JP5415804B2 - Method for producing organic-inorganic composite hydrogel - Google Patents

Description

  The present invention relates to a method for producing an organic-inorganic composite hydrogel sheet comprising a polymer of a water-soluble organic monomer having a polymerizable vinyl group and a clay mineral.

  Acrylamide-based hydrogels exhibit excellent water swellability, and can be used for medical materials, water-absorbing and drainage materials, soil improvement materials and the like by taking advantage of their characteristics. In particular, as a nanocomposite material exhibiting excellent mechanical properties, an organic-inorganic composite hydrogel in which a clay mineral is uniformly dispersed in an organic polymer has been disclosed by the inventors of the present invention (for example, Patent Document 1). According to this report, a water-swellable clay mineral is dispersed in an aqueous medium, and then a monomer of an acrylamide derivative or a methacrylamide derivative is added, and the monomer is radically polymerized in the presence of a polymerization initiator and a catalyst. Describes that an organic-inorganic composite hydrogel having good mechanical properties can be produced.

  In such a method for producing an organic-inorganic composite hydrogel, it is important to prevent inhibition of radical polymerization reaction due to oxygen contamination as much as possible in order to ensure the mechanical properties and safety of the organic-inorganic composite hydrogel. Moreover, in the manufacturing method of the organic inorganic composite hydrogel known until now, in order to shape | mold a gel in the target shape, the polymerization reaction was performed within the container of the target shape. For example, in order to obtain a sheet-like product, a reaction solution was charged in a flat container so as to have a thin film thickness, and a polymerization reaction was performed while maintaining the state. At the time of production, the entire container charged with the reaction solution had to be placed in an extremely low oxygen environment.

  In addition, in the conventional production methods, polymerization and molding are performed using a general-purpose resin, glass, or metal cast container. However, this method requires a large amount of cast containers, and has problems in mass production, such as cost problems, handling of large quantities of containers, cleaning and inspection during reuse, and the like.

  On the other hand, in addition to the problems at the time of mass production, the organic-inorganic composite hydrogel produced using the above cast container is, for example, poorly peelable from a stainless steel container, and the gel using a resin container is Defects such as increased amount of eluate due to poor polymerization were likely to occur.

JP2002-53762

  The problem to be solved by the present invention is to provide a production method suitable for mass production of an organic-inorganic composite hydrogel. In particular, another object of the present invention is to provide a method for producing an organic-inorganic composite hydrogel that is suitable for mass production and can reduce the amount of eluate from the hydrogel due to poor polymerization.

  As a result of various investigations on production methods suitable for mass production of organic-inorganic composite hydrogels, the present inventors have filled a reaction solution for producing organic-inorganic composite hydrogels into a resin film and polymerized it, so that mass production is possible. It has been found that an excellent manufacturing method can be realized.

  Furthermore, the present inventors have found that when a resin film having an oxygen permeability of a certain value or less is used, the amount of eluate such as plastic gel derived from poor polymerization can be reduced without inhibiting polymerization.

  When a hydrogel was produced by polymerizing a reaction solution of an organic-inorganic composite hydrogel in various resin film bags, it was observed that a sticky layer was formed on the surface of the hydrogel due to the difference in the resin film. This phenomenon appeared even when the reaction solution was polymerized in a sealed state where no oxygen was present in the bag. As a result of investigating the cause, it was found that a resin film having a higher oxygen permeability produces a sticky layer. This is because in the case of a resin film having a high oxygen permeability, even when the polymerization is started by removing oxygen as much as possible, oxygen enters through the resin film from the outside of the bag during the polymerization and comes into contact with the inner surface of the bag. It is presumed that the polymerization behavior is influenced, and as a result, a layer such as a plastic gel is formed on the surface of the gel.

That is, the present invention provides a reaction solution prepared by dispersing a water-swellable clay mineral in a mixture of a radical polymerizable water-soluble organic monomer and water and further mixing a polymerization initiator, and has an oxygen permeability of 100 ml / m. ^{2. A} method for producing an organic-inorganic composite hydrogel comprising filling a bag-like container made of a resin film of ² · day · MPa or less and polymerizing the water-soluble organic monomer under conditions in which oxygen is not substantially present. It is to provide.

  According to the manufacturing method of the present invention, a dedicated cast container is not required because a bag-like container made of a resin film is used. Accordingly, it is possible to save the cost of preparing a large amount of cast containers at the time of mass production of the hydrogel, and the trouble of handling and cleaning and inspecting a large number of containers when they are used repeatedly.

  Moreover, the surface defect of a hydrogel can be prevented by using the bag-shaped container made from a resin film with low oxygen permeability. As a result, the eluate of the hydrogel after manufacture can be reduced, and a highly safe hydrogel can be provided.

It is the schematic of the state which filled the reaction solution into the bag-shaped container, and was pinched | interposed into the thickness control board, the upper figure is the side view, and the lower figure is the figure which looked at it from the upper part.

  Hereinafter, embodiments of the method for producing the organic-inorganic composite hydrogel of the present invention will be described. This embodiment shows a preferable form of the invention, and the invention is not limited to this.

Preferred embodiments of the present invention are:
(1) a step of producing a reaction solution by continuously dispersing a water-soluble organic monomer having a polymerizable vinyl group and a water-swellable clay mineral in water using an in-line stirrer;
(2) a step of continuously mixing the polymerization initiator and the catalyst into the reaction solution with a vibration stirrer,
(3) A method for producing an organic-inorganic composite hydrogel, in which a bag-like container is filled with the water-soluble organic monomer in a reaction solution mixed with the polymerization initiator and polymerized.

(Organic inorganic composite hydrogel)
The organic-inorganic composite hydrogel produced by the present invention comprises a water-swellable organic polymer, a water-swellable clay mineral that can be uniformly dispersed in water, and water as essential constituents, and the water-soluble organic polymer and the water-swellable clay mineral comprise It is a hydrogel that incorporates water in a three-dimensional network complexed at the molecular level.

(Water-soluble organic monomer having a polymerizable vinyl group)
The water-soluble organic monomer having a polymerizable vinyl group used in the present invention has a property of dissolving in water, interacts with a water-swellable clay mineral that can be uniformly dispersed in water, and can form a noncovalent bond. Those having a functional group capable of forming a hydrogen bond, an ionic bond, a coordination bond, a covalent bond and the like with a clay mineral are preferable. Specific examples of water-soluble organic monomers having these functional groups include water-soluble polymerizable unsaturated groups having amide groups, amino groups, ester groups, hydroxyl groups, tetramethylammonium groups, silanol groups, epoxy groups, and the like. Examples thereof include organic monomers. Among them, a polymerizable unsaturated group-containing water-soluble organic monomer having an amide group or an ester group is preferable. Particularly preferred are acrylamide monomers. In addition, as water used by this invention, it is a mixed solvent with the organic solvent mixed with water other than water alone, and the thing which has water as a main component is contained.

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

  Examples of the polymer of the water-soluble organic monomer include a single (meth) acrylamide monomer polymer and a (meth) acrylate monomer polymer, and a plurality of different water-soluble organic monomers selected from these. It is also effective to use a copolymer obtained by polymerizing. Also, a copolymer of the above water-soluble organic monomer and other organic solvent-soluble polymerizable unsaturated group-containing organic monomer should be used as long as the obtained polymer exhibits water solubility or hydrophilicity. Can do.

  Examples of organic solvents miscible with water include methanol, ethanol, propanol, glycerin, diglycerin, polyglycerin, ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dimethylacetamide, dimethylformamide, Examples thereof include dimethyl sulfoxide and a mixed solvent thereof.

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

(Polymerization initiator and polymerization catalyst)
The polymerization initiator and catalyst used in the present invention can be appropriately selected from conventional radical polymerization initiators and catalysts. Preferably, those having dispersibility in water and uniformly contained in the entire system are used. Particularly preferred is a cationic radical polymerization initiator having a strong interaction with the clay mineral exfoliated in layers. Specifically, a water-soluble peroxide as a polymerization initiator, such as potassium peroxodisulfate or ammonium peroxodisulfate, a water-soluble azo compound, for example, VA-044, V-50 manufactured by Wako Pure Chemical Industries, Ltd. V-501 or the like is preferably used. In addition, a water-soluble radical initiator having a polyethylene oxide chain is also used.

  As the catalyst, tertiary amine compounds such as N, N, N ′, N′-tetramethylethylenediamine and β-dimethylaminopropionitrile are used. The polymerization temperature is set in the range of 0 ° C. to 100 ° C. according to the type of water-soluble organic polymer, polymerization catalyst and initiator used.

(Production method)
In the method for producing the organic-inorganic composite hydrogel of the present invention, the water-soluble organic monomer is preferably used after removing the polymerization inhibitor using an activated alumina column, and the polymerization initiator is pure water at a concentration of about 2%. It is preferable to use it after diluting with an aqueous solution and using pure water obtained by distilling ion-exchanged water, bubbling high-purity nitrogen in advance, and removing oxygen contained therein.

(Process 1)
The water-swellable clay mineral was dispersed in the water by adding pure water to the tank that had been purged with nitrogen and adding and stirring the water-swellable clay mineral using an in-line mixer that was circulated through the tank. A solution is produced. Thereafter, DMAA (N, N-dimethylacrylamide) is added and stirred to prepare a colorless and transparent solution.

  The amount ratio of the polymer of the water-soluble organic monomer and the water-swellable clay mineral is preferably within a range in which both form a three-dimensional network in a solvent composed of water or a mixture of water and an organic solvent. The mass ratio of the mineral / water-soluble organic monomer polymer is preferably 0.01 to 3, more preferably 0.1 to 3, and particularly preferably 0.3 to 2.5. When the mass ratio is less than 0.01, it is difficult to form an effective three-dimensional network, while when it exceeds 3, it is often difficult to disperse the water-like swellable clay mineral in a layered manner.

(Process 2)
Next, a solution in which the water-soluble organic monomer and water-swellable clay mineral prepared in Step 1 are uniformly dispersed in water is fed to a vibration stirrer, and two additive inlets provided in the vibration stirrer Add and stir the catalyst solution and the polymerization initiator solution.

  As the vibration stirrer used in the present invention, a known vibration stirrer can be used as long as the effects of the present invention can be obtained. As a known vibration stirrer, there is a Vibro mixer (manufactured by Chilling Industries Co., Ltd.).

  The amount ratio of the polymer of the water-soluble organic monomer and the polymerization initiator is preferably 0.001 to 0.10, more preferably 0.005 to 0.00 as the mass ratio of the polymerization initiator / polymer of the water-soluble organic monomer. 01. If the mass ratio is less than 0.001, it is difficult to form an effective three-dimensional network, while if it exceeds 0.10, it is often difficult to disperse the polymerization initiator in the monomer / clay solution. .

  The continuously discharged reaction solution is continuously filled into a bag-like container that can be sealed by, for example, heat sealing, sandwiched between thickness adjusting plates so as to have an arbitrary thickness, and polymerization is performed in a constant temperature bath of 20 to 100 ° C. FIG. 1 shows a state where the reaction solution is filled in a bag-like container and sandwiched between thickness adjusting plates. In particular, in order to reduce the influence of oxygen, it is also effective to perform polymerization in a nitrogen atmosphere in which the inside of the thermostat is deoxygenated or in a water tank that has been subjected to deoxygenation treatment. Within 1 to 30 hours from the start of polymerization, a colorless, transparent, and uniform sheet-like organic-inorganic composite hydrogel consisting of organic polymer and clay mineral is formed in a bag-like container. In addition, it is preferable to perform all these operations from solution preparation to filling in nitrogen atmosphere which interrupted | blocked oxygen.

  In the present invention, the state in which oxygen is blocked means that the polymerization of the reaction solution used in the present invention is not inhibited, the eluate of the hydrogel after production, which is the effect of the present invention, can be reduced, and a highly safe hydrogel can be provided. Any state may be used, and “a condition in which substantially no oxygen is present” in this specification refers to such a state.

(Bag-like container)
The bag-like container used for the polymerization reaction is not particularly limited as long as it is a form and material capable of obtaining the effects of the present invention. For example, a laminate film having at least two kinds of layer configurations may be used. it can. It is preferable to use the following as such a film. That is, in the present invention, a bag having a low oxygen permeability is formed on the outside of the bag-like container, and the film is fused to each other by thermocompression bonding for processing into a bag product or sealing the reaction solution on the inside. It is preferable to use a sealant film that can be used as a container.

  Examples of the film having low oxygen permeability include stretched polyvinyl alcohol (PVA), ethylene / vinyl alcohol copolymer (EVOH) resin, stretched nylon (ONy), and polyvinylidene chloride (PVDC). A high-oxygen barrier film obtained by vacuum-depositing aluminum, silica, alumina, or a mixture thereof on a low-stretched polyethylene terephthalate (PET) or stretched nylon (Ny) base material can be used.

  As the sealant film, general low density polyethylene (LDPE) or unstretched polypropylene (CPP) can be selected in consideration of heat resistance against the polymerization temperature. Further, if necessary, a film such as stretched nylon may be laminated between these two layers of laminate material in order to improve the tear resistance.

(Oxygen permeability of bag-like container)
The oxygen permeability of the bag-like container used in the present invention is 100 ml / m ² · day · MPa or less, preferably 20 ml / m ² · day · MPa or less, and 15 ml / m ² · day · MPa or less. More preferably.

(Reaction solution filling)
The method of filling the reaction solution prepared in Step 2 into the bag-like container is to fill a plurality of bag-like containers prepared in advance in a bag shape by thermocompression bonding, or roll using a liquid bag filling and packaging machine. The film can be continuously filled while making a bag immediately before filling the reaction solution.

  The former allows ultra-low oxygen conditions because oxygen can be replaced under reduced pressure, and the latter allows high-speed filling, so that a large amount of processing can be performed in a short time.

  The oxygen permeability of each film was measured at 23 ° C. and 90% RH in accordance with JIS K7126 using an oxygen permeability measuring device (OX-TRAN100, manufactured by Modern Control).

Example 1
9.5 L of pure water was charged into the solution tank whose inside was replaced with nitrogen, and 320 g of Laponite XLG (water swellable synthetic hectorite: manufactured by ROCKWOOD) was circulated in the solution tank. ) And uniformly dispersed. 980 g of DMAA (N, N-dimethylacrylamide) was added and stirred to prepare a colorless and transparent solution.

  Next, the above solution was continuously transferred to a vibration stirrer at 0.75 L / min, and mixed with an aqueous solution of KPS (potassium peroxodisulfate: manufactured by Kanto Chemical Co., Inc.) supplied at 35 mL / min. The reaction solution continuously discharged from the vibration type stirrer is continuously filled into a 24 cm × 35 cm resin film laminated bag (lamination configuration: transparent vapor-deposited PET 12 μm / Ny15 μm / CPP 60 μm) that has been previously purged with nitrogen to a thickness of 2 mm. Thus, the film was sandwiched between thickness adjusting plates and allowed to stand in a thermostatic bath at 50 ° C. for 18 hours for polymerization. The operations from preparation of the solution to filling were all performed in a nitrogen atmosphere in which oxygen was blocked. A colorless, transparent, and uniform sheet-like polymer gel consisting of an organic polymer and clay mineral was formed in a resin film laminate bag. The synthesized polymer gel was a hydrogel having a water content ([water / gel dried product] × 100 =) of 760% by mass. The obtained hydrogel was shaken with distilled water (500 g) at 37 ° C. for 6 hours with respect to 10 cm × 10 cm, and the supernatant was freeze-dried. The solid residue obtained after lyophilization was weighed to be 0.03 g. The recovery rate of the residue with respect to the solid content was 1%.

(Example 2)
The reaction solution prepared in Example 1 was continuously filled into a 24 cm × 35 cm resin film laminated bag (laminate configuration: barrier ONy 18 μm / ONy15 μm / LLDPE 70 μm), which had been previously purged with nitrogen, and applied to a thickness adjusting plate so as to have a thickness of 2 mm. The mixture was sandwiched and allowed to stand in a thermostatic bath at 50 ° C. for 18 hours for polymerization. The operations from preparation of the solution to filling were all performed in a nitrogen atmosphere in which oxygen was blocked. A colorless, transparent, and uniform sheet-like polymer gel consisting of an organic polymer and clay mineral was formed in a resin film laminate bag. The synthesized polymer gel was a hydrogel having a water content ([water / gel dried product] × 100 =) of 760% by mass. The obtained hydrogel was shaken with distilled water (500 g) at 37 ° C. for 6 hours with respect to 10 cm × 10 cm, and the supernatant was freeze-dried. The solid residue obtained after lyophilization was weighed and weighed 0.05 g. The recovery rate of the residue with respect to the solid content was 1.5%.

(Example 3)
The reaction solution prepared in Example 1 was continuously filled into a 24 cm × 35 cm resin film laminate bag (laminate configuration: barrier ONy 18 μm / ONy 15 μm / LLDPE 70 μm) without replacing with nitrogen, and the thickness was adjusted to 2 mm. The mixture was sandwiched and allowed to stand in a thermostatic bath at 50 ° C. for 18 hours for polymerization. The operations from preparation of the solution to filling were all performed in a nitrogen atmosphere in which oxygen was blocked. A colorless, transparent, and uniform sheet-like polymer gel consisting of an organic polymer and clay mineral was formed in a resin film laminate bag. The synthesized polymer gel was a hydrogel having a water content ([water / gel dried product] × 100 =) of 760% by mass. The obtained hydrogel was shaken with distilled water (500 g) at 37 ° C. for 6 hours with respect to 10 cm × 10 cm, and the supernatant was freeze-dried. The solid residue obtained after lyophilization was weighed to be 0.15 g. The recovery rate of the residue with respect to the solid content was 5%.

(Comparative Example 1)
The reaction solution prepared in Example 1 was continuously filled into a 24 cm × 35 cm low density polyethylene bag (LDPE; thickness 200 μm) previously substituted with nitrogen, and sandwiched between thickness adjusting plates so as to have a thickness of 2 mm. Polymerization was carried out for 18 hours in a thermostatic bath. The operations from preparation of the solution to filling were all performed in a nitrogen atmosphere in which oxygen was blocked. A colorless, transparent, and uniform sheet-like polymer gel consisting of organic polymer and clay mineral was formed in a low-density polyethylene bag. The synthesized polymer gel was a hydrogel having a water content ([water / gel dried product] × 100 =) of 760% by mass. The obtained hydrogel was shaken with distilled water (500 g) at 37 ° C. for 6 hours with respect to 10 cm × 10 cm, and the supernatant was freeze-dried. The solid residue obtained after lyophilization was weighed to be 0.42 g. The recovery rate of the residue with respect to the solid content was 14%.

(Comparative Example 2)
The reaction solution prepared in Example 1 was continuously filled in a 24 cm × 35 cm unstretched polypropylene bag (CPP; thickness: 40 μm) previously substituted with nitrogen, and polymerization was carried out in a thermostatic bath at 50 ° C. for 18 hours. The operations from preparation of the solution to filling were all performed in a nitrogen atmosphere in which oxygen was blocked. A colorless, transparent, and uniform sheet-like polymer gel composed of an organic polymer and clay mineral was formed in a CPP bag. The synthesized polymer gel was a hydrogel having a water content ([water / gel dried product] × 100 =) of 760% by mass. The obtained hydrogel was shaken with distilled water (500 g) at 37 ° C. for 6 hours with respect to 10 cm × 10 cm, and the supernatant was freeze-dried. The solid residue obtained after lyophilization was weighed to be 0.48 g. The recovery rate of the residue relative to the solid content was 16%.

(Comparative Example 3)
The reaction solution prepared in Example 1 was continuously filled into a 24 cm × 35 cm unstretched PET bag (thickness: 100 μm) previously substituted with nitrogen, and polymerization was carried out in a thermostatic bath at 50 ° C. for 18 hours. The operations from preparation of these solutions to polymerization filling were all performed in a nitrogen atmosphere in which oxygen was blocked. A colorless, transparent, and uniform sheet-like polymer gel composed of an organic polymer and clay mineral was formed in an unstretched PET bag. The synthesized polymer gel was a hydrogel having a water content ([water / gel dried product] × 100 =) of 760% by mass. The obtained hydrogel was shaken with distilled water (500 g) at 37 ° C. for 6 hours with respect to 10 cm × 10 cm, and the supernatant was freeze-dried. The solid residue obtained after lyophilization was weighed to be 0.27 g. The recovery rate of the residue relative to the solid content was 9%

1: Bag-shaped container holding plate 2: Reinforcing angle 3: Spacer 4: Tightening bolt 5: Bag-shaped container

Claims (3)

A reaction solution prepared by dispersing a water-swellable clay mineral in a mixed solution of a radical polymerizable water-soluble organic monomer and water and further mixing a polymerization initiator, has an oxygen permeability of 100 ml / m 2 · day · MPa or less. A method for producing an organic-inorganic composite hydrogel, characterized in that the water-soluble organic monomer is polymerized under a condition of filling a resin film bag-like container and blocking oxygen . The method for producing an organic-inorganic composite hydrogel according to claim 1, wherein the bag-shaped container filled with the reaction solution is sandwiched between two flat plates and the water-soluble organic monomer is polymerized while maintaining the state. The method for producing an organic-inorganic composite hydrogel according to claim 1 or 2, wherein the reaction solution is filled after deoxidizing the inner surface of the bag-like container in advance.

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