Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-12-28
2002-05-07
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S531000, C524S005000, C106S729000
Reexamination Certificate
active
06384141
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a shrinkage reducing agent for hydraulic materials, a method of producing the same and an additive composition for hydraulic materials.
PRIOR ART
Hydraulic materials can give cured produces excellent in strength and durability, among others, and therefore are in wide use in the form of cement compositions such as cement pastes, mortar and concrete. They are now indispensable in building civil engineering and architectural structures. Such hydraulic materials, however, have a problem. After curing, the unreacted water remaining in the inside disperses according to ambient temperature, moisture and other conditions and drying shrinkage progresses presumably due to such moisture dissipation to cause cracks to appear in cured products, lowering the strength and durability thereof. Decreases in strength and durability of civil engineering and architectural structures produce serious problems such as endangered safety and increased repairing costs.
The government regulations with respect to these problems are going to be tightened. For instance, the Japanese law concerning the promotion of assurance of the quality of houses as enacted in June, 1999 includes concrete cracking among the defects to be repaired. Further, in Japan, there is the possibility of specifications, with respect to cracking due to drying shrinkage, for performance-oriented ready mixed concrete being introduced into JIS A 5308 in or after 2005. Under the circumstances, the importance of shrinkage reducing agents for hydraulic materials which prevent the progress of shrinkage due to drying of cured hydraulic materials has been well recognized and various technological innovations have been made.
Thus, the following agents have been disclosed for reducing the shrinkage of cement mixes upon drying. C
1-4
alcohol-alkylene oxide adducts (Japanese Kokoku Publication Sho-56-51148), dihydric to octahydric alcohol-ethylene oxide and propylene oxide coadducts (Japanese Kokoku Publication Hei-01-53214), lower alkylamine-alkylene oxide adducts (Japanese Kokoku Publication Hei-01-35215), polypropylene glycol species in the range of oligomers (Japanese Kokai Publication Sho-59-152253), low-molecular-weight alcohols (Japanese Kokoku Publication Hei-06-6500) and C
8
2-ethylhexanol-alkylene oxide adducts (JP2825855), among others. All these compounds are oligomers or low-molecular compounds with a molecular weight of not more than about 1,000.
Among them, those shrinkage reducing agents which have been put into practice use and are commercially available are reviewed, for example, in “Konkurito Konwazai no Kaihatsu to Saishin Gijutu (Development and State-of-the-art Technologies of concrete Admixtures)” (first edition, published Sep. 18, 1995 by CMC Co.). However, the standard addition amounts of these shrinkage reducing agents are as high as 2 to 6% on the unit cement content basis, so that when used in concrete, they increase the cost of concrete and can never be said to be general purpose agents.
Meanwhile, as regards high-molecular-weight agents for reducing shrinkage due to drying, Japanese Kokai Publication Hei-08-268741 discloses a cement dispersing agent of the drying shrinkage reducing type which comprises a graft polymer derived from a polycarboxylic acid (or a salt thereof) by the chemical bonding of an oligoalkylene glycol or polyhydric alcohol to side chains thereof. However, this is not easy to synthesize.
For obtaining high-molecular-weight compounds with ease, there are known methods which comprise graft polymerizing an ethylenically unsaturated monomer onto a polyether compound. Laid-open European Patent Application No. 0271435 (A2) discloses the use of a graft polymer constituted of a main chain polyether polymer and a side chain polymer resulting from polymerization of an unsaturated ethylenic monomer as a superplasticizer or water reducing agent for cement compositions and Japanese Kokai Publication Hei-11-139855 discloses the use, as a cement additive, of a graft polymer comprising a specific monomer and having a weight average molecular weight of not less than 6,000. However, these graft polymers are intended to improve the strength and other properties of cured cement products by reducing water and curing cement compositions while maintaining the flowability thereof. Nothing is disclosed at all therein of the use thereof as agents a for reducing drying shrinkage. Therefore, there was a room for studying in order to readily produce agents capable of satisfactorily suppressing the progress of shrinkage due to drying even when the addition amount thereof in hydraulic materials is reduced.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention, which has been made in view of the state of the art mentioned above, to provide a shrinkage reducing agent for hydraulic materials high in general versality and capable of producing a better cracking preventing effect by sufficiently preventing the progress of drying shrinkage of cured products even when the addition amount thereof in hydraulic materials is reduced to thereby cut down the cost of production of hydraulic materials, a method of producing the same, and an additive composition for hydraulic materials.
The present inventors made intensive investigations following careful studying of the problems concerning the shrinkage reducing agents for hydraulic materials which could be used widely in the fields of civil engineering and architecture and, as a result, encountered the fact that a shrinkage reducing agent for hydraulic materials which comprises a polymer having a specific structure can produce an excellent cracking preventing effect by sufficiently suppressing the progress of shrinkage due to drying of cured products even when used at a reduced addition amount to thereby reduce the production cost of hydraulic materials, hence can produce a dramatic effect, increasing the general versatility, improving the safety of civil engineering and architectural structures and suppressing the repairing costs, and have now completed the present invention.
Thus, the present invention lies in a shrinkage reducing agent for hydraulic materials
which comprises at least one polymer selected from the group consisting of
(a) a polymer having a structure derived from the residue of a compound containing 2 to 30 carbon atoms and one active hydrogen atom by the binding thereto of one oxyalkylene chain having a carboxyl-containing side chain,
(b) a polymer having a structure derived from the residue of a compound containing 4 to 30 carbon atoms and two active hydrogen atoms by the binding thereto of at least one oxyalkylene chain having a carboxyl-containing side chain,
(c) a polymer having a structure derived from the residue of a compound containing 1 to 30 carbon atoms and at least three active hydrogen atoms by the binding thereto of at least one oxyalkylene chain having a carboxyl-containing side chain
and (d) a polymer having a structure derived from the residue of an amine by the binding thereto of one oxyalkylene chain having a carboxyl-containing side chain.
DETAILED DESCRIPTION OF THE INVENTION
In the following, the invention is described in detail.
The shrinkage reducing agent of the invention for hydraulic materials comprises at least one polymer selected from the group consisting of the above-mentioned polymer (a), polymer (b), polymer (c) and polymer (d). Although it may contain another component or other components, it preferably comprises the above-mentionedpolymer(s) as a main component(s) These polymers may be used singly or two or more of them may be used in combination. When two or more polymers are used, the weight proportions of the respective polymers are not particularly restricted.
Referring to the above polymers (a), (b) and (c), the term “residue of a compound containing an active hydrogen atom(s)” means a group having a structure resulting from removal of the active hydrogen atom(s) from the active hydrogen-containing compound. The group(s) formed upon reaction with the a
Hirata Tsuyoshi
Nagare Koichiro
Asinovsky Olga
Nippon Shokubai Co. , Ltd.
Seidleck James J.
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