Method for processing of cellulose fiber

FIELD: paper; chemistry.

SUBSTANCE: method of cellulose fiber modification is realised in the following manner. Suspension mass of cellulose fibers is prepared. In process of its bleaching cellulose derivative is added in at least one stage of acid bleaching. pH of suspension mass is in the interval from approximately 1 to approximately 4, and temperature - in interval from approximately 30 to approximately 95°C. As cellulose derivative carboxy-alkyl-cellulose is used, for instance, carboxy-methyl-cellulose. From this suspension of bleached fiber mass paper is produced by means of dehydration of this suspension on the mesh with formation of paper.

EFFECT: higher strength in wet condition and softness of paper.

42 cl, 2 dwg, 1 ex

 

The present invention relates to a method for processing cellulose fibers. The invention also relates to a method for producing paper from these treated fibers and the paper thus obtained. The invention relates also to method of application derived cellulose as an additive for acid stage of bleaching.

The level of technology

In the technical field of paper production there are various ways to improve paper strength in the wet state by using additives, preserving the strength of the paper in the wet state, to cellulose fibers in the suspension of pulp in the formation of paper. The strength of the paper in the wet state is associated with its ability to maintain the physical integrity and resistance to the formation of razmerov, tearing and loosening during use, especially in wet conditions. Another important property of paper increased strength in the wet state is soft, especially thin tissue paper or the like Softness can be defined as the tactile sensation perceived by holding the paper on the skin or in the course of her skin.

In the publication WO 01/21890 describes the modification of cellulose fibers to make paper of high strength in the wet state. However, this method involves adding power the ITA to a suspension of pulp and processing it at a temperature at least 100°that limits the flexibility and scope of this method.

The aim of the present invention is the provision of energy efficient and simple method for the production of paper with increased strength in the wet state and increased softness, as well as other useful properties given to the paper by means of this modification of the fibers. Another object of the present invention is the provision of a method which can be applied using existing standard equipment, machines and mechanisms.

Invention

The present invention relates to a method of modifying cellulose fibers, comprising obtaining a slurry weight of cellulosic fibers, adding a derivative of the pulp in the bleaching process these cellulose fibers, at least one stage of acid bleaching.

Preferably, in addition to the optional addition of an acid or base to adjust pH, the electrolyte is not added together with the addition of a derivative of cellulose. Adding a base or acid, regulating the pH value, can be carried out in an amount of from about 0.001 to about 0.5 M, if a monovalent electrolyte. Adding, for example, Ca2+or other dvuhvalenten the first electrolyte could in some cases increase the risk of precipitation of calcium oxalate. After that, the equipment used in the bleaching process may be clogged such precipitated precipitated substances obtained from electrolytes, because the cellulose in nature may contain, for example, oxalic acid. However, the electrolyte does not have a significant impact on the modification of the fibers.

A suitable pH value of the suspension mass at the stage of acid bleaching is in the range from about 1 to about 7, more preferably in the range of from about 2 to about 6, most preferably from about 2 to about 4.

Temperature during acid whitening suitably ranges from about 30 to about 95°C, preferably from about 60 to about 90°C.

Preferably the content of cellulose fibers based on the dry weight in the suspension of the weight is from about 1 to about 50%, more preferably from about 15 to about 30%, most preferably from about 5 to about 15%.

Whitening appropriately carried out for from about 0.1 hours to about 10 hours, preferably from about 1 hour to about 5 hours, most preferably from about 1 hour to about 3 hours. Stage acid bleaching, in which is added a derivative of cellulose may be any of ADI, where the pulp is treated with chlorine dioxide, ozone, nagkalat, or other stage acid treatment for whitening, preferably represents a stage of treatment with chlorine dioxide. In this case, means that the stage acid treatment are included in the bleaching process, which includes the successive stages of acid whitening, as well as such as leaching, acidification or acid stage of helatoobrazutee, during which can be added derived cellulose.

It was found that the adsorption of cellulose derivatives on cellulose fibers, in particular the adsorption of carboxymethyl cellulose (CMC) fiber, leads to a significant increase of the surface charge compared to wood fibres, not processed SMS.

This may explain why the strength of wet paper produced from pulp processed SMS, in which SMS has been added at the stage of acid bleaching significantly increased, as well as the relative strength in the wet state when the agent that increases the strength in the wet state, sequentially added to get the paper in the paper production process.

Thus, the method according to the present invention can also provide paper production increased softness. Magnetist paper can be evaluated, at least indirectly by using the values of the relative strength in the wet state, which is defined as the ratio between the rate of tensile strength in the wet state and a measure of the tensile strength in the dry state in accordance with the formula RWS (%) = (WS/DS)·100, where RWS is a relative strength in the wet state, WS represents a measure of the tensile strength in the wet state, and DS is a measure of the tensile strength in the dry state paper. RWS is often a good indicator of the smoothness of the paper; the higher the RWS, the higher the softness of the paper.

Modification using a derivative of cellulose may also affect the outcome of any subsequent introduction of chemical additives in the composition of the fibrous mass, which, in turn, can affect the required dosage of chemical additives in the pulp and on the quality of the produced paper products.

It was also noticed that sizing, retention of adhesive and dehydration can improve as a result of modification of cellulose fibers in the manufacturing processes of paper.

In the cellulose-containing modified bleached cellulose fibers, can be added any additional chemical additives for paper, suitable for production is DSTV paper. Such chemicals may include, for example, amplifiers strength in the dry state, amplifiers strength in the wet state, the retaining additives, sizing agent, etc.

Cellulose fibers can be obtained from any type of soft or hard material wood or non-wood bases, for example, the pre belenos, porublennoy or unbleached sulphite, sulphate or soda pulp or unbleached, porublennoy or pre belenos mechanical, thermomechanical, chemical-mechanical and chemi-thermomechanical pulp, and mixtures thereof. As examples of non-wood materials can be specified, for example, bagasse, hemp, fibre, sisal, etc.

Derivative of cellulose, preferably alkyl derivative of cellulose, most preferably carboxymethylcellulose derivative is water-soluble or at least partially soluble in water or is water-dispersible, preferably water-soluble or at least partially soluble in water. Preferably a derivative of cellulose is ionic. Derivative of cellulose may be anionic, cationic or amphoteric, preferably is anionic or amphoteric. Examples of suitable cellulose derivatives include ethers, cellulose, e.g. the measures anionic and amphoteric ethers of cellulose, the alkaline cellulose (alkalizers), cellulose complexes with metals, graft copolymers of cellulose, preferred examples are anionic ethers of cellulose. Derived pulp preferably contains an ionic or charged groups or substituents. Examples of suitable ionic groups include anionic and cationic groups. Examples of suitable anionic groups include groups of the esters of carboxylic acids, such as carboxylic, the group of esters of sulfonic acids, such as sulfoalkyl, the group of esters of phosphoric acid and phosphonic acids in which the alkyl group may be a methyl, ethyl, propyl and mixtures thereof, a suitable group is methyl; a suitable derivative of cellulose contains an anionic group, including the group of ester carboxylic acids, for example carboxialkilnuyu group. The counterion of the anionic group is usually alkali metal or alkaline earth metal, a suitable group is sodium.

Examples of suitable cationic groups of the cellulose derivatives according to the invention include groups of amine salts, suitable are salts of tertiary amines and Quaternary ammonium groups, preferably Quaternary ammonium groups. The substituents attached to the nitrogen atom of amine or Quaternary ammonium groups may be the same Il is different and can be selected from alkyl, cycloalkyl and alkoxyalkyl groups, and one, two or more substituents together with the nitrogen atom can form a heterocyclic ring. Substituents independently of one another typically include from 1 to about 24, preferably from 1 to about 8 carbon atoms. The nitrogen atom of the cationic group may join the cellulose or its derivative through a chain of atoms, suitable chains comprise atoms of carbon and hydrogen and, optionally, the atoms O or N. this is Usually the chain of atoms is alkylenes group containing from 2 to 18 carbon atoms, preferably from 2 to 8 carbon atoms, and optionally containing one or more heteroatoms or substituted by one or more heteroatoms, such as O or N, such as accelerograph or hydroxypropionate group. Preferred derivatives of cellulose containing cationic groups include groups obtained by the interaction of cellulose or its derivative with agent education Quaternary base, selected from chloride 2,3-epoxypropyltrimethylammonium, chloride 3-chloro-2-hydroxypropyltrimethylammonium and mixtures thereof.

Derivatives of cellulose according to the present invention can contain non-ionic groups, such as alkyl or hydroxyalkyl group such as hydroxymethyl, hydroxie the sludge, hydroxypropyl, hydroxybutyl and their combinations, such as metalhydroxide, methylhydroxypropyl, hydroxybutyrate, ethylhydroxylamine, hydroxypropyl, etc. In a preferred embodiment, a derivative of cellulose contains both ionic and non-ionic group.

Examples of suitable cellulose derivatives according to the present invention include karboksimetsiltsellyulozy, for example carboxymethylcellulose, carboximetilzellulozu, carboximetilzellulozu, sulfobacillus, karboksimetiltselljuloza ("CM-HEC), carboxymethyl cellulose in which the cellulose is substituted by one or more non-ionic substituents, preferably carboxymethylcellulose ("CMC"). Examples of suitable cellulose derivatives and methods for their preparation include derivatives and methods described in U.S. patent No. 4940785, which thus included in this description by reference.

The term "degree of substitution" or "DS", when used herein, means the number of the substituted sites cycle beta anhydroglucose rings derived cellulose. As each anhydroglucose ring has three hydroxyl groups available for substitution, the maximum value of DS is 3.0. In accordance with one preferred embodiment of the invention, the degree of substitution, the number is about ionic groups ("DS NI"a derivative of cellulose is about to 0.65, i.e. the average degree of a purely ionic substitution on glucose residue derived cellulose is about to 0.65. Net ionic substitution may be purely anionic, purely cationic or purely neutral. When pure ionic substitution is purely anionic, there is a General excess of anionic groups (pure anionic group = average number of anionic groups minus the average number of cationic groups, if they are present on glucose residue), and the value of DSNIequal to the value of the degree of substitution of pure anionic groups ("DSNA"). When pure ionic substitution is purely cationic, there is an excess of cationic groups (pure cationic group = average number of cationic groups minus the average number of anionic groups, if present, on glucose residue), and the value of DSNIis equal to the degree of substitution of pure cationic groups ("DSNC"). When pure ionic substitution is purely neutral, the average number of anionic and cationic groups, if present, on the glucose residue is the same, and DSNIand DSNAand DSNC0. In accordance with another preferred embodiment of the invention, the degree of substitution derivative of cellulose carboxialkilnuyu groups("DS CA") reaches approximately 0,65, i.e. the degree of substitution derivative of cellulose carboxialkilnuyu groups ("DSCA") based on glucose balance reaches approximately 0,65. When appropriate carboxialkilnuyu groups are carboxymethyl group, then the specified value DSCAequal to the degree of substitution carboxyethylidene groups ("DSCM"). According to such variants of implementation of the present invention, the values DSNIDSNADSNCand DSCAindependently from each other typically reach approximately 0,60, appropriate values are to about to 0.50, preferably up to about 0.45, and more preferably to 0.40, while usually the value DSNIDSNADSNCand DSCAindependently from each other are, at least 0.01, the appropriate value is at least approximately 0.05, preferably at least approximately to 0.10, more preferably at least approximately 0.15. The values of DSNIDSNADSNCand DSCAindependently from each other typically range from about 0.01 to about 0,60 suitable intervals of values are intervals of values from about 0.05 to about 0.50 and preferably from about 0.10 to about 0.45 and more preferably from about 0.15 to about 0.40 in.

Usually the degree of anionic substitution (S NA) cellulose derivatives, which are anionic or amphoteric, is in the range from 0.01 to about 1.0, while DSNIand DSNItake the values defined above; appropriate lower limit of the interval of values of the degree of anionic substitution is the value of approximately 0.05, preferably about 0.10 to, more preferred is approximately 0.15, a suitable upper limit of the intervals of values of the degree of anionic substitution is the value of about 0.75, preferably about 0.5, more preferably about 0.4. The degree of cationic substitution ("DSC"derivative of cellulose, which are cationic or amphoteric, may have values in the range of from 0.01 to about 1.0, while DSNIand DSNCtake the values defined in the description; appropriate lower limit of the interval of values of the degree of cation substitution is approximately 0.02, preferably from about 0.03 to, more preferred from about 0.05 to appropriate upper limit of the intervals of values of the degree of cation substitution is about 0.75, preferred is about 0.5, more preferred is about 0.4. When suitable cationic groups are Quaternary ammonium groups, then the value of the specified DSCequal to the value of the degree of substitution of Quaternary ammonium is a group ("DS QN"). For amphoteric cellulose derivatives according to the present invention DSAor DSCyou can, of course, to take values over of 0.65, while DSNAand DSNCaccordingly, take the values defined above. For example, if DSAequal to 0.75 and DSC0.15, DSNAequal to 0.60.

Suitable solubility in water cellulose derivatives equal at least 85 wt.% based on the total weight of a derivative of cellulose, preferably at least 90 wt.%, more preferably at least 95 wt.%, most preferably at least 98 wt.%.

The average molecular weight derivative of cellulose is usually in the range from at least 20,000, preferably at least 50,000 D, up to about 1000000 D, preferably up to about 50000 D.

Derived cellulose is added in an appropriate amount from about 0.5 to about 50, preferably from about 5 to about 20 and most preferably from about 5 to about 10 kg/t of dry cellulose fibers.

The invention also relates to a paper, which can be obtained by a process comprising dewatering on the wire cellulose modified bleached cellulose fibers obtained in accordance with the method described in this invention, and forming paper from oksanaigorevna pulp.

It will be obvious that the described thus the invention may be made different changes. Such changes should not be distinguished from the scope of the present invention, and qualified in the field of specialist it is clear that all such modifications are included in the scope of claims of the present invention. The following examples illustrate how it can be described the invention, but not limit its scope and field of application. Except where otherwise indicated, all listed parts and percentages are calculated based on weight.

Examples

The purpose of the experiment is to adsorbirovannoi SMS on the fiber at the final stage of acid bleaching, which in this case is the stage of bleaching using chlorine dioxide. Even in the absence of necessity of application of calcium chloride used to increase the adsorption. Apply the pulp passes peristediinae whitening method, Elemental Chlorine Free, and is fully belenos and white is 90% (ISO). The control pulp is treated the same way as SMS-modified cellulose according to the invention, but without the introduction of SMS. The final stage of processing chlorine dioxide is carried out at 80°C for 180 minutes at 10% moisture content of the pulp. Use the following boot chemicals from the payment of the and on dry pulp: 10 kg/t of chlorine dioxide with a content of active chlorine 7 ha/t, 18 kg/t of calcium chloride based on the Ca2+. The final pH value at the application stage chlorine dioxide equal to 2.8. As SMS use the product Finnfix WRH from Noviant. The degree of substitution equal to 0.5, the molecular weight is 1·106. As an additive, giving strength, use Kenores XO that load of 15 kg/t of dry pulp bleached suspension of the fibrous mass. Strength characteristics of CMC-treated fibrous mass evaluated at different degrees of grinding (aboutSR). The grinding is carried out with the use of laboratory grinding machine PFI. The strength characteristics of the crushed pulp, treated with CMC, compared to the strength characteristics of the control of the crushed pulp, not processed SMS, and strength characteristics of the suspension mass, in which the TEXT is added after the stage of bleaching. The final whiteness analyzed cellulose is 90% (ISO), which is reached at the final stage of bleaching using chlorine dioxide.

Chart 1 shows that the strength of the paper in the wet state is significantly increased when adsorbirovannoi SMS at the final stage of processing pulp chlorine dioxide compared to vlagoperenosu paper, obtained with the addition of SMS in the original cellulose, or against whom the paper obtained without adding SMS. In this case, the increase of strength in the wet state obtained paper up to 65%.

Figure 2 presents a plot of relative strength in the wet state on the degree of grinding of the paper, obtained with adsorbed SMS to a final acid bleaching with chlorine dioxide, and adding SMS in the original cellulose paper production process, and control of pulp without addition of SMS. As can be seen from chart 2, the relative strength in the wet state significantly higher in the paper, obtained by adding SMS on stage acid bleaching with chlorine dioxide.

1. The modification of cellulose fibers, comprising obtaining a slurry weight of cellulosic fibers, adding a derivative of the pulp in the bleaching process these cellulose fibers, at least one stage of acid bleaching, where the pH of the suspension mass is in the range from about 1 to about 4 and the temperature is in the range of from about 30 to about 95°C.

2. The method according to claim 1, where the derivative of cellulose is added at the final stage of acid bleaching.

3. The method according to any one of claims 1 or 2, where the derivative of cellulose is carboximetilzellulozu.

4. The method according to l is the Boma one of claims 1 or 2, where the derivative of cellulose is a carboxymethyl cellulose.

5. The method according to claim 3 where the derivative of cellulose is a carboxymethyl cellulose.

6. The method according to any one of claims 1 or 2, where the final stage of acid bleaching is a stage bleaching using chlorine dioxide.

7. The method according to claim 3, where the final stage of acid bleaching is a stage bleaching using chlorine dioxide.

8. The method according to claim 4, where the final stage of acid bleaching is a stage bleaching using chlorine dioxide.

9. The method according to claim 1 or 2, where the derivative of cellulose is added in an amount of from about 0.5 to about 50 kg/ton dry cellulosic fibres.

10. The method according to claim 3, where the derivative of cellulose is added in an amount of from about 0.5 to about 50 kg/ton dry cellulosic fibres.

11. The method according to claim 4, where the derivative of cellulose is added in an amount of from about 0.5 to about 50 kg/ton dry cellulosic fibres.

12. The method according to claim 6, where the derivative of cellulose is added in an amount of from about 0.5 to about 50 kg/ton dry cellulosic fibres.

13. The method according to claim 1 or 2, where the content of the cellulose fibers in the suspension based on dry substance is in the range of from about 1 to about 50 wt.%.

14. The method according to claim 3, where the cellulose content of the filaments is in suspension based on dry substance is in the range of from about 1 to about 50 wt.%.

15. The method according to claim 4, where the content of the cellulose fibers in the suspension based on dry substance is in the range of from about 1 to about 50 wt.%.

16. The method according to claim 6, where the content of the cellulose fibers in the suspension based on dry substance is in the range of from about 1 to about 50 wt.%.

17. The method according to claim 9, where the content of the cellulose fibers in the suspension based on dry substance is in the range of from about 1 to about 50 wt.%.

18. The method according to claim 1 or 2, where later in the suspension of bleached fibrous mass is injected additive to increase the strength in the wet state.

19. The method according to claim 3, where later in the suspension of bleached fibrous mass is injected additive to increase the strength in the wet state.

20. The method according to claim 4, where later in the suspension of bleached fibrous mass is injected additive to increase the strength in the wet state.

21. The method according to claim 6, where later in the suspension of bleached fibrous mass is injected additive to increase the strength in the wet state.

22. The method according to claim 9, where later in the suspension of bleached fibrous mass is injected additive to increase the strength in the wet state.

23. The method according to item 13, where later in the suspension of bleached fibrous mass is injected additive to increase the strength in the wet state.

24. The method according to claim 1 and the 2, subsequently the suspension of bleached fibrous mass is injected additive to increase the strength in the dry state.

25. The method according to claim 3, where later in the suspension of bleached fibrous mass is injected additive to increase the strength in the dry state.

26. The method according to claim 4, where later in the suspension of bleached fibrous mass is injected additive to increase the strength in the dry state.

27. The method according to claim 6, where later in the suspension of bleached fibrous mass is injected additive to increase the strength in the dry state.

28. The method according to claim 9, where later in the suspension of bleached fibrous mass is injected additive to increase the strength in the dry state.

29. The method according to item 13, where later in the suspension of bleached fibrous mass is injected additive to increase the strength in the dry state.

30. The method according to p, where later in the suspension of bleached fibrous mass is injected additive to increase the strength in the dry state.

31. The method according to claim 1 or 2, where the final stage of bleaching is carried out at a pH value in the range of from about 2 to about 4.

32. The method according to claim 3, where the final stage of bleaching is carried out at a pH value in the range of from about 2 to about 4.

33. The method according to claim 4, where the final stage of bleaching is carried out at a pH value in the range of from about 2 to about 4.

34. The method according to claim 6 where the end with the adiya bleaching is carried out at a pH value in the range of from about 2 to about 4.

35. The method according to claim 9, where the final stage of bleaching is carried out at a pH value in the range of from about 2 to about 4.

36. The method according to item 13, where the final stage of bleaching is carried out at a pH value in the range of from about 2 to about 4.

37. The method according to p, where the final stage of bleaching is carried out at a pH value in the range of from about 2 to about 4.

38. The method according to paragraph 24, where the final stage of bleaching is carried out at a pH value in the range of from about 2 to about 4.

39. The method of producing paper comprising obtaining a suspension of bleached fibrous mass according to any one of claims 1 to 38, dehydration specified suspension of the fibrous mass on the grid, and forming paper from the specified dehydrated slurry of the fibrous mass.

40. The paper, which can be obtained by the method according to § 39.

41. The use of a derivative of cellulose as an additive to the suspension of cellulose fibers to be processed at the stage of acid bleaching at a pH value in the range of from about 1 to about 4 and at a temperature in the range of from about 30 to about 95°C.

42. The use of a derivative of cellulose in paragraph 41, where stage bleaching is a stage of acid chlorine dioxide bleaching.



 

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