Patent Application
20240239007
The present invention relates in general to the field of method and apparatus for dry manufacturing of rigid cellulose products having essentially non-flat general shape. The cellulose products may be used for packaging, storing, transporting and/or displaying other products such as electronics, tools, jewelry, food, dairy products, cosmetics, etc., and/or may be used as single/multiple use disposable articles. The present invention also relates to a rigid cellulose product and to a continuous or discontinuous cellulose blank.
There are many situations where it is desirable to provide two-dimensional (2D) or three-dimensional (3D) shaped objects made of sustainable materials. A material commonly used for packaging inserts is wet moulded pulp. Wet moulded pulp has the advantage of being considered as a sustainable packaging material, since it is produced from biomaterials and can be recycled after use. Consequently, moulded pulp has been quickly increasing in popularity for both primary and secondary packaging applications (packaging next to the article and assembly of such packages).
A common disadvantage with all wet-forming techniques is the need for large amounts of water during manufacturing and the need for drying of the moulded product, which is a time and energy consuming step leading to low production speed and substantial high investment cost in machines and tooling. Meaning that the technology will not be feasible to replace fossil-based alternatives in large scale.
Moreover, many modern lean production lines require in-line on-demand package or component manufacturing where a wet-forming process is not preferred or feasible. Lately, new fibre-based materials have been developed with the purpose of enabling dry forming of three-dimensional objects/products. One approach is disclosed by WO2014/142714. WO2014/142714 discloses a dry-laid composite web being an intermediate product for thermoforming of three-dimensionally shaped objects, comprising 40-95 wt-% CTMP fibres, 5-50 wt-% thermoplastic material, and 0-10 wt-% additives, wherein the dry-laid composite web has been impregnated with a dispersion, an emulsion, or a solution containing the thermoplastic material, polymer, and dried, obtaining a density of 50-250 kg/m3, or, if compressed by calendaring 400-1000 kg/m3. According to WO2014/142714, bonding of the polymer is activated by the higher temperature applied in the thermoforming process and contributes to the final strength of the thermoformed object.
Forming a sheet of cellulose fibres in an air/dry-laid process provides in general a weak network strength of said cellulose fibres, i.e., weak self-supporting properties. Said air laid sheet/blank may be an intermediate product in a dry cellulose forming/manufacturing process of essentially non-flat products. Due to the fragile character of said intermediate product it may be necessary to improve its self-supporting properties of said sheet to improve the efficiency and flexibility of the manufacturing process of said rigid cellulose products having essentially non-flat general shape.
It has been identified that the cellulose fibres are very hygroscopic and that the air/dry-laid process is sensitive to electrostatic charges and process conditions such as airflow and humidity. This behaviour of the cellulose fibres makes it difficult to provide an even blank/sheet of cellulose fibres onto a forming structure/web because the cellulose fibres tend to group together and the grammage/thickness of the blank will become uneven/unpredictable. There are attempts within the art to provide a solution of controlling the properties/grammage of the cellulose blank, i.e. using a tower forming unit as in SE1750313 wherein fibre separating brushes and first compacting rollers are used to try to obtain a uniform cellulose blank, both in the axial and transverse directions. Uneven grammage of the cellulose blank may to some degree be compensated with isostatic pressing procedure according to EP3429928. However, this is more complicated in terms of tooling, requires longer process times and is a more complex process. The problem with this formation tower and isostatic pressing process is that it is rather complex with all its mechanical components provided for distributing as even as possible layer of cellulose fibres onto the forming web. A common problem in the pressing step for forming a 3D shaped component/product is that the sheet/blank of cellulose fibres may crack due to complex component structure/design and/or deep products.
There is a need in the art for a more reliable dry cellulose forming/manufacturing process of essentially non-flat rigid cellulose products which reduce or eliminates the risk of creating cracks in the pressing step.
The present invention aims at obviating the aforementioned and other disadvantages and failings of previously known methods and apparatus for dry manufacturing rigid cellulose products, and at providing an improved method and apparatus for dry manufacturing rigid cellulose products having essentially non-flat general shape.
A primary object of the present invention is to provide an improved method and apparatus for dry forming/manufacturing rigid cellulose products having essentially non-flat general shape from cellulose fibres. It is another object of the present invention to provide a method and apparatus for manufacturing rigid cellulose products that entails that the produced cellulose products are free from cracks that otherwise originating from the pressing of the cellulose product. It is another object of the present invention to provide a method and apparatus for manufacturing rigid cellulose products wherein the grammage of the cellulose blank may be tailored in order to obtain final cellulose products having required characteristics/properties such as rigidity, thickness, grammage, etc. It is another object of the present invention to provide a method and apparatus for manufacturing rigid cellulose products that may produce a continuous or discontinuous cellulose blank. It is another object of the present invention to provide a method and apparatus for manufacturing rigid cellulose products that generates less scrap/waste. It is another object of the present invention to provide a method and apparatus for manufacturing rigid cellulose products wherein the blank forming unit is made less complex.
According to the invention at least the primary object is attained by means of the initially defined method and apparatus having the features defined in the independent claims. Preferred embodiments of the present invention are further defined in the dependent claims.
According to a first aspect of the present invention, there is provided an apparatus comprising:
According to a second aspect of the present invention, there is provided a method comprising the steps of:
Thus, the present invention is based on the insight of having non uniform perforation density on the outer surface of the forming drum such that different amount of cellulose fibres attach to different parts of the rotating forming drum and thereby the continuous or discontinuous cellulose blank may have different/varying grammage or surface weight in the axial and/or radial direction.
An advantage of the invention is that the method and apparatus provides appropriate strength and rigidity to the cellulose blank prohibiting the same to crack when producing/pressing said rigid cellulose products having essentially non-flat general shape.
Another advantage of the invention is that the grammage of the cellulose blank can be easily tailored in order to obtain the requested properties of the essentially non-flat rigid cellulose product to be produced.
According to various example embodiments of the present invention the cellulose blank is discontinuous in the axial and/or transvers directions, i.e. perpendicular and/or in parallel to the direction of movement of the support structure/web. The advantage of these embodiments is that individual strips and/or tiles of the cellulose blank, having adequate grammage in the axial and transverse directions may be formed for later use in the pressing tool for producing the essentially non-flat rigid cellulose product.
According to various embodiments of the present invention, the second perforation density of the second area of the outer surface of the forming drum is equal to zero, and as a result the grammage of the cellulose blank originating from these second areas is also zero, i.e. individual sheetlets, i.e. stripes and/or tiles, of the cellulose blank are provided.
According to various embodiments of the present invention, the outer surface of the forming drum comprises a main envelope surface and one or more recesses provided in the main envelope surface, wherein the first area having a first perforation density is located in said one or more recesses, for forming a continuous or discontinuous cellulose blank having higher grammage at the locations originating from said first area than at the locations originating from said second area.
An advantage of having recesses in the forming drum for generating the higher grammage sections of the continuous or discontinuous cellulose blank, i.e. locations having more cellulose fibres, is that it is more easily to screen/encapsulate the production step of air/dry laying cellulose fibres to the forming drum. Thereto, it is evident that the forming drum may be adapted in various ways to the final cellulose product for inter alia enforcing areas prone to crack and/or making predetermined areas of the product more rigid.
According to various embodiments of the present invention, the cellulose blank forming unit further comprises a second forming drum having an outer surface comprising perforations, wherein the outer surface is configured for receiving cellulose fibres and for forming a cellulose blank from a quantity of separated cellulose fibres transported by an air flow, and a second air removing device arranged inside the second forming drum.
The use of a second forming drum is based on the insight of providing a continuous or discontinuous cellulose blank of additional cellulose fibres that are intended to be connected to the continuous or discontinuous cellulose blank of the (first) forming drum, before the rigid cellulose product is produced/pressed. Thereby, the ability to tailor the grammage of different locations of the continuous or discontinuous cellulose blank reaching the product forming unit is further enhanced.
The cellulose fibres from the (first) forming drum and the second forming drum may be applied to the support structure concurrently as a single continuous or discontinuous cellulose blank, or individually wherein the final continuous or discontinuous cellulose blank is formed at the support structure.
According to various embodiments of the present invention the cellulose fibres of the (first) forming drum and the second forming drum are of different types, i.e. different raw material, different fibre size, different additives, etc.
The advantage of these embodiments is that the mechanical properties of the final cellulose product may be tailorized to meet specific requirements.
Further advantages with and features of the invention will be apparent from the following detailed description of preferred embodiments.
A more complete understanding of the abovementioned and other features and advantages of the present invention will be apparent from the following detailed description of preferred embodiments in conjunction with the appended drawings, wherein:
As used herein, the term “air/dry moulding or air/dry laying” means a well-known method according to which separated cellulose fibres are formed into a cellulose blank/sheet.
In air-laying, small fibres having a normal length in the range of 1 to 50 mm are separated and captured by an air stream/flow, and then laid on/applied to a forming mesh/surface, usually using a vacuum/low pressure at the other side of the mesh/surface. The terms “air laying” and “air moulding” are used interchangeably herein. The cellulose fibre carrying air flow may be generated by suitable device located upstream and/or downstream the forming mech/surface.
The inventive apparatus 100 will be generally described with reference to
Said cellulose fibres may be virgin cellulose fibres and/or recycled cellulose fibres and may originate from wood pulps such as kraft pulp, sulphite pulp, mechanical pulp, thermomechanical pulp (TMP), chemical treated mechanical pulp, chemi-thermomechanical pulp (CTMP), and/or from non-wood pulps such as bagasse, bamboo, abaca, hemp, flax, cotton.
The separating unit 3 may according to various embodiments be constituted by a hammer mill. In said separating unit 3 the cellulose raw material is separated into fibres having a normal length in the range of 1 to 50 mm. The length of said fibres may be customized by adjusting the internal properties of the separating unit 3 and/or by choosing a different separating unit 3 and/or by choosing different cellulose raw material. The fibre length for wood pulp is according to various embodiments in the range 0.5-4 mm, preferably in the range 1.7-3.6 mm. According to various embodiments the fibre length for non-wood pulp is in the range 0.5-70 mm.
In an air/dry-forming/air-laid method, in general, wood pulp fibres are individualized/separated using, for example, a hammer mill, transported by an air stream via a dispenser that distributes the fibres substantially uniformly in the transverse direction of the production apparatus. The fibres are laid on a moving perforated surface using the air flow created by the vacuum/low-pressure chambers below the surface. As described above, the cellulose fibre carrying air flow may be generated by suitable device located upstream and/or downstream the perforated surface.
In
Separated cellulose fibres may be flowing with a fibre/air concentration of approx. 500 g cellulose fibre per cubic metre air, and the moisture content of the air is 5-20 g water/kg air in the separating unit 3 and/or in the cellulose blank forming unit 30.
The outer surface of the forming cylinder 15 is perforated. In order to apply said cellulose fibres with air onto the outer surface of the forming drum/cylinder 15 the air inside the forming drum 15 is removed in the angular interval 5, and the cellulose fibres stay attached onto the outer surface having perforations, i.e. the cellulose fibres are sucked against the outer surface of the forming drum 15. The air is removed by means of an air removing device 54 arranged inside the forming drum 15, i.e. at least a part of the air removing device 54 is arranged inside the forming drum 15. The air removing device 54 is configured to remove at least the same amount of air introduced by the fan 4 generating the cellulose fibre carrying air flow. Thereby the separated cellulose fibres will attach/accumulate to the outer surface of the forming drum 15 at the locations having perforations. When the cellulose fibres accumulate at the outer surface of the forming drum 15 the cellulose blank 13 is formed. The amount of cellulose fibres in the air flow from the fan 4, the air flow speed from the fan 4, the speed of the outer surface of the forming drum 15, the perforation density of the outer surface, etc. determine the grammage of the cellulose blank 13 formed. Alternately, the air removing device 54 also perform the task of the fan 4 and is thereby the single device generating the cellulose fibre carrying air flow.
The cellulose blank 13 is removed from the forming drum/cylinder 15 and is applied to or received by the support structure/web 8. For that reason, only said predetermined angular interval 5 of said forming cylinder 15 has said vacuum/low-pressure condition. The angular interval 5 is overlapping the air flow from said fan 4. The vacuum condition is released/terminated in advance of or at the closest position of said outer surface of said forming cylinder 15 to said support structure 8 thereby allowing said cellulose blank/sheet 13 to be released from said forming cylinder 15 and applied onto said support structure 8. The support structure 8 may be as depicted in
The support structure 8 may also be a discontinuous web. Said discontinuous web may be movable back and forth for catching the cellulose blank/sheet and to deliver the cellulose blank/sheet to further process steps. This cellulose blank may be discontinuous, i.e. a stack of multiple sheetlets of the cellulose blank, or may be continuous, i.e. a folded cellulose blank.
The cellulose blank 13 fed into a product forming unit 40, either subsequently in the same line of production as the cellulose blank forming unit 30 or from an intermediate storage between the cellulose blank forming unit 30 and the product forming unit 40. According to various embodiments, the product forming unit 40 comprises a press unit 12 having a moulding tool 11. The moulding tool 11 has a male portion and a corresponding female portion comprising the design/structure of the final rigid cellulose product having essentially non-flat general shape. In
In said moulding tool 11 said cellulose blank 13 is heated to a temperature of 120-200° C. in order to obtain adequate rigidity and strength in the final cellulose product 14. According to various example embodiments the cellulose blank 13 may be preheated to 100° C. prior to reaching the press unit 12 of the product forming unit 40 and in the press unit 12 the cellulose blank is heated to 120-200° C. by said moulding tool 11. According to various example embodiments the cellulose blank is heated to 120-200° C. by said pre-heating unit 16 and no extra heat is delivered to the cellulose blank during the moulding of the final cellulose product 14. According to various example embodiment the heating of the cellulose blank 13 is only taking place in the press unit 12 of the product forming unit 40 during the forming of the final cellulose product 14, i.e. without pre-heating.
The apparatus 100 may be provided with one or a plurality of humidifier units 17a-c. According to various example embodiments a first humidifier unit 17a may be arranged to humidify the surrounding air in the production site and/or an interior volume of the apparatus 100 for ensuring the correct humidity of the cellulose fibres, especially in the disintegrating unit 3 and/or in the cellulose blank forming unit 30. According to various example embodiments a second humidifier 17b may be arranged prior to the separating/disintegrating unit 3, i.e. at the inlet to said separating unit 3, for humidifying the cellulose raw material entering the separating unit 3. According to various example embodiments a third humidifier 17c may be arranged at an outlet of said separating unit 3 for humidifying the cellulose fibres being ejected from said separating unit 3. The third humidifier 17c may be arranged at an inlet of the fan 4 provided for extracting fibrous material from the separating unit 3 and spraying the same fibrous material onto said forming cylinder 15. The third humidifier may also be arranged at said fan 4 for blending incoming air and fibrous material with a desired humidity before allying the cellulose fibres onto the forming cylinder 15. The humidifier 17a, 17b, 17c may provide water in liquid and/or gaseous form. The humidifier 17b and 17c may alternatively be used to provide other additives/chemicals than water, in liquid and/or gaseous form.
The cellulose blank requires a moisture content within a predetermined range. As mentioned above the moisture content of the air is 5-20 g water/kg air in the separating unit 3 and/or in the cellulose blank forming unit 30. According to various example embodiments the moisture content of the air is 9-12 g water/kg air in the separating unit 3 and/or in the cellulose blank forming unit 30. A too low moisture content of the cellulose fibres will result in increased risk of static electricity which will result in uneven cellulose blank formation and thereby affect the grammage of the cellulose blank. A too high moisture content will result in clogging of the cellulose fibres and thereby affect the grammage of the cellulose blank.
According to various example embodiments one or plurality of optional chemical dosing units may be provided and configured for increasing the network strength of the cellulose blank 13. In a first example embodiment at least one first chemical dosing unit 9a-c may be provided for applying a liquid binding agent onto a bottom or top surface of said cellulose blank for forming a support layer.
The liquid binding agent may only be allowed to have a penetration depth less than 50% of a thickness in said cellulose blank 13 from any side of said cellulose blank/sheet 13. According to various example embodiments the penetration depth of said liquid binding agent is between 5-49% of the total thickness of the cellulose blank 13. According to various example embodiments the penetration depth of said liquid binding agent is between 10-30% of the total thickness of the cellulose blank 13. The dosing unit 9a may apply liquid binding agent prior to receiving the cellulose blank 13 onto the support web 8. In this case the liquid binding agent is provided on a bottom side of said cellulose blank. The dosing unit 9b may apply liquid binding agent on top said cellulose blank 13. The dosing unit 9c may apply liquid binding agent prior to the optional pre-heating unit 16 and/or the press unit 12 of the product forming unit 40. In
The final cellulose product 14 is formed in the press unit 12 of the product forming unit 40. The pressure by said press unit 12 onto said moulding tool 11 may be between 40-10000N/cm2. According to various example embodiments said pressure is between 100-4000N/cm2. According to various example embodiments said pressure is above 400N/cm2, preferably between 1000-3900N/cm2.
According to various example embodiments a liquid or a solid agent may be applied onto the cellulose material before the forming/moulding step for altering the hydrophobic and/or oleophobic characteristics/properties of the essentially non-flat cellulose product 14. In
According to various example embodiments the moisture content of the cellulose blank 13 is at least 5% when said cellulose blank is provided into said moulding tool 11. According to various example embodiments said moisture content of said cellulose blank 13 is between 7-12% when said cellulose blank is provided into said moulding tool 11.
The formation of the cellulose blank 13, i.e. the control of the grammage of the cellulose blank 13 is vital for the resulting properties of the final cellulose product 14. When the design/construction of the final cellulose product 14 is complex, the prior art solutions does not provide enough rigidity/strength to the final cellulose product 14 and cracks arise during the pressing in the formation unit 40. The present invention is based on the insight that the cellulose blank 13 has to have different grammage at different locations such that the final cellulose product 14 has the required properties regarding rigidity/strength/grammage and display/comprise no cracks. By having different grammage at different locations of the cellulose blank 13 the final cellulose product 14 may have uniform grammage and/or appointed locations having elevated grammage.
In order to generate/form a cellulose blank at the outer surface of the forming drum 15 having different grammage at different locations, the outer surface of the forming drum 15 comprises a first area having a first perforation density and a second area having a second perforation density that is less than said first perforation density. Perforation density means degree of apertures area in relation to no apertures area. The dimensions of the individual perforation may be the same over the entire forming drum 15, or may differ. Since the first perforation density is higher than the second perforation density, i.e. more air will be drawn through the outer surface of the forming drum 15 at the first area than at the second area and more cellulose fibres will attach to outer surface of the forming drum 15 at the first area than at the second area. Thereby, the forming drum 15 generate a continuous or discontinuous cellulose blank 13 having higher grammage at first locations originating from said first area than at second locations originating from said second area. Higher grammage means more cellulose fibres per area of the cellulose blank 13. The forming drum 15 may have more than two levels of perforation density, and/or the interface between two areas of different perforation density may be a sharp transition or a smooth transition.
According to various embodiments the second perforation density of the second area of the outer surface of the forming drum 15 is equal to zero, i.e. no perforations and thereby no cellulose fibres will attach to the second area(s) of the outer surface of the forming drum 15. Also a small perforation density at the second perforation density of the second area of the outer surface of the forming drum 15 will entail that no significant amount of cellulose fibres will attach to the second area(s) of the outer surface of the forming drum 15. The first area and the second area may be provided on the envelope surface of the forming drum 15. Thereby a cellulose blank 13 is formed that is discontinuous, i.e. having different grammage at different locations. Thus, at some locations the grammage is zero and at other locations the grammage is significant. Each sheetlet of the discontinuous cellulose blank 13 may have uniform grammage or areas of different grammage.
According to various embodiments, the outer surface of the forming drum 15 comprises a main envelope surface 64 and one or more recesses/ingrowths 62 provided in the main envelope surface 64. (See
Said recess(es)/ingrowth(s) 62 is suitable for creating a continuous or discontinuous cellulose blank 13 having locations/areas of different grammage. Thus, the first area of the forming drum 15 having a first perforation density is located in said one or more recesses 62, for forming a continuous or discontinuous cellulose blank 13 having higher grammage at the locations originating from said first area than at the locations originating from said second area. The location of the cellulose blank emanating from an ingrowth 64 has a higher grammage than the location of the cellulose blank emanating from surrounding areas of said outer surface of the forming drum 15 which is lacking such ingrowth.
Each recess 62 may comprise both the first area having the first perforation density and the second area having the second perforation density, and/or the recess may have different depths for the first area and the second area. Preferably, the second area having the second perforation density is located in the main envelope surface 64 and the first area having the first perforation density is located in the recesses.
In
Reference is now made to
The forming drum 15 in
In
According to
Reference is now especially made to
The cellulose blank forming unit 30 comprises two sub-steps, i.e. one additional forming arrangement in addition to the above described forming drum 15.
According to
Separated cellulose fibres 6 are fed into the tower forming unit 7 by at least one fan 4′ arranged between the separating/disintegrating unit 3 and the tower forming unit 7. Separated cellulose fibres 6 that are fed into the tower forming unit 7 are drawn towards a bottom section by a vacuum/low-pressure container 5′. The tower forming unit 7 is arranged above the continuous support structure/web 8 onto which said separated fibres 6 are to be arranged for forming the cellulose blank 13. Directly below the tower forming unit 7 and underneath the support structure 8 is said vacuum/low-pressure container 5′ arranged for removing air fed into the tower forming unit 7 by means of an air-removing device/fan 54′. As the continuous support structure 8 is moving a cellulose blank 13 of a predetermined thickness 34 and grammage is arranged onto a top surface of the support structure 8. The speed of the support structure 8 in combination with the amount of separated fibres per unit air volume in the tower forming unit 7 will determine the thickness and grammage of the cellulose blank 13.
Separated fibres 6 are also fed onto the forming cylinder/drum 15 as described above. The forming drum 15 may be arranged downstream or upstream the tower forming unit 7. For instance, the formation drum 15 apply a continuous or discontinuous sheet of cellulose fibres having varying grammage, as described above, to the uniform cellulose blank originating from the tower forming unit 7. The combined cellulose blank 13 having a planar/uniform cellulose blank 34 emanating from the tower forming unit 7 and sheetlets of cellulose fibre emanating from the forming drum 15.
Thus, the forming drum 15 may produce a continuous cellulose blank as shown in
Reference is now made to
Thus, the second forming drum 15′ has an outer surface comprising perforations, wherein the outer surface is configured for receiving cellulose fibres and for forming a cellulose blank 13 from a quantity of separated cellulose fibres transported by an air flow. Thereto a second air removing device is arranged inside the second forming drum 15′, i.e. at least a part of the air removing device 54′ is arranged inside the forming drum 15′. The second forming drum 15′ may be configured as the (first) forming drum 15.
According to various embodiments, a second fan 4′ for generating a cellulose fibre carrying air flow is associated to the second forming drum 15′. A disintegrating unit 3 is connected to the second fan 4′, either a separate disintegrating unit or the same disintegrating unit serving the (first) forming drum 15. Thus, the outer surface of the second forming drum 15′ is configured for receiving cellulose fibres and for forming a cellulose blank from said quantity of separated cellulose fibres transported by the air flow generated by the second fan 4′. Alternatively one and the same fan may be associated with both the (first) forming drum 15 and the second forming drum 15′. Alternately, the air removing device 54′ also perform the task of the fan 4′ and is thereby the single device generating the cellulose fibre carrying air flow associated to the second forming drum 15′.
According to the illustration in
According to an alternative illustrative embodiment, the (first) forming drum 15 is located upstream the second forming drum 15′. The second forming drum 15′ may generate a continuous cellulose blank on the outer surface of the second forming drum 15′, wherein the continuous cellulose blank on the second forming drum 15′ may be uniform. Sheetlets of the cellulose blank are then added from the (first) forming drum 15 to the second forming drum 15′ as described above, before the cellulose blank 13 having varying grammage is received by the support structure 8.
Reference is now made to
Reference is now made to
Thus, the compression rolls 10 are constituted by one or more compression drums, wherein each drum comprises perforations and air removing means arranged inside. Thereby, the cellulose blank 13 formed on the forming drum 15 is transferred to a first compression drum at a location/interface the angular interface 5 of the forming drum 15 ends and a corresponding angular interface of the first compression drum is active. The transfer from one drum to another is the same throughout the apparatus 100, i.e. one angular interval ends (under-pressure is terminated) and the next angular interval is active (under-pressure is active). A second compression drum is located close to the first compression drum such that at a location/interface they meet the continuous or discontinuous cellulose blank 13 is compressed and also transferred from the first compression drum to the second compression drum. The compressed cellulose blank may be transferred to additional compression drums before the cellulose blank is received by the support structure 8, and during such additional transferring the cellulose blank may be compressed further.
According to an alternative embodiment the second compression drum is exchanged by a compression roll, wherein the cellulose blank 13 is compressed between the first compression drum and such compression roll without transferring the cellulose blank from the first compression drum. Thereafter, the compressed cellulose blank is transferred from the first compression drum to the support structure 8.
According to various example embodiments an intermediate product for dry manufacturing at least one rigid cellulose product 14 having essentially non-flat general shape may be manufactured. Said intermediate product is constituted by a continuous or discontinuous cellulose blank 13 having first locations and second locations, wherein the first locations have higher grammage than the second locations. The grammage of the second location may be zero, etc., as discussed above. Such intermediate product may for instance be provided in the form of individual sheets or on a roll. The first locations of the cellulose blank, i.e. intermediate product, overlap with crack prone areas and/or increased rigidity areas of the following rigid cellulose product 14 having essentially non-flat general shape.
From the intermediate product, i.e. the cellulose blank 13, rigid cellulose product 14 having essentially non-flat general shape may be produced by pressing in a product forming unit 40, wherein the maximum grammage of the rigid cellulose product 14 is less than the maximum grammage of the first location of the cellulose blank 13. Thus, the cellulose fibres of the cellulose blank 13, intermediate product, will become redistributed during the pressing step in response to the non-flat general shape of the final cellulose product 14.
The periphery speed in the separating unit may be in the range of 50-150 m/s. In various example embodiments said periphery speed may be 90-150 m/s. In various example embodiments the size of the cellulose fibres may be 2 mm and the amount of fibres per unit volume air may be 100 g fibre/m3 air with 9-12 g water/kg air. The support structure, continuous forming cylinder and/or the continuous web may have a width of 20-100 cm. In various example embodiments said width is 30-70 cm. The sheet of cellulose fibre 13 may have a weight of 200-2000 g/m2. The pressure in the pressure unit may be in the range of 40-10000N/cm2.
According to one example, discontinuous cellulose blank is formed on the outer surface of the forming drum 15, wherein each sheetlet is about 20 cm times 30 cm. In order to obtain a final cellulose product having a thickness of 0.5 mm, the grammage is about 600 g/m2 at the first areas and 0 g/m2 at the second areas, i.e. between the sheetlets of the discontinuous cellulose blank. The process may generate 2500 sheetlets per hour and the weight of each sheetlet is 36 g, i.e. 90 kg cellulose raw material per hour. In order to obtain about 500 g cellulose fibres per cubic meter air, the requested air flow is 180 m3 air per hour. The air speed at the outer surface of the forming drum 15 shall be about 3-5 m/s, in order to accumulate enough cellulose fibres for each sheetlet of cellulose blank.
The humidity of the air flow shall be in the range 9-12 g per kg air, preferably 11 g per kg air (equal to 14.3 g per m3 air). Depending on the humidity of the surrounding air, different amounts of water have to be added in order to obtain the requested level. The humidity of the surrounding air shall preferably be in the range 55-65% RH at 20 degrees Celsius.
According to one example, discontinuous cellulose blank is formed using two forming drums 15, 15′. A first circular cellulose blank is formed on the outer surface of the (first) forming drum 15, wherein the diameter is 40 cm and grammage is about 500 g/m2, and a second circular cellulose blank is formed on the outer surface of the second forming drum 15′, wherein the diameter is 20 cm and grammage is about 200 g/m2. The process may generate 2500 sheetlets per hour and the weight of each sheetlet is 63+6=69 g, i.e. 172.5 kg cellulose raw material per hour. In order to obtain about 500 g cellulose fibres per cubic meter air, the requested air flow is 345 m3 air per hour.
The invention is not limited only to the embodiments described above and shown in the drawings, which primarily have an illustrative and exemplifying purpose. This patent application is intended to cover all adjustments and variants of the preferred embodiments described herein, thus the present invention is defined by the wording of the appended claims and the equivalents thereof. Thus, the equipment may be modified in all kinds of ways within the scope of the appended claims.
Throughout this specification and the claims which follows, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or steps or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.
It shall also be pointed out that even thus it is not explicitly stated that features from a specific illustrated embodiment may be combined with features from another embodiment, the combination shall be considered obvious, if the combination is possible.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2150604-3 | May 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/050866 | 1/17/2022 | WO |
