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[washing information] introduction to dry-cleaning
Author
화인Tnc
Date
2019-01-18 15:59
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476
▒ Introduction to dry-cleaning
• Means to remove stain with oil solvent rather than with water. Importance skyrocketing these days due to introduction of luxury fabrics and increasing variance of fabrics
▒ Advantages of dry-cleaning
• Less harm on fabric
Certain types of fabrics used in clothing are affinitive to water, and thus weakened during washing by water and detergent. Deformation (expansion or contraction, fuzzes, wrinkles, peeling) may take place. And among the pigments used for fabrics, most of them are water-soluble so they are easily tarnished by water-cleaning, and especially by alkaline detergent.
Even dry-cleaning has some problems of damaging laundry or tarnishing, which may occur according to how fabrics, solvent, detergents are managed.
• Easy to remove oil-soluble stains
Most of stains on clothing consist of oil and other solids including dirt, so the dry-cleaning solvent melts down oily substances, coupled with mechanical power of washer. As these substances get eliminated, the solids which were attached to clothing by these substances are removed as well.
▒ Disadvantages of dry-cleaning
• Uneconomic
Dry-cleaning solvents are more expensive than water, and after use they get evaporated or filtered but those processes entail costs and losses.
• Weak washability
Water is inexpensive and abundant, letting sufficient amount be used for washing, but solvent does not necessitate rinsing, so stains are insufficiently removed.
• Dry-cleaning solvents are insufficient to disperse pollutants out to the solvent, and thus pollutants are easily re-attached to the laundry. (Since dry-cleaning solvents are nonpolar substances, it does not create repulsion due to electronic dual layer between fabric and pollutants, and are only subject to van der Waal’s force.)
• Cannot remove water-soluble stains.
• Petroleum solvent is inflammable, thus having danger of fire or explosion.
• Incombustible solvents release poisonous steams, so are insanitary.
• Certain materials used in clothing may get tarnished or damaged by the solvent.
• The solvent may deform plastics, melt down adhesive and deteriorate rubber.
Dry-cleaning solvents
▒ Conditions of dry-cleaning solvents
• Should decompose and dissolve stains well
• No damages to fabric and color
• No or less poison, no deterioration of dry-cleaning devices
• No or less inflammability
• Easy to remove and purify. No tarnishing while purifying.
• Easy to dry, no odor to remain
• Should be inexpensive
▒ Safety of dry-cleaning solvents
• Threshold Limit Value, TLV
Safe level of TLV (petroleum = 500ppm, perchloroethylene = 100ppm) even when inhaled for 8 hours a day. Lower ppm indicates more danger.
• Vapor Hazard Index, VHI
Danger indicator including TLV and volatility(saturated vapor pressure). The higher the level, the more dangerous. (Petroleum = 13, perchloroethylene = 187)
• followed by ignition point, vapor pressure and etc.
▒ Washability of the solvent
• Kauri Butanol Value, KBV
Amount (ml) of the loaded solvent to the mixture of 20% of natural acryl Kaurigum and butanol 20ml until white turbidity occurs. Larger KBV values indicate higher dissolving capacity of oil-soluble stains. (Petroleum = 27~45, perchloroethylene = 90)
Excessive KBV may result in deterioration of natural luxury fabric by dissolving fat of the fabrics, and also melt down adhesive or plastic components.
• Surface Tension
Less surface tension of solvents increase washability by easily permeating through fabric and stains. (Petroleum = 27.6, perchloroethylene = 32.3)
• Specific Gravity
Larger specific gravity of solvents may increase washability by strengthening physical power formed when solvent rotates and falls, whereas weak fabrics may get damaged by so doing.
▒ Types of solvents
• Hydrocarbon solvents
Compounds consisting of only carbon and hydrogen, including aliphatic hydrocarbon, aromatic hydrocarbon, alicyclic hydrocarbon and such. Difficult to handle, poisonous gas, high inflammability all count towards inappropriateness of the compounds to be used as dry-cleaning solvents.
e.g.) hexane, sichrohexane, benzene, decanol…
• Petroleum solvent
Hydrocarbon compounds obtained from petroleum processing. Exclusive dry-cleaning solvent has higher initial ignition point than that of petroleum therefore less dangerous, and has lower middle ignition point than diesel so therefore easy to remove and dry, with its main components being aliphatic saturated hydrocarbon(paraffin), aromatic and alicyclic hydrocarbon all attributing to good solubility.
Inexpensive, less poisonous, good solubility and low specific gravity. Appropriate for delicate laundry such as silks
• Halogenated hydrocarbon solvent
Petroleum hydrocarbon being inflammable and having high risk of ignition. Chlorine or fluroine combined to hydrocarbon in order to make incombustible synthetic solvent.
Highly poisonous, thus concealed facilities necessary. Disadvantage of deteriorating devices by decomposition when evaporated. Too high specific gravity, pure wool or silk floating around the solvent thereby decreasing washability
e.g.) carbon tetrachloride, trichloroethylene, trichloroethane, perchloroethylene, trichloro-trifluoride ethane
Dry cleaning detergent
▒ What is dry-cleaning detergent?
• Synthetic detergents for home users are affordable without product information and do not need special cautions.
• But for professional laundromats, in order to give high-quality laundry service by correctly understanding various types of fabrics and stains, it is necessary to understand chemicals used in laundry, especially detergents.
• The following describes dry-soap which is also important in washing altogether with oil solvents in dry-cleaning.
▒ Difference from synthetic detergents
• Oil-soluble stains unremovable with water-cleaning whereas most of water-soluble stains are removed without detergents. Thus remove oil-soluble stains to eventually eliminate solid stains attached by the oil-soluble stains with synthetic detergents
• In dry-cleaning, water-soluble stains are unremovable while most of oil-soluble stains are removed by solvent. Thus remove water-soluble stains to eventually eliminate solid stains attached by the water-soluble stains with dry-cleaning detergents.
☞ For your information: what is so called “dry-soap”?
Derived from the composition of the past dry-cleaning detergents, mostly composed of fatty acid chloride (soap) and fatty acid compounds. Precise expression is “dry-cleaning detergent”.
▒ Functions of dry-cleaning detergents
1. Removing water-soluble stains
• Dry-cleaning solvent is effective at removing oil-soluble stains such as oil, but zero-effective at washing off water-soluble stains including mineral pigments, carbon, and protein.
• Oil-soluble solvent used in dry-cleaning is nonpolar and thus unable to be blended with water which is polar compound. It therefore cannot wash off water-soluble stains(mineral pigments, carbon, protein, etc.) which are affinitive to water.
• In order to eliminate water-soluble stains, water to melt them down is necessary. And since water is unable to be blended with solvent, dry-cleaning detergent is needed to solubilize water.
• Application of moisture through dry-cleaning detergents can be categoerized as injection and charging, but this is only methodological difference and the principle is same as both give affinity to the oil-soluble solvent.
2. Increase washing efficiency
• In water-cleaning, basic mechanism of washing is lowering surface tension of water with surfactants in synthetic detergents.
• Dry-cleaning solvents are lower in surface tension than water and easily permeate through hydrophobic(lyphophilic) fabrics, but are difficult to permeate through hydrophilic fabrics. Thus, dry-cleaning detergents are needed.
• Low surface tension and fast permeability weaken coherence between stain and fabric, thereby increasing washability of the solvent.
3. Preventing recontamination
• In dry-cleaning, solid stains attached by oil-soluble stains are easily detached from fabric, but since the solvent is nonpolar, only van der Waal’s force is applied without repulsion between fabric and pollutants or between pollutants themselves due to electric dual layer. Thus, recontamination may occur more easily.
• By adding dry-cleaning detergents, surfactants attach to and arrange hydrophilic substances in direction towards fabric and solid stains while lyphophilic substances in direction of solvent. Thus, fabric and solids become hydrophobic(lyphophilic, affinitive to solvent), easily detaching and eliminating solids and obtaining stable dispersion. Since solid stains are prevented from clotting and attaching to fabric, recontamination should not occur.
4. Anti-static process
• Since oil-soluble solvents and fabrics are nonconductive, electric energy formed by circulation or friction (between fabrics, or between fabric and solvent) within washer creates static. Mostly occurring when drying.
• Static makes pollutants attach to fabrics and clothing becomes prickly.
• Lubrication of dry-cleaning detergents lowers friction energy, and gives fabric and solvent delicate ionic characters along with moisturization in order to contain statics.
5. Shortening washing duration and safeguarding fabric
• Dry-cleaning detergents eliminate water-soluble stains and increase washing efficiency, thereby shortening washing time.
• Shortened washing time can decrease damages to fabric by physical power, and fabric softener included gives satisfactory finishing to the laundry.
6. Miscellaneous
• If water-soluble stains not easily seen with naked eye are not sufficiently removed during washing and then dried, they get oxidized and tarnished to become ingrained stains difficult to be eliminated. Our products are preventive measures for the above phenomenon.
▒ Types of dry-cleaning detergents
1. Categorized as petroleum and tetrachloride ethylene(so-called perchloroethylene) according to the type of solvent
2. According to use
• Injection detergent: moisture included to remove water-soluble stains. Add in every time of washing according to laundry mass. Positive ionic detergent which most of the detergent gets attached to the laundry.
• Charge detergent: solubilzing moisture in solvent to remove water-soluble stains, use proportionate amount to the solvent for pre-treatment when solvent is exchanged or added up
• Injection detergents are used in perchloroethylene which is used in the way of distilling solvent, whereas charge detergents are used in Korean and Japanese markets where petroleum solvents are mainly used.
▒ Role of dry-cleaning detergents
• As explained above, the product is used to increase washing efficiency (increase in washability of solvents, removing water-soluble stains, preventing reverse pollution, dispersion of stains) and prevent laundry problems (fabric damages, tarnishing, ingrained stains, odor).
• Moisture mainly attributes to washing efficiency and laundry problems; to put it in other way around, dry-cleaning detergents are used to manage moisture.
▒ Amount of dry-cleaning detergents
• 0.2~0.3% of concentration in synthetic detergent when water-cleaning recommended. In case of dry-cleaning detergent, there are differences between brands but more amount than the aforementioned is recommended to be used.
• It is because CMC (critical washing concentration) of detergent is low in water but high in solvent.
• Since certain amount of moisture is needed according the level of pollution in terms of water-soluble stains, dry-cleaning detergents need more amount of moisture to be solubilized in solvent.
☞ For your information: what is “solubilization”?
Surfactants cause chemical reaction between two non-blending materials (e.g. water and oil) to produce transparent and even state. Skin toner is one of the examples of solubilization.
In solubilized state, water molecule exists within surfactant’s molecular polymer micelle, so there is little to no damage on fabric by moisture. Cleaning is done in form of the moisture melting down water-soluble stains or clinging to the stains.
▒ Carging moisture (solubilization)
• Required amount of moisture to remove water-soluble stains in dry-cleaning differs by types, forms or levels of pollution. Thus, it is unable to designate the specific amount required.
• Optimal relative humidity for washing off water-soluble stains is approximately 75%, and it is recommended to charge moisture to meet the condition.
• 75% of relative humidity? It means 75% of the whole moisture which dry-cleaning detergent can solubilize, so it is not the absolute amount. In other words, it is the amount of moisture proportionate to dry-cleaning detergent’s capacity.
• This relative humidty is to be kept when washing in basket, and to take into consideration the moisture from the laundry and usage of moisture during pre-treatment, it is recommended to keep the solvent humidity in dry tank at approximately 50%.
• It might be more efficient to use enough moisture during pre-treatment stage rather than to solubilize moisture in the solvent when using charge detergent.
▒ Rtaining concentration of detergent
• For the detergent to work properly, optimal concentration level should be retained, but it gradually decreases as fabric or pollutants attach to the filter.
• The amount lost by attaching to the laundry does not change detergent concentration since only solvent and the mixture of detergent are lost, but the amount lost by attaching to pollutants does affect the concentration level.
• In order to manage the concentration level, increase the amount of detergent about 10~20% of the original level for maintaining certain level of concentration.
▒ Mintaining relative humidity
• Causes of change in relative humidity
• Moisture inflow to laundry or attachment of moisture
• Humidity among atmosphere
• Moisture inhaling during pre-treatment stage
• As the above, there are various causes for changes in relative humidity, but it is nearly impossible in laundromat to measure relatvie humidity.
• However, if relative humidity becomes nearly 100%, which affects quality of laundry, then the solvent shows signs of white turbidity. Then, measures to lower relative humidity should take place.
① Eliminate moisture partially by passing through moisture remover (silica gel or dry cotton fabric)
② Lower the humidity by adding more detergents.
▒ Asessing relative humidity
• If the detergent’s solubility is known and several measurement tools are prepared, then evaluation is available.
• Relative humidity is important in terms of washing efficiency, but since measuring it precisely is difficult in business environment, refer to the below for a simple method.
• The most important thing to consider when selecting the detergent is not “whether moisture is charged” but “if the product is capable of charging moisture & how much it can charge”!
▒ About relative humidity
In dry-cleaning, relative humidity does not merely mean the amount of moisture contained in the solvent, but rather the threshold of the amount of moisture the detergent can solubilize in the solvent.
• Moisture in the solvent refers to the solubilized state where the solvent and moisture are evenly blended (pure and clear); if the solvent is separated from water or the solvent is opaque, then these states are not considered as solubilized.
• Consider an example where the weather is foggy or rainy. In these situations, form of water does not mean humidity but rather “fog = moisture or water fog”, and “rain = rain water or raindrops”.
• Indeed, fog or rain is formed by moisture coagulating due to the atmospheric humidity being near to 100% and therefore no more moisture can be kept in atmosphere.
• Moisture in air is not always consistent at 100% of atmospheric humidity, but differs by temperature and pressure, so this humidity is called relative humidity. (In other words, the amount of moisture is relative)
• Certain amount of moisture indicating specific value of relative humidity may change due to pressure and temperature, while in the solvent it differs by the detergent’s solubility.
▒ Prtion of the detergent at 100% of the solvent humidity
• A detergent with solubility of 10%, solvent = 100 / detergent = 1 / moisture = 0.1
• A detergent with solubility of 100%, solvent = 100 / detergent = 1 / moisture = 1
▒ How to test dry-cleaning detergent’s solubility
• Put approx. 200ml of a dry-cleaning solvent in a transparent glass or PE container. Then put exactly 10ml of a dry-cleaning detergent and shake to blend.
• The detergent in the solvent should be dissolved into pure and clear state.
• It should maintain the transparent state when 1ml of water keeps being added. If white turbidity starts to show up or layer separation occurs, that is the detergent’s solubility threshold, which is 100% of relative humidity.
• Means to remove stain with oil solvent rather than with water. Importance skyrocketing these days due to introduction of luxury fabrics and increasing variance of fabrics
▒ Advantages of dry-cleaning
• Less harm on fabric
Certain types of fabrics used in clothing are affinitive to water, and thus weakened during washing by water and detergent. Deformation (expansion or contraction, fuzzes, wrinkles, peeling) may take place. And among the pigments used for fabrics, most of them are water-soluble so they are easily tarnished by water-cleaning, and especially by alkaline detergent.
Even dry-cleaning has some problems of damaging laundry or tarnishing, which may occur according to how fabrics, solvent, detergents are managed.
• Easy to remove oil-soluble stains
Most of stains on clothing consist of oil and other solids including dirt, so the dry-cleaning solvent melts down oily substances, coupled with mechanical power of washer. As these substances get eliminated, the solids which were attached to clothing by these substances are removed as well.
▒ Disadvantages of dry-cleaning
• Uneconomic
Dry-cleaning solvents are more expensive than water, and after use they get evaporated or filtered but those processes entail costs and losses.
• Weak washability
Water is inexpensive and abundant, letting sufficient amount be used for washing, but solvent does not necessitate rinsing, so stains are insufficiently removed.
• Dry-cleaning solvents are insufficient to disperse pollutants out to the solvent, and thus pollutants are easily re-attached to the laundry. (Since dry-cleaning solvents are nonpolar substances, it does not create repulsion due to electronic dual layer between fabric and pollutants, and are only subject to van der Waal’s force.)
• Cannot remove water-soluble stains.
• Petroleum solvent is inflammable, thus having danger of fire or explosion.
• Incombustible solvents release poisonous steams, so are insanitary.
• Certain materials used in clothing may get tarnished or damaged by the solvent.
• The solvent may deform plastics, melt down adhesive and deteriorate rubber.
Dry-cleaning solvents
▒ Conditions of dry-cleaning solvents
• Should decompose and dissolve stains well
• No damages to fabric and color
• No or less poison, no deterioration of dry-cleaning devices
• No or less inflammability
• Easy to remove and purify. No tarnishing while purifying.
• Easy to dry, no odor to remain
• Should be inexpensive
▒ Safety of dry-cleaning solvents
• Threshold Limit Value, TLV
Safe level of TLV (petroleum = 500ppm, perchloroethylene = 100ppm) even when inhaled for 8 hours a day. Lower ppm indicates more danger.
• Vapor Hazard Index, VHI
Danger indicator including TLV and volatility(saturated vapor pressure). The higher the level, the more dangerous. (Petroleum = 13, perchloroethylene = 187)
• followed by ignition point, vapor pressure and etc.
▒ Washability of the solvent
• Kauri Butanol Value, KBV
Amount (ml) of the loaded solvent to the mixture of 20% of natural acryl Kaurigum and butanol 20ml until white turbidity occurs. Larger KBV values indicate higher dissolving capacity of oil-soluble stains. (Petroleum = 27~45, perchloroethylene = 90)
Excessive KBV may result in deterioration of natural luxury fabric by dissolving fat of the fabrics, and also melt down adhesive or plastic components.
• Surface Tension
Less surface tension of solvents increase washability by easily permeating through fabric and stains. (Petroleum = 27.6, perchloroethylene = 32.3)
• Specific Gravity
Larger specific gravity of solvents may increase washability by strengthening physical power formed when solvent rotates and falls, whereas weak fabrics may get damaged by so doing.
▒ Types of solvents
• Hydrocarbon solvents
Compounds consisting of only carbon and hydrogen, including aliphatic hydrocarbon, aromatic hydrocarbon, alicyclic hydrocarbon and such. Difficult to handle, poisonous gas, high inflammability all count towards inappropriateness of the compounds to be used as dry-cleaning solvents.
e.g.) hexane, sichrohexane, benzene, decanol…
• Petroleum solvent
Hydrocarbon compounds obtained from petroleum processing. Exclusive dry-cleaning solvent has higher initial ignition point than that of petroleum therefore less dangerous, and has lower middle ignition point than diesel so therefore easy to remove and dry, with its main components being aliphatic saturated hydrocarbon(paraffin), aromatic and alicyclic hydrocarbon all attributing to good solubility.
Inexpensive, less poisonous, good solubility and low specific gravity. Appropriate for delicate laundry such as silks
• Halogenated hydrocarbon solvent
Petroleum hydrocarbon being inflammable and having high risk of ignition. Chlorine or fluroine combined to hydrocarbon in order to make incombustible synthetic solvent.
Highly poisonous, thus concealed facilities necessary. Disadvantage of deteriorating devices by decomposition when evaporated. Too high specific gravity, pure wool or silk floating around the solvent thereby decreasing washability
e.g.) carbon tetrachloride, trichloroethylene, trichloroethane, perchloroethylene, trichloro-trifluoride ethane
Dry cleaning detergent
▒ What is dry-cleaning detergent?
• Synthetic detergents for home users are affordable without product information and do not need special cautions.
• But for professional laundromats, in order to give high-quality laundry service by correctly understanding various types of fabrics and stains, it is necessary to understand chemicals used in laundry, especially detergents.
• The following describes dry-soap which is also important in washing altogether with oil solvents in dry-cleaning.
▒ Difference from synthetic detergents
• Oil-soluble stains unremovable with water-cleaning whereas most of water-soluble stains are removed without detergents. Thus remove oil-soluble stains to eventually eliminate solid stains attached by the oil-soluble stains with synthetic detergents
• In dry-cleaning, water-soluble stains are unremovable while most of oil-soluble stains are removed by solvent. Thus remove water-soluble stains to eventually eliminate solid stains attached by the water-soluble stains with dry-cleaning detergents.
☞ For your information: what is so called “dry-soap”?
Derived from the composition of the past dry-cleaning detergents, mostly composed of fatty acid chloride (soap) and fatty acid compounds. Precise expression is “dry-cleaning detergent”.
▒ Functions of dry-cleaning detergents
1. Removing water-soluble stains
• Dry-cleaning solvent is effective at removing oil-soluble stains such as oil, but zero-effective at washing off water-soluble stains including mineral pigments, carbon, and protein.
• Oil-soluble solvent used in dry-cleaning is nonpolar and thus unable to be blended with water which is polar compound. It therefore cannot wash off water-soluble stains(mineral pigments, carbon, protein, etc.) which are affinitive to water.
• In order to eliminate water-soluble stains, water to melt them down is necessary. And since water is unable to be blended with solvent, dry-cleaning detergent is needed to solubilize water.
• Application of moisture through dry-cleaning detergents can be categoerized as injection and charging, but this is only methodological difference and the principle is same as both give affinity to the oil-soluble solvent.
2. Increase washing efficiency
• In water-cleaning, basic mechanism of washing is lowering surface tension of water with surfactants in synthetic detergents.
• Dry-cleaning solvents are lower in surface tension than water and easily permeate through hydrophobic(lyphophilic) fabrics, but are difficult to permeate through hydrophilic fabrics. Thus, dry-cleaning detergents are needed.
• Low surface tension and fast permeability weaken coherence between stain and fabric, thereby increasing washability of the solvent.
3. Preventing recontamination
• In dry-cleaning, solid stains attached by oil-soluble stains are easily detached from fabric, but since the solvent is nonpolar, only van der Waal’s force is applied without repulsion between fabric and pollutants or between pollutants themselves due to electric dual layer. Thus, recontamination may occur more easily.
• By adding dry-cleaning detergents, surfactants attach to and arrange hydrophilic substances in direction towards fabric and solid stains while lyphophilic substances in direction of solvent. Thus, fabric and solids become hydrophobic(lyphophilic, affinitive to solvent), easily detaching and eliminating solids and obtaining stable dispersion. Since solid stains are prevented from clotting and attaching to fabric, recontamination should not occur.
4. Anti-static process
• Since oil-soluble solvents and fabrics are nonconductive, electric energy formed by circulation or friction (between fabrics, or between fabric and solvent) within washer creates static. Mostly occurring when drying.
• Static makes pollutants attach to fabrics and clothing becomes prickly.
• Lubrication of dry-cleaning detergents lowers friction energy, and gives fabric and solvent delicate ionic characters along with moisturization in order to contain statics.
5. Shortening washing duration and safeguarding fabric
• Dry-cleaning detergents eliminate water-soluble stains and increase washing efficiency, thereby shortening washing time.
• Shortened washing time can decrease damages to fabric by physical power, and fabric softener included gives satisfactory finishing to the laundry.
6. Miscellaneous
• If water-soluble stains not easily seen with naked eye are not sufficiently removed during washing and then dried, they get oxidized and tarnished to become ingrained stains difficult to be eliminated. Our products are preventive measures for the above phenomenon.
▒ Types of dry-cleaning detergents
1. Categorized as petroleum and tetrachloride ethylene(so-called perchloroethylene) according to the type of solvent
2. According to use
• Injection detergent: moisture included to remove water-soluble stains. Add in every time of washing according to laundry mass. Positive ionic detergent which most of the detergent gets attached to the laundry.
• Charge detergent: solubilzing moisture in solvent to remove water-soluble stains, use proportionate amount to the solvent for pre-treatment when solvent is exchanged or added up
• Injection detergents are used in perchloroethylene which is used in the way of distilling solvent, whereas charge detergents are used in Korean and Japanese markets where petroleum solvents are mainly used.
▒ Role of dry-cleaning detergents
• As explained above, the product is used to increase washing efficiency (increase in washability of solvents, removing water-soluble stains, preventing reverse pollution, dispersion of stains) and prevent laundry problems (fabric damages, tarnishing, ingrained stains, odor).
• Moisture mainly attributes to washing efficiency and laundry problems; to put it in other way around, dry-cleaning detergents are used to manage moisture.
▒ Amount of dry-cleaning detergents
• 0.2~0.3% of concentration in synthetic detergent when water-cleaning recommended. In case of dry-cleaning detergent, there are differences between brands but more amount than the aforementioned is recommended to be used.
• It is because CMC (critical washing concentration) of detergent is low in water but high in solvent.
• Since certain amount of moisture is needed according the level of pollution in terms of water-soluble stains, dry-cleaning detergents need more amount of moisture to be solubilized in solvent.
☞ For your information: what is “solubilization”?
Surfactants cause chemical reaction between two non-blending materials (e.g. water and oil) to produce transparent and even state. Skin toner is one of the examples of solubilization.
In solubilized state, water molecule exists within surfactant’s molecular polymer micelle, so there is little to no damage on fabric by moisture. Cleaning is done in form of the moisture melting down water-soluble stains or clinging to the stains.
▒ Carging moisture (solubilization)
• Required amount of moisture to remove water-soluble stains in dry-cleaning differs by types, forms or levels of pollution. Thus, it is unable to designate the specific amount required.
• Optimal relative humidity for washing off water-soluble stains is approximately 75%, and it is recommended to charge moisture to meet the condition.
• 75% of relative humidity? It means 75% of the whole moisture which dry-cleaning detergent can solubilize, so it is not the absolute amount. In other words, it is the amount of moisture proportionate to dry-cleaning detergent’s capacity.
• This relative humidty is to be kept when washing in basket, and to take into consideration the moisture from the laundry and usage of moisture during pre-treatment, it is recommended to keep the solvent humidity in dry tank at approximately 50%.
• It might be more efficient to use enough moisture during pre-treatment stage rather than to solubilize moisture in the solvent when using charge detergent.
▒ Rtaining concentration of detergent
• For the detergent to work properly, optimal concentration level should be retained, but it gradually decreases as fabric or pollutants attach to the filter.
• The amount lost by attaching to the laundry does not change detergent concentration since only solvent and the mixture of detergent are lost, but the amount lost by attaching to pollutants does affect the concentration level.
• In order to manage the concentration level, increase the amount of detergent about 10~20% of the original level for maintaining certain level of concentration.
▒ Mintaining relative humidity
• Causes of change in relative humidity
• Moisture inflow to laundry or attachment of moisture
• Humidity among atmosphere
• Moisture inhaling during pre-treatment stage
• As the above, there are various causes for changes in relative humidity, but it is nearly impossible in laundromat to measure relatvie humidity.
• However, if relative humidity becomes nearly 100%, which affects quality of laundry, then the solvent shows signs of white turbidity. Then, measures to lower relative humidity should take place.
① Eliminate moisture partially by passing through moisture remover (silica gel or dry cotton fabric)
② Lower the humidity by adding more detergents.
▒ Asessing relative humidity
• If the detergent’s solubility is known and several measurement tools are prepared, then evaluation is available.
• Relative humidity is important in terms of washing efficiency, but since measuring it precisely is difficult in business environment, refer to the below for a simple method.
• The most important thing to consider when selecting the detergent is not “whether moisture is charged” but “if the product is capable of charging moisture & how much it can charge”!
▒ About relative humidity
In dry-cleaning, relative humidity does not merely mean the amount of moisture contained in the solvent, but rather the threshold of the amount of moisture the detergent can solubilize in the solvent.
• Moisture in the solvent refers to the solubilized state where the solvent and moisture are evenly blended (pure and clear); if the solvent is separated from water or the solvent is opaque, then these states are not considered as solubilized.
• Consider an example where the weather is foggy or rainy. In these situations, form of water does not mean humidity but rather “fog = moisture or water fog”, and “rain = rain water or raindrops”.
• Indeed, fog or rain is formed by moisture coagulating due to the atmospheric humidity being near to 100% and therefore no more moisture can be kept in atmosphere.
• Moisture in air is not always consistent at 100% of atmospheric humidity, but differs by temperature and pressure, so this humidity is called relative humidity. (In other words, the amount of moisture is relative)
• Certain amount of moisture indicating specific value of relative humidity may change due to pressure and temperature, while in the solvent it differs by the detergent’s solubility.
▒ Prtion of the detergent at 100% of the solvent humidity
• A detergent with solubility of 10%, solvent = 100 / detergent = 1 / moisture = 0.1
• A detergent with solubility of 100%, solvent = 100 / detergent = 1 / moisture = 1
▒ How to test dry-cleaning detergent’s solubility
• Put approx. 200ml of a dry-cleaning solvent in a transparent glass or PE container. Then put exactly 10ml of a dry-cleaning detergent and shake to blend.
• The detergent in the solvent should be dissolved into pure and clear state.
• It should maintain the transparent state when 1ml of water keeps being added. If white turbidity starts to show up or layer separation occurs, that is the detergent’s solubility threshold, which is 100% of relative humidity.
