ZA200203357B

ZA200203357B - Use of polymeric material in the treatment of hard surfaces.

Info

Publication number: ZA200203357B
Application number: ZA200203357A
Authority: ZA
Inventors: Alexander Thomas Ashcroft; Melvin Carvell; Karla Mary Humpreys; Ezat Khoshdel; Xiang Yang Liu; Steven Paul Rannard; Andrew Mark Waller
Original assignee: Unilever Plc
Priority date: 1999-12-08
Filing date: 2002-04-26
Publication date: 2003-04-29
Also published as: CA2392587C; AU2837301A; CA2392587A1; EP1235895B1; WO2001042415A1; DE60038458D1; ATE390474T1; AR033505A1; ES2304360T3; DE60038458T2; HUP0203811A3; HUP0203811A2; EP1235895A1

Description

Use of Polymeric Material in the Treatment of Hard Surfaces

Introduction :

The present invention relates to the use of polymeric material in the treatment of hard surfaces to deal with scale forming calcium salts. Scale is an important soil in bathrooms and kitchens and one which is not -easy to remove.

Household water supplies contain varying levels of calcium and magnesium salts. Residual water left after, e.g. bathing, showering, dishwashing, rinsing, etc. will eventually evaporate leading to the deposition of calcium salts on surfaces as scale. . The scale deposits formed can become unsightly, hard and . very difficult to remove. This can happen particularly quickly in hard water areas where the level of calcium in - domestic water is high.

Conventional hard surface cleaners may comprise acid or abrasive in order to assist with the removal of scale. .

However, enamel and marble surfaces are susceptible to acid damage and all surfaces may become scratched and : unsightly due to the excessive use of abrasive.

Polymeric materials have been used in the water treatment art to prevent precipitation of scale forming salts from

Co 30 standing water. However, these require a body of water in which the scale forming salts remain suspended. In domestic hard surfaces, droplets of water containing calcium or magnesium salts will eventually evaporate to dryness and the calcium salts will inevitably be deposited.

Attempts have been made in the art to deposit polymeric - material onto hard surfaces to allow subsequently deposited soil such as grease to be easily removed.

It has not however been generally believed in the art that it is possible to provide a release polymer for limescale.

The present inventors have realised that, whereas it may not be possible to prevent deposition of calcium salts, it will be possible to control the mechanism of calcium salt deposition and thereby affect the strength of bond between - calcium salts and the hard surface.

Scale can deposit onto household surfaces in two main ways: (a) crystallisation in the bulk solution; here, scale can form by homogeneous nucleation or by heterogeneous nucleation onto e.g. dust particles which can act as seeds for nucleation. Bulk heterogeneous nucleation i . and homogeneous nucleation require high supersaturation of scale forming salts and can be rapid. Scales formed under these conditions are likely to be amorphous and adhere only weakly to the substrate. Scales which nucleate via bulk heterogeneous nucleation on dust particles can form at lower supersaturations and tend to form more slowly; they are therefore likely to be more crystalline but will still adhere only weakly to the household surface. (b) crystallisation at the hard surface; here, crystals can form by heterogeneous nucleation in which the household surface acts as the site for nucleation.

In this case, scale is formed at low supersaturation; the process is comparatively slow and results in crystalline deposits which are compact and intimately bound to the surface. :

The present inventors have realised that a polymeric material can be deposited onto a hard surface to inhibit heterogeneous nucleation at that surface. The majority of the nucleation will then occur in the bulk solution leading to the deposition of scale forming salts that are easy to remove. The polymer also reduces further aggregation and toughening of new scale on already excisting scale deposits.

Furthermore it has been found that such polymers provide an anticorrosion benefit when applied to metal surfaces.

Preventing scale from forming or adhering to household surfaces will retain the smoothness of the surface and prevent it from dulling. This is particularly important for surfaces which are likely to come in extensive contact with water such as can be found in bathrooms, toilets, kitchens and the like. Such surfaces are often made of metal, vitreous materials or hard plastics.

Summary of the invention

The present invention accordingly provides the use of a polymeric material to reduce heterogeneous nucleation of calcium and magnesium salts at hard surfaces comprising depositing the polymeric material onto the hard surface.

The invention also provides a process for cleaning metal, vitreous and hard plastic surfaces comprising applying to the surface a cleaning composition comprising a detergent surfactant and a polymeric material able to reduce heterogeneous nucleation of calcium and magnesium salts.

Detailed description of the invention

Polymeric Material

Many types of polymeric material are suitable for use in the present invention. It is simply required that the polymer is one which, when deposited onto a hard surface at a suitable level, will reduce heterogeneous nucleation of scale forming salts at that surface. Preferably, polymeric material achieves a reduction in the nucleation rate (number of nuclei per unit area per unit time) of scale forming salts at the surface. The following test has been derived to determine whether a polymeric material achieves a reduction in nucleation density (number of nuclei per unit area), which can easily be converted into a nucleation rate if the duration of the experiment is also recorded.

The test comprises applying a solution of polymer of known concentration to a first area sample of a hard surface, providing a second area sample of the hard surface having no polymer thereon and flowing a supersaturated solution of 5 a scale forming salt over each area sample of the hard surface for a known period of time and comparing the number of nuclei formed per unit area per unit time for the area sample treated with the polymeric material with the number of scale nuclei formed per unit area per unit time for the untreated area sample to obtain an estimate-of the reduction of the rate of heterogeneous nucleation at the hard surface. -

Brief Description of Drawings

The test for reduction of nucleation density at a hard surface will be described with reference to the accompanying drawings, in which:

Figure 1 is a schematic view of apparatus used in the test.

Figure 2 is a cross-sectional drawing of a mixing device for use in the apparatus of Figure 1.

Figure 3 is a section along line III-III of Figure 2.

Figure 4 shows the motion of fluid on a surface being tested.

Figure 5 is a picture of a surface which has been tested, the right half having been treated with the polymer.

c

Detailed Description of Drawings

The apparatus- for use in the test for determining whether a polymeric material is suitable for reducing nucleation density at a surface is shown in Figure 1. The apparatus 1 ) comprises means for delivering two solutions which, when mixed, will produce a supersaturated solution of scale forming salt. The apparatus for delivering the two solutions comprises a pair of syringes 2 and 3. The syringes 2 and 3 contain solutions A and B respectively.

In order to ensure that the flow rates of the solutions A and B are the same, a common driving mechanism 4 for both syringes is provided. The mechanism 4 is configured to deliver a constant flow of solutions A and B. The mechanism 4 may comprise a dual drive syringe-type pump which can be obtained from CP Instruments, Model 200. A mixing cell 5, which will be described further below is provided to mix the solutions A and B. The mixed solutions

A and B are then directed onto a surface to be tested at 6 in a manner which will be described further below. Spent solution is discharged at 7.

All tubing used in the apparatus comprises PTFE tubing for example OD 3.2 mm, ID 1.5 mm obtainable from Omnifit (Trade

Mark). The apparatus is jacketed in nitrogen to ensure that carbon dioxide is not reabsorbed.

Figures 2 and 3 show the mixing cell 5 in more detail.

Figure 2 is a schematic cross-section, at a larger scale to

Figure 1, of the mixing cell 5S. The mixing cell 5 comprises a block of PTFE which has a hollow spherical space 7 formed in its interior. The spherical space 7 is of volume 1 mm’. Projecting through the block and into the space 7 are two capillary tubes, 8 and 9 along which solutions A and B are delivered respectively. The 5S capillary tubes 8 and 9 terminate in nozzles close to the centre of the hollow space 7. The solutions A and B are directed towards one another and mixed in the centre of the hollow space 7. As the block is formed of PTFE, even . though a supersaturated solution is formed in the space 7, substantially no adhesion or precipitation of crystalline material onto the surface of the space 7 occurs. The resulting mixed solution leaves the hollow space 7 through a duct 10, whence it is delivered to the experimental surface to be tested at 6. The capillaries 8 and 9 have end openings of 100 micrometres diameter.

Figure 4 shows the apparatus 6 in which the mixture of solutions is directed onto a surface to be tested. The surface 11 to be tested is mounted beneath a nozzle 12,

A 20 through which the mixed solution from the mixing cell 5 is delivered to the surface 11. The resulting flow pattern is a wall-jet flow pattern, which is well understood by the person skilled in the art. The flow is radially outwards from the centre of the surface 11 to be tested, and is uniform.

The nozzle 12 is a 0.8 mm internal diameter PTFE nozzle placed 3 mm above the surface 11. The mixed solution is delivered at a flow rate of 4 cm’/min. The wall jet apparatus 6 is jacketed in nitrogen to prevent CO; absorption.

q

All experiments were carried out in an air-conditioned laboratory. The temperature is measured at the start of each run. Temperatures are typically 23°C.

The apparatus allows continual refreshment of the surface with solution of known composition allowing crystal growth to occur under conditions of constant supersaturation. i | :

Method

The apparatus is used to test a surface by the following method.

A supersaturated solution is created in a manner known to - the person skilled in the art by mixing together two stable, undersaturated solutions. The solutions are de- gassed before use using N; to remove dissolved CO.

Solution is flowed over the surface to be treated for a fixed time. A suitable time is 45 minutes.

As a result of the flow of solution over the surface 1ll to be tested, scale forming salt is deposited onto the surface. At the end of each experiment, any crystals at the air/water interface are suctioned away using a small piece of tubing attached to a water pump. The surface is then removed from the apparatus 6, rinsed briefly with a saturated solution of the scale forming salt, dried with nitrogen and inspected under a microscope.

Characterisation of the degree of crystal growth on a ’ surface to be tested can be achieved using a digitised map of the surface produced by micrographics. This map may then be processed using image analysis software (for example Aequitas, Dynamic Data Links Ltd) which allows automated measurements of crystal size, number and distribution over a choice of area. This allows the nucleation density to be measured. :

The surfaces to be tested can be prepared and treated in any way as long as the surface remains reasonably flat.

Sample surfaces are preferably polished to a finish of 1/20 micrometres using 0.05 gamma alumina obtainable from

Buehler.

In order to study the effect of polymer deposited onto the surface 11 to be tested, half of the surface is masked and half is treated with a solution or dispersion of the polymeric material. A 50 microlitre drop of the polymer solution is placed onto the unmasked half of the sample surface and allowed to wet that part of the surface. The drop is left until dry and washed with 10 sprays of deionised water from a trigger spray gun. Drying time may be from 5 minutes to 20 hours, as appropriate.

Figure 5 shows an example of a map obtainable using the apparatus of the invention, which will be described further below under the section “Examples”.

Preferably, the surface 11 to be tested is in the form of a disc.

Preferably, a set of discs of the same size is used, consisting of a stainless steel disc, a ceramic disc, an enamel coated disc, a glass disc and a perspex disc.

The nucleation density on the untreated half can then be compared to the nucleation density on the treated half.

The experiment may be repeated with different types of calcium salt, for example, calcium carbonate or calcium sulphate or with magnesium salts such as magnesium carbonate or magnesium sulphate. - Polymers which are particularly suitable for use in the preserit invention reduce the nucleation density at the surface by at least 10% on at least one of the test surfaces (glass, steel, ceramic, enamel or perspex) with at least one of the salts (calcium carbonate, calcium sulphate, magnesium sulphate, magnesium carbonate). More preferably the polymer will reduce the nucleation rate by at least 20%, even more preferably by at least 30% and most preferably by at least 50%.

It is further is preferred that the polymer should achieve a reduction in nucleation density of at least 10%, more preferably at least 20% with both calcium carbonate and calcium sulphate, on any one of the surfaces, more preferably on both of steel and glass and most preferably on all of steel, glass, ceramic and enamel.

It has also been found that there is a correlation between the contact angle made by a drop of water on a polymer treated steel surface on the one hand and the ease of cleaning the steel surface from scale deposits (measured as set out below) and reduction in nucleation density on the other hand. Thus it has been found that polymers which cause the contact angle to be < 30° or > 60° cause a significant increase in cleaning score compared with polymers which cause a contact angle within these limits.

Preferred are those polymers which cause the contact angle to be < 20° even more preferred are those which cause it to be > 60° or even = 65°. :

Without being bound by theory it is believed that the contact angle is a manifestation of the surface energy at the interface between water and the polymer-treated surface which in turn determines the degree to which developing scale crystal nuclei are bonded to the surface. It appears this bonding is strongest for surfaces causing the contact angle to be between 30° and 60°

The contact angle made by a drop of water on the treated steel surface can be measured by any of the commonly known methods. For the purposes of this invention the measurements can be made using a travelling microscope with a simple goniometer head, in which the eyepiece is fitted with crosshairs. A 20ul drop of water is pipetted onto the horizontal treated steel surface. The crosshairs in the microscope eyepiece are aligned such that the horizontal mark is aligned with the steel surface (i.e., along the

Claims

1. The use of a polymeric material to reduce heterogeneous nucleation of calcium and magnesium salts at a hard surface comprising depositing the polymeric material onto the hard surface.

2. The use according to claim 1, comprising using a ~ polymeric material which achieves a reduction of nucleation density at the hard surface of at least 10% with at least one salt selected from the group consisting of calcium carbonate, calcium sulphate, magnesium sulphate, magnesium carbonate and mixtures thereof, in the method described herein.

3. The use according to claim 2, wherein a polymeric material is used which achieves a reduction in nucleation density of at least 10%, more preferably at least 20% with both calcium carbonate and calcium sulphate on any surface selected from the group consisting of steel, glass, ceramic and enamel.

4. The use according to any preceding claim, wherein a polymeric material having activity at a solid/liquid interface is used.

5. The use according to claim 4, wherein the polymeric material has cationic groups or groups which become cationic at the pH of use.

6. The use according to any preceding claim, wherein the polymeric material has hydrophobic parts.

7. The use according to any preceding claim, wherein the polymeric material is deposited from a container, aerosol can or spray gun applicator.

8. The use according to any preceding claim, wherein the polymeric material is deposited from a hard surface cleaning composition comprising at least one surfactant and other optional hard surface cleaning components.

9. The use according to any preceding claim, for treating household surfaces selected from the group consisting of kitchen surfaces, bathroom surfaces, floors, baths, toilets, wash hand basins, showers, dishwashers, taps, sinks and work surfaces.

10. The use according to any preceding claim wherein the surface is made from metal, vitreous material or hard plastic. ‘

11. The use according to any preceding claim wherein the polymer is chosen from those which cause the contact angle of a drop of water on a steel surface treated with the polymer to be less than 30° or more than 60°.

12. The use according to any preceding claim wherein the polymer is chosen from: JR30m, JR125, JR400, Jaguar Cl3s, Jaguar C162, Crotein C, Lupasol PS, Lupasol SK, Celquat L200, Merquat 3330, Merquat 295 or mixtures thereof.