Abrasion resistant coatings for fertilizers

• US 5,300,135 A
• Filed: 06/09/1993
• Issued: 04/05/1994
• Est. Priority Date: 02/14/1991
• Status: Expired due to Term

• Current Assignee: OMS Investments Incorporated (Scotts Miracle-Gro Company)
• Original Assignee: O M Scott & Sons Company
• Inventors: Hudson, Alice P., Woodward, Fred E.
• Primary Examiner(s): Lander, Ferris
• Application Number:
  US08/074,141
• Time in Patent Office: 300 Days
• Field of Search: 71/28-30
• US Class Current: 71/28
• CPC Class Codes: C05C 9/005 Post-treatment
• CPC Class Codes: C05G 5/36 layered or coated with sulfur
• CPC Class Codes: C05G 5/37 layered or coated with a polymer
• CPC Class Codes: C05G 5/38 layered or coated with wax or resins

Abstract

Mixtures of hydrocarbon waxes and hydrocarbon soluble polymers which have oxygen containing polar groups provide an abrasion resistant sealant coating for sulfur coated urea.

Claims

1. An attrition resistant, free-flowing non-smearing essentially dustless slow release fertilizer composition consisting essentially of:

a particulate water soluble urea core having a sulfur coating layer applied directly onto the surface of said fertilizer core,

said sulfur coating layer being coated with from about 0.75 to about 10 percent (by weight of the fertilizer composition) of a topcoating composition which is essentially non-flowable at ambient temperature and has a melting point of from about 60°

C. to about 105°

C.;

said topcoating composition providing a hard outer coating over said sulfur coating layer and being non-smearing at ambient temperature whereby said sulfur coated fertilizer composition is rendered essentially dust-free on handling,

said top-coating composition comprising a mixture of about 5 to about 50 percent (by weight of the topcoating composition) of a polymer and about 95 to about 50 percent (by weight of the topcoating composition) of a hydrocarbon wax;

said polymer being selected from the group consisting of ethylene-vinyl acetate copolymers in which the weight ratio of ethylene to vinyl acetate is from about 20 to about 2 and the number molecular weight is from about 2000 to 20,000; and

ethylene-acrylic acid copolymers in which the ratio of ethylene to acrylic acid is from about 50 to about 10 and the number molecular weight is from about 2000 to 20,000 and mixtures thereof; and

said hydrocarbon wax being selected from the group consisting of natural petroleum waxes having drop melting points between about 60°

C. and 80°

C., containing less than about 5% oil as determined by ASTM method D721, and being essentially free of aromatic or cyclic structures;

synthetic hydrocarbon waxes melting between about 60°

C. and 105°

C., and having molecular weights between about 400 and 600 and mixtures thereof.

2. The composition of claim 1 in which the hydrocarbon wax is a synthetic olefin mixture with an average molecular weight of greater than 400, and comprises essentially 0.5 to 2% paraffins, 30-40% hydrocarbons with vinylidine double bonds, 8-12% hydrocarbons with internal double bonds, and 50-55% hydrocarbons with alpha double bonds, and a drop melt point of about 69°

to 75°

C.

3. The composition of claim 1 in which the hydrocarbon wax is a paraffin which contains less than 0.5% oil as determined by ASTM D721, and has a drop melting point of about 60°

to 70°

C.

4. The composition of claim 1 in which the polymer is an ethylene vinyl acetate copolymer containing from about 10 to about 30% vinyl acetate.

5. A process for producing an abrasion resistant, free-flowing, non-smearing, essentially dustless slow release particulate fertilizer consisting essentially of:

providing a quantity of sulfur coated urea particles having the sulfur applied directly onto the surface of said fertilizer particles;

adding a metered stream of a topcoating composition to said fertilizer particles, either as a molten liquid or as pellets or prills less than 2 mm in diameter, at a temperature of from about 70°

C. to about 100°

C.;

said topcoating composition being essentially non-flowable at ambient temperatures and having a melting point of from about 60°

C. to about 105°

C., said topcoating composition comprising a mixture of about 5 to about 50 percent (by weight of the topcoating composition) of a polymer and about 95 to about 50 percent (by weight of the topcoating composition) of a hydrocarbon wax;

said polymer being selected from the group consisting of ethylene-vinyl acetate copolymers in which the weight ratio of ethylene to vinyl acetate is from about 20 to about 2 and the number molecular weight is from about 2000 to 20,000;

ethylene-acrylic acid copolymers in which the ratio of ethylene to acrylic acid is from about 50 to about 10 and the number molecular weight is from about 2000 to 20,000 and mixtures thereof;

said hydrocarbon wax being selected from the group consisting of natural petroleum waxes having drop melting points between about 60°

C. and 80°

C., containing less than about 5% oil as determined by ASTM method D721, and being essentially free of aromatic or cyclic structures;

synthetic hydrocarbon waxes melting between about 60°

C. and 105°

C., and having molecular weights between about 400 and 600 and mixtures thereof;

agitating the mixture of topcoating composition and sulfur coated fertilizer particles in a manner such that a mixing of said mixture is achieved; and

cooling the mixture with agitation to ambient temperature to provide a fertilizer having a hard outer coating applied over said sulfur coating layer which is non-smearing at ambient temperature and said fertilizer is essentially dust-free on handling.