AU2003215434A1 - fibre / blinder blender - Google Patents

Description

WO 03/082535 PCT/AU03/00397 1 FIBRE/BINDER BLENDER FIELD OF THE INVENTION The present invention relates to improved resin distribution in blowline resin 5 injection. The invention is particularly directed to a device and a process for improved resin distribution in a mixture of fibre and resin used for the production of a composite material, especially fibreboard. BACKGROUND OF THE INVENTION In the production of composite materials such as fibreboard, wood fibres 1o are typically processed at elevated temperature and pressure in a refiner, then transferred to a blowline in a steam jetstream. Once in the blowline, a suitable binder, typically a resin composition, is then injected into the blowline, typically via one or more nozzles, and the fibres and resin are mixed together by turbulence. The fibre and resin mixture is then typically dried and pressed under elevated 15 pressure and temperature to produce the composite material. However, conventional processes have suffered from the problem of inconsistent and uneven distribution of resin throughout the resin-fibre mixture. This has resulted in the composite materials produced having inferior bond strength and therefore low mechanical strength as well as blemishes ("glue or 20 resin spots") on the surface of the composite material. To compensate for this, prior processes have required increased amounts of resin being introduced into the blowline, resulting in increased cost of production. It would therefore be desirable to provide a process and a device which would improve the distribution of resin in a resin/fibre mixture travelling through a 25 blowline. SUMMARY OF THE INVENTION According to the present invention, there is provided a device comprising an in-line flow blender for use in a blow line used in the manufacture of a composite material, said in-line flow blender comprising a conduit having a 30 plurality of inwardly projecting deflectors disposed therein, wherein, in use, a mixture of fibres and a binder flowing in a first flow direction upstream of said deflectors is deflected such that each deflector causes a portion of said mixture to flow in a direction which crosses said first flow direction.

WO 03/082535 PCT/AU03/00397 2 Throughout the specification, discussion will focus on the use of resin as a suitable binder, and wood fibres as suitable fibres. However it is to be understood that the present invention is applicable to other binder and fibre compositions. The present invention also provides a process for the manufacture of a 5 composite material using a blowline, said process including the step of flowing a mixture of fibres and a binder through an in-line flow blender comprising a conduit having a plurality of inwardly projecting deflectors disposed therein, wherein said mixture flows in a first flow direction upstream of said deflectors, and each said deflector causes a portion of said mixture to flow in a direction which crosses said o10 first flow direction. DETAILED DESCRIPTION OF THE INVENTION Accordingly, there is provided an in-line flow blender comprising a conduit having a plurality of inwardly projecting deflectors, wherein a mixture of fibre and resin is injected into the conduit such that the mixture of fibre and resin flows in a 15 first flow direction and each deflector is arranged to deflect a portion of the mixture of fibre and resin to flow in a direction which crosses the first flow direction. Examples of resin compositions typically used in the process of the invention are urea-formaldehyde resins, melamine-urea formaldehyde resins and derivatives thereof. Usually, these resin compositions are available as 20 compositions comprising approximately 60 to 65% solids in water. These are then typically further diluted, by mixing approximately 75 litres resin to about 21 litres of water, before being introduced into the conduit. Without wishing to be limited to a particular mechanism, it is believed that the increased turbulence, and therefore increased impact of fibre and resin, 25 created using the device and process of the invention results in increased contact between fibres and consequential "wiping" of resin from one fibre to another, thereby assisting in achieving a more even distribution of resin amongst the fibres. Preferably each deflector comprises a projecting element provided on an inner wall of the conduit. The projecting element is shaped and positioned so as 30 to cause a radially inward change of direction of flow of that portion of mixture flowing over it. Preferably, each deflector includes a radially angled deflecting surface which extends radially inwards when moving in a downstream direction. An angled surface assists in the creation of turbulence while minimising actual obstruction of the conduit. The deflecting surface may be planar or curved.

WO 03/082535 PCT/AU03/00397 3 Advantageously, the device of the invention (also called a "static mixer") includes a plurality of deflectors spaced circumferentially about and/or axially along the inner wall of the conduit. The deflectors may comprise circumferentially continuous surfaces spaced axially along the length of the conduit. However, 5 preferably the plurality of deflectors comprise discrete, circumferentially discontinuous surfaces provided both circumferentially and axially on the inner wall. In a particularly preferred embodiment, the deflectors comprise sets of circumferentially spaced surfaces, with each set being spaced axially along the 10 inner wall of the conduit. Preferably, the circumferential arrangement of deflector surfaces within one set differs to that of an adjacent set, such that portions of the fibre and resin mixture which are not deflected by one set of deflectors is deflected by a subsequent set. In such a manner, turbulence is increased and even mixing of the fibres and resin is enhanced. 15 An example of a circumferentially continuous deflector surface is an annular surface provided on the inner conduit wall. Such a surface may be planar or curved. The deflector surface may take the form of the external surface of a toroid, preferably one having a substantially hemispherical cross-section, with the curved portion of the hemisphere extending radially inwards of the conduit. 20 Preferably, however, the deflector surfaces are circumferentially discontinuous. While not wishing to be bound by any particular theory, it is believed that circumferentially discontinuous deflectors increase the turbulence of mixture passing over them because some of the mixture is deflected and some is not, resulting in multi-directional flow. The construction and orientation of the 25 deflectors should preferably be such as to minimise any blockages, and maximise the open area, in the conduit. However, should a partial blockage occur, the steam flow would typically cut through the resin/fibre mixture until the blockage is cleared. Preferably, the deflector surfaces in each set are spaced circumferentially 30 evenly about the inner wall of the conduit. More preferably, there are more than two such surfaces, such as three or four surfaces. While there is no real upper limit on the number of deflector surfaces, too many deflectors may result in a blockage within the conduit due to a reduction in velocity.

WO 03/082535 PCT/AU03/00397 4 The deflector surfaces in each set may be planar or curved. However, in a preferred embodiment, at least some of the deflector surfaces are curved. Advantageously, the deflector surfaces are concave and preferably each surface takes the form of a channel, with the axis of the channel running in a generally 5 downstream direction. Such a channel-like configuration is advantageous because it positively directs the mixture of resin and fibres travelling over it in a downstream direction and focusses it into a concentrated stream. These concentrated streams interact with each other and with the undeflected stream, further enhancing homogeneous mixing of the fibres and resin. Preferably, 10 the deflector surface is provided by an angled surface of a body extending from the inner wall of the conduit. In a particularly preferred embodiment, the deflector surface is provided by a surface of a body having a generally triangular prismatic shape and orientated such that it extends from the inner wall such that the triangular faces of the prism extend substantially parallel to the longitudinal axis of 15 the conduit and that the deflector surface is provided by an upper face of the prism which is angled downstream. As previously discussed, it is preferred that the upper face is curved, more preferably, channel shaped. Where the deflector surfaces are provided by an angled surface of a prism, the prisms are preferably arranged in sets spaced substantially evenly along at 20 least part of the length of the conduit. Each set preferably comprises three or more prisms substantially circumferentially evenly spaced about the inner wall of the conduit. The circumferential arrangement of deflectors in adjacent sets preferably differs relative to each other, such that the arrangement of one set is rotated relative to an adjacent set. 25 An important advantage of the present invention is that in the construction of composite materials there is effective mixing of the resin throughout the fibre resin mixture. As previously noted, if the resin is not distributed evenly throughout the fibre, the final product strength is reduced. This problem can be avoided using the device and process of the invention. Further, effective distribution of 3o resin throughout the fibre-resin mixture allows the amount of resin used to be kept to a minimum therefore reducing the cost of the production. For example, the applicant has found that by using the device of the invention there can be a reduction of 10 to 15% in the amount of resin being required compared with the WO 03/082535 PCT/AU03/00397 5 conventional processes. This translates to a cost saving of about $1 million per year. DESCRIPTION OF DRAWINGS The present invention will now be described, by way of example, with 5 reference to the accompanying drawings, in which: Figure la is an in-line flow blender in accordance with the present invention; Figure lb is a detailed perspective view of a deflector from the flow blender of Figure la; 10 Figures ic to ig illustrate the steps of one process to produce the deflector of Figure 1 b; Figure 2 is a cross-sectional view of the in-line flow blender of Figure 1; Figure 3 is an alternative embodiment of an in-line flow blender in accordance with the present invention; and 15 Figure 4 is a cross sectional view of the in-line flow blender of Figure 3. Referring to Figures la, lb and 2, there is shown an in-line flow blender 10 comprising a conduit 12 having an inner wall 13. A mixture of fibre and resin is injected into the conduit such that the mixture of fibre and resin flows in a first flow direction, generally along a longitudinal axis 16 of the conduit 12. 20 The conduit 12 comprises a cylindrical tube and includes a plurality of inwardly projecting deflectors 14 extending from the inner wall 13. The deflectors 14 are arranged to deflect the flow of fibre and resin passing through the in-line flow blender 10. The deflectors 14 are arranged into a plurality of sets of deflectors 14. In 25 the embodiment shown in Figures 1 a, 1 b and 2, each set of deflectors comprises three deflectors 14 equally spaced circumferentially around the conduit 12. Referring to Figure lb, each deflector 14 comprises a generally triangular prismatic body having a generally convex rear face 18, two triangular side faces 15 and upper and lower faces 17a and 17b respectively. The deflector 14 is 30 positioned in the conduit 12 such that it extends radially inwards from the inner wall 13 (Figure 1) and the triangular side faces (15) of each prism extend substantially parallel to the longitudinal axis 16 of the conduit 12. The upper face 17a of the deflector 14 is generally concave and acts as a deflecting surface such that it deflects a portion of the resin and fibre flow toward the central longitudinal WO 03/082535 PCT/AU03/00397 6 axis 16 of the conduit. Each deflected portion of the resin and fibre flow therefore crosses the path of the other deflected portions of resin and fibre flow. This assists with distributing the resin throughout the fibre. By improving the distribution of the resin within the fibre, the amount of resin required per volume of 5 fibre is decreased resulting in production cost savings. Figures ic to ig illustrate the steps for one possible method of making a deflector 14. A hollow rod 20 having a longitudinal axis A-A and an axial bore 22 therethrough is illustrated in a perspective view in Figure lc. The rod 20 is cut through along the plane X at substantially right angles to axis A-A, resulting in a 10 disk 24 having an outer wall 25. The disk 24 is shown in longitudinal cross section in Figure id. The disk 24 is then machined at either end thereof, such that a conical section 26 is removed leaving an inverted conical face 27 exposed at either end (Figure le). Turning now to Figure 1f which is a view looking down the longitudinal axis A-A, a lateral segment 28 is removed from each side of the 15 disk 24 leaving a generally planar face 29 exposed along each side. The disk 24 is then cut in half along a plane B-B, which runs parallel to axis A-A, with each half forming a generally triangular prism 26. One of the prisms 26 is shown in perspective in Figure 1g. By comparing Figure 1g with Figure lb, it can be seen that the faces 17a and 17b are derived from the sectioned conical face 27, the 20 triangular side faces 15 are derived from planar faces 29 and that the curved edge 30 between the two faces 17a and 17b is derived from the wall of bore 22. The generally convex rear face 18 is derived from the outer wall 25 of the disk 24. Preferably, the radius of curvature of the convex rear face 18 is similar to that of the inner wall 13 of conduit 12 to allow a complementary fit between the two. 25 As can be seen in Figure la, each circumferential set of deflectors 14 is preferably arranged in a position rotated relative to adjacent sets of deflectors 14 such that portions of the fibre and resin flow which are not deflected by one set of deflectors 14 will be deflected by a subsequent set of deflectors 14. Figures 3 and 4 show an alternative embodiment of an in-line flow blender 30 110 in accordance with the present invention. In this embodiment, the deflectors 114 each comprise an annular member 116. The annular members 116 are arranged to extend inwardly from the inner surface of the conduit 112 at intervals along the length of the conduit 112.

WO 03/082535 PCT/AU03/00397 7 Each deflector 114 deflects the fibre and resin flow adjacent the inner surface of the conduit 112 toward the central longitudinal axis 116 of the conduit 112. The deflection of the resin and fibre flow in the cross flow direction assists in distributing the resin throughout the fibres. 5 Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention. 10 15 20 25 30

Claims (16)

1. A device comprising an in-line flow blender for use in a blowline used in the manufacture of a composite material, said in-line flow blender comprising a 5 conduit having a plurality of inwardly projecting deflectors disposed therein, wherein in use, a mixture of fibres and a binder flowing in a first flow direction upstream of said deflectors is deflected such that each deflector causes a portion of said mixture to flow in a direction which crosses said first flow direction. 10

2. The device of claim 1, wherein each deflector comprises a projecting element provided on an inner wall of the conduit and shaped and positioned so as to cause a radially inward change of direction of the portion of said mixture flowing thereover. 15

3. The device of claim 1 or 2, wherein each said deflector includes an angled deflecting surface which extends radially inwards when moving in a downstream direction.

4. The device of any preceding claim wherein said plurality of inwardly 20 projecting deflectors are spaced circumferentially about and/or axially along said inner wall.

5. The device of claim 4, wherein said plurality of deflectors comprise discrete, circumferentially discontinuous surfaces provided both circumferentially 25 and axially on said inner wall.

6. The device of any preceding claim, wherein said plurality of deflectors comprise sets of circumferentially spaced deflecting surfaces spaced axially along said inner wall. 30

7. The device of claim 6, wherein the circumferential arrangement of deflecting surfaces within one set differs to that of an adjacent set. WO 03/082535 PCT/AU03/00397 9

8. The device of claim 6 or 7, wherein each said set comprises about 3 to about 10 deflector surfaces.

9. The device of any one of claims 6 to 8, wherein each of said deflecting 5 surfaces is provided by an angled surface of a prism.

10. The device of claim 9, wherein said prism is a body having a generally triangular prismatic shape which extends from said inner wall such that the triangular faces of the prism are substantially parallel to the longitudinal axis of the 10 conduit and the deflecting surface is provided by an angled upper face of the prism.

11. The device of claim 10, wherein the circumferential arrangement of deflectors in adjacent sets differs such that the arrangement of one set is rotated 15 relative to an adjacent set.

12. The device of claim 3, or of any one of claims 4 to 11 when appended to claim 3, wherein said angled deflecting surface is curved. 20

13. The device of claim 12, wherein said angled deflecting surface is concave, preferably channel shaped so as to positively direct said mixture in a downstream direction.

14. A process for the manufacture of a composite material using a blowline, 25 said process including the step of flowing a mixture of fibres and a binder through an in-line flow blender comprising a conduit having a plurality of inwardly projecting deflectors disposed therein, wherein said mixture flows in a first flow direction upstream of said deflectors, and each said deflector causes a portion of said mixture to flow in a direction which crosses said first flow direction. 30

15. A device according to claim 1, substantially as herein described with reference to the accompanying drawings. WO 03/082535 PCT/AU03/00397 10

16. A process according to claim 14, substantially as herein described with reference to the accompanying drawings. 5 10 15 20 25 30