Process for the production of acrylic fibers

Abstract

A process is described for the preparation of a homogeneous spinning solution for the production of acrylic fibers which comprises the following steps: i) preparation of a homogeneous suspension by mixing a powder homopolymer or copolymer of acrylonitrile with a mixture of DMSO / water ranging from 94.5 / 5.5 to 97 / 3% w / w at a temperature ranging from 5°C to 10°C, preferably a mixture of DMSO / water 95 / 5 at a temperature of 5°C, said mixing being carried out in a time ranging from 5 to 30 minutes, by spraying a stream of the DMSO / water solvent onto a stream of powder homopolymer or copolymer of acrylonitrile, disgregated and premixed; ii) heating the homogeneous suspension coming from step i) to a temperature ranging from 70°C to 150°C in a time ranging of from 0.5 to 30 minutes, until the complete dissolution of the homopolymer or copolymer and the formation of a homogeneous solution. This spinning solution is then fed to a storage tank or to the spinning line.

Description

technical field [0001] The present invention relates to a process for the production of acrylic fibers, in particular to a process for the preparation of spinning solutions for the production of acrylic fibers. [0002] More specifically, the present invention relates to the field of production of acrylic fibers, comprising the preparation of polymers starting from acrylonitrile or mainly from acrylonitrile (90-99% by weight relative to the total weight of the polymer) and one or more A copolymer composed of a comonomer (commonly used in an amount of 1-10 wt% relative to the total weight of the polymer). [0003] Preferred comonomers are: neutral vinyl molecules such as methyl acrylate, methyl methacrylate, vinyl acetate, acrylamide and similar compounds; or molecules carrying one or more acid groups such as acrylic acid , itaconic acid sulfonated styrenes and similar compounds; or other comonomers that can impart different physicochemical characteristics to the material. ...

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Problems solved by technology

[0015] However, this is not an easy method to implement, and in fact, the optimal solvent power of DMSO already at room temperature causes partial dissolution of the surface of the polymer particles in powder form, with the result that the polymer particles tend to stick to each other, forming insoluble Aggregates and insoluble gels (as described in US4403055), which make proper and economical operation of such industrial processes impossible

[0016] The use of DMSO in the batch process as solvent for polyacrylonitrile-based polymers for the spinning solution has in fact significant disadvantages: it leads to the formation of gels and insoluble aggregates and thus clogs the filters of the device in a very rapid time, which Incompatible with proper functional operation of industrial production lines

However, this method has various disadvantages and contraindications, mainly the time required for the slow addition of the powdered polymer to the solvent under agitation is very lengthy, US4403055 shows a time of about 90 minutes in Example 1, This is incompatible with industrial applications and also requires removal of relevant quantities of water by vacuum heating, again requiring long periods of time

In addition to being extremely time-consuming, these methods obviously also imply high energy costs

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