Abrading – Flexible-member tool – per se – Laminate
Reexamination Certificate
1998-05-19
2001-04-17
Scherbel, David A. (Department: 3723)
Abrading
Flexible-member tool, per se
Laminate
C451S536000, C451S539000, C051S298000
Reexamination Certificate
active
06217432
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an abrasive article having a barrier coating coextensive and interposed between a backing and an abrasive coating. The barrier coating prevents components of a flowable abrasive composition from penetrating into a backing.
Some conventional coated abrasive articles have a “make coat” of binder material that secures abrasive particles to a backing. In addition to a “make coat”, a “size coat” of binder material may be placed over the abrasive particles further securing the abrasive particles to the backing. Other coated abrasive articles contain a single abrasive composite layer made from abrasive slurry applied to a backing. Abrasive slurries typically contain abrasive particles dispersed in a radiation or a thermally curable binder precursor and are hardened to form the abrasive composite layer. Both conventional coated and abrasive composite layered abrasive articles are made by applying an abrasive composition in an unhardened, flowable state to the surface of a backing. The abrasive composition is then hardened to form an abrasive coating while in association with a backing.
During manufacture of abrasive articles, components of an abrasive composition may penetrate a backing. Low molecular weight components typically penetrate a backing quicker than higher molecular weight precursors. The unhardened precursors may become trapped in the backing and during hardening are obscured from proper light activation needed for polymerization. Unhardened components remaining in the manufactured abrasive articles may cause portions of abrasive coatings to become dislodged from a backing during use due to poor adherence of abrasive coatings to backings. In addition, having unhardened components penetrate a backing will alter the final composition of the abrasive coating.
Abrasive articles may include additional components such as chemical pretreating agents rendering paper backings waterproof. In recent years, waterproofing agents have switched from a solvent based (sometimes referred to as an oil based treatment) to a water based or latex treatment system. This change from solvent to water based treatments has been facilitated for environmental reasons, such as reducing or eliminating handling and disposal of organic solvents. During the manufacture of abrasive articles, and prior to hardening of abrasive coatings, components of a particular abrasive coating may penetrate into a backing treatment. This penetration may cause swelling of the waterproof treatment or agent. This swelling is likely to decrease the adherence of abrasive coatings to backings causing premature release of abrasive coatings, generally referred to in the abrasive industry as “shelling”. “Shelling” has been known to significantly reduce the effectiveness of abrasive articles during abrading processes.
Certain components of abrasive coatings are highly volatile and/or odorous, making manufacture of abrasive articles difficult. Such volatile and/or odorous components may likely become non-volatile and non-odorous when hardened. If the volatile and/or odorous components penetrate into a backing prior to hardening, they may remain as volatile and/or odorous components in the finished abrasive article. Such volatile and/or odorous components are unpleasant to smell and may volatilize during use of the abrasive article. The unhardened abrasive coating components may cause irritation if such materials come in contact with the skin.
SUMMARY OF THE INVENTION
Abrasive articles of the present invention have a backing, an abrasive coating, and a barrier coating. The abrasive coating is formed from radiation and/or thermally curable binder precursor and typically includes abrasive particles dispersed within the binder precursor. An abrasive coating may be in the form of an abrasive composite layer, a “make” coat, or a “size” coat. One of the starting materials of the abrasive coating may be volatile and/or odorous, such as tetrahydrofurfuryl acrylate. Tetrahydrofurfuryl acrylate normally becomes essentially nonvolatile and non-odorous when polymerized into a network. Application of an unhardened or flowable abrasive composition to a backing may result in volatile precursor monomer, such as tetrahydrofurfuryl acrylate, penetrating into the backing and remaining unhardened in the finished abrasive article. It is undesirable to have unhardened tetrahydrofurfuryl acrylate as part of a backing because unhardened tetrahydrofurfuryl acrylate monomer is a skin irritant. The barrier coating of the present invention prevents tetrahydrofurfuryl acrylate from entering the backing upon the application of an unhardened or flowable abrasive composition to a backing. Essentially all tetrahydrofurfuryl acrylate is then able to polymerize into a nonvolatile polymer during the hardening of the abrasive composition.
The barrier coating is formed from a water-borne composition comprising a crystalline or semi-crystalline resin, a major polyfunctional crosslinking agent having acid functionality, and at least one minor polyfunctional crosslinking agent. The barrier coating is coextensive with and interposed between the abrasive coating and the backing and essentially eliminates penetration of components of the hardened or flowable abrasive composition into the backing. The minor polyfunctional crosslinking agent is a component of the barrier coating that enhances attachment of the abrasive coating to the barrier coating.
The invention also embodies a method of making an abrasive article. The first step is preparing a water-borne composition to a backing. The composition includes a crystalline or semi-crystalline resin, one major polyfunctional crosslinking agent, and one minor polyfunctional crosslinking agent. The water-borne composition is applied to a backing and then partially or fully hardened to form a barrier coating. An abrasive composition typically comprising a binder and abrasive particles is applied over the barrier coating. The abrasive composition is hardened in contact with the barrier coating to form an abrasive coating. During the hardening process, chemical crosslinking at the interfacial boundary between the two coating layers is thought to occur.
The following definitions are used throughout this patent proposal: “Abrasive coating” refers both to a hardened coating comprising an abrasive composite layer(s) and to a hardened coating that comprises a make and/or a size coating.
“Abrasive composite structures” refers to one of a plurality of shaped bodies which can collectively provide a three-dimensional abrasive coating formed from a matrix of abrasive particles dispersed in a binder precursor.
“Precisely shaped” refers to an abrasive composite structure that has a distinct and discernible shape associated with it. This shape may be a geometric shape, random shape or combination thereof. In one embodiment, a precisely shaped abrasive composite is formed by solidifying a binder precursor in the cavities of a tooling. Additional information on precisely shaped abrasive composites can be found in U.S. Pat. No. 5,152,917 (Pieper et al.), incorporated herein after by reference.
“Saturant” refers to a polymeric material, such as a water-proofing agent, applied to a backing prior to the application of a barrier coating.
“Attachment Complex” refers to crosslinking of compounds at or near the interface of the abrasive coating and the barrier coating by a chemical reaction in which the reactants include the minor polyfunctional crosslinking agent of the barrier precursor coating and at least one component of the adjoining coating.
“Volatile” refers to low molecular weight binder precursor components that evaporate readily at normal temperatures and pressures.
“Major” when used to describe the amount of a component in a composition or an article refers to greater than 50 weight percent.
“Minor” when used to describe the amount of a component in a composition or an article refers to less than 50 weight percent.
“Substantially Crystalline” when used to describe a polymer refers to a crystallin
3M Innovative Properties Company
Busse Paul W.
Nguyen George
Scherbel David A.
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