Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1998-07-30
2001-04-03
Zitomer, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S240000, C526S270000, C526S304000, C526S310000, C526S318200, C526S262000
Reexamination Certificate
active
06211317
ABSTRACT:
This invention relates to copolymers based on unsaturated dicarboxylic acid derivatives and oxyalkylene glycol alkenyl ethers, methods of preparing them and use of these copolymers as additives for hydraulic binders, especially cement, to improve the properties of construction materials made therefrom, both during processing and in the hardened state.
It is known that additives in the form of dispersing agents are often mixed with aqueous slurries of powdery inorganic or organic substances such as clays, porcelain slips, silicate dust, chalk, soot, powdered stone, pigments, talcum, powdered plastics and hydraulic binders in order to improve their workability, ie, their kneadability, spreadability, sprayability, pumpability or flow characteristics. These additives, which generally contain ionic groups, are able to break up agglomerations of solids, to disperse the particles formed, and in this way to improve the workability, in particular that of highly concentrated suspensions. This effect is exploited selectively in the preparation of construction-material mixtures which contain hydraulic binders such as cement, lime, gypsum and anhydrite.
In order to obtain these construction materials based on the above-mentioned binders in a ready-to-use, workable state one normally requires a lot more mixing water than is necessary for the subsequent hydration and setting process. The air which is entrained due to the subsequent evaporation of this excess water signicantly impairs the mechanical strength and stability of the finished construction.
To reduce the amount of excess water for a given processing consistency and/or to improve the workability for a given water/binder ratio, use is made of additives which are generally referred to as water reducers or plasticizers. The best-known of these plasticizers are polycondensation products based on naphthalene or alkyl-naphthalene sulfonic acids (cf. EP-A 214 412) and sulfonated melamine formaldehyde resins (cf. DE-PS 16 71 017).
The disadvantage of these additives is that their excellent fluidizing effect only lasts for a short period of time, especially in the case of concrete construction work. The reduction in workability (slump loss) of concrete mixtures within a short period is especially problematical when, eg, due to long transport or hauling distances, a lot of time elapses between mixing and placing the concrete.
There is an additional problem when these plasticizers are used in mining or for interior applications (gypsum plasterboard drying, anhydrite flooring screeds, casting of prefabricated concrete constructions); in such cases, the toxic formaldehyde contained in the mixtures may be set free and can cause substantial pollution at the workplace. For this reason, endeavours were made to develop concrete plasticizers comprising monoesters of maleic acid and styrene, which do not contain any formaldehyde. Such plasticizers are described, eg, in the EP-A 306 449. The fluidity of concrete mixtures containing these additives can be maintained for a sufficiently long period of time; however, due to hydrolysis of the polymeric ester, the initial, very high dispersing effect of the plasticizer itself is very quickly lost if the aqueous formulation is stored.
This problem does not arise with the polymeric plasticizers described in the EP-A 610 699, which consist of copolymers with maleic acid monoester structures, maleic acid amide or imide structures, and vinyl monomers. These products have the disadvantage, however, that an undesirably high proportion of air is entrained, which reduces the strength and stability of the hardened building material. In order to obtain the optimal chain length required for the intended use of the copolymers, it is moreover essential to employ chain-transfer agents such as n- and tertiary dodecycl mercaptan or diisopropyl xanthogen disulfite. Use of these compounds for the preparation of the above-mentioned plasticizers, however, is associated with a very strong and unpleasant smell.
The problem of undesirably high air entrainment is overcome in the case of the copolymers described in the EP-A 736 553, which are based on oxyalkylene glycol alkenyl ethers and unsaturated dicarboxylic acid derivatives, by means of hydrophobic structural elements based on polydimethyl siloxane, (block) polymers containing polypropylene glycol, and/or esters of dicarboxylic acids. In addition, the use of unpleasantly-smelling chain-transfer agents is unnecessary. However, especially in applications where particularly dense and therefore very strong and very stable concrete containing as little water as possible is required, namely in the future-oriented and innovative field of high-performance concrete, polymers of this type, like those described in the EP-A 610 699, do not exhibit optimal properties.
The object of this invention was thus to provide new polymeric compounds which do not have the aforementioned disadvantages of the prior-art but which, at dosages as low as possible, maintain the workability of highly-concentrated construction material mixtures for a suitable period of time, without retarding the setting process and without causing excessive entrainment of air, and which do not necessitate the use of unpleasantly-smelling products during their preparation.
This object was established by means of copolymers as described in claim
1
. Surprisingly, it was found that the products of the invention, which are based on unsaturated dicarboxylic acid derivatives and oxyalkylene glycol alkenyl ethers, impart excellent processing characteristics to aqueous construction material mixtures, without impairing the properties of the construction material in its hardened state.
What was especially surprising was the fact that the copolymers of the invention also display an excellent plasticizing effect in concrete mixtures with extremely low proportions of water, and even when added in larger quantities do not retard setting.
The copolymers of the invention are made up of at least four structural units, a), b), c) and d).
The first structural unit a) is a dicarboxylic acid derivative with the formula Ia) and/or Ib),
where a, M and R
1
mean the following:
M stands, in each case independently, for hydrogen, a mono- or bivalent metal cation, an ammonium ion or an organic amine residue, such organic amine residues preferably being substituted ammonium groups derived from primary, secondary or tertiary C
1
to C
20
alkylamines, C
1
to C
20
alkanolamines, C
5
to C
8
cycloalkylamines and C
8
to C
14
arylamines. Examples of such amines are methylamine, dimethylamine, trimethylamine, ethanolamine, diethanolamine, triethanolamine, methyl diethanolamine, cyclohexylamine, dicyclohexylamine, phenylamine and diphenylamine in the protonated (ammonium) form.
a=½ or 1 depending on whether M is a mono- or bivalent cation.
R
1
can stand for O
a
M, but preferably stands for —O—(C
m
H
2m
O)
n
—R
2
, where R
2
can be H, an aliphatic hydrocarbon residue with 1 to 20 C atoms, a cycloaliphatic hydrocarbon residue with 5 to 8 carbon atoms or an aryl residue, which may be substituted, with 6 to 14 C atoms, and m can be 2 to 4 and n 1 to 200. The aliphatic hydrocarbons can be linear or branched, saturated or unsaturated. Preferred cycloalkyl residues are cyclopentyl and cyclohexyl residues, and preferred aryl residues are phenyl or naphthyl residues which may be substituted with C
1
-C
4
alkyl residues and, especially, with hydroxyl, carboxyl and/or sulfonic acid groups.
Instead of, or in addition to the dicarboxylic acid derivative represented by formula Ia, the structural unit Ia) (dicarboxylic acid derivative) can be present in cyclic form, as represented by formula Ib.
The second structural unit b) corresponds to formula II,
and derives from oxyalkylene glycol alkenyl ethers, in which m, n and R
2
have the aforementioned meanings. R
3
stands for hydrogen or an aliphatic hydrocarbon residue with 1 to 5 C atoms, which again may be linear or branched and also unsaturated. p can assume values between 0 and 3.
In the preferred
Albrecht Gerhard
Kern Alfred
Leitner Hubert
Weichmann Josef
Fulbright & Jaworski LLP
SWK Bauchemie GmbH
Zitomer Fred
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