US3533729A - Process for dyeing polyvinyl chloride fibers - Google Patents

Description

Oct. 13, 1970 c. MAZZOLINI ETAL ,5

PROCESS FOR DYEING POLYVINYL CHLORIDE FIBERS Filed April 21, 19s? I I I INVENTOR! ammo Ima -1M;

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United States Patent 3,533,729 PROCESS FOR DYEING POLYVINYL CHLORIDE FIBERS Corrado Mazzolini, Sergio L0 Monaco, and Giorgio Cazzaro, Mestre, Venezia, Italy, assignors to A.C.S.A. Ap-

plicazioni Chimiche S.p.A., Milan, Italy Filed Apr. 21, 1967, Ser. No. 632,715 Claims priority, appgaafildrfilltaly, May 6, 1966,

Int. Cl. D06p 3/00 US. Cl. 8--162 7 (Zlaims ABSTRACT OF THE DISCLOSURE BACKGROUND or THE INVENTION The present invention relates to a process for dyeing continuously, uniformly and deeply, shaped articles such as fibers, filaments, films, etc. obtained from vinyl chloride and, more particularly, it relates to the dyeing of fibers or other shaped articles of polyvinyl chloride having a high syndiotactic index.

The term polyvinyl chloride with a high syndiotactic index, as used in the present specification and in the claims, comprises both the vinyl chloride homopolymers and its copolymers or mixtures of polymers with at least 85% by weight of vinyl chloride, having a syndiotactic index higher than 1.8 (the syndiotactic index being defined by the absorption ratio at the LR. bands D 635 and D 692 cmf as described by Fordham, Burleigh, and Sturm, J.A.C.S., vol. XLI, pages 7382, 1959).

The polyvinyl chloride with a high syndiotactic index may be transferred into fibers by dry or wet spinning and the fibers thus obtained present excellent chemical and physical properties and an excellent stability to heat and to dry cleaning.

On the contrary, their dyeability is not so good, since the afiinity of these fibers towards dyestuif is slight.

On the other hand, said fibers being hydrophobic and considerably more crystalline than traditional fibers of polyvinyl chloride, it is difficult to make the dye penetrate into the fibers, if the process is not carried out under pressure.

The most satisfactory and practical method for dyeing these fibers is that of incorporating the dye into the spinning solution before its extrusion through the spinneret. This method presents, however, many drawbacks, the main problem being constituted by the fact that a great quantity of fibers of the same color must be prepared since, when a change of color is made, the entire spinning apparatus must first be thoroughly cleaned to remove all the traces of the dye used.

It has now been discovered, which discovery is the object of the present invention, that it is possible to dye in a continuous, rapid, uniform and deep manner, fibers or other shaped articles obtained via the wet or dry spinning of polyvinyl chloride with a high syndiotactic index, by means of a process comprising the following stages:

3,533,729 Patented Oct. 13, 1970 (a) dipping into a dyebath the fibers just spun and which have not as yet been subjected to a drying treatment,

(b) suitably regulating the quantity of dyestuff on the fibers,

(c) subsequently subjecting the colored fibers to a thermal treatment at high temperatures, and

(d) removing excess dyestutf by washing.

In fact, it was surprisingly found that, only by following at once the impregnation of the fiber with a solution or dispersion of dyestutf with a thermal treatment at high temperature, was it possible to dye uniformly and deeply polyvinyl chloride fibers having a high syndiotactic index.

The treatment with a solution or dispersion of at least one dyestutf may be carried out at any stage during the spinning process, but prior to any thermal drying treatment and in which the fibers are in such condition as to be abe to incorporate the dyestulf.

Therefore, for example, this treatment may be carried out during or after coagulation of the fiber, or after the fiber has been coagulated and washed or during or after stretching.

Furthermore, such a treatment may be carried out during the spinning cycle or subsequently, on condition that said fibers have not been subjected to an intermediate thermal drying treatment.

Generally, best results are obtained when the fibers are stretched to the ultimate value desired before being dipped into the dyebath.

However, in practice, it is also possible to partially stretch the fibers before dyeing; and in this case the subsequent stretching to the ultimate value desired is carried out either during the thermal treatment or after drying.

The dyebath may be advantageously composed of an aqueous solution or dispersion of at least one dyestutf, and even nonaqueous solutions or dispersions may be used.

The temperature of the dyebath is not critical with re gard to the shade or the depth of the color which must be obtained.

Consequently, all temperatures ranging between room temperature and C. may be used.

At any rate, one of the advantages of the present invention is that it is possible to obtain a uniform, deep and rapid dyeing by operating at room temperature.

However, in the case that the dyeing is effected during stretching, the temperature, turns out to be higher, since the stretching is carried out at a temperature ranging from 90 and C.

The concentration of the dyestuff in the dyebath depends both on the particular dyestuff used and on the shade and depth of the color which must be obtained.

Generally, such a concentration can vary from a very low concentration, 0.001% by weight up to a saturated solution of dyestutf and also up to the impregnation of the fiber with the dyestuff.

In practice, however, a better penetration of the dyestuff and a uniformity of color are obtained by using relatively dilute solutions as dyebath.

During the dyeing, the concentration of the dyebath is kept constantly at the desired value by adding, in a suitable way, a solution or a dispersion of the dyestuff at a concentration such as to integrate the dyestufl removed by the fibers.

Generally, all water soluble and water dispersible dyestufls, including pigments, may be employed advantageously. Specifically, among those that may be mentioned are vat, sulfur, direct, metallized, basic, acid, azoic, and plastosoluble, etc. dyes.

However, best results are attained by using plasto-soluble dyestuffs.

The time during which the fiber remains dipped in the dyebath is very short and such as not to slow down the spinning cycle. This time depends on the denier of the fibers and not on the number of the filaments composing the tow and generally it varies between some fractions of a second and some seconds, and preferably between 1 to seconds.

In order to regulate the content of the dyestuif on the fibers according to the shade of the color to be obtained, according to the present invention, the fiber coming out of the dyebath are subjected to wringing. The wringing of the fibers can be made in any suitable way. So, for example, the tow can be made to pass either through pressure rollers or through a narrow opening or on an acute angle under tension etc.

Preferably, however, a pair of pressure rollers are used, where the pressure applied to the tow between the two rollers can be varied at will.

According to the present method it is necessary and indispensable to follow the treatment with a solution or dispersion of a dyestuff and subsequent wringing of the fibers with a thermal treatment at high temperatures in order to fix the structure of the fiber and, therefore, to firmly incorporate the dyestutf in the fibers.

Such a thermal treatment is carried out at a temperature comprised between 100 C. and 220 C. and preferably between 130 C. and 170 C.

According to the process of the present invention, the fibers colored after the thermal treatment, are washed with hot water or aqueous solutions of soap or of another detergent, preferably at boiling temperatures, in order to remove excess dyestuff not included into the fibers.

The fibers thus obtained may be subjected to further additional treatments, such as finishing, lubrication, etc. before being dried in air or inert gas at a temperature comprised between 100 C. and 200 C.

The dyed fibers thus obtained exhibit excellent physical properties besides the fact of being dyed in a deep and uniform way, both over their cross section and along their length.

With reference to the figure of drawing, a preferred method of the present invention will now be described. A bundle of filaments (tow) 1 obtained by dry or wet spinning, according to known methods, of vinyl chloride having a high syndiotactic index, at the outlet of the coagulation bath or of the evaporation column is washed, at least partially stretched, passed around guide roller 2 and immersed into the dyebath 3 by means of guide roller 4 and 5. The dyed bundle of filaments 6 is taken from the pressure rollers 7 regulating the quantity of dyestuff on the fibers, thus eliminating excess dyestuff.

The dyed bundle of filaments is subsequently heat treated by making it pass around a series of hot rollers 8. The dyed and dried bundle of filaments thus obtained is thoroughly washed with boiling water which may also contain some detergent and which is subsequently subjected to possible further treatments commonly called finishing treatments, and finally dried.

In order to further illustrate the present invention and the advantages thereof, the following specific examples are given, it being understood that the same are merely intended to be illustrative and not limitative.

EXAMPLE 1 2 kg. of polyvinyl chloride, having a syndiotactic index of 2 and an intrinsic viscosity (1;) of 1.3 dl./g., determined in cyclohexanone at 25 C., were dissolved at 145 C. in 8 kg. of cyclohexanone. The solution obtained was extruded through a spinneret of 500 holes, every hole having 0.125 mm. diameter, into a coagulation bath composed of water, alcohol and cyclohexanone.

The tow thus obtained was collected by a pair of rollers having a peripheral speed of 7 m./min. The tow was then washed with boiling water and stretched about 700% by a second pair of rollers having a peripheral speed of 49 m./min.

The tow 1, by means of the rollers 2, 4 and 5, was dipped into the dyeing vat 3 containing an aqueous dispersion or solution of one of the hereinunder reported dyestuffs.

The tow was taken up and wrung by the pair of rollers 7 and then subjected to a thermal treatment by making it pass around the rollers 8 maintained at 150 C.

Subsequently and continuously, the tow was washed with boiling water, then finished and finally dried.

A tow was thus obtained, having a total count of 1,250 deniers, dyed uniformly and deeply, according to the shades peculiar to the following dyestutf:

EXAMPLE 2 A tow of filaments of polyvinyl chloride with a high syndiotactic index, obtained according to Example 1, at the outlet of the coagulation bath, was collected by a pair of rollers having a peripheral velocity of 7 m./min.

The tow was then washed with boiling water and stretched about 300% by a second pair of rollers having a peripheral speed of 21 m./min.

The tow partially stretched, thus obtained, was dyed via dipping into a dyebath containing any one of the dyestuffs reported in Example 1, then it was thermally treated by passing the same over a series of rollers maintained at 160 C.

The dyed tow, thus obtained, was washed with boiling water, finished, dried and then subjected, in a continuous way, to a successive stretch of 20% by means of a pair of rollers having a peripheral speed of 42 m./rnin.

The tow, thus obtained, has a total count of 1,500 deniers and properties similar to the tow obtained according'to Example 1.

EXAMPLE 3 A tow of 50 filaments, obtained by dry spinning a solution of polyvinyl chloride having a high syndiotactic index in cyclohexanone, was wound on reels. 10 of these reels were placed on a creel and unwound at the speed of 10 m./min. by a pair of rollers, on which the 10 tow of filaments were gathered to form a single tow of 500 ends.

This last was washed and stretched about 500% by a second pair of rollers rotating at a peripheral speed of 50 m./ min.

Subsequently, the tow was dyed by making it pass in a dyebath containing one of the dyestuffs reported in Example 1, then it was thermally treated at 150 C., washed with boiling water and finally dried.

A tow was thus obtained, having a total count of 1,250 deniers, dyed uniformly and deeply.

As many apparently widely different embodiments of this invention can be made without departing from the spirit and scope thereof, it is to be understood that the same is not to be limited to the specific embodiments thereof, except as claimed in the appended claims.

What is claimed is:

1. A process for rapidly, uniformly and deeply dyeing fibers obtained by wetor dry-spinning high syndiotactic vinyl chloride homopolymers, copolymers or mixtures of polymers containing at least by weight of vinyl chloride, comprising dipping the said fibers into a dyebath containing at least one dyestuff, the clipping occuring subsequent to spinning but prior to any drying treatment of the said spun fibers, regulating the amount of dyestuff taken up by the said fibers, subjecting the thus colored fibers to a heat-treatment at a temperature between and about 220 C., and thereafter removing excess dyestuif.

2. The process as defined by claim 1, wherein the fibers are at least partially stretched prior to their entry into the dyebath.

3. The process as defined by claim 1, wherein the fibers are stretched to the ultimate value desired prior to their entry into the dyebath.

5 6 4. The process as defined by claim 1, wherein the References Cited elevated temperatures range from between 130 C. to UNITED STATES PATENTS about 170 C. I

5. The process as defined by claim 4, wherein excess gfifiigg dyestufi is removed by Washing- 5 3 113 327 12 19 3 Moore, 7g 6. The process as defined by claim 4, wherein the dye- 3,242,243 3/1966 Knudsen bath comprises a member selected from the group consisting of an aqueous dispersion and an aqueous solution GEORGE F. LESMES, Primary Examiner of the Said dYcstuff' T J HERBERT JR AssistantE n r 7. The process as defined by claim 6, wherein the con- 10 Xaml e centration of dyestulf in the dyebath ranges from be- US. Cl. X.R.

tween 0.001 percent by weight and saturation level. 8-176; 26478

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