CAKING-PREVENTING COMPOSITION FOR FERTILIZER

Abstract: A fertilizer is effectively prevented from caking with an aqueous composition comprising an aqueous solution obtained by solubilizing a water-insoluble synthetic polymeric compound by a concentrated aqueous solution of a salt of an alkyl sulfate having 6 to l0 carbon atoms, an α-­ olefinsulfonate having 6 to l0 carbon atom, an alkyl­ sulfonate having 6 to l0 carbon atoms or an alkylbenzene­ sulfonate having an alkyl group having 4 to 8 carbon atoms, said aqueous solution containing a wet spread sticking agent in an amount of l.0 to 50% by weight based on the synthetic polymeric compound.

Description: The present invention relates to a caking-preventing composition for fertilizers having a caking tendency, such as urea, ammonium sulfate, ammonium nitrate, ammonium chloride or composite fertilizers. As the caking-preventing composition for the abovementioned caking fertilizers, there has been proposed a solution obtained by solubilizing a substantially water-insoluble polymeric compound by means of concentrated solution of an anionic surface active agent (hereinafter referred to as "solubilized polymer solution") (see Japanese Patent Publication No.17104/1974), and it is said that the solubilized polymer solution exhibits an excellent caking-preventing effect on urea and the like. This solubilized polymer solution is added to a caking fertilizer directly or after it has been diluted to an appropriate concentration, and water is substantially removed to obtain an excellent caking-preventing effect. However, the above-mentioned caking-preventing agent is not completely satisfactory. More specifically, since the viscosity of the abovementioned caking-preventing agent in solution is high, the concentration of the solution cannot be increased, and if the caking agent-preventing agent is sprayed onto a caking fertilizer, it is impossible to cause the caking-preventing agent to adhere uniformly to the fertilizer particles. Moreover, under severe storage conditions where high temperatures and low temperatures occur repeatedly, the stability is not sufficient. JP-B-7417827 discloses the use of aqueous solutions of non-ionisable water soluble polymers and e.g. alkyl sulphates as caking-preventing agents. We have now found that if a wet spread sticking agent is incorporated into the conventional solubilized polymer solution, the defects of the prior art compositions are overcome and the caking-preventing effect is improved. We have now completed the present invention based on this finding. More specifically, in accordance with the present invention, there is provided a caking-preventing agent composition for a fertilizer, which comprises an aqueous solution of a substantially water-insoluble synthetic polymeric compound, a solubilizing agent which is a concentrated aqueous solution of a salt of an alkyl sulfate having 6 to 10 carbon atoms, an α-olefinsulfonate having 6 to 10 carbon atoms or an alkylbenzene-sulfonate having an alkyl group having 4 to 8 carbon atoms, and 1.0 to 50 percent by weight, based on the synthetic polymeric compound, of a wet spread sticking agent which is a water-soluble polymer or a nonionic surfactant, the weight ratio of the solubilizing agent to the polymeric compound being from 1:9 to 9:1. As examples of the substantially water-insoluble synthetic polymeric compound (hereinafter referred to as "water-insoluble polymeric compound") used in the present invention, there can be mentioned polyvinyl acetate, a vinyl acetate/ethylene copolymer, alkyl(meth)acrylate homopolymers and copolymers, vinyl acetate-grafted polyvinyl alcohol copolymers, acetalized polyvinyl alcohol, butyralized polyvinyl alcohol, formalized polyvinyl alcohol, vinyl acetate-vinyl-pyrrolidone copolymers and vinyl acetate-maleic anhydride copolymers. Among these water-insoluble polymeric compounds, polyvinyl acetate is especially preferred. The degree of polymerization of the water-insoluble polymeric compound should be within such a range that the polymeric compound is soluble in a concentrated solution of the solubilizing agent, and generally the degree of polymerization is at least 10, preferably in the range of from 100 to 3000. As examples of alkyl sulfates having 6 to 10 carbon atoms, that can be used in the present invention, there can be mentioned hexyl sulfate, octyl sulfate and decyl sulfate. The solubilizing agent such as an alkyl sulfate as mentioned above is used in the form of a salt with an alkali metal such as sodium, potassium or lithium or an alkaline earth metal such as calcium, magnesium or strontium. As examples of α-olefin sulfonates having 6 to 10 carbon atoms that may be used in the present invention, there can be mentioned a product obtained by treating an α-olefin having 6 to 10 carbon atoms with a sulfonating or sulfating agent such as SO₃ and neutralizing the treated α-olefin with an alkaline agent, and the product includes various isomers depending on the reaction conditions. The α-olefinsulfonate prepared according to a conventional process comprises about 20 to about 60% by weight of an alkenylsulfonate (hereinafter referred to as "alkenyl compound") and about 40 to about 80% by weight of a hydroxyalkylsulfonate (hereinafter referred to as "hydroxyl compound"). The alkenyl compound is composed mainly of unsaturated compounds having a double bond between the 2- and 3- or 3- and 4-positions, and also small amounts of more internally unsaturated compounds. The hydroxyl compound is composed mainly of a 3-hydroxyl compound, with small amounts of isomers having a hydroxyl group at other position. The α-olefinsulfonate used in the present invention may contain various isomers as mentioned above. As examples of the alkysulfonate having 6 to 10 carbon atoms, that may be used in the present invention, there can be mentioned hexylsulfonate, octylsulfonate and decylsulfonate. The alkylsulfonate is used in the form of a salt as described above with respect to the alkyl sulfate. As examples of the alkylbenzenesulfonate having an alkyl group having 4 to 8 carbon atoms that may be used in the present invention, there can be mentioned butylbenzenesulfonate, hexylbenzenesulfonate and octylbenzenesulfonate. The alkylbenzenesulfonate is used in the form of a salt as mentioned above with respect to the alkyl sulfate. An appropriate solubilizing agent is selected from among the above-mentioned solubilizing agents according to the kind of the water-insoluble polymeric compound used, and the ratio of the solubilizing agent to the water-insoluble polymeric compound can be varied over a broad range. However, the ratio where attainment of an excellent effect is expected is naturally limited and this preferred ratio varies greatly according to the kind, molecular weight and synthesis process of the polymeric compound and the kind and purity of the solubilizing agent. However, the ratio of the solubilizing agent to the water-insoluble polymeric compound is within the range of 1/9 to 9/1. Even if the solubilizing agent is used in a larger amount, the water-insoluble polymeric compound can be solubilized, but if the amount of the solubilizing agent is larger than 90%, the caking-preventing effect is reduced and the caking-preventing effect is not substantially different from the caking-preventing effect of the solubilizing agent alone. On the other hand, if the amount of the water-insoluble polymeric compound is larger than 90%, the resulting mixture is highly hydrophilic and no satisfactory caking-preventing effect can be obtained. The wet spread sticking agent used in the present invention improved the ability of the solubilized polymeric compound to wet a fertilizer and assists uniform sticking of the former to the latter. The wet spread sticking agent is either a water-soluble polymer or a nonionic surface active agent. As examples of water-soluble polymers, there can be mentioned polyvinyl alcohol, a water-soluble saponification product of polyvinyl acetate, polyethylene glycol, hydroxypropylcellulose, sodium carboxymethylcellulose and hydroxypropylmethylcellulose, and as examples of the nonionic surface active agent, there can be mentioned polyoxyalkylene-type nonionic surface active agents such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene sorbitol fatty acid ester and polyoxyethylene alkyl ester. A nonionic surface active agent having an HLB value of 5.0 to 15.0 is especially preferred. In the present invention, it is important that the wet spread sticking agent be incorporated in an amount of 1.0 to 50% by weight based on the water-insoluble polymeric compound. If the amount of the wet spread sticking agent is smaller than 1.0% by weight, adhere to a fertilizer is insufficient, and if the amount of the wet spread sticking agent exceeds 50% by weight, the spraying operation becomes difficult because of an increase in the viscosity. It is preferred that the wet spread sticking agent be present in an amount of 5 to 40% by weight based on the water-insoluble polymeric compound. It is especially preferred that the water-soluble polymer and the nonionic surface active agent be used in combination as the wet spread sticking agent. The process for the preparation of the caking-preventing agent of the present invention is not particularly critical. For example, there can be mentioned a process in which a predetermined amount of a granular or emulsified water-insoluble polymeric compound is added to a concentrated aqueous solution (ordinarily 10 to 30% by weight) of the solubilizing agent, the mixture is stirred at room temperature or under heating to dissolve the polymeric compound and the wet spread sticking agent is added to the resulting solution, and a process in which the wet spread sticking agent is added to an aqueous solution of the solubilizing agent or the water-insoluble polymeric compound and dissolution is then effected. In the latter process, the wet spread sticking agent may be added when an emulsion of the water-insoluble polymeric compound is prepared. In the present invention, the caking-preventing agent may be added to a fertilizer according to means customarily adopted in this field. For example, the caking-preventing agent may be added to a fertilizer slurry, or a solution of the caking-preventing agent may be sprayed on the surface of a powdery, crystalline or granular substance to be treated. In the latter case, in order to enhance the spraying efficiency, it is preferred that a solution of the caking-preventing agent be jet-sprayed while the substance to be treated is being transported on a belt conveyor or is falling in the form of a stream from a conveyor or the like. The caking-preventing agent of the present invention is obtained in the form of a concentrated aqueous solution (with a solids content preferably of 25 to 50% by weight.) The solution may be applied to a fertilizer directly or after it has been diluted. The caking-preventing agent of the present invention is applied to the substance to be treated in an amount of 0.005 to 0.5% by weight as the sum of the polymeric compound and solubilizing agent based on the substance to be treated. (Effects of the Invention) By using the caking-preventing agent of the present invention comprising the wet spread sticking agent in an amount of 1.0 to 50% by weight based on the substantially water-insoluble synthetic polymeric compound, the ability to adhere to a substance to be treated is increased and the caking-preventing effect is enhanced. As the secondary effect, an effect of reduction in dust generation by mechanical shock can be attained by using the caking-preventing agent of the present invention. Furthermore, by addition of the wet spread sticking agent to the present invention, the viscosity of the product can be greatly reduced and the concentration can be increased, so that the resulting solution can be sprayed without dilution. (Examples) The present invention will now be described in detail with reference to the following non-limiting examples: Example 1 A 25% by weight aqueous solution of a caking-preventing agent as shown in Table 1 in an amount corresponding to 0.05% by weight of granular urea (1 to 2mm in diameter) was diluted two-fold and uniformly sprayed onto 2 kg of granular urea. Then, 45 g of the urea was charged into a cylindrical mold made of rigid polyvinyl chloride having an internal diameter of 4 cm and compressed under a pressure of 2.0 kg/cm² . The urea was allowed to stand in this state at a temperature of 30°C and a relative humidity of 78% for 28 days. Then, the urea was taken out of the cylinder and its fracture strength measured by using a tensilon compression strength meter (supplied by Toyo Baldwin). The results obtained are shown in Table 1. Example 2 A 600-mℓ ceramic vessel was charged with 300 g of the treated urea obtained in Example 1 (each of receipes 1 through 12), and five spherical ceramic balls, each having a diameter of 2 cm and a weight of 33 g, were put into the ceramic vessel. The treated urea was pulverized for 20 minutes at a speed of 150 rpm. The weight of the resulting dust having a particle size smaller than 32 mesh was measured and the dust ratio was calculated according to the following formula. Recipe No. Dust Ratio (%) Comparative 1 12.4 2 11.8 Present Invention 3 10.0 4 9.0 5 10.1 6 9.7 7 9.8 8 9.9 9 10.0 10 9.5 11 9.4 12 9.0

Claims: A caking-preventing composition for a fertilizer, which comprises an aqueous solution of a substantially water-insoluble synthetic polymeric compound, a solubilising agent which is a concentrated aqueous solution of a salt of an alkyl sulfate having 6 to 10 carbon atoms, an α-olefinsulfonate having 6 to 10 carbon atoms or an alkylbenzene-sulfonate having an alkyl group having 4 to 8 carbon atoms, and 1.0 to 50 percent by weight, based on the synthetic polymeric compound, of a wet spread sticking agent which is a water-soluble polymer or a nonionic surfactant, the weight ratio of the solubilising agent to the polymeric compound being from 1:9 to 9:1. A composition as claimed in claim 1, in which said substantially water-insoluble synthetic polymeric compound has a polymerization degree of 10 to 3000. A composition as claimed in claim 1, which has a solids content of 25 to 50 percent by weight.

Inventors: HOSOKAWA, HITOSHI, IWASAKI, TETSUJI
Applicants: KAO CORPORATION
Application year: 1987
Main classification: C05G3
IPC codes: C05G3, B01J2