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
  • B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
  • B05D5/08—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an anti-friction or anti-adhesive surface
  • B05D5/083—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an anti-friction or anti-adhesive surface involving the use of fluoropolymers
• • 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
  • B05D7/14—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 to metal, e.g. car bodies
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M61/00—Fuel-injectors not provided for in groups F02M39/00 - F02M57/00 or F02M67/00
  • F02M61/16—Details not provided for in, or of interest apart from, the apparatus of groups F02M61/02 - F02M61/14
  • F02M61/166—Selection of particular 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
  • B05D1/02—Processes for applying liquids or other fluent materials performed by spraying
  • B05D1/04—Processes for applying liquids or other fluent materials performed by spraying involving the use of 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
  • B05D1/08—Flame spraying
• • 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
  • B05D1/18—Processes for applying liquids or other fluent materials performed by dipping
  • B05D1/22—Processes for applying liquids or other fluent materials performed by dipping using fluidised-bed technique
  • B05D1/24—Applying particulate materials
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M2200/00—Details of fuel-injection apparatus, not otherwise provided for
  • F02M2200/06—Fuel-injection apparatus having means for preventing coking, e.g. of fuel injector discharge orifices or valve needles
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M2200/00—Details of fuel-injection apparatus, not otherwise provided for
  • F02M2200/90—Selection of particular materials
  • F02M2200/9038—Coatings

Definitions

• the present invention relates to metal surface coating processes, and more particularly to injectors that introduce the fuel upstream of or into the combustion chambers of the injection engines.
• This fouling is due to the formation of deposits on the metal surfaces in contact with the hydrocarbon fluids. These deposits come from the thermal degradation of hydrocarbon fuel, mixed with the combustion oxygen and may contain sulfur in varying amounts.
• the first mechanism occurs mainly at the highest temperatures.
• the metal portion of the injector changes from 150 ° C to possibly about 650 ° C, and the increase in coke deposition rate follows this temperature increase, to the highest levels where pyrolysis cokes the coke. entire deposit.
• the second mechanism begins at about 370 ° C and causes the formation of gum deposits. It involves oxidation reactions involving the oxygen contained in the hydrocarbon fluid, which leads to a polymerization including said formation of gums. These gums are very adherent on the irregularities of the metal surface and constitute the major contribution to the fouling of the injectors.
• PVDF polyvinylidene fluoride
• adhesion agent which consists of a mixture of epoxy resins and PVDF (see US-A-3,111,442).
• adhesion agents have the disadvantage of being sensitive to heat treatments and must be applied to the surface by a very slow process, difficult to envisage for the mass production of parts such as injectors.
• the object of the invention is to provide an economical method of coating a metal surface by a smooth and non-porous PVDF-based deposit, providing said deposit a high adhesion strength and a high resistance to chemical attack, especially by hydrocarbons at a temperature of at least about 400 ° C.
• This method would thus be applicable, in particular, to the coating of the nozzle noses for internal combustion engines, in order to reduce their fouling.
• the subject of the invention is a method for inhibiting the deposition on a metallic surface of products, such as gums, originating from the thermal degradation of hydrocarbons derived from a hydrocarbon fluid mixed with oxygen and / or sulfur, according to which depositing, on said metal surface before use, a polymer coating based on polyvinylidene fluoride , characterized in that: - said coating consists of at least one layer of a mixture of a homopolymer of polyvinylidene fluoride, or a copolymer whose polyvinylidene fluoride is the main component, the other components being present in from 1 to 20% by weight of the polymer, and a glass;
• said coating is obtained from a mixture of polymer particles having a flow index of 10 to 300 grams per 10 minutes determined according to ASTM D1238 condition J and spherical or ovoid glass particles of size between 1 and 300 ⁇ m;
• the ratio between the mass percentages of the glass and the polymer in the mixture is between 0.05 and 0.50;
• the coating of the metal surface is obtained by a fluidized bed method, or by an electrostatic process, or by compressed air, or by flame vaporization, or by an electrostatic fluid bed.
• the glass particles preferably have a diameter of between 5 and 150 ⁇ m.
• the polymer may be a copolymer of which polyvinylidene fluoride is the main component, and the other components are present in a proportion of 2.5 to 10% by weight of the copolymer.
• the polymer may be a copolymer of which polyvinylidene fluoride is the main component, and whose other components are obtained from vinyl fluoride or hexafluoropropylene, or mixtures thereof.
• the glass may be chosen from ordinary glass, simple and compound silicates, borates, phosphates and oxides of sodium, potassium, magnesium, aluminum, zinc, lead and their mixtures.
• the ratio between the mass percentages of the glass and the polymer in the mixture may be between 0.10 and 0.40. Glass particles coated with an adhesion agent can be used.
• the coating may then be covered with a catalytic coating material such as an oxide of at least one metal such as Mo, W, NiW, NiMo, Pt, Pd, which promotes the formation of coke by thermal degradation in a hydrocarbon fluid while inhibiting the formation of gums.
• a catalytic coating material such as an oxide of at least one metal such as Mo, W, NiW, NiMo, Pt, Pd, which promotes the formation of coke by thermal degradation in a hydrocarbon fluid while inhibiting the formation of gums.
• the invention also relates to a metal part, characterized in that it is coated on at least a portion of its surface by a coating obtained by the above method. It can be an injector for introducing a fuel into a combustion chamber of an internal combustion engine.
• the invention is essentially based on the coating of the metal surface to be protected by a mixture comprising:
• a polymer which is either a homopolymer consisting of PVDF, or a copolymer of vinylidene fluoride (mainly present) and one or more other monomers, which may be, for example, vinyl fluoride or vinyl fluoride; hexafluoropropylene;
• a glass present in a proportion of approximately 5 to 50% by weight relative to the weight of polymer, thus representing approximately 5 to 33% by weight of the total of the deposit.
• PVDF-glass blend is coupled with coating processes that provide the formed layer with excellent adhesion to the metal support, and make it compatible with the severe operating conditions encountered at the nose of the jet engine injectors. especially diesel engines.
• the objective to be satisfied is the creation of a polymer-based coating, strongly adherent on the metal support, smooth and non-porous, in order to guarantee its durability at 400 ° C at least, high temperature commonly reached at the nose. injectors. It must be able to reduce the fouling of the injectors by reduction or suppression on its surface of the reactions which lead to the formation of products resulting from the thermal instability of the components of the fuel, whether it is of mineral origin, fossil or vegetable. In other words, the coating must be able to durably prevent the deposition and adhesion to a metal of products of thermal degradation of hot hydrocarbons and products from combustion.
• this is obtained by a single or multilayer coating of the type just mentioned, deposited on the metal surface to be protected, such as the outer surface of the nose and the nozzle holes of the injectors.
• the needle of the injector can also be treated in the same way.
• This coating catalyzes the formation of coke by preventing or inhibiting the formation of gums.
• This coating is also a physical diffusion barrier for hot hydrocarbon, which prevents metal interactions with fuel degradation products from the combustion process in engine cylinders, as well as with oxygen and sulfur. accompanying the hydrocarbon.
• this coating is obtained from a powder comprising:
• a homopolymer or copolymer of PVDF which has a flow index of 10 to 300 grams per 10 minutes, determined according to ASTM D1238, condition J; and a glass whose grain size is from 1 to 300 ⁇ m, preferably from 5 to 150 ⁇ m;
• the ratio between the mass percentages of the glass and the polymer being from 0.05 to 0.50.
• the glass plays in the coating a role of filling and adhesion material. Its addition to the PVDF-based polymer in the proportions and conditions according to the invention makes it possible to solve the problems of adhesion and coating strength which arose in the prior art with the use of the polymer alone.
• the coating is applied to the metal surface by a fluidized bed process, or by an electrostatic process, or by compressed air, or by flame evaporation, or by electrostatic fluid bed.
• a coating adhering firmly to the metal is obtained by forming a smooth surface.
• the layer formed is non-porous, as can be seen using conventional apparatus for porosity research.
• the hardness of the coating surface is improved over that of a polymer coating alone.
• the glass is used in the form of spherical or ovoid particles, with a diameter of 1 to 300 ⁇ m, preferably of 5 to 150 ⁇ m.
• This geometric shape has the additional advantage of being well suited to conventional coating processes, for example the fluidized bed process.
• the formation of the coating of the injectors using such more or less spherical particles makes it possible to limit the reduction in the thickness of the coating due to the thermal stresses of cooling the combustion chamber.
• glass particles can be very varied.
• glass is meant here, in addition to ordinary glass (based on double silicates of sodium and / or potassium and calcium), any amorphous mixture, solidified after a molten state, of inorganic compounds, such as simple silicates and compounds, borates, phosphates and oxides of sodium, potassium, magnesium, aluminum, barium, zinc, lead, and mixtures thereof.
• the surfaces of the glass particles can be pretreated with adhesion agents in order to obtain better bonds between the glass and the polymer and between the glass and the metal substrate.
• the preferred adhesion agents are organofunctional silanes, such as, for example, vinyltrialkoxysilanes, aminoalkylthalcoxysilanes, or their n-substitution products, or silanes which contain epoxy groups, such as, for example, glycidyloxypropyltrialkoxysilanes. .
• the glass particles are added to the powdered PVDF-based polymer, the weight ratio of glass and polymer being between 0.05 and 0.50, preferably between 0.10 and 0.40 to obtain a coating more homogeneous.
• the spherical or ovoid shape of the glass particles makes it possible to achieve a higher degree of filling than with particles that would have a more irregular shape, because of the lower viscosity that they provide to the mixture.
• PVDF is prepared according to the usual methods of polymerization, but the suspension polymerization process is preferred for reasons of ease of application.
• the other component (s) are present in a proportion of 1 to 20% by weight of the copolymer, preferably 2.5 to 10% by weight. A better homogeneity of the solution and a better distribution of the functional principles are obtained.
• This or these other components can be obtained from vinyl fluoride, or hexafluoropropylene, or mixtures thereof, for example.
• the coating of the metal substrate formed according to the invention can itself be subsequently covered by a catalytic coating material promoting the formation of coke by thermal degradation in a hydrocarbon fluid, while simultaneously inhibiting the formation of range.
• a catalytic coating material promoting the formation of coke by thermal degradation in a hydrocarbon fluid, while simultaneously inhibiting the formation of range.
• This catalytic coating is formed, for example, by chemical vapor deposition of an organometallic compound on the polymer.
• the catalytic layer which results can be, for example, an oxide of at least one metal, such as Mo, W, NiMo, NiW, Pt, Pd ...
• the invention makes it possible to reduce the diameter of the orifices of their nozzles up to, for example, 50 ⁇ m, so as to reduce the amount of NOx formed.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Wood Science & Technology (AREA)
• Paints Or Removers (AREA)
• Application Of Or Painting With Fluid Materials (AREA)

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• 2006
  • 2006-01-18 FR FR0600465A patent/FR2896253B1/fr not_active Expired - Fee Related
• 2007
  • 2007-01-12 EP EP07718161A patent/EP1976944A1/de not_active Withdrawn
  • 2007-01-12 WO PCT/FR2007/050645 patent/WO2007083057A1/fr active Application Filing

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