Patent Application
20240408788
The present disclosure relates to a method for producing 3D fiber structures.
Fiber network is an abundant structure among biological (e.g., animal tissues) and industrial materials which its characteristics is determined by individual elements' properties, orientation distribution, local and bulk density, bonding and entanglement between network elements. The morphology of many of biological fibrous structures are three-dimensional (3D) while manmade structures like paper and nonwoven are considered as two-dimensional (2D). In 3D fibrous structures, the constituent fibers are randomly oriented in the 3D space and the material bulk properties are distributed relatively uniform in all directions. In a 2D fibrous structure where constituent fibers are randomly oriented in the plane of the structure, in-plane bulk properties are drastically different compared to that of the normal direction to the plane. Unlike conventional paper, a 3D wood fiber structure is bulky, highly porous, and soft. These properties makes the 3D wood fiber structure a suitable candidate for applications related to absorption properties (shock, noise, moisture) and material transport properties (filtration).
Industrial fibrous structures are made from synthesized or natural fibers using dry- or wet-laying processes where in the latter process, water is used as the carrier medium for the fibers. Alternatively, aqueous foam can be used as the suspending phase to obtain a 3D fiber network which with existing methods the procedure is energy-intensive and time-consuming and therefore it is industrially unfavorable.
Accordingly, there is a need for an improved method which satisfies the accelerated dewatering of the excess water from a foam-formed fibrous mat without deteriorating the bulk of the structure.
It is therefore an object of the present disclosure to provide a method for producing 3D fiber structure to mitigate, alleviate or eliminate one or more of the above-identified deficiencies and disadvantages.
This object is achieved by means of a method as defined in the appended claims.
In accordance with the disclosure there is provided a method according to claim 1 and an apparatus according to claim 10.
The present disclosure relates to a method for producing 3D fiber structures, preferably 3D wood fiber structures, the method comprising the steps of: Firstly, feeding a foamed fiber furnish to an apparatus, the apparatus comprising a liquid-permeable substrate means having a first side and an opposing second side, a dispenser having an outlet, wherein at least one of the dispenser and the substrate means travel with respect to the other. Further the method comprises the steps of: Dispensing, by means of the dispenser, a layer of foamed fiber furnish (or foamed wood fiber furnish) to the first side of said liquid-permeable substrate means to obtain a fibrous mat, wherein the apparatus further comprises at least a reservoir to facilitate an initial natural dewatering of the said fibrous mat for a predetermined time period, and a first vacuum unit associated with the second side of the liquid-permeable substrate means so to collect fluid discharge from the said fibrous mat. The method further comprises the step of applying at least a first dewatering pressure to at least a part of the second side of said substrate means. It should be noted that the foamed fiber furnish applied to the substrate means, takes the form of a fibrous mat. Thus, a layer of foamed fiber furnish is equal to a fibrous mat.
A benefit of the method is that it allows for effectively producing a 3D fiber structure by maintaining an initial connected fiber network after a first natural dewatering which facilitates the use of vacuum pressure to more effectively discharge excess water without deteriorating the bulk of the said fibrous mat. Further, the method allows for a reduced drying time of the fibrous mat to up to 30% compared to solutions not involving vacuum pressure.
The layer of foamed fiber furnish may be dispensed so to comprise a predefined substantially uniform thickness, wherein the apparatus is configured to, preceding the step of applying a dewatering pressure (which may also referred to as suction), by means of the reservoir, collect fluid discharge for a first period of time based on at least the thickness of the layer. The first period of time may be in the range of 1-10 minutes.
The thickness of the layer may be in the range of 1-10 cm.
The first dewatering pressure may be applied for a second period of time, wherein the first dewatering pressure is within the range of 70 kPa-100 kPa (i.e. slightly below atmospheric pressure providing a low suction). The second period of time may be in the range of 2-10 minutes, preferably for 4-6 minutes.
Further, the liquid-permeable substrate means travels in a first direction along a traveling element having a length defined by at least a first and a second portion, wherein the dispenser is arranged to be above the first side of the substrate means in said first portion, wherein the reservoir is arranged in said first portion, wherein the first vacuum unit and a second vacuum unit are arranged sequentially along the length in said second portion, wherein the first vacuum unit is closer to the reservoir than the second vacuum unit. A benefit of this is that it allows for an arrangement where the fibrous mat is produced in a continuous process instead of a batch-wise process.
Thus, reservoir may collect some liquid, wherein the remaining of the water/liquid discharge may be carried out at the vacuum boxes and fibrous mat can then travel forward to a subsequent process.
The dispenser may be a headbox. Further the outlet may be a nozzle configured to dispense the fiber furnish with a defined shear force.
The first vacuum unit may be configured to apply a first dewatering pressure, wherein the second vacuum unit may be configured to apply a second dewatering pressure (thus applying a first and a second suction), wherein the first dewatering pressure is greater than the second dewatering pressure. The first vacuum unit may apply a first dewatering pressure being slightly below atmospheric pressure and wherein the second vacuum unit may apply a second dewatering pressure at a higher vacuum. The second dewatering pressure may be within a range of 50 kPa-80 kPa. In some embodiments, the first and the second dewatering pressure are the same.
The method may further comprise the step of, simultaneous or preceding the step of applying the first dewatering pressure by applying an ultrasonic radiation to the said fibrous mat. The ultrasonic radiation may be performed by a high power airborne ultrasonic unit.
A benefit of this is that the ultrasonic energy facilitates a uniform collapse of foam bubbles throughout the thickness of the said fibrous mat without deteriorating the bulk of the structure while it also makes the fibrous mat highly permeable to air. Consequently, a faster discharge of excess water is possible and as a result the vacuum units may be arranged closer to the dispenser which makes it possible to use the space more efficiently. Additionally, an air permeable fibrous mat facilitates the utilization of more efficient drying technique, i.e., through air drying technology.
The substrate means may travel in the first direction with a velocity in the range of 0.1-10 m/s.
The method may further comprise the step of storing the dewatered fibrous mat at a temperature in the range of 70-120° C.
The foamed fiber furnish comprises a fiber consistency in the range of 0.5-10% based on a dry weight of the fibers, wherein the foamed fiber furnish comprises a total concentration of foaming agents in the range of 0.05-2 g/l, wherein the foamed fiber furnish comprises an air content in the range of 55-70% by volume, wherein the foamed fiber furnish is generated from a pulp slurry. The thickness of dried fibrous mat may be in the range of 5 mm-60 mm. Thus, the thickness of the mat provided by the method in accordance with the present disclosure may be 5 mm-60 mm and is a 3D fiber structure.
There is further provided an apparatus for producing 3D fiber structures, the apparatus comprising: a liquid-permeable substrate means having a first side and an opposing second side, a dispenser having an outlet, wherein at least one of the dispenser and the substrate means travel with respect to the other, a reservoir, at least a first vacuum unit, wherein the apparatus is configured to perform the method in accordance with the present disclosure.
The apparatus may further comprise a second vacuum unit and an ultrasonic unit.
In the following the invention will be described in a non-limiting way and in more detail with reference to exemplary embodiments illustrated in the enclosed drawings, in which:
In the following detailed description, some embodiments of the present disclosure will be described. However, it is to be understood that features of the different embodiments are exchangeable between the embodiments and may be combined in different ways, unless anything else is specifically indicated. Even though in the following description, numerous specific details are set forth to provide a more thorough understanding of the provided method and apparatus, it will be apparent to one skilled in the art that the method and apparatus may be realized without these details. In other instances, well known constructions or functions are not described in detail, so as not to obscure the present disclosure.
The apparatus 1 shown in
The layer 2 of foamed fiber furnish may be dispensed so to comprise a predefined substantially uniform thickness, wherein the apparatus 1 may be configured to (as seen in
As shown in the apparatus in
Further referring to the apparatus in
The configuration of fibers in the bulk of the structure can be described by fiber orientation distribution of all fibers using a pair of angles (θ,Φ), shown in exemplary
| Number | Date | Country | Kind |
|---|---|---|---|
| 2150053-3 | Jan 2021 | SE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/SE2022/050055 | 1/19/2022 | WO |
