Controlled-release fertilizers

Abstract

The present disclosure relates to a controlled-release fertilizer and, more particularly, to a controlled-release fertilizer including: a photodegradable capsule including a binder resin containing a polyolefin and an ethylene vinyl acetate copolymer; and a photocatalytic composite in which a (meth)acrylate compound containing an alkylene glycol repeating unit having 1 to 10 carbon atoms is bonded to the surface or inside of aggregates of inorganic fine particles, and a fertilizer contained in a space surrounded by the photodegradable capsule.

Claims

1. A controlled-release fertilizer, comprising: a photodegradable capsule including a binder resin containing a polyolefin and an ethylene vinyl acetate copolymer; and a photocatalytic composite in which a (meth)acrylate compound containing an alkylene glycol repeating unit having 1 to 10 carbon atoms is bonded to a surface or inside of aggregates of inorganic fine particles, and a fertilizer contained in a space surrounded by the photodegradable capsule.

2. The controlled-release fertilizer of claim 1, wherein the binder resin has a degradation rate of 35% or more which is derived from a weight change of the photodegradable capsule after irradiating a light having a wavelength of 300 to 800 nm to the fertilizer at an intensity of 400 w/m.sup.2 for 224 hours.

3. The controlled-release fertilizer of claim 1, wherein the inorganic fine particles include a primary particle having a cross-sectional diameter of 5 to 50 nm.

4. The controlled-release fertilizer of claim 1, wherein the aggregates of inorganic fine particles have a cross-sectional diameter of 1 μm or less.

5. The controlled-release fertilizer of claim 1, wherein the aggregates of inorganic fine particles have a cross-sectional diameter of 0.05 μm to 0.5 μm.

6. The controlled-release fertilizer of claim 1, wherein the inorganic fine particles are titanium dioxide (TiO.sub.2), zinc oxide (ZnO), or a mixture thereof.

7. The controlled-release fertilizer of claim 1, wherein the photocatalytic composite includes 1 to 500 parts by weight of the (meth)acrylate compound containing an alkylene glycol repeating unit having 1 to 10 carbon atoms relative to 100 parts by weight of the aggregates of inorganic fine particles.

8. The controlled-release fertilizer of claim 1, wherein the aggregates of inorganic fine particles are contained in an amount of 0.1 to 8 parts by weight relative to 100 parts by weight of the binder resin.

9. The controlled-release fertilizer of claim 1, wherein a weight ratio of the polyolefin:ethylene vinyl acetate copolymer in the binder resin is 1:1 to 6:1.

10. The controlled-release fertilizer of claim 1, wherein the polyolefin is at least one selected from the group consisting of a high-density or low-density polyethylene, a linear low-density polyethylene, a polypropylene, an ethylene-propylene copolymer, a polybutene, a butene-ethylene copolymer and a butene-propylene copolymer.

11. The controlled-release fertilizer of claim 1, wherein the ethylene vinyl acetate copolymer includes 1 to 45% by weight of the vinyl acetate repeating unit.

12. The controlled-release fertilizer of claim 1, wherein the (meth)acrylate compound containing an alkylene glycol repeating unit having 1 to 10 carbon atoms includes at least one selected from the group consisting of (meth)acrylates, di(meth)acrylates or esters thereof to which a polyalkylene glycol having a number average molecular weight of 100 to 2,000 is bonded; and trifunctional to octafunctional (meth)acrylates containing an alkylene glycol repeating unit having 1 to 10 carbon atoms, or esters thereof.

13. The controlled-release fertilizer of claim 12, wherein the (meth)acrylates, di(meth)acrylates or esters thereof to which a polyalkylene glycol having a number average molecular weight of 100 to 2,000 is bonded is poly(ethylene glycol)(meth)acrylate or poly(ethylene glycol)methyl ether (meth)acrylate, and the trifunctional to octafunctional (meth)acrylates containing an alkylene glycol repeating unit having 1 to 10 carbon atoms, or esters thereof is trimethylolpropane triacrylate, trimethylol propane ethoxylate triacrylate, trimethylolpropane propoxylate triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol tetraacrylate, pentaerythritol ethoxylate tetraacrylate, dipentaerythritol pentaacrylate, or dipentaerythritol hexaacrylate.

14. The controlled-release fertilizer of claim 1, further comprising a filler dispersed in the binder resin.

15. The controlled-release fertilizer of claim 1, wherein the fertilizer is a granular fertilizer.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 schematically shows the photodegradation mechanism of the controlled-release fertilizer.

DETAILED DESCRIPTION

(2) The present invention will be described in more detail with reference to the following examples. However, these examples are given for illustrative purposes only, and the scope of the invention is not intended to be limited to or by these examples.

EXAMPLES: PREPARATION OF CONTROLLED-RELEASE FERTILIZER

Examples 1 to 4

(3) (1) Preparation of Photocatalytic Composite

(4) 0.43 g of (Meth)acrylate compound containing the alkylene glycol repeating unit shown in Table 1 below was dissolved in tetrachloroethylene, to which TiO.sub.2 (average particle diameter of primary particles: 21 nm) was mixed in an amount shown in Table 1 below, and the mixture was stirred at high speed for 20 minutes by applying a shear rate of 20,000 s.sup.−1.

(5) Then, 0.015 g of a thermal polymerization initiator (AlBN) was added thereto, and the mixture was stirred at 90° C. for 30 minutes under a nitrogen gas atmosphere. Thereby, a dispersion of a photocatalytic composite in which a (meth)acrylate compound containing an alkylene glycol repeating unit was bonded to the surface and inside of the aggregates of inorganic fine particles was prepared.

(6) (2) Preparation of Controlled-Release Fertilizer

(7) The dispersion solution of the photocatalytic composite prepared above, polyethylene[LDPE, MI(melt index, 190° C., load of 2.16 kg, ASTM D1238): about 8 g/10 min, D(density): 0.925 g/cm.sup.3], ethylene vinyl acetate copolymer [MI(melt index, 190° C., load of 2.16 kg, ASTM D1238): about 1.8 g/10 min, D(density): 0.94 g/cm.sup.3, vinyl acetate content of about 20 wt %, melting point of 85° C.], and talc were used in an amount shown in Table 1 below and uniformly stirred and mixed with tetrachloroethylene at 90° C. in the composition ratio shown in Table 1 below to prepare a coating solution so as to have a solid component concentration of 5 wt %.

(8) Then, the coating solution was applied to the nitrogen fertilizer particles using a fluid bed drier to prepare a controlled-release coated fertilizer (Examples 1 to 4).

Comparative Example: Preparation of Coated Fertilizer

Comparative Example 1

(9) Polyethylene [LDPE, MI(melt index, 190° C., load of 2.16 kg, ASTM D1238): about 8 g/10 min, D(density): 0.925 g/cm.sup.3], ethylene vinyl acetate copolymer [MI(melt index, 190° C., load of 2.16 kg, ASTM D1238): about 1.8 g/10 min, D(density): 0.94 g/cm.sup.3, vinyl acetate content of about 20 wt %, melting point of 85° C.], and talc were used in an amount shown in Table 1 below and uniformly stirred and mixed with tetrachloroethylene at 100° C. in the composition ratio shown in Table 1 below to prepare a coating solution so as to have a solid component concentration of 5 wt %.

(10) Then, the coating solution was applied to the nitrogen fertilizer particles using a fluid bed drier to prepare a coated fertilizer (Comparative Example 1)

Experimental Example

Experimental Example 1: Comparison Test of Photodegradation Characteristics

(11) 5 g of each of the controlled-release fertilizers of Examples 1-4 and the coated fertilizers of Comparative Example 1 was taken, and a pinhole was made with a needle for each fertilizer grain. The degradation evaluation was performed on the coating film remaining after the internal fertilizer was completely released.

(12) A light having a wavelength of 300 nm to 800 nm was irradiated to the coating film at an intensity of 400 w/m.sup.2 at a temperature of 50° C. using a Suntest CPS+ equipment (ATLAS).

(13) Then, when light was irradiated for 224 hours under the above conditions, the degradation rate of the binder resin derived from the weight change of the coating film was determined by the following general formula 1, and the results are shown in Table 1 below.

(14) $\begin{array}{cc}\mathrm{Photodegradation}\mathrm{Rate}=\frac{\begin{array}{c}\mathrm{Change}\mathrm{in}\mathrm{weight}\mathrm{of}\mathrm{the}\mathrm{coating}\\ \mathrm{film}\mathrm{after}\mathrm{UV}\mathrm{irradiation}\end{array}}{\begin{array}{c}\mathrm{Weight}\mathrm{of}\mathrm{resin}\mathrm{in}\mathrm{the}\mathrm{coating}\mathrm{film}\\ \mathrm{before}\mathrm{UV}\mathrm{irradation}\left(\mathrm{LDPE}+\mathrm{EVA}\right)\end{array}}\times 100\%& \left[\mathrm{General}\mathrm{Formula}1\right]\end{array}$

(15) TABLE-US-00001 TABLE 1 Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Polyethylene (LDPE) 28 g 28 g 28 g 28 g 28 g EVA copolymer  7 g  7 g  7 g  7 g  7 g TALC 65 g 65 g 65 g 65 g 65 g TiO.sub.2 0.7 g  0.7 g  0.7 g  0.7 g  0.7 g  TiO.sub.2 dispersion — ∘ ∘ ∘ ∘ treatment (Meth)acrylate — Poly(ethylene Poly(ethylene Trimethylolpropane Trimethylolpropane compound containing glycol) glycol) triacrylate ethoxylate an alkylene glycol methacrylate(number methyl ether triacrylate repeating unit average acrylate molecular (number weight: 360) average molecular weight: 480) Degradation rate of 30 ± 3 35 ± 3 35 ± 3 41 ± 3 41 ± 3 binder resin (%)

(16) As shown in Table 1, it was confirmed that the controlled-release fertilizers of Examples 1-4 showed a degradation rate of binder resin of 35% or more, when irradiated with a light having a wavelength of 300 nm to 800 nm at an intensity of 400 w/m.sup.2 for 224 hours. In contrast, it was confirmed that the coated fertilizers of Comparative Example 1 showed a degradation rate of binder resin of less than 35%.

Experimental Example 2: Measurement of Z-Average Dispersion Particle Size of TiO.SUB.2

(17) The z-average dispersion particle sizes of TiO.sub.2 in the dispersion solution of the photocatalytic composite of Example 3 and the dispersion solution containing TiO.sub.2 of Comparative Example 1 were measured using a Dynamic Light Scattering instrument (Malvern Zetasizer Nano ZS90).

(18) The results are shown in Table 2 below.

(19) TABLE-US-00002 TABLE 2 Z-average dispersion particle size of TiO.sub.2 Example 3 Comparative Example 1 z-average dispersion 183 About 2.0 × particle size of TiO.sub.2 10.sup.4 (nm)

(20) As shown in Table 2, it is confirmed that the dispersion solution of the photocatalytic composite of Example 3 had a z-average dispersion particle size of about 183 nm, and thus TiO.sub.2 particles used were homogeneously dispersed and the aggregates of inorganic fine particles having a relatively small average particle size were formed.

(21) In contrast, it is confirmed that TiO.sub.2 of the dispersion solution containing TiO.sub.2 of Comparative Example 1 had a z-average dispersion particle size of about 10,000 nm or more, and thus aggregates of inorganic fine particles having a relatively large average particle size were formed.