JPS5940229B2 - Rust preventive agent and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel water/oil soluble rust preventive agent.

More specifically, the present invention relates to a water- and oil-soluble oligostarch rust preventive agent that is low in toxicity and exhibits excellent rust preventive properties against a wide range of metals. Various types of rust preventive agents have been proposed in the past, but few are known that have low toxicity and can be used on a wide range of metals at the same time.

For example, oil-soluble rust inhibitors of this type include petroleum sulfonates, sorbitan monomonoic acid esters, metal soaps, etc., and water-soluble ones include chromates, phosphates, Inorganic salts such as nitrites, water- and oil-soluble ones include ethanolamine, benzotriazole, alkyl phosphate surfactants, long-chain quaternary ammonium halides, and higher amine salts. Increasingly, there are many substances that have low solubility in solvents, are effective only for certain metals, and cause pollution such as chromates, making them unusable. Furthermore, even if they are mixed together, it is not always possible to obtain a rust preventive agent that combines the advantages of both components; they may not dissolve each other, or the disadvantages of each component may appear, or even the sustainability of the effect may be lost. They often react to form carcinogenic nitrosamines, such as the combination of nitrites and lower amines. Moreover, the use of multiple metals at the same time has become more and more common in recent years, especially when it comes to rust preventives added to brake fluids and antifreeze products, since these brake fluids and antifreeze fluids come into contact with many types of metal surfaces. It was required to have the effect of rust-preventing various types of metals at the same time.

On the other hand, the synthesis and use of starch esters such as acetyl starch has a long history, and higher fatty acid esters of oligostarch, which is a decomposition product of starch such as dextrin, are used as surfactants for food additives and non-polluting cleaning agents. has recently been proposed (Japanese Unexamined Patent Publication No. 53-47546)
, 54-25930).

This higher fatty acid ester of oligostarch has essentially low toxicity, and the development of its uses has been expected from the standpoint of effective utilization of natural products. The present inventors have conducted extensive research to develop a new rust inhibitor that overcomes the drawbacks of conventional rust inhibitors by using higher fatty acid esters of oligostarch. An oligostarch ester with an average degree of glucose polymerization of 2 to 40, in which the ratio of acyl groups of the introduced higher fatty acids is kept within a specified range, is water- and oil-soluble, has a large surface-active effect, and is excellent against a wide range of metals. It was discovered that it has anti-rust properties.

Furthermore, it has been found that by blending silicate, benzotriazole, etc. with this oligostarch ester, each component can be dissolved uniformly and the characteristics of each component can be advantageously exhibited. The present invention has been made based on these findings. That is, the present invention is based on the general formula (wherein X1 to X3 are hydrogen atoms or carbon atoms of 5 to
An acyl group with 19 aliphatic hydrocarbon chains, the ratio of acyl groups is on average 0.01 to 0.5 for every 3 free hydroxyl groups in the glucose unit, and n is on average 2 to 40). The present invention provides a rust preventive agent characterized by comprising the oligostarch higher fatty acid ester shown below.

The oligostarch higher fatty acid ester of the present invention can be produced by esterifying the free hydroxyl group of the glucose unit of oligostarch with a higher fatty acid.

As the oligostarch, those having an average degree of polymerization of glucose units of 2 to 40 are used, and those having a degree of polymerization of 2 to 25 have excellent water solubility. In oligo starch esters, within the range that maintains water solubility, the larger n is more hydrophilic and the HLB
The value increases. The ratio of fatty acid esterification of the free hydroxyl groups of the glucose units of this oligostarch is in the range of 0.01 to 0.5 on average for every 3 free hydroxyl groups,
Preferably it is in the range of 0.05 to 0.2. If the ratio of fatty acid esterification is less than 0.01, the performance will not be sufficiently expressed, and if it exceeds 0.5, the activity will level off, and it will become insoluble in water and the hydrophilic/lipophilic balance of the molecule will become lipophilic. leaning too much towards The aliphatic hydrocarbon chain of the higher fatty acid used for esterification usually has 5 to 19 carbon atoms, preferably 7 to 17 carbon atoms.

The aliphatic hydrocarbon chain may be either straight chain, branched chain, or saturated. Examples of fatty acid compounds used in such fatty acid esterification include methyl laurate, triglycerides (such as beef tallow), and lauric acid. In the present invention, the proportion of acyl groups in the glucose units of oligostarch is It is necessary to keep it within a predetermined range.

When oligodenfuso is dissolved in a mixed solvent of pyridine and dimethyl sulfoxide (DMSO) and treated with lauroyl chloride, a product in which all three free hydroxyl groups in the glucose units of oligostarch are esterified (DS-3) is obtained. . However, such completely esterified products are not preferable because they are insoluble in water and soluble in oil, and have a small surface-active effect. And the use of lauroyl chloride, which is expensive and difficult to handle, is undesirable. In order to obtain a partial esterified product of oligostarch with higher fatty acids suitable for use in the rust preventive agent of the present invention, the reaction temperature is kept relatively low (approximately 70°C or less) to prevent decomposition of the oligostarch itself while water is added. It is necessary to react oligostarch with fatty acid compounds in the presence of lithium oxide. The rust preventive agent of the present invention comprising the oligostarch higher fatty acid ester obtained as described above is used after being dissolved in water or oil.

Its concentration is usually in the range of 0.05 to 3.0%, preferably in the range of 0.1 to 1.5%. In the present invention, at least one member selected from the group consisting of silicate, benzotriazole, mercaptobenzothiazole salt, alkanolamine, and sodium nitrite is added to the rust preventive agent made of oligostarch higher fatty acid ester to assist in rust prevention. It may also be blended as an agent.

Among these antirust additives, benzotriazole and mercaptobenzothiazole have poor water solubility, and sodium nitrite hardly dissolves in organic solvents. Moreover, neither of them dissolves in petroleum-based solvents. Among them, benzotriazole is effective against a relatively wide variety of metals, mainly copper, but is expensive. As mentioned above, sodium nitrite has some problems in terms of toxicity, and it is desirable to use a small amount when it is directly related to the human body. It goes without saying that even if only these antirust auxiliary agents are mixed, a sufficient antirust effect cannot be obtained. Examples of the silicate used here include sodium metasilicate and water glass, and examples of the mercaptobenzothiazole salt include its sodium salt. Examples of the alkanolamine include ethanolamine represented by the following formula. HpN(C2H4OH)3-, (in the formula, p is an integer of O~2) The amount of these rust preventive aids added is 100% of the above oligostarch higher fatty acid ester in the case of ethanolamine.
The amount of mercaptobenzothiazole salt, sodium nitrite and benzotriazole in the range of up to 300 parts by weight based on the oligostarch higher fatty acid ester 100
They are used in amounts of 50 parts by weight or less, 200 parts by weight or less, and 50 parts by weight or less, respectively.

The amount of silicate is in the range of 500 parts by weight or less per 100 parts by weight of oligostarch higher fatty acid ester.
These may be added singly, but with the exception of the combination of sodium nitrite and amine, it is advantageous to add two or three of them at the same time. The rust preventive agent of the present invention contains oligostarch higher fatty acid ester as an active ingredient, and has low toxicity and excellent rust preventive effect, as well as excellent emulsifying power, penetrating power, dispersing power, solubilizing power, etc. Furthermore, oligostarch esters containing one or more selected from silicates, benzotriazole, mercaptobenzothiazole salts, alkanolamines, and sodium nitrite can be used with many kinds of metals, such as soft iron, steel,
At the same time, it exhibits excellent rust prevention effects on aluminum, brass, copper, lead, tin, galvanized iron, solder, etc. Next, the present invention will be explained in more detail based on examples.

Example 1 Acid-baked dextrin (0.31 mol as glucose units) with an average degree of polymerization of 11 was placed in four separable flasks, and dimethyl sulfoxide (DMSO) 20009 (
25.6 monoliths were added and dissolved.

Next, lithium hydroxide 3.29 (0
．． Add 08 mono(c) and heat to about 58°C while stirring under reduced pressure, and add methyl laurate 1809 (0.85
mol) was added dropwise over 1 hour. The reaction was carried out while distilling off methanol produced as a by-product. After the completion of the dropwise addition of methyl laurate, the reaction was continued for about 4 hours, and most of the DMS
The O was removed by evaporation and the solids were washed with hexane. After washing, ethanol was added to precipitate and separate the dextrin ester. Furthermore, this dextrin ester in water? Purification was carried out by repeating the operation of dissolving and precipitating with ethanol. The yield of dextrin ester after drying is 32
In Sample No. 9, it was found from the carbon analysis value that 0.16 of the three free hydroxyl groups in the glucose unit of the dextrin were converted to lauric acid ester. This material is water-soluble and foamable, and the surface tension of a 0.1% aqueous solution at 30°C is 4.
8.6dyne7/CTILll. 0% aqueous solution was 43.3 dyne/CTIL. Next, the ratio of the amount of dextrin charged (4), the amount of methyl laurate (liter), the amount of lithium hydroxide added (C), and the amount of DMSO added (with) was changed, and the reaction was carried out at 60°C for 2 hours. Except for this, dextrin ester was produced in the same manner as above.

The DS of the dextrin ester thus obtained is shown in the following table. Aqueous solution has excellent rust prevention ability, for example, in the sample of Taki 5 (DML-2), it was added to a 1% aqueous solution for 24 hours at 90℃.
r When various metals are immersed at the same time, steel (4) and steel (B)
, copper, and aluminum (B) all showed excellent results with an average of 4 (see Example 3 for metal specifications and measurement methods). Example 2 In four separable flasks, sour dextrin with an average degree of polymerization of 11 5.19 (0.31 as glucose unit)
8.99 (0.01 mol) of mono and tristearin were added and dissolved in DMSO2OO9 (2,56 mono(c)).

Furthermore, 0.32 g of lithium hydroxide (0.008 mol. The solid content was washed with hexane. After washing, ethanol was added to obtain a dextrin ester precipitate. The procedure of dissolving it in water and precipitating it with ethanol was repeated to purify it. The yield after drying was 3.6 g. According to the carbon analysis value, 0.0% of the 3 free hydroxyl groups in the glucose unit.
It was found that 01 was converted into stearic acid ester. The surface tension value of a 0.1% aqueous solution of this dextrin ester is 54.1 dyneΔ, and 4 dyneΔ for a 0.5% aqueous solution.
2.4dyne/40.5dyne in 81.0% aqueous solution
It was hot with e. Example 3 0.05 to 1 of the four types of dextrin esters shown in the following table
．． A 0% aqueous solution was prepared and its antirust ability was tested.

The test method for rust prevention ability is as follows. Test tube with cap (
Pour about 4 ml of sample aqueous solution into 10 ml of
Type of test 1 Metal piece (approximately 20 mm wire or 3 x 20
×1~1.5m7! Immerse the metal plate (L) at the same time,
After shaking at 0° C. for 24 hours or standing at room temperature (15° C.) for 6 months, changes in the metal piece are visually observed and evaluated.

The specifications and evaluation criteria for metal pieces are as follows. The metal pieces were significantly discolored or formed precipitates.Table 3 shows the results of the test conducted in this way after being left standing at room temperature for 6 months, and Table 4 shows the results when shaking at 90°C for 24 hours. Shown below.

From the above results, the rust preventive agent of the present invention has excellent rust preventive power against copper, although there are differences depending on the structure.
Brass was second best, and some aluminum was also good.

Although generally inferior to iron, DML-2 is quite good, and DML
-2 showed excellent effects on various metals on average. Example 4 Table 5 shows the results of a 900C24hr rust prevention test in which one or two types of various rust prevention aids were added to two types of dextrin esters.

Note that the percentage of rust preventive composition in the table indicates the concentration of each component in the aqueous solution. As a result, both Fu 3 and 6 have a remarkable effect on 5 types of metals, and on 11 types of metals, the effect is greater on DMC, which is inferior when used alone, and on eyebrows 3, it is overall better.

/F67 is for iron, 11 is for iron and brass, 10
It has improved overall. 3, 6, and 10 were better than commercially available products.

Claims (1)

[Claims] 1 General formula ▲ Numerical formula, chemical formula, table, etc. ▼ The ratio of groups is on average 0.01 to 0.5 for every 3 free hydroxyl groups in the glucose unit, and n is on average 2 to 40). Rust agent. 2. General formula ▲ Numerical formula, chemical formula, table, etc. oligostarch higher fatty acid ester and silicate, bezotriazole, mercaptobenzothiazole salt, A rust preventive agent comprising at least one member selected from the group consisting of alkanolamine and sodium nitrite. 3 Oligo starch and higher fatty acid ester are reacted at 70°C or lower in the presence of lithium hydroxide to form the general formula ▲ mathematical formula,
There are chemical formulas, tables, etc.▼ (In the formula, X_1 to X_3 are hydrogen atoms or acyl groups having an aliphatic hydrocarbon chain having 5 to 19 carbon atoms, and the proportion of the acyl groups is the free hydroxyl group in the glucose unit. The average is 0.01 to 0.5 per 3 pieces, and n is 2 to 4 on average.
A method for producing a rust preventive agent, which comprises obtaining an oligostarch higher fatty acid ester represented by 0).