METHOD FOR PRODUCING MICROSCALE AND/OR NANOSCALE FIBER MATERIAL

Abstract

The invention relates to a method for producing microscale and/or nanoscale fiber material. The method has at least the step of dispersing (5) dried pre-comminuted pump in a liquid. The method additionally has a step of finely comminuting (6) the pulp dispersed in the liquid such that a fine comminution mixture is produced which contains the liquid and the fiber material with the microscale and/or nanoscale fibril agglomerates.

Claims

1. A method for producing microscale and/or nanoscale fiber material, comprising at least the following method steps: mechanically pre-comminuting pulp substantially without addition of a liquid, in order that the average fiber length of the pulp comes to lie within the range of 0.025 mm-6 mm; dispersing the dry, mechanically pre-comminuted pulp in a liquid; and finely comminuting the pulp dispersed in the liquid such that a fine-comminution mixture is formed, which contains the liquid and also the fiber material containing microscale and/or nanoscale fibril agglomerates.

2. The method as claimed in claim 1, wherein the fine comminution is carried out by mechanical means by means of a mineral material.

3. The method as claimed in claim 1, wherein the average fiber length of the pulp used for the pre-comminution is within the range of 0.6 mm-6 mm.

4. The method as claimed in claim 1, wherein the pulp in the form of pulp sheets and/or flash-dried pulp is used as starting material for the pre-comminution.

5. The method as claimed in claim 1, wherein the pre-comminuted pulp is compacted before the dispersal in the liquid.

6. The method as claimed in claim 1, wherein the dry, pre-comminuted pulp has a water content of not more than 15% by weight, based on the total weight of the dry, pre-comminuted pulp.

7. The method as claimed in claim 1, wherein the fiber material forms a solids content of the fine-comminution mixture resulting from the fine comminution of not more than 40% by weight, based on the total weight of the fine-comminution mixture.

8. The method as claimed in claim 1, wherein the average length of the microscale fibril agglomerates is within the range of 500 nm-1000 m and/or the average length of the nanoscale fibril agglomerates is within the range of 10 nm to 500 nm.

9. The method as claimed in claim 1, wherein the dispersion resulting from the dispersal of the dry, pre-comminuted pulp in a liquid has, in the fine comminution, a liquid content of at least 60% by weight, based on the total weight of the dispersion.

10. The method as claimed in claim 1, wherein the fine-comminution mixture is largely free of visible individual fibrils.

11. The method as claimed in claim 1, wherein the fine-comminution mixture resulting from the fine comminution is dried in a further method step to yield a dried mixture.

12. The method as claimed in claim 11, wherein the dried mixture is largely free of visible individual fibrils.

13. The method as claimed in claim 11, wherein the same liquid or a different liquid is added to the dried mixture in a further method step to yield a rewetted mixture.

14. The method as claimed in claim 13, wherein the rewetted mixture is largely free of visible individual fibrils.

15. The method as claimed in claim 1, comprising the further step of producing, by means of the fine-comminution mixture, an insulation element serving for the electrical insulation of an electrotechnical component.

16. The method as claimed in rewetted mixture as claimed in claim 1, comprising the further step of producing, by means of the fine-comminution mixture, a cosmetics product or a pharmaceutical product or a foodstuff.

17. A material comprising fiber material containing microscale and/or nanoscale fibril agglomerates, the fiber material having been produced by a method comprising at least the following method steps: mechanically pre-comminuting pulp substantially without addition of a liquid, in order that the average fiber length of the pulp comes to lie within the range of 0.025 mm-6 mm; dispersing the dry, mechanically pre-comminuted pulp in a liquid; and finely comminuting the pulp dispersed in the liquid such that a fine-comminution mixture is formed, which contains the liquid and also the fiber material containing microscale and/or nanoscale fibril agglomerates.

18. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0089] Preferred embodiments of the invention are described below on the basis of the drawings, which merely serve for elucidation and are not to be interpreted as limiting. In the drawings:

[0090] FIG. 1 shows a flowchart for illustrating a method according to the invention;

[0091] FIG. 2a shows a view of a fibrillated pulp produced by means of a method of the prior art, which view was created by means of an electron microscope at a magnification factor of 10 000;

[0092] FIG. 2b shows a view of part of a microscale fibril agglomerate produced by means of a method according to the invention, which view was created by means of an electron microscope at a magnification factor of 10 000; and

[0093] FIG. 3 shows an exemplary representation of microscale fibril agglomerates that are present in the fiber material which has been produced by means of a method according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0094] FIG. 1 shows a flowchart which illustrates the individual method steps of a method according to the invention.

[0095] The original starting material used can be wood 1a or annual plants 1b or a combination thereof. The original starting material used for the production of the dry, pre-comminuted pulp or especially for the production of the pulp sheets used for the pre-comminution or of the flash-dried pulp can also be fruits, such as, for example, citrus fruits or apples, grain, such as, for example, wheat or corn, grass or fiber-containing vegetables, such as, for example, peas, pulses or carrots. The production of pulp from fruits, grain, grass or fiber-containing vegetables is known to a person skilled in the art.

[0096] The wood 1a or the annual plants 1b are processed to form pulp 3a or 3b according to a method known to a person skilled in the art. The pulp 3a or 3b is preferably pulp sheets or flash-dried pulp.

[0097] When using wood 1a as starting material, it is first comminuted to form chips 2a or wood chips. The chips 2a are then further processed to form pulp 3a, wherein the pulp 3a can, for example, be pulp sheets, flash-dried pulp or another form of pulp. As a result of the further processing of the chips 2a to form pulp 3a, the wood is delignified and defibered, i.e., the fibers are released from the wood compound. At the same time, an increase in whiteness can be brought about in the further processing to form the pulp 3a.

[0098] The further processing of the chips 2a to form the pulp 3a can be accomplished by means of a purely mechanical treatment of the chips 2a. However, the mechanical treatment can also be combined with a chemical treatment of the chips 2a. Alternatively, the further processing of the chips 2a to form pulp can also be based on a purely chemical treatment.

[0099] If a chemical treatment of the chips 2a is carried out, sulfate, sulfite and/or SO.sub.2 and ethanol can, for example, be used for this purpose. The chemical treatment can in particular be an ASAM (alkaline sulfite method with anthraquinone and methanol), an Organosolv, an Alcell, an Acetosolv, an Acetocell, a Formacell or a Milox method. Carrying out a steam explosion is possible, too.

[0100] If the pulp 3a or 3b is pulp sheets, they are preferably essentially completely or at least overwhelmingly formed from fibers having an average length within the range of 0.6-6 mm, with measurement of the fiber length preferably in accordance with the standard ISO 13322-2, 1st edition of Nov. 1, 2006. The water content of the pulp sheet is preferably not more than 15% by weight, more preferably not more than 10% by weight, yet more preferably 1% by weight-9% by weight, most preferably 5% by weight-8% by weight, based on the total weight of the pulp sheet, with preferred measurement of the water content in accordance with the standard EN 20638 of September 1993.

[0101] If the pulp 3a or 3b is flash-dried pulp, it is preferably essentially completely or at least overwhelmingly formed from fibers having an average length of 0.6-6 mm, with measurement of the average fiber length preferably in accordance with the standard TAPPI T271 pm-91 from 1991. The water content of the flash-dried pulp is preferably not more than 15% by weight, more preferably not more than 10% by weight, yet more preferably 1-9% by weight, most preferably 5-8% by weight, based on the total weight of the flash-dried pulp, with preferred measurement of the water content in accordance with the standard EN 20638 of September 1993. To facilitate handling, the flash-dried pulp is preferably present in the form of bales.

[0102] The pulp 3a or 3b can, for example, be a bleached softwood sulfate pulp, a bleached eucalyptus pulp or pulp obtained from cotton. What is thus possible is especially the use of pulp from softwood and/or from hardwood.

[0103] The pulp 3a or 3b obtained from wood 1a and/or from annual plants 1b is then supplied to the coarse pre-comminution 4. In the coarse pre-comminution 4, it is possible to use pulp 3a, which is based on wood 1a, or pulp 3b, which is based on annual plants 1b, or a combination thereof in the form of pulp sheets, flash-dried pulp or in another form of pulp or a combination thereof.

[0104] For the coarse pre-comminution 4, the pulp 3a and/or 3b is used in a dry state. Dry state means that the pulp 3a or 3b has a moisture usual for pulp, i.e., has no substantial additions of liquid. For example, the pulp 3a, 3b in the dry state can have a water content of 7% by weight, based on the total weight of the pulp. Negligible additions of liquid may be present, but not those which influence the total weight of the pulp excessively, i.e., by more than 15% by weight, preferably by more than 10% by weight, more preferably by more than 5% by weight. The pulp 3a, 3b is not considered dry especially when it has been dispersed in a liquid. Thus, substantially no liquid, preferably no liquid, is added to the pulp 3a or 3b prior to the coarse pre-comminution 4; instead, said pulp continues to have during the pre-comminution 4 a water content of about 7% by weight, preferably of 7% by weight, based on the total weight of the pulp. Advantageously, the dry pulp 3a or 3b is directly supplied to the coarse pre-comminution 4 without any pretreatment.

[0105] If pulp sheets are used, the coarse pre-comminution 4 can, for example, be carried out by means of a fine grinding mill (dry mill), a cutting mill, a hammer mill, a mixer and/or an impact mill If flash-dried pulp is used, a shredder, a cutting mill and/or a hammer mill can, for example, be used. Generally, the apparatus used for the coarse pre-comminution 4 has cutting blades or other comminution tools that have been produced from a metal.

[0106] For the entire method and especially the pre-comminution 4, there is thus no use of a pulper. Moreover, a single passage of the pulp through the apparatus required for the pre-comminution 4, i.e., for example the mill, is sufficient in most cases. The process time for the pre-comminution of the pulp is comparatively short as a result.

[0107] After completion of the coarse pre-comminution 4, the pulp is preferably present in the form of a powder, i.e., a bulk material. At the same time, the water content of the pre-comminuted pulp is not greater than that of the pulp 3a or 3b before the pre-comminution 4. Generally, the water content of the pulp is about the same before and after the pre-comminution 4.

[0108] The average fiber length of the pulp after the dry pre-comminution 4 is preferably within the range of 0.025 mm-6 mm, more preferably within the range of 0.4-1.7 mm. The average fiber length is preferably determined in accordance with the standard TAPPI T271 pm-91 from 1991. As a result of the pre-comminution 4, the fiber length of the pulp is on average preferably shorted by a multiple factor, especially by about a factor of three.

[0109] The pulp available after this method step, i.e., the pre-comminution 4, is suited especially well to storage and transport. It is therefore very easily possible for, firstly, the method steps from the original starting material 1a or 1b to and with the coarse pre-comminution 4 and, secondly, the method steps with a pretreatment 5 and a fine comminution 6, as described further below, to be separated from one another in terms of time and/or location. As a result, what is especially also possible is that, for example, the coarse pre-comminution is carried out by a first company, that the dry, pre-comminuted pulp thereby obtained is stored over a period of up to half a year, for example in the form of pellets, and that the pretreatment 5 and the fine comminution 6 is then carried out by a second company at a different site.

[0110] The dry, coarsely pre-comminuted pulp is then supplied to the pretreatment 5. This involves dispersing the pulp in a liquid which can, for example, be water, especially pure mains water or chemically distilled water. Alternatively, dispersal in a liquid such as, for example, acetone, glycol, ethanol, chloroform, isopropanol or in water to which an enzyme (e.g., a cellulase: endo-1,4--glucanase) has previously been added is, for example, also possible. Preferably, the liquid has a boiling point of 100 C. or less, preferably of less than 100 C. Preferably, the boiling point of the liquid is, moreover, at least 50 C. Most preferably, the boiling point of the liquid is within the range of 50 C.-90 C., at standard pressure (101 325 pascals). The advantage offered thereby is that the liquid can be withdrawn gently from the fiber material, can especially be withdrawn gently by thermal means, without the fiber material being damaged. Also possible is a chemical treatment of the pulp, for example based on a TEMPO oxidation, a carboxymethylation or a phosphoric acid treatment with subsequent dispersal in a liquid such as, for example, water, acetone, glycol, ethanol, chloroform or isopropanol. In this connection, the proportion by weight of the liquid in the dispersion is, in all methods except for that with the enzyme, preferably at least 60% by weight, more preferably at least 80% by weight, yet more preferably within a range of 90% by weight-99% by weight, yet more preferably within a range of 94% by weight-98% by weight, based on the total weight of the dispersion. The solids content of the dispersion is preferably measured in accordance with the standard ISO 4119:1995.

[0111] When dispersing the pulp in water containing added enzyme, the proportion by weight of the pulp in the liquid is preferably approx. 30% by weight, based on the total weight of the dispersion.

[0112] After the pretreatment 5, the pulp dispersed in the liquid, or the dispersion, is supplied to the fine comminution 6. Said fine comminution takes place, for example, in a refiner, a ball mill, a homogenizer, an ultrasound instrument, a microfluidizer, a jet collision instrument and/or a cryocrushing instrument. The use of a refiner comprising a cutter produced from a mineral material is especially preferred. In principle, the use of a refiner having cutters produced from metal is also possible for the fine comminution, though this is disadvantageous in many cases, since very fine blades are required for this purpose and frequently not all fibers are caught by the blades. Moreover, there is the risk of metal abrasion and thus the risk of metal particles getting into the fiber material containing the microscale and/or nanoscale fibril agglomerates that is to be produced and thus into the material to be produced using the fiber material. Metal particles are undesired in materials which are produced using the fiber material according to the invention, such as, for example, foodstuffs, pharmaceutical products, cosmetics products or insulation elements serving for the electrical insulation of an electrotechnical component.

[0113] Advantageously, the same grinding bodies are used for the entire fine comminution 6. This is possible because the pulp fibers are already very short owing to the dry pre-comminution 4 and have a narrow fiber-length distribution.

[0114] The final product of the fine comminution 6 that is present is the fine-comminution mixture comprising the fiber material containing the microscale and/or nanoscale fibril agglomerates. The water content of the fine-comminution mixture corresponds preferably substantially, more preferably exactly, to the water content of the dispersion before the fine comminution. The fibril agglomerates are formed in each case by a multiplicity of individual microfibrils partially or completely separated from one another. The average length of the microscale fibril agglomerates is preferably within the range of 500 nm-1000 m, more preferably within the range of 500 nm-600 m, and yet more preferably within the range of 500 nm -200 m, with ascertainment of these lengths preferably in accordance with the standard ISO 13322-2, 1st edition of Nov. 1, 2006.

[0115] FIG. 3 shows, by way of example, multiple microscale fibril agglomerates that are present in the fiber material which has been produced using a method according to the invention.

[0116] FIG. 2b shows, by way of example, a view of part of a microscale fibril agglomerate produced by means of a method according to the invention, which view was created by means of an electron microscope at a magnification factor of 10 000. What can be easily identified is the typical network structure with the comminuted fibrils within a fibril agglomerate, which fibrils are connected to one another. The fibril agglomerate is largely free of visible individual fibrils, even completely free thereof in the detail shown in FIG. 2b, since they are present only in comminuted form in each case and are moreover incorporated in the networks forming the fibril agglomerates. As comparison, FIG. 2a shows with the same magnification factor a pulp produced by means of a method of the prior art. Here, the individual fibrils are distinctly identifiable and do not form a common network; instead, they are present in an unconnected state and do not form a common structure.

[0117] Following the fine comminution 6, the fine-comminution mixture can be dried, or liquid withdrawn, for example by thermal means or by mechanical means or with application of negative pressure, with thermal drying preferably being carried out with negative pressure. For example, the fine-comminution mixture can be dried to yield a dried mixture in which the solids content is preferably within a range of 70% by weight-100% by weight, more preferably within a range of 80% by weight-97% by weight, yet more preferably within a range of 85% by weight-95% by weight, based on the total weight of the dried mixture. The dried mixture is suited particularly well to storage and transport.

[0118] In a further possible step, liquid can be added to the dried mixture to yield a rewetted mixture, which preferably has a solids content within the range of greater than 0% by weight-40% by weight, based on the total weight of the rewetted mixture. What liquid is added to the dried mixture for rewetting depends, for example, on what material is to be produced by means of the rewetted mixture.

[0119] The fine-comminution mixture, the dried mixture and the rewetted mixture can be used in the production of a material, such as, for example, a foodstuff, a cosmetics product or else a pharmaceutical product. Self-evidently, the fine-comminution mixture, the dried mixture and the rewetted mixture can be used in the production of many other materials.

LIST OF REFERENCE SIGNS

[0120] 1b Starting material, annual plant

[0121] 2a Wood chips

[0122] 3a Pulp

[0123] 3b Pulp

[0124] 4 Coarse pre-comminution

[0125] 5 Pretreatment

[0126] 6 Fine comminution