U.S. patent application number 10/308798 was filed with the patent office on 2006-01-26 for cured applique or label with protective film on arcuate sidewall or tread of pneumatic tire.
Invention is credited to Lewis Timothy Lukich, Ramendra Nath Majumdar, Marvin Wayne Tipton.
Application Number | 20060016543 10/308798 |
Document ID | / |
Family ID | 32312231 |
Filed Date | 2006-01-26 |
United States Patent
Application |
20060016543 |
Kind Code |
A9 |
Majumdar; Ramendra Nath ; et
al. |
January 26, 2006 |
Cured applique or label with protective film on arcuate sidewall or
tread of pneumatic tire
Abstract
An applique having a vulcanizable adhesive layer is co-cured on
a rubber article by precuring the applique of predominantly pale
natural rubber optionally imprinted with a bar code; coating the
upper surface of the applique with a protective self-supporting
film of polyamide less than 0.050 mm (2 mils) thick, or a
non-self-supporting film of polyurethane less than 25.4 .mu.m,
0.0254 mm (1 mil) thick; adhering the applique to the article at a
chosen location; curing the article in a curing mold; and, removing
a cured article from the mold with the protective film adhering to
the surface of the applique, the surface of which is essentially
free from visually observable cracks. The hot flow of rubber in the
curing mold does not substantially change the location of the
applique which is embedded in the article. If the film does not
remain adhered to a cured tire and drops into the mold, it is
difficult to retrieve and, when a subsequent article is cured in
the same mold, results in a scrap tire.
Inventors: |
Majumdar; Ramendra Nath;
(Hudson, OH) ; Lukich; Lewis Timothy; (Akron,
OH) ; Tipton; Marvin Wayne; (Akron, OH) |
Correspondence
Address: |
Alfred D. Lobo & Co., L.P.A.
933 The Leader Building
526 Superior Avenue E
Cleveland
OH
44114
US
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20040103974 A1 |
June 3, 2004 |
|
|
Family ID: |
32312231 |
Appl. No.: |
10/308798 |
Filed: |
December 3, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09365095 |
Jul 30, 1999 |
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10308798 |
Dec 3, 2002 |
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Current U.S.
Class: |
156/110.1 ;
152/209.1; 152/523; 152/524; 152/525; 152/565 |
Current CPC
Class: |
B60C 13/001 20130101;
G09F 3/04 20130101; B29C 2037/80 20130101; B29L 2031/744 20130101;
G09F 3/0297 20130101; B29D 2030/726 20130101 |
Class at
Publication: |
156/110.1 ;
152/524; 152/523; 152/525; 152/565; 152/209.1 |
International
Class: |
B29D 30/06 20060101
B29D030/06; B29D 30/00 20060101 B29D030/00; B60C 11/00 20060101
B60C011/00; B60C 13/00 20060101 B60C013/00 |
Claims
1. A green pneumatic rubber tire comprising a generally toroidal
shaped carcass with a circumferential tread overlying plural belts,
spaced-apart beads and connecting sidewall portions extending
between the tread and beads which together provide the carcass with
an interior surface, the improvement comprising, a pale essentially
fully cured laminar rubber applique less than 1 mm thick, having a
virgin upper surface vertically spaced apart from that of
contiguous rubber of the tire, adhesively secured with a
vulcanizable adhesive on the tire's exterior surface at a location
radially spaced-apart from the tire's bead, the adhesive being
essentially free of an antiozonant and an aromatic oil, and the
location being chosen from "in the sidewall" and from "in the
tread's footprint"; a flexible protective film secured to the
exterior surface of the applique, the protective film requiring a
force of at least 10 Newtons to remove it from the label, but less
force than will tear the film; the protective film being chosen
from a non-self-supporting polyurethane film less than 0.0254 mm
(0.001'' or 1 mil) thick, and a self-supporting polyamide film less
than 50 .mu.m (2 mils, 0.002'') thick dimensionally and thermally
stable at a temperature in the range from about 121.degree. C.
(250.degree. F.) to 200.degree. C. (392.degree. F.).
2. The tire of claim 1 wherein the applique is a logo, more than
80% crosslinked, having a modulus lower than 3 MPa at 300%
elongation, and the location chosen has rubber with a modulus
substantially matched .+-.100% to that of the logo.
3. The tire of claim 1 wherein the applique is a printable label no
greater than about 2.5 cm wide and 5 cm long, more than 80%
crosslinked, the sidewall having a modulus lower than 5 MPa at 300%
elongation, and the location chosen has rubber with a modulus
substantially matched .+-.100% to that of the label.
4. The tire of claim 1 wherein the applique and the vulcanizable
adhesive each have a thickness in the range from about 0.1 mm to 1
mm (4 mils to 40 mils) thick, a modulus substantially matched
.+-.100% to that of the label, the self-supporting film is
6,6-nylon and the non-self-supporting film is derived from a
dispersion of polyurethane.
5. The tire of claim 3 wherein the applique is secured in the
sidewall such that the applique's innermost portion is radially
space-apart from the bead at least 2.5 cm.
6. The tire of claim 3 wherein the applique is a bar code label
printed with a bar code and secured on the tread, the combination
of (i) a zone near the applique's interior surface and (ii) the
vulcanizable adhesive in contact with the black sidewall, is
substantially impermeable to staining ingredients migrating from
the rubber sidewall, and more than 95% of all green tires with bar
code labels secured to the tires are correctly readable by a bar
code scanner.
7. The tire of claim 6 wherein at least a portion of the bar code
label is secured in a groove in the tread.
8. The tire of claim 4 wherein the non-self-supporting film is
pore-free and less than 25.4 .mu.m (1 mil) thick.
9. A method of locating a substantially laminar applique having
upper and lower surfaces in a chosen location on a tread to be
formed in a green tire, the method comprising, back-locating a
circumferential centerline of a groove between lugs to be formed in
a substantially laminar strip of green tread stock opposed ends of
which strip are smoothly spliced together on a tire-building drum,
marking the centerline with a light beam, coating the lower surface
of the applique with a vulcanizable adhesive, adhesively securing
the applique substantially symmetrically about the centerline, and,
removing the green tire after its construction is completed.
10. The method of claim 9 wherein the applique is secured with its
longitudinal axis at right angles to the rotational axis of the
tire.
11. The method of claim 9 wherein the applique is secured with its
longitudinal axis parallel to the rotational axis of the tire.
12. The method of claim 9 including correctly reading a bar code
imprinted on the applique in more than 95% of all tires embedded
with imprinted appliques.
13. In a vulcanized pneumatic rubber tire comprising a generally
toroidal shaped carcass with a circumferential tread overlying
plural belts, spaced-apart beads and connecting sidewall portions
extending between the tread and beads which together provide the
carcass with an interior surface, the improvement comprising, a
pale essentially fully cured laminar rubber applique having a
virgin surface non-removably co-cured and embedded into the surface
of the tire at a location radially spaced-apart from the tire bead,
said location chosen from "in the sidewall" and from "in the
tread's footprint", the applique having an exterior visible surface
and an interior surface in adhesively co-cured contact with black
rubber of the tire; a flexible protective film remaining
self-adhesively secured to the exterior surface of the applique,
both prior to the tire being cured and after the tire is removed
from a mold in which the tire is cured, the protective film
requiring a force of at least 10 Newtons to remove it from the
label; the protective film being chosen from a non-self-supporting
polyurethane film less than 0.0254 mm (0.001'' or 1 mil) thick, and
a self-supporting polyamide film less than 50 .mu.m (2 mils,
0.002'') thick which is thermally and dynamically stable at a
temperature in the range from about 121.degree. C. (250.degree. F.)
to 200.degree. C. (392.degree. F.) in a curing mold without being
torn so as to maintain the virgin surface.
14. The tire of claim 13 wherein the applique is a logo, more than
80% crosslinked, having a modulus lower than 5 MPa at 300%
elongation both prior to, and after the tire is cured.
15. The tire of claim 13 wherein the applique is a printable label
no greater than about 2.5 cm wide and 5 cm long, more than 80%
crosslinked, having a modulus lower than 5 MPa at 300% elongation,
both prior to, and after the tire is cured, and the virgin surface
is imprinted with a bar code.
16. The tire of claim 13 wherein the self-supporting film is
6,6-nylon and the non-self-supporting film is less than 25.4 .mu.m
(1 mil) thick and derived from a dispersion of polyurethane.
17. The tire of claim 15 wherein the applique is embedded in the
sidewall such that the applique's innermost portion is radially
space-apart from the bead at least 2.5 cm.
18. The tire of claim 15 wherein the applique is a bar code label
imprinted with a bar code and embedded in the tread, and more than
95% of all embedded bar code labels on cured tires are correctly
readable by a bar code scanner.
19. A method for co-curing an applique in a chosen location on a
green rubber tire's exterior surface, comprising, applying a
vulcanizable adhesive to the lower surface of a cured laminar
applique of predominantly natural rubber, less than 20 mils thick,
containing from 15% to 50% of titanium dioxide pigment, and
crosslinked to a level of at least 80% as determined by a Mooney
cure meter, coating the upper surface of the applique with a
protective film selected from a self-supporting polyamide film less
than 50 .mu.m (2 mils) thick, and a non-self-supporting film of
polyurethane less than 25.4 .mu.m, 0.0254 mm (1 mil) thick;
adhesively securing the cured applique in the chosen location of
the exterior surface; expanding the tire at least 5% and curing it
in a curing mold; and, removing a cured tire from the mold with the
protective film adhering to the surface of the applique which is
embedded therein, essentially free from distortion and surface
cracks, embedded without substantially changing its location.
20. The method of claim 19 wherein the chosen location is chosen
from "in the sidewall, spaced-apart from the bead of the tire", and
from "in the tread's footprint".
21. The method of claim 19 wherein the applique is imprinted with a
bar code label.
22. The method of claim 19 wherein the applique is a rubber having
a modulus lower than 5 MPa at 300% elongation.
23. The method of claim 22, including correctly reading the bar
code with a scanner in more than 95 out of 100 tires cured.
Description
FIELD
[0001] This invention relates to a rubber applique such as a
decorative design, identifying label or machine readable bar code
on a label ("bar code label"), non-removably incorporated into
either the exterior arcuate convex surface of a rubber sidewall of
a pneumatic tire with a tread having a road-contacting surface of
lugs and valleys, or in the tread's "footprint", which tire is
removed from a curing mold with a protective film firmly adhered to
the surface of the applique. The applique is substantially laminar
and pale in color, the pale color being visually distinct from and
in contrast to black, which is the usual color of the tire's
sidewall and tread.
BACKGROUND OF THE INVENTION
[0002] Sidewalls of tires are routinely marked for a variety of
reasons among which are identification of the manufacturer and
brand of the tire with a distinctive "logo", optionally printed
with a bar code, or a bar code label, each of which is a relatively
small laminar piece of rubber having a width, in the radial
direction, substantially smaller than the width (radial) of the
sidewall, applied to the sidewall just before the tire is cured in
a mold in a curing press. Not so routinely marked in such a manner
are treads on a cured tire, and when so marked they are typically
provided with a plastic or paper bar code label adhesively secured
to the tread after the tire is cured, mainly for inventory
purposes.
[0003] It is essential that the entire applique be clearly visible
after the tire is cured. In particular, it is essential that the
surface of the printed bar code, whether on a label or on a logo,
be protected as if it never was in contact with release agent
sprayed on the inner surface of the mold ("tire paint"). A
preferred tire paint currently in use is an aqueous paint
formulated to provide necessary adhesion and air bleed to minimize
trapped air, for "tread-over-sidewall" tire construction. The
surface of the twice-cured uncontaminated applique, whether from
black tire paint or contaminants from the sidewall's black rubber,
is referred to as a "virgin surface" and it may be printable; when
printed, the printed matter is thermally stable at a temperature at
which the tire is cured. By "thermally stable" is meant that there
is essentially no degradation of the substrate which is
printed.
[0004] To date, numerous attempts have been made to provide a
virgin surface on a white or lightly colored applique co-cured with
the "green" tire, without the applique cracking or deforming so as
to be illegible. In particular, it is essential that (i) a printed
legend on the applique be legible over the entire operating life of
the tire, and (ii) the applique is cannot be removed without
destroying it. This is a difficult challenge on a black side-wall
which flexes greatly; it is a more difficult challenge on a tread
which is formed by plentiful flow of hot rubber forming lugs and
valleys in the tread during cure.
Applique (Bar Code Label) on Sidewall:
[0005] The most effective method of providing an applique embedded
in the sidewall comprises curing a cured rubber bar code label
adjacent the bead of the tire, this being a location subjected to
minimal expansion during cure. By "embedded" is meant that the
surface of the applique is coplanar with the surface of the
contiguous rubber. When the applique is a typical label with a bar
code of black vertical variably spaced-apart lines of varying
thickness, the spaces between the lines being white or pale, the
bar code label is positioned with its longitudinal axis
substantially parallel to the periphery of the bead to minimize
distortion of the bar code due to multiaxial expansion of the
sidewall forming an arcuate convex surface during cure. The bar
code in a "near-bead location" cannot be read because the vertical
lines and spaces are obscured by the periphery of the rim of the
wheel on which the tire is mounted. This inability results from the
typical bar code label being relatively small, usually a
rectangular label no greater than about 2.5 cm wide and 5 cm long,
and the flange of the wheel near the rim being about as wide as the
bar code.
Applique (Bar Code Label) on Tread:
[0006] A bar code label on the tread of a tire allows it to be
identified even when the tread carrying the bar code is in the
middle of a vertical stack of tires. To this end, at present, a
paper or plastic bar code label is adhesively secured on the
surface of a lug of the tread anywhere near the center
(circumferential), that is, in the footprint of the tire, but only
after the tire is cured, so that the label is not embedded in the
cured rubber. It is impractical to adhesively secure the label to
the surface of a valley between lugs. Though the function of such a
paper or plastic bar code is temporary, it must be kept in mind
that its sole function is to identify the tire before it is
installed. When the tire has been installed, the imminent
destruction of the temporary bar code when the tread contacts the
road is of no concern. Despite this limited function of the bar
code, it often fails to fulfil its function because the adhesively
secured bar code label is dislodged when the tire is handled as it
is moved from one location to another.
[0007] It is now deemed essential that a manufacturer be able to
identify its tires even after their tires have been in service for
an extended period, preferably over the life of the tire.
[0008] To read the bar code on a label in the worn tread, it is
critical that the label survive in the groove or valley between
worn lugs. To date, there is no method for non-removably co-curing
a machine-legible bar code label to embed it in a groove between
lugs in a tread. Moreover, since retailers of tires sell tires made
by several different manufacturers, it is envisioned that a logo
(e.g. a blimp) along with a bar code label will be co-cured in the
footprint of the tread of each brand of tires made by competitors
in the marketplace so as to make each competitor's tires visually
more readily identifiable than by reading the brand name on the
sidewall only. A titania-filled white or pale colored logo is
easily seen even from a distance.
[0009] It is readily apparent that the surface of an essentially
fully cured white or pale colored rubber label on a green tread in
which the lugs and valleys are yet to be molded, will be easily
stained when the label is contorted with hot tread rubber flowing
around it in a curing mold. Moreover, unless a rubber bar code
label has the appropriate modulus, it is prone to cracking when
cured, thus giving an inaccurate reading of the bar code. Staining
due to staining ingredients migrating from the cured tread rubber
is a particularly serious problem. Typical staining ingredients
include aromatic oils, antiozonants such as paraphenylenediamine,
carbon black, processing aids, chemicals in a curing package, other
oils and coupling agents, which either individually or in
combination, one with another, generate compounds which migrate
into the applique. Staining sufficient to cause an error of 5% or
more when the imprinted code is read is unacceptable; moreover
substantially error-free reading, that is, better than 95%
accuracy, is required over a period of at least six months after an
imprinted bar code label is cured onto a tire. Such staining is
exacerbated by an applique which is porous or which develops
microscopic cracks. Therefore it is essential that the modulus of
the cured pale rubber substantially match the modulus of the rubber
article being cured, so as to conform in the mold without cracking.
By "substantially match" is meant that the modulus of the applique
is closer than .+-.100% that of the rubber in which it is secured
(before curing the tire) or embedded (after curing the tire),
preferably closer than .+-.50% not only after both, applique and
are co-cured, but also before, that is, on the portion of the green
carcass on which the applique is to be adhered.
[0010] As taught in U.S. Pat. No. 4,625,101 to Hinks et al, the
most successfully read bar codes on a tire are those provided by
even and uneven surface portions, that is, linear troughs and
ridges molded into the surface of the tire, which uneven portions
selectively reflect light from a light source in a scanner. Such
molded bar codes are referred to as "bumpy" bar codes. By
"successfully read" is meant that less than 5% of the bar codes on
various tires, irrespective of size, are incorrectly read either
before the green tire is cured, or after it is cured; that is, bar
code labels on more than 95% of all cured tires with embedded bar
code labels are correctly readable by a bar code scanner. This
limitation is critical as a manufacturer cannot tolerate a higher
misreading of bar codes. Such bumpy bar codes avoid the problems
inherent in using a protective Mylar.RTM. polyester film, and
recovering the film from within the mold when the film becomes
dislodged after the tire is cured. A small piece of film, covered
with tire paint and dropped in a mold covered with tire paint, is
difficult to find; if not found, a tire cured in the mold with the
piece of film somewhere on the tire, will be scrap. However, a
commercially available scanner to read such bar codes, referred to
as "bumpy" bar codes, is too expensive for general use and is
difficult to maintain in satisfactory operating condition.
The Multi-Faceted Problem:
[0011] To co-cure a cured applique on the arcuate convex surface of
a sidewall of a green tire such that the innermost portion of the
applique is radially spaced-apart from the bead of the tire,
preferably at least 2.5 cm away; and, when the tire is mounted on a
wheel, the applique is to be spaced-apart preferably at least 1 cm
from the periphery of the rim, so that the applique is essentially
permanently embedded in the cured sidewall, that is, the upper
surface of the applique is coplanar with the surface of the
contiguous rubber, and the applique is non-removable without
destroying it; and firmly self-adhesively adhered to the applique's
exposed surface is a flexible protective polymeric film; provided,
particularly, that a zone near the applique's interior surface, in
combination with the vulcanizable adhesive in contact with the
black sidewall, is substantially impermeable to staining
ingredients migrating from the rubber sidewall, that is, the
applique is not stained when the tire is cured. Since the applique
is to be thin, less than 1 mm thick, and a bar code imprinted on it
is to be successfully read over a period of at least six months,
preferably over the life of the tire, a zone within the applique
near its lower surface is to function as a barrier against
antiozonants and aromatic oils in the carcass. Therefore the
applique is to be filled with enough of a pale, preferably white,
inert particulate material such as titanium dioxide, to provide a
legible bar code and to help minimize staining, but not so much as
to interfere with providing a substantial match of moduli.
[0012] Since a long period of time may elapse before a tire is
cured, and again, also before a cured tire is further processed
through warehouses and eventually sold, it is essential that, after
the tire is cured, the protective film remain secured to the
"virgin" or printed surface of the applique sufficiently well that,
if the film is removable, a force of at least 10 Newtons,
preferably more than 30 Newtons but less than will tear the film,
is required to remove the protective film.
[0013] Further, to co-cure a small, substantially fully pre-cured,
bar code label which is machine-readable despite the cured label
being on a tire which has been expanded in a curing press, without
cracking the label and without any visually observable distortion
so that incidence of failure to read the bar code is less than 5%,
preferably less than 2%, and most preferably less than 1%; and to
locate the bar code label in the sidewall, or on a lug and/or in
the valley between lugs of the tread.
[0014] Still further, to maintain the protective synthetic resinous
film, either self-supporting or non-self-supporting, adhering to
the applique's surface without an adhesive, and uniformly covering
it so as to be effective against contamination by tire paint which
coats the cured applique during curing of the tire, and against
ambient contaminants and hazards after the tire is cured; and if
the protective film is removable, and it is desired to remove the
protective film, then it should be removable integrally, that is,
without tearing into pieces. By "non-self-supporting" is meant that
the film requires a supporting surface to maintain its
integrity.
Addressing the Problem:
[0015] An attempt to solve a portion of the foregoing problem is
found in European Patent Application 0 249 918 A2, filed in 1986 by
Georg Bohm who recognized that "precure provides integrity and
definition to the applique while the curing operation allows for
complete and total bonding of the applique to the tire." (see
Abstract). He states that "the applique bonds or fuses without
distortion of the applique to the green tire by cure or
vulcanization within the press, . . . " (see pg 3, right hand col,
lines 24-26); thereafter he states " . . . the applique may be
substantially totally cured prior to the molding and curing
operation" (see pg 4, left hand col, lines 37-39) and "Where the
applique 14 is partially precured, form stability is such to (sic)
accommodate the use of appliques 0.020-0.060 inch thick without
perceptible distortion and without compromising adhesion to the
tire. Where fully cured, the applique is preferably adhered to the
tire by an appropriate adhesive." (see pg 4, left hand col, lines
49-55).
[0016] Bohm uses a substrate 12 from which the applique is
transferred to the sidewall; he discloses that the substrate is "an
annular ring constructed of metal such as aluminum or steel having
good heat conductive characteristics. It has also been found that
certain plastics or polymeric materials such as fiber reinforced
plastics are suitable for the substrate construction . . . of
sufficient thickness to provide a degree of rigidity to the annular
ring . . . " Though it is clear that the annular ring provides a
protective barrier layer against contamination by a tire paint used
on the inner surface of the tire mold, he fails to specify the
composition of polymeric materials which are to provide the same
function and yet be removable after surviving curing of the tire
without tearing; nor does he provide any data for the rubber
composition of the applique, which composition must expand with the
expanding tire as they are co-cured, or resist expansion without
itself being dislodged, if the applique is to be distortion-free;
nor does he provide data to support the statements about the
purported freedom from distortion.
[0017] U.S. Pat. No. 5,824,397 to Koops et al teaches a
light-colored base layer of co-curable rubber which is
laser-inscribable, and "The base layer can have a transparent
protective covering, preferably of polyester, polyamide,
perfluorinated polymers or polyimide, if the film also passes
through the label vulcanization process together with the
corresponding rubber part in order to protect against any soiling
of the base layer. Depending on the application of the label,
subsequent removal of the protective film is possible." (see col 3,
lines 11-18). The drawing (FIG. 1) illustrates a protective film of
polyester; the illustrative examples 1 and 2 use protective films
of polyethylene and poly(ethylene naphthalate) "PEN" respectively,
and claim 10 refers to "polyolefins".
[0018] To prevent contamination by ingredients in the black
sidewall, the '397 base layer is enveloped on three sides by a
barrier layer which is chosen from a polyamide or vapor-deposited
aluminum coating, or a film of polyvinylidene chloride or silicon
oxide. In example 1, the base layer is partially pre-crosslinked
(the degree is unspecified) and enveloped in a barrier layer of
ethanolic polyamide.
[0019] As seen in the data provided below, a protective coating of
polyester film, e.g. Mylar, fails in one tire out of five, to
remain on the base rubber layer (label) during curing in a mold.
This incidence of failure is unacceptable because the dislodged
strip of Mylar film must be manually retrieved from the mold before
it is used to mold another tire. Retrieving the strip is difficult
because, the Mylar film is coated with tire paint and it is
difficult to differentiate the coated strip from other thin laminar
pieces of dried tire paint in the mold. Failure to retrieve the
Mylar strip results in the strip being incorporated into the next
tire being molded; such a tire is scrap. It is critical that the
protective film remain self-adhered on the label on at least 98% of
the tires cured, that is, the film remains adhered because of the
adhesive nature of its surface, without the use of an adhesive.
[0020] To avoid the problem of a relatively small strip of Mylar
film being dislodged from the face of the label during cure, a long
strip of film may be wrapped around the peripheral outer surface of
the green toroid so that it will remain in place during cure.
However, the film tears because expansion, due both to the physical
multidirectional stretching of the tire in the mold, as well as the
coefficient of thermal expansion of the film do not correspond to,
or closely enough match, those of the sidewall and tread of the
toroid.
[0021] Polyolefin film, e.g. polyethylene, is thermally unstable
above 150.degree. C., melts at curing temperature in the range from
about 121.degree. C. to 200.degree. C. and becomes opaque when it
mixes with release agent, thus fails to guaranty legibility. When
directly "stitched" to the sidewall without an adhesive, though
with difficulty, polytetrafluoroethylene (PTFE) film fails to
remain in place during cure in one out of five tests (20% failure);
when the PTFE film does remain in place after curing, it is not
readily removable in one piece because it stretches and tears. An
aromatic polyimide film, like the PTFE film is difficult to stitch
into the sidewall, and even then, fails to remain in place when the
tire is cured; when the polyimide film does remain in place, it
tears because its coefficient of thermal expansion does not match
the expansion of the sidewall. Since applicants have now found that
only polyamide film is uniquely effective, it is evident that its
inclusion as the only film which is usable among the six polymeric
films disclosed in the '397 patent, was fortuitous and not an
enabling disclosure. The disclosure is insufficient to allow one
skilled in the art to arrive at the choice of polyamide film to the
exclusion of the others, without undue experimentation.
[0022] Bar code labels coated with protective, transparent, that is
substantially light-permeable, non-self-supporting films of
well-known compounds such as Dow Corning 20, Releasomer BL-3, and a
light-permeable wax, secured to a green tire, then cured
conventionally in a curing press, result in the bar code being
fully masked and therefore illegible. Such compounds are a logical
choice as they are routinely used as release agents.
[0023] Though not disclosed as being effective as a substitute for
Mylar.RTM., or any other film disclosed as having a desirable
protective function, a thin self-supporting polyurethane film less
than 50 .mu.m (2 mils, 0.002'') thick, and not derived from an
aqueous dispersion or two-component solvent-borne polyurethane
(also referred to as "solvent-borne polyurethane lacquers"), is not
effective for the purpose at hand. Such self-supporting
polyurethane films, like film of Mylar, fail to adhere to the
surface of a tire while it is being cured and falls off into the
mold when the cured tire is removed, at least in 5% of all cured
tires, which percentage is too high to be acceptable in tire
manufacture. Only non-self-supporting water-borne and solvent-borne
polyurethanes which provide thin films less than 25.4 .mu.m (1 mil)
thick are effective.
[0024] Dispersions of polyurethane, whether aqueous or not, found
uniquely effective in the invention disclosed herein, have long
been used in a variety of coating applications. In particular, U.S.
Pat. No. 6,093,271 to Majumdar teaches that a water-borne
polyurethane dispersion, "among a variety of clear coating
compositions", provides a transparent coating to protect a white or
colored sidewall on a cured tire. Majumdar found that a
polyurethane film, derived from a water-borne polyurethane
dispersion, on a tire exposed to oxidants and ultraviolet (u-v)
light protected the colored rubber containing antioxidants and
ultraviolet light stabilizers. In addition to the foregoing
protection, since the coating was provided on a colored strip after
it was cured, and the protected strip in turn was adhesively
secured to a cured tire, Majumdar considered suitability of the
coating for its abrasion resistance, adhesion and flexibility on
the cured sidewall. The body of the colored extrudate being raised
relative to the contiguous black rubber, the extrudate was subject
to abrasion. Since he chose not to coat the extrudate before it was
cured, there was no reason for him to consider the coating's
thermal stability under conditions of a curing mold; and there was
no reason for him to consider whether the coating was capable of
repelling the black tire paint used in the mold in which the tire
was cured.
[0025] Taking a cue from the teaching in the foregoing '271 patent,
of the use of a water-borne polyurethane dispersion on the surface
of a cured tire, WO 20 01194453 assigned to Michelin teaches use of
an aqueous dispersion of polyurethane to coat the sidewall of a
vulcanized tire to protect it against ozone, presumably maintaining
a shiny sidewall.
[0026] U.S. Pat. No. 5,834,530 to Ramcke et al teaches a bar code
printed on the surface of a label which is pre-crosslinked directly
below the surface, over the entire area of the label and to a depth
extending to as much as 80% of the thickness of the label. As is
evident from the data below, when a white rubber label imprinted
with a bar code and protected by Mylar film, is uncured over 20% of
its depth, the remaining 80% being substantially fully cured, and
the label cured under conditions of a curing press, uncured rubber
runs out and smears the bar code, making it unreadable, one out of
five times. As this incidence of failure is unacceptable, the
teachings of the '530 patent do not suggest how to rectify the
failure. Partial pre-crosslinking of the label is insufficient to
provide a vulcanized label on which a bar code remains a "sharp,
high-contrast inscription" as stated (see col 6, lines 56-57), the
definition of which is not provided.
[0027] All carcasses of pneumatic green tires are built as a series
of layers of flexible high modulus cords encased in a low modulus
rubber; the cords in each layer are oriented in a chosen path or
direction and substantially equispaced and parallel. The tire is
cured in a curing press using a curing bladder which forces
expansion of the tires. When the carcass is cured, it expands,
forcing the carcass against the indentations in the curing mold to
form the tread, and all components are co-cured so as to provide a
substantially cohesive bond between one and another.
[0028] Expansion upon curing of a radial ply tire is small, in the
range from about 5% to 20% greater than the size of the green
carcass; but expansion of a bias ply tire may range from 30% to
100% or more. The expansion of the sidewall during the formation of
its arcuate convex geometry is in the range from 5% to 20%
depending upon the structure of the tire. The cured applique is
required to be sufficiently biaxially extensible and flexible so
that it conforms to the arcuate surface of an expanded sidewall, or
the crenelated surface of a tread, without being loosened or
dislodged during cure and during operation of the tire.
[0029] A release agent normally coats the entire inner surface of
the curing mold. In this invention, the applique is provided with a
self-adherent, protective film of thermally stable, thermally
expansible, synthetic resinous compound which protects the printed
and/or colored surface of the applique under the film. In the
specific instance where the virgin surface includes a bar code, it
can be read through the protective film.
[0030] European publication No. 1073031 to Majumdar et al discloses
a sidewall to which is non-removably co-cured a bar code label,
protected by a film. The film may be removed after the tire is
cured, or left in place. The film is stated to "be a thermoplastic,
e.g. polyester, thermoset or other material. Desirably the film has
a high modulus at 5% elongation such as of at least 2 or 5 MPa."
There is no clear identification as to which film of what polymer
might effectively discharge its function under conditions of
vulcanization; nor is there any indication that the film remains
adhered to the surface of the bar code label after the tire is
removed from the curing press.
SUMMARY OF THE INVENTION
[0031] A cured pale rubber applique, from about 0.1 mm to 1 mm
thick, containing sufficient pale-colored particulate pigment such
as titanium dioxide or other inorganic compounds to minimize
staining of the applique by contaminants from the rubber or a
vulcanizable adhesive securing the applique to black rubber,
remains flexible enough, and allows itself to be non-removably
embedded in a cured black rubber article, in particular a pneumatic
tire, and vulcanized into either the sidewall, or, the tread. When
the applique is secured to the green tire, its virgin upper surface
is vertically spaced apart from the immediately surrounding rubber;
the virgin surface is protected by a flexible synthetic resinous
polymeric film which may be a self-supporting polyamide film from
about 10 .mu.m to less than 50 .mu.m (2 mils, 0.002'') thick, or a
non-self-supporting polyurethane film from about 5 .mu.m to less
than 25.4 .mu.m, 0.0254 mm (1 mil, 0.001''); the protective film
remains adhered to the surface of the applique even after the cured
tire is removed from the mold in more than 95% of all tires; both
the cured applique and the protective film are thermally stable;
the applique is also dynamically stable so that when a bar code is
provided in the virgin surface, the bar code may be successfully
read through the protective film which has been heated to curing
temperature, typically about 150.degree. C. By "dynamically stable"
is meant that the cured applique expands less than about 10% during
curing of the tire.
[0032] A laminar decorative design or identifying label of pale
rubber filled with from 5% to 20% of a pale-colored particulate
pigment, is coated with a non-self-supporting pore-free
substantially light-permeable film less than 0.0254 mm (0.001'' or
1 mil) thick, preferably in the range from about 1 .mu.m to 10
.mu.m thick, derived from an aqueous dispersion of crosslinkable
urethane, or two-component solvent-borne polyurethane. By
"pore-free" is meant that the film has no pores large enough to
allow tire paint to permeate the film. The lower surface of the
label is calendered to a layer of vulcanizable adhesive having
about the same thickness about 0.1 mm to 1 mm as the applique,
preferably from about 200 .mu.m (8 mils) to 500 .mu.m (20 mils)
thick, which may be coated with a cement or solvent-containing
layer from about 5 .mu.m to 25 .mu.m thick, and secured to the
sidewall of a green tire, the label symmetrically disposed about an
expandable portion of the tire, expandable at least 5%, such as the
circumferential centerline of the sidewall, or the tread. The tire
is then placed in a curing mold, covered with tire paint and cured
at about 150.degree. C., and because both the label and its
protective film are unconfined except by the interior surface of
the mold, each is free to move with the hot flow of sidewall or
tread rubber as directed by the forces in the hot curing mold. Upon
the tire being removed from the mold, the film remains
non-removably adhered to the surface of the label which, despite
being expanded at least 5%, is essentially distortion-free, and
free of lines due to cracking of its surface. By "distortion-free"
is meant that the bar code is successfully read by a commercially
available scanner.
[0033] A bar code label from about 0.20 mm (0.008'' or 8 mils) to
0.50 mm (0.02'' or 20 mils) thick is formed from a "white rubber"
composition filled with from 5% to 20% titanium dioxide pigment.
Upon being essentially fully cured the bar code label has a 300%
modulus of less than 3 MPa, preferably less than 1 MPa (at 300%
elongation). It is matched to a cured sidewall compound having a
300% modulus of less than 5 MPa, preferably less than 3 MPa. The
bar code label is coated with a non-self-supporting film described
above, and adhered with a vulcanizable contact adhesive to the
sidewall. When adhered, the bar code label is typically
symmetrically disposed longitudinally about the sidewall's
circumferential centerline. The sidewall is then covered with tire
paint and cured in a mold at about 150.degree. C. Upon the tire
being removed from the mold, the film remains non-removably adhered
to the surface of the bar code label. The code was "successfully
read". Thicker labels tend to crack, resulting in errors when
reading the bar code.
[0034] The bar code label, coated with the non-self-supporting film
described immediately above, is stitched into the a green tread,
symmetrically disposed transversely about the tread's
circumferential centerline, preferably at right angle thereto. The
tread and tire are covered with tire paint and cured in a mold at
about 175.degree. C. Upon the tire being removed from the mold, the
film remains non-removably adhered to the surface of the bar code
label; and the code was "successfully read".
[0035] When a logo and/or bar code label is protected with a
self-supporting film of nylon, such as 6,6-nylon or 6-nylon, when
the tire is cured, it requires a force of at least 10 Newtons to
remove the film; depending upon whether the cured label is to be
co-cured in the sidewall or the tread, the cured label has a
matching modulus, typically lower than 2 MPa at 300% elongation;
when co-cured in the sidewall the label is spaced apart at least
2.5 cm from the inner periphery of the bead of the tire, and
preferably symmetrically embedded longitudinally about the
sidewall's circumferential centerline, so that its printed surface
is coplanar with the adjacent sidewall surface and the bar code may
be read accurately on more than 95% of tires; when co-cured in the
tread the cured label is placed in a groove between lugs. The 300%
modulus is given because a measurement at 100% elongation or less
is insufficiently informative even if measured with reasonable
accuracy.
[0036] The method of co-curing an applique on a green rubber
article comprises, preparing a laminar applique less than 20 mils
thick of predominantly natural rubber containing from 15% to 70% of
pale inorganic pigment such as titanium dioxide, calcium carbonate
and zinc oxide, optionally imprinted with a bar code; curing the
applique so as to crosslink to at least an 80% level as determined
by a Mooney cure meter; coating the upper surface of the applique
with a protective self-supporting film of a polyamide less than 2
mil thick, or a non-self-supporting film of polyurethane less than
25.4 .mu.m, 0.0254 mm (1 mil) thick; applying a vulcanizable
adhesive to the lower surface of the applique; adhesively securing
the applique to the article at a chosen location on an expandable
surface of the green article; curing the article in a curing mold;
and, removing a cured article from the mold with the protective
film adhering to the surface of the applique free from visually
observable surface cracks. Preferably the article is a pneumatic
tire, and the location is chosen from "in the sidewall,
spaced-apart from the bead of the tire", and from "in the tread's
footprint".
BRIEF DESCRIPTION OF THE DRAWING
[0037] The foregoing and additional objects and advantages of the
invention will best be understood by reference to the following
detailed description, accompanied with schematic illustrations of
preferred embodiments of the invention as well as an embodiment in
which protection of the applique is unsatisfactory, in which
illustrations like reference numerals refer to like elements, and
in which:
[0038] FIG. 1 is a schematic illustration in an elevation view, not
to scale, of a cured tire carcass with a logo of a blimp with a bar
code imprinted on it, embedded in the sidewall; also embedded is an
applique of the manufacturer's identity; a protective film
overlying the applique is transparent and invisible in the
drawing.
[0039] FIG. 2 is a partial cross-sectional elevation, not to scale,
of a cured radial tire showing bar code labels embedded in the
tread at various locations, and in the sidewall, all labels with a
protective film (invisible in the drawing) overlying the
labels.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0040] Before an applique, filled with titanium dioxide pigment to
provide maximum contrast with the black rubber of the tire, is
secured to the tire it is essentially fully cured, that is, at
least 80% crosslinked throughout, as determined by a Mooney cure
meter. The applique containing up to 50% titanium dioxide pigment
is formed from predominantly natural rubber (cis-polyisoprene),
preferably more than 75% natural rubber, to ensure that upon curing
it has a modulus substantially matched to that of the rubber in
which it is embedded, so that it is biaxially extensible at least
10% in each direction. Such extensibility fails to interfere with
the accuracy of the reading of the bar code. If a bar code label,
it is imprinted with a bar code before the label is cured.
[0041] The upper surface of the label is coated with a
light-permeable polyamide film having an area greater than the
label, self-adhered to the label's surface. The lower surface of
the label is coated with a vulcanizable rubber-based adhesive with
a curing agent, e.g. a cementless adhesive disclosed in U.S. Pat.
No. 5,503,940 and the adhesive (referred to as "black adhesive"),
when cured, has a modulus which is substantially matched to that of
the rubber to which the label is adhered. After curing, the
self-supporting film remains adhered to the label's surface which
is coplanar with that of the sidewall, or that portion of tread
immediately adjacent the label's edges.
[0042] Alternatively, the upper surface of the label is coated with
a polyurethane non-self-supporting film derived from either a
two-component solvent-borne polyurethane, or, from an aqueous
dispersion which is typically a one-component, fully-reacted,
predominantly linear polymer modified with hydrophilic groups,
which latter dispersion is preferred for environmentally sensitive
users. The polyurethane film may also be derived from aqueous
blocked polyisocyanates and crosslinking agents. U.S. Pat. Nos.
5,017,673; 5,194,487; 5,227,422; 5,331,039; and 5,369,152 describe
water-borne polyurethane dispersions some of which are commercially
available from a variety of suppliers. Such polyurethane
dispersions include the reaction product of polyisocyanates,
typically aliphatic polyisocyanates, and polyether or polyester
polyols. Dispersing agents are added as separate components or may
be reacted with the polyurethane. Ionic groups (e.g., anionic and
cationic), or, nonionic groups e.g. poly(ethylene oxide) may be
attached to the polyurethane to make it dispersible in water. A
variety of additives including adhesion promoters may also be added
to the urethane dispersion. The polyurethane particles coalesce
into a film upon drying.
[0043] The water and solvent resistance of the film may be enhanced
by crosslinking, e.g. with a carbodiimide, or, an alkoxylated
melamine formaldehyde resin. Ucarlnk.RTM. XL-29SE available from
Union Carbide, Danbury Conn. is a multifunctional carbodiimide
crosslinker. Sancure.RTM. 89 is a modified melamine crosslinker
available from the Noveon Inc., Brecksville, Ohio. Carboxylic acid
functionality present in many anionic modified polyurethanes may be
crosslinked with a polyfunctional aziridine. As the wet coating is
heated to elevated temperatures, crosslinking occurs through the
reaction of the methoxylated melamine resin with the urea or
urethane groups in the polymer.
[0044] Higher molecular weight polymers with higher crosslink
density are obtained from a two-component solvent-borne
polyurethane system but the water and solvent resistance of the
film are relatively poor compared to those for a film derived from
an aqueous dispersion. After curing, the non-self-supporting film
remains adhered to the label's surface and is light-permeable.
Whether the polyurethane is derived from a waterborne or
two-component system, the lower surface of the coated label is
coated with a vulcanizable rubber-based adhesive with a curing
agent commonly used for tread-splicing and retreading tires before
the label is secured to the tire. The vulcanizable adhesive,
typically predominantly polyisoprene, is essentially free of an
anitozonant and an aromatic oil but typically contains a
reinforcing agent such as carbon black, so that the cured adhesive
layer functions as an additional barrier (in conjunction with
titanium dioxide in the applique) to staining ingredients from
within the tire's carcass.
[0045] The rubber of the applique is both thermally and
dimensionally stable under curing conditions; the polymeric film is
thermally stable under curing conditions, but expands as required
after the tire is placed in the curing mold.
Construction of Green Tire Carcass with Applique Protected by
Non-Self-Supporting Film:
Applique of "blimp" Logo Imprinted with Bar Code, Another with
Identifying Label:
[0046] Referring to FIG. 1 there is schematically illustrated a
conventional toroidal green tire carcass, referred to generally by
reference numeral 10, having an applique 11 establishing the
manufacturer's identity, the applique simultaneously functioning as
a bar code label imprinted with a bar code 12. The applique 11 is
stitched into the sidewall 13, and protected by a transparent film
not visible in the drawing. The innermost portion of the applique,
nearest bead 14 of the tire, is about 2.5 cm from the inner
periphery of the bead, and the outermost portion extends into the
shoulder 15 of the carcass 10. The applique 11 is located about
midway between the bead and the shoulder of the tire. A separate
bar code label 16 may also be provided at another location midway
between the bead and the shoulder of the tire. The virgin upper
surface of the applique is vertically spaced apart from that of
contiguous rubber of the tire by the thickness of the applique and
the vulcanizable adhesive on the applique's lower surface. When the
tire is cured, the applique is embedded in the location chosen.
Labels on the tread 17 are not shown in this FIG. 1.
[0047] Referring to FIG. 2, there is schematically shown a partial
cross-section of a conventional cured toroidal rigid breaker,
radial ply tire carcass, referred to generally by reference numeral
20, comprising a circumferential tread 21, spaced beads 22, 22'
(not shown) and connecting sidewall portions 23, 23' (not shown)
extending between the tread and beads, to form a conventional
radial tire. The carcass 20 includes a casing 24 in which the cords
or filaments are disposed in a substantially radial direction
giving a 90.degree. bias or crown angle in relation to the axis of
rotation of the tire. A breaker or belt of several plies 25 of
cords are fitted on top of the casing, under the tread, and laid at
various crown angles, two of the layers having a low crown angle of
the order of 20.degree.. The inner surface of the casing is lined
with a rubber inner liner 26 which is substantially
gas-impermeable. The components of the tire are assembled on a
tire-building drum, the inner liner being the first component
positioned on the drum. Before the tire is removed from the
building drum, one or more generally rectangular bar code labels
31, 32, 33 are stitched into the tread at various orientations
relative to the longitudinal y-axis, which is at right angle to the
axis of rotation (x-axis) of the tire; one bar code label 34 is
stitched into the sidewall. As shown in the drawing, preferably the
labels 31-33 are embedded generally perpendicular to the x-axis,
while label 34 is parallel to it. After the tire is molded, a major
portion of at least one of the bar code labels, preferably all of
it, will lie in a valley between lugs of the tread, as does label
31, to be readable even when the lugs are essentially worn out.
Such placement, so that the label is substantially symmetrically
disposed about the circumferential centerline of the valley to be
formed when a substantially laminar strip of green tread is cured,
is achieved by back-locating the location of the label in the strip
of green tread after its opposed ends are smoothly spliced together
on a tire-building drum; marking the centerline with a light beam;
coating the lower surface of the label with a vulcanizable
adhesive; adhesively securing the label symmetrically about the
centerline, and, removing the green tire after its construction is
completed. For easiest reading of the bar code the label is secured
with its longitudinal axis either at right angles to the rotational
axis of the tire; or, with its longitudinal axis parallel to the
rotational axis of the tire.
[0048] As illustrated, label 32 is embedded partially in a valley
and may be read even after the lugs are partially worn down. Label
33 is on the surface of a lug and legibility of the code will not
survive operation of the tire. Label 34 being in the central zone
of the sidewall will be legible as long as the portion of the
sidewall on which it is secured, is not destroyed. All embedded bar
code labels may be read with a standard hand-held bar code scanner
such as a PowerScan.RTM. RF Bar Code Scanner available from PSC,
Inc., Eugene, Oreg. 97402.
[0049] Prior to the bar code labels 31-34 being stitched into the
sidewall, they are sprayed with a waterborne polyurethane
commercially available as Sancure 776, optionally further
crosslinked, and dried to form a film having a thickness in the
range from greater than about 2 .mu.m to less than 25.4 .mu.m,
0.0254 mm (1 mil).
Self-Supporting Protective Film:
[0050] Labels made from 100% cis-polyisoprene and filled with 10%
titanium dioxide, then essentially fully cured, were protected with
the following polyester films and tested. [0051] (1) Titanium
dioxide-filled polyester film 25.4 .mu.m, 0.0254 mm (1 mil) thick,
with one side treated for better adhesion to rubber. [0052] (2)
"White" polyester film, 0.0254 mm (1 mil) thick, with
photo-printable coating on one side, the other side treated to
accept a curable adhesive. [0053] (3) Light-permeable polyester
film, 0.0254 mm (1 mil) thick, with thermal-printable coating on
one side, the other side treated to accept a curable adhesive.
[0054] (4) 6,6-nylon film 19 .mu.m (0.75 mil thick) and
light-permeable.
[0055] Five samples of each of the foregoing labels are coated with
a vulcanizable adhesive and adhered to a tire sidewall compound
(identify generically) which is cured at 150.degree. C. for 15
min.
Results with Labels (1) (2) and (3):
[0056] In five tests of each sample, one or more of the strips
fails to remain on the label when the cure is completed.
Results with Labels (4):
[0057] In five tests, all five labels have the film remaining on
them when the cure is completed.
Non-Self-Supporting Protective Film:
[0058] A 30% titanium dioxide-filled 100% cis-polyisoprene label is
coated with the following: [0059] (5) several waterborne
dispersions of polyurethane obtained from various sources are each
sprayed on the printed bar code on each label and dried; the
spraying and drying is repeated until a light-permeable film about
19 .mu.m (0.75 mil thick) is obtained; the bar code label is then
adhesively secured to the sidewall with the same vulcanizable
adhesive used for labels (1)-(4), then covered with "outside tire
paint E-366" obtained from Wacker Silicones Corp., and cured in a
mold at about 150.degree. C.
[0060] Among the waterborne polyurethane dispersions used are
Sancure.RTM. 776, Sancure.RTM. 2715 and Bayhydur.RTM. 302 from
Bayer Coatings and Colorants Division, which dispersions may be
further crosslinked with Sancure.RTM. 89 or Ucarlnk.RTM. XL-29SE.
Numerous other effective Sancure.RTM. waterborne polyurethane
systems, e.g. 843, 861, 898, 891, are available. All films remained
on the labels the surfaces of which were uncontaminated and
visually essentially identical to their condition prior to being
cured; the films could be manually removed using a force no greater
than about 30 Newtons. [0061] (6) in a manner analogous to that
described in (5) above, a two-component solvent-borne polyurethane
system obtained from Bayer Corporation is sprayed and dried on
several labels which are then adhered to sidewalls of green tires,
covered with tire paint and cured. All films remained on the
labels, and could not be removed.
[0062] The bar code labels (4-6) were readily legible by a
commercially available bar code scanner such as the Powerscan, a
HHP 3800 LR-12 or HHP 3870 LX-A2 with 100% accuracy both before the
green tires were cured, and after they were cured.
Durability of Legible Bar Code:
[0063] Samples of the bar codes (4-6) on 6.00-6-1QP046 tires were
run and dynamometer tested with variable loads for 30 cycles. All
bar codes remained free from cracks and legible. Further, the bar
codes on the labels were legible even after fifteen (15) simulated
retreading cycles.
[0064] Mechanical Properties of Materials for Appliques and
Protective Films: TABLE-US-00001 50% mod 300% mod Tensile Elong.*
Material (MPa) (MPa) (MPa) % Mylar .RTM. film 176.7 246.9 61.6
Applique, green 1.59 2.44 2.52 320 Applique, cured 1.28 1.87 4.75
940 Adhesive on ap'ue 1.42 2.97 12.70 1287 Cured adhesive on ap'ue
0.86 2.24 12.82 1193 Black sidewall, green 0.20 0.17 0.18 1680
Black sidewall, cured 0.94 2.57 14.03 990 *elongation at break
* * * * *