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
2002-05-13
2004-01-06
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...
C525S212000, C525S213000, C525S220000, C525S221000, C525S222000, C525S240000, C524S543000, C524S547000, C524S551000, C524S556000, C524S557000, C524S570000, C524S576000, C524S773000, C524S780000, C524S783000, C524S788000
Reexamination Certificate
active
06673870
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of polymer compositions that comprise a mixture or blend of polyolefins and hyperbranched polymers. In particular, the present invention relates to such polyolefin-containing compositions that exhibit improved tensile energy-to-break due to the inclusion of hyperbranched polymer.
BACKGROUND OF THE INVENTION
The physical, mechanical, processing, and/or aesthetic properties of polymers can be improved or modified by the incorporation of additives into the polymers. The range of additives available is large and selection of a particular one can be governed by many variables, including type of improvement or modification desired, efficiency of improvement or modification, cost, and effect on processing. For example, mechanical properties of polymers commonly sought to be improved with additives include tensile energy-to-break, elongation-to-break, strength, stiffness, and impact resistance.
In general, additives that modify the mechanical properties of polymers include: 1) chemical additives that are miscible with the polymer; 2) particulate fillers; and 3) fibrous reinforcements.
A wide variety of chemical additives are known for incorporation into polymers. Chemical additives used to modify mechanical properties of the polymer include impact modifiers and plasticizers. Impact modifiers improve the impact strength of the polymer, as the name suggests. Examples include elastomers, such as rubber. Plasticizers are added to improve processability of the polymer melt and/or improve flexibility of the final product. Examples of plasticizers include esters of phthalates, adipates, and mellitates. However, they typically do not substantially increase the tensile strength of the final product. Another disadvantage of plasticizers is that they typically are relatively high volatility materials, and can vaporize in the presence of high temperatures (such as exposure to direct sunlight).
Examples of particulate fillers, often referred to simply as fillers or extenders, are mineral particles such as clay, calcium carbonate, talc, and silicates. Such fillers typically decrease the cost of the final polymer product, although they can increase the weight and can have deleterious effects on mechanical properties of the polymer, such as increased brittleness.
Examples of fibrous reinforcements are glass, carbon, boron, and aramid fibers. Fibrous reinforcements can increase mechanical properties of the polymer, such as tensile strength, however they must typically be used in relatively large amounts in order to achieve a substantial improvement in such mechanical properties. Fibrous reinforcements are commonly added at levels of up to about 60% by weight of the final product. Incorporating such large amounts of additives in polymers can result in significant drawbacks. For example, due to surface energy differences between fillers and polymers, complete dispersion of certain fillers can be difficult, thereby reducing mechanical properties of the composition. In addition, the fibers can cause significant rates of wear on processing equipment. Finally, the density of many fibrous reinforcements can be high compared to that of the polymer, thus adding weight to the final product.
A simple way to estimate the effectiveness of additives to polymers is to calculate the “strengthening ratio”, which can be defined as the ratio of the percentage mechanical property improvement to the weight percent of additive in the polymer (total composition weight basis). For example, if the loading of glass fibers in polypropylene is 30% by weight, and the tensile strength of the polypropylene increases 50% as a result of addition of the filler, the tensile strengthening ratio is 1.67.
It would be desirable to significantly improve the tensile properties of polymers at low addition levels of additive. Polyolefins, as a class of structural polymers are very widely and commonly used and, accordingly, it would be desirable to provide to polyolefins significant improvements in tensile properties at low levels of additive. It is further desirable to identify additives to polymers that can improve tensile properties at tensile strengthening ratios significantly higher than that exemplified above.
SUMMARY OF THE INVENTION
The present invention provides a composition comprising a mixture of polyolefin and hyperbranched polymer, that can have an increased tensile energy-to-break value, versus otherwise similar polymer compositions not containing the hyperbranched polymer, at relatively low levels of addition of the hyperbranched polymer. The tensile energy-to-break value of the composition of the present invention can be at least about 15% greater than the tensile energy-to-break value of the polyolefin.
The composition hereof can comprise a mixture of: polyolefin polymer, having a melt flow index of about 14 g/10 min or greater; from about 0.1% to about 10%, by weight of the polyolefin polymer, of a hyperbranched polymer, wherein the hyperbranched polymer is not covalently bonded to the polyolefin polymer; and from about 0.01 % to about 5%, by weight of the polyolefin polymer, of an ester additive. The ester additive is a compound that is miscible with the polyolefin.
All documents cited herein are, in relevant part, incorporated herein by reference; the citation of any reference is not to be construed as an admission that it is prior art with respect to the present invention.
Notwithstanding the provision of any description or part thereof included in this specification describing the invention as “comprising” any step or element or any combination of steps or elements, the compositions and methods of the present invention can comprise, consist of, or consist essentially of the required elements and/or steps hereof as well as any combination of the required elements and/or steps in combination with any optional elements or steps disclosed herein.
All ranges of numerical values are inclusive of the values at the limits of the range unless otherwise expressly excluded.
DETAILED DESCRIPTION OF THE INVENTION
I. Definitions
As used herein, the term “polymer composition” refers to a composition containing at least one polymer and any additional additives or ingredients that may be present in said composition but excluding, unless otherwise specifically indicated, the hyperbranched polymers of the present invention.
The terms “blend” and “mixture” in reference to “polymers” refer to two or more polymers mixed together.
As used herein, the term “melt flow index” of a polymer refers to the polymer mass that can be extruded per unit time at a polymer-specific extrusion temperature (Te). For example, this extrusion temperature is 230° C. for polypropylene, and 190° C. for polyethylene. The index is measured according to the ASTM standard D 1238—95, and is reported in g/10 min. The value for the T
e
is that value listed for the specific polymer in the above ASTM standard or, if T
e
—
for the polymer is not listed, T
e
is calculated as T
m
(melt temperature) plus 60° C.
As used herein, the terms “energy-to-break” and “tensile energy-to-break” relate to the tensile energy absorbed by the polymer until its failure point (i.e., break point), and is equal to the area under the stress-strain curve (or equivalently, load-elongation curve) in tensile mode. As used herein, the terms “elongation-to-break” or “tensile elongation-to-break” are intended to refer to the tensile elongation of the polymer until its failure point. As used herein, the terms “maximum load” or “tensile maximum load” are intended to refer to the maximum load on the polymer during the tensile test. The tensile test to determine the above terms is conducted according to the ASTM standard D 638-96 Type V. The crosshead speed is 0.17 cm/s (4 in./min), and the tests are conducted without an extensometer. A statistically significant measurable increase in these tensile properties is considered an improvement.
As used herein, the term “hyperbranched polymer(s)” is intended to refer to polymer(s) or oligomer(s) t
Collias Dimitris Ioannis
Jackson Nancy Eckert
Owens Blair Alex
Lewis Leonard W.
Nutter Nathan M.
The Procter & Gamble & Company
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