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
1999-12-28
2002-11-26
Wilson, D. R. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S339000, C525S384000
Reexamination Certificate
active
06486260
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a cement additive having good fluidity and foaming preventing activity, to a cement composition and to a polycarboxylic acid polymer which can be judiciously used as a cement additive or a dispersant for various uses.
BACKGROUND ART
Cement compositions can give cured products excellent in strength and durability and therefore have a wide range of applications, for example as outer wall materials, i.e. sidings, for buildings and structures.
For increasing the air-entraining property and fluidity of such cement compositions, cement additives are generally used in said compositions. The importance of such additives known collectively as additive has recently been more and more recognized and technological innovations have actively been made.
The task of cement additive is to allow cement compositions to exhibit sufficient dispersibility even when the level of addition of water is reduced, to thereby secure the fluidity and processability of the cement compositions and realize improvements in durability and strength as a result of water reduction and, at the same time, give good cement compositions while retaining a proper level of air-entraining property.
U.S. Pat. No. 3,563,930 discloses a cement composition which contains a compound comprising a styrene-maleic anhydride copolymer and/or a styrene-maleic anhydride copolymer half ester. However, although this styrene-maleic anhydride copolymer produces a good air-entraining effect, it has a molecular weight as low as 500 to 5000, hence the half-esterified copolymer also has a low molecular weight; Thus, the number of carboxyl groups and that of polyalkylene glycol residues per molecule are small and, as a result, the ability of said compound to be adsorbed on cement particles is poor and sufficient dispersibility can never be obtained.
JP Kokai H01-92212 discloses a fluidity improving agent for cement compositions which is a styrene-maleic anhydride and maleic acid half ester copolymer whose maleic acid half ester moiety is derived from maleic anhydride units by addition of a polyalkylene glycol. In this copolymer, however, the number of oxyalkylene groups, which are repeating units of the polyalkylene glycol, is not more than 100 and, as a result, said copolymer is insufficient in hydrophilicity and steric repulsion toward cement, so that a required level of dispersibility cannot be obtained. Further, the occurrence ratio between maleic anhydride units and maleic acid half ester units is 1:3 to 1:100 and, thus, the proportion of the carboxyl group is relatively small, so that the ability to be adsorbed on cement particles is poor and no sufficient dispersibility can be obtained.
JP Kokai H07-216026 discloses a fluidizing agent for cement-like compositions which comprises a free acid form or salt form random copolymer composed of a specific hydrocarbon monomer, a maleic acid monomer and a maleic acid half ester monomer derived by addition of a polyalkylene glycol. In this copolymer, however, the number of oxyalkylene groups, which are polyalkylene glycol-derived repeating units, is not more than 100, so that the hydrophilicity and steric repulsion are not sufficient, hence the required level of dispersibility cannot be obtained. Further, the occurrence ratio between the maleic acid monomer and maleic acid half ester monomer is 5:1 to 1:100 and thus the proportion of the carboxyl group is small; the ability to be adsorbed on cement particles is therefore poor and no sufficient dispersibility can be obtained.
JP Kokai H06-256054 discloses a cement dispersing agent which comprises a maleic anhydride copolymer alkyl polyalkylene glycol ester. However, this copolymer, like those mentioned above, not sufficient in hydrophilicity and steric repulsion and cannot have the required level of dispensability. In addition, it is poor in ability to be adsorbed on cement particles and fails to exhibit sufficient dispersibility.
JP H08-268741 discloses a cement dispersing agent for reducing drying shrinkage which comprises a graft polymer derived from a polycarboxylic acid or a salt thereof by chemically binding, to side chains thereof, an oligoalkylene glycol and/or a polyhydric alcohol, together with a polyalkylene glycol or a derivative thereof. However, in this graft polymer, the number of oxyalkylene groups, which are repeating units of the polyalkylene glycol or the derivative thereof, is about 12, so that said graft polymer is insufficient in hydrophilicity and steric repulsion toward cement and no necessary dispersibility can be obtained. A technology is also disclosed of using an ethylene oxide-propylene oxide block copolymer having foaming preventing activity as the polyalkylene glycol or the derivative thereof for adjusting the air-entraining property. This graft polymer, however, cannot have sufficient dispersibility, as mentioned above, so that it cannot contribute to water reduction, hence the intended improvements in durability and strength by synergistic effects of water reduction and foaming prevention cannot be realized.
U.S. Pat. No. 5,660,626 discloses a shrinkage reducing agent which comprises a graft copolymer polycarboxylic acid or a salt thereof whose side chains are modified with an oligoalkylene glycol or the like. This graft copolymer is indeed excellent in drying shrinkage of cement compositions but is insufficient in hydrophilicity and steric repulsion toward cement, hence it fails to acquire the required dispersibility.
Polycarboxylic acid polymers are used as cement additives, as mentioned above and, when they have a dispersing effect on various inorganic powders and pigments, they can be used also as dispersing agents for inorganic pigments for paper coating, dispersing agents for paper filler pigments, dispersing agents for pigments for water paints, dispersing agents for pigments for water inks and like dispersing agents, since they have no coloration problem as compared with such dispersing agents as naphthalenesulfonic acid salts. They can further be used as builders for detergents, descaling agents and so forth. The advent of polycarboxylic acid polymers having sufficient dispersing effects on various inorganic powders and pigments has been awaited.
SUMMARY OF INVENTION
The present invention has for its object to solve the above problems and provide an economical cement additive capable of reducing the amount of water to be added to cement compositions and showing high fluidity, good processability, and a proper level of air-entraining activity owing to sufficient foaming prevention, at low addition levels, a cement composition in which said cement additive is used, and a polycarboxylic acid polymer excellent in dispersing effects on cement particles or inorganic powders or pigments, having no coloration or other problems and capable of being used with advantage as a cement additive or a dispersant for various uses.
The cement additive of the present invention comprises, as a main component, a polycarboxylic acid polymer (X) which has;
a repeating unit (A) represented by the general formula (1);
[wherein R
1
and R
2
are the same or different and each represents a hydrogen atom or a univalent hydrocarbon group containing 1 to 30 carbon atoms and the carbon chains of R
1
and R
2
may partly be bound together; R represents a hydrogen atom, a phenyl group, an alkylphenyl group, a sulfonated phenyl group, an alkyl group containing 1 to 30 carbon atoms, an alkenyl group containing 2 to 30 carbon atoms, or a univalent organic group selected from the group consisting of —OR, —OCOR, —X
1
OR
6
, —O(R
7
O)aR
8
and —CN; R
4
and R
5
each represents a univalent hydrocarbon group containing 1 to 30 carbon atoms; X
1
represents a bivalent hydrocarbon group containing 1 to 3 carbon atoms; R
6
and R
8
each represents a hydrogen atom or a univalent hydrocarbon group containing 1 to 30 carbon atoms; R
7
represents an alkylene group containing 2 to 30 carbon atoms; a represents the average number of moles of the oxyalkylene group represented by —(R
7
O)— as added an
Hirata Tsuyoshi
Kawakami Hirokatsu
Yuasa Tsutomu
Connolly Bove & Lodge & Hutz LLP
Nippon Shokubai Co. , Ltd.
Wilson D. R.
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