[0001] This application claims the benefit of U.S. Provisional Application No. 62/315,731 filed on March 31 , 2016, and U.S. Provisional Application No. 62/315,722 filed on March 31 , 2016, and U.S. Provisional Application No. 62/315,737 filed on March 31, 2016, and U.S. Provisional Application No. 62/315,744 filed on March 31 , 2016, the contents of each of which are incorporated herein by reference.

TECHNICAL FIELD

[0002] The present invention relates to cellulosic composites comprising cellulosic filaments (CF), and methods for producing such cellulosic composites. Embodiments of such composites have improved mechanical properties or moisture resistance when compared to composites derived from conventional cellulosic feedstock.

BACKGROUND ART

[0003] There is increasing demand for cost-effective composite materials derived from renewable feedstock. Cellulosic materials have been previously used as fillers in thermoplastics. For example, wood plastic composites (WPCs) have found application in a multitude of commercial products in recent years, and the overall market for WPCs is estimated to be billions of dollars annually. By and large, the leading uses for WPCs are in construction and automotive applications. When compared to conventional mineral- or glass-filled composites, WPCs have lower specific gravity and are often more cost-effective. They also generally have the look of natural wood, which can be desirable. However, WPCs typically have poorer mechanical properties and moisture resistance compared to mineral- and glass-filled composites.

[0004] Cellulosic composites based on chemically processed pulp have been recently developed and commercialized. Chemically processed pulp is cellulosic material produced using chemical pulping processes, such as kraft or sulfite processes, that involve chemical treatment and high temperatures. These chemical pulping processes remove much of the hemicelluloses and lignin from the pulp, so the resulting chemical pulp contains little or no residual lignin. [0005] When compared to WPCs, composites based on chemically processed pulp generally have improved mechanical properties, lower odor and can be pigmented or colored like conventional thermoplastics. However, composites based on chemically processed pulp are typically more expensive than WPCs and mineral-filled composites. They also have poorer mechanical properties and moisture resistance when compared to mineral- or glass-filled composites. For this reason, the commercial adoption of composites based on chemically processed pulp has been only in niche applications to date.

[0006] The technology described herein relates to cellulosic composites based on cellulosic filaments (CF). Embodiments of these composites have improved moisture resistance and/or improved mechanical properties when compared to cellulosic composites described in the art.

SUMMARY OF INVENTION

[0007] Cellulosic composites comprising cellulosic filaments (CF) and a polymeric matrix are described herein. When CF is incorporated into a polymeric matrix, it is capable of improving certain attributes of the polymeric composites. In certain embodiments, such composites have improved mechanical properties and improved moisture resistance.

[0008] Processes for the preparation of cellulosic composites comprising CF incorporated in a polymeric matrix are also described herein. Embodiments of these processes involve melt processing CF with a relatively high moisture content. In some embodiments, the moisture content of the CF prior to melt processing is greater than 10 wt%; in some embodiments, the moisture content is greater than 20 wt%; in preferred embodiments, the moisture content is greater than 30wt%; and in particularly preferred embodiments the moisture content is greater than 40 wt%. In some embodiments, the moisture content of the CF prior to melt processing is in the range of 30 wt% to 75wt%.

[0009] Such processes can enable the preparation of composites with CF substantially uniformly dispersed in a polymeric matrix. In some embodiments they are used to produce a masterbatch, comprising a high concentration of CF in a polymeric matrix. The masterbatch can be let down (or diluted) with further polymeric matrix to a desired loading level.

[0010] The cellulosic composites described herein may also include one or more additives that further improve the mechanical and/or chemical properties of the composites. For example, in some embodiments, the cellulosic composites include a coupling agent and/or an antioxidant.

[0011] The cellulosic composites described herein may also include one or more additional fillers that further improve the mechanical and/or chemical properties of the composites.

[0012] Embodiments of the cellulosic composites described herein can be converted into articles using conventional extrusion and molding techniques. These articles have utility in a variety of markets including automotive, building and construction, consumer and appliance applications.

BRIEF DESCRIPTION OF DRAWINGS

[0013] In the figures which illustrate by way of example only, embodiments of the present invention,

[0014] FIG. 1 is a simplified flowchart depicting steps in an exemplary process for making cellulosic composites having cellulose filaments and articles manufactured therefrom; and

[0015] FIG. 2 is a flowchart diagram depicting steps involved in a process, exemplary of an embodiment of the present invention, for preparing cellulosic composites comprising cellulosic filaments.

DESCRIPTION OF EMBODIMENTS

[0016] The following terms found in this disclosure are used as follows:

[0017] "Cellulosic Composite" is used to refer to a composite material that comprises a polymeric matrix and a cellulosic filler. [0018] "Cellulosic Filaments" or "CF" is used to refer to a high aspect ratio microfibrillated cellulose (MFC) pulp. This is typically produced by mechanically refining chemically processed pulp or mechanical pulps. The production process can also involve chemical and/or emzymatic processing. "CF" includes cellulose microfibrils (CMF), cellulose nanofibrils (CNF) and nanofibrillated cellulose (NFC).

[0019] "CF Composite" is used to refer to a composite material that comprises a polymeric matrix and a CF filler.

[0020] "Chemically processed pulp" or "chemical pulp" is used to refer to cellulosic material produced using a chemical pulping process, such as kraft or sulfite pulping processes.

[0021] "Mechanically processed pulp" or "mechanical pulp" is used to refer to a cellulosic material produced using a mechanical pulping process or a chemi-mechanical pulping process. For example, "mechanical pulp" includes, thermo-mechanical pulp (TMP), refiner mechanical pulp (RMP), chemi-thermomechanical pulp (CTMP), medium density fiber (MDF), ground wood pulp (GWP), bleached chemi-thermomechanical pulp (BCTMP), and semichemical pulp.

[0022] "Composite" is used to refer to a material comprising a polymeric matrix and a filler.

[0023] "Coupling Agent" is used to refer to an additive that improves the interfacial adhesion between a polymeric matrix and a cellulosic filler.

[0024] "Melt Processable Composition" is used to refer to a formulation that is capable of being melt processed, typically at elevated temperatures, by means of conventional polymer melt processing techniques such as extrusion or injection molding, for example.

[0025] "Melt Processing Techniques" is used to refer to various melt processing techniques that may include, for example, extrusion, injection molding, blow molding, rotomolding, thermal kinetic mixing or batch mixing.

[0026] "Polymeric Matrix" is used to refer to a melt processable polymeric material. [0027] The above summary and the detailed description that follows are not intended to describe all embodiments or every possible implementation of the present technology. The detailed description is intended to provide some illustrative embodiments.

[0028] The present technology relates to composites based on cellulosic filaments (CF) that, in at least some embodiments, have improved moisture resistance and/or have improved mechanical properties when compared to known cellulosic composites. The cellulosic composites described herein comprise CF incorporated into a polymeric matrix.

[0029] Cellulose filaments are ribbon like structures or fibers. The CF used in the composites described herein is characterized by having a high aspect ratio. The aspect ratio of a CF is the ratio of the length of the fiber to the width.

[0030] In some embodiments, the average aspect ratio of the CF is preferably greater than 50; in other embodiments the average aspect ratio is greater than 100; and in yet other embodiments is in the range of 100 to 10,000. Certain embodiments of CF may typically have a length of Ι ΟΟμιη to 500μιη and a typical width of 80nm to 500nm, in which case the aspect ratios may range from 1000 to 6250.

[0031] Examples of suitable CF materials are those available from FP Innovations of Pointe-Claire, QC, Canada. Such materials and methods for their preparation are described in U.S. Patent Application Publication US201 1/0277947A1.

[0032] The CF can be incorporated into any suitable polymeric matrix to form cellulosic composites with enhanced mechanical and chemical properties. In some embodiments, the CF loading in the polymeric matrix is in the range of about 5-99 wt%; in other embodiments, the CF loading is in the range of about 10-95 wt%; and in yet other embodiments the CF loading is between 10-90 wt%. In some embodiments the CF loading in a masterbatch is in the range of 80- 99 wt%. These are weight percentages of CF in the final composite or masterbatch.

[0033] The polymeric matrix may comprise one or more polymers. Non-limiting examples of polymers that can be used in embodiments of the present cellulosic composites include: high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), functional polyolefin copolymers including polyolefin-based ionomers, polypropylene (PP), polyolefin copolymers (e.g., ethylene-butene, ethylene-octene, ethylene vinyl alcohol), polystyrene, polystyrene copolymers (e.g., high impact polystyrene, acrylonitrile butadiene styrene copolymer), polyacrylates, polymethacrylates, polyesters, polyvinylchloride (PVC), fluoropolymers, polyamides, polyether imides, polyphenylene sulfides, polysulfones, polylactic acid (PLA), polyacetals, polycarbonates, polyphenylene oxides, polyurethanes, thermoplastic elastomers (e.g., SIS, SEBS, SBS), or combinations thereof. For some end-use applications, polyolefins are well-suited to serve as polymeric matrices, for example, in articles useful as automotive components.

[0034] Bioplastics polymers useful in this invention include, biobased, biodegradable or compostable polyesters, polyamides, polyurethanes, polyacrylates, polyolefins, thermoplastic starches and cellulosics. Bioplastics of particular interest include biobased, biodegradable or compostable polyesters. Non limiting examples of biobased or biodegradable or compostable polyesters include: PLA (Polylactic acid), PHA (Polyhydroxyalkanoates), PBAT (polybutyrate adipate terephthalate), PBS (polybutylene succinate), PCL (polycaprolactones), PGA (Polygycolic acid).

[0035] Polylactic acid is increasingly proving to be a viable alternative to petrochemical- based plastics in many applications. PLA is produced from renewable resources and is biodegradable. This makes it well suited for green or environmentally sensitive applications. In addition, PLA has unique physical properties that make it useful in several industrial applications including paper coating, fibers, films, and packaging materials and the like.

[0036] The polymeric matrix may optionally contain one or more additives. Non-limiting examples of conventional additives include antioxidants, light stabilizers, fibers, blowing agents, foaming additives, antiblocking agents, heat stabilizers, impact modifiers, biocides, antimicrobial additives, compatibilizers, plasticizers, tackifiers, processing aids, lubricants, coupling agents, flame retardants and colorants. The additives may be incorporated into the melt processable composition in the form of powders, pellets, granules, or in other extrudable forms. The amount and type of additives incorporated in the melt processable composition can be suitably chosen, depending upon the polymeric matrix and the desired physical properties of the finished composition. Those skilled in the art of melt processing are capable of selecting appropriate amounts and types of additives for a specific polymeric matrix and CF filler in order to achieve desired physical properties of the finished composite material.

[0037] Some embodiments of the present cellulosic compositions comprise coupling agents and/or antioxidants as additives. Non-limiting examples of coupling agents include silanes, zirconates, titanates and functionalized polymers. Preferred coupling agents include silane and maleic anhydride grafted polymers. Non-limiting examples of maleic anhydride grafted polymers include those sold under the tradenames Polybond (Addivant), Extinity (NWP), Integrate (Lyondell Basell), and Fusabond (DuPont). Preferred antioxidants include monomeric, polymeric and oligomeric phenols. Non-limiting examples of antioxidants include those sold under the tradenames Irganox, Irgaphos (BASF) and Hostanox (Clariant). Typical loading levels of coupling agents and antioxidants are approximately 0.1 to 5 wt% of the composite formulation.

[0038] Some embodiments of the present cellulosic compositions comprise one or more additional fillers. These can be incorporated in the melt processable composition, and can be used to adjust the mechanical properties of the final cellulosic composite material or articles made therefrom. For example, fillers can function to improve mechanical and thermal properties of the cellulosic composite. Fillers can also be utilized to adjust the coefficient of thermal expansion (CTE) of the cellulosic composite, to make it more compatible with other materials with which it is to be used, for example. Non-limiting examples of fillers include mineral and organic fillers such as talc, mica, clay, silica, alumina, carbon fiber, carbon black, glass fiber and conventional cellulosic materials such as wood flour, wood fibers, non-wood plant fibers, sawdust, wood shavings, newsprint, paper, flax, hemp, wheat straw, rice hulls, kenaf, jute, sisal, peanut shells, soy hulls, or other cellulose containing materials, and optionally lignin. The amount and type of filler in the melt processable composition can be suitably chosen depending upon the polymeric matrix and the desired physical properties of the finished composition. Fillers such as calcium carbonate, talc, clay and cellulosic fiber are well-suited for many applications. In some embodiments, the additional filler makes up 1 wt% to 90 wt% of the composite; in some embodiments, 5 wt% to 75 wt % of the composite; and in some embodiments 1 wt% to 60 wt % of the composite.

[0039] Cellulosic composites based on CF, and incorporating optional additives and/or additional fillers, can be prepared by blending the components into the polymeric matrix. Depending on the type and nature of polymeric matrix, this can be done using a variety of conventional mixing processes. For melt processable thermoplastic compositions, the polymeric matrix and additives can be combined by any suitable blending technique commonly employed in the plastics industry, such as with a compounding mill, a Banbury mixer, or a mixing extruder. The mixing operation is most conveniently carried out at a temperature above the melting point or softening point of the polymeric matrix. In some cases melt-processing of the mixture is performed at a temperature from 80 °C to 400 °C, although suitable operating temperatures are selected depending upon the melting point, melt viscosity, and thermal stability of the composite formulation. Different types of melt processing equipment, such as extruders, may be used to process the melt processable compositions described herein.

[0040] The resulting melt-blended mixture can be either extruded directly into the form of the final product shape or can be pelletized or otherwise comminuted into a desired particulate size or size distribution, and then fed to an extruder, such as a twin-screw extruder, that melt- processes the blended mixture to form the final product shape.

[0041] A flowchart depicted in FIG. 1 illustrates the above exemplary process. An exemplary process S100 starts with mixing CF into a polymer matrix in step S102. If the optional use of additives is desired in step S104 then additives are added to the mixture (step S106), but otherwise the step S106 is bypassed. Similarly, if the optional use of fillers is desired (step S108) then fillers are added to the mixture (step SllO), but otherwise step SllO is bypassed. As noted above, for melt processable thermoplastic compositions, the polymeric matrix and additives can be combined by any suitable blending technique such as with a compounding mill, a Banbury mixer, or a mixing extruder. In Step SI 12 melt processing is used, which in this embodiment may be at a temperature from 80°C to 400°C. Depending on the decision on whether to pelletize/comminute at step SI 14, the output of step SI 12 is either extruded directly into the form of the final product shape (step S120) or can be pelletized or otherwise comminuted (SI 16) into a desired particulate size or size distribution, and then fed to an extruder, such as a twin-screw extruder, that melt-processes the blended mixture to form the final product shape (step SI 20).

[0042] In known processes for the preparation of cellulosic composites, the cellulosic material is typically dry or has a low moisture content. It can be difficult to pull apart or break up the cellulosic material and achieve adequately uniform dispersion of the cellulosic material in the polymeric matrix.

[0043] Preferred embodiments of processes for the preparation of cellulosic composites comprising CF involve melt processing CF with a relatively high moisture content. In some embodiments, the moisture content of the CF prior to melt processing is greater than 10 wt%; in some embodiments, the moisture content is greater than 20 wt%; in preferred embodiments, the moisture content is greater than 30 wt%; and in particularly preferred embodiments the moisture content is greater than 40 wt%. In some embodiments, the moisture content of the CF prior to melt processing is in the range of 30 wt% to 75 wt%.

[0044] It has been found that using CF with a relatively high moisture content can facilitate the dispersion of the CF in the polymeric matrix during melt processing of the mixture. The moisture tends to aid separation of the filaments, and moist CF tends to break apart more easily than dry cellulosic materials which have a tendency to become matted and consolidated. The water is gradually removed (evaporated) during the melt processing steps. This innovative wet processing approach can enable the preparation of composites with CF substantially uniformly dispersed in a polymeric matrix, and can enable the preparation of composites with high loadings of CF in a polymeric matrix. For example, loadings of greater than 95 wt% in the composites can be achieved. [0045] In some embodiments of processes for the preparation of cellulosic composites comprising CF, the CF is provided dry or with a low moisture content, and the water content of the CF is increased prior to melt processing the CF with the polymeric matrix. For example, dry cakes of CF can be rehydrated by adding water, and then the CF can be melt processed with the polymeric matrix and any other desired components of the composite as described herein.

[0046] In some embodiments of processes for preparing the present cellulosic composites and articles made therefrom, the cellulosic composites are produced in a two-step process. First, a masterbatch of the CF composite is produced by melt processing CF with a high moisture content with a thermoplastic polymeric matrix, and optionally other additives or fillers. The resulting masterbatch has a high concentration of CF, and can be subsequently letdown (or diluted) to a more suitable loading level for the final application using a second melt processing step (e.g., compounding, injection molding or extrusion). In preferred embodiments, the masterbatch has a CF content in the range of about 50 wt% to 99 wt%, and the letdown has a CF content in the range of about 5 wt% to 50 wt%.

[0047] The above exemplary process is illustrated in FIG. 2. As shown, an exemplary process S200 starts with obtaining CF in step S201. As noted above, the CF at step S201 may be provided dry or with a low moisture content.

[0048] In step S202 moisture is introduced into the CF, for example, by adding water.

[0049] In step S203 the CF is mixed or combined with the polymeric matrix. If the optional use of additives is desired in step S204 then additives are added to the mixture (step S206), but otherwise the step S206 is bypassed. Similarly, if the optional use of fillers is desired (step S208) then fillers are added to the mixture (step S210), but otherwise step S210 is bypassed.

[0050] In Step S212 a first of two melt processing steps is used to form a masterbatch. The resulting masterbatch may have high concentration of CF. In some embodiments, the resulting masterbatch from step S212 may contain CF that is in the range of about 50wt% to 99wt%. [0051] This masterbatch from step S212 is subsequently let down or diluted in step S214. The diluted masterbatch from step S214 may contain CF in the range of about 5wt% to 50wt%.

[0052] A second melt processing step S216 is subsequently employed to obtain the desired cellulosic composite comprising CF. The melt processing in step S216 may include compounding, injection or extrusion.

[0053] Embodiments of the cellulosic composites described herein have broad utility in the automotive, building and construction, consumer and appliance markets. Non-limiting examples of potential uses of cellulosic composites of this disclosure include automotive components, decking, fencing, railing, roofing, siding, consumer utensils and containers

[0054] Articles produced by melt processing the cellulosic composites described herein can exhibit superior characteristics. For example, they may have improved mechanical properties and/or moisture resistance.

TABLE 1: MATERIALS

TABLE 2: EXPERIMENTAL MASTERBATCH FORMULATIONS TABLE 3: EXPERIMENTAL COMPOSITE SAMPLE FORMULATIONS

[0055] CF (with a moisture content of 50 -70%), was first run through an electric 5" pellet mill (commercially available from Pellet Masters, Chippewa Falls, WI, USA) to densify and pelletize the material. Two different masterbatch samples, MB 1 and MB2, were prepared with different compositions as shown in TABLE 2, each having a high concentration of CF (95%). The masterbatch samples were prepared by dry blending the pelletized moist CF with HDPE or PP, and then gravimetrically feeding the mixture into a 27 mm twin screw extruder (52: 1 L:D, commercially available from Entek Extruders, Lebanon, OR). The compounding was performed using the following temperature profile in zones 1 -13 (°F): 100, 350, 400, 400, 400, 400, 400, 400, 400, 400, 400, 400, 400. The material was run though the extruder with the die removed and collected as a dry particulate.

[0056] Masterbatch samples, MB 1 and MB2, were subsequently letdown (diluted), by mixing with an additional quantity of the thermoplastic polymeric matrix (HDPE or PP), as shown in TABLE 3, to form two composite Samples 1 and 2. The components were dry blended in a plastic bag and gravimetrically fed into a 27 mm twin screw extruder (52: 1 L:D, commercially available from Entek Extruders, Lebanon, OR). The compounding was performed using the following temperature profile in zones 1-13 (°F): 100, 350, 400, 400, 400, 400, 400, 400, 400, 400, 400, 400, 400 and a die temperature of 380 °F. The composites were extruded into strands and pelletized into pellets approximately 1 -2 mm in length. [0057] Samples CEl -4, having compositions as indicated in TABLE 3 were also similarly prepared as comparative examples. The talc and glass fiber were side fed downstream in zone 6. Sample CE5 was obtained from Weyerhaeuser Inc.

[0058] The resulting composite samples were injection molded into test specimens and their properties tested following ASTM D790 (flexural properties) and ASTM D638 (tensile properties). Specific Gravity was determined using Archimedes Method. Impact testing (Izod impact) was performed following ASTM D256. Moisture uptake was determined by gravimetric analysis after 24 and 96 hour submersion in water. The results of this testing are given in TABLE 4 below.

TABLE 4: EXPERIMENTAL RESULTS

[0059] Results for Samples CE1 -CE5 are provided as comparative examples, and demonstrate properties for conventional glass- and talc-filled PP and HDPE composites. CE5 demonstrates properties reported for Thrive™, which is a commercially available cellulose-filled polypropylene composite that includes chemical pulp from a kraft pulping process. Results for Samples 1 and 2 demonstrate properties of cellulosic CF composites according to certain embodiments of the present invention. [0060] The composite samples comprising CF exhibited substantially reduced moisture uptake relative to CE5 (Thrive™).

[0061] Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a wide variety of alternate embodiments or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover adaptations or variations of the embodiments discussed herein. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.