GB2270698A

GB2270698A - Water-based compressed gas aerosol

Info

Publication number: GB2270698A
Application number: GB9302538A
Authority: GB
Inventors: Maxwell John Reynolds
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-09-07
Filing date: 1993-02-09
Publication date: 1994-03-23
Also published as: AU632263B2; AU2619992A; CN1084203A; GB9302538D0

Abstract

An aerosol product which comprises:- an aerosol can including a valve and a dispensing mechanism including a dip tube as desired; a solution or suspension of an active ingredient in a predominantly water based solvent in said can; and an inert gas as propellant at a pressure of at least 620 kPa at 20 DEG C. The inert gas may be selected from nitrogen, nitrous oxide or carbon dioxide.

Description

WATER-BASED COMPRESSED GAS AEROSOL This invention relates to water based compressed gas aerosol products and to methods and apparatus for the manufacture thereof and particularly but not exclusively to such aerosol products where a fine product spray is required.

For many years there has been an as yet unfulfilled need for aerosol products which use neither organic solvents or propellants which are non toxic to humans and which do not damage the environment. Despite suggestions that water-based aerosol products propelled by compressed inert gases are the ideal products, no such products with acceptable dispensing characteristics, product stability, shelf life, fineness of spray, etc., have been produced to date and no method and apparatus for making such products devised.

US Patent No. 3854636 (Conway), for example, discloses that when using nitrogen, nitrous oxide or carbon dioxide as propellant the pressure decreases noticeably as the product is dispensed even if a "high" (undefined) pressure is initially utilised to ensure all product is expelled from the aerosol can but that such high pressures it is necessary to have a low delivery rate to avoid undesirable radical changes in spray characteristics as the contents of the aerosol are dispensed. Conway proposes to overcome the problems identified by providing at least one additional restricted orifice in the design of the valve body of his aerosol can.

In "Principles of Aerosol Technology", Paul A. Sanders, 1990, Van Nostrand Reinhold Company pp 28-33, 60-62, 88-90 & 161-163: "The Science and Technology of Aerosol Packaging", John S. Sciarra and Leonard Stoller, 1974, John Wiley & Sons, pp 136-141, and "Kirk Othmer Encyclopedia of Chemical Technology", Vol. 1, pp 670-685; all relate how, in the 1950's and 1960's, the possible use of nitrogen as a compressed gas propellant for aerosol cans was greeted with considerable enthusiasm as nitrogen was cheap, low in toxicity, inert and stable. However the use of nitrogen was substantially rejected as it is almost completely insoluble in the liquid phase of aerosols.This insolubility results in a greater volume of an aerosol can being required for the propellant than for a liquified (e.g. hydrocarbon, halocarbon or halo-hydrocarbon) gas propellant and in cases of accidental discharge on inversion of the can, compressed gas only may be expelled to the extent that insufficient gas remains to expel all of the product. The use of compressed gases was substantially abandoned for all uses but those which do not require a fine spray.

Other problems associated with the manufacture of general aerosol products and in particular water based aerosol products are the difficulties in the exclusion of air or oxygen and microbes or bacteria which may cause degradation of active, olfactory or other components in the liquid phase resulting in an unacceptably short shelf-life for the aerosol product.Despite the more recent and urgent need to drastically reduce global emissions of greenhouse gases and ozone-damaging gases, such as or including hydrocarbon, halocarbon or halo-hydrocarbon gases there is still no acceptable water based compressed gas aerosol product known or available which can be used for a wide variety of applications from insecticidal aerosols which desirably project the product spray a long distance, to perfumed air fresheners or perfumes where a fine spray is desirable without necessarily requiring such a great projection distance.

It is an object of the present invention therefore to provide a compressed gas water- based aerosol product which can be used for a wide variety of applications and to provide a method and apparatus for the manufacture of such products.

The present invention in one form provides a compressed gas water-based aerosol product which comprises : an aerosol can including a valve and a dispensing mechanism including a dip tube as desired; a solution or suspension of an active ingredient in a predominantly water based solvent in said can; and an inert gas as propellant at a pressure of at least 620 kPag at 20"C.

The present invention in one form also provides a method of manufacturing a water- based aerosol product which comprises: preparing a solution or suspension of an active ingredient in a predominantly water-based solvent; introducing a desired amount of the solution or suspension into an aerosol can; fitting a valve and dispenser to the can; and pressurizing the can to a pressure of at least 620 kPag at 200C with an inert gas sufficient to expel all of the solution or suspension from the aerosol can.

Preferably the water is saturated with the inert gas which is selected from nitrogen, nitraus oxide or carbon dioxide, most preferably nitrogen. Preferably the water is treated to remove oxygen dissolved therein by sparging with the inert gas. Preferably the water-based solution or suspension is filtered to remove impurities and prepared and filled under asceptic conditions.

Preferably the inert gas is added under asceptic conditions.

Preferably the solution or suspension in addition to the active ingredient also includes antioxidants such as ascorbic acid and co-solvents or preservatives or antibacterial alcohols such as ethanol. Preferably the can is a low pressure seamed tin plate can. Preferably the can is a nominal 670 ml can. Preferably the volume of water based active ingredient solution or suspension is about 300 ml and the pressure of inert gas used to pressurize the can is greater than 690 kPag and preferably from 840 to 1000 kPag at 200C.Other nominal can sizes/active ingredient solution or suspension volumes are:- 550 ml/245 ml and 1,400 ml/625 ml (approx.) The present invention also provides in one preferred form apparatus for the manufacture of predominantly water-based aerosol products which comprises: means for forming a solution or suspension of an active ingredient in a water based solvent; means for dispensing measured quantities of said solution or suspension into an aerosol can; means for installing a valve and dispensing means in said can; and means to introduce an inert gas into said can via said valve and dispensing means to a pressure of at least 620 kPag at 20"C.

Preferably the can is a 670 ml nominal volume can. Preferably the dispensing means is set to deliver 300 ml of the solution or suspension to the can. Preferably the pressure is at least 690 kPag and most preferably from 840 to 1000 kPag at 20"C. Preferably the apparatus also includes means for installing a dispensing head and overcap. Preferably the dispensing nozzle or orifice of the dispensing head is 0.3 to 0.5 mm diameter.

Preferred forms of the invention will now be described.

In one preferred method, according to the invention, water is filtered through a series of filters including a carbon or charcoal filter to remove impurities and finally through a sterilized 0.2so filter into a sterilized stainless steel container.

The sterilized water is cooled to 0-5"C and deoxygenated by passing similarly 0.2 > filtered and sterilized carbon dioxide or nitrogen gas through the water until dissolved oxygen level is removed. The container is then pressurized under carbon dioxide or nitrogen to about 100 kPag. The active ingredient, together with any other desirable ingredients, are then sparged into the container using a DEPC doser (bomb bulk system) and mixed to form an aqueous solution or suspension of the active and other ingredients. The solution or suspension is then transferred under pressure to the filling head of an aerosol filling line. 300 ml of solution or suspension is then introduced into a low pressure tin plate seamed can of 670 ml nominal total volume and the valve and actuator are then fitted and crimped on to the can. The can then passes to a gassing station where nitrogen is introduced to a pressure of 840 kPag &commat; 20"C. The dispensing nozzle and any covering cap is then fitted. This provides the equivalent of approximately 3.4 1 of N2 gas at 200C and atmospheric pressure to dispense the 300 ml water based solution or suspension of active ingredients.

For an intermediate pressure one piece monobloc aluminium can the pressure of nitrogen introduced is increased to 950 kPag at 200C.

A preferred formulation for a water based insecticide aerosol is as follows: Active ingredient Pyrethrum extract 1.3 gm (20% approx pyrethroids) Piperonyl butoxide 6.0 gm Odour Peppermint oil 10.0 ml (Co-solvent/antibacterial) Ethanol 50.0 ml Antioxidant Ascorbic acid 0.1 gm Solvent Water to 1000.0 ml Other formulations may be similarly prepared for other aerosol products such as cooking sprays, disinfectants, dusting aids, fabric protectants, adhesives and sealants, detergents, starches, lubricants and personal fragrance or deodorant products.

The requirements in relation to deoxygenation of the water or absolute sterility tf the water and subsequent filling procedures will depnd on whether the active or other ingredients are subject to degradation by oxidation or bactericidal attack in the product during storage.

The Standards Association of Australia Australian Standard AS 2278-1986 for Metal Aerosol containers are required to conform to the following minimum distortion pressure standares.

1. Low pressure containers (seamed tin plate containers) must withstand a pressure of 970 kPa at 550C.

2. Intermediate pressure containers (monobloc aluminium containers) must withstand a pressure of 1100 kPa at 550C.

3. High pressure containers must withstand a pressure of 1265 kPa at 550C for containers of internal diameter less than or equal to 75 mm and nominal (brimful) capacity of less than or equal to 820 ml.

The above preferred method is based on aerosol cans complying with the minimum Australian Standards for low and intermediate pressure cans. It will be appreciated that with cans which exceed the minimum standards as to minimum distortion pressure then the pressure of nitrogen can be accordingly increased. For example if a low pressure can can withstand 1150 kPa without distortion, the nitrogen pressure can be increased to 1000 kPa at 200C which is a far greater pressure than suggested by the prior art.

The above filling pressures are based on the following pressure/temperature table for compressed gases including nitrogen.

1 0 500 960 20 521 1000 30 542 1040 40 564 1080 50 585 1120 55 596 1140 It will be readily apparent that the method and apparatus of the invention may be used to provide a wide range of water based compressed gas aerosol products by preparation of an appropriate water based solvent for a particular active ingredient desired.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A compressed gas water-based aerosol product which comprises:an aerosol can including a valve and a dispensing mechanism including a dip tube as desired; a solution or suspension of an active ingredient or ingredients in a predominantly water-based solvent in said can; and an inert gas as propellant at a pressure of at least 620 kPag at 20 (degree) C.

2. A product as claimed in claim 1, in which the water-based solvent is saturated with the inert gas which is selected from nitrogen, nitrous oxide or carbon dioxide, most preferably nitrogen.

3. A product as claimed in claim 1, or 2 in which the water-based solvent is treated to remove oxygen dissolved therein by sparging with the inert gas.

4. A product as claimed in claim 1, 2, or 3 in which the solution or suspension is filtered to remove impurities and prepared and filled under asceptic conditions.

5. A product as claimed in any one of claims 1 to 4 in which the inert gas is added under asceptic conditions.

6. A product as claimed in any one of claims 1 to 5 in which the solution or suspension, in addition to the active ingredient or ingredients, also includes antioxidants such as ascorbic acid and co-solvents or preservatives or antibacterial alcohols such as ethanol.

7. A product as claimed in claim 1 in which the can is a low pressure seamed tin plate can preferably a nominal 550/670/1,400 ml volume can.

8. A product as claimed in claim 7 in which the volume of water-based active ingredient solution or suspension is respectively about 245/300/245 ml.

9. A product as claimed in any one of claims 1 to 8 in which the pressure of inert gas used to pressurize the can is greater than 690 kPag.

10. A product as claimed in claim 9 in which the pressure of the inert gas is from 840 to 1000 kPag at 200C.

11. A method of manufacturing a water-based aerosol product which comprises: preparing a solution or suspension of an active ingredient or ingredients in a predominantly water-based solvent; introducing a desired amount of the solution or suspension into an aerosol can; fitting a valve and dispenser to the can; and pressurizing the can to a pressure of at least 620 kPag at 200C with an inert gas.

12. A method as claimed in claim 11, in which the water-based solvent is saturated with the inert gas which is selected from nitrogen, nitrous oxide or carbon dioxide, most preferably nitrogen.

13. A method as claimed in claim 11 or 12, in which the water-based solvent is treated to remove oxygen dissolved therein by sparging with the inert gas.

14. A method as claimed in claim 11, 12, or 13, in which the solution or suspension is filtered to remove impurities and prepared and filled under asceptic conditions.

15. A method as claimed in any one of claims 11 to 14, in which the inert gas is added under asceptic conditions.

16. A method as claimed in any one of claims 11 to 15 which the solution or suspension in addition to-the active ingredient also includes anti-oxidants such as ascorbic acid and co-solvents or preservatives or antibacterial alcohols such as ethanol.

17. A method as claimed in claim 11 in which the can is a low pressure seamed tin plate can preferably a nominal 550/670/1,400 ml volume can.

18. A method as claimed in claim 17 in which the volume of water-based active ingredient solution or suspension is respectively about 245/300/625 ml.

19. A method as claimed in any one of claims 11 to 18 in which the pressure of inert gas used to pressurize the can is greater than 690 kPag.

20. A method as claimed in claim 19 in which the pressure of the inert gas is from 840 to 1000 kPag at 20"C.

21. Apparatus for the manufacture of predominantly water-based aerosol products which comprises: means for forming a solution or suspension of an active ingredient in a water-based solvent; means for dispensing measured quantities of said solution or suspension into an aerosol can; means for installing a valve and dispensing means in said can; and means to introduce an inert gas into said can via said valve and dispensing means to a pressure of at least 620 kPag at 20"C.

22. Apparatus as claimed in claim 21, which includes means to saturate the water-based solvent with the inert gas which is selected from nitrogen, nitrous oxide or carbon dioxide, most preferably nitrogen.

23. Apparatus as claimed in claim 21 or 22 ,which includes sparging means to treat the water-based solvent to remove oxygen dissolved therein by sparging with the inert gas.

24. Apparatus as claimed in claim 21, 22, or 23 which includes means to filter the solution or suspension to remove impurities and prepared and means to fill the product under asceptic conditions.

25. Apparatus as claimed in any one of claims 21 to 24 including means to introduce the inert gas under asceptic conditions.

26. Apparatus as claimed in any one of claims 21 to 25, in which the solution or suspension in addition to the active ingredient also includes antioxidants such as ascorbic acid and co-solvents or preservatives or antibacterial alcohols such as ethanol.

27. Apparatus as claimed in any one of claims 1 to 8 which inclues means to introduce the inert gas at a pressure of greater than 690 kPag.

28. A product as claimed in claim 9 in which the pressure of the inert gas is from 840 to 1000 kPag at 20"C.