US3424833A - Synthetic vinyl fibres of high shrink ability - Google Patents

Description

Jan. 28, 1969 Filed July 29, 1964 SHRINK AGE /N WATER U. MAZZOLINII ETA!- SYNTHETIC VINYL FIBRES OF HIGH SHRINKABILI'IY Sheet' of.5

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AGENT United States Patent US. Cl. 264-168 6 Claims Int. Cl. D01d /22; D011? 7/00 ABSTRACT OF THE DISCLOSURE Process for obtaining polyvinylchloride fibers having a shrinkage in boiling water or in saturated steam between 10% and 30% and, after shrinkage, a tenacity greater than 2.5 g./den., an elongation at break between 30% and 55%, an elastic modulus between 20 and 40 g./den. and a shrinkage in trichloroethylene at 40 C. less than 1%, in which fibers of polyvinylchloride having a high syndiotactic index (above 2), obtained according to known spinning methods by dry or wet spinning of the polymer, are subjected to the usual stretch, finishing, drying, heat-conditioning under tension and relaxing, and are further subjected to an additional stretch at a stretch ratio of at least 1.1 and at a temperature between 100 C. and 180 C. (preferably 120 C. to 140 C.).

The present invention relates to synthetic fibers of polyvinylchloride, having high shrinkability on heating and, excellent mechanical characteristics after shrinking, and to a process for obtaining such fibers.

More particularly, the present invention relates to synthetic fibers consisting of polyvinylchloride having high syndiotactic index and stereoregularity or crystallinity, high shrinkability on heating and excellent mechanical characteristics after shrinking, the fibers being capable of being processed into bulk yarns, as well as to a process for obtaining such bulk yarns.

The term polyvinylchloride of high syndiotacticity or high syndiotactic index as used in this description and in the claims, relates to (A) vinylchloride homopolymers prepared at temperatures of from 10 C. to 60 C. and having an intrinsic viscosity (1;) greater than 0.7 dl./ gr. and syndiotactic index greater than about 2 (the syndiotacticity being defined by the ratio between the absorption of the infra-red bands D 635 cm? and D 692 cm. as described by Burleigh, J.A.C.S., 82, page 749, 1960) and (B) copolymers or polymer mixtures containing at least 85% by weight of vinylchloride and satisfying these conditions.

Bulk yarns, generally known as high bulk, prepared by using mixtures of fibers having different heat shrinkability coefficients, are already known to the textile industry.

Thus, fiber mixtures are known which partly consist of fibers of practically no heat shrinkability (i.e., a heat shrinkability below 2%), and partly of fibers with high shrinkability (of about 10-30%). The yarns obtained from these by the usual spinning techniques are bulked by heat treatment, mostly in boiling water or saturated steam, which cause the shrinkage of the shrinkable fibers forming the basic structure of the yarn. The unshrinkable fiber is variously crimped and raised so as to give the yarn a swollen, vaporous and bulky aspect, highly valued in the manufacture of Warm, soft hosiery and looking very like natural wool.

For such a technical application it is of course necessary that the shrinkable fiber, as previously indicated, forms the basic structure of the yarn, and that the high-bulk yarn retains good mechanical characteristics (i.e. strength and stability), so as to be able to tolerate without damage all the stresses to which the yarn is submitted both in the subsequent weaving operations and in the use of the final woven fabric.

Known fibers based on polyvinylchloride are not suited for this purpose. Such fibers, do have a very high shrinkability in boiling water (above 60%), even exceeding the limit required for the application above described, but after shrinking, their mechanical characteristics fall 01f to extremely low values (for example, tenacity (tensile strength) =0.8-1 gr./den.; elongation at break=- elasticity modulus=l015 gr./den.) so that the yarns obtained from them are not, in practice, of much use because of the ease with which they undergo deformation even when subjected to only a small stress.

On the other hand, it is known that it is impossible to confer to the fibers made of highly crystalline polymers (such as for instance polyamides, polyesters, isotactic polypropylene, etc.), a high shrinkability coeflicient in boiling water in as much as, even when these fibers are subjected to elongation by the action of heat or to cold stretching in order to cause a subsequent high shrinkability, they readily assume a stable shape, wherefore they do not appreciably differ from the same unstretched fibers.

In practice, the fibers which have given the best results with the above mentioned bulking treatments are those of the acrylic type (Acrilan, Orlon, Dralon, etc.) which after suitable treatment may present both a high residual shrinkability and a practically no shrinkage in boiling water.

It has now been found that fibers may be obtained based on polyvinylchloride, which shrink markedly under heat and after shrinking retain excellent mechanical characteristics, so as to be particularly suited for the production of high-bulk yarns.

As already stated, it is known that by starting from the usual polymers of polyvinylchloride, fibers may be obtained which are acceptable from the textile point of view and which shrink considerably at temperatures just slightly above 60 C. but in which, after shrinking the mechanical properties decline to extremely low values. Moreover, it is known that starting from polyvinylchloride polymers with a high syndiotactic index it is possible to obtain textile fibers of very high quality which (A) may be processed with ease on conventional textile machinery, (-B) may be dry-cleaned without swelling under the action of the solvents commonly used in drycleaning and (C) show an excellent dimensional stability to heat.

Now it has been surprisingly found that it is possible to obtain polyvinylchloride fibers of high syndiotacticity which have a residual shrinkability in boiling water of between about 10% to about 30% of their initial length, though maintaining unchanged, after being heat-shrunk their mechanical characteristics, their dimensional stability under heat and their stability under the action of drycleaning solvents.

The invention therefore consists in textile fibers comprising polyvinylchloride of high syndiotacticity as herein defined and with a residual shrinkability in boiling water or saturated steam between 10% and 30% of the initial length and which after being shrunk in boiling water or saturated steam, have:

Tenacity Greater than 2.5 g./ den. Elongation at break Between 30% and 55%. Elastic modulus Between 20 and 40 g./den. Shrinkage in trichloroethylene at 40 C Less than 1%.

These novel fibers based on polyvinylchloride of high syndiotactic index are particularly suited for the production of high-bulk yarns with valuable properties.

The process for obtaining fibers according to the present invention consists in imparting to the fibers a high heat-shrinkability by means of a stretching additional to those stretchings normally applied in the spinning practice, and such as to ensure to the fiber the retention of the shrinkability which has thus been imparted to it. The shrinkability which is obtained according to this invention is stable at temperature below about 50 C., but is completely removed by a simple treatment in boiling water, saturated steam or in any other suitable heating medium at such temperature.

According to one preferred method for carrying out the process of this invention, given as an example, a solution of a polyvinylchloride of high syndiotactic index is extruded through a spinneret into a suitable coagulation bath or into an evaporative atmosphere in which the spinning solvent is eliminated; the fibers thus obtained are subjected to hot-stretch at a draw ratio of about 7, to finish ing, drying and thermal conditioning (all under stretch). The fibers are then relaxed, and subjected to an additional stretch treatment at temperature above 100 C. The treatments before the additional stretch are made in order to improve the mechanical and dimensional characteristics.

For the additional stretch treatment machines of the type used by the textile industry for the transformation of tows into tops, such as for instance the Turbo- Stapler, the Seydel or the Tematex converter, may be used.

The top thus obtained possesses the surprising combination of high heat shrinkability with high physical and mechanical strength characteristics which, even more unexpectedly, remain undiminished even after heat-shrink- According to another preferred method of this invention, the fibers obtained from a solution of polyvinylchloride of high syndiotactic index by dry or wet spinning, are subjected to a further heat stretching treatment during the spinning run, so that they have already at the outlet of the spinning machine a high heat-shrinkage so that they may be cut directly into staple of high shrinkage or be processed into high-shrinkage tops.

According to this method the fibers, obtained for example by wet spinning of a solution of polyvinylchloride of high syndiotactic index, e.g., in cyclohexanone into a coagulating bath, are washed, heat-stretched at a stretch ratio between 4 and 7, finished and dried, before the additional heat-stretching is carried out. The additional stretching may be carried out at a stretch ratio of more than 1.1 and up to the maximum allowed by the resistance of the tow and at temperatures between 100 C. and 180 C. and preferably between 120 C. and 140 C.

After the additional stretching the tow may be cooled down under tension, e.g., by means of cold air jets between two sets of rollers turning at the same speed, then crimped at a temperature below 50 C.

The fibers obtained by the above method may be directly worked on machines of the type similar to, for instance, the Pacifico converter or Reiter converter, in order to obtain high-shrinkage tops.

The preferred methods of this invention, as above described, may be applied to all spinning counts comprised between 1 and 40 den/filaments, both for raw and pigmented (dyed) fibers.

The shrinkability is constant, provided the fiber is not subjected to temperatures higher than 50-60 as shown, as shown in the accompanying drawing, in which:

FIGURE 1 represents the behavior in water at various temperatures for an immersion time of 30 minutes of the fiber consisting of polyvinylchloride at high syndiotacticity index and having high shrinkability;

FIGURE 2 represents the behavior in boiling water of the same fiber; and

FIGURE 3 of the drawing shows the stress-strain curves of the fiber obtained according to Example 1 (see below).

For textile fibers comprised between 1 and 8 den/filament, the characteristics of each filament after being shrunk in boiling water are preferably the following:

Tenacity g./den 2.8-3.5 Elongation at break percent 30-50 Elasticity modulus g./den 25-40 By mixing in proper amounts the staple or top of high shrinkability as described above according to the invention with another staple or top having lower or no shrinkability and consisting either of fibers of polyvinylchloride of high syndiotacticity index, or of other natural, artificial or synthetic fibers, regular yarns are obtained, that if shrunk (e.g., in boiling water, steam or other proper heating means) become bulky and assume a good appearance and soft hand like those of wool yarns.

Preferably between 10 and 70% of the fiber according to the invention (e.g., 3060%) are used in such a mixture.

Said yarns present excellent mechanical properties, can be dyed at boiling temperature with dispersed dyes (also in the presence of carriers) and can be dry-cleaned.

Furthermore the presence of fibers of polyvinylchloride of high syndiotactic index imparts to the yarn, the prop erty of non-propagation of flame. This is valuable in mixtures with cellulosic or acrylic fibers.

The following examples are given in order more particularly to describe the invention.

Example 1 parts of polyvinylchloride, obtained by polymerizing vinylchloride at 40 C. and having an intrinsic viscosity (1 )=1.35 dl./g., were dissolved in 450 parts of cyclohexanone.

The solution obtained was extruded through a spinneret with 10,000 holes of p. diameter, into a coagulum bath consisting of a mixture of cyclohexanone, water and ethyl alcohol.

The tow obtained from the coagulum bath was washed in a box containing a water-alcohol solution and stretched in boiling water at a stretch ratio of 7.5.

After stretching, the tow was treated in a box containing a finishing bath with antistatic property (Antistatic PB produced by Lamberti-Albizzate, Varese, Italy) and then dried on rollers at C.

After drying the tow was heat set under tension at 200 C. in presence of superheated steam for 6 seconds and then collected in perforated containers, which were treated in an autoclave at about 115-125 C. in presence of saturated steam for about 30 minutes. A tow was obtained having a total titer of 33,000 den.

On combining 10 of such tows, a tow was obtained having titer 330,000 den. and was processed at the Turbo Stapler in the following conditions:

Feed speed m./minute 20 Stretch ratio 1.3 Stretch temperature C Tear stretch ratio 3.20 Nominal cut "inches" 6 About 10 kilograms of Turbo top (i.e., the top obtained from the Turbo Stapler) was produced. 4.5 kilograms of this were relaxed in an autoclave at 115 C. in presence of steam for about 20 minutes and mixed with the remaining 5.5 kilograms of non-relaxed Turbo top.

The mixture of the two Turbo tops thus obtained was sequentially processed on traditional textile machinery and converted into yarn with metric titer 27/2 and with twist 340Z+220S.

The yarn was successively hank shrunk in a dyeing or hank-dyeing chamber in boiling water for about 30 minutes and thereafter centrifuged and dryed.

With this treatment the yarn shrank about 23% and bulked.

The characteristics of the bulk yarn are compared with the characteristics of a similar high-bulk yarn of acrylic fiber in Table 1.

TABLE 1 High-bulk High-bulk yarn of high yarn of comsyndiotacticity mercial acrylic PVC fiber Tenacity (g./den.) 1. 13 0.85 Elongation at break, percent 44 38 Elastic module (g./den.) 4. 6 4. 8 Specific apparent volume (ml./g.) 2.8 2. 75

The measurement of the specific volume of the yarn was carried out according to the process described by J. B. Hamilton in J. of Textile Institute of October 1961, p. 557, with a winding tension of 0.1 g./den., a winding angle of 3 and a compression strength of 28.5 gr.

In FIGURE 3 are given the corresponding stress-strain curves obtained at the Instron dynamometer, in which the continuous curve relates to a polyacrylonitrile having the same bulkiness.

Example 2 100 parts of polyvinylchloride obtained by polymerization of vinylchloride at 40 C. and having an intrinsic viscosity 7; of 1.30 dl./ g. were dissolved in 450 parts of cyclohexanone. The solution was extruded through a spinneret with 10,000 holes of 125 diameter into a coagulum bath as described in Example 1.

The tow obtained was washed and stretched in boiling water with a stretch ratio of 6 and subsequently finished and dried on heated rollers.

After drying the tow was stretched again with a stretch ratio of 1.35 in a room into which superheated steam was injected at 145 C. The tow was then cooled with cold air, under tension, on cold rollers and finally crimped at room temperature and cut.

The staple obtained had the following characteristics:

Titer "den/have" 2.5 Tenacity g./den 3.85 Elongation at break percent 14.5 Elastic modulus g./den 48 Yield tenacity g./den 0.9 Shrinkage in boiling water percent 25 The mechanical characteristics of the fiber itself after shrinkage in boiling water were:

Titer den./filament 3.1 Tenacity g./den 3.32 Elongation at break percent 46 Elastic modulus -g./den 36 Yield tenacity g./den 0.61 Shrinkage in boiling water percent Shrinkage in trichloroethylene at 40 C. do 0 The staple (before shrinkage in boiling water) was then mixed with polyvinylchloride fibers of high syndiotactic index having practically no shrinkage in the ratio of 45% of high shrinkage fibers and of 55% of fibers with no shrinkage.

The mixture thus obtained was then passed through a worsted wool cycle treatment until the following characteristics are obtained:

Metric count (Nm) 27/2 Twist 340Z+220S The yarn was arranged in hanks and these were then treated with boiling water in a dying vat and finally centrifuged and dried.

The hanks treated as above showed a shrinkage of 23%,

and bulk. The mechanical characteristics of the yarn thus obtained were:

Tenacity g./den 1.3

Elongation at break percent 45 Elastic modulus g./den 5.5

Shrinkage in boiling water percent 0.3

Shrinkage in tryelin do 0.1

We claim:

1. A process for making polyvinyl chloride filaments having a shrinkage in boiling water or in saturated steam comprised between 10% and 30% and showing after shrinkage a tenacity greater than 2.5 g./den., an elongation at break between 30% and 55 an elastic modulus between 20 and 40 g./den. and a shrinkage in trichloroethylene at 40 C. less than 1%, comprising the step of subjecting filaments of polyvinyl chloride having a syndiotactic index of at least 2 and obtained by spinning vinyl chloride polymer polymerized at a temperature of 10 C. to 60 C. and containing at least by weight vinylchloride, after an initial streaching, fiber finishing, drying, heat-conditioning under tension and heat relaxation, to a further stretch with a stretch ratio of at least 1.1, but substantially below the tear stretch ratio, at a temperature between C. and 180 C.

2. The process defined in claim 1 wherein said further stretch is carried out at a temperature between C. and C.

3. The process defined in claim 1 wherein the filaments after said further stretch are subjected to cooling under tension and are thereafter crimped at a temperature below 50 C.

4. A process for making polyvinyl chloride filaments having a shrinkage in boiling water or in saturated steam comprised between 10% and 30% and evidencing after shrinkage a tenacity greater than 2.5 g./den., an elongation at break between 30% and 55%, an elastic modulus between 20 and 40 g./den. and a shrinkage in trichloroethylene at 40 C. of less than 1%, comprising the steps of subjecting filaments of polyvinyl chloride having a syndiotactic index of at least 2 and obtained by spinning vinyl-chloride polymer polymerized at a temperature of 10 C. to 60 C. and containing at least 85% by weight vinyl-chloride, to a first partial stretch in boiling water with a stretch ratio between 4 and 7; finishing and heat-drying under tension the partially stretched filaments; and subjecting the finished and heat-dried partially stretched filaments to a further stretch at a stretch ratio of at least 1.1, but substantially below the tear stretch ratio, at a temperature between 100 C. and C.

5. The process defined in claim 4 wherein said further stretch is carried out at a temperature between 120 C. and 140 C.

6. The process defined in claim 4 wherein the filaments after said further stretch are subjected to cooling under tension and are thereafter crimped at a temperature below 50 C.

References Cited UNITED STATES PATENTS 9/1957 Laval 28-76 5/1961 Isaksen et al. 26092.8

JACOB H. STEINBERG, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,424,833 January 28, 1969 Corrado Mazzolini et al.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below: In the heading to the printed specification, lines 5 and 6, "A.C.S.A. Applioazioni Chimiche S.p.A., Milan, Italy, a corporation of Italy" should read Chatillon Societa Anonima Italiana per le Fibre 'Iessili Artificiali S.p.A., Milan, Italy, a corporation of Italy Signed and sealed this 31st day of March 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, IR.

Edward M. Fletcher, J r.

Commissioner of Patents Attesting Officer

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