Abrasive tool making process – material – or composition – With synthetic resin
Reexamination Certificate
1999-12-20
2001-09-25
Marcheschi, Michael (Department: 1755)
Abrasive tool making process, material, or composition
With synthetic resin
C051S295000, C051S307000, C051S309000
Reexamination Certificate
active
06293980
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the production of coated abrasives engineered to have patterned surfaces with properties specific to the desired application.
The proposal to deposit isolated structures such as islands of a mixture of a binder and abrasive material on a backing material has been known for many years. If the islands have very similar heights above the backing and are adequately separated then, (perhaps after a minor dressing operation), use of the product will result in reduced surface scratching and improved surface smoothness. In addition the spaces between the islands provide a route by which swarf generated by the abrasion can be dispersed from the work area.
In a conventional coated abrasive, investigation of the grinding surface reveals that a comparatively small number of the surface abrasive grits in an active abrading zone are in contact with the workpiece at the same time. As the surface wears, this number increases but equally the utility of some of those abrasive grits may be reduced by dulling. The use of abrasive surfaces comprising a uniform array of isolated islands has the advantage that the uniform islands wear at essentially the same rate such that a uniform rate of abrasion can be maintained for longer periods. In a sense the abrading work is more evenly shared among a larger number of grinding points. Moreover since the islands comprise many smaller particles of abrasive, erosion of an island uncovers new, unused abrasive particles which are as yet undulled.
One technique for forming such an array of isolated islands or dots that has been described is that of the rotogravure printing. The technique of rotogravure printing employs a roll into the surface of which a pattern of cells has been engraved. The cells are filled with the formulation and the roll is pressed against a surface and the formulation in the cells is transferred to the surface. Normally the formulation would then flow until there was no separation between the formulations deposited from any individual cell. Ultimately a layer of essentially uniform thickness would be obtained. By way of illustration, comparative Examples C and D of U.S. Pat. No. 5,152,917 describe a process in which the pattern obtained by a rotogravure process quickly lost all separation of the individual amounts deposited from the cells.
In U.S. Pat. No. 5,014,468 a binder/abrasive formulation was deposited from rotogravure cells on a roller in such a way that the formulation was laid down in a series of structures surrounding an area devoid of abrasive. This is believed to be the result of depositing less than the fill volume of the cell and only from the perimeter of each cell, which would leave the ring formations described.
The problem with the rotogravure approach has therefore always been the retention of a useful shape to the island. To formulate an abrasive/binder mixture that is sufficiently flowable to be deposited and yet sufficiently non-flowable such that it does not slump to an essentially uniform layer coating when deposited on a substrate has proved very difficult.
Chasman et al.,in U.S. Pat. No. 4,773,920 disclosed that using a rotogravure coater, it is possible to apply a uniform pattern of ridges and valleys to the binder composition which, when cured, can serve as channels for the removal of lubricant and swarf. However beyond the bare statement of possibility, no details are given that might teach how this might be carried out.
In U.S. Pat. No. 4,644,703 Kaczmarek et al. used a rotogravure roll in a more conventional fashion to deposit an abrasive/binder formulation to deposit a layer that is then smoothed out before a second layer is deposited by a rotogravure process on top of the smoothed-out first layer. There is no teaching of the nature of the final cured surface.
Another approach has been to deposit the abrasive/binder mixture on a substrate surface and then impose a pattern comprising an array of isolated islands on the mixture by curing the binder while in contact with a mold having the inverse of the desired patterned surface. This approach is described in U.S. Pat. Nos. 5,437,754; 5,378,251; 5,304,223 and 5,152,917. There are several variations on this theme but all have the common feature that each island in the pattern is set by curing the binder in contact with a molding surface.
Yet another approach is described in U.S. Pat. No. 5,863,306 in which a pattern is embossed on a surface of a layer comprising a radiation-curable binder having abrasive particles dispersed therein after the surface of the layer has been modified to increase its viscosity but before curing of the binder has been initiated.
The present invention presents a technique for tailoring the formulation formed into patterns to generate grinding properties that vary with the degree of wear the coated abrasive has experienced.
The present invention therefore provides a flexible and effective route for the production of products uniquely suited to a specific task such that multiple abrading/fining/polishing operations can be avoided.
GENERAL DESCRIPTION OF THE INVENTION
The present invention provides a coated abrasive having a patterned surface comprising a plurality of shaped structures wherein each such structure comprises a curable binder with abrasive particles dispersed therein wherein the improvement comprises providing that the structures are layered such that, as the structure is eroded during use, different properties are revealed.
The term “shaped structure” is intended to convey a structure having a defined contoured shape that is raised above a backing surface upon which the structure is located. A “patterned surface” is a surface comprising a plurality of such shaped structures disposed on a backing surface in a repeating pattern with each shaped structure having a height dimension above the backing surface such that an initial contact plane is defined parallel to the backing surface and passing through only the tops of shaped structures. In preferred patterned surfaces at least 50% of the tops of the shaped structures lie in the initial contact plane. The shape of each “shaped structure” can be exactly replicated either across the whole of the patterned surface or in a number of groups of different repeating shaped structures, each structure within a group being identical, in defined or randomized patterns. Alternatively the shapes may be less exactly replicated as would be the case if an instrumentality imposing the shape were to be removed before the material shaped had completely lost the ability to flow.
The layers which make up the shaped structures comprise a curable binder and, dispersed therein, a particulate material. The nature and/or the amount of the particulate material varies within the shaped structure so as to achieve different properties at different layers of the structure as indicated above.
U.S. Pat. No. 5,863,306 shows a form of this approach in which the structures comprise abrasive particles dispersed in a UV-curable binder and the concentration of the abrasive in the surface layers of an abrasive structure is increased by comparison with the rest of the structure by for example application to the uncured binder/abrasive formulation surface a layer of a functional powder which, during an embossing process to form the shaped structures becomes at least partially incorporated into the surface layer of the structure. The functional powder can be, for example, abrasive particles or particles of a grinding aid or a mixture of both. This approach is described generically in U.S. Pat. No. 5,833,724. In each case the size of the powder particles laid on the surface was the same as or finer than or coarser than the abrasive particles within the shaped structure.
It is also known to deposit layers of grinding adjuvants on the surface of a patterned abrasive in the form of a supersize layer or even a “diamond-like” layer. These are however layers deposited on top of shaped structures rather than forming part of the structures themselves as is the case in the p
Swei Gwo Shin
Wei Paul
Yang Wenliang Patrick
Bennett David
Marcheschi Michael
Norton Company
LandOfFree
Production of layered engineered abrasive surfaces does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Production of layered engineered abrasive surfaces, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Production of layered engineered abrasive surfaces will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2446702