Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-08-20
2003-09-09
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S828000, C524S556000, C524S566000, C524S492000, C524S523000, C524S458000, C525S227000, C525S221000, C525S229000, C526S318400, C526S318600, C264S333000
Reexamination Certificate
active
06617387
ABSTRACT:
The present invention relates to ammonia-free polymer dispersions, polymer powders and granules obtained from the polymer dispersions, as additives in building materials based on hydraulic binders.
Hydraulic binders are understood as meaning mineral substances which are processed together with water and, if required, additives and conventional assistants to give a material which is plastic in the moist state and which, when left alone in the air or under water, with or without the action of elevated temperatures, solidifies to a stone-like substance after a certain time. Examples of hydraulic binders are cement, gypsum, lime and clay.
The use of polymer dispersions or the polymer powders or granules obtainable therefrom for improving the properties of building materials based on hydraulic binder is known in principle. Polymer dispersions for use with hydraulic binders have, as a rule, a high content of polar and/or ionic auxiliary monomers such as (meth)acrylic acid and (meth)acrylamide and a high content of emulsifiers. These measures are intended to improve the stability of the dispersions in the presence of the hydraulic binders, since the high electrolyte content of the hydraulic binders leads to considerable destabilization of disperse systems.
In order to increase the mechanical strength of building materials based on hydraulic binders in the hardened state, polymer dispersions whose polymers have a high glass transition temperature (T
g
) are frequently used. Thus, EP-A-537 411 describes the use of polymer dispersions having a T
g
of >+30° C. as additives for cement. The addition is intended to improve the strength of cement-bonded materials and to increase the open time.
JP-59 146 963 likewise describes polymer dispersions having a high glass transition temperature for this application. These contain more than 90% of a hard monomer, for example styrene, methyl methacrylate, acrylonitrile or vinyl chloride, and only from 0.02 to 10% of a hydrophilic comonomer, such as acrylamide, sodium styrenesulfonate, hydroxyethyl methacrylate or sodium vinylsulfonate. The use of these dispersions as additives for cement leads to cement-containing building materials having higher water resistance and in some cases improved compressive strength.
Building materials based on hydraulic binders which contain such polymer dispersions are comparatively brittle and exhibit in particular poor low-temperature flexibility. This presumably is due to the fact that, owing to the high T
g
of the polymer, no film formation of the latex particles takes place in the building materials.
In order to reduce the brittleness and increase the low-temperature flexibility of hardened building materials based on hydraulic binders, polymer dispersions which contain polymers having a low T
g
are therefore used. Thus, AT-359 904 describes the use of polymer dispersions having a T
g
of from −70 to −8° C. as additives for cement-containing building materials. It is said that mortars which have good low-temperature flexibility after hardening are obtained as a result of adding from 3 to 35% by weight of such dispersions. However, the addition of these dispersions leads to building materials having low strength.
JP-63 055 143 and JP-64 5935 describe polymer dispersions which contain a polymer comprising from 55 to 90% by weight of a C
4
-C
8
-alkyl acrylate, from 5 to 40% by weight of acrylonitrile and/or styrene, from 1 to 10% by weight of acrylic and/or methacrylic acid and from 1 to 10% by weight of at least one 2-hydroxyethyl or 2-hydroxypropyl (meth)acrylate and/or (meth)acrylamide, which polymer is prepared by emulsion polymerization in the presence of a nonionic emulsifier. The use of these polymer dispersions leads to building materials having higher flexibility and less tendency to crack. However, more than 40% by weight of polymer dispersion have to be added. The building materials thus obtained have an unsatisfactorily high water absorption and often have an unpleasant odor. This is presumably due to gaseous ammonia which forms as a result of partial hydrolysis of the polymer.
JP-63 156 048 recommends the use of polymer dispersions which contain as polymerized units, from 2 to 10% by weight of unsaturated monomers having hydroxyl groups and from 30 to 98% by weight of alkyl acrylates without hydroxyl groups and which are essentially free of unsaturated carboxylic acids and carboxamides. The use of these dispersions in cement-containing materials leads to good adhesion and higher mechanical stability. The electrolyte stability of these polymer dispersions and hence their stability in cement-containing material is however insufficient. Moreover, the addition of these dispersions results in an unpleasant odor of the polymer-modified cement-containing material, which is presumably due to the liberation of the ammonia used for neutralizing the dispersions.
It is an object of the present invention to provide aqueous polymer dispersions which have high shear stability and electrolyte stability and, when added to building materials based on hydraulic binders, lead to improved mechanical properties of the building materials in the hardened state. In particular, the dispersions should lead to building materials which have good processibility and at the same time high flexibility, in particular at low temperatures, and strengths. The polymer should have a neutral odor in the presence of the hydraulic binders.
We have found that this object is achieved by aqueous, ammonia-free polymer dispersions which contain at least one copolymer which contains, as polymerized monomers,
a) from 40 to 80% by weight of at least one ester of acrylic acid with C
2
-C
12
-alkanols,
b) from 10 to 40% by weight of at least one vinylaromatic monomer and/or at least one ester of methacrylic acid with C
1
-C
4
-alkanols,
c) from 2 to 15% by weight of at least one monoester of a C
2
-C
10
-alkanediol with acrylic acid or methacrylic acid,
d) not more than 1.0% by weight of ethylenically unsaturated monomers which have at least one acid group, or salts thereof,
e) less than 5% by weight of ethylenically unsaturated nitrites and
f) less than 1% by weight of amides of &agr;,&bgr;-ethylenically unsaturated mono- and dicarboxylic acids.
The present invention accordingly relates to building materials based on hydraulic binders as an additive which contain at least one copolymer in the form of an ammonia-free aqueous polymer dispersion as defined above. The copolymer contained in the novel polymer dispersions acts as a film-forming component. In the context of this invention, building materials based on hydraulic binders are both the hydraulic binders themselves and building materials which contain at least 5, in particular 10, particularly preferably at least 25, % by weight of at least one hydraulic binder based on the total weight of hydraulic binders and additives. The use in building materials which contain cement as a binder is preferred.
The building materials based on hydraulic binders are generally converted into a processible form, mostly in the form of liquid or plastically deformable materials, by adding water (mixing water) and, if required, conventional mineral and/or nonmineral additives. These materials generally harden in the course of time when left to stand. Typical building materials based on hydraulic binders, which are processed in this manner, are cement, mortar, renders, tile adhesives, mineral sealing slurries, concrete and the like. These building materials differ essentially in the amount and type of the additives present and/or the water content during use in construction.
According to the invention, a polymer dispersion as described herein is added to the building materials based on hydraulic binders. The addition can be effected, for example, during conversion of the building materials into the processible form, for example by replacing at least a part of the mixing water with a polymer dispersion as described here. The novel use of the polymer dispersion can also be effected in the form of powd
Dreher Stefan
Pakusch Joachim
Reck Bernd
BASF - Aktiengesellschaft
Sastri Satya B
Wu David W.
LandOfFree
Ammonia-free polymer dispersions as additives in mineral... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ammonia-free polymer dispersions as additives in mineral..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ammonia-free polymer dispersions as additives in mineral... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3098135