AU739760B2 - Dispensing apparatus - Google Patents

Description

-1-

AUSTRALIA

PATENTS ACT 1990 DIVISIONAL APPLICATION NAME OF APPLICANT: BESPAK PLC ADDRESS FOR SERVICE: DAVIES COLLISON CAVE Patent Attorneys 1 Little Collins Street Melbourne, 3000.

INVENTION TITLE: "DISPENSING APPARATUS" The following statement is a full description of this invention, including the best method of performing it known to us: Q:\PER\AXD\220881.NF 30/8/99 "DISPENSING

APPARATUS"

This invention relates to a dispensing apparatus for dispensing pressurised fluid in the form of an aerosol and in particular but not exclusively for dispensing medicine or products in solution or suspension in an alcohol base.

It is known from GB-1201918 for example to provide dispensing apparatus in which pressurised fluid from a pressurised dispensing container is released by a valve in a controlled manner, the valve including elastomeric seals which are annular and which co-operate with a sliding valve stem to open and close fluid ports.

Products to be dispensed are commonly provided in solution or suspension in an alcohol base, this being particularly common in the dispensing of medicinal compounds for inhalation therapy.

Typical apparatus includes a CFC volatile propellant having a liquid phase in which the product together with the alcohol carrier is readily soluble within the container and a typical material for the valve seal is a synthetic rubber such as nitrile o o• rubber.

Recent trends in the production of aerosol dispensers have moved away from CFC propellants because of their environmental hazards and HFC propellants are now being introduced. A problem with such propellants is that alcohol is less soluble in the liquid phase of such propellants and tends to separate within the container thereby exposing the valve seals to a much greater concentration of alcohol than was formerly the case. Seal materials such as nitrile rubber allow alcohol vapour to escape by permeation over extended storage periods so that the P:\OPER\AXD\2208581.DIV 30/8/99 -2remaining quantity of alcohol is significantly depleted.

Advantageously, the present invention provides dispensing apparatus which will allow the use of HFC propellants with alcohol based products without the above disadvantage.

According to the present invention there is provided a dispensing apparatus for dispensing pressurised fluid comprising a valve body defining a chamber, a valve member extending movably through the chamber and through at least one annular seal disposed between the valve member and the body to regulate the discharge of fluid, characterised in that the or at least one of the seals is formed from a material comprising a terpolymer of ethylene, propylene and a diene, and the seal material comprises a mineral filler comprising 10 magnesium silicate and/or kaolin.

It has been found that the extent to which alcohol evaporates from such apparatus "using such seal materials is significantly decreased so that typically a required shelf life of three years can be readily achieved.

Preferably the material comprises a peroxide curing agent.

A peroxide curing agent such as dicumyl peroxide is preferable to other curing agents such as sulphur since its use minimises the formation of extractives 2mercaptobenzothiazole, N-nitrosamines, mercaptobenzothiazole disulphide) resulting from contact between the material and alcohol in use.

Mineral fillers are preferable to carbon black in 3 order to minimise the formation of polynuclear aromatic hydrocarbon compounds.

Advantageously the mineral filler is selected from the group comprising magnesium silicate, aluminium silicate, silica titanium oxide, zinc oxide, calcium carbonate, magnesium carbonate, magnesium aluminium silicate, aluminium hydroxide, talc, kaolin and clay. Preferably the filler is magnesium silicate or kaolin.

Preferably the apparatus comprises a pressurised dispensing container operatively connected to the valve body and containing the fluid to be dispensed and a hydrofluorocarbon propellant comprising propellant type 134a or 227.

15 (The designation of propellant types referred to in the present application is as specified in British Standard BS4580:1970 "Specification for number designations of organic refrigerants". Accordingly, propellant 134a is: 20 1,1,1, 2 -Tetrafluoroethane

CH

2

F-CF

3 and propellant 227 is: 1,1,1,2,3,3,3 Heptafluoropropane

CF

3

-CHF-CF).

Typically the fluid to be dispensed comprises a liquid or particulate product as a solution or suspension in a carrier liquid comprising an alcohol such as ethanol.

A preferred embodiment of the present invention will now be described by way of example.

In a pressurised dispensing container of the type disclosed in GB-1201918, a valve body is provided with two annular valve seals through which a valve member is axially slidable, the seals being disposed at inlet and outlet apertures of a valve chamber so that the valve functions as a metering valve.

Q:AOPER\VUd2208581mm.do-27/08iOI -4- Satisfactory results have been obtained using the seals according to the invention where the fluid to be dispensed comprises up to 50% by weight of ethanol and the propellant is of type 134a.

It has been found that seals formed from a terpolymer of ethylene, propylene and a diene (EPDM) show substantially improved leakage characteristics using magnesium silicate or kaolin as a filler. This is illustrated with reference to Figure 1 and 2 which are graphs showing weight loss of test devices under two different temperature testing regimes at 30'C and 40'C respectively.

In each case, the columns show weight loss from a dispensing device of the type described above in which the containers were filled with propellant 134A ethanol and an active compound. The first column in each case shows the weight loss using a current EPDM material sold under the commercial name RB701C and which contains Ultrasil filler. The remaining columns show weight loss of corresponding devices using magnesium silicate or kaolin as fillers. The respective fillers are indicated on the columns *999 ofthe graphs.

In each case, the left hand axis shows annualised weight loss calculated from tests with groups of ten dispensing devices as time interval of 3 to 6 months after manufacturing and under different temperature regimes as indicated in the headings to the graphs.

o o 9These tests show that using magnesium silicate or kaolin as a filler leads to a reduced weight loss under the test regimes thus indicating lower leakage from the devices.

"Similar results are obtained at ambient temperatures.

Throughout this specification and the claims which follow, unless the context >0 requires otherwise, the word "comprise", and variations such as "comprises" and o "comprising", will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers or steps.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge in Australia.

Claims (6)

1. Dispensing apparatus for dispensing pressurised fluid comprising a valve body defining a chamber, a valve member extending movably through the chamber and through at least one annular seal disposed between the valve member and the body to regulate the discharge of fluid, characterised in that the or at least one of the seals is formed from a material comprising a terpolymer of ethylene, propylene and a diene, and the seal material comprises a mineral filler comprising magnesium silicate and/or kaolin.

2. Dispensing apparatus as claimed in claim 1, wherein the mineral filler further comprises silica.

3. Dispensing apparatus as claimed in claim 2, wherein the mineral filler comprises magnesium silicate, kaolin and silica.

4. Dispensing apparatus as claimed in any preceding claim comprising a pressurised dispensing container operatively connected to the valve body and containing the fluid to be dispensed and a hydrofluorocarbon propellant comprising propellant type 15 134a or 227.

5. Dispensing apparatus as claimed in claim 4, wherein the fluid to be dispensed comprises a liquid or particulate product as a solution or suspension in a carrier liquid comprising alcohol.

6. Dispensing apparatus as claimed in claim 5, wherein the alcohol comprises ethanol. DATED this 2 7 h Day of AUGUST, 2001 BESPAK pci by DAVIES COLLISON CAVE Patent Attorneys for the Applicant