Classifications

• • A—HUMAN NECESSITIES
  • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
  • A01G—HORTICULTURE; CULTIVATION OF VEGETABLES, FLOWERS, RICE, FRUIT, VINES, HOPS OR SEAWEED; FORESTRY; WATERING
  • A01G24/00—Growth substrates; Culture media; Apparatus or methods therefor
  • A01G24/10—Growth substrates; Culture media; Apparatus or methods therefor based on or containing inorganic material
  • A01G24/18—Growth substrates; Culture media; Apparatus or methods therefor based on or containing inorganic material containing inorganic fibres, e.g. mineral wool
• • A—HUMAN NECESSITIES
  • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
  • A01G—HORTICULTURE; CULTIVATION OF VEGETABLES, FLOWERS, RICE, FRUIT, VINES, HOPS OR SEAWEED; FORESTRY; WATERING
  • A01G31/00—Soilless cultivation, e.g. hydroponics

Definitions

• the invention relates to glass fibers for use in the field of agriculture.
• the subject of the invention is more particularly fibers intended to be used as constituents of a substrate for above-ground cultivation.
• a substrate for above-ground cultivation must have sufficient mechanical strength to avoid sagging under the effect of both root development and mechanical stress due to a wetting effect and to circulation.
• nutrient solution within the substrate In addition, it must allow an availability of the nutritive solution for the plant and ensure good ventilation vis-à-vis the roots. The lowest possible cost and density are obviously sought.
• rock wool is obtained from fibers produced by a process known as external centrifugation. These methods usually lead to a relatively large proportion of infibrated particles present in the substrate and to relatively high density products, of the order of 60 to 80 kg / m 3 .
• Above-ground growing substrates made of glass wool have also been proposed.
• This glass wool is obtained from fibers produced by a process known as internal centrifugation, detailed in the following description.
• the density of these substrates can be significantly lower and is most often between 15 and 50 Kg / m 3 .
• Patent EP 201 426 describes a glass composition for fibers intended to be used as a substrate for above-ground cultivation which satisfies well the mechanical and water requirements for above-ground cultivation. However, some of these constituents, released on contact with the nutrient solution, may be unfavorable to certain culture systems.
• the object of the present invention is to provide fibers whose glass composition has characteristics such that they can be fiberized according to the so-called internal centrifugation process, fibers intended for constituting substrates for above-ground cultivation.
• the object of the present invention is to provide a substrate for an above-ground culture of low density, playing a role of root maintenance which is easily impregnated with nutritive solution and which does not harm the growth of plants.
• the aims of the invention are achieved using fibers whose glass composition is as follows: Sibondede 2
• Impurities the sum of the contents of B 2 0 3 , Li 2 0 and F is less than or equal to 1%.
• the impurities include all the constituents not appearing in the preceding list and which are provided by the natural raw materials used to prepare these glass compositions.
• the impurities also include certain constituents from refining agents, such as sulphates, added to the mixture of vitrifiable raw materials.
• the glass fibers according to the invention can be obtained by the so-called internal centrifugation process. This process makes it possible to obtain, in a reproducible manner, fibers practically free of infibrated particles. Furthermore, it is possible by these techniques to produce substrates of low density.
• the glass fibers according to the invention are obtained from glasses which have physical characteristics making it possible to fiberize them according to this process. These characteristics are defined below. They have, in particular, a viscosity of 1000 poises at a temperature generally less than 1200 ° C and, preferably, less than 1150 ° C. Another important physical characteristic for the production of fibers is the devitrification temperatures, that is to say the temperatures corresponding to the crystal formation in the glass mass. These crystals are, in fact, capable of blocking the orifices of the centrifuge.
• the difference between the temperature corresponding to a viscosity of 1000 poises and the temperature of the liquidus is preferably greater than or equal to 50 ° C.
• the DGG of the glasses constituting the fibers according to the invention is preferably less than or equal to 30 milligrams.
• composition of the glass fibers according to the invention is characterized by a low level of boron oxide.
• the glass fiber compositions traditionally used contain around 5% by weight of B 2 0 3 , and up to 2 to 3% of Li 2 0 and F. These elements play an important role vis-à-vis -vis of different properties of glass. In particular, they reduce the viscosity, reduce the risk of devitrification and improve hydrolytic resistance.
• compositions according to the invention make it possible, despite the large decrease in the proportion of this constituent, or even their elimination, to maintain correct physical and chemical properties.
• the Na 2 0 content should not exceed about 18.5%; beyond this value, the DGG of the glass is too high, which affects the mechanical properties of the fibers.
• Other alkaline oxides can be introduced into the composition of the fibers according to the invention.
• K 2 0 and Li 2 0 lower the viscosity without causing a significant decrease in DGG.
• Viscosity and devitrification are also kept within acceptable limits thanks to the alkaline earth oxides CaO and MgO.
• the CaO content must be at least 5% by weight to avoid an excessive increase in viscosity. Above 9%, CaO leads to a significant increase in the risk of devitrification.
• A1 2 0 3 is introduced into the composition of the glass fibers according to the invention in an amount of at least 1% by weight. This essentially has the effect of keeping the DGG at values below 30 milligrams despite the high proportion of alkaline oxides.
• the proportion of Al 2 0 3 in the compositions according to the invention does not exceed 8%; beyond this value, the viscosity and the risks of devitrification increase considerably.
• oxides can be introduced into the composition of the fibers according to the invention, such as ZnO, MnO and Fe 2 0 3 , Ti ⁇ 2 and P 0 5 . These oxides have the effect of thinning the glass without affecting the devitrification of the glass while improving the DGG.
• compositions according to the invention comprise the following constituents within the limits below, expressed as a percentage by weight:
• compositions are differentiated by the substitution of part of the sodium hydroxide by potassium hydroxide, making it possible to limit the release of sodium by the fibers in contact with the nutritive solution. The limits are expressed as a percentage by weight:
• Impurities ⁇ the sum of the contents of B 2 0 3 , Li 2 0 and F is less than or equal to 1%.
• the invention also relates to substrates for above-ground cultivation consisting of fibers obtained from a glass composition according to the invention.
• These substrates produced by the internal centrifugation process advantageously have a low density and are easily impregnated with the nutritive solution.
• These substrates according to the invention play practically no nutritional role vis-à-vis the plant and do not impede the growth of plants: in contact with the nutritive solution, no harmful element is likely to be released at a content as it hampers plant growth.
• a level of boron, lithium and fluorine, released on contact with the nutritive solution greater than 0.5 mg / 1 is harmful to certain culture systems.
• excessive releases of lithium and fluorine have negative effects on certain culture systems.
• the substrates according to the invention release, on contact with the nutritive solution, a content of boron, lithium and fluorine, less than or equal to 0.5 mg / 1.
• a content of boron, lithium and fluorine less than or equal to 0.5 mg / 1.
• the substrates have a particular structure in order to improve the mechanical resistance.
• the substrates according to the invention may have a structure, described in patent application FR 89 03372, in which the fibers are oriented in random directions giving the material isotropic properties, in particular improved mechanical strength.
• Patent application FR 90 158909 describes another structure in order to improve the mechanical strength of the substrate. The latter consists of a mixture of fine fibers and larger fibers. The larger fibers provide improved mechanical strength of the substrate.

Landscapes

• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Environmental Sciences (AREA)
• Glass Compositions (AREA)
• Cultivation Of Plants (AREA)
• Hydroponics (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=9418065

Family Applications (1)

Country Status (11)

Cited By (1)

Families Citing this family (9)

Family Cites Families (5)

• 1991
  • 1991-10-18 FR FR9112866A patent/FR2682556B1/fr not_active Expired - Fee Related
• 1992
  • 1992-10-07 IT IT000811A patent/ITTO920811A1/it unknown
  • 1992-10-14 EP EP92923835A patent/EP0563371A1/fr not_active Withdrawn
  • 1992-10-14 FI FI932828A patent/FI932828L/fi not_active Application Discontinuation
  • 1992-10-14 AU AU29471/92A patent/AU2947192A/en not_active Abandoned
  • 1992-10-14 WO PCT/FR1992/000971 patent/WO1993007741A1/fr not_active Ceased
  • 1992-10-14 JP JP5507487A patent/JPH06503478A/ja active Pending
  • 1992-10-14 KR KR1019930701886A patent/KR930702888A/ko not_active Withdrawn
  • 1992-10-14 CA CA002098705A patent/CA2098705A1/fr not_active Abandoned
  • 1992-10-16 PT PT100977A patent/PT100977A/pt not_active Application Discontinuation
• 1993
  • 1993-06-17 NO NO932243A patent/NO932243D0/no unknown

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events