Abstract:
A marine dye composition comprising a water soluble or dispersible dye, particles of a density controlling material having a bulk density and being present in an amount so as to cause said composition to have a relative density of about 1 and to be capable of floating at the surface of a body of water and a water soluble or dispersible binding agent for binding the dye and particles of density controlling material together.

Description:
This application is a continuation-in-part of application Ser. No. 07/752,610 filed on 10th Oct. 1991, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to marine dye compositions. Marine dye compositions have been used in a number of applications to mark the location of crashed aircraft, life rafts and military equipment, for example rockets. 
     Life preservers used in aircraft in particular have been provided with a fluorescein dye placed in a cotton bag. The bag was sufficiently porous to allow water to seep through and dissolve the fluorescein dye. The disadvantages associated with using this system are as follows: 
     1. The bag could be easily ripped and the dye lost prematurely. 
     2. Once sufficient water had been absorbed by the bag and it became detached, it could float below the surface of the water. 
     3. The dye often caked due to moisture being absorbed by the bag from the air. Furthermore the rate of diffusion of the dye through the cotton bag could not be controlled. 
     The specification of U.S. Pat. No. 3,263,012 discloses a composition which purports to overcome these problems. The composition disclosed comprises a fluorescein compound bound in a matrix of polyvinyl alcohol resin containing glycerine and borax. The composition is pressed into a cake and made into a relatively thin plate like object. The principal object of the invention disclosed in this U.S. patent is to supply a composition that provides a controlled release of dye into water over an extended period of time, for example up to 45 days. The purpose of the glycerine is said to be to swell the polyvinyl alcohol resin and to dissolve the dye thereby permitting the dye to diffuse into the resin and to be encapsulated in the resin matrix. In addition, the specification states that the glycerine partially controls the rate of diffusion of the dye from the polyvinyl alcohol matrix into the water when the device is ejected into the sea. The more glycerine the greater the rate of emission of dye into the water. The presence of borax appears to be for the purpose of maintaining the cohesive strength of the resin matrix. 
     SUMMARY OF THE INVENTION 
     As distinct from the objects of earlier inventions the Royal Australian Navy identified the need for a marine dye composition which could be used to locate a submarine launched pyrotechnic signal (SLMPS). The dye needed to be observable for approximately thirty minutes thereby aiding in the recovery of any message carried by the signal or to locate the submarine that fired the signal. Previously, such signals were provided with a flare that had a duration of seventy-five seconds to two minutes. 
     An object of the present invention is to provide a composition that is capable of releasing dye on the surface of water for a period up to thirty minutes. 
     Accordingly the present invention provides a marine dye composition comprising a water soluble or dispersible dye, particles of a density controlling material having a bulk density and being present in an amount so as to cause said composition to have a relative density of about 1 and to be capable of floating at the surface of a body of water and a water soluble or dispersible binding agent for binding the dye and particles of density controlling material together. 
     Suitable dyes include Fluorescein LT marketed by ICI Australia. It is described in the colour index as CI acid yellow 73 Constitution No. 5350 and is essentially the sodium salt of hydroxy-ortho-carboxy-phenyl fluorene and is of the formula ##STR1## Fluorescein is visible at concentrations in water above 25 p.p.m.. Below this it appears to be colourless. It is especially preferred that the dye comprises from 90 and 98 percent by weight of the composition. 
     Another suitable dye composition is know as &#34;Seamarker Dye Composition&#34; and consists of a mixture of three dye CI acids; Red 51, of the formula ##STR2## Red 50 of the formula ##STR3## and Yellow 73. The predominantly red colouration of this marker comes from the sodium salt of rhodamine disulphonic acid. The sodium salt of fluorescein may also be used. 
     Suitable density controlling materials include any materials that introduce permanent air pockets into the composition. This may be achieved with microballoons of a plastics material such as polyethylene or phenol formaldehyde. Microballoons having a bulk density of approximately 0.01 g/cc are preferred. Microballoons made from polyvinylidene chloride (PVDC) are particularly preferred. 
     Preferred binding agents include water soluble derivatives of cellulose such as sodium carboxy methyl cellulose. Grades of sodium carboxy methyl cellulose are available with varying degrees of solubility. This is regulated by the degree of substitution of the polar groups by carboxy methyl groups. The rate at which the dye dissolves in sea water can therefore be determined by selecting an appropriate grade of sodium carboxy methyl cellulose. 
     Polyvinyl alcohol may also be used as a binder. However, polyvinyl alcohol is not a preferred binder because it was found to be rather messy and time consuming to use. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The relative density of the compositions of the present invention can be adjusted such that it is about 1. Such compositions float at the surface and maximise the aerial visibility of dye dissolved from the composition. Compositions that rapidly provide a patch of dissolved dye on the water surface can also be produced. This can be particularly useful when trying to attract the attention of aircraft especially from a life raft. Dye spots can be produced within 1 minute that are visible from a distance of up to 5 km. 
     The composition of the present invention may be packaged and displayed in a variety of ways depending on the proposed use. Small granules or pellets may be inserted into a vial for attachment to a life jacket. For use as an aerial marker the composition may be formed into larger pellets and packed in bags or containers made of a water soluble material such as polyvinyl alcohol. Bags made from a film of polyvinyl alcohol have been found to be particularly useful. The composition may be packed into the bag and the bag entrance heat sealed to store the composition for use. 
     Preferred embodiments of the invention will now be described by reference to the accompanying examples. 
    
    
     EXAMPLE 1 
     
         ______________________________________Fluorescein LT (ICI Brand) B.S.S. 100                        92 partsPolyvinylidene chloride (EXPANCEL BRAND)                       1.8 partsSodium Carboxy Methyl Cellulose (DIACEL 1130)                       1.3 partsGlycerol                    4.6 parts______________________________________ 
    
     The Fluorescein LT is dried in an oven at 100° C. for twenty-four hours. It is then sieved using a B.S.S. 100 sieve. The sodium carboxy methyl cellulose is dissolved in water to a concentration of 3 g per 100 ml. The glycerol is added to the solution whilst continuing to stir for a further five minutes. The fluorescein is mixed with the microballoons and the solution of sodium carboxy methyl cellulose and glycerine in water is added to the mixture to form a composition having a paste having a thick consistency. The mixture is poured onto a plastic sheet to a thickness of approximately 3 mm and dried in an oven at 40° C. for 72 hours and finally 100° C. for a further 24 hours. The composition is then removed from the oven and the resultant dried biscuit is broken into flakes of approximately 10 mm 2  by flexing the plastic sheet or snapping the flakes off the biscuit with an appropriate tool. 
     By experimentation it has been discovered that the composition is considerably more effective when formed into flakes in this way rather than extruded and cut into pellets. 
     EXAMPLE 2 
     
         ______________________________________Flake Mixture______________________________________Fluorescein LT (ICI Brand) sieved BSS 100                       97.7 partsPolyvinylidene chloride      1.5 partsSodium Carboxyl Methyl Cellulose (DIACEL 1130)                        0.8 parts______________________________________ 
    
     Procedure 
     The SCMC sample is first pre-wetted with ethanol then dissolved in water, stirring whilst heating. When fully dissolved the mixture takes on a viscous &#34;clag-like&#34; appearance and is added while still warm to the dye and microballoon admix and thoroughly blended into a runny paste. 
     The mixture is then poured onto non-stick trays to a thickness of approximately 3-5 mm and dried at 40° C. for 72 hours. The semi-dried cake is inverted to allow proper drying of the reverse side (approximately 48 hours). The cake is then broken into smaller, more manageable sizes and dried at 105° C.±5° C. to remove residual moisture (approximately 48 hours). Once dried the cakes can be broken into the required size (approximately 1 cm square) and stored in a desiccator until needed. 
     EXAMPLE 3 
     Preliminary tests were conducted off-shore with the aim of evaluating various dye packages for the size and duration of the mark produced. The following fluorescein configurations were tested. 
     (i) 7×10 g pellets, density 1.68 g cm -3   
     (ii) 7×10 g pellets, density 1.57 g cm -3   
     (iii) 7×10 g pellets, density 1.54 g cm -3   
     (iv) 32 g loose filled, paper sealed 
     (v) buoyant flakes* 80 g net weight 
     (vi) buoyant foam pellets* 50 g net weight 
     (vii) sieved (BSS 100) 32 g loose packed 
    
     Observations were made of the size of the dye mark produced and its duration. The conditions were overcast with 12-15 knot gusting winds and intermittent showers. The sea was relatively calm at the trial site with a sea-state between 1 and 2. 
     By far the most effective configuration was found to be the buoyant flakes (v). A large area was marked in a very short space of time and the maximum efficiency of the fluorescent properties of the dye emerged because the spot was near the surface. 
     Variation of density in the pressed pellets had only a small effect on the signals produced. All gave a serviceable though &#34;streaky&#34; signal which after 15 minutes was approximately 0.5 m wide by 15 m long. 
     The buoyant pellet configuration (vi) performed rather poorly with the dye leaching out far too slowly and the wind and wave action carrying the pellet far away from the original launch site. 
     The loose filled powder configuration (iv) gave a good initial signal however much of the spot drifted on the surface and was lost with the wind and the tide. In addition the larger grains sank. 
     The sieved BSS 100 sample (vii) also gave a good initial signal but the grains could be seen to sink to the seabed. 
     The following examples illustrate the invention but the formulations are less preferred than the foregoing formulations. 
     EXAMPLE 4 
     
         ______________________________________Fluorescein                 80 gPhenolic microballoons by Union Carbide                       10 gSuper saturated solution of polyvinyl alcohol                       40 g______________________________________ 
    
     The components were mixed and poured into pyrex dishes to dry. The mixture was dried in an oven at 40° C. for 48 hours. The dried mixture was chipped out of the dish to yield 90 g of product. 
     EXAMPLE 5 
     
         ______________________________________Formulation______________________________________Fluorescein              50     gPolyvinyl alcohol powder 30     gPhenolic microballoons (ICI brand)                    20     gWater                    250    ml______________________________________ 
    
     The mixture was stirred at 45° C. until it became runny. Thereafter the mixture was dried at 71° C. for 24 hours in a flat bottomed non-stick tray. Unfortunately, not all of the polyvinyl alcohol dissolved so it remained as white lumps in the flakes of product. The mixture stuck to the tray and was very difficult to get out. 
     EXAMPLE 6 
     
         ______________________________________Formulation______________________________________Sorbitan Monopalmitate   40 gFluorescein              40 g______________________________________ 
    
     Alumino-silicate in the form of fly ash 10 g from Pozzolanic of South Wentworthville, New South Wales. The sorbitan monopalmitate and the fluorescein were dissolved in 250 ml of water. The fly ash was then dissolved in the solution and the solution dried to yield the product. 
     EXAMPLE 7 
     
         ______________________________________Formulation______________________________________Fluorescein                 100    gDiacel 1130 (ICI) at a concentration of 1 g per 100 ml                       200    mlAlumino-silicate in the form of fly ash                       10     g______________________________________ 
    
     Diacel 1130 and fluorescein were mixed with 40 mls of water to form a solution and the fly ash was mixed with the solution and the resultant mixture dried to yield the product. 
     EXAMPLE 8 
     
         ______________________________________Formulation______________________________________Fluorescein                 100    gDiacel 1130 at a concentration of 1 g per 100 ml                       200    mlAlumino-silicate in the form of fly ash                       20     g______________________________________ 
    
     The fluorescein and Diacel 1130 were dissolved in 40 mls of water to yield a solution into which the fly ash was mixed. The mixture was then dried to yield a product. 
     EXAMPLE 9 
     
         ______________________________________Formulation______________________________________Fluorescein                100     gMicroballoons of polyvinylidene chloride (Expancel)                      2 to 5  gSodium carboxy methyl cellulose (Diacel 1130                      100     mlat a concentration of 2 g per 100 ml)______________________________________ 
    
     EXAMPLE 10 
     
         ______________________________________Formulation______________________________________Fluorescein LT              500    gSodium carboxy methyl cellulose glass microballoons                       8      gsold under the name of ercospheres M37 lot No. 6704particle size 62 to 100 micronGlycerol                    20     ml______________________________________ 
    
     The carboxy methyl cellulose was pre-wet with 20 mls of ethanol and dissolved in 100 mls of water which was added drop wise whilst heating and stirring. More water was added as the ethanol evaporated to make a total of 200 mls. 
     EXAMPLE 12 
     
         ______________________________________Formulation______________________________________Fluorescein                1000 gCarboxyl Methyl Cellulose (DIACEL 1130)                       10 gGlass Microballoons as for Example 10                       16 gGlycerine                   40 gFumed silica                40 g______________________________________ 
    
     The sodium carboxyl methyl cellulose was pre wet with ethanol and dissolved in 600 mls of water whilst stirring and heating. Water was added to the mixture to obtain a &#34;thickshake&#34; like consistency. The mixture was dried at 60° C. for 48 hours and then 100° C. for 24 hours. The formulation was deliberately made with a relative density less than that of water so that it would float to the surface from a point beneath the surface.