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
  • C03C25/00—Surface treatment of fibres or filaments made from glass, minerals or slags
  • C03C25/60—Surface treatment of fibres or filaments made from glass, minerals or slags by diffusing ions or metals into the surface
  • C03C25/601—Surface treatment of fibres or filaments made from glass, minerals or slags by diffusing ions or metals into the surface in the liquid phase, e.g. using solutions or molten salts
  • C03C25/602—Surface treatment of fibres or filaments made from glass, minerals or slags by diffusing ions or metals into the surface in the liquid phase, e.g. using solutions or molten salts to perform ion-exchange between alkali ions

Definitions

• ABSTRACT OF THE DISCLOSURE This invention concerns a process for treating a sized fibrous siliceous substrate such as glass fabric with polyvalent metal cations, or a mixture of polyvalent metal cations with alkali metal cations, prior to thermal desizing so that the resultant desized fabric has good whiteness and retains a substantial portion of its original greige strength.
• This invention concerns processes for preparing fibrous siliceous materials having improved physical properties and the products resulting therein.
• this invention relates to improving the thermal and tensile properties of fibrous siliceous substrates through thermally induced ion exchange techniques.
• fibrous as used herein, particularly when used to describe glass (or silica), is used in contradistinction to massive, cast glass or any other nonfibrous siliceous material which possesses little or no applicability to the fabrication of fabrics or textiles.
• the term includes fibers, yarns, threads, ends, rovings and filaments or any other fiber form used in the preparation of textiles.
• siliceous as used herein is used in its generic sense so as to include glass, quartz and related substrates.
• siliceous fibers such as glass
• the fibers are exposed to various stresses due to friction and abrasion incurred during processing.
• a size In order to minimize destructive breakage and wear during processing it is customary in the industry to treat the fibers with a protective lubricant or binder material referred to as a size. Generally, this material is applied in the form of an aqueous dispersion while the fibers are being drawn out. Sizing usually consists of lubricating oils of natural or synthetic origin, starch, incorporated with small quantities of adjuvants such as surfactants, dispersing agents and the like.
• the sizing interferes with further processing and is undesirable.
• the sizing interferes with various operations such as coloring, laminating and finishing. Because of its effect on finishing operations, it is important that the substrate be desized with as little reduction in the finished products strength as possible.
• Sizing can be removed with either chemical or thermal treatment.
• the present chemical treatments are disadvantageous in several respects. For example, they are time consuming and hence costly, and they do not readily produce an acceptable product.
• chemical desizing does not permit weave setting as is possible with thermal treatments. For these reasons chemical desizing is seldom satisfactorily employed.
• Thermal desizing procedures are often classified as high or low temperature according to the process temperature utilized. In most low temperature processes the sized fibrous substrate is heated between about 500 and 700 F. and the size slowly volatilized from the fabric by maintaining the fabric in the temperature environment for between about 55 and hours. A good white product is obtained but at the expense of a considerable decrease in tensile strength of the fired product. Further, weave setting which is a desirable attribute of thermal desizing processes cannot be achieved much below temperatures of about 900 F.
• High temperature desizing is generally accomplished by exposing the sized substrate to temperatures between about 1100 F. to about 1300 F. for very short treatment times, usually for about 210 seconds.
• the high temperature desizing is advantageous in that it gives rise to a very white weave set product.
• the sized material treated with a salt comprising an alkali metal cation such as potassium, cesium or rubidium, preferably in the form of a thermally decomposable oxygen-containing anion is desized by firing between about 600 F. to 1300 F. for a short period of time to heat clean the glass and give it optimum strength.
• Another object of this invention is the development of a process whereby a sized siliceous substrate containing monovalent cations is treated with a composition containing at least one polyvalent cation selected from Groups lI-A and Ill-B of the Periodic Table and possessing a larger atomic radius than sodium, is exposed to elevated temperatures until the sizing is removed and a substantial replacement of monovalent cations with the enu merated polyvalent cations takes place through thermally induced ion exchange.
• a more particular object of this invention is the utilization of the above-described thermal desizing process wherein the treating composition includes an appropriate fluxing substance which reduces the melting point of the treating composition and permits its use at lower process temperatures.
• An even more specific object of this invention described above is application of a treating composition
• a treating composition comprising (a) at least one polyvalent cation selected as described above, combined with (b) at least one fluxing additive selected from the group consisting of sodium, potassium, rubidium and cesium.
• An additional object of this invention is the development of a modified thermal ion exchange process wherein the strengthening process is conducted within or below the temperature range normally required for desizing so that reversible migration of the desired polyvalent cations does not take place and maximum strength is retained.
• a fibrous siliceous substrate to be heat cleaned and containing replaceable monovalent cations is contacted with a strengthening composition comprising at least one polyvalent cation, then heated to a temperature and for a time sufficient to substantially effect thermally induced ion exchange resulting in a heat cleaned substrate possessing high tensile strength.
• the fibrous substrate is usually washed with water to remove soluble salts which are present.
• an acid such as acetic acid
• wetting agents may also be incorporated into the wash liquid to improve the effect of the Washing step.
• the fibrous material is then subjected to the usual finishing operations practiced in the art.
• a glass fabric containing replaceable sodium cations and one or more thermally destructible contaminants such as sizing and lubricants is contacted with a strengthening composition melting below about 1000 F., said strengthening composition comprising at least one polyvalent cation selected from Groups II-A and III-B of the Periodic Tables, said cation having a larger atomic radius than the sodium cation.
• the anionic portion of the polyvalent ion is preferably an oxygen-containing salt which produces oxygen upon heating at elevated temperatures.
• the glass fabric is heated from about 600 F. to about 1300 F., preferably from about 900 F. to about 1200 F., until a substantial portion of the monovalent ions in the fabric have been replaced with polyvalent cations.
• the success of the inventive process is predicated upon the unexpected and substantial gain in physical properties obtained in the final product when the fibrous siliceous substrate impregnated with an excess of at least one polyvalent cation prior to firing, is heated at a temperature and time sufficient to displace smaller monovalent atoms such as hydrogen and sodium with larger sized polyvalent cations, and burn off the sizing. Therefore, no particular theory or mechanism is postulated. However, it may be constructive in the understanding of the instant invention to consider the fibrous substrate prior to firing as containing mobile, replaceable monovalent cations such as so dium and/or hydrogen interspersed in the network formers of the glass structure. During the heating of the substrate impregnated with less mobile polyvalent cations of larger diameter, the smaller monovalent cations are displaced by the larger, less mobile polyvalent cations through thermally induced ion exchange and a stronger article is produced.
• Illustrative anions among many others are the nitrate, chlorate, iodate, bromate, perchlorate, persulfate, carbonate, phosphate, sulfate, acetate, formate and the like.
• the anionic portion of the polyvalent cation should be an oxygen-containing molety which can be thermally decomposed to release oxygen.
• oxygen-releasing anions are preferred since they catalyze the removal of sizing and other components at firing temperatures lower than usually required.
• the anions can be in the form of simple salts, double salts, complex salts or mixtures of one or more salts, as long as they decompose at or below the firing temperature to produce oxygen.
• a fibrous glass substrate to be heat cleaned is contacted with a strengthening composition melting below the upper temperature range used in the burning off process.
• the preferred compositions comprise one or more fiuxing substances which exert a eutectic effect upon the composition, particularly when the relatively high melting Group II-A oxygen-containing salts are employed. While these eutectic type additives can be selected from a variety of substances, particularly good results have been obtained when an oxygenated potassium salt is incorporated with the polyvalent cation into the strengthening composition.
• the concentration of polyvalent cations used to treat the fibrous substrates in the favored and preferred. embodiments is not critical to the invention as long as sufficient cations are applied to assure the replacement of the monovalent cations such as sodium with the polyvalent cations.
• the substrate is treated with from about 0.5 to about 10% by weight, of treating salt in the form of an aqueous solution to obtain a pickup of about 0.l.53.0%, by weight, of cation. Since the cost of the polyvalent cations is low, a large excess of polyvalent cations, over the required quantities can be applied without deleterious efliect.
• the ratio of the eutectic additive to polyvalent cation is a variable depending upon several factors including the polyvalent cation, the additive employed and the temperature at which the treating process is conducted. For this reason no precise ratio of additive to polyvalent cation is suggested. However, when potassium nitrate is used as the additive the ratio of potassium to polyvalent cation ranges from about 0.5 part by weight to 2.0 parts by weight of potassium to each part by weight of polyvalent cation.
• the strengthening compositions can be applied by a variety of techniques in a number of different forms.
• a convenient method is to apply the compositions in the form of their aqueous solutions.
• mixtures of acids and water, alcohol and water with or without acids or other solubilizing agents can be utilized.
• any conventional application technique such as padding, dipping, spraying, coating, etc., can be used.
• Various adjuvants or additives such as softeners, surface active agents and the like, which will aid in the uniform application of the cations to the fibrous substrates can be incorporated into the application solution.
• the salts can also be applied to the fibrous substrate in treatment 6, a 4% aqueous solution is used.
• a wet pickup approximately resulted in a dry concentration of approximately 0.60%, by weight, of the salt while in the sixth treatment a dry concentration of 1.2% is obtained.
• the dried fabric is heat cleaned at the temperatures set forth in Table II, and the thermally desized fabric washed with 3% acetic acid, rinsed with water and finished with an acrylic latex finish to protect the fibers against selfabrasion.
• the salts can be added to the starch-oil size which is commonly applied to fiber glass yarns in the first step of their manufacture. This is useful since the salts are present on both warp and fill yarns and obviates an additional application step.
• the salts can also be applied to the warp yarns only during the conventional warp sizing step.
• the salts are added as a component to warp sizing and the yarns treated in the usual manner.
• the salts are present on the warp yarns with the sizing materials.
• the fabric is then woven and fired to produce the improved, heat cleaned substrate.
• the presence of the polyvalent salts can also exert a favorable effect on the untreated fill yarns.
• the cations can be applied at any stage of fabric manufacture prior to heat cleaning. These include fibers, yarns, rovings, etc. As indicated earlier the inventive process is applicable to fibrous and siliceous materials, including all types of fiber glass which in contrast to massive or cast glass can be made into fabrics.
• the temperature of the heat cleaning, desizing or firing step can vary widely according to the particular siliceous substrate employed, the sizing or other additives present, the cations applied during treatment, the length of heating and the effect sought. Ordinarily the temperature will vary between about 600 F. to about 1300 F. with the greatest benefits under the present invention being obtained at temperatures ranging between about 900 F. and 1200 F.
• the firing time is not critical and as previously stated is dependent upon the firing temperature and the end use to which the product is to be put.
• the broad range of exposure time can range from fractions of a second to about 24 hours or even more. More conventionally the heat treatment will vary between about a second and several hours.
• the mode of heating is not important; any suitable heat treating device such as ovens and/or furnaces can be effectively used. These include forced air ovens and mufile furnaces and the like.
• EXAMPLE I In this example, a casement style E glass fabric of Style S/473 (4.4 oz. per sq. yd., 150 1/0) containing sizing is treated in a textile padder with aqueous solutions of the nitrate salts shown in the table below. In the first five treatments, 2% aqueous solutions are employed, while From the results shown above, it can be seen that Samples 3-6, each treated with the salt solutions of this invention, exhibit improved tensile strength properties compared to the control. Sample 2, had poor strength characteristics compared to the control-this is attributed to the fact that the sodium cation is replaced with a magnesium cation of smaller atomic radius, presumably resulting in the production of an inferior and weakened fabric. All products exhibited excellent whiteness.
• the casement style glass fabric of Style 5/473 is treated with a solution comprising 1% NaNO 1% KNO 1.6% Ca(NO -4H O and 0.4% Ba(NO Good tensile strength retention is obtained after heat cleaning for 4 seconds at 1060 F.
• EXAMPLE III Style 8/604 (a 12 oz./sq. yd. E glass air filtration fabric 42 x 30 warp 1502/2 filling l/4, 9% bulked yarn) is treated with an aqueous solution containing 2% KNO3, and BPI(NO3)2.
• the fabric is dried and then heat cleaned for 15 seconds at 1080 F.
• the fabric is washed with 3% acetic acid, rinsed with water and redried. After finishing with a phenyl methyl silicone emulsion the fabric was tested for tensile strength with the following results:
• Example II Tensile Strength, lbs/inch width Warp Direction Fill Direction As per Example III .2 487 156 Greige Fabric, Untreated. 460 158
• the fabric treated at 1080 F. has a warp tensile strength of 192 as compared to 206 for the greige.
• the 1080 F. fabric had a warp tensile strength of 487 as compared to 466 for the greige.
• the fired fibrous siliceous product is a white material, free from sizing and other degradable products which retains a substantial portion of the original greige strength upon finishing.
• substantial portion of greige strength is meant at least 80% of the original greige fabric strength when finished.
• the products of this invention lend themselves for applications as laminating substrates. Further, the substrates impregnated with polyvalent cations, but unfired, can be stored for long periods of time until required.
• the invention is advantageous in several respects. These include economy and simplicity of operation, relatively mild process conditions and short process cycles. In addition, the process yields reproducible and reliable products employing readily available starting materials and process equipment.
• a process for heat treating sized fibrous siliceous substrates containing monovalent cations without causing substantial degradation of the tensile strength comprising the steps of:
• a process for heat treating sized fibrous siliceous substrates containing sodium cations between about 600 F. to 1300 F. without causing substantial degradation of tensile strength comprising the steps of:
• a process for thermally desizing a fibrous glass substrate containing sodium cations between about 900 F. and 1200 F. without causing substantial degradation ot tensile strength comprising the steps of:
• composition comprising at least two polyvalent cations having an atomic radius larger than sodium, said polyvalent cation being selected from Groups II-A and IIIB of the Periodic Table, at least one monovalent cation selected from the group consisting of sodium, potassium, rubidium, cesium and mixtures of these cations, and at least one oxygen containing anion, said composition melting between about 900 F. to 1200 F., and
• the treating composition includes at least one monovalent cation selected from the group consisting of sodium, potassium, rubidium, cesium, and mixtures of these cations and at least two polyvalent cations having an atomic radius larger than sodium, said polyvalent cations being selected from Group IIA of the Periodic Table.
• ratio of monovalent cation to polyvalent cations ranges from about 0.5 to about 2 parts, by weight, of monovalent cation to each part, by weight, of polyvalent cation.

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• Life Sciences & Earth Sciences (AREA)
• Chemical & Material Sciences (AREA)
• General 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)
• Chemical Or Physical Treatment Of Fibers (AREA)
• Glass Compositions (AREA)
• Surface Treatment Of Glass Fibres Or Filaments (AREA)

Priority Applications (7)

Applications Claiming Priority (1)

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Cited By (3)

Citations (3)

• 1966
  • 1966-08-11 US US571732A patent/US3382135A/en not_active Expired - Lifetime
• 1967
  • 1967-07-27 FR FR115915A patent/FR1540434A/fr not_active Expired
  • 1967-07-31 BE BE702086D patent/BE702086A/xx unknown
  • 1967-08-08 GB GB36411/67A patent/GB1141184A/en not_active Expired
  • 1967-08-09 SE SE11300/67A patent/SE332278B/xx unknown
  • 1967-08-10 DE DE19671719575 patent/DE1719575A1/de active Pending
  • 1967-08-10 NL NL6711024A patent/NL6711024A/xx unknown

Patent Citations (3)

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