CA1124950A - Foamed plastic insulated wire and method for producing the same - Google Patents
Foamed plastic insulated wire and method for producing the sameInfo
- Publication number
- CA1124950A CA1124950A CA318,075A CA318075A CA1124950A CA 1124950 A CA1124950 A CA 1124950A CA 318075 A CA318075 A CA 318075A CA 1124950 A CA1124950 A CA 1124950A
- Authority
- CA
- Canada
- Prior art keywords
- blowing agent
- mixture
- plastic material
- foamed
- density polyethylene
- 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.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/20—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of indefinite length
- B29C44/32—Incorporating or moulding on preformed parts, e.g. linings, inserts or reinforcements
- B29C44/322—Incorporating or moulding on preformed parts, e.g. linings, inserts or reinforcements the preformed parts being elongated inserts, e.g. cables
-
- 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
- H01B13/06—Insulating conductors or cables
- H01B13/14—Insulating conductors or cables by extrusion
-
- 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
- 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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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A30/00—Adapting or protecting infrastructure or their operation
- Y02A30/14—Extreme weather resilient electric power supply systems, e.g. strengthening power lines or underground power cables
Landscapes
- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Extrusion Moulding Of Plastics Or The Like (AREA)
- Processes Specially Adapted For Manufacturing Cables (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A foamed plastic insulated wire having a foamed plastic material insulation layer formed over a conductor. The plastic material includes at least one component having a swelling ratio greater than 55%, and the component comprises at least 20% by weight of the insulation layer. The insulated wire is produced by adding a blowing agent such as a chemical blowing agent and an inert gas and extruding the mixture over a conductor.
A foamed plastic insulated wire having a foamed plastic material insulation layer formed over a conductor. The plastic material includes at least one component having a swelling ratio greater than 55%, and the component comprises at least 20% by weight of the insulation layer. The insulated wire is produced by adding a blowing agent such as a chemical blowing agent and an inert gas and extruding the mixture over a conductor.
Description
~1~4950 t BACKGROUND OF THE INVENTION
This invention relates to a foamed plastic insulated wire and a method for producing the same. More particularly, this invention relates to a type of foamed plastic insulated wire which exhibits high electrical characteristics and high mechanical strength while providing a high degree of expansion in the insulation material. ThiS invention also relates to a method for producing such a foamed plastic insulated wire.
In the field of communication cable, conductors formed with a foamed plastic insulation are widely used. Particularly, foamed polyolefin is commonly used as an insulation layer.
Normally, in these cables, the degree of expansion of the foamed plastic insulator is in a wide range for example 10~ to 90%
under measurement by a specific gravity method.
Generally, foamed plastic insulation is obtained by extrusion method by means of a screw extruder. A chemical blowing agent such as azodicarbonamide, and 4,4'-oxybis (benzenesulfonylhydrazide), or inert gas such as nitrogen, argon, and carbonic acid gases, or gaseous or liquid hydrocarbon of 20 methane, propane, butane, pentane, and hexane, or gaseous or liquidized fluorocarbon such as trichloromonofluoromethane, dichlorodifluoromethane, trichlorotrifluoroethane, and dichloro-tetrafluoroethane is usually employed. The plastic material is generally polyolefin such as low density polyethylene, medium density polyethylene, high density polyethylene, polypropylene, and butyl rubber or the mixture of at least two of these materials.
Polyethylene and polypropylene are the most ordinary materials used as plastic materials.
A foamed plastic insulator having expansion degree of 20 to 30~ is easily produced by using chemical blowing agents or -1- ~
1~24950 1 inert gas and any of the plastic materials mentioned above.
However, recently, foamed plastic insulators having a high expansion degree such as 50~ or more have required in order to enhance electric characteristics and to reduce diameter of the cable. Applicant's various experiments and analysis reveal that elasticity of the plastic materials is the most important factor to obtain a high degree of expansion. Therefore, the swelling ratio which is the index of elasticity of the plastic material is found to be the determinative factor to obtain high degrees of expansion of the insulator.
In order to meet with the above requirement, the applicant has proposed methods for producing foamed plastic insulation having expansion ratio of 67~ or more by using hydrocarbon or fluorocarbon as a blowing agent and plastic materials whose swelling ratio is in a range of 40 to 75~. This is disclosed in Japanese patent2ublica~ion (OPI) No. 73382/7~. How-ever, other kinds of high foamed plastic insulation formed over a conductor and methods for producing such insulation are still required to fulfill wide ranging requirements. Also, in many applications the use of hydrocarbon or fluorocarbon as the blowing agent is unacceptable. Furtherm~re in this prior art example nucleating agents must be used.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide an improved foamed plastic insulated wire exhibiting excellent characteristics in high expansion ratio.
It is another object of this invention to provide a method for producing such cable.
Still another object of this is to provide a foamèd plastic insulated wire formed without the use of hydro or fluoro-carbon or nucleating agents.
112~sa 1 The objects are attained, in accordance with the present invention by using plastic materials having swelling ratio of 55% or more even with the employment of chemical blowing agent such as azodicarbonamide and 4,4'-oxybis (benzenesulfonyl-hydrazide) and/or inert gas such as nitrogen, argon and carbonic acid gases. The present invention employes plastic materials such as low density polyethylene, medium density polyethylene, high density polyethylene and polypropylene, and butyl rubber or a mixture of at least two materials among that group. The mixture should include 20 wt% or more plastic whose swelling ratio is 55% or more. Furthermore, according to the present invention, in order to enhance dimensional stability and mechanical strength of the cable as well as to enhance degree of expansion of the foamed plastic insulator, a solid layer is simultaneously extruded over the outer peripheral surface of the foamed plastic insulation layer extruded over the conductor.
Since the solid layer has a higher mechanical strength and thermal conduct~vity than that the foamed plastic layer, the solid layer is immediately cooled to harden the surface. This increases the mechanical strength and ensures dimensional stability. Addition-ally, since gas or bubbles in the foamed layér is confined in the solid layer, the degree of expansion is further enhanced.
This invention will be explained in detail by tne accompanying drawings and the description of the preferred embodi-ment that follows.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
Fig. 1 is a cross-sectional illustration of a device for producing a cable according to the present invention; and Fig. 2 is a cross sectional view of one example of a cable according to the present invention.
11~4950 Swelling ratio referred to above is calculated by the following equation:
a - d s o SR(%) = X 100 where: ds is an outer diameter of the extruded material and, do is an inner diameter of an orifice provided in an extrusion plastometer defined by JIS K 6760 or ASTM D 1238-70. ds and do are obtained when measuring melt index MI by the extrusion plastometer. Both ds and do are measured at room temperature.
The condition of measurement of the melt index is shown in Table 1.
Table 1 resin temperature load (gram) low density polyethylene (LDPE) 190C 2160 high density polyethylene (HDPE) 190C 2160 polypropylene (PPr) 230C 2160 Furthermore, degree of expansion described above is calculated by the following equation:
P -- P
degree of expansion (%)= X 100 where p0 is a density of the resin before expansion, and p is a density of the resin after expansion.
According to the present invention, in case of employment of a chemical bloWing agent and an inert gas blowing agent, insulated conductor formed with high foamable materials 30 having expansion degree of 55% or more is easily obtained by using plastic materials having swelling ratio of 55%`or more while exhibiting excellent characteristics.
llZ4950 1 The chemical blowing agent used in this invention is selected from azodicarbonamide and 4,4'-oxybis (benzenesulfonyl-hydrazide), and the inert gas blowing agent used in this invention is selected from nitrogen, argon, and carbonic acid gases. The plastic material used in this invention is selected from high density polyethylene, medium density polyethylene, low density polyethylene, polypropylene and butyl rubber, or the mixture of at least two materials. The mixture includes 20% by weight of resin or more, which has swelling ratio of 55% or more.
Furthermore, in order to improve mechanical strength and dimensional stability of the cable, the foamed insulation layer is preferably coated with a solid layer by extruding the same simultaneously with the extrusion of the insulation layer.
As shown in Fig. 1, a conductor 1 passing through a nipple 2 is coated with a foamed plastic material 3 such as polyolefin by an extrusion coating by means of a first die 5. A
non-foamed material 4 is extrusion coated over the foamed plastic material 3 by means of a second die 7. The dies 5 and 7 are coaxially supported by a die holder 6 to thereby obtain a cable comprising a conductor 10, foamed insulation layer 20 and solid layer 30. This is shown in the end sectional view, Fig. 2.
According to this method, since foamed and non-foamed materials are in a molten state, these two are completely fixed with each other to thereby enhance mechanical strength. The materials to be used in the solid layer is polyolefin such as polyethylene and polypropylene in order to obtain thermal bonding to the internal foamed polyolefin. By providing such a solid layer, the mechanical strength and dimensional stability of the cable is improved. That is, since the solid layer has a higher mechanical and thermal conductivity than that of the 1 foamed plastic layer, the solid layer is immediately cooled to harden the same, to thereby increase mechanical strength and ensure dimensional stability. Further, since gas or bubbles in the foamed layer is confined within the solid layer, the degree of expansion of the foamed layer is further enhanced. If the solid layer is not provided over the foamable layer, the foamed insulation may be deflated due to the escape of the gas there-from, or may be deformed during cooling, or deformed into elliptical shape in cross-section by rollers during its travel lO to a take-up device.
The present invention will be more easily understood with reference to Examples described below.
Example 1 By weight of 1.5% of azodicarbonamide was added as a blowing agent to the resin shDwn in Table 2 to produce a cable having conductor diameter of 0.65 mm and insulation diameter of 1.8 mm, and the expansion degree and characteristic of each cables were tested.
Table 2 20 No. resin SR(~) expansion cell size insulation appearance degree (~) bonding to (%) conductor 1 LDPE 24.3 48.0 100 to 200 good good
This invention relates to a foamed plastic insulated wire and a method for producing the same. More particularly, this invention relates to a type of foamed plastic insulated wire which exhibits high electrical characteristics and high mechanical strength while providing a high degree of expansion in the insulation material. ThiS invention also relates to a method for producing such a foamed plastic insulated wire.
In the field of communication cable, conductors formed with a foamed plastic insulation are widely used. Particularly, foamed polyolefin is commonly used as an insulation layer.
Normally, in these cables, the degree of expansion of the foamed plastic insulator is in a wide range for example 10~ to 90%
under measurement by a specific gravity method.
Generally, foamed plastic insulation is obtained by extrusion method by means of a screw extruder. A chemical blowing agent such as azodicarbonamide, and 4,4'-oxybis (benzenesulfonylhydrazide), or inert gas such as nitrogen, argon, and carbonic acid gases, or gaseous or liquid hydrocarbon of 20 methane, propane, butane, pentane, and hexane, or gaseous or liquidized fluorocarbon such as trichloromonofluoromethane, dichlorodifluoromethane, trichlorotrifluoroethane, and dichloro-tetrafluoroethane is usually employed. The plastic material is generally polyolefin such as low density polyethylene, medium density polyethylene, high density polyethylene, polypropylene, and butyl rubber or the mixture of at least two of these materials.
Polyethylene and polypropylene are the most ordinary materials used as plastic materials.
A foamed plastic insulator having expansion degree of 20 to 30~ is easily produced by using chemical blowing agents or -1- ~
1~24950 1 inert gas and any of the plastic materials mentioned above.
However, recently, foamed plastic insulators having a high expansion degree such as 50~ or more have required in order to enhance electric characteristics and to reduce diameter of the cable. Applicant's various experiments and analysis reveal that elasticity of the plastic materials is the most important factor to obtain a high degree of expansion. Therefore, the swelling ratio which is the index of elasticity of the plastic material is found to be the determinative factor to obtain high degrees of expansion of the insulator.
In order to meet with the above requirement, the applicant has proposed methods for producing foamed plastic insulation having expansion ratio of 67~ or more by using hydrocarbon or fluorocarbon as a blowing agent and plastic materials whose swelling ratio is in a range of 40 to 75~. This is disclosed in Japanese patent2ublica~ion (OPI) No. 73382/7~. How-ever, other kinds of high foamed plastic insulation formed over a conductor and methods for producing such insulation are still required to fulfill wide ranging requirements. Also, in many applications the use of hydrocarbon or fluorocarbon as the blowing agent is unacceptable. Furtherm~re in this prior art example nucleating agents must be used.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide an improved foamed plastic insulated wire exhibiting excellent characteristics in high expansion ratio.
It is another object of this invention to provide a method for producing such cable.
Still another object of this is to provide a foamèd plastic insulated wire formed without the use of hydro or fluoro-carbon or nucleating agents.
112~sa 1 The objects are attained, in accordance with the present invention by using plastic materials having swelling ratio of 55% or more even with the employment of chemical blowing agent such as azodicarbonamide and 4,4'-oxybis (benzenesulfonyl-hydrazide) and/or inert gas such as nitrogen, argon and carbonic acid gases. The present invention employes plastic materials such as low density polyethylene, medium density polyethylene, high density polyethylene and polypropylene, and butyl rubber or a mixture of at least two materials among that group. The mixture should include 20 wt% or more plastic whose swelling ratio is 55% or more. Furthermore, according to the present invention, in order to enhance dimensional stability and mechanical strength of the cable as well as to enhance degree of expansion of the foamed plastic insulator, a solid layer is simultaneously extruded over the outer peripheral surface of the foamed plastic insulation layer extruded over the conductor.
Since the solid layer has a higher mechanical strength and thermal conduct~vity than that the foamed plastic layer, the solid layer is immediately cooled to harden the surface. This increases the mechanical strength and ensures dimensional stability. Addition-ally, since gas or bubbles in the foamed layér is confined in the solid layer, the degree of expansion is further enhanced.
This invention will be explained in detail by tne accompanying drawings and the description of the preferred embodi-ment that follows.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
Fig. 1 is a cross-sectional illustration of a device for producing a cable according to the present invention; and Fig. 2 is a cross sectional view of one example of a cable according to the present invention.
11~4950 Swelling ratio referred to above is calculated by the following equation:
a - d s o SR(%) = X 100 where: ds is an outer diameter of the extruded material and, do is an inner diameter of an orifice provided in an extrusion plastometer defined by JIS K 6760 or ASTM D 1238-70. ds and do are obtained when measuring melt index MI by the extrusion plastometer. Both ds and do are measured at room temperature.
The condition of measurement of the melt index is shown in Table 1.
Table 1 resin temperature load (gram) low density polyethylene (LDPE) 190C 2160 high density polyethylene (HDPE) 190C 2160 polypropylene (PPr) 230C 2160 Furthermore, degree of expansion described above is calculated by the following equation:
P -- P
degree of expansion (%)= X 100 where p0 is a density of the resin before expansion, and p is a density of the resin after expansion.
According to the present invention, in case of employment of a chemical bloWing agent and an inert gas blowing agent, insulated conductor formed with high foamable materials 30 having expansion degree of 55% or more is easily obtained by using plastic materials having swelling ratio of 55%`or more while exhibiting excellent characteristics.
llZ4950 1 The chemical blowing agent used in this invention is selected from azodicarbonamide and 4,4'-oxybis (benzenesulfonyl-hydrazide), and the inert gas blowing agent used in this invention is selected from nitrogen, argon, and carbonic acid gases. The plastic material used in this invention is selected from high density polyethylene, medium density polyethylene, low density polyethylene, polypropylene and butyl rubber, or the mixture of at least two materials. The mixture includes 20% by weight of resin or more, which has swelling ratio of 55% or more.
Furthermore, in order to improve mechanical strength and dimensional stability of the cable, the foamed insulation layer is preferably coated with a solid layer by extruding the same simultaneously with the extrusion of the insulation layer.
As shown in Fig. 1, a conductor 1 passing through a nipple 2 is coated with a foamed plastic material 3 such as polyolefin by an extrusion coating by means of a first die 5. A
non-foamed material 4 is extrusion coated over the foamed plastic material 3 by means of a second die 7. The dies 5 and 7 are coaxially supported by a die holder 6 to thereby obtain a cable comprising a conductor 10, foamed insulation layer 20 and solid layer 30. This is shown in the end sectional view, Fig. 2.
According to this method, since foamed and non-foamed materials are in a molten state, these two are completely fixed with each other to thereby enhance mechanical strength. The materials to be used in the solid layer is polyolefin such as polyethylene and polypropylene in order to obtain thermal bonding to the internal foamed polyolefin. By providing such a solid layer, the mechanical strength and dimensional stability of the cable is improved. That is, since the solid layer has a higher mechanical and thermal conductivity than that of the 1 foamed plastic layer, the solid layer is immediately cooled to harden the same, to thereby increase mechanical strength and ensure dimensional stability. Further, since gas or bubbles in the foamed layer is confined within the solid layer, the degree of expansion of the foamed layer is further enhanced. If the solid layer is not provided over the foamable layer, the foamed insulation may be deflated due to the escape of the gas there-from, or may be deformed during cooling, or deformed into elliptical shape in cross-section by rollers during its travel lO to a take-up device.
The present invention will be more easily understood with reference to Examples described below.
Example 1 By weight of 1.5% of azodicarbonamide was added as a blowing agent to the resin shDwn in Table 2 to produce a cable having conductor diameter of 0.65 mm and insulation diameter of 1.8 mm, and the expansion degree and characteristic of each cables were tested.
Table 2 20 No. resin SR(~) expansion cell size insulation appearance degree (~) bonding to (%) conductor 1 LDPE 24.3 48.0 100 to 200 good good
2 LDPE 29.3 59.7 200 or more bad bad
3 LDPE 42.4 52.0 100 to 200 bad bad
4 LDPE 52.8 54.0 200 or more bad bad LDPE 56.0 60.8 50 or less good good 6 LDPE 67.2 65.4 50 or less good good 7 LDPE 72.6 69.7 50 or less good good 11~495~
1 ~Xample 2 ~ .5% by weight of azodicarbonamide was added as a blowing agent to the resin materials shown in Table 3. Further 350cc/min of nitrogen gas was injected in the extruder to produce foamed plastic insulated wire having conductor diameter of 0.4 mm and insulation diameter of 1.55 mm. The expansion degree and characteristics are shown in Table 3.
Table 3 No. resin mixture expansion cell insulation appearance degree (%) diameter bonding to (~) conductor 1 LDPE (15%) 51.0 100 to 200 bad bad PPr (80%3 60.0 50 or less good good 3 LDPE (40~) 64.8 50 or less good good 4 LDPE (80%) 66.2 50 or less good good LDPE (15%) HDPE (40~) 49.8 200 or more bad bad PPr (45~) LDPE (20%) 6 HDPE (40%) 63.3 50 or less good good PPr (40%) _ .. ... _ _ . . . . .
The SR of the pure resins used to make the resin mixtures shown in Table 3 are as follows;
LDPE (low density polyethylene) 67.2 HDPE (high density polyethylene) 45.0%
PPr (polyporpylene) 21.2 Example 3 2~ by weight of silica was added as blowing agent to a resin or resin mixture shown in Table 4, and 500cc/min of nitrogen gas was injected into the extruder to produce foamed 30 plastic insulated wire having a conductor diameter of 0.65 mm 1:3 .
llZ4gS() 1 and insulation diameter of 1.60 mm. The expansion degree and characteristics are shown in Table 4.
Table 4 No. resin or SR(%) expansion cell insulation appearance resin mixture degree size bonding to (%) (~) conductor 1 LDPE 24.3 62.2 200 or more bad bad 2 LDPE 42.4 44.0 100 to 200 bad bad 3 LDPE 56.0 61.5 50 or less good good 4 LDPE 67.2 67.0 50 or less good good 10 5 PPrE (90%) 278 o 56.0 100 to 200 bad bad PPR (80%) 268 o 66.0 50 or less good good _ As is evident from these examples, in case of the employment of the chemical blowing agent and/or inert gas blowing agent, a conductor formed with high foamable plastic insulatibn having excellent characteristics is obtainable at the degree of expansion of 55% or more by using plastic material having swelling ratio of 55% or more. In case of the employment of the resin 20 mixture, the mixture including 20% by weight of resin or more whose swelling ratio is 55% or more exhibits excellent characteristics.
Furthe~, it is possible to apply the present invention for the product of low foamable plastic insulation having expansion degree of 55~ or less. In this case, the use of the plastic materials having swelling ratio of 55% or more reduces the amount of blowing agent in comparison with the use of the plastic materials other than in the present invention. This results in foamed plastic insulated wire having high quality 30 which avoids degradation of electric characteristic and extrusion efficiency due to residue by decomposition of blowing agent.
11~4950 1 Example 4 An extruder was prepared in which inner diameter of cylinders of 65 mm and 32 mm were provided to produce a high foamable layer and a solid layer, respectively by a cross-head shown in Fig. 1. The diameter of a conductor was 0.7 mm the obtained thickness of high foamable insulation layer was 1.10 mm and the obtained thickness of the solid layer formed over the foamed layer was 0.1 mm. In case of the comparative samples shown in Table 5, the thickness of high foamable layer was 1.20 mm.
lO The blowing agent used was azodicarbonamide. The resin used was the mixture of 80~ by weight of low density polyethylene having swelling ratio of 67~ and 20~ by weight of polypropylene having swelling ratio of 21~ and the solid layer used is shown in Table 5.
Table 5 sample 1 sample 2 sample 3 comparative comparative sample 1 sample 2 solid layer polypro- polyethylene plasticized pylene PVC
low high density density constant 1.40 1.40 1.40 1.40 1.60 ellipse 0 05 0.10 0.05 0.30 0.30 *ellipse degree = major diameter - minor diameter These examples prove that the high foamable plastic insulated wires coated with the solid layer exhibits superior results to that not coated with a solid layer in terms of di-electric constant and ellipse degree.
_g_ 1~24950 1 Example 5 High foamable polyethylene insulated wire used in sample 3 was formed with braided copper wires as an outer con-ductor and PVC sheath was formed over the outer conductor to thus produce a coaxial cable having foamed insulation whose outer diameter was approximately 3 mm. Shown in Table 6 are the standards of an ordinary coaxial cable commercially available having an insulation diameter of approximately 3 mm to compare the characteristics of the coaxial cable thus produced.
Table 6 capacitance C characteristic (pF/m) impedance ZO
-characteristic according to the 54.0 74.8 present invention standardized54 0 + 2 75 0 + 3 characteristic * these were measured at frequency of 10 MHz According to Table 6, it is found that the character-istics obtained by the present invention is within the standard-20 ized characteristic,and therefore, the coaxial cable of thisinvention is commercially acceptable.
Example 6 Dichlorotetrafluoroethane was added as a blowing agent to the resin or resin mixture shown in Table 7. The same extruder and a cross head as those used in Example 5 were used to produce cables having conductor diameter of 1.20 mm, I~igh foamable layer, the thickness of which was 1.70 mm, and a solid layer, made of polyolefin, the thickness of which was 0.20 mm.
In comparative samples 1 and 2, the thickness of the high foamable 30 layer was 1.90 mm, because of no provision of the solid layer.
l~Z4950 1 Table 7 No. solid layer foamed layer dielectric ellipse constant of degree insulation layer comparative sample l -- LDPE (SR=67~) 1.30 0.70 1 HDPE LDPE (SR=67%) 1.30 0.10 comparative 1.32 0.50 sample 2 40 wt% of LDPE (SR=67%) 60 wt% of HDPE (SR=15%) 2 LDPE 1. 320.08 1 0 ,, , _ _ --11-- .
'
1 ~Xample 2 ~ .5% by weight of azodicarbonamide was added as a blowing agent to the resin materials shown in Table 3. Further 350cc/min of nitrogen gas was injected in the extruder to produce foamed plastic insulated wire having conductor diameter of 0.4 mm and insulation diameter of 1.55 mm. The expansion degree and characteristics are shown in Table 3.
Table 3 No. resin mixture expansion cell insulation appearance degree (%) diameter bonding to (~) conductor 1 LDPE (15%) 51.0 100 to 200 bad bad PPr (80%3 60.0 50 or less good good 3 LDPE (40~) 64.8 50 or less good good 4 LDPE (80%) 66.2 50 or less good good LDPE (15%) HDPE (40~) 49.8 200 or more bad bad PPr (45~) LDPE (20%) 6 HDPE (40%) 63.3 50 or less good good PPr (40%) _ .. ... _ _ . . . . .
The SR of the pure resins used to make the resin mixtures shown in Table 3 are as follows;
LDPE (low density polyethylene) 67.2 HDPE (high density polyethylene) 45.0%
PPr (polyporpylene) 21.2 Example 3 2~ by weight of silica was added as blowing agent to a resin or resin mixture shown in Table 4, and 500cc/min of nitrogen gas was injected into the extruder to produce foamed 30 plastic insulated wire having a conductor diameter of 0.65 mm 1:3 .
llZ4gS() 1 and insulation diameter of 1.60 mm. The expansion degree and characteristics are shown in Table 4.
Table 4 No. resin or SR(%) expansion cell insulation appearance resin mixture degree size bonding to (%) (~) conductor 1 LDPE 24.3 62.2 200 or more bad bad 2 LDPE 42.4 44.0 100 to 200 bad bad 3 LDPE 56.0 61.5 50 or less good good 4 LDPE 67.2 67.0 50 or less good good 10 5 PPrE (90%) 278 o 56.0 100 to 200 bad bad PPR (80%) 268 o 66.0 50 or less good good _ As is evident from these examples, in case of the employment of the chemical blowing agent and/or inert gas blowing agent, a conductor formed with high foamable plastic insulatibn having excellent characteristics is obtainable at the degree of expansion of 55% or more by using plastic material having swelling ratio of 55% or more. In case of the employment of the resin 20 mixture, the mixture including 20% by weight of resin or more whose swelling ratio is 55% or more exhibits excellent characteristics.
Furthe~, it is possible to apply the present invention for the product of low foamable plastic insulation having expansion degree of 55~ or less. In this case, the use of the plastic materials having swelling ratio of 55% or more reduces the amount of blowing agent in comparison with the use of the plastic materials other than in the present invention. This results in foamed plastic insulated wire having high quality 30 which avoids degradation of electric characteristic and extrusion efficiency due to residue by decomposition of blowing agent.
11~4950 1 Example 4 An extruder was prepared in which inner diameter of cylinders of 65 mm and 32 mm were provided to produce a high foamable layer and a solid layer, respectively by a cross-head shown in Fig. 1. The diameter of a conductor was 0.7 mm the obtained thickness of high foamable insulation layer was 1.10 mm and the obtained thickness of the solid layer formed over the foamed layer was 0.1 mm. In case of the comparative samples shown in Table 5, the thickness of high foamable layer was 1.20 mm.
lO The blowing agent used was azodicarbonamide. The resin used was the mixture of 80~ by weight of low density polyethylene having swelling ratio of 67~ and 20~ by weight of polypropylene having swelling ratio of 21~ and the solid layer used is shown in Table 5.
Table 5 sample 1 sample 2 sample 3 comparative comparative sample 1 sample 2 solid layer polypro- polyethylene plasticized pylene PVC
low high density density constant 1.40 1.40 1.40 1.40 1.60 ellipse 0 05 0.10 0.05 0.30 0.30 *ellipse degree = major diameter - minor diameter These examples prove that the high foamable plastic insulated wires coated with the solid layer exhibits superior results to that not coated with a solid layer in terms of di-electric constant and ellipse degree.
_g_ 1~24950 1 Example 5 High foamable polyethylene insulated wire used in sample 3 was formed with braided copper wires as an outer con-ductor and PVC sheath was formed over the outer conductor to thus produce a coaxial cable having foamed insulation whose outer diameter was approximately 3 mm. Shown in Table 6 are the standards of an ordinary coaxial cable commercially available having an insulation diameter of approximately 3 mm to compare the characteristics of the coaxial cable thus produced.
Table 6 capacitance C characteristic (pF/m) impedance ZO
-characteristic according to the 54.0 74.8 present invention standardized54 0 + 2 75 0 + 3 characteristic * these were measured at frequency of 10 MHz According to Table 6, it is found that the character-istics obtained by the present invention is within the standard-20 ized characteristic,and therefore, the coaxial cable of thisinvention is commercially acceptable.
Example 6 Dichlorotetrafluoroethane was added as a blowing agent to the resin or resin mixture shown in Table 7. The same extruder and a cross head as those used in Example 5 were used to produce cables having conductor diameter of 1.20 mm, I~igh foamable layer, the thickness of which was 1.70 mm, and a solid layer, made of polyolefin, the thickness of which was 0.20 mm.
In comparative samples 1 and 2, the thickness of the high foamable 30 layer was 1.90 mm, because of no provision of the solid layer.
l~Z4950 1 Table 7 No. solid layer foamed layer dielectric ellipse constant of degree insulation layer comparative sample l -- LDPE (SR=67~) 1.30 0.70 1 HDPE LDPE (SR=67%) 1.30 0.10 comparative 1.32 0.50 sample 2 40 wt% of LDPE (SR=67%) 60 wt% of HDPE (SR=15%) 2 LDPE 1. 320.08 1 0 ,, , _ _ --11-- .
'
Claims (11)
1. A foamed plastic insulated wire comprising a foamed plastic material insulation layer formed over a conductor, said plastic material essentially comprising polyolefin selected from the group comprising high density polyethylene/ medium density polyethylene, low density polyethylene, polypropylene, butyl rubber, and a mixture of at least two of said polyolefins, said plastic material including a component having swelling ratio greater than 55%, and said component comprising at least 20 by weight of said insulation layer.
2. A foamed plastic insulated wire as defined in claim 1, further comprising a solid layer formed over said insulation layer, said solid layer comprising polyolefin,
3. A method for producing a foamed plastic insulated wire comprising the steps of:
preparing a plastic material having swelling ratio of at least 55% said plastic material essentially comprising poly-olefin selected from the group comprising high density polyethlene, medium density polyethylene,low density polyethylene, polypropy-lene, butyl rubber, and a mixture of at least two said poly-olefins, adding blowing agent to said plastic material, extruding a mixture of said plastic material and said blowing agent over a conductor, and foaming said mixture to produce foamed insulation layer.
preparing a plastic material having swelling ratio of at least 55% said plastic material essentially comprising poly-olefin selected from the group comprising high density polyethlene, medium density polyethylene,low density polyethylene, polypropy-lene, butyl rubber, and a mixture of at least two said poly-olefins, adding blowing agent to said plastic material, extruding a mixture of said plastic material and said blowing agent over a conductor, and foaming said mixture to produce foamed insulation layer.
4. The method of claim 3, wherein said blowing agent is selected from the group consisting of chemical blowing agent, inert gas blowing agent, and a mixture of chemical blowing agent and inert gas blowing agent.
5. The method of claim 3 further comprising the step of extruding a second plastic material over said mixture simultane-ously with the extrusion of said mixture to form a solid layer.
6. The method of claim 3, wherein said plastic material is a mixture of at least two kinds of polyolefins.
7. The method of claim 5, wherein said plastic material is a mixture of at least two kinds of polyolefins.
8. The method of claim 6 or 7, wherein said mixture con-sists essentially of at least 20 weight percent of polyolefin whose swelling ratio is greater than 55%.
9. The method of claim 5, wherein said solid layer is polyolefin.
10. The method fo claim 4, wherein said chemical blowing agent is selected from the group consisting of azodicarbonamide and 4,4'-oxybis (benzenesulfonylhydrazide).
11. The method of claim 4, wherein said inert gas blowing agent is selected from the group consisting of nitrogen, argon and carbonic acid gases.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15060077A JPS5484288A (en) | 1977-12-16 | 1977-12-16 | Manufacturing process of insulated wire with foamed plastics |
| JP150600/77 | 1977-12-16 | ||
| JP2703/78 | 1978-01-17 | ||
| JP53002703A JPS5811047B2 (en) | 1978-01-17 | 1978-01-17 | Manufacturing method of highly foamed polyolefin insulated wire |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1124950A true CA1124950A (en) | 1982-06-01 |
Family
ID=26336156
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA318,075A Expired CA1124950A (en) | 1977-12-16 | 1978-12-15 | Foamed plastic insulated wire and method for producing the same |
Country Status (5)
| Country | Link |
|---|---|
| AU (1) | AU531473B2 (en) |
| CA (1) | CA1124950A (en) |
| DE (1) | DE2853626C2 (en) |
| FR (1) | FR2412149A1 (en) |
| GB (1) | GB2013960B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4823458A (en) * | 1983-12-21 | 1989-04-25 | Henkel Kommanditgesellschaft Auf Aktien | Foam bodied hair curler |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2461340A1 (en) * | 1979-07-09 | 1981-01-30 | Cables De Lyon Geoffroy Delore | CELL INSULATING ELECTRIC CABLE AND PROCESS FOR PREPARING THE SAME |
| US4716073A (en) * | 1986-06-02 | 1987-12-29 | E. I. Du Pont De Nemours And Company | Thin wall high performance insulation on wire |
| US4711811A (en) * | 1986-10-22 | 1987-12-08 | E. I. Du Pont De Nemours And Company | Thin wall cover on foamed insulation on wire |
| FR2681467B1 (en) * | 1991-09-13 | 1993-11-19 | Alcatel Cable | HIGH DIELECTRIC RIGIDITY INSULATING BODY AND METHOD FOR OBTAINING SUCH A BODY. |
| DE4316863A1 (en) * | 1993-05-19 | 1994-11-24 | Nmc Kenmore Sa | Coextruded composite foam elements and process for their production |
| GB0128649D0 (en) | 2001-11-29 | 2002-01-23 | Isp Alginates Uk Ltd | Process equipment and product |
| DE50302597D1 (en) * | 2003-04-10 | 2006-05-04 | Nexans | Temperature-resistant electrical cable for the transmission of data |
| US6858805B2 (en) * | 2003-05-08 | 2005-02-22 | Commscope Properties Llc | Cable with foamed plastic insulation comprising and ultra-high die swell ratio polymeric material |
| FR2948827B1 (en) * | 2009-07-30 | 2013-04-19 | Courant Sas | PREFILLED SHEATH, METHOD AND DEVICE FOR MANUFACTURING SUCH A SHEATH |
| DE102015221898B4 (en) * | 2015-11-06 | 2017-11-16 | Continental Automotive Gmbh | Method for producing a structural unit and structural unit |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1104450A (en) * | 1965-09-20 | 1968-02-28 | British Insulated Callenders | Improvements in or relating to telecommunication cables |
| GB1391055A (en) * | 1971-04-01 | 1975-04-16 | British Insulated Callenders | Preparation of plastics sheet materials for use in contact with hydrocarbon oils |
| BE790023A (en) * | 1971-10-14 | 1973-04-13 | Int Standard Electric Corp | IMPROVEMENTS IN THE MANUFACTURING OF MULTI-CORE TELEPHONE CABLES |
| JPS5216235B2 (en) * | 1972-01-31 | 1977-05-07 | ||
| CA977099A (en) * | 1972-09-29 | 1975-10-28 | Union Carbide Canada Limited | Process for producing cellular polyolefin |
| FR2214162B1 (en) * | 1973-01-17 | 1979-10-19 | Sumitomo Electric Industries | |
| US3968463A (en) * | 1973-08-08 | 1976-07-06 | Union Carbide Corporation | Coaxial cable with improved properties |
-
1978
- 1978-12-08 AU AU42334/78A patent/AU531473B2/en not_active Expired
- 1978-12-12 DE DE2853626A patent/DE2853626C2/en not_active Expired
- 1978-12-15 CA CA318,075A patent/CA1124950A/en not_active Expired
- 1978-12-15 GB GB7848778A patent/GB2013960B/en not_active Expired
- 1978-12-15 FR FR7835374A patent/FR2412149A1/en active Granted
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4823458A (en) * | 1983-12-21 | 1989-04-25 | Henkel Kommanditgesellschaft Auf Aktien | Foam bodied hair curler |
Also Published As
| Publication number | Publication date |
|---|---|
| AU4233478A (en) | 1979-06-21 |
| GB2013960B (en) | 1982-05-19 |
| AU531473B2 (en) | 1983-08-25 |
| GB2013960A (en) | 1979-08-15 |
| FR2412149A1 (en) | 1979-07-13 |
| DE2853626C2 (en) | 1983-11-24 |
| FR2412149B1 (en) | 1981-09-11 |
| DE2853626A1 (en) | 1979-06-28 |
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