JPS5992989A - Use of natural rubber - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the use of natural rubber (NR) in the production of coated agricultural materials. In particular, the present invention relates to the production of slow release fertilizers by coating fertilizer materials with a coating of NR derived from a modified NR latex.

Many conventional fertilizers are highly soluble in water, and when applied to soils, especially sandy soils, a large proportion of the fertilizer is rapidly leached from the plant's rhizosphere (root zone), providing effective nutrients to the plant. This leaching problem is particularly acute in tropical regions with high rainfall.

Providing an adequate and constant supply of nutrients to the rhizosphere throughout the growing season is a particularly important issue. To overcome these problems, the use of various types of slow release fertilizers has been taught. Such fertilizers release nutrients gradually when applied to the soil, thus providing a more or less continuous supply of nutrients and thus reducing leaching losses.

In our experience, we have found that fertilizers coated with unmodified NR are rapidly leached out despite having a rubber coating. This is believed to be a result of the relatively high permeability and hydrophilicity of the rubber deposited onto the fertilizer from NR Radex. Furthermore, when the latex is not vulcanized, the coated fertilizer particles have a strong tendency to aggregate to an undesirable degree because the rubber film is relatively sticky. Although the use of prevulcanized latex makes it possible to avoid agglomeration problems, the coating film is still sufficiently hydrophilic and permeable that it has no practical value in the production of slow-release fertilizers. do not have.

The use of synthetic polymers has been proposed, but these polymers provide a virtually impermeable film around the fertilizer particles, making distribution of the fertilizer into the rhizosphere slow and impractical. Synthetic polymers are usually biodegradable, but not completely biodegradable (and can result in residues that have harmful effects in the vicinity of plants).

The present invention provides that a particularly useful /-t lance with properties suitable for use as a slow-release fertilizer can be obtained by prevulcanizing the rubber and coating the fertilizer with a modified natural rubber latex in which the proteins have been at least partially degraded. I have found that the product that gives the product is based on G).

Accordingly, the present invention provides a slow release fertilizer comprising a fertilizer coated with a layer of protein-degraded prevulcanized natural comb. The present invention involves contacting fertilizer particles with protein-degraded pre-vulcanized natural rubber latex, and a! Seal, dry the rubber on the fertilizer particles,
The present invention thus includes a method for producing a slow-release fertilizer comprising coating particles with a film of protein-degraded prevulcanized natural rubber.

The particular method of coating protein degraded prevulcanized rubber (PD-PV NR) onto fertilizer particles is not strictly limited to the overall method of the present invention. Pan coating, rotary drum coating and similar methods can therefore be used. However, fluidized bed methods are particularly suitable and therefore form a further aspect of the invention. In another aspect of this invention, the invention provides a fluidized bed of granular fertilizer and introduces protein-degraded prevulcanized natural rubber latex into the bed in the form of droplets, thus drying and condensing the protein-degraded natural rubber latex onto the fertilizer particles. A method for producing a slow-release fertilizer comprising forming a coating of pre-vulcanized natural rubber is provided. This method is carried out by placing the fertilizer preferably in granular form in a container with a perforated base and pumping heated air through the base to fluidize the fertilizer particles.

PD-PV NRL is for example compressed air injection rlFA in the floor.
can be used to atomize it into the fluidized bed. The nozzle of the sprayer is suitably placed within or at the bottom of the fluidized bed. The latex spray forms a coating that converges into a cohesive film on the surface of the fertilizer particles, rapidly resists caking and dries in the hot air stream used for fluidization. Rapid drying of the rubber film avoids the problem that would otherwise cause particles to stick together, thus forming undesirably large coagulates or tearing the rubber film of the particles. After spraying, it is desirable to keep the particles in a fluid state to ensure complete drying of the latex in order to obtain a non-tacky, tough film of PD-PV NR.The particles coated in this way are then subjected to further use. Can be easily stored in bags or drums.

The natural rubber used in the present invention to make the slow-release fertilizer is protein-degraded pre-vulcanized natural rubber latex (PD-PVN).
RL). To the best of the inventors' knowledge, this form of natural rubber latex is new. Pre-vulcanized natural rubber latex (pvNRL) has been known for many years and is used in the manufacture of latex products such as rubber gloves. A method for producing deproteinized rubber (purified rubber) is known, for example, as described in British Patent No. 1366934. In this specification, the latex is treated with a protease to hydrolyze the protein portion of the latex, the latex is typically diluted to a dry rubber content (DRC) of about 3%, and the latex is then coagulated with an acid. It is deproteinized by making solid rubber. The reason for this treatment is to achieve an improvement in the properties and behavior of the rubber produced in the green state and/or after vulcanization of the solid rubber. These improved properties are not particularly relevant to the manufacture of rubber latex articles, in which case separation of the rubber from the protein hydrolysis phase usually involves acid coagulation of the latex.

In the present invention, it is not necessary to separate the comb from the hydrolysis products, and in fact the inventors have found that removing the hydrolysis products from the latex is not advantageous for slow release fertilizer products. Protein hydrolysis is most conveniently carried out by treating the latex with a protease, for example by the method described in British Patent No. 1,366,934.

Although it is not necessary to remove protein degradation products from the latex, we have demonstrated that fully deproteinized pre-vulcanized natural rubber (DP-PV NR) can be used to create a slow-release fertilizer. We have therefore found that this is included in the term "protein-degraded prevulcanized natural rubber". Deproteinized natural rubber latex (DPNRL) can be made by subsequent dilution and concentration, eg, centrifugation of a latex that has had its proteins degraded, eg, by enzymatic hydrolysis. As will be recognized by those skilled in the art, the dilution/concentration method can be used to reduce the proportion of protein degradation products in the rubber flocculated from the latex to a desired degree, thus reducing the desired proportion of protein degradation products in the rubber. Provide a way to select the degree. Completely deproteinized pre-vulcanized rubber latex (
The use of DP-PVNRL) tends to provide fertilizers with extended slow release properties. This suggests that fertilizer coated with PD-PV NR and D
It can be used to advantage by mixing fertilizers coated with P-PV NR. However, DP-P
The use of VNR is not particularly preferred since it involves large additional processing costs, although it is only slightly technically possible.

The latex may be prevulcanized in known manner by heating the latex for 1 to 2 hours, typically at about 70° C., with a suitable vulcanizing agent component such as a mixture of sulfur, zinc diethyldithiocarbamate, and zinc oxide. . It is customary to add a non-volatile alkali such as KOH or a carboxylic acid soap to the latex in a suitable manner to stabilize the latex against condensation during preheating.

PD-PV NRL suitable for the production of slow-release fertilizers can be prepared by first treating the latex with a protease and then pre-vulcanizing it, or by first pre-vulcanizing the latex and subsequently treating it with a protease. The present inventors have discovered. There are no strict restrictions on the form of latex used as starting material, and satisfactory results have been obtained using field latex, concentrated eg centrifugal concentrated latex and skim latex.

Although the present invention relates to covering all a cheek fertilizers,
It is particularly intended to coat water-soluble or easily dispersible fertilizers, since such fertilizers are particularly susceptible to rapid leaching from the rhizosphere. These fertilizers contain inorganic salts such as potassium and ammonium salts of sulfuric acid, nitric acid and phosphoric acid. It is common practice to test the effectiveness of such fertilizers by their potassium (Kl), phosphorus (Pl) and nitrogen (Nl) content. Fertilizers such as urea can also be used. When using ammonia-containing fertilizers such as ammonium salts,
Coating fertilizer with PD-PV 14R reduces nitrogen loss to the atmosphere due to ammonia volatilization. This is especially true in tropical environments where ammonia release from urea is a major drawback of such fertilizers. Fertilizers can be single compounds (straight fertilizers) or mixtures of compounds (compound fertilizers) when desired to be adapted to the individual environment. These fertilizers can be used alone or in combination with other materials having the desired activity in the rhizosphere, such as plant growth regulators, hormones, pesticides, herbicides and agents active against undesirable soil microorganisms. Can be used.

Furthermore, the inventors have found that coated particles containing seeds and fertilizers according to the invention are particularly advantageous.

In this connection, the inventors have found that the invention has general applicability to the coating of granular agricultural materials and is not limited to fertilizers that are unstable to leaching. Accordingly, in another aspect, the invention includes a granular agricultural material coated with a film of protein-reduced prevulcanized natural rubber, and wherein the granular agricultural material is contacted with a protein-reduced prevulcanized natural rubber latex and allowed to coagulate; A process for producing a coated agricultural material comprises drying the rubber on the particles of the agricultural material and thus coating the particles with a film of protein-degraded prevulcanized natural rubber.

Agricultural materials of interest in this aspect of the invention include, in addition to fertilizers, plant growth regulators, hormones, pesticides, herbicides, seeds and agents active against undesirable or desirable soil microorganisms. Contains agents active in promoting. If these materials are not granular, they can be adsorbed onto or absorbed into a suitable granular carrier or an inert granular carrier, which can be another agricultural material.

The rubber film covering granular fertilizers or agricultural materials contains preservatives, stabilizers, antioxidants, surfactants,
Modifications can be made by including materials such as inert fillers, viscosity modifiers, compatibilizers, co-solvents and humectants.

The materials normally used, if used, are added to the rubber latex before setting.

Granular slow-release fertilizers according to the invention typically have a
The particles are made to have an average particle size of 2 mm.

In each case, the precise indicator is selected to be compatible with the intended use of the fertilizer. Pond coated agricultural materials are generally made in a similar particle size range.

The thickness of the PD-PV NR film around the fertilizer particles is an important factor determining the release characteristics of the coated fat particles. However, direct measurement of film thickness is difficult. Therefore, it is generally more convenient to refer to the weight percentage of sitacom based on the fertilizer. Film thickness is a function of the weight percent of rubber, which is also a function of particle size. Therefore, the particles are spherical and their specific gravity is 1.
33 and the specific gravity of the rubber film is 0.92, a 10 wt% coating of rubber on particles of diameter 4 gives an average (calculated) film thickness of about 90μ71L. To achieve this thickness on particles of 2 diameter diameters, approximately 21% by weight of rubber is required, and on particles of 0.5 nm, approximately 108 JfIik% of rubber is required in the coating. Generally the film thickness ranges from 10 to 250 μ2n. Correspondingly, the amount of rubber coated on the particles is generally 1 to 25% by weight, preferably 5% by weight, based on the weight of the fertilizer.
~15 Mfffit%. Within this range, the higher the percentage, the smaller the particle size within the above particle size range, and vice versa. In either case, the rubber barrier in the coating is selected to provide the desired sustained release ratio characteristics, since the thicker the coating film, the slower the fertilizer release.

When it is desired to further slow the leaching of the fertilizer than is obtained with PD-PV NR, this can be achieved by including a small proportion of synthetic polymer in the fertilizer coating.

For this purpose, up to 45% of the coating can be made of synthetic polymers. Preferably, the synthetic polymer is incorporated into the gono latex as a latex or emulsion before setting. The amount of synthetic polymer latex or emulsion used depends on the desired proportion of synthetic polymer in the rubber film, the dry comb content of the PD-PV NRL and the polymer content of the synthetic polymer or latex.

It is not entirely clear why the use of PD-PV NRL in coated fertilizers is as successful as in its presence, but the following factors are believed to contribute to the results. Pre-vulcanization of the latex reduces the water and fertilizer permeability of the rubber film to a reasonable degree, but is not sufficient to give a satisfactory sustained release product. Films made from pre-vulcanized (but not protein-degraded) latex contain a significant proportion of protein material in the latex, made from intact protein or only slightly degraded protein. I believe.

Protein molecules are large and hydrophilic, and when they come into contact with water, they become hydrated and form large hydrophilic channels in the rubber film, thus producing relatively rapid leaching. The relatively high concentration within the coated fertilizer provides a driving force that enhances the effectiveness of the hydrophilic channels. In rubber films formed from FD-PV NRL, protein degradation products are usually present in the original latex. Generally, these degradation agents are much smaller in size than the proteins in non-protein degraded rubber and therefore form smaller new aqueous channels in the rubber film. The presence of degradation products thus imparts to the rubber a degree of hydrophilicity and permeability that can be controlled to some extent by the thickness of the rubber film and the choice of additives. As previously mentioned, the inclusion of synthetic rubber is another method of modifying the hydrophilicity and permeability of the film.

The following examples illustrate the invention. Example 1 illustrates a method for carrying out the pre-vulcanization and protein degradation steps to make PD-PV NRLs suitable for use in the present invention and illustrates some of the properties of such latexes. Example 2 shows the production of slow-release fertilizer according to the present invention, Examples 3-5
indicates its properties.

Example 1 Protein degradation: Proteins in 14R latex were degraded by treating NR latex with proteolytic enzymes as described in UK Patent No. 1,366,934. Both degraded proteins were not removed from the latex. The protein content was calculated by analyzing the nitrogen content 45 of dry rubber obtained by coagulating latex using Ichishun.

Vulcanization: This is cured at about 70℃ for 1 to 2 hours. Both colors are NR.
This was done by heating the latex. The vulcanization components used were a mixture of sulfur, zinc diethyldithiocarbamate and zinc oxide, but other vulcanization/dispersion systems could also be used. The latex can be stabilized, if necessary, by incorporating a female stimulant such as potassium hydroxide or rubosic acid soap.

PD obtained in the above protein °6 formation process and pre-vulcanization process
-PV NRL 13 3% normal pre-vulcanized natural rubber latex (PV NRL) (for comparison)
Dilute to solids content and add acid to coagulate.

The nitrogen content in the coagulated rubber was determined analytically and the corresponding protein content present was determined by multiplying the nitrogen content by a factor of 6.25. The results are shown in Table 1. PD-PV NRL and PV obtained by drying the latex at 70 °C in Osin followed by nitrogen analysis of the total solids film.
Comparing the protein content of NRL latex, it is approximately 1.
It was 9%. Protein degradation pre-vulcanized sample (2) and (
Table 1 shows that 3) has a significantly lower protein content than the prevulcanized NR latex (1).

It has also been shown that proteins can be effectively degraded either before or after vulcanization of latex.

Table 1 Example 2 Particles of a commercially available inorganic fertilizer containing potassium, nitrogen and phosphorus having an average diameter of between about 3 and 4 were fluidized in a bed using a stream of hot air.

PD- into the bed from the bottom at a rate to uniformly coat the particles.
PV NRL was sprayed. The coating weight was 14.2% by weight of rubber. This example was repeated using PV N,RL up to a coating weight of 14.6% by weight of rubber to make a comparative sample. In addition, FD-
This example was further repeated using particles of urea with an average diameter of about 2-3 particles using both PV NRL:1-i and PvNRL (7).

Example 3 Leaching Study: PD-PV NRL, $yohi PD NR
Experiments on leaching of fertilizer coated with L (comparison)
The test was carried out using a glass tube filled with sand and having a diameter of 5 crn and a height of 406 nm.

The coated mineral fertilizer particles made in Example 2 were placed on top of the sand column and 25 g of distilled water was applied every other day. Leaching yields were made weekly with a suction pressure of 100 cIn water applied to the outlet. The leachate was analyzed for nitrogen, phosphorus and potassium.

The comparative results for nitrogen, phosphorus and potassium as shown in Table 2 clearly show that PD-PV NR is much better than PV NR in reducing the leaching rate of these elements. There is.

Example 4 Transfer Studies: Experiments were conducted in a greenhouse on the rate of transfer of fertilizer elements from coated particles when influenced by heat and sunlight. These were carried out by spreading a certain amount of coated inorganic fertilizer particles made in Example 2 on soil placed in a series of pots, and watering the particles every day with a certain amount of rainwater that simulated the rainfall conditions in Malaysia. I did this and was exposed to sunlight. These fertilizer particles were removed once every two weeks and analyzed for the amount of fertilizer elements remaining in them. The results are shown in Table 3.

Comparative data on nitrogen, phosphorus and potassium retention in the coated particles clearly show that PD-PV NR coating is much more effective than pvPAR in reducing the release rate of these elements. There is.

Example 5 Diffusion Study: The diffusion rate of nutrients from the PD-PV NR coated urea made in Example 2 was compared to the diffusion rate of PVNR coated urea. This experiment was conducted by immersing each sample 52 in 500πe distilled water in a flask. Each - every 24 hours
Two samples were taken from seven lascos. In each case, the flask was inverted 10 times before removal. The nitrogen in the aqueous solution was measured. The results are shown in Table 4.

The results show that the PD-PV NR formulation was used as a coating material to control the diffusion of urea into the surrounding aqueous medium.
It completely shows that it is much more effective than that of R.

Procedural amendment document: Go Oi history (η 3, relationship with the person making the amendment Ki ¥ Q - Hiroshi A7p A, office - Ki ≠ 4%' title Petro 9) to Pushona 1 Shi Be. 1/, V'4, agent

Claims (1)

[Scope of Claims] 1. A slow-release fertilizer composition comprising fertilizer particles coated with a layer of protein-degraded prevulcanized natural rubber. 2. A composition according to claim 1, wherein the fertilizer is a potassium or ammonium salt of sulfuric acid, nitric acid or phosphoric acid or urea or a mixture thereof. 3. An agricultural material composition comprising particles of agricultural material coated with a layer of protein-degraded prevulcanized natural rubber. 4. The composition according to any one of claims 1 to 3, wherein the particles have a diameter of 0.5 to 12 ran. 5. The composition according to any one of claims 1 to 4, wherein the rubber layer has a thickness of 10 to 250 μm. 6. The composition according to any one of claims 1 to 5, wherein the amount of rubber in the coating is 1 to 25% by weight of the weight of the particles. 7. Bringing fertilizer particles into contact with protein-degraded prevulcanized natural rubber latex to coagulate and drying the rubber on the fertilizer particles;
Thus, a method for producing a slow-release fertilizer composition comprising coating particles with a film of protein-degraded prevulcanized natural rubber. 8. Contact the particles of agricultural material with the protein-reduced prevulcanized natural rubber latex, coagulate, dry the rubber on the particles of agricultural material, and thus bind the particles with a film of protein-reduced prevulcanized natural rubber. A method for producing a coated granular agricultural material composition, characterized in that it is coated. 9. Creating a fluidized bed of particles and introducing the protein-degraded natural rubber latex in the form of droplets into the bed, thereby forming a coating of protein-degraded natural rubber on the particles. 10. Protein-degraded prevulcanized natural rubber. 11. Protein-degraded preheated natural rubber latex.