GB1591312A - Aerosol package - Google Patents

Abstract

In this pack there are fixed requirements for the cross-section of the outlet opening of the shut-off device, for the ratio of the cross-section of a vapour emergence opening of the shut-off device to that of the immersion tube end piece or to the internal cross-section of the immersion tube, and the sedimentation volume of a spraying agent containing a suspended powder. If these requirements are met there is a reduction in the proportion, arising on spraying the spraying agent, of those constituents which are inhaled by people and deposited in their lungs.

Description

(54) AEROSOL PACKAGE (71) We, UNILEVER LIMITED, a company organised under the laws of Great Britain, of Unilever House, Blackfriars, London, E.C.4., England, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an aerosol package including in combination an aerosol powder spray composition comprising an active ingredient in finely divided form suspended in a liquid phase comprising propellant liquid and a carrier liquid, and a container fitted with a discharge spray valve. When the actuator or button of the valve is operated the composition is discharged in aerosol form through the outlet or terminal orifice, which is usually in the actuator, by the pressure of the propellant vapour within the container. Many marketed antiperspirant aerosol products are of the above type at the present time.

When a composition is discharged as an aerosol from a pressurised pack, some of the aerosol particles may be inhaled by the user or by other persons in the vicinity. The proportion of the product discharged which is capable of reaching and being deposited in the lung is called herein the "respirable fraction" of the product. Industry is concerned that the user should not be exposed unnecessarily to respirable particles. This invention is concerned with the reduction of the respirable fraction of aerosol powder spray products.

The present invention is based upon our finding that improved aerosol packages which give rise to sprays having reduced respirable fractions can be produced by selecting particular combinations of certain parameters or factors of the aerosol package, said parameters or.factors being the pressure within the aerosol container, the area of the terminal or outlet orifice, the ratio of the area of any vapour tap orifice of the valve and either the area of the valve tail piece orifice or the bore of the dip tube of the valve, whichever is the smaller, and the sedimentation volume (as hereinafter defined) of the composition.

Accordingly the present invention provides a package for containing and dispensing a powder including in combination a container having an aerosol spray valve for dispensing liquid in aerosol form and a composition within the container consisting of a powder suspended in a liquid vehicle comprising a mixture of a liquid carrier and a liquefied propellant, the package being such that of the following conditions: (q) the vapour pressure within the container is from 5 to 30 psig at 20"C; (B) the valve has a terminal orifice having an area of at least 3 x 10-4 sq in; (B') the valve has a terminal orifice having an area of at least 4.5 x 10-4 sq in; (C) the ratio of the area of any vapour tap orifice of the valve and either the valve tail piece orifice or the bore of the valve dip tube, whichever is the smaller, is not more than 0.05; and (D) the sedimentation volume of the composition (as herein defined) is at least 40%; there is satisfied the combination of condition A with any one of conditions B', C and D; or the combination of condition A with at least two of conditions B, C and D. Psig stands for pounds per square inch gauge.

The sedimentation volume of the composition is to be understood to mean that volume occupied by the powder after shaking and allowing the composition to stand for 24 hours expressed as a percentage of the total volume of the composition. In practice the sedimentation volume is determined by packaging the composition in a container of transparent material and expressing the sedimental height after 24 hours as a percentage of the total height of the composition.

In one particular embodiment of the invention there is satisfied the combination of conditions A and D with at least one of conditions B and C. In a preferred form of the invention all the conditions A, B, C and D are satisfied.

For a discussion of the construction of aerosol valves reference is made to chapter 6 of "Principles of Aerosol Technology" by Paul A. Sanders (1970).

While the actuator may be a standard actuator or a mechanical breakup actuator, the standard actuator is preferred. The upper limit of the area of the terminal orifice of the valve is not critical but will be limited in practice by the desired spray characteristics of the valve. In the usual case of the terminal orifice being in the actuator, the upper limit of orifice area may also be limited by the finite size of the actuator. Usually the area of the terminal orifice will be in the range from 3 x 10-4 to 12 x 10-4 sq ins, being preferably at least 4.5 x 10-4 sq ins.

With a valve fitted to a standard dip tube (usually of internal diameter 0.150 inches) which fits over the end of the tail piece the area of the tail piece orifice will be smaller than the cross-sectional area of the bore of the dip tube. In the case of a capillary tube (usually of internal diameter of 0.060 inches or less), which is fitted within the tail piece, the ratio in condition C above is determined by the area of the bore of the dip tube or the area of any restricted orifice within the tail piece, whichever is the smaller.

Aluminium chlorhydrate is the most widely used antiperspirant active material at the present time but other antiperspirants can be used in the aerosol package of this invention.

Such other suitable materials are well known and include those referred to in British Patent Specifications Nos. 1,393,860, 1,353,916, 1,343,653, United States Patent Specification Nos. 3,792,068, 3,726,968 and 3,903,258 and Netherlands Patent Application No.

7,601,377.

Although current commercial grades of aluminium chlorhydrate have weight average particles sizes in the range 10 to 25 microns, they will include a fraction having a particle size below 7 microns. We have surprisingly found that the inhalable fraction decreases as the weight percentage of the powder less than 7 microns increases. Antiperspirant materials widely used at the present time comprise particles at least 25% (by number) of which have a size in the range 0 to 6 microns and the present invention is especially applicable to products containing these materials although, of course, it is by no means restricted to the use of such materials.

Although this invention has particular applicability to antiperspirant aerosol powder sprays, the powder may be other than an antiperspirant powder since the nature of the powder is not critical to the invention. A number of powders which can be used in aerosol powder sprays are mentioned in an article by S.C. Elvin entitled "Powder Aerosols" in Aerosol Age, September 1971, page 26.

Furthermore, the powder may be a moisture absorbent organic polymer, especially one having a capacity for absorbing an amount of moisture at least equal to its own weight. Such polymers are described in British Patent Specification No. 1,485,373.

Further examples of powders which may be employed in the package of the invention are those having deodorant properties, for example sodium bicarbonate, sodium carbonate and hexachlorophene.

Mixtures of powders may also be used.

The amount of powder present in the composition may vary over a wide range but will usually be in the range 1 to 25% by weight of the composition. In the case of antiperspirant powders the amount will preferably be from 1% to 10% by weight of the composition, particularly 2% to 7% by weight.

The powder is suspended in a liquid vehicle comprising a mixture of a liquid carrier and a liquefied propellant. Such mixtures are conventional in the art and many materials which may be used have been suggested.

The carrier liquid may for example be a non-volatile non-hygroscopic liquid as suggested in US Patent No. 3,968,203. Especially useful are carrier liquids which have emollient properties and a number of these are referred to in British Patent Specification No.

1,393,860. Especially preferred are fatty acid esters such as isopropyl myristate and those esters referred to in US Patent Specification No. 4,045,548 such as dibutyl phthalate and diisopropyl adipate.

Various other carrier liquids for powder suspension aerosols are suggested in US Patent Specification Nos. 3,974,270, 3,949,066, 3,920,807, 3,833,721 and 3,833,720, and in British Patent Specifications Nos. 1,411,547, 1,369,872, 1,341,748 and 1,300,260. Volatile carrier liquids may also be used such as ethanol as described in South African Patent Specification No. 75/3576, and volatile silicones as described in British Patent Specification No.

1,467,676.

The ratio of total solids in the compositions to the carrier liquid may vary over a wide range, for example from 0.01 to 3 parts of the powder per part by weight of the carrier liquid.

The liquefied propellant can be a hydrocarbon, a halogenated hyrocarbon or a mixture thereof. Examples of materials that are suitable for use as propellants are given in the above-mentioned patents and include trichlorofluoromethane, dichlorodifluoromethane, dichlorotetrafluoroethane, monochlorodifluoromethane, trichlorotrifluoroethane, propane, butane, 1 ,1-difluoroethane, 1 ,1-difluoro-1-chloroethane, dichloromonofluoromethane, methylene chloride, and isobutane, used singly or admixed. Trichlorofluoromethane, dichlorodifluoromethane, dichlorotetrafluoroethane, and isobutane, used singly or admixed, are preferred. The propellant or propellant blend is chosen so as to give a pressure within the aerosol container of from 5 to 30 psig at 200C, preferably 15 to 30 psig.

It is common practice to include in aerosol powder spray compositions a material to assist in the suspending of the powder in the liquid vehicle. The materials prevent compacting of the powder and they may also act as thickening or gelling agents for the liquid vehicle.

Especially preferred are hydrophobic clays and colloidal silicas. Hydrophobic clays are available under the trade mark Bentone, eg Bentone-34 or Bentone-38, and their use as suspending agents as described in a number of patent specifications including US Patent Specification No. 3,773,683. Suitable colloidal silicas include Aerosil 200 and Cab-O-Sil M-5 as well as other grades: the words Aerosil and Cab-O-Sil are trade marks.

A composition with a sedimentation volume of at least 40%, preferably at least 50%, can be obtained by the choice of an appropriate amount of suspending agent and by using high shear mixing conditions for the incorporation of the suspending agent. The amount of the suspending agent may range from 0.1 to 2% by weight of the composition.

Various minor operational ingredients may also be included such as perfumes.

The respirable fraction of the particles produced by an aerosol pack was determined in the following experiments using an Hexhlet elutriator (Brit. J. industr. Med., 1954 11, 284) which separates particles according to their falling velocities in the air. The aerosol is drawn at a controlled horizontal velocity through a parallel plate elutriator; the vertical spacing of the plates is such that particles settling on them during the transit of the aerosol through the elutriator correspond to those which would separate aerodynamically in the upper respiratory tract of man. Thus the particles passing through the elutriator and collected on a filter represent those which would penetrate to the human lungs. The upper aerodynamic size limit for respirable particles collected in the Hexhlet is about 7 microns.

The procedure was as follows. A filter, dried and weighed, was loaded into the Hexhlet sampler and the pressurised pack to be tested was weighed. The vacuum was adjusted so that the gauge on the Hexhlet showed about 300 mm Hg. After thorough shaking, the aerosol was sprayed into a cabinet fitted to the front of the Hexhlet sampler, each spray was of 2 seconds duration, the sprays being repeated with shaking every 20 seconds for a total of 20 sprays. Sampling was continued for 5 minutes after the last spray. The pack was re-weighed to give the weight of product discharged. The filter was removed and heated at 50"C for 24 hours and then re-weighed. In this way the weight of non-volatiles collected was determined and this weight is expressed in milligrams per 100 g of product discharged. This weight is a measure of the respirable non-volatiles in an aerosol cloud and will be referred to hereinafter by the letters NVRF (standing for non-volatile respirable fraction). The use of the Hexhlet in determining respirable fractions is also described in Aerosol Age, Volume 21, No. 11, November 1976, pages 20 to 25.

Experiments will now be described illustrating the effect of the above parameters on the non-volatile respirable fraction of an aerosol spray.

In the experiments described hereinafter a standard package employed contained an aerosol powder spray composition of the following formula, all percentages herein being by weight unless specified otherwise: Aluminium chlorhydrate powder 4.50 (MICRO-DRY) Isopropyl myristate 6.00 Pyrogenic silica (AEROSIL 200) 0.45 Perfume 0.44 Propellant (50:50 mixture of to 100.00 propellants 11 and 12) (Propellant 11 is trichlorofluoromethane) (Propellant 12 is dichlorodifluoromethane) The concentrate, ie the mixture of the aluminium chlorhydrate, isopropyl myristate, pyrogenic silica and perfume, was mixed with part of the propellant and then subjected to high shear in a mixer for 20 minutes. The remainder of the propellant was then added and the resulting composition then filled into an aerosol can.

This composition gave a pressure in the container of 41 psig at 230C. It had a sedimentation volume of 50%. The valve had a vapour tap whose orifice was 0.020 inch in diameter and the diameter of the tail piece orifice was 0.080 inch. The valve was fitted with an actuator having a terminal orifice of diameter 0.020 inch. A standard dip tube of internal diameter 0.15 inch was fitted to the valve.

In the experiments described hereinafter one or more of the above parameters was varied to show the effect of such variation on the respirable fraction of the aerosol cloud produced by the aerosol package.

Experiments showing the effect of can pressure on the respirable fraction of an aerosol powder spray were conducted on the above standard formulation save that the ratio of propellants 11 and 12 was varied to give a range of vapour pressures within the can. The package also differed from the above in that the diameter of the vapour tap orifice was 0.013 inch. The results are given in Table I..

TABLE I Can Pressure at 23"C (psig) NVRF 37 120 32 67 31 46 24 17 19 1 The results given in Table II below show the effect of the size of the actuator terminal orifice on the non-volatile respirable fraction (NVRF).

TABLE II Actuator Terminal Orifice Diameter (thousandths of an inch) NVRF 13 346 15 330 18 209 20 183 25 115 30 97 40 73 Experiments have also been conducted showing the effect of reducing the ratio of the areas of the vapour tap orifice and tail piece orifice from 0.06 to zero through the use of valves having vapour tap orifices of 0.020 inch, 0.013 inch and using a valve with no vapour tap. The results of the experiments are shown in Tables III and IV. The results in Tables III and IV were obtained using blends of propellants 11 and 12, giving can pressures of about 30 and 25 psig at 230C, respectively.

TABLE III Vapour Tap Diameter (thousandths of an inch) NVRF 20 58 13 46 0 19 TABLE IV Vapour Tap Diameter (thousandths of an inch) NVRF 20 54 13 17 0 8 In experiments illustrating the finding that products with increasing sedimentation volumes result in aerosol sprays with a lower respirable fraction, there were employed a number of composition which were obtained by varying the level of the pyrogenic silica in the above composition between 0.20 and 0.60 weight percent.

The results obtained are given in Table V.

TABLE V Sedimentation Volume (%) NVRF 35 283 43 252 56 211 61 194 65 192 In Tables I, III and IV the NVRF values are generally lower than those in Tables II and V. This is because the series of experiments summarised in Tables I, III and IV were carried out at a time when the ambient temperature in the laboratory was substantially lower. The actual NVRF value obtained with a given aerosol package is dependent somewhat on the ambient temperature at which the determination is carried out.

The results of further experiments showing the cumulative effect on the respirable fraction of a decrease in can pressure, reduction in the ratio of the areas of the vapour tap and tail piece orifices, and increase in sedimentation volume are shown in Table VI.

TABLE VI Area Vapour Tap Orifice Can Pressure at Sedimentation 23 C (psig) Area Tail Piece Orifice Volume (%) NVRF 0.0625 35 251 76 244 37 zero 35 185 76 154 0.0625 35 60 76 47 19 zero 35 23 76 16 The cumulative effect of increase in the area of the actuator orifice and decrease in can pressure is shown in Table VII. In these experiments the vapour tap orifice had a diameter of 0.013 inch.

TABLE VII Diameter of Actuator Can Pressure Terminal Orifice at 23 C (psig) NVRF 30 46 0.020 inch 25 17 30 23 0.035 inch 25 7 In experiments to determine the effect on the respirable fraction of using powders containing differing numbers of particles of respirable size, three different commercial grades of aluminium chlorhydrate were used. The materials employed were those manufactured by the Reheis Chemical Company and sold as the "MICRO-DRY", "MICRO-DRY Ultrafine" and "Microspherical" grades, respectively, of "CHLORHYD ROL". (CHLORHYDROL and MICRO-DRY are trademarks). Samples of these materials were examined by means of a scanning electronmicroscope and the weight and number percentages of the particles found in the 0-6 microns range are given in Table VIII.

TABLE VIII Aluminium Weight Percentage Number Percentage Chlorhydrate in Size Range in Size Range 0-6 microns 0-6 microns MICRO-DRY 2.0 56 Ultrafine MICRO-DRY 1.4 35 Microspherical 0.4 20 Respirable fraction data using these different materials in a commercial product (differing from the above standard product and containing 3.5% aluminium chlorhydrate and 3.0% isopropyl myristate) are given in Table IX.

TABLE IX Aluminium Chlorhydrate NVRF MICRO-DRY Ultrafine 131 MICRO-DRY 135 Microspherical 185 It was shown in other experiments that the relatively high NVRF value for the product employing aluminium chlorhydrate having the least number of particles below 6 microns was not due to any breakdown of the particles, it being noted that these particles are in the form of hollow spheres. These further experiments involved use of zero shear and 50 minute shearing of the product concentrate in the processing stage and examination of the sprayed product by scanning electron microscopy. No sign of breakdown was observed.

Although the product containing the least number of particles of aluminium chlorhydrate below 6 microns gave the highest respirable fraction, it has also been shown that for that product the proportion of the respirable material which was aluminium chlorhydrate was the least of the three products. Even if all the particles of the powder were to be above the respirable size, use of the combinations of conditions in accordance with the invention would still be useful for reducing the respirable fraction, which would in such a case consist mainly of the carrier liquid.

The following Table X illustrates examples of packages in accordance with the invention and Tables XI and XII show typical formulae for the aerosol composition for use in such packages.

TABLE X Example The composition: suspension of a powder, especially an antiperspirant material, in a liquid vehicle comprising a carrier liquid and a liquefied propellant Can Pressure Actuator Terminal Vapour Tap Tail Piece Sedimentation (psig at 20 C) Orifice Diameter Orifice Orifice Volume (%) (inches) Diameter Diameter (inches) (inches) 1 25 0.018 0 0.080 30 2 20 0.018 0.013 0.080 35 3 30 0.018 0.020 0.060 60 4 22 0.018 0.020 0.060 45 5 20 0.040 0.020 0.040 35 6 25 0.030 0.020 0.080 30 7 25 0.020 0.013 0.080 35 8 30 0.025 0 0.060 30 9 30 0.030 0.020 0.080 60 10 20 0.020 0.020 0.080 50 11 20 0.018 0 0.060 50 12 28 0.018 0.013 0.080 65 13 25 0.030 0 0.080 60 14 28 0.025 0.013 0.080 50 TABLE XI Composition A B C D E F G H Aluminium chlorhydrate 5.0 - - 3.0 2.0 3.1 4.5 3.5 ZAG - 7.0 3.5 - - - - Isopropyl myristate - - 8.0 - 6.0 - 6.0 1.0 Di-n-butyl phthalate 3.0 - - - - - - Diisopropyl adipate - 3.5 - 0.5 - - - Isopropyl palmitate - - - 0.5 - - - Hexylene glycol - - - - - 1.8 - Volatile silicone - - - - - - - 5.0 Pyrogenic silica qs - - - - qs qs qs Bentone-38 qs qs qs qs qs - - Propylene carbonate qs qs qs qs qs - - Perfume 0.3 0.3 0.4 0.2 - 0.4 0.4 Blend4 Propellants 11 & 12 qs - qs qs qs qs qs qs Blend4 Propellant 114: - qs - - - - - isobutane: Propellant 12 Zirconyl hydroxychloride:aluminium hydroxychloride:glycine complex (7.5:4.6:2).

An appropriate amount is used to give the desired sedimentation volume as indicated in Table X.

Used in an amount of 0.33 by weight of the Bentone.

4 The balance of the composition is an appropriate blend to give the desired can pressure as indicated in Table X.

TABLE XII Composition: I J K Sodium bicarbonate 3.0 - Hexachlorophene - 0.3 Microcrystalline cellulose (AVICEL RC581) - - 3.0 Isopropyl myristate - 4.0 3.0 Isopropyl palmitate 6.5 - Pyrogenic silica qs qs qs Perfume 0.2 1.0 0.2 Blend4 of Propellants 11 and 12 qs qs qs See Table XI 4 See Table XI. Further examples of packages in accordance with the invention are given in Table XIII.

TABLE XIII Ingredients of Composition Example 15 16 17 % % % Aluminium chlorhyrate (MICRO-DRY) - 4.00 4.00 Starch powder 3.50 - Sodium carbonate 0.25 - Isopropyl myristate 3.50 8.00 8.00 Polyoxyethylene polyoxypropylene block copolymer 0.50 - (PLURONIC L62D) Pyrogenic silica (AEROSIL 200) Bentone-38 0.60 0.60 Alcohol/water mixture (95:5) 0.30 0.30 Perfume 0.44 0.50 0.44 Blend of Propellants 11 and 12 (70:30) to 100.00 to 100.00 to 100.00 Pressure at 23 C (psig) 27 27 27 Actuator terminal orifice diameter (inches) 0.030 0.020 0.035 Vapour tap orifice diameter (inches) 0.013 0.013 0.013 Tail piece orifice diameter (inches) 0.080 0.080 0.080 Dip tube diameter (inches) 0.150 0.150 0.150 Sedimentation volume (%) 40 70 45 NVRF 30 61 24 The words AVICEL and PLURONIC in Tables XII and XIII respectively are trade marks.

In divisional application No. 6670/79 (Serial No. 1591365) there is described and claimed a package for containing and dispensing a powder including in combination a container having an aerosol spray valve for dispensing liquid in aerosol form and a composition within the container consisting of a powder suspended in a liquid vehicle comprising a mixture of a liquid carrier and a liquefied propellant, the package satisfying the following conditions: B the valve has a terminal orifice having an area of at least 3 x10 sqin; C the ratio of the area of any vapour tap orifice of the valve and either the valve tail piece orifice or the bore of the valve dip tube, whichever is the smaller, is not more than 0.05; and (D) the sedimentation volume of the composition is at least 40%.

Claims (13)

WHAT WE CLAIM IS:

1. A package for containing and dispensing a powder including in combination a container having an aerosol spray valve for dispensing liquid in aerosol form and a composition within the container consisting of a powder suspended in a liquid vehicle comprising a mixture of a liquid carrier and a liquefied propellant, the package being such that of the following conditions: (A) the vapour pressure within the container is from 5 to 30 psig at 200C; (B) the valve has a terminal orifice having an area of at least 3 x 10-4 sq in; 1B') the valve has a terminal orifice having an area of at least 4.5 x 10-4 sq in; (C) the ratio of the area of any vapour tap orifice of the valve and either the valve tail piece orifice or the bore of the valve dip tube, whichever is the smaller, is not more than 0.05; and (D) the sedimentation volume of the composition (as herein defined) is at least 40%; there is satisfied the combination of condition A with any one of conditions B', C and D; or the combination of condition A with at least two of conditions B, C and D.

2. A package as claimed in claim 1, wherein there is satisfied the combination of conditions A and D with at least one of conditions B and C.

3. A package as claimed in claim 1, wherein all the conditions A, B, C and D are satisfied.

4. A package as claimed in claim 2 or claim 3, wherein the valve has a terminal orifice having an area of at least 4.5 x 10-4 sq in.

5. A package as claimed in any of claims 1 to 4, wherein the pressure within the container is 15 to 30 psig at 200C.

6. A package as claimed in any of claims 1 to 5, wherein the valve has no vapour tap orifice.

7. A package as claimed in any of claims 1 to 6, wherein the sedimentation volume of the composition is at least 50%.

8. A package as claimed in any of claims 1 to 7, wherein the powder is an antiperspirant active material.

9. A package as claimed in claim 8, wherein the antiperspirant active material is aluminium chlorhydrate.

10. A package as claimed in claim 9, wherein the aluminium chlorhydrate is such that 25% or more by number of the particles have a size in the range 0 to 6 microns.

11. A package substantially as herein described with reference to any of Examples 1 to 14.

12. A package as claimed in claim 11 comprising a composition substantially as described with reference to any of Compositions A to K.

13. A package substantially as herein described with reference to any of Examples 15 to 17.