U.S. patent number RE28,780 [Application Number 05/529,625] was granted by the patent office on 1976-04-20 for process for the preparation of free-flowing, lump-free redispersible, synthetic resin powders.
This patent grant is currently assigned to Wacker-Chemie GmbH. Invention is credited to Eduard Bergmeister, Paul-Gerhard Kirst, Heinz Winkler.
United States Patent |
RE28,780 |
Bergmeister , et
al. |
April 20, 1976 |
**Please see images for:
( Certificate of Correction ) ** |
Process for the preparation of free-flowing, lump-free
redispersible, synthetic resin powders
Abstract
This invention relates to a process for the preparation of
free-flowing, lump-free redispersible synthetic resin powders by
spraydrying aqueous dispersions of synthetic resins containing an
added amount of a water-soluble condensation product from melamine,
formaldehyde and containing sulfonate groups.
Inventors: |
Bergmeister; Eduard
(Burghausen, DT), Kirst; Paul-Gerhard (Burghausen,
DT), Winkler; Heinz (Burghausen, DT) |
Assignee: |
Wacker-Chemie GmbH (Munich,
DT)
|
Family
ID: |
27182913 |
Appl.
No.: |
05/529,625 |
Filed: |
December 5, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
185807 |
Oct 1, 1971 |
03784648 |
Jan 8, 1974 |
|
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Current U.S.
Class: |
525/158; 524/3;
524/6; 525/58; 525/911; 525/934; 525/57; 525/917; 525/910 |
Current CPC
Class: |
C04B
28/02 (20130101); C08J 3/122 (20130101); C08J
3/124 (20130101); C08J 3/16 (20130101); C04B
28/02 (20130101); C04B 24/22 (20130101); C04B
24/26 (20130101); C04B 40/00 (20130101) |
Current International
Class: |
C08J
3/16 (20060101); C08J 3/12 (20060101); C04B
28/00 (20060101); C04B 28/02 (20060101); C08L
061/28 () |
Field of
Search: |
;260/29.4R,29.4UA,29.6S,851,856,852,853,855 ;106/90 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Hayes; Lorenzo B.
Attorney, Agent or Firm: Hammond & Littell
Claims
We claim:
1. A process for the preparation of free-flowing lump-free,
water-redispersible synthetic resin powder which consists
essentially in spraydrying an aqueous polymerizate dispersion of a
water-insoluble synthetic resin having a softening point of between
0.degree.C and 40.degree.C and selected from the group consisting
of polymers of acrylic acid esters, copolymers of styrene and
acrylic or methacrylic acid esters, copolymers of styrene and
butadiene, terpolymers of styrene, butadiene and acrylic acid
esters, polymers of vinyl esters, copolymers of vinyl acetate and
straight-chain vinyl esters, copolymers of vinyl acetate and
branched vinyl esters, .[.polymers of vinyl chloride, polymers of
olefins, copolymers of vinyl chloride and olefins, copolymers of
vinyl chloride, acrylic acid esters and vinyl acetate.].
.Iadd.copolymers of vinyl esters and vinyl chloride, copolymers of
vinyl esters and olefins, terpolymers of vinyl esters, vinyl
chloride and olefins, terpolymers of vinyl chloride, acrylic acid
esters and vinyl acetate, .Iaddend.and copolymers of vinylidene
chloride and acrylic acid esters, and having added thereto from 2%
to 30% by weight, based on the solids content of said polymerizate
dispersion, of a water-soluble condensation product of melamine and
formaldehyde containing sulfonate groups in the molar ratio of
melamine:formaldehyde:sulfonate groups of 0.5 to 2:2 to 4:0.5 to 2,
under customary spray-drying conditions of exposure to warm gases
at temperatures of from 30.degree.C to 50.degree.C and recovering
said free-flowing, lump-free, water redispersible synthetic resin
powder.
2. The process of claim 1 wherein said water-soluble condensation
product is added to said aqueous polymerizate dispersion in an
amount of from 5% to 19% by weight, based on the solids content of
said polymerizate dispersion.
3. The process of claim 1 wherein said sulfonate groups in said
condensation product are alkali metal sulfonate groups.
4. The process of claim 1 wherein said molar ratio of melamine:
formaldehyde: sulfonate groups is 1:3:1 and said sulfonate groups
are alkali metal sulfonate groups.
5. The process of claim 1 wherein said water-soluble condensation
product is the condensation product of one mol of melamine, three
mols of formaldehyde and one mol of sodium bisulfite.
6. The product produced by the process of claim 1.
7. A process for improving hydraulic setting masses which consists
in adding from 2% to 25% by weight, based on the hydraulic setting
ingredients, of the product of claim 6 to a hydraulic setting mass.
Description
THE PRIOR ART
Redispersible, synthetic resin powders are prepared by the
spraydraying of aqueous synthetic resin dispersions with the aid of
a unitary or binary nozzle in a hot air stream. Particularly when
starting from synthetic resin dispersions whose polymers have a low
softening temperature, either in the spray drying, a caking of the
particles occurs, or the powder formed tends under the influence of
heat and/or pressure to form lumps. Under these conditions, the
redispersibility and the flow properties of the powders are
destroyed.
One method for the improvement of such dispersion powders consists
in adding, either during the polymerization or before the
spraydraying of the dispersions, large amounts of protective
colloids. By this method, the dispersibility is indeed improved,
but other properties of the powders are impaired, for example the
stability to water spotting and resolution is strongly
diminished.
It has been further known, to add inert substances to the
dispersion before the spraydraying or to the dispersion powder
before the drying. Such adducts only shown an effect, if they are
applied in large amounts, whereby the properties of the synthetic
resin powders are strongly influenced. On the application of small
amounts, the inert substance is enveloped by the synthetic resin,
so that the addition has no effect.
Generally these redispersible synthetic resin powders are utilized
as adducts to hydraulic setting masses. In this use, it is often
found, that the compression, flexural tensile and adhesive strength
of the masses is not sufficient and is, in addition, adversely
affected by the addition of inert substances and protective
colloids.
OBJECTS OF THE INVENTION
An object of the invention is the development of a process for the
production of free-flowing, lump-free redispersible synthetic resin
powders which are free of the above-mentioned drawbacks.
Another object of the invention is the development of a process for
the preparation of free-flowing, lump-free, water-redispersible
synthetic resin powder which consists essentially in spraydrying an
aqueous polymerizate dispersion of a synthetic resin having added
thereto from 2% to 30% by weight, based on the solids content of
said polymerizate dispersion, of a water-soluble condensation
product of melamine and formaldehyde containing sulfonate groups
under customary spraydrying conditions and recovering said
free-flowing, lump-free, water-redispersible synthetic resin
powder.
These and other objects of the invention will become more apparent
as the description thereof proceeds.
DESCRIPTION OF THE INVENTION
The above objects have been achieved and the disadvantages of the
prior art have been overcome by the newly formed process for the
preparation of free-flowing, lump-free water-redispersible
synthetic resin powder by spraydrying of aqueous polymerization
dispersions of synthetic resins under conventional spraydrying
conditions that is characterized in that, before the spraydrying of
the dispersions, water-soluble condensation products from melamine
and formaldehyde containing sulfonate groups are added to the
dispersions in amounts of from 2% to 30% by weight, preferably from
5% to 19% by weight, based on the solids content of the
dispersion.
It is surprising to find that the addition, according to the
invention, prevents a caking of the powders during the preparation
and in addition, increases their storageability. Even under
influence of heat and pressure no caking of the powders occurs, so
that the redispersibility is maintained completely and the powders
are free-flowing.
These advantages are particularly apparent in the application of
the process to the spraydrying of dispersions whose polymeric
constituents have a softening point of from 0.degree.C to
40.degree.C (For the determination of softening point see
"Adhasion", 1966, 3, Pages 57 - 100).
It is also surprising that the adhesive powder of the hydraulic
setting masses, prepared with the powders, according to the
invention, is not reduced and, moreover, an improvement of the
compression and flexural tensile strength occurs.
The claimed process is applicable to many types of aqueous
polymerizate dispersions of synthetic resins. Examples of such
polymer dispersions are homopolymerization, copolymerization and
graft polymerization dispersion products of acrylic acid esters
particularly esters of alkanols having 1 to 18 carbon atoms;
styrene and, acrylic or methacrylic acid esters particularly esters
of alkanols having 1 to 18 carbon atoms; styrene and butadiene;
styrene, butadiene and acrylic acid esters, particularly esters of
alkanols having 1 to 18 carbon atoms; vinyl esters, particularly
esters of alkanoic acids having 2 to 18 carbon atoms such as vinyl
acetate; vinyl acetate and straight-chain vinyl esters of alkanoic
acids with 3 to 18 carbon atoms; vinyl acetate and branched vinyl
esters of branched alkanoic acids with 4 to 18 carbon atoms; vinyl
esters, particularly vinyl esters of straight or branched chain
alkanoic acids having 2 to 18 carbon atoms, and vinyl chloride
and/or olefins, particularly olefins having 2 to 4 carbon atoms;
vinyl chloride, acrylic acid esters, particularly esters of
alkanols having 1 to 18 carbon atoms, and vinyl acetate; vinylidene
chloride and acrylic acid esters, particularly esters of alkanols
having 1 to 18 carbon atoms.
Polymers with a low softening point for which the process is
particularly suitable, are for instance copolymers from vinyl
acetate and/or vinyl chloride and etylene, preferably with up to
30% by weight of ethylene; vinyl acetate and/or vinyl chloride and
vinyl laurate with over 20% by weight of vinyl laurate; vinyl
acetate and acrylic acid esters with alcohols of a chain length of
more than 4 carbon atoms; vinyl acetate and vinyl "Versatic acid"
esters ("Versatic acid", trade name for branched alkanoic acids
having from 8 to 18 carbon atoms) and vinyl propionate
copolymers.
The synthetic resin dispersions are prepared by conventional
processes by free-radical polymerization of the monomers in water
in the presence of emulsifiers and/or protective colloids, and,
optionally, chain-length regulators and buffers as well as other
polymerization auxiliaries.
According to the invention, the condensation product from melamine
and formaldehyde, containing sulfonate groups, is admixed either as
a powder or preferably in aqueous solution to the polymer
dispersions, to be spraydried. Subsequently the mixture is
subjected to known spraydrying process under conventional
conditions of exposure to warm gases such as air to temperature of
from 30.degree. to 50.degree.C.
The water-soluble condensation products from melamine and
formaldehyde containing sulfonate groups which are principally
suitable are the condensation products of melamine, formaldehyde
and containing sulfonate groups in which the molar ratio of
melamine to formaldehyde to sulfonate group is in the range of 0.5
to 2:2 to 4:0.5 to 2. Preferable is the condensation product of
melamine, formaldehyde and sodium bisulfite in a 1:3:1 ratio where
the condensation product has the formula ##EQU1## where n is an
integer from 5 to 300, preferably 10 to 100.
As sulfonates alkali metal bisulfites are preferred. The
condensation products prepared from formaldehyde, melamine and
sulfonates are commercially available, for example, under the
trademark "Melment" of the Suddeutsche Kalk-Stickstoff-Werke AG,
Torstberg, Germany. Also condensation products can be utilized that
contain free sulfonic acid groups.
It may also be advantageous, optionally to add, to the dispersion
before spraydrying protective colloids, such as polyvinyl alcohol,
cellulose derivatives and polyvinylpyrrolidone, or inert
substances, such as kaolin, chalk, silicates, talc, diatomaceous
earth, silicic acid, barium or calcium sulfate, in amounts of from
5% to 50% by weight, based on the solids content of the synthetic
resin powder. Thereby in some cases improvements in the
storageability are also attained.
The redispersible powders, according to the invention, may be used
in all already known application fields. A preferred application is
the addition of these powders for the improvement of hydraulic
setting masses in amounts from 2% to 25% by weight, based on the
hydraulic setting ingredients.
Examples of such hydraulic setting masses are floor tile adhesives,
fillers, plasters for facing, adhesive plasters, concrete mortar,
spakling mortar and concrete flooring. Improvements, above all in
the compression, adhesive and flexural tensile strength are
attained.
Optionally for the prevention of foaming, which is particularly
disturbing in the use in hydraulic setting substances, a known,
solid antifoam agent is added to the dispersions made from the
powders, according to the invention. Such antifoam agents are, for
example, prepared by applying a silicone defoamer or an alcohol to
a porous, inert material and thus the liquid defoamer may be
applied as a solid.
The following examples are illustrative of the invention without
being limitative in any manner.
EXAMPLE
(1a) A synthetic resin dispersion with a 50% by weight solid
content of an ethylene/vinyl acetate copolymer containing 10% by
weight of ethylene was spraydried. There was hardly any powder
separation as more than 80% of the synthetic resin adhered to the
walls of the apparatus.
(b) To the same dispersion were admixed 2% by weight, based on the
solid content of the dispersion, of a melamine-formaldehyde-sodium
sulfonate condensation product (Melment L 10) with a molar ratio of
1:3:1 in the form of a 20% aqueous solution. On spraydrying, the
separation of powder was 95%. The thus prepared powder was well
redispersible and gave films that did not dissolve in a short-term
exposure to water. In addition, the powder stored well. With the
addition of 10% by weight of aluminum silicate, the powder held up
in storage at elevated temperature and pressure.
6% by weight of the so prepared powder 1b were admixed to a
floor-tile adhesive of 30% by weight of Portland cement and 70 % by
weight of finely divided quartz sand. With the aid of this
adhesive, there is an outstanding adhesion of ceramic floor-tiles
on wood, concrete or plaster.
EXAMPLE
(2a) A synthetic resin dispersion with a 48% by weight solid
content of an ethylene/vinyl acetate copolymer containing 30% by
weight of ethylene was spraydried after an addition of 10% by
weight, based on the solid content of the dispersion, of polyvinyl
alcohol with a saponification number of 140 and a viscosity of 5
cP(in a 4% solution at 20.degree.C). Very little powder discharge
resulted.
(b) To the same dispersion was added, before the spraydrying,
instead of the polyvinyl alcohol, 10% by weight, based on the
solids content of the dispersion, of a melamine-formaldehyde-sodium
sulfonate condensation product (Melament F 20) having a molar ratio
of the components of about 1:3:1, dissolved in water. The powder
discharge was 85%.
(c) With an additional charge of 10% be weight of polyvinyl alcohol
with a saponification value of 140 and a viscosity of 5 cP(in a 4%
solution at 20.degree.C) to the dispersion of b), before the
spraydrying, a separation of 98% resulted. To the resin dispersion,
according to a), 30% by weight of the malamine-formaldehyde-sodium
sulfonate condensation product (Melament F 20) were added, as under
b. The separation was 98.3%.
The particle size of the resin powder, according to b was, after
redispersion in water, in a range of from 5 to 20 .mu.. The
particle size of the resin powder, according to c and d was, after
redispersion in water, at a maximum of 5.mu..
Concrete floorings from 25% by weight of Portland cement and 75% by
weight of sharp-edged sand, with a grain size from 0.2 to 7 mm,
that contained 5% by weight, based on the cement, of resin powder
c) or d), had an excellent adhesive strength on conventional
foundations and were elastically deformable. With the addition of
the powders of b, 6% by weight had to be applied, in order to
attain the same effect.
5 .times. 5 cm floor tiles were laid on a concrete of the type 300
DIN 1045 with a floor tile adhesive containing 30% by weight of
Portland cement, 70% by weight of finely divided quartz sand and 6%
by weight, based on the cement of dispersion powder 2a or 2c. After
hardening under water for 28 days a tensile strength for 2a of 4
kp/cm.sup.2, for 2c of 8 kp/cm.sup.2 resulted.
To a mortar prepared according to DIN 1164, each time different
resin powders in amounts of 10% by weight, based on the cement,
were added (water/cement ratio 0.45). After 28 days of dry storage
at 20.degree.C and a relative air humidity of 65% (normal climate),
the following test data were determined on test pieces.
______________________________________ Powder None 1a 1b 2c
______________________________________ Degree of spreading in cm
11.2 15.3 17.9 20 Compression strength 472 380 484 528 Flexural
tensile strength 71 97 115 133
______________________________________
EXAMPLE
(3a) A synthetic resin dispersion with a 50% by weight solid
content of a vinyl acetate/vinyl laurate copolymer, containing 25%
by weight of vinyl laurate, were spraydried. The separation was
about 50%. The powder had a strong tendency for agglomeration.
(b) To the aqueous synthetic dispersion under 3a were added 75% by
weight of a 20% melamine-formaldehyde-sodium sulfonate condensation
product solution (Melment L 300). The mixture was spraydried and
94.5% of powder was discharged in the separation. The powder was
free-flowing and well-dispersible with a maximum particle size of
10 .mu..
EXAMPLE
(4a) A styrene/butadiene copolymer dispersion with a 45% by weight
solid content, containing 60% by weight of styrene, was spraydried.
There resulted a separation of 60.4%. The powder could be
redispersed and a particle size between 15.mu. and 22.mu.
resulted.
(b) With an addition of 50% by weight of a 20% aqueous "Melment F
10" solution to the dispersion under 4a a powder discharge of 97.3%
was attained. On redispersing of this powder, the particle size was
from 2 to 7.mu. .
The preceeding specific embodiments are illustrative of the
practice of the invention. It is to be understood however that
other expedients, known to those skilled in the art or disclosed
herein, may be employed without departing from the spirit of the
invention or the scope of the appended claims.
* * * * *