Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-08-14
2002-01-08
Reddick, Judy M. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C524S459000, C524S503000, C526S201000
Reexamination Certificate
active
06337378
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a suspension polymerization process for polymerizing a vinyl chloride monomer or a mixture of a vinyl chloride monomer and a monomer copolymerizable therewith (hereinafter, referred to as a vinyl chloride-based monomer). In more details, this invention relates to a process for producing a polyvinyl chloride paste blending resin, which is suitable for mixing with a polyvinyl chloride paste resin and then, adding a plasticizer thereto to make a pastisol and an organosol, and whose waste-water treatment in the production process is easy and a quality of waste-water after the treatment is good.
PROIR ART
A polyvinyl chloride paste resin (hereinafter, referred to as a paste resin) is obtained by a process comprising kneading with compounding ingredients such as a plasticizer, a diluent, a stabilizer, a filler and the like to thereby give a plastisol and an organosol (hereinafter, referred to as a sol), and molding thus-obtained sol by such a method as dipping, slush, rotation or coating, followed by heating it for gelation and fusion. A moldability in this process is influenced largely by a flowability of the sol, and particularly in coating method, a paste blending resin (hereinafter, referred to as a paste blending resin) is used together in order to reduce a viscosity of a sol and to improve flowability.
Generally, a paste resins is produced by a micro-suspension polymerization or an emulsion polymerization. By the former process, a particle diameter of a paste resin usually shows a polydisperse-type distribution between 0.1 and 3 &mgr;m, while by the latter process, a particle diameter of a paste resin usually shows several monodisperse-type distribution between 0.1 and 3 &mgr;m.
On the other hand, a paste blending resin used as an improving agent for flowability of a sol has a particle diameter ranging from 20 to 60 &mgr;m, which is larger than that of a paste resin and is smaller than that of an usual polyvinyl chloride resin (hereinafter, referred to as PVC resin) having a particle diameter ranging from 100 to 200 &mgr;m. It is desirable that a shape of the paste blending resin particle is a low porosity, uniform spherical glassy bead having the smooth surface and that it has an appropriate affinity with a plasticizer and that articles molded by heating have excellent mechanical properties. For producing the paste blending resin, a suspension polymerization process for polymerizing a vinyl chloride-based monomer is usually applied.
It is desirable that a quantity of coarse particles in a paste blending resin is as small as possible, because the paste blending resin is used as a part of a paste sol. Thus it is required to lower a production of coarse particles both in steps of polymerization and in steps of dehydration and drying of a slurry after polymerization.
Thus, in order to obtain a paste blending resin having a small particle diameter, it is needed to use a larger quantity of a suspending agent in suspension polymerization, compared with a process for producing an usual PVC resin, and therefore, it is the actual condition that a quality of waste-water from a polymerization step for a paste blending resin is very poor compared with that of an usual PVC resin.
On the other hand, a quality of waste-water has recently been regulated not only by a biochemical oxygen demand (BOD) but also by a chemical oxygen demand (COD). Since a waste-water, the BOD value of which is in the range of the regulation but which is difficult to be biologically decomposed, has largely been highlighted, a technically and economically appropriate treatment for waste-water before a discharge is required in order to meet with these environmental regulations.
Various processes for producing a paste blending resin have been proposed, but generally used is a process which comprises polymerizing with aid of a mechanical dispersion force or combined use thereof with an emulsifier. copolymerizing a particular monomer, adding a particular compound using a water-soluble polymer as a suspending agent. For example, there are proposed a process comprising performing a suspension polymerization by using a water-soluble protein (gelatin etc.) as a suspending agent and treating a polymer obtained thereby by a protease (Japanese Kokai Publication Sho-55-145709); a process comprising using gelatin and polyvinylpyrolidone as suspending agents (Japanese Kokai Publication Sho-5688406); a process comprising polymerizing in the presence of a cellulose-type suspending agent and treating the obtained polymer with cellulase (Japanese Kokai Publication Sho-57-98504); a process comprising performing a polymerization in the presence of ethylene/vinyl acetate copolymer by using a cellulose-type suspending agent (Japanese Kokai Publication Sho-58-103513) and the like.
However, in the process of using a water-soluble protein such as a gelatin as a suspending agent, the water-soluble protein is a natural substance and a stability in a polymerization step and a quality is largely variable, and further a polymer obtained needs to be treated with a protease in order to sustain mechanical properties of the product molded by heating and this treatment makes a cost of its production high. In the process of using polyvinylpyrolydone as a suspending agent, mechanical properties of a product molded by heating is good, but it is needed that a large amount of polyvinylpyrolydone must be added in order to get particles having a small diameter between 20 and 80 &mgr;m and a high price of polyvinylprolydone causes a high cost of its production to be high. Further, there are no appropriate treating methods for its waste-water. In the process of using a cellulose-type suspending agent, there are no appropriate methods by which the cellulose-type suspending agent dissolved in a waste-water coming from polymerization can be treated economically. As mentioned above, every conventional method has both merits and demerits, and it is the present status that any process can not be satisfactory.
SUMMARY OF THE INVENTION
Taking an account of the prior arts, the object of this invention is to provide a process for producing at a low cost and economically a polyvinyl chloride paste blending resin for a plastisol and an organisol which has an improving effect in a flowability of a sol as a paste blending resin and provides excellent mechanical properties for a product after molding by heating, and from which a resin can be produced with only a small quantity of coarse particles, a treatment of a waste-water is easy and a quality of a waste-water after treated is good.
After making many efforts to attain the purposes mentioned above, the inventors have accomplished this invention by finding a suspension polymerization by using a suspending agent mainly comprising a specified poly(vinyl alcohol) (hereinafter, referred to as PVA), to thereby obtain a polymer having excellent mechanical properties and characteristics as a paste blending resin, the waste-water of which can easily be treated by activated sludge after an usual flocculating process.
The first aspect of the present invention is a process for producing a polyvinyl chloride paste blending resin comprising polymerizing a vinyl chloride-based monomer by a suspension polymerization in an aqueous medium, wherein as a suspending agent, both (A) and (B) are used in a mixing weight ratio (A)/(B) of 99/1 to 50/50, and a total amount of said (A) and said (B) is 0.1 to 1.0 part by weight based on 100 parts by weight of the vinyl chloride-based monomer, said (A) being a partially hydrolyzed water-soluble poly(vinyl alcohol) having a viscosity at 20° C. of 4% aqueous solution by weight of 20 to 110 cps and the degree of hydrolysis ranging from 86 to 99 mol %, and said (B) being a partially hydrolyzed water-soluble poly(vinyl alcohol) having a viscosity at 20° C. of 4% aqueous solution by weight of 5 to 10 cps and the degree of hydrolysis ranging from 70 to 80 mol %.
The second aspect of the present invention is a process for producing a polyvinyl chloride paste b
Kobayashi Teiji
Koike Taizou
Kubo Masahiro
Yamamoto Taizou
Connolly Bove & Lodge & Hutz LLP
Kaneka Corporation
Reddick Judy M.
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