DE2128723A1 - Process for bleaching wood pulp - Google Patents

Description

The invention relates to a method for pulping and bleaching wood chips and, more particularly, to a method for single-stage pulping and bleaching of wood chips, whereby high pulp yields are obtained.

Wood pulps can be divided into four groups. One mechanical pulp or ground pulp is made by mechanically breaking up the wood in the presence of water produced, generally by the fact that the debarked logs are pressed against a grinding wheel, which is with rotates at high speeds. The pulp yield is very high and is generally between 90 and 95%. Chemical-mechanical pulps are produced by a very mild chemical Treatment (whereby the wood is softened without significant deforestation) followed by a mechanical one Get crushing,

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Fulpen yields in the range of 80 to 95% are achieved. Semi-chemical pulps are produced under somewhat more severe cooking conditions (with partial deforestation taking place) and received a subsequent defibration with a mechanical treatment. The pulp yields are in the range from 55 to 80%. Chemical pulps are made by a sharp A chemical treatment achieved in which the lignin present between the fibers is removed, so that the Separate fibers from one another without mechanical treatment or using only a slight mechanical treatment can »those obtained in yields of about 42 to 58% Pulps must be heavily bleached as the chemical treatment often results in a pulp that is considerably darker is than the color of the original schnitzel. Chemical pulps also contain high molecular weight lignin fractions, which cannot be easily removed. The chemical pulping can be further converted into the alkaline pulping process (the Kraft process, at which sodium hydroxide and sodium sulfide is used) and divided into the acid pulp method. The chemical pulping processes result in high strength Papers; however, the pulp yield is low and besides . intensive bleaching is required. For a full " constant bleaching usually requires at least four separate stages. At the first stage will Chlorine is used, after which the pulp is extracted with an alkaline solution. The next stage becomes hypochlorite used. The final bleaching usually uses chlorine dioxide. In certain cases one or more of these stages are repeated.

Recently, another chemical pulping process has become known which uses peracetic acid in the first stage and sodium hydroxide in the second stage. This process is disclosed in Canadian Patents 814,309 and

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S14-310 described. The pulp produced in this way eats unbleached and generally darker than the original wood chips, so that intensive bleaching is necessary, which the same pollution problems as the Kraft method poses.

In US Pat. No. 3,428,520, there is a step-by-step process described in which an organic acidic peroxy compound in a gas phase cooking stage at a pH of about 2.0 is used. This is followed by an alkaline extraction stage. This gives an unbleached semi-chemical pulp which is also heavily bleached must become, which poses the same pollution problems.

The known processes suffer from common and increasingly serious problems, namely that of the pulp plants heavily pollute the surrounding atmosphere and, in addition, the wastewater contaminates the groundwater and that creates rivers. It's not just scientist and ecologists but also the population have realized that the contaminants of all kinds are controlled and need to be eliminated. The power process is carried out in a so-called "closed system", but in reality it is not a closed system at all. For example, when the lignin waste is incinerated Released fairly large amounts of hydrogen sulfide, methyl mercaptan and dimethyl sulfide into the atmosphere. Not only are these compounds highly toxic, they are also the most common smelly known compounds. In addition, the wastewater from the bleaching stage of the Kraft process contains chlorides, and chlorinated compounds, which are extremely toxic and undesirable in rivers and groundwater »In addition are the other compounds used, such as chlorine

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dioxide, highly toxic and explosive and require a professional Handling with highly specialized devices *

In the sulphite processes (chemical-mechanical and semi-chemical Methods) are contaminated with lignosulfonic acids, sulfite and sulfur dioxide. The Ligninsulfon " acids that are discharged from the pulp plants into rivers are biochemically hard, i.e. they cannot be bacterial Dismantling are accessible. In addition, the effects of sulfur dioxide in the atmosphere cannot be reduced will.

In the process according to the invention, pulp is obtained in high yield. The yield is comparable to that obtained with semi-chemical pulping. However, this yield is considerably greater than can be achieved with the Kraft process. Dae process of the invention does not degrade the color during the pulping * The pulp obtained is not darker than the color of the wood chips used as Auegangsmaterial, and for this reason, an intensive bleaching is avoided, which is known for other processes, in particular the kraft process, r characteristic. The alkaline tertiary butyl hydroperoxide process of the present invention achieves significant deforestation while protecting the cellulose and avoiding color formation. The paper made from this pulp therefore has better strength than paper obtained by mechanical or semi-chemical processes. Its strength is only slightly lower than the strength of a paper obtained by the Kraft process.

However, the method according to the invention has another important advantage, namely that it does not have any

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Poses pollution problems associated with the previous chemical processes discussed above. In addition, it does not pose any new or dangerous pollution problems. The tert-butyl hydroperoxide is converted into tert-butyl alcohol, which only gives water and carbon dioxide _; when burned with the lignin. E? is so highly combustible that a complete combustion is achieved, whereby not even small amounts of carbon monoxide are produced. Alternatively, tert-butyl alcohol can be obtained as a valuable chemical compound.

The process of the present invention also gives significant bleaching, with the result that there is no need to use bleaching agents which pose contamination problems. The sodium hydroxide used in the process according to the invention is recovered in the same way as in the Kraft process, ie that it is converted into sodium carbonate during the lignin combustion ^: which is reacted with unslaked lime, the sodium hydroxide being regenerated and insoluble potassium carbonate, a non- contaminating chemical compound. ,

The advantage of the present pulp process over the known processes is therefore in the production of bucket J semi-chemical pulp in high yield by an alkaline ^! Pulp process in which no or only a slight further ^; Bleaching is needed. The yields are comparable to the yields of the mechanical and semi-chemical processes, and they are better than those of the force process. The process does not degrade the color of the pulp and, moreover, the paper made from the pulp is stronger than paper made from mechanical or

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chemical pulps. The strength is just a little worse than a Kraft paper. Finally, the method according to the invention is the only method in which the pollution of the environment is practically completely avoided.

According to the invention, therefore, a process for pulping and bleaching wood chips in a single step is proposed, which is carried out by bringing the chips into contact with a mixture of tert-butyl hydroperoxide and sodium hydroxide in an aqueous solution, the temperature in the range of 0-130 ⁰ C and the pressure between atmospheric pressure and the autogenous pressure generated by the reaction temperature! The amount of the hydroperoxide is preferably in the range from 2% by weight to 40% by weight, based on the weight of the dry chips. The amount of sodium hydroxide is chosen such that the weight ratio of tert-butyl hydroperoxide to sodium hydroxide is in the range from 4: 1 to 1: 3, with a range from 2: 1 to 1: 2 being preferred.

Preferably, the digestion is carried out at a temperature in the range of 60-130 ⁰ C. A particularly preferred range ist.80-110 ⁰ C. The mentioned temperatures can be used Digerierungezeiten of 15 min (for the higher temperature) to 120 minutes (for the lower temperatures). The digestion can, however, also be carried out at room temperature with a high efficiency in terms of the utilization of the chemicals, although longer time is of course required. The reaction is therefore time / temperature-dependent, which means that shorter reaction times can be used at higher temperatures, whereas longer reaction times are required at lower temperatures.

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rich from 1: 1 to 3: 1.

The aim of the invention is therefore to provide a method for pulping Create wood chips in a single step.

Another object of the invention is to provide a method for alkaline pulping of wood chips in a single Stage, whereby a pulp is obtained, the color of which is as good or even better than that of the original schnitzel.

Another object of the invention is to provide a method for the one-step alkaline pulping of wood chips create, whereby the pulp is obtained in high yield.

Another object of the invention is to provide a method of pulping wood chips which is practical completely avoids both atmospheric pollution and water pollution.

Another aim of the invention is to provide a method * for create single-stage pulping of wood chips, being an aqueous mixture of sodium hydroxide and tert-butyl hydroperoxide is used.

Further goals can be found in the description of the preferred. Embodiments and the claims.

The method according to the invention can be used with softwood (gymnosperm plants) as well as for hardwood (angiosperm plants). Of the soft woods are the coniferen brewing jaar, such as cedar, fir, hemlock, pine and duty. Examples of hardwoods by the invention Processes can be peened and bleached,

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are alder, aspen, beech, birch, rubber tree, oak and the like.

The inventive method can be performed by those in the art known batch or continuous processes are carried out. The one obtained in the treatment step The liquid contains some unreacted tert-butyl ~ hydroperoxide and also tert-butyl alcohol as well as water-soluble Lignin derivatives. The tert-butyl hydroperoxide and the tert-butyl alcohol can be recovered by distillation and the tert-butyl hydroperoxide recycled to the process will. The tert-butyl alcohol can be sold as a chemical are, and the lignin derivatives dissolved in water can be treated by known methods, wherein a large numbers of valuable connections can be made. In this regard, the present procedure is superior to the force method, since the latter method the lignin is obtained in the form of sulfur derivatives, which are generally also polymerized, so that it is almost impossible is to gain by-products. Instead, the lignin derivatives are simply burned. This of course leads to a pollution of the atmosphere.

In the last few years, tert-butyl hydroperoxide has been used on a large scale Quantities have become accessible. The main method of production is based on the oxidation of Isobutane. This process gives an oxidation product from which tert-butyl hydroperoxide can be obtained in pure form can. The oxidation product can also be used itself, since it consists of a mixture of hydroperoxide and tert-butyl alcohol consists. Dae has tert-butyl hydroperoxide compared to other organic peroid compounds, such as e.g. pereacetic acid and the like, the advantage that it stable and easily under the application of the usual precautionary

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measures can be handled and shipped. In contrast, other organic peroxide compounds are extremely unstable « which makes it difficult to move them, as they may explode.

The hydroperoxide used in the process according to the invention is an ordinary technical product. The procedure will using an aqueous solution of the tert-butyl hydroperoxide and the hydroxide, so that there are no handling problems and no special auxiliary solvents or special devices are necessary «

The digestion of the wood chips in the aqueous solution of tert-butyl hydroperoxide and sodium hydroxide may at temperatures ranging from about 0 ⁰ C to about 150 ^e C, preferably about 60 ° 0 to about 130 ⁰ O, especially from about 80 to 110 ° 0, performed . If so desired. " To achieve maximum utilization of the chemicals, digestion is then carried out at room temperature. At this temperature, however,. Digestion tents of a few hours or days may be required, while at higher temperatures times of about 15 minutes (at temperatures at the high end of the range) to 2 hours or longer (at temperatures at the low end of the range) can be used. The digestion is a reaction with a temperature / temperature dependence. Pressures from atmospheric to the autogenous pressure of the reaction can be used.

The concentration of the hydroperoxide can range from 2 % by weight to 40% by weight based on the weight of the dry chips, although higher concentrations can also be used. A range of 10 to 35 wt%, based on the weight of the dry chips, has been found to be completely satisfactory for most types of wood

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proven »The amount of sodium hydroxide used is in Relationship with the amount of hydroperoxide used, such that the weight ratio of tart ^ butyl hydroperoxide to Sodium hydroxide is in the range of about 4: 1 to 1: 3, with a range of about 2.1 to 1: 2 being preferred. The weight ratio of total liquid to dry wood is preferably in the range of about 1: 1 to 3: 1, although higher or lower ratios for special types of wood and special digestion conditions can be used.

The above mentioned conditions are quite general to the various types of wood chips mentioned above were applicable, but it should be noted that, as is well known in the art, various Species of wood can be pumped more easily than others and that, accordingly, the conditions range from mild to sharp can be changed to suit each to be pulped and match the bleaching type of wood.

In the following examples, the process according to the invention is compared with other pulping and bleaching processes, so that the advantages of the method according to the invention can be better understood.

The most important process is the Kraft process, as two thirds of all wood pulps are made by this process will. Most of the lignin and heml celluloses are converted into a water-soluble form in the digestion stage, whereby an aqueous sodium hydroxide / Sodium sulfide solution is used to cook the wood chips for several hours at 100-200 ° 0. Here remains

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the cellulose fraction (45 to 55% of the original wood) in the form of a heavily discolored pulp.

The main advantage of the Kraft process is that a very strong pulp is obtained, with the lignin fraction is burned to provide the energy for the process. The disadvantage of the Kraft method are the contamination problems, resulting from digestion, incineration and bleaching, as described above. Around To avoid the disadvantages of the Kraft process, processes using oxidizing agents have been developed such as chlorine dioxide, sodium chloride, hydrogen peroxide and peracetic acid. The advantage of this process is higher pulp yields and less contamination. They deliver, however, no paper with an adequate quality high quality at an economical price. Accordingly, comparisons were also made in the following examples between the Kraft process and the peracetic acid process on the one hand and the method according to the invention on the other hand employed.

The raw material for the following examples was made from two peeled aspen trunks, which are put into a 96.5 cm Carthage chipper were chopped with 4 knives into schnitzel of about 16 cubic meters. The schnitzel were on a Sweeo sieve sifted, and large chunks and fibers were made removed with the 2 ~ stitches ~ fraction. The failed ones Schnitzel was further processed in a 12 inch Sprout-Wildron refiner crushed, the one with B-2975-A-Stlftplatten, which were set to a gap width of almost zero, was equipped. After this comminution, the chips were passed through a Sweco sieve, and the fraction that passed through a 4-mesh sieve

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una was retained by a 10 mesh screen used in pulp infestations. These chips were approximately 1.6 to 2.5 mm in diameter and a length of about 16 mm.

The solutions for treating the chips were prepared by adding the required weights of an aqueous 10% (weight) tert-butyl hydroperoxide solution and one 20% (weight) sodium hydroxide solution mixed and then || with water to the specified liquid / wood ratio have been diluted.

The cutlets to be cooked were placed on a polyethylene plate and turned while they calculated with one Amount of the appropriate solutions were splashed to match the various liquid compositions used to achieve. After being splashed, the chips were placed in containers with a capacity of approximately 400 ml transferred. Because of the relatively low liquid / wood ratio, there was practically no free one Liquid present. The containers were sealed and immersed in an oil bath, the temperature of which was controlled became. The oil bath was preheated sufficiently above the selected temperature so that the heat flow in the Container caused the temperature to drop to the desired reaction temperature, which took about 3 minutes. The cooking time included 3 minutes for heating the container to reaction temperature. At the end of the response time were the container removed and cooled in cold water. Known amounts of water were added to facilitate removal of the product from the containers. The schnitzel and the diluted used liquid were overnight at room temperature and at a

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Allowed to cool before the consistency of about 12% Liquid was withdrawn for pH determination. For the yield and lignin determinations, the were boiled Schnitzel washed several times in warm distilled water, soaking for 1 to 2 hours each time, until the piltrate had a pH of 7-7 »5 and was clear.

Klason lignin analyzes were carried out by the method of the "Institute of Paper Chemistry ". The Hr * 428 method was used, which essentially consists of a modification of the TAPPI standard procedure O? 222 consists, where the difference was that the precipitate was on fiberglass filters and was not collected in crucibles.

In the examples below are the cooking dates and the baten of the products are also specified.

Various attempts have been as described above carried out to determine the yield of pulp and to determine the amount of residual lignin in the pulp, wherein a reaction temperature of 100 ⁰ C was used, but the other Eeaktionsbedingungen were changed. The klasson ligain content of the starting pulp was 21 Gev / «-%. The conditions and results are given in Table I below.

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Tabel I. 2 3 4th 5 6th 7th _8th 1 18th 15.3 15.5 0 0 15.3 15.3 18th 0 8th 16 8th 16 16 16 O 0, O O 0 0 0 0 4th 1.2: 1 2: 1 2.4s 1 2: 1 2: 1 2.4: 1 2.4: 1 1.2: 1 60 60 60 60 60 30th 15th 60 5.3 9.3 12.7 11.6 13th 12.7 13th 4.3 96 89 ^b 76 * S4 ^C 76 ^C 79 ^b 96 21st 18th 14th 21st 21st 15th 18th 21st 4th 25th 49 19th 20th 43 30th 4th

Test number t-butyl hydroperoxide, wt - ~% ^a sodium hydroxide, wt .-% ^a acetic acid, wt. -% liquid / EoIz weight ratio

° Since in the bathroom, min ta

Pulp yield, wt% Elason-Lignisi, Ge «» -% of the pulp

', d Elason-Lignin eatferat, Gew # - ^ r ^-

^a Percentage, extracted on an oven-dry wood basis, unless otherwise stated *

^b product at least as light as the color of the schnitzel; ^c Product darkened to leather-colored i based on the Klason lignin content of the schnitzel, 21% by weight.

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In order to understand the relationship between the pulp yield and the weight percent Klason lignin on a dry pulp basis and the weight percent Klason lignin removed, an explanation of these determinations is necessary are removed as contaminant in the liquid because the pulp yield is 76%. Since the lignin content of the pulp was 14%, there is 10.7 g of lignin in the pulp and 10.4 g of lignin in the solids of the liquid. 10.7 g divided by 21 g χ 100 then gives 51% of the original lignin in the pulp and accordingly a removal of 49% of the original lignin. Experiments 1 and 2, in which no sodium hydroxide was used, showed that no substantial deforestation had been achieved. Experiments 4 and 7 show a high degree of deforestation and, in addition, an excellent color of the deforested pulp. Runs 5 and 5 show that in the absence of tert-butyl hydroperoxide the pulp was very poor in color and deforestation was poor.

Example 2

There were further tests at higher temperatures than in Example 1 and under different pH conditions, i.e. with different amounts of sodium hydroxide. Here, too, the pulp yield and the amount of in lignin remaining in the pulp is determined. The results of these tests are given in Table II.

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Trial number Tabel 9 10 II 11 12th 13th 14th 15th 16 Bath temperature ⁰ C 130 130 130 110 110 110 110 110 rs
t-butyl hydroperoxide, wt .-% 20th 20th 20th 20th 20th 20th 20th 20th Sodium hydroxide,% by weight ^a 16 9 0 16 16 16 9 9 HCl concentration? & ^A 0 0 3.0 0 0 0 0 0 Liquid / wood weight
relationship 2s 1 2: 1 2: 1 2: 1 2: 1 2: 1 2: 1 2: 1 Time iff bathroom, min 15th 30th 60 30th 60 90 60 90 OO Final pH 10.6 2.7 12.0 11.5 11.3 8.6 8.5 α »
tr » Pulp yield, Qe ^ "-% 83 ^b 72 ^C 73 ^b 71 ^b 71 85 " 82 ^b - » Klasoii lignin,% by weight of
Falpe 13th 16 nb 13th 13th 13th 16 16 00
Ö Elason lignin removed
Weight -Φ 53 36 nb 56 56 57 37 38

^a Percentage based on oven-dry Holss, unless otherwise stated ^

b f °

Product with color of the schnitzel; —A

c ^ ⁰

dark brown product; CO

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based on the tClason lignin content of the schnitzel, 21% by weight; ¹ ^

^nb not determined.

These experiments show that the pulp yield and the lignin removal are not greatly influenced by the reaction time. They do, however, show that more lignin is removed if the ratio of mitrium hydroxide to tert-butyl hydroperoscide is relatively high. Experiment 11 shows that no sodium hydroxide is used is used, even under the most favorable conditions the product has a dark brown Fs: ebe. .This product v / ar obviously not a product ^T wis it according to the invention is obtained. This result confirms the results of example 1 in tests 1 and 2, with no deforestation taking place either.

A further series of tests was carried out to investigate the influence of temperature and reduced amounts of tert-butyl hydroperoxide to show at the higher pH ranges.

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Test number bath temperature, ⁰ C t-butyl hydroperoxide, wt. Im ι rri Uishydroxid, wt.% Liquid / wood weight ratio

2 time in the bathroom, min Εηά-ρΗ,
Yield,%

KIa s on-lignin, wt -.% Of pulp

Klason-LignxB, removed ,

Tabel III 19th 20th 21st 22nd 17th 18th 110 130 100 100 100 100 15th 15th 10 10 0 15.3 8th 8th 12th 12th 8th 8th 2: 1 2: 1 2.4: 1 2.4: 1 2: 1. ^ »■ *?
GZ, «I. 60 60 30th 60 60 60 8.7 7.9 12.4 12.2 11.6 9.6 86 ^C 85 ^d 85 ° 79 ^d 84 ^b 89 ^C 17th 18th 16 16 21st 18th

19th

25th

30 27

37

40

Percentage based on oven-dry wood base, unless otherwise stated $ brown colored productj .

Product was similarly brightly colored as the schnitzel; Straw-colored product, a little darker than the schnitzel4 based on the Klason content of the schnitzel, 21 wt .- #.

den Reimlt £ tt '* n cvjr it at le 111 s- ^ igt attempt. Ι? · »That in Absence of tert-ButjO-hydroparoxide, the product obtained s is a brown colored material which is heavily bleached weraön would * In addition, there is practically no Enthol.r-itag hurry ?. Experiment 21 shows a high yield with good color and good color

U.N. ^In order to identify the pulps according to the invention, two pulps with the designation "5""and" HP "were produced by Kocb .. in the sections shown in Table IV and additional mechanical defibration, as described here. Vf3-rd. The Pxilpe S was only made with alkaline liquid. The HP pulp contained 10% tert-butylhydric operoxide in a similar liquid. They served f * LSS base by- comparison with other Pulpenc In Table IV, the data of a hand-made paper are _given%, the film obtained from a normal laboratory Espenkraftpulpe produced and from an unbleached ₅ in high yield semi-chemical Espenpulpo (designation HYSC) was made before. This latter pulp was produced with an existing technical mill. The material had been obtained from the first haff inator of the system after 30 minutes at -9 ° 0 with a yield of approximately 90%. These two pulps, as well as pulps S and HP, were beaten in a Valley beater.

109885/1 180 ORIGINAL BATHROOM

To produce the Ριϋχ> βη S \ w.ö. HP, who the lot Tabel3e Tv an, -given hand-head properties bassaBea ^ v / ur ^ aa leads the cooked schnitzel with the liquid through a 9''j5 cm Bauer-185 "" Doppeli3clieibenraffixiator Mndurclig. The Bauer-Ifeschi was heated with live steam before use and when the schnitzel was chopped into a coarse pulp ©. The coarse pulps from the Buuer-Maachine were diluted with water to a consistency of approximately 5% and passed through a 5 cm Sprout-Valdrcm Lahor refiner. The product was then diluted to a consistency of 3% and passed through the same f-tesehiua. Each pulj-.e was drained and grown in a centrifuge *

All four pulps vrardoD Im Yailejf-Schläger geic; -lß 'J'ij? PI-8tan (äpdinethode T 2CO ts-66 geacb

Hana-scooped papiexevnirden from aiii -? * A: cei pulp-n according to ΤΑΡΓΙ standard method T 205 πι ~ ί56 produced. The paper density, the hot length, the I-k-ret factor and the Elmendor-f egg cracking factor were determined according to TaFPI «standard method T 220 m ~ 60 bestisinit.

The tensile energy boron pticneE were determined according to the TUPT.-etarda.rcmethode T 4-94- su ~ 64- messsE ..

To determine the tear length uiid the Zussnerc.i.eahsorptiojQ became a Tlechmodell © inee I / iFtron test devices used .. The initial baking distance is 10.4 cm, the Width of the test gap 2.3 cm and the Ki'ouEikopfgsschv speed 2.5 cm / min.

The results of the testing of the hand creature papers Bi shown in Table IV

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Table IV HP S. 100 100 10 0 12th 12th 2.4: 1 2.4: 1 35 35 81 85 16 21st 38 17th

of the pulp iFZSC S HP Kraft

3adtesiperatüx-, ⁰ C t-3utylhydroperoxid, Gew. ~% ^A

• pt

Sodium hydroxide, wt.%

Liquid / wood weight ratio

_ ^ Time in the bathroom, min

° Final pH 'U ₁ O ' \ eL, * ±

oo yield, wt. -% 90 85 81 50 ^ro

tn Klason lignin, Gevi .-% \ the pulp

2 ^ Klason lignin removes ₀ % by weight

° Properties of the

handmade paper 0.55 0.60 0.55 0.60 0.65 0.55 0.60 0.65 0.70 0.60 0.65 0.70 0.75 Density /

Impact time, min tear length _> J ₃₁₁

Tensile energy absorption g . cta / cm ^

Bursting factor Tear factor (Elmendorf)

5 19th 6th 17th 34 3 19th 31 43 0 5 11 18th N) 5.5 6.2 4.2 5.8 7.4 4.3 6.1 7.7 9.0 5.7 7.1 8.4 9.5 —A
ro 40 44 25th 39 52 24 38 56 75 29 50 70 91 00
-J K)
OJ) 26th 3 ^ 20th 26th 32 18th 28 37 45 21st 32 42 52 49 54 64 58 53 65 58 53 49 59 69 74 74 oven-dry Hdz base unless nothing other specified.

The tear length for the pulp HP was found to be very good. she Covered a much larger area than for the HYBC pulp and also, a wider area than for the S pulp. The tear length range from 4000-9000 m for an aspen pulp (Pulp HP) obtained in 81% yield is the same as it with a spruce pulp obtained in 82% yield is achieved (see Hydholm, pulping Processes, page 284, New York, Interscience 1965).

The tensile energy absorption properties of the handmade Papers made from Pulp HP are also very good. The egg tear resistance of the pulp HP is in comparison to the other pulps at relatively low sheet densities high. These results show that the inventive Process papers with high quality can be obtained, the qualities at least equal to or better than with the semi-chemical pulp papers obtained in high yield and only slightly inferior to the Kraft papers is.

Example 5

Two attempts were made to avoid cooking with tert-butyl hydroperoxide and compare with peracetic acid. As indicated in the prior art paper above Peracetic acid and alkali have been proposed for pulping hardwoods such as poplar in two stages . Tim to determine whether peracetic acid and tert-butyl hydroperoxide are interchangeable in such procedures, the two-stage experiments listed in Table V are specified.

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To carry out these experiments, small schnitzels were sprayed with the appropriate amount of peracetic acid and cooked according to the procedures described. To produce pulps suitable for hand-scooped piping, the cooked schnitzel and the liquid from two containers (40 g oven-dried schnitzel per container) were diluted to M- 1 with distilled water and then processed into pulp using a Sprout-Maldron MaBChine. The pulps were collected, washed with deionized water, thickened, diluted to 10 liters with deionized water and then sieved to prepare pulp suitable for making hand-scooped papers mechanical energy required. The hand-cropped papers were made and tested according to the TAPPI methods above. The same pulps were tested for their GE brightness according to TAPPI standard method T 217 m-40 and 216 iü-59.

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Table V

Trial number

I. Reaction with oxidizing agent

reagent

Bath temperature, ⁰ C amount of oxidizing agent,

% By weight of the wood liquid / wood weight ratio

Time in bath, min initial pH of the liquid

II. Reaction with alkali

Bath temperature, ⁰ G

Sodium hydroxide, weight percent of the wood

Liquid / wood weight ratio Time in bath, min yield,%

III. Comminution to pulp

material remaining on the sieve,

% By weight of the pulp

IV. Properties of pulp and handmade papers

Kappa number

approximate Elason lignin, ~% by weight of the pulp GE brightness,

Density of the paper, g / earö 0.54

■ Tear length, m 4700

* Calculated using the Klason lignin diet method T 236 m-60 specified.

24

t-butylhydroxide
95 Peracetic acid
95 8.8
2.2: 1
60
4.5 8.8
2.2: 1
60
4.5 95
9.8
7: 1
60
85 95
9.8
7: 1
60
77

92 14

0.59 Γ?

^ o

Kappa number χ 0.15, as in TAPPI-Stana = rd ~ ^fs o

~ 25 -

From this comparison it can be seen that tert-butyl hydroperoxide Wood is not deforested under these conditions because the pulp has essentially the same amount of lignin as that Contains original schnitzel. The tear length of the handmade papers was inferior, and therefore it is clear tert-butyl hydroperoxide no equivalent to peracetic acid. Eventually occurs in the two-step treatment process neither with tert-butyl hydroperoxide nor with peracetic acid does not bleach.

Example 6

50 g of poplar wood chips (15 mm), which corresponds to 40 g of oven-dried material, were slowly stirred for 3.5 hours at 85 ° C. in a round-bottom flask together with 20 g of t-butyl hydroperoxide, 8.0 g of sodium hydroxide and 224 g of water. The boiling solution and the schnitzel were slightly yellow in color. The schnitzels were soft and easily parted. After treatment in a Waring mixer with 300 ml of water for 20 seconds and after adjusting the pH to 6.5 by adding 8.0 ml of 10% sodium bisulfite, the pulp was fused, washed several times with water and dried in the oven. The handmade paper weighed 25.6 g, which is 64% of the original schnitzel. The photovolt brightness of the dried handmade paper was 86. For comparison, a CEH force has a value of 79 and a CEHD force has such a value of 9Λ .

Analysis of the pulp for lignin gave an average value of 9.3% by weight of Klason lignin, based on the 64% yield, and a lignin content of 19% of the original Cutlet. So two thirds of the lignin was there removed.

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A parallel experiment, without tert-butyl hydroperoxide, i.e. one Digestion with aqueous sodium hydroxide gave strong yellow colored chips with no physical change Chip structure, i.e. no fiber formation.

In relation to the lignin removal, the appearance of one of it handmade paper and microscopic examination, the product must be classified as light-colored semi-chemical pulp will.

Example 7

Using the conditions described in Example 6, 25 g (corresponding to 20.0 g of oven-dried material) Poplar chips treated with 100 g of a solution containing 10% tert-butyl hydroperoxide and 4% sodium hydroxide » This procedure was repeated for a total of 4 attempts. The filtered solutions from each of the four experiments were on unreacted tert-butyl hydroperoxide and Titrated sodium hydroxide. A total of 5-6 g of tert-butyl hydroperoxide were obtained and 5.6 g of sodium hydroxide consumed.

Handmade paper weighed 10.0 g (oven dried) and had a photovolt rating of 86.

Example 8

Similar results were obtained with wood chips of other types, such as: incense pine, silver fir, light oak, Black fir, hot maple and red oak. All of these wood species have been bleached and lignin removed obtain.

109885/1 180

~ 27 -

Example 9

To show that room temperature treatments are effective, 10 g of aspen wood chips were left to stand at room temperature for one week with an aqueous solution containing 10% by weight of tert-butyl hydroperoxide and 4% by weight of sodium hydroxide t * 50 g of solution i & 10 g oven-dry schnitzel).

The chips were separated and washed with water and then sodium bisulfite was added to pH 6.5 added. After 1 hour treatment in a Hobart mixer, the pulp was converted into a handmade paper with a Weight of 7.2 g (oven dried) and with a photovolt brightness processed by 76 * For comparison, CJSH strength had a value of 79

From the above description and examples it can be seen that the use of tert-butyl hydroperoxide for for the first time a practical process for alkaline pulping without excessive carbohydrate loss and without color formation leads. The process is a practical measure, a color improvement over the original To achieve wood color during pulping. This process results in a complete with a simple re-bleaching bleached merchantable material. The product of the present invention has been found to be a light semi-chemical pulp that has one strength and another physical Has properties that are only slightly worse than Kraft pulp. Bas method according to the invention has numerous advantages over the eraft process because the present process has a high yield of pulp, but not the complicated and expensive one Bleaching must be used, as is required in the Kraft pulp.

109885/1180

Finally, the inventive method of pulping and bleaching eliminates completely eliminates the pollution problems of sulfur pulping (the Kraft or Sulphite process) as well as the pollution problems associated with the one used there Ohlor bleaching processes are linked.

109886/1180

Claims (4)

Claims Process for pulping and bleaching wood chips by treatment with sodium hydroxide, characterized in that the chips are treated in a single stage with a mixture of tert-butyl hydroperoxide and sodium hydroxide in an aqueous solution, the temperature being in the range of 0-15O ⁰ O and the pressure is in the range from atmospheric pressure to the autogenous pressure of the reaction temperature .. 2. The method according to claim 1, characterized in that the temperature is in the range of 60-13O ⁰ O. 3. The method according to claim 1 or 2, characterized in that the concentration of the hydroperoxide from 2 to 40 % By weight, based on the weight of the dry schnitzel, and the ratio of hydroperoxide to sodium hydroxide ranges from about 4: 1 to 1: 3. 4. The method according to claim 1, characterized in that the weight ratio of total liquid to dry wood is in the range of about 1: 1 to 3: 1. 109885/1180 ORfGfNAL INSPECTED