JPH10183009A - Magnesium hydroxide composition and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To elevate the dehydration start temp. of magnesium hydroxide to thereby provide magnesium hydroxide which can be processed at high temps. when used as a filler for imparting flame retardance to a thermoplastic resin. SOLUTION: A magnesium hydroxide compsn. having an elevated dehydration start temp. is obtd. by subjecting magnesium hydroxide and boric acid or a boric acid compd. to wet or dry contact mixing to cause 0.5-20wt.% (in terms of boron oxide and based on magnesium hydroxide) boric acid or boric acid compd. to be present on the surface of magnesium hydroxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnesium hydroxide composition suitable for a filler for resins such as rubber and plastic, and a method for producing the same. More particularly, the present invention relates to a magnesium hydroxide composition having excellent heat stability and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, with the remarkable progress of petrochemistry and organic polymer chemistry, polymer materials have been present as various necessities in our living space. For example, thermoplastic resins such as polyethylene, polypropylene, and vinyl chloride are widely used as interior materials such as carpets and linings for automobiles and homes, and as covering materials for structures of televisions, personal computers and other electric products, and electric wires. ing. However, as is well known, these polymeric materials have the property of emitting high temperatures and burning, so that once a fire occurs, not only the expansion of the fire, but also the generation of a large amount of smoke, toxic gas, corrosive gas, etc. From the point of view of safety and disaster prevention,
It is required to provide more excellent flame retardancy and nonflammability.

[0003] From this point, as a method of flame retarding a polymer material, conventionally, halogen-based flame retardants such as Br-based and Cl-based and inorganic based flame-retardants such as metal hydroxide, tin oxide, antimony oxide, borate and phosphorus compounds have been used. Attempts have been made to add flame retardants to impart flame retardancy to polymer materials.However, these halogen-based flame retardants are gradually becoming tired from the aspects of smoke generation and toxic gas generation, and recently have low toxicity. The development of inorganic flame retardants and the like that have a function of suppressing smoke emission is becoming mainstream.

[0004] Among them, magnesium hydroxide is a flame retardant which exhibits a flame retardant effect from both the endothermic reaction and the dehydration reaction caused by heating, and is a highly safe flame retardant with no generation of toxic gas. Is known to have a smoke suppressing effect.

[0005] Therefore, although various applications have been studied as a flame retardant for a polymer material (for example, a resin), in order to impart sufficient flame retardancy by adding magnesium hydroxide to the resin. Must be added in a large amount, and when magnesium hydroxide is added to the resin and mixed to such an extent that the desired flame retardancy is imparted, problems such as impairing the excellent moldability inherent in the resin arise. Even if a large amount is added, if the temperature of the processing machine is raised, the viscosity is reduced, and the moldability is improved, but magnesium hydroxide is, for example,
"Polymer Flame Retardation-Its Chemistry and Practical Technology, page 72,
Table 5.35 Thermal decomposition characteristics of metal hydroxides, Hitoshi Nishizawa,
As is clear from the description of “Taiseisha”, since the thermal decomposition starts from about 340 ° C, the crystallization water (steam) released from magnesium hydroxide when the temperature at the time of molding is high is high.
Therefore, the material may foam and processing may not be possible.

[0006]

An object of the present invention is to provide magnesium hydroxide having excellent heat resistance, that is, a high dehydration start temperature. More specifically, when used as a filler in a polymer material, particularly a thermoplastic resin, even when the processing temperature of the resin composition is higher than before,
An object of the present invention is to provide magnesium hydroxide which exhibits excellent moldability without foaming of the resin composition.

In view of such circumstances, the present inventors have conducted intensive studies to find magnesium hydroxide that satisfies the above object, and as a result, when magnesium hydroxide contains a specific substance, all of the above objects are satisfied. The inventors have found that the obtained magnesium hydroxide composition can be obtained, and have completed the present invention.

[0008]

That is, the present invention relates to 100 parts by weight of magnesium hydroxide and 0.5 parts by weight of boron oxide.
It is an object of the present invention to provide a magnesium hydroxide composition containing from 20 parts by weight to 20 parts by weight of boric acid or a boric acid compound. Further, in the present invention, magnesium hydroxide and boric acid or a boric acid compound are contact-mixed by a wet method or a dry method, and 0.5 parts by weight to 20 parts by weight in terms of boron oxide with respect to 100 parts by weight of magnesium hydroxide on the surface of magnesium hydroxide. An object of the present invention is to provide a method for producing a magnesium hydroxide composition, characterized by allowing boric acid or a boric acid compound to be present.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The magnesium hydroxide composition of the present invention contains boric acid or a boric acid compound in an amount of about 0.5 parts by weight to about 20 parts by weight, preferably about 1 part by weight to about 10 parts by weight, per 100 parts by weight of magnesium hydroxide. Is required. The boric acid or boric acid compound only needs to be adhered to the surface of magnesium hydroxide, and a more preferable existence form is that boric acid or boric acid compound is partially or completely coated on the surface of magnesium hydroxide in the form of magnesium borate. It is assumed that it is in the state.

In the practice of the present invention, the magnesium hydroxide is not particularly limited, but usually has an average particle diameter of about 0.2 μm to
A thickness of about 4 μm is applied.

The boric acid compound is not particularly restricted but includes, for example, ammonium borate, lithium borate, sodium borate, potassium borate, magnesium borate, calcium borate, manganese borate, zinc borate, lead borate and the like. It is preferable that these boric acid and boric acid compound are capable of forming magnesium borate at least on the surface of the particles in contact with magnesium hydroxide. Therefore, it is recommended to use boric acid, magnesium borate, sodium borate, ammonium borate and the like.

These boric acids or boric acid compounds are used in an amount of about 0.5 parts by weight in terms of boron with respect to magnesium hydroxide.
It is added and present in the range of about 20 parts by weight and used. When the amount of addition to magnesium hydroxide is less than 0.5 part by weight, the heat resistance of magnesium hydroxide is not significantly improved, and when it exceeds 20 parts by weight, the addition of boric acid or a boric acid compound is not achieved. There is no effect of improving the dehydration start temperature of magnesium hydroxide corresponding to the amount, and the release of water of crystallization of boric acid or boric acid compound increases, although the reason is not clear.

The method of adding boric acid or a boric acid compound to magnesium hydroxide in the present invention is not particularly limited, but is usually a wet method in which magnesium hydroxide is mixed with an aqueous solution of boric acid or a boric acid compound, followed by drying and coating, or a boric acid or boric acid compound. A dry method in which the compound and magnesium hydroxide are mixed as a solid and the surface of the magnesium hydroxide is coated with boric acid or a boric acid compound by heat treatment or mechanical treatment may be used. In the case of drying by a wet method, it is preferable to perform the drying without destroying the coating layer and under the condition that the degree of aggregation is low as in a spray drier, a flash jet drier or the like. In the present invention, the magnesium hydroxide composition has an average particle size of about 10 μm or less, preferably about 0.2 μm to about 4.5 μm.
m are suitable for applications such as resin fillers.

The magnesium hydroxide composition thus obtained usually has a dehydration starting temperature of about 350 ° C. or more, usually about 360 ° C. or more, and a dehydration peak temperature of about 420 ° C.
It is a magnesium hydroxide composition having a high heat resistance of at least 430 ° C, usually at least about 430 ° C. Therefore, the magnesium hydroxide composition is preferably used as a resin filler for imparting flame retardancy to a resin, but the magnesium hydroxide composition may be further subjected to a surface treatment, if necessary, at the time of use.
The agent for performing the surface treatment is not particularly limited as long as the properties of the present invention are not impaired. In general, fatty acids such as stearic acid and oleic acid, and metal salts of these fatty acids and stearic acid such as butyl stearate ester,
Various coupling agents such as silane coupling agents, titanate coupling agents, aluminate coupling agents, copolymers such as maleic acid / olefin, alkyl phosphate esters and metal salts thereof, and other surface treatment agents known in the art. Is used.

[0015]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. In the present invention, the physical properties of magnesium hydroxide were measured by the following methods.

Average particle (secondary) diameter: Microtrack M
It was measured by a KII particle size distribution analyzer (SPA model 7997-20, manufactured by Nikkiso Co., Ltd.). BET specific surface area: BET specific surface area measuring device (MODEL
4200, manufactured by Nikkiso Co., Ltd.). Dehydration start temperature and dehydration peak temperature: The values were read from a chart of a heat flux differential scanning calorimeter (DSC-41M, manufactured by Shimadzu Corporation). (As measurement conditions, an empty platinum cell was used as a standard sample, and about 10 mg of a magnesium hydroxide composition to be measured was heated from room temperature to 550 ° C. at a heating rate of 10 ° C./min.) Surface composition: B (boron) ) And Mg (magnesium) element ratio. XPS [X-ray photoelectron spectroscopy (X-ray photoelectron)
spectroscopy) (ESCA5400, manufactured by Perkin-Elmer). Average composition: Element ratio between B and Mg. It was measured by ICP emission analysis.

Example 1 Magnesium hydroxide (average secondary particle diameter 0.7 μm, BET specific surface area: 7.0 g) was added to 1 liter of a 20 g / l boric acid aqueous solution.
(0 m ² / g) 180 g was added and the slurry was stirred for 15 minutes.
It was dried at 0 ° C. × 5 hours. Next, the dried product was ground in a mortar to obtain a magnesium hydroxide composition. The dehydration start temperature, dehydration peak temperature, surface composition and average composition of the obtained magnesium hydroxide composition were examined. Table 1 shows the results.

Example 2 Magnesium hydroxide (average secondary particle diameter 0.7 μm, BET specific surface area: 7.0 g) was added to 1 liter of a 20 g / l boric acid aqueous solution.
(0 m ² / g) 180 g was added and the slurry was stirred and spray-dried (Yamato Chemical Co., Ltd., Model: DL-41)
After drying, a magnesium hydroxide composition was obtained. The dehydration start temperature, dehydration peak temperature, surface composition and average composition of the obtained magnesium hydroxide composition were examined. Table 1 shows the results.

EXAMPLE 3 Magnesium hydroxide (average secondary particle diameter 0.7 μm, BET specific surface area 7.0) was added to 1 liter of a 2 g / l boric acid aqueous solution.
The slurry obtained by adding 198 g of m ² / g) and stirring was dried with a spray drier (manufactured by Yamato Chemical Co., Ltd., Model: DL-41) to obtain a magnesium hydroxide composition. The dehydration start temperature, dehydration peak temperature, surface composition and average composition of the obtained magnesium hydroxide composition were examined. Table 1 shows the results.

Example 4 Magnesium hydroxide (average secondary particle diameter 4.1 μm, BET specific surface area 38) was added to 1 liter of a 20 g / l aqueous solution of boric acid.
(m ² / g) 180 g was added and the slurry was stirred for 150 minutes.
It dried at 5 degreeC x 5 hours. Next, the dried product was ground in a mortar to obtain a magnesium hydroxide composition. Dehydration start temperature of the obtained magnesium hydroxide composition, dehydration peak temperature,
The surface composition and the average composition were examined. Table 1 shows the results.

Example 5 180 g of magnesium hydroxide (average secondary particle diameter 0.7 μm, BET specific surface area 7.0 m ² / g) in 20 g of boric acid
And heated at 150 ° C. × 5 hours. After the heated product was ground in a mortar, a magnesium hydroxide composition was obtained. The dehydration start temperature, dehydration peak temperature, surface composition and average composition of the obtained magnesium hydroxide composition were examined. Table 1 shows the results.

Comparative Example 1 Magnesium hydroxide (average secondary particle diameter 0.7 μm, BET specific surface area 7.0 m ² / g) in 1 liter of ion-exchanged water
The slurry which 180 g was added and stirred was dried at 150 ° C. × 5 hours. Next, the dried product was ground in a mortar to obtain a magnesium hydroxide composition. The dehydration start temperature, dehydration peak temperature, surface composition and average composition of the obtained magnesium hydroxide composition were examined. Table 1 shows the results.

Comparative Example 2 Magnesium hydroxide (average secondary particle diameter 4.1 μm, BET specific surface area 38 m ² / g) was added to 1 liter of ion-exchanged water.
The slurry, to which 80 g was added and stirred, was dried at 150 ° C. × 5 hours. Next, the dried product was ground in a mortar to obtain a magnesium hydroxide composition. The dehydration start temperature, dehydration peak temperature, surface composition and average composition of the obtained magnesium hydroxide composition were examined. Table 1 shows the results.

[0024]

[Table 1] In the table, Td indicates the dehydration start temperature, and Tp indicates the dehydration peak temperature. The surface composition and the average composition indicate B / Mg (element ratio).

[0025]

As described in detail above, the magnesium hydroxide composition of the present invention has a higher dehydration start temperature and a higher dehydration peak temperature than conventional magnesium hydroxide. Processing becomes possible, as well as improved operability, and also enables the addition of large amounts of inorganic fillers, making it possible to impart even more flame retardancy to the resin composition. Is very large.

Claims (10)

[Claims] 1. A magnesium hydroxide composition comprising 0.5 to 20 parts by weight of boric acid or a boric acid compound in terms of boron oxide based on 100 parts by weight of magnesium hydroxide. 2. The magnesium hydroxide composition according to claim 1, wherein the average particle size of the magnesium hydroxide composition is 10 μm or less. 3. The magnesium hydroxide composition according to claim 1, wherein the boric acid or boric acid compound is present on the surface of the magnesium hydroxide. 4. The magnesium hydroxide composition according to claim 1, wherein the boric compound is at least one selected from sodium borate, magnesium borate and ammonium borate. 5. The magnesium hydroxide composition according to claim 3, wherein the boric acid or boric acid compound present on the surface of the magnesium hydroxide is magnesium borate. 6. A mixture of magnesium hydroxide and boric acid or a boric acid compound in a wet or dry manner, and the mixture is mixed with 0.5 parts by weight to 20 parts by weight of boron oxide based on 100 parts by weight of magnesium hydroxide on the surface of magnesium hydroxide. A method for producing a magnesium hydroxide composition, wherein boric acid or a boric acid compound is present. 7. The magnesium hydroxide having an average particle size of 0.
The method for producing a magnesium hydroxide composition according to claim 6, wherein the thickness is 2 µm to 4 µm. 8. The method for producing a magnesium hydroxide composition according to claim 6, wherein the boric compound is at least one selected from sodium borate, magnesium borate, potassium borate and ammonium borate. 9. The method for producing a magnesium hydroxide composition according to claim 6, wherein the boric acid compound is magnesium borate. 10. The method for producing a magnesium hydroxide composition according to claim 6, wherein the boric acid or boric acid compound present on the surface of the magnesium hydroxide is magnesium borate.