Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
1999-02-17
2001-01-23
Wood, Elizabeth D. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S724000, C106S725000, C106S802000, C106S823000, C524S650000, C524S002000, C524S003000, C524S004000, C524S005000, C524S006000, C524S007000, C524S008000, C524S009000, C524S010000, C526S240000, C526S287000
Reexamination Certificate
active
06176921
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to cement dispersants and methods of how to use them to produce better concrete. At work sites where cement compositions are used, it is important to be able to provide high fluidity to cement compositions, to reduce the drop in the provided fluidity with time (“the slump loss”) and to obtain a sufficient early strength during the initial period of hardening such that the frames can be removed quickly and the work efficiency can be thereby improved. This invention relates to cement dispersants which can respond to such requirements, as well as methods of using such cement dispersants to produce concrete with improved quality. This invention related also to concrete produced by using such a cement dispersant.
Examples of prior art cement dispersant for providing fluidity to cement compositions include salts of high condensates of naphthalene sulfonic acid formaldehyde and melamine sulfonic acid formaldehyde, as well as water-soluble vinyl copolymers. Cement compositions prepared by using salts of high condensates of naphthalene sulfonic acid formaldehyde or melamine sulfonic acid formaldehyde, however, have the problem of a high slump loss. Those prepared by using water-soluble vinyl copolymers of the conventionally proposed kind (such as disclosed in Japanese Patent Publications Tokko 58-38380, 59-18338 and 5-11057 and U.S. Pat. Nos. 4,962,173, 5,087,648, 5,290,869 and 5,362,829) have smaller slump losses but there are problems wherein their setting times become longer and hence a sufficient early strength cannot be obtained during the early period of hardening. This problem is particularly significant with high-strength cement compositions with a limited water-to-cement ratio.
SUMMARY OF THE INVENTION
The problem to be overcome by the present invention is that prior art cement dispersants could produce only cement compositions with a large slump loss or incapable of providing a sufficiently large early strength, this problem being particularly significant with high-strength cement compositions with a limited water-to-cement ratio.
The present invention was accomplished as a result of investigations by the present inventors and is based on their discovery that water-soluble vinyl copolymers constituting of specified kinds of constituent units (herein referred to simply as “units”) at a specified ratio and having both the weight average molecular weight and the ratios between the weight average molecular weight and the number average molecular weight within a specified range are suitable as a cement dispersant.
DETAILED DESCRIPTION OF THE INVENTION
This invention relates to cement dispersants which are water-soluble vinyl copolymers constituting of 40-80 molar % of Unit A shown below by Formula (1), 0.5-20 molar % of Unit B shown below by Formula (2), 0.2-18 molar % of Unit C shown below by Formula (3) and 2-40 molar % of Unit D shown below by Formula (4) such that the total is 100 molar %, the weight average molecular weight (hereinafter always pullulan converted by GPC method) being 15000-150000 and the ratio of weight average molecular weight to number average molecular weight being 2-7, Formulas (1)-(5) being as follows:
where R
1
, R
2
and R
3
are each either H or CH
3
, R
4
is H or an alkyl group with 1-3 carbon atoms, X is a group shown below by Formula (5) or (6),
—SO
3
M
2
(Formula 5)
—O—C
6
H
4
—SO
3
M
3
(Formula 6)
A is the residual group obtainable by removing all hydroxyl groups from polyether diol with the repetition number of oxyalkylene units (which consist either only of oxyethylene units or of both oxyethylene and oxypropylene units) being 5-109, M
1
is H, an alkali metal, an alkali earth metal, ammonium or an organic amine, and M
2
and M
3
are each an alkali metal, an alkali earth metal, ammonium or an organic amine.
Cement dispersants of this invention are a water-soluble vinyl copolymers having four constituent units described above but those having as Unit D both Unit E shown below by Formula (7) and Unit F shown below by Formula (8) are preferred:
where R
5
is H or CH
3
, R
6
is an alkyl group with 1-3 carbon atoms, n is an integer 40-109 and m is an integer 5-25. In other words, preferred kinds of water-soluble vinyl copolymers according to this invention include not only Units A, B and C shown by Formulas (1), (2) and (3) but also a relatively long polyoxyethylene graft chain due to Unit E of Formula (7) and a relatively short chain polyoxyethylene graft chain.
These constituent Units A, B, C and D, or Units A, B, C, E and F in the case of an aforementioned preferred example, can all be formed by copolymerizing corresponding vinyl monomers. Examples of vinyl monomers which form Unit A shown by Formula (1) include (1) (meth)acrylic acid, and (2) alkali metal salts, alkali earth metal salts and organic amine salts of (meth)acrylic acid. Of these, alkali metal salts such as sodium and potassium salts of (meth)acrylic acid are preferred.
Examples of vinyl monomers which form Unit B shown by Formula (2) include (1) alkali metal salts, alkali earth metal salts and organic amine salts of methallyl sulfonic acid, and (2) alkali metal salts, alkali earth metal salts and organic amine salts of p-methallyl oxybenzene sulfonic acid. Of these, alkali metal salts such as sodium and potassium salts of methallyl sulfonic acid are preferred.
Examples of vinyl monomers which form Unit C shown by Formula (3) include methyl acrylate and methyl methacrylate. Of these, methyl acrylate is preferred.
Examples of vinyl monomers which form Unit D shown by Formula (4) include (1) alkoxy polyoxyalkylene glycol (meth)acrylate with 1-3 carbon atoms and (2) polyoxyalkylene glycol mono(meth)acrylate, both with repetition number of oxyalkylene units 5-109. Examples of (1) above include methoxy polyethylene glycol (meth)acrylate, methoxy polyethylene glycol polypropylene glycol (meth)acrylate, methoxy polypropylene glycol (meth)acrylate, ethoxy polyethylene glycol (meth)acrylate, ethoxy polyethylene glycol polypropylene glycol (meth)acrylate, ethoxy polypropylene glycol (meth)acrylate, n-propoxy polyethylene glycol (meth)acrylate, n-propoxy polyethylene glycol polypropylene glycol (meth)acrylate, isopropoxy polyethylene glycol mono(meth)acrylate, and isopropoxy polyethylene glycol polypropylene glycol (meth)acrylate. Examples of (2) above include polyoxyalkylene glycol mono(meth)acrylates such as polyethylene glycol mono(meth)acrylate, polyethylene glycol polypropylene glycol mono(meth)acrylate, and polypropylene glycol mono(meth)acrylate. Of these, methoxy polyethylene glycol methacrylate and polyethylene glycol monomethacrylate with oxyalkylene units including only oxyethylene units and their repetition number in the range of 26-95 are preferred.
Examples of vinyl monomers which form Unit E shown by Formula (7) include alkoxy polyethoxyethyl (meth)acrylates with 1-3 carbon atoms and the repetition number of oxyethylene units in the range of 40-109 such as methoxy polyethoxyethyl (meth)acrylate, ethoxypolyethoxyethyl (meth)acrylate, n-propoxy polyethoxyethyl (meth)acrylate, and isopropoxy polyethoxyethyl (meth)acrylate. Of these, methoxy polyethoxyethyl methacrylates with the repetition number of oxyethylene units in the range of 55-100 are preferred.
Examples of vinyl monomers which form Unit F shown by Formula (8) include methoxy polyethoxyethyl methacrylates with the repetition number of oxyethylene units in the range of 5-25. Of these, methoxy polyethoxyethyl methacrylates with the repetition number of oxyethylene units in the range of 7-23 are preferred.
Water-soluble vinyl copolymers to be used as a cement dispersant according to this invention may be obtained by radical copolymerization of vinyl monomers forming Units A-D, or preferably Units A, B, C, E and F at a specified copolymerization ratio in the presence of a radical initiator. The radical copolymerization can be carried out by aqueous solution polymerization using water or a mixed solvent with water and a water-soluble organic solvent
Iida Masahiro
Kinoshita Mitsuo
Okada Kazuhisa
Majestic, Parsons, Siebert & Hsue P.C.
Takemoto Yushi Kabushiki Kaisha
Wood Elizabeth D.
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