Method for the treatment of aramid material and fiber, yarn, and fabric made thereby

Abstract

This invention relates to a method for providing a dyed meta-aramid material, wherein said method comprises at least a step of pretreatment of the material and a subsequent step of dyeing the material, characterized in that the step of pretreatment is carried out under closed conditions, in the presence of an aqueous medium, and at a target temperature of 80 to 130° C. This invention also relates to fibers, yarns, and fabrics obtained from this method.

Description

[0001]The present invention includes the technical field of treatment of dyeable meta-aramid materials, for example fibers known under the trade name NOMEX®, and yarns and fabrics made of such fibers for use in the fabrication of protective articles such as fire protection clothing.[0002]U.S. Pat. No. 7,156,883 to Lovasic & Maini relates to a blend of fibers for use in protective clothing, a lightweight fabric made from such blend, protective articles made from the blend or fabric, and methods for making the fabric. The protective fabrics and articles of this invention have the unique combination of being comfortable, being highly effective against electrical arcs and flash fire hazards and having a pleasing appearance. Specifically, these fabrics can be processed to give the look and feel similar to conventional clothing fabrics such as denim fabrics. U.S. Pat. No. 7,156,883 discloses a fiber blend that comprises amorphous meta-aramid fiber, crystallized meta-aramid fiber, and flam...

AI Technical Summary

Benefits of technology

The patent text describes a method for dyeing aramid fibers without using accelerants or carriers. The fabric is immersed in an aqueous dye bath containing a dye and an acid component, and the temperature of the bath is increased to allow the dye to penetrate the fibers. This method results in suitable color yields without the need for added chemicals. The dye can then be used to create protective garments for fire and thermal hazard protection. However, there may be some issues with fabric quality and color accuracy when using this method. The technical effect of this patent is to provide a simple and cost-effective solution to address these issues and improve the quality of dyeing aramid fibers.

Problems solved by technology

From U.S. Pat. No. 7,156,883 it is known that aramid fabrics are more difficult to dye than traditional apparel fabrics, and the percent crystallinity of aramid fiber dramatically affects the degree to which the fiber may be dyed.

It is especially difficult to give such aramid fabrics the general appearance of a cotton denim fabric due to the differences in aramid fiber crystallinity.

The simple addition of cotton, by blending cotton fiber with the meta-aramid fiber, does not provide a suitable solution to this problem.

This makes any protective apparel made from this fabric less comfortable than apparel made from the untreated fabric.

Even if the process to obtain such batches of products is normally identical and carried out under the same conditions (for example in terms of temperatures and pressures), it cannot be ensured that the yarns obtained from such batches have identical end properties.

In fact, variations in the crystallinity index of the different production batches would require ongoing modification of the dye recipes which cannot be accepted from an industrial point of view.

Hence, the market is confronted with irreversible and reoccurring streakiness in the production of dyed fabrics made of such aramid precursor fibers: these dyed fabrics appear as marked with stripes or linear discolorations and have an uneven character or appearance.

These problems are due to the inherent variations of the morphological structure of said fibers.

Unfortunately these streakiness problems show up only after the fabric has undergone the final dye processing step at the end of the production process.

A visual or quality inspection before the dyeing process is not possible since the aramid material, for example a fabric, does not present a visual specific appearance that would allow anticipating this potential dyeing problem.

This operation, however, adds costs and increases the complexity of the supply chain logistics.

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