US3668302A

US3668302A - Flame retardant textile covered wire

Info

Publication number: US3668302A
Application number: US747757A
Authority: US
Inventors: Daniel Edmund Boland; Leonard S Dewees; Leroy M Towsley
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1968-07-25
Filing date: 1968-07-25
Publication date: 1972-06-06
Anticipated expiration: 1989-06-06
Also published as: FR2013663A1; DE1937345A1; DE1937345B2; SE360203B; ES370034A1; GB1271958A; JPS4823747B1; BE736437A

Abstract

A textile served wire coated with a flame retardant lacquer comprised essentially of a mixture, by weight, of 100 parts cellulose acetate base, 35 parts tricresyl phosphate plasticizer, 42.5 parts tris (2, 3 - dibromopropyl) phosphate flame retardant, and 128.5 parts acetone solvent.

Description

United States Patent Boland et a1.

1541 FLAME RETARDANT TEXTILE COVERED WIRE UNITED STATES PATENTS Lommel et a1. ..106/177 UX 1 1 June 6, 1972 1,981,132 11/1934 Walsh et a1. 106/177 2,126,850 8/1938 Whitehead 106/177 2,178,365 10/1939 Brobst 106/177 2,574,515 11/1951 Walter et 211.. ..106/177 X 2,618,568 11/1952 Meyer et a1... ...,.106/177 2,675,327 4/1954 Gearhart 106/176 3,412,052 1 H1968 Taylor et a1 v.106/15 X 3,515,565 6/1970 Wood et a1. ..106/177 Primary Examiner-Lorenzo B. Hayes Attorney-H. J. Winegar, R. P. Miller and A. J. Nugent [57] ABSTRACT A textile served wire coated with a flame retardant lacquer comprised essentially of a mixture, by weight, of 100 parts cellulose acetate base, 35 parts tricresyl phosphate plasticizer, 42.5 parts tris (2, 3 dibromopropyl) phosphate flame retardant, and 128.5 parts acetone solvent.

4 Claims, 1 Drawing Figure PATENTEDJUR s 1972 INVENTORS Danlel E. Bolund Leonard S. Dewees LeRoy M. Towsley ATTORNEYS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to improvements in flame retardant compositions, and more particularly, to a new and improved flame retardant lacquer for coating textile covered wire, and to new and improved textile covered wire having its covering coated with such flame retardant lacquer.

In the production of textile served wire, which is particularly adapted for use in the so-called U-type distributing frames employed in telephone exchanges, it is common practice to extrude a flexible polyvinyl chloride insulating layer over the conductor wire. Where feasible, this insulating layer incorporates a suitable flame retardant plasticizer. This operation is followed by wrapping of the cotton textile serving over the insulation, whereupon the served wire is passed through an impregnating 'chamber wherein a substantially transparent lacquer coating is applied under pressure to prevent unraveling or fraying of the serving, while permitting visibility of the underlying serving for identification purposes, the thickness of the coating being controlled by passage of the wire out of the chamber through a rubber die having a central aperture'of a predetermined size. The emerging coated wire is continuously wound and air dried on a series of capstans prior to being reeled.

2. Description of the Prior Art A typical prior art lacquer. formulation employed in the above process is as follows:

Ingredients Parts by Weight Cellulose Acetate I Tricresyl Phosphate 20 Triphenyl Phosphate 35 Dimethyl Phthalate 30 Dibutyl Phthalate 8.75

' Acetone 148 (approx.)

While this lacquer possesses the physical characteristics necessary for use in the wire coating process and is effective in serving the desired purposes of visibility of the serving and of preventing unraveling and fraying of such serving, it nevertheless is not sufficiently flame retardant. This is true particularly because of the presence of the phthalate plasticizers, which are flammable and tend to negate the flame retardant characteristics of the phosphate plasticizers.

SUMMARY OF THE INVENTION Accordingly, it is a primary object of the present invention to provide a new and improved flame retardant lacquer which is just as feasible for use in the aforesaid wire coating process and just as effective in permitting visibility of the serving and in preventing unraveling and fraying of such serving, as the aforesaid lacquer. To this end, the present lacquer is comprised essentially of a mixture of a base, a plasticizer, a flame retardant and a solvent present in the following proportions by weight: 100 parts of derivative of cellulose (preferably celluloseacetate) as the base, between about 25 and 35 parts of derivative or cresylic acid and phosphorous oxychloride (preferably 35 parts tricresyl phosphate) as the plasticizer, between about 40 and 45 parts of a brominated monomeric triallyl phosphate (preferably 42.5 parts of tris (2,3 dibromopropyl) phosphate as the flame retardant, and between about 120 and 150 parts of dimethyl ketone, ethyl methyl ketone, ethanol or methanol (preferably 128.5 parts of dimethyl ketone; i.e., acetone) as the solvent.

Another primary object is to provide a new and improved textile covered wire having its covering coated with the aforesaid flame retardant lacquer.

Additional objects and advantages of the invention will become apparent upon consideration of the following detailed description and accompanying drawing, wherein:

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE is an enlarged side elevational view of a textile served wire coated with the inventive flame retardant lacquer and constitutes a preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, the textile served wire is generally indicated at 10, and includes a central conductor 12 surrounded by an insulating layer 14 preferably formed of fire retardant plasticized polyvinyl chloride, a preferably cotton and color coded textile serving 16 wrapped around insulating layer 14 which in turn is impregnated with and surrounded by the inventive flame retardant lacquer coating 18. The coating is substantially transparent for visibility of the underlying serv- Wire 10 is particularly adapted for use in the so-called U- type distributing frames in telephone exchanges, and for this purpose its various elements have the following typical physical characteristics. Conductor 12 is made of 22AWG gauge copper wire, insulating layer 14 has an average wall thickness of 8 mils, serving 16 is made of 20/1 cotton yarn, and the weight of lacquer coating 18 ranges between about 60 and 80 milligrams per foot of wire, with the preferred weight being about 70 milligrams.

In producing wire 10, insulating layer 14 is extruded over conductor 12 and serving 16 is wrapped around layer 14, such serving preferably being provided with a differently colored tracer thread (not shown) for identification purposes. The textile served wire is then unreeled and passed through an impregnating chamber (not shown) into which the lacquer is injected under pressure to form coating 18, the thickness and weight of which is controlled by passage of the coated wire out through a rubber sizing die (not shown) of the desired diame ter. As the coated wire leaves the chamber it is wound continuously over a series of moving capstans (not shown) to air dry lacquer coating 18 and is rereeled.

In order to successfully process wire 10, it is imperative that lacquer coating 18 have the following physical properties. First, it must be sufliciently lubricious to pennit smooth passage through the sizing die. Secondly, it must be suffrciently fast drying to permit winding on the capstans and reels without adhesion of the wire coating thereto or to itself. Third, it must have sufficient film flexibility to prevent the lacquer from cracking on the wire, particularly when wound on the reels.

While the prior art coating referred to above does possess these physical characteristics, it is not sufiiciently flame retardant. Accordingly, the principal problem to overcome was to eliminate the flammable phthalate plasticizers in order to obtain the desired flame retardance, while still maintaining the other physical characteristics necessary for successful coating of the wire. After extensive experimentation, which also involved replacement of the tire retardant phenyl phosphate fire retardant plasticizer with more tricresyl phosphate because of its greater lubricity, the following formulation was developed Comparative flame retardance tests were made between wires which had the physical characteristics described above for wire 10, and were otherwise identical, except for the lacquer coating. In one test, wire 10, with the inventive 3 4 lacquer coating of the example, was placed on several shelves ethyl methyl ketone, ethanol or methanol may be substituted, on a small distributing frame and a 4-inch diameter dish of aldimethyl ketone (i.e.; acetone) is preferred because it is the cohol was placed below a shelf and ignited. The wire most volatile for minimizing drying time and least toxic for withstood 12 minutes exposure to the alcohol flames with only minimizing exposure of personnel to toxic fumes. Slight burning and was self-extinguished immediately after the 5 Within the aforesaid ranges, the percentage of each inalcohol was consumed. In contrast, wire having the aforesaid gredient is critical from the standpoint of both proper operaprior art lacquer coating ignited after about 1 minute in the altion of the coating process and obtaining the maximum practiecho! and the tire slowly spread both horizontally and vertical flame retardance. If too much flame retardant is used; i.e., cally. more than about 45 percent of the base, the formulation will In another test using the distributing frame mentioned cause adhesion to the capstans and will not run. If the above and wire 10 with lacquer 18, the horizontal side of the plasticizer exceeds about 35, percent of the base, it will conframe was ignited and produced a strong fire extending over tribute to the adhesion problems. Should the ratio of the flame several shelves. Wire 10 burned only in the flames in the rere rd nt o h pl i iz r exceed about /2 film gion of the terminals and the fire did not propogate along the flexibility is adversely affected, while a ratio below about 8/7 wire. In a similar test using wire with the prior an lacquer, the 1 0/35) un esi ably re uc s fl me retardance- This critical flames from the terminals spread along the wire and enlarged property is also adversely affected if the ratio of the combined the fire. percentage of the flame retardant and plasticizer to the base Accordingly, it is evident that wire coated with the inventive f l below about 1 Likewise, the ratio f he lacquer exhibits greatly improved flame retardance ove that total of the other ingredients to the solvent should not exceed coated with the prior art lacquer. At the same time, the invenabout nor Should it be 1888 than about l tive lacquer oating 18 al o o e e the h i l ha (165/ 150), in order to control the viscosity for obtaining a teristics of lubricity, fast drying and film flexibility necessary p pe amount of lacquer coating on the wire, the optimum for efficient and effective processing of the wire during and amount being obtained h he pr rr r io f th examafter coating, drying and rereeling. The coated wire 10 also 1 about v has been found to possess better handling characteristics than M the mvfmuve lacquer descnbe? harem ls espec'ally the same wire coated with the prim. an lacquer, the improve; suitable for coating the textile covered wire referred to herein,

ment being attributed to a smoother outer surface. 5 also may be F to coat other objects or y be formed Although the formulation of the example represents a into filaments, ribbons, sheets, or other convenient forms by preferred embodiment of the inventive lacquer, this formulaany f m know" m the tion can be varied within certain limits and still produce an acwhat 15 claimed is: ceptable flame retardant lacquer coating. For example, while A f covered havmg covermg coated I a cellulose acetate is preferred because of its electrical insulatsubstajnuany transParerft flame retardant l Conslstmg ing properties, other suitable derivatives of cellulose such as essenua'uy of a dned mlxmre of base a Pi f a flalne cellulose formate among the esters and ethyl cellulose among retardarft and a Solvent present Pnor to m the followmg the ethers y be used as the base proportions by weight: 100 parts of a derivat ve of cellulose as The preferred derivative of cresylic acid and phosphorous the base F Y about 25 and 35 parts of mciesyl pho sphate oxychloride for use as the plasticizer is tricresyl phosphate, the Plasnclzert between about and Parts of ms(2,3' because it not only provides the needed die lubrication and dlbmmopropyl phosphate asthe flame retardant and between film flexibility but also contributes to flame retardance. Howabout 120 and 150 parts of dimethyl ketone' ethyl methyl ever, the amount of this ingredient may vary between about 25 40 ketone' ethanol or [methanol as the and 35 parts per 100 parts of base 2. The wire of claim 1 wherein said base 18 cellulose acetate. AS for the flame retardant a partially brominated 3. The wire of claim 2 wherein said solvent is dimethyl ketone.

monomeric triallyl phosphate is usable, but the fully brominated phosphate of the example is preferred because of its greater flame retardance. This ingredient also functions as a secondary plasticizer and may vary in amount between 4. The wire of claim 3 wherein said base, plasticizer, flame 45 retardant and solvent are present prior to drying in the following proportions: 100 parts cellulose acetate, 35 parts tricresyl about 40 and 45 parts per 100 pans of base phosphate, 42.5 tris (2, 3 dibromopropyl) phosphate,

While the quantity of solvent may range between about 120 and 128's pans dlmethyl ketone' and 150 parts per 100 parts of base, and other solvents such as STATESAT was I 3,668 ,302 Data June a 1972 Patent inventor) Daniel E. Boland-Leonard S. DeWees-Leroy M. Towsley It is certifiedmaterror appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the specification, Column l, line 35 Claim 1 insert following the word "cellulose", -selected from the group consisting of cellulose esters and cellulose ethers--.'

Signed and sealed this 14th day of January 1975.

(SEAL) Aittests McCOY M. GIBSON' JR; 0; MARSHALL DANN Cissioner of Patents Attesting Officer L-566-PT 3,668 ,302 Datea June 6, 1972 Patent No.

inventor) Daniel E. Boland-Leonard S. DeWees-Leroy M. Towsley It is certified- (hazelnut appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

I In the specification, Column line 35 Claim 1 insert following the word "cellulose", ---selected. from the group consi stinjg of cellulose esters and cellulose ethers-.

Signed and sealed this 14th day of January 1975.'

(SEAL) Attests' McCOY M. GiBSON' JR. Attesting Officer 0; MARSHALL 1mm Commissioner of Patents

Claims

2. The wire of claim 1 wherein said base is cellulose acetate.
3. The wire of claim 2 wherein said solvent is dimethyl ketone.
4. The wire of claim 3 wherein said base, plasticizer, flame retardant and solvent are present prior to drying in the following proportions: 100 parts cellulose acetate, 35 parts tricresyl phosphate, 42.5 parts tris (2, 3 - dibromopropyl) phosphate, and 128.5 parts dimethyl ketone.