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
2002-06-24
2003-11-04
Lipman, Bernard (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...
C106S728000, C524S005000, C525S384000
Reexamination Certificate
active
06642320
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to multi-functional cement dispersants and hydraulic cement compositions. Hydraulic cement compositions such as mortar and concrete are required to have several characteristics simultaneously. Not only should they have a superior fluidity, but it should not deteriorate quickly over the time, and hardened objects obtained therefrom should have a superior early strength, a small dry shrinkage ratio and a high resistance against freezing and thawing. This invention relates to multi-functional cement dispersants capable of providing such multiple functions simultaneously to hydraulic cement compositions, as well as hydraulic cement compositions possessing such multiple functions simultaneously.
BACKGROUND OF THE INVENTION
Many kinds of compounds of polycarboxylic acid have been known as a cement dispersant capable of providing hydraulic cement compositions with superior fluidity which does not deteriorate over the time (U.S. Pat. Nos. 4,471,100 and 4,962,173, EPA 753,488, and Japanese patents 2507280, 2541218 and 2676854). These prior art cement dispersants were not satisfactory because they were not sufficiently effective in reducing the dry shrinkage of hardened objects obtained therefrom and in providing resistance to such hardened objects against freezing and thawing. Many kinds of agents for reducing dry shrinkage for use with hydraulic cement compositions have also been known (U.S. Pat. No. 4,547,223, Japanese Patent Publications Tokko 56-51148 and 6-6500) and are being used together with such compounds of polycarboxylic acid as mentioned above in order to improve conditions when they are used as cement dispersant. In such applications, however, the work of preparing hydraulic cement composition becomes complicated and the quality control becomes difficult. If it is attempted to obtain a practical effect in reducing dry shrinkage, it is necessary to add a large amount of such an agent and this affects the cost of production, but there still remains the problem of low efficiency in providing resistance against freezing and thawing to hardened objects. Although cement dispersants with the effect of reducing dry shrinkage of hardened objects have been known (Japanese Patent Publications Tokkai 8-268741 and 2000-34151), such prior art cement dispersants have the problems such that hardened objects obtained therewith do not show early strength and are still not sufficiently effective in providing hardened objects with resistance against freezing and thawing.
SUMMARY OF THE INVENTION
The problem for the invention is to provide multi-functional cement dispersants such that hydraulic cement compositions produced therewith have a superior fluidity which does not deteriorate over the time and hardened objects obtained therefrom have a superior early strength, a low dry shrinkage and a high resistance against freezing and thawing.
The invention is based on the discovery by the present inventors as a result of their diligent researches in view of the object described above that graft copolymers of a certain kind or their salts should be used.
The invention relates to multi-functional cement dispersants characterized as comprising graft copolymers obtained by the following two steps which are herein referred to as the “first step” and the “second step”. The first step is a step of obtaining copolymers with average numerical molecular weight 3000-50000 by radical polymerization of a mixture of radical polymerizable monomers containing maleic anhydride and monomers of the form given by Formula 1 given below, together in an amount of 85 molar % or more of the mixture and at molar ratio of 50/50-80/20, Formula 1 being:
CH
2
═CH—CH
2
—O—A—O—R (Formula 1)
where R is acyl group with 1-18 carbon atoms, alkyl group with 1-3 carbon atoms or hydrogen, and A is a residual group obtained by removing all hydroxyl groups from polyalkylene glycol with repetition number of oxyalkylene units equal to 5-80, the oxyalkylene units consisting only of oxyethylene units or of both oxyethylene units and oxypropylene units.
The second step is a step of obtaining the graft copolymers by a graft reaction, in the presence of a basic catalyst, of 100 weight parts of the copolymers obtained in the first step and 3-35 weight parts of one or more selected from the group consisting of polyoxyalkylene monoalkylester (having a block addition of a total of 2-10 moles of ethylene oxide and propylene oxide to one mole of aliphatic carboxylic acid with 1-6 carbon atoms), polyoxyalkylene monoalkylether (having a block addition of a total of 2-10 moles of ethylene oxide and propylene oxide to one mole of aliphatic alcohol with 1-6 carbon atoms), and polypropyleneglycol with repetition number of oxypropylene units equal to 3-15.
The invention also relates to multi-functional cement dispersants characterized as comprising salts of graft copolymers obtained by the aforementioned two steps and also still another step which is herein referred to as the “third step” and is a step of obtaining the salts of graft copolymers by neutralizing the graft copolymers obtained in the second step with one or more selected from the group consisting of alkali metal hydroxide, alkali earth metal hydroxide and amines.
The invention further relates to hydraulic cement products characterized as being obtained by adding any of aforementioned multi-functional cement dispersants in an amount of 0.05-4.0 weight parts to 100 weight parts of cement.
In summary, multi-functional cement dispersants comprising (1) graft copolymers obtained by the aforementioned first and second steps and (2) salts of graft copolymers obtained by the aforementioned first, second and third steps are both within the scope of this invention. The first step is for obtaining copolymers by radical polymerization of a mixture of radical polymerizable monomers. According to this invention, the first step uses a mixture containing maleic anhydride and monomers of Formula 1 at a molar ratio of 50/50-80/20, and preferably 60/40-70/30.
Examples of what A may be in Formula 1 include (1) residual groups obtained by removing all hydroxyl groups from (poly)ethylene glycol of which oxyalkylene units consist only of oxyethylene units, and (2) residual groups obtained by removing all hydroxyl groups from (poly)ethylene (poly)propylene glycol of which oxyalkylene units consists of both oxyethylene units and oxypropylene units. In the case of (2), the combination of oxyethylene units and oxypropylene units may be by random addition or block addition, but (1) is preferred. The repetition number of the oxyalkylene units in A is 5-80, but it is preferably 15-70.
Examples of what R may be in Formula 1 include (1) acyl groups with 1-18 carbon atoms such as formyl group, acetyl group, propionyl group, butyryl group, isobutyryl group, valeryl group, isovaleryl group, hexanoyl group, heptanoyl group, octanoyl group, nonanoyl group, decanoyl group, hexadecanoyl group, octadecanoyl group, hexadecenoyl group and octadecenoyl group, (2) alkyl groups with 1-3 carbon atoms such as methyl group, ethyl group, propyl group and isopropyl group, and (3) hydrogen. Among these, acyl groups with 1-18 carbon atoms are preferred and acetyl group is particularly preferred.
Practical examples of monomers of Formula 1 used in the first step according to this invention include (1) &agr;-allyl-&ohgr;-alkyloyl-(poly)oxyethylene, (2) &agr;-allyl-&ohgr;-alkyloyl-(poly)oxyethylene (poly)oxypropylene, (3) &agr;-allyl-&ohgr;-alkyl(with 1-3 carbon atoms)(poly)oxyethylene, (4) &agr;-allyl-&ohgr;-alkyl(with 1-3 carbon atoms)-(poly)oxyethylene (poly)oxypropylene, (5) &agr;-allyl-&ohgr;-hydroxy-(poly)oxyethylene, and (6) &agr;-allyl-&ohgr;-hydroxy-(poly)oxyethylene (poly)oxypropylene.
The mixture of radical polymerizable monomers in the first step contains maleic anhydride and monomers of Formula 1 together in an amount of 85 molar % or more, and preferably 90 molar % or more. In other words, radical polymerizable monomers of other types may be contained in an amou
Ishimori Masaki
Kinoshita Mitsuo
Nakanishi Hiroshi
Sugamata Takumi
Sugiyama Tomomi
Beyer Weaver & Thomas LLP
Lipman Bernard
Taiheiyo Cement Kabushiki Kaisha
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