METHOD AND MACHINE FOR MAKING FIBRE PRODUCTS FROM STOCK AND A NEW TYPE OF FIBRE PRODUCT
The present invention relates to a method and a machine for making a fibre product. The invention also relates to a shaped body produced by the inventive method. According to the invention, a fibre product is formed on a first tool. The formed fibre product is then sandwiched between the first tool and a second tool and the surface of the second tool is heated to at least 220° C. to evaporate water from the fibre product. The tools are permeable to air and water When the fibre product has been dewatered to a dry solids content of at least 70%, the fibre product is subjected to microwave heating.
The invention relates to the production of fibre products from stock and especially to three-dimensional objects such as egg cartons, and other packaging products but also to objects such as drinking cups for beverages or trays, e.g. food trays.
BACKGROUND OF THE INVENTIONFibre products such as for example egg boxes can be made from stock in a process where a fibre layer is created and shaped to a desired form whereafter the so shaped fibre product is dewatered and possibly subjected to some form of post-processing operation.
U.S. Pat. No. 6,103,179 discloses a method for producing a fibre product which is where a first male mould is immersed in a moulding tank containing stock. By means of vacuum, a fibre layer of predetermined thickness for the fibre product is formed. The first male mould is then removed from the moulding tank. A cyclical sequence of movements is performed with a female mould in which, in a first pressing stage, the female mould is brought under force against the male mould so that a first expressing of stock water occurs following which the fibre product is transferred to the female mould which is moved to a second position. The fibre product is then subjected to a second expressing whereafter the fibre product is subjected to final drying using microwave or IR radiation.
U.S. Pat. No. 6,451,235 discloses a method for forming a three dimensional fibre truss from a fibre slurry. In this method, a wet-forming station is used which comprises a substantially rigid moveable wet-forming die with a three-dimensional first forming surface and a substantially rigid fixed wet-forming die with a second forming surface. A deckle comprises a substantially rigid impermeable frame that surrounds a deckle interior space comprising a prismatic volume including a cross-sectional outline that encompasses a peripheral surface of the first die so that the moveable wet-forming die can traverse an axial length of the prismatic volume of the deckle interior space. Within the deckle interior space, above a predetermined area of the second forming surface, there is a slurry space. There are also filling means for adding fibre slurry to the slurry space and a pressing means for urging the moveable wet-forming die along the axial length of the prismatic volume. The method includes adding a predetermined quantity of fibre slurry to the slurry space and compressing at a pre-selected rate the fibre slurry contained in the slurry space. A pre-form fibre truss is then removed from the deckle interior space and moved to a truss finishing station. In the truss finishing station, the 5 moist pre-form fibre truss is compacted further and dried under pressurized constraint between heated forming dies to produce the finished fibre truss. After treatment in the finishing station, a caul carries the finished fibre truss to a post-processing station. The post-processing is stated to include such operations as bonding to skins.
U.S. Pat. No. 6,582,562 discloses a method for producing moulded parts from a slurry by the use of first and second mating porous molds. In this method, the first mould is moved into the slurry and a vacuum is supplied to the first mold to cause the slurry to form onto the first mold to a desired thickness. The second mold is heated by hot air from a hot air source and the first and second moild are mated and a vacuum is supplied to the first and second molds during mating of the first and second molds. After this, the molded part is ejected from the first mold and the molded part travels with the second mold. The second mold is moved and the vacuum on the second mold is released to permit the molded part to be separated from the second mold. This can be done in connection with a conveyor belt. It is stated that drying temperatures of 300° F. can be used (corresponding to about 149° C.).
U.S. Pat. No. 6,136,150 discloses a method and a device for achieving a flow of stock in a moulding tank. It is stated that the moulding tank is used to produce a fibre product such as an egg carton or other packaging product. In this patent, is it proposed that a flow of stock in the moulding tank is pumped into the bottom of the moulding tank and allowed to flow up over the brim of the tank. It is stated that this results in a flow that is directed upwards and that this should be important for forming a fibre layer of even thickness on a male tool used in the method.
During production of fibre products such as for example egg boxes and drinking cups, it is desirable that the shape of the final product can be controlled in a reliable way. For many applications, it is also desirable that the final product has substantially even strength properties so that the final product does not bend easier in one direction than in another. If heat is used to dewater the fibre product, it is also desirable that the heat does not burn the surface of the fibre product. It is also desirable that vaporized water can be evacuated efficiently.
It is an object of the present invention to provide an improved method and an improved machine for producing fibre products from stock. In preferred embodiments of the invention, the method is carried out in such a way and the machine is so designed that improved control of the shape of the final product is achieved. In advantageous 5 embodiments of the invention, the final product also obtains substantially even properties of strength. Further objects of the invention include efficient dewatering and avoidance of burning of the surface of the final product.
DESCRIPTION OF THE INVENTIONThe invention relates to a method for producing a fibre product from stock. The inventive method comprises providing a first tool that is permeable to air and water and providing a second tool. The second tool is heated to a surface temperature of at least 220° C. A moulding tank is provided and stock is fed to the moulding tank. The first tool is immersed in the stock in the tank and an embryonic fibre product is formed on the first tool by applying suction through the first tool. The first tool is then removed from the stock and the first tool is brought against a second tool such that the formed fibre product is sandwiched between the first and the second tool. The formed fibre product is heated by the second tool such that at least a part of the water in the formed fibre product is vaporized.
The formed fibre product may subsequently be subjected to at least one additional step of dewatering where the fibre product is sandwiched between a pairs of opposed tools. Water is removed from the fibre product until it has reached a dry solids content of preferably at least 70%. When the fibre product has reached a dry solids content of at least 70%, it may be subjected to final drying by microwaves. Prior to final drying by microwaves, the fibre product can be subjected to steam in order to achieve a more even moisture content.
The heating and vaporizing step that is carried out between the first tool and the second tool should preferably last for no more than 1 second. During the forming step, the fibre product is suitably dewatered to a dry solids content of 18-22% by weight, preferably 20% by weight.
The stock used can suitably have a dry solids content of 0.4-0.7% by weight. Preferably, the stock has a dry solids content of 0.5% by weight. A suitable stock can be made from chemithermomechanical pulp (CTMP).
In preferred embodiments of the invention, no stock is fed to the moulding tank during the actual forming step. This can be achieved, for example, by means of causing stock from a machine vat to by-pass the moulding tank during the forming step. After the forming step, the stock from the machine vat can once again be fed to the moulding tank. The forming step preferably takes 1-2 seconds.
The first tool and the second tool should preferably be pressed against each other with a force that generates an overpressure of no more than 1 MPa and preferably no more than 900 KPa. In fact, it can be suitable in some cases to use a very low pressure and the pressure may be in the range of 10-900 KPa. It is also conceivable that no mechanical pressure at all is applied.
Suction should preferably be applied to the first tool also when the fibre product is sandwiched between the first tool and the heated second tool. In preferred embodiments, also the second tool is permeable to air and water. Suction is then applied also to the second tool when the fibre product is sandwiched between the tools so that steam and water is evacuated through both the first tool and the second tool.
The invention also relates to a machine for producing fibre products from stock. The machine comprises a moulding tank for holding stock and a first tool that is permeable to air and water. The machine further comprises a second tool that is permeable to air and water. The machine has means connected to the first tool for lowering the first tool into the tank and lifting the first tool out of the tank and for bringing the first tool against the second tool. A suction device, i.e. a source of underpressure is connected to the first tool. A source of heat, i.e. a heating device, arranged to heat the second tool and capable of heating the surface of the second tool to a temperature of at least 220° C. in order to vaporize water in a wet fibre product when the wet fibre product is sandwiched between the first and the second tool. The machine further comprises a microwave heater for additional removal of water from a fibre product that has previously been dewatered between the first and the second tool. There are also means for transferring a fibre product from the second tool to the microwave heater.
Preferably, a machine vat is arranged to supply stock to the moulding tank through a conduit. There may also be a by-pass conduit that can be used selectively such that stock from the machine vat can be either passed directly to the moulding tank or pumped around in a looped flow.
In advantageous embodiments, a steam shower can be arranged before the microwave heater so that a fibre product to be passed through the microwave heater can be showered with steam before it is treated by the microwave heater.
Preferably the first tool comprises particles that have been sintered together to form a porous body. In preferred embodiments, also the second tool comprises particles that have been sintered together to form a porous body. Of course, it should be understood that also other tools than sintered tools could be considered.
In advantageous embodiments, the first and second tools are mounted on holders that can be rotated between different angular positions.
In addition to the first and the second tool, additional tools may be arranged in a path from the pair of the first and second tool to the microwave heater, the additional tools forming cooperating pairs of tools where a fibre product may be subjected to additional dewatering and the additional tools further being arranged to convey a fibre product towards the microwave heater.
Reference will now be made to
The function of the process will now be explained with reference to
The initial forming step may take about 1-2 seconds. When the initial forming step is completed, the first tool 1 (the forming tool) is lifted from the stock 19 as indicated in
Reference will now be made to
As can be seen most clearly in
With reference to
In
The design of the tools 1, 3, 11, 12 according to a possible embodiment of the invention shall now be explained in more detail with reference to
The porosity of the tool 1 may be about 40%. The value of 40% porosity can apply to all layers. Embodiments of the invention can also be envisaged where different layers of the tool have different porosity.
The smaller spheres 31 form a fine surface layer that contributes to giving the fibre product a smooth surface while the interior layers 29, 28 improve permeability. The channels 27 that pass through the sintered structure may have pointed tips that reach the surface of the tool which improves permeability.
Reference will now be made to
The porous structure provided by the sintered metal particles 31, 32, 33 has the advantage that water and vapour can escape easily through the tools 1, 3, 11, 12. This reduces the risk of delamination during the vaporization process. The sintered structure also has the advantage that steam can escape in a very even way over the whole surface of the tool.
The high temperature entails the advantage that an efficient dewatering is achieved. Pressing with a relatively high pressure before the microwave heater (when the fibre product is wet) entails the advantage that good surface properties can be achieved before microwave drying. Therefore, it will not be necessary to press the fibre product after microwave drying which could be harmful to the fibre product. The microwave heating step entails the advantage of improved hygiene. The use of the high temperature also entails the advantage that the surface of the fibre product becomes more compact which is advantageous in view of bending stiffness.
It should be understood that, in certain embodiments, the microwave heating can be deleted or replaced by some other heating method, for example IR heating.
It should be understood that the idea of halting the feeding of stock to the mould 6 during forming can be used independently of how the process is otherwise performed.
The invention also relates to a fibre product that can be obtained by the above described method. In
A further major advantage according to the invention is that very smooth surfaces on both sides of the body may be produced. Products produced according to the invention may easily obtain a roughness in the range of about 750-1.000 ml/min. (ISO 8791-2, Bendtsen), whereas conventional moulded pulp products at least on one side normally have a roughness well above 1.500 ml/min. It may be mentioned that one of the reasons why conventional products normally present a higher roughness is that most conventional techniques do use a wire mesh to form the surface.
A further advantage according to the invention is that the product will achieve a high tensile index, normally in the range of 65-100 kNm/kg., which indeed is a significant advantage compared to traditional moulded pulp products. (see
Finally it is of course an advantageous aspect of a product according to the invention that it may be achieved without any after pressing which otherwise will increased production costs and as has been mentioned above also negatively effect the at least some or one quality aspect/s. In
Claims
1-29. (canceled)
30. A method for producing a fibre product from stock, the method comprising the steps of:
- a) providing a first tool that is permeable to air and water;
- b) providing a second tool and heating the second tool to a temperature of at least 220° C.;
- c) providing a moulding tank and feeding stock to the moulding tank;
- d) immersing the first tool in the stock in the tank;
- e) forming an embryonic fibre product on the first tool by applying suction through the first tool;
- f) removing the first tool from the stock;
- g) bringing the first tool against the second tool such that the formed fibre product is sandwiched between the first and the second tool and heated by the second tool such that at least a part of the water in the formed fibre product is vaporized; and
- h) dewatering the formed fibre product until it has reached a dry solids content of at least 70% after which the fibre product is subjected to drying by microwaves.
31. A method according to claim 30, wherein the heating and vaporizing step that is carried out between the first tool and the second tool lasts for no more than 1 second.
32. A method according to claim 30, wherein, during the forming step, no stock is fed to the moulding tank.
33. A method according to claim 32, wherein, during the forming step, stock from (New) A machine vat is caused to by-pass the moulding tank and that, after the forming step, the stock from the machine vat is fed to the moulding tank.
34. A method according to claim 30, wherein the forming step lasts 1-2 seconds.
35. A method according to claim 30, wherein the fibre product is dewatered in several dewatering steps between opposed tools and subsequently subjected to steam before it is dried by microwaves.
36. A method according to claim 30, wherein the stock has a dry solids content of 0.4-0.7% by weight.
37. A method according to claim 30, wherein the stock has a dry solids content of 0.5% by weight.
38. A method according to claim 30, wherein during the forming step the fibre product is dewatered to a dry solids content of 18-22% by weight.
39. A method according to claim 30, wherein during the forming step the fibre product is dewatered to a dry solids content of 20% by weight.
40. A method according to claim 30, wherein the first tool and the second tool are pressed against each other with a force generating an overpressure of no more than 1 MPa.
41. A method according to claim 30, wherein the first tool and the second tool are pressed against each other with a force generating an overpressure of no more than 900 KPa.
42. A method according to claim 30, wherein the pressure is in the range of 10-900 KPa.
43. A method according to claim 30, wherein the stock is made from chemithermomechanical pulp (CTMP).
44. A method according to claim 30, wherein suction is applied to the first tool also when the fibre product is sandwiched between the first tool and the heated second tool.
45. A method according to claim 44, wherein also the second tool is permeable to air and water and that suction is applied also to the second tool when the fibre product is sandwiched between the tools so that steam and water can be evacuated through both the first tool and the second tool.
46. A machine for producing fibre products from stock, the machine comprising:
- a) a moulding tank for holding stock;
- b) a first tool that is permeable to air and water;
- c) a second tool that is permeable to air and water;
- d) means connected to the first tool for lowering the first tool into the tank and lifting the first tool out of the tank and for bringing the first tool against the second tool;
- e) a source of underpressure connected to the first tool;
- f) a source of heat arranged to heat the second tool and capable of heating the surface of the second tool to a temperature of at least 220° C. in order to vaporize water in a wet fibre product when the wet fibre product is sandwiched between the first and the second tool;
- g) a microwave heater for additional removal of water from a fibre product that has previously been dewatered between the first tool and the second tool; and
- h) means for transferring a fibre product from the second tool to the microwave heater.
47. A machine according to claim 46, wherein a machine vat is arranged to supply stock to the moulding tank through a conduit and that there is also a by-pass conduit that can be used selectively such that stock from the machine vat can be either passed directly to the moulding tank or pumped around in a looped flow.
48. A machine according to claim 46, wherein a steam shower is arranged before the microwave heater so that a fibre product to be passed through the microwave heater can be showered with steam before it is treated by the microwave heater.
49. A machine according to claim 46, wherein the first tool comprises particles that have been sintered together to form a porous body.
50. A machine according to claim 49, wherein also the second tool comprises particles that have been sintered together to form a porous body.
51. A machine according to claim 46, wherein the first and second tools are mounted on holders that can be rotated between different angular positions.
52. A machine according to claim 46, wherein, in addition to the first and the second tool, additional tools are arranged in a path from the pair of the first and second tool to the microwave heater, the additional tools forming cooperating pairs of tools where a fibre product may be subjected to additional dewatering and the additional tools further being arranged to convey a fibre product towards the microwave heater.
51. Shaped body mainly comprising fibres, which fibres form a web which is continuous and form stable, and which preferably forms a three dimensional body, wherein the grammage is in the range 150-600 g/m2 and wherein the orientation of the fibres is stochastic such that substantially the same strength properties are obtained independent of direction within the plane of the web, wherein the density is in the range 600-900 kg/m3.
52. Shaped body according to claim 51, wherein the density is at least 700.
53. Shaped body according to claim 51, wherein corners and/or areas having a sharp radius also presents substantially the same kind of continuous, homogenous web as a substantially flat surfaces of the body.
54. Shaped body according to claim 51, wherein the roughness of a substantial portion of the surfaces on both sides of the body is within the range 750-3.000 ml/min. according to bendtsen ISO 8791-2.
55. Shaped body according to claim 51, wherein the roughness of a substantial portion of the surfaces on both sides of the body is within the range 750-2.000 ml/min. according to bendtsen ISO 8791-2.
56. Shaped body according to claim 51, wherein the roughness of a substantial portion of the surfaces on both sides of the body is within the range 750-1.500 ml/min. according to bendtsen ISO 8791-2.
57. Shaped body according to claim 51, wherein the tensile index is in the range 50-100 kNm/kg.
58. Shaped body according to claim 51, wherein the tensile index is in the range 65-100 kNm/kg.
59. Shaped body according to claim 51, wherein the tensile index is in the range 80-100 kNm/kg.
60. Shaped body according to claim 51, wherein the tensile index is in the range 90-100 kNm/kg.
61. Shaped body according to claim 51, wherein the tear index is within the range 5-15 Nm2/kg.
62. Shaped body according to claim 51, wherein the tear index is within the range 8-15 Nm2/kg.
63. Shaped body according to claim 51, wherein the bonding strength of a surface layer of the body is in the range of 5-50% higher than the bonding strength of an intermediate layer near the centre portion of the web forming the body.
64. Shaped body according to claim 51, wherein the bonding strength of a surface layer of the body is in the range of 7-30% higher, higher than the bonding strength of an intermediate layer near the centre portion of the web forming the body.
65. Shaped body according to claim 51, wherein air resistance for the web, including corners/sharp bends of the body, is in the range of 60-200 sek by gurley.
66. Shaped body according to claims 65, wherein air resistance for the web, including corners/sharp bends of the body, is at least 70 sek.
67. Shaped body according to claims 65, wherein air resistance for the web, including corners/sharp bends of the body, is at least 80 sek.
68. Shaped body according to claim 51, wherein the body is obtainable without any after pressing.
69. Shaped body according to claim 51, wherein the body is obtainable without any after pressing action above 1.5 MPa after having obtained a dry solids content of at least 70%.
70. Shaped body according to claim 51, wherein the body is obtainable without any after pressing action above 1.5 MPa after having obtained a dry solids content of at least 80%.
71. Shaped body according to claim 51, wherein the body is obtainable without any after pressing action above 1.5 MPa after having obtained a dry solids content of at least 90%.
Type: Application
Filed: Nov 25, 2005
Publication Date: Jun 4, 2009
Inventors: Bjorn Nilsson (Kimstad), Lars Graffton (Bettna), Leif Baskman (Norrkoping), Torbjorn Hansson (Vallentuna)
Application Number: 11/719,796
International Classification: D21J 3/10 (20060101); D21F 1/66 (20060101);