Telephone cords

A polyvinyl chloride surface, such as plasticized polyvinyl chloride telephone cord jacket, is coated with a coating formulation comprising a medium molecular weight methyl methacrylate copolymer, cellulose acetate butyrate and a carbalkoxy benzyl phthalate plasticizer. The coating affords good adhesion, fast drying and stain resistance.

TECHNICAL FIELD 
This invention relates to telephone cords having a coated jacket and 
particularly to coated plasticized polyvinyl chloride jacketed telephone 
cords. 
BACKGROUND OF THE INVENTION 
Electrical wire insulated with plasticized polyvinyl chloride (PVC) is used 
widely for many applications including telephone cords such as those 
connecting telephone station equipment with wall or floor line junctions 
and for retractile telephone cords and telephone handsets. It is also used 
for electrical cords on consumer appliances. In these applications, the 
cords typically have high visibility coupled with high exposure to wear, 
staining and environmental degradation. With the increasing demand for 
cords that are coordinated in color with appliances or interior decor, the 
aesthetic appearance of the telephone cord is of ever increasing 
importance. 
Notwithstanding the fact that previously used cords are often stained and 
discolored or have other aesthetic problems associated therewith, the 
cords nevertheless are suitable for reuse in an electrical sense in that 
electrical integrity and conductivity have not been affected. It has 
generally been found to be economical in the telephone industry to 
refurbish used telephone cords. In order for these telephone cords to be 
suitable for reinstallation with new phones or replacement equipment in 
the home or business, the cord must aesthetically appear new. 
Consequently, substantial quantities of recycled telephone cords must be 
painted or otherwise coated so as to give the telephone cord as 
aesthetically new appearance. 
To be suitable for this purpose, any paint applied to the cords, must, 
especially in the case of retractile telephone cords, be flexible and 
resistant to cracking and peeling. It is also desirable to have a paint 
formulation which is relatively stain resistant, which can hold sufficient 
pigment to allow single coat coverage and which dries to a tack-free 
condition relatively quickly even in fairly humid conditions. Generally, 
to be suitable formulations should dry to a tack-free condition at 
relative humidities of 50% in not more than 20 minutes. 
Previously, vinyl paint formulations were employed as coatings for the 
plasticized polyvinyl chloride jackets on telephone cords. These 
formulations tended to exhibit adhesion problems after a period of time. 
The adhesion problems were manifested by cracking and peeling of the 
coating. Furthermore, the stain resistance of the vinyl paints were 
relatively poor. More recently, the use of urethane paint became 
widespread for coating telephone cords. While the adhesion problem of the 
vinyl paints was substantially overcome with the newer urethane 
formulations, the urethane paint offered only minimal stain resistance. 
Moreover, processing problems such as reproducibility, the need for 
multiple coating, and long drying, times were encountered utilizing the 
urethane coating formulations. 
Consequently, it would be extremely advantageous to employ a paint 
formulation which has good adhesion to the jacketed surface of the 
telephone cord and which can hold high pigment levels so as to allow one 
coat coverage while being relatively fast drying and stain resistant. 
SUMMARY OF THE INVENTION 
A polyvinyl chloride surface, such as a plasticized polyvinyl chloride 
telephone cord jacket, is coated, such as by dip coating or electrostatic 
coating, with a methyl methacrylic based coating formulation. The coating 
composition comprises (a) a resin binder comprising a medium molecular 
weight methyl methacrylate copolymer, (b) a cellulose acetate butyrate 
resin and (c) a carbalkoxy benzyl phthalate plasticizer. With respect to 
the aforementioned components, the solid copolymer is present in an amount 
of from 75 to 90 weight percent, the cellulose acetate butyrate resin from 
5 to 15 weight percent and plasticizer from 5 to 10 weight percent. 
Optionally, the composition may include other components such as a 
viscosity reducing solvent, a bubble breaker, a slip agent, and pigments 
in the form of an opacifier and/or a colorant. 
DETAILED DESCRIPTION OF THE INVENTION 
While the present invention is described in terms of a paint for 
refurbishing or coating electrical cable such as telephone cords including 
retractile and multiconductive cords, it should be understood that the 
novel paint formulation may also be used for coating surfaces other than 
telephone cords or other electrical cable. As previously stated, since 
most telephone cords are jacketed with a highly plasticized polyvinyl 
chloride jacket, the novel paint formulation will be particularly suitable 
for coating any plasticized polyvinyl chloride surface. 
It has been discovered that when coating a plasticized PVC jacketed 
telephone cord with a coating formulation comprising a binder comprising 
(a) 75 to 90 weight percent of a medium molecular weight methyl 
methacrylate copolymer, (b) 5 to 15 weight percent cellulose acetate 
butyrate resin and (c) 5 to 10 weight percent of a carbalkoxy benzyl 
phthalate plasticizer, and wherein the binder is dissolved in an aromatic 
based solvent, e.g., toluene or toluene-isopropanol mixture, unusual and 
unexpected synergistic results are obtained. These unexpected results were 
especially apparent at coating thicknesses of from about 3/4 of a mil to 
11/4 mils. 
One of the unexpected results which were achieved was found when pigments 
were added to the novel formulation. Pigments are generally added to 
attain improved hiding power and for attaining desired colors for color 
coordination. It was thought to be the rule that as pigment concentration 
in a coating formulation is increased, adhesion to the substrate 
decreased. Unexpectedly, using the novel formulations of this invention, 
as pigment concentration was increased, up to about a pigment to binder 
weight ratio of about 1.6, the adhesion to the substrate also increased. 
Another unexpected result relates to the stain resistance of the coating. 
Generally, upon adding a plasticizer to a resin coating formulation the 
resultant coating tends to lose stain resistant properties due to the 
combination of the stain with the plasticizer and migration of the stain 
containing plasticizer in the coating. Unexpectedly, stain resistance was 
not adversely effected by the inclusion of the carbalkoxy benzyl phthalate 
plasticizer of the novel coating formulation. The addition of plasticizer 
is necessary in order to insure the flexibility of the coating and prevent 
cracking of the coating when the telephone cords, such as retractile 
cords, are flexed. 
Still another unexpected property of the novel coating formulation of this 
invention is its ability to dry, even in humid conditions of, for example, 
50% or greater relative humidity. Generally, resins which have been 
plasticized to the extent required for retractile spring cords would be 
difficult to dry in humid conditions. The novel coating formulation, 
however, can be dried in relatively short periods of time at relative 
humidities as high as 85%. This property is important in the commercial 
processing of coated telephone cords and other materials. It is believed 
that the cellulose acetate butyrate resin in the formulation promotes 
drying. 
Furthermore, the ability of the resin to be pigmented at high levels while 
maintaining and, in fact, increasing adhesion to the substrate allows for 
one coat coverage of the plasticized polyvinyl substrate resulting in a 
significant cost reduction where multiple coatings would otherwise be 
required. 
In addition to the components of the primary binder composition set forth 
above, other additives may be included in the formulation. For example, 
one may add a solvent to reduce viscosity for handling of the primary 
binder-solvent system. The secondary solvent can for example be ethyl 
acetate. In addition a slip agent, such as a low molecular weight, 
non-contaminating silicone which is available as DC-11 silicone (5% 
solution) sold by Dow Corning may be included to reduce friction on the 
product after drying has occurred. Further, a bubble breaker to prevent 
the formation of, or break, the bubbles which may tend to otherwise form 
during the coating process may be included. An example of a suitable 
bubble breaker is polyvinyl isobutyl ether. This material is preferably 
added as a 5% solution in toluene. A variety of opacifiers and colorants 
may be added depending upon the color decided for the coating. For 
example, titanium dioxide may be added as an opacifier or whitener and 
aluminum pigment such as aluminum pigment 6571 available from Alcoa 
Company may be added to obtain a silver coloration. Other colorants or 
pigments may of course be added such as chromium oxide or other oxides or 
any of the other well known colorants or pigments used in the coating art. 
Similarly, secondary solvents, friction reducing agents and bubble 
breakers other than those cited above are suitable for use with the novel 
binder. Such materials are well known in the coating art. 
The novel formulations may be applied to the substrate to be coated by 
various methods. 
Applicable methods include, for example, dip coating, automatic 
electrostatic spray coating (low conductivity) or manual electrostatic 
spray coating (high conductivity). In each of these coating methods, a 
second silver solvent is added to the coating formulation which is 
appropriate to the specific method. Generally, solvent systems used in dip 
and electrostatic spray coating techniques are well known in the art and 
any of the prior art solvent systems which are compatible with a methyl 
methacrylate binder can be employed. Preferred solvent systems for dip and 
electrostatic spray coating of the novel formulations have been found. 
Generally, the primary constituents in these systems are alkyl acetates, 
e.g., isobutyl acetate. A preferred solvent system for dip coating is a 
one-to-one volume mixture of the basic coating formulation with isobutyl 
acetate solvent. The basic coating formulation, as used herein, means the 
binder, additives and solvent which make up the basic formulation which is 
then further diluted with a second solvent system. A preferred solvent 
system for automatic electrostatic spraying of the coating formulation is 
a one-to-three volume mixture of the basic coating formulation to a second 
solvent wherein the second solvent comprises by volume 30% methyl ethyl 
ketone, 68 % isobutyl acetate, and 2% ethylene glycol monobutyl ether. A 
preferred solvent system for manual electrostatic spraying of the coating 
is also a one-to-three volume mixture of the basic coating formulation to 
a second solvent wherein the second solvent in this instance comprises, by 
volume, 2% butyl cellosolve (ethylene glycol monobutyl ether), 15% 
n-butanol, 35% isobutyl acetate, 5% cyclohexanone and 43% methyl ethyl 
ketone. 
The preferred coating formulations comprise a binder comprising (a) 75-90 
weight percent of a medium molecular weight copolymer of methyl 
methacrylate and 2-ethyl hexyl acrylate, (b) 5-15 weight percent cellulose 
acetate butyrate having a viscosity of from about 1.9 to 2.1 poise, an 
average butyryl content of about 37 weight percent and an average acetyl 
content of about 13 weight percent, and (c) 5-10 weight percent of a 
carbalkoxy benzyl phthalate plasticizer which is the condensation product 
of benzyl phthalate and the esters derived from the condensation of 2,2,4 
trimethyl 1,3 pentanediol with isobutyric acid. Prior to mixing with the 
other components of the formulation, the methacrylate copolymer is 
preferably first dissolved in a toluene based solvent, e.g., one 
consisting of 80% toluene to 20% by weight isopropanol or other low 
molecular weight alcohol to give a solution representing 40% by weight of 
copolymer solids to 60% by weight of solvent. A preferred secondary 
solvent useful in preparing the basic formulation and further dissolving 
the binder is ethyl acetate. When the novel formulation is used to coat 
electrical conductors such as telephone cords, it is preferred to use an 
ethyl acetate solvent having a purity of at least about 99% such that the 
resistivity of the solvent is at least 20 megohms. 
The novel formulation can be used to make a clear coating, in which event 
no pigment, i.e., opacifier or colorant, is added. Alternatively, if an 
opaque or colored coating is desired, opacifier and/or colorant it added 
to the basic formulation. 
Since it is desirable for cost and ease of processing to be able to coat 
the telephone cords in a single coating operation the amount of opacifier 
or colorant used should at least be sufficient to achieve this goal. The 
actual amount to be used depends upon the particular opacifier or colorant 
and the nature and color of the telephone cord or base material to be 
coated. For example, if the colors of the plasticized polyvinyl chloride 
jacket and the coating to be applied thereto are the same, less pigment 
will probably be required than if coating a lighter color over a darker 
base material. The determination of the amount of pigment to be used is 
within the knowledge of those skilled in the art. Since adhesion has been 
found to increase with the amount of pigment added, up to a limit, it may 
be desirable to add more pigment than the minimum required for one coat 
coverage in order to increase adhesion. The optimum amount used for 
practical purposes, however, must be weighed based upon a cost factor as 
well as a performance factor since the cost increases with increasing 
amounts of additives. Furthermore, as the amount of pigment increases, the 
formulation tends to be thicker and handling and processing may become 
more difficult. Therefore the actual amounts of additives to be 
incorporated in the formulation to attain proper viscosity for ease of 
handling, one coat coverage, good adhesion and optimum cost factor is a 
variable which may easily be determined by one skilled in the art for the 
particular use of the formulation. 
We have found that the replacement of any of the basic constituents in the 
binder of the novel formulation by materials similar to the constituents 
of the novel binder adversely affects the resultant formulation. This fact 
highlights the unexpected and synergistic results attained with the novel 
formulation. This observation can better be shown with reference to the 
comparative examples set forth below. 
The coating formulation of each of the subsequent examples was coated on a 
highly plasticized polyvinyl chloride telephone cord jacket. The telephone 
cord was coated by dipping it into a dip coating formulation comprising a 
mixture of the coating formulation given in the respective examples mixed 
with a 1:1 volume ratio of isobutyl acetate. The time required for drying 
the coating was determined at 80.degree. F. and 70% relative humidity. The 
specific test used to determine drying time involves drying a 12 foot 
telephone spring cord for a designated period of time and then applying a 
2 pound compressive force on the spring cord helix for 5 minutes. The 
force is then removed and if the coils of the spring cord release within 8 
seconds from removal of the force, the cord is considered dried and 
tack-free. The dried and tack-free cord may then be tested for adhesion of 
the coating on the polyvinyl chloride substrate. Adhesion is determined by 
a variation of adhesion test method 6301.1 found in Federal Test Method 
Standards, Vol. 141. This adhesion test involves placing an adhesive tape 
(Scotch Brand No. 600 or equivalent) over the surface to be tested and 
removing the tape after a period of time. The area of coating removed from 
the substrate upon removal of the tape is then determined. The greater the 
percent of surface area removed by the adhesive tape, the lower the actual 
adhesion. Percent adhesion, represents the ratio of surface area remaining 
divided by the total area tested for adhesion times 100.

EXAMPLE I 
A. A preferred clear coating formulation consists of 633 grams of DuPont 
Elvacite 6014 methyl methacrylate copolymer in an aromatic solvent, 19.4 
grams of Eastman CAB-381-0.5 cellulose acetate butyrate, 19.4 grams of 
Monsanto santicizer 278, 245.3 grams ethyl acetate, 9.8 grams Dow Corning 
DC-11 silicone and 9.8 grams polyvinyl isobutyl ether. The Elvacite 6014 
contains 40% by weight solids, or 253.2 grams of solid copolymer, in a 
solvent consisting of 80 parts toluene to 20 parts isopropanol. Another 
suitable available copolymer is DuPont's Elvacite 2014. This is available 
in bead form. The copolymer is a medium molecular weight methyl 
methacrylate copolymerized with ethyl hexyl acrylate. It has an acid 
number of 13 and a Knoop hardness number of 4. 
The Eastman CAB 381-0.5 cellulose acetate butyrate has a viscosity of 1.9 
to 2.1 poise, an average butyryl weight percent of about 37 weight percent 
and an average acetyl weight percent of about 13 weight percent. This 
material functions as a drying agent. 
The Monsanto Santicizer 278 is a carbalkoxy benzyl phthalate plasticizer 
derived from the condensation of benzyl phthalate with the ester obtained 
from the condensation of isobutyric acid and 2,2,4 trimethyl 1,3 
propanediol. 
The ethyl acetate solvent used in the formulation is at least 99% pure and 
has an electrical resistivity of at least 20 megohms. This solvent is 
added to reduce viscosity for handling purposes. The Dow Corning DC-11 
silicone is a 5% silicone solution of a low molecular weight 
non-contaminating silicone which is added as a slip agent. The polyvinyl 
isobutyl ether is added as a 5% solution in toluene for the purpose of 
preventing the formation of bubbles. The total amount of binder in this 
formulation is therefore the sum of 253.2 grams of solid copolymer 
representing 86.8% of the binder, 19.4 grams of cellulose acetate butyrate 
representing 6.6 weight percent of the binder and 19.4 grams of the 
plasticizer representing 6.6 weight percent of the binder. 
B. The coating formulation of this Example represents the preferred 
formulation for a satin silver coating on a plasticized polyvinyl chloride 
jacketed telephone cord. The formulation of this Example is identical to 
the formulation given in Example I-A except that the formulation includes 
24.3 grams titanium dioxide opacifier and 39.0 grams of Alcoa 6571 
aluminum pigment. The pigment to binder ratio in this formulation is 
therefore 63.3 grams pigment to 292 grams binder or 0.2:1. 
C. The same formulation as set forth in Example I-A is used herein except 
that the formulation includes 370 grams titanium dioxide and 39 grams of 
the aluminun pigment giving a total pigment weight of 409 grams and a 
pigment to binder ratio of 1.4:1. 
D. The coating formulation was prepared consisting of 657 grams of Elvacite 
6014 copolymer resin (40% solids in toluene/isopropanol), 14.6 grams 
Eastman CAB-381-0.5 cellulose acetate butyrate, 14.6 grams Monsanto 
Santicizer 278, 245.3 grams ethyl acetate, 9.8 grams DC-11 silicone (5% 
solution), 9.8 grams polyvinyl isobutyl ether (5% in toluene), 24.3 grams 
titanium dioxide and 39 grams aluminum pigment. This formulation 
represents a binder consisting of 90% copolymer, 5% cellulose acetate 
butyrate and 5% plasticizer. 
E. The formulation set forth in Example I-D is repeated except that 547.5 
grams of Elvacite 6014 resin (40% solids in toluene/isopropanol), 43.8 
grams of the cellulose acetate butyrate and 29.2 grams of the Santicizer 
278 were employed. This formulation represents one wherein the binder 
consists of 75% copolymer, 15% CAB and 10% plasticizer. 
EXAMPLE II 
Examples II-A through II-E which are presented for comparative purposes are 
identical to the formulations set forth in Examples I-A through I-E, 
respectively, except that DuPont's Elvacite 2009 is substituted for the 
Elvacite 6014 resin of the novel formulations of Example I. DuPont's 
Elvacite 2009 is a medium molecular weight non-copolymerized methyl 
methacrylate polymer having an acid number of zero and a Tukon hardness 
Knoop number of 17. 
EXAMPLE III 
The formulations of Examples III-A through III-E which are also for 
comparative purposes are identical to those of Examples I-A through I-E, 
respectively, except that DuPont Elvacite 6028 is used in place of the 
DuPont Elvacite 6014 of the novel surface formulation. Elvacite 6028 is a 
low molecular weight methacrylate copolymer as opposed to the medium 
molecular weight methyl methacrylate copolymer of 6014. 
The Table shown below summarizes the adhesion and drying times observed for 
coatings derived from formulations I-A through I-E, II-A through II-E and 
III-A through III-E. 
______________________________________ 
Pig./ Wt. % Drying 
Binder CAB in Time 
Ratio Binder % Adhesion (Minutes) 
______________________________________ 
IA 0 6.6 88. 18 
IB .2 6.6 89.5 16 
IC 1.4 6.6 98 12 
ID .2 5.0 91.8 20 
IE .2 15.0 87.0 10 
IIA 0 6.6 60 48 
IIB .2 6.6 48 45 
IIC 1.4 6.6 15 42 
IID 0.2 5.0 50 50 
IIE 0.2 15.0 43 30 
IIIA 0 6.6 65 63 
IIIB 0.2 6.6 60 59 
IIIC 1.4 6.6 30 56 
IIID 0.2 5.0 63 65 
IIIE 0.2 15.0 53 45 
______________________________________ 
One can readily see from the above Table that only the formulations 
exemplified by Examples I-A through I-E results in coatings having 
superior adhesion which increases with increasing pigment-to-binder ratio. 
Furthermore, it is also readily observable that only the novel 
formulations of Example I result in coatings having drying times of 20 
minutes or less. 
Similar experiments to the ones shown above have been performed wherein the 
plasticizer was butyl benzyl phthalate or dibenzyl phthalate or where 
other cellulose acetate butyrate resins having viscosities other than 1.9 
to 2.1 were employed. In each of these instances, both adhesion and drying 
times were poorer than those observed in Examples I-A through I-E. 
In addition to testing adhesion and drying times, clear coatings prepared 
in accordance with Examples I-A, II-A, and III-A were tested for stain 
resistance and compared. The stain indication employed was smoke 
permeation causing increased yellowness as the stain indicator. The coated 
telephone cord was exposed to smoke for a predetermined time and the cord 
was then measured on a Hunter D25D3 colorimeter with a reflectance 
attachment thereon in order to determine the increase in yellowness. It 
was found that coatings prepared in accordance with formulation I-A 
resulted in only a 20% yellowness increase while coatings prepared in 
accordance with formulations II-A and III-A resulted in yellowness 
increases of 48 and 52%, respectively.