DE2254862A1 - PROCESS FOR WHOLE WASTE PAPER WHOLE - Google Patents

Description

Patent attorneys Dipl.-Ing. F. Weickmann,

Dipl.-Ing. H.Weickmann, Dipl.-Phys. Dr K. Fincke Dipl.-Ing. F. A-Weickmann, Dipl.-Chem. Ä. ', Hubbr

8 MUNICH 86, DEN 2 2 '5 A 8 6

PO Box 860 820

MÖHLSTRASSE 22, CALL NUMBER 98 39 21/22

3078 / Dr.K.

Hooker Chemical Corporation, Niagara Palls, Π.Υ. 14302, T.St.A,

Process for bleaching waste paper pulp

The invention relates to a method for bleaching waste paper stock or pulp using ClOg. The invention relates in particular to a one-step bleaching process, in which chlorine dioxide is used as the sole bleaching agent to turn waste paper whole into a highly effective one and economical way to bleach.

With the increased awareness of environmental protection, there is a return waste paper has become an issue of no small importance. So far, waste paper returns are

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management processes have been considered uneconomical since There are relatively high costs for cleaning, removing the printer's ink and bleaching. Recently but technological advances have been made in technical cleaning and ink removal processes, which have resulted in a better and more economically recyclable type of whole waste paper or pulp. As a result, therefore, there are increased amounts of waste paper stock has become available for recycling to the paper industry. The recovery is however due to the high Cost and complexity of equipment and chemicals required for traditional bleaching been prevented.

The aim of the invention is therefore to provide a technically feasible method for bleaching waste paper stock To provide a product with an industry-acceptable gloss and clarity shall be. The method of the invention is also intended to be an efficient and economical process for Represent bleaching of waste paper blanket from which printing inks have been removed. Furthermore, a minimum number of bleach stages and only a single bleach can be used. Mixtures of whole waste paper should also be used and unbleached or partially bleached wood pulp can be bleached. After all, supposed to the one-step bleaching process can be carried out within a short period of time.

Regarding the purity of the products obtained from the processing of bleached waste paper stock, high demands are made. Much of the impurities found in the final product are agitated of printing inks and printing inks, pigments or decolorizing

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th fiber bundles. The extent to which the whole Were freed from the aforementioned impurities . depends in part on how well the ink removal cleaning operations are have been carried out.

For the removal of printing ink and / or cleaning of waste paper many methods are known. The present invention is therefore not limited to any particular method. An ink removal and cleaning process removes old magazines, newspapers, manufacturing waste, small amounts of wood pulp (up to about 7%) and various waste papers that coated a variety of Cellulosic fibrous materials are initially treated in any suitable manner relative to the paper to divide small pieces. This is followed by a pretreatment with a solvent to remove resinous, bituminous, tar-like and similar substances and the printing inks contained therein. This is done in the Way carried out that you put the waste paper in a hopper brings in and through the paper body a solvent such as benzene, carbon tetrachloride, trichlorethylene or the like, with the solvent being recovered for reuse. Then becomes water added to form a dilute aqueous suspension. To reduce the surface tension, etc., various Additives are added. The mass obtained is then washed, sieved, dried or otherwise for Storage prepared before the bleaching process.

As already stated, the purity of the whole thing depends in no small way on how good it is Ink removal and / or cleaning procedures have been carried out. Naturally, set economic considerations the extent of the purification a limit to what that

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Whole stuff is subjected to these measures. Practice has shown that a purified whole is the most careful ink removal and / or cleaning techniques has been subjected, still contains a certain amount of dyes and impurities that mainly due to the presence of printing inks or traces of ink.

The main purpose of bleaching the waste paper stock is to increase the gloss of the stock or pulp, by oxidizing traces of ink and other impurities without affecting the viscosity of the Cellulose material is considerably diminished and being only a minimum residence time in the bleaching device is provided. This is often done by stringing them together of bleaching stages which include treatments using, for example, chlorine, hypochlorite, chlorine dioxide, alkali, etc. The oxidation of the impurities occurs most easily with individual fibers that are exposed to the influence of the Bleaches are more accessible.

From the above, it can be seen that in a bleaching process In addition to a brighter whole, a cleaner whole can also be expected, i.e. a whole with fewer colored contaminants than in the case of unbleached whole garments. In terms of The ability of one thing is one of the currently high demands placed on the gloss of the bleached fabric Bleaching process to lighten the whole thing is of great importance. In this context it can be mentioned that in many cases only 10 spots of insufficiently bleached impurities per square meter of the sheet-like whole lead to such a reduction in quality that the whole product is sold at a reduced price got to.

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It is already known, fresh Zelluloser-Ganz fabric with chlorine or chlorine dioxide, either separately or in mixture to bleach I The chlorine bleaching of fresh whole toy or the fresh pulp is usually carried out at low temperatures (preferably below 21.1 ⁰ C) and At low _o he consistency (2.5 to k.5%) and during short bleaching periods (30 to 90 minutes). The low whole consistency is chosen for two reasons, namely, firstly, to achieve rapid, uniform mixing of the chlorine in the whole stock suspension, which is necessary to obtain uniform chlorination of the whole stock with rapid reaction between the chlorine and the lignin, and secondly, in order to avoid abrupt temperature rises in the whole product suspension due to strong exothermic reactions between the chlorine and the lignin, since high temperatures during chlorine bleaching lead to an uncontrollable oxidative decomposition of the whole material. The chlorine dioxide bleaching of fresh whole stuff is usually carried out at high temperatures (26.7 to 82.2 ⁰ C), higher consistencies (4.0 to 12.0%) and bleach longer periods (3 to 6 hours) due to the lower oxidizing ability . In contrast to the bleaching of the fresh stock, the prior art bleaching of the recycled waste paper stock has been limited to chlorine or hypochlorite processes. Chlorine dioxide is considered a milder bleach than chlorine or hypochlorite. It has also been believed that the presence of difficult-to-bleach inks and various other colored and paper-coating contaminants in the waste paper stock prevent uptake by the fibers. Furthermore, because of the presence of these difficult-to-bleach impurities, it would be expected that larger amounts of chlorine dioxide would be required to achieve a gloss, with higher unit costs and higher bleaching periods

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If

which comes close to, but is inferior to, that which is available with chlorine or hypochlorite.

It has now surprisingly been found that a recycled waste paper stock can be bleached to a higher gloss when using the technical viscosities, with unexpectedly short residence times in the chlorination device and at reduced technical costs, if chlorine dioxide is used as the sole bleaching agent. Accordingly, one proceeds according to the invention in such a way that a single-phase bleaching sequence is carried out in which the waste paper pulp is brought into contact with up to about 1.096 ClOpt, which equates to about Z _t Sk% CI2, so that a gloss response of up to about 92% is obtained while maintaining minimal viscosity change in the pulp. This shows that ClOg is an effective bleaching agent for treating waste paper stock.

The temperature of the whole suspension during the bleaching process can be varied widely. The temperature used will depend in large part on the equipment available at the particular paper mill. The process can be carried out at relatively low or high temperatures. Only short periods of time are required at high temperatures, while longer periods of time are used at low temperatures. The temperature range can / extend depending on the facilities of the mill of etv a 10.0 to about 82.2 ⁰ C (50 to 180 ⁰ F). A range of about 60.0 to about 82.2 ⁰ C (140 to about 18O ⁰ F) has been found to be preferred. The whole suspension can be heated during or after its production, for example by treatment with steam or by using it with hot water.

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The bleaching process is carried out at a pH of about 2 to about 5, preferably at a pH of about 3 to about 4, carried out. , Although the pH of the aqueous whole suspension should be kept close to the specified ranges during the bleaching stage, the setting can also before or simultaneously with the addition of the ClOp bleach take place. The pH can be adjusted by adding acids or alkali, for example sodium hydroxide.

Despite the degrees of freedom described above with regard to the choice of time and the setting of the pH value, it has become however, it has proven advantageous to adjust the pH of the suspension to certain values before adding the bleaching agent. The purpose of such pre-setting of the pH is to ensure that with the above Areas as much as possible of the bleach is consumed and that conversely as little as possible of the bleach is evaporated and lost. Thus, the pH before adding the bleach to the Whole product suspension preferably adjusted to approximately neutral. After pre-pH adjustment and after addition of the bleaching agent for the bleaching stage can be another Adjustment may be required to bring the pH of the suspension into the specified range for the bleaching process bring in.

After the end of the bleaching process, the bleached whole fabric can be washed in a paper mill system with a normal entry that goes into the paper machine. Due to the effectiveness of the bleaching process according to the invention, the bleached whole product can be discolored with an entry of any color

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be turned. In contrast, it has hitherto been necessary to select a particularly bleached whole product, which . be introduced into an entry of a jev / hasty coloring could. This fact is obviously of significant importance with regard to the handling of look at quality control. The bleached whole can also be stored in the watery state or in the oven-dried state for later use. This fact also makes the process according to the invention superior to the known chlorine or hypochlorite process, because in the method according to the invention in comparison to the methods of the prior art, the gloss reversal is less ekut.

The invention is illustrated in the examples. All parts therein are based on weight.

example 1

So much water became an oven-dried, unbleached, ink-stripped commercial waste paper blanket given, so that an aqueous whole ^ stuff mixture with a consistency of 3.5? 6 cellulose fibers and $ 96.5 of water was received. The aqueous whole product mixture was then divided into separate samples, each sample large enough to contain 25 grams of the cellulosic fiber components contained. According to the standard TAPPI test, viscosity, pH and gloss were found to be as follows Results determined:

viscosity 15.1 cp pH 7.0 shine 78.9

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Example 2

A sample containing 25 g of the cellulose fiber components The aqueous whole stock mixture of Example 1 was as follows subjected to two-stage bleaching sequence:

First phase:

A sufficient amount of a 0.5% Clp / HpO solution was placed in a covered container together with the sample so that a solution was obtained which contained 0.3 % by weight CIp, calculated on the cellulose fiber component. The solution was then allowed to react without stirring at 26.7 ° C for 10 minutes.

Second phase;

Immediately at the end of the 10-minute reaction period of the first phase, a 2.0% NaOH solution was added to the reaction product, so that a solution would be formed which contained 0.6 % NaOH, based on the cellulose fiber component, contained. The solution was then allowed to react without stirring at 26.7 ° C for 30 minutes.

After the 30-minute reaction period has ended, the In the second phase, the whole product was examined according to the standard TÄPPI test of Example 1 with the following results:

viscosity 14.7 PH 11.2 shine 86.6

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One hour after the completion of the 30 minute second phase reaction period, the standard TAPPI test was followed of Example 1- examined the gloss of the whole fabric, the following result being obtained:

shine

85.5

Eighteen hours after the completion of the 30 minute reaction period of the second phase, the whole garment was tested according to the standard TAPPI test of Example 1 examined for gloss, the following result being obtained:

shine

Examples 3 to 10

83.9

Samples (each with 25 g of the cellulose fiber component) of the aqueous whole product mixture of Example 1 were the subjected to the biphasic bleaching sequence of Example 2 with the following modifications and results:

at
game First
% ci ₂ phase
Reak
ions
Time Second
% NaOH phase
Reak
ions
Time Visco
sity pH GI an ζ
End 1 h
value 86.6 18 h 3 0.3 10 0.6 60 14.8 11.3 87.7 86.0 84.8 4th 0.3 10 0.6 90 14.6 11.1 87.2 87.0 84.1 5 0.5 10 0.8 60 14.7 11.5 88.2 85.6 85.1 6th 0.5 10 0.8 30th 14.7 11.4 86.6 86.9 83.9 7th 0.5 10 1.0 60 14.7 11.3 88.2 87.5 85.0 8th 0.5 5 1.0 60 14.7 11.2 88.7 87.0 85.7 9 1.0 5 1.5 60 13.8 11.0 88.5 87.4 85.1 10 1.5 5 2.0 60 13.3 10.2 89.1 85 /

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Example 11

. To a quantity of the oven-dried, long-bleached, ink-free commercial waste paper, stuff of Example 1 was given such an amount of water that an aqueous whole material mixture with a consistency was made up of 4.0% cellulosic fibers and 96.0% water. The aqueous whole ware mixture was then divided into separate samples, each sample being large enough that it contained 25 g of cellulose fiber components. The standard TAPPI test methods the viscosity, pH and gloss of the three samples were the same as in Example 1.

A sample (containing 25 g of cellulose fibers) of the aqueous pulp as prepared above was placed _{in a covered container along with sufficient 0.5% C10 2} / H ₂ 0 solution so that a solution was obtained which was 0.114 wt. -% ClO ₂ (0.3% by weight Cl ₂ equivalent), based on the cellulose fiber component. This solution was then allowed to react at 71 * 1 ° C. for 180 minutes without stirring. At the end of the 180 minute reaction period, the whole fabric was tested according to the standard TAPPI test of Example 1 with the following results:

viscosity 14.4 pH 5.8 shine 90.4

One hour and again 18 hours after the end of the 180-minute reaction time roughness, the whole product was after the standard TAPPI test of Example 1 was examined for gloss with the following results:

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1 hour '18 hours of gloss 89.5 87.7

Examples 12-13

Samples (with 25 g of the cellulose fiber component) of the aqueous whole fabric mixture were produced and according to Example 11 bleached with the following modifications and results:

With equivalent visco-pH gloss

play% C10 ₂ % Cl ₂ sity final value 1h 18 h

12 0.19 0.5 14.4 5.4 90.4 89.8 88.0

13 0.38 1.0 13.7 4.3 90.7 90.0 88.7

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Claims (1)

Pat e η ta η s ρ r ü ehe ' / '' 1. One-step process for bleaching whole waste paper, characterized in that an aqueous mixture of the whole product with chlorine dioxide brings in touch. 2 »The method of claim 1, characterized in that one carries out the bleaching at temperatures of from about 10.0 to about 82.2 ⁰ C (50 to about 18O ⁰ F). 3. The method according to claim 2, characterized in that the bleaching is carried out at temperatures of about 60.0 to about 82.2 ⁰ C (140 to 180 ⁰ F). 4. The method according to any one of claims 1 to 3, characterized characterized in that up to about 1.0% chlorine dioxide is brought into contact with the whole product. 5. The method according to any one of claims 1 to 4, characterized characterized by bleaching · at a pH of about 2 to about 5 undertakes. 6. The method according to any one of claims 1 to 5 »characterized in that one. uses a scrap paper stock containing up to about 7% wood pulp. . 30 9 8 2 0/0964