NO131117B - - Google Patents

Description

Procedure for reducing evaporation from water surfaces and media containing water.

The present invention relates to a method for reducing the evaporation of water from water-containing media in order to prevent loss of water, lowering the water temperature and further to suppress the drying out of moist bodies, such as e.g. the soil, water-cement pastes and the like, and further to raise the temperature in the soil.

The theoretical studies of water evaporation into air or gas phase through a mono- or polymolecular film of various substances spread on the water surface have been carried out a long time ago (Langmuir, I., Journal of Physical Chemistry, Vol. 31, p. 1719, (1927); Sebba, F., and Briscoe, E. V. A., Journal of the Chemical Society, p. 106,

(1940). However, the practical application of these films for reducing the evaporation of water and for reducing the loss of water due to the evaporation from ponds and reservoirs has not been fully exploited because there is no suitable agent that has a strong evaporation reducing ability and at the same time is easy to use and which can be produced at low cost.

Studies have now been carried out to improve the temperature conditions when growing rice plants in the rice fields and to raise the water temperature in the rice fields and thus promote the growth of rice plants in the rice fields using the aforementioned theory of water evaporation. For this purpose, methods have been investigated and explored in which suitable agents with strong evaporation retarding ability, for example high normal aliphatic alcohols, were distributed as a thin film on the water surface, but they had the disadvantage that a larger amount of solvents was required to spread the alcohols and form thin films on the water surface. However, further investigations succeeded in developing a method where materials with a strong evaporation-reducing effect are used, which materials are cheap and can be produced in a simple way from cheap raw materials and which do not present difficulties of any kind when applied to the water surface.

The present invention thus relates to a method for reducing evaporation from water surfaces and media containing water, and the distinctive feature of the method according to the invention is that the water surface or the water-containing medium is applied to a reaction product of the mixture of normal aliphatic alcohols which is obtained by direct hydration or by transesterification and hydration of fats or oils containing a glyceride containing at least 40% by weight of normal fatty acids with 16-22 C atoms, and up to 2/3 parts by weight of ethylene oxide, calculated on the weight of the alcohol mixture, as the ethylene oxide derivatives may optionally be mixed with 5-20 weight percent water-soluble salts of carboxymethyl cellulose or with 10-50 weight percent water-soluble alginates, calculated on the weight of the ethylene oxide derivatives.

Fats or oils containing a glyceride containing at least 40 percent by weight of normal fatty acids with 16 to 22 carbon atoms are directly catalytically hydrogenated or hydrogenated in after transesterification and the separated glycerine is removed. The alcohol mixture obtained in this way and which contains at least one normal aiphatic alcohol with 16 . to 22-C atoms are used as raw material without further separation or purification. The aforementioned mixture of normal aliphatic alcohols is then reacted at 100° to 130°C with: 2/3 parts by weight of ethylene oxide in the presence of less than 5% anhydrous sodium hydroxide or about 1% sodium methylate.

The degree of evaporation reduction

(which is hereafter expressed as a percentage by the ratio between the difference in the weight of water that evaporates from the free surface of water that has not been treated and the weight of the water that evaporates from the surface of water that has been treated using the method, in relation to the weight of water evaporating from the surface of untreated water), as well as the numerical increase in water temperature (which is the difference between the temperature of water that has been treated and that of untreated water) for the above-mentioned products amounted to over 80 per cent, respectively 6° C The product used is a mixture of ether compounds with the following formulas:

For normal docosanol with C atomic number 22, m = 21 and n rg 5.

Although a majority of ethers consisting of the reaction product of normal aliphatic alcohols with less than 18 C atoms with ethylene oxide have been used as surfactants, they are nevertheless emulsifying agents and are prepared with more than 5 mol of ethylene oxide in order to obtain the strong hydrophilic effect, and consequently cannot form a molecular film on a water surface, and has completely different application purposes.

The purpose of associating ethylene oxide with the raw material as described above and of limiting the amount of this to less than 2/3 parts by weight calculated on the weight of the alcohol mixture is to impart hydrophilic properties to the said alcohol mixture, which in itself is almost insoluble in water, without it becomes water-soluble, and thus both a strong evaporation-reducing effect and good spreadability on water surfaces can be achieved at the same time.

Furthermore, the addition of some high-molecular electrolytes, namely water-soluble salts of carboxymethyl cellulose, e.g. sodium, potassium or ammonium salt, and water-soluble salts of alginic acid, e.g. sodium, potassium and ammonium alginate, to ethylene oxide derivatives of the aforementioned mixture of normal aliphatic alcohols, improve their dispersibility on water surfaces even at low water temperatures and can make the method of application easier. A suitable amount of these substances which can be added is 5 to 20% by weight in the case of the water-soluble salt of carboxymethylcellulose, and 10 to 50% by weight in the case of the water-soluble salt of alginic acid. The finished product is obtained by mixing the ethylene oxide derivatives of normal aliphatic alcohols in a molten state at approx. 70° C. to the water-soluble salt of carboxymethylcellulose or alginic acid dissolved in hot water; it is thoroughly mixed and then vacuum-dried at a temperature below 80°C.

The application is quite simple in that the agent can be wrapped in net cloth in an intact state or can be crushed together with water and then carried out on the water surface so that it spreads and forms a monomolecular film in a continuous form. The amount to be used is quite small, i.e. approx. 5 mg per square meters. This is also an amount that is necessary to form a monomolecular film and this can be confirmed by measuring the surface tension with a film scale of the vertical type, whether or not a monomolecular film is formed on the water surface. When the agent, on the other hand, is used on wet bodies, it can be sprayed in the form of a suspension in water where the concentration is approx. 100 to 1000 times as large as that applied to a water surface.

The effect of the mentioned means is measured by means of the size of the reduction in evaporation and the increase in the water temperature. The first can either be determined by measuring the weight of evaporated water in vessels on a test table indoors or in large enameled vessels on a large test table set up in the open, and the second can be obtained by measuring the temperature difference between water treated with the agent and untreated water in the tubs on the large test table in the open air. The degree of evaporation reduction when carrying out the method according to the invention changes to over 88 per cent and the increase in the water temperature goes up to 9.5° C.

As described above, the evaporation reducing agents used according to the invention can not only show their effect when they are used on water surfaces, but also when they are used on the surface of wet bodies, such as e.g. soil, water-cement pastes and the like, they can form thin films and reduce water evaporation and thus prevent the drying out of these bodies and raise the temperature in the soil. As mentioned in the following examples in the description, these agents, when used in nurseries, drift benches or greenhouses, can reduce the amount and number of waterings and thus save labor and further promote the growth of the crops.

The following examples serve to illustrate the effect, the production methods and the instructions for use for the evaporation reducing agents used according to the present invention.

Example I.

A mixture of 1.5 liters (1.38 kg) of rapeseed oil and 250 cc of methanol was refluxed for 5 min. with stirring at 80° C. in the presence of 5.4 kg of sodium hydroxide. After standing at the same temperature for 1 hour, the lower layer (which was waste and essentially consisted of glycerin) was drained off and the upper layer was washed 3 times with 5 liters of hot water at approx. 50° C. The mixture of the methyl residues of the higher fatty acids obtained in this way was dried with 75 to 100 g of anhydrous sodium sulfate, yield 1.25 kg (90.5 percent of the theoretical amount).

670 grams of a mixture of the higher fatty acid methyl esters mentioned above were hydrogenated in the presence of 34 g of copper-chromium catalyst at 260°C and under a pressure of 300 kg/cm<2>. The reaction was complete in 3 hours, the catalyst was filtered off and the product was a mixture of higher alcohols; yield 604 g (90 per cent).

To 260 g of this aforementioned mixture of higher aliphatic alcohols in an autoclave was added 1.3 g of sodium hydroxide. After replacing the air in the autoclave with nitrogen, 52.8 g of gaseous ethylene oxide were introduced. The contents were heated to 100° to 130° C. with stirring. The turnover was completed within approx. 1 hour and a mixture of ethylene oxide derivatives of the higher aliphatic alcohols was obtained;

yield 312 g (99.5 percent).

The indoor measurement of the magnitude of the evaporation reduction was carried out using a small rotary test table with 70 cm. diameter, rotation speed 1 round per min., and with 12 glass shards containing 200 cc. distilled water and heated using an infrared lamp (100 volts, 250 watts) for 3 hours from a distance of 20 cm from above. Some of the vessels had been treated with the agent and some had not. The size of the reduction in evaporation was calculated from the weight of the evaporated water in each vessel before and after the test.

In the open field, the measurement of the magnitude of the reduction in evaporation and the increase in water temperature was carried out by using a large rotating test table with a diameter of 150 cm, the rotation speed was 1 round every 5 min. White enameled vessels (40 x 50 cm) containing 3000 cc of distilled water were placed on the table. In the same way as in the indoor test, the size of the reduction in evaporation and the rise in the water temperature were measured after 6 hours of sunshine.

When an amount necessary to form a monomolecular film and 5 and 10 times this amount, respectively, of the above-mentioned ethylene oxide derivative of normal aliphatic alcohols (hereinafter abbreviated OED-M) was used, the degree of evaporation reduction and rise in water temperature were as follows :

Example II

When 35 g, 105 g and 175 g of ethylene oxide were used instead of 52.8 g as in the reaction in example I, the final product was 294.5 g, 364.0 g, and 435.0 g respectively of ethylene oxide derivatives of the mixture of normal aliphatic alcohols .

The degree of evaporation reduction for these agents was measured indoors in the same way as in example I and was as follows:

Example III

To 100 g of said OED-M prepared in the same way as in example I and melted by heating at approx. At 70° C, 5 g, 10 g, respectively 20 g of sodium carboxymethyl cellulose dissolved in 200 cc of hot water were added. The mixed solution was stirred at 75° to 95° C. for approx. 30 minutes and dried under reduced pressure at a temperature below 80°C.

When this product was tested in the same manner as in Example I, the rate of evaporation reduction and the increase in water temperature were as follows:

Example IV

To 100 g of OED-M, 12.5 g, 25 g, respectively 50 g of sodium alginate were added in the same way as in example III.

The magnitude of the reduction in evaporation and the rise in water temperature for the products obtained were as follows:

Example V

Proceeding as in Example IV, the mixture of higher normal aliphatic alcohols obtained by transesterification and subsequent hydrogenation of whale oil and soybean oil was reacted with 16 to 17 weight percent ethylene oxide and the product thus obtained was mixed with 10 weight percent sodium carboxymethyl- cellulose in the same manner as in Example III. The magnitude of the evaporation reduction for the final product was indoors 69.5 percent, 68 percent, respectively. The amount used was that necessary to form monomolecular film.

Example VI

The measurement of the rise in water temp.

roughness caused by OED-MC (which stands for the product obtained by mixing OED-M and 10% by weight of sodium carboxymethyl cellulose in the same way as in ex. III)

was performed for water in a cement container,

(approx. 30 m-) on open ground, which had a

muddy bottom with the intention of imitating the practical conditions in the rice fields with approx. 3 cm water depth. The agent was wrapped in net cloth as it was kneaded with water and carried over the surface of the water so that its monomolecular film formed continuously. The trial began at 9 about the mother gene on the first day. In the following overview, the rise in water temperature, which is the difference in water temperature between the treated and the untreated part over the course of 2 days, is shown:

Example VII

After rice plants were planted in a rice field (0.8 ar), the paste of OED-MC was spread on the water surface so that a continuous monomolecular film was formed. The difference in the highest water temperature between the treated and the untreated part was measured for each day for 11 days and the result is shown in the following table:

As a result of the rise in water temperature, the growth of the rice plants was promoted by approx. 20 percent in the treated part compared to the untreated part.

Example VIII

An aqueous suspension of OED-MC was

sprayed on the top layer of soil in flower pots. The amount used was 0.2 g, 2.0 g, respectively 20.0 g per m<2>. All the pots were placed in the sunshine and the amount of evaporated water from the flower pots that had been treated with the agent was compared with the amount from the untreated flower pots. The result is shown in the following table:

Example IX

A plot of land (90 x 90 cm) was sprayed with 24.3 l of water and then showered with a 0.1% water suspension of OED-MC. The amount of the agent used was 4 g per m-. After 4 or After 12 days, there was a further shower with 0.2 g per m-. The increase in soil temperature caused by the agent is shown for 17 days in the following table:

Example X

A water suspension of OED-MC was showered on planting fields sown with rice seeds and then covered with PVC. The amount used was 5 g per m<2>. Unevenness in the growth of the rice sprouts occurred in the planting fields that had not been treated with the agent. In the plant fields that had been treated with the agent, on the other hand, the amount of evaporated water from the soil surface in the plant field and the amount of condensed water on the inside of the cover film was very small, and the air temperature near the film was maintained high, and running water from the condensate along the inside of the film did not occur, so that uneven water content in the soil was not observed. As a result, the growth of the rice sprouts was very good and even.

The following table shows the results of the comparison between the number of times and the amount of irrigation after sowing the rice seeds; the water distribution in the soil and the difference in the growth of the sprouts in the plant fields that were treated with the agent and in the fields that were not treated.

Claims (1)

Process for reducing evaporation from water surfaces and media containing water, characterized in that the water surface or the water-containing medium is applied to a reaction product of the mixture of normal aliphatic alcohols obtained by direct hydration or by transesterification and hydration of fats or oils containing a glyceride containing at least 40% by weight normal fatty acids with 16 - 22 C atoms, and up to 2/3 parts by weight of ethylene oxide, calculated on the weight of the alcohol mixture, as the ethylene oxide derivatives may optionally be mixed ■ that with 5-20% by weight of water-soluble salts of carboxymethyl cellulose or with 10-50% by weight of water-soluble alginates, calculated on the weight of the ethylene oxide derivatives.