Process for manufacture of superabsorbent-coated yarn

Details Process for manufacture of superabsorbent-coated yarn Process for manufacture of superabsorbent-coated yarn

2000-03-06

2001-11-20

Cameron, Erma (Department: 1762)

Coating processes

With post-treatment of coating or coating material

Heating or drying

C427S389900

Reexamination Certificate

active

06319558

ABSTRACT:

BACKGROUND OF THE INVENTION.
1. Field of the Invention
The invention relates to a process for the manufacture of yarn provided with a superabsorbent material.
Said yarn can be utilized in cables, more particularly optical communications cables, in this way functioning simultaneously as reinforcing member and as water blocking agent.
A yarn provided with a superabsorbent material and the manufacture of such a yarn are known from European Patent Applications 482,703 and 351,100, U.S. Pat. No. 5,635,569, and PCT application WO 93/18223. According to these publications yarns are impregnated with a superabsorbent material in a water-oil emulsion. After being impregnated the treated yarn is dried, so that a film is formed in and around the yarn's interstices. The resulting product is used as reinforcing material for the manufacture of a communications cable with water blocking properties.
However, there are drawbacks to the above-mentioned methods of applying a superabsorbent material to a cable or yarn surface. A major disadvantage is the release of organic materials, in particular isohexadecane, during the process of drying the yarn. Such organic materials form an unacceptable environmental burden, and isohexadecane must be eliminated by burning or by treatment in a waste gas unit. Such step requires expensive equipment and uses substantial amounts of energy. It is therefore an advantage to eliminate the use of water-oil emulsions, and to apply materials which are water soluble.
The drawback to impregnating an aramid yarn with a superabsorbent material dispersed in an aqueous system is that, due to the superabsorbent material's high viscosity enhancing action, uniform feeding of it is extremely difficult, if not impossible. Further, on account of the limited concentration of superabsorbent material in the impregnating liquid only a small quantity of it can be applied to the yarn per treatment. Another drawback to this method is that the comparatively large amount of impregnating liquid which is applied to the yarn with the superabsorbent material has to be removed again by evaporation.
SUMMARY OF THE INVENTION
The present invention obviates the aforesaid drawbacks. Moreover, the invention provides an aramid multifilament yarn of excellent water absorbing capacity without using organic solvents or excessive amount of water.
The invention consists of a process for the manufacture of a yarn provided with a superabsorbent material having a swelling value of at least 60 and having hydrophilic properties which is capable of absorbing and retaining quantities of water, characterized in that an aqueous solution comprising a water-soluble pre-superabsorbent material is applied onto the yarn, after which the yarn is dried and heated in order to cross-link or to polymerize the water-soluble pre-superabsorbent material to the superabsorbent material.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Thus no superabsorbent material as such is longer used but a water-soluble precursor which after heat treatment polymerizes or cross-links to superabsorbent material. This process may be followed by a step wherein a finish is applied onto the yarn. Alternatively, the aqueous solution already comprises the finish.
The yarn obtained must have a swelling value greater than 60. The swelling value is a measure of the quantity of water absorbed by the yarn when it is contacted with water in the liquid form. The method of experimentally determining the swelling value will be illustrated in greater detail below. It was found that the yarn according to the invention has swelling values comparable to the above-mentioned prior art yarns. Preferably, the swelling value of the yarn according to the invention is at least 80, more particularly at least 100, and more particularly still at least 150.
The term multifilament yarn has the meaning it customarily has in the art, i.e., the fibers of which it is made are endless filaments.
Textile Terms and Definitions
(1988), pages 289-290 is referred to in this respect. Within the framework of the invention the fibers used in making the yarns according to the invention are filaments which may have any linear density common in actual practice, and yarns may be made up of any desired number of endless filaments. Generally, the filaments or the yarns composed thereof will have a linear density of 0.01 to 20 000 dtex, while the endless filament yarns will be composed of 1 to 20 000 filaments.
As suitable types of fibers may be mentioned fibers of organic as well as inorganic origin. The fibers of organic origin may be either natural or synthetic. Examples of natural fibers include cellulose fibers such as cotton, linen, jute, etc., and fibers of animal origin such as wool, silk, etc. Examples of synthetic organic fibers include fibers of regenerated cellulose, rayon, polyesters, aliphatic and aromatic polyamides, acrylonitrile, polyolefins, polyvinyl alcohol, polyvinyl chloride, polyphenylene sulfide, elastomers, and carbon. Examples of inorganic fibers include fibers of glass, metals, silica, quartz, etc., ceramic fibers, and mineral wool. In addition, fibers made up of mixtures of said materials or copolymers thereof or mixtures of said fibers may be employed. The aforementioned types of fibers and other ones suitable for use in the process according to the invention have been described in Kirk-Othmer,
Encyclopedia of Chemical Technology
, 3
rd
Edition, Vol. 10 (1980), pp. 148-197.
Preference is given to fibers composed of aramid, polyethylene terephthalate, nylon-6, nylon-6,6, regenerated cellulose, or glass. Also highly suitable as a substrate are fibers composed of two or more of the aforementioned materials, e.g. bicomponent fibers. They may be of the sheath-core or the side by side type, or of some other well known type. Other suitable types of fibers are satellite fibers and split fibers.
The fibers may be either solid or hollow. They may be round or flat or of any other desired cross-sectional shape, e.g. elliptical, triangular, star-shaped, kidney-shaped, etc.
Aramid yarns are most preferred. By aramid yarns is meant according to the invention yarns composed of polymers built up wholly or substantially from recurring units of the general formula:
Herein A
1
, A
2
, and A
3
represent different or the same divalent, one or more aromatic rings-containing rigid radicals which may also contain a heterocyclic ring, the chain-extending bonds of which radicals are in the position para to each other or are parallel and oppositely directed. Examples of such radicals include 1,4-phenylene, 4,4′-biphenylene, 1,5-naphthylene, and 2,6-naphthylene. They may contain substituents or not, e.g. halogen atoms or alkyl groups. In addition to amide groups and the aforementioned aromatic radicals the chain molecules of the aromatic polyamides may optionally contain up to 35 mole % of other groups, e.g. m-phenylene groups, non-rigid groups such as alkyl groups, or ether groups, urea groups or ester groups. Preferably, the aramid yarn is made up wholly or in part, more particularly for over 90 wt. %, of poly-(p-phenylene terephthalamide).
By a pre-superabsorbent material is meant according to the invention a material that after heating polymerizes or cross-links to a superabsorbent material having hydrophilic properties which is capable of absorbing and retaining a comparatively large quantity of water, optionally under pressure. In order to simply apply the solution onto the yarn it is required that the pre-superabsorbent material dissolved in an aqueous solution has a viscosity smaller than 1000 mm
2
sec
−1
. Preferably, the viscosity is smaller than 500 mm
2
sec
−1
, and most preferably between 10 and 200 mm
2
sec
−1
. Particularly suitable for use as pre-absorbent materials are derivatives of polyacrylic acid. These include the water-soluble monomers, oligomers, and polymers derived from acrylamide, from acrylamide and sodium acrylate, and from acrylamide and dialkylaminoethyl methacrylate. These compounds are selected from the groups of water-sol

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