METHOD OF MANUFACTURING BIOCOMPOSITE MATERIALS COMPRISING CELLULOSE

Abstract

Method for manufacturing a composite material, comprising the following steps: a) plasticizing a binder in an extruder, wherein the binder comprises a polymer; b) providing a mixture of a cellulosic material and a hydrophobic agent dissolved and/or dispersed in a liquid carrier; c) mechanically shearing and drying the mixture in an extruder whereby liquid is at least partly extracted from the mixture or is not present in liquid form anymore; and d) blending the dried mixture with the plasticized binder.

Claims

1. Method for manufacturing a composite material, comprising: a) Plasticizing a binder in an extruder, wherein the binder comprises a polymer; b) Providing a mixture of a cellulosic material and a hydrophobic agent dissolved and/or dispersed in a liquid carrier; c) Mechanically shearing and drying the mixture in an extruder whereby liquid is at least partly extracted from the mixture or is not present in liquid form anymore; and d) Blending the dried mixture with the plasticized binder.

2. The method according to claim 1, wherein a mass ratio of hydrophobic agent to cellulosic material is at least 1:200, preferably at least 1:100, more preferably at least 1:50, even more preferably at least 1:20, most preferably at least 1:15.

3. The method according to claim 1, wherein a mass ratio of hydrophobic agent to cellulosic material is at most 2:1, preferably at most 1:1, more preferably at most 1:2, most preferably at most 1:5.

4. The method according to claim 1, wherein the liquid carrier comprises water and/or an alcohol, preferably an alcohol with 1 to 3 carbon atoms, most preferably 2 carbon atoms, preferably ethanol, optionally processing aids such as an initiator, a cross-linking agent, a surfactant, an emulsifier, a protective colloid that stabilizes the emulsion or dispersion, a biocide, a pigment, a flame retardant and/or an antifoaming agent.

5. The method according to claim 1, wherein the hydrophobic agent comprises a lipid and/or a polyurethane and/or an acrylate.

6. The method according to claim 1, wherein the dried mixture after step d) has a hydrophobicity of at most 0.1%, wherein the hydrophobicity is expressed by the water absorption (%) of solid material after storage for at least 24 h in standard climate (50.0±5.0) % and (23.0±1.0) % relative humidity in accordance with DIN EN ISO 62:2008.

7. The method according to claim 1, wherein the drying in step c) is performed in a deliquification extruder and optionally comprises heating the mixture.

8. The method according to claim 1, wherein step c) comprises a sequence of one or more mechanical shearing steps and one or more drying steps.

9. The method according to claim 1, wherein the blend of the dried mixture and the plasticized binder is homogenized, preferably at a temperature of 120° C. to 240° C., more preferably at a temperature of 160° C. to 230° C.

10. The method according to claim 1, wherein the mean particle length of the cellulosic material is within the range from 100 nm to 40 mm, preferably from 10 μm to 20 mm, and/or wherein the mean particle width of the cellulosic material is within the range from 5 nm to 10 mm, preferably from 80 nm to 2 mm.

11. The method according to claim 1, wherein the binder is provided as a granulate material and/or a powder, and wherein the binder is dosed into a main line of an extrusion apparatus, preferably gravimetrically, wherein the main line preferably comprises a hotmelt extruder (2) with a feeding section (4), a plasticization section (6), an inlet section (12) for blending the dried mixture with the plasticized binder and a dispersion section (14), wherein the hotmelt extruder (2) preferably further comprises one or more deliquification sections (8, 10) arranged before the inlet section (12) and/or a compression section (16) arranged behind the dispersion section (14).

12. The method according to claim 11, wherein the extruder for shearing and drying the mixture in step c) comprises a deliquification extruder (18) connected to the main line of the extrusion apparatus, preferably to the inlet section (12) of the hotmelt extruder (2), wherein the deliquification extruder (18) preferably comprises a feeding section (22) and a section for shearing and deliquification (24).

13. The method according to claim 1, wherein step b) comprises mixing the cellulosic material with the hydrophobic agent dissolved and/or dispersed in the liquid carrier, preferably in an extruder.

14. The method according to claim 13, wherein the cellulosic material, before mixing, has a gravimetric water content which is larger than the gravimetric water content of the dried mixture.

15. The method according to claim 1, wherein the hydrophobic agent after step c) is bonded covalently and/or via secondary valencies to the cellulosic material, wherein the extractable proportion of the hydrophobic agent after step c) is at most 10%, more preferably at most 5%, most preferably at most 1%, wherein the extractable hydrophobic agent is determined in a two-step (water followed by ethanol) extraction procedure in accordance with the Laboratory Analytical Procedure (NREL/TP-510-42619) for the Determination of Extractives in Biomass, and by correction of the naturally occurring extractives in the cellulosic material.

Description

[0105] With reference to the Figures, the inventive method for manufacturing a composite material is further explained.

[0106] FIG. 1 shows an extrusion device suitable for use with the invention

[0107] FIG. 2 shows a schematic representation of the screw design of a deliquification extruder;

[0108] FIG. 3 shows an example of a hydrophobic agent consisting of a water-dispersible, hydrolysable polyester-polyurethane.

[0109] An extrusion device suitable for performing the method according to the invention (see FIG. 1) may comprise a homogenization extruder 2, which may comprise a main feeding section 4, a plasticization section 6 for plasticization and compression, a venting section 8, a degassing section 10, a fiber inlet section 12, a dispersion section 14 for dispersing the dried mixture with the plasticized binder, and a compression section 16, preferably in this order. The compression section 16, which is also called discharge section may be attachable, e.g. via a flange, to peripheral devices. For example, discharge section 16 may be attached to a strand die, an air quench conveyor and/or a pelletizer enabled to produce material granulates for injection molding. Temperature may be independently controllable for each of these sections, e.g. in a range from 20 to 300° C. The feeding section 4 may be maintained at e.g. 30-50° C. to facilitate proper feeding of binder in its non-plasticized state. A suitable temperature profile along the homogenization extruder 2 may be increasing from the feeding section 4 towards the discharge section 16 with the highest temperature being e.g. 30-40° C. above the melting point of the polymeric binder possessing the highest melting point and starting with a temperature of e.g. 10-20° C. above the melting point of the polymeric binder possessing the highest melting point. (e.g. for PLA: section 4: 30° C., section 6: 190° C., section 8: 185° C., section 10: 175° C., section 12: 175° C., section 14: 170° C., section 16: 165° C.)

[0110] The extrusion device may further comprise a deliquification extruder 18 (see FIGS. 1 and 2), which may comprise a feeding and wetting section 22 including a feed throat for solid feeding and a liquid dosing system, a degassing and shearing section 24, and a material transfer section 26. Temperature may be independently controllable for each of these sections, e.g. in a range from 20 to 300° C. Thus, the feeding sections 22a, 22b may be maintained at e.g. 30-95° C. to facilitate proper feeding of cellulosic material and water-based dispersion below the boiling point of the liquid(s) (e.g. for water below 100° C.). The screw speed of each of the consecutive sections 22-26 can be varied between 10 rpm and 300 rpm independently, depending on the process. For example, a Extricom RE 3 XPV 40 D, co-rotating, multi-shaft extruder (screw diameter: 30 mm, distance between wall and screw flank: 1.3 mm, length/diameter ratio: 40, ratio outer screw diameter to inner screw diameter: 1.74/1) may be used as the deliquification extruder 18. To prevent material transfer in liquid, solid or gaseous state towards the gear box, screw elements showing a small helix angle were implemented prior to the feeding section 22, in section 28. In order to facilitate a good deliquification and shearing performance, a pressure gradient is controlled by screw geometry. Therefore, screws are segmented and assembled on splined shafts. An exemplary screw configuration in accordance with the invention is given in FIG. 2 and Tab. 1. As indicated in FIG. 2, all the sections except for the shearing zone 24d may comprise conveying elements CE, whereas the shearing zone 24d may comprise kneading elements KE and mixing element ME. The helix angle of the conveying elements may be different for different sections. For example, in the feeding section 22a the pitch is preferably designed to be equal to the screw diameter (so called square pitch) and the resulting helix angle is preferably equal to 17.6568°. In sections 22b, 24a, 24c, 24d the relative helix factor is preferably <1 (where the relative helix factor is calculated by helix angle divided by helix angle of the square pitch) (17.6568°). In sections 24b, 24e and 26 the relative helix factors are preferably >1. For example the following helix factors may be employed: section 22a: 1.00; section 22b: 0.79; section 24a: 0.58-0.68; section 24b: 1.42; section 24c: 0.58-0.68; section 24d: 0.58; section 24e:1.21; and section 26: 1.42.

[0111] The extrusion device preferably includes a feeder 30, preferably a side-feeder 30, which feeds the homogenization extruder with the dried mixture obtained after step c.

TABLE-US-00001 TABLE 1 Description of the screw design including functions and temperature profile (exemplary) Barrel Temperature Section (for Polyester N.sub.0 Description Function Characteristics Polyurethane) 28 Backflow To prevent material transfer conveying elements showing a small  40° C. prevention in liquid, solid or gaseous helix angle state towards the motor drive 22a Feeding (solids) Feeding of the cellulosic freely cut screw profile with a high  40° C. material and material free cross-sectional area to increase distribution in process feed capacity volume  Flighted conveying elements 22b Feeding Feeding and establishing a Piston pump transfers dispersion to  80° C. (dispersion) dispersion containing the the process chamber. Section cellulosic material, showing a screw profile with lower hydrophobic agent, cross- helix angle for thorough wetting of linker and processing aids the material. Optionally, mass transfer elements which engage in a non-sealing manner to allow further improved material transfer to the full process volume 24a Compression Pressure build up Alternating sequence of conveying, 150° C. mixing and kneading elements with successively decreasing helix angle for pressure build-up  Mixing, compressing and shearing 24b Deliquification 1 Strong change in volume Conveying (flighted) elements with 150° C. and deliquification by rapid higher helix angle which translates decompression and heating into a higher free screw volume, of the volatile component which facilitates that volatile under an atmospheric vent materials can escape. Vent Stuffer attached to the barrel    material is transported into the process room; gases and vapors are routed through the stuffer screw channels 24c Compression Pressure build up Conveying elements with 150° C. successively decreasing helix angle for pressure build-up 24d Shearing pressure build-up and Kneading elements (e.g. 3-lobal) 150° C. mechanical shearing and intermeshing elements to reduce free volume (compression) and enhance mechanical force (shearing) 24e Deliquification 2 Strong change in volume See section 24b 150° C. and deliquification by rapid decompression and superheating of the volatile component under a vacuum vent 26 Material transfer Pressure build-up Conveying elements with smaler  80° C. helix angle for pressure build-up;

[0112] The binder may be prepared by plasticizing the binder at elevated temperatures in a co-rotating twin-screw extruder as the homogenization extruder, e.g. a Berstorff ZE 42 (screw diameter 42, length-to-diameter ratio L/D 44, Germany). The binder may be plasticized at an appropriate screw speed, preferably at a screw speed from 80 rpm to 300 rpm, most preferably 160 rpm, and an appropriate feeding rate, preferably 30 kg/h to 60 kg/h, most preferably 46.66 kg/h. The temperature of the plasticized binder at the inlet of the dried mixture, i.e. in the fiber inlet section 12, as obtained after degassing the plasticized binder in section 10 is preferably 120° C. to 210° C., most preferably 180° C.

[0113] For a fast heating of the binder and in order to reduce matrix viscosity an increasing temperature profile from 30° C. to 200° C. may be chosen. The feed throat section may be set to a temperature well below the melting point of the polymer to prevent the polymer to melt prematurely. To prevent overheating of the polymeric binder as soon as the binder comes into contact with the dried mixture, the barrel temperatures in the later sections may be successively cooler than in the plasticization section 6.

[0114] A dispersion comprising a hydrophobic agent and optionally one or more processing aids (i.e. additives) is prepared.

[0115] The hydrophobic agent comprises a polymer, preferably a polyester polyurethane (PE-PU). A polyester polyurethane is a polymer in which the repeating units contain urethane and ester moieties. Aqueous polyurethane dispersions (PUD) are preferably produced by a multi-step copolymerization reaction scheme containing polyisocyanates and different functional monomers such as polyols, multifunctional polyesters and chain extenders to give high-molecular-weight polymer dispersions exhibiting urethane bonds. Furthermore, since conventional polyurethanes are insoluble in water, ionic and/or nonionic hydrophilic segments are preferably incorporated in the polymeric backbone structure. For example, in U.S. Pat. No. 3,905,929 A a polyurethanes having a nonionic polyoxyethylene segment —(—O—CH.sub.2—CH.sub.2—)— is described.

[0116] An example of such a hydrophobic agent containing urethane linkages is shown in FIG. 3, where “U” denotes a urethane linkage and “OCN” and “NCO” each denotes a free isocyanate group.

[0117] The resulting mixture preferentially comprises unbound NCO-groups for further reaction with reactive hydrogen comprising groups such as alcohol (OH—) groups.

[0118] Furthermore, other moieties may be included such as ether and aromatic moieties, while hydrolysable ester linkages (such as in polycaprolactonediols) or hydrolysable urea linkages must be present for degradation by microbes producing free amine and free carboxylic acid groups, respectively.

[0119] Free carboxylic acid in the polymer leads to autocatalytic hydrolysis, which accelerates the process of biodegradation. Dependent on the segment length of the hydrolysable polyester the degradation can be tuned due to accessibility by microorganisms/enzymes.

[0120] A chain extender can contribute to the flexibility of the hydrophobic agent which provides better coating performance. Multifunctional segments may be introduced to provide highly reactive sites (functional groups) for a better cross-linking performance. Soft segments may be introduced for yielding an amorphous rubbery phase.

[0121] The pot life, which is the period for which the hydrophobic agent and the cross-linker remain usable when mixed is highly dependent on the pH. As mentioned before, the coagulation is favored at pH higher than 7.5. To reduce pot life, i.e. in the mentioned case the cross-linking, pH has to be elevated. This is accomplished in the process by continuously removing water and thus gradually elevating the pH.

[0122] Biodegradation by microorganisms is highly dependent on properties such as molecular orientation, crystallinity, cross-linking and chemical groups present in the polymeric backbone which determine accessibility by the organisms.

[0123] Another possible hydrophobic agent is a substance based on a copolymer containing acrylic groups such as described in U.S. Pat. No. 6,716,911 B2. In an example the urethane linkages can be (fully or partly) replaced by acrylate linkages (e.g. ethyl acrylate, butyl acrylate, ethylhexyl acrylate and mixtures thereof) such as in BioTAK® S100 acrylic waterborne adhesive to give an acrylic hydrophobic agent. Here, processing aids such as hydrophobic tackifiers like rosin ester dispersions (Superesters E-650, E-720 and E-730-55, Arakawa Chemical, Japan) can be used in order to provide sufficient initial bond strength. Furthermore water-soluble plasticizers can be added and can help to provide enough elasticity.

[0124] For thorough dispersion of the components and to obtain the maximum effect, the addition is preferably done under constant stirring using a dissolver such as DISPERMAT® CN80 (VMA-Getzmann GmbH, Germany) or any other equipment having a stirrer ready for such task.

[0125] To elevate the performance, the dispersion is optionally stirred for 12 h under constant stirring prior to use and the pH is kept below 7.5 to prevent extensive coagulation.

[0126] The cellulosic material is fed into the feed throat of the deliquification extruder. This may be done gravimetrically. The feeding rate may be set appropriately, e.g. to 10 kg/h to 50 kg/h, preferably to 20 kg/h based on pre-dried cellulosic material. The dispersion comprising the hydrophobic agent and optionally the processing aid(s), i.e. additives, is metered into the deliquification extruder by a liquid feeding system at an appropriate feeding rate, e.g. 10 kg/h to 50 kg/h, preferably 22 kg/h, to give a desired proportion of cellulosic material to hydrophobic agent, e.g 9:1 (w/w) for final composition.

[0127] The cellulosic material may be gravimetrically metered to the feeding throat of the deliquification extruder, e.g. by loss-in-weight metering feeders. The hydrophobic agent, the optional cross-linker and the optional processing aids, which are dispersed in water, may be, preferably simultaneously, fed to the feeding throat of the deliquification extruder by a liquid dosing system (e.g. a piston pump).

[0128] The deliquification extruder is used to process the mixture, containing a suspension of a plant material and a hydrophobic agent. Here a liquid (predominately water) is used as a carrier to lower the viscosity of the hydrophobic agent and for a better film forming ability on the surface of the plant material. Furthermore, due to the sometimes slow kinetics of chemical and physical bond formation, it is known to use compression, heat and shearing which are readily realized in extrusion operations by rotating screws, to enhance the relative amount of non-removable hydrophobic agents attached to and incorporated in the plant material. The deliquification efficiency is influenced by several factors such as residence time under the vent, temperature, surface area of the material that should be deliquefied, surface renewal, and vacuum level. Parameters to be varied include screw speed, feed rate, temperature and temperature profile, and vacuum level. Readouts are motor electric power consumption and throughput. These readouts can be used to quantify the shearing calculated according to Philip J. Brunner, Joshua T. Clark, John M. Torkelson, Katsuyuki Wakabayashi (2012) Processing-Structure-Property Relationships in Solid-State Shear Pulverization: Parametric Study of Specific Energy. Polymer Engineering and Science, 52 (7), 1555-1564, referred to as Brunner et al. (2012). The evaluation of the extent of shear and compression applied to the material showed the specific energy input E.sub.SME to be in the range of 67 kJ/kg-55,000 kJ/kg, depending on the following parameters: torque: 0.1-0.55 kJ, rotation speed of the screws: 20-300 s.sup.−1, overall material throughput: 0.003-0.03 kg s.sup.−1, residence time: 20 s-180 s.

[0129] The concept of specific energy input according to Brunner et al. (2012) can be used across different models and screw designs to describe approximately the degree to which shear stresses and compressive forces do work on the material during processing in extruder setups. Dependent on screw design, screw speed, barrel temperature, throughput (feed rate), feed shape/size (unique to solid state shear), feed content and considerably on the nature of the material(s) involved. Specific mechanical energy input (E.sub.SME) values are based on power contributions in the motor drive with and without material simply extracted from the instrumentation display. Thus, the E.sub.SME value is the maximum energy that could be translated to the material. In practice, however, the actual amount of energy consumed by the materials alone would be less than the actual E.sub.SME values reported due to various practical energy losses, which is friction of samples against barrel walls (heat loss) and the power to mix and move solid material forward within the barrels.

[0130] The extent of shear and compression applied to the material can be varied by the residence time (t) and the specific mechanical energy input (E.sub.SME). E.sub.SME quantifies the mechanical energy input to process a unit mass of the mixture and can be calculated using equation 3.

[00002]$\begin{array}{cc}{E}_{\mathrm{SME}}=\frac{\tau .Math.N}{\stackrel{.}{m}}& \left(3\right)\end{array}$

where τ is the torque (kJ), N is the rotation speed of the screws (s.sup.−1), and {dot over (m)} is the overall material throughput (kg s.sup.−1). The residence time can be determined by introducing a tracer (e.g. a radio tracer like .sup.64Cu) at the extruder inlet and measuring the tracer concentration at the die.

[0131] Any gaseous phase including the vaporized carrier (e.g. water) can be subjected to further devolatilization in one or more vent zones of the deliquification extruder. At least one vent zone is located in the region downstream in relation to the direction of conveying of the mixture, preferentially within zone 24b and/or zone 24e. The devolatilization is done at atmospheric pressure or with the aid of suction. In the vent zones one or more so called vent ports are fitted to the barrel of the deliquification extruder. Vent ports are openings in the extruder barrel which allow volatiles to be removed from the process chamber. A vacuum pump (e.g. water ring pumps with an absolute pressure of 30 mbar) can be attached to the vent port to assist in the removal of volatiles. The venting ports can be arranged at variable positions in relation to the direction of conveying the mixture. The best results were obtained with zone 24b being located at 10 to 20 L/D and zone 24e being located at 21 to 30 L/D, preferentially 14 L/D and 27 L/D for zone 24b and zone 24e, respectively. Cooled condensers immediately downstream of the gas output (e.g. directly attached by a flange) may be used for gaseous-liquid-phase change to prevent extensive water vapour emissions. To prevent an extensive exiting of solid cellulosic material and hydrophobic agent through the vent port, so called vent port stuffer may be attached to vent ports with a flange and the suction device (e.g. a vacuum pump) may be connected at the motor side of the screws. The deliquification extruder may comprise a ring extruder with at least one stuffer, preferably at least two, wherein each stuffer preferably comprises a vacuum pump, each vacuum pump creating a pressure difference of less than 60 mbar, preferably less than 20 mbar.

[0132] After mechanically shearing and drying the mixture, the mixture may be optionally fed into a throat section of the side feeder 30, preferably via a pressure resistant sealed transfer section. Care may be taken that the side-feeder 30 is constantly underfed to avoid piling up of material. For example, a twin-screw side feeder (ZSFE 40) with twin auger screws may be used for constantly metering the material to the homogenization extruder 2, e.g. at a screw speed of 20 rpm to 300 rpm, preferably 120 rpm. The side-feeder 30 is attached to the homogenization extruder 2 via a flange to give under-pressure conditions (e.g. 600 mbar, preferably <1 atm) in the transfer zone. This prevents that the homogenization extruder 2 is fed with a too high proportion of entrained gas fraction.

EXAMPLE

[0133] Example 1 was carried out using a combination of a homogenization extruder and a deliquification extruder as shown in FIGS. 1 and 2 and with the extrusion conditions shown in Tables 1 and 2. The deliquification extruder was an Extricom RE 3 XPV 40 D, co-rotating, multi-shaft extruder (screw diameter: 30 mm, distance between wall and screw: 1.3 mm length/diameter ratio: 40, ratio outer screw diameter to inner screw diameter: 1.74/1, helix angles: section 22a: 1.00; section 22b: 0.79; section 24a: 0.58; section 24b: 1.42; section 24c: 0.58; section 24e:1.21; and section 26: 1.42.) and the homogenization extruder was a co-rotating twin-screw extruder of the type Berstorff ZE 42 (screw diameter 42, length-to-diameter ratio L/D 44, Germany). To prevent material transfer in liquid, solid or gaseous state towards the gear box of the deliquification extruder, screw elements showing a small pitch were implemented in section 28, prior to the feeding sections 22a and 22b. In order to facilitate a good deliquification and shearing performance, a pressure gradient was controlled by screw geometry. Therefore, screws were segmented and assembled on splined shafts.

Step a: Plasticizing a Binder in an Extruder

[0134] In example 1, polylactic acid (PLA) was used as the binder. As an additive, Tego® Antifoam 4-94 at a concentration of 0.01% in relation to the hydrophobic agent was used in order to avoid extensive foaming. (For the hydrophobic agent see step b below.)

[0135] The PLA and the additive were fed to the feeding section of the homogenization extruder. In the homogenization extruder the binder was prepared by plasticizing the PLA at an elevated temperature well above the melting range of PLA, which is 150° C. to 160° C., preferably at a temperature of 190° C., at a screw speed of 160 rpm and at a feeding rate of 46.66 kg/h. The temperature of the plasticized binder at the inlet of the dried mixture (Section No. 12 in Table 2) as obtained after the first degassing section 8 was 185° C.

TABLE-US-00002 TABLE 2 Extrusion conditions in the homogenization extruder Barrel Section Temperature N.sub.0 Description Task screw geometry (characteristic) for PLA 4 Feeding Feeding of polymers and freely cut screw profile with a high  30° C. additives and conveying free cross-sectional area to increase feed capacity 6 Plasticization Plasticization with successively lower pitch, 190° C. kneading screw elements 8 Venting change in volume and Changing the shape of the screw 185° C. degassing by change in (higher pitch or helix angle) pressure to atmospheric pressure (optionally additionally vacuum degassing) and additional external heat 10 Degassing Vacuum degassing conveying elements with higher pitch 175° C. which translates into a higher free screw volume, which facilitates that volatile materials can escape 12 Fiber-inlet Treated fiber inlet freely cut screw profile with a high 175° C. free cross-sectional area to increase feed capacity, 14 Dispersion Fiber dispersion Kneading elements and multi-process 170° C. elements 16 Compression Compression and Tightly intermeshing conveying 165° C. Discharge elements 30 Side-Feeder Fiber feeding Twin-screw side feeder (ZSFE 40)  30° C. with twin auger screws

[0136] For a fast heating of the binder and in order to reduce matrix viscosity a decreasing temperature profile was chosen. The feed throat section was set to 30° C. to prevent the polymer to melt prematurely. To prevent overheating of the polymeric binder as soon as the binder comes in contact with the dried mixture, the barrel temperatures in the later sections are successively cooler than in the plasticization section.

Step b (1): Preparation of a Dispersion Containing a Hydrophobic Agent Dispersed in a Liquid Carrier

[0137] A dispersion containing the hydrophobic agent and processing aids was prepared by first diluting the hydrophobic agent Epotal® P100 ECO by adding water, resulting in the water-based hydrophobic agent Epotal® P100 ECO with 40% solids content, i.e. 40% hydrophobic agent content (also denoted “Epotal® P100 ECO(40%)”).

[0138] To 18 kg of water, 5 kg of a hydrophobic agent dispersed in water (Epotal® P100 ECO (40%)) and 0.25 kg of an emulsifiable cross-linker (Basonat® LR 9056) were added. Furthermore, 0.025 kg of the surfactant Lumiten® I-SC and 0.005 kg of the antifoaming agent Tego® Antifoam 4-94 were added.

[0139] For thorough dispersion of the components and to obtain the maximum effect, the addition was done under constant stirring using a DISPERMAT® CN80 (VMA-Getzmann GmbH, Germany) dissolver. To elevate the performance, the dispersion was stirred for 12 h under constant stirring prior to use and the pH was kept below 7.5 to prevent extensive coagulation.

[0140] The composition of the dispersion obtained in step b1 is summarized in table 3.

TABLE-US-00003 TABLE 3 The final composition of the dispersion obtained in step b1 Relative proportion Weight Substance Characteristics (%) (kg) Water Liquid carrier & liquid 90.642 21   medium Epotal ® P100 ECO Hydrophobic agent 8.633 2.sup.1   Basonat ® LR 9056 Cross-linking agent 0.647 0.15  Lumiten ® I-SC Surfactant (processing aid) 0.065 0.015 Tego ® Antifoam Antifoaming agent 0.013 0.003 4-94 (processing aid) .sup.1Based on solids content of Epotal ® P100 ECO
Step b (2): Providing a Mixture of a Cellulosic Material and a Hydrophobic Agent Dissolved and/or Dispersed in a Liquid Carrier

[0141] WoodForce Fast natural (Sonae Arauco) was used as a cellulosic material.

[0142] The cellulosic material (WoodForce Fast natural, Sonae Arauco) was gravimetrically metered into a feed throat of the deliquification extruder located at 2 D (measured from the beginning of section 22a (drive side) in the direction of material transport, i.e. towards section 26 (material outlet) where D denotes ‘diameter’ and would mean that 2D is the distance equal to 2 times the screw diameter) by a loss-in-weight metering feeder at a feeding rate of 20 kg/h (based on pre-dried cellulosic material). Simultaneously, the dispersion as prepared in step b1 was metered into the deliquification extruder by a liquid dosing system (here: Etatron AP Series Dosing Piston Pump) located at 5 D ((measured from the beginning of section 22a (drive side) in the direction of material transport, i.e. towards section 26 (material outlet) where D denotes ‘diameter’ and would mean that 2D is the distance equal to 2 times the screw diameter) at a feeding rate of 22 kg/h to give a proportion of cellulosic material to hydrophobic agent of 9:1 (w/w).

[0143] The final dispersion containing the dispersion obtained in step b1 and the cellulosic material prior to deliquifaction had weight proportions of liquid (water), cellulosic material, hydrophobic agent, cross-linking agent, surfactant, and antifoaming agent of 50.79%, 43.97%, 4.84%, 0.36%, 0.04%, and 0.01%, respectively.

Step c: Mechanically Shearing and Drying the Mixture

[0144] In the step of mechanically shearing and drying of the mixture performed in section 24a-24d of the deliquification extruder a screw speed of 120 rpm was used.

[0145] The deliquification efficiency is influenced by several factors such as residence time, temperature, surface area of the material that should be deliquefied, surface renewal rate, and level of suction of the vacuum pump(s). Parameters to be varied include screw speed, feed rate, temperature and temperature profile, and vacuum control by means of frequency drive (variable speed drive) regulation of the pump. Readouts are extruder motor torque, overall material throughput, mean material temperature. Readouts can be used to quantify the shearing calculated according to Brunner et al. (2012). The evaluation of the extent of shear and compression applied to the material showed the specific energy input ESME to be in the range of 67 kJ/kg-55,000 kJ/kg, depending on the following parameters: torque: 0.1-0.55 kJ, rotation speed of the screws: 20-300 s−1, overall material throughput: 0.003-0.03 kg s−1, residence time: 20 s-180 s.

[0146] Any gaseous phase including the vaporized carrier (e.g. water) can be subjected to further devolatilization in one or more vent zones of the deliquification extruder. At least one vent zone is preferably located in the region downstream in relation to the direction of conveying of the mixture, preferentially within zone 24b and/or zone 24e. The devolatilization may be done at atmospheric pressure or with the aid of suction. In the vent zones one or more so called vent ports may be fitted to the barrel of the deliquification extruder. Vent ports are openings in the extruder barrel which allow volatiles to be removed from the process chamber. A vacuum pump (e.g. water ring pumps with an absolute pressure of 30 mbar) can be attached to the vent port to assist in the removal of volatiles. The venting ports can be arranged at variable positions in relation to the direction of conveying the mixture. The best results were obtained with zone 24b being located at 10 to 20 L/D and zone 24e being located at 21 to 30 L/D, preferentially 14 L/D and 27 L/D for zone 24b and zone 24e, respectively. Cooled condensers immediately downstream of the gas output (e.g. directly attached by a flange) may be used for gaseous-liquid-phase change to prevent extensive water vapour emissions. To prevent an extensive exiting of solid cellulosic material and hydrophobizing agent through the vent port, one or more so called vent port stuffers may be attached to vent ports with a flange and the suction device (e.g. a vacuum pump) may be connected at the motor side of the screws. The deliquification extruder may comprise a ring extruder with at least one stuffer, preferably at least two, wherein each stuffer preferably comprises a vacuum pump, each vacuum pump creating a pressure difference of less than 60 mbar, preferably less than 20 mbar.

[0147] The dried mixture at the end of step c had a gravimetric water content of <500 ppm (0.045%) as determined according to NREL/TP-510-42621. The extractable hydrophobic agent after step c) was <1% (0.9%) as determined in accordance to the Laboratory Analytical Procedure (NREL/TP-510-42619).

Step d) Blending the Dried Mixture with the Plasticized Binder

[0148] After mechanical shearing and drying, the mixture was fed into the throat section of a side feeder via a pressure resistant sealed transfer section. Care was taken that the side-feeder is constantly underfed to avoid piling up of material. For this reason, a twin-screw side feeder (ZSFE 40) with twin auger screws was used for constantly metering the material to the homogenization extruder in the transfer zone at a screw speed of 120 rpm. The side-feeder is attached to the homogenization extruder via a flange to give under-pressure conditions (<1 atm). This prevents that the extruder is fed with a too high proportion of entrained gas fraction. In this way the extruder is additionally vented by the upstream opening of the deliquification section. The proportion of matrix binder to cellulosic material after step d was 2.33:1 and the ratio of cellulosic material to hydrophobic agent was 10.75:1

[0149] The dried mixture after step d) had a hydrophobicity of 0.7% and a diffusion coefficient of 1 10.sup.−6 mm.sup.2/s (as determined from the Fickian diffusion model), wherein the hydrophobicity was determined by the water absorption (%) of solid material after storage for at least 24 h in standard climate at 50.0±5.0% relative humidity and a temperature of 23.0±1.0° C. in accordance with DIN EN ISO 62:2008. In contrast to a hydrophobicity of 3% and a diffusion coefficient of 1 10.sup.−4 mm.sup.2/s, observed for a composite material containing the same proportion of the cellulosic material in a PLA matrix in the absence of a hydrophobic agent.

[0150] However, the above embodiment is only one possibility of implementing the invention.

[0151] Some other preferable material combinations and the respective processing settings are shown in Table 4. The processing settings in Table 4 refer to the ones aforementioned in example 1. However, with an appropriate adaption of the processing settings, the shown material combinations may also be processed in other devices.

TABLE-US-00004 TABLE 4 Composite processing conditions and material combinations Example Binder Type and relative proportion binder/cellulosic material (by weight) No. PLA PCL PBS PHBH PBAT PBSA PHB PHBV PBT PET PTT Sub Cut 1 7:3 — — — — — — — — — — — — 2 7:3 — — — — — — — — — — — — 3 3:7 — — — — — — — — — — — — 5 1:1 — — — — — — — — — — — — 6 7:3 — — — — — — — — — — — — 7 — 7:3 — — — — — — — — — — — 8 — — 7:3 — — — — — — — — — — 9 — — — 7:3 — — — — — — — — — 10 — — — — 7:3 — — — — — — — — 11 — — — — — 7:3 — — — — — — — 12 — — — — — — 7:3 — — — — — — 13 — — — — — — — 7:3 — — — — — 14 — — — — — — — — 7:3 — — — — 15 — — — — — — — — — 7:3 — — — 16 — — — — — — — — — — 7:3 — — 17 — — — — — — — — — — — 7:3 — 18 — — — — — — — — — — — — 7:3 19 95:5  — — — — — — — — — — — — 20 95:5  — — — — — — — — — — — — 21 7:3 — — — — — — — — — — — — 22 7:3 — — — — — — — — — — — — 23 7:3 — — — — — — — — — — — — 24 7:3 — — — — — — — — — — — — 25 7:3 — — — — — — — — — — — — 26 7:3 — — — — — — — — — — — — 27 7:3 — — — — — — — — — — — — 28 7:3 — — — — — — — — — — — — 29 7:3 — — — — — — — — — — — — 30 7:3 — — — — — — — — — — — — 31 7:3 — — — — — — — — — — — — 32 7:3 — — — — — — — — — — — — 33 7:3 — — — — — — — — — — — — 34 7:3 — — — — — — — — — — — — 35 7:3 — — — — — — — — — — — — 36 7:3 — — — — — — — — — — — — 37 7:3 — — — — — — — — — — — — 38 7:3 — — — — — — — — — — — — 39 7:3 — — — — — — — — — — — — Mixture composition (liquid dispersion prior to deliquification) Example cellulosic material (%) liquid carrier (%) hydrophobic agent (%) No. MFC BC WF CEL NF H.sub.2O EtOH PE-PU BTAK LA OA CLW 1 — — 43.97 — — 50.78 — 4.84 — — — — 2 — — 43.99 — — 50.81 — 4.84 — — — — 3 — — 43.99 — — 50.81 — 4.84 — — — — 5 — — 43.99 — — 50.81 — 4.84 — — — — 6 — — 43.99 — — 50.81 — 4.84 — — — — 7 — — 43.99 — — 50.81 — 4.84 — — — — 8 — — 43.99 — — 50.81 — 4.84 — — — — 9 — — 43.99 — — 50.81 — 4.84 — — — — 10 — — 43.99 — — 50.81 — 4.84 — — — — 11 — — 43.99 — — 50.81 — 4.84 — — — — 12 — — 43.99 — — 50.81 — 4.84 — — — — 13 — — 43.99 — — 50.81 — 4.84 — — — — 14 — — 43.99 — — 50.81 — 4.84 — — — — 15 — — 43.99 — — 50.81 — 4.84 — — — — 16 — — 43.99 — — 50.81 — 4.84 — — — — 17 — — 43.99 — — 50.81 — 4.84 — — — — 18 — — 43.99 — — 50.81 — 4.84 — — — — 19 43.99 — — — — 50.81 — 4.84 — — — — 20 — 43.99 — — — 50.81 — 4.84 — — — — 21 — — — 43.99 — 50.81 — 4.84 — — — — 22 — — — — 43.99 50.81 — 4.84 — — — — 23 — — 43.99 — — 50.81 — — 4.84 — — — 24 — — 43.99 — — 40.65 8.47 — — 4.84 — — 25 — — 43.99 — — 40.65 8.47 — — 4.84 — — 26 — — 43.99 — — 40.65 8.47 — — — 4.84 — 27 — — 43.99 — — 40.65 8.47 — — — — 4.84 28 — — 43.99 — — 40.65 8.47 — — — — — 29 — — 43.99 — — 40.65 8.47 — — — — — 30 — — 43.99 — — 40.65 8.47 — — — — — 31 — — 43.99 — — 40.65 8.47 — — — — — 32 — — 43.99 — — 40.65 8.47 — — — — — 33 — — 43.99 — — 40.65 8.47 — — 4.84 — — 34 — — 43.99 — — 40.65 8.47 — — 4.84 — — 35 — — 43.99 — — 45.61 — 9.68 — — — — 36 — — 43.99 — — 45.61 — — 9.68 — — — 37 — — 43.99 — — 50.81 — 2.42 — 2.42 — — 38 — — 43.99 — — 50.81 — 1.21 — 3.63 — — 39 — — 43.99 — — 50.81 — 3.63 — 1.21 — — Mixture composition (liquid dispersion prior to deliquification) Example hydrophobic agent (%) processing aid (%) No. CBW RW LO SO WO AF LT T80 TX LC BA TTT 1 — — — — — 0.01 0.04 — — — 0.36 — 2 — — — — — — — — — — 0.36 — 3 — — — — — — — — — — 0.36 — 5 — — — — — — — — — — 0.36 — 6 — — — — — — — — — — 0.36 — 7 — — — — — — — — — — 0.36 — 8 — — — — — — — — — — 0.36 — 9 — — — — — — — — — — 0.36 — 10 — — — — — — — — — — 0.36 — 11 — — — — — — — — — — 0.36 — 12 — — — — — — — — — — 0.36 — 13 — — — — — — — — — — 0.36 — 14 — — — — — — — — — — 0.36 — 15 — — — — — — — — — — 0.36 — 16 — — — — — — — — — — 0.36 — 17 — — — — — — — — — — 0.36 — 18 — — — — — — — — — — 0.36 — 19 — — — — — — — — — — 0.36 — 20 — — — — — — — — — — 0.36 — 21 — — — — — — — — — — 0.36 — 22 — — — — — — — — — — 0.36 — 23 — — — — — — — — — — 0.36 — 24 — — — — — — — 1.69 — — 0.36 — 25 — — — — — — — 1.69 — — 0.36 0.1 26 — — — — — — — 1.69 — — 0.36 — 27 — — — — — — — 1.69 — — 0.36 — 28 4.84 — — — — — — 1.69 — — 0.36 — 29 — 4.84 — — — — — 1.69 — — 0.36 — 30 — — 4.84 — — — — 1.69 — — 0.36 — 31 — — — 4.84 — — — 1.69 — — 0.36 — 32 — — — — 4.84 — — 1.69 — — 0.36 — 33 — — — — — — — — 1.69 — 0.36 — 34 — — — — — — — — — 1.69 0.36 — 35 — — — — — — — — — — 0.72 — 36 — — — — — — — — — — 0.72 — 37 — — — — — — — — — — 0.36 — 38 — — — — — — — — — — 0.36 — 39 — — — — — — — — — — 0.36 — Example deliquification extruder homogenization extruder No. T (° C.) screw speed (rpm) feeding (kg/h) T (° C.) screw speed (rpm) feeding (kg/h) 1 150 120 42 180 160 46.66 2 150 120 42 180 160 46.66 3 150 120 49 180 160 9.99 5 150 120 49 180 160 23.33 6 150 30 42 180 80 46.66 7 150 120 42 180 160 46.66 8 150 120 42 180 160 46.66 9 150 120 42 180 160 46.66 10 150 120 42 180 160 46.66 11 150 120 42 180 160 46.66 12 150 120 42 180 160 46.66 13 150 120 42 180 160 46.66 14 150 120 42 240 160 46.66 15 150 120 42 240 160 46.66 16 150 120 42 240 160 46.66 17 150 120 42 180 160 46.66 18 150 120 42 180 160 46.66 19 150 30 30.63 180 80 277.04 20 150 30 30.63 180 80 277.04 21 150 30 42 180 80 46.66 22 150 30 42 180 80 46.66 23 150 120 42 180 160 46.66 24 150 120 42 180 160 46.66 25 150 120 42 180 160 46.66 26 150 120 42 180 160 46.66 27 150 120 42 180 160 46.66 28 150 120 42 180 160 46.66 29 150 120 42 180 160 46.66 30 150 120 42 180 160 46.66 31 150 120 42 180 160 46.66 32 150 120 42 180 160 46.66 33 150 120 42 180 160 46.66 34 150 120 42 180 160 46.66 35 150 120 42 180 160 46.66 36 150 120 42 180 160 46.66 37 150 30 42 180 80 46.66 38 150 30 42 180 80 46.66 39 150 30 42 180 80 46.66

LIST OF ABBREVIATIONS

Matrix Binder

[0152] PLA Polylactic acid [0153] PCL Polycaprolactone [0154] PBS Polybutylene succinate [0155] PHBH Polyhydroxyalkanoates such as poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [0156] PBAT Polybutyrate [0157] PBSA Polybutylene succinate adipate [0158] PHB Polyhydroxybutyrat [0159] PHBV Polyhydroxybutyrate-co-hydrovalerate [0160] PBT Polybutylene terephthalate [0161] PET Polyethylene terephthalate [0162] PTT Polytrimethylene terephthalate [0163] PC Polycarbonate [0164] Sub Suberin [0165] Cut Cutin

Cellulosic Material

[0166] MFC Microfibrillated cellulose (Exilva F 01-V, Borregaard) [0167] BC Bacterial cellulose (Nata de Coco) [0168] WF Wood fiber (WoodForce Natural Fast, Sonae Arauco Deutschland AG) [0169] CEL Man-made cellulose (Viscose, Danufil® KS, 1.7 dtex, 4 mm) [0170] NF Natural fiber (Flax chopped 2 mm, Ekotex)

Hydrophobic Agent

[0171] PE-PU Polyester Polyurethane (Epotal® P100 ECO, BASF) [0172] BTAK BioTAK® S100 (acrylic waterborne adhesive) [0173] LA Linoleic acid [0174] OA Oleic acid [0175] CLW Candelilla wax [0176] CBW Carnauba wax [0177] RW Rice wax [0178] LO Linseed Oil [0179] SO Sunflower Oil [0180] WO Walnut oil

TABLE-US-00005 Processing aids AF Antifoaming agent Organo-modified siloxane emulsion (Tego ® Antifoam 4-94) LT Surfactant (Lumiten ® I-SC) Polysorbate surfactant with a fatty acid ester moiety and a long polyoxyethylene chain T80 Surfactant (Tween ® 80) Polysorbate with a fatty acid ester rest moiety and a long chain polyoxyethylene chain with oleic acid as the fatty acid TX Surfactant (Triton X-100) Polyoxyethylene containing an alkylphenyl group LC Surfactant (Lecithin) Mixture of glycerophospholipids phosphatidic acid including phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, BA Crosslinking agent A water-emulsifiable polyfunctional (Basonat ® LR 9056) isocyanate crosslinker containing hexamethylene diisocyanate (HDI) TTT Initiator (Trigonox 301) 3,6,9-Triethyl-3,6,9-trimethyl-1,4,7- triperoxonane in solution (41%)