WO1992010600A1

WO1992010600A1 - Yarn comprising polyalkene fibres and a process for producing the yarn

Info

Publication number: WO1992010600A1
Application number: PCT/NL1991/000252
Authority: WO
Inventors: Johannes Elizabeth Adrianus Kriele
Original assignee: Dsm N.V.
Priority date: 1990-12-06
Filing date: 1991-12-05
Publication date: 1992-06-25
Also published as: NL9002686A

Abstract

A yarn having good properties and a favourable cost price comprises a core section running in the longitudinal direction of the yarn and a sheath section surrounding the core section, the core section comprising 1 - 50 % by weight polyalkene fibres having a strength of at least 1.5 GPa and a modulus of at least 40 GPa, with at least the sheath section comprising natural fibres.

Description

YARN COMPRISING POLYALKENE FIBRES AND A PROCESS FOR PRODUCING THE YARN

The invention relates to a yarn comprising a core section running in the longitudinal direction of the yarn and a sheath section surrounding the core section, the core section comprising fibres having a high tensile strength an the sheath section comprising natural fibres.

Such a yarn is disclosed by the US Patent Specification No. 4,922,701. In the yarn from the abovementioned patent specification, the core consists entirely of fibres having a high strength. A disadvantage o the known yarn is therefore the high price of the yarn, as result of which the yarn is useable only to a limited extent. Surprisingly, a yarn is obtained whose strength ha remained at a sufficiently high level if, and this characterises the invention, the core section comprises polyalkene fibres as strong fibres having a initial modulus of at least 40 GPa and a tensile strength of at least 1.5 GPa, while the content of polyalkene fibres in the core section is only 1 - 50% by weight.

In general, a cheaper yarn is also obtained. The yarn furthermore has a large number of improve properties, such as a higher resistance to wear, a higher flexibility and an improved resistance to fatigue. When use in clothing, the yarn gives an excellent wear comfort.

Examples of natural fibres, which can be used in the sheath section of the yarn of the invention, are cotton, jute, wool and linen. In a yarn according to the invention, in which the abovementioned advantages find still better expression, the core section comprises 3 - 30% by weight of the polyalkene fibres, more preferable the core section comprises 5 - 15% by weight of polyalkene fibres.

A yarn according to the invention in which a very good cohesion exists between the core section and the sheath section is obtained if the core section comprises the same kind of natural fibres as the sheath section.

Preferably, relatively thin polyalkene fibres having a titre of not more than 5 denier, more preferably having a titre of not more than 2 denier is used in the yarn according to the invention.

Polyalkene fibres very suitable for the object of the invention are obtained if the polyalkene fibres are produced with the aid of the gel spinning process which is described, for example, in GB-A-2,042,414 and GB-A-2,051,667. This process essentially comprises producing a solution of the polyalkene, which preferably has a weight-average molecular weight of at least 600,000 g/mol, forming the solution into filaments at a temperature above the dissolution temperature, cooling the filaments to below the dissolution temperature so that gelation occurs and stretching the gelated filaments while the solvent is removed. Then the filaments are reduced to fibres by means of one of the processes known therefor, for example by cutting or chopping the filaments. The length of the fibres is preferably between 1 and 50 ram, more preferably between 2 and 25 mm and still more preferably between 3 and 10 mm.

Preferably, the polyalkene of the polyalkene fibre is linear polyethylene. Here linear polyethylene is understood as meaning polyethylene having less than 1 side chain per 100 carbon atoms, preferably less than 1 side chain per 300 carbon atoms and, in addition, being able to contain up to 5 mol-% of one or more other alkenes copolymerisable therewith, such as propylene, butene, pentene, 4-methylpentene, octene. Other polyalkenes are also suitable, such as, for example, propylene, homo- and copolymers. The polyalkenes used may furthermore contain small amounts of one or more other polymers, in particular 1-alkene polymers.

The yarn can be produced with the aid of one of th processes known therefor. In a preferred embodiment the yarn is produced by rotor spinning, also called open-end spinning. This technique is known per se, e.g. from the Encyclopedia of Materials Science and Engineering, ed. M.B. Beaver, Pergamo Press 1986, Volume 7, pages 4882-4883. In this embodiment a roving, comprising a homogeneous mixture of polyalkene staple fibers and natural staple fibers, having a polyalkene fiber content of 1-50 %, preferably of 3-30 %, more preferably of 5-15 % by weight i used as the starting material. Surprisingly the composition of the fiber obtained from this homogeneous roving by the rotor spinning process is no longer homogeneous, but it has appeared that the core section has a considerably larger polyalkene fiber content than the sheath section of the fiber. Moreover the outer layer of the sheath section virtually contains only natural fibers and no polyalkene fibers.

In an other preferred embodiment, the process for producing the yarn comprises passing at least one roving which comprises the polyalkene fibres and at least one roving which comprises the natural fibres simultaneously bu separately through a stretching device for the rovings, winding the roving comprising the natural fibres around the roving compris-ing the polyalkene fibres after they have left the stretching device and simultaneously rotating the yarn so produced around its axis. One of the advantages of such a method is that the core section and the sheath section in the yarn have a still further improved cohesion. An example of such a process is given in US Patent Specification 4,922,701. Very good results are obtained if the yarn is treated with an agent for rendering it flame-r-etardant. A method for treating a yarn comprising natural fibres and polyalkene fibres with flame-retardant agents is described in EP-A-377,243.

Textile structures, such as woven and knitted fabrics, which comprise the yarn according to the inven-tio are also included in the invention.

The invention will be elucidated by means of the following example, without being restricted thereby.

Example I; As polyalkene fibers, polyethylene cut-fibers of 32 mm. length were used with a tensile strength of 2.6 GPa, an initial modulus of 87 GPa, and a titer of 1.0 denier. The fibers were first crimped using the Stuffer box method. A homogeneously mixed roving, consisting of 10 weight % polyalkene fibers and 90 weight % cotton fibers was passed into the rotor of a Suessen rotorspin box and spun to a yarn.

The yarn obtained by this rotorspin process was visually inspected with respect to the distribution of the polyalkene fibers by colouring the cotton fibers and by unravelling the yarn. The outside of the yarn was homogeneously coloured, no polyalkene fibers could be observed at the outside of the yarn. The yarn appeared to have a non homogeneous distribution of polyalkene fibers with a core section enriched with polyalkene fibers and a sheath section consisting mainly of cotton fibers. The outside consisted only of cotton fibers.

The tensile strength was measured on an Uster Tensile meter. The tensile strength of the polyalkene fiber reinforced yarn was 15 cN/tex.

A rotorspun yarn consisting of cotton fibers only had a tensile strength of 10 cN/tex.

Claims

C L A I M S

1. Yarn comprising a core section running in the longitudinal direction of the yarn and a sheath sectio surrounding the core section, the core section comprising fibres having a high tensile strength and t sheath section comprising natural fibres, characterise in that the core section comprises polyalkene fibres as strong fibres having an initial modulus of at least 40 GPa and a tensile strength of at least 1.5 GPa, the content of polyalkene fibres in the core section being - 50% by weight.

2. Yarn according to Claim 1, characterised in that the content of polyalkene fibres in the core section is 3 - 30% by weight.

3. Yarn according to Claim 1, characterised in that the content of polyalkene fibres in the core section is 5 - 15% by weight.

4. Yarn according to one of Claims 1 - 3, characterised in that the core section comprises the same kind of natura fibres as the sheath section.

5. Yarn according to one of Claims 1 - 4, characterised in that the polyalkene fibres have a titre of not more tha 5 denier.

6. Yarn according to one of Claims 1 - 4, characterised in that the polyalkene fibres have a titre of not more tha 2 denier.

7. Yarn according to one of Claims 1 - 6, characterised in that the polyalkene fibres are produced with the aid of the gel spinning process.

8. Yarn according to one of Claims 1 - 7, characterised in that the polyalkene of the polyalkene fibres is linear polyethylene.

9. Yarn according to one of Claims 1 - 8, characterised in that the yarn is treated with an agent for rendering it flame-retardant.

10. Textile structure which comprises the yarn according to one of Claims 1 - 9 or as is described in the text of this application.

11. Process for producing a yarn according to anyone of claims 1 - 9 by rotor spinning a roving, which comprises a homogeneous mixture of polyalkene staple fibers and natural staple fibers.

12. Process for producing a yarn according to one of Claims 1 - 9, characterised in that the process comprises passing at least one roving comprising the polyalkene fibres and at least one roving comprising the natural fibres simultaneously but separately through a stretching device for the rovings, winding the roving comprising the natural fibres around the roving comprising the polyalkene fibres after they have left the stretching device and simultaneously rotating the yarn so produced around its axis.

13. Yarn, process or textile structure as is described in the text of this application.