Preparation method of high-swelling semi-interpenetrating structure hydrogel for soil water retention

Abstract

The invention discloses a preparation method of a high-swelling semi-interpenetrating structure hydrogel for soil water retention. The method comprises the following steps: dissolving polyvinyl alcohol (PVA) at high temperature, cooling to room temperature, and sequentially adding Arabic gum (AG) and a pre-neutralized acrylic acid (AA) solution; the preparation method comprises the following steps: adding a cross-linking agent N, N '-methylenebisacrylamide (MBA) and a photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methyl propiophenone (Irgacure 2959) into a mixed solution, fully mixing, carrying out ultrasonic oscillation, and finally completing a polymerization reaction under ultraviolet irradiation to prepare the hydrogel. The method is simple in preparation process and convenient to operate, and the prepared hydrogel shows efficient water absorption capacity and a long-term water retention effect and can continuously provide required moisture for plant growth. After the gel is used for many times, the gel can still maintain good swelling performance, and the service life is prolonged. The hydrogel disclosed by the invention is suitable for the application fields of water absorption and retention in agriculture and the like.

Description

Technical Field

[0001] The invention relates to the field of agricultural soil water conservation, and in particular to a method for preparing a highly swellable semi-interpenetrating structure hydrogel for soil water conservation. Background Art

[0002] With the rapid development of human society, food production has become an important part of agricultural development. Globally, the instability of rainfall in arid and semi-arid regions has led to water shortages for crops, which in turn has caused serious losses to agricultural production. Therefore, researchers are developing various methods to deal with the problem of water shortage in agriculture. Superabsorbent hydrogels (SAHs) are three-dimensional cross-linked polymer networks that are insoluble in water and can absorb and retain large amounts of aqueous solutions or biological fluids within their structures even under high pressure conditions, helping to reduce irrigation water in agricultural production. Over the years, materials such as polyacrylamide and polyacrylic acid have been widely used to prepare superabsorbent materials.

[0003] However, growing environmental issues have put forward higher requirements for the production and use of SAHs. Therefore, natural polymers such as cellulose, chitosan, gum arabic, etc., due to their biosafety, low cost, sustainability and environmental friendliness, have been widely used to replace synthetic polymers or combined with them to prepare SAHs, and have received extensive attention and application in the fields of environment and agriculture. In order to maximize the role of hydrogels in agricultural production, in addition to paying attention to the key issue of their biosafety, we also need to consider their service life and further optimize their synthesis process and application technology.

[0004] This study aims to develop a new type of highly swellable semi-IPN hydrogel to meet the demand for high-performance hydrogel materials in the field of soil water retention. To this end, we selected polyvinyl alcohol (PVA) with excellent hydrophilicity as the linear material. By using UV curing technology, a fast reaction speed and low energy consumption method, PVA was interspersed in the polymer network of gum arabic (AG) grafted polyacrylic acid (PAA) to construct semi-interpenetrating polymer networks (Semi-IPNs). This structural design can not only enhance the swelling ability and water retention performance of the hydrogel, but also effectively extend the service life of the hydrogel through its excellent re-swelling performance. These characteristics make the hydrogel show great application potential in the agricultural field, especially in water saving. Summary of the invention

[0005] In view of the shortcomings of the above-mentioned traditional highly water-absorbent hydrogel materials, the purpose of the present invention is to provide a method for preparing a highly swellable semi-interpenetrating structure hydrogel for soil water retention.

[0006] A method for preparing a highly swellable semi-interpenetrating structure hydrogel for soil water retention comprises the following steps:

[0007] Step (1): adding a certain amount of polyvinyl alcohol (PVA) into deionized water, and dissolving it in a constant temperature water bath at 80-90°C with magnetic stirring to obtain a PVA solution;

[0008] Step (2): cooling the PVA solution obtained in step (1) to room temperature, adding a certain amount of gum arabic (AG), and fully dissolving it under magnetic stirring;

[0009] Step (3): slowly drop a certain amount of sodium hydroxide (NaOH) solution into the acrylic acid (AA) solution under stirring in an ice bath, and after the neutralization reaction is complete, the solution is returned to room temperature to obtain a neutralized acrylic acid solution;

[0010] Step (4): slowly pour the mixed solution obtained in step (3) into the mixed solution in step (2), then add the crosslinking agent N,N'-methylenebisacrylamide (MBA) and the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959), stir evenly and then perform ultrasonic vibration;

[0011] Step (5): transferring the mixed solution obtained in step (4) into a mold, placing it in a UV curing box to undergo a polymerization reaction, and obtaining a hydrogel after UV curing.

[0012] Step (6): The hydrogel is physically cut into block gels of the same size, and the obtained gels are immersed in anhydrous ethanol and then placed in an oven for drying.

[0013] The amount of PVA in step (1) is 2.5-10.0% of the monomer mass.

[0014] The amount of AG in step (2) is 5.0-10.0% of the monomer mass.

[0015] The amount of AA in step (3) is 4-8 mL.

[0016] In step (3), the degree of neutralization of AA is between 60-85%.

[0017] The amount of MBA in step (4) is 0.1-0.5% of the monomer mass.

[0018] In the step (4), the amount of Irgacure 2959 accounts for 0.5-1.0% of the monomer mass.

[0019] In the step (5), the mold is made of a plastic plate and a silicone pad.

[0020] In the step (5), the ultraviolet light irradiation time is controlled to be within 15 minutes.

[0021] The diameter of the hydrogel block after physical cutting in step (6) does not exceed 15 mm.

[0022] Compared with the prior art, the present invention has the following benefits

[0023] (1) The present invention provides a highly water-absorbent semi-IPN hydrogel prepared by ultraviolet light in-situ polymerization. Compared with the existing methods, the ultraviolet light polymerization reaction is fast and easy to operate. The prepared hydrogel has excellent swelling and water retention properties. Its excellent re-swelling performance effectively prolongs the service life of the hydrogel.

[0024] (2) The present invention provides a highly absorbent hydrogel for use in the field of water absorption and water retention in agriculture. The material has gum arabic (AG) grafted with polyacrylic acid (PAA) as the main chain, and polyvinyl alcohol (PVA) is interspersed therein as a linear material to form a semi-interpenetrating network structure. This structural design makes full use of the hydrophilic properties of PVA, improves the swelling rate and water retention capacity of the hydrogel, and thus gives the hydrogel significant application advantages in the fields of agriculture and forestry.

[0025] (3) The gum arabic (AG) used in this study is a natural polysaccharide macromolecule with a large number of hydroxyl and carboxyl active sites, which can be easily chemically modified to give AG more properties. In addition, AG itself has a good water-retention effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to make the purpose, technical solution and beneficial effects of the present invention clearer, the present invention provides the following drawings for illustration:

[0027] Figure 1 It is the swelling property of the highly absorbent hydrogel prepared in the present invention.

[0028] Figure 2 This is the water retention rate curve of the highly absorbent hydrogel prepared in Example 2 of the present invention after swelling.

[0029] Figure 3 This is a graph showing the cyclic swelling performance of the highly absorbent hydrogel prepared in Example 2 of the present invention.

[0030] Figure 4 This is a diagram showing the soil planting effect of the highly absorbent hydrogel prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below through an implementation case. This implementation case is implemented on the premise of the technology of the present invention. A detailed implementation method and a specific operation process are given to illustrate that the present invention is creative, but the protection scope of the present invention is not limited to the following implementation cases.

[0032] Example 1

[0033] A method for preparing a highly swellable semi-interpenetrating structure hydrogel for soil water retention, the method specifically comprising the following steps:

[0034] Step (1): adding 0.1313 g of polyvinyl alcohol (PVA) into deionized water, and stirring the mixture with a magnetic force in a constant temperature water bath at 80-90° C. to obtain a PVA solution;

[0035] Step (2): The PVA solution obtained in step (1) was cooled to room temperature, and 0.2625 g of gum arabic (AG) was added to fully dissolve under magnetic stirring;

[0036] Step (3): slowly drop a certain amount of 8 mol / L sodium hydroxide (NaOH) solution into 5 mL of acrylic acid (AA) solution under stirring in an ice bath, wherein the degree of neutralization of the acrylic acid is 80%. After the neutralization reaction is complete, the solution is returned to room temperature to obtain a neutralized acrylic acid solution;

[0037] Step (4): slowly pour the mixed solution obtained in step (3) into the mixed solution in step (2), add 0.0131 g of cross-linking agent N,N'-methylenebisacrylamide (MBA) and 0.0525 g of photoinitiator Irgacure 2959, stir evenly and then perform ultrasonic vibration;

[0038] Step (5): transferring the mixed solution obtained in step (4) into a mold, placing it in a UV curing box for polymerization for 10 minutes, and obtaining a hydrogel after the UV curing is completed;

[0039] Step (6): Physically cut the hydrogel into block gels of the same size, soak the obtained gels in anhydrous ethanol, and then place them in an oven for drying.

[0040] Example 2

[0041] A method for preparing a highly swellable semi-interpenetrating structure hydrogel for soil water retention, the method specifically comprising the following steps:

[0042] Step (1): adding 0.2625 g of polyvinyl alcohol (PVA) to deionized water, and stirring the mixture with a magnetic force in a constant temperature water bath at 80-90° C. to obtain a PVA solution;

[0043] Step (2): The PVA solution obtained in step (1) was cooled to room temperature, and 0.2625 g of gum arabic (AG) was added to fully dissolve under magnetic stirring;

[0044] Step (3): slowly drop a certain amount of 8 mol / L sodium hydroxide (NaOH) solution into 5 mL of acrylic acid (AA) solution under stirring in an ice bath, wherein the degree of neutralization of the acrylic acid is 80%. After the neutralization reaction is complete, the solution is returned to room temperature to obtain a neutralized acrylic acid solution;

[0045] Step (4): slowly pour the mixed solution obtained in step (3) into the mixed solution in step (2), add 0.0131 g of cross-linking agent N,N'-methylenebisacrylamide (MBA) and 0.0525 g of photoinitiator Irgacure 2959, stir evenly and then perform ultrasonic vibration;

[0046] Step (5): transferring the mixed solution obtained in step (4) into a mold, placing it in a UV curing box for polymerization for 10 minutes, and obtaining a hydrogel after the UV curing is completed;

[0047] Step (6): Physically cut the hydrogel into block gels of the same size, soak the obtained gels in anhydrous ethanol, and then place them in an oven for drying.

[0048] Example 3

[0049] A method for preparing a highly swellable semi-interpenetrating structure hydrogel for soil water retention, the method specifically comprising the following steps:

[0050] Step (1): adding 0.3938 g of polyvinyl alcohol (PVA) into deionized water, and stirring the mixture with a magnetic force in a constant temperature water bath at 80-90° C. to obtain a PVA solution;

[0051] Step (2): The PVA solution obtained in step (1) was cooled to room temperature, and 0.2625 g of gum arabic (AG) was added to fully dissolve under magnetic stirring;

[0052] Step (3): slowly drop a certain amount of 8 mol / L sodium hydroxide (NaOH) solution into 5 mL of acrylic acid (AA) solution under stirring in an ice bath, wherein the degree of neutralization of the acrylic acid is 80%. After the neutralization reaction is complete, the solution is returned to room temperature to obtain a neutralized acrylic acid solution;

[0053] Step (4): slowly pour the mixed solution obtained in step (3) into the mixed solution in step (2), add 0.0131 g of cross-linking agent N,N'-methylenebisacrylamide (MBA) and 0.0525 g of photoinitiator Irgacure 2959, stir evenly and then perform ultrasonic vibration;

[0054] Step (5): transferring the mixed solution obtained in step (4) into a mold, placing it in a UV curing box for polymerization for 10 minutes, and obtaining a hydrogel after the UV curing is completed;

[0055] Step (6): Physically cut the hydrogel into block gels of the same size, soak the obtained gels in anhydrous ethanol, and then place them in an oven for drying.

[0056] Example 4

[0057] A method for preparing a highly swellable semi-interpenetrating structure hydrogel for soil water retention, the method specifically comprising the following steps:

[0058] Step (1): adding 0.5250 g of polyvinyl alcohol (PVA) into deionized water, and stirring the mixture with a magnetic force in a constant temperature water bath at 80-90° C. to obtain a PVA solution;

[0059] Step (2): The PVA solution obtained in step (1) was cooled to room temperature, and 0.2625 g of gum arabic (AG) was added to fully dissolve under magnetic stirring;

[0060] Step (3): slowly drop a certain amount of 8 mol / L sodium hydroxide (NaOH) solution into 5 mL of acrylic acid (AA) solution under stirring in an ice bath, wherein the degree of neutralization of the acrylic acid is 80%. After the neutralization reaction is complete, the solution is returned to room temperature to obtain a neutralized acrylic acid solution;

[0061] Step (4): slowly pour the mixed solution obtained in step (3) into the mixed solution in step (2), add 0.0131 g of cross-linking agent N,N'-methylenebisacrylamide (MBA) and 0.0525 g of photoinitiator Irgacure 2959, stir evenly and then perform ultrasonic vibration;

[0062] Step (5): transferring the mixed solution obtained in step (4) into a mold, placing it in a UV curing box for polymerization for 10 minutes, and obtaining a hydrogel after the UV curing is completed;

[0063] Step (6): Physically cut the hydrogel into block gels of the same size, soak the obtained gels in anhydrous ethanol, and then place them in an oven for drying.

[0064] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for preparing a highly swellable semi-interpenetrating hydrogel for soil water retention, characterized in that The method specifically comprises the following steps: (1) Add a certain amount of polyvinyl alcohol (PVA) into deionized water and dissolve it in a constant temperature water bath at 80-90°C with magnetic stirring to obtain a PVA solution; (2) cooling the PVA solution obtained in step (1) to room temperature, adding a certain amount of gum arabic (AG), and fully dissolving it under magnetic stirring; (3) slowly adding a certain amount of sodium hydroxide (NaOH) solution to the acrylic acid (AA) solution under stirring in an ice bath, and after the neutralization reaction is complete, returning the solution to room temperature to obtain a neutralized acrylic acid solution; (4) Slowly pour the mixed solution obtained in step (3) into the mixed solution in step (2), then add the crosslinking agent N,N'-methylenebisacrylamide (MBA) and the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959), stir evenly and then perform ultrasonic vibration; (5) transferring the mixed solution obtained in step (4) into a mold, placing it in a UV curing box to undergo a polymerization reaction, and obtaining a hydrogel after UV curing; (6) The hydrogel is physically cut into blocks of gel of the same size, and the obtained gel is immersed in anhydrous ethanol and then dried in an oven.

2. The method for preparing a highly swellable semi-interpenetrating hydrogel for soil water retention according to claim 1, characterized in that: In step (1), PVA accounts for 2.5-10.0% of the monomer mass.

3. The method for preparing a highly swellable semi-interpenetrating hydrogel for soil water retention according to claim 1, characterized in that: The amount of AG in step (2) is 5.0-10.0% of the monomer mass.

4. The method for preparing a highly swellable semi-interpenetrating hydrogel for soil water retention according to claim 1, characterized in that: In step (3), the amount of AA is 4-8 mL, the concentration of NaOH solution is 5-10 mol / L, and the degree of neutralization is 60-85%.

5. The method for preparing a highly swellable semi-interpenetrating structure hydrogel for soil water retention according to claim 1, characterized in that: In step (4), N,N'-methylenebisacrylamide (MBA) accounts for 0.1-0.5% of the monomer mass, and the photoinitiator Irgacure 2959 accounts for 0.5-1.0% of the monomer mass.

6. The method for preparing a highly swellable semi-interpenetrating hydrogel for soil water retention according to claim 1, characterized in that: The mold in step (5) can be made of a plastic plate and a silicone pad.

7. The method for preparing a highly swellable semi-interpenetrating hydrogel for soil water retention according to claim 1, characterized in that: In step (5), the ultraviolet light irradiation time is controlled within 15 minutes.

8. The method for preparing a highly swellable semi-interpenetrating hydrogel for soil water retention according to claim 1, characterized in that: The diameter of the hydrogel block after physical cutting in step (6) does not exceed 15 mm.

9. The method for preparing a highly swellable semi-interpenetrating hydrogel for soil water retention according to claim 1, characterized in that: The hydrogel prepared by the method has high water absorption and water retention, can still maintain good water absorption performance after multiple cycles of swelling, and is reusable.

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