[One]Cross-Citation with Related Application(s)
[2]
This application is based on Korean Patent Application No. 10-2019-0172494 on December 20, 2019, Korean Patent Application No. 10-2020-0148077 on November 6, 2020, and Korean Patent Application No. 10-2020 on January 20, 2020 Claims the benefit of priority based on -0007114 and Korean Patent Application No. 10-2020-0175607 filed on December 15, 2020, and all contents disclosed in the documents of the Korean patent applications are incorporated as a part of this specification.
[3]
[4]
The present invention relates to a method for preparing a super absorbent polymer composition. More specifically, it relates to a method for preparing a super absorbent polymer composition in which the amount of fine powder is significantly reduced.
background
[5]
Super Absorbent Polymer (SAP) is a synthetic polymer material that can absorb water 500 to 1,000 times its own weight. Material), etc., are named differently. The superabsorbent polymer as described above started to be put to practical use as a sanitary tool, and is now widely used as a soil repair agent for horticulture, water-retaining material for civil engineering and construction, sheets for seedlings, freshness maintenance agent in the food distribution field, and materials for poultice. .
[6]
Such superabsorbent polymers are mainly used in the field of sanitary materials such as diapers and sanitary napkins. In the sanitary material, the superabsorbent polymer is generally included in a state spread in the pulp. However, in recent years, efforts have been made to provide sanitary materials such as diapers having a thinner thickness, and as a part of that, the content of pulp is reduced or, further, so-called pulpless diapers, etc. in which no pulp is used at all Development is actively underway.
[7]
As such, in the case of a sanitary material in which the content of pulp is reduced or in which pulp is not used, the superabsorbent polymer is included in a relatively high ratio, so that the superabsorbent polymer particles are inevitably included in multiple layers in the sanitary material. In order for the entire superabsorbent polymer particles included in multiple layers to more efficiently absorb a large amount of liquid, such as urine, the superabsorbent polymer needs to exhibit not only high absorption performance but also a fast absorption rate.
[8]
Meanwhile, the superabsorbent polymer is generally prepared by polymerizing a monomer to prepare a hydrogel polymer containing a large amount of moisture, and drying the hydrogel polymer and then pulverizing the hydrogel polymer into resin particles having a desired particle size. However, as described above, when the hydrogel polymer is dried and then pulverized, a large amount of fine powder is generated, thereby deteriorating the physical properties of the superabsorbent polymer finally manufactured.
[9]
In addition, in order to reuse the fine powder, it is common to mix the fine powder with water to agglomerate to prepare a fine powder re-assembly, and then add the fine powder re-assembly prepared by a process such as drying/pulverization/classification. However, due to the water used at this time, energy consumption increases during the drying process, and problems such as an increase in load on the device may occur, thereby reducing productivity in manufacturing the superabsorbent polymer.
[10]
Accordingly, in order to fundamentally solve this problem, there is a continuous demand for the development of a technology capable of manufacturing a super absorbent polymer without generation of fine powder.
[11]
DETAILED DESCRIPTION OF THE INVENTION
technical challenge
[12]
Accordingly, the present invention relates to a method for producing a superabsorbent polymer composition, which can be pulverized to a normal particle level without agglomeration between particles by adding an additive having a specific structure to the hydrogel polymer and pulverizing, thereby significantly reducing the amount of fine powder generated during the process. it's about
means of solving the problem
[13]
In order to solve the above problems, the present invention,
[14]
1) cross-linking and polymerizing a water-soluble ethylenically unsaturated monomer having an acid group at least partially neutralized in the presence of an internal cross-linking agent and a polymerization initiator to form a hydrogel polymer;
[15]
2) mixing the hydrogel polymer with a carboxylic acid-based additive and pulverizing it to prepare water-containing superabsorbent polymer particles and a pulverized product containing the additive; and
[16]
3) drying the pulverized product to prepare a superabsorbent polymer composition including superabsorbent polymer particles and the additive;
[17]
The carboxylic acid-based additive is at least one selected from the group consisting of a carboxylic acid represented by the following formula (1) and a salt thereof, a method for preparing a superabsorbent polymer composition is provided:
[18]
[Formula 1]
[19]

[20]
In Formula 1,
[21]
A is alkyl having 5 to 21 carbon atoms,
[22]
B 1 is -OCO-, -COO-, or -COOCH(R 1 )COO-,
[23]
B 2 is -CH 2 -, -CH 2 CH 2 -, -CH(R 2 )-, -CH=CH-, or -C≡C-,
[24]
Here, R 1 and R 2 are each independently an alkyl having 1 to 4 carbon atoms,
[25]
n is an integer from 1 to 3,
[26]
C is a carboxyl group.
[27]
Effects of the Invention
[28]
According to the method for preparing the superabsorbent polymer composition of the present invention, the water-containing gel polymer is pulverized in the presence of the carboxylic acid-based additive to produce a superabsorbent polymer composition comprising superabsorbent polymer particles having a desired particle size without aggregation between the pulverized particles. manufacturing is possible. In addition, as the hydrogel polymer is pulverized to a normal particle level, the amount of fine powder generated during the preparation of the superabsorbent polymer composition may be significantly reduced.
Brief description of the drawing
[29]
1 is a flowchart of a conventional method for manufacturing a super absorbent polymer.
[30]
2 is a flowchart illustrating a method of manufacturing a super absorbent polymer composition according to an exemplary embodiment.
[31]
3 is a photograph showing the evaluation of particle aggregation properties of the hydrogel polymer prepared in Example 3.
[32]
4 is a photograph showing the evaluation of particle aggregation properties of the hydrogel polymer prepared in Example 7.
[33]
5 is a photograph showing the evaluation of particle aggregation properties of the hydrogel polymer prepared in Comparative Example 3.
[34]
6 is a photograph showing the evaluation of particle aggregation properties of the hydrogel polymer prepared in Comparative Example 6.
Modes for carrying out the invention
[35]
The terminology used herein is used to describe exemplary embodiments only, and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present specification, terms such as "comprise", "comprising" or "having" are intended to designate that an embodied feature, step, element, or a combination thereof is present, and includes one or more other features or steps; It should be understood that the possibility of the presence or addition of components, or combinations thereof, is not precluded in advance.
[36]
Since the present invention may have various changes and may have various forms, specific embodiments will be illustrated and described in detail below. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.
[37]
Since the present invention may have various changes and may have various forms, specific embodiments will be illustrated and described in detail below. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.
[38]
Hereinafter, a method for manufacturing a super absorbent polymer and a super absorbent polymer according to specific embodiments of the present invention will be described in more detail.
[39]
Before that, the terminology used herein is for the purpose of referring to particular embodiments only, and is not intended to limit the present invention. And, as used herein, the singular forms also include the plural forms unless the phrases clearly indicate the opposite.
[40]
[41]
According to one embodiment of the invention,
[42]
1) crosslinking and polymerizing a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized in the presence of an internal crosslinking agent and a polymerization initiator to form a hydrogel polymer (step 1);
[43]
2) mixing the hydrogel polymer with a carboxylic acid-based additive and pulverizing it to prepare water-containing superabsorbent polymer particles and a pulverized product including the additive (step 2); and
[44]
3) drying the pulverized product to prepare a superabsorbent polymer composition including superabsorbent polymer particles and the additive (step 3);
[45]
The carboxylic acid-based additive is at least one selected from the group consisting of a carboxylic acid represented by the following formula (1) and a salt thereof, a method for preparing a superabsorbent polymer composition is provided:
[46]
[47]
[Formula 1]
[48]

[49]
In Formula 1,
[50]
A is alkyl having 5 to 21 carbon atoms,
[51]
B 1 is -OCO-, -COO-, or -COOCH(R 1 )COO-,
[52]
B 2 is -CH 2 -, -CH 2 CH 2 -, -CH(R 2 )-, -CH=CH-, or -C≡C-,
[53]
Here, R 1 and R 2 are each independently an alkyl having 1 to 4 carbon atoms,
[54]
n is an integer from 1 to 3,
[55]
C is a carboxyl group.
[56]
[57]
As used herein, the term “polymer” or “polymer” refers to a polymerized state of a water-soluble ethylenically unsaturated monomer, and may cover all water content ranges or particle diameter ranges. Among the above polymers, a polymer having a water content (moisture content) of about 30% by weight or more in a state before drying after polymerization may be referred to as a hydrogel polymer, and particles obtained by pulverizing and drying the hydrogel polymer may be referred to as a crosslinked polymer. there is.
[58]
In addition, the term "super absorbent polymer particles" refers to a particulate material comprising a crosslinked polymer comprising an acidic group and a water-soluble ethylenically unsaturated monomer in which at least a part of the acidic group is neutralized and crosslinked by an internal crosslinking agent.
[59]
In addition, the term "super absorbent polymer" refers to a crosslinked polymer obtained by polymerizing a water-soluble ethylenically unsaturated monomer containing an acidic group and neutralizing at least a portion of the acidic group, or powder consisting of particles of a superabsorbent polymer obtained by pulverizing the crosslinked polymer, depending on the context. It refers to a base resin in the form of (powder), or to the crosslinked polymer or the base resin through additional processes, for example, drying, pulverization, classification, surface crosslinking, etc. used Accordingly, the term “super absorbent polymer composition” may be interpreted as including a composition including a super absorbent polymer, that is, a plurality of super absorbent polymer particles.
[60]
Also, the term “normal particles of super absorbent polymer” refers to particles having a particle diameter of 150 μm to 850 μm among super absorbent polymer particles.
[61]
Also, the term “fine powder” refers to particles having a particle diameter of less than 150 μm among the superabsorbent polymer particles. The particle size of the resin particles may be measured according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 220.3 method.
[62]
In addition, the term "chopping" refers to shredding the hydrogel polymer into small pieces to increase drying efficiency, and is used separately from pulverizing to a normal particle level.
[63]
[64]
Conventional superabsorbent polymers are prepared by drying the hydrogel polymer and then pulverizing the hydrogel polymer to a desired particle size. ) process is in progress. However, due to the adhesiveness of the hydrogel polymer in this chopping process, the hydrogel polymer cannot be pulverized to the level of micro-sized particles and becomes an agglomerated gel. When the hydrogel polymer in the aggregated gel form is left to dry, a plate-shaped dry body is formed, and in order to pulverize it to the level of micro-sized particles, a multi-stage pulverization process is required. come.
[65]
[66]
Specifically, FIG. 1 is a flowchart of a conventional method for manufacturing a super absorbent polymer. Referring to FIG. 1 , a conventional super absorbent polymer has been prepared including the following steps.
[67]
(Polymerization) forming a hydrogel polymer by cross-linking and polymerizing a water-soluble ethylenically unsaturated monomer having an acid group at least partially neutralized in the presence of an internal crosslinking agent and a polymerization initiator;
[68]
(Chopping; chopping) chopping the hydrogel polymer;
[69]
(Drying) drying the chopped hydrogel polymer; and
[70]
(Grinding/Classification) classifying the dried polymer into normal particles and fine powder after grinding;
[71]
As described above, the chopped hydrogel polymer has an agglomerated gel form with a size of about 1 cm to 10 cm, and this chopped hydrogel polymer is laminated on a belt with a perforated bottom and supplied from the bottom or top. dried by hot air. Since the polymer dried by the drying method exhibits a plate shape rather than a particle shape, the classification step after pulverization is performed so that the produced particles become normal particles, that is, particles having a particle diameter of 150 μm to 850 μm, after coarse pulverization It has been performed as a step of classifying and then pulverizing again and then classifying. Since the amount of fine powder separated in the final classification step by this manufacturing method is about 10% to about 20% by weight relative to the total weight of the final manufactured superabsorbent polymer, the separated fine powder is mixed with an appropriate amount of water to re-assemble the fine powder It was reused as a method of inputting the post-chopping step or the pre-drying step.
[72]
[73]
However, there have been problems such as causing an increase in device load and/or energy consumption when reintroducing the fine powder re-assembly mixed with water to the pulverization or drying process for reuse of the fine powder, and the fine powder remaining unclassified This caused deterioration of the physical properties of the superabsorbent polymer.
[74]
[75]
Therefore, the present inventors understood that the amount of fine powder generated in the conventional manufacturing method is greatly affected by the particle size input to the grinding process, and in the chopping process, the hydrogel polymer can be pulverized to a micro size without agglomeration between the hydrogel polymers. If there is, it was determined that the amount of fine powder generated during the manufacturing process could be reduced. Accordingly, as a result of experimenting with various kinds of additives that can lower the adhesiveness of the hydrogel polymer in the chopping process, when the hydrogel polymer is mixed with the above-described carboxylic acid-based additive and then pulverized, the The present invention was completed by confirming that the hydrogel polymer was able to be pulverized into micro-level particles due to the low adhesiveness of the hydrogel polymer. This is because the carboxylic acid-based additive mixed with the hydrogel polymer is adsorbed to the surface of the hydrogel polymer to prevent aggregation of the pulverized hydrogel polymers. In addition, since the drying process proceeds in the form of micro-sized particles, not only drying is facilitated, but a separate grinding process is not required after the drying process, so that the content of generated fine powder can be significantly reduced.
[76]
[77]
Specifically, FIG. 2 is a flowchart illustrating a method for preparing a super absorbent polymer composition according to an exemplary embodiment. Referring to FIG. 2 , unlike the prior art, after preparing the hydrogel polymer, it is pulverized to a normal particle level and then dried to prepare a superabsorbent polymer composition.
[78]
In this case, the carboxylic acid-based additive has a hydrophobic functional group and a hydrophilic functional group at the same time. On the other hand, since the water-soluble ethylenically unsaturated monomer contains an acidic group (-COOH) and/or a neutralized acidic group (-COO- ) , on the surface of the hydrogel polymer prepared by polymerization, acidic groups remaining without participating in polymerization A large amount of hydrophilic moieties due to (-COOH) and/or neutralized acidic groups (-COO - ) are present. Therefore, when the additive is mixed with the hydrogel polymer, the hydrophilic functional group of the additive is adsorbed to at least a part of the hydrophilic portion present on the surface of the hydrogel polymer, and the surface of the polymer to which the additive is adsorbed is different from that of the additive. Hydrophobicity is exhibited by the hydrophobic functional group located at the terminal. Accordingly, aggregation between the resin particles can be suppressed.
[79]
More specifically, in the carboxylic acid-based additive, the hydrophobic functional group is an alkyl group having 5 to 21 carbon atoms (part A), the hydrophilic functional group is a C part, a carboxyl group (COOH), and in the case of a salt, a carboxylate group (COO - ), The hydrophobic functional group and the hydrophilic functional group are located at both ends of the additive, respectively. In particular, the carboxylic acid-based additive further includes a (B 1 -B 2 ) portion in addition to the A and C portions at both ends, and the (B 1 -B 2 ) portion is for the polymer surface, which may be insufficient with only the C portion. It plays a role in improving the adsorption performance. Accordingly, the additive having the structure of Formula 1 has superior adsorption performance to the surface of the polymer exhibiting hydrophilicity, compared to the compound having an AC structure without a (B 1 -B 2 ) moiety, thereby preventing aggregation of the superabsorbent polymer particles. can be effectively suppressed.
[80]
Accordingly, the hydrogel polymer can be pulverized to a normal particle level without agglomeration between particles, and the amount of fine powder generated during the process can be significantly reduced as the drying process proceeds after the hydrogel polymer is pulverized to the normal particle level. In addition, since the method of manufacturing the superabsorbent polymer composition according to the exemplary embodiment does not necessarily require a grinding process and a classification process after drying, the manufacturing cost of the superabsorbent polymer can be greatly reduced.
[81]
In addition, when the hydrogel polymer is pulverized in the presence of the carboxylic acid-based additive, part A, which is a hydrophobic functional group included in the additive, imparts hydrophobicity to the surface of the pulverized superabsorbent polymer particles to relieve friction between the particles, resulting in superabsorbent properties. While the apparent density of the resin is increased, the hydrophilic functional group C portion included in the additive is also bound to the superabsorbent polymer particles so that the surface tension of the resin is not reduced. Accordingly, the superabsorbent polymer composition prepared according to the above-described manufacturing method may exhibit an equivalent level of surface tension and have a higher apparent density compared to a composition not using such an additive.
[82]
[83]
Hereinafter, the method for preparing the superabsorbent polymer composition of one embodiment will be described in more detail for each step.
[84]
[85]
(Step 1)
[86]
The step is a step of cross-linking and polymerizing a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized in the presence of an internal crosslinking agent and a polymerization initiator to form a hydrogel polymer, wherein the water-soluble ethylenically unsaturated monomer, an internal crosslinking agent and polymerization It may consist of a step of preparing a monomer composition by mixing an initiator, and a step of thermally or photopolymerizing the monomer composition to form a hydrogel polymer.
[87]
[88]
The water-soluble ethylenically unsaturated monomer may be any monomer commonly used in the preparation of super absorbent polymers. As a non-limiting example, the water-soluble ethylenically unsaturated monomer may be a compound represented by the following Chemical Formula 2:
[89]
[Formula 2]
[90]
R-COOM'
[91]
In Formula 2,
[92]
R is an alkyl group having 2 to 5 carbon atoms including an unsaturated bond,
[93]
M' is a hydrogen atom, a monovalent or divalent metal, an ammonium group, or an organic amine salt.
[94]
Preferably, the monomer may be at least one selected from the group consisting of (meth)acrylic acid and monovalent (alkali) metal salts, divalent metal salts, ammonium salts and organic amine salts of these acids.
[95]
As such, when (meth)acrylic acid and/or a salt thereof is used as the water-soluble ethylenically unsaturated monomer, it is advantageous because a superabsorbent polymer with improved water absorption can be obtained. In addition, the monomer includes maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2-methacryloylethanesulfonic acid, 2-(meth)acryloylpropanesulfonic acid or 2-(meth) ) acrylamide-2-methyl propane sulfonic acid, (meth)acrylamide, N-substituted (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, methoxypolyethylene Glycol (meth)acrylate, polyethylene glycol (meth)acrylate, (N,N)-dimethylaminoethyl (meth)acrylate, (N,N)-dimethylaminopropyl (meth)acrylamide and the like can be used.
[96]
Here, the water-soluble ethylenically unsaturated monomer may have an acidic group, and at least a portion of the acidic group may be neutralized by a neutralizing agent. Specifically, in the mixing of the water-soluble ethylenically unsaturated monomer having an acidic group, the internal crosslinking agent, the polymerization initiator, and the neutralizing agent, at least a portion of the acidic groups of the water-soluble ethylenically unsaturated monomer may be neutralized. In this case, as the neutralizing agent, a basic material such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, etc. that can neutralize an acidic group may be used.
[97]
In addition, the degree of neutralization of the water-soluble ethylenically unsaturated monomer, which refers to the degree of neutralization by the neutralizing agent among the acidic groups included in the water-soluble ethylenically unsaturated monomer, is 50 to 90 mol%, or, 60 to 85 mol%, or 65 to 85 mole %, or 65 to 75 mole %. The range of the degree of neutralization may vary depending on the final physical properties, but if the degree of neutralization is too high, the neutralized monomer is precipitated and it may be difficult for polymerization to proceed smoothly. It can exhibit properties like elastic rubber, which is difficult to handle.
[98]
[99]
In addition, the term 'internal crosslinking agent' used in this specification is a term used to distinguish it from a surface crosslinking agent for crosslinking the surface of the superabsorbent polymer particles to be described later. serves to make The crosslinking in the above step proceeds without a surface or internal division, but when the surface crosslinking process of the superabsorbent polymer particles to be described later proceeds, the surface of the particles of the superabsorbent polymer finally produced has a structure crosslinked by a surface crosslinking agent, The inside has a structure crosslinked by the internal crosslinking agent.
[100]
As the internal crosslinking agent, any compound may be used as long as it enables the introduction of a crosslinking bond during polymerization of the water-soluble ethylenically unsaturated monomer. As a non-limiting example, the internal crosslinking agent is N,N'-methylenebisacrylamide, trimethylolpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol (meth)acrylate, polyethylene glycol di( Meth) acrylate, propylene glycol di (meth) acrylate, polypropylene glycol (meth) acrylate, butanediol di (meth) acrylate, butylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylic Rate, hexanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipentaerythritol pentaacrylate, glycerin tri Multifunctional crosslinking agents such as (meth)acrylate, pentaerythol tetraacrylate, triarylamine, ethylene glycol diglycidyl ether, propylene glycol, glycerin, or ethylene carbonate may be used alone or in combination of two or more, It is not limited. Preferably, among them, polyethylene glycol di(meth)acrylate may be used.
[101]
The crosslinking polymerization of the water-soluble ethylenically unsaturated monomer in the presence of such an internal crosslinking agent may be carried out by thermal polymerization, photopolymerization or hybrid polymerization in the presence of a polymerization initiator, optionally a thickener, plasticizer, storage stabilizer, antioxidant, etc. There, the specific details will be described later.
[102]
In the monomer composition, the internal crosslinking agent may be used in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. For example, the internal crosslinking agent is 0.01 parts by weight or more, 0.05 parts by weight or more, or 0.1 parts by weight or more, 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 It can be used in parts by weight or less, or 0.7 parts by weight or less. If the content of the upper internal crosslinking agent is too low, crosslinking does not occur sufficiently, and it may be difficult to implement strength above an appropriate level.
[103]
[104]
In addition, the polymerization initiator may be appropriately selected depending on the polymerization method. When using the thermal polymerization method, a thermal polymerization initiator is used, and when using the photopolymerization method, a photopolymerization initiator is used, and a hybrid polymerization method (thermal and light). both of the thermal polymerization initiator and the photopolymerization initiator can be used. However, even by the photopolymerization method, a certain amount of heat is generated by light irradiation such as ultraviolet irradiation, and a certain amount of heat is generated according to the progress of the polymerization reaction, which is an exothermic reaction, so a thermal polymerization initiator may be additionally used.
[105]
The photopolymerization initiator may be used without limitation in its composition as long as it is a compound capable of forming radicals by light such as ultraviolet rays.
[106]
As the photopolymerization initiator, for example, benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, benzyl dimethyl ketal Ketal), acyl phosphine (acyl phosphine) and alpha-aminoketone (α-aminoketone) may be used at least one selected from the group consisting of. On the other hand, specific examples of acylphosphine include diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, phenylbis (2,4,6-trimethylbenzoyl) phosphine oxide, ethyl (2,4,6- trimethylbenzoyl)phenylphosphinate etc. are mentioned. A more diverse photoinitiator is well described in Reinhold Schwalm's book "UV Coatings: Basics, Recent Developments and New Application (Elsevier 2007)" p115, but is not limited to the above-described examples.
[107]
In addition, as the thermal polymerization initiator, at least one selected from the group consisting of a persulfate-based initiator, an azo-based initiator, hydrogen peroxide, and ascorbic acid may be used. Specifically, examples of the persulfate-based initiator include sodium persulfate (Na 2 S 2 O 8 ), potassium persulfate (K 2 S 2 O 8 ), ammonium persulfate (Ammonium persulfate; (NH 4 ) 2 S 2 O 8) and the like, and examples of the azo initiator include 2,2-azobis-(2-amidinopropane) dihydrochloride (2,2-azobis(2-amidinopropane) dihydrochloride), 2,2-azobis -(N,N-dimethylene)isobutyramidine dihydrochloride (2,2-azobis-(N,N-dimethylene)isobutyramidine dihydrochloride), 2-(carbamoylazo)isobutyronitrile (2-(carbamoylazo) )isobutylonitril), 2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride ), 4,4-azobis-(4-cyanovaleric acid) (4,4-azobis-(4-cyanovaleric acid)) and the like. More various thermal polymerization initiators are well described in Odian's book 'Principle of Polymerization (Wiley, 1981)', p203, and are not limited to the above-described examples.
[108]
The polymerization initiator may be used in an amount of 2 parts by weight or less based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. That is, when the concentration of the polymerization initiator is too low, the polymerization rate may be slowed and the residual monomer may be extracted in a large amount in the final product, which is not preferable. Conversely, when the concentration of the polymerization initiator is higher than the above range, the polymer chain constituting the network is shortened, so that the content of the water-soluble component is increased and the physical properties of the resin may be lowered, such as lowered absorbency under pressure, which is not preferable.
[109]
[110]
The monomer composition may further include additives such as a thickener, a plasticizer, a storage stabilizer, and an antioxidant, if necessary.
[111]
In addition, the monomer composition including the monomer may be in a solution state dissolved in a solvent such as water, and the solid content in the monomer composition in the solution state, that is, the concentration of the monomer, the internal crosslinking agent, and the polymerization initiator It may be appropriately adjusted in consideration of time and reaction conditions. For example, the solids content in the monomer composition may be 10 to 80% by weight, or 15 to 60% by weight, or 30 to 50% by weight.
[112]
When the monomer composition has a solid content in the above range, it is not necessary to remove unreacted monomers after polymerization by using the gel effect phenomenon that occurs in the polymerization reaction of a high concentration aqueous solution, and the pulverization efficiency when pulverizing the polymer to be described later is improved. It can be advantageous to control.
[113]
The solvent that can be used at this time can be used without limitation in its composition as long as it can dissolve the above-mentioned components, for example, water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, propylene glycol , Ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl amyl ketone, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethyl ether , toluene, xylene, butyrolactone, carbitol, methylcellosolve acetate and N,N-dimethylacetamide may be used in combination.
[114]
[115]
On the other hand, cross-linking polymerization of a water-soluble ethylenically unsaturated monomer having at least a partially neutralized acidic group may be carried out without particular limitation on the structure, as long as the hydrogel polymer can be formed by thermal polymerization, photopolymerization, or hybrid polymerization.
[116]
Specifically, the polymerization method is largely divided into thermal polymerization and photopolymerization depending on the polymerization energy source. In general, when thermal polymerization is carried out, it may be carried out in a reactor having a stirring shaft such as a kneader. The process may be carried out in a reactor equipped with a conveyor belt or in a flat-bottomed vessel, but the polymerization method described above is an example, and the present invention is not limited to the polymerization method described above.
[117]
For example, as described above, the hydrogel polymer obtained by thermal polymerization by supplying hot air or heating the reactor to a reactor such as a kneader having a stirring shaft is fed to the reactor outlet according to the shape of the stirring shaft provided in the reactor. The discharged hydrogel polymer may be in the form of several centimeters to several millimeters. Specifically, the size of the obtained hydrogel polymer may vary depending on the concentration and injection speed of the injected monomer composition, and a hydrogel polymer having a weight average particle diameter of 2 to 50 mm can be obtained.
[118]
In addition, as described above, when photopolymerization is performed in a reactor equipped with a movable conveyor belt or a flat-bottomed container, the form of the hydrogel polymer obtained may be a hydrogel polymer on a sheet having the width of the belt. At this time, the thickness of the polymer sheet varies depending on the concentration of the injected monomer composition and the injection rate or injection amount, but it is preferable to supply the monomer composition so that a polymer sheet having a thickness of usually about 0.5 to about 5 cm can be obtained. Do. When the monomer composition is supplied so that the thickness of the polymer on the sheet is too thin, the production efficiency is low, which is not preferable. When the thickness of the polymer on the sheet exceeds 5 cm, the polymerization reaction occurs evenly over the entire thickness due to the excessive thickness it may not be
[119]
In this case, the hydrogel polymer obtained by this method may have a moisture content of 30 to 70 wt%. For example, the water content of the hydrogel polymer may be 35% by weight or more, 40% by weight or more, 45% by weight or more, or 50% by weight or more, and 70% by weight or less, 65% by weight or less, or 60% by weight or less. . If the water content of the hydrogel polymer is too low, it may not be effectively pulverized because it is difficult to secure an appropriate surface area in the subsequent pulverization step. it can be difficult to do
[120]
Meanwhile, throughout the present specification, "moisture content" refers to a value obtained by subtracting the weight of the polymer in a dry state from the weight of the hydrogel polymer as the content of moisture occupied with respect to the total weight of the hydrogel polymer. Specifically, it is defined as a value calculated by measuring the weight loss due to evaporation of moisture in the polymer during drying by raising the temperature of the polymer in the crumb state through infrared heating. At this time, the drying conditions are set to 40 minutes including 5 minutes of the temperature rise step in such a way that the temperature is raised from room temperature to about 180° C. and then maintained at 180° C., and the moisture content is measured.
[121]
The hydrogel polymer formed through step 1 has a three-dimensional network structure in which main chains formed by polymerization of the water-soluble ethylenically unsaturated monomers are crosslinked by the internal crosslinking agent. As such, when the hydrogel polymer has a three-dimensional network structure, the water holding capacity and absorbency under pressure, which are general physical properties of the superabsorbent polymer, can be significantly improved compared to the case of a two-dimensional linear structure that is not further crosslinked by an internal crosslinking agent.
[122]
[123]
(Step 2)
[124]
In the above step, the hydrogel polymer is mixed with the carboxylic acid-based additive and then pulverized to prepare a pulverized product containing the water-containing superabsorbent polymer particles and the additive, rather than chopping the hydrogel polymer, but a final product To prepare water-containing superabsorbent polymer particles pulverized to a particle size of about 150 μm to about 850 μm that can be applied to, the carboxylic acid-based additive is used for this purpose.
[125]
[126]
In this case, the carboxylic acid-based additive is at least one selected from the group consisting of the carboxylic acid represented by Formula 1 and a metal salt thereof. Specifically, the carboxylic acid-based additive is a carboxylic acid represented by Formula 1, an alkali metal salt of the carboxylic acid represented by Formula 1, and an alkaline earth metal salt of a carboxylic acid represented by Formula 1 at least one selected from More specifically, the carboxylic acid-based additive is one of the carboxylic acid represented by the formula (1), an alkali metal salt of the carboxylic acid represented by the formula (1), and an alkaline earth metal salt of the carboxylic acid represented by the formula (1).
[127]
[128]
In Formula 1, A is a hydrophobic portion and may be a linear or branched alkyl group having 5 to 21 carbon atoms, but when A is an alkyl group having a linear structure, in terms of inhibiting aggregation of pulverized particles and improving dispersibility more advantageous When A is an alkyl group having less than 5 carbon atoms, there is a problem that the aggregation control of the pulverized particles is not effectively achieved due to the short chain length, and when A is an alkyl group having more than 21 carbon atoms, the mobility of the additive is reduced and the hydrogel It may not be effectively mixed with the polymer, or there may be a problem in that the cost of the composition increases due to an increase in the cost of the additive.
[129]
Specifically, in Formula 1, A is a linear alkyl having 5 to 21 carbon atoms, that is, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decanyl, n-undecanyl , n-dodecanyl, n-tridecanyl, n-tetradecanyl, n-pentadecanyl, n-hexadecanyl, n-heptadecanyl, n-octadecanyl, n-nonadecanyl, n- icosanil, or n-heticosanyl.
[130]
More specifically, A may be a linear alkyl having 6 to 18 carbon atoms. For example, A may be -C 6 H 13 , -C 11 H 23 , -C 12 H 25 , -C 17 H 35 , or -C 18 H 37 .
[131]
[132]
In addition, in Formula 1, the (B 1 -B 2 ) part serves to improve the adsorption performance on the polymer surface, which may be insufficient only with the C part, and when the carbon number of B 2 is 3 or more, the B 1 part As the distance between the portion C and C increases, the adsorption performance for the hydrogel polymer may be deteriorated.
[133]
In this case, R 1 and R 2 are each independently, linear or branched alkyl having 1 to 4 carbon atoms, more specifically, R 1 and R 2 are each independently, methyl, ethyl, propyl, isopropyl , butyl, isobutyl, sec-butyl, or tert-butyl, but in terms of adsorption of the additive to the superabsorbent polymer particles, it is advantageous that the molecular structure of the additive is not bulky, so R 1 and R 2 may be all methyl.
[134]
Also, in Formula 1, n may be 1, 2, or 3. More specifically, n, meaning the number of (B 1 -B 2 ), is that the (B 1 -B 2 ) part is for reinforcing the adsorption performance for the C part, and the carboxylic acid-based additive is a hydrogel Considering the molecular length for effectively adsorbing to the polymer, n is preferably 1.
[135]
[136]
Specifically, in Formula 1, B 1 may be , , , or , where * is a binding site with a neighboring atom.
[137]
For example, B 1 may be , or .
[138]
[139]
In addition, in Formula 1, B 2 may be , , , , , or , where * is a binding site with a neighboring atom. At this time, in terms of improving the adsorption performance of the additive to the crosslinked polymer together with the C moiety, B 2 is preferably , , or .
[140]
[141]
In addition, in Formula 1, part C is a hydrophilic part and is a carboxyl group (COOH), but when the carboxylic acid-based additive is a salt, it is a carboxylate group (COO - ).
[142]
[143]
In other words, the carboxylic acid-based additive may be a compound represented by the following Chemical Formula 1a:
[144]
[Formula 1a]
[145]

[146]
In Formula 1a,
[147]
M is H + , a monovalent cation of an alkali metal, or a divalent cation of an alkaline earth metal,
[148]
k is 1 if M is H + or a monovalent cation of an alkali metal, and 2 if M is a divalent cation of an alkaline earth metal,
[149]
Descriptions of A, B 1 , B 2 and n are the same as defined in Formula 1 above.
[150]
[151]
More specifically, when the carboxylic acid-based additive is an alkali metal salt of a carboxylic acid represented by Formula 1, the additive may be represented by Formula 1':
[152]
[Formula 1']
[153]

[154]
In Formula 1',
[155]
M 1 is an alkali metal, for example sodium or potassium,
[156]
Descriptions of A, B 1 , B 2 and n are the same as defined in Formula 1 above.
[157]
[158]
In addition, when the carboxylic acid-based additive is an alkaline earth metal salt of a carboxylic acid represented by Formula 1, the additive may be represented by Formula 1”:
[159]
[Formula 1"]
[160]

[161]
In Formula 1", M 2 is an alkaline earth metal, for example, calcium,
[162]
Descriptions of A, B 1 , B 2 and n are the same as defined in Formula 1 above.
[163]
[164]
For example, the carboxylic acid-based additive may be any one carboxylic acid selected from the group consisting of:
[165]

[166]
.
[167]
[168]
Alternatively, the carboxylic acid-based additive may be any one alkali metal salt selected from the group consisting of:
[169]

[170]

[171]
above,
[172]
M 1 is each independently an alkali metal.
[173]
[174]
Alternatively, the carboxylic acid-based additive may be any one alkaline earth metal salt selected from the group consisting of:
[175]

[176]

[177]
above,
[178]
M 2 is each independently an alkaline earth metal.
[179]
[180]
For example, the carboxylic acid-based additive may be any one of compounds represented by the following Chemical Formulas 1-1 to 1-7, but is not limited thereto:
[181]
.
[182]
[183]
Meanwhile, the carboxylic acid-based additive may be used in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the hydrogel polymer. When too little of the additive is used, it is not uniformly adsorbed on the surface of the hydrogel polymer, which may cause re-agglomeration of the particles after pulverization. can be For example, the carboxylic acid-based additive is 0.01 parts by weight or more, 0.015 parts by weight or more, or 0.1 parts by weight or more, and 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, relative to 100 parts by weight of the hydrogel polymer; Or 1 part by weight or less may be used.
[184]
[185]
A method of mixing these additives with the hydrogel polymer is not particularly limited as long as it is a method capable of uniformly mixing them with the hydrogel polymer, and may be appropriately adopted and used. Specifically, the additive may be mixed in a dry manner, dissolved in a solvent and then mixed in a solution state, or the additive may be melted and then mixed.
[186]
Among them, for example, the additive may be mixed in a solution state dissolved in a solvent. In this case, as the solvent, any type of solvent may be used without limitation, including an inorganic solvent or an organic solvent, but water is most appropriate in consideration of the ease of the drying process and the cost of the solvent recovery system. In addition, the solution is prepared by mixing the additive and the hydrogel polymer into a reaction tank, or by putting the hydrogel polymer in a mixer and spraying the solution, or by continuously supplying the hydrogel polymer and the solution to a continuously operated mixer and mixing them. etc. can be used.
[187]
[188]
After mixing the hydrogel polymer and the additive, the mixture may be pulverized to prepare a pulverized product in which the water-containing superabsorbent polymer particles and the additive are mixed. Specifically, the pulverizing step may be performed so that the pulverized water-containing superabsorbent polymer particles have a particle size of a normal particle size.
[189]
At this time, the pulverizer used for pulverization is a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, and a cutter mill. , a disc mill, a shred crusher, a crusher, a chopper, and a disc cutter may include any one selected from the group consisting of a grinding device, but Examples are not limited.
[190]
Alternatively, as a grinder, a pin mill, a hammer mill, a screw mill, a roll mill, a disk mill, or a jog mill may be used. , but is not limited to the above example.
[191]
Among them, the grinding may be performed by a chopper, more specifically, a meat chopper. In this case, the meat chopper may include a perforated plate, and the perforated plate may be provided with a plurality of small cut holes having a predetermined size. In addition, the hole size (meaning the diameter of the hole) of the small hole provided in the perforated plate may be 0.2 mm to 5 mm. In other words, it can be seen that the pulverization is performed by pushing the hydrogel polymer mixed with the additive to be pulverized while passing through the fine holes of the perforated plate. At this time, an extruder may be used to extrude the hydrogel polymer, for example, a single or multiple screw type extruder may be used.
[192]
In addition, the pulverization may be performed while passing through two or more perforated plates. To this end, as the meat chopper, one including a chopper module in which two or more perforated plates are connected in series may be used, or two or more meat choppers including one perforated plate may be used by connecting in series.
[193]
For example, when using a meat chopper having two or more perforated plates, the perforated plates may be arranged in series in the order of screw-knife-perforated plate-knife-perforated plate in the meat chopper, at this time It is more preferable that the distance between the stencil and the knife be 1 mm or less in order to increase the cutting efficiency.
[194]
More specifically, the hydrogel polymer mixed with the carboxylic acid-based additive may be pulverized using a meat chopper including a mincing module equipped with a first porous plate and a second porous plate. The hole sizes of the small cut holes provided in each of the first and second perforated plates may be the same as or different from each other. It is preferable that the first perforated plate is smaller than the hole size of the small hole provided. For example, the hole size of the small hole provided in the first perforated plate is about 1 mm to about 5 mm, and the hole size of the small hole provided in the second perforated plate is about 0.2 mm to about 1 mm. can
[195]
As such, after passing the hydrogel polymer mixed with the carboxylic acid additive primarily through the first perforated plate having a plurality of small holes having a hole size of 1 mm to 5 mm, the hole size is 0.2 mm to 1.0 When the pulverization is performed by passing it through the second perforated plate having a plurality of fine cut holes of mm in diameter, the particle size distribution at the same level as that of the product is realized after drying, so that the process of pulverizing the dried body can be omitted. It has the advantage of being able to fundamentally prevent the occurrence.
[196]
[197]
Here, the "water-containing superabsorbent polymer particles" included in the pulverized material are particles having a water content (moisture content) of about 30% by weight or more. It may have a moisture content of 30 to 70% by weight.
[198]
In addition, the water-containing superabsorbent polymer particles may have a particle size of a normal particle level, that is, a particle diameter of 150 μm to 850 μm. Specifically, the pulverized product contains 89 wt% or more, 90 wt% or more, 92 wt% or more, 93 wt% or more, 94 wt% or more, or It may contain 95% by weight or more. The particle size of the resin particles may be measured according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 220.3 method. Alternatively, the content of the water-containing superabsorbent polymer particles having a particle diameter of 150 μm to 850 μm in the pulverized product is considered that an additional pulverization process is not performed after drying and surface crosslinking when preparing the superabsorbent polymer composition. It can be seen that the content of the superabsorbent polymer particles having a particle diameter of 150 μm to 850 μm in the superabsorbent polymer composition is the same.
[199]
[200]
Meanwhile, at least some of the additives included in the pulverized material may be present on the surface of the water-containing superabsorbent polymer particles. Here, “at least a portion of the additive is present on the surface of the water-containing superabsorbent polymer particles” means that at least a portion of the additive is adsorbed or bonded to the surface of the water-containing superabsorbent polymer particle. Specifically, the additive may be physically or chemically adsorbed on the surface of the superabsorbent polymer. More specifically, the hydrophilic functional group of the additive may be physically adsorbed to the hydrophilic portion of the surface of the superabsorbent polymer by intermolecular force such as dipole-dipole interaction. As such, the hydrophilic portion of the additive is physically adsorbed to the surface of the superabsorbent polymer particle to surround the surface, and the hydrophobic portion of the additive is not adsorbed to the surface of the resin particle, so that the resin particle has a type of micelle structure. As an additive may be coated. This is because the carboxylic acid-based additive is not added during the polymerization process of the water-soluble ethylenically unsaturated monomer, but is added after the polymer is formed. The phenomenon of re-agglomeration between the superabsorbent polymer particles may be further suppressed.
[201]
[202]
(Step 3)
[203]
The step is a step of drying the pulverized material to prepare a superabsorbent polymer composition including the superabsorbent polymer particles and the additive, and drying the pulverized material to dry moisture in the water-containing superabsorbent polymer particles am. Specifically, the drying of the pulverized product may be performed so that the moisture content of each of the plurality of superabsorbent polymer particles included in the prepared superabsorbent polymer composition is about 10% by weight or less, specifically, about 0.01 to about 10% by weight. can
[204]
In this case, the drying of the pulverized product may be performed in a moving type. This moving type drying is divided into fixed-bed type drying and the presence/absence of flow of material during drying.
[205]
The moving type drying refers to a method of drying the drying body while mechanically stirring. At this time, the direction in which the hot air passes through the material may be the same as or different from the circulation direction of the material. Alternatively, the material may be circulated inside the dryer, and the heat medium fluid (fruit oil) may be passed through a separate pipe outside the dryer to dry the material.
[206]
On the other hand, fixed-bed type drying refers to a method in which a material to be dried is stopped on a floor such as a perforated iron plate through which air can pass, and hot air passes through the material from the bottom to dry.
[207]
Therefore, it is preferable to dry the pulverized material in a fluidized drying method in terms of preventing aggregation between the water-containing superabsorbent polymer particles in the pulverized material to be dried in the above step, and drying can be completed within a short time.
[208]
As an apparatus capable of drying by such a fluid drying method, a horizontal-type mixer, a rotary kiln, a paddle dryer, a steam tube dryer, or a generally used A fluid dryer or the like may be used.
[209]
At this time, the temperature in the dryer may be about 80 ℃ to about 250 ℃. When the temperature in the dryer is too low, the drying time may be excessively long. When the drying temperature is too high, only the surface of the polymer is dried, and there is a risk that the physical properties of the superabsorbent polymer finally formed may decrease. Therefore, preferably, the temperature in the dryer may be carried out at a temperature of about 100 °C to about 240 °C, more preferably at a temperature of about 110 °C to about 220 °C.

WE CLAIMS

1) forming a hydrogel polymer by crosslinking and polymerizing a water-soluble ethylenically unsaturated monomer having at least a partially neutralized acidic group in the presence of an internal crosslinking agent and a polymerization initiator; 2) mixing the hydrogel polymer with a carboxylic acid-based additive and pulverizing it to prepare water-containing superabsorbent polymer particles and a pulverized product containing the additive; and 3) drying the pulverized product to prepare super absorbent polymer particles and a super absorbent polymer composition including the additive, wherein the carboxylic acid-based additive is a carboxylic acid represented by the following Chemical Formula 1 and a salt thereof At least one selected from the group consisting of, a method for preparing a superabsorbent polymer composition: [Formula 1] In Formula 1, A is an alkyl having 5 to 21 carbon atoms, B 1 is -OCO-, -COO-, or -COOCH(R 1 )COO-, and B 2 is -CH 2 -, -CH 2 CH 2 -, -CH(R 2 )-, -CH=CH-, or -C≡C-, wherein R 1 and R 2are each independently an alkyl having 1 to 4 carbon atoms, n is an integer of 1 to 3, and C is a carboxyl group.
[Claim 2]
The method of claim 1, wherein the hydrogel polymer has a water content of 30 to 70 wt%.
[Claim 3]
According to claim 1, wherein in Formula 1, A is -C 6 H 13 , -C 11 H 23 , -C 12 H 25 , -C 17 H 35 , or -C 18 H 37 of the superabsorbent polymer composition. manufacturing method.
[Claim 4]
The method of claim 1, wherein in Formula 1, B 1 is , or , where * is a bonding site with a neighboring atom.
[Claim 5]
The method of claim 1, wherein in Formula 1, B 2 is , , or , where * is a bonding site with a neighboring atom.
[Claim 6]
The method of claim 1 , wherein the carboxylic acid-based additive is at least one selected from the group consisting of a carboxylic acid represented by Formula 1, an alkali metal salt thereof, and an alkaline earth metal salt thereof.
[Claim 7]
The method according to claim 1, wherein the carboxylic acid-based additive is any one of compounds represented by the following Chemical Formulas 1-1 to 1-7: .
[Claim 8]
The method of claim 1, wherein the carboxylic acid-based additive is used in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the hydrogel polymer.
[Claim 9]
The method of claim 1 , wherein the carboxylic acid-based additive is mixed in a solution state dissolved in a solvent.
[Claim 10]
The method of claim 1, wherein the pulverization is performed by a meat chopper.
[Claim 11]
The method of claim 10 , wherein the meat chopper includes a perforated plate, and the perforated plate is provided with a plurality of small holes having a predetermined size.
[Claim 12]
The method of claim 11 , wherein the hole size of the small hole provided in the perforated plate is 0.2 mm to 5 mm.
[Claim 13]
The method of claim 1 , wherein the water-containing superabsorbent polymer particles have a moisture content of 30 to 70% by weight.
[Claim 14]
The method of claim 1 , wherein the pulverized material contains 89 wt% or more of water-containing superabsorbent polymer particles having a particle diameter of 150 μm to 850 μm relative to the total weight.
[Claim 15]
The method of claim 1 , wherein at least some of the additives in the pulverized material are present on the surface of the water-containing superabsorbent polymer particles.
[Claim 16]
The method of claim 1 , wherein the drying is performed in a moving type.
[Claim 17]
The method of claim 1 , wherein the drying is performed at a temperature of 80° C. to 250° C. for 10 minutes to 3 hours .
[Claim 18]
The method of claim 1 , wherein the prepared superabsorbent polymer composition contains less than 10% by weight of fine powder having a particle diameter of less than 150 μm relative to the total weight.
[Claim 19]
The method of claim 1 , wherein after the drying of the pulverized material, an additional pulverizing step is not included.
[Claim 20]
The method of claim 1 , further comprising forming a surface crosslinking layer on at least a portion of the surface of the superabsorbent polymer particles in the presence of a surface crosslinking agent.