Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-11-10
2002-10-22
Mulcahy, Peter D. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S487000, C524S519000, C524S523000, C524S527000
Reexamination Certificate
active
06469079
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a chlorinated vinyl chloride resin composition and pipes obtained by extruding the resin composition. More particularly, it relates to a chlorinated vinyl chloride resin composition having excellent thermal stability in molding and to extruded pipes obtained therefrom.
BACKGROUND OF THE INVENTION
Chlorinated vinyl chloride resin moldings are characterized by their high heat resistance and have been applied to use in relatively high temperatures in which conventional vinyl chloride resin moldings undergo heat deformation and do not stand use. For example, having a heat distortion temperature 20 to 40° C. higher than that of vinyl chloride resin moldings, chlorinated vinyl chloride resin molded pipes can be used as pipes for hot water. Additionally, chlorinated vinyl chloride resins can be molded into pipes by means of general-purpose extrusion equipment used for polyvinyl chloride. This is one of the factors broadening the utility of chlorinated vinyl chloride resins. The higher heat distortion temperature of chlorinated vinyl chloride resin moldings is also taken advantage of for use as sheeting for appliances that may be exposed to heat.
However, chlorinated vinyl chloride resins are inferior to vinyl chloride resins in thermal stability and are liable to scorch during molding. For example, they tend to undergo yellowing or in some cases develop burn marks during extrusion into pipes for hot water, only to produce products having no commercial value. Or, they tend to undergo yellowing or in some cases develop burn marks during calendering in obtaining heat-resistant sheeting, only to produce sheeting having no commercial value.
SUMMARY OF THE INVENTION
An object of the invention is to provide a chlorinated vinyl chloride resin composition having excellent thermal stability and extruded pipes thereof.
The above object is accomplished by a chlorinated vinyl chloride resin composition comprising 100 parts by weight of a chlorinated vinyl chloride resin and 0.2 to 1.5 parts by weight of zeolite, a chlorinated vinyl chloride resin composition containing a hydroxypolycarboxylic acid salt, or a chlorinated vinyl chloride resin composition comprising 100 parts by weight of a chlorinated vinyl chloride resin containing a hydroxypolycarboxylic acid salt and 0.2 to 1.5 parts by weight of zeolite.
The chlorinated vinyl chloride resin composition containing a hydroxypolycarboxylic acid salt and/or zeolite exhibits appreciably improved thermal stability. The chlorinated vinyl chloride resin composition containing both a hydroxypolycarboxylic acid salt and zeolite exhibits outstandingly improved thermal stability. The compositions of the invention are extremely advantageous for producing piping or sheeting.
DETAILED DESCRIPTION OF THE INVENTION
The vinyl chloride resin, which can be used as a starting material for the chlorinated vinyl chloride resin in the invention, includes homopolymers of vinyl chloride and copolymers of vinyl chloride and copolymerizable monomers, such as ethylene, propylene, vinyl acetate, allyl chloride, allyl glycidyl ether acrylic esters, and vinyl ethers.
The vinyl chloride resin preferably has an average degree of polymerization of 600 to 1500, still preferably 600 to 1300, particularly preferably 600 to 1200. Resin compositions prepared from vinyl chloride resins whose average degree of polymerization is less than 600 tend to have insufficient mechanical strength, and those prepared from vinyl chloride resins having an average degree of polymerization exceeding 1500 tend to be difficult to process.
The degree of the chlorinated vinyl chloride resin is preferably 62 to 70% by weight, still preferably 63 to 70% by weight, particularly preferably 64 to 70% by weight. Chlorinated vinyl chloride resins having a degree of chlorination of less than 62% by weight tend to fail to provide resin compositions with sufficient heat resistance, and those having a degree of chlorination exceeding 70% by weight have an increased melt viscosity so that the resulting resin compositions meet processing difficulties.
The resin composition according to the first aspect of the invention is characterized by comprising 0.2 to 1.5 parts by weight of zeolite per 100 parts by weight of a chlorinated vinyl chloride resin. Zeolite may be either naturally-occurring zeolite or synthetic one. In particular, calcium-substituted A type zeolite having a residual sodium content of not more than 10% by weight in terms of Na
2
O and a degree of calcium substitution of 42% or more is preferred; for it hardly develop foams during molding. CS-100, an additive for plastics available from Kousei K.K., is known as calcium-substituted A type zeolite having the above-described composition.
Zeolite is added in an amount of 0.2 to 1.5 parts by weight per 100 parts by weight of a chlorinated vinyl chloride resin. Addition of less than 0.2 part by weight of zeolite is practically ineffective in improving thermal stability. Because the effect of zeolite addition is saturated at 1.5 parts by weight, addition of more than this amount not only brings about no further improvement but causes foaming in molding.
The chlorinated vinyl chloride resin composition according to the second aspect of the invention is characterized in that the chlorinated vinyl chloride resin contains a hydroxypolycarboxylic acid salt. Addition of a hydroxypolycarboxylic acid salt brings about marked improvement in thermal stability. The hydroxypolycarboxylic acid salt which can be used in the invention includes salts formed of at least one carboxyl groups of hydroxypolycarboxylic acids, such as tartaric acid, malic acid, tartronic acid, &agr;-methylmalic acid, tetrahydrosuccinic acid, citric acid, and 1,2-dihydroxy-1,1,2-ethanetricarboxylic acid, with sodium, potassium, etc. The salt may have a free carboxyl group, and may have both sodium and potassium per molecule. Of these salts, sodium tartrate, potassium tartrate, sodium malate, and potassium malate are particularly effective in improving thermal stability.
The hydroxypolycarboxylic acid salt is suitably added to the chlorinated vinyl chloride resin in a concentration of 50 to 5000 ppm. In concentrations less than 50 ppm the effect on thermal stability may be insufficient. In concentrations exceeding 5000 ppm the transparency of the composition tends to be reduced, which is problematical for use as sheeting.
The chlorinated vinyl chloride resin composition according to the third aspect of the invention is characterized by comprising (a) the chlorinated vinyl chloride resin composition containing a hydroxypolycarboxylic acid salt according to the second aspect of the invention and (b) zeolite as used in the first aspect of the invention. The combination of the hydroxypolycarboxylic acid salt and zeolite achieves outstanding improvement on thermal stability in pipe extrusion.
The present invention is particularly effective when applied to chlorinated vinyl chloride resin compositions containing an impact modifier, an organotin heat stabilizer, and a lubricant as are commonly employed in the art. The combined use of these additives brings about enhanced usefulness of the composition in molding into piping or sheeting.
Useful impact modifiers include those generally used in chlorinated vinyl chloride resins, such as a methyl methacrylate-butadiene-styrene polymer (MBS), an acrylonitrile-butadiene-styrene polymer (ABS), butadiene or styrene-butadiene rubber to which methyl methacrylate-styrene-acrylonitrile is grafted (MABS), chlorinated polyethylene (CPE), and impact modifiers mainly comprising acrylic rubber.
In order to balance impact resistance with heat resistance, it is preferred to use the impact modifiers in a total amount of 3 to 14 parts by weight per 100 parts by weight of the chlorinated vinyl chloride resin. For the same purpose, it is preferred to use MBS and CPE jointly.
While MBS as an impact modifier is not particularly limited, MBS having a butadiene content less than 60% by weight is preferred. MBS having a butadiene content
Isshiki Minoru
Okuhara Toshio
Shiota Hiroaki
Suzuki Takeyuki
Tadokoro Tadashi
Kaneka Corporation
Mulcahy Peter D.
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