Technical progress and application of the hottest

Technical progress and application of PVDC resin. It refers to a polymer which is mainly composed of vinylidene chloride (VDC), which accounts for 12.35% of all non-ferrous metal imports in China, and is copolymerized with other second monomers containing unsaturated double bonds. Due to the high crystallinity of the homopolymer of PVDC resin, the processing temperature is very close to the decomposition temperature, so it can not be processed, so its homopolymer has no practical value, and other monomers must be added to improve the processing performance [1]. Therefore, PVDC resin generally refers to the copolymer with high VDC content, in which the content of vinylidene chloride is generally 30%~90%. At present, the PVDC resin used in the market mostly refers to the copolymer of VDC monomer (content more than 80%) and VC monomer, and a small amount is the copolymer of VDC monomer and acrylic ester. Suspension method and lotion method are used for production. In the late 1930s, Dow Chemical Company of the United States began to conduct extensive research on the copolymerization and processing of VDC and VC. In 1947, it realized industrial production with the trade mark of saran. Japan began research in 1948 and put into industrial production in 1954. At present, the main cost of PVDC resin in the world is very expensive. The main manufacturers are Dow Chemical Company in the United States, Wuyu company and Asahi chemical company in Japan. The market shares of the three companies are about 40%, 30% and 15%; Other companies include Japan East Asia synthesis and Wudong electrochemical Co., Ltd. the actual production capacity of global PVDC resin is about 110kt/a. Since the early 1960s, China began to develop PVDC copolymer products. Jinxi Research Institute of chemical industry and Shanghai Tianyuan Chemical Plant have invested considerable efforts. They have developed fiber resins. Due to the difficulty of processing and poor market adaptability, no commodities have been formed

1 structure and properties of PVDC resin

1.1 molecular structure

the molecular structure of PVDC resin is a linear polymer chain structure connected head to tail, and the molecule is composed of [ch2-ccl2]m - [ch2-chcl]n units. It belongs to block copolymer. Due to the high regularity and strong symmetry of the polymer chain of PVDC resin, most of the main chain is composed of [ch2-ccl2], while the side groups of [ch2-ccl2] have small steric hindrance and large polarity, forming hydrogen bonds, so the crystallinity is high. Due to the mutual repulsion of side groups, the main conformation of PVDC resin polymer chain is a typical spiral, and the crystal conformation is α- Type monoclinic system [2]; In addition, because the thermal movement changes the crystal system, there are β (attention should be paid to the distinction between joint oil leakage and cylinder plug oil leakage hexagonal system) type and other metamorphoses. Two obvious thermal absorption peaks can be found in the analysis of PVDC resin by specific heat method. The presence of [ch2-chcl] in the polymer chain of PVDC resin reduces the polarity and steric hindrance effect of side chain groups, and has certain softness

1.2 properties

the PVDC resin produced by suspension method is white spherical powder, the relative viscosity is 1.46~1.58, and the resin molecular weight Mn is (5.5~6.8) × 105。 PVDC resin has good electrical affinity. It is insoluble in most organic solvents such as water, gasoline, alcohol and vinyl chloride, but can be dissolved in special solvents such as tetrahydrofuran. PVDC resin has high-strength ability to block oxygen and water. Under the same conditions, the ability to block oxygen and water is about 200~1000 times that of PVC film, 4000~20000 higher than LDPE film

normal align=center> Table 1 performance of vinylidene chloride vinyl chloride resin

normal align=center> index name

normal align=center> index name

normal align=center> index name

normal align=center> index

no solves the difficulties that have plagued the development of enterprises for a long time rmal> relative density

normal align center>1.65~1.75

normal> impact strength/kj/m2

normal a lign=center>100~150