Investigations into Domestic Household Aerosols Air Freshener and body spray

Transcription

1 ILASS Europe 2010, 23rd Annual Conference on Liquid Atomization and Spray Systems, Brno, Czech Republic, September 2010 Investigations into Domestic Household Aerosols Air Freshener and body spray R.A. Sharief * Lionstar Corp. Ltd/ Stockport College, England, UK Abstract With increasing legislation on volatile-organic-compounds, there is interest in either reducing the hydrocarbon content in aerosol cans or removing it completely, i.e. using inert compressed gas propellant. However both these approaches give relatively poor atomisation unless improvements in atomisation performance are made. This paper describes experiments that have been carried out to explore the effects of flow control devices on the flashing flow and the quality of the spray and which are leading to new generation of household aerosols. Domestic aerosols such as air fresheners and body sprays are commonly used all over the world. Aerosols generally consist of a pressurised canister containing a product and a liquified volatile propellant. The aerosols work consistently using the same principle; where the product and the propellant are actuated through a simple nozzle. Flash atomization of the propellant takes place to break up the product into a cloud of droplets This paper is related to an innovation patents WO (A1) and WO (A1),WO (A1) (1, 2, 3 and 4) The aims of this investigation are, to develop improved, aerosol actuators using a new manufacturing technology, to reduce VOC content of existing aerosol cans, e.g. butane reduction and ethanol replacement by water, to achieve spray performance at least matching the characteristics of existing aerosol air fresheners, and body sprays, to gain improved understanding of internal flashing flows. More advanced designs of actuators have been made depending on the inventions related to shape chambers, multiple passages of flow and throttles. It is now possible to manufacture household can aerosols such as air fresheners, body sprays and hair sprays with massive reduction in hydrocarbons or volatile organic compounds (VOC). Internal features of Raj designs and the cyclonic device have developed for spraying air fresheners and other viscous and none viscous products, below results show a matched droplet size of the market nozzle, market propellant cans with an improved spray angle and spray penetration length. It has been found that droplet size produced at the outlet orifice of a nozzle can be controlled by incorporating a number of different control features into the fluids flow passageway between the inlet and the outlet which modify the characteristics of the fluid as it flows through the passageway for example it has been found to be particularly beneficial to form two or more expansion chambers along the fluids passageway, each chamber having a constricted inlet opening arranged so that the fluids is sprayed into the chamber. By use of internal shaped chambers and channels in the spray nozzle the spray quality can be improved. By changing the geometry of the external exit of the nozzle spray, an improvement can be achieved. More complex designs of household aerosol can actuators have been made possible by using a new manufacturing technology. This has made feasible the use of various flow control devices and multiple orifice actuators, with no cost penalty. An experimental research programme has systematically applied these flow control devices in specially made actuator models for the cases of spraying those very different types of products, body spary and air-freshener. The experiments have shown that these flow control devices permit control of droplet size, control of flow rate, spray pattern manipulation, the production of narrower droplet size distributions, and reduction of can VOC content. From the experiments carried out by Raj Designs on several products, it has proven that great improvements on reduction of drop sizes and crucial reduction on inhalables by keeping the flow rate the same with comparison to the original cap *Corresponding author: rajab.sharief@yahoo.co.uk

2 Introduction Because of the ease of atomising by using a flashing propellant, there has been remarkably little published research on how the internal geometry of the actuator affects performance, where the actuator is the cap of the can, which fits on the valve and contains the exit orifice. The exit may be a simple orifice, such as for antiperspirants, or a swirl-insert, for example for polish and paint sprays. Currently the propellants used are blends of liquefied hydrocarbon, mainly butane and these are classified as Volatile Organic Compounds (VOC s). Legislation controlling VOC use is becoming increasingly strict and is already affecting the household aerosol market in California []. The key performance parameters of an aerosol are the discharge rate, the particle size and the cone angle. Safety is also a key requirement. The present invention relates to an atomising nozzle more particularly, but not exclusively, the present invention relates to an atomising nozzle for an aerosol canister and an aerosol canister comprising such an atomising nozzle. Nozzles are often used to provide a means of generating sprays of various fluids. In particular, nozzles are commonly fitted to the outlet valves of pressurised fluid-fitted containers, such as so called aerosol canisters to provide means by which the fluids stored in to container can be dispensed in the form of a spray or mist. A large number of commercial products are presented to consumers in this form, including, for example, antiperspirant sprays, de-odorant sprays, perfumes, air fresheners, antiseptics, paints, insecticides, polish, hair care products, pharmaceuticals, water and lubricants. In addition, pump or trigger-actuated nozzle arrangements, i.e. arrangements where the release of fluid from a non-pressurised container is actuated by the operation of a manually operable pump or trigger that an integral part of the arrangement, are also frequently used to generate a spray or mist of certain fluid products. Examples of products that are typically dispensed using a pump or trigger nozzle device include various lotions, insecticides, as well as various garden and household sprays. Nozzles are also used in any industrial applications to deliver a fluids or mixture of fluids in the form of a spray. The optimum size of the droplets required in a particular product concerned and the application for which it is intended. For example, pharmaceutical sprays that contain a drug intended to be inhaled by a patient (e.g. an asthmatic) usually requires very small droplets, which can be penetrated deep into the lungs. In contrast, a polish spray preferably comprises spray droplets with larger diameters to promote the particularly if the spray is toxic, to reduce the extent of inhalation. The size of the aerosol droplets produced by such conventional nozzle arrangements is dictated by a number of factors, including the dimensions of the outlet orifice and the pressure with which the fluid is forced through the nozzle. However, problems can be arising if it is desired to produce a spray that comprises small droplets with narrow droplet size distributions, particularly at low pressure. The use of low pressures for generating sprays is becoming increasingly desirable because it enables low pressures nozzle devices, such as the manually-operated pump or trigger sprays, to be used instead of more expensive pressurized containers and, in case of pressurized fluid-filled containers, it enables the quality of propellant present in the spray to be reduced, or alterative propellants which typically produce lower pressure (e.g. compressed gas) to be used. The desire to reduce the level of propellant used in aerosol canisters is topical issue at the moment and is likely to become more important in the future due to legislation planned in certain courtiers, which proposes to impose restrictions on the amount of propellant that can be used in hand-held aerosol canisters. The reduction in the level of propellant causes a reduction in pressure available drive the fluid through the nozzle arrangement and also results in less propellant being present in the mixture to assist with the droplet break up. Therefore, there is a requirement for different types of designs of nozzle arrangement that is capable of reducing an aerosol spray composed of suitably small droplets at low pressure. A further problem with known pressurised aerosol canisters filled with conventional nozzle arrangements is that the size of aerosol droplets generated tends to increase during the lifetime of aerosol canister, particularly towards the end of the canisters life as the pressure within the canister reduces as propellant becomes gradually depleted. This reduction in pressure causes an observable increase in the size of the aerosol droplets generated and thus, the quality of the spray is compromised. Accordingly, it is an object of the present work and inventions to provide design of nozzles that is adapted to generally reduce the size of the droplets generated when compared with conventional nozzle devices, as well as to narrow the droplet size distributions. Also to enable small droplets of fluid to be generated at low pressures, i.e. when fluids contains reduced or depleted levels of propellant, or a relatively low-pressure propellant such as compressed gas, is used, or a low pressure systems is used, such as a pump or trigger. The problem of providing a high spray at low pressures is further exacerbated if the fluid concerned has a high viscosity because it becomes harder to atomize the fluid into sufficiently small droplets. Also the aim of this work is to have designs capable of generating a spray from viscous fluids at low pressures. Below one of the designs could solve low voc products. Spray painting and coating processes are used widely in decoration and protecting substrate. This includes techniques such as electro-deposition, auto-deposition, roller or power coating. The paint and coating atomizers should be capable to produce fine drop sizes. Moreover, these atomizers must provide acceptable emissions of volatile organic compounds to meet the legislations to control their effects on the environment. On household applications, there are a very wide field of so called aerosols cans or packaged aerosols. Examples of 2

3 these are; aerosol cans, such as deodorants, hair-spray, anti-perspirants, air fresheners, polishes, cooking oils, cleaning spray and insecticides. This invention, (1-4) helps to develop designs of actuators which help the reduction of VOC in the cans. This is a new innovation which has been developed and tested to enhance the quality of spray of aerosol products with very low volatile organic compound (VOC). The partitions have been used in the chamber where the flow passage of the design actuator.partitions can takes different shapes. The key design of these shapes is made to obstruct the flow in the centre of the flow. Apparatus, Methodology and Procedures: An experimental programme has used transparent actuator caps, with high-speed video recording, brass models also have been used because they last for longer. Droplet sizing using a laser diffraction instrument (Malvern and Spray Tec.), an average of three tests had been taken for each data, flow rate was measured by weighing the can, normally average reading will be taken for three times reading, the spray time on average of five seconds. Because consistency of spraying throughout can life is important, droplet sizes and flow rate are measured for full cans, and, typically, for 7%, 0%, and 2% full. Spray distances from the lenses are 10mm for body sprays, mm for hair spray, oil, paint and polish and 00mm for air freshener. The actuators in the research programme have been specially machined from Perspex (Plexiglas) and Brass, a method of unit construction has been developed so that combinations of different shapes and sizes of inlets, exits, internal passages and flow control devices may be tested systematically, Figure 3 shows the internal features the design, as developed for spraying anti-perspirant. because of variation of temperature difference between summer and winter, all tests must be done at room temperature, say 20 centigrade. Internal features of Raj. designs, as developed for spraying air fresheners, anti-perspirant, body spray, hair spray, polish, oil and paint, key features of the devices are the inlets, pre-throttles, shaped chambers, partitions, throttle(s), straight or angled, leading to the pre-chamber and exits, exits could take different forms from a simple exit to a swirl. New Actuator Manufacturing Method The practical utilization of more complex designs of nozzles in household aerosols is made possible by a new manufacturing procedure. Figure 1 show a typical aerosol can were the actuators is that part that fits on the valve most actuators are in two parts, the main body and the exit orifice insert. a new injection moulding technique, allows the actuator and exit orifice to be made as one part, as illustrated in Figure 2 [6]. This is achieved by moulding a hinged cap as one unit that fold together after manufacture. Apart from the advantage of cost, it is now possible to incorporate a wide range of flow control devices and orifice designs into a single injection moulded part.. Key features of the devices are the throttle(s), leading to the pre-chamber and exit, and Fig. 4 and Table 1, illustrate some of the designs that have been used for the throttle and exit sections with codes that are referred to subsequently. As seen in Figure 4, there is a throttle stage leading to a pre-chamber followed by an exit orifice stage. Figure 4 shows a selection of the different throttle and exit stages that have been tested for different products. Figure 1: Typical aerosol can and valve system (Courtesy BAMA, London) Figure 2: New actuator technology design [6]. 3

4 g o o s e n e c k p r e - th r o t tle d o g l e g c h a m b e r th r o tt le ( s ) e x it m i d d le s e c ti o n p r e - c h a m b e r 1THA7 2TH v a lv e s te m p o s iti o n Figure 4: Throttles and exits models 2THA20 3THA TH 4THA1 Design. Throttle/Exit 1TH One throttle 1THC One throttle with chamber 1TH A7 o One throttle angled 7 o 2TH Two throttles 2TH A20 o Two throttles angled 20 o 3TH Three throttles 3TH A30 o A10 o Three throttles angled 30 o & 10 o 4TH A1 o Four throttles angled 1 o TH Five throttles TH A 10 o Five throttles angled 10 o 1 EX One exit, Simple pre-chamber 3 EX 1 o Three exits angled 1 o Table 1: Design and description TH THA10 3EX 1 1EX 1TH 1THC 4

5 Discussion Systematic tests were undertaken, in the first instance in order to attempt to reduce the inhalable fraction of droplets, i.e. the percentage of droplets smaller than 7 microns. Figures 3 illustrate flow control devices that have been explored, including a "dogs-leg", for breaking up unsteadiness and segregation after the valve and corner, and a pre-chamber before the exit orifice. The throttle provides a local pressure drop which causes vaporisation of a proportion of the hydrocarbon. Systematic tests enabled selection of optimum combinations of exit orifice and throttle sizes with the aim of producing fine sprays but with reduced inhalable fraction of droplets. This is achieved by producing a nearhomogeneous two-phase mixture in the pre-chamber which completes atomisation inside and just downstream of the exit orifice. Minimisation of liquid film on the exit orifice wall also appears to assist in reducing the width of the size distribution Most of the products are reduced VOC As shown in figures to 9, model designs consist of inlet, could take different shapes, horizontal, tangential or vertical inlet, inlets also could control the flow rate. pre-throttle works with body spray as flow control as well as create more fine droplets with no penalty to flow rate, pre-throttle sizes has to be optimised to be effective otherwise using wrong size could be counter productive, more experience needed to match such deigns with such products. throttle stage, could take different forms, such as two throttles hitting each other figure 4(1ThA7), a pre chamber which create more droplet breaks or single or more angled throttles hitting the wall as shown in figure a which convert kinetic energy into pressure energy near the wall leading to a pre-chamber, chamber shape and sizes can be determined by knowing the product and other characteristics required followed by an exit orifice stage. It has been shown that in some designs long chambers after inlets could give better mixing to produce finer droplets Rajab s diamond shaped chambers as shown in figure consist of divergence conical leading to a chamber followed by convergence conical. The chamber length of the chamber can be optimized and determined depending on several factors such as flow rate required and the type of product. Converged Conical chambers behaves well since create local pressure drop, converged or diverged conical chambers can also be used as exits as illustrated in figures. It has also been shown that a small around tip on the exit could narrow the drop size distributions, reduces large droplets on the sides, also can reduce liquid collection. Raj s shapes partitions can be positions in cambers shown in figure. These shapes can help to create more turbulence, Throughout the paper, all Raj., designs are selections include different straight or angled throttle(s), shaped chambers, partitions, conical(s) and exit stages that have been tested for different products. Systematic tests were undertaken, in order to reduce the drop size diameter as well as the inhalable fraction of droplets, i.e. the percentage of droplets smaller than 7 microns, with no effect to the flow rate. Raj designs illustrate flow control devices that have been explored, including a shaped chambers, Raj diamond, Raj partitions for breaking up unsteadiness and segregation after the valve and corners, and a pre-chamber before the exit orifice convergence and divergence conical and throttle(s) provides a local pressure drop which causes vaporisation of a proportion of the hydrocarbon. Systematic tests enabled selection of optimum combinations of exit orifice and throttle sizes, chamber shapes and partitions with the aim of producing fine sprays but with reduced inhalable fraction of droplets. This is achieved by producing a near-homogeneous two-phase mixture in the pre-chamber which completes atomisation inside and just downstream of the exit orifice. Minimization of liquid film on the exit orifice wall also appears to assist in reducing the width of the size distribution. Applications of Raj.s designs is achievement of a major reduction in hydrocarbon content for air-freshener sprays, hair spray and body spray with no adverse effect on the drop size distribution. In order to do this hydrocarbon propellant level is reduced in the can during the filling operation, and also the liquid propellant must be replaced by water. This produces problems in obtaining good atomisation for three reasons; (1) the can pressure is reduced, (2) flash vaporization is reduced, and (3) surface tension and viscosity of the liquid phase are increased. Development work showed that to solve these problems it was considered necessary to (1) ensure significant vapour release occurred within the actuator, (2) produce a highly turbulent flow, but at length scale small compared with the flow geometry, and (3) minimise the size of the exit orifice. Reduction in can VOC content is obtained without worsening the drop size distribution (volume and median diameter is around 40 micron for air fresheners), 30 to 60 microns for different types of reduced VOC. Figure d shows a design working well with reduced VOC body spray, producing fine droplets with minimum inhalables and keeping the flow rate within average, again this has shown that the diamond shaped chamber are proven to be a unique and successful design. As seen in Fig. a, b and c, reduced VOC body spray design in Fig a produces finer drop size with compassion to Fig. b, when adding two divergent throttles hitting inside convergent chamber and acting as exit. Figure 6a, b and c shows air freshener designs, a comparison show how vertical design Figure 6 perform much better than horizontal design ( figure 7) by five microns finer on Dv, Figure 6 and 7 shows how angled throttle of 20 degree produce better results than 1 degree,

6 Dv (µm), %<6.3 µm <6.3µ-Raj BS Flow rate-raj BS Dv-Raj HS Figure d: Body Spray, Product I Raj BS (a) (b) ( a ) Figure a, b, c: vs RVOC BS prod. I Figure 6a: Air Freshener Vertical Design, D30HV Dv (µm), %<6.3 µm Dv-org AF <6.3µ-Raj V 20 AF Flow rate-org AF <6.3µ-org AF Dv-Raj V 20 AF Flow rate-raj V 20 AF Figure 6b: Air Freshener, Original V Raj V20º Dv (µm), %<6.3 µm Dv-Raj V 1 deg. <6.3µ-Raj V 1 deg. <6.3µ-Raj V 1 vs Raj H20Raj V 20. Dv-Raj V 20. Flow rate-raj V 1 deg. Flow rate-raj V 20 deg. Figure 6c: Air Freshener, Raj V1º v Raj V20º Raj BS ( b ) Figure 7a: Air Freshener Horizontal Design, D30H Raj BS ( c ) Dv (µm), %<7.74 µm Dv-Raj BS prod. H <7.74µ-Raj BS prod. H Flow rate-raj BS prod. H <7.74µ-Raj BS prod. H Dv-Raj BS prod. H Flow rate-raj BS prod. H Dv (µm), %<6.3 µm Dv-Raj H <6.3µ- Raj H <6.3µ-Raj V 1. Dv-Raj V 1. Flow rate-raj H Flow rate-raj V 1. Figure 7b: Air Freshener, Raj H v Raj V1º 6

7 Figure 6a, b and c shows air freshener designs, a comparison show how vertical design Figure 6 perform much better than horizontal design ( figure 7) by five microns finer on Dv, Figure 6 and 7 shows how angled throttle of 20 degree produce better results than 1 degree. Figure 8, illustrate vertical design for air fresheners and Figure 9 illustrate Horizontal design for air fresheners. Figure 7, Performance of design 3TH, with air freshener spray products using multi throttles with a single exit. Another example of application of the new actuator technology is the achievement of a major reduction in hydrocarbon content for air-freshener sprays, with no adverse effect on the drop size distribution. In order to do this hydrocarbon propellant level is reduced in the can during the filling operation, and also the liquid propellant must be replaced by water. This produces problems in obtaining good atomisation for three reasons; (1) the can pressure is reduced, (2) flash vaporization is reduced, and (3) surface tension and viscosity of the liquid phase are increased. Development work showed that to solve these problems it was considered necessary to (1) ensure significant vapour release occurred within the actuator, (2) produce a highly turbulent flow, but at length scale small compared with the flow geometry, and (3) minimise the size of the exit orifice. Figure 16 shows a design which provides a very significant reduction below the typical current level of around 30% VOC. Reduction in can VOC content is obtained without worsening the drop size distribution (volume and median diameter is around 40 micron for air fresheners). It can be seen from Fig. 10, that the multiple sprays, produces by the multiple small exit orifices soon combine downstream. The multiple throttles act as turbulence generators, whilst also producing vapour release. Figure 8, Vertical design for Air freshener 7 Figure 9, Horizontal design for Air freshener

8 Concluding Remarks More complex designs of household aerosol can actuators have been made possible by using a new manufacturing technology. This has made feasible the use of various flow control devices and multiple orifice actuators, with no cost penalty. An experimental research programme has systematically applied these flow control devices in specially made actuator models for the cases of spraying those very different types of products, anti-perspirant, hair spray and air-freshener. The experiments have shown that these flow control devices permit control of droplet size, control of flow rate, spray pattern manipulation, the production of narrower droplet size distributions, and reduction of can VOC content. From the experiments carried out by Raj Design on several products, it has proven that great improvements on reduction of drop sizes and crucial reduction on inhalables by keeping the flow rate the same with comparison to the original cap. References [1] An atomizing Nozzle and An aerosol canister comprising an atomizing Nozzle, UK patent publication No. WO (A1), World Intellectual Property organization application No. W02006GB ( ), inventor, Rajab Sharief. Shaped Chamber, Nozzle arrangement, UK patent Publication No. WO (A1), World Intellectual Property organization application No. W02004GB ( ), inventors Keith Laidler, Rajab Sharief and Hassan Abduljailil. [3] Multiple Passages, Nozzle arrangement, UK patent publication No. WO (A1), world intellectual property organization Application No. W02004GB ( ), inventors Keith Laidler, Rajab Sharief and Hassan Abduljailil. Figure, 10 Multi exits and multi throttle models for air freshener with reduced VOC Flap Arrangement, Nozzle arrangement, UK patent publication No. WO (A1), world intellectual Property Organisation Application No.W02004GB ( ), inventors Keith Laidler, Rajab Sharief and Hassan Abduljailil. BAMA, Scoping study: the futures of aerosols". British Aerosol Manufacturing Association, London, Nov Ten Cate Plasticum, Netherlands, 200 8