Front-loading washing machine

The traditional materials used for washing-machine tanks has always been either stainless steel or the cheaper vitreous-enamelled mild steel. However, prior to 1976 Philips were producing a non-load carrying top-loader washing machine which incorporated a tank injection moulded in compact, i.e. solid, PP, Now it was evident that there would be a big demand for front-loading washing machines in the UK and Philips decided that before they went into production it would be a very opportune time to look into alternatives to the metal tank. 

Front-loading washing machines can hold as much as 18 pounds of clothing. To find out how much your loads weigh, first weigh yourself, then weigh yourself holding... 

The tank of an automatic front-loader washing machine has to withstand the following punishing conditions it is exposed to soapy water, heated to near boiling point, agitated with up to 5 kg wet washing, pumps out the water, rinses several times, and finally spins the whole load at speeds of about 800 rpm - and it does this perhaps several times a day, every day, for about 10 years. 

FIGURE 8.1 Overfoaming in front-loading drum-type washing machine due to absence of... 

Front-Loading Drum-Type Textile Washing Machines... 

Control of foam in front-loading drum-type textile washing machines probably represents the most important application of antifoam technology by the detergent industry. Suitable antifoams and methods of incorporation in detergent powders and liquids for this application are therefore described in this section and in Section 8.4, respectively. 

As in the example of the detergent formulation used to obtain the foam profiles shown in Figure 8.4, early attempts to develop praetieal washing powder formulations suitable for foam-intolerant, front-loading drum-type laundry washing machines utilized the antifoam effect of calcium soaps in mixed anionic and ethoxylated alcohol surfactant systems. The approach appears to have been entirely empirical. The foam behavior of ternary mixtures of anionie surfaetants, sueh as sodium alkylbenzene sulfonates, various ethoxylated alcohols, and soaps, was optimized for low foamabil-ity in relevant machines by systematie trial. Obviously, polyvalent metal ion (especially calcium) activity as determined by temperature, water hardness, and builder type and concentration represented an additional variable. Wash temperature and pH... 

It is known that fatty adds and soaps act as effective promoters for hydrocarbon oil-based antifoams [27]. Such mixtures exhibit the usual synergistic effect and have, not surprisingly, been claimed as antifoams and equivalent precursors for detergent powders. Mixtures of hydrocarbons and either fatty acids or soaps are, for example, claimed by Schweigl and Best [37] to be suitable for front-loading drum-type washing machines. However, the claims are exemplified by use of combinations of soaps and hydrocarbons where these materials are incorporated into a detergent... 

Mixtures of ethylene and methylene distearamide with hydrocarbons have also been claimed to be effective particle-oil antifoams for control of detergent foam in front-loading textile washing machines [38]. Such mixtures represent weU-known antifoams for general application (see, e.g.. Table 4. A3). They may be prepared by milling the mixtures or by cooling a melt of the mixtures (since the solubility of distearamides at ambient temperatures is low) to form particulate dispersions in hydrocarbons. The particles of these alkylene distearamides are intrinsically hydro-phobic [39] and have the properties necessary for rupture of the relevant pseudoemulsion films (see Chapter 4). Unlike the soaps and alkyl phosphoric acid esters, there is no requirement for interaction with any ingredient, such as water hardness, present in the wash solution. 

Mixtures of polydimethylsiloxanes oils and hydrophobed silicas have formed the basis of many patents concerned with the control of detergent foam in front-loading drum-type textile washing machines. It is likely that this type of antifoam is actually included in many commercial detergent powders designed for that application. 

As we have seen, the presence of ethoxylated non-ionic surface-active compounds can enhance the susceptibility of the foam of solutions of anionic surfactants to antifoam. This appears to be a general phenomenon that is also manifest with PDMS-hydrophobed silica antifoams in wash cycles with drum-type, front-loading, textile washing machines. This well-known effect is exemplified in Figure 8.13 where the addition of ethoxylated alcohols is seen to diminish the foam profile of solntions of sodinm alkylbenzene snlfonate (LAS) in the presence of PDMS-hydrophobed silica antifoam. Sawicki [7] has shown that the effect of these ethoxylated componnds does not concern either the precipitation of cloud phase drops (see Section 4.6.3.2) or marked changes in dynamic or equilibrium air-water solution snrface tensions. One possible explanation could concern a putative inhibiting effect of ethoxylated compounds upon the rate of PDMS-hydrophobed silica antifoam deactivation. However, this would afford no explanation for the effect of those componnds on the antifoam action of hydrophobic precipitates where no oil is present (see Section 8.2.2). 

A list of early patents concerning the incorporation of PDMSs in detergent powders designed for the washing of textiles in drum-type front-loading machines is given... 

In the case of washing machines, there are differences in preference for top-loading versus front-loading machines - in the UK almost all the machines purchased are front loaders whilst in Erance the reverse is true. 

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