Note: Descriptions are shown in the official language in which they were submitted.
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MASKING MATERIALS AND METHOD OF USE
BACKGROUND OF THE INVENTION
TECHNICAL FIELD
This invention relates to masking materials and to their use during the
application
of two or more coating materials to a surface. In particular the invention
relates to
masking materials having a curved edge strip which is removable from the
remainder of
the masking material.
Description of the Related Art
Masking foam tape comprising a foam substrate having on part of its outer
surface
a layer of pressure-sensitive adhesive is known. A preferred tape has a cross-
section
comprising a curved surface e.g., circular or elliptical, since such masking
tape allows a
"feathered edge" or "soft edge", to be attained during surface coating
operations, such as
painting. The masking tape is positioned such that the curved surface
overhangs the
surface to be painted and thus when the paint is sprayed only paint projected
at certain
angles will pass beneath the overhanging portion of the masking tape and the
paint
thickness will be thinner, the edges beneath the overhang allowing a smooth
transition to
the adjacent painted area to be attained. The use of foam allows paint
impinging thereon
to be absorbed preventing it running off the masking material and marring the
surface
being treated. Such masking material is commercially available from 3M United
Kingdom plc under the trade name Soft Edge Masking Foam Tape.
Soft edge masking foam tape (SEMFT) may be produced from a foam web by
compression over a predetermined area with a blunt rotary cutter so that a
cold-welded
seam is fvrmed which secures opposing surfaces of the web to each other at the
region of .
the weld, thereby forming a curved surface. An array of circular or elliptical
adjacent
foam strips which are readily separable may be fonmed by passing a foam web
through a
plurality of parallel blunt rotary cutters causing compression and welding of
the foam
along parallel lines. The production of such foam strips is disclosed in EP-B-
0384626.
Other masking materials comprising foam, which may be cold-welded are
disclosed in
GB-2254811 and GB-2288137.
SEMFT is commonly used to mask the inside of door apertures to prevent paint
or
primer spray from contaminating the inside of the vehicle. After applying
primer to a car
panel it is desirable to apply the paint in a manner such that it extends
beyond the primer
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to ensure the primer is completely covered and not left
exposed. In such situations the SEMFT may be removed after
application of the primer and repositioned. Alternatively,
the SEMFT may be gently pushed in an attempt to displace it
and position it away from the primer edge. Neither
technique is satisfactory since it is labour intensive and
not desirable if the primer is still wet.
The invention has been made with this point in
mind.
SUMMARY OF THE INVENTION
According to one aspect of the invention there is
provided a masking material comprising an elongate strip at
least partially coated with a layer of a pressure-sensitive
adhesive, the strip having a curved surface which is convex
when the strip is viewed in cross-section and is positioned
such that when the strip is adhered to a substrate by the
layer of pressure-sensitive adhesive a portion of the curved
surface overhangs the substrate, wherein the masking
material comprises a removable edge portion comprising said
portion of the curved surface detachably secured to a
remainder of the strip which may be removed to expose a
second curved surface on the remainder of the strip which is
convex when viewed in cross-section and which is positioned
to overhang the substrate, said removable portion and the
remainder of the strip having different cross-sectional
dimensions.
According to a second aspect of the invention
there is provided a method of coating an area of a surface
of a substrate with layers of a first and second coating
mater.ial which comprises the steps of: (i) providing a
masking material comprising an elongate or endless strip at
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least partially coated with a layer of a pressure-sensitive
adhesive, the strip having a curved surface which is convex
when the strip is viewed in cross-section and is positioned
such that when the strip is adhered to a substrate by the
layer of pressure-sensitive adhesive a portion of the curved
surface overhangs the substrate, in which the masking
material comprises a removable edge portion comprising said
portion of the curved surface, detachably secured to the
remainder of the strip which may be removed to expose a
second curved surface on the remainder of the strip which is
convex when viewed in cross-section and which is positioned
to overhang the substrate, said removable portion and
remainder,of the strip having different cross-sectional
dimensions, (ii) applying said masking material to the
substrate such that the curved surface is adjacent the edge
of the area to be coated, (iii) applying the first coating
material over said area of the surface up to said masking
material, (iv) detaching and removing said removable portion
of the masking material, and (v) applying the second coating
material over the first coating material and up to the
remainder of the masking material.
In the preferred embodiment the cross-sectional
dimension of the removable portion is smaller than the
cross-sectional dimension of the remainder of the strip.
The masking material of the invention is simple
and effective to use. The elongate strip is applied to the
surface in the normal manner with the curved surface
adjacent the edge of the area of the surface to be coated.
After application of a first coating material, e.g., primer,
the curved surface is readily removable to expose a second
curved surface slightly extending the area to be coated such
that the second coating will completely overlap the first
coating while ensuring a feathered edge is obtained. Thus,
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repositioning of the masking material between successive
coating operations is unnecessary.
The masking material is preferably made of foam
and may conveniently be produced by cold-welding foam web by
the techniques disclosed in EP-0384626. Polyurethane foam
is preferred for use in the cold-welded embodiments of the
invention. The foam preferably has a density of about
26Kg/m3. A preferred cold-weldable foam is commercially
available from Caligen Foam Limited under the trade
designation "Grade 4273A".
The removable edge of the masking material may be
achieved in various ways.
In one embodiment, the elongate strip may be
formed with a circular or elliptical cross-section and a
layer of foam or similar material releasably secured to and
following the contour of the curved surface extends as a
strip along the length of the masking material to form a
removable edge. The removable strip may be secured by
pressure-sensitive adhesive, welding or a combination
thereof.
Such a masking material may be made by a method
which comprises the steps of:
(a) providing a first cold-weldable foam web;
(b) applying at least two parallel stripes of a
pressure-sensitive adhesive to a surface of the foam web;
(c) applying a second cold-weldable foam web
having a thickness less than that of the first web to the
first web such that the second web overlaps but does not
completely cover the adjacent parallel stripes of pressure-
sensitive adhesive;
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(d) compressing the first and second cold-weldable webs midway between the
adjacent stripes of pressure-sensitive adhesive using a blunt rotary cutter so
that a cold-
welded seam is formed which secures the two webs to each other at the region
of the weld
thereby forming a curved surface; and
(e) compressing the first web using a blunt rotary cutter so that a cold-weld
is
formed which secures opposing surfaces of the web to each other in the region
of the weld
thereby forming a curved surface, said web(s) being compressed along at least
three
parallel lines to form at least two cords of circular or oval cross-section.
The elongate strip may comprise a plurality of removable edge portions in the
form
of layers of foam following the contour of the curved surface and extending
along the
length of the strip. Such masking materials may be made by a method comprising
the
steps of:
(a) providing a first cold-weldable foam web;
(b) providing at least two second cold-weldable foam webs having a thickness
and width smaller than that of the first cold-weldable foam web;
(c) adhering said second webs to a surface of the first web with pressure-
sensitive adhesive to form parallel strips of said second webs;
(d) compressing said first and second cold-weldable webs using a blunt rotary
cutter so that a cold-welded seam is formed which secures the first and second
webs
together at the region of the weld thereby forming a curved surface, said webs
being
compressed along at least two parallel lines along the longitudinal axis of
the second webs
to form at least one cord of circular or oval cross-section; and
õ .. .. .. .,. . .. . .. ..>., . . ....Eea.. - ... ,applying a pressure-
sensitive adhesive to>thesurfac,e. ofthe-first web in the
region between the second webs prior to cold-welding or to the surface of the
first web of
the cord between the second webs after cold-welding.
In a further embodiment the masking material may comprise a primary cord of
circular or elliptical cross-section having a strip of pressure-sensitive
adhesive coated
thereon and a secondary cord parallel to the primary cord releasably secured
thereto. The
secondary cord may readily be formed simultaneously with the primary cord from
a foam
web by cold-welding.
Such a masking material may be made by a method comprising the steps of:
(a) providing a cold-weldable foam web;
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(b) compressing said foam web using at least one blunt rotary cutter so that a
cold-welded seam is formed which secures opposing surfaces of the web to each
other at
the region of the weld, thereby forming a curved surface, said web being
compressed
along at least three parallel lines to form at least two cords having a pair
of longitudinal
weld seams and a circular or oval cross section, two cords being releasably
secured by a
common weld and having different dimensions; and
(c) applying a stripe of pressure-sensitive adhesive to the web in the region
of
the cord having the larger dimension prior to cold-welding or to the cord of
larger
dimension after cold-welding.
In a further embodiment of the invention the masking material may be in the
form
of an endless elongate strip e.g., a closed curve, such as a circle or ellipse
or other shape,
e.g., square, hexagon etc. A concentric array of such strips may be formed
e.g., by
compressing and cold-welding foam, adjacent strips being separable from each
other by
tearing the weld. Examples of such an array are disclosed in GB-225481 1. In
use, the
user removes sufficient strips which define an aperture having the area of the
surface to be
coated and the masking material is applied to the surface. After the first
coating e.g.,
primer has been applied, the inner strip is removed and the second coating
applied
overlapping the first coating.
BRIEF DESCRIPTION OF THE DRA.WINGS
The invention will now be described with reference to the accompanying
drawings
in which:
, - a Figures la and b illustrate the production-of amasking material.in
acc.prdance with
one embodiment of the invention;
Figures 2a and b illustrate the use of the masking material of Figure 1;
Figures 3a and b illustrate the production of a masking material in accordance
with
a second embodiment of the invention;
Figures 4a and b illustrate the use of the masking material of Figure 3;
Figures 5a and b illustrate the production of a further masking material in
accordance with the invention; and
Figure 6 illustrates masking material for use in the invention.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figures la and b illustrate the production of a masking material in accordance
with
one embodiment of the invention. Figure la shows, in cross-section, a portion
of a foam
web (2) on which is coated a stripe of pressure-sensitive adhesive (4). The
foam web is
passed through a multi-slitter fitted with crush cutter blades (6). Three
crush cutter blades
(6) are shown which are spaced an appropriate distance apart to form a primary
cord (8)
and a secondary cord (10). A repeating arrangement of such cutter blades may
extend
across the full width of the web to produce a multiple array of masking
strips.
The crush cutter blades compress the foam web and form a cold-weld which holds
the foam in the curved configuration shown in Figure lb. A primary cord (8)
having the
stripe of pressure-sensitive adhesive (4) is formed joined to a secondary cord
(10) by a
common cold-weld. The secondary cord (10) is readily separable from the
primary cord
(8) by tearing along the weld.
Figures 2a and b illustrate the use of the masking material. The masking
material
is secured to a surface (12) to be coated by the pressure-sensitive adhesive
stripe (4). The
masking material is positioned such that the secondary cord (10) contacts the
surface (12)
and is adjacent the area to be coated. A first coating (14) (shown in
exaggerated
thickness) is applied. Typically the first coating (14) will be a primer. It
will be noted that
the coating (14) extends under the curvature of the secondary cord (10)
resulting in a
tapered or feathered edge to the coating (14).
The secondary cord (10) is removed by tearing along the cold-weld. The primary
cord (8) remains in position and a second coating (16) (shown in exaggerated
thickness) is
applied= over-.the.first:.coating .(14). The second coating (1z6) extends.
Qv.erathe edge of the
coating (14) and under the overhanging curvature of the primary cord (8)
thereby assuring
that none of the coating (14) is exposed and providing a feathered edge to the
coating (16).
Thereafter, the primary cord (8) is removed.
The dimensions of the primary and secondary cords may be varied by suitable
selection of the thickness of the foam web and spacing of the crushed cutter
blades.
Suitable masking materials have been produced from a foam web having a
thickness of
about 15mm to produce a substantially cylindrical primary cord having a
diameter of
approximately 13mm. Secondary cords of approximately 3, 6 and 7mm attached to
the
primary cord have been formed by suitable spacing of the crushed cutter
blades.
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Figures 3a and b illustrate the production of a masking material in accordance
with
a second embodiment of the invention. A foam web (20) is coated with two
stripes of
pressure-sensitive adhesive (22, 24) and a second thinner foam web (25) e.g.,
having a
thickness of 2 to 5mm, is placed such that it overlaps, but does not
completely cover, the
adhesive strips (22, 24). The composite web is fed into a multi-slitter fitted
with crushed
cutter blades the positions of which are shown at 26. The crush cutter blades
compress the
foam web forming cold-welds resulting in the production of two separate
masking strips
(28). Each masking strip (28) comprises a substantially cylindrical portion
(30) formed
from the foam web (20), an adhesive stripe (22, 24) and a removable edge
portion (32)
formed from the foam web (25) which is secured to the cylindrical portion (30)
by the
adhesive stripe (22, 24) and a cold-weld. The removable edge (32) follows the
cylindrical
contour of the core (30).
Figures 4a and b illustrate use of the masking material (28). The masking
material
is positioned on a surface (12) to be coated and secured by the pressure-
sensitive adhesive
stripe (22, or 24, not shown). The masking material is positioned such that
the removable
edge (32) is adjacent the edge of the area to be coated. A first coating
material (14), e.g.,
primer, is applied, some of which extends beneath the overhang of the curve of
the
removable edge (32) to provide a feathered edge to the coating. Thereafter,
the removable
edge (32) is stripped from the core (30) without displacement of the core
thereby exposing
the curved surface of the core adjacent the edge of the area to be coated. A
second coating
(16) is applied over the first coating. The second coating (16) completely
overlays the
first coating and extends under the overhang of the curve of the core (30)
thereby
;,prouiding a feathered edgeto the second coating. Thhere.after,
the,maslCing,~atexial is .
removed.
Figures 5a and b illustrate the production of a masking material similar to
that
disclosed in Figures 3 and 4 but having two removable edges. The masking
material is
formed from a foam web (31) on which two thin foam strips (33) are adhered by
a
pressure-sensitive adhesive or double sided pressure sensitive adhesive tape
(not shown).
The two foam strips (33) are separated by a gap (34) on which a stripe of
pressure-
sensitive adhesive is applied either before or after cold-welding. The
composite web is fed
into a multi-slitter fitted with crusher blades (36) which compress the foam
and form a
cold-weld. The resultant masking material is shown in Figure 5b and comprises
an array
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of masking material each comprising a central core (38) and a pair of
removable edges
(40). Adjacent masking strips are adhered to each other by the cold-weld but
are readily
separable. Each masking strip may be used in the manner described with
reference to
Figures 4a and b.
Figure 6 of the accompanying drawings illustrates a variable size painting
mask
which is made by die stamping a foam web e.g., 5mm thick, in a manner such
that the die
steel does not cut all the way through the foam but the foam is marked with a
series of
concentric cold-welds. The overall masking material may be in the region of 1
metre
square and comprise a plurality of concentric welds (50a to 50d) defining
annular
segments (52a to 52d). In use, one or more segments of the mask large enough
to
completely reveal the area to be painted is removed e.g., segment (52a), and
the mask
applied to the surface and held in place by a layer of adhesive (not shown). A
first coating
material is applied, the mask allowing formation of a feathered edge due to
the curvature
caused by the cold-weld. The inner segment of the mask e.g., segment (52b) is
then
removed by tearing the cold-weld thereby exposing a further curved surface. A
second
coating material is applied over the first coat, the curve of the remaining
masking material
causing a feathering effect at the edge of the top layer. It will be
appreciated that a variety
of shapes other than circular may be employed for the variable size painting
mask.
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