JP2005290072A - Method for producing hydrogel containing clay mineral - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simplified energy-saving method for producing a hydrogel containing a clay mineral and having essentially high clay content and high mechanical strength such as tensile strength and compression strength. <P>SOLUTION: The hydrogel containing a clay mineral is produced by adding a water-soluble organic monomer or the monomer and a polymerization initiator and a catalyst to an aqueous dispersion of a water-swelling clay mineral dispersed in water or a mixture of water and an organic solvent, charging the obtained mixture to a container, rotating the container around an external axis while rotating on its own axis to uniformly disperse the components in the mixture and carrying out the polymerization reaction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a clay mineral-containing hydrogel in which water is contained in a three-dimensional network formed by combining a water-soluble organic polymer and a water-swellable clay mineral that can be uniformly dispersed in water. .

A clay mineral-containing hydrogel composed of a water-soluble organic polymer and a water-swellable clay mineral is a particularly useful material having both excellent transparency and mechanical properties.
This known clay mineral-containing hydrogel is produced by dispersing a water-swellable clay mineral in water, dissolving a water-soluble organic polymer constituent monomer in this dispersion, and adding a polymerization initiator or a catalyst to cause a polymerization reaction. Is disclosed (see Patent Document 1).
In such a production method, although a clay mineral-containing hydrogel having excellent physical properties can be obtained, when the water-swellable clay mineral is dispersed in water, increasing the content of the water-swellable clay mineral increases the viscosity of the dispersion liquid, which is uniform. It is difficult to obtain a simple dispersion. In particular, when the viscosity of the water-swellable clay mineral aqueous dispersion in the vibration type viscometer is 300 mPa · s or more, bubbles in the liquid do not escape, and uniform mixing of water-soluble organic monomers, polymerization initiators, catalysts, etc. It becomes difficult.
For this reason, when producing a hydrogel with a high clay mineral content, first, increase the amount of water in which the water-swellable clay mineral is dispersed, and prepare a dispersion solution that lowers the clay mineral concentration and suppresses the viscosity increase of the dispersion. To do. Next, a water-soluble organic polymer constituting monomer, a polymerization initiator, a catalyst and the like are uniformly mixed, and then a polymerization reaction is performed. Furthermore, it is necessary to produce a hydrogel having a high clay mineral content by removing water in the obtained clay mineral-containing gel by drying, and the process is complicated. In addition, in this drying process, a difference in moisture content occurs between the surface and the center of the clay mineral-containing hydrogel, so that a very long drying time is required to make this uniform, and energy efficiency is inferior. become.
JP 2002-53629 A

  The present invention is a method for producing a clay mineral-containing hydrogel that is substantially energy-saving when producing a clay mineral-containing hydrogel having a high clay content and a high mechanical strength such as tensile strength and compressive strength. The purpose is to provide.

The present inventor, in view of the problems in the method for producing a clay mineral-containing hydrogel, as a result of diligent research, revolved and rotated a container to which a dispersion composed of a water-swellable clay mineral, a water-soluble organic monomer, water and the like was added. It was found that, by polymerization after the polymerization, a uniform clay mineral-containing hydrogel can be produced very easily even if the water dispersion of the water-swellable clay mineral has a high viscosity. In addition, by using water at 5 ° C. or lower at that time, a more uniform water-swellable clay mineral aqueous dispersion was obtained, and it was found that labor saving in the production process was achieved, and the present invention was achieved.
That is, the present invention revolves a container in which a water-swellable clay mineral is dispersed in water or a mixture of water and an organic solvent and a water-soluble organic monomer or the monomer, a polymerization initiator, and a catalyst are added. The present invention relates to a method for producing a clay mineral-containing hydrogel, characterized in that a polymerization reaction is carried out after the components contained in the system are uniformly dispersed by rotating while rotating.

  INDUSTRIAL APPLICABILITY The present invention can produce a hydrogel having a high content of high strength and homogeneous water-swellable clay mineral by a simple operation.

  It is considered that the water-soluble organic monomer used in the present invention becomes a polymer by polymerization and substantially forms a three-dimensional network due to some interaction with the water-swellable clay mineral. In this regard, a polymer gel composed of a polymer of a water-soluble organic monomer and a water-swellable clay mineral swells with water or a hydrophilic organic solvent, and the gel is hardly treated even when treated at 20 ° C. for 500 hours or more. The water-swellable clay mineral and the water-soluble organic monomer polymer are not extracted.

  The water-soluble organic monomer has a property of being dissolved in water, and preferably has an interaction with a water-swellable clay mineral that can be uniformly dispersed in water, for example, a clay mineral and a hydrogen bond, an ionic bond, a coordinate bond, Those having a functional group capable of forming a covalent bond or the like are preferable. Specific examples of water-soluble organic monomers having these functional groups include water-soluble polymerizable unsaturated groups having amide groups, amino groups, ester groups, hydroxyl groups, tetramethylammonium groups, silanol groups, epoxy groups, and the like. Examples thereof include organic monomers. Among them, a polymerizable unsaturated group-containing water-soluble organic monomer having an amide group or an ester group is preferable. The water referred to in the present invention includes a mixture of water and an organic solvent miscible with water in addition to water alone.

  Specific examples of the polymerizable unsaturated group-containing water-soluble organic monomer having an amide group include acrylamides such as N-alkylacrylamide, N, N-dialkylacrylamide, and acrylamide, or N-alkylmethacrylamide, N, N- And methacrylamides such as dialkylmethacrylamide and methacrylamide. Here, an alkyl group having 1 to 4 carbon atoms is particularly preferably selected. Specific examples of the polymerizable unsaturated group-containing water-soluble organic monomer having an ester group include methoxyethyl acrylate, ethoxyethyl acrylate, methoxyethyl methacrylate, and ethoxyethyl methacrylate.

  Examples of the water-soluble organic monomer polymer include poly (N-methylacrylamide), poly (N-ethylacrylamide), poly (N-cyclopropylacrylamide), poly (N-isopropylacrylamide), and poly (acryloylmorpholine. ), Poly (methacrylamide), poly (N-methylmethacrylamide), poly (N-cyclopropylmethacrylamide), poly (N-isopropylmethacrylamide), poly (N, N-dimethylacrylamide), poly (N, N-dimethylaminopropylacrylamide), poly (N-methyl-N-ethylacrylamide), poly (N-methyl-N-isopropylacrylamide), poly (N-methyl-Nn-propylacrylamide), poly (N, N-diethylacrylamide), poly N-acryloylpyrrolidine), poly (N-acryloylpiperidine), poly (N-acryloylmethylhomopiperadine), poly (N-acryloylmethylpiperazine), poly (acrylamide), poly (methoxyethyl acrylate), Examples include poly (ethoxyethyl acrylate), poly (methoxyethyl methacrylate), and poly (ethoxyethyl methacrylate). The water-soluble organic monomer polymer may be a polymer from a single polymerizable unsaturated group-containing water-soluble organic monomer as described above, or a plurality of different polymerizable unsaturated group-containing water-soluble organic materials selected from these. It is also effective to use a copolymer obtained by polymerizing monomers. A copolymer of the water-soluble organic monomer and the other organic solvent-soluble polymerizable unsaturated group-containing organic monomer can also be used as long as the obtained polymer exhibits water solubility and hydrophilicity. .

  The polymer of the water-soluble organic monomer in the present invention has water-solubility or hydrophilicity (including amphiphilicity) having a property of absorbing water, and among them, it responds to heat, pH, light, etc. Those having characteristics such as functionality, biocompatibility including bioabsorbability, biodegradability, and the like are more preferably used depending on the application. For example, water-soluble organic monomer polymers that have characteristics that polymer properties in aqueous solution (for example, hydrophilicity and hydrophobicity) vary greatly with slight temperature changes before and after the lower critical solution temperature (LCST) Specific examples thereof include poly (N-isopropylacrylamide) and poly (N, N-diethylacrylamide). Examples of biocompatibility include poly (methoxyethyl acrylate) and poly (methacrylamide).

  As the water-swellable clay mineral used in the present invention, those having a property of swelling in water and preferably swelling between layers by water are used. More preferably, it is a layered clay mineral that can be at least partially exfoliated and dispersed in layers in water, and particularly preferably a lamellar clay mineral that can be exfoliated and dispersed uniformly in water with a thickness of 1 to 10 layers. For example, water-swellable smectite or water-swellable mica is used. More specifically, water-swellable hectorite containing sodium as an interlayer ion, water-swellable montmorillonite, water-swellable saponite, water-swellable synthetic mica, etc. Is mentioned.

  The solvent in the present invention is water, but may contain an organic solvent miscible with water as long as the intended polymer hydrogel can be prepared. An aqueous solution containing a salt or the like can also be used. It is also possible to replace the whole with an organic solvent miscible with water after the preparation of the polymer gel composite material. Organic solvents that are miscible with water include methanol, ethanol, propanol, glycerin, diglycerin, polyglycerin, ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dimethylacetamide, dimethylformamide, Examples thereof include dimethyl sulfoxide and a mixed solvent thereof.

  Such water or a mixture of water and an organic solvent is preferably 5 ° C. or lower when used. By using the water or the mixed liquid at such a temperature or lower, by rotating the container in which the water-swellable clay mineral and the water-soluble organic monomer or the monomer, the polymerization initiator, and the catalyst are mixed, revolves more. A uniformly dispersed aqueous dispersion can be provided. That is, when the temperature of water or a mixed liquid of water and an organic solvent is higher than 5 ° C., long-time stirring is required to obtain a uniform aqueous dispersion.

The polymerization initiator and catalyst used in the present invention can be appropriately selected from conventional radical polymerization initiators and catalysts. Preferably, those having dispersibility in water and uniformly contained in the entire system are used. Particularly preferred is a cationic radical polymerization initiator having a strong interaction with the clay mineral exfoliated in layers. Specifically, a water-soluble peroxide as a polymerization initiator, such as potassium peroxodisulfate or ammonium peroxodisulfate, a water-soluble azo compound, for example, VA-044, V-50 manufactured by Wako Pure Chemical Industries, Ltd. V-501 or the like is preferably used. In addition, a water-soluble radical initiator having a polyethylene oxide chain is also used.
As the catalyst, tertiary amine compounds such as N, N, N ′, N′-tetramethylethylenediamine and β-dimethylaminopropionitrile are preferably used. The polymerization temperature is set in the range of 0 ° C. to 100 ° C. according to the type of water-soluble organic polymer, polymerization catalyst and initiator used. The polymerization time also varies depending on the polymerization conditions such as the catalyst, initiator, polymerization temperature, polymerization solution amount (thickness) and cannot be generally defined, but it is generally carried out in the range of several tens of seconds to several tens of hours.

The ratio of the water-soluble organic monomer to the water-swellable clay mineral varies depending on the water-soluble organic monomer used and the type of the clay mineral, and is not necessarily limited. It is preferable that 1 to 90% by mass of the solid content constituting the resulting polymer hydrogel is a water-swellable clay mineral, more preferably 3 to 70% by mass, and particularly preferably 10 to 50% by mass. %. In particular, when the content of the water-swellable clay mineral is large, the effect of the present invention is more exhibited. If the amount is within the above range, the resulting polymer hydrogel is particularly excellent in physical properties.
Further, the polymerization initiator and the catalyst are preferably 0.01 to 1% by mass with respect to the water-soluble organic monomer, although depending on the type and reaction temperature.

  In the present invention, the amount of the liquid mixture with water or an organic solvent is such that the water content of the resulting polymer hydrogel is preferably 30 to 99% by mass, more preferably 40 to 95% by mass, and particularly preferably 50 to 90%. It is adjusted to be mass%.

Hereinafter, the method for producing the polymer hydrogel of the present invention will be described in more detail.
An aqueous dispersion in which a water-swellable clay mineral is dispersed in water or a mixed liquid of water and an organic solvent is prepared. At this time, it is recommended that water or a mixed solution of water and an organic solvent be kept at 5 ° C. or lower because dispersibility is further improved. Further, the aqueous dispersion is prepared so as to be preferably 300 mPa · s or more, more preferably 300 to 500,000 mPa · s as measured with a vibration viscometer.
An aqueous dispersion of a water-swellable clay mineral having such a viscosity exhibits strong thixotropic properties, and when stirred with a normal stirring blade, the water-soluble organic monomer, polymerization initiator and catalyst to be added are uniformly dispersed, and bubbles are not generated. Although a dispersion liquid not containing it cannot be obtained, the production method of the present invention enables a uniform dispersion liquid. The method of the present invention can be carried out even when the viscosity is lower than the above viscosity.
Next, a water-soluble organic monomer or the monomer, a polymerization initiator, and a catalyst are added to this aqueous dispersion, and the container containing them is rotated while revolving. The revolution and rotation of the container at this time can be performed using, for example, a centrifugal device described in Japanese Utility Model Publication No. 5-32110 and Japanese Patent No. 2711964, and the speed of revolution is not particularly limited. The rotation speed is preferably 50 to 1000 × g, and the rotation speed is not particularly limited, but is preferably 0.1 to 1 times the revolution speed. In the case where one of the revolution and the rotation is not performed, bubbles remain in the finally obtained hydrogel, and the water-swellable clay mineral remains, which causes a decrease in strength.
By the above treatment, an aqueous dispersion in which the contents are uniformly dispersed is obtained, and then the water-soluble organic monomer is polymerized. The aqueous dispersion before polymerization is prepared so as to be preferably 300 mPa · s or more, more preferably 300 to 500,000 mPa · s as measured with a vibration viscometer. By preparing an aqueous dispersion having such a viscosity, there is the same merit as an aqueous dispersion of the above water-swellable clay mineral and water or a mixed liquid of water and an organic solvent. The viscosity of the aqueous dispersion is important.
The polymerization reaction of the water-soluble organic monomer can be performed by radical polymerization using a conventional method such as heating or ultraviolet irradiation. During the polymerization reaction, a three-dimensional network of the polymer of the monomer and the water-swellable clay mineral is formed by the interaction between the water-soluble organic monomer and the water-swellable clay mineral, whereby a clay mineral-containing hydrogel can be produced.

  The clay mineral-containing hydrogel obtained by the production method of the present invention has excellent transparency, mechanical properties, etc., taking advantage of its characteristics, in a wide range of fields such as daily necessities, medicine / medicine, agriculture, civil engineering, industrial fields, etc. It is a useful material for buffer materials, medical materials, optical materials, water absorption materials, soil improvement materials, and the like.

Example 1
94.5 g of ion-exchanged water was measured in a 150 ml plastic container equipped with a nitrogen inlet and a charging port. While stirring this ion-exchanged water with a magnetic stirrer, nitrogen gas was bubbled for 15 minutes to remove dissolved oxygen and at the same time cooled to 5 ° C. in an ice bath.
In a nitrogen atmosphere, 12.0 g of water-swellable synthetic hectorite (“Laponite XLG” manufactured by Rockwood Additives, UK), which was vacuum-dried at 100 ° C. for 2 hours, was put into ion-exchanged water. After 15 seconds, the viscosity increased and magnetic stirring became impossible.
After removing the magnetic stir bar, the container was placed in a 35 ° C. water bath and left for 10 minutes in a nitrogen atmosphere, and a transparent dispersion of water-swellable synthetic hectorite containing bubbles was obtained.
It was 2000 Pa * s when the viscosity of this dispersion liquid was measured using the vibration type viscometer (CBC Materials Co., Ltd. viscomate VM-110A type, probe: PR-100A-L).
Thereafter, 9.91 g of N, N′-dimethylacrylamide (“DMAA” manufactured by Kojin Co., Ltd.) passed through an activated alumina column, 80 μl of N, N, N ′, N′-tetramethylethylenediamine and 2% aqueous potassium persulfate solution 5. After each 0 g was added, the container was sealed.
The container was set in a centrifuge (AR-250, manufactured by Shinky Co., Ltd.) in which the upper direction of the rotation axis was inclined 45 ° inside the horizontal revolution axis and the revolution radius at the center of the bottom of the container was 140 mm. When this centrifuge was operated at a rotation speed of 800 rpm and a revolution speed of 2000 rpm for 30 seconds, the entire reaction solution in the container was uniformly and transparently dispersed.
When the viscosity of the uniform dispersion was measured using the vibration viscometer, it was 400 Pa · s.
The time required from the addition of the water-swellable synthetic hectorite to the ion exchange water to the start of the polymerization reaction was 12 minutes.
Next, this reaction solution was placed in a 20 ° C. water bath together with the container for polymerization for 15 hours. After the reaction, the obtained clay mineral-containing hydrogel was homogeneous and colorless and transparent, and there was no mixing of bubbles.

(Comparative Example 1)
In Example 1, the same operation was performed except that the rotation of the centrifuge was stopped and the container was not rotated. The reaction liquid in the vessel remained air bubbles throughout and was separated into two phases.
Subsequently, this reaction solution was placed in a 20 ° C. water bath together with the container for polymerization for 15 hours. After the reaction, the obtained clay mineral-containing hydrogel was non-uniform, with bubbles remaining and some unreacted parts.

(Comparative Example 2)
In Example 1, the same operation was performed except that the revolution of the centrifuge was stopped and the container was not revolved. The reaction liquid in the vessel remained air bubbles throughout and was separated into two phases.
Subsequently, this reaction solution was placed in a 20 ° C. water bath together with the container for polymerization for 15 hours. After the reaction, the obtained clay mineral-containing hydrogel was non-uniform, with bubbles remaining and some unreacted parts.

Claims (5)

By revolving a container in which a water-swellable organic monomer or a monomer, a polymerization initiator and a catalyst are added to a water dispersion in which a water-swellable clay mineral is dispersed in water or a mixture of water and an organic solvent while rotating. A method for producing a clay mineral-containing hydrogel, characterized by carrying out a polymerization reaction after uniformly dispersing and / or defoaming components contained in the system. The method according to claim 1, wherein the viscosity of the water dispersion obtained by dispersing the water-swellable clay mineral in water is 300 mPa · s or more as measured with a vibration viscometer. The viscosity of the water-swellable clay mineral and the water-soluble organic monomer or the mixed liquid in which the monomer, the polymerization initiator and the catalyst are uniformly dispersed in water is 300 mPa · s or more as measured with a vibration viscometer. The manufacturing method according to claim 1. The manufacturing method according to claim 1, wherein the water or a mixed solution of water and an organic solvent is 5 ° C. or lower. The production method according to claim 1, wherein the clay mineral is water-swellable hectorite.