JP2522923B2 - Modified magnesium borate and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to modified magnesium borate and a method for producing the same.

(Prior art) With the development of science and technology and the diversification of needs, high-performance and multi-functional materials are actively developed. Even in the plastics industry, various researches on the development of conductive polymer materials are attempted. For example, a polymer material using carbon particles or fibers or a metal powder such as copper, silver and gold as a conductive filler has been proposed. However, carbon particles, carbon fibers, and metal powders such as copper, silver, and gold each have a black or metal-specific color tone, which limits their use. Moreover, these conductive fillers have no reinforcing property except carbon fiber. Carbon fiber is a reinforcing conductive filler, but it is difficult to make the fiber length uniform, and the aspect ratio is not uniform, so the moldability is poor, and the surface smoothness and abrasiveness of the molded product are poor. Inferior in.

In view of the actual situation as described above, many known fillers are already on the market, but many of them have a defect that particles are coarsened or fibers are sintered, and it is difficult to obtain an excellent conductive material. It was.

(Problems to be Solved by the Invention) An object of the present invention is to provide a modified magnesium borate having excellent heat resistance and reinforcing properties.

Another object of the present invention is to provide a modified magnesium borate capable of giving a molded product excellent in molding processability, surface smoothness and abrasiveness.

(Means for Solving the Problems) The present invention is represented by the general formula MgxByOz (where x, y, and z are positive real numbers satisfying 0 <x ≦ 4,0 <y ≦ 4,0 <z ≦ 10). Magnesium borate is used in a mixed atmosphere of (a) hydrocarbon or (b) hydrogen gas or ammonia gas and / or inert gas.
The present invention relates to a modified magnesium borate obtained by heating and baking at a temperature of 500 to 1350 ° C. and a method for producing the same.

The material of the present invention, magnesium borate, has the general formula MgxB
yOz (where x, y and z are positive real numbers of 0 <x ≦ 4,0 <y ≦ 4,0 <z ≦ 10), and this magnesium borate is generally ASTM powder X-ray. It gives an X-ray diffractogram similar to that of dwarf card 16-168, but is unique in that the [201] and [402] planes are well developed. The magnesium borate is also provided in the form of whiskers.

This magnesium borate whisker contains, for example, a magnesium supply component selected from oxides of magnesium, hydroxides and inorganic acid salts, and a boric acid supply component selected from oxides of boron, oxyacids and alkali metal salts thereof. , Sodium halide and potassium halide, in the presence of at least one kind of melting agent, it can be produced by heating to a temperature of 600 to 1000 ° C. to react.

As the magnesium supply component in this method, in addition to oxides and hydroxides of magnesium, magnesium compounds such as inorganic acids such as magnesium salts of carbonic acid, sulfuric acid, nitric acid and hydrohalic acid are used. Examples of such compounds include magnesium oxide, magnesium hydroxide, basic magnesium carbonate, magnesium sulfate, magnesium chloride, magnesium bromide and the like. These may be used alone or in combination of two or more.

Next, as a boric acid supply component, an oxide of boron, such as boron oxide, or an oxygen acid of boron, such as forthoboric acid (H ₃ BO ₃ ), tetraboric acid (H ₂ B ₄ O ₇ ), metaboric acid ( HBO ₂ )
Alternatively, these alkali metal salts such as sodium borate, sodium pyroborate, potassium pyroborate, and sodium metaborate are used. These may be used alone or in combination of two or more.

The magnesium supply component and the boric acid supply component are mixed at a molar ratio of magnesium to boron in the range of 1: 4 to 1: 1 and a melting agent is added in the range of about 10 to 95% by weight based on the total weight. Then, the desired magnesium borate whiskers can be produced by heating and reacting at a temperature in the range of about 600 to 1000 ° C. The heating temperature at this time is 60
If the temperature is below 0 ° C, the reaction progresses extremely slowly, and 1000 ° C.
If it exceeds the above range, a large amount of triclinic prismatic magnesium borate is by-produced in addition to the desired magnesium borate whiskers, which is not preferable. The reaction time is usually in the range of 15 minutes to 2 hours.

To isolate the whiskers from this reaction product, they are first treated with hot or cold water to remove the melting agent and other water-soluble components. When there are by-products depending on the raw material composition used, the fibrous material is separated from the residue by means such as decantation, hydration and air bubble separation. Then, the crude magnesium borate whiskers thus obtained are treated with an alkali,
For example, pure magnesium borate whiskers can be obtained by removing impurities by washing with an aqueous solution of sodium hydroxide and an acid, for example, an aqueous solution of acetic acid or cold dilute hydrochloric acid.

In the X-ray diffraction spectrum, the magnesium borate whiskers thus obtained had a d value of 4.47 [201] plane and a d value in comparison with ASTM powder X-ray diffraction card 16-168.
The diffraction angle on the [402] plane of 2.823 is strong, and the d-value of 2.557 is [01]
2) The diffraction intensity of the surface is relatively weak, and accordingly,
This can be identified as a fibrous compound.

Magnesium borate is generally a powder or a fibrous single crystal, but in the present invention, any of these forms can be used. However, among them, fibrous substances are preferable, of which fiber length is 5 μm or more, aspect ratio is 20 or more,
In particular, 100 or more is suitable as the reinforcing filler.

The hydrocarbons used in the present invention are roughly classified into aliphatic hydrocarbons and aromatic hydrocarbons. As the aliphatic hydrocarbon, a saturated hydrocarbon represented by the general formula C _n H _{2n + 2} (where n is a positive integer of 1 to 20) and an ethylene represented by the general formula C _n H _2n (n is the same as above) Examples thereof include hydrocarbons and acetylene hydrocarbons represented by the general formula C _n H _2n-2 (n is the same as above). Examples of aromatic hydrocarbons include benzene, toluene, xylene and their homologues, polynuclear aromatic hydrocarbons such as naphthalene and anthracene, and halides of the above-mentioned various hydrocarbons. These hydrocarbons may be mixed and used as needed.

Nitrogen gas is a typical example of the inert gas used in the present invention, but argon, helium, xylene, and other inert gases can also be used.

The modified magnesium borate of the present invention is generally the above-mentioned magnesium borate at a temperature of about 500 to 1350 ° C. in a hydrocarbon alone or a mixed atmosphere of a hydrocarbon and an organic gas and / or an inert gas. It is manufactured by heating and firing. As another method, it is possible to carry out a heating reaction by suddenly substituting hydrogen from room temperature without performing nitrogen substitution, but there is a drawback that the cost increases due to an increase in the amount of hydrogen used.

One of the points to be noted in the practice of the present invention is the decomposition temperature of hydrocarbons and the attachment temperature to the modified magnesium borate. That is, the object of the present invention is to make the magnesium borate and the carbon particles adhere to the surface simultaneously with the extraction of oxygen, so that if the above temperature is improperly selected, it is preferable. Hard to get good results.
The decomposition temperature of hydrocarbons differs depending on the type, and the optimum precipitation temperature range of carbon and the optimum adhesion temperature range of magnesium borate differ depending on the hydrocarbon species used. For example, in the case of methane, the precipitation temperature range of carbon is about 900-950 ℃.
In the case of n-propane, it is about 950 to 1000 ° C.
In the case of benzene, the temperature is low and carbon precipitates at about 750-800 ° C. It should be noted that, without adding hydrogen gas or ammonia gas, about 500 ~ 1000 under nitrogen gas replacement / nitrogen gas flow
Conductivity can also be obtained by a method of introducing and reacting a hydrocarbon at ℃.

There is no critical mixing ratio of hydrogen gas or ammonia gas and hydrocarbon, and usually a range of 90:10 to 10:90 is preferable. Considering the carbon deposition amount, a ratio of about 50:50 is particularly preferable. Is.

When the heating reaction of magnesium borate is completed, the temperature is lowered to room temperature, and it is preferable to lower the temperature while flowing an inert gas, hydrogen gas, hydrocarbon gas or a mixed gas thereof during that time. If oxygen or air is mixed in during the temperature lowering process, carbon adhering to the surface of magnesium borate may burn.

The heating temperature in the present invention is usually in the range of about 500 to 1350 ° C, preferably about 600 to 1100 ° C. The heating time is usually about 20 to 180 minutes, preferably about 30 to 90 minutes. The heating time within the above range is particularly preferable because it imparts excellent conductivity without impairing the shape of magnesium borate.

(Effects of the Invention) The modified magnesium borate of the present invention has various physical properties, particularly heat resistance, which magnesium borate had before firing.
It retains features such as reinforcement and surface smoothness when used as a composite material. Therefore, it is excellent in application suitability as an antistatic agent, static eliminator, and conductive material, and has high industrial applicability as a conductive treatment agent for conductive materials such as sheets, paper, cloth, and films. . In addition to the above, the modified magnesium borate of the present invention is widely used in various applications such as a plastic reinforcing material and a conductive ink.

(Examples) Hereinafter, examples will be described.

Example 1 Magnesium borate (5 g) was filled in a platinum container having a capacity of 50 ml, transferred into a tubular electric furnace made of Siliconit, and nitrogen gas was allowed to flow at room temperature at a flow rate of 150 ml / min for about 1 hour to prepare an atmosphere.
Subsequently, the temperature was raised to 500 ° C. while introducing nitrogen gas. Next, the introduced gas was switched to propane gas, and the flow rate of this gas was changed to 12
While introducing at a rate of 0 ml / min, the temperature was raised to 850 ° C. and kept at the same temperature for 30 minutes, the propane gas was cut off, the mixture was allowed to cool to room temperature while flowing nitrogen gas, and when taken out of the furnace, it turned black blue. A modified magnesium borate having conductivity was obtained.

Example 2 Magnesium borate (5 g) was charged into a platinum container having a capacity of 50 ml, transferred into a silicon electric tube furnace, and nitrogen gas was flowed at room temperature at a flow rate of 150 ml / min for about 1 hour to prepare an atmosphere, and then nitrogen was continuously supplied. The temperature was raised to 500 ° C. while continuing to introduce the gas. Next, the introduced gas was switched to hydrogen gas, and the temperature was raised to 850 ° C. while introducing the same gas at a flow rate of 120 ml / min. Therefore, benzene gas was introduced at a rate of 50 ml / min for 30 minutes through a branch tube previously attached to the hydrogen gas introduction tube, while the tubular electric furnace was heated to 950 ° C and kept at the same temperature for 10 minutes, and then electricity was supplied. When the furnace was turned off and allowed to cool with hydrogen gas flowing, and when the temperature dropped to 300 ° C, the introduced gas was switched to nitrogen gas and allowed to cool to room temperature, then taken out of the furnace.
A dark blue-tinted modified magnesium borate was obtained.

Example 3 In the same manner as in Example 2 except that the nitrogen gas was introduced without switching the nitrogen gas to the hydrogen gas, a modified magnesium borate colored in black blue was obtained.

Example 4 Magnesium borate whiskers (5 g) were placed in a platinum container having a volume of 50 ml, transferred into a tubular electric furnace made of Siliconit, and reduced under the same conditions as in Example 1 to have blackish blue conductivity. A modified magnesium borate whisker was obtained.

Test Example After thoroughly mixing 90 parts of each modified magnesium borate obtained above with 10 parts of fluid paraffin in a mortar, press for 10 minutes under the condition of 50 kg / cm ² using a mold having an inner diameter of 10 mm and a length of 20 mm. ,
After molding, silver paste was applied to both surfaces of the molded body, conductivity was measured using a digital multimeter (manufactured by Takeda Riken Co., Ltd.), and volume resistivity was converted and calculated according to the following formula. The results are shown in Table 1.

Claims (6)

(57) [Claims] 1. A magnesium borate represented by the general formula MgxByOz (where x, y and z are positive real numbers satisfying 0 <x ≦ 4,0 <y ≦ 4,0 <z ≦ 10) is carbonized (a). Hydrogen or (b) about this in a mixed atmosphere of hydrogen gas and / or ammonia gas and / or an inert gas.
Modified magnesium borate obtained by heating and baking at a temperature of 500 to 1350 ° C. 2. The modified magnesium borate according to claim 1, wherein the hydrocarbon is an aliphatic hydrocarbon. 3. The modified magnesium borate according to claim 1, wherein the hydrocarbon is an aromatic hydrocarbon. 4. The modified magnesium borate according to claim 1, wherein the inert gas is nitrogen gas. 5. The modified magnesium borate according to claim 1, wherein the magnesium borate is fibrous. 6. Magnesium borate represented by the general formula MgxByOz (where x, y and z are positive real numbers of 0 <x ≦ 4,0 <y ≦ 4,0 <z ≦ 10) are carbonized (a). Hydrogen or (b) about this in a mixed atmosphere of hydrogen gas and / or ammonia gas and / or an inert gas.
A method for producing a modified magnesium borate characterized by comprising heating and firing at a temperature of 500 to 1350 ° C.