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WO1979000767A1 - Procede de revetement d'un substrat avec un film en materiau thermoplastique - Google Patents

Procede de revetement d'un substrat avec un film en materiau thermoplastique Download PDF

Info

Publication number
WO1979000767A1
WO1979000767A1 PCT/EP1979/000014 EP7900014W WO7900767A1 WO 1979000767 A1 WO1979000767 A1 WO 1979000767A1 EP 7900014 W EP7900014 W EP 7900014W WO 7900767 A1 WO7900767 A1 WO 7900767A1
Authority
WO
WIPO (PCT)
Prior art keywords
substrate
fibers
filaments
substrates
temperature
Prior art date
Application number
PCT/EP1979/000014
Other languages
German (de)
English (en)
Inventor
C Guignard
Original Assignee
Battelle Memorial Institute
C Guignard
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Battelle Memorial Institute, C Guignard filed Critical Battelle Memorial Institute
Priority to DE19792940988 priority Critical patent/DE2940988A1/de
Publication of WO1979000767A1 publication Critical patent/WO1979000767A1/fr

Links

Classifications

    • 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
    • B05D1/00—Processes for applying liquids or other fluent materials
    • 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
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/007—Processes for applying liquids or other fluent materials using an electrostatic field
    • 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
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/02—Processes for applying liquids or other fluent materials performed by spraying
    • B05D1/12—Applying particulate materials
    • B05D1/14—Flocking
    • 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
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/26—Processes for applying liquids or other fluent materials performed by applying the liquid or other fluent material from an outlet device in contact with, or almost in contact with, the surface
    • 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
    • B05D2252/00—Sheets
    • B05D2252/02—Sheets of indefinite length
    • 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
    • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
    • B05D3/02—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by baking
    • B05D3/0254—After-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
    • B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
    • B05D5/10—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an adhesive surface

Definitions

  • This invention relates to a process for coating a substrate with a film of thermoplastic material, in particular a thermoplastic polymer or an adhesive having hard and soft states according to its temperature.
  • British Patent Specification No. 933 250 describes a process which consists in covering a Substrate with a layer of thermoplastic material in powder form by electrostatic means, and melting subsequently the covering powder to obtain a continuo ⁇ s film adhering to the Substrate.
  • the thickness of the film depends on the granulation of the powder. However, when it is desired to deposit very thin films, of the order of 10 microns, it becomes difficult to ensure with this method a sufficient uniformity of the film, and the latter may have microporous areas.
  • US Patent MO. 2723 646 describes an electrostatic atomizer for a liquid, designed to ccat surfaces with this liquid.
  • This apparatus is essentially adapted for the application of substances in solution such as paints.
  • the solvent has to be evaporated in order to obtain the desired coating.
  • a process is also-known for producing filaments by electrostatic means from a molten thermoplastic material, being the subject of British Patent No. 1 484 584. This process makes it possible in particular to deposit a non-woven coating on a substrate.
  • the object of the present invention is to provide a coating process by means of which it is possible to obtain a coating which is continuous and of uniform thickness whatever the shape of the substrates.
  • a process for coating a Substrate with a film of thermoplastic material is characterized in that fibers or filaments of said material are .distributed uniformly on said Substrate by raising their temperature, at least in the proximity of the Substrate to be coated , to a value at least equal to the melting temperature of the aforesaid material during a period of sufficient length to cause the totality of said fibers or filaments to melt in order to cover said Substrate uniformly with the said material.
  • Figure 1 is a perspective view showing a first embodiment and a modification thereof
  • - Figure 2 shows a second embodiment in side elevation
  • Figure 3 shows a third embodiment in side elevation
  • Figure 4 is a partly perspective view of a fourth embodiment.
  • Figure 5 is a view in elevation of a fifth embodiment.
  • the installation shown in Figure 1 comprises a feeder assembly 1 having two parallel endless chains 2 mounted on three pairs of guiding sprocket ⁇ 4a, 4b and 4c located at the vertices of a triangle and of which one, 4a, is fast with the drive shaft of a motor M.
  • Electrical conductor wires 5 are tensionei transversely between the two parallel chains 2 and constitute a plurality of earthed electrodes. These wires are to be heated by the Joule effect with the aid of a direet-current source DC and two busbars. 8 and 9.
  • An electrostatic powder dispenser station is mounted at a location on the path of the wires 5. This station comprises essentially a hopper 6 associated with a vibrator (not shown), and an electrode 7, connected to a terminal of an electrostatic generator GE 1 supplying a potential of the order of 15 kV for example, located at the outlet of the hopper 6.
  • This electrode 7 is designe to impart an electric charge to the powder contained in the hopper 6 and composed of a dielectric thermoplastic material such as polyethylene, polypropylene, polystyrene a polyamide, a polyester, etc.
  • the Substrate to be coated is an aluminum foil 10 passing from a feed roll 11 to a take-off roll 12 by way of two guiding rolls 13 and 14 arranged to convey this foil initally parallel to a portion of the feeder assembly , and then through an oven 15.
  • the foil 10 is connected to a terminal of an electrostatic generator GE 2 , supplying a voltage of the order of 20 to 30 kV, for example.
  • the shafts of the rolls 11, 12, 13 and 14 are insulated, in order to keep the aluminum foil at the potential of the electrostatic generator GE 2 .
  • the powdered dielectric thermoplastic material which is to be used for c ⁇ ating the foil 10 with a thin film of the order of 5 to 10 ⁇ m. thick, is placed in the hopper 6.
  • the powder leaving this hopper is charged electrostatically by comi ⁇ g into contact with the electrode 7.
  • the powder thus charged is attracted by the earthed wires.5 and forms a deposit on their surfaces, forming a uniform layer.
  • these wires are heated by a current from the direct-current source De.
  • the wires 5 are moved, at right angles to their length round a triangular path by the chains 2 and 3 and the motor M in the direction indicated by the arrow F, whilst the aluminum foil 10 is moved in the direction of the arrow F 1 .
  • the heated wires 5 melt the powder deposited on them, and constitute a source or donor substrates for the thermoplastic material.
  • the thus molten dielectric material arrives at a position facing the foil 10, charged to a high potential by the generator GE 2 , the forces exerted on this material by the electrostatic field draw out a plurality of filaments which are deposited on the foil.
  • the non-woven product formed by the aecumulation of the filaments on the foil 10 then passes into the oven 15, the temperature of which is at least equal to the melting point of the thermoplastic material, so as to cause the filaments to melt to form . a continuous film on the foil 10.
  • the thickness of the film thus formed obviously depends on the quantity of deposited material and, in consequence, on the mean size of the filaments and on the relative speed between the foil 10 and the feeder assembly 1. Tests have shown that it is possible to form by this process a film having a thickness of the order of 5 to 10 ⁇ m, of perfect continuity and devoid of any porosity, ensuring complete coating of the Substrate in spite of the very small thickness of the Movie. If it is taken into aecount that in order to obtain the same result by depositing the powder directly on the foil 10, without passing through the filament stage, it is necessary to deposit a material layer of the order of 50 ⁇ m thick, the considerable saving in plastic material achieved by the present process will be appreciated.
  • the film may be formed, not by melting a non-woven product deposited on the foil 10, but by heating the space between the feeder assembly 1 and the foil 10, for example with the aid of two infrared bars 16 placed one at each end of this space, so as to prevent the solidification of the filaments, thus causing them to be deposited on the foil 10 in the molten state and to form the film progressively without passing through an intermediate non-woven stage as previously described.
  • the oven 15 can be dispensed with.
  • the filaments are deposited on a Substrate the temperature of which is not less than the melting temperature of the filament material.
  • the feeder assembly 1 ' is mounted around five pairs of pulleys 4'a, 4'b, 4'c, 4'd and 4'e_, insulated from earth.
  • the electrodes 5 ' are charged to the potential of the electrostatic generator GE.
  • the thermoplastic powder is distributed by a hopper 6 'at earth potential, and the powder deposited on the electrodes 5' is melted during the movement of these electrodes 5 'through an oven 17.
  • the Substrate is an aluminum foil 10 ', hot-formed in an oven 18 and leaving the oven at a temperature which is higher than the melting temperature of the thermoplastic material, so that the filaments which are deposited on the Substrate 10 'melt on contact with the latter at the rate at which they are deposited on the hot Substrate, thus forming a film coating on this Substrate as described in connection with Figure 1.
  • this second embodiment is not limited to the coating of a hot-formed substrates, but can also be applied to a flat substrates. It was simply intended as an example in which it is advantageous to deposit the filaments on a hot substrates. Conversely, deposition on a non-flat substrates can be performed in the embodiment illustrated in Figure 1.
  • the uniformity and the minimum thickness of the deposited film depend on the interfacial tension between the receiving Substrate and the thermoplastic material, which is essentially a function of the wettability of the surface of the Substrate, and on the surface tension of the molten thermoplastic material.
  • the surface of the substrates has to be totally covered by the powder, so that the thickness of the film thus formed is a function of the powder grain size.
  • the density of the filaments per unit surface area can be selected at will, in particular by controlling the speed of advance of the receiving substrates in front of the donor substrates, the minimum density of filaments required to form homogeneous film on the receiving Substrate being determined by the inter facial tension between the thermoplastic material and the receiving Substrate (it should be noted that the surface tension of the plastic material can be modified by the addition of wetting agents). It is for this reason that the process described above makes it possible to obtain a substantially thinner coating film than the powder or pulverization. processes already known. An important element in determining the thickness of the film is constituted by the possibility of making the fibers much finer than the powder grains.
  • the grain size of the powder is several tens of microns
  • the thickness of the film is directly related to the size of the fibers. Thus it is possible to form very thin films, of less than 10 ⁇ m.
  • Thick it is possible to obtain a layer the mean thickness of which is of the order of 5 ⁇ m-
  • a deposit of parallel fibers can be obtained by adjusting the relative velocity between the electrode wires 5, 5 'and the receiving Substrate to a value at least equal to the rate of production of the fibers, or substantially higher, for example 100 m / min, which gives a quite regular fiber layer and makes it possible to form a continuous film after heating, of the order of 15 to 20 g / m 2 of polypropylene, for example.
  • the orientation of the fibers can also be achieved by means of a current of air.
  • the starting material is already in the form of fibers or filaments instead of a layer of molten material.
  • Figures 3 and 4 illustrate two ways of putting this into effect.
  • Figure 3 refers to a conventional installation for electrostatic flock formation, which comprises a hopper, 19 filled with fibers, at the outlet of which is an electrode 20 connected to one of the poles of an electrostatic generator GE, and the other pole of which is connected to a rectangular electrode 21 below the path of a foil 10b to be coated.
  • This installation further comprises a blower 22 and a heating unit 23.
  • the fibers leaving the hopper 19 are charged by the electrode 20, which generates an ionized atmosphere at the outlet of the hopper, and are oriented within the field generated between the electrodes 20 and 21 in such a manner that they move, and are oriented, perpen- dicular to the surface of the foil 10b_.
  • the blower 22 drives an air current contrary to the direction of movement of the foil 10b as indicated by the arrow F, which current lays the fibers parallel against each other, in which position they are melted by the heating unit 23.
  • a wad of filaments 24 is unwound onto the foil 10c to be coated.
  • an electrostatic field is generated between a charging electrode 25 which charges the filaments, and an electrode 26 mounted below the foil 10c.
  • a heating unit 27 serves to melt the filament layer spread on the foil 10c.
  • Figure 5 illustrates a mode of execution in which the filaments are produced by a multiple extruder 28, an electrostatic field being established between this extruder, connected to one of the poles of an electrostatic generator GE, and an electrode 29 connected to the other pole of the same generator.
  • the filaments are deposited on a foil 10d moving in the direction of the arrow F at a speed which at least equals the rate of extrusion of the filaments, in such a manner that the filaments, held at a uniform distance from each other between the extruder 28 and the foil 10d by the effect of the field, are deposited in parallel to each other on the foil.
  • the invention is not limited to the coating of electrically conductive substrates.
  • the fibers are deposited on a cold substrate.
  • Good results were achieved in tests, by briefly heating a layer of parallel thermoplastic fibers deposited on cardboard to a temperature substantially higher than the melting temperature of the plastic material. The shorter the heating period, the less the molten plastic will tend to be absorbed by the cardboard.
  • a film could be obtained by heating a layer of polypropylene of 15 - 20 g / m 2 to about 200 ° C for about 3 seconds. The duration of heating can be further reduced by raising the temperature still higher.

Landscapes

  • Application Of Or Painting With Fluid Materials (AREA)
  • Laminated Bodies (AREA)

Abstract

Procede de revetement d'un substrat (10) avec un film en materiau thermoplastique dans lequel les fibres ou filaments du materiau sont appliques sur le substrat et sont fondus pour former un film continu. Le materiau peut etre applique en formant sur un substrat donneur (5) une couche de ce materiau a l'etat fondu, en produisant un champ electrostatique entre les substrats (5, 10) pour tirer de ladite couche une pluralite de filaments qui se deposent sur le substrat recepteur (10), et finalement en formant le film sur le substrat recepteur en faisant fondre lesdits filaments. Ce procede peut etre utilise specialement pour former des films tres fins. Il peut s'appliquer aux materiaux adhesifs ainsi qu'aux polymeres thermoplastiques.
PCT/EP1979/000014 1978-03-15 1979-03-14 Procede de revetement d'un substrat avec un film en materiau thermoplastique WO1979000767A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
DE19792940988 DE2940988A1 (de) 1978-03-15 1979-03-14 Process for coating a substrate with a film of thermoplastic material

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH2798/78 1978-03-15
CH279878 1978-03-15

Publications (1)

Publication Number Publication Date
WO1979000767A1 true WO1979000767A1 (fr) 1979-10-04

Family

ID=4241817

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP1979/000014 WO1979000767A1 (fr) 1978-03-15 1979-03-14 Procede de revetement d'un substrat avec un film en materiau thermoplastique

Country Status (9)

Country Link
JP (1) JPS55500152A (fr)
BE (1) BE874830A (fr)
ES (1) ES478661A1 (fr)
FR (1) FR2419769A1 (fr)
GB (1) GB2035844B (fr)
IT (1) IT1111547B (fr)
NL (1) NL7902026A (fr)
SE (1) SE7909387L (fr)
WO (1) WO1979000767A1 (fr)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2723646A (en) * 1950-04-01 1955-11-15 Ransburg Electro Coating Corp Apparatus for electrostatic atomization and coating
GB933250A (en) * 1960-12-08 1963-08-08 Siemens Ag Improvements in or relating to methods of applying a coating to a body of material
FR1337865A (fr) * 1962-08-07 1963-09-20 Sames Mach Electrostat Procédé et appareil perfectionnés pour le revêtement électrostatique d'objets
AU487398B2 (en) * 1974-03-14 1975-09-18 Toyo Ink Mfg. Co., Ltd Coating method and apparatus
US3979529A (en) * 1972-10-31 1976-09-07 Usm Corporation Electrostatic application of thermoplastic adhesive

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2723646A (en) * 1950-04-01 1955-11-15 Ransburg Electro Coating Corp Apparatus for electrostatic atomization and coating
GB933250A (en) * 1960-12-08 1963-08-08 Siemens Ag Improvements in or relating to methods of applying a coating to a body of material
FR1337865A (fr) * 1962-08-07 1963-09-20 Sames Mach Electrostat Procédé et appareil perfectionnés pour le revêtement électrostatique d'objets
US3979529A (en) * 1972-10-31 1976-09-07 Usm Corporation Electrostatic application of thermoplastic adhesive
AU487398B2 (en) * 1974-03-14 1975-09-18 Toyo Ink Mfg. Co., Ltd Coating method and apparatus

Also Published As

Publication number Publication date
SE7909387L (sv) 1979-11-14
IT7920988A0 (it) 1979-03-14
FR2419769A1 (fr) 1979-10-12
IT1111547B (it) 1986-01-13
ES478661A1 (es) 1979-06-01
BE874830A (fr) 1979-09-14
GB2035844B (en) 1982-05-06
NL7902026A (nl) 1979-09-18
GB2035844A (en) 1980-06-25
JPS55500152A (fr) 1980-03-21

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