CA1099116A - Coated abrasive having a coextruded polyester support film backing - Google Patents
Coated abrasive having a coextruded polyester support film backingInfo
- Publication number
- CA1099116A CA1099116A CA273,353A CA273353A CA1099116A CA 1099116 A CA1099116 A CA 1099116A CA 273353 A CA273353 A CA 273353A CA 1099116 A CA1099116 A CA 1099116A
- Authority
- CA
- Canada
- Prior art keywords
- acid
- layer
- polyester
- adhesion
- coated abrasive
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
F.N. 912,882 ABSTRACT
Coated abrasive sheet material having a support film backing which comprises a biaxially oriented, heat-set coextruded laminate formed from two or more polyester polymers, one layer of the laminate being highly crystalline and the coated layer being tough and non-crystalline.
Coatings of binder material and abrasive, which normally adhere poorly to a biaxially oriented heat-set highly crystalline monofilm adhere firmly to the non crystalline surface of the laminate.
Coated abrasive sheet material having a support film backing which comprises a biaxially oriented, heat-set coextruded laminate formed from two or more polyester polymers, one layer of the laminate being highly crystalline and the coated layer being tough and non-crystalline.
Coatings of binder material and abrasive, which normally adhere poorly to a biaxially oriented heat-set highly crystalline monofilm adhere firmly to the non crystalline surface of the laminate.
Description
~.N. ~12,~53~
~9gl~6 COATED ABRASIVE HAVING A
COEXTRUDED POLYESTER SUPPORT FILM BACKING
The invention relates to coated abrasive products having a coextruded biaxially oriented, heat-set polyester support film backing.
The backings employed typically for coated abrasive products include paper, metal foil, cloth, film-forming plastic material, and the like. Biaxially oriented and heat-set films of highly crystalline polymeric materials such as polyethylene terephthalate (PET), polycyclohexanedimethyl terephthalate (PCDT) and polyethylene naphthalate (PEN) are particularly attractive candidates for use as coated abrasive backings because of their high tear-resistance, dimensional stability, chemical resistance, wear resistance, strength, abrasion resis-tance and temperature stability. Such films, however, typically have a smooth, tough, abrasion-resistant, chemical-resistant, dense surface to which conventional adhesive materials bond only with difficulty. Numerous attempts have been made to render the surface of such films more receptive to coatings.
While many of these attempts have some merit, none has produced a film which is substantially universally receptive to a wide variety of binder materials typically used for abrasive products.
One method employed to make such films more receptive is to roughen their surfaces by mechanical or chemical means.
Mechanical roughening involves making minute cuts into the surface of the film, tending to weaken it structurally.
Chemical treatments with strong acids or bases are generally undesirable because they not only tend to degrade the polymer and weaken the film but also are extremely toxic and hazardous to use.
Ano-ther method of making the surface of oriented heat-set films more receptive is to apply a primer layer of a chem:i.cally related but more receptive ma-terial by solvent casting or lamina-tion. Because of the unreceptive nature of the surface of biaxially oriented heat-set PET, PCDT
and PEN films, even these primer coatings tend to easily delam:inate, producing products which have at best, a very short useful life.
According to the present invention, there is provided composite coated abrasive sheet material, comprising, in combination:
(1) a biaxially oriented and heat-set coextruded support film comprising (A) a base layer of highly dimensionally s-table crystalline polyester having a surface which has a low receptivity to polymeric coatings, (B) a thin adhesion-promoti.ng layer of polyester having a minor degree of crystallinity and melting at a temperature less than about 230C; and
~9gl~6 COATED ABRASIVE HAVING A
COEXTRUDED POLYESTER SUPPORT FILM BACKING
The invention relates to coated abrasive products having a coextruded biaxially oriented, heat-set polyester support film backing.
The backings employed typically for coated abrasive products include paper, metal foil, cloth, film-forming plastic material, and the like. Biaxially oriented and heat-set films of highly crystalline polymeric materials such as polyethylene terephthalate (PET), polycyclohexanedimethyl terephthalate (PCDT) and polyethylene naphthalate (PEN) are particularly attractive candidates for use as coated abrasive backings because of their high tear-resistance, dimensional stability, chemical resistance, wear resistance, strength, abrasion resis-tance and temperature stability. Such films, however, typically have a smooth, tough, abrasion-resistant, chemical-resistant, dense surface to which conventional adhesive materials bond only with difficulty. Numerous attempts have been made to render the surface of such films more receptive to coatings.
While many of these attempts have some merit, none has produced a film which is substantially universally receptive to a wide variety of binder materials typically used for abrasive products.
One method employed to make such films more receptive is to roughen their surfaces by mechanical or chemical means.
Mechanical roughening involves making minute cuts into the surface of the film, tending to weaken it structurally.
Chemical treatments with strong acids or bases are generally undesirable because they not only tend to degrade the polymer and weaken the film but also are extremely toxic and hazardous to use.
Ano-ther method of making the surface of oriented heat-set films more receptive is to apply a primer layer of a chem:i.cally related but more receptive ma-terial by solvent casting or lamina-tion. Because of the unreceptive nature of the surface of biaxially oriented heat-set PET, PCDT
and PEN films, even these primer coatings tend to easily delam:inate, producing products which have at best, a very short useful life.
According to the present invention, there is provided composite coated abrasive sheet material, comprising, in combination:
(1) a biaxially oriented and heat-set coextruded support film comprising (A) a base layer of highly dimensionally s-table crystalline polyester having a surface which has a low receptivity to polymeric coatings, (B) a thin adhesion-promoti.ng layer of polyester having a minor degree of crystallinity and melting at a temperature less than about 230C; and
(2) a coating of binder material and abrasive granules firmly adherently bonded to the face of said (B) layer, the base layer and adhesion-promoting layer being conjoined at an interface, said interface being an integral layer of intermingled base layer and adhesion-promoting layer polyesters.
In the present invention, a coated abrasive is provided which employs a novel support film backing which has at least two distinct but firmly united coextruded layers. The support film is biaxially oriented and heat-set and has a highly dimensionally stable base layer formed of a crystalline thermoplastic polyester, especially PEN, PCDT or PET, and a thin layer of a thermoplastic adhesion-promoting polyester. The coated abrasive products of the invention are dimensionally stable, strong, resist delamination under a wide variety of use conditions, and are economical to prepare, avoiding mechanical surface treatment of films, solvent and hazardous chemical handling steps.
Coextrusion is a process for forming composi.te layers of thermo-plastic material, as exemplified by United States patent number 3,767,523, and involves simultaneously extruding the constituent layers of a composite D
film through a di.e so that the layers meet under lam:inar flow cond;.tions, intermingling at the interface and becoming :Eirmly united. Such a process, although known for the production of laminated films, has not been known for use in producing abrasive products of the type described herein.
- 2a -~, It has surprisingly been discovered that coextruded biaxially oriented, heat-set polyester backings, where one layer is crystalline PEN, PCDT or PET, and the layer which is to be coated is oriented but less crystalline, are not only flexible, tough, wear-resistant, chemical-resistant, strong, and have the other desirable properties of heat-set, biaxially oriented PET, PCDT or PEN film but also forms a tough, adherent bond with a wide variety of binder materials typically employed to bond abrasive yranules.
PET is prepared by reaction of terephthalic acid with ethylene glycol. In this reaction, the acid may be converted to the dimethyl ester which is allowed to react with the glycol by ester interchange. Typica11y, equimolar amounts of the glycol and the acid are reacted, generally in the presence of an excess of glycol. Minor amounts of another dicarboxylic acid such as isophthalic, phthalic, 2,5- or 2,7-naphthalene-dicarboxylic, succinic, sebacic, adipic, azelaic, suberic, pimelic, glutaric, etc., or a diester thereof, e.g., up to 10 mole percent, may be substituted for the terephthalic acid without deleteriously affecting the properties of the resultant composite film. Additionally, minor amounts of another glycol such as l,3-propanediol, 1,4-butanediol, neo-pentyl glycol, l,4-cyclohexanedimethanol, etc., e.g., up to 10 mole percent, may be substituted for the ethylene glycol without deleterious effects.
The preparation of PEN is analogous to the preparation of PET, except that the terephthalic acid is replaced by a free dibasic acid or lower alkyl diester of 2,6-naphthalene dicarboxylic acid. The same minor amounts and types of other dibasic acids or glycols may also be included. The preparation of PCDT is analogous to the preparation of PET except the ethylene glycol is replaced by l,4-cyclohexane dimethanol and minor amounts of another dibasic acid not terephthalic acid should be present to produce a film which can be biaxially oriented without substantial degradation. For this purpose, the other dibasic acid is present, on a molar basis, typically at least about 10% (preferably at least about 15%).
The thermoplastic adhesion-promoting layer is a polyester which melts below 230C., does not crystallize rapidly, and is substantially non-crystalline between about 20C. and 230C. "Substantially non-crystalline" means not more than a minor amount of crystallinity between about 20C.
and 230C.
Preferred polyesters for use in the invention, having the properties defined above, may be produced by the condensation reaction of a dicarboxylic acid component consisting of ~rom about 10 to about 100 mole percent of a dicarboxylic acid such as isophthalic acid, hexahydroterephthalic acid, sebacic acid, succinic acid, adipic acid, azelaic acid, suberic acid, pimelic acid, glutaric acid, or mixtures thereof, or the diesters of such acids and correspondingly from 90 to zero more percent of terephthalic acid, and a glycol component, in substantially equimolar proportions with the dicarboxylic acid component. The glycol is preferably polymethylene glycol having the formula HO(CH2)nOH, wherein n is an integer of 2-10, e.g., ethylene glycol, 1,3-propanediol and 1,4-butanediol, with ethylene glycol being preferred. Other useful glycols include neopentyl glycol, l,4-cyclohexane dimethanol and aromatic glycols such as bisphenol A.
As previously stated, the support film backing is formed by a coextrusion process, wherein the individual layers meet under laminar flow conditions and are expelled from the die as an integral, mul ti-layer film structure. Coextruded films prepared in this manner look much like monolayer films.
Such coextrusion processes are well known as exemplified by aforementioned U.S. Pat. No. 3,767,523 and by U.S. Pat. No.
In the present invention, a coated abrasive is provided which employs a novel support film backing which has at least two distinct but firmly united coextruded layers. The support film is biaxially oriented and heat-set and has a highly dimensionally stable base layer formed of a crystalline thermoplastic polyester, especially PEN, PCDT or PET, and a thin layer of a thermoplastic adhesion-promoting polyester. The coated abrasive products of the invention are dimensionally stable, strong, resist delamination under a wide variety of use conditions, and are economical to prepare, avoiding mechanical surface treatment of films, solvent and hazardous chemical handling steps.
Coextrusion is a process for forming composi.te layers of thermo-plastic material, as exemplified by United States patent number 3,767,523, and involves simultaneously extruding the constituent layers of a composite D
film through a di.e so that the layers meet under lam:inar flow cond;.tions, intermingling at the interface and becoming :Eirmly united. Such a process, although known for the production of laminated films, has not been known for use in producing abrasive products of the type described herein.
- 2a -~, It has surprisingly been discovered that coextruded biaxially oriented, heat-set polyester backings, where one layer is crystalline PEN, PCDT or PET, and the layer which is to be coated is oriented but less crystalline, are not only flexible, tough, wear-resistant, chemical-resistant, strong, and have the other desirable properties of heat-set, biaxially oriented PET, PCDT or PEN film but also forms a tough, adherent bond with a wide variety of binder materials typically employed to bond abrasive yranules.
PET is prepared by reaction of terephthalic acid with ethylene glycol. In this reaction, the acid may be converted to the dimethyl ester which is allowed to react with the glycol by ester interchange. Typica11y, equimolar amounts of the glycol and the acid are reacted, generally in the presence of an excess of glycol. Minor amounts of another dicarboxylic acid such as isophthalic, phthalic, 2,5- or 2,7-naphthalene-dicarboxylic, succinic, sebacic, adipic, azelaic, suberic, pimelic, glutaric, etc., or a diester thereof, e.g., up to 10 mole percent, may be substituted for the terephthalic acid without deleteriously affecting the properties of the resultant composite film. Additionally, minor amounts of another glycol such as l,3-propanediol, 1,4-butanediol, neo-pentyl glycol, l,4-cyclohexanedimethanol, etc., e.g., up to 10 mole percent, may be substituted for the ethylene glycol without deleterious effects.
The preparation of PEN is analogous to the preparation of PET, except that the terephthalic acid is replaced by a free dibasic acid or lower alkyl diester of 2,6-naphthalene dicarboxylic acid. The same minor amounts and types of other dibasic acids or glycols may also be included. The preparation of PCDT is analogous to the preparation of PET except the ethylene glycol is replaced by l,4-cyclohexane dimethanol and minor amounts of another dibasic acid not terephthalic acid should be present to produce a film which can be biaxially oriented without substantial degradation. For this purpose, the other dibasic acid is present, on a molar basis, typically at least about 10% (preferably at least about 15%).
The thermoplastic adhesion-promoting layer is a polyester which melts below 230C., does not crystallize rapidly, and is substantially non-crystalline between about 20C. and 230C. "Substantially non-crystalline" means not more than a minor amount of crystallinity between about 20C.
and 230C.
Preferred polyesters for use in the invention, having the properties defined above, may be produced by the condensation reaction of a dicarboxylic acid component consisting of ~rom about 10 to about 100 mole percent of a dicarboxylic acid such as isophthalic acid, hexahydroterephthalic acid, sebacic acid, succinic acid, adipic acid, azelaic acid, suberic acid, pimelic acid, glutaric acid, or mixtures thereof, or the diesters of such acids and correspondingly from 90 to zero more percent of terephthalic acid, and a glycol component, in substantially equimolar proportions with the dicarboxylic acid component. The glycol is preferably polymethylene glycol having the formula HO(CH2)nOH, wherein n is an integer of 2-10, e.g., ethylene glycol, 1,3-propanediol and 1,4-butanediol, with ethylene glycol being preferred. Other useful glycols include neopentyl glycol, l,4-cyclohexane dimethanol and aromatic glycols such as bisphenol A.
As previously stated, the support film backing is formed by a coextrusion process, wherein the individual layers meet under laminar flow conditions and are expelled from the die as an integral, mul ti-layer film structure. Coextruded films prepared in this manner look much like monolayer films.
Such coextrusion processes are well known as exemplified by aforementioned U.S. Pat. No. 3,767,523 and by U.S. Pat. No.
3,486,196 and No. 3,476,627. Canadian Pat. No. 929,455 discloses the preparation oF coextruded films which may be useful in the present invention. The patentee does not, however, suggest that such films be coated with another poly-meric layer to provide improved composite articles such as a coated abrasive but rather that it be overlapped and heat-sealed to itself to enclose a comestible.
The freshly coextruded support film, formed as described above, is amorphous. It is thereafter endowed with improved physical properties by biaxial orientation and heat-setting. Biaxial orientation involves stretching the film in two directions normal to each other, generally in the machine direction and at right angles thereto. In a typical operation, the freshly extruded molten film is fed onto a cooling drum to produce a quenched amorphous film which is briefly heated and stretched in the machine direction, and then conducted through a tenter frame where it is stretched transversely with moderate heating. Machine direction stretch-ing may be accomplished by passing between two sets oF nip rolls, the second set rotating at a higher speed than the first. Stretching typically increases the Film area by a factor of at least 6, the stretching usually being equal in 30 each direction. For applications requiring a higher tensile support film, this factor will be larger, e.g., above 14, and the stretching may be greater in one direction than the other.
Heat-setting, or heat-stabilization of the stretched coextruded film is accomplished by restraining the film in its stretched dimension and heating briefly, then quenching.
Such heating is typically in the range of 175C. - 230C.
Tentering of plastic films or sheet material is illustrated in U.S. Pat. No. 2,823,421.
The coextruded biaxially oriented support film back-ing should have a total thickness of at least 1 mil with atleast 1/4 mil of this thickness being the polyester adhesion-promoting layer. Film thicknesses up to about 10 mils are contemplated for the coated abrasive articles herein described, but thicknesses in excess of 10 mils may be desired for some purposes. The adhesion-promoting layer should not be thicker than 1/4 of the total thickness of the coextruded film and preferably is no more than 1 mil thick even for film thick-nesses up to 10 mils.
The coextruded support film backing described above provides a unique backing layer for coated abrasive products.
The thermoplastic adhesion-promoting layer provides a surface which will form an adherent bond with any of a variety of natural or synthetic resinous binder materials typically used as binders for coated abrasive products without the use of prime coatings or surface treatments. The resinous binder materials which have been found to adherently bond to this adhesive surface include varnish, hide glue, polyurethane, phenolic resins such as phenol formaldehyde, epoxy resins, etc. Upon suitable formulation, each of these resinous binder materials can be coated upon the surface adhesion-promoting layer with abrasive granules to provide coated abrasive products.
The invention will be better understood by referring to the drawing wherein:
The Figure depicts an abrasive coated sheet product according to the invention in a greatly enlarged fragmentary cross-section view.
Abrasive granules 18 are adhered to the surface of layer 13 of support film 11 formed of a layer 12 of tough, flexible, dimensionally stable crystalline polyester and a layer 13 of adhesion-promoting polyester by means of binder 16, which may include a conventional "make" coat 17 and a sandsize coat 21. The adhesive binder or "make coat", which may be any suitable resin or varnish binder presently known or suited for use in the manufacture of coated abrasives, optionally contains calcium carbonate or other filler. The resins and varnishes are basically initially liquid materials, but, depending on their use, they may be modified in various ways to give shorter or longer drying times, greater strength, more flexibility or other desirable properties. A preferred binder is a thermo-setting adhesive such as phenol-formaldehyde.
The abrasive particles 18 can be any of a wide variety of such material known for this use. The abrasive particles will typically vary in size from smaller than about 1 micron for extra fine polishing to larger than 30 mesh for extra coarse abrading. Examples of useful abrasive mineral which may be utilized include flint, emery, garnet, aluminum oxide, diamond, alumina-zirconia and silicon carbide.
The invention is further illustrated by reference to the following examples wherein all parts are by weight unless otherwise specified.
Example 1 An abrasive sheet was prepared in accordance with the invention by coating a 7-mil biaxially oriented heat-set support film consisting of a 6.75-mil polyethylene terephtha-late layer and a 0.25-mil copolyester layer having a terephthale/
isophthalate ratio of 80/20 with grade 150 aluminum oxide abrasive particles at a particle density of 42 grains per 24 square inches. The abrasive sheet was prepared by first roll coating the copolyester surface at 6.5 grains (dry weight) per 24 square inches with a uniform make coating of phenol-formaldehyde (1:1.95 mole ratio) base catalyzed resin, electro-statically depositing the abrasive particles, precuring the resin at 190F. for four hours, and roll coating the resultant coated abrasive surface with the same resin to provide a 11.4 grains (dry weight) per 24 square inch size coating. The size coating was then precured at 190F. for two hours and the resultant coated abrasive sheet was drum cured for ten hours at 212F.
The abrasive sheet hereinafter identified as Example 1 was evaluated against Control Examples A-C which were prepared of common commercial materials. For each of Examples A-C, as for Example 1, the abrasive mineral was grade 150 aluminum oxide, coated at the mineral weights shown in Table VI. Control A had an "E" weight paper backing,a glue make coating and phenolic resin size coating (same phenolic resin as Example 1). Controls B and C had cloth backings and a make and size resin coating of filled phenolic resin.
A test belt, (3 inches wide by 84 inches long) was prepared from each coated abrasive test Example described 9~1~
above. Each test belt was entrained around a smooth-surfaced 14 inch diameter 3 inch wide rubber-covered contact wheel, the rubber having a hardness value of 80-85 (Shore A). The belt was operated at a speed of 7300 surface feet per minute.
A previously weighed 2 inch by 2 inch by 7 inch mild steel (1018) work piece was reciprocally urged against the abrasive belt with 19 pounds force, the grinding occurring along its 2 inch by 7 inch face being abraded. The test was discontinued after 3 minutes of abrasion, the bar cooled to room temperature, cleaned and weighed. Abrading was continued for an additional period of 3 and 6 minutes respectively and the cooling, cleaning and weighing repeated. Results, which reveal the abrasive sheet material prepared according to the invention to be substantially as good as such sheets prepared of common commercial materials, are shown below:
TABLE VI
Mineral Wt.~eight Loss (g) per 4 x 6per cut time (min) Example (qrains) 3 6 12 Control A 40 87 166 299 Control B 62 111 221 366 Control C 54 105 203 359 Example 2 Coextruded Support Film A 3-mil coextruded support film was prepared as follows:
Granular polyethylene terephthalate resin having a solution intrinsic viscosity of 0.60 and melting point of 250C. was extruded at a barrel temperature ranging from 9~6 \
240-290C., a die temperature of 300C. and a feed rate of 90 lbs. per hour. Simultaneously, a granular copolyester resin having an intrinsic viscosity of 0.61, a melting point of 197C. and consisting of 80/20 poly(ethylene terephthalate/
isophthalate) was extruded at a barrel temperature ranging from 200C. - 300C. and a feed rate of 25 - 30 lbs. per hour.
The resultant molten composite film was cast onto a 12-inch diameter casting wheel maintained at 60C. and rotated at 8 feet per minute, producing a quenched film 30 mils in thickness having a 22 mil thick polyethylene terephthalate layer and an 8 mil thick copolyester layer. The quenched film was then oriented in the machine direction by stretching between a series of idler nip rolls having outlet nip rolls operated at three times the speed of inlet nip rolls while heating the film at 80C. The uniaxially oriented composite film was then fed into a tenter oven heated at 95C. wherein it was stretched 3 times in the transverse direction. The biaxially oriented composite film was heat-set by briefly heating under restraint at 205C., producing a 3 mil coextruded film.
Twelve parts of a mixture consisting of one part of 3 micron diamond particles and 1.4 part of the phenolic resin described in Example 1 was blended with 88 parts of ethyl cellosolve to make a slurry which was knife-coated (1.5 mil knife opening) on the surface of the coextruded 3 mil polyester support film described above. The resultant coating was cured for 1 hour at 250F. to provide a coated abrasive layer which could not be stripped from the backing by scraping with a sharp edge without destruction of the support film.
Example 3 A coated abrasive sheet having an epoxy resin binder and 3 micron diamond abrasive particles was prepared according to the invention. The epoxy resin was a 50:50 5 mixture of (1) a linear polyamide resin condensation product of dimeric fatty acid with a polyamine having an amine value of 290-320 (sold under the trade designation "Versamide 125"*) and (2) an epoxy resin of the bisphenol A type having an epoxy equivalent of 180-195 (sold under the trade designation 10 "Epon 828"*).
One part diamond particles was mixed with 1.4 parts resin, as a slurry, which was knife coated (1.5 mil knife opening) on a 3 mil coextruded polyester film of the type described in Example 2. The resultant coating was cured by 15 heating at 125F in a forced air oven for 8 hours.
The resultant coated abrasiYe sheet material was used to hand lap a tungsten carbide block.
Example 4 A coated abrasive sheet material was prepared 20 using, as a backing layer, the 3 mil coextruded support fjlm described in Example 2. The make coat (3 grains per 4" x 6") and the size coat (6 grains per 4" x 6!') were urea-formaldehyde resin, with 12 grains per 4" x 6!' of 220 grade aluminum oxide abrasive particles and a supersize of zinc stearate applied 25 as a 26% solids zinc stearate solution in glycol to a reflec-tance of 1000 (as described in U.S. Pat. No. 3,043,673~.
The resultant coated abrasive sheet was utilized for the removal of paint and primer with excellent results.
*Trademark -- 1 ~ -Example 5 A coated abrasive sheet material was prepared, using the 3 mil coextruded support film described in Example 2.
The film was coated with an epoxy varnish make coat, 12 grains per 4" x 6" grade 400 silicon carbide abrasive grains and 8 grains per 4" x 6" alkyd varnish size coat. Enamel was easily removed from a panel with the resultant coated abrasive sheet.
The freshly coextruded support film, formed as described above, is amorphous. It is thereafter endowed with improved physical properties by biaxial orientation and heat-setting. Biaxial orientation involves stretching the film in two directions normal to each other, generally in the machine direction and at right angles thereto. In a typical operation, the freshly extruded molten film is fed onto a cooling drum to produce a quenched amorphous film which is briefly heated and stretched in the machine direction, and then conducted through a tenter frame where it is stretched transversely with moderate heating. Machine direction stretch-ing may be accomplished by passing between two sets oF nip rolls, the second set rotating at a higher speed than the first. Stretching typically increases the Film area by a factor of at least 6, the stretching usually being equal in 30 each direction. For applications requiring a higher tensile support film, this factor will be larger, e.g., above 14, and the stretching may be greater in one direction than the other.
Heat-setting, or heat-stabilization of the stretched coextruded film is accomplished by restraining the film in its stretched dimension and heating briefly, then quenching.
Such heating is typically in the range of 175C. - 230C.
Tentering of plastic films or sheet material is illustrated in U.S. Pat. No. 2,823,421.
The coextruded biaxially oriented support film back-ing should have a total thickness of at least 1 mil with atleast 1/4 mil of this thickness being the polyester adhesion-promoting layer. Film thicknesses up to about 10 mils are contemplated for the coated abrasive articles herein described, but thicknesses in excess of 10 mils may be desired for some purposes. The adhesion-promoting layer should not be thicker than 1/4 of the total thickness of the coextruded film and preferably is no more than 1 mil thick even for film thick-nesses up to 10 mils.
The coextruded support film backing described above provides a unique backing layer for coated abrasive products.
The thermoplastic adhesion-promoting layer provides a surface which will form an adherent bond with any of a variety of natural or synthetic resinous binder materials typically used as binders for coated abrasive products without the use of prime coatings or surface treatments. The resinous binder materials which have been found to adherently bond to this adhesive surface include varnish, hide glue, polyurethane, phenolic resins such as phenol formaldehyde, epoxy resins, etc. Upon suitable formulation, each of these resinous binder materials can be coated upon the surface adhesion-promoting layer with abrasive granules to provide coated abrasive products.
The invention will be better understood by referring to the drawing wherein:
The Figure depicts an abrasive coated sheet product according to the invention in a greatly enlarged fragmentary cross-section view.
Abrasive granules 18 are adhered to the surface of layer 13 of support film 11 formed of a layer 12 of tough, flexible, dimensionally stable crystalline polyester and a layer 13 of adhesion-promoting polyester by means of binder 16, which may include a conventional "make" coat 17 and a sandsize coat 21. The adhesive binder or "make coat", which may be any suitable resin or varnish binder presently known or suited for use in the manufacture of coated abrasives, optionally contains calcium carbonate or other filler. The resins and varnishes are basically initially liquid materials, but, depending on their use, they may be modified in various ways to give shorter or longer drying times, greater strength, more flexibility or other desirable properties. A preferred binder is a thermo-setting adhesive such as phenol-formaldehyde.
The abrasive particles 18 can be any of a wide variety of such material known for this use. The abrasive particles will typically vary in size from smaller than about 1 micron for extra fine polishing to larger than 30 mesh for extra coarse abrading. Examples of useful abrasive mineral which may be utilized include flint, emery, garnet, aluminum oxide, diamond, alumina-zirconia and silicon carbide.
The invention is further illustrated by reference to the following examples wherein all parts are by weight unless otherwise specified.
Example 1 An abrasive sheet was prepared in accordance with the invention by coating a 7-mil biaxially oriented heat-set support film consisting of a 6.75-mil polyethylene terephtha-late layer and a 0.25-mil copolyester layer having a terephthale/
isophthalate ratio of 80/20 with grade 150 aluminum oxide abrasive particles at a particle density of 42 grains per 24 square inches. The abrasive sheet was prepared by first roll coating the copolyester surface at 6.5 grains (dry weight) per 24 square inches with a uniform make coating of phenol-formaldehyde (1:1.95 mole ratio) base catalyzed resin, electro-statically depositing the abrasive particles, precuring the resin at 190F. for four hours, and roll coating the resultant coated abrasive surface with the same resin to provide a 11.4 grains (dry weight) per 24 square inch size coating. The size coating was then precured at 190F. for two hours and the resultant coated abrasive sheet was drum cured for ten hours at 212F.
The abrasive sheet hereinafter identified as Example 1 was evaluated against Control Examples A-C which were prepared of common commercial materials. For each of Examples A-C, as for Example 1, the abrasive mineral was grade 150 aluminum oxide, coated at the mineral weights shown in Table VI. Control A had an "E" weight paper backing,a glue make coating and phenolic resin size coating (same phenolic resin as Example 1). Controls B and C had cloth backings and a make and size resin coating of filled phenolic resin.
A test belt, (3 inches wide by 84 inches long) was prepared from each coated abrasive test Example described 9~1~
above. Each test belt was entrained around a smooth-surfaced 14 inch diameter 3 inch wide rubber-covered contact wheel, the rubber having a hardness value of 80-85 (Shore A). The belt was operated at a speed of 7300 surface feet per minute.
A previously weighed 2 inch by 2 inch by 7 inch mild steel (1018) work piece was reciprocally urged against the abrasive belt with 19 pounds force, the grinding occurring along its 2 inch by 7 inch face being abraded. The test was discontinued after 3 minutes of abrasion, the bar cooled to room temperature, cleaned and weighed. Abrading was continued for an additional period of 3 and 6 minutes respectively and the cooling, cleaning and weighing repeated. Results, which reveal the abrasive sheet material prepared according to the invention to be substantially as good as such sheets prepared of common commercial materials, are shown below:
TABLE VI
Mineral Wt.~eight Loss (g) per 4 x 6per cut time (min) Example (qrains) 3 6 12 Control A 40 87 166 299 Control B 62 111 221 366 Control C 54 105 203 359 Example 2 Coextruded Support Film A 3-mil coextruded support film was prepared as follows:
Granular polyethylene terephthalate resin having a solution intrinsic viscosity of 0.60 and melting point of 250C. was extruded at a barrel temperature ranging from 9~6 \
240-290C., a die temperature of 300C. and a feed rate of 90 lbs. per hour. Simultaneously, a granular copolyester resin having an intrinsic viscosity of 0.61, a melting point of 197C. and consisting of 80/20 poly(ethylene terephthalate/
isophthalate) was extruded at a barrel temperature ranging from 200C. - 300C. and a feed rate of 25 - 30 lbs. per hour.
The resultant molten composite film was cast onto a 12-inch diameter casting wheel maintained at 60C. and rotated at 8 feet per minute, producing a quenched film 30 mils in thickness having a 22 mil thick polyethylene terephthalate layer and an 8 mil thick copolyester layer. The quenched film was then oriented in the machine direction by stretching between a series of idler nip rolls having outlet nip rolls operated at three times the speed of inlet nip rolls while heating the film at 80C. The uniaxially oriented composite film was then fed into a tenter oven heated at 95C. wherein it was stretched 3 times in the transverse direction. The biaxially oriented composite film was heat-set by briefly heating under restraint at 205C., producing a 3 mil coextruded film.
Twelve parts of a mixture consisting of one part of 3 micron diamond particles and 1.4 part of the phenolic resin described in Example 1 was blended with 88 parts of ethyl cellosolve to make a slurry which was knife-coated (1.5 mil knife opening) on the surface of the coextruded 3 mil polyester support film described above. The resultant coating was cured for 1 hour at 250F. to provide a coated abrasive layer which could not be stripped from the backing by scraping with a sharp edge without destruction of the support film.
Example 3 A coated abrasive sheet having an epoxy resin binder and 3 micron diamond abrasive particles was prepared according to the invention. The epoxy resin was a 50:50 5 mixture of (1) a linear polyamide resin condensation product of dimeric fatty acid with a polyamine having an amine value of 290-320 (sold under the trade designation "Versamide 125"*) and (2) an epoxy resin of the bisphenol A type having an epoxy equivalent of 180-195 (sold under the trade designation 10 "Epon 828"*).
One part diamond particles was mixed with 1.4 parts resin, as a slurry, which was knife coated (1.5 mil knife opening) on a 3 mil coextruded polyester film of the type described in Example 2. The resultant coating was cured by 15 heating at 125F in a forced air oven for 8 hours.
The resultant coated abrasiYe sheet material was used to hand lap a tungsten carbide block.
Example 4 A coated abrasive sheet material was prepared 20 using, as a backing layer, the 3 mil coextruded support fjlm described in Example 2. The make coat (3 grains per 4" x 6") and the size coat (6 grains per 4" x 6!') were urea-formaldehyde resin, with 12 grains per 4" x 6!' of 220 grade aluminum oxide abrasive particles and a supersize of zinc stearate applied 25 as a 26% solids zinc stearate solution in glycol to a reflec-tance of 1000 (as described in U.S. Pat. No. 3,043,673~.
The resultant coated abrasive sheet was utilized for the removal of paint and primer with excellent results.
*Trademark -- 1 ~ -Example 5 A coated abrasive sheet material was prepared, using the 3 mil coextruded support film described in Example 2.
The film was coated with an epoxy varnish make coat, 12 grains per 4" x 6" grade 400 silicon carbide abrasive grains and 8 grains per 4" x 6" alkyd varnish size coat. Enamel was easily removed from a panel with the resultant coated abrasive sheet.
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Composite coated abrasive sheet material, comprising, in combination:
(1) a biaxially oriented and heat-set coextruded support film comprising (A) a base layer of highly dimensionally stable crystalline polyester having a surface which has a low receptivity to polymeric coatings, (B) a thin adhesion-promoting layer of polyester having a minor degree of crystallinity and melting at a temperature less than about 230°C; and (2) a coating of binder material and abrasive granules firmly adherently bonded to the face of said (B) layer, the base layer and adhesion-promoting layer being conjoined at an interface, said interface being an integral layer of intermingled base layer and adhesion-promoting layer polyesters.
(1) a biaxially oriented and heat-set coextruded support film comprising (A) a base layer of highly dimensionally stable crystalline polyester having a surface which has a low receptivity to polymeric coatings, (B) a thin adhesion-promoting layer of polyester having a minor degree of crystallinity and melting at a temperature less than about 230°C; and (2) a coating of binder material and abrasive granules firmly adherently bonded to the face of said (B) layer, the base layer and adhesion-promoting layer being conjoined at an interface, said interface being an integral layer of intermingled base layer and adhesion-promoting layer polyesters.
2. The composite coated abrasive sheet material of claim 1 wherein said base layer is of a polyester selected from the group consisting of polyethylene terephthalate, polycyclohexane dimethyl terephthalate and polyethylene naphthalate.
3. The composite coated abrasive sheet material of claim 1 wherein said adhesion-promoting layer is a polyester produced by the condensation reaction of a dicarboxylic acid component consisting of from about 10 to about 100 mole percent of a dicarboxylic acid selected from the group consisting of isophthalic acid, hexahydroterephthalic acid, sebacic acid, succinic acid, adipic acid, azelaic acid, suberic acid, pimelic acid, glutaric acid, or mixtures thereof, or the diesters of such acids and correspondingly from 90 to zero mole percent of terephthalic acid, and a glycol component, in sub-stantially (Claim 3 cont...) equimolar proportions with the dicarboxylic acid component, wherein the glycol component is selected From the group con-sisting of polymethylene glycol of the Formula HO(CH2)nOH, wherein n is an integer of 2-10, neopentyl glycol, 1,4-cyclo-hexane dimethanol and bisphenol A.
4. The article of claim 1 wherein said binder material is selected from the group consisting of polyurethane, phenolic resins, epoxy resins, varnish and hide glue.
5. The article of claim 1 wherein said adhesion-promoting polyester layer comprises from about one-fourth of the total thickness of said support layer to about 1 mil thick.
6. The article of claim 1 wherein said binder is a phenolic resin.
7. The article of claim 1 wherein said binder material is a thermosetting resin.
8. The article of claim 7 wherein said thermo-setting adhesive is polyurethane.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA273,353A CA1099116A (en) | 1977-03-07 | 1977-03-07 | Coated abrasive having a coextruded polyester support film backing |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA273,353A CA1099116A (en) | 1977-03-07 | 1977-03-07 | Coated abrasive having a coextruded polyester support film backing |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1099116A true CA1099116A (en) | 1981-04-14 |
Family
ID=4108091
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA273,353A Expired CA1099116A (en) | 1977-03-07 | 1977-03-07 | Coated abrasive having a coextruded polyester support film backing |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1099116A (en) |
-
1977
- 1977-03-07 CA CA273,353A patent/CA1099116A/en not_active Expired
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4011358A (en) | Article having a coextruded polyester support film | |
| EP0793560B1 (en) | Coated abrasive article | |
| EP0494658B1 (en) | Polymer backed material with non-slip surface and method of making same | |
| EP0702615B1 (en) | Patterned abrading articles and methods making and using same | |
| US5355636A (en) | Tear resistant coated abrasive article | |
| US6383585B2 (en) | Sealable polyester film with high oxygen barrier, its use and process for its production | |
| EP0885091B1 (en) | Coated abrasives and backing therefor | |
| US5304224A (en) | Coated abrasive article having a tear resistant backing | |
| KR100729711B1 (en) | Biaxially oriented polyester film comprising a cycloolefin copolymer and process for its production | |
| US20030170476A1 (en) | White, high-gloss, polyester film containing cyclo-olefin copolymers (COC), a method for the production thereof and the use of the same | |
| CA2103929C (en) | Coated abrasive having combination backing member | |
| US3306718A (en) | Abrasive product | |
| JP2004504459A (en) | Opaque polyester film containing cycloolefin copolymer and having good adhesiveness, method for producing the same and use thereof | |
| US20030180560A1 (en) | White, biaxially- oriented polyester film with cycloolefin copolymer (coc), which is matt on at least one side, method for production and use thereof | |
| US6358579B1 (en) | Multiple-pack system comprising a sealable polyester film | |
| US6787219B2 (en) | Transparent polyester film having at least three layers and process for its production | |
| CA1099116A (en) | Coated abrasive having a coextruded polyester support film backing | |
| US20030064214A1 (en) | Transparent, multilayer, biaxially oriented polyester film, and process for its production | |
| US5433979A (en) | Method of producing a non-slip sheet | |
| US3246969A (en) | Abrasive coated backing of linear polymono-alpha-olefinic hydrocarbon | |
| US20030113562A1 (en) | Biaxially oriented polyester film with good metal adhesion, its use, and process for its production |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |