Glass fibers

Abstract

Glass fibers have a chemical composition that includes the following constituents, in a weight content that varies within the limits defined below: SiO.sub.2 50-70%, Al.sub.2O.sub.3 0-5%, CaO+MgO 0-7%, Na.sub.2O 5-15%, K.sub.2O 0-10%, BaO 2-10%, SrO 2-10%, ZnO <2%, and B.sub.2O.sub.3 5-15%.

Claims

1. Glass fibers, the chemical composition of which comprises the following constituents, in a weight content that varies within the limits defined below: TABLE-US-00006 SiO.sub.2 50-70% Al.sub.2O.sub.3 0-5% CaO + MgO 0-7% Na.sub.2O 5-15% K.sub.2O 0-10% BaO 2-10% SrO 2-10% ZnO .sup.<2% B.sub.2O.sub.3 5-15%. wherein the chemical composition is free of bismuth oxide and the fibers are adapted for incorporation into paper sheets to be formed into filters or battery separators, wherein the fibers are adapted for incorporation into the paper sheets by placing the fibers in an aqueous suspension on a filter belt, removing liquid from the aqueous suspension by suction, and drying a resulting fibrous sheet.

2. The glass fibers as claimed in claim 1, such that the SiO.sub.2 content is within a range extending from 55% to 68%.

3. The glass fibers as claimed in claim 1, such that the Al.sub.2O.sub.3 content is within a range extending from 1% to 4%.

4. The glass fibers as claimed in claim 1, such that the CaO content is within a range extending from 1% to 4%.

5. The glass fibers as claimed in claim 1, such that the MgO content is within a range extending from 1% to 3%.

6. The glass fibers as claimed in claim 1, such that the BaO content is within a range extending from 3% to 8%.

7. The glass fibers as claimed in claim 1, such that the SrO content is within a range extending from 2% to 5%.

8. The glass fibers as claimed in claim 1, such that the ZnO content is at most 1%.

9. The glass fibers as claimed in claim 1, such that the B.sub.2O.sub.3 content is within a range extending from 8% to 13%.

10. The glass fibers as claimed in claim 1, a mean diameter of which is within a range extending from 0.1 to 3 m.

11. A sheet of paper comprising fibers as claimed in claim 1 wherein the sheet of paper is made by the placing the fibers in an aqueous suspension on a filter belt, removing liquid from the aqueous suspension by suction, and drying the resulting fibrous sheet.

12. A filter or a battery separator comprising at least one sheet of paper as claimed in claim 11.

13. An insulation panel core, formed by the superposition of a plurality of sheets of paper or webs as claimed in claim 11.

14. A vacuum insulation panel, comprising a core as claimed in claim 13, positioned inside a gastight envelope, generally made of a multilayer plastic film that is aluminized or that incorporates at least one sheet of aluminum, the assembly being placed under vacuum and sealed so that the internal pressure in the envelope is of the order of less than 0.5 mbar.

15. A process for manufacturing a sheet of paper using glass fibers as claimed in claim 1, comprising melting a glass having substantially the same chemical composition as that of said fibers, then fiberizing the glass, followed by the placing the fibers in an aqueous suspension on a filter belt, removing liquid from the aqueous suspension by suction, and drying the resulting fibrous sheet.

16. The glass fibers as claimed in claim 2, such that the SiO.sub.2 content is within a range extending from 60% to 67%.

17. The glass fibers as claimed in claim 3, such that the Al.sub.2O.sub.3 content is within a range extending from 1.5% to 2.5%.

18. The glass fibers as claimed in claim 4, such that the CaO content is within a range extending from 1.5% to 3%.

19. The glass fibers as claimed in claim 5, such that the MgO content is within a range extending from 1% to 2%.

20. The glass fibers as claimed in claim 6, such that the BaO content is within a range extending from 3% to 6%.

21. The glass fibers as claimed in claim 7, such that the SrO content is within a range extending from 2% to 4%.

22. The glass fibers as claimed in claim 8, such that the ZnO content is zero.

23. The glass fibers as claimed in claim 9, such that the B.sub.2O.sub.3 content is within a range extending from 9% to 12%.

24. The process as claimed in claim 15, wherein the fiberizing is done by flame attenuation.

25. Glass fibers, the chemical composition of which comprises the following constituents, in a weight content that varies within the limits defined below: TABLE-US-00007 SiO.sub.2 50-70% Al.sub.2O.sub.3 0-5% CaO + MgO 2.5%-5% Na.sub.2O 5-15% K.sub.2O 0-10% BaO 2-10% SrO 2-10% ZnO <2% B.sub.2O.sub.3 5-15%. wherein the chemical composition is free of bismuth oxide the fibers are adapted for incorporation into paper sheets to be formed into filters or battery separators by placing the fibers in an aqueous suspension on a filter belt, removing liquid from the aqueous suspension by suction, and drying a resulting fibrous sheet.

Description

(1) The following examples illustrate the invention in a nonlimiting manner.

(2) Fibers having the chemical composition indicated in table 1 below were obtained by flame attenuation fiberizing.

(3) Table 1 also indicates some characteristic temperatures denoted Tx and corresponding respectively to the temperature at which the glass has a viscosity of 10.sup.x poise (1 poise=0.1 Pa.Math.s), the values of x being 2, 2.5, 3, 3.5 and 4. All these temperatures are expressed in C.

(4) TABLE-US-00004 TABLE 1 Example 1 SiO.sub.2 65.0 Al.sub.2O.sub.3 1.9 B.sub.2O.sub.3 10.3 Na.sub.2O 8.8 K.sub.2O 2.8 MgO 1.3 CaO 2.1 BaO 4.3 SrO 2.8 Impurities 0.7 T2 1296 T2.5 1153 T3 1053 T3.5 979 T4 922

(5) The fibers were subjected to a short-term biopersistence test by intratracheal instillation as required by note Q of Directive 97/69/EC. The half-life was less than 40 days.

(6) Sheets of paper intended to be used in filters were manufactured by a papermaking process from the fibers. In terms of filtration properties after wet aging, the performance levels of the sheets obtained are better than those of the sheets obtained from standard (biopersistent) fibers. The mechanical properties (tensile strength, rigidity) are also comparable, or even better.

(7) The glass having the composition of example 1 was also subjected to a hydrolytic resistance test. According to this method, a glass powder ground in order to form a powder with a particle size of 360 to 400 micrometers is immersed in water heated to reflux for 5 hours. After a rapid cooling, the mixture is filtered and the solids contained in the filtrate are measured. The amount of dissolved material expressed in milligrams per gram of glass treated is 40.7.

(8) Table 2 below presents other examples of fibers according to the invention.

(9) TABLE-US-00005 TABLE 2 Example 2 Example 3 Example 4 SiO.sub.2 60.1 63.7 63.7 Al.sub.2O.sub.3 2.1 1.8 2.8 B.sub.2O.sub.3 10.8 11.0 11.0 Na.sub.2O 9.3 8.6 9.0 K.sub.2O 4.0 3.2 3.2 MgO 1.2 1.3 1.3 CaO 1.8 2.0 2.0 BaO 5.1 4.2 4.3 SrO 5.5 3.0 2.3 Impurities 0.1 1.2 0.4