U.S. patent application number 11/388042 was filed with the patent office on 2007-09-06 for additive building material mixtures containing ionically swollen microparticles.
This patent application is currently assigned to ROEHM GMBH & CO. KG. Invention is credited to Holger Kautz, Gerd Lohden, Jan Hendrik Schattka.
Application Number | 20070204543 11/388042 |
Document ID | / |
Family ID | 38068792 |
Filed Date | 2007-09-06 |
United States Patent
Application |
20070204543 |
Kind Code |
A1 |
Schattka; Jan Hendrik ; et
al. |
September 6, 2007 |
Additive building material mixtures containing ionically swollen
microparticles
Abstract
The present invention relates to the use of polymeric
microparticles in hydraulically setting building material mixtures
for the purpose of enhancing their frost resistance and cyclical
freeze/thaw durability.
Inventors: |
Schattka; Jan Hendrik;
(Hanau, DE) ; Kautz; Holger; (Hanau, DE) ;
Lohden; Gerd; (Hanau, DE) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
ROEHM GMBH & CO. KG
Darmstadt
DE
|
Family ID: |
38068792 |
Appl. No.: |
11/388042 |
Filed: |
March 24, 2006 |
Current U.S.
Class: |
52/309.17 ;
106/677; 428/312.4; 428/327; 428/408; 52/309.4; 521/55; 521/83;
524/5; 524/7; 524/8 |
Current CPC
Class: |
C04B 24/2664 20130101;
C04B 2111/29 20130101; C04B 28/02 20130101; C04B 24/2641 20130101;
C04B 16/085 20130101; C04B 2103/0049 20130101; C04B 28/02 20130101;
C04B 16/085 20130101; C04B 2103/0058 20130101; Y10T 428/254
20150115; C04B 28/02 20130101; Y10T 428/249968 20150401; C04B
24/2641 20130101; Y10T 428/30 20150115; C04B 24/2641 20130101; C04B
24/2641 20130101; C04B 20/008 20130101; C04B 20/008 20130101; C04B
20/1029 20130101; C04B 20/1029 20130101 |
Class at
Publication: |
52/309.17 ;
524/5; 524/7; 524/8; 106/677; 428/312.4; 428/327; 428/408;
52/309.4; 521/55; 521/83 |
International
Class: |
E04C 1/00 20060101
E04C001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 1, 2006 |
DE |
10 2006 009 823.4 |
Claims
1.1. Use of polymeric microparticles, containing a void, in
hydraulically setting building material mixtures, characterized in
that the core of these particles is swollen by means of ionic
bases.
2.2. Use of polymeric microparticles, containing a void, in
hydraulically setting building material mixtures, according to
claim 1, characterized in that the base used for swelling is
selected from the group of sodium hydroxide, potassium hydroxide,
barium hydroxide or a mixture thereof.
3. Use of polymeric microparticles, containing a void, according to
claim 1, characterized in that the outer shell may contain
acid-containing monomers and/or hydrophilic, nonionic monomers.
4. Use of polymeric microparticles, containing a void, according to
claim 3, characterized in that the outer shell contains 0 to 15% by
weight, based on the total monomer mixture of the shell, of one or
more monomers containing acid groups and/or 0 to 25% by weight,
based on the total monomer mixture of the shell, of one or more
hydroxyl-, amino-, amido- and/or cyano-containing monomers.
5. Use of polymeric microparticles, containing a void, according to
claim 3, characterized in that the outer shell contains 0.2% to 8%
by weight of one or more acid-containing monomers and/or 0.5% to
15% by weight of hydrophilic, nonionic monomers.
6. Use of polymeric microparticles, containing a void, according to
claim 1, characterized in that the microparticles are composed of
polymer particles which comprise a polymer core (A), which is
swollen by means of an ionic aqueous base and contains one or more
unsaturated carboxylic acid (derivative) monomers, and a polymer
envelope (B), which is composed predominantly of nonionic,
ethylenically unsaturated monomers.
7. Use of polymeric microparticles, containing a void, according to
claim 1, characterized in that the outer shell contains nonionic,
ethylenically unsaturated monomers selected from styrene,
butadiene, vinyltoluene, ethylene, vinyl acetate, vinyl chloride,
vinylidene chloride, acrylonitrile, acrylamide, methacrylamide
and/or C1-C12 alkyl esters of acrylic or methacrylic acid.
8. Use of polymeric microparticles, containing a void, according to
claim 5, characterized in that the unsaturated carboxylic acid
(derivative) monomers of the core A are selected from the group of
acrylic acid, methacrylic acid, maleic acid, maleic anhydride,
fumaric acid, itaconic acid and crotonic acid.
9. Use of polymeric microparticles, containing a void, according to
claim 1, characterized in that the microparticles have a polymer
content of 2% to 98% by weight.
8. Use of polymeric microparticles, containing a void, according to
claim 1, characterized in that the microparticles have an average
particle size of 100 to 5000 nm.
9. Use of polymeric microparticles, containing a void, according to
claim 8, characterized in that the microparticles have an average
particle size of 200 to 2000 nm.
10. Use of polymeric microparticles, containing a void, according
to claim 9, characterized in that the microparticles have an
average particle size of 250 to 1000 nm.
11. Use of polymeric microparticles, containing a void, according
to claim 1, characterized in that the microparticles are used in an
amount of 0.01% to 5% by volume, based on the building material
mixture.
12. Use of polymeric microparticles, containing a void, according
to claim 11, characterized in that the microparticles are used in
an amount of 0.1% to 0.5% by volume, based on the building material
mixture.
13. Use of polymeric microparticles, containing a void, according
to claim 1, characterized in that the building material mixtures
are composed of a binder selected from the group of cement, lime,
gypsum and anhydrite.
14. Use of polymeric microparticles, containing a void, according
to claim 1, characterized in that the building material mixtures
are concrete or mortar.
Description
[0001] The present invention relates to the use of polymeric
microparticles in hydraulically setting building material mixtures
for the purpose of enhancing their frost resistance and cyclical
freeze/thaw durability.
[0002] Decisive factors affecting the resistance of concrete to
frost and to cyclical freeze/thaw under simultaneous exposure to
thawing agents are the imperviousness of its microstructure, a
certain strength of the matrix, and the presence of a certain pore
microstructure. The microstructure of a cement-bound concrete is
traversed by capillary pores (radius: 2 .mu.m-2 mm) and gel pores
(radius: 2-50 nm). Water present in these pores differs in its
state as a function of the pore diameter. Whereas water in the
capillary pores retains its usual properties, that in the gel pores
is classified as condensed water (mesopores: 50 nm) and
adsorptively bound surface water (micropores: 2 nm), the freezing
points of which may for example be well below -50.degree. C. [M. J.
Setzer, Interaction of water with hardened cement paste, Ceramic
Transactions 16 (1991) 415-39]. Consequently, even when the
concrete is cooled to low temperatures, some of the water in the
pores remains unfrozen (metastable water). For a given temperature,
however, the vapor pressure over ice is lower than that over water.
Since ice and metastable water are present alongside one another
simultaneously, a vapor-pressure gradient develops which leads to
diffusion of the still-liquid water to the ice and to the formation
of ice from said water, resulting in removal of water from the
smaller pores or accumulation of ice in the larger pores. This
redistribution of water as a result of cooling takes place in every
porous system and is critically dependent on the type of pore
distribution.
[0003] The artificial introduction of microfine air pores in the
concrete hence gives rise primarily to what are called expansion
spaces for expanding ice and ice-water. Within these pores,
freezing water can expand or internal pressure and stresses of ice
and ice-water can be absorbed without formation of microcracks and
hence without frost damage to the concrete. The fundamental way in
which such air-pore systems act has been described, in connection
with the mechanism of frost damage to concrete, in a large number
of reviews [Schulson, Erland M. (1998) Ice damage to concrete.
CRREL Special Report 98-6; S. Chatterji, Freezing of air-entrained
cement-based materials and specific actions of air-entraining
agents, Cement & Concrete Composites 25 (2003) 759-65; G. W.
Scherer, J. Chen & J. Valenza, Methods for protecting concrete
from freeze damage, U.S. Pat. No. 6,485,560 B1 (2002); M. Pigeon,
B. Zuber & J. Marchand, Freeze/thaw resistance, Advanced
Concrete Technology 2 (2003) 11/1-11/17; B. Erlin & B. Mather,
A new process by which cyclic freezing can damage concrete-the
Erlin/Mather effect, Cement & Concrete Research 35 (2005)
1407-11].
[0004] A precondition for improved resistance of the concrete on
exposure to the freezing and thawing cycle is that the distance of
each point in the hardened cement from the next artificial air pore
does not exceed a defined value. This distance is also referred to
as the "Powers spacing factor" [T. C. Powers, The air requirement
of frost-resistant concrete, Proceedings of the Highway Research
Board 29 (1949) 184-202]. Laboratory tests have shown that
exceeding the critical "Power spacing factor" of 500 .mu.m leads to
damage to the concrete in the freezing and thawing cycle. In order
to achieve this with a limited air-pore content; the diameter of
the artificially introduced air pores must therefore be less than
200-300 .mu.m [K. Snyder, K. Natesaiyer & K. Hover, The
stereological and statistical properties of entrained air voids in
concrete: A mathematical basis for air void systems
characterization, Materials Science of Concrete VI (2001)
129-214].
[0005] The formation of an artificial air-pore system depends
critically on the composition and the conformity of the aggregates,
the type and amount of the cement, the consistency of the concrete,
the mixer used, the mixing time, and the temperature, but also on
the nature and amount of the agent that forms the air pores, the
air entrainer. Although these influencing factors can be controlled
if account is taken of appropriate production rules, there may
nevertheless be a multiplicity of unwanted adverse effects,
resulting ultimately in the concrete's air content being above or
below the desired level and hence adversely affecting the strength
or the frost resistance of the concrete.
[0006] Artificial air pores of this kind cannot be metered
directly; instead, the air entrained by mixing is stabilized by the
addition of the aforementioned air entrainers [L. Du & K. J.
Folliard, Mechanism of air entrainment in concrete, Cement &
Concrete Research 35 (2005) 1463-71]. Conventional air entrainers
are mostly surfactant-like in structure and break up the air
introduced by mixing into small air bubbles having a diameter as
far as possible of less than 300 .mu.m, and stabilize them in the
wet concrete microstructure. A distinction is made here between two
types.
[0007] One type--for example sodium oleate, the sodium salt of
abietic acid or Vinsol resin, an extract from pine roots--reacts
with the calcium hydroxide of the pore solution in the cement paste
and is precipitated as insoluble calcium salt. These hydrophobic
salts reduce the surface tension of the water and collect at the
interface between cement particle, air and water. They stabilize
the microbubbles and are therefore encountered at the surfaces of
these air pores in the concrete as it hardens. The other type--for
example sodium lauryl sulfate (SDS) or sodium
dodecyl-phenylsulfonate--reacts with calcium hydroxide to form
calcium salts which, in contrast, are soluble, but which exhibit an
abnormal solution behavior. Below a certain critical temperature
the solubility of these surfactants is very low, while above this
temperature their solubility is very good. As a result of
preferential accumulation at the air/water boundary they likewise
reduce the surface tension, thus stabilize the microbubbles, and
are preferably encountered at the surfaces of these air pores in
the hardened concrete.
[0008] The use of these prior-art air entrainers is accompanied by
a host of problems [L. Du & K. J. Folliard, Mechanism of air
entrainment in concrete, Cement & Concrete Research 35 (2005)
1463-71]. For example, prolonged mixing times, different mixer
speeds and altered metering sequences in the case of ready-mix
concretes result in the expulsion of the stabilized air (in the air
pores).
[0009] The transporting of concretes with extended transport times,
poor temperature control and different pumping and conveying
equipment, and also the introduction of these concretes in
conjunction with altered subsequent processing, jerking and
temperature conditions, can produce a significant change in an
air-pore content set beforehand. In the worst case this may mean
that a concrete no longer complies with the required limiting
values of a certain exposure class and has therefore become
unusable [EN 206-1 (2000), Concrete--Part 1: Specification,
performance, production and conformity].
[0010] The amount of fine substances in the concrete (e.g. cement
with different alkali content, additions such as flyash, silica
dust or color additions) likewise adversely affects air
entrainment. There also may be interactions with flow improvers
that have a defoaming action and hence expel air pores, but may
also introduce them in an uncontrolled manner.
[0011] All of these influences which complicate the production of
frost-resistant concrete can be avoided if, instead of the required
air-pore system being generated by means of abovementioned air
entrainers with surfactant-like structure, the air content is
brought about by the admixing or solid metering of polymeric
microparticles (hollow microspheres) [H. Sommer, A new method of
making concrete resistant to frost and de-icing salts, Betonwerk
& Fertigteiltechnik 9 (1978) 476-84]. Since the microparticles
generally have particle sizes of less than 100 .mu.m, they can also
be distributed more finely and uniformly in the concrete
microstructure than can artificially introduced air pores.
Consequently, even small amounts are sufficient for sufficient
resistance of the concrete to the freezing and thawing cycle.
[0012] The use of polymeric microparticles of this kind for
improving the frost resistance and cyclical freeze/thaw durability
of concrete is already known from the prior art [cf. DE 2229094 A1,
U.S. Pat. No. 4,057,526 B1, U.S. Pat. No. 4,082,562 B1, DE 3026719
A1]. The microparticles described therein are notable in particular
for the fact that they possess a void which is smaller than 200
.mu.m (diameter), and this hollow core consists of air (or a
gaseous substance). This likewise includes porous microparticles on
the 100 .mu.m scale which may possess a multiplicity of relatively
small voids and/or pores.
[0013] With the use of hollow microparticles for artificial air
entrainment in concrete, two factors proved to be disadvantageous
for the implementation of this technology on the market. On the one
hand the production costs of hollow microspheres in accordance with
the prior art are too high, and on the other hand relatively high
added quantities are required in order to achieve satisfactory
resistance of the concrete to freezing and thawing cycles.
[0014] The object on which the present invention is based was
therefore that of providing a means of improving the frost
resistance and cyclical freeze/thaw durability for hydraulically
setting building material mixtures that develops its full activity
even in relatively low added quantities. A further object was not,
or not substantially, to impair the mechanical strength of the
building material mixture as a result of said means.
[0015] Moreover, the effect of this means ought not to be
influenced by shorter or longer mixing and processing times, in
order to allow harmonized metering of the means.
[0016] This object and also further objects not explicitly
identified yet readily derivable or comprehensible from the
circumstances discussed at the introduction herein are achieved by
core/shell microparticles which possess a base-swellable core which
has been swollen by means of ionic bases (such as sodium hydroxide,
potassium hydroxide or barium hydroxide).
[0017] Such particles are produced preferably by emulsion
polymerization.
[0018] It has been found that these particles of the invention are
suitable even in very low added quantities for producing effective
resistance towards frost and freeze/thaw cycling.
[0019] These microparticles, containing a void, are added to the
building material mixture, wherein they remain for a shorter or
longer time prior to processing of the mixture. It has been found
that the longer the time the microparticles remain in the building
material mixture before the mixture cures, the higher the added
quantity of microparticles must be in order to achieve the same
level of effective resistance towards frost and freeze/thaw
cycling.
[0020] Surprisingly it has been found that in the case of
microparticles swollen with ionic bases in accordance with the
invention there is no significant deactivation in binder activity
over time.
[0021] According to one preferred embodiment the microparticles
used are composed of polymer particles which possess a core (A) and
at least one shell (B), the core/shell polymer particles having
been swollen by means of an ionic base.
[0022] The preparation of these polymeric microparticles by
emulsion polymerization and also their swelling by means of bases
such as alkali or alkali metal hydroxides and also ammonia or an
amine, for example, are described in European patents EP 22 633 B1,
EP 735 29 B1 and EP 188 325 B1.
[0023] The core (A) of the particle contains one or more
ethylenically unsaturated carboxylic acid (derivative) monomers
which permit swelling of the core; these monomers are preferably
selected from the group of acrylic acid, methacrylic acid, maleic
acid, maleic anhydride, fumaric acid, itaconic acid and crotonic
acid and mixtures thereof. Acrylic acid and methacrylic acid are
particularly preferred.
[0024] The shell (B) is composed predominantly of nonionic,
ethylenically unsaturated monomers. As such monomers use is made
preferably of styrene, butadiene, vinyltoluene, ethylene, vinyl
acetate, vinyl chloride, vinylidene chloride, acrylo-nitrile,
acrylamide, methacrylamide, C1-C12 alkyl esters of (meth)acrylic
acid or mixtures thereof. Preference is given to using styrene
and/or n-hexyl(meth)acrylate and/or n-butyl(meth)acrylate and/or
isobutyl(meth)acrylate and/or propyl(meth)acrylate and/or ethyl
methacrylate and/or ethylhexyl(meth)acrylate.
[0025] The (meth)acrylate notation here denotes both methacrylate,
such as methyl methacrylate, ethyl methacrylate, etc., and
acrylate, such as methyl acrylate, ethyl acrylate, etc., and also
mixtures of both.
[0026] The polymer envelope or shell (B) may further comprise
monomers, which enhances the permeability of the shell for the
ionic bases. These may be, on the one hand, acid-containing
monomers such as acrylic acid, methacrylic acid, maleic acid,
maleic anhydride, fumaric acid, monoesters of fumaric acid,
itaconic acid, crotonic acid, maleic acid, monoesters of maleic
acid, acrylamidoglycolic acid, methacrylamidobenzoic acid, cinnamic
acid, vinylacetic acid, trichloroacrylic acid,
10-hydroxy-2-decenoic acid, 4-methacryloyloxyethyl-trimethylic
acid, styrenecarboxylic acid,
2-(isopropenylcarbonyloxy)ethane-sulfonic acid,
2-(vinylcarbonyloxy)ethanesulfonic acid,
2-(isopropenylcarbonyl-oxy)propylsulfonic acid,
2-(vinylcarbonyloxy)propylsulfonic acid,
2-acrylamido-2-methylpropanesulfonic acid,
acrylamidododecanesulfonic acid, 2-propene-1-sulfonic acid,
methallylsulfonic acid, styrenesulfonic acid, styrenedisulfonic
acid, methacrylamidoethanephosphonic acid, vinylphosphonic acid,
and mixtures thereof.
[0027] These acid-containing monomers are added to the polymer
envelope B preferably in amounts of 0 to 15% by weight (based on
the total monomer mixture of the shell), particular preference
being given to amounts of 0.2% to 8% by weight; the most preferred
are amounts of 0.5% to 4% by weight.
[0028] On the other hand the permeability can also be enhanced by
means of hydrophilic, nonionic monomers, of which mention may be
made here, as examples, of acrylonitrile, (meth)acrylamide,
cyanomethyl methacrylate, N-vinylamides, N-vinylformamides,
N-vinylacetamides, N-vinyl-N-methyl-acetamides
N-vinyl-N-methylformamides, N-methylol(meth)acrylamide,
vinylpyrrolidone, N,N-dimethylpropylacrylamide, dimethylacrylamide,
and also other hydroxyl-, amino-, amido- and/or cyano-containing
monomers and/or mixtures thereof.
[0029] These hydrophilic monomers are added to the polymer envelope
B preferably in amounts of 0 to 25% by weight (based on the total
monomer mixture of the shell), particular preference being given to
amounts of 0.5% to 15% by weight; the most preferred are amounts of
1% to 8% by weight.
[0030] Hydrophilic and acid-containing monomers together make up
preferably not more than 25% by weight in the composition of the
polymer envelope (B) (based on the total monomer mixture of the
shell); particular preference is given to amounts between 0.2% and
18% by weight, the most preference to amounts between 0.5% and 10%
by weight.
[0031] In a further preferred embodiment the monomer composition of
the core and of the shell does not change with a sharp
discontinuity, as is the case for a core/shell particle of ideal
construction, but instead changes gradually in two or more steps or
in the form of a gradient.
[0032] Where the microparticles are constructed as multishell
particles, the composition of the shells located between core and
outer shell is often oriented to the shells adjacent on either
side, which means that the amount of a monomer Mx in general
between the amount M(x+1) in the next-outer shell (which may also
be the outer shell) and the amount M(x-1) in the next-inner shell
(or the core). However, this is not mandatory, and in further
particular embodiments the compositions of such intermediate shells
may also be freely selected, provided it does not stand in the way
of the preparation and the ordered structure of the particle.
[0033] Depending on the diameter and the water content, the polymer
content of the microparticles employed may be 2% to 98% by weight
(weight of polymer relative to the total weight of the water-filled
particle).
[0034] Preference is given to polymer contents of 5% to 60% by
weight, particular preference to polymer contents of 10% to 40% by
weight.
[0035] The microparticles of the invention can be prepared
preferably by emulsion polymerization and preferably have an
average particle size of 100 to 5000 nm; particular preference is
given to an average particle size of 200 to 2000 nm. The most
preferred are average particle sizes of 250 to 1000 nm.
[0036] The average particle size is determined by, for example,
counting a statistically significant amount of particles by means
of transmission electron micrographs.
[0037] In the case of the preparation by emulsion polymerization
the microparticles are obtained in the form of an aqueous
dispersion. Correspondingly, the addition of the microparticles to
the building material mixture takes place preferably likewise in
this form.
[0038] Within the context of the present invention, however, it is
also readily possible to add the water-filled microparticles to the
building material mixture directly as a solid. For that purpose the
microparticles, for example, are coagulated and isolated from the
aqueous dispersion by typical methods (e.g. filtration,
centrifugation, sedimentation and decanting) and the particles are
subsequently dried.
[0039] Where addition as a solid is desired or necessary on
processing grounds, further preferred drying methods include spray
drying and freeze drying.
[0040] The water-filled microparticles are added to the building
material mixture in a preferred amount of 0.01% to 5% by volume, in
particular 0.1% to 0.5% by volume. The building material mixture,
in the form for example of concrete or mortar, may in this case
include the customary hydraulically setting binders, such as
cement, lime, gypsum or anhydrite, for example.
[0041] A substantial advantage through the use of the water-filled
microparticles is that only an extremely small amount of air is
introduced into the concrete. As a result, significantly improved
compressive strengths are achievable in the concrete. These are
about 25%-50% above the compressive strengths of concrete obtained
with conventional air entrainment. Hence it is possible to attain
strength classes which can otherwise be set only by means of a
substantially lower water/cement value (w/c value). Low w/c values,
however, in turn significantly restrict the processing properties
of the concrete in certain circumstances.
[0042] Moreover, higher compressive strengths may result in it
being possible to reduce the cement content of the concrete that is
needed for strength to develop, and hence a significant reduction
in the price per m.sup.3 of concrete.
* * * * *