "pot life" were measured at a temperature of 25°C. Example 2 (a) Procedure as described in Example 1(a) except that 48 parts of water are added to a reactor containing 1115 parts of ethylene glycol monoethyl ether, 1000 parts of ethyl silicate "40" and 3 parts of zinc chloride. Repeat. About 40 parts of zinc chloride is added to about 1000 parts of the hydrolyzate thus formed and the mixture is heated at 45°C for 2 hours to form a vehicle composition. (b) Example 2(a) instead of the vehicle prepared in Example 1(a).
A coating composition is made according to Example 1(b), except using the vehicle composition prepared in Example 1(b). The composition was applied onto a steel plate and the hardness values were measured after drying for 1 hour at a temperature of 77°C (25°C) and 50% relative humidity, and after 24 hours of drying under the same conditions. Measure. The properties are specified in the table below. Example 3 (a) The procedure described in Example 1(a) is followed except that 60 parts of water are added to a reactor containing 1140 parts of ethylene glycol monoethyl ether, 1000 parts of ethyl silicate "40" and 3 parts of zinc chloride. Repeat. A vehicle composition is made by adding about 40 parts of zinc chloride to about 1000 parts of the hydrolyzate made as described above. (b) Example 3(a) instead of the vehicle prepared in Example 1(b).
Other than using a vehicle composition prepared in
A coating composition is made according to Example 1(b). This composition was applied on a steel plate and heated to a temperature of 77〓 (25℃).
The hardness value is measured after one hour of drying at 50% relative humidity, and after 24 hours of continued drying under the same conditions. Properties are shown in the table below. Example 4 (a) The procedure described in Example 1(a) is followed except that 72 parts of water are added to a reactor containing 1128 parts of ethylene glycol monoethyl ether, 1000 parts of ethyl silicate "40" and 3 parts of zinc chloride. Repeat. The resulting hydrolyzate is then added to Hydrolyzate 1000
40 parts per part zinc chloride to form a vehicle composition. (b) Make a coating composition according to Example 1(b), except that the vehicle composition made in Example 4(a) is used in place of the vehicle in Example 1(a). The coating composition was applied to a steel plate, dried for 1 hour at a temperature of 77°C (25°C) and 50% relative humidity, and then the hardness values were measured, and the hardness values were determined after 24 hours of further drying under the same conditions. Measure. The properties of the composition are shown in the table below. Example 5 (a) The procedure described in Example 1(a) is followed except that 96 parts of water are added to a reactor containing 1096 parts of ethylene glycol monoethyl ether, 1000 parts of ethyl silicate "40" and 3 parts of zinc chloride. Repeat. The resulting hydrolyzate is then added to Hydrolyzate 1000
40 parts per part zinc chloride to form a vehicle composition. (b) A coating composition is made according to Example 1(b), except that the vehicle composition made in Example 5(a) is used in place of the vehicle in Example 1(a). This composition is applied to a steel plate and the hardness values are measured after drying for 1 hour and after drying for 24 hours at a temperature of 77°C (25°C) and a relative humidity of 50%. The properties of the composition are shown in the table below. Example 6 (a) For comparison purposes, 1000 parts of ethyl silicate “40” was mixed with 1200 parts of ethylene glycol monoethyl ether.
Example 1(a) but mixed with 1 part and 3 parts of zinc chloride
Make the composition according to the procedure described in . The composition is then mixed with zinc chloride at a ratio of 40 parts zinc chloride per 1000 parts of the composition to form a vehicle. (b) A coating composition is made according to Example 1(a), except that the vehicle composition of Example 6(a) is substituted for the vehicle of Example 1(a). Apply this to the steel plate, 77〓
(25° C.) and 50% relative humidity, and the hardness values are determined after 1 and 24 hours. The properties of the composition are shown in the table below. Example 7 (a) For comparison purposes, a vehicle composition is made according to the procedure described in Example 1(a) but omitting the use of 40 parts of zinc chloride. (b) A coating composition is made according to Example 1(b), except that the vehicle composition made in Example 7(a) is used in place of the vehicle in Example 1(a). This is applied to a steel substrate and the properties of the composition are then determined according to Example 1(b).
The results are shown in the table below. Example 8 (a) For comparison purposes, 20 parts of zinc chloride are mixed with a hydrolyzate made according to the procedure described in Example 1(a). (b) The resulting vehicle composition is then mixed with zinc dust according to Example 1(b), except that the vehicle composition made in Example 8 is used in place of the vehicle in Example 1(b). The composition thus produced is applied to a steel substrate. The properties of this composition are shown in the table below. Example 9 (a) 1000 parts of ethyl silicate "40" is hydrolyzed by mixing with 1220 parts of ethylene glycol monoethyl ether, 44 parts of water and 3 parts of zinc chloride according to the procedure described in Example 1(a). make things Approximately 1000 parts of the hydrolyzate thus produced contains 124 parts of zinc chloride.
45 parts and stirred the mixture for 2 hours.
℃ to form the vehicle composition. (b) by adding 735 parts of zinc powder with a particle size of 2 to 7 microns, 25 parts of "Celite 499" and 3 parts of "Bentone 27" to about 241 parts of the vehicle composition made in 9(a) above. to form a coating composition and then stir it in an inert atmosphere for 0.5 hour. The properties of the coating composition thus produced are shown in the table below. Example 10 (a) For comparison purposes, 1500 parts of tetraethyl orthosilicate were mixed with 655 parts of ethylene glycol monoethyl ether according to the procedure described in Example 1(a).
A hydrolyzate is made by mixing with 154 parts of water and 3 parts of zinc chloride. Add 40 parts of zinc chloride to about 1000 parts of this hydrolyzed composition and stir the mixture for 2 hours.
Make the vehicle composition by heating to 45°C for an hour. (b) A vehicle composition made in 10(a) above of about 241 parts of Celite 499, 3 parts of Bentone 27, and about 735 parts of zinc dust with a particle size of 2 to 7 microns.
The coating composition is made by adding 100 ml of 100 ml of 100 ml of 100 ml of 100 ml of 100 ml of 100 ml of 100 ml of 100 ml of chlorine, each of which is 0.5 h, then stirred in an inert atmosphere for 0.5 h. The properties of the coating composition thus produced are shown in the table below.

Table: From the table above, it can be seen that coating compositions containing zinc chloride and ethyl polysilicate hydrolyzed to a level of 50 to 65% have a "shelf life" of more than 3 months, whereas It is observed that similar coating compositions in which the ethyl polysilicate is hydrolyzed to a level of at least 70% have a "shelf life" of only 10 days or less. Moreover, if zinc chloride is removed from a coating composition containing ethyl polysilicate hydrolyzed to a level of 50%, both the 1-hour hardness as well as the 24-hour hardness will be unacceptable. The table shows. Furthermore, if tetraethyl orthosilicate is used instead of ethyl polysilicate and hydrolyzed to the same extent, the hardness value of the coating layer after 1 hour will be unsatisfactory, and the hardness value after 24 hours will be lower than that of the coating layer of the present invention. It can be seen that it is inferior to that of .

Claims (1)

[Claims] 1. Zinc dust, a hydrolyzed alkyl polysilicate with a hydrolysis level of 50 to 65%, an organic solvent, and 3 to 5.5% by weight of zinc chloride based on the total amount of hydrolyzate. The hydrolyzate is approximately SiO ₂
40% of the alkyl polysilicate in the presence of an organic solvent and an amount of water from about 0.08 to about 0.21 mole per mole of alkoxy groups present on the alkyl polysilicate at a pH of about 1.0 to 6.5. A coating composition obtained by. 2. The coating composition according to claim 1, wherein the alkyl polysilicate is ethyl silicate "40".