CA1284861C - Conductive case using electrically conductive fiber - Google Patents
Conductive case using electrically conductive fiberInfo
- Publication number
- CA1284861C CA1284861C CA000523420A CA523420A CA1284861C CA 1284861 C CA1284861 C CA 1284861C CA 000523420 A CA000523420 A CA 000523420A CA 523420 A CA523420 A CA 523420A CA 1284861 C CA1284861 C CA 1284861C
- Authority
- CA
- Canada
- Prior art keywords
- layer
- parison
- electrically conductive
- blow
- conductive
- 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 - Lifetime
Links
- 239000000835 fiber Substances 0.000 title claims abstract description 18
- 238000002156 mixing Methods 0.000 claims abstract description 4
- 238000000071 blow moulding Methods 0.000 claims description 12
- 238000000034 method Methods 0.000 claims description 7
- 229920000098 polyolefin Polymers 0.000 claims description 7
- 230000008569 process Effects 0.000 claims description 4
- 239000000463 material Substances 0.000 abstract description 13
- 229920000049 Carbon (fiber) Polymers 0.000 abstract description 7
- 239000004917 carbon fiber Substances 0.000 abstract description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 5
- 239000006229 carbon black Substances 0.000 abstract description 3
- 239000006258 conductive agent Substances 0.000 abstract 1
- 239000000203 mixture Substances 0.000 description 10
- 239000002952 polymeric resin Substances 0.000 description 9
- 229920003002 synthetic resin Polymers 0.000 description 9
- 239000004698 Polyethylene Substances 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 4
- -1 polyethylene Polymers 0.000 description 4
- 229920000573 polyethylene Polymers 0.000 description 4
- 239000012815 thermoplastic material Substances 0.000 description 4
- 239000004020 conductor Substances 0.000 description 3
- 230000005611 electricity Effects 0.000 description 3
- 229920001903 high density polyethylene Polymers 0.000 description 3
- 239000004700 high-density polyethylene Substances 0.000 description 3
- 238000000465 moulding Methods 0.000 description 3
- 230000003068 static effect Effects 0.000 description 3
- 238000003860 storage Methods 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 101150034533 ATIC gene Proteins 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- 239000011796 hollow space material Substances 0.000 description 1
- 229920001519 homopolymer Polymers 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- NLYAJNPCOHFWQQ-UHFFFAOYSA-N kaolin Chemical compound O.O.O=[Al]O[Si](=O)O[Si](=O)O[Al]=O NLYAJNPCOHFWQQ-UHFFFAOYSA-N 0.000 description 1
- 229920000092 linear low density polyethylene Polymers 0.000 description 1
- 239000004707 linear low-density polyethylene Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Landscapes
- Blow-Moulding Or Thermoforming Of Plastics Or The Like (AREA)
- Laminated Bodies (AREA)
- Packaging Frangible Articles (AREA)
Abstract
ABSTRACT
A blow-molded container provides protection for electrically sensitive devices by blending conductive fibers such as carbon fibers with polymeric materials in the outer layer of a multi-layer parison. Slough or mark-off problems sometimes associated with the use of carbon powder or carbon black as a blending conductive agent are avoided.
A blow-molded container provides protection for electrically sensitive devices by blending conductive fibers such as carbon fibers with polymeric materials in the outer layer of a multi-layer parison. Slough or mark-off problems sometimes associated with the use of carbon powder or carbon black as a blending conductive agent are avoided.
Description
6~
CONDUCTIVE CASE USING ELECTRICALLY CONDUCTIVE FIBER
FIELD OF THE INVENTION
The field of the invention encompasses portable containers for the transportation of electrostatic discharge sensitive devices. More particularly, the present invention includes containers which, while closed, protect the contents of the container from external electrical forces.
BACKGROUND OF THE INVENTION
When two bodies~ particularly of unlike materials, are brought together into intimate contact, a redistribution of electrons across the interface is likely to occur. An attractive force is established as equilibrium is achieved. Work must be done in opposition to these attractive forces if and when the bodies are separated. The energy so expended manifests itself as an increase in electrical tension or voltage between the respective surfaces, which are said to be electrically charged with respect to each other. If a conductive path is available, the charges thus separated will reunite immediately. If no such path is available, as in the case of non-conductorsl the potential increase with separation may reach values of several thousand volts.
The charge on a charged object will be located on the ex$erior surface thereof, and these forces have a strong influence on nearby objects.
~04/851113/2/1 ' ' ' ., ' ~' : .
~3fl~36~
IE a naighborin~ obJect ls a conductor it will experience a separation of charges by induction. Its repelled charge is free to give or receive electrons as the case may be; if another conductor is brought near, the transfar may occur through the agency of the spark, very often an energetic spark.
Such charge transfer actions may aclversely effect or even electronically destroy a number of electronic devices sensitive to electricity such as static electricity. Micro-circuit devices such as integrated circuit chips may be destroyed by electros$atic discharge prior to their incorporation into the electrical or electronic equipment for which they were designed. Electronic devices which can be damaged by electrostatic discharge of less than 15.000 volts or 100 microjoules energy are classified as electrostatic discharge (ESD) sensitive.
To prevent electrostatic breakdown, containers in which such devices are stored and transported have been provided with means for short circu-ting the device terminals or pins during storage. This short circuiting serves to prevent ehe accumulation of potentially damaging static charges on the device.
U. S. Patent No. 4,171,049 discusses the utilization of a series of conductive slots or grooves in which ESD sensitive devices may be in-serted and later dispensed to manufacturing equipment.
Other containers have been developed for portable use as for example in the device replacement market. These are typically small box like containers that house conductive sponge or foam sheets into which the device terminals are temporarily imbedded. An example is found in U. S.
Patent No. 4,333,565.
In addition to the requirements for inhibiting electrostatic charge build up and shielding the ESD sensitive contents from electrical fields, a container useful for transporting an ESD should also provide protection from mechanical shock and vibration. In addition, such a con-tainer should be of light weight construction and convenient to use when ~l~3~
~ 3 - 6~530-592 gaining access to the equipment to be repaired. The contalner should also be adaptable to the storage of different sizes and shapes of ESD sensitive devices without change in the size and shape of the container itselE. Reuseability, tamper security, and cost economy are also important considerations.
Many of the containers referred to above are designed for online in-factory production use and do not meet many of the requirements desirable in a portable container. For example, many of the prior art containers are not adaptable to ESD sensitive devices of different shapes and sizes.
Another means well known in the art for providing protection of ESD
sensitive devices is the use of carbon black or carbon powder in varying amounts in the material forming the container for the ESD sensitive devices.
Cases made conductive with carbon powder, while effective in protecting from ESD, may sometimes tend to slough or mark off on contact. This is clearly an undesirable feature in a container to be used to store, transport and clispense ESD sensitive devices.
U.S. Patent No. 4,4g4,651 issued to Malcolm discloses a portable work station in which electrically conductive material, such as carbon black parti-cles, aluminum particles, and metal filings, may be blended with thermoplastic material to make an electrically conductive case.
It is therefore desirable to provide an electrically conductive container with the requirements for protection of the ESD sensitive devices stored in the container, but without the undesirable Eeatures of conventional containers.
SU~ Y OF T~lE INVEN'l'lON
In one aspect of the present invention, a container comprises electrically conductive body and cover portions comprising an outer layer of a blend of a polymeric resin and carbon fibers, and an inner layer of a po:Ly~eric resin.
~a'~86~L
~ 64536-592 In another aspect, the invention provicles a process for making a blow-molded electrically conductive containe-r comprising:
a) blending a polyoleEin with electrically conductive fibers;
b) coextruding a tubular, multi-layer parison so that the parison comprises i) an electrically conductive radially outer layer, bonded at one major surface to ii) a radially inner layer of a polyolefin; and c) blow-molding the tubular, multi-layer parison to provide a multi-layer body and cover portion in which the electrically conductive fiber-filled layer encloses each of the body and cover portions.
D~FINITIONS
The term "electrically conductive", and similar terms, are used here-in to describe a property of a mater-Lal or container that involves its ability to transfer electricity, and as used herein refers to containers having sufEi-cient conductivity to prevent static or electrical damage to electrically sensitive devices stored in the container.
The term "parison" is used herein to refer to a hollow tube or other preformed shape of a thermoplastic material or blend or aggregation of thermo-plastic materials which is inflated ins:Lde a mold in the blow-molding process.
"Polymeric resin" is used herein to generally include for example homopolymers, copolymers, terpol-ymers etc., and blends and modificatLons there-of.
The term "outer layer" is used herein to refer to a layer of a multi-layer film which comprises an outside surface thereof.
The term "inner layer" is used herein to refer to a layer of a multi-layer film which comprises an inside surface thereof.
The term "intermediate layer" is used herein to refer to a layer of multi-layer film positioned between an outer layer and an inner layer.
The term "regrind" is used herein to refer to waste material such as axcess parison material from blow-molding opera~ions, which is reclaimed by for example shredding or granulating of the excess material. This regrind material is generally mixed with other unprocessed material at some predetermined percentage.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a fragmented sectional view of a coextruded multi-layer film in accordance with the present invention.
Figure 2 is a schematic side view of a blow-molded container utilizing the multi-layer film.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Figure 1, a multi-layer film 10 is coextruded prior to forming into a parison. Film 10 includes an outer layer 12 comprising a polymeric resin blended with electrically conductive fibers. The preferred polymeric resin is a polyolefin, more preferably high density polyethylene or linear low density polyethylene. Preferred conductive fibers are carbon fibers, which are present in the blend material preferably in a range of from about 10% to 14% by weight of the blend layer. More preferably, the conductive fibers such as carbon fibers form about 12% by weight of the outer layer 12 of the multi-layer coextruded parison 10.
An inner layer 14 of a polymeric resin is coextruded with outer layer 12. This inner layer 14 is preferably relatively thick in comparison to the relatively thin outer layer 12, and preferably is a polyolefin such as polyethylene, and more preferably high density polyethylene. Inner layer 14 preferably comprises the same polymeric resin as that of outer layer 12, although for example different polyolefins may be used for outer layer 12 and inner layer 14 respectively. The inner layer 14 should comprise a polymeric resin with sufficient strength to prevent breaking of the parison during the molding process.
~n optional intermediate layer 16 may be coextruded simultansously with outer layer 12 and inner layer 14. Intermediate layer 16 is preferably made of a regrind material, for example a regrind h:igh density polyethylene or other polyethylene or polyolefin materials. When the optional intermediate layer 16 is used, the inner layer 14 and intermediate layer 16 should in combination provide sufficient strength to prevent the parison from breaking during the subsequent blow-molding process. The use of regrind material provides cost savings in the production of electrically conductive containers, without jeopardizing the effectiveness of the container for the storage and transport of electrically sensitive devices.
Preferably, the outer layer 12 comprises between about 5% and 15%
of the total thickness of the multi-layer parison, and the inner layer 14 and intermediate layer 16 each comprise between about 35% and 55% of the total thickness of the parison.
More preferably the outer layer 12 comprises about 10% of the total thickness of the multi-layer parison, and the inner layer 14 and intermediate layer 16 each comprise about 45% of the total thickness of the parison.
Where no intermediate layer 16 is present, the inner layer preferably comprises between about 85% and 95% of the total thickness of the parison.
More preferably, the inner layer comprises about 90% of the total thickness of the parison.
Of course, similar ranges of thickness apply to the conductive container resulting from blow-molding the parison.
It should be noted that carbon fibers or other conductive fibers could not normally be used indiscriminately in a blow-molding process because these fibers resist the requisite stretching during the molding process and, if used throughout the multi-layer parison, would result in breaking of the parison during the blow-molding operation. These fibers are - 7 - ~iS36-5~2 there~ore confined to the outer layer of t'he multi-layer parison to impart the required electricaL conductivity to the resulting blow-molded container but without affecting the blow-molding vperation. It should be clear to someone o-f ordinary skill in the art that a reduction in the preferred percentage oE carbon fibers or other conductive fi'bers in the outer blend layer permi-ts, to some extent, a relative thickening of the outer layer in relation to the total multi-layer parison thickness without seriously affecting the blGw-molding operation. Conversely, an increase in the percentage of carbon Eibers or other fibers in the ou-ter blend layer permits, to some extent, a relative thinning of -the outer layer in rela-tion to the total multi-layer parison thickness, without losing the desired electrical conductivity of the case.
However, alteration of the concentration of carbon fibers in the outer layer may also effect -the degree o electrical conductivity of the case, par-ticularly in the surface portions of the container.
A preferred method o~ manufacturing the container is blow-molding. Blow-moldiny is generally well known to t'hose of ordinary skill in the art, as illustrated by U.S. Patent Nos. 3,452,l25 and 3,317,955 disclosing blow molding techniques and methods.
In practice, a blend of a polymeric resin such as poly-ethylene, and more preferably'high density polyethylene, is blended with conductive fibers such as carbon fi.bers in a relatively small percentage, for example about 12% of the fibers in relation to t'he total weight of t'he blend layer. This blend is 1~L~81~3~
- 7a - 64536-592 then coextruded with an inner layer of a polymeric resin such as polyethylene, and optionally with an intermediate layer of a re-grind material. The materials are heated to a temperature whereby the thermoplastic materials may be extruded as a parison and blow-molded into the desired shape or configuration as is well known in the art.
Figure 2 shows a resulting blow-molded container 18 wherein the fiber filled outer layer encloses each of the cover portion 20 and body portion 22 of the con-tainer. Figure 2 also illustrates the inner layer and optional intermediate layer, and the hollow space formed by the blow molding process, and resulting in a double wall cover portion 20 and body portion 22. The electrically cond~lctive outer layer 12 of the contalner, having the conductive fibers, provides electrical conductivity and therefore protection of ESD sensitive devices stored and transported within the container.
Although the present invention has been described in connection with preferred embodiments, one skilled in the art will understand that modifications may be made without departing from the scope of the invention.
404/~51113/2/8
CONDUCTIVE CASE USING ELECTRICALLY CONDUCTIVE FIBER
FIELD OF THE INVENTION
The field of the invention encompasses portable containers for the transportation of electrostatic discharge sensitive devices. More particularly, the present invention includes containers which, while closed, protect the contents of the container from external electrical forces.
BACKGROUND OF THE INVENTION
When two bodies~ particularly of unlike materials, are brought together into intimate contact, a redistribution of electrons across the interface is likely to occur. An attractive force is established as equilibrium is achieved. Work must be done in opposition to these attractive forces if and when the bodies are separated. The energy so expended manifests itself as an increase in electrical tension or voltage between the respective surfaces, which are said to be electrically charged with respect to each other. If a conductive path is available, the charges thus separated will reunite immediately. If no such path is available, as in the case of non-conductorsl the potential increase with separation may reach values of several thousand volts.
The charge on a charged object will be located on the ex$erior surface thereof, and these forces have a strong influence on nearby objects.
~04/851113/2/1 ' ' ' ., ' ~' : .
~3fl~36~
IE a naighborin~ obJect ls a conductor it will experience a separation of charges by induction. Its repelled charge is free to give or receive electrons as the case may be; if another conductor is brought near, the transfar may occur through the agency of the spark, very often an energetic spark.
Such charge transfer actions may aclversely effect or even electronically destroy a number of electronic devices sensitive to electricity such as static electricity. Micro-circuit devices such as integrated circuit chips may be destroyed by electros$atic discharge prior to their incorporation into the electrical or electronic equipment for which they were designed. Electronic devices which can be damaged by electrostatic discharge of less than 15.000 volts or 100 microjoules energy are classified as electrostatic discharge (ESD) sensitive.
To prevent electrostatic breakdown, containers in which such devices are stored and transported have been provided with means for short circu-ting the device terminals or pins during storage. This short circuiting serves to prevent ehe accumulation of potentially damaging static charges on the device.
U. S. Patent No. 4,171,049 discusses the utilization of a series of conductive slots or grooves in which ESD sensitive devices may be in-serted and later dispensed to manufacturing equipment.
Other containers have been developed for portable use as for example in the device replacement market. These are typically small box like containers that house conductive sponge or foam sheets into which the device terminals are temporarily imbedded. An example is found in U. S.
Patent No. 4,333,565.
In addition to the requirements for inhibiting electrostatic charge build up and shielding the ESD sensitive contents from electrical fields, a container useful for transporting an ESD should also provide protection from mechanical shock and vibration. In addition, such a con-tainer should be of light weight construction and convenient to use when ~l~3~
~ 3 - 6~530-592 gaining access to the equipment to be repaired. The contalner should also be adaptable to the storage of different sizes and shapes of ESD sensitive devices without change in the size and shape of the container itselE. Reuseability, tamper security, and cost economy are also important considerations.
Many of the containers referred to above are designed for online in-factory production use and do not meet many of the requirements desirable in a portable container. For example, many of the prior art containers are not adaptable to ESD sensitive devices of different shapes and sizes.
Another means well known in the art for providing protection of ESD
sensitive devices is the use of carbon black or carbon powder in varying amounts in the material forming the container for the ESD sensitive devices.
Cases made conductive with carbon powder, while effective in protecting from ESD, may sometimes tend to slough or mark off on contact. This is clearly an undesirable feature in a container to be used to store, transport and clispense ESD sensitive devices.
U.S. Patent No. 4,4g4,651 issued to Malcolm discloses a portable work station in which electrically conductive material, such as carbon black parti-cles, aluminum particles, and metal filings, may be blended with thermoplastic material to make an electrically conductive case.
It is therefore desirable to provide an electrically conductive container with the requirements for protection of the ESD sensitive devices stored in the container, but without the undesirable Eeatures of conventional containers.
SU~ Y OF T~lE INVEN'l'lON
In one aspect of the present invention, a container comprises electrically conductive body and cover portions comprising an outer layer of a blend of a polymeric resin and carbon fibers, and an inner layer of a po:Ly~eric resin.
~a'~86~L
~ 64536-592 In another aspect, the invention provicles a process for making a blow-molded electrically conductive containe-r comprising:
a) blending a polyoleEin with electrically conductive fibers;
b) coextruding a tubular, multi-layer parison so that the parison comprises i) an electrically conductive radially outer layer, bonded at one major surface to ii) a radially inner layer of a polyolefin; and c) blow-molding the tubular, multi-layer parison to provide a multi-layer body and cover portion in which the electrically conductive fiber-filled layer encloses each of the body and cover portions.
D~FINITIONS
The term "electrically conductive", and similar terms, are used here-in to describe a property of a mater-Lal or container that involves its ability to transfer electricity, and as used herein refers to containers having sufEi-cient conductivity to prevent static or electrical damage to electrically sensitive devices stored in the container.
The term "parison" is used herein to refer to a hollow tube or other preformed shape of a thermoplastic material or blend or aggregation of thermo-plastic materials which is inflated ins:Lde a mold in the blow-molding process.
"Polymeric resin" is used herein to generally include for example homopolymers, copolymers, terpol-ymers etc., and blends and modificatLons there-of.
The term "outer layer" is used herein to refer to a layer of a multi-layer film which comprises an outside surface thereof.
The term "inner layer" is used herein to refer to a layer of a multi-layer film which comprises an inside surface thereof.
The term "intermediate layer" is used herein to refer to a layer of multi-layer film positioned between an outer layer and an inner layer.
The term "regrind" is used herein to refer to waste material such as axcess parison material from blow-molding opera~ions, which is reclaimed by for example shredding or granulating of the excess material. This regrind material is generally mixed with other unprocessed material at some predetermined percentage.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a fragmented sectional view of a coextruded multi-layer film in accordance with the present invention.
Figure 2 is a schematic side view of a blow-molded container utilizing the multi-layer film.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Figure 1, a multi-layer film 10 is coextruded prior to forming into a parison. Film 10 includes an outer layer 12 comprising a polymeric resin blended with electrically conductive fibers. The preferred polymeric resin is a polyolefin, more preferably high density polyethylene or linear low density polyethylene. Preferred conductive fibers are carbon fibers, which are present in the blend material preferably in a range of from about 10% to 14% by weight of the blend layer. More preferably, the conductive fibers such as carbon fibers form about 12% by weight of the outer layer 12 of the multi-layer coextruded parison 10.
An inner layer 14 of a polymeric resin is coextruded with outer layer 12. This inner layer 14 is preferably relatively thick in comparison to the relatively thin outer layer 12, and preferably is a polyolefin such as polyethylene, and more preferably high density polyethylene. Inner layer 14 preferably comprises the same polymeric resin as that of outer layer 12, although for example different polyolefins may be used for outer layer 12 and inner layer 14 respectively. The inner layer 14 should comprise a polymeric resin with sufficient strength to prevent breaking of the parison during the molding process.
~n optional intermediate layer 16 may be coextruded simultansously with outer layer 12 and inner layer 14. Intermediate layer 16 is preferably made of a regrind material, for example a regrind h:igh density polyethylene or other polyethylene or polyolefin materials. When the optional intermediate layer 16 is used, the inner layer 14 and intermediate layer 16 should in combination provide sufficient strength to prevent the parison from breaking during the subsequent blow-molding process. The use of regrind material provides cost savings in the production of electrically conductive containers, without jeopardizing the effectiveness of the container for the storage and transport of electrically sensitive devices.
Preferably, the outer layer 12 comprises between about 5% and 15%
of the total thickness of the multi-layer parison, and the inner layer 14 and intermediate layer 16 each comprise between about 35% and 55% of the total thickness of the parison.
More preferably the outer layer 12 comprises about 10% of the total thickness of the multi-layer parison, and the inner layer 14 and intermediate layer 16 each comprise about 45% of the total thickness of the parison.
Where no intermediate layer 16 is present, the inner layer preferably comprises between about 85% and 95% of the total thickness of the parison.
More preferably, the inner layer comprises about 90% of the total thickness of the parison.
Of course, similar ranges of thickness apply to the conductive container resulting from blow-molding the parison.
It should be noted that carbon fibers or other conductive fibers could not normally be used indiscriminately in a blow-molding process because these fibers resist the requisite stretching during the molding process and, if used throughout the multi-layer parison, would result in breaking of the parison during the blow-molding operation. These fibers are - 7 - ~iS36-5~2 there~ore confined to the outer layer of t'he multi-layer parison to impart the required electricaL conductivity to the resulting blow-molded container but without affecting the blow-molding vperation. It should be clear to someone o-f ordinary skill in the art that a reduction in the preferred percentage oE carbon fibers or other conductive fi'bers in the outer blend layer permi-ts, to some extent, a relative thickening of the outer layer in relation to the total multi-layer parison thickness without seriously affecting the blGw-molding operation. Conversely, an increase in the percentage of carbon Eibers or other fibers in the ou-ter blend layer permits, to some extent, a relative thinning of -the outer layer in rela-tion to the total multi-layer parison thickness, without losing the desired electrical conductivity of the case.
However, alteration of the concentration of carbon fibers in the outer layer may also effect -the degree o electrical conductivity of the case, par-ticularly in the surface portions of the container.
A preferred method o~ manufacturing the container is blow-molding. Blow-moldiny is generally well known to t'hose of ordinary skill in the art, as illustrated by U.S. Patent Nos. 3,452,l25 and 3,317,955 disclosing blow molding techniques and methods.
In practice, a blend of a polymeric resin such as poly-ethylene, and more preferably'high density polyethylene, is blended with conductive fibers such as carbon fi.bers in a relatively small percentage, for example about 12% of the fibers in relation to t'he total weight of t'he blend layer. This blend is 1~L~81~3~
- 7a - 64536-592 then coextruded with an inner layer of a polymeric resin such as polyethylene, and optionally with an intermediate layer of a re-grind material. The materials are heated to a temperature whereby the thermoplastic materials may be extruded as a parison and blow-molded into the desired shape or configuration as is well known in the art.
Figure 2 shows a resulting blow-molded container 18 wherein the fiber filled outer layer encloses each of the cover portion 20 and body portion 22 of the con-tainer. Figure 2 also illustrates the inner layer and optional intermediate layer, and the hollow space formed by the blow molding process, and resulting in a double wall cover portion 20 and body portion 22. The electrically cond~lctive outer layer 12 of the contalner, having the conductive fibers, provides electrical conductivity and therefore protection of ESD sensitive devices stored and transported within the container.
Although the present invention has been described in connection with preferred embodiments, one skilled in the art will understand that modifications may be made without departing from the scope of the invention.
404/~51113/2/8
Claims
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for making a blow-molded electrically conductive container comprising: a) blending a polyolefin with electrically conductive fibers; b) coextruding a tubular, multi-layer parison so that the parison comprises i) an electrically conductive radially outer layer, bonded at one major surface to ii) a radially inner layer of a polyolefin; and c) blow-molding the tubular, multi-layer parison to provide a multi-layer body and cover portion in which the electrically conductive fiber-filled layer encloses each of the body and cover portions.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US85249086A | 1986-04-16 | 1986-04-16 | |
| US852,490 | 1986-04-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1284861C true CA1284861C (en) | 1991-06-18 |
Family
ID=25313484
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000523420A Expired - Lifetime CA1284861C (en) | 1986-04-16 | 1986-11-20 | Conductive case using electrically conductive fiber |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS62251374A (en) |
| CA (1) | CA1284861C (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5514299A (en) * | 1994-07-11 | 1996-05-07 | Bridgestone/Firestone, Inc. | Static dissipative container liner and method of making same |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5778706A (en) * | 1980-11-04 | 1982-05-17 | Oriental Metal Seizo Co | Conductive laminate |
| JPS6137670U (en) * | 1984-08-09 | 1986-03-08 | 株式会社東芝 | Parts mounting device with adjustable mounting angle |
-
1986
- 1986-11-20 CA CA000523420A patent/CA1284861C/en not_active Expired - Lifetime
-
1987
- 1987-03-16 JP JP62059103A patent/JPS62251374A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPS62251374A (en) | 1987-11-02 |
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