GB2505075A

GB2505075A - A culture medium made from wood fibre chemically bonded to carbon black

Info

Publication number: GB2505075A
Application number: GB1312179.3A
Authority: GB
Inventors: Robert Lavery; Mark Hamill
Original assignee: Westland Horticulture Ltd
Current assignee: Westland Horticulture Ltd
Priority date: 2013-07-08
Filing date: 2013-07-08
Publication date: 2014-02-19
Anticipated expiration: 2033-07-08
Also published as: GB2505075B; GB201312179D0

Abstract

A homogeneous culture medium for plants comprising microporous wood fibre particles chemically bonded to carbon black particles having a particle size >10Âµm, obtained by grinding and binding the particles together under pressure at elevated temperature in the presence of steam. The elevated temperature may be above 100ÂºC. The wood fibres may be at least partially rolled up on themselves. The carbon black particles are chemically bonded to the wood fibre particles, and will not separate through normal handling. That is, the colouring effect of the carbon black particles is 'permanent'.

Description

Wood Fibre Process The present invention relates to a culture medium for plants based on wood fibres.

Culture media containing wood fibres are known from FR2248781. EP0147349 uses a culture medium based on wood fibres obtained directly after grinding and without undergoing any subsequent treatment However, such wood fibres still tend to clump together so that spaces between the fibres are permanently reduced, which hinders the growth of roots.

EP0947130 describes a culture medium for plants based on wood fibres obtained by grinding and steam cooking the fibres so that they at least partially roll up on themselves as the beginnings of twists or spirals, and are thus capable of hooking into one another. EP0947130 also describes a method for obtaining such a culture medium to give it a structure that is naturally ventilated based on sufficient spaces being available based on the uibres being entangled.

EP0947130 also discusses the possibility of adding a colouring agent to the culture medium. However, such colouring agents are merely mixed with the wood fibres and will easily be displaced during use, especially being absorbed by users' hands or gloves. For that reason, colouring of culture medium is rare in practice, such that commercial culture media are generally provided only as their tnatural' colouring.

It is an object of the present invention to provide a distinctly coloured culture medium for plants with improved handling properties.

Thus, according to one aspect of the liresent invention, there is provided a homogeneous culture medium for plants comprising microporous wood fibre particles chemically bonded to carbon black pa rdel as having a particle size >lOilm, obtained by grinding and binding the particle.s together under pressure at elevated temperature in the presence of steam.

In this way, the carbon black particles are chemically bonded to the wood fibre particles, and will not separate through normal handling. That is, the colouring effect of the carbon black particles is permanent', as the carbon black particles fit perfectly into the spaces created between the microporous wood fibre particles, and along with the elevated temperature and steam cooking, are chemically bonded thereto.

The wood fibre particles may be obtained from any suitable source, including but not limited to mechanical shearing of wood chips. Wood chips or other suitable wood pieces can be steamed at pressures of about 6 bar to 10 bar, and at temperatures of about 1SOOC to 1800C. After cooking, the chips or particles become brittle and grinding can be carried out by means of rotating discs (for example a rotor disc and stator disc) which shears the chips into fibres.

The carbon black particles can be obtained from any suitable source of carbon black, many forms of which are commercially available either directly as particles having a particle size <10km, or by grinding a suitable source of carbon black into particles using grinding methods known in the art.

The wood fibre particles and carbon black particles can be ground and bonded together based on an elevated temperature, generally being above ambient temperature and optionally above 100°C, and the presence of steam. The skilled man is aware of various apparatus and methods for achieving such grinding and binding based on such parameters, including mechanical operations and operators.

This could inc]ude using rotating drums, screws or discs, optionally along a suitable channel(s) such as a barrel or multiple barrels) and optionally constricted and elongate. Generally) there is at least one inlet, optionally one inlet per ingredient, and at least one outlet.

Tile present invention able to provide a homogeneous culture medium, wherein the binding of ti-1e cCi Hon black particles to and within the wood fibre particles ensures a uniform and homogeneous colouring of the wood fibre particles. It also ensures that the material is colour secure, with no issues concerning colour fastness.

Colour fastness in very important in gardening and horticulture. It avoids colour being deposited upon the handling of the wood fibres by a user. It also reduces the potential for spoiling of packaging materials. Furthermore, it reduces the potential for staining of surfaces upon which pots or other containers containing the culture medium may be placed. That is, the watering of the culture medium of the present invention in such pots etc. does not release the carbon black particles from the wood fibre particles, which would otherwise result in a coloured and usually staining water seeping therefrom. The staining of flagstones, patios, wood decking etc. by watering plant pots containing culture mediums with conventional colouring agents is a common problem.

The present invention also provides that there are reduced or no issues with fugitive dust emissions that might impair handling or product performance in relation to porosity.

In particular, the present invention provides a chemical/mechanical process whereby the pore structures that are developed and multiplied by the combination of the mechanical fibre creation and the porous optimization in the presence of steam, allows the chemical distribution of the fine carbon black particles within the microporous structures of the created wood fibres.

Optionally, the culture medium of the present invention further comprises a culture fertilizer.

The microporous nature of the coloured wood fibre-based culture medium, and the presence of carbon, also acts as a site for beneficial microbes such as mycorrhizac fungi and Rhizobia [nitrogen fixing) bacteria to thrive, which promote root development and plant growth in natural symbiosis when planted.

Carbon black in particular improves the water-holding cation exchange capacity or CEC of wood fibres, because of its minute particle size (generally being <lORm] after high shear mixing and homogenization, which gives each carbon black particle an expansive surface area. Due to the unique microporous structure, this enables the S carbon black particles to have a very large affinity for retention of water and vital plant nutrients.

According to a second aspect of the present invention, there is provided a method of forming a homogeneous culture medium for plants comprising microporous wood fibre particEes chemically bonded to carbon black particles having a particle size >lORm, comprising the steps of grinding and binding the particles together under elevated temperature in the presence of steam.

Optionally, the method of the present invention further comprises drying the wood fibre particles prior to use. The wood fibre particles may be dried using any suitable drying process or dryer, generally involving an elevated temperature and optionally a vented fluid such as air thereacross.

Various modifications and variations to the described embodiments of the invention will be apparent to those skilled in the art without departing from the scope of the invention as defined herein. Although the invention has been described in connection with specific preferred embodiments) it should be understood that the invention as defined herein should not be unduly limited to such specific embodiments.

Claims

Claims 1. A homogeneous culture medium for plants comprising microporous wood fibre particles chemically bonded to carbon black particles having a particle size >10im, obtained by grinding and binding the particles together under pressure at elevated temperature in the presence of steam.
2. A culture medium as claimed in claim 1 wherein the wood fibre particles are obtained from mechanical shearing of wood chips.
3. A culture medium as claimed in any one of the preceding claims further comprising a culture fertiliser.
4. A culture medium as claimed in any one of the preceding claims obtained by defibration of the wood fibre particles.
5. A culture medium as claimed in any one of the preceding claims wherein the elevated temperature is above 1OtPC.
6. A culture medium as claimed in any one of the preceding claims wherein the wood fibre particles are at least partially rolled up on themselves.
7. A method of forming a homogeneous culture medium for plants comprising microporous wood fibre particles chemically bonded to carbon black particles having a particle size >lORm, comprising the steps of grinding arid binding the particles together tinder elevated temperature in the presence of steam.
H. A method as claimed in claim 7 further comprising drying the wood fibre particles prior to use.
9. A method as claimed in claim 7 or claim 8 wherein the grinding aiid binding steps are provided by shear mixing and homogenizing the particles together.
10. A homogeneous culture medium substantially as described herein.
11. A method of forming a homogeneous culture medium comprising microporous wood fibre particles chemically bonded to carbon black particles having a particle size >lORm substantially as described herein.