SK12442000A3 - Method and apparatus for preparation of mineral fibre based growth medium, a plant growth medium and use of it - Google Patents

Abstract

A process for the preparation of a plant growth medium having a density gradient, comprising the steps of providing a primary web comprising mineral fibre material and a curable binding agent, compressing the primary web in at least one longitudinally extending zone in such a manner that the applied pressure increases substantially continuously in the latitudinal direction of the zone, forming a secondary web by bringing the primary web overlap itself, optionally compressing said secondary web and curing the binding agent.

Description

Technical field

The present invention relates to a method of preparing a mineral fiber forming a plant for growing plants with a density gradient.

BACKGROUND OF THE INVENTION

It is known in the art to use products composed of a mineral fiber-containing material as a plant growth agent. These plant growth agents have the advantage that they are very porous and thus allow plant roots to obtain both the desired water and nutrition as well as air. Typically, the fibers absorb less than 5% by volume of the composition, which ideally leaves 95% by volume for roots, air, water and / or plant nutrition.

The mineral fiber-forming agent for plant growth is generally lightweight and also easy to handle and economical to transport, and is additionally sufficiently strong and chemically inert to withstand decomposition when used on the roots of a host plant for extended periods of time.

Water absorption and retention is one of the primary tasks of a plant growth agent. If the composition has a low water retention capacity, water will flow through the composition when watering and the plant will dry out between the time of watering or watering will have to be done very often, resulting in a large waste of water. On the other hand, if the plant growth composition has a high effective water retention capacity, the plant will not be able to extract water from the composition and, moreover, the roots of the plants could suffocate due to lack of air in the composition.

It is known from DK 170 034 B1 that there is a mineral fiber material forming plant growth agents, the advantage of which is the ability to retain water. These compositions have a density gradient or a roughness gradient in the direction of the product height, provided that the fibers have the highest density or the lowest roughness up and the lowest density or the greatest roughness down. In this way, the possibility of reducing the effect of attraction by capillary action has been shown. By increasing the density of the composition or reducing its roughness to a height, the pore size is generally reduced to a size which then again increases the capillary effect and thus draws water up into the composition.

According to DK 170 034 B1, such a preferred plant growth agent can be obtained by stacking and bonding a plurality of individually manufactured glass fiber layers, each having an increased surface weight or reduced fiber roughness proportional to the previous layer.

However, it is a challenging method of producing these plant growth agents. In addition, in order to obtain such a composite product from a plurality of individually manufactured layers having sufficient adhesion between said layers, it is necessary to use a plurality of binders between the layers and thus impair the ability to diffuse water between said layers and increase manufacturing costs.

US 5,009,030 discloses a similar plant growth substrate that does not contain soil, showing a controlled gradient of water to the thickness of the composition. The water retention gradient is obtained using a density gradient or a fineness gradient in the composition. Different density or fineness is obtained according to the document by stacking on it a plurality of layers of glass wool fibers, each having a different density or fineness.

Although an acceptable water retention gradient can be obtained according to US 5,009,030, the method of manufacturing it is rather difficult since several layers of mineral fiber tissue must be joined into one. In addition, these layers will have to adhere to each other in order to provide sufficient breaking strength to the layers and such placement of a binder between different layers could disrupt the movement of water and other substances across the boundaries of the layer. Furthermore, the composition itself provides only a gradual gradient of water retention and not a continuous gradient.

Accordingly, it is desirable to obtain an improved process for preparing an improved mineral fiber forming a plant growth agent.

SUMMARY OF THE INVENTION

This object is achieved by the method according to the invention, which consists in preparing a primary fiber comprising a mineral fiber and a binder which compresses the primary fiber at least in the longitudinally extending zone in such a way that the applied pressure increases substantially continuously in the transverse direction of the zone by causing a pressure gradient in said direction, a secondary fiber is further formed by causing the primary fiber to fold itself by depositing it in a plurality of layers in the transverse direction of the secondary fiber and separating the secondary fiber to form a plant growth agent.

The invention is based on the recognition that by applying pressure to the primary tissue it is possible to substantially maintain compression until the binder in the composition is vulcanized or cured. Thus, it is possible to squeeze some portions of the primary tissue more than other portions to obtain compositions having different densities. In addition, knowing where the primary tissue sections are headed, when the primary tissue is formed and deposited on top of one another, it is possible to predict where the denser portion will end up in the final composition.

A typical and preferred way to force the primary tissue to store itself is by means of a pendulum divider, as is known in the art. In this way, the secondary tissue is formed by a plurality of slightly spaced layers of primary tissue that have been laid transversely to the longitudinal direction of said secondary tissue. The secondary tissue is arbitrarily compressed and the binder in the composition is vulcanized or cured. The secondary tissue thus cured can be cut into a number of compositions having virtually any desired shape.

A suitable method of depositing mineral fiber tissue using a shuttle distributor is a drawbar. described in WO 88/03509 or WO 97/03509.

With this method, one side edge of the primary tissue will eventually form the topsheet of the finished device and the opposite side edge will form the bottomsheet of the device. Therefore, by continuously compressing the primary tissue continuously with increasing force in the direction from one edge to the opposite one, it is possible to obtain a density gradient to the height (bottom to top) of the final composition.

The process according to the invention is simpler with respect to the prior art in terms of the number of process steps. Therefore, it is now possible to carry out the process in a continuous manner and no layering and / or bonding is necessary. Moreover, the advantage of the method according to the invention is that the absolute density and the density gradient diagram can be individually controlled only by controlling the applied pressure.

The compression may be accomplished by any means capable of causing a substantially continuous pressure gradient. The pressure may be e.g. by means of belt conveyors, one or more cylindrical mills having a more or less angular axial suspension relative to the surface of the primary tissue and / or by means of cylinders having a conical shape.

Compression of the tissue by means of a plurality of rollers is preferred. Preferably, rollers are used which each have a separate suspension. By using a plurality of individually hinged rollers, it is possible to control the pressure force applied by each means separately and thus it is also possible to immediately switch between pressure diagrams and / or compressed band assemblies.

It is particularly suitable to use rollers having a diameter of from 5 cm to 70 cm, more preferably from 15 cm to 50 cm and most preferably from 20 cm to 40 cm. If the rollers are too small, the primary tissue will form at the head of the rollers and the process will eventually have to be stopped for cleaning. Too large rollers are generally more difficult to handle.

Any number of rollers may be used to compress the primary tissue, but it has proven to be particularly advantageous to use rollers having a width of from 30 mm to 60 mm, more preferably from 50 mm to 300 mm, and most preferably from 80 mm to 150 mm.

The rolls may be arranged close together or longitudinally spaced apart, in both the longitudinal and transverse directions of the tissue. It has proven to be particularly advantageous to place the rollers in two rows arranged one after the other in the longitudinal direction of the primary tissue, the rollers being placed close together in the transverse direction of the tissue with a gap between the rollers in such a way that cylinders from the second row.

In accordance with the preferred method according to the invention, it has proven suitable to use rollers or rolls which are somewhat flexible. Suitable rollers include a flexible suspension and / or a flexible coating, e.g. like tires. Thus, the rollers are able to compensate for the unevenness of the primary tissue. Furthermore, by using rollers having such a resilient surface or suspension, it is possible to reduce the damage caused to the primary tissue by compression in terms of minor damage or shredded fibers.

However, it has proven to be particularly suitable to use pressure-carrying rollers having a smooth non-adherent surface, e.g. of metal or polytetrafluoroethylene.

In this way, it is possible to achieve that the primary tissue does not adhere to the rollers, which could otherwise cause a serious problem in the pre-compression step.

The compression may be performed during one or more operations using a plurality of compressed means. The density gradient diagram may be linear or non-linear depending on the shape or operation of the compressed means. The surface of the compressed means may be smooth or have a sample.

Naturally, it is possible to compress only a part or a few parts of the primary tissue e.g. with the result that there is a greater density gradient in the means towards the height. In addition, the secondary tissue may be cleaved into multiple means having one or more density gradients. However, it is preferable to cause a density gradient over the entire width of the primary tissue, i. by compressing the entire tissue, thus creating a density gradient over the entire height of the secondary tissue.

It should be noted that the benefits of the present invention can be obtained by any method of the aforementioned kind, wherein at least a portion of the primary tissue is compressed before the primary tissue, e.g. either by a pendulum divider or by prior cutting into portions as described in EP 0 297 111 B1, forced to be interleaved to form a secondary tissue which is arbitrarily compressed and vulcanized, and where a substantially continuous density gradient towards the height of the finished composition can be obtained.

When the tissue is compressed using rollers, it is preferable to compress the primary tissue in the range of 0 kg / m to 400 kg / m (roll width), more preferably from 0 kg / m to 250 kg / m and even more preferably from 0 kg / m to 100 kg / m at one edge of the zone and in the range of from 500 kg / m to 3000 kg / m, preferably from 750 kg / m to 2500 kg / m and even more preferably from 1000 kg / m to 2000 kg / m at the opposite edge. Compressing the primary tissue using a continuous pressure gradient yields a product not only of the desired density. By applying pressure within the above ranges, it is possible to distribute or crush a plurality of fibers when the highest pressure is applied, and substantially no fibers break down or crush when the lowest pressure is applied. This also provides a continuous fiber roughness gradient, which even increases the water retention capability of the product in terms of controlled capillary effect.

Suitably, the resulting density of the composition is 40 kg / m ³ to 180 kg / m ³ , more preferably 50 kg / m ³ to 120 kg / m ³ on the top surface and 10 kg / m ³ to 120 kg / m ³ , more preferably 30 kg / m 3 ³ to 120 kg / m ³ on the bottom surface, and the average density of the composition is 30 kg / m ³ to 180 kg / m ³ , more preferably 30 kg / m ³ to 120 kg / m ³ and even more preferably 40 kg / m ³ to 80 kg / m ³ .

According to a preferred method of the invention, 0.5% to 10% by weight, more preferably 0.5% to 5% and even more preferably 1% to 3% by weight are added to the primary tissue. binder. All percentages by weight of binder are based on the final formulation.

In addition, a suitable method according to the invention is to compress the secondary tissue in the longitudinal direction, i. as described e.g. in US 4,632,685, CH 620,861 or US 2,500,690.

Although the composition obtained by the process of the invention is particularly suitable for use as a plant growth composition, it can also be used as thermal or acoustic insulation.

The invention also relates to a mineral fiber forming a plant growth agent obtainable by the process according to the invention.

The composition obtainable by the process of the present invention is superior to the prior art compositions in that it does not involve any substantial surface collection and that the density gradient is substantially continuous rather than sequential.

The compositions of the invention can be adapted to meet almost all requirements in terms of water collection, air penetration and strength.

The compositions according to the invention can therefore be manufactured to adapt to the needs of a wide variety of plants including tomatoes, cucumbers, roses and kalanchoe.

The invention furthermore relates to the use of a composition obtainable by the process according to the invention for the cultivation of plants and in particular for the aforementioned plants, as well as an apparatus for carrying out the process according to the invention.

Therefore, the device according to the invention is characterized in that it comprises means for securing the primary tissue containing the mineral fiber and binder, means for compressing the primary tissue in at least one longitudinally extending band of said means which are capable of compressing the primary tissue in such a way increases substantially continuously in the transverse direction of the band to cause a compression gradient in said direction, means for generating secondary tissue of said means capable of causing primary tissue to fold itself by folding into a plurality of layers in the transverse direction of secondary tissue, and means for splitting secondary tissue to form a plant growth agent.

The invention will be further explained by means of the figures.

Figure 1 shows how the density changes in the width direction of the primary tissue after compression using a plurality of rollers compressing in the load axis from 0 kg / m up to 1000 kg / m for each roll and wherein each roll has a width of 100 mm.

After formation of the secondary tissue by means of the pendulum divider, the substantially continuous weight gradient increases towards the height of the secondary tissue. Therefore, compositions having this substantially continuous density gradient can be cut off from the secondary tissue.

Figure 2 shows a composition according to the invention having a relatively low bottom density, a relatively high top density and a substantially continuous bottom-up density gradient.

Figure 3 shows the steps of manufacturing secondary tissue from which the means are finally cut. The first step involves forming the mineral fibers from the mineral fiber melt produced in the furnace 1 and which is fed from the furnace nozzle 2 to all four rapidly rotating spinning wheels 3 to which the melt-forming mineral fiber is added as a mineral fiber melt stream. Since the mineral fiber stream in the form of the melt 4 is fed to the spinning wheels 3 in a bow-shaped direction, at the same time the gas flow is proportionally supplied to the rapidly rotating spinning wheels 3 in their axial direction, causing single mineral fibers or bundles or tufts of mineral fibers 5 to be formed. 3. The gas stream may produce a so-called gas stream heat treatment, normally a gas stream cooling. The mineral fiber shred 5 accumulates on the continuously functioning first belt conveyor 6 to form a primary mineral fiber tissue 7. The thermosetting binder is optionally added to the mineral fiber primary tissue 7 either directly into the mineral fiber primary tissue 7 or in the ejection phase. mineral fibers from spinning wheels 3, ie. in the formation of individual mineral fibers. The binder may of course be any known binder for use in combination with mineral fibers, i. also a thermoplastic binder. The first belt conveyor 6, as seen from Figure 3, consists of two parts. The first portion of the belt conveyor is inclined with respect to the horizontal direction and with respect to the second, substantially horizontal portion of the belt conveyor. The first part forms the collection part, while the second part forms the transport part. Of course, this can be accomplished by other methods known in the art. Conveyor belts (belt conveyors) used to collect the fibers are suitably preferred and provided with means (not shown) that suck air through the belts to facilitate fiber layering. This increases the homogeneity of the primary tissue 7, furthermore ensuring a better fiber distribution, i. as regards the low fiber density sites having the greatest air passage through the belt, it then leads to the lamination of multiple fibers at that location, etc.

The compression of the primary tissue 7 is effected by a roller 8 which tends from one side of the tissue to the other, thus causing a continuous gradient of compression over the entire width of the primary tissue in such a way that the primary tissue 9 retains a substantial amount by pressing, i.e. more pressing on one side than on the other side. Of course, the inclination of the cylinder may be adapted to provide any compression pattern. A similar effect can be obtained using a number of rollers or strips and / or conical shaped rollers. In most cases, it is preferred to compress the primary tissue in the band along one side as much as possible while on the other hand no compression is performed. Various known means can be used, e.g. with respect to compression aids or the like, to ensure a proper density gradient maintained / obtained in the final composition.

The first part of the first belt conveyor 6 comprises, as mentioned above, a collecting part, while the second part of the belt conveyor 6 is formed by a conveying part by which the primary mineral fiber-containing tissue having a continuous compression gradient in the width direction is moved to the second and third continuously operating belt conveyors 10 and 11, respectively, which operate in synchronization with the first belt conveyor 6, which inserts the compressed mineral fiber web 9 between two adjacent surfaces of the second and third belt conveyors 10 and 11, respectively.

The second and third belt conveyors 10 and 11, respectively, are connected to a fourth belt conveyor 12 which forms a collector belt conveyor on which the secondary mineral fiber tissue 13 is collected because the second and third belt conveyors, respectively, swing over the top surface of the fourth belt conveyor 12. Thus, the secondary mineral fiber web 13 is made by aligning the primary mineral fiber web 9 when folded generally in the transverse direction of the fourth belt conveyor 12.

By producing secondary mineral fiber tissue 13 from compressed primary tissue containing mineral material 9 as shown in Figure 3, a secondary tissue is produced in which the density varies substantially continuously in height (thickness), then the lowest density is down, and the highest density is at the top. The cubes cut off from the appropriately vulcanized / reinforced secondary tissue are exceptional for use as a plant growth agent due to the controllable water retention gradient, i. improved water retention.

As used herein, the term primary mineral fiber tissue refers to a new formed mineral fiber tissue having a typical height (thickness) of from 3 cm to 7 cm that is maintained to be interleaved by a plurality of corresponding primary tissue layers, preferably formed by the same primary tissue to obtain secondary tissue. A particularly suitable method for obtaining these primary and secondary mineral fiber tissues is described in WO 97/01006.

The term water retention capability as used herein defines the water retention capability of the compositions as measured by volume percent.

The term mineral fiber forming plant growth agent as used herein includes any composition suitable as a host for plant roots, and wherein the composition comprises a significant amount of mineral fibers, suitably in an amount of from 1% to 10% by volume, more preferably from 5% to 5% vol.

The plant growth composition of the invention may contain a number of ingredients in addition to mineral fibers, e.g. lignite, clay and organic compounds such as coconut peat.

The term mineral fiber as used herein includes all types of mineral fibers produced, such as stone, glass or slag fibers, especially fibers used in materials for thermal or acoustic insulation and as fillers in cement, plastics or other materials, or those fibers which are used as a means of growing plants.

The term binder as used herein includes any material that is suitable as a binder in mineral fiber materials to the aforementioned compositions, e.g. urea-formaldehyde phenol, acrylic copolymer, resorcinol, furan, or melamine resin. These binders are added to the mineral fiber material suitably in the form of aqueous suspensions.

The invention will now be described in more detail by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a density gradient along the width of the primary tissue.

Fig. 2 shows a device according to the invention.

Fig. 3 shows a suitable method of manufacturing a plant growth agent according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

The mineral fibers are obtained by spinning in a spinning chamber and are manufactured to be placed on a belt conveyor during the formation of a primary tissue having a width of 1.8 m and a surface weight of 500 g / m ² . The binder containing urea-formaldehyde phenol in the aqueous suspension is continuously applied to the fibers in air in the spinning chamber before the fibers are laid on the belt conveyor, the binder being added in an amount corresponding to a final urea-formaldehyde phenol concentration of 3% by weight of the final composition. The primary tissue is compressed across its width by a cylindrical cylinder suspended in such a way that it presses against the tissue at one edge of the primary tissue at a pressure of 0 kg / m and a pressure of 1000 kg / m on the opposite edge of the primary tissue. two; values between the edges of the primary tissue.

The primary tissue is deposited by pendulum splitting to form a secondary tissue having a width of 2 m, the secondary tissue as seen in cross section contains approximately 12 layers of primary tissue. The obtained secondary tissue is compressed to a height of 100 mm and cured in a curing oven. Finally, a plant growth agent of the desired size is obtained from this vulcanized secondary tissue by cutting.

The plant growth composition prepared by the method of the invention has a continuous density gradient ranging from 35 kg / m ³ from below to 130 kg / m ³ above. The plant growth agent according to the invention shows no evidence of layer cleavage and has excellent water retention / diffusion capability.

Claims (13)

PATENT CLAIMS CLAIMS 1. A method of preparing a mineral fiber composition comprising a density gradient, comprising providing a primary tissue comprising a mineral fiber material and a binder, compressing the primary tissue at least one longitudinally extending zone in such a way that the applied pressure increases substantially continuously in the transverse direction of the band to cause a pressure gradient in said direction, forming a secondary tissue by forcing the primary tissue to fold itself by stacking itself in a plurality of layers in the transverse direction of the secondary tissue, and splitting the secondary tissue to form a plant growth agent. Method according to claim 1, characterized in that the compression is performed using one or more substantially cylindrical cylinders. The method of claim 1, wherein the compression is performed using one or more substantially conical shaped rollers. Method according to any one of the preceding claims, characterized in that the compression is performed at a pressure of from 0 kg / m to 400 kg / m at one edge of the compressed zone and at a pressure of from 100 kg / m to 2000 kg / m at the opposite edge. compressed zone. Method according to any one of the preceding claims, characterized in that the compression gradient caused in the compressed zone has a linear diagram. Method according to any one of claims 1 to 4, characterized in that the compression gradient caused in the compressed zone has a non-linear diagram. Method according to any one of the preceding claims, characterized in that the compressed zone extends only on one part of the transverse direction of the primary tissue. Method according to any one of claims 2 to 6, characterized in that two or more individual zones of primary tissue are compressed and that the secondary tissue is divided into layers in planes parallel to the main surface of the plane in the tissue. The method of any one of claims 1 to 4, wherein the entire primary tissue is compressed using one or a set of rollers. Plant growth agent, characterized in that it can be obtained by a process according to any one of the preceding claims. The plant growth composition according to claim 10, characterized in that it has an average density of from 30 kg / m ³ to 120 kg / m ³ . Use of a plant growth agent according to claim 10 or 11 for growing plants. 13. Apparatus for preparing a mineral fiber comprising a plant growth agent having a density gradient, characterized in that it comprises primary tissue securing means comprising a mineral fiber material and a binder, means for compressing the primary tissue in at least one longitudinally extending zone said means capable of compressing the primary tissue in such a manner that the applied pressure increases substantially continuously in the transverse direction of the band to cause a gradient of compression in said direction, means for forming a secondary tissue of said means capable of causing the primary tissue to fold itself by depositing itself on a plurality of layers in the transverse direction of the secondary tissue and means for splitting the secondary tissue to form a plant growth agent.