Note: Descriptions are shown in the official language in which they were submitted.
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DBCRIPI ION
COATING COMPOSITION FC~R FIBERS
L~C~lcA~ 71~,0
This invention rielates to impregnant or coating compositions
for fibers. The coating compositions of the present invention are
especially useful for coating continuous glass strands for use as an
overwrap on a fiber optical cable.
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d_tll.OUllD ARr
The use of coating compositi3ns on fibers is well known and
coating compositions are applied to the surIace of the fibers for
-`j several reasons. While coating compo~itions are usuRlly applied tothe fibers for the purpose of protecting the fibers during processing
2 5 subsequent to their formation, such compositions can also have
incorporated into their compositions cerhin components which
impart properties which ~cilihte their usage. Such properties which
can be improved include impact strength, compressive strength,
strand integrity, flexibility, toughness, and improved adherence
30 between the fiber~nd ~ matrix resin.
Such coated fiber are useful in overcoatin~ or wrapping fibers
or cables such as, i`or example9 optical ~Mes. Typically, glass fibers
are used as ~n overwrap on a cable or fiber and a thermoplastic resin
is soli~ified on the glasis ffbers typic~lly by an extruded overcoat~
`` 35 There is no adhesion between the extruded jflcket ~nd the braided,
helically wound or otherwise applied overwrap. While installing a
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cable, grips are attached to the ends of the cable. Due to the poor
adhesion between the braided glass overwrap and the extruded
coating the grips tend to pull the extruded coating off the cable. The
use of the thermoplastic impregnated strands, according to the
present invention, prevents this by adhering to the extruded overcoat.
An object of the present invention is to provide a slurry or
coating composition for coating glass fibers useful as an overwrap or
CoAting on cables or fibers. It is a further object to proYide a coating
composition which does not suffer the drawbacks OI conventionally
15 coated fibers. In cables currently produced special members are
required to prevent buckling. These members are expensive and
difficult to use. The thermoplastic impregnated overwrap of the
present invention becomes the anti-buckling member after it is fused.
u It is still a futher object to provide d coating composition which can
~0 be totally bound to an extruded protective coating which typicelly
surrounds the cable or fiber.
DISCLOSURE OF INVENTION
The present invention provides fln aqueous coating composition
2 5 useful for glass strands which comprises a thermoplastic resinous
dispersion with a film formin~ polymer.
The coating of the present invention comprises: a thermoplastic
resin (preferably polyethylene polymer powder~ a surfactant, a film
forming polymer (preferably a polyurethane latex polymer~, a gel or
30 thickening agent, the balance being water.
According to one preferred use of the present invention, the
thermoplastic resin polymer is suspended in the aqueous coating
composition in the powdered form when coated on a bundle or strand
OI fibers or filaments. The coated strand is then wrapped around a
rj' 35 cable or core. After the cable or core has been wrapped with the
strand, a thermoplastic jacket is e~truded over the top of the cable
or core~ The heat of the molten polymer causes the thermoplastic
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polymer powder in the overwrflp to melt and flow. The strand can
also be preheated prior to the extrusion of the thermoplastic jacket
to provide a more complete fusion of the powdered polymer on the
overwrap. Upon c~lin~,? the wrapped cQble stiffens imparting anti-
buckling and stiffness to the cable without adding a separate stiffness
0 member.
The present invention achieves a desirable cable without the
need to use self crosslinking resinous materials to provide partial
curing Ol to reduce tackiness of the coatingO The present invention
further does not require the use of any lubricants.
15The aqueous coating composition is especially useful in
impregnating continuous glass strands in conventional in-line or off-
line coating processes.
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- These and other aspects and adv~ntages of the present
invention will become more clear aIter consideration is given to the
20 detailed description of the invention which follows.
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BEST MODE OF CARRYING OUT INVENTION
The present invention is employable with any glass fiber
25 conventionally utilized Ior the reinforcement of polymeric resins.
The term "glass fibers" as used herein shall mean filaments formed by
attenuation of one or more streams of molten glass and to strands
` formed when such glass fiber ~llaments are gathered together in
forming. The term sh~ll also mean yarns and cords formed by
31~ applying and/or twisting a multiplicity of strands together and to
woven and non-woven fabrics which are formed of such glass fiber
strands, yarns, or cords. Preferflbly, the coating formulation OI the
present invention is us~ble with conventionally available fibers.
The glass fibers used as input to an off-line process can be sized
with any conventîonally known sizing composition, which is well
known to those skilled in the art~
The individufll components utilized in the practice of this
invention are commerclally available and cAn thus be simply blended
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with one another in the preparation of the formulations embodyingthe features of the present invention.
The invention comprises an aqueous coating composition
comprising, approximately, on a weight percent basis:
Weight percent
thermoplastic polymer powder 5 - 50
surfactant .5- 1.5
film former polymer .5 - 5
a thickening agent 0 - .1
water balance
15 Final solids content ranges from 6 to 56 weight percent. The coating
composition is applied so as to deposit a dried coating on the fibers
corresponding to about 5 to 50 weigh$ percent of the weight of the
fibers (LOI)~
Preferably the aqueous coating composition comprisin~,
20 approximately, on a weight percent basis-
Weight percent
thermoplastic polymer powder 18 - 24
surfactant .75- 1.0
film fomer polymer 1- 3
a thickening agent 0 - .05
water balance
; Final solids content ranges from 20 to 28 weight percent. The
coatin~ composition is applied so as to deposit a dried coating on the
3~ ffbers corresponding to about 24 to 30 weight percent of the weight
of the fibers (LOI).
The thermoplastic resin used in the aqueous coating
composition may be selected îrom among conventional thermoplastic
resin powders such as, ~or example, polyesters, polyethylenes,
35 polypropylenes, polyamides and other such con~rentional polymers
available in a powde~ed formO The particle size of these powdered
polymers should be less than 100 microns. One such material is a
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polyethylene polymer, Microthene FN 510 R available from USI
Chemicals Co. In a preferred embodiment the average particle size
of the thermoplastic powder is in the range of about 20 microns or
~; less. It is desired th/lt the resins useful for coating cables (especially
optic~l fibers) have good impact strength, a high modulus of
elasticity, good flexibility, and good Qdhesion to polyethylene and
PVC jacketing materi~ls.
The surfactant used in the aqueous co~ting composition may be
a conventional polyether polyol, such as, for example an alkyl aryl
polyether alcohol sold by the trade name TRITON X 100 R available
from the Rohm ~c Haas Co.
The dispersible or emulsifiable film forming polymer used in
the aqueous coating composition rnay be a conventional elastomeric
polyurethane polymer, such as, for example, RUCO 2010 L ~v~ilable
from the RUCO Polymer Corp.
2 0 The gel or thickening ~gent used in the aqueous co~ting
composition m~y be chosen ~rom a wide range of conventional
thickening agents. Drewfloc 270, a polyamide ~rom Drew Chemical
Co., has been found to be particularly useful in this application.
The arnount of water in the aqueous coating composition is that
25 amount necessary to giYe a total solids (nonaqueous) content of the
aqueouQ coating composition Rufficient to co~t the fibers. It is
preferred to hAve the total solids content in the range of about 5 to
50 weight percent, most preferably about 20-28 weight percent.
In the preferred method of formulation of the aqueous coating
30 composition, the surfactant is dissolved in about three fourths of the
water forming a main mixture. The therrnoplastic tesin powder is
dispersed into the main mixture. The film foming polymer is then
added directly to the resulting main mixture. The thickening agent is
dissol~ed il~ the ~naaining water, and there~fter added to the main
3 5 mixture. The resulting agueous coating composition has a good
consistency, low viscosity, and good stability.
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The aqueous coating composition can be applied to continuous
strand glass fibers in coaventional off-line or in-line processes. In
the in-line process the coating is applied as a sizing in the fiber
forming operation. In the off-line process a bundle of input strands
of glass fibers are pulled through an impregnation bath comprising
the aqueous coating composition. The excess coating composition is
removed by a stripper die. 1~he resulting wet impregnAted or coflted
bundle is dried in a conventional manner. The coated glass strands
may be dried at elevated temper~tures in an oven by any of the
processes known to those skilled in the art to remove a substantial
15 flmount of the water. They may also be dried using a dielectric oven.
The drying of the coated glass strand at elevated temperatures does
;~; not melt or Iuse the thermoplastic resin. The thermoplastic resin is
held to the glass fiber by the film forming polymer.
In one process a package is formed by taking up the dry or
20 nearly dry strand on a winder. The package typically has a 5-20
percent by weight residual moisture. Further moisture is then
removed by oven drying the package. The oven temperature must be
`~ below the melting point of the powdered polymer. The resultant
coated strand is plyable and has excellent powder holding capability.
i 25 The coated glass fiber is especially useful fiS an overwrap on
`: any type OI c~ble, or on a fiber optic cable. It is also within the
contemplated scope of the preseot invention that the coated glass
fiber can be used in any of a number of reinforcement products. The
coated glass flber is overwrapped on a cable or fiber in a manner
30 known to those skilled in the art.
A glass fiber coated with the aqueous coating composition of
the present invention is superior to the conventionally coated or
otherwise sized fibers currently available since the coated glass
fibers have a desirably higher loading content of thermophstic resin
!~'i 35 powder. The glass strand, as coated, is fle~cible, and Is as easily
processed as conventionally sized glass flbers.
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It is also within th~ contemplated scope of the present
inYention that such oYerwrapped cable have a secondary coating or be
further ( oated with an extrusion of some type of thermoplastic resin
; such that the thermoplastic resin on the glass fibers not only fuses
together with itself, but also is totally bound with the secondary
thermoplastie coat. This then provides a coated glass fiber whi~h
behaves both 8S a tension member and as a compression memberO As
a compression member the glass Iiber overwrap on the cable serves
as an antibuckling element to prevent damage to the core fiber or
cable during processing, installation or in-use curing temperature
cyclin~, especially eold temperature exposures (-40C).
INDUSTRIAL APPLICABILITY
`: EXAMPLE 1
~0An inventive coating composition prepared from the following
ingredients:
Weight
percent
thermoplastic polymer powder,
Microthene FN 510 from
USI Chemicals Co. 25
alkyl aryl polyether alcohol surfactAnt
T~ITON X100 from Rohm Sc Haas 0.89
polyurethane latex film forming polymer
RUCO 2010 L from RUCO Polymer (::orp. 2.0
~ 30 poly acrylamide thickening agent,
Drewfloc 270 from
Drew Chemical Co. .048
water balance
Final solids content was about 27 weight percent. The coating
35 composition is applied onto a conventionQlly sized glass, here an H-15
76~ sized glass available from Owens~Corning Fiberglas Corporation
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so as to deposit a dried coating on the fibers corresponding to about
26 weight percent of the weight of the fibers (LOI).
Meating the coated fibers to about 150~C causes the adhered
thermoplastic resin to flow and fuse, thereby producing a fiber
reinforced product especially suitable for use as A coating or
overwrap for ~ cable or fiber. The coated, cured fiber reinforced
10 product when overwrapped on a cable provides a cable having the
necessary flexibility and proper degree of stiffness for subsequent
processing.
The fiber reinforced optical fiber or cable can have a secondary
coating comprising, for example a thermoplastic resinous material
which further protects the op~ical fiber. In a preferred embodiment
the thermoplastic resinous material of the secondary coating is
essentially the same thermoplastic resinous material used in the
- aqueous coating cornposition.
While the invention has been described in detail and with
reference to specific embodiment thereof, it will be apparent to one
skilled in the art that various changes and modification can be made
therein without departing frorn the spirit and scope thereof.
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