搪胶工艺（Tangjiao process）

搪胶工艺（Tangjiao process） 搪胶工艺(Tangjiao process) Structure, morphology and properties of 1 and PVC paste resins PVC paste is a paste dispersion system formed by PVC paste resin in plasticizer. PVC paste has a certain fluidity, so it can be formed by coating, dipping and dipping, and then heating and plasticizing. PVC paste molding method has the advantages of less equipment investment, simple production process and diversified products, and has been increasingly widely used. PVC paste resin can be divided into two categories: emulsion method and micro suspension method according to polymerization methods. The structure morphology (degree of polymerization, particle morphology, etc.) of PVC paste resin is closely related to the properties of PVC paste (paste viscosity, gel, plasticizing and foaming properties, etc.). ? (1) the degree of polymerization of PVC paste resins? Different types of PVC paste resins, the degree of polymerization is usually between 800~1700. The degree of polymerization not only influences the mechanical strength of PVC paste, but also affects the gelation, plasticization and foaming properties of PVC paste. ? (2) the particle morphology of PVC paste resin. PVC paste resin forms primary particles during polymerization, and the particle size of primary particles is usually between 0.1~0.2. The primary particles coalesce into secondary particles during drying. Have important effect on the performance of secondary particles close degree of coalescence of paste resin, resin particles coalescence loose, secondary particles are relatively easy to disintegrate into primary particles discrete, the performance of the formation of PVC paste is mainly determined by the morphological characteristics of primary particles. The agglomerated secondary particles are not easy to disintegrate, and the morphology of secondary particles has an important influence on the properties of PVC paste. The morphology of primary particles mainly includes mean particle size and particle size distribution. The particle size distribution can be divided into single peak narrow distribution, single peak width distribution and Shuangfeng distribution. Among them, the single peak width distribution and the Shuangfeng distribution belong to the type of wide particle size distribution. This type of paste resin has a lower paste viscosity. The morphology of primary particles also has an effect on gelation and plasticization. (3) the paste viscosity and flow properties of PVC paste. The paste viscosity of PVC paste is determined by viscometer. PVC paste resin 100 mass fraction is usually added with 100 mass fraction or 60 mass fraction of two benzoic acid two octyl ester (DOP). The paste viscosity is measured on B viscometer, and the determination temperature is usually 25 degrees. Paste viscosity is one of the most important performance indexes of PVC paste resin. The paste viscosity is directly related to the particle morphology of PVC paste resin. The paste viscosity mainly depends on the morphology of primary particles when the secondary particles are loosely agglomerated and easy to disintegrate into discrete primary particles. The particle size of the primary particles is wider and has lower paste viscosity. The viscosity of PVC paste is also related to the shear rate. According to the relationship between paste viscosity and shear rate, 3 flow types of PVC paste can be divided. The viscosity of paste decreases with the increase of shear rate, which is called pseudoplastic flow. The viscosity of paste increases with the increase of shear rate, which is called swelling flow. There are also some paste resins whose viscosity does not change as the shear rate changes, which is called Newtonian flow. In addition, some PVC pastes do not flow at low shear rate, and flow occurs when shear rate exceeds a critical value, which is called thixotropy. (4) the gelation characteristics of PVC paste? The gelation of PVC paste refers to the process in which the PVC paste diffuses into the resin particles and makes the PVC paste lose its fluidity in the process of heating. The gelled PVC paste is in a dry state with a mechanical strength close to zero". Gelation is a kind of intermediate state in the process of PVC paste, and it needs further plasticizing to produce finished products. The degree of polymerization, particle morphology and paste viscosity of paste resin have an important influence on the gelation properties of PVC paste. The increase of polymerization degree can increase the gelation temperature. The increase of paste viscosity can decrease the gelation temperature. (5) plasticization and foaming properties. The difficulty of plasticization of PVC paste is directly related to the polymerization degree of paste resin. The plasticizing temperature of the varieties with lower polymerization degree is lower. Foaming properties are related to gelation properties. In general, the foaming properties of paste resins with lower gelation temperature are better. (6) other properties? The properties of PVC paste resin, the stability of paste viscosity during storage, and the degassing property. After PVC paste is prepared, it is usually stored for a period of time and then used. In the storage process, paste viscosity should not rise significantly, that is, paste viscosity is more stable in storage. For PVC paste need vacuum deaeration, it is required to have good degassing. 2, PVC paste resin model PVC paste resins are classified into different models according to polymerization degree, paste viscosity and gelling properties. 3, PVC paste resin selection The paste viscosity and flow characteristics, gelation and foaming properties of PVC paste, and mechanical properties of PVC paste should be taken into account in the rational selection of paste resin. Shenyang chemical Limited by Share Ltd produces 8 brands of paste resins, which are suitable for different uses. PSH-10, for example, is a high degree of polymerization and low viscosity paste, suitable for use in the surface layer of artificial leather or floor leather. PSM-31 polymerization degree is moderate, paste viscosity is low, foaming performance is good, it is suitable for making foam wallpaper. The production of wallpaper, floor leather and other products generally requires PVC paste resin with lower paste viscosity. PSH-10, PSM-31 and PSL-31 belong to varieties with low viscosity, so they can adapt to the needs of these products. In the production of high foaming content artificial leather, it is necessary to select varieties with good foaming properties and high viscosity, such as PSM-70. In order to improve the mechanical properties of the products, the varieties with higher polymerization degree, such as PSH-10, should be selected. In order to reduce the plasticizing temperature, the varieties with low polymerization degree, such as PSL-31, should be used. Two. Selection of auxiliaries Additives for PVC soft products include plasticizers, stabilizers, fillers, colorants, foaming agents, etc.. Among them, plasticizer is the most important additive of PVC soft products. Plasticizer can be divided into two categories: plasticizer and polymer plasticizer. Small molecule plasticizers are usually liquid, and after adding PVC, plasticized, liquid plasticizer diffuses to PVC macromolecule, forming homogeneous and soft material. Polymer plasticizer is usually polymer elastomer, polymer plasticizer "plasticizing" PVC, in essence is the elastomer and PVC blending. The types of plasticizers commonly used in soft PVC are as follows. ??? (1) phthalate two formic acid phenol? Commonly used varieties of dibutyl phthalate (DBP), adjacent benzene two formic acid two ester (DOP) phthalate two formic acid and two isodecyl phthalate (DIDP), two formic acid and two isononanoic vinegar (DINP), butyl benzyl phthalate (two formic acid BBP) etc.. Among them, DOP is the most widely used plasticizer, usually used as the main plasticizer. In a variety of phthalate two formic acid plasticizers, the volatility of plasticizers decreases with the increase of the molecular weight of the alcohol used. ? (2) fatty acid esters, including adipic acid esters. Two esters and two esters of sebacic acid. The commonly used varieties are adipic acid two octyl ester (DOA) and sebacic acid two octyl ester (DOS). These plasticizers are mainly used as cold resistant plasticizers for PVC. ??? (3) phosphate ester? Phosphate plasticizers is PVC flame retardant plasticizer, the main varieties of tricresyl phosphate (TCP), three phenyl ester (TPP), two isooctyl phenyl phosphate (EPOP), and the newly developed Reofos 50. ??? (4) epoxy plasticizer epoxidized soybean oil, the main varieties of epoxy octyl stearate, PVC auxiliary plasticizer, with low volatility, migration advantages, and there is a synergistic effect of stability and heat stabilizers for PVC. (5) chlorinated plasticizer, the main variety of chlorinated paraffin, is a cheap plasticizer for PVC. It has synergistic flame retardant effect with three antimony oxide two. (6) the main variety of the main amino acid is TOTM three, which is a plasticizer for heat resistance and durability. (7) polyol esters have increased the price of traditional plasticizer DOP in recent years due to the rise in prices of octanol and other raw materials. Therefore, polyol esters are valued as alternative species. The main products are: two diethylene glycol benzoate (DEDP), its contamination resistance, oil resistance, water extraction resistance good. ??? (8) other types of low molecular plasticizer PVC low molecular plasticizer and alkyl phenyl sulfonate (also called oil ester, product name T-50, M50}), citric acid ester, benzene and two formic acid ester, terephthalic acid ester plasticizer. (9) reactive plasticizers, which have active groups in the molecule, can react chemically to form a network structure. The main varieties are phthalate two formic acid diallyl ester (DAP) and so on. (10) polyester plasticizer polyester plasticizer is a polymerization plasticizer, the molecular weight is smaller than the general plasticizer, but higher than the polymer plasticizer. Such as adipic acid propylene glycol, polyester molecular weight is 1500~4000. Because of its large molecular weight, the volatility is very small and can be used for durable products. The disadvantage is that the compatibility with PVC is poor and plasticizing efficiency is low. (11) polymer plasticizers used in PVC plasticizer should have lower glass transition temperature and have good compatibility with PVC. Commonly used ethylene vinyl acetate copolymer (EVA), nitrile rubber (NBR), chlorinated polyethylene (CPE) and so on. Selection of raw materials for PVC soft products First pages, a total of 3 pages