WO2016069280A2 - Method of increasing crystallization temperatures in polypropylene - Google Patents

Abstract

Disclosed is a method of increasing the crystallization temperature of polypropylene comprising melt deforming a base polypropylene in the absence of external nucleating agents, the melt deformation, resulting in an deformed polypropylene having a Tc from 4 to 20°C higher than the base polypropylene; wherein the melt deformation is accomplished in one or multiple deformation steps and at a Specific Energy Input of at least 0.05 kW-hr/kg.

Description

METHOD OF INCREASING CRYSTALLIZATION

TEMPERATURES IN POLYPROPYLENE

PRIORITY CLAIM TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application Serial No. 62/073,384 filed October 31, 2014, and European Application No. 15150234.1 filed January 7, 2015, the disclosures of which are fully incorporated herein by their reference.

FIELD OF THE INVENTION

[0002] The present invention relates to a method of increasing the crystallization temperature in polypropylenes in the absence of external nucleators, and in particular to a method of melt deformation of polypropylenes.

BACKGROUND OF THE INVENTION

[0003] Increasing the crystallization temperature (T_c) to enhance the crystallization kinetics of propylene based polymers ("polypropylene", or "PP") is highly desirable to improve processability (e.g., reduction of cycle time in injection molding) as well as mechanical properties. Increase of T_c is conventionally achieved via addition of nucleating agents [e.g., Gahleitner et al, in INTERN. POLYMER PROCESSING XXVI, 1-20, (201 1); and Pvomankiewicz et al, in 53 POLYM. INT., 2086-2091, (2004)] in the polypropylene granules and powders from the reactor during the extrusion process to make pellets. Increase of T_c during the extrusion process without addition of external nucleators is highly desirable, since it results in manufacturing cost savings.

[0004] The inventors have surprisingly found that an increase of T_c of various polypropylene homopolymers was advantageously achieved preferably by use of certain extruder equipment and extrusion conditions without the addition of external nucleating agents. Addition of external nucleating agents during extrusion or in-situ during the polymerization process the common practice for the skilled in the art for increase of composition crystallization temperature.

[0005] Some other relevant publications include Navarro-Pardo et al, "Shear effect in beta-phase induction of polypropylene in a single screw extruder," J. APPL. POLYM. SCI. 2932-2937, (2013); Phillips et al, "Polymorphism in sheared isotactic polypropylene containing nucleant particles," 298 MACROMOL. MATER. ENG., 991-1003, (2013); Reid et al, "Strong memory effect of crystallization above the equilibrium melting point of random copolymers," 46 MACROMOLECULES, 6485-6497, (2013); and Menyhard et al. in 45 EUROPEAN POLY. J., 3138-3148, (2009); Cho et al, "Real time in situ X-ray diffraction studies on the melting memory effect in the crystallization of β-isotactic polypropylene", 43 POLYMER 1407-1416 (2002); Romankiewicz et al, "Structural characterization of a- and β-nucleated isotactic polypropylene", 53 POLYM. INT. 2086-2091 (2004); Li et al, "Influence of the memory effect of a mesomorphic isotactic polypropylene melt on crystallization behavior" 9 SOFT MATTER 8579-8588 (2013); Li et al, "New Understanding on the Memory Effect of Crystallized rPP" 32 CHINESE J. POLY. SCI. 1224-1233 (2014); Maus et al."Memory effect in isothermal crystallization of syndiotactic polypropylene -role of melt structure and dynamics?" 23 EUR. PHYS. J. E. 91-101 (2007).

SUMMARY OF THE INVENTION

[0006] Disclosed a method of increasing the crystallization temperature of polypropylene comprising melt deforming a base polypropylene in the absence of external nucleating agents, wherein the polypropylene has a crystallization temperature T_c, an MFR from 1.0 to 10.0 g/10 min or Mw from 50,000 to 500,000 g/mol, an average meso run length determined by ¹³C NMR of at least 50 mol % meso pentads (mmmm) content of greater than 0.890; and recovering a deformed polypropylene having a second crystallization temperature ²T_C from 4 to 20°C higher than the base polypropylene; characterized in that, upon heating the deformed polypropylene to a temperature within a range from 200 to 300°C, the second deformed polypropylene has a third crystallization temperature ³T_C within ±2°C of ²T_C; wherein the melt deformation is accomplished in one or multiple deformation steps and at a Specific Energy Input of at least 0.05 kW-hr/kg.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a representative plot of loss tangent (tan8) as a function of temperature for two comparative and three inventive examples of the invention, demonstrating the increase in the crystallization temperature, T_c, upon melt deformation;

[0008] Figure 2 is a representative plot of the complex viscosity as a function of temperature for two comparative and three inventive examples of the invention, demonstrating the increase in the crystallization temperature, T_c, upon melt deformation;

[0009] Figure 3 is a representative plot of the crystallization half-time (to_.s) as a function of the isothermal crystallization temperature for base polypropylene granules of Example 4 compared to 1-step extruded polypropylene (Comparative Example 4) and 2-step extruded polypropylene (Inventive Example 5B);

[00010] Figure 4 is a representative plot of the % increase in crystallization rate as a function of the isothermal crystallization temperature for Inventive Example 5 and Comparative Example 4 relative to the base polypropylene granules of Example 4; [00011] Figure 5 is a representative bar chart of the peak crystallization temperature T_C; (10°C/min) of polypropylene base granules of Example 4, 1-step extruded polypropylene (Comparative Example 4) and 2-step extruded polypropylenes (Inventive Examples 5A, 5B) for both total polymer ("total" referring to the polymer before execution of xylene solubles fractionation) and corresponding xylene insoluble fractions; and

[00012] Figure 6 is a representative image of crystalline morphology by polarized optical microscopy (POM) observed at T=144°C after 48 minutes for comparative Example 4 (a) and inventive (b) Example 5A.

DETAILED DESCRIPTION

[00013] It has been surprisingly found that certain propylene based compositions exhibit unusually high crystallization temperatures (T_c) without use of external nucleating agent(s) when processed on certain extruder equipment and conditions to create pellets and/or fabricated articles. It has been unexpectedly observed that an increase of T_c on the order of about 4 to 20°C was achieved for a variety of homopolymer polypropylenes (hPP) over the T_c (or, a second crystallization temperature, ²T_C) of conventional non-nucleated hPPs (about 1 10 to 112°C) without the addition of nucleating agents/additives, when processed on a variety of extruders of either twin or single screw configuration, either in a single or multiple extrusion steps. This ²T_C is maintained even when further heating by, for example, any form of melt deformation that applies shear forces to the polymer, causes the temperature of the polypropylene to be between 200 to 300°C. This effect is both novel and advantageous, because the increased T_c leads to improved processability such as reduced cycle time (e.g., injection molding) eliminating the cost of external nucleators that are conventionally used to enhance crystallization kinetics. The increased T_c can be also advantageous in melt spinning and spunbond nonwovens, leading to improved spinnability, since crystallization is generally a stabilizing mechanism to external disturbances reducing fiber breaks. While not wishing to be bound by this theory, it is believed that the cause of this unexpected phenomenon is associated with an unusual melt memory effect that the propylene composition experiences which is induced by processing (combination of flow deformation and chain orientation).

[00014] Thus, disclosed herein is a method of increasing the crystallization temperature (Tc) of polypropylene comprising (or consisting essentially of) melt deforming a base polypropylene in the absence of external nucleating agents, the melt deformation (such as by extrusion, spinning, injection molding or other shear-inducing process), resulting in an deformed polypropylene having a ²T_C from 4 to 20°C higher than the base polypropylene; wherein the melt deformation is accomplished in one or multiple, preferably one or two, deformation steps and at a Specific Energy Input of at least 0.05 kW-hr/kg. The process, or deformed polypropylene, is characterized in that, upon heating the deformed polypropylene to a temperature within a range from 200 to 300°C, the second deformed polypropylene has a third crystallization temperature ³T_C within ±2°C of ²T_C.

[00015] In any case, the Specific Energy Input may be within the range from 0.05, or 0.10, or 0.20, or 0.25, or 0.30 kW-hr/kg to 0.80, or 1.00, or 1.20, or 2.00 kW-hr/kg. Preferably, when an extruder is performing the melt deformation, the length-to-diameter ("L/D") ratio of the extruder is within a range from 5: 1 to 10: 1 or 20: 1 or 50: 1 or 100: 1. In any embodiment, the base polypropylene is blended with peroxide during extrusion or deformation. In particular embodiments, after melt deformation the base polypropylene is blended with peroxide during a second extrusion or deformation.

[00016] The "melt deformation" is any process that induces shear forces in the polypropylenes used herein, most preferably accomplished using a single screw extruder, a double screw extruder, by injection molding, and/or fiber spinning or melting through a fiber spinning or melting die.

[00017] As used herein, an "extruder" is any device suitable for intimately mixing and blending materials by agitation and/or sheer force such that at least one polypropylene is present and the sheer force and/or added heat melts the polypropylene. This process is desirably used to form "pellets" of polymeric material, which may take place in the presence or absence of oxygen.

[00018] As used herein, the term "polypropylene" refers to one or a combination of propylene-based polymers comprising at least 50 or 60 wt% propylene-derived units [by weight of the propylene-based polymer(s)], or a composition comprising propylene-based polymers having a total content of at least 50 or 60 wt% propylene-derived units. Examples of "polypropylene" includes polypropylene homopolymers, ethylene-propylene copolymers, propylene impact copolymers (e.g., an intimate blend of polypropylene homopolymer and an ethylene-propylene elastomer), thermoplastic polyolefin compositions (with and without fillers), and blends thereof. Preferably, "polypropylene" or "base polypropylene" refers to polypropylene homopolymers and polypropylene copolymers, wherein polypropylene copolymers comprise within a range from 0.1 to 5 wt% ethylene and/or C₄ to Cio a-olefins. Most preferably, "polypropylene" refers to polypropylene homopolymers. The term "base" polypropylene simply refers to the polypropylene to be melt deformed (e.g., extruded) in the inventive process. Most desirably, the base polypropylene is a polypropylene where nucleating agents are absent. In any embodiment, crystallization temperature, T_c, of the polypropylene (and "base" polypropylene) is within a range from 100, or 102, or 105, or 110°C to 1 12, or 114, or 1 16, or 1 18, or 120, or 125°C. The melting point temperature (Tm) of the base polypropylenes useful in the invention are within the range from 130, or 140, or 150, or 155°C to 165, or 170, or 175°C.

[00019] Also, in any embodiment, the base polypropylenes have an MFR (2.16 kg/230°C) from 1.0, or 2.0 g/10 min to 5.0, or 8.0, or 10.0 g/10 min or Mw from 50,000 or 60,000, or 80,000 g/mol to 300,000, or 500,000 g/mol, an average meso run length determined by ¹³C NMR of at least 50, or 60, or 70 mol% meso pentads (mmmm) content of greater than 0.890;

[00020] The polypropylenes referred to herein can be made by any suitable means. In a particular embodiment, they are made using so called "Ziegler-Natta" catalysts. Other catalysts are also suitable such as "metallocene", and other "single-site" catalysts. The terms "catalyst" and "catalyst compound" are defined to mean a compound capable of initiating catalysis. In the description herein, the catalyst may be described as a catalyst precursor, a pre-catalyst compound, or a transition metal compound, and these terms are used interchangeably.

[00021] As used herein, a "Ziegler-Natta" catalyst is defined as a transition metal compound bearing a metal-carbon bond— excluding cyclopentadienyls or ligands isolobal to cyclopentadienyl— and able to carry out a repeated insertion of olefin units. Definitions and examples of Ziegler-Natta catalyst used for propylene polymers can be found in Chapter 2 of "Polypropylene Handbook" by Nello Pasquini, 2^nd Edition, Carl Hansen Verlag, Munich 2005. Examples of Ziegler-Natta catalysts include first and second generation T1CI2 based, the MgCl₂ supported catalysts etc., as described in the "Polypropylene Handbook" by N. Pasquini.

[00022] As used herein, "metallocene catalyst" means a Group 4 or 5 transition metal compound having at least one cyclopentadienyl, indenyl or fluorenyl group attached thereto, or ligand isolobal to those ligands, that is capable of initiating olefin catalysis, typically in combination with an activator. Definitions and examples of metallocene catalysts can be found in Chapter 2 of "Polypropylene Handbook" by Nello Pasquini, 2^nd Edition, Carl Hansen Verlag, Munich 2005.

[00023] As used herein, "single-site catalyst" means a Group 4 through 10 transition metal compound that is not a metallocene catalyst and capable of initiating olefin catalysis, such as Diimine-ligated Ni and Pd complexes; Pyridinediimine-ligated Fe complexes; Pyridylamine- ligated Hf complexes; Bis(phenoxyimine)-ligated Ti, Zr, and Hf complexes. Other examples of single-site catalysts are described in G. H. Hlatky, "Heterogeneous Single-Site Catalysts for Olefin Polymerization," 100, CHEM. REV., 1347-1376, (2000) and K. Press, A. Cohen, I. Goldberg, V. Venditto, M. Mazzeo, M. Kol, "Salalen Titanium Complexes in the Highly Isospecific Polymerization of 1-Hexene and Propylene," in 50 ANGEW. CHEM. INT. ED., 3529-3532, (2011) and references therein. Examples of single-site catalysts include complexes containing tert-butyl-substituted phenolates ([Ligi_₃TiBn₂]), complex [Lig₄TiBn₂] featuring the bulky adamantyl group, and the sterically unhindered complex [LigsTiB^].

[00024] The terms "visbreaking" and "chain scission" are used interchangeably and are defined as the process of using one or more free radical initiators to increase polymer melt flow rate (MFR). This is described in U.S. 6,747, 114, which is incorporated here by reference in its entirety. A polymer undergoes chain scission in accordance with this invention when the base polymer, or a blend of polymers, is treated with a free radical initiator, for example, peroxide, preferably while the polymer is in a melted state, more preferably in a fully melted state. Preferably, the chain scission is controlled. For example, when a free radical initiator is used, free radicals of the polymers being treated are produced by thermal scission of the peroxide. Other sources of free radicals such as diazo compounds, oxygen, or other compounds may also be utilized. In any case, it is contemplated that the free radicals produced from the initiator (e.g., peroxide) abstract the tertiary hydrogen on the propylene residue of the polymer. The resulting free radical disproportionates to two lower molecular weight chains, one with an olefin near the terminus and the other a saturated polymer. This process can continue with the generation of successively lower molecular weight polymers. Thus, under the appropriate conditions, chain scission is initiated to cause controlled degradation of the polymer or polymer blend.

[00025] In one embodiment, the visbreaking agent is a peroxide compound, and an organic peroxide compound in another embodiment, wherein at least a methyl group or higher alkyl or aryl is bound to one or both oxygen atoms of the peroxide. In yet another embodiment, the visbreaking agent is a sterically hindered peroxide, wherein the alkyl or aryl group associated with each oxygen atom is at least a secondary carbon, a tertiary carbon in another embodiment. Non-limiting examples of sterically hindered peroxides ("visbreaking agents") include 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, 2,5-dimethyl-2,5-bis-(t-butylperoxy)- hexyne-3,4-methyl-4-t-butylperoxy-2-pentanone, 3,6,6,9,9-pentamethyl-3-(ethylacetate)- 1,2,4,5-textraoxy cyclononane, a,a'-bis-(tert-butylperoxy)diisopropyl benzene, and mixtures of these and any other secondary- or tertiary-hindered peroxides. A preferred peroxide is 2,5- bis(tert-butylperoxy)-2,5-dimethyl-hexane, also known with the commercial name: Luperox™ 101 or Trigonox™ 101. Luperox™ 101 or Trigonox™ 101 can be fed in the extruder pure in liquid form or as a masterbatch blend in mineral oil (e.g., 50/50 weight/weight blend of Trigonox™ 101/mineral oil). Another common peroxide used as a visbreaking agent for polypropylene is di-t-amyl peroxide, most commonly known with the commercial name DTAP. Alternatively, the free radical initiator may include a diazo compound, or any other compound or chemical that promotes free radicals in an amount sufficient to cause degradation as specified herein.

[00026] As used herein, "reactor-grade polymer" means a polymer that has been produced by catalytic formation of carbon-carbon bonds between olefins to form a polymer having a certain molecular weight profile (Mw, Mn, and Mz) and not otherwise treated in any other way to effect its average molecular weight profile. As used herein, "visbroken" (or "controlled rheology") means that the polymer has been thermally or chemically treated to break one or more carbon-carbon bonds in the polymer to create shorter chain lengths and alter its molecular weight profile, most preferably lowering Mw, such treatment preferably effected by treatment of the polymer with a chain scission agent well known in the art such as a peroxide, typically under mild heating and shear conditions such as in a screw extruder.

[00027] For purposes of this invention and the claims thereto, when a polymer is described as having an "absence of nucleating agent" or "no external nucleator", it means that no external nucleating agents have been added to the polymer either during melt deformation or in the polymerization reactor. Unless stated otherwise, "base" resins contain no external nucleator. A "nucleator" is a molecule having a molecular weight of less than 1,000 g/mole that increases the crystallization time of thermoplastic materials, examples of which include metal salts or organic acids, sodium benzoate, and other compounds known in the art.

[00028] A variety of additives may be incorporated into the polypropylene before or during melt deformation as described in this invention as long as they do not have a nucleating effect on the polypropylene. Such additives include, for example, stabilizers, antioxidants, fillers, colorants, slip additives, etc. Primary and secondary antioxidants include, for example, hindered phenols, hindered amines, and phosphates. Other additives such as dispersing agents, for example, Acrowax™ C, can also be included. Slip agents include, for example, oleamide, and erucamide. Catalyst deactivators are also commonly used, for example, calcium stearate, hydrotalcite, calcium oxide, acid neutralizers, and other chemicals known in the art. The present invention relates to significant enhancement of crystallization temperature without the addition of external nucleating agents (nucleators). External nucleating agents or nucleators include, for example, sodium benzoate, talc, and derivatives thereof. Also, other nucleating agents may be low weight average molecular weight (less than 30,000 g/mol) Ziegler-Natta olefin products or other highly crystalline polymer.

[00029] In any case, the base polypropylene, with or without additives, but excluding nucleating agents, can be melt deformed as described to increase its Tc. Either in the first or subsequent deformation step, the base polypropylene is deformed at a melt temperature within the range from 180, or 190, or 200, or 210, or 220°C to 300, or 320, or 340°C. In any embodiment, the deformation process occurs under 2 purge. In a particular embodiment, the base polypropylene is pre-purged with 2 before fed into the extruder or otherwise deformed. In particular embodiments, the melt deformation process occurs under air (O2) purge. In any embodiment, the deformed polypropylene is cooled to a solid in any form (flake, granule, or pellets) and is melt deformed (e.g., extruded or spun) a second time to form a second deformed polypropylene. In particular embodiments, as mentioned above, after melt deformation, the base polypropylene (in flake, granule, or pellet form) is blended with peroxide during the second extrusion or deformation.

[00030] In any embodiment, the proportion of low molecular weight polypropylene component (polypropylene having a weight average molecular weight of less than 30,000, or 20,000, or 10,000, or 5,000 g/mole) in the deformed polypropylene is higher than in the base polypropylene. In any embodiment, the base polypropylene has within the range from 0.5, or 1.0, or 2.0 wt% to 8.0, or 10.0 wt%, by weight of the base polypropylene, of the low molecular weight polypropylene component having a weight average molecular weight (Mw) of less than 30,000, or 20,000, or 10,000, or 5,000 g/mole.

[00031] Preferably, the base polypropylene or polypropylene after the melt deformation step(s) has a MFR of 0.1, or 1, or 5, or 10, or 20, to 500, or 1000, or 1500, or 2000 dg/min. Also preferably, the base polypropylene or polypropylene after the melt deformation step(s) has a Mw of 30,000, or 40,000, or 50,000 g/mole to 150,000, or 200,000, or 300,000, or 500,000, or 1,000,000 g/mol.

[00032] Preferably, the deformed polypropylene has a second crystallization temperature ²T_C from 4 to 10, or 15, or 20°C higher than the base polypropylene. In any embodiment, this increase in Tc may be facilitated by an increasing amount of low molecular weight polypropylene generated during melt deformation. In any embodiment, the polypropylene after the extrusion or deformation step(s) (the "deformed polypropylene") has a ²Tc of greater than 113, or 114, or 1 15, or 1 18, or 120, or 125°C, or within a range from 113, or 114, or 1 15°C to 120, or 125, or 130°C. Otherwise, the deformed polypropylene will maintain properties identical to, or within ±2 or 3% of the base polypropylene. [00033] Preferably, the invention includes extruding a base polypropylene having an initial crystallization temperature Tc as described herein, then recovering the "deformed" or "extruded" polypropylene having a ²T_C that is at least 4°C higher than Tc. This recovered polypropylene having ²T_C can preferably be cooled and formed into pellets or "pelletized". These pellets can then be used in any number of applications wherein they are sheared, heated or otherwise "deformed" again, most preferably to form an article, where upon this second deformation process the polypropylene will have a third crystallization temperature ³T_C that is within ±2 of the ²T_C. Thus, "recovering" may include forming pellets, flakes, blocks, or other forms that polypropylene are known to be formed into, especially those convenient for storage and/or transport.

[00034] Thus, also disclosed herein is a "deformed" polypropylene composition having a peak crystallization temperature ²T_C from 4 to 20°C higher than the base polypropylene without the addition of external nucleating agents during the reactor polymerization or subsequent polymer processing (fabrication and/or melt deformation) of the base polypropylene and the composition maintaining ²T_C from 4 to 20°C higher than the base polypropylene or T_c from 113°C to 130°C after melt deformation at a temperature within the range from 200 to 300 °C, wherein the composition and base polypropylene having a MFR from 0.1 to 3,000 dg/min or Mw from 30,000 to 2,000,000 g/mol, an average meso run length determined by ¹³C NMR of at least 50 mol% meso pentads (mmmm) content of greater than 0.890. This deformed polypropylene is made of course by the methods described herein, and may have the characteristics such as described for the deformed polypropylenes as described herein.

[00035] The deformed polypropylenes are useful to make many articles, including fibers and/or fabrics that can then be formed into diapers, hygiene products, medical gowns and masks, filters, insulation, sheets, films, and layered as sheets or films in such articles as pallets. The deformed polypropylenes may also be made into articles via injection molding, thermoforming, compression molding, and/or foam extrusion. Suitable articles would include automotive components, appliance components, drinking cups, food containers, food plates, and any number of other items.

[00036] The various descriptive elements and numerical ranges disclosed herein for the inventive methods can be combined with other descriptive elements and numerical ranges to describe the invention(s); further, for a given element, any upper numerical limit can be combined with any lower numerical limit described herein, including the examples. The features of the inventions are demonstrated in the following non-limiting examples. TEST METHODS

[00037] Melt Flow Rate (MFR). MFR is defined in gr of polymer per 10 min (g/10 min or its equivalent unit dg/min and was measured according to ASTM D1238 (2.16 kg, 230°C). For reactor granule and/or powder polypropylene samples that are not stabilized, the following sample preparation procedure is followed before measuring the MFR. A solution of Butylated Hydroxy Toluene (BHT) in hexane is prepared by dissolving 40 ± 1 grams of BHT into 4000 ± 10 ml of Hexane. Weigh 10 ± 1 grams of the granule/powder polypropylene sample into an aluminum weighing pan. Add 10 ± 1 ml of the BHT/Hexane solution into the aluminum pan under a Hood. Stir the sample, if necessary, to thoroughly wet all the granules. Place the sample slurry in a vacuum oven at 105° ± 5°C for a minimum of 20 min. Remove the sample from the oven and place in a nitrogen purged desiccator a minimum of 15 minutes allowing the sample to cool. Measure the MFR following ASTM D1238 procedure.

[00038] Differential Scanning Calorimetry (DSC) for Determination of Crystallization and Melting Temperatures. Peak crystallization temperature (T_c), peak melting temperature (T_m) and heat of fusion (Δ¾) were measured via Differential Scanning

Calorimetry (DSC) using a DSCQ200 (TA Instruments) unit. The DSC was calibrated for temperature using indium as a standard. The heat flow of indium (28.46 J/g) was used to calibrate the heat flow signal. A sample of 3 to 5 mg of polymer, typically in pellet or granule form, was sealed in a standard aluminum pan with flat lids and loaded into the instrument at room temperature. In the case of determination of T_c and T_m corresponding to

10°C/min cooling and heating rates, respectively, the following procedure was used. The sample was first equilibrated at 25°C and subsequently heated to 200°C using a heating rate of 10°C/min (first heat). The sample was held at 200°C for 5 min to erase any prior thermal and crystallization history. The sample was subsequently cooled down to 25°C with a constant cooling rate of 10°C/min (first cool). The sample was held isothermal at 25°C for 5 min before being heated to 200°C at a constant heating rate of 10°C/min (second heat). The exothermic peak of crystallization (first cool) was analyzed using the TA Universal Analysis software and the peak crystallization temperature (T_c) corresponding to 10°C/min cooling rate was determined. The endothermic peak of melting (second heat) was also analyzed using the TA Universal Analysis software and the peak melting temperature (T_m) corresponding to 10°C/min heating rate was determined. Unless otherwise indicated, reported values of T_c T_m in this invention refer to a cooling and heating rate of 10°C/min, respectively.

[00039] Differential Scanning Calorimetry (DSC) for Study of Melt Memory Effect

Melt memory effects were studied using a Perkin-Elmer Diamond DSC instrument calibrated with Indium as a calibration standard. A sample of 3 to 5 mg of polymer, typically in pellet or granule form, was sealed in a standard aluminum pan with flat lids and loaded into the instrument at room temperature. The sample was heated at a given temperature (T_meit) in the range 170-300 °C (1^st heat) and kept at T_melt for 5 min, unless otherwise indicated. The sample was then cooled at -80 °C at a cooling rate of 10 °C/min (first cool) to determine the peak crystallization temperature (T_c) and subsequently it was heated up the T_meit at a heating rate of 10 °C/min to determine the peak melting temperature (T_m). The purpose of these experiments was to determine the effect of T_meit (below and above the equilibrium melting temperature of polypropylene, i.e., 187 °C) on T_c.

[00040] Isothermal DSC Experiments for Determination of Half Crystallization Times and Crystallization Rates. Isothermal crystallization kinetics experiments to determine the half crystallization times and rate of crystallization were carried out using a Perkin-Elmer Diamond DSC instrument calibrated with Indium as a calibration standard. For each polymer sample studied, approximately 3 to 6 mg of sample was encapsulated in the sample pans using the sample preparation press and the sample pans purchased from Perkin- Elmer.

[00041] For the isothermal crystallization experiments, initially the polymer sample is melted at 200°C and kept for 10 min at 200°C, a time sufficient, to erase the melt memory of any previous thermal history. After the melt annealing step the sample was quickly brought to the chosen isothermal crystallization temperature at a cooling rate of 100°C/min to avoid any crystallization during the cooling step. Following the cooling step, sample was held at chosen crystallization temperature isothermally to completely crystallize and the heat flow released during the isothermal crystallization process is monitored as a function of time. The time taken for half the crystallization called half-time is obtained from the isothermal crystallization exotherm. The overall crystallization rates are estimated from the half-time of the isothermal exotherms obtained by holding the sample at the chosen crystallization temperature for sufficient time to assure complete transformation.

[00042] Crystallization via SAOS rheology. Crystallization was monitored via SAOS rheology, where the sample was cooled down from the molten state (at 190°C) at a fixed cooling rate using a 25 mm parallel plate configuration on an ARES 2001 (TA Instruments) controlled strain rheometer. Sample test disks (25 mm diameter, 2.5 mm thickness) were made with a Carver Laboratory press at 190°C. Samples were allowed to sit without pressure for approximately 3 minutes in order to melt and then held under pressure for three minutes to compression mold the sample. The disks were originally approximately 2.5 mm thick; however, after sample trimming off the parallel plates, a gap of 1.9 mm between the plates was used. Thermal expansion of the tools was taken into account during SAOS testing to maintain a constant gap throughout the test. The sample was first heated from room temperature to 190°C. The sample was equilibrated at 190°C (molten state) for 15 min to erase any prior thermal and crystallization history. The temperature was controlled reproducibly within ± 0.5°C. The sample was then cooled from 190°C at a constant cooling rate of l°C/min and an angular frequency of 1 rad/s using a strain of 1% lying in the linear viscoelastic region. For termination of the experiment, a maximum torque criterion was used. Upon the onset of crystallization during the rheological test, the instrument goes into an overload condition when maximum torque is reached and the test is stopped automatically. All experiments were performed in a nitrogen atmosphere to minimize any degradation of the sample during rheological testing. Crystallization was observed by a steep/sudden increase of the complex viscosity and a steep/sudden (step-like) decrease of the loss tangent tan δ (i.e., a plot of complex viscosity vs. temperature and loss tangent vs. temperature depict a neck- like region of sudden change in the rheological properties due to occurrence of crystallization).

[00043] The "onset crystallization temperature via rheology," T_C r eol ^1S defined as the temperature at which a steep (i.e., neck-like) increase of the complex viscosity and a simultaneous steep decrease of tan δ is observed. The reproducibility of T_{c rneo}i is within ± 1°C. From the storage (G') and loss (G") dynamic moduli [C. W. Macosko, Rheology Principles, Measurements and Applications (Wiley -VCH, New York, 1994)], the loss tangent (tan 5) is defined as:

(1) The norm of the complex viscosity or simply complex viscosity |?7^*(<y)| is calculated from G' and G" as a function of angular frequency ω as follows [C. W. Macosko, Rheology Principles, Measurements and

The reproducibility of the complex modulus and dynamic moduli as a function of

temperature is within about 3%.

[00044] Study of evolution of crystalline morphology via Polarized Optical Microscopy (POM). POM (Mitutoyo microscope set up equipped with Lumenera™ LU 165 color CCD camera and two polarizers) was used in conjunction with an Anton Paar MCR- 502 rotational rheometer in order to study the evolution of crystalline structure. In a typical experiment, the test specimen is prepared by compression molding of the resin at about 200°C and pressure of about 500 kPa. The test specimen is placed in the space between two glassy parallel plates (43 mm in diameter). After reaching the desired gap size of 0.1 mm, the test specimen was equilibrated at 200°C for 15 min in order to eliminate the crystallization and thermal histories before cooling to the desired crystallization temperature (I44°C in the Examples of the present invention) at the rate of 10°C/min. The crystalline microstructure, which is formed within the polymer melt matrix over time, is observed in situ with the microscope. The gap size should be adjusted to about 0.1 mm to allow Sight transmission through the sample thickness in order to observe clearly the crystals formed during crystallization. The morphology developed during crystallization as a function of time at the specified temperature was captured as a video at 15 frames/s (fps) and then was decompiled to frames using Matlab. The number of nucleation sites was estimated as the ratio of the number of crystals within the images divided by the volume.

[00045] Xylene Soluble Fractionation. Xylene soluble fractionation was performed according to ASTM D5492. For each sample, two fractions were recovered: the xylene soluble (XS) fraction corresponding to low molecular weight and/or atactic species and the xylene insoluble (XIS) fraction representing the isotactic / crystalline portion of the polymer.

EXAMPLES

[00046] As an overview of the examples, various base polypropylenes have been extruded under identifiable conditions to produce an extruded polypropylene. The data in Table 1 contains comparative examples from a commercial ZSK 320 extruder, where in the absence of a nucleator, a normal Tc is obtained (typically <112°C), while only in the presence of a nucleator (commercial polypropylene using NaBZ) is an enhanced T_c of 117°C obtained with the commercial extruder.

[00047] The data in Tables 2-7 contains inventive examples for a different extruder and different base polypropylenes: ZSK-92, ZSK-30, ZSK-57 extruders, and a Prism (twin screw) extruder. In Tables 2-7, the reported crystallization temperatures T_c were determined according to the procedure described under "Differential Scanning Calorimetry (DSC) for Determination of Crystallization and Melting Temperatures" under TESTING METHODS. The Examples of Table 3 are so-called "2-step polypropylenes", or inventive extruded polypropylenes, of high T_c generated on ZSK-92 twin screw extruder. This demonstrates the enhanced T_c and nucleation effect without existence of an external nucleator. The following Table 1 describes in more detail the "base" or "base" polypropylene used in the examples, listing the melt flow rate (ASTM 1238, 230°C/2.16 kg), the crystallization temperature (T_c), and the melting point temperature (T_m).

[00048] The data of Figure 1 were generated with a small angle oscillatory shear (SAOS) crystallization rheological experiment as described in "TEST METHODS". In Figure 1, the onset of crystallization is depicted via the vertical arrows as a steep decrease of tan δ indicative of increase of system elasticity and structure formation due to occurrence of crystallization. The data of Figure 2 were generated with a SAOS crystallization rheological experiment as described in "TEST METHODS". In Figure 2, the onset of crystallization is depicted via the vertical arrows as a steep decrease of complex viscosity indicative of increase of structure formation due to occurrence of crystallization.

Table 1A. Description of Base Polypropylenes used in the Examples. The Base Polypropylene resins do not contain any external nucleators.

Table IB. Percentage weight of Xylene Soluble (XS) Fractions for selective Inventive and Comparative Examples and Base Polypropylenes. The %XS data were generated accordin to ASTM D5492.

[00049] As an overview of the examples, various base polypropylenes (the terms "base polypropylene" "base polypropylene resin", "base polypropylene granules" and "base" may be used interchangeably) have been extruded under identifiable conditions to produce an extruded polypropylene. The data in Tables 2A, 2B contains comparative examples from a commercial ZSK 320 extruder, where in the absence of a nucleator, a normal Tc is obtained (typically <1 12°C) unless otherwise indicated (inventive), while in the presence of a nucleator (commercial polypropylene using sodium benzoate as nucleator, NaBz) an enhanced T_c of > 1 17°C is obtained, as expected. The data in Table 2C contains comparative and inventive examples without an external nucleator from a commercial ZSK 300 extruder, where in the absence of a nucleator, a normal T_c is obtained (typically <112°C) for the comparative examples and a Tc of 1 16-122°C for the inventive examples. Commercial Scale Extrusions above 200 mm die bore

[00050] The data in Tables 2A-2C where generated in extruders greater than 200 mm bore diameter. Because of the nature of these extruders, it was difficult to completely clean the bore of any potential nucleator and/or particles from previous extrusions, and thus, these data are shown for completeness to demonstrate that the achievement of a ²T_C can occur, but not reproducibly.

[00051] More particularly, the data in Tables 2A and 2B were generated on a ZSK-320 extruder (Coperion) having a 320 mm bore diameter and L/D=26.3 co-rotating intermeshing twin screw configuration. The data in Table 2C were generated on a ZSK-300 extruder (Coperion) having a 300 mm bore diameter and L/D=22.4 co-rotating intermeshing twin screw configuration. Most of the Examples of Tables 2A and 2B are comparative examples, as there is no significant improvement in the Tc (<3°C) upon extrusion relative to the corresponding base polypropylene granules listed in Table 1, with the exception of Inventive Example ID. Examples 1 A-D and 2 A, B are homopolymer polypropylenes without external nucleator. Example 3 is a 2 MFR homopolymer polypropylene in pellet form with the following additive package: Goodrite™ 31 14: 0.06%, Irgafos™ 168: 0.06%, calcium stereate (CaSt): 0.02%, DHT-4V: 0.02% (weight/weight percentages). Example 4 is a 15.5 dg/min MFR peroxide cracked (visbroken) homopolymer polypropylene pellet made from 2 MFR base granules as shown in Table 1 and containing the following additive package: Goodrite™ 3114: 0.06%, Irgafos™ 168: 0.06%, CaSt: 0.02%, DHT-4V: 0.02% (weight/weight percentages). Comparative examples 2A, 2B, and 4C are commercial homopolymer polypropylenes with an external nucleator (sodium benzoate) having a T_c of about 118°C as expected due to the presence of an external nucleator (an increase of about 9°C relative to the T_c of their respective base polypropylene resins as shown in Table 1). In contrast, Inventive Examples 4E and 4F demonstrate a T_c of 121.8°C and 116.4°C, respectively, despite the absence of an external nucleator (an increase of about 7-13°C relative to the T_c of their respective base polypropylene resins as shown in Table 1). The samples of Table 2A and 2B were extruded according to the conditions included in the respective Tables. Since all Examples of Tables 2A, 2B, 2C involve one thermal history of the base granules on ZSK 320 (Tables 2A, 2B) or ZSK 300 (Table 2C) twin screw extruder, the resulting polypropylene pellets are called "one-step extruded polypropylene".

[00052] Unless otherwise indicated, in this and following Tables, when the base polypropylene is indicated as "granule", the final product is called "1-step extruded polypropylene" or simply "1-step" (one extruder thermal history), while when the base polypropylene is indicated as "pellet", the final product is called "2-step extruded polypropylene" or simply "2-step" (two extruder thermal histories).

Lab Scale Extrusions below 200 mm die bore

[00053] The data in Tables 3-7 contains inventive examples for different extruders and different base polypropylenes including ZSK-92, ZSK-30, ZSK-57 (Coperion) twin screw extruders, and a TSE 16 TC (Thermo Prism 16 mm twin screw) extruder.

[00054] The inventive Examples of Table 3 are so-called "2-step extruded polypropylenes", of surprisingly high T_c (>116°C) in the absence of an external nucleator generated on ZSK-92 twin screw extruder. This demonstrates the enhanced T_c without existence of an external nucleator. The base polypropylene PP-B-3 for the Examples of Table 3 is in pellet form made on ZSK 320 (pellets of Example 3, Table 2) without use of an external nucleator. Since the final pellets of the Examples of Table 3 experienced two extrusion histories (one history on ZSK 320 to make the base pellets from base granules and one history on ZSK 92 to make the peroxide cracked pellets), we call the final pellets of the examples of Table 3 as "two-step extruded polypropylenes". A peroxide level of 210 to 330 ppm Lupersol™ 101 (2,5-bis(tert-butylperoxy)-2,5-dimethylhexane) was used to crack the 2 MFR base pellets of Examples of Table 3 to a higher MFR in the range of 14-19 dg/min (Table 3). The peroxide was dry blended in the base pellets and the pellets were fed into the hopper of the extruder. The crystallization temperatures T_c of the samples were measured and recorded in the table.

[00055] SAOS crystallization rheological curves of Inventive and Comparative Examples are shown in Figures 1 and 2. Crystallization half times and crystallization rate enhancements of Inventive vs. Comparative Examples are shown in Figures 3 and 4.

[00056] The data in Table 4 (Examples 8-12) were generated on a ZSK-30 with 2 MFR homopolymer polypropylene granules unless otherwise indicated with the extrusion conditions listed. The vent position was closed on the extruder for each of the extrusion examples here. The crystallization temperatures of the samples were measured. The ZSK-30 extruder consists of two intermeshing, co-rotating screws driven by a 15 horse power motor. The barrel is made up of 5 sections, including two feed and one vent section. Four sections are electronically heated and water cooled, while the primary feed section is only water cooled. The maximum output rate is 65 lbs/hr. There is no breaker plate in the extruder.

[00057] The data in Tables 5A and 5B (Examples 13-19) were generated on a ZSK-30 twin screw extruder as above, from base polypropylene granules PP-B-5 of 4.9 dg/min MFR as listed in Table 1. The vent position was closed on the extruder for each of the extrusion examples here.

[00058] The data in Tables 6A/B (Examples 20-25) were generated on a ZSK-57 twin screw extruder, from base polypropylene granule of 4.9 dg/min MFR as listed in Table 1, and in Tables 6C/D (Examples 26-27) from base polypropylene granule of 1 dg/min MFR as listed in Table 1. In Examples 24 and 25, the base granules were pre-purged with N₂ for 48 hours and 2 was purged in the hopper during extrusion. For all other examples in Tables 5A and 5B: granules were used as received from the reactor without 2 pre-purge and 2 was purged into the hopper during extrusion. The crystallization temperatures of the samples were measured.

[00059] The data in Table 7 (Examples 28-32) are Inventive extrusion examples using base polypropylene granules of 4.9 dg/min MFR as shown in Table 1 without the use of peroxide reactive extrusion with and without additives, but in all cases no external nucleator was used. The extrusions were done in a Thermo Prism 16 mm twin-screw extruder (TSE 16 TC) of 40 L/D and motor power of 1.25 kW at 500 rpm). The crystallization temperatures of the samples were measured.

[00060] It was surprisingly found that by dissolving (i) the base polypropylene granules of 2 dg/min MFR PP-B-2 (see Table 1A) corresponding to Example 4, (ii) the 1-step comparative polypropylene pellet (Example 4) and (iii) the 2-step inventive polypropylene pellets (Examples 5A, 5B) in xylene and precipitating the solution at room temperature to recover the XIS fractions upon filtration according to ASTM D5492, the crystallization temperature T_c of the XIS fractions was about the same for all three cases. This indicates potential loss of the melt memory induced in the high T_c two-step extruded pellets of Inventive Examples 5A, 5B due to dissolution in the xylene solvent. This is shown graphically in Figure 5. The xylene insoluble fractions were obtained upon xylene dissolution, fractionation and filtration according to ASTM D5492. It is postulated that dissolution in the solvent erased the extruder process induced melt memory of the polymers of Inventive Examples 5A and 5B. This is supported by the fact that the XIS polymers of Comparative (4) and Inventive (5A, 5B) Examples have approximately the same T_C; after erasing the melt memory induced by the extrusion process.

[00061] As shown in Figure 6, Inventive Example 5A shows more nucleation sites per unit volume despite the absence of external nucleating agent contributing to higher crystallization temperature over comparative Example 4 (Tables 2, 3). The nucleation site density of inventive Example 5 A is approximately 10 times higher than that of comparative Example 4 as estimated with the method described under TEST METHODS

[00062] As shown in Figure 3, The decrease of to_.5 of inventive Example 5B is noticeable over comparative Example 4 and its corresponding polypropylene base granules. As shown in Figure 4, the crystallization rate is approximated by the inverse of the crystallization half- time (to.5). The increase in crystallization rate on the order of 800-1200% for the Inventive Example 5 relative to the polypropylene base granules over the studied range of isothermal crystallization temperature is noticeable. This implies a significant reduction of injection molding cycle time for Inventive Example 5 over Comparative Example 4 despite the absence of external nucleator

[00063] In Table 9A, the effect of T_melt (as defined under "Differential Scanning Calorimetry (DSC) for Study of Melt Memory Effect" under TESTING METHODS) on T_c is shown for a polypropylene resin (without external nucleating agent) similar to that of inventive example 5B (different production lot). It is shown that the high T_c » 114 °C is surprisingly maintained despite pre-heating the system at T_melt up to 300 °C which is well above the equilibrium melting temperature T_m° = 187 °C (Brandrup, J.; Immergut, E. H.; Grulke, E. A. Polymer Handbook, 4th ed.; Wiley-Interscience: New York, 1999). T_m° is the temperature required to completely randomize or relax the polymer melt, since by theory it is the temperature required to melt infinitely long perfect crystals formed by infinite molecular weight chains (Alamo et al. "A re-examination of the relation between the melting temperature and the crystallization temperature: linear polyethylene", Macromolecules 28: 3205-3213 (1995)). It was unexpectedly observed that the melt memory effect is maintained for the inventive polypropylene at temperatures up to at least 300 °C much greater than T_m°, which is manifested by the fact that T_c does not return to that of the corresponding base PP PP-B-3 (Table 1A), i.e., T_c much greater than 109.7 °C. This is surprising, since literatures shows maintenance of melt memory effect of polypropylene for up to about 174 °C, (e.g. Li et al, "New Understanding on the Memory Effect of Crystallized PP" 32 CHINESE J. POLY. SCI. 1224-1233 (2014) or up to 220 °C for mesomorphic isotactic polypropylene, e.g. Li et al, "Influence of the memory effect of a mesomorphic isotactic polypropylene melt on crystallization behavior" 9 SOFT MATTER 8579-8588 (2013).

[00064] In In Table 9B, the effect of T_mei_t (as defined under "Differential Scanning Calorimetry (DSC) for Study of Melt Memory Effect" under TESTING METHODS) on T_c is shown for a polypropylene resin (without external nucleating agent) similar to that of comparative examples 1A, IB (different production lot). For T_mei_t up to 300 °C, the T_c of the comparative 1-step polypropylene resin is relatively low (T_c = 11 1-113 °C) compared to that of the inventive polypropylene of Table 9A (T_c = 117-120 °C).

[00065] For the inventive polypropylene of Table 9A (2-step resin), the T_c was determined at T_meit = 200 °C and T_meit = 300 °C (both above equilibrium melting temperature of 187 °C) with holding times at T_meit of 5, 10, 30, 60, 90 min. In all cases, melt memory could not be erased and the high Tc was surprisingly maintained (1 19-123 °C). This is a surprisingly novel finding over what is taught in the prior art, where melt memory (melt conformational order) of isotactic polypropylene was able to be erased when polymer was melted at 180 °C below equilibrium melting temperature (187 °C) for 1 hr (Li et al, "Influence of the memory effect of a mesomorphic isotactic polypropylene melt on crystallization behavior" 9 SOFT MATTER 8579-8588 (2013).

Ampoule Experiments

[00066] Polypropylene degradation experiments were carried out in sealed glass ampoules, referred to below simply as "ampoules" under various controlled conditions to elucidate the effect of additives and oxygen on crystallization temperature of controlled rheology polypropylenes. A methodology similar to the ampoule testing performed for the purposes of this invention is described in Tzoganakis et al, "Production of Controlled-Rheology Polypropylene Resins by Peroxide Promoted Degradation by Extrusion" 28 POLYMER ENGINEERING AND SCIENCE 170-180 (1988).

[00067] The ampoules used were standard Pyrex glass tubing of 7 mm OD and 5 mm ID and 0.3 m long. For each test, twenty five ampoules were used. Sets of 5 ampoules were immersed in the oil bath for time intervals of 1, 2, 3, 4 and 5 minutes. Upon removal from the oil bath, ampoules were immersed in water and subsequently in liquid nitrogen. Following that, ampoules were wiped and then broken to remove the solidified polymer contents which were ground in a rotary blender.

[00068] All experiments were carried out at 240°C in an oil bath following the recipes described in Table 8. The reactants, consisting of polypropylene granules with or without peroxide and additives according to Table 8, were loaded into the glass ampoules which were sealed. For samples 37-41, peroxide was added to the polypropylene granules in the form of an acetone solution to ensure uniform distribution and coating of the polypropylene granules with peroxide. Following this addition, the granules were allowed to dry overnight to ensure removal of acetone. For sample 42, peroxide was mixed with Drakeol at a ratio 1 : 1 before addition to the polypropylene granules. Additives (wt/wt) in the Examples in Table 8 are: Goodrite 3114: 0.06%, Irgafos 168: 0.06%, CaSt: 0.02%, DHT-4V: 0.02% unless otherwise indicated. For all examples of Table 8, base polypropylene granules PP-B-2 (Table 1) was used.

[00069] A standard high vacuum line was used for degassing the samples. The degassing procedure was as follows: (1) each ampoule was connected to the vacuum manifold, (2) the valve connecting the ampoule to the manifold was opened and the ampoule was evacuated for several minutes, (3) then the valve was closed and (4) the ampoule was sealed with torch at the neck just below the glass joint. For tests that did not require degassing, the ampoules were simply sealed without applying any vacuum. For tests that required nitrogen, after degassing and removal of air from the ampoules, nitrogen was fed to the vacuum line and was allowed to fill the ampoules for several minutes before sealing.

Table 2A. Inventive and Comparative Examples for ZSK 320 Twin Screw Extruder

Table 2B. Inventive and Comparative Examples for ZSK 320 Twin Screw Extruder

Table 2C. Inventive and Comparative Examples for ZSK 300 Twin Screw Extruder

Table 3. Inventive Examples for ZSK 92 twin screw extruder

(The base polypropylene of the examples of Table 3 are the pellets of Example 3 (Table 1) made on ZSK 320)

Table 4. Inventive Examples for ZSK 30 twin screw extruder

Table 5A. Inventive Examples for ZSK 30 twin screw extruder

Table 5B. Inventive Examples for ZSK 30 twin screw extruder

Table 6A. Inventive Examples for ZSK 57 twin screw extruder

Table 6B. Continuation of Table 6A, Inventive Examples for ZSK 57 twin screw extruder

Table 6C. Inventive Examples for ZSK 57 twin screw extruder

Table 6D. Continuation of Table 6C, Inventive Examples for ZSK 57 twin screw extruder

Table 7. Inventive Examples for 16 mm twin screw Thermo Prism extruder

Table 8. Ampoule Experiments. The base polypropylene granules used for all ampoule experiments are PP-B-2 (Table 1A).

Table 9A. Melt Memory Studies For 2-Step Polypropylene Resin. The Resin is Similar to That of Inventive Example 5B (Different Production Lot).

Table 9B. Melt Memory Studies For 1-Step Polypropylene Resin. The Resin is Similar to That of Comparative Examples 1 A, IB (Different Production Lot).

[00070] Now, having described and demonstrated the various features of the inventive methods and compositions, described here in numbered paragraphs is:

PI . A method of increasing the crystallization temperature of polypropylene comprising: melt deforming a base polypropylene in the absence of external nucleating agents, wherein the polypropylene has a crystallization temperature T_c, an MFR from 1.0 to 10.0 g/10 min or Mw from 50,000 to 500,000 g/mol, an average meso run length determined by ¹³C NMR of at least 50 mol% meso pentads (mmmm) content of greater than 0.890; and

recovering a deformed polypropylene having a second crystallization temperature ²T_C from 4 to 20°C higher than the base polypropylene;

characterized in that, upon heating the deformed polypropylene to a temperature within a range from 200 to 300°C, the second deformed polypropylene has a third crystallization temperature ³T_C within ±2°C of ²T_C;

wherein the melt deformation is accomplished in one or multiple deformation steps and at a Specific Energy Input of at least 0.05 kW-hr/kg. P2. The method of numbered paragraph 1, wherein the melt deformation is accomplished in a single or twin-screw extruder, of screw diameter D of at least 9 mm, of extruder L/D of at least 5: 1.

P3. The method of numbered paragraph 2, wherein the length-to-diameter ("L/D") ratio of the extruder is within a range from 5: 1 to 100: 1.

P4. The method of numbered paragraph 1, wherein the melt deformation is accomplished using a single screw extruder, a double screw extruder, by injection molding, and/or fiber spinning or melting through a fiber spinning or melting die.

P5. The method of any one of the previous numbered paragraphs, wherein the base polypropylene is blended with peroxide during melt deformation.

P6. The method of any one of the previous numbered paragraphs, wherein after melt deformation the base polypropylene is blended with peroxide during a second melt deformation.

P7. The method of any one of the previous numbered paragraphs, wherein the base polypropylene is blended with antioxidants during melt deformation.

P8. The method of any one of the previous numbered paragraphs, wherein the base polypropylene is a Ziegler-Natta produced polypropylene.

P9. The method of any one of the previous numbered paragraphs, wherein the T_c of the base polypropylene is within a range from 105, or 110°C to 114, or 1 16, or 1 18, or 120, or 125°C.

P10. The method of any one of the previous numbered paragraphs, wherein the melt deformation is conducted at a Specific Energy Input within the range from 0.05, or 0.10, or 0.20, or 0.25, or 0.30 kW-hr/kg to 0.80, or 1.00, or 1.20, or 2.00 kW-hr/kg.

P 1 1. The method of any one of the previous numbered paragraphs, wherein the base polypropylene has within the range from 0.5, or 1.0, or 2.0 wt% to 8.0, or 10.0 wt%, by weight of the base polypropylene, of a low molecular weight polypropylene component having a weight average molecular weight (Mw) within the range of from 5,000 to 30,000 g/mole.

PI 2. The method of numbered paragraph 9, wherein the proportion of low molecular weight polypropylene component in the deformed polypropylene is higher than in the base polypropylene.

PI 3. The method of any one of the previous numbered paragraphs, wherein the deformed polypropylene is cooled to a solid and is melt deformed a second time to form a second deformed polypropylene. PI 4. The method of any one of the previous numbered paragraphs, wherein the base polypropylene is deformed at a melt temperature within the range from 180, or 190, or 200, or 210, or 220°C to 300, or 320, or 340°C.

PI 5. The method of any one of the previous numbered paragraphs, wherein the deformed polypropylene having a T_c from 2 to 10°C higher than the base polypropylene.

PI 6. The method of any one of the previous numbered paragraphs, wherein the melt deformation process occurs under 2 purge.

PI 7. The method of any one of the previous numbered paragraphs, wherein the melt deformation process occurs under air (O2) purge.

PI 8. The method of any one of the previous numbered paragraphs, wherein the base polypropylene is pre-purged with 2 before being melt deformation.

PI 9. The method of any one of the previous numbered paragraphs, wherein the increase in ²Tc of the deformed polypropylene occurs induced by the extruder process so that the high ²T_C is maintained despite further processing ("deformation") at melt temperatures as high as 200 to 300 °C.

P20. The method of any one of the previous numbered paragraphs, wherein the base polypropylene or polypropylene after the melt deformation step(s) has a MFR of 0.1 to 2000 dg/min.

P21. The method of any one of the previous numbered paragraphs, wherein the base polypropylene or polypropylene after the melt deformation step(s) has a Mw of 30,000 to 1,000,000 g/mol.

P22. The method of any one of the previous numbered paragraphs, wherein the polypropylene after the melt deformation step(s) has a Tc of greater than 1 13, or 114, or 115, or 116, or 118, or 120, or 124°C.

P23. The method of any one of the previous numbered paragraphs, wherein the base polypropylene or polypropylene after the melt deformation step(s) has an average meso run length determined by NMR of at least 50 or 60 or 70 or 80, or having a percentage molar meso pentads (mmmm) content of greater than 0.890 or 0.900%.

P24. A fiber and/or fabric made from the deformed polypropylene of any one of the previous numbered paragraphs.

P25. An article made from the deformed polypropylene of any one of the previous numbered paragraphs via injection molding, thermoforming, BOPP process (biaxially oriented PP), compression molding, foam extrusion, etc. P26. A deformed polypropylene composition having a second crystallization temperature ²T_C from 4 to 20°C higher than the base polypropylene Tc made by the process of any one of the previous numbered paragraphs 1 to 23.

[00071] Also disclosed is the use of an extruder to increase the Tc of a base polypropylene as described in any of the previous numbered paragraphs. Also disclosed is the use of a deformed polypropylene to form fibers, fabrics, pallets, automotive components, and appliances.

[00072] For all jurisdictions in which the doctrine of "incorporation by reference" applies, all of the test methods, patent publications, patents and reference articles are hereby incorporated by reference either in their entirety or for the relevant portion for which they are referenced.

Claims

1. A method of increasing the crystallization temperature of polypropylene comprising: melt deforming a base polypropylene in the absence of external nucleating agents, wherein the polypropylene has a crystallization temperature T_c, an MFR from 1.0 to 10.0 g/10 min or Mw from 50,000 to 500,000 g/mol, an average meso run length determined by ¹³C NMR of at least 50 mol% meso pentads (mmmm) content of greater than 0.890; and

recovering a deformed polypropylene having a second crystallization temperature ²T_C from 4 to 20°C higher than the base polypropylene Tc;

characterized in that, upon heating the deformed polypropylene to a temperature within a range from 200 to 300°C, the second deformed polypropylene has a third crystallization temperature ³T_C within ±2°C of ²T_C;

wherein the melt deformation is accomplished in one or multiple deformation steps and at a Specific Energy Input of at least 0.05 kW-hr/kg.

2. The method of claim 1, wherein the melt deformation is accomplished in a single or twin-screw extruder, having screw diameter D of at least 9 mm, and a length to diameter ratio (L/D) of at least 5: 1.

3. The method of claim 2, wherein the length-to-diameter ("L/D") ratio of the extruder is within a range from 5: 1 to 100: 1.

4. The method of claim 1, wherein the melt deformation is accomplished using a single screw extruder, a double screw extruder, by injection molding, and/or fiber spinning or melting through a fiber spinning or melting die.

5. The method of claim 1, wherein recovering the deformed polypropylene includes cooling to a temperature to form a solid, preferably pellets.

6. The method of claim 1, wherein the step of heating the deformed polypropylene includes any heating and/or melt deformation method such as fiber forming, a second extrusion, or injection molding.

7. The method of claim 1, wherein the base polypropylene is blended with peroxide during melt deformation.

8. The method of claim 1, wherein after melt deformation the base polypropylene is blended with peroxide during a second melt deformation.

9. The method of claim 1, wherein the base polypropylene is blended with antioxidants during melt deformation.

10. The method of claim 1, wherein the base polypropylene is a Ziegler-Natta produced polypropylene.

1 1. The method of claim 1 , wherein the T_c of the base polypropylene is within a range from 100°C to 125°C.

12. The method of claim 1, wherein the melt deformation is conducted at a Specific Energy Input within the range from 0.05 kW-hr/kg to 2.00 kW-hr/kg.

13. The method of claim 1, wherein the base polypropylene has within the range from 0.5 wt% to 10.0 wt%, by weight of the base polypropylene, of a low molecular weight polypropylene component having a weight average molecular weight (Mw) within the range of from 5,000 to 30,000 g/mole.

14. The method of claim 13, wherein the proportion of low molecular weight polypropylene component in the deformed polypropylene is higher than in the base polypropylene.

15. The method of claim 1, wherein the base polypropylene is deformed at a melt temperature within the range from 180°C to 340°C.

16. The method of claim 1, wherein the melt deformation process occurs under 2 purge.

17. The method of claim 1, wherein the melt deformation process occurs under air (O2) purge.

18. The method of claim 1, wherein the base polypropylene is pre-purged with 2 before melt deformation.

The method of claim 1, wherein the increase in Tc of the deformed polypropyli occurs due to a melt memory phenomenon induced by the extruder process.

20. The method of claim 1 , wherein the base polypropylene or polypropylene after the melt deformation step(s) has a MFR of 0.1 to 2000 dg/min.

21. The method of claim 1 , wherein the base polypropylene or polypropylene after the melt deformation step(s) has a Mw of 30,000 to 1,000,000 g/mol.

22. The method of claim 1, wherein the polypropylene after the melt deformation step(s) has a Tc of greater than 113°C.

23. A fiber and/or fabric made from the deformed polypropylene of claim 1.

24. An article made from the deformed polypropylene of claim 1 via injection molding, thermoforming, BOPP process (biaxially oriented PP), compression molding, or foam extrusion.

25. A deformed polypropylene composition having a second crystallization temperature 2T_C from 4 to 20°C higher than the base polypropylene Tc made by the process of claim 1.