Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
1999-09-25
2001-07-10
Green, Anthony (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S724000, C106S727000, C106S728000, C106S802000, C106S808000, C106S823000, C524S005000
Reexamination Certificate
active
06258162
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Technical Field
The present invention relates to a cement additive, and more particularly, to a cement additive having excellent fluid retainability of a cement composition such as cement paste, mortar or concrete, and further, excellent mortar kneadability.
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 quantity of water in concrete. Thus, a lot of technological innovation is carried out to cement admixtures which have much influence on the quality and the capability of cement mixtures.
Especially, as to polycarboxylic cement dispersants, many proposals were made, because the polycarboxylic cement dispersants exhibit higher water reducibility than conventional cement dispersants such as naphthalenic ones. For example, JP-A-06-321596 and JP-A-06-279082 propose polymers as formed from a (meth)acrylic monomer in which an ester bond between polyalkylene glycol and (meth)acrylic acid is made through propylene oxide. However, even as to these polycarboxylic acids with oxyalkylene groups, it is insufficient to achieve excellent fluid retainability and excellent mortar kneadability.
As to the oxyalkylene group, as things stand, the above known patent publications (JP-A-06-321596 and JP-A-06-279082) disclose only oxyalkylene groups of which the chain length of ethylene oxide as linked to polypropylene oxide is short in acrylic esters.
As is mentioned above, the above conventional cement dispersants have problems in that they lack the fluid retainability and are still insufficient to shorten the kneading time of mortar and concrete.
SUMMARY OF THE INVENTION
A. Object of the Invention
An object of the present invention is to provide a cement additive which can achieve excellent fluid retainability and has excellent mortar kneadability, therefore, can shorten the production time of mortar and concrete and thereby enhance the productivity thereof.
B. Disclosure of the Invention
Acrylic esters have much more excellent mortar kneadability and water reducibility than methacrylic esters. However, on the other hand, acrylic esters more easily undergo hydrolysis of ester bonding in a cement alkali and more easily decrease the mortar or concrete fluidity with time than methacrylic esters. The present inventors diligently studied and, as a result, completed the present invention by finding that if the structure in a polyalkylene glycol ester unit is specified, it is possible to suppress the hydrolyzability of the ester moiety of the acrylic ester to thereby allow the acrylic ester to thoroughly exhibit its excellent performance, in other words, it is possible to achieve excellent fluid retainability and to enhance the mortar kneadability.
The structure in a polyalkylene glycol ester unit, as specified by the present invention, is described in detail below, but the point is briefed as follows:
(1) an alkylene oxide chain with a large number of carbon atoms is bonded to the ester bonding moiety (thereto the ethylene oxide chain is not bonded); and
(2) the proportion of the ethylene oxide chain in the alkylene oxide chain is high.
Thus, the present invention provides cement additives as shown in <1>to <4>below.
<1>The object is achieved with a cement additive which comprises copolymer (A) having polyalkylene glycol ester unit (I) of general formula (1) below as a repeating unit and carboxylic unit (II) of general formula (2) below as a repeating unit,
wherein general formula (1) is:
where:
R
1
O denotes an oxyalkylene group with 3 to 7 carbon atoms or a mixture of two or more thereof, wherein the mixture may be formed by either block addition or random addition;
R
2
O denotes an oxyalkylene group with 2 to 18 carbon atoms or a mixture of two or more thereof, wherein the mixture may be formed by either block addition or random addition;
R
3
denotes a hydrocarbon group with 1 to 3 carbon atoms;
n is an average molar number of addition of R
1
O and denotes a number of 1 to 50;
m is an average molar number of addition of R
20
and denotes a number of 35 to 300; and
not less than 80 mol % of the oxyalkylene groups (total of R
1
O and R
2
O) are oxyethylene groups;
and wherein general formula (2) is:
where:
R
4
denotes hydrogen or a methyl group; and
M denotes hydrogen, a monovalent metal, a divalent metal, ammonium, or an organic amine.
<2>The object is achieved also with a cement additive which comprises copolymer (B) as obtained by a process including the step of copolymerizing a monomer mixture including polyalkylene glycol ester monomer (IV) of general formula (3) below and carboxylic monomer (V) of general formula (4) below,
wherein general formula (3) is:
where the symbols are the same as those in general formula (1) above;
and wherein general formula (4) is:
where the symbols are the same as those in general formula (2) above.
<3>The object is achieved also with a cement additive which comprises copolymer (C) having polyalkylene glycol ester unit (VII) of general formula (5) below as a repeating unit and carboxylic unit (VIII) of general formula (6) below as a repeating unit,
wherein general formula (5) is:
where:
R
5
O denotes an oxyalkylene group with 4 to 7 carbon atoms or a mixture of two or more thereof, wherein the mixture may be formed by either block addition or random addition;
R
6
O denotes an oxyalkylene group with 2 to 18 carbon atoms or a mixture of two or more thereof, wherein the mixture may be formed by either block addition or random addition;
R
7
denotes a hydrocarbon group with 1 to 3 carbon atoms;
p is an average molar number of addition of R
5
O and denotes a number of 1 to 50;
q is an average molar number of addition of R
6
O and denotes a number of 1 to 300; and
not less than 80 mol % of the oxyalkylene groups (total of R
5
O and R
6
O) are oxyethylene groups;
and wherein general formula (6) is:
where:
R
8
denotes hydrogen or a methyl group; and
M′ denotes hydrogen, a monovalent metal, a divalent metal, ammonium, or an organic amine.
<4>The object is achieved also with a cement additive which comprises copolymer (D) as obtained by a process including the step of copolymerizing a monomer mixture including polyalkylene glycol ester monomer (X) of general formula (7) below and carboxylic monomer (XI) of general formula (8) below,
wherein general formula (7) is:
where the symbols are the same as those in general formula (5) above;
and wherein general formula (8) is:
where the symbols are the same as those in general formula (6) above.
These and other objects and the advantages of the present invention will be more fully apparent from the following detailed disclosure.
DETAILED DESCRIPTION OF THE INVENTION
The cement additive according to the present invention comprises at least one copolymer selected from the group consisting of copolymers (A) to (D).
Copolymer (A) is a copolymer which has repeating units (I) and (II). Copolymer (A) can be obtained by a process including the step of copolymerizing a monomer mixture including a monomer to give repeating unit (I) of general formula (1) above and a monomer to give repeating unit (II) of general formula (2) above. In addition, copolymer (A) can also be obtained by a process including the step of directly esterifying an alkoxypolyalkylene glycol with a polyacrylic acid or a poly(acrylic acid-methacrylic acid) copolymer.
In addition, copolymer (B) is a copolymer as obtained by a process including the step of copolymerizing a monomer mixture including monomers (IV) and (V).
Copolymer (C) is a copolymer which has repeating units (VII) and (VIII). Copolymer (C) can be obtained by a process including the step of copolymerizing a monomer mixture including a monomer to give repeating unit (VII) of general formula (5) above and a monomer to give repeating unit (VIII) of general formula (6) above. I
Hirata Tsuyoshi
Kawakami Hirokatsu
Niwa Hirokazu
Tanaka Hiromichi
Yuasa Tsutomu
Green Anthony
Nippon Shokubai Co. , Ltd.
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