Process for the manufacture of an insulating product based on mineral fibres

Abstract

A process for the manufacture of an insulating product based on mineral fibres bonded by an organic binder, includes applying a sizing composition to the mineral fibres, forming an assembly of the mineral fibres, heating the assembly of mineral fibres until the sizing composition has cured, wherein the sizing composition includes the following constituents within the limits defined below, expressed as fractions by weight with respect to the total weight of the composition: from 80% to 98% of water, from 2% to 20% of water-soluble poly(furfuryl alcohol) and less than 0.5% of furfuryl alcohol, and the mineral fibres are fibres of aluminosilicate glass including aluminum oxide, Al.sub.2O.sub.3, in a fraction by weight of between 14% and 28%.

Claims

1. A process for the manufacture of an insulating product based on mineral fibres bonded by an organic binder, comprising: a. applying a sizing composition to the mineral fibres, b. forming an assembly of the mineral fibres, c. heating said assembly of mineral fibres until the sizing composition has cured, wherein: the sizing composition comprises the following constituents within the limits defined below, expressed as fractions by weight with respect to the total weight of the composition: from 80% to 98% of water, from 2% to 20% of water-soluble poly(furfuryl alcohol), which is obtained by polycondensation of furfuryl alcohol, and less than 0.5% of furfuryl alcohol, the mineral fibres are fibres of aluminosilicate glass comprising aluminium oxide, Al.sub.2O.sub.3, in a fraction by weight of between 14% and 28%, wherein a sum of the fractions by weight of the poly(furfuryl alcohol) and of the water is at least 95%, and wherein the sizing composition applied to the mineral fibres has a pH in a range from 5 to 8.

2. The process according to claim 1, wherein the mineral fibres have a fraction by weight of SiO.sub.2 of between 32% and 50%.

3. The process according to claim 1, wherein a sum of the Al.sub.2O.sub.3 and SiO.sub.2 fractions by weight of the mineral fibres is between 46% and 78%.

4. The process according to claim 1, wherein the mineral fibres have an Al.sup.3+/(Al.sup.3++Si.sup.4+) molar ratio of greater than 0.25.

5. The process according to claim 4, wherein the mineral fibres have an Al.sup.3+/(Al.sup.3++Si.sup.4+) molar ratio of greater than 0.35.

6. The process according to claim 1, wherein the mineral fibres additionally comprise the oxides CaO and MgO, a sum of the fractions by weight of the oxides being between 7% and 32%.

7. The process according to claim 1, wherein the mineral fibres additionally comprise the oxides Na.sub.2O and K.sub.2O, a sum of the fractions by weight of the oxides being between 1% and 15%.

8. The process according to claim 1, wherein the mineral fibres have a dissolution coefficient of greater than 100 ng.Math.cm.sup.−2.Math.h.sup.−1, the dissolution coefficient being calculated from the amount of SiO.sub.2 of the mineral fibres which is dissolved in a synthetic pulmonary fluid of pH 4.5, thermally regulated at 37° C., after 14 days.

9. The process according to claim 8, wherein the dissolution coefficient is greater than 400 ng.Math.cm.sup.−2.Math.h.sup.−1.

10. The process according to claim 1, wherein a content of furfuryl alcohol of the sizing composition is less than 0.1%.

11. The process according to claim 1, wherein said sizing composition additionally comprises one or more adjuvants chosen from coupling agents, dust-preventing agents, hydrophobic agents, retardants, antistatic agents, softening agents, conditioning agents, colouring agents or opacifying agents.

12. The process according to claim 11, wherein a fraction by weight of adjuvants and additives of the solid part of the sizing composition does not exceed 25%.

13. The process according to claim 12, wherein the fraction by weight of adjuvants and additives of the solid part of the sizing composition does not exceed 20%.

14. The process according to claim 1, wherein the application of the sizing composition of stage a) to the mineral fibres is carried out by spraying by means of spray nozzles.

15. The process according to claim 1, wherein stage c) comprises the heating of the assembly of mineral fibres at a temperature of between 100° C. and 250° C. for a period of time of between 1 minute and 10 minutes.

16. The process according to claim 15, wherein the heating of the assembly of mineral fibres is in a thermally regulated atmosphere.

17. The process according to claim 1, wherein a sum of the fractions by weight of the poly(furfuryl alcohol) and of the water is at least 98%.

18. The process according to claim 1, wherein the pH is from 6.0 to 8.0.

19. The process according to claim 1, wherein the pH is from 5.5 to 8.

Description

(1) The contribution of the present invention is clearly illustrated by the two examples described below and the figures to which these two examples refer.

(2) FIG. 1 is an electron micrograph of the interface between a flat mineral substrate having the composition Glass 1 and an organic coating obtained by crosslinking the sizing composition 1 (comparative).

(3) FIG. 2 is an electron micrograph of the interface between a flat mineral substrate having the composition Glass 1 and an organic coating obtained by crosslinking the sizing composition 2 (comparative).

(4) FIG. 3 is an electron micrograph of the interface between a flat mineral substrate having the composition Glass 1 and an organic coating obtained by crosslinking the sizing composition 3 (which can be used according to the invention).

(5) FIG. 4 is an electron micrograph of the interface between a flat mineral substrate having the composition Glass 2 and an organic coating obtained by crosslinking the sizing composition 1 (comparative).

(6) FIG. 5 is an electron micrograph of the interface between a flat mineral substrate having the composition Glass 2 and an organic coating obtained by crosslinking the sizing composition 2 (comparative).

(7) FIG. 6 is an electron micrograph of the interface between a flat mineral substrate having the composition Glass 2 and an organic coating obtained by crosslinking the sizing composition 3 (which can be used according to the invention).

(8) In the examples, a sizing composition which can be used according to the invention is compared with two sizing compositions which are according to the state of the art and which do not make it possible to solve the technical problem. The sizing composition which can be used according to the invention was used on two glass compositions for mineral fibres sensitive to acids. For comparison purposes, the two sizing compositions according to the state of the art were used on the same two glass compositions for mineral fibres sensitive to acids.

(9) The quality of the effect of the acidity of the sizing compositions was determined by comparing the quality of the interfaces formed between the said sizing compositions, once cured or crosslinked, and the two glass compositions for mineral fibres put into the form of flat substrates. The use of flat substrates, instead of fibres, is preferred for practical reasons. This is because they make it possible to simulate the interface between the fibres and the said sizing compositions and to make easier the observation thereof using a microscope. The quality of the interface provides qualitative information on the level of adhesion between the substrate and the fibre, in particular after an ageing test. In particular, the presence of cracks or of detachments will be the manifestation of a deterioration in the surface of the substrate by the sizing composition which has been deposited thereon.

(10) The two glass compositions biosoluble at pH 4.5 used for the flat substrates are those presented in Table 1. The substrates were manufactured according to the usual methods of the glass industry. This table also shows the values of the sums of the fractions by weight, Al.sub.2O.sub.3+SiO.sub.2, CaO+MgO and Na.sub.2O+K.sub.2O, of the Al.sup.3+/(Al.sup.3++Si.sup.4+) molar ratio and of the dissolution coefficient, k, calculated from the amount of SiO.sub.2 of the said glass fibres which is dissolved in a synthetic pulmonary fluid of pH 4.5, thermally regulated at 37° C., after 14 days, according to the protocol which was referred to above.

(11) The three sizing compositions, and also their pH values, are described in Table 2. The sizing compositions 1 and 2 correspond to sizing compositions according to the state of the art. The sizing composition 3 is a sizing composition which can be used according to the invention.

(12) The sizing composition 1 is prepared in two stages: a) maleic anhydride and tetraethylenepentamine are mixed in a first container and then the mixture is put in reserve at a temperature of between 20° C. and 25° C. for 15 minutes; b) the mixture obtained in stage a), the sucrose, the ammonium sulfate and the silane are mixed with stirring until the constituents have completely dissolved.

(13) The sizing compositions 2 and 3 are prepared by mixing all of the constituents in a single stage.

(14) For the purposes of the tests, the sizing compositions have a greater concentration of resin than the sizing compositions used for the application to the mineral fibres. The concentration of each composition is chosen in order for the viscosity to be suitable for application to a flat substrate, and the conditions of the heat treatment are chosen in order for the kinetics of the possible reactions between the said sizing compositions and the said substrates to be accelerated. The same results can be obtained with sizing compositions exhibiting a greater degree of dilution of resin by allowing the water which they contain to further evaporate. The test is thus representative of the formation of a film of binder at the surface of the glass under the conditions of manufacture of the mineral wool.

(15) The protocol used for the test of determining the quality of the effect of the acidity is as follows: cleaning the surfaces of the flat substrates with deionized water and with ethanol; flame treating the said surface using a laboratory burner, so as to remove any contamination of organic nature; cooling the surfaces to ambient temperature; depositing the sizing compositions on the flat substrates by screen printing in order to form a cured or crosslinked coating having a thickness of approximately 20 μm; curing the samples thus manufactured at 210° C. for 20 min in a suitable oven, the oven having been preheated to 550° C. and then cooled in order to prevent any contamination of organic nature; accelerated ageing of the samples in an autoclave at 105° C., 1.2 bars for 15 min; cutting the samples in cross section so as to be able to observe the interface between the organic coating and the flat substrate; observing the sections thus obtained using a scanning electron microscope, the acceleration voltage of which is set at 15 kV, the magnification of which is set at ×10 000 and the detection mode of which is the secondary electron detection mode.

(16) TABLE-US-00001 TABLE 1 Compositions of the glass fibres, expressed in fractions by weight of oxides. Glass 1 Glass 2 SiO.sub.2 43 41.5 Al.sub.2O.sub.3 24.2 15.4 Na.sub.2O 6.6 1.7 K.sub.2O 4 1.5 CaO 14.5 25.6 MgO 1.5 6.4 Fe.sub.2O.sub.3 5.5 5.5 B.sub.2O.sub.3 — — P.sub.2O.sub.5 0.7 0.4 Al.sub.2O.sub.3 + SiO.sub.2 67.2 56.9 CaO + MgO 16 32 Na.sub.2O + K.sub.2O 10.6 3.2 k (ng .Math. cm.sup.−2 .Math. h.sup.−1) ~600 ~250 Al.sup.3+/(Al.sup.3+ + Si.sup.4+) 0.40 0.30

(17) TABLE-US-00002 TABLE 2 Compositions of the sizing solutions, expressed in fractions by weight of the dry constituents. Composition 1 Composition 2 Composition 3 (comparative) (comparative) (invention) Sucrose 34 Tetraethylenepent- 4.9 amine Maleic anhydride 5.1 Ammonium sulfate 6 Maltitol 30.3 Citric acid 24.6 Poly(furfuryl alcohol) 66.3 Sodium hypophos- 2.4 phate Silane 2.5 2.4 2.5 Water 47.5 40.3 31.2 pH 6 1-2 5

EXAMPLE 1

(18) In the first example, the three sizing compositions of Table 2 were deposited on a flat substrate with the composition Glass 1 of Table 1 according to the protocol described above. FIGS. 1, 2 and 3 exhibit the electron micrographs of the interfaces obtained between the said substrate and the three organic coatings respectively. The substrate is located at the bottom of the micrographs and the coating at the top. In FIGS. 1 and 2, which are obtained with sizing compositions according to the state of the art, the interfaces are degraded. In FIG. 1, the interface is cracked and fractured. In FIG. 2, the interface exhibits microcracks which propagate in the substrate and the organic coating. On the other hand, in FIG. 3, which corresponds to a product obtained with a sizing composition which can be used according to the invention, the interface is smooth and flat and does not exhibit any cracking or detachment defect.

EXAMPLE 2

(19) In the second example, the three sizing compositions of Table 2 were deposited on a flat substrate with the composition Glass 2 of Table 1 according to the protocol described above. FIGS. 4, 5 and 6 exhibit the electron micrographs of the interfaces obtained between the said substrate and the three organic coatings respectively. The substrate is located at the bottom of the micrographs and the organic coating at the top. In FIGS. 4 and 5, which are obtained with sizing compositions according to the state of the art, the interfaces are degraded. They are cracked and fractured with a pronounced separation of the material. On the other hand, in FIG. 6, obtained with a sizing composition which can be used according to the invention, the interface is smooth and flat and does not exhibit any cracking or detachment defect.

EXAMPLE 3

(20) In the third example, two industrial insulating products were manufactured using two sizing compositions, one according to the state of the art and the other which can be used according to the invention. These two sizing compositions respectively correspond to the sizing compositions 1 and 3 with a greater dilution. The fractions by weight of their constituents are shown in Table 3. The composition of the mineral fibres on which these two sizing compositions were applied is that of Glass 1 of Table 1. The mineral fibres were coated with sizing composition before being assembled and heated at 200° C. The density of the industrial products obtained is approximately 16 kg.Math.m.sup.3. The fraction by weight of binder in the final product, obtained following the drying and the curing of the sizing compositions, is approximately 5%.

(21) The mechanical strength of the insulating products depends on the quality of the interfaces between the binder and the fibres. This quality can change over time with the ageing of the product. It can in particular degrade. This degradation increases as the degree of degradation of the mineral fibres by the binder or the degree of degradation of the binder itself increases. The measurement of the variations in the mechanical strength before and after ageing thus provides a qualitative and quantitative indication of the degree of degradation of the mineral fibres by the binder or of the degree of degradation of the binder itself.

(22) For the purposes of demonstrating the advantages of the invention, the two insulating products were subjected to a climatic treatment for 15 minutes in a chamber thermally regulated at 105° C. with a relative humidity of 100% in order to simulate their ageing in accelerated fashion. The tensile strength of the industrial insulating products, before and after climatic treatment, was measured using a mechanical test according to Standard ASTM C686-71T. Before and after climatic treatment, a series of samples was cut out from each product by stamping. Each sample has the shape of a ring having a length of 122 mm, a width of 46 mm, a radius of curvature of the cut-out of the exterior edge equal to 38 mm and a radius of curvature of the cut-out of the interior edge equal to 12.5 mm. The sample is positioned between two cylindrical mandrels of a testing device, one of which is movable and moves at a constant rate. The tensile strength is the ratio of the breaking force F, measured in newtons, to the weight W of the sample. The unit of the tensile strength is the newton/gram or N.Math.g.sup.−1.

(23) The values of the mechanical strengths of the two products before and after climatic treatment are shown in Table 4. Before climatic treatment, the two insulating products have comparable tensile strength values. This is remarkable and all the more surprising as the size according to invention is 10 times more acidic than the size of the comparative example. After climatic treatment, the value of the tensile strength of the product 1, manufactured using a sizing composition according to the state of the art, decreases by 53%, whereas that of the product 2, manufactured using a sizing composition which can be used according to the invention, only decreases by 14%. After ageing, the loss in tensile mechanical strength is thus nearly four times smaller for a product capable of being obtained according to the invention than for a product capable of being obtained according to the state of the art.

(24) TABLE-US-00003 TABLE 3 Compositions of the sizing solutions, expressed in fractions by weight of the dry constituents. Composition 1, Composition 3, diluted diluted (comparative) (invention) Sucrose 3.9 Tetraethylenepentamine 0.5 Maleic anhydride 0.6 Ammonium sulfate 0.7 Poly(furfuryl alcohol) 5.8 Furfuryl alcohol <0.02 Silane 0.3 0.2 Water 94 94

(25) TABLE-US-00004 TABLE 4 Tensile strengths (N .Math. g.sup.−1) of the industrial insulating products manufactured using the sizing composition of Table 3. Product 1 Product 3 (comparative) (invention) Composition of the mineral Glass 1 Glass 1 fibres Sizing composition Composition Composition 1, diluted 3, diluted Tensile strength Before treatment climatic 3.8 N .Math. g .sup.−1 3.6 N .Math. g.sup.−1 After climatic treatment 1.8 N .Math. g.sup.−1 3.1 N .Math. g.sup.−1