This invention describes the use of man- made ce!lulosic fibres, in particular !yocefl and modal for the construction of ropes, nets and meshes for use as supports for the cultivation of marine cultures such as molluscs, particularly mussels and edible seaweed. The key properties are that the supports are of sufficient strength to carry the weights of the growing cultures without breakage yet are marine biodegradable after use.

Synthetic fibres and plastics lost to the oceans account for 80% of all marine pollution and apart from the danger posed to marine life can enter the human food chain through being ingested by fish etc. The marine biodegradability of the supports made from modal and iyocell remove this risk even if the supports are unintentionally lost.

Prior Art

Marine products produced by farming

The world mussel production is in excess of 2 million tonnes and is either by on-bottom or off-bottom culture. The on-bottom culture system is also called the broadcast technique. The off bottom culture system includes stake or pole method, rack, raft and long line. These systems are also called the hanging or suspended culture techniques and are particularly relevant to the invention.

Nylon and polypropylene are most commonly used for the rope material (12mm thick) and because they are not biodegradable can typically be used for 4 seasons. Synthetic ropes are durable and are of sufficient strength to hold the full weight of the fully grown mussels, but are not sustainable nor marine biodegradable, so pose a risk to sealife if lost.

Where synthetic fibres are used, the mussels need to be scraped from the rope and the ropes washed for reuse. Fibre particles are inevitably lost during this process that enter the water courses and oceans and will never degrade. Ropes can also be lost due to poor weather conditions and are unable to degrade causing dangers to sea creatures. Continuous filament yams are widely used in the textile industry to produce fabrics with a distinct character compared to fabrics produced from yarns made using staple fibre. A continuous filament yam is one in which all of the fibres are continuous throughout any length of the yarn. A continuous filament yam will commonly consist of 20 to 200 or more individual fibres which are ail parallel to each other and the axis of the yam when produced. The yam is produced by extruding a solution or melt of a polymer or a polymer derivative and then winding the yarn produced onto a bobbin or reel or by forming a cake by centrifugal winding.

Synthetic polymer continuous filament yarns are common. For example, nylon, polyester and polypropylene continuous filament yams are used in a wide variety of fabrics. They are produced by melt spinning a molten polymer through a spinneret with a number of holes corresponding to the number of fibres required in the yarn produced. After the molten polymer has started to solidify, the yarn may be drawn to orient the polymer molecules and improve the properties of the yarn.

Nowadays concern is growing regarding the build- up of synthetic fibre and micro plastic particles in the world's oceans. About 80% of marine pollution is shown to be attributable to synthetic and non-biodegradable fibre particles in addition to the larger more easily seen pollutants such as PET bottles etc.. Many publications detail concerns about such pollution, for example Marine Pollution Bulletin 44 (2002) 842-852, The pollution of the marine environment by plastic debris: a review, which details the growing problem of nonbiodegradable synthetic polymers in the world's oceans.

Besides synthetic fibers also man-made celluiosic fibers are known to the public, in particular manufactured according to the viscose, modal and lyoceil process.

Problem in view of the disadvantages of the state of the art in the described field of supporting marine crops during growth there is a need for materials which will perform their required function for a sufficient period of time but without leaving a persistent residue. Furthermore such materials shall allow the marine crop they are supporting to be harvested readily. It would be even more beneficial if such a material is sustainable and can be incinerated with no net increase in atmospheric carbon.

Description it is an object of the present invention to provide a rope suitable for use as a support and growth medium for marine organisms which comprises at least one man-made cellulosic yarn, preferably made from modal or lyoceii fibres, most preferably made from lyocell fibres. The term "rope" includes the definition of a twine as well. The term "fiber" for the purposes of the present invention shall include staple fibers as well as continuous filaments.

Surprisingly it has been found that a functional support for the growth of marine organisms including marine plants and shellfish can be produced using yarns produced from manmade cellulosic fibres including lyocell and modal fibre.

These two man-made cellulosic fibres are of particular interest in this field as they have been shown to be marine biodegradable (see examples 1 and 2 - test result and accreditation) and also lyoceii is non-toxic to aquatic organisms (see example 3)

Viscose fibre is produced by extruding a solution of a cellulose derivative through very small spinneret holes and then precipitating by changing the pH and by converting the derivative back to cellulose.

Cellulose as wood pulp is usually used as the starting materia! although other sources of cellulose such as bamboo and cotton linters are also used. The wood pulp is steeped in sodium hydroxide and then reacted with carbon disulphide to convert it to cellulose xanthate. The xanthate is dissolved in a sodium hydroxide solution to yield a viscous, golden coloured liquid which is commonly called viscose.

The viscose is de-aerated and filtered. It is then extruded through precious metal spinnerets into a spinbath consisting of sulphuric acid, sodium sulphate and zinc sulphate. The acid reacts with the sodium hydroxide in the viscose to cause precipitation of the cellulose xanthate. The acid also reacts with the cellulose xanthate converting it back to cellulose.

While the newly formed fibre is still in a plastic state it is stretched to increase the orientation of the cellulose molecules with the axis of the fibre and encourage crystallisation. The fibre may then be cut into lengths to form staple fibre or it may be kept as continuous filament or tow depending on the design of the spinning machine and the product required.

In the remainder of the process the fibre is washed to remove non-cellulose products of the reaction such as sodium sulphate and hydrogen sulphide, finished with lubricants and anti-stats to aid downstream processing and dried.

Modern viscose plants are designed to recover as much of the by-products of the process as possible. This is essential to avoid environmental pollution and to ensure the safety of the workforce and surrounding community. Better recovery and recycling of by-products can also give a positive economic benefit.

Viscose is not seen as appropriate for the invention as it has low wet strength and low wet modulus leading to high wet elongation.

Modal fibre is a high wet modulus fibre produced using a modified version of the viscose process. An additive is mixed with the spinning solution which slows down the regeneration of the cellulose during spinning. Together with modified spinbath and viscose composition, the additive allows the fibre to be stretched to a much greater extent than normal viscose. This gives a fibre with a higher orientation which is stronger than viscose and has a modulus closer to that of cotton. Modal fibre is often used in blend with cotton to give softer fabrics than would be made with cotton aione. It is used widely in knitted fabrics for lingerie and ladies apparel.

At the plant of Lenzing Aktiengesellschaft, located in Lenzing, Austria, a pulp mill and the viscose and modal production are linked together so that undried wood pulp is fed directly to the viscose making stage. The non-ceilulosic parts of the wood used in the pulp mill are incinerated and used to generate the power used by the pulp mill and most of the power for the viscose and modal process. Further chemicals are recovered before incineration such as acetic acid, xylitol or wood sugar and furfural. Xyiitol is used as a low calorie sweetener.

The newest of the three main manmade cellulosic fibres is lyocell. It is produced by a solvent spinning process. The solvent is an amine oxide, which is non-toxic. A slurry of cellulose in a mixture of amine oxide and water is prepared. Water is removed from the slurry by evaporation and as the water content decreases, the cellulose dissolves in the amine oxide producing a solution which is a viscous liquid above 80°C. The solution is extruded through spinneret holes into a water bath. The solvent is diluted by the water and the cellulose precipitates to form a fibre. In the remainder of the process, the fibre is washed to remove any amine oxide solvent, cut into staple fibre, finished with a lubricant and anti-stat and then dried.

The amine oxide solvent is recycled in a closed loop in the factory. Recovery rates of greater than 99.5% are achieved. Recycling of the additive means that the effect of the process on the environment is very low. It is also essential for the economics of the process.

Lyocell is much stronger than viscose and is stronger than cotton in both the wet and the dry state, it is used in apparel, home furnishings, workwear and nonwovens. Over 90% of the world's lyocell production is produced by Lenzing Aktiengesellschaft, Lenzing, Austria, and branded TENCEL®.

The support for the growth of marine organisms can be produced from manmade cellulosic staple fibre which has been spun into a yarn by any conventional spinning method, it may also be produced using manmade celluiosic continuous filament yarn.

Therefore in a preferred embodiment of the invention the fibers are staple fibers. Staple fibers are beneficial due to their many fiber ends, and also due to the fibrillation of the fiber surface; both properties allow a strong fixation of the marine organisms. The thickness of such staple fiber yarns usually is measured as yarn number. While in principle a broad range of yarn thickness is suitable for the purposes of the present invention, a thickness of between Nm 5 and Nm 20 is preferred, in particular preferred are yarns with from Nm 6 to Nm 15. Nevertheless also continuous filaments are suitable for the invention; suitable filament yarns may consist of 20 to 200 or even more individual filaments per yam.

A rope or twine can be produced by twisting together a multitude of manmade celluiosic yarns constructed from staple fibres or continuous filament. A rope may be produced by first twisting yarns together to produce an intermediate folded yam and then twisting together a number of intermediate folded yarns to produce a rope of the desired linear density.

A rope or twine may also be produced by braiding manmade celluiosic yarns together.

In a preferred embodiment the rope of the invention further comprises a second celluiosic fibre such as cotton, modal or viscose fiber. in another preferred embodiment the rope of the invention further comprises a biodegradable polymeric fibre such as polytactic acid fibre suitable for use as a support and growth medium for the marine organisms.

The modal, viscose and biodegradable polymeric fibers can be used in the form of staple fibers or continuous filaments; the skilled in the art may choose the form most suitable for the individual application. Even bicomponent yarns consisting of or containing staple fibers and filaments of the above mentioned materials are possible and are within the scope of the present invention. The rope according to the invention preferably consists of folded yams or folded and twisted yarns. It preferably shows a thickness of between 3 and 30 mm, more preferably between 3 and 20 mm.

Ropes or twines produced from manmade cellulosic fibres can be used as direct replacements for the synthetic or cellulosic ropes or twines currently used.

Therefore another aspect of the invention is the use of the rope as described above as a support and growth medium for marine organisms in one out of the group containing the following culture methods: Bouchot culture, long line marine growing culture, raft marine growing culture, intertidal pole marine growing culture, stake marine growing culture, on-bottom marine growing culture or any combination of these culture methods.

Preferably the rope is used in the form of a mesh. The term "mesh" for the purposes of this invention shall include nets as well.

Manmade cellulosic ropes and twines may be used in the Bouchot culture method as an alternative to coir ropes used to collect mussel spats and to support the growth of mussels.

Manmade cellulosic ropes and twines may be used in the stake culture method as an alternative to the polypropylene ropes between bamboo poles.

Manmade cellulosic ropes and twines may be used in the long line culture method for the horizontal ropes and for the droppers that support growing mussels and for the anchor ropes.

A mesh may be produced by knitting manmade cellulosic yarns. A mesh of this type can be used in the raft culture method by anchoring the mesh to the sea bed.

Knitting on a circular knitting machine with manmade cellulosic yarns can be used to produce a sock like tube. Tubes produced in this way can be used in long line culture as a sock to support the mussel spats during their initial period of growth prior to attachment to the vertical ropes.

In each method, seeds of marine plants are adhered to or entangled in the rope twine or mesh according to methods already known in the art for synthetic fiber materials.

In each method eggs of molluscs or other marine organisms are adhered to or entangled in the rope twine or mesh.

There are many different methods of using textile structures as a support for the growth of marine organisms. The important feature of the present invention is that the textile structure is made using manmade ceiiuiosic fibres. This gives the advantage that any of the textile structure which is released into the environment due to accident, storm damage, negligence or any other cause will degrade in a reasonable time and not leave non-degradable residues.

The method of using manmade ceiiuiosic textile structures in marine culture may be varied to suit the particular organism, the geography of the location, the methods normally used and personal preferences of the operator.

There are many techniques used for growing mussels worldwide, and examples are given below:

Bouchot (or intertidal Pole Culture)

The oldest and main method used in France on the Atlantic Ocean and English Channel.

Mussel spats are collected on ropes made of coir. These spat bouchots are situated offshore and consist of parallel rows of poles with horizontal coir ropes for collecting seeds. When the seeds are a few months old, they are removed from the ropes, placed in mesh tubes and transferred to bouchots for growth. Ropes with spats attached are wound around large vertical poles (bouchots) in the intertidal zone. The mussels are harvested from each pole annually.

Stake Culture

Mussels grown on bamboo poles, staked in a circle and tied at the top to form a wigwam structure. Mussels settle on the submerged stakes.

A variation on this is where two polypropylene ropes, 2 metres apart are tied to the bamboo poles in a zigzag manner.

On-bottom Culture

Widely used in Netherlands, Denmark and Germany. The culture is based on the principle of transferring seeds from areas of great abundance where growth is poor to culture plots in lower density to obtain better growth.

Long line Culture

This is the most successful method used in open sea mussel farming. A rope is stretched horizontally near the water surface and maintained 1-2m from the surface with buoys. Mussels are grown on vertical ropes known as "droppers" which hang from the horizontal rope for a length of ~4m. Mussel seeds are collected from natural beds and transplanted onto the ropes into a continuous sock-like cotton tube, which is approximately 17.5cm in width. Small mussels stripped from the collection ropes are inserted and the sock is wound around the dropper. The mussels grow and attach to the ropes using their byssal threads and the cotton sock slowly disintegrates and fails away. The droppers are placed a minimum of 0.5m apart and have at least 4m of free space from the bottom. Anchor ropes extend from the end of the horizontal ropes to anchors buried in the mud at the bottom.

Raft Culture

Similar to long line in that the mussels are suspended from the raft instead of the long lines. The raft itself is anchored to the seabed removing the need for several anchor systems. Long line culture however, created less visual impact and the droppers can be spaced further apart to maximise the use of available phytoplankton.

In general the following steps will be included in most methods:

The rope, twine or mesh is weighted at one end and lowered into the culture site.

A float is attached to the rope, twine or mesh at the opposite end to the weight

After an appropriate time to allow growth of the organisms the rope, twine or mesh is raised and the newly grown marine organisms are separated from it.

The rope, twine or mesh is retained for disposal at an appropriate place by composting.

If the rope, twine or mesh is accidently released from its site due to storms or similar events, it will decompose in the seawater in a reasonable time.

The rope, twine or mesh can be used as a growing medium for marine animals such as mussels and other molluscs.

The rope, twine or mesh can be used as a growing medium for edible seaweed.

The invention will now be illustrated by examples. These examples are not limiting the scope of the invention in any way. The invention includes also any other embodiments which are based on the same inventive concept

Example 1

Lyoceil fibre of 1.7dtex and 38mm cut length was subjected to a marine biodegradation test according to ASTM D6691 (2009) "Standard Test Method in Determining Aerobic Biodegradation of Plastic materials in the Marine Environment by a Defined Microbial Consortium in Natural Seawater Innoculum (2009)"

The test was carried out in triplicate, incubating at 30°C (+-2°C) for a total of 63 days duration.

Biodegradation is deemed to be valid if >70% of a reference material (natural cellulose powder - Avicel) is degraded at test end.

After 28 days iyocel) had 41% degradation and after 63 days 96.3%.

Lyocell was therefore awarded the Certificate and Use of "OK Biodegradable Marine" Conformity Mark (No. 016-2042-A) issued by AIB-Vincotte International.

Example 2

Modal fibre of 1.7dtex and 39mm cut length was subjected to a marine biodegradation test according to ASTM D6691 (2009) "Standard Test Method in Determining Aerobic Biodegradation of Plastic materials in the Marine Environment by a Defined Microbial Consortium in Natural Seawater Innoculum (2009)"

The test was carried out in triplicate, incubating at 30°C (+-2°C) for a total of 28 days duration.

Biodegradation is deemed to be valid if >70% of a reference material (natural cellulose powder - Avicel) is degraded at test end.

After 28 days modal had 88.2% degradation; after 63 days it was 100% degraded.

Modal was therefore awarded the Certificate and Use of "OK Biodegradable Marine" Conformity Mark (No. 016-2042-A) issued by AIB-Vincotte International. Example 3

A net was constructed from Nm 10 lyocell yam, made of lyocell staple fibers with single fiber titer 1,3 dtex,, combining into 3-strands (diameter 4mm) and knitting the nets out of that on a RL~warp kitting machine RS8 EL6M 50", 18E.

This net can be used as a growing medium for marine cultures.

Example 4

A lyocell yarn was produced in Nm10. The yarn was then folded to produce Nm 10/7 to produce a twine of diameter 4 mm. That twine showed a breaking load of 0,2 kN.

This twine is suitable for subsequent use as a support structure in a marine environment.

Example 5

A lyocell yam was produced Nm8 and folded to produce a twine in Nm8/7. This 8/7 twine was then twisted together as 3 strands to produce a lyocell rope of 16mm diameter.

This rope was now suitable for use as support rope for mussel growing using long line or raft culture production.