Aug. 4, 1942.
R. M. WILEY ETAL
2,291,670
METHOD OF COATING WIRE AND THE LIKE
Filed Aug. 31, 1959
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Patented Aug. 4, 1942
' 2,291,676
UNITED STATES,PATENT OFFICE
2,291,670
METHOD OF COATING WIRE AND THE LIKE
' Ralph M. Wiley, Midland, and Arthur I. Dubord,
assignors to The Dow
Jr., Battle Creek, Mich,
Chemical Company, Midland, Mich, a corpo
ration of Michigan
Application August 31, 1939, Serial No. 292,908
4 Claims.
(or. 13-59)
The present invention relates to a method of
coating wire or other ?lamentous articles with
plastics, and especially with those plastics which
are crystalline by X-ray criteria.
Most synthetic resins are non-crystalline, even
when examined by X-ray methods. These resins
and polymers are not as strong and ?exible as the
few known synthetic resins and polymers which
wire, coated with an oriented sheath of a crystal
line polymer. Other objects will become ap
parent from the following description of the
invention.
‘
In the following description, .the term “?la
mentous article” is intended to include any
article such as wire, string, thread, or tape, which
has a relatively great length as compared with its
width and thickness, and which has near enough
to a uniform cross-section throughout its length
capable of being made. The principal polymers 10 so that it may be coated in a continuous process.
are crystalline according to X-ray criteria are
and resins having this property, hereinafter re
ferred to simply as crystalline polymers, are the
polymer of vinylidene chloride and certain of its
To the accomplishment of the foregoing and
related ends, the invention then consists of the
method and product hereinafter fully described
co-polymers wherein the vinylidene chloride 15 and particularly pointed out in the claims, the
predominates and generally wherein there is
annexed drawing and the following description
less than 20 per cent of the co-polymerized con
setting forth in detail one mode of carrying out _'
the invention, such disclosed mode illustrating,
however, but one of various ways in which the
strength and ?exibility when they have been
principle of the invention may be used.
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treated in a manner to orient the polymer mole
In the said annexed drawing:
cules parallel to one another and to a major sur
Fig. l is a longitudinal sectional view through
face of the shaped article. This treatment, in
a portion of a wire-coating system wherein the
the case of many crystalline polymers, requires
inventoin is carried out.
the steps of heating the crystalline polymer to a 25 Fig. 2 is a cross-sectional view taken along
stituent. The crystalline polymers form shaped
articles which are much improved in their
temperature above its softening point but below
its decomposition temperature, and then chilling
lines 2-—2 of Fig. 1.
'
Fig. 3 is across-sectional view taken along
the polymer to a temperature preferably near or
lines 3—-3 of Fig. 1.
below room temperature, thereby to supercool '
Fig. 4 is a cross-sectional view taken along
the polymer. While the polymer is in the super
lines 41-4 of Fig. 1.
30
cooled state, it may be drawn, rolled, or otherwise
Fig. 5 is a cross-sectional view taken along
plastically deformed under moderate pressures to
orient the molecules in the manner aforesaid,
and a substantial strength increase is obtained.
In coating wire with resins by the extrusion
lines 5-5 of Fig. 1.
Fig. 6 is a longitudinal view of an enlarged
section of a stretching device alternative to that
shown in Fig. 1.
method employing crystalline polymers, a prob 85 According to the invention, wire or other ?la
lem is presented which does not appear in the
mentous article is coated with a crystalline poly
heretofore customary coating operations using
mer in oriented form, by extruding the crystal
non-crystalline polymers. The suggested prob
line but unoriented polymer at a temperature
lem is that of providing a coating of maximum
preferably above its softening point, through an
40
toughness and ?exibility, which coating has been
extrusion nozzle wherein is centered an axially
drawn or stretched to orient the molecules there
bored mandrel through which the wire to be
in. Methods of wire coating heretofore known
coated is passed. The wire is drawn through
have not had to provide for such a step and none
the mandrel and out of the nozzle at a greater
of them are adapted to effect the desired result. 45 linear velocity than that at which the crystal
It is accordingly among the objects of the in
line polymer is being extruded. Owing to the
vention to provide a method of coating wire,
string, thread, tape or similar ?lamentous ar
ticles with a coating preferably of uniform thick
ness, of a stretched and oriented form of a
presence of the mandrel in the nozzle, the poly
mer coating emerges therefrom distributed
around the wire with a space annular in cross
section between the wire and the coating. To
crystalline polymer. It is a particular object to 50 assure continued centering of the wire in the
provide such a method whereby a stretched and
coating, the extrusion nozzle may preferably be
oriented coating of a crystalline polymer or co
in a vertical position, with the wire being drawn
polymer of vinylidene chloride may be applied
downward through the coating mechanism. The
to a ?lamentous article. It is a further object
polymer coating is chilled in a cooling zone to
to provide filamentous articles, and particularly 66
2
convert it to the supercooled state. and then is
passed through a constricting device wherein the
supercooled polymer is shrunk down onto the
wire, eliminating said space from between the
wire and the coating. The greater velocity of
coatingbetweentheextmsionnoxaleandthe
or il,resuitsinstretching
thewarmzoneadjacentthe
tingmeansmustact
the wire as compared with that of the extruded
coating, results in stretching the supercooled
coating while passing through the constricting
ii. to prevent the force from being transmitted
back to the zone of thermoplasticity near the ex
means. As the coated wire emerges from the
constricting means, the coating has necessarily 10
acquired the velocity of the wire. and the ?nished
trullsi‘hzn ori?ce.
article is coated with a molecularly oriented
sheath of tough. ?exible crystalline polymer.
Referring now to the drawing wherein the‘ ap
paratus illustrated in Figs. 1 and 6 may be em 15
ployed either in vertical or horizontal position, a
wire It is fed continuously through an axially
bored mandrel it which is centered in the neck
I! ofanextrusion nozzle ll. Acrystalline poly
mer I! is fed into the said neck I! under pressure.
and at a temperature preferably above its soften
ing point, from a suitable supply source (not
shown). The wire II is moved at a greater
crystalline vinylidene chloride co-poly
linear velocity than the coating material it is
extruded from the nozzle. The mandrel It
causes the formation of a space annular in cross
section II between the wire II and its coating as
the two leave the nozzle II. It is preferable to
provide means for equalizing the pressure in said
space with that of the atmosphere, and this may
be done by using a mandrel bored slightly larger
than the wire to be coated. The wire is then led
through a cooling zone it wherein its loose sheath
of coating material It is chilled to the super
cooled state. The wire and coating are drawn
through a constricting means, which may be
one or more pairs of pro?led rollers I‘I, to press
the coating down onto the wire. As the coated
wire ll leaves the constricting means, the veloc
ity of the wire and coating are necessarily the
the coating now having attained the higher
initial velocity of the wire. Thus. the coating
which enters the constricting rollers I1’ is simul
taneously stretched and pressed down onto the
wire by the action of these rollers in order to at
tain its ultimate velocity equal to that of the “
wire, and to ?t snugly around the wire. By
proper selection of the relative velocities of the
wire III, the extruded polymer II as the latter
leaves the nozzle, and the diameter of rollers l‘l.
for example,
pellent ?sh-lines, or it may
vide coated tapes of metal,
bility. The coated wire of the invention may be
of a size and coating thickness tor electrical serv
ice.oritmaybe very?newire,e.g. froml to2
m?s diameter, coated with an oriented crystalline
polymer for use as a ?shing leader of improved
tensileandshearstrengthsand havinghigh
flexibility.
Other modes of applying the principle of our
invention may be employed instead of the one ex
plained, change being made as regards the meth
We therefore particularly point out and dis
tinctly claim as our invention:
_ 1. The method of coating ?lamentous articles
rollers IT. This ratio of velocities will be ad
comprising continuously moving the ?lamentous
justed in practical operation according to the
known amount of stretch required to orient the
molecules in the particular crystalline polymer ssmandrel
centrally of an extrusion head.
employed. Thus, a crystalline co-polymer of
vinylidene chloride and vinyl chloride may be
oriented when stretched to about 4 times its
length in the extruded, supercooled, but un
oriented state.
therebetween, the velocity of the ?lamentous ar
,In Fig. 6 is shown another modi?cation of a
ticle being greater than that of the surrounding
constricting means for use in place of the pro?led
sheath, chilling the so-extruded sheath to super
rollers l1 shown in Fig. l. A die I! having a
cool the same, passing the ?lamentous article
tapered throat 20, and which may or may not be
and surrounding sheath through a constricting
provided with a sphincter 2| is used to bring the
means operative on the sheath to press it down
coating it down onto wire II to provide the ?n
ished coated article It.
forming a coating thereon. and
articletobecoatedthroughanaxiallybored
_
tension on the coated ?lamentous
article beyond the said constricting means to
ity of the wire as compared with that of the ex
truded and supercooled crystalline polymer, re 70 e?ect a stretching of the coating while passing
the constricting means. thereby to
equalize the velocities of the coating and the ar
coating on the wire.
ticle and to orient the molecules in the crystalline
It should be noted that any pull exerted on the 76 polymer to provide a tough. ?exible coating ad
herent to the ?lamentous article. the said con
2,291,670
stricting means being adapted to prevent trans
mission of tension, applied to the coated article,
to the extruded sheath between the said means
and the extrusion ori?ce.
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4. The method as claimed in claim 1, wherein
the ?lamentous article is wire and the coating
material is selected from the group consisting of
the polymer of vinylidene chloride and its crys
2. The method as claimed in claim 1, wherein 6 talline co-polymers.
the coating material is selected from the group
RALPH M. WILEY.
consisting of the polymer of vinylidene chloride
ARTHUR J. DUBORD, JR.
and its crystalline co-polymers.
3. The method as claimed in claim 1, wherein
the ?lamentous article is wire.
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