Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to an improved foaming agent
having a greater capacity for producing foam. This
invention is particularly directed to such foaming agents to
be used in the making of gypsum products and to the products
so made, to other end uses, for instance, fire fighting
foams.
PRIOR ART
Samuel Cukier, in C.P. 1,085,880 dated 16 September
1980 and in U.S. 4,156,615, discloses an alkyl ether sulfate
having an improved performance for the manufacture of
gypsum, wherein said alkyl ether sulfate is:
CH3(cH2)xcH2-(ocH2cH2)y OS03M
in which:
CH3(CH2)xCH2 is the alkyl group
(OCH2CH2)y is the ether group
M is the cation (NH4 or Na)
wherein x is between 6 and 8, and has an average value of
6.5-7.5 and y is between 1.5 and 2.5 (which herein is also
referred to as Type A).
It should be noted that: in Cukier's patent the
performance is measured on the basis of the stiffening time
of the gypsum slurries (Example 1), heat savings (Example 2)
and reduced product consumption to achieve similar thermal
set times (Example 3).
U.S. 4,678,515 as invented by Green et al discloses
surfactants with improved foaming properties by means of
mixing about 11 to 33% of alkyl ether sulfates in which x =
10 to 12 and y = 1 to 3.0, with surfactants of Type A as
described above to obtain an average x between 6 to 12.
In Green et al's patent performance is measured on the
*
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basis of the amount of foam and foam stability produced by
the surfactants when added to the supernatant liquid of a
saturated gypsum solution, as seen in column 2, line 34 of
the patent, from which gypsum, which is mainly composed of
calcium sulfate, has been removed. By operating in this
manner, the foaming tests are conducted in the presence of a
constant or "static" amount of Ca ions, which is determined
by the solubility product of calcium sulfate.
Alkyl ether sulfate surfactants are sensitive to Ca
ions: they react to form the calcium salt of the ether
sulfate which may be water insoluble.
In a Ca ion "static" system, as that used by Green et
al to conduct the foaming tests, when a free Ca ion reacts
with the ether sulfate to form an insoluble surfactant, the
reacted Ca ion cannot be replaced by another Ca ion, as
governed by the solubilty product because the source of Ca
ions, i.e, gypsum, has been removed from the system.
In the actual manufacturing of gypsum board, the ether
sulfate is exposed to a continuous flow of Ca ions, in the
sense that for every free Ca ion removed from solution due
to reaction with ether sulfate, another Ca ion is supplied
by the gypsum material (to maintain constant the solubilty
product) which, in turn, may form another insoluble Ca
surfactant, and so on.
As a result of this, the foaming profile of an ether
sulfate surfactant may be different in a "static " foaming
test and in the actual manufacturing of gypsum board,
specially if the "static" foaming test is carried-out under
conditions in which the surfactant is tested using great
amounts of surfactant relative to the amount of free and/or
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replaceable Ca ions than the foaming agent may encounter
during the actual manufacturing of gypsum board.
It should be borne in mind that in the Green et al
patent there is not indication o-f the performance of the
foaming agents on the actual manufacturing of gypsum
material made from gypsum slurries in terms of foam
entrained in finished gypsum, as in the real manufacturing,
i.e. when the foaming agent is exposed to a continuous flow
of free Ca ions. In fact, Green et al best results are
obtained when the foamers are evaluated in "static" foaming
tests with large amounts of surfactants, i.e. undér excess
of foaming agent relative to the "static" amount of Ca ions.
'1'~; lN V~. LlON
Broadly stated, the invention is directed to a foaming
agent comprising a blend of alkyl sulfates and alkyl ether
sulfates having an improved foaming performance, wherein
said blend has the general formula:
Rx ~ (OCH2CH2 ) y~OS03M~ wherein
at least 90% of x is between 8 and lO,
said Rx forming an alkyl chain selected from at
least one member of the group consisting of linear and
branched chains, the average y is between 0.4 and 1.3, and
wherein M is a cation producing a water soluble surfactant.
The invention i6 also directed to an improvement in a
method of making gypsum board using a blend of alkyl
sulfates and alkyl ether sulfates having the general
formula:
Rx ( CH2 CH2 ) y OS03M as
described above, the improvement comprising mixing with
gypsum a catalytic amount of said sulfates, wherein at least
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90% of x is between 8 and 10, said Rx forming an
alkyl ch~in selected from at least one member of the
group consisting of linear and branched chains, the average
y is between 0.4 and 1.3 and wherein M is a cation producing
a water soluble surfactant.
The invention is also directed to a new gypsum product
containing the residual foaming agent as defined above. The
improved foaming performance can be evidenced, for instance,
from Table III and IV on pages 12 and 13.
~K~KK~V WAY OF CAKK~lNG OUT THE lNv~NllON
A preferred way of carrying out the invention consists
in reacting in a molar ratio in the order of 0.4-1.3:1 and
most preferably 0.8:1 ethylene oxide with linear and/or
branched fatty alcohols having at least 90~, preferably 98%
and more, of 8-lO carbon atoms, in the presence of a
catalyst to incorporate the ethylene oxide groups. Typical
examples of such catalysts include NaOH and KOH. Once the
ethylene oxide groups are incorporated, the ethoxylated
fatty alcohols are then sulfated with a sulfating agent and
then neutralization is accomplished to obtain directly the
new foaming agent.
Typical examples of a cation producing a water soluble
surfactant includes sodium, potassium, calcium, magnesium
and the like, and preferably ammonium.
The foaming agent i6 preferably diluted with a carrier
wherein the foaming agent i6 the ma;or constituent, i.e. at
least 50%. Typical carriers are preferably alcohols having
low molecular weight such as methanol, ethanol, propanol.
` This foaming agent is particular useful in the making
3~ of gypsum board and used in catalytic amounts. Preferably
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that catalytic amount is 0.03+0.01% per 100 parts of stucco
as determined by the (CTFA) method 8-1 of the Cosmetic
Toiletry & Fragrance Association of Washington, D.C. This
foaming agent is generally used for such a purpose in a
diluted form such as those described hereinbelow.
The novel product contains a greater % foam in gypsum
product with respect to the amount on weight basis of
foaming agent.
OT~R MEANS OF CAKK~lNG OUT THE lN V~N'l'lON
There are other indirect ways of carrying out the
invention such as by blending fatty alcohols with
ethoxylated fatty alcohols to obtain the average y of
between 0.4-1.3 and preferably 0.7-0.9, followed by
sulfation of the blend with a sulfating agent and then
neutralizing the mixture, or by reacting fatty alcohols with
a sulfating agent neutralizing it and blending this reaction
product with an alkyl ether sulfate to obtain the average y
of between 0.4-1.3 and preferably 0.7-0.9.
The following examples will serve to illustrate
particular embodiments of the invention.
EXANPLES 1-6
The foaming agent of Example 1 was prepared by blending
25% of the ethoxylate of Sample A with 75% of a linear fatty
alcohol wherein at least 90% of x is between 8 and 10 and
having 0 as y value (which we will call Sample E) and then
sulfating the blend.
The foaming agent of Example 2 was prepared by blending
50% of Sample E and 50% of the ethoxylate of Sample A and
then sulfating the blend.
The foaming agent of Example 3 was prepared by the
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direct method.
The foaming agent of Example 4 was prepared as in
Example 3 but replacing approximately 50% of linear octanol
by an equivalent amount of branched ethyl hexanol.
The foaming agent of Example 5 was prepared by blending
25% of Sample E and 75% of the ethoxylate of Sample A and
then sulfating the blend.
The foaming agent of Example 6 was prepared by blending
50% of the ethoxylate of Example 3 and 50% of the ethoxylate
of Sample A and then sulfating the blend.
THE GYPSUM BLOCR METHOD
Using a method simulating the manufacture of gypsum
wallboard, gypsum blocks were made as follows:
1. The foaming agent is diluted in water to obtain a
solution having a concentration of 0.50% for a 100% active
basis alkyl ether sulfate wherein at least 90% of x is
between 8 andl0 and the average y is as shown in Table 1.
2. The following blend is then prepared: 10g of above
solution; 145g of water; 200g of stucco; and about 2g of
additives normally used in the manufacturing of wallboard,
such as binders, accelerators, etc.
3. The above blend is allowed to stand for 30 sec. and
then mixed for 15 sec. in a Hamilton Beach Mixer.
4. The resulting slurry is poured into plastic moulds.
The blocks are then dried at 43C for 48 hrs.
5. The performance of the foamers i~ measured in terms of
% foam entrained in the blocks. This value is obtained via
a simple mathematical calculation which considers the weigh
of the blocks before and after drying and the density of
stucco. The % foam of the gypsum blocks is shown in Table
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1, Examples 1-6.
The same was carried out according to the prior art:
Sample A using Cukier's patent.
Samples C and D using amongs the best species of Table
52 of Green et al patents i.e. Material Tested I and IV of
Table 2 Column 2 of the patent.
Results are shown in Table 2, as Samples A, C and D.
TABLE 1
y average % volume foam
Ether in gypsum
ExamPle Group Blocks
1 0.4 25.6
2 0.8 26.4
3 0.8 26.4
4 0.8 26.0
1.3 26.1
6 1.3 25.8
1 33743~
TABLE 2
x value y average % foam in
Sample (Alkyl qroup) (Ether group) gypsum blocks
A) Cukier's about 50% by 2.2 24.4
patent weight of x=6
and 50% of x=8
B) about 50% by 3.0 23.0
weight of x=6
and 50% of x=8
C) As per Table 2, Example I of Green et al's patent
a mixture of surfactant of
Sample A and 12.5% of surfactant
having about 67% of x=lO
with an average y value of 1.2 22.S
D) As per Table 2, Example IV of Green et al's
a mixture of 75% of Sample B
and 25% of surfactant having
about 67% of x=lO and 33% of x = 12
with an average y value of
of 3.0 19.9
The performance of the foaming agents as can be clearly
seen, are directly assessed by the actual making of gypsum
products, i.e. blocks, and measuring in the gypsum blocks,
the "% volume of foam" which relates to the amount of air
entrained in the blocks. This is contrary to the prior art
that use arbitrary and indirect methods. According to this
test in the making of the gypsum blocks containing the
foaming agent left as residuum, the higher the % volume of
foam the lighter the block and, therefore, the better the
performance of the foamer.
1 33-7435
-
-- 10 --
As can be seen, Example 1 of Green et al produces a
gypsum block having 22.5% volume foam (our sample C).
Example IV produces a gypsum block having 19.9% volume foam
(our sample D). Cukier's product yields a gypsum block
having 24.4% volume foam, as compared to applicant's product
of 25.8 to 26.4%. This means substantial improvement of
applicant's product and particularly improvement of 10-25%
over the products made according to the Green et al's
teaching. No foaming agent is taught in the prior art which
shows the % volume foam in gypsum blocks that is equal to
those shown in Examples 1-6. It is clear that foaming
agents comprising a blend of alkyl ether sulfates as
described in Examples 1 to 5 have substantial improved
foaming performance.
Such a result cannot be obtained when following Green
et al's patent (19.9-22.5%) an even when following Cukier's
patent.
Applicant has also determined the distribution ratio of
the oxyethylene oligomers of the foaming agents by High
Performance Liquid Chromotography (HPLC).
RX (OCH2CH2)y~OH
y=o
~(CH2CH2)y~H
y=n
n = 0, 1, 2, 3, 4, 5, ..... 12
The denominator represents the total oligomeric
content.
Results are shown in Table III in % weight and Table IV in
% mole, where a Sample E when y=0 and a new Sample ~ when
y=3 were introduced to clearly demonstrate applicant's
invention.
1 337435
As seen herein below, the distribution ratio of the
oligomers is an important characteristic of the foaming
agents since the distribution affects both the sensitivity
to Ca ions and the intrinsic foaming performance of the
foaming agents.
1 337435
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1 337435
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1 337435
- 14 -
It is clear from Table III that best performance in %
foam gypsum blocks is when the % weight ratio is between 85
and 25 for the oligomer y=o and 96 to 80 for y = the sum of
oligomers from 0 to 5.
It is also clear from Table IV that the % mole must be
for y = the sum of oligomers from 0-3 of between 70 to 92.
It is also clear that applicant's invention yields a foaming
agent having improved foaming performance. The % foam in
the gypsum block as made herein, having at least 25.6% foam
as compared against 19.9 - 22.5 for Green et al and 24.4 for
Cukier's patent according to the above test.
In summary two criteria are of the outmost importance
to produce a foaming agent having improved foaming
performance in the making of gypsum panels: the carbon
length of the alkyl group Rx and the
degree of ethoxylation.
The alkyl group is determined by x, and ideally x
should be between 8 and 10. However since the foaming agents
are usually made from industrial grade fatty alcohols of
mixed carbon lengths, it is from a practical purpose
acceptable to have at least 90%, but preferably 98% and
more, of said x between 8 and 10. Other carbon lengths for
which x is not between 8 andlO, particularly those greater
thanlO are detrimental and inhibit the foaming properties,
since in the presence of gypsum products, when y is low the
sulfates having x greater than 10form a water insoluble
product with gypsum that precipitates out of the water, and
as it precipitates out, additional amounts of the water
soluble foaming agent react with additional amounts of the
30 A gypsum products to cause further precipitations, and thereby
1 337435
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to that extent reducing the effectiveness of the blend as a
foaming agent. This problem increases as the length of x
increases, (over x=10). This problem is effectively
evaluated only when the foaming agent for gypsum products is
evaluated in situ with the gypsum products (the CaSO4
reacting). Any simulation with a clear solution of CaSO4
does not give the concentration and equilibrium in
production lines.
The average y must be between 0,4 and 1.3 as
illustrated in Table III and IV.
Alkyl ether sulfates are sensitive to Ca ions, they may
react to form the calcium salt of the ether sulfate which
depending upon the length of the alkyl group (x) and the
degree of ethoxylation (y) may be water insoluble, and
thereby may produce low foamers.
If we go back to prior art, Green at al patent is based
on their claim that enhanced foaming performance is obtained
when ether sulfates having an alkyl group in which x is lO
to 12 are added to ether sulfates in which x=6 to 8.
According to Green, "this is quite surprising since
compounds in which x-lO to 12 are poor foam generators
compared to their homologs in which x=6 to 8" (column 2,
lines 19-22). This foam enhancement is based on foaming
tests conducted with saturated gypsum solutions from which
gypsum has been removed before the foaming test is done:
our application ~hows that the ether sulfates covered by
Green are inferior to our foamers when their performance is
measured not in foaming tests but in the making of gypsum
~ blocks using recipes typical of gypsum board manufacturing,
as in the real life. This is clearly stated on Table 2.
- 16 - 1 3 3 7 4 3 5
Nost important is that our patent application is
pointing away from Green et al regarding the composition of
the alkyl group. In Green et al patented foamers, the
content of the alkyl group in which x=6 to 8 must be 89%
maximum and 67% minimum, and the rest must be x=10 to 12.
(column 6, lines 53 to 60). We teach the opposite, i.e.,
the content of the alkyl group in which x=8 tolO must be 90%
minimum.
This is a key and a very clear difference: for Green,
when a minimum of 11% of a foamer having x=10 to 12 is added
to a foamer having x=6 to 8, the result is a product with
enhanced foaming performance. For us, the result is the
opposite, i.e. inferior performance. As a result, what for
Green is a must (ie, addition of at least 11% of ether
sulfates in which x=10 to 12) for applicant is something to
be totally avoided (ie, 10% is the most - not the least -
which is tolerable for x other than 8 to 10).
The degree of ethoxylation or y value of the ether
group is also very important because the sensitivity of the
foaming agents to the Ca ions and its intrinsic foaming
profile is also affected by the value of y: As the y value
increases, the sensitivity of the foaming agents to the Ca
ions decreases, but its intrinsic foaming characteristic
that is of the essence, also decreases. Therefore, finding
the right balance between low Ca ion 6ensitivity and high
foaming characteristics, i.e., the y value is key in a
foaming agents intended for wallboard manufacturing. Cukier
patent excludes foamers in which the y value is less than
1.5. We are teaching a y value between 0.4 and 1.3, i.e.
completely different to Cukier's range.
1 337435
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The reason for this difference is clearly shown in our
Tables III and IV. Sample A is the core of Cukier's patent
(y value of 2.2). Sample E is outside Cukier's patent (and
Green) since y=0. Our examples 1, 2, and 4 were prepared by
blending appropriate proportions of samples A and E. In
other words, the blending of Cukier's product with an
inferior foamer resulted in a synergistic effect, since the
blends were superior to the individual products. This is
clearly illustrated in Tables III and IV.
Having described the invention, modifications will be
evident to those skilled in the art without departing from
the spirit of the invention, as defined in the appended
claims.
