THEREOF

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority of United States Provisional Patent Application Serial No. 62/891,524 filed August 26, 2019, which is incorporated herein by reference.

TECHNICAL FIELD

[0002] The present invention generally relates to the field of composite materials, and more specifically to adjust the intrinsic viscosity (IV) for specific applications by addition of graphene based materials into masterbatch composite materials, such as polyethylene terephthalate (PET).

BACKGROUND

[0003] Graphene is an allotrope of carbon in the form of a two-dimensional, atomic-scale, honey-comb lattice in which one atom forms each vertex. Allotropy or allotropism is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of these elements. Allotropes are different structural modifications of an element; the atoms of the element are bonded together in a different manner. Graphene is one of the basic structural element of carbon allotropes, including graphite, charcoal, carbon nanotubes and fullerenes. Graphene is a highly versatile material with unique properties in terms of mechanical strength, electrical conductivity and thermal conductivity. The superior performance of graphene makes it perfectly suited for coatings, membranes and thermoplastics. The desired properties of graphene are at least partly dependent on the two dimensional structure of the carbon allotrope. [0004] In the real-world applications, graphene-type materials include single-layer graphene, double-layer graphene, few-layer graphene, graphene oxide (GO), reduced graphene oxide (rGO), exfoliated graphene nanoplatelets, and ultra-thin graphite because all of these materials can enhance same properties.

[0005] Exfoliated graphene nanoplatelets are new types of graphene-type materials made from graphite. These nanoparticles consist of small stacks of graphene that are 1 to 20 nano meters thick, with diameters ranging from sub-micrometer to 100 micrometers. U.S. Patent Publication 2010/0092809 describes a process for forming exfoliated graphite nanoparticles. [0006] A material with less than 100 nm dimension in any direction is considered a nanomaterial. Ultra-thin graphite with average thickness in between 20 to lOOnm is also considered as a graphene-type material which can give similar performance enhancement like graphene in many real-world applications.

[0007] It is known that a mixture of graphene type material and other nano-carbon materials can synergistically improve properties of many applications, especially in composite applications. Such nano-carbon materials include carbon blacks, carbon nanotubes (CNT), carbon nanofibers, carbon nanocaps, carbon nanobuds, carbon nanopods, carbon nanotorus, graphene flower, and fullerenes.

[0008] Also a mixture of graphene type material and ceramics with high thermal conductivity can enhance thermal conductivity of composite materials. Such ceramics include boron nitride (BN), aluminum nitride (AiN), beryllium oxide (BeO), silicon carbide (SiC), aluminum oxide / alumina (AI2O3), and silicon nitride (S13N4).

[0009] Economical fillers are widely used in composite applications. Such fillers include calcium carbonate (CaC0 ₃ ), Mica, silica (S1O2), glass beads/bubbles, wollastonite, alumina, and calcium sulfite. In general, these materials do not have high thermal conductivity. However, these materials can be coated with graphene type material and the coated filler can transfer heat efficiently in a composite materials.

[0010] Compounding is a process of melt blending plastics with other additives. Compounding changes the physical, thermal, electrical, and/or aesthetic characteristics of the plastic. The final product is called a compound or composite. Compounding starts with a base resin or polymer. The resins have unique characteristics that make each suitable for use in certain applications. By incorporating an extensive range of additives, fillers, and reinforcers, a wide range of properties can be achieved in conductivity, flame retardance, wear resistance, structural, and pre-coloration. The suitable additives are selected based on performance criteria. For example, glass fibers can be added at various levels to increase stiffness in a resin that is more flexible than desired.

[0011] Compounding is done in several steps. Resin and additive(s) are fed and mixed together through an extruder or an continuous mixer where additives are dispersed in the resin. The melted compound exits the extruder or mixer in strands about the diameter of yam. These strands are cooled and cut into pellets. The pellets are thoroughly inspected and quality checked before being delivered to customers for use in further molding processes such as injection molding, blow molding, rotational molding, compression molding, extrusion molding, or thermoforming.

[0012] Masterbatch (MB) is a pre-compounded additives/resin mixture with relatively high additive loading in it. A masterbatch used for coloring plastics is called as color masterbatch and a masterbatch used for impairing other properties to plastics is called additive masterbatch. Masterbatch is a concentrated mixture of additives encapsulated in a carrier resin which comes in pellets, granulates, powders, strands, elastomers, waxes, gels, or liquid form. Masterbatch allows the processor to color or impair properties to raw polymer economically during the industrial plastics manufacturing process. [0013] Melt compounding is the most industrially accessible process for manufacturing of thermoplastic resin masterbatch. When utilizing melt compounding for incorporating graphene nanoplatelets, the most significant challenge is obtaining a uniform dispersion of graphene nanoplatelets in a thermoplastic resin. In this process, graphene can be pre-mixed with a thermoplastic resin to improve the mechanical and thermal properties of the thermoplastic resin. Very often, a master batch with high filler loading is prepared and later diluted into different filler content for final products in the industrial plastic manufacturing.

[0014] Polyethylene terephthalate (PET) is widely used in many applications, especially in the food packaging applications, because it is lightweight, safe, re-sealable, recyclable, flexible, transparent, stable, moldable to many different shapes, and cost-effective to produce food packaging. However, it is important to select a specific type of PET to manufacture a specific type of product since the process conditions to produce each product are precisely optimized for such a specific type of PET to fulfil the necessary requirements for each application. [0015] The most important characteristics of the PET to be selected are the molecular weight and the intrinsic viscosity (IV). The polymer chain length in PET determines the molecular weight of the material and with it the physical properties that make PET such a useful packaging material. Intrinsic Viscosity (IV) is a measure of the polymers molecular weight and therefore reflects the material’s characteristics. The IV of PET is strongly related to its process conditions, and specific process conditions for specific application requires PET with specific IV range.

[0016] In the current manufacturing processes, people choose a PET from an appropriate IV range to make a specific product for specific application, and keep the IV in the same range during the entire manufacturing processes.

[0017] However, a problem that is often encountered is the adjustment of the intrinsic viscosity (IV) of PET. Since a specific IV of PET is required for specific applications, the IV needs to be controlled accurately. However, additives like graphene can change the IV of PET when formulated into a masterbatch. When adding thermally conductive graphene in low IV PET, especially for high content masterbatch processing, The IV of PET can be reduced too much, causing processing difficulty.

[0018] Therefore, there is a need to control the IV of PET while adding graphene type material into PET masterbatch and other thermoplastic based masterbatch.

SUMMARY OF THE INVENTION

[0019] A process for dispersing graphene material in a thermoplastic to form a masterbatch includes loading a first thermoplastic with a specific initial intrinsic viscosity (IV) into an extruder or a continuous mixer, loading a graphene material into the extruder, heating the first thermoplastic to a molten state in the presence of the graphene material to form the masterbatch having a mixture IV, and adjusting the mixture IV to a preselected target IV. The graphene material being single-layer graphene, double-layer graphene, few-layer graphene, graphene oxide, reduced graphene oxide, exfoliated graphite nanoplatelets, ultra-thin graphite, or a mixture of any combination thereof. The graphene material being dispersed in an amount of between 0.001 and 60 total weight percent of the masterbatch. The resulting masterbatch being used in injection molded parts or monofilament, thermoforming parts/sheets/films, technical and tire cord filaments, and industrial fibers, bottles, or textiles.

BRIEF DESCRIPTION OF THE DRAWINGS [0020] The present invention is further detailed with respect to the following drawings that are intended to show certain aspects of the present of invention, but should not be construed as limit on the practice of the invention, wherein: [0021] FIG. 1 is a flowchart of a method for controlling the IV of PET and other thermoplastics while adding graphene type material into PET masterbatch and other thermoplastic based masterbatch in accordance with embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION [0022] The present invention has utility as a process for controlling the intrinsic viscosity (IV) of PET and other thermoplastics while adding graphene type material into PET masterbatch and other thermoplastic based masterbatch. In inventive embodiments a masterbatch is made with a starting PET with higher than appropriate IV range and later further diluted it to an appropriate IV, in order to control the required intrinsic viscosity of the masterbatch. In a specific inventive embodiment, an initial graphene/PET batch is made by mixing PET with higher than appropriate IV and graphene type material so that the IV of the resulted graphene type material/PET masterbatch will be in a certain range. In specific inventive embodiments, the masterbatch formed via melt compounding has a final concentration of graphene at a level of 0.01 total weight percent to 30 total weight percent of the total weight of the masterbatch.

[0023] It is to be understood that in instances where a range of values are provided that the range is intended to encompass not only the end point values of the range but also intermediate values of the range as explicitly being included within the range and varying by the last significant figure of the range. By way of example, a recited range of from 1 to 4 is intended to include 1-2, 1-3, 2-4, 3-4, and 1-4.

[0024] As used herein, weight percent (wt. %) is defined as the percent of the weight of a species in a mixture or composition. [0025] The following description of various embodiments of the invention is not intended to limit the invention to these specific embodiments, but rather to enable any person skilled in the art to make and use this invention through exemplary aspects thereof.

[0026] All publications, patent applications, patents and other references mentioned herein are incorporated by reference in their entirety.

[0027] Unless indicated otherwise, explicitly or by context, the following terms are used herein as set forth below.

[0028] As used in the description of the invention and the appended claims, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0029] Also, as used herein, “and/or” refers to and encompasses any and all possible combinations of one or more of the associated listed items, as well as the lack of combinations when interpreted in the alternative (“or”).

[0030] As used herein, graphene is defined as a two-dimensional material constructed by close-packed carbon atoms including a single-layer graphene, double-layer graphene, few- layer graphene, and graphene nanoplatelets.

[0031] As used herein double-layer graphene is defined as a stack graphene of two layers, few- layer graphene is defined as a stack of graphene of 3-10 layers, graphene nanoplatelet is defined as a stack of graphene of more than 10 layers. The graphene materials can be made by chemical or mechanical exfoliation of graphite, chemical vapor deposition, physical vapor deposition, microwave plasma, sonication/cavitation in solvent, organic synthesis, and epitaxy growth on a substrate.

[0032] As used herein, graphene oxide is defined as graphene with various oxygen-containing functionalities such as epoxide, carbonyl, carboxyl, and hydroxyl groups and a total oxygen content of 10-60wt%, typically around 20-50wt%. [0033] As used herein, reduced graphene oxide is defined as graphene oxide that has been chemically or thermally reduced with a total oxygen content of typically in the range of 10%- 50% depending on the extent of the reduction.

[0034] As used herein, a nanoplatelet is defined as having planar dimensional in orthogonal direction of each independently between 2 and 20 nanometers.

[0035] It is appreciated the other thermoplastics besides polyethylene terephthalate (PET) may be used in the inventive method of controlling the intrinsic viscosity of the thermoplastics with dispersed graphene. Additional thermoplastics operative as a matrix illustratively include polyesters such as glycol-modified polyethylene terephthalate (PETG), polyethylene isophthalate (PEI), polybutylene terephthalate (PBT), polybutylene adipate terephthalate (PBAT), polycyclohexylene dimethylene terephthalate (PCT), glycol-modified polycyclohexane dimethyl terephthalate (PCTG) , Poly trimethylene Terephthalate (PTT), co polyesters of any combinations of the aforementioned polyesters including PET, polycarbonate (PC), acrylonitrile butadiene styrene (ABS), acrylonitrile styrene acrylate (ASA), other thermoplastic elastomers, polyethylene (PE), polypropylene (PP), impact-modified polypropylene, thermoplastic polyolefin (TPO), other polyolefins, polyamide 6 (PA6), polyamide 66 (PA66), polyamide 11 (PA11), polyamide 12 (PA12), other polyamides, thermoplastic polyurethanes (TPU), block copolymers where any of one or combination thereof constitute a majority by monomeric subunit percent of the resulting copolymer, of mixtures of any of the aforementioned.

[0036] Examples of other thermoplastics operative in the present invention and are provided in Table 1. [0037] Table 1. Typical Polymer Systems used with Various Additives and xGnP

[0038] Nano-carbon materials can be combined with graphene type material in this invention. Such carbon nanomaterials include carbon blacks, carbon nanotubes (CNT), carbon nanofibers, carbon nanocaps, carbon nanobuds, carbon nanopods, carbon nanotorus, graphene flowers, and fullerenes.

[0039] Ceramics with high thermal conductivity can be combined with graphene type material in this invention. Such ceramics include boron nitride (BN), aluminum nitride (AiN), beryllium oxide (BeO), silicon carbide (SiC), aluminum oxide / alumina (AI2O3), and silicon nitride (Si3N4). The properties of such materials are provided in Table 2. [0040] Table 2. Typical Ceramic Materials with High Thermal Conductivity

[0041] In addition to an additive being dispersed in thermoplastic as a separate additive, it is appreciated that in some embodiments, the graphene is applied as a coating onto a filler particle. A process for forming a graphene coated particulate is detailed in US20170101571A1. [0042] Exemplary filler particles so coated with graphene are summarized in Table 3 along with thermal conductivity value of unmodified filler materials.

[0043] Table 3. Typical Filler Materials which can be coated with Graphene Type Material

[0044] A dispersion of graphene nanoplatelets in thermoplastic resin, either alone, in combination with ceramic particulate, as a coating on a filler particulate, or coating on a filler particulate in combination with ceramic particulate improves the mechanical and thermal properties of the thermoplastic resin relative to conventional thermoplastic resin absent such inclusions. However, a master batch with such inclusions that is later diluted with conventional, unadulterated resin as part of industrial plastic manufacturing often has modified intrinsic viscosity (IV) properties that are not suitable for routine material processing parameters. According to the present invention, the graphene inclusive masterbatch IV is measured and modified so as to process without modification of manufacturing parameters relative to the use of only conventional resins.

[0045] Intrinsic viscosity (IV) is measured in the present invention per ASTM D4603 using a 0.5% concentration of the polymer dissolved in 60/40 phenol/1,1, 2, 2-tetrachloroethane solution. Solvent and solution flow times are measured at 30°C using a suspended-level Ubbelohde type viscometer for both measurements.

[0046] The method requires that three successive flow times are obtained within 0.2s of the mean.

[0047] Typical IV values for some common application are provided in Table 4 and obtained according to the present invention.

[0048] Table 4. Typical IV Range for Specific Product / Application. [0049] The present invention is further detailed with respect to the following non limiting examples. These examples are not intended to limit the scope of the invention but rather highlight properties of specific inventive embodiments and the superior performance thereof relative to comparative examples.

EXAMPLES

Example 1

[0050] PET with IV of 0.84 was mixed with 0.1 total weight percent of graphene type material (xGnP™ C-300) by a desktop mini-compounder to make a masterbatch. The process temperature was 260°C and the residence time in the extruder was 1 min. The mixed molten polymer was extruded as a strand and cut into pellets. The IV of the masterbatch pellets was measured as 0.76 per ASTM D4603. In general, PET with IV of 0.84 cannot be used in the water bottle applications, but because of the controlled IV, the resulted PET masterbatch can be used in subsequent water bottle manufacturing equipment upon dissolution in convention PET (IV 070-0.78) to produce water bottles with enhanced material properties associated with graphene therein.

Example 2

[0051] PET with IV of 0.82 was mixed with 1 total weight percent of graphene type material (xGnP™ R-10) by a continuous mixer to make a masterbatch. The process temperature was 260°C and the residence time in the continuous mixer was about 30 sec. The mixed molten polymer was fed into a single screw extruder with set temperature of 260°C and extruded as a strand and cut into pellets. The residence time in the single screw extruder was about 1 min. The IV of the masterbatch pellets was measured as 0.65 per ASTM D4603. In general, PET with IV of 0.82 cannot be used in bi-axial oriented film applications, but because of the controlled IV, the resulted PET masterbatch can be used in subsequent biaxially oriented film manufacturing equipment upon dissolution in conventional PET (IV 0.60-0.70) to produce films with enhanced material properties associated with graphene therein.

Example 3

[0052] PET with IV of 0.82 was mixed with 5 total weight percent of graphene type material (xGnP™ R-10) by a continuous mixer to make a masterbatch. The process temperature was 260°C and the residence time in the continuous mixer was about 30 sec. The mixed molten polymer was fed into a single screw extruder with set temperature of 260°C and extruded as a strand and cut into pellets. The residence time in the single screw extruder was about 1 min. The IV of the masterbatch pellets was measured as 0.59 per ASTM D4603. In general, PET with IV of 0.82 cannot be used in fiber and textile applications, but because of the controlled IV, the resulted PET masterbatch can be used in subsequent fiber and textile manufacturing equipment upon dissolution in conventional PET (IV 0.40-0.70) to produce fibers and textiles with enhanced material properties associated with graphene therein.

Example 4

[0053] PET with IV of 0.82 was mixed with 10 total weight percent of graphene type material (xGnP™ R-10) by a continuous mixer to make a masterbatch. The process temperature was 260°C and the residence time in the continuous mixer was about 30 sec. The mixed molten polymer was fed into a single screw extruder with set temperature of 260°C and extruded as a strand and cut into pellets. The residence time in the single screw extruder was about 1 min. The IV of the masterbatch pellets was measured as 0.57 per ASTM D4603. In general, PET with IV of 0.82 cannot be used in fiber and textile applications, but because of the controlled IV, the resulted PET masterbatch can be used in subsequent fiber and textile manufacturing equipment upon dissolution in conventional PET (IV 0.40-0.70) to produce fibers and textiles with enhanced material properties associated with graphene therein.

[0054] In all the examples shown above, the starting PET cannot be used in the target applications due to mismatching IV. However, because of the controlled IV by adding graphene, the resulted masterbatch pellets can be used in the intended applications with enhanced material properties associated with graphene therein.

Other Embodiments

[0055] While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the described embodiments in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient roadmap for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes may be made in the function and arrangement of elements without departing from the scope as set forth in the appended claims and the legal equivalents thereof.