JPH0131787B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an antifouling pigment used in an antifouling paint for the purpose of preventing and protecting ships, underwater structures, etc. from adhesion of fouling organisms. A wide variety of fouling animals live in the sea, from ascidians, which are protochordates ranked next to vertebrates in animal taxonomy, to protozoa, the lowest protozoa. Polluted plants are growing. The antifouling agents used in antifouling paints have a remarkable long-term control effect against a wide variety of fouling organisms, and at the same time, they have low toxicity to the human body and have few environmental health problems. is required. In recent years, trialkyltin compounds, triphenyltin compounds, organic chlorine compounds such as DDT and BHC, and organic sulfur compounds such as tetraalkylthiuram disulfides and zinc dialkyldithiocarbamates have been used in antifouling paints as antifouling agents. Generally, these organic antifouling agents are selectively effective only against specific fouling organisms, but are completely ineffective against other organisms, and cannot be expected to be particularly effective in preventing the adhesion of seaweed. Furthermore, there are still many problems in practical use, such as the fact that if it were to have an antifouling effect against all fouling organisms in general, it would become more toxic to the human body. On the other hand, taking cuprous oxide, a typical copper yarn antifouling agent, as an example, this compound shows a remarkable antifouling effect against all fouling organisms, while its toxicity to the human body is low, making it a highly practical antifouling agent. It has been used since ancient times as a staining agent. However, cuprous oxide, or cuprous oxide, is unstable and gradually changes to divalent copper salt when oxidized in seawater, and the elution rate of copper ions necessary for antifouling is maintained at 10 μg/cm ² /day. However, despite the presence of copper compounds in the paint film, it is recognized that the antifouling effect is eventually lost. This is because cuprous oxide dissolves in seawater as a monovalent copper ion, but it is oxidized to become a divalent copper ion, which then reacts with hydroxide ions and carbonate ions, which are present in large amounts in seawater, and finally forms a base. This is thought to be due to the change to copper carbonate. Looking at this as a change in solubility, the solubility of cuprous oxide in seawater is 5 to 3 x 10 ^-5 mol/at a pH of 8.2 and a temperature of 20°C.
On the other hand, the solubility of basic copper carbonate is 4 to 2 x 10 ^-6 mol/under the same conditions, so there is a difference of 10 times. The present inventors researched a method for preventing or suppressing the oxidation of monovalent cuprous oxide into divalent copper compounds in seawater, and found that monovalent copper ions or divalent ions have a redox potential. Properties of metals that are subordinate to copper, namely bismuth, tin, lead, nickel, vanadium, cobalt, cadmium, iron, gallium, zinc, selenium, tellurium, manganese, diumconium, germanium, titanium, aluminum, and magnesium, as well as nonmetallic properties. Focusing on the property of being reduced by substances such as antimony, arsenic, and phosphorus that form cations with We searched for substances whose redox reactions proceed over a long period of time and which pose fewer problems in terms of environmental health. The redox reaction of these substances needs to proceed at a stable rate over a long period of time in an alkaline region. Therefore, magnesium and sodium, which have strong redox power and hydrolyze seawater, are quickly depleted in seawater and do not last long. Excluding phosphorus that loses its properties, aluminum and cobalt that react with each other to form insoluble copper compounds produced by redox reactions, and cadmium and arsenic, which are undesirable from an environmental standpoint, tin, antimony, zinc, chromium, By adding at least one element or alloy of iron, nickel, lead, and titanium, not only cuprous oxide but also
It has been found that the dissolution of sparingly soluble copper compounds such as cupric hydroxide and basic copper carbonate having a solubility in seawater of 3×10 ^-6 mol/or less can be promoted. As a result of further studies, in order to maintain the long-term antifouling performance of antifouling paints, particles of copper compounds and reducible elements or alloys must be densely and uniformly dispersed in antifouling paint compositions. Therefore, rather than adding both components separately during the production of paint, the reducing element or gold is added in advance during the production of the copper thread antifouling agent, and the antifouling pigment produced in this way is added to the antifouling paint. It has been found that it is more effective to use it in the production of In other words, as a result of this, it is possible to achieve a dense and uniform dispersion of the copper compound and the reducing element or alloy, and as a result, the antifouling performance of the copper compound can be exhibited for a long period of time with a relatively small amount of the reducing element or alloy. In the case of copper oxide, the storage stability is also achieved, that is, the effect of preventing monovalent cuprous oxide from being oxidized in the air and changing to divalent copper oxide, thereby reducing its original solubility. The antifouling pigment of the present invention is characterized in that a reducible element or alloy that has a lower redox potential than the copper compound and is sparingly soluble in water is blended into the sparsely soluble copper compound antifouling agent. The poorly soluble copper compound mentioned here has a solubility in seawater with a pH of 8.2 of 1 x 10 ^-4 mol/mole at 20°C.
The following copper compounds are generally said to be insoluble,
Specifically, they are cuprous oxide and copper rhodanide. As the reducible element or alloy, tin, antimony, zinc, chromium, iron, nickel, lead, titanium and alloys thereof, particularly zinc, antimony, tin, and alloys thereof can be used. The combination and composition ratio of the copper compound and the reducing element or alloy used in the present invention vary depending on the method and purpose of use of the antifouling paint, but generally the reducing element or alloy is 30% by weight or less based on the compound. It is appropriate to mix an alloy. Generally, the particle size of the reducible element or alloy is preferably finer than 250 mesh in order to disperse it closely and uniformly with the copper compound. The antifouling pigment of the present invention is produced by adding a reducible element or alloy during the production of an antifouling copper compound. As is well known, methods for producing cuprous oxide include (a) diaphragm electrolysis of copper electrode plates using an aqueous sodium chloride solution as the electrolyte; and (b) a monovalent copper compound, such as cuprous chloride, in an aqueous salt solution. Chemical conversion method in which an alkaline solution is reacted (c) There is a dry method using thermal decomposition or thermal oxidation of copper sulfate, copper oxide, metallic copper powder, etc. Copper rhodanide is produced by reacting divalent copper in a copper sulfate solution with rhodan salt while reducing it with a reducing agent. In either case, after the reaction, the product goes through processes such as aging, washing, filtration, drying, and pulverization, and is packaged and shipped. The reducible element or alloy is added to the copper compound according to the present invention in the above manufacturing method by: (1) Adding in the cleaning step, (2) Adding in the surface treatment step, (3) Adding in the drying step, and (4) Grinding. Adding in the process (5) Achieved by means such as mixing after making the product. The manufacturing and coating methods for antifouling paints are the same as when using copper-based antifouling pigments that do not contain reducible substances or alloys. The invention will be illustrated by the following examples. Examples and percentages are by weight unless otherwise specified. Example 1 A precipitate of cuprous oxide produced by an electrolytic method was aged for crystal growth, and the soluble chlorine content was reduced.
Rinse with water until the slurry concentration is 0.1% or less.
500 g of cuprous oxide adjusted to 500 g as Cu ₂ O
and 40 g of zinc powder as a reducing element were placed in a mixing tank, mixed and stirred for 2 hours, transferred to a surface treatment tank, treated with glycerin, filtered, dried, and crushed to produce an antifouling pigment. Place 5 g of this pigment in a 500 ml Erlenmeyer flask, add 300 ml of seawater, and store while stirring. During storage, the seawater was refreshed once a week, and a portion of the sample was taken out at regular intervals and its solubility in seawater adjusted to pH 8.2 and temperature 20°C was measured. Example 2 800 g of cake-like cuprous oxide with a moisture content of 30%, which was produced by the electrolytic method as in Example 1 and subjected to aging, washing, and surface treatment, was charged into a vacuum dryer equipped with a stirrer. 50 g of zinc powder was added as a reducible element, dried at 80° C. or below for 5 hours, taken out and crushed to produce an antifouling pigment, and the solubility of copper was measured. Examples 3 and 4 Antifouling pigments were produced by repeating the procedure of Example 1, except that antimony and tin were used instead of zinc as the reducing element, and the solubility of copper in each was measured. Example 5 To 250 g/aqueous solution 1 of copper sulfate CuSO ₄ 5H ₂ O, 150 ml of an aqueous solution of 640 g/potassium rhodanide KSCN was added while passing sulfur dioxide, and the resulting precipitate of copper rhodanide was aged and then washed with water. Soluble salts were removed. Next, 500 g of copper rhodanide with a slurry concentration adjusted to 200 g/2 and 60 g of zinc powder as a reducing element were placed in a mixing tank.
After mixing and stirring for a period of time, the mixture was filtered, dried, and crushed to produce an antifouling pigment. The solubility was measured in the same manner as in Example 1. Comparative Example 1 In the same manner as in Example 1, the cuprous oxide precipitate produced by the electrolytic method was treated without adding zinc powder to produce an antifouling pigment, and the solubility of copper was measured. Comparative Example 2 In the same manner as in Example 5, copper rhodanide was produced by adding potassium rhodanide to an aqueous copper sulfate solution while passing sulfur dioxide through it, without adding zinc powder, to produce an antifouling pigment, and to determine the solubility of copper. It was measured. Table shows the solubility of copper in pigments of Examples and Comparative Examples.
Shown in 1.

[Table] As is clear from Table 1, it has been found that the antifouling pigment containing a reducing element according to the present invention significantly increases the solubility of poorly soluble copper compounds. Examples 6 to 10 The antifouling pigments of Examples and Comparative Examples in Table 1 are shown in Table 1.
Prepare the actual antifouling paint according to the formulation in 2.
They painted it to a thickness of 100 microns and hung it on a raft in the Tamano waters of Okayama Prefecture, and pulled it up at regular intervals to measure the elution rate of copper ions eluted from the paint film. The results are shown in Table-3.

【table】

[Table] The antifouling paint using the antifouling pigment of the present invention showed remarkable results in elution rate compared to the comparative example. The reason why the dissolution rate is especially high over a long period of time (12 months or more) is thought to be due to the uniform dispersion effect caused by the addition of the pigment manufacturing reducing element. The minimum elution rate required for antifouling is 10 μg/cm ² /day.
Storage stability of the pigments of the present invention: The pigments of Examples 1 to 4 and Comparative Example 1 were spread in a glass dish on the shelf of a glass desiccator whose bottom was filled with water, and left indoors for one month. A sample was taken out and the solubility of copper was measured under the conditions described in Example 1, and compared with the solubility before storage. The results are shown in Table 4.

[Table] Represents.
As is clear from Table 4, it was found that the antifouling pigment according to the present invention maintains a higher solubility even after storage than a pigment that does not contain a reducing element.

Claims (1)

[Claims] 1. A poorly soluble copper compound selected from cuprous oxide and copper rhodide, and a copper compound selected from tin, antimony, zinc, chromium, iron, nickel, lead, titanium, and alloys thereof. An antifouling pigment characterized by containing a reducing elemental metal or alloy that has a lower redox potential and is hardly soluble in water. 2. The antifouling pigment according to claim 1, wherein the reducible metal or alloy is zinc, antimony, tin, or an alloy thereof. 3. The antifouling pigment according to claim 1 or 2, wherein the proportion of the reducing elemental metal or alloy to the copper compound in the antifouling pigment is 30% by weight or less.