GB1600335A - Electrically conductive thermoplastic materials and process for their production - Google Patents

Electrically conductive thermoplastic materials and process for their production Download PDF

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Publication number
GB1600335A
GB1600335A GB1112178A GB1112178A GB1600335A GB 1600335 A GB1600335 A GB 1600335A GB 1112178 A GB1112178 A GB 1112178A GB 1112178 A GB1112178 A GB 1112178A GB 1600335 A GB1600335 A GB 1600335A
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United Kingdom
Prior art keywords
electrically conductive
synthetic resin
dispersion
carbon black
weight
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GB1112178A
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Reuter Technologie GmbH
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Reuter Technologie GmbH
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Priority to GB1112178A priority Critical patent/GB1600335A/en
Publication of GB1600335A publication Critical patent/GB1600335A/en
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/20—Compounding polymers with additives, e.g. colouring
    • C08J3/205—Compounding polymers with additives, e.g. colouring in the presence of a continuous liquid phase
    • C08J3/21—Compounding polymers with additives, e.g. colouring in the presence of a continuous liquid phase the polymer being premixed with a liquid phase
    • C08J3/215—Compounding polymers with additives, e.g. colouring in the presence of a continuous liquid phase the polymer being premixed with a liquid phase at least one additive being also premixed with a liquid phase
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D7/00—Producing flat articles, e.g. films or sheets
    • B29D7/01—Films or sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2995/00—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds
    • B29K2995/0003—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds having particular electrical or magnetic properties, e.g. piezoelectric
    • B29K2995/0005—Conductive

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Conductive Materials (AREA)
  • Compositions Of Macromolecular Compounds (AREA)

Description

(54) ELECTRICALLY CONDUCTIVE THERMOPLASTIC MATERIALS AND PROCESS FOR THEIR PRODUCTION (71) We, REUTER TECHNOLOGIE GmbH, of Am Rauhen Berge, 2844 Lem fare, Federal Republic of Germany, a Body Corporate organised under the laws of the Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention is concerned with electrically conductive materials which can be further processed thermoplastically and with a process for the production thereof.
It is known to produce electrically conductive synthetic resin materials by, for example, rolling or stirring electrically conductive carbon in the form of carbon black or graphite into synthetic resin materials in a more or less plastic state. Because of the large surface area dimensions of carbon black, which are between 300 and 1500 square metres per gram, or of their high powder densities, it is not possible, even with the best stirring or mixing machines, to incorporate more than 15% by weight of carbon black in synthetic resin materials without considerably affecting the original physical properties of the synthetic resin materials. Permanent, stable conductivity can be ensured only with a carbon black content from about 25 to 30% by weight or even more.
In addition, it is known to disperse from 25 to 30% by weight of carbon black in organic solutions of thermoplastic and/or thermosetting synthetic resin materials and then to evaporate the organic solvent in order to produce electrically conductive synthetic resin materials. A disadvantage of this process is that large amounts of solvents have to be evaporated off, which entails the risk of explosions and/or which are toxic.
Furthermore, the particles of carbon are partly encapsulated by the synthetic resin material deposited upon evaporation of the solvent and the chains of carbon black particles still present, which provide the conductivity are, to a large extent, destroyed again in subsequent calendering or during further processing by blow moulding, so that even with a carbon black content of up to 30% by weight, conductivity is dependent upon the processing.
It is an object of the present invention to provide a process with which it is possible to work without the use of organic solvents and which process provides electrically conductive synthetic resin materials, the electrically conductivity of which is retained even after further processing, for example by calendering, blow moulding, extrusion or injection moulding.
Thus, according to the present invention, there is provided a process of producing an electrically conductive material which can be further processed thermoplastically from polymers and electrically conductive particles, wherein an aqueous dispersion of thermoplastic synthetic resin is mixed with an aqueous dispersion of the electrically conductive particles, the resulting mixture is applied in a layer on to a support, whereafter the water is evaporated at a temperature above the softening point of the synthetic resin, this procedure being repeated; if necessary, one or more times until the layer has achieved the desired thickness, whereafter the layer is removed from the substrate.
The present invention also provides elec trically conductive materials which can be further processed thermoplastically and are obtained in this manner which materials can be used, for example, for the production of electrically conductive conveyor belts.
According to the present invention, the particles of thermoplastic synthetic resin are not homogeneously filled with electrically conductive particles, such as carbon black, but merely coated on their surfaces. Due to plastic interflowing of the synthetic resin particles with the evaporation of the water, which is not harmful to the environment, there can be obtained, for example, an electrically conductive sheet on a fabric carrier band coated with "Teflon". ("Teflon" is a Registered Trade Mark). After drying, the sheet can be stripped off the fabric carrier band. having been given a texture corresponding to that of the carrier band. In this case, which is a preferred embodiment of the present invention, the finished sheet is not subjected to the strain of further processing so that its conductivity is fully retained.By means of this process, it is possible to combine up to 50% by weight of carbon black with thermoplastic materials, without the flexibility of the sheet being impaired. The amount of carbon black incorporated is preferably at least 25% by weight and more preferably 30 to 40% by weight. Because of the fabric-like texture of the sheet, the latter "hangs" considerably less rigidly than a non-textured material.
The method of the present invention for the production of electrically conductive materials which can be further processed thermoplastically is, therefore, based upon mixing aqueous dispersions of thermoplastic synthetic resins with aqueous dispersions of carbon black, which are commercially available, the selection of the synthetic resin dispersion determining the physical properties of the electrically conductive, thermoplastically processable materials obtained and the type of carbon black and the quantities thereof determining the conductivity of the sheet.
Synthetic resin dispersions which can be used include, for example, those based on acrylic esters (for example, the "Acronals" marketed by BASF) and polyisobutylene (for example, "Oppanol" marketed by BASF) either singly or mixed with one another, preferred aqueous dispersions being those of age-resistant polyacrylates and of polyisobutylene. The carbon black used, which is preferably an acetylene carbon black in the form of a 30% by weight carbon black dispersion. is merely briefly mixed with a synthetic resin dispersion in a stirrer. The low viscosity liquid and sprayable mixture obtained can be applied to a rotating conveyor belt by means of a spray gun. situated on a spraying bridge. The conveyor belt can be, for example, a glass fibre fabric coated with "Teflon", with a width of 1 metre.The rotating fabric belt is guided through a drying tunnel with a length of about 5 metres, preferably at a temperature of from 100 to 130 , the water thereby being evaporated and cross-linking possibly taking place. Downstream of the drying zone, the sheet can be continuously stripped off and wound up or may be left for the time being on the belt. If the sheet is not stripped off, an increasingly thicker sheet or board, which can be used, for example, as a conductive conveyor belt, can be built up by repeated coating. From the thicker boards, it is possible for example, to make stampings, such as heelpieces, sealing rings and the like.
The electrically conductive particles may be of carbon, for example carbon black or graphite, of noble metals or of base metals coated with noble metals or of non-metallic substances. However, according to the present invention, it is preferable to use carbon black and particularly acetylene carbon black, such as is commercially available in the form of aqueous dispersions.
The following Examples are given for the purpose of illustrating the present invention: EXAMPLE 1 Production of an electrically conductive cross-linked sheet 100 parts by weight of a 50% by weight aqueous dispersion of a copolymer capable of cross-linking at 1200C. and based upon ethyl acrylate are added to 100 parts by weight of a 30% by weight dispersion of carbon black and the two dispersions are mixed for 6 minutes in a slow-running stirrer. The final dispersion obtained, which has a viscosity of 60 cP, is fed to a spray gun.
The spray gun, which has a fan type nozzle, is mounted on a carriage in such a manner that, during the spraying operation, the entire width of a belt running past it is wetted by the liquid dispersion. The conveyor belt running past under the spray gun has a width of 90 cm. The carrier conveyor belt is adjusted to a speed of 3 metres per minute by means of a continuously adjustable regulator. The carrier conveyor belt, which consists of a 'XTeflon"-coated fabric band, is wetted on its upper face by the dispersion sprayed on to it. The wetted belt passes through a drying tunnel at a temperature of 1200C. After being dried. the sheet, which adheres only lightly to the conveyor belt, is stripped off. Depending upon the speed of the belt and the spraying adjustment, sheet weights of from 30 to 250 grams per square metre can be produced. The finished product is an elastic, permanently electrically conductive sheet having a fabric like texture which retains its electrical conductivity even when subjected to either mechanical or thermal stressing. During the production process, no toxic gases are liberated, the system is not harmful to the environment and there is no danger of explosion in the installation. Calenders or blowing equipment or extruders preceding the installation are not required. The installation can also be used for other spraying and drying operations.
In addition to thin sheets, it is also possible to produce boards having a thickness of up to 4mm., such as are required for producing stampings or for conductive conveyor belts. In this case, the sheet is stripped off from the conveyor belt only after repeated coating or after several passages through the spraying plant.
EXAMPLE 2 Production of an electrically conductive copolymer capable of further thermoplastic processing and based upon ethyl acrylate An aqueous dispersion of a copolymer based upon ethyl acrylate is mixed with sufficient aqueous dispersion of carbon black to enable the subsequent synthetic resin material to contain 35% by weight of carbon black. It is thus ensured that the electrical conductivity will be retained even when the material is subjected to further processing in blow or injection moulding machines and presses. The mixture is made so highly viscous that the almost paste-like dispersion obtained can be spread out on to a belt coated with "Teflon".After passing through a drying tunnel at 100"C., i.e. at a temperature at which no cross-linking occurs, a sheet with a thickness of about 1 mm. is obtained which is electrically conductive and can be subjected to subsequent thermoplastic processing.
EXAMPLE 3 Production of a thermoplastic oil-and petrolresistant tank with electrical conductivity properties As synthetic resin dispersion, a copolymer ("Acronal" 330D, marketed by BASF) is mixed with a synthetic resin dispersion (Propiofan 325D, marketed by BASF) in a weight ratio 1:1.5. Both these dispersions form oil-and petrol-resistant films. 50 parts by weight of a 45% by weight aqueous dispersion of carbon black are added to 100 parts by weight of this mixture and stirred for 10 minutes. The highly viscous mixture is spread on to a rotating "Teflon" carrier belt, a layer with a thickness of about 1.5 mm. being formed. The coated belt passes through a drying tunnel which has forced ventillation and in which the drying temperature reaches precisely 100"C. so that practically no cross-linking occurs.During the drying, the water is evaporated out of the mixture. The dried material is readily removed from the "Teflon" carrier belt and is then communicated to such an extent that it can be passed through an extruder to a blow moulding plant. The material can be injection moulded and can also be worked up in press tools.
In accordance with the above described process, excellent physical properties can be obtained by mixing the most varied kinds of dispersions of synthetic resin materials with one another. The method of the present invention enables permanent conductivity to be obtained, this conductivity also being retained even when the material is subjected to further processing in injection or blow moulding plants. The process is also not harmful to the environment because only water is liberated.
WHAT WE CLAIM IS 1. A method of producing an electrically conductive material which can be further processed thermoplastically from polymers and electrically conductive particles, wherein an aqueous dispersion of thermoplastic synthetic resin is mixed with an aqueous dispersion of the electrically conductive particles, the resulting mixture is applied in a layer on to a support, whereafter the water is evaporated at a temperature above the softening point of the synthetic resin, this procedure being repeated, if necessary, one or more times until the layer has achieved the desired thickness, whereafter the layer is removed from the substrate.
2. A method according to claim 1, wherein an age-resistant polyacrylate dispersion or a polyisobutylene dispersion is used as the aqueous dispersion of thermoplastic synthetic resin.
3. A method according to claim 1 or 2, wherein the aqueous dispersion of electrically conductive particles used is a dispersion in which the electrically conductive particles are noble metals, non-metallic materials coated with noble metals or carbon.
4. A method according to claim 3, wherein the carbon used is carbon black or grahite.
5. A method according to claim 1 of producing electrically conductive materials which can be further processed thermoplastically, substantially as hereinbefore described and exemplified.
6. Electrically conductive materials which can be further processed thermoplastically, whenever produced by the process according to any of claims 1 to 5.
7. An electrically conductive sheet according to claim 6, wherein the material which can be further processed thermoplastically is a cross-linked copolymer based upon ethyl acrylate.
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. electrically conductive sheet having a fabric like texture which retains its electrical conductivity even when subjected to either mechanical or thermal stressing. During the production process, no toxic gases are liberated, the system is not harmful to the environment and there is no danger of explosion in the installation. Calenders or blowing equipment or extruders preceding the installation are not required. The installation can also be used for other spraying and drying operations. In addition to thin sheets, it is also possible to produce boards having a thickness of up to 4mm., such as are required for producing stampings or for conductive conveyor belts. In this case, the sheet is stripped off from the conveyor belt only after repeated coating or after several passages through the spraying plant. EXAMPLE 2 Production of an electrically conductive copolymer capable of further thermoplastic processing and based upon ethyl acrylate An aqueous dispersion of a copolymer based upon ethyl acrylate is mixed with sufficient aqueous dispersion of carbon black to enable the subsequent synthetic resin material to contain 35% by weight of carbon black. It is thus ensured that the electrical conductivity will be retained even when the material is subjected to further processing in blow or injection moulding machines and presses. The mixture is made so highly viscous that the almost paste-like dispersion obtained can be spread out on to a belt coated with "Teflon".After passing through a drying tunnel at 100"C., i.e. at a temperature at which no cross-linking occurs, a sheet with a thickness of about 1 mm. is obtained which is electrically conductive and can be subjected to subsequent thermoplastic processing. EXAMPLE 3 Production of a thermoplastic oil-and petrolresistant tank with electrical conductivity properties As synthetic resin dispersion, a copolymer ("Acronal" 330D, marketed by BASF) is mixed with a synthetic resin dispersion (Propiofan 325D, marketed by BASF) in a weight ratio 1:1.5. Both these dispersions form oil-and petrol-resistant films. 50 parts by weight of a 45% by weight aqueous dispersion of carbon black are added to 100 parts by weight of this mixture and stirred for 10 minutes. The highly viscous mixture is spread on to a rotating "Teflon" carrier belt, a layer with a thickness of about 1.5 mm. being formed. The coated belt passes through a drying tunnel which has forced ventillation and in which the drying temperature reaches precisely 100"C. so that practically no cross-linking occurs.During the drying, the water is evaporated out of the mixture. The dried material is readily removed from the "Teflon" carrier belt and is then communicated to such an extent that it can be passed through an extruder to a blow moulding plant. The material can be injection moulded and can also be worked up in press tools. In accordance with the above described process, excellent physical properties can be obtained by mixing the most varied kinds of dispersions of synthetic resin materials with one another. The method of the present invention enables permanent conductivity to be obtained, this conductivity also being retained even when the material is subjected to further processing in injection or blow moulding plants. The process is also not harmful to the environment because only water is liberated. WHAT WE CLAIM IS
1. A method of producing an electrically conductive material which can be further processed thermoplastically from polymers and electrically conductive particles, wherein an aqueous dispersion of thermoplastic synthetic resin is mixed with an aqueous dispersion of the electrically conductive particles, the resulting mixture is applied in a layer on to a support, whereafter the water is evaporated at a temperature above the softening point of the synthetic resin, this procedure being repeated, if necessary, one or more times until the layer has achieved the desired thickness, whereafter the layer is removed from the substrate.
2. A method according to claim 1, wherein an age-resistant polyacrylate dispersion or a polyisobutylene dispersion is used as the aqueous dispersion of thermoplastic synthetic resin.
3. A method according to claim 1 or 2, wherein the aqueous dispersion of electrically conductive particles used is a dispersion in which the electrically conductive particles are noble metals, non-metallic materials coated with noble metals or carbon.
4. A method according to claim 3, wherein the carbon used is carbon black or grahite.
5. A method according to claim 1 of producing electrically conductive materials which can be further processed thermoplastically, substantially as hereinbefore described and exemplified.
6. Electrically conductive materials which can be further processed thermoplastically, whenever produced by the process according to any of claims 1 to 5.
7. An electrically conductive sheet according to claim 6, wherein the material which can be further processed thermoplastically is a cross-linked copolymer based upon ethyl acrylate.
8. An electrically conductive material
according to claim 6 which can be further processed thermoplastically, which is crosslinked.
9. An electrically conductive material according to any of claims 6 to 8 which can be further processed thermoplastically, which contains at least 25% by weight of carbon black.
10. An electrically conductive material according to claim 10 which can be further processed thermoplastically, which contains from 30 to 40% by weight of carbon black.
GB1112178A 1978-03-21 1978-03-21 Electrically conductive thermoplastic materials and process for their production Expired GB1600335A (en)

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GB1112178A GB1600335A (en) 1978-03-21 1978-03-21 Electrically conductive thermoplastic materials and process for their production

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Application Number Priority Date Filing Date Title
GB1112178A GB1600335A (en) 1978-03-21 1978-03-21 Electrically conductive thermoplastic materials and process for their production

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2145096A (en) * 1983-08-15 1985-03-20 Gen Electric Electromagnetic wave attenuating coating composition

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2145096A (en) * 1983-08-15 1985-03-20 Gen Electric Electromagnetic wave attenuating coating composition

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