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
1998-08-07
2001-06-26
Mullis, Jeffrey (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...
C525S301000, C525S309000, C525S313000
Reexamination Certificate
active
06252005
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for making thermally stable polymers of polymerizable acrylic monomers and grafted polymers of a propylene polymer material and a polymerizable acrylic monomer.
BACKGROUND OF THE INVENTION
Alpha-substituted polymers such as polymerized methacrylates, methacrylonitriles, and alpha-methylstyrene are thermally unstable and are known to depolymerize to their corresponding monomers at temperatures greater than ~180° C., depending upon the molecular weight of the polymer. Above 300° C., poly(methyl methacrylate)(PMMA) depolymerizes rapidly at high conversions (about 95% or more). Typical extruding and molding temperatures for such polymers are 200°-290° C. Significant depolymerization to the respective monomers would occur in this temperature range, affecting the safety of the operation as well as the properties of the resulting product. Polymethacrylates, and in particular PMMA, are the alpha-substituted polymers most widely used in commercial applications. In order to broaden the range of applications for these polymers it is critical to improve their thermal oxidative stability.
In the manufacture of grafted polymers comprising a backbone of a propylene polymer material, to which is grafted PMMA, small amounts of monomers such as methyl acrylate, butyl acrylate and styrene are typically copolymerized with the methyl methacrylate to improve thermal stability, since polymers of these monomers are much more stable to heat and undergo degradation at relatively higher temperatures. However, addition of these monomers affects the mechanical properties of the resulting grafted polymers as well as the molecular weight of the polymers and the efficiency of the graft polymerization reaction.
There is still a need for a method to increase the thermal oxidative stability of grafted polymers that include polymerized acrylic monomers, compared with that achievable with the comonomers currently used for this purpose.
SUMMARY OF THE INVENTION
The graft copolymer of this invention comprises a backbone of a propylene polymer material to which is graft polymerized chains of (i) an ester or salt of an unsubstituted or 1-3 C alkyl-substituted acrylic acid or (ii) an ester or salt of an unsubstituted or 1-3 C alkyl-substituted acrylic acid and about 1 to about 10 mole %, based on the total monomers added, of an unsubstituted or 1-3 C alkyl-substituted acrylic acid, having 4-ethylidene-substituted 5-12 C cyclic 1-alkene groups at the chain ends.
Another embodiment of this invention comprises a polymer of monomers selected from the group consisting of (i) an ester or salt of an unsubstituted or 1-3 C alkyl-substituted acrylic acid and (ii) an ester or salt of an unsubstituted or 1-3 C alkyl-substituted acrylic acid and about 1 to about 10 mole %, based on the total monomers added, of an unsubstituted or 1-3 C alkyl-substituted acrylic acid, having end groups comprising 4-ethylidene-substituted 5-12 C cyclic 1-alkene groups.
In another embodiment, the method of this invention for improving the thermal oxidative stability of acrylic grafted polymers comprises:
(a) graft polymerizing monomers selected from the group consisting of (i) an ester or salt of an unsubstituted or 1-3 C alkyl-substituted acrylic acid and (ii) an ester or salt of an unsubstituted or 1-3 C alkyl-substituted acrylic acid and about 1 to about 10 mole %, based on the total monomers added, of an unsubstituted or 1-3 C alkyl-substituted acrylic acid, to a backbone of a propylene polymer material in the presence of a 4vinyl-substituted 5-12 C cyclic 1-alkene, wherein the total amount of polymerized monomer is about 20 to about 200 parts per hundred parts of the propylene polymer material and the 4-vinyl-substituted cyclic 1-alkene is present in an amount of about 1 mole % to about 30 mole %, based on the total moles of monomers added, and
(b) removing any unreacted grafting monomer from the resulting grafted propylene polymer material, decomposing any unreacted initiator, and deactivating any residual free radicals in the material,
wherein steps (a) and (b) are carried out in a substantially non-oxidizing environment.
The 4-ethylidene-substituted cyclic 1-alkene groups attach at the ends of the chains of polymerized acrylic monomer and significantly increase the thermal oxidative stability of grafted as well as ungrafted polymer. The room temperature mechanical properties and molecular weight of the grafted polymer, and the grafting efficiency of the process are not adversely affected.
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Montell Technology Company BV
Mullis Jeffrey
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