Latex blend binder compositions for asbestos sheets

A binder composition for asbestos fibers comprises a latex blend in which the dispersed phase comprises (1) from about 80 to 99.5 weight percent of a synthetic rubber and (2) from about 0.5 to 20 weight percent of a highly carboxylated polymer. The highly carboxylated polymer is a copolymer or terpolymer containing (1) an .alpha.,.beta.-unsaturated carboxylic acid, (2) an alkyl ester of an .alpha.,.beta.-unsaturated carboxylic acid, and optionally (3) an ethylenically unsaturated organic monomer which is copolymerizable with monomers (1) and (2) to form a stable latex.

FIELD OF THE INVENTION 
This invention relates broadly to new binder compositions for asbestos 
fibers and aggregates and to asbestos sheets prepared therefrom. The 
binder compositions are latex blends wherein the dispersed phase comprises 
(1) from about 80 to about 99.5 weight percent of a conventional rubber 
binder and (2) from about 0.5 to about 20 weight percent of a highly 
carboxylated polymer. The highly carboxylated polymer latex comprises a 
copolymer or terpolymer of an .alpha.,.beta.-unsaturated carboxylic acid, 
an alkyl ester of an .alpha.,.beta.-unsaturated carboxylic acid and 
optionally, an ethylenically unsaturated organic termonomer as defined 
herein. The asbestos sheets produced from blending asbestos fibers with 
this binder composition are uniformly coated with synthetic rubber. 
DESCRIPTION OF THE PRIOR ART 
The first step in the preparation of a rubber-bonded asbestos sheet is to 
bring together a synthetic rubber latex and an asbestos slurry which was 
subjected to high mechanical shear. It has been the object of prior art to 
deposit uniformly and evenly a coating of synthetic rubber particles with 
a slight negative charge onto the cationic chrysotile fibers. Various 
methods of controlling or improving this precipitation have been proposed 
including the use of chelating and sequestering agents, polymeric 
dispersing agents and crocidolite (an asbestiform mineral with negative 
charge). These methods have been proven only moderately successful at 
accomplishing their objective since it is difficult even in the laboratory 
to completely separate the individual fibrils from the compact fiber 
bundles and aggregates of the chrysotile mineral. 
Generally, the slurry of asbestos fiber and aggregates coated with 
synthetic rubber is formed into a sheet on conventional papermaking 
machinery, i.e., a Fourdrinier wire or cylinder machine. The water is 
removed from the slurry by suction and the rate at which it drains governs 
the speed of the papermaking machinery. In the case of a slurry containing 
completely dispersed chrysotile fibers, the fibers lay down parallel to 
the plane of the sheet forming a tight, impermeable mat and preventing 
easy drainage. Larger aggregates or clumps of chrysotile lay down loosely 
with channels and voids between them allowing fast drainage of the water. 
Thus, most water-laid, rubber-bonded asbestos sheet is by necessity 
prepared from incompletely dispersed asbestos and contains a considerable 
amount of chrysotile clumps. These clumps, not having been dispersed, 
contain fiber in their cores which is not coated with synthetic rubber. 
It is therefore a primary object of this invention to provide a binder 
composition which can permeate any undispersed asbestos clumps and 
strengthen the interfiber bonding. It is also an object of this invention 
to provide an improved process for preparing water-laid, rubber bonded 
asbestos sheets with improved strength properties. These and other objects 
of the invention will become apparent from a reading of the following 
disclosure. 
SUMMARY OF THE INVENTION 
This invention provides a new binder composition for asbestos fibers, said 
composition being a latex blend wherein the dispersed phase comprises from 
about 80 to about 99.5 weight percent of a conventional synthetic rubber 
binder and (2) from about 0.5 to about 20 weight percent of a highly 
carboxylate polymer. The highly carboxylated latex comprises a copolymer 
or terpolymer containing (a) from about 30 to about 85 parts by weight of 
an unsaturated carboxylic acid of the formula. 
##STR1## 
in which R is methyl or ethyl, (b) from about 5 to about 50 parts by 
weight of an unsaturated carboxylic acid ester of the formula 
##STR2## 
in which R.sub.1 is alkyl of from 1 to 8 carbon atoms, preferably alkyl of 
from 1 to 4 carbon atoms, and R.sub.2 is hydrogen, methyl or ethyl, and 
(c) from 0 to about 20 parts by weight of an ethylenically unsaturated 
organic monomer which is copolymerizable with monomers (I) and (II) above 
to form a stable latex. 
The termonomer (3), which is critical in obtaining terpolymers of the 
proper characteristics for this invention, can be represented by the 
formula 
##STR3## 
wherein R.sub.3 is hydrogen, methyl, ethyl, or halogen such as chlorine, 
bromine, iodine or fluorine, X.sub.1 is hydrogen or C.sub.1 -C.sub.18 
alkoxycarbonyl, and X.sub.2 is a member selected from the group consisting 
of aryl, aminocarbonyl, cyano, C.sub.1 -C.sub.4 alkoxy, carboxy, C.sub.1 
-C.sub.18 alkoxycarbonyl, halo, acyl, aldehyde, keto, isocyanato, C.sub.3 
-C.sub.9 heterocyclic, C.sub.1 -C.sub.4 alkyl, C.sub.2 -C.sub.4 alkenyl, 
halomethylene, acetomethylene, sulfo, C.sub.1 -C.sub.4 alkoxysilane and 
hydrogen. 
The highly carboxylated latex and the conventional rubber binder latex are 
blended to provide an excellent binder composition for use in the 
manufacture of asbestos felts and sheets. The product is characterized by 
superior interfiber bonding. Furthermore, the drainage of water from 
asbestos slurries containing the latex blends of this invention is greatly 
accelerated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Asbestos sheets suitable for use as a substrate for vinyl flooring are 
generally produced with fibers ranging in length from 1/32 to 1/8 inch. 
Fibers with these lengths are classified by the Quebec Asbestos Producers 
Association as Grades 5, 6 and 7. These grades and mixtures thereof are 
generally used in the manufacture of asbestos sheets but other fibers, 
e.g., cellulose, are occasionally introduced. 
The desired amount of asbestos fiber, generally from 0.3 to 8% by weight of 
the total slurry, is added to the water. The slurry is then refined in a 
Hydropulper, Jordan engine, beater, disc refiner or the like. The water at 
this point is hot (about 38.degree. C.) and it is recycled from the wet 
end of the papermaking machinery. After the fiber bundles are broken down 
the slurry is transferred to a tank where binder latex is added. The 
mixture is then formed into sheets and the sheets are then pressed and 
dried. 
The conventional rubber binder latex used in the latex blends of this 
invention is typically and optionally carboxylated styrene-butadiene latex 
containing from about 50 to about 70 weight percent of styrene, from about 
30 to about 50 weight percent of butadiene and from 0 to about 5 weight 
percent of a carboxylic acid monomer such as, for example, acrylic acid, 
methacrylic acid, fumaric acid or itaconic acid. Alternatively, the latex 
may be a copolymer of acrylonitrile and butadiene, a neoprene latex, or 
other synthetic rubber latices known in the art. Additionally, the latices 
may also contain emulsifiers, chain transfer agents, preservatives and 
other modifiers which are well known to those skilled in the art. 
The highly carboxylated latices are prepared by a low temperature, single 
stage emulsion polymerization process described more fully below. The 
polymers resulting from this polymerization comprise the repeating units: 
##STR4## 
wherein R, R.sub.1, R.sub.2, R.sub.3, X.sub.1 and X.sub.2 are as defined 
hereinabove. 
In a preferred mode of practice of the present invention, the highly 
carboxylated latex should contain the following ingredients in the 
following proportions: 
(1) From about 30 to about 85 percent, preferably from 50 to 80 percent in 
copolymer latices and from 50 to 70 percent in terpolymer latices, by 
weight of an .alpha.,.beta.-monoethylenically unsaturated carboxylic acid 
of Formula I, preferably methacrylic acid, ethacrylic acid or a mixture 
thereof with other unsaturated carboxylic acids such as acrylic acid. The 
amount of such other unsaturated carboxylic acids which can be employed in 
such mixtures can vary up to about 50% or more of such mixtures depending 
upon the concentration and hydrophobic nature of the carboxylic acid ester 
units in the resulting polymer. As the concentration and/or hydrophobic 
nature of the ester increases, increasing amounts of such other 
unsaturated carboxylic acids, e.g., acrylic acid, can be employed to the 
extent that a stable latex can still be obtained. 
(2) From about 5 to about 50 percent, preferably from 20 to 50 percent in 
copolymer latices, and from about 20 to about 30 percent in terpolymer 
latices, by weight of at least one alkyl ester of an 
.alpha.,.beta.-unsaturated carboxylic acid, a predominant portion of said 
ester having 1 to 8 carbon atoms in the alkyl moiety. 
(3) From 0 to about 20 percent, preferably from about 3 percent to 8 
percent, by weight, of an ethylenically unsaturated organic termonomer of 
Formula III. The terpolymer of Formula III includes such illustrative 
monomers as styrene, vinyltoluene, chlorostyrene, acrylamide, 
methacrylamide, N-isopropyl acrylamide, acrylonitrile, methacrylonitrile, 
vinylidene cyanide, methylvinyl ether, ethylvinylether, butyl vinyl ether, 
halfacid ethylmaleate, halfacid 2-ethylhexyl maleate, halfacid 
ethylfumarate, halfacid ethylitaconate, diethylmaleate, dibutyl maleate, 
diethyl fumarate, vinylchloride, vinylidene chloride, vinylbromide, 
vinylidene fluoride, vinylacetate, vinylpropionate, vinylchloroacetate, 
vinylbenzoate, vinylthioacetate, acrolein, methacrolein, 
methylvinylketone, ethylvinylketone, isopropenyl methyl ketone, vinyl 
isocyanate, isopropenyl isocyanate, vinyl isothiocyanate, 
N-vinyl-2-pyrrolidone, N-vinyl-2-oxazolidinone, vinylfurane, indene, 
2,3-dihydrofurane, vinyl succinimide, butadiene, isoprene, chloroprene, 
allyl chloride, allylacetate, allyl laurate, methallyl chloride, vinyl 
sulfonic acid, sodium vinyl sulfonate, vinyltriethoxy silane, vinyl 
triisopropoxy silane, ethylene, propylene, and the like. 
It is to be understood that all the foregoing percentages are based on the 
total copolymer weight, and they have to total 100%. 
Besides the aforedescribed termonomer types, small amounts of a 
bifunctional ethylenically unsaturated crosslinking monomer may also be 
added to the mixture. This monomer has to be capable of polymerizing under 
free radical conditions so as to covalently bond different chains of the 
polymer. Polyfunctional monomers, such as divinyl benzene, 
polyethyleneglycol-dimethacrylate, methylene-bis-acrylamide, etc., are 
illustrative examples. Other monomers, which can render the polymer 
curable (through heat treatment) or otherwise crosslinkable, such as 
methylolacrylamide, glycidylmethacrylate, epoxybutadiene, etc., can also 
be used as comonomers. 
The preferred method of polymerization is essentially a free 
radical-catalyzed batch polymerization of monomers which are dispersed in 
the aqueous phase with suitable surface active agents and protective 
colloids. A redox initiator system is recommended. The exothermic 
polymerization is carried out under an inert gas and is complete after a 
period of about 10 minutes to about 2 hours. The particles of the 
resulting latex are extremely small in size and have a high anionic 
surface charge. The emulsions typically have from about 10 percent and 
preferably from about 20 percent to about 50 percent solids content. The 
average particle size of the emulsion may be from 500 Angstroms or smaller 
to about 3000 Angstroms or greater. The reaction temperature applied 
depends, in the first place, on the polymerization catalyst and the 
monomers used. In general, the polymerization is carried out at a 
temperature in the range of from 5.degree. C. to 120.degree. C. When the 
catalyst is a redox system, the recommended initial temperature range is 
5.degree. C. to 80.degree. C., advantageously, 15.degree. C. to 60.degree. 
C. 
It is advisable to operate with exclusion of oxygen, for example under a 
neutral gas such as nitrogen, argon, and the like. Sometimes it may also 
be advantageous to run the reaction under elevated or reduced pressure. 
The polymerization can be run conveniently by a single stage procedure, 
whereby all the ingredients are charged to the reactor at the same time. 
Since the polymerization reaction is exothermic, the initiation thereof 
can be evidenced by the increasing temperature resulting from the addition 
of the reactants. When the polymerization has proceeded to the extent that 
the consumption of the monomers is practically complete, the terminal 
point is indicated by the cessation in the rise of the temperature, 
followed by a temperature drop. The time period necessary for the 
aforedescribed operation can range from about 10 minutes to about 2 hours. 
Chain transfer agents can be used to regulate the average molecular weight 
of the polymer. Preferred agents are mercaptans such as 
t-dodecylmercaptan. 
The preparation of the terpolymers is carried out in an emulsion system. 
The term "emulsion" as used herein is intended to mean a true colloidal 
dispersion of the terpolymers in water. 
Polymerization is effected in the presence of a catalyst or initiator, 
preferably one which serves as a thermally activated source of free 
radicals. Among such catalysts may be mentioned peracetic acid, hydrogen 
peroxide, persulfates, perphosphates, perborates, percarbonates, etc. The 
preferred catalyst is ammonium persulfate, as it provides efficient 
reaction rates and contains a fugitive cation. The amount of initiator 
used is normally about 0.03 to about 3.0 percent by weight of the total 
monomers and preferably from about 0.25 to about 0.5 percent. Preferably 
the initiator is a redox combination of the water soluble persulfate as 
the oxidizing component and a hydrosulfite, e.g., sodium hydrosulfite, as 
the reducing component of the redox combination. Water soluble bisulfites, 
metabisulfites or thiosulfates, reducing sugars, formaldehyde sulfoxalate, 
etc., may be used in lieu of the hydrosulfites. Other typical redox 
combinations, such as sodium azide and ceric ammonium sulfate, titanium 
trichloride and hydroxylamine, and the like may also be used. Generally 
useful proportions of the indicated persulfatehydrosulfite system are from 
about 0.01 to about 1.0 percent for the oxidizing component and from about 
0.15 to about 1.5 percent for the reducing component based on the amount 
of monomers. 
The redox combination can be further activated by the presence of 
polyvalent metal ions at the lower oxidation stage, e.g., ferrous sulfate, 
cuprous sulfate and the like. The preferred amount of these metal salts 
may be between 5 ppm and 10 ppm by weight, based on the total amount of 
the monomers. 
The aqueous medium for polymerization contains some emulsifiers to help to 
disperse the monomers in the aqueous medium, and to protect the particles 
formed. Salts of the higher molecular weight sulfonic acids, e.g., alkyl 
aryl sodium sulfonates, are eminently suitable for the purpose, though 
other surfactants may also be used with good results. 
The amount of surfactant employed can be varied considerably, but 
ordinarily from about 0.1 percent to about 10 percent, and more 
particularly from about 0.2 percent to about 1.0 percent, by weight, based 
on the total weight of the comonomers, will be used. Some additive such as 
alcohols can also be used in order to enhance the solubilization of the 
water insoluble ingredients. The concentration of these materials can be 
varied between 0.1 percent and 2.0 percent by weight, based on the weight 
of the comonomers. The emulsion can also contain a small amount of a 
protective colloid, such as water soluble cellulose derivatives, poly 
(vinylpyrrolidone), alkali metal polyacrylates, water soluble alginates, 
and the like. The amount of such a colloid used can range, for example, 
from about 0.1 percent to about 2 percent and more particularly from about 
0.5 percent to about 1 percent. 
Only a small amount of highly carboxylated latex is required to produce 
significant improvements in the physical properties of the slurry and the 
finished sheet. The highly carboxylated latex may be blended with 
conventional rubber binder latex provided that the two are compatible. 
Such blends may contain as little as 0.5 parts to as much as 20 parts of 
the highly carboxylated additive polymer in 100 parts of the dry weight. 
The preferred amount of highly carboxylated polymer is from about 1 part 
to about 8 parts in 100 parts of the total polymer dry weight. The 
resulting slurry with asbestos and 15 parts of binder will contain from 
about 20 ppm to about 800 ppm of highly carboxylated polymer. The exact 
amount of highly carboxylated polymer needed to achieve the desired 
performance characteristics will depend on the properties of the binder 
latex with which it is blended. 
While not wishing to be bound by any theoretical considerations or 
mechanisms, it is currently believed that the effectiveness of the latices 
employed in the present invention in improving the properties of the 
asbestos felt, lies in the highly charged character of said latices, due 
to the high concentration of carboxyl groups. The presence of the 
termonomer as defined herein improves the drainage of the asbestos felt 
significantly. This is believed to be attributable to the ability of the 
termonomer to separate vicinal carboxyl groups, thus increasing the number 
of dissociated carboxyl groups and diminishing the number of inactive 
ion-bound carboxyls. The termonomer does that through its reactivity with 
the two comonomers. 
Latices for asbestos felts are evaluated by preparing hand sheets and 
subjecting them to conventional paper testing. A blend of 25 parts of 
Quebec grade 5 and 75 parts of Quebec grade 7 asbestos is dispersed in 
water (38.degree. C.) to about a 5% consistency. The slurry is agitated 
using a 2.5 inch split disc impeller at 1000 rpms for 8 minutes. 
Sufficient latex is added to give 15 parts of polymer in 100 parts of 
asbestos and the stirring continued for 7 minutes. The resulting slurry is 
uniform and homogeneous and suitable for forming sheets in a Williams 
sheet mold after being diluted to a 3% consistency. The sheets are then 
pressed on a Williams hydraulic press and dried on the Williams standard 
sheet dryer. 
Water (35.degree. C.) is added to the stock to bring the consistency to 2%. 
The drainage of water from the asbestos slurries is measured with a 
Schopper-Riegler freeness tester. Low numbers indicate fast drainage. 
The tensile strengths are determined by pulling 1 inch strips of the sheet 
on an Instron 1130 test instrument at a crosshead speed of 2 in/min. A 
cold test is done at room temperature (21.degree. C.); a hot test is done 
by heating the strip to 190.degree. C.; a plasticizer tensile is run after 
the sample is soaked for 18 hours in butyl benzyl phthalate to simulate 
the plasticizers which may be used in some vinyl coatings in flooring 
manufacture. 
For a fuller understanding of the nature and objects of this invention, 
reference may be made to the following examples. These examples are given 
merely to illustrate the invention and are not to be construed in a 
limiting sense. All parts, percentages, proportions and other quantities 
are by weight unless otherwise indicated. 
EXAMPLE I 
Preparation of 90/10 Ethylacrylate-Methacrylic Acid Copolymer 
Apparatus: 3 liter resin kettle, equipped with mechanical stirrer, reflux 
condenser, thermometer and gas inlet tube. 
Procedure: Under a blanket of nitrogen, the following ingredients of the 
reaction were charged, with agitation, in the following order and amounts: 
1694.2 g distilled water 
8.6 g Siponate DS-10, 25% (Product of Alcolac Co.) 
6.4 g n-butanol 
42.9 g methacrylic acid 
386.1 g ethylacrylate 
0.123 g divinylbenzene (60%) 
1.71 g of a 10% ammonium persulfate solution 
2.86 g of a 0.1% ferrous sulfate solution 
At this point, the agitation was stopped, and 2.14 g. of a 10% solution of 
concentrated sodium hydrosulfite (Lykopon) was introduced. Five minutes 
later, slow agitation was started, as a slight temperature rise (from 
19.degree. C. to 21.degree. C.) signaled that the reaction had already 
begun. Five minutes later, at 26.degree. C., the speed of the agitation 
was adjusted to 150 rpm. After that the temperature rose steadily, and it 
peaked 10 minutes later at 56.degree. C. After that the system allowed to 
cool to room temperature, and the product--a free flowing milky latex--was 
discharged through a 100 mesh screen. 
EXAMPLE II 
Emulsion copolymer is prepared by the process described in Example I, 
except that the ratio of methacrylic acid and ethylacrylate is 20/80 by 
weight. 
EXAMPLE III 
Emulsion copolymer is prepared by the process described in Example I, 
except that the ratio of methacrylic acid and ethylacrylate is 30/70 by 
weight. 
EXAMPLE IV 
Emulsion copolymer is prepared by the process described in Example I, 
except that the ratio of methacrylic acid and ethylacrylate is 40/60 by 
weight. 
EXAMPLE V 
Emulsion copolymer is prepared by the process described in Example I, 
except that the ratio of methacrylic acid and ethylacrylate is 50/50 by 
weight. 
EXAMPLE VI 
Emulsion copolymer is prepared by the process described in Example I, 
except that the ratio of methacrylic acid and ethylacrylate is 60/40 by 
weight. 
EXAMPLE VII 
Emulsion copolymer is prepared by the process described in Example I, 
except that the ratio of methacrylic acid and ethylacrylate is 70/30 by 
weight. 
EXAMPLE VIII 
Emulsion terpolymer is prepared by the process described in Example I. The 
polymer consists of methacrylic acid, ethylacrylate and a termonomer. The 
percentages of the ingredients are 70, 28, and 2 by weight, respectively. 
The termonomer is acrylamide. 
EXAMPLE IX 
Emulsion terpolymer similar to that described in Example VIII, is prepared, 
except that the termonomer is acrylonitrile, and percentages of the 
ingredients are 66, 28 and 6, respectively. 
EXAMPLE X 
Emulsion terpolymer similar to that described in Example IX, is prepared, 
except that the termonomer is n-butylvinyl ether. 
EXAMPLE XI 
Emulsion terpolymer similar to that described in Example IX, is prepared, 
except that the termonomer is chlorostyrene. 
EXAMPLE XII 
Emulsion terpolymer similar to that described in Example IX, is prepared, 
except that the termonomer is diethylmaleate. 
EXAMPLE XIII 
Emulsion terpolymer similar to that described in Example IX, is prepared, 
except that the termonomer is 2-ethylhexyl halfacid maleate. 
EXAMPLE XIV 
Emulsion terpolymer similar to that described in Example IX is prepared, 
except that the termonomer is isobutyl vinyl ether. 
EXAMPLE XV 
Emulsion terpolymer similar to that described in Example IX is prepared, 
except that the termonomer is styrene. 
EXAMPLE XVI 
Emulsion terpolymer similar to that described in Example IX is prepared, 
except that the termonomer is triethoxyvinylsilane. 
EXAMPLE XVII 
Emulsion terpolymer similar to that described in Example IX is prepared, 
except that the termonomer is vinyl acetate. 
EXAMPLE XVIII 
Emulsion terpolymer similar to that described in Example IX is prepared, 
except that the termonomer is N-vinyl-2-pyrrolidone. 
EXAMPLE XIX 
The latices of Examples I through VII contained about 20% solids. These 
latices were blended with a 40% solids carboxylated styrene-butadiene 
(CSB) (60% styrene, 36% butadiene and 4% fumaric acid) latex so that the 
resulting total solids contained 92% of the CSB latex and 8% of the highly 
carboxylated polymer. These blends were tested for asbestos sheet 
manufacture using the procedure described above. 
The latex blends show the influence of the methacrylic acid content of the 
highly carboxylated latex additive upon the asbestos felt performance. The 
drawing is a plot of cold tensile and stiffness against content of 
methacrylic acid (and inverse content of ethyl acrylate). The cold tensile 
with the base carboxylated styrene butadiene latex was 38.4 pounds per 
inch and the stiffness was 102. As the methacrylic acid content of the 
additive latex was increased, a significant 50% increase in both tensile 
strength and stiffness was observed. Other properties, including drainage, 
were unaffected. 
EXAMPLE XX 
The latices of Examples VIII through XVIII contained about 20% solids. 
These latices were blended with a 40% solids CSB (60% styrene, 36% 
butadiene and 4% fumaric acid) latex so that the resulting total solids 
contained 4% of the highly carboxylated polymer. Three different 
commercial strength additives and a carboxylated styrene-butadiene latex 
without any additive were also tested. The results are shown in the 
following Table: 
Table 
______________________________________ 
Schopper 
Tensile (lbs/in) 
Example Riegler (.degree.) 
cold hot plasticizer 
______________________________________ 
VIII 17.5 48.9 22.6 23.7 
IX 17.3 49.0 23.0 21.4 
X 20.0 57.9 25.1 22.0 
XI 15.0 53.6 21.0 21.3 
XII 15.5 53.2 20.5 21.7 
XIII 15.1 54.6 20.1 20.8 
XIV 15.7 56.6 22.5 23.6 
XV 16.2 51.7 20.1 21.3 
XVI 16.8 56.6 23.3 23.0 
XVII 16.0 50.8 22.6 23.8 
XVIII 18.2 50.1 21.1 22.6 
Commercial X Additive* 
23.8 55.9 20.2 24.8 
Commercial Y Additive** 
23.4 52.6 23.0 20.4 
Commercial Z Additive*** 
20.9 51.6 22.0 22.2 
CSB - no additive 
22.0 44.6 21.2 17.0 
______________________________________ 
The commercial additives are as follows: 
*polyamideepichlorohydrin resin Polycup resin available from Hercules 
Incorporated, Wilmington, Delaware. 
**acrylic polymer Accostrength 862 resin available from American Cyanami 
Co. 
***Accostrength 100 VKA resin 
All of the eleven blends according to this invention impart a higher cold 
tensile strength than the carboxylated styrene butadiene latex without any 
additive. The average improvement in cold tensile was 18%. Three of the 
blends--Examples X, XIV and XVI--yielded better than a 25% improvement in 
cold tensile. Six of the eleven blends according to this invention 
imparted higher hot tensile than carboxylated styrene butadiene latex 
without the additive. All eleven blends of this invention gave higher 
plasticizer tensile than carboxylated styrene butadiene latex without any 
additive; the average improvement was 22%. Along with the tensile strength 
increases, there was an average lowering of the Schopper Riegler by 24%. 
Although tensile strength was improved with the commercial additives, 
there was no significant improvement in drainage.