Caking-preventing agent for fertilizer

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 10 carbon atoms, an .alpha.-olefinsulfonate having 6 to 10 carbon atoms, an alkylsulfonate having 6 to 10 carbon atoms or an alkylbenzenesulfonate having an alkyl group having 4 to 8 carbon atoms, said aqueous solution containing a wet spread sticking agent in an amount of 1.0 to 50% by weight based on the synthetic polymeric compound.

The present invention relates to a caking-preventing agent for fertilizers 
having a caking tendency, such as urea, ammonium sulfate, ammonium 
nitrate, ammonium chloride or composite fertilizers. 
STATEMENT OF PRIOR ARTS 
As a caking-preventing agent for the above-mentioned caking fertilizers, 
there has been proposed a solution obtained by solubilizing a 
substantially water-insoluble polymeric compound by a 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. The 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 above-mentioned 
caking-preventing agent is too high, the concentration cannot be 
increased, and if the caking-preventing agent is sprayed on a caking 
fertilizer, it is impossible to uniformly stick the caking-preventing 
agent to fertilizer particles. Moreover, under severe storage conditions 
where high temperatures and low temperatures appear repeatedly, the 
stability is not sufficient. 
SUMMARY OF THE INVENTION 
We made research with a view to overcoming the foregoing defects, and as 
the result, it was found that if a wet spread sticking agent is 
incorporated in the conventional solubilized polymer solution, the 
foregoing defects 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 for a fertilizer, which comprises an 
aqueous solution obtained by solubilizing a substantially water-insoluble 
synthetic polymeric compound by a concentrated aqueous solution of a salt 
of an alkyl sulfate having 6 to 10 carbon atoms, an 
.alpha.-olefinsulfonate having 6 to 10 carbon atom, an alkylsulfonate 
having 6 to 10 carbon atoms or an alkylbenzenesulfonate having an alkyl 
group having 4 to 8 carbon atoms, said aqueous solution containing a wet 
spread sticking agent in an amount of 1.0 to 50% by weight based on the 
synthetic polymeric compound. 
As 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/vinylpyrrolidone 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 the alkyl sulfate having 6 to 10 carbon atoms, that is 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 the .alpha.-olefin sulfonate having 6 to 10 carbon atoms, that is used 
in the present invention, there can be mentioned a product obtained by 
treating an .alpha.-olefin having 6 to 10 carbon atoms with a sulfonating 
or sulfating agent such as SO.sub.3 and neutralizing the treated 
.alpha.-olefin with an alkaline agent, and the product includes various 
isomers according to the reaction conditions. The .alpha.-olefinsulfonate 
prepared according to an ordinary 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 small amounts of more internal 
unsaturated compounds are contained therein. The hydroxyl compound is 
composed mainly of a 3-hydroxyl compound, and small amounts of isomers 
having a hydroxyl group at other position are contained therein. The 
.alpha.-olefinsulfonate used in the present invention may contain various 
isomers as described above. 
As the alkylsulfonate having 6 to 10 carbon atoms, that is 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 the alkylbenzenesulfonate having an alkyl group having 4 to 8 carbon 
atoms, that is 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 changed within 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. In 
general, the ratio of the solubilizing agent to the water-insoluble 
polymeric compound is in the range of from 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 
degraded and the caking-preventing effect is not substantially different 
from the caking-preventing effect of the solubilizing agent. On the other 
hand, if the amount of the water-insoluble polymeric compound is larger 
than 90%, the resulting mixture shows a high hydrophilic property and no 
satisfactory caking-preventing effect can be obtained. 
The wet spread sticking agent used in the present invention improves the 
ability of the solubilized polymeric compound in wetting a fertilizer and 
assists uniform sticking of the former to the latter. As the wet spread 
sticking agent, there can be used a water-soluble polymer and a nonionic 
surface active agent. As the water-soluble polymer, there can be mentioned 
polyvinyl alcohol, a water-soluble saponification product of polyvinyl 
acetate, polyethylene glycol, hydroxypropylcellulose, sodium 
carboxymethylcellulose and hydroxypropylmethylcellulose, and as 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 should 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, sticking 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 incorporated 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 
solubilize the polymeric compound and the wet spread sticking agent is 
added to the formed 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 solubilization 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 the solid content 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 
sticking ability 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 shocks 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 obtained solution can be 
directly scattered and sprayed without dilution.

(EXAMPLES) 
The present invention will now be described in detail with reference to the 
following examples that by no means limit the scope of the invention. 
EXAMPLE 1 
A 25% by weight aqueous solution of a caking-preventing agent shown in 
Table 1 in an amount corresponding to 0.05% by weight of granular urea (1 
to 2 mm in diameter) was diluted two-fold and uniformly sprayed on 2 kg of 
granular urea. Then, 45 g of the urea was filled in a cylindrical mold 
made of rigid polyvinyl chloride having an inner diameter of 4 cm and 
pressed under a pressure of 2.0 kg/cm.sup.2. The urea was allowed to stand 
still in this state at a temperature of 30.degree. C. and a relative 
humidity of 78% for 28 days. Then, the urea was taken out of the cylinder 
and the fracture strength was measured by using a tensilon compression 
strength meter (supplied by Toyo Baldwin). 
The obtained results are shown in Table 1. 
TABLE 1 
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Caking-Preventing Agent Fracture 
Recipe Polymeric Mixing 
Strength 
No. Compound 
Solubilizing Agent 
Wet Spread Sticking Agent 
Ratio 
(kg/cm.sup.2) 
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Compa- 
1 -- -- -- -- 7.4 
rative 
2 PVAc sodium octyl sulfate 
-- 1/4 3.5 
Present 
3 PVAc sodium octyl sulfate 
polyvinyl alcohol (MW = 6000) 
1/4/0.1 
0.4 
Invention 
4 PVAc sodium octyl sulfate 
POE(10) nonyl phenyl ether 
1/4/0.1 
0.6 
5 PVAc sodium octyl sulfate 
polyvinyl alcohol (MW = 6000) 
1/4/0.05 
0.1 
POE(10) nonyl phenyl ether 
/0.05 
6 PVB sodium decyl sulfate 
water-soluble saponified 
1/7/0.04 
0.7 
polyvinyl acetate 
7 PVF sodium .alpha.-olefin (C.sub.8)- 
POE(5) lauryl ether 
1/3/0.2 
0.5 
sulfonate 
8 EVA sodium hexylbenzene- 
sodium carboxymethylcellulose 
1/6/0.05 
0.7 
sulfonate 
9 PVAcl sodium hexyl sulfate 
polyvinyl alcohol (MW = 1000) 
1/6/0.05 
0.7 
10 PVAc sodium octyl sulfate 
polyvinyl alcohol (MW = 6000)* 
1/4/0.1 
0.2 
11 PVAc sodium octyl sulfate 
POE(10) nonyl phenyl ether* 
1/4/0.1 
0.2 
12 EVA sodium hexylbenzene- 
sodium carboxymethylcellulose* 
1/6/0.05 
0.5 
sulfonate 
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Note 
PVAc: polyvinyl acetate having a degree of polymerization of 500 
(emulsion) 
PVB: polyvinyl butyral having a degree of polymerization to 1100 and a 
degree of butyralization of 62% 
PVAcl: polyvinyl acetoacetal having a degree of polymerization of 1100 an 
a degree of acetalization of 32% 
PVF: polyvinyl formal having a degree of polymerization of 900 and a 
degree of formalization of 87% 
EVA: 1/1 ethylene/vinyl acetate copolymer having a degree of 
polymerization of 2000 
*wet spread sticking agent was added while the waterinsoluble polymer 
emulsion was prepared (emulsion polymerization) 
EXAMPLE 2 
A 100-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 30 g, were put into 
the ceramic vessel. The treated urea was pulverized for 20 minutes at a 
speed of 150 rpm. The weight of dusts having a size smaller than 32 mesh 
was measured and the dust ratio was calculated according to the following 
formula. 
##EQU1## 
The obtained results are shown in Table 2. 
TABLE 2 
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Recipe 
No. Dust Ratio (%) 
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Compara- 1 12.4 
tive 2 11.8 
Present 3 10.0 
Invention 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 
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