Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-06-19
2002-08-13
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C528S271000, C526S317100, C526S332000, C524S745000, C524S770000
Reexamination Certificate
active
06433114
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method of producing polyetherester monomer and cement dispersion agents (or cement dispersants). It has been known to produce polyetherester monomer as an intermediate product by an esterification reaction of polyalkyleneglycol with a closed end and unsaturated carboxylic acid and to copolymerize this polyetherester monomer with vinyl monomers which are copolymerizable therewith to obtain vinyl copolymers that can be used widely as a dispersant, an antistatic agent, an antifogging agent, an emulsifier or an adherent. In such applications, the quality of the monomer to be used in such a copolymerization reaction, and in particular the quality of polyetherester monomer, is known to significantly affect the quality of the produced vinyl copolymer serving as a dispersant, an antistatic agent, an antifogging agent, an emulsifier or an adherent. In other words, if the quality of polyetherester monomer obtained as the intermediate product is not sufficiently high, vinyl copolymers produced therefrom cannot function satisfactorily as a dispersant, an antistatic agent, an antifogging agent, an emulsifier or an adherent.
U.S. Pat. Nos. 4,962,173 and 5,362,829, for example, disclosed water-soluble vinyl copolymers having polyalkyleneglycol chain as a side chain serving as cement dispersants capable of providing a superior fluidity characteristic with a small slump loss to hydraulic cement compositions such as mortar and concrete. Such a water-soluble vinyl copolymer is usually produced by first preparing polyetherester monomer as an intermediate product by an esterification reaction of polyalkyleneglycol with a closed end and unsaturated carboxylic acid and then copolymerizing it with vinyl monomers capable of copolymerizing therewith. In this case, the quality as a cement dispersant of the water-soluble vinyl copolymer which is obtained is significantly dependent on the quality of the monomer, and in particular that of polyetherester monomer, that is used in the copolymerization reaction. In other words, if the polyetherester monomer serving as an intermediate product is of a poor quality, fluidity cannot be provided to a satisfactory manner to a hydraulic cement composition when the water-soluble vinyl copolymer obtained therefrom is used as a cement dispersant. The lowering with time of the fluidity which has been provided (slump loss) is large in such a case, and products obtained by hardening such a hydraulic cement composition have a low compressive strength.
As disclosed in Japanese Patent Publications Tokkai 11-71151, 2000-159882, 2000-159883 and 2000-212273, such polyetherester monomers as described above have conventionally been produced by using an organic solvent with a low boiling point such as benzene in an esterification reaction of polyalkyleneglycol with a closed end and unsaturated carboxylic acid. Use of such an organic solvent with a low boiling point is advantageous in that it is possible to obtain polyetheresters of a fairly high quality. On the other hand, the solvent which has been used for the reaction must be collected and the cost of equipment therefor adds to the total production cost of the polyetherester, or that of the vinyl copolymer to be used as the intermediate product and that of the water-soluble vinyl copolymers serving as a cement dispersant. In addition, the workers will be forced to work in an undesirable environment due to some of the properties of these substances.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide a method of producing polyetherester monomer of a high quality without using a solvent.
It is another object of this invention to provide water-soluble vinyl copolymers capable of serving as a cement dispersant with improved properties, obtainable from such polyetherester monomer.
The present inventors discovered, as a result of work in view of the above objects, firstly that it is essentially important to use polyalkyleneglycol with a closed end of a high quality must be used as a starting material in order to obtain polyetherester monomers of a high quality. Polyalkyleneglycol with a closed end obtained by ring-opening addition reaction of alkylene oxide to a corresponding monohydroxy compound is usually used as the starting material and although such polyalkyleneglycol with a closed end obtained by a ring-opening addition reaction is produced industrially by a mass production process and stored until it comes to be used, that is, until polyetherester monomers are to be produced by an esterification reaction with unsaturated carboxylic acid, the present inventors also discovered that free acids which are mostly lower carboxylic acids such as formic acid, acetic acid and propionic acid are generated as by-products and remain, depending on the conditions of the ring-opening addition reaction and the refinement after the reaction. Similar free acids are generated and remain, depending in particular on the conditions at the time of the storage, and polyetherester monomers of a high quality cannot be produced from such polyalkyleneglycol with a closed end if the concentration of the residual free acids exceeds a certain minimum value.
As a result of further investigations, it was discovered that polyetherester monomers of a high quality can be obtained by an esterification reaction between polyalkyleneglycol which h as been refined such that the concentration of residual free acids (converted to acetic acid) is less than a specified value and unsaturated carboxylic acid under a specified condition in the absence of any solvent and presence of a specified amount of p-benzoquinone and/or phenothiazine. The present inventors also discovered that water-soluble vinyl copolymers obtained by a radical copolymerization reaction of such polyetherester monomers of a high quality with vinyl monomers which are copolymerizable therewith inside a water solution can be used as a cement dispersant with superior quality.
DETAILED DESCRIPTION OF THE INVENTION
This invention relates, on one hand, to a method of producing polyetherester monomer, shown by Formula 3 given below, through an esterification reaction of polyalkyleneglycol with a closed end, shown by Formula 1 given below, with the concentration of residual free acid (converted to acetic acid) less than 0.03 weight % and unsaturated carboxylic acid, shown by Formula 2 given below, in the absence of any solvent and under a heated and reduced-pressure condition in the presence of p-benzoquinone and/or phenothiazine in an amount corresponding to 0.03-0.5 weight % of the polyalkyleneglycol with a closed end, by using an acid catalyst and distilling away generated water:
R
1
—O—A—OH (Formula 1)
where R
1
is alkyl group with 1-22 carbon atoms, benzyl group, phenyl group or alkylphenyl group having alkyl group with 1-12 carbon atoms, R
2
and R
3
are each H or methyl group, and A is residual group obtained by removing all hydroxyl groups from polyalkyleneglycol of which the repetition number of oxyalkylene units (consisting either only of oxyethylene units or of both oxyethylene units and oxypropylene units) is 5-250. This invention relates, on the other hand, to cement dispersants characterized as comprising water-soluble vinyl copolymer obtained by a radical copolymerization reaction of polyetherester monomer produced by a method described above and vinyl monomers that can be copolymerized therewith.
Next, a method of producing polyetherester monomers of this invention will be explained. According to this invention, use is made of polyalkyleneglycol with a closed end shown by Formula 1 which has been refined such that the concentration of residual free acid (converted to acetic acid concentration) is less than 0.03 weight %, preferably less than 0.015 weight % and even more preferably less than 0.01 weight %. As explained above, polyalkyleneglycol with closed end is obtained by a ring-opening addition reaction of alkylene oxide with corresponding monohydroxy compound but lower carboxylic acids such as for
Kinoshita Mitsuo
Sugita Tetsuaki
Acquah Samuel A.
Beyer Weaver & Thomas LLP
Takemoto Yushi Kabushiki Kaisha
LandOfFree
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