The appearance of polyvinyl alcohol (PVA) is white powder, which is a water-soluble polymer and widely used. Its performance is between plastic and rubber, and its uses can be divided into fiber and non-fiber.

PVA is widely used in the production of coatings, adhesives, paper processing AIDS, emulsifiers, dispersants, films and other products because of its unique strong adhesion, film flexibility, smoothness, oil resistance, solvent resistance, protective colloid, gas barrier, wear resistance and water resistance after special treatment, and its application scope covers textiles, food, medicine, construction, wood processing and papermaking.

1 mode of production

Polyvinyl alcohol was first discovered by German chemists W.O.Herrmann and Dr. W.W.Hachnel in 1924. Because it can carry out typical chemical reactions of polyols and denature them by insolubilization, it has different functions, thus producing a series of synthetic materials, which are widely used in industrial and agricultural production and medical treatment. 1926 PVA industrialization, large-scale industrialization of products in 1950s.

According to different raw materials, the process routes for producing polyvinyl alcohol can be divided into ethylene method and acetylene method.

Direct synthesis of 1. 1 ethylene

The direct synthesis of petroleum pyrolysis ethylene was first successfully developed by Kolili Company of Japan (formerly Cangfu Rayon Company) and used in industrial production. At present, the main process route of PVA production in the world is ethylene method, which accounts for 72% of the total production capacity. The United States has completed the transition from acetylene process to ethylene process, and the Japanese ethylene process accounts for more than 70%, while only two manufacturers in China are ethylene process.

Its technological process includes five steps: obtaining ethylene, synthesizing vinyl acetate, rectifying, polymerizing, alcoholysis of polyvinyl acetate, and recovering acetic acid and methanol.

The process characteristics of petroleum ethylene process are: the production scale is larger than that of acetylene process, the product quality is good, the equipment is easy to maintain, manage and clean, the heat utilization rate is high, the energy saving is obvious, and the production cost is lower than that of acetylene process by more than 30%.

1.2 direct synthesis of acetylene by pyrolysis of natural gas

Acetylene synthesis method can be divided into calcium carbide acetylene synthesis method and natural gas cracking acetylene synthesis method according to the different sources of raw materials.

1.2. 1 calcium carbide acetylene synthesis method

The synthesis method of calcium carbide and acetylene is the first to realize industrial production.

The process characteristics of calcium carbide acetylene method are simple operation, high yield and easy separation of by-products, so there are still 10 factories in China still using this process, and most of them are produced by high alkali method. However, due to the high energy consumption, low quality and high cost, the impurities produced in the production process also seriously pollute the environment, and the cost is higher than that of PVA produced by the other two methods (800 ~1000 yuan /t), which lacks market competitiveness and belongs to the process of gradual elimination. As early as 1970s, advanced foreign countries had all adopted low-alkali production technology.

1.2.2 cracking acetylene with natural gas

Direct synthesis of acetylene in areas rich in natural gas, coal and electricity, natural gas acetylene method still has vitality. Europe, North Korea and other countries mainly use natural gas acetylene method, and China has a set of production equipment using this method.

Boden method with natural gas acetylene as raw material is not only mature in technology, but also beneficial to the comprehensive utilization of acetylene. The production cost of VAc is 50 ~ 70% lower than that of calcium carbide acetylene method. But the investment and technology of natural gas acetylene are difficult.