JP5435835B2 - Polymer gel and method for producing the same - Google Patents

Description

  The present invention relates to a polymer gel and a method for producing the same.

  Since polymer gel can contain a large amount of solvent (eg water), it is excellent in transparency, flexibility, solvent absorption, adsorptivity and permeability of specific solutes, analysis, chemical industry, It is expected to be widely used as a soft material, a water absorbing material, an adsorbent, a selective separating material, a vibration absorbing material, etc. in many fields including agriculture, civil engineering, architecture, and medical fields. However, there have been few polymer gels that have both functional properties and mechanical properties, and many of the polymer gels have the disadvantage that they are particularly weak or brittle. The most commonly used polymer gel is obtained by crosslinking between polymer chains using an organic crosslinking agent or by irradiating γ rays or electron beams. For example, a polymer gel known as a superabsorbent resin is used. Known are cross-linked sodium acrylate, poly (N, N-dimethylacrylamide) gel obtained by crosslinking with N, N′-methylenebisacrylamide, and the like. However, these polymer gels (hereinafter abbreviated as organic cross-linked polymer gels) have only very low mechanical properties, and all have the problem of brittle fracture with weak force due to stretching of 20 to 30% or less. .

  In contrast, amide group-containing polymers such as poly (N-isopropylacrylamide) (hereinafter abbreviated as PNIPA) and poly (N, N-dimethylacrylamide) (hereinafter abbreviated as PDMAA) and clays such as hectorite. It has been reported that polymer gels obtained by complexing minerals at the nanometer level to form a three-dimensional network exhibit extremely excellent mechanical properties as well as excellent functionality (transparency and high swellability). (For example, refer to Patent Document 1). For example, a polymer gel composed of PDMAA and clay mineral exhibits excellent mechanical properties having a break elongation exceeding 1500% and a high break strength as well as excellent transparency and high swellability (see Non-Patent Document 1, for example). ). In addition, the polymer gel composed of PNIPA and clay minerals showed excellent functionality such as rapid swelling / shrinkage due to temperature change in addition to excellent mechanical properties including elongation at break of around 1000% (for example, non-patent literature) 2 and 3). Accordingly, polymer gels in which amide group-containing polymers and clay minerals form a three-dimensional network are expected to be used effectively in many industrial fields due to their excellent mechanical properties and functionality.

  However, such a polymer gel is presumed that the amide group-containing polymer as a constituent component and the clay mineral are bonded mainly by hydrogen bonding and / or relatively weak non-covalent interaction (for example, Non-Patent Documents 2 and 3). As a result, for example, a three-dimensional network structure may be destroyed by adding a specific solute component, and the polymer gel may be liquefied. Therefore, a more stable polymer gel is required. In contrast, the organic cross-linked polymer gel is highly stable because the polymer chains are linked by covalent bonds, and the three-dimensional network structure is not destroyed by contact with a solvent or solute, Due to the formation of a large number of random cross-linking points, it is very weak and brittle mechanically as described above.

JP 2002-053629 A Haraguchi et al., Macromolecules, vol.36, No.15, 5732-5741 (2003). Haraguchi et al., Advanced Materials, vol.14, No.16, 1120-1124 (2002). Haraguchi et al. (K. Haraguchi et.al.), Macromolecules, vol.35, No.27, 10162-10171 (2002).

The problem to be solved by the present invention is a polymer gel in which an amide group-containing polymer and a clay mineral form a three-dimensional network, which has excellent mechanical properties and stability of the three-dimensional network. It is to provide a molecular gel.

  As a result of diligent research to solve the above problems, the present inventor, in a polymer gel composed of an amide group-containing polymer and a clay mineral, the amide group-containing polymer and the clay mineral form a three-dimensional network, and It has been found that a polymer gel having both excellent mechanical properties and three-dimensional network stability can be obtained by making at least a part of the bond between the amide group-containing polymer and the clay mineral a covalent bond and / or an ionic bond. The present invention has been completed.

That is, the present invention relates to a polymer gel in which a amide group-containing polymer and a clay mineral that has been exfoliated in layers and dispersed in the form of a molecule form a three-dimensional network, wherein the three-dimensional network contains a solvent, and Provided is a polymer gel characterized by having at least one of a covalent bond and an ionic bond between the amide group-containing polymer and the clay mineral.

  The polymer gel obtained by the present invention is excellent in mechanical properties and swelling properties because the amide group-containing polymer and the clay mineral form a three-dimensional network, and between the amide group-containing polymer and the clay mineral. Since at least a part of the bonds consists of covalent bonds and / or ionic bonds, the three-dimensional network becomes a polymer gel having high stability with respect to the solvent or solute. The polymer gel according to the present invention is flexible and tough and can be formed into a fiber, fine particle, membrane, or hollow fiber form, and widely applied in many fields where stability to solutes and solvents is required. it can.

The polymer gel obtained in the present invention is a polymer gel in which an amide group-containing polymer and a clay mineral form a three-dimensional network, and at least a part of the bond between the amide group-containing polymer and the clay mineral. Consists of covalent bonds and / or ionic bonds.

  The amide group-containing polymer forming the polymer gel is obtained by polymerizing an amide group-containing vinyl monomer having a property of being dissolved in water as a main component, and the resulting amide group-containing polymer is dissolved in water or Those that swell are particularly preferred.

  Specific examples of the amide group-containing vinyl monomer as a main component for obtaining an amide group-containing polymer include N-alkylacrylamide, N, N-dialkylacrylamide, N-alkylmethacrylamide, N, N-dialkylmethacrylamide, Examples include one or more monomers selected from amide group-containing vinyl monomers such as acrylamide, and a small amount of monomers having functional groups capable of covalent or ionic bonding with clay minerals are used in combination with these monomers. It is done.

  More specifically, N-methylacrylamide, N-ethylacrylamide, N-cyclopropylacrylamide, N-isopropylacrylamide, methacrylamide, N-methylmethacrylamide, N-cyclopropylmethacrylamide, N-isopropylmethacrylamide, N N-dimethylacrylamide, N, N-dimethylaminopropylacrylamide, N-methyl-N-ethylacrylamide, N-methyl-N-isopropylacrylamide, N-methyl-Nn-propylacrylamide, N, N-diethylacrylamide N-acryloylpyrrolidine, N-acryloylmorpholine, N-acryloylpiperidine, N-acryloylmethylhomopiperadine, N-acryloylmethylpiperazine, acrylamide, etc. It is exemplified.

  Further, the combined use of the amide group-containing vinyl monomer and other polymerizable monomers is possible as long as the polymer gel referred to in the present invention is formed. In addition, a stimulus-responsive water-soluble polymer having a critical temperature showing a phase transition such as poly (N-isopropylacrylamide) or poly (N, N-diethylacrylamide) and changing the gel volume by external stimulus is Particularly preferably used.

  In the amide group-containing polymer of the present invention, a functional group capable of covalent bonding and / or ionic bonding with a clay mineral in a polymer chain obtained by polymerizing the amide group-containing vinyl monomer as the main component. It is essential to contain. Specifically, an Si-OR group (R is hydrogen or an alkyl group having 1 to 5 carbon atoms), an Si-Cl group, and / or an ionic bond with a clay mineral that enables a siloxane bond with a clay mineral. A preferable embodiment includes a quaternary ammonium ion (cation) group that can be used. Such a functional group has a characteristic that it can selectively react with a layered exfoliated clay mineral which is an inorganic component in the present invention. That is, since silanol groups (SiOH) exist on the surface of the layered exfoliated clay mineral, it is effective and easy to form a siloxane bond (Si—O—Si) for bonding. Furthermore, since the layered exfoliated clay mineral has a negative charge on its surface, it tends to form ionic bonds with quaternary ammonium ions (cations). The method for introducing the functional group into the amide group-containing polymer chain is not particularly limited. For example, a vinyl monomer containing the functional group is mixed with the main component amide group-containing vinyl monomer for polymerization. Alternatively, a method in which a vinyl monomer containing the functional group is reacted with a clay mineral in advance and then reacted with an amide group-containing vinyl monomer is used. In addition, the vinyl monomer containing this functional group may further contain an amide group in the same monomer. Specific examples of the vinyl monomer having a functional group include methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldimethoxysilane, O-methacryloxy-N-triethoxysilylpropylurethane, methacryloxydimethylmethoxysilane, glycidyl methacrylate, N , N, N-trimethyl-N- (2hydroxy-3-methacryloyloxypropyl) ammonium chloride and the like. The amide group-containing polymer may be a polymer having other functional groups having an affinity for water (for example, a hydroxyl group, an amino group, a carboxylic acid group, etc.). Furthermore, together with the vinyl monomer, tetraalkoxysilane (alkyl chain number is 1 to 5) and its low condensate, monomethyltrialkoxysilane, monophenyltrialkoxysilane, etc. are used in combination with the functional group-containing vinyl monomer. This is effective to increase the stability of the gel.

A small amount of vinyl monomer (C) having a functional group capable of covalently bonding with a clay mineral or vinyl monomer (D) having a functional group capable of ionic bonding with a clay mineral, relative to the amide group-containing vinyl monomer (B) as the main component It is preferably included. From the viewpoint of good mechanical properties and stability of the three-dimensional network, the molar ratio of monomer (D) / monomer (B) or monomer (C) / monomer (B) is 1 × 10 ^{−5 to} 5 × 10. ⁻¹ , more preferably 1 × 10 ⁻⁴ to 1 × 10 ⁻¹ , and particularly preferably 5 × 10 ^{−4 to} 5 × 10 ⁻² .

  The clay mineral that forms the polymer gel is preferably a water-swellable clay mineral that has a charge on the surface of the clay layer and swells or dissociates in layers in water, more preferably a single layer or a small number of layers. The unit is finely dispersed in water. Specific examples of preferable clay minerals include water-swellable hectorite containing sodium as an interlayer ion, water-swellable montmorillonite, water-swellable saponite, and water-swellable synthetic mica.

  The amount of the amide group-containing polymer and the clay mineral forming the polymer gel obtained in the present invention is not particularly limited as long as the amide group-containing polymer and the clay mineral can form a three-dimensional network. The mass ratio of the group-containing polymer compound is preferably 0.001 to 10, more preferably 0.05 to 5, particularly preferably 0.1 to 1.

  The polymer gel obtained by the present invention can contain a solvent in the three-dimensional network. As the solvent, water or an organic solvent miscible with water or a mixed solvent thereof is used. Water or a solvent containing water as a main component is preferable.

  In the polymer gel obtained in the present invention, the amide group-containing polymer and the clay mineral form a three-dimensional network, and at least a part of the bond between the amide group-containing polymer and the clay mineral is a covalent bond and It is essential that it is / or an ionic bond. Here, the kind of the covalent bond is not necessarily limited, but a clay mineral whose surface or end is bonded to an amide group-containing polymer via a siloxane bond (Si—O—) is preferably used. The type of ionic bond is not necessarily limited, but an ionic bond in which an anion of a clay mineral and a quaternary ammonium ion (cation) contained in an amide group-containing polymer interact is preferably used.

  As a production method for obtaining the polymer gel in the present invention, for example, an amide group-containing vinyl monomer (B) and a vinyl monomer (C or D) having a functional group having a function of covalently or ionically bonding a clay mineral Is effective together with the clay mineral (A). For example, after preparing an aqueous solution containing the monomer (C) and / or the monomer (D) together with the clay mineral (A) and the monomer (B), the monomer (B) and the monomer (C) and / or the monomer (D) The method of making it polymerize in clay mineral (A) presence is mentioned. Preferably, it is effective to set experimental conditions such as the order of addition so that the clay mineral (A) first reacts with the monomer (C) and then the monomer (B) polymerizes. Further, a method in which the clay mineral (A) is reacted with the monomer (C) and / or the monomer (D) in advance and the monomer (B) is reacted in the presence thereof.

  Here, the polymerization reaction can be carried out by radical polymerization using a conventional method such as the presence of peroxide, heating, or ultraviolet irradiation. The radical polymerization initiator and the catalyst 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 radical polymerization initiator having a strong interaction with the layered clay mineral.

  Specifically, a water-soluble peroxide as a polymerization initiator, such as potassium peroxodisulfate or ammonium peroxodisulfate, a water-soluble azo compound, for example, VA-044, V-50 manufactured by Wako Pure Chemical Industries, Ltd. V-501 or the like is preferably used. In addition, a water-soluble radical initiator having a polyethylene oxide chain is also used.

  As the catalyst, tertiary amine compounds such as N, N, N ′, N′-tetramethylethylenediamine and β-dimethylaminopropionitrile are preferably used. The polymerization temperature is set in the range of 0 ° C. to 100 ° C. according to the type of water-soluble organic polymer, polymerization catalyst and initiator used. The polymerization time also varies depending on the polymerization conditions such as the catalyst, initiator, polymerization temperature, polymerization solution amount (thickness) and cannot be generally defined, but it is generally carried out in the range of several tens of seconds to several tens of hours.

  The polymer gel obtained by the present invention is excellent in mechanical properties and swelling properties because the amide group-containing polymer and the clay mineral form a three-dimensional network, and between the amide group-containing polymer and the clay mineral. Since at least a part of the bonds consists of covalent bonds and / or ionic bonds, the three-dimensional network becomes a polymer gel having high stability with respect to the solvent or solute.

  Specifically, a polymer gel in which an amide group-containing polymer and a clay mineral form a three-dimensional network includes an aqueous solution of a nonionic surfactant, an aqueous solution of a water-soluble polymer having a polyoxyethylene chain or a polyol chain, Moreover, it is unstable with respect to an amide group-containing polar solvent and the like, and a part or all of them exhibit a phenomenon of being dissolved by contact with an aqueous solution or solvent. However, the polymer gel having a covalent bond and / or an ionic bond between the clay mineral and the polymer chain in the present invention is stable in these aqueous solutions and solvents, and the dissolution is kept low, or does not dissolve at all. .

  Furthermore, the polymer gel obtained according to the present invention is improved in stability and durability against mechanical deformation of the polymer gel because the network is composed of stronger bonding points. Specifically, permanent deformation at the time of large stretching or compression deformation, or creep deformation under a constant load becomes small or disappears.

  EXAMPLES Next, although an Example demonstrates this invention more concretely, this invention is not limited only to the Example shown below from the first.

(Examples 1 to 3 and Comparative Example 1)
A water-swellable synthetic hectorite (trademark Laponite XLG, manufactured by Nippon Silica Co., Ltd.) having a composition of [Mg _5.34 Li _0.66 Si ₈ O ₂₀ (OH) ₄ ] Na + _0.66 was used as a clay mineral. As the organic monomer, N-isopropylacrylamide (NIPA: manufactured by Kojin Co., Ltd.) was recrystallized using a mixed solvent of toluene and hexane and purified into colorless needle crystals before use.

  The polymerization initiator is used as an aqueous solution by dissolving potassium peroxodisulfate (KPS: manufactured by Kanto Chemical Co., Inc.) in pure water deoxygenated at a rate of KPS / water = 0.20 / 10 (g / g). did. As the catalyst, N, N, N ′, N′-tetramethylethylenediamine (TEMED: manufactured by Kanto Chemical Co., Inc.) was used. All pure water was used after bubbling high-purity nitrogen in advance for 3 hours or more to remove oxygen.

  A homogeneous mixed solution of 18.02 g of pure water, 0.305 g of Laponite XLG and 2.26 g of NIPA was prepared in a flat bottom glass container having an inner diameter of 25 mm and a length of 80 mm, the inside of which was replaced with nitrogen. Next, in Example 1, methacryloxypropyltrimethoxysilane (Methacryloxypropyltrimethoxylilane) was added at a molar ratio of 0.0005 to NIPA, and in Example 2, methacryloxypropylmethyldimethoxysilane was added at a molar ratio to NIPA. In Example 3, 0.005 was added in a molar ratio of Methacryloxypropyldimethylmethoxysilane to NIPA, and in Comparative Example 1, nothing was added. went. Thereafter, 1.0 g of an aqueous KPS solution and 16 μl of TEMED were added so as to be uniformly dispersed at a low temperature (about 1 ° C.). A part of this solution was transferred to three glass tube containers having a closed inner diameter of 5.5 mm and a length of 150 mm so as not to come into contact with oxygen, and then sealed at the top, and placed in a constant-temperature water bath at 20 ° C. The polymerization was carried out by standing for a period of time.

  After the polymerization reaction, an elastic and flexible uniform columnar gel was generated in the glass tube container. Thermogravimetric analysis (TG-DTA220: Seiko Denshi Kogyo Co., Ltd .: room temperature to 600 ° C.), Fourier transform infrared absorption spectrum measurement (Fourier transform infrared spectrophotometer FT / manufactured by JASCO Corporation) IR-550), and by dry weight measurement, the obtained gel was polymerized in 93.5% or more of the monomer (NIPA) in any of Examples 1 to 3 and Comparative Example 1, and almost the same ratio as the initial reaction solution. It was confirmed that the polymer gel contains a clay mineral (Laponite XLG). Wide-angle X-ray diffraction (Science Instruments: X-ray diffractometer RINTULTIMA) and transmission electron microscope observation (JEOL Ltd. JEM-200CX: acceleration voltage 100 KV) cause the clay mineral to delaminate inside the gel and become molecular It was confirmed that it was dispersed. In addition, it was confirmed that by immersing the dried polymer gel in water at 20 ° C., the polymer gel absorbs water and returns to an elastic gel having the same shape as before drying. It was confirmed that a three-dimensional network structure mainly composed of -isopropylacrylamide) and clay was formed.

  As a result of the mechanical stretching test (tensile test device, manufactured by Shimadzu Corporation: desktop universal testing machine AGS-H), the elastic modulus and elongation at break were 1.64 kPa and 800%, respectively (Example 1). 2.36 kPa, 450% (Example 2), 1.42 kPa, 850% (Example 3), 1.25 kPa, 1200% (Comparative Example 1), all having softness and toughness. It was confirmed. Further, the polymer gels obtained in Examples 1 to 3 and Comparative Example 1 both exhibited the property of swelling (transparent) at a specific temperature (Tc) or lower and shrinking (white turbidity) at a temperature higher than Tc. . From the volume change of swelling / shrinking, Tc was about 33 ° C.

  The obtained polymer gel was cut into a disk shape having a diameter of 5.5 mm and a length of about 1 mm, and about 1 g in total was added to a nonionic surfactant (New Coal 520: manufactured by Nippon Emulsifier Co., Ltd.) in ultrapure water: HLB = 19.0) was put in 100 g of each aqueous solution in which 5% by mass (Example 4) was dissolved, and was slowly stirred and held in a 20 ° C. constant temperature water bath. In order to investigate the stability of the polymer gel in the aqueous solution of the nonionic surfactant, a small amount of liquid obtained so as not to enter the gel was taken into a quartz cell with a screw cap every 40 minutes, The light transmittance (wavelength 600 nm) was measured. The blank used 40 degreeC ultrapure water. The above measurements were performed for a holding time of up to 500 hours. As a result, in all of Examples 1 to 3, the light transmittance remains almost 100% and does not change until 500 hours, and the polymer gel is dissolved in the nonionic surfactant solution, including visual observation. It was confirmed that they existed stably. On the other hand, in the polymer gel obtained in Comparative Example 1, the light transmittance at a liquid temperature of 40 ° C. decreased with the passage of the holding time in a 20 ° C. constant temperature water bath. This is because in Comparative Example 1, PNIPA, which is a constituent polymer, dissolved from the polymer gel into the surrounding liquid, and the liquid became cloudy (at 40 ° C, which is higher than the phase transition temperature of PNIPA (32 ° C)). It was concluded that the polymer gel was dissolved by the effect of the nonionic surfactant in the liquid. The results obtained are summarized in Table 1.

(Examples 4 to 6 and Comparative Example 2)
A polymer gel dissolution test was conducted in the same manner as in Examples 1 to 3 and Comparative Example 1 except that an amide polar solvent (dimethylacetamide) was used instead of the nonionic surfactant aqueous solution. In Example 4, the same polymer gel as in Example 1, in Example 5, in Example 2, in Example 6, in Example 3 and in Comparative Example 2 as in Comparative Example 1 was used. As a result, in Examples 4 to 6, 440% (Example 4), 375% (Example 5), and 425% (Example 6) swelled in the dimethylacetamide solvent, and only dissolved. Not observed. On the other hand, in Comparative Example 2, it was observed that the shape was gradually lost and dissolved.

(Example 7)
Using N, N, N-trimethyl-N- (2hydroxy-3-methacryloyloxypropyl) ammonium chloride in a molar ratio of 0.01 with respect to NIPA instead of Methacryloxypropyltrimethoxylilane; Except for not carrying out ultrasonic treatment, it was prepared in the same manner as in Example 1 to obtain a polymer gel. The obtained polymer gel had an elastic modulus of 0.85 kPa and an elongation at break of 700%, and dissolution in an aqueous nonionic surfactant solution measured in the same manner as in Example 1 was not observed.

It is flexible and tough and can be molded into a fiber, fine particle, membrane, or hollow fiber form, and is useful as a molding material in a wide range of daily necessities, medicine, medicine, agriculture, civil engineering, and industrial fields.

Claims (7)

In the polymer gel in which the amide group-containing polymer and the clay mineral (A) dispersed exfoliated and dispersed in a molecular form form a three-dimensional network,
An amide group-containing polymer
(I) Amide group-containing vinyl monomer (B), Si-OR group (wherein R represents hydrogen or an alkyl group having 1 to 5 carbon atoms) or Si-Cl group, and a monomer having both vinyl groups ( A polymer obtained by polymerizing C), or (II) an amide group-containing vinyl monomer (B);
A polymer obtained by polymerizing a monomer (D) having both a quaternary ammonium cation and a vinyl group,
A polymer gel comprising a solvent in the three-dimensional network and having at least one of a covalent bond and an ionic bond between the amide group-containing polymer and the clay mineral. The polymer gel according to claim 1, wherein the covalent bond is a siloxane bond (—Si—O—). The polymer gel according to claim 1, wherein the ionic bond is a bond containing a quaternary ammonium ion. Clay mineral (A),
An amide group-containing vinyl monomer (B);
After preparing an aqueous solution containing a Si—OR group (wherein R represents hydrogen or an alkyl group having 1 to 5 carbon atoms) or a Si—Cl group and a monomer (C) having both vinyl groups, the monomer (B ) And monomer (C) in the presence of clay mineral (A) to form a polymer, and at least a part of monomer (C) reacts with clay mineral (A) to form a siloxane bond. The method for producing a polymer gel according to claim 1 or 2. Clay mineral (A),
An amide group-containing vinyl monomer (B);
After preparing an aqueous solution containing the quaternary ammonium cation and the monomer (D) having both vinyl groups, the monomer (B) and the monomer (D) are polymerized in the presence of the clay mineral (A) to form a polymer. The method for producing a polymer gel according to claim 1 or 3, wherein at least a part of the monomer (D) forms an ionic bond with the clay mineral (A). The method for producing a polymer gel according to claim 4 or 5, wherein the molar ratio of the monomer (C) or the monomer (D) to the amide group-containing vinyl monomer (B) is 1 x 10-5 to 5 x 10-1. The polymer gel according to any one of claims 1 to 3 , wherein the clay mineral (A) is water-swellable and the amide group-containing vinyl monomer (B) is water-soluble.