Aqueous process for recycling acetal polymer and moldings thereof

Abstract

This invention relates to an aqueous process for recycling polyacetal, and moldings thereof, into formaldehyde monomer solution, said process occurring at elevated temperature and pressure and in the presence of an acid decomposition catalyst, such as sulfuric acid. The resultant formaldehyde monomer solution can be reacted to form trioxane and then be cycled into a trioxane-based polyacetal manufacturing process or, alternatively, it can be further treated and then be cycled into a formaldehyde-monomer-based polyacetal manufacturing process.

I claim: 
     
       1. An aqueous process for recycling acetal polymer, and moldings thereof, into a formaldehyde monomer solution by heating, under pressure, a slurry of at least one acetylpolymer, water, and an acid decomposition catalyst until the acetyl polymer is dissolved, thereby resulting in a solution comprised of formaldehyde monomer. 
     
     
       2. The process of claim 1 wherein the acid decomposition catalyst is selected from the group consisting of sulfuric acid, p-toluene sulfonic acid, phosphoric acid, acetic acid, and formic acid. 
     
     
       3. The process of claim 1 wherein the slurry is heated in the range of 140° C. to 160° C. under corresponding pressures ranging from 40 psig to 70 psig. 
     
     
       4. The process of claim 1 wherein the acetal polymer is selecting form the group consisting of acetal homopolymer, acetal copolymer, mixtures of acetal homopolymer and acetal copolymer. 
     
     
       5. The process of claim 1 wherein the acetal polymer is selected from moldings of acetal homopolymer, moldings of acetal copolymer, and moldings of mixtures of acetal homopolymers and acetal copolymers. 
     
     
       6. The process of claim 1 wherein the acetal polymer additionally contains at least one of thermal stabilizers, antioxidants, UV stabilizers, pigments, tougheners, fillers, glass, lubricants, polytetrafluoroethylene, and nucleants. 
     
     
       7. The process of claim 1 wherein the resultant formaldehyde monomer solutions is filtered, purified, and neutralized and then cycled into a formaldehyde-monomer-based polyacetal manufacturing process. 
     
     
       8. The process of claim 7 wherein the formaldehyde monomer solution is purified by passing it through an ion exchange bed. 
     
     
       9. The process of claim 1 wherein the resultant formaldehyde monomer solution is reacted to form a trioxane solution. 
     
     
       10. The process of claim 9 wherein the reaction to form trioxane occurs simultaneously with the dissolution of the acetal polymer, said reaction to trioxane occurring by a distillation step. 
     
     
       11. The process of claim 9 wherein the trioxane solution is purified and cycled into a trioxane-based acetal manufacturing process.