JP7463215B2 - Antifreeze composition - Google Patents

Description

The present invention relates to an antifreeze composition containing sodium chloride.

In cold, snowy regions, melting snow and preventing freezing on road surfaces are important for ensuring traffic safety and the road environment in winter. Measures to melt snow and prevent freezing on road surfaces include installing road heating systems and snow melting pipes, but these have the disadvantage of being expensive to construct, and in reality their application is limited to some cases where they are necessary.
On the other hand, spraying antifreeze does not require special capital investment and can be applied over a wider area at relatively low cost.

Commercially available antifreeze agents include chlorides such as calcium chloride, sodium chloride, and magnesium chloride; urea; and acetates such as CMA (based on calcium acetate and magnesium acetate) and KAC (based on potassium acetate solution).
Of these, chlorides such as calcium chloride, sodium chloride, and magnesium chloride are widely used in Japan from the standpoint of economy and anti-freezing effect.

However, chlorides are highly corrosive to metals, and when they are sprayed on the road, they corrode metal parts such as automobile bodies and road signs, making it essential to add a rust inhibitor.
The examples in Patent Document 1 describe examples in which sodium chloride is used as an antifreeze component, and (A) sodium gluconate or a combination of sodium gluconate and sodium tartrate, and (B) sodium hexametaphosphate are used as rust-preventive components in a mass ratio of (A)/(B) of 50:50 or 75:25.

Patent No. 5274751

For example, there is a method of spraying a solution in which an antifreeze component and an anticorrosive component are dissolved in water as a measure to melt snow and prevent freezing on road surfaces. In the examples of Patent Document 1, a corrosion test is carried out using a low-concentration aqueous solution, assuming the environment after spraying.
When sodium chloride is used as the antifreeze component, the sodium chloride concentration in the spray solution is set relatively high in order to obtain a sufficient antifreeze effect.
According to the findings of the present inventors, in an aqueous solution in which an antifreeze agent containing both sodium chloride and a rust-preventing component is dissolved in water, precipitates may form over time. If precipitates form in the spray solution, they may accumulate in the pipes and nozzles used for spraying, resulting in problems such as reduced spray efficiency, extended spray time, or inability to spray due to clogging.
The present invention has been made in order to solve the above problems, and has an object to provide an antifreeze composition that can suppress corrosion of metals and prevent the formation of precipitates in an aqueous solution.

The present invention has the following aspects.
[1] An antifreeze composition comprising an antifreeze component and a rust-preventing component, wherein the antifreeze component comprises sodium chloride, and the rust-preventing component comprises an oxycarboxylate and a polymerized phosphate;
An antifreeze agent composition, wherein a mass ratio of the oxycarboxylate to the polymeric phosphate, expressed as oxycarboxylate/polymeric phosphate, is 90.00/10.00 to 99.99/0.01.
[2] The antifreeze composition of [1], further comprising at least one pH adjuster selected from the group consisting of hydroxides, carbonates, and bicarbonates of alkali metals, and hydroxides, carbonates, and bicarbonates of alkaline earth metals.
[3] The antifreeze composition according to [1] or [2], further comprising water.
[4] The antifreeze composition according to [3], having a pH of 5 to 9.

The antifreeze composition of the present invention can suppress corrosion of metals and can prevent the formation of precipitates over time even when used as an aqueous solution.

The antifreeze composition of the present embodiment contains an antifreeze component and an antirust component, and may further contain a pH adjuster.
<Anti-freezing ingredients>
The antifreeze component includes sodium chloride, and may further include other chlorides (calcium chloride, magnesium chloride, etc.) known as antifreeze components other than sodium chloride.
Sodium chloride is preferable because it has a high antifreeze performance, is inexpensive compared to CMA, urea, etc., and is economically advantageous.
The content of sodium chloride relative to the total mass of the antifreeze component is preferably 15 mass% or more, more preferably 50 mass% or more, even more preferably 90 mass% or more, and particularly preferably 100 mass%.

<Rust prevention ingredients>
The rust-preventive component includes an oxycarboxylate and a polymeric phosphate. By using an oxycarboxylate and a polymeric phosphate in combination, the rust-preventive performance is effectively exhibited even when highly corrosive sodium chloride is used as an antifreeze component.
The composition may further contain known rust-preventive components other than the oxycarboxylate and the polymeric phosphate, provided that the effect of the present invention is not impaired.

Examples of the oxycarboxylic acid include lactic acid, citric acid, tartaric acid, gluconic acid, heptonic acid, and malic acid.
The salt of the oxycarboxylic acid is preferably an alkali metal salt or an alkaline earth metal salt, and more preferably a sodium salt in terms of solubility, availability and economy.
The oxycarboxylate may be used alone or in combination of two or more kinds.

Examples of polymerized phosphoric acid include pyrophosphoric acid, tripolyphosphoric acid, tetraphosphoric acid, trimetaphosphoric acid, and hexametaphosphoric acid.
As the salt of the polymerized phosphoric acid, an alkali metal salt or an alkaline earth metal salt is preferable, and a sodium salt is more preferable in terms of excellent solubility, availability and economy.
In the alkali metal salt or alkaline earth metal salt of the polymerized phosphoric acid, a part of the alkali metal or alkaline earth metal may be substituted with hydrogen.
The polymerized phosphate may be used alone or in combination of two or more kinds.

The mass ratio of the oxycarboxylate to the polymerized phosphate (oxycarboxylate/polymerized phosphate) is 90.00/10.00 to 99.99/0.01. When the mass ratio is within the above range, the occurrence of precipitation over time in an aqueous solution containing sodium chloride and a rust-preventing component is excellent.
The total content of the oxycarboxylate and the polymerized phosphate is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 99% by mass or more, and particularly preferably 100% by mass, based on the total mass of the rust-preventive components.

The total mass of the anti-rust components is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of the anti-freezing components. If it is equal to or more than the above lower limit, a sufficient anti-rust effect is likely to be obtained. Also, from an economical point of view, the total mass of the anti-rust components is preferably 50 parts by mass or less, per 100 parts by mass of the anti-freezing components.

<pH Adjuster>
The pH adjuster is preferably at least one selected from the group consisting of hydroxides, carbonates and hydrogencarbonates of alkali metals, and hydroxides, carbonates and hydrogencarbonates of alkaline earth metals.
The amount of the pH adjuster to be added can be set according to the desired pH.

<Other ingredients>
In addition to the above-mentioned antifreeze component, antirust component and pH adjuster, the antifreeze composition may contain other components within the range that does not impair the effects of the present invention.
In addition, the raw material may contain impurities other than the target component (purity). For example, natural salt containing mineral components (calcium, magnesium, potassium, etc.) in addition to sodium chloride may be used as an antifreeze component. Natural salt is preferable because it is inexpensive. The content of sodium chloride in the natural salt is preferably 95% by mass or more, and the total content of calcium, magnesium, and potassium is preferably less than 3%. Examples of natural salt include rock salt, sea salt, and lake salt.
The other components are preferably those that have a small impact on the human body and the global environment, and are preferably substances approved as food additives.
The total content of the other components is preferably 5 mass % or less, and more preferably 1 mass % or less, based on the solid content of the antifreeze composition.

<Antifreezing agent composition>
The antifreeze composition may be a solid antifreeze composition (hereinafter also referred to as a solid antifreeze) in which an antifreeze component, an antirust component, an optional pH adjuster, and other components are mixed, or may be an aqueous solution containing water (hereinafter also referred to as a liquid antifreeze).
The antifreeze composition can be transported, stored, and sprayed in a solid state (solid antifreeze). It may be transported and stored in a solid state and, if necessary, dissolved in water to form an aqueous solution. It may also be transported, stored, and sprayed in the form of an aqueous solution (liquid antifreeze).
When the antifreezing agent composition is sprayed in the form of an aqueous solution, it is preferable that the pH of the spray liquid (liquid antifreezing agent) is 5 to 9, since this tends to reduce the burden on pavement materials and the environment. The pH in this specification is the value at 20°C.
The content of the antifreezing component is preferably 10 to 25% by mass, more preferably 15 to 20% by mass, and even more preferably 17 to 20% by mass, based on the total mass of the liquid antifreezing agent. If it is equal to or more than the lower limit of the above range, sufficient antifreezing performance is easily exhibited, and if it is equal to or less than the upper limit, the stability of the antifreezing component is excellent, and problems such as precipitation of the antifreezing component are unlikely to occur.

The antifreeze composition of the present embodiment can prevent the occurrence of precipitates over time even when used as an aqueous solution.
Specifically, as shown in the examples below, no precipitation occurs even when a spray solution (liquid antifreeze) in which a solid antifreeze agent is dissolved in water is kept at 5° C. for 3 hours.
Therefore, for example, when a solid antifreeze agent is dissolved in water in a storage tank to prepare a spray solution to prevent road surfaces from freezing, and then the solution is divided into small portions and sprayed onto the roads by a spray truck, the formation of precipitates over time can be prevented.

Furthermore, the antifreeze composition of the present embodiment can suppress corrosion of metals while containing sodium chloride.
Specifically, as shown in the examples described later, in a corrosion test in which the antifreeze composition is continuously immersed in an aqueous solution, and in a corrosion test using a wet-dry cycle method that simulates the repeated occurrence of immersed and dry states in a natural environment, the composition exhibits excellent anticorrosive effects, with a corrosion rate at or below the level of water.

Furthermore, the antifreeze composition of this embodiment can be produced without using volatile organic solvents (VOCs), acetic acid compounds, or ammonium salts. Not using these substances results in no foul odor and less adverse effects on the global environment and human body. As a consideration for the human body and the global environment, it is also possible for each component constituting the antifreeze composition of this embodiment to be composed only of substances approved as food additives.

The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.
<Evaluation method>
[Precipitation test]
The aqueous solution of the solid antifreeze agent was kept at 5° C. for 3 hours, after which the presence or absence of precipitates was visually confirmed. The content of the antifreeze component in the aqueous solution was 18% by mass.

[Method for calculating metal corrosion rate by continuous immersion corrosion test]
(1) A test piece made of cold-rolled steel plate (length 50 mm × width 30 mm × thickness 2 mm, surface area 33.2 cm ² ) was polished with #400 emery cloth, degreased with acetone, and dried.
(2) The aqueous solution of the solid antifreeze agent was kept at 50° C. so as to accelerate the corrosion rate, and the above test piece was hung in this aqueous solution so that the entire surface was immersed.
(3) After keeping for 7 days (168 hours), the test specimen was taken out, the corrosion products on the surface were removed, and the specimen was dried.
(4) The mass of the test piece was measured before and after immersion, and the corrosion rate was calculated using the following formula.
Corrosion rate (unit: mdd) = (A-B)/C/7
A: Mass of the test piece before the test (unit: mg)
B: Mass of the test piece after the test (unit: mg)
C: surface area of the test piece (unit: dm ² )
The unit of corrosion rate, "mdd", stands for "mg/( ^dm2 ·day)".
Moreover, the surface area of the test piece, "33.2 cm ² ", is defined as "0.332 dm ² ".

[Method of calculating metal corrosion rate using cyclic dry-wet corrosion testing]
(1) A test piece made of cold-rolled steel plate (length 50 mm × width 30 mm × thickness 2 mm, surface area 33.2 cm ² ) was polished with #400 emery cloth, degreased with acetone, and dried.
(2) The aqueous solution of the solid antifreeze agent was kept at 23° C. so as to accelerate the corrosion rate. The above test piece was hung in this aqueous solution so that the entire surface was immersed.
(3) After immersion for 24 hours, the test pieces were taken out and air-dried for 24 hours.
(4) This immersion and drying was repeated for 7 days (168 hours), and then on the 8th day, the test pieces were taken out, the corrosion products on the surfaces were removed, and the pieces were dried.
(5) The mass of the test piece was measured before and after the above cycles, and the corrosion rate was calculated in the same manner as above.

<Ingredients>
The raw materials shown in the table are as follows:
(Anti-freezing ingredient)
Sodium chloride: rock salt. Sodium chloride content is 95% by mass or more, and also contains calcium salts, magnesium salts, potassium salts, etc. In the formulations of the following examples, sodium chloride is considered to be 100% by mass.
Calcium chloride: granular.
(oxycarboxylate)
Sodium Gluconate: Sodium Gluconate, Powder.
Sodium Tartrate: Sodium tartrate, powder.
(Polyphosphate)
Sodium hexametaphosphate: Sodium hexametaphosphate, powder.
Sodium Tripolyphosphate: Sodium tripolyphosphate, powder.
Sodium Pyrophosphate: Sodium pyrophosphate, powder.

(Examples 1 to 9, Comparative Examples 1 to 8)
The solid antifreeze agents containing the raw materials in the compositions shown in Tables 1 and 2 were dissolved in water to prepare aqueous solutions, and the precipitation test and corrosion test were carried out by the above-mentioned method. The results are shown in Tables 1 and 2.
The solid antifreeze agent in each example contains sodium hydroxide as necessary so that the pH of the aqueous solution used in the precipitation test is 5 to 9.

The corrosion rate of Comparative Example 1 is the corrosion rate of water and is set as the target value.
As shown in the results of Tables 1 and 2, the generation of precipitates over time was prevented in Examples 1 to 6, in which the mass ratio of oxycarboxylate/polymeric phosphate was 90.00/10.00 to 99.99/0.01. Although a precipitation test was not conducted for Examples 7 to 9, it can be predicted based on the results of Examples 1 to 6 that no precipitates will be generated.
Therefore, the solid antifreezing agents of Examples 1 to 9 are prevented from forming precipitates over time even when used as liquid antifreezing agents, and are excellent in stability.
Moreover, in the continuous immersion corrosion test and the cyclic dry-wet corrosion test, Examples 1 to 9 exhibited a slower corrosion rate than Comparative Example 1, and thus exhibited excellent corrosion prevention performance.

On the other hand, Comparative Examples 4 to 8 contain oxycarboxylate and polymeric phosphate as rust-preventive components and have anticorrosive properties, but the content of polymeric phosphate is higher than that of Examples 1 to 9, and precipitates were generated in the precipitation test. Therefore, the stability is inferior when used as a liquid antifreeze agent.
In addition, in Comparative Examples 6 to 8, since precipitates were generated in the precipitation test, the corrosion test was not performed.

In addition, Comparative Examples 2 and 3, which contain chlorides as antifreeze components but no rust-preventing components, did not produce any precipitates in the precipitation test, but the corrosion rate was significantly faster and more corrosive than Comparative Example 1 in the continuous immersion corrosion test and the cyclic dry-wet corrosion test.

The antifreeze composition of the present invention can be used as an antifreeze agent, snow melting agent, dust suppressant, etc.

Claims (4)

An antifreeze composition comprising an antifreeze component and an antirust component,
the antifreeze component comprises sodium chloride;
The rust-preventive component contains an oxycarboxylate and a polymerized phosphate,
An antifreeze agent composition, wherein a mass ratio of the oxycarboxylate to the polymeric phosphate, expressed as oxycarboxylate/polymeric phosphate, is 90.00/10.00 to 99.99/0.01. The antifreeze composition according to claim 1 further contains, as a pH adjuster, at least one selected from the group consisting of hydroxides, carbonates, and bicarbonates of alkali metals, and hydroxides, carbonates, and bicarbonates of alkaline earth metals. The antifreeze composition according to claim 1 or 2, further comprising water. The antifreeze composition according to claim 3, having a pH of 5 to 9.