JP2011219640A - Magnesium hydroxide-based flame retardant, method for producing the same, and resin composition and molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnesium hydroxide-based flame retardant satisfying all of resistance to whitening by carbon dioxide gas, mechanical properties, hardness and insulation characteristics.SOLUTION: This flame retardant is obtained by forming, as a first layer, an inorganic film selected from colloidal silica and colloidal alumina at a rate of 0.5-3 mass% in terms of SiOor AlObased on 100 mass% of magnesium hydroxide on the surface of synthetic magnesium hydroxide particle with 8-20 m/g BET specific surface area and 0.5-1.0 μm average particle diameter; and forming, as a second layer, a film comprising an organic silane agent at a rate of 0.5-3 mass% based on 100 mass% of magnesium hydroxide.

Description

  The present invention relates to a magnesium hydroxide flame retardant as a so-called non-halogen flame retardant, a flame retardant resin composition containing the flame retardant, and a molded body thereof. In particular, for the purpose of non-halogen flame retardant coating materials for communication cables (optical fibers and metals), magnesium hydroxide flame retardants that satisfy all the requirements for mechanical properties, hardness, insulation properties, and carbon dioxide whitening resistance are provided. .

  Thermoplastic resins are widely used in coating materials such as optical fiber and metal communication cables, indoor power cables, household electrical appliances, and fine electric wires for automobiles, etc. because they are excellent in moldability and electrical insulation and are inexpensive. ing. Conventionally, a large amount of polyvinyl chloride resin has been used for such applications.

  However, cables using polyvinyl chloride resin, etc., generate a large amount of smoke in the event of a fire, and have hindered evacuation and fire fighting activities in sealed spaces such as underground malls, subways, ships, etc. There was a possibility of waking up. Therefore, there has been a demand for a resin material that generates less smoke during a fire and generates less harmful gas such as carbon monoxide even when burned. More recently, polyvinyl chloride-based resins are concerned about environmental problems such as dioxins, and have come to be further avoided. For example, non-halogen-based resins are often replaced with polyolefin-based resins. Yes. However, polyolefin resins are more flammable than polyvinyl chloride resins, and it has been studied to add magnesium hydroxide as a non-halogen flame retardant in order to make the polyolefin resins flame retardant.

  By the way, there are many requirements for the characteristics of non-halogen flame retardant coating materials for recent communication cables (optical fibers and metals). For example, it has become necessary to satisfy not only flame retardancy but also requirements for mechanical properties, hardness, insulating properties, and carbon dioxide whitening resistance. In particular, in terms of hardness, it has become customary for bearfish to breed in the summer, mainly in the western part of Japan, and to lay eggs in the covering material. Therefore, there is a problem that communication conductors (for example, glass fiber conductors, etc.) are damaged by the spawning of bearfish, resulting in poor communication. Therefore, a material that is hard enough not to lay eggs is desired as a covering material.

  In particular, in the whitening resistance of carbon dioxide gas, magnesium hydroxide itself easily reacts with an acid. Therefore, when a coating material containing the magnesium hydroxide is exposed to water containing carbonic acid for a long time, the surface of the basic magnesium carbonate is formed on the surface. This causes the problem of precipitation and whitening of the surface, which impairs the appearance of the coating material. Therefore, various surface treatment methods for magnesium hydroxide have been proposed since the past. However, the magnesium hydroxide flame retardant produced by the methods described in Patent Documents 1 to 3 described below, although satisfying carbon dioxide whitening resistance, was not satisfactory in all of mechanical properties, hardness, and insulation properties.

JP 6-2843 JP2003-253266 JP-A-10-338818

  An object of the present invention is to blend a magnesium hydroxide flame retardant satisfying all of carbon dioxide whitening resistance, tensile strength and elongation mechanical properties, hardness, and insulation properties, a manufacturing method thereof, and a magnesium hydroxide flame retardant. It is in providing a resin composition and a molded object.

The magnesium hydroxide flame retardant of this invention is
(1) BET specific surface area of 8 to ²⁰ m ² / g, (2) On the surface of synthetic magnesium hydroxide particles having an average particle size of 0.5 to 1.0 μm, (3) First layer selected from colloidal silica or colloidal alumina The formed inorganic film is formed at a ratio of 0.5 to 3% by mass with respect to 100% by mass of magnesium hydroxide in terms of SiO ₂ or Al ₂ O ₃ , and (4) a film composed of an organosilane agent is water as the second layer. It is formed at a ratio of 0.5 to 3% by mass with respect to 100% by mass of magnesium oxide.

The method for producing the magnesium hydroxide flame retardant of the present invention is as follows:
(1) A BET specific surface area of 8 to ²⁰ m ² / g and (2) an emulsified slurry in which synthetic magnesium hydroxide having an average particle size of 0.5 to 1.0 μm is emulsified in water,
To the emulsified slurry, an aqueous solution of colloidal silica or colloidal alumina is added so that the colloidal silica or colloidal alumina has a ratio of 0.5 to 3% by mass with respect to 100% by mass of magnesium hydroxide in terms of SiO ₂ or Al ₂ O _3. And
Next, the organic silane agent is added to the emulsified slurry so as to have a ratio of 0.5 to 3% by mass with respect to 100% by mass of magnesium hydroxide. Preferably, after the addition of the organic silane agent, the emulsified slurry is surface-treated while being heated, and after the surface treatment, it is filtered by vacuum filtration or the like, washed, dried, and pulverized.

  The present invention further lies in a flame retardant resin composition characterized in that 5 to 500 parts by mass of the flame retardant according to claim 1 is blended with 100 parts by mass of a polyolefin resin.

  The present invention also resides in a molded article comprising the flame retardant resin composition according to claim 3.

(1) The BET specific surface area of magnesium hydroxide is 8 to ²⁰ m ² / g, preferably 10 to 18 m ² / g, more preferably 12 to 16 m ² / g. If it is less than 8 m ² / g, the tensile strength and hardness are insufficient. If it exceeds 20 m ² / g, the elongation is insufficient.
(2) The average particle diameter of magnesium hydroxide is 0.5 to 1.0 μm, preferably 0.6 to 0.9 μm, and more preferably 0.7 to 0.8 μm. If it is less than 0.5 μm, it becomes bulky and it is difficult to fill the flame retardant powder into the resin. If it exceeds 1.0 μm, the tensile strength and hardness are insufficient.
(3) The first layer of the surface treatment agent uses colloidal silica or colloidal alumina. Good effect on carbon dioxide whitening resistance. Those having a low content of alkali metal ions such as Na ⁺ are preferred, and alkali metal ions other than Na ⁺ are substantially not included in most cases, so the limitation to the Na ⁺ concentration will be described below. The Na + concentration with respect to the solid content of SiO ₂ or Al ₂ O _{3 in the} colloidal silica or colloidal alumina solution is preferably 0.5% by mass or less, particularly preferably 0.2% by mass or less. If a material having a high Na content is used, it tends to remain in the flame retardant powder, and the insulation properties of the flame retardant resin composition containing this become insufficient. The processing amount of colloidal silica or colloidal alumina is 0.5 to 3% by mass in terms of SiO ₂ or Al ₂ O ₃ . If it is less than 0.5% by mass, the whitening resistance to carbon dioxide gas becomes insufficient. If it exceeds 3% by mass, the Mg (OH) ₂ content decreases and the original properties (flame retardant) as a flame retardant become insufficient.
(4) The second layer of the surface treatment agent uses an organosilane agent. There is little decrease in tensile strength and hardness, and it has a great effect on the whitening resistance of carbon dioxide gas by a synergistic effect with colloidal silica or colloidal alumina. When an organic silane agent is used alone, the carbon dioxide whitening resistance is poor. The processing amount of the organosilane agent is 0.5 to 3% by mass. If it is less than 0.5% by mass, the whitening resistance to carbon dioxide gas becomes insufficient. If it exceeds 3% by mass, the Mg (OH) ₂ content decreases and the original properties (flame retardant) as a flame retardant become insufficient. The organic silane agent is, for example, a silane agent having an organic functional group for the purpose of chemical bonding with a synthetic resin (silane coupling agent), and vinyl-based materials such as vinyltrimethoxysilane, vinyltrichlorosilane, and vinyltriethoxysilane. Silanes, epoxy silanes such as 2-epoxycyclohexyl-ethyltrimethoxysilane, 3-glycidoxypropyl-trimethoxysilane, 3-glycidoxypropyl-triethoxysilane, and styryls such as p-styryltrimethoxysilane Silanes, 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane and other acryloxy or methacryloxy silanes, 3-aminopropyltrimethoxysilane and other amino silanes, 3-chloropropyltrimethoxysilane Etc. Roarukiru silane of, mercapto silane such as 3-mercaptopropyltrimethoxysilane, have isocyanate silane such as 3-isocyanate propyl triethoxysilane. In addition, a silane agent having an organic functional group for the purpose of improving the affinity with a synthetic resin can be mentioned, for example, alkyl such as decyltrimethoxysilane (CH ₃ (CH ₂ ) ₉ ) Si (OCH ₃ ) ₃ ) Silanes of silane may be used, and the alkyl skeleton is arbitrary such as a hexyl group instead of a decyl group and a phenyl group. The functional group for chemically bonding with the inorganic material may be an ethoxy group or a chloro group instead of the methoxy group (OCH ₃ ) ₃ and hydrolyzes to generate a silanol group (Si-OH). Hydrogen bond or dehydration condensation with colloidal silica or colloidal alumina.
(5) Magnesium hydroxide-based flame retardant with high tensile strength, large elongation, high hardness, excellent insulation, and excellent carbon dioxide whitening resistance when formed into a resin molded body by a combination of the above conditions Is obtained.

  Hereinafter, the present invention will be described in detail based on examples and comparative examples. However, the present invention is not limited to these examples.

  After producing a flame retardant composed of magnesium hydroxide particles, this flame retardant was blended with a predetermined resin to obtain a flame retardant resin composition. Further, this composition was molded into a molded body, and the physical properties of the resin were evaluated. Specifically, it is as follows.

(Manufacture of flame retardant)
Put 2 L of 3.8N-HCl solution into a 3 L polyethylene container and add 222 g of general-purpose magnesium hydroxide (hereinafter also referred to as “Mg (OH) ₂ ”) powder while stirring. Then, it vacuum-filtered with the filter paper No. 5C. HCl and Mg (OH) ₂ were dissolved in an equivalent amount, and the artificial MgCl ₂ solution obtained by filtration was quantitatively analyzed by EDTA titration method. As a result, the MgCl ₂ concentration was 170 g / L. 1310 ml of this artificial MgCl ₂ solution was taken, and 510 ml of an 8.3N NaOH solution was slowly added to this with stirring (the molar ratio of Mg ²⁺ to OH ⁻ was 1: 1.8, 122 g of Mg (OH) ₂ Corresponding precipitation) and pure water were further added to prepare a 2 L suspension. This suspension was poured into an autoclave having a 3 L capacity Hastelloy C-276 wetted part and hydrothermally treated at 150 ° C. for 5 hours with stirring.

The slurry after the hydrothermal treatment was subjected to vacuum filtration, and then thoroughly washed with 20 times or more of pure water with respect to the solid content. Thereafter, it was returned again to pure water, and an emulsified slurry having a Mg (OH) ₂ solid content concentration of 100 g / L was prepared. 1 L of this emulsified slurry was collected in a ₂ L SUS316 container (corresponding to 100 g as the Mg (OH) ₂ solid content mass), and the slurry was heated to 80 ° C. while stirring. Thereafter, a colloidal silica solution having a concentration of 20% by mass at 80 ° C. (Snowtex O, manufactured by Nissan Chemical Industries, Ltd., Na + concentration of 0.2% by mass or less with respect to the SiO ₂ solid content in the solution) was added to Mg (OH) ₂ solid content. 1% by mass as SiO ₂ was added to the mass. Thereafter, vinyl trimethoxysilane (KBM-1003 manufactured by Shin-Etsu Chemical Co., Ltd.) was added in an amount of 1% by mass in terms of vinyl trimethoxysilane with respect to the mass of Mg (OH) ₂ solid content. After the addition, the surface treatment was performed by stirring at 80 ° C. for 8 hours. The surface treatment temperature is preferably 20 to 90 ° C., and the surface treatment time is preferably 1 to 20 hours. Thereafter, vacuum filtration was performed, and washing was performed with 5 times or more pure water with respect to the solid mass of Mg (OH) ₂ . After washing, drying and pulverization gave Mg (OH) ₂ powder (a flame retardant of the present invention). During the surface treatment, the entire amount of colloidal silica adheres to the surface of the magnesium hydroxide to form the first layer inorganic coating, and the organosilane agent adheres to the entire surface of the colloidal silica to form the second layer of organic silane coating. It was.

(Production of flame retardant resin composition and molded product)
After mixing and mixing 100 parts by mass of the flame retardant powder and 0.5 part of carbon to 100 parts by mass of ethylene-ethyl acrylate copolymer (trade name: A-1150, manufactured by Nippon Polyethylene Co., Ltd.), Laboplast Using a mill (manufactured by Toyo Seiki Co., Ltd.), kneading was performed at 150 ° C. for 5 minutes at a rotation speed of 50 rpm, and press molding was performed at 150 ° C. to obtain press sheets of various thicknesses.

(Analysis and evaluation method)
About a flame retardant and a molded object, it analyzed and evaluated as follows. The results are shown in Table 1 for Example 1 and Examples 2 to 9 described later. The results are shown in Table 2 for Comparative Examples 1 to 10 described later.
(1) Measurement of BET specific surface area and average particle diameter After hydrothermal treatment, the BET specific surface area of magnesium hydroxide powder obtained by washing, drying and grinding is measured by nitrogen adsorption method, and the average particle diameter is measured by laser diffraction scattering. The particle size was measured with a particle size distribution analyzer (Microtrack HRA manufactured by Nikkiso Co., Ltd.).
(2) Tensile test
In accordance with JIS-K-7113, the above-mentioned 2 mm-thick press sheet was punched into a No. 2 type dumbbell, and the test speed was 200 mm / min. The target values were 1.3 kgf / mm ² or more for tensile strength and 300% or more for elongation.
(3) Hardness
In accordance with JIS-K-7215, the hardness (Shore D) of the 2 mm thick press sheet was measured with a durometer / D type. The target value was 40 or more on Shore D.
(4) Insulation characteristics (volume resistivity)
In accordance with JIS-K-6911, leave the above 2mm thick press sheet (length 130mm x width 130mm) in an atmosphere at a temperature of 30 ° C and a relative humidity of 50% for 3 hours, and then use the resistivity measuring electrode. A voltage of 500 V was applied and the volume resistance value after charging for 1 minute was measured and converted to a volume resistivity value. The target value was a volume resistivity of 1 × 10 ¹⁴ Ω · cm or more.
(5) Carbon dioxide gas whitening resistance (carbon dioxide mass increase rate)
The 2 mm-thick press sheet (20 mm long × 20 mm wide) was placed in a 50 ml beaker filled with 30 ml of pure water, and the container was placed in a desiccator and continuously vented at a carbon dioxide gas flow rate of 100 ml / min. In this state, carbon dioxide was contacted at 25 ° C. for 5 days, and then the pure water in the beaker was heated and evaporated at 120 ° C. for 12 hours, and the mass increase rate of the molded body was measured. The more the mass increases, the more basic magnesium carbonate is produced, and the carbon dioxide whitening resistance is poor. The target value was + 0.5% or less in mass increase rate.

  Except that the temperature of the hydrothermal treatment was set to 170 ° C., the same operation as in Example 1 was performed to prepare a flame retardant powder, which was analyzed and evaluated.

  Except that the hydrothermal treatment temperature was set to 130 ° C., the same operation as in Example 1 was performed to prepare a flame retardant powder, which was analyzed and evaluated.

A flame retardant powder was prepared and analyzed in the same manner as in Example 1 except that a 20 mass% colloidal silica solution was added in an amount of 0.5 mass% as SiO ₂ with respect to the Mg (OH) ₂ solid mass.・ Evaluated.

A flame retardant powder was prepared and analyzed in the same manner as in Example 1 except that 3% by mass of 20% by mass colloidal silica solution was added as SiO ₂ to the Mg (OH) ₂ solid mass.・ Evaluated.

Except for adding 0.5% by mass of vinyltrimethoxysilane to ₂ % by mass of Mg (OH) ₂ , the same operation as in Example 1 (containing 1% by mass of colloidal silica) was performed to prepare a flame retardant powder, Analyzed and evaluated.

Except for adding 3% by mass of vinyltrimethoxysilane to ₂ % by mass of Mg (OH) _{2 in the same} manner as in Example 1 (containing 1% by mass of colloidal silica), a flame retardant powder was prepared, Analyzed and evaluated.

Instead of colloidal silica solution, 20 mass% colloidal alumina solution (Nissan Chemical Industry Co., Ltd. alumina sol 520, Na + concentration relative to Al ₂ O ₃ solid content in the solution is 0.2 mass% or less), Mg (OH) ₂ Except for adding 1% by mass as Al ₂ O _{3 based} on the mass of the solid content, the same operation as in Example 1 (containing 1% by mass of vinyltrimethoxysilane) was carried out to prepare a flame retardant powder for analysis and evaluation. Went.

Instead of vinyltrimethoxysilane, decyltrimethoxysilane (KBM-3103C manufactured by Shin-Etsu Chemical Co., Ltd.) was added in an amount of 1% by mass with respect to the mass of Mg (OH) ₂ solid content. (1% by mass of colloidal silica), a flame retardant powder was prepared and analyzed and evaluated.

(Comparative Example 1)
Except that the hydrothermal treatment temperature was set to 190 ° C., the same operation as in Example 1 was performed to prepare a flame retardant powder, which was analyzed and evaluated.

(Comparative Example 2)
Except that the temperature of the hydrothermal treatment was changed to 110 ° C., the same operation as in Example 1 was performed to prepare a flame retardant powder, which was analyzed and evaluated.

(Comparative Example 3)
Except that no vinyltrimethoxysilane was added, the same operation as in Example 1 was carried out to prepare a flame retardant powder, which was analyzed and evaluated.

(Comparative Example 4)
Except for not adding the 20 mass% colloidal silica solution, the same operation as in Example 1 was performed to prepare a flame retardant powder, which was analyzed and evaluated.

(Comparative Example 5)
1 L of Mg (OH) ₂ emulsified slurry obtained by the synthesis of Example 1 was collected in a ₂ L capacity SUS316 container (corresponding to 100 g as the mass of Mg (OH) ₂ solid content) and stirred until it reached 80 ° C. with stirring. Was warmed. Then, after adding 1 mass% of No. 3 sodium silicate (JIS K1408) as SiO ₂ to Mg (OH) ₂ solid mass, sulfuric acid was added over 1 hour until the pH of the slurry became 9, and decyl Example 1 except that 1% by mass of trimethoxysilane (KBM-3103C manufactured by Shin-Etsu Chemical Co., Ltd.) was added at 1% by mass based on the mass of Mg (OH) _{2 and} stirred for 8 hours at 80 ° C. The same operation was performed to prepare a flame retardant powder, which was analyzed and evaluated.

(Comparative Example 6)
A flame retardant powder was prepared, analyzed and evaluated in the same manner as in Comparative Example 5 except that No. 3 sodium silicate was added in an amount of 3% by mass as SiO ₂ with respect to the solid mass of Mg (OH) _2. It was. Sulfuric acid was added until the pH of the slurry reached 9.

(Comparative Example 7)
In place of decyltrimethoxysilane, except for adding 1% by mass of vinyltrimethoxysilane to the mass of Mg (OH) ₂ solid content, the same operation as in Comparative Example 5 was performed to prepare a flame retardant powder, and the analysis・ Evaluated.

(Comparative Example 8)
A flame retardant powder was prepared, analyzed and evaluated in the same manner as in Comparative Example 5 except that 3% by mass of decyltrimethoxysilane was added to the mass of Mg (OH) ₂ solid content.

(Comparative Example 9)
1 L of the Mg (OH) ₂ emulsified slurry obtained by the synthesis of Example 1 was collected in a ₂ L capacity SUS316 container (corresponding to 100 g as the mass of Mg (OH) ₂ solid content), and 20.6 g of NaOH in solid content was added and stirred. After the dispersion, an aluminum chloride hexahydrate aqueous solution having a concentration of 10 g / L was added as Al ₂ O ₃ over 30 minutes with respect to the Mg (OH) ₂ solid mass, and 0.9 mass% was added over 30 minutes, followed by stirring and holding for 30 minutes. . After that, it was heated to 80 ° C, and with sufficient stirring, an aqueous solution of sodium oleate was added in an amount of 0.3% by weight based on the solid mass of Mg (OH) ₂ and the surface treatment was carried out with stirring for 30 minutes. The same operation as in Example 1 was performed to prepare a flame retardant powder, which was analyzed and evaluated.

(Comparative Example 10)
1L of Mg (OH) ₂ emulsified slurry obtained by the synthesis of Example 1 was collected in a 2L capacity SUS316 container (corresponding to 100g as the mass of Mg (OH) ₂ solid content) and stirred until it reached 80 ° C while stirring. Was warmed. Then, an aqueous solution of sodium salt of stearyl alcohol phosphate adjusted to a temperature of 80 ° C. at a concentration of 10 g / L (monoester: diester = 1: 1 molar ratio) was 3% by mass relative to the solid mass of Mg (OH) ₂ A flame retardant powder was prepared, analyzed and evaluated in the same manner as in Example 1 except that the surface treatment was performed by adding and stirring for 30 minutes.

  Although not shown in the table, the oxygen index was measured for flame retardancy (JIS-K-7201), but any of the molded bodies of Examples and Comparative Examples had a target of 26 points or more and had no problem. .

  From Examples 1 to 9, colloidal silica and colloidal alumina are almost the same, and the organic silane agent is not limited to a silane agent having an organic functional group for the purpose of chemical bonding with a synthetic resin such as vinyltrimethoxysilane. It turns out that the silane agent which has an organic functional group for the purpose of affinity improvement with synthetic resins, such as trimethoxysilane, may be sufficient. From Examples 1 to 3 and Comparative Examples 1 and 2, it can be seen that the BET specific surface area and average particle diameter of magnesium hydroxide are important for obtaining appropriate tensile strength, elongation, and hardness. From Example 1 and Comparative Example 3, it can be seen that the whitening resistance to carbon dioxide gas is insufficient when the organosilane agent is lacking. From Comparative Example 4, it can be seen that even when an organic silane agent is contained, the carbon dioxide gas whitening resistance is also insufficient when the coating layer of colloidal silica or colloidal alumina is lacking. From Examples 4 to 7 and Comparative Examples 5 to 7, it can be seen that there is a synergistic effect between colloidal silica or colloidal alumina and the organosilane agent, and appropriate tensile strength and hardness can be obtained by this combination. . Furthermore, it can be seen that the volume resistivity decreases when sodium silicate is used (Comparative Examples 5 to 8) or NaOH is used to deposit an aluminum hydroxide film (Comparative Example 9).

Claims (4)

(1) BET specific surface area of 8 to ²⁰ m ² / g, (2) On the surface of synthetic magnesium hydroxide particles having an average particle size of 0.5 to 1.0 μm, (3) First layer selected from colloidal silica or colloidal alumina The formed inorganic film is formed at a ratio of 0.5 to 3% by mass with respect to 100% by mass of magnesium hydroxide in terms of SiO ₂ or Al ₂ O ₃ , and (4) a film composed of an organosilane agent is water as the second layer. A magnesium hydroxide-based flame retardant, which is formed at a ratio of 0.5 to 3% by mass with respect to 100% by mass of magnesium oxide. (1) A BET specific surface area of 8 to ²⁰ m ² / g and (2) an emulsified slurry in which synthetic magnesium hydroxide having an average particle size of 0.5 to 1.0 μm is emulsified in water,
To the emulsified slurry, an aqueous solution of colloidal silica or colloidal alumina is added so that the colloidal silica or colloidal alumina has a ratio of 0.5 to 3% by mass with respect to 100% by mass of magnesium hydroxide in terms of SiO ₂ or Al ₂ O _3. And
Subsequently, the organosilane agent is added to the emulsified slurry so as to have a ratio of 0.5 to 3% by mass with respect to 100% by mass of magnesium hydroxide.   5. A flame retardant resin composition comprising 5 to 500 parts by mass of the flame retardant according to claim 1 per 100 parts by mass of a polyolefin resin.   The molded object which consists of a flame-retardant resin composition of Claim 3.