Abrasive tool making process – material – or composition – With synthetic resin
Reexamination Certificate
2002-07-11
2003-02-18
Marcheschi, Michael (Department: 1755)
Abrasive tool making process, material, or composition
With synthetic resin
C051S295000, C051S294000, C051S299000, C051S307000, C051S309000
Reexamination Certificate
active
06521005
ABSTRACT:
BACKGROUND
The present invention relates to surface conditioning articles formed from an organic matrix coated and engulfed by organic binders. The present invention also relates to a method for making a layered composite from which a surface conditioning article may be machined.
Surface conditioning articles are surface treatment articles formed from an organic polymeric matrix formed of a solid or foamed organic polymer or a nonwoven fiber web find utility in treating a surface to prepare it for further coatings. Burrs and flashing from cast, drilled or punched parts must be removed to produce a desired shape or surface finish. Surface conditioning articles in the form of wheels, discs, or belts operating at high speeds and high pressures must have sufficient strength and durability when subjected to high use pressure against the workpiece. It is desirous for the article to be flexible to intrude into crevices in the workpiece. In addition, the propensity of the article to smear onto the workpiece must be taken into consideration. Smearing is generally considered deleterious.
As used herein the term “smear-resistant” is meant to denote embodiments of the invention exhibiting substantially no visible signs of the surface treatment article remaining on the workpiece after the workpiece article has been treated. The articles of the invention call be urged against a workpiece at high operating speeds and/or pressures without smearing of the article onto the workpiece. The term “surface conditioning” is used here to include all steps between preliminary removal of material and final polishing or finishing step. Those steps comprise, grinding, lapping, deburring and the like.
Polymeric resinous binders used to bond the matrix or to secure abrasive particles within the matrix of such products have generally been either of the hard thermosetting type or the strong, tough elastomeric type. Hard thermosetting resins, such as base catalyzed phenol formaldehyde, are widely used to secure abrasive particles to sheet-like backing or to the fibers of a nonwoven web. Such hard resin binders, while usually having high tensile strength, low elongation at break or failure, and resistance to significant change when subjected to elevated temperatures, are undesirably susceptible to brittle fracture. Strong, tough elastomeric resin binders are more desirable in certain applications which require tougher, more durable surface treatment products. Such elastomeric binders have excellent tensile strength, a very high elongation at break, and resistance to brittle fracture but may exhibit significant softening at elevated temperatures as might be encountered when the surface treatment article is urged against a workpiece at high speeds and pressures. Such softening may result in smearing or transfer of portions of the article to the surface of the workpiece, which as described previously is not desired by the user.
The surface conditioning industry is continually striving for articles which more closely meet user demands. In addition, methods of producing surface conditioning articles that are kind to the environment, particularly the air and water, are especially strived for.
In light of the above user-driven demands it would be advantageous if surface conditioning articles could be developed which, by virtue of simple adjustment of binder ingredients, can be tailored to be flexible, substantially non-smearing at use pressure and temperature, all while using water-base formulations in the manufacturing processes which do not require use and subsequent removal of volatile organic hydrocarbons.
Specific properties needed for the coatings are linked to the final product applications. The product has to be flexible to be used in narrow and short belts form for example; it has to be conformable to allow uses on complicated surfaces; it has to be resistant to abrasion, and has to show resistant to brittle fracture to avoid an excessive wear of the product when used. It has to be resistant to high temperature occurring when used at high pressure/speed, and has not to let any smearing coating on the treated surfaces.
The standard reference product currently existing is made with urethane resins used in a solvent based system and catalyzed with an MDA (methylene dianiline). Several trials have been run to find a water base alternative to this resins use.
These articles have been made by the following generally known scheme. A first or “prebond” coating of a binder precursor solution without containing abrasive particles, which includes one or more of the above-named resins, is coated on the web and cured by, exposure to heat in order to impart sufficient strength to the nonwoven web for further processing. Then a “make” or “slurry” coating based on a resinous organic binder is applied to the web to secure fine abrasive grains throughout the lofty fibrous mat and cured. Thereafter, a “size” coating of resinous binder material and abrasive particles is applied, usually by spray-coating, over the prebonded web to increase the abrasive characteristics of the article, such as preventing the abrasive mineral from shelling. Then, the size coating is cured. The resins of the various “prebond”, “slurry”, and “size” coatings may be different.
The use of solvent-coated crosslinked urethanes in the “prebond” provides the requisite elasticity and protect nylon fibers of the web from attack by subsequently applied phenolic make coates used for bonding of mineral abrasive into the web.
The prebond coat is the most important one as far as smear resistance is concerned, because it protects the fibers from softening when using the article in heavy, high pressure.
Phenolic resin binders, in particular, are used extensively to manufacture nonwoven abrasive articles as a binder for the abrasive particles because of their thermal properties, availability, low cost, and case of handling. The monomers used in greatest volume to produce phenolic resins are phenol and formaldehyde.
In order to reduce emissions of “VOCs” (volatile organic compounds), it has been suggested to increase the water compatibility of phenolic resins. J. D. Fisher, in an article entitled “Water Compatible Phenolic Resins” in
Proceedings of the American Chemical Society, Division of Polymeric Materials: Science and Engineering;
no. 65, pp. 275-276 (1991), describes methods of making “water compatible” phenolic resins, their benefits, and their shortcomings.
Also, a compatibility problem arises from the use of the phenolic binder in particular together with a nonwoven web based on polyamide fibers. A particularly useful known nonwoven abrasive article is one comprising a web of polyamide fibers and resole-type phenolic resins as the curable binder. Such a composition provides for strong, tough, temperature resistant abrasive articles that may be made economically.
Rubber-modified phenolic resins have also been used in the manufacture of nonwoven abrasive articles, such as in the disclosure of commonly assigned U.S. Pat. No. 2,958,593 (Hoover et al.), as an optional rubber treatment disposed on one side of the structure to increase the resistance of the overall abrasive article structure to tearing and shredding. For example, Hoover et al. exemplifies a nylon fiber web being first coated with a phenol-formaldehyde and amine terminated polyamide resin-containing coating, followed by transmitting the phenol exposed web to a curing oven where the coated web is so heat-treated such that the emitted treated web is cured to a nontacky state while still warm, and, only thereafter, a rubbery composition based on a butadiene acrylonitrile copolymer latex (viz. trade designation “HYCAR LATEX 1561”, from B.F. Goodrich Co.) is applied to the opposite side of the web and heat-cured in an oven.
The modification of a phenolic resin precursor system used for binding, lower tenacity polyamide web fibers by the presence of a low rate of butadiene acrylonitrile latex, less than 40%, as a modifier agent therewith which alleviates the degradation of polyamide fibers in the presenc
3M Innovative Properties Company
Marcheschi Michael
Pribnow Scott R.
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