JPS6039106B2 - Secondary refrigerant composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to propyresoglycol-water based secondary refrigerant compositions.

Generally, in order to maintain manufacturing equipment at a low temperature, a system that uses only so-called primary soot such as ammonia or Freon (direct cooling method) is operated in combination with a system that uses secondary cold soot such as an aqueous solution of calcium chloride or an aqueous propylene glycol solution. There are two methods: maintaining the temperature at a predetermined low temperature (indirect cooling method).

If you consider them from the standpoint of thermal efficiency, it is obvious that the former is superior, but on the other hand, the latter is often more advantageous in terms of equipment and operation. For example, in beer production, the fermentation process is kept at 5℃ or below for 7 to 12 days, but a large amount of heat is released at once during brewing, so if a direct cooling method is used, a very large refrigerator is required. Refrigerators are more likely to malfunction due to rapid heat release. For this reason, secondary refrigerants such as aqueous calcium chloride solutions have generally been used as shock absorbers, but conventional refrigerants have the disadvantage of severely corroding the material and significantly shortening the life of the equipment. For example, Table 1 shows the results of an immersion test on the rust prevention properties of currently used typical inorganic and organic secondary soots against mild steel. Table-1 Rust prevention test conditions for various secondary refrigerants Temperature: 6000 Test piece European steel method Dilution period: 14 days It is clear from these results that if such secondary cold soot is used as it is in manufacturing equipment, it will completely dry out in a short period of time. Corrosion occurs, causing the secondary refrigerant to turn red and eventually creating holes, which can contaminate the product.

Furthermore, even in a state where there is not much corrosion, the thermal conductivity deteriorates and more thermal energy is lost than necessary. Moreover, if corroded parts increase in the system, it may cause failure of attached equipment such as pumps. An object of the present invention is to eliminate the above-mentioned drawbacks and provide a secondary soot composition with excellent rust prevention properties.

Another object of the present invention is to provide a secondary refrigerant composition that has excellent rust prevention properties, stability, low toxicity, and workability, and is free from crystal precipitation. The secondary cold soot composition of the present invention is a propylene glycol-water based soot, containing a phosphoric acid salt, a phosphoric acid di-salt, an organic acid and an alkali compound,
It is characterized by being in H7.0-8.5. The secondary cold soot of the present invention is based on a 20-8% by weight aqueous propylene glycol solution, preferably 40-60% by weight.

The phosphoric acid monosalts and phosphoric acid di-salts used in the present invention are alkali metal salts, ammonium salts, etc. of phosphoric acid, and include sodium phosphate, potassium phosphate, monoammonium phosphate, disodium phosphate, and di-phosphate. Examples include potassium.

In addition, organic acids include lactic acid, citric acid, malic acid, fumaric acid, grape acid, tartaric acid, etc., and alkaline compounds include sodium carbonate, sodium hydrogen carbonate, sodium hydroxide, potassium hydroxide, etc. However, weakly alkaline compounds are preferably used.

The above additives include 0.01 to 1% phosphoric acid salt (based on weight, the same applies hereinafter), preferably 0.02 to 0.5%, and 0.02 to 5% phosphoric acid di-salt based on the propylene glycol aqueous solution.
% preferably 0.1-1%, organic acids 0.01-1% preferably 0.02-0.5%, alkali compounds 0.0
Blended at a ratio of 1 to 5%, preferably 0.05 to 1%,
The secondary cold soot composition of the present invention is obtained by adjusting the pH to a range of 7.0 to 8.5.

The secondary refrigerant composition of the present invention has excellent rust prevention properties such as not losing the luster of the metal surface, has good workability because it is weakly alkaline, and is stable such that no phosphate precipitation is observed even at low temperatures. The properties are also good.

In addition, it has extremely low toxicity and is odorless, so it can be particularly suitably used in the food industry, such as the production of carbonated beverages and dairy products.

The secondary refrigerant composition of the present invention requires the addition of four components, monosalt of phosphate, disalt of phosphate, organic acid, and alkaline compound, to the propylene glycol aqueous solution, and any one of these components is absent. However, it is not possible to obtain an excellent refrigerant.

For example, phosphoric acid di-salt alone can provide some degree of rust prevention, but the stability of crystal precipitation is poor, the luster of the metal surface cannot be maintained unless an organic acid is added, it lacks corrosion resistance, and the pH is within a certain range due to the presence of alkaline compounds. If not, workability and crystal precipitation stability will be poor.

In addition, the phosphoric acid salt can alleviate rapid pH changes and increase the stability of the system.
The present invention will be explained in more detail below with reference to Examples.

Example 1 Ion-exchanged water 40 parts phosphoric acid-soda 50 parts 9 parts, disodium phosphate 600 parts 9 parts, citric acid 50 parts 9 parts, NaOH 15 parts
Add 9 of 0 and mix and dissolve.

After that, add 60 tbsp of propylene glycol and turn on the lamp. When this mixed solution was tested under the conditions below, it showed extremely excellent rust prevention properties. [1} General physical properties Appearance
Colorless transparent PH
84 specific gravity 20/20d
CI. 0441 Freezing point (q
○) -60.2 (no precipitates even in this state) ■ Rust prevention test Test conditions Temperature 4000 test pieces Steel laying method Air blowing bond test 100'/min Duration
The LO test results are shown in Table 2.

Table 2 Example 2 Mix 70 parts of ion-exchanged water, 30 parts of potassium phosphoric acid, 600 parts of disodium phosphate, 30 parts of malic acid, and 100 parts of sodium carbonate, then add propylene glycol for 30 minutes and mix. do.

The test was conducted in the same manner as in Example 1. '1} General physical properties appearance
Colorless transparent PH
8.23 specific gravity 20/
2000 1.0264 Freezing point (℃) -13.0 (2- Rust prevention test result table 3 Example 3 20 minutes of ion-exchanged water and 10 minutes of phosphoric acid-ammonium,
Add 300ml of dipotassium phosphate, 10 parts of tartaric acid, and 50 parts of sodium bicarbonate (NaHC03) and mix.

Further, propylene glycol was added for 80 minutes and thoroughly mixed. The test was conducted in the same manner as in Example 1. '1} General physical properties Appearance Colorless and transparent PH
8.60
Specific gravity 20/20q0 1.0
459 Freezing point (00) -60
．． 8 (2) Rust prevention test results table 4

Claims (1)

[Claims] 1 A propylene glycol-water-based secondary refrigerant composition containing a phosphoric acid monosalt, a phosphoric acid disalt, an organic acid, and an alkali compound, and having a pH of 7.0 to 8.5.