Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
2001-04-23
2002-09-24
Marcantoni, Paul (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S727000, C106S823000
Reexamination Certificate
active
06454850
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Technical Field
The present invention relates to a cement admixture and a cement composition comprising this. More specifically, the invention relates to: a cement admixture which is mixed into cement mixtures, such as cement paste, mortar, and concrete, and thereby can give the cement mixtures excellent cracking inhibition effect and excellent fluidity; and a cement composition comprising this admixture.
B. Background Art
In general, cement mixtures, such as cement paste, mortar, and concrete, are used in order to construct such as civil engineering structures and building structures. However, hitherto, there are problems in that: according to such as outside air temperature or humidity conditions, the volatilization of unreacted water from the concreted cement mixtures might promote the drying shrinkage to crack the hardened products, and the resultant cracks cause the deterioration of the strength and watertightness of the above structures. Furthermore, in recent years, there is a movement to bind in duty to give a guarantee against cracks due to the drying shrinkage. For example, a law regarding the promotion to ensure the house quality, which intends to add cracking of concrete to objects of a guarantee against defects, is put in effect. Therefore, it is desired to take effective countermeasures to suppress the drying shrinkage of the cement mixtures to thereby prevent cracking.
As to the means to suppress the drying shrinkage of the cement mixtures to a small one, it is effective to decrease the quantity of water (unit water quantity) for knead-mixing of concrete. For example, the Architectural Society of Japan prescribes that the upper limit value of the unit water quantity in high durable concrete should be 175 kg. Hitherto, high-performance water-reducing agents such as salts of &bgr;-naphthalenesulfonic acid-formaldehyde condensation products are conventionally used to satisfy this prescription.
However, in the case where the high-performance water-reducing agents are used, there are problems in that: chemical or physical cohesion of cement particles proceeds with the passage of time after knead-mixing, and the fluidity is therefore apt to decrease with the passage of time, with the result that there occur troubles with execution of works.
On the other hand, various studies are carried out also about shrinkage-reducing agents to suppress the drying shrinkage of the cement mixtures to a small one. For example, JP-B-051148/1981 proposes alkylene oxide adducts to alcohols having 1 to 4 carbon atoms, and JP-B-053214/1989 proposes ethylene oxide-propylene oxide co-adducts to di- to octahydric alcohols, and JP-B-053215/1989 proposes alkylene oxide adducts to lower alkylamines, and JP-A-152253/1984 proposes oligomeric polypropylene glycol, and JP-B-006500/1994 proposes low-molecular alcohols, and Japanese Patent No. 2825855 proposes alkylene oxide adducts to 2-ethylhexanol having 8 carbon atoms.
However, all these shrinkage-reducing agents are oligomers or low-molecular compounds having a molecular weight of not larger than hundreds, and therefore involve problems in that: for example, as is also described in “The Development of Concrete Admixture and Its Newest Technology” (1st edition, issued by CMC Co., Ltd. on Sep. 18, 1995), these shrinkage-reducing agents need to be used in a large standard amount of 2 to 6% of the unit cement weight, therefore the cost of concrete increases.
SUMMARY OF THE INVENTION
A. Object of the Invention
An object of the present invention is to provide: a cement admixture which displays excellent cracking inhibition effect and brings about good fluidity even if the quantity of the cement admixture as added is small; and a cement composition comprising this cement admixture.
B. Disclosure of the Invention
The present inventors diligently studied to solve the above-mentioned problems. As a result, they have completed the present invention by finding that: if a polyalkylene glycol having a specific molecular weight is allowed to coexist in a specific ratio with a polyalkylene glycol mono(meth)acrylate/unsaturated carboxylic acid-based copolymer having a polyalkylene glycol chain portion of which the average molecular weight is nearly equal to that of the above-mentioned polyalkylene glycol (the difference between these molecular weights is in a definite range), then the resultant mixture is a cement admixture which is extremely excellent in both properties of the drying shrinkage reducibility and the dispersibility.
Namely, a cement admixture, according to the present invention, comprises a polyalkylene glycol (A) and a polyalkylene glycol mono(meth)acrylate/unsaturated carboxylic acid-based copolymer (B), wherein: the average molecular weight (X) of the polyalkylene glycol (A) is in the range of 400 to 10,000; the average molecular weight (X) of the polyalkylene glycol (A) and the average molecular weight (Y) of a polyalkylene glycol chain portion of the copolymer (B) satisfy the following equation (1):
0.9<(X/Y)<1.1 (1);
and
the weight ratio of the polyalkylene glycol (A) to the copolymer (B) is in the range of (A)/(B)=0.02 to 0.3.
In addition, a cement composition, according to the present invention, at least comprises the above cement admixture according to the present invention, water, and cement.
These and other objects and the advantages of the present invention will be more fully apparent from the following detailed disclosure.
DETAILED DESCRIPTION OF THE INVENTION
The cement admixture, according to the present invention, comprises a polyalkylene glycol (A) (which might hereinafter simply be abbreviated to component A) and a polyalkylene glycol mono(meth)acrylate/unsaturated carboxylic acid-based copolymer (B) (which might hereinafter simply be abbreviated to component B). Hereinafter, each of them is explained in detail.
Polyalkylene glycol (A)
The component A in the present invention is, for example, represented by the following general formula (2):
R
1
O (AO)
m
H (2)
wherein:
AO represents an oxyalkylene group having 2 to 18 carbon atoms (wherein: the AO-repeating units may be either identical with or different from each other and, if the AO-repeating units are in the form of a mixture of at least two thereof, they may be formed by any of block addition, random addition, and alternating addition);
m is an average molar number of addition of the oxyalkylene groups and represents a number of 8 to 250; and
R
1
represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms.
R
1
in the formula (2) is especially favorably a hydrocarbon group having 1 to 30 carbon atoms, more favorably 1 to 22 carbon atoms, still more favorably 1 to 18 carbon atoms, particularly favorably 1 to 12 carbon atoms. In particular, favorably for obtaining high drying shrinkage reducibility, R
1
is a hydrocarbon group having 4 to 12 carbon atoms. Specific examples of R
1
include: alkyl groups having 1 to 30 carbon atoms; benzene ring-containing aromatic groups having 6 to 30 carbon atoms, such as a phenyl group, alkylphenyl groups, phenylalkyl groups, alkyl group-substituted or phenyl group-substituted phenyl groups, and a naphthyl group; and alkenyl groups having 2 to 30 carbon atoms.
AO in the formula (2) is particularly favorably a linear or branched oxyalkylene group having 2 to 8 carbon atoms. Examples thereof include an oxyethylene group, an oxypropylene group, an oxybutylene group, and an oxystyrene group. Of these groups, the oxyethylene group, the oxypropylene group, and the oxybutylene group are favorable.
Specific examples of the component A include: alkoxypolyalkylene glycols obtained by addition reactions of alkylene oxides having 2 to 18 carbon atoms to any of the following alcohols: saturated aliphatic alcohols having 1 to 30 carbon atoms, such as methanol, ethanol, 2-propanol, 1-butanol, octanol, 2-ethyl-1-hexanol, nonyl alcohol, lauryl alcohol, cetyl alcohol, and stearyl alcohol; unsaturated aliphatic alcohols having 3 to 30 carbon atoms, such as allyl alcohol, methal
Hirata Tsuyoshi
Mitsukawa Hiroshi
Yamashita Akihiko
Haugen Law Firm PLLP
Marcantoni Paul
Nippon Shokubai Co. , Ltd.
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