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
  • 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
  • B05D1/06—Applying particulate 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
  • B05D1/12—Applying particulate 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
  • B05D1/28—Processes for applying liquids or other fluent materials performed by transfer from the surfaces of elements carrying the liquid or other fluent material, e.g. brushes, pads, rollers

Definitions

• This invention relates to a powder composition for use in the detection of defects on surfaces and to its method of use in surface finishing processes.
• the invention also relates to an applicator means for dispensing and applying such a powder composition.
• the guide coats generally comprises a dilute paint mixture which is sprayed over the surface to be treated to provide a light paint coating. As the surface is abraded the guide coat is removed from the higher portions of the surface leaving the visible guide coat on the lower areas. Thus, the surface irregularities are clearly visible to the operator, enabling him to abrade and fill the appropriate areas.
• the present invention provides an alternative system for use as a guide coat. Disclosure of the Invention
• an adhesive-free, dry, free-flowing powder composition suitable for use in surface defect detection.
• the inventive powder composition comprises a physical mixture of particles of a colorant and particles of an extender, which mixture includes particles of colorant and particles of extender each having a particle size of less than lOO ⁇ m.
• the powder compositions of the invention provide a simple, effective guide coat which readily highlights surface imperfections, such as scratches, orange peel effect and dry over-spray.
• the compositions do not require the presence of solvents and therefore there is no drying time and the surface may be abraded immediately after application of the guide coat.
• many powder compositions of the invention can substantially reduce the abrading time compared to the use of a guide coat formed by a dilute paint mixture.
• Figure 1 represents a perspective view of an applicator for a powder composition in accordance with the invention.
• Figure 2 represents a cross-section through a reservoir of powder composition.
• the powder compositions of the invention are free from adhesive, thereby readily allowing the composition to be distributed readily over a large surface area.
• at least 50%, preferably at least 90% by weight of the particles of the powder composition have a nonzero particle size of less than lOO ⁇ m, in order to reveal defects in a surface having dimensions up to lOO ⁇ m.
• the average particle size of all the particles used is less than 40 ⁇ m, more preferably substantially all the particles have a particle size less than 40 ⁇ m. It is preferred that the compositions contain some particles less than lO ⁇ m in particle size order to reveal fine scratches. More preferably the average particle size of the powder composition, overall, is about lO ⁇ .
• particle size it is meant the greatest cross-sectional diameter of the particle.
• the colorant is selected to contrast with the surface to which the composition will be applied.
• any dry, free-flowing colored particles may be used in the compositions of the invention.
• many organic pigments or dyes are not economical and/or do not spread evenly over the surface.
• Inorganic colorants are preferred, e.g., carbon black, iron oxide, etc.
• the most preferred colorant is carbon black, particularly activated carbon black. Mixtures of colorant may be employed.
• the extender is generally a light-colored particulate material which dilutes the colorant.
• Suitable extenders include calcium carbonate, titanium dioxide, talc, magnesium stearate, zinc stearate, calcium stearate and aluminium stearate.
• the preferred extender in terms of economy and performance is calcium carbonate.
• Mixtures of extenders may be employed.
• the morphology of the particles is not believed to be important providing the particles are free-flowing and will spread evenly.
• the colorant is generally present in an amount of less than 50% by weight of the composition and is preferably in the range 25 to 40% by weight.
• a preferred guide coat composition of this invention comprises about 30-40% by weight carbon black(s) (total, if a combination is used) and about 60-70% by weight calcium carbonate.
• One preferred guide coat composition of the present invention is formulated to involve a physical mixture, by weight, of about 66% calcium carbonate (e.g., SnowcalTM 30); about 6% of a first type of carbon black (e.g., RavenTM 2000D) ; and about 28% a second type of carbon black except that it is an activated carbon black (e.g., Chemviron Type C) .
• SnowcalTM 30 calcium carbonate powder can be commercially obtained from Croxton & Garry Ltd., Dorking, Surrey England, and is composed of 96% calcium carbonate, 2.0% silica, 0.1% ferric oxide, 0.2% alumina, and small residue of copper and lead.
• SnowcalTM 30 has a weight medium diameter of 4.6 ⁇ m; a specific gravity of 2.7; oil absorption (rub out method) of 15g/100g; and the percentage (%) retained on 125 ⁇ m sieve is 0.2, % retained on 63 urn sieve is 5.0, and & retained on 45 ⁇ m sieve is 12, with the % by weight of particles finer than 2 ⁇ m being 30.
• RavenTM 2000D carbon black powder commercially available from Columbia Chemicals Co., Atlanta GA. , USA, has a particle size of 18 nm (i.e., the arithmetic mean particle size as measured by electron microscopy) ; a surface area of about 200 m 2 /g; a DBP oil absorption of 70 cc/lOOg; and a powder density of 16 lb./ft 3 (i.e. 2.57 x 10 "2 g/cm 3 ) .
• Chemviron Type C activated carbon black is commercially available from Chemviron Carbon Limited, Southlink Great Britain, and is a powder activated carbon having iodine number of 900 minutes; a moisture content of 2% maximum; an ash content of 14% maximum; a bulk density of 0.3 to
• Desirable guide coat compositions would include those achieving as many as possible of the following desired characteristics: safe to use; ready to use (no mixing/preparation) ; clean to use (not messy) ; quick to use (covers the area quickly) ; easy to see on surfaces (must be able to see before and during sanding) ; can be used on all sandable surfaces; easy to remove excess; over-paintable; does not damage; heat resistant; must not load/clog abrasive; low cost; must not deleteriously influence sanding time; must spread evenly; needs to look good once applied; easy to remove during sanding; and swarf must not stain the newly sanded surface.
• mixtures of carbon black and chalk of this invention are highly suitable as they fulfill most of these desired properties and are economical as compared with other materials.
• the powder composition may be distributed over the surface by any suitable means, e.g., by sprinkling powder onto the surface and spreading with a cloth, pad or sponge. Only small amounts of powder composition are required and it is possible to apply a guide coat to the complete body work of a medium-sized automobile using about 9 grams of powder composition.
• the powder composition is generally employed in amounts of from 0.5 to 10g/m 2 based on the amount of colorant and extender having a particle size of less than lOO ⁇ m.
• the powder composition will generally be applied to surfaces to which filler has been applied and/or coated with primer, paint lacquer, and so forth, since these are the stages in the refinish industry where guide coats are generally employed.
• the guide coat compositions may be applied directly to non- treated surfaces if required, e.g., wood, metal, such as steel, plastic, fibre glass, and the like.
• the powder composition may be stored and dispensed onto the surface from a bag, sachet or container similar to a salt or pepper shaker.
• the powder composition may be impregnated within the fibres of a fleece, mop, woven or non-woven fabric, or foam which may be wiped over the surface to deposit the powder.
• the powder composition may be contained within the reservoir of an applicator and dispensed when the applicator is wiped over the surface.
• the powder is stored in a reservoir adapted to accommodate the applicator in order to load the applicator with powder prior to use. It is also possible to apply the powder material in a gas stream.
• the applicator means (1) comprises a handle (2) secured to a back-up pad (4) which supports an applicator pad (6) .
• the handle (2) and back-up pad (4) also can be an integral molded body, such as a single integral element of molded rigid foam.
• the applicator pad (6) may comprise a mop, fleece or foam.
• a preferred applicator pad is formed of CaligenTM 4200 polyester polyurethane foam.
• the applicator pads are removable from the back-up pad in order that they may be replaced.
• Any suitable fixing system may be employed such as those commonly used for attaching abrasive paper to the back- up pads of sanding devices.
• the foam may be coated with a pressure-sensitive adhesive and adhered to the back-up pad.
• the pad may be laminated to brushed nylon on one surface which cooperates with a hook system provided on the surface of the back-up pad.
• the applicator can comprise a a layer of molded foam onto which the brushed nylon is laminated to the backside thereof. This brushed nylon, as described above, provides an attachment surface for the hooks of the back-up pad.
• the powder is applied to the applicator pad (6), then applied to a surface, or, the powder is applied directly to the surface to be coated from a separate container.
• the handle (2) may be hollowed to provide a space for storing a supply of dry guide coat powder.
• a powder storage handle can be associated with a delivery system which will feed powder through the back-up pad (4) and applicator pad to allow application of the powder to a surface.
• the delivery system may comprise one or more holes through the back-up pad, which may be selectively opened and closed.
• a feed mechanism such as an Archimedes' screw or a power- assisted mechanism using a spring or compressed gas or propellant may facilitate delivery of the powder from the reservoir to the applicator pad.
• the applicator pad may be impregnated or loaded with the powder composition and thereafter attached to the back- up pad prior to use.
• the applicator pad may be loaded with powder prior to use by use of a refill container device as shown in Figure 2.
• the refill container (8) comprises two basic components: an applicator pad support and powder delivery element (10) and a removable hollow cap (15) for storage of powder (12) .
• the element (10) can be an integral member of molded rigid plastic comprising an open end (14); a horizontal, circular apertured surface (20) (such as having radial slot openings or channels (11) therethrough) having a horizontal annular flange (16) at its periphery; an upstanding circumferential rim (18) on its front side; and an upstanding circumferential flange (17) on its back side to permit removable attachment of removable cap element (15) which serves as a storage reservoir for refill powder (12) .
• the outside surfaces of such flange (17) are ribbed to allow for interlocking with protrusion (13) provided on the inside wall of cap member (15), to allow these two members to be removably held together and detachable.
• the rim (18) is dimensioned to accommodate the applicator pad (6) of the applicator therewithin such that the pad may be supported on the horizontal flange (16) .
• the rim (18) has a plurality of circumferentially-spaced lugs or inward projections (tabs) (19) provided on the upper end of the rim (18) to assist in retaining an applicator pad during powder refill or handling. These lugs can be spaced equidistantly around the circumference of the rim end surfaces.
• the horizontal apertured surface (20) extends across the opening to provide additional support for the applicator pad (6).
• the element (20) alternatively, can be provided as a separate component attached to the upper surfaces of flange 16, such as where the element (20) is mesh or gauze.
• the refill device (8) provides a useful support and replacement powder storage device for the applicator which prevents contamination of the applicator pad (6) .
• the applicator pad (6) is readily loaded with powder by simply inverting or shaking the refill device (10) and applicator assembly, as fitted together.
• the presence of a uniform array of apertures, such as a plurality of radial slots (11) (e.g., radially eminating from a center of surface (20) ) or in mesh or gauze, in element (20) assists in uniform loading of the powder over the surface of the applicator pad (6) .
• a removable, non-apertured separator sheet (not shown) can be interposed between surface (20) , and a replacement applicator pad itself (not shown) and similar to pad (6) that is prepackaged within and provided as part of the refill device (8) when sold in commerce, so as to prevent powder flow from the cap reservoir into the replacement pad before usage of the refill device.
• the powder composition is readily spread over a surface by application of light pressure to wipe the applicator pad over a surface.
• the invention will now be illustrated by the following Examples in which all percentages are by weight unless otherwise indicated. Test Method Each powder composition was tested on a primed RoverTM 200 bonnet (hood of an automobile) within 24 hours of painting. All work was carried out on a bench with the bonnets in a horizontal plane.
• the surfaces were sanded with 3M 255P P180 HOOKITTM 150mm diameter, 6 hole discs, one per bonnet, using a D/A 5mm orbital sander with dust extraction.
• the swarf was removed with a solvent wipe.
• the primer used was beige in color and comprised:
• Powder 1 gram was sprinkled onto the surface and wiped over by hand with a foam pad. Aerosol: A light coating of paint was applied to the primed surface.
• the guide coated surfaces were sanded with 3M 255P
• Carbon black designated product “R2500” commercially available from Columbian Chemicals.
• Carbon black designated product “R410” commercially available from Columbian Chemicals.
• the following 31 different guide coat compositions summarized in Table 1 were prepared by mixing the indicated proportions (in wt.%) of each of carbon black and calcium carbonate.
• the guide coat compositions summarized in Table 1 were prepared, where, for each composition, the amount by weight % of carbon black contained is indicated in the left-hand column and the amount by weight % of calcium carbonate contained therewith is indicated in the adjacent right-hand column.
• the guide coat compositions described above in Table 1 were evaluated by the test method described above. All of the above compositions proved to be acceptable as guide coats having a sanding time per unit area in the range 3.5 to 5 minutes, which is less than the average time required using conventional aerosol paint as a guide coat.
• compositions having higher carbon black content were darker but provided no obvious advantage in terms of sanding time.
• Activated carbon black was more effective than non-activated carbon black.
• Composition comprising 25 to 40% by weight carbon black are preferred in terms of acceptable performance and economy.
• the sanding performance of five dry powder guide coat systems was compared with a black aerosol guide coat using the above test method.
• the powders for each test powder sample of this example comprised 30% by weight carbon black and 70% by weight calcium carbonate. The results are indicated in Table 2.
• the black powder paints used generally comprise a mix of pigment (carbon black) , adhesive (starch) and filler (calcium carbonate) ; their proportions vary depending upon their end use and the manufacturer.
• Black powder paints from the Early Learning Centre (ELC) , Calder Colours and Partners were used. The test method described above was again used. The results are summarized in Table 3.
• talc Whilst talc, Ti0 2 and stearates may be used as extenders they do not appear to offer advantages over calcium carbonate.
• Sico Red L3750 an organic colorant commercially available from BASF.
• Milori Blue L6697 an inorganic colorant commercially available from BASF.
• Heliogen Blue L6920 a phthalocyanine commercially available from BASF.

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• Paints Or Removers (AREA)
• Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)

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• 1994
  • 1994-05-06 GB GB9409015A patent/GB9409015D0/en active Pending
• 1995
  • 1995-04-21 EP EP95917633A patent/EP0758272B1/de not_active Expired - Lifetime
  • 1995-04-21 DE DE69508072T patent/DE69508072T2/de not_active Expired - Fee Related
  • 1995-04-21 ES ES95917633T patent/ES2128056T3/es not_active Expired - Lifetime
  • 1995-04-21 JP JP7528987A patent/JPH09512914A/ja not_active Ceased
  • 1995-04-21 WO PCT/US1995/004978 patent/WO1995030493A1/en active IP Right Grant
  • 1995-04-21 CA CA002188024A patent/CA2188024A1/en not_active Abandoned
• 1996
  • 1996-11-05 KR KR1019960706237A patent/KR970702761A/ko not_active Application Discontinuation

Non-Patent Citations (1)

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