US 2728680 A
Description (OCR text may contain errors)
United States Patent FLAME RETARDING AGENT Donald Duane, Highland Park, N. J., assignor to National Lead Company, New York, N. Y., a corporation of New Jersey No Drawing. Application October 30, 1951, Serial No. 253,973
2 Claims. (11. 106-15) This invention relates to the treatment of cellulosic material. More specifically it relates to the treatment of fibrous cellulosic materials to render the same fireresistant and to solutions used in such treatment.
Many types of agents have been proposed for rendering cloth, paper and other fibrous materials fire-resistant and some have been successfully employed, but few have the necessary properties to be able to withstand the rigors of handling and cleaning, particularly of washing and laundering. Some of the known treating agents are capable of being washed and laundered to a limited degree, but most of them appreciably alter the appearance, texture or tensile strength of the treated cellulosic material. In addition many of the known agents are not suificiently adherent and tend to separate from the treated material in the form of fine dust.
Among the fire-retarding agents which are non-launderable are the alkali phosphate, borate and sulfamate types. Launderable types of agents include resins, chlorinated resins or waxes added in combination with inorganic oxides, such as antimony oxide. They, however, have the disadvantage of altering the appearance of the material considerably, and that they must be added in large quantity. Titanium has been added in several fire-resistant processes, but in most of these the titanium has been added as titanium dioxide in order to obtain opaque pig- 'ment effects.
An object of this invention, therefore, is to produce fire-resistant fibrous cellulosic material. Another object is to provide a treating agent suitable for rendering the material fire-resistant. Still another object is to provide an agent for treating fibrous, cellulosic materials to impart flame and glow resistant properties thereto which will not be affected by washing or laundering. A further object is to produce fire-resistant fibrous cellulosic materials in which the appearance, texture and tensile strength of the materials have not been altered by the treating agent. These and other objects of the present invention will become apparent as the invention is more fully described.
In its broadest aspects this invention contemplates? a treating agent for rendering fibrous cellulosic materials fire-resistant or non-inflammable, said treating agent coinprising an aqueous solution of tetravalent titanium chloride and a soluble phosphate: murther clontemplatespfoduction of a fire-resistant cellulosic material by impregnating the same with such a solution, gelatinizing said solution on said material to form a transparent gel, alkalizing said gel-containing material with an alkaline neutralizing agent, and subsequently washing and drying said material. For improved flame-resistance and resistance to afterglow, the titanium chloride-soluble phosphate solution may advantageously also contain antimony chloride and this improved solution is also contemplated by the present invention.
Although substantially any soluble chloride or mixture of soluble chlorides of tetravalent titanium may be used, it is preferred to have from about 1.3 to 2.0 parts of chloride for each part of titanium in solution. Solutions "ice containing about 1.5 parts of chloride for each part of titanium are especially desirable. The soluble phosphate may be present in amount to give from 0.02 to 0.17 part of phosphorus for each part of titanium but it is preferred to have from 0.05 to 0.08 part of phosphorus for each part of titanium. Satisfactory results are obtained when the titanium concentration in the aqueous solution is between 50 and 150 g. p. 1. preferably 60-100 g. p. 1. As stated above, the addition of antimony trichloride to the titanium chloride-soluble phosphate solution results in improved flame-resistance, and glow-resistance, and also has a beneficial effect upon resistance to removal by laundering. Any amount of antimony chloride up to about 4 parts antimony may be used, although the effects are obviously not as pronounced when smaller amounts are employed, and it is preferred to use from about 1.4 to about 2.8 parts antimony. Amounts over 2.8 parts antimony, up to about 4 parts, contribute further, but the increased effect is less pronounced for further additions of antimony. When antimony is included in the solution, an additional amount of chloride should then be present to form antimony trichloride. The chloride values of the antimony chloride are in addition to the chloride values of the titanium chloride solution.
Dissolved alkali metals may be present in the solution without any harmful effect. When they are present they will normally be present as chlorides, and the chloride values present in these alkali chlorides are also in addition to the chloride values of the titanium chloride solution.
Fibrous cellulosic materials, which may be rendered fire-resistant by the process of the instant invention, include fabrics such as cotton, linen, regenerated cellulose, viscose and cellulose acetate, also natural fibers such as kapok, hemp, wood and wood products such as pressed board, cardboard, batting, paper, wood flour, sawdust, and the like. The cellulosic material is treated with the titanium salt solution by any convenient means such as by dipping the material in the solution or by spraying the solution on the material. Any excess solution on the cellulosic material may be removed, for example, by squeezing between rolls, deliquoring in a centrifuge, or any other appropriate method, depending upon the physical nature of the material. It is preferred to leave a quantity of solution on the material about equal to the weight of the material itself, i. e. a weight pick-up of about The titanium salt solution impregnated in the cellulosic material is gelatinized, for example by exposing the treated material to the atmosphere for a short interval of time. Satisfactory results have been obtained when the exposure is such as to reduce the Weight of solution held by the cellulosic material to about /2 to A of its original weight. The cellulosic material .containing the gelatinized treating agent is then subjected to an alkalizing agent in order to raise the pH of the treated material to above 7.5, preferably above 9.0, but not exceeding 12.0. The type of alkalizing agent used is unimportant although weak alkalizing agents such as for example sodium carbonate or ammonium hydroxide or carbonate are preferred. It has been found to be desirable, although not essential, to use alkalizing solution: which contain small amounts of soluble silicates, such a: the alkali silicates, since these agents increase the eflicacy of the treatment and contribute toward improved resistance to after-glow. The material is then rinsed well witl water for example by decantation in order to remove the soluble salts therefrom and subsequently dried.
It has been found that the preferred amount of impreg nant on the final material (dry basis) is about 7 to 14% of the weight of the fibrous cellulosic material when thc titanium chloride and soluble phosphate solution is user alone, while about 15 to 30% is preferred when the combination of titanium chloride, soluble phosphate and antimony chloride is employed. The entire process may be carried out at room temperature although if desired temperatures up to 60 C. may be used.
The exact nature of the physical and chemical changes that take place during this process is not completely understood. However, the solution of titanium chloride and soluble phosphate is apparently converted to a transparent gel which adheres tenaciously to the cellulosic material and is not removed by subsequent washing. It may be held in the pores or between the fibers of the cellulosic naterial, may be absorbed or adsorbed on the surface, or may react to some extent with the cellulosic material itself. To illustrate preferred embodiments of this invention the following examples are presented:
EXAMPLE I 80.5 parts of aqueous 36% HCl and 37.4 parts of con- :entrated phosphoric acid (85.5% H3PO4) and 925 parts of water were mixed in an acid resistant vessel. 450 parts of antimony trioxide were added to the acid mixture and agitated with a rotary paddle mixer. Agitation was con- :inued while 850 parts of titanium tetrachloride were added to the slurry. The titanium tetrachloride was added over a period of /2 hour during which time cooling was supplied by means of a cooling jacket to keep the temperature at about 60 C. The resulting solution contained 152 g.p.l. of titanium, 466 g.p.l. of chloride, 7.15 g.p.l. of phosphorus and 266 g.p.l. antimony This solution was diluted with water to produce a solution containing 60 g.p.l. of titanium, which was used for treating cloth. The cloth was cotton twill weighing 8.2 ounces per sq. yard. The cloth was immersed in the solution for 2 minutes and was passed through a hand wringer. The immersing and wringing operation was repeated to obtain thorough soaking. The treated cloth was then partially dried by exposing the cloth to the atmosphere for 1 /2 hours to gelatinize the treating agent on the cloth. The gelatinized treated cloth was then im mersed for minutes in a solution of sodium carbonate and sodium silicate containing 150 g.p.l. NazCOs and 16 g.p.l. sodium silicate to alkalize the solution retained on the cloth. The pH of the retained solution held by the cloth was 9.5. The excess solution was squeezed out of the cloth by passing the cloth through a hand wringer. The cloth was then washed well with water until the retained solution had a pH of 8.0 and thoroughly dried. The entire treatment procedure was carried out at room temperature. The treated cloth was subjected to the standard flame test and the results are recorded in Table I. -The standard flame test is called the microburner test and consists of exposing the smooth side of the fabric at an angle of 45, inch above the top of a burner. The flame, 1% inches in length is played on the fabric for 12 seconds. The extent of the charred area is recorded as well as the after-flaming and after-glow data in seconds. The procedure and apparatus assembly has been developed by the Quartermaster Corps of the United States Army and is described in Flameproofing Textile Fabrics by Robert W. Little, Reinhold Publishing Corporation, 1947, pages 1l7119.
EXAMPLE II 45 parts of phosphoric acid (85.5% H3PO4) and 1000 parts of aqueous 36% HCl were added to a vessel and agitated as described in Example I. Agitation was continued while 397 parts of sodium titanate powder containing 46.4% Ti were added to the acid mixture over a period. of A hour. Cooling was supplied during the addition of sodium titanate by means of a water jacket surrounding the vessel to hold the temperature below C. Agitation was continued for 1 hour at 60 C. in order to insure thorough dissolution of the sodium titanate. The resulting solution contained 179 g.p.l. titanium, 340 g.p.l. chloride, 11.8 g.p.l. phosphorus. A portion of this solution was diluted to 60 g.p.l. titanium and used for treating another portion of the same cloth described in Example I. The treatment procedure employed was substantially the same as that described in Example I. The treated cloth was subjected to the standard flame test and the results are recorded in Table I. A second portion of the undiluted solution was stored for six months and then diluted and tested in a similar manner. The storage was found to have no effect on its appearance or flameproofing characteristics.
Table I clearly illustrates that flame resistant properties are imparted to cloth treated with a solution of titanium chloride and soluble phosphate when used alone or in combination with antimony chloride; when titanium chloride and soluble phosphate are used in combination with the antimony chloride the cloth also exhibits glow resistant properties.
EXAMPLE III A third portion of the titanium chloride-soluble phosphate solution used in Example II was diluted to 60 g.p.l. titanium and used for treating wood flour.
The wood was immersed in the solution and agitated for 10 minutes to insure thorough soaking. The excess solution was separated from the wood flour by deliquoring on a filter press. The filter cake was then removed from the press and partially dried by 3 hours exposure to the atmosphere to gelatinize the solution on the wood flour. This treated partially dried wood flour was then immersed in a solution of g.p.l. sodium carbonate and agitated for 10 minutes to alkalize the solution on the wood flour and again deliquored. The pH of the retained solution in the wood flour was 9.5. The wood flour was then thoroughly washed in water until the pH of the retained solution was 8.0 and dried. The treated wood flour was tested for flame retardancy by holding it in the flame of a Bunsen burner for several seconds. It was observed to char but did not flame. Untreated wood flour when tested similarly flamed immediately and was almost entirely consumed.
While the above examples have shown the use of phosphoric acid as the soluble phosphate, it is to be understood that any soluble phosphate may be substituted therefor, to give an equivalent amount of phosphorus in solution. Among such soluble phosphates are the alkali phosphates, magnesium phosphate, calcium phosphate and the like.
By means of the present invention it has also been found that fibrous cellulosic material treated with titanium chloride and soluble phosphate retain flame resistance after laundering. The laundering is carried out in a tumbling chamber with 0.5% neutral soap solution at 70 C. When the preferred method of this invention is employed utilizing the combination of titanium and antimony compounds as described, the superior flame and glow resistant characteristics are retained even after repeated laundering. After 6 launderings, for instance, results are almost equal to those before laundering.
These results are compared in Table II with the results obtained from a well-known treating agent which consists of a mixture of borax, boric acid and diammonium hydrogen phosphate.
Table II A fibrous cellulosic material treated with a solution of titanium chloride and soluble phosphate retains a useful measure of flame resistant properties upon laundering. However, when the cellulosic material is treated with a combination of agents, that of a solution of tetravalent titanium chloride, soluble phosphate, and antimony chloride, the flame and glow resistant characteristics are maintained after repeated laundering. In addition to its favorable efiects upon flame and glow resistance the antimony chloride appears to have a beneficial effect upon the resistance of the titanium compounds to removal by laundering.
Recoveries of both titanium and antimony values are substantially 100% during processing. The amounts of titanium and antimony originally absorbed on the fibrous cellulosic material are equal to the amounts retained in the final material after processing.
When the titanium values are present in cellulosic materials in substantially opaque form the treated material has an unpleasant, chalky tone and a white dust may be continually removed from the surface. When the process of this invention is employed, however, the titanium values are fixed in the material in a form which does not substantially alter the appearance or texture of the material. The treatment process is simple, convenient and economical to use. By employment of this invention fibrous celluby the examples shown it is not intended to be strictly limited thereto and other modifications and variations ma be employed within the scope of the following claims.
1. An aqueous phosphate stabilized titanium solutior useful for treatment of fibrous cellulosic materials to impart flame-resistance thereto and capable of being storec for extended periods of time without deterioration comprising: an admixture of tetravalent titanium chloride and a soluble inorganic phosphate, the titanium of said titanium chloride being present in amount from about 50 tc 150 grams per liter and the chloride of said titanium chloride being present in amount from about 1.3 to about 2.C parts for each part of titanium, said soluble inorganic phosphate being present in said solution in amount from about 0.02 to about 0.17 part phosphorous for each part of titanium.
2. An aqueous phosphate stabilized titanium solution, useful for treatment of fibrous cellulosic materials to impart flame resistance thereto and capable of being stored for extended periods of time without deterioration comprising: an admixture of tetravalent titanium chloride, a
" soluble inorganic phosphate, and antimony trichloride,
losic materials may be treated to render them permanently the titanium of said titanium chloride being present in amount from about 50 to about 150 grams per liter, and the chloride of said titanium chloride being present in amount from about 1.3 to about 2.0 parts per each part of titanium in addition to the chloride content of the antimony trichloride, said soluble inorganic phosphate being present in said solution in amount from about 0.02 to about 0.17 part phosphorous for each part of titanium, and said antimony trichloride being present in amount from about 1.4 to about 4 parts antimony for each part of titanium.
References Cited in the file of this patent UNITED STATES PATENTS 1,804,633 McKee May 12, 1931 1,945,714 Winogradow Feb. 6, 1934 2,128,296 Baker et a1. Aug. 30, 1938 2,413,146 Larson Dec. 24, 1946 2,461,302 Truhlar et al Feb. 8, 1949 2,570,566 Lane et al Oct. 9, 1951