Compact system for packaging microfibrillated cellulose

Abstract

The present invention relates to a system for the compact packaging of microfibrillated cellulose, which comprises a packaging, which comprises at least one polymer material. Said packaging encompasses a content that essentially consists of microfibrillated cellulose (“MFC”) that is present as a suspension in a solvent. The resulting system is of an essentially round or essentially rectangular or oval outer circumference, as defined by the dimensions of the packaging once fully filled out by the content. The system of the invention has the advantage, among others, to provide a solid and firm essentially round packaging shape. The resulting units of packaged MFC can be easily stacked on a pallet. The packaging maintains the water retention capacity of the suspension (paste). The present invention also relates to a process for making such a system.

Claims

1. A system comprising: a packaging that comprises at least one polymer material; a content of the packaging that is fully encompassed by the packaging, wherein said content essentially consists of microfibrillated cellulose that is present in at least one solvent; wherein the microfibrillated cellulose and the at least one solvent form a suspension of microfibrillated cellulose in said at least one solvent, wherein a solids content of microfibrillated cellulose in relation to an overall weight of the suspension is from 2% weight/weight to 50% w/w, wherein the packaging, when entirely filled out with the content, defines an outer circumference of the system that is essentially round or essentially rectangular, or of oval shape, and wherein a length of said system is at least 1.5 times a largest width defining a cross-section of said circumference, wherein the packaging is filled with the content in its entirety, and wherein a weight of the system is from 1 kg to 50 kg per unit, wherein the packaging has a tensile strength as measured in accordance with the standard ASTM D882-02, published June 2002, in a range of from 5 MPa to 500 MPa.

2. The system according to claim 1 wherein the packaging is essentially round and preferably is a tubing or tube-shaped.

3. The system according to claim 1 wherein the at least one polymer is not an elastomer.

4. The system according to claim 1, wherein the packaging is realized as a film.

5. The system of claim 4, wherein the film has a thickness of from 50 μm to 5 mm.

6. The system according to claim 1, wherein the at least one polymer of the packaging is selected from polymers used in food packaging and non-food packaging applications and include at least one of the following: polyethylene, polypropylene, polycarbonate, PET, any combination thereof, or any combination with other materials.

7. The system according to claim 1, wherein a diameter of the system is from 2 cm to 50 cm.

8. The system of claim 7, wherein the diameter is from 5 cm to 30 cm.

9. The system according to claim 1, wherein the at least one solvent essentially consists of water.

10. The system of claim 1, wherein the microfibrillated cellulose has been prepared by a process, which comprises at least the following steps: (a) subjecting a cellulose pulp to at least one mechanical pretreatment step; (b) subjecting the mechanically pretreated cellulose pulp of step (a) to a homogenizing step, which results in fibrils and fibril bundles of reduced length and diameter vis-a-vis the cellulose fibers present in the mechanically pretreated cellulose pulp of step (a), said step (b) resulting in microfibrillated cellulose; wherein the homogenizing step (b) involves compressing the cellulose pulp from step (a) and subjecting the cellulose pulp to a pressure drop.

11. The system of claim 1, wherein the solids content of microfibrillated cellulose in relation to the overall weight of the suspension is from 5% w/w to 12% w/w.

12. The system of claim 1, wherein the length of said system is at least 3 times the largest width.

13. The system of claim 1, wherein the packaging has a tensile strength as measured in accordance with the standard ASTM D882-02, published June 2002, in a range of from 20 MPa to 300 MPa.

14. The system of claim 1, wherein the at least one solvent comprises at least 90% water.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) The invention is described in more detail in the following, with reference to the enclosed figures, which are only meant to be illustrative, wherein:

(2) FIG. 1 shows microfibrillated cellulose at a dry matter content of approx. 8% to 12%; the “paste”-like structure is apparent

(3) FIG. 2 shows MFC as packaged in accordance with the present invention (right panel); even after removing the packaging, the MFC keeps its dimensional stability; no loss of water is observed (left panel)

(4) FIG. 3 shows a schematic depiction of a line and process for filling MFC into the packaging of the present invention

(5) As already indicated above, the at least one polymer used in the packaging of the present system may be selected from polymers used in food packaging and non-food packaging applications. Preferred polymers therefore include polyethylene, in particular HDPE, LDPE and LLDPE, polypropylene, polycarbonate, PET, and any combination thereof, or any combination with other materials, such as fibers, metal coatings/foils etc.

(6) Low density polyethylene or LDPE is a thermoplastic packaging that is easy to process, and that may be blended with other polymers and/or additives, like EVA, HDPE, LLDPE, fillers, pigments to alter its basic properties.

(7) Linear low-density polyethylene (LLDPE) has similar properties as LDPE but has higher tensile and impact strength and better heat sealability, whereas LDPE provides higher clarity, ease of processing and higher gloss.

(8) Metallocene polyethylene or mPE is a low density polyethylene which is made by utilizing a metallocene catalyst. This technology allows for rapid sealing. The resulting packaging has excellent puncture resistance and permeability to oxygen and good tensile strength at break and is much stronger than ordinary polyethylene.

(9) High density polyethylene or HDPE is a milky white, semi-translucent thermoplastic that is flexible but more rigid and stronger than LDPE and has good impact strength and superior puncture resistance. HDPE is stiffer than other polyethylene films, which is an important characteristic for packages that need to maintain their shape.

(10) Polypropylene or PP is a thermoplastic of high clarity, high gloss and good tensile strength. The two most important types of PP are cast unoriented polypropylene (CPP) and biaxially oriented polypropylene (BOPP). Both types have high gloss, exceptional optics, good or excellent heat sealing performance, high heat resistance, and good dimensional stability. In general, CPP has higher tear and impact resistance, better cold temperature performance and better gas barrier and heat-sealing properties, whereas BOPP has the higher tensile strength, higher modulus (stiffness), lower elongation, and lower haze.

(11) Polycarbonate (PC) is an amorphous engineering thermoplastic which has excellent mechanical, optical, electrical, and thermal properties. It is extremely tough and has outstanding impact resistance and high optical clarity. PC films are used for film applications that require high scratch, chemical, and weathering resistance and high crystal clear transparency.

(12) Vinyl film also known as polyvinyl chloride, or PVC is a versatile, cheap thermoplastic of good dimensional stability, good impact strength, and excellent weathering properties that can be easily die-cut and that is printable with conventional screen and offset printing methods.

(13) Polyester film is a high-performance, crystal clear thermoplastic made from polyethylene terephthalate (PET). In comparison with other common plastic films, PET film has high tensile strength, excellent dimensional stability, low moisture absorption, and good retention of physical properties over a fairly wide temperature range.

(14) Polyvinylidene chloride (PVDC) is a synthetic thermoplastic produced by the polymerization of vinylindene chloride. The most common type is biaxial oriented film. PVDC has outstanding oxygen and moisture barrier properties and is also printable using common ink systems and provides excellent bond strength, high heat resistance, and low water absorption.

(15) Polyamide (PA), also known as Nylon, is a clear and printable thermoplastic that has a relatively high melting point, exceptional strength and toughness, and good oxygen barrier properties. The two most common types are cast and biaxial oriented Nylon film. Biaxial oriented polyamide or BOPA film can be used for a wide variety of applications especially where high gas barrier properties are required.

(16) As already indicated above, in principle, any type of microfibrillated cellulose (MFC) can be used for the content of the packaging as used in accordance with the present invention, as long as the fiber bundles as present in the original cellulose pulp are sufficiently disintegrated in the process of making MFC so that the average diameter of the resulting fibers/fibrils is in the nanometer-range and therefore more surface of the overall cellulose-based material has been created, vis-à-vis the surface available in the original cellulose material. MFC may be prepared according to any of the processes described in the art, including the prior art specifically cited in the “Background”-Section above.

Origin of the Cellulose Used to Prepare the MFC

(17) In accordance with the present invention, there is no specific restriction in regard to the origin of the cellulose, and hence of the microfibrillated cellulose. In principle, the raw material for the cellulose microfibrils may be any cellulosic material, in particular wood, annual plants, cotton, flax, straw, ramie, bagasse (from sugar cane), suitable algae, jute, sugar beet, citrus fruits, waste from the food processing industry or energy crops or cellulose of bacterial origin or from animal origin, e.g. from tunicates.

(18) In a preferred embodiment, wood-based materials are used as raw materials, either hardwood or softwood or both (in mixtures). Further preferably softwood is used as a raw material, either one kind or mixtures of different soft wood types. Bacterial microfibrillated cellulose is also preferred, due to its comparatively high purity.

Modified (Derivatized) and Non-Modified (Un-Derivatized) Cellulose/MFC

(19) In principle, the microfibrillated cellulose in accordance with the present invention may be unmodified in respect to its functional groups or may be physically modified or chemically modified, or both.

(20) Chemical modification of the surface of the cellulose microfibrils may be achieved by various possible reactions of the surface functional groups of the cellulose microfibrils and more particularly of the hydroxyl functional groups, preferably by: oxidation, silylation reactions, etherification reactions, condensations with isocyanates, alkoxylation reactions with alkylene oxides, or condensation or substitution reactions with glycidyl derivatives. Chemical modification may take place before or after the defibrillation step.

(21) The cellulose microfibrils may, in principle, also be modified by a physical route, either by adsorption at the surface, or by spraying, or by coating, or by encapsulation of the microfibril. Preferred modified microfibrils can be obtained by physical adsorption of at least one compound. The MFC may also be modified by association with an amphiphilic compound (surfactant).

(22) However, in preferred embodiments, the microfibrillated cellulose is not physically modified.

(23) In a preferred embodiment of the present invention, the microfibrillated cellulose is prepared by a process, which comprises at least the following steps: (a) subjecting a cellulose pulp to at least one mechanical pretreatment step; (b) subjecting the mechanically pretreated cellulose pulp of step (a) to a homogenizing step, which results in fibrils and fibril bundles of reduced length and diameter vis-à-vis the cellulose fibers present in the mechanically pretreated cellulose pulp of step (a), said step (b) resulting in microfibrillated cellulose; wherein the homogenizing step (b) involves compressing the cellulose pulp from step (a) and subjecting the cellulose pulp to a pressure drop.

(24) The mechanical pretreatment step preferably is or comprises a refining step. The purpose of the mechanical pretreatment is to “beat” the cellulose pulp in order to increase the accessibility of the cell walls, i.e. to increase the surface area.

(25) A refiner that is preferably used in the mechanical pretreatment step comprises at least one rotating disk. Therein, the cellulose pulp slurry is subjected to shear forces between the at least one rotating disk and at least one stationary disk.

(26) Prior to the mechanical pretreatment step, or in addition to the mechanical pretreatment step, enzymatic (pre)treatment of the cellulose pulp is an optional additional step that may be preferred for some applications. In regard to enzymatic pretreatment in conjunction with microfibrillating cellulose, the respective content of WO 2007/091942 is incorporated herein by reference. Any other type of pretreatment, including chemical pretreatment is also within the scope of the present invention.

(27) In the homogenizing step (b), which is to be conducted after the (mechanical) pretreatment step, the cellulose pulp slurry from step (a) is passed through a homogenizer at least once, preferably at least two times, as described, for example, in PCT/EP2015/001103, the respective content of which is hereby incorporated by reference.

EXAMPLES

Example 1

Preparation of Microfibrillated Cellulose

(28) MFC as used in the system/packaging of the present invention is commercially available and commercialized by Borregaard as “Exilva F01-V”, based on cellulose pulp from Norwegian spruce (softwood).

(29) The MFC in step (i) was present as a paste, having a solids content of 10%. The solvent was water.

Example 2

Packaging of Microfibrillated Cellulose

(30) FIG. 3 illustrates an exemplary process for filling the packaging with MFC paste from Example 1.

(31) In step 1, said MFC paste is transported by conveyer(s) from the final de-watering step of a process for making MFC out of cellulose pulp. This MFC is then transported to an extruder. The MFC was transported in portions (as shown in FIG. 3).

(32) In step 2, the MFC is further mixed, homogenized and extruded through a nozzle and into the packaging, at a constant rate. The extruder was a KS Pump System (vacuum filler) as commercialized by Karl Schnell. Without wishing to be bound by theory, it is believed that the extrusion process as used during packaging, and in accordance with the present invention, further stabilizes and homogenizes the MFC. Therefore, with this inventive packaging, the water retention properties of the MFC are by-and-large retained, as opposed to other known storage and transportation systems.

(33) In step 3, in a clipping machine, the tube-shaped packaging (including the MFC as content) is closed, with two clips at each end of the tube.

(34) Conveyors are used for transport between the different stations [step (4) in FIG. 3]. The entire process is fully automated.

(35) Further devices used in the process are a labelling device (5) for labeling each tube, for example with batch number, product type, manufacturing date etc., a case erector (7) for the corrugated board or cardboard boxes for transport, as well as a palleting machine for packaging the corrugated board or cardboard boxes on pallets.

(36) Robots (6) are used to lift filled tubes into carton board boxes and/or to lift the corrugated board or cardboard boxes.

(37) Overall, many successful trials have been executed with an extruder that homogenize and fill the packaging with MFC.

(38) FIG. 2 shows that the product is completely homogenized after the packaging has been removed.