CN100558760C - Method for producing super absorbent resin - Google Patents

Abstract

A high-hydroscopicity resin in powder form, not dissolved in water, able to absorb water, urine and blood and low in soluble component is prepared from: 1) adding a cross-linking agent into an acid group-containing monomer aqueous solution with a neutralization rate of more than 50mole% to perform free radical polymerization reaction, wherein the acid group-containing monomer can be selected from acrylic acid, methacrylic acid, 2-allylamine-2-methylpropanesulfonic acid or a mixture thereof, and the monomer aqueous solution contains 0-5 wt% of water-soluble polymer; 2) the monomer solution, the catalyst and the water-absorbent resin with the particle size less than 100 μm stay in a mixer with at least one screw for 3-600 seconds; 3) drying with hot air at 100-250 deg.C, pulverizing, and sieving; 4) coating treatment of a surface cross-linking agent; 5) heating the surface at 80-230 deg.C; and 6) adding an inert inorganic salt powder.

Description

Manufacturing method of superabsorbent resin

technical field

The present invention mainly provides a method for producing superabsorbent resin, through which the polymerization reaction can be made more uniform to reduce the soluble content of the water-absorbent resin, and the operability of the recycling process or finished fine powder can be improved.

Background technique

The superabsorbent resin has a strong water retention capacity, can absorb a hundred times or even a thousand times its own weight of water, and can swell after absorbing water, and maintain a non-flowing state, even if pressure is applied, it will not leak, and the absorbed water Can be released slowly in the atmosphere. Due to the above characteristics, it was first used as a soil water retaining agent in agriculture and forestry. In recent years, due to considerable progress in the production technology of superabsorbent resin, it is also widely used in sanitary products such as diapers, adult incontinence products and women's hygiene. Water-absorbing agent for supplies and fresh-keeping applications for food preservation, etc.

The component materials of the superabsorbent resin include hydrolyzed starch-acrylonitrile (hydrolyzedstarch-acrylonitrile) graft polymer (Japanese Open Patent Gazette 49 (1974)-43,395), neutralized starch acrylic acid graft polymer (Japan Publication Showa 51(1976)-125,468), saponified ethylene propylene acetate copolymer (Japanese Patent Publication Showa 52(1977)-14,689), hydrolyzed acrylonitrile copolymer or acrylamide copolymer (Japanese Patent Publication Showa 531978) -15,959), and partially neutralized polyacrylic acid (Japanese Patent Publication Showa 55 (1980)-84,304), etc. Among them, the superabsorbent resin obtained by using acrylic acid and acrylate for cross-linking polymerization accounts for the largest part and is the most economical. The reason is that acrylic acid can be quickly obtained from the market, and the obtained superabsorbent resin has high water absorption capacity, and It has low manufacturing cost and the most economic benefits, so it has become the most popular superabsorbent resin.

At present, the method of polymerizing acrylic acid and acrylate to form a superabsorbent resin has been successfully developed in many aspects, and many of them have been used in industrial production. (1973)-42,466, Japanese Laid-Open Patent Publication Showa 58(1983)-49,714 carrying out polymerization reaction on a conveyor belt, Japanese Laid-Open Patent Publication Showa 59(1984)-37,003 carrying out reverse phase suspension polymerization reaction, or monomer Japanese Patent Publication Showa 62(1987)-53,309, etc., which are sprayed or coated on a fiber substrate for polymerization.

In addition to acrylic acid, other carboxyl-containing monomers required for the superabsorbent resin produced by the present invention can also use other water-soluble monomers with unsaturated double bonds, such as: methacrylic acid, or maleic acid, or fumaric acid acid, or 2-propenylamine-2-methylpropanesulfonic acid, etc. There are no specific restrictions on the selection of monomers. Only one type can be used, and multiple monomers can also be used together. Other hydrophilic monomers with unsaturated double bonds can also be added according to the situation, such as: acrylamide, methacrylamide , 2-hydrocarbyl ethyl acrylate, 2-hydrocarbyl ethyl methacrylate, methyl acrylate, ethyl acrylate, dimethylamine acrylamide, acrylamide trimethylammonium chloride, but the amount added is not to damage the superabsorbent resin The physical properties are the principle.

Before free radical polymerization, the concentration of monomer aqueous solution should be controlled between 20wt% and 55wt%, and the appropriate concentration is between 30wt% and 45wt%. When the concentration is below 20wt%, the hydrated body after polymerization is too soft It is viscous and unfavorable to mechanical processing. The added concentration is above 55wt%, which is close to the saturation concentration.

The carboxylic acid group of the carboxyl-containing monomer should be partially neutralized to control the pH value of the finished product, making it neutral or slightly acidic. The neutralizer is lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, Potassium Carbonate, Lithium Bicarbonate, Sodium Bicarbonate, Potassium Bicarbonate and Ammonia. The carboxylic acid groups of the carboxyl-containing monomers will be partially neutralized into lithium salts, sodium salts, potassium salts, ammonium salts or two or more mixed salts, the neutralization concentration molar percentage is 45mol% to 85mol%, and the appropriate concentration is 50mol% to 75mol%, the pH value of the finished product will be low when the neutralization concentration molar percentage is below 45mol%, and the pH value of the finished product will be high when the neutralization concentration molar percentage is above 85mol%, if the pH value of the finished product is not neutral or slightly acidic When it comes into contact with the human body accidentally, it is not suitable or safe.

Water-soluble polymers can also be added to the monomer aqueous solution before free radical polymerization to reduce costs, such as: partially saponified or fully saponified polyvinyl alcohol, polyethylene glycol, polyacrylic acid, Polyacrylamide, starch or starch derivatives such as methyl cellulose, methyl cellulose acrylate, ethyl cellulose and other polymers; the molecular weight of these water-soluble polymers is not particularly limited, and the preferred water-soluble polymers For starch, partially saponified or fully saponified polyvinyl alcohol, etc. alone or in combination. The appropriate percentage by weight of these added water-soluble polymers in the superabsorbent resin is 0 to 20wt%, but 0 to 10wt% is better, and 0 to 5wt% is especially preferred. Adding more than 20wt% will affect the physical properties and make the physical properties change. Difference.

Before free radical polymerization, a free radical polymerization crosslinking agent should be added to the unreacted monomer solution. The free radical polymerization crosslinking agent can be selected from a compound with two or more unsaturated double bonds, such as : N,N-Bis(2-propenyl)amine, N,N'-Methylenebisacrylamide, N,N'-Methylenebismethacrylamide, Propylene Acrylate, Ethylene Glycol Diacrylate , polyethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, glycerin triacrylate, glycerin trimethacrylate, trimethylolpropane trimethacrylate, three Methanol propane triacrylate, N, N, N-tris(2-propenyl) amine, ethylene glycol diacrylate, dipropylene triethylene glycol ester, etc., and those with two or more epoxy groups can also be selected Compounds such as sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, diglycerol polyglycidyl ether Glyceryl ether etc. After the free radical reaction, the superabsorbent resin can have a proper degree of crosslinking, so that the colloid of the superabsorbent resin can have proper processability. The radical polymerization crosslinking agent can be used alone or in combination of two or more. The appropriate additive amount of free radical polymerization crosslinking agent is between 0.001wt% and 5wt% by weight (based on the total solid content of the reactant), and the more appropriate amount is between 0.01wt% and 3wt%. When the amount is less than 0.001wt%, the hydrated body after polymerization is too soft and viscous, which is not conducive to mechanical processing, and when the additive amount is more than 5wt%, the water absorption is too low, which reduces the performance of the resin.

The polymerization reaction starts with the generation of free radicals by the decomposition of the radical polymerization initiator. Free radical initiator can be selected thermal decomposition type initiator, suitable thermal decomposition type initiator has peroxide, as: hydrogen peroxide, di-tert-butyl peroxide, peroxide amide or persulfate (ammonium salt, alkali Metal salts), etc., and azo compounds such as: 2,2'- azobis (2-amidinopropane) dihydrochloride; also can use a reducing agent to make a redox initiator, such as: acidic sub Sulfate, thiosulfate, ascorbic acid or ferrous salt; or a combination of redox initiators and thermal decomposition initiators. First, the redox initiators react to generate free radicals. When the free radicals are transferred to the monomer That is to initiate the polymerization reaction, because a large amount of heat will be released during the polymerization reaction and the temperature will rise. When the temperature reaches the decomposition temperature of the thermal decomposition initiator, it will trigger the decomposition of the second thermal decomposition initiator. , so that the entire polymerization reaction is more complete. Generally, the appropriate amount of free radical polymerization initiator is 0.001wt% to 10wt% (based on the weight of the neutralized acrylate), and the more appropriate amount is between 0.1wt% and 5wt%. When the amount is below 0.001wt%, the reaction Too slow is unfavorable to economic benefits, and when the usage amount is above 10wt%, the reaction heat is difficult to control if the reaction is too fast.

The monomer solution can be polymerized on a conveyor belt reactor or a horizontal reactor equipped with stirring blades. The prepared superabsorbent gel is first cut into small gels with a diameter of less than 20mm by a mincer. The diameter is better below 10mm, so as to facilitate the subsequent drying step.

The drying temperature can be dried at 100°C to 250°C, and the drying temperature is suitable for drying at 120°C to 180°C. When the drying temperature is below 120°C, the drying time will not be economical if the drying time is too long. The drying temperature is 180°C. Drying above ℃ makes the cross-linking agent carry out the cross-linking reaction earlier, so that in the subsequent drying process, the residual monomer cannot be effectively removed due to the high cross-linking, so as to achieve the effect of reducing the residual monomer.

After drying, it is crushed, screened to fix the particle size, and then coated with a surface cross-linking agent. Screening and fixed particle size is preferably between 0.06mm and 1.00mm, preferably between 0.10mm and 0.850mm. Fine powder with a particle size below 0.06mm will increase the dust of the finished product, and particles with a particle size above 1.00mm will slow down the water absorption rate of the finished product.

The water-absorbent resin is an insoluble hydrophilic polymer, and the resin has a uniform bridging structure inside. Generally, in order to improve the quality, such as: increase the absorption rate, increase the colloid strength, improve the anti-caking property, liquid permeability, etc., will Further bridging is carried out on the surface of the resin. This surface cross-linking treatment uses a multi-functional cross-linking agent that can react with acid groups. Many patents have been proposed before this; such as: dispersing super absorbent resin and The cross-linking agent is subjected to surface cross-linking treatment in an organic solvent (JP-A-56-131608, JP-A-57-44627, JP-A-58-42602, JP-A58-117222), and the cross-linking agent is directly mixed with an inorganic powder. Linking agent and crosslinking agent solution are mixed with super absorbent resin for treatment (JP-A60-163956, JP-A-60-255814), steam treatment after adding crosslinking agent (JP-A-1-113406), using organic solvent , water and polyalcohol for surface treatment (JP-A-63-270741, JP-A-64-50707, JP-A-1-292004), just use organic solution, water, ether (ether) compound (JP-A -2-153903), etc.; although these surface treatment methods can increase the absorption rate and increase the water absorption rate under pressure, they will cause excessive reduction in retention and reduce the performance of practical applications.

After screening and fixing the particle size, according to the present invention, the cross-linking agent that can react simultaneously when the surface can be treated is a polyhydric alcohol such as: glycerol, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, etc. Glycol, propylene glycol, 1,4 butanediol, trihydrocarbyl methylpropane, sorbitol, etc.; or polyamines such as: ethylenediamine, diethylenediamine, triethylenediamine, polyethylenediamine can be used; or Use compounds with two or more epoxy groups such as: sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol Alcohol dimer glycidyl ether, diglycerol polyglycidyl ether, etc.; also can use alkylene carbonate such as: ethylene glycol carbonate, 4-methyl-1,3-dioxolane-2- Ketone, 4,5-dimethyl-1,3-dioxolan-2-one, 4,4-dimethyl-1,3-dioxolan-2-one, 4- Ethyl-1,3-dioxolan-2-one, 1,3-dioxan-2-one, 4,6-dimethyl-1,3-dioxane alkan-2-one or 1,3-dioxepan-2-one, etc. The surface crosslinking agent can be used alone or in combination of two or more. The appropriate additive amount of the surface crosslinking agent is between 0.001wt% and 10wt% by weight (based on the total solid content of the reactant), and the more appropriate amount is between 0.005wt% and 5wt%. When the weight percent is less than 0.001wt%, the effect cannot be shown, and when the surface crosslinking agent additive amount is more than 10wt%, the water absorption is too low and the performance of the resin is reduced.

When the surface cross-linking agent is coated, the addition of the surface cross-linking agent can be directly added to the surface cross-linking agent, or added as a surface cross-linking agent aqueous solution, or added as a surface cross-linking agent hydrophilic organic solvent aqueous solution, hydrophilic Water-based organic solvents such as methanol, ethanol, propanol, isobutanol, acetone, methyl ether, diethyl ether, etc. are not particularly limited, as long as they can form a solution, methanol and ethanol are preferred. When the surface crosslinking agent is added, inert inorganic salt powder can be added to the superabsorbent resin to help the solution disperse. The inert inorganic salt powder can be aluminum sulfate, or silicon dioxide, or aluminum oxide, or magnesium oxide, etc. or a mixture thereof. Among them, aluminum sulfate and silicon dioxide are preferred. The addition range of the inert inorganic salt powder is between 0.005wt% and 10.0wt%, preferably 0.01wt% to 4.0wt%.

After coating the surface crosslinking agent, heat treatment at 80° C. to 230° C. enables the surface crosslinking agent to undergo a crosslinking reaction and the internal crosslinking agent to undergo a crosslinking reaction to achieve the effect of the present invention. If the processing temperature is below 80°C, the cross-linking reaction time is too long, which is not economical. When the processing temperature is ≥230°C, the resin is easy to deteriorate and affect the quality. As for the treatment time, the appropriate time is 2 to 150 minutes, which is adjusted according to the treatment temperature. The higher the temperature, the shorter the time, and the lower the temperature, the longer the time.

Since the superabsorbent resin has the phenomenon of agglomeration after moisture absorption, in order to avoid the agglomeration after moisture absorption of the superabsorbent resin used in high-humidity areas, which will cause rough processing, the surface of the superabsorbent resin is generally coated with inert inorganic salt powder or Surfactant, make the surface slightly lipophilic so that the superabsorbent resin retains the property that it is not easy to agglomerate after absorbing moisture. This inert inorganic salt powder can be selected from aluminum sulfate, or silicon dioxide, or aluminum oxide, or magnesium oxide, or calcium oxide, or kaolin, or calcium carbonate, or magnesium carbonate, etc. or a mixture thereof; usually the addition of this inert inorganic salt powder The amount is related to the particle size of the inorganic salt powder. If the particle size is smaller, the specific surface area of the inorganic salt powder is larger, so the effective amount of the inert inorganic salt powder can be smaller, and the range of addition of the inert inorganic salt powder is between 0.005wt% and 10.0wt% by weight, wherein 0.01 % by weight to 4.0% by weight is preferred. The particle size of the inert inorganic salt powder is 0.001μM to 100μM. If the inorganic salt powder with particles smaller than 0.001μM is used, the cost will be too high and it is not conducive to industrial production. If the inorganic salt powder with particles larger than 100μM is used, the addition amount will affect the high water absorption. The problem of resin absorption. Inert inorganic salt powder can be added alone or along with surfactants or organic compounds with viscosity. The surfactants or organic compounds with viscosity can be selected from non-ionic surfactants with an HLB value of 12 or more, or water-soluble anionic surfactants , or cationic surfactants, or anionic and positive amphoteric surfactants, or mixtures thereof, usually surfactants or viscous organic compounds can use glycerin, ethylene glycol, hexyl alcohol, polyoxyethylene alcohol, or polyethylene glycol Alcohol, or polyethylene glycol stearate, or polyethylene glycol hexaester stearate, or polyoxyethylene nonphenylene ether, or polyoxyethylene octylphenyl ether, or polyoxyethylene dodecylphenyl ether, or Polyoxyethylene alkyl ether, or polyoxyethylene lauryl ether, etc., this surfactant or viscous organic compound can be added in the form of an aqueous solution or added separately, and the appropriate amount of surfactant or viscous organic compound additive is in weight percent Between 0.001wt% and 5wt% (based on the total solid content of the reactants), the more appropriate weight percentage is between 0.01wt% and 3wt%.

1. At present, there are many methods of polymerizing acrylic acid and acrylate to form superabsorbent resins, which have been used in industrial production, including the Japanese Open Patent Publication Showa 48 (1973)-42,466 of cast film polymerization, which is polymerized on the conveyor belt The Japanese Laid-Open Patent Publication Showa 58(1983)-49,714 of the reaction, the Japanese Laid-open Patent Publication Showa 59(1984)-37,003 of the reverse phase suspension polymerization reaction, or the method of spraying or coating the monomer on the fiber substrate to carry out the polymerization reaction Japanese Patent Publication Showa 62(1987)-53,309, etc. However, the above polymerization methods all have the disadvantages that the reaction is not easy to control and the process is unstable, and the soluble content of the obtained superabsorbent resin is relatively high.

2. Generally speaking, the dried superabsorbent resin needs to be pulverized, screened to fix the particle size, and then coated with a surface crosslinking agent. The suitable particle size for screening is between 60 μm and 1000 μm, more preferably between 100 μm and 850 μm. The water-absorbent resin with a particle size greater than 850 μm will slow down the water absorption rate of the final product and needs to be ground again; the water-absorbent resin with a particle size of less than 100 μm will cause a high amount of dust in the finished product, so recycling steps are required to save costs and Increase productivity. In general, recovery methods can be:

(1) On the premise that the quality of the finished product is not affected, the water-absorbent resin with a particle size of 100 μm to 850 μm is mixed with the water-absorbent resin with a particle size of less than 100 μm in an appropriate ratio.

(2) In the way of humidification, the water-absorbing resin with a particle size of less than 100 μm is adhered to the surface of the water-absorbing resin with a particle size of 100 μm to 850 μm, so as to achieve the functions of recycling and reducing dust.

The above two recovery methods have the disadvantages of high dust volume in operation or poor recovery efficiency.

Contents of the invention

The object of the present invention is to provide a method for producing a superabsorbent resin.

In order to achieve the above object, the present invention provides a powdery, water-insoluble superabsorbent resin that can absorb water, urine or blood and has a low content of soluble matter. Its manufacturing method includes:

1) Adding a crosslinking agent to carry out free radical polymerization in an aqueous solution of carboxyl-containing monomers with a neutralization rate of 50 mole% or more. The carboxyl-containing monomers can be selected from acrylic acid, methacrylic acid, and 2-propenylamine-2-methylpropanesulfonate Acid or its mixture, and the monomer aqueous solution contains 0-5wt% water-soluble polymer;

2) The monomer aqueous solution, the polymerization initiator and the water-absorbent resin with a particle size of less than 100 μm are retained in a mixer with at least one screw for 5 to 600 seconds;

3) Drying, crushing and screening with hot air at a temperature of 100°C to 250°C;

4) Surface crosslinking agent coating treatment;

5) Surface treatment by heating at a temperature of 80°C to 230°C; and

6) Add inert inorganic salt powder.

In the method, the water-soluble polymer is polyvinyl alcohol, starch or starch derivatives or a mixture thereof.

In the method, the crosslinking agent can be a water-soluble compound having two or more functional groups that can participate in free radical reactions.

The method, wherein the neutralizing agent can be lithium hydroxide, or sodium hydroxide, or potassium hydroxide, or lithium carbonate, or sodium carbonate, or potassium carbonate, or lithium bicarbonate, or sodium bicarbonate, or potassium bicarbonate or a mixture thereof.

In the method, the polymerization initiator can be a thermal decomposition initiator or a redox initiator.

In the described method, among the polymerization initiators, the thermal decomposition initiators can be hydrogen peroxide, hydrogen peroxide, di-tert-butyl peroxide, amide peroxide, persulfate, 2,2'-even Nitrobis(2-amidinopropane) dihydrochloride or 2.2'-azobis(N,N-dimethyleneisobutyramide) dihydrochloride.

In the method, among the polymerization initiators, the redox initiators may be acidic sulfites, thiosulfates, ascorbic acid, ferrous sulfates or persulfates.

Described method, its mixer comprises following assembly:

1) Reactive monomer feed pipe containing crosslinking agent;

2) Polymerization initiator feeding pipe;

3) Feed port for superabsorbent resin with fine particle size;

4) more than one screw;

5) Mixer body;

6) Fine particle recovery machine port;

7) Reaction material outlet.

In the described method, the residence time is preferably 20 to 30 seconds, more preferably within 20 seconds, especially 10 seconds.

In the described method, if the residence time is less than 5 seconds, the reaction materials will not be mixed uniformly, and the polymerization reaction temperature in the latter stage will be unstable, and there will be a phenomenon of high local temperature, and the soluble content will be relatively high.

According to the method, the particle size distribution range after screening is between 0.05mm and 1mm.

In said method, the surface cross-linking agent is polyhydric alcohol, or polyethylene glycol diglycidyl ether, or alkylene carbonate or a mixture thereof.

In the method, the range of adding the surface crosslinking agent is 0.005wt%-5.0wt%.

In said method, the inert inorganic salt powder can be aluminum sulfate, or aluminum oxide, or magnesium oxide, or calcium oxide, or kaolin, or silicon dioxide, or calcium carbonate, or magnesium carbonate or a mixture thereof. 15. The method according to claim 14, wherein the addition range of the inert inorganic salt powder is 0.01wt%-4.0wt%.

In detail, 1) The method for producing superabsorbent resin provided by the present invention uses a mixer with at least one screw to uniformly mix the reaction materials before polymerization, and then discharge them into the reactor to complete the polymerization reaction, as follows Its process description (see Figure 1): the reactive monomer containing the crosslinking agent enters the mixer body from the reactive monomer feeding pipe 1 in Figure 1, and the polymerization initiator enters the mixer body from the polymerization initiator feeding pipe 2 After entering the body, the reaction monomer and the polymerization initiator are pushed forward uniformly and unidirectionally through the rotation of more than one screw 3, and finally discharged from the reaction material outlet 7 into the belt reactor or batch reactor to complete Polymerization. Utilizing the production mode provided by the present invention can not only improve the mixing uniformity of the monomer solution and the catalyst, but also make the reaction temperature more stable and improve the production quality. In addition, the use of a mixer with at least one screw can ensure that the material moves forward in one direction without backflow, thereby avoiding the formation of a gel-like solid caused by the polymerization reaction material staying in the mixer for too long, causing the process Operational inconvenience. The length of the residence time will affect the uniformity of the mixing of the reaction monomer and the catalyst, and then affect the reaction situation and the soluble content of the finished product. Generally speaking, if the residence time is long, the reaction monomer and the catalyst have enough time to mix, the reaction will be more uniform and stable, and the soluble content is relatively low, but the residence time should not be too long to avoid excessive formation of reaction materials in the mixer. Viscous prepolymer or gelatinous solid. As for the residence time, it can be controlled by the length and rotational speed of the screw.

2) The method for recovering fine-particle-diameter water-absorbent resin provided by the present invention is described as follows: the reactive monomer containing the crosslinking agent enters the mixer body from the reactive monomer feed pipe 1 in Fig. 2, and the polymerization initiator The polymerization initiator feed pipe 2 enters the body, and the water-absorbent resin with a particle size of less than 100 μm enters the body from the recycling machine 6 through the fine-particle water-absorbent resin feed port 3, and then reacts monomers, polymerization initiators and fine particles. The water-absorbent resin with particle size is rotated by more than one screw, and is pushed forward uniformly and unidirectionally, and finally discharged from the reaction material outlet 7, and enters the belt reactor or batch reactor to complete the polymerization reaction.

In the present invention, before the polymerization reaction, the monomer containing the crosslinking agent, the polymerization initiator and the water-absorbing resin with a particle size of less than 100 μm are retained in a mixer with at least one screw, and the reaction can be achieved by adjusting the residence time. The monomer and the catalyst are fully mixed to improve the uniformity of the reaction, and can also achieve the effect of recovering the fine particle size water-absorbing resin. In this way, the uniformity and stability of the entire polymerization reaction are relatively improved, and the recovery process or the steps of the finished fine powder are simplified.

In order to make the process of the present invention more stable, reduce the soluble content and recover the characteristics of fine particle size water-absorbent resin, the following analysis and records must be done:

(1) Soluble matter content: First weigh 0.5 g of superabsorbent resin, then add 185 g of 0.9% saline, stir at 500 rpm for one hour, and filter out the SAP extract with filter paper. Finally, 20 g of the extract was weighed, first titrated with 0.1N NaOH, and then back-titrated with 0.1N HCl to obtain the content of SAP solubles.

(2) Process stability: record the reaction temperature every 15 minutes as a basis for judgment. In addition, attention should be paid to the mixing and recovery of the reaction material and the fine particle size water-absorbent resin.

(3) Absorption rate of the finished product: First weigh 2 g of superabsorbent resin, then add 50 ml of 0.9% saline solution, observe and record the time when the vortex disappears at 600 rpm.

(4) The absorption rate of the finished product under a pressure of 49g/cm ² .

Description of drawings

Fig. 1 is a schematic diagram of a screw mixer of the present invention.

Fig. 2 is a schematic diagram of a screw mixer combined with a fine powder recovery machine of the present invention.

Detailed ways

The following examples illustrate the present invention, but the patent and technical scope of the present invention are not limited by these examples.

Embodiment one:

(1) First add 17.35kg of 49% sodium hydroxide aqueous solution and 30.52kg of water in a 100L reaction tank, and then slowly add 22.53kg of acrylic acid into the aqueous sodium hydroxide solution under ice bath for neutralization; at this time, the monomer Concentration 38.6wt% aqueous solution, in which 68mole% acrylic acid is partially neutralized to sodium acrylate.

(2) Add 33.80 g of glycerol polyethylene glycol triglycidyl ether (n=7) to the partially neutralized acrylic acid aqueous solution, and maintain the temperature at about 20°C.

(3) Control the flow rate of the above-mentioned sodium acrylate solution to be 70.4kg/hr, and then make it enter the mixing body from 1 in Fig. 2 of the description of the present invention.

(4) Control the feeding amount of the water-absorbing resin with a particle size of less than 100 μm (hereinafter collectively referred to as fine powder) to 1.02 kg/hr, and enter the mixing body from 6. in Figure 2 of the specification of the present invention.

(5) Control the flow rate of L-ascorbic acid, sodium persulfate and 2,2-azobis(2-amidinopropane) to 12.99g/hr, 162.40g/hr and 162.40g/hr respectively, so that it can pass through the invention 2 in Figure 2 of the instruction manual enters the mixing body.

(6) Utilize a mixer with at least one screw to uniformly mix the above-mentioned sodium acrylate solution, polymerization initiator and fine powder, control the screw speed so that the residence time of the reaction material is 10 seconds, and the viscosity of the discharged reaction material is 7.0 cP (measured with a B-type viscometer).

(7) The uniformly mixed reaction materials are continuously discharged into the belt reactor to complete the polymerization reaction. The results showed that the temperature of the polymerization reaction was stable, and there was no colloid formation on the screw or at the outlet elbow.

(8) Cut the colloid into gels with a diameter of 2 mm or less by means of a cutting mill.

(9) Dry at 170° C. for 1 hour; use a sieve to sieve with a fixed particle size of 0.1 mm to 0.85 mm to obtain a powdery superabsorbent resin.

(10) Weigh 100 g of the superabsorbent resin, add 4 g of ethylene glycol carbonate/water/methanol=1/1/1 (weight ratio) solution, and heat at 215° C. for 10 minutes.

(11) After cooling, add 1g of calcium carbonate (product name produced by Formosa Plastics: NS-2000) and 2g of 20% glycerin aqueous solution, and mix uniformly to obtain a high-performance superabsorbent resin. The analyzed soluble content is 2.43%. The speed is 75.24 seconds, and the absorption rate under the pressure of 49g/cm ² is 25.48g/g.

Embodiment two:

Repeat embodiment one, but the feeding amount of step 4 changes 1.53kg/hr into. The results showed that the reaction material and the fine powder were well mixed, the temperature of the polymerization reaction was stable, and there was no colloid formed on the screw or at the outlet elbow. The viscosity of the discharged reaction material is 7.2cP, the soluble content of the finished product is 2.51%, the absorption rate is 71.75 seconds, and the absorption rate under the pressure of 49g/ ^cm2 is 25.39g/g.

Embodiment three:

Repeat embodiment one, but the feeding amount of step 4 changes 2.04kg/hr into. The results showed that the reaction material and the fine powder were well mixed, the temperature of the polymerization reaction was stable, and there was no colloid formed on the screw or at the outlet elbow. The viscosity of the discharged reaction material is 7.8cP, the soluble content of the finished product is 2.49%, the absorption rate is 67.23 seconds, and the absorption rate under the pressure of 49g/ ^cm2 is 25.17g/g.

Embodiment four:

Repeat embodiment one, but the feeding amount of step 4 changes 3.06kg/hr into. The results showed that the reaction material and the fine powder were well mixed, the temperature of the polymerization reaction was stable, and there was no colloid formed on the screw or at the outlet elbow. The viscosity of the discharged reaction material is 8.5cP, the soluble content of the finished product is 2.50%, the absorption rate is 61.02 seconds, and the absorption rate under the pressure of 49g/ ^cm2 is 24.87g/g.

Embodiment five:

Repeat embodiment one, but the feeding amount of step 4 changes 4.08kg/hr into. The results showed that some fine powders were suspended on the reaction materials and the reaction temperature increased compared with the previous jump range, but there was still no colloid formed on the screw or the outlet elbow. The viscosity of the discharged reaction material is 9.4cP, the soluble content of the finished product is 2.71%, the absorption rate is 55.46 seconds, and the absorption rate under the pressure of 49g/ ^cm2 is 24.01g/g.

Embodiment six:

Repeat embodiment one, but the feeding amount of step 4 changes 5.12kg/hr into. The results showed that the amount of fine powder suspended on the reaction material increased and the reaction temperature was unstable, and some colloids formed by the fine powder after absorbing water adhered to the screw. The viscosity of the discharged reaction material is 11.2cP, the soluble content of the finished product is 3.42%, the absorption rate is 50.89 seconds, and the absorption rate under the pressure of 49g/ ^cm2 is 22.89g/g.

Embodiment seven:

(1) First add 23.93kg of 49% sodium hydroxide aqueous solution and 44.07kg of water into a 100L reaction tank, and then slowly add 32.00kg of acrylic acid into the aqueous sodium hydroxide solution under ice bath for neutralization; at this time, the monomer Concentration 38.44wt% aqueous solution, in which 66mole% acrylic acid is partially neutralized to sodium acrylate.

(2) Add 98.45 g of glycerol polyethylene glycol triglycidyl ether (n=20) to the partially neutralized acrylic acid aqueous solution, and maintain the temperature at about 20°C.

(3) Control the flow rate of the above-mentioned sodium acrylate solution to be 60.5kg/hr, so that it enters the mixing body from 1. in Fig. 2 of the description of the present invention.

(4) Control the feeding amount of the water-absorbing resin with a particle size of less than 100 μm (hereinafter collectively referred to as fine powder) to 0.88 kg/hr, and enter the mixing body from 6. in Figure 2 of the specification of the present invention.

(5) Control the flow rate of L-ascorbic acid, di-tert-butyl hydroperoxide and potassium persulfate to be 11.25g/hr, 139.13g/hr and 139.13g/hr respectively, so that it passes through 2 in Fig. 2 of the present invention .Into the twin-screw mixing body.

(6) Utilize at least a mixer above the screw rod to uniformly mix the above-mentioned sodium acrylate solution, polymerization initiator and fine powder, control the screw speed so that the residence time of the reaction material is 10 seconds, and the reaction material viscosity of discharging is 13.1cP (with B-type viscometer measured).

(7) The uniformly mixed reaction materials are continuously discharged into the belt reactor to complete the polymerization reaction. The results showed that the mixing of the reaction material and the fine powder was good, but due to the slightly high viscosity, it was not easy to disperse on the belt reactor, and there were a few local reactions with high heat.

(8) Cut the colloid into gels with a diameter of 2 mm or less by means of a cutting mill.

(9) Dry at 170° C. for 1 hour, and sieve through a sieve with a fixed particle size of 0.1 mm to 0.85 mm to obtain a powdery superabsorbent resin.

(10) Weigh 100 g of the superabsorbent resin, add 4 g of ethylene glycol carbonate/water/methanol=1/1/1 (weight ratio) solution, and heat at 215° C. for 10 minutes.

(11) After cooling, add 1g of calcium carbonate (product name produced by Formosa Plastics: NS-2000) and 2g of 20% glycerin aqueous solution, and mix evenly to obtain a high-performance superabsorbent resin. The analyzed soluble content is 4.2%. The speed is 70.85 seconds, and the absorption rate under the pressure of 49g/cm ² is 24.63g/g.

Embodiment eight:

Repeat embodiment one, but the feeding amount of step 4 changes 1.32kg/hr into. The results showed that some fine powders were suspended on the reaction materials and the reaction temperature increased compared with the previous jump range, but there was still no colloid formed on the screw or the outlet elbow. The viscosity of the discharged reaction material is 13.4cP, the soluble content of the finished product is 4.7%, the absorption rate is 67.41 seconds, and the absorption rate under the pressure of 49g/ ^cm2 is 24.21g/g.

Embodiment nine:

Repeat embodiment one, but the feeding amount of step 4 changes 1.75kg/hr into. The results showed that the amount of fine powder suspended on the reaction material increased and the reaction temperature was unstable, and part of the colloid formed by the fine powder after absorbing water adhered to the screw. The viscosity of the discharged reaction material is 14.5cP, the soluble content of the finished product is 5.1%, the absorption rate is 63.97 seconds, and the absorption rate under the pressure of 49g/ ^cm2 is 23.85g/g.

Embodiment ten:

Repeat embodiment one, but the feeding amount of step 4 changes 3.51kg/hr into. The results show that, in addition to the increase in the amount of fine powder suspended on the reaction material and the unstable reaction temperature, there are also lumps formed by the fine powder absorbing water on the screw and the outlet elbow. The viscosity of the discharged reaction material is 14.1cP, the soluble content of the finished product is 6.4%, the absorption rate is 61.11 seconds, and the absorption rate under the pressure of 49g/ ^cm2 is 24.14g/g.

Comparative example one:

Repeat Example 4, but sodium polyacrylate, polymerization initiator and fine powder are retained in the mixer with only one screw. As a result, it was found that a large amount of fine powder was suspended on the reaction material, and massive colloids were slowly formed on the screw rod and the outlet elbow. The viscosity of the discharged reaction material is 8.8cP, the soluble content of the finished product is 8.1%, the absorption rate is 68.81 seconds, and the absorption rate under the pressure of 49g/ ^cm2 is 25.12g/g.

Comparative example two:

Repeat Example 4, but sodium polyacrylate, polymerization initiator and fine powder are retained in a vertical stirring tank with a stirring blade in the center. It was found that the reaction temperature fluctuated greatly, and some fine powder adhered to the tank wall of the stirring tank, which needed to be cleaned every 2-4 hours. The viscosity of the discharged reaction material is 8.3cP, the soluble content of the finished product is 10.3%, the absorption rate is 68.27 seconds, and the absorption rate under the pressure of 49g/ ^cm2 is 24.91g/g.

Claims (13)

1. a powdery, water insoluble can absorb the low super absorbent resin of water liquid, urine or blood and solubles content, and its manufacture method comprises:

1) adds linking agent and carry out Raolical polymerizable containing more than neutralization ratio 50mole% in the carboxylic monomer aqueous solution, contain carboxylic monomer and be selected from acrylic or methacrylic acid, and containing the water-soluble polymer of 0～5wt% in the monomer solution, this water-soluble polymer is polyvinyl alcohol or starch;

2) monomer solution, polymerization starter and particle diameter have in the mixing machine more than the screw rod in one less than the absorbent resin of 100 μ m and were detained 5～600 seconds;

3) carry out drying, pulverizing, screening with 100 ℃ to 250 ℃ hot blasts of temperature;

4) surface crosslinking agent coating processing;

5) 80 ℃ to 230 ℃ heating surface of temperature are handled; And

6) add the inert inorganic salt powder.

2. powdery according to claim 1, water insoluble can absorb the low super absorbent resin of water liquid, urine or blood and solubles content, and its linking agent is to have the water-soluble cpds that two or more can participate in the functional group of free radical reaction.

3. powdery according to claim 1, water insoluble, can absorb the low super absorbent resin of water liquid, urine or blood and solubles content, its neutralizing agent is lithium hydroxide or sodium hydroxide or potassium hydroxide or Quilonum Retard or yellow soda ash or salt of wormwood or lithium bicarbonate or sodium bicarbonate or saleratus.

4. powdery according to claim 1, water insoluble can absorb the low super absorbent resin of water liquid, urine or blood and solubles content, and its initiators for polymerization is thermolysis type initiator or oxidation-reduction type initiator.

5. powdery according to claim 4, water insoluble, can absorb the low super absorbent resin of water liquid, urine or blood and solubles content, in its initiators for polymerization, thermolysis type initiator is hydrogen peroxide, two-tert-butyl peroxide, peroxidation acid amides or persulphate, or 2, two (2-amidine propane) dihydrochlorides of 2 '-azo-group.

6. powdery according to claim 4, water insoluble, can absorb the low super absorbent resin of water liquid, urine or blood and solubles content, in its initiators for polymerization, the oxidation-reduction type initiator is acid accumulator sulfite, thiosulphate, xitix, ferrous sulfate or persulphate.

7. powdery according to claim 1, water insoluble can absorb the low super absorbent resin of water liquid, urine or blood and solubles content, and its mixing machine comprises following assembly:

1) contains the reaction monomers feeding pipe of linking agent;

2) polymerization starter feeding pipe;

3) particle diameter is less than the fine grain size super absorbent resin feeding mouth of 100 μ m;

4) screw rod more than;

5) mixing machine body;

6) fine powder reclaims the machine mouth;

7) reaction mass relief outlet.

8. powdery according to claim 1, water insoluble, can absorb the low super absorbent resin of water liquid, urine or blood and solubles content, the monomer whose aqueous solution, polymerization starter and particle diameter are 10～20 seconds less than absorbent resin residence time in mixing machine of 100 μ m.

9. powdery according to claim 1, water insoluble can absorb the low super absorbent resin of water liquid, urine or blood and solubles content, and the particle size distribution range after its screening is between 0.05mm to 1mm.

10. powdery according to claim 1, water insoluble can absorb the low super absorbent resin of water liquid, urine or blood and solubles content, and its surface crosslinking agent is polyvalent alcohol or polyethyleneglycol diglycidylether or alkylene carbonate.

11. powdery according to claim 1, water insoluble can absorb the low super absorbent resin of water liquid, urine or blood and solubles content, it is 0.005wt%～5.0wt% at weight percent that its surface crosslinking agent adds scope.

12. powdery according to claim 1, water insoluble, can absorb the low super absorbent resin of water liquid, urine or blood and solubles content, its inert inorganic salt powder is Tai-Ace S 150 or aluminum oxide or magnesium oxide or calcium oxide or kaolin or silicon-dioxide or lime carbonate or magnesiumcarbonate.

13. powdery according to claim 1, water insoluble can absorb the low super absorbent resin of water liquid, urine or blood and solubles content, it is 0.01wt%～4.0wt% at weight percent that its inert inorganic salt powder adds scope.

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