United States Patent Office Patented Oct
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3,281,225 United States Patent Office Patented Oct. 25, 1966 2 One such material that has been commonly used is METHOD oF INCREASNG3,281.225 iHE DURABILITY OF sulfur trioxide gas, usually introduced into or formed GLASSWARE within an annealing lehr wherein the glassware is being James J. Hazdra, Joliet, and Arthur S. Gunderson, Lock treated so as to create an acid gas atmosphere therein. port, Ill., assignors to Brockway Glass Company, Inc., 5 However, with this method of utilizing sulfur trioxide Brockway, Pa. gas, it has been very difficult to effectively reach the in No Drawing. Filed Sept. 30, 1965, Ser. No. 491,902 terior surfaces of glass containers, since the containers 8 Claims. (C. 65-30) enter the lehr filled with air which must be displaced. A further practical consideration is that the gas is ex This application is a continuation-in-part of applica 0 tremely hazardous and difficult to confine in plant opera tion Serial No. 157,839 filed December 7, 1961, and now tional equipment, which limits its commercial use in the abandoned. above form. Sometimes, when small glassWare con The present invention relates to a method of treating tainers for which the interior surfaces must have their glassware so as to remove surface alkalinity therefrom. alkalinity reduced, sulfur either in the form of pellets The invention is more particularly related to an im or powder has been introduced therein. The sulfur upon proved method of removing surface alkalinity from the heating and in the presence of oxygen will react to form interior surfaces of glass containers such as are to be sulfur trioxide. Any unreacted sulfur at the end of this used in the storage of pharmaceutical or medicinal process is difficult to remove from the interior of the glass products. container. Sulfur also produces exteremely low yields During the formation of glass containers, small amounts 20 of sulfur trioxide. Sulfur dioxide gas had been utilized of alkali, normally in the form of sodium or other alkali in the same manner as elemental sulfur. The yields of metal compounds, are brought to the surface of the sulfur trioxide from sulfur dioxide are low because the glassware. Water and other liquids commonly placed in activation energy of the oxidation of sulfur dioxide is glass containers, upon storage will often leach out alkalies too high. For efficient conversion the presence of a present at the alkali-rich glass surfaces. For many pur catalyst is required. Sulfur dioxide is also unpleasant poses to which glass containers are normally put, the to smell and presents toxicity problems. In addition, Sul small amounts of alkali found at the surface of glass fur dioxide when used to saturate the lehr atmosphere containers will not be harmful. When the glass con is adsorbed by the refractories in the lehr. The ad tainers are, however, used to store medicinal or pharma sorbed gases slowly evolve to put an undesirable sodium ceutical preparations the leashing of surface alkali into 30 sulfate bloom on the outside of glass containers being the medicinal or pharmaceutical preparation can be ex annealed in the lehr for a day or two after the actual tremely harmful in many cases. For this reason, the use of sulfur dioxide was terminated. interior surface alkalinity of pharmaceutical or medicinal Another acidic material that has been used in alu glass containers should be kept to a minimum. minum chloride; however, aluminum chloride is very The ability of glassware to resist leaching by the water hydroscopic and is therefore handled with much difficulty or liquids often stored therewithin is commonly termed under atmospheric conditions. Ferric sulfate has also the "chemical durability' of glass containers. This in been utilized to some degree. Upon decomposition, fer vention, therefore, relates to a method of improving the ric sulfate yields not only sulfur trioxide, but also water chemical durability of glass containers. insoluble ferric oxide which presents problems of re Tests and standards for determining the durability of 40 moval from the inside of the glass container upon com glassware have been set up the U.S. Pharmacopeia, which pletion of the surface alkalinity removal operation. Am standards must be successfully met before glass containers monium salts containing both sulfur and oxygen such as will be acceptable for the storage of pharmaceutical or ammonium sulfate, ammonium bisulfate, or ammonium medicinal preparations. Such a standard or test (Type thiosulfate have also been utilized and, as in the above II) is set out in the U.S. Pharmacopeia XVI, pages 918 mentioned procedures the ammonium compounds are satis 920 (1960). This test is based upon the fact that hot factory in removing surface alkalinity of glassware. The high purity water placed in such containers will pick up ammonia gas, however, produced during the decomposi or leach alkalies and can thereafter be titrated against tion of the ammonium compounds, is not consumed in an acid so as to determine the amount of alkali picked the dealkalization process. Ammonia, although not so up by the water. Such a procedure comprises autoclaving 50 toxic as sulfur dioxide gas, is extremely noxious. a sealed glass container having high purity water therein. It is therefore an object of this invention to provide The water contained in the glassware is then titrated an improved method of reducing the surface alkalinity of against 0.02 N sulfuric acid using methyl red as an glass containers so that glass containers so treated will indicator to determine the increase of alkalinity of the pass the U.S. Pharmacopoeia Type II test, without the water. This procedure provides a base or standard that 5 5 undesirable effects of prior art practice. can be used in determining the amount of reactive ma Another object of this invention is to provide an im terial to be placed within glassware containers for satis proved method of reducing the interior surface alkalinity factorily reducing the therein contained surface alkalinity of glass containers by introducing into such glass contain to such an extent that they will qualify under the U.S. ers an oxygen and sulfur containing material, which when Pharmacopeia test. 60 heated will release an active agent capable of reacting Several different methods and materials for removing with the glass surface alkalies to form a water soluble glass-surface alkalinity have been or now are being used. product. These materials are acidic of themselves or, upon heat Another object of this invention is to provide an im ing, will decompose or pyrolyze into said gases which proved method of reducing the interior surface alkalinity 65 of glass containers by introducing into such glass con either by themselves or in combination with water to tainers an oxygen and sulfur containing material, which form acid substances therefrom, will combine with the when heated will form a water soluble salt and sulfu alkalies present at the surface glassware to react there trioxide which reacts with the glass surface alkalies to with. These previous methods are satisfactory in remov later form a further water soluble salt. ing surface alkalinity. However, they are subject to 70 A further object of this invention is to provide an undesirable characteristics which limit their commercial improved method of reducing the interior surface alkalin lSC. ity of glass containers by introducing into the interior of 3,281,225 3 4. such glass containers a material which when heated re glass surface to obtain immediate contact of the pyrolytic leases products which are ultimately consumed including sulfur trioxide therefrom produced upon pyrolysis with an active agent capable of reacting with the glass surface the alkaline material present at the surface of the glass alkalies to reduce the alkalinity of such glass surfaces. ware and thus has the advantage of localized action. Another object of this invention is to provide an im Examples of the present invention are as follows: proved method of reducing the interior surface alkalinity of glass containers by introducing into such glass contain Example I ers an oxygen and surfur containing material, which when Twenty-four randomly selected previously untreated heated is completely consumed by such heating to produce 0.132 ounce soda-lime glass vials were filled with special a high yield of an active agent capable of reacting with 0. distilled water, sealed and autoclaved in the manner set surface alkalies to form water soluble salts. forth in the U.S. Pharmacopeia. This water was col A still further object of this invention is to provide lected from the vials and then titrated against .02 normal an improved method of increasing the chemical durability sulfuric acid. It required 6 ml. of the sulfuric acid to of glassware by introducing a heat decomposable non neutralize the alkaline sodium material leached from the volatile alkali metal acid sulfate into glassware containers 5 interior surfaces of the untreated glass vials during the whereon upon heating, such material is entirely consumed autoclaving. That is, 0.00012 equivalents of alkaline and produces in situ sulfur trioxide gas, which reacts with Sodium material or 0.00024 mole of sodium ions were surface glass alkalies to form water soluble sulfate salts. present at the interior surface of the glass vials. Since The specific nature of this invention, as well as other two moles of sodium bisulfate are need to produce one objects and advantages thereof, will become apparent 20 mole of sulfur trioxide, 0.00048 mole of anhydrous sodium from the following detailed description. bisulfate are needed to neutralize the alkaline material As an aid in understanding the present invention ref present at the surfaces of the 24 vials. This amounts to erence is had to the following basic equations: 0.059 gram of anhydrous sodium bisulfate or 0.067 gram 230-320° C.