US3903337A

US3903337A - Method for processing cellulose containing material to impart flame resistance

Info

Publication number: US3903337A
Application number: US457847A
Authority: US
Inventors: Kosuke Yamamoto; Masahiro Kono
Original assignee: Mitsui Toatsu Chemicals Inc
Current assignee: Mitsui Toatsu Chemicals Inc
Priority date: 1974-04-04
Filing date: 1974-04-04
Publication date: 1975-09-02
Anticipated expiration: 1992-09-02

Abstract

This invention relates to a new method for imparting flame resistance coupled with excellent resistance to washing to cellulose containing fibrous materials by treatment with a methylene ether bond bearing phosphorus compound.

Description

States Yamamoto et a1.

atet 1 1 14- 1 Sept. 2, 1975 METHOD FOR PROCESSING CELLULOSE CONTAINING MATERIAL TO IMPART FLAME RESISTANCE [75] Inventors: Kosuke Yamamoto, Kamakura;

Masahiro Kono, Manazuru-machi, both of Japan [73] Assignee: Mitsui Toatsu Chemicals,

Incorporated, Tokyo, Japan [22] Filed: Apr. 4, 1.974

[21] Appl. No.: 457,847

52 us. c1. 427/390;-lO6/l5 FR; 252/8.1;

260/932; 427/394; 8/116 P 51 Int. c1. c091 3/28 58 Field of Search 117/136, 143 R; 252/31;

[56] References Cited UNITED STATES PATENTS 3,374,292 3/1968 Zahir 117/136 X 3,381,062 4/1968 Zahir 117/143 R 3,381,063 4/1968 Zahir 260/937 3,577,270 5/1971 Guth et'al 1 17/136 3,679,778 7/1972 Nachbur et a1. 117/136 X 3,700,403 l0/1972 Nachbur et al. 117/136 X Primary Examiner-William D. Martin Assirtant ExaminerJanyce A. Bell Attorney, Agent, or FirmLane, Aitken, Dunner & Ziems 57 1 ABSTRACT 7 Claims, 1 Drawing Figure METHOD FOR PROCESSING CELLULOSE CONTAINING MATERIAL TO IMPART FLAME RESISTANCE BACKGROUND OF THE INVENTION For imparting flame resistance to cellulose containing fibrous materials, the urea phosphate process is conventionally employed (see, for example, Japanese Patent Publication No. 4950/1962). The cloth processed in such a manner, however, suffers from many defects, for example, p; or resistance of the flameproofing to washing, a rough finish and extremely bad feel, as well as a large reduction in strength.

A relatively new process for flameproofing is disclosed in Japanese Pat. No. 69 l ,726. Japanese Pat. No. 691,726 discloses that certain N-methylolated phosphorus compounds bearing a methylene ether bond are effective in processing cellulose containing fibrous materials to impart flame resistance thereto. Then N- methylolated phosphorus compounds disclosed therein are obtained by the condensation of 3-dimethylphosphonopropionic acid methylolamide, in the presence of an organic solvent such as toluene or benzene, followed by methylolation with a reagent capable of generating formaldehyde. At lines 17-19 of column 21 of the specification of Japanese Pat. No. 691,726, it is taught that the non-methylolated intermediates afford no permanent flameproofing effect. The non-methylolated intermediates include the compounds represented by formula (l) appearing at the bottom of page 38. If n of formula l0) equals 2, then formula becomes:

/PCH2CH2CNHCH2OCH2NHCCH2CHZP (I) R0 I wherein R may be the same or different alkyl, alkenyl or alkoxyalkyl groups.

The N-methylolated phosphorus compounds containing a methylene ether bond, i.e., the end products used in the process as described in Japanese Pat. No. 691,726, emit a formaldehyde odor and generate formaldehyde in the course of the processing of cellulose containing fibrous materials. The noxious odor of the formaldehyde produces an undesirable working environment.

OBJECT OF THE INVENTION An object of the present invention is to impart to cellulose containing fibrous materials permanent flame resistance, that is flame resistance coupled with excel lent resistance to washing.

Another object of the present invention is to provide novel flameproofing agents which do not emit a formaledhyde odor and which will not generate formaldehyde in the course of flameproofing processing, thus improving the working environment for the flameproofing process.

Still another object of the present invention is to provide and advantageous method for the preparation of flameproofing agents with which the above enumerated objects can be achieved.

SUMMARY OF THE INVENTION The present invention provides a method by which the phosphorus compounds of formula I, having a 5 methylene ether bond but no N-methylol groups, can

be utilized to impart permanent flame resistance to cellulosic fibers; that is, flame resistance coupled with excellent resistance to washing. As previously noted, the compounds of formula I have not previously been recognized to have such a utility.

In accordance with the method of the invention, it is possible to greatly improve the working environment for the flameproofing processing of cellulose containing fibrous materials.

The present invention also provides an easy method for the preparation of phosphorus compounds having a methylene ether bond out no N-methylol group, i.e. the compounds represented by formula I.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows an infrared adsorption spectra chart for one of the compounds of formula I, i.e. N,N'- oxymethylenebis (dimethylphosphonopropion) amide.

DETAILED DESCRIPTION OF THE INVENTION As previously noted, the present invention provides a method for the utilization of the phosphorus compounds having a methylene ether bond but no N- methylol groups represented by formula I(hereinafter referred to as phosphorus compounds I) as agents for flameproofing cellulose containing fibrous materials.

On the other hand, phosphorus compounds similar to those of formula I and represented by the following general formula II 35 R 0 OR PCH2CH2CNHCH2HNCCH2CH2P (II) R 0 OR 2 o o o o 4 (I) (II) +CI-I O However, when cellulose containing fibrous materials are processed for flameproofing with the phosphorus compounds I in accordance with the method of the present invention, the conversion of methylene ether bond into the methylene bond does not occur under general processing conditions. Although it is not completely clear why the methylene ether bond in the phosphorus compounds of formula I does not change into a methylene bond under general processing conditions,

it is theorized that, since the bond to the cellulose is a phosphorus compounds of formula I used in the monomolecular attachment, as in acid hydrolysis in almethod of the present invention is optional; however, cohol, the methylene ether bond splits off and simultathe following three processes are preferred: neously reacts with the hydroxy group in the cellulose The first process comprises condensation with water fiber thereby attaching to the cellulose fiber in the form 5 removal, in the presence of an acid catalyst such as of phosphonopropionamidomethyl ether. p-toluenesulfonic acid, of the monomethylol derivative As described in the foregoing, the methylene ether of, for example, d-dimethylphosphonopropionamide, bond in the phosphorus compounds I used in the as described in the published specification of Japanese method of the present invention is a potential func- Patent No. 646,127, This reaction may be represented tional group which splits off under processing condiby the following equation 2:

-H O PCH CH CNHCH OH 9 I (2 R26 O O tions and reacts with the cellulose fiber. Accordingly, With this first process, however, it is difficult to proother functional groups reactive with cellulose fibers, 2O duce phosphorus compounds I of relatively high purity such as the N-methylol radicals of the compounds used n h r f orma de yd tends to remain n h in the process of the above described Japanese Pat. No. produ t. 691,726, are unnecessary. A second and more preferred process comprises con- The specification of japanese Pat. No. 691,726 densation of N,N'-oxydimethylenebisacrylamide and a teaches that the phosphorus compounds I exhibit no phosphorous acid diester, either in the presence of a permanent flameproofing effect. However, phosphorus solvent such as dioxane or in the absence of a solvent, compounds I show an excellent permanent flameproofand in the presence of a basic catalyst such as sodium ing effect as demonstrated by the following examples: methoxide, as depicted in the following equation 3:

R O (CH =CHCNHCH o POH---' (I) (3) The discrepancy with regard to observations as to the However, the process for the preparation of N,N'-

permanent flameproofing effect of compounds I indioxydimethylenebisacrylamide used as the starting ma cates, as will be shown in the examples to follow, that terial in this second method is relatively complicated the phosphorus compounds I must be produced with and moreover the impurities contained in the N,N'- carefully controlled process conditions. oxydimethylenebisacrylamide adversely affect the cat- In the steps for manufacturing the phosphorus com- 40 alyst used in the reaction depicted above by equation pounds I and, in particular, in the step in hich the 3, and requires purification by methods such as recrysmethylene ether bond is introduced it is necessary to tallization. As a consequence, this method represents a carefully adjust reaction conditions. When the reaction relatively expensive route for the production of the conditions are not optimized, for example when the pH compounds of formula I. in the reaction system is too low, when the reaction The third process, which is the most preferred of the .temperature is too high or when the water content in three, comprises condensing a phosphonopropionathe reaction system is too high, the methylene ether mide, in the presence of an acid catalyst, with a formalbond changes into a methylene bond as depicted in dehyde source to directly produce the phosphorus equation 1. Accordingly, it may be theorized that the compounds I, as depicted in the following equation 4:

PCH CH CH CNH CH O 5:21 (I) H O (4) R 0 u n O 0 process described in the published specification in Jap- It is well known in the art that when an acid amide anese Pat. No. 691,726 must not have been properly is condensed with formaldehyde under acid conditions, controlled and either did not actually produce the comthe corresponding methylenebisamide compound pounds represented by formula I or produced a mixture forms. A phosphonopropionamide, when condensed containing only small amounts of those compounds. with formaldehyde, forms a methylene compound as The particular process for the preparation of the depicted by the following equation 5:

PCH CH CNH CH O) (II) H The formation of a methylene compound in accordance with the reaction depicted in equation 5, however. takes place only when the pH of the reaction system is strongly acidic, that is, not higher than 0.5. When the pH of the reaction system is in the range of form 0.5 to 5 reaction (5) does not occur but, rather, a phosphorus compound of formula 1 forms according to the reaction as depicted by equation 4. Thus, when the condensation reaction of a phosphonopropionamide with formaldehyde is conducted in an acidic medium, it is possible to restrict the reaction to the production of methylene ether bond bearing phosphorus compounds I, only, without forming by-product methylene compounds, only if the pH in the reaction system is closely controlled.

The optimum pH in the reaction system for the pro duction of the phosphorus compounds I according to the process represented by equation 4 will vary to some degree with the reaction temperature, although it should generally be within the range of from 0.5 to 5, and preferably within the range of 2 to 4. The use of a pH outside the range of 0.5 to 5 is undesirable because when the pH of the reaction system is less than 0.5 methylene compounds form. On the other hand, when the pH of the reaction system is above about 5, a higher temperature and a longer reaction time are required and side reactions resulting in the formation of impurites are increased. Such side reactions include, for example, the Cannizzaro reaction of formaldehyde, hydrolytic reactions of amide groups and hydrolytic reactions of the phosphoric acid esters.

Suitable acidic agents for the adjustment of the pH of the reaction system to 0.5 to 50 to include, for example, inorganic acids such as hydrochloric acid, sulfuric acid and phosphoric acid, organic acids such as p-toluenesulfonic acid, and strongly acidic ion exchange resins.

The reaction temperature in the process of equation 4 should be set in accordance with the pH of the reaction system, although it should generally be within the range of from 30 to 140C and preferably within the range of 50 to 90C.

Suitable formaldehyde sources which may be used in this process include any compound capable of releasing formaldehyde in an acidic medium, for example, polyoxymethylenedialkylethers, trioxane, tetraoxane, para-.

formaldehyde or an aqueous formaldehyde solution. From the standpoint of the ease of the reaction procedure, paraformaldehyde in concentrations not higher than 80 percent by weight and aqueous formaldehyde solutions are preferred formaldehyde sources.

The reaction depicted by equation 4 is a reversible equilibrium reaction. It is therefore desirable, for achieving complete conversion of the starting materials to the phosphorus compounds of formula I, to remove from the reaction system by-product Water as Well as that water introduced with the formaldehyde source. For removal of water from the reaction system, distillation under normal pressure suffices, although, from the standpoint of depression of side reactions and inhibition of vaporization of the formaldehyde source, it is more advantageous to employ a method wherein the water is distilled off under reduced pressure or wherein the water is azeotropically removed. Solvents suitable for use in azeotropic distillation include those solvents which, after cooling, seprate from the aqueous phase,

' for example benzene, toluene, cyclohexane and carbon tetrachloride.

The methylene ether bond in the phosphorus compounds I obtained by the above enumerated varied processes can easily be quantitatively determined by, for example, infrared absorption spectroscopy, or chemical analysis wherein the formaldehyde content after decomposition with a dilute aqueous acid solution is quantitatively determined.

In the phosphorus compounds I used in the method according to the present invention, R to R are the same or different alkyl, alkenyl or alkoxyalkyl groups and each have not more than 10 carbon atoms, and preferably not more than 4 carbon atoms. Of these groups, the alkyl and halogen alkyl groups are preferred and R R R and R are preferably methyl, isopropyl or chloroethyl groups.

The reaction catalysts used for treating cellulose containing materials with the phosphorus compounds of formula I are conventional. Those catalysts known to be useful in curing amino resins, for example, ammonium chloride, orthophosphoric acid, magnesium chloride, zinc nitrate or Zinc borofluoride, can be used.

The concentration in the processing bath of the particular phosphorus compound of formula I used may vary with the desired degree of flame resistance to be imparted. A suitable concentration range is from 5 to percent by weight, and preferably from 20 to 50 percent by weight.

In impregnating a cellulosic material with the above described processingsolution, a variety of conventional methods may be applied, such as pressing between rolls, spraying or centrifugation. In addition, the manner of drying may be by any means and drying at any temperature between room temperature and 200C suffices. With regard to curing conditions, satisfactory results are obtainable by curing at temperatures, of the order of from 120 to 200C for periods of time of from 30 seconds to 10 minutes.

In conjunction with the method of the present invention, amino resins may be applied without difficulty. Suitable amino resins include reaction products of a variety of low molecular amino compounds usually used as the starting materials for the manufacture of amino resins, for example, urea, melamine, thiourea, ethylene urea, guanidine or urone, with formaldehyde, as well as the alkoxylated derivatives thereof.

When such amino resins are applied in conjunction with the present invention, however, the working environment will be adversely affected due to the generation of formaldehyde. On the other hand, when the phosphorus compounds I are used alone in accordance with the method of the invention, formaldehyde is not generated and therefore the working environment is not adversely affected. For this reasons, the use of the phosphorus compounds I without the presence of amino resins is preferred.

EXAMPLE 1 A solution of 184 g (1 mole) N,N- oxymethylenebisacrylamide and 242 g (2.2 moles) dimethyl phosphite in 300 cc dioxane is heated to 40C and a methanolic sodium methoxide solution (8 g sodium, g methanol) as catalyst added in portions with stirring. After the addition of approximately twothirds volume of the sodium methoxide solution, an exothermic reaction takes place and the reaction temperature rises. Subsequently, the catalyst is added in portions in such a manner as to maintain the reaction temperature at 80C. When the addition of the catalyst is complete, stirring is continued at the same temperature for about one hour to complete the reaction. The reaction mixture is distilled under reduced pressure to remove dioxane and excessive dimethyl phosphite. thus giving 407 g N,N-oxymethylenebis( dimethylphosphonopropion) amide (general formula (1), R R CH as a clear viscous liquid.

No free formaldehyde was found in this product but formaldehyde in the form of methylol or methylene ether was 0.08 or 14.71 percent (as formaldehyde), respectively. These values indicate the product to be of 99.1 percent purity.

The infrared spectra for this product is shown in FIG. 1.

A cotton twill was then treated in a processing bath containing a 30 percent aqueous solution of N,N- oxymethylenebis (dimethylphosphonopropion) amide and 0.4 percent ammonium chloride, dried at 90C and cured at 150C for 4 minutes. The processed cloth was incombustible in the flame resistance test conducted after washing.

EXAMPLE 2 A flame resistance test was conducted with a cotton twill processed with various N,N-omymethylenebis (phosphonopropion) amides. The compositions of the respective processing baths as well as the test results before and after washing are shown in Table l.

The processing procedure was as follows: The cloth was, after impregnation, picked up (80 percent by weight pick up), dried at 90C for 4 minutes and cured at 150C for 4 minutes.

The cured cloth was subjected to minutes soaping at 40C using a 0.2 percent by weight detergent (manufactured by Kao Sekken Co., Ltd.; Trade Name ZABU) aqueous solution and then rinsed for 5 minutes with water. This procedure was repeated five times. The finally dried cloth was used as the test cloth The flame resistance test was conducted in accordance with Japanese Industrial Standards (JIS) -L- 1091 A- 1. This test method is the 45 microburner method. The test cloth is spread over a 25 X 15 cm frame and set in a combustion test chamber at an angle of 45. The microburner is ignited, the cloth heated for one minute and the flame duration time (the length of time from the end of heating to a point where flaming of the test cloth ends) is determined. The microburner is adjusted beforehand in a manner such that the length of the flame is 4.5 cm and the tip thereof is in contact with the test cloth. Subsequently the test cloth is separated from the flame and the carbonized length and area are determined. Picked up means squeezed, rung, etc. 80 percent by weight pick up means that 80 percent of the water was removed.

EXAMPLE 3 41 g of an aqueous solution containing 80 percent by weight paraformaldehyde was suspended in 181 g 1.0 mole) dimethylphosphonopropionamide and the reaction system adjusted to a pH of 3.0 by the addition of p-toluenesulfonic acid and heated, with stirring, to 80C. In 2 hours the suspension became a clear solution. The solution was stirred for an additional three hours to complete the reaction. The reaction mixture was distilled under reduced pressure to remove water and excessive formaldehyde. The product was N,N- oxydimethylenebis( dimethylphosphonopropion) amide of 97.4 percent purity with a yield 202 g.

A flameproofing bath was prepared from a 35 percent by weight aqueous solution of the above product to which solution 3 percent phosphoric acid had been added, and the processing conducted as in Example 2, whereupon no odor of formaldehyde was detected.

The processed cloth was subjected to 5 minutes soaping with an aqueous solution containing 0.3 percent sodium carbonate and 0.3 percent ZABU. Subsequently, the procedure of 15 minutes soaping at C in a 0.3 percent aqueous ZABU solution and 3 minutes rinsing at 50C was repeated five times and the cloth finally dried at 100C for 3 minutes.

The flame resistance test results with this test cloth were as follows: carbonized area 20 cm; carbonized length 6.0 cm; and flame duration or lasting time 0 secfor after washing. d

Table 1 R,,R;. Processing Bath (71 by weight) Before Washing After Washing Carbo- Carbo- Flame Carbo- Carbo- Flame nized nized lasting nized nized lasting Active T- MgCl L length area time length area time (CH agent 36* NH,C1 H PO, GH O (cm) (cm'-') (sec) (cm) (cm'-) (sec) 25 s 0.5 6.8 20 0 7.0 22 0 II l5 8 (1.5 6.6 23 U 6.6 25 O (C H 35 8 3 6.8 22 0 6,7 27 0 (ClCH CH 25 8 3 6.7 21 0 6.9 24 0 (C1 C ,H 25 s 3 6.8 22 0 as 23 0 (B,.CH CH 30 8 3 618 22 O 6.8 26 ca-I 25 x 3 6.9 23 0 7.4 32 0 0,11,00,11, 30 s 2 7.0 20 0 7.7 36 0 (C,,H 25 s 2 6.6 23 0 6.9 29 0 CH,,, C. .H,, 25 0 2 6.6 22 0 6.8 31 0 (C H 30 8 0.5 6.7 23 0 7.0 28 O (i-C;,H;) 25 x 0.5 as 22 0 7.3 32 0 Trade name --Ulamine T-3l1" for /r aqueous melhoxymethylnlmelamine solution manufacture by Mitsui Toatsu Chemical Co., Ltd.

We claim: 2. The method of claim 1 wherein R R R and R 1. A method for flameproofing cellulose containing are alkyl or halogenalkyl groups having not more than material comprising: 4 carbon atoms.

providing a solution containing a phosphorus com- 3. The method of claim 1 wherein the phosphorus pound represented by the following general for- 5 compound is prepared by condensing a phosphonopromula: pionamide with paraformaldehyde in the presence of an acid catalyst. R 0R 4. The method of claim 2 wherein R R R and R are a met y groups. /PCH CH CNHCH OCH NHCCH CH P l0 5. The method of claim 2 wherein R R R and R are all iso r0 1 rou s. 2 g A B4 6. The r t let dif claim 2 wherein R R R and R are all chloroethyl groups.

7. The method of claim 1 wherein the material is apwherein R to R are the same or different alkyl, alkeplied the form of an aqueous Solution containing n l, h l lk l or lk lk l groups; 5-80 percent by weight of said compounds to wet the applying said oluti t th ll l i containing material and wherein the wetted material is dried and material; and cured at a temperature within the range of 120 to drying the cellulosic containing material.

Claims

1. A METHOD FOR FLAMEPROOFING CELLULOSE CONTAINING MATERIAL COMPRISING: PROVIDING A SOLUTION CONTAINING A PHOSPHORUS COMPOUND REPRESENTED BY THE FOLLOWING GENERAL FORMULA: R1-O-P(=O)(-O-R2)-CH2-CH2-CO-NH-CH2-O-CH2-NH-COCH2-CH2-P(=O)(-O-R3)-O-R4 WHEREIN R1 TO R4 ARE THE SAME OR DIFFERENT ALKYL, ALEKNYL, HALOGENALKYL OR ALKOXYALKYL GROUPS, APPLYING SAID SOLUTION TO THE CELLULOSIC CONTAINING MATERIAL, AND DRYING THE CELLULOSIC CONTAINING MATERIAL.

2. The method of claim 1 wherein R1, R2, R3 and R4 are alkyl or halogenalkyl groups having not more than 4 carbon atoms.

3. The method of claim 1 wherein the phosphorus compound is prepared by condensing a phosphonopropionamide with paraformaldehyde in the presence of an acid catalyst.

4. The method of claim 2 wherein R1, R2, R3 and R4 are all methyl groups.

5. The method of claim 2 wherein R1, R2, R3 and R4 are all isopropyl groups.

6. The method of claim 2 wherein R1, R2, R3 and R4 are all chloroethyl groups.

7. The method of claim 1 wherein the material is applied in the form of an aqueous solution containing 5-80 percent by weight of said compounds to wet the material and wherein the wetted material is dried and cured at a temperature within the range of 120* to 200*C.