JP4759165B2 - Organic / inorganic composite hydrogel and method for producing the same - Google Patents

Organic / inorganic composite hydrogel and method for producing the same Download PDF

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JP4759165B2
JP4759165B2 JP2001158634A JP2001158634A JP4759165B2 JP 4759165 B2 JP4759165 B2 JP 4759165B2 JP 2001158634 A JP2001158634 A JP 2001158634A JP 2001158634 A JP2001158634 A JP 2001158634A JP 4759165 B2 JP4759165 B2 JP 4759165B2
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water
organic
inorganic composite
composite hydrogel
hydrogel
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JP2002053629A (en
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和敏 原口
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一般財団法人川村理化学研究所
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Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an organic / inorganic composite 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, The present invention relates to a body and a manufacturing method thereof.
[0002]
[Prior art]
Gels have intermediate properties between liquids and solids, and are obtained by stably incorporating a solvent into a three-dimensional network such as an organic polymer. In particular, gels using water as a solvent (hereinafter referred to as hydrogels or aqueous gels) are important constituent materials in living organisms, and so far in the fields of medicine, medical care, foods such as food, packaging, hygiene products, and cosmetics, as well as agriculture. It is also widely used in the civil engineering and industrial fields (eg, Yoshihito Nagata, Sakakibara “Gel Handbook”, NTS Corporation, 1997).
[0003]
The hydrogel contains at least two components. That is, a three-dimensional network and water bridged in various ways. As a component of the three-dimensional network, either an organic compound or an inorganic substance can be used. For example, in a hydrogel of an organic compound, an organic polymer or an organic molecule is crosslinked by a covalent bond, a hydrogen bond, an ionic bond, a hydrophobic bond, or the like, or a physical entanglement or a microcrystal is used as a crosslinking point to form a three-dimensional network. ing.
[0004]
Specifically, as an organic molecule that forms a three-dimensional network, a cross-link is formed by a coordinate bond with ovalbumin or serum albumin that is cross-linked by a hydrophobic bond, gelatin or agarose by a helix formation, or an alkaline earth metal ion. In addition to polyacrylic acid, polystyrene sulfonic acid, two types of polymer (polycation and polyanion) composites that crosslink by ionic bonds, fully saponified polyvinyl alcohol that crosslinks by hydrogen bonds, etc., heat, radiation, light, and plasma are irradiated. However, many are known in which a crosslink by a covalent bond is formed between organic polymers by adding an organic crosslinking agent.
[0005]
On the other hand, as a material that forms a three-dimensional network with inorganic substances, metal oxides prepared by hydrolysis polycondensation of metal alkoxides (so-called sol-gel reaction) and layered clay minerals having cations between layers are known, A three-dimensional network is formed by agglomeration of fine particles by ion interaction or the like, and a gel composed of an inorganic substance and water is prepared.
[0006]
Inorganic hydrogels are brittle with small strength and elongation, and are therefore rarely used as a single hydrogel material. On the other hand, hydrogels composed of organic compounds, especially organic polymer three-dimensional networks by covalent bonds, and water have better mechanical properties than inorganic hydrogels, and can exhibit the properties of organic polymers in hydrogels. Because of its properties, it is being developed as a soft material and a functional gel material in a wide range of industrial fields.
[0007]
In order to expand the usefulness of such organic cross-linked hydrogels, the gel uniformity, transparency, mechanical properties, mechanical properties, etc. are further improved, absorption (water absorption) characteristics are further improved, Therefore, the development of new hydrogels that more effectively express the properties of organic polymers is desired.
[0008]
[Problems to be solved by the invention]
The problem to be solved by the present invention is a novel organic / inorganic composite hydrogel having excellent uniformity, transparency, mechanical properties, water absorption, and swelling / shrinking properties, its production method, and removal of water from the hydrogel Another object of the present invention is to provide a dried product of the organic / inorganic composite hydrogel obtained as described above.
[0009]
[Means for Solving the Problems]
As a result of diligent research to solve the above-mentioned problems, the present inventors polymerized component monomers constituting a water-soluble organic polymer in the presence of water-swellable clay mineral that can be uniformly dispersed in water and water. Then, (A) a water-soluble organic polymer and (B) a water-swellable clay mineral that can be uniformly dispersed in water are combined in a three-dimensional network formed at the molecular level. It was found that an organic / inorganic composite hydrogel (hereinafter referred to as organic / inorganic composite hydrogel) was obtained, and the present invention was completed.
[0010]
That is, the present invention includes (C) water in a three-dimensional network formed by combining (A) a water-soluble organic polymer and (B) a water-swellable clay mineral that can be uniformly dispersed in water. In the presence of (B) water-swellable clay mineral that can be uniformly dispersed in water and (C) water, (A) the constituent monomer of the water-soluble organic polymer ( An organic / inorganic composite hydrogel obtained by polymerizing A ′). The present invention also provides a dried organic / inorganic composite hydrogel obtained by removing water from the organic / inorganic composite hydrogel.
[0011]
Furthermore, the present invention provides a homogeneous solution comprising (A) a monomer (A ′) that is a constituent of a water-soluble organic polymer, (B) a water-swellable clay mineral that can be uniformly dispersed in water, and (C) water. And (B) a method for producing an organic / inorganic composite hydrogel in which a monomer (A ′), which is a constituent component of a water-soluble organic polymer, is polymerized in the presence of water.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The (A) water-soluble organic polymer referred to in the present invention includes an organic polymer having a property of swelling in water, in addition to those soluble in water. Such water solubility and water swellability may be achieved under specific polymer concentration, temperature, pressure conditions, and coexistence of other additive components. The water-soluble organic polymer may be a polymer from a single monomer or a copolymer obtained by polymerizing a plurality of types of monomers.
[0013]
The (A) water-soluble organic polymer used in the present invention preferably has an interaction with (B) a water-swellable clay mineral that can be uniformly dispersed in water, for example, (B) with hydrogen bonds, ionic bonds, and coordination. Those having a functional group capable of forming a bond, a covalent bond and the like are preferable.
[0014]
Specific examples of the organic polymer having these functional groups include organic polymers having an amide group, amino group, hydroxyl group, tetramethylammonium group, silanol group, epoxy group, and the like. Further, as the water-soluble organic polymer used in the present invention, those having functionality are particularly preferable. For example, polymer properties (for example, hydrophilicity and hydrophobicity) in an aqueous solution are LCST (lower critical eutectic temperature, Lower Critical Solution Temperature) Organic polymers with characteristics that change greatly with slight temperature changes before and after.
[0015]
(A) Specific examples of water-soluble organic polymers are selected from acrylamide, N-substituted acrylamide derivatives, N, N-disubstituted acrylamide derivatives, N-substituted methacrylamide derivatives, and N, N-disubstituted methacrylamide derivatives. Water-soluble organic polymer obtained by polymerizing one or more of the above. It is also possible to use the above monomers in combination with other organic monomers as long as a uniform organic / inorganic composite hydrogel is formed.
[0016]
Such water-soluble organic polymers include poly (acrylamide), poly (N-methylacrylamide), poly (N-ethylacrylamide), poly (N-cyclopropylacrylamide), poly (N-isopropylacrylamide), poly (methacrylic). Amide), poly (N-methylmethacrylamide), poly (N-cyclopropylmethacrylamide), poly (N-isopropylmethacrylamide),
[0017]
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-acryloylpyrrolidin), poly (N-acryloylpiperidine), poly (N-acryloylmethylhomopiperazine), Examples thereof include poly (N-acryloylmethylpiperazine).
[0018]
The water-soluble organic polymer (A) used in the present invention may be one that dissolves or swells in a mixed solvent of water and an organic solvent miscible with water, in addition to those that dissolve and swell in water. . As a mixed solvent of water and an organic solvent miscible with water, a mixture of water and one or more organic solvents miscible with water (forming a homogeneous phase) is used. Examples of these organic solvents include polar solvents such as methanol, acetone, methyl ethyl ketone, and tetrahydrofuran. The mixing ratio of water and these organic solvents can be arbitrarily selected as long as the water-swellable clay (B) can be uniformly dispersed.
[0019]
The (B) water-swellable clay mineral that can be uniformly dispersed in water in the present invention is a clay mineral that can swell and uniformly disperse in water, and is particularly preferably molecular (single layer) or in water. It is a layered clay mineral that can be uniformly dispersed at a close level. For example, water-swellable smectite or water-swellable mica is used. Specifically, water-swellable hectorite containing sodium as an interlayer ion, water-swellable montmorillonite, water-swellable saponite, water-swellable synthetic mica, etc. Can be mentioned.
[0020]
In the present invention, the water-swellable clay mineral needs to be finely and uniformly dispersed in the aqueous solution before the water-soluble organic polymer monomer is polymerized, and is particularly dissolved in the aqueous solution. Is desirable. Here, dissolution means a state in which there is no large clay mineral aggregate that causes precipitation of a clay mineral or a cloudy aqueous solution. More preferably, the material is dispersed with a thickness of about 1 to 10 nanometers, and particularly preferably the material is dispersed with a thickness of about 1 or 2 layers.
[0021]
As the component (C) water of the present invention, water or a mixed solvent of water and an organic solvent miscible with water may be used, and a water-swellable clay mineral and organic monomer that are uniformly dispersed are used. . In the case of using a mixed solvent, the gel contains an organic solvent in addition to water, but here, for convenience, these are all referred to as a hydrogel.
[0022]
The organic-inorganic composite hydrogel of the present invention comprises (C) a three-dimensional network formed by combining (A) a water-soluble organic polymer and (B) a water-swellable clay mineral that can be uniformly dispersed in water. ) Organic / inorganic composite hydrogel containing water. That is, (A) and (B) were combined at the molecular level in water, so that (A) was bridged by (B) or (B) was bridged by (A). A three-dimensional crosslinked product comprising A) and (B) is formed including water.
[0023]
That is, the organic / inorganic composite hydrogel in the present invention is a hydrogel that can be formed without an organic crosslinking agent, and is an organic polymer crosslinked product obtained by polymerizing an organic crosslinking agent added to a conventionally known organic monomer. It has excellent properties different from hydrogel (hereinafter referred to as organic crosslinked hydrogel).
[0024]
Also, the dried organic / inorganic composite hydrogel in the present invention needs to once form such an organic / inorganic composite hydrogel, and the dried organic / inorganic composite hydrogel can be obtained by drying them.
[0025]
For example, as shown in Comparative Examples 5 to 8, when each aqueous solution of (A) and (B) is prepared and then simply mixed, even if it is composed of the same component composition as the present invention, The organic / inorganic composite hydrogel of the invention cannot be obtained.
[0026]
The ratio of (A) water-soluble organic polymer and (B) water-swellable clay mineral that can be uniformly dispersed in water in the organic / inorganic composite hydrogel of the present invention is a three-dimensional network comprising (A) and (B). It is sufficient that the organic / inorganic hydrogel having the above is prepared, and it is not necessarily limited depending on the types of (A) and (B) to be used, but from the viewpoint of the ease and uniformity of hydrogel synthesis, it is preferably B / A The weight ratio is 0.01 to 10, more preferably 0.03 to 2.0, and particularly preferably 0.1 to 1.0.
[0027]
When the weight ratio of B / A is less than 0.01, the gel characteristics referred to in the present invention are often insufficient, and when it exceeds 10, the resulting hydrogel becomes brittle or uses a large amount of water. Problem arises. On the other hand, the ratio of (C) water to (A + B) can be arbitrarily set in a wide range from 0 to a very large value depending on the purpose by adjusting the amount of water in the polymerization process or by subsequent swelling or drying.
[0028]
The maximum amount of water contained in the organic / inorganic composite hydrogel obtained in the present invention, that is, the maximum water absorption amount (Cmax) at equilibrium swelling is the type and ratio of the components A and B, and environmental conditions such as temperature and pH. The organic / inorganic composite hydrogel of the present invention is characterized in that Cmax is larger than that of a conventional organic crosslinked hydrogel, although it varies depending on the above.
[0029]
Generally, Cmax decreases as B / A increases. The maximum amount of (C) under a certain condition (equilibrium swelling water absorption Cmax) is measured by holding the organic / inorganic composite hydrogel in excess water for a long time under the condition. For example, when an organic / inorganic composite hydrogel synthesized at a certain water content is kept in excess water at a temperature of 20 ° C., further water is taken into the hydrogel and finally an equilibrium swelling (maximum swelling) at 20 ° C. To reach.
[0030]
Therefore, by taking out the hydrogel soaked in excess water from time to time and measuring the weight, it is possible to know the time dependency of the swelling of the hydrogel and the water content during equilibrium swelling. The water content [{Cmax / (A + B)} × 100] at the time of equilibrium swelling varies depending on the component type and composition of A and B as described above, and also on environmental conditions such as temperature, pH, or salt concentration. It is possible to vary from a low value of 100% by weight or less to a high value of 100000% by weight or more.
[0031]
The organic / inorganic composite hydrogel in the present invention is characterized in that Cmax is larger than that of a conventional organic crosslinked hydrogel. When the organic / inorganic composite hydrogel of the present invention is equilibrated and swollen at 20 ° C., for example, {Cmax / (A + B)} × 100] is usually 2000% by weight or more, more preferably 3000% by weight or more, and particularly preferably 4000% by weight or more.
[0032]
In addition, the organic / inorganic composite hydrogel in the present invention has a characteristic that the swelling (water absorption) speed is larger than that of the conventional organic crosslinked hydrogel. It is estimated that this is because the three-dimensional cross-linking between (A) and (B) does not inhibit the water absorption characteristics of (A) and is formed uniformly. In addition, when (A) has a property of swelling and shrinking due to a temperature change as described below, it has a feature that not only the swelling but also the shrinking speed is large.
[0033]
The organic / inorganic composite hydrogel of the present invention has a critical temperature (Tc) that is transparent and / or swollen on the low temperature side, and opaque and / or volume contracted on the high temperature side, with Tc as the boundary. Those having the characteristics that the transparency and volume can be reversibly changed by the temperature change up and down are included.
[0034]
Such an organic / inorganic composite hydrogel can be prepared using an organic polymer exhibiting LCST (lower critical solution temperature) in an aqueous solution as the organic polymer. The Tc of the organic / inorganic composite hydrogel may change at the same temperature as the LCST of the organic polymer.
[0035]
The organic / inorganic composite hydrogel of the present invention has a high water absorption as compared with the conventional organic cross-linked hydrogel, high transparency, high volume ratio and change in transparency at the time of expansion and contraction before and after Tc, Those having some or all of the characteristics such as large swelling and / or shrinking speed, excellent mechanical properties and mechanical properties are included.
[0036]
For example, in an organic cross-linked hydrogel, when the cross-linking agent concentration is increased and the cross-linking density is increased, cross-linking becomes non-uniform and transparency may be lost (Comparative Example 4 and T. Tanaka, Scientific American, Vol. 244, 110-123 (1981), the organic / inorganic composite hydrogel of the present invention using the same organic polymer does not lose uniformity and exhibits high transparency.
[0037]
Specifically, the organic / inorganic composite hydrogel of the present invention includes (A) 10-fold amount (weight ratio) of water-soluble organic polymer (C) water and an organic / inorganic composite hydrogel having a thickness of 25 mm. , The light transmittance of visible light is 80% or more, more preferably 85% or more, particularly preferably 90% or more. Also, a dried product obtained by drying the organic / inorganic composite hydrogel can have transparency because the water-swellable clay mineral is finely dispersed.
[0038]
In addition, since the organic / inorganic composite hydrogel of the present invention maintains a clear transition characteristic at Tc, as shown in FIG. 1, the organic crosslinked hydrogel having a relatively high crosslinking density (Comparative Example 4) changes in transparency before and after Tc. In contrast, there is almost no mechanical property, and it has reversible reversibility with high mechanical properties and high transparency before and after Tc (Example 1).
[0039]
Further, with respect to the swelling and shrinkage of the hydrogel before and after Tc, as shown in FIG. 2, the organic-inorganic composite hydrogel (Example 1) was compared with the organic crosslinked hydrogel (Comparative Example 4) at the time of swelling and shrinkage. The volume ratio is high. The volume ratio of the organic / inorganic composite hydrogel of the present invention during swelling and shrinkage can be set according to the purpose, and generally the volume of swelling / shrinking is higher than that of the organic crosslinked hydrogel using the same water-soluble organic polymer. The ratio is large, usually 10 or more, preferably 20 or more, more preferably 30 or more.
[0040]
The organic / inorganic composite hydrogel of the present invention includes those having excellent mechanical properties such as strength, elongation and toughness. In particular, it is characterized in that those having excellent mechanical properties in addition to the above-mentioned high water absorbability, transparency, and various properties such as transparency change and volume change are included. The mechanical and physical properties of the organic / inorganic composite hydrogel vary depending on the water content of the hydrogel. Therefore, the mechanical and mechanical properties of the organic / inorganic composite hydrogel of the present invention were tested using a hydrogel having a water content within a certain range. It is expressed by the result.
[0041]
Specifically, {C / (A + B)} × 100 is 600 to 1000, that is, (C) a hydrogel containing 600 to 1000% by weight of water with respect to the organic + inorganic component (A + B) is used, or (A) It is expressed as a result of testing using a water-soluble organic polymer containing 10 times the amount (weight ratio) of (C) water.
[0042]
Furthermore, since the organic / inorganic composite hydrogel in the present invention has a large elongation at break and the cross-sectional area changes during the test, the cross-sectional area (initial cross-sectional area) of the hydrogel at the start of the test is 0.237 cm.2(Equivalent to a circle having a radius of 0.275 cm) was used as a test material.
[0043]
The organic / inorganic composite hydrogel of the present invention has the above water content and initial cross-sectional area, that is, the water content defined by {C / (A + B)} × 100 is 600 to 1000% by weight, and the initial cross-sectional area is 0. .237cm2And those having a tensile breaking load of 0.1 N or more, preferably 0.5 N or more, more preferably 1 N or more, and particularly preferably 2 N or more, measured using a hydrogel.
[0044]
The organic / inorganic composite hydrogel of the present invention has a tensile elongation at break of 100% or more, more preferably 200% or more, more preferably 300% or more, measured using the hydrogel having the above water content and initial cross-sectional area. Particularly preferably, it is 500% or more, and the load at a tensile elongation of 100% is 0.01N or more, more preferably 0.05N or more, particularly preferably 0.1N or more. It is.
[0045]
On the other hand, the organic crosslinked hydrogels shown in Comparative Example 3, Comparative Example 4 and Comparative Examples 9 to 12 are extremely weak compared to the organic / inorganic composite hydrogel of the present invention, and are weakly attached to the chuck in the tensile test. In most cases, the physical property values could not be measured due to destruction immediately after the test, even if they were devised.
[0046]
Further, the organic / inorganic composite hydrogel of the present invention exhibits good mechanical properties even at the time of water absorption, and has toughness that can withstand, for example, compression, tension, or bending deformation.
Specifically, (A) an organic-inorganic composite hydrogel having a diameter of 5.5 mm and a length of 30 mm containing water (C) containing 10 times the amount (weight ratio) of the water-soluble organic polymer is 1 in the thickness direction. Compressive deformation to a thickness of / 3 or less, preferably 1/5 or less, and / or stretch deformation to a length of 2 times or more, preferably 4 times or more in the length direction. And / or a material whose shape is not destroyed by bending deformation at an angle of 100 degrees or more, preferably 150 degrees or more at the center point of the length.
[0047]
In contrast, (B) the organic cross-linked gel having the same composition except that an organic cross-linking agent was used instead of the water-swellable clay mineral, the crack was generated and the shape was destroyed by any or all of the above deformation operations. Or loss occurs.
[0048]
The organic / inorganic composite hydrogel of the present invention needs to form a three-dimensional network composed of an organic polymer and a clay mineral, and can be produced by the following method. Coexistence of (B) after preparing a uniform solution containing (A ′) a monomer of the water-soluble organic polymer (A), (B) a water-swellable clay mineral that can be uniformly dispersed in water, and (C) water. The polymerization of (A ′) is performed below. As a result, fine complexation of (A) and (B) at the molecular level is achieved, and an organic / inorganic composite hydrogel gelled by three-dimensional network formation is obtained.
[0049]
Specifically, organic / inorganic that radically polymerizes (A ′) in the presence of (B) finely dispersed in water using a solution having a composition containing (A ′), (B), and (C) as essential components A method for producing a composite hydrogel, wherein a clay mineral uniformly dispersed at a nanometer level of preferably 1 to 10 layers, more preferably 1 or 2 layers, functions as a crosslinking agent (A ′), A) and (B) are combined in (C) to form a three-dimensional network.
[0050]
The radical polymerization reaction can be performed by a known method such as the presence of peroxide and / or ultraviolet irradiation in the absence of molecular oxygen. Furthermore, this polymerization reaction can be accelerated by heating or ultraviolet irradiation. As the radical polymerization initiator and the catalyst, known and commonly used radical polymerization initiators and catalysts can be appropriately selected and used. Preferably, those having water dispersibility and uniformly contained in the entire system are used.
[0051]
Specifically, as a polymerization initiator, a water-soluble peroxide such as potassium peroxodisulfate or ammonium peroxodisulfate, a water-soluble azo compound such as VA-044, V-50, V-501 (all of which are Wako Pure Chemical Industries, Ltd.) In addition to Yaku Kogyo Co., Ltd.), water-soluble radical initiators having a polyethylene oxide chain are exemplified. On the other hand, as the catalyst, N, N, N ′, N′-tetramethylethylenediamine which is a tertiary amine compound, β-dimethylaminopropionitrile, or the like is preferably used.
[0052]
The polymerization temperature can be set in the range of 0 ° C. to 100 ° C. according to the type of polymerization catalyst and initiator. The polymerization time varies depending on the polymerization conditions such as the catalyst, initiator, polymerization temperature, and amount (thickness) of the polymerization solution, and can generally be carried out for several tens of seconds to several hours. In order to perform polymerization uniformly throughout the system, for example, (A ′) and a polymerization initiator dissolved in water are added to a mixture obtained by uniformly mixing (B) and water in advance. It is effective to devise methods such as adding a polymerization catalyst dissolved in the solution.
[0053]
It is also possible to produce an organic / inorganic composite hydrogel in the form of fine particles by coexisting a known surfactant in the radical polymerization reaction.
In the polymerization of the organic / inorganic composite hydrogel of the present invention, the polymerization yield of (A ′) is high, and the water-soluble organic polymer obtained by polymerization is taken together with the clay mineral into the hydrogel and eluted as a water-soluble component. The amount is small. This is confirmed by the high polymerization yield after washing with water. This result is presumed to be due to the fact that the finely dispersed clay layer acts as an effective cross-linking agent for the water-soluble organic polymer in the polymerization of (A ′) in the presence of (B).
[0054]
Furthermore, in the present invention, for the purpose of improving the properties of the organic / inorganic composite hydrogel, an organic crosslinking agent may be included in the aqueous solution together with the essential components (A ′) and (B) as necessary. The concentration of the organic crosslinking agent contained is not particularly limited and can be selected according to the purpose.
[0055]
Examples of the organic crosslinking agent that can be included as required include conventionally known N, N′-methylenebisacrylamide, N, N′-propylenebisacrylamide, di (acrylamidomethyl) ether, 1,2-di (). Bifunctional compounds such as acrylamide ethylene glycol, 1,3-diacryloyl ethylene urea, ethylene diacrylate, N, N′-diallyl tartaramide, N, N′-bisacrylyl cystamine, triallyl cyanurate, Examples are trifunctional compounds such as triallyl isocyanurate.
[0056]
In the production of the organic / inorganic composite hydrogel of the present invention, hydrogels having various shapes can be prepared by changing the shape of the container. For example, an organic / inorganic composite hydrogel having an arbitrary shape such as a fibrous shape, a rod shape, a flat plate shape, a cylindrical shape, a spiral shape, or a spherical shape can be prepared.
[0057]
In addition to (A), (B), and (C), the organic / inorganic composite hydrogel in the present invention and the dried product thereof, if necessary, for example, an anionic activator, an organic molecule such as an organic dye or an organic pigment, It is possible to include an organic polymer such as a water-soluble polymer or a fibrous substance that does not dissolve in water, inorganic fine particle components such as carbon, silica, and titania at any stage of production. Furthermore, it can be combined (dispersed, laminated, etc.) with other materials according to the purpose.
[0058]
The present invention includes a dried product of the organic / inorganic composite hydrogel obtained by removing water from the organic / inorganic composite hydrogel of the present invention. The method for removing moisture is not particularly limited, but can be performed by appropriately changing conditions such as temperature, airflow, and reduced pressure. Specifically, a hot air circulating dryer or a vacuum dryer is used. The amount of water removed from the hydrogel is not particularly limited, and it can be arbitrarily prepared from a product from which water has been completely removed to a product in which water remains as required.
[0059]
The dried body of the organic / inorganic composite hydrogel of the present invention contains a clay mineral, but can be transparent because the clay mineral is finely dispersed. Therefore, in the case of absorbing a colored aqueous solution or the like in the hydrogel or its dried product, the absorption state can be detected by light transmission or light reflection. Also, when other organic components and inorganic components are dispersed in the hydrogel in advance, there is an advantage that the dispersion state can be clearly grasped.
[0060]
The organic / inorganic composite hydrogel can be crushed, classified, molded, etc. after being hydrogel or in the course of drying or as a dried gel, and can take a form suitable for the purpose of transportation, processing and use. Specific examples include a spherical shape, a scale shape, a powder shape, a film shape, a fiber shape, and a pellet shape. Regarding the size, for example, in the case of powder, those having an average particle size of usually 10 to 1000 μm are used, but are not particularly limited.
[0061]
The dried organic / inorganic composite hydrogel can be reversibly returned to the hydrogel by contact with water such as water, aqueous solution, or moisture. The novel organic / inorganic composite hydrogel of the present invention and a dried product thereof are useful in a wide range of fields such as daily necessities, medicine / medicine, agriculture, civil engineering, and industrial fields.
[0062]
【Example】
EXAMPLES Next, although an Example demonstrates this invention more concretely, this invention is not limited only to the Example shown below from the first.
[0063]
Example 1
As a clay mineral, [Mg5.34Li0.66Si8O20(OH)4] Na+ 0.66A water-swellable synthetic hectorite (trademark Laponite XLG, manufactured by Nippon Silica Co., Ltd.) having the following composition was vacuum-dried at 100 ° C. for 2 hours and used. As the organic monomer, N-isopropylacrylamide (IPAA: manufactured by Kojin Co., Ltd.) was recrystallized using a mixed solvent of toluene and hexane (1/10 weight ratio) and purified into colorless needle crystals before use.
[0064]
As the polymerization initiator, potassium peroxodisulfate (PPS: manufactured by Kanto Chemical Co., Inc.) was diluted with pure water at a ratio of PPS / water = 0.384 / 20 (g / g) and used as an aqueous solution. As the catalyst, N, N, N ′, N′-tetramethylethylenediamine (TMEDA: manufactured by Kanto Chemical Co., Inc.) was used by diluting at a ratio of TMEDA / water = 160 μl / 20 g. As the water, pure water obtained by distilling ion-exchanged water was used. All water was used after bubbling high-purity nitrogen in advance for 3 hours or more to remove oxygen.
[0065]
In a constant temperature room at 20 ° C., 16.96 g of pure water and a Teflon stirrer were placed in a flat bottom glass container having an inner diameter of 25 mm and a length of 80 mm, the inside of which had been replaced with nitrogen, and 0.662 g of Laponite XLG was bubbled into the container while stirring. A small and clear solution was prepared by adding little by little with care.
[0066]
To this, 2.0 g of IPAA was added and stirred for 5 minutes to obtain a colorless transparent solution. Next, 1.06 g of PPS aqueous solution and 2.0 g of TMEDA aqueous solution were added with stirring, and further stirred for about 15 seconds to obtain a colorless transparent solution (D). A portion (3 ml × 3) of (D) was transferred to three glass tube containers having a closed inner diameter of 5.5 mm and a length of 150 mm so as not to come into contact with oxygen, and then sealed at the top, at 20 ° C. And allowed to stand for 15 hours for polymerization.
[0067]
The remaining solution (D) was also allowed to stand in a flat bottom glass container at 20 ° C. for 15 hours for polymerization. The operations from preparation of the solution to polymerization were all performed in a nitrogen atmosphere in which oxygen was blocked. After 15 hours, elastic, tough, colorless, transparent, uniform columnar and rod-like gels were formed in the flat bottom glass container and the glass tube container, and were carefully taken out from both containers.
[0068]
No heterogeneous or opaque aggregation due to clay minerals or the like was observed in the gel. It was found that the gel was a hydrogel containing {C / (A + B)} × 100 = 750% by weight of water by drying the gel with a vacuum dryer at 100 ° C. until the weight became constant. The following purification operation was repeated 3 times on the removed hydrogel to obtain a purified hydrogel.
[0069]
The purification was repeated (taken out by being immersed in 2 L of water for 2 days and then taken out by being immersed in 1 L of 70 ° C. water for 2 hours). The purified hydrogel was dried at 100 ° C. under reduced pressure to obtain a dried hydrogel from which moisture was removed. It was confirmed that the dried gel body was immersed in water at 20 ° C. to return to an elastic hydrogel having the same shape as before drying.
[0070]
The dried gel is subjected to Fourier transform infrared absorption spectrum (FT-IR) measurement by KBr method (using a Fourier transform infrared spectrophotometer FT / IR-550 manufactured by JASCO Corporation), and poly (N-isopropylacrylamide). Inherent infrared absorption (eg 1460cm-1, 1550cm-1, 1650cm-12920cm-12970cm-1) And infrared absorption inherent in Laponite XLG (eg 460 cm)-1650cm-1, 1005cm-1) Was observed.
[0071]
Further, thermogravimetric analysis (TG-DTA220 manufactured by Seiko Denshi Kogyo Co., Ltd .: raised to 600 ° C. at 10 ° C./min) under air flow, and B / A = 0.333 (weight ratio) was performed. Obtained.
[0072]
From the above, the gel obtained in this example is a hydrogel composed of an organic polymer (poly (N-isopropylacrylamide)), a clay mineral, and water having a component ratio according to the charged composition, and the organic polymer. Despite the absence of the addition of a crosslinking agent in the synthesis of the above, it becomes a colorless, transparent and uniform hydrogel, and the dried gel (solid) obtained by removing water from the hydrogel is immersed again in water. It was concluded that a three-dimensional network in which organic polymer and clay mineral were combined at the molecular level was formed in water. The organic polymer synthesized under the same conditions except that no clay mineral coexists became a polymer aqueous solution and did not become a hydrogel.
[0073]
Unrefined rod-like organic / inorganic composite hydrogel (cross-sectional area = 0.237 cm2) Is attached to a tensile testing device (manufactured by Shimadzu Corporation, desktop type universal testing machine AGS-H) so that there is no slippage at the chuck part, and the distance between grades is 20 mm, and the pulling speed is 100 mm / min. As a result of the test, the breaking load was 1.1 N, the breaking elongation was 550%, and the load at a tensile elongation of 100% was 0.09 N.
[0074]
After refining a rod-like organic / inorganic composite hydrogel cut to a length of 10 mm, it is immersed in water at six temperatures ranging from 20 ° C. to 50 ° C., left to stand for 1 day, and the volume is measured. The change in contraction was measured. The results are shown in FIG. 1 together with the results of Comparative Example 4 (organic crosslinked hydrogel).
[0075]
The organic / inorganic composite hydrogel obtained in this example had the toughness as described above, had a critical temperature (Tc), swelled at a temperature below Tc, and contracted at a temperature below Tc. The volume ratio during swelling and shrinking at 20 ° C. and 50 ° C. showed a high value of 24.
[0076]
After purifying the columnar organic / inorganic composite hydrogel taken out from the flat-bottomed glass container, the one immersed in water at five temperatures of 20 ° C. to 50 ° C. is cut out with a thickness of 2 mm, and NDH manufactured by Nippon Denshoku Industries Co., Ltd. The light transmittance was measured using -300A. The results are shown in FIG. 2 together with the results of Comparative Example 4. The organic / inorganic composite hydrogel obtained in this example showed a clear change in transparency at the boundary of Tc, and became highly transparent at a temperature below Tc, and became opaque (white turbid) at a temperature below Tc.
[0077]
(Examples 2 to 4)
Polymerization was conducted in the same manner as in Example 1 except that the amount of clay mineral (Laponite XLG) was changed to 0.132 g (Example 2), 0.264 g (Example 3), and 1.322 g (Example 4). The organic-inorganic composite hydrogel was prepared. In Examples 2 to 4, a colorless and transparent uniform hydrogel was obtained at room temperature.
[0078]
The hydrogel evaluation results measured in the same manner as in Example 1 are shown below. {C / (A + B)} × 100 is 940 wt% (Example 2), 880 wt% (Example 3), 600 wt% (Example 4), and the B / A ratio is 0.065 (Example 2). ), 0.135 (Example 3), and 0.66 (Example 4).
[0079]
When the temperature of the obtained hydrogel was raised, all had a critical temperature (Tc) around 35 ° C., and were colorless and transparent below Tc, and became opaque and contracted below Tc. The volume ratio during swelling and shrinking in water at 20 ° C. and 50 ° C. was 31 (Example 2) and 13 (Example 4). In addition, shrinkage occurred in a short time within 1 minute due to temperature change, and swelling occurred in a shorter time than Comparative Example 3.
[0080]
The results of the tensile test measurement were as follows: breaking load: 0.65 N (Example 3), 7.0 N (Example 4), breaking elongation: 430% (Example 3), 650% (Example 4), elongation: 100 % Load was 0.033 N (Example 3) and 0.40 N (Example 4). Moreover, the water content {Cmax / (A + B)} × 100 contained in the hydrogel obtained by equilibrium-swelling in 20 ° C. water after cutting the obtained hydrogel into 5 mm squares was 11300 wt% (Example 2), 7200 wt. % (Example 3) and 5000% by weight (Example 4).
[0081]
(Examples 5-7)
As an organic monomer, the IPAA described above was used in Example 5, N, N-dimethylacrylamide (DMAA: Wako Pure Chemical Industries, Ltd.) in Example 6, and N, N-diethylacrylamide (DEAA: Wako Pure) in Example 7. Yakuhin Kogyo Co., Ltd.) was used. DMAA and DEAA were used after removing a polymerization inhibitor by using a silica gel column (manufactured by Merck) in a volume of 80 ml with respect to 100 ml of the organic monomer.
[0082]
In a constant temperature room at 20 ° C., 18.96 g of pure water and a Teflon stirrer were placed in a flat bottom glass container having an inner diameter of 25 mm and a length of 80 mm, the inside of which had been purged with nitrogen. A small and clear solution was prepared by adding little by little with care. To this, 2.0 g of IPAA (Example 5), 2.0 g of DMAA (Example 6) or 2.0 g of DEAA (Example 7) was added and stirred until a colorless transparent solution was obtained.
[0083]
To this, 160 μl of TMEDA was added, and then 1.06 g of an aqueous PPS solution was added with stirring, followed by stirring for 5 minutes to obtain a colorless transparent solution (D ′). (D ') The stirring bar was removed from the solution, and the mixture was sealed and allowed to stand at 20 ° C. to gel the entire system (the contents did not move even when the container was placed on its side). All the above operations were performed in a nitrogen atmosphere in which oxygen was blocked. Then N2While maintaining the atmosphere, the mixture was allowed to stand in a 70 ° C. water bath for 2 hours for polymerization. After 2 hours, the cylindrical gel produced in the flat bottom glass container was carefully removed from the container.
[0084]
In Examples 5 and 7, uniform cloudy gels having elasticity and toughness were obtained, and in Example 6, transparent gels having elasticity and toughness were obtained. None of the non-uniform or opaque aggregation due to clay minerals or the like was observed in the cloudy gel.
[0085]
The {C / (A + B)} × 100 measured in the same manner as in Example 1 was 750% by weight, and B / A was 0.33, which was a uniform organic material composed of an organic polymer, clay mineral, and water. / It was found to be an inorganic composite hydrogel. The cloudy hydrogels of Example 5 and Example 7 did not change to transparent even when the temperature was lowered. Moreover, even if the transparent hydrogel of Example 6 changed temperature at 0-70 degreeC, it remained transparent without becoming cloudy.
[0086]
(Examples 8 to 12)
As the organic monomer, N-isopropylacrylamide (IPAA) is used in Example 8, N, N-dimethylacrylamide (DMAA) is used in Example 9, and N, N-diethylacrylamide (DEAA) is used in Example 10. In Example 11, acryloylmorpholine (ACMO; manufactured by Kojin Co., Ltd.) was used, and in Example 12, N, N-dimethylaminopropylacrylamide (DMAPA; manufactured by Kojin Co., Ltd.) was used.
[0087]
For IPAA (Example 8), 0.75 times (weight ratio) of toluene was added to IPAA, dissolved at 40 ° C., returned to room temperature, and then added 7.5 times (weight ratio) of hexane. Stirring gave needle-like colorless crystals. Finally, IPAA obtained by removing the solvent by filtration and vacuum drying at room temperature was used. DMAA (Example 9), DEAA (Example 10) and ACMO (Example 11) were used in the same manner as in Examples 6 and 7, except that the polymerization inhibitor was removed.
[0088]
DMAPA (Example 12) was used by adding 20% by volume of acetone to DMAPA to lower the viscosity, removing the polymerization inhibitor with an activated alumina column (80 cc / 100 ml monomer), and then removing the acetone with a rotary evaporator. .
[0089]
All the water used was used after pure oxygen obtained by distilling ion-exchanged water was bubbled with high-purity nitrogen gas for 3 hours or more in advance to remove the contained oxygen. In this example, all operations before polymerization (all operations from the preparation of the solution to the removal of the hydrogel) were performed in a nitrogen atmosphere or a nitrogen stream from which oxygen was removed. In addition, the catalyst and the initiator aqueous solution were prepared in a nitrogen atmosphere in which oxygen was blocked in the same manner as the above operation.
[0090]
Into a two-necked flask which was purged with nitrogen inside the water bath at 20 ° C., 85.3 g of pure water from which dissolved oxygen was removed and a Teflon stirrer were placed, and 2.98 g of Laponite XLG was bubbled into the mixture while stirring. A small and clear solution was prepared by adding little by little with care. To this, 9.0 g of IPAA (Example 8), 9.0 g of DMAA (Example 9), 9.0 g of DEAA (Example 10), 9.0 g of ACMO (Example 11), or 9.0 g of DMAPA (Example 12) And stirred until a homogeneous transparent solution was obtained.
[0091]
The weight ratio of XLG / monomer is 0.331. Next, after the flask was cooled in an ice bath, 72 μl of TMEDA that had been cooled separately in an ice bath was added and stirred for 30 seconds, and then similarly cooled in an ice bath. 4.77 g of the same PPS aqueous solution was added with stirring and stirred for 30 seconds to obtain a uniform transparent solution. The solution was allowed to stand in a 15 ° C. water bath for 20 hours to complete the polymerization.
[0092]
In any of Examples 8 to 12, an elastic hydrogel in which the entire system was gelled (the contents did not move even when the container was placed sideways) was obtained in the flask. No aggregation due to non-uniform or opaque clay mineral or polymer was observed in the hydrogel. As a result of examining the transparency of the hydrogel obtained by polymerization at an ice bath temperature (about 1 ° C.), Examples 8, 9, 11 and 12 were uniformly transparent, and Example 10 was uniformly translucent. .
[0093]
As a result of measuring the visible light transmittance of the hydrogel cut to a thickness of 25 mm using NDH-300A manufactured by Nippon Denshoku Industries Co., Ltd., the total transmittance was 95% (Example 8) and 81% (Example 9). ), 40% (Example 10), 85% (Example 11), and 90% (Example 12).
[0094]
Next, the ice bath was changed to a 50 ° C. warm water bath to examine the change in transparency. In Examples 9, 11 and 12, the transparency hardly changed, but in both Examples 8 and 10, the total transmittance changed to opaque with 10% or less.
[0095]
On the other hand, the hydrogel obtained by polymerization was cut into a rod shape having a diameter of 5.5 mm and a length of 30 mm, and compressed to 1/3 and 1/5 in the thickness direction, and doubled and quadrupled in the length direction. And a test of bending deformation at angles of 100 degrees, 150 degrees and more at the center point of the length. As a result, in any of the samples of Examples 9 to 12, in the above test, the shape was not broken, cracked, or lost, and the original state was restored.
[0096]
Further, in the bending deformation test, any deformation of 180 ° or more returned to the original state after the test without causing destruction or cracking. Further, the obtained hydrogel had a diameter of 5.5 mm (cross-sectional area of 0.237 cm).2), Cut out to a length of 50 mm, sandwiched by round sandpaper so that the top and bottom 10 mm are not damaged and do not slide, using the same tensile test apparatus as in Example 1, distance between gauge points = 30 mm, pulling speed = 100 mm A tensile test was conducted at 1 min.
[0097]
As a result, in Example 8, the breaking load was 2.9 N, the breaking elongation was 1001%, the load at a tensile elongation of 100% was 0.103 N, and in Example 9, the breaking load was 2.4 N and the breaking elongation was 1112%. The load at a tensile elongation of 100% was 0.089N. In Example 10, the breaking load was 4.8N, the breaking elongation was 892%, and the load at a tensile elongation of 100% was 0.173N.
[0098]
Moreover, the water content {Cmax / (A + B)} × 100 contained in the hydrogel obtained by equilibrium swelling in 20 ° C. water after cutting the obtained hydrogel into 5 mm square was 6200 wt% (Example 8), 5000 wt. % (Example 9), 3700% by weight (Example 10), and 4700% by weight (Example 11). In addition, by measuring the weight of the dried product obtained by purification in the same manner as in Example 1, the polymerization yield of the monomers was 99% or more in all of Examples 8 to 11, indicating a high yield. It was done.
[0099]
(Example 13) Using 3.15 g of acrylamide (AAM: manufactured by Kanto Chemical Co., Inc.) purified using ethanol and toluene as organic monomers, and using 2.8 g of water-swellable layered clay mineral XLG (XLG / monomer) = 0.89 weight ratio), 50 g in total as water, 0.05 g potassium peroxodisulfate as initiatorAndPolymerization experiments and evaluation tests were conducted in the same manner as in Example 8 except that the polymerization temperature was 23 ° C.
[0100]
As a result, a transparent and uniform organic / inorganic composite hydrogel having a transparency (total transmittance) at a measurement temperature of 1 ° C. of 85% at a thickness of 25 mm and having toughness was obtained. Further, even when the measurement temperature of transparency was 50 ° C., the total transmittance hardly changed.
[0101]
(Example 14)
1.788 g of XLG is used as a clay mineral, and at the same time, an organic crosslinking agent (N, N′-methylenebisacrylamide: BIS: manufactured by Kanto Chemical Co., Inc.) is used at 0.5 mol% of the organic monomer, and the polymerization temperature is set. A polymerization solution was prepared and a polymerization experiment and an evaluation test were performed in the same manner as in Example 9 except that the temperature was 30 ° C.
[0102]
As a result, a transparent and tough organic / inorganic composite hydrogel gel was obtained. The total transmittance at a thickness of 25 mm (measurement temperature: 1 ° C.) was 90%, and the transparency was hardly changed even when the measurement temperature was 50 ° C. A rod-shaped hydrogel cut to a diameter of 5.5 mm and a length of 30 mm is subjected to a compression deformation test up to 1/5 in the thickness direction, a stretch deformation test of 4 times in the length direction, and a bending deformation test up to 180 degrees at the center of the length. In any case, the shape was not destroyed and returned to the original shape after the test.
[0103]
(Examples 15 to 17)
A mixed solvent of water and methanol is used instead of water, and the mixed solvent ratio (weight ratio) of water: methanol is 80:20 (Example 15), 60:40 (Example 16), 40:60 (Example) 17) and the polymerization experiment was conducted in the same manner as in Example 2 except that the polymerization temperature was 15 ° C.
[0104]
As a result, in any of Examples 15 to 17, a uniform and tough organic / inorganic composite hydrogel composed of poly (N-isopropylacrylamide), XLG, water, and methanol was obtained. The transparency of the hydrogel after polymerization (ice bath temperature: measured at about 1 ° C.) was transparent in Example 15 and opaque in Examples 16 and 17. In particular, Example 17 was completely white.
[0105]
Then, it refine | purified using the pure water by the method similar to Example 1. FIG. After purification, Tc was measured by changing the water temperature using an organic / inorganic composite hydrogel swollen in 20 ° C. water. As a result, the organic / inorganic composite hydrogels obtained in Examples 15 to 17 all show a critical temperature (Tc) at 33 ° C., and are colorless and transparent and swell at temperatures below that, and are white and opaque above Tc. To cause volume contraction.
[0106]
From the above results, it was shown that the organic / inorganic composite hydrogel in the present invention can be obtained even using a mixed solvent of water and an organic solvent miscible with water. As a result of thermogravimetric analysis of the dried product, B / A (weight ratio) was 0.066 in all cases.
[0107]
(Examples 18 to 21)
Polymerization was carried out in the same manner as in Example 8 in Example 18, Example 9 in Example 19, Example 10 in Example 20, and Example 11 in Example 21 except that the polymerization temperature was 50 ° C. In all cases, a tough uniform organic-inorganic composite hydrogel was obtained.
[0108]
The transparency at the polymerization temperature immediately after polymerization was transparent in Examples 19 and 21, and white and opaque in Examples 18 and 20. Then, when it cooled to 1 degreeC, it was transparent in Example 18, Example 19, and Example 21, and was opaque-translucent in Example 20. The resulting hydrogel was cut to a thickness of 25 mm and the total visible light transmittance measured at 1 ° C. was 84% (Example 18), 93% (Example 19), 30% (Example 20), 88%. (Example 21).
[0109]
(Example 22)
As an organic monomer, water (85.3 g), XLG (2) were used in the same manner as in Example 8, except that 4.5 g of N-isopropylacrylamide (IPAA) and 3.94 g of N, N-dimethylacrylamide (DMAA) were used. .98 g), TMEDA (72 μl) and PPS (4.77 g in aqueous solution) were prepared and polymerized at 15 ° C. An elastic and uniform translucent hydrogel was obtained.
[0110]
No aggregation due to non-uniform or opaque clay mineral or polymer was observed in the hydrogel. The hydrogel obtained by polymerization was cut to a width of 25 mm, and the transparency was measured while changing the temperature. As a result, the translucency (total transmittance of about 40 to 35%) was changed to opaque (total transmittance of 5% or less). Change (LCST) occurred at about 40-50 ° C. In Example 8 using IPAA alone, compared with the rapid change from transparent (total transmittance of 90%) to opaque (total transmittance of 6%) at 32 ° C. to 34 ° C., the change is shifted to the high temperature side. It became wide.
[0111]
On the other hand, the hydrogel obtained by polymerization is cut into a rod shape having a diameter of 5.5 mm and a length of 30 mm and compressed to 1/3 and 1/5 in the thickness direction, and up to 2 times and 4 times in the length direction. A test for stretching and a test for bending deformation at angles of 100 degrees, 150 degrees and more at the center point of the length were performed. As a result, in any of the tests, the shape was not broken, cracks, or defects were not caused, and the original state was restored. Further, in the bending deformation test, any deformations of 180 degrees or more did not cause destruction or cracks, and returned to the original state after the test.
[0112]
(Examples 23 and 24)
The amounts of the water-swellable clay mineral XLG and the organic monomer IPAA are as follows: in Example 23, XLG = 2.98 g, IPAA = 0.45 g, XLG / IPAA = 6.62 weight ratio; in Example 24, XLG = 0 Experiments were conducted in the same manner as in Example 8, except that 0596 g, IPAA = 4.5 g, and XLG / IPAA = 0.003. As a result, in both Example 23 and Example 24, uniform solutions could be prepared, and uniform transparent gels were obtained as a result of polymerization. The total transmittance of the gel cut to a thickness of 25 mm was 95.1% (Example 23) and 98.2% (Example 24).
[0113]
(Examples 25 and 26)
As a water-swellable clay mineral, instead of XLG, in Example 25, XLS (6% by weight of sodium pyrophosphate in XLS and peptizer: Nippon Silica Kogyo Co., Ltd.), in Example 26, synthetic smectite SWN The experiment was conducted in the same manner as in Example 8 except that (Coop Chemical Co., Ltd.) was used. As a result, in both Example 25 and Example 26, uniform solutions could be prepared, and uniform transparent gels were obtained as a result of polymerization. The total transmittance of the gel cut to a thickness of 25 mm was 90.4% (Example 25) and 83.8% (Example 26).
[0114]
(Comparative Example 1)
Polymerization was carried out at 20 ° C. for 15 hours in the same manner as in Example 1 except that no clay mineral was added. In both the flat bottom glass container and the glass tube container, only a colorless transparent solution in which poly (N-isopropylacrylamide) was dissolved in water was obtained, and no gel was formed. Further, when the temperature of the solution was raised, a polymer gel that became cloudy at about 32 ° C. or more was obtained in a state separated from water, and then when the temperature was lowered to 20 ° C., it returned to the aqueous solution again.
[0115]
In addition, the polymer in the obtained solution was confirmed by diluting in 5 L of water, holding it in a 50 ° C. water tank, causing the lysate to flocculate, and centrifuging (20 ° C., 10,000 rpm, 60 minutes). The sample was separated and further subjected to reprecipitation purification using water, acetone, and hexane, and then the sample was analyzed (infrared absorption spectrum measurement, nuclear magnetic resonance spectrum measurement).
[0116]
(Comparative Example 2)
Polymerization was carried out in the same manner as in Comparative Example 1 except that NaOH was adjusted to pH 11. As a result, a colorless and transparent solution of poly (N-isopropylacrylamide) was obtained as in Comparative Example 1, and no gel was produced. . From this, it was confirmed that there was no influence of the pH increase accompanying the clay mineral addition of Example 1.
[0117]
(Comparative Examples 3 and 4)
The same procedure as in Example 1 was carried out except that the IPAA monomer was added without using the clay mineral, and then an organic cross-linking agent was added at 1 mol% (Comparative Example 3) and 5 mol% (Comparative Example 4) of IPAA. Then, polymerization was carried out at 20 ° C. for 15 hours. As the organic crosslinking agent, N, N′-methylenebisacrylamide (BIS) (manufactured by Kanto Chemical Co., Inc.) was used as it was. In Comparative Example 3, a colorless and transparent gel was obtained, and in Comparative Example 4, a cloudy gel was obtained. As a result of measurement in the same manner as in Example 1, {C / (A)} × 100 was 990% by weight (Comparative Example 3) and 935% by weight (Comparative Example 4), and was confirmed to be an organic crosslinked hydrogel. It was.
[0118]
In Comparative Example 3, Tc was around 33 ° C., transparent and swollen on the lower temperature side than Tc, and white turbid and contracted on the higher temperature side than Tc. The volume ratio during swelling and shrinking at 20 ° C. and 50 ° C. was about 8. On the other hand, in Comparative Example 4, all remained cloudy even when the temperature was changed. Although it swelled on the low temperature side at about 33 ° C. and contracted on the high temperature side, the volume ratio during swelling and contraction at 20 ° C. and 50 ° C. was about 5. Changes in volume and total transmittance due to temperature changes in Comparative Example 4 are shown in FIGS. 1 and 2 together with the results of Example 1. FIG.
[0119]
(Comparative Examples 5 and 6)
In an aqueous solution obtained by dissolving 1 g of poly (N-isopropylacrylamide) obtained in Comparative Example 1 in 10 g of water, 0.331 g (Comparative Example 5) or 0.066 g (Comparative Example 6) of clay mineral (Laponite XLG) was stirred. However, in each case, a hydrogel having uniform toughness could not be obtained, although an attempt was made to prepare a composite composed of an organic polymer having the same composition as Example 1 and Example 2, a clay mineral, and water. It was.
[0120]
(Comparative Example 7)
Except for using DEAA monomer, 0.15 g of poly (N, N-diethylacrylamide) obtained in the same manner as in Comparative Example 1 was added to a transparent aqueous solution obtained by dissolving 14.85 g of water in 0.2 g of clay mineral (Laponite XLG). A clear solution of 9.8 g in water was added while gradually stirring to prepare a mixture. When the XLG aqueous solution was added to 0.88 g (B / A = 0.117), a white floating substance was precipitated in the solution according to the amount of added XLG, and changed to a cloudy solution. Further addition was continued, and the mixture remained a cloudy solution even when the addition amount was 3.88 g (B / A = 0.517), for example.
[0121]
These cloudy mixed solutions were heterogeneous solutions in which white aggregates floated in water, and when this was heated, it was observed that the cloudiness further increased at a temperature higher than about 28 ° C. However, in any case, a uniform hydrogel was not obtained. Furthermore, even when the amount of clay added was increased or the initial polymer solution concentration was increased, a uniform and tough hydrogel as obtained in the examples could not be obtained.
[0122]
(Comparative Example 8)
A mixture containing an organic polymer, a clay mineral, and water was prepared in the same manner as in Comparative Example 7, except that a poly (N, N-diethylacrylamide) aqueous solution was gradually added to 10 g of the XLG aqueous solution. By adding and mixing, a white turbid solution was obtained. By heating to Tc or higher, the turbidity was further increased, and a hydrogel with uniform toughness could not be obtained in any case.
[0123]
(Comparative Examples 9-12)
After adding DEAA (Comparative Examples 9 and 10) or ACMO (Comparative Examples 11 and 12) without using clay minerals, the organic cross-linking agent N, N′-methylenebisacrylamide (BIS) was added to 1 mol of DEAA or ACMO. % (Comparative Examples 9 and 11) and 5 mol% (Comparative Examples 10 and 12), except that they are used in the same manner as in Example 10 or Example 11, and left in a water bath at 15 ° C. for 20 hours for polymerization. Completed.
[0124]
In any of Comparative Examples 9 to 12, a hydrogel in which the entire system was gelled (the contents did not move even when the container was placed on the side) was obtained in the flask. None of the non-uniform aggregation was observed in the hydrogel. As a result of examining the transparency of the hydrogel obtained by polymerization at an ice bath temperature (about 1 ° C.), Comparative Examples 9 and 11 were uniformly transparent, and Comparative Examples 10 and 12 were opaque. As a result of measuring the visible light transmittance of the hydrogel cut to a thickness of 25 mm using NDH-300A manufactured by Nippon Denshoku Industries Co., Ltd., the total transmittance was 98% (Comparative Example 9) and 24% (Comparative Example 10). ), 98% (Comparative Example 11), and 22% (Comparative Example 12).
[0125]
On the other hand, in Comparative Examples 9 to 12, polymerization was carried out under the above conditions using a glass tube having an inner diameter of 5.5 mm and a length of 150 mm as a polymerization vessel to obtain a rod-like organic crosslinked hydrogel. The obtained hydrogel was cut into a rod shape with a length of 30 mm, compressed to 1/3 in the thickness direction, tested to stretch twice in the length direction, and bent at an angle of 100 degrees at the center of the length. A test was conducted.
[0126]
As a result, in all the samples of Comparative Examples 9 to 12, cracks occurred in the above test, and the shapes were broken or lost. Furthermore, the hydrogel obtained in Comparative Examples 9-12 was 5.5 mm in diameter (cross-sectional area 0.237 cm).2), Carefully cut out to a length of 50 mm, sandwiched by round sandpaper so as not to damage 10 mm above and below, and using the same tensile test apparatus as in Example 1, distance between gauge points = 30 mm, pulling speed = An attempt was made to perform a tensile test at 100 mm / min, but the sample was brittle and most of the sample was broken before being attached to the chuck. Moreover, even those lightly attached to the chuck were broken immediately after the test, and no physical property values were obtained.
[0127]
(Comparative Examples 13 and 14)
Except for using a glass tube container having an inner diameter of 5.5 mm and a length of 150 mm, Comparative Example 13 was compared with Comparative Example 3 and Comparative Example 14 was a bar-shaped organic bridge having an outer diameter of 5.5 mm by the same method as Comparative Example 4. A hydrogel was obtained by polymerization. The obtained hydrogel was cut out to a length of 30 mm, compressed to 1/3 in the thickness direction, tested to extend twice in the length direction, and tested to bend and deform at an angle of 100 degrees at the center point of the length. went.
[0128]
As a result, in all the samples of Comparative Examples 13 and 14, cracks occurred in the above test, and the shapes were broken or lost. Further, it was cut out to a length of 50 mm, sandwiched between round sand papers so as not to damage and slip 10 mm above and below, and using the same tensile test apparatus as in Example 1, the distance between gauge points = 30 mm, the pulling speed = 100 mm / Attempts were made to perform a tensile test in minutes, but the samples were brittle and any sample broke before being mounted on the chuck, and no physical property values were obtained.
[0129]
Further, the obtained organic cross-linked hydrogel was cut into approximately 5 mm square, and then the water content {Cmax / (A)} × 100 contained in the organic cross-linked hydrogel obtained by equilibrium swelling in 20 ° C. water was 1500% by weight (comparative example) 13) and 800% by weight (Comparative Example 14).
[0130]
【The invention's effect】
The present invention is a novel organic / inorganic composite hydrogel having excellent functionality such as uniformity, transparency, mechanical properties, mechanical properties, water absorption, swelling / shrinkage properties, a method for producing the same, and removing water from the hydrogel Thus, a dried body of the organic / inorganic composite hydrogel obtained can be provided.
[0131]
The organic / inorganic composite hydrogel obtained by the present invention includes a tough and tough hydrogel, a transparent or uniform white hydrogel, a transparent and / or volume-swelled state on the low temperature side, and opaque and / or volume on the high temperature side. Those having a critical temperature (Tc) that reversibly changes to a contracted state are included, and the dried gel of the organic-inorganic composite hydrogel can be reversibly returned to the hydrogel by immersion in water. It is useful in a wide range of fields such as daily necessities, medicine / medical care, agriculture, civil engineering, and industrial fields.
[Brief description of the drawings]
1 is a diagram showing volume changes during swelling and shrinkage of the organic / inorganic composite hydrogel obtained in Example 1 and the organic crosslinked hydrogel obtained in Comparative Example 4 with temperature in water. FIG. The vertical axis represents the hydrogel volume (mm3) Represents the temperature (° C.) on the horizontal axis.
2 is a graph showing changes in transparency of the organic / inorganic composite hydrogel obtained in Example 1 and the organic crosslinked hydrogel obtained in Comparative Example 4 depending on the temperature. FIG. The vertical axis represents total transmittance (%), and the horizontal axis represents temperature (° C.).

Claims (17)

  1. (C) Water is contained in a three-dimensional network formed by combining (A) a water-soluble organic polymer and (B) a water-swellable layered clay mineral that can be uniformly dispersed in water. An inorganic composite hydrogel comprising :
    The component monomer (A ′) of the water-soluble organic polymer (A) is an acrylamide derivative and / or a methacrylamide derivative,
    (B) The organic / inorganic composite hydrogel, wherein the water-swellable layered clay mineral that can be uniformly dispersed in water is water-swellable smectite or water-swellable mica.
  2.   (B) The water-swellable layered clay mineral that can be uniformly dispersed in water is uniformly dispersed in a thickness of 1 to 10 layers, and is combined to act as a crosslinking agent for the (A) water-soluble organic polymer. The organic-inorganic composite hydrogel according to claim 1.
  3.   The organic / inorganic composite hydrogel according to claim 1 or 2, wherein (A) the water-soluble organic polymer and (B) the water-swellable layered clay mineral that can be uniformly dispersed in water are complexed at a molecular level.
  4.   The organic-inorganic composite hydrogel according to claim 1, wherein the three-dimensional network is formed without using an organic crosslinking agent.
  5. (C) Water is contained in a three-dimensional network formed by combining (A) a water-soluble organic polymer and (B) a water-swellable layered clay mineral that can be uniformly dispersed in water. It inorganic composite hydrogel der,
    The component monomer (A ′) of the water-soluble organic polymer (A) is an acrylamide derivative and / or a methacrylamide derivative,
    (B) The water-swellable layered clay mineral that can be uniformly dispersed in water is water-swellable smectite or water-swellable mica,
    Further, (B) an organic / inorganic composite hydrogel in which the water-swellable layered clay mineral that can be uniformly dispersed in water forms a three-dimensional network as a main crosslinking agent.
  6.   (B) A water-swellable layered clay mineral that can be uniformly dispersed in water is dissolved in water, and (B) in the presence of water-swellable layered clay mineral that can be uniformly dispersed in water and (C) water, The organic-inorganic composite hydrogel according to any one of claims 1 to 5, which is obtained by polymerizing a constituent monomer (A ') of A) a water-soluble organic polymer.
  7. The organic / inorganic composite hydrogel according to claim 1, wherein the (B) water-swellable layered clay mineral is water-swellable hectorite.
  8. The organic / inorganic composite hydrogel according to any one of claims 1 to 7 , wherein a weight ratio of (B) water-swellable layered clay mineral / (A) water-soluble organic polymer is 0.01 to 10.
  9.   9. A critical temperature (Tc) that is transparent and / or volume swelled on the low temperature side and reversibly changes to opaque and / or volume contracted on the high temperature side. Organic / inorganic composite hydrogel.
  10. The water content defined by {C / (A + B)} × 100 is 600 to 1000% by weight, and the tensile breaking load is 0.1 N or more measured using a hydrogel having an initial cross-sectional area of 0.237 cm 2 . The organic-inorganic composite hydrogel according to any one of claims 1 to 9, wherein a tensile breaking elongation is 100% or more and a load at a tensile elongation of 100% is 0.01 N or more.
  11.   The organic-inorganic composite gel according to any one of claims 1 to 10, wherein a water content {Cmax / (A + B)} × 100 at equilibrium swelling in water at 20 ° C. is 2000% by weight or more.
  12. A dried product of an organic / inorganic composite hydrogel obtained by removing water from the organic / inorganic composite hydrogel according to any one of claims 1 to 11 .
  13. A method for producing an organic-inorganic composite hydrogel according to claim 1 or 5,
    (A) A monomer (A ′) that is a constituent of a water-soluble organic polymer and (B) a water-swellable layered clay mineral that can be uniformly dispersed in water are dissolved in (C) water, and the (B) water Water-swellable layered clay mineral that can be uniformly dispersed in (C) monomer (A ′) that is a constituent of water-soluble organic polymer in the presence of water in the absence of molecular oxygen and A method for producing an organic / inorganic composite hydrogel that is polymerized by ultraviolet irradiation .
  14. Were uniformly dispersed in the thickness of 1 to 10 layers (B) be present as a crosslinking agent uniformly dispersible water-swellable layered clay mineral in water, the polymerization of the monomer (A '), according to claim 13, wherein A method for producing an organic / inorganic composite hydrogel.
  15. The weight ratio of the monomer of (B) water-swellable layered clay mineral that can be uniformly dispersed in water / (A ′) water-soluble organic polymer (A) is 0.01 to 10, according to claim 13 or 14 . A method for producing an organic / inorganic composite hydrogel.
  16. Tensile strength of the resulting organic / inorganic composite hydrogel was measured using a hydrogel having a water content defined by {C / (A + B)} × 100 of 600 to 1000 wt% and an initial cross-sectional area of 0.237 cm 2. The organic-inorganic composite according to any one of claims 13 to 15 , wherein the breaking load is 0.1N or more, the tensile breaking elongation is 100% or more, and the load at a tensile elongation of 100% is 0.01N or more. A method for producing a hydrogel.
  17. The resulting organic-inorganic composite hydrogel, water content at equilibrium swelling in water at 20 ℃ {Cmax / (A + B)} × 100 is 2000% by weight or more, according to any one of claims 13 to 16 Manufacturing method of organic / inorganic composite gel.
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