Recycling Industrialization Of Waste Poly(Vinyl Alcohol) Collodion

The polyvinyl formal collodion(PVF)is a material which was prepared by reaction between poly(vinyl alcohol)and formaldehyde and was used widely in medical,filter and cleaning materials because of its excellent chemical and physical properties.A large number of waste PVF are generated during it's manufacturing process.Due to the our concerns on the environmental pollution,more and more attention has been attracted to the recycling of waste PVF.There are many problems in the avilable recycling technology,such as low recycling efficiency,high cost and so on.Therefore,it is of great significance for developing a new and efficient technology to reduce the cost and environmental pollution.This study is based on the problems encountered in the actual recycling of PVF collodion by Jiaxing Jackson Travel Products Co.,Ltd..We mainly facus on improving the recycling efficiency of waste PVF collodion.In our previous work,we have found that the PVF can be hydrolysis by HCl and the hydrolysis products can be reused as the raw material to make new PVF collodion.However,this method requires the addition of PVA in the recycling process to obtain qualified products.The highest amount of waste PVF containing in the collodion products can only reach 25 %(i.e.,recycling efficiency = 25 %).Therefore,it is of great practical significance to further improve the recycling rate and to optimize the method to realize the recycling of all waste PVF.In this paper,Influence of the hydrolysis process of PVF and the structure of hydrolyzate was characterized by NMR and FT-IR.The root cause of low efficiency for PVF recycling in the previous technology was founded.Base on this founding,the hydrolysis degree of PVF was improved by adding auxiliary hydrolysis reagent and the industrial production of all waste PVF was achieved.The products prepared from waste PVF performance have reached the first-class quality requirements.(1)The effects of various parameters on the degree of hydrolysis of PVF were studied,and the structure of the hydrolyzate was characterized by NMR and FT-IR.It was found that when HCl was used as the auxiliary hydrolytic reagent of PVF hydrolysis,however,the hydrolysis is very small and the hydrolysis product remains a high degree of acetalization(~56.5%).The hydrolysate was precipitate out when adding to the water.The effect of PVA as a hydrolysis reagent on the hydrolysis of PVF was studied.It was found that the formaldehyde molecules in the PVF acetal structure were transferred to the PVA molecule and resulting in a decrease in the average degree of acetalization per molecule.The results indicated that the degree of hydrolysis of PVF could be improved by the addition of additives that can react with formaldehyde to form a stable structure.Meanwhile,the results provide a guideline for improving the recycling rate of waste PVF.(2)The effect of adding other hydrolysis reagent on the degree of hydrolysis of PVF was studied and the experiment of improving the recycling rate of waste PVF was carried out.when small molecular alcohol(ethanol,ethylene glycol,glycerol)was used as the assistant hydrolysis reagent.It was found that the ethanol hydrolysis of PVF was the best candidates and the acetalization degree of hydrolyzate can be reduced to 9.3%.Under this condition,however,the recycling ratio of waste PVF can only be increased to 50%.The effects of reagent A as assistant reagent on the hydrolysis of PVF were also studied,and the structure of the product was characterized by NMR and FT-IR.The results showed that PVF could be completely hydrolyzed.The recycling process is optimized and the recycling of waste PVF were achieved.(3)The effects of the concentrations of waste PVF,hydrochloric acid and formaldehyde on the performance of recycled products were studied.The optimum amount of each material in the recycling process was determined as: the concentration of waste PVF,HCl and formaldehyde are 8.42 ~ 9.38 wt%,3.25 ~ 3.75 wt% and 5.04 ~ 5.52 wt% respectively.The 100-fold scale-up experiments for laboratory was achieved and recycled products reached the first-class quality.Furthermore,the recycling method of waste PVF collodion proposed in this paper,which has the advantages of simple operation,low cost of recycling and the collodion dyeing does not need to add new pigment.Thus,reducing the cost of recycling production but also reducing the pollution to the environment of pigment.Meanwhile,the recycling method also has good application prospects for polyvinyl acetal plastic.