Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-07-27
2002-08-20
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C526S318420
Reexamination Certificate
active
06437027
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a powdery dispersant suitable for producing hydraulic compositions, such as cement, of excellent fluidity; a process for producing the dispersant; and a hydraulic composition containing the dispersant. More particularly, the invention relates to a powdery dispersant which can be incorporated in advance into a pre-mixed hydraulic composition product; a process for producing the dispersant; and a variety of hydraulic compositions containing the dispersant.
BACKGROUND ART
Mechanical strength and durability of hardened cement-containing compositions such as concrete and mortar increase as the water/cement ratio (W/C) decreases, whereas fluidity and workability of the compositions become poor as the W/C ratio decreases. Therefore, a cement dispersant is added to hydraulic compositions in order to assure sufficient fluidity thereof, even though the compositions have a low W/C ratio. Liquid-type dispersants and powdery dispersants predominantly containing a naphthalenesulfonate salt-formalin condensate or a melaminesulfonate salt-formalin condensate are widely employed as the aforementioned dispersants for preparing hydraulic compositions. However, when these dispersants are added to a hydraulic composition, fluidity thereof greatly decreases with elapse of time, thereby disadvantageously lowering workability. Therefore, there have also been employed dispersants containing, as an active ingredient, a polycarboxylate polymer obtained from an acid such as acrylic acid or methacrylic acid.
Since dispersants containing a polycarboxylate polymer are generally in the form of liquid, they cannot be incorporated into a pre-mixed product, which is frequently employed as a plastering material. As compared with powdery dispersants, liquid dispersants require care for transportation and containers, as well as additional treatment of the containers, to thereby increase cost for use of liquid dispersants. In addition, since formalin which is contained in a sulfonate salt-formalin condensate is a hazardous substance, restriction is imposed on handling and use of dispersants containing a formalin condensate.
Thus, pulverization of a dispersant containing a polycarboxylate polymer as a predominant ingredient has been investigated. However, when a powdery dispersant having high solubility to water is produced through a conventional pulverization technique (Japanese Patent Publication (kokoku) No. 7-14829), an insoluble gel is formed during pulverization and the thus-obtained powder has poor characteristics, e.g., poor dispersibility.
Pulverization by means of a spray-drier is also a known technique (Japanese Patent No. 2669761). Since a large amount of inorganic powder must be used in combination in the above technique, the polycarboxylate polymer content in the formed dispersant decreases or the polymer is adsorbed with the inorganic powder, to thereby disadvantageously lower dispersion performance during use in an aqueous solution. Furthermore, when an attempt is made to produce such a dispersant at high content, i.e., approximately 100%, a portion of the product is adsorbed inside a drying tower, thereby lowering production yield thereof. When pulverization of a high-viscoelasticity polymer is attempted, overload of a motor prevents continuous and safe operation. In addition, water removed during a drying step tends to exhibit a high COD, to thereby require additional wastewater treatment.
In view of the foregoing, an object of the present invention is to provide a high-performance powdery dispersant for preparing a high-fluidity hydraulic composition, which dispersant contains a polycarboxylate polymer having a polyalkylene glycol chain. Another object of the invention is to provide a process for effectively producing the dispersant. Still another object is to provide a hydraulic composition containing the dispersant.
DISCLOSURE OF THE INVENTION
The present inventors have conducted earnest studies, and have found that when a reducing agent is added to polycarboxylate polymer having a polyalkylene glycol chain and the resultant mixture is dried and pulverized, there is effectively produced a powdery dispersant which imparts excellent fluidity to a hydraulic composition. The present invention has been accomplished on the basis of this finding.
Accordingly, the present invention provides a process for producing a powdery dispersant for preparing a hydraulic composition, which process comprises adding a reducing agent to a liquid predominantly containing a polycarboxylate polymer having a polyalkylene glycol chain, and drying and pulverizing the resultant mixture. The invention also provides the thus-produced powdery dispersant for preparing a hydraulic composition.
Further, the present invention provides a granular hydraulic composition containing hydraulic material and the aforementioned powdery dispersant for preparing a hydraulic composition.
Further, the present invention provides a cement grout composition containing a binder, an aggregate, an expansion accelerator, and the aforementioned powdery dispersant for preparing a hydraulic composition.
Still further, the present invention provides a self-leveling cement composition containing a binder, a fine aggregate, a defoaming agent, and the aforementioned powdery dispersant for preparing a hydraulic composition.
Still further, the present invention provides a quick-setting grout composition containing a quick-setting cement, gypsum, and the aforementioned powdery dispersant for preparing a hydraulic composition.
Still further, the present invention provides a quick-setting self-leveling composition containing a quick-setting cement, gypsum, a defoaming agent, and the aforementioned powdery dispersant for preparing a hydraulic composition.
Still further, the present invention provides a cement composition which contains the aforementioned powdery dispersant for preparing a hydraulic composition, and a cement predominantly containing calcium aluminates.
BEST MODE FOR CARRYING OUT THE INVENTION
No particular limitation is imposed on the polycarboxylate polymer compounds having a polyalkylene glycol chain which may be employed in the present invention, so long as the compounds may be employed as cement dispersants. Examples of such polymer compounds include (A) (meth)acrylate copolymers having a polyalkylene glycol chain and (B) maleate copolymers having a polyalkylene glycol chain (in the case of (B), multi-valent metal salts thereof are excluded). These may be employed singly or in combination of two or more species.
Of copolymers (A), preferable ones are (meth)acrylate copolymers having a polyalkylene glycol chain and a group —COOM (wherein M represents a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium, or an organic amine). Of copolymers (B), preferable ones are polyalkylene glycol alkenyl ether-maleic anhydride copolymers (with multi-valent salts thereof being excluded).
In the aforementioned (meth)acrylate copolymers (A), M of the group —COOM is preferably a hydrogen atom; an alkali metal such as sodium or potassium; an alkaline earth metal such as calcium or magnesium; ammonium; or an organic amine.
In the aforementioned copolymers (A) and (B), a polyalkylene glycol chain is preferably a C2-C4 polyalkylene glycol chain, more preferably a chain represented by —O(CH
2
CH(R
3
)O)
n
—. In the chain —O(CH
2
CH(R
3
)O)
n
—, R
3
represents a hydrogen atom or a methyl group, and n is 2-200, preferably 5-109, more preferably 20-109, still more preferably 30-109.
Of the aforementioned copolymers (A), preferable ones are acrylate or methacrylate polymer compounds comprising at least two different structural units represented by the following formulas (1) and (2):
(wherein each of R
1
, R
2
, and R
3
, which may be identical to or different from one another, represents a hydrogen atom or a methyl group; R
4
represents a C1-C3 alkyl group; M
1
represents a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium, or an organic amine; Y represents—CH
2
O— or —COO—; and n is 2-2
Hayashi Hiroshi
Isomura Hirotaka
Makino Kenjiro
Soeda Koichi
Takimoto Masaki
Michl Paul R.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Taiheiyo Cement Corporation
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