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
1999-09-29
2001-08-21
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S239000, C525S331500, C524S465000, C524S455000, C524S568000, C428S339000, C428S518000
Reexamination Certificate
active
06277915
ABSTRACT:
FIELD OF INVENTION
The present invention relates to improved thermoplastic formulations exhibiting an improved combination of properties. A block chlorinated polyolefin can be added to vinyl halide resin compositions such as post chlorinated polyvinyl halide (CPVC) and polyvinyl chloride (PVC) to enhance the properties of impact modifiers selected from high rubber graft copolymers and conventional randomly chlorinated polyethylene (CPE). The synergetic effect of the block chlorinated polyolefin with the selected impact modifier dramatically enhances the impact properties of PVC and CPVC compositions. Blends of PVC, CPVC, and PVC/CPVC resins with the block chlorinated polyolefin and the selected impact modifiers have enhanced impact resistance, while retaining high heat distortion temperature (relative to the base CPVC or PVC) and good stress strain properties. The block chlorinated polyolefin comprises a polymeric product having both high chlorine content blocks (e.g., up to 50-75 wt. % chlorine) and relatively non-chlorinated crystallizable polyolefin blocks. The resulting polymer is characterized as blocky. The crystallizable polyolefin blocks are generally part of the same polymer that is chlorinated.
BACKGROUND OF INVENTION
Polyvinyl chloride and post chlorinated polyvinyl chloride, in order to perform adequately for the intended use is generally formulated with impact modifiers, and flow enhancing additives among other additives to arrive at a balance of properties. Each additive chosen for one particular advantage is often accompanied by a corresponding undesired effect in another property. Additives such as conventional randomly chlorinated polyethylenes (e.g., Tyrin® from Dupont Dow Chemical) have been used in PVC or CPVC blends, generally as a processing aid and impact modifier. These chlorinated polyethylenes have been randomly (relatively homogeneously) chlorinated by using a swelling solvent and/or a chlorinating temperature above the crystalline melting temperature of the polyethylene. Traditionally those who chlorinated polyethylene wanted to eliminate the crystalline polyethylene phase by chlorinating the crystallizable polyethylene segments, which inhibits or prevents further crystallization of the polyolefin. Residual crystalline fractions in a chlorinated polyethylene would require a processing temperature above the melting point while amorphous polyethylene fractions can be processed at a lower temperature. The use of higher chlorination temperatures and swelling solvents (which decrease residual crystallinity) also increase the rate of the chlorinating reaction, thus reducing costs. It has even been postulated that highly crystalline polyethylene would not be effectively chlorinated unless either it was heated above the crystalline melting temperature or the crystallinity was reduced by using a swelling solvent. This invention relates to the use of block chlorinated polyolefins as additives to improve the efficiency of selected impact modifiers such as high rubber graft copolymers or chlorinated polyethylenes in CPVC and PVC formulations.
SUMMARY OF INVENTION
Block chlorinated polyolefins (e.g., polyethylenes) can be prepared having from about 10 or 20 to about 60 wt. % bound chlorine based on the weight of the chlorinated polyolefin (e.g., polyethylene) and having from above about 25 to about 99 wt. % residual crystallizable polyolefin blocks, wherein said wt. % residual crystallizable blocks are expressed as a percentage based on the weight of crystallizable polyolefin in the polymer before chlorination. Such block chlorinated polyolefins can be prepared by a chlorination process employing a semi-crystalline polyolefin precursor comprising reacting the semi-crystalline polyolefin in a generally unswollen state at a temperature below its crystalline melting temperature with chlorine for a short period of time. Depending on the reaction conditions chosen (mostly time, chlorine pressure, and temperature), a free radical source, a catalyst, and/or UV radiation may be useful in the chlorination process. When the reaction conditions are suitable for quick chlorination, the amorphous portion of the polyolefin becomes highly chlorinated while the crystalline portion of the polyolefin remains significantly in the crystalline state.
Additives such as the block chlorinated polyolefin (e.g., block chlorinated polyethylene) can improve the performance of selected impact modifiers such as high rubber graft copolymers or conventionally chlorinated polyethylenes (amorphous chlorinated polyethylene) by enhancing their dispersability in PVC, CPVC, or PVC/CPVC blends. Without wishing to be bound by theory of invention it is believed that the block chlorinated polyolefins of this invention improve the adhesion between the impact modifier rubber phase and the PVC and/or CPVC.
DETAILED DESCRIPTION OF THE INVENTION
Block chlorinated polyolefins can be used to greatly enhance the impact performance of selected impact modifiers in PVC, CPVC, and PVC/CPVC blends. The resulting PVC, CPVC, or blended PVC/CPVC compound can be used for generally any application (e.g., vinyl siding, sheathing, tubing or pipe, molded articles, etc.). The impact modifiers arc selected from high rubber graft copolymers and conventional randomly chlorinated polyethylenes or mixtures thereof. These impact modifiers are currently used in PVC and CPVC formulations to impart good processability and impact strength. When a block chlorinated polyolefin is added in the proper amount to a high rubber graft copolymer or to a conventional chlorinated polyethylene impact modifier, the resulting impact properties of the PVC or CPVC formulations are dramatically enhanced. The block chlorinated polyolefins of the present invention enhance the properties of impact modifiers such as high rubber graft copolymers or randomly chlorinated polyethylenes.
The block chlorinated polyolefins are prepared by a chlorinating a polyolefin at low temperatures such that a substantial portion of the crystalline regions of the polyolefin backbone (e.g., polyethylene) remain crystalline and less effectively chlorinated than the amorphous regions of the polyolefin backbone. This results in a blocky polymer as each polymer chain usually has both crystalline and amorphous regions in the backbone. The semi-crystalline polyolefin precursor to the block chlorinated polyolefin has desirably at least above about 25 wt. %, desirably at least 30 wt. %, more desirably at least 45 wt. %, and preferably at least 50 wt. % crystalline polyolefin portions in the backbone. Unless otherwise defined weight percent (wt. %) crystallinity is measured by differential scanning calorimeter (DSC) on prepared samples of the polyolefin using a heating rate of 10C/min. starting at −150° C. and ending at 250° C. For the purpose of calculations the heat of melting (&Dgr;H) of crystalline polyolefin precursor is measured by DSC. For the chlorinated polyolefins the sample weight for &Dgr;H measurements excludes the weight of bound chlorine.
The polyolefin precursor desirably contains at least 85, more desirably at least 90, preferably at least 95 mole %, and more preferably at least 98 mole % repeat units polymerized from monoolefins of 2 to 10 carbon atoms. Preferably the repeating units of the polyolefin are polymerized from alpha-monoolefins having from 2 to 4 carbon atoms. Preferred alpha-monoolefins include ethylene, propylene, and butene, most preferably ethylene. The polyolefin can be prepared by any polymerization process but Ziegler-Natta, Phillips, and metallocene polymerization processes are preferred as they result in high weight percentages of crystallinity. The foregoing olefinic monomers can be polymerized with other copolymerizable monomers so long as the polymer properties are not deleteriously affected. Preferably the polyolefins have densities at 25° C. of from about 0.93, or 0.94 to about 0.965, 0.97, or 0.98 g/cc. Desirably they have crystalline melting temperatures from about 110-160° C. or 124° C. to about 130, 135 or 160° C. and melt index v
Detterman Robert Edwin
Lepilleur Carole Angele
Asinovsky Olga
Calloway Valerie L.
Dunlap Thoburn T.
Nutter Nathan M.
PMD Holdings Corporation
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