JP2011153174A - Organic-inorganic composite hydrogel, dried body thereof and method for producing them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic-inorganic composite hydrogel not only having excellent mechanical properties but also having high swellability with physiological salt solution and high swellability with water, to provide a dried body thereof, and to provide a method for producing them. <P>SOLUTION: The organic-inorganic composite hydrogel having both of the high swellability with the physiological salt solution and the high swellability with the water, and formed of a water-soluble polymer of acrylic monomers, and a water-swellable clay mineral is obtained by using both of a monomer represented by formula (1) (wherein, R<SP>1</SP>is hydrogen or methyl; R<SP>2</SP>is 2-3C alkylene; n is an integer of 10-99; and Y is methoxy or hydroxy) and an ionic monomer as the water-soluble acrylic monomers. The dried body thereof has excellent flexibility. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polymer hydrogel used in the fields of medicine, hygiene products, agriculture, food, architecture, civil engineering, machinery, transportation, electronic components, household items, sewing, and the like, and a dried product thereof.

  A polymer hydrogel is a material that stably holds a large amount of water in a three-dimensional network formed by a polymer, and is generally known as a water-absorbing material. At present, it is used in many places as materials such as disposable diapers, sanitary products, soft contact lenses, and freshness-keeping materials. In recent years, polymer hydrogels are expected to develop significantly as functional materials. For example, research in the fields of medical and regenerative medical materials such as drug delivery systems (DDS), cell culture substrates, wound dressings, and cartilage substitute materials has been actively conducted. However, the conventional polymer hydrogel has an essential problem derived from the cross-linked structure, that is, it has a drawback of being mechanically fragile, so that it can be used as many materials required for strength and durability. It was difficult.

  In recent years, acrylamide derivatives such as poly (N-isopropylacrylamide) and poly (N, N-dimethylacrylamide) and water-swellable inorganic clay minerals such as hectorite have been combined at the nanometer level to form a three-dimensional network. It has been reported that the obtained organic-inorganic composite hydrogel exhibits extremely excellent mechanical properties (Patent Document 1). For example, an organic-inorganic composite hydrogel composed of dimethylacrylamide and clay mineral has a tensile breaking strength of several tens to several hundreds kPa and a breaking elongation exceeding 1500%.

  However, the organic-inorganic composite hydrogel composed of the above-mentioned acrylamide derivative and clay mineral has excellent mechanical properties but is higher in water swellability than the conventional acrylamide derivative organic cross-linked gel, but is a commercially available highly water-absorbent polyacrylic resin. Water absorption is inferior compared with sodium acid cross-linked product. In order to improve this, the inventors synthesized an organic-inorganic composite hydrogel having a carboxylic acid group by copolymerization of an acrylamide derivative and sodium acrylate in the presence of a clay mineral, and the organic-inorganic composite exceeding 2000 times the water absorption ratio. A hydrogel was found (Patent Document 2). However, since the organic-inorganic composite hydrogel having a carboxylic acid group is ionic like a commercially available sodium polyacrylate crosslinked product, the water absorption performance in pure water is high, but the water absorption performance is greatly reduced in saline. Had a problem. In addition, conventional organic / inorganic hydrogels mainly composed of acrylamide derivatives have a drawback that they are difficult to handle as medical members such as wound dressings required for flexibility because their dried bodies are hard and brittle. It was.

JP2002-53762 JP 2009-046553 A

  The problem to be solved by the present invention is an organic-inorganic composite hydrogel formed from a polymer of a monomer containing a water-soluble acrylic monomer and an ionic monomer and a water-swellable clay mineral, and only with excellent mechanical properties. It is another object of the present invention to provide a hydrogel having high water swellability and high saline swellability, a dried product thereof, and a method for producing them.

  The present invention is an organic-inorganic composite hydrogel formed of a polymer of a monomer containing a nonionic acrylic monomer and an ionic monomer and a water-swellable clay mineral, and the nonionic acrylic monomer is represented by the following formula (1): The organic-inorganic composite hydrogel can be given high salt swellability by using a monomer represented by Further, by using sodium acrylate, sodium 2-acrylamido-2-methylpropanesulfonate, or the like as the ionic monomer, the organic-inorganic composite hydrogel can have high water swellability. In the present invention, by using a nonionic acrylic monomer and an ionic monomer in combination, an organic-inorganic composite hydrogel having not only excellent mechanical properties but also high water swellability and high saline swellability can be obtained. The present inventors have found and completed an organic-inorganic composite having excellent flexibility and high swellability by drying a hydrogel at a low temperature.

That is, the present invention is an organic-inorganic composite hydrogel formed of a polymer (A) of a water-soluble acrylic monomer (a) and a water-swellable clay mineral (B),
The water-soluble acrylic monomer (a) has the formula (1)

（式中、Ｒ^１は、水素原子又はメチル基、Ｒ^２は炭素数２又は３のアルキレン基、ｎは１０〜９９の整数、Ｙはメトキシ基又は水酸基を表す。）
で表されるモノマーとカルボン酸塩構造及び/又はスルホン酸塩構造を有するモノマー（Ｃ）とを含むことを特徴とする有機無機複合ヒドロゲルを提供するものである。

(In the formula, R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkylene group having 2 or 3 carbon atoms, n represents an integer of 10 to 99, and Y represents a methoxy group or a hydroxyl group.)
And a monomer (C) having a carboxylate structure and / or a sulfonate structure.

  The present invention also provides a method for producing the organic-inorganic composite hydrogel, wherein the monomer represented by the formula (1) and the (meth) acrylamide derivative, the water-swellable clay mineral (B), water ( E) and a polymerizable monomer (C) having a carboxylate structure or a sulfonate structure is added simultaneously with the polymerization initiator or immediately after the addition of the polymerization initiator, 1) The polymer (A) is produced by polymerizing the monomer represented by 1) and a (meth) acrylamide derivative and a polymerizable monomer having the carboxylate structure or sulfonate structure. A method for producing an inorganic composite hydrogel is provided.

  The organic-inorganic composite hydrogel of the present invention is a hydrogel formed from a polymer of a water-soluble acrylic monomer and a water-swellable clay mineral. The water-soluble acrylic monomer is ionic with the monomer represented by the formula (1). By using monomers such as sodium acrylate and sodium 2-acrylamido-2-methylpropanesulfonate together, the resulting organic-inorganic composite hydrogel uses the monomer represented by formula (1) and the ionic monomer alone. Compared with the case, the swellability in saline was significantly improved. In addition, the present invention gives the flexibility of the dried organic-inorganic composite hydrogel obtained by using the monomer represented by the formula (1), and by using the ionic monomer, the salt of the dried hydrogel is obtained. An organic-inorganic composite having high swellability in water and pure water and having a balance between flexibility and swellability can be easily obtained. The organic-inorganic composite hydrogel of the present invention and a dried product thereof are suitably used as water-absorbing materials including wound dressings, disposable diapers and sanitary products in medical applications because of excellent swelling properties with saline and pure water.

It is a figure which shows the breaking strength and elongation of the hydrogel obtained in Examples 1, 2 and Comparative Examples 1, 2, 3. FIG. 3 is a graph showing the degree of swelling of the hydrogels obtained in Example 1 and Comparative Example 1 with physiological saline. FIG. 3 is a diagram showing the degree of swelling of the hydrogel obtained in Example 1 and Comparative Example 1 with pure water. FIG. 3 is a graph showing the degree of swelling of the hydrogels obtained in Example 2 and Comparative Examples 2 and 3 with physiological saline. FIG. 3 is a diagram showing the degree of swelling of the hydrogels obtained in Example 2 and Comparative Examples 2 and 3 with pure water. It is a figure which shows the breaking strength and elongation of the hydrogel obtained in Examples 3, 4, and 5. It is a figure which shows the swelling degree in the physiological saline of the hydrogel obtained in Example 3, 4, and 5. FIG. It is a figure which shows the swelling degree in the pure water of the hydrogel obtained in Example 3, 4, and 5. FIG. FIG. 3 is a graph showing the breaking strength and elongation of the hydrogels obtained in Examples 6, 7, and 8. FIG. 4 is a graph showing the degree of swelling of the hydrogel obtained in Examples 6, 7, and 8 with physiological saline. It is a figure which shows the swelling degree in the pure water of the hydrogel obtained in Example 6,7,8. FIG. 3 is a graph showing the breaking strength and elongation of the hydrogels obtained in Examples 9, 10, and 11. It is a figure which shows the swelling degree in the physiological saline of the hydrogel obtained in Example 9,10,11. It is a figure which shows the swelling degree in the pure water of the hydrogel obtained in Example 9,10,11.

  The organic-inorganic composite hydrogel of the present invention is formed by radical polymerization of a water-soluble acrylic monomer (a) in an aqueous solution of a water-swellable clay mineral.

  The water-soluble acrylic monomer (a) used in the present invention may have any property that dissolves in water and has an interaction with the water-swellable clay mineral (B) that can be uniformly dispersed in water. , Acrylamide, methacrylamide, and derivatives thereof (N- or N, N-substituted (meth) acrylamide) and acrylates are preferably used.

  As the water-soluble acrylic monomer (a), a polyethylene glycol (PEG) chain represented by the formula (1) or polypropyl is used to improve the saline swelling property and flexibility of the obtained organic-inorganic composite hydrogel and its dried product. Nonionic acrylic monomers with glycol (PPG) chains are used.

（式中、Ｒ^１は、水素原子又はメチル基、Ｒ^２は炭素数２又は３のアルキレン基、ｎは１０〜９９の整数、Ｙはメトキシ基又は水酸基を表す。）

(In the formula, R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkylene group having 2 or 3 carbon atoms, n represents an integer of 10 to 99, and Y represents a methoxy group or a hydroxyl group.)

  The number of ethylene glycol repeating units of the acrylic monomer represented by the formula (1) used in the present invention can be appropriately selected from 10 to 99. In general, as the number of ethylene glycol repeating units increases, the degree of swelling of the resulting organic-inorganic composite hydrogel in physiological saline tends to increase. Therefore, the number of ethylene glycol repeating units in the monomer of formula (1) is preferably 13 to 80, and particularly preferably 15 to 60.

  Moreover, in order to bring about the mechanical strength of the obtained organic-inorganic composite hydrogel, the water-soluble acrylic monomer (a) is one or more selected from (meth) acrylamide, N-substituted (meth) acrylamide, acryloylmorpholine and the like ( It is preferable to use meth) acrylamide and its derivatives in combination. Specifically, N-methylacrylamide, N-ethylacrylamide, N-cyclopropylacrylamide, N-isopropylacrylamide, N-methylmethacrylamide, N-cyclopropylmethacrylate Amides, N-isopropylmethacrylamide, N, N-dimethylacrylamide, N-methyl-N-ethylacrylamide, N-methyl-N-isopropylacrylamide, N-methyl-Nn-propylacrylamide, N, N-diethylacrylamide , Acryloylmol Examples include folin, N-acryloylpyrrolidine, N-acryloylpiperidine, N-acryloylmethylhomopiperadine, N-acryloylmethylpiperazine. Of these, N, N-dimethylacrylamide and the monomer represented by formula (1) are preferably used in combination from the viewpoint of swelling, and acryloylmorpholine and formula (1) are represented from the viewpoint of safety to living bodies. From the viewpoint of functionality, N-isopropylacrylamide, N, N-diethylacrylamide having LCST (lower critical solution temperature) and a monomer represented by the formula (1) are used in combination. It is preferable to do.

  In the present invention, an ionic monomer is further used in order to increase the swelling property, particularly the water swelling property, of the organic-inorganic composite hydrogel and its dried product. Examples of ionic monomers include unsaturated carboxylic acids such as acrylic acid, maleic acid, itaconic acid, crotonic acid, and fumaric acid, and salts thereof, 2-acrylamido-2-methylpropane sulfonic acid, methacrylamide sulfonic acid, vinyl sulfonic acid, Examples include allyl sulfonic acid, p-styrene sulfonic acid and salts thereof, and sodium methacryloxyoxyethyl sulfonate. Among these, acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid are particularly preferably used from the viewpoint that an organic polymer having excellent water swellability can be easily obtained.

  In the present invention, the use ratio of the acrylic monomer represented by the formula (1) contained in all monomers used in the polymerization is preferably 1% by mass to 70% by mass, more preferably 3% by mass to 60% by mass. %, Particularly preferably 5% by mass to 50% by mass. When the content of the acrylic monomer represented by the formula (1) in all monomers is within this range, the organic-inorganic composite hydrogel and the dried product obtained are sufficiently effective for improving physical properties such as saline swelling and flexibility. Is obtained, and the mechanical properties of the hydrogel are not significantly lowered.

  Further, in the monomer composition of the present invention, if the copolymerization ratio of the ionic monomer is too high, the mechanical properties of the obtained hydrogel are lowered. On the other hand, if the copolymerization ratio is too low, the high water absorption of the hydrogel of the present invention cannot be exhibited. Therefore, the copolymerization ratio of the ionic monomer having a carboxylic acid group or a sulfonic acid group of the present invention is preferably 0.1 to 50 mol%, more preferably 0.3 to 40 mol%, based on the whole monomer. Particularly preferred is 0.5 to 30 mol%, and most preferred is 1 to 20 mol%.

  The water-swellable clay mineral used in the present invention needs to have a property of swelling between layers in water or an aqueous solution. More preferably, at least a part can be peeled and dispersed in layers in water, more preferably in water to a thickness of 1 to 10 layers, particularly preferably in water to a thickness of 1 to 3 layers. It is a layered clay mineral that can be dispersed uniformly. For example, water-swellable smectite or water-swellable mica can be used. Specifically, water-swellable hectorite containing sodium as an interlayer ion, water-swellable montmorillonite, water-swellable saponite, water-swellable synthetic mica Is mentioned.

  The ratio of the water-soluble acrylic monomer (a) and the clay mineral constituting the organic-inorganic composite hydrogel used in the present invention is appropriately selected depending on the type of monomer and clay mineral used. The range to be formed is preferable, and the mass ratio of the water-swellable clay mineral (B) / water-soluble acrylic monomer (a) polymer (A) is preferably 0.01 to 5, more preferably 0.03 to 3, especially. Preferably it is 0.05-1.5. Within such a mass ratio range, preparation is easy, and a controlled elastic modulus (softness) and high strength can be obtained over a wide range while maintaining high stretchability.

  The organic-inorganic composite hydrogel used in the present invention includes a solvent containing a mixed solvent with an organic solvent miscible with water in addition to water.

  In the present invention, the amount of water or solvent contained in the organic-inorganic composite hydrogel is set according to the purpose and is not unconditionally defined, but is preferably a polymer of an acrylic monomer in the organic-inorganic composite hydrogel and a water-swellable clay mineral. Those having a mass ratio of water or solvent to the total mass of 50 or less are more preferably 0.1-30.

  The organic-inorganic composite hydrogel of the present invention can be produced by the following method. Polymerization of a nonionic acrylic monomer, which is a monomer of the organic polymer (A), and an ionic monomer is carried out in the presence of the layer-peeled water-swellable clay mineral (B). During the polymerization process, the water-swellable clay mineral (B) acts as a monomer crosslinking agent due to the interaction between the monomer of the organic polymer (A) and the water-swellable clay mineral (B). Complexation at the molecular level with the water-swellable clay mineral (B) is achieved, and an organic-inorganic hybrid hydrogel gelled by three-dimensional network formation is obtained.

  Specifically, a (meth) acrylamide derivative and an acrylic monomer of formula (1) are added to an aqueous solution of a water-swellable clay mineral (B) finely dispersed in water, and have a carboxylic acid group or a sulfonic acid group at a low temperature. An ionic monomer and a radical polymerization initiator are added, and then polymerization is performed at a predetermined temperature. Here, the addition order of the ionic monomer having a carboxylic acid group or a sulfonic acid group is important. When an ionic monomer having a carboxylic acid group or a sulfonic acid group is added together with the acrylamide derivative and the acrylic monomer of formula (1), the clay mineral aggregates due to strong interaction with the carboxylic acid group or the sulfonic acid group. End up. The hydrogel obtained in this way not only becomes cloudy but also exhibits a tendency to greatly reduce the mechanical properties. In addition, the reaction system may remarkably thicken and gel due to the interaction between the clay mineral and the carboxylic acid group or sulfonic acid group. Therefore, the polymerization initiator cannot be dispersed in the reaction system, and a uniform hydrogel cannot be obtained. In order to minimize agglomeration of clay minerals, a (meth) acrylamide derivative and an acrylic monomer of formula (1) are first added to the clay mineral aqueous dispersion followed by an ionic monomer having a carboxylic acid group or a sulfonic acid group. By adding a polymerization initiator all at once or by adding an ionic monomer having a carboxylic acid group or a sulfonic acid group after adding a polymerization initiator, radical polymerization is performed together with the dispersion of the monomer, and the entire system is gelled. This method is effectively used. When adding a polymerization initiator and an ionic monomer having a carboxylic acid group or a sulfonic acid group separately, it is preferable to add the monomer immediately after adding the polymerization initiator. When the polymerization initiator is added, the polymerization of the (meth) acrylamide derivative and the acrylic monomer of the formula (1) previously added to the aqueous dispersion starts. Therefore, when a polymerization initiator is added, it is preferable to add an ionic monomer having a carboxylic acid group or a sulfonic acid group as soon as possible to promote random copolymerization and exhibit the effects of the present invention.

  The above radical polymerization reaction can be performed by a known method such as radical polymerization initiator and / or radiation 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. Particularly preferred is a radical polymerization initiator having a strong interaction with the water-swellable clay mineral (B) exfoliated in layers.

  Specifically, as the polymerization initiator, water-soluble peroxides such as potassium peroxodisulfate and ammonium peroxodisulfate, water-soluble azo compounds such as VA-044, V-50, V-501, And water-soluble radical initiators having an ethylene oxide chain. On the other hand, as the catalyst, tertiary amine compounds such as N, N, N ′, N′-tetramethylethylenediamine and β-dimethylaminopropionitryl are of course used, but in the present invention, they are used as monomers. Since the polymerizable monomer having a carboxylic acid group or a sulfonic acid group functions as a catalyst, the above-mentioned radical polymerization catalyst may not be added.

  The polymerization temperature can be set in the range of 0 ° C. to 100 ° C. according to the type of initiator. The polymerization time varies depending on other polymerization conditions, and is generally carried out for several tens of seconds to several tens of hours.

  The organic-inorganic composite hydrogel having an ionic group and a PEG chain of the present invention retains the characteristics of an organic-inorganic hydrogel, and has higher water absorption than conventional organic crosslinked gels, as well as excellent mechanical properties. Show. For example, the organic / inorganic composite hydrogel of the present invention is all superior to the organic crosslinked gel in terms of mechanical properties such as strength, elongation, and toughness.

Since the mechanical properties of the organic-inorganic composite hydrogel vary depending on the water content and shape of the hydrogel, the mechanical properties of the organic-inorganic composite hydrogel having an ionic group and a PEG chain according to the present invention are within a certain range. It is represented by the result of testing using a hydrogel having In this specification, specifically, an organic-inorganic composite hydrogel having an ionic group and a PEG chain is used as a test material having a cross-sectional area (initial cross-sectional area) of a film-like hydrogel of 0.25 cm ² at the start of the test. The mechanical properties of the water (E) content (water content) of 90% by mass were measured.

  The organic-inorganic composite hydrogel having an ionic group and a PEG chain of the present invention has a tensile strength of 10 to 300 kPa, more preferably 15 to 250 kPa, when measured using the hydrogel having the above water content and initial cross-sectional area. Particularly preferred is 20 to 200 kPa, and further, the tensile elongation at break is 100 to 3000%, more preferably 200 to 2500%, and particularly preferably 300 to 2000%.

  In the organic-inorganic composite hydrogel having an ionic group and a PEG chain of the present invention, the maximum degree of swelling Wgel / Wdry in pure water is preferably 50 or more. Here, the maximum degree of swelling Wgel / Wdry is the mass number of the hydrogel swollen per 1 g of the dried gel. Wdry is the solid content of the hydrogel, and Wgel is the mass of the gel swollen by immersing the hydrogel in a large amount of water. The maximum swelling degree Wgel / Wdry is more preferably 50 to 10,000, and particularly preferably 100 to 6000.

  In the organic-inorganic composite hydrogel having an ionic group and a PEG chain of the present invention, the equilibrium swelling degree Wgel / Wdry in physiological saline is preferably 20 or more. More preferably, it is 25 or more, and particularly preferably 30 or more.

  The organic-inorganic composite hydrogel having an ionic group and a PEG chain of the present invention includes those that are extremely excellent in transparency. For example, the light transmittance of an organic-inorganic composite hydrogel obtained by copolymerization of ACMO with an acrylic monomer of formula (1) and an acrylate or 2-acrylamido-2-methylpropanesulfonate is 85% or more.

  The organic-inorganic composite hydrogel of the present invention can be prepared in various sizes and shapes by changing the shape of the polymerization vessel at the time of polymerization, or by cutting after polymerization, for example, film shape, flat plate shape, fiber shape, rod shape A cylindrical shape, a hollow shape, a cylindrical shape, a spiral shape, or a spherical shape can be used. In particular, a film-like hydrogel is suitably used as a wound dressing because of its high physiological saline swelling property. In the present invention, the obtained organic-inorganic composite hydrogel can be dried by a conventional method to obtain an organic-inorganic composite from which part or all of the solvent has been removed. Such a drying temperature is preferably 80 ° C. or lower, more preferably 60 ° C. or lower. When the drying temperature exceeds 80 ° C., crosslinking due to a covalent bond occurs in a part of the polymer, so that the salt swellability of the obtained organic-inorganic composite may be lowered, which is not preferable. The drying time varies depending on the thickness of the hydrogel film to be used, the drying method and the drying temperature, but is usually several hours to several tens of hours.

  In the present invention, flexibility is imparted to the obtained organic-inorganic composite by using the acrylic monomer represented by the formula (1). The softness | flexibility changes with the usage-amount of the acrylic monomer represented by Formula (1) to be used, and the content rate of a clay mineral. For example, a dry film having a thickness of 0.1 to 0.3 mm obtained by drying the hydrogel film described above is represented by the formula (1) used on the basis that it is not broken even if it is bent 135 ° repeatedly. The amount of acrylic monomer used is preferably 20% by mass or more, more preferably 25% by mass or more, and particularly preferably 30% by mass or more based on the total monomers. Further, the content of the clay mineral to be used is preferably 20% by mass or less, more preferably 16% by mass or less, and particularly preferably 13% by mass or less with respect to the solid content. If the amount of the acrylic monomer represented by the formula (1) and the content of the clay mineral are within the above ranges, the obtained organic-inorganic composite film has flexibility to fit the human body, Alternatively, it can be immersed in water and regenerated into a hydrogel film to be used as a wound dressing.

The present invention will be described more specifically with reference to the following examples and comparative examples, but is not limited thereto.
(Measurement condition)
<Measurement of breaking strength and elongation>
In the following examples and comparative examples, the tensile test was performed by chucking an unpurified film-like hydrogel (width = 10 mm, thickness = 2.5 mm) using a tabletop universal testing machine AGS-H manufactured by Shimadzu Corporation. The test piece was mounted on a tensile test apparatus so that there was no slip at the part, and the measurement was performed at a distance between gauge points = 30 mm and a pulling speed = 100 mm / min.
<Measurement of swelling degree in physiological saline>
The degree of swelling of the hydrogel in physiological saline was determined from the time dependence of the increase in mass of a film-like hydrogel having a side of 30 mm and a thickness of 2.5 mm immersed in a large amount of physiological saline. In addition, the degree of swelling of the dried hydrogel film in physiological saline is about 0.03 g of a dry film having a thickness of about 0.2 mm is immersed in 50 ml of 37 ° C. physiological saline for 25 to 100 hours until the mass does not increase. The equilibrium swelling degree of was measured.
<Measurement of swelling degree in pure water>
The degree of swelling of hydrogel in pure water was determined from the time dependence of the mass increase of about 0.2 g hydrogel immersed in a large amount of water. Further, the maximum swelling degree in water of the dried hydrogel film was determined from the weight until the mass did not increase after immersing about 0.03 g of a dry film having a thickness of about 0.2 mm in 50 ml of water for 25 to 100 hours. .
<Evaluation of flexibility>
In a dry film obtained from a hydrogel film having a thickness of about 0.1 to 0.2 mm, those that can be bent 180 ° repeatedly represent excellent flexibility with ◎, those that can be bent 135 ° repeatedly represent ○ with flexibility, 135 ° Bending and cracking means “no flexibility”.

(reagent)
・ Clay minerals
XLG: Water-swellable synthetic hectorite (Trademark LAPONITE XLG, manufactured by Nippon Silica Co., Ltd.)
XLS: 6% sodium pyrophosphate-containing water-swellable synthetic hectorite (Trademark Laponite XLS, manufactured by Nippon Silica Co., Ltd.)
·alkali
Na ₂ CO ₃ : Sodium carbonate (Wako Pure Chemical Industries, Ltd.)
NaOH: granular NaOH (Wako Pure Chemical Industries, Ltd.)
·monomer
DMAA: N, N-dimethylacrylamide (manufactured by Wako Pure Chemical Industries, Ltd.), activated alumina was used after removing the polymerization inhibitor.
NIPAM: N-isopropylacrylamide (manufactured by Kojin Co., Ltd.), recrystallized using a mixed solvent of toluene and hexane and purified into colorless needle crystals before use.
ACMO: used after removing the polymerization inhibitor using acryloylmorpholine (manufactured by Kojin Co., Ltd.) and activated alumina.
DEAA: N, N-diethylacrylamide (manufactured by Kojin Co., Ltd.) and activated alumina were used after removing the polymerization inhibitor.
AAc: Acrylic acid (manufactured by Wako Pure Chemical Industries, Ltd.) and the reagent were used as they were.
AMPS: 2-acrylamido-2-methylpropanesulfonic acid (manufactured by Wako Pure Chemical Industries, Ltd.) and the reagent were used as they were.
AM-30G: CH ₂ ═CHCO (OC ₂ H ₄ ) _n OCH ₃ n = 3 NK ester AM-30G (manufactured by Shin-Nakamura Chemical Co., Ltd.), the reagent was used as it was.
AM-90G: CH ₂ ═CHCO (OC ₂ H ₄ ) _n OCH ₃ n = 9 NK ester AM-90G (manufactured by Shin-Nakamura Chemical Co., Ltd.), the reagent was used as it was.
AM-130G: CH ₂ ═CHCO (OC ₂ H ₄ ) _n OCH ₃ n = 13 NK ester AM-130G (manufactured by Shin-Nakamura Chemical Co., Ltd.), the reagent was used as it was.
AM-230G: CH ₂ ═CHCO (OC ₂ H ₄ ) _n OCH ₃ n = 23 NK ester AM-230G (manufactured by Shin-Nakamura Chemical Co., Ltd.), the reagent was used as it was.
M-450G: CH ₂ ═C (CH ₃ ) CO (OCH ₂ CH ₂ ) _n OCH ₃ n = 45 NK ester M-450G (manufactured by Shin-Nakamura Chemical Co., Ltd.), the reagent was used as it was.
M-900G: CH ₂ ═C (CH ₃ ) CO (OCH ₂ CH ₂ ) _n OCH ₃ n = 90 NK ester M-900G (manufactured by Shin-Nakamura Chemical Co., Ltd.), the reagent was used as it was.
PME-2000: CH ₂ ═C (CH ₃ ) CO (OCH ₂ CH ₂ ) _n OCH ₃ n = 45 Blemma PME-2000 (manufactured by NOF Corporation), the reagent was used as it was.
PME-4000: CH ₂ ═C (CH ₃ ) CO (OCH ₂ CH ₂ ) _n OCH ₃ n = 90 Blemma PME-4000 (manufactured by NOF Corporation) was used as it was.
BIS: N, N′-methylenebisacrylamide (manufactured by Kanto Chemical Co., Inc.) and the reagent were used as they were.
・ Polymerization initiator
KPS: potassium peroxodisulfate (manufactured by Kanto Chemical Co., Inc.), diluted with pure water at a ratio of KPS / water = 0.2 / 10 (g / g), and used as an aqueous solution.
・ Polymerization catalyst
TEMED: N, N, N ', N'-tetramethylethylenediamine (manufactured by Wako Pure Chemical Industries, Ltd.)

(Example 1 and Comparative Example 1)
In a flat bottom glass container, 24.5 g of pure water and 0.96 g of XLS were stirred to prepare a uniform solution. DMAA 4.5g and PME-2000 0.3g were added to this, and nitrogen bubbling was carried out for 15 minutes. Subsequently, immediately after stirring and adding 1.5 g of KPS aqueous solution in an ice bath, a mixed solution of 1.2 g of AAc (26 mol% with respect to the total amount of monomers), 1 g of sodium carbonate, 4 g of H2O and 0.024 g of TEMED was stirred. In addition, a homogeneous solution was obtained. The obtained uniform solution was transferred to a polystyrene container (8 cm × 12 cm) previously purged with nitrogen so as not to come into contact with oxygen, and then the lid was tightly sealed, followed by standing polymerization at 20 ° C. After 15 hours, a uniform film-like hydrogel having elasticity and toughness was produced in a polystyrene container. The hydrogel was purified by immersion in a large amount of water. The obtained purified hydrogel was dried at 100 ° C. under reduced pressure to obtain a dried hydrogel from which moisture was removed. It was confirmed that when the dried gel was immersed in water at 20 ° C., it returned to a stretchable hydrogel having the same shape as before drying.

  From the above, the gel obtained in this example is a hydrogel composed of an organic polymer, a clay mineral, and water, and a uniform hydrogel, although no crosslinking agent is added in the synthesis of the organic polymer. The three-dimensional network in which organic polymer and clay mineral are combined at the molecular level is obtained by immersing the dried gel obtained by removing water from the hydrogel into water and returning it to its original shape. It was concluded that 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.

  An unpurified film-like hydrogel was subjected to a tensile test, and the results are shown in FIG. In addition, measurement results of swelling properties with physiological saline and pure water are shown in FIGS.

  In Comparative Example 1 having the same composition as that of Example 1 except that no ionic monomer was used, the swellability with physiological saline and pure water was inferior to that of Example 1 as shown in FIGS. In particular, Example 1 significantly increased the swelling property with pure water compared with Comparative Example 1.

(Example 2 and Comparative Examples 2 and 3)
A hydrogel of Example 2 was synthesized in the same manner as Example 1 with the composition shown in Table 1. The resulting film-like hydrogel was subjected to a tensile test, and the results are shown in FIG. In addition, measurement results of swelling properties with physiological saline and pure water are shown in FIGS. 4 and 5. FIG.
In Comparative Example 2 having the same composition as in Example 2 except that the acrylic monomer PME-2000 having the PEG chain of the formula (1) was not used, the swelling property with physiological saline as shown in FIG. Inferior.
Also, instead of acrylic monomer PME-2000 having a PEG chain of formula (1) (ethylene glycol repeating unit number 45), acrylic monomer AM-30G of formula (1) having a short PEG chain (ethylene glycol repeating unit number 3) In Comparative Example 3 having the same composition as in Example 2 except that) was used, the swelling property with physiological saline was inferior to that in Example 2 as shown in FIG.

(Examples 3, 4, 5)
Hydrogels of Examples 3, 4, and 5 were synthesized in the same manner as in Example 1 with the compositions shown in Table 2. The results of a tensile test of the obtained film-like hydrogel are shown in FIG. In addition, measurement results of swelling properties with physiological saline and pure water are shown in FIGS. As shown in the figure, Examples 3, 4, and 5 not only had excellent mechanical properties, but also had a very high degree of swelling in physiological saline and pure water.
(Examples 6, 7, 8)
Hydrogels of Examples 6, 7, and 8 were synthesized in the same manner as in Example 1 with the compositions shown in Table 3. The results of the tensile test of the obtained film-like hydrogel and the measurement results of the swellability with physiological saline and pure water are shown in FIGS. As shown in FIGS. 10 and 11, it was found that as the content ratio of the ionic monomer sodium acrylate increases, the degree of swelling in physiological saline and pure water increases. The light transmittance of the 2.5 mm thick hydrogel film obtained in Example 6 was measured and found to be 92%.

(Examples 9, 10, and 11)
Hydrogels of Examples 9, 10, and 11 were synthesized in the same manner as in Example 1 using 2-acrylamido-2-methylpropanesulfonic acid (AMPS) instead of acrylic acid, with the composition shown in Table 4. The results of the tensile test of the obtained film-like hydrogel and the measurement results of the swelling property with physiological saline and pure water are shown in FIGS. The light transmittance of the 2.5 mm thick hydrogel film obtained in Example 10 was measured and found to be 88%.

(Example 12 and Comparative Examples 4 and 5)
A hydrogel of Example 12 was synthesized in the same manner as Example 1 with the composition shown in Table 5. Next, the obtained hydrogel film was dried with hot air at 50 ° C. to obtain a dried hydrogel film. As a result of using a large amount of the acrylic monomer M-450G of the formula (1), the hydrogel dry film was given flexibility, and even when it was repeatedly bent by 135 °, it did not crack. Moreover, since the ionic monomer sodium acrylate was used, the degree of swelling in physiological saline and pure water increased. On the other hand, in Comparative Example 4 in which no ionic monomer was used, the degree of swelling in physiological saline, particularly pure water, was extremely low. On the other hand, in Comparative Example 5 in which the acrylic monomer of formula (1) was not used, the hydrogel dry film was hard and brittle, so it could not be bent even at 90 °. These measurement results are summarized in Table 5.

(Examples 13, 14, 15)
Hydrogel dry films of Examples 13, 14, and 15 were prepared in the same manner as in Example 12 with the compositions shown in Table 6. The obtained dry film was excellent in flexibility and had a very high degree of swelling in physiological saline and pure water. These measurement results are summarized in Table 6.

Claims (6)

An organic-inorganic composite hydrogel formed of a polymer (A) of a water-soluble acrylic monomer (a) and a water-swellable clay mineral (B),
The water-soluble acrylic monomer (a) has the formula (1)

(In the formula, R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkylene group having 2 or 3 carbon atoms, n represents an integer of 10 to 99, and Y represents a methoxy group or a hydroxyl group.)
And a monomer (C) having a carboxylate structure and / or a sulfonate structure. The organic-inorganic composite hydrogel according to claim 1, wherein the monomer represented by the formula (1) is contained in an amount of 1% by mass to 70% by mass with respect to all monomer components. The organic-inorganic composite hydrogel according to claim 1, wherein the monomer (C) having a carboxylate structure and / or a sulfonate structure is sodium acrylate and sodium 2-acrylamido-2-methylpropanesulfonate. The organic-inorganic composite hydrogel according to claim 1 or 3, wherein the monomer (C) having a carboxylate structure and / or a sulfonate structure is contained in an amount of 0.1 mol% to 50 mol% based on the total monomer components. The organic inorganic composite obtained by drying the organic inorganic composite hydrogel as described in any one of Claims 1-4. It is a manufacturing method of the organic inorganic composite hydrogel of Claims 1-4, Comprising: The monomer represented by the said Formula (1), a (meth) acrylamide derivative, the said water-swellable clay mineral (B), and water (D And a polymerizable monomer (C) having a carboxylate structure or a sulfonate structure is added simultaneously with the polymerization initiator or immediately after the addition of the polymerization initiator, and the above formula (1) is prepared. ) And a (meth) acrylamide derivative and a polymerizable monomer having a carboxylate structure or a sulfonate structure to produce the polymer (A). A method for producing a composite hydrogel.

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