CH402800A - Process for treating acrylic textile fibers, with a view to improving their whiteness - Google Patents

Description

  

  Process for treating acrylic textile fibers, with a view to improving their whiteness The present invention relates to a process for treating acrylic textile fibers, with a view to improving their whiteness and promoting the fixing of basic dyes thereon; it relates in particular to the treatment of textile fibers composed of polymers, copolymers, terpolymers and higher-order interpolymers of acrylonitrile, as well as mixtures thereof.



  During their production most acrylic fibers acquire a slight yellowish sheen or a yellowish color which is unfortunate. Numerous methods have been proposed to eliminate this troublesome staining. The bleaching agents conventionally used in the textile industry have been used, among others, but without success, in the sense that, although these conventional bleaching methods have eliminated initial coloring defects, the fibers thus treated are not stable at ultraviolet light; this unwanted color is usually found after about 2 hours of exposure.

   In addition, temperatures close to 1500 ° C. or higher than this tend to increase this coloring of the acrylic textile fibers. It has also been proposed to carry out first an acid treatment (phosphoric, pyrophosphoric) then a treatment with chlorite (French patent No. 1205810).



  The present invention provides acrylic textile fibers exhibiting acceptable whiteness, maintaining that whiteness when exposed to ultraviolet light and heat and more readily absorbing basic dyes.



  The process according to the invention is characterized in that the fibers are treated with a bath comprising hypophosphorous acid or a mixture of hypophosphorous acid and at least one of its metal salts.



  It is possible, for example, to treat the fibers with an aqueous solution of hypophosphorous acid, the concentration of which can range from 0.01% to approximately 1.0%, with an optimum concentration of between 0.1% and 0, 50%;

       It is obvious that higher concentrations of the acid can be employed, but this is of no economic benefit.

   In addition to the acid indicated above, it is possible to use an aqueous mixture of the acid and its water-soluble metal salts, such as, for example, the water-soluble alkali and alkaline-earth metal salts of hypophosphorous acid. , in an amount necessary to maintain the concentration of the hypophosphite ions as given above. The pH of the solution is maintained at 7 or below, with an optimum pH below 4. This solution can be applied to the fibers by spraying, using wicks or rolls, or by any type. suitable method.



  The treated fibers can be in homopolymers or in copolymers of acrylonitrile, for example in binary, ternary or lower order copolymers containing at least 80104 by weight of acrylonitrile;

   they can be in mixtures comprising polyacrylonitrile or polymers comprising acrylonitrile, with 2 to 50% of another polymerized product,

   the mixture comprising a total percentage of polymerized acrylonitrile of at least 80% by weight. Although the polymers which lend themselves best to the present invention are those containing at least 80% acrylonitrile,

          Generally considered as acrylonitrile polymers capable of forming fibers, it is understood that the present invention is also applicable to acrylic textile fibers containing less than 80% of acrylonitrile.



  The polymer may, for example, be a copolymer consisting of 80 to 98% acrylonitrile and 2 to 20% of another monomer containing the> C = C <bond and copolymerizable with acrylonitrile.



  The polymer can also be a ternary or higher-order interpolymer, such as, for example, products obtained by interpolymerization of acrylonitrile with 2 or more than 2 monomers other than acrylonitrile. More precisely, it is preferable that the ternary polymer consists of acrylonitrile,

   of methacrylonitrile and 2-vinylpy- ridine. It is advantageous that the terminal polymers contain 80 to 98% acrylonitrile, 1 to 101% vinylpyridine or 1-vinylimidazole,

            and from 1 to 18% of another compound such as methacrylonitrile or vinyl chloride.



  The polymer can also consist of a mixture of polyacrylonitrile or of a binary interpolymer comprising from 80 to 99% of acrylonitrile and from 1 to 200/11 of at least one other compound containing the group> C = C < , with 2.

   at 50% by weight of the mixture of a copolymer comprising from 10 to 70% acrylonitrile and from 30 to 90% of at least one other polymerizable monomer containing the group <B>> C = C <. </ B> When the polymer contains a mixture,

   it is advantageous that it is a mixture of a copolymer comprising from 90 to 98 ro / o of acrylonitrile and from 2 to 10 '% of another mono-olefinic monomer, such as acetate vinyl,

   with a sufficient proportion of a copolymer consisting of 10 to 70% acrylonitrile with 30 to 90 (% of a vinyl-substituted tertiary heterocyclic amine, such as vinylpyridine or 1-vinylimidazole,

      so as to obtain a mixture capable of being dyed in which the percentage of vinyl tertiary heterocyclic amine is 2 to 10% relative to the weight of the mixture.



  The following examples illustrate the present invention.



  <I> Example 1 </I> Fibers in a copolymer of 93% acrylonitrile and 7% vinyl acetate, are treated by passing them through 2000 ml of an additional 40 ml bath. of 50% concentrated hypophosphorous acid.

   The fibers are then dried. The colorimetric measurements, carried out by reflection on a General Electrie spectrophotometer, give a purity of 2.2 and a brightness of 85.1; from the purity and brightness, the whiteness is calculated to be 89.8.



  <I> Example 2 </I> Fibers in a copolymer of 93% acrylonitrile and 7% vinyl acetate are treated by passing them through 2000 ml of a bath added to 8 ml

      50% concentrated hypophosphorous acid. The fibers are then dried. Under the conditions indicated in Example 1, their purity is 3.2 and their brightness is 85.2. and their whiteness of 82.9.



  <I> Example 3 </I> Fibers of a copolymer of 93% acrylonitrile and 7% vinyl acetate are treated by passing them through 2000 ml of an additive bath <RTI

   ID = "0002.0177"> 40 ml of 50% hypophosphorous acid and 4 g of sodium hypophosphite. The fibers are then dried. Under the conditions given in Example 1, it is found that their purity is 1.9, their brightness 84.1 and their whiteness 90.6.



  <I> Example 4 </I> Fibers in a 93% copolymer:% acrylonitrile and 7% vinyl acetate are treated by passing them through 2000 ml of a bath to which 8 ml has been added.

  50% hypophosphorous acid and 20 g of sodium hypophosphite. The fibers are then dried. Under the conditions indicated in Example 1, their purity is 3.9, their brightness is 85.3 and their whiteness is 77.0.



  <I> Example 5 </I> Fibers of a copolymer of 93% acrylonitrile and 7% vinyl acetate are treated by passing them through 2000 ml of a bath with addition of 8 ml of 50% hypophosphorous acid and

    4 g of sodium hypophosphite. The fibers are then dried. Under the conditions indicated in Example 1, their purity is 3.5, their brightness 85.6 and their whiteness 80.5.



  <I> Example 6 </I> Fibers of a copolymer of 93% acrylonitrile and 7% vinyl acetate are treated by passing them through 2000 ml of a bath supplemented with 4 ml of 50% hypophosphorous acid and 20 # g

      of sodium hypophosphite. The fibers are then dried and then dyed with Sevron Blue 2G, CI Basic Blue 22 .. The proportion of fixing of the basic dyes is 6.01% whereas it is only 3.71% without the treatment in accordance with the present invention.



  Thus, the treatment agents specific to the present invention not only make it possible to obtain fibers which are whiter than in the past, but also an increase in the absorption of basic dyes is obtained. The process in accordance with the present invention thus confers better dyeing qualities as well as better coloring of the fibers, which has the effect of improving the coloring after dyeing.

 

Claims (1)

CLAIM Process for the treatment of acrylic textile fibers, with a view to improving their whiteness and promoting the fixing of basic dyes thereon, characterized in that the fibers are treated with a bath comprising acid hypophosphorous or a mixture of this acid with at least one of its water-soluble metal salts. SUB-CLAIMS 1. Process according to claim, characterized in that mixtures of hypophosporous acid with at least one of its water-soluble metal salts are employed. 2. Process according to claim, characterized in that white fibers consisting of at least 80% acrylonitrile and up to 20% of another copolymerizable mono-olefinic monomer are treated. 3. Process according to claim, characterized in that white fibers consisting of 93% acrylonitrile and 7% vinyl acetate are treated. 4. Method according to sub-claim 3, charac terized in that one operates at a pH below 7. 5. Method according to sub-claim 4, charac terized in that one operates with a bath of hypophosphorous acid. 6. Process according to sub-claim 4, characterized in that one operates with a bath comprising a mixture of hypophosphorous acid and sodium hypophosphite. 7. Method according to sub-claim 4, characterized in that one operates with a bath comprising a mixture of hypophosphorous acid and potassium hypophosphite. 8. Process according to sub-claim 4, characterized in that the operation is carried out with a bath comprising a mixture of hypophosphorous acid and calcium hypophosphite.