TW202348695A - Superabsorbent polymers and method of fabricating the same - Google Patents

Abstract

A superabsorbent polymer and a method of forming the same are provided. The method includes performing a free radical polymerization reaction to a superabsorbent polymer components to obtain a colloid gel. The colloid gel is smashed and screened to obtain superabsorbent polymer particles. The superabsorbent polymer particles are performed a surface cross-linking reaction with surface cross-linking agent and ionomer to obtain the superabsorbent polymer. The superabsorbent polymer has a great saline flow conductivity.

Description

Water-absorbent resin and manufacturing method thereof

The present invention relates to a water-absorbent resin and a manufacturing method thereof, in particular to a water-absorbent resin with better liquid flow conductivity and a manufacturing method thereof.

Water-absorbent resins have a wide range of applications, such as water retaining agents in agriculture or horticulture, anti-dew condensation agents in building materials, materials for removing water from petroleum, outer waterproof coatings in cables, and personal hygiene products (such as diapers, feminine hygiene products and disposable wipes, etc.), of which diapers are the bulk.

The absorbency of diapers depends on the absorption rate, absorption capacity and dryness. In recent years, diapers have been committed to the goal of thinning. This is to reduce the amount of pulp (hydrophilic fiber) and increase the amount of water-absorbent resin to achieve thinner diapers by increasing the proportion of water-absorbent resin in the absorbent structure of the diaper. change. However, the reduction in the amount of hydrophilic fiber will reduce the water storage space in a short period of time, slowing down the penetration of liquid, making the liquid unable to be absorbed in time and leaking out. In addition, in addition to having a good absorption rate, the water-absorbent resin must also have high permeability to liquids. If the permeability of the liquid is poor, the water-absorbent resin will block the gaps between the particles when absorbing the liquid, forming a colloid blocking phenomenon, causing the liquid to flow out of the absorbent body of the diaper, thereby reducing the absorbent performance of the diaper.

Therefore, improving the absorption rate and permeability of water-absorbent resin is one of the current research focuses in this field. In conventional methods, polyvalent metal cations (polyvalent metal cations) can be used for surface modification or aluminum dihydroxyacetate can be used to improve the liquid flow conductivity of the water-absorbent resin. Thermoplastic polymers such as polyethylene or polypropylene can also be used in the heat treatment step, or an amino-containing azo compound can be added as a foaming agent to the acid group-containing monomer aqueous solution to improve the liquid permeability of the water-absorbent resin. . In addition, adding an encapsulated blowing agent or a water-soluble alkoxysilane compound to the acid-group-containing monomer aqueous solution can respectively make the water-absorbent resin produced have a better absorption rate or good performance. colloidal stability. Furthermore, it is known that water-soluble multivalent metal powder, adhesive and water-absorbent resin can be mixed to improve the diffusivity and liquid permeability of the water-absorbent resin after absorbing liquid.

In addition, conventional water-absorbent resins undergo surface cross-linking treatment to further bridge the surface of the water-absorbent resin to achieve effects such as increasing absorption rate, colloidal strength, caking resistance, and liquid permeability. For example, conventional methods include dispersing a water-absorbent resin and a cross-linking agent in an organic solvent for surface cross-linking treatment; or using inorganic powder to be mixed into the water-absorbing resin for cross-linking treatment; or adding a cross-linking agent and then steaming it. ; Or use organic solvents, water and polyols for surface treatment; or use organic solvents, water and ether compounds for surface treatment, etc. However, although conventional surface treatment methods can increase the absorption rate and water absorption rate under pressure, they may cause a significant decrease in the retention capacity of the water-absorbent resin, thus reducing the effectiveness of practical applications.

In view of this, there is an urgent need to provide a water-absorbent resin and a manufacturing method thereof that can simultaneously improve the liquid flow conductivity and water absorption rate under pressure of the water-absorbent resin while still maintaining a high retention force.

One aspect of the present invention is to provide a method for manufacturing a water-absorbent resin, which uses a reactive polymer to participate in a surface cross-linking reaction to improve the liquid flow conductivity of the produced water-absorbent resin.

Another aspect of the present invention is to provide a water-absorbent resin, which is prepared by the above aspect.

According to one aspect of the present invention, a method for manufacturing a water-absorbent resin is provided. The method includes subjecting the water-absorbent resin composition to radical polymerization to obtain a gel. The water-absorbent resin composition includes an unsaturated monomer aqueous solution, a polymerization initiator and a free radical polymerization cross-linking agent. Next, the gel is crushed and screened to obtain a plurality of water-absorbent resin particles; and the water-absorbent resin particles are subjected to a surface cross-linking reaction with a surface cross-linking agent and a reactive polymer to obtain a water-absorbent resin, wherein the reactive polymer includes Polyethylene segments and polyacrylic acid segments.

According to one embodiment of the present invention, the above-mentioned reaction polymer is an ethylene acrylic acid polymer, and the ethylene acrylic acid polymer includes a polyethylene segment represented by the following formula (1) and a polyacrylic acid segment represented by the following formula (2), (1) (2) Where M is a hydrogen atom, a Group IA element or a Group IIA element; and based on the ethylene acrylic acid polymer is 100 wt%, the polyethylene segment is 80 wt% to 99 wt%, and the polyacrylic acid segment is 1 wt% to 20wt%.

According to an embodiment of the present invention, when the weight of the polyethylene segment in the reaction polymer is 100 wt%, the weight of the polyacrylic acid segment is 8 to 20 wt%.

According to one embodiment of the present invention, when the weight of the above-mentioned water-absorbent resin particles is 100 wt%, the added amount of the reactive polymer is 0.01 wt% to 10%.

According to another aspect of the present invention, a water-absorbent resin is provided, which is prepared by the above method, and the T20 value of the water-absorbent resin is no more than 180 seconds.

According to an embodiment of the present invention, the liquid flow conductivity of the above-mentioned water-absorbent resin is not less than 30×10 ^-7 cm ³ -s/g.

According to an embodiment of the present invention, the retention force of the water-absorbent resin is greater than 20 g/g.

By applying the water-absorbent resin and its manufacturing method of the present invention, the reactive polymer participates in the surface cross-linking reaction to achieve the effect of improving the liquid flow conductivity and water absorption rate under pressure of the water-absorbent resin, and at the same time, the water-absorbent resin can be maintained relatively High holding power, so it can be used in practical applications.

As used herein, "around", "about", "approximately" or "substantially" generally means within 20% of the stated value or range, or Within 10%, or within 5%.

Based on the above, the present invention provides a water-absorbent resin and a manufacturing method thereof. By participating in a surface cross-linking reaction with a reactive polymer, the liquid flow conductivity and water absorption rate under pressure of the water-absorbent resin can be improved, and at the same time, it can It maintains high holding power of water-absorbent resin, so it has practical applicability.

The manufacturing method of the water-absorbent resin provided by the present invention includes first subjecting the water-absorbent resin composition to a free radical polymerization reaction to obtain a gel. In some embodiments, the water-absorbent resin composition includes an unsaturated monomer aqueous solution, a polymerization initiator, and a free radical polymerization cross-linking agent.

In some embodiments, the unsaturated monomer aqueous solution in the water-absorbent resin composition includes acid-based monomers with unsaturated double bonds, such as acrylic acid. In some embodiments, the unsaturated monomer aqueous solution can be methacrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, maleic acid (maleic acid), maleic anhydride, Fumaric acid (fumaric acid) and fumaric acid anhydride. The unsaturated monomer aqueous solution may include but is not limited to one monomer, and two or more of the above monomer aqueous solutions may also be selected.

In some embodiments, the concentration of the above-mentioned unsaturated monomer aqueous solution may be, but is not limited to, 20 wt% to 55 wt%, preferably 30 wt% to 45 wt%. Generally speaking, if the concentration of the acid-based monomer aqueous solution is 20 wt% to 55 wt%, the viscosity of the polymerized product will be moderate, easier to machine, and the heat of reaction during free radical polymerization will be easier to control.

In other embodiments, other hydrophilic monomers with unsaturated double bonds may be optionally added, such as acrylamide, methacrylamide, 2-carboxyethyl acrylate, and 2-carboxyethyl methacrylate. Ester, methyl acrylate, ethyl acrylate, dimethylamine acrylamide, acrylamide trimethylamine chloride. However, the addition amount of the above-mentioned hydrophilic monomer is based on the principle of not destroying the physical properties (such as holding power and absorption rate) of the water-absorbent resin.

In some embodiments, the acid-based monomer aqueous solution can be directly polymerized; or a neutralizing agent can be used to partially neutralize the acid-based monomer aqueous solution to make it neutral or weakly acidic, and then the polymerization reaction can be performed. In such embodiments, the neutralizing agent includes a hydroxide or carbonic acid compound of the alkali metal group or alkaline earth metal group (e.g., sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate), Amine compounds and combinations thereof. In some embodiments, the neutralization concentration of the aqueous acid-based monomer solution is 45 mol% to 85 mol%. When the neutralization concentration of the acid-based monomer aqueous solution is within the aforementioned range, the acid-based monomer aqueous solution can have a pH value that is more suitable for free radical polymerization, and can reduce possible harm if it accidentally comes into contact with the human body. It should be supplemented that the neutralization concentration described in this article is defined as the ratio of the molar number of the alkaline solution to the molar number of the acidic monomer aqueous solution, which can also be regarded as the acidic group of the acidic monomer aqueous solution. The percentage of neutralization.

In some embodiments, the pH value of the acid-based monomer aqueous solution is no less than 5.5, preferably 5.5 to 7.0, more preferably 5.5 to 6.5. If the pH value of the acid-based monomer aqueous solution is 5.5 to 7.0, it is less likely that a large amount of unreacted monomer will remain in the aqueous solution after polymerization, and the subsequently produced water-absorbent resin will have better physical properties and a larger absorption capacity.

In some embodiments, water-soluble polymers can also be selectively added to the water-absorbent resin composition to reduce preparation costs. In some embodiments, the water-soluble polymer includes partially saponified or fully saponified polyvinyl alcohol, polyethylene glycol, polyacrylic acid, polyacrylamide, starch or starch derivatives (such as methyl cellulose, methyl acrylate Starch, ethyl cellulose, etc.), preferably starch and partially saponified or fully saponified polyvinyl alcohol alone or in mixture. In the foregoing embodiments, the molecular weight of the water-soluble polymer is not limited, and when the amount of the unsaturated monomer aqueous solution is 100 wt%, the amount of the water-soluble polymer added is based on the principle of not reducing the physical properties of the water-absorbent resin. Usually It is 0wt% to 20wt%, preferably 0wt% to 10wt%, more preferably 0wt% to 5wt%.

The prepolymerization reaction begins with the decomposition of the polymerization initiator to generate free radicals. In some embodiments, based on the amount of unsaturated monomer aqueous solution being 100 wt%, the appropriate amount of polymerization initiator is 0.001 wt% to 10 wt%, preferably 0.1 wt% to 5 wt%. If the amount of the polymerization initiator is within the aforementioned range, the free radical polymerization rate will be more appropriate, the economic benefits will be better, the reaction heat will be easier to control, and the formation of a gel-like solid due to excessive polymerization will be avoided.

In some embodiments, the polymerization initiator includes a thermal decomposition initiator, a redox initiator, and combinations thereof. In some embodiments, the thermally decomposable initiator includes a peroxide [such as hydrogen peroxide, di-tert-butyl peroxide, amide peroxide, or persulfate (including ammonium salts and alkali metal salts)] and azo compounds [such as 2,2-Azobis(2-amidinopropane) dihydrochloride, 2,2-Azobis(N,N-dimethylisobutyramidine) dihydrochloride salt]. In some embodiments, the redox initiator includes acidic sulfite, ascorbic acid, or ferrous salts. The polymerization initiator is preferably used in combination with a thermal decomposition initiator and a redox initiator. The oxidation-reduction initiator is first reacted to generate free radicals. When the free radicals are transferred to the monomer, initiator is initiated. The polymerization reaction proceeds, and the large amount of heat released by the polymerization reaction will increase the temperature of the reaction system. When the reaction system reaches a specific temperature, the decomposition of the thermally decomposable initiator can be further initiated to make the polymerization reaction more complete, thus avoiding leaving too much unreacted monomer.

The free radical polymerization cross-linking agent in the water-absorbent resin composition can make the water-absorbent resin composition have an appropriate degree of cross-linking, thereby improving the processability of the water-absorbent resin composition after polymerization. In some embodiments, the free radical polymerization cross-linking agent can be a compound containing two or more unsaturated double bonds, such as N,N-bis(2-propenyl)amine, N,N-methine Bisacrylamide, N,N-methylmethacrylamide, allyl acrylate, ethylene glycol diacrylate, polyethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol Alcohol dimethacrylate, glycerin trimethacrylate, glycerin plus ethylene oxide triacrylate or trimethacrylate, trimethylol propane trimethacrylate, trimethylol propane triacrylate, N,N , N-tris(2-propenyl)amine, ethylene glycol diacrylate, polyoxyethylene glyceryl triacrylate, diethyl polyoxyethylene glyceryl triacrylate, dipropylene triethylene glycol, etc. In some embodiments, the free radical polymerization cross-linking agent can be a compound containing two or more epoxy groups, such as sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, and ethylene glycol diglycidyl ether. Ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, diglycerol polyglycidyl ether, etc. Two or more radical polymerization cross-linking agents can be used alone or in mixture.

In some embodiments, the acid-based monomer aqueous solution is 100 wt%, and the free radical polymerization cross-linking agent is 0.001 wt% to 5 wt%, preferably 0.01 wt% to 3 wt%. If the added amount of the free radical polymerization cross-linking agent is within the aforementioned range, the viscosity of the polymer aqueous solution after the reaction will be moderate, easier to machine, and the subsequently produced water-absorbent resin will have a larger absorption capacity, that is, water-absorbent resin. The performance is better.

In some embodiments, the above-described free radical polymerization reaction can be performed in a batch reaction vessel or a conveyor belt reactor.

In some embodiments, the gel can optionally be cut into particles with a particle size of no greater than 20 mm using a mincer, preferably with a particle size of no greater than 10 mm, and then subjected to the screening step. In some embodiments, the screening step is to first screen out gels with a particle size of less than 2.0 mm, preferably 0.05 mm to 1.50 mm. Gels with a particle size greater than 2.0 mm must be returned to the reactor for further chopping. The particle size must be controlled within the aforementioned range to avoid producing a higher amount of fine powder in the back-end process, and it must have better thermal conductivity properties to avoid excessive residual monomers in the finished product. Generally speaking, the narrower the particle size distribution of the gel, the better the physical properties and will be beneficial to the subsequent drying process.

In some embodiments, the gel may be optionally subjected to a drying process before subsequent operations. In some embodiments, the drying process is performed at a temperature of 100°C to 180°C. Using the aforementioned temperature range for the drying process can effectively control the drying time and the degree of cross-linking to avoid a large amount of unreacted monomer remaining.

Next, the manufacturing method of the water-absorbent resin includes crushing and screening the gel to obtain water-absorbent resin particles. In some embodiments, the particle size of the water-absorbent resin particles is selected from 0.06 mm to 1.00 mm, preferably from 0.10 mm to 0.85 mm. Controlling the particle size of the water-absorbent resin particles to the aforementioned range can reduce the amount of fine powder in the finished product and improve the absorption performance of the water-absorbent resin. Similarly, the narrower the water-absorbent resin particle size distribution, the better the physical properties.

Then, the water-absorbent resin particles, the surface cross-linking agent and the reactive polymer are subjected to a surface cross-linking reaction to obtain a water-absorbent resin. Since the water-absorbent resin is a hydrophilic polymer that does not dissolve, it has a uniform bridging structure inside the resin. In order to increase the absorption rate, improve the colloidal strength, improve the anti-caking property, and improve the body permeability and other characteristics, it is necessary to make additional coatings on the resin surface. Build further bridges. The surface cross-linking reaction is carried out by using a surface cross-linking agent with functional groups that can react with acid groups. In addition, in the present invention, in order to further improve the liquid flow conductivity of the produced water-absorbent resin, a reactive polymer such as an ionomer is added to jointly perform a surface cross-linking reaction.

In some embodiments, the surface cross-linking agent includes polyols, polyamines, compounds with two or more epoxy groups, and alkylene carbonates, where the polyols can be, for example, glycerol, ethylene glycol, dihydrogen, Ethylene glycol, triethylene glycol, polyethylene glycol and propylene glycol; polyamines can be, for example, ethylenediamine, diethylenediamine and triethylenediamine; epoxy-containing compounds can be, for example, sorbitol polyglycidyl ether, Polyglycerol polyglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether and diglycerol polyglycidyl ether; alkylene carbonate can be, for example, ethylene glycol carbonate, 4-methyl -1,3-dioxolane-2-one, 4,5-dimethyl-1,3-dioxolane-2-one, 4,4-dimethyl-1,3 -dioxol-2-one, 4-ethyl-1,3-dioxol-2-one, 1,3-dioxan-2-one, 4,6 -Dimethyl-1,3-dioxan-2-one and 1,3-dioxan-2-one. The reaction can be carried out alone or by mixing two or more surface cross-linking agents. In addition, according to the selected surface cross-linking agent, the surface cross-linking agent can be added directly, or the surface cross-linking agent can be first prepared into an aqueous solution or a hydrophilic organic solution and then added. Hydrophilic organic solvents include but are not limited to methanol, ethanol, propanol, isobutanol, acetone, methyl ether, ether, etc.

In some embodiments, the amount of water-absorbent resin particles is 100 wt%, and the amount of surface cross-linking agent is 0.001 wt% to 10 wt%, preferably 0.005 wt% to 5 wt%. When the added amount of the surface cross-linking agent is within the aforementioned range, the surface of the water-absorbent resin can have a bridging structure, thereby achieving better absorption performance.

The water-absorbent resin and the reactive polymer must be mixed evenly to effectively achieve the effects of the present invention, so a mixing device with better mixing effect must be used. In some embodiments, the mixing device may be a V-shaped mixer, a column mixer, a high-speed stirring mixer, a spiral mixer, an airflow mixer, a two-arm kneader, an two-arm conical mixer, or a ribbon mixer. , dense wall mixer, crushing kneader, rotary mixer or screw extruder.

The above-mentioned ionic polymers are polymers containing repeating units composed of ionic units in a macromolecule of electrically neutral repeating units, where the ionic groups are part of the actual polymer backbone. In some embodiments, the ionic group may be, for example, a carboxylic acid group. In these embodiments, the ionic polymer may be an ethylene-acrylic acid copolymer (EAA), which includes a polyethylene segment having the following formula (1) and a polyacrylic acid chain having the following formula (2) segment compound, (1) (2) Where M is a hydrogen atom, a Group IA element (such as lithium, sodium or potassium) or a Group IIA element (such as calcium or magnesium). In this example, the acrylic acid polymer is 100 wt% based on ethylene, the polyethylene segments are 80 to 99 wt%, and the polyacrylic acid segments are 1 to 20 wt%.

In other embodiments, the ionic polymer may be an ethylene acrylic acid compound having the following formula (3): (3) Where M is a hydrogen atom, a Group IA element (such as lithium, sodium or potassium) or a Group IIA element (such as calcium or magnesium). In some embodiments, M is preferably a Group IA element.

In some embodiments, in the ethylene acrylic acid compound, when the weight of the polyethylene segment (ie, formula (1)) is 100 wt%, the weight of the polyacrylic acid segment (ie, formula (2)) is 8 wt% to 20wt%. In ethylene acrylic acid compounds, the polyethylene segment is a hydrophobic group, while the polyacrylic acid segment is a hydrophilic group, so it is easier to absorb water. Therefore, if there are too many polyethylene segments (for example, the weight of polyacrylic acid segments is less than 8 wt%), the absorption capacity of the water-absorbent resin will be reduced; conversely, if there are too many polyacrylic acid segments (for example, the weight of polyacrylic acid segments is greater than 20 wt%) %), the ionic polymer itself will absorb moisture in the atmosphere and cause agglomeration, resulting in poor mixing effect with the water-absorbent resin particles, and the desired effect of the present invention will not be achieved.

In some embodiments, when the weight of the water-absorbent resin particles is 100 wt%, the added amount of the reactive polymer is 0.01 wt% to 10%. When the added amount of the reactive polymer is within the aforementioned range, the effect of increasing the absorption capacity of the water-absorbent resin (such as the water absorption rate under pressure) can be effectively achieved.

In some embodiments in which the ionic polymer is an ethylene acrylic compound, the above-mentioned surface cross-linking reaction includes heat treatment at a temperature of 150°C to 210°C. Heat treatment at the aforementioned temperature can completely melt the ethylene acrylic acid compound, and produce a water-absorbent resin with better quality, that is, a water-absorbent resin with better water-absorbing capacity.

As mentioned above, the present invention can produce a water-absorbent resin that can have liquid flow conductivity (saline flow conductivity, SFC), and the liquid flow conductivity can be used to evaluate liquid permeability. When the water-absorbent resin has better liquid permeability, it can reduce the problems of rewet, poor dryness and leakage of the absorbent body. Liquid flow conductivity indicates that the water-absorbent resin has the permeability to liquid under high pressure after absorbing liquid, so that when another liquid enters the absorber, it can easily pass through the water-absorbent resin that has absorbed the liquid and spread to other unabsorbed liquids. of water-absorbent resin. The liquid flow conductivity of the water-absorbent resin of the present invention is not less than 30×10 ^-7 cm ³ -s/g, preferably not less than 40×10 ^-7 cm ³ -s/g.

Furthermore, the water-absorbent resin needs to have good retention capacity (Centrifuge Retention Capacity, CRC) and absorption against pressure (AAP) to ensure that after the water-absorbent resin absorbs liquid, it will not be applied to the absorbent body due to external forces. The pressure may cause damage or affect the ability to absorb liquid. In some embodiments, the retention force of the water-absorbent resin of the present invention is no less than 20 g/g, preferably no less than 25 g/g. In some embodiments, the water absorption rate under pressure of the water-absorbent resin of the present invention is greater than 15 g/g, preferably greater than 20 g/g, and more preferably greater than 23 g/g.

In addition, the ability of the dry water-absorbent resin to absorb liquid upon initial contact with liquid can be expressed by the T20 value. When the water-absorbent resin has a lower T20 value, it means that the dry water-absorbent resin easily absorbs liquid. The T20 value of the water-absorbent resin of the present invention is no more than 180 seconds, preferably no more than 160. It should be added that the T20 value is defined as the time required for 1 gram of water-absorbent resin to absorb 20 grams of physiological saline and 0.01 wt% alcohol ethoxy compound aqueous solution under a pressure of 0.3 psi, and the alcohol ethoxy compound is The base compounds have 12 to 14 carbon atoms. In some embodiments, the T20 value of the water-absorbent resin of the present invention is less than 180 seconds, preferably less than 160 seconds. The water-absorbent resin of the present invention has both a low T20 value and a high liquid flow conductivity, which can reduce the amount of back seepage of the absorbent body and improve the dryness of diapers.

The absorbent system utilizes the water-absorbent resin and hydrophilic fiber of the present invention to form a sheet-shaped absorbent body. In actual application, the above absorbent body can be placed on a liquid-impermeable polyethylene (PE) film, and a liquid-permeable non-woven fabric can be used as the surface layer; or the water-absorbent resin can be fixed on the pulp fiber material (airlaid) and/or On non-woven fabric. Pulp fiber can be pulverized wood pulp, cross-linked cellulose fiber, cotton, wool, vinyl acetate fiber, etc. Generally speaking, based on 100 wt% of the absorbent body, the content of the water-absorbent resin (or core concentration) in the absorbent body is 20 wt% to less than 100 wt%, preferably 40 wt% to less than 100 wt%. More preferably, it is 50 wt% to less than 100 wt%. Using such a high content of water-absorbent resin in the core concentration can significantly bring out the effect of the present invention. Generally speaking, the basis weight (weight per unit area) of the above-mentioned absorbent body is 0.01 g/cm ² to 0.30 g/cm ² , and the thickness of the absorbent body is not more than 30 mm.

Several examples are used below to illustrate the application of the present invention, but they are not intended to limit the present invention. Those with ordinary knowledge in the technical field of the present invention can make various changes and modifications without departing from the spirit and scope of the present invention. polish. Preparation of reaction polymer Production example 1

Take 1180 g of ethylene acrylic acid compound (CAS NO.9010-86-0, purchased from Aldrich-Sigma, containing 18wt% polyacrylic acid chain segment), 118 g of sodium hydroxide and 5 g of pure water, and mix it with a Banbury mixer Mix at a temperature of 150° C. for 30 minutes to prepare an ethylene acrylic acid compound (A) having neutralized sodium ions. Manufacturing example 2-3

Repeat Production Example 1. The difference from Production Example 1 is that the ethylene acrylic acid compound of Production Example 2 contains 15 wt% polyacrylic acid segment (CAS NO. 9010-77-9, purchased from Aldrich-Sigma, containing 15 wt% polyacrylic acid chain segment). Acrylic acid segment); Production Example 3 is to replace sodium hydroxide with 172 g of magnesium hydroxide to prepare ethylene acrylic acid compound (B) with neutralized sodium ions and ethylene acrylic acid compound (C) with neutralized magnesium ions respectively. Manufacturing example 4-5

Repeat Production Example 1. The difference from Production Example 1 is that an ethylene acrylic acid compound (purchased from Exxon) is used. Production Example 4 is Escor ^TM 5080 containing 10 wt% polyacrylic acid segment, and Production Example 5 contains 7.5 wt%. Escor ^TM 5020 with polyacrylic acid chain segments to prepare ethylene acrylic acid compounds (D) and (E) with neutralized sodium ions respectively. Preparation of Water Absorbent Resin Example 1

Slowly add 503.12 g of 48 wt% sodium hydroxide aqueous solution into a 2000 c.c. Erlenmeyer flask containing 621.03 g acrylic acid and 670.74 g water. The dropping ratio of sodium hydroxide/acrylic acid is in the range of 0.85 to 0.95, and the dropping time is 2 hours, and keep the temperature of the neutralization reaction system in the bottle within the range of 15°C to 40°C to obtain an unsaturated monomer aqueous solution with a monomer concentration of 42 wt%, in which 70 mol% of acrylic acid is partially neutralized into sodium acrylate. The pH value is 5.69.

Next, 1.36 g of N,N’-methylene bisacrylamide (free radical polymerization cross-linking agent) was added to the unsaturated monomer aqueous solution, and the temperature was maintained at about 20°C. Then, 0.35 g hydrogen peroxide, 4.15 g sodium bisulfite and 4.15 g ammonium persulfate were added as polymerization initiators to perform free radical polymerization.

Use a cutter to chop the gel obtained by the reaction, and screen out the gel with a particle size of less than 2 mm in diameter. Next, it was dried at a temperature of 130° C. for 2 hours. Then use a sieve with a fixed particle size of 0.1 mm to 0.85 mm to obtain water-absorbent resin particles.

Next, weigh 200 g of the water-absorbent resin particles obtained above, add 2.5 g of surface cross-linking agent, which is an aqueous solution of ethylene glycol, aluminum sulfate and water in a volume ratio of 1:0.5:2, and add 0.1 g The ethylene acrylic acid compound (A) having neutralized sodium ions is heat-treated at 160°C for 1 hour, and after cooling, a water-absorbent resin can be obtained. Examples 2 to 6

The water-absorbent resins of Examples 2 to 6 were prepared using similar process steps as those of Example 1. The difference is that the amount of ethylene acrylic acid compound (A) in Example 2 is 1.0 g; Example 3 uses 0.1 g of ethylene acrylic acid compound (B) instead; Example 4 uses 0.1 g of ethylene acrylic acid compound (B) instead. C); Example 5 uses 0.1 g of ethylene acrylic acid compound (D); Example 6 uses 4.63 g of polyethylene glycol 600-diacrylate (UM82-080, manufactured by Risheng Chemical) instead of N, N '-Methyl bisacrylamide is used as a cross-linking agent in free radical polymerization. Comparative Examples 1 to 6

The water-absorbent resins of Comparative Examples 1 to 6 were also produced using similar process steps as Example 1. The difference is that Comparative Example 1 uses unneutralized ethylene acrylic acid compound (CAS NO.9010-86-0, purchased from Aldrich-Sigma, containing 18 wt% polyacrylic acid segment) to replace ethylene with neutralized sodium ions. Acrylic acid compound (A); Comparative Example 2 uses 0.1 g of ethylene acrylic acid compound (E); Comparative Example 3 does not add ethylene acrylic acid compound; Comparative Example 4 uses 5 g of ethylene acrylic acid compound (E); Comparative Example 5 uses The heat treatment was performed at a temperature of 140°C; Comparative Example 6 was heat treated at a temperature of 250°C. Evaluation method

In order to evaluate the characteristics of the water-absorbent resin of the present invention, its physical properties were analyzed by the following test methods. Unless otherwise stated, the following measurement conditions were carried out at room temperature of 23±2°C and relative air humidity of 45±10%. Absorbent resins should be thoroughly mixed before analysis. Retentivity

The retention capacity (Centrifuge Retention Capacity, CRC) is tested in accordance with the test method ERT 441.3(10) specified by the European Disposables and Nonwovens Association (EDANA). The retention test results of the water-absorbent resin are shown in Table 1. Water absorption rate under pressure

The absorption against pressure (AAP) is tested in accordance with the test method ERT442.3(10) specified by EDANA. Under a pressure of 4.9 kPa, a 0.9% sodium chloride aqueous solution is tested for 60 minutes of water absorption under pressure. magnification. The test results of the water absorption rate under pressure of the water-absorbent resin are shown in Table 1. liquid flow conductivity

Liquid flow conductivity (SFC, unit: 10 ^-7 cm ³ -sec/g) is measured and calculated according to the method described in U.S. Patent No. 5,562,646. The water-absorbent resin is first placed in Jayco synthetic urine. After 60 minutes in the liquid, measure the flow conductivity of the 0.118M sodium chloride aqueous solution at a pressure of 0.3 psi. The flow conductivity of the water-absorbent resin is shown in Table 1. T20 value

The T20 value (unit: seconds) is measured and calculated according to the method described in U.S. Patent No. 9,285,302, which is based on 1 gram of water-absorbent resin absorbing 20 grams of physiological saline and 0.01 wt% under a pressure of 0.3 psi. The time required for the aqueous solution of the alcohol ethoxylate, and the alcohol ethoxylate has 12 to 14 carbon atoms. The average results of three repeated experiments are shown in Table 1.

Table 1 Preparation of absorbent body

Using an absorbent forming machine, 10.0 grams of water-absorbent resin and 10.0 grams of crushed wood pulp are mixed and formed. The forming mesh is a 400 mesh (38 μm) metal mesh, and the absorbent area is 160 square centimeters (8 cm × 20 cm). Place the formed absorbent body on top of the polyethylene film, and then place the non-woven fabric. Then, press the absorbent body with a pressure of 18.39 kPa (area 160 square centimeters, weight 30kg) for 5 minutes, and then stick it around with white glue to obtain the absorbent body for testing. Examples 7 to 12 and Comparative Examples 6 to 10

Examples 7 to 12 are absorbers prepared using the water-absorbent resins of Examples 1 to 6, respectively, by the above-mentioned method; and Comparative Examples 7 to 12 are respectively prepared by using the water-absorbent resins of Comparative Examples 1 to 6, and similarly prepared by the above-mentioned method. Absorbent body. The basis weight and thickness of the absorber are shown in Table 2. Absorbent back-infiltration performance

The lower the rewet (ie, dryness) of the absorbent body, the better the urine resistance of the water-absorbent resin. The test method is to place a weight of 4.8 kPa (area 160 square centimeters, weight 7.8kg) on the absorbent bodies prepared in the above-mentioned Examples 7 to 12 and Comparative Examples 7 to 12, and place 180 ml of synthetic urine (U.S. Patent) at the center point. Jayco synthetic urine described in Publication No. 20040106745) was added dropwise in 3 times (30 minutes apart each time). After the addition was completed, remove the heavy object above the absorbent body after another 30 minutes. Then, place 30 pieces of filter paper (8 cm x 20 cm) with a pre-measured total weight W1 on the absorber, and immediately place a 4.8 kPa weight on the absorber for 5 minutes to allow the filter paper to absorb the re-infiltrated liquid. Then, the weight W2 of 30 pieces of filter paper was measured. The amount of synthetic urine re-infiltrated into the absorber is (W2-W1). The test results are shown in Table 2.

Table 2

According to the above test results, compared to Comparative Examples 1 to 6, Examples 1 to 6 utilize a specific amount of ethylene acrylic acid compound with neutralized metal ions to participate in the surface cross-linking reaction, and both can obtain higher liquid flow conductivity. and water-absorbent resins with lower T20 values. In other words, the water-absorbent resins of Examples 1 to 6 not only have excellent liquid flow conductivity, but also have better liquid diffusivity and conductivity in a dry state. Furthermore, according to Examples 7 to 12, that is, the absorbent body prepared with the water-absorbent resin of Examples 1 to 6 can have a liquid reinfiltration amount of less than 3.0 g, which is significantly lower than the liquid of Comparative Examples 7 to 12. The amount of reinfiltration indicates that the dryness is also excellent.

Therefore, by applying the manufacturing method of the water-absorbent resin of the present invention and utilizing the reactive polymer to participate in the surface cross-linking reaction of the water-absorbent resin particles, the liquid flow conductivity and the liquid flow conductivity of the water-absorbent resin produced in the dry state can be effectively improved. It has good diffusibility and can maintain high holding power of water-absorbent resin at the same time, so it can have practical application.

Although the present invention has been disclosed in several embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field to which the present invention belongs can make various modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended patent application scope.

without

without

Domestic storage information (please note in order of storage institution, date and number) without Overseas storage information (please note in order of storage country, institution, date, and number) without

Claims (7)

A method for manufacturing water-absorbent resin, including: A water-absorbent resin composition is subjected to a free radical polymerization reaction to obtain a gel, wherein the water-absorbent resin composition includes an unsaturated monomer aqueous solution, a polymerization initiator and a free radical polymerization cross-linking agent ; Crushing and screening the gel to obtain a plurality of water-absorbent resin particles; and The water-absorbent resin particles are subjected to a surface cross-linking reaction with a surface cross-linking agent and a reactive polymer to obtain the water-absorbent resin, wherein the reactive polymer includes polyethylene segments and polyacrylic acid segments. The method for manufacturing a water-absorbent resin as claimed in claim 1, wherein the reaction polymer is an ethylene acrylic acid polymer, and the ethylene acrylic acid polymer includes the polyethylene segment represented by the following formula (1) and the following formula (2) The polyacrylic acid segment shown, (1) (2) Where M is a hydrogen atom, a Group IA element or a Group IIA element; and based on 100 wt% of the ethylene acrylic acid polymer, the polyethylene segment is 80 wt% to 99 wt%, and the polyacrylic acid segment is 1 wt% to 20 wt%. The method for manufacturing a water-absorbent resin as claimed in claim 1, wherein when the weight of the polyethylene segment in the reaction polymer is 100 wt%, the weight of the polyacrylic acid segment is 8 wt% to 20 wt%. . The manufacturing method of water-absorbent resin as described in claim 1, wherein when the weight of the water-absorbent resin particles is 100 wt%, the added amount of the reaction polymer is 0.01 wt% to 10%. A water-absorbent resin produced by the manufacturing method as described in any one of claims 1 to 7, wherein the T20 value of the water-absorbent resin is no more than 180 seconds. The water-absorbent resin according to claim 5, wherein the liquid flow conductivity of the water-absorbent resin is not less than 30×10 ^-7 cm ³ -s/g. The water-absorbent resin according to claim 5, wherein the water-absorbent resin has a retention force greater than 20 g/g.