Note: Descriptions are shown in the official language in which they were submitted.
~S1678
This invention relates to mortar compounds for setting
tile and in particular for setting ceramic tile, More partic-
ularly, the invention relates to dry set mortar compositions
which, in addition to being sag resistant, have high bond strength.
At present, tile and particularly ceramic tile is set
in many cases by dry-set Portland cement mortars, Prior to the
advent of dry-set mortars, the Portland cement compositions that
were used had to be applied to the substrate in a very thick bed
and generally also required a thin mortar coat for setting the
tile, These thick bed mortar setting methods were referred to
as mud-method tile setting systems, The mud-method Portland
cement mortars have now been replaced to a great extent by thin-
bed Portland cement dry-set mortars. Typical dry-set mortars
are princi~ally comprised of Portland cement, sand, and a water
retentive cellulose ether, such as methyl cellulose or
hydroxyethyl cellulose, The dry-set mortars are generally
delivered to the job site in the dry state and water is added
on the job site to mix the mortar into a slurry. United States
Letters Patent No: 2,934,932 (Wagner; issued May 3, 1960) and
United States Letters Patent No: 3,243,307 (Selden; issued
March 29, 1966) are illustrative of the dry-set mortars which
are currently used to set tile in thin-beds. In addition, dry-
set mortars can be provided with a rubber or polymer latex which
is added to the dry mix to make a mortar which is then called a
latex Portland cement mortar.
The dry-set mortars both with and without latex may
also contain additives to provide or improve specific properties.
Originally, the dry-set mortars also contained asbestos
fibers or similar fibrous materials which provided the mortar
with the sag resistance. Sag resistance is a property or a
characteristic relating to the ability of the mortar to resist
movement under load until a certain load level is reached, This
-- 1 --
:115~67B
property or characteristic is vitally important in dry-set mortars
and also to a latex mOrtAr since a mortar, to be Iunctional, must
be in a slurry or paste form on the one hand, but also must be
capable of supporting the load imposed on it by the tiles set in
the mortar. It is, therefore, very important that the mortar
support the tile without any appreciable slippage of the tile
from the trowelled mortar surface during the period in which the
mortar is setting. In wall applications, sag resistance is even
more critical because the mortar must hold the tile in position
on the wall during the period in which the mortar is setting.
Sag resistance is defined by a test method that is part of the
American National Standard Specification for Dry-Set Portland
Cement Mortars-A1118.1.
Recently the tile industry, led by the Tile Council
of America Inc., has developed dry-set mortars which do not
require the use of asbestos ~ibers. Rather than asbestos fibers,
the dry-set mortars have been provided with other additives to
afford sag resistance. United States Letters Patent No: 4,082,563
(Ellis et al; issued April 4, 1978) discloses a dry-set mortar
containing hydrated and anhydrous salts and similar ingredients
to provide a sag resistance rather than the asbestos
Tile Council of America has also developed a superior
asbestos-free dry-set mortar which contains long chain organic
polymers. Anionic and nonionic long chain polyacrylamide
materials are illustrative of the long chain organic polymers
which provide the new improved mortar with sag resistant char-
acteristics. The use of montmorillonite clays, attapulgite clays
and mixtures of these clays have also been developed for use in
mortars both alone and in combination with the long chain organic
polymers. These developments are set forth in United States
Letters Patent Nos. 4,021,257 (Bernett, May 3, 1977) and
4,043,827 (Bernett, August 23, 1977).
~:~5~6'78
It has now been found that the new improved high sag
resistant dry-set mortars can be provided with enhanced bond
strength by using a critical formulation.
It is an object of the present invention to provide a
dry-set mortar having good sag resistance and high bond strength
without the use ~f asbestos fibers.
It is a further object of the present invention to
provide a dry-set mortar which has an improved skinning char-
acteristic which as a necessary concomitant affords enhanced
bonding.
In brief the composition of the invention is a Portland
cement based mixture comprised of Portland cement, sand, about
0.5 to 0,6 parts by weight of a cellulose ether and from .007
to .015 parts by weight of an anionic polyacrylamide. The com-
position is improved by from 0.0 to 0,9 Sodium Bentonite Clay.
Additives are also included in the preferred embodiment of the
composition. Thus, the composition provides a mortar having
excellent sag resistance and in addition enhanced bond strength.
A preferred embodiment of this invention comprises a
composition which is used to set ceramic tile, bricks, small
stones and other similar products both on walls and on floors.
The composition has suitable properties for holding the tile
or other material on the wall or floor securely and firmly and
is capable of adjusting for elevational differences in the
tiles on the floor and for irregular positioning of tiles on the
wall.
One of the most significant properties of the mortar
is bond strength. Bond strength is the capacity or capability
of the mortar to hold tile on the wall or floor long after the
mortar has set. In effect, it is the property which determines
how tenaciously the tile or other material that is being set,
can be held to the wall or floor by the mortar,
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1~51678
One of the phenomena that relates to bond strength is
known as skinning Skinning is a condition that occurs in part,
as a result of chemicals in the mortar composition. Although
the applicant is not committed to or bound by any theory, it is
believed that skinning will be more prominent when chemicals
having crosslinking or matrix forming characteristics are used
in a composition. Skinning is the formation of a thin-skin or
a membranous film over the surface of the mortar In effect,
the skin or membrane acts as a barrier between the tacky mortar
material and the bisque or lower surface of the tile to which
the mortar must adhere in order to hold the mortar on the wall
or floor. In practice, the placing of a tile on mortar which
has the skin or membrane formed on the surface will destroy or
rupture some of the membrane thereby exposing the tacky adhesive
mortar to the bisque in the portion where the skin has been
destroyed. It is axiomatic that the more skin that is ruptured
the more tacky mortar will be exposed to the tile bisque and the
more mortar there is to hold and retain the tile on the wall or
floor. Accordingly, the more skin that is destroyed or con-
versely the less skin that is present to form a barrier between
the tacky mortar material and the bisque, the more surface area
will be covered with mortar and the bond between the mortar and
the individual tile will be greater since more mortar is directly
exposed and adhering to the tile.
Thus, the composition of the present invention has
been found to provide an ideal mortar composition wherein the
sag resistance is as good as the sag resistance provided by any
prior art composition including the Wagner and Selden dry-set
adbestos fiber compositions and the Bernett organic polymer
dry-set mortars. In addition, the skinning is held to a minimum
thereby providing enhanced bond strength for the mortar.
The composition of the mortar of the present invention
~S:1~i7~3
in the dry state includes the customary or conventional dxy-set
mortar ingredients, such as, sand, Portland cement, gelvatol
9000 (polyvinyl alcohol~ and additives, such as colloids 770 DD
and urea, and approximately 0 5-0.6 parts by weight of a
cellulose ether ? such as, methyl cellulose, hydroxyethyl
cellulose, hydroxypropyl cellulose, etc. The critical ingredient
both quantitatively and qualitatively in the composition is an
anionic polyacrylamide used in a proportion from 0.008 to 0.015
parts by weight of the dry composition. In addition, the use
of Bentonite Clay in a proportion of 0 0 to 0.9 improves the
composition. It is noted that of the Bentonite Clays, Sodium
Bentonite Clay is somewhat more suitable than the others, such
as, Magnesium or Calcium. In use, the dry composition is mixed
with water to provide a slurry.
The following examples have been run for both sag
resistance and skinning. The examples have been run using a
base composition and varying the polyacrylamide and cellulose
ether component The base composition for Examples 1 through 5
is chosen to provide a mortar suitable for setting wall tiles.
The base composition for examples 1 - 5 is comprised of 50 parts
sand, 0.18 parts polyvinyl alcohol, 0.5 parts Sodium Bentonite
Clay and 48 72 parts Portland cement The sand used in the
examples is a Grade D sand which is a clean, graded, white silica
sand having a particle size wherein not more than lO~o pass 140
mesh, not more than 3% remain on 30 mesh and which peaks on
70 mesh The Portland Cement is Type 1 conforming the ASTM
Standard Specification C 150. The following chart shows the
ingredients added to the base composition in each respective
example and the resultant performance of the mortar when tested
for skinning and sag resistance. All parts are by weight.
The methyl cellulose ingredient used in the examples
is the Dow Chemical Company type K 4M which has a viscosity of
~5~713
~- 3,700 to 4,300 centipoises (2.OC~0 aqueous 20C). The anionic
~- polyacrylamide used in the examples is SEPARAN AP 273 which is
also a Dow Chemical Company product, Further, the pre-ferred
range for Sodium Bentonite Clay for wall mortar is .3 - .8% by
weight,
-- 6 --
. . .
1~LS1678
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~LlS1~7~3
The following Rxamples 6 through 10 are shown with the
polyacrylamide and methyl cullulose ingredients added to a base
floor mortar mix, The floor mortar mix is comprised of 60 parts
by weight sand (grade B), 0.12 parts by weight polyvinyl alcohol,
*
q~ 0,08 parts by weight anti-foam (COLLOIDS 770 DD), 0.08 parts by
weight urea, and 0.075 parts by weight Sodium Bentonite Clay with
the remainder Portland Cement to total 100 parts by weight. The
preferred range for Sodium Bentonite Clay for floor mortar is
0.05 to 0.7.
The following display shows the methyl cellulose and
polyacrylamide added for each respective example and the per-
formance of the mortar in both sag resistance and skinning,
ilSl~i78
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~5~67~
The sag resistance figures displayed in the Examples
1 through 10 are shown in terms of 6~ths of an inch, For example,
the two tiles that were tested l'or sag resistance when set with
the mortar of Example 1 show a sag of 1,5/~4ths of an inch, The
mortar of Example 3 showed respectively 2/64ths and 2.5/64ths of
an inch sag. The sag resistance values were obtained by testing
in accordance with the procedures for measuring "sag on vertical
surfaces" from the American National Standards Specification For
Dry-Set Portland Cement Mortar-A1118.1 - 1967,
The sag resistance results can be evaluated by a com-
parison with the performance characteristics for mortars set
forth in col, 11, lines 51-56 United States Letters Patent
No: 4,021,257 wherein a sag of 0 to 2/64ths is excellent. A sag
of 2/64ths to 8/64ths is very good. A sag of 8/64ths to 16/64ths
is good, A sag of 16/64ths to 64/64ths is fair and anything
over 64/64ths is regarded as poor,
Accordingly, the sag resistance for the mortars of
Examples 1 through 10 is excellent in all respects with the
exception of ~xample 10 and there performance is very good,
The skinning test is also performed in accordance with
American National Standard Institute Test A1118.4. The test
determines the shear bond strength of the mortar after various
intervals. The results reported are in terms of pounds of shear
bond load, The figures indicate the load in pounds that is
required to break the bond for the respective tests, The higher
the figure, the greater the load required to break the bond.
Conventional asbestos and polyacrylamide dry-set floor
and wall mortars were also tested against the dry-set mortar of
this invention. In one example the mortars were tested when
mixed in a ratio of 25 milliliters of water to 100 grams of dry
composition and in another, the water dry composition mix was
made under conditions simulating field conditions, The com-
- 10 -
~5~67~
position of the Wall Mortar of the Invention for Example 11 is
50 parts by weight sand (Grade D), 0,18 parts by weight po].y-
vinyl alcohol, 0,7 parts by weight Sodium Bentonite Clay,
0.511 parts by weight K 4M methyl cellulose and 0.009 parts by
weight SEPARAN AP 273, with the remainder Portland Cement to
obtain 100 parts by weight for the mix.
The composition for the Floor Mortar of the Invention
for Example 11 is 60 parts by weight sand (Grade B), 0.12 parts
by weight polyvinyl alcohol, 0.08 parts by weight urea, 0.12
parts by weight Sodium Bentonite Clay, 0.10 parts by weight
*
~ anti-foam (COLLOIDS DD), 0,5896 parts by weight K 4M methyl
`~ cellulose and 0,0103 parts by weight SEPARAN AP 273 with the
remainder Portland Cement to obtain 100 parts by weight for the
mix. The results of the comparative tests are as follows:
~ ~e~ C~, ~i"),
_ 11 --
~5~67~
EXAI~PL~ 11
]~;ORTARS OF SAG SKINNING (l~s.)
IJ r INVEl~TIONRESISTA~CE
-1/64 ln. 5 10 15 2025(11i~
Floor PSortar
25 ml H2n/100 ~ms 2.0 767422 123
field mix 5.0 835337 713
l?all Plortar
25 ml H20/100 gms 2.5 419285 0
field mix 2.0 -612429 69
CO~VENTIONAL
AS~ESTOS ~ORTAR
Eloor ~ortar
25 ml H20/100 gms 25.25 842392 462
field ~ix failed 708555 248
l~zll Mlortar
25 ml H20/100 ~s 30 75 1545914 608
field mix failed 826629 308
CON~TEl~TIONAL
POLYACRYLAMIDE MOP~TAR
Floor Mortar
25 ml H20/100 gms 2.5 651388 24
field mix 3,5 533333 216
~'211 Mortar
25 ml H20/100 gms 2.5 90098 0
field Plix 3.0 1024106 8
The comparison shows that the bond strength and sag
resistance of the mortar of the invention are improved over the
conventional polyacrylamide mortar and the bond strength of the
mortar of the invention is about the same as the bond strength
of the asbestos mortar, but the sag resistance is greatly
improved.
- 12 -
~151678
It has also been discovered that the improved mortars
of the invention perform superior to prior art mortars if clay
is absent from the formulation. The following examples illus-
trated the performance of mortar formulations of the invention
formulated without clay. The compositions for Examples 11 - 15
are as follows:
R~}AMPLE EXAMPLE EXAMPLE EXA~lPLE
12 13 14 15
INGREDIENT PARTS PARTS PARTS PARTS
BY WEIGHTBY WEIGHTBY WEIGHTBY WEIGHT
SAND "B" 3000 3000
SAND "D" 2500 2500
PORTLAND CEMENT 2461 2461 1961,5 1961.5
METHYL CELLULOSE 29.48 29,58 24,07 24,15
(K 4M)
~4 POLYACRYLAMIDE ~ .52 ,42 .43 ,35
(SEPARAN AP 273)
POLY VINYL ALCOHOL 9.0 9.0 6.0 6.0
(GELVATOL 9000) ~
ANTI-FOAM ~ 4.0 4.0
(COLLOIDS 770 DD)
llREA 4~0 4
~ J, ~
-- 13 --
678
The mortars of Examples 12 - 15 were mixed at field
consistency. The performance of the mortars obtained by sag
resistance and skinning tests set forth earlier in this specifi-
cation are:
SAG Milliliters SKINNING ( lbs . )
RESISTANCE WAThR/100 gms
1/64 in. of dry mix 0 5 10
EXAMPLE 12 2.5 26,5 ?1200 570 295
EXAMPLE 13 5.5 27,0 ?1200 884 200
EXAMPLE 14 2,5 26,0 ~1200 ~12001200
EXAMPLE 15 2,0 26.0 ~1200 9321020
Examples 12 and 13 are wall mortars and can be compared
with mortars of Examples 1 - 5 and the conventional wall mortars
of Example 11. Examples 14 and 15 are floor mortars and can be
compared with the mortars of Examples 6 - 10 and the conventional
floor mortars of Example 11,
From a comparison of data the mortar formulations of
the invention made without clay are superior to the prior art
mortars, Further, mortar formulations of the invention which do
not contain clay are only slightly less desirable as mortars than
the clay-containi~g mortar formulation.
The basic reason that the clay containing Iormulation
is superior to the formulation without clay is revealed when
the skinning test is extended to determine the performance over
a longer period of time.
- 14 -
11S167~
The following data enables a comparison:
Ml WATER SKINNING (lbs.)
100 gm 15 (Min.) 20 25 30 35 40
CONVENTIONAL 26,5852 513 443 415 46 52
Asbestos F].oor
Mortar
CONVENTIONAL 26,5660 367 32 0 0 0
Polyacrylamide
Floor Mortar
CONVENTIONAL 26,51158 653 578 0 0 0
Asbestos Wall
Mortar
CONVENTIONAL 26.5 40 0 0 0 0 0
Polyacrylamide
Wall Mortar
FLOOR MORTAR 28.5500 370 416 159 36 0
of Patent with
Clay
WALL MORTAR 28.0606 295 240 65 190 0
of Patent with
Clay
Example 11 27.5522 560 535 15 0 0
Example 12 27.5951 660 152 0 0 0
Example 13 26.5857 860 692 30 0 0
Example 14 26.0726 811 169 282 45 0
- 15 -
