MARINE DYE COMPOSITION

Abstract: The invention concerns a marine dye composition. The composition comprises a water soluble or dispersible dye, a water soluble or dispersible binding agent and a means for adjusting the relative density of the composition by variation of its content in the composition. Microballoons of a plastics material such as polyethylene or phenol formaldehyde exemplify such means.

Description: MARINE DYE COMPOSITION 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. Patent 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. 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, a density controlling means that enables the relative density of the composition tσ be adjusted by variation of its content in the composition and a water soluble or dispersible binding agent for binding the composition together. Suitable dyes include Fluorescein LT marketed by ICI Australia. It is described in the colour index as Cl acid yellow 73 Constitution No. 5350 and is essentially the sodium salt of hydroxy-ortho-carboxy-phenyl fluorene. Fluorescein is visible at concentrations in water above 25 p.p.m.. Below this it appears to be colourless. Another suitable dye composition is known as "Seamarker Dye Composition" and consists of a mixture of three dye Cl acids; Red 51, Red 50 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 means may comprise any means for introducing 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 .01 g/cc are preferred. Microballoons made from polyethylene 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. 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 maximize 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 10 minutes 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 lift 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 parts Phenolic Microballoons (DEs include wte Brand) 1.8 parts 5 Sodium Carboxy Methyl Cellulose 1.3 parts (DIACEL 1130) Glycerol 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. 10 100 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 15 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 20 for a further 24 hours. The composition is then removed from the oven and the resultant dried biscuit is broken 2 into flakes of approximately 10 mm by flexing the plastic sheet or snapping the flakes off the biscuit with an appropriate tool. 25 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 30 Flake Mixture Fluorescein LT (ICI Brand) sieved BSS 100 97.7 parts Phenolic Microballoons (DE Brand) 1.5 parts Sodium Carboxyl Methyl Cellulose 0.8 parts (DIACEL 1130) 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 "clag-like" appearance and is added while still warm to the dye and microballooon 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. _3 (i) 7 x 10 g pellets, density 1.68 g cm _3 (ii) 7 x 10 g pellets, density 1.57 g cm _3 (iii) 7 x 10 g pellets, density 1.54 g cm (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 " *Configuration (v) used fluorescein in combination with phenolic microballoons with polyvinyl acetate (PVA) as a binder and (vi) used an open-cell foam pellet into which the dye had been secreted. 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 "streaky" 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 was lost with the larger grains sinking. The sieved BSS 100 sample (vii) also gave a good initial signal but the grains could be seen to sink to the sea-bed.

Claims: CLAIMS : 1. A marine dye composition comprising a water soluble or dispersible dye, a density controlling means for adjusting the relative density of the composition by variation of its content during manufacture of the composition and a water soluble or dispersible binding agent for binding the composition together. 2. A marine dye composition according to Claim 1 wherein the density controlling means comprises a means for introducing permanent air pockets into the composition. 3. A composition according to Claim 1 wherein the density controlling means comprises microballoons of a plastics material. 4. A marine dye composition according to Claim 3 wherein the plastics material is polyethylene. 5. A marine dye composition according to Claim 3 wherein the plastics material is phenol formaldehyde. 6. A marine dye composition according to Claim 3 wherein the plastics material has a bulk density of about .01 g/cc. 7. A marine dye composition according to any one of Claims 1 to 6 wherein the water soluble or dispersible dye is fluorescein. 8. A marine dye composition according to any one of Claims 1 to 6 wherein the water soluble or dispersible dye is a mixture of red 51, red 50 and yellow 73 Cl acids. 9. A marine dye composition according to any one of Claims 1 to 8 wherein the water soluble or dispersible binding agent is a water soluble derivative of cellulose. 10. A marine dye composition according to Claim 9 wherein the water soluble derivative of cellulose is a sodium carboxy methyl cellulose. 11. A marine dye composition according to any one of Claims 1 to 8 wherein the water soluble or dispersible binding agent is polyvinyl alcohol or polyvinyl acetate. 12. A marine dye composition according to any one of the preceding claims wherein the composition has a relative density that is about 1. 13. A marine dye composition according to Claim 6 wherein the microballoons comprise from 1.5 to 1.8 percent by weight of the composition. 14. A marine dye composition according to any one of Claims 1 to 13, wherein the water soluble or dispersible dye comprises from 90 to 98 percent by weight of the composition. 15. A marine dye composition according to Claim 14 wherein the water soluble or dispersible binding agent comprises from 0.8 to 1.3% by weight of the composition. 16. A marine dye composition according to any one of the preceding claims, wherein the composition includes up to 5% by weight of glycerol. 17. A method of making a marine dye composition according to Claim 1 comprising the steps of mixing the water soluble or dispersible dye with the density controlling means to form a premix; mixing the water soluble or dispersible binding agent with water to form a solution or dispersion of tne binding agent in water; mixing the solution or dispersion with the premix to form a paste; pouring the paste into moulds to a depth of about 3 mm; drying the paste in an oven at a temperature of less then 50 C until most of the water has been evaporated; drying the paste for about a further 24 hours at a temperature of about 100°C; removing the composition from the moulds and breaking it into pellets or flakes suitable for use. 18. Pellets formed from a marine dye composition according to any one of Claims 1 to 17. 19. Flakes formed from a marine dye composition according to any one of Claims 1 to 17. 20. Vials containing a marine dye composition according to any one of Claims 1 to 17. 21. Heat sealed polyvinyl alcohol bags containing a marine dye composition according to any one of Claims 1 to 17.

Inventors: SWINTON ROBERT JAMES, SWINTON, ROBERT, JAMES
Applicants: COMMW OF AUSTRALIA, COMMONWEALTH OF AUSTRALIA
Application year: 1990
Main classification: C09K11
IPC codes: C09B67, C09K11