WO2001062397A1

WO2001062397A1 - Method and apparatus for spraying a material

Info

Publication number: WO2001062397A1
Application number: PCT/NL2001/000159
Authority: WO
Inventors: Adriana Marijke De Jager-Schouten; Gui Gérard DE JAGER
Original assignee: Advanced New Materials S.A.; De Jager-Schouten, A., M.
Priority date: 2000-02-25
Filing date: 2001-02-26
Publication date: 2001-08-30
Also published as: AU4126601A

Abstract

The invention relates to a method and apparatus for spraying a material for producing jets, ligaments, dispersions, droplets and such. The spraying is done by electrohydrodynamic spraying and the material is substantially free of solvents and is brought in a flowable state with high viscosity by heating.

Description

METHOD AND APPARATUS FOR SPRAYING A MATERIAL

The present invention relates to a method and apparatus for spraying a material, comprising making the material flowable and forming at least one jet thereof. It is known to spray material such as paints, coatings and such by first diluting the material with a solvent to a suitable low viscosity for making it sufficiently flowable. A et of the diluted material is formed by means of a spray gun or such.

The solvent evaporizes during and after the spraying. At least a part of the evaporized solvent is expelled into the environment, which is considered to be unfavorable .

Therefor it is an object of the invention to provide a method of the kind set forth above with which this drawback is at least reduced.

According to the invention this object is achieved in that the forming of the jet is done by means of electrohydrodynamic spraying, said material being at least substantially free of solvent agents and being made flowable with a high viscosity by heating.

The invention is based on the insight that only a slight flowability of the material can be sufficient for electrohydrodynamic spraying. Generally the flowability of the material only has to be such that it can be advanced to a spraying nozzle.

Accordingly, the present invention provides a method for jetting and/or dispersing materials that have a viscosity of from 0.5 to 50.000 Pas.

According to a preferred embodiment of the invention, the flowable material is supplied through a channel in a nozzle under such low pressure that the material just flows through this channel.

It is noted that electrohydrodynamic spraying is known as such e g. from the article " Electrohydrodynamic atomization m the cone-jet mode, physical modeling of the liquid cone and jet" m J. Aerosol Sci . Vol 30, No. 7, pp 823-849, 1999. This article reflects work of a.o. J.C.M. Maπjnissen who has also contributed m studies related to the invention.

The invention also relates to an apparatus for applying the method according to the invention. It comprises at least one nozzle, heating means, supply means for supplying material to the nozzle, electrodes near the nozzle and at a distance therefrom, high voltage generating means connected to the electrodes and elements for adjusting the distance between the nozzle and a control electrode.

With regard to its mechanical construction, the applicator apparatus according to the present invention is extremely simple compared with conventional jetting and dispersion devices are driven by electric forces, as it requires no mechanical wear parts.

Basically, it converts non-flowable material to flowable material and improves flowability where there is little or no flow capability. A plurality or more preferably a multiple assemblies of jetting and dispersion devices can be applied within a very large application zone, whereby a sufficient jetting and dispersion capacity is available.

The invention can be used with a diversity of materials such as bio materials, coating compounds, enamel, fats, lubricants, metal oxides, oils -including fuel oil-glyceπne-grease- , organic materials / paint resins / polymers, rare earth, waxes such as paraffins and petrolatums, and other flowable or semi- flowable materials or mixtures thereof, m emulsions, gels, slurries / suspension and/or including electric ink, solvents, suspensions of foreign materials such as additives and the like.

The coating compounds can comprise of bitumen blends, Ethylene/acrylate copolymers (EA) ,

Ethylene/acrylic copolymers (EAA) , Isocyanate resins, Modified phenolic resins, Silicone elastomers (LSR A.RTV 2K) mcl. Auxiliaries, Unsaturated polyester reins (UP) . , and including electrically controlled materials and other 'smart materials' (e.g. electrorheological fluids, piezoelectric materials, polymers and polymer gels) . Said paint resins can e.g. comprise of Alkyd resins, Paint auxiliaries, Phenol/fonnaidehyde resms (PF) , Polyvinyl acetates (PVAC) , Polyvmyl alcohols (PVAL) , Polyvmyl butyrals, Urea/formaldehyde resms.

The invention can specifically well be used with polmers such as thermoplastic polymers, thermosettmg polymers, thermoplastic elastomers, rubber, natural polymers, mesophase pitch and mixtures thereof and also including binder and precursor materials.

The rare earth materials preferably are selected from the group consisting of Yttrium, Gadolinium, Lanthanum, Europium, Holmium, and the like.

The flowable or semi-flowable materials can range from liquids to gels.

Useable thermoplastic polymers are Acrylonitrile- butadiene-styrene (ABS) , Acetal homo and copolymers (POM), Acrylomtrile styrene acrylic ester (ASA), Acrylonitπle- (ethylene-propylene diainine modified) - styrene (AES) , Liquid crystal polymer (LCP) , Polyacryletherketone (PAREK) , Polyacrylonitπle (PAN) , Polyalkylene terephthalate such as polybutylene terephthalate (PBT) , Polyannide 6, polyamide 6.3 - 6 6 - 6.4 - 6.10 - 6.12, polyamiαe I 1, polyamide 12 (PA), Polyarylamide (PA MXD6), Polyaryl sulfone (PAS), Polybutene terephtalate (PBT) , Polycarbonate (PC) , PolyetheresterPolyethylene (ultra-high, high- and low- density) (PE) , Polyethylene terephthalate (PET) , Poly (aryl) -etherketone (PAEK), Polyether-etherκetone (PEEK), Polyetherketoneketone (PEKK), Polyetherketoneetherketone etone (PEKEKK) , Polyether- lmide (PEI) , Polyether sulfone (PES) , Polyimide (PI) , Polymethyl methacrylate (PMMA) , Polypropylene (PP) , Polyphenylene oxide (PPO) , Polyphenylene sulphide (PPS), Polystyrene (PS) , Polytetrafluoroethylene (PTFE) , Polysulfone (PSU) , Polyvmyl chloride (PVC) , Polyvmylidene fluoride (PVDF) , Styrene acrylonitπle (SAN) , Styrene maleic anhydride (DSMA) , Thermoplastic polyurethane (TPU) , and pre-polymers (monomers) of thermoplastics; and the possible blends, foams, mixtures and/or copolymers of two or more of the foregoing thermoplastics and/or or pre-polymers (monomers) such as Polyamide, Polycarbonate, Polyarylate, Polybutylene terephthalate . Preferred examples of the thermosettmg polymers are Epoxy, Furane, Ketone, Maleic, Melamme, Phenol, Polydiallyl phthalate (PDAP) , Polyester, Urea/formaldehyde and Vinyl ester resms.

Said thermoplastic elastomers are selected from the group consisting of Oleofm copolyesters (EP(D)M), Polyamide 12 elastomer, Polyether block amide, Polyetherester elastomers, Polyisocyanate, PUR- elastomers, SBS-teleblockpolymer, SEBS-blockpolymer, thermoplastic PUR-elastomer, TPV-thermoplastic vulcanized material and Polybutadiene .

Suitable rubbers are Acrylic (ACM) , Acrylnitπl butadiene, Brommebutyl , Butadiene, Butyl (IIR), Chlorinated polyethylene (CM), Chlormebutyl , Chloroprene, Chlorosulfanated Polythylene (CSM) , Cιs-1,4 polybutadiene (BR) , Cιs-1,4 polyisoprene (IR),

Epichlorohydrm (Co, ECO, ETER) , Ethylene/polypropylene terpolymers (EDPM) , EthyleneNAC-copolymers (ENA) , Fluoro (FPM) (CFM) MFQ) , Hydrogenated Acrylonitπle/butadiene , Natural, Nitπle, Polysulfide, Silicone, Styrene and Urethane rubbers.

The monomers mentioned preferably form a thermoplastic polymer and a catalyst, which becomes a part of the polymer chain, initiates the polymerization of the resm. The monomers preferably are cyclic monomers such as lactones and lactams, which polymerize by ring opening, and these can be mixed with the appropriate quantity of catalyst under controlled heating m order to b obtain one or more partly or completely polymerized monomers .

This polymerization is performed up to a stage whereby the partly polymerized mixture has a viscosity that is adequate for being jetted and dispersed. The polymerization can be performed by electropolymerisation. If small quantities of solvents are used, these are selected from the group consisting of Ketones, Esters, Ethers, Aromatics, or Alcohols, more specifically Acetic acid, Acetic anhydride, Acetone, Acetophenone , Amyl acetate, Benzaldehyde , Butyl acetate, Butyl alcohol, Butyl amme, Carbon tetrachloπde , Chloroform, Cyclohexanol , Cyclohexanone, Ethanol , Ethylene carbonate, Ethylene glycol, Hexyl alcohol, Methanol , Methyl ethyl ketone, Methyl acetate, Methyl chloride and Methylene chloride and Gas-solvents

As mentioned before, additives can be used, for instance absorbents, accelerators, activators, additive concentrates, additives for electrospray paints, adhesion promoters, adipates, ageing stabilizers, agents biozides, aluminium tπhydrate, amme accelerator, arnme steπcally hindered, ammonium persulfate, anti-blockmg agents, antifoam agents, antimony trioxide, antistatics, antioxidants , binders, biologically active agents, black pigments, flame proofing agents, blowing agents, carbon black (e g acetylene black), coloring pigments, colorants, agents, ceramics, cement or concrete, citric acid, diluents, dispersing agents, dissolvers, dyestuffs, elasticators , emulsifiers, fire protection agents, fillers, flame retarding agents, flexibilizers , flow auxiliaries, flow control agents, foaming agents, foarn stabilizers, gypsum, hardeners, heat stabilizers, hollow fillers, impact modifiers, inhibitors, initiators, light stabilizers, linking agents, lubricants, master batches, microbicides , mineral plasticizers , matting agents, nucleating agents, optical bπghteners, organic phosphates, ozone restrictors, plasticizers, piezoelectric materials, pigments, polyaniline, polaπzable particles, polymerization catalysts/initiators, polymerization auxiliaries, pore forming agents, porosity regulators, preservatives, reinforcing agents, release agents, salts (e.g. LιCF3S0) , shape memory alloys, (fumed) silica, silicones, stabilizers sodium bicarbonate, solid lubricants, solvents, stabilizers, superalloys, surfactants, talc, thickeners, UV absorbers or stabilizaters , vulcanization accelerator, vulcanization inhibitors, vulcanizing agents, washing mixtures, waxes, white pigments, zmc oxide and auxiliary processing materials.

Furthermore the material can comprise fillers such as flakes, grains, needles, platelets, whiskers and the like. Suitable binder materials can be selected from the group consisting of Hexamethylenetetramme, Polymethyl methacrylate , Polyalkylene carbonate, Polypropylene carbonate or an Olefm polymer, preferably Polyethylene or Polypropylene, or a water-soluble binder, e.g. Methyl cellulose, which are "clean combustion" binders, which can be removed after molding of the impregnated semifinished product.

The mentioned precursor materials preferably are selected from the group comprising Organo-metallic compounds with a base of Silicon, a Polysilane or

Polysilazane, and Polymer-Metallo-organic mixtures and Carbon precursor polymer binders, which leave behind a considerable amount of Carbon after pyrolysis, such as: Bulk Mesophase/Pitch, Epoxy, Furane, Furftiryl alcohol, Furftuyl ester, Polyaryl acetylene (PAA) , Polyamide (PA) , Polybenzimid azole (PBI) , Polyphenylene sulphide (PPS) or Phenolic polymer or mixtures thereof.

The heating and/or melting of the material can be performed by electrical induction, halogen, infrared, laser, microwave, shear-forces, ultrasonic or mixtures thereof and the like.

The heating and/or melting temperature can be reached only m the last part of the supply conduit . The heating can be performed to a temperature just below the melting temperature of said flowable or semi- flowable material .

The apparatus according to the invention preferably comprises a cone-jet electro hydrodynamic jetting and/or dispersion device and is provided with a control electrode order to e nance the stability of jetting and/or dispersion. The distance of a capillary opening slit or tube of the cone-jet system to the control electrode is fixed or adjustable between 0 1 and 1C cm, and preferably is 0.5 to 4 cm. In order to control the nature, dimensions and pattern of the resulting jetting and/or dispersion.

The capillary opening slit or tube has a diameter of 0.01 to 20 mm, preferably 0.02 to 10 mm, more preferably 0.03 to 5 mm.

The at least one nozzle is fixed m an electrically non-conducting material, preferably heat-resistant ceramic material and is operated by means of an electrode with a voltage from 0.01 to 100 KV .

In a preferred embodiment the nozzles are provided with means to increase tie surface of electrical contact charging of said materials m order to enhance the electrical contact charging of said materials. The area ranging from the nozzle to a counter electrode is encapsulated by an electrically insulated housing in order to prevent unwanted interferences with downstream equipments and/or materials.

The method according to the invention can be applied for optionally depositing or spraymg chopped or continuous random distributed or oriented reinforcement fibers or filaments m all or part of the jets, ligaments, dispersions, droplets and/or other fluid paths or on the preform srenns or combinations thereof. Furthermore the metnod and apparatus of the invention can advantageously be used for:

Production of (optionally coated) foams, powders and microspheres Coating of (outside and/or inside of all types of materials and shapes) beads, braids, cables, fabrics, filaments, fibers also transmission glass fiber, fiber bundles, granules, non-woven, pipes, plates, powders, parts, road-marks, roofs, ropes, sheets, substrates, tablets, yams, wires and/or webs. burning dispersions of medium- and high viscosity fuels as diesel engines, and gas turbine burners, and other burners . - Burning dispersions of medium- and high viscosity materials scrap, such as polymers, rubber

Removing layers of flowable material from a substrate, such as removal of anti-oxidizmg oil from sheet metal, removal of oil spills and such In these latter cases a carrier having a high tension electrode will be held near the material and a counter electrode at a distance thereabove . Due to the high tension field the material will be rejected from the substrate and can be collected near the counter electrode. Optionally multiple nozzle assemblies can be placed on one or more robot arms or the like for moving over materials to be coated.

From the above it will be clear that the invention can be used with a wide variety of materials and m a wide variety of fields of the technique.

Claims

1. Method for spraying a material comprising bringing the material in a flowable state and forming at least one jet thereof, characterized in that the forming of the jet is done by means of electrohydrodynamic spraying, said material is at least substantially free of solvent agents and is brought in a flowable state with high viscosity, by heating.

2. Method according to claim 1, wherein the flowable material is supplied through a channel in a nozzle under such low pressure that the material just flows through this channel .

3. Method according to claim 1 or 2 , characterized in that the electrohydrodynamic spraying is done such that the material is atomized.

4. Method according to claim 3, wherein the material is atomized in a heated space such that the material is deposetid on a carrier in a flowable state.

5. Method according to claim 1 or 2 , wherein the electrohydrodynamic spraying is done such that filaments are formed of the material.

6. Method according to claim 1, wherein said flowable material has a viscosity from 0.1 to 50.000 Pa s., preferably 0.5 to 10.000. Pa s . , and more preferably I to 2.000 Pa s . at fluid or melting temperature before, during or after jetting and/or dispersion.

7. Method according to claim 1, wherein said material has a electrical conductivity of between 0,01 and 100 micro Siemens per cm, preferably between 0,05 and 50 micro Siemens per cm, more preferably between 0,1 and 20 micro Siemens per cm

8. Method according to claim 1 or 2 , wherein said material has a surface tension from 1 to 500 dyne/cm preferably 10 to 100 dyne/cm and more preferably 15 to 50 dyne/cm.

9. Method according to claim 1 or 2 , wherein said material is selected from the group consisting of bio materials, coating compounds, enamel, fats, lubricants, metal oxides, oils -including fuel oil- glycerme-grease- , organic materials / paint resms / polymers, rare earth, waxes such as paraffins and petrolatums, and other flowable or semi- flowable materials or mixtures thereof, m emulsions, gels, slurries / suspension and/or including electric ink, solvents, suspensions of foreign materials such as additives and the like.

10. Apparatus for applying the method according to one of the preceding claims comprising at least one nozzle, heating means, supply means for supplying material to the nozzle, electrodes near the nozzle and at a distance therefrom, high voltage generating means connected to the electrodes and elements for adjusting the distance between the nozzle and a control electrode.