CN111040096A - Method for preparing polyacrylic acid series water-absorbent resin - Google Patents
Method for preparing polyacrylic acid series water-absorbent resin Download PDFInfo
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- CN111040096A CN111040096A CN201911413827.4A CN201911413827A CN111040096A CN 111040096 A CN111040096 A CN 111040096A CN 201911413827 A CN201911413827 A CN 201911413827A CN 111040096 A CN111040096 A CN 111040096A
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F290/00—Macromolecular compounds obtained by polymerising monomers on to polymers modified by introduction of aliphatic unsaturated end or side groups
- C08F290/02—Macromolecular compounds obtained by polymerising monomers on to polymers modified by introduction of aliphatic unsaturated end or side groups on to polymers modified by introduction of unsaturated end groups
- C08F290/06—Polymers provided for in subclass C08G
- C08F290/062—Polyethers
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/12—Powdering or granulating
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/30—Sulfur-, selenium- or tellurium-containing compounds
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/34—Silicon-containing compounds
- C08K3/36—Silica
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2351/00—Characterised by the use of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives of such polymers
- C08J2351/08—Characterised by the use of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives of such polymers grafted on to macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/30—Sulfur-, selenium- or tellurium-containing compounds
- C08K2003/3045—Sulfates
- C08K2003/3081—Aluminum sulfate
Abstract
The invention discloses a method for preparing polyacrylic acid water-absorbent resin, which comprises the following steps: (a) the method comprises the following steps of (a) obtaining a monomer aqueous solution containing an unsaturated acrylic monomer and a crosslinking agent, (b) polymerizing the monomer aqueous solution to form a water-containing gel-like crosslinked polymer, (c) granulating the water-containing gel-like crosslinked polymer to form gel-like water-absorbent resin particles, and then drying, grain refining, screening, surface crosslinking and post-treatment, wherein one or more of monomer residue control agents such as a peroxy initiator, an azo initiator or an inorganic reducing agent are added in any one or more processes after the grain refining step, and the method has the following beneficial effects: after the monomer residue control agent is added, the water-absorbent resin has a monomer residue ratio of 1.5 to 38.4% and an extractable matter change ratio of 0 to 53.4%, and the water-absorbent resin can be efficiently produced and obtained without affecting the liquid-absorbing properties of the water-absorbent resin, and has a high liquid-absorbing rate and an acrylic acid monomer residue of not more than 500 ppm.
Description
Technical Field
The present invention relates to a method for producing a polyacrylic acid water-absorbent resin. In particular to absorbent articles suitable for use, for example: paper diapers (disposable diapers), sanitary napkins, incontinence pads, bed pads, pet pads, wound care materials, building materials, soil water retention materials, and the like.
Background
Super Absorbent Polymer (SAP), also known as Super absorbent resin, is a crosslinked polymer that contains strongly hydrophilic groups, is insoluble in water, but can absorb tens, hundreds, or even thousands of times the weight of water. The super absorbent resin is widely applied to various fields such as sanitary products such as paper diapers, physiological sanitary napkins, adult incontinence products and the like, soil moisturizers and the like. In the present days, crosslinked materials obtained by partially neutralizing polyacrylic acid, hydrolysates of starch-acrylic acid graft polymers, saponified vinyl acetate-acrylic acid ester copolymers, crosslinked materials of acrylonitrile copolymers, crosslinked materials of acrylamide copolymers, and crosslinked materials of cationic monomers are known as water-absorbent resins.
In recent years, the structure of the diaper is developed to be thinner, which is required to reduce the fiber content in the product and simultaneously increase the absorbent content, and the thinner structure not only improves the wearing comfort but also can reduce the packaging, storage and transportation costs. The thinner diaper structure imposes a great demand on the performance of the absorbent, wherein it is important that the water-absorbent resin has an ability to conduct and distribute liquid, a liquid retention ability, and an absorption capacity under pressure, and particularly, the absorption rate of the water-absorbent resin (liquid absorption amount per unit mass of the water-absorbent agent per unit time) becomes an important criterion for evaluating whether the diaper having a high content of the water-absorbent resin can rapidly absorb liquid when it is first contacted with liquid. However, there is a trade-off between various properties of the water-absorbent resin, and if the liquid-absorbing rate thereof is greatly increased, deterioration of the ability to conduct and distribute liquid, the liquid-retaining ability, or the absorption capacity under pressure is inevitably caused, which becomes a bottleneck in development of the water-absorbent resin having a rapid liquid-absorbing rate.
In addition, the acrylic monomer residue is often out of the limits during the preparation of the water-absorbent resin having a rapid imbibition rate, especially during the drying process. The reason is as follows: (1) the water-absorbent resin with high liquid absorption rate needs to provide higher specific surface area in the processing process, and in the drying stage, the higher specific surface area leads to higher contact surface with air, the moisture on the surface of gel particles is quickly lost, so that free radicals generated by heating decomposition cannot contact with residual monomers, the consumption rate of the monomers is reduced, and the monomer residue is higher; (2) in the drying process, as the contact area between the gel and the air is increased, free radicals generated by thermal decomposition and residual free radicals in the system after polymerization are combined with oxygen to form oxygen free radicals which can not effectively consume acrylic acid, the consumption rate of monomers is reduced, and the residual quantity is increased.
For the application field of paper diapers, some potential safety hazards and product odor problems are often attributed to the excessive residual monomer amount, so that for the super absorbent resin with rapid liquid absorption rate, the effective control of the residual monomer amount becomes a limiting factor of the development of the super absorbent resin.
As techniques for controlling the residual monomer content in a water-absorbent resin, there are known: (1) a method (CN104086938B) of adding a peroxide or an inorganic reducing agent to a fine powder having an excessively high monomer content in the course of granulation of the fine powder; (2) a method for preparing a hydrophilic polymer with low residual monomer content from a hydrogel polymer comprises the steps of contacting a gas with a hydrogel polymer at a dew point of 50-100 ℃ and a temperature of 80-250 ℃ for drying, wherein the residual monomer content of a water-absorbent resin can be effectively controlled (CN 1015180B); (3) by adding a reducing substance such as sodium bisulfite to the hydrogel polymer after the polymerization process is completed, before or during drying (US 5866678); (4) the method of optimizing the drying procedure to achieve effective control of the monomer residue amount, drying the hydrogel polymer at a temperature below 90 ℃ in the drying process of the hydrogel polymer to reduce the water content of the hydrogel polymer to 15-40 wt%, then keeping the temperature at 70-120 ℃ for more than 10 minutes to make the water content change rate within 5 wt%, and finally performing heating dehydration drying (US 6207796).
However, the technique disclosed in the patent is still insufficient in that the monomer-remaining amount of the water-absorbent resin is reduced. The above techniques have a limited degree of controllability of the residual monomer amount, and particularly have a remarkably high residual monomer amount (>1000ppm) after drying, which is greatly reduced in the preparation of a water-absorbent resin having a high liquid-absorbing rate. In addition, in the above techniques, although the amount of the monomer remaining can be reduced, it is difficult to achieve a reduction in other physical properties at the same time, and particularly, the extractable content is greatly increased.
Disclosure of Invention
The present invention aims to provide a process for efficiently producing a water-absorbent resin having a high liquid-absorption rate without affecting the liquid-absorption characteristics of the water-absorbent resin, with a low residual monomer amount, and to obtain a water-absorbent resin having a high liquid-absorption rate and a controllable residual monomer amount.
The invention provides a method for preparing polyacrylic acid series water-absorbing resin, which comprises the following steps:
(a) obtaining a monomer aqueous solution containing an unsaturated acrylic monomer and a crosslinking agent,
(b) polymerizing the aqueous monomer solution to form a water-containing gel-like crosslinked polymer,
(c) granulating the water-containing gel-like crosslinked polymer into gel-like water-absorbent resin particles, drying, grain-refining, sieving, surface crosslinking, and post-treating, wherein one or more of a peroxy initiator, an azo initiator, or an inorganic reducing agent-based monomer residue control agent is added in any one or more processes after the grain-refining step,
(c1) during or after the monomer residue control agent and the water-absorbent resin are mixed, in the processing process of the water-absorbent resin, the water content of the water-absorbent resin in at least one processing section is 8.2-20.8 wt%;
(c2) and heating or insulating the water-absorbent resin to enable the material temperature to reach 60-190 ℃ in the mixing process of the monomer residue control agent and the water-absorbent resin and/or after mixing.
The ratio of the monomer residual control amount to the water-absorbent resin acrylic monomer residual amount before addition is 0.23-13.8.
The ratio of the monomer residue control amount to the water-absorbent resin acrylic monomer residue amount before addition is 1.38-7.2.
The monomer aqueous solution of the unsaturated acrylic monomer and the crosslinking agent is a mixed solution of acrylic acid and/or water-soluble salt of acrylic acid as a main component; the crosslinking agent is selected from one or more of a compound containing a plurality of vinyl groups in a molecule, a compound containing at least one vinyl compound and at least one functional group capable of reacting with a carboxyl group on the unsaturated monomer in a molecule, and a compound containing a plurality of functional groups capable of reacting with a carboxyl group on the unsaturated monomer in a molecule.
The peroxy initiator is one or more of peroxide, hydroperoxide and persulfate.
The peroxy initiator is one or more of hydrogen peroxide, sodium persulfate, potassium persulfate, ammonium persulfate, calcium peroxide, magnesium peroxide, zinc peroxide, potassium peroxymonosulfate, strontium peroxide, tert-butyl peroxide and methyl ethyl ketone peroxide.
The azo initiator is one or more of azodiisobutyronitrile, azodiisoheptanonitrile, azodiisovaleronitrile, azodicarbonamide, azodiisobutyramidine hydrochloride, diisopropyl azodicarboxylate and diazoaminobenzene.
The inorganic reducing agent is one or more of sulfite, bisulfite, pyrosulfite, dithionite and thiosulfate.
During or after the monomer residue control agent and the water-absorbent resin are mixed, the water content of the water-absorbent resin in at least one processing section in the processing process of the water-absorbent resin is 11.7-20.8 wt%.
And heating or insulating the water-absorbent resin after the monomer residue control agent and the water-absorbent resin are mixed in and/or are mixed, so that the material temperature of the water-absorbent resin reaches 90-180 ℃.
The extractable content of the water-absorbent resin is 0 to 53.4% after the addition of the monomer residue-controlling agent, as compared with a water-absorbent resin to which no monomer residue-controlling agent has been added.
The extractable content of the water-absorbent resin is 0 to 18.2% after the addition of the monomer residue-controlling agent, as compared with a water-absorbent resin to which no monomer residue-controlling agent has been added.
The water-absorbent resin has a monomer residue ratio of 1.5 to 38.4% after the addition of the monomer residue-controlling agent, as compared with a water-absorbent resin to which no monomer residue-controlling agent has been added.
The water-absorbent resin has a monomer residue ratio of 1.5 to 27.8% after the addition of the monomer residue-controlling agent, as compared with a water-absorbent resin to which no monomer residue-controlling agent has been added.
The invention discloses a method for producing a water-absorbent resin with high liquid absorption rate, which has the beneficial effect of not influencing the liquid absorption property of the water-absorbent resin, and can simultaneously ensure that the extractable change rate of the water-absorbent resin is 0-60 percent after a monomer residue control agent is added compared with the water-absorbent resin without the monomer residue control agent. The water-absorbent resin has a monomer residual ratio of 3 to 60%. A water-absorbent resin having a high liquid-absorbing rate and an acrylic acid monomer residual amount of not more than 500ppm can be produced and obtained with high efficiency.
Detailed Description
The polyacrylic acid-based water-absorbent resin, the composition, and the method for producing the same of the present invention will be described in detail below, but the scope of the present invention is not limited to these descriptions.
[1] The method for producing the polyacrylic acid-based water-absorbent resin of the present invention
A method for producing a polyacrylic acid-based water-absorbent resin, comprising:
(a) obtaining a monomer aqueous solution containing an unsaturated acrylic monomer and a crosslinking agent,
(b) polymerizing the aqueous monomer solution to form a water-containing gel-like crosslinked polymer,
(c) granulating the water-containing gel-like crosslinked polymer into gel-like water-absorbent resin particles, drying, grain-refining, sieving, surface crosslinking, and post-treating, wherein one or more of a peroxy initiator, an azo initiator, or an inorganic reducing agent-based monomer residue control agent is added in any one or more processes after the grain-refining step,
(c1) during or after the monomer residue control agent and the water-absorbent resin are mixed, in the processing process of the water-absorbent resin, the water content of the water-absorbent resin in at least one processing section is 8.2-20.8 wt%;
(c2) and heating or insulating the water-absorbent resin to enable the material temperature to reach 60-190 ℃ in the mixing process of the monomer residue control agent and the water-absorbent resin and/or after mixing.
The ratio of the monomer residual control amount to the water-absorbent resin acrylic monomer residual amount before addition is 0.23-13.8.
The water-absorbent resin can be ensured to have an extractable change rate of 0 to 53.4% after the addition of the monomer residue control agent, as compared with a water-absorbent resin to which no monomer residue control agent has been added. The water-absorbent resin has a monomer residual ratio of 1.5 to 38.4%.
1.1 monomer solution
A step of obtaining an aqueous solution containing an unsaturated acrylic monomer and a crosslinking agent. The following is a detailed description.
The monomer (monomer) used in the present invention is a monoethylenically unsaturated acid group-containing monomer having an unsaturated double bond and capable of forming a water-absorbent resin by radical polymerization, and is not particularly limited, and acrylic acid, methacrylic acid, ethacrylic acid, α -chloroacrylic acid, α -cyanoacrylic acid, β -methacrylic acid (crotonic acid), α -phenylacrylic acid, β -acryloyloxypropionic acid, sorbic acid, α -chlorosorbic acid, 2' -methylisotalonic acid, cinnamic acid, p-chlorocinnamic acid, β -stearic acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, aconic acid, maleic acid, cinnamic acid, fumaric acid, tricarboxyethylene and maleic anhydride can be cited.
Other types of monomers may be used to copolymerize with the carboxyl group-containing monomer. The following may be mentioned: anionic unsaturated monomers and salts thereof such as vinylsulfonic acid, allyltoluenesulfonic acid, vinyltoluenesulfonic acid, styrenesulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, and 2-hydroxyethyl (meth) acryloylphosphate; a mercapto group-containing unsaturated monomer; a phenolic hydroxyl group-containing unsaturated monomer; amide group-containing unsaturated monomers such as (meth) acrylamide, N-ethyl (meth) acrylamide, and N, N-dimethyl (meth) acrylamide; and amino group-containing unsaturated monomers such as N, N-dimethylaminoethyl (meth) acrylate, N-dimethylaminopropyl (meth) acrylate, and N, N-dimethylaminopropyl (meth) acrylamide.
These unsaturated monomers may be used alone or in combination of 2 or more, and acrylic acid-based water-absorbent resins containing acrylic acid and/or a salt thereof (for example, a salt such as a sodium salt, a lithium salt, a potassium salt, an ammonium salt, and an amine) can be preferably used in view of the performance and cost of the water-absorbent resin powder.
The neutralization rate of these unsaturated acid group-containing monomers is not particularly limited, and may be partially or completely neutralized, preferably partially neutralized, and if necessary, the polymerization gel may also be neutralized after polymerization. The degree of neutralization of the unsaturated acid group-containing monomer is preferably 25 to 100 mol%, particularly preferably at least 40 to 95 mol%, and more preferably 50 to 90 mol%. The neutralization of the unsaturated acid group-containing monomers can be carried out before or after the polymerization. Neutralization can be carried out using alkali metal hydroxides, alkaline earth metal hydroxides, ammonia, and carbonates and bicarbonates. In addition, any other base that can form a water-soluble salt with the acid can be used. Neutralization can also be carried out using a variety of bases. Neutralization with ammonia or alkali metal hydroxides is preferred, and neutralization with sodium hydroxide is particularly preferred.
The amount of acrylic acid and/or its salt used as the polyacrylic acid-based water-absorbent resin powder is usually 60 mol% or more, preferably 75 mol% or more, preferably 90 mol% or more, and more preferably 95 mol% or more, based on the whole monomer component (excluding the crosslinking agent).
The concentration of the monomer is also not particularly limited, and the concentration of the aqueous solution of the unsaturated acid group-containing monomer and the crosslinking agent is 20 to 60 wt%, preferably 22 to 55 wt%, and more preferably 24 to 50 wt%. When the monomer concentration is less than 20% by weight, productivity is lowered and thus it is not preferable. When the monomer concentration is higher than 60 wt%, the pulverization load increases, resulting in deterioration of production stability. The solvent for the monomers is water, and a small amount of organic solvent may be used in combination.
The internal crosslinking agent is one or more selected from the group consisting of a compound having a plurality of vinyl groups in a molecule, a compound having at least one vinyl compound and at least one functional group capable of reacting with a carboxyl group of the unsaturated monomer in a molecule, and a compound having a plurality of functional groups capable of reacting with a carboxyl group of the unsaturated monomer in a molecule. Previously well known internal cross-linking agents may be used. Specifically, for example, there may be mentioned: one or more of N, N' -methylenebisacrylamide, trimethylolpropane tri (meth) acrylate, ethylene glycol di (meth) acrylate, polyethylene glycol diacrylate, polyethylene glycol di (meth) acrylate, polyethylene glycol diallyl ether, pentaerythritol tetraacrylate, triarylamine, ethylene glycol diglycidyl ether, ethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 4-butanediol, glycerol, pentaerythritol, polyethylene glycol, and vinyl carbonate, and these internal crosslinking agents may be used in consideration of the reactivity. Among these, one or more of trimethylolpropane tri (meth) acrylate, polyethylene glycol diacrylate, ethylene glycol diglycidyl ether, polyethylene glycol, and 1, 4-butanediol are preferable, and one or more of trimethylolpropane tri (meth) acrylate, polyethylene glycol diacrylate, and ethylene glycol diglycidyl ether are more preferable.
The amount of the internal crosslinking agent to be used is determined in accordance with the physical properties of the water-absorbent resin to be required, and is preferably 0.001 to 5 mol%, more preferably 0.005 to 2 mol%, and still more preferably 0.01 to 1 mol% based on the monomer content. If the amount of the internal crosslinking agent used is less than 0.001 mol%, the water-absorbent resin obtained has an increased water-soluble matter content, and the water absorption capacity under pressure cannot be sufficiently ensured. If the amount of the internal crosslinking agent used exceeds 5 mol%, the chemical crosslinking density becomes too high, and the water absorption capacity of the resulting water-absorbent resin powder becomes insufficient. Further, the internal crosslinking agent may be added to the reaction system at once or may be added to the reaction system in portions.
1.2 polymerization step
The polymerization step is a step of polymerizing the aqueous monomer solution. The polymerization process may be carried out under normal pressure, reduced pressure or increased pressure, and is preferably carried out under normal pressure.
As the polymerization initiator used in the present step, there is no particular limitation, and any initiator which can form radicals under polymerization conditions and is generally used for producing a water-absorbent resin may be used. The polymerization can also be initiated by applying an electron beam to the polymerizable aqueous monomer solution. The polymerization can also be initiated by the action of high-energy radiation in the presence of a photoinitiator. One or more polymerization initiators are selected from those generally used in the production of water-absorbent resins, depending on the kind of monomers to be polymerized, polymerization conditions, and the like.
The polymerization initiator is preferably a peroxide, a hydroperoxide, hydrogen peroxide, a persulfate, and an azo compound. Preferably, a water-soluble initiator is used. Specifically, the following are listed: thermal decomposition type initiators such as persulfates of sodium, potassium, ammonium persulfate and the like; peroxides such as hydrogen peroxide, t-butyl peroxide and methyl ethyl ketone peroxide, azo compounds such as azonitrile compounds, azoamidine compounds, cyclic azoamidine compounds, azoamide compounds, alkyl azo compounds, 2 '-azobis (2-amidinopropane) dihydrochloride and 2, 2' -azobis [2- (2-imidazolin-2-yl) propane ] dihydrochloride; or photodegradable initiators such as benzoin derivatives, benzil derivatives, acetophenone derivatives, benzophenone derivatives, azo compounds, and the like. Among these initiators, from the viewpoint of cost and the ability to reduce residual monomers, a thermal decomposition type initiator is preferable, and a persulfate is more preferable.
In addition, the decomposition of these polymerization initiators can be promoted by using a reducing agent in combination. Therefore, a redox system initiator may be used. The reducing agent is not particularly limited, and may be selected from: sodium metabisulfite, sodium sulfite, sodium bisulfite and other sulfurous acid (salts), L-ascorbic acid (salts), metal salts (such as iron (II) ions or silver ions), amines and the like. In the case of using an oxidative polymerization initiator and a reducing agent as in the case of the redox initiator, they may be separately combined with the monomer solution, or the reducing agent may be mixed in advance with the monomer solution.
In the polymerization, a hydrophilic polymer such as polyethylene glycol, starch, a starch derivative, cellulose, a cellulose derivative, polyvinyl alcohol, polyacrylic acid (salt), or a crosslinked polyacrylic acid (salt) may be added to the reaction system before or during the polymerization, if necessary; or a chain transfer agent such as hypophosphorous acid (salt), a chelating agent, etc. As the hydrophilic polymer, a water-soluble resin or a water-absorbent resin can be preferably used, and the viscosity of the reaction system can be increased. The amount of the hydrophilic polymer used is preferably 0 to 30 wt%, more preferably 0.001 to 20 wt%, and still more preferably 0.01 to 10 wt% based on the monomer.
The polymerization method used in this step is not particularly limited. Preferred are radical polymerization in the homogeneous phase (e.g., radical polymerization in an aqueous solution), precipitation polymerization from an organic solvent, suspension polymerization, emulsion polymerization, miniemulsion polymerization, or the like. The radical polymerization in a homogeneous system is preferable, and the radical polymerization in an aqueous solution is more preferable. The aqueous solution polymerization method includes a static polymerization method in which an aqueous monomer solution is polymerized in a static state, and a stirring polymerization method in which polymerization is performed in a stirring apparatus. Further, polymerization methods are classified into batch-wise polymerization and continuous polymerization according to continuous productivity. Particularly suitable for solving the problem are aqueous solution polymerizations, especially continuous belt polymerizations or continuous kneader polymerizations.
The apparatus for producing the water-absorbent resin of the present invention is not particularly limited, and a continuous conveyer polymerization apparatus or a continuous stirring polymerization apparatus is preferable.
The polymerization apparatus is preferably an endless belt type continuous static polymerization apparatus, and the belt is made of fluororesin or coated with fluororesin. Further, it is preferable to use a system including a heating device or a heat retaining device and recovering and reusing water and/or vapor of the monomer solution generated during polymerization.
The continuous stirring polymerization apparatus may be a single-shaft stirring apparatus or a stirring apparatus having a plurality of stirring shafts, such as a continuous kneader, and the use of a multi-shaft stirring apparatus is preferable from the viewpoint of productivity.
The polymerization initiation temperature refers to the real-time temperature of the polymerization system when the initiator is added to the monomer solution. In the step of polymerizing the aqueous monomer solution, the polymerization start temperature is 0 to 120 ℃, preferably 0 to 110 ℃, and more preferably 0 to 100 ℃. If the polymerization initiation temperature is less than 0 ℃, the polymerization time is long, the productivity is greatly lowered, and the physical properties of the water-absorbent resin may be lowered. If the polymerization initiation temperature is higher than 100 ℃, the physical properties of the water-absorbent resin may be deteriorated. The polymerization time is not particularly limited, and is appropriately determined depending on the kinds of the monomer and the polymerization initiator, the polymerization temperature, and the like, but from the viewpoint of productivity, the shorter the polymerization time, the better.
1.3 crushing step
The step of pulverizing the crosslinked hydrogel polymer obtained as described above may be performed during or after polymerization. A kneader may be used for the pulverization during the polymerization, and a slitter, a meat chopper or the like may be used for the pulverization after the polymerization. The size of the gel particles after crushing is preferably 0.2-10 mm, if the size of the gel particles is too small, the risk of higher monomer residue is brought, if the hydrogel-like polymer is not crushed or the size of the gel particles is too large, the final granular product cannot be obtained, and particularly in the subsequent heating and drying step, the water in the hydrogel is difficult to evaporate.
1.4 Heat drying step
The heating and drying step is to dry the hydrogel-like crosslinked polymer to remove water from the gel. The drying is usually carried out at a temperature of 60 to 300 ℃ as a heating medium, preferably 100 to 250 ℃, more preferably 120 to 220 ℃. The drying time depends on the surface area and the moisture content of the polymer and the type of dryer, chosen to obtain the target moisture content (moisture content is measured by the 3 hour loss on drying at 105 ℃).
The water content of the water absorbent resin used in the present invention is not particularly limited, and the water content is more preferably 0.2 to 30 wt%, further preferably 0.3 to 15 wt%, and particularly preferably 0.5 to 10 wt%. Too high a water content not only impairs flowability and thus affects production, but also makes comminution of the water-absorbent resin impossible and may lose control over a particular particle size distribution.
As the drying method used is not particularly limited, various methods may be employed to obtain the target water content, specifically listed are: heat drying, hot air drying, drying under reduced pressure, infrared drying, microwave drying, dehydration by azeotrope with hydrophobic organic solvents and drying with high humidity using high temperature steam.
1.5 Fine granulation and sieving step
In order to obtain a water-absorbent resin having a specific particle size (particle size is adjusted in conjunction with the fine powder granulation process described below), a step of finely granulating and sieving the dried crosslinked polymer is required.
Machines for obtaining an absorbent resin having an irregular crushed shape and a particle diameter which can be effectively controlled, and for grain refining, include shearing coarse crushers, impact powder crushers, and high-speed rotary powder crushers. And further sieving the resin particles after the grain refining.
The mass median particle diameter (D50) of the water-absorbent resin is preferably adjusted to 200 to 650. mu.m, more preferably 200 to 550. mu.m, and still more preferably 300 to 500. mu.m. The proportion of particles having a diameter of less than 150 μm is controlled to be 0 to 8 wt%, preferably 0 to 5 wt%, more preferably 0 to 2 wt%. In addition, the smaller the proportion of particles having a diameter of more than 850 μm, the better, the more preferably 0 to 8 wt%, preferably 0 to 5 wt%, and more preferably 0 to 2 wt%. In the present invention, the surface crosslinking is preferably carried out under the condition that the proportion of particles of 150 to 850 μm is 95 wt% or more, more preferably 98 wt% or more. Logarithmic standard deviation (σ) of particle size distributionζ) Preferably 0.20 to 0.40, more preferably 0.20 to 0.38, and more preferably 0.20 to 0.36.
1.6 control of the residual monomer content
In order to better control the monomer residue in the water-absorbent resin, one or more monomer residue control agents of peroxy initiator, azo initiator or inorganic reducing agent are added in the processing process. Wherein the peroxy initiator is selected from one or more of peroxide, hydroperoxide and persulfate. Further preferred are one or more of hydrogen peroxide, sodium persulfate, potassium persulfate, ammonium persulfate, calcium peroxide, magnesium peroxide, zinc peroxide, potassium peroxymonosulfate, strontium peroxide, t-butyl peroxide, and methyl ethyl ketone peroxide. Most preferably one or more selected from sodium persulfate, potassium persulfate or ammonium persulfate. The azo initiator is selected from one or more of azodiisobutyronitrile, azodiisoheptonitrile, azodiisovaleronitrile, azodicarbonamide, azodiisobutyramidine hydrochloride, diisopropyl azodicarboxylate and diazoaminobenzene. The inorganic reducing agent is selected from one or more of sulfite, bisulfite, pyrosulfite, dithionite and thiosulfate.
The adding section of the monomer residue control agent is carried out in at least any one of the processing processes of the screening process of the semi-finished product, the surface cross-linking process and the surface cross-linking process. The addition method is not limited, and it is preferable to directly mix the water-absorbent resin with the aqueous solution, and it is more preferable to rapidly mix the water-absorbent resin with the atomized liquid droplets. According to the difference and requirement of the processing working section, an organic phase solvent can be added into the monomer residue control agent or directly mixed with the additive solution of the water-absorbent resin post-treatment working section. The monomer residue control agent is used in a concentration of 0.2 to 15 wt%, preferably 0.5 to 14 wt%, and more preferably 1 to 12 wt%. The concentration is too low, and excessive moisture needs to be introduced to ensure the effective addition amount, so that the subsequent dehydration and drying process needs to be added; too high concentration results in deterioration of the liquid-absorbing property of the water-absorbent resin.
The amount of the monomer residue-controlling agent is 0.2 to 40, preferably 0.2 to 30, and most preferably 0.3 to 20 in the ratio of the effective amount to the acrylic monomer residue of the water-absorbent resin before addition.
The water-absorbent resin in at least one of the processing stages has a water content of 6 to 30 wt%, preferably 6 to 28 wt%, and most preferably 7 to 25 wt% during or after the mixing of the monomer residue-controlling agent and the water-absorbent resin and during the heating of the water-absorbent resin.
The monomer residue control agent and the water-absorbent resin are heated or insulated during and/or after mixing, so that the material temperature of the water-absorbent resin reaches 50-190 ℃, preferably 60-180 ℃, more preferably 70-170 ℃, and most preferably 80-160 ℃.
Compared with the water-absorbent resin without the monomer residue control agent, the water-absorbent resin with the monomer residue control agent is provided with a monomer residue ratio of 3-60% and an extraction change ratio of 0-60%.
1.7 Recycling of Fine-grained Water-absorbent resin
In the present invention, the amount of generation of small-particle-diameter fine particles (particles smaller than 150 μm) is controlled by reusing the fine-particle water-absorbent resin.
The water-absorbent resin particles with small particle size (particles smaller than 106 microns) obtained by grain refining and screening can be re-polymerized by returning to a monomer solution, or can be agglomerated by mixing with a large amount of hot water (the weight ratio of the water-absorbent resin particles with small particles to the hot water is 2: 1-1: 2) so as to be restored to a hydrogel-like product again, or can be directly mixed with a hydrogel-containing polymer in a solid powder form. And then readjusted to the water absorbent resin particles of the target particle size through the steps of granulation, drying, grain refinement and the like. The amount of waste material can be reduced by recovering and regenerating particles outside the target range.
[2] Physical Properties of polyacrylic acid Water-absorbent resin
The polyacrylic acid-based water-absorbent resin of the present invention has a particulate water-absorbing agent having an irregular pulverized shape, and specific physical properties are as follows.
2.1 centrifuge Water holding Capacity (CRC)
The centrifugal water retention capacity (CRC) of the sodium chloride aqueous solution of 0.9 wt% is preferably 10 to 60g/g, more preferably 20 to 55g/g, further preferably 25 to 50g/g, and particularly preferably 25 to 45 g/g. In terms of absorption capacity. The higher the CRC, the better, but in actual use, it is necessary to balance with other physical properties as the case may be.
2.2 vortex absorption Rate
The water-absorbent resin of the present invention has a swirl absorption rate of less than 60sec/g, preferably 1 to 55sec/g, more preferably 2 to 45 sec/g. A water-absorbing agent having an absorption rate of more than 60sec/g may not achieve a sufficient effect.
2.3 particle size and distribution
The mass median particle size (D50) of the water-absorbent resin of the present invention is preferably adjusted to 200 to 650. mu.m, more preferably 200 to 550. mu.m, and still more preferably 300 to 500. mu.m. The proportion of particles having a diameter of less than 150 μm is controlled to be 0 to 8 wt%, preferably 0 to 5 wt%, more preferably 0 to 2 wt%. In addition, the smaller the proportion of particles having a diameter of more than 850 μm, the better, the more preferably 0 to 8 wt%, preferably 0 to 5 wt%, and more preferably 0 to 2 wt%. In the present invention, the surface crosslinking is preferably carried out under the condition that the proportion of particles of 150 to 850 μm is 95 wt% or more, more preferably 98 wt% or more. The logarithmic standard deviation (. sigma.. zeta.) of the particle size distribution is preferably controlled to 0.20 to 0.40, more preferably 0.20 to 0.38, and still more preferably 0.20 to 0.36.
2.4 residual amount of monomer
The water-absorbent resin of the present invention has a monomer-remaining amount of less than 1000ppm, preferably less than 800ppm, and further preferably less than 500 ppm. Monomer residues above 1000ppm can lead to safety risks in practical applications.
2.5 extractable content
The water-absorbent resin of the present invention has an extractable content of 3 to 35 wt%, preferably 4 to 30 wt%, and more preferably 5 to 25 wt%. An extractable content of less than 3% by weight causes a problem of insufficient liquid-absorbing ability of the water-absorbent resin, while an extractable content of more than 35% by weight, in practical use, causes discomfort of skin contact. In principle, the lower the extractables content, the better without affecting the other criteria.
[3] Use of polyacrylic acid-based water-absorbent resin
The particulate water-absorbent resin of the present invention is not particularly limited in its application, and can be used for absorbent articles such as disposable diapers, sanitary napkins, incontinence pads and the like, preferably for thin absorbent substrates and absorbent articles such as thin absorbent articles.
The absorbent article generally contains other absorbent materials (pulp fibers and the like), and the content of the water-absorbent resin is 30 to 100 wt%, preferably 40 to 100 wt%, more preferably 50 to 100 wt%, and still more preferably 60 to 100 wt%.
[4] Examples of the embodiments
The present invention will be illustrated with the following examples and comparative examples, but the present invention is not limited to the following examples.
Various properties of the water-absorbent resin were measured by the following methods. The water absorbing resin, the water absorbing agent and the absorbent article were used under conditions of 25. + -. 2 ℃ and 50% RH (relative humidity), unless otherwise specified. The physiological saline solution used was a 0.90 wt% aqueous sodium chloride solution.
4.1 centrifuge Water holding Capacity (CRC)
The Centrifuge Retention Capacity (CRC) represents the water absorption capacity of a 0.90 wt% aqueous sodium chloride solution (also referred to as physiological saline) after absorbing water for 30 minutes without pressure and then centrifuging the solution.
0.20g of a water-absorbent resin was weighed out and the weight recorded was W0The cloth bag is put into a cloth bag made of non-woven fabric, sealed and immersed into a physiological saline solution controlled at 25 +/-2 ℃. After 30 minutes, the bag containing the water-absorbent resin was taken out from the aqueous salt solution. Dewatering at 250G for 3 min by centrifuge, and weighing to obtain weight W2. The weight W of the bag was measured after a similar operation without using any water-absorbing agent1. The centrifuge retention capacity (g/g) was calculated as follows.
Centrifugal water retention capacity (g/g) ((W2(g) -W1(g))/W0(g)) -1
4.2 vortex absorption Rate
In a 100mL beaker with a stirrer, 50mL of a sodium chloride solution was added by a pipette, and the beaker was placed on a magnetic stirrer and stirred at 500. + -. 50r/min, thereby confirming that a stable vortex was generated in the liquid surface. 2.000g of the water-absorbent resin was accurately weighed and added to the vortex, and a stopwatch was used to start timing, and when the vortex on the liquid surface disappeared and the liquid surface became horizontal, the end point was set and the time was recorded.
4.3 particle size and distribution
Particle size and distribution were tested by sieving. A quantity of superabsorbent powder is separated into atmospheres of different particle sizes by passing through a series of standard sieves arranged in sequence. The powders for each particle size range were weighed and reported as a percentage of the total weight.
Ensure the sieve is dry. Each screen is checked for light for damage or uncleanness. The damaged screen is replaced. The residual particles were removed with a brush. The tray and each empty sieve (to the nearest 0.1g) were weighed and recorded. The sieves were placed in the correct order (850 microns, 600 microns, 300 microns, 150 microns, 45 microns) on a shaker (fine bottom, coarse top). 100g (to the nearest 0.1g) of the sample to be tested are weighed into a beaker1. The weighed sample was poured into the uppermost sieve. The screen cover is closed as instructed by the manufacturer. The screen oscillator was set as follows: oscillation intensity (70 ± 2)% (according to the settings of the Retsch VE 1000 oscillator), amplitude 1.0 mm, oscillation time 10 min. The shaker was turned on and after 10 minutes each sieve and tray was carefully removed and weighed to the nearest 0.01g, m2. The percentage (w) of each sample was calculated as follows:
the particle diameter corresponding to 50% by weight of R is determined as the mass median particle diameter (D)50). Logarithmic standard deviation (σ)ζ) Represented by the formula, where σ is the smaller valueζMeaning a narrower particle size distribution.
σζ＝0.5×ln(X2/X1)
Wherein, X1And X2Particle sizes were 84.1 wt% and 15.9 wt%, respectively.
4.4 residual amount of monomer
1.00g of the water-absorbent resin particles or the particulate water-absorbing agent was weighed and dispersed in 200mL of 0.90 wt% saline, and a residual monomer was extracted by stirring with a magnetic stirrer (rotation speed 500. + -.50 r/min) for 60 minutes with a stirrer having a length of 25 mm. After 60 minutes, stirring was stopped, and the sample was allowed to stand for 5 minutes and filtered through a 0.45 μm filter (aqueous phase) to prepare a residual monomer measurement sample.
Mobile phase: acetonitrile 90 wt% phosphoric acid aqueous solution 1:9
Flow rate: 1mL/min
And (3) analyzing the column: c18 column
Protection of the column: c18
A detector: UV detector, wavelength 210nm
4.5 extractable content
A test sample is prepared for testing. 200mL of sodium chloride solution was accurately added using a measuring cylinder and transferred to a 250mL conical flask or beaker with a magnetic stirrer. 1.000g of the water-absorbent resin was weighed out accurately, and the weight was recorded. Dissolution was carried out with sodium chloride solution to ensure that all samples were transferred clean. The flask stopper was capped and stirred for 16 hours at 500. + -. 50r/min using an electromagnetic stirrer. A200 mL sodium chloride solution was prepared as a titration blank for the same conditions as the sample. After 16 hours the stirring was stopped and the gel was allowed to settle. The supernatant was filtered off with a buchner funnel with filter paper and no less than 50mL of liquid was collected. The standard NaOH solution was added using a 50mL burette, 50mL of blank sodium chloride solution was titrated to a pH of 10.0, then titration with standard hydrochloric acid solution was continued to a pH of 2.7 and the volume of standard NaOH or hydrochloric acid titrant required for each endpoint was recorded. A burette was used to add standard NaOH solution, titrate 50mL of sample filtrate solution to pH 10.0, then continue to titrate with standard HCl solution to pH 2.7, and record the volume of standard NaOH or HCl titrant required for each endpoint.
Total amount of carboxylic acids (e.g., polycarboxylic acids, etc.) in the supernatant, nCOOHExpressed in molar concentration, given by equation (1),
nCOOH＝(VNaOH，s-VNaOH，b)cNaOH(1)
in the formula (I), the compound is shown in the specification,
VNaOH，s- - -volume, mLTitrating the filtered sample supernatant to the volume required when the pH is 10.0 by using a standard NaOH solution;
VNaOH，bvolume, mL, volume required to titrate a NaOH solution blank to pH 10.0 with a standard NaOH solution;
cNaOHconcentration, mol/L, as titrant, the concentration of NaOH solution titrated to pH 10.0.
Total amount of carboxylate in supernatant, ntotExpressed in moles, given by equation (2),
ntot＝(VHCl，s-VHCl，b)cHCl(2)
in the formula (I), the compound is shown in the specification,
VHCl，svolume, mL, required for titration of sample filtrate solution from pH 10.0 to 2.7
VHCl，bVolume, mL, required for titration of sodium chloride blank solution from pH 10.0 to 2.7
cHClConcentration, mol/L, concentration of HCl solution used as titrant for titrating the pH from 10.0 to 2.7
Total amount of neutralized carboxylic acid in supernatant, nCOONaExpressed in moles, given by equation (3)
nCOONa＝ntot-nCOOH(3)
Relative mass of carboxylic acid, mCOOHRelative mass of sodium carboxylate, mCOONa
Respectively expressed by formula (4) and formula (5),
mCOOH＝nCOOH×MCOOH×Fdil(4)
mCOONa＝nCOONa×MCOONa×Fdil(5)
in the formula (I), the compound is shown in the specification,
MCOOHthe molar mass of acrylic acid being equal to 72g/mol
MCOONaThe molar mass of sodium acrylate is equal to 94g/mol
Fdil-a dilution factor equal to 200/50 ═ 4
The extractables content, w, in percent by mass in the superabsorbent polymer is given by formula (6),
in the formula (I), the compound is shown in the specification,
msmass, g, weight of sample to be measured
4.6 saline absorption in one minute
1.000g of water-absorbent resin are weighed out and the weight recorded is W0(g) The cloth bag is put into a cloth bag made of non-woven fabric, sealed and immersed into a physiological saline solution controlled at 25 +/-2 ℃. After 1 minute, the bag containing the water-absorbent resin was taken out from the saline solution. Suspended for dehydration for 1 minute, and then weighed to obtain a weight W2(g) In that respect The weight W of the bag was measured after a similar operation without using any water-absorbing agent1(g) In that respect The amount of saline absorbed in one minute (g/g) was calculated according to the following formula.
One minute absorbed saline water (g/g) ═ W2(g)-W1(g))/W0(g))-1
Production example 1
The acrylic acid/sodium acrylate mixed monomer solution (acrylic acid/sodium acrylate molar ratio is 2.2/7.8) was transported through a pipeline, the acrylic acid/sodium acrylate monomer concentration was 44.0 wt%, and the monomer solution flow rate was 5932 kg/h. The temperature of the monomer solution is 80-90 ℃. Polyethylene glycol diacrylate (molecular weight 522) having a concentration of 11.3% by weight was fed into the branch of the monomer solution line at a flow rate of 35 kg/h. Further, an aqueous solution of sodium persulfate having a concentration of 4% by weight (a flow rate of 77kg/h) was fed to the monomer through a branch port of the monomer solution pipe by a feed pump to initiate polymerization. The reaction liquid is sprayed to the reaction bed for polymerization reaction to obtain the hydrogel polymer. Crushing the water-containing gel polymer twice by a granulator (the aperture of a primary crushing granulator is 16 mm; the aperture of a secondary crushing granulator is 16 mm) to obtain gel particles with the particle size of 10 micrometers-5 mm, and then drying the gel particles at 180-210 ℃ for 35 minutes to obtain the cross-linked structure polymer. The crosslinked polymer is ground, ground and sieved into water-absorbent resin 1-1 with the particle size of 106-850 microns, the water content is 3.2 wt%, the CRC is 46.5g/g, the monomer residual quantity is 1124ppm, and the extractable content is 18.2 wt%.
Example 1
100 parts by weight of the water-absorbent resin 1-1 of production example 1 was heated to 67 ℃ and 5.05 parts by weight of a mixed surface-crosslinking agent solution comprising 1, 2-propanediol, 1, 4-butanediol, ethylene glycol diglycidyl ether and water (weight ratio 0.658:0.395:0.046:4) and 8 parts by weight of a 10 wt% aqueous solution of sodium persulfate were added to the water-absorbent resin by atomization (residual-control-agent effective amount/monomer-remaining amount: 7.1), and the water-absorbent resin had a water content of 12.7 wt% as calculated, and was heated at 180 ℃ for 40 minutes. 100 parts by weight of the above water-absorbing agent were mixed with 1.317 parts by weight of an aluminum sulfate solution having a concentration of 10.3% by weight and 0.184 part by weight of silica (particle diameter: less than 100 nm) powder, respectively, to obtain water-absorbing agent 1, CRC of 32.5g/g, one minute saline absorption of 27.8g/g, monomer residual amount of 426ppm, monomer residual rate of 37.9%, and extractable content of 15.5% by weight.
Example 2
100 parts by weight of water-absorbent resin 1-1 in production example 1 was heated to 67 ℃ and 5.05 parts by weight of a mixed surface-crosslinking agent solution comprising 1, 2-propanediol, 1, 4-butanediol, ethylene glycol diglycidyl ether, and water (weight ratio 0.658:0.395:0.046:4) was added to the water-absorbent resin by atomization and heated at 180 ℃ for 40 minutes to obtain water-absorbing agent 2', CRC of 33.5g/g, monomer-remaining amount of 1106ppm, and extractable content of 14.3 wt%. 100 parts by weight of water-absorbing agent 2' was mixed with 16 parts by weight of a 5% by weight aqueous solution of sodium persulfate (residual-controller-effective amount/monomer-remaining amount ═ 7.2), and the water-absorbing resin had a water content of 13.1% by weight, as calculated, and heated at 130 ℃ for 30 minutes, followed by mixing with 1.317 parts by weight of a 10.3% by weight aqueous solution of aluminum sulfate and 0.184 parts by weight of silica (particle diameter less than 100 nm) powder, to give water-absorbing agent 2, CRC of 33.8g/g, one minute absorbed saline amount of 26.8g/g, monomer-remaining amount of 226ppm, monomer-remaining rate of 20.4%, extractable content of 15.8% by weight, and extractables change rate of 10.5%.
Example 3
The same procedure as in example 1 was repeated except that an aluminum sulfate solution and a sodium persulfate solution were simultaneously atomized and mixed with the water-absorbent resin 1-1 (effective amount of residual control agent/residual monomer amount: 7.1) to adjust the water content of the water-absorbent resin to 14.0% by weight, followed by heating at 190 ℃ for 30 minutes, to obtain a water-absorbing agent 3 having a CRC of 33.2g/g, a one-minute saline absorption of 26.3g/g, a residual monomer amount of 211ppm, a residual monomer amount of 18.8%, an extractable content of 16.0% by weight, and an extractables change of 11.9%.
Example 4
The same procedure as in example 1 was conducted except that the heating temperature was lowered to 90 deg.C, except that the water-absorbent resin had a water content of 13.1% by weight, to obtain a water-absorbing agent 4 having a CRC of 33.4g/g, a monomer-remaining amount of 236ppm, a monomer-remaining ratio of 20.1%, an extractables content of 15.4% by weight, and an extractables change ratio of 7.7%, by carrying out the same treatment (effective amount of residual control agent/residual monomer amount of 7.1%).
Example 5
The water-absorbent resin had a water content of 13.1% by weight, and was subjected to the same treatment as in example 2 except that the heating temperature was lowered to 60 ℃ and the heating time was increased to 60 minutes (effective amount of residual control agent/residual monomer amount: 7.2), to obtain a water-absorbing agent 5 having a CRC of 33.8g/g, a residual monomer amount of 162ppm, a residual monomer ratio of 14.6%, an extractable content of 15.2% by weight and an extractables change ratio of 6.3%.
Example 6
The amount of sodium persulfate was increased to 25 parts by weight (effective amount of residual control agent/residual monomer amount of 11.3), the water content of the water-absorbent resin was 19.0% by weight, and the same treatment as in example 2 was conducted to obtain a water-absorbing agent 6 having a CRC of 34.3g/g, a residual monomer amount of 62ppm, a residual monomer ratio of 5.6%, an extractable content of 17.9% by weight, and a change in extractable content of 25.2%.
Example 7
The amount of sodium persulfate was reduced to 10 parts by weight (effective amount of residual control agent/residual monomer amount of 4.5), the water content of the water-absorbent resin was 8.6% by weight, and the same treatment as in example 2 was conducted to obtain a water-absorbing agent 7 having a CRC of 32.3g/g, a residual monomer amount of 425ppm, a residual monomer ratio of 38.4%, an extractable content of 15.1% by weight, and a change in extractable content of 5.6%.
Example 8
The same procedures as in example 2 were repeated except that sodium persulfate was replaced with sodium sulfite (effective amount of residual control agent/residual monomer amount of 7.2) and the water-absorbent resin had a water content of 13.1% by weight, to give a water-absorbing agent 8 having a CRC of 33.3g/g, a residual monomer amount of 225ppm, a residual monomer ratio of 20.3%, an extractable content of 16.9% by weight and an extractables change ratio of 18.2%.
Comparative example 1
The same procedures as in example 2 were carried out except for replacing the sodium persulfate solution with 5 parts by weight of a solution having a concentration of 10% by weight (effective amount of residual control agent/residual monomer amount of 4.5) and adjusting the water content to 4.3% by weight, to give comparative water-absorbing agent 1 having a residual monomer amount of 846ppm, a residual monomer ratio of 76.5%, an extractable content of 15.9% by weight and an extractables change ratio of 11.2%.
Comparative example 2
The same procedures as in example 2 were conducted except that the heating temperature was lowered to 40 c, the effective amount of the residue-controlling agent/the residual monomer amount was 7.2, the water content of the water-absorbent resin was 13.1% by weight, and the heating time was increased to 60 minutes, to obtain comparative water-absorbing agent 2 having a CRC of 34.2g/g, a residual monomer amount of 796ppm, a residual monomer ratio of 72.0%, an extractable content of 15.1% by weight, and a change in extractable content of 6.2%.
Comparative example 3
The same procedures as in example 8 were conducted except that the sodium sulfite concentration was replaced with 15% by weight (effective amount of residual-controlling agent/residual monomer amount of 21.6), the water-absorbent resin had a water content of 11.7% by weight, the heating temperature was increased to 180 deg.C, and comparative water-absorbing agent 3 was obtained, the CRC being 34.3g/g, the residual monomer amount being 212ppm, the residual monomer ratio being 19.2%, the extractable content being 23.6% by weight, and the extractables change ratio being 65%.
Comparative example 4
The same procedures as in example 8 except for replacing the sodium sulfite concentration by 0.1% by weight (effective amount of residual-controlling agent/residual monomer amount of 0.144) and the water-absorbent resin having a water content of 13.8% by weight were conducted to obtain comparative water-absorbing agent 4 having a CRC of 34.6g/g, a residual monomer amount of 656ppm, a residual monomer ratio of 59.3%, an extractable content of 15.4% by weight, and a change in extractables ratio of 7.7%.
Production example 2
49.0000g of prepared 10 wt% polyethylene glycol diacrylate solution, 24.5000g of 10 wt% sodium persulfate solution and 4.9000g of 10 wt% azodiisobutyl amidine hydrochloride solution are accurately weighed respectively. 4211.50g of a 26 wt% acrylic acid diluted solution was accurately weighed and placed in a 6.5L reaction vessel. Meanwhile, 500.00g of the dilute acrylic acid solution is accurately weighed. The above solutions were mixed, the flow of nitrogen was adjusted to 5L/min, and polymerization was initiated at 6 ℃. When the peak temperature decreases, the polymerization reaction is considered to be complete. Entering a curing section and continuing to react for 15 min. And crushing the water-containing gel polymer for three times by using a granulator, adding a sodium hydroxide solution in the gel crushing process to neutralize the gel, wherein the particle size of the gel is 10 micrometers-5 millimeters, and then drying the gel particles at 140 ℃ for 40 minutes to obtain the cross-linked structure polymer. The crosslinked polymer is crushed, ground and sieved into a water absorbent resin 2-1 with the particle size of 106-850 microns, the CRC is 43.0g/g, the monomer residual quantity is 2282ppm, and the extractable matter content is 8.7 wt%.
Example 9
100 parts by weight of the water absorbing resin 2-1 in production example 1 and 3.8 parts by weight of a mixed surface cross-linking agent solution containing 1, 2-propanediol, ethylene glycol diglycidyl ether and water (weight ratio 1.2:0.07:2.53) were mixed and subjected to surface treatment at 140 ℃ for 30 minutes to obtain a water absorbing agent 9' having a CRC of 33.8g/g, a monomer remaining amount of 2172ppm and an extractable content of 7.3 wt%. 100 parts by weight of water-absorbing agent 2' was mixed with 15 parts by weight of a 10% by weight aqueous sodium sulfite solution (residual-controller-effective amount/monomer-remaining amount ═ 6.9) and the water-absorbent resin had a water content of 11.7% by weight, and heated at 60 ℃ for 40 minutes, followed by mixing with 1.317 parts by weight of a 10.3% by weight aluminum sulfate solution and 0.184 parts by weight of silica (particle size less than 100 nm) powder to obtain water-absorbing agent 9 having CRC of 33.3g/g, one-minute salt water absorption of 32.8g/g, monomer-remaining amount of 350ppm, monomer-remaining rate of 16.1%, extractables content of 8.4% by weight, and extractables change rate of 15.1%.
Example 10
The amount of the sodium sulfite solution used in example 9 was reduced to 10 parts by weight at a concentration of 0.5% by weight (effective amount of residual control agent/residual monomer amount of 0.23) and the water-absorbent resin had a water content of 8.2% by weight, and otherwise the same procedures as in example 9 were repeated to obtain water-absorbing agent 10 having a CRC of 33.6g/g, a one-minute amount of saline absorbed water of 33.4g/g, a residual monomer amount of 603ppm, a residual monomer ratio of 27.8%, an extractable content of 7.3% by weight and an extractables change ratio of 0%.
Example 11
A water-absorbing agent 11 was obtained by changing the sodium sulfite solution in example 9 to a sodium hydrogen sulfite solution having a concentration of 2% by weight (effective amount of the residual controlling agent/residual amount of monomer ═ 1.38) and a water content of the water-absorbent resin of 12.8% by weight in the same manner as in the treatment of example 9, and had a CRC of 33.7g/g, a one-minute absorbed saline solution amount of 32.6g/g, a residual amount of monomer of 425ppm, a residual rate of monomer of 19.6%, an extractable content of 8.6% by weight and a change rate of extractables of 17.8%.
Example 12
A water-absorbing agent 12 was obtained in the same manner as in the treatment of example 9 except that the sodium sulfite solution in example 9 was changed to 30 parts by weight of a 10% strength by weight sodium metabisulfite solution (effective amount of residual control agent/residual monomer amount: 13.8) and the water-absorbent resin had a water content of 20.8% by weight, and a CRC of 34.2g/g, a one-minute saline absorption amount of 32.8g/g, a residual monomer amount of 32ppm, a residual monomer amount of 1.5%, an extractable content of 11.2% by weight and an extractable content of 53.4%.
Example 13
Water-absorbing agent 13 was obtained in the same manner as in example 9 except that the sodium sulfite solution in example 9 was changed to a sodium persulfate/azobisisobutyramidine hydrochloride mixed solution having a concentration of 5% by weight (mass ratio 1:1, effective amount of residual control agent/residual monomer amount of 3.5), the water-absorbent resin had a water content of 12.4% by weight, and water-absorbing agent 13 had a CRC of 34.2g/g, a saline-absorbing amount per minute of 30.8g/g, a residual monomer amount of 455ppm, a residual monomer ratio of 20.9%, an extractable content of 8.2% by weight, and a change in extractables ratio of 12.3% was obtained.
Example 14
Water-absorbing agent 14 was obtained in the same manner as in example 9 except that the sodium sulfite solution in example 9 was changed to 8 parts by weight of a 5% strength by weight sodium persulfate solution and 7 parts by weight of a 5% strength by weight sodium sulfite solution (effective amount of residual control agent/residual monomer amount of 1.84), and the water-absorbent resin had a water content of 11.7% by weight, and the treatment of example 9 was repeated, the CRC was 33.5g/g, the one-minute saline absorption amount was 31.2g/g, the residual monomer amount was 255ppm, the residual monomer ratio was 11.7%, the extractable content was 8.0% by weight, and the extractables ratio was 9.6%.
Comparative example 5
The same procedure as in example 9 was repeated except that the sodium sulfite concentration was reduced to 1% by weight, the amount was reduced to 5 parts by weight (effective amount of residual control agent/residual monomer amount of 0.23), the water content was adjusted to 4.8% by weight, and the heat treatment temperature was reduced to 35 deg.c, to obtain comparative water-absorbing agent 5 having CRC of 33.7g/g, one-minute amount of brine absorbed of 33.5g/g, residual monomer amount of 1890ppm, residual monomer amount of 87.0%, extractable content of 7.6% by weight, and change rate of extractables of 4.1%.
Comparative example 6
The same procedure as in example 9 was repeated except that the sodium sulfite concentration was increased to 25% by weight and the amount was increased to 25 parts by weight (effective amount of residual controlling agent/residual monomer amount: 28.8), the water content was adjusted to 15.0% by weight, and the heat treatment temperature was increased to 190 ℃ to obtain comparative water-absorbing agent 6 having a CRC of 34.7g/g, a one-minute salt water absorption of 29.5g/g, a residual monomer amount of 106ppm, a residual monomer amount of 4.9%, an extractable content of 13.6% by weight, and an extractables change rate of 86.3%.
As is clear from examples 1 to 14 and comparative examples 1 to 6, the present invention can effectively reduce the monomer residue in the water-absorbent resin by controlling the kind and amount of the monomer residue control agent, the water content during the addition, and the heat treatment temperature, and the water-absorbent resin has a monomer residue ratio of 1.5 to 38.4% and an extractable change ratio of 0 to 53.4% after the addition of the monomer residue control agent, as compared with a water-absorbent resin to which no monomer residue control agent is added. Both can satisfy the above numerical value range at the same time, but the monomer residue control agent is not added, and as seen from the comparative example, when the monomer residue ratio is satisfied, the extractables change rate cannot be within the above range of values, and if the extractables change rate is thus satisfied, the monomer residue ratio of the water-absorbent resin cannot be within the above range of values, and therefore, by adding the monomer residue control agent, it is possible to realize an index that does not affect the extractables content of the water-absorbent resin, etc., and it is possible to efficiently produce a super-absorbent resin having a high liquid-absorption rate.
Thus, the present invention provides a method which can efficiently produce a water-absorbent resin having a high liquid-absorption rate, and obtains a water-absorbent resin having a high liquid-absorption rate.
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, or direct or indirect applications in other related fields, which are made by the contents of the present specification, are included in the scope of the present invention.
Claims (14)
1. A method for producing a polyacrylic acid-based water-absorbent resin, comprising:
(a) obtaining a monomer aqueous solution containing an unsaturated acrylic monomer and a crosslinking agent,
(b) polymerizing the aqueous monomer solution to form a water-containing gel-like crosslinked polymer,
(c) granulating the water-containing gel-like crosslinked polymer into gel-like water-absorbent resin particles, drying, grain-refining, sieving, surface crosslinking, and post-treating, wherein one or more of a peroxy initiator, an azo initiator, or an inorganic reducing agent-based monomer residue control agent is added in any one or more processes after the grain-refining step,
(c1) during or after the monomer residue control agent and the water-absorbent resin are mixed, in the processing process of the water-absorbent resin, the water content of the water-absorbent resin in at least one processing section is 8.2-20.8 wt%;
(c2) and heating or insulating the water-absorbent resin to enable the material temperature to reach 60-190 ℃ in the mixing process of the monomer residue control agent and the water-absorbent resin and/or after mixing.
2. The method for producing a polyacrylic acid-based water-absorbent resin according to claim 1, wherein the ratio of the amount of the monomer residue control agent to the amount of the acrylic monomer residue of the water-absorbent resin before the addition is 0.23 to 13.8.
3. The method for producing a polyacrylic acid-based water-absorbent resin according to claim 1, wherein the ratio of the amount of the monomer residue control agent to the amount of the acrylic monomer residue of the water-absorbent resin before the addition is 1.38 to 7.2.
4. The method for producing a polyacrylic acid-based water-absorbent resin according to claim 1, wherein the aqueous monomer solution of the unsaturated acrylic monomer and the crosslinking agent is a mixed solution containing acrylic acid and/or a water-soluble salt of acrylic acid as a main component; the crosslinking agent is selected from one or more of a compound containing a plurality of vinyl groups in a molecule, a compound containing at least one vinyl compound and at least one functional group capable of reacting with a carboxyl group on the unsaturated monomer in a molecule, and a compound containing a plurality of functional groups capable of reacting with a carboxyl group on the unsaturated monomer in a molecule.
5. The method for producing a polyacrylic acid-based water-absorbent resin according to claim 1, wherein the peroxy initiator is one or more of a peroxide, a hydroperoxide, and a persulfate.
6. The method for producing a polyacrylic acid-based water-absorbent resin according to claim 4, wherein the peroxy initiator is one or more of hydrogen peroxide, sodium persulfate, potassium persulfate, ammonium persulfate, calcium peroxide, magnesium peroxide, zinc peroxide, potassium peroxymonosulfate, strontium peroxide, t-butyl peroxide, and methyl ethyl ketone peroxide.
7. The method for producing a polyacrylic acid-based water-absorbent resin according to claim 1, wherein the azo initiator is one or more selected from the group consisting of azobisisobutyronitrile, azobisisoheptonitrile, azobisisovaleronitrile, azobisformamide, azobisisobutyramidine hydrochloride, diisopropyl azodicarboxylate, and bisazo aminobenzene.
8. The method for producing a polyacrylic acid-based water-absorbent resin according to claim 1, wherein the inorganic reducing agent is one or more of sulfite, bisulfite, pyrosulfite, dithionite, thiosulfite.
9. The method for producing a polyacrylic acid-based water-absorbent resin according to claim 1, wherein the water-absorbent resin has a water content of 11.7 to 20.8 wt% in at least one stage of the process of the water-absorbent resin during or after the mixing of the monomer residue-controlling agent with the water-absorbent resin.
10. The method for producing a polyacrylic acid-based water-absorbent resin according to claim 1, wherein the water-absorbent resin is heated or kept at a temperature of 90 to 180 ℃ during and/or after the mixing of the monomer residue-controlling agent with the water-absorbent resin.
11. The method for producing a polyacrylic acid-based water-absorbent resin according to claim 1, wherein the extractable content of the water-absorbent resin after the addition of the monomer residue control agent is 0 to 53.4% as compared with a water-absorbent resin to which no monomer residue control agent is added.
12. The method for producing a polyacrylic acid-based water-absorbent resin according to claim 1 or 11, wherein the extractable content of the water-absorbent resin after the addition of the monomer residue-controlling agent is 0 to 18.2% as compared with a water-absorbent resin to which no monomer residue-controlling agent has been added.
13. The method for producing a polyacrylic acid-based water-absorbent resin according to claim 1, wherein the water-absorbent resin has a monomer residue ratio of 1.5 to 38.4% after the addition of the monomer residue-controlling agent, as compared with a water-absorbent resin to which no monomer residue-controlling agent has been added.
14. The method for producing a polyacrylic acid-based water-absorbent resin according to claim 1 or 13, wherein the water-absorbent resin has a monomer residue ratio of 1.5 to 27.8% after the addition of the monomer residue-controlling agent, as compared with a water-absorbent resin to which no monomer residue-controlling agent has been added.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113402199A (en) * | 2021-07-30 | 2021-09-17 | 中国水利水电第七工程局有限公司 | Additive, cement stabilized base applying additive and preparation method of cement stabilized base |
| CN113603379A (en) * | 2021-07-30 | 2021-11-05 | Oppo广东移动通信有限公司 | Ceramic composite material, shell, preparation method of shell and electronic equipment |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1939955A (en) * | 2005-09-30 | 2007-04-04 | 株式会社日本触媒 | Method for manufacturing particulate water-absorbing agent and particulate water-absorbing agent |
| CN110372891A (en) * | 2019-06-17 | 2019-10-25 | 宜兴丹森科技有限公司 | The manufacturing method of polyacrylic water-absorbing resin |
-
2019
- 2019-12-31 CN CN201911413827.4A patent/CN111040096A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1939955A (en) * | 2005-09-30 | 2007-04-04 | 株式会社日本触媒 | Method for manufacturing particulate water-absorbing agent and particulate water-absorbing agent |
| CN110372891A (en) * | 2019-06-17 | 2019-10-25 | 宜兴丹森科技有限公司 | The manufacturing method of polyacrylic water-absorbing resin |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113402199A (en) * | 2021-07-30 | 2021-09-17 | 中国水利水电第七工程局有限公司 | Additive, cement stabilized base applying additive and preparation method of cement stabilized base |
| CN113603379A (en) * | 2021-07-30 | 2021-11-05 | Oppo广东移动通信有限公司 | Ceramic composite material, shell, preparation method of shell and electronic equipment |
| CN113402199B (en) * | 2021-07-30 | 2023-07-21 | 中国水利水电第七工程局有限公司 | Additive, water-stable base layer using the additive and preparation method thereof |
| CN113603379B (en) * | 2021-07-30 | 2023-08-08 | Oppo广东移动通信有限公司 | Ceramic composite material, shell, preparation method of shell and electronic equipment |
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