Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-02-16
2001-02-13
Henderson, Christopher (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S287000
Reexamination Certificate
active
06187887
ABSTRACT:
SPECIFICATION
This invention relates to water-soluble and water-swellable copolymers containing sulfonic groups, methods of preparing them, and the use of these polymers in aqueous building materials based on hydraulic binders such as cement, lime, gypsum, anhydrite etc., and in water-based painting and coating systems.
As a rule, water-soluble, non-ionic polysaccharide derivatives, especially cellulose and starch derivatives, are used in aqueous building material mixes in order to prevent or at least delay the undesired evaporation of water required for hydration and processing, or the draining off of the water into the substrate.
Being able to regulate the water content in paint systems, plasters, adhesive mortars, trowelling compounds and joint fillers, as well as in shotcrete for tunnel construction and in underwater concretes, with these additives has far-reaching practical consequences. The additives have a considerable influence on the properties of the building material while it is in workable condition, and also on its properties when it has set and/or dried. By way of improving water retention capacity, these modifiers also influence consistency (plasticity), the open time, smoothing property, segregation, tackiness, adhesion (to the substrate and to the tool), non-sag property and slip resistance, tensile bond and compressive strength, and also shrinkage.
The most common water retention agents, according to Ullmann's Enzyklopädie der Technischen Chemie (4th edition, vol. 9, pages 208-210, publishing house Chemie Weinheim), are synthetic, non-ionic cellulose and starch derivatives such as methyl cellulose (MC), hydroxyethyl cellulose (HEC) and hydroxyethylmethyl cellulose (HEMC). However, the prior art also decribes the use of microbially produced polysaccharides such as Welan gum, and of naturally occurring polysaccharides (hydrocolloids) that are isolated by extraction, such as alginates, xanthanes, carageenanes, galactomannanes etc., to regulate water content and the rheology of aqueous building materials and paint systems.
The DE-OS 43 35 437 describes the preparation of alkyl celluloses, eg, methyl cellulose from sodium cellulose and methyl chloride.
The EP-A 292 242 discloses the synthesis of hydroxypropylmethyl cellulose from cotton linters, methyl chloride and propylene oxide. To prepare the HEMC derivatives described in the DE-OS 33 16 124, use is made of ethylene oxide instead of propylene oxide.
The disadvantage of these products is the use of raw materials such as ethylene oxide, propylene oxide and methyl chloride in the production process, which are known to pose a physiological risk.
The use of non-ionic cellulose derivatives in the building materials and paints sectors is described in a number of publications, eg, in the DE-OS 39 34 870. Such products exhibit low thermal flocculation points, and as a result water retention decreases drastically attemperatures above 30° C. An additional disadvantage is that the rheological properties of these products are unsatisfactory in paint systems, because pigments are not dispersed properly due to the additives'lacking the necessary adsorptive force. These problems can be solved by using cellulose ethers which contain ionic groups.
The U.S. Pat. No. 5,372,642, for example, describes methylhydroxyalkyl carboxymethyl celluloses which, used in lime- and cement-based mixes, do not cause a reduction in water retention when the application temperature is raised from 20 to 40° C. However, a general incompatibility with multivalent cations such as Ca
2+
and Al
3+
, which would lead to flocculation and render these products ineffective, cannot be altogether excluded.
Sulfo-alkylated cellulose derivatives are described, among other publications, in the EP-A 0 554 749. Compared to carboxymethylated products, they exhibit excellent compatibility with multivalent cations, but when used in adhesive mortars or in plasters they delay setting. An additional disadvantage of such products is the inadequate sag or slip resistance in adhesive mortars, especially where heavy tiles are used.
The sag or slip resistance can be increased, as described in the U.S. Pat. No. 4,021,257, by modifiying or formulating cellulose ethers with polyacrylamide. The disadvantage here, however, is that under alkaline conditions polyacrylamide releases ammonia, making interior applications appear problematic.
The object of this invention was thus to develop water-soluble or water-swellable copolymers, with which the aforementioned disadvantages of the prior art are at least partially overcome, and which, in particular, are effective at comparatively high temperatures, which can be readily prepared by way of environmentally sound methods, and which, in addition, confer excellent applicational properties on building material mixes and paint systems, both when they are in workable condition and after they have set and/or dried.
This object was established with the copolymers according to claim
1
. Surprisingly, it was found that even when used in small quantities, copolymers containing sulfonic groups serve as very effective and highly compatible water retention agents in building material mixes and paint systems, and have properties which are superior to those of products currently in use.
The copolymers described in this invention contain at least four structural components a), b), c) and d). The first structural component is a substituted acrylic or meithacrylic derivative which contains a sulfonic group and has the formula l:
where R
1
=hydrogen or methyl, R
2
, R
3
and R
4
=hydrogen, an aliphatic hydrocarbon radical with 1 to 6 C atoms, an aryl radical with 6 to 14 C atoms, which may be substituted with C
1
-C
6
alkyl groups, eg, a phenyl radical which may be substituted with methyl groups, and M=hydrogen, a mono- or bivalent metal cation, ammonium or an organic amino radical, and a=½ or 1. As mono- or bivalent metal cation, use is made preferably of sodium, potassium, calcium and/or magnesium ions. As organic amino radicals, use is made preferably of substituted ammonium groups, which are derived from primary, secondary or tertiary C
1
-C
20
alkylamines, C
1
-C
20
alkanolamines, C
5
-C
8
cycloalkylamines and C
6
-C
14
arylamines. Examples of such amines are methylamine, dimethylamine, trimethylamine, ethanolamine, diethanolamine, triethanolamine, cyclohexylamine, dicyclohexylamine, phenylamine and diphenylamine in the protonated ammonium form.
The structural component a) is derived from monomers such as 2-acrylamido-2-methylpropane sulfonic acid, 2-methacrylamido-2-methylpropane sulfonic acid, 2-acrylamidobutane sulfonic acid, 3-acrylamido-3-methylbutane sulfonic acid, and 2-acrylamido-2,4,4-trimethylpentane sulfonic acid. Special preference is given to 2-acrylamido-2-methylpropane sulfonic acid.
The second structural component b) has the formula IIa and/or IIb:
where R
1
has the meaning already given. R
5
and R
6
stand, independently of one another, for hydrogen, an aliphatic hydrocarbon radical with 1 to 20 C atoms, an alicyclic hydrocarbon radical with 5 to 8 C atoms, or an aryl radical with 6 to 14 C atoms. These radicals may contain one or more substituents, such as hydroxyl, carboxyl and/or sulfonic groups.
In formula
11
b
, Q stands for hydrogen or —CHR
5
R
7
. Where Q≠H in structure IIb, R
5
and R
6
can also stand together for a —CH
2
—(CH
2
)
y
-methylene group in which y=1 to 4 and which, in combination with the rest of formula IIb, can form a five-to eight-membered heterocyclic ring.
R
7
may be a hydrogen atom, a C
1
, to C
4
alkyl radical, a carboxylic acid group or a carboxylate group —COOM
a
, where M and a have the meanings already given.
As monomers which form structure IIa, preference is given to the following compounds: acrylamide, methacrylamide, N-methylacrylamide, N,N-dimethyl acrylamide, N-ethyl acrylamide, N-cyclohexyl acrylamide, N-benzyl acrylamide, N-methylol acrylamide, N-tertiary butyl acrylamide etc. Examples of monomers on which structur
Albrecht Gerhard
Huber Christian
Kern Alfred
Schuhbeck Manfred
Weichmann Josef
Fulbright & Jaworksi LLP
Henderson Christopher
SKW Bauchemie GmbH
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