CA1151678A - Dry-set mortar composition having enhanced bonding characteristics - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A dry-set mortar composition is disclosed for setting tiles and in particular ceramic tiles. The mortar has a good sag resistance and high bond strength without the use of asbestos fibers. The mortar composition is adapted to be mixed with water having in the dry state a composition of sand, Portland cement and cellulose ether, the improvement comprising 0.0070 to 0.0150 parts by weight anionic polyacrylamide and 0.0 to 0.9 parts by weight Bentonite Clay.

Description

~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 :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, 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, . . .

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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 O ~D ~ ~ O O
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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-~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.

~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

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, ~

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.

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

Claims (12)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a dry-set mortar composition adapted to be mixed with water having in the dry state a composition of sand, Portland cement and cellulose ether, the improvement comprising 0.0070 to 0.0150 parts by weight anionic polyacrylamide and 0.0 to 0.9 parts by weight Bentonite Clay.

2 The dry-set mortar composition according to claim 1 further comprising polyvinyl alcohol.

3 The dry-set mortar composition according to claim 1 wherein the cellulose ether is methyl cellulose of 3,700 -4,300 viscosity at 20°C, 2% aqueous solution and the methyl cellulose comprises about 0.5 - 0.6 parts by weight of the dry composition.

4 The dry-set mortar composition according to claim 2 wherein the composition in the dry state is about 50 parts by weight sand, 0 18 parts by weight polyvinyl alcohol, 0.3 - 0.8 parts by weight Bentonite Clay, 0.6 parts by weight methyl cellulose having a viscosity of 3,700 - 4,300 at 20°C, 2%
aqueous solution, between 0 0085 and 0.0150 parts by weight anionic polyacrylamide and the remainder of the composition in the dry state is Portland Cement; the composition comprising 100 parts in total

5. The dry-set mortar according to claim 2 wherein the composition in the dry state is about 64 parts by weight sand, 0.12 parts by weight polyvinyl alcohol, 0.10 parts by weight anti-foam, 0.08 parts by weight UREA, 0.120 parts by weight Bentonite Clay, from 0.007 to 0.013 parts by weight polyacrylamide and the remainder of the dry composition is Portland Cement; the composition comprising 100 parts in total.

6. The dry-set mortar according to any of claims 1, 2 or 3 wherein the Bentonite Clay is Sodium Bentonite Clay.

7. A dry-set mortar according to claim 4 or claim 5 wherein the Bentonite Clay is Sodium Bentonite Clay.

8 In a dry-set mortar composition adapted,to be mixed with water having in the dry state a composition of sand, Portland Cement and cellulose ether, the improvement comprising 0.0070 to 0.0150 parts by weight anionic polyacrylamide.

9. The dry-set mortar composition according to claim 8 further comprising polyvinyl alcohol.

10. The dry-set mortar composition according to claim 8 wherein the cellulose ether is methyl cellulose of 3,700 -4,300 viscosity at 20°C, 2% aqueous solution and the methyl cellulose comprises about 0.5 - 0.6 parts by weights of the dry composition

11. The dry-set mortar composition according to claim 8 suitable for wall mortar wherein the composition in the dry state is 50 parts by weight sand, 0.18 parts by weight polyvinyl alcohol, 0.6 parts by weight methyl cellulose, between 0.0085 -0.0150 parts by weight anionic polyacrylamide and the remainder of the composition in the dry state being Portland Cement with the total sum of the parts equaling 100 parts by weight.

12. The dry-set mortar composition according to claim 8 suitable for floor mortar wherein the composition in the dry state is about 60 parts by weight sand, 0.12 parts by weight polyvinyl alcohol, 0.10 parts by weight anti-foam, 0.08 parts by weight UREA, and from 0.007 to 0.013 parts by weight poly-acrylamide with the remainder of the dry composition being Portland Cement, the composition totaling 100 parts by weight.