Simple preparation process of α-cyanoacrylate adhesive

Alpha-cyanoacrylate adhesive, referred to as a-gel, is a unique monomer-type quick-setting adhesive that has fast curing, wide range of adhesive materials, low viscosity, thin adhesive layer, transparent film, oil resistance and electrical appliances. Insulation, penetration, ease of use and so on. Ardis first synthesized a-cyanoacrylate since 1949, 1956 c. Coover unwittingly discovered the adhesive properties of a-cyanoacrylate, and by 1958 Eastman Kadark officially launched the world's first a-gel, soon to be electronic, mechanical, technological, archaeological, artifacts, everyday Supplies and other aspects have been widely used. Since 1962 in China as a commodity production research, there are currently research institutes and production companies in Beijing, Shanghai, Liaoning, Zhejiang, Shandong, Xi'an and other places in research and production. According to reports in 1990, at the time, the domestic annual output was only over 20 tons, while Japan’s annual output has reached more than 400 tons, which is far from satisfying the demand. As a one-component reactive adhesive with unique properties, it should be vigorously developed. In the industry, cyanoacetic acid and formaldehyde are often cracked after being polymerized to make them.

1. Synthesis of raw material intermediates

Ethyl cyanoacetate is an a-gel intermediate. Most of its synthesis is based on chloroacetic acid, and the reaction process of neutralization, cyanation, esterification, etc., to obtain more than 94% of ethyl cyanoacetate.

2. Preparation of monomeric a-cyanoacrylates

2.1 raw material formula

1 Ethyl cyanoacetate (>94%) 126 g, 2 Dichloroethane 80-100 ml, 8 Formaldehyde (37%) 82 g, 4 Hexahydropyridine 0.4-0.5 ml, 5 Phthalic acid Dibutyl 40 ml, 6 p-toluenesulfonic acid 1 g, 7 Phosphorus pentoxide 7 g, 8 Hydroquinone 2.5 g, 9 Sulfur dioxide traces.

2.2 Preparation method

The preparation method was to add 1 3 to a three-necked bottle, and the heating was stopped after heating to 70°C. Slowly add the 9 4 mixture with agitation funnel and add it in about 15 minutes. When the reaction is not hot, it will return to the violent reflux, and the water will be removed through the water separator. After about 1 hour, the water will be separated by 70-72m1. Add person 56 to reflux again and distill out 2 until the vapor temperature exceeds 83°C. After cooling to 60 ~ 70c, add 75g 82g, stir, and then replaced by vacuum distillation device. The pyrolysis was carried out under a negative pressure of 1.33 KPa. The crude product with a boiling point of 90-180 C was collected at about 110-120 g, and the receiving flask was filled with 7 2 g of 8 O. 5g. The crude product is in the atmosphere of SO2. Re-evaporated at 2.67 KPa under negative pressure. Collecting 80 to 100°C fractions yielded 87 to 95 g of the fine monomer (a-cyanoethyl acrylate). Followed by a-cyanoethyl acrylate 94%, polymethyl methacrylate 3%, tricresyl phosphate 3%, trace amounts of hydroquinone, traces of sulfur dioxide, the proportion of a-gel.

China a-gel development time is not long. At present, most manufacturers still produce ordinary type a-gel. There are few varieties with special properties. Many products still have poor heat resistance, poor moisture resistance, short storage period, and brittleness. The gap is poor, and it is not advisable to bond porous materials and many other disadvantages. Since the 1980s, many breakthroughs have been made abroad in the study of the shortcomings of a-glue, and products with a heat-resistance of 150°C and high impact resistance have appeared. Also appeared oil surface a-plastic, conductive a-plastic, flame-retardant a-plastic and other new varieties. With the continuous deepening of reform and opening up, the continuous development of the national economy, a-plastic has broad application prospects in our country. Domestic related research departments and manufacturers also need to conduct in-depth research on the modification of a-gels and develop modified products with excellent performance as soon as possible to meet the different needs of many industries.