Process for preparing a thermoplastic composite of cellulose pulp modified with waxes or with polymer emulsion, and thermoplastic composition

Abstract

The present invention aims to provide a process for preparing a thermoplastic composite from cellulose pulp modified with waxes, or with polymer emulsions, and a thermoplastic composite prepared by means of both of said processes. The process is used to modify cellulose in the form of chemical pulp, microfibrillated cellulose (MFC) or nanofibrillated cellulose (NFC) by means of extrusion with waxes, or with a polymer emulsion, for subsequent use of the product obtained as a reinforcement in composites with thermoplastic resin.

Description

PROCESS FOR PREPARING THERMOPLASTIC COMPOSITE FROM CELLULOSE PULP MODIFIED WITH WAXES OR POLYMER EMULSION, AND THERMOPLASTIC COMPOSITE TECHNICAL FIELD

[0001] The present invention pertains to the field of thermoplastic composite materials and relates to a process for preparing a thermoplastic composite from cellulose pulp modified with waxes or polymer emulsions, and to a thermoplastic composite prepared from each of said processes. Said thermoplastic composites exhibit good cellulose fiber dispersion characteristics and better mechanical properties than synthetic thermoplastic polymers. Modification of the cellulose pulp with waxes is performed prior to obtaining the composite with the thermoplastic polymer, thus also providing benefits in the processing of thermoplastic composites. BACKGROUND OF THE INVENTION

[0002] In the current context in which sustainability has gained increasing relevance, the search for thermoplastic composites consisting of high-quality materials from renewable sources has intensified, in which the replacement of synthetic polymers with natural polymers is particularly advantageous.

[0003] Lignocellulosic materials can be used as fillers or reinforcing agents in thermoplastic composites, and such materials have become important in polymer matrices due to their advantages over other inorganic or synthetic materials. The addition of mineral fillers and synthetic fibers, aimed at improving mechanical properties, leads to a reduction in non-renewable content.

[0004] Eucalyptus or pine cellulose fibers can be subdivided into chemical, semi-chemical bleached and unbleached cellulose pulp, and have several advantages, such as low density, natural and renewable origin, low cost, and good mechanical properties.

[0005] Furthermore, chemical cellulose pulp is a commodity, composed mainly of cellulose and comes from a natural and renewable source, favoring interest in its use in a more sustainability-oriented approach.

[0006] In this sense, cellulose is an attractive candidate for materials development due to its biocompatibility, biodegradability, and chemical modification potential. Specifically, cellulose fiber has excellent properties, such as lightness, high mechanical strength, high modulus of elasticity and low linear thermal expansion, and its use in obtaining reinforced thermoplastic composites is strategic.

[0007] Similarly, reinforced polymer composites with improved properties can replace conventional materials such as metals, plastics, and wood in many types of applications, for example, the construction, packaging, automotive, furniture, and aerospace industries.

[0008] Furthermore, the use of additives in polymer processing is common. However, the use of waxes to improve polymer yield, physical properties, and processing still presents several barriers, primarily due to the low compatibility between the wax and the synthetic thermoplastic polymer.

[0009] WO 2000 / 076322 A1 discloses a cellulose composite composition comprising hydrophobic wax, anionic polymer, and cellulose. The composite composition is formed by coagulating, regenerating, and drying a mixture consisting of a hydrophobic wax emulsion, anionic polymer emulsion, and viscose. The composite thus formed has a hydrophobic surface with reduced adhesion to hydrophilic surfaces compared to regenerated cellulose alone, or compared to cellulose comprising only paraffin wax or cellulose comprising only anionic polymer.

[0010] Document US 2019 / 0023882 A1 relates to a thermoplastic resin composition containing a thermoplastic synthetic resin, cellulose in a content of 10 to 70 parts by mass relative to 100 parts by mass of the thermoplastic synthetic resin, and an organic peroxide. The document reveals that the process employing the organic peroxide as an additive is capable of conveniently and uniformly dispersing the cellulose in a resin with a high hydrophobic property and is also capable of improving the mechanical strength of the molded material that was formed by molding the resin composition obtained by the process.

[0011] Furthermore, US 8,663,425 B2 refers to a method for manufacturing microfibrous cellulose composite sheets, which includes a process in which a polymer emulsion is mixed with an aqueous suspension containing microfibrous cellulose, the mixed fluid is dewatered onto a porous base material through filtration, and then dried. According to the document, it is possible to provide a manufacturing method in which a microfibrous cellulose composite sheet can be produced extremely efficiently, and the resulting composite sheet exhibits excellent strength characteristics.

[0012] Indeed, there are a number of challenges related to the processing of synthetic solid polymers, particularly with regard to compatibility with other components.

[0013] In particular, cellulose fiber is highly hydrophilic and therefore has low affinity for hydrophobic resins (such as polypropylene, polyethylene and similar), so that simple mechanical mixing through an extruder or similar method does not generate composites with good fiber dispersion and therefore with satisfactory mechanical properties.

[0014] Thus, considering that cellulose pulp is a hydrophilic material, that is, it has an affinity for water, and that synthetic polymers are hydrophobic, that is, they are resistant to water, the preparation of a thermoplastic composite material that combines a hydrophilic element and a hydrophobic element is still a challenge.

[0015] In this sense, the production of a composite containing cellulose fiber and a thermoplastic resin with high hydrophobic properties, such as polypropylene, polyethylene and similar, represents a great challenge due to the low dispersion property of cellulose fiber, which makes it very difficult to form a composite with adequate properties.

[0016] Additionally, there are several problems associated with this non-uniform dispersion of cellulose fibers in a polymer matrix. Indeed, cellulose pulp agglomerates, and thus, the dispersion of a polymer matrix in a non-polar material presents processing difficulties regarding achieving good compatibility and anchoring the cellulose fibers to the polymer matrix to provide good mechanical properties.

[0017] Furthermore, the lower the amount of polymer in the cellulose fiber / polymer mixture, the more difficult it becomes to disperse the cellulosic fiber in the polymer matrix.

[0018] In turn, as the amount of fiber increases, the more viscous the fiber / polymer mixture becomes, making it more difficult to move the fibers within the polymer matrix to provide dispersion.

[0019] Therefore, a thermoplastic composite preparation process that combines two materials with different characteristics is still needed. In this context, it is advantageous to develop new process alternatives for preparing composite materials that combine highly hydrophilic components, such as cellulose pulp, and hydrophobic components, such as polymers, to facilitate the dispersion of a polymer matrix in a non-supporting material.

[0020] Therefore, the present invention relates to a novel and inventive process for modifying cellulose pulp with polyolefin waxes (polyethylene and polypropylene), petroleum waxes, or synthetic waxes, or polymer emulsions, to prepare thermoplastic composite materials that exhibit good dispersion characteristics and improved mechanical properties compared to thermoplastic polymers. The present invention also relates to a thermoplastic composite prepared by each of the aforementioned processes. SUMMARY OF THE INVENTION

[0021] The present invention discloses a process for preparing thermoplastic composites of cellulose pulp modified with polyolefin, petroleum or synthetic waxes, or with polymer emulsions, and the thermoplastic composite prepared from each of said processes, for coating cellulose fibers, with low polarity polymeric materials, so that it presents good dispersion of the fibers and without the presence of fiber agglomerates, in addition to good mechanical properties.

[0022] Specifically, the invention relates to a process for treating cellulose fibers with solid waxes, or with an emulsion of polymers or waxes, in which the cellulose fibers are modified so as to facilitate subsequent dispersion in a thermoplastic polymer, thus forming a composite containing cellulose and the thermoplastic polymer.

[0023] One embodiment of the invention relates to a process for preparing a thermoplastic composite of cellulose pulp modified with polyolefin, petroleum or synthetic waxes, comprising the following steps: a) dewatering the wet pulp, microfibrillated cellulose (MFC) or nanofibrillated cellulose (NFC) by pressing and filtration; b) adding a wax to the dewatered pulp in a mixer; c) extruding the mixture from step b) generating a wax-treated pulp; d) drying the wax-treated pulp; e) processing and composting the material obtained in step d) with a thermoplastic resin; and f) obtaining a composite material.

[0024] In another embodiment of the invention, a thermoplastic composite of cellulose pulp modified with polyolefin, petroleum or synthetic waxes is described, in which the cellulose pulp treated with wax has better compaction characteristics compared to untreated pulp, and this allows for greater ease in feeding and processing the treated pulp.

[0025] Another embodiment of the invention relates to a process for preparing a thermoplastic composite of cellulose pulp modified with a polymer emulsion or an emulsion of polyolefin, petroleum or synthetic waxes, which comprises the following steps: a) dewatering the wet pulp, microfibrillated cellulose (MFC) or nanofibrillated cellulose (NFC) by pressing and filtration; b) adding a polymer or wax emulsion to the dewatered pulp in a mixer, generating an emulsion-treated pulp; c) drying the emulsion-treated pulp; d) grinding and extruding the material obtained in step c) with a thermoplastic polymer; and e) obtaining a composite material.

[0026] In another embodiment of the invention, a thermoplastic composite of cellulose pulp modified with polymer or wax emulsion is described, in which the cellulose pulp treated with polymer or wax emulsion presents good mechanical properties and good fiber dispersion characteristics in the polymer matrix compared to an untreated pulp.

[0027] Therefore, the present invention relates to a new and inventive process for preparing thermoplastic composite materials and to a thermoplastic composite obtained from said process, in which said thermoplastic composite presents an increase in the modulus of elasticity, good dispersion characteristics, as well as improved mechanical properties in relation to the synthetic thermoplastic polymer, in which the cellulose present in the composite acts as a reinforcing agent in the thermoplastic matrix. BRIEF DESCRIPTION OF THE FIGURES

[0028] To assist in identifying the main characteristics of the process of preparing a thermoplastic composite and the thermoplastic composite obtained from said process, some figures are presented to which reference is made, as follows:

[0029] FIG. 1 is a flowchart illustrating the processes for preparing a thermoplastic composite material from cellulose pulp modified with waxes or polymer emulsion.

[0030] FIG. 2 is a flowchart illustrating the process of preparing a thermoplastic composite material from wax-modified cellulose pulp.

[0031] FIG. 3 is a representative image of the starting material, i.e., a never-dried bleached Kraft eucalyptus pulp with a solids content of 15%.

[0032] FIGS. 4A-4B represent images of injection-molded specimens of high-density polyethylene (HDPE) composites with bleached Kraft eucalyptus pulps treated with paraffin wax or polyolefin wax.

[0033] FIG. 4A is an image of a HDPE composite with 18% bleached Kraft eucalyptus pulp treated with 15% paraffin wax.

[0034] FIG. 4B is an image of a HDPE composite with 18% bleached Kraft eucalyptus pulp treated with 15% polyethylene (PE) wax.

[0035] FIG. 5 is an illustrative image of the composite in pellet form after extrusion.

[0036] FIG. 6 is an illustrative image of a thin film pressed with a thickness of 0.5 mm from the extruded noodle with a composition containing 18% cellulose, 4.5% paraffin wax compatible with 4% Licocene, 1% CaCOs and 72.5% HDPE.

[0037] FIG. 7 is a flowchart illustrating the process of preparing a thermoplastic composite material from bleached Kraft eucalyptus pulp modified with polymer emulsion.

[0038] FIG. 8A is a representative image of a blend of bleached Kraft eucalyptus wet pulp at 15% solids and polycaprolactone (PCL) emulsion at 17.6% solids before drying, with a ratio of 80% cellulose and 20% PCL.

[0039] FIG. 8B is a representative image of a mixture of wet bleached Kraft eucalyptus pulp and polycaprolactone (PCL) emulsion after drying, with up to 80% solids.

[0040] FIG. 8C is a representative image of materials mixed prior to the composite extrusion step, with the following composition: 50% bleached Kraft eucalyptus pulp treated with PCL emulsion, 1% CaCOs, high-density polyethylene (HDPE) and 4% compatibilizer (Licocene 6452).

[0041] FIGS. 9A-9D represent images of injection-molded specimens of high-density polyethylene (HDPE) composites with bleached Kraft eucalyptus pulps treated with polymer emulsions.

[0042] FIG. 9A is an image of a HDPE composite with 18% bleached Kraft eucalyptus pulp treated with PCL emulsion.

[0043] FIG. 9B is an image of a HDPE composite with 18% bleached Kraft eucalyptus pulp treated with paraffin wax emulsion.

[0044] FIG. 9C is an image of a HDPE composite with 36% bleached Kraft eucalyptus pulp treated with PCL emulsion.

[0045] FIG. 9D is an image of a HDPE composite with 50% bleached Kraft eucalyptus pulp treated with PCL emulsion. DETAILED DESCRIPTION OF THE INVENTION

[0046] In particular, composite materials represent the union or combination of two different materials with the aim of forming a new material with characteristics and properties specific to the materials used.

[0047] Despite the known difficulty related to the incompatibility of hydrophilic compounds (cellulose) with hydrophobic compounds (synthetic polymers), the inventors of the present invention were unexpectedly able to obtain a method that can be employed to prepare a thermoplastic composite with better dispersion characteristics, which can be observed from pressed films with 0.5 mm thickness where the absence of visible agglomerates indicates good dispersion, and better processing, in addition to more desirable mechanical properties of specific polymers and ensuring a good mixing of the polymer with waxes or with polymer emulsions.

[0048] The terms “treated pulp”, “treated cellulose pulp”, “modified pulp” and “modified cellulose pulp” are interchangeable and should be understood as cellulose pulp that has undergone a treatment, in which the cellulose fibers have been modified, so that the composite obtained from the processes of the present invention presents better dispersion and processing characteristics.

[0049] Cellulose fiber is selected from the group consisting of cellulose pulp, microfibrillated cellulose (MFC) and nanofibrillated cellulose (NFC), originating from hardwood (short fiber) such as eucalyptus or softwood (long fiber) such as pine.

[0050] Similarly, the terms “pulp treatment”, “fiber treatment”, “pulp modification”, “fiber modification” and “cellulose modification” are also interchangeable and should be understood as the process of treating cellulose pulp, in which the cellulose fibers are modified through their coating, in order to improve the dispersion of the fibers in the polymer matrix.

[0051] The present invention relates to a process for preparing a thermoplastic composite from cellulose pulp modified with polyolefin waxes, petroleum or synthetic, or with synthetic polymer emulsions, and a thermoplastic composite prepared from each of the aforementioned processes.

[0052] The process involves modifying cellulose in the form of chemical pulp, microfibrillated cellulose (MFC) or nanofibrillated cellulose (NFC) via extrusion with waxes, or with polymer emulsions, and its subsequent use as reinforcement in composites with thermoplastic resin.

[0053] Specifically, the aforementioned thermoplastic composite presents good dispersion characteristics of cellulose fibers, better mechanical properties, increased modulus of elasticity, in addition to presenting processing benefits in relation to the synthetic thermoplastic polymer.

[0054] As indicated herein, the prior art already presents thermoplastic composites of cellulose pulp. However, it fails to reveal or suggest an environmentally friendly product, in which the cellulose pulp (or microfibrillated cellulose (MFC) or nanofibrillated cellulose (NFC)) is modified via an extrusion process with polyolefin waxes, petroleum waxes, or synthetic waxes, or polymer emulsions, to allow for better dispersion of the cellulose fibers in the polymer matrix.

[0055] Surprisingly, the inventors of the present application have developed a process for preparing a thermoplastic composite that combines Kraft eucalyptus cellulose pulp, i.e., a highly hydrophilic component, with a thermoplastic polymer, a hydrophobic component, without the problems of incompatibility and difficulty in dispersion known in the prior art.

[0056] The treatment of cellulose pulp with wax or polymer emulsion provides the modification of cellulose fibers by coating them with a low-polarity material, such as a polymer, allowing a good dispersion characteristic of the fibers in the polymer matrix.

[0057] Thus, the process of preparing thermoplastic composite from cellulose pulp modified with waxes, or polymer or wax emulsions, allows obtaining a product with good mechanical properties for later use as reinforcement in a thermoplastic matrix.

[0058] Furthermore, the treatment of cellulose pulp with waxes allows for greater ease in processing and feeding into the extruder to prepare the thermoplastic composite due to the greater compaction provided by the wax.

[0059] In particular, a process for preparing composites of cellulose fibers and thermoplastic polymers is disclosed, in which the cellulose fiber in the form of pulp, microfibrillated cellulose or nanofibrillated cellulose is initially treated directly with waxes or emulsions of polymers or waxes, followed by drying and extrusion with the thermoplastic polymer matrix, in which ease of processing and / or high dispersion of the fibers is achieved.

[0060] This process uses a raw material from a renewable source as reinforcement, which guarantees an environmentally friendly character of the process of the present invention in relation to processes already existing in the state of the art and which use a non-renewable raw material, such as, for example, glass fibers, talc, among others.

[0061] In a first embodiment, the process for preparing thermoplastic composite from cellulose pulp modified with polyolefin, petroleum and synthetic waxes comprises the following steps: a) dewatering the wet pulp or nanofibrillated cellulose (NFC) by pressing and filtration; b) adding a wax to the dewatered pulp in a mixer; c) extruding the mixture from step b) generating a wax-treated pulp; d) drying the wax-treated pulp; e) processing and composting the material obtained in step d) with a thermoplastic resin; and f) obtaining a composite material.

[0062] Optionally, a compatibilizer is used in step e). Preferably, the compatibilizer is from the class of polypropylene copolymers functionalized with maleic anhydride with an acidity of 37-45 mgKOH / g corresponding to 8-12% maleic anhydride, such as, for example, Lycocene 6452. Compatibilizing agents with other maleic anhydride contents, including copolymers with styrene, acrylate and ethylene, can also be used, since they have the same function.

[0063] Other examples of compatibilizers are: Orevac CA 100(PP-g-MA), Synthomer G-3015, Epolene E25, E-43 and E-43P, Orevac 18732 RBP, among others.

[0064] In some embodiments, the wet pulp, microfibrillated cellulose (MFC), or nanofibrillated cellulose (NFC) from step a) has a solids content of at least 10%, originating from hardwood such as eucalyptus or softwood such as pine. In preferred embodiments, the solids content of the wet pulp or NFC is in the range of 10 to 15%. More preferably, the solids content of the wet pulp or NFC is 15%.

[0065] In some embodiments, the wet cellulose pulp is a chemical or semi-chemical pulp, bleached or unbleached, mechanical pulp, thermomechanical pulp, chemical-thermomechanical pulp, enzymatic pulp, among others. Preferably, the wet cellulose pulp is a bleached eucalyptus Kraft pulp.

[0066] In some embodiments, the wet pulp, microfibrillated cellulose (MFC) or nanofibrillated cellulose (NFC) is dewatered by pressing and filtering until the solids content is as high as possible, preferably until the solids content is greater than about 25%. Preferably, these materials are obtained from wet Kraft pulp of bleached eucalyptus pulp.

[0067] In some embodiments, the wax added to the dewatered pulp from step b) is in the form of flakes, shavings, or powder, and may be a polyolefin wax such as polyethylene and polypropylene, oxidized or not, petroleum wax such as micro or macro paraffin wax or paraffin, or synthetic wax such as Fisher-Tropsch wax.

[0068] Modifying fibers with waxes in the form of flakes, shavings, or powder presents mixing difficulties due to the flow characteristics of the cellulose pulp. Therefore, pulp modification with waxes is performed in the presence of water and at a temperature suitable for melting the wax and thus coating the cellulose fibers in mixing step b).

[0069] In preferred embodiments, the synthetic wax is selected from the group consisting of paraffin wax, microcrystalline paraffin wax, macro paraffin wax, polypropylene wax and its copolymers with ethylene, polyethylene wax, oxidized polyethylene wax, paraffin, stearic, Fisher Tropsch synthetic wax, among others.

[0070] In some embodiments, the wax added to the cellulose pulp is in the proportion of 5 to 15% wax to dry cellulose.

[0071] In some embodiments, the mixer in step b) is a solids mixer, such as a ribom blender, or similar.

[0072] In some embodiments, the extruder used in step c) is a twin-screw extruder with a degassing zone and the extrusion temperature is in the range of 80 2 C to 200 2 C. Preferably, the extrusion temperature is in the range of 90 2 C to 130 2 W.

[0073] In some embodiments, drying step d) is performed in a dryer with counterflow of hot air and, optionally, a vacuum drying chamber can be used at the extruder outlet.

[0074] After the treated pulp dries, the fibers are dispersed.

[0075] In some embodiments, the material obtained after drying step d) has a residual water content in the range of 15 to 25%.

[0076] In some embodiments, the thermoplastic resin of step e) is a polyolefin. In preferred embodiments, the polyolefin is selected from the group consisting of high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polypropylene (PP), and copolymers of propylene and ethylene.

[0077] In some embodiments, the material obtained in step e) undergoes a processing step, in which the material may be mixed with the polyolefin or added directly to the addition hopper or by side feeding, for example, via a side feeder. In preferred embodiments, processing is performed in a twin-screw extruder with an in-head granulation system to produce the composite material with excellent dispersion of the cellulosic fibers.

[0078] According to the present invention, the process consists of modifying cellulose pulp (or microfibrillated cellulose (MFC), or nanofibrillated cellulose (NFC)), never dry, with low water content, via extrusion with waxes and its subsequent direct use as reinforcement in a thermoplastic matrix.

[0079] Another embodiment of the present invention relates to a thermoplastic composite obtained from the modification of cellulose pulp with waxes through an extrusion process.

[0080] Wax-treated cellulose pulp has better compaction characteristics than untreated pulp, making it easier to feed the treated pulp into the extruder and process it.

[0081] The thermoplastic composite of cellulose pulp modified with waxes of the present invention is a composite of cellulose fiber in a polymer matrix, in which the cellulose fiber is a cellulose pulp, microfibrillated cellulose (MFC) or nanofibrillated cellulose (NFC) that acts as a reinforcing agent, that is, it is related to mechanical properties of thermoplastic polymers.

[0082] The starting material for obtaining the thermoplastic composite is eucalyptus pulp obtained through the Kraft process, bleached but never dried, which has a solids content of at least 10%.

[0083] Coating cellulose fibers with low-polarity materials such as polymers allows for improved dispersion of the fibers in the polymer matrix.

[0084] Furthermore, modification of cellulose pulp with waxes also allows for improved processing of the thermoplastic composite due to the increased compaction provided by the wax.

[0085] Thus, the thermoplastic composite of cellulose pulp modified with waxes presents improvements in mechanical properties in relation to synthetic polymers.

[0086] Specifically, the wax-modified cellulose pulp thermoplastic composite exhibits improved elastic modulus, tensile strength, and elongation at break relative to a synthetic polymer.

[0087] In another embodiment, the process for preparing a thermoplastic composite of polymer emulsion-modified cellulose pulp comprises the following steps: a) dewatering the wet pulp, microfibrillated cellulose (MFC) or nanofibrillated cellulose (NFC) by pressing and filtration; b) adding a polymer or wax emulsion to the wet pulp in a mixer, generating an emulsion-treated pulp; c) drying the emulsion-treated pulp; d) grinding and extruding the material obtained in step c) with a thermoplastic polymer; and e) obtaining a composite material.

[0088] Optionally, a compatibilizer is used in step d). Preferably, the compatibilizer is from the class of maleic anhydride-functionalized propylene copolymers, such as Licocene 6452. Other examples of maleic anhydride-functionalized propylene copolymers are: Orevac CA 100(PP-g-MA), Synthomer G-3015, Epolene E25, E-43 and E-43P, Orevac 18732 RBP, among others.

[0089] In some embodiments, the wet pulp, microfibrillated cellulose (MFC), or nanofibrillated cellulose (NFC) from step a) has a solids content of at least 10%, originating from hardwood such as eucalyptus or softwood such as pine. In preferred embodiments, the solids content of the wet pulp, MFC, or NFC is in the range of 10 to 15%. More preferably, the solids content of the wet pulp, MFC, or NFC is 13.7%.

[0090] In some embodiments, the wet cellulose pulp is a chemical or semi-chemical pulp, bleached or unbleached, mechanical pulp, thermomechanical pulp, chemical-thermomechanical pulp, enzymatic pulp, among others. Preferably, the wet cellulose pulp is a bleached eucalyptus Kraft pulp.

[0091] In some embodiments, the wet pulp, microfibrillated cellulose (MFC) or nanofibrillated cellulose (NFC) is dewatered by pressing and filtering until the solid content is as high as possible, preferably until the solid content is greater than about 25%.

[0092] In the process of treating cellulose pulp with polymer emulsions, the material is already dispersed and coats the cellulose fibers immediately in the mixing step b).

[0093] In some embodiments, the emulsion is added to the pulp via a pump, being a synthetic polymer or paraffin wax emulsion.

[0094] The synthetic polymer or wax emulsion is added directly to the wet pulp at a solids content of 15 to 60%. In preferred embodiments, the emulsion's solids content is in the range of 15 to 40%. More preferably, the emulsion's solids content is in the range of 15 to 30%.

[0095] In the case of a polymer emulsion, the polymer must be from the non-caking category, such as polycaprolactone (PCL), polyhydroxybutyrate (PHB), polyvinyl acetate (PVAC), among others. In the case of a wax emulsion, the wax is a polyolefin wax (polyethylene or polypropylene), petroleum waxes such as paraffins, microparaffinic waxes, macroparaffinic waxes, and synthetic waxes such as Fisher-Tropsch.

[0096] In some embodiments, the mixer in step b) is a solids mixer such as a ribom blender, or similar.

[0097] In some embodiments, drying step c) is carried out by passing a current of hot air, but at a temperature below the melting point of the polymer or wax that make up the emulsion.

[0098] In some embodiments, the material obtained in step d) is subjected to a processing step, in which the dry material is crushed or dismembered, and then extruded in a twin screw extruder with a degassing zone with a thermoplastic polymer to generate the composite material with excellent dispersion of the cellulosic fibers.

[0099] In some embodiments, the thermoplastic polymer of step d) is a polyolefin. In preferred embodiments, the polyolefin is selected from the group consisting of high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polypropylene (PP), and copolymers of propylene and ethylene.

[0100] According to the present invention, the process consists of modifying cellulose pulp (or microfibrillated cellulose (MFC) or nanofibrillated cellulose (NFC)), never dried, with low water content, via extrusion with polymer emulsions, and its subsequent direct use as reinforcement in a thermoplastic matrix.

[0101] Another embodiment of the present invention relates to a thermoplastic composite obtained from the modification of cellulose pulp with synthetic polymer emulsions through an extrusion process.

[0102] Cellulose pulp treated with polymer or wax emulsion has a higher modulus of elasticity, in addition to good mechanical properties and good fiber dispersion characteristics in the polymer matrix compared to untreated pulp.

[0103] The thermoplastic composite of cellulose pulp modified with polymer or wax emulsion of the present invention is a composite of cellulose fiber in a polymer matrix, in which the cellulose fiber is a cellulose pulp, microfibrillated cellulose (MFC) or nanofibrillated cellulose (NFC) that acts as a reinforcing agent, that is, it is related to the mechanical properties of thermoplastic polymers.

[0104] The starting material for obtaining the thermoplastic composite of the present invention is a never-dried bleached Kraft eucalyptus pulp that has a solids content of at least 10%.

[0105] Coating cellulose fibers with low-polarity materials such as polymers allows for improved dispersion of the fibers in the polymer matrix.

[0106] Thus, the thermoplastic composite of cellulose pulp modified with polymer emulsion presents improvements in mechanical properties in relation to synthetic polymers.

[0107] Specifically, the thermoplastic composite of the present invention exhibits improved elastic modulus, tensile strength, and elongation at break relative to a synthetic polymer. EXAMPLES

[0108] The following examples, described in detail, serve to illustrate embodiments of the present invention without, however, having a limiting character to the scope of protection thereof. Example 1 - Process for preparing thermoplastic composite from cellulose pulp modified with waxes

[0109] The following is a process for preparing a thermoplastic composite of cellulose pulp modified with waxes.

[0110] The process consists of modifying never-dried Kraft eucalyptus cellulose pulp with low water content, via extrusion with polyolefin or paraffin waxes and its subsequent direct use as reinforcement in a thermoplastic matrix. [01 1 1 ] In the process, wet bleached eucalyptus Kraft pulp, microfibrillated cellulose or nanofibrillated eucalyptus cellulose (with a solids content (ST) of 10 - 15%) is dewatered by pressing and filtration to the maximum possible solids content (greater than about 25%).

[0112] To this material (dewatered pulp), a solid wax in the form of flakes, shavings, or powder is then added in a conventional mixer for solid materials, such as a ribbon blender or similar. This wax can be a polyolefin wax (e.g., polyethylene or polypropylene), petroleum waxes (paraffin, and micro- and macro-paraffinic waxes), and synthetic waxes such as Fischer-Tropsch, as well as ethylene-propylene copolymer waxes, stearic waxes, etc.).

[0113] Wax should be used in a proportion of 5 to 15% wax to dry cellulose.

[0114] The material is then extruded in a twin-screw extruder with a degassing zone, generating material that must be dried in a dryer with a counterflow of hot air, and a vacuum drying chamber can optionally be used at the extruder outlet.

[0115] The material obtained after drying with a water residue of 15 to 25% is crushed and composted with thermoplastic resin (preferably a polyolefin).

[0116] For processing, the material can be blended with polyolefin or added via a side feeder. Processing should preferably be performed in a twin-screw extruder with a granulation system in the head to produce the composite material with excellent dispersion of the cellulosic fibers, as shown in FIG. 6, where the absence of visible agglomerates can be seen in a 0.5 mm thick pressed film. Example 2 - Composition of exemplary formulations of high-density polyethylene (HDPE) composites with wax-treated pulps

[0117] The following is an illustrative table showing the composition of some HDPE composite formulations with wax-treated pulps prepared according to the present invention. The formulations were prepared with different types and proportions of wax, as well as different proportions of pulp, and with and without compatibilizer. Paraffin wax and polyethylene wax were used for the wax, and Licocene 6452 was used for the compatibilizer.

[0118] Table 1 indicates the components and their respective proportions in each of the exemplary formulations. Table 1 Example 3 - Mechanical Properties Test Results in Tensile

[0119] After completing the development of exemplary formulations of composites of HDPE with wax-treated pulps, as identified in Table 1 above, tensile mechanical property tests were performed in accordance with ASTM D638 or equivalent to evaluate and compare the results obtained for the thermoplastic composites of wax-modified cellulose pulp in relation to the results obtained for the synthetic thermoplastic polymer. The test speed was 10 mm / min.

[0120] Table 2 below illustrates the results of the mechanical properties of the tested samples of the synthetic polymer and of the exemplary formulations of thermoplastic composites with wax-treated pulps, specifically in relation to the elastic modulus (GPa), tensile strength (MPa) and elongation at break (%) of each of these samples. Table 2: Mechanical properties in tension Example 4 - Process for preparing thermoplastic composite from cellulose pulp modified with polymer emulsion

[0121] The following is a process for preparing a thermoplastic composite of cellulose pulp modified with polymer emulsion.

[0122] The process consists of modifying “total” or partial cellulose pulp that has never been dried with a low water content, via extrusion with an emulsion of a synthetic polymer and its subsequent direct use as reinforcement in a thermoplastic matrix.

[0123] In the process, wet bleached eucalyptus Kraft pulp, microfibrillated cellulose or nanofibrillated eucalyptus cellulose (with a solids content (ST) of 10 - 15%) is dewatered by pressing and filtration to the maximum possible solids content (greater than about 25%).

[0124] In a conventional mixer, such as a ribo-blender or similar, a caprolactone (PCL) polymer emulsion with a solids content of 25 to 60% is added directly to the wet pulp. The emulsion is 20% PCL with a cellulose base (i.e., the mixture is 80% cellulose / 20% PCL). After mixing, the material is dried by passing a current of hot air through it, but at a temperature below the melting point of PCL.

[0125] The dry material is then crushed or dismembered and then extruded in a twin screw extruder with a degassing zone with the thermoplastic polymer (preferably a polyolefin), to generate a composite material with excellent dispersion of the cellulosic fibers. Example 5 - Composition of exemplary formulations of high-density polyethylene (HDPE) composites with eucalyptus pulps treated with emulsions

[0126] The following is an illustrative table showing the composition of some HDPE composite formulations with emulsion-treated chemically bleached eucalyptus pulps prepared according to the present invention. The formulations were prepared with different emulsion types and proportions, as well as different pulp proportions, and with and without surfactants.

[0127] Additionally, all formulations were prepared with the addition of a compatibilizer at a content of 4% w / w and calcium carbonate (CaCOs) at a content of 1% w / w.

[0128] For the emulsion, synthetic polymer emulsions (PCL) or paraffin wax emulsion with a melting point of 60 / 65 °C and a solids content of 60% were used, and for the compatibilizer, the commercial compatibilizer Licocene PP-g-MA 6452 PF = 134 was used. 2 C (graft polypropylene wax copolymer with maleic anhydride with an acid number of 37 to 45 mgKOH / g).

[0129] Table 3 indicates the components and their respective proportions in each of the exemplary formulations. Table 3 Example 6 - Mechanical Properties Test Results in Tensile

[0130] After completing the development of exemplary HDPE composite formulations with emulsion-treated pulps, as identified in Table 3 above, tensile mechanical property tests were performed in accordance with ASTM D638 or equivalent to evaluate and compare the results obtained for the thermoplastic composites of emulsion-modified cellulose pulp with those obtained for the synthetic thermoplastic polymer. The test speed was 10 mm / min.

[0131] Table 4 below illustrates the results of the mechanical properties of the tested samples of the synthetic polymer and of the exemplary formulations of thermoplastic composites with pulps. treated with emulsions, specifically in relation to the elastic modulus (GPa), tensile strength (MPa) and elongation at break (%) of each of these samples. Table 4: Mechanical properties in tension

[0132] It is understood that when a parameter range is given, all whole numbers and ranges within that range, as well as tenths and hundredths, are also given by the modalities. For example, "5-10%" includes 5%, 6%, 7%, 8%, 9%, and 10%; 5.0%, 5.1%, 5.2%, 9, 8%, 9.9%, and 10.0%; and 5.00%, 5.01%, 5.02%, 9.98%, 9.99%, and 10.00%; as well as, for example, 6-9%, 5.1%-9.9%, and 5.01%-9.99%. Similarly, when a list is presented, unless otherwise indicated, it should be understood that each individual element of that list and each combination of components of that list is a separate modality. For example, “1, 2, 3, 4 and 5” includes, among numerous modalities, 1; 2; 3; 1 and 2; 3 and 5; 1, 3 and 5; and 1, 2, 4 and 5.

[0133] It should be understood that the embodiments described above are merely illustrative and that various modifications may be made by a person skilled in the art to them without departing from the scope of the present invention. Consequently, the present invention should not be considered limited to the exemplary embodiments described in this application. Furthermore, the present disclosure may include subject matter not currently claimed but which may be claimed in the future in combination with or separately from the features claimed herein.

Claims

CLAIMS 1. Process for preparing thermoplastic composite from wax-modified cellulose pulp, comprising the following steps: a) dewatering the wet pulp, microfibrillated cellulose (MFC) or nanofibrillated cellulose (NFC) by pressing and filtration; b) adding a wax to the dewatered pulp in a mixer; c) extruding the mixture from step b) to generate a wax-treated pulp; d) drying the wax-treated pulp; e) processing and composting the material obtained in step d) with a thermoplastic resin; and f) obtaining a composite material.

2. Process according to claim 1, characterized in that a compatibilizer is used in step e).

3. Process according to any one of claims 1 to 2, characterized in that the wet pulp, microfibrillated cellulose (MFC) or nanofibrillated cellulose (NFC) of step a) has a solids content of at least 10%.

4. Process according to any one of claims 1 to 3, characterized in that the solids content after pressing and filtration in step a) is greater than about 25%.

5. Process according to any one of claims 1 to 4, characterized in that the wax added to the dewatered pulp from step b) is in the form of flakes, shavings or powder.

6. Process according to claim 5, characterized in that the wax is selected from the group consisting of polyolefin wax, such as polyethylene wax and polypropylene wax, paraffin wax, petroleum wax, such as micro and macro paraffin wax, ethylene and propylene copolymer wax, stearic wax, synthetic wax of the Fischer-Tropsch type, among others.

7. Process according to any one of claims 1 to 6, characterized in that the wax added to the cellulose pulp is in the proportion of 5 to 15% wax in relation to the dry cellulose.

8. Process according to any one of claims 1 to 7, characterized in that the extrusion temperature of step c) is in the range of 80 2 C to 200 2 W.

9. Process according to any one of claims 1 to 8, characterized in that drying step d) is carried out in a dryer with counterflow of hot air.

10. Process according to any one of claims 1 to 9, characterized in that a vacuum drying chamber is used at the outlet of the extruder.

11. Process according to any one of claims 1 to 10, characterized in that the cellulose fibers are dispersed after step d) of drying the wax-treated pulp.

12. Process according to any one of claims 1 to 11, characterized in that the residual water content after drying step d) is in the range of 15 to 25%.

13. Process according to any one of claims 1 to 12, characterized in that the thermoplastic resin of step e) is a polyolefin selected from the group consisting of high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polypropylene (PP) and copolymers of ethylene and propylene.

14. Process according to any one of claims 1 to 13, characterized in that it further comprises an additional processing step after step e) in an extruder 15. Process for preparing thermoplastic composite from cellulose pulp modified with polymer emulsion characterized by the fact that it comprises the following steps: a) dewatering the wet pulp, microfibrillated cellulose (MFC) or nanofibrillated cellulose (NFC) by pressing and filtration; b) adding a polymer emulsion to the wet pulp in a mixer generating an emulsion-treated pulp; c) drying the emulsion-treated pulp; d) crushing and extruding the material obtained in step c) with a thermoplastic polymer; and e) obtaining a composite material.

16. Process according to claim 15, characterized in that a compatibilizer is used in step d).

17. Process according to any one of claims 15 to 16, characterized in that the emulsion added to the wet pulp of step b) is a synthetic polymer or wax emulsion.

18. Process according to any one of claims 15 to 17, characterized in that the synthetic polymer emulsion is selected from the group consisting of polycaprolactone (PCL) emulsion or polyolefin wax emulsion, such as polyethylene wax and polypropylene wax, paraffin wax, petroleum wax, such as micro and macro paraffin wax, stearic waxes, synthetic wax of the Fischer-Tropsch type, among others.

19. Thermoplastic composite obtained by the process as defined in any one of claims 1 to 14, characterized in that it comprises a synthetic thermoplastic polymer and cellulose fiber modified with waxes.

20. Thermoplastic composite according to claim 19, characterized in that the wax is selected from the group consisting of paraffin wax, polyethylene wax, polypropylene wax, ethylene and propylene copolymer wax, paraffins and stearics.

21. Thermoplastic composite obtained by the process as defined in any one of claims 15 to 18, characterized in that it comprises a synthetic thermoplastic polymer and cellulose fiber modified with polymer or wax emulsion.

22. Thermoplastic composite according to claim 21, characterized in that the emulsion polymer is of the non-caking category.

23. Thermoplastic composite according to claim 22, characterized in that the polymer is selected from the group consisting of polycaprolactone (PCL), polyhydroxybutyrate (PHB) and polyvinyl acetate (PVAC).

24. Thermoplastic composite according to claim 21, characterized in that the emulsion wax is a paraffin wax, polyethylene wax, polypropylene wax, among others.

25. Thermoplastic composite according to any one of claims 19 to 24, characterized in that the cellulose fiber is selected from the group consisting of cellulose pulp, microfibrillated cellulose (MFC) and nanofibrillated cellulose (NFC).

26. Thermoplastic composite according to any one of claims 19 to 25, characterized in that it further comprises a compatibilizer.

27. Thermoplastic composite according to any one of claims 19 to 26, characterized in that the synthetic thermoplastic polymer is a polyolefin selected from the group consisting of high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polyethylene terephthalate (PET). (LDPE), linear low-density polyethylene (LLDPE), polypropylene (PP) and ethylene and propylene copolymers.

28. Thermoplastic composite according to any one of claims 19 to 27, characterized in that it presents improved dispersion of the cellulosic fibers in relation to a synthetic thermoplastic polymer.

29. Thermoplastic composite according to any one of claims 19 to 28, characterized in that it further presents improved mechanical properties in relation to a synthetic polymer, which are selected from the group consisting of elastic modulus, tensile strength and elongation at break.

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