Impact strength retention in aged recycled polycarbonate formulations

Abstract

An aging-resistant recycled polycarbonate formulation having improved impact strength on aging is provided. The aging-resistant recycled polycarbonate formulation comprises at least 25 wt% recycled polycarbonate based on the total weight of the polycarbonate. The formulation comprises a core-shell impact modifier in an amount of at least 1 wt% greater than the amount of impact modifier that provides the maximum initial impact strength, wherein the amount of the core-shell impact modifier is based on the total weight of the recycled polycarbonate formulation. The Izod impact strength at room temperature decreases less than 50% when heat aged for 7 days at 90C at 95% humidity. A process for producing the aging-resistant recycled polycarbonate formulation is also disclosed.

Description

IMPACT STRENGTH RETENTION IN AGED RECYCLED POLYCARBONATE FORMULATIONSFIELD OF THE INVENTION

[0001] The present invention generally relates to a recycled polycarbonate having improved impact strength after aging.DESCRIPTION OF THE RELATED ART

[0002] There is an industry-wide focus on sustainability and identifying ways to reduce the carbon footprint of manufacturing processes. There are various ways to lower carbon footprints including recycling, reusing, reduction in materials, and developing more energy efficient processes.

[0003] Recycled thermoplastics often present unique challenges. Thermoplastic compositions are often formulated for specific applications and may therefore have varying compositions that contain different components, such as, for example, processing aids, impact modifiers, pigments, stabilizers, etc. When recycling such compositions, these additives may adversely affect the properties of the thermoplastic compared to a virgin thermoplastic composition. Additionally, the extra processing that is required to produce a useable recycled thermoplastic may alter the thermoplastic. For example, shear forces used to chop or grind articles for recycling may decrease the molecular weight of the thermoplastic. The decrease in molecular weight of recycled polycarbonate results in increased melt flow when the percentage of recycled polycarbonate increases.

[0004] Polycarbonate is a useful thermoplastic material often used where strength and clarity are desirable. Because polycarbonate can be brittle on its own, impact modifiers are typically added in polycarbonate formulations to improve the impact strength.

[0005] It has been found that recycled polycarbonate is particularly susceptible to reduced impact strength when aged.

[0006] Therefore, it is desirable to develop recycled polycarbonate formulations that have improved impact strength when aged.BRIEF SUMMARY OF THE INVENTION

[0007] A first aspect of the present invention relates to an aging-resistant recycled polycarbonate formulation. The formulation comprises a polycarbonate, wherein the polycarbonate comprises at least 25 wt% recycled polycarbonate based on the total weight of the polycarbonate. The formulation further comprises a core-shell impact modifier, wherein the core-shell impact modifier is present in an amount of at least 1 wt% greater than the amount of impact modifier that provides the maximum initial impact strength, wherein the amount of the core-shell impact modifier is based on the total weight of the recycledpolycarbonate formulation. The Izod impact strength, measured at room temperature, decreases less than 50% when heat aged for 7 days at 90°C at 95% humidity.

[0008] A second aspect of the present invention relates to a process for producing an agingresistant recycled polycarbonate formulation comprising providing a polycarbonate comprising at least 25 wt% recycled polycarbonate based on the total weigh of the polycarbonate, and adding a core-shell impact modifier to the polycarbonate to form the polycarbonate formulation. The core-shell impact modifier is present in an amount of at least 1 wt% greater than the amount of impact modifier that provides the maximum initial impact strength, wherein the amount of the core-shell impact modifier is based on the total weight of the recycled polycarbonate formulation. The Izod impact strength, measured at room temperature, decreases less than 50% when heat aged for 7 days at 90°C at 95% humidity.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 is a graph showing the impact strength of a 100% virgin polycarbonate formulation.

[0010] FIG. 2 is a graph showing the impact strength of polycarbonate formulations having varying amounts of recycled polycarbonate content.

[0011] FIG. 3 is a graph comparing the impact strength of recycled polycarbonate formulations.DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention provides an aging-resistant recycled polycarbonate formulation and a process for producing an aging-resistant recycled polycarbonate formulation. The aging-resistant recycled polycarbonate formulation has improved impact strength even when the recycled polycarbonate formulation is aged.

[0013] The present inventor has discovered that recycled polycarbonate formulations exhibit significant decreases in impact strength when aged. The inventor has found that while recycled polycarbonate formulations may exhibit similar impact strengths to virgin polycarbonate formulations when they are produced, the impact strength of recycled polycarbonate formulations significantly decreases when aged as the percentage of recycled polycarbonate increases. FIG. 1 shows that a 100% virgin polycarbonate formulation exhibits very little drop in impact strength when heat aged for 7 to 14 days according to the heat aging process disclosed below. When the percentage of recycled polycarbonate increases, the impact strength of the recycled polycarbonate formulations decreases significantly after heat aging, as shown in FIG. 2. As seen in FIG. 2, the initial impact strength of the recycled polycarbonate formulations is substantially the same as 100% virgin polycarbonate. However, heat aging causes greater decreases in the impact strength as the percentage ofrecycled polycarbonate increases. The polycarbonate formulations shown in FIG. 2 each contain 5 wt% of an impact modifier based on the total weight of the polycarbonate formulation.

[0014] The inventor has surprisingly discovered that increasing the amount of impact modifier in excess of amounts that affect the impact strength at room temperature of recycled polycarbonate formulations prior to aging (i.e. initial impact strength of the recycled polycarbonate formulations) can significantly improve the impact strength of recycled polycarbonate formulations after aging, as indicated by the heat aging process described below. For example, increasing the amount of impact modifier from 5 wt% to 7 wt% based on the total weight of the recycled polycarbonate formulation may not increase the impact strength of the recycled polycarbonate formulation prior to aging, but the small change in the amount of impact modifier significantly improves the impact strength of the aged recycled polycarbonate formulation.

[0015] Unless otherwise specified, reference to the impact strength refers to the notched Izod impact strength measured according to ASTM D256 at room temperature.

[0016] One aspect of the present invention relates to an aging-resistant recycled polycarbonate formulation.

[0017] The aging-resistant recycled polycarbonate formulation comprises at least 25 wt% recycled polycarbonate based on the total weight of the polycarbonate present in the formulation. Preferably, the aging-resistant recycled polycarbonate formulation comprises at least 50 wt% recycled polycarbonate based on the total weight of the polycarbonate present in the formulation. More preferably, the aging-resistant recycled polycarbonate formulation comprises at least 75 wt% recycled polycarbonate based on the total weight of the polycarbonate present in the formulation.

[0018] The recycled polycarbonate can be post-consumer or post-industrial recycled polycarbonate. Post-consumer recycled polycarbonate comprises polycarbonate recovered from waste streams after an article is used by a consumer. Post-industrial recycled polycarbonate may comprise waste polycarbonate from the making of polycarbonate articles, excess polycarbonate formed during the production of polycarbonate, or other sources of polycarbonate prior to use by a consumer. Preferably, the recycled polycarbonate is post-consumer recycled polycarbonate.

[0019] The aging-resistant recycled polycarbonate formulation comprises a core-shell impact modifier. The core-shell impact modifier is present in an amount of at least 1 wt% greater than the amount of impact modifier that provides the maximum initial impact strength, wherein the amount of the core-shell impact modifier is based on the total weight of the recycled polycarbonate formulation. As used herein, the phrase “amount of impact modifierthat provides the maximum initial impact strength” means the amount of impact modifier that is added to a recycled polycarbonate formulation where an additional 5% of impact modifier based on the total amount of impact modifier provides less than a 5% increase in the initial impact strength of the recycled polycarbonate formulation at room temperature, i.e., the slope of the initial impact strength of the recycled polycarbonate formulation at room temperature has substantially plateaued. As used herein, the phrase “initial impact strength” means the notched Izod impact strength as measured according to ASTM D256 using a recycled polycarbonate formulation made within 1 day of testing, where the recycled polycarbonate formulation has not been subjected to heat aging. Preferably, the core-shell impact modifier is present in an amount of at least 1 .5 wt% more than the amount of impact modifier that provides the maximum initial impact strength, where the impact strength is measured at room temperature. Even more preferably, the core-shell impact modifier is present in an amount of at least 2 wt% more than the amount of impact modifier that provides the maximum initial impact strength at room temperature.

[0020] For example, for a recycled polycarbonate formulation, the maximum initial impact strength, at room temperature, typically occurs when a core-shell impact modifier is added in an amount of about 5 wt% based on the total weight of the recycled polycarbonate formulation. No significant increase in the initial impact strength of the recycled polycarbonate formulation is achieved by adding additional impact modifier. However, significant improvements in impact strength may be observed in the recycled polycarbonate formulation when the amount of core-shell impact modifier is increased to at least 6 wt% when heat aged for 7 or 14 days. Preferably, the amount of core-shell impact modifier present in the recycled polycarbonate formulation is at least 6.5 wt% based on the total weight of the recycled polycarbonate formulation. Even more preferably, the amount of core-shell impact modifier present in the recycled polycarbonate formulation is at least 7 wt% based on the total weight of the recycled polycarbonate formulation. Preferably, the core-shell impact modifier is present in an amount less than 20 wt%, and more preferably less than 15 wt%, based on the total weight of the recycled polycarbonate formulation.

[0021] In addition to the impact strength improvement, the recycled polycarbonate formulations of the present invention may also improve the melt flow of the formulation. Typically, the melt flow increases as the percentage of recycled polycarbonate increases. The greater amount of the core-shell impact modifier may lead to improvements in the melt flow of the recycled polycarbonate formulations by leading to a lower increase in the melt flow as the percentage of recycled polycarbonate increases.

[0022] The core-shell impact modifier may comprise a multistage polymer. As used herein, the term “multistage polymer” refers to a polymer that is made by forming (i.e., polymerizing)multiple polymers in steps or stages. The multistage polymer may comprise two or more stages. For example, the multistage polymer may comprise two stages, including a first stage and a second stage formed on the first stage. Alternatively, the multistage polymer may comprise a first stage, one or more intermediate stages, and then a final stage, where the final stage forms the outermost layer of the multistage polymer. A first polymer, called the “first stage polymer” or the “initial stage polymer,” may form the core of the multistage polymer. Then, in the presence of the initial stage polymer, an additional polymer called the “latter stage,” which can be an intermediate stage or the final stage of the multistage polymer, is formed on the initial stage polymer. The multistage polymer may comprise additional stages, which may be formed before or after the latter stage polymer. Each intermediate stage is formed in the presence of the polymer resulting from the polymerization of the stage immediately previous to that intermediate stage. In such embodiments wherein each subsequent stage forms a partial or complete shell around each of the particles remaining from the previous stage, the multistage polymer that results is known as a “core-shell” polymer, where the initial stage polymer comprises the core and each subsequent stage comprises a shell on the preceding stage with the final stage forming the outermost shell. Thus, the latter stage polymer will comprise at least part of the shell in a core-shell multistage polymer.

[0023] As used herein, the terms “glass transition temperature” or “Tg” refers to the temperature at or above which a glassy polymer will undergo segmental motion of the polymer chain. Glass transition temperatures of a copolymer can be estimated by the Fox equation (Bulletin of the American Physical Society, 1 (3) Page 123 (1956)) as follows:1 / Tg = w1 / Tg(1 ) + w2 / Tg(2)

[0024] For a copolymer, w1 and w2 refer to the weight fraction of the two comonomers, and Tg(1 ) and Tg(2) refer to the glass transition temperatures of the two corresponding homopolymers made from the monomers. For polymers containing three or more monomers, additional terms are added (wn / Tg(n)). The glass transition temperatures of the homopolymers may be found, for example, in the “Polymer Handbook,” edited by J. Brandrup and E.H. Immergut, Interscience Publishers. The Tg of a polymer can also be measured by various techniques, including, for example, differential scanning calorimetry (“DSC”). As used herein, the phrase “calculated Tg” shall mean the glass transition temperature as calculated by the Fox equation. When the Tg of a multistage polymer is measured, more than one Tg may be observed. The Tg observed for one stage of a multistage polymer may be the same as the Tg that is characteristic of the polymer that forms that stage (i.e. , the Tg that would be observed if the polymer that forms that stage were formed and measured inisolation from the other stages). When a monomer is said to have a certain Tg, it is meant that a homopolymer made from that monomer has that Tg.

[0025] The core-shell impact modifier may contain the core, for example, in an amount of 10 wt% or more, or 20 wt% or more, or 50 wt% or more, based on the total weight of the core-shell impact modifier. The core-shell impact modifier may contain the core in an amount of 98 wt% or less, or 95 wt% or less, or 90 wt% or less, based on the total weight of the coreshell impact modifier.

[0026] The core may contain polymerized units derived from one or more multifunctional monomers. Multifunctional monomers contain two or more functional groups that are capable of participating in a polymerization reaction. Suitable multifunctional monomers include, for example, divinylbenzene, allyl methacrylate, ethylene glycol methacrylate, and 1 ,3-butylene dimethacrylate. When present, the core may contain polymerized units derived from a multifunctional monomer in an amount of 0.01 wt% or more, or 0.03 wt% or more, or 0.1 wt% or more, based on the weight of the total weight of the core. When present, the core may contain polymerized units derived from a multifunctional monomer in an amount of 5 wt% or less, or 2 wt% or less, based on the weight of the total weight of the core.

[0027] The core of the core-shell impact modifier may contain polymerized units derived from one or more diene monomers. Suitable diene monomers include, for example, butadiene and isoprene. The core may contain polymerized units derived from diene monomers in an amount of 2 wt% or more, or 5 wt% or more, or 10 wt% or more, or 20 wt% or more, or 50 wt% or more, or 75 wt% or more, based on the total weight of the core. The core contains polymerized units derived from diene monomers in an amount of 100 wt% or less, or 98 wt% or less, or 90 wt% or less, based on the total weight of the core.

[0028] The core of the core-shell impact modifier may contain polymerized units derived from one or more of styrene, substituted styrene, or mixtures thereof. The core may contain polymerized units derived from one or more of styrene and substituted styrene in an amount of 1 wt% or more, or 2 wt% or more, or 5 wt% or more, or 10 wt% or more, based on the total weight of the core. The core may contain polymerized units derived from one or more of styrene and substituted styrene in an amount of 80 wt% or less, or 50 wt% or less, or 25 wt% or less, or 10 wt% or less, or 5 wt% or less, based on the total weight of the core.

[0029] The core of the core-shell impact modifier may contain polymerized units derived from acid-functional monomers. An acid-functional monomer is a monomer that has an acid group, for example, a sulfonic acid group or a carboxylic acid group. Suitable acid-functional monomers include, for example, acrylic acid and methacrylic acid. The core may contain polymerized units derived from one or more acid functional monomers in an amount of 3wt% or less, or 2 wt% or less, or 1 wt% or less, or 0.5 wt% or less, based on the total weight of the core.

[0030] Preferably, the core comprises butadiene, more preferably crosslinked butadiene.

[0031] The shell of the core-shell impact modifier may comprise polymerized units derived from one or more substituted or unsubstituted styrene and one or more substituted or unsubstituted alkyl (meth)acrylate monomers.

[0032] Suitable alkyl groups in the at least one alkyl (meth)acrylate monomers include straight or branched C1 to C12 alkyl groups. Preferred alkyl groups include methyl, ethyl, propyl, butyl, hexyl, 2-ethylhexyl, and octyl groups. Preferably, the alkyl (meth)acrylate monomers comprise methyl methacrylate.

[0033] Suitable substituted styrenes include, for example, alpha-alkyl styrenes (e.g., alphamethyl styrene).

[0034] Preferably, the weight ratio of the at least one alkyl (meth)acrylate to styrene in the shell ranges from 5:95 to 95:5. For example, the weight ratio of the at least one alkyl (meth)acrylate to styrene in the shell may be at least 10:90, at least 20:80, at least 30:70, at least 40:60, or at least 50:50, and the weight ratio of the at least one alkyl (meth)acrylate to styrene in the shell may be at most 90:10, at most 80:20, or at most 70:30..

[0035] The shell may have a Tg of 50°C or more, or 75°C or more. The shell may have a Tg of 200°C or less, or 150°C or less.

[0036] The core-shell impact modifier may contain the shell, for example, in an amount of 2 wt% or more, or 10 wt% or more, or 20 wt% or more, based on the total weight of the multistage polymer. The core-shell impact modifier may contain the shell, for example, in an amount of 50 wt% or less, or 25 wt% or less, or 10 wt% or less, based on the total weight of the core-shell impact modifier.

[0037] Preferably, the shell contains polymerized units derived from monomers having a Tg of 50°C or higher in an amount of 50 wt% or higher, or 75 wt% or higher, or 90 wt% or higher based on the total weight of the shell.

[0038] The weight ratio of the core to the shell may range, for example, from 0.1 :1 or higher, or 0.2:1 or higher, or 0.4:1 or higher, or 1 :1 or higher, or 1 .5:1 or higher, or 3:1 or higher, or 4:1 or higher. The weight ratio of the core to the shell may range, for example, from 50:1 or lower, or 25:1 or lower, or 20:1 or lower.

[0039] The core-shell impact modifier may contain one or more intermediate stage polymers. The total sum of the intermediate stage polymers may be present in an amount of 1 wt% or more, or 2 wt% or more, or 5 wt% or more, or 10 wt% or more, based on the total weight of the core-shell impact modifier. The total sum of the intermediate stage polymersmay be present in an amount of 60 wt% or less, or 2 wt% or less, or 5 wt% or less, or 10 wt% or less, based on the total weight of the core-shell impact modifier.

[0040] The core-shell impact modifier is preferably made by aqueous emulsion polymerization. Emulsion polymerization involves the presence of one or more initiator. An initiator is a compound that forms one or more free radical, which can initiate a polymerization process. The initiator is usually water-soluble. Some suitable initiators form one or more free radical when heated. Some suitable initiators are oxidants and form one or more free radical when mixed with one or more reductant, or when heated, or a combination thereof. Some suitable initiators form one or more free radical when exposed to radiation such as, for example, ultraviolet radiation or electron beam radiation. A combination of initiators is also suitable. When using emulsion polymerization, the core-shell impact modifier can isolated by coagulation or spray drying.

[0041] Preferably, the core-shell impact modifier is a methacrylate butadiene styrene coreshell impact modifier.

[0042] The aging-resistant recycled polycarbonate formulation of the present invention exhibits less than a 50% decrease in the notched Izod impact strength at room temperature when heat aged for 7 days as measured according to the heat aging process described below. Preferably, the aging-resistant recycled polycarbonate formulation of the present invention exhibits less than a 33% decrease in the notched Izod impact strength at room temperature when heat aged for 7 days. Preferably, the aging-resistant recycled polycarbonate formulation of the present invention exhibits less than a 50% decrease in the notched Izod impact strength at room temperature when heat aged for 14 days. More preferably, aging-resistant recycled polycarbonate formulation of the present invention exhibits less than a 33% decrease in the notched Izod impact strength at room temperature when heat aged for 14 days.

[0043] Preferably, the aging-resistant recycled polycarbonate formulation of the present invention exhibits less than a 55% decrease in the notched Izod impact strength at 0 °C when heat aged for 7 days. More preferably, the aging-resistant recycled polycarbonate formulation of the present invention exhibits less than a 50% decrease in the notched Izod impact strength at 0 °C when heat aged for 7 days.

[0044] Preferably, the aging-resistant recycled polycarbonate formulation of the present invention exhibits less than a 55% decrease in the notched Izod impact strength at 0 °C when heat aged for 14 days.

[0045] Another aspect of the present invention relates to a process for producing an agingresistant recycled polycarbonate formulation. The process comprises providing a polycarbonate comprising at least 25 wt% recycled polycarbonate based on the total weightof the polycarbonate and adding a core-shell impact modifier to the polycarbonate to form the polycarbonate formulation, wherein the core-shell impact modifier is present in an amount of at least 1 wt% greater than the amount of impact modifier that provides the maximum initial impact strength based on the total weight of the polycarbonate formulation. Preferably, the core-shell impact modifier is present in an amount of at least 1 .5 wt% greater than the amount of impact modifier that provides the maximum initial impact strength, and even more preferably, the core-shell impact modifier is present in an amount of at least 2 wt% greater than the amount of impact modifier that provides the maximum initial impact strength, wherein the amount of the core-shell impact modifier is based on the total weight of the recycled polycarbonate formulation.

[0046] The core-shell impact modifier may be added to the polycarbonate by any method known in the art. For example, the core-shell impact modifier may be added to the polycarbonate in powder form and blended within an extruder.Examples

[0047] Polycarbonate formulations were prepared by blending virgin polycarbonate, postconsumer recycled polycarbonate, and a core-shell impact modifier in an extruder. Postconsumer recycled polycarbonate supplied in chunks was pelletized into smaller pieces to make it easier to feed into the extruder. To get uniform pellet size, virgin polycarbonate was also pelletized. Both polycarbonates were bag mixed first and then core-shell impact modifier powder was added to the mix and bag mixed again. The core-shell impact modifier powder was well coated on the polycarbonate pellets. The pre-mix was then fed to an extruder via a hopper. Extrusion was done on a twin-screw extruder to ensure uniform mixing of all three components under controlled heat and shear. Homogeneous molten polymer exited from the die in the form of a strand that passed through a water tank to cool the strand, which was then fed to a pelletizer to obtain uniform pellets. In the next step, extruded pellets were predried in hot air oven to remove moisture and then fed to an injection molding machine to prepare impact test specimens.

[0048] The virgin polycarbonate was LEXAN™ 191 polycarbonate, and the post-consumer recycled polycarbonate (PCR PC) was obtained from a post-consumer recycle stream]. The core-shell impact modifier was PARALOID™ EXL-2691 J, an MBS impact modifier available from The Dow Chemical Company. Formulations according to Table 1 were prepared, where the values in Table 1 are weight percentages based on the total weight of the formulation.Table 1Impact Strength Testing

[0049] Notched Izod impact strength was tested for each sample according to ASTM D256.Melt Flow Testing

[0050] Melt flow index was measured according to ASTM 1238 at 300 °C with a 1.2 kg weight. As seen in Table 2, the inventive examples (IE1 and IE2) showed much less of an increase in melt flow index from the 100% virgin polycarbonate example (CE1) compared to the equivalent comparative examples (CE4 and CE%). This indicates that the inventive examples would be expected to behave more similarly to virgin polycarbonate formulations.Table 2Heat Age Testing

[0051] Each polycarbonate formulation was subjected to simulated aging by heat aging for 7 or 14 days. Heat aging test was conducted in a humidity chamber that precisely controlled temperature and humidity. Injection molded samples were positioned in the chamber using a hanger to get uniform conditioning on all sides. The temperature of the chamber was maintained at 90°C while humidity in the chamber was maintained at 95%. A first set of samples were removed from the chamber after 7 days and tested for impact strength at room temperature and low temperature (0 °C). A second set of samples were removed from the chamber after 14 days and then tested for impact strength at room temperature and low temperature (0 °C).Results

[0052] The results of the impact strength testing at room temperature are shown below in Table 3. As can be seen in Table 3, the inventive examples (IE1 and IE2) exhibited significantly less decrease in the impact strength after heat aging for both 7 and 14 days. When comparing similar post-consumer recycled polycarbonate content, IE1 exhibited a decrease in impact strength at room temperature of 25%, which is significantly better than the 63% decrease in impact strength observed for comparative example CE4 after 7 days of heat aging, and a 25% decrease compared to a 72% decrease for CE4 after 14 days of aging. Similarly, IE2 exhibited a decrease in impact strength at room temperature of 27% compared to the 72% decrease exhibited for CE5 after 7 days of heat aging, and a decrease of 31 % for IE2 compared to a 72% decrease for CE5 after 7 days of heat aging. An additional 2 wt% of the core-shell impact modifier cut the decrease in impact strength after heat aging by more than half. All of the samples for CE1 exhibited clean breaks. All of the samples for the inventive examples (IE1 and IE2) exhibited hinged breaks. The initial samples for CE2 to CE6 exhibited hinged breaks for the initial samples, but clean breaks for the 7 and 14 day heat aged samples.

[0053] FIG. 3 shows a graph comparing comparative examples CE4 and CE5 compared to inventive examples IE1 and IE2. CE4 and IE1 both contain 50 wt% post-consumer recycled polycarbonate, and CE5 and IE2 both contain 75 wt% post-consumer recycled polycarbonate.

[0054] Table 3

[0055] Table 4 below shows the results of the impact strength testing at 0 °C. Comparing similar post-consumer recycled polycarbonate contents demonstrates a significant improvement in the retention of the impact strength at low temperatures following heat aging. IE1 exhibited a 48% decrease in impact strength at 0 °C after 7 and 14 days of heat aging. IE2 exhibited a 47% decrease in impact strength at 0 °C after 7 days of heat aging and 52% after 14 days of heat aging. CE5 exhibited a 60% decrease in impact strength after 7 days of heat aging and 58% after 14 days of heat aging. The data for CE4 deviates from the trend when comparing the values for CE2 to CE6 and was considered to be a statistical outlier in the data.Table 4

[0056] Unless otherwise indicated by the context of the specification, all amounts, ratios and percentages are by weight, and all test methods are current as of the filing date of this disclosure. The articles “a”, “an” and “the” each refer to one or more. It is to be understood that the appended claims are not limited to express and particular compounds, compositions, or methods described in the detailed description, which may vary between particular embodiments which fall within the scope of the appended claims. With respect to any Markush groups relied upon herein for describing particular features or aspects of various embodiments, different, special, and / or unexpected results may be obtained from each member of the respective Markush group independent from all other Markush members.Each member of a Markush group may be relied upon individually and or in combination and provides adequate support for specific embodiments within the scope of the appended claims.

[0057] Further, any ranges and subranges relied upon in describing various embodiments of the present invention independently and collectively fall within the scope of the appended claims, and are understood to describe and contemplate all ranges including whole and / or fractional values therein, even if such values are not expressly written herein. One of skill in the art readily recognizes that the enumerated ranges and subranges sufficiently describe and enable various embodiments of the present invention, and such ranges and subranges may be further delineated into relevant halves, thirds, quarters, fifths, and so on. As just one example, a range “of from 0.1 to 0.9” may be further delineated into a lower third, i.e., from 0.1 to 0.3, a middle third, i.e., from 0.4 to 0.6, and an upper third, i.e., from 0.7 to 0.9, which individually and collectively are within the scope of the appended claims, and may be relied upon individually and / or collectively and provide adequate support for specific embodiments within the scope of the appended claims. In addition, with respect to the language which defines or modifies a range, such as “at least,” “greater than,” “less than,” “no more than,” and the like, it is to be understood that such language includes subranges and / or an upper or lower limit. As another example, a range of “at least 10” inherently includes a subrange of from at least 10 to 35, a subrange of from at least 10 to 25, a subrange of from 25 to 35, and so on, and each subrange may be relied upon individually and / or collectively and provides adequate support for specific embodiments within the scope of the appended claims. Finally, an individual number within a disclosed range may be relied upon and provides adequate support for specific embodiments within the scope of the appended claims. For example, a range “of from 1 to 9” includes various individual integers, such as 3, as well as individual numbers including a decimal point (or fraction), such as 4.1 , which may be relied upon and provide adequate support for specific embodiments within the scope of the appended claims.

[0058] The term “composition,” as used herein, includes material(s) which comprise the composition, as well as reaction products and decomposition products formed from the materials of the composition.

[0059] The term “comprising,” and derivatives thereof, is not intended to exclude the presence of any additional component, step or procedure, whether or not the same is disclosed herein. In order to avoid any doubt, all compositions claimed herein through use of the term “comprising” may include any additional additive, adjuvant, or compound, whether polymeric or otherwise, unless stated to the contrary. In contrast, the term, “consisting essentially of” excludes from the scope of any succeeding recitation any other component,step or procedure, excepting those that are not essential to operability. The term “consisting of” excludes any component, step or procedure not specifically delineated or listed.

Claims

CLAIMSWhat is claimed is:1 . An aging-resistant recycled polycarbonate formulation having improved impact strength on aging, comprising: a polycarbonate, wherein the polycarbonate comprises at least 25 wt% recycled polycarbonate based on the total weight of the polycarbonate; a core-shell impact modifier, wherein the core-shell impact modifier is present in an amount of at least 1 wt% greater than the amount of core-shell impact modifier that provides the maximum initial impact strength, wherein the amount of the core-shell impact modifier is based on the total weight of the polycarbonate formulation, wherein the Izod impact strength at room temperature decreases less than 50% when heat aged for 7 days at 90°C at 95% humidity.

2. The formulation of claim 1 , wherein the polycarbonate comprises at least 50 wt% recycled polycarbonate based on the total weight of the polycarbonate.

3. The formulation of claim 1 or 2, wherein the polycarbonate comprises at least 75 wt% recycled polycarbonate based on the total weight of the polycarbonate.

4. The formulation of any one of the preceding claims, wherein the recycled polycarbonate is post-consumer recycled polycarbonate.

5. The formulation of any one of the preceding claims, wherein the core-shell impact modifier is present in an amount of at least 6 wt% relative to the total weight of the polycarbonate composition.

6. The formulation of any one of the preceding claims, wherein the core-shell impact modifier is a methacrylate butadiene styrene core-shell impact modifier.

8. A process for producing an aging-resistant recycled polycarbonate formulation comprising: providing a polycarbonate comprising at least 25 wt% recycled polycarbonate based on the total weight of the polycarbonate; adding a core-shell impact modifier to the polycarbonate to form the polycarbonate formulation, wherein the core-shell impact modifier is present in an amount of at least 1 wt%greater than the amount of core-shell impact modifier that provides the maximum initial impact strength, wherein the amount of the core-shell impact modifier is based on the total weight of the polycarbonate formulation, wherein the Izod impact strength at room temperature decreases less than 50% when heat aged for 7 days at 90°C at 95% humidity.

9. The process of claim 8, wherein the polycarbonate comprises at least 50 wt% recycled polycarbonate based on the total weight of the polycarbonate.

10. The process of claim 9, wherein the polycarbonate comprises at least 75 wt% recycled polycarbonate based on the total weight of the polycarbonate.1 1. The process of any one of claims 8 to 10, wherein the core-shell impact modifier is present in an amount of at least 6 wt% relative to the total weight of the polycarbonate formulation.

12. The process of claim 1 1 , wherein the core-shell impact modifier is present in an amount ranging from 7 to 20 wt% relative to the total weight of the polycarbonate formulation.

13. The process of any one of claims 8 to 12, the recycled polycarbonate is post-consumer recycled polycarbonate.

14. The process of any one of claims 8 to 13, the core-shell impact modifier comprises a methacrylate butadiene styrene core-shell impact modifier.

15. The process of any one of claims 8 to 14, wherein the Izod impact strength at room temperature decreases less than 33% when heat aged for 7 days at 90°C at 95% humidity.

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