US3775155A

US3775155A - Flame retarding celluloscis using tetrakis (hydroxymethyl) phosphonium chloride

Info

Publication number: US3775155A
Authority: US
Inventors: R Eggenweiler; J Duffy
Original assignee: Hooker Chemical Corp
Current assignee: Occidental Chemical Corp
Priority date: 1971-11-04
Filing date: 1971-11-04
Publication date: 1973-11-27
Anticipated expiration: 1990-11-27
Also published as: BE790943A; NL174074B; DE2253976A1; FR2158453A1; IT970213B; JPS4856994A; CA990909A; NL7214855A; NL174074C; GB1388696A; DE2253976C2; FR2158453B1

Abstract

A process for imparting flame-retardant character to cellulosic containing material has been devised in which the cullolosic material is impregnated with an aqueous solution of a tetrakis(hydroxymethyl)phosphonium compound, preferably partially neutralized tetrakis(hydroxymethyl)phosphonium chloride, the impregnated material is at least partially dried, e.g., to about 5 to 25 percent by weight moisture retention, without fixation of the phosphonium compound on the material, the partially dried material is cooled and then treated with dry ammonia gas optionally in the presence of water vapor whereby the phosphonium compound is cured on the material and a fire-retardant character is imparted thereto.

Description

United States Patent [191 Eggenweileret a].

TETRAKIS (HYDROXYMETHYL) PHOSPHONIUM CHLORIDE Inventors: Robert B. Eggenweiler, West Seneca; James J. Duffy, Buffalo, both of NY.

Hooker Chemical Corporation, Niagara Falls, NY.

Filed: Nov. 4, 1971 Appl. No.: 195,843

Assignee:

References Cited UNITED STATES PATENTS 9/1971 Beninate et al ll7/62.2 6/1957 Reeves et al 1 17/136 UX 8/1963 Ullman 1 17/622 Nov. 27, 1973 3,236,676 2/1966 Coates et al. ll7/62.2 3,421,923 l/l969 Guth ll7/136X Primary Examiner-William D. Martin Assistant Examiner-J-larry J. Gwinnell AttorneyPeter F. Casella et al.

[57] ABSTRACT A process for imparting flame-retardant character to cellulosic containing material has been devised in which the cullolosic material is impregnated with an aqueous solution of a tetrakis(hydroxymethyl)phosphonium compound, preferably partially neutralized tetrakis(hydroxymethyl)phosphonium chloride, the impregnated material is at least partially dried, e.g., to about 5 to 25 percent by weight moisture retention, without fixation of the phosphonium compound on the material, the partially dried material is cooled and then treated with dry ammonia gas optionally in the presence of water vapor whereby the phosphonium compound is cured on the material and a fireretardant character is imparted thereto.

8 Claims, No Drawings This invention relates to a processof producing flame retardant cellulosic containing materials. More particularly it relates to a process of incorporating a phospho-- rus containing polymer in and on cellulosic containingmaterials.

BACKGROUND OF INVENTION The treatment of cellulosic containing materials to impart fire-retardant characterthereto has been the subject of much effort and many such processes have been proposed. However most, if not all, of these known procedures have. defects which militate against their complete acceptance by those working, in this area. I

As discussed in US. Pat. No. 3,236,676 many of the prior processes involving the use of tetrakis (hydroxymethyl)phosphonium condensation produces to impart flame-resistant properties to cellulosic materials possessed the defect of the tendency of the phosphonium compound to migrate to the surface of the material during the curing step.

Another defect of the prior art processes resides in the undesirable effects the flame retardant chemicals produce on the tensile properties of the treated materials.

U. S. Pat. No. 3,236,676 discloses a process wherein a phosphonium compound is fixed on the cellulosic material prior to curing with an agent such as ammonia. The process disclosed therein involves the steps ofimpregnating cellulosic materials with a solution of a tetrakis (hydroxymethyl) phosphonium salt, having a pH in the range of 3 to 9.5, heating the material between 100 C and 180 C., to dry the material and to fix the phosphonium salt on the fiber and thereafter treating the heat treated material with ammonia to cure the phosphonium salt on the material. This procedure, while generally successful in imparting flame-resistance to cellulosics has the disadvantages of requiring the heat fixation step, an additional processing step requiring the expenditure of time and capital, and often results in the tendering or otherwise depreciating the physical character of the cellulosic material.

OBJECTS OF THE INVENTION It is thus a principal object of this invention to devise a process for imparting fire retardancy to cellulosic containing materials which does not otherwise alter the physical properties of the treated material.

Another object is to devise a simple, economical, and effective process for treating cellulosic containingw materials with aqueous solutions of tetrakis(hydroxymethyl) phosphonium compounds to render such materials fire-retardant.

Other objects will be obvious from the following description of this invention.

BRIEF DESCRIPTION OF THE INVENTION In accordance with the present invention, cellulosic containing material is impregnated with a solution containing tetrakis(hydroxymethyl )phosphonium chloride, or a partially neutralized derivative thereof, the impregnated material is heated to at least partially dry it, without fixation of the phosphonium compound thereon, and then, after cooling the heated material,

DETAILED DESCRIPTION OF THE INVENTION A preferred mode of carrying out the process of the present invention comprises padding a cotton cloth with an aqueous solution of about 20 to about 40 percent by weight of tetrakis(hydroxymethyl)- phosphonium chloride which has been partially neutralized with about to about percent of the stoichiometric amount of caustic alkali. The padded cloth, containing about 25 to percent of its weight of the padding liquor, is dried at least partially, preferably to about 5 to about 25 percent moisture retention, without fixation of the phosphonium compound on the cloth, the partially dried cloth, is cooled and then is exposed to gaseous ammonia, preferably in the presence of water vapor to fix the phosphonium compound on the cloth, and thereby to impart thereto fire-retardant properties which are fast to repeated washings. The treated cloth is preferably rinsed with an aqueous solution of an oxidizing agent, such as hydrogen peroxide, sodium perborate and the like, which after treatment removes color and odor from the treated material.

The padding solution used may be merely an aqueous solution of tetrakis(hydroxymethyl)phosphonium chloride. However such solutions have a pH value of about 1 and may be detrimental to the textile material being treated. Preferably the solution is partially neturalized to a pH within the range of about 5 to 6.5. Alkaline materials such as sodium or potassium hydroxides, soda ash, organic amines such as triethanolarnine, triethyl amine and the like can be used to adjust the pH of the padding liquor.

It is preferred to dry the impregnated cloth, to remove at least a portion of the aqueous liquor. This drying step can be effected in a drying oven, by moving the padded cloth over heated cans, by hot pressing the cloth, and the like. Preferably the impregnated material is dried to a 5 to 25 percent by weight moisture retention. It has been found that this partial drying of the impregnated material does not result in the fixation of any noticable amount of the phosphonium compound on the fiber. It has also been found that the impregnated material can be dried substantially completely, at a moderate temperature, e.g., about 200 degrees Fahrenheit, without fixation of the phosphonium compound, and thereafter the dried material cooled by rewetting before treating with ammonia to fix the phosphonium compound.

Following the drying of the padded material, it has been found essential to cool the material prior to passage thereof into the curing apparatus. It has been found that by curing the dried impregnated material immediately aftr removal from the drier, or by maintaining the dried material hot, as by immediately placing and holding the material between layers of insulating cloth and then curing the resin on the material, little or no fixation of the resin on the material occurs on curing. Accordingly, it is an essential step of the process of this invention, to cool the material after removal from the drier for at least about one minute and preferably longer. Cooling of the hot dried material can be accomplished by holding the material at ambient temperature in air, by passing the material through a cold box, over cold cans or by spraying with water or the like.

Other salts than tetrakis(hydroxymethyl)phosphonium chloride can be used. Thus the corresponding acetate, bromide, sulfate, phosphate and the like can be used. The chloride, being the salt commonly available commercially, is preferred for this reason. The following examples will illustrate the process of the present invention. Parts and percentages are by weight and temperatures are given in degrees Fahrenheit, unles otherwise indicated.

EXAMPLE l A 40 percent aqueous solution of tetrakis(hydroxymethyl) phosphonium chloride was partially neutralized with about 80 percent of the theoretical amount of sodium hydroxide. The resulting solution was used to pad samples of 4.5 ounce per square yard cotton flannel. The padded cloth was then heated in a 200 oven for times specified in the following table. The partially dried cloth was extracted with water. A sample of the extract was evaporated to dryness and the residue analyzed.

About parts of the extract was admixed with 50 parts of methanol and the mixture was gassed with ammonia until no further reaction was evident. The precipitate which formed was separated by filtration, dried and analyzed. The results obtained are set out in the following table.

TABLE 1 Sample Sample Sample I 2 3 Wt. of F1annel-parts 39.6 37.3 38.5 Wt of Sample after Padding-parts 82.2 78.7 79.6 Time of Drying at 200 minutes 7.5 1.75 0 Wt. of aqueous Extractparts 4 l .9 39.5 40.9 Analysis of Extracted Solid Carbon 24.9 24.9 23.7 Hydrogen 6.7 6.9 6.9 Phosphorous 16.6 16.0 16.0 Chlorine 11.3 13.3 11.1 Wt. of Extract Sample Taken 5.1 5.1 5.2 Wt. of Ppt. 2.7 2.9 2.7 m.p. of Ppt C. 211-212 211-212 211-212 Analysis of Ppt Carbon 32.2 34.4 32.9 (38.4) Hydrogen 6.2 6.7 6.2 Nitrogen 13.7 14.7 13.9 (14.3) Phosphorous 23.9 25.7 23.7 (27.1

(Data in parentheses are analytical results from a product obtained by passing ammonia into an aqueous solution of tetrakis(hydroxymethy1)- phosphonium chloride).

These data indicate that the drying and/or heating of the phosphonium compound on the cloth does not fix or chemically alter the compound in this process.

EXAMPLE 2 This experiment illustrates the effect of cooling, i.e., the temperature of the padded cloth at the time of the curing step on the amount of resin fixed on the cloth.

An aqueous solution containing 27.5 percent of tetrakis-(hydroxymethyl)phosphonium chloride was neutralized with about percent of the stoichiometric amount of sodium hydroxide to give 27.5 percent of the partially neutralized species. Samples of 4.5 ounce per square yard of cotton flannel were impregnated with this solution to a wet pick up of about -95 percent. The impregnated cloth samples were dried for various periods at 200 and then exposed to gaseous ammonia to cure the resin. The treated material was then scoured in an aqueous alkaline bath containing sodium perborate and dried. Two of the samples were treated thusly directly from the drier with a relatively short, i.e., about 2 to 3 minutes cooling period. One sample was taken from the drier held in air for about one minute and passed over a perforated pipe emitting steam and then exposed to ammonia gas. One sample was passed over the perforated pipe emitting steam twice. Two samples were removed from the drier, held hot by placing in a hot pressing iron for about 5 minutes and immediately inserted between insulated cloth layers to minimize cooling and then exposed to ammonia gas. The weight of cured resin fixed to the cloth samples was determined in each instance. The treated samples were evaluated for fire retardance according to AATCC Standard Test Method 34-1966, initially, after 10 standard home washes and after 25 such washes.

The data obtained in these tests are set out in the following Table 11.

TABLE II Sample 1 2 3 4 5 6 'IHPC, percent 27. 5 27. 5 2 7. 5 27. 5 27. 5 27. 5 Wet pick up, percent- 91 96 94 95 96 Dried time at 200 2 6 1 6 1 6 3 6 3 6 Resin in cured sample, percent. 13.2 16.0 14.5 11.6 0 0 Initial char, in. 4. 3 2. 5 3. 7 5. 0 Burn Burn 10 Home washes.. 5.1 5.0 5. 0 6. 2 Burn Burn 25 home washes 4. 0 4. 2 4. 6 5.0 Burn Burn 1 Steamed by passing over perforated pipe once. I Steamed by passing over perforated pipe twice. {Heated in pressing iron and 119511191: W

These data indicate that heating the dried cloth without cooling before curing results in no resin add on. They also indicate the equivalence of curing the partially dried cloth after cooling with or without steammg.

EXAMPLE III In the manner described in Example 2, above, samples of 4.5 ounce cotton flannel were impregnated with a 27.5 percent aqueous solution of partially neutralized tetrakis(hydroxymethyl)phosphonium chloride. The samples were then heated at 200 for periods indicated in the following table following which the partially dried samples were treated as follows.

One sample was removed from the drier, held in air for about one minute and exposed to gaseous ammonia.

One sample was removed from the drier, held in air for about one minute, immediately heated in a flat bed press, removed therefrom, placed between layers of insulated cloth to prevent cooling and then exposed to gaseous ammonia.

One sample was removed from the drier, held in air for at least one minute, passed over a perforated pipe emitting steam and then exposed to gaseous ammonia.

One sample removed from the drier, passed two times over the perforated steam pipe and then exposed to gaseous ammonia.

One sample removed from the drier, placed in the flat bed press, sprayed with a fine water mist spray, and then exposed to gaseous ammonia.

Four samples removed from the drier, held for about 16 hours at ambient temperature and then exposed to gaseous ammonia.

All samples were weighed to determine the amount of resin add on and evaluated for fire retardance.

The data from this series of tests are compiled in the following Table III.

16.5, 17.4, and 17.5 percent respectively. The partially dried samples were cooled slightly and then exposed to a mixture of gaseous ammonia and wet steam by passing the samples over a perforated pipe emitting the steam-ammonia mixture. The cured samples were scoured in an aqueous alkaline bath containing sodium perborate.

Each of the cured resin impregnated cloth samples was tested for fire retardance and found to possess equivalent retardance which was permanent, that is the samples were still about equally resistant to charing even after 50 home washes.

By contrast, a sample of the cotton flannel was impregnated with the aqueous solution as described TABLE III Sample 1 2 3 4 5 6 7 s 9 Partially neutralized THPC.percent 27.5 27.5 27.5 27.5 27.5 27.5 27.5 27.5 27.5. Wet pick up, percent 91 93 93 92 97 92 91 90 89. Dry time at 200" ,Imin 6 6 a 6 a 6 10 2. Treatment N 0ne Hot time. One pass Two pass Hot cure Hold 16 Hold 16 Hold 16 Hold 16 steam. steam. spray. hrs. hrs hrs. rs. Resin add on, percent 11.2 2.0 9.9 13.7 11.3 10. Initial char, in 20.0 Burns... 3.6 3.0 4.1 10 hornew 4. J 4.0 3.2 5.5L home wash 3.8 do 3.7 4.2

These data indicate that resin impregnated on hot above and the impregnated cloth was heated for one wet cloth will cure better than resin impregnated on hot dry cloth; that resin impregnated on cool wet cloth will cure better than resin on hot wet cloth and that spraying with a water mist, steaming or holding for an extended period will reactive resin on a hot dry cloth substrate.

EXAMP E 4 An aqueous solution containing 22.5 percent of partially neutralized (85 percent) tetrakis(hydroxymethyl)phosphonium chloride, was used to impregnate three samples of 4.5 ounce cotton flannel. The wet pick up of the three samples was 92.5, 91.7, and 94.5 percent respectively.

One sample was held for about 16 hours at ambient temperature, and the resin add on was 15.7 percent, after exposure to gaseous ammonia. The cloth sample was tested for fire retardance and found to give an initial char of 3.7 inches.

The other two samples were heated at 200 for 1.5 and 3.0 minutes respectively and the partially dried cloth hung in air at ambient temperature for about 16 hours, and then cured.

The resin add on of these two samples was 14.6 and 17.3 percent respectively.

Both of these samples were fire retardant giving an initial char of 4.2 and 3.8 inches respectively.

These experiments show that impregnated material can be cured even after a holding period following partial drying without effect on the fire retardant characteristic. g

, XAMP E5 An aqueous solution containing 22.5 percent of partially neutralized tetrak-is( hydroxymethyl )phosphonium chloride was used to impregnate samples of 4.5 ounce cotton flannel. The samples had an add on of between about 85 and 90 percent.

The samples (three) were partially dried for one minute at 200, for 1.75 minutes at 200 and for 1.75 minutes at 250. The resin add on was determined to be minute at 200. The heated cloth was then exposed to a mixture of an ammonia gas and air to cure the resin on the cloth. The resin add on in this instance was 15.6 percent. The fire retardant characteristic of the treated cloth was substantially the same as that of the above samples. However, after 50 home washes, the fire retardance of this sample was substantially inferior to the above samples, the char increasing to about twice of that of the initial char length (3.94 inch initial; 6.58 inch after 50 home washes).

These data indicate the permanence of the fire retardant character of the material when cured with gaseous ammonia in the presence of water vapor.

What is claimed. is:

1. A method for producing fire retardant cellulosic containing materials which comprises a. impregnating a cellulosic containing material with an aqueous composition comprising a tetrakis(hydroxymethyl)phosphonium compound or a partially neutralized derivative thereof,

b. heating to at least partially dry the impregnated material without fixing the phosphonium compound thereon,

c. cooling said material for at least about one minute,

and

d. treating said material with gaseous ammonia or mixtures of gaseous ammonia and water vapor to produce a substantially insoluble polymer formed from said phosphonium compound and ammonia on and in said cellulosic containing material.

2. The method of claim 1 wherein the impregnated material contains from 5 to 25 percent by weight moisture retention after the heating step.

3. The method of claim 1 wherein the impregnated material is held at ambient temperature for at least about 1 minute after the heating step.

4. The method of claim 1 wherein the cooled material is exposed to steam and gaseous ammonia.

5. The method of claim 1 wherein the cooled material is exposed to gaseous ammonia.

. compound 8. The method of claim 1 wherein the phosphonium compound is tetrakis(hydroxymethyl)phosphonium chloride partially neutralized with from about '70 to about percent of the stoichiometric amount of a caustic alkali.

Claims

2. The method of claim 1 wherein the impregnated material contains from 5 to 25 percent by weight moisture retention after the heating step.
3. The method of claim 1 wherein the impregnated material is held at ambient temperature for at least about 1 minute after the heating step.
4. The method of claim 1 wherein the cooled material is exposed to steam and gaseous ammonia.
5. The method of claim 1 wherein the cooled material is exposed to gaseous ammonia.
6. The method of claim 1 wherein the heated material is cooled by spraying with water and thereafter exposed to gaseous ammonia.
7. The method of claim 1 wherein phosphonium compound is tetrakis(hydroxymethyl)phosphonium chloride.
8. The method of claim 1 wherein the phosphonium compound is tetrakis(hydroxymethyl)phosphonium chloride partially neutralized with from about 70 to about 90 percent of the stoichiometric amount of a caustic alkali.