JPH0143685B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to imogolite having a higher degree of polymerization than known imogolite, a method for producing the same, and a flexible film containing the same as a main component. Imogolite is a type of aluminosilicate mineral that can occur naturally or synthetically. Typical aluminosilicates include kaolin (clay), acid clay, and zeolite, which are used as raw materials for ceramics, firebricks, cement, etc., or as pharmaceuticals, adsorbents, water softeners, and catalysts for chemical reactions. Although it is used for supports, molecular sieves, etc., its usage form is usually limited to powder or granule form. On the other hand, a method is also known in which aluminosilicate is made into fibers and used as heat-resistant fibers. For example, high-purity calcined kaolin, with a small amount of additives added as necessary, is melted in an electric furnace and then flowed out through pores, and steam is injected into it to make it into fibers. flocculent)
In addition to being used in silicic acid gel and other binding materials, it can be formed into blankets, felt, paper, rope, woven fabric, blocks, boards, etc., or used as coating cement. These fiber products can be used safely and continuously at temperatures around 1250℃, are not brittle, are lightweight, and have excellent insulation and workability, so they can be used as fireproof insulation materials, insulation seals for expansion parts, and filling of joints. It has a wide range of uses, including for erosion protection coatings. However, since aluminosilicate has a high melting point and is insoluble in ordinary solvents, the only way to make it into fibers is by melting it in an electric furnace, which is disadvantageous industrially, and in particular, making it into a uniform film is not practical. It was extremely difficult. It is also known that among the aluminosilicate minerals, imogolite has a fibrous structure and can form small film-like pieces by casting from a dispersion in water etc. (for example, JP-A-53-124199, 55-
(See No. 10498). However, since the conventionally known natural or synthetic imogolites are mixtures of different degrees of polymerization, it has not been possible to form a self-supporting and flexible film by casting. The inventors of the present invention have conducted extensive research into producing molded products from aluminosilicate minerals using an industrially easy method, and have discovered imogolite with a high degree of polymerization. The inventors have discovered that a flexible film and the like can be easily obtained industrially, and have arrived at the present invention. That is, the present invention uses an acetic acid aqueous solution with pH=3.5 as a dispersion solvent, and the value of the dispersion liquid viscosity (ηsp/c) measured at 30°C and a concentration of 0.2% by weight is 5.0 or more, preferably 9.0 or more, particularly preferably It is imogolite with a high degree of polymerization of 12.0 or higher. Imogolite is a hollow fibrous aluminosilicate polymer with an outer diameter of approximately 20 Å and an inner diameter of approximately 7 Å, which is naturally found in volcanic ash soil and weathered pumice layers, and its chemical composition is approximately SiO ₂ Al ₂ O. It is expressed by _3.2 ~3H ₂ O. Such imogolite can be obtained by a known method, for example, by dispersing soil containing imogolite in water, collecting floating matter mainly composed of imogolite, and refining this floating matter in accordance with the method described in the Clay Handbook (edited by the Clay Society of Japan). It can be obtained by
That is, the iron content was removed by the Jackson method (sodium citrate-sodium hydrosulfite-sodium bicarbonate extraction method), and the organic matter contained as impurities was decomposed and removed by heating with H ₂ O ₂ water, and 2%
By boiling with Na ₂ CO ₃ to remove free aluminum and silicic acid, a gel-like purified product of imogolite is obtained. Alternatively, this imogolite may be dispersed in an acidic aqueous solution such as hydrochloric acid, and then precipitated and gelled with an alkali, common salt, etc. to obtain a more purified gel-like imogolite. The imogolite used in the present invention may be synthetic. As a synthesis method,
A method for synthesizing imogolite by heating refluxing aluminum hydroxide and a silicate complex in an acidic aqueous solution (Japanese Patent Application Laid-Open No. 124199/1982), and aluminum hydroxide obtained by hydrolyzing aluminum alkoxide and tetraalkyl silicic acid in acid. A method is known in which imogolite is synthesized by heating and refluxing a silicate in an acidic aqueous solution (Japanese Unexamined Patent Publication No. 10498/1983). The natural imogolite or synthetic imogolite obtained by purification in this way is a mixture of various degrees of polymerization, and the dispersion viscosity (η sp / c) is 30 °C and 0.2% by weight
Less than 5.0 when measured in concentration. In the present invention, the imogolite thus obtained is treated with an acidic aqueous solution to extract and remove imogolite having a relatively low degree of polymerization and impurities such as allofene. The acids used include organic acids such as acetic acid and trifluoroacetic acid, and inorganic acids such as hydrochloric acid, with acetic acid and trifluoroacetic acid being preferred. These acids are usually used as an aqueous solution having a pH of 2 to 6, preferably 3 to 5. The method of treating imogolite with an acidic aqueous solution is not particularly limited as long as imogolite with a relatively low degree of polymerization can be extracted and removed. A method of extraction with a hot acidic aqueous solution can be adopted. The extraction time is generally several hours to several tens of hours, and it is preferable that about 10% by weight of the imogolite used is extracted. By this treatment, impurities such as imogolite and allofene, which have a relatively low degree of polymerization, are extracted and removed, and imogolite, which has a relatively high degree of polymerization, is obtained as an extraction residue. The imogolite having a relatively high degree of polymerization obtained as described above is dispersed in a suitable dispersion medium to prepare a dispersion liquid. For dispersion, heating or ultrasonication may be used, but ultrasonication causes cleavage of imogolite molecules, so
Although it depends on the ultrasonic intensity, it is appropriate to limit the treatment to 10 minutes at most. After removing the undispersed matter by sedimentation of the dispersed imogolite by means such as centrifugation, the viscosity of the dispersion liquid (ηsp/c), that is,
If the dispersion has a viscosity of 5.0 or more when measured at 30°C and a concentration of 0.2% by weight using an acetic acid aqueous solution with a pH of 3.5 as a dispersion solvent, it can be used as is for making films, etc. . Furthermore, according to the present invention, by allowing the prepared dispersion to stand after performing the extraction operation, it is separated into two layers, an emulsion layer (upper layer) and a transparent layer (lower layer). ), a component with a higher dispersion viscosity (ηsp/c) is obtained. Depending on the dispersion liquid, accelerated separation can be performed by high-speed centrifugation (10,000 to 30,000 G) instead of standing still. On the other hand, in the case of a dispersion liquid that was not subjected to the extraction operation, not only did the dispersion liquid viscosity (ηsp/c) be low, but it also rarely separated into two layers even after being allowed to stand for more than one month. If you need a film with high bending strength,
When a dispersion liquid viscosity (ηsp/c) of 9.0 or more is required, and a film that is resistant to bending and does not break even after being bent five times is required, a film with ηsp/c of 12.0 or more is required. In such cases, the ηsp/c of the lower layer separated into two layers is often 9.0 or more, so by separating both layers and using only the lower layer,
A film with high bending strength can be created. In addition, when the dispersion conditions are mild, for example, when dispersion is performed for 5 minutes using Branson's ultrasonic dispersion device type 350 with Out Put Control 5 and Duty Cycle 50%, ηsp/c is 12.0 or more. You can also get things. The flexible film containing imogolite as a main component of the present invention is produced by preparing a dispersion liquid in which a dispersoid containing imogolite as a main component is dispersed as described above, casting this, and then removing the dispersion medium from the dispersion liquid. obtained by doing. Dispersion media include water, dimethylformamide, dimethyl sulfoxide, and other organic solvents, but acidic solvents, especially PH
is 3 to 5 water. Acids for pH adjustment include inorganic acids such as hydrochloric acid, nitric acid, perchloric acid, and sulfuric acid, organic acids such as formic acid, acetic acid, propionic acid, monochloroacetic acid, and trifluoroacetic acid, and mixtures of these acids. , monochloroacetic acid, trifluoroacetic acid, and other halogenated acetic acids are preferred from the viewpoint of dispersibility of imogolite. In the present invention, 20% by weight of the total dispersoids
Dispersoids other than imogolite within the following ranges, such as kaolin, acid clay, mica, synthetic mica,
Inorganic dispersoids such as glass fiber and water glass, or
Polymers such as silicone, polyvinyl alcohol, and fluorine resins can also be used in combination with imogolite. The concentration of the dispersion is between 0.2 and 4% by weight, preferably
Preferably, it is in the range of 0.5 to 2% by weight. In addition,
The dispersion in the present invention means anything other than a true solution, such as a suspension, a colloidal liquid, or an emulsion, and a true solution. The dispersion thus obtained is then casted. Conventionally known materials can be used as the casting surface, but fluororesin, polyester, acrylic resin, polycarbonate plates, and metal plates coated with these resins are particularly suitable, and if necessary, a silicone-based mold release agent is used. may be applied. After casting, the dispersion medium is removed from the dispersion by heating if necessary under reduced pressure or normal pressure. In this way, a flexible film containing imogolite as a main component of the present invention is obtained, and this film may then be subjected to heat treatment under appropriate conditions. In the present invention, the film refers to a film or sheet having a thickness of about 2 mm or less, and the film of the present invention is self-supporting and has sufficient flexibility. Depending on the manufacturing method, the film is generally transparent or translucent and has a tensile strength of 5 to 10 kg/
mm ² and Young's modulus of 500 to 800 Kg/mm ² or more, a film with good flexibility can be obtained. In the case of a film using a dispersion liquid with a dispersion liquid viscosity of 9.0 or more, a film that does not break even when bent can be obtained, and in particular, when a dispersion liquid with a dispersion liquid viscosity of 12.0 or more is used, a film with a dispersion liquid of 5.
A film with high bending strength that does not break even when bent by diffraction can be obtained. The flexible film containing imogolite as a main component of the present invention can be used as a heat-resistant and flame-resistant film material by taking advantage of its heat-resistant and flame-resistant properties. It can be used as a catalyst or catalyst support, and also as a film-like molecular sieve. The present invention will be explained in detail with reference to Examples below. In addition, the viscosity of the dispersion of imogolite (ηsp/c)
For the measurement, use acetic acid aqueous solution with pH = 3.5 as the dispersion solvent.
It was carried out using an Ubbelohde viscometer at 30° C. and at a concentration of about 0.2% by weight. The dispersion liquid was subjected to ultrasonic treatment for 30 minutes using a Bransonique ultrasonic cleaner model 220 before being subjected to measurement. Also, the accurate measurement concentration is 15
The dispersion was collected in a 1ml porcelain crucible, the water was evaporated at 50°C, and then baked at 500°C for 2 hours in an electric furnace.The viscosity was calculated from the weight of the residue, and the measured viscosity was set to 0.2% by weight of ηsp/c. Converted. All percentages in the examples are percentages by weight. Example 1 Water was added to the collected weathered pumice layer containing a large amount of imogolite, and the mixture was sufficiently stirred, and then water suspended matter was separated using a sieve (10 to 20 mesh). After removing impurities such as tree roots, a 7% imogolite gel was obtained on a wet basis. The separated imogolite gel was purified using a conventionally known purification method, that is, 80 parts of sodium citrate, 2 parts of NaHCO ₃ and 500 parts of ion-exchanged water were added to 400 parts of imogolite gel, heated and dissolved in a hot bath at 80°C, and Na ₂ S ₂ Add 5 parts of _O5 powder, stir, hold for 15 minutes, remove iron by suction, then add 2%
Na ₂ CO ₃ was added and the mixture was boiled for 5 minutes to remove Al and undergo silicic acid treatment, and then heated with 30% H ₂ O ₂ to remove organic substances contained as impurities and purify. The thus obtained purified imogolite gel was subjected to Soxhlet extraction with an acetic acid aqueous solution (PH3.5) for 60 hours. The extract contains a fine powder precipitate containing a small amount of iron (imogolite with a relatively low degree of polymerization).
was recognized. The imogolite gel of the Soxhlet extraction residue was dispersed in an acetic acid aqueous solution (PH3.5) for 6 minutes at an output of 60 W using a Kubota ultrasonic dispersion device model 200M (oscillation frequency 9 KHz). High-speed centrifuge (16000 rpm, 30 minutes) undispersed material
The supernatant was concentrated using a rotary evaporator to obtain a dispersion with a concentration of 0.77%. PH＝
Dispersion viscosity in acetic acid acidic solution of 3.5 (ηsp/c)
was 6.2. The dispersion was poured onto a polyester film coated with a silicone-based mold release agent and dried at room temperature, resulting in a slightly opaque, flexible film of about 20 microns. Example 2 When the dispersion of Example 1 was left for one week, it separated into two layers, and the upper layer was slightly milky.
The lower layer was colorless and transparent. As shown in Table 1, the measurement results of the viscosity (ηsp/c) of the imogolite dispersion contained in each layer showed that components with higher viscosity were separated in the lower layer of the dispersion. Observation results using an electron microscope also showed that the upper layer of the dispersion had more impurities, while the lower layer had fewer impurities and the presence of imogolite with a high degree of polymerization was observed.

[Table] As a result of forming the upper and lower layers of the dispersion into a film using the method of Example 1, the lower layer was transparent and did not break even when folded, and a film of approximately 20 μm was obtained, whereas the upper layer did not break when folded. A film was obtained that easily broke when bent. Comparative Example 1 An experiment was conducted in which the Soxhlet extraction of the purified imogolite gel with an acetic acid aqueous solution (PH3.5) in Example 1 was omitted. A dispersion of imogolite gel in an acetic acid aqueous solution was emulsified, the concentration of the dispersion was 0.82%, and ηsp/c was 4.5. Even after the dispersion was left for one month, no separation into two layers was observed. The resulting film was milky, brittle, and easily broke when bent. Comparative Example 2 The Soxhlet extraction of the purified imogolite gel with an acetic acid aqueous solution (PH3.5) in Example 1 was omitted, and imogolite was directly dispersed in a hydrochloric acid aqueous solution (PH3.2) in the same manner as in Example 1. Ta.
When an acidic aqueous solution of hydrochloric acid was used, the dispersibility was somewhat poorer than that of an aqueous acetic acid solution, the dispersion was also milky, and ηsp/c was as low as 4.1. Further, even when the dispersion was left for one month, no separation into two layers was observed. The molded film was milky and brittle and easily broke when bent. Example 3 The collected lapilli containing a large amount of imogolite was separated in the same manner as in Example 1 to obtain a 5% imogolite gel on a wet basis. The separated imogolite gel was purified and dispersed in the same manner as in Example 1. As a result, the imogolite gel was easily dispersed, and when left for 2 days, it separated into two layers as shown in Table 2. While the lower layer of the dispersion produced a transparent and flexible film, the upper layer of the dispersion produced cracks during film formation and a good film could not be obtained.

[Table] For comparison, the purified imogolite gel was dispersed and formed into a film under the same conditions except that the heating extraction operation with an acetic acid aqueous solution was omitted. The dispersion was milky, had a low ηsp/c of 3.7, and no separation into two layers was observed even after being left for one month. The molded film was also brittle. Example 4 Outputting only the ultrasonic dispersion conditions in Example 1
I changed it to 20W, 10 minutes and dispersed it. Although the dispersibility decreased considerably, when the dispersion was left for one week, it separated into two layers, and as shown in Table 3, an improvement in ηsp/c was observed. The formed film had better flexibility in the lower layer of the dispersion, and a film that did not break even when bent several times was obtained.

[Table] Example 5 The imogolite gel of the Soxhlet extraction residue obtained in Example 1 was dissolved in an acetic acid aqueous solution (PH3.5) using a Branson ultrasonic dispersion device type 350 (oscillation frequency
20KHz), Output Control5, Duty
Dispersion was performed for 5 minutes at Cycle 50%. When the dispersion was allowed to stand for one week, it separated into two layers, with the upper layer being slightly milky and the lower layer being transparent. ηsp/c
As shown in Table 4, an improvement was observed compared to Example 1, and the molded film also had a high transparent bending strength of about 15μ when the dispersion lower layer was used, and even after repeated bending five times. A film that did not break was obtained.

[Table] Example 6 A film was formed using the dispersion lower layer of Example 5, and instead of a polyester film coated with a release agent, a Teflon plate, a polycarbonate plate, a polyester plate, an acrylic resin plate, and a glass plate were used. , was conducted on a stainless steel plate. Teflon film has the highest peeling resistance, followed by polyester film coated with a release agent, followed by polyester film,
No difference was observed between polycarbonate and acrylic resin. Example 7 Instead of the acetic acid aqueous solution of Example 1
Soxhlet extraction and dispersion were performed using a CF ₃ COOH acidic aqueous solution (PH3.0) (however, the dispersion conditions were the same as in Example 5). The amount of undispersed matter was smaller than that in the case of acetic acid acidic aqueous solution, and an improvement in dispersibility was observed. The dispersion was transparent and separated into two layers after standing for one week, yielding a dispersion with a high ηsp/c as shown in Table 5. The molded film is approximately 10μ
The film was transparent and did not break even after being repeatedly folded five times.

[Table] Example 8 In Example 1, a monochloroacetic acid aqueous solution (PH3.3) was used as the dispersion liquid, and the ultrasonic dispersion conditions were output.
I changed it to 40W and 6 minutes to disperse it. Although the dispersibility decreased somewhat, when the dispersion was allowed to stand for one week, it separated into two layers, and as shown in Table 6, an improvement in ηsp/c was observed. The formed film had better flexibility in the lower layer of the dispersion, and a film that did not break even when bent was obtained. Furthermore, as shown in Table 6, the results of measuring tensile strength and Young's modulus using a tensile tester were better in the dispersion lower layer having a larger ηsp/c.

[Table] Example 9 Dispersion was carried out in the same manner as in Example 5 except that an acidic aqueous solution of nitric acid (PH3.2) was used as the dispersion liquid. The amount of undispersed matter was somewhat larger than in Example 5, and a decrease in dispersibility was observed. The dispersion was transparent and separated into two layers when left for two weeks, with ηsp/c as shown in Table 7.
A dispersion liquid with a high Further, in the molded film, as in Example 5, the lower layer of the dispersion had better flexibility. Similar results were obtained with hydrochloric acid and perchloric acid aqueous solutions as with nitric acid aqueous solutions.

[Table] Example 10 0.3 g of glass fiber cut into 3 mm pieces was added to 200 ml of the lower layer of the dispersion of Example 2, and aqueous ammonia was added to adjust the pH to 8 to form a gel, followed by thorough mixing using a mixer. When poured onto a Teflon plate and dried at room temperature, a film with high bending strength was obtained. Comparative Example 3 Imogolite was used in Example 3 of JP-A-55-10498.
It was synthesized using the method of That is, 15 mmol of AL(OC ₄ H ₉ ) ₃ is added to Si
(OC ₂ H ₅ ) ₄ mixed with 7.5 mmol and this mixture 75
The mixture was poured into 100 ml of millimolar HClO ₄ with vigorous stirring and stirred overnight until the milky white color disappeared.
After removing solids by centrifugation, Al concentration
The Si concentration was diluted to 40 mmol and the Si concentration was 20 mmol, and the mixture was reacted for 4 days under heating and reflux. The reaction solution was concentrated to about 1/3 using a rotary evaporator, and then transferred to a high-speed centrifuge (16,000 rpm, 30
After removing the precipitate for 2 minutes), the mixture was dialyzed for 2 days using a cellulose dialysis membrane while running water. A gel was produced by dialysis, and the pH after dialysis was 7.6. The resulting gel was sedimented by centrifugation, and the pH was adjusted with an acetic acid aqueous solution.
3.5 to disperse the gel. The dispersion obtained in this way has ηsp/c of 1.2
The film formed under the same conditions as in Example 1 cracked during film formation, and a good film could not be obtained.

Claims (1)

[Claims] 1. Imogolite with a relatively high degree of polymerization obtained by treating imogolite with an acidic aqueous solution and extracting and removing imogolite with a relatively low degree of polymerization is dispersed in acidic water to form a dispersion liquid, and this is separated into two layers. A method for producing imogolite with a high degree of polymerization, which consists of subsequently collecting the transparent layer (lower layer).