Water soluble polymer suspensions in dibasic potassium phosphate

Aqueous suspensions of hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, methylhydroxypropylcellulose, 1-(butoxy)-2-hydroxypropylhydroxyethylcellulose, ethylhydroxyethylcellulose, hydrophobically modified hydroxyethylcellulose, methylhydroxypropylcellulose, guar gum, carboxymethylhydroxypropylguar, hydroxypropylguar and carboxymethylguar in dibasic potassium phosphate are stabilized with xanthan gum to provide improved thickeners for joint compounds and latex paint.

FIELD OF THE INVENTION 
The invention relates to salt suspensions of polymer in water. In 
particular, the invention relates to polysaccharide polymer suspensions in 
concentrated aqueous solutions of dibasic potassium phosphate. 
BACKGROUND OF THE INVENTION 
U.S. Pat. No. 4,283,229 (Girg et al.) discloses that stable suspensions of 
nonionic cellulose ethers can be prepared in a solution of 4 to 12% 
electrolyte if alumina is added to the suspension. Prior art aqueous fluid 
suspensions of water soluble polymers are further described in U.S. Pat. 
Nos. 4,883,536 and 4,883,537. U.S. Pat. No. 4,883,536 covers the use of 
ammonium salts such as diammonium sulfate (DAS), diammonium phosphate 
(DAP) and ammonium polyphosphate for preparing fluid suspensions of water 
soluble polymers. U.S. Pat. No. 4,883,537 covers the use of concentrated 
aqueous potassium carbonate for preparing suspensions of sodium 
carboxymethylcellulose. 
The art of U.S. Pat. No. 4,883,536 is limited in that the compositions 
described all contain ammonium ion. This chemical species is 
disadvantageous due to the possible release of small amount of ammonia 
when incorporated into a number of end use applications such as joint 
compound or paint. In contrast to this, the present invention does not 
contain ammonium ion and thus can not generate undesirable fumes in end 
use applications. 
The art of U.S. Pat. No. 4,883,537 describes suspensions of water soluble 
polymers in concentrated aqueous potassium carbonate media. The drawback 
to this latter prior art technology is that suspensions prepared according 
to this art exhibit very high pH (greater than 12.5). The high pH of this 
prior art is severely limiting since the use of such a thickening agent 
can cause adverse reactions. In addition, the high pH of this prior art 
thickener makes it a hazardous material requiring extreme caution in 
handling. In contrast to this, the present invention exhibits a moderate 
pH of about 9.0 that is acceptable for use in a number of applications 
where the prior art may be precluded from use. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide an improved suspension of 
water-soluble polymers in a concentrated aqueous salt solution. This 
composition-of-matter consists of three essential components: water, 
dibasic potassium phosphate and a non-ionic or anionic water-soluble 
polymer. A minor amount of a stabilizing agent such as sodium alginate, 
CMC or xanthan may also be added to the suspension to provide long term 
stability and to prevent settling. 
The compositions include either nonionic or anionic water soluble polymers 
dispersed in an amount equal to or greater than 20% by weight in an 
aqueous medium containing not less than 12% K.sub.2 HPO.sub.4 by weight 
based on the total suspension weight.

DETAILED DESCRIPTION OF THE INVENTION 
It was discovered that suspensions of water soluble polymers in 
concentrated aqueous dibasic potassium phosphate provide a composition 
more useful as a liquid thickening agent in many application than ones of 
the prior art. 
The nonionic and anionic water-soluble polymers found to be operable in the 
present invention include methylhydroxypropylcellulose, 
hydroxyethylcellulose, methylcellulose, 
1-(butoxy)-2-hydroxypropylhydroxyethylcellulose, carboxymethylcellulose, 
ethylhydroxyethylcellulose, carboxymethylhydroxyethylcellulose, 
hydrophobically modified hydroxyethylcellulose, guar gum, 
hydroxypropylguar, carboxymethylguar and methylhydroxyethylcellulose. It 
is thought that a number of other water soluble polymers would also be 
operable in the present invention. 
Suspensions of water soluble polymers in compositions of the present 
invention that utilize dibasic potassium phosphate were found to perform 
more effectively in applications such as joint compounds and paint 
compared to suspensions of water-soluble polymers prepared according to 
the prior art that incorporated salts such as ammonium sulfate, ammonium 
phosphate or potassium carbonate. 
The invention has industrial applicability in construction and coating 
materials such as joint compounds and latex paints. All parts and 
percentages in the following examples are by weight unless otherwise 
indicated. 
EXAMPLE 1 
A fluid suspension of Natrosol.RTM. 250GR hydroxyethylcellulose (available 
from Aqualon) was prepared according to the present invention by adding 
59.8 parts by weight of water to a mixing vessel then dissolving in 
sequence 1.0 parts of CMC-7L1T sodium carboxymethylcellulose (available 
from Aqualon), then 14.2 parts by weight of dibasic potassium phosphate 
(DPP). After the DPP had dissolved, 25 parts by weight of Natrosol 250GR 
was added to the suspension and stirred to disperse. A stable fluid 
suspension was obtained with a Stormer viscosity of 107 Krebs Units. 
For comparative purposes, a suspension of Natrosol.RTM. 
hydroxyethylcellulose was prepared according to the art in U.S. Pat. No. 
4,883,536. In this latter case, 59.8 parts by weight CMC-7L1T, 14.2 parts 
of diammonium phosphate (DAP) and 25 parts of Natrosol 250GR HEC were 
added in sequence in the same manner as above. In this case, a fluid 
suspension with a Stormer viscosity of 97 Krebs Units was obtained. 
It was shown by the above experiments that dibasic potassium phosphate and 
DAP were very similar with respect to effectiveness in preparing fluid 
suspensions of hydroxyethylcellulose. 
Paints were prepared which incorporated each of the above suspensions. 
Tests were conducted with a 63 PVC interior flat paint formulation. This 
formulation is given in the appendix of Aqualon Brochure 250-18A, 
formulation IUF 70-2151. 
Standardized application tests were conducted with the paints prepared 
incorporating the thickening agent of the present invention, designated 
0135-99-2, as well as the prior art thickener 0135-99-1. The results from 
these tests are shown in Table 1. It was found that a paint incorporating 
the fluidized polymer suspension 0135-99-2 of the present invention 
exhibited a higher scrub value in standard paint panel scrub tests that 
the paint that incorporated the fluidized suspension 0135-99-1 of the 
prior art. It was also found that the paint made with 0135-99-2, the 
thickener of the present invention, showed no ammonia odor while the paint 
prepared with the prior art fluidized polymer suspension 0135-99-1 had a 
slight, but undesirable, ammonia odor. 
It was thus shown that the present invention, a fluid suspension of a water 
soluble polymer in an aqueous medium containing dissolved dibasic 
potassium phosphate, had improved utility for thickening flat latex paints 
compared to a fluid suspension of the same water-soluble polymer prepared 
according to the prior art. 
EXAMPLE 2 
A suspension of 1-(butoxy)-2-hydroxypropylhydroxyethylcellulose (HMHEC-B 
available from Aqualon) was prepared according to the present invention by 
dissolving 0.2 parts of xanthan gum in 63.7 parts water, then dissolving 
16 parts of dibasic potassium phosphate into the xanthan solution, and 
finally dispersing 20 parts of HMHEC-B into the solution. In addition, 0.1 
parts of Proxel.RTM. GXL preservative was added to the final suspension. 
The homogeneous fluid suspension was designated 0195-3-4. 
For comparative purposes an alternative suspension of HMHEC-B was prepared 
with diammonium phosphate (DAP) substituted for dibasic potassium 
phosphate in the same procedure employed above. The resulting suspension 
was similar in characteristics compared to the above suspension of the 
present invention. This product was given the designation 0195-3-2. 
As a second comparative example, diammonium sulfate (DAS) was substituted 
for dibasic potassium phosphate in the above formulation and a like fluid 
suspension was obtained. This product was given the designation 0195-3-3. 
As a third comparative example, potassium carbonate (PC) was substituted 
for dibasic potassium phosphate in the above formulation and a fluid 
suspension was obtained, with the designation of 0195-3-1. 
These tests show that various salts named in the prior art U.S. Pat. Nos. 
4,883,536 and 4,883,537 were capable of preparing fluid suspensions of 
HMHEC-B in aqueous media. It was found in further tests, however, that 
when each of these products was employed in joint compound preparation, 
undesirable performance properties were observed whereas the present 
invention, a suspension of water soluble polymer in concentrated aqueous 
dibasic potassium phosphate gave superior performance in this application 
as is described below. 
In the tests conducted, joint compounds were prepared with each of the 
above fluidized polymer suspensions at equal active polymer dosage. The 
joint compounds were prepared by adding 231 parts by weight of water to a 
Hobart mixer then adding sequentially, with stirring, 2.8 parts by weight 
of propylene glycol, 0.4 parts preservative, 23 parts by weight of 
propylene glycol, 0.4 parts of preservative, 23 parts by weight of 
UCAR.RTM. 133 (Union Carbide) latex, 0.33 parts by weight of Nopco.RTM. 
PD-1 defoamer, 489 parts of Georgia White #9 calcium carbonate, 13.3 parts 
of gel B attapulite clay, 20 parts by weight of Mica P-80K, and finally 20 
parts by weight of fluidized polymer suspension. The joint compounds were 
mixed for 5 minutes with one scrape down and placed into storage 
containers. 
The joint compound properties obtained with each of the four fluidized 
polymer thickening agents, including joint compound viscosity, adhesion 
and odor were then evaluated and compared as shown in Table 2. 
It was observed that the prior art fluid suspensions of HMHEC-B utilizing 
ether DAS or DAP salts according to the prior art produced unacceptable 
ammonia odor in the joint compounds that contained these agents. In indoor 
construction environments, the strong noticeable odor liberated by these 
joint compounds would be unacceptable and thus these fluidized polymer 
suspensions prepared according to the prior art would have little utility 
for use in this application. 
In other joint compound tests, it was found that a joint compound prepared 
incorporating 0195-3-1, a fluidized polymer suspension prepared with 
potassium carbonate according to the prior art of U.S. Pat. No. 4,883,537, 
gave unacceptably poor adhesion to joint compound taping paper in standard 
laboratory tests. By comparison, the adhesion of the joint compound 
thickened with 0195-3-4, the thickener of the present invention, was found 
to be acceptable. 
The poor results for each of the prior art fluid suspensions of the HMHEC-B 
in the joint compound application showed that this prior art had no 
practical utility for use as joint compound thickening agents. By 
comparison, the present invention, a fluid suspension of water soluble 
polymer in aqueous media containing dissolved dibasic potassium phosphate, 
was shown to exhibit viable performance in the joint compound application. 
EXAMPLE 3 
A sample of CMC-7M8SXF (available from Aqualon) was prepared in fluid 
suspension form according to the present invention by first dissolving 0.5 
parts of Kelgin LV sodium alginate in 40 parts water, then adding 
sequentially with stirring 39.5 parts of dibasic potassium phosphate, 
stirring to dissolve, then adding 20 parts by weight of CMC-7M8SXF. The 
so-prepared product was a fluid suspension with a Stormer viscosity of 115 
Krebs units and a pH of 9.8. 
For comparative purposes, a suspension was prepared according to the art of 
U.S. Pat. No. 4,883,537. In this latter case, 0.5 parts by weight of 
Kelgin LV was dissolved in 40 parts of water then 39.5 parts of potassium 
carbonate was dissolved in the water with stirring and 20 parts of 
CMC-7M8SXF was added with stirring to disperse. In this latter case, the 
fluid suspension of the CMC-7M8SXF was observed with a viscosity of 110 
Krebs units and a pH of 12.9. 
In this example, it was shown that the present invention and the prior art 
of U.S. Pat. No. 4,883,537 could be employed to prepare a fluid suspension 
of CMC-7M8SXF. However, it was shown that the present invention was 
superior to the prior art in exhibiting a lower, less hazardous pH. It was 
attempted to reduce the pH of the suspension containing potassium 
carbonate to 10.0 with the addition of acetic acid, however, this resulted 
in the gelation of the sample at pH 11. 
EXAMPLE 4 
A series of suspensions of CMC-7M8SXF were prepared in concentrated aqueous 
dibasic potassium phosphate media in which the ratio of K.sub.2 HPO.sub.4 
was varied according to the compositions shown in Table 3. It was found in 
these tests that ratios of 20-40% K.sub.2 HPO.sub.4 salt in water did not 
produce fluid suspensions of the CMC but that thick gels were observed. It 
was found that a relatively high dibasic potassium phosphate ratio of 50% 
salt/salt+water was required to prepare a fluid suspension of the CMC 
7M8SXF. 
For comparative purposes, it was attempted to prepare a suspension of 
CMC-7M8SXF in the prior art salt of ammonium phosphate dibasic. However, 
as shown in the table, it was found that it was not possible to prepare a 
20% by weight fluid suspension of CMC in aqueous diammonium phosphate even 
at high concentration. 
This example distinguishes the dibasic potassium phosphate salt from the 
prior art salt diammonium phosphate for preparing fluid suspensions of 
CMC. 
EXAMPLE 5 
A series of fluid suspensions were prepared by first dissolving 0.2 parts 
of xanthan in 59.8 parts of water, then dissolving 20 parts of dibasic 
potassium phosphate in the water and finally adding in 20 parts of water 
soluble polymers and stirring to disperse. The various water soluble 
polymers that were screened in this suspension recipe included 
hydroxypropylcellulose, Natrosol.RTM. Plus type 330 hydrophobically 
modified hydroxyethylcellulose (Aqualon), Culminal.RTM. MC methylcellulose 
20,000 PR (Aqualon), and Polyox 301 polyethylene oxide (Union Carbide). In 
all cases, fluid pourable suspension were observed that showed no 
indication of polymer settling for greater than 3 weeks' storage time. 
When added to dilution water, each of these fluid polymer suspensions was 
observed to thicken readily. This example showed the broad utility of the 
present invention in preparing functional fluid suspensions of a number of 
water soluble types. 
EXAMPLE 6 
Data obtained from the previous examples was compiled into the tables which 
follow: 
TABLE 1 
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Paint Performance Test Results For Flat Paint 
Containing Fluidized Polymer Suspension Thickeners 
Paint Thickener 
0135-99-1 0135-99-2 
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Salt Type diammonium dibasic potassium 
phosphate phosphate 
Paint Properties 
Thickener Dosage 
0.93% active 0.93% active 
ICI Viscosity 
86 KU 89 KU 
Sag, mm 21 21 
Spatter (subjective) 
5 4 
Scrub Cycles 100 129 
Till Failure 
Odor noticeable ammonia 
No ammonia 
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TABLE 2 
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Joint Compound Test Results for Various Fluidized 
Water Soluble Polymer Suspensions 
Joint Thickener 
Compound Properties 
0195-3-1 0195-3-2 0195-3-3 
0195-3-4 
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Viscosity Brabender 
600 510 560 550 
Units 
Odor Ammonia Ammonia No No 
ammonia 
ammonia 
Adhesion Good Good Poor Good 
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TABLE 3 
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Suspensions of CMC-7M8SXF in Aqueous Solutions 
Containing Dissolved Diammonium Phosphate 
or Dibasic Potassium Phosphate 
Test No. 
1 2 3 4 5 
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Ingredients: 
Water (grams) 
60 60 50 50 80 
K.sub.2 HPO.sub.4 (grams) 
40 -- 50 -- 20 
(NH.sub.4).sub.2 HPO.sub.4 
-- 40 -- 50 -- 
(grams) 
CMC-7M8SXF 25 25 25 25 25 
(grams) 
Observations 
Thick Thick Fluid Thick Thick 
Paste Paste Pourable 
Gel Gel 
Dispersion 
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