CN102702425A - Salt-tolerant cationic super-absorbent resin and preparation method and application of salt-tolerant cationic super-absorbent resin - Google Patents

Abstract

The invention discloses a cationic superabsorbent resin and a preparation method thereof. The superabsorbent resin forms a three-dimensional network skeleton mainly containing cationic groups by introducing acrylamide, tertiary amine cationic monomers and quaternary ammonium salt cationic monomers. The preparation method is as follows: add acrylamide, tertiary amine monomer, quaternary ammonium salt monomer, deionized water, crosslinking agent, and initiator solution into the reactor in a certain proportion, pass in nitrogen protection, start stirring, and heat Raise the temperature to 30-95°C and allow the polymerization reaction to proceed for 0.5-3.0h to obtain the product. This cationic superabsorbent resin has good water absorption performance, salt resistance, gel strength and repeated water absorption performance. The most important thing is that it effectively overcomes the easy shrinkage of anionic superabsorbent resins in saline environments containing high-valent metal ions. It is suitable for extensive promotion and development in agriculture, and can also be used in the field of medical and health care to adsorb salt solutions such as urine and blood.

Description

A salt-resistant cationic superabsorbent resin and its preparation method and application

technical field

The invention relates to a salt-resistant cationic superabsorbent resin and its preparation method and application.

Background technique

Superabsorbent Polymers ("SAP" for short), commonly known as water-retaining agents, refer to high-molecular substances with particularly strong water-absorbing capabilities. Superabsorbent resin can quickly absorb deionized water hundreds or even thousands of times heavier than itself, and saline water that is tens to nearly a hundred times heavier than itself. Superabsorbent resin has excellent water absorption, water retention and repeated water absorption properties, so it is widely used in the field of agriculture and forestry to promote plant root development, improve the survival rate of transplanted seedlings, retain water and fertilizer, increase production and income, windbreak and sand fixation, etc. In addition, because superabsorbent resin has a certain ability to absorb salt water, it is also widely used in the field of medical and health care.

At present, the most widely used and the largest output in practical applications is polyacrylic acid (salt) superabsorbent resin, which is mainly divided into synthetic and grafted. The synthetic type is a superabsorbent resin prepared by copolymerization of acrylic acid (salt) and other monomers such as acrylamide. This type of superabsorbent resin can be obtained with high gel strength, strong water retention capacity, and high A product with high water absorption and strong salt resistance. The graft type is a superabsorbent resin prepared by cross-linking and copolymerizing acrylic acid (salt) and natural polymer materials such as starch. Its water absorption performance is poor, but its cost is low.

The groups that play the role of water absorption in the polyacrylic acid (salt) superabsorbent resin structure are mainly anionic groups (this type of superabsorbent resin is called anionic superabsorbent resin), such as carboxylate -COO ^- . During the water absorption process of the anionic superabsorbent resin, the anionic groups are gradually dissociated, and because they are fixed in the three-dimensional network skeleton of the anionic superabsorbent resin, they will repel each other, so that the anionic superabsorbent resin swells and further absorbs water , and finally reach equilibrium. However, salt ions are often encountered in the actual application environment of superabsorbent resins, especially salt water environments containing high-valent metal ions, such as well water for irrigation and root exudates secreted by plants in the soil. The metal ions contained in these salt water environments, especially high-valent metal ions, such as Ca ²⁺ , Mg ^{2+ ,} etc., are easy to chelate with the anion groups in the anionic superabsorbent resin, causing secondary crosslinking , The network structure shrinks or even disintegrates, thereby reducing or even losing its salt resistance and repeated water absorption properties, which limits the promotion of super absorbent resins in practical applications.

At present, there are many studies to improve its salt resistance and anti-salt ion monomer by introducing non-ionic monomers, anionic monomers, cationic monomers and zwitterionic monomers with obvious salt ion resistance into the polyacrylic acid (salt) superabsorbent resin system. However, the superabsorbent resin prepared by this method still maintains the anion skeleton of polyacrylic acid (salt) superabsorbent resin, and cannot avoid the network structure contraction caused by its complexation with high-valent metal ions in the environment. and reduced water absorption.

Contents of the invention

Aiming at the problems existing in the practical application of anionic superabsorbent resins, the invention provides a novel salt-resistant cationic superabsorbent resin and a preparation method thereof.

The general structural formula of the salt-resistant cationic superabsorbent resin provided by the present invention is shown in Formula I:

(formula Ⅰ)

In formula I, n is an integer of 1-10; X represents halogen (including F, Cl, Br, I); Y can be NH or O; R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ can be the same or different, and can be hydrogen, alkyl, alkoxy, alkenyl, aryl, etc.

The cationic superabsorbent resin provided by the present invention is prepared by introducing two kinds of cationic monomers, tertiary amines and quaternary ammonium salts, into polyacrylamide superabsorbent resin, and the main cationic groups in the three-dimensional network skeleton are prepared. super absorbent resin.

The cationic superabsorbent resin can effectively repel metal salt ions in the external water environment, and because the resin skeleton does not contain anionic groups, it effectively overcomes the disadvantage of shrinkage of the anionic superabsorbent resin.

The above-mentioned cationic superabsorbent resin can be prepared specifically according to the method comprising the following steps: under the protection of inert gas, using three monomers acrylamide, tertiary amine cationic monomer, and quaternary ammonium cationic monomer as raw materials, in Under the action of the initiator and the cross-linking agent, the cross-linking polymerization reaction is carried out to obtain the cationic superabsorbent resin.

Wherein, the quaternary ammonium salt cationic monomer adopts a compound containing a quaternary ammonium salt group and a carbon-carbon double bond, and its general chemical structure is as shown in formula II:

(Formula II)

Among them, n is an integer of 1-10; X represents halogen (including F, Cl, Br, I); Y can be NH or O; R ₁ , R ₂ , R ₃ , R ₄ can be the same or different, all can be hydrogen, alkyl, alkoxy, alkenyl, aryl, etc.

The tertiary amine cationic monomer is a compound containing a tertiary amine group and a carbon-carbon double bond, and its general chemical structure is shown in formula III:*

(Formula III)

Among them, n is an integer from 1 to 10; Y can be NH or O; R ₅ , R ₆ and R ₇ can be the same or different, and they can all be hydrogen, alkyl, alkoxy, alkenyl, aryl, etc. .

The cross-linking agent has the function of cross-linking the monomers into a cationic superabsorbent resin with a relatively tight three-dimensional network structure. The present invention preferably uses a neutral cross-linking agent N,N-methylenebis Acrylamide (MBA).

The initiator can effectively initiate the polymerization reaction between monomers, and the present invention preferably adopts potassium persulfate or ammonium persulfate that can produce potassium salt or ammonium salt that is beneficial to plant absorption after reaction decomposition.

In the above method, the mass ratios of the three monomers acrylamide, tertiary amine cationic monomer and quaternary ammonium cationic monomer can be (2.25-4.25): (2.25-2.55): (3.50-5.20).

The added amount of the crosslinking agent is 0.005-0.08wt% of the total mass of the three monomers.

The added amount of the initiator is 0.5-4.5wt% of the total mass of the three monomers.

The reaction temperature of the cross-linking polymerization reaction is 30-95°C, and the reaction time may be 0.5-3.0h.

The reaction solvent of the cross-linking polymerization reaction is water, preferably deionized water.

The inert gas includes nitrogen, argon and other gases.

The cationic superabsorbent resin prepared according to the above method can have a water absorption rate of 200-800 times for deionized water, 30-70 times for 0.9wt% NaCl aqueous solution, and 140-160 mg/LCa ^{2 +} and 40-60mg/LMg ²⁺ of tap water can absorb water up to 80-120 times.

Compared with the industrial polyacrylic acid (salt) anionic superabsorbent resin, the cationic superabsorbent resin prepared by the present invention still does not shrink even if soaked in tap water for 20 hours, while the anionic superabsorbent resin shrinks up to 40-90%. . This shows that the cationic superabsorbent resin prepared by the present invention has excellent salt resistance performance and is suitable for popularization and development in practical applications.

The cationic superabsorbent resin prepared by the present invention was subjected to repeated water absorption experiments in deionized water, 0.9wt% NaCl aqueous solution and tap water, and it was found that even if repeated water absorption-loss experiments were performed five times, the prepared cationic superabsorbent The water absorption rate of the resin can still be maintained at 20-70% of the first water absorption rate, which indicates that the cationic superabsorbent resin has good repeated water absorption capacity and gel stability.

The cationic superabsorbent resin of the present invention has better water absorption performance, salt resistance performance, gel strength and repeated water absorption performance. The defect of shrinkage is suitable for extensive promotion and development in agriculture, and can also be used in the field of medical and health care to adsorb salt solutions such as urine and blood.

Description of drawings

Fig. 1 is the infrared spectrogram of polyacrylamide (a) and cationic superabsorbent resin (b) prepared in Example 1.

Detailed ways

The present invention will be described below through specific examples, but the present invention is not limited thereto.

The experimental methods described in the following examples, unless otherwise specified, are conventional methods; the reagents and materials, unless otherwise specified, can be obtained from commercial sources.

Embodiment 1, preparation cationic superabsorbent resin

Pass N ₂ into the reaction device for 30min, then add 25g of deionized water, start the mechanical stirring; weigh 4.25g of acrylamide, 2.25g of dimethylaminopropylacrylamide, Add 3.50g of ammonium chloride and 0.0005g of MBA into the reaction device, continue to stir and dissolve all the monomers; weigh 0.05g of potassium persulfate and dissolve it in 5mL of deionized water, add all of them into the reaction system, and turn on the heating to control the reaction temperature 30°C; continue to react for 30 minutes after polymerization, wash, dry, and pulverize to obtain a light yellow solid, which is cationic superabsorbent resin.

Figure 1 is the infrared spectrograms of (a) polyacrylamide and (b) cationic superabsorbent resin. It can be seen from the figure that there are characteristic absorptions of salt ion groups at 952cm ^-1 , 1223cm ^-1 , and 1138cm ^-1 peak, indicating that the cationic superabsorbent resin has been successfully prepared.

The cationic superabsorbent resin has a deionized water absorption rate of 350.9g/g, a 0.9wt% NaCl aqueous solution absorption rate of 30.4g/g, and a tap water absorption rate of 85.5g/g. , The rate of absorbing 0.9% normal saline and absorbing tap water can reach 123.7g/g, 15.0g/g and 8.5g/g respectively.

Embodiment 2, preparation cationic superabsorbent resin

Pass N ₂ into the reaction device for 30min, then add 25g of deionized water, start mechanical stirring; weigh 3.75g of acrylamide, 2.35g of diethylaminoethyl methacrylate, 3-acrylamidopropyl trimethyl chloride Add 3.90g of ammonium and 0.0017g of MBA into the reaction device, continue to stir and dissolve all the monomers; weigh 0.15g of potassium persulfate and dissolve it in 5mL of deionized water, add all of them into the reaction system, and turn on the heating to control the reaction temperature to 50 ℃; continue to react for 1.0h after polymerization, wash, dry, and pulverize to obtain a light yellow solid, which is cationic superabsorbent resin.

The cationic superabsorbent resin has a deionized water absorption rate of 467.5g/g, a 0.9wt% NaCl aqueous solution absorption rate of 34.3g/g, and a tap water absorption rate of 87.3g/g. , The rate of absorbing 0.9% normal saline and absorbing tap water can reach 187.6g/g, 19.5g/g and 10.4g/g respectively.

Embodiment 3, preparation cationic superabsorbent resin

Pass N ₂ into the reaction device for 30min, then add 25g of deionized water, start mechanical stirring; weigh 3.25g of acrylamide, 2.45g of ethyl N,N-dimethylaminoacrylate, acryloyloxyethyltrimethyl Add 4.30g of ammonium chloride and 0.0036g of MBA into the reaction device, continue to stir and dissolve all the monomers; weigh 0.25g of potassium persulfate and dissolve it in 5mL of deionized water, add all of them into the reaction system, and turn on the heating to control the reaction The temperature is 55°C; continue to react for 1.0h after polymerization, wash, dry, and pulverize to obtain a light yellow solid, which is cationic superabsorbent resin.

The cationic superabsorbent resin has a deionized water absorption rate of 514.4g/g, a 0.9wt% NaCl aqueous solution absorption rate of 37.0g/g, and a tap water absorption rate of 94.2g/g. , The rate of absorbing 0.9% normal saline and absorbing tap water can reach 231.3g/g, 22.2g/g and 14.1g/g respectively.

Embodiment 4, preparation cationic superabsorbent resin

Pass N ₂ into the reaction device for 30min, then add 25g of deionized water, start mechanical stirring; weigh 2.75g of acrylamide, 2.50g of dimethylaminopropylmethacrylamide, 3-methacrylamidopropyltri Add 4.75g of methylammonium chloride and 0.0069g of MBA into the reaction device, continue to stir and dissolve all the monomers; weigh 0.35g of potassium persulfate and dissolve it in 5mL of deionized water, add all of them into the reaction system, and turn on the heating. Control the reaction temperature to 70°C; continue to react for 1.5 hours after polymerization, wash, dry, and pulverize to obtain a light yellow solid, which is the cationic superabsorbent resin.

The cationic superabsorbent resin has a deionized water absorption rate of 623.8g/g, a 0.9wt% NaCl aqueous solution absorption rate of 40.3g/g, and a tap water absorption rate of 100.6g/g. After five times of repeated water absorption, it absorbs deionized water , The rate of absorbing 0.9% normal saline and absorbing tap water can reach 311.5g/g, 26.2g/g and 18.9g/g respectively.

Embodiment 5, preparation cationic superabsorbent resin

Pass _N2 into the reaction device for 30min, then add 25g of deionized water, start mechanical stirring; weigh 2.25g of acrylamide, 2.55g of dimethylaminoethyl methacrylate, methacryloyloxyethyl trimethyl chloride Add 5.20g of ammonium chloride and 0.008g of MBA into the reaction device, continue to stir and dissolve all the monomers; weigh 0.45g of potassium persulfate and dissolve it in 5mL of deionized water, add them all to the reaction system, and turn on the heating to control the reaction temperature 95°C; continue to react for 3.0 hours after polymerization, wash, dry, and pulverize to obtain a light yellow solid, which is cationic superabsorbent resin.

The cationic superabsorbent resin has a deionized water absorption rate of 698g/g, a 0.9wt% NaCl aqueous solution absorption rate of 46g/g, and a tap water absorption rate of 113g/g. The % normal saline rate and tap water can reach 383.9g/g, 32.2g/g and 23.9g/g respectively.

Claims (10)

1. general structure is suc as formula the cationic water-absorbing resin shown in the I:

(formula I)

In the formula I, n is the integer of 1-10; X represents halogen; Y is NH or O; R ₁, R ₂, R ₃, R ₄, R ₅, R ₆, R ₇Identical or different, its all be selected from following any one: hydrogen, alkyl, alkoxyl group, alkenyl and aryl.

2. cationic water-absorbing resin according to claim 1 is characterized in that: said cationic water-absorbing resin has the three-dimensional network skeleton structure.

3. cationic water-absorbing resin according to claim 1 and 2 is characterized in that: said cationic water-absorbing resin prepares according to each said method among the claim 4-9.

4. the method for preparing claim 1 or 2 described cationic water-absorbing resins; Comprise the steps: under protection of inert gas; With acrylamide monomer, quaternaries cation monomer, tertiary amines cationic monomer is raw material; Under the effect of initiator and linking agent, carry out cross-linking polymerization, obtain said cationic water-absorbing resin.

5. method according to claim 4 is characterized in that: said quaternaries cation monomer, and its general structure is suc as formula shown in the II:

(formula II)

In the formula II, n is the integer of 1-10; X represents halogen; Y is NH or O; R ₁, R ₂, R ₃, R ₄Identical or different, its all be selected from following any one: hydrogen, alkyl, alkoxyl group, alkenyl and aryl;

Said tertiary amines cationic monomer, its general structure is suc as formula shown in the III:

(formula III)

In the formula III, n is the integer of 1-10; Y is NH or O; R ₅, R ₆, R ₇Identical or different, its all be selected from following any one: hydrogen, alkyl, alkoxyl group, alkenyl and aryl.

6. according to claim 4 or 5 described methods, it is characterized in that: said linking agent has can make the monomer crosslinked function of the cationic High hydrophilous resin of three-dimensional net structure comparatively closely that becomes; Said linking agent is specially N,N methylene bis acrylamide; Said initiator is Potassium Persulphate or ammonium persulphate.

7. according to each described method among the claim 4-6, it is characterized in that: said acrylamide monomer, tertiary amines cationic monomer, the monomeric mass ratio of quaternaries cation are followed successively by (2.25-4.25): (2.25-2.55): (3.50-5.20).

8. according to each described method among the claim 4-7, it is characterized in that: the add-on of said linking agent is the 0.005-0.08% of three kinds of monomer total masses; The add-on of said initiator is the 0.5-4.5% of three kinds of monomer total masses.

9. according to each described method among the claim 4-8, it is characterized in that: the temperature of reaction of said cross-linking polymerization is 30-95 ℃, and the reaction times is 0.5-3.0h; The reaction solvent of said cross-linking polymerization is a water.

Among the claim 1-3 each described cationic water-absorbing resin in agricultural Application for Field or the application in medicine and hygiene fields.

Images