The present invention refers to a paste-like thixotropic detergent or cleaning concentrate which is able to form a stable (non separating) alkaline parent lye for use as cleansing agent or detergent, preferably for the machine cleaning of textiles, a parent lye containing said concentrate and to a method for washing textiles using said concentrate in diluted form as a parent lye.
In industrial laundries nowadays the single washing machines are centrally supplied with the solution of a detergent or cleaning agent, the so called parent lye, to maximize the capacity of the laundry and the machinery and to optimise the course of the process. Generally, the central supply proceeds using a parent lye which contains 5 to 15 wt.-% of the cleaning agent or detergent and which is distributed from a reservoir to the single washing machines, in most cases without further diluting. Accordingly, a cleaning agent or detergent suitable for use in industrial laundries must be capable to form a stable (non separating) alkaline cleaning or detergent solution to ensure a constantly excellent cleaning or washing performance.
Cleaning and detergent compositions formulated in particulate form are well known to form stable (non separating) alkaline cleaning or detergent solutions. However, generally large amounts of parent lye are prepared and stored in a reservoir to be subsequently distributed to the single washing machines. This means a corresponding amount of solid detergent or cleaning agent, respectively, has to be dissolved to form the parent lye, which takes a lot of time and effort.
Moreover, large amounts of solid, especially particulate, detergents show problems with respect to homogeneity if they are stored before being used to form the parent lye and not consumed at one go. This is because the single components in the detergent exhibit different volumes and densities which results in the active components migrating to the bottom of the reservoir upon storage. Accordingly, if the parent lyes are prepared using a detergent powder stored in a reservoir, this migrating process may take place therein while consuming the parent lye. The following parent lyes may then exhibit a more and more decreased cleaning performance due to the more and more decreasing content of active agent in the solid detergent. The parent lye formed from the detergent on the bottom of the reservoir, where the active ingredient accumulated, then again exhibits excellent cleaning performance.
Accordingly there is a need to provide stable homogenous paste-like detergent or cleaning concentrates which are easily batched and dissolved to form a stable parent lye and exhibit excellent cleaning properties, especially in laundry application.
Yet, the actually known paste-like detergent and cleaning concentrates do not exhibit this combination of properties. In particular, a large amount of a non-ionic surfactant blend is required as liquid component to provide those concentrates with a viscid to highly viscous consistency. Accordingly, when forming a parent lye, those concentrates generally show poor solubility and do not form stable (non separating) solutions. Even the use of emulsifiers in large amounts which increases costs and complicates the disposal of the resulting waste water, did not provide a homogenous, stable parent lye. This results in the requirement of vigorous stirring in the vessel during storage of the parent lye to ensure a more or less homogenous distribution of the detergent concentrate. In most cases not even vigorous stirring provides a homogenous parent lye.
Moreover, nowadays it is very important to provide cleaning agents and detergents which do not only exhibit excellent cleaning properties but which are as well accessible to the common waste water purification systems. If the waste water and/or a part of the detergent solution accumulating after the washing process has been carried out is treated by membrane filtration, many non-ionic surfactants cause considerable problems. Depending on the choice of non-ionic surfactant, this may even lead to blocking-up of the membranes. This point is to be deemed particularly critical in membrane filtration processes in the course of which at least one reverse osmosis step occurs.
Therefore, the object of the present invention is to provide a cleaning or detergent concentrate which on one hand forms a stable paste as such and on the other hand also forms a stable (non separating) alkaline cleaning or detergent solution when dissolved in water. Additionally, it should be possible to purify waste water resulting from the cleaning or washing process and containing said concentrate on common membrane filtration units, especially ones using one or more reverse osmosis steps, without blocking the membrane or causing other damages.
Surprisingly, the underlying problem is solved by providing a paste-like, thixotropic, alkaline detergent or cleaning concentrate comprising based on the whole concentrate
- a) 0,5 to 15 wt% of at least one first component selected from one or more compounds represented by the general formula (I),
R1-(OC2H4)n-(OC3H6)m-OH (I)
wherein R1 represents an unbranched or branched alkyl or alkenyl group having 4 to 8, preferably 5 to 7, carbon atoms, and wherein the sum of the average degree of ethoxylation n and propoxylation m ranges from 1 to 9, preferably from 3 to 7, with one of n and m optionally being 0, and - b) 5 to 90 wt% of at least one second component selected from one or more compounds represented by the general formula (II),
R2-(OC2H4)0-(OC3H6)p-OH (II)
wherein R2 represents an unbranched or branched alkyl or alkenyl group having 9 to 22, preferably 10 to 16, carbon atoms, and wherein the sum of the average degree of ethoxylation o and propoxylation p ranges from 1 to 9, preferably from 3 to 7, with one of o or p optionally being 0, - c) at least 1 wt% of at least one alkanolamine the cleaning concentrate exhibiting at 25°C a viscosity of from 80 000 mPas to 250 000 mPas at 5 revolutions per minute and a viscosity of from 20 000 mPas to 80 000 mPas at 50 revolutions per minute, each measured using a Brookfield rotational viscometer (spindle no. 7) under otherwise identical conditions.
In this context thixotropic means that the concentrate exhibits such a structural viscosity that it does not flow under the influence of gravity. However, on shear the viscosity tremendously decreases which enables the concentrate to flow under the influence of gravity. The dosing of thixotropic composition is then preferably performed by shearing the concentrate to reduce viscosity at first and afterwards dosing and transmitting the free-flow concentrate using for example a feed pump. The above mentioned viscosity values refer to reading after a detection time of 3 minutes to take the time dependency of the thixotropic effect into account. The decrease of viscosity on shear is to a great extent reversible, i. e. after having stopped the shear the concentrate will return to its original physical condition without separation.
It has to be taken into account that the viscosity may change while an equilibrium adjusts within the concentrate after its preparation. Accordingly, viscosity values measured during the manufacturing process or directly afterwards may falsify the result. Thus, the viscosities are determined after the equilibrium is adjusted and the final viscosity is reached. Storing for one month is generally sufficient to obtain reliable values.
In a preferred embodiment a mixture of two or more compounds represented by general formula II is used wherein R2 is C10, C13 and/or C12-14, o is 3, 4 and/or 5 and p is 0 or 5. In these cases it is especially preferred to use at least one compound represented by the general formula I wherein R1 is C6, n is 5 and m is 0.
The preferred amount of the compound(s) represented by the general formula (I) is in the range of from 1 to 10 wt.-% and most preferred from 2 to 5 wt.-% based on the whole concentrate.
The one or more compounds represented by the general formula (II) should be present in an amount of from 5 to 90 wt.-%, preferably from 15 to 70 wt.-% and most preferred from 20 to 50 wt.-% based on the whole concentrate.
The alkalinity may be achieved using any compound known in the state of the art which when dissolved in water shows an alkaline reaction, like for example alkali hydroxides, especially sodium or potassium hydroxide, ammoniumhydroxide, alkaline-earth hydroxides, alkali carbonates, like soda or mixtures thereof. The preferred alkalinity generating compound is represented by soda.
In a further preferred embodiment amorphous alkali silicate may be added as alkalinity source. Sodium meta silicate with a ratio of Na2O: SiO2 in the range of 1 : 0,8 to 1 : 1,3, preferably 1 : 1 is especially appropriate.
Moreover, one or more phosphates, can be used instead of or in addition to the amorphous alkali silicate. However, this should only be in case that the use of phosphates does not cause harm because of a phosphate eliminating waste water purification step following the cleaning or washing steps.
The phosphates are preferably selected from at least one of primary orthophosphates represented by the general formula MIH2PO4 or MII(H2PO4)2, secondary orthophosphates represented by the general formula MI2HPO4 or MIIHPO4 or tertiary orthophosphates represented by the general formula MI3PO4 or MII3(PO4)2, as well as condensed phosphates derived therefrom, the so called meta phosphates and poly phosphates, with M being a metal cation, MI preferably being an alkali metal and MII preferably being an alkaline-earth metal.
In one especially preferred embodiment the phosphate is a tripolyphosphate, preferably sodium tripolyphosphate (Na5P3O10).
The content of the alkalinity source is chosen such that the pH value of a use solution containing the inventive concentrate should advantageously be in the range of from 9 to 13, preferably 10 to 12. Correspondingly, the total amount of the alkalinity source preferably ranges from 25 to 70 wt.-%, more preferably from 30 to 60 wt-% and most preferred from 50 to 58 wt.-%, based on the whole concentrate.
In preferred embodiments soda is used in amounts of from 15 to 60 wt.-%, preferably 25 to 55 wt.-%. The amount of amorphous alkali silicate, especially sodium meta silicate, with the above mentioned Na2O : SiO2 ratio, preferably ranges from 10 to 20 wt.-%, and especially is 15 wt.-%. The phosphor compound should be contained in an amount of at most 40 wt.-%, preferably in an amount of 30 wt.-% or below, especially in a range of from 20 to 30 wt.-% based on the whole concentrate.
It is also possible to further add an alkaline compound in form of a solid or an aqueous solution when diluting the concentrate before use. However, it is most preferred to not add further alkaline compound when preparing the use solution from the inventive concentrate.
The inventive concentrate comprises at least 1 wt.-% based on the whole concentrate of at least one alkanolamine. Preferably the sum of alkanolamines contained in the concentrate is contained in an amount above 2 wt.-% and lies within the range of from 2 to 10 wt-%, and in particular from 3 to 5 wt.-%, based on the whole concentrate.
In a preferred embodiment at least one of the alkanolamines is represented by the general formula (III),
Those compounds may function as solutizer and thus improve the homogeneity of the inventive concentrate when diluted to form the use solution, for example the parent lye. Moreover, alkanolamines additionally represent an alkalinity source. As they are liquid they help to avoid the use of water to provide the paste-like concentrate.
The paste-like concentrate comprises a solid phase which is dispersed in a liquid phase as homogeneous as possible. The composition according to the present invention forming the above concentrate enables the water content to be reduced to an amount preferably of less than 3 wt.-%, more preferred less than 2 wt.-%, and most preferred less than 1 wt.-% based on the whole concentrate. Said water content is meant to refer to free water only. Additional water may be present in form of water of crystallisation or water of constitution. To improve the physical stability as well as the chemical stability the concentrate may additionally comprise dehydration agents, for example in form of salts which bind water of crystallisation like anhydrous sodium acetate, calcium sulfate, calcium chloride, sodium hydroxide, magnesium silicate or metal oxides like CaO, MgO, P4O10 or Al2O3 or mixtures thereof.
The concentrate may additionally contain at least one alkyl polyglucoside having from 8 to 14 carbon atoms in the alkyl group and from 1 to 5 glucose moieties. The amount of the alkyl polyglucosid should be in the range of from 1 to 6 wt.%, preferably from 1,5 to 3 wt.%.
Such compounds have a strongly hydrophobic alkyl moiety and a strongly hydrophilic glucosid moiety and, accordingly, are very much appropriate to function as stabilizer of the paste-like concentrate.
Additionally, the concentrate may comprise one or more further additives generally used in cleaning agents or detergents like further soil release agents, cobuilders, optical brighteners, dyes and fragrances, small quantities of neutral salts such as sulfates and chlorides in the form of their sodium or potassium salts, provided that these do not impair the positive properties. Other suitable additives to the product may be enzymes, foam regulators, redeposition inhibitors, soil release agents, bleaching agents from the class of per compounds, which are conventionally used together with activators, active chlorine compounds as well as dyes, dye transfer inhibitors or dye intensifiers and fragrances.
When preparing the inventive concentrate for practical reasons the liquid components should be pre-mixed before the solid components and further ingredients are incorporated. In case that the particulate solids are not fine enough to provide a homogeneous, paste-like concentrate, they may be grinded one or more times before incorporation.
The inventive concentrate as described above can be used to prepare a stable parent lye. Especially for usage in laundry applications the parent lye contains the inventive concentrate in amounts of from 0,5 to 25 wt.-%, preferably 5 to 15 wt.-% based on the detergent solution. Generally, the concentrate is dissolved in pure water to form the parent lye. However, it is also possible to use water in which further additives, like hydrophilic auxiliaries, are dissolved.
Although the main emphasis for the usage of the concentrate or the solution containing the inventive concentrate, respectively, is on laundry detergents, it may as well be applied as cleaning agent in warewashing, clean in place cleaners and sanitizers, food an dairy formulations and other applications in which such alkaline cleaning solutions may be applied. Preferably, the solution containing the concentrate is used as parent lye for the industrial machine cleaning of textiles.
Moreover, the present invention provides a method for washing textiles comprising one step in which a parent lye is prepared by diluting the concentrate according to claims 1 to 12 such that the parent lye contains the concentrate in an amount of from 0,5 to 25 wt.-%, preferably of from 5 to 15 wt.-% based on the detergent solution.
The concentrate according to the invention is metered from a storage reservoir using a metering equipment which is suitable to meter paste-like substances by influence of shearing force. An appropriate equipment is described for example in
To accelerate the blending the mixture is advantageously agitated. The resulting parent lye may than either directly be distributed to the single washing machines or stored for usage in washing cycles to be performed later. Preferably, the parent lye is shortly agitated after having been stored before it is distributed to the single washing machines to guarantee a homogeneous distribution of the active agent in the parent lye. When transmitted to the single washing machines the parent lye may be further diluted depending on the desired detergent concentration.
It is also possible to pre-portion the paste-like concentrate, for example to wrap it in foil bags. Since the concentrate essentially does not contain water the concentrate may be wrapped in foils which are water soluble. In this case when preparing the parent lye the required number of foil bags is poured into a tank, the appropriate amount of water is added and after the foils are dissolved by the water the parent lye may be obtained by stir ring.
A further advantage resulting from the composition of the concentrate is that it allows the purification of the waste water which is accumulated during the cleaning or washing process using common membrane filtration units without blocking them or causing other damages. The membrane filtration may as well comprise at least one ultra filtration and/or reverse osmosis step. Said purification processes succeed best with a concentrate according to the invention which contains one or more phosphates.
The following table presents examples for appropriate compositions (C1 to C10) for the inventive concentrate. The cited values refer to wt.-%, based on the whole concentrate. The paste-like concentrates exhibited good storage stabilities, i. e. they did not separate over a period of at least 12 months, provided stable parent lyes when being stirred and optionally warmed up to 30-40°C, i. e. they essentially did not separate over a period of at least 1 week, when diluted in water in an amount such that the content of the concentrate was 10 wt.-% based on the parent lye. Generally, slightly stirring was sufficient to obtain a stable parent lye. Moreover, the concentrate when used as a 10 wt.-% aqueous parent lye exhibited excellent cleaning properties. Especially when applying the concentrates in examples C3, C6, C7 and C9 the waste water accumulated during the washing process could be purified by membrane filtration even using ultra filtration steps.