US2521446A - Treatment of cellulose - Google Patents

Description

Patented Sept. 5, 1950 I I 2,521,446. TREATMENT OF onLLULosE Howard M. Buckwalter, Detroit, and Phillip D.

Montgomery, Oak Park, Mich., assignors to 1 United States Rubber Company, New York; N. Y., a corporation of New Jersey No Drawing. Application January 11, 1950, Serial No. 138,068

8 Claims.

This invention relates to the protection of native and regenerated cellulose fibers against deterioration by heat aging.

Deterioration of cellulose fiber upon subjection to elevated temperatures for prolonged periods of time is a very serious problem in the art. This problem is encountered particularly in the case of rubber articles which are reinforced with cellulose fiber, almost invariably stranded and in the form of cords or fabric, which may be a woven fabric having warp and woof threads or a so-called weftless fabric or web fabric composed of parallel cords joined together by a dry deposit of rubber latex, as described for example in the patent to Hopkinson, No. 1,424,020. Such cellulose fiber reinforced articles include pneumatic tires, steam hose, power transmission belts, conveyor belts, etc. These articles are subjected to levated temperatures in normal use, either bec use they are subjected to external heating, or because they generate heat within themselves by reason of repeated rapid flexing, as in the case of pneumatic tires. The deterioration of the reinforcing cellulose fiber under the action of heat is particularly evidenced by progressive reduction in tensile strength of the fiber, leading to eventual breakage. This deteriorating action of prolonged heating on cellulose fibers is a principal cause of failure of such articles as pneumatic tires and steam hose.

The principal object of the present invention is to provide an improved method of protecting cellulose fiber, especially when stranded and in the form of a fabric, against deterioration by heat aging. Another object is to provide articles of manufacture embodying cellulose fibers protected against heat deterioration, such articles of manufacture including cellulose fibers themselves, whether unstranded, stranded, or in the form of fabric, and vulcanized rubber articles reinforced with such cellulose fibers, such as pneumatic tire casings reinforced therewith. Other objects of the invention will more fully hereinafter appear.

According to the present invention, cellulose fiber is protected against deterioration by heat aging by treatment with guanazole, sometimes 'fective chemical in imparting to cellulose fibers the ability to withstand deterioration by the acknown as the tautomer of 3,5-diamino-1,2,4-

triazole. Guanazole has the structural formula NH.NH

have found that guanazole is a remarkably eftion of heat over extended periods of time.

In carrying out the invention, the guanazole may be applied to the cellulose fiber in any suitable manner, conveniently by immersing the fiber to be treated in a solution or dispersion of the guanazole fora time suflicient for the fiber to become substantially impregnated with the guanazole solution. The cellulose fiber employed is usually ordinary grey cotton fiber although the process of the invention may also be employed advantageously with the various regenerated cellulose fibers, such as viscose rayon. The invention is applicable to native cellulose fibers in general, such as fiax, hemp, etc., as well as to scoured, bleached and mercerized cotton. In place of immersing the fiber in the treating solution, we may incorporate the g'uanazole in the fiber in any other suitable manner, such as by spraying or brushing.

For convenience, we usually employ the guanazole in the form of an aqueous solution, typically at a concentration of from 1 to 15% by weight, although marked improvement in heat age resistance is also obtainable with surpris- 'ingly dilute solutions, e. g., solutions containing 0.5% of guanazole. If desired, more concentrated solutions may be employed, e. g., a 15 to 25% solution, although there is ordinarily only minor advantage in using solutions more concentrated than about 15%. Organic solvents, e. g. alcohol, may be substituted for the water if desired.

The treatment with guanazole may be carried out at room temperature, or at elevated temperatures, for example, up to the boiling point of the aqueous solution. The time of contact between the cellulose fiber and the guanazole solution should be sufllcient to permit substantial penetration of the fiber. Usually treatment times of from 30 seconds to 2 minutes at the boiling point are adequate for this purpose, although longer treatment times are without adverse effect and may be employed if desired.

In order to obtain the benefits of the treatment of this invention it is necessary that the guanazole remain in the cellulose fiber and be actually present in the fiber at the time the fiber is subjected to the heating which would ordinarily cause deterioration. I have found that guanazole present in the cellulose fiber in amount of at least 0.25% on the weight of the fiber, and usually in amount of from 0.5% to 7%, is effective to produce substantial improvement in the heat age resistance of the fiber. Larger amounts 3 than 7%, e. g. 10% or more, may be used if desired, but are generally unnecessary.

The following examples will illustrate the practice of my invention in more detail.

EXAMPLE 1 Samples of grey (native) cotton tire cord and viscose rayon tire cord were immersed in hot (95 to 100 C.) aqueous solutions of guanazole of 1% to 10% concentration for 2 minutes, as indicated in Table 1 below. The cord was then removed from the solution, and the excess solution was allowed to drain off the cord. The cord was then dried at 110 C. The cord was thereafter aged in the air at a temperature at 165 C. for 72 hours. This procedure is known as open heat aging. The 165 C. aging temperature is considerably in excess of the temperature at which. cotton cord ordinarily suffers-serious progressive irreversible loss of tensile strength due to chemical deterioration of the cotton by the action of thefiheat, namely 125 C. After such aging the te sile strength of the treated cord was determined at 70 F. and 60% relative humidity, and the results obtained were compared to control samples as indicated in Table 1.

tube and subjected to heat aging for 72 hours at 165 C., following which the tube was broken r stantially impervious rubber. Under sealed heat aging conditions, the improvement obtained was excellent both on rayon and cotton.

The foregoing examples show that the heat stabilizing activity of the guanazole increases with advancing concentrations of the aqueous solutions from which it is applied and hence is a direct function of the amount deposited on the cellulose. Results equal to those shown in the examples are obtained with a treating (immersing) time of thirty seconds at 100 0., or for longer periods of time at temperatures below 95"- Table i.E17ect of guwnazole on th open heat aging resistance of native cotton and viscose rayon tire cord Period of Cotton Rayon Concentration of Guanazole In 3? Aqueous Treating solmm Aging at Tensile Relative Tensile 252; Relative 165 0. Strength Retained Strength Strength Retained Strength Hours Lbs. Per cant I Lbs. Per cent 0 per cent 0 16-6 100 21. 0 100 0 per cent. 72 6. 0 36 100 8. 7 42 100 l per can 72 10. 2 61 171 8. 41 98 3 per cent. 72 12. 3 74 207 9. 0 43 103 5 per cent. 72 12. 9 78 216 ll. 1 63 l28 per cent 72 13- 2 80 222 12. 5 59 143 Table 2.Efiect of guanazole on the sealed tube heat aging resistance of native cotton and viscose rayon tire cord Period of 9" Concentration oi' Guanazo le In g Aqueous Tmatmg mm Aging at Tensile Relative Tensile g ggg Relative 165 0. Strength Retained Strength Strength Retained Strength Hours Lbs. Per cent Lou. Per cent 0 per cent 0 16. 6 100 21. 0 100 0 per cent 7 5. 2 3 100 4. 6 22 100 10 per cent 7 14- 4 87 278 16. 8 80 366 EXAMPLEZ Grey cotton tire cord and viscose rayon tire cord were treated with aqueous guanazole solutions of varying concentration for two minutes at 95 to 100 C. in the same manner as in Example 100 C. In all cases it is desirable that the treating conditions be such as to eflect the deposition of at least 0.25%, and preferably at least 0.5% of guanazole in the cellulose. When water is the solvent, solutions containing 1 to 15% of guanazole result in deposition of 0.5% to 7% of the material in the cellulose.

The guanazole used in these examples was prepared by the method of Stolle and Krauch (ibid.).

- The material was recrystallized from water in the form of white anisotropic crystals melting at 205-7" 0. It is not essential for purposes of this invention that the product be purified by recrystallization. Good results are obtained using the crude material, after removing the excess reactants.

1.. The cords were similarly drained, dried, and

thereafter subjected to sealed heat aging conditions, that is, the cords were sealed in a, glass From the foregoing it is evident that the invention provides a method of treating cellulose fibers, whether grey cotton fibers or other forms of cellulose fiber such as regenerated cellulose. whether in the form of fibers as such, or as yarn, cord or fabric, whereby the resistance of the fiber to the deteriorating effect of prolonged exposure to elevated temperature is substantially enhanced. Thus, the improved cellulose fibers of this invention containing guanazole are capable of improved serviceability especially when employed for such purposes as reinforcing tires, steam hose, and similar rubber-fabric composite articles which normally have a limited service life because of the deteriorating action of heat on the fiber reinforcement therein.

The guanazole treated fiber can be encased in rubber which may be subsequently vulcanized at elevated temperatures to a dense, strong product without any adverse efiects due to the presence of the guanazole. This is in contrast to certain other chemicals previously proposed for improving the heat age resistance of rayon tire cords and the like, but which are impractical because they decompose at vulcanizing temperatures with liberation of gases, causing blowing in the tire carcass assembly. Because the guanazole is comparatively stable at vulcanizing tem- Having thus described our invention. what we claim and desire to protect by Letters Patent is:

peratures it retains its chemical identity and re- 7 mains in the fiber, and is available for protecting the fiber on subsequent exposure of the vulcanized articles to high temperature conditions over extended periods of service.

The guanazole is not decomposed or removed by temperatures ordinarily employed in drying or baking tire cord after the cord, usually in the form of a web fabric, has been treated with rubber latex compositions.

While we have described our invention with particular reference to a preferred treatment of cellulose fibers intended to be used for reinforcing rubber articles, it will be understood that the improved guanazole-containing cellulose fibers of this invention are susceptible of many other uses where resistance to heat is a desirable characteristic. However, the improved cellulose fibers containing guanazole are especially adapted to production of vulcanized rubber-fabric composite articles, because the guanazole has no deleterious effect on the vulcanization, and resists vulcanizing temperatures, thereby resulting in improved vulcanized rubber-fabric composite articles.

1. The method of improving the resistance of cellulose fibers to the deteriorating effects of heat aging which comprises incorporating guanazole in the cellulose fiber in amount of at least 0.25% by weight.

.2. The method of improving the resistance of cellulose fibers to the deteriorating effects of heat aging which comprises impregnating the fibers with an aqueous solution containing at least 0.5% by weight of guanazole.

3. The method of improving the resistance of grey cotton fibers to thedeteriorating effect 01' heat aging which comprises impregnating the grey cotton fibers with an aqueous solution containing at least 0.5% by weight of guanazole.

4. The method of improving the resistance of regenerated cellulose fibers to the deteriorating effect of heat aging which comprises impregnating the regenerated cellulose fibers with an aqueous solution containing at least 0.5% by weight of guanazole.

5. A cellulose fiber characterized by improved resistance to the deteriorating effect of heat aging containing at least 0.25% by weight of uanazole.

6. A grey cotton fiber characterized by improved resistance to the deteriorating eflect of heat aging containing at least 0.25% by weight of uanazole.

'7. A rayon fiber characterized by improved resistance to the deteriorating effect of heat aging containing at least 0.25% by weight of guanazole.

8. A vulcanized rubber article reinforced with cellulose fibers containing at least 0.25% by weight of guanazole.

HOWARD M. BUCKWALTER. PHILLIP D. MONTGOMERY.

REFERENCES CITED UNITED STATES PATENTS Name Date DAlelio Feb. 20, 1945 Number

Claims (1)

1. THE METHOD OF IMPROVING THE RESISTANCE OF CELLULOSE FIBERS TO THE DETERIORATING EFFECTS OF HEAT AGING WHICH COMPRISES INCORPORATING GUANAZOLE IN THE CELLULOSE FIBER IN AMOUNT OF AT LEAST 0.25% BY WEIGHT.