Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1996-10-17
2002-06-18
Aftergut, Jeff H. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S140000, C156S169000, C156S173000, C156S175000, C451S532000, C451S534000, C451S536000, C451S539000
Reexamination Certificate
active
06406576
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to coated abrasive articles, and particularly to coated abrasive belts with endless, seamless backings containing an organic polymeric binder and a fibrous reinforcing material. Additionally, this invention pertains to methods of making endless, seamless backings for use in coated abrasive belts.
BACKGROUND ART
Coated abrasive articles generally contain an abrasive material, typically in the form of abrasive grains, bonded to a backing by means of one or more adhesive layers. Such articles usually take the form of sheets, discs, belts, bands, and the like, which can be adapted to be mounted on pulleys, wheels, or drums. Abrasive articles can be used for sanding, grinding, or polishing various surfaces of, for example, steel and other metals, wood, wood-like laminates, plastic, fiberglass, leather, or ceramics.
The backings used in coated abrasive articles are typically made of paper, polymeric materials, cloth, nonwoven materials, vulcanized fiber, or combinations of these materials. Many of these materials provide unacceptable backings for certain applications because they are not of sufficient strength, flexibility, or impact resistance. Some of these materials age unacceptably rapidly. Also, some are sensitive to liquids that are used as coolants and cutting fluids. As a result, early failure and poor functioning can occur in certain applications.
In a typical manufacturing process, a coated abrasive article is made in a continuous web form and then converted into a desired construction, such as a sheet, disc, belt, or the like. One of the most useful constructions of a coated abrasive article is an endless coated abrasive belt, i.e., a continuous loop of coated abrasive material. In order to form such an endless belt, the web form is typically cut into an elongate strip of a desired width and length. The ends of the elongate strip are then joined together to create a “joint” or a “splice.”
Two types of splices are common in endless abrasive belts. These are the “lap” splice and the “butt” splice. For the lap splice, the ends of the elongate strip are bevelled such that the top surface with the abrasive coating and the bottom surface of the backing fit together without a significant change in the overall thickness of the belt. This is typically done by removing abrasive grains from the abrasive surface of the strip at one of the ends, and by removing part of the material from the backing of the elongate strip at the other end. The bevelled ends are then overlapped and joined adhesively. For the butt splice, the bottom surface of the backing at each end of the elongate strip is coated with an adhesive and overlaid with a strong, thin, tear-resistant, splicing media. Although endless coated abrasive belts containing a splice in the backing are widely used in industry today, these products suffer from some disadvantages which can be attributed to the splice.
For example, the splice is generally thicker than the rest of the coated abrasive belt, even though the methods of splicing generally used involve attempts to minimize this variation in the thickness along the length of the belt. This can lead to a region(s) on the workpiece with a “coarser” surface finish than the remainder of the workpiece, which is highly undesirable especially in high precision grinding applications. For example, wood smith areas having a coarser surface finish will stain darker than the remainder of the wood.
Also, the splice can be the weakest area or link in the coated abrasive belt. In some instances, the splice will break prematurely before full utilization of the coated abrasive belt. Belts have therefore often been made with laminated liners or backings to give added strength and support. Such belts can be relatively expensive and under certain conditions can be subject to separation of the laminated layers.
In addition, abrading machines that utilize a coated abrasive belt can have difficulty properly tracking and aligning the belt because of the splice. Further, the splice creates a discontinuity in the coated abrasive belt. Also, the splice area can be undesirably more stiff than the remainder of the belt. Finally, the splice in the belt backing adds considerable expense in the manufacturing process of coated abrasive belts.
SUMMARY OF THE INVENTION
The present invention is directed to coated abrasive articles, particularly to coated abrasive belts made from endless, seamless backing loops. By the phrase “endless, seamless” it is meant that the backings, i.e., backing loops, used in the belts are continuous in structure throughout their length. That is, they are free from any distinct splices or joints. This does not mean, however, that there are no internal splices in, for example, a fibrous reinforcing layer, or that there are no splices in an abrasive layer. Rather, it means that there are no splices or joints in the backing that result from joining the ends of an elongate strip of backing material.
Thus, the coated abrasive articles of the invention do not exhibit many of the disadvantages associated with coated abrasive belts made from backing loops containing a splice. The coated abrasive belts of the invention can readily be prepared with substantially the same thickness or caliper along the entire length, i.e., circumference, of the belt. Typically, the thickness of the endless, seamless backing loops of the present invention does not vary by more than about 15% along the entire length of the loop and preferably varies less than 10%, more preferably less than 5% and most preferably less than 2%.
A coated abrasive belt of the present invention includes a backing in the form of an endless, seamless loop, which contains an organic polymeric binder material and a fibrous reinforcing material. Typically, the binder weight in the backing is within a range of about 40-99 wt-%, preferably within a range of about 50-95 wt-%, more preferably within a range of about 65-92 wt-%, and most preferably within a range of about 70-85 wt-%, based on the total weight of the backing. The polymeric binder material can be a thermosetting, thermoplastic, or elastomeric material or a combination thereof. Preferably it is a thermosetting or thermoplastic material. More preferably it is a thermosetting material. In some instances, the use of a combination of a thermosetting material and an elastomeric material is preferable.
The remainder of a typical, preferred, backing is primarily fibrous reinforcing material. Although there may be additional components added to the binder composition, a coated abrasive backing of the present invention primarily contains an organic polymeric binder and an effective amount of a fibrous reinforcing material. The phrase “effective amount” of fibrous reinforcing material refers to an amount sufficient to give the desired physical characteristics of the backing such as reduction in stretching or splitting during use.
The organic polymeric binder material and fibrous reinforcing material together comprise a flexible composition, i.e., flexible backing, in the form of an endless, seamless loop with generally parallel side edges. The flexible, endless, seamless backing loop includes at least one layer of fibrous reinforcing material along the entire length of the belt. This layer of fibrous reinforcing material is preferably substantially completely surrounded by (i.e., engulfed within) the organic polymeric binder material. That is, the layer of fibrous reinforcing material is embedded or engulfed within the internal structure of the loop, i.e., within the body of the loop, such that there are regions of organic binder material free of fibrous reinforcing material on opposite surfaces of the layer of fibrous reinforcing material. In this way, the surfaces, e.g., the outer and inner surfaces, of the loop have a generally smooth, uniform surface topology.
The fibrous reinforcing material can be in the form of individual fibrous strands or a fibrous mat structure. The endless, seamless loops, i.e., backing loops, of the present in
Bange Donna Wendeln
Benedict Harold Wayne
Zimny Diana Denise
3M Innovative Properties Company
Aftergut Jeff H.
Allen Gregory D.
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