WO2012054968A1

WO2012054968A1 - Cellulose fibre composition

Info

Publication number: WO2012054968A1
Application number: PCT/AU2011/001360
Authority: WO
Inventors: Martin Charles Ernegg
Original assignee: Zeo Ip Pty Ltd
Priority date: 2010-10-26
Filing date: 2011-10-26
Publication date: 2012-05-03
Also published as: ZA201303724B; AU2011320014A1; CA2815386A1; AP2013006888A0; BR112013010074A2; MX2013004607A; JP2013540913A; US20140352903A1; EP2633119A4; EP2633119A1; CN103339322A

Abstract

A cellulosic composition comprising fibres having a length weighted average fibre length ("LWAFL") of 0.25 to 0.40mm.

Description

CELLULOSE FIBRE COMPOSTION

Technical Field

The disclosure relates to cellulosic compositions that are useful as structural building components for objects including, but not limited to, buildings,

furniture, car parts, coffins, cabinets & cases,

electronic housing, structural building pillars, beams, boards, sheets, veneers, chairs, musical instruments, and toys .

Background

Large amounts of waste generated in the pulp and paper processing industry are typically disposed to landfill. Disposal to landfill, however, is becoming increasingly problematic due to the environmental

constraints associated with land availability and

land/soil contamination. As such, there is significant pressure to reduce the amount of waste disposed to landfill, one means of reduction being recycling.

Recycling of paper and textile materials reguires the breakdown of such materials into fibres or fibre-like material which may then be reformed into material to provide paper and paper-like products. As an alternative to reforming into material to provide paper and paper-like products, a recycling process has previously been

developed for producing moulded pieces out of cellulose fibres in which the specific gravity of the moulded pieces approaches that of pure cellulose, 1.5. The process involves finely chopping and grinding cellulose fibres in the presence of water into micro-fibres prior to forming a fibre-water mixture in which the cellulose fibre content is about 1-15% by weight. The process subseguently involves shaping and drying the mixture of cellulose fibres and water into the moulded pieces. Details of the process and the moulded pieces produced by the process are set out in US Patent No. 6,379,594. Efforts have continued in the production of

cellulosic based compositions derived from pulp and paper processing waste and plant fibres which have high load bearing capacities and the ability for use as structural components .

Summary

The disclosure provides a cellulosic composition comprising fibres having a length weighted average fibre length ("LWAFL") of 0.25 to 0.40mm.

Preferably, 0.28 to 0.38mm.

The disclosure also provides a cellulosic composition comprising, by weight:

(a) 15% to 25% fibres of a length weighted average fibre length of 0.001 mm to 0.2 mm;

(b) 40% to 60% fibres of a length weighted average fibre length of 0.2 mm to 0.5 mm;

(c) 8% to 35% fibres of a length weighted average fibre length of 0.5 mm to 1.2 and

(d) less than 3% fibres of a length weighted average fibre length of 1.2 mm to 2.0 mm.

The length weighted average fibre length ("LWAFL") provides a measure of the average length of the fibres in a sample of fibres which is weighted by the length of the individual fibres. The LWAFL gives emphasis to the longer fibers in the sample and imparts less emphasis to the shorter fibers and fines. The LWFAFL is sometimes referred to as just the weighted average fibre length or "WAFL" . The LWAFL can be compared to other measures of the average length of the fibres in a sample such as the arithmetic or numerical average (AFL) and the weight weighted average fiber length (WWAFL) . These averages are obtained through the following calculations: ∑( * ¾)

AFL Where:

N

bin it

LWAFL ∑(/*'¾) bin median length

∑(&·%) bin fiber count

total number of

fibers counted.

WWAFL ∑(!-¾)

∑(/* · n_x)

Preferably, the composition has a Water Retention Value (WRV) of 600% to 2000%, more preferably, 700% to 1300%.

The water retention value (WRV) is defined as the amount of water that participates in the swelling of the fibrous material and that which is not released under the application of a centrifugal force. The WRV is also highly correlated to the bonding ability of kraft fibers. The test to determine the WRV is carried out by placing a pad of moist fibers in a centrifuge tube that has a fritted glass filter at its base. The centrifuge is accelerated at 3000g for 15 minutes to remove water from the outside surfaces and lumens of the fiber. The remaining water is believed to be associated with submicroscopic pores within the cell wall. The centrifuged fibers are weighed, dried at 105°C, and then reweighed. The WRV can then be

calculated from the ratio of the water mass to the dry mass. The apparatus used to measure the WRV is shown schematically in Figure 1.

In an embodiment, the composition comprises, by weight :

(b) 45% to 55% fibres of an a length weighted

average fibre length of 0.2 mm to 0.5 mm;

(c) 20% to about 30% fibres of a length weighted average fibre length of 0.5 mm to 1.2 mm and (d) less than 1% fibres of a length weighted average fibre length of 1.2 mm to 2.0 mm.

The cellulosic composition may be in a wet or dry state .

In an embodiment, the cellulosic composition are dried in the form of pellets, granules or powders. In the dry state, the cellulosic composition may be conveniently stored and transported.

The dry pellets, granules or powders may be mixed with water to form mouldable, fine pulps that may be dried to create materials for use as structural components.

The mouldable, fine pulps may be moulded using any suitable method including, but not limited to, spray molding, injection molding, extrusion or three stage molding. The moulded or green articles may be subsequently dried to form a product

The density of the product produced from a

composition according to the disclosure may be from 0.5 g/cm3 to 1.5 g/cm3. The tensile modulus of the product may be from 3500 MPa to 10800 MPa and the tensile strength may be from 27 MPa to 115 MPa.

Whilst functional additives (such as dyes and pigments for colouring, resins and waxes for

waterproofing, lime, fire retardants including natron silicate, glues, metal powders and graphites for

electrical conductivity, latex for flex and waterproofing, fillers and very long fibres of 1.5-6.0mm in length for increased tensile strength) may be added to the pulp of dry cellulosic powders/granules/pellets mixed with water, there is no need for the addition of any functional additives or the application of pressure to dry and harden the pulp.

In an embodiment, the composition may be prepared by any one or combination of processing methods including, but not limited to, ultra friction grinding, high pressure homogenizing, cryo grinding, extrusion, steam explosion, ultra sonic treatment, enzyme-fibre separation, high consistency/medium consistency/low consistency refining, chemical treatment or Whitewater fines recovery.

Components of the composition may be prepared separately and mixed together. In an embodiment, two or more intermediary compositions with different fibre length distributions may be prepared and mixed in the reguired proportions to form the compositions defined above.

Various raw materials may be used in the preparation of the compositions as described herein, including, but not limited to, short/ultra short cellulose fibres/fines recovered from waste streams, for example, recovered paper, recovered fines in Whitewater from paper & pulp processing and recovered cotton fibers. Additional raw materials may also include any cellulosic fibers used in pulp & paper processing and various plant fibers having a high cellulosic content, for example, hemp, flax, cotton, abaca, sisal and jute.

The disclosure also provides a product made from a composition as described herein.

Brief description of the Figures

Embodiments will now be described, with reference to the accompanying Figures, in which:

Figure 1 is a schematic view of an apparatus for measuring the Water Retention Value (WRV) of fibre samples;

Figures 2-6 depict Norval Wilson stained microscope images of wet pulp compositions derived from wastepaper a the scales indicated;

Figure 7 depicts Norval Wilson stained microscope images of wet pulp compositions derived from hemp

cellulose at the scales indicated; and

Figures 8-13 are graphs of the fibre length

distributions for the wet pulp compositions shown in Figures 2-7. Detailed Description of the Embodiments

Embodiments provide cellulosic composition made up of fibres having different specific lengths, a high degree of fibrillation and a high water retention capacity. These composition may be subsequently moulded and dried to produce finished wood-like or horn-like articles of high strength and which therefore can be used as load bearing products .

The composition comprise fibres having a length weighted average fibre length ("LWAFL") of 0.25 to 0.40mm, preferably 0.28 to 0.38mm. The fibre lengths in the composition are distributed in a skewed bell curve, with the composition comprising, by weight:

(b) 40% to 60% (preferably 45% to 55%) fibres of a length weighted average fibre length of 0.2 mm to 0.5 mm;

(c) 8% to 35% (preferably 20% to 30%) fibres of a length weighted average fibre length of 0.5 mm to 1.2 and

(d) less than 3% (preferably less than 1%) fibres of a length weighted average fibre length of 1.2 mm to 2.0 mm .

Thus the composition consists of a significant amount of fines (fibre length <0.2mm) mixed with short length fibres (fibre length of 0.2-1.2mm) .

Additionally, the composition has a high degree of fibrillation indicatd by a high Water Retention Value (WRV) of 600-2000%, preferably, 700-1300%.

The composition is prepared by any one or combination of processing methods including, but not limited to, ultra friction grinding, high pressure homogenizing, cryo grinding, extrusion, steam explosion, ultra sonic

treatment, enzyme-fibre separation, high

consistency/medium consistency/low consistency refining, chemical treatment or Whitewater fines recovery. Components of the composition may be prepared separately and mixed together. In some embodiments, two or more intermediary compositions with different fibre length distributions are prepared and mixed in the required proportions to form the composition.

Various raw materials may be used in the preparation of the composition, including, but not limited to, short/ultra short cellulose fibres/fines recovered from waste streams, for example, recovered paper, recovered fines in Whitewater from paper & pulp processing and recovered cotton fibers. Additional raw materials may also include any cellulosic fibers used in pulp & paper processing and various plant fibers having a high

cellulosic content, for example, hemp, flax, cotton, abaca, sisal and jute.

The composition may be dried for transport and/or storage in the form of pellets, granules or powders. From these forms, the compositions may be re-wetted to form moldable, fine pulps. Alternatively, the compositions may be prepared as a pulp and used directly in a molding process. The compositions as a pulp may be moulded by any moulding operations known to persons skilled in the art, for example, spray molding, injection molding, extrusion or three stage molding. The moulded or green articles may be subsequently dried to form a product.

Advantageously, the composition can be used to create a material with appropriate hardness, strength and ductility to be used as a structural material yet remains (as a wet pulp) capable of being readily handled during processing and manufacture of articles from the

composition, including very large articles. Furthermore, the composition does not require excessive energy to produce and is therefore economically viable.

Accordingly when molded and dried, the composition can be used to create structural and industrial components such as coffins, electronic housings, structural building pillars, beams, boards, sheets, veneers, boxes, chairs, cabinets, cases and other furniture, car parts and toys.

It will be appreciated that due to a variation in the compositions of the raw materials in terms of, for example, lignin content, ash content, OH bonding capacity and degree of entanglement/fibrillation, as well as the choices of fibre processing parameters, the physical properties of the final product produced from the

composition will vary. For example, the density may vary from 0.5 to 1.5g/cm3, the tensile modulus may vary from

3500 to 10800MPa and the tensile strength may vary from 27 to 115MPa.

Examples

Fibre furnish and degree of fibrillation

Five samples (A to E) based on waste paper, RCW80 de- inked recovered waste paper from Amcor, and one sample (F) based on hemp cellulose, Hempcell B from Celesa in Spain, were subjected to grinding in a high consistency 22" refiner. The fibre (solids) content in the pulp was 16wt% and the flow rate of pulp through the refiner was

approximately 200L/min. The specific energy (the amount of energy transferred from the refiner's motor to the fibre) input was for each of the Samples:

Sample A 1.8kWh/kg

Sample B 1.8kWh/kg

Sample C 1.8kWh/kg

Sample D 1.6kWh/kg

Sample E 2. OkWh/kg

Sample F 1.9kWh/kg The specific edge load (the amount of energy applied across one meter of refiner plate's bar edge and

transferred to the pulp in one second) was between 4-8Ws/m at the beginning of the refining process and this load was gradually reduced to between l-4Ws/m by the end of the process .

The fibres were processed until the spread of the average fibre length matched a known "bell curve". From experience and knowing the process inputs, this occurs after a certain time period of processing. However, the fibres may be sampled to confirm that they have this distribution of fibre lengths.

A light microscope and a Norval Wilson stain was used on the prepared slides containing dispersed fibre samples and images were taken of each sample as depicted in

Figures 2 to 7. As can been seen from these Figures, a high degree of fibrillation is observed for the six samples and most of the fibres were broken or cut into very small fragments.

Suspension properties: morphological properties as well as resistance to dehydration and swelling behaviour 0.2g (dry weight) of each Sample A-F after the grinding process described above were strongly diluted by pre-suspending in water, stirring, and subseguently filling with water to 5000 ml. From this suspension, 25 ml were taken (corresponding to 1.0 mg (dry weight) fibrous material) and photographed. The photographs were subseguently analysed (double determination) using

FibreLab 3.0" equipment to determine the fibre- morphological properties and distribution parameters for the separated and suspended fibres, including the fibre length. The results for fibre length are provided in Table 1 below. Table 1 - Fibre length

The results in Table 1 show that all samples (A to F) contain extremely shortened fibres. The arithmetic average of the measured fibre lengths is skewed somewhat by the presence of fines (<0.2mm) . This can be mathematically corrected (reduced) , by weighting the lengths and masses, ie . by referring to the LFAFL or WWAFL .

In practice the length weighted average fibre length (LFAFL) is typically used for the comparison of fibrous materials with one another. From the values of the LFAFL for all Samples in Table 1, it can be seen that similar values are obtained for all Samples based on wastepaper (A to E) with a slightly shorter value for the Sample based on hemp cellulose (F) .

The results shown in Table 2 below are an evaluation of the distribution of fibre lengths within certain length ranges. The majority of fibres of all six Samples (A to F) after processing are 0.2-0.5mm, which is considered to be the short fibre or fibre fragment range. This is also shown graphically in Figures 8-13. Each of these Figures (for respective samples) contains two graphs. The top graph in each of Figures 8-13 shows the distribution of fibres having lengths of <0.06mm whilst the lower graph in each of these Figures shows the distribution of fibres having lengths of >0.1mm. Table 2 - Distribution of fibre lengths (length weighted average length in length ranges) by weight%

The fines content of the ground samples were investigated further by determining the fraction of the fines (fibres <0.2mm) in each Sample based on the arithmetic average fibre length (AFL) . This fraction for each Sample is compared to the length weighted fraction of fines (as per Table 2) is shown in Table 3 below. As can be seen from Table 3, the fines content of all Samples (A to F) is very high. The hemp cellulose Sample F, notably contained markedly more fine material than the wastepaper samples (A to E) .

Table 3 - Fine material contents

Further measurements of the diameter, wall thickness and calculated (curvature) parameters using the Fibrelab equipment show that samples A to E derived from wastepaper have similar values whereas sample F derived from hemp cellulose has smaller fibre dimensions and a smaller curvature. This result corresponds with the fibre lengths determined as well as with the fibre fragments present.

Table 4 - Further fibre data

Determination of the Water Retention Capacity (WRC) according to Zellcheming fact sheet IV/33/57

All Samples A to F (after grinding described above) were homogenised by mixing prior to sampling for

determination of their Water Retention Capacity (WRC) .

The Samples of fibrous material were dehydrated (to a solids content of approximately 25wt%) on a G2 frit in the absence of a vacuum and transferred to a swell tube

(according to DIN 53814) . The swell tube was filled to approximately two-thirds capacity (resulting in a solids content of approximately 0.150wt%) . The swell tube was sealed with a plug and subjected to a centrifugal force of 3000g for 15 minutes. Six parallel determinations were performed .

The water not participating in the swelling of the fibres was removed from the fibrous material by the centrifugation . The swelling water and the water retention capacity were gravimetrically determined by drying the fibrous material at 105°C until a constant mass solids content was achieved. The results are shown in Table 5. Table 5 - Water Retention Capacity

The values of the water retention capacity are extremely high and atypical particularly compared to commercially available, strongly ground celluloses. The higher WRC generally equates to a denser material which when moulded and dried into a final product results in a product which has a lower tear or tensile strength but a higher load bearing capacity and Young's modulus. A preferred range for Water Retention Capacity is generally between 700 and 1200% as above this range, the low tear strength makes it difficult to form sheets - as was found with Sample C.

Material properties: physical/strength properties

Samples A to F were ground as described above and mixed with water in a mixer to a solids concentration in the range between 0.3 and 0.4wt% (3 to 4 g/L) as per Table 8 below.

Table 8

The objective was to produce test sheets with an average grammage of m_A of 80±2 g/m², for use in subsequent strength testing according to the Rapid-Kothen method (in accordance with ISO 5269-2) . It is noted that due to the very low dehydration capability of all of the Samples, the ISO 5269-2 test specifications had to be adapted by reducing the volume of filling water in the cylinder and varying the period of drop and suction to suit the required conditions for sheet forming for each of Samples A to F.

After producing the test sheets for each of the Samples, the test sheets were acclimatised in standard climate conditions (23C°/50% relative air humidity) .

The grammage of the acclimatised test sheets was ten determined according to DIN EN ISO 536. The results of the grammage testing are shown in Table 9.

Table 9 - Sample Grammage

Due to the characteristics of the materials it was very difficult to produce test sheets with uniform grammage. This was especially the case of sample C wherein the targeted value (80±2 g/m²) could not be realised despite repeated corrections. This is due to the very high Water Retention Capacity (WRC) of the Samples. In order to compensate for the non-uniformity in grammage between the test sheets, the strength values have been corrected with respect to grammage.

The test sheets were subjected to thickness and apparent sheet density testing, the results of which are shown in Table 10. Table 10 - Sheet thickness and apparent sheet density

By virtue of the high proportion of very short, fine fibres, the thickness at the grammage strived for was small and the density very high. This corresponds to the normal behaviour at high packing densities that are achieved with very short fibres. The test sheets were subjected to tensile testing according to DIN EN ISO 1924-2, the results of which are shown in Table 11 below.

The values for breaking force, elongation, breaking length and Young's modulus determined from this testing are not corrected with respect to the grammage, but are corrected with respect to the breaking length (represented as the Tensile Index) :

Table 11 - Tensile test results

From the results in Table 11, the tensile strength, expressed as tensile index, corresponds to that of ground cellulose. Whilst the tensile strength values for the Samples differ, there is little variation in the Young's modulus of the Samples which is high. The high Young's modulus of each of the Samples is indicative that the Samples can withstand tensile loads elastically for long periods of time. Without wishing to be bound by theory, it is expected that this is due to the high amount of fibrillation of the fibres and the subseguent linkages between the fibrillated fibres.

The test sheets were cut into strips and subjected to tear resistance testing according to DIN EN 21974. The results are shown in Table 12. The resistance to tearing is not corrected according to the grammage, only according to the tear index. Table 12 - Tear Resistance

The tearing strength of all samples, measured on "standard" celluloses, is at a very low level, i.e. the resistance to tear is low. This can be attributed

primarily to very short fibres.

In the claim which follows and in the preceding description, except where the context reguires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or

"comprising" is used in an inclusive sense, ie . to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments .

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms part of the common general knowledge in the art, in Australia or any other country.

Claims

CLAIMS :

1. A cellulosic composition comprising fibres having length weighted average fibre length ("LWAFL") of 0.25 0.40mm.

2. A cellulosic composition as claimed in claim 1, the composition comprising, by weight:

A cellulosic composition comprising, by weight:

4. A cellulosic composition as claimed in any one of preceding claims, wherein the composition has a Water Retention Value (WRV) of 600% to 2000%.

5. A cellulosic composition as claimed in any one of the preceding claims, wherein the composition comprises, by weight :

(a) 15% to 25% fibres of a length weighted average fibre length of 0.001 mm to 0.2 mm; (b) 45% to 55% fibres of an a length weighted average fibre length of 0.2 mm to 0.5 mm;

(c) 20% to about 30% fibres of a length weighted average fibre length of 0.5 mm to 1.2 mm and

(d) less than 1% fibres of a length weighted average fibre length of 1.2 mm to 2.0 mm.

6. A cellulosic composition as claimed in any one of the preceding claims, wherein the cellulosic composition is in the form of pellets, granules or powder.

7. A cellulosic composition as claimed in any one of the preceding claims, wherein the composition also comprises one or more functional additives.

8. A cellulosic composition as claimed in claim 7, wherein the functional additives are selected from dyes and pigments for colouring, resins and waxes for

waterproofing, lime, fire retardants including natron, silicate, glues, metal powders and graphites for

electrical conductivity, latex for flex and waterproofing, fillers and very long fibres of 1.5-6.0mm in length for increased tensile strength^

9. A cellulosic composition as claimed in any one of the preceding claims, wherein the composition is prepared by any one or combination of processing methods including ultra friction grinding, high pressure homogenizing, cryo grinding, extrusion, steam explosion, ultra sonic

treatment, enzyme-fibre separation, high

consistency/medium consistency/low consistency refining, chemical treatment or Whitewater fines recovery.

10. A cellulosic composition as claimed in any one of the preceding claims, wherein components of the composition are prepared separately and mixed together.

11. A cellulosic composition as claimed in claim 10, wherein two or more intermediary compositions with different fibre length distributions are prepared and mixed in the required proportions to form the composition.

12. A cellulosic composition as claimed in any one of the preceding claims, wherein the raw material used in the preparation of the compositions comprises one or more of short/ultra short cellulose fibres/fines recovered from waste streams, recovered paper, recovered fines in

Whitewater from paper & pulp processing and recovered cotton fibres, any cellulosic fibres used in pulp & paper processing and plant fibres having a high cellulosic content such as hemp, flax, cotton, abaca, sisal and jute.

13. A product made from a composition as claimed in any one of the preceding claims..

14. A product as claimed in claim 13, wherein the density of the product is from 0.5 g/cm3 to 1.5 g/cm3.

15. A product as claimed in claim 13 or 14, wherein the tensile modulus of the product is from 3500 MPa to 10800 MPa.

16. A product as claimed in any one of claims 13-15, wherein the tensile strength of the product is from 27 MPa to 115 MPa.