U.S. patent application number 10/946410 was filed with the patent office on 2005-03-17 for pigments and compositions for use in laser marking.
This patent application is currently assigned to Tyco Electronics Corporation. Invention is credited to Daga, Vijay, Dahl, Klaus J..
Application Number | 20050058939 10/946410 |
Document ID | / |
Family ID | 22955376 |
Filed Date | 2005-03-17 |
United States Patent
Application |
20050058939 |
Kind Code |
A1 |
Daga, Vijay ; et
al. |
March 17, 2005 |
Pigments and compositions for use in laser marking
Abstract
Pigments and compositions for use in laser marking. A colorless
UV-absorbing pigment at least partially coated with a synergist has
the formula [R.sub.m(SiO.sub.n)].sub.pR'.sub.q, wherein (a) m is 1
to 3, n is 1 to 3, p is at least 1, and q is 0 to 3, and (b) at
least one R or R' is a substituent that upon pyrolysis generates a
black material suitable for providing a mark. Such pigments are
useful in fluoropolymers used for wire and cable insulation.
Inventors: |
Daga, Vijay; (Cupertino,
CA) ; Dahl, Klaus J.; (Atherton, CA) |
Correspondence
Address: |
TYCO ELECTRONICS CORPORATION
MAIL STOP R20/2B
307 CONSTITUTION DRIVE
MENLO PARK
CA
94025
US
|
Assignee: |
Tyco Electronics
Corporation
Middletown
PA
|
Family ID: |
22955376 |
Appl. No.: |
10/946410 |
Filed: |
September 21, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10946410 |
Sep 21, 2004 |
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09990107 |
Nov 21, 2001 |
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6825265 |
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60252286 |
Nov 21, 2000 |
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Current U.S.
Class: |
430/270.1 |
Current CPC
Class: |
Y10T 428/2933 20150115;
C09C 1/04 20130101; C01P 2002/84 20130101; Y10T 428/2995 20150115;
C01P 2004/84 20130101; H01B 3/306 20130101; H01B 3/445 20130101;
C08K 9/06 20130101; C01P 2006/12 20130101; C01P 2004/54 20130101;
C09C 1/043 20130101; C09C 1/3684 20130101; C01P 2006/60 20130101;
C01P 2006/80 20130101; C01P 2004/03 20130101; C01P 2004/50
20130101; H01B 3/305 20130101; C01P 2004/62 20130101; C09C 3/12
20130101; B41M 5/267 20130101; C08K 9/06 20130101; C08L 27/12
20130101 |
Class at
Publication: |
430/270.1 |
International
Class: |
G03C 001/492 |
Claims
1. A colorless UV-absorbing pigment at least partially coated with
a synergist having the formula [R.sub.m(SiO.sub.n)].sub.pR'.sub.q,
wherein (a) m is 1 to 3, n is 1 to 3, p is at least 1, and q is 0
to 3, and (b) at least one R or R' is a substituent that upon
pyrolysis generates a black material suitable for providing a
mark.
2. A pigment according to claim 1 wherein m is 2 or 3 and each R is
the same substituent.
3. A pigment according to claim 1 wherein m is 2 or 3 and each R is
a different substituent.
4. A pigment according to claim 1 wherein at least one R or R' upon
pyrolysis produces carbon black, silicon carbide, silicon
oxycarbide, or mixtures thereof.
5. A pigment according to claim 1 wherein at least one R is the
same as R'.
6. A pigment according to claim 1 wherein at least one of R and R'
comprises an aryl group.
7. A pigment according to claim 1 which comprises TiO.sub.2, ZnO,
or ZnS.
8-21. (canceled).
22. A pigment according to claim 1 wherein the synergist comprises
a silsesquioxane or a polyhedral oligomeric (POSS).
23. A pigment according to claim 22 wherein the synergist comprises
dodecaphenylsilsesquioxane.
24. A pigment according to claim 1 wherein the synergist is present
at at least 20% by weight of the pigment.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is an application under 35 USC 111(a) and
claims priority under 35 USC 119 from Provisional Application Ser.
No. 60/252,286, filed Nov. 21, 2000 under 35 USC 111(b). The
disclosure of this provisional application is incorporated herein
by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to pigments and compositions
containing such pigments, particularly fluoropolymer compositions,
and their use in laser marking of substrates.
[0004] 2. Introduction to the Invention
[0005] Polymers such as fluoropolymers are commonly used as
insulating materials for substrates such as wire and cable. For
such applications, the fluoropolymer generally surrounds a central
wire or provides a jacket around one or more insulated wires. In
order to identify particular wires, it is often necessary to mark
the insulation or jacketing material with numbers, letters, or
other indicia. Laser marking is one preferred method of marking, as
it can provide a relatively permanent, highly legible mark on the
surface of the insulation and does not produce mechanical damage or
require good adhesion of an ink to the polymer.
[0006] Laser marking often uses a ultraviolet (UV) laser such as an
excimer laser. Because fluoropolymers are transparent to UV
radiation, it is generally necessary that a UV light absorbing
compound or pigment be added to the fluoropolymer in order to
produce marks. A commonly used additive is titanium dioxide
(TiO.sub.2). When a laser is directed at the additive-containing
polymer composition, the photosensitive TiO.sub.2 changes color as
a result of the laser-induced reduction of Ti.sup.4+ (colorless) to
Ti.sup.3+ (blue-black) in the TiO.sub.2 lattice. The use of
TiO.sub.2 in a fluoropolymer is disclosed in U.S. Pat. Nos.
5,560,845 and 5,789,466 (both Birmingham et al.), which provide
details on laser marking of pigmented melt-processible
fluoropolymer substrates that use titanium dioxide pigment coated
with organosilane. These documents rely on the organosilane to
increase the dispersion of the TiO.sub.2 pigment, reducing the
number of TiO.sub.2 agglomerates and increasing the quality of the
mark. In the disclosed compositions, the organosilane is present in
an amount from about 0.1 to about 5 weight percent based on the
amount of the organosilane and the pigment.
BRIEF SUMMARY OF THE INVENTION
[0007] We have now found that laser marks of improved contrast can
be produced if the pigment is coated with or in close proximity to
a synergist that contains a substituent that upon pyrolysis
generates a black material, e.g. carbon, that provides a mark. Such
pigments can be used in compositions that are exposed to excimer
laser radiation, for example in insulation for wires and cables.
Different types of synergists can be used to accommodate the
different processing and use conditions of the polymer. In
particular, we have found laser marks formed using the pigments of
the invention and compositions comprising them retain good contrast
under heat aging conditions.
[0008] In a first aspect this invention provides a colorless
UV-absorbing pigment at least partially coated with a synergist
having the formula
[R.sub.m(SiO.sub.n)].sub.pR'.sub.q,
[0009] wherein
[0010] (a) m is 1 to 3,n is 1 to 3, p is at least 1, and q is 0 to
3,
[0011] (b) at least one R or R' is a substituent that upon
pyrolysis generates a black material suitable for providing a
mark.
[0012] In second aspect, the invention provides a composition
suitable for laser marking when exposed to radiation from an
excimer laser, said composition comprising
[0013] (1) a fluoropolymer having a processing temperature
T.sub.p,
[0014] (2) 0.1 to 25% by weight of the composition of a colorless
UV-absorbing pigment, and
[0015] (3) a synergist according to the first aspect of the
invention, said synergist being (i) present at at least 10% by
weight of the pigment present in the polymer composition, (ii) heat
stable at a temperature of at least T.sub.p, and (iii) in physical
proximity with the pigment.
[0016] Particularly preferred are compositions in which the
synergist and pigment are used in polytetrafluoroethylene (PTFE).
Therefore, in a third aspect, this invention provides a composition
suitable for laser marking when exposed to radiation from an
excimer laser, said composition comprising
[0017] (1) polytetrafluoroethylene,
[0018] (2) 0.1 to 50% by weight of the composition of a colorless
UV-absorbing pigment, and
[0019] (3) a synergist having the formula
[R.sub.m(SiO.sub.n)].sub.pR'.sub.q,
[0020] wherein
[0021] (a) m is 1 to 3, n is 1 to 3, p is at least 1, and q is 0 to
3, and
[0022] (b) at least one R or R' is a substituent that upon
pyrolysis generates a black material suitable for providing a
mark,
[0023] said synergist being (i) present at at least 0.1% by weight
of the pigment present in the polymer composition, (ii) heat stable
at a temperature of at least T.sub.p, and (iii) in physical
proximity with the pigment
[0024] Pigments and compositions of the invention are particularly
useful for insulating materials. Therefore, in a fourth aspect,
this invention provides an insulated conductor which comprises
[0025] (A) an elongate wire, and
[0026] (B) an insulating layer surrounding said wire, said layer
comprising a composition of the second aspect of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0027] Pigments of the invention absorb UV radiation, i.e.
radiation less than about 400 nm. They are preferably substantially
colorless. For purposes of this specification, "white" indicates an
absence of color and therefore white pigments are colorless.
Suitable pigments include titanium dioxide (TiO.sub.2), zinc oxide
(ZnO), and zinc sulfide (ZnS). Particularly preferred for its
opacity, high refractive index, and response to UV radiation is
crystalline TiO.sub.2. Either rutile or anatase forms of TiO.sub.2
can be used. It is preferred that the average particle size of the
pigment be less than 1 .mu.m, preferably less than 0.5 .mu.m
particularly less than 0.4 .mu.m, especially less than 0.3
.mu.m.
[0028] The pigment is at least partially coated with or in contact
with a synergist (also referred to herein as a coating) having the
formula
[R.sub.m(SiO.sub.n)].sub.pR'.sub.q,
[0029] in which m is 1 to 3, n is 1 to 3, p is at least 1 and q is
0 to 3. At least one of R and R' is a substituent that, upon
pyrolysis, e.g. resulting from UV radiation, generates a large
amount of black material, e.g. carbon black, silicon carbide,
silicon oxycarbide, or mixtures thereof. If R is greater than 1,
each of the R elements may be the same or different; and if R' is
greater than 1, each of the R' elements may be the same or
different. R' can be absent depending on the selection of m, n, and
p. For example, if m=1, n=1.5, and p is very large, then R' is
essentially absent. For cyclic analogs of (I), R' is absent. R and
R' may be same or different substituents. For R or R', aryl groups,
either substituted or un-substituted, are preferred The synergist
is preferably itself substantially colorless, and should be
heat-stable (i.e. does not degrade) and non-volatile to remain
relatively unchanged throughout all processing and subsequent
product use conditions.
[0030] The heat for the pyrolysis results from absorption of
excimer laser light by the pigment. Therefore, it is important that
the synergist be directly in contact with the pigment or
sufficiently close, generally in physical proximity, that heat
transfer is easily achieved. The synergist must be coated upon the
pigment or be able to migrate to its surface during polymer
processing to form a coating that remains closely adjacent to the
pigment surface throughout all processing and product use
conditions. If coated on the pigment, the synergist may partially
cover, e.g. cover at least 25% of the surface area of the pigment,
or completely cover the pigment.
[0031] Preferred synergists are silsesquioxanes and Polyhedral
Oligomeric Silsesquioxanes (POSS). The POSS materials have the
generic structure (RSiO.sub.1.5).sub.n where R can be any organic
residue, but preferably an aromatic group such as phenyl or
napthyl, and n can be 8, 10, 12 or larger. In addition, various
oligomeric and polymeric silicones of structure R--(SiO[R.sup.1,
R.sup.2].sub.2).sub.n--R are suitable additives where R, R.sup.1,
and R.sup.2 can be the same or different. Preferably one of the
substituents R, R.sup.1, or R.sup.2 is phenyl, which should be
present as a significant substituent, a typical example being a
silicone that contains a significant number of phenyl groups (one
or two per silicon atom). Suitable phenyl-POSS compounds include
octaphenyl-POSS, dodecaphenyl-POSS, and polyphenyl-POSS (available
from Hybrid Plastics under the Molecular Silica.TM. brand, product
numbers MS0380, MS0802, and PM1270, respectively).
Dodecaphenyl-POSS, which has the structure
[(C.sub.6H.sub.5)SiO.sub.1.5].sub.12, has a cage structure. Heat
treatment, e.g. at 200.degree. C. for 1.5 hours, will remove any
clathrated solvent used in the manufacture of the
dodecaphenyl-POSS; such solvent may have an adverse effect on the
stability of any composition into which the synergist is mixed.
Although the phenyl-POSS compounds are not known as a laser marking
additive or as additives for perfluoropolymers, they have
significant advantages in that they are (1) stable at processing
temperatures of greater than or equal to 360.degree. C., which is
necessary for processing of some polymers, including
perfluoropolymers, and (2) colorless in visible light.
[0032] Also suitable for use are phenylalkoxy silanes, e.g.
phenyltrimethoxy silane such as that available from Sivento Inc.
under the name CP0330. Both the phenyl POSS materials and phenyl
silanes are stable at high temperature.
[0033] The synergist is generally present in an amount of more than
5% by weight of the total amount of synergist and pigment,
preferably at least 10% by weight, particularly at least 20% by
weight, especially at least 30% by weight, and can be present at
much higher percentages, e.g. 50% or more. These quantities are
particularly appropriate for melt-processible polymers (as
described below) containing a phenyl silane or silicone. However,
for melt-processible polymers comprising silsesquioxanes or POSS
synergists, or for non-melt-processible polymers comprising any of
the designated synergists, the amount of synergist present may be
much lower, e.g. at least 0.1% by weight of the total amount of
synergist and pigment, preferably at least 0.5% by weight,
especially at least 1% by weight.
[0034] The pigments described above may be used to enhance laser
marking in compositions comprising any suitable polymer, including
polyolefins such as polyethylene and polypropylene. However, of
particular interest, especially for airframe wire, are
fluoropolymers. These include melt-processible fluoropolymers such
as ethylene/tetrafluoroethylene copolymer (ETFE) and
melt-processible perfluoropolymers in which each hydrogen directly
attached to a carbon atom is replaced by fluorine. Suitable
melt-processible perfluoropolymers include tetrafluoroethylenel
hexafluoropropylene copolymer (FEP), tetrafluoroethylene/propyl
vinyl ether copolymer (PFA), and tetrafluoroethylene/methyl vinyl
ether copolymer (MFA). Such polymers may be melt-processed using
any suitable equipment, e.g. extrusion Polytetrafluoroethylene
(PTFE), which is not melt-processible, may also be used.
Compositions comprising PTFE may be processed by ram extrusion,
followed by sintering. Processing of either melt-processible or
non-melt-processible polymers can be carried out by alternative
techniques, e.g. by electrostatic coating or dispersion coating in
which the composition is deposited onto a substrate and then
heat-treated. The polymer of the composition has a processing
temperature T.sub.p which is defined as the highest temperature the
composition is exposed to during normal processing of the
composition. For crystalline polymers, T.sub.p is generally greater
than the melting temperature T.sub.m which is defined as the peak
of the exotherm on a differential scanning calorimeter (DSC)
trace.
[0035] Perfluoropolymers of high purity are particularly preferred
for use, as they provide maximum contrast at a given concentration
of pigment and coating. High purity PFAs are fully end-capped with
fluorine, having fewer than six nonfluorinated end groups per
million carbon atoms. Such polymers are disclosed in U.S. Pat. No.
4,743,658 (Imbalzano et al.), the disclosure of which is
incorporated herein by reference.
[0036] The compositions of the invention comprise a substantially
colorless UV-absorbing pigment, e.g. TiO.sub.2, in an amount of 0.1
to 70% by weight of the total composition, preferably 0.1 to 50%,
particularly 0.1 to 25%, especially 0.1 to 10%. Also present is a
synergist as described above. The synergist is selected to be heat
stable at a temperature of at least T.sub.p. It may be in direct
physical contact with the pigment, e.g. crosslinked to the pigment
prior to adding to the polymer. Alternatively, it can migrate close
enough to the pigment during processing to have sufficient physical
proximity for heat transfer during UV radiation.
[0037] We have found that the order of addition of the synergist
and pigment to the molten polymer may have an effect on the final
contrast. In general, if the synergist is added after the pigment,
it preferentially coats the high surface energy pigment particles.
However, if the synergist is added after the pigment, it may be
dispersed in the polymer homogeneously and not be available to coat
the pigment as well, resulting in a lower contrast. In addition,
the temperature of mixing can affect the contrast of the final
composition, with lower processing temperatures often giving better
contrast. In particular, very high processing temperatures of
perfluoropolymers may generate hydrofluoric acid (HF), which can
adversely affect the synergist structure. If the synergist melts,
processing at a temperature above that melting range may allow
better contact to the pigment. For example, DPOSS shows melting
regions at temperatures up to about 375.degree. C., so that
processing above this temperature allows the synergist to melt and
coat the pigment.
[0038] Particularly preferred for use with PTFE is polyphenyl
silsesquioxane (PPSQ; available from Gelest under the name
SST-3P01). PPSQ has a ladder structure. We have found that this
material may be crosslinked, so that when it is coated onto a
pigment, it forms a coating that stays on the pigment and is
resistant to certain types of solvent used in the manufacture of
PTFE tapes. One suitable crosslinking procedure is described in
Example 15, below.
[0039] Compositions of the invention are particularly suitable for
use on an insulated conductor in which an elongate element, e.g. a
wire, cable, or bundle of wires, is surrounded at least in part by
an insulating layer comprising the composition. Compositions can
also be used to surround an elongate element which is a fiber optic
cable. If the composition is based on a melt-processible polymer,
the composition may be extruded over the element. Alternatively, if
the composition comprises a non-melt-processible polymer, e.g.
PTFE, it may be ram extruded or tape-wrapped over the element One
or more layers of different or the same thickness and/or
composition may be present between the wire or cable and the layer
of composition. Such layers may include a mica tape such as is
disclosed in U.S. application No. 09/587,229 (Nyberg et al.) and
International Publication No. WO 00/74075 (Tyco Electronics
Corporation et al.), the disclosure of which is incorporated herein
by reference. In general, the contrast is greater as the wall
thickness of the insulating layer containing the pigment and
synergist increases.
[0040] The conductor may comprise an outer layer of polymer which
does not contain the pigment or synergist. Such a layer must be
sufficiently thin, e.g. less than 0.1 mm, to allow the laser
radiation to penetrate through it to mark the underlying pigmented
layer. This outer layer may improve the abrasion resistance of the
conductor, while still providing a conductor with acceptable
contrast.
[0041] Contrast, expressed as a percent, is the difference between
the reflectance of the mark and the background on which the mark is
placed. Contrast produced using the pigments and compositions of
the invention is at least 70%, preferably at least 75%,
particularly at least 80%, and remains at a high level even after
heat-aging at an elevated temperature for 24 hours or more.
[0042] As a general rule, for infusible polymers (e.g. PTFE),
precursors to thermosets, or polar thermoplastics (e.g.
polyethylene terephthalate, polybutylene terephthalate,
polyvinylidene fluoride, or polyvinyl chloride), the synergist is
preferably [C.sub.6H.sub.5SiO.sub.1.5].sub.n coated onto the
pigment and crosslinked thereupon. For less polar thermoplastic
polymers (e.g. PFA, FEP, polypropylene or polyethylene), the
synergist can be [C.sub.6H.sub.5SiO.sub.1.5].sub.n, or a low
molecular weight variant that can migrate to the pigment dispersed
in the polymer matrix during thermoplastic processing to form a
coating on such pigment, which remains in this location during
product use. A preferred compound is dodecaphenylsilsesquioxane,
[C.sub.6H.sub.5SiO.sub.1.5].sub.1- 2.
[0043] The compositions of the present invention are particularly
useful for airframe wire insulation. For example, one commercial
PTFE tape for aircraft wire comprises about 4% TiO.sub.2. When this
tape is illuminated with an excimer laser at 308 nm it provides
about 60 to 70% laser mark contrast Examples of PTFE compositions
of the invention exhibit contrast of more than 75%.
[0044] While the invention generally has been disclosed in terms of
silicon-based synergists, a more general description is that
synergist has the formula
[R.sub.sX].sub.t, (II)
[0045] where R is as previously defined (i.e. a substituent that is
chosen to afford upon pyrolysis a large amount of black bodies), X
is a structural unit comprising one or more elements, s is given by
the remaining-valences of X, and t is at least 1. Examples of
synergist H are aryl-substituted siloxanes, silanes,
silsesquioxanes, phosphine oxides, phosphonates, phosphazenes, and
their oligomers or polymers.
[0046] The present invention also includes a method of providing a
mark onto a polymer substrate, the method comprising (1) providing
a composition of the invention, and (2) exposing the composition to
an excimer laser to pyrolyze a substituent of the synergist and
produce black material for a mark.
[0047] The invention is illustrated by the following examples, in
which Examples 20, 23, 31, 32, and 33 are comparative examples.
Melt-Processible Compositions
EXAMPLE 1 to 30
[0048] The formulations set forth in Table I were prepared and
granulated or pelletized using the ingredients described in Tables
II (in which "MFR" means melt flow rate as identified by the
manufacturer), III, and IV, and following the procedures set forth
below. Table I lists the total % coating as a percentage of the
amount of pigment, as determined by [weight % coating/(weight %
coating+weight % pigment)], as well as the total amount of pigment
present in the composition by weight of the total composition.
EXAMPLE 1
[0049] The polymer was introduced into a 250 cc Brabender mixing
bowl heated to about 350.degree. C. and melted. The DPOSS was added
to the polymer and mixed, then the TiO.sub.2 pigment was added and
mixed. The composition was removed from the mixing bowl, cooled,
and granulated. The granulated composition was then extruded at a
temperature of about 375-385.degree. C., using a 25.4 mm extruder
having a length/diameter ratio of 24:1, over a 20 AWG nickel-coated
copper 19 strand wire to give a wall thickness of about 0.20 mm
(0.008 inch). Samples of each extruded wire were then laser marked.
AU laser marking was conducted by Spectrum Technologies PLC (UK),
using a Capris 100 XeCl excimer laser at 308 nm wavelength with 800
mJ/cm.sup.2 fluence. The contrast measurements were also conducted
by Spectrum, using a Capris CMS2 system. The contrast, expressed as
a percent, is the difference between the reflectance of the mark
and the background on which the mark is placed.
EXAMPLE 2
[0050] The procedure of Example 1 was followed, except that after
the polymer was melted, the TiO.sub.2 was then added, followed by
the DPOSS. Comparison of the contrast data of Examples 1 and 2
showed that the addition of the coating material after the pigment
produced higher contrast.
EXAMPLE 3
[0051] Dodecaphenyl POSS was heated at 385.degree. C. for one hour
to render it infusible and more soluble in toluene. This material
was then dissolved in toluene. Two parts of Kronos 2078 TiO2 to I
parts of DPOSS were mixed in the DPOSS/toluene solution and
stirred; the toluene was removed by heating above its boiling point
The resulting coated TiO.sub.2 was ground to 200 mesh screen size,
added to melted polymer, and mixed, cooled, and granulated. The
composition was then extruded as in Example 1.
EXAMPLE 4
[0052] Following the procedure of Example 3, DPOSS-coated TiO.sub.2
was prepared in a ratio of 4 parts TiO.sub.2 to 1 part DPOSS. The
procedure of Example 1 was then followed.
EXAMPLE 5
[0053] Following the procedure of Example 3, DPOSS-coated TiO.sub.2
was prepared in a ratio of 8 parts TiO.sub.2 to 1 part DPOSS. The
procedure of Example 1 was then followed.
EXAMPLE 6
[0054] Following the procedure of Example 3, DPOSS-coated TiO.sub.2
was prepared in a ratio of 16 parts TiO.sub.2 to 1 part DPOSS. The
procedure of Example 1 was then followed.
EXAMPLE 7 to 12
[0055] Following the procedure of Example 2, the TiO.sub.2 was
added to the melted polymer, followed by the DPOSS. The procedure
of Example 1 was then followed except that the extrusion was
conducted at about 400.degree. C.
EXAMPLE 13
[0056] 100 parts Kronos 2078 TiO.sub.2 and 25 parts of
phenyltrimethoxy silane (CP0330) were used. The phenyltrimethoxy
silane was prehydrolyzed by adding 3 moles of water to each mole of
silane. HCl was then added reach a pH of 2. Ethanol was added while
vigorously stirring the mixture until a single phase resulted. The
mixture was covered and stirred for 3 hours. A slurry of the
TiO.sub.2 in water was prepared and the prehydrolyzed silane was
added and mixed well. The mixture was heated at 100.degree. C. in a
forced air oven until it was dry, then the dried, treated TiO.sub.2
was broken into small pieces, was jet milled to about 8.5 .mu.m
average particle size, and then ground cryogenically. 1.75% by
weight of the ground pigment was added to the melted polymer, and
mixed (at about 370.degree. C.), granulated, and extruded (at about
400.degree. C.) as in Example 1.
EXAMPLE 14
[0057] The procedure of Example 13 was followed to prepare the
phenyltrimethoxy silane-coated TiO.sub.2, except that the dried
treated pigment was ground to pass through a 200 mesh sieve. The
ground pigment was mixed at 360.degree. C., and then granulated and
extruded (at 385.degree. C.) as in Example 1.
EXAMPLE 15
[0058] Kronos 2078 was coated with Gelest SST-3P01
polyphenylsilsequioxane (PPSQ) in a ratio of 4:1 TiO.sub.2:PPSQ by
the following method. A 5-liter, 3-neck round bottom flask was-
equipped with a mechanical stirrer, a dropping funnel, two
thermometers, a distillation unit via a trap, and an electric
heating mantle mounted on jack. The reaction system was
continuously purged with nitrogen. The reactor was charged with
1200 ml of deionized water and, with the stirrer turned on, 300 g
of TiO.sub.2 was added at room temperature. The suspension was
stirred at room temperature for 2 hours. Separately, 75 g of PPSQ
were dissolved in about 175 ml of toluene. This solution was added
via a dropping funnel to the well-stirred suspension of the
TiO.sub.2 within 20 minutes; residual PPSQ in the dropping funnel
was rinsed over with about 20 ml of toluene. The resultant
suspension-emulsion was stirred at room temperature for about 2
hours, then the temperature was increased to about 90.degree. C. to
distill the toluene/water (80/20, wt/wt) azeotrope (nominal boiling
point: 85.degree. C.). In order to minimize foam from forming there
was a relatively large unused reactor volume and the addition of
about 5 ml of deionized water near the end of the azeotropic
distillation (which suppressed foaming to some extent). In addition
the trap prevented the foam from entering the distillation unit.
Increasing the nitrogen flow at the end of the distillation and
keeping the pot temperature at or below 90.degree. C. facilitated
the removal of residual toluene. Then, 1.75 g of concentrated
ammonia, dissolved in about 30 ml of deionized water, was added to
catalyze the crosslinking of the PPSQ coating on the titanium
dioxide particles and to minimize agglomeration during the
subsequent product drying. The heating was turned off, while
maintaining stirring until the reaction slurry had cooled to room
temperature. The slurry was centrifuged at 10,000 rpm for 0.5 hour
and the turbid. supernatant fluid was decanted from the centrifuge
cake, which was then dried for >1 hour at 100.degree. C. to
afford a soft powder. This powder was further dried at 150.degree.
C. and 200.degree. C. (to complete the crosslinking) for one hour
each under a nitrogen purge to afford 357 g of product. Scanning
electron microscopy showed a uniformly coated powder. The powder
was then jet milled to a finer particle size, was added to the
melted polymer, and was mixed, granulated, and extruded (at
385.degree. C.) as in Example 1.
EXAMPLE 16
[0059] 8.7 gms of Kronos 2078 and 8.7 gms of polyphenyl POSS
(Hybrid Plastics PM 1270) were dissolved in 500 ml of toluene. The
toluene was removed by heating and the resultant material was dried
in a vacuum oven at 200.degree. C. for one hour. The dried material
was ground by mortar and pestle to give a relatively coarse powder
having a ratio of 1:1 TiO.sub.2:PPOSS. The PPOSS-coated TiO.sub.2
was added to the melted polymer, mixed (at 365.degree. C.),
granulated, and extruded (at 375.degree. C.) as in Example 1.
EXAMPLE 17
[0060] Following the procedure of Example 13, 100 parts Kronos 2078
TiO2 and 10 parts of phenyltrimethoxy silane (CP0330.) were used to
prepare a treated TiO.sub.2 which was ground to pass through a 200
mesh sieve. 1.1% by weight of the ground pigment was then added to
the melted polymer, and mixed (at about 350.degree. C.),
granulated, and extruded as in Example 1.
EXAMPLE 18
[0061] Following the procedure of Example 13, 100 parts Kronos 2078
TiO2 and 20 parts of phenyltrimethoxy silane (CP0330.) were used to
prepare a treated TiO.sub.2 which was ground to pass through a 200
mesh sieve. 1.2% by weight of the ground pigment was then added to
the melted polymer, and mixed (at about 350.degree. C.),
granulated, and extruded as in Example 1.
EXAMPLE 19
[0062] Following the procedure of Example 2, the TiO.sub.2 was
added to the melted polymer, followed by the DPOSS. The procedure
of Example 1 was then followed except that the extrusion was
conducted at about 400.degree. C.
EXAMPLE 20 (COMPARATIVE)
[0063] 25% by weight Kronos 2078 TiO2 and 75% by weight Dyneon PFA
8502 UHP were fed together into a 27 mm corotating Leistritz twin
screw extruder heated to about 380.degree. C. and
compounded/pelletized to form a masterbatch (Masterbatch 1). 4% by
weight of the masterbatch and 96% by weight of Dyneon PFA8502 UHP
were dry-blended and extruded at 400.degree. C. as in Example
1.
EXAMPLE 21
[0064] 93.02% by weight of Masterbatch 1 of Example 20 was fed into
the Leistritz extruder along with 6.98% by weight DPOSS and
compounded/palletized to form Masterbatch 2. 4.3% by weight of
Masterbatch 2 and 95.7% by weight of Dyneon PFA 8502 UHP were
dry-blended and extruded at 400.degree. C. as in Example 1.
EXAMPLE 22
[0065] The same procedure was followed as for Example 21, except
that the dry-blended material was extruded at 400.degree. C. over a
24 AWG nickel-coated copper 19 strand wire to give a wall thickness
of about 0.20 mm (0.008 inch).
EXAMPLE 23 (COMPARATIVE)
[0066] TiO.sub.2 was added to the melted polymer and the mixture
was mixed (at 370.degree. C.), granulated, and extruded as in
Example 1.
EXAMPLES 24 to 27
[0067] Prior to compounding, the DPOSS was heat-treated at
200.degree. C. for 1.5 hours to remove solvent. Following the
procedure of Example 2, the TiO.sub.2 was added to the melted
polymer, followed by the heat-treated DPOSS. The mixture was then
mixed, cooled, granulated, and extruded as in Example 1.
EXAMPLE 28
[0068] Following the procedure of Example 2, TiO2 was added to the
melted polymer, followed by DPOSS, and then 0.75% of Wilson FEP
blue color concentrate. The mixture was mixed, granulated, and
extruded as in Example 1.
EXAMPLES 29 and 30
[0069] Following the procedure of Example 2, TiO2 was added to the
melted polymer, followed by DPOSS, and the mixture was mixed,
granulated, and extruded as in Example 1. The use of normal purity
FEP, rather than high purity FEP, resulted in lower contrast.
1 TABLE I Polymer Coating Pigment Example Type % Type % Type % %
Coating % Pigment Contrast % 1 PFA1 98.0 DPOSS1 1 TiO.sub.21 1 50 1
81.4 2 PFA1 98.0 DPOSS1 1 TiO.sub.21 1 50 1 87.7 3 PFA1 98.5 DPOSS1
0.5 TiO.sub.22 1 33 1 89.5 4 PFA1 98.8 DPOSS1 0.24 TiO.sub.23 0.96
20 0.96 87.2 5 PFA1 98.87 DPOSS1 0.13 TiO.sub.24 1 11 1 82.3 6 PFA1
98.94 DPOSS1 0.06 TiO.sub.25 1 5.9 1 81.5 7 PFA2 98.3 DPOSS1 0.2
TiO.sub.21 1.5 11.8 1.5 83 8 PFA2 98.2 DPOSS1 0.3 TiO.sub.21 1.5
16.7 1.5 85 9 PFA2 98.1 DPOSS1 0.4 TiO.sub.21 1.5 21 1.5 86 10 PFA2
97.7 DPOSS1 0.3 TiO.sub.21 2.0 13 2 82 11 PFA2 98.2 DPOSS1 0.3
TiO.sub.26 1.5 16.7 1.5 84 12 PFA2 98.2 DPOSS1 0.3 TiO.sub.27 1.5
16.7 1.5 75 13 PFA3 98.25 PhS 0.35 TiO.sub.28 1.4 20 1.4 76 14 PFA4
98.8 PhS 0.24 TiO.sub.28 0.96 20 0.96 71 15 PFA2 98.33 PPSQ 0.33
TiO.sub.29 1.34 20 1.34 77 16 PFA1 98.0 PPOSS 1 TiO.sub.210 1 50 1
79 17 PFA1 98.9 PhS 0.1 TiO.sub.211 1 9.1 1 78 18 PFA1 98.8 PhS 0.2
TiO.sub.212 1 16.7 1 80 19 PFA5 98.3 DPOSS1 0.5 TiO.sub.21 1.2 29.4
1.2 88 20 PFA3 99.0 -- 0 TiO.sub.21 1 0 1 53 21 PFA3 98.7 DPOSS1
0.3 TiO.sub.21 1 23 1 76 22 PFA3 98.7 DPOSS1 0.3 TiO.sub.21 1 23 1
74 23 FEP1 99.0 -- 0 TiO.sub.21 1 0 1 56 24 FEP2 98.0 DPOSS2 1
TiO.sub.21 1 50 1 89 25 FEP3 98.0 DPOSS2 1 TiO.sub.21 1 50 1 81 26
FEP1 98.0 DPOSS2 1 TiO.sub.21 1 50 1 82 27 FEP1 98.4 DPOSS2 0.6
TiO.sub.21 1 37.5 1 77 28 FEP1 97.25 DPOSS2 1 TiO.sub.21 1 50 1 80
29 FEP4 98.4 DPOSS2 0.6 TiO.sub.21 1 37.5 1 63 30 FEP4 97.4 DPOSS2
0.6 TiO.sub.21 2 23.1 2 62
[0070]
2TABLE II Component Designation Manufacturer Comments
Perfluoroalkoxy resins PFA1 PFA 440 HPB DuPont High purity,
fluorine end-capped; MFR 14 PFA2 PFA 445 HP DuPont High purity,
fluorine end-capped; MFR 5 PFA3 8502 UHP Dyneon High purity,
fluorine end-capped; MFR 2 PFA4 PFA 340 DuPont Normal purity; MFR
14 PFA5 PFA 950 HP DuPont High purity, fluorine end-capped; PEVE
comonomer; MFR 1.7-3.0 Fluorinated ethylene/propylene copolymers
FEP1 FEP 5100J DuPont High purity, end capped; MFR 22 FEP2 FEP 100J
DuPont High purity, end capped; MFR 6.6 FEP3 FEP 100 DuPont Normal
purity; MFR 6.6 FEP4 FEP 5100 DuPont Normal purity; MFR 22
[0071]
3TABLE III Component Designation Manufacturer Comments DPOSS1
MS0802 Hybrid Dodecaphenyl polyhedral Plastics oligomeric
silsequioxane; cage structure; initial particle size .about.120
.mu.m; (C.sub.6H.sub.5SiO.sub.1.5).sub.12 DPOSS2 DPOSS1
heat-treated at 200.degree. C. for 1.5 hours to remove solvent. PhS
CP0330 Sivento Inc. Phenyltrimethoxy silane PPSQ SST-3P01 Gelest
Polyphenyl silsesquioxane; ladder structure PPOSS PM1270 Hybrid
Polyphenyl Plastics polyhedral oligomeric silsesquioxane; cage
structure in a polymer chain; initial particle size .about.40
.mu.m
[0072]
4TABLE IV Component Designation Manufacturer Comments TiO.sub.2
TiO.sub.21 2078 Kronos Rutile; no coating; particle size
.about.0.27 .mu.m TiO.sub.22 2:1 2:1 Kronos 2078:DPOSS1 TiO.sub.23
4:1 4:1 Kronos 2078:DPOSS1 TiO.sub.24 8:1 8:1 Kronos 2078:DPOSS1
TiO.sub.25 16:1 16:1 Kronos 2078:DPOSS1 TiO.sub.26 AHR-F Huntsman
Anatase; some organic coating; crystal size .about.0.13 .mu.m
TiO.sub.27 TiPure R103 DuPont Rutile; 0.25% organic treatment; 3.2%
alumina; particle size .about.0.23 .mu.m TiO.sub.28 4:1 4:1 Kronos
2078:PhS (CP0330) TiO.sub.29 4:1 4:1 Kronos 2078:XLPPSQ TiO.sub.210
1:1 1:1 Kronos 2078:phenyltrimethoxy silane TiO.sub.211 10:1 10:1
Kronos 2078:PhS (CP0330) TiO.sub.212 5:1 5:1 Kronos 2078:PhS
(CP0330) TiO.sub.213 TiPure R100 DuPont Rutile; 0.2% organic
treatment; 1.7% alumina; particle size .about.0.32 .mu.m
TiO.sub.214 Tiona RCL-4 Millennium Rutile; 97% TiO.sub.2 minimum;
alumina and Inorganic organic coating; particle size .about.0.27
.mu.m Chemicals TiO.sub.215 2:1 2:1 Kronos 2078:XLPPSQ
[0073] PTFE Tape Wrapped Samples
EXAMPLES 31 TO 38
[0074] Unsintered PTFE tapes were prepared by the following
process: the designated TiO.sub.2 pigment as shown in Table V was
jet-milled to reduce the particle size, and was then added to the
PTFE (613A, available from DuPont) in a low shear mixing process,
followed by a high shear mixing process to enhance the dispersion
of the pigment. A lubricant was added to the PTFE/pigment mixture
under low shear mixing conditions. Preforms of the lubricated
PTFE/pigment mixture were prepared, followed by aging, ram
extrusion into tape form, and calendaring to a desired thickness.
Lubricant was then removed by heat-treatment below 250.degree. C.,
and the tape was slit to the desired width.
[0075] One or more unsintered PTFE tapes were wrapped over
nickel-copper wire wrapped with mica tape using an EJR tape
wrapper. The mica tape was prepared as described in Example 4 of
U.S. application Ser. No. 09/587,229 (Nyberg et al.) and
International Publication No. WO 00/74075 (Tyco Electronics
Corporation et al.), the disclosure of which is incorporated herein
by reference. The PTFE insulation was sintered at a temperature of
380 to 400.degree. C. for a period of about I minute. The outer
diameter of the completed conductor, as well as the contrast
measured as described in Example 1, are shown in Table V. The
percent coating and pigment numbers in Table V refer only to the
outermost layer of the conductor if more than one polymer layer is
present.
5 TABLE V Outer Coating Pigment Wire Diameter Contrast Example Type
% Type % (AWG) (mm) % 31 -- 0 TiO.sub.213 4 20 1.42 69.6 32 -- 0
TiO.sub.214 4 20 1.45 60.2 33 -- 0 TiO.sub.214 4 24 1.22 66.0 34
PPSQ 0.33 TiO.sub.215 1.34 24 1.24 86.0 35 PPSQ 0.33 TiO.sub.215
1.34 24 1.23 86.0 36 PPSQ 0.24 TiO.sub.29 0.96 24 1.23 76.0 37 PPSQ
0.33 TiO.sub.215 1.34 20 1.33 77 38 PPSQ 0.33 TiO.sub.215 1.34 20
1.47 81
EXAMPLE 31 (COMPARATIVE)
[0076] Mica tape was wrapped on the wire with 50% overlap. Two
layers of 0.051 mm (0.002 inch) thick commercial PTFE tape (DuPont
613 A) containing 4% TiPure R100 TiO.sub.2 were overlapped 52%.
EXAMPLE 32 (COMPARATIVE)
[0077] Mica tape was wrapped on the wire with 50% overlap. Three
layers of 0.038 mm (0.0015 inch) thick commercial PTFE tape (DuPont
613 A) containing 4% RCL-4 TiO.sub.2 were overlapped 52%.
EXAMPLE 33 (COMPARATIVE)
[0078] Mica tape was wrapped on the wire with 50% overlap. Two
layers of 0.076 mm (0.003 inch) thick commercial PTFE tape (DuPont
613A) containing 4% of RCL-4 TiO.sub.2 were overlapped 52%.
EXAMPLE 34
[0079] Using the procedure described in Example 15, Kronos 2078 was
coated with Gelest SST-3P01 polyphenylsilsequioxane (PPSQ) in a
ratio of 2:1 TiO.sub.2:XLPPSQ. This coated pigment was used to
prepare an unsintered 0.076 mm (0.003 inch) thick PTFE tape
containing 2% by weight of the coated pigment, by the process
described above. A conductor was prepared by wrapping mica tape on
the wire with 50% overlap. A first layer of the unsintered PTFE
tape was overlapped 52%, and a second identical unsintered PTFE
tape was placed over the first PTFE layer and overlapped 52%.
EXAMPLE 35
[0080] Mica tape was wrapped on the wire with 50% overlap. A first
layer of 0.076 mm (0.003 inch) thick commercial PTFE tape (DuPont
613 A) containing 4% of RCL-4 TiO2 was overlapped 52%, and covered
with a layer of the 0.076 mm (0.003 inch) PTFE tape containing 2%
by weight of the coated pigment described in Example 34 having 52%
overlap.
EXAMPLE 36
[0081] Kronos 2078 was coated with Gelest SST-3P01
polyphenylsilsequioxane (PPSQ) in a ratio of 4:1 TiO.sub.2:XLPPSQ
as described in Example 15, and 1.25% by weight of the coated
pigment was mixed with PTFE to prepare an unsintered 0.076 mm
(0.003 inch) thick PTFE tape. A conductor was prepared by wrapping
mica tape on the wire with 50% overlap. The mica tape was covered
by first and second layers of the unsintered 0.076 mm (0.003 inch)
thick PTFE tape, each overlapped 52%.
EXAMPLE 37
[0082] Mica tape was wrapped on the wire with 50% overlap. It was
covered with one layer of the 0.076 mm (0.003 inch) PTFE tape
containing 2% by weight of the coated pigment described in Example
34, and overlapped 52%. The contrast was lower with a single layer
of PTFE tape than with two layers, as compared with Example 35.
EXAMPLE 38
[0083] Mica tape was wrapped on the wire with 50% overlap. It was
covered with one layer of the 0.076 mm (0.003 inch) PTFE tape
containing 2% by weight of the coated pigment described in Example
34, and overlapped 69%. Increased wall thickness (resulting from
the increased overlap) produced higher contrast, as shown by
comparing Examples 37 and 38.
[0084] Heat Aging of Marked Samples
[0085] Heat aging was conducted on laser-marked samples at the
temperatures and for the times indicated in Table VI. Examples 31
and 32 are comparative examples. Even after heat-aging,
compositions of the invention showed high contrast
6TABLE VI Initial Contrast Aging T Aging time Aged Contrast Example
(%) (.degree. C.) (hours) (%) 11 83 310 24 82 12 75 310 24 72 13 76
310 24 68 19 88 310 3 90 310 6 89 310 12 86 310 24 83 31 70 290 168
65 290 336 65 260 677 65 32 60 290 168 40 290 678 37 260 678 37 35
86 310 24 73 37 77 310 24 69 38 81 310 24 75
* * * * *