Production technology of Handern solution casting film method in Wuhan
DATE：2020/5/2 8:22:00 / READ： / SOURCE：This station
Production technology of Handern solution casting film method in Wuhan
The casting solution used in Wuhan's Handern casting film method generally requires pretreatment of the resin before preparation. www.handern.com Cast film equipment1. Pretreatment of raw materials
For the PNA cast film, a polyvinyl alcohol resin with a polymerization degree of 1750 and an alcoholysis degree of 99% can be selected. The main methods of PVA are soaking, washing, dehydration and drying. The pretreatment is mainly to remove sodium acetate in PVA resin by soaking, washing and removing. Because the presence of sodium acetate will cause the PNA resin to accelerate its decomposition under heating and make the PVA film yellow; sodium acetate is easily deposited in the PNA solution and adheres to the surface of the cast steel strip, resulting in film fogging and transparency decline. After pretreatment of cellulose triacetate, it should be dried to make its moisture content (mass fraction) less than 1%.
2. The equipment of the solution www.handern.com cast film equipment
The casting solution is mainly composed of resin, solvent, plasticizer and surfactant. The solid content (mass fraction) of the solution is about 15% to 20%. PVA solution uses water as solvent and glycerin as plasticizer; cellulose triacetate solution uses chloroform, monochloromethane, methanol and butanol as solvents, triphenyl phosphate and dibutyl phthalate as plasticizers Agent; Surfactant can choose non-ionic surfactant. A small amount of impurities and solids will be mixed in the dissolved and mixed solution, which needs to be removed by the filter; the solution will produce foam during the mixing and stirring process. After the solution is prepared, it needs to stand for defoaming or add a small amount of defoamer. www.handern.com Cast film equipment
3. Cast film
The prepared solution needs to be filtered again before entering the casting die. The mixed solution passes through the casting die and is distributed onto the continuously running steel belt to form a very thin layer of colloidal solution. The entire casting coating device is sealed in a room, and 65 ° C hot air is blown in the oven in the reverse direction to continuously evaporate the water in the solution, forming a thin film layer on the surface of the steel strip; the film runs forward with the steel strip and passes through the steam Rewet, keeping the film with 15% -20% solvent. The thickness of the cast film can be controlled by changing the running speed of the steel strip, the casting rate of the solution casting, the distance between the casting die and the surface of the steel strip, and the viscosity of the solution (content of the solvent). Difficulties in the production of Liuting film include the dissolution of PVA resin, the cleanliness of the production equipment, the peeling of the film and the steel strip, and the control of the moisture content of the film. www.handern.com Cast film equipment
4. Post-processing of the membrane
The cast PVA film contains a certain amount of moisture. PVA film with low water content will harden and kneel, while PVA film with high water content will be sticky. The PNA film peeled from the steel strip generally needs to be dried again. Re-drying can be done by drying or ironing. Drying can be done in an oven; ironing is to flatten the FPVA film through multiple heating rollers. No matter which method is adopted, the drying of the film is carried out step by step, and the volatile content (mass fraction) of the final product should be less than 1%. Cast PVA film can also be unidirectional or biaxially stretched to improve the mechanical and optical properties of the film. Because solution casting uses a lot of solvents and plasticizers, and has been in production
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