CA2435719A1 - Flame retardant foam under layer having refined micro-cellular structure - Google Patents
Flame retardant foam under layer having refined micro-cellular structure Download PDFInfo
- Publication number
- CA2435719A1 CA2435719A1 CA 2435719 CA2435719A CA2435719A1 CA 2435719 A1 CA2435719 A1 CA 2435719A1 CA 2435719 CA2435719 CA 2435719 CA 2435719 A CA2435719 A CA 2435719A CA 2435719 A1 CA2435719 A1 CA 2435719A1
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- Canada
- Prior art keywords
- under layer
- flame retardant
- micro
- foam under
- particles
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
- H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
- H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
- H01B3/44—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins
- H01B3/441—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins from alkenes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
- H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
- H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
- H01B3/44—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins
- H01B3/443—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins from vinylhalogenides or other halogenoethylenic compounds
- H01B3/445—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins from vinylhalogenides or other halogenoethylenic compounds from vinylfluorides or other fluoroethylenic compounds
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
- H01B7/29—Protection against damage caused by extremes of temperature or by flame
- H01B7/295—Protection against damage caused by extremes of temperature or by flame using material resistant to flame
Landscapes
- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Insulated Conductors (AREA)
- Compositions Of Macromolecular Compounds (AREA)
Abstract
A flame and smoke retardant dual insulation design for insulated conductors in a telecommunication cable is disclosed. The insulation comprises an elongate substantially cylindrical fluoro-polymer outer layer and an under layer interposed between the conductor and the outer layer. The under layer includes a metallocene type polyolefin having PTFE micro-particles, a halogen type flame retardant package, clay based nanocomposite type particles and a light metal (Mg or Al) hydroxide, or any combination thereof.
There is also disclosed a foam under layer for interposition between an electrical conductor and a cable jacket wherein the foam is fabricated from an exfoliated clay-based nanocomposite. During fabrication the exfoliated clay-based nanocomposite nucleates the foam under layer providing for the formation of micro-cells of less than 25µm.
There is also disclosed a foam under layer for interposition between an electrical conductor and a cable jacket wherein the foam is fabricated from an exfoliated clay-based nanocomposite. During fabrication the exfoliated clay-based nanocomposite nucleates the foam under layer providing for the formation of micro-cells of less than 25µm.
Description
TITLE OF THE INVENTION
FLAME RETARDANT FOAM UNDER LAYER HA\/ING DEFINED MICRO-CELLULAR STRUCTURE
FIELD OF THE INVENTION
The present invention relates to a flame retardant insulation design for electrical cabling. In particular; the present invention relates to a flame and smoke retardant insulation design for telecommunications cables having at least one insulated conductor and a covering jacket where the insulation design is comprised of a layer of ~~luoro-polymer covering .an under layer having a polymer formulation that includes a light metal hydroxide. During fabrication the foam under layer is nucleated using an exfoliated clay-based nanocomposite causing the formation of micro-cells of less than 25pm.
BACKGROUND
In plenum applications, where electrical cabling is run in the spaces created by suspended ceilings or false floors which are also used for the movement of environmental air, building codes and fire regulations typically place very strict requirements in terms of a cable's resistance to open flame and emission of non-toxic fumes and smoke at high temperatures. T'ipically, in order to meet these requirements, the cabling is enclosed in suitable ducting or, alternatively, cables fabricated using special jackets and other non-toxic and fire retardant materials are used.
The prior art shows an increasing use of nanocomposites comprising organically modified nanoclays and polyolefin copolymers in the fabrication of materials having flame retardant and smoke retardant properties. For example, in US Patent No. 6,414,070 organically modified nanoclays are used exclusively with polyolefin copolymers 'to significantly improve the flame retardant properties of the resulting polymeric nanocomposites. In a previous disclosure (US Pat. 5,773,502) it was shown that adding organically modified nanoclays and a polytetrafiuoroethylene (PTFE) additive to a polyester material in conjunction with a bromine based organic flame retardant package (with antimony oxide) improved the overall performance of the compound in terms of flame retardation. Thus, the improved formulation rias maintained the same flame retardant properties as the original formulation despite a reduction in the initial bromine flame retardant package from 31 % to 18%. ~ne drawback, however, is that bromine based organic flame retardant packages typically generate high smoke levels.
In a more recent disclosure (US Patent No. 6,492,453) it was shown that the addition of organically modified nanoclays to polyolefin copolymers, in conjunction with a non-halogen package containing nnainly magnesium hydroxide, resulted in both highly flame retardant and highly smoke retardant formulations. Such polymer formulations, as taught in US Patent No.
6,492,453, were used as insulating dielectrics in cable constructions that have met NFPA 262 and UL 9'10 test requirements. However, these types of materials contain between 60% and 40% of magnesium hydroxide and, consequently, are difficult to process and typically have very low tensile strength when compared with materials containing a bromine based organic flame retardant package. In a previous disclosure (US Patent No. 5,563,377), Arpin and the undersigned have shown that a cable construction with a Dual Insulation Design (DID) comprised of a top Fluorinated Ethylene Propylene (FEP) layer (for example TeflonT"") and a flame retardant polyolefin under-layer that may contain a bromine based organic flame retardant package, should also meet the NFPA 262 and UL 910 test requirements.
FLAME RETARDANT FOAM UNDER LAYER HA\/ING DEFINED MICRO-CELLULAR STRUCTURE
FIELD OF THE INVENTION
The present invention relates to a flame retardant insulation design for electrical cabling. In particular; the present invention relates to a flame and smoke retardant insulation design for telecommunications cables having at least one insulated conductor and a covering jacket where the insulation design is comprised of a layer of ~~luoro-polymer covering .an under layer having a polymer formulation that includes a light metal hydroxide. During fabrication the foam under layer is nucleated using an exfoliated clay-based nanocomposite causing the formation of micro-cells of less than 25pm.
BACKGROUND
In plenum applications, where electrical cabling is run in the spaces created by suspended ceilings or false floors which are also used for the movement of environmental air, building codes and fire regulations typically place very strict requirements in terms of a cable's resistance to open flame and emission of non-toxic fumes and smoke at high temperatures. T'ipically, in order to meet these requirements, the cabling is enclosed in suitable ducting or, alternatively, cables fabricated using special jackets and other non-toxic and fire retardant materials are used.
The prior art shows an increasing use of nanocomposites comprising organically modified nanoclays and polyolefin copolymers in the fabrication of materials having flame retardant and smoke retardant properties. For example, in US Patent No. 6,414,070 organically modified nanoclays are used exclusively with polyolefin copolymers 'to significantly improve the flame retardant properties of the resulting polymeric nanocomposites. In a previous disclosure (US Pat. 5,773,502) it was shown that adding organically modified nanoclays and a polytetrafiuoroethylene (PTFE) additive to a polyester material in conjunction with a bromine based organic flame retardant package (with antimony oxide) improved the overall performance of the compound in terms of flame retardation. Thus, the improved formulation rias maintained the same flame retardant properties as the original formulation despite a reduction in the initial bromine flame retardant package from 31 % to 18%. ~ne drawback, however, is that bromine based organic flame retardant packages typically generate high smoke levels.
In a more recent disclosure (US Patent No. 6,492,453) it was shown that the addition of organically modified nanoclays to polyolefin copolymers, in conjunction with a non-halogen package containing nnainly magnesium hydroxide, resulted in both highly flame retardant and highly smoke retardant formulations. Such polymer formulations, as taught in US Patent No.
6,492,453, were used as insulating dielectrics in cable constructions that have met NFPA 262 and UL 9'10 test requirements. However, these types of materials contain between 60% and 40% of magnesium hydroxide and, consequently, are difficult to process and typically have very low tensile strength when compared with materials containing a bromine based organic flame retardant package. In a previous disclosure (US Patent No. 5,563,377), Arpin and the undersigned have shown that a cable construction with a Dual Insulation Design (DID) comprised of a top Fluorinated Ethylene Propylene (FEP) layer (for example TeflonT"") and a flame retardant polyolefin under-layer that may contain a bromine based organic flame retardant package, should also meet the NFPA 262 and UL 910 test requirements.
Recent NFPA 262 and UL 910 tests have shown that the substitution of the bromine based organic flame retardant package with a chlorine based organic flame retardant package results in dual insulation cable constructions anrith considerably improved properties in terms of flame retardant and smoke emissions. However, these constructions have not substantially reduced the amount of FEP required and therefore lead to a smoke and flame retardant jacket that is more expensive then standard plenum jackets.
SUMMARY OF THE INVENTION
The present invention addresses the above and other drawbacks by providing a flame and smoke retardant dual insulation design for conductors, in particular in a telecommunication cable. The dual insulation comprises an elongate substantially cylindrical fluoro-polymer outer layer and an under layer interposed between the conductor and the outer layer. The under layer includes a metallocene type polyolefin having PTFE micro-particles, a halogen type flame retardant package, clay based nanocomposite particles, and a light metal (Mg or AI) hydroxide, or any combination thereof.
There is also provided for a foam under layer for interpasition between an electrical conductor and a cable jacket, the foam under layer comprising micro ceffs which are less than 25pm. During fabrication the micro cells are nucleated in the foam under layer by an exfoliated clay-based nanocomposite.
DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS
In the present disclosure, we claim that the addition of organically modified nanoclays, a PTFE additive and a light metal (Mg or AI) hydroxide to a polyolefin with a chlorine based organic flame retardant package improves the UL 910 test performance of DID cable constructions. These improvements can result in either a further reduction in the thickness of the FEP layer or in the substitution of the high cost low smoke PVC jacket for a lower cost low smoke PVC jacket, or both.
In an illustrative embodiment, 3% to 8°/~ of organically modified nanoclays, 0.5% to 40% PTFE micro-particles and 5% to 40% light metal hydroxide are added to the original chlorine based organic flame retardant package in the form of a master batch comprising the above additive, dispersed in a matrix of a metallocene type flexomer or elastomer polyolefin. Alterroativeiy, the amount of the chlorine based organic flame retardant additives could be reduced by dilution wi h the metallocene or polyolefin while adding the same amounts of 3% to 8% of organically modified nanoclays, 0.5% to 40% PTFE micro-particles and 5% to 40% light metal hydroxide.
A reduction in the chlorine based organic flame retardant additives results in a corresponding reduction in the smoke emission during the UL 910 test. The addition of the 3% to 8% of organically modified nanoclays, 0.5% to 40% PTFE
micro-particles and 5% to 40% light metal hydroxide compensates for the reduction in the chlorine based organic flame retardant additives thereby providing the overall cable with equivalent flame retardant characteristics and improved performance in terms of smoke emissions.
We also claim that the performance of a bromine type flame retardant package is also improved upon the addition of PTFE micro-particles and/or organically modified nanoclays.
Recent UL 910 tests have also shown that a dual insulation construction comprising:
~ a 0.201 inch solid copper conductor;
~ a 2.5 mils under-layer metallocene type polyolefin efastomer containing about 40% PTFE micro-particles;
~ a 5 mils FEP top transparent layer; and ~ a standard Low Smoke PVC jacket (SC 111 8511 ) does not meet current test requirements.
However, when the under-layer was substituted with a 20% foamed composition comprising 50% of the same metallocene type polyolefin elastomer with 40% PTFE micro-particles and 50% of a polyolefin containing a bromine type flame retardant package, the ~JL 910 test requirements were met.
There is also disclosed an improved micro-cellular foam insulation under-layer due to the presence of clay-based nanocompositEa in the under-layer. In particular, exfoliated clay-based nanocomposites have a higher potential than either intercalated clay-based nanocomposites or standard) spherical particles and therefore are able to nucleate a higher volume of micro-cells having smaller dimensions. These micro cells have dimensions which are less than 25pm, i.e. at least half or less than the micro-cells revealed by the prior art.
This is due mainly to the aspect ratio of clay-based nanocomposites, which is much greater than that of standard spherical particles, and the improved dispersion of exfoliated clay-based nanocomposites. Together these allow formation of well-distributed nano-sized micro-cells without the risk of coalescence.
The resulting foam insulation is more robust, has a higher modulus of elasticity and is consequently more crush resistance than othier known types of f~am insulation made with standard spherical nucleating agents. This is due in large part to the reinforcing effects of the clay-based nanocomposites and the much smaller cell size. The dielectric constant will be also reduced in relation to the gas volume in the final insulation.
The process for the extrusion of micro-cellular foam insulation should be understood to include chemical foaming, gas injection as well as, preferably, supercritical gas injection.
We, therefore, claim that the addition of organically modified nanoclays and a light metal hydroxide to the latter polymer formulation of the under-layer will bring about further reductions in the FEP layer and still result in a dual insulation cable construction that will meet the lJL 910 test requirements with good margins.
We also claim a foam under layer for use in a cable jacl~et fabricated using exfoliated clay-based nanocomposites.
Although the present invention has been described h~ereinabove by way of an illustrative embodiment thereof, this embodiment can be modified at will without departing from the spirit and nature of the subject invention.
SUMMARY OF THE INVENTION
The present invention addresses the above and other drawbacks by providing a flame and smoke retardant dual insulation design for conductors, in particular in a telecommunication cable. The dual insulation comprises an elongate substantially cylindrical fluoro-polymer outer layer and an under layer interposed between the conductor and the outer layer. The under layer includes a metallocene type polyolefin having PTFE micro-particles, a halogen type flame retardant package, clay based nanocomposite particles, and a light metal (Mg or AI) hydroxide, or any combination thereof.
There is also provided for a foam under layer for interpasition between an electrical conductor and a cable jacket, the foam under layer comprising micro ceffs which are less than 25pm. During fabrication the micro cells are nucleated in the foam under layer by an exfoliated clay-based nanocomposite.
DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS
In the present disclosure, we claim that the addition of organically modified nanoclays, a PTFE additive and a light metal (Mg or AI) hydroxide to a polyolefin with a chlorine based organic flame retardant package improves the UL 910 test performance of DID cable constructions. These improvements can result in either a further reduction in the thickness of the FEP layer or in the substitution of the high cost low smoke PVC jacket for a lower cost low smoke PVC jacket, or both.
In an illustrative embodiment, 3% to 8°/~ of organically modified nanoclays, 0.5% to 40% PTFE micro-particles and 5% to 40% light metal hydroxide are added to the original chlorine based organic flame retardant package in the form of a master batch comprising the above additive, dispersed in a matrix of a metallocene type flexomer or elastomer polyolefin. Alterroativeiy, the amount of the chlorine based organic flame retardant additives could be reduced by dilution wi h the metallocene or polyolefin while adding the same amounts of 3% to 8% of organically modified nanoclays, 0.5% to 40% PTFE micro-particles and 5% to 40% light metal hydroxide.
A reduction in the chlorine based organic flame retardant additives results in a corresponding reduction in the smoke emission during the UL 910 test. The addition of the 3% to 8% of organically modified nanoclays, 0.5% to 40% PTFE
micro-particles and 5% to 40% light metal hydroxide compensates for the reduction in the chlorine based organic flame retardant additives thereby providing the overall cable with equivalent flame retardant characteristics and improved performance in terms of smoke emissions.
We also claim that the performance of a bromine type flame retardant package is also improved upon the addition of PTFE micro-particles and/or organically modified nanoclays.
Recent UL 910 tests have also shown that a dual insulation construction comprising:
~ a 0.201 inch solid copper conductor;
~ a 2.5 mils under-layer metallocene type polyolefin efastomer containing about 40% PTFE micro-particles;
~ a 5 mils FEP top transparent layer; and ~ a standard Low Smoke PVC jacket (SC 111 8511 ) does not meet current test requirements.
However, when the under-layer was substituted with a 20% foamed composition comprising 50% of the same metallocene type polyolefin elastomer with 40% PTFE micro-particles and 50% of a polyolefin containing a bromine type flame retardant package, the ~JL 910 test requirements were met.
There is also disclosed an improved micro-cellular foam insulation under-layer due to the presence of clay-based nanocompositEa in the under-layer. In particular, exfoliated clay-based nanocomposites have a higher potential than either intercalated clay-based nanocomposites or standard) spherical particles and therefore are able to nucleate a higher volume of micro-cells having smaller dimensions. These micro cells have dimensions which are less than 25pm, i.e. at least half or less than the micro-cells revealed by the prior art.
This is due mainly to the aspect ratio of clay-based nanocomposites, which is much greater than that of standard spherical particles, and the improved dispersion of exfoliated clay-based nanocomposites. Together these allow formation of well-distributed nano-sized micro-cells without the risk of coalescence.
The resulting foam insulation is more robust, has a higher modulus of elasticity and is consequently more crush resistance than othier known types of f~am insulation made with standard spherical nucleating agents. This is due in large part to the reinforcing effects of the clay-based nanocomposites and the much smaller cell size. The dielectric constant will be also reduced in relation to the gas volume in the final insulation.
The process for the extrusion of micro-cellular foam insulation should be understood to include chemical foaming, gas injection as well as, preferably, supercritical gas injection.
We, therefore, claim that the addition of organically modified nanoclays and a light metal hydroxide to the latter polymer formulation of the under-layer will bring about further reductions in the FEP layer and still result in a dual insulation cable construction that will meet the lJL 910 test requirements with good margins.
We also claim a foam under layer for use in a cable jacl~et fabricated using exfoliated clay-based nanocomposites.
Although the present invention has been described h~ereinabove by way of an illustrative embodiment thereof, this embodiment can be modified at will without departing from the spirit and nature of the subject invention.
Claims (2)
1. A flame and smoke retardant dual insulation for an electrical cable having at least one insulated conductor, comprising:
an elongate substantially cylindrical outer layer; and a foam under layer interposed between the conductor and said jacket;
wherein said foam under layer includes:
a metallocene type polyolefin having PTFE micro-particles;
a halogen type flame retardant package;
clay based nanocomposite type particles; and a light metal (Mg or Al) hydroxide;
or any combination thereof.
an elongate substantially cylindrical outer layer; and a foam under layer interposed between the conductor and said jacket;
wherein said foam under layer includes:
a metallocene type polyolefin having PTFE micro-particles;
a halogen type flame retardant package;
clay based nanocomposite type particles; and a light metal (Mg or Al) hydroxide;
or any combination thereof.
2. A foam under layer for interposition between an electrical conductor and a cable jacket, the foam under layer comprising micro cells which are less than 25µm and wherein the micro cells are nucleated in the foam under layer by an exfoliated clay-based nanocomposite.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2435719 CA2435719A1 (en) | 2003-07-21 | 2003-07-21 | Flame retardant foam under layer having refined micro-cellular structure |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2435719 CA2435719A1 (en) | 2003-07-21 | 2003-07-21 | Flame retardant foam under layer having refined micro-cellular structure |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2435719A1 true CA2435719A1 (en) | 2005-01-21 |
Family
ID=34069923
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2435719 Abandoned CA2435719A1 (en) | 2003-07-21 | 2003-07-21 | Flame retardant foam under layer having refined micro-cellular structure |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2435719A1 (en) |
-
2003
- 2003-07-21 CA CA 2435719 patent/CA2435719A1/en not_active Abandoned
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| Date | Code | Title | Description |
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| FZDE | Dead |