KR100255827B1 - Process for preparation of a particle reinforced super absorbent polymer - Google Patents

Abstract

PURPOSE: A process for preparing the titled highly water-absorbable polymer by adding an inorganic or organic filler having a melting point higher than that of a highly water-absorbable polymer to a monomer solution, polymerizing and subjecting to capture in highly water-absorbable polymer gel is provided. Whereby, the obtained polymer has excellent physical properties such as absorption power and salt absorption power as well as maintaining basic physical properties without lowering absorption power. CONSTITUTION: This titled polymer is prepared by the process consisting of: mixing 1 to 40% by weight of an inorganic or organic filler having a melting point higher than that of a highly water-absorbable polymer and a particle size of 50 to 1,000 micrometer with 0.01 to 10% by weight of a dispersing agent having an HLB value of 5 to 20 and a monomer; dispersing in a monomer solution having high fluidization; solution-polymerizing at 90 to 140deg.C for 5 to 60 min, subjecting to capture in a highly water-absorbable polymer; drying; and pulverizing.

Description

Manufacturing method of filler-containing superabsorbent polymer

The present invention relates to a method for preparing a filler-containing superabsorbent polymer, and more particularly, has excellent resin properties such as absorbency and salt absorption ability, and the absorption rate is much higher than that of existing products while maintaining the basic properties without degrading the absorption ability. It relates to a method for producing a fast super absorbent polymer (hereinafter also referred to as "super absorbent polymer").

Superabsorbent polymers are widely used as diapers, feminine sanitary napkins, hygiene products, soil repair agents, industrial sealing agents, wire moisture barriers, and moisture removal agents in organic solvents.

Particularly, the absorption rate is one of the important properties for the final product. If the absorption rate is poor, the flow rate is larger than the absorption rate when the fluid is instantaneously flowed, so the feeling of wearing is poor and the object is uncomfortable. Not good because it also flows. However, if the absorption rate is fast enough, it is very comfortable to wear by absorbing the fluid within a short time when the fluid is introduced, and there is little risk of leakage. Therefore, the rate of absorption in the application of superabsorbent polymer is a very important evaluation item along with other absorption capacity and gel strength.

In order to improve the absorption rate, many attempts have been made to increase the surface area of the superabsorbent polymer particles. US Pat. No. 4,649,164 uses sodium bicarbonate, ammonium carbonate, etc. as a blowing agent to neutralize the acid of the monomer. The generation of carbon dioxide caused bubbles in the polymer during polymerization, resulting in a significant surface area of the substrate of the superabsorbent polymer, thus improving the physical properties such as moisture absorption rate. However, the above method is difficult to manufacture a product of technically uniform physical properties because the conditions for uniformly controlling the foaming is difficult due to the characteristics of the blowing agent by using a carbonate compound which simultaneously occurs the neutralization reaction of the monomer and foaming. In addition, International Publication No. WO88 / 09801 has developed a technique of using an organic blowing agent as a blowing agent in order to solve the disadvantage of the patent. According to the above patent, nitrogen is generated by pyrolysis by using an organic blowing agent, and thus, a high density of bubbles is generated in the medium of the superabsorbent polymer, and thus the surface area is very large. However, low molecular weight compounds are generated by decomposition of the organic foaming agent, and these low molecular weight compounds may have a disadvantage in that they may adversely affect the human body when they are eluted or evaporated by absorption of water in the final use. There is a disadvantage in that a large amount of scattering particles are generated in the crushing process, which is a process of making a foamed superabsorbent polymer into a powder.

The inventors of the present invention have studied a method for increasing the absorption rate, and as a result, the matrix of superabsorbent polymer is completely different from the effect of increasing the surface area due to the foaming effect of volatiles generated by the existing heat or chemical reaction. We have developed a method to increase the absorption rate of superabsorbent polymers by increasing the absorption rate of absorbed water by inserting inorganic or organic fillers, especially polymer particles, into the matrix.

Accordingly, an object of the present invention is to provide a method for preparing a superabsorbent polymer having excellent resin properties such as absorption capacity and salt absorption capacity, and having an extremely high absorption rate than existing products while maintaining basic physical properties without degrading the absorption capacity.

In the method of the present invention for achieving the above object, in the method of preparing a super absorbent polymer, an inorganic or organic filler having a melting point higher than the polymerization temperature of the superabsorbent polymer is added and stirred together with the monomer solution in a highly fluidizable monomer solution. Dispersing and polymerizing it to trap the filler in the superabsorbent polymer gel with reduced fluidity, which is then dried and ground.

Hereinafter, the method of the present invention will be described in more detail.

The new superabsorbent polymer according to the present invention is a superabsorbent polymer which is a polymer prepared by neutralizing 50 to 95 mol% of an existing superabsorbent resin, that is, a monomer having a carboxyl or carboxylate group or a carboxylic anhydride monomer with a salt. Prepared from the polymer.

Suitable water-soluble monomers used in the present invention include vinylcarboxylic acid, vinylsulfonyl acid, vinylamide derivatives and the like, which are typically acrylic acid, methacrylic acid, fumaric acid, acrylic metal salts, methacrylic metal salts, Monomers including acryl amido methyl propane, allyl sulfonic acid, dimethyl amine ethyl methacrylate, and the like are used. These monomers are mixed with water as a solvent to form a polymerization system in which the concentration in the aqueous phase is generally between 25 and 45 wt%, preferably between 30 and 40 wt%. If the concentration is lower than these concentrations, the reaction time is long, and at 45 wt% or more, the monomer may reach a limit solubility and precipitate the monomer. Therefore, the polymerization may not proceed well. The mainly used monomer is acrylic acid.

On the other hand, an inorganic or organic filler having a melting point above the polymerization temperature of the superabsorbent polymer is added together with the monomer solution during the superabsorbent polymer polymerization and stirred to disperse it in a highly fluidizable monomer solution, which is then applied to polymerization means such as heat or light. The filler is entrapped in the superabsorbent polymer gel with reduced fluidity. The superabsorbent polymer gel including the organic or inorganic filler is dried and pulverized to produce superabsorbent polymer particles containing organic or inorganic evenly.

Absorption rate of the polymer prepared as described above is generally increased up to 60% compared to the superabsorbent polymer containing no inorganic or organic filler. In particular, it was possible to prepare a superabsorbent polymer having very good water or salt absorption rate without significantly impairing the existing properties, such as the decrease in absorption capacity and the salt absorption capacity being almost similar.

The polymerization method usable in the present invention is a solution polymerization method or a reverse phase suspension polymerization method, and shows an excellent effect especially in the solution polymerization method. The polymerization temperature at the time of solution polymerization is 60 to 200 degreeC, Preferably it is 90 to 160 degreeC, More preferably, it is between 90 to 140 degreeC. Below 60 ° C., the reaction time was too long, and the addition of inorganic or organic fillers caused precipitation depending on the polymerization method, making it difficult to obtain uniform physical properties. In some cases, the fillers were agglomerated. If the temperature exceeds 200 ° C., the polymerization time is too fast, and in this case, the reaction control is difficult, so that the self-crosslinking reaction of the superabsorbent polymer is excessive, resulting in poor physical properties of the superabsorbent polymer. In addition, the reaction time is carried out for 2 to 120 minutes of polymerization, preferably 5 to 60 minutes for polymerization, and longer than 60 minutes, not only discoloration due to pyrolysis but also increase in crosslinking density due to self-crosslinking. Is lowered.

The polymerization apparatus may use a reactor equipped with a stirrer or may perform stationary polymerization in a vessel. In addition, even when the inorganic or organic filler is stirred well with the monomer solution without polymerization, the uniformly dispersed solution is placed in a container made of a shallow plate, nitrogen-substituted to remove oxygen, and the sealed container is put in an infrared oven or polymerized in a fruit. The polymerization may be carried out by placing the polymerization liquid on the conveyor belt. At this time, the conveyor belt is polymerized while driving, and when the polymer is introduced into the oven, the polymerization rate is further increased when nitrogen is blown to replace oxygen. In the same apparatus, ultraviolet rays may be reacted at low temperature, or photopolymerization by ultraviolet rays and thermal polymerization by infrared rays may be used together.

The inorganic or organic material used in the present invention may be any material having a melting point higher than the polymerization temperature of the superabsorbent polymer, and in particular, the inorganic material is manganese dioxide, silicon dioxide, titanium dioxide, calcium oxide, magnesium oxide, or zirconium. Metal oxides such as oxides. The metal oxide may use a metal oxide surface treated to remove polarity, or may use a metal oxide that is not surface treated. Organic materials include PMMA (polymethylmethacrylate), polystyrene (polystyrene), PVC (polyvinylchloride), polyisoprene, styrene-acrylate copolymer, styrene copolymer, acrylic ester (acrylester) Insoluble water polymer particles or latex solutions, such as copolymers or polyvinyl chorde copolymers, may be used, and single and copolymer flake types such as polyethylene or polypropylene may be used.

On the other hand, the size of the organic or inorganic filler to be added is not particularly limited, but may be a filler of 50 ~ 1000 ㎛ size. Preferably it is 0.01-500 micrometers, More preferably, the filler of 0.1-200 micrometers size is used. The amount of the inorganic or organic filler added may be increased by about 140 wt% of the monomer used in the polymerization, preferably about 5 to 25 wt%, without increasing the basic physical properties of the superabsorbent polymer. At this time, when the added amount exceeds 40wt%, the fluidity of the polymerized monomer solution is poor, and it is difficult to evenly disperse these fillers in the monomer solution, making it difficult to secure uniformity of physical properties, and the polymerization rate is too slow, resulting in normal polymerization. Is difficult. In addition, if less than 1wt% there is a disadvantage that the increase in the rate of absorption as expected is not expressed. When the filler to be added is added in the form of latex, it is best to disperse it in water, but even when using latex dispersed in an organic solvent, it is not a problem at all. In addition, when the inorganic and organic fillers to be added are not well dispersed in the polymerization solution, a dispersing agent having a HLB (Hydrophilic Lipophilic Balance) value of 5 to 20 may be used to assist the dispersion thereof. In this case, as a dispersant used, there is no problem in using a suspending agent which is generally used, but it should not include a functional group capable of reacting with a functional group in a polymer. Suspending agents that satisfy the above conditions may be water-soluble or water-dispersible, and such materials include sorbitol fatty acid, sorbitol fatty acid ether, and sodium laurylbenzene sulfonate. Or anionic surfactants or cationic surfactants such as sodium dodecylbeazene sulfonate. The amount to be used is not particularly limited but can be used in an amount of 0.01 to 10% by weight, preferably 0.1 to 5% by weight, and more preferably 0.5 to 2% by weight, based on the monomers. If it exceeds 10% by weight, the performance of the superabsorbent polymer is lowered. If it is less than 0.01% by weight, the dispersibility of the crosslinking agent to be used decreases, resulting in uneven performance of the superabsorbent polymer.

The initiator used in the polymerization reaction according to the present invention may be a dialkylperoxide, alkylperester, peroxides, redox initiators, or azo initiators. have. These polymerization initiators may be used alone or in combination of two or more. The amount used is in the range of 0.01 to 1% by weight based on the monomer, but the amount generally used is between 0.1 and 0.5% by weight, very preferably 0.2 to 0.5% by weight.

The crosslinking agent used in the present invention is an important factor because it affects the absorption performance of the superabsorbent polymer. Generally, a monomer having a multifunctional vinyl group is used. Commonly used crosslinking agents include trimethylpropane trimethacrylate, trimethylolpropane triacrylate, ethyleneglycol diacrylate, ethylene glycol dimethacrylate (trimethylopropane trimethacrylate). Ethylene glycol dimethacrylate, N, N-methylenebisacrylamide, and polyglycidyl ethers are mainly used such as ethylene glycol diglycidyl ether. Polymethacrylate monomers having low sensitivity depending on the content are mainly used. The amount used varies depending on the type, but may be used between 0.001 and 2 mol% of the super absorbent polymer monomer to be used. If used more than this, the absorption characteristics of the superabsorbent polymer is inferior, and if it is used less, the water-soluble ratio is increased, which is not good for the environment / hygiene, and also the absorption characteristic is inferior. More preferably, between 0.05 and 0.2 mol% of the monomers are very good.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to the following examples. On the other hand, the physical property evaluation method of the super absorbent polymer according to the present invention is as follows.

[Property evaluation method]

Water Absorption: The water absorption capacity was measured by dipping 0.2g of superabsorbent polymer in 1000ml of deionized water in Tea-Bag made of non-woven fabric, preventing it for 1 hour, and taking out Tea-Bag that absorbed water. After standing, the weight is measured to determine the absorption ratio.

Water Absorption = (Weight of Tea-Bag Absorbed-Tea-Bag Weight) / 0.2

Salt absorption capacity: Tea-Bag containing 0.5 g of superabsorbent resin in 0.9 wt% aqueous sodium chloride solution, and left for 1 hour, then taken out and left in air for 30 minutes, and then measured its weight to measure salt absorption learning. .

Salt absorption capacity = (weight of total Tea-Nag absorbed-weight of Tea-Bag) / 0.5

Absorption rate: 0.5g superabsorbent polymer is weighed accurately and the superabsorbent polymer is added to a 250ml beaker containing 100ml of demineralized pure water at 1000rpm. Absorption rate was measured (method 1). In addition, the absorption rate may be determined by measuring the amount of fluid absorbed at 10 second intervals by inserting the Tea-Bag in particular (Method 2).

Example 1

A caustic soda solution in which 170 g of sodium hydroxide was dissolved in 590 g of deionized water was prepared. After cooling the temperature of the solution to room temperature, 320 g of acrylic acid was slowly added to neutralize the acrylic acid. In the above process, the temperature of the solution was all lower than room temperature to prevent the possibility of thermal polymerization. 21% of 1 wt% trimethylpropane trimethacrylate aqueous solution was added to the solution as a crosslinking agent, and 26 g of 10 wt% sorbitan monolaurate aqueous solution was added thereto, followed by stirring for several minutes. While stirring, 40 g of fumed silica (fumed silica, 0.011 micron) was slowly added thereto. After completely dispersing it in the above solution, 13 g of sodium bisulfite 1wt% aqueous solution and 15 g of 1wt% ammonium persulfate aqueous solution were added as a total initiator, followed by stirring. Place and pass the infrared heater. At this time, the temperature of the infrared heater was maintained at 100 ℃ UT to adjust the speed of the conveyor belt was allowed to stay in the infrared heater for 30 minutes to complete the polymerization. The polymerization was carried out under a nitrogen atmosphere. The prepared sample was cut into small specimens, dried in a vacuum dryer, and ground to separate particles between 100 and 1000 μm. As a result of evaluating the physical properties of the superabsorbent polymer, the water absorption capacity per unit weight of the dry sample was 635 times, the salt absorption capacity was 63 times, and the salt solution absorption capacity was 36 times after 1 minute and the salt absorption capacity was 56 times after 10 minutes.

Example 2

Same as Example 1, but 80g of the added silica content. As a result, the water absorption capacity was 543 times, the salt absorption capacity was 61 times, the salt absorption rate was 21 times after 1 minute, and the salt absorption rate was 10 times after 10 minutes.

Comparative Example 1

The experiment was carried out under the same conditions as in Example 1, but the polymerization experiment was conducted without adding silica. As a result of evaluating the physical properties after drying and pulverizing, the water absorption capacity was 627 times and the salt absorption capacity was 67 times, and the salt absorption ratio after 1 minute was 17 times, and the salt absorption ratio after 10 minutes was 62 times (measured by Method 2). .

Example 3

The additive was used in the same manner as in Example 1, but the additives were tested using PVC (HCC EM2070 Grade) latex instead of silica, and 5 wt% of acrylic acid (based on the weight of resin in latex) using the added amount was used. After the preparation as in Example 1, it was poured onto a crawler conveyor belt and passed through an infrared electric machine at 120 ° C. to perform polymerization continuously. The polymerization process was carried out under a nitrogen atmosphere. As a result, the water absorption was 558 times, the salt absorption was 69 times, and the absorption rate was 26 seconds.

Example 4

The experiment was carried out under the same conditions as in Example 3, except that 10% by weight (based on the weight of the resin in the latex) compared to acrylic acid using PVC (HCC EM2070 Grade) latex, which was an additive used. As a result, the water absorption was 465 times, the salt absorption was 69 times, and the absorption rate was 23 seconds.

Example 5

It is the same as Example 3 except using the used additive 20 weight% of acrylic acid. As a result of evaluating the sample, the water absorption capacity was 523 times, the salt absorption capacity was 57 times, and the absorption rate was 22 seconds.

Example 6

The experiment was conducted in the same manner as in Example 3, except that polyvinyl chloride (P-1300, manufactured by HCC) and 5% by weight of the acrylic acid monomer were used as the additive. As a result, the water absorption was 584 times, the salt absorption was 67 times, and the absorption rate was 28 seconds.

Example 7

The experiment was carried out in the same manner as in Example 3, except that polyvinyl chloride (P-1300 Grade, HCC Co., Ltd.) was used at 20% by weight relative to acrylic acid. As a result, the water absorption capacity was 644 times, the salt absorption capacity was 75 times, and the absorption rate was 30 seconds.

Comparative Example 2

The same experiment as in Example 3 was conducted, but no additives were used. As a result, the water absorption capacity was 621 times, the salt absorption capacity was 64 times, and the absorption rate was 48 seconds (measured by the method 1).

Example 8

5 wt% of a styrene-acrylate copolymer powder produced by itself as an additive was used, and the polymerization was carried out in the same manner as in Example 3, except that stationary polymerization was performed for 40 minutes in an oven at 90 ° C. As a result of evaluating the prepared superabsorbent polymer, the water absorption capacity was 573 times, the salt absorption capacity was 63 times, and the absorption rate was 21 seconds.

Example 9

The experiment was conducted in the same manner as in Example 8 except that the content of the additive was used by 15 wt%. As a result, the water absorption capacity was 549 times, the salt absorption capacity was 61 times, and the absorption rate was 26 seconds.

Comparative Example 3

The same experiment as in Example 8 was conducted except that no additives were added. As a result, the water absorption capacity was 601 times, the salt absorption capacity was 65 times, and the absorption rate was 39 seconds.

Example 10

The same experiment as in Example 8 was carried out, except that 3 wt% of sorbitan monostearate was used as a suspending agent to disperse the additive in the polymerization solution in a short time. As a result, the water absorption capacity was 497 times, the salt absorption capacity was 59 times, and the absorption rate was 32 seconds.

The high-moist water-based polymer prepared according to the present invention has various advantages. First, since the absorption rate is up to 60% faster than that of the conventional product, it can absorb all the fluids without leaking the fluid when it is poured at a time. Because of this, you can make products with excellent fit. Secondly, the filler added during polymerization does not participate in the reaction or only participates in the minimum reaction, so it is easy to control the reaction, and thirdly, since it is rarely involved in the reaction, as in the conventional foaming technology, It is more hygienic and environmentally friendly by not generating low molecular weight compounds. Fourth, since the superabsorbent polymer can be produced more economically by selectively using inorganic or organic substances added in the preparation of the superabsorbent polymer, the price is superior to the existing superabsorbent polymer. In addition, there is an effect that can also minimize the content of the finely dispersed particles generated in the grinding process in the production of the super absorbent polymer prepared by the present invention.

Claims (4)

In the method for producing a super absorbent polymer, 1 to 40% by weight of an inorganic or organic filler having a melting point equal to or higher than the polymerization temperature of the superabsorbent polymer and having a particle size of 50 μm to 1000 μm, and a HLB value of 0.01 to 10 of a dispersant of 5 to 20. The weight percent and the remainder are added together with the monomer solution and stirred to disperse in the large fluidized fluid solution, and the solution is polymerized at 90 to 140 ° C. for 5 to 60 minutes to trap the filler in the superabsorbent polymer having reduced fluidity. Drying and grinding the method for producing a super absorbent polymer, characterized in that. The method of claim 1, wherein the inorganic material is manganese dioxide, silicon dioxide, titanium dioxide, calcium oxide, magnesium oxide, or zirconium oxide. The method of claim 1, wherein the organic material is a polymer particle or latex solution of PMMA, polystyrene, PVC, polyisoprene, styrene-acrylate copolymer, styrene copolymer, acrylic copolymer or PVC copolymer, or polyethylene or polypropylene Method for producing a superabsorbent polymer, characterized in that the flake form of the single and copolymer. The method of claim 1, wherein the dispersant is sorbitol fatty acid, sorbitol fatty acid ether, sodium laurylbenzene sulfonate, or sodium dodecylbenzene sulfonate.