U.S. patent application number 14/531150 was filed with the patent office on 2015-02-19 for compositions for compounding, extrusion and melt processing of foamable and cellular fluoropolymers.
The applicant listed for this patent is Cable Components Group, LLC. Invention is credited to Kenneth R. Boyle, Charles A. Glew, Jeffrey A. Hrivnak, Bradley Lane Kent.
Application Number | 20150051303 14/531150 |
Document ID | / |
Family ID | 40100245 |
Filed Date | 2015-02-19 |
United States Patent
Application |
20150051303 |
Kind Code |
A1 |
Glew; Charles A. ; et
al. |
February 19, 2015 |
COMPOSITIONS FOR COMPOUNDING, EXTRUSION AND MELT PROCESSING OF
FOAMABLE AND CELLULAR FLUOROPOLYMERS
Abstract
The present invention relates generally to the use of talc as a
chemical foaming agent in perfluoropolymers to form foamable and
foamed compositions. For example, in one aspect, a foamable
composition is disclosed, which comprises (i) one or more base
perfluoropolymers comprising at least 50 percent by weight of the
composition, and (ii) talc blended with the one or more base
perfluoropolymers, where the talc comprises 3 percent to about 15
percent by weight of the composition. Each of the perfluoropolymers
is selected from the group consisting of
tetrafluoroethylene/perfluoromethylvinyl ether copolymer (MFA),
hexafluoropropylene/tetrafluoroethylene copolymer (FEP) and
perfluoroalkoxy (PFA) and any blend thereof, where
hydrogen-containing fluoropolymers are absent from the composition.
The one or more base perfluoropolymers are melt-processable at one
or more elevated processing temperatures of at least about
600.degree. F. at which the talc functions as a chemical foaming
agent for extrusion or mold processing of the composition into a
foamed article having uniform cell structures.
Inventors: |
Glew; Charles A.;
(Charlestown, RI) ; Boyle; Kenneth R.; (Freehold,
NJ) ; Kent; Bradley Lane; (Woolrich Township, NJ)
; Hrivnak; Jeffrey A.; (Arese, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cable Components Group, LLC |
Pawcatuck |
CT |
US |
|
|
Family ID: |
40100245 |
Appl. No.: |
14/531150 |
Filed: |
November 3, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13632560 |
Oct 1, 2012 |
8877823 |
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14531150 |
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13109532 |
May 17, 2011 |
8278366 |
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13632560 |
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12221280 |
Aug 1, 2008 |
7968613 |
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13109532 |
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60963322 |
Aug 3, 2007 |
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60953729 |
Aug 3, 2007 |
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Current U.S.
Class: |
521/91 |
Current CPC
Class: |
C08J 2327/20 20130101;
H01B 7/02 20130101; Y10T 428/249976 20150401; H01B 13/06 20130101;
Y10T 428/2929 20150115; C08J 9/08 20130101; C08J 2327/18 20130101;
H01B 13/148 20130101; C08J 9/06 20130101; Y10T 428/249977 20150401;
C08J 2203/18 20130101; C08J 2203/02 20130101; H01B 7/0275 20130101;
C08J 2327/16 20130101; C08J 2207/06 20130101; C08J 2327/12
20130101; C08J 2429/10 20130101; C08J 9/12 20130101; H01B 3/445
20130101; C08J 9/0066 20130101 |
Class at
Publication: |
521/91 |
International
Class: |
C08J 9/06 20060101
C08J009/06 |
Claims
1-20. (canceled)
21. A method for manufacturing a foamed article comprising: heating
a composition comprising a melt-processable perfluoropolymer and
talc to a processing temperature of at least 600.degree. F. at
which said talc functions as a chemical foaming agent, thereby
causing the foaming of said composition at a foaming rate in a
range from 20% to 50% so as to form a foamed article, wherein said
talc comprises about 2 percent to 3 percent by weight of said
composition; wherein said melt-processable perfluoroploymer is
selected from the group consisting of
tetrafluoroethylene/perfluoromethylvinyl ether copolymer (MFA),
hexafluoropropylene/tetrafluoroethylene copolymer (FEP),
perfluoroalkoxy (PFA) and any blend thereof, wherein said talc is
the only foaming agent in said composition and wherein said foaming
is achieved without gas injection, and wherein hydrogen-containing
fluoropolymers are absent from the composition.
22. The method of claim 21, wherein said processing temperature is
in a range of about 600.degree. F. to about 660.degree. F.
23. The method of claim 21, wherein said processing temperature is
in a range of about 630.degree. F. to about 660.degree. F.
24. The method of claim 21, wherein said processing temperature is
in a range of about 640.degree. F. to about 660.degree. F.
25. The method of claim 21, wherein said talc comprises recycled
talc.
26. The method of claim 21, wherein said perfluoropolymer comprises
recycled perfluoropolymer.
27. The method of claim 21, wherein said foamed article comprises
any of a separator, wire insulation or cable jacketing.
28. The method of claim 21, further comprising extruding said
foaming composition to form said foamed article.
29. The method of claim 21, further comprising mold processing said
foaming composition to form said foamed article.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/221,280, titled, "Compositions for
Compounding, Extrusion and Melt Processing of Foamable and Cellular
Fluoropolymers", filed 1 Aug. 2008, which claims priority to U.S.
Provisional Application No. 60/963,322, filed Aug. 3, 2007 and
titled: "Compositions for Compounding and Extrusion of Foamed
Fluoropolymers for Wire and Cable Applications" and U.S.
Provisional Application No. 60/953,729, filed Aug. 3, 2007 and
titled: "Perfluoropolymer Foamable Composition," each of which is
hereby expressly incorporated by reference in its entirety.
FIELD OF INVENTION
[0002] Wire and cable applications, especially those using copper
conductors, utilize the insulative properties of specific polymers
over the conductors as insulation and over the entire cable core of
insulated conductors as jackets. Cable fillers of varying shapes
and size are used as well for their insulative properties and more
specifically in communications designs to minimize pair-to-pair
crosstalk within a cable as will as mitigating crosstalk between
adjacent cables which is commonly referred to as "alien crosstalk."
Jackets and cable fillers provide mechanical and physical
properties as well as an ever evolving requirement for enhanced
fire performance i.e. (reduced flame spread, ignitability, and
smoke evolution.) These mechanical, physical and fire retardancy
performance requirements apply to fiber optic cables as well. Cable
design demands a balance of these performance requirements and the
attributes of processing cellular foam improves both insulation
values e.g. (lower crosstalk in communications cables) while
lowering material content and therefore the amount of combustible
materials used in a cable. These added performance characteristics
through cellular or microcellular foaming can additionally lower
cost of the overall cable design. This application relates to
perfluoropolymer compositions suitable for wire insulation, cable
fillers (e.g. crossweb, tapes, tubes) and cable jacketing for
communication cables that are run through air plenums.
BACKGROUND OF INVENTION
[0003] Communication cables have evolved continuously over the
years as we have evolved from a voice-based telecommunication
network environment to the new structured cabling designs for
high-speed data transmission which are commonly referred to as
Local Area Networks or LAN's. Technical requirements, standards and
guidelines of the Telecommunication Industry Association and
Electronic Industry Association (TIA/EIA) and International
Standard Organization (ISO) have been developed and published to
support high-speed data communication of voice, internet and video.
In addition, these requirements continue to evolve with more and
more stringent electrical performance needs such that cellular foam
insulation and fillers play an increasing role in the cable
designs. The primary communications cable designs incorporate
twisted copper pairs together to form a balanced transmission line,
coaxial cables, and fiber optic cables. All of these cables may be
run in a network of a building (LAN's) as separate functional
cables or in hybrid or combination cable design.
[0004] Furthermore, TIA/EIA has defined standards that are
published and recognized as well as industry drafts of soon-to-be
published standards for commercial building telecommunication
networks. Table 1, which follows, provides those published and
pending, or soon-to-be adopted and published Technical Service
Bulletin "TSB" standards.
TABLE-US-00001 TABLE 1 TIA/EIA Standards Category 5e Frequency
ANSI/TIA/EIA-568-A ISO Class D Bandwidth Commercial Building 1 to
100 mhz Telecommunications Standard Part 2: Balanced Twisted Pair
Cabling Component; 2001 Category 6 Frequency ANSI/TIA/EIA-568-B.2-1
ISO Class E Bandwidth Commercial Building 1 to 250 mhz
Telecommunications Standard Part 2: Addendum 1: Transmission
Specification for 4 pair 100 ohm Category 6 Cabling; 2002 Category
6A Frequency ANSI/TIA/EIA-568-B.2-10 ISO Class E.sub.A Bandwidth
Commercial Building 1 to 500 mhz Telecommunications Standard Part
2: Addendum 10: Transmission Specification for 4 Pair 100 ohm
Augmented Category 6 Cabling; TSB pending publication Category 7
Frequency TIA not actively developing standard; ISO Class F
Bandwidth ISO/EIA-11801, 2.sup.nd Ed. Information 1 to 600 mhz
Technology - Generic Cabling for Customer Premises, 2002
[0005] Each of the standards of Table 1 illustrate continued
widened bandwidth enabling greater data transmission. The
broadening of communication cable bandwidth enhances the electrical
characteristics or data bit rate based on the evolving needs of
software, hardware and video transmission. The terminology within
the standards for testing can be defined as electrical performance
within the cable as measured by impedance, near end and far end
crosstalk (NEXT & FEXT), attenuation to crosstalk ratio (ACR),
ELFEXT, ELNEXT, Power Sum, etc., and the electrical performance
that may be transferred to the adjacent cable a.k.a. (alien cross
talk) which are measured within similar performance parameters
while incorporating a power sum alien cross talk requirement.
[0006] Electromagnetic noise that can occur in a cable that runs
alongside one or more cables carrying data signals can create alien
crosstalk. The term "alien" arises from the fact that this form of
Crosstalk occurs between different cables in a group or bundle,
rather than between individual wires or circuits within a single
cable. Alien Crosstalk can be particularly troublesome because of
its effect on adjacent 4 pair cables which degrades the performance
of a communications system by reducing the signal-to-noise
ratio.
[0007] Traditionally, alien crosstalk has been minimized or
eliminated by aluminum Mylar.sup.R shields and/or braid in shielded
cable designs i.e. (Category 7 or ISO Class F shielded designs) to
prevent electromagnetic fields from ingress or egress from the
cable or cables. The use of foamed or blown constructions for
symmetrical and asymmetrical airspace designs further improve
electrical performance characteristics in that the overall modulus
and elasticity of the resulting foamable compounds are reduced
leading to final conformations that more closely approach optimal
geometries. Specifically, the ability to form inner structures of
cables such that these inner structures have little or no plastic
memory once the cabling process is completed, ensures that the
nested pairs remain in the desired geometric configuration and that
the use of foamed fillers, insulations and jackets using air as an
insulator act to mitigate alien crosstalk in Unshielded Twisted
Pair (UTP) designs i.e. (Category 6 or ISO Class E and Category 6
Augmented or ISO Class E.sub.A).
[0008] Further developments have also recently embraced the cable
fillers components, designed either to prevent cross-talk or alien
cross-talk. As the TIA electrical requirements have moved from
Augmented Cat. 6 to Augmented Cat. 6a, the electrical requirements
also of the cable fillers materials are becoming more and more
critical. Therefore the cable fillers are moving to
perfluoropolymers such as FEP and TFE/perfluoroalkylvinylether
copolymers to meet the attenuation requirements. As previously
mentioned, the cable fillers' (like cross-webs') main function is
to prevent cross-talk between the pairs.
[0009] More and more cables (for instance for data transmission
between computers, voice communications, as well as control signal
transmission for building security, fire alarm, and temperature
control systems) are often installed in the air return space above
the suspended ceiling without the use of metal conduits.
Combustible materials (insulating or jacketing materials as well as
fillers from cables) are thus accumulating in plenums in
ever-increasing amounts.
[0010] While solutions for implementing physical foaming have been
largely proposed in the past, this technology requires complex
extrusion lines and accurate control of feeding of foaming agents.
Standard equipments of LAN cables manufacturers cannot be
efficiently retrofitted to produce foamed components by physical
foaming. Intensive capital expenditure and increased operational
costs are thus related to the implementation of physical foaming
technologies. Moreover, fine cells are difficult to be obtained in
foamed materials by physical foaming.
[0011] U.S. Pat. No. 6,064,008 discloses communication cables is
provided having at least one elongate electrical conductor
surrounded by a layer of insulating material, said layer including
a chemically blown fluorinated polymer having a melting point of
greater than about 480.degree. F. The fluorinated polymer is
preferably a high melting fluorinated polymer and is chemically
blown by a blowing agent such as the barium salt of
5-phenyltetrazole. Nevertheless, this process requires the use of
highly costly chemical blowing agent; also, due to the low thermal
stability of the same, accurate control of processing is required
for obtaining suitable foaming of the fluoropolymers having high
melting point.
[0012] The designers of the first plenum cables used
perfluoropolymers, the best available fire resistant and low smoke
producing materials at the time. The first plenum cables listed had
Fluorinated Ethylene Propylene (FEP) insulation and jackets,
basically the same materials used today to meet the NFPA 262 or the
limited combustible listing requirements of 25/50/8. Nevertheless,
electrical performances of FEP are limited: even if bare FEP could
be used, materials with improved electrical performance are desired
to give more freedom with their design and give companies cables
with a competitive advantage exceeding the minimum standards.
Actually FEP bare or virgin material is hardly suitable for the
manufacture of all parts of cables such as those for Gigabit
Ethernet and future higher speed LAN applications, e.g. those
complying with transmission requirements of ANSI/TIA/EIA 568-B.2,
Addendum 1, Category 6 (so-called "category 6-cables"). Use of
recycled FEP and other polymers for wire and cable and filler
materials thereof can be utilized to improve properties and
mitigate costs.
[0013] These Electrical Performance Standards especially for UTP
cables (Category 5e, 6, 6A and 7) necessitate improved insulative
performance wherein foamed perfluoropolymers optimize their
inherently excellent insulative values i.e. (dielectric constant
and dissipation factor.)
[0014] Foamed perfluoropolymers also offer lower cost and lower
material content while improving fire retardancy performance by
lowering the amount of combustible material in a cable and the
overall fire load of Local Area Network cables within a
building.
[0015] The Applicant has demonstrated that melt-processable
per(halo)fluoropolymers, including FEP, PFA and MFA, can be
compounded into pellets and subsequently chemically foamed via an
extrusion process. The resulting foamed extrudate therefrom, in at
least certain embodiments, would comply with the above-mentioned
fire and smoke requirements and with sheathing requirements for
next generation LAN cable.
[0016] A brief review of the Fire Performance Requirements both in
North America and Globally follows:
[0017] In 1975, the National Fire Protection Agency (NFPA)
recognized the potential flame and smoke hazards created by burning
cables in plenum areas, and adopted within the United States, the
National Electric Code (NEC), a standard for flame retardant and
smoke suppressant cables. The National Electrical Code presently
requires that such cables be either placed within a metal conduit
or be insulated with materials that result in low flame and low
smoke emission. This standard, commonly referred to as "the Plenum
Cable Standard", was later adopted for North America Communications
Cabling by Canada and Mexico. The standard permits the use of
power-limited type cables that includes communication cables
without conduit, so long as the cable exhibits low smoke and flame
retardant characteristics.
[0018] The premise of the standard is based on the concerns that
flame and smoke could travel along the extent of a building plenum
area if the electrical conductors and cable were involved and were
not flame and smoke resistant. The National Fire Protection
Association ("NFPA") developed the standard to reduce the amount of
flammable material incorporated into insulated electrical
conductors and jacketed cables. Reducing the amount of flammable
material would, according to the NFPA, diminish the potential of
the insulating and jacket materials from spreading flames and
evolving smoke to adjacent plenum areas and potentially to more
distant and widespread areas within a building. The cellular foam
fluoropolymer products of this disclosure can typically reduce the
quantity of combustible materials by 30 to 60% based on the extent
of the foaming process within insulations, fillers and jacket
materials.
[0019] Nevertheless, all these designs require the development of
improved fluoropolymer materials as cable fillers components having
improved electrical properties, and still possessing adequate
flammability properties. In order to meet the ever more stringent
fire standards (NFPA 262 and/or "LC") and to achieve electrical
performances for novel LAN structures (Cat. 6 or 6a), it would be
useful to find alternative insulation solutions which can provide
improved properties both for reducing cross-talk and smoke/flame
generation, and which enable achievement of these targets with
potential reduction in cost. It has been thus proposed to use
perfluoromaterials under the form of foams, so as to effectively
reduce the mass of potentially combustible material while
maximizing insulation and shielding performances. Basically,
foaming of a perfluoropolymer can be obtained by physical foaming,
i.e. by introduction of a suitable foaming agent (i.e. an inert
gas) in the extrusion line processing the material in the melt
state, or by chemical foaming, ie. by extrusion of a composition
comprising suitable precursors undergoing thermal decomposition at
processing temperatures so as to in situ generate the foaming agent
required to form the cellular structure.
[0020] The accumulation of combustible materials in air return
plenum spaces has caught the attention of American associations
like the National Building Code Community, the National Fire
Protection Association (NFPA) and two key groups within the NFPA
(the 90A Heating and Ventilating Group, and the 70 National
Electrical Code Group) because cables can present a larger fire
load than wall coverings or furniture. NFPA 262 standard prescribes
the methodology to measure flame travel distance and optical
density of smoke for insulated, jacketed, or both, electrical wires
and cables and optical fiber cables that are to be installed in
plenums and other spaces used to transport environmental air
without being enclosed in raceways.
[0021] The test method for measuring these characteristics is
commonly referred to as the Steiner Tunnel Test. The Steiner Tunnel
Test has been adapted for the burning of cables according to the
following test protocols: NFPA 262, Underwriters Laboratories
(U.L.) 910, or Canadian Standards Association (CSA) FT-6. The test
conditions for each of the U.L. 910 Steiner Tunnel Test, CSA FT-6,
and NFPA 262 are as follows: a 300,000 BTU/hour flame is applied
for 20 minutes to a calculated number of cable lengths based on
their diameter that fills a horizontal tray approximately 25 feet
long with an enclosed tunnel. This test simulates the horizontal
areas (ceilings) in buildings wherein these cables are run.
[0022] The pass/fail criteria require the cables to possess in the
standardized Steiner tunnel test an Average Optical Density (AOD)
(i.e. smoke) of <0.15, a Peak Optical Density (POD) (i.e. smoke)
of <0.5 and a Flame Propagation Distance (FPD) of 5 <ft.
Further, even more stringent requirements have been settled for
plenum permanent building materials so as to comply with the
"Limited Combustible" (LC) requirement. The pass/fail criteria for
materials such as wallboard and ceiling tile, which are either used
to manufacture these spaces or will be exposed to the air flow, is
controlled by the NFPA-255 and 259 tests; it is thus required to a
"Limited Combustible" (LC) material to pass the 25/50/8 test. i.e.
having a Flame Spread Rating of <25, a Smoke Developed Index of
<50 per NFPA-255 and a Potential Heat Value of <3,500 Btu/lb
(equal to 8,141 kJ/kg) per NFPA-259.
[0023] In response to the request of safer cables, manufacturers
have introduced a new plenum cable with higher fire safety
characteristics. This new classification of cable is called
"Limited Combustible Cable" and is identified by the listing mark
"Limited Combustible FHC 25/50 CMP". To evaluate cable
performances, it has appeared "logical" to apply the 25/50/8
requirements of LC materials for cables as tested per NFPA's 255
and 259. The primary difference between traditional combustible
plenum cables and the limited combustible cable is that the latter
is both insulated and jacketed with materials complying with the
25/50/8 requirements according to NFPA's 255 and 259.
[0024] Whichever is the fire safety characteristic which the plenum
cables have to comply with (either NFPA 262 or "LC"), it is clear
that a deep redesign of cable components, including materials for
both primary insulation, cable fillers and jackets, has been found
necessary.
[0025] The products of the present disclosure have alternatively
been developed to support the possible adoption of a new NFPA
standard referenced as NFPA 255 entitled "Limited Combustible
Cables" with less than 50 as a maximum smoke index and NFPA 259
entitled "Heat of Combustion" which includes the use of an oxygen
bomb calorimeter that allows for materials with less than 3,500
BTU/lb. for incorporation into cabling systems and buildings
wherein survivability of the communication network from fires is
required i.e. (military installation such as the Pentagon in
Washington D.C.).
[0026] Table 2 provides a hierarchy of fire performance standards
for North America and Europe.
TABLE-US-00002 TABLE 2 Flammability Test Methods and Level of
Severity for Wire and Cable Cable Type Test Method Ignition Source
Output Duration Limited UL2424/NFPA 8,141 KJ/kg 10 min Combustible
259/255/UL723 (3,500 BTU/lb.) CMP Steiner Tunnel 88 kW (300 k
BTU/hr.) 20 min. UL 910/NFPA 262 CMR RISER 154 kW (527 k BTU/hr.)
30 min. UL 1666/UL2424/NFPA 259 CPD Single Burning Item 30 kW (102
k BTU/hr.) 30 min. Class D (20 min burner) CPD Modified IEC 60332-3
30 kW (102 k BTU/hr.) 20 min. Class D (Backboard behind ladder
(heat impact)) CM IEC 60332-3 20.5 kW (70 k BTU/hr.) 20 min. CMX
Vertical Tray 20.5 kW (70 k BTU/hr.) 20 min. CMUC IEC
60332-1/ULVW-1 Bunsen Burner 1 min. (15 sec. Flame) Cable Fire
Performance (Levels of Severity) NFPA 255 & NFPA 259/LC/CPD
Class B1+/UL 2424 (most stringent) NFPA 262/EN 50289/FT-6/CPD Class
B1/UL 910 | UL 1666 Riser/FT-4/CPD Class C & B2 | UL 1581
Tray/IEC 60332-3/FT-2/CPD Class D | VW 1/IEC 60332-1/FT-1/CPD Class
E (least stringent)
[0027] There is thus a strong need in the art to provide for
alternative foamable perfluoropolymer compositions useful as cable
components, which can be easily processed in the melt using
conventional equipments, able to comply with the limited
combustible requirements and which possess outstanding electrical
properties, making it suitable for so-called -augmented category 6
or 6a-cables" to be used in Gigabit Ethernet and future higher
speed LAN applications.
[0028] This disclosure relates to improved materials that can be
used as wire insulation, cable fillers (e.g. crosswebs) and cable
jacketing for communication cables which are run through air
plenums without the use of a metal conduit and which notably
conform to Telecommunication Industry Association (TIA),
Underwriters Laboratories (UL) and National Electrical Code
standards.
[0029] For these applications requiring survivability from flame
spread and smoke generation, the cellular products of the present
disclosure will be an effective method for reducing material
content and the fuel load of cables in such critical
environments.
SUMMARY OF THE INVENTION
[0030] In the present disclosure the term blowing agent(s) and
foaming agent(s) are synonymous and may be used interchangeably.
The term nucleating agent(s) are used in materials that provide
sites for the formation of cells resulting from blowing agents or
gas injection
[0031] The present disclosure refers to talc as natural or
synthetic hydrated magnesium silicate. It has been discovered that
talc acts independently as a chemical blowing agent in combination
with the perfluoropolymers and fluoroplymers of the present
invention without the need for additional blowing agents or the
need for any nucleating agent. In certain cases, the talc used to
produce the fluorinated polymeric foamable products described may
act as both a chemical blowing agent and a nucleating agent.
[0032] This disclosure provides a composition, method and system
for producing foamed or blown cellular insulation articles
utilizing fluorinated polymers (either perfluoropolymers or
fluoropolymers) to create a lower cost communications cable,
conductor separator, conductor support-separator, jacketing, tape,
tube, crossweb, wrap, wire insulation and as well as a conduit tube
for individual components or several combined configurations that
exhibit improved electrical, flammability and optical
properties.
[0033] The foamable perfluoropolymers disclosed yield the inherent
benefits of reducing the amount of combustible materials within a
cable as well as enhancing electrical properties while reducing
costs. Blown, foamed or cellular perfluoropolymers or fluoropolymer
insulating jacket or filler material using a nucleating/foaming
agent of talc the chemical composition of which includes MgSiOH;
3MgO+4SiO.sub.2+H.sub.2O; MgOH+H.sub.2O+SiOH or any derivative
thereof that synergistically reacts with the perfluoropolymers at
their elevated or higher extrusion operating temperatures with or
without a chemical blowing agent or gas blowing agent are also a
portion of the subject of this disclosure. The foaming agent
properties of talc create a cellular foam ideally suited for the
requirement of Category 6 and 6A UTP fillers i.e. (crosswebs,
circular profiles, tubes and tapes) and is a highly cost effective
replacement for the traditionally used Boron Nitride which costs
approximately $60.00 per lb. versus the cost per lb. of talc of
approximately $1.00 per lb.
[0034] The cost reduction benefit due to the change from Boron
Nitride to talc is further enhanced by the fact that insulation,
jacketing and filler extrusion may be performed by a relatively
simplistic and robust chemical reaction that uses varying extrusion
temperatures to foam at various desired percentages based on
varying talc loadings. Noteworthy, under specific extrusion
conditions which are described in further detail, talc itself
"foams". Traditional foaming of perfluoropolymers has been via a
gas injection extrusion process and the use of nucleated
perfluoropolymers with Boron Nitride. The cost benefits of chemical
foaming vis-a-vis gas foaming of perfluoropolymers enable standard
high temperature extruders to run foam perfluoropolymers without
the need to port the barrel with a highly sophisticated gas valve.
The use of talc also works effectively with traditional gas
injection extrusion processes.
[0035] An added benefit of using talc is that it neutralizes the
acidity of hydrogen fluoride (HF) which may evolve during
extrusion. HF is highly acidic and causes corrosion in extrusion
barrels, screws and extrusion head, tools and dies. Traditional
metals or non-Hasteloy or Inconel surfaces cannot be used to
extrude perfluoropolymers under normal process conditions and the
use of talc significantly reduces the acidity of the HF, thus
mitigating corrosive wear on standard extrusion equipment.
[0036] The introduction of talc has the benefit of being an acid
(HF) scavenger when compounded into pellets prior to extrusion and
acts as both a nucleating as well as a foaming agent. Furthermore,
when enhanced with the addition of a pelletized perfluoropolymer
with MgCO.sub.3 and CaCO.sub.3 and AClyn.RTM. wax (a registered
trademarked wax provided by Honeywell) perfluoropolymer foaming
levels are further enhanced. This foaming agent of magnesium
carbonate and calcium carbonate may be added as a separate pellet
in a tumble blended mix or compounded together in a single
homogenous pellet of talc (MgSiOH; 3MgO+4SiO.sub.2+H.sub.2O;
MgOH+H.sub.2O+SiOH) and MgCO.sub.3/CaCO.sub.3/AClyn.RTM. wax. The
single homogenous pellet can then be extruded for insulations,
jackets, or fillers in a very simplistic chemically foamed
extrusion process for perfluoropolymers. The foaming rate from 20%
to 50% can be raised or lowered based on the percentage of each
constituent used as well as by adjustments in extrusion
temperatures.
[0037] The present disclosure also refers to talc as natural or
synthetic hydrated magnesium silicate. It has been discovered that
talc acts independently as a chemical blowing agent in combination
with the perfluoropolymers and fluoropolymers of the present
invention without the need for additional blowing agents or the
need for any nucleating agent. In certain cases, the talc is used
to produce the fluorinated polymeric foamable pellets from which
foamed products may be obtained, where the pellets contain talc
that acts as a chemical blowing agent and in some cases as a
nucleating agent when the pellets are heated and extruded.
[0038] The family of perfluoropolymers wherein these compounded
foaming and in some cases nucleating agents may be used are at
least the following:
[0039] The perfluoropolymers that are characterized here are the
melt processable materials for which this disclosure is focused:
[0040] 1. FEP (Fluorinated Ethylene Propylene) [0041] 2. PFA
(Perfluoroalkoxy) [0042] 3. MFA
(Polytetrafluoroethylene-Perfluoromethylvinylether)
[0043] It should be emphasized that the use of talc may be
independent of the use of MgCO.sub.3/CaCO.sub.3/AClyn.RTM. wax or
talc may be used in any combination with
MgCO.sub.3/CaCO.sub.3/AClyn.RTM. wax to produce the desired
foamabled compositions.
[0044] The perfluoropolymers described are a subset of
fluoropolymer resins that can be used and may include copolymers of
TFE with one or more copolymerizable monomer chosen from
perfluoroolefins having 3-8 carbon atoms and perfluoro (alkyl vinyl
ethers) (PAVE) in which the linear or branched alkyl group contains
1-5 carbon atoms. Preferred perfluoropolymers include copolymers of
TFE with at least one hexafluoropropylene (HFP) unit and one PAVE
(unit). Preferred comonomers include PAVE in which the alkyl group
contains 1-3 carbon atoms, especially 2-3 carbon atoms, i.e.
perfluoro (ethyl vinyl ether) (PEVE) and perfluoro (propyl vinyl
ether) (PPVE). Additional fluoropolymers that can be used include
copolymers of ethylene with TFE, optionally including minor amounts
of one or more modifying comonomer such as perfluorobutyl ethylene.
Representative fluoropolymers are described, for example, in ASTM
Standard Specifications D-2116, D-3159, and D-3307. Such
fluoropolymers are non-functional fluoropolymers if they have
essentially no functional groups, but are functionalized
fluoropolymers if functional groups are added, e.g., by grafting.
Alternatively or additionally, preferred fluoropolymers are
non-elastomeric, as opposed to elastomeric.
[0045] Functionalized fluoropolymers include fluoropolymers such as
those described in the foregoing paragraph and additionally
containing copolymerized units derived from functional monomers. If
the concentration of functional monomer is high enough in a TFE
copolymer, however, no other comonomer may be needed. Usually, but
not necessarily, the functional groups introduced by such monomers
are at the ends of pendant side groups. Functional monomers that
introduce pendant side groups having such functionality can have
the general formula CYZ wherein Y is H or F and Z contains a
functional group. Preferably, each Y is F and --Z is --Rf--X,
wherein Rf is a fluorinated diradical and X is a functional group
that may contain CH.sub.2 groups. Preferably, Rf is a linear or
branched perfluoroalkoxy having 2-20 carbon atoms, so that the
functional comonomer is a fluorinated vinyl ether. Examples of such
fluorovinylethers include CF.sub.2 CF[OCF.sub.2 CF(CF.sub.3)]m
--O--(CF.sub.2)n CH.sub.2 OH as disclosed in U.S. Pat. No.
4,982,009 and the alcoholic ester CF.sub.2
--CF[OCF.sub.2CF(CF.sub.3)]m --O--(CF.sub.2)n --(CH.sub.2)p
--O--COR as disclosed in U.S. Pat. No. 5,310,838. Additional
fluorovinylethers include CF.sub.2CF[OCF.sub.2 CF(CF.sub.3)]m
O(CF.sub.2)n COOH and its carboxylic ester CF.sub.2CF[OCF.sub.2
CF(CF.sub.3)]m O(CF.sub.2)n COOR disclosed in U.S. Pat. No.
4,138,426. In these formulae, m=0-3, n=1-4, p=1-2 and R is methyl
or ethyl. Preferred fluorovinylethers include
CF.sub.2CF--O--CF.sub.2 CF.sub.2--SO.sub.2F;
CF.sub.2CF[OCF.sub.2CF(CF.sub.3)]O(CF.sub.2).sub.2--Y wherein --Y
is --SO.sub.2F, --CN, or --COOH; and
CF.sub.2.CF[OCF.sub.2CF(CF.sub.3)]O(CF.sub.2).sub.2--CH.sub.2--Z
wherein --Z is --OH, --OCN, --O--(CO)--NH.sub.2, or
--OP(O)(OH).sub.2. These fluorovinylethers are preferred because of
their ability to incorporate into the polymer backbone and their
ability to incorporate functionality into the resultant
copolymer.
[0046] One embodiment is the use of talc at about 7% by weight
combined with about 93% neat resin.
[0047] One embodiment is that foaming will occur with the use of
talc at 10% by weight with 90% neat resin.
[0048] Pellets of the compounds described above can be created at
600-610 Deg F and as low as 570 F within the extruder barrel.
[0049] One embodiment of the present application includes a first
composition comprising a blend of perfluoropolymer such as, MFA
(polytetrafluoroethylene-perfluoromethylvinylether) MgCO.sub.3,
CaCO.sub.3, and AClyn.RTM. wax as a powder blend homogeneously
mixed; a second composition, wherein the blowing or foaming agent
is comprised of the first composition plus a perfluoropolymer that
is melted, blended and extruded to provide a pelletized master
batch; a third composition which is a nucleating/foaming agent
comprising perfluoropolymer plus talc or other talc derivative
(which may include Mg.sub.3Si.sub.4O.sub.10(OH).sub.2) which is
blended, melted and extruded into a pelletized form; and a fourth
composition may or may not comprise the second composition (foaming
agent) and the third composition (nucleating/foaming agent) tumble
blended into a homogenous pelletized form of the second and third
compositions for extrusion that allows for blowing or foaming with
or without gas injection and with or without another chemical
foaming agent. Furthermore, the second composition may be
compounded with the third composition along with a perfluoropolymer
that is melted into a single pellet enabling a simple and straight
forward single step chemically foamable perfluoropolymers.
[0050] It should be noted that AClyn.RTM. wax is only one of
several waxes that can be used as a processing aid and that other
processing aids exist which provide similar or better processing
conditions.
[0051] A specific embodiment includes mixtures by weight of the
first composition comprising a blend of perfluoropolymer (94.8%),
MgCO.sub.3 (3.79%), CaCO.sub.3 (0.94%), and AClyn.RTM. wax (0.47%)
as a powder blend mixed homogeneously; a second composition that is
the blowing or foaming agent comprised of the first composition
(20%) and a perfluoropolymer (80%) which is heated to a selected
melting point, blended and extruded to provide a pelletized master
batch; a third composition which is a nucleating/foaming agent
comprising perfluoropolymer pellets (85%) and talc (15%) which is
compounded together via heating to a selected melting point and
extruded into a pelletized form; and a fourth composition
comprising the second composition (blowing or foaming agent -30%)
and the third composition (nucleating/foaming agent -70%) tumble
blended in pelletized form for subsequent extrusion such that the
pellets are placed in an extruder, heated to a selected melting
point allowing for manufacture of blown or foamed insulative
components. The third composition may be used exclusively as a
nucleating and foam agent in a tumbled blend of 30% nucleating foam
agent and 70% perfluoropolymer pellets.
[0052] Another embodiment includes a first composition of a
specific perfluoropolymer and third composition comprising a
different perfluoropolymer.
[0053] An additional embodiment includes blending the second
composition in a ratio range of 1% to 99% and the third composition
in a ratio range of 1% to 99% by weight to create the fourth
composition.
[0054] An additional embodiment includes the third composition
comprising a singular perfluoropolymer or a mixture of different
perfluoropolymers or recycled perfluoropolymers wherein the
recycled perfluoropolymers comprise from 1-100% of the
perfluoropolymers.
[0055] A further embodiment also includes the optional addition of
organic or inorganic salts to the third composition or to the
fourth composition together with or in lieu of the use of talc.
[0056] In another embodiment of the third composition, additional
nucleating agent may be used in combination with the talc in an
amount from 1% to 10% by weight.
[0057] In another embodiment the third composition comprises talc
in an amount from 2%-20% by weight.
[0058] In another embodiment the fourth composition comprises
inorganic or organic salt(s) together with a perfluoropolymer.
[0059] Another embodiment includes the talc of the third
composition, during blowing or foaming, reacting synergistically
with the aforementioned fourth composition to form smaller, more
uniform cell structures in the foamed or blown fourth
composition.
[0060] Additionally an embodiment is where the third composition
comprises 100% non-recycled talc powder combined with 100%
non-recycled perfluoropolymer wherein the ratio of talc to
perfluoropolymer is 0.5%-20% by weight.
[0061] In another embodiment the talc and/or the perfluoropolymer
may be recycled or virgin.
[0062] An embodiment including the perfluoropolymer of the fourth
composition comprises a fluoropolymer or a perfluoropolymer such as
MFA (polytetrafluoroethylene-perfluoromethylvinylether), FEP
(fluoronated ethylene propylene), or PFA (Perfluoroalkoxy) as a
singular perfluoropolymer formulation or as a mixture of one or
more perfluoropolymer formulations.
[0063] Another embodiment includes the extruded fourth composition
comprising a foamed or blown cell structure wherein the cell
structures are consistent and as small as 0.0005 inches to 0.003
inches with an average size of 0.0008 inches.
[0064] In another embodiment the third composition comprises talc
in an amount from 0.5%-20% by weight.
[0065] In another embodiment the third composition comprises
inorganic or organic salt(s) and a perfluoropolymer.
[0066] Another embodiment includes the talc of the third
composition, during blowing or foaming, reacting synergistically
with the fourth composition to form smaller, more uniform cell
structures in the foamed or blown fourth composition.
[0067] An embodiment includes blending the fourth composition
comprising a second composition (35%), a third composition (30%)
and selected non-recycled perfluoropolymer (35%) in pelletized form
and tumble blended.
[0068] In another embodiment the cellular insulation is 100%
recyclable.
[0069] Another embodiment is that the fourth composition may
comprise either inorganic or organic additives or both that include
inorganic salts, metallic oxides, silica and silicon oxides as well
as substituted and unsubstituted fullerenes.
[0070] Also in an embodiment the fourth composition is capable of
meeting specific flammability and smoke generation requirements as
defined by UL 910, UL 2424, NFPA[[APA]]262, 259, 255, and EN
50266-2-x, class B test specifications.
[0071] Another embodiment includes the use of a twin-screw extruder
for melting, blending and pelletizing the second composition and
third composition. In more detail, the compounding process utilizes
a two-step system to insure the foaming components are thoroughly
distributed and dispersed in the base polymer of the final
compound. The first step requires a masterbatch blend be made of
the foaming agents. The foaming agents are in a fine powder form
and a high intensity blender, (i.e. Henschel type) is used to
prepare the powder blend according to the specified formulation. A
certain amount of resin, also in powder form, can be used in the
first blending step as a mechanism to predisperse the foaming
agents and aid in the second extrusion compounding step. The second
stage of the compound preparation process utilizes a twin screw
extrusion compounding system to incorporate the foaming agent
masterbatch blend with the base resin. The design of the
compounding screw is such that there is sufficient heat and
mechanical energy to fully thermally melt the base polymer and
incorporate the masterbatch blend with proper distribution and
dispersion during mixing for homogeneity, but yet mild enough to
keep the processing temperature of the compound below that in which
foaming may be prematurely initiated. The final compound can be
strand extruded and pelletized or alternatively an underwater
pelletizing technique may be used (in other words air or water
cooling is acceptable).
[0072] Another embodiment is a method and system for blowing or
foaming the fourth composition to encapsulate metallic conductive
media as an insulative coating to improve electrical performance,
reduce combustibility and reduce costs over present methods.
[0073] Another embodiment is a method and system for blowing or
foaming the fourth composition by extrusion through one or more
dies to manufacture cable support-separators, conduit tubes,
jackets, tapes or wraps.
[0074] Another embodiment is a method and system for heating the
powder of the first composition and a selected pelletized
perfluoropolymer or fluoropolymer thereby creating a melt blendable
second composition, extruding the molten second composition,
cooling the molten second composition and forming the solid second
composition into a pelletized foaming agent.
[0075] Another embodiment is a method and system for heating the
talc powder and a selected pelletized perfluoropolymer or
fluoropolymer creating a melt blendable third composition,
extruding the molten third composition, cooling the molten third
composition and forming the solid third composition into a
pelletized nucleating and foaming agent.
[0076] Another embodiment is a method and system for tumble
blending the pelletized foaming agent of the second composition and
the pelletized nucleating agent of the third composition creating a
fourth composition that may extruded or otherwise heated such that
a foamed or blown extrusion profile is formed.
[0077] One embodiment involves a system and method for producing a
high performance multi-media cable including a plurality of
transmission media with metal and/or optical conductors that are
individually insulated, where the insulation is comprised of
blowing or foaming the fourth composition and wherein the
composition is provided for as individual conductors as twisted
pair and may be isolated by a cable support-separator that is
foamed or blown through a die utilizing the same composition. The
separator may be optionally wrapped, taped or have an outer jacket
of a blown or foamed with the same fourth composition while
maintaining the plurality of data transmission media in a proper
position with respect to the core.
[0078] Another embodiment includes the use of a twin-screw extruder
for melting, blending and pelletizing the composition. In more
detail, the compounding process utilizes a two-step system to
insure the foaming components are thoroughly distributed and
dispersed in the base polymer of the final compound. The first step
requires a masterbatch blend be made of the foaming agents. The
foaming agents are in a fine powder form and a high intensity
blender, (i.e. Henschel type) is used to prepare the powder blend
according to the specified formulation. A certain amount of resin,
also in powder form, can be used in the first blending step as a
mechanism to predisperse the foaming agents and aid in the second
extrusion compounding step. The second stage of the compound
preparation process utilizes a twin screw extrusion compounding
system to incorporate the foaming agent masterbatch blend with the
base resin. The design of the compounding screw is such that there
is sufficient heat and mechanical energy to fully thermally melt
the base polymer and incorporate the masterbatch blend with proper
distribution and dispersion during mixing for homogeneity, but yet
mild enough to keep the processing temperature of the compound
below that in which foaming may be prematurely initiated. The final
compound can be strand extruded and pelletized or alternatively an
underwater pelletizing technique may be used (in other words air or
water cooling is acceptable).
[0079] Another embodiment is a method and system for heating the
talc powder and a selected pelletized perfluoropolymer or
fluoropolymer creating a melt blendable composition, extruding the
molten composition, cooling the molten composition and forming the
solid composition into a pelletized nucleating and foaming
agent.
[0080] Another embodiment includes a communications cable,
conductor separator, conductor support-separator, jacketing, tape,
wrap, wire insulation and in some cases a conduit tube individually
comprising the same blown or foamed fourth composition or may
utilize the fourth composition that includes selected
perfluoropolymers or fluoropolymers.
[0081] Additionally disclosed is a composition of MFA powder,
calcium carbonate, magnesium carbonate and AClyn.RTM. wax as a
second composition and MFA, FEP or PFA (in pellet or powdered form)
and talc as a third composition wherein the second composition and
the third composition are combined in a ratio of thirty percent and
seventy percent respectively, tumble blended and provide for a
blowing agent to form a foamed or blown insulation.
[0082] Additionally disclosed is a composition of FEP powder,
calcium carbonate, magnesium carbonate and AClyn.RTM. wax as a
second composition and FEP, MFA or PFA and talc as a third
composition wherein the second composition and the third
composition are combined in a ratio of thirty percent and seventy
percent respectively, tumble blended and provide for a blowing
agent to form a foamed or blown insulation.
[0083] Additionally disclosed is a composition of PFA powder,
calcium carbonate, magnesium carbonate and AClyn.RTM. wax as a
second composition and PFA, MFA or FEP (in pellet or powdered form)
and talc as a third composition wherein the second composition and
the third composition are combined in a ratio of thirty percent and
seventy percent respectively, tumble blended and provide for a
blowing agent to form a foamed or blown insulation.
[0084] Another embodiment of the disclosure includes the use of a
foamed core and/or the use of a hollow center of the core, which in
both cases significantly reduces the material required along the
length of the finished cable. The effect of foaming and/or
producing a support-separator with a hollow center portion should
result in improved flammability of the overall cable by reducing
the amount of material available as fuel for the UL 910 test,
improved electrical properties for the individual non-optical
conductors, and reduction of weight of the overall cable.
[0085] A method and system wherein the blown and/or foamed
perfluoropolymer composition cable, support-separator, conduit
tube, jacketing, wrapping and/or taping line speeds are at or about
75 to 1500 ft/min.
[0086] Additional benefits of the embodiments include reduction of
the overall material mass required for conventional spacers,
insulation and jacketing which contributes to flame and smoke
reduction.
[0087] Another embodiment of the disclosure includes the use this
foam process, either chemical or gas, and placing foam skin with
both being the same materials e.g. (Perfluoropolymers) in a
coextrusion or a second extrusion of a thermoplastic
non-fluoropolymer as a skin or encapsulated by a layer of foam or
solid perfluoropolymer skin as an insulation, cable filler or
jacket.
[0088] Additionally, a cellular foaming extrusion process wherein a
perflouropolymer or non-fluorinated polymer skin is formed over
cellular foam during the extrusion process and where the process is
performed using a single or dual head extruder such that the
cellular foam is formed by either chemical or gas injection means
is another object of the disclosure.
[0089] This disclosure also provides for an extrusion process where
extrusion of a composition capable of forming cellular foam is
extruded in an extruder using an extruder that is specifically
designed to minimize mechanical shear and increased heating. This
allows for mitigating premature foaming during the process of
melting, blending, extruding and pelletizing of the desired
compositions.
[0090] The desired perfluoropolymer compositions include adding
into an extruded melt of a base perfluoropolymer resin, in
sequential steps, sufficient talc to accomplish a loading of talc
in a range of 0.5 to 20% in combination with perfluoropolymer resin
for forming compound pellets such that the compositions may be used
for subsequent heat extrusion or molding processes and provide
cellular or foamed or blown perfluoropolymer end products.
[0091] The perfluoropolymer compositions may also be used to make
extruded or molded desired shapes and geometries without
palletizing and in so doing, talc is acting as a nucleating agent,
a foaming agent or both during extrusion or molding.
[0092] It is thus an object of the present disclosure to provide a
foamable perfluoropolymer composition having: [0093] at least one
melt-processable per(halo)fluoropolymer [polymer (A)]; and a
blowing agent having an effective amount of magnesium carbonate;
and [0094] an active nucleating agent chosen among: at least one
metal carbonate different from magnesium carbonate having
decomposition temperature exceeding 350.degree. C., generally
chosen among CaCO.sub.3, BaCO.sub.3, ZnCO.sub.3 and PbCO.sub.3; at
least one natural or synthetic talc derivative including hydrated
magnesium silicate; and mixtures thereof.
[0095] The composition of the disclosure can be chemically foamed
yielding homogeneous foamed insulating structures which excel
simultaneously in providing excellent insulating properties on
metal wires or optical fibers, outstanding processing parameters
for high speed cable manufacture and high performance ratings on
flammability, smoke generation and fuel load.
[0096] The Applicant has surprisingly found that the above
mentioned combination of a magnesium carbonate as blowing agent and
an active nucleating agent as above described, enables obtaining
per(halo)fluoropolymer chemically foamed structures in traditional
wire extrusion/cable processing machines, thus enabling decreasing
the final amount of material in the cable design (with significant
cost and flammability advantages)
[0097] In an embodiment of the present disclosure it has been found
that talc, generally known as a nucleating agent in foamed
plastics, exhibits blowing agent properties without the presence of
a blowing agent.
[0098] Another embodiment combines talc, as a blowing agent, with
resin(s) in the absence of any additional chemical blowing agent
wherein the talc comprises 2-50% by weight of the resin and wherein
the resulting composition is extruded into an extrudate
product.
[0099] In another embodiment the talc is combined with a resin as a
masterbatch in a percentage of up to 15% talc by weight to resin
and extruded as a pellet.
[0100] In another embodiment the talc is combined with a recycled
resin as a masterbatch in a percentage of up to 20% talc by weight
to recycled resin and extruded as a pellet.
[0101] In another embodiment the resin(s) may be perfluoropolymers
as a subset of fluoropolymers FEP, MFA, PFA perfluotopolymers or
semicrystalline fluoroploymers ECTFE, ETFE, PVDF, etc. as pure
resin, recycled resin, as a single resin or in combination with
other resins.
[0102] In yet another embodiment the extrudate is a pellet, cross
web, insulation, jacketing, wire insulation.
[0103] In another embodiment the extrudate is at a sufficiently low
temperature so that the resin(s) are thermally constrained from
foaming and subsequently extruded into pellet, jackets, separators,
insulation, etc.
[0104] In another embodiment the pellets are extruded at a
sufficiently high temperature so that the resin is receptive to the
talc blowing agent wherein the product is a foamed article.
[0105] In another embodiment the pellets may optionally include and
a color concentrate.
[0106] Another object of the disclosure is a foamed insulation
comprising said composition.
[0107] Still an object of the invention is a process for
manufacturing the composition.
[0108] Still another object of the disclosure is a process for
manufacturing foamed insulation from the composition.
[0109] Other objects of the disclosure include recycled or waste
materials to form these compositions (pelletized or otherwise),
which can be processed and tumble blended with or without virgin or
bare perfluoropolymer or fluoropolymers to obtain acceptable
foamable compositions after heating and extrusion.
[0110] In another embodiment the resin(s) may be perfluoropolymers
as a subset of fluoropolymers FEP, MFA, ECTFE, etc. as pure resin,
recycled resin, as a single resin or in combination with other
resins.
[0111] In yet another embodiment the extrudate is a pellet, cross
web, insulation, jacketing, wire insulation.
[0112] Another object of the disclosure is a foamed insulation
comprising said composition.
[0113] Still an object of the invention is a process for
manufacturing the composition.
[0114] Still another object of the disclosure is a process for
manufacturing foamed insulation from the composition.
[0115] Other objects of the disclosure include recycled or waste
materials to form these compositions, which can be processed and
tumble blended with or without virgin or bare
per(halo)fluoropolymer to obtain acceptable foamable
compositions.
[0116] Additionally it is known that foamed or blown articles or
foamed composition produced with a gas blowing agent can be used in
combination with talc leading to an increase in the percentage of
cellular structure within a foamed or foamable composition when the
combination of talc and either a chemical or gas blowing agent is
used.
[0117] The disclosure includes and defines a cable utilizing the
compositions described above.
DETAILED DESCRIPTION OF THE INVENTION
[0118] For the purpose of the present invention, the expressions
"fluoropolymer" and "polymer (A)" are intended to denote any
polymer comprising recurring units (R), more than 25 wt % of said
recurring units (R) being derived from at least one ethylenically
unsaturated monomer comprising at least one fluorine atom
(hereinafter, fluorinated monomer).
[0119] The fluoropolymer comprises preferably more than 30% wt,
more preferably more than 40% wt of recurring units derived from
the fluorinated monomer.
[0120] The fluorinated monomer can further comprise one or more
other halogen atoms (Cl, Br, I). If the fluorinated monomer is free
of hydrogen atom, it is designated as per(halo)fluoromonomer. Shall
the fluorinated monomer comprise at least one hydrogen atom, it is
designated as hydrogen-containing fluorinated monomer.
[0121] Non-limitative examples of fluorinated monomers are notably
tetrafluoroethylene (TFE), vinylidene fluoride (VdF),
chlorotrifluoroethylene (CTFE), and mixtures thereof. Optionally,
the fluoropolymer may comprise recurring units derived one first
monomer, said monomer being a fluorinated monomer as above
described, and at least one other monomer [comonomer (CM),
hereinafter].
[0122] Hereinafter, the term comonomer (CM) should be intended to
encompass both one comonomer and two or more comonomers.
[0123] The comonomer (CM) can notably be either hydrogenated (i.e.
free of fluorine atom) [comonomer (HCM), hereinafter] or
fluorinated (i.e. containing at least one fluorine atom) [comonomer
(FCM), hereinafter].
[0124] Non limitative examples of suitable hydrogenated comonomers
(HCM) are notably ethylene, propylene, vinyl monomers such as vinyl
acetate, acrylic monomers, like methyl methacrylate, acrylic acid,
methacrylic acid and hydroxyethyl acrylate, as well as styrene
monomers, like styrene and p-methylstyrene.
[0125] Non-limitative examples of suitable fluorinated comonomers
(FCM) are notably: [0126] C.sub.3-C.sub.8 fluoro- and/or
perfluoroolefins, such as hexafluoropropene, pentafluoropropylene,
and hexafluoroisobutylene; [0127] C.sub.2-C.sub.8 hydrogenated
monofluoroolefins, such as vinyl fluoride; [0128]
1,2-difluoroethylene, vinylidene fluoride and trifluoroethylene;
[0129] perfluoroalkylethylenes complying with formula
CH.sub.2.dbd.CH--R.sub.f0, in which R.sub.f0 is a C.sub.1-C.sub.6
perfluoroalkyl; [0130] chloro- and/or bromo- and/or
iodo-C.sub.2-C.sub.6 fluoroolefins, like chlorotrifluoroethylene;
fluoroalkylvinylethers complying with formula
CF.sub.2.dbd.CFOR.sub.f1 in which R.sub.f1 is a C.sub.1-C.sub.6
fluoro- or perfluoroalkyl, e.g. --CF.sub.3, --C.sub.2F.sub.5,
--C.sub.3F.sub.7; fluoro-oxyalkylvinylethers complying with formula
CF.sub.2.dbd.CFOX.sub.0, in which X.sub.0 is a C.sub.1-C.sub.12
oxyalkyl, or a C.sub.1-C.sub.12 (per) fluorooxyalkyl having one or
more ether groups, like perfluoro-2-propoxy-propyl;
fluoroalkyl-methoxy-vinylethers complying with formula
CF.sub.2=CFOCF.sub.2OR.sub.f2 in which R.sub.f2 is a
C.sub.1-C.sub.6 fluoro- or perfluoroalkyl, e.g. -CF.sub.3,
--C.sub.2F.sub.5, --C.sub.3F.sub.7 or a C.sub.1-C.sub.6
(per)fluorooxyalkyl having one or more ether groups, like
--C.sub.2F.sub.5--O--CF.sub.3; fluorodioxoles, of formula:
##STR00001##
[0131] wherein each of R.sub.f3, R.sub.f4, R.sub.f5, R.sub.f6,
equal or different each other, is independently a fluorine atom, a
C.sub.1-C.sub.6 fluoro- or per(halo)fluoroalkyl, optionally
comprising one or more oxygen atom, e.g. --CF.sub.3,
--C.sub.2F.sub.5, --OCF.sub.3, --OCF.sub.2CF.sub.2OCF.sub.3.
[0132] In a first embodiment of the invention, the polymer (A) is a
hydrogen-containing fluoropolymer.
[0133] By "hydrogen-containing fluoropolymer" it is meant a
fluoropolymer as above defined comprising recurring units derived
from at least one hydrogen-containing monomer. The
hydrogen-containing monomer may be the same monomer as the
fluorinated monomer or can be a different monomer.
[0134] Thus, this definition encompasses notably copolymers of one
or more per(halo)fluoromonomer (for instance tetrafluoroethylene,
chlorotrifluoroethylene, hexafluoropropylene,
perfluoroalkylvinylethers, etc.) with one or more hydrogenated
comonomer(s) (for instance ethylene, propylene, vinylethers,
acrylic monomers, etc.), and/or homopolymers of hydrogen-containing
fluorinated monomers (for instance vinylidene fluoride,
trifluoroethylene, vinyl fluoride, etc.) and their copolymers with
fluorinated and/or hydrogenated comonomers.
[0135] The hydrogen-containing fluoropolymers are preferably chosen
among: [0136] (A-1) TFE and/or CTFE copolymers with ethylene,
propylene or isobutylene (preferably ethylene), with a molar ratio
per(halo)fluoromonomer(s)/hydrogenated comonomer(s) of from 30:70
to 70:30, optionally containing one or more comonomers in amounts
of from 0.1 to 30% by moles, based on the total amount of TFE
and/or CTFE and hydrogenated comonomer(s) (see for instance U.S.
Pat. No. 3,624,250 and U.S. Pat. No. 4,513,129); [0137] (A-2)
Vinylidene fluoride (VdF) polymers, optionally comprising reduced
amounts, generally comprised between 0.1 and 15% by moles, of one
or more fluorinated comonomer(s) (see for instance U.S. Pat. No.
4,524,194 and U.S. Pat. No. 4,739,024), and optionally further
comprising one or more hydrogenated comonomer(s); and mixtures
thereof.
[0138] According to a second preferred embodiment of the invention;
the polymer (A) is a per(halo)fluoropolymer.
[0139] For the purpose of the invention, the term
"per(halo)fluoropolymer" is intended to denote a fluoropolymer
substantially free of hydrogen atoms.
[0140] The term "substantially free of hydrogen atom" is understood
to mean that the per(halo)fluoropolymer consists essentially of
recurring units derived from ethylenically unsaturated monomers
comprising at least one fluorine atom and free of hydrogen atoms
[per(halo)fluoromonomer) (PFM)].
[0141] The per(halo)fluoropolymer can comprise recurring units
comprising one or more other halogen atoms (Cl, Br, I).
[0142] The per(halo)fluoropolymer can be a homopolymer of a
per(halo)fluoromonomer (PFM) or a copolymer comprising recurring
units derived from more than one per(halo)fluoromonomer (PFM).
[0143] Non limitative examples of suitable per(halo)fluoromonomers
(PFM) are notably: [0144] C.sub.2-C.sub.8 perfluoroolefins, such as
tetrafluoroethylene (TFE) and hexafluoropropene (HFP); chloro-
and/or bromo- and/or iodo-C.sub.2-C.sub.6 per(halo)fluoroolefins,
like chlorotrifluoroethylene; [0145]
per(halo)fluoroalkylvinylethers complying with general formula
CF.sub.2.dbd.CFOR.sub.f3 in which R.sub.f3 is a C.sub.1-C.sub.6
per(halo)fluoroalkyl, such as --CF.sub.3, --C.sub.2F.sub.5,
--C.sub.3F.sub.7; [0146] per(halo)fluoro-oxyalkylvinylethers
complying with general formula CF.sub.2.dbd.CFOX.sub.01, in which
X.sub.01 is a C.sub.1-C.sub.12 per(halo)fluorooxyalkyl having one
or more ether groups, like perfluoro-2-propoxy-propyl group; [0147]
per(halo)fluoro-methoxy-alkylvinylethers complying with general
formula CF.sub.2.dbd.CFOCF.sub.2OR.sub.f4 in which R.sub.f4 is a
C.sub.1-C.sub.6 per(halo)fluoroalkyl, such as --CF.sub.3,
--C.sub.2F.sub.5, --C.sub.3F.sub.7 or a C.sub.1-C.sub.6
per(halo)fluorooxyalkyl having one or more ether groups, such as
--C.sub.2F.sub.5--O--CF.sub.3; [0148] per(halo)fluorodioxoles of
formula:
##STR00002##
[0149] wherein each of R.sub.f3, R.sub.f4, R.sub.f5, R.sub.f6, are
equal or different than each other, is independently a fluorine
atom, a C.sub.1-C.sub.6 perfluoroalkyl group, optionally comprising
one or more oxygen atoms, e.g. --CF.sub.3, --C.sub.2F.sub.5,
--C.sub.3F.sub.7, --OCF.sub.3, --OCF.sub.2CF.sub.2OCF.sub.3;
preferably a per(halo)fluorodioxole complying with formula here
above, wherein R.sub.f3 and R.sub.f4 are fluorine atoms and
R.sub.f5 and R.sub.f6 are perfluoromethyl groups (--CF.sub.3)
[perfluoro-2,2-dimethyl-1,3-dioxole (PDD)], or a
per(halo)fluorodioxole complying with formula here above, wherein
R.sub.f3, R.sub.f5 and R.sub.f6 are fluorine atoms and R.sub.f4 is
a perfluoromethoxy group (--OCF.sub.3)
[2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole or
perfluoromethoxydioxole (MDO)].
[0150] The per(halo)fluoropolymer is advantageously chosen among
homopolymers of tetrafluoroethylene (TFE) or copolymers of TFE with
at least one per(halo)fluoromonomer (PFM).
[0151] Preferred per(halo)fluoropolymer is selected among TFE homo-
and copolymers comprising recurring units derived from at least one
per(halo)fluoromonomer (PFM) chosen among the group consisting
of:
[0152] perfluoroalkylvinylethers complying with formula
CF.sub.2.dbd.CFOR.sub.f'' in which R.sub.f is a C.sub.1-C.sub.6
perfluoroalkyl, e.g. --CF.sub.3, --C.sub.2F.sub.5,
--C.sub.3F.sub.7; and/or per(halo)fluorodioxoles of formula:
##STR00003##
[0153] wherein each of R.sub.f3, R.sub.f4, R.sub.f5, R.sub.f6,
equal of different each other, is independently a fluorine atom, a
C.sub.1-C.sub.6 perfluoroalkyl group, optionally comprising one or
more oxygen atom, e.g. --CF.sub.3, --C.sub.2F.sub.5,
--C.sub.3F.sub.7, --OCF.sub.3, --OCF.sub.2CF.sub.2OCF.sub.3.
[0154] More preferred per(halo)fluoropolymers are selected among
TFE homo- and copolymers comprising recurring units derived from at
least one fluorinated comonomer chosen among the group consisting
of: [0155] perfluoroalkylvinylethers complying with formula
CF.sub.2.dbd.CFOR.sub.f', in which R.sub.f' is a group chosen among
--CF.sub.3, --C.sub.2F.sub.5, --C.sub.3F.sub.7; and/or
per(halo)fluorodioxoles of formula:
##STR00004##
[0156] wherein R.sub.f3 and R.sub.f4 are fluorine atoms and
R.sub.f5 and R.sub.f6 are perfluoromethyl groups (--CF.sub.3)
[perfluoro-2,2-dimethyl-1,3-dioxole (PDD)], or wherein R.sub.f3,
R.sub.f5 and R.sub.f6 are fluorine atoms and R.sub.f4 is a
perfluoromethoxy group (--OCF.sub.3)
[2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole or
perfluoromethoxydioxole (MDO)].
[0157] The per(halo)fluoromonomer (PFM) is present in the TFE
copolymer in an amount of advantageously at least 0.01, preferably
0.1% by moles, with respect to the total moles of TFE and
per(halo)fluoromonomer (PFM).
[0158] The per(halo)fluoromonomer (PFM) is present in the TFE
copolymer in an amount of advantageously at most 3% by moles,
preferably 1% by moles, with respect to the total moles of TFE and
per(halo)fluoromonomer (PFM).
[0159] Good results have been obtained with TFE homo- and
copolymers wherein the fluorinated comonomer is one or more than
one perfluoroalkylvinylether as above specified; particularly good
results have been achieved with TFE copolymers wherein the
fluorinated comonomer is perfluoromethylvinylether (of formula
CF.sub.2.dbd.CFOCF.sub.3), perfluoroethylvinylether (of formula
CF.sub.2.dbd.CFOC.sub.2F.sub.5), perfluoropropylvinylether (of
formula CF.sub.2.dbd.CFOC.sub.3F.sub.7) and mixtures thereof.
[0160] Best results have been obtained with TFE homo- and
copolymers wherein the fluorinated comonomer is
perfluoromethylvinylether, a mixture of perfluoromethylvinylether
and perfluoropropylvinylether, a mixture of
perfluoroethylvinylether and perfluoropropylvinylether, or
perfluoropropylvinylether.
[0161] According to a first embodiment of the invention, polymer
(A) is chosen among TFE copolymers comprising recurring units
derived from HFP and optionally from at least one
perfluoroalkylvinylether, as above defined.
[0162] Preferred polymers (A) according to this embodiment are
selected among TFE copolymers comprising (preferably consisting
essentially of) recurring units derived from tetrafluoroethylene
(TFE) and hexafluoropropylene (HFP) in an amount ranging from 3 to
15 wt % and, optionally, from 0.5 to 3 wt % of at least one
perfluoroalkylvinylether, as above defined.
[0163] A description of such polymers (A) can be found notably in
U.S. Pat. No. 4,029,868, in U.S. Pat. No. 5,677,404, in U.S. Pat.
No. 5,703,185, and in U.S. Pat. No. 5,688,885.
[0164] Polymer (A) according to this embodiment are commercially
available under the trademark TEFLON.RTM. FEP 9494, 6100 and 5100
from E.I. DuPont de Nemours, or from Daikin (e.g. FEP NP-101
material), or from Dyneon LLC (FEP 6322).
[0165] Best results have been obtained with TFE copolymers
comprising (preferably consisting essentially of) recurring units
derived from tetrafluoroethylene (TFE) and hexafluoropropylene
(HFP) in an amount ranging from 4 to 12 wt % and either
perfluoro(ethyl vinyl ether) or perfluoro(propyl vinyl ether) in an
amount from 0.5 to 3% wt.
[0166] According to a second embodiment of the invention, the
polymer (A) is chosen among TFE copolymers comprising recurring
units derived from at least one perfluoroalkylvinylether, as above
defined.
[0167] Good results within this second embodiment have been
obtained with TFE copolymers wherein the fluorinated comonomer is
one or more than one perfluoroalkylvinylether as above specified;
particularly good results have been achieved with TFE copolymers
wherein the fluorinated comonomer is perfluoromethylvinylether (of
formula CF.sub.2.dbd.CFOCF.sub.3), perfluoroethylvinylether (of
formula CF.sub.2.dbd.CFOC.sub.2F.sub.5), perfluoropropylvinylether
(of formula CF.sub.2.dbd.CFOC.sub.3F.sub.7) and mixtures
thereof.
[0168] Best results within this second embodiment have been
obtained with TFE homo- and copolymers wherein the fluorinated
comonomer is perfluoromethylvinylether, a mixture of
perfluoromethylvinylether and perfluoropropylvinylether, a mixture
of perfluoroethylvinylether and perfluoropropylvinylether, or
perfluoropropylvinylether.
[0169] According to a preferred variant of the second embodiment of
the invention, the polymer (A) is advantageously a TFE copolymer
consisting of: [0170] (a) from 7 to 13% by weight of recurring
units derived from perfluoromethylvinylether; [0171] (b) from 0 to
3% by weight of recurring units derived from one or more than one
fluorinated comonomer different from perfluoromethylvinylether and
selected from the group consisting of perfluoroalkylvinylethers, as
above detailed and/or perfluoro-oxyalkylvinylethers, as above
detailed; preferably derived from perfluoroethylvinylether and/or
perfluoropropylvinylether; [0172] (c) recurring units derived from
tetrafluoroethylene, in such an amount that the sum of the
percentages of the recurring units (a), (b) and (c) is equal to
100% by weight.
[0173] MFA and PFA suitable to be used for the composition of the
invention and are commercially available from Solvay Solexis Inc.
under the trade name of HYFLON.RTM. MFA and PFA.
[0174] For the purpose of the present invention, by the term
"melt-processable" is meant that the polymer (A) can be processed
(i.e. fabricated into shaped articles such as cross-webs (x-webs),
insulation(s), jacket coatings, films, fibers, tubes, wire coatings
and the like) by conventional melt extruding, injecting or casting
means. This generally requires that the melt viscosity at the
processing temperature be no more than 10.sup.6 Pa-sec, preferably
from 10 to 10.sup.6 Pa-sec.
[0175] Thus, polymer (A) is distinguishable from "non
melt-processable" fluoropolymers, like notably PTFE, which cannot
be processed by conventional melt extruding, injecting or casting
means, and which generally exhibit a melt viscosity at the
processing temperature exceeding 10.sup.6 Pa-sec.
[0176] The melt viscosity of the polymer (A) can be measured
according to ASTM D-1238-52T, using a cylinder, orifice and piston
tip made of a corrosion-resistant alloy, charging a 5.0 g sample to
the 9.5 mm inside diameter cylinder which is maintained at a
temperature exceeding melting point, extruding the sample 5 minutes
after charging through a 2.10 mm diameter, 8.00 mm long
square-edged orifice under a load (piston plus weight) of 5 kg.
Melt viscosity is calculated in Pa-sec from the observable
extrusion rate in grams per minute.
[0177] Also, polymer (A) typically has a dynamic viscosity at a
shear rate of 1 sec-.sup.1and at a temperature exceeding melting
point of about 30.degree. C., preferably at a temperature of
Tm2+(30.+-.2.degree. C.) is comprised between 10 and 10.sup.6
Pa-sec, when measured with a controlled strain rheometer, employing
an actuator to apply a deforming strain to the sample and a
separate transducer to measure the resultant stress developed
within the sample, and using the parallel plate fixture.
[0178] The polymer (A) typically has a dynamic viscosity at a shear
rate of 1 sec-.sup.-1 in the above specified conditions preferably
comprised between 20 and 2000 Pa-sec, more preferably between 70
and 700 Pa-sec.
[0179] The polymer (A) of the invention is advantageously
thermoplastic.
[0180] The term "thermoplastic" is understood to mean, for the
purposes of the present invention, polymers existing, at room
temperature (25.degree. C.), below their melting point if they are
semi-crystalline, or below their Tg if amorphous. These polymers
have the property of becoming soft when they are heated and of
becoming rigid again when hey are cooled, without there being an
appreciable chemical change. Such a definition may be found, for
example, in the encyclopedia called "Polymer Science Dictionary",
Mark S. M. Alger, London School of Polymer Technology, Polytechnic
of North London, UK, published by Elsevier Applied Science,
1989.
[0181] Thermoplastic polymers are thus distinguishable from
elastomers.
[0182] To the purpose of the invention, the term "elastomer" is
intended to designate a true elastomer or a polymer resin serving
as a base constituent for obtaining a true elastomer.
[0183] True elastomers are defined by the ASTM, Special Technical
Bulletin, No. 184 standard as materials capable of being stretched,
at room temperature, to twice their intrinsic length and which,
once they have been released after holding them under tension for 5
minutes, return to within 10% of their initial length in the same
time.
[0184] Polymer resins serving as a base constituent for obtaining
true elastomers are in general amorphous products having a glass
transition temperature (Tg) below room temperature (25.degree. C.).
In most cases, these products correspond to copolymers having a Tg
below 0.degree. C. and including reactive functional groups
(optionally in the presence of additives) allowing the true
elastomer to be formed.
[0185] Preferably, the polymer (A) is semi-crystalline.
[0186] The term "semi-crystalline" is intended to denote a polymer
having a heat of fusion of more than 1 J/g when measured by
Differential Scanning calorimetry (DSC) at a heating rate of
10.degree. C./min, according to ASTM D 3418.
[0187] Preferably, the semi-crystalline polymer (A) of the
invention has a heat of fusion of at least 3 J/g, more preferably
of at least 5 J/g, most preferably at least 10 J/g.
[0188] According to a first embodiment of the invention, the
per(halo)fluoropolymer (A) possesses a dielectric constant of
advantageously at most 3.1, preferably at most 2.85, most
preferably at most 2.6.
[0189] Compositions according to the first embodiment of the
invention are particularly suitable for cable jacketing.
[0190] According to a second embodiment of the invention, the
per(halo)fluoropolymer (A) possesses a dielectric constant of
advantageously at most 2.4, preferably at most 2.3, most preferably
at most 2.2. Excellent results have been obtained with
per(halo)fluoropolymers having dielectric constant from about 2.0
to about 2.1.
[0191] Compositions according to the second embodiment of the
invention are particularly suitable for primary insulation of cable
conductors and cable fillers.
[0192] It is also understood that the foamable composition, once
foamed so as to obtain a cellular structure, will generally possess
a significantly lower dielectric constant, ranging from 1.5 to 2.0,
preferably from 1.6 to 1.8, as a function of void fraction.
[0193] The blowing agent of the present invention optionally
includes magnesium carbonate (MgCO3); it is well known that
magnesium carbonate generally undergoes decomposition below
350.degree. C., thus typically at temperatures of processing of the
polymer (A).
[0194] Preferably up to 15 parts by weight of MgCO.sub.3 per 100
parts by weight of polymer (A) can be used. More preferably, there
are about 0.5 to about 10 parts by weight of MgCO.sub.3 per 100
parts by weight of polymer (A), most preferably between 2 to 6
parts by weight of MgCO.sub.3 per 100 parts by weight of polymer
(A). Particularly good results have been obtained using 4 parts by
weight of MgCO.sub.3 per 100 parts by weight of polymer (A).
[0195] The nucleating agent advantageously provides sites for the
formation of cells generated by the blowing agent. The use of
nucleating agents results in a greater number of finer cells than
would form without a nucleating agent.
[0196] To the purpose of the invention, the term "active"
nucleating agent is intended to denote a compound which both acts
as nucleating agent, as above described and, at the same time,
participates in blowing, by at least partially decomposing to yield
gaseous components.
[0197] The applicant has surprisingly found that the use of
carbonates having decomposition temperature exceeding 350.degree.
C., and thus which are thermally stable at typical temperatures of
processing of the polymer (A) is particularly useful, because these
carbonates can be intimately admixed in the melt during processing
and foaming within the per(halo)fluoropolymer matrix without
significant decomposition, so as to obtain a very homogeneous
distribution of nucleating sites.
[0198] Also, when combined with MgCO.sub.3 or CaCO.sub.3, these
carbonates actively participate in evolving carbon dioxide during
foaming process, thanks to the combined effect of acid evolvement
and temperature. These active nucleating agents are particularly
useful for blowing foams of polymer (A), as its intrinsic basicity
enables capture and neutralization of eventual traces of HF acid
which might evolve from the molten material. Also hydrogen fluoride
can advantageously react with the metal carbonate forming carbon
dioxide. It is believed that the formation of this carbon dioxide
provides sites for initiation or nucleation of cells forming from
the blowing agent.
[0199] As used here, a blowing agent comprising "primarily talc"
achieves at least most of its blowing function from talc. In
certain exemplary embodiments wherein the blowing agent comprises
primarily talc, the blowing agent is at least 30 weight percent
talc. That is, in such embodiments talc is at least 30 weight
percent of all materials operative as a blowing agent in the
composition in the intended extrusion or other forming operation.
In certain exemplary embodiments the blowing agent is at least 10
weight percent talc. In certain exemplary embodiments the blowing
agent is at least 20 weight percent talc. In certain exemplary
embodiments the blowing agent consists essentially of talc. In
certain exemplary embodiments talc is used in combination with
other blowing agents, including, e.g., boron nitride and/or other
known blowing agents as well as derivatives of talc.
[0200] Preferably up to 5 parts by weight of above mentioned active
nucleating agent per 100 parts by weight of polymer (A) can be
used. More preferably, there are about 0.5 to about 3 parts by
weight of active nucleating agent per 100 parts by weight of
polymer (F).
[0201] Additionally, the following working examples are
representative of the present disclosure;
WORKING EXAMPLE 1
[0202] A first composition including MgCO.sub.3, CaCO.sub.3 and
AClyn.RTM. wax and a fine powder of the perfluoropolymer e.g. (MFA)
are placed in a powder form and blended as a master batch in a high
intensity mixer i.e. (Henschel type Powder Blender). The master
batch of this first composition is (94.8%) e.g. (MFA)
perfluoropolymer powder, 3.79% MgCO.sub.3, 0.94% CaCO.sub.3 and
0.47% AClyn.RTM. wax. This master batch of the first composition is
further extruded into a pellet form in a second stage utilizing a
twin screw extrusion process that allows for incorporating the
master batch of the first composition at 20% sequentially along
feeder sections of the twin screw while incorporating 80%
perfluoropolymer base resin (e.g. FEP) with temperature zones 1
through 6 starting at 520, 530, 540, 560, 580, and 600 degrees
Fahrenheit, respectively. This 80% pellet of base perfluoropolymer
resin and the 20% powder master batch (of the first composition)
are formed into a pellet via underwater pelletization.
[0203] A third composition includes talc (MgSiOH;
3MgO+4SiO.sub.2+H.sub.2O; MgOH+H.sub.2O+SiOH) or other talc/talc
derivatives such as Mg.sub.3Si.sub.4O.sub.10(OH).sub.2 which is/are
sequentially added into the feeder section with a base
perfluoropolymers resin e.g. (FEP) in a ratio of 15% talc and 85%
perfluoropolymer resin. The process temperature of zones 1 through
6 of the twin screw extruder are 520, 530, 540, 560, 580, and 600
degrees Fahrenheit respectively. The extrusion of the base resin
perfluoropolymer e.g. (FEP) is under water pelletized into a single
pellet.
[0204] The first composition described above (that is MgCO.sub.3,
CaCO.sub.3 and AClyn.RTM. wax)--as a pellet--is then tumble blended
with the third composition (talc or talc derivative)--as a
pellet--in a ratio of 5% of the first composition, 45% of the third
composition and 50% of the base resin of perfluoropolymer e.g.
(FEP). The aforementioned tumble blended materials are placed in
the hopper of a 30 to 1 ratio high temperature extruder with heat
zones 1 through 6 at 530, 550, 570, 600, 610, and 630 degrees to
form one of several products including an extruded profile such as
used for separators, wire insulation, or jackets for cabling.
WORKING EXAMPLE 2
[0205] Two other alternatives may be used in the manufacturing
process:
[0206] The first and third composition may be added in the
aforementioned percentages (or varying other percentages depending
on the required physio-chemical properties) and temperatures to
manufacture a single compounded pellet, thereby eliminating the
tumble blending requirement. The single composite pellet is then
placed in the 30 to 1 ratio high temperature extruder with the
aforementioned heat profile by zones to form one of several
products including an extruded profile such as used for separators,
wire insulation, or jackets for cabling.
WORKING EXAMPLE 3
[0207] The third composition (with talc or talc derivative) may be
tumble blended alone without the first composition in a 50/50 ratio
with a base resin of a perfluoropolymer e.g. (FEP). The process
temperatures of zones 1 through 6 of the 30 to 1 ratio high
temperature extruder requires a slightly elevated temperature
profile and pressure, in comparison with Examples 1 and 2 above.
Temperature zones of 525, 535, 550, 580, 640 and 660 is necessary
when the first composition (described in Working Example 1) is not
included in the present formulation of this example in order to
form one of several products including an extruded profile such as
used for separators, wire insulation, or jackets for cabling.
WORKING EXAMPLE 4
[0208] The tumble blending step described in Working Example 3, of
the third composition (with talc) at a 50/50 ratio with the base
polymer resin of a perfluoropolymer e.g. (talc), may be eliminated
by the use of the aforementioned twin screw compounding equipment.
The talc, instead, is added into the extruded melt of the base
perfluoropolymer resin in sequential steps to accomplish a 7.5%
loading of the talc in the perfluoropolymer resin. The temperature
profile for zones 1 through 6 would be as follows: 520, 530, 540,
560, 580 and 600 degrees Fahrenheit. The process temperatures of
this single compound pellet with 7.5% talc and 92.5%
perfluoropolymer resin is then extruded on a 30 to 1 ratio high
temperature extruder with temperature zones of 525, 535, 550, 580,
640 and 660 degrees Fahrenheit for the extrusion of profiles,
insulations and jackets.
[0209] In the rest of the text, the expressions -melt-processable
per(halo)fluoropolymer" and "polymer (A)" are understood, for the
purposes of the invention, both in the plural and the singular,
that is to say that the inventive composition may comprise one or
more than one polymer (A).
[0210] Preferably, the composition of the invention comprises only
one polymer (A).
[0211] The per(halo)fluoropolymer can comprise one or more halogen
atoms (Cl, Br, I), different from fluorine.
[0212] The TFE copolymers as above detailed comprise advantageously
at least 2% wt. preferably at least 5% wt, more preferably at least
7% wt of recurring units derived from the per(halo)fluoromonomer
(PFM).
[0213] The TFE copolymers as above detailed comprise advantageously
at most 30% wt, preferably at most 25% wt, more preferably 20% wt
of recurring units derived from the per(halo)fluoromonomer
(PFM).
[0214] Good results have been obtained with TFE copolymers as above
detailed comprising at least 2% wt and at most 30% wt of recurring
units derived from the per(halo)fluoromonomer (PFM). [0215] 1.
perfluoro-oxyalkylvinylethers complying with general formula
CF.sub.2.dbd.CFOX.sub.0, in which X.sub.0 is a C.sub.1-C.sub.12
perfluorooxyalkyl having one or more ether groups, like
perfluoro-2-propoxy-propyl group; and/or [0216] 2. C.sub.3-C.sub.8
perfluoroolefins, such as hexafluoropropene (HFP); and/or
per(halo)fluorodioxoles of formula:
##STR00005##
[0217] wherein each of R.sub.f3, R.sub.f4, R.sub.f5, R.sub.f6,
equal of different each other, is independently a fluorine atom, a
C.sub.1-C.sub.6 perfluoroalkyl group, optionally comprising one or
more oxygen atom, e.g. --CF.sub.3, --C.sub.2F.sub.5,
--C.sub.3F.sub.7, --OCF.sub.3, --OCF.sub.2CF.sub.2OCF.sub.3.
[0218] Composition according to claim 2, wherein the
per(halo)fluoropolymers [polymers (A)] is selected among TFE
copolymers comprising recurring units derived from at least one
per(halo)fluoromonomer (PFM) chosen among the group consisting of:
[0219] 1. perfluoroalkylvinylethers, as above defined;
perfluoro-oxyalkylvinylethers, as above defined; [0220] 2.
C.sub.3-C.sub.8 perfluoroolefins, as above defined. [0221] 3.
According to a first embodiment of the invention, the polymer (A)
is chosen among TFE copolymers comprising recurring units derived
from HFP and optionally from at least one perfluoroalkylvinylether,
as above defined. [0222] 4. Preferred polymers (A) according to
this embodiment are selected among TFE copolymers comprising
(preferably consisting essentially of) recurring units derived from
tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) in an
amount ranging from 3 to 15 wt % and, optionally, from 0.5 to 3 wt
% of at least one perfluoroalkylvinylether, as above defined.
[0223] The Applicant has surprisingly found that the use an active
nucleating agent chosen among: at least one metal carbonate
different from magnesium carbonate having decomposition temperature
exceeding 350.degree. C., generally chosen among
CaCO.sub.3,BaCO.sub.3, ZnCO.sub.3 and PbCO.sub.3; at least one talc
derivative;
[0224] and mixtures thereof,
[0225] which are thermally stable at typical temperatures of
processing of the polymer (A) is particularly useful, because these
carbonates can be intimately admixed in the melt during processing
and foaming within the per(halo)fluoropolymer matrix without
significant decomposition, so as to obtain a very homogeneous
distribution of nucleating sites.
[0226] Also, when combined with MgCO.sub.3, these active nucleating
agents actively participate in evolving carbon dioxide/water vapor
during foaming process, thanks to the combined effect of acid
evolvement and temperature. These active nucleating agents are
particularly useful for blowing foams of polymer (A), as its
intrinsic basicity enables capture and neutralization of eventual
traces of HF acid which might evolve from the molten material. Also
hydrogen fluoride can advantageously react with the metal carbonate
forming carbon dioxide. It is believed that the formation of this
carbon dioxide/water vapor provides sites for initiation or
nucleation of cells forming from the blowing agent.
[0227] Preferably up to 5 parts by weight of above mentioned active
nucleating agent per 100 parts by weight of polymer (A) can be
used. More preferably, there are about 0.5 to about 3 parts by
weight of active nucleating agent per100 parts by weight of polymer
(A).
[0228] The most preferred thermally stable metal carbonate is
calcium carbonate. The particle size of the calcium carbonate can
be up to about 10 microns, and is preferably from 0.1 to 0.3
microns. The calcium carbonate which is most preferred is a
precipitated grade having an average diameter of about 0.03
microns. However, larger size particles have been successfully
used, including particles having an average diameter size between
0.7 microns and 3.0 microns.
[0229] Particularly good results have been obtained using 1 part by
weight of CaCO.sub.3 per 100 parts by weight of polymer (A).
[0230] For the purpose of the invention, the term "talc derivative"
is intended to denote a hydrate magnesium silicate mineral,
typically having an exfoliated of fibrous crystal habit.
[0231] Typically, the talc derivative can comprise in addition to
magnesium hydrosilicate of formula 3MgO.SiO.sub.2.H.sub.2O
(SiO.sub.2.dbd.63.5% wt, MgO.dbd.31.90% wt, H.sub.2O.dbd.4.75% wt)
other minerals such as magnesite, chlorite, calcite, magnetite,
carbonate, dolomite.
[0232] Generally, the talc derivative has the following
composition:
TABLE-US-00003 SiO.sub.2 35 to 65% wt. MgO 30 to 35% wt.
FeO/Fe.sub.2O.sub.3 0 to 6% wt. Al.sub.2O.sub.3 0 to 15% wt. CaO 0
to 2% wt. CO.sub.2 0 to 15% wt. H.sub.2O 3 to 10% wt.
[0233] The talc derivative has generally a density of 2.7 to 2.9
g/cm.sup.3 and a specific surface area of 5 to 10 m.sup.2/g (as
determined by B.E.T. method using N.sub.2 as gas).
[0234] Talc derivatives have been found particularly useful in
combination with the MgCO.sub.3 blowing agent in the composition of
the invention. By introduction of talc as active nucleating agent,
preferably in combination with at least one metal carbonate
different from magnesium carbonate having decomposition temperature
exceeding 350.degree. C., it has been possible obtaining a very
homogenous cell size distribution and a multiplicity of cells
having small dimension.
[0235] According to a first embodiment of the invention, the
composition comprises an active nucleating agent comprising at
least one metal carbonate different from magnesium carbonate having
decomposition temperature exceeding 350.degree. C. The composition
according to this first embodiment of the invention preferably
comprises CaCO.sub.3.
[0236] According to a second embodiment of the invention, the
composition comprises an active nucleating agent comprising a talc
derivative. Optionally, the composition can further comprise at
least one metal carbonate different from magnesium carbonate having
decomposition temperature exceeding 350.degree. C., which
synergistically cooperates with the talc derivative.
[0237] Preferably up to 20 parts by weight of above mentioned talc
derivative per100 parts by weight of polymer (A) can be used. More
preferably, there are about 0.2 to about 3 parts by weight of talc
derivative per 100 parts by weight of polymer (A).
[0238] The composition of the invention is preferably free from
traditional chemical blowing agents; in other words, the magnesium
carbonate and the active nucleating agent as above described, are
preferably the unique components to behave as blowing agents, i.e.
generating a blowing gas at processing temperatures of
per(halo)fluoropolymer (A).
[0239] Typically, the composition of the invention is free from
chemical blowing agents such as: [0240] hydrazodicarboxylates
having the formula: ROOC--HN--NH--COOR' wherein at least one of R
and R' is selected from the group consisting of secondary and
tertiary alkyl groups having from 3 to 5 carbon atoms and the other
of R and R' is selected from the group consisting of straight-chain
and branched-chain alkyl groups having from 1 to 8 carbon atoms,
cycloalkyl radicals having from 5 to 8 carbon atoms, aryl radicals
having from 6 to 10 carbon atoms, and alkaryl and alkaryl radicals
having from 7 to 10 carbon atoms. The most preferred blowing agent
within this class being diisopropyl hydrazodicarboxylate. [0241]
azocarbonamides, such as Azodicarbonamid (ADC); [0242] bis-suifohy
drazides, such as, notably, oxi-bis-sulfo-hydrazid (OBSH), 25
Toluol-sulfo-hydrazid (TSH), Benzol-sulfo-hydrazid (BSH),
oxybisenzenesulphonylhydrazide (OBSH); [0243] 5-Phenyl-tetrazol
derivatives (5-PT), e.g. barium salt thereof; [0244]
semicarbazides, like para-toluol-sulfonyl-semicarbazid (PTSS);
[0245] sodium boron hydride and derivatives thereof.
[0246] The composition of the present invention preferably
comprises also a processing aid, which facilitate processing and
improve surface aspect. Processing aids for fluoropolymers
well-known to those skilled in the art can be used. Materials which
have been found to yield particularly good results in the
composition of the invention are processing aids based on
polyolefin polymers, in particular on polyethylene polymers, more
precisely on functionalized polyethylene polymers comprising acid
functionalities, e.g. ethylene/acrylic acid copolymers, in general
salified with appropriate salts. These materials, generally
referred to as polyethylene ionomers, are notably commercially
available under the trade mark AClyn.RTM. from Honeywell. The use
of salified polyethylene ionomers is particularly advantageous, as
these materials further cooperates in capturing acidity optionally
generated during melt processing of the composition of the
invention.
[0247] The composition of the present invention generally further
contains at least one inert nucleating agent. There can be up to 30
parts of nucleating agent, preferably from 0.1 to 5 parts of
nucleating agent per hundred parts of polymer (A).
[0248] The term "inert" nucleating agent is intended to the purpose
of the invention as opposed to "active" nucleating agent, that is
to say that the composition can comprise also a nucleating agent
which is intended to only provide sites for the formation of cells
generated by the blowing agent, and which does not participate in
blowing my means of substantial decomposition phenomena yielding
gaseous fluids.
[0249] According to an embodiment of the invention, the composition
comprises an inert nucleating agent comprising titanium dioxide, at
least one inorganic salt selected from the group consisting of
lithium carbonate, calcium carbonate, calcium tetraborate,
strontium carbonate, sodium carbonate sodium tetraborate, sodium
sulfite, potassium tetraborate potassium pyrosulfate, potassium
sulfate, barium nitrate, aluminum phosphate, sodium fluorosilicate
and combinations thereof, and at least one sulfonic acid salt,
phosphonic acid salt or combinations thereof.
[0250] The applicant has surprisingly found that this nucleating
agent composition, which has been in the past applied with success
to physical foaming of fluoropolymers using gaseous nitrogen as
blowing agent (see U.S. Pat. No. 6,395,795), can be used with
success also in chemical foaming (which indeed proceeds with
completely different mechanism) in the compositions of the
invention, in combination with MgCO.sub.3 and thermally stable
carbonates or talc derivatives, as above described.
[0251] The inert nucleating agent of this second embodiment
preferably has about 50 ppm to about 2,000 ppm titanium dioxide by
weight based on the total weight of the composition, about 25 ppm
to about 3,000 ppm inorganic salt selected from the group selected
from the group consisting of lithium carbonate, calcium carbonate,
calcium tetraborate, strontium carbonate, sodium carbonate sodium
tetraborate, sodium sulfite, potassium tetraborate potassium
pyrosulfate, potassium sulfate, barium nitrate, aluminum phosphate,
sodium fluorosilicate and combinations thereof by weight based on
the total weight of the composition, and about 100 to about 3,000
ppm sulfonic acid salts, phosphonic acid salts or combinations
thereof by weight based on the total weight of the composition.
[0252] Sodium tetraborate (Na.sub.2B.sub.4O.sub.7) and calcium
tetraborate (CaB.sub.4O.sub.7), however, are preferred, with sodium
tetraborate being particularly preferred.
[0253] The sulfonic acid salts that are preferred in this invention
are those salts of CF.sub.3CF.sub.2(CF.sub.2CF.sub.2).sub.n
CH.sub.2CH.sub.2SO.sub.3X where X is either H or NH.sub.4 and
n=1-10, predominantly n=2-4, preferably the barium salt. A useful
sulfonic acid salt for the invention is ZONYL.RTM. BAS, which is
barium salt of ZONYL.RTM. TBS, both available from E.I. DuPont de
Nemours and Company ("DuPont"), Wilmington, Del., USA. Other
sulfonic acid salts that can be used are potassium perfluorooctane
sulfonate sold under the trademark FLUORAD.RTM. FC-95, potassium
perfluorobutane sulfonate (L-7038) both available from 3M, St.
Paul, Minn., USA and perfluoroalkyl sulphonic acid available under
the tradename FORAFAC.RTM. 01176 from Atofina Chemicals,
Philadelphia, Pa., USA.
[0254] An inert nucleating agent which yielded particularly good
results according to this embodiment of the invention was composed
of 750 ppm of ZONYL.RTM. BAS, 250 ppm TiO.sub.2 and 100 ppm Sodium
Tetra Borate, with respect to the weight of polymer (A).
[0255] The present invention also concerns a process for the
manufacture of the foamable composition as above detailed.
[0256] Generally, the process of the invention comprise dry
blending of the polymer (A), the blowing agent based on magnesium
carbonate; and the active nucleating agent, based on above detailed
metal carbonates.
[0257] These materials can be blended in standard equipments
well-known to those skilled in the art.
[0258] The polymer (A) to be used in the process of the invention
is generally under the form of a powder having an average particle
size comprised between 1 and 1500 preferably between 50 and 1000
.mu.m.
[0259] Typically, the composition of the invention can be
manufactured as a powder mixture by dry blending the polymer (A),
the blowing agent and the active nucleating agent, and all other
optional ingredients, as above details, using high intensity
mixers. Henschel-type mixers are preferred equipments. So obtained
powder mixture can comprise the polymer (A), the blowing agent and
the active nucleating agent in the weight ratios as above detailed,
suitable for obtaining effective foaming, or can be a concentrated
mixture to be used as masterbatch and diluted in further amounts of
polymer (A) in subsequent processing steps.
[0260] It is also possible to manufacture the composition of the
invention by further melt compounding the powder mixture as above
described with or without an additional quantity of polymer
(A).
[0261] It is generally preferred to incorporate the powder mixture
as above described in an additional quantity of polymer (A).
[0262] Conventional melt compounding devices can be used.
Preferably, extruders, more preferably twin screw extruders can be
used. Specially flighted extruders, i.e. extruders specifically
designed to effectively control temperature such that foaming or
nucleation is not prematurely initiated and such that the
composition may be melted, blended, extruded and palletized without
premature foaming of the composition are particularly
preferred.
[0263] The design of the compounding screw, e.g. flight pitch and
width, clearance, length as well as operating conditions will be
advantageously chosen so that sufficient heat and mechanical energy
is provided to advantageously fully melt the powder mixture as
above detailed and advantageously obtain a homogeneous distribution
of the different ingredients, but still mild enough to
advantageously keep the processing temperature of the composition
below that in which foaming may be prematurely initiated.
[0264] Provided that the processing temperature is kept at most at
600.degree. F. (315.degree. C.), i.e. above the melting point of
the polymer (A), but below the decomposition temperature of the
blowing agent, it is advantageously possible to obtain extrudates
of the composition of the invention which have not undergone
significant foaming. Such strand extrudates can be chopped by means
e.g. of a rotating cutting knife aligned downwards the die plate,
generally with an underwater device, which assures perfect cutting
knife to die plate alignment, and collected under the form of
pellets, which can be used for the manufacture of final foamed
parts.
[0265] Final foamed parts can be advantageously manufactured by
melt processing the composition as above detailed at a
predetermined temperature exceeding 600.degree. F. (315.degree.
C.), above the melting point of the polymer (A) and the required
temperature for the blowing agent: in these conditions, the
magnesium carbonate and the active nucleating agents advantageously
cooperate to yield chemically foamed final parts with no need of
additional injection of gazes.
[0266] The skilled in the art would determine using standard
techniques and routine work, temperature, power and residence time
of the composition in the extruder so as to obtain final foamed
parts having the desired void fraction or foaming level.
[0267] As a function of the extruder die, several different foamed
parts can be obtained, including separators, wire insulators,
jackets and the like.
[0268] Foamed articles obtained from the foamable composition as
above described are also objects of the present invention.
[0269] The present invention also provides a method of making a
communications cable having flame retardant properties comprising
the steps of manufacturing the foamable composition as above
defined at a temperature of at most 600.degree. F. (315.degree.
C.), melt processing such composition at a predetermined
temperature exceeding 600.degree. F. (315.degree. C.) above the
melting point of the fluorinated polymer and the required
temperature for the blowing agent, extruding a metered amount of
the melted composition around an advancing electrical conductor and
allowing the composition to foam and expand (e.g. to a thickness of
typically less than 25 mil) to produce an insulated conductor with
a chemically blown per(halo)fluoropolymer insulation.
[0270] A twisted pair of the insulated conductors may then be
formed from two of the conductors and a jacket formed around the
twisted pair to form a communications cable.
[0271] The layer of foamed fluorinated polymer insulating material
surrounding the conductor can be applied in a relatively thin layer
(generally less than about 25 mils) and has excellent uniformity of
thickness and uniformity of electrical properties along the length
of the wire. Further, the foamed per(halo)fluoropolymer insulation
provides a cable having a high velocity of propagation which can
meet very close manufacturing tolerances. The insulated wire can be
produced at high throughput using traditional processing
equipments.
[0272] Otherwise coaxial cables comprising a round conducting wire,
surrounded by an insulating spacer, surrounded by a cylindrical
conducting sheath, usually surrounded by a final insulating layer
(jacket), generally having a nominal thickness of 0.008'' can also
be formed, the foamable composition of the invention being used the
first insulating spacer and/or for the outer insulating layer
(jacket). A thickness of 0.025'' to 0.125'' of the foamed
insulating layer (spacer or jacket) is generally required, with a
foaming level which ranges approximately between 2 and 60%.
[0273] The invention will be now described in more detail with
reference to the following examples, whose purpose is merely
illustrative and not intended to limit the scope of the
invention.
EXAMPLE 5
Manufacture of a Powder Mixture (Masterbatch Composition)
[0274] MgCO.sub.3, CaCO.sub.3 and AClyn.RTM. wax commercially
available from Honeywell and a fine powder of HYFLON.RTM. MFA
commercially available from Solvay Solexis Inc. were placed in a
powder form and blended as a master batch in a high intensity mixer
i.e. in a Henschel type Powder Blender. The composition of this
powder mixture was the following: [0275] 94.8% of MFA powder;
[0276] 3.79% MgCO.sub.3; [0277] 0.94% CaCO.sub.3; [0278] 0.47%
AClyn.RTM. wax.
EXAMPLE 6
Manufacture of a Pelletized Foamable Composition
[0279] This master batch prepared as detailed in example 1 was
further extruded into a pellet form utilizing a twin screw
extrusion process.
[0280] The powder mixture of example 1 was thus incorporated in a
per(halo)fluoropolymer resin, namely TEFLON.RTM. FEP in a weight
ratio powder mixture/per(halo)fluoropolymer 20/80 by sequential
additions through the feeder sections of the twin screw extruder.
Temperature profile in the melt twin screw extruder was the
following (from zone 1 to 6): 520.degree. F. (270.degree. C.),
530.degree. F. (277.degree. C.), 540.degree. F. (282.degree. C.),
560.degree. F. (293.degree. C.), 580.degree. C. (304.degree. C.),
and 600.degree. F. (315.degree. C.). The extruder was equipped with
an underwater pelletizer providing pellets of the composition as
above detailed with constant and regular shape.
EXAMPLE 7
Manufacture of a Powder Mixture of Polymer (A) and Talc Derivative
(Masterbatch Composition)
[0281] A talc derivative of chemical composition
Mg.sub.3Si.sub.4O.sub.10(OH) was melt compounded with a
per(halo)fluoropolymer resin, namely TEFLON.RTM. FEP in a weight
ratio talc/per(halo)fluoropolymer 15/85 w/w, in a twin screw
extruder with underwater pelletizer, with the following temperature
profile: 520.degree. F. (270.degree. C.) 530.degree. F.
(277.degree. C.) 540.degree. F. (282.degree. C.), 560.degree. F.
(293.degree. C.), 580.degree. C. (304.degree. C.), and 600.degree.
F. (315.degree. C.).
EXAMPLE 8
Manufacture of Foamable Compositions From a Mixture of Pellets of
Example 2 and Example 3;
[0282] Pellets obtained from example 2 and pellets obtained from
example 3 were tumble blended with base resin TEFLON.RTM. FEP in
the following weight ratio (pellets of ex. 2)/(pellets of ex.
3)/polymer (A)=5/45/50.
[0283] The aforementioned tumble blended materials were then placed
in the hopper of a 30 to 1 ratio high temperature extruder with
heat zones 1 through 6 set at the following temperatures
530.degree. F. (277.degree. C.), 550.degree. F. (288.degree. C.),
570.degree. F. (299.degree. C.), 600.degree. F. (315.degree. C.),
610.degree. F. (320.degree. C.), and 630.degree. F. (330.degree.
C.) to form one of several foamed articles including an extruded
profile such as used for separators, wire insulation, or jackets
for cabling.
[0284] Foamable articles were found to possess an outstanding cells
structure, with tunable foaming level, and outstanding insulating
properties as described in the following working examples;
WORKING EXAMPLE 9
[0285] A foamed perfluoropolymer insulation was extruded over 24
gage wire by using a cross head with a tip and die. The extruder
was a high temperature 11/2 inch, 30:1 ratio device. The screw
design was a 4:1 high compression screw. The line speeds were in a
range from 400 ft/min. to 1200 ft/min. The screw rpm were from 12
rpm to 35 rpm with pressure ranging from 1500 psi to 2000 psi. The
melt temperature was 678 F. The extruder was loaded with pellets
containing 10% talc and 90% FEP. This resulted in an insulation
extrudate that was 41% foamed with an average foamed cell size of
0.0007 inches.
WORKING EXAMPLE 10
[0286] A cross web cable support-separator was manufactured with a
11/2 inch high temperature extruder using the following materials
and conditions;
[0287] Use of a cross web die with a high compression screw, a line
speed of 148 ft./min. at a pressure of 1700 psi with a 48 RPM screw
speed and a melt temperature of 649 F. The extruder was loaded with
a pellet master batch, the pellet comprising 15% talc and 85% FEP.
The pellet master batch was blended in a 50:50 ratio with 100% FEP.
Therefore, the final blend ratio was 50% master batch pellets and
50% FEP. This resulted in a cross web extrudate that was 40% foamed
with an average foamed cell size of 0.0006 inches.
WORKING EXAMPLE 11
[0288] A Double Helix cable support-separator was manufactured
using a 11/2 inch extruder with the following materials and
conditions;
[0289] A web cable support-separator was manufactured using a
profile extrusion die with a high compression screw, a line speed
of 75 ft./min. at a pressure of 1850 psi with a 40 RPM screw speed
and a melt temperature of 646 F. The extruder was loaded with
master batch pellets containing 15% talc and 85% FEP. This master
batch was blended with 100% FEP. The final blend ratio was 70%
master batch pellets and 30% FEP. This resulted in a web extrudate
that was 33% foamed with an average foamed cell size of 0.0007
inches.
WORKING EXAMPLE 12
[0290] A foamed perfluoropolymer insulation was extruded over 24
gage wire by using a cross head with a tip and die. The extruder
was a high temperature 11/2 inch, 30:1 ratio device. The screw
design was a 4:1 high compression screw. The line speeds were in a
range from 300 ft/min. to 900 ft/min. The screw rpm were from 12
rpm to 30 rpm with pressure ranging from 1500 psi to 2000 psi. The
melt temperature was 680 F. The extruder was loaded with pellets
containing 10% talc and 90% FEP. This resulted in an insulation
extrudate that was 35% foamed with an average foamed cell size of
0.0007 inches.
[0291] Other desired embodiments, results, and novel features of
the present invention will become more apparent from the following
drawings, detailed description of the drawings, and the
accompanying claims.
BRIEF DESCRIPTION OF THE DRAWING
[0292] FIG. 1 is a schematic which are representative of processes
used to produce the disclosed compositions.
DETAILED DESCRIPTIONS OF DRAWING
[0293] The following description will further help to explain the
inventive features of the system, method and compositions of the
present disclosure.
[0294] There are four distinct compositions that are created by the
system and are noted as a first composition [100], a second
composition [200], a third composition [300] and a fourth
composition [400]. The first composition comprises a blend of
selected perfluoropolymer [110], magnesium carbonate (MgCO.sub.3)
[120], calcium carbonate (CaCO.sub.3) [130], and AClyn.RTM. wax
[140] as a powder blend mixed homogeneously. The second composition
[200] is a blowing or foaming agent comprised of the first
composition [100] and a selected perfluoropolymer [110] that is
melted by heat, blended, extruded and pelletized by a specially
flighted extruder [250] wherein the extruder is specifically
designed to minimize heat transfer such that foaming or nucleation
is not prematurely initiated and such that the composition may be
melted, blended, extruded and pelletized without premature foaming
of the composition. The third composition [300] which is a
nucleating agent is comprised of a selected perfluoropolymer [110]
and talc [310] (magnesium silicate hydroxide or other talc
derivative) (Mg.sub.3Si.sub.4O.sub.10(OH).sub.2) which is blended,
melted by heat extruded and pelletized in a specially flighted
extruder [350]. The fourth composition [400] is comprised of the
second composition [200] and the third composition [300] which are
tumble blended for use in a profile extruder [450].
[0295] The first composition [100] comprises a selected
perfluoropolymer [110] that may be MFA, FEP, or PFA, as a selected,
uniform, pure perfluoropolymer [110] or as a mixture of one or more
different perfluoropolymers [110] at or about 94.8 percent by
weight. The perfluoropolymer [110], magnesium carbonate [120] at or
about 3.79 percent, calcium carbonate [130] at or about 0.94
percent and AClyn.RTM. wax [140] at or about 0.47 percent are mixed
into a homogeneous powder in a Henschel blender.
[0296] The second composition [200] is comprised of the first
composition [100] and a selected perfluoropolymer [110]. The ratio
of perfluoropolymer [110] to first composition [100] is at or about
80 percent to at or about 20 percent by weight. The
perfluoropolymer [110] may be MFA, FEP, or PFA, as a selected,
uniform, pure perfluoropolymer [110] or as a mixture of one or more
different perfluoropolymers [110]. The perfluoropolymer [110] may
be substituted with fluoropolymer [115]. The first composition
[100] and selected perfluoropolymer [110] are then placed in a
extruder that minimizes mechanical shear and increased heating
thereby mitigating premature foaming [250] during the process of
melting blending, extruding and pelletizing.
[0297] The third composition [300] is comprised of magnesium
silicate hydroxide, commonly known as talc [310] and
perfluoropolymer [110]. The ratio of talc [310] is at or about 15
percent with the perfluoropolymer [110] at or about 85 percent by
weight, however the talc [310] may range in concentration from 0.2
to 20 percent. The perfluoropolymer [110] component of the third
composition [300] may be MFA, FEP, or PFA, as a selected, uniform,
pure perfluoropolymer
[0298] or as a mixture of one or more different perfluoropolymers
[110] or 100 percent recycled and/or blended with non-recycled
perfluoropolymers [110] in any ratio from 1 to 99 percent. The
third composition [300] is then placed in an extruder specifically
designed to minimize heat transfer such that foaming or nucleation
is not prematurely initiated [350] and such that the composition
may be melted, blended, extruded and pelletized. Additionally, an
organic or inorganic salt [320] may be added to the third
composition [300].
[0299] The fourth composition [400] is comprised of the second
composition [200] and third composition [300]. In pellet form, it
is tumble blended at a ratio of 30 percent of the second
composition [200] and 70 percent of the third composition [300]. It
is also possible to form chemically foamed or gas injected foamed
components [600] using 100 percent of the third composition [300]
only. An additional blend of the fourth composition [400] includes
approximately a 35 percent second composition [200], a 30 percent
third composition [300] and 35 percent of a selected
perfluoropolymer [110]. The blended fourth composition [400] or
third composition alone [300] is then ready for use in profile
extrusion. The fourth composition [400] may also comprise inorganic
and/or organic additives that include inorganic salts, metallic
oxides, silica and silicon oxides as well as substituted and
unsubstituted fullerenes. Any combination of compositions [200],
[300], and [400] may be combined in any ratio to form a single
pelletized product or may be individually pelletized to form a
single pelletized product.
[0300] The profile extrusion unit [450] may optionally utilize air
or inert gas in addition or in lieu of chemical foaming to adjust
the cellular size of the foamed end products [600] which are high
performance multi-media cable insulative components [500] for
example: wire insulation [510], fiber optic sheathing [520], cable
support-separators [530], jacketing [540], wraps [550] and tapes
[560]. The blown or foamed insulative components [600] exhibit a
smaller and more consistent cell structure than has been previously
achieved and at a lower cost than any known present methods.
[0301] It will, of course, be appreciated that the system, method
and compositions that have been described have been given simply by
the way of illustration, and the disclosure is not limited to the
precise embodiments described herein; various changes and
modifications may be effected by one skilled in the art without
departing from the scope or spirit of the invention as defined in
the inventive claims.
* * * * *