The term"rayon-containing fabrics"as used herein means all fabrics that are composed of rayon fibers not only wholly, but also partially.

For eons, fabrics made of hemp or ramie have been extensively used as materials for the production of summer season or warm climate clothing due to their being ventilative and feeling stiff to the touch. Such natural fiber fabrics are, however, virtually impossible to produce on a large scale because they involve much labor and require intricate procedures for their preparation. Accordingly, there is always an undersupply of the fabrics, resulting in an increase in their price.

As for viscose rayon fibers, their preparation generally begins with a pulp sheet containing about 90-94 % pure cellulose through a so-called steeping or mercerizing process. That is, immersion of the pulp sheet in a 17.5% NaOH solution allows the cellulose to be solubilized to give alkaline cellulose. After being deprived of the sodium hydroxide, the

cellulose is let to experience shredding, aging, xanthation, mixing, filtering and ripening to produce a viscose solution suitable for spinning. Then, the viscose solution is spun through a spinneret and passed through a coagulation bath to yield viscose rayon fibers.

SUMMARY OF THE INVENTION Knowledge of mercerization allows modification and adaptation leading to the present invention. Mercerization is usually applied for the solubilization of cellulose in making rayon fibers, but has not yet been used for the finishing of rayon fabrics for the fear that the fabrics would be damaged.

However, the intensive and thorough research on the preparation of rayon-containing fabrics, repeated by the present inventors, resulted in the finding that mercerization does not damage, but allows cotton-rayon blended fabrics to be improved in luster and dye absorptivity and to feel like bast fiber fabrics.

Therefore, it is an object of the present invention to provide a method for preparing rayon-containing fabrics that feel like bast fiber fabrics.

It is another object of the present invention to provide a method for preparing bast fiber fabric-like rayon-containing fabrics at a low cost on a large scale.

Based on the present invention, the above objects could be accomplished by a provision of a method for preparing bast fiber fabric-like rayon-containing fabrics, in which rayon- containing fabrics are let to experience mercerization, whereby the rayon-containing fabrics feel like bast fiber fabrics.

DETAILED DESCRIPTION OF THE INVENTION Mercerization is a finishing technique used to increase luster such as that of silk, dye absorptivity, and strength in cotton and linen goods: the cloth is put into a heated solution of caustic soda, e. g., NaOH, at a controlled temperature, then washed, neutralized, and rinsed. It is mercerized while being tensioned or in a relaxed condition.

Usually, mercerization is conducted under a tension.

The present invention is characterized in that mercerization is applied to rayon-containing fabrics, which have been known as unable to be mercerized owing to the erosion or damage by caustic soda, to alter the surface condition of rayon fibers, allowing the rayon-containing fabrics to feel like bast fiber fabrics. This effect, to our knowledge, is attributed to the fact that the caustic soda reacts with the rayon fibers to make their surface stiff.

When mercerization is conducted for rayon-containing

fabrics, the solubilization of rayon in a solution of caustic soda requires that the concentration and temperature of the caustic soda solution, and the processing period of time should be controlled with dependence on a desired level in the sense of touch and the use of the fabrics. The mercerization of rayon-containing fabrics is preferably conducted at a sodium hydroxide concentration of 14 Be° or more at not more than 25 °C and more preferably at a sodium hydroxide concentration of 23-25 Be° at 15-18 °C, but these conditions do not limit the scope of the present invention. As the sodium hydroxide solution is higher in concentration, rayon- containing fabrics are preferably mercerized in a shorter period of time.

Neutralization of the rayon-containing fabrics with an agent preferably follows the mercerization.

A better understanding of the present invention may be obtained in light of the following examples which are set forth to illustrate, but are not to be construed to limit the present invention.

EXAMPLE A dobby fabric made of cotton and rayon plied fibers was mercerized by passage at a speed of 20 m/min through a bath containing a concentration of 23-25 Be° of a sodium hydroxide

solution maintained at 15 °C, and then, neutralized by passage at a speed of 30 m/min through a bath containing an aqueous acetic acid solution maintained at 80 °C. The dobby fabric was dyed by being immersed in a dye solution at 80 °C for 60 min.

COMPARATIVE EXAMPLE The same procedure as in Example was repeated except that the mercerization and the neutralization were not conducted.

When being compared, the two fabrics obtained in Example and Comparative Example were different from each other in the sense of touch. The fabric which experienced the mercerization of Example provided the same sense of touch as that of bast fiber fabrics. In contrast, no similarity in the sense of touch was found between the fabric of Comparative Example and bast fiber fabrics. In addition, the fabric of Example was found to be as good in strength as the fabric of Comparative Example.

As described hereinbefore, rayon-containing fabrics, which can be mass-produced, can be provided with the same sense of touch as that of bast fiber fabrics, in accordance with the present invention.

The present invention has been described in an

illustrative manner, and it is to be understood that the terminology used is intended to be in the nature of descriptions rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, it is to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.