Elongated component for a manufacturing machine of a fibrous cellulosic web, its use and method for recycling

Abstract

An elongated planar or profiled component for a manufacturing machine of a fibrous cellulosic web, such as paper, board or tissue web, is at least partially formed from a composite material having a continuous polymer matrix, and reinforcing inorganic fibers embedded in the continuous polymer matrix. The continuous polymer matrix is biodegradable and the reinforcing inorganic fibers are biodegradable glass fibers. A method is disclosed for recycling elongated planar and/or profiled components used for manufacture of a fibrous web.

Claims

1. A doctor blade for a fibrous cellulose web manufacturing machine, the doctor blade extending in a cross-machine direction and a machine direction and having a doctor blade thickness, the doctor blade comprising: a continuous polymer matrix comprised of at least one of polylactic acid; polycaprolactone; a polyhydroxyalkanoate, polyhydroxybutyrate; poly(alkylene succinate), and poly(butylene succinate); and reinforcing inorganic biodegradable glass fibers embedded in the continuous polymer matrix; wherein the doctor blade thickness is in a range of 1-4 mm.

2. The doctor blade of claim 1 wherein the composite material further comprises mineral filler particles embedded in the continuous polymer matrix.

3. The doctor blade of claim 1 wherein the composite material comprises: 50-80 weight-% of polymer matrix; 10-50 weight-% of inorganic fibers; and 0-30 weight-% of mineral filler particles.

4. The doctor blade of claim 3 wherein the composite material comprises: 60-70 weight-% of polymer matrix; 10-30 weight-% of inorganic fibers; and 0.1-30 weight-% of mineral filler particles.

5. The doctor blade of claim 1 wherein the component is a doctor blade having a blade thickness in a range of 2-3 mm.

6. The doctor blade of claim 1 wherein the inorganic fibers are chopped biodegradable glass fibers, which have a fiber length of 0.5-3 mm.

7. The doctor blade of claim 6 wherein the biodegradable glass fibers are randomly and uniformly embedded in the continuous polymer matrix.

8. The doctor blade of claim 1 wherein the inorganic fibers are continuous biodegradable glass fibers forming at least one woven structure embedded in the continuous polymer matrix.

9. The doctor blade of claim 1 wherein the doctor blade is formed of material having a property selected from the group consisting of: a heat deflection temperature of ≥85° C. determined according to standard ISO 75 method A; a value for tensile strength at break of at least 50 MPa determined according to standard ISO 527; a tensile modulus value of at least 7500 MPa determined according to standard ISO 527; a distortion value ≤0.3 mm/m; and a flexural modulus value of at least 7300 MPa determined according to standard ISO 178.

10. A method of manufacture of a fibrous cellulosic web, comprising: on a web manufacturing machine employing at least one doctor blade which extends in a cross-machine direction and a machine direction and having a doctor blade thickness in a range of 1-4 mm; and wherein the at least one doctor blade has a biodegradable continuous polymer matrix comprised of at least one of polylactic acid; polycaprolactone; a polyhydroxyalkanoate, polyhydroxybutyrate; poly(alkylene succinate), and poly(butylene succinate), and wherein reinforcing inorganic fibers of biodegradable glass fibers are embedded in the continuous polymer matrix.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows schematically a first example of an elongated profiled component for a manufacturing machine of a fibrous cellulosic web according to one embodiment of the present invention.

(2) FIG. 2 shows schematically a second example of an elongated profiled component for a manufacturing machine of a fibrous cellulosic web according to one embodiment of the present invention.

(3) FIG. 3 shows schematically a third example of an elongated profiled component for a manufacturing machine of a fibrous cellulosic web according to one embodiment of the present invention.

(4) FIG. 4 shows schematically a possible life cycle of an elongated planar or profiled component according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) In FIG. 1 is seen a rod-bed assembly 1, which comprises a first example of an elongated profiled component, which is a rod-bed 2. The rod-bed assembly 1 further comprises a rod 3 for dosing a coating or sizing medium in a coating or sizing device (not shown). The rod 3 is rotatably supported by the rod-bed 2. The rod-bed 2 comprises an elongated profiled body 4 with a recess adapted to receive the rotatable rod 3. The elongated profiled body 4 of the rod bed is formed from a biodegradable composite material comprising a continuous polymer matrix and reinforcing glass fibers embedded in the continuous polymer matrix, wherein both the polymer matrix and the reinforcing fibers are biodegradable.

(6) In FIG. 2 is seen a sealing arrangement 21 for a suction roll (not shown). The sealing arrangement comprises a seal holder 22 and a sealing element 23 arranged in the seal holder 22. Both the seal holder 22 and the sealing element 23 extend essentially over the length of the suction box. The second example of an elongated planar component according to the present invention is the sealing element 22, which is formed from a biodegradable composite material comprising a continuous polymer matrix and reinforcing glass fibers embedded in the continuous polymer matrix, wherein both the polymer matrix and the reinforcing fibers are biodegradable.

(7) In FIG. 3 is seen a doctor arrangement 31 suitable for use in a manufacture of a fibrous cellulosic webs, such as paper, board, tissue, or the like. The doctor arrangement 31 comprises a frame component 32 to which a blade holder 34 is connected. A doctor blade 36 and a pressure plate 38 are arranged to the blade holder 34. The doctor blade 36 provides the third example of an elongated planar component according to the present invention. The doctor blade is formed from a biodegradable composite material comprising a continuous polymer matrix and reinforcing glass fibers embedded in the continuous polymer matrix, wherein both the polymer matrix and the reinforcing fibers are biodegradable. The tip 36′ of the doctor blade 36 made from biodegradable composite material is less prone to wear and the blade maintains its sharpness for a longer period. It is also possible to form the blade holder 34, pressure plate 38 and/or the frame component 32 from a biodegradable composite material in accordance with the present invention. In this manner the amount of biodegradable material can be significantly increased in the manufacturing process of paper, board, tissue or the like.

(8) FIG. 4 shows schematically a possible life cycle of an elongated planar or profiled component according to the present invention, named as “Product1”. After its working life has come to an end Product1 is granulated or comminuted. After granulation, the obtained granules can be disposed of by composting (arrow 1). Alternatively obtained granules can be taken care of by a plastic recycling vendor, who can use the granules for manufacture of new products (arrow 2). After their use, these new products can also be disposed of by composting. According to a further alternative, the granules from Product1 can be used for production of a new elongated planar or profiled component, here denoted “Product2” (arrow 3). Typically, the Product2 has lower material requirements than Product1. After the working life of Product2 ends, it can be granulated or comminuted and preferably disposed of by composting.

EXPERIMENTAL

(9) Some embodiments of the invention are described in the following non-limiting experiments.

(10) Blade samples according to the invention were compared with blades made of materials typically used in prior art doctor blades. Blade samples of 5 different material compositions A-E were made as follows. Sample A (Comparative example): UHMW-PE—unreinforced, a piece of a commercial doctor blade; Sample B: 70 weight-% of biodegradable resin (matrix), reinforced with 30 weight-% of chopped biodegradable glass fibers; Sample C (Comparative example): 70 weight-% of biodegradable resin (matrix) and 30 weight-% of mineral filler; Sample D (Comparative example): epoxy resin matrix, reinforced by non-biodegradable E-glass fiber, a piece of a commercial doctor blade Sample E: 60 weight-% of biodegradable resin (matrix), reinforced with 10 weight-% of chopped biodegradable glass fibers and 30 weight-% of mineral filler particles.

(11) The length and width of each blade sample A to E was identical, 75 mm×20 mm, with blade stick-out of 40 mm simulating true operation of a doctor blade while in its holder. The tip of the blades was bevelled to provide maximum sharpness and cleaning effect.

(12) Experiment 1

(13) Test equipment comprised of a PU-covered test roll, i.e., a Polyurethane covered roll, of Shore hardness 10.6 P&J. The roll was rotated with a speed of 1000 m/min. Samples A-D were tested simultaneously by holding each sample by its holder in a contact against the roll surface with a blade angle 25° and line pressure 180 N/m. Water lubrication on the roll surface was provided by a water shower. The roll was rotated for 2 weeks after which the samples were removed. The blades were visually inspected of their wear and of keeping the tip sharpness/bevel shape. Also, the surface of the roll was visually inspected for any damage or if traces or residuals of the blade material was left on the surface. Results are shown in Table 1 below.

(14) Experiment 2

(15) In Experiment 2 Sample B according to the invention and the comparative Sample C were tested for their applicability for recycling as a raw material for manufacturing of new products. The samples B and C were compared for maintaining their mechanical properties after exposure to wet conditions for several weeks. The Shore D hardness, ISO 178 flexural strength and flexural modulus of samples were measured before and after immersing in 40° C. water for 4 weeks. Results are shown in Table 1 below.

(16) TABLE-US-00001 TABLE 1 Results of Experiments 1 and 2 Flexural Flexural Roll Shore D strength Modulus Blade surface Hardness [MPa] [MPa] thickness Blade Blade quality, before/ before/ before/ Sample [mm] wear sharpness residuals after after after A (Ref.) 5 major major some — — — loss B 4 none/ kept no 74/72 131/72 7520/5340 minor C (Ref.) 4 none/ kept no 77/73  99/65 6130/4560 minor D (Ref.) 2 none/ kept no — — — minor
Experiment 3

(17) Samples and test arrangement were the same as in Experiment 1. The focus was on optimizing blade thickness further in order to minimise the material usage. The comparative samples A and D had a thickness that is typically used in commercial blades made of that material, but the blade thickness of samples B, C and E was varied. Doctoring performance was monitored by inspecting the ability of the sample to keep the roll surface dry of the water as blade wear and warp both result in failure to keep the roll surface dry. Blade warp or bend was visually compared to that of the non-biodegradable glass fiber blade (comparative sample D). Blade wear and roll surface quality were inspected as in Experiment 1. Results are shown in Table 2.

(18) TABLE-US-00002 TABLE 2 Results of Experiment 3. Blade Doctoring Roll surface thickness failed after/ Blade quality, Sample [mm] days Blade wear warp residuals A (Ref.) 5 3 major — some B 3 >14 none/minor no no B 2 >14 none/minor no no C (Ref.) 3 6 non-acceptable yes some C (Ref.) 2 3 non-acceptable yes some D (Ref.) 2 >14 none/minor no no (but roll surface fine- grooved) E 3 >14 none/minor no no E 2 12 none/minor yes no

(19) It can be seen from results in Table 2 blades according to the invention have competitive properties compared with the conventional blades of the prior art. Sufficient stiffness properties were achieved with optimized thickness. A low thickness was desired not only in order to reduce the amount of material and thus the amount of waste but also for improved doctoring performance. The thin blade according to the invention is less prone to lose its bevelled tip and thus less prone to hydroplaning or floating. It keeps a good contact with the surface to be doctored and still without damaging the roll surface or leaving rubbed residuals on the surface during contact.

(20) Despite its biodegradable nature the composite material used in the blades of the invention maintains certain mechanical properties that are important in terms of recycling as a raw material. Especially surface hardness is maintained after exposure to water and wet conditions. Strength properties are decreased but not too much for not being applicable to a second round as raw material, especially for a component with less demanding requirements. For material used in Samples B and C it has been found that a drop in mechanical properties is remarkable only after the second or third melting. Comparative Sample C with mineral filler but without biodegradable glass fiber reinforcement performed acceptably with a blade thickness of 4 mm (Table 1) but when the blade thickness was reduced to 3 or 2 mm, it failed (Table 2). Inventive Samples B (with biodegradable glass fiber, without mineral filler) and E (with mineral filler and biodegradable glass fibers in proportion of 3:1) achieved a good performance level even with blade thickness of 2 mm, as seen from Table 2. Thus, it was concluded that the presence of biodegradable glass fibers is advantageous in doctor blades. Samples B and E according to the invention even seemed to exceed the prior art Sample D in terms of maintaining roll surface quality during doctoring.

(21) Even if the invention was described with reference to what at present seems to be the most practical and preferred embodiments, it is appreciated that the invention shall not be limited to the embodiments described above, but the invention is intended to cover also different modifications and equivalent technical solutions within the scope of the enclosed claims.