U.S. patent application number 17/042862 was filed with the patent office on 2021-01-21 for abrasive products comprising impregnated woven fabric and abrasive particles.
The applicant listed for this patent is HABASIT AG. Invention is credited to Mark DAVIES, Michael TYLER, Brent WHITEHEAD, Bodo WIXMERTEN.
Application Number | 20210016419 17/042862 |
Document ID | / |
Family ID | 1000005165097 |
Filed Date | 2021-01-21 |
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United States Patent
Application |
20210016419 |
Kind Code |
A1 |
WHITEHEAD; Brent ; et
al. |
January 21, 2021 |
ABRASIVE PRODUCTS COMPRISING IMPREGNATED WOVEN FABRIC AND ABRASIVE
PARTICLES
Abstract
An abrasive product comprising an impregnated woven fabric
comprising: a) A first layer of first uncrimped weft multifilaments
(301-308) b) a second layer of second uncrimped weft multifilaments
(309-316); wherein for each of the first uncrimped weft
multifilaments (301-308) there is one corresponding second
uncrimped weft multifilament (309-316), and vice versa, to form
successive multifilament pairs (301/309, 302/310, 303/311, 304/312,
305/313, 306/314, 307/315, 308/316) of first and second uncrimped
weft multifilaments; c) crimped warp filaments (41-44) having four
different weave types d-c4, but each weave type consisting of
entwining around first uncrimped weft multifilaments; passing
between first and second uncrimped weft multifilaments; entwining
around second uncrimped weft multifilaments; and passing again
between first and second uncrimped weft multifilaments; d)
uncrimped warp filaments (4) passing between first (301-308) and
second (309-316) uncrimped weft multifilaments of all multifilament
pairs (301/309, 302/310, 303/311, 304/312, 305/313, 306/314,
307/315, 308/316). The abrasive product furthermore comprises
either a first particulate abrasive material (9) embedded into the
first topmost surface (8) of the first top layer (7), or a
prefabricated abrasive sheet (101) comprising a matrix material, a
first top sheet surface (111) and first abrasive particles (91)
embedded into the first top sheet surface (111).
Inventors: |
WHITEHEAD; Brent; (Bacup,
Lancashire, GB) ; TYLER; Michael; (Harrogate, GB)
; DAVIES; Mark; (Sketty, Swansea, GB) ; WIXMERTEN;
Bodo; (Allschwil, CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HABASIT AG |
Reinach |
|
CH |
|
|
Family ID: |
1000005165097 |
Appl. No.: |
17/042862 |
Filed: |
March 25, 2019 |
PCT Filed: |
March 25, 2019 |
PCT NO: |
PCT/EP2019/057433 |
371 Date: |
September 28, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B24D 11/02 20130101;
D03D 11/00 20130101; D03D 25/005 20130101; D03D 13/004
20130101 |
International
Class: |
B24D 11/02 20060101
B24D011/02; D03D 11/00 20060101 D03D011/00; D03D 25/00 20060101
D03D025/00; D03D 13/00 20060101 D03D013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 27, 2018 |
EP |
18164287.7 |
Claims
1. An abrasive product comprising i) a woven fabric which is
impregnated with an impregnation (6) comprising or consisting of a
thermoplastic, thermoplastic elastomer, thermoset, elastomer or
mixture thereof; the fabric comprising: a) A first layer (A) of
first uncrimped weft multifilaments (301-308) running essentially
in parallel to each other and being spaced apart from each other by
a distance D; b) a second layer (B) of second uncrimped weft
multifilaments (309-316) running essentially in parallel to each
other and being spaced apart from each other by said distance D;
wherein for each of the first uncrimped weft multifilaments
(301-308) there is one corresponding second uncrimped weft
multifilament (309-316), and vice versa, to form successive
multifilament pairs (301/309, 302/310, 303/311, 304/312, 305/313,
306/314, 307/315, 308/316), each such successive multifilament pair
being designable with a unique and ascending integer index N; c)
crimped warp filaments (41-44) having one of the following weave
types c1-c4: c1-entwine around first uncrimped weft multifilaments
(302, 306) of all multifilament pairs (302/310, 306/314) with
indexes N fulfilling (N mod 4)=0, such indexes N being designated
as N.sub.A; pass between first (303, 307) and second (311, 315)
uncrimped weft multifilaments of all multifilament pairs (303/311,
307/315) with indexes N fulfilling (N mod 4)=1, such indexes N
being designated as N.sub.B; entwine around second uncrimped weft
multifilaments (312, 316) of all multifilament pairs (304/312,
308/316) with indexes N fulfilling (N mod 4)=2, such indexes N
being designated as N.sub.C; and pass between first (301, 305) and
second (309, 313) uncrimped weft multifilaments of all
multifilament pairs (301/309, 305/313) with indexes N fulfilling (N
mod 4)=3, such indexes N being designated as N.sub.D; or c2-entwine
around second uncrimped weft multifilaments (310, 314) of all
multifilament pairs with said indexes N.sub.A; pass between first
(303, 307) and second (311, 315) uncrimped weft multifilaments of
all multifilament pairs (303/311, 307/315) with said indexes
N.sub.B; entwine around first uncrimped weft multifilaments (304,
308) of all multifilament pairs (304/312, 308/316) with said
indexes N.sub.C; and pass between first and second uncrimped weft
multifilaments of all multifilament pairs (301/309, 305/313) with
said indexes N.sub.D; or c3-pass between first (302, 306) and
second (310, 314) uncrimped weft multifilaments of all
multifilament pairs (302/310, 306/314) with said index N.sub.A;
entwine around first uncrimped weft multifilaments (303, 307) of
all multifilament pairs (303/311, 307/315) with said indexes
N.sub.B; pass between first (304, 308) and second (312, 316)
uncrimped weft multifilaments (304/312, 308/316) of all
multifilament pairs with said indexes N.sub.C; and entwine around
second uncrimped weft multifilaments (309, 313) of all
multifilament pairs (301/309, 305/313) with said indexes N.sub.D;
or c4-pass between first (302, 306) and second (310, 314) uncrimped
weft multifilaments of all multifilament pairs (302/310, 306/314)
with said indexes N.sub.A; entwine around second uncrimped weft
multifilaments (311, 315) of all multifilament pairs (303/311,
307/315) with said indexes N.sub.B; pass between first (304, 308)
and second (312, 316) uncrimped weft multifilaments of all
multifilament pairs (304/312, 308/316) with said indexes N.sub.C;
and entwine around first uncrimped weft multifilaments (301, 305)
of all multifilament pairs (301/309, 305/313) with said indexes
N.sub.D; d) uncrimped warp filaments (1) passing between first
(301-308) and second (309-316) uncrimped weft multifilaments of all
multifilament pairs (301 /309, 302/310, 303/311, 304/312, 305/313,
306/314, 307/315, 308/316); and e) optionally, crimped antistatic
warp filaments having one of the weave types c1, c2, c3 or c4
defined above; provided that crimped warp filaments (41-44) of all
four above defined weave types c1, c2, c3 and c4 are present;
wherein the fabric does not comprise any other crimped warp
filaments, besides said crimped warp filaments (41-44) and said
optional crimped s antistatic warp filaments; and wherein (N mod 4)
designates the remainder obtained by Euclidean integer division of
N by 4; and either: iia) immediately adjoining to one side of the
impregnated fabric a first top layer (7) with a first topmost
surface (8) comprising or consisting of the same thermoplastic,
thermoplastic elastomer, thermoset, elastomer or mixture thereof as
in the impregnation (6) but being devoid of fabric, and iiia) a
first particulate abrasive material (9) embedded into the first
topmost surface (8) of the first top layer (7); or iib) optionally,
immediately adjoining to one side of the impregnated fabric, a
first cover layer (71) comprising or consisting of the same
thermoplastic, thermoplastic elastomer, thermoset, elastomer or
mixture thereof as in the impregnation (6) but being devoid of
fabric; iiib) adjoining to said one side of the impregnated fabric,
or, if the first cover layer (71) is present, to said first cover
layer (71), a first prefabricated abrasive sheet (101) comprising a
matrix material, a first top sheet surface (111) and first abrasive
particles (91) embedded into the first top sheet surface (111),
wherein said matrix material is different from the impregnation
(6).
2. The abrasive product of claim 1, wherein each uncrimped warp
filament (1) is separated in weft direction from the next uncrimped
warp filament (1) by an even number of crimped warp filaments
(41-44), said even number being at least 2.
3. The abrasive product of claim 1, wherein each uncrimped warp
filament (1) is sandwiched in weft direction by two immediately
adjacent crimped warp filaments (42,43).
4. The abrasive product of claim 1, wherein the crimped warp
filaments of weave types c1 (41) and c2 (42) defined in claim 1 are
always present pairwise and immediately adjacent to each other in
weft direction, and the crimped warp filaments of weave types c3
(43) and c4 (44) defined in claim 1 are always present pairwise and
immediately adjacent to each other in weft direction.
5. The abrasive product of claim 1, wherein the numerical ratio of
crimped warp filaments c) (41-44) to uncrimped warp filaments d)
(1) is in the range of 4:1 to 12:1.
6. The abrasive product of claim 1, wherein the crimped warp
filaments c) (41, 42, 43, 44) and the uncrimped warp filaments d)
(4) are arranged in repetitive units in weft direction, in which
repetitive units the order in which the uncrimped warp filaments d)
(1) and the crimped warp filaments of above weave types c1 (41), c2
(42), c3 (43) and c4 (44) are arranged in weft direction is always
the same.
7. The abrasive product of claim 1, comprising the crimped
antistatic warp filaments e).
8. The abrasive product of claim 1, consisting of first uncrimped
weft multifilaments a) (301-308), second uncrimped weft
multifilaments b) (309-316), crimped warp filaments c) (41-44),
uncrimped warp filaments d) (1) and optional crimped antistatic
warp filaments e).
9. The abrasive product of claim 1, comprising iia) and iiia)
defined in claim 1.
10. The abrasive product of claim 9, which is an endless abrasive
belt, and wherein the warp direction of the fabric is in the travel
direction of the belt.
11. The abrasive product of claim 9, furthermore comprising: iv)
immediately adjoining to the other side of the impregnated fabric a
second top layer with a second topmost surface and being made of
the same thermoplastic, thermoplastic elastomer, thermoset,
elastomer or mixture thereof as in the impregnation (6) in the
fabric but being devoid of fabric; and v) a second particulate
abrasive material embedded into the second topmost surface of the
second top layer.
12. The abrasive product of claim 1, comprising iib) and iiib)
defined in claim 1.
13. The abrasive product of claim 12, furthermore comprising: iv)
optionally, immediately adjoining to the other side of the
impregnated fabric, a second cover layer (72) comprising or
consisting of the same thermoplastic, thermoplastic elastomer,
thermoset, elastomer or mixture thereof as in the impregnation (6)
but being devoid of fabric; v) adjoining to said other side of the
impregnated fabric, or, if the second cover layer (72) is present,
to said second cover layer (72), a second prefabricated abrasive
sheet (102) comprising a matrix material, a second top sheet
surface (112) and second abrasive particles (92) embedded into the
second top sheet surface (112), wherein said matrix material is
different from the impregnation (6).
14. The abrasive product of claim 12, which is an abrasive pad or
abrasive disk.
15. The abrasive product of claim 1, wherein the impregnation (6)
is of a thermoplastic or thermoplastic elastomer, in particular a
TPU.
Description
TECHNICAL FIELD
[0001] The present application relates to fabric containing
abrasive products.
PRIOR ART
[0002] Abrasive products are widely established and used in a
variety of industries, such as aerospace, automotive equipment
manufacturing, general industries, marine, metal working, paint
preparation, precision grinding and finishing, primary metal,
thermal spraying, transportation heavy equipment and
woodworking.
[0003] Abrasive products may comprise of a base fabric, which is
usually of polyester, cotton or aramid, a fabric coated layer which
may e.g. be of rubber, elastomer, thermoplastic or thermoset
materials which are either/or chemically or physically attached to
the base fabric and a top layer comprising of various abrasive
compounds and particles. Categories of abrasive products are,
without limitation: wet/dry bands, file, narrow, portable, super
abrasive and micro-finishing, wide and flat finishing belts and
materials. Abrasive products may be in the form of pads, disks or
belts.
[0004] Abrasive products inevitably experience a strong shear
stress during their usage. The shear occurs because of the
adherence of the backside of the abrasive product to the moving
support and because of the friction between the front, abrading
side of the abrasive product and the surface of the application to
be abraded. The two forces acting on the backside and the front
side of the abrasive product point in opposite directions, thus
causing shear inside the abrasive product. This shear may be
unidirectional, if the abrasive product is an abrasive belt running
in only one direction while abrading the application to be abraded.
The shear may however also be bidirectional, if the abrasive
product is e.g. a pad which is moved in two directions, in
particular in an approximately circular motion, over the
application to be abraded.
[0005] JP 2013/240839 discloses an abrasive cloth containing a
fabric base material which may be a plain, twill or satin weave.
The warps are at least in part core-sheath fibres. The cloth is
used in an abrasive belt.
[0006] JP 2011/093083 discloses a laminated polishing pad
comprising a multifilament hard-twist-yarn textile and a base
material whose Asker A hardness is 60. The textile may be plain
weave, twill weave or satin, wherein plain weave is preferable in
view of strongest binding force of warp and weft.
[0007] WO 2012/042040 mentions that in coated abrasives in the form
of "sheets, belts, mop discs, flap discs" for bonding the abrasives
"mainly phenolic resins are used" if high performance is needed,
otherwise "urea resins and also animal glue", and for wet grinding
"epoxy, urethane or alkyd resins".
[0008] US 2010/0323574 discloses a fabric having 4 layers of weft
filaments extending in levels N1, N3, N5 and N7; warp fibres A, B
and C all having the same weave type and being interwoven with said
weft filaments of levels N1, N3, N5 and N7; warp fibres G, H and I
all having the same, second weave type, and also being interwoven
with said weft filaments of levels N1, N3, N5 and N7; further weft
filaments extending in levels N2, N4 and N6; and warp filaments D,
J, E, K, F and L not being interwoven with any weft filaments. This
fabric is for use in producing composite material parts such as
stays, rods and struts of landing gear.
[0009] GB 1 390 603 discloses a fabric containing upper and lower
layers of weft filaments, reinforcing wires (extending in the warp
direction), warp-wise extending yarns running in parallel with the
reinforcing wires and not being interwoven with the upper and lower
weft filaments, binder weft yarns being interwoven with both the
upper and lower weft filaments, and warp yarns being interwoven
either only with the upper weft filaments or only with the lower
weft filaments. It also discloses a conveyor belt comprising that
fabric and being impregnated with an elastomeric material,
preferably a PVC plastisol.
[0010] The present invention aims to provide improved fabrics for
abrasive products and abrasive products containing them.
SUMMARY
[0011] The present invention provides
[0012] [1] A woven fabric comprising:
[0013] a) A first layer (A) of first uncrimped weft multifilaments
running essentially in parallel to each other and being spaced
apart from each other by a distance D;
[0014] b) a second layer (B) of second uncrimped weft
multifilaments running essentially in parallel to each other and
being spaced apart from each other by said distance D;
[0015] wherein for each of the first uncrimped weft multifilaments
there is one corresponding second uncrimped weft multifilament, and
vice versa, to form successive multifilament pairs, each such
successive multifilament pair being designable with a unique and
ascending integer index N;
[0016] c) crimped warp filaments having one of the following weave
types c1-c4:
[0017] c1-entwine around first uncrimped weft multifilaments of all
multifilament pairs with indexes N fulfilling (N mod 4)=0, such
indexes N being designated as N.sub.A; pass between first and
second uncrimped weft multifilaments of all multifilament pairs
with indexes N fulfilling (N mod 4)=1, such indexes N being
designated as N.sub.B; entwine around second uncrimped weft
multifilaments of all multifilament pairs with indexes N fulfilling
(N mod 4)=2, such indexes N being designated as N.sub.C; and pass
between first and second uncrimped weft multifilaments of all
multifilament pairs with indexes N fulfilling (N mod 4)=3, such
indexes N being designated as N.sub.D; or
[0018] c2-entwine around second uncrimped weft multifilaments of
all multifilament pairs with said indexes N.sub.A; pass between
first and second uncrimped weft multifilaments of all multifilament
pairs with said indexes N.sub.B; entwine around first uncrimped
weft multifilaments of all multifilament pairs with said indexes
N.sub.C; and pass between first and second uncrimped weft
multifilaments of all multifilament pairs with said indexes
N.sub.D; or
[0019] c3-pass between first and second uncrimped weft
multifilaments of all multifilament pairs with said index N.sub.A;
entwine around first uncrimped weft multifilaments of all
multifilament pairs with said indexes N.sub.B; pass between first
and second uncrimped weft multifilaments of all multifilament pairs
with said indexes N.sub.C; and entwine around second uncrimped weft
multifilaments of all multifilament pairs with said indexes
N.sub.D; or
[0020] c4-pass between first and second uncrimped weft
multifilaments of all multifilament pairs with said indexes
N.sub.A; entwine around second uncrimped weft multifilaments of all
multifilament pairs with said indexes N.sub.B; pass between first
and second uncrimped weft multifilaments of all multifilament pairs
with said indexes N.sub.C; and entwine around first uncrimped weft
multifilaments of all filament pairs with said indexes N.sub.D;
[0021] d) uncrimped warp filaments passing between first and second
uncrimped weft multifilaments of all multifilament pairs; and
[0022] e) optionally, crimped antistatic warp filaments having one
of the weave types c1, c2, c3 or c4 defined above;
[0023] provided that crimped warp filaments of all four above
defined weave types c1, c2, c3 and c4 are present;
[0024] wherein the fabric does not comprise any other crimped warp
filaments, besides said crimped warp filaments and said optional
crimped antistatic warp filaments.
[0025] [2] The fabric of above [1], wherein each uncrimped warp
filament is separated in weft direction from the next uncrimped
warp filament by an even number of crimped warp filaments, said
even number being at least 2.
[0026] [3] The fabric of above [1] or [2], wherein each uncrimped
warp filament is sandwiched in weft direction by two immediately
adjacent crimped warp filaments.
[0027] [4] The fabric of one of above [1] to [3], wherein the
crimped warp filaments of weave types c1 and c2 defined in above
[1] are always present pairwise and immediately adjacent to each
other in weft direction, and the crimped warp filaments of weave
types c3 and c4 defined in above [1] are always present pairwise
and immediately adjacent to each other in weft direction.
[0028] [5] The fabric of one of above [1] to [4], wherein the
numerical ratio of crimped warp filaments c) to uncrimped warp
filaments d) is in the range of 4:1 to 12:1.
[0029] [6] The fabric of one of above [1] to [5], wherein the
crimped warp filaments c) and the uncrimped warp filaments d) are
arranged in repetitive units in weft direction, in which repetitive
units the order in which the uncrimped warp filaments d) and the
crimped warp filaments of above weave types c1, c2, c3 and c4 are
arranged in weft direction is always the same.
[0030] [7] The fabric of one of above [1] to [6], comprising the
crimped antistatic warp filaments e).
[0031] [8] The fabric of one of above [1] to [7], consisting of
first uncrimped weft multifilaments a), second uncrimped weft
multifilaments b), crimped warp filaments c), uncrimped warp
filaments d) and optional crimped antistatic warp filaments e).
[0032] [9] An abrasive product comprising:
[0033] i) a fabric according to any one of above [1] to [8] which
is impregnated with an impregnation comprising or consisting of a
thermoplastic, thermoplastic elastomer, thermoset, elastomer or a
mixture thereof;
[0034] ii) immediately adjoining to one side of the impregnated
fabric a first top layer with a first topmost surface comprising or
consisting of the same thermoplastic, thermoplastic elastomer,
thermoset, elastomer or mixture thereof as in the impregnation in
the fabric, but being devoid of fabric, and
[0035] iii) a first particulate abrasive material embedded into the
first topmost surface of the first top layer.
[0036] [10] The abrasive product of above [9], which is an endless
abrasive belt.
[0037] [11] The abrasive product of above [9], furthermore
comprising:
[0038] iv) immediately adjoining to the other side of the
impregnated fabric a second top layer with a second topmost surface
and comprising or consisting of the same thermoplastic,
thermoplastic elastomer, thermoset, elastomer or mixture thereof as
in the impregnation (6) in the fabric, but being devoid of fabric;
and
[0039] v) a second particulate abrasive material embedded into the
second topmost surface of the second top layer.
[0040] [12] An abrasive product comprising:
[0041] i) a fabric according to any one of above [1] to [8] which
is impregnated with an impregnation comprising or consisting of a
thermoplastic, thermoplastic elastomer, thermoset or elastomer or a
mixture thereof;
[0042] ii) optionally, immediately adjoining to one side of the
impregnated fabric, a first cover layer comprising or consisting of
the same thermoplastic, thermoplastic elastomer, thermoset,
elastomer or mixture thereof as in the impregnation in the fabric,
but being devoid of fabric;
[0043] iii) adjoining to said one side of the impregnated fabric,
or, if the first cover layer is present, to said first cover layer
a first prefabricated abrasive sheet with a first top sheet surface
containing first abrasive particles embedded into the first top
sheet surface.
[0044] [13] The abrasive product of above [12], furthermore
comprising:
[0045] iv) optionally, immediately adjoining to the other side of
the impregnated fabric, a second cover layer comprising or
consisting of the same thermoplastic, thermoplastic elastomer,
thermoset, elastomer or mixture thereof as the impregnation in the
fabric, but being devoid of fabric;
[0046] iv) adjoining to said other side of the impregnated fabric,
or, if the second cover layer is present, to said second cover
layer, a second prefabricated abrasive sheet with a second top
sheet surface containing second abrasive particles embedded into
the second top sheet surface.
[0047] [14] The abrasive product of above [12] or [13], which is an
abrasive pad or abrasive disk.
[0048] [15] The abrasive product of one of above [11] to [14],
wherein the impregnation is comprises or consists of a
thermoplastic or thermoplastic elastomer, in particular a TPU.
BRIEF DESCRIPTION OF THE FIGURES
[0049] FIGS. 1-3 are schematic representations of an embodiment of
the fabric of the invention, namely FIG. 1 as a cross-sectional
view in warp direction, FIG. 2 as a top view, and FIG. 3 again as
cross-sectional view, but with only one crimped warp filament,
either under unsheared condition (top of FIG. 3) or under attempted
20.degree. shear (bottom of FIG. 3);
[0050] FIG. 4 contains a schematic representation of a prior art
fabric;
[0051] FIG. 5 contains schematic representations of the fabric of
the invention of FIG. 1, as a cross-sectional views in weft
direction;
[0052] FIGS. 6 and 7 are schematic cross-sectional views of an
embodiment of an abrasive belt and of an abrasive pad or disk of
the invention, respectively, each containing the fabric of FIG.
1.
DETAILED DESCRIPTION OF THE INVENTION
[0053] This invention provides to use a matrix of a thermoplastic,
thermoset or elastomer material or mixture thereof, which matrix is
flooded directly into the unidirectional reinforced multi-layer
woven fabric component woven joined layers, providing a fully
impregnated, physical entanglement of matrix and fabric, wherein
the fabric is embedded and entangled in the matrix. Such
entanglement aids in minimising layer separation, improves the
polymer matrix bonding/adhesion characteristics and resistance to
product ingress/commination issues and generally improves belt
performance and service life, through good wear characteristics
whilst providing good integral and dimensional flexibly.
[0054] The motion of inventive abrasive products over the good to
be abraded may be either in the warp or the weft direction of the
fabric, or both. In one special embodiment the motion may be
approximately, or exactly, circular. The inventive fabric and the
abrasive products of the invention containing it exhibit equally
good resistance to shear delamination when shearing is in either
warp direction or weft direction. This is surprising because the
inventive fabric differs in both weave structure and filament
density in warp direction from weave structure and filament density
in weft direction. The differences in weave structure are e.g.
because one of the directions of the fabric (warp or weft
direction, typically the warp direction) must also satisfy the
requirements of a traction layer in an abrasive belt; this
requirement is not necessary in the other direction (weft or warp
direction, typically the weft direction). From the sole point of
view of equally good resistance to shear delamination in both warp
and weft direction a fabric having identical weave structure and
filament count in both warp and weft directions would be most
desirable.
[0055] Since the inventive fabric offers equally good resistance to
shear delamination in either warp direction or weft direction, the
orientation of the fabric within the inventive abrasive products
with respect to the predominant, or sole, abrasive motion direction
does not matter. If the abrasive product is however an abrasive
belt, then it is preferred that the warp direction of the fabric is
in the travel direction of the belt.
[0056] A possible theoretical explanation for the improvement in
resistance to shear delamination in warp direction of the inventive
fabric will be given with reference to FIGS. 1-4. The fabric of the
invention firstly offers good resistance to shear delamination in
weft direction because all weft filaments are multifilaments,
engaging more intimately with an impregnation adhering to them than
monofilaments possibly could. A possible further theoretical
explanation for the improvement in resistance to shear delamination
in weft direction will be given with reference to FIG. 5.
[0057] In the inventive fabric all uncrimped weft filaments are
multifilaments (designated in the following as "uncrimped weft
multifilaments"). The uncrimped weft multifilaments are preferably
made of polyester, such as PET. The titer of the uncrimped weft
multifilaments, particularly if made of polyester such as PET, is
preferably in the range of 670 to 2100 dtex. Also preferably, the
tenacity of the uncrimped weft multifilaments is preferably in the
range of 15 to 250 cN/tex, more preferably in the range of 30 to
100 cN/tex and most preferably of 60 to 80 cN/tex. Also preferably,
their heat shrinkage (percentual length reduction under heating for
2 min at 180.degree. C.) is in the range of 0.5 to 15%, more
preferably of 0.5 to 5% and most preferably of 1 to 2%. Also
preferably, the uncrimped weft multifilaments may preferably have a
slight or S- or Z-twist, or no twist at all, with the number of
turns per metre preferably being in the range of 0 to 50, more
preferably of 0 to 30 and most preferably of 0 to 10. The uncrimped
weft multifilaments may optionally be spun together with staple
fibres, such as polyester or a natural fibre such as cotton, e.g.
by the known "core-spinning" process (see e.g. U.S. Pat. No.
2,992,150 A), to further enhance the adhesion of the impregnation
thereto. Preferably however, the uncrimped weft multifilaments are
devoid of such staple fibres. The impregnation adheres sufficiently
to such weft multifilaments even in the absence of staple fibres,
by virtue of the overall inventive fabric.
[0058] The fabric of the invention contains first and second
uncrimped weft multifilaments of the abovementioned type. To each
of the first uncrimped weft multifilaments there is one
corresponding second uncrimped weft multifilament, and vice versa,
to form successive multifilament pairs, to each of which is
assignable an integer index N. This index N is arbitrary, provided
that it increases with the order of the successive multifilament
pairs in warp direction. The index N may be in a range of N.sub.min
to N.sub.max, wherein N.sub.min is the lowest possible index
typically assigned to the first multifilament pair of the specimen
of fabric in question, and wherein N.sub.max is the highest
possible index typically assigned to the last multifilament pair of
the specimen of fabric in question. Whether a given index N is
assigned the designation N.sub.A, N.sub.B, N.sub.C or N.sub.D
depends on the result of the modulo 4 operation performed on N,
which as used here is the remainder obtained by the so-called
"Euclidean integer division" of N by 4.
[0059] All crimped warp filaments are preferably also
multifilaments, spun yarns or a combination of multifilament yarns
and staple fibres spun together by the commonly known
"core-spinning" process. Any such crimped warp filaments are
preferably devoid of natural fibres, such as cotton, jute, hemp or
cellulose-based fibres. The impregnation adheres sufficiently to
the inventive fabric even in the absence of such natural fibres.
The crimped warp filaments are preferably made of polyester such as
PET. The titer of the crimped warp filaments is preferably in the
range of 550 to 2000 dtex, particularly if made from polyester such
as PET. Also preferably, the tenacity of the crimped warp filaments
is preferably in the range of 15 to 250 cN/tex, more preferably in
the range of 15 to 40 cN/tex and most preferably of 20 to 30
cN/tex. Also preferably, their heat shrinkage (percentual length
reduction under heating for 2 min at 180.degree. C.) is in the
range of 0.5 to 15%, more preferably of 5 to 15% and most
preferably of 8 to 12%. Also preferably, the crimped warp yarns may
preferably have an S- or Z-twist, with the number of turns per
metre preferably being in the range of 0 to 400, more preferably of
250 to 400 and most preferably of 300 to 400. Alternatively, their
degree of twisting may preferably be in the range of 5 to 15%, more
preferably of 7 to 13% and most preferably of 9 to 11%.
[0060] The crimped warp filaments have one of four different weave
types c1-c4. These four weave types are as in following Table 1,
using the above indexes N.sub.A-N.sub.D to define the multifilament
pairs in question:
TABLE-US-00001 TABLE 1 weave type N.sub.A N.sub.B N.sub.C N.sub.D
c1 entwine pass between entwine pass between around first first and
second around second first and second uncrimped weft uncrimped weft
uncrimped weft uncrimped weft multifilament multifilaments multi
multifilaments of such of such multifilament of such multifilament
multifilament of such multifilament pairs pairs multifilament pairs
pairs c4 pass between entwine pass between entwine first and second
around second first and second around first uncrimped weft
uncrimped weft uncrimped weft uncrimped weft multifilaments
multifilaments multifilaments multifilaments of such of such of
such of such multifilament multifilament multifilament
multifilament pairs pairs pairs pairs c2 entwine pass between
entwine pass between around second first and second around first
first and second uncrimped weft uncrimped weft uncrimped weft
uncrimped weft multifilaments multifilaments multifilament
multifilaments of such of such of such of such multifilament
multifilament multifilament multifilament pairs pairs pairs pairs
c3 pass between entwine pass between entwine first and second
around first first and second around second uncrimped weft
uncrimped weft uncrimped weft uncrimped weft multifilaments
multifilament multifilaments multifilament of such of such of such
of such multifilament multifilament multifilament multifilament
pairs pairs pairs pairs
[0061] That is, the above weave types c1, c4, c2 and c3 differ only
in that their entwining around first uncrimped weft multifilaments,
their passing between first and second uncrimped weft
multifilaments, their entwining around second uncrimped weft
multifilaments and their passing between first and second uncrimped
weft multifilaments is permutated cyclically over the indexes
N.sub.A, N.sub.B, N.sub.C and N.sub.D when going from c1 to c4 to
c2 to c3.
[0062] It is preferred for the fabric of the invention that crimped
warp filaments of above weave types c1 and c2 always appear
pairwise and immediately adjacent to each other in weft direction,
and that crimped warp filaments of above weave types c3 and c4
always appear pairwise and immediately adjacent to each other in
weft direction.
[0063] The fabric of the invention contains crimped warp filaments
of all weave types c1-c4 discussed above. Preferably it contains
crimped warp filaments of each of the four weave types c1, c2, c3
and c4 in equal numbers, more preferably also in equal numbers
within each above discussed repetitive unit.
[0064] All uncrimped warp filaments are preferably multifilaments,
or a plurality of such multifilaments, e.g. 3-8 such
multifilaments, arranged in parallel and immediately adjacent to
each other. The uncrimped warp filaments are preferably made of
polyester, in particular of PET, or aramid. The titer of the
uncrimped warp filaments (or, if there is a plurality of
multifilaments, the sum of the titer of all them) is preferably in
the range of 500 to 5000 dtex. More preferably, if the uncrimped
warp filaments are of polyester such as PET, their titer (or, if
there is a plurality of multifilaments, the sum of the titer of all
them) is in the range of 550 to 2000 dtex; if they are of aramid,
then their titer (or, if there is a plurality of multifilaments,
the sum of the titer of all them) is more preferably in the range
of 440 to 3500 dtex. Also preferably, the tenacity of the uncrimped
warp filaments (or, if there is a plurality of multifilaments, the
overall tenacity of the entire plurality) is preferably in the
range of 15 to 250 cN/tex, more preferably in the range of 30 to
100 cN/tex and most preferably of 60 to 80 cN/tex. Also preferably,
their heat shrinkage (percentual length reduction under heating for
2 min at 180.degree. C.) is in the range of 0.5 to 15%, more
preferably of 0.5 to 5% and most preferably of 1 to 2%. Also
preferably, the uncrimped warp multifilaments may preferably have a
slight S- or Z-twist, or no twist, with the number of turns per
metre preferably being in the range of 0 to 400, more preferably of
50 to 300 and most preferably of 70 to 140.
[0065] It is more preferred for the fabric of the invention that
the crimped warp filaments and the uncrimped warp filaments are
present in repetitive units in weft direction, wherein the order in
which crimped warp filaments with weave type c1, crimped warp
filaments with weave type c2, crimped warp filaments with weave
type c3, crimped warp filaments with weave type c4 and uncrimped
warp filaments are arranged in weft direction is always the
same.
[0066] Preferably also, each uncrimped warp filament is separated
in weft direction from the next uncrimped warp filament by an even
number of crimped warp filaments, wherein that even number is at
least 2. More preferably here, any crimped warp filaments
immediately adjacent have either the above discussed weave types
c1/c2 or the weave types c3/c4.
[0067] More preferably also each uncrimped warp filament is
sandwiched in weft direction by two immediately adjacent crimped
warp filaments. That is, two successive uncrimped warp filaments
are preferably never immediately adjacent to each other in weft
direction; there is preferably always at least one, preferably two
(see above) crimped warp filaments in between.
[0068] There are typically 4 to 12 crimped warp filaments per
uncrimped warp filament, wherein the specific ratio of 12:1 applies
in particular to the above mentioned embodiment of the uncrimped
warp filament being a plurality of filaments arranged in parallel
and immediately adjacent to each other. Another most preferred
embodiment is a ratio of crimped warp filaments to uncrimped warp
filaments of 4:1.
[0069] In one specific preferred embodiment of the fabric the ratio
of crimped warp filaments to uncrimped warp filaments may be 4:1.
If therein these warp filaments occur in repetitive units, wherein
the order of the filaments in these repetitive units is always the
same, then exemplary such orders are C(c1)-C(c2)-UC-C(c3)-C(c4) or
any cyclic permutation thereof, wherein C designates crimped warp
filaments and UC designates an uncrimped warp filament, and the
weave types are indicated in parentheses.
[0070] In another preferred embodiment of the fabric the ratio of
crimped warp filaments to uncrimped warp filaments may be 12:1. If
therein the warp filaments occur in repetitive units, wherein the
order of the filaments is always the same, then exemplary such
orders are C(c3)-C(c4)-C(c1)-C(c2)-C(c3)-C(c4)-UC-C(c1)
-C(c2)-C(c3)-C(c4)-C(c1)-C(c2) or any cyclic permutation thereof,
wherein C and UC are as above, and the weave types are indicated in
parentheses.
[0071] All of the foregoing uncrimped weft, crimped warp and
uncrimped warp multifilaments may preferably be in the form of
bicomponent fibres. Subclasses of such bicomponent fibres are those
wherein a plurality of filaments of a higher-melting polymer are
combined with a plurality of filaments of lower-melting polymer; or
a plurality of filaments of a higher-melting polymer is embedded
in, or sheathed by, a lower-melting polymer Here, "higher melting"
and "lower melting" are relative to each other. The purpose of such
bicomponent fibres is that either upon weaving or thereafter, the
bicomponent fibres are heated such that only the lower-melting
material softens, fusing adjacent multifilaments together, in
particular at the overcrossing sections thereof. Upon re-cooling, a
fabric results which, due to the hotmelt adhesive joining of the
overcrossing sections, exhibits increased resistance towards
deformation under shear, and thus towards shear delamination.
[0072] Examples of bicomponent fibres wherein a plurality of
filaments of a higher-melting polymer is embedded in lower melting
polymer are the so-called "islands-in-a-sea" filaments; examples of
bicomponent fibres wherein a plurality of filaments of a
higher-melting polymer is sheathed by a lower molecular weight
polymer are the "core-sheath" fibres, e.g. of mass ratio
core:sheath of 50:50 to 80:20; and either concentric or eccentric.
Preferred are said core-sheath bicomponent fibres, most preferred
of the concentric type.
[0073] The difference in melting point or melting interval may be
controlled e.g. by having the same type of polymer, but with two
different molecular weights, or by combining two chemically
different but compatible polymers. Examples of polymer material
pairs for the higher melting and lower melting polymer are e.g.
higher and lower molecular weight polyester, in particular PET;
polyester and polyamide-6,6; polyamide-6,6 and copolyester.
[0074] Combining two different types of polymer in one bicomponent
multifilament may result in a self-curling or self-crimping of the
bicomponent fibres, which is less preferred for the purposes of the
invention. In order to counteract that it may be preferable that in
a cross-section of the bicomponent fibre either the two pluralities
of filaments are uniformly distributed; or the regions of lower
melting polymer are uniformly distributed, or are arranged such
that they have an at least approximate C.sub.n symmetry, wherein
the rotation axis runs along the central axis of the bicomponent
fibre and n is an integer number equal or greater than 2. In the
case of the most preferred concentric core-sheath bicomponent
fibres, n would be infinity.
[0075] All these types of bicomponent fibres as such are
conventional and well known in the art.
[0076] The fabric of the invention may optionally contain crimped
antistatic warp filaments e) of one of the above defined weave
types c1-c4. These antistatic filaments preferably are spun yarns,
e.g. of carbon fibres, or are conductive polyester, cotton, nylon
or aramid fibres having a metallic conductor adhered thereto,
coated there onto or embedded therein. Such conductive fibres are
as such conventional. The tenacity of the crimped antistatic warp
filaments is preferably in the range of 15 to 250 cN/tex, more
preferably in the range of 15 to 40 cN/tex and most preferably of
20 to 30 cN/tex. Also preferably, their heat shrinkage (percentual
length reduction under heating for 2 min at 180.degree. C.) is in
the range of 0.5 to 15%, more preferably of 5 to 15% and most
preferably of 8 to 12%. Also preferably, the crimped antistatic
warp filaments may preferably have an S- or Z-twist, with the
number of turns per metre preferably being in the range of 0 to 400
and more preferably of 100 to 400. More preferably there is exactly
one crimped antistatic warp filament separated by every four
consecutive uncrimped warp filaments.
[0077] In warp direction the fabric of the invention does not
comprise any other types of crimped filaments, besides the crimped
warp filaments and optional crimped antistatic warp filaments with
one of above weave types c1, c2, c3 or c4. More preferably, the
fabric of the invention does in warp direction not comprise any
other types of filaments, besides the crimped warp filaments and
optional crimped antistatic warp filaments with weave types c1, c2,
c3 or c4 and the uncrimped warp filaments. In weft direction the
fabric of the invention preferably does not comprise any other
filaments, besides the uncrimped first and second weft filaments.
Most preferably, the fabric of the invention does not comprise any
other filaments, besides the uncrimped first and second weft
filaments, uncrimped warp filaments, crimped warp filaments and
optional crimped antistatic warp filaments.
[0078] If the warp filaments occur in repetitive units, wherein the
order of the filaments in these repetitive units is always the
same, and crimped antistatic warp filaments are also present, then
preferably again these crimped antistatic warp filaments are
included always at the same position within a repetitive unit.
Apart from that, their number and position(s) in a repetitive unit
is arbitrary. Preferably there is one such crimped antistatic warp
filament per repetitive unit.
[0079] The fabric tensile of the overall fabric is preferably in
the range of 4000 to 8000 N/50mm, more preferably of 5000 to 7000
N/50mm in warp direction and preferably 6000 to 9000 N/50mm, more
preferably 6500 to 8500 N/50mm in weft direction.
[0080] A fabric of the invention being impregnated with a
thermoplastic, thermoplastic elastomer, elastomer or thermoset may
be a precursor to an abrasive product of the invention.
[0081] The thermoplastic as the impregnation may preferably be
selected from the group consisting of thermoplastic polyolefins
(such as polyethylene or polypropylene), substantially random
ethylene/C3-12-.alpha.-olefin copolymers (examples of the
.alpha.-olefin being 1-propene, 1-butene, 1-pentene, 1-hexene and
1-octene), thermoplastic polyamides, ethylene-vinylacetate
copolymers, poly(vinylacetate) and PVC.
[0082] The thermoplastic elastomer as the impregnation may
preferably be selected from the group consisting of thermoplastic
elastomeric block copolymers (such as styrenic block copolymers, in
particular styrene-butadiene-styrene, styrene-isoprene-styrene,
styrene-ethylene/butylene-styrene and
styrene-ethylene/propylene-styrene block copolymers), copolymers of
hard blocks of medium density polyethylene and of soft blocks of
ethylene/.alpha.-olefin copolymers, thermoplastic polyurethanes
(such as copolymers of polyester diols or polyether diols with
diisocyanates), polyether-/ester block amides and thermoplastic
elastomeric ionomers.
[0083] The thermoset as the impregnation may e.g. be a
phenol-formaldehyde resin, a thermosetting polyurethane, an epoxy
resin, or a polycarboxylic acid such as a poly(meth)acrylic acid
which is crosslinked by a glycol, such as glycerol.
[0084] The elastomer as the impregnation may e.g. be a
polyurethane, a natural rubber, polyisoprene, polybutadiene,
styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR),
ethylene-propylene-diene rubber (EPDM) or an acrylate rubber. All
of these may be crosslinked or vulcanized preferably simultaneously
during the impregnation step or thereafter. The elastomer may
beforehand have been blended with a thermoplastic as exemplified
above.
[0085] The impregnation is preferably made of a thermoplastic
elastomer, more preferably of a TPU. Suitable TPU's may be obtained
by reacting diisocyanate-containing hard block segments with
polyester diol soft block segments.
[0086] Such impregnated fabric may e.g. be obtained by the
following steps:
[0087] a) a fabric of the invention is provided;
[0088] b) one of the sides of the fabric is sealed with a
relatively thin layer of the thermoplastic or thermoplastic
elastomer, typically using a solution thereof in a suitable
solvent, such as DMF, acetone, dimethyl sulfoxide or other, and
using a suited coating method such as knife over air, knife over
air, or kiss-roller or transfer coating;
[0089] c) the solvent is evaporated, optionally under heat or other
types of radiation and/or under reduced pressure, to provide a thin
primer coating of the thermoplastic or thermoplastic elastomer on
the concerned fabric side; this coating is still porous and
gas-permeable;
[0090] d) on the opposite side of the fabric a relatively thick
film coating of thermoplastic, thermoset or elastomer or mixture
thereof as in the primer coating is applied, e.g. by calendaring or
extrusion, and pushed into and through the fabric until it meets
the primer coating; allowing entrapped gas to escape through the
primer coating, whereby the impregnated fabric is obtained.
[0091] The finished impregnated fabric will typically have
impregnating material on both sides of the inventive fabric, such
as that no filament portions of the fabric are exposed to the
environment. On one of the sides of the fabric the impregnation
will form a continuous layer of geometrically well defined surface,
this continuous layer completely embedding the fabric. This
continuous layer may preferably also comprise a first top layer
consisting only of impregnation material and being completely
devoid of fabric. This first top layer is, when the above described
process is used, normally on the side of the fabric onto which the
relatively thick film coating of thermoplastic, thermoset,
elastomer or mixture thereof was applied by calendaring or
extrusion. The thickness of this first top layer, if present, is
designated as D.sub.i and is typically in the range of 100 to 500
micrometres. If present, the first top layer will form said
geometrically well defined surface. The thickness D.sub.i may be
determined using ultrasound reflection. Namely, an appropriate
ultrasound probe may be placed onto said geometrically well defined
surface. The time difference between the emission of an ultrasound
pulse from the probe into the belt and the detection of the first
ultrasound echo, which is reflected from the surface of the
embedded fabric, can be measured. If the longitudinal speed of the
ultrasound in the used thermoplastic or thermoplastic elastomer is
known, then D.sub.i can be determined. For the longitudinal speed
of sound in the used thermoplastic or thermoplastic elastomer
reference is made e.g. to the chapter 60 "Acoustic properties of
polymers" of the "Physical Properties of Polymers Handbook", second
edition, by James E. Mark, its Table 60.1 and the references cited
there. Such belt thickness measurement devices and appropriate
probes are in fact known and available on the market. An example is
the 38DL Plus from NDT Instruments with a single element transducer
as the probe.
[0092] Optionally, and as an optional step e) in the above
described process, a sheet of the same thermoplastic, thermoset,
elastomer or mixture thereof as used in the impregnation can be
laminated or calendared to the other side of the impregnated
fabric. In the above described process this is the side that was
initially sealed with the relatively thin layer of thermoplastic,
thermoset, elastomer or mixtures thereof. This will then form on
said other side of the fabric an optional second top layer with a
second geometrically well defined topmost surface.
[0093] The abrasive product of the invention contains at least one
type of particulate abrasive material. The particulate abrasive
material(s) as such is(are) conventional. Examples of abrasive
materials include, without limitation, alumina (e.g. fused
aluminium oxide including brown aluminium oxide, heat treated
aluminium oxide and white aluminium oxide; ceramic aluminium oxide;
corundum; ruby; sapphire; or doped alumina), refractory carbides
(e.g. silicon carbide; boron carbide; tungsten carbide; titanium
carbide or cementite (Fe.sub.3C)), refractory nitrides (e.g. boron
nitride, titanium nitride, silicon nitride, zirconium nitride;
tungsten nitride; vanadium nitride; chromium nitride; tantalum
nitride or niobium nitride), chromia, alumina zirconia, diamond,
iron oxide, titanium diboride, ceria, garnets (e.g. pyrope;
almandine; spessartine; uvarovite and andradite), powdered glass,
metal particulates and combinations thereof. The abrasive particles
may typically have a mass median diameter (MMD) ranging from 0.01
to 30 micrometres, preferably from 0.05 to 10 micrometres, and more
preferably from 0.1 to 5 micrometres, as obtainable by laser
diffraction determination of the particle size distribution. The
abrasive particles may typically have a Mohs' hardness of at least
about 7, preferably of at least 8.
[0094] The abrasive product of the invention may be prepared by
providing an impregnated fabric, as described above, and applying a
particulate abrasive material, as described above. This may be done
in several ways.
[0095] In a first preferred embodiment the abrasive product
contains the abrasive particles embedded into the topmost
surface(s) of the top layer(s) itself(themselves). The material of
the impregnation, and thus of the top layer(s), is a thermoplastic,
thermoset, elastomer or mixture thereof, thus a material that
softens or melts upon heating. The topmost surface(s) of the top
layer(s) may in one alternative be uniformly heated, such as with
an array of IR lamps, to soften it(them) up up to nearly its
(their) melting point. Immediately following the heating the
particulate abrasive is uniformly sprayed or dusted, such as by
electrostatic spraying, onto the softened surface(s). Alternatively
the abrasive particles may be electrostatically sprayed onto the
still cold topmost surface(s) and this is then passed through
heated calendar rolls to simultaneously soften the thermoplastic,
thermoset, elastomer or mixtures thereof and to embed the abrasive
particles into the softened surface(s). In either of these two
alternatives after cooling, an abrasive article having the abrasive
particles directly embedded into the topmost surface(s) is
obtained. The overall thickness of each abrasive-containing top
layer, D.sub.i', may again be determined using ultrasound
reflection as outlined above for the top layer still devoid of
abrasive particles. If the abrasive particles are very small with
respect to the expected thickness of the abrasive-containing
uppermost continuous top layer, e.g. when their mass median
diameter (MMD, see above) is in the range of 0.01 to 0.5
micrometres, then the time difference between ultrasound pulse
generation and the echo, reflected from the surface of the embedded
fabric, can be taken. The D.sub.i' will then be essentially the
same as D.sub.i discussed above. If the abrasive particles are of
greater MMD, then the ultrasound probe will not lie directly on the
outermost surface but on the apexes of the abrasive particles. In
this case the time difference between the first echo, reflected
from the outermost surface, and the second echo, reflected from the
surface of the embedded fabric, can be taken.
[0096] If the particulate abrasive material is directly embedded
into the thermoplastic, thermoset, elastomer or mixture thereof
comprised in the top layer(s), as outlined above, then one
maximally takes advantage of the enhanced resistance impregnation
against delamination from the inventive fabric under shear stress,
because there are no further layers and there is thus no concern
about any other possible interlayer separations during use in
abrasion.
[0097] A second preferred way to obtain an abrasive article of the
inventions is to apply one or two prefabricated sheets containing
abrasive particles, as described above, onto one or both of the
surfaces of the impregnation (if no top layer(s) of the same
thermoplastic or thermoplastic elastomer as in the impregnation is
or are present) or onto the surface(s) of the top layer(s), if such
top layer(s) is(are) present. Including the abrasive particles in
the form of prefabricated sheets containing them may allow to take
advantage of the diversity of such sheets that are available on the
market and of the experience of the respective producers in
manufacturing them in the desired uniformity. It may also allow to
impart the abrasive article further mechanical rigidity, which is
favourable in view of better abrasive action onto the substrate to
be abraded.
[0098] In this second embodiment, the term "apply a prefabricated
sheet containing abrasive particles" is firstly understood to mean
to the joining of the compound of impregnated fabric/optional top
layer(s) and the prefabricated abrasive sheet by means of heat and
pressure, such as by heated calendaring rolls, wherein the
impregnation material itself may act as a hotmelt adhesive, or with
co-use of an additional, thermoplastic or thermosetting or
elastomer adhesive or adhesion primer. It is secondly understood to
mean the simple laying of the prefabricated abrasive sheet onto the
compound of impregnated fabric/optional top layer(s) without any
measures to effect a physical or chemical bonding between them, to
obtain an abrasive article of the invention wherein the
prefabricated abrasive sheet can easily be replaced once spent or
worn down.
[0099] As in the first above described embodiment, each of the
optional first and second top layer(s) will again have a thickness
D.sub.i1 and D.sub.i2, respectively, and each of the first and
second prefabricated sheets containing abrasive particles will have
a thickness D.sub.i1' and D.sub.i2', respectively. Each of these
thicknesses is again measurable by ultrasound as described above,
particularly also because the thermoplastic or thermoplastic
elastomer of the impregnation and optional first and second top
layer(s) will normally be different from the matrix material of the
prefabricated abrasive sheet(s), so that a further ultrasound echo
is obtained on each respective phase boundary.
[0100] The term "prefabricated sheet containing abrasive particles"
may mean any planar sheet like material, such as in the form of
sheets, ribbons, tapes or disks. These prefabricated sheets contain
abrasive particles embedded in a plastic support, such as typically
of polyester, optionally with use of an adhesive, or may be of the
sandpaper type. The latter is in particularly preferred for the
abovementioned abrasive articles without physical or chemical
bonding to the compound of impregnated fabric/optional top
layer(s).
[0101] If the prefabricated abrasive sheet is bonded to the
compound of impregnated fabric/optional top layer(s) then the
resistance to delamination of the resulting abrasive product under
shear during use may be similar as in the above outlined first way
of directly embedding abrasive particles into the impregnation.
[0102] If the prefabricated abrasive sheet is simply applied to the
compound of impregnated fabric/optional top layer(s) without
physical or chemical bonding then adhesion between them during use
in abrasion occurs typically because of the pressure that the
abrasive product will exert against the surface of the good to be
abraded, taking advantage of the static coefficient of friction
between surface of the impregnation and bottom side of the
prefabricated abrasive sheet. If said bottom side has a notable
surface roughness or surface unevenness, such as by an explicit
surface profiling or embossing, then, during use in abrasion, that
uneven bottom surface may in time start to snugly fit the surface
of the impregnation or of the uppermost continuous top layer: The
use in abrasion generates friction heat, and the impregnation, of
moderate Shore A hardness at room temperature and becoming softer
when heated, will in time slightly deform to match the said uneven
bottom surface.
[0103] There are many companies that offer abrasive particles
and/or prefabricated abrasive sheets on the market, examples being,
at the time of filing of this application, Minnesota Mining &
Manufacturing (USA), D.K. Holdings Limited (UK), KGS Diamond
International AG (Netherlands, Portugal) and SIA Abrasives
(Switzerland).
[0104] In any of the foregoing embodiments, the abrasive particles,
whether as such or used in the form of a prefabricated abrasive
sheets, may eventually cover only a fraction of the outermost
surface of the abrasive product of the invention. Sections of the
outermost surface that are not covered by abrasive particles or
abrasive sheet may constitute recessed channels through which
abraded material and/or excess friction heat may be removed.
Furthermore, if only a fraction of the outermost surface is
covered, then the pressure that is exerted onto the surface of the
good to be abraded increases by the reciprocal of that fraction, if
the remainder of the parameters of the abrading process are left
unchanged.
[0105] The overall thickness of an abrasive product of the
invention, D.sub.tot, is typically in the range of 0.5 to 5 mm,
preferably of 1 to 3 mm. The thickness D.sub.tot can be measured
with an ordinary gauge, if necessary by applying a weak
overpressure such as of 0.2 bar.
[0106] The abrasive product of the invention can have any
essentially sheet-like shape of sufficient surface such as to be
able to abrade a sufficient portion of the surface of a good to be
abraded. The abrasive product may be used in planar shape or wound
up to a cylindrical shape. The abrasive product may be hand-driven
or power-driven, e.g. by a power drill which has a circular rubber
support disk onto which the abrasive product of the invention is
fixed or laid upon. Preferably it has the shape of an abrasive
belt, or of an abrasive disk or abrasive pad. In an abrasive belt
of the invention the abrasive particles are preferably embedded
directly into the topmost surface of a fabric-devoid top layer made
of the same thermoplastic or thermoplastic elastomer as the
impregnation in the fabric (see above). Abrasive belts are normally
operated similar as an ordinary conveyor belt, that is, in endless
shape using driving and idler pulleys. For an inventive abrasive
belt it is preferred that it has abrasive particle coating only on
one side (the outer side), but not at the other side facing said
pulleys. The abrasive belts of the invention contain thermoplastic
or thermoplastic elastomer and they can thus be made endless by any
of the customary end-joining techniques for conveyor belts using
that thermoplastic, thermoset, elastomer or mixture thereof as a
hotmelt adhesive, such as by the so-called "finger end" or overlap
joining technique. Abrasive pads are preferably planar and have
preferably the shape of a square, rectangle, triangle, or of a
sector of a circular arc or of a sector of a circle, preferably
also with rounded edges. Abrasive disks of the invention have a
preferably an essentially or exactly circular shape and are
preferably intended to be used for circular abrasion motion. In
abrasive pads or disks of the invention abrasive coatings may be
applied to one or both sides of the impregnated fabric; preferably
they are applied only to one side thereof. The abrasive coating is
preferably applied in the form of prefabricated abrasive sheets,
either directly to the impregnated fabric or to a fabric-devoid
cover layer consisting of the same material as the
impregnation.
[0107] The abrasive product of the invention can have, depending on
the contained abrasive and shape, widely diverse applications.
Non-limiting examples are deburring (such as deburring internal
diameters), blending (such as blending corners), buffing, chrome
stripping, cleaning, coating removal, descaling, sanding (such as
drum sanding; edge sanding; mould sanding; wide belt sanding;
portable belt sanding or stroke sanding), edge bevelling, edge
seaming, finishing (such as contour finishing; fine finishing; flat
area finishing; intermediate finishing; stainless steel finishing;
straight line brushed finishing; superfinishing; weld removal
finishing or power train micro-finishing), gate removal, grinding
(such as high pressure grinding; light grinding; plate grinding;
right angle grinding; sheet grinding; swing frame grinding; slab
grinding or centreless & cylindrical grinding), mill scale
removal, parting line removal, polishing (such as plate polishing;
polishing internal diameters; sheet polishing or coil polishing),
prepping metal prior to paint, radiusing, refining, setting the
grain, shaping, etc.
[0108] The resistance of the inventive fabric against delamination,
when used in an abrasive article and the abrasive motion is in warp
direction of the fabric, will now be discussed with reference to
FIGS. 1-4.
[0109] FIG. 1 (cross-sectional view) and FIG. 2 (top view) show an
exemplary fabric of the instant invention. This fabric has
uncrimped warp filaments 1, first and second uncrimped weft
multifilaments (shown in cross-section in FIG. 1), designated with
numerals 301-308 and 309-316, respectively, and crimped warp
filaments 41-44. To each of the first uncrimped weft multifilaments
301 resp. 302 resp. 303 resp. 304 resp. 305 resp. 306 resp. 307
resp. 308 there is one corresponding second uncrimped weft
multifilament 309 resp. 310 resp. 311 resp. 312 resp. 313 resp. 314
resp. 315 resp. 316, and vice versa, to form successive
multifilament pairs 301/309, 302/310, 303/311, 304/312, 305/313,
306/314, 307/315, 308/316. Each of these successive multifilament
pairs is designable with an integer index; e.g. according to the
following Table 2:
TABLE-US-00002 TABLE 2 multifilament pair Exemplary index N for
multifilament pair 301/309 239 (=N.sub.D, because (N mod 4) = 3)
302/310 240 (=N.sub.A, because (N mod 4) = 0) 303/311 241
(=N.sub.B, because (N mod 4) = 1) 304/312 242 (=N.sub.C, because (N
mod 4) = 2) 305/313 243 (=N.sub.D, because (N mod 4) = 3) 306/314
244 (=N.sub.A, because (N mod 4) = 0) 307/315 245 (=N.sub.B,
because (N mod 4) = 1) 308/316 246 (=N.sub.C, because (N mod 4) =
2)
[0110] FIG. 3 is a schematic side view of the crimped warp filament
41 of the fabric of FIG. 1, once (upper part of FIG. 3) without
shear and once (lower part of FIG. 3) at attempted 20.degree.
shear. This crimped warp filament 41 has falling filament portions
(one indicated with numeral 411) of a length V and rising filament
portions (one indicated with numeral 412) of a length W, wherein
W=V in the unsheared state.
[0111] If the fabric is sheared, the rising filament portions 412
come under tensile stress. However, if the uncrimped warp filament
1 and the crimped warp filaments 41-44 are assumed of reasonably
high tenacity then the half pitch L and the length W of the rising
filament portions 412 may be assumed unchanged in unsheared and
sheared state. The falling filament portions 411, when under shear,
come under compressible stress and their length V' becomes
schematically shorter under that compressible stress.
[0112] This schematic shortened length V' of the falling filament
portions 411 under shear is exactly calculable based on the shear
angle, the filament diameters and the interfilamentous distances,
and under said assumptions of L and W remaining constant as
follows:
V'= {square root over (W.sup.2+4Lsin(.delta.)(Lsin (.delta.)-
{square root over (L.sup.2sin.sup.2(.delta.)+H.sup.2)}))} (1)
wherein W is said length of the rising filament portions 412 (being
equal in unsheared state and sheared state, being furthermore equal
in unsheared state to the length V of the falling filament portions
411), this W being calculable as follows:
W= {square root over (L.sup.2+H.sup.2-(X+Y).sup.2)} (2);
wherein L is said half-pitch, H is the distance in vertical
direction by which the centres of adjacent uncrimped weft
multifilaments are matched in corresponding pairs (e.g. 308/316); X
is the diameter of the uncrimped weft multifilament(s) 301-316; Y
is the diameter of the crimped warp filament 41; and .delta. is the
shear angle.
[0113] For meaningful shear angles .delta. the sin(.delta.) is
greater than or equal zero, and L and H are always greater than
zero. Then always in (1):
Lsin(.delta.)< {square root over
(L.sup.2sin.sup.2(.delta.)+H.sup.2)}
This means that the term in brackets in (1) is always smaller than
zero, the V' calculated with (1) is always smaller than W (=V), and
the ratio V':V is always smaller than 1.
[0114] At given H and .delta., the term
4Lsin(.delta.) (Lsin(.delta.)- {square root over
(L.sup.2sin.sup.2(.delta.)+H.sup.2)})
appearing in (1) becomes closer to zero with increasing half-pitch
L, and the V' calculated with (1) at given H, X, Y, and 8 becomes
closer to W. Accordingly, the ratio of V':V (=V':W) becomes closer
to unity with increasing half-pitch L.
[0115] In the exemplary embodiment of FIGS. 1-3, wherein D=15
units, L=30 units, H=15 units, X=4.35, Y=4.35 units and
.delta.=20.degree., one obtains with the above formulae: W=V=32.39
units, V'=26.29 units, and V':V (=V:W)=0.831. This corresponds to a
schematic shortening of the falling filament portions 611 at
attempted 20.degree. shear of 16.9%.
[0116] The presumed real reaction of the falling filament portions
411 to such compressible stress is (for monofilaments) some bulging
outwards from their longitudinal axis or (for multifilaments) some
fluffing up of the individual filaments contained therein or some
bulking up of the multifilament. This presumed reaction of the
falling filament portions 411 to the compressible stress is
believed to be a major reason for possible delamination of an
impregnation adhering to these falling filament portions 411, and
thus for delamination of such impregnation adhering to the warp
filament 41. This presumed real reaction of the falling filament
portions 411 to compressible stress cannot be adequately shown in
FIG. 3. Instead FIG. 3 shows said schematic shortening of the
length of the falling filament portions 411 from V, unsheared
state, to V', sheared state. The more pronounced the schematic
shortening V' of the falling filament portions 411 is, the more
pronounced said real reaction of the falling filament portions 411
to compressible stress is predicted to be.
[0117] If a crimped warp filament 5 which simply entwines around
first and second uncrimped weft multifilaments, 301-308 and
309-316, respectively, in alternating manner, as shown in FIG. 4,
without ever passing between any uncrimped weft multifilaments
301-316, was used in the inventive fabric, then the half pitch L
for that alternatingly entwining crimped warp filament 5 would be
equal to D and thus only 15 instead of 30. If the length W of its
rising filament portions 52 could be assumed constant under shear
and all other parameters were assumed identical as for FIGS. 1-3
then one would obtain with the above formulae (1) and (2) for the
falling filament portions 51 of such alternatingly entwining
crimped warp filament 5 at a shear angle of 20.degree.: W=V=19.35
units, V'=12.42 units and V':V (=V':W)=0.642, which corresponds to
a schematic shortening of these falling filament portions 51 at
20.degree. shear of 35.8%. This is much more than the 16.9%
observed for the crimped warp filament 41 of inventive fabric of
FIG. 1 and is indicative of a more significant real reaction of the
falling filament portions 51 in such alternatingly entwining
crimped warp filament 5 to compressible stress, and thus of a more
significant tendency of an impregnation adhering to the falling
filament portions 51 of such filament to delaminate under
shear.
[0118] In the inventive fabric the half pitch L of the weave in
warp direction is about twice the distance D between centres of
adjacent uncrimped weft filaments, because there are always extra
filament pairs which allow passing of the crimped warp filaments
41-44 between their first and second uncrimped filaments. The
formula for calculating the schematic distance H' between the
centres of first uncrimped weft multifilament (e.g. 303 or 308 in
FIG. 3) and second uncrimped weft multifilament (e.g. 311 or 316 in
FIG. 3) in any such multifilament pairs in sheared state of the
fabric is:
H'= {square root over
(L.sup.2sin.sup.2)}(.delta.)+H.sup.2-Lsin(.delta.) (3)
wherein H, L and .delta. are as defined above. Since L and H are
always greater than zero, and since for meaningful shear angles
.delta. the sin(.delta.) is greater than or equal zero, the H'
calculated with formula (3) becomes smaller with increasing
half-pitch L. The H' by formula (3) is equal to H when the shear
angle .delta. is zero and becomes smaller than H when .delta. is
greater than zero. The greater the half pitch L is, the faster H'
of formula (3) converges towards zero with increasing shear angle
.delta..
[0119] By the above behaviour of above formula (3) it is secondly
possible to predict that, by virtue of H' becoming smaller with
increasing shear angle .delta., the said extra multifilament pairs
(e.g. 303/311 in FIG. 3) will start to laterally compress the
falling filament portions 411, which will partially counteract
their said bulging outwards, bulking up or fluffing up, thus
furthermore preventing delamination of the impregnation adhering to
these falling filament portions 411.
[0120] By the above behaviour of above formula (3) it is thirdly
possible to predict that, by virtue of H' converging faster towards
zero with increasing half pitch L, the reduction of the distance H'
will be more pronounced in the inventive fabric of FIGS. 1-3 than
in a fabric having crimped warp filaments 5 as shown in FIG. 4,
because for such simply alternating crimped warp filaments the
half-pitch L is only equal to that distance D, not twice the
distance D. Accordingly it its predicted that the inventive fabric
of FIGS. 1-3 cannot be sheared to the same extent as a fabric
containing warp filaments 5, because of its tendency to become
compressed (the more pronounced reduction of H') rather than
becoming sheared. The schematic representation in the lower part of
FIG. 3 actually predicts that the inventive fabric of FIGS. 1-3
resists a shearing to 20.degree., in view of the graphical overlap
of the uncrimped weft filaments 301-316 with the crimped warp
filament 41 and with the uncrimped warp filament 1.
[0121] The above considerations were made specifically for the
crimped warp filament 41 appearing in FIGS. 1-2, but can be applied
to any of the other crimped warp filaments 42, 43 and 44 shown
therein, since they all have the same weaving type as crimped warp
filament 41.
[0122] In view of all the foregoing the fabric of FIG. 1, when
impregnated and formed into an abrasive product, is predicted to be
less prone to shear delamination, when the abrasive motion is in
warp direction of the fabric, than a fabric having alternatingly
entwining warp filaments 5 as shown in FIG. 4.
[0123] Essential for this improved resistance to shear delamination
under abrasive action in warp direction of the fabric is thus that
the fabric of the invention contains both crimped warp filaments
41-44 of the weave type discussed for FIG. 1-2 and contains
uncrimped warp filaments 1, but does not contain any crimped warp
filaments 5 simply entwining around the first and second uncrimped
weft multifilaments in alternating manner without ever passing
between uncrimped weft filaments, as depicted in FIG. 4.
[0124] The improved resistance of the inventive fabric against
delamination, when used in an abrasive article and the abrasive
motion is in weft direction of the fabric, will now be discussed
with reference to FIG. 5.
[0125] FIG. 5 shows four cross-sectional views of the inventive
fabric of FIG. 1 in weft direction. The first cross-sectional view
is through the successive multifilament pair with uncrimped weft
multifilaments 302, 310; the second one through the successive
multifilament pair with uncrimped weft multifilaments 303, 311; the
third one through the successive multifilament pair with uncrimped
weft multifilaments 304, 312; and the fourth one through the
successive multifilament pair with uncrimped weft multifilaments
305, 313. In each of the four cross-sectional views a dashed box
indicates a repetitive unit in weft direction. This repetitive unit
in all cross-sectional views also comprises one crimped warp
filament passing between first and second uncrimped weft
multifilament of each successive multifilament pair: In the first
and third cross-sectional views it is the crimped warp filament 43,
and in the second and fourth cross-sectional views it is the
crimped warp filament 42. The passing of the crimped warp filaments
42, 43 between first and second uncrimped weft multifilaments is
indicated by vertical lines; these being upward solid and downward
dashed if the crimped warp filaments 42, 43, upon passing between
first and second uncrimped weft multifilaments, form a rising
filament portion 412 (as discussed in FIG. 3); or these vertical
lines being upward dashed and downward solid if the crimped warp
filaments 42, 43, upon passing between first and second uncrimped
weft multifilaments, form a falling filament portion 411 (as
discussed in FIG. 3). The crimped warp filaments 42, 43, both pass
pass between first/second uncrimped weft multifilaments 302/310,
303/311, 304/312 and 305/313, and entwine around first uncrimped
weft multifilaments 302-305 and around second uncrimped weft
multifilaments 310-313. So the crimped warp filaments 42, 43 cannot
rotate at all around their central axis and thus firstly prevent an
axial displacing movement of said first uncrimped weft
multifilaments 302-305 and said second uncrimped weft
multifilaments 310-313 in opposite directions. Such axial
displacing movement would actually be favoured by the uncrimped
warp filaments 1, which possibly could act as a roller,
facilitating such axial displacing movement of said first uncrimped
weft multifilaments 302-305 and said second uncrimped weft
filaments 310-313 in opposite directions by rotation around their
central axis. If the uncrimped weft multifilaments 302-305 and
310-313 are close enough, or come close enough upon shear in weft
direction, the crimped warp filaments 42, 43 also prevent further
axial displacement thereof in opposite directions by friction,
since they cannot rotate.
[0126] If, as also shown in FIG. 5, the repetitive unit contains
still further crimped warp filaments 41, 44 the inhibition of axial
displacement of the uncrimped weft multifilaments 302-305 and
310-313 in opposite directions is even more pronounced, for the
same reasons as discussed for the crimped warp filaments 42,
43.
[0127] In summary it is predicted that the fabric of FIG. 1 is also
resistant to shear, and thus to shear delamination, in its weft
direction.
[0128] The resistance to shear delamination predicted to be
particularly pronounced if the direction of shear is simultaneously
in warp direction (to bring about a stronger compression of the
fabric, as discussed with reference to FIG. 3), and in weft
direction (to use said stronger compression of the fabric, to cause
increased friction between uncrimped weft filaments 302-305 and
310-313 and uncrimped warp filament 1, which in turn prevents shear
in the weft direction, as discussed with reference to FIG. 5).
[0129] The resistance to shear delamination of the inventive
abrasive products under abrasive action can easily be
experimentally tested in a Taber abrader (Taber industries).
Instead of the standardized Taber abrading wheels a custom abrading
wheel of the same size, but containing as the abrasive outer face a
ribbon of the abrasive product of the invention to be tested, is
used. This setup allows to test for shear of the abrasive product
of the invention in any direction of the weave of the fabric
contained therein (warp, weft, or a combination of both). The
ribbon only needs to be cut out from the abrasive product of the
invention in a suited orientation.
[0130] FIG. 6 is a schematic cross-sectional view of an abrasive
belt of the invention containing the fabric of the invention, along
its longitudinal direction, cutting through the uncrimped warp
filament 1 and the first and second uncrimped weft multifilaments,
301-308 and 309-316, respectively. The longitudinal (warp)
direction of the fabric is also considered to be the abrasive
belt's travel direction. The first and second uncrimped weft
multifilaments 301-308 and 309-316, respectively, are made of
polyester and in the exemplified embodiment have a thickness of
0.25-0.45 mm. The uncrimped warp filament 1 is typically a
multifilament made of polyester or, more preferable, of aramid. The
crimped warp filaments 41-44 are typically multifilaments made of
polyester and in the exemplified embodiment have a titer of 550 to
2000 dtex. There are typically 4 or 12 crimped warp filaments 41-44
per uncrimped warp filament 1. The abrasive belt has an
impregnation 6, typically of a TPU, such as of Lubrizol's
Estane.RTM. TPU types, and an uppermost continuous top layer 7
consisting of the same impregnation material as the impregnation 6,
and being completely devoid of fabric. The boundary between
uppermost continuous top layer 7 and impregnated fabric is
indicated by a dashed line. The uppermost continuous top layer 7
has a top surface 8 with abrasive particles 9 embedded directly
therein. The uppermost continuous top layer has, after having the
abrasive particles embedded, a thickness D.sub.i', measurable by
ultrasound as outlined above. Embedding the abrasive particles 9
directly into the top surface 8 of the top layer 7 helps in
reducing the overall thickness D.sub.tot of the belt, which is
favourable in view of its bendability over pulleys. This abrasive
belt of the invention has an overall thickness D.sub.tot of
typically in the range of 1 to 3 mm, measurably by gauge as
described above.
[0131] FIG. 7 is a schematic cross-sectional view of an abrasive
pad or disk of the invention containing the fabric of the
invention, along its longitudinal direction, cutting through the
uncrimped warp filament 1 and the first and second uncrimped weft
multifilaments, 301-308 and 309-316, respectively. It contains a
fabric of the invention, an impregnation 6 and on one side of the
impregnated fabric a first cover layer 71 of a thickness D.sub.i1,
consisting of the same impregnation material as the impregnation 6,
but being completely devoid of fabric. In the shown embodiment
there is also a second cover layer 72 of thickness D.sub.i2, also
consisting of the same impregnation material as the impregnation 6,
but being completely devoid of fabric. This abrasive pad or belt
contains first abrasive particles 91 in the form of a first
prefabricated sheet 101 of thickness D.sub.i1' and containing these
first abrasive particles 91 embedded into its first top sheet
surface 111. It may e.g. be an abrasive tape of type 262L, or a
so-called "micro-finishing film" of type S, both produced by
Minnesota Mining & Manufacturing. This first prefabricated
sheet 101 has been laminated under heat and pressure, optionally
with co-use of a compatible hotmelt adhesive (not shown) to the
first top layer 71. A second prefabricated sheet 102, identical to
the first prefabricated sheet 101 or different therefrom, of
thickness D.sub.i2' and containing further abrasive particles 92
(which may be same as the abrasive particles 91 or different
therefrom) embedded into its second top sheet surface 112 has been
laminated to the second top layer 72. This second prefabricated
abrasive-containing layer is optional.
* * * * *