AT10525U1 - METHOD FOR THE PRODUCTION OF CELLULOSIC FORM BODIES USING BAMBOO PULP AND FORM BODY FROM THIS METHOD - Google Patents

Description

2 AT 010 525 U1

It has been known since 1939 (US Pat. No. 2,179,181) that cellulose can be dissolved without chemical conversion with the aid of tertiary amine oxides. The cited patent also describes that by precipitation of these cellulose solutions cellulosic shaped bodies, such as e.g. Fibers, can produce. In the 80s and 90s of the twentieth century, the companies Courtaulds and Lenzing worked intensively to implement this principle on a large scale in order to produce cellulose fibers commercially. Since the late 80s, there are fibers with the generic name Lyocell (brand name Tencel®) on the market. These fibers are used for the production of woven and knitted textiles in the clothing sector, technical textiles and nonwovens. The process for producing lyocell fibers is commonly referred to as the amine oxide process.

The state of the art today describes the use of a thin film evaporator for the continuous production of spinnable cellulose solutions as described in EP 0356419 B1 (Filmtruder).

In order to ensure the environmental friendliness and economy of the process, it is necessary to recover the amine oxide from the spinning bath in order to use it again in the preparation of the solution. A simple and effective measure to ensure the stability of the dope and thus the safety of the process is described in EP 0695324 B1.

The inherent tendency of the spinning mass to decompose is massively increased by dead spaces in the plant in which the spinning mass practically does not move over long periods of time. EP 0781356 B1 describes how to design parts of installations in which dead spaces can not be completely avoided, e.g. Spinning mass filter.

For the production of Lyocell fibers, a dry / wet spinning process is used. EP 0584318 B1 describes how excellent spinning behavior also results for large nozzles.

The textile chain requires fibers that run on modern high-capacity textile machines. The crimping plays a decisive role in the processability of the fibers. EP 0797696 B1 describes a method suitable for this purpose.

To date, around 1200 different types of bamboo are known, of which around 35 are used as raw material for the pulp and paper industry. There are varieties that thrive in tropical and temperate climates. Some form only a few cm thick shoots, while others can turn into 30-meter-tall plants in 3-4 years.

Depending on the variety, the bamboo fiber is either more like a short fiber or a long fiber. There are many properties of bamboo that offer great potential for use in the paper and pulp industry.

Currently, the production capacity of bamboo pulp worldwide is around 1.5 million tons per year. Asia has relatively small forest areas that can be used as raw material for pulp production. Therefore, especially in Asian countries is trying to use the widespread bamboo increasingly. Beyond paper pulp production, bamboo is known as a raw material for the production of viscose pulp in Asian countries, especially India. There are also companies and institutes in China dealing with the use of bamboo pulp for viscose fiber production.

What is new about it is that bamboo fiber viscose fibers are marketed as "bamboo fibers". Recently, there are also textiles for the end user on the market, which were made from these so-called "bamboo fibers". However, according to BISFA, this designation is not correct, since it is actually viscose fibers. As such, the fibers are clearly distinguishable from native bamboo fibers or bamboo fibers in the pulp.

WO 2005/068697 A1 describes terry goods made of so-called bamboo fiber. However, there is no further description of the type of fiber production. It's just a faint indication that it's supposed to be cellulose regenerate fibers. Therefore it can be assumed that a bamboo pulp is used as raw material.

EP 1679394 A1 describes yarns and fabrics made therefrom, which were also produced from bamboo pulp. The fibers are produced by means of viscose or cupro processes. In this document, however, neither the preparation of the spinning solution nor the spinning process are described in detail.

Bamboo pulps available on the market are mostly paper pulps. These have a low content of fiber-forming alpha-cellulose, which also has a very high average degree of polymerization. The pulps are therefore highly viscous. For the production of viscose fibers specially refined bamboo pulps are produced with a higher content of alpha-cellulose, ie, chemical pulps whose viscosity is adjusted accordingly. There are at least 2 manufacturers of commercial bamboo rayon fibers on the market. The use of bamboo pulp for the production of viscose fibers is described, for example, in CN1194119C.

The production of lyocell fibers from bamboo pulp is also described in the patent literature.

For example, JP 2005-126871 A describes the production of lyocell fibers with antibacterial properties from bamboo pulps with an alpha-cellulose content of 93% or more. It addresses the problem of keeping hemicellulose and other organic compounds away from the dope. This problem is solved by a suitably designed pulp cooking process.

CN 1383965 A describes the preparation of a Lyocell suitable bamboo pulp. As final steps of pulp production, an alkaline wash and a subsequent wash with a 0.1% aqueous solution of a chelating agent are mentioned.

CN 1190531 C discloses a spinning process for the production of lyocell fibers from bamboo pulp, which is intended to allow the use of pulps in a wide range of polymerization.

CN 1544223 A describes a process for producing bamboo lyocell fibers comprising both an alternative pulping process and the subsequent use of the pulp thus prepared for spinning. The process works with few pulp cleaning steps. However, the lyocell fibers produced by this process show unusually low strengths.

CN 1760412 A uses a bamboo paper pulp as raw material. The problem of the high degree of polymerization is achieved by a degrading pretreatment of the commercially available paper pulp, which is intended to replace a previously used for such pulps second pulp cooking and more economical than this. The higher levels of insoluble impurities known to be contained in paper pulps are then to be removed from the dope by a two-stage filtration. As degrading pretreatments hydrolysis with water at 120-200 ° C, the acid cleavage with sulfuric or hydrochloric acid at elevated temperatures over several hours and an enzymatic cleavage are called. 4 AT 010 525 U1

CN 18511115 A proposes, as a degrading pretreatment for a bamboo paper pulp, treatment with high energy radiation in order to achieve a degree of polymerization suitable for the lyocell process.

The production of bamboo pulp for lyocell spinning pulp described in the literature does not fundamentally differ from that for viscose. There is no indication in the literature of the stability of the spun masses produced. But if one uses a bamboo pulp, as it is used for the production of viscose, for the production of lyocell spinning masses, it will be found that the spinning mass is not very stable. Fundamental studies on the stability of the dope are made by Buijtenhuis et. al, Das Papier 40 (1986) pp. 615-619.

At least there is an increased degradation of the cellulose chains and an associated uncontrolled reduction in viscosity. This viscosity loss leads to problems with the spinning stability on the spinning machine and to fluctuating or poor properties of the lyocell fibers.

Impurities of the pulp with heavy metals can lead to the spinning mass thermally becoming so unstable that it can lead to a rapid exothermic reaction (exothermic or deflagration). EP 0781356 B1 describes a method with which the tendency of the spinning mass to decompose can be determined, the so-called "thermal stability test".

Furthermore, when using bamboo pulps for lyocell spinning compositions, it has been found that insoluble particulate impurities of the pulp occurred which, depending on size, cause severe problems in the dope filtration or on the spinning machine. In addition, it is always possible that particles are due to external silicon-containing impurities of the raw material such as sand or loam. One possible effect of high particle loads is a curtailment of production due to a bottleneck in the dope filtration. The worst case is the blocking of the filters. Very high stress on the dope with very fine particles which are not filtered may also lead to problems in spinning safety.

The object of the present invention was therefore to process pulp from the renewable raw material bamboo safely, that is to say without exothermic decomposition of the spinning pulp and with high spinning safety to form lyocell products of high quality.

The solution to this problem is a process for producing cellulosic products by the amine oxide process from a bamboo cellulosic cellulosic raw material containing between 30% and 100% bamboo pulp, in which the bamboo cellulosic cellulosic raw material contains a maximum of 10 ppm iron.

The bamboo pulp-containing cellulosic raw material may be a pure bamboo pulp or else a mixture of a bamboo pulp with a conventional pulp of another plant species, e.g. Deciduous or coniferous trees.

If the bamboo pulp-containing cellulosic raw material is made from a mixture of several pulps, the various pulps may be mixed prior to the addition of aqueous amine oxide solution, for example by feeding roll pulps to pulp crushing or by co-pulping the pulps in an aqueous medium , or both pulps are comminuted separately, mixed with aqueous amine oxide solution and then mixed.

Preferably, the bamboo cellulosic cellulosic raw material contains a maximum of 2.5 ppm copper. 5 AT 010 525 U1

Preferably, the bamboo pulp-containing cellulosic raw material contains a maximum of 2.5 ppm manganese.

Preferably, the bamboo cellulosic cellulosic raw material contains a maximum of 100 ppm, more preferably a maximum of 50 ppm SiO 2.

An embodiment of the invention is that the bamboo cellulosic cellulosic raw material is correspondingly purified of heavy metals. The necessary process steps are preferably carried out at the pulp manufacturer during the cooking, during the bleaching or after bleaching, wherein the bamboo cellulosic cellulosic raw material is preferably acid washed after the bleach stage and before dissolution in aqueous amine oxide.

As an alternative to acid washing, the bamboo pulp-containing cellulosic raw material after the bleaching stage and before the dissolution in aqueous amine oxide is preferably washed with an aqueous solution of a complexing substance in a very low concentration. The concentration of the chelating agent in the aqueous solution is preferably less than 0.07% by weight, more preferably less than 0.05% by weight. However, a chelating agent concentration of 0.001% by weight should not be undercut in order to achieve a satisfactory result. A preliminary alkaline wash is not required. The complexing substance used is mainly EDTA.

The reduction of the content of particulate impurities can be achieved during pulp production with a washing and sorting of the bamboo stems, a pre-sorting of the raw pulp and with a re-sorting of the bleached pulp.

It is important to thoroughly wash the bamboo stalks before processing to remove adherent soil and other contaminants.

The pre-sorting of the raw pulp serves primarily to separate non-digested wood components such as branches, splinters and bark parts as so-called rejects from the fiber suspension (accepts). Experience has shown that even large parts of the inorganic particles can be separated with the rejects. The better the pre-sorting, the fewer particles go through the many process steps to re-sorting, where they can be divided and smaller. The principle of presorting is a separation of the particles from the fiber suspension due to different size, shape and deformability with the aid of sieves. The sieves can be flat or cylindrical (screen basket), the suspension can be filtered with static pressure or with increased pressure. Screening with 4-25 mm holes is used for coarse sorting. For fine sorting, use 0.8-2.4 mm round holes or preferably 0.2-0.8 mm wide slots. The fabric density can be up to 4% for printing screens.

In the after-sorting, which takes place between the bleaching stage and the dissolution of the pulp in aqueous amine oxide, the remaining particles are selectively separated from the pulp fibers by hydrocyclones, for example with so-called centricleans, because of the density difference. Since the separation of especially very small particles is very expensive, a well-functioning pre-sorting is important. It has proved to be advantageous for the present invention to work in the post-sorting in the hydrocyclone with material densities between 0.1 and 1.0%. This separation can be done in combination with the acid wash or even without combination with acid wash.

The process parameters of the hydrocyclone separation are adjusted so that silicates are separated from the bamboo pulp. How this has to be done in detail, the expert is familiar with as soon as he has knowledge of the separation task. 6 AT 010 525 U1

A further embodiment of the invention comprises mixing the bamboo pulp, either untreated or treated by one of the abovementioned washing steps, with an amount of conventional chemical pulp such that the content of the pulp mixture in Fe is at most 10 ppm and the content of manganese and copper is in each case not more than 2, 5 ppm, the content of SiO 2 is at most 100 ppm, preferably at most 50 ppm.

The present invention also provides a cellulosic product which is prepared by the process described here.

This cellulosic product is preferably a staple fiber or an endless filament of the genus Lyocell. However, all other products which can be prepared by the amine-oxide process, such as films, hoses, sponges, cellulose beads or the products obtained therefrom by comminution, for example wet or dry milling or cutting, can be produced by the process according to the invention.

Such a cellulosic product produced by the amine-oxide process is characterized in that it contains a maximum of 10 ppm of iron.

The cellulosic product according to the invention preferably contains a maximum of 2.5 ppm of copper.

The cellulosic product according to the invention preferably contains a maximum of 2.5 ppm of manganese.

The cellulosic product according to the invention preferably contains not more than 100 ppm, more preferably not more than 50 ppm SiO 2.

The cellulosic product according to the invention is particularly preferably a staple fiber, an endless filament or a sheet of the genus Lyocell.

In the following the invention will be explained by means of examples. However, these examples do not limit the scope of the invention.

Example 1 - acidic laundry

All of our available bamboo pulp samples had consistently high heavy metal contents. The contents of heavy metals and Si were measured by ICP trace element determination according to EN ISO 11885 (Table 1).

Table 1

Zst 1 Zst 2 Zst 3 Zst 4 Zst 5 Fe (ppm) 20.5 46.5 13.6 15.4 20.1 Mn (ppm) 3.4 0.4 1.51 0.4 0.31 Cu ( ppm) 2.0 1.9 10.3 1.9 2.6 SiO 2 (ppm) 837 71 699 109 310

The pulp Zst 3 was acid washed in the laboratory under the following conditions: 100 g of the pulp were beaten in a plastic cup to a consistency of 3% and at a temperature of 70 ° C and a pH = 2, which was adjusted by adding sulfuric acid, Stirred for 60 minutes. Subsequently, the pulp was dewatered on a glass frit and washed neutral with deionized water. Finally, the pulp was dried in air. This pattern is referred to below as Zst 3a.

Example 2 - Washing with EDTA 7 AT 010 525 U1

The pulp Zst 3 was washed in the laboratory under the following conditions with the complexing agent EDTA: 100 g of the pulp were beaten in a plastic cup to a consistency of 3%. Then, the pH was adjusted to 5.5 with sulfuric acid and 0.55 g of EDTA was added so as to have an EDTA concentration of about 0.017 wt%. The suspension was stirred at a temperature of 70 ° C for 60 minutes. Subsequently, the pulp was dewatered on a glass frit and washed with deionized water. Finally, the pulp was dried in air. This pattern is referred to below as Zst 3q.

The heavy metal contents could be significantly reduced with both treatments (see Table 2).

Table 2

Zst 3 Zst 3a Zst 3q Fe (ppm) 13.6 5 8.3 Mn (ppm) 1.51 <0.2 <0.2 Cu (ppm) 10.3 1.3 0.7 SiO 2 (ppm ) 699 496 518

From the pulps, kneader spinning masses were produced in the laboratory and a thermostability test was carried out with these spinning masses, as described in EP 0781356. The untreated pulp has a significantly increased tendency to decompose compared to a standard lyocell pulp. Both the acidic wash and the EDTA treatment significantly improved the tendency to decompose. This can be clearly seen from Figure 1, in which the thermal stability of bamboo pulp is shown with different treatment. The temperature difference (in [° C]) between sample &amp; Sheath measured as a function of the jacket temperature (in [° C]).

The influence of the treatments of the bamboo pulp on the degree of polymerization and thus on the viscosity is just as clear in FIG. The relative degradation of the viscosity was measured by the method of EP 0 670 917. In Figure 2, the complex viscosity (in% of the initial value) was measured as a function of time (in min.). All the bamboo pulp treated according to the invention show a significantly lower degradation than the untreated one.

The combination of acidic wash and subsequent EDTA treatment has proved to be particularly advantageous.

In addition, the pulp samples Zst 3, Zst 3a and Zst 3q were used to prepare 13% spinning pulps, which were subsequently spun at the laboratory spinning machine (Davenport) into fibers having a denier of 1.3 dtex. At a spinning temperature of 115 ° C. and blowing with a relative humidity of 30 g / kg of air at 35 ° C., the following textile-physical data were obtained (Table 3: FFk: Fineness-related fiber strength, conditioned, FDk: fiber elongation, conditioned):

Table 3

Zst 3 Zst 3a Zst 3q FFk (cN / tex) 33 38 38 FDk (%) 9.8 9.7 9.4

Example 3 - Post-sorting attempt: 8 AT010 525U1

The attempt to reduce silicate impurities of the pulp Zst 3 was carried out on a pilot plant, which is composed of the following components: A Schwerstoffcleaner (hydrocyclone) from. NOSS, type Radiclone AM80-C; a storage tank with a propeller stirrer and a centrifugal pump, one control valve each for Accept content and Reject content, and two receptacles for Accept fraction and Reject fraction. First of all, 3,000 g of the pulp Zst 3 in the storage container were added to a consistency of 0.6%. Subsequently, this pulp suspension was fed into the cleaner at 100 l / min and returned to the circulation tank in the feed tank. The reject rate was set to 10%. At this setting, the entire pulp suspension was run over the cleaner and the Accept portion and the reject portion were collected in the two containers. The Accept portion was then dried in a convection oven at 60 ° C. The SiO 2 content of the pulp could be reduced from 699 ppm to 47 ppm.

Example 4 - Blend of chemical pulp and bamboo pulp

In the laboratory kneader three spun masses with 13% cellulose were produced. For the first spinning mass 100% of a commercial standard Lyocell-chemical pulp "Zst6" were used, for the second pulp 100% of a bamboo-chemical pulp "Zst4" and for the third pulp a mixture consisting of 70% standard chemical pulp Zst6 and 30% Bamboo pulp Zst4. The corresponding metal contents can be found in Table 4.

Table 4

Zst 6 Zst 4 Mixture Standard Bamboo 70:30 Fe (ppm) 1.2 15.4 5.5 Mn (ppm) 0.6 0.4 0.54 Cu (ppm) 0.2 1.9 0.71 SiO 2 (ppm) 24,109 49

The bamboo pulp Zst 4 is outside the required range for Fe and SiO 2. By contrast, the pulp mixture lies within the claimed range.

These three spinning masses were investigated for exothermic decomposition tendency on the Sikarex and viscosity reduction on the rheometer according to the above-mentioned methods. Zst 4 has a slightly increased decomposition. The mixture is practically at the same level as Zst 6 (Figure 3). The viscosity reduction of bamboo pulp Zst 4 is already in an undesirable range. However, the mixture is almost at the chemical pulp level (Figure 4).

In addition, lyocell fibers were produced on a laboratory scale. The textile-physical data of the mixture with 30% bamboo pulp do not differ significantly from the data of the chemical pulp Zst 6. The pulp mixture can be used to produce high-quality lyocell fibers for textile finishing (see Table 5).

Table 5

Zst 6 Zst 4 Blend FFk (cN / tex) 37.6 33.9 36.7 FDk (5%) 10.2 10.2 10.1

Claims (1)

9 AT010 525U1 Claims: 1. 2. 3. 4. 5. A process for the production of cellulosic moldings by the amine oxide process from a bamboo pulp-containing cellulosic raw material containing between 30% and 100% bamboo pulp, characterized in that the bamboo pulp -containing cellulosic raw material contains a maximum of 10 ppm iron. The method of claim 1, wherein the bamboo pulp-containing cellulosic raw material contains a maximum of 2.5 ppm copper. The method of claim 1, wherein the bamboo pulp-containing cellulosic raw material contains a maximum of 2.5 ppm manganese. The method of claim 1, wherein the bamboo cellulosic cellulosic raw material contains a maximum of 100 ppm, preferably a maximum of 50 ppm SiO 2. The method of claim 1, wherein the bamboo cellulosic cellulosic raw material is acid washed after the bleaching step and prior to dissolution in aqueous amine oxide. 6. The method of claim 1, wherein the bamboo pulp-containing cellulosic raw material is washed after the bleaching stage and prior to dissolution in aqueous amine oxide with an aqueous solution of a complexing substance. A method according to claim 1, wherein the bamboo pulp-containing cellulosic raw material is passed through a hydrocyclone between the bleaching stage and the dissolution in aqueous amine oxide in the form of a dilute slurry having a consistency of 0.1 to 1.0%. 8. 9. 10. 11. 12. 13. 14. The method according to claim 5, wherein in the hydrocyclone silicates are separated from the bamboo pulp-containing cellulosic raw material. Cellulosic product, characterized in that it is produced by the process according to claim 1. Cellulosic product according to claim 9, characterized in that it is a staple fiber, a continuous filament or a sheet of the genus Lyocell. Cellulosic product according to claim 9, characterized in that it contains a maximum of 10 ppm of iron. Cellulosic product according to claim 9, characterized in that it contains a maximum of 2.5 ppm of copper. Cellulosic product according to claim 9, characterized in that it contains a maximum of 2.5 ppm of manganese. Cellulosic product according to claim 9, characterized in that it contains not more than 100 ppm, preferably not more than 50 ppm SiO 2. For this purpose 2 sheets of drawings