Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TITLE
PAPER-MAKI~dG BELTS OF FUSED :POLYMERIC FILAM~NTS
GRO;I~:U or 1'U INVENTION
In ~he preparation o paper, woven support
5 bellts are used for the initial castirlg and subæequent
txeatment of the paper. These belts are known as
paper clo~hing~ ~ variet:y o materials has been used
in the manufacture o~ such belts, incl-lding metals
and, more recently, thermoplastic monofilaments and
10 multifilaments.
While paper-making belts of therm~plastic
materials have provided al numb~r o~ advantages, paper
clothing prQpared ~rom l~hermopla tic ma~erials
c:ccasionally exhibi~s poor dimensional stability and
15 high water absorption. Various techn1qlles have been
sugg~sted for the improvement of dimensional
stabilit~, includirlg the use of thermoplastic
mono:Ei1aments having different degr~es of orientation
in ~he machine and tran~verse directions or the use
20 of multifilaments having exceptionally high modulus
of elasticity. ~Iowever, previously sugges~ed
ce~mbinations of materials and filam~nt configurations
have no~ fully satisf ied ~he need for paper clothing
having excellent dimensional stability and low water
25 absorption and which is easily cleaned after
lon~-term operation.
The instant invention provides, in a woven,
heat set, paper-making belt of mac:hine and ~ransverse
30 direc~ion thermoplastic filaments, the improvement
wherein the filamerlts in at least one of the machine
and transverse directions are coextruded
mono~ilaments having a core of a polymer selec'ced
from nylon 66; polyethylene ~rephthalate; and a
35 tetrapolymer of tere- and iso- phthalic acids,
'7~
1,4-butane dlol, and po].ytetramethylene ether glycol
and a sheath of a polymer selected from the group
consisting of nylon 11; nylon 12; nylon 6; nylon 610;
nylon 612; polybutylene terephthalate; and a tetra-
polymer of tere and iso- phthalic ac.ids, 1,4-butane
diol, and polytetramethylene ether glycol wherein the
shea-th is adhered to the core and has a melting po.int
at least about 25 Celsius degrees lower than the core,
and wherein the machine and transverse direction filaments
are bonded together at the intersections of the filaments
by the substance of at least one of the filaments.
DETAILED DESCRIPTION OF THE INVENTION
The monofilaments used in at least one
direction in the woven structures of the present paper
clothing are coextruded structures having a sheath and
a core. These monofilaments are prepared by conventional
coextrusion techniques, as described, for example, in
U.S. Patent 2 936 482.
The materials which can be used for the core
of the monofilaments include poly~examethylene adi-
pamide (nylon 66), polyethylene terephthalate and a
tetrapolymer of tere- and iso- phthalic acids, 1,4-
butane diol and polytetramethylene ether glycol
containing less than 50 weight percent of the resulting
butane diol terephthalate.
Polymers which can be used for the sheath
component of the monofilaments include
polyundecanoamide (nylon 11), polydodecanoamide
(nylon 12), polycaprolactam (nylon 6),
polyhexamethylene decanoamide (610 nylon),
polyhexamethylene dodecanoamide (nylon 612),
polybutylene terephthalate, and a tetrapolymer of
tere- and iso- phthalic acids, 1,4-butane diol and
polytetramethylene ether glycol wherein the resulting
butane diol terephthalate comprises about from 70 to
90 weight percent of a tetrapolymer.
The tetrapolymers of the terephthalic acids,
polytetramethylene ether glycol, and l,~-butane diol
which can be used for the core and the sheath can be
prepared according to the teachings of Witsiepe, U.S.
Patents 3 651 014 and 3 763 109, respectively.
The sheath component of the monofilament must
be adhered to the core. In this regard, certain com-
binations of sheath and core polymers are well suited
for the preparation of a monofilament charac-terized
by excellent adhesive bonding between the sheath and
core. These combinations include nylon 11 with either
nylon 66 or polyethylene terephthalate; nylon 12 with
either nylon 66 or polyethylene terephthalate; nylon
6 with nylon 66; nylon 610 with nylon 66; nylon 612
with either nylon 66 or polyethylene terephthalate;
the terephthalic acid tetrapolymers with each other
or with polyethylene terephthalate; and polybutylene
terephthalate with polyethylene terephthalate. The
sheath material should be selected to provide a final
structure in which the polymeric sheath has a melting
point at least about 25 Celsius degrees below the
melting point of the core polymer.
Particularly desirable combinations of
polymers in the instant invention include a core of
nylon 66 with a sheath of nylon 11, a core of nylon
66 with a sheath of nylon 612, and a core of either
polyethylene terephthalate or the terephthalic acid
terpolymer with a sheath of terephthalic acid
tetrapolymer high in butane diol terephthalate.
The relative concentration o~ ~hea~h and
core polymers in the monofilament c:an vary widely.
~lowever, to fully reali2e ~he benefit of relatively
low water absorption hy ~he sheath polymer, it shollld
5 compr ise at leas~ about 5~ by weight e~f ~che
monoilament, and can comprise up to about 50% of the
total weight o the monofilament. For ease of
operation, the sheath preferably comprises at least
about 10% by weight of the monofil~mentO
After extrusion and quenching of the
monofilaments, they should be c~riented about from 3.4
to 6. 0 times their ox iginal leng'ch, arld pre~erably
abc:ut from 3~5 to 4.75 ~imes ~cheir original leng~ch to
increase the mono ilament streng~h. The
15 mono:Eilamen'cs generally have D diameter of about ~rom
6 to 32 mils (0.15-0.81 millimeter~.
- The coextruded mono~ilaments c:~n be used in
one or both of the machine and tran~verse dire tions
oE the paper-makin~ belts. When used in only one
20 direction, it is preferred that ~he coextruded
monofilaments make l~p the trarl~verse, or fill,
dire~tion filaments. Other filaments which can be
used for the machine~ or s~arp~ direction are
i?olymeric homogenous monofilamen~ or multifilament.
25 Polymeric resins which can be used in SUCil filaments
include poly(metaphenylene diamine isophthalamide),
polye~hylene tereph~halate t nylon 6, nylon 66,
polybutylene terephthalate, polyhexamethylene
adipamide~ and polyacrylonitrile.
The filaments are woven into paper-making
belts according to conventional weaving techni~ues.
The type and density of th~ weave will, of course,
depend on the ~ype of paper and paper~making
operation for which the belt is to be used. After
. 35 weaving, the belts are heat set ~o stabilize ~he
weave and fuse ~he mono~ilaments at their
intersections by meltlng or so~tening of the shea1:h
polymer o~ the coex~ruded monofilamen~s. The sheath
polymQr will fuse to similar sheath polymers if a
coextruded monofilament is used in both directions of
the weave, or to the homogenous monof ilament or
multifilament used in the machine direction of the
weave. Specific conditions for such annealiny or
~using will, of course, va.ry wi.th the pol~rer,
filament geometry and weave, but will typically
involve heating under tension Por about from 15
minutes to 1 hour at a ~emperature o~ about from 150
to 235C. l'ypically a hot air oven or radiant
h~aters are u~d Por the hea~ing. Fusion of the
int:~rsections of the filaments ln this manner
eli.minates ~he need for ~he immersion o~ a woven belt
in a separa~e r~sin for stabilizing the wea-re. Re~in
treatmen~ can, of cc)ur~e, be included ~r other
puxposes, i~ desired.
2a The paper~making bel~s of ~he present
invention exhibit excellent dimensional stability and
performance characteristics. The core materials of
the monoilaments provide the ~trength neces~ary for
long-term operation of a paper-making belt while the
lowex melting sheath compcnents not only fuse to
sta~ e the weave of the bel~ but may also reduce
the amount of water absorption by the belt in
operation. Moreover, the monof ilamentary structure
exhibi ts less t~ndency to pick up debr is in
operation, and, when the belt does become fouled, it
is eas ier to clean .
The present invention is fur~her illustrated
by the following specif ic example .
EXAMPLE
Monofilament was melt ~xtruded on a
coex~rusion apparatus with a core of nylon B6 and a
~heath of nylon 612, and ori0n~ed by ~'cret::hing about
5 4., ûX in a radiant oven at a temp~rature of 600C.
The filament was then relaxed in a sec~ond radiant
oven at 600C to con~rol shrinkage. The oriented
monofilamen~ had a diameter of 20 mil~.
P~ paper-making be L~ was woven using ~he
10 monofilamerlt in the fill or ~ransverse dire~tion.
The lc:~ngitudinal or machine direction ~ilamen~s were
poly (methaphenylene diaminel i~ophthalamide)
multifilaments of 1200 den~era Tlle filament~ in the
woven be].~ were used at their intersection~ by
lS heAting ~he belt to a temperature of 232~C ~o effect
bonding. The resulting woven belts were evalua~ed
and found ~o exhibit ou~standing perf~rmance
character ~stics or paper --making operation~ .
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