Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2000-05-15
2001-04-03
Edwards, N. (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S395000
Reexamination Certificate
active
06210799
ABSTRACT:
The present invention relates to a PA 6,6 industrial yarn consisting of filaments having a total linear density of 900 to 2100 dtex and produced by melt-spinning and drawing of polyamide-6,6 having a pellet viscosity RV >75 at a winding speed v
sp
which has to meet the following conditions:
v
sp
=(
Ft
o
/Ft
x
)
3
*v
spo
, where Ft=tenacity, Ft
o
=84
cN/tex
, Ft
x
=eff Ft in cN/tex and v
spo
=2750 m/min (1)
in the presence of water, and also to a process for producing a low-defect industrial yarn.
As well as its serimetry, its level of defects is a significant quality factor of an industrial yarn. At winding speeds of more than 2750 m/min, polyamide industrial yarns generally have an excessively high defect level of the order of more than 1.5 defects per km. To reduce defects, it was hitherto necessary to reduce the spinning speed, which entails reduced productivity. It has now been found that the defect level depends not only on the spinning and winding speed but also, strongly, on the moisture content of the polyamide polymer fed into the extruder.
It is known to moisten PA 66 polymer ahead of the extruder or in the melt. In each case the purpose is to ensure consistent melt quality. The moisture is added in controlled fashion via moist N
2
or as direct metered addition of water, for which the melt pressure ahead of the spinning pump can be utilized as control variable.
EP-B-0 092 898 discloses controlling physical properties of meltable polyamides by depolymerization by means of moisture. In said reference, water is added to keep the viscosity constant. The object is considered to be to produce a polymer melt having constant physical properties.
The present invention has as its object to provide a PA 66 industrial yarns having a tenacity of at least 84 cN/tex, very rapid processing and a minimum of defects.
This object is achieved according to the invention when the PA 6,6 filament combines a tenacity of >84 cN/tex and with less than 1.5 defects/km.
In a variant featuring a pellet viscosity RV >90, a moisture content >0.06% and a tenacity Ft
x
>90 cN/tex, it is possible to obtain at a spinning speed v
spo
greater than the spinning speed calculated by the formula (1) an industrial yarn having a high linear density and a surprisingly low number of defects conforming to the following formula:
defects
F
1<(
Ft
x
/Ft
o
)
3
* v
spx
/v
spo
*Tt
x
/Tt
o
, where (2)
Tt
o
is a linear density of 940 [lacuna] and Tt
x
is the linear density at the winding speed v
spx
.
The advantage is a low defect level which, if dry PA 66 polymer pellets are used, can otherwise only be achieved at low spinning-drawing speeds.
It is particularly advantageous for the water content of the polymer pellets ahead of the extruder to be in the range of 0.04-0.14% by weight, especially 0.06-0.12% by weight.
REFERENCES:
patent: 4648240 (1987-03-01), Hallsworth et al.
patent: 5106946 (1992-04-01), Clark, III et al.
patent: 6023824 (2000-02-01), Fishcher et al.
Berger Luzius
Fischer Klaus
Luvizotto José
Edwards N.
Rhodia Filtec AG
Striker Michael J.
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