Classifications

• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D13/00—Making of soap or soap solutions in general; Apparatus therefor
  • C11D13/14—Shaping
  • C11D13/18—Shaping by extrusion or pressing

Definitions

• the present invention relates to improvements relating to a process for the manufacture of soap forms and apparatus for use in said process.
• the invention is particularly concerned with improvements to the so-called soap 'plodder' and to a process which uses an improved plodder. While the invention is described with particular reference to the manufacture of soap bars it should be understood that the term 'soap' extends to materials comprising non- soap surfactants, including synthetic surfactants and the term 'forms' extends to other three-dimensional solid forms including soap bars, billets, tablets and so-called noodles.
• the starting material for the production of a soap bar or billet is a mixture containing surfactants, other functional ingredients and water at appropriate proportions. Depending upon the composition of this mixture, its rheological and processing characteristics vary a great deal.
• processing/finishing of such a mixture involves various process steps such as homogenisation, shear working, and forming into a required shape.
• a plodder One of the devices very commonly employed to carry out one or more of the above operations is a plodder.
• the function of a simple plodder is to form the mixture into bars or billets of required cross-sections which may subsequently be cut into smaller bars or stamped into tablets of required shape by suitable other means.
• the function of a refiner plodder is to clean the mixture free of gritty particles or impurities and additionally homogenise/shear work the same to achieve the required degree of homogeneity or phase structure.
• the plodders may also be used to convert loose aggregates/chips/flakes into noodles for intermediate storage or for feeding subsequent process operations.
• the heart of a plodder is a screw extruder.
• the simplest plodder has an extruder with a single worm.
• the feed stock either in homogenised and worked form or in the form of noodles or crimpled chips, fed through the hopper enters the extruder barrel and fills the annular space between the extruder worm (screw) and the barrel.
• the barrel is stationary and the worm rotates inside the barrel. Frictional/viscous drag forces act on the material, both at the barrel as well as at the worm surfaces.
• the resultant force is responsible for the forward transportation of the processed mass towards the discharge end.
• the extruder may have a perforated plate, through which the processed mass is forced. This is generally known in the art as a 'noodle plate' .
• the processed mass emerges in the form of rods/ribbons/sheets from the perforated plate.
• the objective is to enhance homogenisation or shear working or to filter out gritty particles, then it is advantageous to fit a wire gauze in front of the perforated plate but it tends to reduce throughput.
• a cone and die/eye plate are provided at the discharge end of the extruder along with or without the noodle plate. The extruder forces the mixed mass through these end fittings to product the noodles, billets or bars. Designs of perforated plates, cones and die/eye plates vary considerably from application to application. It should be noted that the throughput rate is very sensitive to the resistance offered by wire mesh screens, perforated plates, cones and dies.'
• Machines called duplex or twin worm plodders have two worms (or screws) which are parallel, non-intermeshing and mounted tangentially with respect to each other within a barrel.
• the worms may be co-rotating but usually they are counter-rotating.
• Intermeshed and co-rotating twin screw extruders are also known for processing of soap/detergent mass.
• drag forces similar to those encountered in single worm plodders act on the processed mass and push the same in the forward direction.
• Screw extrusion is apparently a simple operation, but the results in terms of quality of product, throughput rate, specific energy consumption, etc. can be influenced by a number of factors in a rather complex way.
• plodding is affected by soap factors and by machine factors. It is important to balance the various factors so as to achieve the best results.
• the functions of the screw extruder in the soap making process include mixing, working and conveying materials.
• Other apparatus exists for the performance of some or all' of these process operations.
• mixing can be performed in Z or Sigma-blade mixers: products can be worked by chilled rolls and transported using conveyors.
• these apparatus also have their disadvantages e.g. mixers generally only operate in batch mode, chilled rolls are expensive to manufacture and maintain and sticky products are difficult to transport on conveyors.
• a first aspect of the present invention provides a process for the manufacture of soap forms which includes the step of treating a soap feedstock by passage through a twin screw, intermeshing, counter-rotating extruder.
• a second aspect of the present invention provides apparatus for the manufacture of soap forms which comprises a twin screw, intermeshing, counter-rotating extruder.
• the extruder comprises two oppositely-threaded, closely intermeshing screws mounted for rotation within a barrel having a first end and a second end, said screws having a minimal screw-to-screw and screw to barrel clearance such that as the feedstock passes along at least a part of the barrel from said first end and towards said second end it is divided into a plurality of discrete, substantially C-shaped segments bounded by the screw and barrel surfaces and conveyed in a path whereby the bulk of the feedstock move substantially parallel to the rotational axis of the screws.
• F is the theoretical flowrate of output
• m is the number of starts on the shaft
• N is the shaft speed
• v is the volume of the C-shaped segment mentioned above.
• volumetric efficiencies of above 60% can be attained using the present invention whereas in single screw plodders according to the prior art the volumetric efficiency was typically 9-19%. It is particularly convenient that the screws should be a matching pair, i.e. that they should have the same diameters and be substantially different only as regards the handedness of the screw.
• the screws are preferably detachable from the extruder whereby whenever necessary the screws can be changed with another pair of screws having different screw layout.
• the screw may be either continuous or segmented.
• the segmented screws have removable sections which can have varying pitches so that they can be manipulated depending upon the composition of the material being processed.
• the screws may be single-start or multi-start.
• apparatus will further comprise means for rotating the screws in mutually opposite directions.
• the positive pumping characteristic of extruders according to the present invention can be used either to increase the throughput of the extruder at a given rotational speed or to reduce the rotational speed required for a given throughput. Reduction in screw speed is particularly advantageous as it reduces the extent to which the product is heated during treatment, and enables the power input to be reduced.
• apparatus according to embodiments of the present invention will further comprise means for supplying the feedstock to the barrel of the extruder at the first end of the barrel.
• said means for supplying the feedstock comprise hopper means located above one end of the screws.
• An advantage associated with the use of counter-rotating screws is that a nipping action occurs and the feedstock is drawn from the hopper into the barrel of the extruder.
• apparatus according to embodiments of the present invention will further comprise means for forming the feedstock into soap forms at the second end of the barrel.
• Such means are well-known in the art.
• the forms can comprise noodles, bars and/or billets.
• the precise nature of the means for forming the feedstock will depend on the nature of the forms desired. Where noodles are desired said means comprise a perforated plate through which the feedstock is extruded. Where bars or billets are desired a conventional cone and eyeplate can be employed.
• the pitch angle of the screws decreases in the direction of flow.
• the pitch angle is 20-30 degrees adjacent the first end of the barrel and 10-20 degrees adjacent the second end of the barrel. This is particularly useful where feedstock is being compacted and its overall density is increasing during progress down the screw from the first to the second end of the barrel.
• the width of the flights increases in the direction of flow relative to the width of the channel between the flights.
• the width of the channel is at least three times the flight width adjacent the first end of the barrel and less than three times the flight width adjacent the second end of the barrel. This is particularly useful where feedstock is being compacted and its overall density is increasing during progress down the screw from the first to the second end of the barrel.
• cooling means are provided to cool the feedstock within the barrel.
• the cooling means can include means for circulating a cooling fluid through a cooling jacket
• RECTIFIED SHEET (RULE 91) ISA/EP around the barrel and/or through passages within one or both of the screws. While cooling means are generally employed in single screw extruders, the cooling means are optional in the present invention.
• some degree of cooling can be employed if it is desirable to cool the process stream during its passage through the extruder, thus enabling the apparatus according to the invention to replace the chilled rolls used in conventional plant.
• the efficiency of cooling can be improved by cooling the screws in addition to the barrel.
• Q is the overall heat transfer rate
• M is the mass flowrate of the coolant
• C is the specific heat capacity of the coolant
• Dt is the temperature rise in the coolant.
• the cooling means in embodiments of the present invention can include means for circulating a cooling fluid through a cooling jacket around the barrel and through passages within one or both of the screws and this can significantly improve the heat transfer rate, by increasing the heat transfer area.
• the apparatus according to the present invention can apply the process of the invention to a wide range of feedstocks and use is not limited to those feedstocks which comprise synthetic, non-soap surfactants.
• the invention can be applied to the processing of transparent and/or translucent soap formulations which are known to be of high viscosity and difficult or expensive to process, or to soap forms comprising structuring and/or hardening aids. It is envisaged that all manner of aerated/solid and/or toilet/laundry soaps can be manufactured by a process according to the present invention.
• the apparatus according to the present invention need not be manufactured to the same high engineering tolerances required in the manufacture of conventional counter-rotating extruders thereby further reducing set-up and manufacturing costs.
• a particular advantage as regards manufacturing is that the screws can be at least in part cast rather than machined from a blank.
• Fig. 1 shows a schematic view of an extruder with an open sectional view of the screws for carrying out the method according to the invention
• Fig. 2 shows a cross-sectional view of the extruder barrel
• Fig. 3 shows a transverse cross-sectional profile of the screw
• Fig. 4 shows a perspective view of two intermeshed screws according to a preferred embodiment of the present invention
• Fig. 5 shows a comparison of actual and theoretical volumetric efficiencies through an apparatus embodying the present invention for a range of soap blends as compared with a single screw plodder;
• Fig. 6. shows (as 6a and 6b) details of two embodiments of the present invention
• the extruder comprises two closely intermeshed screws 1 and 2 mounted within a jacketed barrel 3 and driven by a motor 4.
• the two screws are oppositely threaded and closely intermeshed with each other. When one screw rotates clockwise, the other screw rotates anticlockwise.
• the screws shown are single-start screws, but they may even be multi-start ones.
• a cross section of a typical screw is shown in figure 3.
• a hopper 5 is typically provided, through which the soap/detergent material enters the extruder.
• a perforated plate (not shown)
• a cone jacket (not shown)
• an eye plate (not shown)
• the eyeplate, jacket and plate would be mounted on the flange at the output end of the extruder as shown in figure 1.
• FIG 6b A less preferred embodiment of the invention, with partially intermeshing screws is shown in figure 6b, whereas figure 6a shows the more preferable arrangement having closely intermeshed screws. It should be noted that the screws of figure 6 do not have the particular features of the embodiment shown in figure 4 but rather represent the two extremes of the variation in flight width which occurs in figure 4.
• extruders described above all have single-stage extruder mechanism, it will be appreciated that the invention may equally be carried out using two- or other multi- stage extruders and in particular those which correspond to multi-stage vacuum plodders or refiners.
• a particular advantage of those embodiments of the present invention in which closely intermeshing screws are used is that the soap/detergent material to a considerable extent is prevented from rotating with the screws. This ensures that the bulk of the material moves substantially parallel to the extruder axis and thereby avoids any rheological or structural damages or rise in temperature in the material and results in soap/detergent mass with better downstream processing qualities.
• Such a process delivers a higher throughput at a giver rpm, i.e. a better volumetric efficiency and a lower specific energy consumption in comparison to plodding methods hitherto being used in the soap/detergent industry.
• dissipation per unit throughput is around a factor of five as compared with the single screw unit.

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• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Wood Science & Technology (AREA)
• Organic Chemistry (AREA)
• Detergent Compositions (AREA)
• Extrusion Moulding Of Plastics Or The Like (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 1992
  • 1992-12-17 GB GB929226309A patent/GB9226309D0/en active Pending
• 1993
  • 1993-12-13 DE DE69303495T patent/DE69303495T2/de not_active Expired - Fee Related
  • 1993-12-13 WO PCT/EP1993/003561 patent/WO1994013778A1/en active IP Right Grant
  • 1993-12-13 ES ES94903791T patent/ES2089914T3/es not_active Expired - Lifetime
  • 1993-12-13 BR BR9307677A patent/BR9307677A/pt not_active IP Right Cessation
  • 1993-12-13 EP EP94903791A patent/EP0675948B1/de not_active Expired - Lifetime
  • 1993-12-13 AU AU58118/94A patent/AU5811894A/en not_active Abandoned

Non-Patent Citations (1)

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