JP5456344B2 - Organic-inorganic composite hydrogel and method for producing the same - Google Patents

Description

  The present invention relates to a polymer hydrogel used in the fields of sanitary goods, agriculture, food, medicine, architecture, civil engineering, machinery, transportation, electronic components, household goods, sewing, and the like.

  The polymer hydrogel can contain a large amount of water as a solvent in the network of crosslinked polymers, so it has excellent transparency, flexibility, solvent absorption, adsorbability and permeability of specific solutes, etc. They are expected to be widely used as soft materials, water-absorbing materials, vibration-absorbing materials, and high-performance materials in a wide range of fields such as chemical industry, agriculture, civil engineering, architecture, medicine, medicine and food. However, there have been few polymer hydrogels so far that have both functional properties and mechanical properties, and many of the polymer hydrogels have the disadvantage that they are particularly weak or brittle. The most commonly used polymer gel is one in which polymer chains are crosslinked by using an organic crosslinking agent or by irradiating γ rays or electron beams. A sodium acid cross-linked product is well known. However, in order to obtain high water absorption, sodium polyacrylate is slightly cross-linked, and there are disadvantages that the mechanical properties after water absorption are weak and the shape is difficult to maintain. Further, it is known that the sodium polyacrylate cross-linked product in water absorption has high water absorption performance in pure water, but is ionic, so that the performance is greatly reduced in saline.

  In contrast, a three-dimensional network is formed by combining an acrylamide derivative such as poly (N-isopropylacrylamide) or poly (N, N-dimethylacrylamide) and a water-swellable inorganic clay mineral such as hectorite at the nanometer level. It has been reported that the organic-inorganic composite hydrogel obtained by the formation 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 has excellent mechanical properties, but is higher in water swellability than the conventional acrylamide derivative organic cross-linked gel, but is a commercially available superabsorbent sodium polyacrylate cross-linked Water absorption is inferior compared to the body. In order to meet market needs, there is a strong demand for further improvement of the swellability in water, particularly saline.

  On the other hand, in the presence of clay minerals, it has been reported that an organic-inorganic composite hydrogel obtained by combining dimethylacrylamide and an acrylate having a polyethylene glycol (PEG) chain can be used as a humidity control material (Patent Document 2). However, in this report, a polyethylene glycol chain having 2 to 9 ethylene glycol repeating units was used, and the PEG chain length was short, so that the swelling property in saline was low.

JP2002-53762 JP2007-297550A

  The problem to be solved by the present invention is an organic-inorganic composite hydrogel formed from a polymer of a water-soluble acrylic monomer and a water-swellable clay mineral, and a hydrogel having both excellent mechanical properties and high swellability It is in providing a dry body and those manufacturing methods. In particular, the problem to be solved by the present invention is to provide a hydrogel having good swellability in saline, a dried product thereof, and a method for producing them.

  The present invention is an organic-inorganic composite hydrogel formed from a polymer of a water-soluble acrylic monomer and a water-swellable clay mineral, and a monomer represented by the following formula (1) is used as the water-soluble acrylic monomer. Thus, an organic-inorganic composite hydrogel having both excellent mechanical properties and high swellability can be obtained, and an organic-inorganic composite having both excellent flexibility and high swellability can be found by drying the hydrogel at a low temperature. It has been completed.

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を含有することを特徴とする有機無機複合ヒドロゲル及びその乾燥体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.)
The organic-inorganic composite hydrogel characterized by containing the monomer represented by these, and its dry body are provided.

  The present invention also relates to a method for producing the organic-inorganic composite hydrogel, wherein the water-soluble acrylic monomer (a) containing the monomer represented by the formula (1) is mixed with an aqueous medium, The present invention provides a method for producing an organic-inorganic composite hydrogel characterized by polymerizing the water-soluble acrylic monomer (a) with a polymerization initiator in the presence of a clay mineral (B).

  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, and the monomer represented by the formula (1) is used as the water-soluble acrylic monomer. As a result, the swelling property of the obtained organic-inorganic composite hydrogel in physiological saline was greatly improved. In addition, by using the monomer represented by the formula (1) in the present invention, the flexibility of the dried organic-inorganic composite hydrogel obtained is given, and the usability as well as the swelling property are remarkably improved. Furthermore, in the present invention, by using the monomer represented by the formula (1), the polymerization rate of the acrylic monomer, particularly dimethylacrylamide, is suppressed, the solution in the reaction system does not thicken during the production, and it is industrially organic. The production of the inorganic composite hydrogel is facilitated.

FIG. 2 is a diagram showing the breaking strength and elongation of hydrogels obtained in Examples 1, 2, 3 and Comparative Examples 1, 2. It is a figure which shows the swelling degree in the physiological saline of the hydrogel obtained by Example 1,2,3 and Comparative Example 1,2,3. FIG. 4 is a graph showing the breaking strength and elongation of the hydrogels obtained in Examples 4, 5, 6, 7, and 8. It is a figure which shows the swelling degree in the physiological saline of the hydrogel obtained in Example 4,5,6,7,8. FIG. 6 is a graph showing the breaking strength and elongation of the hydrogels obtained in Examples 9, 10, 11, 12 and Comparative Example 4. FIG. 6 is a graph showing the degree of swelling of the hydrogels obtained in Examples 9, 10, 11, 12 and Comparative Example 4 with physiological saline. It is a figure which shows the temperature responsiveness of the hydrogel obtained in Example 9,10,11,12. FIG. 6 is a graph showing the breaking strength and elongation of hydrogels obtained in Examples 13, 14, 15 and Comparative Example 5. 6 is a graph showing the degree of swelling of the hydrogels obtained in Examples 13, 14, 15 and Comparative Example 5 with physiological saline. FIG.

  The organic-inorganic composite hydrogel of the present invention is composed of a water-soluble acrylic monomer (a) polymer (A) and a water-swellable clay mineral (B).

  The water-soluble acrylic monomer (a) used in the organic-inorganic composite hydrogel of the present invention has a property of dissolving in water and interacting with a water-swellable clay mineral (B) that can be uniformly dispersed in water. For example, acrylamide, methacrylamide, and derivatives thereof (N- or N, N-substituted (meth) acrylamide) and acrylate esters are preferably used.

  As the water-soluble acrylic monomer (a) used in the present invention, the acrylic monomer represented by the formula (1) is used in order to improve the swelling characteristics and flexibility of the obtained organic-inorganic composite hydrogel and its dried product. .

（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 water-soluble acrylic monomer (a) is preferably used in combination with one or more monomers selected from (meth) acrylamide, N-substituted (meth) acrylamide, acryloylmorpholine, and the like. -Methylacrylamide, N-ethylacrylamide, N-cyclopropylacrylamide, N-isopropylacrylamide, N-methylmethacrylamide, N-cyclopropylmethacrylamide, N-isopropylmethacrylamide, N, N-dimethylacrylamide, N-methyl- N-ethylacrylamide, N-methyl-N-isopropylacrylamide, N-methyl-Nn-propylacrylamide, N, N-diethylacrylamide, acryloylmorpholine, N-acryloylpyrrolidine, N-acryloylpiperidine, N -Acrylloy Methyl homo piperazinyl Laden, such as N- acryloyl methylpiperazinyl Laden are exemplified. 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.

  The organic-inorganic composite hydrogel of the present invention exhibits excellent mechanical properties and swelling characteristics, and also facilitates the production of the hydrogel, so that the acrylic monomer having the amide group and the acrylic monomer represented by the above formula (1) Need to be used as a copolymer. The use ratio of the acrylic monomer represented by the formula (1) included in all acrylic monomers used in the polymerization is preferably 1% by mass to 70% by mass, more preferably 3% by mass to 60% by mass. Yes, 5 mass%-50 mass% is especially preferable. When the content of the acrylic monomer represented by the formula (1) in all acrylic monomers is within this range, the organic-inorganic composite hydrogel obtained and its dried product have sufficient effects for improving physical properties such as swelling characteristics and flexibility. It is preferable because it is obtained and the mechanical properties of the hydrogel are not significantly lowered.

  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 of the monomer of formula (1) is preferably 14 to 99, more preferably 20 to 60, and particularly preferably 45 to 60.

  In addition, the optimum range of the number of repeating units of ethylene glycol varies depending on the type of (meth) acrylamide derivative used in combination. For example, in a system in which dimethylacrylamide and the monomer represented by formula (1) are used in combination, the number of ethylene glycol repeating units in the monomer of formula (1) is preferably 10 in order to obtain a high degree of swelling in physiological saline. It is -99 pieces, More preferably, it is 23-60 pieces, It is especially preferable that it is 45-60 pieces.

  The water-swellable clay mineral (B) 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 and 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 (B) constituting the organic-inorganic composite hydrogel used in the present invention is appropriately selected depending on the type of the water-soluble acrylic monomer and clay mineral used. The range in which both form a three-dimensional network 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. 0.03 to 3, particularly preferably 0.05 to 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, Those having a mass ratio of water or solvent to the total mass of 50 or less are more preferably 0.1-30.

  Since the organic-inorganic composite hydrogel used in the present invention has a three-dimensional network structure composed of a polymer (A) of a water-soluble acrylic monomer and a water-swellable clay mineral (B), a tensile strength of 20 kPa or more, and It is a flexible and tough material that can realize excellent physical properties such as an elongation at break of 200% or more, and preferably has a tensile strength of 25 kPa or more and an elongation at break of 300% or more.

  Since the organic-inorganic composite hydrogel in the present invention does not have ionicity, it is excellent in salt resistance and extremely swellable in saline. The level of salt water swellability can be judged by the salt water swelling degree (Wgel) / (Wdry) obtained by dividing the mass (Wgel) of the hydrogel swollen by the saline by the solid content mass (Wdry) of the gel. The hydrogel of the present invention preferably has (Wgel) / (Wdry) of 20 to 120 in physiological saline. More preferably, it is 25-100.

  The organic-inorganic composite hydrogel of the present invention has a critical temperature (Tc) that is transparent and / or volume swelled 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. Such an organic-inorganic composite hydrogel can be prepared using a temperature-sensitive monomer exhibiting LCST (lower critical solution temperature) in an aqueous solution as an organic monomer, such as N-isopropylacrylamide or N, N-diethylacrylamide. When copolymerizing with an acrylic monomer of formula (1) having a polyethylene glycol chain, the LCST of the thermosensitive monomer tends to disappear. In order to have both high water swellability and temperature sensitivity, the content ratio of the acrylic monomer of the formula (1) in all monomers is preferably 2 to 50% by mass, more preferably 4 to 45% by mass, especially Preferably it is 6-40 mass%. When the content of the acrylic monomer represented by the formula (1) is less than 2% by mass, a sufficient effect for improving the saline swelling property of the obtained organic-inorganic composite hydrogel cannot be obtained, and when the content is more than 50% by mass, There is a possibility that the temperature responsiveness of the hydrogel may be lost, which is not preferable.

  The organic-inorganic composite hydrogel used in the present invention is produced by a polymerization reaction of a water-soluble acrylic monomer (a) in the presence of a water-swellable clay mineral (B). The polymerization reaction can be carried out by a conventional radical polymerization method using a radical polymerization initiator. Specifically, first, a uniform dispersion containing a water-soluble acrylic monomer (a), a water-swellable clay mineral (B), and water is prepared, and then water-soluble in a nitrogen atmosphere in the presence of the water-swellable clay mineral (B). An organic-inorganic composite hydrogel is prepared by polymerizing the polymerizable acrylic monomer (a). Here, the water-swellable clay mineral (B) exfoliated in layers forms a three-dimensional network of the polymer (A) of the water-soluble acrylic monomer (a) and the water-swellable clay mineral (B) by acting as a crosslinking agent. An organic-inorganic composite hydrogel having formed therein is obtained. Since the organic-inorganic composite hydrogel has a three-dimensional network structure formed in this way, it can hold water or an aqueous solution of water and an organic solvent in the interior and achieve the above-described excellent physical properties.

  The radical polymerization initiator and the polymerization accelerator can be appropriately selected from conventional radical polymerization initiators and polymerization accelerators, preferably have water dispersibility and are uniformly contained in the entire system. Things can be used. Particularly preferred is a radical polymerization initiator having a strong interaction with the water-swellable clay mineral (B) exfoliated in layers. Specifically, water-soluble peroxides such as potassium peroxodisulfate, ammonium peroxodisulfate, and water-soluble azo compounds can be preferably used. As the water-soluble azo compound, VA-044, V-50, V-501 and the like manufactured by Wako Pure Chemical Industries, Ltd. can be preferably used. In addition, a water-soluble radical initiator having a polyethylene oxide chain can also be used. As the polymerization accelerator, tertiary amine compounds such as N, N, N ′, N′-tetramethylethylenediamine and β-dimethylaminopropionitrile can be preferably used.

  The temperature at the time of the polymerization reaction is appropriately selected according to the types of water-soluble acrylic monomers (a), polymerization accelerators and initiators that are generally used, and can be set in the range of 0 ° C. to 100 ° C., for example. The optimum polymerization temperature varies depending on the type of water-soluble acrylic monomer (a). For example, in a system using dimethylacrylamide and isopropylacrylamide in combination with the monomer represented by the formula (1), low temperature polymerization at 20 ° C. is most preferable. On the other hand, in a system using acryloylmorpholine (ACMO) and the monomer represented by formula (1) in combination, phase separation occurs when both monomers are polymerized at a low temperature of 20 ° C. Polymerization at a temperature, for example 50 ° C., is preferred. The polymerization time varies depending on polymerization conditions such as a polymerization accelerator, an initiator, a polymerization temperature, and a polymerization solution amount (thickness) and cannot be generally defined, but generally may be adjusted between several tens of seconds to several tens of hours.

  In the organic-inorganic composite hydrogel of the present invention, a part of the polymer of the acrylic monomer in the organic-inorganic composite hydrogel can be crosslinked by a covalent bond for the purpose of improving its properties such as elastic modulus (hardness). By covalently bonding a part of the polymer of the acrylic monomer in the organic-inorganic composite hydrogel, the shape stability is improved when the solvent is absorbed and swollen.

  The method for cross-linking a part of the polymer of acrylic monomer by covalent bond is not particularly limited as long as the flexibility and toughness of the organic-inorganic composite hydrogel can be maintained. Examples thereof include a method used and a method in which the organic-inorganic composite hydrogel is irradiated with radiation to covalently bond the acrylic monomer polymers to each other.

  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. For example, covering the wound with a hydrogel film, protecting the wound surface from bacteria, absorbing exudate from the wound, and also providing a moist environment to the dry wound surface, sore the wound Healing can be promoted while reducing.

  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 repeatedly bent by 90 °. 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, a tensile test for measuring the breaking strength and elongation was performed using an unpurified film-like hydrogel (thickness = thickness) using a tabletop universal testing machine AGS-H manufactured by Shimadzu Corporation. (2.5 mm, width = 10 mm) was attached to a tensile test apparatus without slipping at the chuck portion, and 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 both sides 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 was determined by immersing about 0.03 g of a dry film having a thickness of about 0.2 mm in 50 ml of 37 ° C. physiological saline for 25 to 100 hours until the mass did not increase. The equilibrium swelling degree was measured.
<Evaluation of flexibility>
In a dry film having a thickness of about 0.1 to 0.2 mm obtained from a hydrogel film, those that can be bent 150 ° repeatedly represent excellent flexibility with ◎, those that can be bent 90 ° repeatedly represent ○ with flexibility, 90 ° Bending and cracking means “no flexibility”.
<Measurement of light transmittance>
The temperature dependence of the light transmittance was measured using a UV-visible spectrophotometer V-530 manufactured by JASCO Corporation as it was by synthesizing a hydrogel in a prismatic transparent polystyrene cell.

(reagent)
・ Clay minerals
XLG: Water-swellable synthetic hectorite (Trademark LAPONITE XLG, manufactured by Nippon Silica Co., 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 to 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.
AM-90G: CH ₂ = CHCO (OC ₂ H ₄ ) nOCH 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 ) nOCH ₃ n = 13 Molecular weight 550 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 ) nOCH ₃ n = 23 Molecular weight 1000 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 ) nOCH ₃ n = 45 Molecular weight 2000 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 ) nOCH ₃ n = 90 Molecular weight 4000 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 ) nOCH ₃ n = 45 Molecular weight 2000 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 ) nOCH ₃ n = 90 Molecular weight 4000 Blemma PME-4000 (manufactured by NOF Corporation), the reagent 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 Examples 1, 2, 3)
While stirring 28.5 g of pure water in a flat bottom glass container, 0.96 g of XLG was added to prepare a colorless and transparent solution. DMAA 5.4g and PME-2000 0.6g (10 mass% with respect to the monomer total) were added to this, and nitrogen bubbling was carried out for 15 minutes. Subsequently, 24 μl of TEMED and 1.5 g of an aqueous KPS solution were sequentially added in an ice bath to obtain a uniform solution. 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 24 hours, a film-like hydrogel having elasticity and toughness was formed in the polystyrene container. The obtained hydrogel was dried at 50 ° C. under reduced pressure to obtain a dried hydrogel from which moisture was removed. It was confirmed that by immersing this dried gel in water at 20 ° C., it returned to a stretchable hydrogel having the same shape as before drying.

  As described above, the gel obtained in the present example is a uniform hydrogel despite the absence of a crosslinking agent in the synthesis of organic polymer, and a dried gel obtained by removing water from the hydrogel. It was concluded that a three-dimensional network in which organic polymers and clay minerals were combined at the molecular level was formed in water.

  An unpurified film-like hydrogel was cut into a predetermined shape and subjected to a tensile test and a swelling experiment with physiological saline. The results are shown in FIGS. Further, Comparative Example 1 in which the acrylic monomer of formula (1) is not used, Comparative Example 2 in which PEG acrylate having a short polyethylene glycol (PEG) chain length is used in place of the acrylic monomer of formula (1), and organic instead of clay mineral The hydrogels of Comparative Example 3 using a crosslinking agent were synthesized in the same manner as in Example 1, and the tensile properties and the swelling properties with physiological saline were evaluated. As shown in FIG. 1, in the example using the acrylic monomer of the formula (1), the hydrogel was softer than the comparative examples 1 and 2, but still had a sufficiently high breaking strength. On the other hand, in the swelling property with physiological saline, as shown in FIG. 2, the degree of swelling and the swelling speed of Example 1 were significantly improved as compared with the comparative example. Although the gel of Comparative Example 3 was extremely brittle, an attempt was made to conduct a tensile test, but most of the samples were 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.

(Examples 2 and 3)
Hydrogels of Examples 2 and 3 were prepared in substantially the same manner as in Example 1 except that the amount and type of the acrylic monomer represented by the formula (1) were changed. As shown in FIG. 1 and FIG. 2, Examples 2 and 3 maintained higher mechanical properties than the comparative example, and significantly improved the degree of swelling and the swelling rate in physiological saline.

(Examples 4 to 8)
Hydrogels of Examples 4, 5, 6, 7, and 8 were prepared in the same manner as in Example 1 with the compositions shown in Table 2. As shown in FIG. 3 and FIG. 4, Examples 4 to 8 did not significantly reduce the mechanical properties compared with the comparative example, and the swelling degree and swelling speed in physiological saline were improved. In particular, Example 8 having a high content of the acrylic monomer represented by the formula (1) showed a very high degree of swelling.

(Examples 9-12, Comparative Example 4)
Each hydrogel film was prepared in the same manner as in Example 1 using NIPAM instead of DMAA and the composition shown in Table 3. Further, Comparative Example 4 was prepared in the same manner as in Example except that the acrylic monomer of formula (1) was not used. As shown in FIG. 5, in the example using the acrylic monomer of the formula (1), the hydrogel was softer than the comparative example, but still maintained a sufficiently high breaking strength and elongation. On the other hand, in the swelling property with physiological saline, as shown in FIG. 6, the swelling degree of each example was improved as compared with the comparative example. In particular, Example 11 having a high content of the acrylic monomer of formula (1) showed a high degree of swelling. In addition, as shown in FIG. 7, although the examples used hydrophilic acrylic monomers of the formula (1), the obtained hydrogel had a large change in light transmittance around 34 ° C. It was found to have LCST (Lower Critical Solution Temperature).

(Examples 13-15, Comparative Example 5)
Each hydrogel film was prepared using ACMO instead of DMAA in the same manner as in Example 1 under the composition and synthesis conditions shown in Table 4. Further, Comparative Example 5 was prepared in the same manner as in Example except that the acrylic monomer of formula (1) was not used. As shown in FIGS. 8 and 9, all of Examples 13 to 15 did not significantly reduce the mechanical properties as compared with the comparative example, and the swelling degree and swelling speed in physiological saline were improved.

(Example 16 and Comparative Example 6)
A hydrogel film of Example 16 was prepared in the same manner as in Example 1 with the composition shown in Table 5. Next, the gel film was washed with pure water, air-dried overnight at room temperature, and then further hot-air dried at 50 ° C. for 4 hours. The resulting dry film was repeatedly bent at 90 ° and showed excellent flexibility. In addition, the degree of swelling in physiological saline at 37 ° C. also showed a high value. In contrast, the dry film of Comparative Example 6 prepared in the same manner as in Example 16 except that the monomer represented by the formula (1) was not used was extremely brittle and tried to bend at 90 °, but was not bent. cracked. These measurement results are shown in Table 5.
(Examples 17 to 19)

  Dry films of Examples 17, 18, and 19 were produced in the same manner as Example 16 except that the amount of the monomer represented by the formula (1) and the clay mineral content were changed. Table 5 summarizes the flexibility and the swelling ratio in 37 ° C. physiological saline. Example 17 having a low clay mineral content and a high monomer content of the formula (1) could be repeatedly bent at 150 °, and exhibited extremely excellent flexibility.

(Examples 20 to 25)
Dry films of Examples 20 to 25 were produced in the same manner as in Example 16 with the compositions and synthesis conditions shown in Table 6. Both the flexibility of the film and the swelling rate with physiological saline at 37 ° C. are good, and the values are summarized in Table 6.

Claims (5)

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 14 to 99, and Y represents a methoxy group or a hydroxyl group.)
The organic-inorganic composite hydrogel characterized by containing the monomer represented by these. The polymer (A) is a polymer obtained by polymerizing a water-soluble acrylic monomer (a) containing 1% by mass to 70% by mass of the monomer represented by the formula (1) with respect to all monomer components. The organic-inorganic composite hydrogel according to claim 1. An organic-inorganic composite obtained by drying the organic-inorganic composite hydrogel according to claim 1 or 2. The organic-inorganic composite according to claim 3, which is dried at a temperature of 80 ° C or lower. A method for producing an organic-inorganic composite hydrogel according to claim 1 or 2,
The monomer represented by the formula (1) is mixed with an aqueous medium, and the water-soluble acrylic monomer (a) is polymerized with a polymerization initiator in the presence of the water-swellable clay mineral (B). A method for producing an organic-inorganic composite hydrogel.

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