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
• • 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
  • C11D17/00—Detergent materials or soaps characterised by their shape or physical properties
  • C11D17/0047—Detergents in the form of bars or tablets
  • C11D17/006—Detergents in the form of bars or tablets containing mainly surfactants, but no builders, e.g. syndet bar

Definitions

• the present invention relates to the field of making soap bars, particularly to a process for making high-moisture soap bars using ploughshare mixers.
• Conventional toilet soaps generally include predominantly soap (e.g., >70 % TFM, Total Fatty Matter), 10 to 13 % water and the usual additives (e.g., soda, salt, dyes and perfumes). These bars are typically produced by mixing soap and/or other synthetic surfactants with useful additives, followed by milling, plodding and stamping. Soap bars are produced on a commercial scale by two well known processes; a comparatively newer ploughshare mixer (PSM) process and a relatively older crutcher/Mazzonni/ Spray drier process.
• PSM ploughshare mixer
• Plodded soap bars are produced by subjecting the neutralized soap to various finishing steps.
• the soap Prior to conversion, the soap is first dried from a moisture level of approximately 30 % to a level in the range of about 10 % to about 14 %.
• the dried soap is generally sent to a simple paddle-type mixer where a variety of additives can be introduced. From this mixer the soap is then sent either directly to a refiner or optionally to a three-roll mill and then to the refiner. Both the refiner and the mill subject the soap to compression and an intense shearing action. After refining, the soap is compressed into a dense, coherent form in a plodding operation which forms solid portions which are suitable for stamping into bars.
• the drying step is necessary to remove the "gummy" texture and excessive pliability of the soap mass which exist typically at higher moisture levels.
• Drying on a commercial basis is achieved by several different methods.
• One procedure employs a water-chilled roll in combination with a second feed roll to spread molten, neutralized soap into a thin, uniform layer.
• the cooled soap is then scraped from the roll to form chips and dried to a specific moisture level in a tunnel dryer.
• Soap chips already having a low moisture level are further dried by repeatedly conducting the chips through close-set water cooled steel rolls (i.e., three-roll mill) in the procedure known as milling, which has been already described.
• a modern technique for the drying of soap is known as spray drying. This process directs molten soap to the top of a tower via spray nozzles. The sprayed soap hardens and then dries in the presence of a current of heated air. Vacuum may be applied to facilitate removal of water.
• the moisture level of plodded soap bars is maintained in the range of about 10 % to about 14 %.
• the Mazzoni /Spray Drying process essentially involves a step of vacuum drying. In this process, first a saponified soap mix having excess moisture is made. Then the unwanted moisture is removed. Although this process is extremely energy intensive due to the need for removal of excess moisture, just like spray-drying, this process remains the favoured process for making soap bars containing up to and around 14 to 16 % moisture.
• the earlier BLS-Mazzoni/ Spray drying system consisted of multi-head metering pump followed by high shear mixer and a residence time vessel. The function of the metering pump is to facilitate a stoichiometric addition rate of caustic, distilled fatty acid (DFA), brine and water to the mixer. From the pump-head; caustic, brine and water combine and go through a heat exchanger where the temperature rises up to about 90°C. The DFA separately goes through one heat exchanger where the temperature rises to about 95°C.
• DFA distilled fatty acid
• Both the streams from heat exchangers are fed to the suction of Supraton high shear mixer. After mixing, the mixture goes through the residence time vessel where the complete reaction takes place. This soap goes through the back pressure control valve, which provides pressure enough to prevent flashing of water from soap in the line and the reaction vessel and after this the product goes to appropriate pans. From the pans the neat soap is taken in the crutchers where preservatives and other ingredients are added. From crutchers, soap goes to series of heat exchangers for a temperature rise up to 140°C, and then to a flash chamber where soap is dried.
• Process related problems include production of soft soap mass which is difficult to mill, plod and stamp. For these reasons, the soap bars sold in some countries generally contain only 12 to 13 % moisture.
• WO9209679A1 discloses a process for making rigid framed soap bars (i.e. melt cast bars) having high moisture.
• Fatty acid precursor, propylene glycol, sodium chloride, and added water are mixed and heated.
• Caustic solution is added and the mixture is stirred until smooth forming an aqueous molten liquid comprising from 15% to 94% water and from 5.5% to 75% soap.
• the molten liquid mixture is poured into shaped molds and cooled to form shaped bars. It is also disclosed that when the process is used for making conventional plodding or freezer process, then very soft bars or no bars are formed. Therefore, a limitation of the process disclosed in this application is that is applies only to melt-cast bars. Similarly, in US'271 also, the bars are made by mixing from pre-neutralised soap noodles with other bar ingredients.
• CN1 182789A discloses a process for producing a high moisture laundry bar having improved firmness.
• the process comprises preparing a premix of 75 to 90% neat soap, 3 to 20% added water, 1 to 10% electrolyte salt and forming the mixture into a shaped bar.
• the premix that is prepared in accordance with this disclosure contains pre-saponified soap which is mixed with water to further make bars.
• the ploughshare mixer is very commonly used in processes requiring granulation of detergent powders and to produce powders by dry neutralisation. Typically, the ploughshare mixer does the following tasks in the powder mixing process; mixing of ingredients, agglomeration and de-agglomeration of particles, unification of the mean particles sizes and layering of material. Until recently, such mixers were not used for making soap bars.
• a typical process involves neutralisation/saponification of fatty acids with e.g. caustic soda. This step is continued i.e. caustic soda is added until the acid is completely neutralised. When the saponification is over, glycerine, chelators, common salt, sodium sulphate and some other minors are added. The resultant mass is extruded through a noodler plate.
• a typical plough share mixer is primarily designed for powder mixing but is also an efficient mixer for soap saponification at moisture content of 15 % to 20 %.
• the main parts of the mixer are a jacketed barrel, axial rotating shaft through the centre of the barrel (longitudinally), plough-shaped blades mounted on the axial shaft, and chopper.
• the ploughs and the high-speed chopper are the mixing elements. Since the gap between the plough surface and the barrel is 3 to 8 mm, the material gets sheared significantly while mixing.
• a typical mixer has barrel volume of 60 litres, plough rpm of 200 and chopper rpm of 3000. The plough area to barrel volume is approximately 0.002 cm "1 .
• Viscosity of saponified mass is generally 80,000 to 100,000 cP (at 25°C). This viscosity is necessary for downstream processing. However, when an attempt was made to increase the moisture content of the mass by addition of water, the viscosity of the saponified mass reduced. For example, in order to get soap noodles having 24 % moisture, when necessary amount of added water was added to the mixer, the resultant mix was found to have a viscosity of about 4000 to 10,000 cP.
• the term "added water” is used to distinguish this water from the water of neutralisation which is generated in-situ when distilled fatty acids are saponified with an alkali. Some ingredients such as caustic soda also contain water.
• a holding tank can be fitted between the plough share mixer and the chilled rolls.
• the tank helps in ensuring a steady supply of saponified mass to the chilled drum in a controlled manner.
• installation of such holding tanks is not possible in all manufacturing set-ups because in some factories, there is not much space between the mixer (PSM) and the chilled rolls. Installation of holding tanks also involves capital expenditure.
• a further problem with holding tanks is that it is difficult to synchronise the speed at which the holding tank is emptied with a typical PSM batch cycle time which is 20 to 30 minutes. Many times it may so happen that the holding tank has only partially emptied but the next batch of saponified mass is ready for further processing.
• the PSM process is generally not considered suitable for making soap bars with higher moisture content (generally 20 % or more).
• saponified mass having about 30 % moisture is dried down to about 14 to 17 % moisture. This is achieved by raising the temperature of neat soap from 90 to 95°C to 140 to 145°C by passing through a heat exchanger/heat exchangers followed by spray-drying under vacuum (approximately 100 mm Hg pressure). This process is generally not recommended for making soap bars with more than 20 % moisture. The reasons have been explained earlier.
• the viscosity of the saponified mass increased to 80,000 to 120,000 cPs.
• the electrolyte can be added separately or it can be mixed with the water. It is preferred that the electrolyte is added as an aqueous solution, i.e. mixed with the added water.
• Preferred electrolytes include sodium halides especially sodium chloride, potassium halides especially potassium chloride and lithium halides, especially lithium chloride.
• Other less preferred electrolytes include nitrates, nitrites, sulphate, sulphites, chlorates, carbonates, bicarbonates and acetates of sodium, potassium or lithium. It was observed that direct addition of sodium sulphate to the mixer as a solid (solid dosing) had a limitation. Addition of excess sodium sulphate in this form lead to products (soap bars) which showed crystal growth on storage. Such a phenomenon is not desirable.
• the soap composition has at least 20 % moisture. More preferably, moisture content of the soap composition is 20 % to 32 %, preferably 22 to 30 % and most preferably 24 % to 26 %. Moisture content can be determined by any means, such as by drying at 105°C. It is preferred that free alkali content of the noodles is 0.01 % to 0.1 %. It is preferred that Iodine value of the soap composition is 30 to 60 g l 2 /100 g, more preferably 35 to 50 g l 2 /100 g and most preferably 40 to 45 g l 2 /100 g.
• the soap composition so formed is generally further processed.
• the soap base is in the form of a viscous liquid which is dried and plodded into homogenized noodles or chips.
• the soap noodles/chips are then processed into finished products such as bars/tablets.
• the process disclosed herein is used for making soap composition.
• a particularly preferred form of the soap composition is bars.
• Another preferred form is noodles or chips.
• the process disclosed herein is for making milled and plodded soap compostion in the form of bars or noodles, or the like. This process is unsuited for making framed bars, or freezer bars or melt-cast soap bars.
• Milling is meant the homogenization of the soap in the sense of eliminating granules of abnormal size and hardness contained in soap paste, thus making it uniform and of a very fine grain by touch.
• Soap milling can be effected either by making the material pass through mesh nets by successive extrusions (a relatively modem process) or by making it pass through successive rolling cylinders having different peripheral speeds (a traditional process). Milling involves feeding pressurized soap continuously from a chamber and under pressure into a nip of adjustable dimensions.
• the nip is formed between a pair of rolls counter-rotating at different peripheral speeds and detaching milled soap from the rolls.
• Table 2 a formulation sheet is shown for a batch size of 1650 kg, which (after processing) gives the soap noodles with the composition of Table 1 .
• the sodium chloride was added into an empty PSM mixer. Then the chopper and the plough were started. The fatty acids and caustic soda were added together next, followed by glycerine, water and sodium sulphate. This step of addition of the fatty acids to the sodium sulphate lasted for 12 minutes.

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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)

Priority Applications (4)

Applications Claiming Priority (4)

Publications (1)

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Citations (4)

• 2013
  • 2013-06-18 ES ES13729376.7T patent/ES2574602T3/es active Active
  • 2013-06-18 BR BR112015000666A patent/BR112015000666A2/pt active Search and Examination
  • 2013-06-18 WO PCT/EP2013/062599 patent/WO2014016055A1/en active Application Filing
  • 2013-06-18 EP EP13729376.7A patent/EP2875114B1/en not_active Not-in-force
• 2015
  • 2015-01-14 IN IN99MUN2015 patent/IN2015MN00099A/en unknown

Patent Citations (4)

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