Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
1999-01-01
2001-09-25
Green, Anthony (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S724000, C106S727000, C106S728000, C106S808000, C106S810000, C106S823000
Reexamination Certificate
active
06294015
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Technical Field
The present invention relates to a cement admixture and a cement composition, and more particularly, to a cement admixture and a cement composition, both of which have excellent fluid retainability of cement paste, mortar or concrete at high temperature and further display excellent fluidity even at low temperature.
B. Background Art
Since early deterioration of concrete structures became social problems in 1981, it has been strongly required to improve execution and durability of the concrete structures by decreasing the unit water quantity of concrete. Thus, a lot of technological innovation is carried out to a cement admixture which gives much influence to the quality and the capability of a cement mixture.
As to conventional methods, a fluidizing construction method is carried out, in which raw concrete of low fluidity (hereinafter, the fluidity is referred to as “slump”) containing an AE agent or AE water-reducing agent is produced in a plant, and then transported to a building site with a raw concrete car, and then fluidized by adding a fluidizing agent, thereby raising the slump to a predetermined value. However, this construction method, for example, has the following problems: environmental problems due to noises and exhaust gases which are generated when adding the fluidizing agent to the concrete and then stirring and mixing them on the raw concrete car; problems of where the responsibility for the quality of the resultant fluidized concrete is assigned; and problems of great slump-decreasing with time of the fluidized concrete (hereinafter, the “slump-decreasing with time” is referred to as “slump loss”).
Thus, a so-called high performance AE water-reducing agent which can be added in a raw concrete plant is energetically developed. However, it is the present condition that there are cases where the slump loss cannot sufficiently be suppressed under hard usage conditions such that the resultant raw concrete is transported to a remote place in summer.
On the other hand, in winter when the temperature is low, the water-reducibility deteriorates, and the required amount of the water-reducing agent added to obtain a predetermined fluidity therefore increases, so there are problems about the quality management of the concrete.
SUMMARY OF THE INVENTION
A. Object of the Invention
It is an object of the present invention to provide a cement admixture and a cement composition, both of which displays little dependence of the water-reducibility upon temperature in that these cement admixture and cement composition involve little slump loss at high temperature and little increase in the amount of addition at low temperature.
B. Disclosure of the Invention
Conventional cement admixtures, comprising a copolymer as obtained by copolymerizing a polyalkylene glycol (meth)acrylate with an unsaturated carboxylic acid, are disclosed in JP-A-08-268741, JP-A-08-053522, JP-A-07-247150, JP-A-06-092703, and JP-A-06-144906. In addition, a cement admixture, comprising two copolymers as obtained by copolymerizing a polyalkylene glycol (meth)acrylate with (meth)acrylic acid, is disclosed in JP-A-09-040446.
The cement admixtures as disclosed in the above publications all have an object to reduce the unit water amount or to prevent the slump loss, but none of them has an object to lessen the dependence of the water-reducibility upon temperature, namely, to prevent the slump loss at high temperature and to reduce the amount of addition at low temperature.
The present inventors studied with encouragement to themselves to accomplish the above object of the present invention. As a result, the inventors have completed the present invention by finding that the above object of the present invention cannot be achieved until a copolymer is obtained by copolymerizing comonomers which include at least two specific monomers as the polyalkylene glycol (meth)acrylate and merely have an unsaturated carboxylic acid content of 45 weight % or less, wherein the specific monomers have an average molar number of addition of the oxyalkylene groups, constituting a polyalkylene glycol chain, of 10 or more and includes a terminal aliphatic or alicyclic hydrocarbon group with 1 to 30 carbon atoms.
Thus, a cement admixture, according to the present invention, comprises either or both of the following components:
copolymer (A) which includes constitutional unit (I) of general formula (1) below and constitutional unit (II) of general formula (2) below as essential constitutional units and may further include constitutional unit (III) of general formula (3) below, wherein the content of constitutional unit (III) is 45 weight % or less of copolymer (A); and
copolymer salt (B) which is obtained by further neutralizing copolymer (A) with an alkaline substance;
wherein general formula (1) is
wherein: each of R
1
O and R
3
O denotes one kind of oxyalkylene group with 2 to 18 carbon atoms or a mixture of two or more kinds thereof, wherein the mixture may be formed by either block addition or random addition; each of m and n is an average molar number of addition of the oxyalkylene groups and denotes a positive number of 10 or more; and each of R
2
and R
4
denotes an aliphatic or alicyclic hydrocarbon group with 1 to 30 carbon atoms, and
wherein general formula (3) is
wherein: R
5,
R
6
and R
7
, independently of each other, denote a hydrogen atom, a methyl group or a (CH
2
)
p
COOX group; X denotes a hydrogen atom, a monovalent metal, a divalent metal, an ammonium group or an organic amine group; and p denotes an integer of 0 to 2; wherein two COOX groups may form an anhydride, if any.
Another cement admixture, according to the present invention, comprises either or both of the following components:
copolymer (C) which is obtained by copolymerizing comonomers including monomer (a) of general formula (4) below and monomer (b) of general formula (5) below, wherein the comonomers may further include unsaturated carboxylic monomer (c) in a ratio of 45 weight % or less of the comonomers; and
copolymer salt (D) which is obtained by further neutralizing copolymer (C) with an alkaline substance;
wherein general formula (4) is
wherein: each of R
1
O and R
3
O denotes one kind of oxyalkylene group with 2 to 18 carbon atoms or a mixture of two or more kinds thereof, wherein the mixture may be formed by either block addition or random addition; each of m and n is an average molar number of addition of the oxyalkylene groups and denotes a positive number of 10 or more; and each of R
2
and R
4
denotes an aliphatic or alicyclic hydrocarbon group with 1 to 30 carbon atoms.
A cement composition, according to the present invention, comprises cement, either of the present invention cement admixtures as mentioned above, and water.
In comparison, the conventional copolymer, which is disclosed in JP-A-08-268741 above, merely has a short polyalkylene glycol chain, and the conventional copolymer which is disclosed in JP-A-08-053522 above is a copolymer as produced using large amounts of unsaturated carboxylic acid and hydrophobic monomer, and the conventional copolymer which is disclosed in JP-A-06-144906 above has an aromatic group at a terminal of the polyalkylene glycol chain. Therefore none of these conventional copolymers can achieve both the slump loss prevention at high temperature and the reduction in the amount of addition at low temperature. In addition, the conventional copolymers, which are disclosed in JP-A-07-247150, JP-A-06-092703, and JP-A-09-040446 above, all have a hydroxyl group at a terminal of the polyalkylene glycol chain and therefore easily gelate and involve difficulty in their industrial production. Even if these copolymers could be produced in a laboratory and were used as cement admixtures, a large amount of chain transfer agent to prevent the gelation would need to be added, so the water-reducibility would greatly deteriorate. However, in the present invention, a terminal of the polyalkylene glycol chain is an aliphatic or alicyclic hydrocarbon group, so the gelation doe
Hirata Tsuyoshi
Niwa Hirokazu
Yamashita Akihiko
Yuasa Tsutomu
Green Anthony
Nippon Shokubai Co. , Ltd.
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