Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/02—Direct processing of dispersions, e.g. latex, to articles
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/18—Manufacture of films or sheets
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2301/00—Characterised by the use of cellulose, modified cellulose or cellulose derivatives
  • C08J2301/02—Cellulose; Modified cellulose
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2301/00—Characterised by the use of cellulose, modified cellulose or cellulose derivatives
  • C08J2301/08—Cellulose derivatives
  • C08J2301/22—Cellulose xanthate
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2301/00—Characterised by the use of cellulose, modified cellulose or cellulose derivatives
  • C08J2301/08—Cellulose derivatives
  • C08J2301/22—Cellulose xanthate
  • C08J2301/24—Viscose

Definitions

• the present invention provides an optimised method of processing cellulose in which a non-dissolving cellulose-containing pulp is used to prepare a viscose solution for the preparation of cellulose films or cellulose shaped articles, such as fibres.
• cellulose-containing pulp In addition to its utility in the industrial production of paper, cellulose-containing pulp has a number of other applications, including the industrial manufacture of cellulose films and cellulose shaped articles, such as fibres.
• Pulp is generally prepared from those raw materials by treatment to separate out and remove lignin and hemiceilulose, so as to maximise the cellulose content of the pulp.
• pulp can be prepared mechanically, by milling or grinding the raw material to physically separate cellulose fibres from hemi-cellulose and lignin.
• the raw material can be chemically treated to dissolve lignin and hemiceilulose, ideally without disrupting the cellulose fibres native to the raw material
• chemical pulping processes include the Kraft process and the Sulphite process.
• hybrid pulping processes where chemical processing steps are employed in a mechanical pulping process, or vice versa. Examples of such processes include thermomechanical processes, where, in addition to mechanical comminution, wood chips or other raw materials are also exposed to heat, and chemithermomechanical processes, where wood chips are firstly exposed to chemicals used in chemical pulping processes before comminution and exposure to heat,
• cellulose regeneration there are two classes of pulp obtained from chemical pulping processes. Firstly, there are 'dissolving pulps' or 'dissolving grade pulps', which are used as feedstocks in the viscose process. Dissolving pulps are characterised by a high cellulose content, around 90% or higher. As their name suggests, they are soluble in solvents or dopes used in commercial cellulose regeneration processes.
• the other class of pulps are 'non-dissolving pulps', examples of which include 'market pulps' or 'fluff pulps'. These have limited utility in the viscose process and in other processes for producing cellulose films or cellulose shaped products because, as their name suggests, they are not soluble in conventionally used processing solutions or dopes, Accordingly, they are principally used in applications other than cellulose regeneration. For example, over 80% of all fluff pulp is used in the production of baby diapers.
• Non-dissolving pulps examples include Pearl 429 (Weyerhauser), Peach (Weyerhauser), Fluff 416 (Weyerhauser), Port Wentworth SBSK (Weyerhauser) and Bleached Eucalyptus pulps available from Fibria, UP and ENCE.
• non-dissolving pulps differ from dissolving pulps in a number of ways. For example, they generally have a higher hemi- cellulose content, a lower alpha-cellulose content, are less refined, have higher degrees of polymerisation (DP) and / or have lower quality control than dissolving pulps.
• DP polymerisation
• the viscose process as generally practiced includes the steps of dissolving or slurrying a pulp in caustic soda, steeping it in the caustic solution, xanthating the cellulose with carbon disulphide, and re-dissolving it in an aqueous caustic solution to form viscose.
• Viscose is typically filtered and refiltered in order to maximise the purity of the material to improve product quality. It is then formed into a desired shape using techniques known to those in the art, for example by extruding it through a slit or rollers to form a sheet of film, or by extruding it through a spinnerette to form a fibrous material. The formed viscose is then contacted with an acidic casting solution to regenerate the cellulose from viscose.
• the extruded cellulose film may also be passed through additional rollers and baths to clean and soften the film, and to obtain the desired optical and mechanical properties.
• the steeped cellulose slurry or solution may be subjected to mercerisation, where a portion of the caustic liquid is removed, for example by pressing, to achieve an alkali cellulose having a target cellulose and soda content.
• the purpose of this step is to improve the properties of the cellulose, notably by reducing its degree of polymerisation (DP).
• the resulting viscose solution will have unacceptably low filterability for film/shape forming applications. It is this adverse effect on the filterability of viscose solutions which has prevented non-dissolving pulps being used in the viscose process in proportions greater than about 5% to 10% by weight of the total pulp.
• Dissolving pulps which are optimised for use in the viscose process can be used to produce viscose liquids exhibiting a high level of filterability. Filterability can be measured using a number of different testing methods.
• the clog constant (Rv) is a calculated by taking the slope of the curve generated by plotting the weight of viscose passed through a filter cloth in five minute intervals.
• TVW is a measure of the total amount of viscose filtered within a thirty minute period.
• Ball fall velocity measured in seconds, is a measure of the time it takes for a steel ball weighing 0.13g +/- 0.02g to sink to the bottom of a sample of viscose solution having a depth of 205mm,
• the fibre count method can be used, in which the quantify of residual fibres in the solution is measured.
• a process for producing cellulose film or cellulose shaped articles comprising the steps of steeping a non-dissolving cellulose-containing pulp in a basic liquid, xanthating the steeped cellulose-containing pulp with carbon disulphide, dissolving the xanthated cellulose-containing pulp in a basic liquid to form a viscose solution, and casting a cellulose film or cellulose shaped article from the viscose solution, wherein one or more of the following optimised processing conditions are employed: steeping is carried out, at least partially, at a temperature of about 30°C to about 50°C, steeping is carried out in a basic liquid having a concentration of base of about 16% to about 18% by weight, xanthation is carried out using about 30% to about 40% carbon disulphlde by weight of cellulose present, xanthation is carried out at a temperature of about 20°C to about 30°C, dissolution is carried out, at least partially, at a
• the optimised processing conditions of the present invention can be used to form high-quality viscose solutions, which are suitable for use in the preparation of cellulose films or cellulose shaped articles, from non-dissolving pulps.
• the shaped articles which are produced according to the processes of the present invention are most preferably fibres.
• Other products which may also be formed include ropes, yarns, cloths or cigarette filters. These other products may be formed directly from the cellulose solution, or may be formed from fibres spun from the cellulose solution.
• steps b) and c) to cellulose-containing pulp it will be appreciated that the pulp will not necessarily be in the form of a pulp per se, but may be in the form of a processed version of the pulp, for example a slurry, solution or crumb prepared from the non- dissolving pulp.
• pulps exhibit one or more of the following properties: relatively high hemi-cellulose content (typically about 10% or greater), relatively low alpha-celiulose content (typically about 90% or less, more typically about 83% to about 89%), less refined, relatively high degrees of polymerisation (DP) (typically about 700 to about 1200) and / or have relatively low quality control, as compared to dissolving pulps.
• relatively high hemi-cellulose content typically about 10% or greater
• relatively low alpha-celiulose content typically about 90% or less, more typically about 83% to about 89%
• DP relatively high degrees of polymerisation
• a slurrying or dissolution step is preferably performed prior to step a.
• This step involves forming a solution or slurry of cellulose-containing pulp in a basic liquid, for example a caustic solution, typically comprising an aikali metal hydroxide such as sodium hydroxide.
• a basic liquid for example a caustic solution, typically comprising an aikali metal hydroxide such as sodium hydroxide.
• concentration of the caustic solution used with dissolving pulps is 18% to 20% by weight.
• the concentration of the cellulose in the solution or slurry is typically in the range of about 2% to 15% by weight.
• a solution or slurry of cellulose is steeped in a basic solution for a period of time.
• the basic liquid is generally a caustic solution, typically comprising an alkali metal hydroxide such as sodium hydroxide.
• the concentration of the caustic solution used with dissolving pulps is 18% to 20% by weight.
• the concentration of the cellulose in the solution or slurry is typically in the range of about 2% to 15% by weight.
• Steeping is generally conducted for about 10 to 120 minutes and at a temperature equal to or greater than about 50°C.
• step a) is performed by steeping non-dissolving pulp in a caustic solution of about 16% to about 18% alkali metal hydroxide.
• the non-dissolving pulp is steeped in a caustic solution having a concentration of about 16.5% to about 17.5%, about 17.5% to about 18%, about 17% to about 18%, about 18.6% to about 17.0%, or about 17.2% to about 17.8% alkali metal hydroxide by weight.
• Caustic solutions of the same concentrations may be used in the slurrying or dissolution step outlined above.
• steeping is performed, at least partially, at a temperature in the range of about 30°C to about 50°C, about 35°C to about 48X, about 35°C to about 45X, about 38°C to about 42°C, or about 40°C to about 48°C.
• the preferred steeping conditions of the present invention which can be used to produce viscose solutions exhibiting good filterability, may result in the removal of less hemicellulose from the cellulose pulp than if conventional steeping conditions are used with dissolving pulps. It was previously considered that the greatest possible amount of hemicellulose should be removed from the pulp to maximise filterability of the resulting viscose solution. However, it has unexpectedly been found that while a significant proportion of native hemicellulose should be removed from the pulp, retention of a small amount appears to actually contribute to the quality of the resulting viscose solution.
• the viscose solution formed in step (c) preferably contains from 0.1 % to about 1.0%, about 0.8%, about 0.8% or about 0.5% of hemicellulose, by weight of the total amount of cellulose present.
• manganese may be added to the steeping liquor to reduce the DP of the cellulose pulp. It is typically added in an amount of 40 to SOOppm (by weight of the mixture). Manganese may be employed in the same way in the process of the present invention.
• One or more steeping additives may be present in or added to cellulose containing slurries or solutions employed in the process of the present invention. These function by holding open the cellulose structure and the skilled artisan will be familiar with such materials. Examples of steeping additives which may be used include glycerol and / or alkoxylated alcohols, especially ethoxylated alcohols.
• a steeping additive such as Berol 388 is preferably added in an amount of about 0.1 % to about 5.0%, about 0.5% to about 5%, about 1 % to about 4%, or about 0.5% to about 2% by weight of cellulose.
• one or more swelling agents may be present or added to the slurry or solution processed in the present invention.
• the one or more swelling agents are added to the slurry or solution in step a) and / or any slurrying or dissolution step which is performed.
• Specific examples of swelling agents that may be employed in the process of the present invention include propylene glycols, polyethylene glycols, polyvinyl alcohols or poiyacryfates.
• a slurry or solution comprising cellulose pulp may be subjected to drainage steps (to remove excess basic liquid, for example by pressing), shredding and / or aging steps. If performed, the drainage step and / or the shredding step will preferably result in a cellulose crumb product.
• the alkali cellulose product obtained from any drainage step which is performed preferably includes about 32% or less of cellulose and / or about 18% or less alkali material (most preferably alkali metal hydroxide, such as sodium hydroxide).
• xanthation is achieved by contacting alkali cellulose obtained from a dissolving pulp at a temperature of 30°C or higher with 26% to 29% carbon disulphide, by weight of the cellulose present.
• alkali cellulose may be added to a churn into which gaseous, liquid or aqueous carbon disulphide is introduced (churn xanthation).
• non-dissolving cellulose pulp may be subjected to some conventional processing conditions in the xanthation step performed in the process of the present invention, it has unexpectedly been found that optimal results are obtained when the conventional processing conditions are adjusted.
• non-dissolving cellulose pulp, or crumb, slurries or solutions formed from such pulp are subjected to a xanthation step, this is preferably carried out at a temperature of about 30°C or lower, more preferably at about 20°C to about 30°C S about 22°C to about 28°C, about 24°C to about 26°C, or about 25°C to about 30°C.
• said pulp, crumb, slurry or solution is preferably contacted with about 30% or more carbon disulphide, by weight of the cellulose present, more preferably about 30% to about 40%, about 30% to about 35% carbon disulphide, about 32% to about 38% carbon disulphide or about 34% to about 38% carbon disulphide. It has unexpectedly been found that increasing the quantity of carbon disulphide used during xanthation reduces the viscosity of viscose solutions formed from the xanthated cellulose.
• dissolution is achieved by dissolving the non-dissolving pulp (or crumb, slurry or solution prepared therefrom) in a basic liquid, for example a caustic solution, typically comprising an alkali metal hydroxide such as sodium hydroxide.
• a basic liquid for example a caustic solution, typically comprising an alkali metal hydroxide such as sodium hydroxide.
• the liquid is preferably aqueous,
• a quantity and concentration of basic liquid is preferably used which resu!ts in a viscose solution having a cellulose content (CIV) of about 5% to 15%, about 5% to 13%, about 5% to about 10%, or about 7% to about 10% and / or a caustic content (SIV) of about 2% to about 10%, about 4% to about 8%, about 5.5% to about 7.5%, or about 6% to about 7%
• CIV cellulose content
• SIV caustic content
• Dissolution is preferably carried out at a temperature of about 10°C to about 25°C, about 15°C to about 20°C, about 18°C to about 22°C or about 16 C C to about 18°C.
• a mercerisation step may be performed. This will preferably be performed following steeping and / or prior to xanthation.
• the purpose of the mercerisation step is to improve the properties of the cellulose contained in the pulp, for example, by reducing the degree of polymerisation in the cellulose.
• the mercerisation step involves removing a portion of an alkali liquid (and optionally adding fresh alkali liquid) from a slurry or solution of dissolving cellulose pulp in alka!i liquid to attain a target cellulose content and / or a target alkali or soda content, for example at least about 33% cellulose and / or at least about 16% alkali.
• Such processing conditions may be employed in the process of the present invention.
• an alkali cellulose product optimally includes about 32% or less of cellulose and / or about 16% or less alkali material (most preferably alkali metal hydroxide, such as sodium hydroxide).
• the mercerisation step can be excluded from the process.
• a slurry or solution containing cellulose, subjected to a steeping step (step a) is cooled to prevent mercerisation occurring.
• the solution or mixture may be cooled to a temperature of about 50°C or less, about 40°C or less, about 30 S C or less, or most preferably, to a temperature of about 25°C or less.
• the viscose solution formed from a pulp processed according to the method of the present invention preferably exhibits a K value of at least 400, more preferably of at least 500, at least 800, or at least 700,
• the viscose solution formed from a pulp processed according to the method of the present invention preferably exhibits one or more of the following characteristics: an Rv of about 200 or higher, more preferably about 500 or higher, a TVW of about 100 or higher and a fibre count of about 100 fibres / gram or lower, or more preferably 20 fibres / gram or lower.
• viscose solutions formed entirely from non-dissolving pulps may be prepared.
• those skilled in the art may nevertheless wish to produce viscose solutions from a mixture of dissolving and non-dissolving puips. Accordingly, in preferred processes of the present invention, at least about 15% of the pulp used in the process of the present invention will be non-dissolving pulp.
• At least about 15% of the cellulose steeped in step (a) and / or present in the viscose solution formed in step (c) and / or present in the viscose solution from which the cellulose film or cellulose shaped article is cast in step (d) will be obtained from a non-dissolving pulp
• at least about 25%, about 50%, about 70% about 90% about 95% or even about 98% of the cellulose steeped in step (a) and / or present in the viscose solution formed in step (c) and / or present in the viscose solution from which the cellulose film or cellulose shaped article is cast in step (d) will be obtained from a non-dissolving pulp.
• the process of the present invention further comprises the step of casting a cellulose film or a cellulose shaped article from the viscose solution.
• the techniques for doing so will be well known to those skilled in the art.
• a cellulose film is cast
• conventional casting techniques may be employed in which the solution is extruded through a slit to form the desired shape.
• the extruded material is then contacted with a casting solution, for example by feeding it into a casting bath.
• the extruded cellulose film may also be passed through additional rollers and baths to clean and soften the film, and to obtain the desired optical and mechanical properties.
• those fibres are preferably formed by extruding the cellulose solution through a spinnerette, to produce a fibrous material.
• any fibre-forming techniques and apparatus may be employed.
• the cellulose solution may be moulded, formed or shaped into the desired arrangement using conventional techniques known to those skilled in the art.
• the cellulose fibres may be converted into those articles using any techniques known to those skilled in the art.
• the shaped cellulose solution is preferably then transferred into a casting bath including a casting solution.
• the cellulose-containing pulp employed therein may be subjected to one or more treatment steps in addition to steeping, xanthation dissolution and casting.
• the cellulose-containing pulp may be subjected to electron beam treatment.
• electron beam radiation to treat cellulose-containing pulps is known and has been employed in commercial processes for many years.
• the treatment of pulps with electron beam radiation has typically been carried out by passing a layer or sheet of pulp by a fixed electron beam source, for example, using a conveyor.
• Electron beam radiation may be emitted from any number of locations, for example, from one, two, three, four, five or six locations. However, in preferred aspects of the present invention, electron beam radiation is emitted from two locations, most preferably, from above and below the pulp.
• the electron beam radiation may be emitted from a single, fixed or movable electron beam source, or from a plurality of electron beam sources which may independently be fixed or movable.
• the emission of electron beam radiation from the plurality of locations may be simultaneous or sequential.
• the voltage of the electron beam radiation to which the non-dissolving pulp is exposed will be the same as or lower than that used in conventional electron beam treatment processes.
• the electron beam radiation emitted from one, some or all of the locations will be about 10 meV or lower, about 5 meV or lower, about 1.5 meV or lower, about 1 ,0 meV or lower, about 800 keV or lower, about 600 keV or lower, about 500 keV or lower, about 400 keV or lower, about 300 keV or lower, about 250 keV or lower, or even about 200 keV or lower.
• Any electron beam emitting apparatus known to those skilled in the art which is capable of emitting the required voltage and dose of radiation may be employed in the process of the present invention.
• medium voltage equipment capable of delivering doses of electron beam radiation at a voltage of 750 keV to 1 .5 meV can be used.
• Treatment services employing such equipment are offered by a range of companies, for example AquaMed.
• Such apparatus is advantageous as the pulp processing speeds (i.e. the treatment speeds) are high.
• low voltage equipment may be employed. Such equipment is typically used in coating curing systems and examples of such apparatus are provided, at least in the UK, by PCT Engineering Systems.
• the apparatus is capable of delivering curtain beam doses of electron beam radiation at a voltage of up to 300 keV.
• the width of the beam is adjustable depending on the area of pulp to be treated and treatment is achieved with an acceptable level of consistency.
• minimal shielding is required, making the apparatus more manipuiable for treating pulp from a plurality of locations and / or using a plurality of said devices in different locations simultaneously and / or sequentially without any risk to the user's health.
• treatment of the non-dissolving pulp with equal amounts of electron beam radiation from the different locations is preferred.
• the amount of radiation emitted from the different locations varies by about 100 keV or lower, about 80 keV or lower, about 80 keV or lower, about 50 keV or lower, about 40 keV or lower, about 30keV or lower, about 20 keV or lower, about 10 keV or lower, or about 5 keV or lower.
• the overall dose of electron beam radiation to which the pulp is exposed may vary.
• the pulp is exposed to a dose of electron beam radiation in the order of about 0.5 to about 5.0 mRad (about 5 to about 50 kgy), about 1.0 to about 4.0 mRad (about 10 to about 40 kgy), about 1.5 mRad to about 3.5 mRad (about 15 to about 35 kgy), about 2.0 mRad to about 3.0 mRad (about 20 to about 30 kgy), or about 1.0 to about 2.0 mRad (about 10 to about 20kgy).
• the feed speed can be controlled to ensure that the target dose is administered.
• the dose and voltage of radiation to which the non-dissolving pulp is exposed may be varied depending on the source, density, area, thickness and / or weight of the pulp being treated.
• the pulp which is treated in accordance with the present invention may have a thickness ranging from about 0,1 mm, about 0.5mm, about 1.0mm, about 5.0mm, or about 10.0mm to about 100mm, about 50mm, about 20mm, about 15mm, or about 10mm.
• the weight of the pot which is treated in the process of the present invention may range from about 200 g/m 2 , about 400 g/m 2 , about 800 g/m 2 , or about 700 g/m 2 to about 2000 g/m 2 , about 1500 g/m 2 , about 1200 g/m 2 , about 1000 g/m 2 , or about 800 g/m 2 .
• the non-dissolving pulp may be exposed to the electron beam radiation on a continuous basis (e.g. through use of conveyor means) or on a batch basis.
• the treated pulp will preferably exhibit a degree of polymerisation of about 600 or lower, about 500 or Sower, about 400 or Sower, or most preferably about 300 or lower. This constitutes a significant improvement over the degree of poSymerisation of untreated non-dissolving pulps, which typically is around 800 to 1400. Surprisingly, these advantageous results can be obtained using significantly lower voltage and / or doses of radiation than have been employed conventionally.
• fluff pulps these may be supplied in sheet form and it may be desirable to fluff or shred them, for example using a high shear mixer.
• the pulp may be subjected to a drying step, for example, by placing it in an oven and heating it to a temperature of, e.g., about 40°C to 100°.
• pulp may be deiaminated.
• the pulp is subjected to reduced temperature treatment.
• reduced temperature treatment it is believed that by exposing pulp to cold temperatures, the fibrous nature of the wood pulp is disrupted, potentially breaking hydrogen bonding and making the cellulose fibres more accessible.
• Reduced temperature treatment is achieved by exposing the pulp to low temperatures, for example 0°C or lower, -50°C or lower, -lOfTC or lower, -150 or lower or -180°C or lower.
• Reduced temperature treatment can be effected by storing or holding the pulp in a low temperature environment, for example, an industrial freezer, Additionally or alternatively the pulp may be exposed to a low temperature agent, for example cryogenic liquid such as liquid nitrogen, liquid helium, liquid hydrogen, liquid oxygen, liquid neon or mixtures thereof. If a liquid low temperature agent is employed, the pulp is preferably saturated and / or submerged therein.
• the reduced temperature treatment has a duration of about 80 minutes or less, more preferably about 30 minutes or less, about 20 minutes or less, or about 15 minutes or less.
• a cellulose film or a cellulose shaped article obtained according to the method of the first aspect of the present invention.
• references to features of the first aspect of the present invention discussed above are optionally applicable to the product of the second aspect of the present invention, where appropriate.
• Example 1 Optimised Steeping Conditions - aOH Concentration of Steeping Liquor
• concentration of the a!kaii iiquid used to steep cellulose-containing pulps was investigated, A softwood dissolving pulp was steeped in sodium hydroxide solutions having a concentration of 18.3% and 17.5% by weight for 30 minutes at 50°C.
• the resulting slurry was mercerised, xanthated and dissolved using conventional processing conditions.
• the resulting viscose solution exhibited the following properties:
• Viscose solutions were prepared according to the following processing conditions. As can be seen, the oniy variable was the concentration of the caustic solution used to steep the cellulose.
• Viscose solutions were prepared in accordance with the following processing conditions. As can be seen, the only variable was the temperature at which steeping was conducted.
• Weyerhauser Pearl pulp (a non-dissolving pulp) was steeped in a liquor having a concentration of 17.1 % NaOH for 15 minutes at 20°C, 40°C, 50°C and 60°C. This was then xanthated using 31 % CS 2 by weight of cellulose present at a temperature of 30°C. The resulting product was then dissolved at 17,3°C to obtain a viscose solution having a Cellulose in Viscose (CIV) content of 9.3% and a Soda in Viscose (SIV) content of 6.5%
• Figure 2 confirms that steeping temperature has a significant effect on final viscose quality, with the optimum temperature being 40°C for the pulp tested.
• Viscose solutions were prepared from Weyerhauser Pearl pulp (a non-dissolving pulp) using the following processing conditions:
• Viscose solutions were prepared in accordance with the following processing conditions. As can be seen, the only variable was the quantity of carbon disufphide employed in the xanthatlon step.
• Viscose solutions were prepared in accordance with the following processing conditions. As can be seen, the only variable was the temperature at which the xanthatlon step was conducted. Weyerhauser Pearl pulp (a non-dissolving pulp) was steeped in a liquor having a concentration of 17,5% NaOH at 40°C for 15 minutes. This was then xanthated using 31 % CS2 by weight of cellulose present at temperatures of 25°C, 30°C and 40°C. The resulting product was then dissolved at 17.3°C to obtain a viscose solution having a Cellulose in Viscose (CIV) content of 9,3% and a Soda in Viscose (SIV) content of 6.5%
• CIV Cellulose in Viscose
• SIV Soda in Viscose
• Viscose solutions were prepared from Weyerhauser Pearl pulp (a non-dissolving pulp) using the following processing conditions:
• Viscose solutions were prepared in accordance with the following processing conditions. As can be seen, the only variable was the S ⁇ f content of the viscose.
• Weyerhauser Pearl pulp (a non-dissolving pulp) was steeped in a liquor having a concentration of 17,5% aOH at 40°C for 15 minutes. This was then xanthated using 31 % CS2 by weight of cellulose present at a temperature of 25 . The resulting product was then dissolved at 17.3°C to obtain a viscose solution having a Cellulose in Viscose (CIV) content of 9,3% and a Soda in Viscose (SIV) content of 5.5%, 8%, 6.5% and 7%
• Viscose solutions were prepared from Weyerhauser Pearl pulp (a non-dissolving pulp) using the following processing conditions: Table 5:
• Viscose solutions were prepared in accordance with the following processing conditions. As can be seen, the only variable was the temperature at which dissolution occurred.
• Example 11 Effect of Hemicelfufos® on Viscose Solution 89.2g of Weyerhauser Pear! pulp (a non-dissolving pulp) was slurried with 1800mls of NaOH at varying temperatures, times and concentrations. The slurry was then pressed using a slurry press at 7 tonnes for 30 seconds. The excess NaOH was collected, weighed and tested for hemi-cellulose content.

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