GB1571983A

GB1571983A - Sol of ultra-fine particles of layered structure material

Info

Publication number: GB1571983A
Application number: GB598276A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-05-16
Filing date: 1977-05-16
Publication date: 1980-07-23

Description

(54) SOL OF ULTRA-FINE PARTICLES OF LAYERED STRUCTURE MATERIAL (71) I, MOTOYUKI IMAI, a Japanese national of 7-7-905, Hiroo 1-chome, Shibuyaku, Tokyo, Japan, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a sol of particles of layered structure material, the said particles having been made hydrophobic by treatment with defined organic materials, and further relates to a heat-resistant, water-resistant and electrically insulating article prepared from such a sol.

A layered structure silicate material such as naturally occurring montmorillonite, or natural or synthetic hectorite, tetra-silicic mica or taeniolite has a unique property that it is swollen and cleaved by hydration to form a stable sol. A sol, being a fluid colloidal system, has the solid particles in the state of ultra-fine particle, and these sols of layered structure materials are remarkably active chemically. This activity is due to the inherent properties of ultra-fine particles cloven to a size close to molecular size, and to the electro-chemical properties of ultra-fine particle crystals.

The above mentioned layered structure minerals generally have a crystal structure having a three-layered lattice as a unit, which comprises two SiO4 tetrahedral layers disposed at the upper and lower parts of the lattice and one octahedral layer composed of six anions 4(0)2(OH) or 4(0)2(F) disposed between the two tetrahedral layers.

Pyrophyllite has a structure wherein two thirds of the openings in the octahedral layer of the three-layered lattice is occupied by aluminium atoms and is electrically equilibrated.

In the pyrophyllite structure, when a part of the aluminium atoms of the octahedral layer are replaced by magnesium atoms and a part of the silicon atoms of the SiO4 tetrahedral layer are replaced by aluminium atoms, negative electrical charges in the three-layered lattice become free. Naturally occurring montmorillonite, Wij3(X,Y++) (Si4O10)(OH)2 (W = Na; X = Fe, Al, Mn; Y = Mg) has a crystal structure wherein Ca- or Na enters and is co-ordinated between adjacent layers of the three-layered lattice to electrically neutralize the negative electrical charges formed as described above.

Tetra-silicic mica can be artificially synthesized by replacing OH of water of crystallization with F, and can be represented by the formula NaMg2~lX2 (Si40l(,)F2 or Ca1;2Mg21,2(Si4Ot)F2 (2.5-octahedral type) wherein all of the aluminium atoms of the octahedral layer are replaced with magnesium.

Taeniolite can be represented by the formula NaMg2Li(Si4O11)F2 or Ca1,2Mg2Li- (Si40,0)F2 or LiMg2Li(Si40",)Fr (3-octahedral type) wherein all of the aluminium atoms of the octahedral layer are replaced with magnesium and lithium atoms.

Synthetic montmorillonite is similarly prepared by replacing OH of water of crystallization with F, and can be represented by the formula, NaMg2213Li1-(Si4O10)F2.

Hectorite can be represented by the formula, Na1/3M2-2/3Li1/3(Si4O10)F2 or Lil,3Mg2~2, 3Li "3-(Si40 1 (j)F2 These layered structure materials are all classified as a three-layered structure mineral, and have the common properties that the bond between layers is weak and that alkali metal ions co-ordinated between the layers are very easily hydrated. Due to these properties, these layered structure materials are easily swollen and cloven to produce sols containing ultra-fine particles by introducing a large amount of water of hydration between the layers.

The strength of this tendency is in the following order; synthetic taeniolite < synthetic tetra-silica mica < naturally occurring montmorillonite < synthetic hectorite. The bonds in the particles of the structure material is strong in a direction parallel the layer, but between the layers is very weak. Accordingly, the shape of the cloven ultra-fine particles is flake-like. The cloven ultra-fine particles have a size close to molecular size, i.e. a thickness of 10 - 50 A and a particle diameter (disk diameter) 100 to 1,000 times as large as the thickness. The ultra-fine particles in the sol have an extremely large surface area, i.e. about l()() m2/g.Consequently, the ultra-fine particles in the sol have a very high chemical activity synergetically accelerated by the electro-chemical properties of the crystals of the ultra-fine particles.

The ultra-fine particles have negative electrical charges on their surfaces, and conequently these particles in water are charged with negative electricity. Due to the electrical repulsion between the particles, they disperse uniformly in a solvent to form a stable sol.

The ultra-fine particles of these layered structure materials can be formed into an article having excellent electrical insulation properties by treating the alkaline ions of the particles.

The particle thus formed also has an excellent heat-resistance since it is made from inorganic material. A notable feature of the particles of these layered structures is that the particles are bonded to each other without using any binder by the action of Van der Waals molecular cohesion forces by evaporating and drying the sol thereby forming a film which is very flexible and has a high tensile strength. Thus, the sol of ultra-fine particles of these layered structure materials can be used to prepare a film, cloth or other sheet-like materials having excellent heat-resistance and electrical insulation properties. However, the article prepared in accordance with conventional techniques has disadvantages in that it still has a porosity of 10 - 15 C/c and that its tear strength is low.Moreover, it has the disadvantage that it is hygroscopic and absorbs water.

According to the present invention, these undesired properties, particularly rehydration are reduced or removed. Water is bonded as a polar water molecule with negative electrical charges on the oxygen in the crystal structure of a layered structure material in the manner of hydrogen bonds. and forms a water molecule layer. Since oxygen molecules on the surface of the layered structure material are oriented in the form of a hexagonal reticulated plane. the water molecules are also oriented just above or below the oxygen molecules in the form of hexagonal reticulated layers arranged in parallel. This water is generally referred to as "water between layers" or "rigid water molecule layer".

This water molecule layer can form a further water molecule layer on its exterior depending on the bond strength between layers and hydration energy. The tendency of the ions between the layers to form more water molecule layers is in the order, Ca < Na < Li.

The weaker is the bond strength between layers, the more water molecule layers are wormed. That is, the number of water molecule layers increased in the order, synethetic taeniolite < synthetic tetra-silicic mica < naturally occurring montmorillonite < synthetic hectorite.

Sols (or gels) of the above mentioned layered structure material are very hydrophillic colloids since the layered structure material has a very high reactivity and the colloid is formed bv the reaction of the layered structure material with water. The electrical properties of a product obtained from the sol of the layered structure material is poor due to this hvdrophillic property. In order to overcome this disadvantage, the water molecule layers should be removed from the layered structure material if it is to be used for industrial uses.

For this purpose, ions have high hydration energies, for example Li, Na, or Ca should be removed from between the layers. The removal of such ions from between layers can be done by chemical treatment by the addition of an electrolyte or by electrical treatment by hydrolysis. By these techniques, the above mentioned hydratable ions between the layers are ion-exchanged with cations such as K+, NHI, Pb2+, Zn2, Sn2+, Boa2+, So2+, A13+, Sub2+* or Bi2+. However, even after ion-exchanging, mono-hydrate water will still remain.

An object of this invention is to provide a sol of layered structure materials rendered hydrophobic, which can be used to prepare various molded articles having excellent heat-resistance, water resistance and electrical insulating properties.

Another object of this invention is to provide a molded product prepared by combining the sol of this invention with organic material, which has improved heat-resistance, water resistance and electrical insulating properties as well as physical strength.

The bonding mechanism of the layered structure material with organic material according to this invention is quite different from the conventional bonding mechanism of an aggregate with a binding agent. That is, the bonding in accordance with this invention is supported by chemical reaction, while the bonding in accordance with conventional techniques is made by a simple mixing system.

Heretofore, it was known to react layered structure materials such as naturally occurring montmorillonite or hydrated halloysite with organic materials such as glycols or amines.

However, the organic materials used in the conventional techniques were all hydrophillic and polar. Consequently, a product prepared using the conventional sol was easily re-hydrated and is not suitable for a practical use.

Reactions between layered structure materials and organic treating agents are classified into two types of reactions, that is, "solvation reactions" and "base-exchange reactions".

The "solvation reaction" is carried out by reacting the hydrogen atom of a hydroxyl group of an organic treating agent with negative-charged oxygen atom co-ordinated between layers of the layered structure material having alkali metal ions between the layers ion-exchanged with other cations. Thus, the basic radical of the organic treating agent is introduced between the upper and lower layer lattices of the layered structure material and is regularly co-ordinated between them. The above reaction takes place due to the fact that the bond between the negative-charged oxygen layer and the layer of the layered structure material is weak. The negative-charged oxygen layer is positioned on both upper and lower sides of the layer of the layered structure material.The organic treating agent used is a compound having high dielectric constant, the molecule of which can be wholly introduced between the layers. Compounds which are polar or which can form hydrogen bonds can be easily introduced between the layers.

Organic treating agents used in the solvation reaction in accordance with this invention include titanic acid esters; zirconic acid esters; silanes having at least one methoxy-, ethoxyand silanol-radical and at leat one of vinyl-, epoxy-, acrylic- or amino-radical; and ss-diketones mixed with lauryl amine. These treating agents are introduced between the layers of the layered structure material in which ions between the layers were ion-exchanged with cations, and form co-ordinate bonds. In this manner, a sol of the layered structure material is rendered hydrophobic, and a dry product prepared therefrom has excellent heat-resistance and electrical insulating properties.

In the present invention, titanic acid ester or zirconic acid ester is hydrolyzed in water to form very fine particles of TiO2 or ZrO2. These very fine particles are positively charged in water, and enter between the layers to neutralize the negative charges. When a composite is prepared using synthetic resin and a sol of the layered structure material rendered hydrophobic by treatment with a silane, the methoxy-, ethoxy- or silanol-radical of the silane undergoes a condensation reaction with the oxygen of the layered structure material, while the vinyl epoxy- or amino-radical of the silane reacts with the synthetic resin and accelerates the cross-linking reaction of the resin thereby strengthening the bond between the layered structure material and the synthetic resin and improving the adhesive strength.

In the reaction between layered structure materials and ss-diketones (e.g. acetyl acetone) mixed with lauryl amine, the ss-diketone is easily introduced between the layers of the layered structure material due to the polarity of the amine, thus making a chelate bond between the layers. For example. the enol-form of acetyl acetone may react with A13+ ions to form aluminium acetyl acetonate, and lauryl amine is also co-ordinated between the layers, thereby substantially completely rendering hydrophobic the layered structure material due to combined action of the two compounds.

The "base-exchange reaction" takes place in a more intensive manner than the solvation reaction. The characteristic of this reaction is that ion-exchange of alkali metal ions located between the layers is conducted simultaneously with the reaction.

If a solution of a polar organic compound is added to a sol of untreated layered structure material having alkali metal ions co-ordinated between the layers, the polar organic compound is introduced between the layers to form a co-ordinate bond. That is, alkali metal ions such as Cm2+, Nave, or Li+ are exchanged with the organic compound, and a co-ordinate bond is formed between the layers. Thus, ions between the layers and water between the layers are both replaced at the same time, and accordingly the base-exchange reaction is more efficient than the solvation reaction. The organic materials which are used in the base-exchange reaction in accordance with this invention are metal chelate type titanium amide or zirconium amide or a cationized silicone oil, which are hydrophobic.

The advantages of the sol of the layered structure material of this invention are as follows: A product prepared by using the sol of the layered structure material of this invention is resistant to rehydration.

Layered structure material used in this invention is swollen by hydration and is cleft to produce a stable sol of ultra-fine particles. The ultra-fine particles of the hydrated layered structure material used in this invention exhibit various useful properties in that they can be electro-chemicallv cation-exchanged; they can uniformly be dispersed in organic vehicles; they can be formed into film-like products by drying; they can be used to increase the viscosity of oil and fat material; they can be adhesive; and in that they can be used as a heat-resistant material.However, the ultra-fine particles of the layered structure material provide a dry product which forms a water layer between the lattice layers due to the bonding action of the negative-charged oxygen atoms on the surfaces of the particles with water molecules even after alkali metal ions between the layers have been ion-exchanged with other cations. Since alkali metal ions are not present, the hydration of the product does not extend to cleavage but merely results in a water layer being formed between the lattice layers. However the water layer thus formed, causes the electrical insulating properties of the product to be inferior.That is, due to the dipolar action of the hydrogen bonded water molecules derived from the polar water molecules, the electrical insulating properties deteriorate; the volume insulation resistance is 105 - 107 ohm and the dielectric strength is less than 1,000 V/0.1 mm. These values do not reach the standard values required of electrical insulators, i.e. a volume insulation resistance of higher than 10l2 ohm and a dielectric strength of higher than 1,200 V/0.1 mm.

According to the present invention, the water molecules between the layers which cause deterioration of the electrical insulating properties are replaced by an organic compound and the negative-charged oxygen is bonded to the organic material. Consequently, since water molecules are not introduced, the electrical insulating properties of the thus treated material are remarkably improved. That is, the volume insulation resistance of a product prepared using the sol of the layered structure material of this invention is more than 10l2 ohm and the dielectric strength is at least 3,000 V/0. 1 mm. These values remain constant in use. When a hydrophobic silicone type organic material is used as a treating agent. the dry product provides water repellency.The heat-resistance of a product prepared by using the sol of the layered structure material of this invention is also remarkably improved.

In the case of the conventional composite of inorganic material with organic material, the heat-resistance is improved to some extent in proportion to the amount of inorganic material present, but the organic material deteriorates at the inherent temperature limit of the organic material with respect of heat-resistance.

However, in the case of a composite of the layered structure material rendered hydrophobic with organic material (e.g. synthetic resin) prepared in accordance with this invention, the organic material present not only between the layers of the layered structure material but also between the flake-like particles of the layered structure material make co-ordinate bonds, and consequently the temperature limit of deterioration of the organic material is raised thereby improving the heat-resistance of the composite.

For example, cationized silicone oil modified with higher alcohols containing an amino radical usually deteriorates at about 1800C, but when it is introduced between layers of lithium hectorite by the ' the base-exchange reaction", it deteriorates at about 350"C. When acetyl acetone mixed with lauryl amine is used as an agent for rendering the material hydrophobic, and is introduced between the layers of barium hectorite Ba"3Mg2~2,3Li"3 (Si4O1())F2 by "the solvation reaction", it deteriorates at about 280"C although it inherently deteriorates at 1400C.

Hydrophillic sols of the layered structure materials can be converted to hydrophobic sols having lipophilic properties by reacting them with organic material in accordance with this invention.

The organic material used to render the materials hydrophobic must be carefully selected. For example, saturated hydrocarbons, unsaturated hydrocarbons and halides are generally useful to render materials hydrophobic but they are not effective to remove water molecules from between the layers of layered structure materials. Therefore, organic materials used in the treatment to render materials hydrophobic in accordance with this invention should be the materials as specified in the claims. They may be modified by incorporating a cationized amine or may be used in combination with an amine compound, in order to increase their polarity and water solubility.

When a solution of the above-mentioned organic material is added to a hydrated sol of the layered structure materials. the mixture forms a gel-like or flocculent cohered material although the form of the cohered material varies slightly depending on the activity of the organic material and the viscosity of the layered structure material used. This gel is filtered by press or suction filtration or heated to remove water to such an extent that only a small amount of water remains in the cohered material. The cohered material is then washed with a higher alcohol such as butanol or fractionated to remove the water in the presence of an organic solvent such as xylol having a higher boiling point than water. The washed cohered material is dispersed again in an oily solution to form a stable suspension. The lipophilic sol thus obtained can be used to prepare a paint having excellent heat-resistance by mixing it with at least one of the solvent type synthetic resins such as epoxy, polyester, acrylic, styrene. fluoroplastic, silicone and urethane resins and at least one of the water soluble type synthetic resins such as phenol, vinyl and melamine resins. The lipophilic sol of this invention can further be used as a thickening agent for oil and fat materials.

The heat-resistance of the paint prepared in this manner is much better than that of conventional heat-resistant paint. For instance, conventional heat-resistant paint such as silicone type paint is flame-retardant but is gradually decomposed and peeled off when contacted by a flame. However, a paint prepared by mixing the hydrophobic sol of this invention with a solvent type resin (e.g. epoxy-modified silicone resin) or a water soluble type resin (e.g. malamine resin) is not blistered nor peeled off when contacted by a flame because flakes of the layered structure material are overlapped in parallel to form fire-resistant layers. Since the organic material is sealed by the flakes of the layered structure material, it is merely carbonized between the flakes. The carbonized material remains between the flakes of the layered structure material and is not burnt.As mentioned above, a paint prepared by using the sol of this invention provides excellent fire-resistance and heat-resistance properties.

When a silane type coupling agent is used in "the solvation type" hydrophobing reaction, it is very effective to strongly unite the layered structure material with synthetic resins such as epoxy, vinyl, acrylic, polyester, melamine, urea, polyethylene, phenol, or polypropylene resins.

The amount of organic treating agent used to render hydrophobic the layered structure materials in accordance with this invention is generally 10 - 50% by weight (on the basis of the total amount of layered structure material and organic treating agent), and preferably 20 - 30% by weight. The amount of synthetic resin mixed with the layered structure material is generally 2 - 80% by weight (on the basis of the total amount of layered structure material and resin) and preferably 30 - 60% by weight.

The invention may be put into practice in various ways and some specific embodiments will be described to illustrate the invention with reference to the following examples, in which all parts and percentages are by weight.

EXAMPLE 1 Sols of layered structure materials were prepared in the following manner: Preparation of Sol No. 1 Tetra-silicic mica having the formula NaMg2 5(Si4010)F2 was immersed in 100 times its weight of water and stirred. The mica was rapidly swollen and cleft to form a stable sol containing ultra-fine particles in water. The sol thus formed was concentrated to 2% solids by heating.

The sol was then subjected to an ion-exchange treatment by mixing the sol with an ion-exchange solution containing KC1 in an amount of two times the weight of the mica content of the sol. The ion-exchange was carried out according to the following equation.

NaMg25(Si40,(,)F2(Sol-like) + KC1 < KMg2.5(Si4O10)F2 + Na+ + Cl The ion-exchange sol was then washed to remove sodium ions.

Preparation of Sol No. 2 Synthetic hectorite having the formula, Na1,3MG 8,3LI"3)SI40,(,)F2 was immersed in water and stirred, and then concentrated to prepare a 2% solids sol in the same manner as in the preparation of Sol No. 1.

The sol was then subjected to an ion-exchange treatment in the same manner as in the ion-exchange of Sol No. 1. The ion-exchange of Sol No. 2 can be represented by the following equation.

Na"3Mg 8,3Lil,(Si40l")F2 + KC1 < K1,3Mg 3Li113-(Si4O10)F2 + Na+ + Cl The treating agent used to render hydrophobic the layered structure material was a 5% ethyl alcohol solution of aminoethyl modified silane coupling agent (H2N(CH2)2 NH(CH2)3Si(OCH3)2CH3).

300 cc of the ethyl alcohol solution of the aminoethyl modified silane coupling agent was mixed with 300 cc of the above prepared Sol No. 1 to carry out the solvation reaction and to form a jelly-like cohered material in the liquor.

The jelly-like material was filtered by a suction filter, and the filter cake was washed with 200 cc of butyl alcohol. The washed material was dried to obtain 95% solid material. The dried material was mixed with 50 cc of xylene, and was dispersed again by means of ultrasonic waves (28 KHz). To this dispersion was added 2() g of epoxy resin (400 cps) diluted with xylene. and the mixture was coated on a substrate made of Teflon (R.T.M.).

The coated film was then dried at 30 - 40"C for 10 hours, and was heated at 1800C for 2 hours to complete polymerization and curing. The film thus obtained had a size of 0.1 x 300 x 300 mm.

EXAMPLE 2 Sol No. 2 was treated in exactly the same manner as Sol No. 1 in Example 1.

EXAMPLES 3 AND 4 In order to substantiate the effect of the treatment to render the material hydrophobic similar films were prepared without conducting the treatment to render the material hydrophobic with the silane solution, and the films were compared with the films of Examples l and 2 with respect to physical and electrical properties. Thus. Sol No. 1 (Example 3) and Sol No. 2 Example 4) were filtered respectively by a suction filter, and the filter cakes were fully washed with butyl alcohol. The washed material was dried at 12()GC tor 2 hours to obtain (98 /r solid material.The dried material was mixed with xylene to disperse it once again after which it was mixed with epoxy resin to obtain a film of t). I x 300 x 3(J() mm in the same manner as described above in Example 1.

The above prepared films of the present invention and the comparative films were allowed to stand in an atmosphere of 95% RH for 14 hours, and were checked with respect to moisture content absorbed and electrical insulation.

The film of Example I had an absorbed moisture content of 0.2%. and volume insulation resistance of X x 1015 ohm. The film of Example 2 had an absorbed moisture content of ().l 'Xc and volume insulation resistance of is x 1015 ohm. The comparative film of Example 3 had an absorbed mositure content of 1.,2s and volume insulation resistance of 5 x 1015 ohm. The comparative film of Example 4 had an absorbed moisture content of 2.3'4 and volume insulation resistance of 7 x l(Jx ohm.

EXAMPLE 5 preparation qf Sol No. 3 Synthetic sodium taeniolite having the formula. NaMg2Li(S4O10)F2 was immersed in water and stirred. and then concentrated to prepare a 2% solids sol in the same manner as - in the preparation of Sol No. l.

The following silicone compound solution was prepared as a treating agent to render the layered structure material hydrophobic. First, silicone oil was cationized by introducing amino radicals into a methyl silicone molecule. and the cationized silicone oil was then dissolved in isopropyl alcohol. The cationized silicone oil solution was diluted with ethyl alcohol to prepare a 5(4) solution.

The cationized silicone oil used in this invention is a water soluble oil which is a silane compound having amine bonded in its molecule.

For example: (a) imino alkoxy silicane (KBM-6()3 manufactured by Shinetsu Kagaku K.K.)

H2N(CH2)2NH(CH2)3. Si(OCH3)3 (nonionic state) t addition of inorganic acid such as HCI o o H2N (CH2)2NH(CH2) ,.Si(OCH 4 ) (cationized state) H H (b) cationized water soluble silicone oil (KF 858 manufactured by Shinetsu Kagaku K.K.)

Thus. an amino-nitrogen atom bonded to carbon is easily cationized in the presence of acid.

200 cc of Sol No. 3 was mixed with 30 cc of the above prepared silicone oil solution by stirring. After stirring the mixture for 20 minutes, cohered jelly-like material was obtained.

The cohered material was then filtered by a suction filter, and the filter cake was washed until no alkali metal ions were found in the washed solution. The washed material was further washed with 200 cc of isopropyl alcohol. and a 7% solids solution containing the cohered material was prepared by adding isopropyl alcohol. The cohered material was then -dispersed again by means of ultrasonic waves (28 KHz) to prepare a uniform sol or colloidal solution.

The colloidal solution was then cast in a mold made of polyethylene to produce a film of 3 x '()() x r()U mm. The film was dried in a drier at 40 - 50 C for 4 hours, and then further dried at 120 C for I hour and 2000C for 2 hours to finally obtain a dry film having a thickness of 0.04 mm.

EXAMPLE 6 Preparation of Sol No. 4 Synthetic lithium hectorite having the formula, Li113Mg 8/3Li1/3(Si4O 1())F2 was immersed in water and stirred, and then concentrated to prepare a 2 solids sol in the same manner as in the preparation of Sol No. 1.

20 cc of Sol No. 4 was mixed with 40 cc of the same silicone oil solution as used in Example 5 by stirring.

The procedure was then identical to Example 5.

The above prepared two films of Examples 5 and 6 were allowed to stand in an atmosphere of 90% RH for 10 hours, after which they were checked with respect to absorbed moisture content and electrical insulation. The absorbed moisture contents of the films were both less than ().3n/(. and the dielectric strengths of the films were both more than 4.000 V/().1 mm, and the volume insulation resistances of the films were both more than 10 x 10l4 ohm. These electrical properties were maintained up to 2200C.

EXAMPLES 7 AND 8 Sol No. 3 used in Example 5 was rendered hydrophobic by means of the following two kinds of organic material.

(a) 2% ethyl alcohol solution of chelate type titanium amide (Example 7) (b) 2% ethyl alcohol solution of chelate type zirconium amide (Example 8). 300 cc portions of Sol No. 3 were separately mixed with 30 cc of each of the above treating agents (a) and (b). After stirring the mixtures for 20 minutes, cohered material was obtained. The cohered materials were filtered by a suction filter. The filter cakes had a water content of 70%. The filter cakes were then washed with distilled water until no alkali metal ions were found in the washed solution. The filter cakes were further washed with 100 cc of butyl alcohol. and solutions containing the cohered material as a solid content in an amount of 10% were prepared by adding ethyl alcohol.The cohered materials were then uniformly dispersed again by means of ultrasonic waves (28 KHz) in the same manner as described above in Example 1. The dispersions were then coated on a substrate made of polyethylene to prepare films having a thickness of 3 mm. The coated films were dried in a drier at 30 50"C for 5 hours, at 100 - 1200C for 1 hour and at 2000C for 2 hours to prepare dry films of 0.05 x 250 x 250 mm.

EXAMPLES 9 AND 10 Examples 7 and 8 were repeated using Sol No. 4 of Example 6.

The films of Examples 7, 8. 9 and 10 were allowed to stand in an atmosphere of 90% RH for 24 hours, and were checked with respect to absorbed moisture content and electrical insulation. The results are as shown in following table.

TABLE Example Water % Volume Dielectric absorption insulation strength resistance (ohm) (Kv/0.1 mm) 7 0.1 8 x 10l4 4.5 8 0.2 7 x 10'4 4.5 9 0.3 7 x 10t4 3.2 10 0.4 7 x 10l4 2.8 EXAMPLE 11 A sol of layered structure material was prepared in the following manner: Preparation of Sol No. 5 Synthetic sodium taeniolite having the formula, NaMg2Li(Si4O1)F2 was immersed in water and stirred. and then concentrated to prepare a 2% solids sol in the same manner as in the preparation of Sol No. 1.

The sol was then subjected to an ion-exchange treatment with an aqueous solution of aluminium trichloride in an amout of two times the weight of the mica content of the sol.

The ion-exchange was carried out according to the following equation.

NaMg2Li(Si4O1,1)F2 + 1/3AlCl~AI, AMg2Li(Si4O,(,)F2 + Na+ + C1 The resulting hydrated sol contained aluminium taeniolite having the formula, Al, zMg2Li(Si401(,)F. in an amount of 13.7% (solids content).

The aluminium taeniolite was prepared by exchanging ions between layers of synthetic taeniolite with aluminium.

1 .000 cc of Sol No. 5 was mixed with 400 cc of enol-type acetylacetone and then 500 cc of xylene solution containing 1% of lauryl amine (C12H25NH2). After stirring the mixture with a glass rod for about 20 minutes. gel-like cohered material was obtained in the liquor. The gel-like cohered material was then filtered. and the filtered cohered material was squeezed using a filter cloth to remove water. The cohered material was then put into a fractional distillation apparatus. and xylol was added to the apparatus and heated to fractionate the water. When the temperature of tlle apparatus had risen above 100"C, the cohered sol was taken out of the apparatus.

1 part of the solid component of the cohered sol thus prepared was mixed with 5 parts of epoxy-modified silicone resin (epoxy resin 3068Ze). The mixture was diluted with xvlene to prepare a paint having a solids content of 20%. The paint was then coated on a degreased tin plate. and was dried at 5()0C for I hour and further heated at 2000C for 1 hour to obtain a dry film having a thickness of 20 microns on the tin plate.

EXAMPLE 12 For the purpose of comparison. epoxy-modified silicone resin paint not containing the sol of this invention was coated on a degreased tin plate in the same manner as above thereby obtaining a comparative film having a thickness of 20 microns on the tin plate.

The two plates were heated at 350"C. and the appearance of the films was checked. The film of Example 11 showed no change even after heating for 30 minutes. while the comparative film of Example 12 was blistered.

The purpose of the treatment to render the materials hydrophobic is: to free the layered structure material of water; to make the layered structure material more resistant to absorption of water; to prevent the layered structure material from being rehydrated with water; and to make the layered structure material have affinity with organic material to ensure the firm bonding between the layered structure material and organic material when a composite of the two is prepared.

WHAT WE CLAIM IS: 1. A sol of particles comprising montmorillonite. or natural or synthetic hectorite, tetrasilicic mica or taeniolite, the said particles having been made hydrophobic by treatment with a titanic acid ester; a zirconic acid ester; a silane having at least one methoxy-. ethoxyor silanol-radical and at least one vinyl-, epoxy-. acrylic- or amino-radical: a ss-diketone mixed with laurvl amine; a titanium amide; a zirconium amide; our a cationized silicone oil.

'. A sol as claimed in Claim 1 substantially as specifically described herein with reference to anv one of Examples 1. 2 or 5 to 11.

3. A mixture of a sol as claimed in Claim 1 or Claim 2 and a synthetic resin.

A. A method of making a heat-resistant electrically insulating layer which comprises dispersing montmorillonite, or natural or synthetic hectorite, tetra-silicic mica, or taeniolite in water wherebv the said materials are swollen and cleaved into a sol. mixing this sol with a solution in an organic solvent of a zirconic acid ester. a titanic acid ester. a silane having at least one methoxv-. ethoxy- or silanol-radical and at least one vinyl. epoxy-. acrylic-. or amino-radical, a ss-diketone mixed with lauryl amine, a titanium amide. a zirconium amide or a cationized silicone oil. separating the cohered material formed thereby. washing it with an organic solvent. drying the material to at least 9550 solids, dispersing the solid as a solution in an organic solvent. forming the mixture into a layer and removing the sois ent or blending the said mixture with a solution of a resin in the same organic solvent, forming the blend into a layer and removing the solvent.

5. A method as claimed in Claim 4 substantially as specifically described herein with reference to anv one of Examples 1. 2. 5. 6. 7. 8. 9, 10 or 11.

6. A heat resistant electrically insulating layer whenever made by a method as claimed in Claim 4 or Claim 5.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. The resulting hydrated sol contained aluminium taeniolite having the formula, Al, zMg2Li(Si401(,)F. in an amount of 13.7% (solids content). The aluminium taeniolite was prepared by exchanging ions between layers of synthetic taeniolite with aluminium. 1 .000 cc of Sol No. 5 was mixed with 400 cc of enol-type acetylacetone and then 500 cc of xylene solution containing 1% of lauryl amine (C12H25NH2). After stirring the mixture with a glass rod for about 20 minutes. gel-like cohered material was obtained in the liquor. The gel-like cohered material was then filtered. and the filtered cohered material was squeezed using a filter cloth to remove water. The cohered material was then put into a fractional distillation apparatus. and xylol was added to the apparatus and heated to fractionate the water. When the temperature of tlle apparatus had risen above 100"C, the cohered sol was taken out of the apparatus.

'. A sol as claimed in Claim 1 substantially as specifically described herein with reference to anv one of Examples 1.

2 or 5 to 11.

3. A mixture of a sol as claimed in Claim 1 or Claim 2 and a synthetic resin.