SK279966B6 - Manufacturing process of an anti-frost chemical agent for winter maintenance of roads - Google Patents

Abstract

A manufacturing process of an anti-frost chemical agent for winter maintenance of roads based on a mixture of alkaline earth of acetic acid, which is processed in an aqueous solution of the product. The product thus obtained is filtrated or skimmed from the reaction mixture. Calcium oxide, lime hydrate or calcite or the mixtures thereof with the content of magnesium are used as a source of calcium with an admixture of magnesium. As a source of acetate component is used acetic acid or the ester thereof. The concentration of the said aqueous solution ranges from 10 to 30 wt.%. A temperature of the reaction ranges from 20 to 60 degrees Celsius. The product separated therefrom is shaped and dried, or, pre-dried, shaped and post-dried.

Description

Technical field

The invention relates to a process for the production of an antifreeze chemical composition based on the calcium magnesium salt of acetic acid.

BACKGROUND OF THE INVENTION

Most of the chemical materials used for winter road maintenance use the de-icing effect of alkali metal or alkaline earth chlorides. The fact that they are salts of hydrochloric acid also brings about the known negative effects of soil salinisation and considerable corrosion stress on the metal construction materials of vehicles and structures.

The starting point of this situation is the use of more environmentally acceptable materials based on alkali salts or alkaline earth salts of organic carboxylic acids, in particular acetic acid. More recently, it is mainly the calcium-magnesium salt as well as mixtures of calcium acetate and magnesium (U.S. Pat. No. 5,223,250).

The manufacture of these salts is simple, but to produce a product having a sufficient defrosting effect depends not only on the chemical composition, but also on the final formulation of the composition, especially the size of the granules, which must guarantee disruption of the icing layer through sufficient distribution of the communications treatment agent. At the same time, however, the particles must not be removable by the wind, which is usually quite intense at the time of communication. Alkaline salt acetate production itself can take place in a number of ways, which will ultimately be reflected in the economy of production of these devices, which in the near future will probably not be used to treat all roads, but only their selected sections, especially in historic city centers, waterways and for example on highway bridges.

The synthesis can be conducted in a sufficient quantity of water which is finally evaporated on drying the product (PCT INT. APPL. 88 05456). Attempts have also been made to produce concentrated acetic acid and solids of calcium and magnesium sources (U.S. Pat. No. 4,699,725), and the apparatus must be constructed with a special and corrosion-resistant material.

SUMMARY OF THE INVENTION

According to the production method, the antifreeze chemical for winter maintenance of roads is produced by reacting calcium oxide, calcium hydroxide or calcium carbonate, or a mixture thereof with a magnesium content of max. 2 wt. with acetic acid or methyl acetate, or a mixture of acetic acid and methyl acetate, in the present aqueous solution of the product, which is either the filtrate from the previous batch or an aqueous solution of the product. The concentration of this solution may be from 10 to 30 wt. preferably the concentration is the same as the saturated aqueous solution. The feed order of the starting materials may be arbitrary or alternating. The reaction is carried out at a temperature of 20 to 60 ° C. The reaction product is separated from the reaction mixture by centrifugation by filtration or by means of a hydrocyclone, and in the next step it is formed into a desired granule size by pelletizing, granulating or simultaneously granulated and dried by fluidic drying with a spray of water or another suitable agent. The advantage of this process is that an easily separable application active product is prepared, and the process ensures its waste-free production.

Further data on carrying out the process of the invention as well as other advantages are apparent from the examples.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

2600 L of calcium acetate solution containing 1 wt.% Was pumped into a 6-volume neutralization reactor with duplicator and stirrer. Mg in the dry product of a density of 1130 kg / m3. 200 kg of calcium hydroxide was added during stirring. After stirring the suspension, 280 L of concentrated acetic acid was started so that the temperature did not exceed 60 ° C. The reaction mixture was stirred for an hour then cooled to 20 ° C and centrifuged on a centrifuge. The cake obtained was pelletized on a 4 mm 5 mm diameter roller pellet press, which was then dried in a fluid-bed dryer. The resulting product contained 3% moisture and was used for frost preventive treatment of pavements.

Example 2

2600 L of the filtrate of Example 1 were metered into the neutralization boiler, and 155 kg of calcium oxide containing 2 wt.% Mg were added cautiously in portions and with cooling. The further procedure was identical to that of Example 1. The resulting product contained 5% moisture and was used to treat the roadway.

Example 3

A suspension of 270 kg of dolomite in 2600 l of mother liquors from previous productions was prepared as in Example 1. 280 L of acetic acid was then carefully added to keep the foaming to a maximum of 2/3 of the reactor. The remainder was treated as in Example 1 except that a belt dryer was used for drying. The product was used to treat the roadway on a steel bridge.

Example 4

3200 l of mother liquors from previous productions were fed into the reaction boiler to which 240 kg of calcium hydroxide was fed. The reactor was heated to 40 ° C and 800 L of a mixture of methyl acetate and methanol (65% by weight, methyl acetate + 35% by weight methanol) was gradually added, and the reaction was carried out at 45 ° C for 15 minutes, then 1 was added. 1 concentrated (95 wt.%) Acetic acid. The reaction mixture was allowed to react for 45 minutes and then cooled to 20 ° C. Using a vacuum rotary filter, the product was separated and granulated with a roller rotary granulator into granules with a diameter of 5 mm, which were then dried in a cabin dryer to a moisture content of 5%. The mother liquor was diluted with water and passed to a rectification column where methanol and unreacted methyl acetate were distilled off. The distillation residue was used to produce another batch of deicing medium.

Example 5

Mother liquors as in Example 1 were metered into the reaction boiler and 200 kg of calcium hydroxide were added. After heating to 45 ° C, 800 L of the methyl acetate-methanol alcohol (65% methyl acetate) azeotrope was added followed by the remaining 40 kg of calcium hydroxide. The product was separated by a hydrocyclone and placed in a batch fluid drier, where after spraying the feed, water was sprayed with the aid of an additional device.

After 10 minutes the drying was stopped and the product was sieved. Approximately 250 kg of a fraction having a particle size of 3-5 mm was obtained. The remaining product was used to prepare a saturated product solution, which was partly used for further production and partly for preventive frost maintenance of the pavement.

Industrial usability

The method according to the invention is particularly useful in the chemical industry for the production of environmentally friendly winter road maintenance means.

Claims (5)

PATENT CLAIMS Process for the production of an antifreeze chemical composition for winter maintenance of roads based on a mixture of alkaline salts or alkaline-earth salts of acetic acid, characterized in that the reaction of calcium oxide, calcium hydroxide, calcium carbonate or a mixture thereof containing max. 2 wt. with acetic acid or acetic acid ester or a mixture thereof in the present aqueous product solution, then the reaction product is separated from the reaction mixture and finally treated. Process according to claim 1, characterized in that as the present aqueous product solution, the filtrate from the previous reaction or an aqueous product solution prepared by dissolving the solid product in water to a concentration of 10 to 30% by weight is used. preferably to a saturated solution concentration. Process according to claims 1 to 2, characterized in that the reaction temperature is maintained in the range of 20 to 60 ° C. Process according to claims 1 to 3, characterized in that the reaction product is separated from the reaction mixture by sedimentation, centrifugation filtration or by means of a hydrocyclone. The process according to claims 1 to 4, characterized in that the product after separation is formed by granulation, pelletization and then dried or in one stage dried and granulated in a fluidized bed sprayer with a water spray or an aqueous solution of polyvinyl alcohol.