Washing Process Presentation

LTC

Independent Expertise

C

Washing Processes

LTC & DTC 2014

© LTC&DTC Ltd 2014

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Wash Process Additives

Emulsifiers

• An alternative way of improving the release of oily or fatty soiling is to use an emulsifier in the wash. This is a neutral liquid designed to help solubilise oily fatty globules by splitting them and lifting them off the fabric without aggressive chemistry.

EMULSIONOIL

WATER

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Wash process additives Sour (Acid)• To neutralise alkalis from the wash process

Antichlor• To neutralise residual hypochlorite bleach

Fabric Conditioner• To make the fabric feel ‘softer’ and reduce static

Starch• Impart a ‘stiffer’ feel to the fabric-can be natural –

Rice or synthetic - PVA

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Wash Process Design

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BleachesUsed within the wash or rinse sections depending upon thetype of bleach used.

2 Families of Bleach - Oxidizing and Reducing

Oxidizing bleaches for protein soiling and vegetable dyes• Sodium hypochlorite - 60ºC Max – otherwise excess

fabric damage• Hydrogen Peroxide - 65ºC+

Reducing used to remove dye (Sodium dithionite/ Sodium hydrosulphite)

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Sinners Circle – 4 principle elements

WATER

DetergencyDetergency Mechanical ActionMechanical Action

TimeTime TemperatureTemperature

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Ingredients for a good wash…..

WATER

• Quality – Clean, colourless, odour and bacteria free

• Soft (more than 5ºClarke – 72ppm too hard)

• Hard water contains Calcium and Magnesium Salts.

• Right amount in the right place at the right time at the correct temperature

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Some problems caused by hard water

• Destroys some of the detergent • Can make loads feel greasy if soap is within the

formulation • Leads to scale build up in the CBTW which prevents

transfer occurring and can lead to blockages.• Leads to a hard skin forming around greasy and oily

soiling making it harder to remove. • Makes fabrics feel hard and harsh.• Any water hardness has some effect on washing quality,

and the higher the hardness the greater the problem.

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Time

Different stages of the wash process need different amounts

of time. Typical examples are

• Pre-wash: 4-8 minutes to remove loose particulate soiling• Main wash: 5-14 minutes to remove ingrained soiling• Rinses: 3-5 minutes to dilute chemicals

• Spin: 3-8 minutes depending upon fabric type.

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Degree of Loading• All washing machines are usually referred to by their

maximum loading capacity of dry 100% cotton textiles (e.g. a 90kg machine). This figure is usually calculated using dry 100% cotton sheeting as the standard classification.

• Above this designated weight, mechanical action will be reduced by the restricted movement and drop of the linen. Overloading will therefore result in poor wash quality.

• Below this target weight (under-loading), increased mechanical action will occur which can increase fabric damage. Wash costs also increase as the same amount of water, chemicals and energy are used for a smaller amount of work.

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Temperature

• Different types of soiling need different temperatures (Oily – high, Protein Low)

• Fabrics, dyes and soiling behave differently at high and low temperature

• Chemicals activity increases with higher temperature

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Temperature• 38ºC - Protein stains (blood and perspiration) start to set

above this temperature

• 40ºC - Optimum temperature for enzyme activity to digest protein stains. Some enzymes are designed to work at higher temperatures.

• 60ºC - Maximum temperature for sodium hypochlorite use, to avoid fabric damage.

• 65ºC - Minimum temperature for using Hydrogen Peroxide

• 80ºC - Normal minimum temperature for heavy mineral oil removal, but the latest systems can work at lower temperatures.

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Detergency

• Each chemical reacts in various ways with both the soiling and the fabric

• Detergency to match the particular stage of the process

• Chemicals are affected by the concentration (amount added to the machine) as well as the temperature they are used and the time which they have to react

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75ºC39ºC 60ºC 25ºC

Pre-wash drain

Main-wash drain

Rinse waterIn /flow meter

Membrane pressTank pumpRinse

drain

Wash f lowmeter

Pre-wash flush

Pre-wash Flush pump

Wash Processes in a CBTW

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Time12 stage CBTW - Total cycle time is 30minutes,30mins÷ 12 compartments = 2½minutes

Therefore the process is likely to be set up

• Pre-wash/Wetting out – Sections 1 & 2 = 2 x 2½mins = 5 minutes.

• Main wash stage – sections 3 – 8 = 6 x 2½mins = 15 minutes.

• Rinse stage – sections 9-12 = 4 x 2½mins = 10 minutes

• Total time: 30 mins.

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Mechanical Action• Machine inner basket rotational speed – normally

pre-set during manufacture

• Correct reversing (to avoid tangles)

• Operational speeds - Rocking and Transfer (fabric type)

• Mechanical action from the contraflow of water and/or the bath transfer

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Degree of Loading• The principles of over and under loading apply with

CBTW’s. In CBTWs overloading has an additional problem which can cause blockages.

• With CBTW underloading wash costs also increase as the same amount of water, chemicals and energy are used for a smaller amount of work.

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Pre-wash drain

Main-wash drain

Rinse waterIn /f low meter


drain

Wash f lowmeter

Pre-wash f lush

Pre-wash Flush pump

Water levels

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Temperature

• Within CBTW’s the same rules for temperature apply for soiling types and fabrics.

• There are inbuilt inflexibilities with using CBTW’s as it is a continuous process which must be taken into account

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Pre-wash drain

Main-wash drain

Rinse waterIn /flow meter


drain

Wash f lowmeter

Pre-wash flush

Pre-wash Flush pump

Temperature

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Detergency

• The rules on detergency still apply

• Within CBTW’s there are inbuilt inflexibilities which must be taken into account

• Careful detergency planning and management will give you flexibility in soil removal

Washing Process Presentation

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