GB1571617A

GB1571617A - Apparatus for flame retarding textile materials

Info

Publication number: GB1571617A
Application number: GB31379A
Authority: GB
Original assignee: Hooker Chemicals and Plastics Corp
Current assignee: Occidental Chemical Corp
Priority date: 1972-04-17
Filing date: 1976-10-25
Publication date: 1980-07-16

Description

(54) APPARATUS FOR FLAME RETARDING TEXTILE MAThRiM:s (71) We, HOOKER CHEMICALS & BR< PLASTICS CORP., a corporation organised and existing under the laws of the State of New York, United States of America, of Niagara Falls, New York 14302, United States of America, do. hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement - This invention relates to an apparatus suitable for use in the treatment of textile materials to render them flame retardant.

United States Patent Specification No.

3,607,356 discloses a process for treating fibrous materials to render them flame retardant. The process involves impregnating a cellulose-containing material with an aqueous solution containing an equilibrium mixture of tris (hydroxymethyl) phosphine {"THP") and tetrakis l(hydroxymethyl} phosphonium hydroxide ("THPOH"), drying the impregnated material, and then treating the dried material with gaseous ammonia in an enclosed cabinet to polymerize the monomers. The gaseous ammonia treatment step requires from one or two to 6 minutes exposure time depending upon the character, i.e. the weight and fibrous nature, of the treated material. In many textile processes, the materials are processed in equipment operating at high speed in a continuous man ner.Accordingly, operations involving processing times of several minutes duration require either static operation or units of a size wherein such relatively long residence times can be obtained. It is, therefore, desired to provide apparatus for the treatment of textile materials in which shorter residence times consistent with high speed continuous operations can be obtained in a practical manner.Moreover, the treatment according to the process of United States Patent Specification No. 3,607,356, when used with available ammonia treatment cabinets, has been found to produce finishes on cellulosic materials which tend to dust and the durability of the finished materials often failed to meet stringent United States Government standards (Department of Commerce Standards FF-3-71) which require that the treated materials withstand at least fifty home washing and drying cycles.

The enclosed chamber for carrying out an ammonia treatment commonly used in this field comprises a series of perforated pipes housed in a box-like enclosure having a large opening in the top. The partially dried im pregnated material which is passed over the perforated pipes through which ammonia gas is forced. The excess ammonia gas is vented through the opening in the top of the enclosure, and discharged into the atmosphere. This venting of considerable quantities of ammonia gives rise to a severe pollution problem. The process disclosed in United States Patent Specification No.

3,607,356 not only results in a highly in efficient utilization of ammonia but also is hardly practical for the lighter, open weave, materials and leaves much to be desired when processing heavier and/or close knit materials.

It is known also, as disclosed in United States. Patent Specification No. 2,983,623, to cure further polymerizable methylol-phos phorus polymeric material containing at least one free methylol group attached to a phos phorus atom incorporated in a cellulosic mat erial, by exposing such material in the dry state to the action of gaseous ammonia fol lowed by subjecting it to an aqueous ammo nia treatment. In this process, the further polymerizable resins disclosed are solutions of reaction products of terakis (hydroxy methyl phosphonium chloride and urea which solutions are relatively strongly acid and are applied in the presence of buffers which adjust the pH of the solutions to a pH of about 3.5 to 4.The impregnated material is thoroughly dried, exposed to ammonia gas for 5 to 10 or more minutes, and then immersed in aqueous ammonia for 10 or more minutes to complete the cure of the resin on and in the material. Such a process also requires relatively long time cycles of treatment, especially in the aqueous ammonia bath, and therefore is hardly applicable with modern high speed processing techniques.

The problem of the long time cycles and efficiency of the polymerization has been substantially overcome by use of the process and apparatus described and claimed in, respectively, British- Specifications Nos.

1,432,601 and 1,432,602. The process of Specification No. 1,432,601 comprises impregnating a cellulose-containing material with an aqueous solution having a pH of from 7 to 9 and containing from 10 to 40 percent of tetrakis (hydroxymethyl) phosphonium hydroxide; drying the impregnated material to a moisture retention of from 0 to 8 percent by weight; and exposing to an atmosphere containing at least 50 percent by volume of gaseous ammonia in an enclosed chamber for from 5 to 45 seconds to polymerize the tetrakis (hydroxymethyl) phosphonium hydroxide in and on-the cellulose-containing material, the conditions of the process being such that the cellulosecontaining material is provided with an effective flame-retardant amount of tetrakis (hydroxymethyl) phosphonium hydroxide polymer.Uuder certain mill conditions, it was found that substantial amounts of formaldehyde were formed during the-gaseous ammonia exposure step. Additionally, when the cured fabric was batched in rolls or on trucks immediately after exiting from the ammonia chamber, it was noted that an odour of formaldehyde rapidly developed in the batched, processed, materials and also that a considerable amount of heat was given off by the material. In such materials, i.e. when the odour of formaldehyde was detected and/or heat was given off, the durability of the flame retardant property of the materials was reduced.It is believed that the formaldehyde which is produced by decomposition of the polymerized or partially polymerized monomer confined in and on the material, had reacted with the polymer or partially polymerized polymer to form a moisture sensitive reaction product which may deleteriously affect the durability of the flame retardant treatment.

The apparatus of the present invention makes possible the use of a process which both prevents the disadvantageous production of formaldehyde and is suitable for use with currently used high speed textile processing equipment.

The present invention provides an apparatus suitable for use in the treatment of textile material, which apparaus comprises a housing; a gas inlet disposed in an upper portion of the housing; a gas outlet disposed in a lower portion of the housing; a textile material inlet and a textile material outlet disposed in the lower portion of the housing above the gas outlet; a partition disposed tznsversely across the housing below the s ialçt and above the gas outlet, textile mateajaI:inlet and textile material outlet so as to form a gas treatment chamber in the upper portion of the housing, the parti tion including apertures therein for the introduction into or removal from the gas treatment chamber of textile material to be treated therein while minimizing the passage of treatment gas from the gas treatment chamber; a water inlet, connected to a supply means; a water outlet disposed in the lower portion of the housing below the partition and the gas outlet; and conveying means for conveying textile material to be treated in through the textile material inlet into and out of the gas treatment chamber through the apertures in the partition, and out of the textile material outlet, the conveying means being disposed below the gas inlet; such that the gas treatment chamber comprises a first zone wherein a textile material is exposed to treatment gas, a second zone wherein the exposed material is contacted with water and a third zone wherein the material is again exposed to treatment gas.

. In co-pending Application No. 44255/76 (Specification No. 1571616), we have described and claimed a process for rendering cellulose-containing materials flame retar dant, which process comprises (a) impregnating the material with an emulsion or solution having a pH of from 2 to 9 and containing from 10 to 40 percent by weight of a poly(hydroxymethyl) phosphonium cation or a cation derived by reaction of said poly(hydroxymethyl) phosphonium cation with an amino- or amido nitrogen-containing organic compound or with the reaction product of an aldehyde and one of said nitrogen-containing organic compounds; (b) drying the impregnated material so that the dried material contains from 0 to 8 percent by weight of dried material, of the continuous phase of the emulsion or solvent of the solution of step (a); ; (c) aerating the dried material by directing a current of air through the dried material; (d) exposing the aerated material to an atmosphere containing at least 50 percent by volume of gaseous ammonia in an enclosed chamber for from 5 to 60 seconds to cure the cation constituent in and on the material; (e) contacting the material exposed to ammonia with water; and (f) exposing the water-contacted material to an atmosphere containing at least 40 percent by volume of gaseous ammonia for up to 10 seconds; the conditions of the process being such that the cellulose-containing material is pro vided with an effective flame-retardant amount of the cured cation constituent of the emulsion or solution employed in step (a).The apparatus of the present invention is particularly suitable for use in -the am monia treatment steps, step (d) and (f), andthe water treatment step, step (e), of this process. In accordance with this process the aerated material from step (c) is exposed to gaseous ammonia, in step (d) of the process, in the gas treatment chamber of the apparatus of the present invention wherein the resin monomer (the poly(hydroxymethyl) phosphonium cation or cation derived by reaction of said poly(hydroxymethyl) phosphonium cation with an aminoor amido -nitrogen- containing organic compound or with reaction product of an aldehyde and one of said nitrogen-containing organic compounds) reacts rapidly and substantially completely to form an insoluble polymer within the material.The gaseous atmosphere which comprises at least 50 percent, preferably from 70 to 95 percent or more, by volume of gaseous ammonia, provides an effective, efficient and surprisingly rapid reactant for the resin curing step. It has been found that the curing step is completed, under these conditions, in up to 60 seconds, generally in less than about 45 seconds, and sometimes in as short a period of time as 5 seconds. Preferably, the curing step is effected from 15 to 30 seconds. Many prior art procedures required from 1 to 6 minutes for substantially complete polymerization and curing of the impregnated composion. Under optimum conditions, the process of this invention proceeds with efficient utilization of the gaseous ammonia charged to the process. Prior art processes often preferred up to a 15 fold excess of the ammonia reactant.This huge excess of ammonia presented a serious air pollution problem, which has been eliminated in the process and apparatus of this invention.

The apparatus of this invention is illustrated in the accompanying drawing which shows a schematic cross-section through the apparatus.

Refering to this drawing, the apparatus comprises a housing 1 containing a gas inlet 2 in an upper portion of housing 1, and a gas outlet 3 in a lower portion of housing 1. The gas outlet 3 is conveniently connected to a suction means (not shown). The housing 1 is provided also with a textile material inlet 4 and a textile material outlet 5 for the entry of a dried impregnated textile material and the exit of a cured material, respectively. Material guides 6 are provided for conveying the impregnated material through the housing 1. A partition 7 extending transversely across the interior of the housing 1 serves to form a gas treatment chamber in the upper part of the housing 1 in which the material is contacted with a gas.The partition 7 includes flaps 8 and 9 covering apertures which permit the material to be treated to enter- the gas treatment chamber and the treated material to exit said chamber, while minimizing the pasage of treatment gas out of the chamber. The material guides 6 convey the material to betreated into the housing 1, through the textile material inlet 4, through flap 8 into the gas treatment chamber, out of the gas treatment chamber through flap 9 and out of the housing 1 through textile material outlet 1. A gas distribution device 10 shown as a perforated plate is provided to assist in the distribution of the gas stream entering through gas inlet 2 evenly throughout the gas treatment chamber.Sensing ports 11 are provided in the gas treatment chamber for removal of samples of the gaseous atmosphere for analysis to to-monitorthe concentration of the treatment gas. A water inlet 12 connected to supply means 13 is provided in the gas treatment chamber for the water treatment operation, step (e).

The housing 1 may be provided with a cooling means (not shown) to cool the treatment chamber and to regulate the temperature of the gaseous atmosphere within the treatment chamber. A liquid condensate discharge port (water outlet) (not shown) is positioned in the lower portion of the housing 1 for removal of condensate from the chamber at a lower point in housing 1 than material inlet 4, material outlet 5 and gas outlet 3.

The housing 1 can be fabricated from conventional materials of construction such as wood, metal, glass or plastics or any combination thereof. The partition 7 may be constructed from like materials or from rubber. The flaps 8 and 9 suitably are fabricated from - flexible materials such as rub ber, leather or plastics film and are attached to the partition 7 in any convenient manner.

It is important that the flaps 8 and 9 do not impede the passage of the material there- through but do substantially prevent the free flow of the treatment gas into and out of the treatment chamber.

In operating this apparatus to carry out steps (d), (e) and (f) of the process of Application No. 44255/76 (Specification No.

1571616), ammonia gas is fed into the unit through the gas inlet 2 at a rate sufficient to provide an ammonia atmosphere within the gas treatment chamber having at least 50 percent and preferably from 70 percent to 90 percent, ammonia by volume. Textile material which has been impregnated with the solution of the polyfhydroxymethyl) phosphonium cation and dried to contain from 0 to 8 percent by weight of dried material, of the continuous phase of the emulsion or solvent of the solution of step (a) of the process of Application No.

44255/76 (Specification No. 1571616) is admitted to the apparatus, preferably in a continuous manner through inlet 4, and is passed over material guides 6, through partition 7 via flap 8, into the gas treatment chamber wherein the impregnated material is exposed to the ammonia atmosphere. After exposure to the ammonia atmosphere for the requisite time, the textile material is water treated with water from supply means 13. The material is again exposed to the ammonia atmosphere and then leaves the gas treatment chamber passing through flap 9 of partition 7 and exits the housing 1 through material outlet 5. The passage of air into the gas treatment chamber is minimized in part by the partition 7 and in part by the withdrawal of gas from the housing 1 through gas outlet 3, which is connected to a mild suction means, e.g. a vacuum pump.

The rate of flow of ammonia gas into the apparatus preferably should be adjusted to provide at least one mol of ammonia per mole of tetrakis (hydroxymethyl) phosphonium hydroxide available for reaction, i.e. curing, on the impregnated material.

Preferably about 20 percent molar excess of ammonia is supplied. This amount of ammonia can be approximated by the following calculation: Lbs. of impregnated material Yds. % ThPOII % Wet pick-up x-x x Yard of material Min. 100 100 x ---- = Mols of THPOH/min.

172 Mols THPOH 359 fit.5 x x 1.2 = cu. ft.NH3 gas/min.

min. mol.

The cured material is then contacted with water within the enclosed gas treatment chamber. Supply means 13 may be, for example, a trough, pipe or sprayhead, or any combination of these, located at any con venient position within the housing 1. For example, referring to the accompanying drawing, a trough may be located above or below the partition 7. Alternatively, the trough may be an integral portion of par tition 7 through which the material is guided with or without additional material guides.

Similarly, a pipe or, as shown in the drawing, a sprayhead may also be utilized. A com bination of these may also be used to apply water treatment to the cured material. Pre ferably, water is applied as a fine spray.

Several means for accomplishing this will be obvious to those skilled in this art. For example, a spray head or several heads may be suitably positioned with regard to flap 9. Most preferably, the spraying means is one or several air atomizing water spray heads which supply water in the form of an atomized spray to the cured material before the material leaves the gas treatment chamber through flap 9.

Sufficient water should be added to the cured material to provide a pick-up of 10 to 60 percent, preferably from 20 to 30 percent, by weight of water. This water not only cools the hot material but also results in the deactivation of formaldehyde and, thus, prevents its further reaction with the phosphonium salt polymer. It is believed -that the water supplied at this stage of the l) icess provides a reaction medium for the joidehyde to react with any -ammonia which may be present to form hexamethylene tetramine. This latter product does not react with the phosphonium salt polymer present in and on the textile material.

It has beeen found that further treatment of the cured material, after treatment with water, with gaseous ammonia at a concentration of at least 40%, preferably at least 50%, by volume of gaseous ammonia has an additional beneficial affect unpin the polymerized material. Treatment with gaseous ammonia for from less than 1 to 10 seconds, preferably from 1 to 6 seconds, reduces further the already substantially reduced odour of formaldehyde to an extent that this odour is no longer readily apparent.

To carry out this further treatment, water supply means 13 may be located at a point away from the material outlet 5 so that the textile material will remain in the enclosed gas treatment chamber for a ,time after water treatment before leaving housing 1. A nip roll, doctor blade or similarly functioning device may be positioned immediately after the water supply means 13 to decrease the amount of water carried by the material when undergoing the additional ammonia cure.

Such devices have been found to ;be effective but are not necesseary to the operation of the process.

The apparatus of this invention is readily adaptable to use with modern high speed commercial textile processing equipment.

Substantial savings of time and of consumption of ammonia gas, in the range of about 100 to 200 percent, are effected by this improved process.

Claims

WHAT WE CLAIM IS:-

1. An apparatus suitable for use in the treatment of textile material, which apparatus comprises a housing; a gas inlet disposed in an upper portion of the housing; a gas outlet disposed in a lower portion of the housing; a textile material inlet and a textile material outlet disposed in the lower portion of the housing above the gas outlet; a partition disposed transversely across the housing below the gas inlet and above the gas outlet, textile material inlet and textile material outlet so as to form a gas treatment chamber in the upper portion of the housing, the partition including apertures therein for the introduction into or removal from the gas treatment chamber of textile material to be treated therein while minimizing the passage of treatment gas from the gas treatment chamber; a water inlet, connected to a supply means; a water outlet disposed in the lower portion of the housing below the partition and the gas outlet; and conveying means for conveying textile material to be treated in through the textile material inlet into and out of the gas treatment chamber through the apertures in the partition, and out of the textile material outlet, the conveying means being disposed below the gas inlet; such that the gas treatment chamber comprises a first zone wherein a textile material is exposed to treatment gas, a second zone wherein the exposed material is contacted with water and a third zone wherein the material is again exposed to treatment gas.

2. An apparatus as claimed in claim 1, wherein the gas inlet is disposed at the top of the housing.

3. An apparatus as claimed in claim 1 or 2, wherein a gas distributor is disposed in the gas treatment chamber in the upper portion thereof between the uppermost conveying means and the gas inlet.

4. An apparatus as claimed in any one of the preceding claims, wherein the apparatus includes suction means attached to the gas outlet.

5. An apparatus as claimed in any one of the preceding claims, wherein the water supply means is a trough located above or below the transverse partition.

6. An apparatus as claimed in any one of the claims 1 to 4, wherein the water supply means is a trough which is an integral part of the partition.

7. An apparatus as claimed in any one of the claims 1 to 4, wherein the water supply means is a pipe.

8. An apparatus as claimed in any one of claims 1 to 4, wherein the water supply means is a sprayhead.

9. An apparatus as claimed in any one of claims 1 to 4, wherein the water supply means is any combination of the supply means of claims 5 to 8.

10. An apparatus as claimed in any one of the preceding claims, wherein a nip roll or doctor blade is positioned immediately after the water supply means.

11. An apparatus as claimed in claim 1, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.