EP1688534A1 - Use of Arabinoxylanes in paper production - Google Patents

Abstract

A modified cellulose pulp is prepared by contacting an arabinoxylan in a form of a concentrated solution comprising arabinoxylan or a suspension comprising arabinoxylan, with a cellulose pulp. Independent claims are also included for: (1) a modified cellulose pulp comprising cellulose pulp; and 0.1-40 wt.% arabinoxylan; and (2) an arabinoxylan comprising 5-20 wt.% arabinose substituents, and less that 5 wt.% 4-O-methylglucuronic acid substituents.

Description

The present invention relates to the use of arabinoxylans as an additive in papermaking.

The mechanical properties of paper are influenced by a number of different parameters, both chemical and physical. Several theories for explaining the tear strength properties of paper have been proposed, most of which emphasize the particular relevance of fiber-to-fiber bonding. Among the most frequently cited is the theory which includes the factors of interfiber bond force of bonded surface and fiber length.

There is general agreement that hemicelluloses natively present in the pulp improve tear strength and contribute to the formation of stronger fiber bonds. These hemicelluloses are, however, depending on the raw material and pulping process during the pulp production greatly changed and destroyed to a significant percentage.

The use of xylans as an additive in papermaking is basically known. Thus, Naterova et al. (Papir a celuloza, 41, (7-8), V23-V30, 1986) the addition of corn xylans to kraft paper. By adding 2% xylan, the flexural strength could be increased by 172%.

DE 44 09 372 A1, US Pat. No. 5,810,972 and WO 2004/031477 A1 describe the addition of highly milled birch pulp and lenzing xylan in the range of 0.005 to 0.14% WO 2004/031477 A1) or 0.15 to 1, 5% (US 5,810,972, DE 44 09 372 A1) to tissue products. A positive effect of the xylans or the xylan-rich highly milled birch pulp on the softness of the tissue product and the behavior of the paper web on the drying cylinder is described. The fracture strength could be increased by 15 to 73% in the machine direction and by 17 to 90% across the machine direction. Apparently, the behavior in the dryer section was positively influenced, but this could not be numerically recorded, but judged by the experience of the papermaker

In the above applications, the use of xylans from the raw material wood and its secondary product pulp is discussed. In particular, the use of hardwood acetyl-4-O-methylglucuronoxylan and softwood arabino-4-O-methylglucurornoxylan is mentioned. The examples of the use of xylans call the lenzing xylan. This product is obtained by alkaline extraction of beech wood pulp in the viscose process and has only low degrees of polymerization of about 35.

Thus, various xylans have been investigated for their properties for fiber properties or as a paper additive. However, the work mentioned shows that an improvement in the breaking length is accompanied by a decrease in other strength properties or unacceptable deterioration of the optical properties.

There is therefore still a need for a low-cost paper additive which brings about an improvement in the paper properties, in particular the strengths, the bulk and the optical properties.

It has now surprisingly been found that the addition of arabinoxylans to the pulp during papermaking enables a marked improvement in paper properties. By using arabinoxylan, the tearing length, tear resistance and also the bulk i.e.. the volume of papers improved. By improving the bulk, in addition to the strength properties, the optical properties of the papers are also improved. Surprisingly, in comparison with other xylans, such as 4-O-methylglucuronoxylan from hardwoods or Lenzing xylans, a significantly higher improvement in paper properties is achieved.

An object of the invention is therefore the use of arabinoxylans as an additive in papermaking.

Suitable arabinoxylans are polysaccharides which are described, for example, in various annual plants and agricultural residues such as e.g. Oat husks, straw or corn is included. The arabinoxylans can be prepared by a variety of extraction techniques, e.g. be recovered with water, steam or solvents using a variety of auxiliary chemicals and by enzymatic isolation and purification steps. Preferably, alkaline extracted arabinoxylans, and in particular arabinoxylans from oat hulls, are used, e.g. by extracting the oat husks with aqueous alkaline solution to obtain an alkaline extract and then precipitating the alkaline extract in a precipitation bath of water and a water-miscible organic liquid A, whereby the alkaline extract is not neutralized before precipitation.

The peculiarity of the arabinoxylans from oat husks in comparison to the xylans from hardwood and softwood is that they have a comparatively high number of arabinose substituents but not the 4-O-methylglucuronic acids occurring in deciduous and coniferous xylans. Compared to xylans from pulps such as Lenzing xylan, the arabinoxylans have a much higher chain length.

In the context of the present invention, arabinoxylans are understood to mean those xylans which have 5 to 20% (w / w based on the total sample), preferably 7 to 15%, particularly preferably 8 to 13%, arabinose substituents on their main chain and less than 5 %, preferably less than 2%, more preferably less than 1% carry 4-O-methylglucuronic acid substituents (chromatographic determination of sugar after acid hydrolysis).

Arabinoxylans obtained by extraction of oat hulls with aqueous alkaline solution to yield an alkaline extract and subsequent precipitation of the alkaline extract in a precipitation bath of water and a water-miscible organic liquid A, whereby the alkaline extract is not neutralized prior to precipitation, are particularly preferred. Such arabinoxylans usually have chain lengths of at least 100 after a possible bleaching stage. In most cases, the chain lengths of these arabinoxylans are in the range 120 to 240.

Another object of the invention is a process for producing a pulp comprising contacting a concentrated solution or suspension of a arabinoxylans with pulp or a pulp system containing pulp.

In one embodiment of the invention, the arabinoxylan solution or suspension is added to the fiber suspension prior to foliar formation. The action of the arabinoxylan also takes place in combination with other paper chemicals which are introduced into the pulp before, after or together with the arabinoxylan. As a result, the use of arabinoxylan for the various products of the paper industry is advantageous.

Common other paper chemicals include, for example, wet strength agents, fillers, retention aids, fixatives, defoamers, deaerators, sizing agents, optical brighteners, and colorants.

A homogeneous solution or suspension of arabinoxylans can be achieved, for example, by strong mechanical stress such as stirring, by the action of temperature or by means of chemicals, preferably basic chemicals such as alkali metal or alkaline earth metal hydroxides, preferably NaOH. The concentration of the arabinoxylan solution or suspension can be varied within a wide range of 0.1% to 40% (w / w). Preferably, the range is from 0.1 to 25% (w / w), more preferably the range from 0.5% to 10% (w / w).

The arabinoxylan solution or suspension may then be incubated with the pulp and the desired paper aides and high consistency additives (solids content) of up to 20% before the pulp enters the headbox of the paper machine. Then you can go through Squeezing off the supernatant solution may use unadsorbed chemicals for the next batch.

In another embodiment of the invention, the pulp in the headbox, i. immediately before entering the papermaking machine with the additives and the arabinoxylan solution or suspension in any order. The addition of arabinoxylans in the headbox usually achieves better results than the previous incubation with the pulp.

In a further embodiment of the invention, arabinoxylan solution or suspension is added to the pulp suspension prior to grinding the pulp fibers.

In most cases, in a product formulation after reaching an optimum amount by further increasing the Arabinoxylaneinsatzes no further increase in the strengths and the bulk is effected. The optimum amount used depends on which other paper auxiliaries are used in the mass, so that the amount of arabinoxylans used in relation to pulp in a wide range of 0.1% up to 40% (w / w) can be. Preferably, however, amounts of from 0.5 to 10% of arabinoxylan are used. In most cases, the use of paper additives already at lower Arabinoxylankonzentrationen the optimum increase in strength is achieved.

The invention will be illustrated below by some embodiments, without, however, limiting it thereto.

Examples

In the following examples, unless stated otherwise, the compositions of xylans are given as% w / w based on the total sample, obtained by chromatographic determination of sugar after acid hydrolysis

4-O-methylglucuronic Example 1 (according to the invention)

An arabinoxylan from oat husks (9.5% arabinose, <1% 4-O-methylglucuronic acid, DP ca. 160) was dissolved under heating to form a 5% solution in water. 20 g of softwood sulfite pulp were suspended in water and mixed with the xylan solution in the amounts indicated in Table 1. For tests with higher amounts of xylan solution, correspondingly smaller amounts of water were used to suspend the pulp. After addition of the xylan suspensions, the pulp consistency was 7.1% in each case. The experimental batches were each incubated for 2 h at 50 ° C. After incubation, the pulp was sucked through a suction filter.

The pulp was then ground to ISO 5264-3 in a Jokro mill for 2.5 minutes and test sheets were produced according to ISO 5269-2 (Rapid-Köthen method). The testing of the strengths was carried out according to ISO1974 (DIN EN 21974). <b> Table 1 </ b> Amount of arabinoxylan in% (w / w) bzg. on pulp Tear length (km) 0 (reference) 2734 7.5 3473 22.5 3935 37.5 4199

The data in Table 1 show that compared to the reference pulp without xylan use, the pulps treated with arabinoxylan from oat husks have significantly higher strengths. The tear length increases with increasing use of xylan. The highest increase in the breaking length due to the addition of arabinoxylan from oat husks is 1465 m.

Example 2 (comparative example)

A 4-O-methylglucuronoxylan from birch wood (no arabinose side chains, 8.8% molar ratio of 4-O-methylglucuronic acid based on xylose units, determined by ¹ H-NMR, DP about 95) was used as a 5% solution in water dissolved under heating. 20 g of softwood sulfite pulp were suspended in water and mixed with the xylan solution. For tests with higher amounts of xylan solution, correspondingly smaller amounts of water were used to suspend the pulp. After addition of the xylan suspensions, the pulp consistency was 7.1% in each case. The experimental batches were each incubated for 2 h at 50 ° C. After incubation, the pulp was sucked through a suction filter.

The pulp was then ground to ISO 5264-3 in a Jokro mill for 2.5 minutes and test sheets were produced according to ISO 5269-2 (Rapid-Köthen method). The testing of the strengths was carried out according to ISO1974 (DIN EN 21974). <b> Table 2 </ b> Amount of 4-O-methylglucuronoxylan in% (w / w) bzg. on pulp Tear length (km) 0 (reference) 2734 7.5 2983 22.5 3126 37.5 3189

The data in Table 2 show that birchwood 4-O-methylglucuronoxylan can only provide very little increase in strengths. The effect of this xylan is less than 31% of the effect of arabinoxylan from oat hulls.

Example 3 (comparative example)

The Lenzing xylan from beech wood pulp (no arabinose side chains, about 1% 4-O-methylglucuronic acid, DP about 35) was dissolved as a 5% solution in water with heating. 20 g of softwood sulfite pulp were suspended in water and mixed with the xylan solution. For tests with higher amounts of xylan solution, correspondingly smaller amounts of water were used to suspend the pulp. After addition of the xylan suspensions, the pulp consistency was 7.1% in each case. The experimental batches were each incubated for 2 h at 50 ° C. After incubation, the pulp was sucked through a suction filter.

The pulp was then ground to ISO 5264-3 in a Jokro mill for 2.5 minutes and test sheets were produced according to ISO 5269-2 (Rapid-Köthen method). The testing of the strengths was carried out according to ISO1974 (DIN EN 21974).

The data in Tab. 3 show that the "Lenzing xylan" of beech wood pulp can only bring about a very small increase in the strengths. The effect of this xylan is only 36% of the effect of arabinoxylan from oat hulls. <b> Table 3 </ b> Amount of Lenzing xylan in% (w / w) bzg. on pulp Tear length (km) 0 (reference) 2734 7.5 3010 22.5 3000 37.5 3260

Example 4

An arabinoxylan (9.5% arabinose, <1% 4-O-methylglucuronic acid, DP ca. 160) from oat husks was dissolved as a 5% solution in water with heating. A softwood pulp was then ground to ISO 5264-3 in a Jokro mill for 2.5 minutes and test sheets were produced according to ISO 5269-2 (Rapid-Köthen method). The arabinoxylan solutions were added in each case in the chest, which is used for the portioning of the suspension for the individual test sheets. In the chest each 16 g of pulp in a total liquid of 6.67 1 are equalized with a consistency of 0.24%. The arabinoxylan solution was added according to the respective amount used. After 5 minutes, the portioning and the formation of the test sheets. All experiments were carried out at room temperature. The testing of the strengths was carried out according to ISO1974 (DIN EN 21974). <b> Table 4 </ b> Influence of arabinoxylan from oat husks on the tenacity of softwood sulfite pulp The arabinoxylan feed was applied at a consistency of 0.24% after pulp grinding Arabinoxylan use% (w / w) bzg. on pulp Tear length (km) reference 2830 4.7 3759 9.4 4216 28.1 4031

The tear length can be improved by the addition of arabinoxylan from oat husks compared to the reference experiment by more than 1000 m. In this addition mode, increases in strength can be achieved even at lower levels of arabinoxylan use.

Example 5

An arabinoxylan from oat husks (9.5% arabinose, <1% 4-O-methylglucuronic acid, DP about 160) was dissolved as a 5% solution in water with heating. A softwood pulp was then ground to ISO 5264-3 in a Jokro mill for 2.5 minutes and test sheets were produced according to ISO 5269-2 (Rapid-Köthen method). The xylan solutions were added in each case in the chest, which is used for the portioning of the suspension for the individual test sheets. In the chest each 16 g of pulp in a total liquid of 6.67 1 are equalized with a consistency of 0.24%. A cationic polyamide-epichlorohydrin resin was added as a paper aid and stirred into the suspension for 5 min. The dosage of the paper additive was consistent with a charge density of 0.013 meq / g of pulp in all experiments carried out. Subsequently, the metered addition of the Arabinoxylanlösungen was made. After 5 minutes, the portioning and the formation of the test sheets. All experiments were carried out at room temperature. The testing of the strengths was carried out according to IS01974 (DIN EN 21974). <b> Table 5 </ b> Influence of arabinoxylan from oat husks on the tenacity of softwood sulfite pulp with the simultaneous use of a paper additive. The Arabinoxylaneinsatz was carried out at a consistency of 0.24% after grinding of the pulp Xylan insert% (w / w) bzg. on pulp Arabinoxylan with paper additive tear length (km) reference 3944 0.09 3992 0.93 4698 2.3 5486 4.7 5629 7.0 5710 9.4 5728

The tear length can be significantly increased again by the addition of arabinoxylan compared to the reference experiment. It is clear from the reference that the strengths are generally at a higher level due to the use of the paper additive. However, a synergistic effect becomes apparent in the interaction with the paper additive for the action of the arabinoxylan. The increases in the breaking length are now even up to about 1800 m. The higher increases in strength are effective even at significantly lower Arabinoxylaneinsatzmengen than in the trials without paper additive.

Example 6

An arabinoxylan from oat husks (9.5% arabinose, <1% 4-O-methylglucuronic acid, DP about 160) was dissolved as a 5% solution in water with heating. Beechwood sulfite pulp was milled to ISO 5264-3 in a Jokro mill for 2.5 minutes, 5 minutes, 10 minutes, 15 minutes and 20 minutes. Subsequently, test sheets were produced according to ISO 5269-2 (Rapid-Köthen method). The arabinoxylan solutions were added in each case with 9.4% (based on pulp) in the chest, which is used for the portioning of the suspension for the individual test sheets. In the chest each 16 g of pulp in a total liquid of 6.67 1 are equalized with a consistency of 0.24%. 5 min after the addition of the arabinoxylan solution, the portioning and the formation of the test sheets were carried out. All experiments were carried out at room temperature. The testing of the strengths was carried out according to ISO1974 (DIN EN 21974). Light scattering coefficients were determined according to SCAN C 27:76.

The investigations showed that not only the tensile strength (Tensile), but also the tear strength (Tear) of the pulp was increased by the Arabinoxylan addition. The Tear Tensile Plot gives the possibility tensile strength and tear resistance of all samples from the To study the degree of freeness (Figure 1, Influence of arabinoxylan from oat husks (9.38% on pulp) on the Tear Tensile plot of beech sulfite pulp). It becomes clear that the samples with addition of the arabinoxylan have significantly better values in both strengths, so that the entire curve is shifted to a higher level.

The specific volume of the pulps is indicated by the bulk, which is plotted against Tensile Tensile Strength in FIG. 2. (Influence of Arabinoxylan from Oat Flakes (9.38% on Pulp) on the Bulk Tensile Plot of Beech Sulfite Pulp) , It becomes clear that the curve for the different points of the freewheeling curve is shifted to higher bulk values. To produce a product with the desired strengths, a higher sheet volume can be generated by adding the arabinoxylan. The increased bulk leads to an increase in the light scattering coefficient and thus to better optical properties.

Claims (10)

Use of arabinoxylans as an additive in papermaking. A process for preparing a pulp comprising contacting a concentrated solution or suspension of an arabinoxylan with pulp or a pulp containing pulp. A method according to claim 2, characterized in that the proportion of arabinoxylans based on pulp is between 0.1 and 40%. A method according to claim 1 or 2, characterized in that the arabinoxylan is incubated with the pulp at fabric densities up to 20% before further paper additives are used in the process. Process according to Claim 1 or 2, characterized in that the arabinoxylan is incubated with the pulp at substance densities of up to 20 after the addition of paper additives Method according to one of claims 2 or 3, characterized in that the arabinoxylan is added to the pulp in the headbox or just before the headbox. Method according to one of claims 2 or 3, characterized in that the pulp is subjected to the addition of arabinoxylan a grinding in suitable aggregates, preferably refiners. Pulp containing pulp and 0.1% up to 40% (w / w, based on pulp) of arabinoxylan. Pulp pulp according to claim 8, characterized in that the arabinoxylan carries on its main chain 5 to 20% arabinose substituents and less than 5% of 4-O-methylglucuronic acid substituents. Arabinoxylans, characterized in that they contain on their main chain 5 to 20% (w / w, based on total sample), preferably 7 to 15%, particularly preferably 8 to 13% arabinose substituents, and less than 5%, preferably less than 2 %, more preferably less than 1% carry 4-O-methylglucuronic acid substituents.

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