CN1312185C - Silicatel multifunctional organic alkoxy silane cross linked polyacrylate water suction resin and its preparing method - Google Patents

Abstract

The invention discloses a preparation method of a silicate/multifunctional organoalkoxysilane cross-linked polyacrylate water-absorbing resin. Including: first dilute the acrylic acid monomer into a 40-70% aqueous solution, and neutralize the acrylic acid monomer solution with alkali in an ice-water bath; add silicate or multifunctional organoalkoxysilane as a crosslinking agent, add Initiator, heat up and react for a certain period of time; the product is cooled, dried and pulverized to obtain a polymer water-absorbing resin. The invention provides a new type of cross-linking agent system, and the obtained water-absorbing resin can absorb distilled water and physiological saline up to 1200ml/g and over 100ml/g respectively. The water-absorbing resin of the present invention has a relatively fast degradation rate after being swelled by absorbing liquid.

Description

Preparation method of silicate/multifunctional organoalkoxysilane crosslinked polyacrylate water-absorbent resin

technical field

The invention relates to a synthesis method of polyacrylic acid water-absorbent resin, in particular to a preparation method of silicate/multifunctional organoalkoxysilane cross-linked polyacrylate water-absorbent resin.

Background technique

Water-absorbing resin, also known as super-absorbent, is a new type of functional polymer material that has developed rapidly in the past 20 or 30 years. Because it has dozens of times or even thousands of times its own water absorption capacity and the performance of not dehydrating under pressure, it has been widely used in agriculture, forestry, medical and health, chemical, building materials and other industries. Among them, the cross-linked polyacrylate water-absorbing resin has become the most important commercial water-absorbing resin in the synthetic water-absorbing resin due to its non-toxic safety, high liquid absorption rate, good water retention performance, high mechanical strength of the gel, easy polymerization, and relatively cheap. Resin varieties.

Water-absorbent resins are actually cross-linked hydrophilic polymers. The crosslinking agent of polyacrylic water-absorbing resin is generally a multifunctional organic compound that can react with carboxyl groups, such as bisamide, polyol, unsaturated polyether, allyl ester, urea ester, etc.; or a multivalent metal cation, Such as Ca ²⁺ , Zn ²⁺ , Fe ²⁺ , Cu ²⁺ and other hydroxides, oxides, inorganic salts and organic metal salts. The invention provides a method for synthesizing polyacrylic water-absorbing resin with silicate or polyfunctional organoalkoxysilane as a new crosslinking agent. By controlling the pH value of the system, sodium silicate or polyfunctional alkoxysilane can hydrolyze a large number of silanols formed in the solution. These silanols are more reactive than methanol, which is structurally similar (Synthetic Rubber Industry 1998, 21(6):365-368). Yin WS, Gu TR and others have proved that in the system of polyacrylic acid and its derivatives, silanol groups will condense with each other under the catalysis of acid to form aggregates of Si-O-Si network structure, and some silanol groups will Condensation reaction with carboxylate (COOH) to form Si-OC linkage (Polymer 1997, 38(20), 5173-5178) (Journal of Applied PolymerScience 1997, 64(5), 903-909). In the reaction system of the present invention, acrylic acid is partially neutralized, and the system is still weakly acidic. The silanol groups formed by silicate or polyfunctional organoalkoxysilane are catalyzed by the acid, on the one hand, self-condensation, and at the same time, part The silanol group will undergo a condensation reaction with the carboxylate (COOH) to form a Si-OC link, thereby acting as a crosslink. Finally, a polyacrylic acid water-absorbent resin with high liquid absorption capacity and large liquid absorption rate is obtained. (The research results have been published in Journal of Applied Polymer Science 2004, 91(2), 936-940)

Since the Si-O-C bond has a certain degree of hydrolysis, the water-absorbent resin prepared by this method has a much faster degradation rate than the water-absorbent resin crosslinked by common crosslinking agents after absorbing liquid and swelling, generally within a few days to several days. It can be completely degraded within a month. However, the water-absorbent resin cross-linked by common cross-linking agents is usually difficult to completely degrade after months or even years.

Super absorbent materials have different usage times depending on their usage. For disposable products, such as napkins, sanitary napkins, paper diapers or diapers, incontinence tablets, hemostatic cotton, etc., the products require fast water absorption and large water absorption; at the same time, such products generally consume a lot and waste a lot , environmental pollution must be considered, and water-absorbing materials that are easily degradable should be used as much as possible. The water-absorbing resin of the present invention is very suitable for these occasions. It not only has a high liquid absorption rate and a fast liquid absorption speed, but also is easy to degrade after absorbing water, and is a kind of environmentally friendly water-absorbing material. Studies have proved that the water-absorbing resin of the present invention can also be used as an admixture for moisturizing and improving workability of cement-based materials (such as mortar, concrete, etc.) (Journal of South China University of Technology (Natural Science Edition) 2003, 31 (11), 41 -44) (Chemical Building Materials 2004, (5), 53-56).

Contents of the invention

The purpose of the present invention is to provide a preparation method of silicate/polyfunctional organoalkoxysilane crosslinked polyacrylate water-absorbing resin, obtain a kind of fast degradation speed after absorbing liquid swelling, and has higher Silicate/polyfunctional organoalkoxysilane cross-linked polyacrylate water-absorbent resin with water and saline solution absorption capacity.

The preparation method of the silicate/multifunctional organoalkoxysilane crosslinked polyacrylate water-absorbing resin of the present invention comprises the following steps:

(1) acrylic acid is first formulated as an aqueous solution with a weight concentration of 40 to 70%;

(2) Add silicate or polyfunctional organoalkoxysilane to the monomer solution prepared in step (1) as a crosslinking agent, and neutralize the monomer solution with an alkali neutralizer in an ice-water bath The degree of neutralization is 60-90%; the molar ratio of silicon group to monomer is 0.02-0.25;

When inorganic silicate is used as the cross-linking agent, the cross-linking agent and alkali neutralizing agent are prepared into a mixed solution, and the above-mentioned mixed solution is used to neutralize the monomer solution in an ice-water bath until the neutralization degree is 60-90%. ;

When multifunctional organoalkoxysilane is used as the crosslinking agent, the multifunctional organoalkoxysilane crosslinking agent is directly added to the neutralization agent which has been neutralized with an alkali neutralizing agent in an ice-water bath until the degree of neutralization is 60-90%. in monomer solution;

(3) Adding an initiator of 0.01 to 0.5% by weight of the monomer to the monomer solution obtained in step (2); heating up to 60 to 80°C for reaction, and the reaction time is 0.5 to 2 hours;

(4) After the reaction product obtained in step (3) is cooled, it is placed in an oven at 80-150° C. for drying, and after drying, it is pulverized to obtain a powdery water-absorbing resin.

The above reaction system is a homopolymerization system.

The present invention can also add a second monomer before step (1) or step (3) after step (2), the weight ratio of the second monomer to acrylic acid is 5～50:95～50;

The second monomer is acrylic monomers other than acrylic acid, ester vinyl monomers, acrylamide monomers, nitrile vinyl monomers, vinyl alcohol monomers, vinyl alkyl ethers Monomer, vinylpyrrole, vinylpyridine, dicarboxylic acid monomer or anhydride monomer.

The reaction system at this time is a copolymerization system.

In the present invention, whether it is a homopolymerization system or a copolymerization system, the weight concentration of the total monomers in the reaction system is 15-40%.

The alkali neutralizing agent described in step (2) is sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate or ammoniacal liquor.

The crosslinking agent described in step (2) is inorganic silicate.

The crosslinking agent described in step (2) is an organoalkoxysilane with two or more functional groups.

The initiator described in step (3) is persulfate, hydrogen peroxide or redox initiator.

The initiator used in the present invention is persulfate, hydrogen peroxide or redox initiator, such as potassium persulfate, ammonium persulfate, hydrogen peroxide, ceric nitrate, persulfate-sodium bisulfite, hydrogen peroxide - ferrous sulfate, etc., the amount of which accounts for 0.01 to 0.5% of the weight of the monomer.

The crosslinking agent used in the present invention is selected from inorganic silicates, such as sodium silicate, sodium metasilicate, potassium silicate, etc.; it can also be selected from organoalkoxysilanes with more than two functional groups (containing two functional groups), such as Dimethyldiethoxysilane, diphenyldiethoxysilane, phenyltriethoxysilane, aminopropyltriethoxysilane, etc.

Compared with the prior art, the beneficial effects of the present invention are as follows:

(1) Using silicate or multifunctional alkoxysilane as a new type of crosslinking agent, a water-absorbing resin with the ability to absorb distilled water and saline can reach 1200ml/g and 100ml/g respectively;

(2) The water-absorbent resin prepared by the cross-linking method of the present invention has a faster degradation rate after absorbing liquid and swelling, and its complete degradation time is several days to several months. The degradation rate mainly depends on the liquid absorption of the water-absorbing resin and its absorption rate. The type of liquid. The greater the liquid absorption, the faster the degradation; gels imbibed distilled water degraded faster than gels imbibed saline solutions; gels imbibed monovalent cation salt solutions degraded faster than gels imbibed polyvalent cation salt solutions. The water-absorbing resin of the present invention is suitable for disposable products such as napkins, sanitary napkins, paper diapers or diapers, incontinence tablets, hemostatic cotton, etc., and is a kind of environment-friendly water-absorbing material;

(3) The water-absorbing resin of the present invention can also be used as an admixture for moisturizing and improving workability of cement-based materials (such as mortar, concrete, etc.).

Detailed ways:

Example 1

Weigh 100g of acrylic acid, dilute with 50g of distilled water, weigh 10-25% of the weight of acrylic acid sodium silicate (Na ₂ SiO ₃ 9H ₂ O), for example, 10g, 15g, 20g, 23g of sodium silicate, Dissolve sodium silicate in 110 g of 40% NaOH solution, place the acrylic acid solution in an ice-water bath and stir continuously, add the above mixed lye solution dropwise to the acrylic acid solution for neutralization within 30 minutes, after the neutralization solution is cooled, add 0.01～0.5% potassium persulfate initiator of acrylic acid weight, the present embodiment selects potassium persulfate 0.014g, 0.03g, 0.05g, 0.09g, 0.15g, after stirring evenly, the solution to be reacted is moved into the reaction vessel, and the temperature is raised to 60 ~80°C triggers the reaction of the aqueous phase solution, such as 65°C, 70°C, 75°C, 80°C, the reaction time is 0.5-2 hours, this embodiment chooses 0.5, 0.75, 1.0, 1.25, 1.5 hours, after the product is cooled, place it in Dry in an oven at 100-120°C, and then pulverize to obtain a powdery water-absorbing resin.

Example 2

Weigh 100g of acrylic acid, dilute it with 50g of distilled water, place the acrylic acid solution in an ice-water bath and stir continuously, add 110g of 40% NaOH solution to the acrylic acid solution continuously within 30 minutes for neutralization, after the neutralization solution is cooled, drop while stirring Add polyfunctional organoalkoxysilanes with a molar ratio of silicon groups to acrylic acid of 0.02 to 0.25, such as dimethyldiethoxysilane, diphenyldiethoxysilane, phenyltriethoxysilane, and aminopropyl base triethoxysilane, etc. In this embodiment, the molar ratio of the silicon group content of the polyfunctional organoalkoxysilane to the acrylic acid is selected as 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18. 0.01～0.5% potassium persulfate initiator, the present embodiment selects potassium persulfate 0.014g, 0.03g, 0.05g, 0.09g, 0.15g, after stirring evenly, move the solution to be reacted into the reaction vessel, and heat up to 60～80 °C triggers the reaction of the aqueous solution, such as 60 °C, 65 °C, 70 °C, 75 °C, the reaction time is 0.5 to 2 hours. Dry in an oven at 120°C, and then pulverize to obtain a powdery water-absorbing resin.

Example 3

Weigh 70g of acrylic acid, dilute with 73g of distilled water, weigh 14g of sodium silicate (Na ₂ SiO ₃ 9H ₂ O), dissolve the sodium silicate in 78g of 40% NaOH solution, and place the acrylic acid solution in an ice-water bath for continuous stirring , add the above mixed lye to the acrylic acid solution continuously within 30 minutes for neutralization, after the neutralization solution is cooled, add 30g of acrylamide to dissolve, add 0.03g of potassium persulfate initiator, stir the solution to be reacted into the reaction container In the process, the temperature is raised to 75°C for reaction, and the reaction time is 1.5 hours. After the product is cooled, it is placed in an oven at 100-120°C for drying, and after drying, it is crushed to obtain a powdery water-absorbing resin.

Example 4

Weigh 70g of acrylic acid, dilute with 73g of distilled water, place the acrylic acid solution in an ice-water bath and stir continuously, add 78g of 40% NaOH solution to the acrylic acid solution continuously within 30 minutes for neutralization, after the neutralization solution is cooled, drop while stirring Add 20g of aminopropyltriethoxysilane, add 30g of acrylamide to dissolve, add 0.03g of potassium persulfate initiator, stir evenly, transfer the solution to be reacted into the reaction container, heat up to 70°C for reaction, and the reaction time is 1.5 hours, the product After cooling, place it in an oven at 100-120°C for drying, and then pulverize after drying to obtain a powdery water-absorbing resin.

Claims (7)

1. The preparation method of silicate/polyfunctional organoalkoxysilane cross-linked polyacrylate water-absorbing resin, which is characterized in that it comprises the following steps: (1) acrylic acid is first formulated as an aqueous solution with a weight concentration of 40 to 70%; (2) Add silicate or polyfunctional organoalkoxysilane to the monomer solution prepared in step (1) as a crosslinking agent, and neutralize the monomer solution with an alkali neutralizer in an ice-water bath The degree of neutralization is 60-90%; the molar ratio of silicon group to monomer is 0.02-0.25; When inorganic silicate is used as the cross-linking agent, the cross-linking agent and alkali neutralizing agent are prepared into a mixed solution, and the above-mentioned mixed solution is used to neutralize the monomer solution in an ice-water bath until the neutralization degree is 60-90%. ; When multifunctional organoalkoxysilane is used as the crosslinking agent, the multifunctional organoalkoxysilane crosslinking agent is directly added to the neutralization agent which has been neutralized with an alkali neutralizing agent in an ice-water bath until the degree of neutralization is 60-90%. in monomer solution; (3) Adding an initiator of 0.01 to 0.5% by weight of the monomer to the monomer solution obtained in step (2); heating up to 60 to 80°C for reaction, and the reaction time is 0.5 to 2 hours; (4) After the reaction product obtained in step (3) is cooled, it is placed in an oven at 80-150° C. for drying, and after drying, it is pulverized to obtain a powdery water-absorbing resin. 2. The preparation method according to claim 1, characterized in that a second monomer is added in step (1) or before step (3) after step (2), and the weight ratio of the second monomer to acrylic acid is 5～50:95～50; The second monomer is acrylic monomers other than acrylic acid, ester vinyl monomers, acrylamide monomers, nitrile vinyl monomers, vinyl alcohol monomers, vinyl alkyl ethers monomer, vinylpyrrole, vinylpyridine, dicarboxylic acid monomer or anhydride monomer. 3. The preparation method according to claim 1 or 2, characterized in that the weight concentration of the total monomers in the reaction system is 15-40%. 4. The preparation method according to claim 1 or 2, characterized in that the alkali neutralizing agent in step (2) is sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate or ammonia water. 5. The preparation method according to claim 1 or 2, characterized in that the crosslinking agent in step (2) is an inorganic silicate. 6. The preparation method according to claim 1 or 2, characterized in that the cross-linking agent in step (2) is an organoalkoxysilane with two or more functional groups. 7. The preparation method according to claim 1 or 2, characterized in that the initiator in step (3) is persulfate, hydrogen peroxide or redox initiator.