WO2004078892A1

WO2004078892A1 - Coir pith

Info

Publication number: WO2004078892A1
Application number: PCT/GB2004/000962
Authority: WO
Inventors: Geoffrey Nutland
Original assignee: Dainton Limited
Priority date: 2003-03-07
Filing date: 2004-03-08
Publication date: 2004-09-16
Also published as: EP1608724A1; GB0305191D0

Abstract

A process for the production of a coir pith product comprises forming the coir pith into a dust with the desired particle size range and forming the dust into granules. The invention also provides a coir granule formed from a coir pith dust. Preferably the coir is in admixture with at least one of wood sawdust and chopped straw.

Description

COIR PITH

Field of Invention

The invention relates to coir pith which is the residue from coconut husk after the fibrous material is removed for rope manufacture and the like.

Background to the Invention

Coir pith is normally dried and compressed into briquettes, blocks or bales (hereinafter collectively referred to as "briquettes") for export to a country such as the United Kingdom by the producers.

The briquettes are reconstituted by the addition of large volumes of water to produce a product for use as a peat substitute, in GB-A-2 308 538 there is disclosed a process for reconstituting the briquettes back into the original dry form from the briquettes, this process is carried out by converting the coir pith dust by a milling, cutting, chopping, hammering or flailing process without the use of water as the reconstituting agent.

Statements of the Invention

According to the present invention there is provided a process for the production of a coir pith product, the process comprising forming the coir pith into a dust with a desired particle size range and forming said dust into granules.

The starting point for the process is coir pith which may be utilised as the untreated residue from coconut husks. As an alternative the coir pith may be a compressed material. For instance it may be a material formed by drying and compressing the coconut husk residue into briquettes, blocks or bales or other bulk form. In the process of the present invention the coir pith can be processed in a wet or dry state using mechanical methods to reduce the material down to the required size prior to granule forming. These methods include any one or more of milling, grinding, liquidising, pulverising and effecting changes of temperature.

Preferably the coir pith is in a milled form.

Preferably the coir pith has a particle size of up to 5mm.

Preferably the coir pith is in a mixture including at least one of wood sawdust and chopped straw. More preferably the amount of wood sawdust and/or chopped straw present is up to 20% by volume.

The coir pith dust having the required particle size range is then converted into granules. Various methods may be used examples of which are as follows:-

1. The coir pith dust is mixed to a paste with or without addition of agents. It is then extruded through a screen to produce a desired granule size. The density of the granule will depend, at least partially on the pressure in the extrusion device as well as the liquid content. Air can be incorporated into the coir pith dust to alter the density and structure of the granules, or to assist in the extrusion process. The extruded paste is subjected to a drying process to produce a finished product with absorbent properties.

2. The coir pith dust is pressed within a chamber or series of rollers to form a compressed material having the appropriate integrity for granule maintenance. Liquids of various compositions and/or assisting agents may be incorporated for specific purposes.

3. The coir pith dust, optionally mixed with agents and liquids, is pressed through a forming die to produce the required granule size. This method can utilise heat generated by friction when pushing the material through the die. It may be dried from heat generated internally or externally. Drying can be achieved in the context of a cooling process as well as by the use of heat.

In any of the above methods, use may be made of heat in the form of, for instance, a cooking process, in order to assist in the formation of the granules.

The present invention also provides a granular coir pith product formed from coir pith dust having a desired particle size range.

In addition the present invention provides a method of fluid absorption comprising contacting together a fluid and the granular coir product of the invention (or formed by the method of the present invention).

The highly effective absorption properties of the granular coir pith may be utilised in many different situations including the following:-

(a) cat litter and other types of pet bedding and litters;

(b) an absorbent cleaning agent for use in, for instance, workshops, kitchens, highways and public areas;

(c) in the absorption and fixing of various chemical materials;

(d) as a carrying agent for use in a variety of situations including the holding of enhancing agents, repellents and binders for various uses including agricultural, industrial and domestic;

(e) to form masking and odour control agents for dealing with both natural and non-natural (or chemical) odours and fumes. The present invention also provides a coir granule formed from coir pith dust.

Preferably the coir granule comprises a mixture of coir and at least one of wood sawdust and chopped straw. More preferably the wood sawdust and/or chopped straw is present in an amount up to 20% by volume.

Further Details of the Invention

The term "granules", as used herein, is intended to cover granules and granular-like materials such as grains and pellets.

Although coir pith dust has a very high absorbency capability, it is a dust and this imposes certain restrictions on its use as loose absorbent material. By contrast the granular product produced by the process of the invention is dust free and therefore usable in environments where the use of dust is not permitted or advisable. It is found that the granules produced by the process of the present invention are, as with coir pith dust, highly absorbent.

In a process in accordance with the present invention, granules of different sizes and properties may be produced for various uses and applications, the parameters including the following:

(a) size;

(b) degree of compaction and density;

(c) surface area;

(d) incorporation of agents for particular purposes, including binders, digesters and surfactants;

(e) incorporation of fillers and colorants to change appearance and weight; (f) texture including texture of the whole granule and also that of the surface of the granule.

Examples of the Invention

The invention will now be further described, by way of examples only: Example 1

Tests were carried out to establish the required die sizes for successful absorbent pellet manufacture using a combination of compressed organic materials.

Two samples were prepared using coir milled as described in GB-A-2308538 to a mixed particulate size varying from fines up to a fibre length of about 4 to 5 mm. This milled coir was then mixed with alternative materials (straw and wood sawdust) both of which are prepared to broadly similar dimensions.

The coir/sawdust combination was then treated by the addition of a natural material (code A001 Clumping agent) to promulgate clumping of the pellets when in use.

The mixtures were then pelleted using an industrial pellet mill (model CL3) with the addition of further moisture as necessary. It was found that, using a die with a 4.8mm hole diameter a pellet length of 13mm resulted in successful pellet manufacture whereas a pellet length of 19mm blocked the die.

The pellets produced were of good and consistent diameter and were of a sufficiently firm texture and build to withstand moderate pressure. Colouration was slightly random mottled dark to mid-brown.

In absorbency tests, a measured amount of pellets were placed on a shallow container to which twice the volume of water was added. Comparison control samples were used having an identical volume of similar pellets manufactured solely from wood sawdust, again placed on a shallow container with twice their volume of water.

Observations were then made to determine the speed and completion of absorbency. These were the same for the two coir-based products, both of which were noticeably quicker and more effective than the pure wood sawdust pellets.

Accordingly it was concluded that successful pellet manufacture of coir-based materials could be achieved using standard industrial pellet presses. Furthermore it was possible to compute the likely die specifications for ongoing production.

Example 2

Pellets of pure coir were produced on a flat bed die, having pre-conditioned milled material with steam prior to the pressing process.

The coir/chopped straw combination comprised 33.32 litres coir (83.3% by volume) and 6.68 litres straw (16.7% by volume), a ratio of coir to straw of 5:1 and a total volume of 40 litres.

The coir/sawdust combination comprised 32 litres of coir (79.6% by volume) and 8 litres sawdust (19.9% by volume), the ratio of coir to sawdust being 4:1. A clumping agent (code A001) was added in the amount of 0.2 litres (0.5% by volume). The total volume of the mixture was 40 litres.

The coir/straw mixture had a moisture content of 18.7% and the coir/wood sawdust mixture had a moisture content of 16%. The moisture level of the coir was between 30 and 35%.

Relatively high pressures were required to get the material through the die, as compared with those for a coir/sawdust mix. The resultant pellets were of a dark brown colour, highly polished and were rather brittle, having a length up to 8 cm. Using a mixture of coir pith and pine sawdust in a ratio of 50%/50% and with the sawdust moisture level at approximately 16%, pellets were prepared using the flat bed die. The pelleting process required less pressure and generated less heat than that for the pure coir product. The pellets were of a mottled mid-brown appearance with a polished outer surface. The average length was from 2 to 3 cm. The pellets could be broken with moderate force and pellet cross-section observations suggested a fairly even material mix.

Pellets were subjected to absorbency testing using the method of a leading pellet manufacturer according to which pellets are placed in a glass container and twice the volume of clean water is added. In the original tests one litre of pellets were added to two litres of water but in these tests smaller quantities were used because of the limited volume of pellets available.

Where the pellets were made of pure coir the uptake of water was quite slow over a period of some 30 minutes, with very little expansion of the pellet. Even after 30 minutes the pellets still retained their original shape, albeit slightly enlarged, and free water was still present in the container.

With a 50/50 coir/sawdust mix formed from one measure of pelletes and two measures of water, the pellets started to expand in 10 seconds and the rate of expansion increased as the pellets expanded. After 25 seconds the expansion was progressing rapidly and the level of free water was dropping rapidly. All free water was absorbed after one minute 25 seconds.

The pellets had all expanded to the same degree, with no unexpanded pallets present. The resultant material resembled a magnified version of the original pellet mass, a mottled mousse of sawdust and coir mixture that was quite moist to the touch but not "sopping wet". No free water was present although water could be released from the mousse by application of pressure (squeezing by hand). Where tests were carried out on a similar 50%/50% coir/sawdust mixture but using larger quantities (one litre of pellets and two litres of water) the results were very similar. However, the absorption process was quicker with all the water being absorbed in 55 seconds. For comparison purposes, the test was applied to pure sawdust pellets. One measure of pellets was added to two measures of water in a large open bowl. The pellets began to expand in 20 seconds and the rate of expansion increased slightly as the body of the pellets expanded.

At 50 seconds, the expansion was continuing steadily, this rate being maintained for three minutes. After this time a little free water, judged to be between 5 and 10% of the original volume, was observed in the base of the container.

It was apparent that the pellets near the upper surface of the bowl had not expanded at the same rate as those below, suggesting that they need to be in contact with free water for a period of time in order to commence absorption, as opposed to drawing moisture from contiguous pellets. All free water was absorbed after four minutes.

The pellets had all expanded to create a mousse of sawdust that was extremely wet to the touch and, although no free water was evident, it required very little pressure to squeeze out water. It was unlikely that the pellets could have absorbed any more water.

The addition of coir to sawdust increases the speed of absorption, compared to sawdust pellets, by a factor of at least three.

Although, in the examples above, pure coir pellets seem less effective than those made of a mixture of coir and sawdust, different results may be obtained by, for instance, reducing die depth, increasing or decreasing bore diameter, increasing or decreasing bore count (per die) and increasing or decreasing moisture level within the coir.

Claims

1. A process for the production of a coir pith product, the process comprising forming the coir pith into a dust with a desired particle size range and forming said dust into granules.

2. A process according to Claim 1, wherein the coir pith is in a milled form.

3. A process according to Claiml or Claim 2„ wherein the coir pith has a particle size of up to 5mm.

4. A process according to any of Claims 1 to 3, wherein the coir pith is in admixture with at least one of wood sawdust and chopped straw.

5. A process according to Claim 4, wherein the amount of wood sawdust and/or chopped straw present is up to 20% by volume.

6. A process according to any of the preceding claims, wherein the coir pith is mixed to a paste prior to granule formation.

7. A process according to Claim 6, wherein the paste is extruded through a screen to produce a desired granule size.

8. A process according to any of Claims 1 to 5, wherein the coir pith dust is pressed within a chamber or series of rollers to form a compressed material.

9. A process according to any of Claims 1 to 5, wherein the coir pith dust is pressed through a forming die to produce the required granule size.

10. A coir granule formed from coir pith dust.

11. A coir granule comprising a mixture of coir pith and at least one of wood sawdust and chopped straw.

12. A coir granule according to Claim 11, wherein the amount of wood sawdust and/or chopped straw present is up to 20% by volume.