Compositions: coating or plastic – Coating or plastic compositions – Metal-depositing composition or substrate-sensitizing...
Patent
1982-05-04
1985-10-15
Bell, M. L.
Compositions: coating or plastic
Coating or plastic compositions
Metal-depositing composition or substrate-sensitizing...
106104, 106314, C04B 735
Patent
active
045472238
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to a shrinkage-reducing agent for cements and to a cement composition.
2. Background Art
A major disadvantage inevitable to cement mortar and concrete (hereinafter referred to as "concrete and the like" has been that they tend to crack on drying due to their considerable drying shrinkage. For this reason appearance of concrete and the like which will dry with a minimum of contraction has been desired.
With cements, alkylene oxide adducts have hitherto been employed as admixtures to serve varied purposes. For example, polyoxyethylene alkylaryl ethers (in which the alkyl radical usually has from 8 to 10 carbon atoms and the number of moles of the ethylene oxide added usually ranges from 2 to 30 per mole of alkylphenol) are in use as air-entraining agents for cements, admixtures for backing mortar, emulsion stabilizers for cement-containing latexes, etc. Polyoxyethylene-oxypropylene block copolymers (with the total number of moles of the alkylene oxide usually in the range of 30-250) function as cement dispersants, water-content-reducing agents, etc. Higher-alcohol alkylene oxide adducts (with usually 5-30 moles of the alkylene oxide added to each mole of the higher alcohol containing 8 or more carbon atoms) have applications such as air-entraining agents for cements or emulsion stabilizers for cement-containing latexes. Further, polyoxyalkylene glycols (polymers with usually about 15-30 mole alkylene oxide) are in use as dispersants for cement-containing fibers of asbestos, glass wool, etc., or together with ligninsulfonic acid or other cement dispersants to attain greater dispersion.
The alkylene oxide adducts in common use as the cement admixtures are either those with a large number of added moles of the alkylene oxides or those having higher alkyl radicals, and they have functions generally known as surfactants, including dispersing, foaming, and wetting actions. In fact, they are being employed to perform those functions. Nevertheless, those alkylene oxide adducts have no or inadequate, if any, effect as shrinkage-reducing agents for cements.
DISCLOSURE OF THE INVENTION
After our intensive investigations in search of a cement-shrinkage-reducing agent and a cement composition which could yield concrete and the like which will undergo no drying shrinkage in the course of setting and will maintain strength as desired without sacrificing the noncombustibility of the cement itself, the present invention has now been perfected. Briefly, the invention resides in:
A shrinkage-reducing agent for cements comprising a compound of the general formula represents one or more C.sub.2-3 alkylene radicals, and n has a value of 1-10; and
A cement composition comprising a cement and, as a cement-shrinkage-reducing agent, a compound of the general formula represents one or more C.sub.2-3 alkylene radicals, and n has a value of 1-10.
A compound represented by the general formula (1) is easily obtained by adding an alkylene oxide, such as ethylene oxide and/or propylene oxide, to an alcohol having not more than 7 carbon atoms in the molecule.
In the general formula (1), R denotes a C.sub.1-7 alkyl or C.sub.5-6 cycloalkyl radical. Such radicals include, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-pentyl, isopentyl, cyclopentyl, cyclohexyl, n-hexyl, isohexyl, n-heptyl, and isoheptyl-radicals. Of these radicals, C.sub.1-5 alkyl or cyclohexyl radicals, particularly butyl radicals, are desirable for their cement-shrinkage-reducing effects. Alkyl radicals with 8 or more carbon atoms are undesirable because they reduce the cement solubility in water, give less shrinkage-controlling effects, and/or, where more alkylene oxide is added to make the compound fully water-soluble, they may function as surfactants, imparting excessive foamability to the concrete. (Admixture of cement with a foamable compound will seriously decrease the strength of the resulting concrete and the like due to excessive air entrainment.)
In the formula given above, A signifies
REFERENCES:
patent: 1633927 (1927-06-01), Davidson
patent: 3498921 (1970-03-01), Edwards et al.
patent: 3528920 (1970-09-01), Niizeki et al.
patent: 3991122 (1976-11-01), Gritti
Goto Takaharu
Ii Motohiko
Sakai Kouzou
Sato Takeshi
Bell M. L.
Nihon Cement Co. Ltd.
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