Acrylic fiber with non-fugitive antimicrobial activity and its production process.

The following is how acrylic fibers with non-fugitive antimicrobial activity were developed. Also in this same development, a synergistic mixture of microbicidal compounds was discovered, which conferred a wide range of actions against various types of microorganisms.

Two patents were generated which can be accessed at the following addresses:

• BR9601471A: Process for producing acrylic fiber with non-fugitive antimicrobial activity. https://worldwide.espacenet.com/patent/search/family/004063905/publication/BR9601471A?q=pn%3DBR9601471A

• BR9601472A: Acrylic fiber with non-fugid antimicrobial activity. https://worldwide.espacenet.com/patent/search/family/004063906/publication/BR9601472A?q=pn%3DBR9601472A

This development was carried out in a pilot plant for the wet spinning of acrylic fiber for the production of textile articles. Knowledge of the details of the process is of fundamental importance in order to understand the phenomenology involved.

For example, acrylic fibers can be obtained by the following processes:

• Dry spinning, where the polyacrylonitrile solution is extruded onto a spinning column and the solvent is evaporated by a heated gas stream. The filaments produced in this way have a much denser structure.

• Wet spinning, where the acrylonitrile solution is extruded into a coagulation vat, the solvent is transferred to a non-solvent medium and the fibers are coagulated, washed to remove the residual solvent, drawn and dried.

The main difference between the two acrylic fibers produced by these different spinning processes is in their morphology. The acrylic fibers produced by wet spinning are more porous.

In the wet spinning process, there is also another interesting phenomenon: up to the assaying vat, the porosity of the fibers can reach around 50%, but during the drying stage the micro-holes collapse and the density of the fibers approaches that of the polymer, around 1.17 g/cc, as can be seen in the following diagram:

The microbicidal agents are preferably added to the drying vat, so that when the microporosity of the fibers collapses during drying, the active agent remains inside and is gradually exuded, guaranteeing the desired microbicidal effect.

The microbicide agent developed and applied to the acrylic fibers in the drying vat exploits a synergistic effect between compounds based on halogenated phenoxyphene and isothiazolinone derivatives.

The acrylic fibers produced in this way proved to be effective in combating various microorganisms, such as grain-positive and grain-negative bacteria, ammonia-producing bacteria, fungi, yeasts and others.

These antimicrobial characteristics remained in the textiles produced, even after 30 drastic and sequential washes. No changes were detected in the physical-chemical characteristics of the fibers, nor in their affinity for dyes and other additives.

This is a case of success in the development of new products, but it didn't go ahead at the time, as the company had decided to leave the acrylic textile fiber business in a business relocation. Just to reinforce that the above patents have already entered the public domain.