Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-03-02
2003-02-18
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S603000, C524S801000, C524S845000
Reexamination Certificate
active
06521679
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a polyester aqueous dispersion having excellent properties in waterproof, weatherproof, processibility, adhesion, etc. and a method for preparing the aqueous dispersion in a high efficiency at low production costs.
TECHNICAL BACKGROUND
Organic solvents have been heretofore employed in large quantities in the fields of paints, ink, coating agents, adhesives, primers and various agents for treating fiber materials or paper. However, a shift to a technology of using alternative materials for the organic solvent has been desired in view of saving petroleum resources, prevention of environmental pollution, improvement on safety in terms of flammability, etc., improvement in the working environment or the like in these years. For these purposes, a variety of techniques using the aqueous system, powder system or high solids system, etc. have been proposed and attempted to apply these techniques so far. Inter alia, aqueous dispersions are most suitable for general-purpose use because of easy handling and are considered to be promising.
As substances for use in aqueous dispersions, polyester type resins will be potential candidates that are to be used widely in the application fields of paints, ink, coating agents, adhesives, primers, etc., since these resins possess excellent coating processability and good adhesion to various base materials.
In view of the foregoing state of art, it has been attempted to develop techniques that enable to use polyester type resins in the aqueous system but special plants or complicated production steps are required or introduction of hydrophilic groups into the resins results in a reduced waterproof property. Thus, it is the actual situation that any useful technique has not yet been developed in terms of industrial application.
For the aqueous dispersion system of polyester, for example, a method through graft modification of low molecular weight polyesters is known by U.S. Pat. No. 3,634,351, Japanese Patent Publication No. Sho 57-57065 and U.S. Pat. No. 4,517,322. Furthermore, Japanese Patent Application Laid-Open Nos. Sho 59-223374 and 62-225510, Japanese Patent Publication No. Sho 61-57874 and Japanese Patent Application Laid-Open No. Hei 3-294322 are known to provide unsaturated copolymerized polyesters of high molecular weight. However, these proposals are yet unsatisfactory in terms of adhesion, processibility or productivity.
For dispersion of high molecular weight copolymerized polyester resins in water, there is also known a method for copolymerizing hydrophilic raw materials in copolymerized polyester resins. For example, methods for homopolymerizing or copolymerizing materials containing raw material containing metal sulfonates group, polyalkylene glycol or aliphatic dicarboxylic acids, etc. are also known (e.g., see Japanese Patent Application Laid-Open Nos. Hei 3-234760, 7-216210 and 8-245769).
Polyester dispersions may be obtained either by dispersing these polyester resins in water-containing solvent all together or by previously dissolving polyester resins in an organic solvent and then adding water to the solution at a later step.
In the aqueous dispersion thus obtained, however, many hydrophilic groups are introduced into the resins so that the resulting films and fine particles are extremely hygroscopic. For this reason, waterproof, weatherproof and adhesion properties are poor. Moreover, when large quantities of resins are dissolved in a small amount of organic solvent, a very heavy load is placed on production facilities such as a dissolution tank equipped with a stirrer and, it takes long time until resins are dissolved, which leads to increased costs. These were the defects in preparation.
In addition, conventional techniques for converting polyesters to the aqueous dispersion system only give aqueous dispersions of low solid contents, which encounter various problems for practical use. For instance, problems involved are the large volume due to a large quantity of water, which in turn requires extensive space and much labor for storage, packaging, transportation, etc.; freezing at low temperatures; limited allowances in controlling physical properties of liquid such as solid contents, pH, viscosity, etc.; and much time and energy are required for drying to powders.
As described above, the foregoing polyester aqueous dispersions proposed by conventional techniques involved various problems to be solved in terms of physical properties, production and practical use.
As one proposal to solve the problems described above, Japanese Patent Publication No. Hei 7-8933 discloses an aqueous dispersion containing an olefin resin, an olefin polymer containing a specific amount of carboxylates, an anionic surfactant and water, as well as a method for preparing the aqueous dispersion by adding a specific amount of basic material and water to a molten kneaded mixture thereby to cause phase inversion of the molten resin into the desired aqueous dispersion. Japanese Patent Application Laid-Open No. Hei 10-139884 discloses a method in which ionic functional groups or functional groups that can be converted into ionic groups are dispersed in an aqueous dispersion medium using a twin screw extruder.
The present inventors extensively investigated techniques that could produce superior polyester aqueous dispersions to those known proposals and as a result, have reached the present invention.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a polyester aqueous dispersion having excellent properties in waterproof, weatherproof, processibility, adhesion, etc., which can control physical properties more freely by post-treatment and is also advantageous in converting the dispersion into dry powders.
Another object of the invention is to provide a method for preparing such a polyester aqueous dispersion having excellent properties efficiently and readily at low costs.
In order to achieve the foregoing objects, the inventors have made further studies. As a result, the inventors have found that for preparing the aqueous dispersion of polyester (i), polyester (ii) having a good compatibility with (i) and containing a specific amount of sulfonates as a hydrophilic group is extremely effective as a dispersing agent.
That is, the present invention provides a polyester aqueous dispersion comprising:
(A) a water-insoluble polyester (i) and,
(B) a polyester (ii) containing a sulfonate group bound to a polymer in a concentration of 0.1 to 1.5 mmol equivalents when calculated as —SO
3
−
group per gram of the polymer.
In a preferred embodiment of the invention, the polyester aqueous dispersion is solid in appearance and by adding water thereto, the solid component is uniformly dispersible in an aqueous phase as fine particles.
Therefore, the present invention also provides an polyester aqueous dispersion in which the polyester aqueous dispersion is dispersed in water or in a basic aqueous solution.
Furthermore, the invention provides, as a method that can provide such an excellent polyester aqueous dispersion, a method which comprises
a step of melt-kneading a resin composition comprising (i) a water-insoluble polyester and (ii) a polyester containing a sulfonate group bound to a polymer in a concentration of 0.1 to 1.5 mmol equivalents when calculated as —SO
3
−
group per gram of the polymer
and a step of phase inversion of adding water or a basic aqueous solution to the molten kneaded mixture thereby to shift the resin composition into the aqueous dispersion.
In a preferred method of the invention, water or a basic aqueous solution is added in the phase inversion step in such an amount that the polyester aqueous dispersion contains 1 to 40 wt % of water or a basic aqueous solution.
In a still preferred embodiment of the invention, the method comprises performing the melt-kneading step and the phase inversion step described above, by means of a twin screw extruder.
SPECIFIC EMBODIMENTS OF THE INVENTION
Hereinafter the polyester aqueous dispersion of the invention and the met
Kaya Hidenori
Okada Yasuo
Tokita Suguru
Birch & Stewart Kolasch & Birch, LLP
Mitsui Chemicals Inc.
Yoon Tae H.
LandOfFree
Polyester aqueous dispersion and method for preparation thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polyester aqueous dispersion and method for preparation thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polyester aqueous dispersion and method for preparation thereof will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3176430