The preparation of PHBHQ type thermoset Liquid crystalline epoxy
Use toluene as the solvent, concentrated sulfuric acid and boric acid as the catalyst, add into the three-necked flask of equal amount of hydroxybenzoic acid and 1,4-hydroquinone, have reaction at 120~130 °C for 6 h; after cooling, repeatedly wash with distilled water, and obtain the p-hydroxybenzoic acid p-hydroquinone ester after vacuum dry (white solid, yield 87.5%).
Dissolve the above product in an excess amount of epichlorohydrin, further add tetramethylammonium chloride and have reaction at 60~70 °C for 10 h; add drop wise of excess amount of aqueous 45% NaOH solution (the addition takes 6 h). Excess amount epichlorohydrin was distilled off under reduced pressure; wash the reaction mixture with acetone-methanol mixed solution for crystallization; it is further subject to vacuum drying to obtain a white PHBHQ-type thermosetting liquid crystalline epoxy resin (with the yield being 37.5%). Mix PHBHQ and hardener stoichiometrically for heating and melting, casting with the curing process being 90 ℃ × 1h; 120 ℃ × 2h; 150 ℃ × 2h; 180 ℃ × 2h.
Crystallise the chloride from EtOH, EtOH/CHCl3, EtOH/diethyl ether, acetone/EtOH (1:1), isopropanol or water. Traces of the free amine can be removed by washing with CHCl3. [Beilstein 4 IV 145.]
1. It can be used as polarographic analysis reagents which is widely used in the electronics industry.
2. Tetramethylammonium chloride is the phase transfer catalyst in organic synthesis with its catalytic activity being stronger than triphenylphosphine and triethylamine. At room temperature, it is a white crystalline powder, and is volatile, irritant, and easy to absorb moisture. It is easily soluble in methanol, soluble in water and hot ethanol but insoluble in ether and chloroform. Being heated to above 230 °C causes its decomposition into trimethylamine and methyl chloride. Median lethal dose (mice, intraperitoneal) is around 25mg/kg. It is also used for the synthesis of liquid crystal epoxy compound, and Pope and polarographic analysis, as well as electronic industry.
Electrolytic preparation of tetramethylammonium hydroxide
Tetramethylammonium hydroxide is a kind of organic base, and has a broad range of application in the field of both industry and scientific research.
In our own country, it is mainly used as the catalyst in the synthesis of organic silicon products, such as synthetic silicone oil, silicone rubber, and silicone resin. Although it has a low usage amount, but it can significantly affect both the yield and quality of the product.
In abroad, it is mainly used for polyester-based polymers, textiles, plastics, food, leather, wood processing, electroplating, and some kinds of microorganisms.
Now tetramethylammonium hydroxide has entered the advanced technology areas. For example, in the field of manufacturing industry of electronic circuit and microscopic sheets production, it can be used as the cleaning agent of integrated circuit board as well as the anisotropic corrosive agents of the Si-SiO2 interface in semiconductor microfabrication technique. With the development of science and technology, the requirements of this type of chemicals are also increasing, posing higher requirements for both the quality and the quantity of the tetramethylammonium hydroxide.
The basic principle of using electrolytic method for preparation of tetramethylammonium hydroxide is that the aqueous solution of tetramethylammonium chloride in the anode compartment of the electrolytic bath, under the action of the electric force, has its chloride ions migrate to the direction of anode until discharge of anode occurs to generate chlorine. Meanwhile, because of the selective permeability of the ion-exchange membrane, chloride can’t penetrate through the ion-exchange membrane through diffusion. Instead, only tetramethylammonium ions can selectively penetrate into the cathode compartment through, and be enriched over there. The water molecule in the electrolyzer cathode chamber is decomposed into hydrogen and hydroxyl ions. The latter one exactly binds to the tetramethylammonium ions migrated from the anode chamber to generate tetramethylammonium hydroxide. With the increase of electricity, tetramethylammonium hydroxide concentration continues to improve, finally achieving the desired final concentration of crude.
The anodic electrochemical reaction is:
(CH3) 4NCl → (CH3) 4N ++ Clˉ2Clˉ-2e → Cl2 ↑
The cathodic electrochemical reaction is:
H2O → H + + OHˉ (CH3) 4N ++ OHˉ → (CH3) 4NOH 2H ++ 2e → H2 ↑
The total reaction is:
2 (CH3) 4NCl + 2H2O → 2 (CH3) 4NOH + H2 ↑ + Cl2 ↑
The hydrogen generated during electrolysis is vented with the resulting chlorine absorbed by alkaline solution to generate sodium hypochlorite which is major raw materials for producing bleach.
Therefore, this method of producing tetramethylammonium hydroxide is simple with high purity and causing no environmental pollution.
Chemical intermediate, catalyst, inhibitor.
Catalyst of Organic synthesis
Tetramethylammonium chloride is the phase transfer catalyst in organic synthesis phase with its catalytic activity being stronger than triphenylphosphine and triethylamine. At room temperature, it is a white crystalline powder, and is volatile, irritant, and easy to absorb moisture. It is easily soluble in methanol, soluble in water and hot ethanol but insoluble in ether and chloroform. Being heated to above 230 °C causes its decomposition into trimethylamine and methyl chloride. Median lethal dose (mice, intraperitoneal) is around 25mg/kg. It is also used for the synthesis of liquid crystal epoxy compound, and Pope and polarographic analysis, as well as electronic industry.
The above information is edited by the chemicalbook of Dai Xiongfeng.