Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-09-27
2004-08-17
Choi, Ling-Siu (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S271000, C526S333000, C526S318200, C526S279000
Reexamination Certificate
active
06777517
ABSTRACT:
The present invention relates to copolymers based on unsaturated monocarboxylic or dicarboxylic acid derivatives and oxyalkylene glycol alkenyl ethers, a process for preparing them and the use of these copolymers as additives for aqueous suspensions of inorganic or organic solids.
It is known that additives in the form of dispersants are often added to aqueous slurries of pulverulent inorganic or organic substances such as clays, porcelain slips, silicate flour, chalk, carbon black, ground rock, pigments, talc, polymer powders and hydraulic binders for improving their processability, i.e. kneadability, spreadability, sprayability, pumpability or flow. These additives, which generally contain ionic groups, are able to break up agglomerates of solids, disperse the particles formed and in this way improve the processability of, in particular, highly concentrated suspensions. This effect is also exploited in a targeted manner in the production of building material mixtures based on cement, lime and hydraulic binders based on calcium sulfate, optionally in a mixture with organic (e.g. bituminous) components and also for ceramic compositions, refractory compositions and oilfield chemicals.
To convert these building material mixtures based on the abovementioned binders into a ready-to-use, processable form, it is generally necessary to use significantly more make-up water than would be necessary for the subsequent hydration or curing process. The voids formed in the component as a result of later evaporation of the excess water leads to significantly impaired mechanical strengths and stabilities.
To reduce this excess water content at a given processing consistency and/or to improve the processability at a given water/binder ratio, use is made of additives which are generally referred to as water reduction agents or fluidizers. Known agents of this type are, in particular, polycondensation products based on naphthalenesulfonic or alkylnaphthalene-sulfonic acids (cf. EP-A-0 214 412) or melamine-formaldehyde resins containing sulfonic acid groups (cf. DE-C 16 71 017).
A disadvantage of these additives is the fact that their excellent fluidizing action, especially in concrete construction, is maintained over only a short period of time. The deterioration in the processability of concrete mixtures (“slump loss”) in a short time can lead to problems especially where there is a long period of time between make-up and installation of the fresh concrete, for example as a result of long conveyance and transport paths.
An additional problem arises when such fluidizers are employed in mining and in interior applications (drying of cardboard-faced plasterboard, anhydrite screed applications, manufacture of finished concrete components), since release of the toxic formaldehyde present in the products as a result of the manufacturing method can occur and thus lead to considerable occupational hygiene problems. For this reason, attempts have already been made to develop formaldehyde-free concrete fluidizers based on maleic monoesters and styrene, for example as described in EP-A-0 306 449. The flow of concrete mixtures can be maintained over a sufficiently long period of time by means of these additives, but the original, very high dispersant action is lost very quickly after storage of the aqueous fluidizer formulation as a result of hydrolysis of the polymeric ester.
This problem does not occur in the case of fluidizers based on alkylpolyethylene glycol allyl ethers and maleic anhydride as described in EP-A-0 373 621. However, these products are, like those described above, surface-active compounds which introduce undesirably high proportions of air pores into the concrete mixture, resulting in deterioration in the finished state [sic] and stability of the cured building material.
For this reason it is necessary to add antifoams such as tributyl phosphate, silicone derivatives and various water-insoluble alcohols in concentrations of from 0.1 to 2% by weight, based, on the solids content, to the aqueous solutions of these polymeric compounds. Mixing-in these antifoam components and maintaining a storage-stable homogeneous form of the corresponding formulations is very difficult even when these antifoams are added in the form of emulsions.
The problem of demixing can be solved by complete or at least partial incorporation of a foam-inhibiting or air-repellant structural unit into the copolymer, as described in DE 195 13 126 A1.
However, it has been found that the high effectiveness and the low “slump loss” of the copolymers described here often leads to unsatisfactory 24-hour strengths of the concrete. Furthermore, such copolymers do not have optimum properties, especially where a particularly dense and therefore high-strength and high-stability concrete is to be produced using the lowest possible proportion of water and steam curing (finished parts industry) for accelerating the curing process is to be dispensed with.
It is therefore an object of the invention to provide new copolymers which do not have the abovementioned disadvantages of the known agents, i.e. which maintain the processability of highly concentrated building material mixtures for an appropriate length of time even in small amounts and at the same time give an increased strength in the cured state of the building material due to a drastic decrease in the water/binder ratio.
This object is achieved according to the invention by copolymers based on radicals of unsaturated mono-carboxylic or dicarboxylic acid derivatives and oxyalkylene glycol alkenyl ethers, which are characterized in that they comprise
a) from 51 to 95 mol % of structural units of the formula Ia and/or Ib and/or Ic
where R
1
=hydrogen or an aliphatic hydrocarbon radical having from 1 to 20 carbon atoms,
X=O
a
M, —O—(C
m
H
2m
O)
n—R
2
, —NH—(C
m
H
2m
O)
n—R
2
,
M=hydrogen, a monovalent or divalent metal cation, an ammonium ion or an organic amine radical,
a=½ or 1,
R
2
=hydrogen, an aliphatic hydrocarbon radical having from 1 to 20 carbon atoms, a cycloaliphatic hydrocarbon radical having from 5 to 8 carbon atoms, a substituted or unsubstituted aryl radical having from 6 to 14 carbon atoms,
Y=O, NR
2
,
m=2 to 4 and
n=0 to 200,
b) from 1 to 48.9 mol % of structural units of the general formula II
where
R
3
is hydrogen or an aliphatic hydrocarbon radical having from 1 to 5 carbon atoms,
p is from 0 to 3
and R
2
, m and n are as defined above,
c) from 0.1 to 5 mol % of structural units of the formula IIIa or IIIb
where
S=H, —COO
a
M, —COOR
5
,
—W—R
7
—CO—[NH—(CH
2
)
3
]
s
—W—R
7
—CO—O—(CH
2
)
z
—W—R
7
—(CH
2
)
z
—V—(CH
2
)
z
—CH=CH—R
2
—COOR
5
in the case of S=—COOR
5
or COO
a
M
U
1
=—CO—NH—, —O—, —CH
2
O—
U
2
=—NH—CO—, —O—, —OCH
2
—
V=—O—CO—C
6
H
4
—CO—O— or —W—
R
4
=H, CH
3
,
R
5
=an aliphatic hydrocarbon radical having from 3 to 20 carbon atoms, a cycloaliphatic hydrocarbon radical having from 5 to 8 carbon atoms, an aryl radical having from 6 to 14 carbon atoms,
r=2 to 100
s=1, 2
z=0 to 4
x=1 to 150
y=0 to 15 and
d) from 0 to 47.9 mol [lacuna] of structural units of the general formula IVa and/or IVb
where a, M, X and Y are as defined above.
It has surprisingly been found that very small amounts of the copolymers of the invention based on unsaturated monocarboxylic or dicarboxylic acid derivatives and oxyalkylene glycol alkenyl ethers added to aqueous building material suspensions give the suspensions excellent processing properties without delaying strength development. It was particularly surprising that a drastic decrease in the water/binder ratio still leads to highly fluid building materials when the copolymers of the invention are added and no segregation of individual constituents of the building material mixture occurs.
The copolymers of the invention comprise at least three, but preferably four, structural units a), b), c) and d).
Albrecht Gerhard
Grassl Harald
Hübsch Christian
Kern Alfred
Leitner Hubert
Choi Ling-Siu
Degussa Construction Chemicals GmbH
Fulbright & Jaworski L.L.P.
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