JPH0351653B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention utilizes the conventionally known magnesium hydroxide Mg
(OH) has a different X-ray diffraction structure from ₂ , e.g.
It has significantly superior effects compared to conventionally known magnesium hydroxide for applications such as flame retardants for blending thermoplastic synthetic resins, flame retardants for water-based paints, and magnesium oxide precursors for annealing separators for silicon steel. The present invention relates to a synthetic magnesium hydroxide having a novel structure shown in FIG. More specifically, the present invention provides crystal grains that are represented by the following formula Mg(OH) ₂ , have a strain in the <101> direction in X-ray diffraction of 3.0×10 ^-3 or less, and have a crystal particle diameter of 800
The present invention relates to a synthetic magnesium hydroxide having a BET specific surface area of less than 20 m ² /g but more than 1 m ² /g. Magnesium hydroxide has been known for a long time.
Used in a wide range of fields. For example, it is also used to impart flame retardancy to thermoplastic synthetic resins by blending them into the resins. If it is blended into a thermoplastic synthetic resin in an amount sufficient to impart a usable flame retardant effect, the physical properties of the resin, particularly impact resistance and elongation, may deteriorate, and molded articles may not be formed from this composition. This reduces resin flow during molding, impairs molding suitability, and lowers molding efficiency. Furthermore, there are other disadvantages such as a flash pattern appearing on the resulting molded product, which impairs the appearance of the molded product. The inventors of the present invention have conducted research into the causes of the above-mentioned disadvantages and defects. As a result, it was discovered that such disadvantages or defects originate from the inherent structural characteristics of magnesium hydroxide. In particular, it has been discovered that the structural distortion of magnesium hydroxide and furthermore the crystal particle size are important factors that cause the disadvantages or defects mentioned above. As is well known, conventionally known magnesium hydroxide has a large structural strain, and the minimum strain in the <101> direction in X-ray diffraction is approximately 3.6×.
10 ^-3 , reaching approximately 10×10 ^-3 . Furthermore, its crystal grain size is small, at most 800 Å.
It is within the range of 100 to 800 Å, and its BET specific surface area is large, with a minimum of 20 m ² /g and 20 to 100 Å.
It is within the range of m ² /g. The large structural strain described above means that magnesium hydroxide has a highly polar crystallite surface, and also indicates that the crystallites have a structure that facilitates secondary aggregation using water as a medium. There is. For this reason, secondary aggregation easily occurs and aggregates to a size of 10 to 100μ, and due to this secondary aggregation, a non-negligible amount of water molecules and air are trapped in the aggregate even after drying of magnesium hydroxide. and remain. Conventionally known magnesium hydroxide has the above-mentioned structural feature of large distortion, so it has poor affinity with thermoplastic synthetic resins, especially resins with high hydrophobicity or non-polarity, such as resins such as polyolefins. Moreover, it is assumed that the dispersibility in the resin is extremely poor due to the strong secondary agglomeration of crystallites, and in fact, as mentioned above, resin compositions containing magnesium hydroxide have poor moldability and reduce molding efficiency. In addition, poor affinity with resins tends to cause interfacial separation between the resin and magnesium hydroxide particles, leading to a decrease in physical properties, especially impact strength and elongation, and making it difficult to uniformly disperse the particles into the resin. Make it. Furthermore, the presence of water molecules and air associated with secondary aggregation of crystallites, presumably because these are released during molding, causes deterioration in the appearance of the molded product, such as the occurrence of flash patterns. Furthermore, secondary aggregation of crystallites results in bulkiness, making it difficult to perform a smooth extrusion operation during extrusion molding of the resin, and causing secondary defects such as worsening of uniform dispersion in the resin. Become. The present inventors conducted research to overcome the disadvantages or defects derived from the structural characteristics of conventionally known magnesium hydroxide as detailed above. As a result, it is possible to provide magnesium hydroxide having novel structural features that are clearly distinguishable from the above-mentioned structural features inherent to previously unknown magnesium hydroxide, and that magnesium hydroxide having this new structure is different from conventionally known magnesium hydroxide. It has been discovered that magnesium hydroxide has excellent properties that can overcome the disadvantages and defects described above. Furthermore, it has been discovered that this previously unknown magnesium hydroxide having a new structure can be industrially and advantageously produced by a method that has never been used before, but is extremely easy. Therefore, an object of the present invention is to provide magnesium hydroxide having excellent improved properties and a novel structure. Another object of the present invention is to provide an industrially advantageous manufacturing method for producing magnesium hydroxide having such a novel structure. A third object of the present invention is to provide an intermediate useful for providing magnesium hydroxide having the above-mentioned novel structure and a method for producing the same. A fourth object of the present invention is to provide use of magnesium hydroxide having the above-mentioned novel structure. The above objects and many other objects and advantages of the present invention will become more apparent from the following description. The magnesium hydroxide of the present invention is represented by Mg(OH) ₂ and has a strain in the <101> direction as determined by X-ray diffraction of 3.0×10 ⁻³ or less. Conventional magnesium hydroxide is expressed as Mg(OH) ₂ , but the above strain is 3.6×
10 ^-3 or more, while the above distortion is 3.0×10 ^-3
The magnesium hydroxide of the present invention can be distinguished from the following. The strain in the <101> direction in the X-ray diffraction method of magnesium hydroxide of the present invention is, for example,
It is usually in the range of 3.0×10 ^-3 or less to 0.1×10 ^-3 or more. The crystal particle diameter in the <101> direction in the X-ray diffraction method of magnesium hydroxide of the present invention is 800
More than Å. While the particle size of conventional magnesium hydroxide is 100 to 800 Å, the magnesium hydroxide of the present invention exhibits a characteristic structure even with this crystal particle size. The crystal particle size of the magnesium hydroxide of the present invention is typically greater than 800 Å and less than 50000 Å, for example. While the BET specific surface area of conventional magnesium hydroxide is 20 to 100 m ² /g, the magnesium hydroxide of the present invention has a BET specific surface area of 20 to 100 m 2 /g.
Although the specific surface area is less than 20 m ² /g, it exceeds 1 m ² /g, and this specific surface area is also characteristic. In addition, as mentioned above, conventional magnesium hydroxide easily causes secondary aggregation and
Whereas the particles have an average secondary particle size (average particle size including secondary agglomerated particles) of 100μ, the magnesium hydroxide of the present invention does not easily cause secondary agglomeration,
Even if agglomeration occurs, the average secondary particle size is 5μ
For example, it is about 0.5 to 2μ. The magnesium hydroxide with the novel structure of the present invention exhibiting optimally improved properties combines the above characteristics. That is, the strain in the <101> direction in the X-ray diffraction method is 3.0 × 10 ^-3 or less, the crystal grain size in this direction exceeds 800 Å, and the BET specific surface area is 20 m ² /g.
However, it exceeds 1 m ² /g. Magnesium hydroxide having the above-mentioned novel structure has the following formula Mg(OH) ₂ − which is different from either the conventional magnesium hydroxide represented by Mg(OH) ₂ or the conventional magnesium hydroxychloride represented by Mg(OH)Cl. xAx・mH ₂ O In the formula, A is Cl or NO ₃ and x is 0<x<0.2
It can be obtained by heating basic magnesium chloride or nitrate, where m is a number from 0 to 6, in an aqueous medium under pressurized conditions. Furthermore, the basic magnesium chloride or nitrate which can be represented by the above formula is prepared by combining magnesium chloride or magnesium nitrate and an alkaline substance in an aqueous medium in a controlled amount relative to the magnesium chloride or magnesium nitrate; In particular, it can be produced by reacting an alkaline substance in an amount of 0.5 to 0.95 equivalents. The strain in the <101> direction in the X-ray diffraction method of the present invention is 3.0×10 ^-3 or less, and the crystal grain size in this direction is 800
The above Mg(OH) ₂ −xAx・
When producing mH ₂ O [where A is Cl or NO ₃ , 0<x<0.2, preferably 0.02≦x<0.2, m is a number from 0 to 6], an alkaline substance [OH] and magnesium chloride or Magnesium nitrate and [Mg ²⁺ ] meet the above equivalence relationship, that is, 2
In addition to carrying out the reaction so as to satisfy the relationship of [OH]/[Mg ²⁺ ]=0.5 to 0.95, it is preferable to carry out the reaction under conditions where chloride ions are sufficiently present. For this purpose, it is preferable to carry out the reaction by adding an alkaline substance, such as calcium hydroxide, in a controlled amount that satisfies the above equivalence relationship to a mixed aqueous solution containing, for example, calcium chloride in addition to magnesium chloride. According to conventional methods, Mg
Adopting the conditions under which (OH) ₂ is formed, then,
Even by heating under pressurized conditions in an aqueous medium, it is not possible to form magnesium hydroxide having the novel structure of the present invention. Basic magnesium nitrate can be produced in the same manner except that magnesium nitrate is used in place of the above magnesium chloride, and can be similarly utilized in the production of the novel Mg(OH) ₂ of the present invention. The above base magnesium chloride or nitrate
Mg(OH) ₂ −xAx・mH ₂ O [However, A is Cl or
NO ₃ , m is a number from 0 to 6, 0<x<0.2] formation reaction is performed at a temperature of, for example, about 0 to about 50°C, preferably about
It is best to do this at a temperature of about 30℃. The reaction may be carried out in an aqueous medium under conditions that allow sufficient contact between magnesium chloride or magnesium nitrate and an alkaline substance. For example, the reaction may be carried out in an aqueous medium of magnesium chloride, magnesium nitrate, or magnesium chloride and calcium chloride under stirring conditions. This can be carried out by adding calcium hydroxide so as to satisfy the above equivalence relationship. Examples of the above-mentioned alkaline substances include, in addition to calcium hydroxide, ammonia,
Examples include alkali metal hydroxide and magnesium oxide. Magnesium hydroxide having a strain in the <101> direction of 3.0×10 ^-3 or less in the X-ray diffraction method of the present invention is
Basic magnesium chloride or basic magnesium nitrate Mg(OH) ₂ − formed by means as described above.
xAx・mH ₂ O [However, A is Cl or NO ₃ , m is 0 to 6
0<x<0.2] in an aqueous medium under pressurized conditions, preferably at least about 5 Kg/ ^cm2 , e.
It can be produced by heating under pressurized conditions of about 30 kg/cm ² . At this time, it is not necessary to isolate the basic magnesium chloride from the basic magnesium chloride-forming reaction product system, and the reaction product system can be heated as it is under pressurized conditions. It is preferable to do so. This preferred embodiment is particularly suitable for industrial implementation, since the Mg(OH) ₂ −xAx·mH ₂ O is a relatively unstable compound, but is relatively stable in the reaction mother liquor. Furthermore, there is an additional advantage that the isolation operation can be omitted. Even if ordinary magnesium hydroxide or magnesium hydroxychloride is heated under pressurized conditions in the presence or absence of an alkali in an aqueous medium, magnesium hydroxide having the novel structure of the present invention cannot be formed. Can not. Above basic chloride- or nitric acid-magnesium Mg(OH) ₂ −xAx・
mH ₂ O [A, x, m are the same as above] is
It may be formed by other means. The heat treatment in an aqueous medium under the above-mentioned pressurized conditions can be performed at a temperature of about 150 to about 250°C, for example. As mentioned above, the magnesium hydroxide having the new structure of the present invention has significantly smaller strain in the <101> direction in X-ray diffraction compared to conventional magnesium hydroxide, and has a crystal particle size in this direction. It is large and has an abnormally small BET specific surface area. Due to these characteristic structures, the surface polarity of the crystallites is extremely small and almost disappears, secondary aggregation hardly occurs, non-bulky, and the concentration of lattice defects is low. For this reason, various disadvantages and defects such as poor affinity with the previously mentioned resins, poor moldability, and poor molded product surfaces occur when conventionally known magnesium hydroxide is blended with thermoplastic resins. is overcome, and furthermore the defect of a reduction in the physical strength of the molded article obtained is also avoided. In the present invention, the strain in the <101> direction in X-ray diffraction, the crystal grain size in this direction, and the BET method specific surface area refer to values determined by the following measurements. Method for measuring strain in <101> direction and crystal grain size: - Using the following relational expression, plot sinθ/λ on the horizontal axis and βcosθ/λ on the vertical axis, and calculate the crystal grain size (ε) from the reciprocal of the intercept. Find the strain (η) by multiplying the slope by 1/2. βcosθ/λ=1/ε+2ηsinθ/λ Where, λ: Wavelength of X-ray used, 1.542Å for Cu-Kα ray θ: Black angle β: True half-value width, unit: radian The above β is calculated by the following method. demand. The diffraction profiles of the (101) and (202) planes of Cu were generated using an X-ray source of 35 KV and 15 mA.
-Measure using Kα radiation. The measurement conditions were gonio speed 1/4°/min, chart speed 10mm/min,
The slit width is 1°-0.3mm-1° for the (101) plane and 2°-0.3mm-2° for the (202) plane in the order of divergence slit, receiving slit, and scattering slit. Measure. For the obtained profile, the width (B ₀ ) at 1/2 of the height from the background to the diffraction peak is measured.
From the relationship of the split widths (δ) of Kα ₁ and Kα ₂ with respect to 2θ shown in FIG. 1, the δ with respect to 2θ of the (101) and (202) planes can be read. Next, based on the above values of B ₀ and δ, B is determined from the relationship between δ/B ₀ and B/B ₀ shown in FIG. High purity silicon (99.999% purity)
, measure each diffraction profile with a slit width of 1/2° - 0.3 mm - 1/2° and find the half value width (b). Plot this against 2θ and create a graph showing the relationship between b and 2θ. b/B is calculated from b corresponding to 2θ of the (101) and (202) planes and is shown in FIG. b/B and β/
Find β from the relationship B. BET method specific surface area: - Determined using the 3-point plot method using the nitrogen adsorption method.
However, the molecular adsorption cross section of N ₂ is calculated as 16.2 Å ² . In addition, each measurement sample is subjected to a nitrogen adsorption test after being vacuum treated at 100°C for 30 minutes. Known basic magnesium chloride whose existence has been confirmed and registered with ASTM is the compound shown below.

[Table] As mentioned above, among the known basic magnesium chlorides, the compound most similar to the basic magnesium chloride of the present invention has x of the minimum 1/5 (=0.2)
These are known compounds of ASTM No. 12-123 and No. 7-409. The X-ray diffraction data of the above-mentioned known compound (as described by ASTM) and the X-ray diffraction data of the novel basic magnesium chloride of the present invention measured by the same method are shown below. ASTM No.12-123:-

【table】 ASTM No.7-409:-

【table】

【table】 Basic magnesium chloride of the present invention:-

[Table] From the above X-ray diffraction data, Mg of the present invention
It is clear that (OH) ₂ -xClx·mH ₂ O (where x and m are the same as above) is a compound having a structure different from that of known compounds. Furthermore, a new compound basic magnesium nitrate Mg(OH) ₂ −x(NO ₃ )x·mH ₂ O which is an intermediate of the present invention
(However, x and m are the same as above) The same data as in Table 1 are shown in the table below. The presence of basic magnesium nitrate is not described in ASTM.

[Table] Example 1 1.5 mol/magnesium chloride aqueous solution (liquid temperature
15℃) into a reaction container of about 10, and stir thoroughly with a Chemister stirrer. Add 10mol/
of ammonia water (liquid temperature 15°C) to magnesium chloride, add the entire amount of 1.35 equivalent to 0.9 equivalent over about 10 minutes. A portion of the obtained suspension was immediately filtered under reduced pressure and thoroughly washed with water and then with acetone. After drying at room temperature for about 2 hours, X-ray diffraction and chemical analysis were performed. As a result of X-ray diffraction, this substance was identified as basic magnesium chloride of the present invention. As a result of chemical analysis, the composition of this substance is Mg(OH) _1.903
It was shown that Cl _0.097 ·mH ₂ O. In addition, crystal water can be measured by DTA (differential thermal analysis) or TGA (thermogravimetric analysis).
Confirmed by law. Immediately after the reaction, most of the remaining suspension was placed in a 20 capacity autoclave and hydrothermally treated at 180°C for 8 hours. Approximately 2 hours from the end of the reaction until processing in the autoclave
I got there in time. This is because the hydrothermal treatment is performed while the unstable substances are not decomposed. After hydrothermal treatment, filter under reduced pressure, wash with water, and dry. The substance thus obtained was confirmed to be magnesium hydroxide by X-ray diffraction. <101> of this substance
The strain in the direction was 0.970×10 ⁻³ , the crystal grain size in the <101> direction was 4200 Å, and the BET was 6.7 m ² /g. Example 2 The same operation as in Example 1 was carried out except that 1.05 equivalent of aqueous ammonia was added to magnesium chloride in a total amount of 0.7 equivalent over about 7 minutes. A portion of the resulting suspension was immediately filtered under reduced pressure, thoroughly washed with water and then with acetone, and subjected to X-ray diffraction and chemical analysis. As a result, this substance was confirmed to be a new substance shown in Table 1. Chemical analysis showed that the composition of this substance was Mg(OH) _1.892 Cl _0.108 ·mH ₂ O. On the other hand, immediately after the reaction was completed, the reaction product solution was put into an autoclave with a capacity of 10, and heated to 170℃ for 8 hours.
Hydrothermally treated for hours. After treatment, it was filtered under reduced pressure, washed with water, and dried. The thus obtained magnesium hydroxide had a strain in the <101> direction of 1.20×10 ^-3 , a crystal grain size in the <101> direction of 5260 Å, and a BET of 4.2 m ² /g. Example 3 In Example 1, 1.425 equivalent to 0.95 equivalent of ammonia water was added to magnesium chloride.
The same operation as in Example 1 was performed except that the entire amount was added in 10 minutes. Excluding one part of the reaction solution, reduce the total volume to 10
Immediately transfer to an autoclave at 200°C.
Hydrothermal treatment was carried out for 4 hours. Immediately after the reaction, a portion of the reaction solution was filtered under reduced pressure, washed with water, washed with acetone, and then subjected to X-ray diffraction and chemical analysis. As a result of X-ray diffraction, this substance was confirmed to be a new substance shown in Table 1. As a result of chemical analysis, the composition of this substance is Mg(OH) _1.931 Cl _0.069 .
It was shown that mH ₂ O. Moreover, the hydrothermally treated product was dried under reduced pressure, filtered, washed with water, and then dried. The strain in the <101> direction of the magnesium hydroxide thus obtained is 2.05×10 ^-3 , and the crystal particle size in the <101> direction is 2840
Å, BET was 8.9 m ² /g. Example 4 Mixed aqueous solution of magnesium chloride and calcium chloride (a by-product produced in the process of producing sodium chloride from seawater by the ion exchange fat membrane method)
(Mg ²⁺ = 1.58 mol/, Ca ²⁺ = 0.765 mol/) 10
and equivalent to 0.8 equivalents of magnesium chloride
1.54 mol/calcium hydroxide aqueous solution 8.2 each is kept at 30°C. Pour 1 water in advance into a reaction tank with a capacity of 2 and equipped with an overflow, stir with a Chemister stirrer, and control the liquid temperature at 30°C. A mixed aqueous solution of magnesium chloride and calcium chloride was added to this reaction tank using a metering pump at 100 ml/min, 85 mL/min, respectively.
Supplied by a metering pump at a supply rate of ml/min,
Let the reaction take place. After the reaction was completed, the resulting suspension 16 was immediately transferred to an autoclave with a capacity of 30 and subjected to hydrothermal treatment at 145°C for 8 hours. The remainder of the reaction product solution was subjected to X-ray diffraction and chemical analysis after being vacuumed, filtered, washed with water and acetone, and dried at room temperature for 4 hours. As a result of X-ray diffraction, this substance was confirmed to be a new substance shown in Table 1. As a result of chemical analysis, the composition of this substance is Mg(OH) _1.909
It was shown that Cl _0.091 ·mH ₂ O. The hydrothermally treated product was filtered under reduced pressure, washed with water, and then dried. The strain in the <101> direction of the magnesium hydroxide thus obtained is 1.80×10 ^-3 , and the crystal particle size in the <101> direction is:
2250 Å, BET was 12.7 m ² /g. Example 5 2 mol/magnesium nitrate (liquid temperature 15°C) 2
Place the mixture in a reaction container of about 5 mL and stir thoroughly with a Chemister stirrer. To this, add 4 mol/aqueous ammonia (liquid temperature 15℃) to magnesium nitrate.
Add the entire amount of 1.8 equivalent to 0.9 over about 20 minutes. The resulting suspension 2 was immediately subjected to hydrothermal treatment at 170° C. for 4 hours in an autoclave with a capacity of 5. Immediately after the reaction was completed, the remaining 1.8 was filtered under reduced pressure, thoroughly washed with acetone, and subjected to X-ray diffraction and chemical analysis. This substance was confirmed to be a new substance shown in Table 2 as a result of X-ray diffraction. As a result of chemical analysis, the composition of this substance is Mg(OH) _1.827 (NO ₃ ) _0.173 .
It was shown that mH ₂ O. The hydrothermally treated product was subjected to reduced pressure, filtered, washed with water, and then dried. The strain in the <101> direction of the magnesium hydroxide obtained in this way is 2.40.
×10 ^-3 , crystal grain size is 4200Å, BET is 9.6m ² /
It was hot at g. Comparative Example 1 1.5 mol/magnesium chloride 2 was kept at 40°C and stirred thoroughly.
Add the entire amount of calcium hydroxide aqueous solution equivalent to 2 equivalents to magnesium chloride in about 60 minutes. The resulting reaction solution was filtered under reduced pressure and washed with water. The dehydrated product was dried at 80°C for 10 hours and was found to be magnesium hydroxide by X-ray diffraction. Also, wash the dishes with water for 6 minutes.
of water and hydrothermally treated at 250°C for 8 hours using a 10 volume autoclave. The hydrothermally treated product was filtered under reduced pressure, washed with water, and dried. of this substance
The strain in the <101> direction was 3.70×10 ^-3 , the crystal grain size in the <101> direction was 568 Å, and the BET was 32 m ² /g. In addition, the material before hydrothermal treatment has a strain of 4.76 in the <101> direction.
×10 ^-3 , crystal grain size in <101> direction is 549 Å, BET
was 21 m ² /g. Comparative example 2 1.5 mol/magnesium chloride 4 and
2.0 mol/calcium hydroxide 4 each
Keep at 20℃. Pour 500 ml of water into a 1.5-sized reaction tank with a capacity overflow and stir thoroughly. A metering pump is used to supply each sample at a rate of 40 ml/min. The supply of alkali is equivalent to that of magnesium chloride. After about 100 minutes, the reaction was completed,
A portion of the resulting suspension was filtered under reduced pressure, washed with water, and washed with acetone. As a result of X-ray diffraction, this material was found to be magnesium hydroxide. Immediately after the reaction, most of the remaining suspension was hydrothermally treated at 170°C for 8 hours in a 10 volume autoclave. The hydrothermally treated product was filtered under reduced pressure, washed with water, and dried. This substance is <101
The strain in the <101> direction was 3.70×10 ^-3 , the crystal grain size in the <101> direction was 647 Å, and the BET was 26 m ² /g. In addition, the material before hydrothermal treatment has a strain of 4.83× in the <101> direction.
10 ^-3 , crystal grain size in <101> direction is 476 Å, BET31
m ² /g. Reference example 1 The strain in the <101> direction obtained in Example 2 is 1.20×
10 ^-3 , crystal grain size in <101> direction is 5260 Å, BET
2.2Kg of magnesium hydroxide with 4.2m ² /g at 150℃
The mixture was re-dried for 3 hours, mixed with 1.8 kg of polypropylene (MI 6.0, density 0.91) using a Henschel mixer, and then melt-kneaded through an extruder at a resin temperature of about 230°C. The obtained resin composition was injection molded to form a plate-shaped body. Physical properties and flame retardancy were measured and evaluated in accordance with ASTM and UL standards. The results obtained are shown in Table 3. Reference example 2 Magnesium hydroxide obtained in Example 2 2.2Kg
10×10 ^-3 mol/sodium stearate aqueous solution
10 and maintained under stirring at 80° C. for 2 hours to coat the surface of the magnesium hydroxide with stearic acid. This was filtered under reduced pressure, washed with water, dried, and treated in the same manner as in Reference Example 1. The results are shown in Table 3. Reference Example 4 The strain in the <101> direction obtained in Comparative Example 1 was 4.76×
10 ^-3 , crystal grain size in <101> direction is 549 Å, BET21
Table 3 shows the results when 2.2 kg of m ² /g magnesium hydroxide was used in place of the magnesium hydroxide used in Reference Example 1. Reference Example 4 The strain in the <101> direction obtained in Comparative Example 2 is 3.70×
10 ^-3 , crystal grain size in <101> direction is 647 Å, BET26
The results of using m ² /g of magnesium hydroxide in place of the magnesium hydroxide used in Reference Example 1 are shown in the third example.
Shown in the table. Reference Example 5 Table 3 shows the results when the polypropylene used in Reference Example 1 was molded alone.

【table】 [Brief explanation of drawings]

FIGS. 1 to 3 are graphs for explaining a method for measuring and determining strain in the <101> direction and crystal grain size in X-ray diffraction in the present invention.

Claims (1)

[Claims] 1 Represented by the following formula Mg(OH) ₂ , the strain in the <101> direction in X-ray diffraction is 3.0×10 ^-3 or less, and the crystal grain size in the <101> direction is 800 Å. Exceeding and BET method specific surface area of 20m ² /g
Synthetic magnesium hydroxide characterized in that it has an area of less than 1 m ² /g but more than 1 m 2 /g.