CN111154039A - Preparation method of water-based acrylic resin modified starch-based hydrogel water-retaining agent particles - Google Patents
Preparation method of water-based acrylic resin modified starch-based hydrogel water-retaining agent particles Download PDFInfo
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Abstract
The invention provides a preparation method of water-based acrylic resin modified starch-based hydrogel water-retaining agent particles, which comprises the steps of preparing oxidized starch dispersion liquid, preparing vinyl oxidized starch dispersion liquid, preparing polyacrylate prepolymer emulsion and carrying out gel reaction. The invention utilizes a vinyl silane coupling agent to carry out vinylation modification, adopts full-aqueous phase free radical polymerization reaction to realize the cross-linking copolymerization and gelatinization of the water-borne acrylic resin and the vinylation oxidized starch, and develops a novel starch/water-borne acrylic resin composite hydrogel material. The water-based acrylic resin modified starch-based hydrogel water-retaining agent particles are prepared by heat drying and granulation, and have excellent structural bearing strength, water absorption, water retention, fertilizer retention and biodegradability. As a natural polymer-based composite hydrogel water and fertilizer retention agent, the hydrogel has wide application prospect in modern precision agriculture.
Description
Technical Field
The invention relates to a preparation method of water-based acrylic resin modified starch-based hydrogel water-retaining agent particles, belonging to the field of natural high polymer materials.
Background
Worldwide, grain loss due to drought stress may exceed the sum of yield losses due to other factors. The dry land area of China accounts for 52.5 percent of the total land area of China, and drought is an important factor for restricting the sustainable development of agriculture of China. In nearly 10 years, the agricultural water consumption of China accounts for more than 60% of the total water consumption of China, along with the continuous aggravation of the agricultural water crisis of China, agriculture develops towards high and stable yield, and the water-saving and water-retaining technology for dry farmlands is developed by applying great force, so that the limited rainfall resources are fully utilized, and the sustainable development of agricultural production is ensured. The application of the water-retaining agent is an effective measure, can achieve the aims of soil improvement, water saving and yield increase, and particularly, the water-retaining agent is greatly popularized in dry farming agricultural areas in the north of China. The water-retaining agent is a high molecular material with strong water absorption capacity, is known as a micro reservoir, can absorb hundreds of times of water, can absorb water repeatedly and slowly release the water for plants to absorb and utilize, and can play a role in drought and relieve drought conditions due to the characteristics. While the water retaining agent performs molecule bonding imbibition and swelling imbibition, nutrient ions in the solution can enter the molecular structure of the water retaining agent simultaneously to be wrapped and held, and then are slowly released along with the release of water and the relaxation of the molecular network structure, thereby playing the sustained release effect of the nutrient ions. Meanwhile, the physical characteristics of soil can be improved, the germination of seeds is promoted, the survival rate is improved, and the irrigation requirement is reduced.
The existing synthetic water-retaining material has the problems of high production cost, difficult degradation of residues and the like. With the introduction of various polymer materials into the lives of people, high attention has been paid to some polymer materials, such as renewable, easily biodegradable, recyclable waste, environment-friendly and the like, wherein the research of preparing green and biodegradable composite materials by using natural polymer materials is the most prominent. Starch is a hot direction of scientific research due to its abundant natural resources, low cost, reproducibility and biodegradability. In the past decades, starch and its composite materials have been widely used in many technical fields such as modern agriculture, medicine, cosmetics, textile and paper industry. As natural polymer-based water retention agents, starch, cellulose and the like are widely applied due to good water absorption and retention properties, but the application of the starch is limited to a certain extent because the chemical structure of the starch has some inherent defects, such as low hydrogel strength, poor agglomeration force, easy loose loss, poor salt resistance and stability, too short decomposition time and difficulty in long-acting soil moisture retention and water storage. The starch molecules are chemically modified by different polymers, and the improvement of the comprehensive application performance of the starch-based composite material becomes a new research direction.
The current data report mainly uses starch and acrylic resin to blend, or adds a certain amount of acrylic monomer into starch dispersion liquid to directly carry out free radical polymerization to prepare the water-based acrylic resin modified starch water-retaining agent particles. However, due to the association of a large number of hydrogen bonds among starch molecules, the starch mainly exists in the form of aggregate particles, is difficult to dissolve in water and common organic solvents, is diluted and dispersed by only water or organic solvents, has poor reaction accessibility, long time and low grafting rate, and the cross-linking bonding mainly occurs on the surfaces of the starch dispersed particles, so that the polymerization reaction is difficult to be uniformly and thoroughly carried out, the reaction reproducibility is poor, and the water-retaining agent prepared by the acrylic resin modified starch still has low water gel strength, poor aggregation force is easy to loose and run off, the decomposition time is short, and the water-retaining and fertilizer-retaining effects are poor.
Disclosure of Invention
The invention provides a preparation method of water-based acrylic resin modified starch-based hydrogel water-retaining agent particles aiming at the problems in the prior art, and the preparation method takes Starch (ST), which is a green, cheap, renewable and biodegradable natural high polymer material, as a raw material. According to the special molecular structure of Starch (ST) and a large number of active groups (-OH) distributed on the molecular chain of polysaccharide, the ST is chemically modified and functionalized. ST is oxidized by a clean and efficient electro-Fenton oxidation technology, so that the reaction accessibility is improved, and the reaction activity of the hydroxyl on the surface of the starch is enhanced. And then vinyl silane coupling agent is utilized to carry out vinylation modification, and full-aqueous phase free radical polymerization reaction is adopted to realize the cross-linking copolymerization and gelatinization of the water-based acrylic resin and the vinylation oxidized starch, so as to develop a novel starch/water-based acrylic resin composite hydrogel material. The water-based acrylic resin modified starch-based hydrogel water-retaining agent particles are prepared by heat drying (80-90 ℃), crushing and granulating (10-35 meshes), and the following purposes are achieved:
(1) improving the hydrogel body strength;
(2) the degradation period is prolonged;
(3) the water and fertilizer retention performance is improved;
(4) the structural stability of the soil is improved.
In order to solve the problems, the invention adopts the following technical scheme:
a preparation method of water-based acrylic resin modified starch-based hydrogel water-retaining agent particles comprises the steps of preparing oxidized starch dispersion liquid, preparing vinylation oxidized starch dispersion liquid, preparing polyacrylate prepolymer emulsion and carrying out gel reaction.
The following is a further improvement of the above technical solution:
the preparation method comprises the steps of adding a certain amount of water and starch into a reaction kettle, adjusting the pH to 2.9-3.1, preferably 3, heating to 48-52 ℃, preferably 50 ℃, adding a ferrous salt complex solution, and carrying out constant current electrolysis with the current density of 10-30A/m2Dropwise adding hydrogen peroxide for 0.9-1.1h, adjusting the temperature to 60-70 ℃ after the temperature is stable, preserving the temperature for 60-90min, stopping electrolysis, and cooling.
The mass ratio of the water to the starch is 2-3: 1; preferably 2.3-2.4: 1;
the volume-mass ratio of the ferrous salt complex liquid to the starch is as follows: 1ml is 11-21 g;
the concentration of the ferrous salt complex solution is 0.08-0.12 mol/L;
the mass ratio of the hydrogen peroxide to the starch is as follows: 1:6.6-10.
Preparing a vinylation oxidized starch dispersion, adjusting the pH of the oxidized starch dispersion to 4.0-4.5, dropwise adding a vinyl silane coupling agent to carry out vinylation reaction, adjusting the temperature to 44-46 ℃, preferably 45 ℃, keeping the temperature for 60-90min, and adjusting the pH to 6.5-7.0 to prepare the vinylation oxidized starch dispersion;
the mass ratio of the vinyl silane coupling agent to the starch is as follows: 1: 14-21;
the dripping time is 35-45 min.
The preparation method comprises the steps of adding acrylic acid, methacrylic acid, maleic anhydride, acrylamide, dimethylaminoethyl methacrylate and a pH buffering agent into a reaction kettle filled with quantitative deionized water, quickly stirring and emulsifying for 13-17 min, reducing the stirring speed to 150-200r/min, heating to 78-82 ℃, adding 9-11% of the total amount of an initiator, and preserving heat for 10-15 min when blue light appears to prepare the polyacrylate prepolymer emulsion.
The mass ratio of the water to the acrylic acid is 10-14: 1;
the mass ratio of the methacrylic acid to the acrylic acid is 0.35-1: 1;
the mass ratio of the maleic anhydride to the acrylic acid is 0.32-0.67: 1;
the mass ratio of the acrylamide to the acrylic acid is 1-1.7:1
The mass ratio of the dimethylaminoethyl methacrylate to the acrylic acid is 0.35-0.7: 1;
the mass ratio of the pH buffer to the acrylic acid is 0.02-0.053: 1;
the mass ratio of the initiator to the acrylic acid is 4-6: 1;
the rapid stirring is carried out at the rotating speed of 500-600 r/min.
The mass ratio of the acrylic acid to the starch is as follows: 1: 8-14;
and (2) performing gel reaction, namely heating the vinyl oxidized starch dispersion to 78-80 ℃, adding the vinyl oxidized starch dispersion into the polyacrylate prepolymer emulsion under rapid stirring, stirring for 10-15 min, reducing the stirring speed, adding a neutralizing agent to neutralize to pH 6.5-7.0, dropwise adding the rest of the initiator, continuing to perform 80-85 ℃ after dropwise adding is completed within 1.5-2 h, keeping the temperature for 60-90min, and finishing the gelation reaction when the phenomenon of rod climbing occurs in a polymerization system.
The rapid stirring speed is 500-600r/min, and the reduced stirring speed is 150-200 r/min.
The starch is one of corn starch, potato starch, cassava starch or wheat starch; the content of amylose in the starch is 22-26%.
The vinyl silane coupling agent is one of vinyl trimethoxy silane, vinyl triethoxy silane and vinyl tri (β -methoxyethoxy) silane.
The ferrous salt complex solution is a complex ferrous salt solution obtained by stirring and mixing ferrous sulfate and one of sodium citrate, sodium tartrate and sodium oxalate, and adjusting the pH value to 3.0 by using dilute sulfuric acid.
The pH buffering agent is one of sodium bicarbonate or disodium hydrogen phosphate;
the initiator is one of sodium persulfate, potassium persulfate or ammonium persulfate;
the neutralizing agent is ammonia water or one of triethylamine or sodium hydroxide.
Compared with the prior art, the invention has the following technical effects:
1) the invention adopts full aqueous phase emulsion polymerization to realize the chemical crosslinking modification of the water-based acrylic resin to the vinyl oxidized starch, and has environmental protection significance.
2) The invention utilizes green, cheap and renewable starch as raw material, greatly solves the problems of difficult biodegradation, long degradation period, high cost and the like of the conventional water-based acrylic resin water-retaining agent, and is more easily accepted by the industry. The market price of the imported environment-friendly biodegradable water-retaining agent is 1.5-2.0 ten thousand yuan/ton at present, and the cost price of the product is 5000-9000 yuan/ton.
3) The water-based acrylic resin modified starch-based hydrogel water-retaining agent particles prepared by the invention have good water retention and fertilizer retention properties, biocompatibility, degradability, mechanical strength, structural stability and the like. The water absorption multiple of the composite material water-retaining agent can reach 600-800 times, the slow release rate of 30 d of nitrogen is 33.2% (the fertilizer-retaining property of the water-retaining agent is reflected), the tensile strength of the hydrogel is 1-3 MPa, the maximum thermal decomposition temperature is 345.8 ℃, and the SBF simulated body fluid degradation period is 90-120 days. The application amount of the water-retaining agent is 200 g/plant, the water retention rate of the soil can reach 70-80% by 0.1-0.3% of the application amount, and the consumption of agricultural irrigation water can be effectively reduced. After the water-retaining agent is applied, the water around the root system is sufficient, and the fertilizer can be better dissolved and stored, so that the water and fertilizer of plants are sufficient for a long time, the growth is vigorous, the yield is increased, and the yield increase amplitude can reach 15-45%. After the water-retaining agent is applied, the drought problem can be solved only by little rainwater or irrigation water, crops can grow normally under the condition of no watering for 2-3 months continuously, the constant humidity of soil can be kept for a long time (60-80%), the watering frequency is reduced by more than half, and the watering cost is saved by more than 50%.
4) The product is applied to the precise farming of field crops in the agricultural industry, is beneficial to the improvement of the soil structure and forms a good soil aggregate structure. Meanwhile, the soil film residue problem is effectively solved due to good biodegradability, and the soil film residue treatment method has wide market demand.
5) The water-retaining agent (absorbing more than 400 times of water) dips the seedlings into roots, and the survival rate can reach more than 95 percent even if the seedlings are planted after long-distance transportation.
Drawings
FIG. 1 is a flow chart of the preparation process of the product of the invention.
Detailed Description
Example 1 preparation method of waterborne acrylic resin modified starch-based hydrogel water-retaining agent particles
The method comprises the following steps:
(1) preparation of oxidized starch Dispersion
490 g of water and 210 g of corn starch are added into a 1L five-neck flask, and then the mixture is turnedStirring uniformly at the speed of 150 r/min, adding dilute sulfuric acid to adjust the pH value to 3.0, heating to 50 ℃, adding 15 mL0.1 mol/L ferrous salt complex solution (the molar ratio of ferrous sulfate to sodium tartrate is 1: 2), inserting an electrode, taking a graphite electrode as an anode, a titanium electrode as a cathode and a calomel electrode as a reference, switching on an electrochemical analysis system for constant current electrolysis, wherein the current density is 10-30A/m2. Dropwise adding 27.3 g of hydrogen peroxide, dropping for about 1 hour, rapidly increasing the temperature in the period, adjusting the temperature to 60-70 ℃ after the temperature is stable, keeping the temperature for 90min, closing an electrochemical analysis system, taking out an electrode, and cooling for later use.
(2) Preparation of a dispersion of a vinylated oxidized starch
And (2) adjusting the pH value of the oxidized starch dispersion liquid obtained in the step (1) to 4.0-4.5, dropwise adding 10 g of vinyl trimethoxy silane to carry out vinylation reaction, dripping for 40 min, adjusting the temperature to 45 ℃, keeping the temperature for 90min, and adjusting the pH value to 6.5-7.0 by using a sodium hydroxide solution to obtain the vinylated oxidized starch dispersion liquid for later use.
(3) Preparation of polyacrylate prepolymer emulsion
Adding 210 g of water, 15 g of acrylic acid, 10 g of methacrylic acid, 10 g of maleic anhydride, 25 g of acrylamide, 10 g of dimethylaminoethyl methacrylate and 0.8 g of baking soda into a 2L four-neck flask, stirring and emulsifying for 15 min at 500 r/min, reducing the stirring speed to 180 r/min, heating to 80 ℃, adding 0.09 kg of potassium persulfate (dissolved by 20 times of water), and preserving heat for 10-15 min when blue light appears to prepare polyacrylate prepolymer emulsion;
acrylic acid, maleic anhydride, acrylamide and dimethylaminoethyl methacrylate are used as polymerization monomers, and baking soda is used as a pH buffering agent.
(4) Gel reaction
Heating the product obtained in the step (2) to 80 ℃, adding the product into the prepolymer emulsion obtained in the step (3) at a stirring speed of 500 r/min, stirring for 10-15 min, reducing the stirring speed to 180 r/min, adding ammonia water to neutralize to pH 6.5-7.0, dropwise adding 0.81 kg of potassium persulfate (dissolved by 20 times of water), continuously preserving heat for 60-90min at 80-85 ℃ within 1.5-2 h, cooling to 50-60 ℃ after a polymerization system has a rod climbing phenomenon and a gelation reaction is finished, taking out of a kettle, pouring into a mold, putting into a drying room, blowing for drying at 50-60 ℃, crushing and granulating, and screening through 18-mesh sieve holes to obtain the water-based acrylic resin modified starch hydrogel water-retaining agent particle.
Example 2 preparation method of waterborne acrylic resin modified starch-based hydrogel water-retaining agent particles
The method comprises the following steps:
(1) preparation of oxidized starch Dispersion
490 g of water and 210 g of potato starch are added into a 1L five-neck flask, the mixture is uniformly stirred at the rotating speed of 150 r/min, dilute sulfuric acid is added to adjust the pH value to 3.0, the temperature is increased to 50 ℃, 18 mL0.1 mol/L ferrous salt complex liquid (the molar ratio of ferrous sulfate to sodium citrate is 1: 2) is added, an electrode is inserted, a graphite electrode is an anode, a titanium electrode is a cathode, a calomel electrode is a reference, an electrochemical analysis system is switched on to carry out constant-current electrolysis, and the current density is 10-30A/m2. Dropwise adding 31.5 g of hydrogen peroxide, dropping for about 1 hour, rapidly increasing the temperature in the period, adjusting the temperature to 60-70 ℃ after the temperature is stable, keeping the temperature for 90min, closing an electrochemical analysis system, taking out an electrode, and cooling for later use.
(2) Preparation of a dispersion of a vinylated oxidized starch
And (2) adjusting the pH value of the oxidized starch dispersion liquid obtained in the step (1) to 4.0-4.5, dropwise adding 12 g of vinyltriethoxysilane for vinylation reaction, dripping for 40 min, adjusting the temperature to 45 ℃, keeping the temperature for 90min, and adjusting the pH value to 6.5-7.0 by using a sodium hydroxide solution to obtain the vinylated oxidized starch dispersion liquid for later use.
(3) Preparation of polyacrylate prepolymer emulsion
255 g of water, 25 g of acrylic acid, 10 g of methacrylic acid, 8 g of maleic anhydride, 30 g of acrylamide, 12 g of dimethylaminoethyl methacrylate, 0.5 g of baking soda and stirring and emulsifying at the speed of 600r/min for 15 min are added into a 2L four-neck flask, the stirring speed is reduced to 150 r/min, the temperature is increased to 80 ℃, 0.1 kg of ammonium persulfate (dissolved by 20 times of water) is added, and the temperature is kept for 10-15 min when blue light appears, so that the polyacrylate prepolymer emulsion is prepared.
(4) Gel reaction
Heating the product obtained in the step (2) to 80 ℃, adding the product into the prepolymer emulsion obtained in the step (3) at a stirring speed of 500 r/min, stirring for 10-15 min, reducing the stirring speed to 180 r/min, adding a sodium hydroxide solution to neutralize to pH 6.5-7.0, dropwise adding 0.9kg of ammonium persulfate (dissolved by 20 times of water), continuously preserving heat for 60-90min at 80-85 ℃ after the dropwise adding is finished within 1.5-2 h, cooling to 50-60 ℃ after a polymerization system has a pole climbing phenomenon and a gelation reaction is finished, taking the product out of a kettle, pouring the product into a mold, putting the product into a drying room, blowing and drying at 50-60 ℃, crushing and granulating, and sieving through a 10-mesh sieve to obtain the water-based acrylic resin modified starch-based hydrogel water-retaining agent particles.
Example 3 preparation method of waterborne acrylic resin modified starch-based hydrogel water-retaining agent particles
The method comprises the following steps:
(1) preparation of oxidized starch Dispersion
490 g of water and 210 g of cassava starch are added into a 1L five-neck flask, the mixture is uniformly stirred at the rotating speed of 150 r/min, dilute sulfuric acid is added to adjust the pH value to 3.0, the temperature is increased to 50 ℃, 10 mL0.1 mol/L ferrous salt complex liquid (the molar ratio of ferrous sulfate to sodium oxalate is 1: 2) is added, an electrode is inserted, a graphite electrode is an anode, a titanium electrode is a cathode, a calomel electrode is a reference, an electrochemical analysis system is switched on to carry out constant-current electrolysis, and the current density is 10-30A/m2. Dropping 21.0 g of hydrogen peroxide, dropping for about 1 hour, rapidly increasing the temperature in the period, adjusting the temperature to 60-70 ℃ after the temperature is stable, preserving the temperature for 90min, closing an electrochemical analysis system, taking out an electrode, and cooling for later use.
(2) Preparation of a dispersion of a vinylated oxidized starch
And (2) adjusting the pH value of the oxidized starch dispersion liquid obtained in the step (1) to 4.0-4.5, dropwise adding 15 g of vinyl tri (β -methoxyethoxy) silane to carry out vinylation reaction, finishing dropping for about 40 min, adjusting the temperature to 45 ℃, keeping the temperature for 90min, and adjusting the pH value of a sodium hydroxide solution to 6.5-7.0 to obtain the vinylated oxidized starch dispersion liquid for later use.
(3) Preparation of polyacrylate prepolymer emulsion
Adding 180 g of water, 15 g of acrylic acid, 15 g of methacrylic acid, 5 g of maleic anhydride, 15 g of acrylamide, 8 g of dimethylaminoethyl methacrylate and 0.6 g of baking soda into a 2L four-neck flask, stirring and emulsifying for 15 min at 500 r/min, reducing the stirring speed to 200r/min, heating to 80 ℃, adding 0.07 kg of sodium persulfate (dissolved by 20 times of water), and preserving heat for 10-15 min when blue light appears to prepare the polyacrylate prepolymer emulsion.
(4) Gel reaction
Heating the product obtained in the step (2) to 80 ℃, adding the product into the prepolymer emulsion obtained in the step (3) at a stirring speed of 500 r/min, stirring for 10-15 min, reducing the stirring speed to 180 r/min, adding 30% sodium hydroxide solution to neutralize to pH 6.5-7.0, dropwise adding 0.66 kg of sodium persulfate (dissolved by 20 times of water), continuously preserving heat for 60-90min at 80-85 ℃ after dropwise adding is completed within 1.5-2 h, cooling to 50-60 ℃ after gelation reaction is finished when a 'rod climbing' phenomenon occurs in a polymerization system, taking the product out of a kettle, pouring the product into a mold, putting the product into a drying room, blowing for drying at 50-60 ℃, crushing and granulating, and sieving through a 35-mesh sieve to obtain the water-based acrylic resin modified starch-based water-retaining agent particles.
Example 4 preparation method of waterborne acrylic resin modified starch-based hydrogel water-retaining agent particles
The method comprises the following steps:
(1) preparation of oxidized starch Dispersion
490 g of water and 210 g of wheat starch are added into a 1L five-neck flask, the rotation speed is 150 r/min, the mixture is uniformly stirred, dilute sulfuric acid is added to adjust the pH value to 3.0, the temperature is increased to 50 ℃, 13 mL0.1 mol/L ferrous salt complex liquid (the molar ratio of ferrous sulfate to sodium tartrate is 1: 2) is added, an electrode is inserted, a graphite electrode is an anode, a titanium electrode is a cathode, a calomel electrode is a reference, an electrochemical analysis system is switched on to carry out constant-current electrolysis, and the current density is 10-30A/m2. Dropwise adding 29.4 g of hydrogen peroxide, dropping for about 1 hour, rapidly increasing the temperature in the period, adjusting the temperature to 60-70 ℃ after the temperature is stable, keeping the temperature for 90min, closing an electrochemical analysis system, taking out an electrode, and cooling for later use.
(2) Preparation of a dispersion of a vinylated oxidized starch
And (2) adjusting the pH value of the oxidized starch dispersion liquid obtained in the step (1) to 4.0-4.5, dropwise adding 13 g of vinyl trimethoxy silane to carry out vinylation reaction, dripping for about 40 min, adjusting the temperature to 45 ℃, keeping the temperature for 90min, and adjusting the pH value to 6.5-7.0 by using a sodium hydroxide solution to obtain a vinylated oxidized starch dispersion liquid for later use.
(3) Preparation of polyacrylate prepolymer emulsion
210 g of water, 20 g of acrylic acid, 7 g of methacrylic acid, 8 g of maleic anhydride, 28 g of acrylamide, 7 g of dimethylaminoethyl methacrylate, 0.7 g of baking soda and 500 r/min stirring for emulsification for 15 min, reducing the stirring speed to 180 r/min, heating to 80 ℃, adding 0.08 kg of potassium persulfate (dissolved by 20 times of water), and preserving the temperature for 10-15 min when blue light appears to prepare the polyacrylate prepolymer emulsion.
(4) Gel reaction
Heating the product obtained in the step (2) to 80 ℃, adding the product into the prepolymer emulsion obtained in the step (3) at a stirring speed of 500 r/min, stirring for 10-15 min, reducing the stirring speed to 180 r/min, adding triethylamine to neutralize to pH 6.5-7.0, dropwise adding 0.73 kg of potassium persulfate (dissolved by 20 times of water), after dropwise adding within 1.5-2 h, continuously preserving heat for 60-90min at 80-85 ℃, cooling to 50-60 ℃ after a polymerization system has a rod climbing phenomenon and a gelation reaction is finished, taking out of a kettle, pouring into a mold, putting into a drying room, blowing for drying at 50-60 ℃, crushing and granulating, and sieving through a 10-mesh sieve to obtain the water-based acrylic resin modified starch hydrogel water-based water-retaining agent.
The water absorption multiple of the prepared hydrogel water-retaining agent particles can reach 500-800 times, the slow release rate of nitrogen is not more than 40% after 30 d, the structure stability is good, the maximum thermal decomposition temperature is 345.8 ℃, the SBF simulated body fluid degradation period is about 110 d, and the moisture retention rate of soil with the application amount of 0.1-0.3% can permanently reach 70-80% of humidity range suitable for crop growth.
The following examples are used to illustrate the use of the product for field crop cultivation.
Example 5
The dosage of the water-retaining agent particles is as follows: 4-5 kg/mu, and is suitable for barley, wheat, corn and various legume crops. The wet land adopts a dry application method: uniformly mixing water-retaining agent particles with 10-30 times of dry fine soil, and uniformly applying the mixture into a sowing ditch; the wet application method is adopted in a dry way: firstly, the water-retaining agent absorbs water by more than 400 times to form a gel, and then the gel is uniformly applied into the sowing trench; mixing with ditch soil, sowing seeds into planting ditch, covering soil, and watering according to conventional method to ensure water-retaining agent in water storage state. If the machine seeding is carried out, the water-retaining agent can be firstly mixed with soil, then the mixture is scattered into a field block along with the base fertilizer, and watering is carried out immediately after the seeding is finished. After the water-retaining agent is applied, the problem of drought can be solved only by little rainwater or irrigation water, and crops can grow normally without watering for 2-3 months continuously. The constant humidity of the soil can be kept for a long time (60-80%), the watering frequency is reduced by more than half, and the watering cost is saved by more than 50%.
Example 6
The application amount of the water-retaining agent is 500 g/plant of fruit trees 100-. Is suitable for most fruit trees. The application mode is as follows: strip application or hole application.
Application time: a. adopting a dry application method (absorbing water in rainy season and releasing water in dry season) 5-10 days before the rainy season; b. applying mixed fertilizer in winter (before and after picking fruit) or spring (wet application method can be adopted); c. applying mixed fertilizer 20 days before flowering (wet application method can be adopted). Digging long-strip grooves with the depth of more than 20 cm at the 'dripping line' position of a fruit tree to form fibrous roots (only one side is needed), or digging 2-5 soil holes (deep to form the fibrous roots) at the 'dripping line' position of the fruit tree.
The dry application method can be adopted before rainy season or in places with water sources: the water-retaining agent dry particles are directly sprinkled into ditches or holes (fertilizer can be applied at the same time), then fully and uniformly stirred with hole soil, covered with soil into a concave shape (so as to collect water), and immediately watered.
In dry season or winter and spring, the wet application method is adopted, the water-retaining agent absorbs more than 400 times of water to form gel, and then the gel is applied into the ditch or the cave (fertilizer can be applied at the same time), and then the gel is fully and uniformly mixed with the cave soil, covered with soil to form a concave shape (so as to collect rainwater), and watered once again immediately under the condition.
The survival rate is generally only 70-90% due to the water loss of the roots during the transplanting of the seedlings. If the water-retaining agent (absorbing more than 400 times of water) of the invention is used for dipping the seedlings into roots, the survival rate can reach more than 95 percent even if the seedlings are planted after long-distance transportation.
Claims (10)
1. A preparation method of water-based acrylic resin modified starch-based hydrogel water-retaining agent particles is characterized by comprising the following steps: comprises the steps of preparing oxidized starch dispersion liquid, preparing vinylation oxidized starch dispersion liquid, preparing polyacrylate prepolymer emulsion and carrying out gel reaction.
2. The preparation method of the water-based acrylic resin modified starch-based hydrogel water-retaining agent particles as claimed in claim 1, wherein the preparation method comprises the following steps:
preparing oxidized starch dispersion liquid, adding a certain amount of water and starch into a reaction kettle, adjusting the pH to 2.9-3.1, heating to 48-52 ℃, adding a ferrous salt complex solution, and performing constant current electrolysis with the current density of 10-30A/m2Dropwise adding hydrogen peroxide for 0.9-1.1h, adjusting the temperature to 60-70 ℃ after the temperature is stable, preserving the temperature for 60-90min, stopping electrolysis, and cooling.
3. The preparation method of the water-based acrylic resin modified starch-based hydrogel water-retaining agent particles as claimed in claim 2, wherein the preparation method comprises the following steps:
the mass ratio of the water to the starch is 2-3: 1;
the volume-mass ratio of the ferrous salt complex liquid to the starch is as follows: 1ml is 11-21 g;
the concentration of the ferrous salt complex solution is 0.08-0.12 mol/L;
the mass ratio of the hydrogen peroxide to the starch is as follows: 1:6.6-10.
4. The preparation method of the water-based acrylic resin modified starch-based hydrogel water-retaining agent particles as claimed in claim 1, wherein the preparation method comprises the following steps:
the preparation method comprises the steps of preparing a vinylation oxidized starch dispersion, adjusting the pH value of the oxidized starch dispersion to 4.0-4.5, dropwise adding a vinyl silane coupling agent to carry out vinylation reaction, adjusting the temperature to 44-46 ℃, keeping the temperature for 60-90min, and adjusting the pH value to 6.5-7.0 to prepare the vinylation oxidized starch dispersion.
5. The preparation method of the water-based acrylic resin modified starch-based hydrogel water-retaining agent particles as claimed in claim 4, wherein the preparation method comprises the following steps:
the mass ratio of the vinyl silane coupling agent to the starch is as follows: 1: 14-21;
the dripping time is 35-45 min.
6. The preparation method of the water-based acrylic resin modified starch-based hydrogel water-retaining agent particles as claimed in claim 1, wherein the preparation method comprises the following steps:
the preparation method comprises the steps of adding acrylic acid, methacrylic acid, maleic anhydride, acrylamide, dimethylaminoethyl methacrylate and a pH buffering agent into a reaction kettle filled with quantitative deionized water, quickly stirring and emulsifying for 13-17 min, reducing the stirring speed to 150-200r/min, heating to 78-82 ℃, adding 9-11% of the total amount of an initiator, and preserving heat for 10-15 min when blue light appears to prepare the polyacrylate prepolymer emulsion.
7. The preparation method of the water-based acrylic resin modified starch-based hydrogel water-retaining agent particles as claimed in claim 6, wherein the preparation method comprises the following steps:
the mass ratio of the water to the acrylic acid is 10-14: 1;
the mass ratio of the methacrylic acid to the acrylic acid is 0.35-1: 1;
the mass ratio of the maleic anhydride to the acrylic acid is 0.32-0.67: 1;
the mass ratio of the acrylamide to the acrylic acid is 1-1.7:1
The mass ratio of the dimethylaminoethyl methacrylate to the acrylic acid is 0.35-0.7: 1;
the mass ratio of the pH buffer to the acrylic acid is 0.02-0.053: 1;
the mass ratio of the initiator to the acrylic acid is 4-6: 1;
the rapid stirring is carried out at the rotating speed of 500-600 r/min.
8. The preparation method of the water-based acrylic resin modified starch-based hydrogel water-retaining agent particles as claimed in claim 1, wherein the preparation method comprises the following steps:
and (2) performing gel reaction, namely heating the vinyl oxidized starch dispersion to 78-80 ℃, quickly stirring, adding the vinyl oxidized starch dispersion into the polyacrylate prepolymer emulsion, stirring for 10-15 min, reducing the stirring speed, adding a neutralizing agent to neutralize to pH 6.5-7.0, dropwise adding the rest of the initiator, keeping the temperature at 80-85 ℃ for 60-90min after dropwise adding is completed within 1.5-2 h, and finishing the gelation reaction after the polymerization system has a pole climbing phenomenon.
9. The preparation method of the water-based acrylic resin modified starch-based hydrogel water-retaining agent particles as claimed in claim 2, wherein the starch is one of corn starch, potato starch, tapioca starch or wheat starch; the content of amylose in the starch is 22-26%.
10. The preparation method of the water-based acrylic resin modified starch-based hydrogel water-retaining agent particle as claimed in claim 4, wherein the vinyl silane coupling agent is one of vinyl trimethoxy silane, vinyl triethoxy silane and vinyl tris (β -methoxyethoxy) silane.
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| CN110452484A (en) * | 2019-09-04 | 2019-11-15 | 仲恺农业工程学院 | A kind of pair of carbon dioxide has modified starch/PVA fruit-vegetable plastic wrap and preparation method thereof of sensitive property |
| CN113061277A (en) * | 2021-04-27 | 2021-07-02 | 杭州圣立新材料有限公司 | Biodegradable intelligent water-permeable moisturizing film and preparation method and application thereof |
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