BINDER COMPOSITION ON AN OLIGOESTER BASIS, PRODUCTION THEREOF, AND USE THEREOF FOR BINDING ORGANIC OR MINERAL FIBRES

Abstract

The present invention relates to a thermosetting binder composition containing water and a water-soluble oligomeric ester of at least one saccharide chosen from reducing sugars, non-reducing sugars and hydrogenated sugars, the hydrogenated sugars being chosen from the group consisting of erythritol, arabitol, xylitol, sorbitol, mannitol, iditol, maltitol, isomaltitol, lactitol, cellobitol, palatinitol, maltotritol and hydrogenation products of hydrolyzates of starch or of lignocellulose materials, and of at least one polycarboxylic acid, the binder composition having a dry matter content of between 50% and 80% by weight, the water-soluble oligomeric ester representing at least 80% by weight, preferably at least 90% by weight, of the cry matter content of the thermosetting binder composition, and the thermosetting binder composition containing less than 10% by weight, preferably less than 5% by weight, with respect to its dry matter content, of free sorbitol.

It also relates to the use of such a binder composition for the manufacture of a product based on mineral or organic fibers which are bonded by an insoluble organic binder.

Claims

1. A thermosetting binder composition, comprising: water; and a water-soluble oligomeric ester of at least one saccharide selected from the group consisting of reducing sugars, non-reducing sugars, and hydrogenated sugars, wherein the hydrogenated sugars are at least one selected from the group consisting of erythritol, arabitol, xylitol, sorbitol, mannitol, iditol, maltitol, isomaltitol, lactitol, cellobitol, palatinitol, maltotritol, and hydrogenation products of hydrolyzates of starch or of lignocellulose materials, and of at least one polycarboxylic acid, wherein the binder composition has a dry matter content of between 40% and 80% by weight, wherein the water-soluble oligomeric ester represents at least 80% by weight of the dry matter content of the thermosetting binder composition, and wherein the thermosetting binder composition contains less than 10% by weight, with respect to its dry matter content, of free sorbitol.

2. The thermosetting binder composition as claimed in claim 1, wherein the reducing sugars are at least one selected from the group consisting of monosaccharides and disaccharides.

3. The thermosetting binder composition as claimed in claim 1, wherein the hydrogenated sugars are at least one selected from the group consisting of xylitol, maltitol, sorbitol and hydrogenation products of hydrolyzates of starch or of lignocellulose materials.

4. The thermosetting binder composition as claimed in claim 1, wherein the polycarboxylic acid(s) is at least one selected from the group consisting of dicarboxylic acids, tricarboxylic acids, and tetracarboxylic acids.

5. The thermosetting binder composition as claimed in claim 1, wherein the polycarboxylic acid is citric acid.

6. The thermosetting binder composition as claimed in claim 5, wherein the saccharide/citric acid weight ratio is between 25/75 and 55/45.

7. The thermosetting binder composition as claimed in claim 1, having a Brookfield viscosity, determined at 20 C. at a solids content of 70% by weight, between 0.25 and 4.0 Pa.Math.s.

8. The thermosetting binder composition as claimed in claim 1, having a pH of between 1 and 7.

9. The thermosetting binder composition as claimed in claim 1, comprising less than 10% by weight, with respect to the content of solid matter, of residual free polycarboxylic acid.

10. The thermosetting binder composition as claimed in claim 1, further comprising: at least one esterification catalyst selected from the group consisting of strong acids and Lewis acids.

11. The thermosetting binder composition as claimed in claim 5, further comprising: sodium hypophosphite.

12. A process for the manufacture of a product based on mineral or organic fibers which are bonded by an organic binder, said process comprising: (a) diluting the thermosetting binder composition as claimed in claim 1 with water down to a content of solid matter of between 2% and 10% by weight, to obtain a sizing composition; (b) applying the sizing composition to mineral or organic fibers; (c) forming a collection of sized mineral or organic fibers; and (d) the heating of heating the collection of sized mineral or organic fibers until the sizing composition has cured.

13. The process as claimed in claim 12, wherein the diluting stage (a) further comprises adding one or more additives selected from the group consisting of dust-preventing additives, silicones, and coupling agents.

14. The process as claimed in claim 12, wherein the fibers are mineral fibers and that the collection of fibers is mineral wool.

15. The process as claimed in claim 12, wherein the sizing composition, when it is applied to the mineral or organic fibers, comprises at least 80% by weight, with respect to its total dry matter content, of water-soluble oligomeric ester.

16. The process as claimed in claim 12, wherein the sizing composition, when it is applied to the mineral or organic fibers, comprises less than 10% by weight, with respect to its total dry matter content, of free sorbitol.

17. The thermosetting binder composition as claimed in claim 1, wherein the water-soluble oligomeric ester represents at least 90% by weight of the dry matter content of the thermosetting binder composition, and wherein the thermosetting binder composition contains less than 5% by weight, with respect to its dry matter content, of free sorbitol.

18. The thermosetting binder composition as claimed in claim 5, wherein the saccharide/citric acid weight ratio is between 30/70 and 50/50.

19. The thermosetting binder composition as claimed in claim 1, having a Brookfield viscosity, determined at 20 C. at a solids content of 70% by weight, between 0.3 and 1.5 Pa.Math.s.

20. The thermosetting binder composition as claimed in claim 1, comprising less than 5% by weight, with respect to the content of solid matter, of residual free polycarboxylic acid.

Description

EXAMPLES

[0071] Synthesis of an Oligomer of Xylitol and of Citric Acid

[0072] In a reactor thermostatically controlled at 150 C., 70 parts by weight of xylitol are heated until completely melted, then 30 parts by weight of citric acid and 1 part of sodium hypophosphite are added thereto all at once with stirring. Stirring is maintained and the temperature of 150 C. is maintained for the entire duration of the reaction.

[0073] After 5, 10, 30, 60, 90 and 120 minutes, an aliquot of reaction mixture is withdrawn and diluted with water down to a content of solid matter of 70% by weight.

[0074] This concentrated oligomer solution is used for the determination of the viscosity (Anton Paar MCR302 rheometer, 20 C., shear rate of 100 s.sup.1) and for the determination of the crosslinking start temperature by dynamic thermal mechanical analysis (DTMA).

[0075] FIG. 2 shows the change in the viscosity and in the crosslinking start temperature as a function of the reaction time.

[0076] It is observed that the viscosity of a concentrated oligomer solution (70% by weight of solid matter) increases steadily throughout the reaction. After 2 hours, it is greater than 1.6 Pa.Math.s.

[0077] The crosslinking start temperature decreases sharply during the first hour from more than 130 C. to approximately 115 C., then appears to reach a plateau at approximately 110 C.

[0078] The reaction mixture obtained after 60 minutes of oligomerization at 150 C. is used to compare its crosslinking kinetics with those of a xylitol/citric acid/SHP mixture (70/30/1).

[0079] For this, the reaction mixture is diluted in water until a diluted solution having a content of solid matter of 20% by weight is obtained. As comparison, an aqueous solution of non-preoligomerized xylitol/citric acid/SHP (70/30/1) having the same content of solid matter is prepared.

[0080] Two series of glass fabrics are respectively impregnated with these two aqueous binding compounds and then the fabrics are passed over a suction device which makes it possible to remove the surplus solution. The impregnated glass fabrics are subsequently hardened in a drying oven thermostatically controlled at 220 C. After curing for 18 seconds, 25 seconds, 35 seconds, 50 seconds and 70 seconds, a sample is subjected to a determination of the tensile strength. For this, the fabrics are cut into bands (250 mm50 mm) and their ends are inserted into the jaws of a tensile testing device.

[0081] FIG. 3 shows the change in the tensile strength as a function of the curing time at 220 C. of the fabrics of glass fibers impregnated with a binding compound according to the invention containing oligomers of xylitol and of citric acid and SHP, in comparison with glass fabrics impregnated with a binding compound containing xylitol, citric acid and SHP.

[0082] It is observed that the crosslinking speed of the binding compound according to the invention is significantly higher than that of the comparative nonpreoligomerized composition. After 35 seconds, the breaking strength of the sample according to the invention exhibits a tensile strength of approximately 80 N, whereas that of the comparative sample is only 20 N. The two curves converge after 70 seconds of curing, that is to say the final mechanical properties are the same for both fabrics bonded by a completely hardened binder.

[0083] These results show that, by virtue of the pre-oligomerization of the hydrogenated sugar and of the polyacid, it is possible to shorten the curing time of the binder, that is to say to accelerate the line or else to shorten the dimensions of the curing oven, which in both cases represents a saving in energy.

[0084] The same two binding compounds are used to produce glass wool on a pilot line.

[0085] Glass wool is manufactured by the internal centrifugation technique in which the molten glass composition is converted into fibers using a tool referred to as a centrifugation spinner, comprising a pan forming the chamber for receiving the molten composition and a peripheral strip pierced with a multitude of orifices: the spinner is rotated about its vertically arranged axis of symmetry, the composition is ejected through the orifices under the effect of the centrifugal force and the material escaping from the orifices is drawn into fibers with the assistance of a stream of drawing gas.

[0086] Conventionally, a size-spraying ring is arranged beneath the fiberizing spinner so as to distribute the binding compound evenly over the glass wool that has just been formed.

[0087] The mineral wool thus sized is collected on a belt conveyor fitted with internal suction chambers which hold the mineral wool in the form of a felt or of a lap at the surface of the conveyor. The conveyor then circulates in a curing oven maintained at 200 C. where the constituents of the size polymerize to form a binder. The insulating product obtained exhibits a nominal density equal to 10.5 kg/m.sup.3, a nominal thickness of approximately 80 mm and a loss on ignition of the order of 5%.

[0088] Table 1 below shows the quantities of different acidic chemical species detected in the gaseous emissions captured at the stack overhanging the inlet of the curing tank.

TABLE-US-00001 TABLE 1 Concentration of the acid in the gaseous emissions of the stack (mg/Nm.sup.3) Comparative Preoligomerized binding binding Reduction compound compound (%) Citric acid 360 105 70 Citraconic acid 405 250 38 Itaconic acid 55 25 55 Propionic acid 45 25 44 Acetic acid 12 9 25

[0089] It is observed that the pre-oligomerization of the reactants substantially reduces the emissions of acidic species.