CS258817B1 - Method of manufacturing coated industrial fertilizers and prolonged efficiency - Google Patents

Abstract

The essence of the solution lies in the fact that in the production of coated fertilizers with extended effectiveness, where the product resulting from the condensation of urea with formaldehyde, or higher aldehydes, is used as the coating material, polyvinyl alcohol is added during the preparation of the coating mixture or during the creation of the coating in order to influence the properties of the coating. The fertilizer is suitable for use on inten

Description

The present invention relates to a process for the production of coated fertilizers with extended efficacy.

One way to obtain extended fertilizer fertilizers is to coat conventional fertilizer granules with a semi-permeable coating that reduces the dissolution rate of the fertilizer in water. A number of both inorganic (gypsum, insoluble polyphosphates, sulfur, etc.) and organic (fats, waxes, polymers, etc.) materials have been proposed as a coating agent.

A product of the condensation of urea with formaldehyde with a molar ratio of formaldehyde to urea of more than one has also been proposed as a possible coating material. The disadvantages of the fertilizers produced in this way are their less suitable mechanical properties, especially the brittleness of the packaging, which leads to the formation of cracks, often during preparation, and especially during handling and application, thereby undesirable reduction of the efficiency of the packaging. A further disadvantage is that at the chosen ratio of formaldehyde to urea, the permeability of the coating can only be influenced by its thickness. According to the present invention, the method of producing coated fertilizers with prolonged efficacy is eliminated by using a product resulting from the condensation of urea with formaldehyde or higher aldehydes, which comprises adding polyvinyl alcohol in the preparation of the coating composition and / or forming the coating. in an amount of 0.1 to 30 wt. based on the weight of the package.

According to a further feature of the invention, the surface of the coated granules is further treated by applying a protective layer, for example by waxing.

The basic effect of the process according to the invention is that the granule shell has more suitable physical properties, so that cracks do not occur which result in a rapid washing out of the granule content. In addition, the amount of polyvinyl alcohol used affects its permeability at the chosen molar ratio of aldehyde to urea and given coating thickness. In this way, the fertilizers produced in this way become more efficient in comparison to the fertilizers produced by known production processes.

The manufacture may be continuous, discontinuous, or a combination of both. For example, fertilizer is applied to the layer of heated and moving granules,. with simultaneous drying, the individual components described below, or any mixture thereof, or a total mixture thereof, and a mineral acid and / or an acid-reactive feedstock. The components of the coating composition are urea-condensate pre-condensate with an aldehyde having an aldehyde / urea molar ratio greater than one and polyvinyl alcohol in an amount such that its content in the finished container is 0.1 to 30% by weight. The precondensate is acidified immediately before and / or during application such that the pH value is less than 6.

The production method of the invention is described in more detail below with reference to specific embodiments.

Example 1

A total of 120 g of an acidified aqueous solution of urea-formaldehyde precondensate containing 3.6% by weight was sprayed onto a 300 g granular NPK-1 fertilizer in a geyser layer in a laboratory apparatus equipped with heating and warm air drying. polyvinyl alcohol. The temperature was maintained at about 80 ° C. The precondensate solution to form the coating was prepared by the gradual addition of urea to a boiling mixture of 36% by weight formaldehyde. and polyvinyl alcohol at reflux such that the molar ratio of formaldehyde to urea was 1.6. Prior to application to fertilizer granules, the precondensate was acidified by the addition of 6 ml of saturated aqueous ammonium sulfate solution at 20 ° C.

The obtained coated fertilizer had an average coating weight of 8.9% by weight. and a nutrient / dissolution test revealed a nutrient release time of about 140 times longer than the original fertilizer.

Example 2

The process was conducted as in Example 1 with the difference that granulated amophos was used instead of NPK-1 fertilizer.

Example 3

The process was conducted as in Example 1 except that granular urea was used instead of NPK-1 fertilizer.

Example

The process was conducted as in Example 1 except that paraffin was applied to the surface of the coated granules in an amount of about 1% by weight. weight per granule.

The time to release nutrients was further extended by about 8%.

Coated fertilizers produced in this way are suitable for use on intensively managed and irrigated soils, eg in the cultivation of vegetables, ornamental plants, special crops, etc.

Claims (2)

SUBJECT OF THE INVENTION Process for the production of coated fertilizers with prolonged efficacy, wherein the coating material is a product formed by the condensation of urea with formaldehyde or possibly higher aldehydes, characterized in that 0.1% of polyvinyl alcohol is added in the preparation of the coating mixture and / or in the packaging up to 30 wt. based on the weight of the package. 2. A method according to claim 1, characterized in that the surface of the coated granules is further treated by applying a protective layer, for example by waxing.