JPH09157096A - Surface-coated whisker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain surface-coated whiskers having a large specific surface area, excellent in dispersibility in a synthetic resin and producing a high reinforcing effect by coating the surfaces of whiskers with hyperfine particles of a metal oxide and/or a metal hydroxide. SOLUTION: Compds. as starting materials for producing whiskers such as potassium titanate whiskers, e.g. TiO2 and K2 CO3 , are mixed and heated to about 900-1,100 deg.C to form an aggregate of false fibers. This aggregate is disintegrated by immersion in water, a water-soluble metallic salt such as NaAlO2 or an aq. soln. of the salt is added to the resultant slurry and this slurry is neutralized by adding an acid such as hydrochloric acid or an alkali such as NaOH. The false fibers are then separated by filtration, dried and fired to obtain the objective whiskers surface-coated with hyperfine particles of a metal oxide and/or a metal hydroxide having nm unit or below.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to surface-coated whiskers.

The surface-coated whiskers of the present invention have extremely preferable properties such as an increased specific surface area, excellent dispersibility in a matrix such as a synthetic resin, and a high reinforcing effect as compared with untreated whiskers.

Among the surface-coated whiskers of the present invention, those coated with ultrafine particles of metal oxides or metal hydroxides other than titanium dioxide have good weather resistance,
It has the excellent property that it is difficult to decompose even when it is exposed to ultraviolet rays.

Among the surface-coated whiskers of the present invention, the surface-coated potassium titanate whiskers have the characteristic of not releasing potassium, in addition to the above-mentioned preferable characteristics.

[0005]

The alkali metal titanate whiskers have the general formula M ₂ O.mTiO ₂ .nH ₂ O.
(In the formula, M represents an alkali metal, m represents an integer of 1 to 10, and n represents an integer of 0 or 1 to 10.), and has a fiber diameter of 0.1 to 1 It is a whisker of about 0.0 μm and a fiber length of about 5 to 50 μm. Specifically, potassium titanate whiskers, sodium titanate whiskers, lithium titanate whiskers, etc. are known, and among these, potassium titanate whiskers are commonly used. There is.

[0006] Potassium titanate whiskers are mainly used as a reinforcing material for synthetic resins and paints, a material for engine oil filters, and the like. The synthetic resin containing the whiskers is widely used by being molded into brake pads for passenger cars, keyboard parts for OA equipment, gears for watches and the like. Potassium titanate whiskers have good properties in various applications, but there is still room for improvement. For example, since the dispersibility in the synthetic resin is rather poor and it is difficult to increase the addition amount, the reinforcing effect tends to be insufficiently exhibited. Further, since potassium titanate whiskers release potassium, it is common to perform surface treatment with a silane coupling agent or the like in order to use it as a reinforcing material for synthetic resins that are susceptible to decomposition by potassium such as polycarbonate resins. However, it is unavoidable that potassium elutes. Further, when the synthetic resin containing potassium titanate whiskers is exposed to ultraviolet rays, the TiO in the whiskers is increased.
₂ may be decomposed to release active oxygen, which may oxidize and deteriorate a matrix such as a synthetic resin.

On the other hand, it has been conventionally practiced to coat the surface of the potassium titanate whiskers with a conductive substance such as a conductive metal or a carbonaceous substance in order to impart conductivity. For example, in Japanese Examined Patent Publication No. 5-22648, an aqueous solution of a metal compound containing a conductive metal such as tin, indium, antimony, niobium, tungsten, and molybdenum is added to an aqueous slurry of already manufactured potassium titanate whiskers, A method for producing a conductive whisker by removing the insoluble matter by filtration and then heat-treating is disclosed, and a method for adding an acid at the same time as an aqueous solution of a metal compound is also known (Japanese Patent Publication No. Hei 7).
-23221). However, in the conductive whiskers obtained by these methods, the particles of the metal oxide attached to the surface thereof have a size exceeding the nm unit, so that, for example, a marked increase in the specific surface area is not observed.

Further, JP-A-2-221460 discloses a potassium hexatitanate whisker whose surface is coated with titanium dioxide. This is a mixture of (a) a titanium compound and a potassium compound, and is 900 to 120
Firing at 0 ° C. to give a temporary fiber aggregate, disaggregating this aggregate in water to obtain a slurry, and the pH of the slurry is 9.3.
To 9.7, and then to pH 8.0 to 9.1, and then heated to 600 ° C. or higher, or (b) titanium dioxide and alkali in an aqueous slurry of potassium hexatitanate whiskers already produced. (In the example, the pH of the slurry was adjusted to 6.0), the hydrated oxide of titanium was attached to the surface of the potassium hexatitanate whiskers, and the mixture was added again to 6
It is produced by heating to 00 ° C or higher. However, the potassium hexatitanate whiskers obtained by the method (a) do not have titanium dioxide uniformly attached to the surface thereof. Further, in the potassium hexatitanate whiskers prepared by the method (b), since the titanium dioxide attached to the surface is anatase type, it is unavoidable that the reinforcing effect is lowered. Furthermore, the surface-coated potassium hexatitanate whiskers obtained by any of the methods (a) and (b) have titanium dioxide particles having a size larger than nm, so that the ratio is No significant increase in surface area is observed.

In addition, these conventional techniques do not suggest a method of adding a water-soluble metal salt and performing a neutralization operation in the process of producing potassium titanate whiskers themselves.

[0010]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has added a specific metal compound to an aqueous slurry of temporary fibers when producing potassium titanate whiskers. And by performing the neutralization operation,
Compared to untreated whiskers, the specific surface area (BET specific surface area, the same applies below) increases, the dispersibility in the synthetic resin matrix is excellent, the weather resistance is good, and it is difficult to decompose even when it is exposed to ultraviolet rays. Obtaining surface-coated potassium titanate whiskers having extremely favorable properties such as extremely low elution and high reinforcing effect, and performing the same treatment on other inorganic whiskers that can be produced in the same manner as potassium titanate whiskers It was found that the same remarkable effect can be obtained by. The present invention has been completed based on such findings.

That is, the present invention is characterized in that the whisker surface is coated with at least one selected from ultrafine particles of metal oxide and ultrafine particles of metal hydroxide having a size of nm or less. And the surface-covered whiskers.

The surface-coated whiskers of the present invention have the following remarkable effects as compared with untreated whiskers.

(1) Since the specific surface area is large, for example, an oil filter manufactured by using it has remarkably improved filtration characteristics and can remarkably contribute to the extension of oil life.

(2) Since the dispersibility in the synthetic resin matrix is good, the filling amount in the synthetic resin can be increased and a higher reinforcing effect can be exhibited.

(3) The properties of the surface-coated whiskers obtained depending on the metal species of the metal oxide or metal hydroxide to be coated are somewhat different. For example, when copper oxide is coated, the specific surface area is not so much increased. Although not observed, the water absorption is significantly reduced, and a surface-coated whisker useful as a filler for a brake material can be obtained.

Further, among the surface-coated whiskers of the present invention, the surface-coated potassium titanate whiskers have the following characteristics in addition to the above preferable characteristics.

(4) Those coated with ultrafine particles of metal oxides and / or metal hydroxides other than titanium dioxide are
The weather resistance is improved, active oxygen is not released so much even when it is exposed to ultraviolet rays, and the oxidation of the matrix and subsequent deterioration do not occur.

(5) The amount of potassium eluted is significantly smaller than that of general potassium titanate whiskers.

On the basis of these effects, the surface-coated whiskers of the present invention can remarkably improve the reinforcing effect on the matrix such as the synthetic resin, and the reinforcing effect can be maintained for a long time.

The reason why these effects are achieved is not fully clear, but the treatment according to the present invention enables the treatment of whisker surfaces with n.
It is considered that this is because the ultrafine metal oxide particles and / or metal hydroxide particles having a size of m units or less are uniformly attached. It is considered that the improvement of dispersibility is due to the change of the electric potential on the surface of the whiskers due to the adhesion of ultrafine particles.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The surface-coated whiskers of the present invention are
The surface of the whiskers is coated with at least one selected from ultrafine particles of metal oxide and ultrafine particles of metal hydroxide having a size of nm or less, preferably ultrafine particles of metal oxide. Characterize.

Usually, in a whisker whose surface is coated with a metal oxide or the like by a conventional method, the surface of the whisker is observed by a transmission electron microscope (magnification: about 50,000 times). Particles are observed. The particles are larger than nm by magnification. However, even when the surface-coated whiskers of the present invention are observed at the same magnification, there is almost no unevenness on the surface, and no particulate matter is observed on the surface.

The following points can be cited as evidence that the surface of the surface-coated whiskers of the present invention is coated with a metal oxide or the like.

First, the results of elemental analysis such as fluorescent X-ray analysis are given. X-ray fluorescence analysis confirms the presence of a metal oxide other than the components of the whiskers.

Further, the surface-coated whiskers of the present invention have a larger specific surface area than the uncoated whiskers.

Further, the surface-coated whiskers of the present invention have at least one inflection point when the correlation between the ζ potential (electrokinetic potential) and pH is shown in a line graph.
Although the surface-coated whiskers of potassium titanate do not have an inflection point, the surface-coated whiskers have an inflection point, which means that the surface has an inflection point. This proves that it is uniformly coated with a metal oxide and / or a metal hydroxide.

From the above evidence, it is clear that the surface-coated whiskers of the present invention have the surface thereof uniformly coated with the metal oxide and / or the metal hydroxide, while the transmission electron Almost no particle shape is observed even when observed under a microscope with a magnification of about 50,000. Therefore, the surface metal oxide and / or metal hydroxide may be ultrafine particles having a size of nm unit or less. Be inferred.

Among the surface-coated whiskers of the present invention, ultrafine particles of metal oxide, particularly Al ₂ O ₃ , Fe ₂ O ₃ and Zr.
Those coated with ultrafine particles of at least one metal oxide selected from the group consisting of O ₂ , CuO and SiO ₂ have better properties.

The surface-coated whiskers of the present invention can be manufactured in the same manner as the conventional whiskers except that the water-soluble metal salt or its aqueous solution is added at a specific stage of the conventional whisker manufacturing process.

The conventional whiskers include potassium titanate whiskers and inorganic whiskers which can be produced in the same manner as the potassium titanate whiskers.

Although many methods for producing potassium titanate whiskers have been known in the past, the present invention can widely utilize conventionally known production methods in which a neutralization step can be set during the production step. Specifically, for example, a firing method,
Melting method, hydrothermal method, flux method, slow cooling firing method, etc. (New functional fiber utilization handbook, Industrial Research Institute Co., Ltd.,
(First edition issued June 2, 1988), and among these, a firing method, a melting method, a flux method, a slow cooling firing method and the like are preferable.
More specifically, for example, a sintered body or a melt obtained by heating a mixture of raw material compounds for producing whiskers (both aggregates of temporary fibers) is defibrated in water, and an acid or alkali is added to the obtained slurry. Was added to adjust pH (neutralize), the slurry was filtered to collect solids, which were dried,
It is a method of obtaining whiskers by heating (baking).

Examples of inorganic whiskers other than potassium titanate whiskers include sodium titanate whiskers, calcium silicate whiskers, aluminum borate whiskers, magnesium borate whiskers, zinc silicate whiskers, basic magnesium sulfate whiskers, magnesium oxide whiskers, carbonization. Silicon whiskers and the like can be mentioned. Among these, potassium titanate whiskers, sodium titanate whiskers, calcium silicate whiskers, aluminum borate whiskers, magnesium borate whiskers and the like are preferable, and potassium titanate whiskers and sodium titanate whiskers are particularly preferable.

As described above, the surface-coated whiskers of the present invention can be produced by adding a water-soluble metal salt or an aqueous solution thereof before the neutralization step in the general whisker production method including the neutralization step. .

More specifically, an aggregate of temporary fibers such as a sintered body and a melt obtained by heating a mixture of raw material compounds for producing whiskers is defibrated in water, and a water-soluble metal salt is added to the resulting slurry. Alternatively, it can be produced by adding an aqueous solution thereof, followed by neutralization, filtration, drying and heating (calcination) according to a usual method. Since the temporary fibers are monodispersed at the time of defibration, it is considered that the surface of the temporary fibers is coated with the metal salt very uniformly.

According to this method, it is possible to easily control the specific surface area of the surface-treated whiskers to be obtained by appropriately changing the amount and type of the water-soluble metal salt to be added, and to damage the whiskers themselves. The object can be obtained in a small amount and in a significantly simpler and cheaper manner than the conventional conductive metal coating on the whiskers.

The water-soluble metal salt is not particularly limited, and known ones can be used regardless of whether they are conductive or non-conductive.
Those capable of forming a hydroxide are preferred. Specifically, for example, an alkali metal (Na, K, etc.), an alkaline earth metal (Mg, Ca, Sr, Ba, etc.), an alkali metal and an alkaline earth metal, the third periodic element (Al, Si
Etc.), the 4th periodic element excluding alkali metals and alkaline earth metals (Ti, Fe, Co, Ni, Cu, Zn, etc.), the 5th periodic element excluding alkali metals and alkaline earth metals (Zr, At least one of metals such as Sn, Mo, etc.)
A water-soluble salt containing a seed, and examples of the water-soluble salt include halides, oxides, nitrates, sulfides, sulfates,
A hydroxide etc. can be mentioned. More specifically, for example, AlCl ₃ , CoCl ₂ , ZrCl ₄ , SnCl ₂ ,
SnCl ₄ , TiCl ₃ , TiCl ₄ , FeCl ₂ , FeC
l ₃ , CuCl ₂ , NiCl ₂ , MoCl ₅ , MgCl ₂ ,
Chlorides such as CaCl ₂ , SrCl ₂ and BaCl ₂ , Al
_{2 (SO 4) 3, CoSO} 4, CuSO 4, FeSO 4 sulfates such _{as, Na 4 SiO 4, K 2} Si 4 silicate product of O _9, etc., Zr
Examples thereof include Cl ₂ O and NaAlO ₂ , and among these, AlCl ₃ , NaAlO ₂ , FeCl ₂ and FeC.
l ₃ , CuCl ₂ , ZrCl ₂ O, Na ₄ SiO _{4 and the} like are preferable. The water-soluble metal salts may be used alone or in combination of two or more. The amount of the water-soluble metal salt to be used can be appropriately selected from a wide range depending on the purpose of use of the obtained surface-coated whiskers, the type and amount of raw materials for producing whiskers, the heating (firing) temperature, time, etc. About 0.01 to 100% by weight, preferably about 0.1 to 100% by weight, based on the theoretical amount of whiskers produced, which is determined by the type and amount used.
It may be about 05 to 10% by weight. By adding a water-soluble metal salt or an aqueous solution thereof and then performing neutralization, drying and firing, the metal oxide and / or metal hydroxide can be uniformly attached to the surface of the whiskers.

Hereinafter, one example of the method of selecting potassium titanate whiskers as the whiskers and applying the surface coating to the whiskers will be described more specifically.

First, the raw material compounds for producing whiskers are mixed. The raw material compound for the production of potassium titanate whiskers is
Titanium compounds and potassium compounds.

Examples of the titanium compound include titanium dioxide such as anatase type titanium dioxide and rutile type titanium dioxide, and a titanium compound which produces titanium dioxide by firing. The titanium compound that forms titanium dioxide by firing is not particularly limited, and examples thereof include hydrous titanium oxide, rutile ore, titanium hydroxide, and titanium chloride. The titanium compounds may be used alone or in combination of two or more.

As the potassium compound, for example, potassium dioxide, a potassium compound which produces potassium dioxide by firing, and the like can be mentioned. The potassium compound that produces potassium dioxide by firing is not particularly limited, and examples thereof include potassium hydroxide, potassium carbonate, and potassium nitrate. The potassium compounds may be used alone or in combination of two or more.

The mixing ratio of the titanium compound and the potassium compound is not particularly limited and can be appropriately selected from a wide range.
the molar ratio of K ₂ O produced by TiO ₂ and K ₂ O or calcined to produce the iO ₂ or calcined (TiO ₂ / K ₂ O)
However, both may be mixed so as to be usually about 1 to 10, preferably about 2 to 6.

Then, a mixture of the titanium compound and the potassium compound is heated at about 900 to 1100 ° C. for about 1 to 10 hours to form an aggregate of temporary fibers. During this heating, for example, KCl, KF, KBr, KI, K
A known flux such as ₂ SO ₄ , K ₂ MoO ₄ , K ₃ PO ₄ or the like may be added. The obtained aggregate of temporary fibers is cooled and soaked in water to be defibrated to obtain an aqueous slurry. Water at this time may be room temperature water, or may be warm water or cold water. The pH value of this aqueous slurry is preferably in the alkaline range before adding the water-soluble metal salt or its aqueous solution.

Subsequently, a water-soluble metal salt or an aqueous solution thereof is added with stirring, if necessary, and the mixture is sufficiently stirred, and an acid or an alkali is further added for neutralization (pH adjustment). Neutralization in the present invention is to adjust the added water-soluble metal salt to a pH range in which hydroxide can be formed. At this time, the pH value as a guide is about 6 to 8, preferably around 7. is there.
The acid used for pH adjustment is not particularly limited, but examples thereof include inorganic acids such as hydrochloric acid, sulfuric acid, oxalic acid, nitric acid, phosphoric acid, and organic acids such as acetic acid. The alkali is not particularly limited, and examples thereof include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, and ammonia. When the pH value is in the acidic range,
It is not preferable because the amount of anatase-type titanium dioxide as a by-product increases and the effect of the obtained whiskers as a reinforcing material decreases. On the other hand, when the pH value is in the alkaline range, the metal oxide may be dissolved and the coating efficiency may be reduced, and potassium tetratitanate may remain, which is not preferable.

After adjusting the pH, the temporary fiber is filtered and dried,
Bake. Drying is usually performed at a temperature of about 50 to 200 ° C., preferably about 80 to 150 ° C., and is usually completed in about 1 to 10 hours, preferably about 2 to 5 hours. Firing is usually about 300 to 800 ° C, preferably 500 to
It is performed at a temperature of about 700 ° C., and is usually completed in about 10 minutes to 2 hours, preferably about 20 to 60 minutes. A sintered body (aggregate of whiskers) obtained after firing is defibrated according to a usual method, and dried if necessary, whereby a target surface-coated whisker is manufactured.

The surface-covered whiskers of the present invention obtained in this manner are about the same size as general whiskers, and often have a diameter of about 0.1 to 1.0 μm and a length of about 5 to 50 μm. Especially, the length is about 10 to 20 μm.

The surface-coated whiskers of the present invention have N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, in order to further improve the dispersibility in the matrix, if necessary. The surface may be further treated with a known surface treatment agent such as a silane coupling agent such as ethoxysilane or a titanate coupling agent.

The surface-covered whiskers of the present invention have water or a suitable organic binder added, and are usually 50 μm to 5 mm.
You may use it, after granulating to a suitable size.

The surface-treated whiskers of the present invention are not covered by the surface treatment, whiskers such as whiskers surface-coated by conventional methods, glass fibers, carbon fibers, rocks, etc., as long as the effect is not impaired, depending on the application. It can also be used in combination with inorganic fibers such as cotton fibers and powdered inorganic materials such as talc, calcium carbonate, titanium oxide and silica.

The surface-coated whiskers of the present invention can be used in virtually all fields in which whiskers have been conventionally used. For example, various synthetic resins such as thermoplastic resins and thermosetting resins, metallic materials, etc. It is very useful as a reinforcing material. The synthetic resin containing the surface-treated whiskers of the present invention can be applied to, for example, sliding members such as brake pads, keyboard parts, OA equipment such as gears, gears, switches, electrical / electronic-related equipment, precision equipment parts, various paints, and adhesives. Other than agents,
It can also be used for applications such as building materials and medical parts materials. In addition, the filter produced using the surface-coated whiskers of the present invention exhibits excellent filtration characteristics.

The surface-treated whiskers of the present invention exhibit various properties depending on the type of the whiskers themselves, the type of the metal oxide and / or the metal hydroxide to be surface-coated, and the uses thereof. . For example, when the whiskers are potassium titanate whiskers, if the metal oxide is an aluminum oxide such as alumina, it is particularly useful as a brake lining material or a filter material due to the increase in the specific surface area. If it is copper oxide, it is particularly useful as a brake pad material due to a decrease in water absorption, and if the metal oxide is zirconium oxide, the braking force is improved by stabilizing the friction coefficient, and is particularly useful as a brake pad material. Is.

[0051]

The present invention will be specifically described below with reference to examples and comparative examples. In the following, "%" means "% by weight".

Examples 1 to 7 50 g of titanium dioxide powder and 25 g of potassium carbonate were mixed, and this mixture was reacted at 1000 ° C. for 4 hours. After cooling, the reaction product was defibrated in water, water-soluble metal salt was added at the addition amount (%) shown in Table 1 and mixed, and then sulfuric acid or potassium hydroxide was added to adjust the pH of the reaction product to 7. The pH was adjusted (neutralized) to 0, stirred for 30 minutes, and then the pH was adjusted to 7.0 again. The theoretical amount of potassium titanate whiskers produced in this example is 57 g. After neutralization, the solid matter was collected by filtration, dried at 110 ° C. for 4 hours, and then baked at 600 ° C. for 30 minutes to produce potassium titanate whiskers.

The specific surface area of the obtained potassium titanate whiskers was measured. The equipment and measurement conditions used for measuring the specific surface area are as follows.

Specific surface area measuring device: Micromeritics GEMINI
2360, manufactured by Shimadzu Corporation Pretreatment equipment: Micromeritics Flow Prep060, manufactured by Shimadzu Corporation Specific surface area pretreatment condition: pretreatment temperature 120 ° C, N ₂ gas purge: 60 minutes Specific surface area measurement condition: BET multipoint method ( Relative pressure: 0.1
0.3P / P0 5 points), measuring cell 6cc.

The results are also shown in Table 1.

Comparative Example 1 A conventional potassium titanate whisker was manufactured in the same manner as in the above-mentioned example except that the water-soluble metal salt was not added. The specific surface area of this potassium titanate whisker was also measured. Table 1 shows the results.

Comparative Example 2 In accordance with Example 1 of Japanese Examined Patent Publication No. 7-23221, a conductive whisker in which the surface of potassium titanate whisker was coated with SnO ₂ and Sb ₂ O ₃ was produced. That is, 10 g of potassium titanate whiskers (commercial item, trade name: Tismo D, manufactured by Otsuka Chemical Co., Ltd.) are dispersed in 100 ml of water,
Stir for 30 minutes with a stirrer to form a slurry. Next, this dispersion slurry was heated to 90 ° C. in an oil bath, and 17 g of stannic chloride and 1.7 of antimony chloride were added to this hot slurry.
g in 30 g of 3.7 N-hydrochloric acid aqueous solution and 92 ml of 3.7 N-sodium hydroxide aqueous solution,
While maintaining the liquid temperature of the hot slurry at 90 ° C. and the pH at 8 to 9 at the same time with stirring for 1 hour, the pH was adjusted to 6.5 using 3.7N-hydrochloric acid aqueous solution, and the liquid temperature was further adjusted to 90. ℃
It was left still for 1 hour while being held at. Next, the reaction solution was allowed to cool to room temperature, the solid matter was collected by filtration, washed with water, dried, and then heat-treated at 600 ° C. for 2 hours to produce the conductive whiskers. The specific surface area of this whisker was also measured.
Table 1 shows the results.

[0058]

[Table 1] From Table 1, it can be seen that the surface-coated potassium titanate whiskers of the present invention generally have an increased specific surface area as compared with conventional potassium titanate whiskers and conductive whiskers, and significantly increase depending on the type of water-soluble metal salt. Is clear.

Test Example 1 The product of the present invention obtained in Example 6 and the product of the present invention obtained in Example 7 were analyzed by fluorescent X-ray analysis. Also, regarding the potassium titanate whiskers obtained in Comparative Example 1,
It was analyzed by X-ray fluorescence analysis. Table 2 shows the results.

The equipment and test conditions used for the fluorescent X-ray analysis are as follows.

Fluorescent X-ray analysis and measurement device: RIX-300
0, manufactured by Rigaku Denki Kogyo Co., Ltd. Pressure molding machine: manufactured by Shimadzu Corporation, (pressure = 7t → 10
Press at t → 15t (aluminum ring)) Aluminum ring: Cat No. 3481M1 inner diameter 32
mm, manufactured by Rigaku Denki Kogyo Co., Ltd.

[0062]

[Table 2] From the above results, it is understood that the product of the present invention of Example 6 is coated with Fe ₂ O ₃ and the product of the present invention of Example 7 is coated with ZrO ₂ .

Example 8 The product No. of the present invention. 1; CuSO _4.5 as water-soluble metal salt
Surface-coated whiskers of the present invention were produced in the same manner as in Examples 1 to 7 except that H ₂ O was used and the addition amount was 20%.

The product No. of the present invention. 2; C as a water-soluble metal salt
The surface-coated whiskers of the present invention were produced in the same manner as in Examples 1 to 7 except that uSO ₄ .5H ₂ O was used and the addition amount was 20%.

Blank No. 1; Potassium titanate whiskers were produced in the same manner as in Examples 1 to 7 except that the water-soluble metal salt was not added.

The product No. of the present invention. 3; C as a water-soluble metal salt
uSO ₄ .5H ₂ O was used, the amount added was 20%, and p
Surface-coated whiskers of the present invention were produced in the same manner as in Examples 1 to 7 except that H was adjusted to 8.0.

Blank No. 2; Potassium titanate whiskers were produced in the same manner as in Examples 1 to 7 except that the pH was adjusted to 8.0 without adding the water-soluble metal salt.

Inventive product No. 1-3 and blank No.
The specific surface area and water absorption of each of the various whiskers 1 and 2 were measured.

The method for measuring the specific surface area is the same as described above.

The water absorption was measured as follows.
First, 1 g of whiskers was collected in a beaker, dried at 110 ° C. for 60 minutes, and cooled in a desiccator for 30 minutes. Water was added dropwise to this sample with a buret, and the point at which thixotropy appeared (titration amount) was read to determine the water absorption. Table 3 shows the results.

[0071]

[Table 3] Further, the product No. of the present invention. 2-3 and blank No. Fluorescent X-ray analysis was performed for each of the various whiskers of 1. Table 4 shows the results.

[0072]

[Table 4] From Table 4, it can be seen that in this example, the use of the water-soluble copper salt gives a surface-coated whisker coated with copper oxide. Further, from Table 3, it can be seen that the coating of copper oxide can provide surface-coated whiskers with significantly reduced water absorption.

Test Example 2 The ζ potential of each whisker was measured by the following method.

Equipment used: Streaming potential measuring device: ZP-10B, Shimadzu Corporation data processing device: PC-9801Fx, NEC Corporation
Data processing software: ZP-10B-PC1 Ver2.
12, Shimadzu Corporation Sample filling cell: 2 mm, Shimadzu Corporation glass filter paper: 16 mm in diameter, GB100R, manufactured by Advantech Toyo Corporation.

Preparation of sample: (1) 100 ml of fluid (1 volume of 1 g sample was adjusted to an intended pH with an aqueous solution containing potassium chloride at a ratio of 0.001 mol / liter, and fluid resistance was 800 Ω). Solution) was added and stirred for 10 minutes to disperse the sample, and an aqueous slurry was obtained.

(2) The aqueous slurry was filled on glass filter paper using a 2 mm filled cell.

(3) This was set in the streaming potential measuring device to measure the streaming potential (22 to 26 ° C.), and the data was processed by the data processing software.

The results are shown in FIG. In FIG. 1, each symbol is as follows.

◯: Inventive product of Example 1 (Al ₂ O ₃ coating) Δ: Inventive product No. of Example 8 3 (CuO coating) □: Inventive product of Example 6 (Fe ₂ O ₃ coating) ▽: Inventive product of Example 7 (ZrO ₂ coating) ×: Potassium titanate whiskers (commercial product, trade name: Tismo D) From Otsuka Chemical Co., Ltd. From FIG. 1, it is clear that the surface-coated whiskers of the present invention have inflection points. Since these are potassium titanate whiskers having no inflection point and coated with a metal oxide, it is clear that the surface of the whiskers is uniformly coated with the metal oxide.

Test Example 3 The surface-treated whiskers of Example 1 and the conductive whiskers of Comparative Example 2 were used as a transmission electron microscope (trade name: JEM201).
0, manufactured by JEOL Ltd.) at a magnification of about 50,000.

The surface-treated potassium titanate whiskers of Example 1 had no irregularities on the surface, and the specific surface area was increased or the inflection point was recognized despite the fact that the surface treatment was performed 50,000 times. It is considered that the surface is covered with ultrafine particles having a size that cannot be observed at a magnification of, that is, a size of nm unit or less.

On the other hand, it was observed that the conductive whiskers of Comparative Example 2 had irregularities on the surface thereof, and particles having a diameter of about 0.01 to 0.1 μm covered the surface.

From the above results, it is understood that the surface-coated potassium titanate whiskers of the present invention are novel substances different from the conventional conductive whiskers.

Test Example 4 The product No. of the present invention of Example 8 was tested. In the same manner as in Test Example 3, the sample No. 1 was observed with a transmission electron microscope at a magnification of about 50,000, and an electron micrograph of the product of the present invention was taken. The electron micrograph is shown as FIG.

From FIG. 2, it can be seen that the surface of the product of the present invention has no unevenness derived from the attached copper oxide.

[Brief description of the drawings]

FIG. 1 is a line graph showing the correlation between ζ potential and pH of the surface-coated whiskers of the present invention.

FIG. 2 is a transmission electron micrograph (magnification: about 50,000 times) showing the fiber shape of the surface-coated whiskers of the present invention.

Claims (4)

[Claims] 1. A surface characterized in that the whisker surface is coated with at least one selected from ultrafine particles of metal oxide and ultrafine particles of metal hydroxide having a size of nm unit or less. Coated whiskers. 2. The surface-covered whisker according to claim 1, wherein the surface-coated whisker has at least one inflection point in a line graph showing a correlation between ζ potential and pH. 3. A whisker-producing raw material compound is mixed and heated, the resulting aggregate of temporary fibers is defibrated in water, and a water-soluble metal salt or an aqueous solution thereof is added to the resulting slurry, followed by acid or alkali. The surface-covered whisker according to claim 1 or 2, which is obtained by neutralizing by adding the above, and then filtering to separate the temporary fiber, and further drying and heating the temporary fiber. 4. The surface-covered whiskers according to claim 1, wherein the whiskers are potassium titanate whiskers.