AU2017100484B4

AU2017100484B4 - Water soluble granule of MCPA salt and preparation method thereof

Info

Publication number: AU2017100484B4
Application number: AU2017100484A
Authority: AU
Inventors: Shuai Chen; Yongsheng Hou; Xuelin Lu; Guoqing SUN; Yong Wu
Original assignee: Shandong Weifang Rainbow Chemical Co Ltd
Current assignee: Shandong Weifang Rainbow Chemical Co Ltd
Priority date: 2016-08-03
Filing date: 2017-05-04
Publication date: 2017-07-13
Anticipated expiration: 2024-08-30
Also published as: CN107686777A; AU2016101531A4; CN107686777B; AU2017100484A4

Abstract

The present invention relates to the technical field of pesticides, and discloses a water soluble granule of 2-methyl-4-chlorophenoxy acetic acid (MCPA) salt and preparation method thereof. The water soluble granule of the present invention consists of the MCPA salt as well as a specific surfactant, a chelator and a filler. A water soluble granule of MCPA salt capable of achieving better storage stability, solubility and dissolving stability as well as persistent foamability in high concentration of hard water is prepared in the present invention by adjusting the adjuvant types of the water soluble granule of MCPA salt and using in combination with proper adjuvants. It is particularly suitable for countries and regions of higher water hardness.

Description

WATER SOLUBLE GRANULE OF MCPA SALT AND PREPARATION

METHOD THEREOF

Field of the invention

The present invention relates to the technical field of pesticides, and particularly to a water soluble granule of 2-methyl-4-chlorophenoxy acetic acid (MCPA) salt.

Background of the invention 2-methyl-4-chlorophenoxy acetic acid (MCPA) is a selective herbicide of 2-methyl-4-chlorophenoxy carboxylic acid category, has strong systemic conductivity, and is mainly used in post-emergence stem and leaf treatment. It passes through the stratum corneum and plasma membrane, and is ultimately transported to various parts and produces various impacts on nucleic acid and protein synthesis at different sites: inhibiting nucleic acid metabolism and protein synthesis at the top of the plant, such that the growing points stop growing, the young leaves cannot spread out, till the photosynthesis cannot normally proceed; increasing nucleic acid and protein synthesis when the reagent is transported to the bottom of the plant, which promotes abnormal cell division, root tip enlargement and loss of the ability to obsorb nutrients, causing stem twisted and deformed, sieve tube plugged, phloem destructed, transportation of organics disrupted, thereby undermining the normal viability of the plant, eventually leading to death of the plant. For years, MCPA is widely used on wheat fields, corn fields, paddy fields, city lawns and hemp crops for the controlling of annual or perennial broadleaf weeds and part of sedges; it can also be used as rice root removal agent, which can improve the efficacy of evulsing. When used in soil treatment, it also has some controlling effect on the buds of annual grasses and perennial weeds propagated by seed. It is widely used because of its advantages of low cost, rapid onset, no residue and safety to the afterculture crops, etc.

Pure product of MCPA is non-volatile colorless crystal, and its industrial product is a yellow to white solid powder. Its solubility at 25 °C in water is about 300 mg, and it is easily dissolved in organic solvents. In practical application, MCPA is typically required to be prepared as water-soluble salts or oil-soluble esters such as MCPA dimethylamine salt, MCPA isooctyl ester, MCPA sodium, MCPA thioethyl ester, MCPA ethyl ihioester, MCPA isopropylamine salt, MCPA ethyl butyrate, etc., as solubility of MCPA is extremely low in water. Currently, the main preparations of MCPA include aqueous solution, water-soluble powder and emulsifiable concentrate. Wherein, the effective content of the aqueous solution is 13% with the rest ingredients to be primarily water, and such a preparation increases transportation cost with low active ingredient but high dosage, and is unbeneficial to environment protection with a waste of resources. The water-soluble powder consists mainly of 56% of sodium salts. Although a solid formulation, there are safety risks for producers and users as it is a powdery material and thus easy to form dusts. The emulsifiable concentrate contains plenty of organic solvents and thus belongs to environmental-harmful preparation which would significantly damage the environment, wherein great safety risks for producers and users are presented by some of the solvents.

Water soluble granule (SG or WSG) rapidly disintegrates into water with high solubility to form a stable solution in the case of reasonable formula. Therefore, the utilization rate of the active ingredient is also higher. The requirements for the formulation and the preparation process of water soluble granules are higher, and the selection of adjuvants should be adapted to the main agents, otherwise the good solubility cannot be obtained by a WSG prepared with unsuitable adjuvant selection, leading to a long disintegration time and low suspension rate of the prepared waler soluble granule. A water soluble granule of MCPA salt and the preparation method thereof were disclosed in China patent CN104705301A, which is prepared from MCPA salt, a specific surfactant and a water-soluble filler to improve the suspension rate and decrease disintegration time and foamability. However, after testing research, it is found that the beneficial effects of the product in various aspects are suitable only for countries and regions of less higher water hardness, while employment of the above described water soluble granules in countries with commonly high concentration of hard water such as Australia still exhibits phenomena of unsatisfactory product qualities, such as poor stability for storage, weak solubility and dissolving stability, and persistent lower foamability, such that the efficacy of MCPA cannot be fully achieved.

Summary of the invention

In view of this, the object of the present invention is to provide a water soluble granule of MCPA salt and the preparation method thereof, such that the water soluble granule of MCPA salt has better storage stability, solubility and dissolving stability as well as persistent foamability in high concentration of hard water.

To achieve the object above, the present invention provides the following technical solution: A water soluble granule of MCPA salt, characterized in that it consists of the MCPA salt, a surfactant, a chelator and a filler.

The surfactant is one selected from the group consisting of alkylphenol polyoxyethylene polyoxypropylene ether, lauryl alcohol polyoxyethylene ether, fatly amine polyoxyethylene ether, allcylnaphthalenesulfonate, fatty alcohol polyoxyethylene ether alkylnaphthalenesulfonic acid formaldehyde condensate, dodecylsulfate; or both ethylene oxide-propylene oxide block copolymer and alkyl glycoside; or both polycarboxylate and polyethylene glycol; or both melhyloxirane and polyoxyethylene fatty acid ester.

The chelator is one or more selected from the group consisting of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate and sodium tripolyphosphate.

Aiming at the defect of the existing water soluble granule of MCPA salt in not suitable for high concentration of hard water, the adjuvant types are adjusted, the chelator is added and the specific combination of surfactant and chelator is defined in the present invention. On this basis, the problem of poor product performance of water soluble granule of MCPA salt in high concentration of hard water is solved.

Preferably, the surfactant and chelator are used in one of the following combinations: (1) alkylnaphthalenesulfonate and disodium ethylenediaminetetraacetate; (2) ethylene oxide-propylene oxide block copolymer, alkyl glycoside and ethylenediamine tetraacetic acid; (3) melhyloxirane, polyoxyethylene fatty acid ester and tetrasodium ethylenediaminetetraacetate; (4) alkylphenol polyoxyethylene polyoxypropylene ether and ethylenediamine tetraacetic acid; ' (5) lauryl alcohol polyoxyethylene ether and tetrasodium ethylenediaminetetraacetate; (6) fatty alcohol polyoxyethylene ether and sodium tripolyphosphate; (7) fatty alcohol polyoxyethylene ether alkylnaphthalenesulfonic acid formaldehyde condensate and tetrasodium ethylenediaminetetraacetate; (8) sodium dodecylsulfate and sodium tripolyphosphate; (9) polycarboxylate, polyethylene glycols and sodium tripolyphosphate.

Preferably, by weight percentage, the water soluble granule comprises 10%-90% of the MCPA salt, l%-20% of the surfactant, 1%-10% of the chelator and the balance of the filler; more preferably, 30%-90% of the MCPA salt, 1%-10% of the surfactant, l%-6% of the chelator and the balance of the filler; further preferably, 50%-90% of the MCPA salt, l%-5% of the surfactant, 1.5% of the chelator and the balance of the filler; most preferably, 90% of the MCPA salt, 2% of the surfactant, 1.5% of the chelator and the balance of the filler.

In some particular embodiments of the present invention, the weight percentage of each component can be chosen as follows: (1) 90% of the MCPA salt, 2% of the surfactant, 1.5% of the chelator and the balance of the filler; (2) 80% of the MCPA salt, 2% of the surfactant, 1.5% of the chelator and the balance of the filler; (3) 50% of the MCPA salt, 10% of the surfactant, 6% of the chelator and the balance of the filler; (4) 30% of the MCPA salt, 2% of the surfactant, 1.5% of the chelator and the balance of the filler; (5) 10% of the MCPA salt, 2% of the surfactant, 1.5% of the chelator and the balance of the filler; (6) 50% of the MCPA salt, 2% of the surfactant, 1.5% of the chelator and the balance of the filler; (7) 90% of the MCPA salt, 3.5% of the surfactant, 0.5% of the chelator and the balance of the filler; (8) 70% of the MCPA salt, 9.5% of the surfactant, 3.5% of the chelator and the balance of the filler; (9) 40% of the MCPA salt, 12% of the surfactant, 4% of the chelator and the balance of the filler; (10) 10% of the MCPA salt, 20% of the surfactant, 6% of the chelator and the balance of the filler; (11) 60% of the MCPA salt, 12% of the surfactant, 3% of the chelator and the balance of the filler; (12) 40% of the MCPA salt, 15% of the surfactant, 5% of the chelator and the balance of a filler; (13) 20% of the MCPA salt, 20% of the surfactant, 6% of the chelator and the balance of the filler;

Preferably, the alkylnaphthalenesulfonate is Morwel EFW which can be purchased from AkzoNobel; the ethylene oxide-propylene oxide block copolymer is PE6200 which can be purchased from BASF; the polyoxyethylene fatty acid ester is selected from A (OEO) series of emulsifier, and the A (OEO) series of emulsifier is preferably A-105 emulsifier, all of which are commercially available; the polycarboxylate preferably is TERSPERSE-2700, which can be purchased from Hunstman.

Preferably, the MCPA salt of the present invention is MCPA potassium salt, MCPA sodium salt, MCPA dimethylamine salt, MCPA amine salt, MCPA isopropylammonium salt, MCPA choline salt or MCPA triisopropanolamine salt. Each of the MCPA salt can be purchased or self-made, and the process for self-making can refer to the following process:

Mixing MCPA with alkaline substance for 10-15 min, adding 12-16% of water, and reacting for 50-70 min at a condition of 45-55 °C to obtain the MCPA salt. Wherein, the alkaline substance can be selected from the group consisting of sodium hydroxide, potassium carbonate, potassium hydroxide, potassium bicarbonate, ammonium bicarbonate, ammonia water, isopropyl amine, sodium carbonate, sodium bicarbonate, dimethylamine, triisopropanolamine and choline based on the required type of MCPA salt. The molar ratio of the MCPA salt acid to the alkaline substance is 1:(1-1.1), preferably 1:1.04.

Preferably, the filler is one or more selected from the group consisting of ammonium sulfate, diammonium hydrogen phosphate, sodium sulfate, sodium chloride, urea, potassium nitrate, ammonium nitrate, ammonium chloride, dipolassium hydrogen phosphate, sucrose, potassium sulfate and sodium tripolyphosphate.

Meanwhile, the present invention also provides a method for preparing the water soluble granule of MCPA salt: homogeneously mixing the MCPA salt with the surfactant, the chelator and the filler, and then adding water and mixing, extruding, granulating, and dring to obtain the water soluble granule.

Preferably, the drying is carried out under a condition of 50-75 °C.

The water soluble granule of MCPA salt of the present invention is compared with the products of Example 13-Example 47 in the prior patent CN104705301A in storage stability, solubility and dissolving stability as well as persistent foamability in high concentration of hard water. The results show that the water soluble granule of MCPA salt is significantly superior to the products of the prior patent.

Meanwhile, the present invention selects a chelator different from those employed in the present invention, and various types of surfactant for contrast test. The results show that, the excellent product performance can be exhibited in circumstance of high concentration of hard water only on the premise of the combination of the surfactant and chelator selected by the present invention.

It can be known from the above technical solution that, a water soluble granule of MCPA salt capable of achieving better storage stability, solubility and dissolving stability as well as persistent foamability in high concentration of hard water is prepared in the present invention by adjusting the adjuvant types of the water soluble granule of MCPA salt and using in combination with proper adjuvants. It is particularly suitable for countries and regions of higher water hardness.

Detailed description of the invention

The example of the present invention discloses a water soluble granule of MCPA salt and the preparation method thereof. Those skilled in the art can use the content herein for reference to achieve by appropriately improving the process parameters. It should be particular noted that all the similar substitutions and modifications will be apparent to those skilled in the art, and they are all considered to fall within the scope of the present invention. The water soluble granule of MCPA salt and the preparation method thereof have been described through preferred examples, and for an ordinary skilled in the art, modifications or proper alternations and combinations can be made to the product and method described in the present invention without departing from the content, spirit and scope of the present invention, to achieve and apply the technology of the present invention.

Each of the mass percentage of the water soluble granule is the percentage of the amount of each component in the total feeding. While in the purchased or self-made MCPA salt, the purity is generally not 100%, and the amount of MFC A salt in tire total feeding refers to an impurity-containing MPCA salt, while the mass percentage of MCPA salt is the percentage of pure MCPA salt amount in the total feeding.

The water soluble granule of MCPA salt and the preparation method thereof provided by the present invention are further illustrated below.

Example 1: Preparation of MCPA salt 421.1 g of MCPA technical material (purity of 95%) together with an alkaline substance (purity of higher than 99%) were put into a 1 L kneader equipped with a heating device and mixed for 10 min-15 min under a condition of normal temperature and pressure. 12-16% of water was added and heated up to 45°C-55°C to react for 50 min-70 min to obtain the MCPA salt. Wherein the reaction conditions for each MCPA salt is shown in Table 1.

Table 1. Preparation conditions for MCPA salt

Example 2: Water soluble granule of 90% MCPA potassium salt 93.75 g of MCPA potassium salt (purity of 96%), 2 g of Morwet EFW (AkzoNobel, alkylnaphthalenesulfonate), 1.5 g of disodium EDTA and 2.75 g of sucrose were weighed and mixed, then 3% of water was added and the mixture was put into a 1 L kneader for sufficient kneading, extruded to granulate and dried, to obtain a finished product of water soluble granule having MCPA potassium salt in 90% mass fraction, yield 99.7%.

Example 3: Water soluble granule of 80% MCPA potassium salt 83.3 g of MCPA potassium salt (purity of 96%), 2 g of Morwet EFW (AkzoNobel, alkylnaphthalenesulfonate), 1.5 g of disodium EDTA and 13.2 g of sucrose were weighed and mixed, then 3% of water was added and the mixture was put into a 1 L kneader for sufficient kneading, extruded to granulate and dried, to obtain a finished product of water soluble granule having MCPA potassium salt in 80% mass fraction, yield 99.5%.

Example 4: Water soluble granule of 50% MCPA potassium salt 52.1 g of MCPA potassium salt (purity of 96%), 2 g of Morwet EFW (AkzoNobel, alkylnaphthalenesulfonate), 1.5 g of disodium EDTA and 44.4 g of sucrose were weighed and mixed, then 2.5% of water was added and the mixture was put into a 1 L kneader for sufficient kneading, extruded to granulate and dried, to obtain a finished product of water soluble granule having MCPA potassium salt in 50% mass fraction, yield 99.3%.

Example 5: Water soluble granule of 30% MCPA potassium sail 31.3 g of MCPA potassium salt (purity of 96%), 2 g of Morwet EFW (AkzoNobel, alkylnaphthalenesulfonate), 1,5 g of disodium EDTA and 65.2 g of sucrose were weighed and mixed, then 1.5% of water was added and the mixture was pul into a 1 L kneader for sufficient kneading, extruded to granulate and dried, to obtain a finished product of water soluble granule having MCPA potassium salt in 30% mass fraction, yield 99.1%.

Example 6: Water soluble granule of 10% MCPA potassium salt 110.4 g of MCPA potassium salt (purity of 96%), 2 g of Morwet EFW (AkzoNobel, alkylnaphthalenesulfonate), 1.5 g of disodium EDTA and 86.1 g of sucrose were weighed and mixed, then 1.5% of water was added and the mixture was put into a 1 L kneader for sufficient kneading, extruded to granulate and dried, to obtain a finished product of water soluble granule having MCPA potassium salt in 10% mass fraction, yield 99.0%.

Example 7: Water soluble granule of 90% MCPA dimethylamine salt 93.75 g of MCPA dimethylamine salt (purity of 96%), 2 g of Morwet EFW (AkzoNobel, alkylnaphthalenesulfonate), 2.75 g of disodium EDTA and 1.8 g of sucrose were weighed and mixed, then 4% of water was added and the mixture was put into a 1 L kneader for sufficient kneading, extruded to granulate and dried, to obtain a finished product of water soluble granule having MCPA dimethylamine salt in 90% mass fraction, yield 99.0%.

Example 8: Water soluble granule of 80% MCPA isopropylamine salt 83.3 g of MCPA isopropylamine salt (purity of 96%), 2 g of Morwet EFW (AkzoNobel, alkylnaphthalenesulfonate), 1.5 g of disodium EDTA and 13.2 g of sucrose were weighed and mixed, then 3.5% of water was added and the mixture was put into a 1 L kneader for sufficient kneading, extruded to granulate and dried, to obtain a finished product of water soluble granule having MCPA isopropylamine salt in 80% mass fraction, yield 98.7%.

Example 9: Water soluble granule of 50% MCPA choline salt 52.1 g of MCPA choline salt (purity of 96%), 2 g of Morwet EFW (AkzoNobel, alkylnaphthalenesulfonate), 1.5 g of disodium EDTA and 44.4 g of sucrose were weighed and mixed, then 4.5% of water was added and the mixture was put into a 1 L kneader for sufficient kneading, extruded to granulate and dried, to obtain a finished product of water soluble granule having MCPA choline salt in 50% mass fraction, yield 98.5%.

Example 10: Water soluble granule of 90% MCPA potassium salt 993.75 g of MCPA potassium salt (purity of 96%), 1.5 g of PE6200 (BASF, ethylene oxide-propylene oxide block copolymer), 2% of APG (alkyl glycoside), 0.5 g of EDTA and 2.25 g of ammonium sulfate were weighed and mixed, then 3.2% of water was added and the mixture was put into a 1 L kneader for sufficient kneading, extruded to granulate and dried, to obtain a finished product of water soluble granule having MCPA potassium salt in 90% mass fraction, yield 99.2%.

Example 11: Water soluble granule of 70% MCPA potassium salt 72.9 g of MCPA potassium salt (purity of 96%), 6.5 g of T-7200 (Hunstman, polycarboxylafe), 3 g of polyethylene glycol, 3.5g of sodium tripolyphosphate, 5 g of sodium chloride and 9.1 g of potassium nitrate were weighed and mixed, then 4,2% of water was added and the mixture was put into a 1 L kneader for sufficient kneading, extruded to granulate and dried, to obtain a finished product of water soluble granule having MCPA potassium salt in 70% mass fraction, yield 98.8%.

Example 12: Water soluble granule of 40% MCPA potassium salt 41.7 g of MCPA potassium salt (purity of 96%), 10 g of methyloxirane, 2 g of A-105 (emulsifier A(OEO) series), 4.0 g of tetrasodium EDTA, 20 g of ammonium nitrate and 22.3g dipotassium hydrogen phosphate were weighed and mixed, then 8.2% of water was added and the mixture was put into a 1 L kneader for sufficient kneading, extruded to granulate and dried, to obtain a finished product of water soluble granule having MCPA potassium salt in 40% mass fraction, yield 98.5%.

Example 13: Water soluble granule of 10% MCPA potassium salt 10.4g of MCPA potassium salt (purity of 96%), 20 g of allcylphenol polyoxyethylene polyoxypropylene ether, 6.0 g of EDTA, 40 g of ammonium chloride, and 23.6 g of diammonium hydrogen phosphate were weighed and mixed, then 10.0% of water was added and the mixture was put into a I L kneader for sufficient kneading, extruded to granulate and dried, to obtain a finished product of water soluble granule having MCPA potassium salt in 10% mass fraction, yield 98.1%.

Example 14: Water soluble granule of 60% MCPA sodium salt 62.5g of MCPA sodium salt (purity of 96%), 12 g of lauryl alcohol polyoxyethylene ether, 3.0 g of tetrasodium EDTA, 20g of sodium chloride and 2.5 g of urea were weighed and mixed, then 5.0% of water was added and the mixture was put into a 1 L kneader for sufficient kneading, extruded to granulate and dried, to obtain a finished product of water soluble granule having MCPA sodium salt in 60% mass fraction, yield 98.3%.

Example 15: Water soluble granule of 50% MCPA ammonium salt 52.1 g of MCPA ammonium salt {purity of 96%), 10 g of fatty alcohol polyoxyethylene ether, 6.0 g of sodium tripolyphosphate and 31.9 g of sodium sulfate were weighed and mixed, then 6.0% of water was added and the mixture was put into a 1 L kneader for sufficient kneading, extruded to granulate and dried, to obtain a finished product of water soluble granule having MCPA ammonium salt in 50% mass fraction, yield 98.0%.

Example 16: Water soluble granule of 40% MCPA triisopropanolamine salt 41.7g of MCPA triisopropanolamine salt (purity of 96%), 15 g of fatty alcohol polyoxyethylene ether alkylnaphthalenesulfonic acid formaldehyde condensate, 5.0 g of tetrasodium EDTA, 30 g of potassium sulfate and 8.3 g of potassium sulfate were weighed and mixed, then 7.0% of water was added and the mixture was pul into a 1 L kneader for sufficient kneading, extruded to granulate and dried, to obtain a finished product of water soluble granule having MCPA triisopropanolamine salt in 40% mass fraction, yield 98.1%.

Example 17: Water soluble granule of 20% MCPA choline salt 20.8 g of MCPA choline salt (purity of 96%), 20 g of sodium dodecylsulfate, 6.0 g of sodium tripolyphosphate, 40 g of potassium sulfate and 13.2 g of ammonium chloride were weighed and mixed, then 9.0% of water was added and the mixture was put into a 1 L kneader for sufficient kneading, extruded to granulate and dried, to obtain a finished product of water soluble granule having MCPA choline salt in 20% mass fraction, yield 98.0%.

Example 18: Contrast test

Controls: 1. The products of Example 13-Example 47 in CN104705301A (hereinafter abbreviated as CN13-CN47); 2. Substitution of the chelators to the ones other than those used in the present invention based on the formulations of Example 2, Example 10, Example 11 and Example 15, with the same amount, respectively: Example 2: citric acid; Example 10: tartaric acid; Example 11: calcium gluconate; Example 15: sodium metaphosphate; (hereinafter abbreviated as controls 1-4); 3. Substitution of the alkylnaphthalenesulfonates to the ones other than Morwet EFW based on the formulation of Example 2, with the same amount, respectively: Tamol NN 8906 (BASF), Morwet D-400 (AkzoNobel), TP04 (CRODA); (hereinafter abbreviated as controls 5-7); 4. Addition of the chelators other than those used in the present invention based on the formulations of CN13-CN17, with the amount of 1.5%, respectively: CN13: tartaric acid; CN14: sodium gluconate; CN13: sodium diacetate; CN16: sorbitol; CN17: sodium metaphosphate; (hereinafter abbreviated as controls 8-12);

The performance index test was conducted on all of the products in the present invention and the above 4 types of controls in the same high concentration of hard water (3 times of D water, hardness of 1026 mg/L, pH=6.0-7.0, Ca3+:Mg3+=4:l). For the test, reference can be made to the methods provided in “Physical-Chemical method of Pesticide Technical Material and Formulalion-CIPAC Handbook”; and for the quality standard, reference can be made to “FAO Handbook of pesticide standard formulation and application” and “Standard preparation specifications for water soluble powder pesticide product”, as specifically shown in Table 2.

Table 2. Standard for test

The test results are shown in Table 3.

Table 3. Test results

It is clear from the results in Table 3 that the water soluble granules of MCPA salt according to the present invention meet all of the requirements of the three product performances, i.e. storage stability, solubility and dissolving stability as well as persistent foamability, and perform much better than that required by the standards under the circumstance of high concentration of hard water; wehreas, the prior patent products and the control products essentially do not meet the requirement of the standards, and also exhibit significant difference as compared to the performance of the present invention.

Meanwhile, the results of controls 1-4 illustrated that not all of the chelators could obtain the ideal product performance through combination with the other components of the present invention; the results of controls 5-7 illustrated that the better performance could be achieved only by the combinations of surfactants and chelators suitable to the present invention; the results of controls 8-12 illustrated that it is incapable of improving the product performance based on prior patent products even if some chelators beyond the defined range in the present invention are added.

Example 19: Efficacy test

The efficacy test of the example product of the present invention was earned out in New South Wales state, Australia (high concentration of hard water quality), with the crop to be wheat and the control target to be wild radish (Raphanus raphanistrum). The controlling was conducted since the wild radish was grown to 2 leaf stage, with a temperature of 11° C and a moisture of 79% on the administration day. The test field was acid lateritic soil with a pH of 5.4, and the dosage was 2175 a.i/ha. The results are shown in Table 4:

Table 4. Efficacy comparison (35 d after administration)

It can be known from the test of efficacy in Table 4 that the controlling efficacy of the water soluble granule of MCPA salt of the present invention on wild radish is obviously superior to that of the product of control patent under the circumstance of high concentration of hard water.

The above described illustrations are used only to understand the method and core concept of the present invention. It should be noted that, for an ordinary skilled in the art, some improvements and modifications can be made to the present invention without departing from the principles of the present invention. These improvements and modifications also fall within the protection scope of the present invention.

Claims

1. A water soluble granule of 2-mcthyl-4-chlorophenoxy acetic acid (MCPA) salt, consisting of, by weight percentage, 50%-90% of the MCPA salt, l%-5% of a surfactant, 1.5% of a chelator and the balance of a filler; wherein, the surfactant is one selected from the group consisting of alkylphenol polyoxyethylene polyoxypropylene ether, Iauryl alcohol polyoxyethylene ether, fatty amine polyoxyethylene ether, alkylnaphthalenesulfonate, fatty alcohol polyoxyethylene ether alkylnaphthalenesulfonic acid formaldehyde condensate, dodecylsulfate; or both ethylene oxide-propylene oxide block copolymer and alkyl glycoside; or both polycarboxyl ate and polyethylene glycol; or both methyloxirane and polyoxyethylene fatty acid ester; the chelator is one or more selected from the group consisting of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate and tetrasodium ethylenediaminetetraacetate;

2, The water soluble granule of MCPA salt according to claim 1, wherein the surfactant and chelator are used according to one of the following combinations: (1) alkylnaphthalenesulfonate and disodium ethylenediaminetetraacetate; (2) ethylene oxide-propylene oxide block copolymer, alkyl glycoside and ethyl enediamine tetraacetic acid; (3) methyloxirane, polyoxyethylene fatty acid ester and tetrasodium ethylenedi aminetetraacetate; (4) alkylphenol polyoxyethylene polyoxypropylene ether and ethylenediamine tetraacetic acid; (5) Iauryl alcohol polyoxyethylene ether and tetrasodium ethylenediaminetetraacetate; (6) fatty alcohol polyoxyethylene ether alkylnaphthalenesulfonic acid formaldehyde condensate and tetrasodium ethylenediaminetetraacetate.

3. The water soluble granule of MCPA salt according to claim 1, wherin the MCPA acid is MCPA potassium salt, MCPA sodium salt, MCPA dimethylamine salt, MCPA amine salt, MCPA isopropylammonium salt, MCPA choline salt or MCPA triisopropanolamine salt; the filler is one or more selected from the group consisting of ammonium sulfate, diammonium hydrogen phosphate, sodium sulfate, sodium chloride, urea, potassium nitrate, ammonium nitrate, ammonium chloride, dipotassium hydrogen phosphate, sucrose, potassium sulfate and sodium tripolyphosphate.

4. A method for preparing the water soluble granule of MCPA salt according to claim 1, comprising homogeneously mixing the MCPA salt with the surfactant, the chelator and the filler, and then adding water and mixing, extruding to granulate and drying, to obtain the water soluble granule of MCPA salt.