Abstract: The invention relates to a process for digesting woodchips used in papermaking. The process employs a digester additive, which is a mixture of (a) a polyglycoside, and (b) a polyoxyalkylene glycol. The digester additives are compatible and stable at elevated temperatures in the highly alkaline white liquor used in the digestion of woodchips into pulp. The invention also relates to the digester additive compositions.

Abstract: A method of dispersing hydrophobic particles in aqueous suspensions comprising adding to the suspension an effective amount of an ethylene oxide-propylene oxide block copolymer, wherein the copolymer has a molecular weight of from about 1,000 to about 50,000 and a HLB of from about 1 to about 4 and compositions comprising the ethylene oxide-propylene oxide block copolymer.

Abstract: Separation of dissolved and colloidal high molecular weight organic by-products from liquors or filtrates in a cellulosic pulping process to improve the overall efficiency of the process.

Abstract: Pulps or papers, especially chemimechanical or thermomechanical pulps or papers, which still contain lignin, have enhanced resistance to yellowing when they contain an effective stabilizing amount of a hindered amine compound which preferably is a nitroxide, a hydroxylamine or an ammonium salt thereof. This performance is often further enhanced by the presence of one or more coadditives selected from the group consisting of the UV absorbers, the polymeric inhibitors, the nitrones, the fluorescent whitening agents, metal chelating agents, sulfur containing stabilizers, metal salts and diene compounds. Combinations of nitroxides, hydroxylamines or their salts, benzotriazole or benzophenone UV absorbers and a metal chelating agent are particularly effective. Selected derivatives of 1-oxyl-2,2,6,6-tetramethyl-piperidin-4-ol and selected hydroxylamine salts are novel compounds and are surprisingly effective for this purpose.

Abstract: Pulps or papers, especially chemimechanical or thermomechanical pulps or papers, which still contain lignin, have enhanced resistance to yellowing when they contain an effective stabilizing amount of a hindered amine compound which preferably is a nitroxide, a hydroxylamine or an ammonium salt thereof. This performance is often further enhanced by the presence of one or more coadditives selected from the group consisting of the UV absorbers, the polymeric inhibitors, the nitrones, the fluorescent whitening agents, metal chelating agents, sulfur containing stabilizers, metal salts and diene compounds. Combinations of nitroxides, hydroxylamines or their salts, benzotriazole or benzophenone UV absorbers and a metal chelating agent are particularly effective. Selected derivatives of 1-oxyl-2,2,6,6-tetramethylpiperidin-4-ol and selected hydroxylamine salts are novel compounds and are surprisingly effective for this purpose.

Abstract: The invention relates to a process for digesting woodchips used in papermaking. The process employs digester additive, which comprises a sultaine or mixtures of a sultaine with a nonionic surfactant selected from the group consisting of (a) polyglycosides, (b) polyoxyalkylene glycols, and (c) mixtures thereof as digester additives. The digester additives are compatible and stable at elevated temperatures in the highly alkaline white liquor used in the digestion of woodchips into pulp. The invention also relates to the digester additive compositions.

Abstract: A method of stabilizing hydrogen peroxide in an aqueous solution, such as a circulating water slurry, comprising a peroxide, such as hydrogen peroxide. The aqueous solution may include organic matter. The method comprises adding an aldehyde donor, such as a methylolhydantoin, to the solution (or slurry). The inventors have discovered that aldehyde donors significantly reduce the decomposition of hydrogen peroxide by catalase and other peroxide decomposing enzymes, which are often present in recycled paper. As a result, less hydrogen peroxide needs to be added to a solution to effectively bleach organic matter in the solution. Furthermore, aldehyde donors are safe to handle and cost effective. Another embodiment is a method of bleaching recycled papers in a circulating water slurry comprising organic matter. The method comprises adding hydrogen peroxide and an aldehyde donor to the slurry.

Abstract: An integrated process for the combined fermentation and the conversion of liquid and solid residues generated by the cane sugar industry into a variety of useful products. The process also relates to the treatment of other biomass materials. The process combines elements of alcohol-based organosolv pulping with fermentation in a fully integrated operation. This process eliminates the need for separate costly facilities, thus reducing capital and operating costs, providing opportunities for heat and energy reduction and a high degree of internal process recycle. The process would replace costly waste and residue treatment operations with revenue generating operations.

Abstract: A process for producing paper and absorbent products of increased strength includes extracting wood particulates with a solvent selected from methanol, ethanol, and acetone at a pressure less than 50 psi to reduce the pitch and volatile organic compounds of the particulates without significant dissolution of lignin and cellulosic components. The wood particulates are pulped to produce a pulp with reduced pitch content. A slurry is prepared from the pulp and used to form paper products.

Abstract: Paper and absorbent products having reduced pitch content and enhanced properties, including increased tensile index, tear index, burst index, Scott Bond, smoothness, and stiffness. Further, pulps of the invention, although having slightly reduced brightness, are more responsive to bleach chemicals thereby permitting the use of less chemicals to achieve a specific brightness. The products are produced by a process that includes extracting wood particulates with a solvent for naturally-occurring volatile organic compounds and pitch. The extracted wood particulates are then pulped and formed into paper and absorbent products with enhanced properties. Due to the extraction of volatile organic compounds, the pulping and paperforming stages of the process are substantially free of emissions of volatile organic compounds that occur naturally in wood. Moreover, the extraction of pitch reduces or eliminates pitch fouling of equipment and permits the production of paper products of enhanced qualities.

Abstract: Pulps or papers, especially chemimechanical or thermomechanical pulps or papers, which still contain lignin, have enhanced resistance to yellowing when they contain an effective stabilizing amount of a hindered amine compound which preferably is a nitroxide, a hydroxylamine or an ammonium salt thereof. This performance is often further enhanced by the presence of one or more coadditives selected from the group consisting of the UV absorbers, the polymeric inhibitors, the nitrones, the fluorescent whitening agents, metal chelating agents, sulfur containing stabilizers, metal salts and diene compounds. Combinations of nitroxides, hydroxylamines or their salts, benzotriazole or benzophenone UV absorbers and a metal chelating agent are particularly effective. Selected derivatives of 1-oxyl-2,2,6,6-tetramethyl-piperidin-4-ol and selected hydroxylamine salts are novel compounds and are surprisingly effective for this purpose.

Abstract: A method of treating cellulose pulp mill condensates having an MeOH content using an evaporator and a steam stripper having a reboiler, comprising: (a) Collecting a feed liquor stream having at least 50% of the pulp mill MeOH. (b) Feeding the feed liquor stream to the evaporator having at least two heating element sections separated on a motive steam side. (c) Evaporating the liquor in the evaporator to produce a vapor containing at least 40% of the at least 50% of the pulp mill MeOH. (d) Compressing the vapor from (c) to increase the vapor pressure. (e) Using the vapor from (d) as condensing heating media in (c) for the evaporation in a first heating element section of the evaporator and venting a portion of the vapor through the first heating element section. (f) Compressing the vented vapor from the heating elements of the evaporator from (e) to increase the vapor pressure to be used as heating media in the reboiler.

Abstract: The present invention is related to a method of producing paper pulp from a fibrous raw material. According to the invention, such pulpwood is used in which the content of phenol compounds or phenolic derivatives is clearly, advantageously at least 20% lower than the average content of such compounds in the native grade of the raw material. Advantageously, the content of parahydroxy-benzoic acid (PHBA) is determined from the pulpwood and pulpwood containing low PHBA levels is used as pulping raw material.

Abstract: Deinking of impact and nonimpact printed paper is accomplished by repulping the printed paper in an alkali aqueous medium containing a deinking composition comprising one or more nonionic surfactants and/or alkanols. The presence of the deinking composition causes ink particles to agglomerate, which are removed from the aqueous medium by size and density separation. The invention provides an agglomeration method with high ink removal from all types of impact and nonimpact printed paper.

Abstract: An improved process for delignification of lignocellulosic raw material, such as wood chips, for the production of cellulose pulps for use in the manufacture of paper or paperboard and an improved pulping aid composition for use in said process are disclosed wherein the wood chips are treated in a closed reaction vessel with an alkaline pulping liquor with an amount of a cyclic keto compound, such as anthraquinone, included therein for achievement of a determined pulp yield, wherein the improvement comprises a reduction in the amount of anthraquinone required to achieve said yield by the addition to said alkaline pulping liquor, in addition to a reduced amount of the anthraquinone, a surfactant mixture comprising at least one alkyl alcohol alkoxylate and at least one polyoxyalkylene glycol ether of an ester of an acid selected from the group consisting of ricinoleic acid and 12-hydroxystearic acid.

Abstract: A continuous solvent pulping process is practiced with oxygen free gas (e.g. nitrogen) purges of all major treatment vessels during the time when the process is arrested or terminated. The wood chips or other cellulosic fibrous material to be pulped is steamed in a first horizontal steaming zone at pressure of about 10-20 psi, and then in a second horizontal steaming zone at a pressure of about 20-75 psi. The first and second zones are isolated by a low pressure feeder. Steam is introduced into the material in the second steaming zone to flow cocurrently with it. Gases, including vaporized solvent (e.g. ethanol or other alcohol) are vented from the steaming zones, and solvent is added to the steamed material prior to feeding to a high pressure feeder. The high pressure feeder introduces the material into the top of a single digesting vessel, liquid and chips being separated at the top of the digester vessel without mechanical means that could cause a spark.

Abstract: This invention provides for the recovery of lignin and other by-products from the pulping of fibrous plant material. In accordance with this invention, solvents and filtrates are recovered and recycled for reuse. This results in significant solvent and energy savings. Filtrates from the bleaching and delignification of the pulp are recycled for reuse in pulping, separation, and recovery of lignin and other by-products which results in significant energy savings and mitigation if not the elimination of pollution typically associated with bleaching. This invention also relates to products derived from the process and apparatus for carrying out the process. Lignins of various molecular weights and by-products of the pulping process are also recovered. The lignins are precipitated in high yields and at a high rate from a black liquor produced by pulping wood at high temperature and pressures. As a by-product of this process a purified furfural product is recovered.

Abstract: A method for separating lignocellulosic material into (a) lignin, (b) cellulose, and (c) hemicellulose and dissolved sugars. Wood or herbaceous biomass is digested at elevated temperature in a single-phase mixture of alcohol, water and a water-immiscible organic solvent (e.g., a ketone). After digestion, the amount of water or organic solvent is adjusted so that there is phase separation. The lignin is present in the organic solvent, the cellulose is present in a solid pulp phase, and the aqueous phase includes hemicellulose and any dissolved sugars.

Abstract: A bleached pulp having a high viscosity for a given permanganate number is formed by pretreating never dried pulp with an organic solvent medium to produce a treated pulp composed of said never dried pulp in the medium and then bleaching that treated pulp using ozone at a pH of 1.5-5 to provide a bleached pulp while reducing the viscosity loss during the ozone bleaching step significantly compared to that what would occur if the medium used in the ozone bleaching were water.

Abstract: An apparatus and process for the solvent pulping and washing of pulp using vessels purged of oxygen free gas when the process is arrested or terminated. The washing is accomplished by first continuously passing the pulp to a pressure diffuser, then to a first multi-stage drum displacer washer, and then to a second multi-stage drum displacer. In the pressure diffuser the lignin is washed out of the pulp, utilizing as wash liquid a mixture of solvent and water having a solvent concentration equal to or higher than that required by the extraction process within the digester, and at a pressure at least about 350 psi. The pressure in the second and third stages is lower, and water is the wash liquid in the third stage. Alcohol can be recovered from the spent wash liquid of the first wash stage, so that all but about ten gallons or less of alcohol per ton of pulp is recovered.

Abstract: In the deinking of feed waste papers comprising magazines and newspapers at a weight ratio of magazine to newspaper of from 5/95 to 60/40, a reclaimed pulp with excellent qualities can be obtained by adjusting the treating temperature in the flotation step to 40.degree. to 80.degree. C. and adding a deinking agent, which contains an alkylene oxide adduct of an oil or fat, wherein said alkylene oxide adduct comprises ethylene oxide and propylene oxide added at a molar ratio of ethylene oxide to propylene oxide of from 1/1 to 5/1, and has a cloud point of 45.degree. to 90.degree. C., at least in one of the steps of the deinking process.

Abstract: A method for controlling foam in the papermaking operation comprising a polyether surfactant and polyethoxylated sorbitol hexaoleate.

Abstract: An improved oxygen bleaching process wherein the pulp is bleached in an aqueous organic medium wherein a polyhydric alcohol constitutes between 10 and 70% by weight of the medium to produce a pulp having a viscosity at least 2.5 cp higher than a similar pulp bleached using the same conditions in an aqueous atmosphere to the same kappa no. of 8 ml.

Abstract: The present invention provides a process for the oxidative bleaching of wood pulps and for deinking waste paper by means of hydrogen peroxide and a stabilizing agent, wherein, as stabilizing agent, there is used 2-oxo-2-(4-hydroxyphenyl)-acethydroximic acid chloride (N,4-dihydroxy-.alpha.

Abstract: A method for conditioning the felts in a papermaking process utilizing deinked secondary fiber in the furnish by adding a felt conditioner consisting of from 5-33% of a nonionic surfactant, from 5-33% of a dispersant, or blends thereof, with the remainder water; wherein the nonionic surfactant is selected from the group consisting of ethoxylated nonylphenols having moles of ethoxylation of from 7.5 to 30 and an HLB of about 12 to 17.2 and di-alkyl phenol ethoxylates having moles of ethoxylation of from 15 to 24 and an HLB of about 13 to 15.1; and wherein the dispersant is selected from the group consisting of the sodium salt of naphthalene sulfonate formaldehyde-condensate having an average molecular weight of from about 700 to 3500, the potassium salt of polymerized alkyl naphthalene sulfonic acid having an average molecular weight of approximately 1000, or the sodium or ammonium salt of lignosulfonate. Additionally, from 1 to 5% of an alkylether hydroxypropyl sultaine enhances performance.

Abstract: A stable defoamer composition and method of defoaming an aqueous system is disclosed. The composition comprises an alcohol alkoxylate, at least one surfactant having a melting point less than 20.degree. C., and a low HLB, ethylene oxide/propylene oxide block copolymer, said block copolymer carried in a mixture comprising polybutene.

Abstract: A high solids black liquor which has solids content of at least 65% by weight of liquor is mixed with a viscosity reducing additive prior to firing in a chemical recovery furnace. The additive is an admixed compound consisting of monoethylene glycol, diethylene glycol and triethylene glycol.

Abstract: A process for bleaching pulp by impregnating the pulp with an aqueous organic solvent medium and then bleaching in an ozone stage (Z stage) to form a bleached pulp characterized in that organic solvent in the organic solvent medium accompanying the pulp through the ozone stage is neutralized and stripped from the bleached pulp leaving the ozone stage and the separated organic solvent is recovered for reuse.

Abstract: Disclosed is a method of removing ink from xerographically printed paper. The method comprises pulping said printed paper in an aqueous slurry at a non-acidic pH to a consistency of about 8% or less. Next, added to the pulp slurry is a sufficient amount of long chain alcohol, the long chain alcohol having a melting point above room temperature, for a time sufficient with heating at a temperature sufficient, whereby an agglomeration of long chain alcohol and ink particles is formed. Next, the heating is stopped whereby the agglomeration solidifies into particles that settle to the bottom of the pulp slurry. Then, the agglomeration of solidified particles is removed from the pulp slurry thereby leaving a remaining slurry of deinked paper fiber and water. Optionally, the remaining slurry is subjected to flotation to remove substantially any remaining minute ink left particles behind after the agglomeration.

Abstract: A process for the delignification of cellulose fiber plant raw material for the production of pulp using separate impregnating and delignifying stages, each using alcohol and alkali. The process may be carried out in batch or in a continuous process. Less alcohol is used in the delignification stage than in the delignification stage. The pulp produced has very good properties because different amounts of alcohol are being used in the impregnation stage and in the delignification stage.

Abstract: A process for enhancing pulp washing efficiency is disclosed. An anionic surfactant is added within the washing or pulping operation to enhance the removal of lignin and spent cooking chemicals from pulp.

Abstract: A process for deinking wastepaper by combining a water-miscible organic solvent with inked paper to create a solvent/paper slurry, agitating the solvent/paper slurry to assist in releasing ink from the paper, separating the ink-ladden solvent from the paper, and washing residual ink and solvent from the paper.

Abstract: A composition comprising a .beta.-branched aldol ether alcohol having the structure: ##STR1## wherein X=5 to 8, at least one surfactant and water which is useful to prevent or reduce foam present in the aqueous medium of paper processing operations.

Abstract: A process for producing bleached pulp from a fibrous plant material (e.g., wood), wherein the material is contacted with an alcohol solvent in a pulping zone to extract lignin from the fibrous plant material. The resulting pulp is then treated with a hydroperoxide or peroxide bleaching agent in a bleaching zone to form bleached pulp. Alcohol formed from the hydroperoxide or peroxide during the bleaching process may be recycled to the pulping zone. A preferred alcohol is tert-butyl alcohol, while a preferred hydroperoxide is tert-butyl hydroperoxide.

Abstract: A method of hardening wood using a pulping agent for the chemical separation of lignin from cellulose in the wood without damage to either component. The pulping agent comprises the reaction product of (a) a compound produced by electrolytic oxidation of a predetermined amount of a loweralkanolamine in aqueous solution and neutralized with a strong mineral acid, with (b) the loweralkanolamine used in excess relative to the predetermined amount of loweralkanolamine subjected to the electrolytic oxidation. Also disclosed are processes utilizing such a pulping agent for chemically debarking whole logs as well as for converting soft wood into hard wood.

Abstract: The present invention is directed to the use of certain ethoxylated compounds to increase the yield of green liquor semi-chemical pulping processes, the compound have the following structures: ##STR1##

Abstract: An improved wood pulping process for the delignification of wood in a solvent wherein the solvent is a supercritical fluid under supercritical conditons and contains a delignification agent such as sodium hydroxide, sodium sulfide and/or sodium bisulfate.

Abstract: The chemical components of lignocellulosic material which have been dissociated by a steam explosion process can be extracted from the mixture of components using a solvent extraction process. The solvents are water, alcohol and a mild caustic in that order, or the alcohol step can be by-passed and only water and caustic are used. The caustic is a stronger solvent and it will extract the alcohol solubles along with the caustic only solubles. The eluant from the these extractions contains a range of lignin derived substances, which have different applications, such as thermoplastic and thermosetting characteristics. This invention describes a method for partitioning these lignin components into reproducible fractions having definable characteristics for particular applications. For instance, many copolymer applications require a thermosetting only fraction of the lignin. Other applications require a thermoplastic only lignin.

Abstract: In the method of chemical pulping of wood including a chlorination stage pulp bleaching step followed by alkaline extraction, a method of reducing the amount of dioxins and furans produced thereby is disclosed wherein the brownstock pulp is first washed with alcohol prior to bleaching.

Abstract: The invention relates to a method and an equipment for preparing NaCMC, in which (a) cellulose is slushed in the reaction medium until a consistency of c. 5-15%, preferably 5-10%, (b) the fibre suspension obtained in step (a) is thickened to a consistency of c. 20-35% and (c) the pulp containing reaction medium obtained in the second step is homogenized by means of a screw conveyor having a screw pitch which decreases from an inlet opening thereof towards an outlet opening thereof, in order to increase the reactivity, whereby a mercerization activating the cellulose is carried out after step (b) and/or (c), and the cellulose thus pretreated is etherified in a manner known per se.

Abstract: A method for the continuous countercurrent production of lignins and sugars from wood and other ligno cellulosic materials by organosolv delignification or saccharification at elevated temperatures and pressures is disclosed. The novel method comprises: (a) continuously introducing comminuted lignocellulose materials with a natural mositure content into a reaction vessel from one end; (b) continuously introducing a cooking liquor comprising a major proportion of organic solvent, a minor proportion of water, and a slight amount of inorganic acid countercurrently into the reaction vessel from the opposite end; (c) causing the comminuted lignocellulosic material to be contacted by the cooking liquor; and (d) continuously withdrawing cooking liquor from the reaction vessel after it has commingled with and has dissolved sugars and lignin and other substances from the comminuted lignocellulosic material.

Abstract: A process for the separation of the fibres from each other in lignocellulosic (straw, bagasse, wood) composites, and at the same time to dissociate the Lignin and the Xylan in the middle lamella and the primary wall of the lignocellulosic material, to enable a simple non reactive solvent extraction of the middle lamella and primary wall components while substantially retaining the structural integrity of the fibre bundle, sometimes referred to as the S2 layer, which is the strength member of the lignocellulosic fibre. The purpose of this process is to produce a fibre suitable to replace conventional Chemical Thermal Mechanical Pulp, for paper or as a carrier for high absorbency Cellulose in diaper and similar absorbent material applications, and at the same time to recover the chemical components of the middle lamella and the primary wall of the fibre, as co-products in a marketable, chemically reactive form.

Abstract: The chemical components of lignocellulosic material that have been dissociated by a stream explosion process can be extracted from the mixture of components using a solvent extraction process. The dissociated lignocellulosic material is put in a column and the substances which are soluble in water, alcohol and caustic are leached out of the mixture by solvent extraction with relatively small volumes of those solvents. No agitation is used. Substantially pure cellulose remains in the column and it can be bleached before removal from the column.

Abstract: A process for the pulping of lignocellulose-containing material, wherein the material is contacted with a pulping medium containing at least 75% by weight of a solvent system, which solvent system comprises from 20 to 95% by weight formic acid; from 5 to 80% by weight of at least one member selected from primary alcohols having from 1 to 3 carbon atoms and esters of formic acid with primary alcohols having from 1 to 3 carbon atoms; and up to 70% by weight of at least one component selected from acetic acid and esters of acetic acid with primary alcohols having from 1 to 3 carbon atoms; and allowing the material to digest at a temperature in ther range of from 140.degree. to 200.degree. C.

Abstract: An improved method of brown stock washing is disclosed. A nonionic surfactant in combination with a polyelectrolyte dispersant, and preferably a solvent, are utilized in the washing step in the pulping of virgin cellulosic fiber. The methods of the invention provide for the enhanced removal and recovery of cooking chemicals and organics from the pulp.

Abstract: A process for preparing a cellulose paste by treatment of lignocellulose materials which comprises impregnating wood or vegetable shavings in divided form with an aqueous solution containing 2 to 20% by weight of alkaline metal hydroxides, alkali metal salts, or alkaline earth metal hydroxides, adjusting the weight of the solution retained by impregnation to a value representing 1 to 3 times the weight of treated material, the ratio of the weight of the impregnated mass to the dry weight of the lignocellulosic material being preferably not more than about 2.6:1, subjecting the impregnated masses to cooking treatment by exclusively indirect heating at a temperature varying from 150.degree. to 200.degree. C. without exerting any mechanical disintegrating action for a period varying from 15 to 60 minutes, and pressing the cooked product so as to extract therefrom the solubilized lignin in the form of a black liquor containing about 50% of dry material.

Abstract: A sulphite cooking process is described for the production of pulp from materials containing lignocelluloses, with recovery of the cooking chemicals, in which the cooking, the blowing, the washing and the bleaching are performed sucessively. The waste liquor is subjected to several thermal treatments for the recovery of the cooking chemicals. For the cooking of the lignocellulosic materials, alkaline sulphite solutions are used, to which one or, in mixture, several low-boiling solvents are added, as well as at least one compound suitable as a redox catalyst.

Abstract: Lignin is precipitated in high yields and at high rates from a black liquor produced by pulping wood at high temperatures and pressures with an aqueous lower aliphatic alcohol solvent. The lignin is precipitated by diluting the black liquor with water and an acid to form a solution with a pH of less than about 3, an alcohol content of less than about 30% by volume and a temperature of less than about 75.degree. C. The precipitated lignin, when subsequently dried, is in the form of a powder which requires little or no crushing to convert it into a fine uniform size suitable for use without further significant processing.

Abstract: A process for the delignification of cellulosic materials, wherein a high-yield cellulose pulp and high-value by-product, such as reactive lignins of low molecular weight are produced, which comprises degassing lignocellulosic material, rapidly heating the lignocellulosic material in a liquor comprising water, an organic solvent and a buffer thereby maintaining a substantially neutral solvent extraction, such that said lignocellulosic material is cooked in the liquor as it is heated from a temperature of 150.degree. C. to a selected maximum temperature in the range of 200.degree. to 280.degree. C.; and rapidly cooling the mixture to a temperature less than 150.degree. C. The reaction is controlled to maximize reactive lignin solvation while suppressing cellulose degradation.

Abstract: A process for the production of sugars, and optionally cellulose and lignin, from lignocellulosic vegetable materials which comprises subjecting the vegetable materials to a chemical pretreatment with a mixture of water and lower aliphatic alcohols and/or ketones at a temperature from 100.degree. to 190.degree. C. for a period of from 4 hours to 2 minutes with control of the breakdown of the hemicellulose components followed by separation of residue and a subsequent main chemical treatment with a similar solvent mixture at elevated temperatures for a further period of from 6 hours to 2 minutes.