JPS61179390A - Improvement in mechanical properties of chemical or semi-chemical bagasse pulp - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to a method for improving the mechanical properties of pitch-containing chemical or semi-chemical bagasse pulp.

BACKGROUND OF THE INVENTION Bagasse is a ligno-cellulosic material that generally contains significant amounts of pitch. Pitch is formed from cellulosic components, i.e. parenchyma (1) arenchila, which does not have a fibrous structure and cannot be used for paper production.

Before cooking for pulping, the bagasse is generally subjected to a mechanical refining pretreatment, the purpose of which is to remove a portion of the pitch it contains.

Chemicals and semi-chemicals manufactured from cellulosic materials
Chemical pulps, especially bagasse pulps, are commonly subjected to treatment with oxidizing agents to reduce their lignin content and improve their whiteness. These known methods are generally sequential processes, which are interspersed with several successive bleaching stages 1, possibly with washing, dilution and/or concentration stages. In order to reach the desired level of residual lignin and brightness, chemical and semi-chemical bagasse pulps are exposed to the oxidizing effect of chlorine in acidic medium, then this step is followed by an alkaline extraction step and hypochlorite in alkaline medium. An oxidation step with chlorate follows, thereby giving rise to the abbreviation CEH [PULP AND P
APERINTERNATIONAL), June 197
5, San Francisco (5anFranCiSCG
), A Inter Benzinger (HEINZBENZI)
HGER) rToday's bagasse technology J (TOda'
V'Sbagasse technology) 42
- pages 44 and 57 pages 44, last section and page 57;
Left column, lines 1-14] achieves the bleach-synthesized genin continuity. Other sequences utilizing chlorine dioxide (D stage) or hydrogen peroxide (Pff1 floor) have also been proposed.
OURNAL), Volume 40, August 1957, Atlanta (
Atlanta ) DO HINRICH
3) etc. “Sugar cane bagasse (5u
oarcane Bagasseas a Fibro
us Papjrmaking Material ＞
■Bleaching Hawaiian bagasse pulp
g of Hawaiian Bagasse Pu1p)
J, pp. 637-645, paragraphs 1, 3 and 4 and 1.
lines 0-18].

These known bleaching and delignification processes are not always able to give pulps with high brightness levels and good mechanical properties. Additionally, they use large amounts of chlorine chemicals, which are responsible for the dark color and polluting nature of the effluent.

U.S.-A-440404061 patent [J, J. Kale (
CAEL), International Paper Company (INTERt4ATIONAL PAPERCo)
] discloses a process for delignification and bleaching of lignocellulosic materials with peroxomonosulfuric acid or salts of this acid, which allows cellulose to be more easily separated from non-cellulosic materials (column 1, 50-56).
lines and lines 25-28). Among the ligno-cellulosic materials, bagasse is cited (column 2, line 61).

SUMMARY OF THE INVENTION The present invention overcomes the disadvantages of known methods by providing a new method for improving the mechanical properties of chemical and semi-chemical bagasse pulps containing a high proportion of pitch. whiteness while significantly reducing the coloration and contamination burden of the effluent.

To this end, the present invention relates to a method for improving the mechanical properties of chemical or semi-chemical bagasse pulp containing at least 25% by weight of pitch, according to which the pulp is treated with an oxidizing agent; The oxidizing agent is selected from persulfates and their salts.

According to the present invention, the term bagasse refers to the husks of cereals, sugar cane and stalks of plants other than wood, belonging to the monocotyledonous species such as bamboo, corn stalks, rushes and reeds, and maize. means a fibrous tube bundle. The invention is particularly applicable to crushed stalks of domestic sugar cane, which are produced after sugar extraction operations.

The method of the invention applies to all chemical or semi-chemical
Bagasse pulp, i.e. sodium sulfide in alkaline medium (kraft or sulfate cooking), sulfur dioxide or metal salts of sulfite in acidic medium (sulfite cooking), sulfite in neutral medium (neutral sulfite semi-chemical Steamed MatamaN
These chemical pulps have been subjected to a delignification treatment in the presence of chemicals such as (known as 5SG) and those semi-chemical pulps obtained by mechanical defibration followed by treatment with cold caustic soda.

The invention particularly relates to pulps with a high pitch content, such as pulps in which this content is between 25 and 40% and preferably between 30 and 40%.

According to the invention, the delignification and bleaching sequence of the pulp is initiated by treatment with an oxidizing agent selected from persulfates and their salts. In principle, all persulfates in liquid state or in aqueous or organic solution are suitable;
The same applies to all salts of these acids. In implementation,
Ammonium, alkali metal and alkaline earth metal salts of peroxymonosulfates and persulfates are preferred. Caroos! ! ! Peroxymonosulfuric acid, also known as peroxymonosulfuric acid, is preferred.

In the process according to the invention, the amount of oxidizing agent to be used depends, inter alia, on the nature of the bagasse chosen, on the refining pretreatment it undergoes, on the pulping method chosen, on the oxidizing agent chosen, on any subsequent bleaching sequences. It depends on a number of parameters including the stage and degree of whiteness desired. The oxidizing agent is generally used in an amount sufficient to obtain a high final brightness for the pulp, often greater than the ISO standard of 80 degrees at the end of a complete bleaching series. Good results are generally obtained by using Karlos acid in amounts between 0.1 and 8 g per 100 g of dry pulp. Most often it is between 0.5 and 5g/100g dry pulp.

The temperature at which the oxidizing agent treatment is carried out is not critical.

It generally ranges from 298 to 343K. The selection of the optimum value for the temperature depends on the possibilities of the equipment used. Moderate temperatures in the range of 298 to 313K are generally preferred.

In the process according to the invention, the consistency or weight content of the mixture formed from bagasse pulp and oxidizing agent is generally at least 2% and most often at least 3%. Generally it does not exceed 40% and most often 30%.

In the method of the invention, the treatment of the bagasse pulp with an oxidizing agent is carried out in the presence of additives such as acidic compounds or pH moderators such as buffers. The acidic compound can be sulfuric acid, hydrochloric acid, nitric acid or orthophosphoric acid. Sulfuric acid is preferred. Alkali metal or ammonia bicarbonates, alone or in mixtures with acidic compounds, can be chosen as EIH modifiers. The process of the invention is generally carried out in the presence of sulfuric acid. The amount of sulfuric acid is generally from 0.1 to 20% of the weight of the dry bagasse. With other additives, such as sequestering agents and stabilizers, surfactants, agents capable of protecting the cellulosic chains to prevent depolymerization, wetting agents, activators and corrosion inhibitors. It is also possible.

The length of treatment with an oxidizing agent can vary and depends on various factors, in particular the nature of the bagasse, the pulping method used, the oxidizing agent chosen and the operating temperature. In principle, there is no maximum limit to the length of treatment with oxidizing agents and
If care is taken to exceed the minimum time required for physicochemical equilibrium, which is often in the range of 50 to 80 minutes, e.g. if the existing equipment characteristics impose a residence time, the pulp It is possible to extend the treatment without damaging the Generally, the length of treatment with the oxidizing agent is from 15 to 150 minutes and most often from 60 to 105 minutes.

In a preferred embodiment of the method according to the invention, the oxidizing agent used is peroxymonosulfuric acid or Karlos' acid. In this embodiment of the method according to the invention, Karlos' acid is preferably used in the form of a solution.

The solvent is usually water. The amount of solvent is advantageously at least 0.1% and generally the bagasse pulp, solvent,
Not more than 99.5% of the total weight of the mixture consisting essentially of Karlos acid and any additives. If the solvent is water, it is used in an amount of at least 0.5% and most often at least 1% of the total weight of the mixture.

Generally the amount of water used does not exceed 95%, most often 90% and preferably 85% of the total weight of the mixture.

In this embodiment of the invention, treatment with Karlos acid is carried out at acidic or neutral pH within a wide range of pH values from 1 to 7.
Implemented under H. The selection of the particular pH value should be made as a function of the type of cooking to which the pulp has been subjected and as a function of the alkali or acid content of the pulp. Preferred E
The lH value is between 1 and 3.

In the process according to the invention, the treatment with oxidizing agents is chlorine in acidic medium (C stage Wi), caustic soda (E stage of alkaline extraction), sodium hypochlorite or calcium hypochlorite in alkaline medium (H step), followed by a conventional bleaching sequence using known bleaching agents for bleaching bagasse pulp such as hydrogen peroxide in an alkaline medium (P step) and chlorine dioxide in an acidic medium (D step). I can do it. CEH or CEHH sequences are generally preferred. The amount of drug used in each of these steps can vary.

They must be carefully adjusted as a function of the nature of the bagasse used and the whiteness goals required.

The application of pretreatment with oxidizing agents according to the method according to the invention often makes it possible to substantially reduce the amount of these agents, especially the amount of chlorine agents. The effect of this is a significant advantage of a reduction in the chloride ion content and organochlorine compound content of the effluent from the bleach plant and thus a significant reduction in environmental pollution.

Moreover, the process according to the invention allows the production of pulps with better brightness and which generally have better mechanical properties than those obtained by prior art processes. All other things being equal, it thus allows the use of bagasse with a higher residual pitch content, which reduces the cost of refining or depitching pretreatment. Bagasse with a residual pitch content of generally between 30 and 40% is most suitable.

The purpose of the following practical application examples is to illustrate the invention and is not intended to further limit its scope.

Examples 1R and 2R This is not according to the invention.

The initial whiteness is 37.6°ISO when steamed with lime.
Kappa index 39.6> and still 25 to 35% by weight
Chemical pulp made from sugarcane bagasse from Iraq containing pitch up to CEHH (Example 1R) or PCEH (Example 2R) under secondary working conditions subjected to four stages of conventional continuous bleaching. . The drug percentages are given relative to the dry pulp weight.

Example 1R Example 2R First Yurika: Consistency 3% 12% Time l! 1 1 hour 1.5 hours 2nd stage: Consistency 10% 3% Time 2 hours 1 hour Staff: Drugs NaC + 0.2% NaO 8,2% Active chlorine NaOH, 0,3% Temperature 313K Consistency 10 at 333 % 10% Time 3 hours 2 hours 4th stage: Drugs NaCl 0.1% NaC + 0.1.2% active chlorine Active chlorine NaOH, 0.2% NaOH, 0.2% Temperature 31
3K 313 Consistency 10% 10% Time 3 hours At the end of each of the two bleaching sequences, the pulp was evaluated as follows: K-0 Color: 1 according to standard 15O2470 Viscosity: Standard T
According to APPI T230 - Lignin content: Standard 5
Kappa index according to CAN C1:59 Drainage properties: Tensile strength and elongation at break according to French standard NFQ50-003: Standard l5O1924
- Tear strength: according to standard ISO 1974 - Bursting strength: according to standard ISO 2758 - Bending resistance: according to standard AS
First effluent color according to TM D643: NCASI method [National Co.
uncil of Air and Stream I
urovement), Guispil, Frotsugu (G
Ainsvillee, Florida), US
Chemical oxygen demand (COD) of the first effluent according to A: HACH method (
Bach Reactor Cooking COD>.

Results are reported in Table I.

The fence quality index was calculated as follows: 0.5 Ql-(T1.Bl) where TI and BI are the tear and burst indices, respectively.

Examples 3 to 6 According to the invention, the same bagasse pulp as used in Examples 1R and 2R was treated with an aqueous solution of Carl's acid in accordance with the method according to the invention, and then similar to Examples 1 and 2R. A similar CEH bleach sequence was applied in three stages. The working conditions were as follows: ! ■Betsuchodan Dan Otsu 56
Parv preparation 1% 12 12
12 12 hours, hours
1.5 1.5 1.5
1.51” (C) Consistency 1% 3 3
3 3 hours, hours
1 1 1 1 Second stage (E) Drug: NaOH,% 2 2
2 2 temperature, K 33
3 333 333 333 consistency 9
% 10 10
1G 10 hours, hours
2 2 2 2 3rd stage (H
) Drug: NaCl0. % active chlorine 0.6 G
, 15 0.2 2NaOH,%
1.5 0.03 0.04
0.3 temperature, K 313
313 313 313 consistency 1%
10 10 1
G 10 hours, hours
3 3 3 3 Table ■ is Example 1R
and presents the results of an evaluation carried out on pulps bleached according to a method similar to 2R. The designation CA represents treatment with Karlos' acid.

The results of the evaluation of the mechanical properties of pulps bleached using the method according to the invention (Examples 3-6) and those of pulps bleached according to the prior art sequence (Examples 1R and 2R) are Figure 2 illustrates the advantages of the method according to the invention. Moreover, if Example 6 is compared with Reference Example 1R, the pretreatment with Karlos acid consistent with the method according to the invention causes the last hypochlorite step in the alkaline medium to be omitted, and 6. It makes it possible to obtain a brightness higher by 5° ISO and to reduce the total active chlorine burden of the bleaching sequence from 8 to 6.6%, which represents a reduction of 17.5%. You will understand. Examples 3 and 4 also show that it is possible to obtain by the method according to the invention such as obtained by the reference CEHH series (Example 1R).

Claims (8)

[Claims] (1) A method for improving the mechanical properties of a chemical or semi-chemical bagasse pulp containing at least 25% by weight of pitch, characterized in that the pulp is treated with an oxidizing agent selected from persulfuric acid or its salts. How to do it. (2) The method according to claim (1), wherein the oxidizing agent is peroxymonosulfuric acid. (3) Claim No. (1) or (2) characterized in that lime-steamed chemical bagasse pulp is selected.
The method described in section. (4) Claims (1) to (3) characterized in that treatment with an oxidizing agent is followed by treatment with chlorine in an acidic medium.
) The method described in any one of the paragraphs. (5) Process according to claim 4, characterized in that the treatment with chlorine is followed by alkaline extraction with sodium hydroxide and subsequent treatment with sodium hypochlorite in an alkaline medium. (6) treatment with an oxidizing agent at a pH between 1 and 7;
Process according to any one of claims 1 to 5, characterized in that it is carried out at a temperature between 98 and 343 K. (7) according to one of claims 1 to 6, characterized in that the treatment with an oxidizing agent is carried out on a pulp with a consistency between 3 and 30%. Method. (8) Any one of claims (1) to (7), characterized in that the treatment with an oxidizing agent is carried out with an amount of oxidizing agent between 0.5 and 5 g/100 g dry pulp. 1
The method described in section.