Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Polymer powder
The present invention relates to polymer powders
whose polymer, in polymerized form, i8 composed of
from 60 to 85% by weight of methyl methacrylate
(monomer a),
from 15 to 25% by weight of at least one ~ mono-
ethylenically unsaturated carboxylic acid of 3 to 6
carbon atoms (monomer b) and
from 0 to 15% by weight of other copolymerizable monomer~
(monomer c),
with the proviso that
the composition of the monomer~ a, b and c is chosen 80
that, according to the Fox relationship for a polymer
composed of these monomers, a glass transition tempera-
ture of from 70 to 150C results and
the K value of the polymer, determined ~or the fully
acidic form of the polymer in dimethylformamide at 23C
and at a polymer content of 0.1% by weight, is from 45 to
100 .
The present invention furthsrmore relatez to
processes for the preparation of these polymer powders
and their use, in dry or aqueous form, as additives for
cement-containing mineral building materials ha~ing
binding properties.
Mineral building materials having binding proper-
ties include formulations which contain, as essential
component~, min~ral binders, such a~ cement, lime or
gypsum, and sands, gravels or crushed rocks Derving as
additive~, or other fillers, for example pigments, and
natural or sy~thetic fibers, and which, after mixing with
water, ~olidify and harden (set) in the air and in some
ca~es also under water.
In many cases, it i~ now desirable on the one
hand for the mineral building material having binding
properties and mixed in ready-to-use form to exhibit
advantageou~ flow behavior, ie. a high flow limit (the
flow limit is defin0d as the shear stress above which an
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engineering makerial behave3 like a liquid, ie. flows,
whereas it behaves like a solid, ie. does not flow, under
the action of 3hear ~tresses below the flow limit), and,
under the action of shear ~tresses above the flow limit,
very low flow resistance and a very low dynamic viscosity
~ and, on the other hand, for the set mineral building
- material having binding properties to posisessi high
~ internal ~trength (flexural tensile strength and compres-
,~ sive strength) and good adhesion to the substrate.
Mortars for repair purposes are an example of
such requirement~. They should have a viscosity ~uitable
for proce~sing when in the ready-to-use mixed ~tate but
should not run off, ie. ~hould exhibit ~tability, im-
mediately after application to the generally vertical
repair site~ under the shear stre~s of their own weight.
Moreover, they should, in the set state, adhere well to
the substrate to be improved and en~ure high mechanical
,~ 8 trength.
- Adheeive mortar~ for mounting ceramic tile~
con~titute a further example of the abovementioned
requirements.
It is now generally known that the properties of
"~ mineral building material~ having binding properties can
`~ be modified by adding agueous polymer disper~ions (in
aqueous or dried form). As a rule, however, this i~
accompanied by an increase in the time required for said
mineral building material to reach its strength suitable
for uEe.
It i~ an object of the present invention to
j30 provide polymer powders which, when added (in dry or
'agueou~ form) to cement-containing mineral building
-, ~ materials ha~ing binding propertie~, in a freshly mixed
~tate, impart advantageous flow behavior to ~aid building
materials without sub~tantially in$1uencing the ~etting
time before the strength suitable for ueie ii reached, and
which at the same time improves the mechanical strength
and the adhesion to the iubstrate.
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We have found that this object is achieved by the
polymer powders defined at the outset.
The ~ value i~ a relative visco~ity n~her which
is determined similarly to DIN 53,726. It expre~es the
flow rate of pure dimethylformamida (DMF) relative to the
flow rate of DMF containing 0.1% by weight, based on the
total weight, of polymer (in this ca3e in fully acidic
form) and characterizes the average molecular weight of
the polymer (cf. Cellulosechemie 13 (1932), 58-64, and
Kirk-Othmer, Encyclopedia of Chemical Technology,
Vol. 23, page~ 967-968). A high X value corresponds to
a high average molecular weight.
According to Fox (T.G. Fox, Bull. Am. Phys. Soc.
(Ser. II) 1 (1956), 123), a good approximation for the
glas~ transition temperature of copolymers i~
Xl X~ xn
2 -- + -- ~' ............. --
Tg Tgl Tg2 Tg~
¦ where Xl, X2, .... , X~ are the mass fractions of ~he
20 monomer~ 1, 2, , n and Tgl, Tg2, , Tgn are the glass
transition te~peratures of the particular poly~ers
composed only of one of the monomers 1, 2, ... or n, in
degrees Kelvin.
The gla~ transition temperature of these homo-
polymers of the monomers a, b and c are known and arestated in, for example, J. Brandrup and E.~. Immergut,
Polymer Handbook 1st ~d. J. Wiley, New York 1966 and 2nd
Ed. J. Wiley, New York 1975. In particular, the glass
transition temperature~ of the homopolymer~ of the
i 30 monomers a and b appear in Ullmann's Encyclopedia of
Industrial Chemistry, Verlag Chemie, Weinheim (1992),
Vol. A21, Tab. 8, page 169. A gla~ transit~on tempera-
ture of ~rom 90 to 130C is preferably calculated accord-
ing to Fox or the monomer mixture~ to be polymerized
according to the i~vention.
J. Appl. Polym. Sci. 11 (1970), 897-909 and 911-
928 disclo~e~ a~ueous polymer di~persions which have been
obtained by free radical amul~ion polymerization o~
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monomer mixtures consisting of 80% by weight of methyl
methacrylate and 20% by weight of methacrylic acid.
Since there is no mention of the presence of molecular
- weight regulators, the R value of these emulsion polymers
is from 40 to 60.
EP-A 262 326 and EP-A 332 067 relate to processes
for the preparation of a redispersible polymer powder by
drying a polymer di~per~ion containing a dispersed
polymer having a dynamic freezing point T~ of from 60 to
150C and composed of from 20 to 60% by weight of acrylic
and/or methacrylic acid and from 40 to 80% by weight of
lower alkyl ester~ of acrylic and/or methacrylic acid or
a mixture thereof with styrene and, if required, further
comonomers, by special spray-drying methods. They
recommend using the redispersed polymer powder for the
production of coatings for drugs.
German Published Application DAS 1,669,903,
BE-A 8 454 499, JP-A 54/43285, US-A 4 225 496, DE-A 32 20
384, DE-A 28 37 898, US-A 3 232 899 and JP-A 91/131 533
recommend aqucous polymer di~persions of emulsion poly-
~ mero containing polymerized a,B-monoethylenically un-
- saturated carboxylic acid~, a~ additives for cement-
containing mineral building materials having binding
-~ propertie~. However, owing to the fact that their glass
transition t~parature is too low and/or their content of
polymerized a,g-monoethylenically unsaturated carboxylic
acids i~ too high or too low, ~hese emulsion polymers
cannot completely satisfactorily achieve the object of
this invention.
EP-A 537 411 reaommends the general use of
polymer dispersion~ of polymers having a high Tg as
additives for cement mortar. However, the property of a
high glass transition temperature of the di~persed
polymer is not sufficient for achieving the object of
this invention.
DE-A 39 07 013 relates to aqueous polymer di~per-
~ion~ whose emul~ion polymers aro compoeed of from 60 to
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95~ by weight of methyl methacrylate, from 5 to 40% by
weight of acrylic and/or methacrylic acid and, if
required, other comonomers, with the proviso that their
gla 8 tran~ition temperature i~ from 60 to 125C. These
aqueou~ polymer disper~ions are recommended as binders
for moldings. The range of from 5-103 to 5-106, prefer-
ably from 2-105 to 2-106 is stated as the number average
molecular weight of the emulsion polymers, and the
preferred monomer composition i~ from 60 to 75% by weight
of methyl methacrylate, from 5 to 30% by weight of
methacrylic acid and from 0 to 10% by weight of acrylic
acid.
According to the invention, acrylic and meth-
acrylic acid are preferred a~ monomer~ b, the content of
which i8 preferably from 20 to 25% by weight, based on
the polymer. The total amount of the monomer~ b present
in the polymer in polymerized form therefore preferably
compri~es at least 50% by weight of at least one of these
two monomers. The monomera b particularly advantageously
20 compri3e exclusively methacrylic acid.
Suitable monomers c are vinyl aromatic monomers,
such a~ styrene or vinyltoluenes, nitrile~ of ~ mono-
ethylenically unsaturated carboxylic acid~ of 3 to 6
carbon atom~, ester~, other than methyl methacrylate, of
25 ~,B-monoethylenically un~aturated carboxylic acid of 3 to
6 carbon atoms and alkanols of 1 to 12 carbon atom~,
f unsub~tituted or substituted ~mides of ~,B-mono-
ethylenically unsaturated carboxylic acid~ of 3 to 6
~ carbon atoms, a~ well as monomers having a polar atruc-
,` 30 ture, ~uch as acrylamidopropanesulfonic acid, vinyl-
pyrrolidone, hydroxyethyl acrylate or quaternary vinyl-
imidazole. The novel polymer pref~rably contains not
more than 5% by weight of monomers c aa polymerized unit~
and i~ particularly advantageou~ly free of monomers c.
The novel polymer therefore particularly advan-
tageously has the following compo~ition in polymerized
form:
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from 70 to 85% by weight of methyl methacrylate and
from 15 to 25% by weight of methacrylic acid.
The novel polymer powders can be prepared, for
example, by polymerizing a monomer mixture of the corres-
ponding composition in a conventional manner by themethod of free radical aqueous emulsion polymerization,
ie. as a rule in the presence of dispersants and free
radical polymerization initiators, and then drying the
resulting aqueous polymer disper~ion. If the free
radical aqueous emulsion polymerization is carried out in
the absence of molecular weight regulator~, the resulting
a~erage molecular weights with the use of conventional
amounts of polymerization initiators, usually from 0.3 to
2% by weight, based on ths monomers to be polymerized,
are customarily in the K value range according to the
invention, which is preferably from 50 to 80. The
poly~merization temperature i~ in general from room
temperature to 100C, preferably from 60 to 90C.
Suitable free radical polymerization initiators
are all tho~e which are capable of initiating a free
radical aqueous ~mulsion polymerization in the ~tated
t~mperature range. They may be both peroxide, for
example alkali metal peroxydisulfates (in particular
sodium psroxydi~ulfate), and azo co~pounds.
Suitable dispersant~ are both the protective
colloids usually used for carrying out free radical
aqueous emul~ion polymerizations and emulsi~ier~.
Examples of suitable protective colloids are polyvinyl
alcohols, ~ellulose derivati~e~ and vinylpyrrolidon2-
containing copolymer~. The agueous polymsr disper~ion~
are preferably prepared in the ab~ence of protectiv~ col-
loids, ie. emulsifiers whose relati~e molecular weight~,
in contrast to the protective colloids, are u~ually below
1,000 are preferably exclu~ively used as dispersants.
They are preferably anionic and/or nonionic. Convontion-
al ~mulsifiers are, for example, ethoxylated mono-, di-
and trialkylphenols (degree of ethoxylation: from 3 to
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50, alkyl radical: C4. to Cg), ethoxylated fatty alcohols
(degree of ethoxylation: from 0 to 50, alkyl radical: C8
to C36) and alkali metal and ammonium salts of alkyl-
sulfates (alkyl radical: C8 to Cl2), of sulfuric half-
5 esters of ethoxylated alkylphenols (degree of ethoxyla-
tion: from 3 to 50, alkyl radical: C~ to Cl5) and, par-
ticularly preferably, ethoxylated alkanol~ (degree of
ethoxylation: rom 0 to 30, alkyl radical: C10 to Cl~).
Based on the amount of monomers to be polymerized,
10 usually from 0.5 to 3% by weight are u~ed.
The emul~ion polymerization is preferably carried
out in such a way that some of the dispersant~ (up to 10%
J by weight, ba~ed on the total amount thereof u~ed) and
some of the polymerization initiator (up to 20% by
15 weight, ba~ed on the required total amount) are initially
taken in the aqueou~ phase, the latter i~ heated to the
polymerization temperature and the monomers to be poly-
merized are then pre-emulaified in the aqueous pha~e
while maintaining the polymerization temperature, and,
20 simultaneou~ly with this, an aqueoua ~olution of the
remaining amount of polymerization initiator i8
continuou~ly added to the polymerization ~es~el (a~ a
~' rule in the cours~ of a few hours). After the end of the
addition o monomer~ and initiator, the polymerization is
usually continued for a further one to two hours while
maintaining the polymerization temperature. Usually, the
aqueou~ poly~er dieper~ion~ are produced with a solid~
content of from 10 to 30% by wsight. The conver~ion in
the polymerization i8, a~ a rule, at lea~t 99.8~ by
weight.
For example, the following methods can be used
for converting the aqueou~ polymer disper~ions into
, polymer powd~rs:
`` Spray drying of the aqueou~ polymer disper~io~ and
freeze-drying of the aqueou~ polymer disperaion.
Anothar po~ible method for the preparation of
the novel polymer powders comprioe~ polymerization of the
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correRponding monomers by the free radical suspension
polymerization method and sub~equent milling of the
au~pension polymer.
Spray drying of the aqueous polymer di~persion
proves particularly advantageou3, and conventional
anticaking agentR and ~pray a~istants may be pre~ent.
However, it is particularly advantageous that the novel
aqueous polymer disperuion~ are obtainable by the method
of EP-A 262 326 or EP-A 332 067 even in the absence of
spray assistantR, a~ polymers redispersible in an alka-
line aqueous medium. The novel polymers can of couree
contain, as polymerized units, monomsrs having acidic
functions (for example the monomers b) in neutralized
form ~for example with alkali metal hydroxide or ammonia
or amines). The neutralization can be effected, for
example, immediately before spray drying. Acidic mono-
mers b and c can, however, al~o be used in the neutral-
ized $orm for the polymerization.
It is particularly important that the novel
polymer powder~ to be produced by the abovementioned
preparation proces~ are redispersible in an alkaline
aqueous medium.
Since the usual commercial form of mineral
building materials having binding properties is the dry
- 25 mixture thereof, which traditionally comprise~ the
mineral binder and the additives, the novel powder form
is of particular importance and permit~ the novel modifi-
cation in the form of a commercial dry mixture which i8
immediately ready for u~e after mixing with water.
Xowever, the u~e form of the polymer-modified mineral
building materials having binding propertiea can of
course aleo be obtained by adding the novel polymer~
directly as aqueous polymer dispsrsion~ (thi~ may be both
the aqueous starting polymer di~persion and the agueous
di~persion of redi~persed polymer powder).
The novel polymer powder~ are particularly
~uitable a~ additive~ for aemsnt-containing minsral
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building materialA having binding properties. The
mineral binder on which ~aid building materialA are baAed
preferably comprises at least 50%, based on its weight,
of cement. The novel effect is particularly advan-
tageously displayed when mineral binders compri~ingfrom 70 to 100% by weight of cement and
from 0 to 30% by weight of gypsum
are used. The u3e, according to the invention, in
mineral building materials having binding properties and
containing exclusively cement as the mineral binder
proves very particularly advantageou~. The effect
according to the invention is sub~tantially dependent on
the type of cement. Depending on reguirement~, it is
possible to use, for example, blast furnace cement,
bituminou~ cement, Portland cament, hydrophobic Portland
cement, fast-setting cement, expanding cement or high-
alumina cement, the u~e of Portland cement proving
particularly advantageou~.
The novel polymer powders are particularly
suitabl~ a~ additives for mortar~ for carrying out
repairs. Their dry composition i8, a~ a rule, a~
follows:
from 20 to 60% by weight of mineral binder (preferably
exclu~ively cement),
from 1 to 20 (preferably from 2 to 10) % by weight, based
on the amount of the mineral binder, of novel polymer and
from 0 to 5% by weight of co~ventional assi~tanta (for
example antifoams), the remaining amount comprising
sand, usually having a particle ~ize of from 0.05 to
3 mm.
The use for~ i~ obtainable tharefrom by adding
water until the desired consistency is obtained. The
latter u~ually corre~pond~ to the water/mineral binder
(cement) weight ratio of from 0.3 to 0.6.
At the visco~ity suitable for processing, mortar~
for carrying out repairs which have been mixzd in thi3
way prove to be stable and, after setting, exhibit high
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adhesive, flexural and compres~ive strength.
EXAMPLES
1. Preparation of aqueous disper~ions Da to De
Da: A mixture consisting of
220 g of water,
OO5 g of a 28% strength by weight aqueous solution
of the ~odium salt of a mixture of ~ulfuric half-
e~ters of ethoxylated Cl,/C~4-fatty alcohols (having
a degree of ethoxylation of 2.8) = emulsifier
solution i and
20 g of feed I
was heated to 85C and, beginning at the Qame time
and while maintaining the 85C, the remaining amount
of feed I and Rimultaneou~ly feed II were added
continuously in the cour~e of 2 hours. Stirring was
then continued for a further hour at 85C.
Feed 1: 3 g of Yodium peroxydisulfate in
100 g of water;
Feed 2: 240 g of methyl methacrylate,
60 g of methacrylic acid,
15.6 g of amulsifier solution i and
391 g of water.
The R value of the reeulting emulsion polymer wa~
66.
- 25 Db: As for Da, but feed II contained an additional 2.4 g
of mercaptoethanol (molecular weight regulator).
The R value of the ro~ulting emulsion polymer was
35.
Dc: AE for Da, but the monomer compo~ition was 70% by
weight of methyl msthacrylate and 30% by weight of
methacrylic acid. The ~ value of the resulting
emulsion polymer was 62.
Dd: As for Da, but the monomer composition was 95% by
welght of metffll methacrylate and 5% by weight of
methacrylic acid. The R value of the re~ulting
e~ul~ion polymer wa~ 580
De: As for Da, but the monomer composition was
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50% by weight of n-butyl acrylate,
30% by weight of methyl methacrylate and
20% by weight of methacrylic acid.
The R value of the re~ulting emulsion polymer was
63.
2. Preparation of a polymer powder Pa
The aqueous polymer ~tarting di~per~ion Da was
spray-dried in a conventional manner by the ~pray-drying
method (inlet temperature: 130C, outlet temperature:
60C) in the absence of anticaking agents or spray
assi~tant~ to give a finely divided polymer powder.
3. Testing the performance characteristics of cement
mortar~ modified with the polymer di~per~ions Da to
De and with the polymer powder Pa
40 g of Portland cement PZ 35 were dry-blended
with 60 g of atandard ~and (DIN 1164 Part 7) and then
stirred with use of water and the varioua polymer disper-
sion~ ae tha poly~er powder at a polymer/cement weight
ratio of 0.1, ~o-that ~tirred mortar~ having a standard
~tability re~ulted.
The mortar~ were then introduced into a pri~matic
mold and compacted by ~ibration. The mortar pri~m~ were
then ~tored in the mold for 28 dayn at 23C and 95%
relative humidity. Thereaftar, the pri~m~ were remoYed
from the mold and their flexural ten~le ~trength and
compres~ive ~trength were te~ted. The re~ults are shown
in the Table below. A polymer-free mortar formulation
~uitable for proces~ing and havlng the same stability
could not be prepared, and the Table thereforQ contain~
no values for poly~mer-free mortar formulation~.
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. TABLE
; Polymer system Flexural tensile Co~pressive
u~ed strength ~trength
(N/mm2) (N/mm2)
Da 15.55 57.6
Pa 15.95 60.4
: Db 3.78 20.1
Dc 4.49 29.4
Dd 7.70 42.0
De 6.81 41.5
The novel ~ystema Da and Pa have unexpected
advantages over the comparativ- syatem~.
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