JP5212965B2 - Synthetic clay material and clay film - Google Patents

Description

  The present invention relates to a synthetic clay material and a clay film.

  Conventionally, display devices such as liquid crystal displays and organic EL displays have been mainly formed on glass substrates. However, these display devices have recently been demanded to enable curved surface display and to be lightweight and large. Therefore, there is an increasing demand for forming a display device on a flexible film substrate.

  A film substrate used for such applications is required to have excellent gas barrier properties as well as flexibility. As a film substrate with such a gas barrier property, by forming an inorganic thin film such as silicon oxide, aluminum oxide, or silicon nitride on a resin film such as polyethylene terephthalate, the gas barrier property such as water vapor or oxygen is improved. What was made known is known. At present, these are mainly used as packaging materials for materials that dislike alteration such as foods and pharmaceuticals (see, for example, Patent Document 1).

In addition, as a film base material having gas barrier properties, a film in which clay materials are uniformly dispersed in a nano-order in a polyamide resin such as nylon has been proposed, thereby improving gas barrier properties and mechanical strength. (For example, refer to Patent Document 2 and Non-Patent Document 1). In addition, as a film base with excellent gas barrier properties, heat resistance, and flexibility, clay films formed by laminating clay materials, and waterproof treatments such as fluorine-based films, silicon-based films, metal-deposited films on the surface, etc. An applied clay film has been proposed (see Patent Documents 3 and 4).
Japanese Patent No. 2700019 JP-A-62-74957 JP 2006-77237 A JP 2006-188408 A Hirofumi Nonaka, Industrial Materials, Vol. 51, no. 12 (52-56)

  However, a resin film substrate based on a resin film as in Patent Document 1 has a problem that gas barrier properties are inferior to a glass substrate. When such a resin film substrate is used for a display application, water vapor, oxygen, etc. permeate the resin film substrate and enter an element portion of a liquid crystal display, an organic EL display, etc., and characteristics such as a thin film transistor, a liquid crystal material, and a light emitting material Which degrades the display quality. In addition, if an inorganic thin film layer such as silicon oxide, aluminum oxide, silicon nitride or the like is formed thick, the gas barrier property is improved. It will decrease. On the other hand, when the inorganic thin film layer is formed thin, the flexibility is improved, but an excellent gas barrier property cannot be obtained. That is, since flexibility and gas barrier properties are in a trade-off relationship, a film satisfying both performances cannot be obtained, making it difficult to apply to display applications. Moreover, even if the heat resistance of resin films, such as a polyethylene terephthalate, is high, it is 300 degrees C or less, and cannot apply to the display use which requires high temperature processes, such as formation of the polysilicon film on a film.

  In addition, in the case of a clay nano-dispersed film in which a clay material is uniformly dispersed in the nano order as in Patent Document 2, it is difficult to add the clay material to the resin material at a high concentration. Can be reduced only to about 1/2 before the addition of clay material. For this reason, although such a film can be used for a packaging use etc., it does not satisfy the gas barrier property requested | required of displays, such as a liquid crystal display and an organic electroluminescent display. Moreover, since this clay nano-dispersed film also contains a resin, it is difficult to ensure heat resistance of 300 ° C. or higher.

  On the other hand, a clay film formed by laminating clay materials as in Patent Document 3 is excellent in gas barrier properties, heat resistance, and flexibility. Moreover, this clay film is lighter than glass while having transparency equivalent to glass. However, a clay film made of such a clay material does not have a sufficient water vapor barrier property. Usually, the shape of the clay material is flaky particles, and when the solvent is removed from the dispersion in which these particles are dispersed and dried to form a film, the clay particles are oriented in the form of a film. Therefore, the clay film has an excellent barrier property against gases such as oxygen and nitrogen. However, since the conventional clay film has a hygroscopic property, the barrier property against water vapor is not sufficient.

  In order to improve this point, Patent Document 4 proposes that the surface of the clay film is subjected to waterproofing treatment such as a fluorine-based film, a silicon-based film, and a metal vapor-deposited film. However, in this case, the heat resistance of the clay film obtained when the film provided on the surface is organic is not sufficient, and the flexibility of the clay film obtained when it is inorganic is not sufficient. In other words, the clay film subjected to the above-described surface treatment cannot achieve both the heat resistance inherent in the clay film and the flexibility.

  Therefore, the present invention provides a synthetic clay material and a clay film capable of forming a clay film that is sufficiently excellent in water vapor barrier properties as compared with conventional clay films while maintaining the excellent flexibility and gas barrier properties inherent in clay materials. The purpose is to do.

  Conventional clay materials are known to disperse in water when immersed in water. For example, a smectite clay material contains flaky particles and exhibits dispersibility in water. By utilizing this dispersibility, an aqueous dispersion of clay material is prepared and further dried to obtain a clay film in which clay particles are oriented. This clay film exhibits excellent barrier properties against dry gases such as oxygen and nitrogen. The present inventors diligently studied paying attention to the fact that the dispersibility in water is related to the hygroscopicity of the clay material. And when the clay material lost the dispersibility to water, it discovered that hygroscopicity decreased and water vapor | steam barrier property could be improved significantly.

  That is, this invention provides the synthetic clay material which shows the dispersibility with respect to water, and loses the said dispersibility by heat processing at 400 degreeC. Here, the presence / absence of dispersibility in water (hereinafter referred to as “water dispersibility”) is determined by determining the layer structure of the clay material in water after stirring the water charged with the clay material with physical energy such as ultrasonic waves. This can be determined by checking. For example, as a result of examining the layer structure of the clay material by the X-ray diffraction method, if the peak indicating the layer interval peculiar to the clay material can be clearly confirmed, it can be determined that the water dispersibility is lost (or no water dispersibility). . On the other hand, if the peak indicating the layer spacing peculiar to the clay material cannot be confirmed or hardly confirmed, it can be determined that water dispersibility is exhibited (or water dispersibility exists).

  Since the synthetic clay material of the present invention exhibits dispersibility in water (hereinafter referred to as “water dispersibility”), the clay film produced from this synthetic clay material has an excellent barrier against dry gases such as oxygen and nitrogen. Have sex. Moreover, since the synthetic clay material of the present invention loses water dispersibility and hygroscopicity by heat treatment at 400 ° C., it is possible to form a clay film that is sufficiently superior in water vapor barrier properties.

  In addition, when the clay material is heated at a temperature exceeding 400 ° C. to lose water dispersibility, the main component of the clay material is sintered at the same time and loses flexibility, so that the form as a clay film is also lost. . That is, the heat dispersibility at 400 ° C. does not lose water dispersibility, and a clay material that loses water dispersibility when heated at a temperature exceeding 400 ° C. does not form a clay film.

  The present inventors presume that the factors that cause the synthetic clay material of the present invention to lose water dispersibility and hygroscopicity are as follows. That is, the clay material has a layer in which an octahedral sheet and a tetrahedral sheet are laminated, and has exchangeable cations between the layers. Water dispersibility and hygroscopicity are due to the hydration power of the exchangeable cation. Therefore, the water dispersibility and hygroscopicity of the clay material are lost if the exchangeable cation is in some form difficult to hydrate. The present inventors believe that the heat dispersibility and hygroscopicity are lost because the exchangeable cation moves into the layer of the clay material and is not hydrated by the heat treatment at 400 ° C.

  From this point of view, the present invention mainly provides an octahedral sheet having an octahedral crystal structure having aluminum ions and / or magnesium ions and oxygen ions and / or hydroxide ions, and a tetrahedron mainly having silicon ions and oxygen ions. Provided is a layer comprising a tetrahedral sheet having a body crystal structure, and a synthetic clay material containing lithium ions sandwiched between the layers.

  Moreover, when the synthetic clay material of this invention is used, the clay film which maintained the crystal structure which clay material originally has can be formed. Such a clay film also has excellent heat resistance and transparency. Furthermore, the clay film obtained from the synthetic clay material of the present invention can maintain high transparency even when it has lithium ions. Therefore, it can be suitably used as a substrate film for flexible displays such as liquid crystal displays and organic EL displays.

  The synthetic clay material of the present invention contains exchangeable cations in an ion exchange capacity of 50 to 150 meq / 100 g, and the ion exchange capacity is preferably reduced to 30 meq / 100 g or less by the heat treatment described above. Thereby, since the synthetic clay material of this invention shows water dispersibility more reliably, it is excellent in film moldability, and can improve water vapor | steam barrier property more reliably by the said heat processing.

  In the synthetic clay material of the present invention, it is preferable that 80 atomic% or more of the exchangeable cations are lithium ions. Since lithium ions easily move between the layers of the clay material and do not hydrate, using this synthetic clay material makes it possible to more reliably form a clay film with improved water vapor barrier properties.

  The synthetic clay material of the present invention preferably has mainly a montmorillonite structure and / or a stevensite structure. This makes it possible to obtain a clay film that is further excellent in water vapor barrier properties.

  The synthetic clay material of the present invention preferably has an ion exchange capacity of sodium ions as exchangeable cations of 20 meq / 100 g or less. Even if the clay material is heat-treated, it is difficult to reduce the hydration power caused by sodium ions. Therefore, by reducing the ion exchange capacity of sodium ions as described above, the hydration power of the synthetic clay material can be easily reduced with heat treatment, and the water vapor barrier property of the clay film can be further improved. Become.

  The synthetic clay material of the present invention has a water absorption rate of 10% or more, and it is preferable that the water absorption rate is reduced to 5% or less by the heat treatment. A clay film formed from such a synthetic clay material has excellent water vapor barrier properties. The water absorption rate was increased from 25 ° C. to 300 ° C. after the moisture absorption, based on the mass of the synthetic clay material after sufficient moisture absorption by leaving it in an atmosphere with a relative humidity of 60% and a temperature of 25 ° C. It is shown as a percentage of mass loss when heated.

  The present invention provides a clay film formed by forming the above synthetic clay material into a film. The clay film of the present invention is obtained from the above synthetic clay material. Therefore, a clay film having a water vapor barrier property sufficiently superior to that of a conventional clay film can be obtained by further heating the clay film at 400 ° C. while maintaining flexibility and gas barrier properties.

  According to the present invention, there are provided a synthetic clay material and a clay film capable of forming a clay film having a water vapor barrier property sufficiently superior to that of a conventional clay film while maintaining the excellent flexibility and gas barrier property inherent to the clay material. can do.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as necessary. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

The present invention provides a synthetic clay material that exhibits dispersibility in water (hereinafter referred to as “water dispersibility”) and loses water dispersibility by heat treatment at 400 ° C. FIG. 1 schematically shows a layer structure of a synthetic clay material according to the preferred embodiment. A synthetic clay material 100 according to the present embodiment is present between a layer 10 having an octahedral sheet 1 having an octahedral crystal structure and a pair of tetrahedral sheets 3 having a tetrahedral crystal structure, and between a plurality of layers 10, that is, between layers. Lithium ion. In the layer 10, the pair of tetrahedral sheets 3 sandwich the octahedral sheet 1. The octahedral crystal structure mainly has aluminum ions (Al ³⁺ ) and / or magnesium ions (Mg ²⁺ ), oxygen ions (O ²⁻ ), and / or hydroxide ions (OH ⁻ ). The octahedral crystal structure is preferably composed of aluminum ions and / or magnesium ions and oxygen ions and / or hydroxide ions, but may have a small amount of iron ions, zinc ions, and the like. On the other hand, the tetrahedral crystal structure mainly has silicon ions (Si ⁴⁺ ) and oxygen ions. The tetrahedral crystal structure is preferably composed of silicon ions and oxygen ions, but may contain a trace amount of aluminum ions.

In the present embodiment, a material having a smectite structure can be suitably used as the synthetic clay material. The smectite structure has a negative charge in the layer 10 because a part of the metal element of the tetrahedral sheet 3 or the octahedral sheet 1 has isomorphous substitution with a low-valent metal element or a defect. In order to compensate for this negative charge and maintain electrical neutrality, when the synthetic clay material 100 has a smectite structure, the layer 10 has lithium ions (Li ⁺ ) that are exchangeable cations.

  As specific structures of smectite, structures such as montmorillonite, beidellite, saponite, hectorite, stevensite, and soconite are known. Of these, the structure of the synthetic clay material is preferably a montmorillonite and / or a stevensite structure. In these structures, the octahedral sheet 1 is negatively charged due to isomorphous substitution and defects with a low-valent metal element in a part of the metal element. As a result, these structures have vacant sites in the octahedron sheet 1, and lithium ions after movement described later can exist stably.

  In this specification, “smectite structure”, “montmorillonite structure”, “Stevensite structure” and the like are layers in which an octahedral sheet composed of an octahedral crystal structure is sandwiched between a pair of tetrahedral sheets composed of a tetrahedral crystal structure. Means the basic structure. That is, a crystal structure in which lithium ions are held in the octahedral sheet 1 can also be included in the “smectite structure”, “montmormonite structure”, “Stevensite structure”, and the like.

  The synthetic clay material 100 has lithium ions as exchangeable cations existing between layers. Thereby, the synthetic clay material 100 loses dispersibility by heat treatment at 400 ° C. The radius of a cation existing between layers in a conventional clay material is, for example, 0.097 nm for sodium ions. On the other hand, the ionic radius of lithium ions is 0.068 nm, which is smaller than the above sodium ions. According to the present embodiment, lithium ions existing between the layers 10 of the synthetic clay material 100 have a small ionic radius, and thus can be moved into the octahedral sheet by heat treatment. The above knowledge is obtained independently by the present inventors.

Although lithium ion is shown as the exchangeable cation in FIG. 1, the synthetic clay material 100 may further have other exchangeable cation. Specific examples thereof include sodium ion (Na ⁺ ), potassium ion (K ⁺ ), and ammonium ion (NH ₃ ⁺ ). The synthetic clay material 100 may have one of these exchangeable cations alone or in combination of two or more.

  However, 80 atomic% or more of the exchangeable cations are preferably lithium ions, more preferably 90 atomic% or more are lithium ions, and still more preferably 95 atomic% or more are lithium ions. When the number of cations that cannot move from between the layers 10 into the octahedral sheet 1 by heat treatment described below exceeds 10 atomic%, the water absorption of the clay film increases and the water vapor barrier property tends to decrease.

  The exchangeable cation content in the synthetic clay material 100 is preferably 50 to 150 meq / 100 g in terms of ion exchange capacity. If this ion exchange capacity is less than 50 meq / 100 g, since there are few exchangeable cations that adsorb water, it becomes difficult to form a stable dispersion due to swelling in water. Tends to be difficult to form. On the other hand, when the ion exchange capacity exceeds 150 meq / 100 g, the ionic bond strength between the layers 10 becomes strong, so that it becomes difficult to form a stable dispersion by swelling in water, and clay having excellent orientation It tends to be difficult to form a film. Here, the “ion exchange capacity” is the amount of cations existing between layers including the octahedral sheet (layer 10 in the present embodiment) and can be measured by the Schlenberger method.

  The ion exchange capacity of sodium ions as exchangeable cations is preferably 20 meq / 100 g or less, and more preferably 10 meq / 100 g or less. Since sodium ions have particularly high hydration power among exchangeable cations, when the ion exchange capacity exceeds 20 meq / 100 g, the water vapor barrier property of the finally obtained clay film tends to be lowered.

  The synthetic clay material 100 of the present embodiment exhibits water dispersibility by having the above-described configuration. This is because the exchangeable cations existing between the layers 10 are hydrated. The synthetic clay material 100 preferably has a water absorption rate of 10% by mass or more. The synthetic clay material 100 can form a good film with high orientation.

  The synthetic clay material 100 of this embodiment loses water dispersibility by heat treatment at 400 ° C. This is because lithium ions existing between the layers 10 move into the layer 10 by the heat treatment, so that exchangeable cations are reduced and hydration power is reduced. In addition, the synthetic clay material 100 has a water absorption rate of 5% by mass or less due to the heat treatment, and more preferably 1% by mass or less. In such a synthetic clay material 100, the redispersibility in water is more effectively suppressed, and the water vapor barrier property of the finally obtained clay film is further improved.

  Furthermore, the synthetic clay material 100 of the present embodiment preferably has an ion exchange capacity of 30 meq / 100 g or less, more preferably 15 meq / 100 g or less by the above-described heat treatment. In such a synthetic clay material 100, most of the highly hydratable exchangeable cations move into the layer 10 by heat treatment. As a result, the water vapor barrier property of the clay film is further improved.

  Note that the temperature of the heat treatment may be 150 to 400 ° C. at which lithium ions can move quickly into the layer 10.

  For the synthetic clay material 100, the water dispersibility, water absorption and ion exchange capacity before and after the heat treatment are, for example, the structure of the clay material (for example, selecting a montmorillonite structure) and the exchangeable positive existing between the layers 10. It can be controlled by adjusting the types of ions and their ion exchange capacities.

  Then, the suitable manufacturing method of the said synthetic clay material 100 is demonstrated. FIG. 2 is a process diagram schematically showing a method for producing the synthetic clay material 100 according to the present embodiment. The method for producing the synthetic clay material 100 is a first step of preparing a first clay material containing a layer 10 having an octahedral sheet 1 and a pair of tetrahedral sheets 3 and a cation existing between the layers 10. A second step of dispersing the first clay material in water, a third step of substituting at least part of the cations with lithium ions to obtain a second clay material, and drying the second clay material. And a fourth step of obtaining the synthetic clay material 100. Hereinafter, each step will be described in detail.

(First step)
In the first step, a layer 10 having an octahedral sheet 1 composed of an octahedral crystal structure and a pair of tetrahedral sheets 3 composed of a tetrahedral crystal structure, and exchangeable cations existing between the layers 10, that is, between the layers, are included. A first clay material is prepared. In the layer 10, the pair of tetrahedral sheets 3 sandwich the octahedral sheet 1. The octahedral crystal structure mainly has aluminum ions and / or magnesium ions and oxygen ions and / or hydroxide ions. The octahedral crystal structure is preferably composed of aluminum ions and / or magnesium ions and oxygen ions and / or hydroxide ions, but may have a small amount of iron ions, zinc ions, and the like. On the other hand, the tetrahedral crystal structure mainly has silicon ions and oxygen ions. The tetrahedral crystal structure is preferably composed of silicon ions and oxygen ions, but may contain a trace amount of aluminum ions.

  In the present embodiment, the first clay material is obtained, for example, by hydrothermal synthesis of a slurry in which exchangeable cations are added to a metal oxide coprecipitated gel. More specifically, first, a magnesium salt solution such as magnesium sulfate or magnesium chloride and / or an aluminum salt solution such as aluminum sulfate or aluminum chloride and a sodium silicate solution are maintained at a predetermined pH to generate a precipitate. Next, the precipitate is washed with water and filtered to obtain a coprecipitation gel.

  Although it does not specifically limit as an exchangeable cation added to a coprecipitation gel, For example, a sodium ion, potassium ion, and ammonium ion are mentioned. These exchangeable cations are added to the coprecipitation gel as an aqueous solution of sodium hydroxide, potassium hydroxide and ammonia and further stirred. A slurry is thus obtained.

  Next, the obtained slurry is charged into an autoclave and subjected to hydrothermal treatment for several hours to several days under conditions of 100 ° C. to 450 ° C. and an autogenous pressure. Thereby, a desired first clay material is obtained.

  In addition, the 1st clay material synthesize | combined in this way shows water dispersibility, and a film can be produced by drying the aqueous dispersion. However, the obtained clay film is inferior in water resistance, and when it is immersed in water, it is easily redispersed and becomes an aqueous dispersion. Conventionally, in order to prevent dispersion of the clay film in water, heat treatment (for example, 600 ° C. or more) until the clay layered structure is destroyed must be performed. This means that the clay film does not have flexibility as well as water dispersibility, and cannot be stably present as a clay film.

  As the above-mentioned desired first clay material, smectite, which is a conventional synthetic clay material, can be suitably used. Smectite has a negative charge in the layer 10 because some of the metal elements of the tetrahedral sheet 3 or the octahedral sheet 1 have isomorphous substitution and defects with the low-valent metal element. In order to compensate for this negative charge and maintain electrical neutrality, the smectite has at least one kind of cation such as sodium ion, potassium ion, calcium ion, magnesium ion between the layers 10.

  Known smectites include montmorillonite, beidellite, saponite, hectorite, stevensite, and soconite. Of these, montmorillonite and / or stevensite are preferred. In these smectites, the octahedral sheet 1 is negatively charged because some of the metal elements have isomorphous substitution and defects with low-valent metal elements. As a result, these smectites have vacant sites in the octahedron sheet 1, and lithium ions after migration can exist stably when forming a clay film described later.

  Fig.2 (a) is a figure which shows typically the layer structure of the 1st clay material prepared at a 1st process. The first clay material has a plurality of layers 10 and sodium ions that are exchangeable cations existing between the layers 10. The layer 10 includes an octahedral sheet 1 and a tetrahedral sheet 3 that sandwiches the octahedral sheet 1. The octahedral sheet 1 is mainly composed of an octahedral crystal structure having aluminum ions and / or magnesium ions and oxygen ions and / or hydroxide ions. On the other hand, the tetrahedral sheet 3 is mainly composed of a tetrahedral crystal structure having silicon ions and oxygen ions. Sodium ions exist between the layers 10 including the octahedral sheet 1 having a negative charge, and maintain the electrical neutrality of the first clay material.

(Second step)
In the second step, the first clay material is dispersed in water to obtain a clay dispersion. FIG. 2B is a diagram schematically showing the layer structure of the first clay material when dispersed in water. Since the first clay material has sodium ions which are exchangeable cations having high hydration power between the layers 10, it can be easily dispersed in water to obtain a clay dispersion. At this time, water (adsorbed water) is adsorbed to sodium ions between the layers 10. Moreover, it is preferable to disperse | distribute a 1st clay material in water with lithium ion, and it is preferable to perform a 2nd process and the 3rd process mentioned later simultaneously.

(Third step)
In the third step, in the above clay dispersion, at least a part of the exchangeable cations existing between the layers 10 is replaced with lithium ions to obtain a second clay material. When a lithium compound is added to the clay dispersion liquid of the first clay material, the cation and lithium ion between the layers 10 are ion-exchanged. Thereby, the 2nd clay material by which at least one part of the cation which existed between the layers 10 of the 1st clay material was substituted by the lithium ion can be obtained.

  Examples of the lithium compound used here include one or more lithium compounds such as lithium hydroxide, lithium chloride, and lithium sulfate. Among these, lithium hydroxide is most preferable because it does not contain an anion that becomes an impurity. The lithium compound is preferably added in an amount of 1 to 30 times the ion exchange capacity of the first clay material from the viewpoint of sufficient ion exchange.

  FIG. 2C is a diagram schematically showing the layer structure of the second clay material dispersed in water. The second clay material has lithium ions between the layers 10 by the ion exchange described above. Water (adsorbed water) is adsorbed on the lithium ions between the layers 10. In the ion exchange, it is preferable to leave the lithium compound for 5 minutes to 3 hours after adding the lithium compound to the clay dispersion. If the standing time in the ion exchange is less than 5 minutes, the ion exchange reaction hardly reaches an equilibrium, and a large amount of exchangeable cations contained in the first clay material from the beginning tend to remain between the layers 10. When the standing time exceeds 3 hours, the ion exchange reaction reaches an equilibrium, and even if it is left for a longer time, the ion exchange rate from the exchangeable cation contained in the beginning to the lithium ion is not improved.

  The ion exchange temperature may be room temperature or may be heated to about 80 ° C. Heating increases the ion exchange rate and shortens the standing time.

  Moreover, you may perform the following operation further in the case of ion exchange. First, after the above-mentioned standing, the clay dispersion is separated into a supernatant and a sedimented second clay material by centrifugal sedimentation or the like. Next, after discarding the supernatant, water is added again to the second clay material, which is a sediment, to prepare a clay dispersion. Then, a lithium compound is added to the clay dispersion and left to stand. By repeating this series of operations, the ion exchange rate is improved.

(4th process)
In the fourth step, the synthetic clay material 100 is obtained by drying and removing moisture from the second clay material. At this time, the water hydrated with the exchangeable cation containing lithium ions is removed. The synthetic clay material 100 is usually formed in a film shape, but may be pulverized thereafter.

  The synthetic clay material 100 thus obtained exhibits water dispersibility and loses water dispersibility by heat treatment at 400 ° C. This is because lithium ions, which are exchangeable cations, move into the layer 10 by heat treatment, and water cannot be adsorbed. Therefore, the clay film obtained using the synthetic clay material 100 as a raw material has an advantageous effect of exhibiting a water vapor barrier property sufficiently better than the conventional clay film while maintaining the original excellent flexibility and gas barrier property. Play.

  In addition, the synthetic clay material 100 exhibits heat resistance that is equal to or better than that originally possessed by the clay material and gas barrier properties against dry gas such as oxygen and nitrogen. Furthermore, since the synthetic clay material 100 is different from the natural clay material, it is substantially free of impurities. As a result, the synthetic clay material 100 is less colored and excellent in transparency, and is suitable for the production of a transparent film for display device applications.

  In particular, the synthetic clay material 100 is formed by laminating the layer 10 whose basic structural unit is the pair of tetrahedral sheets 3 and the octahedral sheet 2 sandwiched between the pair of tetrahedral sheets 3 as described above. The advantageous effects described above can be further enhanced. Furthermore, 50 to 150 milliequivalents / 100 g of exchangeable cations are present between the layers 10, and 80 atomic% or more of them are lithium ions, so that the above advantageous effect becomes more remarkable.

  Next, a suitable method for producing a clay film using the synthetic clay material 100 as a raw material will be described. The clay film manufacturing method according to this embodiment includes a fifth step of forming the synthetic clay material 100 into a film shape, and a sixth step of manufacturing the clay film by subjecting the film-like synthetic clay material 100 to heat treatment. Have.

(5th process)
First, in the fifth step, the synthetic clay material 100 is dispersed in water to obtain a dispersion, and then moisture is removed by drying to obtain a film-like synthetic clay material 100. The content of the synthetic clay material 100 in the dispersion is preferably 0.5 to 10% by mass. When the content of the synthetic clay material 100 in the dispersion is less than 0.5% by mass, drying tends to require a long time. Further, when the content of the synthetic clay material 100 exceeds 10% by mass, the dispersibility of the synthetic clay material 100 is lowered, and it tends to be difficult to form a film having a uniform film thickness. is there. Further, from the viewpoint of obtaining a dense film-like synthetic clay material 100 having a more uniform film thickness, the drying temperature is preferably less than the boiling point of water. The drying rate is preferably 0.01 to 1.0 g / cm 2 · h as the evaporation rate of water from the surface of the dispersion by controlling the temperature and relative humidity in the drying apparatus. When the evaporation rate is less than 0.01 g / cm ² · h, it tends to require a long time to dry and remove moisture. When the evaporation rate exceeds 1.0 g / cm ² · h, it tends to be difficult to obtain a dense film.

(6th process)
Next, in a sixth step, the film-like synthetic clay material 100 is subjected to heat treatment to produce a clay film. By subjecting the synthetic clay material 100 to heat treatment, at least part of the lithium ions between the layers 10 can be moved into the octahedral sheet 1. Conditions of the heat treatment, the heating temperature is 150 to 600 ° C.. The heating time is preferably 1 minute to 1 hour. When the temperature of the heat treatment is lower than 150 ° C., movement from the lithium ion layer 10 into the octahedral sheet 1 tends not to occur. When the temperature of the heat treatment exceeds 600 ° C., the structural water in the synthetic clay material 100 is dehydrated and becomes a crystalline phase different from smectite, so that flexibility tends to be lost. Although there is no problem if the heat treatment time exceeds 1 hour, it is not practical. On the other hand, if the heat treatment time is less than 1 minute, the time required for the movement of lithium ions from between the layers 10 into the octahedral sheet 1 is short, so that a lot of lithium ions tend to remain between the layers 10. The heat treatment can be performed in normal air.

  FIG. 3 is a diagram schematically showing the layer structure of the clay film obtained by the above-described production method. The clay film has a tetrahedral crystal structure in which an octahedral sheet 2 composed mainly of an octahedral crystal structure having aluminum ions and / or magnesium ions and oxygen ions and / or hydroxide ions has mainly silicon ions and oxygen ions. A plurality of layers 20 sandwiched between a pair of tetrahedral sheets 3 made of Further, at least some of the octahedral sheets 2 have lithium ions.

  The clay film having such a layer structure can sufficiently reduce the amount of water adsorbed between the layers 20 constituting the clay film, that is, the water absorption of the clay film, and is excellent in water vapor barrier properties. Further, even when immersed in water, it hardly swells or dissolves, and is excellent in water resistance.

  The ion exchange capacity of the heat-treated clay film is preferably 30 meq / 100 g or less, and more preferably 20 meq / 100 g or less. When the ion exchange capacity exceeds 30 meq / 100 g, the amount of water absorption increases and the water vapor barrier property tends to decrease.

  The layer 10 contained in the clay film preferably has a montmorillonite structure and / or a stevensite structure.

  The clay film obtained by the present embodiment has an advantageous effect that the water vapor barrier property is sufficiently excellent while maintaining the flexibility and gas barrier property inherent to the clay film. Furthermore, since this clay film is obtained by incorporating lithium ions into the octahedron sheet 2 while maintaining the crystal structure inherent to the clay material, it has the advantageous effect of having excellent heat resistance and transparency. Play.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. That is, there is no particular limitation as long as the synthetic clay material exhibits water dispersibility and loses water dispersibility by heat treatment at a temperature of 400 ° C. or lower.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

Example 1
<Preparation of the first clay material (first step)>
First, 17.2 g of No. 3 water glass (SiO ₂ content ratio: 28% by mass) was added to 100 g of water to prepare a diluted solution. Next, 6 mL of 16 N nitric acid was added to the diluted solution, and then 33 mL of 1 mol / liter aqueous aluminum chloride solution and 7 mL of 1 mol / liter aqueous magnesium chloride solution were further added. Subsequently, 1N aqueous sodium hydroxide solution was further added to adjust the pH to 10. The coprecipitated gel thus produced was filtered, washed 5 times with 300 mL of pure water, and then water was added so that the total amount became 120 mL. A 1N aqueous sodium hydroxide solution was added thereto to adjust the pH to 10.5 to obtain a slurry.

  Subsequently, the slurry was placed in a stainless steel autoclave and subjected to a hydrothermal reaction at 350 ° C. for 24 hours under a self-generated pressure condition. The obtained reaction product was dried at 80 ° C. and further pulverized. Thus, a first clay material which is a montmorillonite type synthetic clay material having sodium ions as exchangeable cations was obtained.

<Ion exchange (second, third and fourth steps)>
2 g of the obtained first clay material is put in a beaker, 50 g of pure water (20 ° C.) is added thereto, and the mixture is stirred with a Teflon (registered trademark) rotor, whereby the first clay material is dispersed in water. A dispersion was obtained. To this dispersion, 0.8 g of lithium hydroxide monohydrate was added and left at 25 ° C. in the air for 1 hour.

  Thereafter, using a commercially available centrifuge, the supernatant was removed from the dispersion by rotating at a centrifugal acceleration of 3000 G for 10 minutes, and 50 g of pure water was added (centrifugation operation 1). This centrifugal separation operation 1 was repeated a total of three times to obtain a dispersion in which at least a part of sodium ions between the layers of the first clay material was replaced with lithium ions.

  Next, using the above-mentioned centrifuge, the supernatant was removed from the dispersion by rotating at a centrifugal acceleration of 3000 G for 10 minutes, and 50 g of pure water was added again (centrifugation operation 2). This centrifugation operation 2 was repeated a total of 3 times to wash away excess lithium ions. Thereafter, the supernatant was removed from the dispersion under the above centrifugal separation conditions to obtain a precipitate. The sediment was dried at 80 ° C. and further pulverized to obtain a synthetic clay material in which at least a part of the exchangeable cation was lithium ion.

<Production of clay film (5th and 6th steps)>
0.5 g of the obtained synthetic clay material was put in a beaker, 25 g of pure water (20 ° C.) was added thereto, and the mixture was stirred with a Teflon (registered trademark) rotor to disperse the synthetic clay material in water. A liquid was obtained. This dispersion was poured into a rectangular parallelepiped polypropylene container having a 5 cm square bottom to a height of 5 mm. Next, the container was housed in a hot-air circulating dryer (product name: EPFH, manufactured by Isuzu Co., Ltd.) and heated at 60 ° C. for 4 hours to dry and remove moisture in the dispersion. Thus, a film-like synthetic clay material having a thickness of about 80 μm having lithium ions between layers was obtained.

  Next, the synthetic clay material was subjected to a heat treatment at 300 ° C. for 30 minutes in the same hot air circulation dryer, and lithium ions between the layers were moved into the layer to obtain a clay film.

(Example 2)
A synthetic clay material and a clay film were prepared in the same manner as in Example 1 except that 0.8 g of lithium chloride was used instead of 0.8 g of lithium hydroxide monohydrate.

(Example 3)
A clay film was produced in the same manner as in Example 1 except that the conditions of the heat treatment applied to the synthetic clay material were changed from 300 ° C. for 30 minutes to 150 ° C. for 1 hour.

Example 4
A synthetic clay material and a clay film were produced in the same manner as in Example 1 except that the preparation of the first clay material (first step) was changed as follows.

First, 17.2 g of No. 3 water glass (SiO ₂ content ratio: 28% by mass) was added to 100 g of water to prepare a diluted solution. Next, 6 mL of 16 N nitric acid was added to the diluted solution, and then 56 mL of a 1 mol / liter aqueous magnesium chloride solution was further added. Subsequently, 1N aqueous sodium hydroxide solution was further added to adjust the pH to 10. The coprecipitated gel thus produced was filtered, washed 5 times with 300 mL of pure water, and then water was added so that the total amount became 120 mL. A 1N aqueous sodium hydroxide solution was added thereto to adjust the pH to 10.5 to obtain a slurry.

  Subsequently, the slurry was charged into a stainless steel autoclave and subjected to a hydrothermal reaction under the conditions of 250 ° C. and 3 hours of autogenous pressure. The obtained reaction product was dried at 80 ° C. and further pulverized. In this way, the 1st clay material which is a steven site type | mold synthetic clay material which has a sodium ion as an exchangeable cation was obtained.

(Comparative Example 1)
A clay film was obtained in the same manner as in Example 1 except that ion exchange (second, third and fourth steps) was omitted and the production of the clay film (fifth and sixth steps) was as follows.

  The first clay material was dispersed in water by adding 0.5 g of the first clay material into a beaker, adding 25 g of pure water (20 ° C.) to the beaker, and stirring with a Teflon (registered trademark) rotor. A dispersion was obtained. This dispersion was poured into a rectangular parallelepiped polypropylene container having a 5 cm square bottom to a height of 5 mm. Next, the container was housed in a hot-air circulating dryer (product name: EPFH, manufactured by Isuzu Co., Ltd.) and heated at 60 ° C. for 4 hours to dry and remove moisture in the dispersion. Thus, a film-like first clay material having a thickness of about 80 μm having sodium ions between layers was obtained.

  Next, the first clay material was subjected to a heat treatment at 300 ° C. for 30 minutes in the same hot air circulation dryer to obtain a clay film.

<Evaluation of synthetic clay materials>
About the said synthetic clay material, the water dispersibility before and behind heat processing was evaluated by the X ray diffraction measurement. In addition, the water absorption and ion exchange capacity of the synthetic clay material before and after the heat treatment were also evaluated.

[Evaluation of water dispersibility]
A synthetic clay material was put into water and sufficiently stirred by ultrasonic waves. Thereafter, the water in which the synthetic clay material was mixed was set in an X-ray diffractometer (trade name “ATX-G”, manufactured by Rigaku Corporation), and the X-ray diffraction of the synthetic clay material in water was measured. . The measurement was performed using CuKα rays by scanning 2θ from 2 degrees to 70 degrees at 2 degrees / minute. As a result, when the peak due to the spacing of the (001) plane that the synthetic clay material should have is not recognized, it is judged that water dispersibility is “present”, and when such a peak is recognized, water dispersion It was judged that there was no sex. The results are shown in Table 1.

  Next, the synthetic clay material was subjected to heat treatment at 400 ° C. for 30 minutes in the above-described hot-air circulating dryer. The synthetic clay material after the heat treatment was put into water and stirred in the same manner as described above, and then X-ray diffraction in water was measured. As a result, the presence or absence of water dispersibility was determined in the same manner as described above. The results are shown in Table 1.

[Water absorption measurement]
The synthetic clay material was left in an atmosphere with a relative humidity of 60% and a temperature of 25 ° C. to sufficiently absorb moisture. The mass of the synthetic clay material after the moisture absorption was measured. Subsequently, the synthetic clay material after moisture absorption was set in a cell of a thermogravimetric analyzer, and thermogravimetric analysis was performed. The measurement conditions were a heating rate of 10 ° C./min, an air flow rate in the system of 50 cc / min, and a measurement temperature range of 25 ° C. to 300 ° C. The water absorption rate was derived from the mass loss rate by thermogravimetric analysis. The results are shown in Table 1.

  Next, the synthetic clay material was subjected to heat treatment at 400 ° C. for 30 minutes in the above-described hot-air circulating dryer. The water absorption was derived in the same manner as described above for the synthetic clay material after the heat treatment. The results are shown in Table 1.

[Measurement of ion exchange capacity]
First, the exchangeable cation in the synthetic clay material was exchanged with ammonium ion by the Schlenberger method. Thereafter, the ammonium ions were further exchanged with sodium ions, and the ammonium ions eluted at that time were quantified. Specifically, first, 1 g of synthetic clay material was weighed, mixed with 5 g of silica, and filled into a leaching tube. Next, 100 mL of 1N ammonium acetate solution was dropped into the leaching tube over 10 hours to exchange exchangeable cations with ammonium ions. Thereafter, an 80 mass% ethanol aqueous solution was dropped into the leaching tube over 1 hour to wash away excess ammonium ions. Next, a 10% sodium chloride solution was dropped into the brewing tube over 5 hours to extract ammonium ions. Then, the extracted ammonium ions were quantified by ion chromatography, and the ion exchange capacity was calculated. The results are shown in Table 1.

  Next, the synthetic clay material was subjected to heat treatment at 400 ° C. for 30 minutes in the above-described hot-air circulating dryer. The ion exchange capacity of the synthetic clay material after the heat treatment was measured in the same manner as described above. The results are shown in Table 1.

<Evaluation of clay film>
Using the clay film as a sample film, an immersion test, an X-ray diffraction measurement, and a water vapor transmission rate measurement were performed. Moreover, the film-like synthetic clay material obtained in the middle of the production of the clay film of Example 1 (fifth and sixth steps) was used as a sample film, and the immersion test, the X-ray diffraction measurement, and the water vapor transmission rate measurement were similarly performed. went.

[Immersion test]
After immersing 4 cm ² of the sample film in 100 g of pure water and allowing it to stand at 25 ° C. for 24 hours, the shape was visually observed while the sample film was held in pure water to determine the presence or absence of deformation. The results are shown in Table 1.

[X-ray diffraction measurement (XRD)]
The X-ray diffraction of the sample film was measured using the same X-ray diffractometer as described above. The measurement was performed using CuKα rays by scanning 2θ from 2 degrees to 70 degrees at 2 degrees / minute. From the measurement results, the surface spacing of the (001) plane of the sample film was determined. The interplanar spacing of the (001) plane of Na-type montmorillonite used as a raw material was compared with the interplanar spacing of the (001) plane obtained from the measurement results. The results are shown in Table 1.

[Water vapor permeability measurement]
Water vapor permeability was measured using a humidity sensor (Lyssy, trade name: L80-5000 type). The lower atmosphere was adjusted to a relative humidity of 100% and the upper atmosphere was adjusted to a relative humidity of 9.9% or less, respectively, with a 50 cm ² sample film vertically separated. Then, the water vapor transmission rate (g / (m ² · day)) is calculated from the time until the relative humidity of the atmosphere on the upper side of the sample film is changed from 9.9% to 10.1% by the water vapor passing through the clay film. Calculated. The results are shown in Table 1.

It is a schematic diagram which shows partially the layer structure of the synthetic clay material which concerns on embodiment. It is process drawing which shows typically the manufacturing method of the synthetic clay material which concerns on embodiment. It is a schematic diagram which shows partially the layer structure of the clay film obtained from the synthetic clay material which concerns on embodiment.

Explanation of symbols

  1, 2 ... octahedron sheet, 3 ... tetrahedron sheet, 10, 20 ... layer, 100 ... synthetic clay material.

Claims (7)

A synthetic clay material mainly having a montmorillonite structure and / or a stevensite structure,
A clay film formed by forming a synthetic clay material which exhibits dispersibility in water and loses the dispersibility by heat treatment at 400 ° C. into a film shape and heat-treats at 150 to 600 ° C. The synthetic clay material contains exchangeable cations in an ion exchange capacity of 50 to 150 meq / 100 g , and the heat treatment at 400 ° C. reduces the ion exchange capacity to 30 meq / 100 g or less. The clay film described. The clay film according to claim 2, wherein in the synthetic clay material, 80 atomic% or more of the exchangeable cations are lithium ions. The clay film according to any one of claims 1 to 3, which has a water vapor transmission rate of 5.7 (g / (m ² · day)) or less . The clay film as described in any one of Claims 1-4 whose ion exchange capacity of the sodium ion as the said exchangeable cation is 20 meq / 100g or less in the said synthetic clay material . The clay film according to any one of claims 1 to 5, wherein the synthetic clay material has a water absorption rate of 10% or more, and the water absorption rate is reduced to 5% or less by the heat treatment at 400 ° C.   A synthetic clay material mainly having a montmorillonite structure and / or a stevensite structure,
  A method for producing a clay film, wherein a synthetic clay material that exhibits dispersibility in water and loses the dispersibility by heat treatment at 400 ° C. is formed into a film and heat-treated at 150 to 600 ° C.

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