Ultra high molecular weight polyethylene multifilament yarns, and process for producing thereof

1. A gel spun, ultrahigh molecular weight polyethylene (UHMWPE) multifilament yarn, wherein the yarn comprises individual monofilaments having a coefficient of variation of their linear density, hereafter CV intra , of less than 30%, wherein the CV intra of a monofilament was determined from linear density values corresponding to a number of 20 representative lengths randomly extracted by cutting from said monofilament and using Formula 1

CV

INTRA

=

∑

i

=

1

n

⁢

(

x

i

-

x

_

)

2

n

-

1

×

1

x

_

×

100

Formula

⁢

⁢

1

wherein x i is the linear density of any one of the representative lengths extracted from the monofilament under investigation and x is the averaged linear density over the n=20 measured linear densities of said n=20 representative lengths.

2. A gel spun, ultrahigh molecular weight polyethylene (UHMWPE) multifilament yarn, wherein the yarn has a coefficient of variation in linear density between the monofilaments comprising said yarn, hereafter CV inter , of less than 50%, wherein CV inter is determined by using linear density values of a number of 50 representative lengths, wherein each of said lengths corresponds to a different randomly chosen monofilament and is extracted by cutting thereof and using Formula 2

CV

INTER

=

∑

i

=

1

n

⁢

(

x

i

-

x

_

)

2

n

-

1

×

1

x

_

×

100

Formula

⁢

⁢

2

wherein x i is the linear density of any one of said representative lengths and x is the averaged linear density over the n=50 measured linear densities of the n=50 representative lengths corresponding to the randomly chosen monofilaments.

3. The yarn of claim 1 having a tensile strength of at least 1.2 GPa.

4. A process of producing gel spun UHMWPE multifilament yarns according to claim 1 comprising the steps of:

a) feeding to an extruder a slurry containing an UHMWPE in a spinning solvent;

b) converting the slurry in the extruder into a solution of UHMWPE in the spinning solvent;

c) spinning a multifilament yarn by passing the solution of step b) through a spinning plate containing a plurality of spin holes to form the monofilaments comprising said yarn;

d) cooling the obtained monofilaments to form gel monofilaments;

e) removing at least partly the spinning solvent from the gel monofilaments; and

f) drawing the monofilaments in at least one drawing step before, during or after removing the spin solvent; wherein

a chamber is present before the spinning plate such that no further partitioning of the UHMWPE solution obtained at step b) takes place before said solution being finally partitioned into individual monofilaments in step c) and in which chamber the solution has a residence time τ at a constant throughput of UHMWPE solution of at least 50 sec.

5. The process of claim 4 , wherein the residence time τ is at least 60 sec.

6. The process of claim 4 wherein the average shear rate to which the UHMWPE solution is subjected inside the chamber is at most 10 sec −1 .

7. The process of claim 1 , wherein a spinning plate is used having at most 20 spin holes per cm 2 .

8. A rope, net, medical cable or a composite comprising a yarn according to claim 1 .

9. A product comprising the yarn according to claim 1 , the product chosen from the group consisting of

a roundsling;

a fishing net;

a protective textile such as a cut-resistant textile, a scratch-resistant textile and an abrasion-resistant textile, in particular a protective glove;

a sports equipment, in particular a fishing line, a kite line and a yacht line;

an anti-ballistic product, in particular an anti-ballistic vest, an anti-ballistic helmet, an armored vehicle;

an air cargo net and an air freight container.