KR20030045357A - Three powder synthesis of layered double hydroxides with inorganic anions - Google Patents

Abstract

PURPOSE: Provided are layered composite hydroxides having a structure of Mg-Al-Zn and CO3 as an interlayer material, respectively by a hydrothermal method. The resultant layered mixed hydroxides have thermal stabilization against Cl-contained resin like PVC. CONSTITUTION: The layered composite hydroxides are prepared by hydrothermal reacting layer materials, insoluble salts such as Mg(OH)2, Al(OH)3 and ZnO, and interlayer materials, inorganic anions(CO3 2-) supplied from NaHCO3, NH4HCO3 and CO2 gas, at 140-180deg.C for 0.5-5hrs, wherein the pressure of supplied CO2 gas is in a range of 20.8-32.4atm. Therefore, the hydrothermal method enables easy surface treatment in termination of reaction and excludes the washing of products, Mg-Al-Zn layered composite hydroxides.

Description

Three powder synthesis of layered double hydroxides with inorganic anions}

The present invention relates to a method for producing a layered complex hydrate having a layered complex hydrate used as a vinyl chloride resin (PVC) heat stabilizer by layer hydrothermal synthesis and layered with Mg-Zn-Al and a CO ₃ interlayer material.

Layered complex hydrates, also called hydrotalcite-like compounds, anion clay mimerals, layered mixed metal hydroxides, and layered double hydroxides (LDH) Mixed hydroxides are naturally present in some regions, in Snarum and Ural mountains in Norway, with reserves of 2,000 to 3,000 tonnes worldwide. Natural hydrotalcite always contains other minerals, such as penninite and muscovite, and also contains large amounts of impurities such as heavy metals. The removal of these impurities is practically impossible and industrialization is impossible. However, layered complex hydrate is a compound that can be easily synthesized in the laboratory and is represented by the following general formula.

M (II) _1-x M (III) _x (OH) ₂ X ^m- _{x / m} . nH ₂ O

x = M (III) / {M (II) + M (III)}

M (II) is Mg ²⁺ , Ni ²⁺ , Zn ²⁺ , Mn ^{2+ and the like} , M (III) is Al ³⁺ , Fe ³⁺ , Co ³⁺ , Cr ^{3+ and the like and} X ^m- is NO ₃ ^{2 -} , CO ₃ ^2- , Cl ^- and the like, and the range of x is 0.17 <x <0.33.

In the early stages of layered complex hydrate research, the research on the structure of natural materials has been mainly conducted, but in recent 20 years, the synthesis method, intercalation of anions, the synthesis of crosslinked materials, catalytic activity, thermal stability, antacid capacity, memory effect Much research has been done on the nature of rehydration reactions and the characterization of chemical reactions. Currently, studies on the industrial use of LDH have been actively conducted, and researches on the utilization of polymers in surface treatment and the removal of environmental pollutants are being actively conducted.

LDH has characteristics that can be applied to a wide range of industrially and is expected to increase its range of application, and is currently used as an additive in polymers. The classification according to the purpose to be added is as follows. Catalytic inactivators and neutralizers that inhibit the activity of the ziegler catalyst used in the production of polyolefin resins are used in PE, LDPE, LLDPE, HDPE and PP, and are added to polymers to suppress secondary damage with flame retardants and flame retardants. It has been used in PVC, chlorinated rubber, etc. as a thermal insulation agent for use of furnace, as a heat insulating agent using infrared absorption effect on agricultural vinyl, and as a heat stabilizer of chlorine-containing resin.

There are coprecipitation method and hydrothermal method for the preparation of LDH. The preparation of LDH by coprecipitation method uses magnesium chloride and nitrate (MgCl ₂ , MgNO ₃ ) as water-soluble salts as magnesium source, and magnesium as aluminum source The same water-soluble salt, aluminum chloride or aluminum nitrate, is used as an aqueous solution and sodium hydroxide (NaOH) aqueous solution is added at a fixed rate to prevent the pH from dropping. The reaction temperature is selected from the range of 40-100 ℃ to carry out the filtration after the maintenance reaction, and stirred for a certain time in an aqueous solution of carbonate ions, washed and dried. The advantage of this reaction is that it has a relatively easy reaction condition, but requires the excessive washing by soluble anions.

The production of LDH by hydrothermal synthesis is carried out in an autoclave using Mg (OH) ₂ and Al (OH) ₃ , which are sparingly soluble salts. An aqueous solution of sodium bicarbonate (NaHCO ₃ ) in which soluble salts are dissolved After slurried in, it is transferred to an autoclave reactor and reacted in the range of 120-180 ° C. It is a reaction governed by reaction temperature, reaction time and pressure. Difficult to establish the reaction conditions, but the disadvantage is that the reaction process is simple and easy to clean. As a disadvantage, since NaOH is generated, the generation of water pollutants due to the generation of by-products and the rise of pH is a problem of industrialization.

In addition, literatures applying Mg-Al-Zn-based layered complex hydrates as thermal stabilizers to chlorine-containing resins are difficult to find, and their manufacturing processes are generally manufactured by coprecipitation, which leads to a washing process, making the manufacturing process complex, reaction and Aging time of more than 24 hours is not suitable for use in commercial manufacturing processes.

Meanwhile, stabilizers formulated in PVC have been used a lot of heavy metal fatty acids, Sn-based, Ba-based and Pb-based for a long time, the toxicity of the human body is a problem, non-toxic formulations have become common in recent years. Zn and Ca fatty acid salts are utilized as non-toxic stabilizers. However, since the effect of Zn and Ca compounds is lower than that of Cd, Ba, Pb, and Sn compounds, which have been conventionally used for PVC, studies on applying layered complex hydrates with excellent thermal stability and no toxicity are actively conducted. It is becoming.

In Japanese Patent Laid-Open No. 7-157704, hydrotalcite is added to remove chlorine by adding to a chlorinated polyolefin-containing printing ink composition, and in Japanese Patent Laid-Open No. 2001-0011009, hydrotalcite is added to thermoplastic rubber to add thermoplastic rubber. To reduce the chlorine content In Korea Patent Publication 10-0193317, Li-Al-based hydrotalcite was used as a resin stabilizer. The inventions described above use Mg-Al-based hydrotalcite, and have a disadvantage of low economical efficiency by using expensive Li as a resin stabilizer without adding Zn having excellent initial thermal stability.

In the present invention, as a result of research efforts to improve the existing problems, magnesium oxide (Mg (OH) ₂ ) as a magnesium feed material, aluminum hydroxide (Al (OH) ₃ ) as an aluminum feed material, oxidized to a zinc feed material Zinc (ZnO) was used and sodium bicarbonate (NaHCO ₃ ), ammonium bicarbonate (NH ₄ HCO ₃ ) and carbon dioxide (CO ₂ ) were used as CO ₃ feed materials. And the manufacturing process adopts hydrothermal synthesis method using a high pressure reactor. The present invention does not require pH control like coprecipitation, the reaction and aging time can be shortened to 0.5-5 hours, preferably 1-3 hours, and does not require any washing process after the completion of the reaction, thus simplifying the manufacturing process effectively. You can.

In addition, by adding the Mg-Al-Zn-based layered complex hydrate prepared in the present invention to PVC, it is excellent in heat resistance characteristics compared to existing stabilizers and is applied as a PVC compound stabilizer that is harmless to humans.

The present invention relates to a method for producing a layered complex hydrate of Mg-Al-Zn-based having a heat stabilizing effect on a chlorine-containing resin, firstly, three kinds of powder material, namely magnesium hydroxide (Mg (OH)), which is a poorly soluble salt as a layered material source. ₂ ), using aluminum hydroxide (Al (OH) ₃ ) and zinc oxide (ZnO), select carbonate (CO ₃ ^2- ) as the inorganic anion as an interlayer, and source sodium bicarbonate (NaHCO ₃ ), ammonium bicarbonate Select one of (NH ₄ HCO ₃ ) and carbon dioxide (CO ₂ ) into a high-pressure reactor, respectively, the reaction temperature is 120-210 ℃, preferably 140-180 ℃, the reaction and aging time is 0.5-5 hours To prepare a layered complex hydrate of Mg-Al-Zn system having a thermal stability to the chlorine-containing resin, preferably 1-3 hours.

The present invention will be described in more detail as follows.

In the present invention, Zn ²⁺ ions are added to a conventional hydrotalcite, that is, Mg-Al-based layered complex hydrate, to synthesize the layered complex hydrate. A general molecular formula is as follows.

Mg ₃ ZnAl ₂ (0H) ₁₂ A ^y- _{2 / y} . nH ₂ O

Wherein A is a carbonate ion (CO ₃ ^2-), sulfate ion (SO ₄ ^2-), nitrate ion (NO ₃ ^-) and halogen ions ^{(X -: Cl -, Br} -, F -) . However deulsu the like, the The invention seeks to intercalate carbonate ions. And sources of magnesium, zinc and aluminum are shown below.

Magnesium sources include magnesium hydroxide, magnesium oxide, magnesium chloride, magnesium nitrate, and magnesium sulfate, with magnesium hydroxide being suitable in the present invention.

Examples of aluminum sources include aluminum hydroxide, aluminum oxide, aluminum chloride, aluminum minus, aluminum iodide, aluminum nitrate, aluminum sulfate, and the like. Aluminum hydroxide is suitable in the present invention.

Zinc sources include zinc chloride, zinc nitrate and zinc oxide, but zinc oxide is suitable in the present invention.

Sodium carbonate, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate and carbon dioxide may be used as the carbonate feed material, but ammonium bicarbonate, ammonium carbonate and carbon dioxide are suitable in the present invention.

As a reactor, an autoclave type, a high temperature reactor having a reaction temperature of up to 600 ° C., a pressure of up to 6,000 psig, and a stirring speed of up to 1,800 rpm was used.

The thermal stability test for chlorine-containing resins was carried out using the Mg-Al-Zn-based layered complex hydrate prepared in the present invention as a comparative example to heat zinc stearate, calcium stearate and commercial Mg-Al-based hydrotalcite commonly used as heat stabilizers. A stability test was made.

Example 1

80.00 g of magnesium hydroxide (content 98.5%), 73.95 g of aluminum hydroxide (content 95%), 37.03 g of zinc oxide (content 99%), and 35.90 g of ammonium bicarbonate (content 99.2%) were placed in a 2L high pressure reactor. 1.2 L was added and stirred. At this time, pH was 9.5 ± 0.5. The reactor was sealed and the stirring speed was increased to 650 rpm to slowly increase the temperature to 130-210 ° C., preferably 150-190 ° C., and the reaction and aging time was 0.5-5 hours, preferably 1-3 hours. It was. When the reaction is completed, open the pressure release port of the reactor at 80-110 ℃ to lower the internal pressure to the atmospheric pressure and the ammonia gas generated at this time is collected by passing through the hydrochloric acid trap. The terminated reactant was subjected to surface treatment at 0.5-5%, preferably 1-3%, to the resultant composite of stearic acid while maintaining the temperature at around 70 ° C. After the surface treatment was completed, dehydration and drying at 100 ℃ to form a Mg-Al-Zn-based layered complex hydrate (sample name Zn-LDH-01).

Confirmation of the prepared compound, ie, layered complex hydrate, was carried out using X-ray diffractometer (XRD) to confirm the crystal morphology, surface analysis and component analysis using EDX (Energy Dispersive X-ray). Confirmed using SEM).

Example 2

The method of Example 1 was repeated except that ammonium carbonate (content 99.0%) was used instead of 35.90 g ammonium bicarbonate as the carbonate feed material to form an Mg-Al-Zn based layered complex hydrate (sample name Zn-LDH-02). I was.

Example 3

80.00 g of magnesium hydroxide (content 98.5%), 73.95 g of aluminum hydroxide (content 95%), 37.03 g of zinc oxide (content 99%), and 35.90 g of ammonium bicarbonate (content 99.2%) were placed in a 2L high pressure reactor. 1.2 L was added. The carbon dioxide gas was added until the reactor pressure reached 20.8-32.4 atm, preferably 21.7-26.0 atm while maintaining the reactor internal temperature of 30 ° C. Then, the reaction temperature was increased to 100-150 ° C and the stirring speed was 650 rpm. The reaction was conducted for -6 hours to form a synthesized Mg-Al-Zn-based layered complex hydrate (sample name Zn-LDH-03), which was subjected to surface treatment as in Example 1 for characterization.

Application example 1

Hereinafter, the thermal stability effect will be described by adding Mg-Al-Zn-based layered complex hydrate according to the present invention to chlorine-containing resin, specifically vinyl chloride resin (PVC).

In order to confirm the thermal stability effect of the Mg-Al-Zn-based layered composite hydrate synthesized by the present invention on the vinyl chloride resin (PVC polymerization degree 1100), a specimen of vinyl chloride resin was prepared, molded, and tested by the following formulation.

Compounding ratio weight part

Vinyl chloride resin (PVC polymerization degree 1100) 100

DOP 40

Thermal Stabilizer 2

Release Agent / Gluent (Zinc Stearate) 0.5

The molding method was kneaded for 5 minutes at 160 rpm in a roll mill at 20 ° C. for 5 minutes, and a specimen of 0.6 mm thickness was produced in a 170 ° C. compressor. The stability test was performed by cutting the specimens to a certain size and arranging them on a glass plate. Put it out every 10 minutes to check for discoloration and measure the chromaticity with the colorimeter Minolta CM-508i. The stabilizer names used in the tests are given in Table 1 and Table 2.

Name of stabilizer used for testing Sample name Stabilizer Name Added A Zn-LDH-01 synthesized in the present invention B Zn-LDH-02 synthesized in the present invention C Zn-LDH-03 synthesized in the present invention D Zinc stearate E Calcium Stearate F Mg-Al-based hydrotalcite

Thermal Stability Test Results minute A B C L a b L a b L a b 0 85.27 2.73 -1.11 83.99 3.46 -0.02 84.88 3.29 -0.79 10 84.83 2.64 0.26 75.23 10.48 8.47 81.97 2.81 3.79 30 83.39 2.34 2.93 70.07 14.00 15.45 82.47 2.92 5.11 50 82.14 2.38 8.33 62.94 19.77 20.48 81.46 2.79 9.83 80 73.81 6.96 23.73 58.93 26.62 17.26 75.02 5.38 23.50 minute D E F L a b L a b L a b 0 84.49 3.04 -1.66 85.6 2.35 -2.03 84.00 3.62 -1.03 10 30.11 0.19 0.95 82.73 2.58 3.28 73.89 10.84 6.42 30 30.26 0.13 1.51 77.63 4.32 16.00 69.57 13.57 12.30 50 30.19 0.51 2.15 73.13 6.64 22.21 63.08 19.76 20.04 80 30.83 0.53 1.90 31.68 1.27 0.75 57.02 26.04 15.99

In the method for preparing the layered complex hydrate synthesized by the present invention, a metal ion source was used as hydroxide and metal oxide salts, which are poorly soluble salts. All are discharged in the form of ammonia, and the addition of carbon dioxide gas at a constant pressure provides a production method that produces no by-products at the end of the reaction. In addition, the heat stabilizer prepared in the present invention has excellent thermal stability, and provides a heat stabilizer of the chlorine-containing resin to improve the color change characteristics by heat.

Claims (2)

A method of preparing a layered complex hydrate including Mg-Al-Zn by adding an interlayer material in a range of 20.8-32.4 atm to a method of supplying a source of layered material as a poorly soluble salt. Mg-Al-Zn-based layered complex hydrate in which Zn is substituted in molar ratio of 0.15 to 0.2 in the heat stabilizer of chlorine-containing resin.