Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
  • F21V3/00—Globes; Bowls; Cover glasses
  • F21V3/04—Globes; Bowls; Cover glasses characterised by materials, surface treatments or coatings
• • A—HUMAN NECESSITIES
  • A62—LIFE-SAVING; FIRE-FIGHTING
  • A62C—FIRE-FIGHTING
  • A62C3/00—Fire prevention, containment or extinguishing specially adapted for particular objects or places
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
  • B05D5/12—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain a coating with specific electrical properties
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
  • C09D5/24—Electrically-conducting paints
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
  • F21V15/00—Protecting lighting devices from damage
  • F21V15/01—Housings, e.g. material or assembling of housing parts
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
  • F21V25/00—Safety devices structurally associated with lighting devices
  • F21V25/12—Flameproof or explosion-proof arrangements
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
  • H01B1/06—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances
  • H01B1/12—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances organic substances
  • H01B1/124—Intrinsically conductive polymers
  • H01B1/128—Intrinsically conductive polymers comprising six-membered aromatic rings in the main chain, e.g. polyanilines, polyphenylenes
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05F—STATIC ELECTRICITY; NATURALLY-OCCURRING ELECTRICITY
  • H05F1/00—Preventing the formation of electrostatic charges
  • H05F1/02—Preventing the formation of electrostatic charges by surface treatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D2201/00—Polymeric substrate or laminate
  • B05D2201/02—Polymeric substrate
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
  • B05D7/50—Multilayers
  • B05D7/52—Two layers
  • B05D7/53—Base coat plus clear coat type

Definitions

• the present invention relates to a method, presented in the preamble of the appended claim 1 , for making an article electroconductive, as well as to an antistatic article, such as an illuminator, presented in the preamble of the appended claim 9.
• Explosive zones are divided, e.g. in the European standard EN 50014, into three different zone classes: 0, 1 , 2.
• Class 0 (Zone 0) is the most demanding class of all
• class 1 (Zone 1) is a slightly more moderate class
• class 2 (Zone 2) has further relaxed requirements.
• Slightly deviating from the European practice is the classification currently in use in the USA, where explosive zones are divided into two classes: Division 1 and Division 2.
• Division 1 corresponds basically to the classes 0 and 1 of the European standard EN 50014
• Division 2 corresponds to class 2.
• Explosive zones include oil refineries, oil rigs, mines, and several chemical plants. These sites may have zones which differ in their explosive zone classification, e.g. zones to be classified in classes 1 and 2, and part of the zones can be unexplosive zones.
• the controlled discharge of static electricity must be secured without sparkling.
• This can be achieved for example by making the device to be placed in an ex- plosive zone at least partly electroconductive and by connecting it to the earth potential.
• the devices are also mechanically implemented to resist impacts and knocks, because e.g. breaking an illuminator may cause a situation that the illuminating element (lamp) inside the illuminator is broken and the resulting sparkling or heating effect causes a danger of explosion.
• illuminators intended for use under explosive conditions are implemented in a way that the illuminator has a frame part which is at least partly electroconductive, and the frame part is equipped with a protective cover which is at least partly transparent, a lamp being placed inside the protective cover.
• the protective cover is typically made of thick glass, whereby it resists impacts and dropping. A sufficiently thick protective cover of glass is relatively heavy, which in- creases the weight of the illuminator excessively.
• electroconductive plastics are non-transparent or their strength does not comply with the requirements for use under explosive conditions; consequently, the use of electroconductive plastic materials in protective covers for such illuminators is not possible with currently known solutions.
• conductive plastic composites of this kind are disclosed e.g. in U.S. patent 5,219,492: polyacetylene, poly-p- phenylene, polypyrroie, polythiophen, and polyaniline. It is an aim to use such conductive polymers as electroconductors to replace e.g. metal conductors and semiconductors in many applications, such as batteries, photoelectric cells, circuit boards, antistatic package materials, and structures protecting from electromagnetic interference (EMI).
• EMI electromagnetic interference
• EP patent publication 545 729 discloses a method for bringing electroconductive polyaniline into an easily processable, melt-workable form by heat treatment with sulphonic acid or its derivative at a temperature of ca. 40...250 °C.
• the resulting melt-workable material has an acid pH value, which causes problems of corrosion in the equipment for manufacturing and processing the material.
• EP application publication 582 919 presents a method for adjusting the acidity of doped polyaniline further with a neutralizing compound.
• FI application publication 940625 presents a simplified method for manufacturing an electroconductive, melt-workable polyaniline which has substantially neutral acidity and is electroconductively and thermally stable.
• US patent 5,626,795 provides an extensive description of polyanilines and their properties.
• the protective cover e.g. a plastic which is at least partly transparent.
• the use of plastic has further the advantage that it can be moulded relatively easily, wherein it is possible to manufacture protective covers of different shapes and sizes.
• illuminators, eye shields, etc. intended for use in explosive zones, special attention must be paid on the strength of the structure of the protective cover.
• conventional plastic cannot be used as such, which increases the risk of static electric discharges.
• the corrosive effect of the coating on the plastics has prevented their use in the treatment of transparent plastic materials to become electroconductive.
• the method according to the invention is characterized in what will be pre- sented in the characterizing part of the appended claim 1.
• the invention is based on the idea that the article is subjected to surface treatment with a mixture containing polyaniline as a component, the article is evaporated for some time to dry the mixture, whereafter the article is subjected to retreatment with said mixture and evaporated again for drying the mixture.
• the article can also be heated.
• the article according to the present invention is characterized in what will be presented in the characterizing part of the appended claim 9. The present invention gives significant advantages to the prior art.
• the method of the invention can be used to treat plastic articles to become electroconductive, whereby they can be used in explosive zones.
• the illuminator of the invention has the advantage that, thanks to a slight discolouration caused by the mixture used in the treatment of the protective cover of the illuminator, possible damages can be detected and the protective cover be replaced with a new one.
• the protective cover can be easily changed e.g. in unexplosive service rooms, wherein the illuminator does not need to be sent to the manufacturer or distributor for repair.
• Fig. 1 is a schematic diagram showing a use site including a zone which is classified as explosive and a zone which is classi- fied as unexplosive,
• Fig. 2 is a perspective view on an illuminator suitable for use in explosive zones
• Fig. 3 is a side view and a partial cross-section on an illuminator according to Fig. 2.
• FIG. 1 shows a processing plant 1 with a process building 2 classified as explosive (e.g. class 1 in the standard EN 50014) as well as a service building 3 classified as unexplosive.
• the process building 2 is equipped e.g. with an illuminator 4. Electricity to the illuminator 4 is supplied via an input cable 5 from the service building 3.
• the service building 3 is equipped with a transformer 6 whereby e.g. the voltage of 230 V from the electric network is transformed to a low voltage of 48 V, and furthermore, the transformer 6 limits the strength of the current to be conducted to the input cable 5 so that the electric power in the input cable 5 does not exceed the limit set for the classification of the explosive zone. This upper limit for electric power depends e.g. on the zone class to which said process building 2 belongs.
• the illuminator 4 is connected via the input cable 5 to the ground potential, whereby any electric charge possibly accumulating in the frame of the illuminator 4 is discharged in a controlled manner to the ground.
• FIG 2 shows, in a perspective view, an antistatic illuminator 4 according to an advantageous embodiment of the invention.
• the illuminator consists of a frame part 7, which is preferably made of an elec- troconductive plastic by casting, injection moulding, or with a corresponding method.
• the frame part consists of two end parts: a first end part 7a and a second end part 7b. Between these end parts 7a, 7b, e.g. screws (Fig. 3) or other fixing means are used to fix a protective cover 9 which is made at least partly of transparent plastic, such as polycarbonate, and made electroconductive. The way of making the protective cover 9 electroconductive will be described below in this specification.
• the fixing of the protective cover 9 can also be implemented by gluing, but thus it is to be considered that the glue used in the fixing should not corrode the end parts 7a, 7b or the protective cover 9. Moreover, a glued protective cover 9 cannot be removed as easily as a protective cover 9 fixed with fixing means 8, which complicates the maintenance of such an illuminator.
• the protective cover 9 as well as the ends of the frame part are further provided with sealing means (not shown) to secure that the structure is dust- and/or water-proof.
• the first end part 7a is equipped with means 10 for fixing a lamp 11 in the illuminator 4, as well as means 12 for conducting electric energy via an input cable 5 to the lamp 11 (Fig. 3).
• Fig. 2 does not illustrate the lamp 11 , the lamp fixing means 10 and the means 12 for conducting electric en- ergy, which are placed inside the protective cover.
• Fig. 3 shows, in a reduced manner, a side view and a partial cross-section of an antistatic illuminator 4 according to a preferred embodiment of the invention, as shown in Fig. 2.
• the lamp 11 is advantageously a fluorescent lamp, e.g. because of its better efficiency and impact resistance in comparison with an incandescent lamp.
• As the lamp 11 it is also possible to use e.g. a Cooper-Hewitt lamp or a corresponding lamp type which is resistant to concussions.
• the lamp 11 has a base part 11 a with electroconductive means, such as conductive strips 13a, 13b for supplying electricity to the lamp 11.
• the means 12 for conducting electric energy comprise preferably counterparts 12a, 12b for the conductive strips, wherein when the lamp 11 is fixed to the lamp fixing means 10, the conductive strips 13a, 13b and the corresponding counterparts 12a, 12b constitute an electric connection.
• the counterparts 12a, 12b are coupled to conductors 5a, 5b of the input cable 5.
• the conductors 5a, 5b of the electric cable are coupled to output voltage pins 14a, 14b of a transformer 6 in an unexplosive zone, e.g. in a service building 3.
• the current supply circuit of the lamp must also be equipped with ignition means (not shown), such as a choker, for lighting the fiuores- cent lamp.
• the ignition means are placed e.g. in connection with the transformer 6, or they can be arranged inside the illuminator 4.
• a structure placed inside the illuminator 4 is presented in a parallel Finnish patent application by the same applicant, filed simultaneously with the present patent application.
• the following example is a description how a protective cover 9, preferably made of a polycarbonate tube, having a diameter of ca. 45 mm and a length of ca. 363 mm, is treated to become electroconductive.
• Polycarbonate is classified as an insulator, but its mechanical strength, light weight, formability, and transparency make polycarbonate very practicable in illuminators intended for explosive zones.
• a mixture is made of electroconductive polyaniline, a varnish, and a hardening agent. Powdered polyaniline is dissolved first in toluene, whereafter a varnish and a hardening agent are mixed into the solution.
• the electroconductivity of the treated protective cover 9 must be sufficient, in the order of 10 -9 to 10" 6 S (resistivity 10 9 to 10 6 ⁇ /m) or better.
• the transparency of the protective cover 9 must be sufficiently good for illuminator applications.
• the stability of the electroconductivity under demanding use conditions must be taken into account in the composition and treatment process of the mixture. In experiments made, the most suitable mixture ratio was found to be ca. 70 % of polyaniline solution, ca.
• the protective cover 9 is subjected to surface treatment with said mixture, wherein toluene used in the solution of polyaniline starts to corrode the surface of the protective cover.
• the first surface treatment is followed by an evaporation stage, wherein the varnish starts to harden.
• the hardening of the varnish will slow down the corrosion, wherein the mechanical properties of the protective cover 9 cannot be impaired to a significant degree.
• a mixture containing polyaniline has adhered to the protective cover 9, whereby sufficiently good electroconductivity (antistatic property) is achieved in the protective cover 9.
• the duration of the first evaporation stage is advantageously in the order of 10 to 20 min, preferably ca. 15 min.
• the protective cover is surface treated with the mixture still a second time, followed by a second evaporation stage, whose duration is advantageously in the order of 8 to 12 min, preferably ca. 10 min. This second treatment improves the stability of the electroconductivity also under very demanding use conditions.
• the protective cover 9 may still contain residual toluene which might cause corrosion of the protective cover; consequently, the protective cover 9 can still be subjected to thermal treatment, whereby toluene residues can be eliminated to a sufficient degree.
• thermal treatment the temperature is raised to for example ca. 80°C, and the duration of the treatment is for example ca. one hour. With regard to the temperature, one should be careful not to exceed the melting point of the material used in the protective cover 9. The duration of the treatment is not a critical factor; a longer treatment time secures the removal of toluene.
• the significance of the hardener in the above-presented mixture in- volves e.g. a significant acceleration in the hardening of the mixture, wherein the structure of the protective cover 9 cannot be impaired (bristle) during evaporation.
• the hardener used can be a hardening agent known as such.
• a protective cover treated by the above-presented method was used to manufacture an illuminator 4, in which the lamp used was a fluorescent lamp of 11 W.
• the illuminator was placed in a climate chamber, where the temperature was set at ca. 90°C and the relative humidity was in the order of 85 %.
• the illuminator 4 was maintained under these condi- tions for 720 hours, after which tests were carried out for the electroconductivity and for the resistance to impacts with a so-called shot test. After the tests, it could be stated that the electroconductivity of the illuminator had remained substantially unaltered. Also the shot test did not impair the properties of the illuminator, but the transparency of the pro- tective cover 9 was sufficient and no changes were found due to em- brittlement.
• the polyaniline can be a known polyaniline polymer with internal electroconductivity.
• the term polyaniline covers also derivatives having the polymeric stem specific to polyaniline.
• As the solvent of polyaniline toluene can be replaced by also other organic solvents.
• the article to be treated can be also different from a protective cover for an illuminator.
• Examples include antistatic packages, where in addition to the antistatic property, also transparency is needed at least partially, e.g. for perceiving the contents of the package without opening the package.
• transparency and the antistatic property are required also in different eye shields in certain work tasks.
• work tasks include e.g. the handling of chemicals in explosive zones and the handling of electronic components vulnerable to static electric dis- charges which is usually conducted in unexplosive zones.
• Transparent shields are also used in connection with some machine tools to protect a worker who must, however, have a visual contact to the machining operation.
• the present method for treatment of transparent plastic articles to become electroconductive is well suited, because the plasticity and light weight of plastic is better compared to e.g. glass, which is used in shields of prior art.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Emergency Management (AREA)
• Business, Economics & Management (AREA)
• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Health & Medical Sciences (AREA)
• Public Health (AREA)
• Materials Engineering (AREA)
• Wood Science & Technology (AREA)
• Organic Chemistry (AREA)
• Paints Or Removers (AREA)
• Elimination Of Static Electricity (AREA)
• Treatments Of Macromolecular Shaped Articles (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8549010

Family Applications (1)

Country Status (8)

Cited By (2)

Citations (1)

• 1997
  • 1997-06-09 FI FI972450A patent/FI118280B/fi not_active IP Right Cessation
• 1998
  • 1998-06-08 ES ES98924354T patent/ES2268777T3/es not_active Expired - Lifetime
  • 1998-06-08 AU AU76580/98A patent/AU7658098A/en not_active Abandoned
  • 1998-06-08 DE DE69836018T patent/DE69836018T2/de not_active Expired - Lifetime
  • 1998-06-08 EP EP98924354A patent/EP0992181B1/en not_active Expired - Lifetime
  • 1998-06-08 KR KR1019997011607A patent/KR20010049184A/ko not_active Application Discontinuation
  • 1998-06-08 CA CA002293574A patent/CA2293574A1/en not_active Abandoned
  • 1998-06-08 WO PCT/FI1998/000486 patent/WO1998057527A1/en active IP Right Grant

Patent Citations (1)

Non-Patent Citations (1)

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