Patent Application
20080020678
1. Field of the Invention
This invention relates to abrasive materials and surfaces. More particularly this invention relates to discontinuous abrasive surfaces employing discrete areas containing abrasive particles that are continuously released in free form during wet low speed sanding, grinding, and polishing operations. The discontinuous abrasive surfaces of the present invention may consist of abrasive containing protrusions attached to rigid or flexible surfaces, a raised portion and a cavity portion, or alternatively may be comprised of closed cell foam compositions impregnated with abrasive materials such as aluminum oxide. The voids present in the discontinuous abrasive surfaces of the present invention serve to hold water and remove debris.
2. Description of the Related Art
There are numerous methods that may be employed to sand surfaces. One of the more common methods employs sand paper. Sand paper is a thin sheet material usually made of paper that has an abrasive material securely bonded onto one side. Despite its name, the abrasive is rarely if ever sand. Commonly used abrasives such as aluminum oxide and silicon carbide are significantly harder than sand and are therefore more effective. This may be especially true when sanding hard materials such as glass or steel.
Sand paper may be used by hand. This process is often referred to as hand sanding. The process of hand sanding involves using manual labor to repeatedly slide the sand paper back and forth and/or in a circular motion over the surface until smooth. Numerous textures of abrasives are available. Often sanding starts out with a relatively course grade of sand paper of about 80 grit followed by finer grades of several hundred grit to finish the job.
One drawback often associated with sand paper is the production of dust. Sanding surfaces often produces dust that clogs the sand paper and may create an inhalation hazard as well. This is especially true for sanding hazardous materials such as lead paint. One way to alleviate this problem is by using wet or dry Emery cloth. Wet or dry Emery cloth is an abrasive coated cloth having a wide variety of grades. It is designed for use with water thereby reducing clogging effects and significantly or even completely eliminating the production of air bourn dust.
Another drawback with using sand paper is the tendency for the abrasive to become dull and fall off from the sand paper backing surface.
Sanding by hand using sand paper is not always practical owing to the amount of labor required. This is especially true for large jobs that may take a long time resulting in fatigue.
In order to alleviate the worker fatigue issue in hand sanding operations, numerous power sanding techniques and/or equipment have been developed. Drum sanding, belt sanding, disc sanding, and orbital sanding are commonplace. These standard power sanding tools often employ some form of sand paper and therefore often suffer from many of the previously mentioned drawbacks. In particular is the need to change the sanding surface at regular intervals.
Numerous modifications to ordinary sand paper have been made in order to improve the overall process. For example, sand paper having a lowered surface density of abrasive particles is available. This particular sand paper is made by 3M Corporation of ST. Paul Minn. and is designed for use in sanding relatively soft materials that quickly gum up ordinary sand paper. Significant improvements in sand paper life may be realized by reducing the tendency of particulate matter to clog the needed spaces between adjacent abrasive particles.
Another improvement that may be made to ordinary sand paper involves the use of flexible and conformable foam backing. Such backing materials allow the sand paper to conform to surface contours thereby more rapidly smoothing contoured surfaces. Individual pieces of sand paper may be applied to foam pads or conversely, foam pads having previously attached sand paper may be employed. For example, Finishing Buddies (Mona Lisa Products 10770 Moss Ridge Road Houston, Tex., 77043) is a complete sanding tool kit consisting of a steel wool pad, oval sanding disc, and coarse, medium, and fine sanding pads. The oval pad is relatively rigid, and the three other sanding pads have a softer foam backing that has a greater degree of flexibility. This sanding kit is designed for slow hand sanding and finishing operations.
There are numerous flexible sanding surfaces, components, and articles comprised of abrasive materials fixedly attached to flexible foam backings. Of particular interest is a sanding system employing a relatively thin rigid foam backing disclosed in U.S. Pat. No. 6,923,840 and assigned to 3M Innovative Properties Company, St. Paul Minn. (US). U.S. Pat. No. 6,923,840 discloses a flexible abrasive product comprised of an open cell foam backing, a foraminous barrier coating, and a shaped foraminous abrasive coating. The top abrasive coating is discontinuous and allows for holding lubricants such as water as well as spaces for removal of debris.
U.S. Pat. No. 6,949,128 also assigned to 3M, discloses a method for making a foam backed abrasive article having embossed raised areas.
U.S. Pat. No. 3,401,490 discloses a method for forming an abrasive article having a resiliently yielding open cell meltable base which is passed under a heated roll to melt the surface to a desired depth followed by application of abrasive particles to the melted surface. The result is a flexible foam based abrasive article capable of following irregular, uneven, or sunken surfaces.
U.S. Pat. No. 6,997,794 by James Matthew Pontieri discloses a disposable sanding device fabricated as a continuous rope like article adapted for selective segmentation. This device may employ a foam central portion along with an abrasive outer portion. In particular the flexible cylindrical geometry illustrated in several embodiments of the invention lends itself to the hand sanding of difficult to reach contours and may prove especially useful in woodworking applications.
There are numerous flexible foam based cleansing and scouring pads having added abrasive materials. An example of this can be found in U.S. Pat. No. 3,377,151. U.S. Pat. No. 3,377,151 discloses a method for making flexible resilient cleansing and scouring pads having an abrasive surface. A thermoplastic foam web material is hot laminated to abrasive web material. In addition, one or more cleansing materials may be added.
U.S. Pat. No. 3,619,843 discloses sponges having dry impregnated materials. In this invention, impregnated sponges are prepared by a process that deposits particulate material on one surface of the sponge and subsequently pierces the sponge with spikes to form crevices followed by drawing particulate material into the crevices. The result is a modified sponge suitable for surgical and sanitizing applications.
Also of interest are flexible open cell foam scouring and cleaning pads having numerous protrusions. These pads are disclosed in U.S. Pat. No. 4,055,029 by Heinz Kalbow, Lichgasse. The flexible pad has numerous protrusions on the working surface having an abrasive layer. U.S. Pat. No. 4,111,666 also by Heinz Kalbow discloses a method of manufacturing flexible abrasive cleaning pads along with improvements in tear resistance.
U.S. Pat. No. 4,421,526 discloses polyurethane foam cleaning pads composed of a densified flexible sponge like polyurethane foam material impregnated with various cleansing additives. Excessive mixing of the freshly blended polymers inhibits foam formation long enough to add the cleansing ingredients. The resulting pads have added strength due to collapsed, ruptured, and distorted cells along with fibers that result from the specific mixing process employed. The result is an unusually strong dense flexible cleaning pad capable of absorbing substantial amounts of water that releases additives along with absorbed water on gentle squeezing.
U.S. Pat. No. 4,594,362 discloses a dry type textile cleaning article comprised of a friable hydrophilic polyurethane foam with incorporated abrasive particles as well as other additives. The abrasive particles are chemically bonded to the foam using silane coupling agents thereby reducing their tendency to separate from the mass and subsequently damage cloth material.
While the above described examples of foam based abrasive articles provide a wide variety of uses, there exists a need in the art for lightweight semi-rigid or rigid closed cell foam abrasive articles suitable for hand and/or low speed wet sanding, and/or wet grinding, and/or wet polishing operations.
Many of the above described examples outline the use of foam with abrasive materials in order to achieve certain advantageous and desirable properties. Still others outline some of the more simple methods and materials commonly employed in sanding, grinding, and polishing operations. While generally effective for sanding, grinding, and polishing, there exists a need in the industry for further improvements in low speed wet sanding, grinding, and polishing operations. For example, lapping is a process that uses special equipment to grind surfaces to a high degree of flatness. Unfortunately, this equipment tends to be expensive and bulky. In addition, producing a good flat grind may require certain acquired skills to master. This results in difficulties for small shops and individuals in the hobby field in grinding surfaces flat.
Another example where further improvements in low speed wet sanding, grinding, and polishing operations may be realized is in the area of sanding cloths. Flexible abrasive cloth materials such as emery rapidly become dull and shed abrasive particles. Because of this, sanding operations often require several pieces of emery cloth to complete. While making discrete zones of attached adhesive may serve to reduce the tendency of debris to build up in the sanding surface, the issue of rapid dulling and shedding of surface abrasive particles still remains a major issue to be resolved.
Finally, flexible abrasive surfaces employing foam have certain added benefits that may be realized in numerous applications. Many of the earlier patents referenced in this application fall under this class of abrasive surfaces.
Despite numerous advancements in the field of abrasives there is a need for discontinuous abrasive particle releasing surfaces for wet sanding, grinding, and polishing operations.
It is an object of this invention to provide wet low speed sanding, grinding and polishing surfaces.
It is a further object of this invention to provide numerous grades of wet sanding, grinding, and polishing surfaces.
It is a further object of this invention to provide wet sanding, grinding, and polishing surfaces resistant to excess build up of debris
It is a further object of this invention to provide wet sanding, grinding, and polishing surfaces in both rigid and flexible forms.
It is a further object of this invention to provide wet sanding, grinding, and polishing surfaces that are low in cost.
It is a further object of this invention to provide simple methods for producing wet sanding, grinding, and polishing surfaces.
Finally it is an object of this invention to provide wet sanding, grinding, and polishing surfaces that may be used for extended periods of time without wearing out.
The present invention is for discontinuous abrasive surfaces employing discrete areas containing abrasive particles that are continuously released in free form during wet low speed sanding, grinding, and polishing operations. The discontinuous abrasive surfaces of the present invention may consist of abrasive containing protrusions attached to rigid or flexible surfaces, a raised portion and a cavity portion, or alternatively may be comprised of closed cell foam compositions impregnated with abrasive materials such as aluminum oxide. The closed cell foam compositions of the present invention may soften with water to provide a cushioning layer for abrasive particles at the working surface. The voids present in the discontinuous abrasive surfaces serve to hold water and remove debris.
A more complete appreciation of the invention and many of the advantages thereof will be readily obtained as the same becomes better understood by reference to the detailed description when considered in connection with the accompanying drawings, wherein:
Polymeric resin based materials such as epoxy may be cast in a suitable mold. For example, a laminate construction may be assembled having numerous protruding spherically shaped particles. The laminate may then be treated with a suitable release coating and used to make a silicone rubber mold. Once the mold is cured, the laminate may then be removed. The now vacant mold may then be used to cast a lapping surface. Abrasive powder may be first sprinkled evenly in the numerous voids in the mold that are to become protrusions. Abrasive loaded polymeric resin such as epoxy may then be added on top of the already existing free abrasive particles residing within the individual discrete protrusion cavities within the mold. If desired, further addition of abrasive particles to the epoxy resin in the mold may then be carried out followed by allowing the above described composition to set into a hard mass.
West system 105 epoxy resin (West Systems Inc. PO Box 665 Bay City, Mich. 48707 USA) has been used for producing working prototypes employing aluminum oxide abrasive. It should be noted that aluminum oxide is a dense material and therefore tends toward settling to the bottom of the mold. Other dense abrasive materials include silicon carbide, zirconia, diamond, ceria, cubic boron nitride, garnet, ground glass, quartz, and combinations thereof. Since the bottom of the mold represents the tops of the protrusions in the final part, this method of manufacture may be employed to keep numerous abrasive particles on the outer exposed surfaces of the protrusions themselves. This particular configuration may help to facilitate the initial release of abrasive particles. This technique may be employed to improve the initial release of abrasive particles on first time use. Once the process of abrasive particle release starts, it becomes self sustaining.
Alternatively, it may be desirable to have the abrasive particles dispersed uniformly throughout the material matrix. A high loading density of abrasive particles within the uncured resin may help to keep abrasive particles more uniform throughout the mix by forming a paste. Rapid cure times and high resin viscosity may also contribute to the abrasive particles being dispersed in a substantially uniform manner throughout the material matrix.
When abrasive particles are uniformly distributed within the material matrix, the new surface may not have suitable initial abrasive properties owing to a glaze over the abrasive particles. In order to provide initial aggressive abrasive properties this glaze may be removed by sanding, sand blasting, cutting, or grinding.
During use, abrasive particles embedded within the material matrix become dislodged and contribute to the overall process of wearing down lapping surface 2. These abrasive particles may fall away from the working surface relatively quickly or remain on the working surface continuously grinding away at lapping surface 2. The grinding away of lapping surface 2 may help to facilitate the exposure and subsequent release of more abrasive particles from the material matrix. Additionally, the released abrasive particles may grind away at the substrate surface (not shown) that is lapped. This may result in the formation of a paste at the working surface during wet lapping. This paste may contain abrasive particles in free form and finely divided particles from both lapping surface 2 and the substrate surface (not shown). Paste formation may help to keep the abrasive particles active on the working surface and depends on numerous factors. These factors include surface topography, rate of lapping, and the amount of water used in the process. Depending on the process used, it may be desirable to enhance or retard the formation of abrasive paste at the working surface.
Lapping block 14 is suitable for lapping small articles flat. The article may be glued to a holder and lapped in a circular motion by hand, or alternatively lapped at a relatively slow rate by machine. Some articles may also be held directly by hand and subsequently lapped flat. In many instances water in pure form or with special additives may be employed in the process. Generally speaking the lapping surfaces of this invention will retain water in the voids between surface protrusions. Employing water as a lubricant may also help to flush debris from the area being used. When finished, the lapping surface may be cleaned of residual debris with running water. When the lapping surface portion 20 of lapping block 14 becomes worn out, it can be replaced at a reasonable cost. Removable attachment means such as pressure sensitive adhesives may be employed to achieve this end.
Abrasive particle releasing disc 33 is suitable for wet rotary sanding operations. A shaft may be attached using central hole 39 and a threaded screw. The shaft may be subsequently fitted into the chuck of a low speed rotary tool such as a drill. A relatively low speed of about 50 to 500 RPM may be employed to wet sand numerous surfaces. It should be noted that high RPM conditions of 1000 or more may result in excess loss of water employed in wet sanding operations.
The abrasive foam compositions of the present invention are intended for low speed wet mechanical as well as wet hand sanding, grinding, and polishing operations. In general, no reinforcement is needed and the compositions may be adjusted to attain desirable levels of rigidity, strength, and rate of wear. Various compositions may be used with different foam densities. The foam materials used in the present invention may be formed from numerous polymeric materials, however special attention will now be paid to polyurethane pour foam compositions.
Polyurethane pour foam comprises a class of two component reactive foaming agents that when combined react with each other to polymerize and produce gaseous products during the polymerization process. The result is polyurethane foam. The polyurethane pour foam compositions employed in the present invention are rigid closed cell foams. The above described rigid polyurethane pour foam compositions may be comprised of a first component isocyanate containing prepolymer resin and a second component reactive prepolymer resin containing numerous hydroxyl groups. The isocyanate containing prepolymer resin may contain the higher oligomers of methyl diisocyanate along with other reactive diisocyanates such as 4,4-diphenylmethane diisocyanate. The second component hydroxyl group prepolymer resin may contain reactive oligomers having poly hydroxy functionality such as hydroxy terminated polyglycol ethers. Rigid closed cell polyurethane pour foam materials are commercially available in various foam densities. Foam density may be considered to be the overall density of the fully cured foam. Foam density is often given in units of pounds per cubic foot. A low density 2 pound foam refers to a foam having a cured density of 2 pounds per cubic foot. Such foam materials are often employed where lightweight properties are desirable. It should be noted that ordinary water has a density of about 62 pounds per cubic foot and therefore a 2 pound foam would be 1/30 the density of water.
Generally speaking, the lower the density of the foam, the more rapid will be the wear rate of the abrasive foam composition. Furthermore, the addition of excess abrasive materials to the polymeric foam compositions of the present invention may result in rapid wear degradation of the foam and associated rapid release of abrasive particles. These abrasive particles may then find their way into crevices thereby enhancing sanding, grinding and polishing operations. In order to achieve this end, the abrasive materials may each have a percent composition in the mix that has the above described unique desirable properties. Discussed below are several examples of the abrasive loaded polyurethane closed cell foam compositions of the present invention.
It may be desirable to modify the hardness of the exposed abrasive surface during wet operations. When a surface is wet sanded with sand paper, the sand paper starts out having a high degree of abrasive properties. This may be due to the abrasive particles themselves having a high degree of exposure on the paper surface. During sanding, these abrasive particles become dull. Additionally, the spaces between abrasive particles tend to fill with debris. After a relatively short timeframe the sand paper may loose enough abrasive qualities to render it no longer useful. At this point the sand paper is discarded and replaced with a new piece to continue with the sanding operation. Because the sand paper becomes less abrasive during use a fresh piece of sand paper of the same grit will start sanding more aggressively than the last used piece.
The abrasive foam compositions of the present invention may differ substantially from sand paper. In particular, the grit used in the foam composition behaves finer than if it were used to make sand paper. For example, a foam sanding block of the present invention having embedded within the foam material matrix a 220 grit silicon carbide abrasive may behave in a similar manner to fresh sand paper of 400 grit or finer. Because of this, it is important to bear in mind that the abrasive particle size used may be sufficient to produce surface scratches. One way of alleviating this issue is to render the working surface of the abrasive foam somewhat soft and pliable on exposure to water. The depth of this zone of softness need not be very deep so long as it provides a cushion effect for the abrasive particles when they become exposed and subsequently released.
With rigid closed cell polyurethane foam systems, this may be accomplished by using a slight excess of one component. For example, if a slight excess of the hydroxyl functional polyol component is used, the molecular weight will be significantly reduced and the resulting polymeric foam rendered somewhat hydrophilic. The mixture need not be modified very much from the ideal mixture quoted by the manufacturer. An excess of 10% of either component will drastically affect molecular weight. This has to do with the inherent properties of condensation polymers. In order for a two component reactive condensation polymer to achieve a high molecular weight, exact proportions need to be combined and subsequently allowed to react to completion. If the mixture is off by even a small amount, the reaction stops as soon as the first reactant runs out. The result is limited molecular weight with the polymeric chains terminated by the excess reactant. If the excess reactant has hydrophilic properties (polyol reactant) then the resultant polymer may exhibit increased hydrophilic properties. Additionally, one or more reactive hydrophilic polyol additives may be employed that chemically bond to polymers to modify the mix.
Under certain circumstances, polyurethane foam compositions containing abrasive materials like silicon carbide may be produced having a controlled limited molecular weight combined with hydrophilic properties. Such compositions may be prepared by using a slight excess of the polyol reactant that may be on the order of a few percent to about 10 percent by weight of the mix.
Foam abrasive surfaces of articles made in this way may soften on exposure to water rendering them somewhat compressible. This compressibility may be used to provide a cushion effect to abrasive particles released from the working surface during use. This cushion effect may help to prevent deep surface scratches that may otherwise be produced by rubbing abrasive particles between two hard surfaces. It is important to bear in mind that the abrasive foam compositions of the present invention have abrasive properties resembling sand paper of a much finer grit than what was employed in the mix. This effect may be quite substantial. The actual grit size may be over twice as coarse as the rating of the sanding surface. For example, an abrasive foam sanding surface of the present invention having an abrasive particle size of 200 grit may have similar abrasive properties to fresh sand paper having an abrasive particle size of 400 grit or finer.
5.0 grams of foam A (2 pound per cubic foot density pour foam type rigid closed cell) polyurethane foam pre-polymer from Plastic Depot (2900 San Fernando Blvd Burbank, Calif. 91054) were placed into a small plastic cup. To this were added 5.0 grams of 70 grit aluminum oxide abrasive. The mixture was then stirred with a wooden popsicle stick until uniform. In a separate plastic cup were placed 5.0 grams of foam B polyurethane pre-polymer from the same source as the foam A. To this were added 5.0 grams of 70 grit aluminum oxide abrasive and the mixture stirred until uniform. Then two mixtures were then combined and stirred until uniform. The resultant mixture was then poured into a small polyethylene container and allowed to foam and subsequently cure. The cured foam composition was then allowed to sit overnight to stabilize. The foam abrasive composition was then removed from the polyethylene container. A small section of the outside portion was cut off with a sharp knife to expose the foam cells underneath the outside skin. A small amount of water was placed on this exposed surface. This wet exposed surface was then used to sand the paint off of a soda can. Removal of the thin paint layer occurred within a few seconds leaving a scratched surface behind. It should be noted that the aluminum surface underneath the paint did not bind up as often happens with sand paper but rather tended to disperse in the water and accumulate in the exposed voids of the foam.
The experiment of example 1 was repeated with increasing concentrations of 70 grit aluminum oxide abrasive. At a concentration of 70% by weight, the foam composition became exceedingly weak and readily broke off when wet sanding rough surfaces. The resulting particles formed a mixture of broken off foam and free aluminum oxide abrasive. This particular mixture was exceedingly efficient at sanding rough and irregular surfaces.
The experiment of example 2 was then repeated with 100 grit aluminum oxide abrasive. It was found that a concentration of aluminum oxide of 66% was required to attain similar results.
The experiment of example 3 was repeated with finely divided aluminum oxide polishing powder. It was found that a concentration of this finely divided aluminum oxide of about 50% by weight was required to disrupt the polyurethane foam to a level sufficient to cause its break up during use. The resulting use of this composition produced good polishing properties to rough wet surfaces.
5.0 grams of foam A polyurethane foam pre-polymer from Plastic Depot (2900 San Fernando Blvd Burbank, Calif. 91054) were placed into a small plastic cup. To this were added 8.0 grams of finely divided ferric oxide abrasive. The mixture was then stirred with a wooden popsicle stick until uniform. In a separate plastic cup were placed 5.0 grams of foam B polyurethane pre-polymer from the same source as the foam A. To this were added 8.0 grams of finely divided ferric oxide abrasive and the mixture stirred until uniform. The two mixtures were then combined and stirred until uniform. The resultant mixture was then poured into a small polyethylene container and allowed to foam and subsequently cure. The cured foam composition was then allowed to sit overnight to stabilize. The foam abrasive composition was then removed from the polyethylene container. A small section of the outside portion was cut off with a sharp knife to expose the foam cells underneath the outside skin. A small amount of water was placed on this exposed surface. This wet exposed surface was then used to polish rough sanded automotive paint. Polishing was quick with noticeable results occurring within a few seconds leaving a polished surface behind. It should be noted that the resulting debris tended to disperse in the water and accumulate in the exposed voids of the foam.
Abrasive particle releasing disc 53 is suitable for wet rotary sanding operations. A shaft may be attached using central hole 59 and a threaded screw. The shaft may be subsequently fitted into the chuck of a low speed rotary tool such as a drill. A relatively low speed of about 50 to 500 RPM may be employed to wet sand numerous surfaces. It should be noted that high RPM conditions of 1000 or more may result in excess loss of water employed in wet sanding operations.
It should be noted that the protrusions themselves provide points of high pressure that facilitate wet sanding and grinding operations. It should also be noted that water absorbent flexible fabric 48 employed allows individual abrasive loaded polymeric resin protrusions to follow surface contours during wet sanding operations in addition to absorbing and releasing excess water during these same operations. This may be used to significantly control the moisture of surfaces during wet sanding operations. Individual protrusions 54 may have grooves like those shown in
The above described abrasive loaded polymeric resin protrusions of
Fifteen grams of West systems 105 epoxy resin were mixed with 3.0 grams of West systems 205 fast curing catalyst. The mixture was stirred thoroughly followed by the addition of 36 grams of 70 grit coarse aluminum oxide abrasive. The mixture was then stirred until completely uniform. Immediately after mixing the resultant abrasive paste was placed into the voids in the silicone mold. A flat edge was then dragged against the mold surface to level the resin mixture in the voids. The resin was allowed to cure for twenty four hours. Once cured, the abrasive protrusions were removed from the mold and inspected for quality. The best sixty samples were then ground flat on their largest side and attached to the front surface of a cotton glove using West systems 105 epoxy resin and 205 hardener. Unfortunately, the glove tended to absorb the low viscosity resin. The abrasive protrusions were then removed and wiped clean with a paper towel. The glove with the still wet adhesive was then stuffed with paper towels to prevent the resin from gluing the glove shut. The resin was allowed to harden somewhat. The paper towels in the glove were then removed and the resin on the glove allowed to thoroughly cure. Five minute epoxy was then applied to the widest side of each abrasive protrusion and the protrusions glued to the glove at the positions corresponding to the previously cured spots of resin on the glove. This approach worked exceptionally well with the resultant glove having sixty abrasive protrusions firmly attached to the required areas for hand sanding operations.
The above described glove was then tested against numerous surfaces including automotive paint on plastic, automotive paint on metal, aluminum, painted aluminum, and glass. This testing was carried out with and without water. The dry sanding produced numerous coarse scratches in the above mentioned surfaces while the wet sanding was more rapid and complete with more uniform finer sanding. It should be noted that this particular sanding glove rapidly wet sanded all of the above described surfaces by hand in a matter of seconds.
The above descriptions of
Lapping block 108 is suitable for lapping small articles flat. As with lapping block 14 of
Abrasive particle releasing lapping surface 112 of lapping block 108 is shown having a relatively large percentage of the particle releasing surface 112 flat with a relatively small percentage of lapping surface 112 comprised of cavities. Particle releasing lapping surface 112 of lapping block 108 has a discontinuous surface topography due to the presence of surface cavities 114.
Numerous materials including polyurethane and epoxy resins may be used for polymer matrix material 116. Of particular interest is the use of polyurethane condensation polymers having both rapid wear and hydrophilic properties. Polyurethane condensation polymers may be prepared having a slight excess of polyol reactant thereby providing reduced molecular weight as well as hydrophilic properties. Alternatively, one or more reactive hydrophilic polyol additives may be employed.
Several formulations were used for making high foam density abrasive articles employing 8 pound per cubic foot density rigid closed cell polyurethane two component pour foam. The 8 pound per cubic foot rigid closed cell polyurethane pour foam used was from Silpack INC 470 East Bonita AVE., Pomona, Calif. 91767. Their telephone number is (909) 625-0056. The product name is 8# rigid foam SP-328-8. This product comes in two components. Component A and component B. They are formulated to combine into equal volumes. Component A has a density of 8.5 pounds per gallon. Component B has a density of 7.5 pounds per gallon. Blending these foam components into equal parts by weight results in an excess of component B (the poly hydroxyl functional component). This results in a final foam having significantly reduced molecular weight along with enhanced hydrophilic properties. When prepared in this manner, blended with abrasive materials, cured into a hard mass, and cut open. The resulting exposed abrasive surface will soften on exposure to water and cushion abrasive particles released during use.
The following formulations were used to make large hand sanders.
100 grams of SP-328-8 A from Silpack were placed into a polypropylene plastic bowl. To this were added 183 grams of 220 grit silicon carbide abrasive from Lortone. A wooden tongue depressor was used to blend the abrasive and resin. 183 more grams of 220 grit silicon carbide were added to completely cover the surface of the mix. 100 grams of resin SP-328-8 B from Silpack were then carefully poured on top of the abrasive. This top layer of abrasive prevents the resins from mixing until vigorously stirred to break the layer. This provides some extra time to mix and pour before the foam starts to set. The contents of the plastic bowl were then rapidly blended together by mixing with the original tongue depressor. After about 45 seconds of mixing, the contents of the bowl were then poured into a silicone rubber mold to cast the part. After a few hours of room temperature cure, the part was removed from the mold. The working surface had a large excess of foam protruding outward. This foam was trimmed off with a saw to expose the active working abrasive surface. The experiment was repeated using 320 grit and 400 grit silicon carbide abrasive. The amount of abrasive for the finer grit values was reduced slightly. The following formulations were used. For the 320 grit sanding tool, 100 grams of resin A, 170 grams of 320 grit silicon carbide abrasive, another 170 grams of silicon carbide abrasive and 100 grams of resin B. For the 400 grit sanding tool, 100 grams of resin A, 160 grams of 400 grit silicon carbide abrasive, another 160 grams of 400 grit silicon carbide abrasive and 100 grams of resin B.
The three resulting tools were allowed to cure for an additional 48 hours. The exposed working surface of each tool was sprayed with water and allowed to stand for several minutes. The wet working surface softened to a limited depth. The wet surfaces of the tools were then used to sand down numerous painted metal surfaces. The 220 grit hand sanding tool behaved like new 400 grit wet sand paper. The 320 grit hand sanding tool behaved like new 600 grit wet sand paper. The 400 grit hand sanding tool behaved like new 800 grit wet sand paper.
The above described tools were used for a significant period of time (about half an hour). During this timeframe the sanding remained consistent. Although there were abrasive particles released from the working surface of the tool, they were cushioned by the thin soft outer tool layer. No deep scratches were observed in the painted metal surfaces that had been sanded in this manner.
During use, abrasive particles were released from the working surface of the tool. These abrasive particles sanded down the paint while at the same time renewing the abrasive surface by sanding down the foam of the tool. This clearly indicates that this particular rigid polymeric closed cell foam composition is wearable at the major surface by the plurality of the abrasive particles released. This debris formed an abrasive paste with the wet surface. Some of this abrasive paste found its way into the surface irregularities of the tools thereby keeping abrasive particles active on the working surface. It should be noted that the abrasive particles released in free form facilitated in wearing away the major working surface of these tools. Additionally it should be noted that the release of abrasive particles from the major working surfaces of these tools creates additional voids. These additional voids further facilitated to wear away major working surfaces of these tools. The abrasive particles released in free form helped to further abrade the major working surfaces of these tools. Once the sanding operation was complete, the tools were rinsed off with water and allowed to dry.
Numerous materials may be used for water soluble particles 148. Included in this list are sugar (both powdered and granular), dextrin, non-ionic, anionic, and cationic water soluble surfactants (surfactant materials may provide further benefit as well). It should be noted that compounds containing hydroxyl groups may interact with the isocyanate components of polyurethane resin systems.
The above described abrasive scouring pad 164 was produced in the following manner. 17 grams of 341-A polyurethane resin from Plastic Depot (2907 San Fernando Blvd. Burbank, Calif. 91504. Telephone number (818) 843-3030) were mixed with 17 grams of 341-B polyurethane resin until uniform. To this mixture were rapidly added 63 grams of 400 grit silicon carbide along with 3 grams of West System 407 low density fairing filler. West systems INC. P.O. box 665. Bay City Mich. 48707 USA. Telephone number (866) 937-8797. The mixture was rapidly mixed until uniform and spread out onto a piece of 8″×10″ denim cloth before the urethane resin mixture became too viscous to handle. The spread out area was then allowed to cure for one hour. Once cured, the rigid construction was rendered flexible by bending to form numerous cracks and grooves into the major abrasive surface portion of the abrasive article.
This scouring pad was then cut into 2″×2″ pieces. One of these pieces was used to scour dirty dishes. This pad slowly wore out over a period of 60 days. After this timeframe, the pad was discarded.
Although the present invention has been described in detail with respect to certain embodiments and examples, variations and modifications exist which are within the scope of the present invention as defined in the following claims.
This is a Continuation-in-Part of application Ser. No. 11/503,058 filed Aug. 3, 2006, which claimed priority to provisional application No. 60/764,110 filed on Feb. 1, 2006 and provisional application No. 60/818,571 filed on Jul. 5, 2006.
| Number | Date | Country | |
|---|---|---|---|
| 60764110 | Feb 2006 | US | |
| 60818571 | Jul 2006 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11503058 | Aug 2006 | US |
| Child | 11828270 | Jul 2007 | US |
