ACCELERATED PULPING PROCESS

This invention relates to an iinproved process of breaking the lignin bond of fibrous materials in a form ranging from that of a moderately diges ed product feed to pulps that can be utilized as chemical or semi-cheπiical pulp for packaging papers and boards, bleachable pulps for white papers, highly purified pulp for dissolving pulp and to simpiy develop surface Tjinbonded lignin on fibrous structures to act as a binder.

_Thε invention relates to a -ignin nitration pulping process in v/hich the nitration can be carried out either in an acid or alkaline solution the time of v/hich is substantially shor ened by the inclusive use of aluininium compounds.

This invention also relates to a pulping process in v/hich theligneous conponents extracted fron ligno-cellulose raw material is recombineά 'ith the pulped fibers to provide a ded streng h characteristics for packaging papers anά paperboarάs or to act as a binder for defibered, in natural or se i-pulped state ligno-cellulosic structures.

The use of the inherent flexibili y of the process ti e, temperature and cheπiical concentrations perinits controlled delignification and defibering to produce aniπal feed, building board, packaging board and paper, bleached papers and dissolvin pulp..

The potential use of nitrate containing cheπicals, specifically nitric acid, as a specific pulping agεnt for cellulosic structures has been recogniεeά for r.ar.y years. the processes varied v/iάely in time and acid concentration and v/ere -nostly applied to the very easil;/ pulped fibrous structure such as straw or slivered v/ood or h^.rdvvoods. The processes depεnded on partial nitration, final oxidation anά subse uent hydrolΥsis of the lignin structure - consuπυtion w s

high and the fiber χ.roduced had brittle characteristics .

In such a process producing a chemical type pulp ₃ recovery of c emical reπains unsolved.

It appears that pulping processes using nitric aci have never been commercially successful . The followin exGerp from pat ents granted or suggested processes on easily pulped fibrous materials are indicative of the scope and problems ( sometimes hazardous) involved in such processes here high acid concentrations and usage with lengthy process times make comπercial practice unworkable and uneconomic with no concεiv advantages over present day convenxional processes .

Cascy - Puln & Paoer , Vol . I

Nitric Acid Puloin of Poolar V ood ^~ a ^{^} e n " e e

Ttτ . 'VIUSS Hiles ^~ §ö oϊ ecnnx

Acid Concentration (#) 6 8 { Time of Di gestion ( hours) 3 9 1. 5 Temper ture ( °C ) SO 100

ITitric Acid Puloing of V/ood V afe s ( 1/100 inch t Acid Concentration (jo) 42

Acid Temperature ( C) 63

Acid Consu ption/ Ton Pulp 15

Kitric Acid Puloinπ: of Baεasse

Acid Concentration (^) ς Cooking Time (hours) . 1.0

Cooking Temperature (°C) SO

Acid Consumption /Ton Pulp 1 -^

ITitric Acid Pαlning of Stra Acid Concentration (fό) 2 - 6.0 Cooking Time (hours) ' 4 - 6.0 Cooking Temperature ( C) 90

Alte nativelT' Acid Concentration (f->) ' 42.0 Cooking Time (hours) ι 4.0

_OMPI ^~ o

In the process of the present invention chemical concen¬ trations are lower, processing time greatly reduced and ni- trating chemical consumption does not exceed 5% on pulp yield.

The pulping process of the present invention is based on the nitration of the lignin -molecule, which is not soluble in an acid solution, using a variety of chemicals as the nitrating agent, either acid or nitrate salts, and making said nitrated lignin soluble in an alkaline solution, either in one or two Steps, preferably under conditions of atmospheric pressure and temperatures below 100°C, in times substantially lower than conventional chemical pulp pro¬ cesses.

The invention relates to a process for treating fibrous ligno-cellulosic material to form defibered pulp material co prising the steps of submerging in or spraying of the fibrous ligno-cellulosic material with aqueous nitric acid or nitrate salts such as NaNO^ or KNO-. or NH. 0 ₃ , having a nitrate ion concentration of about 0.001 to 9.0 wt.% so as to nitrate ligneous component of said material; draining the nitrated ligno-cellulosic material from said nitric acid or nitrate salt solution and thereafter defibering directly by mechanical means to obtain said pulp material, or treating the said nitrated ligno-cellulosic material with an alkaline extraction liquor so as to dissolve lig¬ neous component out of the material and separating the resultant cellulosic pulp from the lignin containing ex¬ traction liquor as well as, optionally, recombining a part or all of the ligneous component of the lignin containing extraction liquor with the cellulosic pulp.

The treatment of the ligno-cellulosic material with nitric acid (acidic pulping) is conducted in the presence of an aluminum compound in an amount of at least 0.01 parts by weight of aluminum ions per each 10 parts by weight of HNO^ whereas an aluminum compound is not necessary when pulping with nitrate salts (alkaline pulping) . ^ _• "TTREJT?^

OMPI

Nitrates can be adväntageously used in an alkaline solu¬ tion for pulping. For example,fibrous structures such as straw can be pulped in one hour at 70°C using a concentra tion of for example 0.0125% nitrate ions in an alkaline solution of pH 11 - 13.5 using either NH.N0 ₃ or H 0 ₃ as nitrate sources. Board ade with the above described pro¬ cess characteristics is approximately equivalent in test and Performance values to semichemical board made by con- ventional NSSC pulping processes at high pressures (125 psi) and temperature (175°C) from wood chips in 15 - 20 minutes. Furthermore, for woody fibre structures, such as coniferous trees, bamboo, sugar cane, cotton Stocks, etc. nitrate pulping in alkaline solution is suitable as well. However, nitrate ion concentration would then preferably be increased, for example to 0.025% of nitrate ions.

Nitric acid added as a nitrate source for nitration and si ultaneous delignification of spruce wood chips in a co centration of for example 0.025% in an alkaline solution produces a chemical type pulp of medium strength in 1.5 hours at at ospheric pressure and at 100°C. The pulp is light in colour with a Kappa No.of 125.

Rather than greatly extend the time of processing of the above alkaline pulping process to obtain pulp of higher purity (i.e. less lignin) and higher strength'characteri¬ stics, it is advisable to pulp under acidic conditions . with H0 ₃ together with Al ₂ (SO.) ₃ (or another aluminum _- salt) as an accelerator, followed by alkaline extraction of the lignin. In this acidic approach the nitrate ion co centration will preferably Vary from 0.015 - 1.5% for pul ping straw and preferably from 2.5% - 5.0% for pulping wood dependent on species cooked and pulp purity desired. However, lower nitric acid concentrations can be used, in particular when pulping grassy structures, such as straw.

Spruce chips, for example, can be cooked to a high streng pulp and Kappa No. 75 with a nitrate concentration in the

acidic cooking liquor of 3.8%.

The nitrate ion used in contacting the dry cellulose mate¬ rial can thus vary from a ini um of 0.001% in the case of straw in the alkaline pulping process (one step process combining nitration step and alkaline delignification step) . o a aximum of 5.5% in the case of wood in the aci¬ dic pulping process (followed by an alkaline delignifica¬ tion step) -

In a particular embodiment the process of the invention is carried out with a nitrate ion concentration between 0.001 and 0.15%, e.g. up to 0.14%, preferably between 0.01. and 0.15%. This. embodiment preferably relates to the alkaline pulping process which can ^' be used for pulping both grassy and woody structures.

In a further embodiment with the acidic pulping process the alkaline delignification step may..be omitted when the ni- tric acid concentration is increased, i.e. above 1.5% in the case of straw and above 5.5% in the case of wood.

Actual usage of nitrating chemical with recycling does not exceed 5% and alkali usage — again with recycling of the black liquor - is 4 - 6%. Together this total chemical usage compares favorably with the rnake-up chemicals used in the Kraft process where füll, expensive and complicated, chemical recovery is practiced.

Since the cooking liquors of this invention are simple solutions of purchased off the Shelf-chemicals no complex system of liquor πanufacture or control is necessary and the low concentrations and recycling capability make for low uεag anά cost and elimination of a recovery System.

V/he e the black liquor that is pur ed is desireά as a source of energy rather than be recoπbined with the pulp, it can of course follow the conventional j-system in whic the recovery boiler uses the heat of coπbustion of the lignin to recover chemicals and nrovide Drocess hpst. _^ -rr--- -; ^• --—--

^~ ^- RE (

Conventional pulp mills require lai-ge capital Investment due to the minimuπ size that is economic 250 tons of pulp per day) ,to the high temperatures anά pressures involv and the absolute need to recover and mix the complex cooking chemicals. -Further, substantial Investment is required for both air and water pollution control. The process of this invention uses simple chemicals, does not require either vacuu or superatmospheric pressure or temperatures over 100 C - offe minimal and easily avoidable problems of air and water polluti and offers high value usability of the ligneous products of pulping, ormally disposed of by burning or asted by duraping.

Furthermore, it has been found that in the chemical pulping process involving nitration of particulate, fibrous ligno- cellulose raw material with nitric acid which pulping may be coincidental with or followed by an alkaline extraction of the nitrated lignin from the fibrous material leaving softened, partially defibered cellulosic structures which can further be completely defibered by normal mechanical means, the total time required for nitration/extraction can be substantially shortened by including a proportionate amount of aluminum compounds to the nitrating solution. V/hile the precϊse ,time reσuired for the nitration/extraction process either simultaneous or sequential is dependent upon the variables of particle thickness, tempera and reagent concentration, it can be säid for the process of t present invention that total process time is greatly reduced. Por example, for chemical type high yield wood pulps from coniferous wood chiυs the total υrocess time is 90 minutes usi atmospheric pressure and temperatures not exceeding iθO°C. Th time is to be compared with conventional sulphit^ process time 6 - 7-5° hours and the sulphate k-raft process of 2.5 - 5.0 hou at high pressure and temperatures. i ^•

-~~r. \ ^■ * er* ,- ^- _

^ - r* 3- rχ ij

l UJ.-Λll-l-i l'UO.HÜ li'l'Λl OOll ΛH l ⁾

Liquor Total

Concenbration Cooking Temperature Pressure F w . Time P.S.I.G S

1. ^'

Sul ph o-B-leach Grade Calcium Base 6.0 6.25 Urs. 140 80 V/ Λmoni.a Base 6.0 7-50 Urs. 146 80 C

2. Casey, pp. 0 - 264

Sulphate - High Yield 18.5 2.50 Urs 170 WO Sulphate - ßleachable 22.0 5.00 IIΓ 'sΪ . (1) 160 100 Sout (.1 ) includcö time to bring P to bernpera ure

3. TΛPPI CΛ Report, 2, PI>. 17 - 19

Bjyaaggaassssee -- Soooαdaa Pfrroocceessss 6.5 26.50 Min. (2) 170 114 B (?) .ineludes cooking tirne in b.low ban

TΛPPI CΛ Reporb 52, pp. 26 27 Bamboo Kraft Process 17-19 1.25 Urs. 150 85 B

5. Λcceleratod Pulping - Sequential

Process (I) 10% of AI., (SO^) ₃ ^• 10 H ₂ 0, based on the HNO3 (100%). (4) alkaline delignificati fi-xamples ( Invention ) IM), (3) NaOH ⁽ 4 ⁾ e*

IIi.(;h Yield Pulp 5.5 0.3 90 Min. 85-100 None U.

The pulping with HNO, under acidic conditions is conducted in the presence of an aluminum compound. Examples for such alumin co pounds are aluminum sulfate (alum) , aluminum Chloride, alu¬ minum oxides, such as Al-O., • 1/2 H_0 _f aluminum phosphates, al minum nitrate, etc. These salts should be soluble in the aque nitric acid used in the pulping process.

With aluminum Chloride it is preferred to use a hydra- ted product or a hydrated product with additional water to avoid violent reactions when adding it to the pulping liquor. To avoid excessive hydrolysis of the aluminum Chloride to aluminum hydroxide or oxide hydrate which ust be redissolved later, nitric acid can be added. When using aluminum nitrate as starting material the introduction of forεign ions is avoided.

The stated aluminum compounds should be used in amounts leading to similar aluminum ion concentrations in the pulping liquor as compared to the use of aluminum sul- phate (paper akers alum) in the process described hereinbefore which alum is used in an amount of about 0.8 to 1.3 parts by weight per each 10 parts by weight of HNO-, (100%) . Comparing the ole- cular weights of the alum (Al ₂ (S0 ₄ ) ₃ - 18 H ₂ 0 = 666) with, for example, A1 ₂ 0, • 1/2 H O (111 ) , it follows that

for achieving the same aluminum ion concentration in the pulping liquor the aluminum oxide should be used in an amount of 1/6 co pared to the alum. In terms of aluminum ion concentration (or aluminum concentration) this means that it should be from 0.065 to 0.105 parts by weight of aluminum ions per each 10 parts of HN0 ₃ (100%) .

While it has been noted that there is a minimum amount of aluminum ions to achieve a rεmarkable effect, e.g. 0.01, 0.02, 0.03 or 0.04 parts by weight of aluminum ions per each 10 parts of HN0 ₃ , there is actually no strict _^ upper limit, and the alqminum ion concentration could well go above 0.105, for example up to 0.15, 0.2, or even more.

It has been found, however, that with exceeding a cer- tain aluminum level no further advantage as to time rε- duction is obtained so that higher amounts are not desirable under economic and environmental pollution point of views.The perferred ränge is 0.065 to 0.105 parts by weight of aluminum ions per each 10 parts by weight of HN0 ₃ , a value of about 0.08 giving desirable results in the practice of the process ^' of the invention.

Besides reduction in process time, a further point of view is the inherent strength characteristicsof the fiber obtained according to the process of the invention which characteristics can be influenced by the amount of aluminum. Thus, for every kind of ligno-cellulosic material, e.g. bagasse or bamboo, the optimum amount of aluiiiinum can vary depending on what reduction in process time and what fiber characteristics are demanded.

The ability of the present process' to be conducted at atmosriheric pressure eli inates the explosive rεlease of pressure that is nor ally used in conventional Systems to

•' ! e pty the digester . This pressure release additionally defxbe at least partially the natural fiber structure . The basic pre servation of the fibrous structure permitted by the non pressu r n OwMPpIi

system per its reduced chemical usage by easy drainage of cooki liquor and washing out of the residual -cooking and black liquor leaving the fibrous structure still substantially intact. Defiberization is then accomplished mechanically with inimum . loss of fiber length and degradation of basic fiber structure. The defiberization can be closely controlled to preserve long thin iber bundles from fibrous structures made up of very sb-ort (under 0.5mm) fibers thus improving strength and aintainin oo drainage characteristics eventhrough the bleaching process wher repeated washings present a ajor problera if drainage is poor.

All for s of ligno-cellulosic materials can be subjected to the pulping process of the present invention. That includes without imitation, woody materials such as U.S. Southern pine, spruce, beech, and bamboo, as well as grassy materials which fi usage such as straws, bagasse, and kenaf. In addition to these normally used sources of papermaking fibers, other, now wasted, fibrous plants, such as rape seed .straw, and rice husks, which resist conventional pulping methods, can be reduced to com erci useful fiber by this process. High yield shrub growth, sucn a coppice willow, or agricultural waste, such as cotton staiks, presently unused, produces, including its bark, an acceptable, economically useful fibrous material with my process.

Besi es such virgin materials, the prooess of the present invention can be used to delignify and further defiber papεr wastes, such as v/aste nev/sprint made from mechanical (groundwo pulp or waste corrugated boxes containing semichemical board.

Additionally, using the instant invention, it is practical to economically pulp accu ulations of chippe v;ood slab waste and also sawdust, which is generally discarded.

The raw material should be in a uniformly sized particula form before being submitted to the nitrktion step. Virgin pla material, for example, can be chopped, crushed, chipped, la ed defibered, depending on the initial fibrous form to be procesεe Paper wastes should be mechanically pulped in water to the defibered State, for example, to obtainja slurry containing about 5 to 9 v/t. cellulose. Paper as _t es are readily im- pregnated and. reacted with the nitratin ^' agent. In the process mechanical and semimechanical pulps can be effectively u graded

~-TRE I~

OMPI

through efibration of uncooked fiberbundles by deligni ication . The pulping process of the invention also peππits the simultaneous renoval of waste paper conta inants such as ink , plastics and wax , due to' the temperatures used and the open vessel processing v/hich permi Separation of the contaminants . At the temperatures required for the pulping proce ss and the low consis ency duririg which reaction takes place these contaminants are rel eased, rise to th surface , and can be aspirat ed easily from the vortex cen er of a second hydrapulper here they ccncentrat e . Such contaminants which can represent 1 - 2% of the waste fiber furnish can be αumpeα along with the v/ire , rope and other extraneous contents found with v/aste paper .

Waste papers -are pulped in a normal way in a hydrapulper and the v/ire, rope, wood, sheet, or film plastic re oved by the conventional ragger.

The Suspension of v/aste fiber is then pu ped to a second hydrapulper where it is nitrated at 80 - 90°C with only moderate turbulence to permit the aspiration from the vortex_of the wax, ink, styrofoa and plastic residues that will accu ulate there.

The nitrated, cleaned material is then passed through a high density press to remove excess acid, then passed over a washer to remove any residual weak acid. After treat ent with alkali excess lignin and alkali are removed by high density pressing and washing.

After defibering, conventional paper machinε practice is followed.

The black liquor derived from the press can be re- cycled to the extraction step to fully utilise any unex- pended alkali or partly diverted to the papεr machine wher it can be precipitated on the fibers or to a settling basin where it can be precipitated and concentrated.

The nitration .{cooking) ₀ f the ligno-cellulosic raw material is ^• accomplished by submer-ing or etting with recycled n^^-oiiε

pre erably about 7 to 100°C, to accelerate penetration of t fibrous structure and react with the lignin. In order to pe the use of a non pressure open vessel for the nitration step with minimu emission of har ful nitrogen oxide vapors when using nitric acid as the nitrating agent, it is pre erred to use as dilute nitrating agent as possible with the limiting factors of time and pulp quality factors considered. The exact percentage u will be dependent on the type of fibrous structure being pul the required level of deilgni-ffe.etion, time li itations and p quality desired.

The ligno-cellulosic raw material may be subjected to steaming-_ _. and/or impregnation step _. be ore the cooking-nitrati step. The impregnation is done with a dilute concentration the cooking liquor -at low temperatures (e.g. about 70 C or b e.g. about 0°C or below) and serves three purposes: a) utilization of drained concentrated liquor after the cook process together with the dilute cooking liquor from the washing process, b) conservation of heat and chemicals by recycling liquor, c) even moisture distribution throughout the fibrous struct before cooking.

The amount of nitrating agent used in the nitration ste should be sufficient to completely submerge or contact by recirculation the particulate ligno-cellulosic material and adequate, on a stoichiometric basis, to nitrate substanxiall all of the readily accessible lignin content of the raw mate This will usually mean, for example, for ation of a ixture about ^~ parts of liquid nitrating agent to about 1 part of dry wood to about 10 parts of liquid nitrating agent for 1 p of dry grass fiber (straw). V/here the nitration liquor can circulated and heated indirectly, lower ratios can be used. Additionally, the nitrating agent can be sprayed or it can b foamed In low concentration v/here minimum quartities but ove intimate contact is needed.

The temperature at which the nitrating cooking step is perfor ed should be adequate to effect nitration of the lig but is pre erably not so high (over 100°C) as to cause de- gradation of the cellulosic fibers or so low - belo. _r _, O PI to take excessive reaction time. Te-mυeratu es in

of about 75 to 98°C, in particular about 85 - 95°C, are preferred. With the use of the pulping process of the inven¬ tion for making building and packaging boards higher tempe¬ ratures up to 160°C, for example 130 or 150°C, can be em- ployed for Short periods to effect curing of the lignin.

The nitration-extraction process of the present invention can be perfor ed in a short period of time, under atmospheric pressure conditions, although above atmospheric pressu es, e.g up to about 10, 15 or 35 p.s.i.g., can be used if it is desire to shorten further the time, but can be used chiefly to provide ease of productioh on a continuous basis. The pressure_ may be up to about 150 p.s.i.g. and such may be particularly advisable in certain situations as noted below. The improvement provided by the present invention is independe of whether the process is conducted under atmospheric pressure or at εlevated pressures. The introduction of a non-pressure System is designed specifically for use in new and relatively s all pulping installation (10 - 0 tons per day) throughout the world. However, it is recognized that the requirement for larger production units can be met by larger or multiple units and that in many instances existing ρulρ ill equipment could be utilized to reduce further Investment costs while minimizing present pollution problems. '

All present commercial Systems employ high pressures εnd temperatures coupled with long cooking periods for pulping woody fibers to chemical grade pulps. It has been found that by cooking with light pressures (e.g. up to about 15 to 35 p.s.i.g.) while holding temperatures certainly below 110 C and preferably below about 100°C, the nitration period can be shortened to about 5 to 7 or 10 minutes for wood flakes, straw, etc. Conventional sized wood chips are usually too irregulär in size for cooking by the instant process and shoul be made uniform and generally smaller ih, size to achieve uni- formly cooked and defiberable pulp of normal quality levels in one hour's time. I

Using light pressures with either wood flakes or chips akes practical the conversion of existing sulphite pulp lll to the process of this invention, however the use of pressure for pulping any fibrous structure or wood flakes or chips is not necessary and is recommended only to fill the utilization possibilities of existing installations.

Pulping Systems such as the "Kamyr" or "Pandia", v/hich are continuous, operate at high pressure, about 1 0 to 175 p.s.i.g. These units are also adaptable for processing v/ood chips in one stage in accordance v/ith the present invention to produce a semi-che ical type product or füll chemical pulp

Typical times and conditions at these different pressure for treating several ligno-cellulosic materials and where an alkali delignification state is being used, are in Table 2a.

1 '

abJ e 2a G'O-IPΛRATIVE UNO,*_-) PRESSU.RIZED NITRATION CYCLES

CHEMICAL OR DKLIGNIFIED PULP WITH ALKALI STΛGE

A. ,Non-Prosπure System - Wood Flakes oi- Equivolent

Pi e Spruce Beech

I

Cooking Time Minubea 15 15 15

Temperabure 0 85-100 85-100 85-100

Liquor Conconbration # HN0 ₃ 5.5 .0 4.0

B. Pressure 15 - 35 P.S.I.G. - V/ood -Flakes o.r Equivalenb

P;ιne Beech Straw

Cooking Time Minutes 7 7 5

Temperature °C 95_i0θ 95-100 95-100

Liquor Concentration % H 0 ₃ 5.5 3-5 0.

C. Non-Proπr-uro System - V/ood Chips

Spruce Beech

Cooking Time Migutes 60

Temperature 0 95 - 100 95 - 100

Liquor Concentration °o HNO ₃ 4.0 3.5

D. Pressure - 120 P.S.I.G. - Wood Chips

B Beeeecchh

Spruce Beech Semi-Chemical

Cooking Time Minutes 45 3300 1155

Temperature °G 9955__!ι0θ00 9955--110000 9955 -- 110000

Liquor C oncenbrabion . HNO3 4.0 3.5 3.0

θ $ * ^{} 1 0%} ° ^{~ Λl} 2 ^(S0 4 ^, 3 ^{" 1 ö π} 2 ⁰ ' ^{based on} «N0 ₃ ( 100%)

Additionally, it has been found that the use of pressure permits füll defibering of wood fibrous structures in the aci nitration stage, and a lignin alkali extraction stage may thu be avoided since the lignin component issolubilysed by this " stage. This can be accomplished when nitric acid is the nitrating agent by raising, dependent on fibrous structure processed, the HNO-, liquor concentration by about 2.5 to 3 - 5% over that employed for the normal nitration-alkali deligni- fication sequence, and extending the time of rεaction sli htl e.g., by about 3 - 5 or more minutes. Thus, without using pressure, conducting the process under approxi ately atmospheric pressure _^ conditions, the HN0 ₃ liguor concentration is pre- ferably at most 5.5 weight percent, in particular at most 5 weight percent. When employing pressure, the H _NO -, con¬ centration can go up to 9.0 weight percent and preferably it is no more than 7.5 or 7.0 weight percent. Of course, the lower concentrations as stated for the pressurized ni¬ tration step can be advantageously used.

Por grassy fibrous structures pressure is not necessary and only a 0.5 - 1# additional acid concentration is required for achieving füll defibering in the acid nitration stage.

This embodiment of the present invention without an alkal stage produces a fiber wit different strength characteristics from that obtained v/hen d-llgnification is accomplished by alkali extraction. The fiber is, however, of very light colou and high yield.

Regardless of the pressure employed, it is not necessary to vent any gases, in fact It is preferable, since ith the gases contained and retained in the treating vessel, a false pressure is created, per itting the _. keeping of operating temperatures below 100 C thus avoiding cellulosc degradation.

The degreε of false pressure created is dεpendant on nitratin agent concentration.

Typical times and conditions at different elevatεd pressu for treating several ligno-cellulosic materials without there being an alkali delignifaction state, are in Table 2b. V/here additional pressure is needed, as in the "Kamyr" pulping proce

• it can easily and economically be obtained with

The low temperatures involved reduce the chronic scaling and maintenance to a minimum.

Table 2b

Comparative IΪNO-?)Pressurized Nitration Cycles, Alkali Deligni action Stage Eliminated

A. Pressure 15 - 35 p.s.i.g. - V/ood Flakes or Equivalent

Chemical Pulp

Pine Beech Straw Bambo

Cooking Time Minutes 10 10 6 10

Temperature 95_ιoθ 95 - 100 95 - 100 95 - Nitric Λcid % 9.0 5-5 1.5 5.

B. Pressure 100 - 1 0 p.s.i.g. - Wood Chips

Chemical Pulp

Spruce Beech

Cooking Time Minutes 45 45

-Temperaturo-- 95-.KLO 95 - 100 -Nitric Λαid - 8.0 5.5

Pressure 35 - 0 p.s.i.g. - Wood Chips

Semi-Ghemical Pulp Mixed Hard oods

The abllity to conduct the nitration step at atmospheric pressure means that non-pressure vessels can be employed, pro- viding a substantial savings in .equipment and operating cost co pared to conventional high-pressurε pulping processes. lthough a non pressure vessel is employed for the nitration step, it is preferred to maintain closure with recycling of any vapors to prevent heat loss and possible emissions. Present environmental lav/s in the U.S.A. permit a maximum nitro oxide e ission level of only 185 ppm. The precise temperature at v/hich nitrogen oxide or other gases can be released from the slurry in the nitration step will depend upon the concent- ration and form of the nitrating agent, since the higher the concentration, the lower will be the temperature at v/hich vapor emissions v/ill oecur.

When a closed, non-pressure vessel is being used to con¬ duct the nitration step in the process of the present invention it will usually be preferred to employ a temperature no higher than about 90 to 95°C, e.g. within the ränge of about 85 to 95° Hov/ever, as stated hereinbefore, when operating the nitration step under pressure, a temperature of up to 100°C or somewhat over 100°C may be employed. It is an outstanding advan--tagε of the process of the present invention that it can be perfor e in non-pressure vessels in economically short time periods, v/ithout causing difficult air pollution'problems. Additionally the elimination of the usual chemical recovery System eliminate emission of dust particulates v/hich are a major source of air pollution.

The nitration step, and indeed the entire process of the present invention, can be carried out continuously, semi-con- tinuously, or batchv/ise, hichever is desired. Selection of equipment v/ill of course deυend unon that choiee. It is genera more economical to conduct the process αontinuously, in which event the nitration step can be conducted in a ^* scrεw conveyor unit. Batchv/ise nitratibns can be carried out c well in a modified hydrapulper, aking possible the econo ic

The nitrating agent impregnation and! cooking steps are con ducted for a time sufficient to produce the required re^lf u^ L

The time required to effect the desired άεgree of nitrεtio is dependent, of course, on the strength of the nitrating agent used, as well as the temperature employed, since higher strengt and temperatures promote the nitration reaction. Additional considerations are the type and particle size of the ligno- cellulosic material being processed. In general, with the process of the present invention the total nitration time can be as short as about minutes or as long as about 30 minutes or to about 90 minutes if wood chips are used. Por straw or bagasse v/hich v/ill go into storage before delignification, a simple spray or foam application at- lo er levels of nitrating agεnt concentration at room temperatures is all that is necess¬ ary to obtain the desired level of nitration.

Pollowing the nitration step" the ligno-cellulosic material is separated from the nitrating agent solution and washed v/ith wa er to remove surface chemical. The v/ash water is preferably hot, e.g. at a temperature of about 85 to 100 C, and Is used in minimal amounts. One efficient ethod, if a continuous system is used, is ^' by reverse flov/ washing or v/ith reverse flow waεhing on a vacuum fil er. Alte natively, draining, followed by floodlng with wash water and a second draining can be used.

V/hen the cellulosic raw material is from v/aste paper pro- άucts, the removal of the excess chemical is accomplished with a high density press.

The separated nitrating agent is advantageously returned to the nitration step to be used over again, as is any v/ash water. The recycled nitrating agent strea will be fortifiεd with concentrated chemical and v/ith a fresh source of aluminium ions so as to restore the concentrations of those reagents to the desired levels.

The nitrated fibrous structures remain intact and appear to be essentially the same as when those particles were intro- duced to the nitrating agεnt submersion step, except for a slight softening and darkεr colour. The nitrated fibrous structures can be held in storage for onths without either deteriorating or causing problems in the lignin extraction and defibering steps which follow. This storabilit/ featurε can be

of spεciai advantage in the case v/here straw, bagasse or si ila grassy plant s are to be pulped since grassy plants are usually harvested during relatively short seasons . This presents a Problem because grassy plants are particularly susceptible to dεterioration during storage . By the process of the present invention the excess raw material can be nitrated by spraying or foa ing a dilute solution of acid to obtain intimate , overal contact with the fiber and held in storage in that form without being degraded. E tended periods of storage have._ been ex- periencεd up to one year in contact with the acid at a oisturε level of about 2 $ permitting usage of a lower percentage of acid to dry fiber .

The nitrated ligno-cellulosic material can next be sub- merged in an alkaline , aqueous extraction solution, e . g. a solution of sodium , calcium, potassium and/or ammonium hydroxid or mixtures of same so as to dissolve mo st of the nitrated llgn out of the fibrous structure . The lignin nitrate is substantia ir.soluble in acidic aqueous media, but is readily dissolved in basic aqueous media, for example havlng a pH of about 7 _* 5 to 12 The alkaline concentration of the extraction solution must be sufficient that the solution will leach out , or dissolve , most of the nitrated ligneous material in the fibrous structure . Usually it is preferred to use an alkaline strength ( alkali metal bases such as NaOH or KOH, or NH DH of about 0.1 to 0 .3 v/ The alkaline consumption is basically one of bringing the starting pH to about 12 and can therεfore be dependent upon the concentration of residual nitrating agent rεmaining if it is acidic .

Thε amount of the alkaline extraction solution used should be adequate to completely submεrge or continuously contact the ligno-cellulosic material and dissolve out most of the nitrated ligneous components . Usually the amount of 'alkaline extractio solution used v/ill be in the ratio of 6 or 10 to one part cellulose fibrous structures , dependent on process used and fiber structure being processed .

The temperature at which the alkaline extraction step is conducted should be sufficiently high to effect dissolution of most of the nitrated ligneous material . Preferabl^r a temperatu

of about 7 or 85 to 100°C is used, normally 95 to 100 C. Temperatures as low as about 65°C can be used for grasses v/hich will extend the time necessary for delignification. These low temperatures are particularly important in producing animal feed or partially defibered pulp from agricultural residues. Where straw as an example for an agricultural residue has been sprayed with nitric acid as a nitrating agent and held in storage, delignification with alkali at about 00 v/ill pro- duce v/ith mechanical defibering a fully defibered pulp suitable for the manufacture of corrugating medium .

The alkaline extraction step is also performed under atmos¬ pheric pressure conditions, thereby permitting the use of non-pressure vessels and avoidance of expensive high pressure eσuipment. Closure of the vessel is desired only to conserve hεat. There are no fumes or chemical gases given off unless NH.OH is used. Pressure equipment could be used but increasεd temperatures using dilute alkaline solutions v/ill normally resul in degradation of the cellulose and loss of fiber strength.

It v/ill be recognized that the time required to effect the desired degree of extraction is dependent on the strength of the alkaline extraction solution used, the particle size and type of the ligno-cellulosic material and the temperature at v/hich the extraction is conducted. In gener l, however, the total time required for the lignin extraction v/ill be no more than about 30 minutes, being within the ränge of about "to 15 minutes for agricultural residues and v/ood flakes and 30 minutes for wood chips.

Per the extraction step, it can advantageously be In a hydr pulper or a screw conveyor may be preferred for continuous operations. ,

After treat ent with the alkaline extraction solution, the fibrous, cellulosic material is separated from the lignin

mechanical defiberization, be maintained as whole and complete

fibers — for example straw fibers neas ring about 1.2 mm in length and only about 0.006 mm in v/idth are preserved int

Convenτ-ional paper aking fibers (pine). measure about 0.05 ™ in width. The principal benefit of preserving fiber length, either indiviάual fibers or chains of small fibers, is that it enables one to manufacture higher strength paper out of t final pulp and improves drainage characteristics.

V/hen the desired degree of cellulose purity is obtained the cooked delignified fibrous structure is mechanically de¬ fibered and then. conveyed to screens v/here any remaining out fiber bundles are screened out and retumed to the cooking steps for further lignin extraction and defiberization. Fro this point on, the separated cellulosic pulp is subjected to normal paper mill operations of cleaning and formation of the fiber web on the paper -machine to malte board or paper.

After the extraction step, the alkaline solution. contai dissolved ligneous components and is dark reddish brovn in c and is com only referreά to as "black liquor".

As the alkaline black licuor is recycled to the lignin extraction process, the content of dissolved solids in the black liquor vill grow to a maximum tolerable concentration, e.g., somev/here in the ränge of about 10 to 2 w .#, general less than 20 .% . An approprlate port on of the black liqu should be purged regulä ly (5 - 10$) and replaced v/ith'make- alkali in order to prevent excess increase in the concentrat of the dissolved solids and to maintain'required pH level. The black licuor purge stream can be disposed of by various such as by duπping as waste, or by concentrating and burning in the conventional sulphate recovery System. Alte natively the black liquor purge stream can be combined v/ith the compl defibered pulp to supply ligneous binder for fiber web produ prepared from the pulp, especially pape boardl _{to d} evelo _p or tend paper sizing materials or to act as binding material in t manufacture of building or heavy packaging ^' board.

M?I

In the manufacturing of paperboard and the like, where coiorati. is not critically important, it .has been found aάvantageous to add the lignin-containing extraction liquor up to 1 ^~ 5- black liquor solids to the cellulosic pulp v/hich results in a darker but accεptable paperboard product, due to the preciptiation of the lignin on thε fiber. In the course of forming thε paperboard product on the paper machine from thε cellulosic pulp, aluminium sulphate (papermake ' s alum) is normally a deά to the pulp in an amount sufficient to lower the pH of the pulp wi hin the ränge of about -0 to 6.5« V/hen the dissolved lignεous material has bεen adάεd back to thε pulp in accorάancε with the present invention, such subsequent lowering of the pulp'_s pH causes an amorphous precipitate of thε lignin to form, which deposits itself on the cellulosic fibers. A - ajor portion of the very finε fibers suspendεd in the ρulρ adherε to anά are rεtained by the precipitate as weil. This is bene- ficial because in the conventional paper making processεs cellulose dεbris and short fibers, v/hich offen amount to about 0.3 to 2.5 wt.# of thε total fibers, are not retained on the fiber web, but instead are lost with the dr in ^* and v/ash water, exacer ating the pollution problems or build up concentration in the overall papermaking process, requiring addition of retention agεnts to assist retention in thε fiber web.

A further benefit of adding the extracted ligneous material back to the cellulosic pulp accordlng to thε process of the present invention is that the paperboard or other fiber eb produceά fror- the lignin-containing pulp will be in most physica propertieε stronger than if thε lignin erε nct present, this bei ^ particularly so v/hen waste paper fibers are inccrporatεd into the ultimate paper product.

The extracted ligneous component may be addεά back to the cellulosic pulp in aqueous solution form. This can be done by sir:ply adding thε untreated black liquor dirεctly back to the ρulp, -Alternatively, -the- ligneous material can be re ^m oved fron solution in thε black liquor and then mixed v/ith the pulp. To remove thε ligneous material from solution in the black liquo an acid, preferably nitricacid, canbe added to the black liquor

at a temperature of about 15 to O C to ca ce the ligneous material to precipitate as an amorphous flocculant. Separation of the precipitate from the mother licuor can be efficiently accomplished by cεntrifugation or by dεcanτation in a settling basin. The amount of acid used is preferably a quantity sufficient to lower the pH of the black liquor to about 7.0 v/ith alum used therεafter to bring it to lower levels. The mother liquor is clear but slightly colored and contains some dissolved solids, usually less than 0.5 ^~ -τ . thereof. Thε πothe liquor can bε rεcyclεd to the nitrating agεnt impregnation step or alternatively v/here the nitrating agεnt is nitric acid it αεy be usεd again'> as a sourcε of acid in the precipitation of the ligneous material from the black liquor. The precipitated concsntrated ligneous component can bε resolubilized v/ith alkali but this is not necessary for addition to fiber slurry or paper eb.

V/hen the alkali lignin extraction process is complete, the of thε black liquor v/ill be about 8.5 to 9«5 ₅ which is lower tha that of conventional alkaline processes v/hich are usually in the ränge of 11 to 12. It is recognizeά that the neutral εulphite process for semicbe-rnical pulp (NSSC) produces a neutral pH 7.0 black liquor. However, this licuor has no value either for the purpoε of chemical recovery or for its lignin constituents and is there- fore onε of the ajor polluting processes in use unless tied int a kraft π ll Operation for chemical recovery. Sulphite acid Systems produce black liquor in a pH ränge of 1.0 to 2.0. The factor of an essentially neutral pH makes the black liquor ob¬ tained v/ith the present invention substantially more amenable to handling and use in subsequent chemical processing. Ad ition- ally, thε black liquor of thε present invention has a low r nge of 30-Dj. (Biological Oxygen -Demanü - 5 day) and C0D (Chemical Oxygen Demand) , permitting its dischargε, if it becarae necessary. in controlled amounts, e.g., up to 30o, in the normal urbar, effluent stream. Typical comparative pollution data aitas follc.

Valueε in Present Invention V/aste ^• Sulphite ' mg/liüer Accεlerated Pulping Pauεr Kill Ξlack

Black Liαuor Ξf luent Licuor

5 day biological oxygen de and 1500 εoio —fcj-

-Chemical oxygen demand 5685 16700 250,000

Per anganate nu bεr 11215 _-/* KZAΪ co,000 f O PI

,,. Y/IPO ^\, .

Che 30D-- value v:hen relaτed to recently r^corüeά ( ^" orth Ar-e ic- ΞCD,- discharges per ton of pulp produced εhows the followi g values: sulphite mill 109 kg; in ^' tegrated sulphate pulp and pape. mills, 15 kg; v/aste paper mill, 10 kg-;- and thε accεlerated pulping process, 30 kg. Thε low figure of the sulphate mill iε reached only by burning all the black liquor solids produced to recover the major portion of the chemicals used in the prccε- and by additional strict control of the rε aining pollutants.

An alternative use for all or part of the solid ligneous material removed from solution in the black licuor is to fertilize plants. Ey using potassium hydroxide or ammonium hydroxide as thε alkaline extraction agεnt, followed by phcsphcr acid to completely neutralize the black liquor, a material iε obtained v/hich can be used as a balanced fertilizer for plants containing nitrogεn values from the nitric acid and ammonium hydroxide or al e natively potassium from the uεe of potassium hydroxide, phosphorus values from the phcsphoric acid precipit- εtion step, εnd humus-supplying values from the ligneous com- ponents. In dry form the ligneous solid is brov/n in colour, nc maicdorcus (having a mild vanillin scent), al ost tastεless and hygroscopic. Normally, expected usage would be in the form of liquid fertilizer.

Thε ligneous solid that can be obtained from the black liquor produced in the process of this invention can be especial useful as a plant fertilizer because it is low in toxic phenolic compounds, gsnεrally containing no ore. of thosε compounds than are present in the original plant fiber structure. V/hen tested for toxicity and as fertilizer on barley and oat εeεds in inert clay, the lignεous solid of this invention performed well, as evidencεd by the fact that ?5 ^" ό of the seeds germinated and 5 ^' ^ of the plants exhibite normal growth.

! In εura ary, the black licuor obtained in the process of the present invention may be utilized with only ir.or odification uniςuely and economically in a variety of v/ays as a binder, wate repellant or size, ex ender for fortified rosin size, εtiffeniπr agent in paperboard, hygroscopic fertili-ϊing additive to seil, extender for resins such as phenolics anci retention agent in papermaking.

The solids, i.e. nonvolatiles, in the black liquor are referred to εs the ligneous component. Although there are presεnϋ chemicals other than lignin and lignin nitrate, such as gum.s, waxes, etc., in the ligneous component, thε lignin and lignin-nitrate co prise thε major component. The useful ligneous component can bε precipitated from its mother black liquor by acidifying, prεferably to a pH of about 4-.5 to 5 _* 5, v/ith any mineral acid or acid salt, but of particular ussfulnεε-. are ordinary paper akεr's alum (alu inium εulphatε) , rεcyclεd nitrating agent from thε process and phosphoric acid.

Por normal papermaking thε black liquor or thε black liquor precipitate resulting from εcidification, e.g, v/ith nitric acid and/or alum, can be added to the cellulosic pulp. The black liquor n its neutral pH form or ^' acidifiεd can be foamed and added to the pulp at the size press αr v/εt prεssεs. Unlike kraft liquor thε black liquor undεr any normal trεatment either in solution or precipitated exhibits a minimum and non-troublesc amount of foa ing. Thε foa ing of thε black licuor, εi her itseif or in- concentrated form (precipitated ligneous componen . and beforε or after ixing with the pulp, can bε donε by adding to v/ater a com ercial εurfaetant, hydrophylic or hydrophobic foaming chemical, and then foaming thε ixture v/ith air and then add as required the black liquor and other additives such as starch etc. Poaming of various dilute solutions or suspεnsic iε gεnerally known, howεver, not with the high percent solids for ed by the ligneous component produced in the prεsεnt in¬ vention. Addition of the precipitatεd black liquor solids to the pulp slurry from v/hich thε black liquor is sεparated, lov/ers the stock frεeneεs, i.e. drainage rate, since it hclds or re ains the ine, εuεpended particles usually lost without; thε use of retention agents through drainage on thε papεr machine v/i. Addition of the black licuor to paper fibers in inor but sufficient a ounts, say .0'= up to about 15;^, and gεnεrally in an a ounτ of about 2.0o to 5.0;ό, based on the solids and calcul- ateα on the dry weight of the fibεr, v/ill incrεase most paper strength propertiεs, in an approxi εtε rεtio of improvεmεnt of 2:1 for εqual v/εight of cεllulosε fiber. Depending on thε degree of ouenness of the fiber web makir-r uu the -Dauer and on

~ή levels ranging fror. -0 - 6.5, i provεments in burst; and εüiffness shcv/ i provement ratios of 25:1 corr.pεred to an ecuivalent fiber weight. V/hen black licuor solids are combinεd v/ith an aqueous starch solution and added at high temperatures (e.g. about 65 C or above) at the size press, a satisfactory sizing of paperboard (Cobb O - 50 will be obtained and the εffectiveness of the starch in i proving paper ^■ : uality ^' is greεtiy improved permitting reduced starch usage. A small percentage, say about 0.4- to 1.0 percent of black liquor solids. based on the dry fiber content is generally εufficient for this purpoεe in εddition to showing improvemεnts in burst.

The acidified or neutral form of the black liquor can also add its _^ binding properties to such resins as mεlε inεs or phenolics, permitting extension of these relatively expensive products. The black liquor can be usεd in thε prεparation of resins since its nitrated form is co pεtible chemically v/ith that of many other resins.

Considεring a comparison of thε pulping process of the present invention with previous procεssεs, several advantages are apparent. Chief among the is the ability to havε a clbsed wa er and chemical cycle in a systε which is economically feaεible. As mild nitrating agent conditions are used and a pressurized syste is not required, capital Investment for my process is reduced by at least 25-^ v/hen co parεd to present day ills.

Pulping installaticns (producing from 10 to 50 tons or ICO tor-s of pulp a day) becomε possible when the conventional chemical recovery syεte (v/hich opεratεε arginally only on a minimum produetion of 250 tons per day of pulp produetion) is eliminated. The time re uirεd for chε ical trεat ent of the process of the present invention iε lεεs than one half the tiae of the most rapid prεsεnt day chε icεl procεss for chemical pulp.

The process of the invention develops no percepti-ble oöcur. Cxtrastinσiy, those dεveloped by the kraft pulp mills can still be ob.jectionεb ^" many iles away. Por this reaεon y pulping process can be located without objeetion near any co r-urity that has a rεquisit. fibsr sourcε.

Historically, black liquor has had to be disposed of by evaporation and εubεequent burning, or by discharge into lakec, rivers or thε sεa. Thεse disposal mεthods contribute, of cour to air and v/ater pollution. To so ε ex ent, εome black liquor ^' is used in the manufacture of tall oil, vanilla, drilling uds. and bonding extenders, but for the most part these operations are εrginally econo ical. This invention contemplates the upgradεd and profitable usage of 100$ of the black liquor, prc viding a v/aste-free system.

It is a feature of this invention that in thε case of fibrous structurεs, such as straw, both nitration and dεligni- fication can be accomplished in one step using a solution of nitrate salts such as NalsO-, NH.KO- or ϊ<0-, v/ith alkalization of the mixturε to a basic pH of about 11 to 13, e.g. about 12, with NaOH, KOH, ϊ.H,,0H, in combination if desired, or other suitabls alkalieε. Generally in this one step Operation temp¬ eratures in the r nge of 85 to 100°C, preferably 95 to 100°C, are used. In the onε stεp opεrεtion using nitrate salts as the trating agent for pulping grassy materials into füll chemical type pulps, abc

O. jo - 0.8. solution of nitrate salt, e.g. ITa-SO,, is vseά at a temperature of about 95 - 100oC for approximately 30 - 60 minutes, alkalizsd by using RaOH, KOH, or PH^OH to a pE of about 11 to 12.

Thε ease of nitration in this case is dictated by the thi structure of these fibrous εtεrials and thεir low pεrcεntagε o extranεous materials, such as axes and resins and other hydrc- philic materials. V/ood chips can, hov/ever, be easily pulped by the one step Operation producing a fiber that shcv/s that nitration has proceeάεd only to thε iddlε lamella, lεaving the lignin in the fiber wall itself virtualiy untouched. Total tim for- processing re ains essentially the same as that of thε sequential process.

The process of delignification serveε to dissociatε the fibεrs aking up the natural fibεr structure frεεing the ligni εnd providing fibers v/hich can be formεd into a web for ^" prcduct of paper or board. On a odifiεd or rεducεd scalε of dεligni- ficaticn in a relatively dry εtate (30 - 50jά oisturε) the li can be released in εitu to act as ε binder for thε

building board in v/hich thε fibrous structure rε ains εcsenticll intact. Delignification v/ill also increase the digestibility of fibrous structures for herbivores,' cov/s a,nd sheep etc. Ani al feed is being produced today from strav/ by addition of ca. 5^ KaOH to the dry v/eight of strav/ in a process which makes cubes or pellets v/ith additional food additives. Additionally, v/ork has been done with NH^OH, liquid or gaseous KH-, but this has not proven practical. Utilization of feed produced v/ith HaOH iε limited because the -improvement in digestibility (food valuε) is low εnd the alkali content is high. An improvement to so e 3 ^,: v/ould be required to eet the food value of com sileage. Level- of improvement presently obtained processing strav/ are one tenth of this, and maximum utilization in the animal' s diεt has not exceeded ^-1 -^.

This invention provides a controlled ethod of delignificatic v/hich increases digestibility by up to about 1 0/ό to the point that the processed straw can comprise a minimum of ^O^ό of the animal ¹ s total diet. Mixed during compounding v/ith othεr food supplε εnts, as olasses, urea, protein, etc., a complete food can be formulated. Of equal i portance is the potential of this process to be economic in small installatlons v/hich further makeε possible a Joint produetion facility producing alternatively, as required, anii-sal feed and paper making fiber, providing flexl- bility to meet market demands local and Q-ong distance.

It is characteristic of agricultural residues that they are bulky msking it i possible to meet minimum weight rεquirements 01 shipping carriers resulting in high freight costs. Processing undεr this invsntion makes viable the produetion of co pact finished or semi-finished product of high density v/hich grsatly rεducεs freight and handling cost.

The alternatives urovided b this invention in acco nlishinE

1 nitration and subsequent delignification; of agricultural residues extend to choiees of acidic (nitric acid) or a variety of nitrate saltε in nitration, various levels of chemical concentration varying time and temperature for both nitration and delignificatic stεps and a choieε of alkaline chemicals! (KOH, NaOH, KH.OH) to accomplish the pH level n cessary for solution of the nitrated lignin. ;

For example the process may be i ple ented using shredd grassy residue materials such as _. wheat straw, bagasse or shredded v/oody ste s such as can be derived from 2 - 37 ^{~ ~~} r coppice willow or cotton stalks.

As a specific example: Baled wheat straw is shredded, a nitrating agent co prising nitric acid plus AI3 (304)3 ^• 18 in a ratio oi 10 parts ENG, (100#) to 1 part alumlnium sulph (100#) is sprayed evenly on the shredded straw; 1% - # nit agent to the- dry weight of the strav/.

The nitrated straw is he t treated in for example a ro dryer at anair emperature of approxi ately 120 C, for approxima 20 minutes. During this interval the straw is completely di with he-chemical. The lignin component reacts with the nit agent to form lignin nitrates and/or oxidized products solub in alkaline pH (7-0 +) solutions.

The pH levels of the straw leaving the heat treatment v/i characterlstically be approximately about 6.0 pH v/hen U nitrating agent is used,to a pH of about 3 - - v/hen .0$ nit agent is used.

The nitrs.ted straw can be i mediately treated v/ith hot solution comprising an aqueous solution of about 1.5 to % H KOH or H 0H in an amount sufficient to co prise about 2 - by weight of straw and heat treated at about 9 - 100°C for about 10 - 15 minutes to obtain fiber release or softening of the fiber structure. Control of pH from ε.O to 13-0 during t stagε will rεs lt in increasing amounts of lignin being solub ized as the pH level increased.

Alternatively and more economically, the nitrated strav/ be washed by submerglng or spra ing v/ith water to remove exce acid and then pass .to the alkalizing step for release of the lignin. The acidic v/ash v/ater can thenjbe used for bringing the pulp to a neutral pH level. The nitrating agent and alka can also be added si ultaneously to the ■ strav/ before enterin the dryer in such a ratio of use that aipH of 11 - 12 is ain tained.

-TlaOH v/ould of pulp for pape

urea CO( ^" ;-^)„ αre oreferablc cince the sodium ion IG cii-r.ir.- ated or reduced but; can be used in combinα ion v/ith I- ^' cOH to ore easily control the pH level.

?or cubed straw by extrusion the dry form of thε nitrated straw is intimately mixed v/ith the alkalizing solution rεising the moisturs contεnt to not morε than 1 ?» to effect the formatio- of a firm Condensed cube. In this form the straw can be economically transported and proceεsεd further in a not solution for the produetion of paper or paper board or εnimal fεed.

The choiee between the use of nitrate salts vs. nitric acid oulά be dietated by economics: (1) Twice as much salt would be neces¬ sary to achieve the same level of delignification as with nitric acid which is generally low in cost. (2) The capital investment by using salts is reduced, since stainless steel would not be required for processing equipment. (3) The desired chenical Con¬ tent of the black liquor can be altered by changing alkalis, e.g. an undesirable sodium ion built up in the soil, if the black liquor is used as fertilizer, can be avoided. (4) Differences in aeeept- ability and digestibility by various aniir-als ¹ digestive System or the chemical requirenents needed for further processing of the residual black liquor into sizing, binders or resin extenders .

h ^' he ability to εp a/ or foa ths nitrating liquid on dry agricultural residues makes possible a process that is eεssntial- rv and pεr its the surface leachi g out of the nitrated lignin after the alkaline liquor is added by spray or foam (an εction t: can be simultaneous v/ith or follow immeάiε ely after the nitrati: stεge) v/hen the masε(lO - 15^> moisturs after drying if necessary) is subjscted to heat and pressure. Ξnough εur acε lignin is released to t-rovidε c binding material εufficient to bind thε shredded material. i.'hεn it iε then subjeeted to εn εppropristε hεrdening agent such as alum,v/hich also pro- vides v/ater resist--u-.ee and within the usual pressures εnά temperatures used in the manufacture of flakε or particie boεrc αerivεd from v/ood residues, an inexpenεive, v/ater rεsiεtcu builάing board, packaging board or fuel briquettes can be made from any defibered, flakeü or chipped material by generaτing

' its ov/n binding materials, eliminαting or reducing the uj of exnenεive resins such as uhenolics.

The follcwing examples are given as illustrations of the pres invention, although it is not intended that they limit its sc in any way. Alum or Al ₂ (SO.) ₃ always means Al-tSO. ' 18 H ₂ 0 which, if applicable, is used in an amount of 10% based on th nitric acid (100%). In the examples, and in the specification and clai s, all percentages refer to weight if not otherwise stated.

"p-srnniβ

Shredded wheat straw or barlεy strav/ v/ith 22'. ^" -?- moi3ture fed into a covered, non-pressure hydrapulper in v/hich v/ate in the weight ratio of 9 "• 1 of the air dry straw is circu v/ith a temperature of 75 C . ϊTE^KO-, is added εqu l to 0.1 the B.D. (bcne dry) straw and the solution is adjusted to pK 13 with ϊlεOΞ. The mixture is allowed to digest for 90 minutes , ho the temperature at 75°C , then drained of black licuor or p through a high density ures; •α τn r-epnn n __ n -, oereα as reou re

At this point the fiber can be washed of residual chemical, aά.jusx pH to 6.5 v/ith acid and alum εnd foilow normal pape procedure . V.'ashing is not necessary - but additional neut εcid v/ill be reαuired to offset residual alkali in the fib

Example 2

Example 1 is repeated, only substituting. HNC for NH ₄ NO-, in amount of 0.10% to the B.D. straw, and changing reaction tim to 60 minutes. Test results , which are equivalent to semi- chemical corrugating board ade from wood, are for a 115 gr. sheet

Concora (CMT 30) kg/cm2 25.6

Burst (M llen) Kpa 385

-,---p.r--n ' P_ üD] v/ood chius in thε amount äquivalent to 1C00 g . 3.D., are im erεεd in a cooking solution of 50C0 cc and held at 100 C in a closed non-pressure Container for 90 minutes. The cooking liquor is madε up of 0.75-^ of HNO--. to thε B.D. wood togethεr v/ith 7- ^ of NaOH to thε B.D. fibεr or 1.5P concentration as a solution. Thε black liquor is drained from thε chips and rεcyclεd to chemical exhaustion. The fiber after defiberization is soft and very licht in colour. al the Kappa l ^' o. of 125 sho s a relatively low percentage of delignif ication. Test results on defibered, screεned pulp v/εrε as follov/s:

Black Licuor Sol:

Test Baεe Sheet Added 2.S25S

-Basis Weight "g ./m2 ^" 117 123

Schopper Kegler Dεgrεe 3 3

Apparent Density gr/cm3 0.513 0.512

Burst Zpa 271 ^' 570

El^enάorf Tεεr -i ^' 1185 1154

Tensilε Htr 4400 4625

Elongεricn ?i 1.S5 2 ^c - - y ^~ y ^~

Hins Crush CD. Kn/m 1.20 1.05 M.D. Kn/m 1.47 1.14

Thε black liquor εolidε v/ere added to the pulp in dilute εuspension and prεcipitεtεd on thε fiber by ad.iusting thε

Example 4

Spruce v/ood chips v/ere cooked in a covered non-pressure vessel - hydrapulper - under the follov/ing conditions:

H-:0-, - Al (S0„)- Stage

Concentration

Time 60 Minutes o

Temperature 95 100°C

Drain and V/ash Recycl. aOH Sta^e pH Level 12.5 Time 30 Minutes

Temperature 95° - ιoo°c Drain Rεcyclε

re m n--: v/e:

Bone Dry Yiεld . ?0. yyι,

Kappa llo. 55

Initial Schopper RLegler 15°

-Final Schopper Riemer 30°

Basis Weight 137 gr/m2

Apparent Density 0. ,694 gr/cm3

Burst 6. ,2 Kpa

Ξi εndorf Tear 2060 l'?

Tensile 5009 m

Elongation 2. ,94 °P

Double Fold 21^0

Ring Crush 1. ,62 Kn/m

)le 5

Rice strav/ was cooked in the tv/o stage acid-alkali proceε in varying percentagε concεntration of EK0, - Al^CSO^)- under thε foilov/ing conditions: closed, non-pressure, rotating veεs operating at 95 - 100 C. Time to tempεraturε each sequence 10 minutes - total cooking time: 50 minutes v/ith intervεning v/ash cycle., Alkali stage pH 11.5«

Test results after defibεring - refining, but no scrssnin v/ere εε follov/s:

Triεl 1 2 ^' _

Acid Concentration % 1.00 0.50 0.25 ünblεschεd Yield 39.6 52.4 5".°

Bleεched Yield ^c ,ό 35.6 46.3 49.7

Initial G.E. Brightness 43 39 27

-Final G.E. " εo SO n ^~

Kappa Ico. 8.5 20.2 54.5

Ash ^' 1.6 11.2. 11.1

Alpha Cellulosε % 83.2 67.9 52.0

Eolo Celluloεε 95.9 79.5 ^.

Schopper ϊ&egler° 40 56 62

Basis εight gr/m2 61.0 59.2 62.5

Eurs 261 361 124

Tensile 3736 4651 223^-

Example 6

Defibered cotton stalks , coppice v/illow or similar growth bushes or grassy materials as εtraw are intimately mixed v/ith neutral pH black liquor solids from the instant process in an amount of 10 - 35?^ of the dry fibrous material and the mixtu: dried in a rotary dryer to 10 - 15$ inoi sture content . Paper- maker' s alum is added to bring the pH down to 4.5 - 5 _* 5 and the moisture content controlled to 7 - 10# and the mixture subj ected to pressure of 60 kg/cm2 and 150 C to form panel board in the usual manner of manuf acturing v/ood flake or particlε board.

Ξxamυle 7

Defibered cotton stalks, coppice v/illow or similar growth bushes or grassy materials as straw, containing 30 - 40 moistur are sprayed or foamed to achieve an intimate v/etting v/ith a mixed solution of ΞH0-. and NaOH p6 using , relative to a B.D. fiber, 0.50^ acid and 1.5$ N OH to produce a pH of 12 in the mixture at ^~ >0% moisture content.

The mixture is subjected to a cooking/digester temperature of 13 C and 65 Psi for 5 - 7 minutes which will release solubilized surface lignin on the fibrous structures. After diges ion the mixture is sprayed v/ith minder l acid to bring the pH to 7-0 and then follow or' apply concurrently v/ith an alum solution to bring the pH to 4.5 - 5«5« The mixture is then driε to 7 - 105o moisture in a rotary drier and then run over a continuous solid fiber board machine with heat and pressure to produce packaging board 2 - 6 " EΠ in thickness.

Example 8

Southern oinε wood flakes, cut tangentiallv to the lor circumference to a thickness of about 0J.S mm, are continuously fed into a screw conveyor. The v/ood has a lignin content of about 55 v/t. j. The flakes are sub erged and cooked in about six times their weight of a solution of' weight percent nitric acid to v/hich has been added aluminium isulphate in the ratio of

1 part alumlnium sulnhate to 10 oarts KT0~ for a period of i I -5 ₀ about 15 minutes at a temperature of about 95 ^~ - The slurry

of flakes in acid is then fed into a rotary cereen where t flakes are drained of the acid being washed v/ith a minimal amount of hot v/ater. The drained excess acid and v/ash wat are combined, fortified v/ith alum and concentrated nitric as needed, .and recycled for use in the initial nitration s The flakes are then conducted to a storage vessel, from wh they are fed into a screw conveyor, containing about six t their weight of a solution of about 0.5 weight percent sod hydroxide, giving a pH of 12 - 13, at a temperature of abo 95°C There they are cooked for about 15 minutes. The fl partially defibered, are drained of the alkaline solution (in v/hich the lignin-niträte has dissolved) for its recycl or purging with a rotary screen, then put through a defibr in order- to separate the fibers _r follov/ing v/hich they are v/ashed in a rotary washer v/ith a minimal amount of hot v/at The black liquor that is drained off in the rotary screen recycled to the lignin extraction step.

The pulp leaving the rotary washer has been deligni to the extent required and defiberised. It is then screen by conventional screeniiαg eσuip ent to remove oversised particles which have not been defiberised, v/hich are retu to the nitration step for reprocessing.

Example 9

I

Thisexample simulates the use of a sulphite digester p ducing bleachable pulp (Kappa No. 8) using pressure under conditions as follows:

V/ood Spruce

Form Flakes 0.5 - 0.6 mm thick

Charge 1.5 kg (dry)

Di ester Stationary clrculating

Impregnation Time 15 _Λ Hiuutes

Impregnation Temperature 70°σ .

Impregnation Chemical 1

Concentration •cc' EI 70-, + a lum Cooking Time 15 11: .__{ ^' ~ -~ _* ^~ ~

Time to Cooking Temperature ι-l ^~ ^ -i it : Cooking Temperature S5 - 95 ^~ C

Cooking Chemical 7. fJ .HNO-, + alum

Ratio Licuor to dry v/ood 4 : 1-

Pressure 7 - 22 p.s.i.g.

Gas off None j I

Delignification Stage 20 Minut s

Delignification Temperature 95 - 100 C

Delignification Chemical 0.25^ .H OH _^ -TT _P

Delignification PH

^~ StartiMg 12 ^ iOM_ ^I

resυ ts on the oaner uroαucec . Ol-LCV/S :

Refini .nc ^' ' nut 6S

0 - 7 10

?reeness, SR 21 27 39 46 52

Basis Weight, gr/m2 81.7 80.9 78.5 80.0 8O.9

Caiiper, mm 0.115 O.iOO 0.094 0.089 0.089

Apparent Density, kg/cm3i 00..771100 0.809 0.835 0.899 0,909

Elongation £-> 1.9 2.9 2.8 2.7 3.2 ensil Strength, Ktr 6600 7400 7360 7480 8240

H llen Abs, Kpg 258 360 324 312 380

Müllen Index, Kpa 316 444 412 390 470

Tear - Brecht-Imset , Kn 1118 1187 942 922 11C9

Ξxasrpie 10

A non-pressure process using low concentration circulated chemical and longer times pro ucing linerboard pulp, Kappa No. used thε following conditions:

Wood Soruce Flakεε, 0.5 - 0.6 :

Chargε 1 ^* . 3 kg, dry

Imprεgnation Time 30 Minutes

Impregnation Temperature 50°C

Impregnation Che ical 0. 5?a I-ETO, Solution + alum

Cooking Time 45 Hinutϊs

Cooking Temperatur 95°C

Cooking Chemical 1 .8# EHO- Solution ^{+ a lum}

Ratio of Liquor to dry Wood 6 ^~

Delignification Chemical N3OE

Dεlignification pH Starting 12

Ξxamole 11

A non-pressure process using a hydrapulper producing an animal f eed grade of straw : heat Strav/ 1-ϊeehanically shredded

Charge 1.2kg, dry

Impregnation Time 15 Hinut es

Impregnation Temperatur ε 50°C

Impregnati on Chε ical C . 05 Ε lO- Solution + alum

Ratio of Imprεgnation Chemical - ^> to dry Chargε 0. 6>J

Cooking Tiπε 15_ inutes

Cooking Temperature 95 C

Cooking C hemical 0. 1 . HNO-- Solution. + alu-m Ratio of Cooking Chemical ^ to dry Charge 1 . #

Dεlignification r.aOH, pH 12 , -

-

EyamPl e 12

A spray storage system for straw to produce pulp for packaging papers:

V/hεat Straw Mechanically shredded

Starting Moisture 1 # (beforε εpraying)

Finishing Moisture 35?»

Chemical surayεd 3^ HKO, (100g) of dry fibεr

Heat applied None ° ⁺ alum

Storage Period Six Months

Delignification NaOH, pH 12

Delignification Time 10 ₀ Minutes

Delignification Tεmperaturε 50 C

Exampiε 15

-A Hon-pressure procesε using-an open hydrapulper producing a semi-chemical type pulp for usε as corrugating medium combine v/ith v/aste fibεr and strav/ black liquor (lignin) solids.

Whsat Straw Mechanically shredded

Charge 1.2 kg atro

Imprεgnation Ti ε 15 Kinutεs

Imprεgnation Chε ical 0.05^ ETO, conc. + alum

Ratio of Imprεgnation ^

Chεmical to Chargε - ^* _' '

Impregnation Temperature 50 C

Cooking Time 30 Minutes

Cooking Chemical ^0, o^ ^IN' ° ^conc * ^{+ alum}

Cooking Temperaturε 95 C Ratio of Cooking Chεmical to Charge 1.5-^

Delignification 15 Minutes, NaOH to ?H12, 95"

Board Composition

Defibered unscrsened Pulp 7 - ^" ■

Mixεd V/aste Fibεr 38

Un cdifiεd Lignin Solids 15 ?•»

Test Results - Produced on Paper Machine

Basis Weight, gr/m2 105

Müllen Index, Kpa 233

El εndorf Tεar, Md/Cd/Mn 812/859

Concora, gp 15