JPS59124957A - Composition for coating bottom of marine vessel - Google Patents

Abstract

PURPOSE:To provide a compsn. for use in coating the bottom of marine vessel, which contains a water-soluble gelable polysaccharide as a main component and which serves, just like a nucous substance on the fish skin, to prevent the surface of the bottom from generating wave making resistance in water while retaining subtle unevennesses of the bottom. CONSTITUTION:The titled compsn. is obtd. by using a water-soluble gelable polysaccharide as a main component. Said polysaccharide includes those which are caused to gel only by lowering the temp. of the soln., such as agar-agar or carrageenan, and those which are caused to gel by adding an additive or by changing process conditions, such as alginic acid or its sodium salt. When 0.01- 5wt% copper salt such as copper chloride is added to the polysaccharide, the compsn. exhibits an effect of preventing shellfish from depositing on the bottom of the vessel.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composition for coating the bottom of a ship for suppressing wave-making resistance of a ship.

Recently, energy saving is desired in various fields and departments. Various types of marine fuels are being reviewed from the perspective of optimizing operating costs, and there is a particular need to minimize the wave-making resistance of ships.

In order to suppress the wave-making resistance of ships, various studies have been made, including improvements to the bow section and measures to prevent shellfish from being crushed to pieces on the bottom of the ship, but no satisfactory results have yet been obtained.

As a result of research aimed at minimizing the wave-making resistance of ships, the present inventors found that the body surface structure of fish includes the matter according to 7 based on various references. For fish to be able to swim quickly underwater, the most important factor is the presence of scales on the surface of the fish's body, but in addition to this, slight changes in the surface roughness occur due to the subtle expansion and contraction movements of the surface of the fish's body during swimming. In addition, a mucous substance leaches out onto the surface of the fish's body, which suppresses the resistance that occurs when fish move in water or seawater, allowing them to swim freely through the water.

As a result of further research to apply this principle to a ship, which is a rigid structure, the inventors found that it was only necessary to impart this kind of performance to the underwater part of the ship, that is, the bottom of the ship maintained subtle irregularities. However, they found that it is sufficient to make the surface underwater underwater so that it becomes so-called slimy, similar to the sticky substance on the surface of fish bodies. The present invention was achieved by discovering a scale that reduces wave-forming resistance.

The present invention is a composition for coating the bottom of a ship, which contains a water-soluble polysaccharide having gelling ability as a main component.

Examples of water-soluble polysaccharides having gelling ability include agar,
Those that gel only by lowering the temperature of the solution, such as furcelleran and carrageenan, such as guar gum, locust bean gum, alginic acid and its sodium salt,
Polysaccharides that can be gelled by adding additives or changing system conditions (e.g. pH), such as pectin, xanthan gum, tamarind gum, etc., as well as polysaccharides that have the property of gelling by other methods or means. Can be used. Several types of polysaccharides may be used in combination.

The coating composition containing the water-soluble polysaccharide of the present invention as a main component is
Furthermore, copper salts such as copper chloride, copper hydroxide, and copper sulfate can be contained. This has the effect of preventing the adhesion of shellfish such as oysters. Copper salts can be used in an amount of 0.01 to 5% by weight based on the water-soluble polysaccharide, as copper salts can make polysaccharides insoluble in water when used in excess, and the effect of preventing adhesion to shellfish can be achieved even when added in small amounts. It is preferable to add.

The composition of the present invention may contain any other substance as long as it does not have the effect of interfering with the gelation of the polysaccharide. Inorganic salts such as polyoxyethylene, polypropylene glycol, and Glauber's salt may also be added.

The coating composition of the present invention may be in the form of an aqueous solution of each of the above-mentioned components, but in general, from the viewpoint of storage stability, etc., it exists as a mixture (solid) of each component, and when used, it is dissolved in water. It is preferable to do so.

When coating the bottom of a ship using the coating composition of the present invention, a solution (sol) of a water-soluble polysaccharide having gelling ability or a mixture thereof is added with copper salts and other additives as desired, and then, for example, The solution is applied by conventional means such as dipping, spraying, or brushing at a temperature above the gelling temperature of the solution, and gelled by cooling, drying, or spraying with a gelling agent. The concentration of the polysaccharide in the solution is not particularly limited, but it may be at a concentration that does not gel during the operation, and may generally range from 0.1 to 10% by weight, although it varies depending on the type of polysaccharide. Although care is taken to avoid cracking the gelled coating layer, it is usually preferable to apply multiple layers, each layer consisting of the same or different polysaccharides and other additives. good. Note that it is preferable to apply the paint according to the present invention after applying a normal rust preventive paint.

When a gelled polysaccharide is immersed in water (seawater), it becomes swollen, but does not dissolve and can maintain the above-mentioned slimy state. In addition, imparting unevenness to the coating surface,
This can be achieved by applying the polysaccharide liquid to the bottom of the ship in the vertical, horizontal or diagonal directions or in a grid pattern, varying the number of times at arbitrary intervals. However, even if the coating is applied by ordinary means without changing the number of coatings, a small difference in thickness actually occurs when observed minutely, so there is generally no need to intentionally form irregularities.

Parts and percentages in the examples below relate to weight.

Example 1 A 2.0% carrageenan solution obtained by dissolving kappa carrageenan (manufactured by Mitsubishi Acetate Co., Ltd.) containing potassium as a cation in water at 80° C.
It was applied to the bottom of a model ship, the bottom of which was a galvanized iron plate, at a temperature of 0°C or higher. After the gel had sufficiently dried, the same solution was applied again, and this application was repeated a total of three times.

When a coated boat and an uncoated boat were floated on water and the speeds of both boats were measured under the same horsepower, the following results were obtained. The time the ship was on the water was one day.

Coated ship: 4.6 knots Uncoated ship = 5.0 knots It was thus confirmed that the coating increased ship speed, that is, decreased water resistance. In addition, the polysaccharide in the applied area appeared to be slightly swollen, and the surface was slippery.

Example 2 Two parts of K/ζ carrageenan containing potassium as a cation and 0.6 parts of potassium chloride, which has the effect of promoting gelation of carrageenan, were dissolved in 100 parts of water at 80°C, and the mixture was prepared in the same manner as in Example 1. It was applied to the bottom of the model ship. For comparison with this model ship coated on the bottom, an uncoated model ship was immersed in seawater for 15 minutes.
After immersion at zero, the ship speed was measured at the same horsepower, and the following results were obtained.

Ship with 17 coatings: 46 knots Ship without coating: 5.1 knots As in Example 1, it was confirmed that the boat speed increased by 2.5 knots due to the coating.

A mixed solution prepared by adding 10 parts of a 1% cuprous chloride aqueous solution to 100 parts of the carrageenan/potassium chloride solution of Example 2 was applied in 5 portions to the bottom of a model ship coated with anti-rust paint. . Vessels coated with this coating for 3 months: 4.4 knots; ships without coating with barnacles, etc. attached: 5.1 knots; in addition to the effect of increasing ship speed due to coating without deposits, the copper salt has an effect of preventing shellfish from adhering. confirmed.

Example 4 A 1% aqueous solution of sodium alginate was applied to the bottom of a model ship made of galvanized iron plate, and then an aqueous solution of 1 part of calcium chloride and 6 parts of copper sulfate dissolved in 100 parts of water was applied to gel the alginate. . Further, the same alginate solution was applied and gelatinized in the same manner. This was repeated six times in total, and then the same test as in Example 2 was conducted.

The results were as follows.

Coated ship: 4.4 knots Uncoated ship: 4.9 knots In this case as well, the coated ship with the polysaccharide gel layer did not exhibit a higher speed than the uncoated ship. Admitted.

Claims (1)

[Claims] 1. The main component is a water-soluble polysaccharide having gelling ability.
Composition for ship bottom fabric. 2. The composition according to claim 1, further comprising a copper salt.