CA1321073C

CA1321073C - Abrasive article containing helically crimped fibers

Info

Publication number: CA1321073C
Application number: CA000561471A
Authority: CA
Inventors: Thomas R. Mcavoy; Fred H. Bland
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1987-04-14
Filing date: 1988-03-15
Publication date: 1993-08-10
Anticipated expiration: 2010-08-10
Also published as: EP0287286B1; KR970003494B1; BR8801726A; AU1330188A; ES2087060T3; ZA881967B; EP0287286A3; AU593984B2; JPS63278766A; DE3855339T2; KR880012310A; DE3855339D1; EP0287286A2; MX167892B

Abstract

ABSTRACT OF THE DISCLOSURE
This invention relates to articles for cleaning, buffing, conditioning, or restoring surfaces.
Abrasive articles made from nonwoven fibers have long been used for cleaning floors and other surfaces.
Although previously known nonwoven abrasive articles are extremely useful for the purposes for which they are intended, they rapidly lose their efficiency as they become saturated with dirt.
This invention provides an abrasive article comprising an open, lofty nonwoven web comprising helically crimped synthetic organic fibers. The article can optionally contain stuffer box crimped fibers and melt bondable fibers.
The presence of helically crimped fibers brings about greater durability and greater capacity for absorbing debris.

Description

l 32 l173 ABRASIVE A~TICLE CONTAINING HELICALLY CRIMPED FIBERS

sAcK ROUND OF__HE INVENTION
This invention relates to articles for cleaning, buffing, conditioning, or restoring surfaces.
For at least the last 25 years, abrasive articles made from nonwoven fibers have been used for cleaning floors and other surfaces.
Hoover, et al, U.S. Patent No. 2,958,593 discloses nonwoven fibrous abrasive articles of extremely open structure having an extremely high void volume. This article has been found to be useful in floor maintenance, in hand scouring operations such as performed in domestic kitchens, as well as in various industrial abrasive operations.
McAvoy, U.S. Patent No. 3,537,121 discloses a soft, resilient compressible polishing pad having a lofty fibrous nonwoven structure bonded by a soft, tough resin containing a finely divided soft mineral filler. This pad is comparable to pads made of lamb's wool with respect to ability to impart luster to buffable waxes. This pad can be used to clean and restore the surface of hard polymer coatings without powdering. This pad also does not scratch or abrade the surface, nor does it impart swirl marks to the finish of the surface.
Fitzer, U.S. Patent No. 4,227,350 discloses a low density abrasive product comprising a uniform cross section, porous, lofty web of autogeneously bonded continuous, undulated, interengaged filaments. The web is impregnated with a tough binder resin which adherently bonds the filaments of the web together and also bonds a multitude of abrasive granules, uniformly dispersed throughout the web, to the surface of the filaments.
Although the articles disclosed in the aforementioned patents are extremely useful for the purposes for which they are intended, they rapidly lose their efficiency as they become saturated with dirt. It is known that as the void volume of a nonwoven pad i9 lncreased, lts abllity to absorb more dlrt ls lncreased. However, A8 the vold volume is lncreased the life of the pad 18 slmultaneously decreas-ed. In vlew of thls problem, lt has long been deslred to provlde a nonwoven flbrous pad havlng a hlgh vold volume and a hlgh level of durablllty.
SUMMARY OF THE INVENTION
Thls lnvention provldes a low denslty, nonwoven abraslve artlcle havlny a nonwoven flbrous web comprislng hellcally crlmped flbers derived from synthetlc organlc materlal. At least about 30% by welght of the fibrous web of this product be made of hell-cally crlmped flbers.
The hellcally crlmped flbers must have crlmp frequency hlgh enough so that the web formed therefrom ls lofty and open, but they must not have so hlgh a crlmp frequency that they cannot be processed by conventlonal nonwoven web-maklng equlpment. It ls preferred that the hellcally crlmped flbers be stablllzed or set, preferably by heatlng the flbers, so that subse~uent heatlng thereof wlll not adversely affect the character of the hellcally crlmped flbers and nonwoven webs produced therefrom.
Optlonally, the nonwoven web used ln thls lnvent~on can contaln stuffer box crlmped flbers and melt bondable flbers. When actlvated by heat, the melt bondable flbers help to stablllze the nonwoven webs of thls lnventlon.
Dependlng upon the lntended appllcatlon of the artlcles of thls lnventlon, flllers, colorants, abraslve partlcles, or addltlonal blnders can be lncorporated lnto the nonwoven web.
Because the nonwoven abraslve artlcles of thls lnventlon are more open and lofty than those of the prlor art, they are capable of belng fllled wlth more debrls durlng use. Although they are more open and lofty, they are more durable than nonwoven abrasive articles of the prlor art.

BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view, greatly enlarged, of an article of this invention.
FIG. 2 is a side view in elevation of an article of this invention.

DETAILED DESCRIPTION
As used herein, the term "abrasive article" is intended to include articles which can perform any one or more of the following functions: rubbing, wearing away, polishing, cleaning, buffing, or otherwise conditioning.
The abrasive articles of this invention comprise nonwoven webs that are characterized by being comprised of helically crimped fibers. Fibers are crimped into a helical configuration by relief of bi-lateral differential forces in a fiber or composite fiber. These bi-lateral differential forces are produced by either coextrusion of polymers having at least some stress/strain differential properties, or induction of differential stress by passing the fiber over an edge. Although helically crimped synthetic fibers are well known, the use thereof in nonwoven abrasive products has never been disclosed.
Helically crimped fibers useful in the practice of this invention must have a sufficiently high degree of crimp to form a lofty, open nonwoven web but not so high a level of crimp that these fibers cannot be processed by conventional nonwoven web-makin~ equipment.
Preferably the void volume is maintained within the range of from about 85 percent to at least about 95 percent. Structures wherein the void volume is somewhat less than 85 percent are useful for the purposes of this invention though not ordinarily recommended. On the other hand, where the void volume is decreased below about 75 percent, it has been found that the outstanding and advantageous propertles dlmlnlsh rapldly. For example, the ready flu~hablllty or cleanablllty of the floor cleanlng structures, and therewith the abrasive cutting rate, etc. drops off.
It ls preferred to form the web component of our combl-nation structures from synthetlc flbers such as nylon and poly-esters (e.g., "Dacron~' ). The unlformlty and quallty of such types of flbers can be closely controlled. Also, these flbers retaln substantl~l of thelr physical properties when wet with water or olls. Because the artlcles hereof often are sub~ected to water, olls, cleaners, chemlcals, and the like, flbers should be selected whlch maintain substantlal of thelr essentlal character-istlcs when sub~ected to medla to which they will be exposed ln the deslred partlcular use. However, lt may be mentloned that certain deficlencies, e.g., low wet strength, in some flbers may be lmproved by appropriate treatment thereof.
Typlcally, helically crimped fibers have about 1 to 15 full cycle crimps per 25 mm flber length, whlle stuffer box crimp-ed flbers have about 3 to 15 full cycle crimps per 25 mm flber length. In the artlcles of the present lnventlon, when hellcally crlmped fibers are used in con~unctlon wlth stu~fer box crlmped flbers, lt ls preferred that the hellcally crlmped flbers have fewer crlmps per speclfled length than the conventlonal stuffer box crimped flbers. As a typlcal example, for an artlcle comprl-sed solely of 50 denler flber, hellcally crlmped flbers having about three full cycle crlmps per 25 mm can be advantageously used ln con~unctlon wlth stuffer box crlmped flbers havlng about flve full cycle crlmps per 25 mm. The crlmp frequency ls measured whlle the flbers are placed under very mlld stress. The "Low Load", as glven ln Table I below, ls applled to the lndlvldual flber before countlng the number of full cycle crlmps per 25 mm flber length.
*

Trade-mark TABLE I

Denier range Low load (g) }~igh load ~g) 0 - 25 Denier x 2 x 10 Denier x 50 x 10 26 - 40 0.05 3 41 - 75 0.1 5 76 - 125 0.2 10 126 - 175 0.3 15 10176 - 225 ~.4 20 Crimp index, a measure of fiber crimp elasticity is preferably about 35 to 70 percent for helically crimped fibers, which is about the same as for stuffer box crimped fibers. Crimp index can be determined by measuring fiber length with appropriate "High Load" attached, then subtracting fiber length with appropriate "Low I.oad"
attached, and then dividing the resulting value by fiber length and multiplyinq that value by 100. The crimp index can also be determined after exposing the test fibers to an elevated temperature, e.g. 135C to 175C for 5 to 15 minutes, and this value compared with the index before heat exposure. Crimp index measured after the fiber is exposed for 5 to 15 minutes to an elevated temperature, e.g. 135C
to 175C, should not significantly change from that measured before heat exposure. The load can be applied either horizontally or vertically.
By and large, the length of the fibers which may be employed is dependent upon the limitations of the processing equipment upon which the nonwoven open web is formed. However, depending on types of equipment, fibers of different lengths, or combinations thereof, very likely can be utilized in forming the lofty open webs of the desired ultimate characteristics herein specified. Fiber lengths suitable for helically crimped fibers preferably range from about 60 to about 150 mm, whereas suitable fiber lengths for stuffer box fibers tange from about 25 to about -70 mm. Llkewise, the thickness of the flbers usually ls not cru-clal (apart from processlng), due regard belng had to the re~lll-ence and toughness ultlmately deslred ln the resultlng web.
Generally, larger denler flbers are preferred for more abraslve artlcles, and smaller denler flbers are preferred for less abra-slve artlcles. Flber slze must be suitable for lofty, open, low denslty abraslve products. Typlcally, flber slze ranges from about 6 to about 400 denler per fllament.
The hellcally crlmped flbers are preferably stablllzed or set, preferably by appllcatlon of heat, so that, lf they are subsequently heated to cure a subse~uently applled adherent coat-lng, the crlmp frequency wlll not be signlflcantly changed. To lnsure that crlmp frequency wlll not be changed and that nonwoven webs made from hellcally crlmped flbers wlll not change apprecl-ably ln thlckness when sub~ected to temperatures ln ~he range of 150C to 175C, the temperature for curlng adherent coatlngs, hellcally crlmped flbers are preferably heat set at temperatures at least sllghtly hlgher than these curlng temperatures. Change ln crlmp frequency prlor to or durlng lnltlal flber bondlng pro-cess would cause the thlckness of the nonwoven webs formed ofthese flbers to change excesslvely or cause the webs to become excesslvely weak, and consequently unsultable for use ln lofty, open nonwoven abraslve products.
Mlxtures of hellcally crlmped and conventlonal stuffer box crlmped synthetlc organlc flbers can be used ln the practlce of thi~ lnventlon. Nonwoven webs sultable for preparlng low den~-slty nonwoven abraslve products of thls lnventlon co~prlse at least about 30% by welght of hellcally crlmped synthetlc organlc flbers, more preferably at least about 50% by weight of hellcally crlmped synthetlc organlc flbers, and ~ost preferably at least about 70% by welght of hellcally crlmped synthetlc organlc flbers.

A~

As compared wlth nonwoven low denslty abraslve pads con-talnlng less than about 30~ by welght hellcally crlmped flbers, nonwoven low denslty abraslve pads of thls lnventlon have more reslstance to wear and dlslntegratlon. Increaslng the hellcally crlmped flber content of these nonwoven abraslve pads generally lmproves performance. It should be noted that nonwoven webs and abraslve products made from nonwoven web~ contalnlng at least about 30% by welght hellcally crlmped flbers have greater thlck-ness, glven e~ual flber slze and welght, when compared to webs and abraslve products made from conventional stuffer box crlmped flbers. Although nonwoven, lofty, open abraslve products whlch have greater loft or thlckness for a glven flber welght, flber slze, coatlng materlal, coatlng welght, and abraslve content would be expected to be less reslstant to wear and dlslntegratlon under severe use conditions, the abraslve pads of thls lnventlon, whlch contaln at least 30% by welght hellcally crlmped flbers, exhlblt both a hlgher level of openness and a hlgher level of durabllity than do abraslve pads contalnlng less than 30% by welght hellcally crlmped flbers.
U.S. Patent No. 3,595,738 dlscloses methods for the manufacture of hellcally crimped blcomponent polyester flbers sultable for use ln thls lnventlon. The flbers produced by the method of that patent have a reverslng hellcal crlmp. Flbers havlng a reverslng hellcal crlmp are preferred over flbers that are hellcally crlmped ln a coiled configuratlon llke a colled sprlng. However, both types of hellcally crlmped flbers are sultable for thls lnventlon. U.S. Patent No. 3,868,749, U.S.
Patent No. 3,619,874 and U.S. Patent No. 2,931,089, dlsclose varlous methods of edge crlmplng synthetlc organlc fibers to pro-duce hellcally crlmped flbers. Edge crlmped fibers are usually formed ln a unldlrectlonal colled conflguratlon but may be of the reverslng hellcally crimped type or may be comblnatlons of ,,~ .
,f: . ' .

' ; ' ~ .

' - .

-a-both types. Typically, reversing helically crimped fihers have fewer ~rimps per ~lnit length than do unidlrectionally colled hQlically crimped ~lbers.
Melt bondable fibers can optionally be used in the practice of this invention to provide initial bonding of the filaments of formed nonwoven web to increase web integrity and to help stabilize the web in order to facilitate application of subsequent coatings. Melt bondable fibers suitable for this invention must be activatable at elevated temperatures below temperatures which would adversely affect the helically crimped fibers.
Additionally, these fihers are preferably coprocessable with the helically crimped fibers to form a lofty, open unbonded nonwoven web using conventional nonwoven web forming equipment. Typically, melt bondable fibers have a concenteic core and a sheath, have been stuffer box crimped with about 6 to 12 crimps per 25 mm, and have a cut staple length of about 25 to about 100 mm. Composite fibers have a tenacity of about 2-3 g/denier. Alternatively, melt bondable fibers may be of side-by-side construction or of eccentric core and sheath construction. Preferred deniers of melt bondable fibers are six and larger.
Many types and kinds of abrasive particles and binders can be employed in the nonwoven webs of the articles of this invention. In selecting these components, their ability to adhere firmly to the fibers employed must be considered, as well as their ability to retain such adherent qualities under the conditions of use.
Generally, it is highly preferable that the binder materials exhibit a rather low coefficient of friction in use, e.g., they do not become pasty or sticky in response to frictional heat. However, some materials which of themselves tend to become pasty, e.g., rubbery compositions, can be rendered useful by appropriately filling them with particulate fillers. Binders which have been found to be particularly suitable include phenolaldehyde resins, butylat~d urea aldehyde resins, .

epoxide resins, polyester resins such as the condensation product of maleic and phthalic anhydrides and propylene glycol, acrylic resins, styrene-butadiene resins, and polyureth~nes.
Amounts of binder employed ordinarily are adjusted toward the minimum consistent with bonding the fibers together at their points of crossing contact, and, in the instance wherein abrasive particles are also used, with the firm bonding of these particles as well. Binders and any solvent from which the binders are applied, also should be selected with the particùlar fiber to be used in mind so embrittling penetration of the fibers does not occur.
Representative examples of abrasive materials useful for the nonwoven webs of this invention include, for example, silicon carbide, fused aluminum oxide, garnet, flint, emery, silica, calcium carbonate, and talc. The sizes or grades of the particles can vary, depending upon the application of the article. Typical grades of abrasive particles range from about 36 to about 1000.
Conventional nonwoven web making equipment can be used to make webs of helically crimped fibers or blends of helically crimped and stuffer box crimped fibers with or without melt bondable fibers. Air laid nonwoven webs comprising helically crimped fibers can be made using equipment commercially available from Dr. O. Angleitner (DOA), Proctor & Schwarz, or Rando Machine Corporation.
Mschanical laid webs can be made using equipment commercially available from Hergeth KG, Hunter, or others.
During manufacture of crimped fibers, lubricants are typically used to facility processing. However, excessive lubricant coatings on the crimped fibers may impede processing crimped fibers into nonwoven webs.
The following non-limiting examples will further serve to illustrate this invention.

1 32 ~ 073 Exampl e A random air-laid nonwoven web having a weight of about 460 y/m2 and a thickness of about S0 mm was formed by means of a DOA machine, a commercially available web forming device. The web was formed from a preblended mixture o~ 70% by weight 60 denier helically crimped polyethylene terephthalate polyester (PET~ staple fibers and 30% by weight 15 denier stuffer box crimped bicomponent polyester melt bondable fibers. The helically crimped fibers were formed by edge crimping, were fully tensilized, were cut to 75 to 100 mm staple lengths, had a tenacity of 3.2 g/denier, had 2.7 full cycle crimps per 25 mm, had a crimp index of 42, and had crimp index after heat exposure for 5 minutes at 175~C of 38. The melt bondable fiber was a stuffer box crimped fiber having a bicomponent sheath/core ~modified polyester/polyester) construction, had a tenacity of 3 g/denier, had a staple length of 40 mm, had 9 full cycle crimps per 25 mm, had a crimp index of 9, and had a crimp index of 16 after exposure to heat for 5 minutes at 130C, and were activatable at 120 - 200C.
In an oven, low velocity air heated to approximately 180C was forced through the web for three minutes, causing the bicomponent melt bondable polyester fiber to bond to and stabilize the nonwoven web. The thickness of the nonwoven web was reduced slightly to about 45 mm.
A filled styrene-butadiene rubber latex saturant, having about 70% by weight non-volatile materials was prepared by combining the following ingredients in the amounts indicated:

Amount Inaredlent (part~ bY welaht) Water 3.1 Carbox~lated styrene-butadlene rubber (SBR) latex, contalnlng 65~ styrene (Amsco~es 5900, commerclally avallable from Unlon 011 Chemlcals) 43.4 Hexamethylmethoxymelamlne (HMMM~ resln (Cymel 303, commerclally avallable from Amerlcan Cyanamld) 4.6 Calcium carbonate flller 41.5 Dlammonlum phosphate, 40% by welght ln tap water 0.4 Hydroxypropyl methylcellulose, 3% *by welght dlsperslon ln tap water ~Methocel F4M, commerclally avallable from Dow Chemlcal Co.) 0.8 Slllcone emulslon surfactant (Q2-3168*, commerclally avallable from Dow Cornlng) 0.1 Dloctyl sodlum sulfosucclnate surfactant (Trlton GR5M, commercially avallable from Rohm and Haas) 0.8 The saturant was applled by passlng the nonwoven web between a palr of vertlcally opposed 250 mm dlameter rubber cover-ed squeeze rolls. The rotatlng lower roll, whlch was lmmersed ln the saturant, carrled saturant lnto the nonwoven web, so as to evenly dlsperse lt therethrough. The wet nonwoven web was drled and the saturant cured ln a hot alr oven at 175C for about flve to seven mlnutes. The dry, coated nonwoven web had a thlckness of about 38 mm and welghed about 1110 g/m2. The nonwoven web had breaklng strengths ln the length and cross dlrectlons of 9.5 and 11.4 kg/25 mm sample wldth, respectlvely.
Abraslon resistance of the nonwoven web was determlned by an accelerated wear llfe test on floor bufflng pad~ havlng a dlameter of 430 mm and dle cut from the aforementloned web. A
rotatlng table, havlng a dlameter of 2.4 m and havlng a surface Trade-mark X\
. ' ', . .

1 32 1 ~73 made of fllled vlnyl floor tlle, was rotated at a rate of 10 revo-lutlons per minute ~rpm). To cause accelerated wear, 4 strlps, each of whlch was 100 mm wide and contained 50 grade coated abra-slve, was adhered to the vlnyl floor tlle in a random radlal pat-tern so that the nonwoven floor bufflng pad crossed over these strlps as the table rotated. The floor bufflng pad was driven by a commerclal floor bufflng machlne operating at 175 rpm. The welght of the bufflng machlne forced the bufflng pad agalnst the rotatlng table. The bufflng pad was held and drlven by a conven-tlonal 430 mm dlameter holder/driver, the "Insta-Lok" Brand Driving Assembly, commerclally avallable from Mlnnesota Mlnlng and Manufacturlng Company. The buffing machlnP and holderJdriver had a combined welght of about 59 kg. At the beglnnlng of the test, the table and buffing machlne were caused to rotate and the buf-flng machlne was lowered 50 as to brlng its full welght onto the test pad. The test was contlnued untll the test pad was caused to dlslntegrate by the action of the four abraslve strlps. The tlme elapsed from the beginnlng of the test was recorded.
The average life of the buffing floor pads of thls exam-ple was 6.8 mlnutes; the range was from 2.0 to 11.0 mlnutes.
ComParatlve ExamPle A
A nonwoven web was made from a blend of 30~ by weight 15 denier melt bondable fiber and 70% by welght 50 denler tenslllzed polyester staple flber whlch had been stuffer box crimped, heat set, and cut to a length of 37 mm. The web was made according to the procedure descrlbed ln Example 1. The stuffer box crimped fibers had a tenacity of 4 g/denler, had 5 full cycle crlmps per 25 mm, and had a crlmp lndex of 26 before and after 5 mlnute expo-sure to a temperature of 125C. The nonwoven web welghed 465 g/m2 and was approxlmately 37 mm thlck. After saturatlon with the coating composition and cured as described in Example 1, the drled product welghed Trade-mark ~`

approximately 1170 g/mZ and was about 28 mm thick. When tested by the accelerated wea~ test described in Example 1, the average life of the control floor buffing pads was determined to be 1.1 minutes, with a standard deviation of 0.2 mlnute.

Exam~s 2 - 6 Nonwoven webs were formed from 70% by weight 60 denier helically srimped polyethylene terephthalate polyester fibers and 30% by weight melt bondable fibers as described in Example 1. The webs were then coated with the saturant described in Example 1. 1`able II sets forth the composition of these samples as well as the strength properties and the resistance to wear of the coated webs as determined according to the procedure described in Example 1.
TABLE II
Final Fiber Total thick- Ten2silel 2 20weig2ht weight ness ~10 N/m) Pad life Example (g/m ) (g/m2) (mm) MD XD ~min) SD (min) Control A 465 1170 28 S1 75 1.1 0.2 1 4551110 37 37 44 6.8 4.8 2 4051000 36 35 42 3.6 0.1 3 345 870 32 35 33 2.1 0.8 4 300 715 28 25 32 1.8 0.7 270 590 25 25 25 1.6 0.5 6 230 545 23 18 19 1.3 0.9 lMD means machine direction; XD means cross direction.
2 SD means standard deviation.
The data in Table I I show that buffing pads containing helically crimped fibers have longer pad life than do buffing pads containing only stuffer box crimped fibers, even when tl)e pads containing helically crimped fibers had thicknesses and weights below that of the pads containing only stuffer box cri~ped fibers.

Exa~le 7 A nonwoven web was prepared by blending of 30~ by weight lS denier melt bondable fiber (as described in Example l), 35% by weight 60 denier, helically crimped polyester staple fibers (as described in ~xample 1), and 35% by weight 140 denier helically crimped tensilized polyester staple fiber which had been cut to 75 to 100 mm in length. The 140 denier fiber had 1.6 crimps per 25 mm, had a tenacity of 3.4 g/denier, and had a crimp index of 52 before and after exposure to heat (5 minutes at 175C).
The nonwoven web was heated for three minutes to activate the melt bondable fibers to produce a web havinq a weight of 500 g/m2 and a thickness of 31 mm. After saturation with the saturant described in Example 1 and heat treatment to cure the binder, the total weight of the web was about 1180 g/m2. Thickness of the dry saturated product was 30 mm. Average accelerated wear life was 4.5 minutes, with a standard deviation of l.1 minutes.

Comparative Exam~
A nonwoven web was made by blending 30% by weight 15 denier staple binder fiber (as described in Example 1), 35% by weight 50 denier stuffer box crimped polyester staple fiber ~as described in Comparative Example A), and 35% by weight lO0 denier stuffer box crimped tensilized polyester staple fiber, which had been cut in 75 to 100 mm lengths. The nonwoven web was heated for 6 minutes at 125C to activate the melt bondable fibers. The nonwoven web initially weighed 490 g/m2. After saturation with the saturant described in Example 1 and curing to dry the saturant, the dry product weighed about 12]0 g/m2 and was about 25 mm thick. Average accelerated wear life was 2.7 minutes, with a standard deviation of 0.4 minute.

Example~ 8-11 Nonwoven abrasive products were made havlng various combinations of staple fibers, including conventional stuffer box crimped fibers, bicomponent melt bondable fibers, and helically crimped (edge crimped) fibers. Nonwoven webs were formed from the fibee compositions set forth in Table III by means of a Hergeth mechanical nonwoven forming machine.

T~sLE III
Weight of nonwoven Example Fiber description web (g/m2) 8 50~ 50 denier ~elt bondable copolyester 50% 65 denier helically crimped nylon 66 124 9 25% 50 denier melt bondable copolyesterl 75~ 65 denier helicfllly crimped nylon 66 131 50% 50 denier stuffer box crimped nylon 66 50~ 65 denier helically crimped nylon 66 135 11 100% 65 denier helically crimped 2S nylon 66 135 Comparative C lO0~ 75 denier stuffer box crimped nylon 66 138 Comparative D 50% 75 denier stuffer box crimped nylon 66 50% 50 denier melt bondable copolyester 130 The fiber was of the core and sheath type, the core comprising polyethylene terephthalate, the sheath comprising a copolyester of ethylene terephthalate and isophthalate.
The following table sets forth the properties of the 50 denier melt bondable fibers, 65 denier helically crimped fibers, and 75 denier stuffer box crimped fibers.

TA~LE IV
Crlmps index Crlmps lndex Tenaclty Crimps ~before heat (after heat Length Fiber (~/denler) /25 mm exP_sureLexPosure)(mm) 50 denler melt bondable 2.1 6.5 20.8 -- 70 65 denler hellcally crlmped 4.9 1.8 13.6 13.9 110 75 denler stuffer box crlmped 3.6 7.5 42.8 -- 50 The nonwoven webs of Examples 8, 9, and Comparative Example D were passed at the rate of 6 meters per mlnute through a 4 meter long hot air o~en at 170C to actlvate the melt bondable fibers. Bonded webs of Examples 8, 9, and Comparatlve Example D
and unbonded webs of Examples 10, 11, and Comparatlve Example C
were coated wlth the prebond reslnous blnder descrlbed in Table V
below.
TABLE V
Amount (percent Component by welaht) Polymethylene polyphenyl polylsocyanate (Mondur MRS, commerclally avallable from Mobay Co.) 38.58 Polypropylene glycol, PPG 425 12.86 Xylol . 44.58 Potasslum lactate capsules (75% actlve as descrlbed ln U.S.
Patent No. 3,860,565) 3.94 Slllcone Defoamer Y-30 commerclally avallable from Dow Cornlng Corp.)0.04 The coatlng was applled to the nonwoven web by means of a two-roll coater and then cured by passing the coated web through a hot alr oven 18 meters long at a temperature of 150C and at a Trade~mark _~ !

speed of 6 meters per mlnute.
The slurry coatlng set forth ln Table VI below was then applled by means of roll coatlng to each of the prebonded nonwoven webs of Examples 8, 9, lO, and 11 and Comparative Examples C and D.
TABLE VI
Amount (percent ComPonent bY welght) Propylene glycol monomethyl ether 23.02 Llthlum stearate 1.86 Phenol formaldehyde thermosettlng resln, 70% 22.22 Alumlnum oxlde abraslve, grade 100-15051.90 Colloldal slllca (Cabosll M5) 1.00 After being coated, the nonwoven webs were passed through a 4 meter long hot alr oven at 165C at 1.5 meter per mlnute to cure the reslnous blnder. Web welghts, coatlng welght, web thlcknesses, and tenslle are set forth ln Table VII.
TABLE VII
Flnlshed Flber Prebond Total web Tensile welght added dry welght thlcknessl ~N x 102 ~m~
Exam~le (a/m2) (a/m2) (a/m2) (mm) MD CD

Compar-ative C 138 85 1090 7 2410 30 Compar-ative D 130 85 1030 4 15 6 average of nine web thlckness measured under a pressure of 115 Pa Trade-mark 1 32 1 07~
Discs were cut Erom each of the wehs of Examples 8, 9, lO, and 11 and Comparative Examples C and D. These discs were lS0 mm in diameter and had 32 mm center holes.
The six discs were mounted on an arbor and compressed to 25 mm thickness by flanges 125 mm in diameter having a 32 mm center hole. The compressed and restrained discs were then rotated at 2000 rpm. A workpiece of type 6061 perforated aluminum sheet, S0 mm by 280 mm, was urged for three minutes against the rotating abrasive disc with a 22 ~
force and moved back and forth 150 mm against the rotating discs. The workpiece had 6.4 mm staggered pattern, had 6.4 mm diameter perforations, had holes spaced 8.7 mm on center, was 48~ open, and was 1.63 mm thick. Weight loss of the six discs and weight loss ~cut) of the perforated aluminum sheet were recorded in Table VIII.

~ABLE VIII
Cut Wear Efficiency 20Example ~q)(percent) cut/% wear3 8 0.64 21.2 0.041 9 0.53 13.2 0.049 0.36 7.9 0.062 11 0.47 6.4 0.094 Comparative C 0.30 8.1 0.045 Comparative D 0.61 21.9 0.039 The pads of Examples 10 and 11, which contained 50% or more helically crimped fibers, showed equal or better cut and much greater efEiciency than the pad of Comparative Example C. The pads of Examples ~ and 9 showed enhanced cut or efficiency when compared with the pad of Comparative Example D.
Various modifications and alterations of this invention will become apparent to those skilled in the art without departing from the scope and spirit of this ` -19- 1 32 1 073 invention, and it should be understood that this invention is not to be unduly limited to the illustrative embodiments set forth herein.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

l. An abrasive article comprising an open, lofty nonwoven web comprising helically crimped synthetic organic fibers wherein the web comprises at least 30% by weight of helically crimped fibers.
2. The article of claim 1 wherein the web comprises at least 50% by weight of helically crimped fibers.
3. The article of claim 1 wherein the web comprises at least 70% by weight of helically crimped fibers.
4. The article of claim 1 wherein said web further comprises melt bondable fibers.
5. The article of claim 1 wherein said web further comprises stuffer box crimped fibers.
6. The article of claim l wherein said helically crimped fibers are stabilized.
7. The article of claim l wherein said helically crimped fibers have from about 1 to about 15 crimps per mm.
8. The article of claim 1 wherein said helically crimped fibers have a crimp index from about 35% to about 70%.
9. The article of claim l wherein said helically crimped fibers comprise polyethylene terephthalate.
10. The article of claim l wherein said helically crimped fibers comprise nylon.
11. The article of claim 1 wherein said web further contains a binder.
12. The article of claim 1 wherein said web further contains abrasive particles.