SK153794A3 - Manufacturing process of anti-frost chemical agent for winter maitenance 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 anti-freeze chemical composition for winter maintenance of roads prepared from a solution of the reaction product of oxide, hydroxide or calcium carbonate with the addition of magnesium and acetic acid or methyl acetate as starting materials. The product cake produced is separated from the mother liquors and finally shaped and dried.

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 attack of metallic construction materials of vehicles and buildings.

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 calcium-magnesium salt, as well as mixtures of calcium acetate and magnesium (U.S. Pat. No. 5,223,250).

The production of these salts is easy, 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 frozen layer through sufficient distribution of the composition on the communication. 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 be conducted in a number of ways, which will ultimately be reflected in the economics of production, these means which in the near future will probably not be used to treat all roads, but only selected sections, especially in historic city centers, water resources and for example on highway bridges.

The synthesis can be conducted in a sufficient quantity of water which is finally evaporated when the product is dried (PCT INT.APPL.88 05456). Attempts are also made to produce from concentrated acetic acid, and sources of calcium and magnesium in the solid phase. US Pat. file no. 4699725 whereby the equipment must be specially constructed and of a special corrosion-resistant material.

According to this method of manufacture, the antifreeze chemical composition for winter road maintenance is produced by reacting magnesium hydroxide or calcium carbonate, or mixtures thereof, containing magnesium with acetic acid or methyl acetate, or mixtures thereof, in a pre-treated aqueous solution. a 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% by weight. preferably the concentration is the same as the saturated aqueous solution. The dosing order of the starting materials can be arbitrary or alternating. The reaction is carried out at 20-60 ° 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 shaped to a desired granule size by pelletizing, granulating, or simultaneously granulated and dried by fluid drying with a spray of water or other 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 production method of the invention as well as other advantages are apparent from the examples.

EXAMPLE 1 A cake was pelletized in a diameter of 4 mm, 5

To a 6 m neutralization reactor, equipped with a duplicator and stirrer, 2600 L of calcium acetate solution containing 1% w / w was pumped. Mg in the dry product of a density of 1130 kg / m @ 2. 200 kg of calcium hydrate was added with 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 additional hour and then cooled to 20 ° C and centrifuged on a centrifuge. The obtained pellet press mill was then dried in a fluidized bed dryer. The resulting product contained 3% moisture and was used for frost preventive treatment of pavements.

Example 2

To the neutralization boiler of Example 1 there was carefully added 155 kg of calcium oxide with a procedure identical to that of containing 5% moisture and 2600 L portions were charged and cooled with Mg 2% by weight. Another example 1. The resulting product is for roadway treatment.

Example 3

A suspension of 270 kg of dolomite in 2600 l of inoculum liquors from previous productions was prepared as in Example 1. Subsequently, 280 L of acetic acid was carefully added to the mixture so as to maintain foaming to a maximum of 2/3 of the reactor. The other part was worked up as in example one, 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 introduced into the reaction boiler and 240 kg of calcium hydrate were dosed.

The reactor was heated to 40 ° C and a mixture of 800 L of methyl acetate / methanol (65% methyl acetate + 35% methanol) was added gradually, and the reaction was carried out at 45 ° C for 15 min and then 1 L concentrated (95%) was added. wt) acetic acid. The reaction mixture was allowed to react for 45 minutes and then cooled to 20 ° C. It was separated using a vacuum rotary filter. The product was granulated with a roller granulator to a 5 mm diameter granulator, which was then dried in a oven to 5% humidity.

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

The mother liquor as in Example 1 was metered into the reaction boiler and 200 kg of calcium hydrate was added thereto. After heating to 45 ° C, 800 L of azeotrope methyl acetate, methyl alcohol (65% methyl acetate) was added, followed by the remaining 40 kg of calcium hydrate. The product was separated by a hydrocyclone and placed in a batch fluid drier, where after spraying the batch, 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 3 to 5 mm fraction were obtained. The other product was used to prepare a saturated solution of the product, which was partly used for further production and partly for preventive frost maintenance of the pavement.

Industrial use:

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

Claims (6)

PATENT CLAIMS A process for the production of an antifreeze chemical composition for winter maintenance of roads based on a mixture of alkali salts or alkaline earth salts of acetic acid, characterized in that the reaction of oxide, hydroxide, calcium carbonate or a mixture thereof containing magnesium with acetic acid or acetic acid ester , or mixtures thereof, in a pre-conditioned aqueous product solution, after which the reaction product is separated from the reaction mixture and finally treated. 2. Process according to claim 1, characterized in that the precursor aqueous solution of the product is a 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. preferably to a saturated solution concentration. 3. The method according to claim 1 or 2, characterized in that the order of feed of the feedstocks can also be reversed as in 1, optionally divided into portions. 4. A process according to any one of claims 1 to 3, wherein the reaction temperature is maintained between 20 and 60 ° C. 5. A process according to any one of claims 1 to 4, wherein the reaction product is separated from the reaction mixture by sedimentation, centrifugation filtration, or by means of a hydrocyclone. 6. A process according to any one of claims 1 to 5, characterized in that after separation, the product is shaped by granulation, pelletization and subsequently dried, or dried and granulated in one stage in a fluidized bed sprayer with water or other suitable solution e.g. polyvinyl alcohol solution.