WO1997019157A1

WO1997019157A1 - Cleaning formulation, additive for a cleaning formulation and process for cleaning bottles using such

Info

Publication number: WO1997019157A1
Application number: PCT/EP1996/004992
Authority: WO
Inventors: Michael Thomas Offiler; Willem P. Verbiest
Original assignee: Unilever N.V.; Unilever Plc
Priority date: 1995-11-17
Filing date: 1996-11-13
Publication date: 1997-05-29
Also published as: EP1021507B1; AU7624596A; CA2236209A1; EP1021507A1; CA2236209C; JP2000501129A; JP4361605B2; TR199800875T2; DE69630407T2; DE69630407D1; ZA969615B; AU716488B2; ES2208765T3; BR9611595A

Abstract

The present invention concerns an additive for a cleaning formulation, a cleaning formulation comprising this additive, and a process for cleaning bottles, in particular returnable PET bottles, using such, wherein the additive for the bottle washing formulation, for PET bottles, comprises: a polyacrylate; a polyhydroxy carboxylic acid of the general formula HOCH2- (CHOH)n-CO2H, wherein n = 2-8, and/or soluble salts thereof; and/or a wetting agent of the general formula R1 - (OC2H4)n - (OC3H8)m - OR2.

Description

CLEANING FORMULATION, ADDITIVE FOR A CLEANING FORMULATION AND PROCESS FOR CLEANING BOTTLES USING SUCH

The present invention concerns an additive for a cleaning formulation, a cleaning formulation comprising this additive, and a process for cleaning bottles, in particular returnable PET bottles, using such. Large quantities of beverages including carbona¬ ted soft drinks such as Cola's are sold in returnable bottles made of either glass or plastic, particularly PET (PolyEthylene Tetraphthalate) . These bottles must be tho¬ roughly cleaned and disinfected before being refilled to ensure product quality is not adversely affected.

One of the main problems with beverage bottles after they have been emptied is that moulds can grow in residual product and produce characteristic mould pads. These are difficult to remove by the main component used in bottle washing detergents (caustic soda) unless additional components, namely chelating agents are also present. The preferred chelating agent from the point of view of mould pad removal is EDTA. However, there is considerable pressu¬ re from environmental groups and some governments to reduce or preferably eliminate the use of EDTA. An additional drawback of EDTA is that it makes bottle washing solutions more prone to foam. This can adversely affect the perfor¬ mance of the cleaning process unless an antifoam is added. Not only is such an addition costly, it increases the pollution capability of the detergent solution and where plastic bottles are concerned, it can increase chemical damage of the bottles due to stress cracking.

Instead of EDTA, an alternative chelating agent is sodium gluconate. This has the advantages of being readily biodegradable and not increasing the foaming ten¬ dency of cleaning solutions. However, it is a weaker chela- ting agent and does not remove mould pads as effectively as EDTA, especially at relatively low caustic levels as requi¬ red for low chemical damage when washing plastic bottles.

An object of the present invention is to yield an effective detergent additive not having the environmental drawbacks ensuing from the use of EDTA.

According to a first aspect of the invention, there is provided an additive for a bottle washing lOritiuld.- tion according to claim 1. This additive, which is free of EDTA or similar chelating agents, is preferably used with an alkaline washing formulation, most preferably a caustic soda based washing formulation, at a concentration of between 0.25 and 3%, preferably 1-2%, whereby in the case of PET bottles the concentration most preferably does not exceed 1.5% in order to minimize stress cracking. This formulation is effective at achieving detergency, particularly against mould pads.

Sodium gluconate offers the advantages of being commercially available and readily soluble in both alkaline and acidic solutions, thus making the development of con¬ centrated additives possible. Furthermore sodium gluconate will chelate both divalent and trivalent ions. As a result, in addition to facilitating the removal of mould pads, it will remove rust stains from the tops of crown capped bottles and prevent sodium aluminate precipitates forming when washing bottles which carry aluminium foil labels. Another consequence of its trivalent ion chelation capabi¬ lity is that clays extracted from old labels in the wash bath will be dispersed and not precipitate on the bottles being washed.

A wetting agent is an agent for reducing surface tension in order to increase the intimacy between the cleaning formulation and the soil. According to the present invention the wetting agent has the following general formula: R, - ( OC₂H₄ ) _n - ( OC₃H₈ ) _m - 0R₂ ,

wherein R, = alkyl chain of length between C₈ and C₂₀ (preferably C_]0 to C₁₅)

R₂ = H, alkyl (C, to C₅) or benzyl n = 1-20 (preferably 2 to 10) m = 0 - 15 (preferably below 5 for biogradability)

and is preferably present as a component of a non-ionic blend, which is a blend further comprising an antifoaming agent and a rinsing agent, in order to optimize cleaning. A preferred wetting agent is Plurafac LF 131.

Polyacrylates offer the advantages of being substantially inert, whereby environmental problems associ¬ ated herewith are limited, being easily precipitated out of waste water, for example, with sewage. Due to their ready solubility they can be used at very concentrated levels, thereby increasing the effectiveness of the detergent additive.

Further preferred features of the additive accor¬ ding to the present invention are found in the accompanying claims .

The additive according to the present invention was primarily developed for use in cleaning formulations in soft water areas. When desired for use in hard water areas, a scale forming preventing agent, a phosphonate such as Dequest 2000™ or Bayhibit AM™, is preferably added.

The additive can be formulated to be alkaline, acidic or ph-neutral, in the latter case preferably inclu¬ ding a preservative, for example formaldehyde, to prevent micro-organisms feeding off the additive and causing this to deteriorate.

According to a second aspect of the present invention there is provided a bottle washing formulation comprising the above mentioned additive. According to a third aspect of the present inven¬ tion there is provided a process for cleaning bottles, in particular returnable PET beverage bottles.

This cleaning process is preferably carried out below a maximum temperature of 60°C, above which thermal damage to PET bottles is possible, and between 50°C and 80°C for glass bottles.

The invention will now be described by way of the following examples. A number of new PET bottles were soiled with tomato juice which had been inoculated with the mould Aspergillus niger. The soil was allowed to remain in the bottles for 6 weeks after which the moulds had grown into visible colonies which were strongly attached to the PET surface. Cleaning tests were carried out in laboratory scale bottle washer at 60°C which is the maximum safe temperature for washing PET bottles. The detergent soluti¬ ons were sprayed as a pencil jet onto the inside base of an upturned bottle at a flow rate of 4 1/min. The time for all visible soil to be removed was noted. For each detergent, 3 bottles were cleaned. The table below gives the total time for the 3 bottles to be cleaned.

Three reference solutions are included: a) 1% caustic soda b) 1% caustic soda plus 0.5% base adjunct (20% sodium gluconate + 1.2% nonionic blend) c) 1% caustic soda plus 0.3% SU 860, wherein SU 860 is a commercially produced adjunct based on EDTA (between 30% and 35% as EDTA Na₄) , and additionally compri- sing sodium gluconate (<10%) and nonionic wetting and antifoaming agents (<3%) .

The remaining test solutions consisted of soluti¬ on b) plus 500 mg/1 of the test additive. TABLE

No. Test Solution Total cleaning time for 3 bottles (min) 1 a) 1% caustic soda >22

2 b) 1% caustic soda

+ 0.5% base adjunct 14

3 c) 1% caustic soda + 0.3% SU 360 IC

4 b) + Sokalan PA 50 (Polyacrylate, M.W. 30,000 ex BASF) 12

5 b) + Sokalan PA 25 PN (Polyacrylate,

M.W. 4000 ex BASF) 11

6 b) + Versicol E7 (Polyacrylate,

M.W. 26,000 ex Allied Colloids) 9 7 b) + Norasol LMW 45 (Polyacrylate,

M.W. 4500 ex Norso-Haars) 9

8 b) + extra nonionic (180 mg/1) 8

The tests were carried out at caustic soda levels of less than 1.5%, which is the limit for safe washing of

PET bottles. Stress cracking tests showed that the effect of the product on stressed PET was less than that of the currently recommended EDTA based product.

On the basis of the above results, a formulation 9 was developed which consisted of :

Material %

Sodium gluconate 20.0 Norasol LMW 45 11.0

Sodium Cumene Sulphonate (40%) 15.0

Nonionic blend 4.8

Sodium hydroxide (50%) 2.0

water to 100.0 Cleaning tests showed that 1% caustic soda + 0.2% formulation 9 cleaned 3 bottles which had been aged for 12 weeks in an aggregate time of 10 minutes while 1% caustic soda + 0.3% SU 860 required 12 minutes and 1% caustic soda + 0.3% of a known gluconate based adjunct (Stabilon Flϋssig ex Henkel) required 16 minutes.

Although formulation 9 was developed for cleaning

PET bottles, it would be equally suitable for cleaning glass bottles. In this case, it would not be subject to the temperature and caustic level limitations imposed on PET bottle washing.

Claims

1. Additive for a bottle washing formulation, for PET bottles, comprising:

- a polyacrylate,

- a polyhydroxy carboxylic acid of the general formula c ιjrsr<τj I

-< π«ι „v,ι ~ „ -, -! ,_ thereof,

- and/or a wetting agent of the general formula

R, - (0C₂H₄)_o - (OC₃H₈)_m - 0R₂.

0 2. Additive according to claim 1, wherein the polyhydroxy carboxylic acid is gluconic acid.

3. Additive according to claim 1 or 2, wherein the soluble salt of the polyhydroxy carboxylic acid is sodium glucona- te.

4. Additive according to claim 3, wherein sodium gluconate is present within a range of 0.1-40% of the formulation.

5. Additive according to one of the previous claims, whe¬ rein, in the wetting agent of general formula:

R, - (OC₂H₄)_n - (OC₃H₈)_m - 0R₂,

R, = an alkyl chain of length between C₈ and C₂₀, R₂ = H, alkyl (C, to C₅) or benzyl, n = 1-20, and m = 0 - 15.

6. Additive according to claim 5, wherein: R, is C₁₀ to C,j , n = 2-10, and m = 0 - 5

7. Additive according to one of the pevious claims, whe¬ rein the wetting agent is Plurafac LF 131.

8. Additive according to one of the previous claims, whe¬ rein the wetting agent is present in a non-ionic blend.

9. Additive according to one of the previous claims, whe- rein the polyacrylate has a molecular weight of between roughly 3500 to 30000.

10. Additive according to claim 3, wherein the polyacryla¬ te is present in a range of between 0.1 to 20% of the formulation.

11. Additive according to claim 10, wherein the polya¬ crylate belongs to the group consisting of, Sokalan PA 25 PN, Versicol E7, and Norasol LMW 45.

12. Additive according to one of the previous claims for an alkaline washing formulation.

13. Alkaline bottle washing formulation comprising an additive according to any of the claims 1-12.

14. Formulation according to claim 13, wherein the alkali is caustic soda.

15. Formulation according to claim 14, wherein caustic soda is present in a range of between 0.25 and 3%.

16. Formulation according to one of the claims 13-15 fur¬ ther comprising a non-ionic blend.

17. Formulation according to one of the claims 13-16, further comprising a solubilizing agent for solubilizing the non-ionic blend.

18. Formulation according to claim 17, wherein the solubi¬ lizing agent is sodium cumene sulphonate.

19. Process for washing bottles, comprising the step of exposing bottles to a cleaning formulation according to one of the claims 13-18 at a temperature of 60°C or below for PET bottles and between 50°C and 80°C for glass bottles.