Note: Descriptions are shown in the official language in which they were submitted.
MULTICOLOR SAFETY FLOOR 210 3 6 0 ~ 1068B
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FLOOR COVERING
Field of_the invention
This invention relates to a floor covering, in particular to
a safety floor covering having improved slip resistance
characteristics, and more particularly to a multi-color
safety floor covering.
Background to the invention
Floor coverings are known comprising a matrix of
thermoplastic material and a plurality of visually distinct
chips of thermoplastic material embedded therein. By the
term "chips" as used herein, we mean to include both
regularly and irregularly shaped pieces, including flakes,
strips, spheres, shreds, splinters, granules, granulates and
the like. One or a mixture of pigments is included in the
thermoplastic chips and/or in the matrix material, thereby
to produce a multi-color effect.
Safety floor coverings are known in which particulate
abrasive material is dispersed in a matrix of thermoplastic
material. Thus, British patent specification GB 1 231 005
(Welwyn Plastics (1955) Limited) describes a floor covering
containing grits of abrasive material such as alumina having
a size of 0.075 mm to 1.0 mm, the floor covering being
formed by mixing the abrasive material with PVC paste,
coating the mixture on a sheet of base material and curing
the coated sheet. After curing, the material can be
embossed with a textured roller to permit the grits to
penetrate through the top skin. Once this has occurred,
the very hard alumina is sufficiently exposed to give a
MULTICOLOR SAFETY FLOOR 21 ~ 3 6 Q f~ 1068B
flooring with improved non-slip properties and improved hard
wearing properties.
A disadvantage of locating the abLasive grits only at the
surface of the thermoplastic matrix i5 that as the floor
covering becomes worn, by loss of the upper surface, a fresh
surface is exposed with fewer exposed abrasive grits leading
to a loss of the non-slip properties.
In British patent specification GB 2 152 843-B (Welwyn
Plastics (1955) Limited) there is described a floor covering
which, in addition to abrasive grits, comprises colorea
quartz particles to provide a multi-colored effect.
Particles of silicon carbide are applied to the upper
surface of the thermoplastic matrix before it is cured,
which provides a high percentage of abrasive material at the
tread surface while it is brittle and breaks through the
skin of the thermoplastic material. There results a
coating to the base material which maintains its slip
resistant properties throughout the working life of the
floor covering.
Summary of the inven~ion
We have now discovered that a multi-colored floor covering
with long-life slip resistance can be achieved in a simple
and reliable manner.
Thus, according to a first aspect of the invention there is
provided a floor covering comprising a matrix of
thermoplastic material and a plurality of visually distinct
chips of thermoplastic material embedded in the matrix,
wherein particulate alumina is dispersed throughout both the
matrix and the chips.
MULTICOLOR SAFETY FLOOR 1068B
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~y the term "thermoplastic material" we mean any plastic
material which is cured to a form-retaining state by heating
and subsequent cooling. Preferably this material is
polyvinylchloride, a polyolefin resin, mixtures thereof and
mixtures of other synthetic resins and mixtures including
natural materials such as natural rubber. The
thermoplastic material preferably has a softening
temperature between 150C and 210C. Preferably, the
thermoplastic material used for the matrix is the same as
that used for the chips, which has an advantage of providing
a more homogeneous mix. ~uitable plasticisers include
phthalates, adipates and phosphates.
Usually, the matrix is coated on a base material in sheet
form which provides the floorings with strength and
dimensional stability. For the base, various flexible
porous sheet materials such as hessian, woven cotton fabric
felt, paper, metal foil, woven fibre glass or synthetic mesh
material may be used. We prefer to use non-woven polyester
sheet, reinforced with glass fibres to increase tear
resistance. A suitable thickness for the base material is
from 0.1 to 1.0 mm, with a sheet weight of from 20 to
200 g/m2. The base material may include a foam material
where the intended application of the product so demands.
~enerally, the matrix is coated on one side only of the base
material, but it is also possible for the base material to
be embedded in the matrix material.
A suitable thickness for the overall produc~, whether a base
material be present or not, is from 1.0 to 5.0 mm,
preferably from 2.0 mm to 4.5 mm.
In order to ensure a visual distinction between the matrix
MULTICO~OR SAFE~Y FLOOR 1068B
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and the chips, pigments may be included in one or both.
According to the desired color, an appropriate mixture of
pigments may be employed. We prefer to employ a matrix of
one color and a mixture of chips of various other colors,
thereby to achieve a multi-color effect. It is also
possible not to include a pigment in the matrix, so long as
at least one pigment is included in the chips, thereby to
provide the matrix with a substantially transparent
appearance.
The pigments may be organic or inorganic, but are preferably
heat and light stable and compatible with each other and
with the thermoplastic material of the matrix and the
chips. The level of pigment used may be up to 1~ by weight
of the associated thermoplastic material. In addition to
the chips, other particulate material may be dispersed
throughout the matrix. Thus, colored quartz may be
included to add to the multi-color effect and silicon
carbide may be included which, in view of its highly
reflective nature, confers an attractive finish to the
surface of the floor covering.
The alumina used in the floor covering of the invention is
preferably alpha-A12O3, which occurs in nature as
corundum. While in its pure form alumina is colorless, the
presence of various colored impurities when derived from
natural sources is not a disadvantage. Ideally, the
alumina has an average particle size lying within the range
of from 0.1 mm to 2.0 mm, most preferably from 0.4 to
O.7 mm, such as about 0.6 mm.
While not wishing to be bound by theory, it appears that it
is the combination of relatively low cost, hardness,
brittleness, crystalline form and compatibility which
MULTICOLOR SAFETY FLOOR 21~ 3 ~ ~ ~ 1068B
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provides alumina with a unique benefit in the floor
coverings according to the invention.
The amount of alumina present in the matrix and the chips is
preferably such that the ratio of the thermoplastic material
to the alumina is from 100:1 to 1:1 by weight, preferably
from 6:1 to 3:1 by weight, and we have found it suitable to
use the same level of alumina in the matrix as in the chips.
The level of visually distinct chips in the floor covering
according to the invention and their size depends in part on
the clesired multi-colored design, but we have found tha~ a
ratio of matrix to chips of from 1.5:1 to 20:1 by weight,
and an average chip size of from 1.0 mm to 10.0 mm is
suitable. The chips will usually be of irregular shape.
According to a second aspect of the invention there is
provided a method for forming the floor covering, comprising
the secluential steps of:
(i) forming a layer of thermoplastic paste;
(ii) scattering visually distinct chips of thermoplastic
material on the thermoplastic paste layer; and
(iii) curing the thermoplastic paste layer;
wherein the thermoplastic paste and the visually distinct
chips both have particulate alumina dispersed therein.
In one embodiment of the invention, the chips are made as
follows. In a first mixing step, a thermoplastic paste can
be prepared containing a thermoplastic material,
MULTICOLOR SAFETY FLOOR 10 6 8B
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plasticisers, pigment and other optional ingredients. It
is an advantage to mix the alumina in with this paste in a
separate step. Alumina, being abrasive, may tend to cause
excessive wear in the first mixer which has to be operated
under such conditions that a very homogeneous mixture of
ingredients is formed, whereas the alumina need only be
stirred into the paste with sufficient thoroughness to avoid
settling.
The paste mixture may be formed into the necessary layer for
curing by coating on a suitable backing, which may or may
not be identical ~o that used subsequently for supporting
the matrix of the floor covering. Alternatively, the layer
may be formed by extrusion or by calendering.
The layer of thermoplastic paste containing the alumina is
then cured, for example by passing through an oven at a
temperature of from 150C to 200C. A heating time of up
to 5 minutes, say 2 to 3 minutes is suitable. The cured
sheet is now passed to a granulator in which the chips of
desired size and shape are formed. The chips are stored
for later use.
By repeating the process a number of times, varying the
nature and level of the pigment and the mesh size of the
granulator screen plate, chips of various appearance can be
produced. These may be separately stored or immediately
mixed together to form a composite blend.
As an alternative method of forming the chips, the
thermoplastic paste containing the alumina may be applied in
discrete surface areas onto a supporting surface by means of
a rotary screen printing cylinder, the applied paste being
cured by passing the supporting surface adjacent a heat
MULTICOLOR SAFETY FLOOR ~ ~ J ~ ~ ~ 1068B
source and the chips so formed being removed from the
supporting surface.
In the next repeat of the process the alumina-containing
thermoplastic paste is used for forming the matrix of the
floor covering. Again, it may be coated on an appropriate
backing. Before being passed to the curing oven, the
desired composite blend of chips is scattered onto the upper
surface of the paste. After leaving the oven, we prefer
that the product, before cooling, passes between a pair of
pressure rollers which press the chips into the matrix
leaving the product with a substantially flat tread
surface. After cooling, the product may be stored as
desired, for example in the form of rolls or tiles.
In a preferred embodiment of the invention, the matrix is
built up by successive coatings, each coating being cured
and the product cooled before the next coating is applied.
Ideally, the chips are added to each coating, but it is not
essential that chips of the same shape, size and color are
added to each coating. Various design effects can be
achieved by applying different chips to different coatings.
Y 955~ of the invçntion
The invention will now be further described, purely by way
of example, with reference to the accompanying drawings, in
which:
Figure 1 is a diagrammatic representation of an apparatus
useful for forming floor coverings according to the
lnvention; and
MULTICOLOR SAFETY FLOOR 1068B
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Figure 2 is a cross-section, not to scale, of a product
according to the invention.
In the apparatus shown schematically in Figure 1, PVC powder
(labelled PVC), a pigment and a plasticiser (labelled ADD)
are mixed thoroughly in a mixer 10 and the plastisol or
paste so formed is passed to a second mixer 12 where fine
part'cle size alumina (labelled Al2O3) is dispersed
therein. A suitable composition for the paste leaving the
mixer 12 would be (by weight):
PVC
Pigment(s) 6%
Phthalate plasticiser 30
Epoxidised soyabean oil (viscosity modifier) 7
Calcium-zinc stabilisers 3
Alumina 15
The alumina-containing paste then follows one of two
selectable routes. According to a first route the paste is
coated onto a web of base material 13 supplied from a source
14 by way of a coating roller 16 and doctor blade 18. The
coated base material passes through an oven 20 which is at a
temperature of 175C for 2.5 minutes to cure the PVC and
after cooling the colored alumina-containing sheet product
is passed to a granulator 22 where it is broken up into
chips having an average size of 5 mm. The chips are then
passed to one of a number of storage locations 24a, b, c etc
according to chip size and shape and pigment color. By
changing the pigment in the ingredients fed to the mixer 10,
or by omitting the pigment, and by changing the settings of
the granulator 22, a series of chips of different colors,
shapes and sizes can be produced and stored at 24.
MULTICOLOR SAFETY FLOOR 1068B
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The ingredients fed to the mixer 10 are changed again, by
changing the pigment or by omitting the pigment, but now the
output of the mixer 12 is fed to the input of the main
coating line where the PVC paste is coated on a web of base
material 25 supplied from a source 26 by way of a coating
roller 28 and doctor blade 30. In the main coating line a
scatter applicator 32 is positioned between the coating
roller 28 and an oven 34. The scatter applicator 32 is fed
via a mixer 36 with chips from one or more of the storage
locations 24a, b, c etc. selected according to the desired
visual effect. These chips are scattered over the surface
of the un-cured PVC on the base material and become embedded
therein. The coated base material now passes through
oven 34 at a temperature of 175C for 2.5 minutes where the
PVC of the matrix is cured. Before cooling, the product
passes between a pair of rollers 37, 38 where the chips are
pressed into the interior of the PVC and a generally flat
upper surface is achieved. A number of embossing rollers
not shown may follow before the product is cooled at 40 and
wound into a roll 42 for storage.
The product produced by the method set out above has the
appearance in cross-section shown diagrammatically in
Figure 2.
Figure 2 shows the base material 25 supporting a matrix 44
of cured PVC in which are embedded a number of chips 46 also
of cured PVC. The matrix 44 and/or the chips 46 are
pigmented or otherwise adapted to be visually distinct from
each other. Dispersed throughout both the matrix and the
chips are particles 50 of alumina. Other discrete
particles 48 may also be present near the surface or
dispersed throughout the matrix 44 formed of other materials
such as silicon carbide or colored quartz.
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AS the product becomes worn in use, some of the upper
surface is lost, progressively exposing more originally
interior material. As a result of the particulate alumina
being dispersed throughout both the matrix 44 and the
chips 46, some particulate alumina is always present at the
surface. This particulate alumina, being brittle, is
broken up as the floor covering is walked on and, being
hard, digs into the thermoplastic material, whether of the
matrix or of any surface exposed chips, causing microscopic
indentations in the upper surface. It is this effect which
is thought to be responsible for the slip resistance
properties of the product.
The presence of the particulate alumina in both the matrix
and the chips means that this slip resistance benefit is
achieved no matter what the ratio of chips to matrix may be,
thereby giving the designer greater freedom in his choice of
multi-color patterns and ensuring that the slip resistance
is maintained in wet conditions and throughout the wear life
of the flooring.
For the measurement of slip resistance, British Standard
812, Part 114:1989 may be applied using a friction tester
according to the Transport and Road Research Laboratory
design.
