GB2362160A

GB2362160A - Antifreezing agent

Info

Publication number: GB2362160A
Application number: GB0104457A
Authority: GB
Inventors: Toshiyuki Ilzuka
Original assignee: INTER TEC ENGINEERING CO Ltd
Current assignee: INTER TEC ENGINEERING CO Ltd
Priority date: 1998-08-24
Filing date: 1999-08-23
Publication date: 2001-11-14
Anticipated expiration: 2019-08-23
Also published as: GB2362160B; WO2000011100A1; GB0104457D0; CA2341559A1; JP3774571B2; DE19983547T1; DE19983547B4; JP2000063793A

Abstract

An antifreezing agent with which metal rusting can be inhibited at low cost without posing any new problem. The agent is obtained by melting a mixture of at least one chloride selected among sodium chloride, calcium chloride, and magnesium chloride and trisodium citrate at 100 to 250 {C and then drying it.

Description

SPECIFICATION ANTIFREEZING AGENT TECHNICALFIEL1)

The present invention relates to an antifireezing agent. More specifically the present invention relates to an antifreezing agent that inhibits the emergence of rust in metals.

BACKGROUNDART

In wintertime, the runways at airports, bus terminals and platforms as well as roads get frozen with rain and snow especially in cold districts and often cause accidents. Conventionally, sodium chloride, calcium chloride or magnesium chloride has been sprinkled on the roads or other places as an antifreezing agent to prevent the freezing of these surfaces. However, these antifreezing agents such as sodium chloride, calcium chloride and magnesium chloride have the problem of rusting the metals. As a solution to the problem of rusting, it has been suggested to use concurrently various interfacial active agents as a rust inhibitor. However, using interfacial active agents concurrently is costly and reduces the rust inhibiting effect and it invites other problems such as slipperiness caused by the interfacial active agents and also environmental pollution. They have not been practically used yet.

Accordingly, an object of the present invention is to provide an antifreezmg agent that inhibits the emergence of rust in metals at a low cost without causing other problems such that it can be practically used taking into account the above situation.

DISCLOSURE OF THE INVENTION

As set forth in claim 1, the antifreezing agent according to the invention is characterized in that it includes a material obtained through a process of melting and drying a mixture consisting of a citrate and at least one selected from sodium chloride, calcium chloride and magnesium chloride. Thus, the surface of sodium chloride, 1 calcium chloride or magnesium chloride is coated by a citrate by the process of melting and drymg the mixture, thereby to inhibit the emergence of rust.

Further, as set forth in claim 2, the invention is characterized in that the process of melting and drying is a heat-melting-and-drying process.

Still further, as set forth m claim 3, the invention is characterized in that the process temperature of said heat-melting-and-drying process 1S 100t to 25TC. Thus, the surface of chloride can be suitably coated by a citrate without decomposing a citrate, consequently to bring about an excellent function of inhibiting the emergence of rust in metals.

Also, as set forth in claim 4, the invention is characterized in that said citrate is a trisodium citrate, consequently to bring about a more excellent function of inhibiting the emergence of rust in metals.

Further, as set forth in claim 5, the invention is characterized in that the mLxing ratio of said trisodium citrate is 2 to 10 weight parts to 100 weight parts of chlorides. This makes it possible to produce an antifreezing agent having an excellent function of inhibiting the emergence of rust in metals at a low cost.

BRIEF DESCRIPTION OF DRAWING:

Fig.1 is a graph showing the result of the corrosion tests in Embodiment 2 and Embodiment 4.

BEST MODE FOR CARRYING OUT THE INVENTION

The antifreezing agent of the invention is obtained through a process of melting and drying the mixture consisting of the citrate and at least one selected from sodium chloride, calcium chloride and magnesium cl-doride. More specifically, sodium chloride usually includes moisture of 7 to 8 percent by weight in it but, when melted and dried, the moisture melts the citrate and the melted citrate forms a coating by adhering around the sodium chloride. In the cases of calcium chloride and magnesium chloride, 2 since each of them respectively contains two and six molecules of crystallized water, the citrate also becomes coated through the same process as described above.

In applying the invention to practical uses, as regards sodium chloride, calcium chloride and magnesium chloride, any of the ones that have been used conventionally as antifreezing agents can be selected suitably and used without any particular restriction. Each of the chlorides, sodium chloride, calcium chloride and magnesium chloride can be used alone or in combination.

As the citrate used, the ones that are commercially available can be selected suitably and used without any particular restriction. More specifically, they are, for example, trisodium citrate, calcium citrate and magnesium citrate.

Among the citrates, trisodium. citrate is preferable. When trisodium. citrate melts and forms a coating around the chloride, it remains as trisodium citrate if the chloride is sodium chloride and the citrate reacts with the chloride and becomes respectively calcium citrate if the chloride is calcium chloride or magnesium citrate if the chloride is magnesium chloride.

The mixing ratio of the citrate and one selected from sodium chloride, calcium chloride and magnesium chloride can be selected according to the need. More specifically, when the citrate is trisodium. citrate, 2 to 10 weight parts of trisodium. citrate is appropriate to 100 weight parts of the above-mentioned chlorides and 3 to 5 weight parts of trisodium, citrate is preferable. If the mixing ratio of trisodium. citrate is less than 2 weight parts, the effict of inhibiting rust is not enough and the intended object cannot be achieved. On the other hand, if over 10 weight parts is used, the effict of inhibiting rust cannot be expected to increase any more and it becomes uneconomical.

As for the method for melting and drying the mixture, the process of mixing and melting by heating is to be preferred. However, other processes; for example in a vacuum or under a low pressure, and processing with the addition of a catalyst are available. In these cases, heating is not always necessary. More specifically, when 3 the method used is the one that can melt the chloride containing the crystallized water, it is available.

As to the temperature for heat-melting-and-drying, drying at a too high temperature causes the nosition of citrates and is not available. Generally, the temperature for heat-melting-and-drying of 250 'C or under is appropriate and 100 to 1459C is to be preferred. The process time of heat-melting-and-drying is set properly according to the conditions of the heat-melting-and-drying process i.e. the processing temperature, ventilation condition and the desired degree of drying of the mixture. However, 10 to 30 minutes is generally appropriate.

As to the degree of drying, if dried at a too high temperature, the citrate decomposes and no effect can be expected. In the case of a mixture of sodium chloride containing 7 to 12 percent by weight of moisture and tisodium citrate with two H20, the degree of drying where the moisture contained in the mixture is 0.1 to 0.5 percent by weight is appropriate. In the case of a mixture of calcium chloride with two H20 and trisodium citrate with two H20, the degree of drying where a mixture of calcium chloride with one H20 and trisodium citrate with one H20 is formed is appropriate. Further, in the case of a mixture of magnesium chloride with six H20 and trisodium citrate with two H20, the degree of drying where a mixture of magnesium chloride with five H20 and trisodium citrate with one H20 is formed is appropriate.

During the process of heat-melting-and-drying, by processing at 100 to 250 'C as mentioned above, the intended effect of inhibiting the emergence of rust in metals can be obtained. The intended eflect of inhibiting the emergence of rust of metals cannot be obtained for example, (i) when the above chlorides and sodium citrate are just mixed to be a mixture, (E) when the mixture is heat-melted-and-dried at a temperature lower than 100 'C, or (iii) when the above-mentioned chlorides and the citrate have been separately heat-melted-and-dried and are mixed thereafter to be a mixture even though the materials are heat-melted-and- dried at a temperature of 100 to 250 'C, each of the chlorides and the citrate are just mixed.

4 As the means for heat-melting-and-drying the above-mentioned mixture, the means conventionally known are available. More specifically, a tunnel dryer, a hot blast dryer (such as a box type and a tube type), half-tube type heating dryer are the examples.

According to the invention, the material that is produced by melting and drying, under the above-mentioned conditions, either (a) a mixture of sodium chloride and a citrate, (b) a mixture of calcium chloride and a citrate, (c) a mixture of magnesium chloride and a citrate, (d) a mixture of a citrate and any two selected from sodium chloride, calcium cl-doride and magnesium chloride, or (e) a mixture of a citrate and three chlorides of sodium chloride, calcium 61-doride and magnesium chloride, can be used alone or in combination as an antifreezing agent. For example, the combination of 60 percent by weight of a mixture after heat-melting-anddrying of sodium chloride and trisodium citrate and 40 percent by weight of a mixture after heat-melting-anddrying of magnesium chloride and trisodium citrate is preferable as an antifreezing agent.

Each of the above-mentioned mixtures after heat-melting-and-drying can be used alone or in combination with others as a rust inidbitor by mixing into the conventional anffmezing agent consisting of ordinary sodium chloride, calcium chloride or magnesium chloride. In this case, the mixing ratio of the above mixture after heatmelting-and-drying cannot be fixed at one value because it should vary according to the mixing ratio of the citrate in the mixture after heat-melting-and-drying. However, in generaL 2.5 to 10 weight parts to 100 weight parts of a chloride such as sodium chloride is appropriate. When the above mixture after heat-meltingand-drying is used; after mixing in a chloride such as ordinary sodium chloride, an antifreezing agent that has the effect of inhibiting the emergence of rust of metals can be provided.

The present invention is hereinafter described more specifically with the embodiments and comparative examples. However, the scope of the invention is not to be limited by the examples.

EMBODIMENT 1:

Into a half-tube type tunnel dryer of 15 m length with a hot air at a temperature of 180 'C being ventilated at 5 m/sec, a mixture of 100 weight parts of sodium chloride containing 7 to 10 percent by weight of moisture in it and 3 weight parts of trisodium.

chloride with two H20 was supplied at a moving speed of 0.5 m/min and was passed at a temperature of 150. C to heat-melt-and-dry The mixture after heat- melting-and drying was crushed into fine particles of a diameter of 0.3 to 2 min. The amount of moisture contained in the mixture after heat-melting-and-drying was 0. 1 to 0.2 percent by weight.

A corrosion test was applied to the mixture after heat-melting-and-drying. More specifically, a water solution of the mixture after heat-meltingand-dr ying with the concentration of 3 percent by weight was prepared. The operation of leaving 4.5 g of iron for one day after dipping the iron in the water solution for one day was repeated seven times. A new water solution of the mixture after heat-melting-and-drying with the concentration of 3 percent by weight was used for each repetition. The amount of rust that emerged after the operation had been repeated seven times was calculated in percent by weight. Table 1 shows the result of the test.

EMBODIMENT 2:

The same operation as applied to Embodiment 1 was conducted except that a niixture of 100 weight parts of calcium chloride with two H20 and 3 weight parts of trisodium citrate with two H20 was used as the mixture to be supplied into the halftunnel type dryer. A mixture after heat-meltingand-drying was obtained and it was crushed into fine particles. The amount of moisture contained in the mixture obtained was 25 to 28 percent by weight. The same corrosion test as applied to Embodiment 1 was applied to the mixture obtained this time. The result of the test is also shown in Table 1.

EMBODIMENT 3:

The same operation as Embodiment 1 was conducted except that a mixture of 6 weight parts of magnesium chloride with six H20 and 2.91 weight parts of trisodium chloride with two H20 was used as the mixture to be supplied into the halftunnel type dryer. A mixture after heat-melting-and-drying was obtained and it was crushed into fine particles. The amount of moisture contained in the mixture obtained was 40 to 47 percent by weight. The same corrosion test as applied to Embodiment 1 was applied to the mixture obtained this time. The result of the test was as shown in Table 1.

EMBODIMENT 4:

A mixture of 60 percent by weight after heat-melting-and-drying of sodium chloride and trisodium chloride, the same as the one obtained in Embodiment 1, and 40 percent by weight of the mixture after heat-meltingand-drying of magnesium chloride and trisodium chloride, the same as the one obtained in Embodiment 3 was prepared. The same test as applied to Embodiment 1 was applied to the prepared mixture. The result of the test was as shown in Table 1.

Further, the 3-percent-by-weight water solutions of the mixture of materials obtained after heat-melting-and-drying were tested as below. The same test was applied to 3-percent-by-weight water solution of the materials after heat-melting-anddrying obtained in Embodiment 2 and also, as comparative examples, water and 3percent-by-weight water solution of sodium chloride.

Testing method: A specimen piece was dipped into the testing solution and the change of its weight after a specific time was measured. The material formed by corrosion (rust) was removed by rubbing before measurement. Specimen piece: Straightened metal paper clip (of a type commercially available) Usting temperature: Room temperature The result of the test is shown in Table 2 and Fig. I. The values in the table are the ratio of weight decrease (percent by weight). It becomes clear that the antifreezing 7 agent according to the present invention has an increased rust inhibiting effect compared to the case in which a chloride is used alone.

As another test, the test described below was applied to a 3-percent-byweight water solution of the mixture of the materials after heat-meltingand-drying. As comparative examples, city water and a 3-percent-by-weight water solution of sodium chloride were also tested.

Testing institution: The Yokohama City Industrial Technology Assistance Center Date of tests: June 29, 1998 to July 13, 1998 (two weeks) Testing method: The whole specimen piece was dipped in 70 ml of the testing solution and the temperature was kept at 25 'C in a thermostat. The testing solution was replaced three times a week (Monday, Wednesday and Friday). When the solution was replaced, the weight decrease (mg) of the specimen piece caused by corrosion was measured and, the corrosion rate (mdd) was calculated and evaluated. When the material formed by corrosion (rust) was removed to measure the weight decrease caused by corrosion, a fine abrasive was used and the removal operation was also applied to the specimen piece that was not corroded, to compensate the measured values.

mdd the weight decrease caused by corTosion mg/(the area of the specimen piece (dm X the number of days for testing) The pH of the testing solution before dipping the specimen piece and after dipping the piece for 2 days was measured.

Specimen piece: Steel piece used for Hull cell test (2.5 cm wide, 10 cm long, CM2 of area (0.5 dm) of which the zinc galvanizing had been removed by hydrochloric acid.

The result of the test is shown in Table 3. It becomes clear from Table 3 that the 8 corrosion rate of the testing solution according to the present invention is the smallest and the solution has the best rust inhibiting eflect. The corrosion rate is almost constant in the pH range of 5 to 9 for the same testing solution. The measured values of the corrosion rate are considered unafFected. Hole type corrosion emerged for the other two kinds of testing solution but no hole type corrosion was observed for the testing solution according to the present invention. It is also clear from these facts that the present invention has an excellent rust inhibiting effect.

EMBODIMENT 5:

The same operation as Embodiment 1 was conducted except that a mixture of 100 weight parts of magnesium chloride with 6 H20 and 7.5 weight parts of trisodium citrate with 2 H20 was used as the mixture to be supplied into the half-tunnel type dryer. A mixture after heat-melting-and-dn ying was obtained as Embodiment 1. The amount of moisture contained m the material obtained after heat-melting-and-drying was 24 to 28 percent by weight. 40 weight parts of this material obtained after heatmelting-and- drying and 60 weight parts of the sodium chloride that was dried until the amount of moisture contained in it reached 0.1 percent by weight, were mixed and crushed into fine particles with the diameter 0.3 to 2 inni. The same corrosion test as in Embodiment 1 was applied to this mixture of the material obtained after heatmelting-and-drying and sodium chloride with the moisture amount in it of 0.1 percent by weight. The result of the test is shown in Table 1.

EMBODIMENT 6:

Into a half-tube type tunnel dryer of 15 m length with a hot air at a temperature of 180 'C being ventilated at 5 m/see, a mixture of 100 weight parts of sodium chloride containing 7 to 10 percent by weight of moisture in it and 3 weight parts of trisodium. chloride with two H20 was supplied at a moving speed of 0.5 m/min and was passed at a temperature of 150 'C to heat-melt-and-dry The mixture after heat-melting-anddrying was crushed into fine particles of a diameter of 0.3 to 2 min. The amount of moisture contained in the mixture after heat-melting-and-drying was 0. 1 to 0.2 percent 9 by weight.

Consequently, an antifreezing agent was produced by dissolving 3.Og of the mixture after heat-melting-and-drying thus obtained in 100ce of distilled water. As comparative specimens used in the test, there were used distilled water, 3.Og of sodium chloride (reagent chemicals) dissolved in 100cc of distilled water, and 3.Og of calcium chloride (anhydrous reagent chemicals) dissolved in 100cc of distilled water. Then, the following tests were carried out with respect of the aforesaid antifreezing agent of the invention and the comparative specimens.

Ibsting institution: Hokkaido Industrial Research Institute Testing method: As the specimen, a Hull cell testing plate of polished iron (67X50XO.3mm) was used. The testing pieces were immersed beforehand in a solution of 5% of sulfuric acid for about 2 minutes to remove galvanization. Then, the testing pieces were rinsed quickly with water, alcohol and acetone, dried with blowing of nitrogen and kept in a desiccator.

The aforementioned testing pieces were initially weighed, and then, immersed respectively in the four sorts of testing solutions described above for 24 hours at 231C. Thereafter, the aforesaid process was repeatedly carried out within 7 days (the testing pieces were taken out eight days from the commencement of the test).

Subsequently, the testing pieces were immersed in a solution containing 5% of hydrochloric add including 1% of propargyl alcohol for several minutes to about 10 minutes in order to remove rust caused on the testing pieces. (Me remaining rust, which could not completely removed, was filed off with a toothbrush.) The testing pieces free from rust were further rinsed with alcohol and acetone and dried, and finally, weighed.

Last, the corrosion solution rate (mdd) was calculated from the initial weight measured at the outset and the post-weight measured finally to analyze the results of the test.

The result of the test is shown in Table 4. This test reveals that the anti&eezing agent according to the present invention has an excellent function of inhibiting rust.

COMPARATIVE EXAMPLES I to 3:

Using a 3-percent-by-weight water solution of sodium chloride (comparative example 1), a 3-percent-by-weight water solution of calcium chloride (comparative example 2) and city water (comparative example 3), the same test as in Embodiment 1 was conducted. The result of the test is shown in Table 1.

COMPARATIVE EXAMPLE 4:

Sodium chloride was dried until the amount of moisture contained in it reached 0.1 percent by weight. Then 100 weight parts of the sodium chloride and 3 weight parts of trisodium citrate with 2 H20were mixed to obtain a mixture. Then, the same corrosion test as applied to Embodiment 1 was applied to the mixture obtained. The result of the test is shown in Table 1.

[Table 11

The Amount of Rust Emerged C/6) Embodiment 1 1.7 Embodiment 2 1.9 Embodiment 3 1.9 Embodiment 4 1.6 Embodiment 5 1.2 Comparative Example 1 3.2 Comparative Example 2 3.6 Comparative Example 3 2.2 Comparative Example 4 2.9 11 [Table 21 DippingTime 3 days 10 AM 14 a Water 0.132 1.164 1.788 3% sodium chloride water solution 0.850 2.588 3.666 Embodiment 4 0.524 1.410 1.884 Embodiment2 0.463 1.304 1.806 rTable 31

Corrosion pH of the testing solution rate (mdcl) before test after test Enffiodiment 4 4.2 7.61 7-84 3% by weight sodium chloride 5.0 7,85 7.77 water solution city water 4,6 8.00 7.96 [Table 41

Con Rate (mdcl) Solution containing anti&wzing agent 18.7 Distilledwater 10.7 Aqueous sodium chloride 34.2 Aq eous cak!ium clilaride 50.0 INDUSTRIALAPPIJCABI= According to the present invention, an antifreezing agent that can ird2ibit the emergence of rust in metals is provided by a sunple and low- cost means of heatmelting-and-dxying the mixture of citrate and at least one selected from sodium cb1oride, calcium chloride and magnesium chloride, without causing any other problems. The ant&ree2ing agent of the present invention, when it is applied to the practical uses mentioned above, can completely attain the intended object of protecting freezing and inhibiting the emergence of rust in metals at a low cost without causing any other problems.

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Claims

CLAIMS:

1. An antifreezing agent characterized by including a material obtained through a process of melting and drying a mixture consisting of a citrate and at least one selected from sodium chloride, calcium chloride and magnesium chloride.

2. An antifreezing agent according to claim 1, characterized in that said process of melting and drying is a heat-melting-and-drying process.

3. An antifreezing agent according to claim 2, characterized in that the process temperature of said heat-melting-and-drying process is 1000C to 2500C.

4. An antifreezing agent according to claims 1 to 3, characterized in that said citrate is a trisodium citrate.

5. An antifreezing agent according to claim 4, characterized in that the mixing ratio of said trisodium citrate is 2 to 10 weight parts to 100 weight parts of chlorides.

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