TW201900702A - Water absorbent resin and method of producing the same - Google Patents

Abstract

A superabsorbent polymer includes polymer particles and surface cross-linking agents. The polymer particles have cross-linked structures inside the polymer particles. The compositions of the polymer particles include carboxyl groups and alkoxysilyl groups. The surface cross-linking agents are covalently bound to the surfaces of the polymer particles.

Description

Water-absorbent resin and manufacturing method thereof

The present invention relates to a water-absorbent resin and a method for producing the same, and more particularly to a water-absorbent resin having a silane group as a constituent component and a method for producing the same.

Water-absorbent resins are widely used in agricultural or horticultural water retention agents, anti-dew condensation agents in construction materials, and materials that remove water from petroleum, or outer waterproof coatings in cables and sanitary products such as diapers. , Feminine hygiene products, disposable wipes, etc., especially for diapers.

Functional diapers are currently the main development direction, especially for adult diapers. In addition to emphasizing absorption capacity and dryness, they are also oriented towards antibacterial and deodorizing capabilities. Based on this demand, various researches have been actively carried out to develop water-absorbing resins with antibacterial and deodorizing capabilities and maintaining water-absorbing properties.

U.S. Published Patent No. 20140158355 discloses a water-absorbent resin whose internal composition includes acrylamide. The water-absorbent resin not only has good water absorption characteristics, but also has good urine resistance. The preparation method of the water-absorbent resin includes adding acrylamide to a superposition reaction (or polymerization reaction) to make the water-absorbent resin have urine resistance. However, acrylamide is suspected of causing cancer and causing a certain degree of harm to human health, so it is not suitable for use as a hygroscopic resin.

U.S. Patent No. 8,815,770 discloses a method for preparing a water-absorbent resin. The method includes adding an alkaline earth metal (e.g., calcium, strontium, barium, etc.) salts to the superposition reaction to improve the colloidal stability of the water-absorbent resin after it has absorbed liquid. . In addition, U.S. Patent No. 6,703,451 discloses adding a mixture of titanium or zirconium metal and zinc, aluminum, calcium, or magnesium to a water-absorbing resin to improve the colloidal stability of the water-absorbing resin after absorbing liquid. In addition, the Republic of China Invention Patent No. 533,223 discloses coating a phosphate compound on the surface of a water-absorbent resin to improve the colloidal stability of the water-absorbent resin after it absorbs a liquid. However, the above-mentioned metal ions affect the reaction speed of the superposition reaction and increase the content of residual monomers in the water-absorbent resin. In addition, when phosphate-based compounds come into contact with the skin, the skin becomes red and swollen. In addition, if metal ions are coated on the surface of the water-absorbent resin, the absorption capacity of the water-absorbent resin is reduced.

U.S. Patent No. 7,173,086 and U.S. Patent No. 7,812,082 disclose the addition of a thermoplastic polymer such as polyethylene or polypropylene in a heat treatment step for preparing a water-absorbent resin to improve the colloidal stability of the water-absorbent resin after absorbing liquid. However, the above-mentioned thermoplastic polymer reduces the hydrophilic ability of the water-absorbent resin, resulting in a significant decrease in the amount of liquid absorbed, and when using this technology in the heat treatment step, its production operability is not good.

Japanese Laid-Open Patent 1987-36411 mentions the use of a silane compound in the superposition reaction to improve the colloidal stability of the water-absorbent resin after absorbing the liquid. However, the selected silane compound is only soluble in organic solvents, so it is only suitable for reverse suspension polymerization processes. And the absorption rate of the water-absorbent resin produced under pressure is not good, and the stability of the colloid after absorbing liquid is not significantly improved.

In view of this, it is still necessary to provide a water-absorbent resin and a manufacturing method thereof, so that the water-absorbent resin has excellent colloidal stability, water-absorbing properties, and resistance to degradation or deterioration after absorbing liquid, so as to solve the existing water-absorbent resin. The absence of resin.

In view of this, the object of the present invention is to provide a water-absorbent resin and a method for manufacturing the same, in order to solve the defects that the existing water-absorbent resin has poor absorption ratio under pressure and low colloidal stability after absorbing liquid.

According to an embodiment of the present invention, a water-absorbent resin is provided, including resin particles and a surface crosslinking agent. Each resin particle has an internal cross-linked structure, and the composition of each resin particle includes a carboxyl group and a siloxane group, and a surface cross-linking agent is bonded to the surface of each resin particle.

According to another embodiment of the present invention, a method for manufacturing a water-absorbent resin is provided, including (a) preparing an aqueous solution, the composition of which includes an unsaturated monomer having a carboxyl group and a water-soluble silane compound, and performs a radical polymerization reaction, To obtain a water-absorbent resin having an internal cross-linked structure; (b) shredding the water-absorbent resin to obtain water-absorbent resin particles; and (c) adding a surface cross-linking agent to the surface of each water-absorbent resin particle and performing heat treatment .

According to another embodiment of the present invention, each of the resin particles is polymerized by a hydrophilic monomer having an unsaturated double bond and a water-soluble silane compound having an unsaturated double bond.

According to another embodiment of the present invention, the hydrophilic single system is selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, fumaric acid, 2-acrylamine-2-methylpropanesulfonic acid, and cis-butyl. Maleic acid, maleic anhydride, fumaric acid, and fumaric anhydride. According to another embodiment of the present invention, the water-soluble silane compound is a compound represented by the following formula (I): (RO) ₃ Si- (CH ₂ ) _n -O-R '(I)

Wherein RO is methoxy, ethoxy or acetate; R 'is propenyl or methpropenyl; and n is 1, 2 or 3.

According to another embodiment of the present invention, each of the resin particles includes a composition structure of -O- (CH ₂ ) _n -Si (OH) _m (OR) _2-m -OC-, wherein n is 1, 2 or 3 , M is 0, 1, or 2, and OR is methoxy, ethoxy, or acetate.

According to another embodiment of the present invention, the silane group is (HO) _n (RO) _3-n Si-, wherein n is 0, 1, or 2, and OR is methoxy, ethoxy, or acetic acid. base.

According to another embodiment of the present invention, based on the total amount of reactants, the above-mentioned water-soluble silane compound is added in an amount between 0.001 wt% and 5 wt%.

According to another embodiment of the present invention, after the heat treatment, the retention force of the water-absorbent resin particles is higher than 27 g / g, and the liquid permeability index under pressure is higher than 30%.

In the following, specific embodiments of the water-absorbent resin and its production method are described so that those skilled in the art can implement the present invention accordingly. For the specific implementation manners, reference may be made to corresponding drawings, so that these drawings form part of the implementation manner. Although the embodiments of the present invention are disclosed as follows, they are not intended to limit the present invention. Any person skilled in the art can make some modifications and retouching without departing from the spirit and scope of the present invention.

According to an embodiment of the present invention, a method for manufacturing a water-absorbent resin is provided, so as to obtain a water-absorbent resin which has both antibacterial and deodorizing capabilities and does not reduce water-absorbing properties. The method for manufacturing the water-absorbent resin according to the embodiment of the present invention will be described below.

According to an embodiment of the present invention, a method for manufacturing a water-absorbent resin is provided. The method at least includes: providing a water-soluble unsaturated monomer aqueous solution, such as a carboxyl-containing monomer aqueous solution, having a neutralization rate of 45 mole percent or more. After that, a water-soluble silane compound is added to the carboxyl-containing monomer aqueous solution. The water-soluble silane compound can be selected from a single molecule having at least one unsaturated double bond and an organic alkoxysilyl group. compound of. Thereafter, a polymerization initiator and an aqueous solution of a carboxyl group-containing monomer and a silane compound are mixed to perform a radical polymerization reaction to form a hydrogel having a corresponding composition. This is followed by shearing the hydrogel into small hydrogels. After that, the gel is sequentially dried, pulverized, and sieved with hot air at a temperature of 100 ° C to 250 ° C to obtain a water-absorbent resin. Subsequent surface cross-linking reaction is performed on the surface of the water-absorbent resin. After the cross-linking reaction, an aqueous solution containing a weakly acidic silicon-containing compound is added to perform surface treatment on the water-absorbent resin.

The above water-soluble unsaturated monomer may be selected from water-soluble monomers having an unsaturated double bond having an acidic group, such as: acrylic acid, methacrylic acid, maleic acid, fumaric acid, 2-acrylamine-2-methyl Propanesulfonic acid, maleic acid, maleic anhydride, fumaric acid, fumaric anhydride, etc. There is no particular limitation on the selection of monomers, and only one kind can be used, or multiple monomers can be used together. In addition, other hydrophilic monomers with unsaturated double bonds can also be added if necessary, such as: acrylamide, methacrylamide, 2-carboxyethyl acrylate, 2-carboxyethyl methacrylate, methyl acrylate Ester, ethyl acrylate, dimethylamine acrylamide, and propylene amidinotrimethylammonium trimethylammonium, but the added amount is based on the principle that the physical properties of the water-absorbent resin are not damaged.

When performing the radical polymerization reaction, the concentration of the monomer aqueous solution is not particularly limited. Preferably, the weight percentage of the monomer in the overall aqueous solution should be controlled between 20% and 55%, and a more preferred concentration is 30% to 45%. When the weight percent concentration is less than 20%, the hydrogel after polymerization is too soft and viscous, which is not conducive to mechanical processing. However, when the monomer concentration is higher than 55% by weight, the monomer concentration is close to the saturated concentration, which is not only difficult to deploy, And the reaction is too fast, making the reaction heat difficult to control. The pH of the unsaturated monomer aqueous solution is preferably not lower than 5.5. When the pH is lower than 5.5, excessive monomers remain in the hydrogel after polymerization, resulting in poor physical properties of the water-absorbent resin.

Before the radical polymerization reaction, a water-soluble polymer can be added to the monomer aqueous solution to reduce the cost. The above water-soluble polymer may be selected from the group consisting of partially saponified or fully saponified polyvinyl alcohol, polyethylene glycol, polyacrylic acid, polypropylene amidamine, starch, starch derivatives, methyl cellulose, acrylic methyl cellulose, High molecular polymers such as ethyl cellulose. The molecular weight of the water-soluble polymer is not particularly limited. Preferably, the water-soluble polymer is selected from starch, partially saponified, fully saponified polyvinyl alcohol, or a mixture thereof. The weight percentage of the water-absorbing resin containing these added water-soluble polymers is between 0% and 20%, preferably between 0% and 10%, and more preferably between 0% and 5%. . When the amount of the water-soluble polymer added exceeds 20%, the physical properties of the polymer will be affected and the physical properties will be deteriorated.

Before the radical polymerization reaction is performed, a radical polymerization reaction crosslinking agent may be added to the monomer solution. By adding a radical polymerization reaction cross-linking agent, the water-absorbent resin after the reaction can have an appropriate degree of crosslinking, and the water-absorbent resin colloid has proper processability. The radical polymerization crosslinking agent may be used alone or as a mixture of two or more kinds. The weight percentage of the free-radical polymerization cross-linking agent may be between 0.001% and 5% (based on the total solids content of the reactants), preferably between 0.01% and 3%. When the addition amount of the free-radical polymerization crosslinking agent is less than 0.001% by weight, the polymerized hydrogel is too soft and sticky, which is not conducive to mechanical processing. When the amount of the free-radical polymerization cross-linking agent is more than 5% by weight, the water absorption is too low, which reduces the performance of the water-absorbing resin.

The above-mentioned free-radical polymerization crosslinking agent can be selected from compounds having two or more unsaturated double bonds, for example: N, N'-bis (2-propenyl) amine, N, N'-methinebispropylene Ammonium amine, N, N'-methinebismethacrylamide, propylene acrylate, ethylene glycol diacrylate, polyethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol Dimethacrylate, glycerol triacrylate, glycerol trimethacrylate, glycerol triacrylate or trimethacrylate, trimethylolpropane triethylene oxide or trimethacrylate Triacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, N, N, N-tris (2-propenyl) amine, ethylene glycol diacrylate, polyoxyethylene glyceryl triacrylate, Diethyl polyoxyethylene glyceryl triacrylate, dipropylene triethylene glycol ester, etc. Compounds having two or more epoxy groups can also be selected, for example: sorbitol polyglycidyl ether, polyglycerol polyglycidyl Ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, poly Glycol diglycidyl ether, glycerol polyglycidyl ether bis, but is not limited thereto.

In order to control the pH value of the finished product to make it neutral or slightly acidic, the carboxylic acid group of the carboxyl-containing monomer should be partially neutralized. The neutralizing agent used to adjust the pH value may be an alkali gold or alkaline earth group hydroxide or carbonate compound in the periodic table, such as: sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, carbonic acid Potassium hydrogen, ammonia compounds or mixtures thereof. The neutralizing agent may be used alone or in combination. By adding a neutralizing agent, the carboxylic acid group of the carboxyl-containing monomer is partially neutralized to form a sodium, potassium, or ammonium salt. Preferably, the mole concentration of the neutralization concentration is 45 mol% to 85 mol%, and more preferably 50 mol% to 75 mol%. When the mole concentration of the neutralization concentration is 45 mol% or less, the pH value of the finished product is low, and when the mole concentration of the neutralization concentration is more than 85 mol%, the pH value of the finished product is high. When the pH of the finished product is not neutral or slightly acidic, it is not suitable for direct contact with the human body, and it is also less safe.

For the above-mentioned free-radical polymerization reaction, a polymerization initiator should usually be added to the monomer solution, and the free-radical polymerization reaction is generated by the polymerization initiator to generate free radicals. A suitable amount of the polymerization initiator is between 0.001% and 10% by weight (based on the weight of the neutralized acrylate), and more preferably between 0.1% and 5% by weight. When the weight percentage is less than 0.001%, the reaction will be too slow, which is unfavorable to economic benefits. When the weight percentage is 10% or more, the reaction is too fast, making it difficult to control the reaction heat, and it is easy to polymerize excessively to form a gel-like solid.

The polymerization initiator may be a thermal decomposition-type initiator, a redox-type initiator, or a mixture of the two. For a thermal decomposition type initiator, it may be a peroxide or an azo compound. For example, the peroxide may be, for example, hydrogen peroxide, di-third butyl peroxide, ammonium peroxide or persulfate (ammonium salt, alkali metal salt), and the like. The azo compound may be, for example, 2.2'-azobis (2-fluorenylpropane) dihydrochloride, 2.2'-azobis (N, N-dimethylisobutyrazine) dihydrochloride . In addition, for a redox type initiator, it may be a reducing agent, such as: acid sulfite, thiosulfate, ascorbic acid or ferrous salt. In addition, the polymerization initiator may include both a redox type initiator and a thermal decomposition type initiator. For the case where the polymerization initiator also includes a redox initiator and a thermal decomposition initiator, in the initial stage of the radical polymerization reaction, the redox initiator will first react to generate free radicals. When transferred to the monomer, the polymerization reaction is initiated. Since the polymerization reaction releases a large amount of heat and the temperature rises, when the temperature reaches the decomposition temperature of the thermal decomposition initiator, it will cause the decomposition of the second stage thermal decomposition initiator to cause the entire polymerization. The response was more complete.

The above-mentioned radical polymerization reaction can be performed in a conventional batch reaction container or on a conveyor belt reactor. The gel obtained by the reaction is first cut into small gels with a diameter of less than 20 mm by a mincing machine, and more preferably less than 10 mm in diameter.

After the small gel is manufactured, the screening can be performed subsequently. In the screening procedure, it is preferable to screen gels having a diameter of 2.00 mm or less, and more preferably, gels between 0.05 mm and 1.50 mm. For gels with a particle size greater than 2.00 mm, they are returned to the reactor for further shredding. It should be noted that if the gel with a particle size of less than 0.03mm is dried and pulverized, it is easy to cause a higher amount of fine powder in the finished product. If the gel with a particle size of 2.00mm or more is dried, It is easy to cause the shortcomings of poor physical properties due to the poor heat conduction effect, resulting in a high residual monomer in the finished product. According to the embodiment of the present invention, when the particle size distribution of the acrylate gel is narrower, the gel can not only have the best physical properties after drying, but also be beneficial to control the drying time and temperature.

After the above screening process, the drying process is performed. The drying temperature is preferably between 100 ° C and 180 ° C. If the drying temperature is below 100 ° C, the drying time will be too long, which is not economical. If the drying temperature is above 180 ° C, the drying will cause the crosslinking agent to undergo a crosslinking reaction early, so that the subsequent drying process However, because the degree of crosslinking is too high, the residual monomers cannot be effectively removed, and the effect of reducing the residual monomers cannot be achieved.

After the above drying procedure, pulverization and screening are performed to fix the particle size. The screening fixed particle diameter is preferably between 0.06 mm and 1.00 mm, and more preferably between 0.10 mm and 0.850 mm. When the particle size is less than 0.06mm, fine particles will increase the dust of the finished product, and when the particle size is more than 1.00mm, the water absorption rate of the finished product will be slowed down. According to the embodiment of the present invention, the narrower the particle size distribution of the acrylate polymer, the better.

The water-absorbent resin obtained through the above procedure is an insoluble hydrophilic polymer, and the resin has a uniform bridge structure inside. In order to further improve the characteristics of water-absorbent resins, such as: increasing the absorption rate, increasing colloidal strength, improving blocking resistance, increasing liquid permeability, etc., the surface of the resin will be further coated with polyfunctional groups capable of reacting with carboxyl groups. Crosslinking agent to produce crosslink and bridge on the surface of water-absorbent resin. The surface crosslinking agent and surface crosslinking treatment will be described below.

Specifically, after the fixed particle diameter is screened, a surface crosslinking agent coating treatment may be performed, so that the surface of the water-absorbent resin is further crosslinked. Therefore, the surface layer of the water-absorbent resin can be made to have a higher degree of crosslinking with respect to its core. This water-absorbent resin having a high degree of cross-linking in the surface layer and a low degree of core cross-linking is also referred to as a water-absorbent resin having a "core-shell structure".

The manner of adding the surface crosslinking agent will vary depending on the type of surface crosslinking agent. For example, it can be divided into: surface cross-linking agent is added directly, surface cross-linking agent is adjusted to be added as an aqueous solution, or surface cross-linking agent is added to a hydrophilic organic solvent aqueous solution and then added, wherein the hydrophilic organic solvent may be selected from methanol, ethanol , Propanol, isobutanol, acetone, methyl ether, diethyl ether, etc., are not particularly limited and can be formed into a solution, and are more preferably selected from methanol or ethanol (refer to US Pat. No. 6,849,665). The appropriate addition amount of the cross-linking agent is between 0.001% and 10% by weight (based on the total solid content of the reactant), and more preferably between 0.005% and 5%. When the added amount of the cross-linking agent is less than 0.001% by weight, the effect cannot be shown, and when the added amount of the cross-linking agent is more than 10% by weight, the water absorption is too low, causing the resin performance to decrease.

According to an embodiment of the present invention, the above-mentioned cross-linking agent may be a cross-linking agent capable of performing surface treatment and reaction at the same time, such as: polyhydric alcohol, polyamine, compound having two or more epoxy groups, and subcarbonate Hydrocarbon esters or mixtures thereof. Specifically, the polyhydric alcohol may be selected from glycerol, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, or propylene glycol, but is not limited thereto; the polyamine may be selected from ethylenediamine, diethylene glycol Ethylenediamine or triethylenediamine, but not limited to this; compounds having two or more epoxy groups may be selected from sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, ethylene glycol diglycidyl Ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, or diglycerol polyglycidyl ether, etc., but is not limited thereto; the alkylene carbonate may be selected from ethylene glycol carbonate, 4- Methyl-1,3-dioxolane-2-one, 4,5-dimethyl-1,3-dioxolane-2-one, 4,4-dimethyl-1 1,3-dioxolane-2-one, 4-ethyl-1,3-dioxolane-2-one, 1,3-dioxane-2-one, or 4 , 6-Dimethyl-1,3-dioxane-2-one, 1,3-dioxane-2-one, and the like, but are not limited thereto. The usage of the cross-linking agent may be used alone or as a mixture of two or more.

Existing patent documents have disclosed various procedures for surface crosslinking treatment, such as dispersing a water-absorbent resin and a crosslinking agent in an organic solvent for surface crosslinking treatment (JP-A-56-131608, JP-A-57- 44627, JP-A-58-42602, JP-A58-117222); using inorganic powder, directly mixing the cross-linking agent and the cross-linking agent solution into the water-absorbent resin for surface cross-linking treatment (JP-A60-163956, JP -A-60-255814); steam treatment after adding a cross-linking agent (JP-A-1-113406); surface treatment with organic solvents, water and polyols (JP-A-1-292004, US6346569); use Organic solutions, water, ether compounds (JP-A-2-153903), etc. Although the surface cross-linking method disclosed in the current patent literature can increase the absorption rate and increase the water absorption rate under pressure, it also causes The adverse consequences of excessive reduction in holding force reduce the performance of practical applications. In contrast, the method for surface cross-linking treatment performed in the embodiments of the present invention does not have the aforementioned defects. One feature of the present invention is that a water-soluble silane compound containing an unsaturated bond can have a superposition reaction with a carboxyl-containing monomer, so that the corresponding water-absorbent resin can not only maintain certain absorption characteristics, but also have excellent resistance. Ability to degrade or deteriorate. According to an embodiment of the present invention, the water-soluble silane compound may have a structure represented by the following formula (I): (RO) ₃ Si- (CH ₂ ) _n -O-R '(I)

among them,

RO is methoxy, ethoxy or acetate;

R 'is an acryl group or methacryl; and

n is 1, 2 or 3.

Specifically, the unsaturated bond-containing water-soluble silane compound having the above chemical formula may be: 3- (methacrylic acid) propyltrimethoxysilane (manufacturer: Evonik, trade name: Dynasylan MEMO), 3- (acrylic acid) Propyltrimethoxysilane (manufacturer: Gelset, trade name: SIA0200.0), methyltriethoxysilane methacrylate (manufacturer: Gelset, trade name: SIM6482.0), methacrylic acid) propyltriethyl Siloxane (manufacturer: Gelset, trade name: SIM6487.3), methyltrimethoxysilane methacrylate (manufacturer: Gelset, trade name: SIM6483.0), and methyltrimethoxysilane methacrylate (manufacturer: Gelset, Commodity name: SIA0182.0).

Preferably, the added amount of the water-soluble silane compound is between 0.001% and 5% by weight, and more preferably between 0.005% and 5%. When the silane compound is added in an amount of less than 0.001% by weight, the effect cannot be exhibited. When the silane compound is added in an amount of more than 5% by weight, the water absorption capacity is reduced.

Since carbon and silicon belong to the same element (Group 4A), their chemical properties are very similar, and the carbon-silicon bond is very stable and non-polar, so these compounds have low surface energy, while alkoxysilanes (such as methoxysilane) are easy to use. Reacts with water to form very stable siloxane groups. In addition, the siloxy group can form a bond with a hydroxyl group or a carboxylic acid group of the water-absorbent resin. In this way, the strength of the water-absorbent resin can be greatly improved, especially the strength of the gel after water absorption. In other words, if the composition absorbed by the water-absorbent resin includes a siloxane group, after the water-absorbent resin absorbs water, the oxyalkyl group in the siloxane group may be partially substituted with a hydroxyl group. In addition, if the composition of the water-absorbent resin includes both siloxane groups and carboxylic acid groups, after the water-absorbent resin absorbs water, the water-absorbent resin will further produce cross-linking, resulting in -Si-OC- bonding, thereby improving Gel strength after absorbing water.

According to the above embodiments, by adding a water-soluble silane compound to an aqueous solution of a carboxyl-containing monomer and performing a superposition reaction, a product having excellent anti-degradation or degradation functions without reducing the absorption characteristics of the water-absorbent resin can be manufactured. . There are no particular restrictions on the steps used to prepare the above-mentioned water-soluble unsaturated monomers, as long as the water-absorbent resin produced by the method of the present invention can be applied to various types of sanitary products, agricultural and food preservation Water absorbent.

The water-absorbent resin disclosed in the above embodiments is suitable for various types of water-absorbing agents for sanitary products, agriculture and food preservation. It is particularly suitable for absorbers in diapers, especially low-concentration pulp diapers (Fluffless, and a large amount of Absorbent resin) and adult diapers.

For a water-absorbent resin as a diaper absorber, not only must it have a certain capacity to absorb liquid, that is, Centrifuge Retention Capacity (CRC), but it must also have a high pressure permeability index (PUL, Permeability Under Load) value. Specifically, for a water-absorbent resin having both Absorption Against Pressure (AAP) and liquid permeability under high pressure, even when liquid enters an absorbent body that has absorbed liquid, the absorbent body has high pressure. The lower liquid permeability, so that the liquid will easily pass through the water-absorbent resin that has absorbed the liquid, and then diffuse to other water-absorbent resin that does not absorb the liquid, thereby reducing the amount of osmosis (Rewet) of the absorbent body, and improve the dryness of the diaper Sex. At a pressure of 4.9 kPa, for a 0.9% aqueous sodium chloride solution, the PUL value is preferably higher than 30%, more preferably higher than 40%.

According to an embodiment of the present invention, the absorption system has a sheet-like structure by pressing and molding a water-absorbent resin and hydrophilic fibers. A liquid-impermeable polymer film, such as a PE film, may be provided below the absorbent body, and a liquid-permeable non-woven fabric is provided above the absorbent body as a surface layer. In addition, the water-absorbent resin can also be fixed on pulp fiber material (Airlaid) and / or non-woven fabric. The pulp fiber is pulverized wood pulp, crosslinked cellulose fiber, cotton, wool, or vinyl acetate fiber, but is not limited thereto. . The water-absorbent resin content (core concentration) in the absorbent body may be between 20% and 100% by weight, preferably between 40% and 100% by weight, and more preferably between 50% and 100%. According to the embodiment of the present invention, the basis weight (weight per unit area) of the absorbent body is between 0.01 and 0.30 g / cm ² , and the thickness of the absorbent body is 30 mm or less.

By using the water-absorbent resin prepared in the above embodiment as an absorber in diapers, it uses a silane compound to easily react with water to form a very stable siloxane group, which can interact with the water-absorbent resin. The hydroxyl or carboxylic acid groups form a bond, which can greatly increase the strength of the water-absorbent resin, especially the strength of the gel after water absorption.

For the water-absorbent resins currently used in diapers on the market, after absorbing water, the gel strength will depend on the chemical substances in the urine, such as: L-ascorbic acid or its salts, and transition metal ions (such as iron Ions, ferrous ions), thereby reducing the strength of the gel after the water-absorbent resin absorbs water, which in turn causes problems such as excessive diaper re-permeability and poor dryness. In contrast, the water-absorbent resin prepared in the embodiment of the present invention does not reduce the strength of the gel after water absorption of the water-absorbent resin due to the above-mentioned chemical substances in the urine, thereby causing the diaper to have too high repermeability and poor dryness. problem. Therefore, the problem of the existing diaper is effectively solved.

In order to enable a person having ordinary knowledge in the technical field to which the present invention belongs to implement the present invention, the physical property analysis method and specific preparation method of the water-absorbent resin and absorber of the present invention will be described in further detail below. It should be noted that the following examples are merely illustrative and should not be used to limit the interpretation of the present invention. Therefore, without exceeding the scope of the present invention, the materials used in the embodiments, the amounts and ratios of materials, and the processing procedures can be appropriately changed. It should be noted that, unless otherwise stated, the physical property analysis methods below are performed at room temperature 23 ± 2 ° C and relative air humidity 45 ± 10%, and the water-absorbent resin should be thoroughly mixed before analysis.

The following introduces the analysis methods of the physical properties of the water-absorbent resin and absorber. Each analysis item includes: the permeability of the liquid under the pressure of the water-absorbent resin, the water absorption ratio (AAP) under the pressure of the water-absorbent resin, and the liquid permeability under the pressure of the water-absorbent resin. Index (PUL) value, water-absorbent resin retention (CRC), water-absorbent resin residual monomers (RAA: Residual Monomers), gel stability (L-ascorbic acid measurement, gel stability) Determination of iron ions, evaluation of the amount of osmosis of the absorber, deodorant test of the absorber.

＜ Permeability of liquid under water-absorbent resin pressure ＞

The test is performed according to the test method of ERT 443.1 (5) stipulated by EDANA (European Disposables And Nonwovens Association). The liquid permeability of the water-absorbent resin under the pressure of 4.9 kPa is tested, and 8 (g / g) is preferred. Above, more preferably 10 (g / g).

＜ Water absorption ratio under water absorbent resin pressure ＞

According to the test method of ERT 442.2 (5) stipulated by EDANA, test the water absorption rate of the water-absorbing resin under the pressure of 4.9kPa for 0.9% sodium chloride aqueous solution under the pressure of 60 minutes, preferably 15 (g / g ) Above, more preferably 20-30 (g / g).

<Liquid permeability index (PUL) value (unit:%) under water-absorbent resin pressure>

Permeability of liquid under pressure (PDAUP: Gravimeteric Determination of Permeability Dependant Absorption Under Pressure) divided by AAP: Absorption Against Pressure and then expressed as a percentage.

＜ Water-absorbing resin holding power ＞

Tested in accordance with EDANA test method ERT 441.3 (10).

<Gel Stability-L-ascorbic acid determination>

Use 1.000 g of SAP in a 100 mL beaker, and pour 49 mL of artificial urine (artificial urine components: 20 g urea, 8 g sodium chloride, 0.8 g magnesium chloride (6 crystal water), 0.3 g calcium chloride ( 2 crystal water), 0.05 g of L-ascorbic acid and 970.9 g of deionized water, place the beaker in an oven (temperature = 40 ° C) for 24 hours, and then place the beaker on the platform of the STEVENS colloidal strength tester (suspension The drop speed of the suspension pipe is 1.0 mm / sec, and the drop distance is 10 mm. The colloidal strength is measured (unit: g / g), and the stability of the colloid is judged by lightly pressing the colloid.

Grade A: The gel has its original elasticity, is not sticky, feels dry, and the shape of the gel particles is still obvious;

Grade B: The gel has elasticity, but the shape of the gel particles will be destroyed under large pressure;

Grade C: The gel has elasticity, but the shape of the gel particles will be destroyed by light pressure;

Grade D: The gel has no elasticity, some gels become pasty, and the shape of the particles disappears.

<Evaluation of the amount of osmosis (dryness) of the absorber>

Place a weight of 4.8kPa (area of 160 square centimeters and a weight of 7.8Kg) on the test absorbent body, so that the weight of the weight acts on the test absorbent body uniformly, and then add synthetic urine 3 times at the center point (according to A total of 180 ml of Jayco's synthetic urine described in U.S. Published Patent No. 20040106745 (30 minutes each time). After adding, wait for 30 minutes, then remove the weight above the test absorbent body and place it on the test absorbent body. Place 30 sheets of filter paper (8 cm x 20 cm) in which the total weight (W1 (g)) is measured in advance, and then immediately place a 4.8 kPa weight on the test absorbent body for 5 minutes to allow the above-mentioned filter paper to absorb the osmotic liquid, and then measure Weight of 30 filter papers (W2 (g)). The amount of synthetic urine repermeability (g) of the absorbent is W2-W1. The lower the amount of reverse osmosis, the better the urine resistance of the water-absorbent resin.

The following describes the manufacturing method of the water-absorbent resin and the absorbent body.

Manufacturing method of water-absorbent resin

Example 1

(1) Take 437.5g of 48% sodium hydroxide aqueous solution and slowly add 540g acrylic acid and 583.2g water to a 2000c.c conical flask. The dropwise ratio of sodium hydroxide / acrylic acid is in the range of 0.85 to 0.95. Hours, and keep the temperature of the neutralization reaction system in the bottle in the range of 15 ° C to 40 ° C. At this time, the weight percentage concentration of the monomer in the aqueous solution was 42%, of which 70 mol% (molar ratio) of the acrylic acid part was neutralized into sodium acrylate.

(2) 1.1 g of N, N'-methacrylamide is added to the water-soluble unsaturated monomer solution, and the temperature is maintained at about 20 ° C.

(3) Add 0.3 g of hydrogen peroxide, 3.6 g of sodium bisulfite, and 3.6 g of ammonium persulfate to start the reaction.

(4) The gel produced after the reaction is cut with a cutter mill, and a gel having a particle diameter of 2 mm or less is selected.

(5) It is dried at 130 ° C for 2 hours, and then sieved with a fixed-size sieve of 0.1 mm to 0.85 mm to obtain a powdery water-absorbent resin with a measured retention of 40.5 g / g.

(6) Weigh 200g of powdery water-absorbent resin, and add ethylene glycol, 1,4-butanediol (manufactured by Taiwan Plastics Co., Ltd.) and 5/1 / 0.5 mixed aqueous solution of methanol (ethylene glycol, 1,4- The weight ratio of butanediol and methanol is 1: 1: 0.5), and heat treatment is performed at a temperature of 150 ° C. for 1 hour. After cooling, a water-absorbent resin is obtained. The measured holding force is 32.4 g / g, the water absorption rate under pressure is 23.5 g / g, the permeability of the liquid under pressure is 6.3 g / g, and PUL = 26.8%.

Example 2

(1) Take 437.5g of 48% sodium hydroxide aqueous solution and slowly add 540g of acrylic acid and 583.2g of water to a 2000c.c. Conical flask. The dropwise addition ratio of sodium hydroxide / acrylic acid is in the range of 0.85 to 0.95. 2 hours, and keep the temperature of the neutralization reaction system in the bottle in the range of 15 ° C to 40 ° C; at this time, the weight percentage concentration of the monomer in the aqueous solution is 42%, of which 70 mol% (mole ratio) of acrylic acid will be quilted Partially neutralized into sodium acrylate.

(2) Add 1.5 g of polyethylene glycol diacrylate (molecular weight 523) to the water-soluble unsaturated monomer solution, and maintain the temperature at about 20 ° C.

(3) Add 0.3 g of hydrogen peroxide, 3.6 g of sodium bisulfite and 3.6 g of ammonium persulfate starter to carry out the polymerization reaction.

(4) The gel produced after the reaction is cut with a cutter mill, and a gel having a particle diameter of 2 mm or less is selected.

(5) drying at 130 ° C for 2 hours; sieving with a fixed-size sieve of 0.1 mm to 0.85 mm to obtain a powdery water-absorbent resin with a measured retention of 41.3 g / g.

(6) Weigh 200g of powdery water-absorbent resin and add 5g of a mixed aqueous solution of ethylene glycol, 1,4-butanediol and methanol (the weight ratio of ethylene glycol, 1,4-butanediol and methanol is 1: 1: 0.5), heat-treated at 150 ° C for 1 hour, and after cooling, a water-absorbent resin is obtained. The measured holding force was 33.1 g / g, the water absorption rate under pressure was 24.6 g / g, the permeability of the liquid under pressure was 12.2 g / g, PUL = 49.6%, and the residual monomer was 412 ppm.

Example 3

Example 1 was repeated, and in step (2), 0.5 g of 3-acrylic acid propyltrimethoxysilane (manufacturer: Gelset, trade name: SIA0200.0) was additionally added to the water-soluble unsaturated monomer solution. The rest is the same as in Example 1 to obtain a water-absorbent resin. The measured holding force is 32.3 g / g, the water absorption rate under pressure is 23.6 g / g, the permeability of the liquid under pressure is 10.2 g / g, and PUL = 43.2%.

Example 4

Example 1 was repeated, and an additional 0.5 g of methyltrimethoxysilane (manufacturer: Gelset, trade name: SIA0182.0) was added to the water-soluble unsaturated monomer solution in step (2). The rest is the same as in Example 1. A water-absorbent resin was obtained. The measured holding force was 32.1 g / g, the water absorption ratio under pressure was 24.5 g / g, the permeability of the liquid under pressure was 12.3 g / g, and PUL = 50.2%.

Example 5

Example 1 was repeated, and an additional 0.5 g of 3- (methacrylic acid) propyltrimethoxysilane (manufacturer: Evonik, trade name: Dynasylan MEMO) was added to the water-soluble unsaturated monomer solution in step (2). . The rest is the same as in Example 1. A water-absorbent resin was obtained. The measured holding force was 32.6 g / g, the water absorption ratio under pressure was 24.5 g / g, the liquid permeability under pressure was 9.3 g / g, and PUL = 38.0%.

Example 6

Example 3 was repeated, but the amount of 3-acrylic propyltrimethoxysilane added in step (2) was increased to 1.0 g. The rest was the same as in Example 3. A water-absorbent resin was obtained, and the retention was 32.2 g / g. The water absorption rate under pressure is 23.9g / g, the permeability of the liquid under pressure is 11.8g / g, and PUL = 49.4%.

Example 7

Example 2 was repeated, but an additional 0.5 g of methyltrimethoxysilane (manufacturer: Gelset, trade name: SIA0182.0) was added to the water-soluble unsaturated monomer solution in step (2). The rest is the same as in Example 1. A water-absorbent resin was obtained. The measured holding force was 32.7 g / g, the water absorption ratio under pressure was 24.1 g / g, the permeability of the liquid under pressure was 12.3 g / g, and PUL = 51.0%.

Example 8

Example 7 was repeated, but the amount of methyltrimethoxysilane added in step (2) was increased to 1.0 g, and the rest was the same as in Example 7. A water-absorbent resin was obtained. The measured retention was 32.5 g / g and the pressure The lower water absorption rate is 23.8g / g, the permeability of the liquid under pressure is 12.7g / g, PUL = 53.4%.

Example 9

Example 1 was repeated, but in step (2), 0.5 g of methyltrimethoxysilane methacrylate (manufacturer: Gelset, trade name: SIM6483.0) was additionally added to the water-soluble unsaturated monomer solution. The rest is the same as in Example 1. A water-absorbent resin was obtained. The measured holding force was 32.8 g / g, the water absorption ratio under pressure was 24.1 g / g, the permeability of the liquid under pressure was 9.1 g / g, and PUL = 37.8%.

Comparative Example 1

Example 1 was repeated, but the amount of N, N'-methacrylamide added in step (2) was increased to 5 g. The rest is the same as in Example 1. A water-absorbent resin was obtained. The measured holding force was 27.1 g / g, the water absorption ratio under pressure was 24.5 g / g, the liquid permeability under pressure was 6.7 g / g, and PUL = 27.3%.

Comparative Example 2

Example 2 was repeated, but the amount of polyethylene glycol diacrylate added in step (2) was increased by 5 g to obtain a water-absorbent resin. The measured holding force was 27.4 g / g, the water absorption rate under pressure was 24.3 g / g, and the pressure The permeability of the lower liquid is 6.9g / g, PUL = 28.4%.

Comparative Example 3

Example 1 was repeated, but 100 g of the water-absorbent resin prepared in Example 1 was weighed out, 5 g of an aqueous solution of silicon dioxide (manufactured by Wacker, model HDK D1512B) was added, and the mixture was treated with a V-type mixer for 5 minutes to obtain Water-absorbent resin. The measured holding force is 31.1 g / g, the water absorption rate under pressure is 21.5 g / g, the permeability of the liquid under pressure is 6.1 g / g, and PUL = 28.4%.

Comparative Example 4

Example 1 was repeated, but the amount of the ethylene glycol, 1,4-butanediol, and methanol mixed solution in step (6) was increased by 10 g to obtain a water-absorbent resin. The measured holding force was 29.3 g / g under pressure. Water absorption rate is 24.1g / g, the permeability of liquid under pressure is 6.4g / g, PUL = 26.6%.

Comparative Example 5

Example 1 was repeated, but 100 g of the water-absorbent resin prepared in Example 1 was weighed out, and 5 g of kaolin (made by Longmao, model LMC-581, particle size = 2 m, weight ratio of alumina and silica) was 0.86). The rest is the same as in Example 1. A water-absorbent resin was obtained. The measured holding force was 30.1 g / g, the water absorption ratio under pressure was 19.7 g / g, the liquid permeability was 6.0 g / g under pressure, and PUL = 30.5%.

Table 1 shows the results of colloidal stability tests.

[Table I]

Preparation method of absorber

Preparation Example 1

Take the water-absorbent resin obtained in Example 1, and use an absorbent forming machine to mix and shape 10.0 grams of water-absorbent resin with 10.0 grams of crushed wood pulp. The forming mesh is a 400-mesh (38um) metal mesh, and the area of the absorbent is 160 square centimeters. (8 cm x 20 cm). Place the formed absorbent body on top of the PE film, and then place a non-woven fabric. Press the absorbent body with a pressure of 18.39kPa (area of 160 square centimeters and weight of 30Kg) for 5 minutes. Absorber (1). The absorbent body (1) had a basis weight of 0.07 g / cm2 and a thickness of 17 mm.

Preparation Example 2

The absorbent resin obtained in Example 3 was used to prepare an absorbent body (2) by the method for producing an absorbent body described in the evaluation of the performance of the absorbent body, the basis weight was 0.07 g / cm ² , and the thickness was 16 mm.

Preparation Example 3

The water-absorbent resin obtained in Example 4 was used to prepare an absorbent body (3) by a method similar to that of the absorbent body described in Preparation Example 1. The basis weight was 0.08 g / cm ² and the thickness was 16 mm.

Preparation Example 4

The water-absorbent resin obtained in Example 5 was used to prepare an absorbent body (4) by a method similar to that of the absorbent body described in Preparation Example 1. The basis weight was 0.07 g / cm ² and the thickness was 15 mm.

Preparation Example 5

The water-absorbent resin obtained in Example 6 was used to prepare an absorbent body (5) by a method similar to that of the absorbent body described in Preparation Example 1. The basis weight was 0.08 g / cm ² and the thickness was 16 mm.

Preparation Example 6

The absorbent resin obtained in Example 7 was used to prepare an absorbent body (6) in a manner similar to the absorbent body manufacturing method described in Preparation Example 1. The basis weight was 0.07 g / cm ² and the thickness was 16 mm.

Preparation Example 7

The absorbent resin obtained in Example 8 was used to prepare an absorbent body (7) in a manner similar to the absorbent body manufacturing method described in Preparation Example 1. The basis weight was 0.08 g / cm ² and the thickness was 15 mm.

Preparation Example 8:

The water-absorbent resin obtained in Example 9 was used to prepare an absorbent body (8) by a method similar to that of the absorbent body described in Preparation Example 1. The basis weight was 0.08 g / cm ² and the thickness was 16 mm.

Comparative Example 1

Preparation Example 1 was repeated, except that the water-absorbent resin was replaced with the water-absorbent resin of Comparative Example 1. The rest was the same as in Preparation Example 1. An absorbent body (9) was prepared with a basis weight of 0.07 g / cm ² and a thickness of 16 mm.

Comparative Example 2

Preparation Example 1 was repeated, but the water-absorbent resin was replaced with the water-absorbent resin of Comparative Example 2. The rest was the same as that of Preparation Example 1. An absorbent body (10) was prepared with a basis weight of 0.08 g / cm ² and a thickness of 16 mm.

Comparative Example 3

Preparation Example 1 was repeated, but the water-absorbent resin was replaced with the water-absorbent resin of Comparative Example 3. The rest was the same as in Preparation Example 1. An absorbent body (11) was prepared with a basis weight of 0.07 g / cm ² and a thickness of 15 mm.

Comparative Example 4

Preparation Example 1 was repeated, except that the water-absorbent resin was replaced with the water-absorbent resin of Comparative Example 4, and the rest was the same as in Preparation Example 1. An absorbent body (12) was prepared with a basis weight of 0.07 g / cm ² and a thickness of 16 mm.

Comparative Example 5

Preparation Example 1 was repeated, but the water-absorbent resin was replaced with the water-absorbent resin of Comparative Example 5. The rest was the same as in Preparation Example 1. An absorbent body (13) was prepared with a basis weight of 0.08 g / cm ² and a thickness of 15 mm.

Table 2 shows the results of the performance evaluation test of the absorber.

[Table II]

Because the water-soluble silane compound can overlap with the carboxyl-containing monomer, the corresponding water-absorbent resin can not only maintain certain absorption characteristics, but also have excellent resistance to degradation or degradation. According to the experimental data of the synthetic urine reverse osmosis test result in the performance evaluation of the absorber, it is proved that it has the characteristics of high dryness (that is, low reverse osmosis amount). The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the scope of patent application of the present invention shall fall within the scope of the present invention.

no

no

Claims (11)

A water-absorbent resin includes: a plurality of resin particles, each of which has an internal cross-linked structure, wherein the composition of each resin particle includes a carboxyl group and a siloxane group; and a surface cross-linking agent, which is bonded to each The surface of the resin particles. The water-absorbing resin according to item 1 of the scope of the patent application, wherein each of the resin particles is polymerized by a hydrophilic monomer having an unsaturated double bond and a water-soluble silane compound having an unsaturated double bond. The water-absorbent resin according to item 2 of the scope of patent application, wherein the hydrophilic single system is selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, fumaric acid, 2-acrylamine-2-methyl Propanesulfonic acid, maleic acid, maleic anhydride, fumaric acid, and fumaric anhydride. The water-absorbing resin according to item 2 of the scope of the patent application, wherein the water-soluble silane compound is a compound represented by the following formula (I): (RO) ₃ Si- (CH ₂ ) _n -OR '(I ) Wherein RO is methoxy, ethoxy or acetate; R ′ is propenyl or methpropenyl; and n is 1, 2 or 3. The water-absorbent resin according to item 1 of the scope of the patent application, wherein each of the resin particles includes a composition structure of -O- (CH ₂ ) _n -Si (OH) _m (OR) _2-m -OC-, where n Is 1, 2 or 3, m is 0, 1 or 2, and OR is methoxy, ethoxy or acetate. The water-absorbent resin according to item 1 of the scope of the patent application, wherein the siloxane group is (HO) _n (RO) _3-n Si-, where n is 0, 1, or 2, and OR is methoxy , Ethoxy or acetate. A method for manufacturing a water-absorbent resin includes: (a) preparing an aqueous solution, the composition of which includes an unsaturated monomer having a carboxyl group and a water-soluble silane compound, and performing a radical polymerization reaction to obtain an internal cross-linked structure (B) shredding the water-absorbent resin to obtain a plurality of water-absorbent resin particles; and (c) adding a surface cross-linking agent to the surface of each of the water-absorbent resin particles, and performing heat treatment. The method for manufacturing a water-absorbent resin according to item 7 in the scope of the patent application, wherein the unsaturated mono system having a carboxyl group is selected from the following group: acrylic acid, methacrylic acid, maleic acid, fumaric acid, 2-propylene Amine-2-methylpropanesulfonic acid, maleic acid, maleic anhydride, fumaric acid and fumaric anhydride. The method for producing a water-absorbent resin according to item 7 in the scope of the patent application, wherein the water-soluble silane compound is a compound represented by the following formula (I): (RO) ₃ Si- (CH ₂ ) _n -OR '(I) wherein RO is methoxy, ethoxy or acetate; R' is propenyl or methpropenyl; and n is 1, 2 or 3. The method for manufacturing a water-absorbent resin according to item 7 of the scope of the patent application, wherein, based on the total amount of reactants in the aqueous solution, the water-soluble silane compound is added in an amount between 0.001 wt% and 5 wt%. The method for manufacturing a water-absorbent resin according to item 7 in the scope of the patent application, wherein after the heat treatment, the retention of the water-absorbent resin particles is higher than 27 g / g, and the liquid permeability index under pressure is higher than 30%.