Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1998-12-01
2001-05-29
Pezzuto, Helen L. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S318400, C526S318410, C526S318500, C526S320000, C526S328500, C526S329600, C526S332000
Reexamination Certificate
active
06239241
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a copolymer for use in a concrete admixture which improves the workability of hydraulic compositions such as cement paste, mortar, concrete and the like. Namely, the admixture effectively reduces the viscosity of the hydraulic compositions under shear without causing setting retardation of the compositions.
DESCRIPTION OF RELATED ART
High-strength concrete is being used in recent multistoried buildings and large constructions. For those, concrete admixtures are required to have the ability to promote water reduction from concrete paste, the ability to reduce the viscosity of concrete paste being forcibly fed under pumping pressure and the ability to inhibit delayed setting of concrete so as to ensure early removal of the molding frames.
Known high-power water-reducing agents for high-strength concrete, include naphthalenesulfonic acid-formalin condensates (naphthalene-based chemicals), melaminesulfonic acid-formalin condensates (melamine-based chemicals), etc. In addition, recently, water-soluble vinyl copolymers such as copolymers of polyalkylene glycol monoester monomers and acrylic and/or dicarboxylic acid monomers (polycarboxylic acid-based chemicals) have been proposed (see, for example, Japanese Patent Application Laid-Open (JP-A) Sho-58-74552, Sho-62-70250, Sho-62-78137, Sho-62-70252, Sho-62-119147, Hei-3-75252, Sho-59-16263), which have excellent dispersibility. Using these water-reducing agents has made it possible to provide high-strength concrete constructions.
However, conventional high-strength concrete compositions have fluidity characteristics similar to Newtonian flow, have high viscosity under high shear, and require an extremely large pumping load when they are forcibly fed under pumping pressure. Under these circumstances, therefore, they are difficult to forcibly feed under pumping pressure.
On the other hand, conventional admixtures may reduce the viscosity of concrete paste under high shear, but often have poor dispersibility. Therefore, when a relatively large amount of admixture is added to high-strength concrete, there is the problem of setting retardation.
Conventional admixtures could not satisfy the two requirements, one being to reduce the viscosity of concrete paste under high shear, and the other being to prevent setting retardation. The object of the present invention is to provide a concrete admixture free from these problems, more precisely to provide a concrete admixture which is useful in the field of high-strength concrete constructions which improves viscosity reduction without causing setting retardation.
SUMMARY OF THE INVENTION
The present inventors previously studied copolymers for concrete admixtures and the influences of the oxyalkylene group (AO) chain length constituting the copolymers and the compositional ratio of comonomers to form the copolymers on the properties of concrete admixtures, especially with respect to the dispersibility retentiveness and the foam stability of the hydraulic composition. The previous studies verified that copolymers of a monomer having a long-chain AO, a monomer having a relatively short-chain AO and a (meth)acrylic or unsaturated dicarboxylic monomer exhibit specific characteristics (see JP-A Hei-7-247150). Given that situation, the present inventors have further studied still other various copolymers in order to improve viscosity reduction without causing setting retardation. As a result, the present inventors have found that specific copolymers not falling within the scope of the Examples of JP-A Hei-7-247150 and not having been taught previously can satisfy the two requirements of viscosity reduction without causing setting retardation.
More specifically, the present inventors have found that copolymers as formed by polymerizing a monomer having a long-chain AO, a monomer having a short-chain AO and a (meth)acrylic acid monomer in a specific ratio have the ability to attain excellent viscosity reduction without causing setting retardation, and thus have completed the present invention.
Accordingly, the present invention is directed to a copolymer having the formula recited below, and a concrete admixture comprising, as the essential component, a copolymer obtained by polymerizing (A) a monomer of the following formula (a); (B) a monomer of the following formula (b); and (C) a monomer of the following formula (c); in a ratio by weight of (A)/(B)/(C)=(51 to 80)/(10 to 45)/(1 to 40)
wherein
R
1
is a hydrogen or methyl group;
AO is an oxyalkylene group having 2 or 3 carbon atoms;
n
1
is a number of from 80 to 300; and
X
1
is a hydrogen, or alkyl group having from 1 to 3 carbon atoms;
wherein
R
2
is a hydrogen or methyl group;
AO is an oxyalkylene group having 2 or 3 carbon atoms;
n
2
is a number of from 5 to 30; and
X
2
is a hydrogen, or alkyl group having from 1 to 3 carbon atoms;
wherein
R
3
to R
5
each is a hydrogen, methyl group, or (CH
2
) mCOOM
2
;
M
1
, M
2
each is a hydrogen, alkali metal, alkaline earth metal, ammonium, alkylammonium, or substituted alkylammonium; and
m is an integer of from 0 to 2.
The invention further provides a concrete admixture composition comprising, as the essential component, a copolymer as obtained by polymerizing (A) a monomer of formula (a) noted above; (B) a monomer of formula (b) noted above; (C) a monomer of formula (c) noted above; and additionally (D) a monomer of the following general formulae (d-1) to (d-3); and (E) a monomer of the following general formula (e); in a ratio by weight of [(A)+(D)+(E)]/(B)/(C)=(51 to 80)/(10 to 45)/(1 to 40) and in a ratio by weight of (A)/[(D)+(E)]=(50 to 100)/(0 to 50).
wherein
R
6
, R
7
each is a hydrogen or methyl group;
R
8
, R
9
each is an alkylene group having from 2 to 4 carbon atoms;
M
3
to M
6
each is a hydrogen, alkali metal, alkaline earth metal, ammonium, alkylammonium, or substituted alkylammonium;
wherein
R
10
each is a hydrogen or methyl group; and
M
7
each is a hydrogen, alkali metal, alkaline earth metal, ammonium, alkylammonium, or substituted alkylammonium;
wherein
R
11
is a hydrogen or methyl group; and
R
12
is an alkyl group having from 1 to 6 carbon atoms or an alkenyl group having from 2 to 6 carbon atoms;
wherein
R
13
is a hydrogen or methyl group; and
R
14
is a hydroxyalkyl group having from 2 to 6 carbon atoms.
The present invention is also directed to a method of reducing the viscosity without causing setting retardation of a hydraulic composition which comprises adding to said hydraulic composition the copolymer as described above.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Where the concrete admixture of the present invention is used for producing concrete, it is extremely effective for reducing the viscosity of concrete paste even under high shear without causing setting retardation of the concrete. As opposed to this, however, where a mixture of short-chain polymer and long-chain polymer is added to concrete paste, it is presumed that the short-chain polymer will be predominantly adsorbed by concrete in early stages due to the adsorption interference by the long-chain AO, and thereafter the long-chain polymer will then be adsorbed with the passage of time. Thus, in mixture, the two polymers will differ in both the adsorption rate and the adsorption mode, to the cement. Accordingly, it is believed that high concentrations of the short-chain polymer are rapidly absorbed by the cement to cause setting delay, and that the viscosity of the concrete paste is greatly influenced by the characteristics of the long-chain polymer being adsorbed by cement with the lapse of time.
In the case of the inventive cement admixture, it is believed that there will be no difference in terms of the adsorption rate and the adsorption mode of the copolymer used in the present invention which has a long-chain and short-chain graft structure, and that the long-chain moiety of the copolymer will prevent the setting delay while the short-chain moiety thereof will improve the
Hamada Daisuke
Sato Haruyuki
Sato Takahiro
Shirota Kyoichi
Yamato Fuzio
Birch & Stewart Kolasch & Birch, LLP
Kao Corporation
Pezzuto Helen L.
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