AU632263B2

AU632263B2 -

Info

Publication number: AU632263B2
Application number: AU2619992A
Authority: AU
Priority date: 1992-09-07
Filing date: 1992-10-06
Publication date: 1992-12-17
Anticipated expiration: 1998-10-06
Also published as: AU2619992A; CN1084203A; GB9302538D0; GB2270698A

Description

AMYO/01 2 28/5/19 a guatiofl 3.2(2) 0 e

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION PETTY PATENT no o 0~ o 4 *4 4.04 0* 8 S 0 *4 4o 4 0q*S 4i WATER BASED COMPRESSED GAS AEROSOL 8 044(4, The following statement is a full description of this invention, including the best method of performing it known to me 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 i '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 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 'equire 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 iir.i. ri- ld 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 1 5 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 Isolvent In said can; and an inert gas as propellant at a pressure of at least 620 kPag at 20 0

C.

The present invention in one form also provides a method of manufacturing a Swater based aerosol product which comprises: i 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, nitrous 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 solution or suspension is filtered to remove impurities and prepared and filled under asceptlc conditions. Preferably the Inert gas Is added under asceptic conditions.

I_ 3 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 2000C.

The present invention also provides in one preferred form apparatus for the manufacture of predominantly water-based aerosol products which comprise: 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; 1 5 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 200C.

2 e 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 200C.

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 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 o.2g filter into a sterilized stainless steel container. The sterilized water Is cooled to 0-50C and deoxygenated by passing similarly 0.21g filtered and sterilized carbon dioxide or nitrogen gas through the water until dissolved oxygen level is removed. Tie 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 4 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 200C. The dispensing nozzle and any covering cap is then fitted. This provides the equivalent of approximately 3.4 I of N 2 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: t S1, 10 Active ingredient Pyrethrum extract 1.3 gm approx pyrethroids) SPiperonyl butoxide 6.0 gm SOdour Peppermint oil 10.0 ml i (Co-solvent/antibacteri;al) Ethanol 50.0 ml Antioxidant Ascorbic acid 0.1 gm i Solvent Water to 1000.0 ml i Other formulations may be similarly prepared for other aerosol products such as I 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 of 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 5500.

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.

Temp Pressure (kPag) approx 500 960 521 1000 542 1040 564 1080 585 1120 596 1140 it will be readily apparent that the method and apparatus of the invention may be 1 0 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

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 in a predominantly water based solvent in said can; and an inert gas as propellant at a pressure of at least 620 kPag at 200C.

2. An aerosol product as claimed in Claim 1, in which the can has a nominal volume of 670 ml with about 300 ml of said solution or suspension of active ingredient.

3. An aerosol product as claimed in Claim 1 or 2, in which the inert gas is nitrogen preferably at a pressure of at least 840 kPag at 200C. DATED THIS 29TH DAY OF SEPTEMBER, 1992 MAXWELL JOHN REYNOLDS WATERMARK PATENT TRADEMARK ATTORNEYS THE ATRIUM 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRAUA IAS:JC DOC21 AU000300.WPC _J t i ABSTRACT 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 200C.