U.S. patent application number 11/686037 was filed with the patent office on 2007-07-05 for polyvinyl-alcohol-stabilized redispersible powders with plasticized properties.
This patent application is currently assigned to WACKER POLYMER SYSTEMS GMBH & CO., KG. Invention is credited to Thomas Bastelberger, Ulf Dietrich, Reinhard Haerzschel, Armin Hoffmann.
Application Number | 20070155862 11/686037 |
Document ID | / |
Family ID | 32864389 |
Filed Date | 2007-07-05 |
United States Patent
Application |
20070155862 |
Kind Code |
A1 |
Haerzschel; Reinhard ; et
al. |
July 5, 2007 |
Polyvinyl-Alcohol-Stabilized Redispersible Powders With Plasticized
Properties
Abstract
Polyvinyl-alcohol-stabilized redispersible powders which have
plasticizing properties are obtained by drying
polyvinyl-alcohol-stabilized aqueous dispersions of polymers of one
or more monomers from the group of vinyl esters of optionally
branched C.sub.1-18 alkylcarboxylic acids, (meth)acrylic esters of
optionally branched C.sub.1-15 alcohols, dienes, olefins,
vinylaromatics and vinylhalides, in the presence of a copolymer
formed from a) one or more monomers from the group of ethylenically
unsaturated monocarboxylic acids, ethylenically unsaturated
dicarboxylic acids and their anhydrides, each having 4 to 8 carbon
atoms, and salts thereof, b) one or more ethylenically unsaturated
compounds containing sulfonic, sulfuric, and/or phosphonic acid
groups, and salts thereof, and c) one or more monomers from the
group consisting of vinyl esters of optionally branched C.sub.1-18
alkylcarboxylic acids and (meth)acrylic esters of optionally
branched C.sub.1-15 alcohols.
Inventors: |
Haerzschel; Reinhard;
(Burghausen, DE) ; Bastelberger; Thomas;
(Emmerting, DE) ; Dietrich; Ulf; (Ludwigshafen,
DE) ; Hoffmann; Armin; (Neuoetting, DE) |
Correspondence
Address: |
BROOKS KUSHMAN P.C.
1000 TOWN CENTER
TWENTY-SECOND FLOOR
SOUTHFIELD
MI
48075
US
|
Assignee: |
WACKER POLYMER SYSTEMS GMBH &
CO., KG
Johannes-Hess-Strasse 24
Burghausen
DE
84489
|
Family ID: |
32864389 |
Appl. No.: |
11/686037 |
Filed: |
March 14, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10819444 |
Apr 7, 2004 |
|
|
|
11686037 |
Mar 14, 2007 |
|
|
|
Current U.S.
Class: |
524/5 ; 524/556;
524/563; 524/567; 524/571 |
Current CPC
Class: |
C04B 24/2676 20130101;
C04B 24/2641 20130101; C08J 3/122 20130101; C08L 29/04 20130101;
C04B 24/2688 20130101; C04B 2111/62 20130101; C04B 24/2623
20130101; C04B 2103/0057 20130101; C04B 24/163 20130101; C04B
2111/70 20130101; C04B 2103/30 20130101 |
Class at
Publication: |
524/005 ;
524/556; 524/563; 524/567; 524/571 |
International
Class: |
C04B 24/26 20060101
C04B024/26 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 8, 2003 |
DE |
10316079.5E |
Claims
1.-15. (canceled)
16. A polyvinyl alcohol-stabilized redispersible powder having
plasticizing properties, prepared by drying a polyvinyl
alcohol-stabilized, aqueous dispersion of at least one
homopolymeric or copolymeric base polymer comprising polymerized
monomers selected from the group consisting of vinyl esters of
optionally branched C.sub.1-18 alkylcarboxylic acids, (meth)acrylic
esters of optionally branched C.sub.1-15 alcohols, dienes, olefins,
vinylaromatics and vinylhalides, in the presence of a plasticizing
copolymer comprising a copolymerisate comprising: a) at least one
monomer selected from the group consisting of ethylenically
unsaturated C.sub.4-8 monocarboxylic acids, ethylenically
unsaturated C.sub.4-8 dicarboxylic acids, ethylenically unsaturated
C.sub.4-8 dicarboxylic acid anhydrides, and salts thereof, in an
amount of from about 10 to about 50 weight percent, b) at least one
ethylenically unsaturated monomer containing sulfonic, sulfuric,
and/or phosphonic acid groups, and/or salts thereof, in an amount
of from about 10 to about 50 weight percent, and c) at least one
monomer selected from the group consisting of vinyl esters of
optionally branched C.sub.1-18 alkylcarboxylic acids and
(meth)acrylic esters of optionally branched C.sub.1-15 alcohols, in
an amount of from about 20 to about 80 weight percent said weight
percents based on the total weight of said plasticizing
copolymer.
17. The redispersible powder of claim 16, wherein at least one base
polymer is selected from the group consisting of vinyl acetate
homopolymers, copolymers of vinyl acetate with ethylene, copolymers
of vinyl acetate with ethylene and one or more further vinyl
esters, copolymers of vinyl acetate with ethylene and
(meth)acrylate(s), copolymers of vinyl acetate with ethylene and
vinyl chloride, styrene-acrylate copolymers, and
styrene-1,3-butadiene copolymers.
18. The redispersible powder of claim 16, wherein at least one
polyvinyl alcohol is selected from the group consisting of
partially and fully hydrolyzed polyvinyl alcohols having a degree
of hydrolysis of from 80 to 100 mol % and a Hoppler viscosity in 4%
by weight aqueous solution of from 1 to 30 mPas, and partially
hydrolyzed, hydrophobically modified polyvinyl alcohols having a
degree of hydrolysis of from 80 to 95 mol % and a Hoppler viscosity
in 4% by weight aqueous solution of from 1 to 30 mPas.
19. The redispersible powder of claim 18, wherein at least one
polyvinyl alcohol is selected from the group consisting of
partially hydrolyzed polyvinyl alcohols having a degree of
hydrolysis of from 80 to 95 mol % and a Hoppler viscosity in 4% by
weight aqueous solution of from 1 to 30 mPas.
20. The redispersible powder of claim 16, wherein the plasticizing
copolymer comprises as comonomer a) at least one monomer selected
from the group consisting of acrylic acid, methacrylic acid,
crotonic acid, itaconic acid, fumaric acid, maleic acid, and salts
thereof.
21. The redispersible powder of claim 16, wherein the plasticizing
copolymer comprises as comonomer b) at least one monomer selected
from the group consisting of vinylsulfonic acid and its alkali
metal and alkaline earth metal salts, styrenesulfonic acid and its
alkali metal and alkaline earth metal salts, methallylsulfonic acid
and its alkali metal and alkaline earth metal salts,
p-methallyloxyphenylsulfonic acid and its alkali metal and alkaline
earth metal salts, and sulfonic acids of the general formula
CH.sub.2.dbd.CR.sup.1--CO--X--CR.sup.2R.sup.3--R.sup.4--SO.sub.3H
and their alkali metal and alkaline earth metal salts, where X is O
or NH, R.sup.1, R.sup.2, and R.sup.3 are identical or different and
are H or C.sub.1 to C.sub.3 alkyl, and R.sup.4 is C.sub.1 to
C.sub.4 alkylene.
22. The redispersible powder of claim 16, wherein the plasticizing
copolymer comprises as comonomer c) at least one monomer selected
from the group consisting of vinyl acetate, vinyl propionate,
methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate,
n-butyl (meth)acrylate, and 2-ethylhexyl acrylate.
23. The redispersible powder of claim 16, wherein the fraction of
the comonomer units a) is from 10 to 30% by weight, the fraction of
the comonomer units b) is from 10 to 30% by weight, and the
fraction of the comonomer units c) is from 30 to 70% by weight, the
percents by weight based on the total weight of the copolymer, and
wherein the copolymer has a number-average molecular weight Mn of
less than 50,000 daltons.
24. The redispersible powder of claim 16, wherein the fraction of
the plasticizing copolymer in the redispersible powder is from 0.1
to 25% by weight, based on the total weight of the redispersible
powder.
25. A process for preparing the polyvinyl-alcohol-stabilized
redispersible powder having plasticizing properties of claim 16,
comprising drying a polyvinyl-alcohol-stabilized, aqueous
dispersion of at least one homopolymeric or copolymeric base
polymer comprising at least one polymerized monomer selected from
the group consisting of vinyl esters of optionally branched
C.sub.1-18 alkylcarboxylic acids, (meth)acrylic esters of
optionally branched C.sub.1-15 alcohols, dienes, olefins,
vinylaromatics and vinylhalides, in the presence of a plasticizing
copolymer comprising a copolymerizate of a) at least one monomer
selected from the group consisting of ethylenically unsaturated
C.sub.4-8 monocarboxylic acids, ethylenically unsaturated C.sub.4-8
dicarboxylic acids, ethylenically unsaturated C.sub.4-8
dicarboxylic acid anhydrides, and salts thereof, b) at least one
ethylenically unsaturated monomer containing sulfonate, sulfate,
and/or phosphonate groups, c) at least one monomer selected from
the group consisting of vinyl esters of optionally branched
C.sub.1-18 alkylcarboxylic acids, and (meth)acrylic esters of
optionally branched C.sub.1-15 alcohols.
26. The process of claim 25, wherein drying is effected by means of
spray drying following the addition of further polyvinyl alcohol as
a spraying aid.
27. The composition of claim 16 which is a chemical product for the
construction industry, and further comprises at least one
hydraulically setting binder selected from the group consisting of
cement, gypsum, lime and waterglass.
28. The composition of claim 27, wherein said hydraulically setting
binder is a cement selected from the group consisting of Portland,
aluminate, pozzolanic, slag, magnesia, and phosphate cements.
29. The composition of claim 27 which is a construction adhesive,
plaster, render, filling compound, trowel-applied flooring
compound, leveling compound, grout, jointing mortar, or paint.
30. The composition of claim 27 which is a self-leveling
floor-filling compound or flowable screed.
31. A polyvinyl alcohol-stabilized redispersible powder having
plasticizing properties, prepared by drying a polyvinyl
alcohol-stabilized, aqueous dispersion of at least one
homopolymeric or copolymeric base polymer comprising polymerized
monomers selected from the group consisting of vinyl esters of
optionally branched C.sub.1-18 alkylcarboxylic acids, dienes,
olefins, vinylaromatics and vinylhalides, in the presence of a
plasticizing copolymer comprising a copolymerisate comprising: a)
at least one monomer selected from the group consisting of
ethylenically unsaturated C.sub.4-8 monocarboxylic acids,
ethylenically unsaturated C.sub.4-8 dicarboxylic acids,
ethylenically unsaturated C.sub.4-8 dicarboxylic acid anhydrides,
and salts thereof, in an amount of from about 10 to about 50 weight
percent, b) at least one ethylenically unsaturated monomer
containing sulfonic, sulfuric, and/or phosphonic acid groups,
and/or salts thereof, in an amount of from about 10 to about 50
weight percent, and c) at least one monomer selected from the group
consisting of vinyl esters of optionally branched C.sub.1-18
alkylcarboxylic acids and (meth)acrylic esters of optionally
branched C.sub.1-15 alcohols, in an amount of from about 20 to
about 80 weight percent said weight percents based on the total
weight of said plasticizing copolymer.
32. The redispersible powder of claim 31, wherein the base polymer
further comprises from 1 to 10% by weight of auxiliary
monomers.
33. The redispersible powder of claim 22, wherein the auxiliary
monomers are selected from the group consisting of ethylenically
unsaturated monocarboxylic and dicarboxylic acids, ethylenically
unsaturated carboxamides and carbonitriles, monoesters and diesters
of fumaric and maleic acid, maleic anhydride; ethylenically
unsaturated sulfonic acids and their salts, polyethylenically
unsaturated comonomers, glycidyl methacrylate and glycidyl
acrylate, silicon-functional comonomers, and monomers containing
hydroxyl or CO groups, and mixtures thereof.
34. The redispersible powder of claim 32, wherein the auxiliary
monomers are selected from the group consisting of acrylic acid,
methacrylic acid, fumaric acid, maleic acid, acrylamide,
acrylonitrile; fumaric acid, and maleic acid diethyl and
diisopropyl esters; maleic anhydride; vinylsulfonic acid,
2-acrylamido-2-methylpropanesulfonic acid, divinyl adipate, diallyl
maleate, allyl methacrylate, triallyl cyanurate; acrylamidoglycolic
acid (AGA), methylacrylamidoglycolic acid methyl ester (MAGME),
N-methylolacrylamide (NMA), N-methylolmethacrylamide (NMMA),
N-methylolallylcarbamate, alkyl ethers and esters of
N-methylolacrylamide, of N-methylolmethacrylamide, and of
N-methylolallylcarbamate, glycidyl methacrylate, glycidyl acrylate,
acryloyloxypropyltri(alkoxy)silanes,
methacryloyloxypropyltri(alkoxy)silanes, vinyltrialkoxysilanes,
vinylmethyldialkoxysilanes, hydroxyalkyl (meth)acrylates,
hydroxyethyl, hydroxypropyl or hydroxybutyl (meth)acrylates,
diacetoneacrylamide, acetylacetoxyethyl (meth)acrylate, and
mixtures thereof.
35. A chemical construction composition comprising at least one
redispersible powder of claim 31, and at least one hydraulically
settable inorganic binder.
36. The composition of claim 35, further comprising water.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to polyvinyl-alcohol-stabilized
redispersible powders having plasticizing properties, to processes
for preparing them, and to their use in chemical products for the
construction industry.
[0003] 2. Background Art
[0004] Polymer powders stabilized with protective colloid which are
redispersible in water (redispersible powders) are employed as
additives in construction compositions, based for example on cement
or gypsum, in order to improve strength and abrasion resistance, or
in the case of construction adhesives, to improve adhesive tensile
strength. The protective colloid used is frequently polyvinyl
alcohol, since this colloid contributes to improved strength, in
comparison to polymers stabilized with low molecular weight
emulsifiers.
[0005] Redispersible powders of this kind are obtainable by drying
the corresponding protective-colloid-stabilized polymer
dispersions, with the addition during drying of so-called drying
assistants (spraying aids), in order to prevent the formation of
agglomerates. In EP-A 467103 water-soluble copolymers with
carboxyl-functional comonomer units are used as drying assistants.
DE-A 19707746 describes the use of copolymers of ethylenically
unsaturated carboxylic acids and their hydroxyalkyl esters as
drying assistants. EP-A 629650 discloses copolymers containing
acrylamidomethylpropanesulfonic acid units as a spraying aid. EP-A
671435 recommends spray drying in the presence of copolymers
containing hydrophilic, water-soluble, and salt-forming
monomers.
[0006] In many cases modification of construction compositions such
as mortar or concrete with redispersible powders decreases
fluidity. In the case of fluid mortars such as self-leveling
fillers or screeds, however, a liquid consistency which exhibits
little change during processing, is essential. Consequently, in
these applications, additives known as cement plasticizers are
employed. For example, EP-A 549280 describes plasticizers based on
graft copolymers containing four different comonomer units:
(meth)acrylic acid units, hydroxyalkyl (meth)acrylate units,
(meth)acrylamido-2-methylpropanesulfonic acid, and (meth)acrylates
containing EO groups. JP-A 59/162161 describes water-soluble
copolymers containing hydroxyalkyl esters of an ethylenically
unsaturated monocarboxylic acid and ethylenically unsaturated
monocarboxylic or dicarboxylic acid units. EP-A 407889 discloses
redispersible powders which employ phenolsulfonic acid-formaldehyde
condensation products in order to improve their fluidity when used
in hydraulic binders. EP-A 812872 describes processes for preparing
polymer powders with the addition of drying assistants having a
plasticizing effect.
SUMMARY OF THE INVENTION
[0007] An object of the invention is to provide redispersible
powders stabilized with polyvinyl alcohol which improve the
fluidity of construction compounds to which they are added. This
and other objects are achieved through the preparation and use of a
polyvinyl alcohol-stabilized mixture of a first redispersible
polymer or copolymer, and a second copolymer prepared from at least
two acid-containing monomers.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0008] The invention provides polyvinyl-alcohol-stabilized
redispersible powders having plasticizing properties, obtainable by
drying polyvinyl-alcohol-stabilized aqueous dispersions of
homopolymers or copolymers of one or more monomers from the group
of vinyl esters of branched or unbranched ("optionally branched")
alkylcarboxylic acids having 1 to 18 carbon atoms, acrylic and
methacrylic esters ("(meth)acrylic esters") of optionally branched
of alcohols having 1 to 15 carbon atoms, dienes, olefins,
vinylaromatics and vinylhalides ("base polymer"), in the presence
of a copolymer formed from a) one or more monomers from the group
of ethylenically unsaturated monocarboxylic acids, ethylenically
unsaturated dicarboxylic acids and their anhydrides, having in each
case 4 to 8 carbon atoms, and also salts thereof, b) one or more
ethylenically unsaturated compounds containing sulfonic, sulfuric,
or phosphonic acid groups, and also salts thereof, and c) one or
more monomers from the group of vinyl esters of optionally branched
alkylcarboxylic acids having 1 to 18 carbon atoms and acrylic and
methacrylic esters of optionally branched alcohols having 1 to 15
carbon atoms.
[0009] Vinyl esters suitable for the base polymer are those of
carboxylic acids having 1 to 18 carbon atoms. Preferred vinyl
esters are vinyl acetate, vinyl propionate, vinyl butyrate,
vinyl-2-ethylhexanoate, vinyl laurate, 1-methylvinyl acetate, vinyl
pivalate, and vinyl esters of .alpha.-branched monocarboxylic acids
having 9 to 13 carbon atoms, such as VeoVa9.RTM. or VeoVa10.RTM.
(trade names of Resolution Products). Particular preference is
given to vinyl acetate.
[0010] Suitable methacrylic or acrylic esters are esters of
optionally branched alcohols having 1 to 15 carbon atoms, such as
methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl
methacrylate, propyl acrylate, propyl methacrylate, n-butyl
acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, and
norbornyl acrylate. Preference is given to methyl acrylate, methyl
methacrylate, n-butyl acrylate, and 2-ethylhexyl acrylate.
[0011] Examples of olefins and dienes are ethylene, propylene, and
1,3-butadiene. Suitable vinylaromatics are styrene and vinyl
toluene. A suitable vinyl halide is vinyl chloride.
[0012] If desired it is also possible to copolymerize from 0.05 to
50% by weight, preferably from 1 to 10% by weight of auxiliary
monomers, based on the total weight of the base polymer. Examples
of auxiliary monomers are ethylenically unsaturated monocarboxylic
and dicarboxylic acids, preferably acrylic acid, methacrylic acid,
fumaric acid, and maleic acid; ethylenically unsaturated
carboxamides and carbonitriles, preferably acrylamide and
acrylonitrile; monoesters and diesters of fumaric and maleic acid,
such as the diethyl and diisopropyl esters; maleic anhydride; and
ethylenically unsaturated sulfonic acids and their salts,
preferably vinylsulfonic acid and
2-acrylamido-2-methylpropanesulfonic acid. Further examples are
precrosslinking comonomers such as polyethylenically unsaturated
comonomers, examples being divinyl adipate, diallyl maleate, allyl
methacrylate, and triallyl cyanurate; and postcrosslinking
comonomers, examples being acrylamidoglycolic acid (AGA),
methylacrylamidoglycolic acid methyl ester (MAGME),
N-methylolacrylamide (NMA), N-methylolmethacrylamide (NMMA),
N-methylolallylcarbamate, alkyl ethers and esters of
N-methylolacrylamide, of N-methylolmethacrylamide, and of
N-methylolallylcarbamate such as the isobutoxy ethers or esters.
Also suitable are epoxy-functional comonomers such as glycidyl
methacrylate and glycidyl acrylate. Further examples are
silicon-functional comonomers, such as
acryloyloxypropyltri(alkoxy)silanes and
methacryloyloxypropyltri(alkoxy)silanes, vinyltrialkoxysilanes, and
vinylmethyldialkoxysilanes, in which the alkoxy groups present can
be, for example, methoxy, ethoxy, and ethoxypropylene glycol ether
radicals. Mention may also be made of monomers containing hydroxyl
or CO groups, examples being hydroxyalkyl acrylates and
methacrylates such as hydroxyethyl, hydroxypropyl or hydroxybutyl
acrylate or methacrylate, and also compounds such as
diacetoneacrylamide and acetylacetoxyethyl acrylate or
methacrylate.
[0013] Examples of suitable homopolymers and copolymers are vinyl
acetate homopolymers, copolymers of vinyl acetate with ethylene,
copolymers of vinyl acetate with ethylene and one or more further
vinyl esters, copolymers of vinyl acetate with ethylene and
acrylate and/or methacrylate, copolymers of vinyl acetate with
ethylene and vinyl chloride, styrene-acrylate copolymers, and
styrene-1,3-butadiene copolymers, it being possible for the
polymers to also include the aforementioned auxiliary monomers.
[0014] Preference is given to vinyl acetate homopolymers;
copolymers of vinyl acetate with from 1 to 40% by weight of
ethylene; copolymers of vinyl acetate with from 1 to 40% by weight
of ethylene and from 1 to 50% by weight of one or more further
comonomers from the group of vinyl esters having 1 to 12 carbon
atoms in the carboxylic acid radical, such as vinyl propionate,
vinyl laurate, vinyl esters of alpha-branched carboxylic acids
having 9 to 13 carbon atoms, such as VeoVa9, VeoVa10, and VeoVa11;
copolymers of vinyl acetate, from 1 to 40% by weight of ethylene
and, preferably, from 1 to 60% by weight of acrylates and/or
methacrylates of branched or unbranched alcohols having 1 to 15
carbon atoms, especially n-butyl acrylate and/or 2-ethylhexyl
acrylate and/or methyl methacrylate; and copolymers with from 30 to
75% by weight of vinyl acetate, from 1 to 30% by weight of vinyl
laurate or vinyl esters of an alpha-branched carboxylic acid having
9 to 11 carbon atoms, and also from 1 to 30% by weight of acrylic
esters of branched or unbranched alcohols having 1 to 15 carbon
atoms, especially n-butyl acrylate or 2-ethylhexyl acrylate,
further containing from 1 to 40% by weight of ethylene; and
copolymers of vinyl acetate, from 1 to 40% by weight of ethylene
and from 1 to 60% by weight of vinyl chloride; it being possible
for the polymers to also include the aforementioned auxiliary
monomers in the stated amounts, with the figures in % by weight
adding up in each case to 100% by weight.
[0015] Preference is also given to copolymers of n-butyl acrylate
or 2-ethylhexyl acrylate or copolymers of methyl methacrylate with
n-butyl acrylate and/or 2-ethylhexyl acrylate; styrene-acrylate
copolymers with one or more monomers from the group consisting of
methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate,
and 2-ethylhexyl acrylate; vinyl acetate-acrylate copolymers with
one or more monomers from the group consisting of methyl acrylate,
ethyl acrylate, propyl acrylate, n-butyl acrylate, 2-ethylhexyl
acrylate, and, optionally ethylene; and styrene-1,3-butadiene
copolymers; it being possible for the polymers to additionally
include the abovementioned auxiliary monomers in the stated
amounts.
[0016] The selection of monomers and/or the selection of the weight
fractions of the comonomers is made such that in general the
resulting glass transition temperature Tg is from -50.degree. C. to
+50.degree. C., preferably from -30.degree. C. to +40.degree. C.
The glass transition temperature Tg of the polymers can be
determined conventionally by means of Differential Scanning
Calorimetry (DSC). The Tg can also be calculated approximately in
advance using the Fox equation. According to T. G. Fox, BULL. AM.
PHYSICS SOC. 1, 3, page 123 (1956): 1/Tg=x1/Tg1+x2/Tg2+. . .
+xn/Tgn, where xn stands for the mass fraction (% by weight/100) of
the monomer n, and Tgn is the glass transition temperature, in
degrees Kelvin, of the homopolymer of the monomer n. Homopolymer Tg
values are listed in the POLYMER HANDBOOK 2nd Edition, J. Wiley
& Sons, New York (1975).
[0017] Suitable polyvinyl alcohols are partly or fully hydrolyzed
polyvinyl alcohols. Preference is given to partly or fully
hydrolyzed polyvinyl alcohols having a degree of hydrolysis of from
80 to 100 mol %, especially to partly hydrolyzed polyvinyl alcohols
having a degree of hydrolysis of from 80 to 95 mol % and a Hoppler
viscosity, in 4% by weight aqueous solution, of from 1 to 30 mPas
(Hoppler method at 20.degree. C., DIN 53015). Preference is also
given to partly hydrolyzed, hydrophobically modified polyvinyl
alcohols having a degree of hydrolysis of from 80 to 95 mol % and a
Hoppler viscosity, in 4% by weight aqueous solution, of from 1 to
30 mPas. Examples thereof are partially hydrolyzed copolymers of
vinyl acetate with hydrophobic comonomers such as isopropenyl
acetate, vinyl pivalate, vinyl ethylhexanoate, vinyl esters of
saturated alpha-branched monocarboxylic acids having 5 or 9 to 11
carbon atoms, dialkyl maleates and dialkyl fumarates such as
diisopropyl maleate and diisopropyl fumarate, vinyl chloride, vinyl
alkyl ethers such as vinyl butyl ether, and olefins such as ethene
and decene. The fraction of the hydrophobic units is preferably
from 0.1 to 10% by weight, based on the total weight of the partly
hydrolyzed polyvinyl alcohol. It is also possible to use mixtures
of polyvinyl alcohols.
[0018] Greatest preference is given to polyvinyl alcohols having a
degree of hydrolysis of from 85 to 94 mol % and a Hoppler
viscosity, in 4% by weight aqueous solution, of from 3 to 15 mPas
(Hoppler method at 20.degree. C., DIN 53015). These polyvinyl
alcohols are obtainable by methods which are known to one skilled
in the art, and are generally added during the polymerization in an
amount totaling from 1 to 20% by weight, based on the total weight
of the monomers.
[0019] The polyvinyl-alcohol-stabilized polymer dispersions can be
prepared by conventional methods, an example being the emulsion
polymerization described in DE-A 10253046, preferably by means of
free-radical initiated emulsion polymerization.
[0020] The plasticizing copolymer preferably includes as comonomer
a) one or more monomers from the group of acrylic acid, methacrylic
acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, and
salts of these carboxylic acids.
[0021] Preferred monomers b) are vinylsulfonic acid and its alkali
metal and alkaline earth metal salts, styrenesulfonic acid and its
alkali metal and alkaline earth metal salts, methallylsulfonic acid
and its alkali metal and alkaline earth metal salts,
p-methallyloxyphenylsulfonic acid and its alkali metal and alkaline
earth metal salts, and sulfonic acids of the general formula
CH.sub.2.dbd.CR.sup.1--CO--X--CR.sup.2R.sup.3--R.sup.4--SO.sub.3H
and their alkali metal and alkaline earth metal salts, where X is O
or NH, R.sup.1, R.sup.2, and R.sup.3 are identical or different and
are defined as H and C.sub.1 to C.sub.3 alkyl, and R.sup.4 is
C.sub.1 to C.sub.4 alkylene. Particular preference is given to
vinylsulfonic acid, sulfopropyl (meth)acrylate,
2-acrylamido-2-methylpropanesulfonic acid, and methallylsulfonic
acid, and their respective alkali metal and alkaline earth metal
salts.
[0022] Preferred vinyl ester comonomers c) are vinyl acetate and
vinyl propionate. Preferred methacrylic or acrylic esters are
methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl
methacrylate, propyl acrylate, propyl methacrylate, n-butyl
acrylate, n-butyl methacrylate, and 2-ethylhexyl acrylate.
[0023] The weight fraction of the comonomer units a) is preferably
from 10 to 50% by weight, more preferably from 10 to 30% by weight,
based on the total weight of the copolymer. The fraction of the
comonomer units b) is preferably from 10 to 50% by weight, more
preferably from 10 to 30% by weight, based on the total weight of
the copolymer. The fraction of the comonomer units c) is preferably
from 20 to 80% by weight, more preferably from 30 to 70% by weight,
based on the total weight of the copolymer. The copolymer has a
number-average molecular weight Mn of less than 50,000 daltons,
preferably from 5,000 to 20,000 daltons.
[0024] The fraction of the plasticizing copolymer in the
redispersible powder is from 0.1 to 25% by weight, preferably from
2 to 20% by weight, based on the weights of the polymeric
constituents of the redispersible powder.
[0025] To prepare the redispersible powders the aqueous,
polyvinyl-alcohol-stabilized dispersions, together with the
plasticizing copolymer, are dried, for example by means of
fluidized-bed drying, freeze drying or spray drying. The
dispersions are preferably spray dried, more preferably following
the addition of further polyvinyl alcohol as a spraying aid. Spray
drying takes place in conventional spray-drying installations, with
atomization by any suitable means, for example, single-fluid,
two-fluid or multifluid nozzles, or with a rotating disk. The exit
temperature chosen is generally in the range from 45.degree. C. to
120.degree. C., preferably 60.degree. C. to 90.degree. C.,
depending on installation, resin Tg, and desired degree of
drying.
[0026] It is preferred to use polyvinyl alcohol as a spraying aid
in an amount such that the total amount of polyvinyl alcohol prior
to the drying operation is from 3 to 25% by weight, based on the
polymer fraction more preferably from 5 to 20% by weight. Preferred
spraying aids are the polyvinyl alcohols set out above as being
suitable for use with protective colloids.
[0027] In the case of nozzle spraying it has frequently been found
advantageous to include up to 1.5% by weight of antifoam, based on
the base polymer. In order to enhance the storage properties by
improving the blocking stability, particularly in the case of low
glass transition temperature powders, the resulting powder can be
provided with an antiblocking (anticaking) agent, preferably at
preferably up to 30% by weight, based on the total weight of the
polymeric constituents. Examples of antiblocking agents include Ca
or Mg carbonates, talc, gypsum, silica, kaolins, and silicates
having small particle sizes, preferably in the range from 10 nm to
10 .mu.m. The viscosity of the feed to be sprayed is adjusted by
way of the solids content so as to be less than 500 mPas
(Brookfield viscosity, 20 s.sup.-1, at 23.degree. C.), preferably
less than 250 mPas. The solids content of the dispersion for
spraying is preferably greater than 35%, more preferably greater
than 40%.
[0028] In order to improve the performance properties it is
possible to add further ingredients during spraying. Examples of
further constituents of dispersion powder compositions that may be
present in preferred embodiments include pigments, fillers, foam
stabilizers, and hydrophobicizers.
[0029] The water-redispersible polymer powder compositions
obtainable in this way can be employed in the areas typical for
them. For example, in chemical products for the construction
industry, alone or in conjunction with hydraulically setting
binders such as cements, e.g. Portland, aluminate, pozzolanic,
slag, magnesia, and phosphate cements, or gypsum, lime and
waterglass, for the production of construction adhesives,
especially tile adhesives and exterior insulation adhesives,
plasters and renders, filling compounds, trowel-applied flooring
compounds, leveling compounds, grouts, jointing mortars, and
paints, and with particular preference, for self-leveling
floor-filling compounds and flowable screeds.
[0030] Typical formulations of self-leveling, hydraulically setting
compounds include from 100 to 500 parts by weight of cement such as
Portland cement and/or alumina cement, from 300 to 800 parts by
weight of fillers such as sand and/or ground limestone and/or
silica dusts and/or fly ash, from 0 to 200 parts by weight of
anhydrite, hemihydrate and/or gypsum, from 0 to 50 parts by weight
of calcium hydroxide, from 0 to 5 parts by weight of defoamer, from
0.5 to 10 parts by weight of dispersant, from 1 to 100 parts by
weight of redispersible powder, from 0.5 to 5 parts by weight of
retardants such as tartaric acid, citric acid or saccharides, from
0.5 to 5 parts by weight of accelerators, examples being alkali
metal carbonates, and from 0.2 to 3 parts by weight of thickeners
such as cellulose ethers, the amounts adding up to 1,000 parts by
weight, and the dry mix is stirred together with an amount of water
to provide the desired consistency.
[0031] With the redispersible powders of the invention there is no
longer any need to use additional plasticizers in self-leveling
filling compound (SLF) applications. It has been surprisingly
discovered, in addition, that when polyvinyl-alcohol-stabilized
dispersion and plasticizer are spray-dried simultaneously a marked
increase in the plasticizing effect is observed. It has
additionally been found that polyvinyl-alcohol-stabilized powders
modified not in accordance with the invention but instead with the
customary plasticizers containing high proportions of ethylene
oxide and/or propylene oxide units give very poorly redispersing
powders which lack blocking stability and are unsuitable for use in
chemical products for the construction industry.
EXAMPLES
[0032] The redispersible powders prepared by spray drying were
investigated in the self-leveling formulation indicated in table 1.
The individual components were mixed dry and then stirred with 21 g
of water per 100 g of dry mix. TABLE-US-00001 TABLE 1 Amount [g]
Raw material Manufacturer/Supplier 94.0 High alumina cement Fondue
Lafarge Aluminates int. 200.0 Portland cement CEM I 42.5 R
Milke-Zement GmbH & Co.KG 47.0 Anhydrite Hilliges Gipswerke KG
47.0 Light spar W. Priem & Co. 359.0 Quartz sand H 33
Quarzwerke GmbH 226.3 Calcium carbonate Omyacarb 20 BG Omya GmbH
23.0 RD powder/plasticizer 1.2 Tartaric acid Merck Eurolab GmbH 1.0
Li.sub.2CO.sub.3 Merck Eurolab GmbH 1.0 Defoamer, Agitan P 800
Munzing Chemie GmbH 0.5 Cellulose, Tylose H 300 P2 Clariant GmbH
1000
Comparative Example 1
[0033] 20 parts by weight of a redispersible powder based on a
vinyl acetate/ethylene copolymer having a Tg of 17.degree. C. and
containing 8% by weight of partially hydrolyzed polyvinyl alcohol
were blended beforehand with 3 parts by weight of Melflux 1641
(powderous plasticizer from Degussa) and tested in the above
formulation. The results are summarized in table 2.
Comparative Example 2
[0034] 23 parts by weight of a redispersible powder prepared by
spraying an aqueous polymer dispersion based on a vinyl
acetate/ethylene copolymer having a Tg of 17.degree. C. and
containing 8% by weight of partially hydrolyzed polyvinyl alcohol,
and with 10% by weight of Melflux 1641, were tested in the above
formulation. The results are summarized in table 2.
Example 3
[0035] 23 parts by weight of a redispersible powder prepared by
spraying an aqueous polymer dispersion based on a vinyl
acetate/ethylene copolymer having a Tg of 17.degree. C., stabilized
with 8% by weight of partially hydrolyzed polyvinyl alcohol, and
containing 5% by weight of partially hydrolyzed polyvinyl alcohol,
and with 7.4% by weight of plasticizer A (copolymer of 22% by
weight methacrylic acid, 49% by weight ethyl acrylate, 7% by weight
methyl methacrylate, and 22% by weight sulfopropyl acrylate), were
tested in the above formulation. The results are summarized in
Table 2.
Example 4
[0036] Example 3 was followed, but instead of co-spraying with 7.4%
by weight of plasticizer A, 6.7% by weight of plasticizer B
(copolymer of 27% by weight methacrylic acid, 49% by weight ethyl
acrylate, 7% by weight methyl methacrylate, 17% by weight
sulfopropyl acrylate) was used. The results are summarized in Table
2.
Example 5
[0037] Example 3 was followed, but instead of co-spraying with 7.4%
by weight of plasticizer A, 10% by weight of plasticizer A was
used. The results are summarized in table 2.
Comparative Example 6
[0038] 20 parts by weight of a redispersible powder based on a
vinyl acetate/ethylene copolymer having a Tg of 17.degree. C. and
containing 8% by weight of partially hydrolyzed polyvinyl alcohol
were blended beforehand with 3 parts by weight of plasticizer A and
tested in the above formulation. The results are summarized in
Table 2.
Comparative Example 7
[0039] 20 parts by weight of a redispersible powder based on a
vinyl acetate/ethylene copolymer having a Tg of 17.degree. C. and
containing 8% by weight of partially hydrolyzed polyvinyl alcohol
were blended beforehand with 3 parts by weight of plasticizer B and
tested in the above formulation. The results are summarized in
Table 2.
Example 8
[0040] 23 parts by weight of a redispersible powder prepared by
spraying an aqueous polymer dispersion based on a vinyl
acetate/ethylene/VeoVa10 copolymer having a Tg of 5.degree. C. and
stabilized with 8% by weight of partially hydrolyzed polyvinyl
alcohol, together with 5% by weight of partially hydrolyzed
polyvinyl alcohol and 10% by weight of plasticizer A, were tested
in the above formulation. The results are summarized in Table
2.
Performance Tests:
Determination of Slump (Leveling):
[0041] The rheology was determined in accordance with DIN EN 12706
after periods of 1, 15, and 30 minutes.
Determining the Flexural Strength Under Tension (FS):
[0042] The flexural strength under tension was determined after 1
day (1d) and 7 days (7d) and was performed in accordance with prEN
13851 on prisms measuring 40.times.40.times.160 mm.sup.3.
Determining the Compressive Strength (CS):
[0043] The compressive strength was determined after 1 day (1d) and
7 days (7d) and was performed in accordance with prEN 13851 on
standard prisms measuring 40.times.40.times.160 mm.sup.3.
Determination of Blocking Resistance (BR):
[0044] The blocking resistance was determined by introducing the
dispersion powder into an iron tube with a screw fitting and then
subjecting it to the action of a metal ram. After ramming, the tube
was stored in a drying cabinet at 50.degree. C. for 16 hours. After
cooling to room temperature, the powder was removed from the tube
and the blocking stability was determined qualitatively by crushing
the powder. The blocking stability was classified as follows:
[0045] 1-3=very good blocking stability [0046] 4-6=good blocking
stability [0047] 7-8=satisfactory blocking stability [0048]
9-10=not stable to blocking, powder is no longer free-flowing after
crushing. Determining the Settling Behavior RA:
[0049] The settling behavior of the redispersion is a measure of
the redispersibility of the powders. The redispersions were
produced as 50% strength by weight aqueous redispersions, using
strong shearing forces. The settling behavior was then determined
on dilute redispersions (0.5% solids content), by introducing 100
ml of this dispersion into a graduated tube and measuring the
settling height of solid material. The result is reported as mm of
settling after 24 hours. Figures greater than 7 indicate inadequate
redispersion of powder.
[0050] A comparison of comparative Example 1 with Comparative
Example 2 shows that with conventional plasticizers, co-spraying
produces redispersible powders having a reduced plasticizing
effect.
[0051] A comparison of Example 3 with Comparative Example 6 and a
comparison of Example 4 with Comparative Example 7 shows that with
the plasticizers used in accordance with the invention co-spraying
improves the plasticizing effect. TABLE-US-00002 TABLE 2 Leveling
Leveling Leveling FS 1 d/7 d CS 1 d/7 d RA Example 1' [cm] 15' [cm]
30' [cm] [N/mm.sup.2] [N/mm.sup.2] BR 1 h/24 h C. Ex. 1 16.0 16.2
16.4 3.83/4.48 19.64/24.37 3 0.2/1 C. Ex. 2 10.6 9.8 8.5 3.11/4.06
14.72/22.34 10 >7/-- Ex. 3 16.3 16.2 16.1 3.79/5.55 19.12/24.52
4 0.1/1 Ex. 4 15.4 15.5 16.0 3.80/5.53 18.35/26.12 3 0.1/0.8 Ex. 5
16.8 16.3 16.5 4.01/5.78 18.56/25.48 4 0.1/0.9 C. Ex. 6 15.6 15.7
15.4 3.78/4.62 17.91/24.74 3 0.2/1 C. Ex. 7 15.3 15.5 15.2
3.78/4.63 20.72/28.01 3 0.2/1 Ex. 8 16.9 16.7 16.7 3.80/5.52
17.16/23.07 4 0.2/1.2
[0052] While embodiments of the invention have been illustrated and
described, it is not intended that these embodiments illustrate and
describe all possible forms of the invention. Rather, the words
used in the specification are words of description rather than
limitation, and it is understood that various changes may be made
without departing from the spirit and scope of the invention.
* * * * *