US 2979374 A
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United States Patent muons mx'mn CELLULOSIC rrrosrnoNo lg rgg. ETHERS AND PROCESS or PREPA- George L. Drake, In, and Wilson A. Reeves, Meta irle, and John D. Guthrie, New Orleans, La., assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Filed Oct. 31, 1957, Ser. No. 693,787
4 Claims. (Cl. 8-120) (Granted under Title 35, US. Code (1952), sec. 266) A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.
This invention relates to the ethers of fibrous cellulose in which the fibrous form and the properties it produces in textiles, i.e., properties such as hand, feel, tensile strength and the like are retained substantially unaltered or with proper degree of substitution can change all of these properties with the formation of a water-soluble cellulosic material. This invention provides fibrous phosphonomethyl ethers of cellulose; the salts of such ethers; soluble phosphonomethyl ethers of cellulose; a process of reducing the combustibility of fibrous cellulosic materials; and a process of producing fibrous cellulose with high cation exchange capacity.
It is known that Z-phosphatoethyl ethers of cellulose can be made. For example, Leon H. Chance at al. in United States Patent 2,743,232, dated April 24, 1956, had demonstrated that fibrous Z-phosphatoethyl ethers of cellulose can be produced by reacting a cellulosic material with 2-chloroethylphosphoric acid in aqueous alkali. In that patent he converted the hydroxyl groups of the cellulose material to Z-phosphatoethyl groups In his invention he introduced a group into the cellulosic molecule in which the phosphorus is joined to the carbon through an oxygen atom which is an ester linkage. We have found that we can convert the hydroxyl group of the cellulose material to phosphonomethyl groups (--OCH,PO,=). to the carbon atom directly and the linkage between the phosphonomethyl group and the cellulose is an ether linkage. Since this is an ether linkage it should be a more stable link since it is generally known that esters are subject to acid and basic hydrolysis whereas ethers are not. It is reported in the literature [M. I. Kabachnik and T. Ya. Medved. Izvest. Akad. Nauk S.S.S.R., Otdel. Khim. Nauk 1951, 95-7; M.I. Kabaclinik, E. S. Shepeleva. Izvest. Akad. Nauk S.S.S.R., Otdel. Khim. Nauk 1951, 185-91] that the reactivity of the halogen atom on the compound with the structure or its derivative is very low so that the PO, grouping may be said to be passivating rather than activating. It
is surprising, therefore, that contrary to this fact, we have now found that using the proper conditions we can make this halogen react with the hydroxyls of a cellulosic material in the presence of an alkali metal hydroxide even without the use of pressure. We have also found that with proper conditions a water soluble derivative of a cellulose can be obtained.
It is an object of our invention to provide new fibrous metal salts of phosphonomethyl ethers of cellulose. Another object is to produce an new water soluble phosphonomethyl ether of cellulose. Another object is to produce a new fibrous phosphonomethyl ether of cellulose which has a high cation exchange capacity. Another object is to provide a process of reducing the combustibility of fibrous cellulosic materals. Other objects will become apparent hereinafter.
In accordance with the invention we prepare this new phosphonomethyl ether of cellulose by reacting a fibrous cellulosic material containing hydroxyl groups with an aqueous solution of an alkali metal salt of chloromethyl phosphonic acid (or other salts of the acid in which the alkali metal will replace the cations of the salt) and an excess of alkali metal hydroxide. The corresponding phosphonic acid derivative of cellulose can be produced by soaking the phosphonomethyl ether of cellulose in a dilute aqueous solution of a strong mineral acid until all of the alkali metal atoms have been replaced by hydrogen atoms.
Reduction of the combustibility of fibrous cellulosic materials containing hydroxyl groups is produced by converting the phosphonomethyl ether of cellulose to the corresponding free acid derivative in the above way and converting this derivative to the corresponding ammonium salt by reacting with ammonia.
Soluble fibrous phosphonomethyl cellulose is produced by allowing a cellulosic material containing hydroxyl groups to be wet out with a solution consisting of an alkali metal salt of chloromethyl phosphonic acid and excess alkali metal hydroxide dissolved in water, at a temperature which is suflicient to convert the hydroxyl groups of the cellulosic material to phosphonomethyl groups (-0CH,PO where the order of substitution is such In this case the phosphorus is joined that 2% or more phosphorus is introduced.
Cotton fibers, regenerated cotton fibers, aminized cotton fibers, carboxymethylated cotton fibers, paper, sulfoethylated cotton fibers, and other like materials containing one or more hydroxyl groups per anhydroglucose unit are suitable fibrous cellulosic materials. Cotton fiber is the preferred material. The above disclosed reactions can also be extended to cover other types of polysaccharide hydroxyls for example starch, sugar and any material containing one or more hydroxyls per anhydroglucose unit.
Free fibers, sliver, yarn or fabric can be phosphonomethylated, but yarn or fabric is preferred.
Phosphonomethyl groups can be introduced into cellulosic materials by using the metal salt of the chloromethyl phosphonic acid, or the acid chloride. The metal salt is preferred. This invention is not limited to the chloroderivative. Compounds having the following structure are suitable:
O X-CHrQ-(O R):
where X is any of the halogens and R is hydrogen, alkyl, aryl, alkyl-aryl or substituted alkyl, aryl or alkyl-aryl The aqueous solution suitable for use in the present process can be aqueous solutions of the salt and any alkali metal hydroxide containing from about 10% to 30% by weight of unreacted alkali metal hydroxide and from about 1% to 30% by weight of the alkali metal salt of chloromethyl phosphonic acid. Aqueous solutions containing from about 20% to 30% unreacted sodium hydroxide and from 12% to 15% of the sodium salt of the acid are preferred.
A variety of ways can be used to produce the fibrous phosphonomethyl ethers of cellulose. The cellulosic material can be wet out by either of the aqueous solutions first followed by the other, or by wetting out the material using an aqueous solution containing a mixture of the two salts such that the required concentration of salts necessary for the introduction of the phosphonomethyl groups are present. The one solution method is preferred.
The reaction can be conducted at temperatures from about 20 C. to temperatures at which the thermal decompositon of the cellulosic material becomes notitceable. Preferably cotton fabric is padded with an aqueous solution containing chloromethyl phosphonic acid disodium salt and unreacted sodium hydroxide to a pickup of around 125-200% and heating from about 75415 C. for about to 30 minutes or from about 2 to minutes at about 140 to 160 C.
The impregnated fibrous cellulosic material can be heated using any conventional heating apparatus; for example, ovens, hot boxes, heated cans, heated tenter frame, molten metal bath, infrared lamps, lens and sunlight, irons, presses and the like. Excess salts are washed free from the fibrous cellulosic material with water or a wateralcohol mixture and dried by any of the above heating equipment.
The combustibility of the fibrous cellulosic materiaL x preferably cotton, is reduced by phosphonomethylating to a phosphorus content of about 0.2%. Higher contents can be obtained using the proper conditions. The alkali metal salts can be converted to the dibasic acid and then converted to the ammonium salt and with values of about 0.2% phosphorus will produce a black char on burning with no afterglow. Even with such a small add'on this process could be used in aiding other flame retardants where afterglow is a problem or where a tough ash is needed. The ammonium salts of phosphonomethylated fibrous cellulosic material containing about 1 to 3% phosphorus wll not burn even if a small strip is held in the vertical position and lighted at the bottom.
Water soluble cellulosic materials can be obtained by wetting the cellulosic material with an aqueous solution consisting of about 20 to 25% NaOH and about 10 to 20% chloromethyl phosphonic acid and heating from about 5 to 30 minutes at 120 to 150 C. Water solubility can be obtained using fibers, yarn or fabric. For ex-' ample, varying amounts of substitution are necessary dependent on the form of cellulosic material used. Two percent phosphorus on cellulosic yarn is readily soluble in 1% alkali or water. Washing of the soluble yarn is best done using alcohol-water mixtures varying in alcohol content from about 2% to about 80%. The preferred amount is about 20 to 40%. The soluble phosphonm methylated cellulosic material can be reprecipitated in alwho], acetone and other similar solvents. This offers the possibility of making phosphorus containing fibers by extrusion. This water soluble derivative can be further used as a phosphorus containing size for other materials. Since this soluble phosphonomethylated cellulosic material contains reactive groups it is possible to form a permanent size containing phosphorus and also offer some flame retardancy.
The reactive phosphonomethyl groups of the phosphonomethylated cellulose react with ethylene oxide, ethyleneimine or derivatives such as butadiene dioxide, tris l-aziridinyl phosphine oxide or sulfide and the like and enhance the properties of the textile products such as flame retardancy, change the ion exchange capacity and also render the water soluble phosphonomethylated cellulose insoluble.
Combustibility tests The fabric prepared in the following examples was cut into strips 1 cm. wide and at least 5 cm. long. The strips were held with their surface vertical and their long edge at the indicated angle from the vertical and ignited at the specified point. Whether or not the burning would continue along the strip and the presence or absence of afterglow was observed. Strips of the cloth used in each of the examples, prior to treatment, would burn continuously even when held vertically and ignited at the top.
EXAMPLE I Phosphonomethylation 48 x 48 cotton sheeting fabric was padded using 2 dips and 2 nips and light squeeze roll pressure, with a solution consisting of: 15 parts chloromethyl phosphonic dichloride, 25 parts sodium hydroxide and 60 parts water. Solution wet pickup was 143%. The wet fabric was heated for 30 minutes at 110 C. in a forced draft oven, washed with water and dried. The cloth contained 1.99% phosphorus and had an ion exchange capacity of 1.179 meq./gm. A strip of the fabric would pass the angle flame test with a slight afterglow.
Ammonium salt production Preparation of the solution for Example 1 Solution was made as follows: The specified amount of chloromethyl phosphonic dichloride was reacted (keeping the solution cool) with the calculated quantity of NaOH to form the sodium salt of the acid. The water used for the NaOH solution which was used to neutralize the acid chloride was taken from the total amount of water used in the preparation of the desired percent solution. This solution and the required quantity of unreacted NaOH and remaining water was cooled and then mixed.
EXAMPLE II Curing times, curingtemperature, caustic concentrations and chloromethyl phosphonic dichloride concentration in relation to phosphorus content SOLUTIONS Percent Percent Solution Number CICH POCI, H 0
Solutions were re axed ustn rooedure as in re tion Emma L P P 8 D D 1 SOLUTION 1 Strip Nfliflalt Per- Cation Burn Cure Tem- Cure oent Exchange An 10 porature.0 Time Phos- Capacity, on Hi Percent Percent phorus meqJgm Belt, P N
degrees 110 6rn1n 0.36 0.300 45 0.30 0.13 110 30min 0. 0.342 90. 140 6min--- 0.42 0.329 100 140 30111111.. 0.42 0.300 110 Room tem- 18h1s... 0.015 0.073 -black perature ash no alterglow.
SOLUTION 2 0 m P t Ecaltlon SirlplBurn CureTem rature. ureT s ereen xc ange ngeon "(B Phosphorus Capacity, NH salt,
meqJgm. degrees 110 6mtn 0.15 0.160 0-black ash n0 afterglow.
0.015 0.003 0b1eek esh no alterglow.
SOLUTION 3 Strip NHaSalt Per- Cation Burn Cum 'Iem- Cure cent Exchange Angle perature.C. Time Phos- Capacity, on NH. Percent Percent phorus meqJgm. Salt. P N
degrees 110 min. 0.92 0.594 90 0.74 0.38 110 30111111-- 1.72 1.110 175 140 5min- 1.62 1.070 175 140 30m1n 1.50 1.000 140 Roomtem hrs... 0.01 0.073 lJ-black perature ashno alter glow.
SOLUTION 4 Dlssolvod.
EXAMPLE V Phosphonomethylation of aminized cotton fabric A sample of aminized 48 x 48 cotton sheeting containing 0.7% nitrogen was padded with a solution composed of 25% NaOH, 15%
O ClCIEIsl Cl:
and 60% water using 2 dips and 2 nips with a light squeeze roll pressure. The wet sample was heated in a forced draft oven for 30 minutes at 140 C. A good reaction was obtained. The fabric was slimy when wet and had a leather-like feel when wet. When dry it was parchment like. It would pass the 90-110 angle flame test not in the ammonium salt form.
EXAMPLE VI Phosphonomethylation of cotton in yarn form to produce water soluble cotton 12-4s cotton yarn which had been scoured, bleached 8 and mercerized was padded with a solution consisting o! 35.1 parts by weight 0 (Clin -(OH),
96.5 parts by weight of NaOH and 180 parts by weight of water to a wet pickup of 196%. Heated for 30 minutes at 140 C. and washed in 20% ethanol-water solution. Dried. The yarn had a weight increase of 13%. A sample of this yarn when placed in water dissolved immediately. The phosphorus content was 2.12%. The yarn would pass the '-l10 strip bum angle test in the sodium salt form. In the ammonium salt form the yarn could not be ignited.
Empie VII The same solution and procedure used in Example VI was repeated on 48 x 48 cotton sheeting. It was also water soluble and contained 2.4% phosphorus. It took longer to go into solution than the yarn sample in Example VI. The flammability was the equivalent of the yarn in Example VI.
EXAMPLE VIII pH in relation to cation exchange capacity of phosphonomethylated cotton pH VB. CAPACITY Cation Exchange Capacity, meqJgm.
EXAMPLEIX Repeated phosphonomethylation 48 x 48 cotton sheeting was padded through a solution containing 25 unreacted caustic and 15% chloromethyl phosphonic dichloride (converted to the sodium salt by hydrolysis with the calculated quantity of water and then to the sodium salt by adding the calculated quantity of sodium hydroxide) and 60% water. The wet fabric was heated in a forced draft oven for 30 minutes at C., washed and dried. The phosphorus content was 1.84% and the cation exchange capacity was 1.075 meq./gm. The angle strip burn ammonium salt form was This fabric was retreated in the above manner. It had a phosphorus content of 3.96% and a cation exchange capacity of 2.333 meg/gm. The ammonium salt form could not be ignited.
1. A process for preparing chemically modified fibrous cellulosic textile material containing from about 0.02% to about 5.0% phosphorus in the form of phosphonomethyl ether of cellulose comprising: padding a fibrous cellulosic textile material having at least one free hydroxyl group per anhydroglucose unit of the cellulose from to 30 minutes at temperatures of from 16 to 140 C., the higher temperatures being used with the shorter heating times.
2. A process for reducing the combustibility of fibrous cellulosic textile materials comprising: wetting textile fibers having at least one free hydroxyl group per anhydroglucose unit of the cellulose molecule with an aqueous solution containing from 5 to by weight of an alkali metal salt of chloromethyl phosphonic acid and from 15 to by weight of an alkali metal hydroxide to a wet pickup of from 125 to 200%, heating the wetted textile material for from 5 to minutes at a temperature of from to C., employing the shorter times with the higher temperatures, rinsing the heated textile material free of alkali with a 1 to 5% aqueous solution of a strong mineral acid, rinsing the acid-treated textile material in water, and then neutralizing the acid-treated textile material with a 5% aqueous solution of ammonium hydroxide.
3. A chemically modified cellulosic textile in which some of the hydroxyl groups have been converted to --OCH,PO X, groups in which X is a member of the group consisting of hydrogen, alkali metal, and NH the degree of conversion being such that the modified cellulosic textile contains from 0.01% to 4.0% by weight of the modified cellulosic textile of phosphorus.
4. A chemically modified water soluble cotton textile in which some of the hydroxyl groups have been converted to --0CH,PO X, groups in which X is a member of the group consisting of hydrogen, alkali metal, and NH wherein the degree of conversion is such that the modified cotton contains from 2.0% to 4.0% by weight of the modified cotton of phosphorus.
References Cited in the file of this patent UNITED STATES PATENTS 2,743,232 Chance Apr. 24, 1950 2,678,330 Van Gorder May 11, 1954' 2,691,567 Kvalnes Oct. 12, 1954