PT100977A - GLASS FIBERS USED AS CONSTITUENTS OF SUBSTRATES FOR UNIDROUND CULTURES AND SUBSTRATES FOR THE REFERRED CULTURES - Google Patents

Description

The invention relates to glass fibers intended for use in agriculture. The invention relates more particularly to fibers intended to be used as constituents of a substrate for crops without soil.

In general, a substrate for growing without soil must have sufficient mechanical strength to avoid a reduction under the effect of either the root development or a mechanical requirement due to a wetting effect and a circulation of the nutrient solution within the soil. substrate. On the other hand, the substrate must allow for the availability of the nutrient solution to the plant and ensure a good aeration of the roots. A cost and a density as low as possible are, of course, intended.

As is known, soilless substrates are manufactured from rock wool. These substrates have advantageous properties. However, rock wool is obtained from fibers produced by a so-called external spinning process. These processes generally lead to a relatively large proportion of fiber embedded particles present in the substrate and relatively high density products of the order of 60 to 80 kg / m 3.

Non-soil culture substrates consisting of glass wool have also been proposed. This glass wool is obtained from fibers produced by a so-called internal centrifugation process detailed in the following description. The density of these substrates may be appreciably lower and is most often between 15 and 50 kg / m 3.

Fiberglass compositions have already been described in response to the characteristics required for use as a substrate for growing without soil.

Patent EP 201 426 discloses a glass composition for fibers intended to be used as substrate for growing without soil, which responds well to mechanical and hydric demands on crop without soil.

However, some of its constituents, released in contact with the nutrient solution, may be unfavorable to certain culture systems. The object of the present invention is to provide fibers whose vitreous composition exhibits characteristics such that fibers are formed into fibers in accordance with the said internal spinning process, fibers intended for forming substrates for growing without soil. The object of the present invention is to provide a soil-free substrate of low density by performing a root-keeping role which is readily impregnated with a nutrient solution and which does not adversely affect the growth of plants.

The objects of the invention are achieved by means of fibers whose glass composition is as follows: SiO2 55-70% A1203 1-8% Cao 5-9% MgO 1.5-4% Na2O 13-18.5% K20 0.5 - 10% Fe203 0 - 4% ZnO 0 - 4% MnO 0 - 4% tio2 0 - 4% P2 ° 5 - 4% Impurities < 1% whose sum of the contents in B203, Li20 and F is less than or equal to 1%.

Impurities comprise all constituents other than ν '//, / ν. 74 434 appear in the preceding list and which are added by the natural raw materials used to make these glassware compositions. The impurities also comprise certain constituents from refining agents, such as sulphates, added to the mixture of vitrifiable raw materials.

The glass fibers according to the invention are capable of being obtained by said internal centrifugation process. This process enables reproducible production of fibers which are substantially free of non-embedded particles in the fibers. On the other hand, it is possible by these techniques to produce low density substrates.

This type of fiber production technique is the subject of numerous publications. For further detail, reference may be made, in particular, to patents FR 1 382 917 and FR 2 443 436. According to these techniques, the molten glass is introduced into the centrifuge and is projected, under the effect of the centrifugal force, over its peripheral band. A multiplicity of holes are distributed over this band. Through these holes the glass is projected horizontally. The resulting glass wires are advantageously stretched by gaseous streams in order to be transformed into fibers.

The glass fibers according to the invention are obtained from glasses having physical characteristics which allow the formation of fibers by this process. These characteristics are defined below. The glasses have, in particular, a viscosity of 10Âμ Pa · s (1000 poise) at a temperature generally below 1200 ° b, and preferably below 1150 ° C.

Another important physical characteristic for the production of fibers are the devitrification temperatures, that is, the temperatures corresponding to the formation of crystals in the glass mass. These crystals are, in effect, liable to clog the holes of the centrifuge.

There are several temperatures which allow to characterize this devitrification: the temperature at which the growth rate of the crystals is zero, commonly referred to as liquidus, the temperature at which the growth rate of the crystals is maximum.

In general, the difference between the temperature corresponding to a viscosity of 102 Pa.s (1000 poise) and the liquidus temperature is preferably greater than or equal to 50øC. It is desirable to obtain a minimum crystal growth rate; it is less than 3 microns / minute.

Another important feature to consider is the hydrolytic resistance of the composition, particularly when it is to be used as substrate for culture without soil. This resistance is measured according to the standard method of &quot; Deutsche Glastechnische Gesellschaft (DGG) &quot;. The DGG of the glasses constituting the fibers according to the invention is preferably less than or equal to 30 milligrams. The composition of the glass fibers according to the invention is characterized by a reduced rate of boron oxide.

It has been found that when the sum of the B203, Li20 and F by weight exceeds 1%, the quantities of these elements released by the glass fibers in the nutrient solution exceed the tolerance limits of certain plants.

Traditionally used glass fiber compositions contain about 5% by weight of B203 and up to 2 to 3% of Li20 and F. These elements play an important role in the different properties of the glass. In particular, they allow

Reducing the viscosity, reducing the risk of devitrification, and improving hydrolytic resistance.

The compositions according to the invention allow, in spite of the strong decrease in the proportion of this constituent, to suppress their conversion, to convert the correct physical and chemical properties.

Thus, an increase in the rate of alkaline oxides enables the viscosity to be kept within acceptable limits without causing a marked increase in devitrification, with the sodium oxide content always being at least 13%. The Na2 0 content should not exceed about 18.5%; above this value the DGG of the glass is very high which is negative for the mechanical properties of the fibers.

Other alkali oxides may be introduced into the fiber composition according to the invention. Thus, K20 and Li20 decrease viscosity without causing a significant decrease in DGG. Viscosity and devitrification are also kept within acceptable limits, thanks to the alkaline oxides CaO and MgO. In particular, the CaO content should be at least 5% by weight, to avoid a very significant increase in viscosity. Above 9%, CaO introduces a significant increase in the risk of devitrification. The A1203 is introduced into the glass fiber composition according to the invention in the ratio of at least 1% by weight. This essentially has the effect of maintaining the DGG in values lower than 30 milligrams, despite the strong proportion of alkaline oxides. The ratio of Al203 in the compositions according to the invention does not exceed 8%; above this value the viscosity and devitrification risks increase considerably.

Other oxides may be introduced into the fiber composition 74 434

according to the invention, such as ZnO,

MnO and Fe2 O3, TiO2 and p2 O5

These oxides have the effect of fluidizing the glass, without affecting the devitrification of the glass and improving the DGG.

The series of tests, presented in the attached table, illustrate the influence of the constituents present in a glass composition on the described physical characteristics.

Preferred glass compositions according to the invention comprise the following constituents, within the stated limits and expressed as weight percent: 58% Al2O3 4.5 7.5% CaO59% MgO 1.54 % NA20 17 18.5% K20 0.5 4% Fe203 0 3% ZnO 0 3% MnO 0 3% TiO 2 0 3% P 2 ° 5 0 3% Impurities < 1% whose sum of the contents in B203, Ll20 and F is less than or equal to 1%. A further family of preferred glass compositions according to the invention is described below. These compositions are differentiated by the substitution of a part of the soda for potash, allowing to limit the release of sodium by the fibers in contact with the nutritive solution. The limits are expressed as a percentage by weight: SiO2 55 65% Al2O3 4.5 7.5% CaO58% MgO 1.54% Na2O3 17.5% -8-% S33ams &gt; 74 434 K20 4 10% Fe2 ° 3 0 3% ZnO 0 3% MnO 0 3% uncle2 0 3% P2 ° 5 0 3% Impurities < 1% contents in B203, I1I2O Θ F Θ less than 1%. The invention also relates to substrates for growing without soil, consisting of fibers obtained from a glass composition according to the invention.

These substrates, produced by the internal centrifugation process, advantageously have a small density and are easily impregnated by the nutrient solution. These substrates according to the invention have practically no nutritional role for the plant and do not interfere with the growth of plants: on contact with the nutrient solution no possible damage is likely to be released in such a way as to hinder the growth of plants.

In particular, the inventors have shown that a rate of boron, lithium and fluorine, released upon contact of the nutrient solution, greater than 0.5 mg / l is detrimental to certain culture systems. Likewise, excessive releases of lithium and fluorine have negative effects on certain culture systems.

The substrates according to the invention release, in contact with the nutrient solution, a boron, lithium and fluorine content of less than or equal to 0.5 mg / l. The absence of harmful effects on plants is tested by careful observation of the behavior of cultivated plants as well as by observation of their growth.

Advantageously, according to the invention, the substrates have a particular structure in order to improve the

74 434

-9 mechanical resistance.

The substrates according to the invention may have a structure, described in the patent application FR 89 03372, in which the fibers are oriented in random directions giving the material isotropic properties, in particular an improved mechanical strength. patent application FR 90 158909, unpublished, describes another structure in order to improve the mechanical strength of the substrate. The latter consists of a mixture of fine fibers and coarser fibers. The thicker fibers impart improved mechanical strength to the substrate.

Advantages of the invention are evidenced by experimental tests described in the following detailed description. The release of boron, lithium and fluoride from a substrate in contact with the nutrient solution is tested. Two samples of substrates A and B of identical size according to the invention (respectively compositions 4 and 11 in the table) are immersed, separately, for 6 weeks in a bath of nutrient solution of identical composition and pH 5 , 9.

The quantities of boron, lithium and fluoride released after 6 weeks by the two substrates tested are shown in the table below (in mg per liter of nutrient solution): 1 | Substrate | I I A -r 1 I B 1 1 1 | Fluorine | I I o o o \ 1 1 I 0,03 1 1 | Boro | 1 1 0.07 1 1 I 0.09 1 1 | Lithium | 1 I 0.018 1 1 I 0.040 1 1] Total | 0.148 1 1 0.160 1 - 1 -

These tests demonstrate the influence of the composition of the glass fibers constituting a substrate on the lithium boron and fluoride contents released by the said fibers in the nutrient solution and enable the production of glass wool substrates compatible with all the culture systems.

TABLE | Composition | 1 | 2 | 3 | 4 | 5 | 6 I 7 | 1 X 1 1 1 I 1 1 1 I 1 I | I | 1 r 1 s <2 1 1 65,21 | r 63.9 | 62,82 | 1 64,98 | I 64.21 | I 64.21 | 64,21 | 1 ^ 2¾ 1 4,55 | 4,55 | 4,45 | 4,53 | 4,55 | 4,55 | 4,55 | 1 CaO | 7,65 | 7,85 | 7,75 | 7,62 | 7,65 | 7,65 | 7,65 | | MgO | 2,8 | 2,7 | 2,65 | 2,79 | 2,8 | 2,8 | 2,8 | 1 Na2 ° 1 18.2 1 18.4 | 18,45 | 18,14 | 18,2 | 18,2 | 18,2 | | k2 ° | 1,05 | 1,05 | 1 I 1.05 | 1,05 | 1,05 | 1,05 | 1 Fe2 ° 3 1 0.1051 1.05 | 2,4 | I 0.105 | 0,105 | 0,105 | | MnO | 1 I I I 1 I 1 z &quot; 1 1 I I I 1 1 | 1 b2 ° 3 1 1 I 0,35 | I I 1 Ti02 1 1 I I I I 1 2 2 1 1 I I 1 I I 1 p2 ° 5 1 1 I I I | Impurities | 1_ 1 0,435 | 1 0.5 | 1 0,48 | 0,54 | _1 0,435 | _L 0,435 | _L 0,435 | 1 1 1 1 1 1 1 1 1 | Properties | | 1 1 1 1 1 I 1_ 1 1 1 1_1_1_1_ 1 1 r | Temperature a | 1 Γ 1 r 1 Γ I 1 1 | a viscosity | 1 1 1 I 1 | of 102 Pa.s | 1 1 1 I 1 | (1000 poises) | 1 1 1 I 1 | and (d) | I 1 1120 | I 1117 | I 1103 | 1113 | 1 1076 | t 1109 | 1 1110 | 1 1 | Liquidus (* C) | 1 1 1 1 I I I I 1 1 1 -2- 1 I I 960 | 1 970 | I 990 | 958 | | 940 | I 972 | | 1 ! 1 (1) - (1) - (1) | 1 160 | I 1 147 | | 113 | I 155 | I 136 | III | III | III | III | m / mn) | 1.8 I | 1,41 | | 1,58 | 1,7 I | 1,88 | I I | 1,76 | I I | DGG (mg) | 1 29,2 | 1 1 26.5 | I 29,2 | I 30 | I I 29 | TABLE (continued)

T I I I I I I I I Composition 1 8 1 9 I 10 I 11 I 12 13 I 14 I 15 1% 1 1 1 I | I I I | I | 1 H-NMR (300 MHz, CDCl 3):? 4.7 I 4.7 I 6.7 I 6.5 6.5 I 6.6 I 4.5 | CaO | 7.65 | 7.65 I 7.65 I 7.65 I 7.4 7.4 I 5.1 I 7.6 1 MgO | 2.8 | 2.8 I 2.8 I 2.8 I 2.6 2.5 I 2.5 I 2.8 1 Na2 ° | 18.2 j 17.7 I 17.7 I 17.7 I 15.2 17.5 I 17.5 I 17.7 1 K 2 ° 1 1.05 | 0.9 I 0.9 I 1.2 I 5.8 5.8 I 5.8 I 1.2 1 * 2% 10.105 (0.22 I 0.2 I 0.2 I 0.2, 2 I 0.2 I 0.2 I MnO | I 2 IIIII 1 ZnO 1 2 | IIIII 1 B2 ° 3 1 I 0.4 I 0.4 I 0.4 I 0.35 0.3 I 0.5 I 0,4 1 T '° 2 1 I 0,18 I 2,1 I 2,1 I 1,7 1,8 I 1,8 I 2,5 1 Li2 ° 1 IIIIII 1 P2 ° 5 1 IIIIII 1,8 0.935 I _ 0.3 I I 0.3 I I 0.3 I 0.55 0.6 I I 0.1 I I 1.3 0.3 1 1 1 1 1 1 1 1 Properties 1 1 1 1 1 I 1_1_1_1_1_1_1_1_1_ I Temperature at 11 1 IIIII 1 1 I a viscosity 1 IIII 1 | of 102 Pa.s | 1 IIII 1 | (1000 poises) | IIII 1 | (&quot; C) (1) ) 1100 I 1116 I 1119 I 1115 1066 I 1103 1 1100 I Liquidus (° C) | 1 1 1 1 1 1 1 II II 1 1 1 - 1 1 I 1 I 1 1 1 II 1 1 (1) - (2) (° C) 1 1 1 1 1 1 1 1 1 1 1 1 1 Speed 1 1 1 1 1 1 1 1 1 1 1 1 1 of crystallization - 1 1 1 1 1 1 I tion (μτη / mn) 1 1.72 I | 1 1 1 1 1 | DGG (m g) | 1_L 1 28 | 1 22.6 1 1 I 21.7 1 1 I 17.5 1 1 _1_ 1 1 -1_ 1 1 _1_ 21 _

Claims (8)

74 434 -12- Glass fibers for use as constituents of a growing substrate without soil, the composition of which comprises essentially the following constituents, the proportions of which are expressed as weight percent: 55-70% Al2 O3 1 - 8% CaO 5 - 9% MgO 1.5 - 4% Na 2 O - 4% Na 2 O - 4% M 2 O 4 - 4% 0 - 4% Impurities < 1% whose sum of the contents in B203, Li20 and F is less than or equal to 1%. Glass fibers according to claim 1, characterized in that their composition essentially comprises the following constituents, the proportions of which are expressed as weight percent: 58-67% Al2O3 4.5-7.5% CaO 5 - 9% MgO 1.5 - 4% Na 2 O - 3% MnO 0 - 3% thio 2 0 - 4% p205 0 - 4% Impurities < 1% whose sum of the contents in B203, L220 and F is less than or equal to 1%. 74 434 13- Θ / ,, sczsgm iy Glass fibers according to claim 1, characterized in that their composition comprises essentially the following constituents, the proportions of which are expressed as a percentage by weight: 55-65% Al2 O3 4.5-7.5% CaO 5 - 8% MgO 1.5 - 4% Na2 13 - 17.5% K20 4 - 10% Fe2 ° 3 0 - 3% ZnO 0-3% MnO 0-3% 3% Impurities < 1% whose sum of the contents in B203, Li20 and F is less than or equal to 1%. 4 - Substrate for culture without soil, consisting of glass fibers, the composition of which essentially comprises the following constituents, the proportions of which are expressed as weight percent: 55 - 70% A1203 1-8% Cao 5 - 9% MgO 1/5 - 4 % NA20 13 - 18.5% k2o 0.5 - 10% Fe203 0 - 4% ZnO 0 - 4% MnO 0 - 4% uncle2 0 - 4% P2 ° 5 0 - 4% Impurities < 1% whose sum of the contents in B203, Li20 and F is less than or equal to 1%. The substrate for growing without soil according to claim 4, consisting of glass fibers, the composition of which essentially comprises the following constituents, the proportions of which are expressed as weight percent: 58-67% ai2o3 4,5-7,5% CaO 5 - 9% MgO 1.5 - 4% Na 2 O - 3% M 2 O 3 - 3% TiO 2 0 - 3% - 3% Impurities &lt; 1% whose sum of the contents in B203, Li20 and F is less than or equal to 1%. The substrate for soil culture according to claim 4, consisting of glass fibers, the composition of which essentially comprises the following constituents, the proportions of which are expressed as weight percent: 55-65% A1203 4.5 - 7.5% CaO 5 - 8% MgO 1.5 - 4% Na2 ° 13 - 17.5% K20 4 - 10% Fe203 0 - 3% ZnO 0-3% MnO 0-3% thio2 0-3% 3% Impurities < 1% whose sum of the contents in B203, Li20 and F is less than or equal to 1%. Non-soil culture substrate according to claims 4, 5 and 6, characterized in that it consists of fibers which on contact with a nutrient solution release only elements whose nature and concentration in the nutrient solution , are devoid of effects liable to hinder the growth of plants. Soil culture substrate according to claim 7, characterized in that when the substrate is saturated at 75% by volume with a nutrient solution, the boron, lithium or fluoride content released in the latter solution is equal to or less than 0,5 mg / l. Lisbon, By SOCIÉTÉ ISOVER SAINT-GOBAIN (Société Anonyme) = 0 OFFICIAL AGENT =