CONTROLLED-RELEASE FERTILIZERS

Abstract

The present disclosure relates to a controlled-release fertilizer and, more particularly, to 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 surfactant having an HLB value of 1 to 6 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 surfactant having an HLB value of 1 to 6 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 40% or more which is derived from a weight change of the photodegradable capsule is 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 m 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 m to 0.8 m.

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 0.1 to 50 parts by weight of the surfactant having an HLB value of 1 to 6 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 0.05 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 surfactant having an HLB value of 1 to 6 includes at least one selected from the group consisting of SPAN120, SPAN83, SPAN85, SPAN80, SPAN60, SPAN40, polyethylene-block-polyethylene glycol, Brij 52, Brij 72, Brij 93, Triton X35, Triton X15, PEGNOL 24-O, Lecithin, Monoolein, and Phytantriol.

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

14. The controlled-release fertilizer of claim 13, wherein the filler is contained in an amount of 10 to 300 parts by weight relative to 100 parts by weight of the binder resin.

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

Description

BRIEF DESCRIPTION OF DRAWINGS

[0077] FIG. 1 schematically shows the photodegradation mechanism of the controlled-release fertilizer.

DETAILED DESCRIPTION

[0078] 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 5

[0079] (1) Preparation of Photocatalytic Composite 0.09 g of the surfactant 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 sonicated and stirred for 20 minutes. Thereby, a dispersion of a photocatalytic composite in which the surfactant was bonded to the surface and inside of the aggregates of inorganic fine particles was prepared.

[0080] (2) Preparation of Controlled-Release Fertilizer

[0081] 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], 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 %.

[0082] 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 5).

Comparative Examples 1 to 3

Preparation of Coated Fertilizer

Comparative Example 1

[0083] 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 [Ml(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 2 below and uniformly stirred and mixed with tetrachloroethylene at 100 C. in the composition ratio shown in Table 2 below to prepare a coating solution so as to have a solid component concentration of 5 wt %.

[0084] Then, the coating solution was applied to the nitrogen fertilizer particles using a fluid bed drier to prepare a coated fertilizer (Comparative Example 1)

Comparative Examples 2 to 3

[0085] The controlled-release coated fertilizers (Comparative Examples 2 and 3) were respectively prepared in the same manner as in Comparative Example 1, except that the surfactants were changed as shown in Table 2 below.

Experimental Example

Experimental Example 1

[0086] Comparison Test of Photodearadation Characteristics

[0087] 5 g of each of the controlled-release fertilizers of Examples and Comparative Examples and the coated fertilizers of Comparative Examples 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.

[0088] 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).

[0089] 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 Tables 1 and 2 below, respectively.

[00001]$\begin{array}{cc}\begin{array}{c}\mathrm{Photodegradation}\\ \mathrm{Rate}\end{array}=\frac{\begin{array}{c}\\ \begin{array}{c}\begin{array}{c}\begin{array}{c}\mathrm{Change}.Math..Math.\mathrm{in}.Math.\\ \mathrm{weight}.Math..Math.\mathrm{of}.Math..Math.\mathrm{the}.Math.\end{array}\\ \mathrm{coating}.Math..Math.\mathrm{film}.Math..Math.\end{array}.Math.\\ \mathrm{after}.Math..Math.\mathrm{UV}.Math..Math.\mathrm{irradiation}\end{array}\end{array}}{\begin{array}{c}\begin{array}{c}\mathrm{Weight}.Math..Math.\mathrm{of}.Math..Math.\mathrm{resin}.Math..Math.\mathrm{in}\\ \mathrm{the}.Math..Math.\mathrm{coating}.Math..Math.\mathrm{film}\end{array}\\ \begin{array}{c}\mathrm{before}.Math..Math.\mathrm{UV}.Math.\\ .Math.\begin{array}{c}\mathrm{irradiation}\\ \left(\mathrm{LDPE}+\mathrm{EVA}\right)\end{array}\end{array}\end{array}}100.Math.\%& \left[\mathrm{General}.Math..Math.\mathrm{Formula}.Math..Math.1\right]\end{array}$

TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Polyethylene 28 g 28 g 28 g 28 g 28 g (LDPE) 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 Surfactant Span80 Brij 93 Lecithin Oleic acid Polyethylene-block- (HLB value) 0.09 g.sup. 0.09 g.sup. 0.09 g.sup. 0.09 g.sup. polyethylene glycol.sup. (HLB 4) (HLB 4) (HLB 4) (HLB 1) (Ethylene oxide, 20 wt %) 0.09 g.sup. (HLB 4) Degradation rate 50 3 41 3 65 3 49 3 44 3 of binder resin (%)

TABLE-US-00002 TABLE 2 Comparative Comparative Comparative Example 1 Example 2 Example 3 Polyethylene 28 g 28 g 28 g (LDPE) EVA copolymer 7 g 7 g 7 g TALC 65 g 65 g 65 g TiO.sub.2 0.7 g 0.7 g 0.7 g TiO.sub.2 dispersion treatment Surfactant Pluronic F127 Triton X-405 (HLB value) 0.09 g.sup. 0.09 g.sup. (HLB: 22) (HLB: 17.6) Degradation rate of binder 30 8 29 8 30 8 resin (%)

[0090] As shown in Table 2, it was confirmed that the controlled-release fertilizers of Examples showed a degradation rate of binder resin of 40% or more, or 50% 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 Examples showed a degradation rate of binder resin of 30% or less.

Experimental Example 2

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

[0091] The z-average dispersion particle sizes of TiO.sub.2 in the dispersion solution of the photocatalytic composite of Example 1 and the dispersion solution containing TiO.sub.2 of Comparative Example 1 were measured using a Dynamic Light Scattering instrument (Malvern Zetasizer Nano ZS90).

[0092] The results are shown in Table 3 below.

TABLE-US-00003 TABLE 3 Z-average dispersion particle size of TiO.sub.2 Example 1 Comparative Example 1 z-average dispersion particle 556 About 2.0 10.sup.4 size of TiO.sub.2 (nm)

[0093] As shown in Table 3, it is confirmed that the dispersion solution of the photocatalytic composite of Example 1 had a z-average dispersion particle size of about 556 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.

[0094] In contrast, it is confirmed that TiO2 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.