JPS6311389B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a liquid composition useful as a heat absorbing body for solar water heaters and heat collectors, and its purpose is to have excellent heat absorbing properties and to be able to be used stably over a long period of time. The objective is to provide a solar heat absorbing liquid that can absorb heat from the sun. It is conventionally known to expose a black liquid to the sun's rays to absorb solar heat, and then use heat exchange to raise the temperature of ordinary tap water for use in domestic or industrial applications. As such liquid heat absorbers, black dye dissolved in water, black pigment etc. dispersed in water, etc. are used, but if these heat absorbing liquids are used for a long period of time, they will absorb heat. There is a problem that the components of the heat-absorbing liquid may deteriorate or the pH may change, corroding cast iron or brass piping.Furthermore, the presence of such metal ions in the heat-absorbing liquid may cause the heat-absorbing liquid to deteriorate. A problem arises in that the black pigment or dye dispersed therein aggregates and settles, reducing the endothermic effect of the endothermic liquid. Naturally, one way to solve this problem is to include a metal rust preventive agent in the heat-absorbing liquid. No anticorrosion agent has been found to date. As a result of intensive research to solve the drawbacks of conventional endothermic liquids as described above, the inventors of the present invention found that when adding a small amount of a specific organic compound to the endothermic liquid that the inventors had previously developed, The present invention was completed based on the finding that an endothermic liquid can be obtained that overcomes the drawbacks of the prior art described above. That is, the present invention provides a solar heat absorbing liquid comprising a dispersing medium, a dispersing agent, a rust preventive agent, and a black material, in which the dispersing medium is propylene glycol, a mixture of propylene glycol and water, a mixture of glycerin and water, or glycerin, a mixture of propylene glycol and water, the dispersant being polyvinylpyrrolidone and/or caramel;
This liquid for absorbing solar heat is characterized in that the rust preventive agent is thiabendazole and the black material is powdered activated carbon. Next, to explain the present invention in more detail, thiabendazole, which is a rust inhibitor used in the present invention and which mainly characterizes the present invention, has a chemical name of 2-(4
-thiazolyl)-benzimidazole, which is a heterocyclic compound having the following structural formula. The above-mentioned compound has been conventionally used as a fungicidal agent, and although it is hardly soluble in water, it has a certain degree of solubility in the medium of the present invention. Such rust inhibitors are preferably used in amounts ranging from about 0.001 to 1.0% by weight in the endothermic liquid of the present invention. If the amount is below the lower limit of the above range, the object of the present invention is insufficiently achieved, and on the other hand, if the amount is above the upper limit, the effect will not increase proportionally. The other components of the heat-absorbing liquid of the present invention are as detailed in Japanese Patent Application No. 108854/1983 and other specifications by the present inventor, and powdered activated carbon is about 0.001 to 10 parts by weight in 100 parts by weight of the liquid composition. Part by weight proportion, preferably about 0.01
~2 parts by weight, and if the amount is below the lower limit of this range, solar heat absorption will be insufficient, while if it exceeds the upper limit, sunlight will not reach the inside of the liquid.
Heat absorption becomes insufficient. The dispersant is used in an amount of about 0.001 to 30 parts by weight, preferably about 0.5 to 10 parts by weight, and if the amount is below the lower limit of this range, the dispersion stability of the activated carbon powder will decrease. On the other hand, if the upper limit is exceeded, the viscosity becomes too high and the efficiency of heat exchange decreases. The dispersion medium is mainly powdered activated carbon and the remaining parts by weight of the dispersant, and is used in an amount of about 70 parts by weight or more, preferably about 93 parts by weight or more. Below the lower limit of this range, the viscosity and concentration of the resulting endothermic liquid will become too high, resulting in reduced heat exchange efficiency and insufficient heat absorption rate, as described above. The activated carbon used in the present invention is obtained by carbonizing organic substances, and has conventionally been used as a decolorizing, deodorizing, adsorbing, catalyst, etc., and can be used as a coloring agent or filler. Black has a different particle structure. Such activated carbon may be produced by any method such as the zinc chloride method or the steam method, but its particle size must be about 10 μm or less, preferably about 5 μm or less. Such powdered activated carbon can be easily obtained by pulverizing commercially available granular activated carbon or powdered activated carbon using a normal pulverizer, or by grinding it at the same time as dispersion and adjusting the particle size. Can be done. The dispersant used in the present invention is polyvinylpyrrolidone or caramel or a mixture thereof. Regarding polyvinylpyrrolidone, various types having an average molecular weight of about 5,000 to about 500,000 are known, and any of these known polyvinylpyrrolidones can be used in the present invention. Such polyvinylpyrrolidone has been well known as a dispersant (protective colloid) for pigments, etc., but activated carbon powder can be used in combination with propylene glycol, a mixture of propylene glycol and water, a mixture of glycerin and water, or glycerin. It has not been known as a dispersant for stably dispersing in mixtures of propylene glycol and water. According to detailed research by the present inventors, when the above-mentioned dispersion medium contains a relatively small amount of water, polyvinylpyrrolidone with a relatively low molecular weight shows excellent dispersion stability; When the polymer contains a relatively large amount of water, polyvinylpyrrolidone, which has a relatively high molecular weight, exhibits excellent dispersion stability. Caramel, which is used in place of the above polyvinylpyrrolidone or mixed in any proportion, is a substance obtained by heat-treating sugars such as glucose and sugar. It is also called scorched sugar, and has traditionally been widely used as a natural coloring agent. For example, liquid caramel made from glucose, liquid caramel made from sugar, powdered caramel, special liquid caramel, solid caramel, etc. are widely sold by Senba Toka Kogyo Co., Ltd. and others. As a result of extensive research into dispersants for uniformly and stably dispersing powdered activated carbon in the medium described below, the present inventor found that such a caramel is optimal together with the above-mentioned polyvinylpyrrolidone. As mentioned above, the dispersion medium used in the present invention is propylene glycol, a mixture of propylene glycol and water, a mixture of glycerin and water, or a mixture of glycerin, propylene glycol and water. The activated carbon can be uniformly and stably dispersed by the above-mentioned dispersant. Glycerin and/or propylene glycol act as a dispersion medium as well as a dispersion aid and anti-freeze agent for winter use; these vehicles contain at least about 15% by weight of propylene glycol, glycerin, or A mixture of glycerin and propylene glycol should be present. When the amount of glycerin or a mixture of glycerin and propylene glycol is less than about 15%, the dispersion stability of the powdered activated carbon decreases and the freezing point of the medium increases, which may cause freezing problems in winter. The essential components of the endothermic liquid of the present invention are as described above, but in addition, various water-soluble polymers, emulsifiers,
Various additives such as stabilizers and preservatives can be added as necessary. The endothermic liquid of the present invention blends the above-mentioned components,
This can be easily prepared by dispersing it using a conventional dispersing machine such as a pole mill, homomixer, attritor, sand mill, colloid mill, roll, or the like. The heat-absorbing liquid of the present invention thus obtained is a uniform black liquid and is useful as a heat-absorbing liquid for solar water heaters and heat collectors. In other words, in such applications, the temperature is raised and lowered countless times over a long period of time, and is constantly exposed to sunlight (during the day). Good dispersion stability can be maintained for a long period of time. Furthermore, when conventional carbon black is used, the carbon black tends to precipitate and deposit on the inner surfaces of circulation equipment such as pipes of water heaters and collectors, significantly reducing heat absorption and heat exchange performance. In contrast, the endothermic liquid of the present invention hardly exhibits such a tendency. Furthermore, the heat-absorbing liquid of the present invention does not corrode the metal parts of water heaters and heat collectors or metal piping parts even if used continuously for a long period of time. Such excellent performance is due to the action of the thiabendazole, which prevents the components of the endothermic liquid from deteriorating due to long-term use, and suppresses changes in the PH of the liquid even if the components deteriorate. It is also believed that this is to prevent metal ionization. Next, the present invention will be explained in more detail with reference to Examples. Note that parts and percentages in the text are based on weight. Example 1 Activated carbon (Nimura Chemical Industry, Jyoku Taiko Gold A)
Part 5, polyvinylpyrrolidone (BASF. Kollidon)
30) 5 parts, propylene glycol 50 parts and water 40 parts
A dispersion of activated carbon having a particle size of 5 μm or less was prepared by blending and dispersing with a sand mill. Next, 0.01 part of thiabendazole was added to 35 parts of propylene glycol, and after uniformly dissolving it,
2 parts polyvinylpyrrolidone (Kollidon 90), water
61.99 parts and 1 part of the above dispersion were uniformly mixed and stirred,
An endothermic liquid of the present invention having a freezing point of -15°C was prepared. On the other hand, for comparative reference, we created a solution with no thiabendazole added and the other components were the same, and conducted a JIS test on these solutions as a metal corrosion test for antifreeze solutions.
A comparative test was conducted according to K2234. As a result, as shown in the table below, the corrosion increase and loss for each metal was generally effective, but it was particularly noticeable for cast iron and solder.

[Table] Example 2 Activated carbon (Futamura Chemical Industry, Refined Daikon YV-O) 5
Polyvinylpyrrolidone (BASF. Kollidon 30)
5 parts of activated carbon, 50 parts of propylene glycol, 5 parts of thiabendazole, and 35 parts of water.
A dispersion was prepared by dispersing with a sand mill until the particle size was 5μ or less. 1 part of this dispersion, 40 parts of propylene glycol, 30.5 parts of Kollidon, and 54 parts of water were mixed and stirred to obtain an endothermic liquid of the present invention. On the other hand, for comparative reference, a dispersion was prepared in which thiabendazole was not added and the other components were the same, and an endothermic liquid was obtained in the same manner. Then 100ml of these liquids
were placed in a 200 c.c. heat-resistant glass tube, a cast iron test piece (50 mm long, 25 mm wide, 3 mm thick) was added, the tube was sealed tightly, and the weight was continuously heated at 88° C. for 14 days to examine changes in weight. , the amount of decrease in the test piece placed in the inventive solution is
Although the surface condition was good at 0.07mg/ ^cm3 ,
The amount of decrease in the test piece placed in the comparative reference solution was 5.26mg/
cm ³ , and the surface was partially corroded. Example 3 Activated carbon (Nimura Chemical Industries, Taiko M) 5 parts, caramel (Senba Toka Kogyo, S-W) 5 parts, glycerin 30
1 part, 20 parts of propylene glycol, and 40 parts of water were mixed and dispersed in a ball mill until the particle size of activated carbon became 5 μm or less to prepare a dispersion. Next, 0.01 part of thiabendazole was dissolved in 20 parts of propylene glycol, and 1 part of the above dispersion, 30 parts of glycerin, 4 parts of the above caramel, and 44.99 parts of water were mixed and stirred to obtain an endothermic liquid. On the other hand, for comparative reference, a liquid was prepared without the addition of thiabendazole and having the same other compositions. Next, as in Example 2, add 100ml of these liquids.
Each tube was placed in a 200 c.c. heat-resistant glass tube, a solder test piece (50 mm x 25 mm x 3 mm as in Example 2) was added, the tube was sealed tightly, and the tube was continuously heated at 88° C. for 14 days to examine changes in weight. However, the amount of reduction in the test piece placed in the inventive solution was 0.11 mg/cm ² and the surface condition was good, whereas the reduction amount in the test piece placed in the comparative reference solution was 1.93 mg/cm ²
In many cases, the surface state was completely corroded. In addition, the pH of the endothermic liquid was 8.02 for the liquid of the present invention before the test.
However, in the case of the comparison reference solution, the change was larger, from 8.02 to 7.63.

Claims (1)

[Claims] 1. A liquid for solar heat absorption consisting of a dispersing medium, a dispersing agent, a rust preventive agent, and a black material, in which the dispersing medium is propylene glycol, a mixture of propylene glycol and water, a mixture of glycerin and water, or glycerin, propylene glycol, and 1. A liquid for solar heat absorption, which is a mixture of water, a dispersant is polyvinylpyrrolidone and/or caramel, a rust inhibitor is thiabendazole, and a black material is powdered activated carbon.