GB2193594A - Water blocking in cables - Google Patents

Water blocking in cables Download PDF

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Publication number
GB2193594A
GB2193594A GB08619383A GB8619383A GB2193594A GB 2193594 A GB2193594 A GB 2193594A GB 08619383 A GB08619383 A GB 08619383A GB 8619383 A GB8619383 A GB 8619383A GB 2193594 A GB2193594 A GB 2193594A
Authority
GB
United Kingdom
Prior art keywords
cable
filling
microspheres
blowing agent
thixotropic
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.)
Withdrawn
Application number
GB08619383A
Other versions
GB8619383D0 (en
Inventor
John Robert Ivor Bury
Brian Alfred Cranfield
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
STC PLC
Original Assignee
STC PLC
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by STC PLC filed Critical STC PLC
Priority to GB08619383A priority Critical patent/GB2193594A/en
Publication of GB8619383D0 publication Critical patent/GB8619383D0/en
Publication of GB2193594A publication Critical patent/GB2193594A/en
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
    • H01B13/32—Filling or coating with impervious material
    • H01B13/322—Filling or coating with impervious material the material being a liquid, jelly-like or viscous substance
    • 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
    • H01B7/28—Protection against damage caused by moisture, corrosion, chemical attack or weather
    • H01B7/282—Preventing penetration of fluid, e.g. water or humidity, into conductor or cable
    • H01B7/285—Preventing penetration of fluid, e.g. water or humidity, into conductor or cable by completely or partially filling interstices in the cable
    • H01B7/2855—Preventing penetration of fluid, e.g. water or humidity, into conductor or cable by completely or partially filling interstices in the cable using foamed plastic

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Insulated Conductors (AREA)

Abstract

A water-blocking filling for a cable consists of a thixotropic hydrophobic material such as a petrolatum into which is mixed a small percentage by weight, 0.1% in one case, of microspheres. Each of these microspheres is of a polymeric material such as polyvynilidene dichloride filled with a blowing agent such as azodicarbamide. The filling is applied to the cable when unsheathed. The filled but unsheathed cable is now applied to an extruder to give it its outer sheath, e.g. of aluminium or an aluminium alloy. The heat generated during this extrusion causes the microspheres to expand so that interstices in the cable are filled. <IMAGE>

Description

SPECIFICATION Water blocking in cables This invention relates to a method for providing a cable with a water-blocking compound, and is applicable to metallic cables, whether telecommunication cable or power cable. It is also applicabie to optical fibre cables.
One method of providing a cable with a water-blocking filling has been described in our Patent Specification No. 8429077 (W.E.
Simpson et al 19-3-1), in which a water blocking compound for cables comprises a thixotropic hydrophobic material such as a fluid thickened by the addition of silica or bentonite. Further details of the materials thus used are given in the above-identified Patent Specification. The gel properties of the filling material may be temporarily removed by mechancial shearing to allow filling of a cable.
The present invention has as its object the provision of a method which is an improvement over that described in the above-identified Patent Specification.
According to the invention, there is provided a method of providing a cable with a waterblocking filling, which includes applying to the cable at ambient temperature a filling of a thixotropic hydrophobic material with which there is admixed a quantity of microspheres uniformly distributed throughout the filling, wherein the microspheres each consists of a sphere of a polymeric insulating material containing a blowing agent, wherein after the filling has been applied to the cable an outer sheath is extruded on to the cable, and wherein the- heat generated by said extrusion causes the microspheres to expand due to said blowing agent, so that interstices within the cable are filled, thus providing a waterblocking filling.
The cable filling used in the present method is a mixture of a thixotropic hydrophobic material and- a relatively small percentage, less than 1%, of microspheres made of a polymeric material filled with a blowing agent. The thixotropic hydrophobic material can be a petrolatum or other grease, while the microspheres in one case were made of polyvynilidene dichloride, the blowing agent being azodicarbamide. The microspheres have a diameter in the range of 40 to 60 microns, and in one case were present to the extend of 0.1% by weight of the thixotropic hydrophobic material.
The microspheres can be mixed into the other material of the filling by various known methods. Thus it can be effected by adding the microspheres, which are a white, easily flowable, powder, to the melted thixotropic hydrophobic material. This can be done by the use of a membrane pump for dosing the microspheres in, or the microspheres can be vacuum sucked into the other material. This mixing is effected at ambient temperature.
The filling thus produced is then applied to the cable, e.g. by the method described in.the above-mentioned Patent Specification. Thus the cable is placed in a filling head to which the material, i.e. the mixture, is supplied under pressure so that the cable in its unsheathed condition receives its filling. Seals at the ends of the filling head ensure that cleanliness is maintained, and also remove excess filling material when the cable is pulled out of the head via the seals at one end of the head.
The next stage in the manufacture is the application of the outer sheath, which is effected by extruding that sheath on to the cable. The outer sheath can be of aluminium or an aluminium alloy. This extrusion generates heat, and this heat causes the microspheres to expand due to the action of the heat thus generated on the contents of the microspheres. Typically the temperature to which the filling is subjected during this extrusion are in the range of 175 to 200"C. Thus the expanded microspheres fill the interstices of the cable so that a good water blocking filling is obtained in the cable.
Note that the heat used to expand the microspheres is generated by the act of extrusion; hence this heat which in normal cablemaking is often nuisance, is usefully employed.
1. A method of providing a cable with a water-blocking filling, which includes applying to the cable at ambient temperature a filling of a thixotropic hydrophobic material with which there is admixed a quantity of microspheres uniformly- distributed throughout the filling, wherein the microspheres each consists of a sphere of a polymeric insulating material containing a blowing agent, wherein after the filling has been applied to the cable an outer sheath is extruded on to the cable, and wherein the heat generated by said extrusion causes the microspheres to expand due to said blowing agent, so that interstices within the cable are filled, thus providing a waterblocking filling.
2. A method as claimed in claim 1, wherein the thixotropic material is a petrolatum, wherein the polymeric material of which the microspheres are made is polyvynilidene dichloride, and wherein the blowing agent is azodicarbamide.
3. A method as claimed in claim 1 or 2, wherein the filling contains iess than 1% by weight of said microspheres.
4. A method as claimed in claim 1 or 2, wherein the filling contains 0.1% by weight of said microspheres.
5. A method as claimed in claim 1, 2, 3 or 4, wherein the microspheres are mixed into the thixotropic hydrophobic material by a membrane pump to dose the microspheres
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Water blocking in cables This invention relates to a method for providing a cable with a water-blocking compound, and is applicable to metallic cables, whether telecommunication cable or power cable. It is also applicabie to optical fibre cables. One method of providing a cable with a water-blocking filling has been described in our Patent Specification No. 8429077 (W.E. Simpson et al 19-3-1), in which a water blocking compound for cables comprises a thixotropic hydrophobic material such as a fluid thickened by the addition of silica or bentonite. Further details of the materials thus used are given in the above-identified Patent Specification. The gel properties of the filling material may be temporarily removed by mechancial shearing to allow filling of a cable. The present invention has as its object the provision of a method which is an improvement over that described in the above-identified Patent Specification. According to the invention, there is provided a method of providing a cable with a waterblocking filling, which includes applying to the cable at ambient temperature a filling of a thixotropic hydrophobic material with which there is admixed a quantity of microspheres uniformly distributed throughout the filling, wherein the microspheres each consists of a sphere of a polymeric insulating material containing a blowing agent, wherein after the filling has been applied to the cable an outer sheath is extruded on to the cable, and wherein the- heat generated by said extrusion causes the microspheres to expand due to said blowing agent, so that interstices within the cable are filled, thus providing a waterblocking filling. The cable filling used in the present method is a mixture of a thixotropic hydrophobic material and- a relatively small percentage, less than 1%, of microspheres made of a polymeric material filled with a blowing agent. The thixotropic hydrophobic material can be a petrolatum or other grease, while the microspheres in one case were made of polyvynilidene dichloride, the blowing agent being azodicarbamide. The microspheres have a diameter in the range of 40 to 60 microns, and in one case were present to the extend of 0.1% by weight of the thixotropic hydrophobic material. The microspheres can be mixed into the other material of the filling by various known methods. Thus it can be effected by adding the microspheres, which are a white, easily flowable, powder, to the melted thixotropic hydrophobic material. This can be done by the use of a membrane pump for dosing the microspheres in, or the microspheres can be vacuum sucked into the other material. This mixing is effected at ambient temperature. The filling thus produced is then applied to the cable, e.g. by the method described in.the above-mentioned Patent Specification. Thus the cable is placed in a filling head to which the material, i.e. the mixture, is supplied under pressure so that the cable in its unsheathed condition receives its filling. Seals at the ends of the filling head ensure that cleanliness is maintained, and also remove excess filling material when the cable is pulled out of the head via the seals at one end of the head. The next stage in the manufacture is the application of the outer sheath, which is effected by extruding that sheath on to the cable. The outer sheath can be of aluminium or an aluminium alloy. This extrusion generates heat, and this heat causes the microspheres to expand due to the action of the heat thus generated on the contents of the microspheres. Typically the temperature to which the filling is subjected during this extrusion are in the range of 175 to 200"C. Thus the expanded microspheres fill the interstices of the cable so that a good water blocking filling is obtained in the cable. Note that the heat used to expand the microspheres is generated by the act of extrusion; hence this heat which in normal cablemaking is often nuisance, is usefully employed. CLAIMS
1. A method of providing a cable with a water-blocking filling, which includes applying to the cable at ambient temperature a filling of a thixotropic hydrophobic material with which there is admixed a quantity of microspheres uniformly- distributed throughout the filling, wherein the microspheres each consists of a sphere of a polymeric insulating material containing a blowing agent, wherein after the filling has been applied to the cable an outer sheath is extruded on to the cable, and wherein the heat generated by said extrusion causes the microspheres to expand due to said blowing agent, so that interstices within the cable are filled, thus providing a waterblocking filling.
2. A method as claimed in claim 1, wherein the thixotropic material is a petrolatum, wherein the polymeric material of which the microspheres are made is polyvynilidene dichloride, and wherein the blowing agent is azodicarbamide.
3. A method as claimed in claim 1 or 2, wherein the filling contains iess than 1% by weight of said microspheres.
4. A method as claimed in claim 1 or 2, wherein the filling contains 0.1% by weight of said microspheres.
5. A method as claimed in claim 1, 2, 3 or 4, wherein the microspheres are mixed into the thixotropic hydrophobic material by a membrane pump to dose the microspheres into the material.
6. A method as claimed in claim 1, 2, 3 or 4, wherein the microspheres are mixed into the thixotropic hydrophobic material by vacuum sucking.
7. A method as claimed in claim 1, 2, 3, 4, 5 or 6, wherein the sheath which is extruded on to the cable is of aluminium or of an aluminium alloy.
8. A method of providing a cable with a water-blocking filling, substantially as described herein.
9. A cable when provided with a waterblocking filling in the manner claimed in any one of the preceding claims.
GB08619383A 1986-08-08 1986-08-08 Water blocking in cables Withdrawn GB2193594A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB08619383A GB2193594A (en) 1986-08-08 1986-08-08 Water blocking in cables

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB08619383A GB2193594A (en) 1986-08-08 1986-08-08 Water blocking in cables

Publications (2)

Publication Number Publication Date
GB8619383D0 GB8619383D0 (en) 1986-09-17
GB2193594A true GB2193594A (en) 1988-02-10

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB08619383A Withdrawn GB2193594A (en) 1986-08-08 1986-08-08 Water blocking in cables

Country Status (1)

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GB (1) GB2193594A (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2217868A (en) * 1988-04-06 1989-11-01 Synthetic Technology Limited Fibre optic cables
WO1996030180A1 (en) * 1995-03-31 1996-10-03 Exxon Chemical Patents Inc. Foamed rotationally molded articles
US8089000B2 (en) * 2007-10-12 2012-01-03 General Cable Technologies Corporation Waterproof data cable with foam filler and water blocking material
US9435978B1 (en) * 2012-06-14 2016-09-06 Superior Essex Communications Lp Water-resistant optical fiber cables
CN113077930A (en) * 2021-04-13 2021-07-06 宁波容合电线有限公司 Thermal expansion yarn filling cable and processing technology thereof

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1308779A (en) * 1969-11-21 1973-03-07 British Insulated Callenders Telecommunication cables

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1308779A (en) * 1969-11-21 1973-03-07 British Insulated Callenders Telecommunication cables

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2217868A (en) * 1988-04-06 1989-11-01 Synthetic Technology Limited Fibre optic cables
WO1996030180A1 (en) * 1995-03-31 1996-10-03 Exxon Chemical Patents Inc. Foamed rotationally molded articles
US8089000B2 (en) * 2007-10-12 2012-01-03 General Cable Technologies Corporation Waterproof data cable with foam filler and water blocking material
US9435978B1 (en) * 2012-06-14 2016-09-06 Superior Essex Communications Lp Water-resistant optical fiber cables
CN113077930A (en) * 2021-04-13 2021-07-06 宁波容合电线有限公司 Thermal expansion yarn filling cable and processing technology thereof

Also Published As

Publication number Publication date
GB8619383D0 (en) 1986-09-17

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Date Code Title Description
WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)