CN111378201B - A kind of preparation method of environment-friendly high water absorption and water retention material - Google Patents

Abstract

The invention discloses a preparation method of an environment-friendly high water-absorbing and water-retaining material, which takes natural polysaccharide or polysaccharide derivatives as raw materials and prepares the environment-friendly high water-absorbing and water-retaining material by sol-gel and freeze drying technologies. The water absorption rate of the high water absorption and retention material can reach 252 g/g-584 g/g, the water absorption rate can reach 0.554 g/min-1.285 g/min, the water retention rate can reach 69.9% -94.47%, and the tensile strength can reach 39.22 kPa. The material prepared by the invention has the advantages of high water absorption rate, high water retention rate, high mechanical property and the like, and is simple in preparation process, mild in reaction condition, non-toxic, harmless, green, environment-friendly and easy to degrade, and the environment cannot be polluted after the material is used.

Description

A kind of preparation method of environment-friendly high water absorption and water retention material

technical field

The invention belongs to the fields of natural polymers, chemical engineering and environmental engineering, and relates to a functional material, in particular to a preparation method of an environment-friendly high water absorption and water retention material.

Background technique

The distribution of freshwater resources on the earth is uneven, and some areas are already in a state of severe water shortage. At the same time of water shortage, due to economic development and population increase, water consumption is increasing, and sewage discharge is also increasing. Many places are faced with the challenges of wetland degradation, river stoppage, groundwater overexploitation, and reduced seawater intake. . The preparation technology of environment-friendly water-absorbing materials with simple preparation, low cost, high water absorption and water retention rate is an important solution to deal with the crisis of the earth's water resources.

The traditional water-absorbing materials are mostly acrylic and acrylamide products, which are functional polymer materials with particularly strong water-absorbing ability, and are widely used in various fields. However, acrylic cross-linked resin has high cost, low water absorption rate and poor water retention capacity under high concentration electrolyte, and 90% of water absorbent resin is often used in disposable products, most of which will eventually be landfilled or incinerated after use, and cannot be degraded , causing secondary environmental problems related to soil, water and air pollution.

Agriculture, cosmetics, food preservation, sanitary products and other commonly used water-absorbing materials not only require a large amount of water absorption in practical applications, but also have higher requirements on the rate of water absorption, and a higher rate of water absorption can improve the use efficiency of the product.

Aerogel is a three-dimensional network structure material with abundant pores, which can quickly absorb a large amount of water. Natural polysaccharides or polysaccharide derivatives such as cellulose, sodium alginate, chitosan, starch, sodium carboxymethyl cellulose and other polymers can obtain high-porosity three-dimensional network structures through physical or chemical cross-linking and desolvation processes. Natural polysaccharides or polysaccharide derivatives are widely used in different fields due to their excellent properties such as good biocompatibility, biodegradability, non-toxicity, abundant sources, and low prices.

There are few reports on the research of natural polysaccharide or polysaccharide derivative aerogel products in the field of high water absorption and water retention materials.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a preparation method of an environment-friendly high water absorption and water retention material with high water absorption rate, fast water absorption rate, high water retention rate, strong mechanical properties and low preparation cost.

In order to achieve the above purpose, the technical scheme of the present invention is to provide a preparation method of an environmentally friendly high water absorption and water retention material, comprising the following steps:

(1) Preparation of phosphate buffer solution

Take potassium dihydrogen phosphate, dipotassium hydrogen phosphate and water as solvent systems, respectively take a concentration of 0.067mol/L potassium dihydrogen phosphate solution and 0.067mol/L dipotassium hydrogen phosphate solution and mix them in a certain proportion to obtain pH=6.0 phosphoric acid buffer solution;

(2) Preparation of homogeneous solution of natural polysaccharide or polysaccharide derivative

The phosphate buffer solution is placed on a mixer, and the natural polysaccharide or polysaccharide derivative is added and stirred at a stirring speed of 500-1000 r/min to obtain a uniform solution of natural polysaccharide or polysaccharide derivative;

(3) Activation of natural polysaccharides or polysaccharide derivatives

In the homogeneous solution of natural polysaccharide or polysaccharide derivative, slowly add the activator, and stir at a stirring speed of 500～1000r/min for 15～30min to obtain the activated polysaccharide solution;

(4) Preparation of natural polysaccharide or polysaccharide derivative hydrogel

Add the cross-linking agent to the polysaccharide solution, continue stirring for 2 hours at a stirring speed of 500-1000 r/min on the mixer, and then add N,N,N',N'-tetramethylethylenediamine during the stirring process. Let stand for 6 hours during molding to obtain gel, soak the gel in water and repeatedly wash to remove unreacted activator, cross-linking agent and N,N,N',N'-tetramethylethylenediamine to obtain natural polysaccharide or polysaccharide derivative hydrogels;

(5) Drying molding of natural polysaccharide or polysaccharide derivative hydrogel

The natural polysaccharide or polysaccharide derivative hydrogel is freeze-dried to obtain an environmentally friendly high water absorption and water retention material.

Preferably, the total mass of the added natural polysaccharide or polysaccharide derivative accounts for 2% to 4% of the uniform solution volume of the natural polysaccharide or polysaccharide derivative.

Preferably, the activator is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide.

Preferably, the carboxylic acid group in the added natural polysaccharide or polysaccharide derivative and the activator 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, N-hydroxysuccinimide The molar ratio of the amine is 1:0.5-1.25:0.25-0.625.

Preferably, the molar ratio of the carboxylic acid group to the crosslinking agent in the added natural polysaccharide or polysaccharide derivative is 1:0.25-1.25.

Preferably, the molar ratio of the carboxylic acid group to the crosslinking agent in the added natural polysaccharide or polysaccharide derivative is 1:0.75.

Preferably, the natural polysaccharide or polysaccharide derivative is a carboxyl group-containing natural polysaccharide polymer or a carboxylated polysaccharide derivative.

Preferably, the natural polysaccharide or polysaccharide derivative is one of sodium carboxymethyl cellulose, alginate, and carboxymethyl chitosan with a degree of substitution of 0.7-1.2.

Preferably, the crosslinking agent is all compounds containing one or more amino groups, and is one of ethylenediamine, dopamine, dopamine hydrochloride, urea and melamine.

Preferably, the temperature of the freeze-drying is -70～-50°C, and the pressure is 1～10pa.

Preferably, the environment-friendly high water absorption and water retention material can be made into blocks, films, spheres and powders.

The preparation method of the environment-friendly high water absorption and water retention material of the present invention has the following beneficial effects:

1. The raw materials used in the present invention are natural polysaccharide or polysaccharide derivative macromolecular compounds, which have the characteristics of wide source, renewable, easily degradable, low price and environmental friendliness; this makes natural polysaccharide or polysaccharide derivative macromolecular compounds in While preparing the material with high water absorption and water retention characteristics, it incorporates the excellent performance of the raw material that is environmentally friendly.

2. Commonly used superabsorbent and water-retaining materials such as polymer resins cannot be completely degraded, and will cause other environmental pollution after use. However, the superabsorbent and water-retaining material of the present invention is easily degradable and contains nitrogen in its molecular structure. If it is used in agriculture Water-retaining agents can even provide some essential elements for plant growth.

3. The superabsorbent and water-retaining material of the present invention is non-toxic and harmless, has no harm to the human body, and has good skin-friendly properties.

4. The high water absorption and water retention material of the present invention has a high water absorption rate, which can reach 252 g/g to 584 g/g, and can absorb a large amount of water.

5. The high water absorption and water retention material of the present invention has a relatively fast water absorption rate, which can reach 0.554g/min～1.285g/min, which can achieve the purpose of rapid water absorption and improve the efficiency of material use.

6. The present invention adopts the means of aerogelation in the molding and drying process, in order to provide abundant pore structure, so as to ensure that the material can achieve a fast water absorption rate and a high water absorption rate.

7. The high water absorption and water retention material of the present invention has a high water retention rate, up to 69.9% to 94.47%, and a tensile strength of up to 39.22kPa. It is released slowly to meet the practical application requirements of the material.

Description of drawings

Figure 1 is a picture of the change of the super absorbent and water-retaining material in the aqueous solution before and after absorbing water for 6 hours when the molar ratio of the raw material (sodium carboxymethyl cellulose) and the cross-linking agent (dopamine hydrochloride) is 1:0.75.

Fig. 2 is the SEM photograph of the superabsorbent and water-retaining material when the molar ratio of the raw material (sodium carboxymethyl cellulose) and the cross-linking agent (dopamine hydrochloride) is 1:0.75.

Fig. 3 is the water absorption rate of the high water absorption and water retention material of the raw material (sodium carboxymethyl cellulose) and the cross-linking agent (dopamine hydrochloride) according to different molar ratios of the present invention.

Figure 4 is the curve of the water retention rate of the superabsorbent and water-retaining materials prepared when the molar ratio of the raw material (sodium carboxymethyl cellulose) and the cross-linking agent (dopamine hydrochloride) is 1:0.75 in an indoor environment with time.

Figure 5 is the curve of the water absorption rate of the superabsorbent and water-retaining materials prepared when the molar ratio of the raw material (sodium carboxymethyl cellulose) and the cross-linking agent (dopamine hydrochloride) is 1:0.75 with time.

Detailed ways

Example 1

The preparation method of the environment-friendly high water absorption and water retention material of the present invention comprises the following steps:

(1) Preparation of phosphate buffer solution

Mix 12.2 ml of 0.067 mol/L potassium dihydrogen phosphate solution and 87.8 ml of 0.067 mol/L dipotassium hydrogen phosphate solution, respectively, to obtain a phosphate buffer solution with pH=6.0.

(2) Preparation of sodium carboxymethyl cellulose solution

The pH=6.0 phosphate buffer solution was placed on a mixer, and 1.5 g of sodium carboxymethyl cellulose was added and stirred at a stirring speed of 500 r/min to prepare 50 ml of a 3.0% (W/V) homogeneous solution.

(3) Activation of sodium carboxymethyl cellulose

The molar ratio of carboxylic acid group in sodium carboxymethylcellulose to 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide is 1: Add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide at a dosage of 1:0.5, and stir at a stirring speed of 500r/min for 15min.

(4) Preparation of massive sodium carboxymethyl cellulose hydrogel

Dopamine hydrochloride was added with the molar ratio of carboxylic acid groups in sodium carboxymethyl cellulose to dopamine hydrochloride as 1:0.75, and 50 μl of N,N,N',N'-tetramethylethylenediamine was added and stirred continuously for 2h. Put it into a square mold, let it stand for 6 hours, soak the gel in water and wash it repeatedly to remove the residual activator, crosslinking agent and N,N,N',N'-tetramethylethylenediamine.

(5) Drying and molding of bulk sodium carboxymethyl cellulose hydrogel

Freeze-drying the sodium carboxymethyl cellulose hydrogel prepared in step (4) obtains the environmentally friendly high water-absorbing and water-retaining material of the present invention, wherein the freeze-drying temperature is -70° C. and the pressure is 5pa.

Example 2

The preparation method of the environment-friendly high water absorption and water retention material of the present invention comprises the following steps:

(1) Preparation of phosphate buffer solution

Mix 12.2 ml of 0.067 mol/L potassium dihydrogen phosphate solution and 87.8 ml of 0.067 mol/L dipotassium hydrogen phosphate solution, respectively, to obtain a phosphate buffer solution with pH=6.0.

(2) Preparation of sodium carboxymethyl cellulose solution

The pH=6.0 phosphate buffer solution was placed on a mixer, and 1.5 g of sodium carboxymethyl cellulose was added and stirred at a stirring speed of 1000 r/min to prepare 50 ml of a 3.0% (W/V) homogeneous solution.

(3) Activation of sodium carboxymethyl cellulose

The molar ratio of carboxylic acid group in sodium carboxymethylcellulose to 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide is 1: Add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide at a dosage of 0.8:0.6, and stir at a stirring speed of 1000 r/min for 30 min.

(4) Preparation of film-like sodium carboxymethyl cellulose hydrogel (thickness 0.318 cm)

Dopamine hydrochloride was added with the molar ratio of carboxylic acid groups in sodium carboxymethyl cellulose to dopamine hydrochloride at 1:0.5, and 50 μl of N,N,N',N'-tetramethylethylenediamine was added and stirred continuously for 2h. Put the gel into a petri dish with a diameter of 10 cm, let it stand for 6 h, and soak the gel in water to repeatedly wash to remove the residual activator, cross-linking agent and N,N,N',N'-tetramethylethylenediamine.

(5) Drying and molding of film-like sodium carboxymethyl cellulose hydrogel (thickness: 0.318 cm)

The film-like sodium carboxymethyl cellulose hydrogel prepared in step (4) is freeze-dried to obtain the environmentally friendly high water absorption and water-retaining material of the present invention, wherein the freeze-drying temperature is 20° C. and the pressure is 10pa.

Example 3

The preparation method of the environment-friendly high water absorption and water retention material of the present invention comprises the following steps:

(1) Preparation of phosphate buffer solution

Mix 12.2 ml of 0.067 mol/L potassium dihydrogen phosphate solution and 87.8 ml of 0.067 mol/L dipotassium hydrogen phosphate solution, respectively, to obtain a phosphate buffer solution with pH=6.0.

(2) Preparation of sodium carboxymethyl cellulose solution

The pH=6.0 phosphate buffer solution was placed on a mixer, and 1.5 g of sodium carboxymethyl cellulose was added and stirred at a stirring speed of 800 r/min to prepare 50 ml of a 3.0% (W/V) homogeneous solution.

(3) Activation of sodium carboxymethyl cellulose

The molar ratio of carboxylic acid group in sodium carboxymethylcellulose to 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide is 1: Add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide at a dosage of 0.5:0.625, and stir at a stirring speed of 800r/min for 20min.

(4) Preparation of spherical sodium carboxymethyl cellulose hydrogel

Dopamine hydrochloride was added in the molar ratio of carboxylic acid groups in sodium carboxymethyl cellulose to dopamine hydrochloride as 1:1, and 50 μl of N,N,N',N'-tetramethylethylenediamine was added and stirred continuously for 2h. Put it into a spherical mold, let it stand for 6 hours, and soak the gel in water to repeatedly wash to remove the residual activator, cross-linking agent and N,N,N',N'-tetramethylethylenediamine.

(5) Drying and molding of spherical sodium carboxymethyl cellulose hydrogel

Freeze-dry the spherical sodium carboxymethyl cellulose hydrogel prepared in step (4) to obtain the environmentally friendly high water-absorbing and water-retaining material of the present invention, wherein the freeze-drying temperature is 50° C. and the pressure is 3pa.

Figure 1 is a picture of the change of the superabsorbent and water-retaining material of the present invention (block sample as an example) before and after absorbing water in an aqueous solution for 6 hours. From the results in Figure 1, it was found that the volume of sodium carboxymethyl cellulose aerogel increased significantly after 6h of water absorption. During the water adsorption process, the bulk of the sample swells obviously, but there is no dissolution or breakage, which shows that the superabsorbent and water-retaining material prepared by the present invention has good mechanical properties.

FIG. 2 is a SEM photograph of the superabsorbent and water-retaining material of the present invention (block sample as an example). It is found from Figure 2 that the sodium carboxymethyl cellulose aerogel has a rich pore structure. The adsorption of water by the sodium carboxymethyl cellulose aerogel is due to the hydrophilic groups such as -OH, -COOH and -OH on the polymer matrix. -NH ₂ has a strong binding force with water, and the second is the physical adsorption of water by the pore structure, so the abundant pores of sodium carboxymethyl cellulose aerogel can significantly increase the amount of water adsorption.

Fig. 3 is the water absorption rate of the superabsorbent and water-retaining material of the present invention (block sample as an example): respectively take the molar ratio of monomeric carboxylic acid group and dopamine hydrochloride in sodium carboxymethylcellulose as 1:0.25, 1:0.5, 1: 0.75, 1: 1, 1: 1.25 to prepare bulk sodium carboxymethyl cellulose aerogel, soak the aerogel sample in deionized water for 24h at 25°C, after the gel swells and equilibrate, take it out and wipe it quickly Moisture of dry surface, weighed. Calculate the water absorption as follows:

The water absorption rate of sodium carboxymethyl cellulose aerogel can be obtained as shown in Figure 3, which is 252g/g ~ 584g/g, and the molar ratio of carboxylic acid group and dopamine hydrochloride in sodium carboxymethyl cellulose is 1:0.75 The water absorption rate can reach up to 584g/g.

Figure 4 shows the water retention rate of the superabsorbent and water-retaining material of the present invention (block sample as an example): at 25°C, soak the aerogel sample in deionized water for 24 hours, and after the gel is swelled and equilibrated, take out the water on the surface and quickly dry it , weighed. Then, the swelled sodium carboxymethyl cellulose aerogel was stored at room temperature (temperature 20°C, humidity 70%) for 24 hours, the weight of the gel was measured at regular intervals, and the water retention rate was calculated according to the following formula:

The water retention rate of the sodium carboxymethyl cellulose gel can be obtained as shown in Figure 4, ranging from 69.9% to 94.47%. The high water retention rate of the sodium carboxymethyl cellulose gel enables the material to store a large amount of water during use, and then The material is slowly released during use to meet the actual application requirements of the material.

Figure 5: The water adsorption rate of the superabsorbent and water-retaining material of the present invention (block sample as an example): at 25°C, soak the dry gel sample in deionized water, and it is measured that within a certain period of time, the sodium carboxymethyl cellulose gas condenses The variation relationship of the water absorption rate of the glue with time is shown in Figure 5, which is 0.554g/min～1.285g/min, which shows that the superabsorbent and water-retaining material prepared by the present invention has a faster adsorption rate for water. The fast water absorption rate of sodium carboxymethyl cellulose aerogel can make the material quickly achieve high water absorption effect during the use process, and improve the use efficiency of the material.

The above disclosures are only preferred embodiments of the present invention, and of course, the scope of the rights of the present invention cannot be limited by this. Therefore, equivalent changes made according to the claims of the present invention still belong to the scope covered by the present invention.

Claims (6)

1. A preparation method of an environment-friendly high water absorption and water retention material is characterized by comprising the following steps:

(1) preparation of phosphoric acid buffer solution

Taking potassium dihydrogen phosphate, dipotassium hydrogen phosphate and water as solvent systems, and respectively mixing a potassium dihydrogen phosphate solution with the concentration of 0.067mol/L and a dipotassium hydrogen phosphate solution with the concentration of 0.067mol/L according to a certain proportion to obtain a phosphoric acid buffer solution with the pH = 6.0;

(2) preparation of homogeneous solution of natural polysaccharide or polysaccharide derivative

Placing the phosphoric acid buffer solution on a stirrer, and adding and stirring natural polysaccharide or polysaccharide derivatives at a stirring speed of 500-1000 r/min to obtain a uniform solution of the natural polysaccharide or polysaccharide derivatives;

(3) activation of natural polysaccharides or polysaccharide derivatives

Slowly adding an activating agent into the uniform solution of the natural polysaccharide or the polysaccharide derivative, and stirring for 15-30 min at a stirring speed of 500-1000 r/min to obtain an activated polysaccharide solution; the natural polysaccharide or polysaccharide derivative is a carboxyl-containing natural polysaccharide macromolecule or a carboxylated polysaccharide derivative;

(4) preparation of hydrogel of natural polysaccharide or polysaccharide derivative

Adding a cross-linking agent into a polysaccharide solution, continuously stirring for 2 hours on a stirrer at a stirring speed of 500-1000 r/min, adding N, N, N ', N' -tetramethylethylenediamine during stirring, standing for 6 hours during molding of a mold to obtain a gel, soaking the gel in water, repeatedly cleaning to remove unreacted activating agent, the cross-linking agent and the N, N, N ', N' -tetramethylethylenediamine, and obtaining a natural polysaccharide or polysaccharide derivative hydrogel; the cross-linking agent is dopamine hydrochloride; the molar ratio of carboxylic acid groups to the crosslinking agent in the added natural polysaccharide or polysaccharide derivative is 1: 0.75;

(5) dry forming of natural polysaccharide or polysaccharide derivative hydrogel

Carrying out freeze drying on the natural polysaccharide or polysaccharide derivative hydrogel to obtain an environment-friendly high-water-absorption water-retention material;

the total mass of the added natural polysaccharide or polysaccharide derivative accounts for 2-4% of the volume of the uniform solution of the natural polysaccharide or polysaccharide derivative.

2. The method for preparing the environment-friendly high water absorption and retention material according to claim 1, wherein the method comprises the following steps: the activating agent is 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide.

3. The method for preparing the environment-friendly high water absorption and retention material according to claim 2, wherein the method comprises the following steps: the molar ratio of the carboxylic acid groups in the added natural polysaccharide or polysaccharide derivative to the activating agents 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide is 1: 0.5-1.25: 0.25 to 0.625.

4. The method for preparing the environment-friendly high water absorption and retention material according to claim 3, wherein the method comprises the following steps: the natural polysaccharide or polysaccharide derivative is one of sodium carboxymethyl cellulose, alginate and carboxymethyl chitosan with the degree of substitution of 0.7-1.2.

5. The method for preparing the environment-friendly high water absorption and retention material according to claim 1, wherein the method comprises the following steps: the temperature of the freeze drying is-70 to-50 ℃, and the pressure is 1 to 10 pa.

6. The method for preparing the environment-friendly high water absorption and retention material according to claim 1, wherein the method comprises the following steps: the environment-friendly high water absorption and retention material is prepared into blocks, films, spheres or powder.

Images