Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C13/00—Fibre or filament compositions
  • C03C13/001—Alkali-resistant fibres

Definitions

• This invention relates to novel alkali-resistant glass fibers, and their preparation.
• the fibers find particular use in strengthening cement and concrete products, and may find extensive use as substitutes for asbestos in such products.
• Asbestos fibers have long been used to strengthen cement and concrete products. However, since the recognition of the toxicity of asbestos there have been many attempts to develop fibers to replace it.
• One of the most important properties of fibers for use in cement and concrete products is resistance to chemical attack by the alkali in the cement mixtures. Because the diameter of the fibers is usually very small, e.g., about 2 to 20 micrometers, a relatively small degree of attack can cause a large decrease in mechanical strength.
• the fibers are prepared by means of procedures conventionally employed in preparation of glass fibers, i.e., melting of the appropriate admixture of raw materials, followed by drawing or spinning to form the fibers.
• compositions can be readily, and inexpensively, formed from mixtures of naturally occurring slate and limestone.
• Suitable raw materials are not, however, limited to freshly mined slate and limestone, but may include waste slate and waste marble, e.g., materials left over from mechanical working of slate and marble. In addition, other materials such as basalt may be used.
• the raw materials are initally ground, or otherwise reduced, to a suitable particle size, e.g., about 50 to 200 mesh, and are then admixed and melted in suitable refractory vessels such as pots or crucibles of refractory materials such as chromite, alumina, platinum, etc.
• Suitable melt temperatures are obtained by conventional means, such as electric furnaces or gas furnaces, and will generally range from about 1300 to 1400°C, with the optimum depending on various factors such as the specific composition of the melt, raw materials employed, and desired properties of the product fibers.
• the admixture is desirably maintained at the melt temperature for a period of about 3 to 5 hours to ensure complete fusion of the ingredients.
• the molten mixture is then cooled to a temperature, generally about 1100 to 1250°C, suitable for working, and fibers are formed by conventional means such as drawing at high speed through a fine orifice, or by spinning to form a glass wool. Conventional means, such as contacting with screens of appropriate mesh size, are also employed to reduce the fibers to suitable lengths. Optimum diameters and lengths of the fibers will vary with the specific use; however, diameters of about 8 to 12 microns and lengths of about 1/8 to 1/2 inch are generally most suitable for use in cement and concrete products. Fibers thus prepared have been found to have tensil strengths of about 80,000 to 150,000 psi and densities of about 2.75 to 2.95 gm/cc. Alkali resistance of the fibers has been found to be much superior to Pyrex glass and as good as commercially available alkali-resistant glasses.
• Glass fibers were prepared from three mixtures of Vermont slate and limestone, and were compared with fibers of a commercially available alkali-resistant (AR) glass and pyrex glass.
• the mixtures of slate and limestone consisted, respectively, of 40% slate and 60% limestone, 50% each of slate and limestone, and 60% slate and 40% limestone.
• Chemical compositions, in weight %, of the slate-limestone mixtures, as well as the AR and pyrex glasses, are given in Table 1.
• the slate and limestone were ground to a particle size of 100 mesh and thoroughly mixed by means of a ball- mill.
• the mixtures were then melted at 1350°C in air, and were maintained at this temperature for a period of about 3-5 hrs .
• the melt was then cooled to 1150°C, and fibers of a diameter of 20 microns were formed by drawing.
• the fibers were reduced to lengths of 1/2 to 1 inch by means of mechanical cutters .
• These fibers , and similar fibers of AR and pyrex glasses were then tested for alkali resistance by reaction in 5% NaOH solution at 90°C for 4 hours. Results of the tests, as well as properties of the glasses are shown in Table 2. It is evident from the data of the table that the glasses of the invention are much superior to Pyrex and are as good as commercially available AR glasses.

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• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Glass Compositions (AREA)

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• 1982
  • 1982-11-30 JP JP83500191A patent/JPS58502054A/ja active Pending
  • 1982-11-30 WO PCT/US1982/001670 patent/WO1983001947A1/en not_active Application Discontinuation
  • 1982-11-30 EP EP19830900157 patent/EP0095490A1/de not_active Withdrawn

Non-Patent Citations (1)

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