WO2000027606A1

WO2000027606A1 - Method of coating articles and coated articles

Info

Publication number: WO2000027606A1
Application number: PCT/US1999/026840
Authority: WO
Inventors: Warren G. Mang; Kenneth D. Hobbs; Charles P. Marino
Original assignee: Markel Corporation
Priority date: 1998-11-12
Filing date: 1999-11-12
Publication date: 2000-05-18
Also published as: EP1169167A1

Abstract

A method of coating a fabric substrate (10) to form a flexible, abrasion-resistant article, of coating a fabric substrate (10) with heat-curable and UV-curable coating composition (28) to form a dieletric dual-layered coating thereon, and the coated articles formed thereby.

Description

METHOD OF COATING ARTICLES

AND COATED ARTICLES

CROSS-REFERENCE TO RELATED APPLICATION This application claims the benefit of U.S. Provisional Application No. 60/065,214 filed on November 12, 1997.

FIELD OF THE INVENTION

This invention relates to a method of coating articles. More particularly, this invention relates to a method of bonding one or more coating compositions firmly to a fabric substrate to form a thin coating layer thereon and the coated articles formed thereby.

Cables, wires, hoses and the like constructed from metal, plastic, rubber and other materials (collectively referred to herein as conduits) are used widely in applications in which

mechanical stresses such as those caused by repetitive movements and vibration are present. Examples of such applications include the use of conduits in engine compartments, exhaust systems and other areas of automobiles and trucks, as well as other motorized vehicles. In such, applications, conduits are often positioned in circuitous paths in close proximity to repetitively moving or vibrating parts. If left exposed to such movements or vibrations, conduits will wear

through quickly and the systems of which they are a part will become damaged. When such systems are involved in the operation or safety of a vehicle, it is of critical importance that the

conduits of such systems are protected from abrasive failure.

It is known to use fabric sleeving as a physical barrier to protect conduits from the wear

to which they would otherwise be subject. In many applications in which such sleeves are used, it is desirable to use color as a means for distinguishing one sleeve from another. For example,

during the manufacturing of systems which employ a variety of such sleeves, color coding of the

different sleeves makes selection of the proper sleeve easy and efficient. Color is also of benefit in connection with maintenance and repair of such systems where the ready identification of

particular conduits and components retained by such sleeves is desirable.

A variety of fabric materials have been employed in the construction of sleeving for

conduits. A material commonly used in automotive applications is fiberglass. This relatively

inexpensive material is selected for its combination of flexibility and thermal stability both of

which are important properties in such applications. Fiberglass, however, exhibits poor abrasion-

resistance. It is damaged easily by the same repetitive movements and vibrations which cause

damage to the conduits for which it is used. Thus, the protection that fiberglass sleeving affords

is limited by the amount of abrasive force it can withstand before failure. This is also true of other

fabric materials used in the construction of sleeving. In order to improve the abrasion-resistance

of the aforementioned type of sleeving, it is known in the art to apply abrasion-resistant coatings

thereto.

Abrasion-resistant coatings, as well as other types of coatings which are applied to fabrics for other purposes, are often formed from compositions which contain curable constituents. The

use of curable components tends to promote a more secure bond to the substrate on which the coating composition is applied and improves various physical characteristics of the coatings formed therefrom such as, for example, strength, abrasion resistance and durability. Known means for curing include, for example, heat and ultraviolet (UN) radiation. As used herein, curing

by any of such or other means involves the cross-linking of polymer chains comprising the polymeric constituents of compositions at the reactive sites thereof.

The use of UN radiation to effect curing of coating compositions is advantageous for a variety of reasons. While curing by means of heat requires the use of ovens, which adds significantly to the energy and equipment required to achieve a cured product, curing by means

of UV radiation can be achieved efficiently with one or more UV light generating lamps under

ambient temperature conditions. Moreover, many UV-curable coating compositions do not require solvents and thus avoid the risk of air pollution that can result from evaporation of volatile organic compounds, which often comprise such solvents, during the manufacturing process.

Further, because of the rapidity with which curing by means of UV radiation occurs, the curing

step of an overall manufacturing process can be accomplished quickly.

UV-curable coating compositions generally contain photoinitiators that are dormant until

acted upon by a source of UV radiation. Because photoinitiators are sensitive to energy at the

UV wavelengths, exposure to UV radiation triggers a chemical reaction that produces free radical

groups which, in turn, cause cross-linking of the polymer chains of the coating composition. In

order for a complete cure to be effected, however, the UV radiation must activate a substantial

portion of the photoinitiator molecules. While UV curing can be accomplished readily with

colorless coatings, the presence of colorants in the coating compositions, especially pigments,

tends to interfere with the curing process. More specifically, because pigments tend to compete with the photoinitiator for the UV radiation, UV radiation absorbed by the pigment is unavailable

for absorption by the photoinitiator molecules to initiate the curing process. Moreover, as the thickness of the pigment-containing coating composition increases, the ability of UV radiation to

penetrate fully the coating composition to effect a complete through-cure is substantially limited. Further, different pigments have different absorption characteristics, that is, they absorb different wavelengths of UV radiation and to different degrees. As a result, the selection of appropriate

pigments and UV wavelengths to produce a cured coating can be difficult. Indeed, carbon black,

a commonly used pigment, absorbs strongly across the entire UV range. Accordingly, the use of UV radiation to cure pigmented coating compositions has heretofore been limited.

REPORTED DEVELOPMENTS

It is known to prepare coated fabrics by methods which employ the use of release

substrates, doctor blades, or complex combinations of heated calenders to apply coating

compositions and to regulate the thickness and texture thereof.

U.S. Patent No. 3,330,713 discloses a method for coating fabric comprising the steps of extruding a film of an uncured polyurethane composition onto a continuous moving sheet of paper

coated with a release layer of wax, partially curing the composition by heating, applying the fabric to the partially cured film, completing the cure of the polyurethane composition, and separating

the laminate from the wax coated paper sheet. The use of release substrates is also disclosed in

U.S. Patent No. 3,844,862.

U.S. Patent No. 4, 582,660 discloses a method of coating fabric in which a liquid polymeric

coating composition is applied to at least one side of a fabric substrate, partially dried in a heating

unit, and then doctored in order to regulate the thickness of the coating thus formed. Similarly,

U.S. Patent No. 4,062,989 (the '989 patent) discloses a method of coating fabric in which a horizontally oriented continuous length of fabric is coated from below by means of a pressure

manifold from which coating composition is released and from above by means of a hopper from which coating composition is discharged by gravity. The '989 patent teaches the regulation of the

thickness and smoothness of the coating layer by means of scraper bars from below and the downwardly extending hopper wall from above. Penetration of coating composition into the body

of the fabric substrate by these methods is limited to the application of coating compositions which are themselves sufficiently flowable to permeate the interstices of relatively porous fabric

substrates.

In order for coating compositions to be freely flowable into the fabric substrate, the solids content of the coating composition must be low. If a high-solids content coating composition is

used, the flowability is commensurately reduced. Thus, the use of the doctor blades and scraper bars of the prior art do not address the penetration of high-solids coating compositions into the

body of substrates to which they are applied. As a result, the use of doctor blades or scraper bars

is limited to forming coatings from coating compositions which are bonded only to the surface of

the fabric substrate or low-solids coating compositions which are themselves capable of

penetration into the fabric substrate.

Experience has shown that many types of woven or braided sleeves tend to fray at cut

ends. When this occurs, structural integrity is compromised and the useful life of the sleeve is shortened. In the case of fiberglass sleeves, such fraying is accompanied also by the release of

glass fibers. This release is particularly troublesome during handling which can cause glass fibers

to shed from frayed ends directly onto the hands of workers. Fibers are also released into the air

where they find their way onto the exposed skin or into the airways and lungs of workers.

Through such contact, glass fibers cause dermatitis, other forms of skin irritation, and respiratory

problems. Attempts have been made to use coatings to control fray and the consequent release of

fibers from sleeves. The coatings of the prior art, however, have been unsuccessful in restraining fiber fray at cut ends. This is due, at least in part, to the arrangement of the coating layer around

the outside of the sleeve and the nature of the bond between the coating and the sleeve. Because

the coatings do not penetrate into the body of the sleeve to any substantial degree, being adhered only to the exterior surface of the sleeve, fibers located within the interior of the sleeve are not bound to the coating layer and are thus more capable of fraying. As a result, such coatings so applied to the sleeve fail to suppress the release of fibers, particularly glass fibers, onto the hands

of workers or into the air.

SUMMARY OF THE INVENTION The present invention relates to a method of coating an article with one or more high

solids content curable coating compositions to form a thinly coated article and the thinly coated article produced thereby. Depending on the particular coating compositions employed, the article

produced by the method of the present invention possesses superior physical and dielectric

properties. In embodiments which utilize a heat-cured base coating composition and a UV-cured

top coat composition, the resultant dual-layered coated article of the present invention is capable

of exhibiting a wide variety of different colors. The present invention is particularly well-suited

to the formation of flexible, abrasion-resistant and dielectric coated fabric articles for use as

electrical insulation for conduits as well as in the insulation of conduits from external mechanical

stress and vibration.

In accordance with one aspect of the present invention, there is provided a method for

coating a fabric substrate comprising the steps of applying a high solids content coating

composition to the fabric substrate and applying pressure to the fabric substrate whereby a portion of the applied coating composition penetrates into the fabric substrate. The application step provides an initial coating of the coating composition to the fabric substrate. The use of a pressure step then serves to force a portion of the coating composition so applied into the fabric

substrate while, at the same time, removing from the fabric substrate substantially all amounts in excess thereof. Articles produced in accordance with this method display a uniformly continuous thin coating which is bound firmly to the fabric substrate and which serves to minimize fraying of the fibers comprising the fabric substrate.

In accordance with certain embodiments of the present invention in which two different

coating compositions are employed, there is provided a method for coating a fabric substrate

comprising the steps of applying a high solids content heat-cured coating composition to the fabric

substrate, applying pressure to the coated fabric substrate whereby a portion of the heat-cured coating composition penetrates into the fabric substrate, heating the coated fabric substrate,

applying a UV-curable coating composition to the coated fabric substrate, and curing the UV- curable coating composition thereon by exposing the UV-curable coating composition to UV

radiation. Depending on the coating compositions and substrate material used, the methods of

the present invention may include additional process steps. These additional steps, discussed

more fully below, may include a preheating step prior to the application of the high solids content

coating composition, and a shaping step after the application of pressure to the coated fabric

substrate. Preferably, the steps comprising the present invention are part of a continuous production process.

In accordance with another aspect of the present invention, there is provided an article

comprising a fabric substrate and a high solids content coating composition applied to, at least

partially penetrated therein, and heat cured thereon. In certain embodiments of the present

invention which utilize two different coating compositions, there is provided an article comprising a fabric substrate, a high solids content heat-cured coating composition applied to, at least

partially penetrated therein, and heat cured thereon, and a clear UV-curable coating composition applied to and UN cured on the heat-cured coating.

Fabrics considered to be within the scope of the invention are those fabrics capable of having a high solids content coating composition adhered thereto and forced at least partially

therein by the application of pressure. Examples of such fabrics include fabrics comprising

organic fibers or inorganic fibers, or combinations thereof. It is believed that the invention will be used widely in coating fabrics composed of fiberglass. In those embodiments in which fiberglass

sleeving is used, the method of the present invention coats substantially all of the fibers comprising the matrix with the coating composition resulting in a significant enhancement to the ability of the

sleeves to resist fraying and shedding. In embodiments in which the steps comprising the present invention are part of a continuous production process, the fabric substrate is preferably provided

in continuous lengths. In certain preferred embodiments, the fabric substrate will be provided in colored form. In such embodiments, the colorants may comprise dyes, pigments or other types

of colorants which are appropriate for the substrate to be coated. It is contemplated that in such

embodiments the application of colorants to the fabric substrate will occur prior to the application

of the coating composition. In those embodiments in which two different coating compositions

are employed, the colorants may be applied to the fabric substrate prior to the application of the

heat-cured coating or as a component of the heat-cured coating.

The coating compositions considered to be within the scope of the present invention are

those compositions which are capable of being applied to a fabric substrate, penetrating at least

partially therein by the application of pressure, and forming a bond therewith. The method of the

present invention is particularly well suited to the application of coating compositions which are

capable of forming flexible, abrasion-resistant coatings and coatings which exhibit superior dielectric properties. In certain preferred embodiments, the coating compositions will be curable

by exposure to heat or UV radiation. While it is contemplated that suitable coating compositions may be provided in one or more solid, liquid or gaseous phases, or combinations thereof, it is important that the coating composition have a relatively high solids content, preferably of at least about 40 wt.%. In preferred embodiments, the coating composition is provided as an aqueous

dispersion of solid particles.

In those embodiments which utilize two different coating compositions, the high solids content coating compositions are also heat-cured and capable of forming a chemical bond with

a UV-curable coating composition applied thereon. In such embodiments, the UV-curable coating compositions considered to be within the scope of the invention are those compositions which are

capable of being applied to a fabric substrate to which a heat-cured coating composition has been cured thereon, and of forming a chemical bond with such coated fabric substrate. Depending on

the particular coating compositions selected, the combination of coatings to form a dual-layered

coated article provides significant enhancement to the abrasion resistance, durability and dielectric

properties of a fabric substrate and permits the utilization of a wide variety of colorants without

adversely affecting the ability to employ UV curing techniques.

The method of the present invention provides numerous advantages including, for

example, the provision of means for continuous formation of flexible, abrasion-resistant and

dielectric fabrics as well as the effective UV curing of colored fabrics. Further, the coatings of

the present invention can provide significant fray-resistance when the coating compositions of the

present invention are applied to sleeves constructed from fibrous material such as fiberglass.

Through the minimization of fiber release, the structural integrity of the sleeving is preserved and,

in fiberglass sleeve applications, the potential for skin and lung irritation is markedly reduced. The

full range of applications to which the method and articles of the present invention may be put are numerous and varied. It is believed, however, that the method of the present invention is

particularly well-suited to the formation of flexible, abrasion-resistant, and dielectric coated fiberglass sleeves, and the articles of the present invention are well-suited to applications is which

flexible, abrasion-resistant, and dielectric coated fiberglass sleeves are desired or required. Examples of applications in which the use of such sleeves would be advantageous include carbon brush leads, sensor elements, thermocouple wires, and oxygen sensor assemblies in automotive

emissions monitoring systems as well as electrical wiring applications.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a schematic side elevation view of a coating apparatus in accordance with

an embodiment of the present invention in which one coating composition is applied to the fabric

substrate.

Fig. 2 shows a schematic side elevation view of a coating apparatus in accordance with an embodiment of the present invention in which two coating compositions are applied to the

fabric substrate.

DETAILED DESCRIPTION OF THE INVENTION

coating a fabric substrate. The first step in the method of the present invention involves the

application of a coating composition to a fabric substrate. In those embodiments in which two

different coating compositions are to be applied, the first step in the method of the present

invention involves the application of a heat-cured coating composition to a fabric substrate. The

application step may be accomplished in a variety of ways provided that it results in an adequate

delivery of the coating composition to the fabric substrate. Examples of such application methods considered within the scope of the invention include the use of a dip pot, sprayers, rollers and the like. The use of such means will vary depending on, among other things, the form of coating

composition used, the amount required to be initially applied and, if part of a continuous

production processes, the line speed of the fabric substrate. In those embodiments in which the coating composition to be applied is provided in a substantially liquid phase, such as a dispersion of solids in a liquid medium, it is preferred that the application step is accomplished by means of

a dip pot wherein an initial quantity of the coating composition in excess of the amount which will

form a part of the coating layer may be efficiently applied to continuous lengths of fabric. In other

embodiments in which the coating composition is provided in a substantially gas phase, such as a dispersion of solid particles in a gas, or in a substantially solid phase, such as one or more phases

of solid particles, it is preferred that the application step is accomplished by means of sprayers or fluid beds. The thickness of the coating composition initially applied should be sufficient to permit

the formation of a continuous film of coating upon application of pressure in the subsequent

pressure step. Preferably, the initially applied coating composition will form a continuous layer

on the fabric substrate having a thickness of about 0.5 to about 5 mils, and more preferably about

0.5 to about 2.0 mils.

In those embodiments in which the coating composition has a tendency to settle, such as

when the coating composition is provided in the form of a dispersion of solids in a liquid medium,

means for agitating the coating composition are important to maintaining the homogeneity of the

coating composition during the application step and throughout the production process. The

particular agitation means selected is not of particular importance and will vary in accordance

with, among other things, the nature of the composition requiring agitation and the rate and

intensity of agitation required.

The next step in the method of the present invention involves the application of pressure to the coated fabric substrate. The pressure step may be accomplished in any of a number of ways provided that the means for exerting pressure on the coated substrate is capable of imparting the

required compressive force to cause a portion of the coating composition applied on the fabric substrate to penetrate at least partially thereinto while removing therefrom substantially all of the

excess coating composition. Preferably, the pressure step is accomplished by means of a set of pinch rollers wherein the rollers are spaced to form a nip of a preselected size in order to impart

the desired pressure upon the coated fabric substrate. In more preferred embodiments, the coated fabric substrate advances upward through a set of pinch rollers, as shown in Figs. 1 and 2, so that the coating composition in excess of that amount which is driven into the fabric substrate falls

back into the dip pot and is recycled for application onto subsequent lengths of the fabric

substrate. In those embodiments in which the method of the present invention is a part of a continuous production process, the use of pinch rollers permits pressure to be exerted continuously upon the advancing fabric substrate positioned so as to pass therethrough.

The amount of pressure applied to the coated fabric substrate will vary according to,

among other things, the flow characteristics of the coating composition, the relative ease or

difficulty with which such coating composition is capable of penetrating into the fabric substrate

and, in continuous production processes, the line speed of the advancing fabric substrate. For

most applications, the pressure exerted in the pressure application step is preferably about 5 to

about 100 pounds per square inch (psi), and more preferably about 10 to about 40 psi. Upon

application of pressure, the coating composition layer will preferably have a thickness of about

0.25 to about 5.0 mils, and more preferably about 0.5 to about 2.0 mils.

In those embodiments in which pinch rollers are used, the rollers may be constructed from

a variety of materials having a range of hardness provided the rollers formed therefrom are

capable of exerting a sufficient force on the coated fabric substrate. The rollers may also range in surface texture from relatively smooth to relatively rough or patterned provided that such texture does not substantially interfere with the application of pressure or result in undue slippage

of the rollers with respect to the coated fabric substrate. Preferably, the rollers will comprise natural or synthetic rubbers, urethanes and the like having a substantially smooth surface and a

Shore D hardness of at least about 60.

A further step of the present method is curing the coated fabric substrate. The curing step

may be accomplished by any of a variety of curing methods all of which are considered within the scope of the invention provided that the means for curing the coating composition is capable of

effecting an adequate cure. For most applications, the curing step will be accomplished by means of the application of heat or UV radiation. In those embodiments in which heat is used, that is,

where a heat-cured coating composition has been applied to the fabric substrate, it is important that the heat source is capable of imparting a sufficient quantity of thermal energy and is

positioned with respect to the coated fabric substrate so as to cause substantially all of the coating

composition applied thereon to cure. Preferably, such heat curing will employ the use of curing ovens. In those embodiments in which the method of the present invention is a part of a

continuous production process, the curing step will utilize a curing means configured to permit

the advance of a continuous length of coated fabric therethrough.

The temperature range in which the curing of heat-cured coating compositions is effected

will be determined by, among other things, the particular constituents comprising the composition,

the amount of coating composition applied, the time of exposure, and the degree of cure desired.

Similarly, the time period in which heat curing occurs will depend on, among other things, the

particular constituents comprising the coating composition, the amount of such composition

applied, the temperature to which such composition is exposed, and the degree of cure desired.

For certain preferred abrasion-resistant coating compositions, the temperature range and cure times will be selected to permit sufficient curing to form a coating which is appropriately abrasion- resistant for the application in which such coated article will be used. Preferably, such coatings

will exhibit abrasion-resistance of at least about 10,000 cycles, preferably at least about 20,000 cycles, and even more preferably at least about 35,000 cycles before failure as measured by test

method ARP- 1536-A and, when applied to a flexible substrate, are able to withstand at least about

a 50%, and preferably at least about 70% dimensional compression of the substrate without

permanent deformation or crazing. It is believed that the most commonly used compositions will be capable of being cured upon exposure to temperatures of between about 500°F to about

1200°F, preferably between about 700°F to about 1000°F, for a period of about 5 to about 90 seconds, preferably about 5 to about 30 seconds.

In certain embodiments, heat-cured coating compositions will be employed which evolve

water vapor when cured. In such embodiments, it is preferred that the heat source be provided with means for evacuating water vapor so that water vapor evolving from the cross-linking

reaction may be continuously evacuated therefrom. The appropriate water evacuation means may by provided in a variety of ways depending on, among other things, the nature of the heat source

employed. In those embodiments in which a curing oven is used, such water evacuation means

preferably comprise a steady source of fresh air, preferably delivered via a series of compressed

air outlets which direct the flow of fresh air provided by a compressor unit through the curing oven.

In those embodiments in which two coating compositions are applied to the fabric substrate, the method of the present invention comprises additional steps. The first of these

additional steps involves the application of a UV-curable coating composition to the coated fabric

substrate. This application step may be accomplished in a variety of ways provided that it results

in an adequate delivery of the UV-curable coating composition to the coated fabric substrate. Examples of such application methods considered within the scope of the invention include the use of a dip pot, sprayers, rollers and the like. The use of such means will vary depending on,

among other things, the form of UV-curable coating composition used, the amount required to be initially applied and, in continuous production processes, the line speed of the coated fabric

substrate. In those embodiments in which the UV-curable coating composition to be applied is provided in a substantially liquid phase, such as a single-phase liquid or a dispersion of solids in

a liquid medium, it is preferred that this application step is accomplished by means of a dip pot wherein an the liquid phase UV-curable coating composition may be applied readily to continuous

lengths of fabric.

The thickness of the UV-curable coating composition initially applied should be sufficient

to permit the formation of a continuous film of coating upon subsequent processing and may be applied in excess of the amount desired to form the top coat. In those embodiments in which

excess amounts of UV-curable coating composition has been applied, it is preferred that the

coated fabric substrate pass through a sizing die to control the thickness of the UV-curable coating composition applied thereon. Preferably, the UV-curable coating composition will form

a continuous layer on the fabric substrate having a thickness of about 1 to about 50 mils, and more

preferably about 1 to about 20 mils.

In those embodiments in which the UV-curable coating composition has a tendency to

settle, such as when the composition is provided in the form of a dispersion of solids in a liquid

medium, means for agitating the composition are important to maintain homogeneity of the

composition during the application step throughout the production process. As in the prior

application step, the agitation means which may be utilized in connection with this application step

is not of particular importance and will vary in accordance with, among other things, the nature

of the composition requiring agitation and the rate and intensity of agitation required. The next additional step of those embodiments of the present method in which two coating compositions are applied to the fabric substrate involves curing the UV-curable coating

composition by exposure to UV radiation. The curing step may be accomplished in a variety of ways provided that the source of UV radiation is capable of imparting a sufficient quantity of

radiation at the appropriate UV wavelengths and is positioned with respect to the coated fabric substrate so as to cause substantially all of the UV-curable coating composition applied thereon to cure. Preferably, the curing step will employ the use of UV radiation-emitting lamps, and even

more preferably xenon arc or mercury vapor lamps.

The particular number and placement of UV sources utilized will vary in accordance with,

among other things, the nature and intensity of the UV sources, the shape of the article being cured, the curing characteristics of the applied UV-curable coating composition and whether reflectors are also used. In those embodiments in which UV radiation-emitting lamps are used

on continuous lengths of a fabric sleeve, it is preferred that such lamps be employed in groups of

two or three spaced equally about the path of the advancing fabric sleeve and placed about 2 to

about 4 inches from the surface of the coated fabric. In certain preferred embodiments, the use

of reflectors are also be employed. In such embodiments, reflectors serve to enhance the even and

complete delivery of UV radiation to the coated fabric, especially where the surface thereof is

curved or where a limited number of sources of UV radiation is utilized.

While the particular wavelengths of UV radiation will be selected in accordance with,

among other things, the curing characteristics of the particular constituents of the UV-curable

coating composition used, it is believed that for most applications the sources of UV radiation will

be selected to generate wavelengths of UV radiation from about 180 to about 450 nanometers

(nm), preferably about 240 to about 380 nm

The time period in which UV curing occurs will depend on, among other things, the curing characteristics of the particular constituents comprising the UV-curable coating composition, the amount of such composition applied, the intensity of the UV radiation to which such composition

is exposed, and the degree of cure desired. While the particular exposure time will be selected in view of all of the relevant variables and, in particular, the specific coating composition

employed, it is believed that the most commonly used compositions will be capable of being cured within a period of about 1 to about 30 seconds, preferably about 1 to about 20 seconds.

Preferably, the steps of the method of the present invention are performed as a part of a continuous production process wherein the fabric substrate is provided in continuous lengths and

the coating composition or compositions are provided in quantities sufficient to coat the length of fabric used. In such embodiments, the line speed of the fabric substrate through the process line will vary in accordance with a variety of factors including the particular fabric substrate and

coating compositions used, and, if curing or heating ovens are used, the size and temperatures of such ovens. Preferably, the line speed will be about 5 to about 100 feet per minute, more

preferably about 10 to about 50 feet per minute, and even more preferably about 25 to about 40

feet per minute.

The method of the present invention may include additional steps. In certain preferred

embodiments in which a tubular fabric substrate is employed, the method of the present invention

will involve an initial sizing step in which the inside diameter of the fabric substrate is sized in accordance with particular predetermined sizing specifications. The sizing of the inside diameter

of the fabric substrate is important to producing a consistently sized coated article which,

depending on the end use to which it will be put, will be required to meet particular dimensional

specifications. While the sizing step may be accomplished in a variety of ways, all of which are

considered within the scope of the invention, it is believed that in many applications a die will be

used. In such embodiments, the sizing die is positioned so that the fabric substrate passes therethrough prior to further processing. While the dimensions of the sizing die will be selected with reference to the specifications required by the particular application, for most applications

the sizing die will have an inside diameter of about 0.04 to about 2 inches.

Another step which may also be included in certain embodiments is a preheating step.

In the preheating step, the fabric substrate will be preheated prior to the application of any coating composition. This step can serve a number of functions depending on the particular fabric

substrate to be coated. In those embodiments in which fiberglass sleeving is used, the preheating step serves to remove organic starches and binders which are commonly applied in the manufacture of the fiberglass sleeving, to heat set the inside diameter of the fiberglass sleeving,

and to relieve the stress imparted to the fibers comprising the fiberglass sleeving during its

formation. The removal of organic starches and binders is important in preparing the fabric

substrate for coating as the presence of such starches and binders can interfere with the adhesion of the coating composition to the fabric.

The preheating step can be accomplished in a variety of ways provided that the fabric substrate is exposed to a sufficient quantity of heat for a sufficient period of time to prepare the

fabric substrate for the subsequent application of one or more coating compositions. Preferably,

the preheating step occurs in an oven set at between about 700°F to about 1600°F, more

preferably between about 1000°F to about 1600°F, and even more preferably between about

1200°F to about 1400°F. At such temperatures, the oven is sized to permit a residence time of

about 5 to about 60 seconds, preferably about 5 to about 30 seconds. In those embodiments in

which the steps of the method are part of a continuous production process, the oven in which the

preheating step occurs will permit the continuous advance of the fabric substrate. Once the fabric

substrate has passed through the preheating step, it is preferred that it be permitted to cool in a

subsequent cooling step to at least 150°F before any coating composition is applied if the coating composition is such that it will be heat cured in a later processing step. Such a cooling step would not be important if heat-cured coating compositions are not employed.

In certain preferred embodiments in which a tubular fabric substrate is employed, the method of the present invention may also include a shaping step after the pressure step.

Depending on the particular fabric substrate employed, the pressure step may cause the substrate to assume a flattened or distorted shape. In order to prevent the subsequent curing step from

curing the coating composition on a flattened tubular fabric substrate and thereby preserving the

dimensional distortion, the inclusion of a shaping step after the pressure step permits the substrate to resume its tubular shape prior to curing While the shaping step may be accomplished in a variety of ways, all of which are considered within the scope of the invention, it is believed that

in many applications a die will be used.

In those embodiments in which the coating composition is heat cured, the method of the

present invention may also involve a cooling step in which the heat cured coated fabric substrate

is cooled to ambient temperatures prior to take-up or, in embodiments in which a second coating composition is applied, prior to the application of such second coating composition. While the

cooling step may be accomplished by a variety of means all of which are considered within the

scope of the invention, it is believed that in many applications a cooling tube and blower will be

used so that air at ambient temperatures is directed by the blower through the cooling tube

through which the coated fabric travels.

Fabrics considered to be suitable for use in the practice of the present invention are any

which are capable of having a coating composition adhered thereto and penetrated at least partially therein. Such fabrics may be woven, braided, knitted, felted or constructed by any other

method known to the art and may comprise natural or synthetic fibers, or blends of thereof. It is

also important that such fabrics are also capable of withstanding the temperatures to which they will be exposed during the heating step and, if a preheating step is also used, to such preheating. For these and other reasons, it is believed that for most applications the fabric will comprise

inorganic materials, preferably fiberglass.

It is known to construct fiberglass sleeves in a number of ways including circular knit,

braid and a hybrid of these methods known as knit braid. While the particular method of construction not of particular importance to the present invention, it is believed that braided

fiberglass sleeves will be used for many applications as it is provided as thin sleeves with enhanced

structural stability less apt than knitted forms to unravel when cut. In those embodiments which

employ fiberglass sleeves, the coating forms a bond with and penetrates at least partially into the glass fiber matrix. While the precise bonding mechanism is not known, in certain embodiments it is believed to involve the creation of a series of hydrogen bonds between polar functionalities

in the coating and in the glass fibers comprising the sleeve. It is believed that the formation of such bonds serves to minimize fraying of the fiberglass at cut ends thereof. It is contemplated that

the fabric substrate will be provided in colored or uncolored form.

The coating compositions which are considered suitable for use in the practice of the

present invention are those compositions which have a relatively high solids content, as least about

40 wt.%, and are capable of adhering to and penetrating at least partially into fabric substrates.

The coatings formed by such compositions may exhibit a wide range of properties and will be

selected in accordance with the requirements of application to which such coated articles will be

put. For example, in applications in which a flexible, abrasion-resistant sleeving is desirable, the

coating composition will preferably comprise a combination of at least one abrasion-resistant resin, preferably a thermosetting resin, and an elastomer, and will be capable of being cured into

a coating which exhibits abrasion-resistance of at least about 10,000 cycles, preferably at least

about 20,000 cycles, and even more preferably at least about 35,000 cycles before failure as measured by test method ARP-1536-A and, when applied to a flexible substrate, is able to withstand at least about a 50%, and preferably at least about 70% dimensional compression of the

substrate without permanent deformation or crazing. The term "abrasion-resistant resin" means a resin which itself possesses abrasion-resistant properties or a resin which can be converted into

a material which has abrasion-resistant properties. Abrasion-resistant resins which are considered suitable for use in the practice of the present invention are those resins which, when combined

with an elastomer, are capable of being applied to a fabric substrate and cured into a coating

which exhibits abrasion-resistance appropriate to the application in which it will be used.

Examples of such resins are polyurethanes and fluorocarbon polymers. Thermosetting resins are preferred for various reasons including their ability to impart significant abrasion-resistance upon being cured and to form bonds between the coating and the

substrate. Coatings formed therefrom also exhibit fray resistance at cut ends when used in applications involving fibrous substrates. While most thermosetting resins will cure on their own

or upon the application of heat or selected wavelengths of electromagnetic radiation such as UN

radiation, certain embodiments of the present invention include a cross-linking agent to promote

curing and shorten the time required to effect such curing. Such agents are used to promote the

cure of curable resins and decrease cure time. In such embodiments, the thermosetting resin is

combined with a sufficient amount of a cross-linking agent to promote cross-linking upon heating

or the application of UV radiation. Various cross-linking agents are known, including, for

example, peroxides, polymeric melamines and isocyanates. It is believed that for many

applications, the cross-linking agent will comprise benzophenone and its derivatives or a methylolated melamine, preferably hexamethoxymethylmelamine (HMMM) which is sold under

the trademark Cymel^® 303 by Cytec Industries, Inc. of West Patterson, New Jersey.

The amount of cross-linking agent to be used will vary according to the degree of cure desired and the number and nature of the functionalities of the thermosetting resin at which cross- linking reactions can occur. For most applications, the amount of cross-linking agent will be

selected consistent with effecting a sufficient cure to bring the coating formed therefrom within the scope of the invention as herein described. It is believed that in many applications the cross-

linking agent will comprise about 1 to about 5 wt.%, preferably about 1.5 to about 3 wt.% of the composition.

In those embodiments in which two different coating compositions are applied to the fabric substrate, the coating compositions which are considered suitable for use as the base coat are

those heat-cured coating compositions which are capable of adhering to and penetrating at least

partially into fabric substrate on which they are applied and of forming a bond with a UV-curable

coating composition applied to the coated fabric substrate upon the subsequent UV curing thereof. While this may be accomplished in any of a variety of ways, all of which are considered within the scope of this invention, it is preferred that the heat-cured coating composition of such

embodiments be formulated to possess functionalities which are capable of forming bonds with

the UV-curable coating composition upon the application of UV radiation.

In those embodiments in which a colored article is desired and the fabric substrate is

provided in uncolored form, colorants may be included in the heat-cured coating compositions.

As set forth above, colorants may be desirable not only for aesthetic reasons, but also as a means

of distinguishing between various grades and sizes of coated articles. Examples of colorants

which may be used in the practice of the present invention include pigments, dyes and the like.

In those embodiments in which pigments are used, it is believed that the most widely used

pigments will be carbon black and metal oxides, for example, ferric oxide, titanium dioxide and

the like. A particularly preferred pigment is carbon black sold under the trademark Harshaw W-

7012 by Engelhard Corporation. In those embodiments in which pigments are used, the pigment will generally comprise about 2 to about 10 wt.% of the coating composition, preferably about 4 wt.%. In certain preferred embodiments, the coating compositions comprise an aqueous

dispersion of about 42 to about 52 wt.% abrasion-resistant resin, about 42 to about 52 wt.%

elastomer, about 1.5 to about 3 wt.% cross-linking agent, and, optionally, about 2 to about 10

wt.% pigment. In those embodiments in which two different coating compositions are applied, it is important that if colorants are used they are provided as part of the fabric substrate to be coated or included in the heat-cured coating composition so that the colorants do not interfere

with the UV curing process.

Higher degrees of abrasion-resistance may be realized by the addition of polyolefin

powder, preferably high-density, surface-activated polyolefin powder, to the coating compositions applied to the fabric substrate. As used herein, a high-density polyolefin powder refers to a

polyolefin powder which has a density of at least about 0.96 grams per cubic centimeter. For most applications, the polyolefin powders used in coating compositions applied to the fabric

substrate will be those polyolefin powders which are capable of forming coatings which exhibit

abrasion-resistance of at least about 30,000 cycles before failure as measured by test method

ARP-1536-A and, when applied to a flexible substrate, are able to withstand at least about a 50%

dimensional compression of the substrate without permanent deformation or crazing. Particularly

preferred polyolefin powders are high-density, surface-activated polyethylene (HDPE) and

polytetrafluoroethylene (PTFE). Species of such powders are known and are available

commercially.

Surface activation of the polyolefin powder, whether achieved by means of physical or

chemical treatment, can be important in those embodiments of the present invention which utilize

coating compositions comprising dispersions of solids in an aqueous medium. The activated

surface of the polyolefin powder disperses more readily throughout the coating composition providing a more homogenous mixture and a more even distribution in the coating formed therefrom. In those embodiments of the present invention in which polyolefin powders are used,

the amount of polyolefin used will vary according to, among other things, the degree of additional abrasion-resistance desired. In most applications, the polyolefin powder component will comprise

about 1 to about 10 wt.% of the composition, preferably about 3 to about 5 wt.%.

Examples of polyolefin powders that can be used are those having an average particle size of about 10 to about 35 microns, preferably from about 18 to about 25 microns, and even more

preferably, about 18 microns. Because the coatings formed by the compositions of the present invention form a film on the surface of the substrate to which they are applied, the particle size

of the polyolefin powder affects the surface profile of the coated article. More particularly, as the particle size of the polyolefin powder is increased, the coatings containing such powders are

generally rougher in both appearance and feel, and exhibit relatively higher coefficients of friction. For application in which a low coefficient of friction is important, the use of polyolefin powders

having relatively smaller particle sizes permits the formation of smooth coatings having a low

coefficients of friction.

In certain preferred embodiments, the coating compositions comprise an aqueous

dispersion of about 42 to about 52 wt.% thermosetting abrasion-resistant resin, about 42 to about

52 wt.% elastomer, about 1.5 to about 3 wt.% cross-linking agent, and, optionally, about 2 to

about 10 wt.% pigment. In those embodiments in which polyolefin powder is also present, such

coating compositions preferably comprise about 3 to about 5 wt.% polyolefin powder. In those

embodiments of the present invention in which the formation of abrasion-resistant coatings is

important, the coating compositions comprise an aqueous dispersion of about 44 wt.% of a

polyether-based m-tetramethyl xylylene diisocyanate (TMXDI) polyurethane sold under the trade

name LG86-OA by Lyons Coatings, Inc. of Franklin, Massachusetts having a solids content of at least about 50%, about 44 wt.% of a saturated acrylic terpolymer sold under the trademark HyStretch™ Latex V-43 by The B.F. Goodrich Co. of Cleveland, Ohio having a solids content of at least about 50%, about 2.5 wt.% hexamethyoxymethylmelamine, about 4 wt.% carbon black and, optionally about 5 wt.% surface-activated high-density polyethylene powder having an average particle size of about 18 microns and a molecular weight of about 100,000.

In addition to exhibiting a combination of abrasion-resistance and flexibility to the extent

set forth above, certain preferred coatings formed from certain of the coating compositions

suitable for use in the present invention demonstrate superior resilience. Resilience is a measure of the ability of a material to return to its original shape after an applied force is released. A

complete return to the original shape would be considered 100% resilience. When certain preferred coating compositions are applied to materials which are themselves flexible and which

are deformed from their original shape, such as by compression, the resilience of the coatings formed thereon tend to return the material to its original shape after the applied force is released.

Accordingly, coatings formed from such compositions demonstrate resilience close to or at 100%. In those embodiments which employ two different coating compositions, the UV-curable

coating compositions which are considered suitable for use in the practice of the present invention

are those compositions which are capable of adhering to fabric substrates which have been coated

with a heat-cured coating and of forming a bond therewith upon curing. The coatings formed by

such compositions may exhibit a wide range of properties and will be selected in accordance with

the requirements of application to which such coated articles will be put. Preferably, the UV-

curable coating compositions will comprise resins which have vinyl or acrylate functionalies.

Examples of such resins are acrylic urethane elastomers such as Ebecryl 923 manufactured by

Radcure, Inc. It is important to the present invention that the UV-curable coating composition

is provided in a colorless form so that the absorption of UV radiation by the coating composition can occur without competition from such colorants. As a result, the problems associated with

curing colored coating compositions by means of UV radiation may be avoided.

UV-curable resins will often require the use of photo-initiators to initiate and promote

curing and shorten the time required to effect such curing. In embodiments in which the use of a photoinitiator is desired, the UV-curable resin is combined with a sufficient quantity of a

photoinitiator to promote cross-linking upon exposure to a source of UV radiation. Various photoinitiators are known, including, for example, benzoin, benzoin ethers such as benzoin

isopropyl ether, benzil ketals such as benzil dimethyl ketal (BDMK), α-hydroxy-acetophenones such as 2-hydroxy-2-methylphenyl propanone (HMPP) and hydroxycyclohexyl phenyl ketone

(HCPK), dialkoxyacetophenones such as 2,2-diethoxyacetophenone, α-amino acetophenones such

as 2-methyl-l-[4-(methylthio)phenyl]-2-mo holino propanone (MMMP) and 2-benzyl-2-N,N-

dimethylamino-l-(4-morpholinophenyl)butanone (BDMB), phosphine oxides, benzophenone, diphenoxy benzophenone, 4,4'-N,N-dimethylamino benzophenone, thioxanone,

isopropylthioxanone, chlorothioxanone, camphorquinone, bisimidazole, aryldiazonium salts,

arylsulfonium salts, aryliodonium salts, ferrocenium salts, phenylphosphonium benzophenone salts such as p,p-bis[(triphenylphosphono)methyl] benzophenone salt, aryl t-butyl peresters and

titanocene complexes. While all of the above photoinitiators are considered within the scope of the present invention, it is believed that for many applications, the preferred photoinitiator will

comprise benzophenone.

The amount of photoinitiator to be used will vary according to the degree of cure desired

and the number and nature of the functionalities of the UV-curable resin at which cross-linking

reactions can occur. For most applications, the amount of photoinitiator will be selected

consistent with effecting a sufficient cure to bring the coating formed therefrom within the scope

of the invention as herein described. The dual-layered coating provided by the method of the present invention provides

enhanced dielectric properties to the substrate fabric on which such coating is applied. More specifically, in certain preferred embodiments, the dual-layer coated article of the present

invention, when in the form of a sleeve over copper wire and bent by 90 degrees, exhibits a minimum average dielectric breakdown of about 7,000 volts and about 3,500 volts after a period

of sixty days at 190°C. Moreover, because of the combination of colored thermosetting coatings and colorless UV-cured coatings, such dual-layered coatings are capable of displaying a variety

of strong colors without sacrificing the advantages associated with UV curing.

The present invention will be better understood by reference to the following detailed

descriptions of specific embodiments when considered in combination with Figs. 1 and 2 which show schematic diagrams of apparatus for carrying out two embodiments of the method of

coating articles in accordance with the present invention.

With reference to Fig. 1, an indefinite length of braided fiberglass sleeve 10 (fabric

substrate) is supplied continuously from a supply source 12, such as a hopper, and guided around

rollers 14 and 16. The fiberglass sleeve 10 passes through a sizing die 18 before being guided into

an annealing oven 20 where the fiberglass sleeve 10 is preheated to remove organic starches and

binders, to heat set the inside diameter of the fiberglass sleeve, and to relieve stress imparted to

the fibers comprising such sleeves during their formation. After traveling through the annealing

oven 20, the fiberglass sleeve 10 is guided around a roller 22, down into a dip pot 24 and around

roller 26. In this manner, the fiberglass sleeve 10 is drawn through coating composition 28

contained within dip pot 24 to accomplish the coating composition application step.

Once the fiberglass sleeve 10 has been coated in coating composition 28, it travels through

a set of pinch rollers 30 which apply pressure to the coated fiberglass sleeve 10 whereby a portion

of the coating composition 28 penetrates into the fiberglass sleeve 10. The fiberglass sleeve 10 advances through the sizing die 32 to accomplish the shaping step before entering curing oven 34,

which has three compressed air outlets 35 arranged in series, where the coating composition 28

is cured on the fiberglass sleeve 10. The three compressed air outlets 35 direct compressed air

provided from a compressor unit (not shown) into and through the curing oven 34 in order to evacuate therefrom water vapor evolving from the cross-linking reaction. After traveling through

curing oven 34, the fiberglass sleeve 10 is guided around a roller 36 and through cooling tube 38

which is positioned to allow air from blower 40 to pass therethrough. The coated fiberglass

sleeve travels through powered puller rollers 42 and collected onto take-up reel 44.

Fig. 2 shows a schematic diagram of an embodiment of the present invention in which a

dual-layered coated article is formed. As in Fig. 1, an indefinite length of braided fiberglass sleeve

10 (fabric substrate) is supplied continuously from a supply source 12, guided around rollers 14

and 16, and a first coating composition 28 is applied and cured in the same manner as shown in

Fig. 1. Once the fiberglass sleeve has passed through cooling tube 38, the fiberglass sleeve 10 is

guided into a second dip pot 50 and around roller 52. In this manner, the fiberglass sleeve 10 is

drawn through the UV-curable coating composition 54 contained within dip pot 50 to accomplish

the second coating composition application step.

Once the fiberglass sleeve 10 onto which the first coating composition 28 has been cured

is coated in the UN-curable coating composition 54, it advances through a sizing die 56 which

removes excess coating composition and past a series of UV lamps (not shown) positioned within

housing 58 which effect curing. After advancing past the UV lamps, the fiberglass is guided

around roller 60 through the powered puller rolls 62 and collected onto take-up reel 64.

EXAMPLES The following examples are illustrative of the articles produced in accordance with the method of the present invention. Example 1 describes the preparation of a coating composition within the scope of the present invention and the application of the composition to fiberglass

sleeves to form articles within the scope of the present invention.

EXAMPLE 1

Under ambient temperature and pressure conditions, 2.5 gallons of an aqueous dispersion of a polyether-based TMXDI polyurethane sold under the trade name LG86-OA by Lyons Coatings, Inc. of Franklin, Massachusetts, having a solids content of about 50%, were charged

to a 5 gallon mixing vessel. Under constant gentle stirring, 2.5 gallons of an aqueous dispersion

of a saturated acrylic terpolymer sold under the trademark HyStretch™ Latex V-43 by The B.F.

Goodrich Co. of Cleveland, Ohio, having a solids content of about 50.5%, were added. This mixture was homogenized by continuous gentle stirring for about one hour. Five hundred grams of cross-linking agent, hexamethyoxymethylmelamine (HMMM), sold under the trademark

CYMEL^® 303 by Cytec, Inc., were added, and the mixture was homogenized by continuous

gentle stirring for 20 to 30 minutes. Eight hundred grams of carbon black, sold under the

trademark Harshaw W-7012 by Engelhard Corporation were added and the mixture was

homogenized by continuous gentle stirring for 20 to 30 minutes.

The coating composition was applied to a continuous length of braided fiberglass sleeve having an inside diameter of 0.276 in. and a wall thickness of about 13 mils by passing the

fiberglass sleeve through a dip pot containing the coating composition. Pressure was then applied

to the coated fiberglass sleeve by means of a set of pinch rollers. The coating composition was

cured in a curing oven set at 750°F for a period of about 45 seconds. The coated fiberglass sleeve

was then cooled by means of a blower, and collected on a spool or take-up reel. EXAMPLE 2

A coating composition was made in accordance with Example 1. To the coating composition was added 1 kilogram of surface-activated, high-density polyethylene powder, sold

under the trademark VISTAMER^® HD by Composite Particles, Inc., having an average particle size of about 18 microns and a molecular weight of about 100,000.

The coating composition of Example 2 was applied to and cured on a continuous length of the same size braided fiberglass sleeving used in Example 1 in accordance with the procedures

of Example 1.

The abrasion-resistance of four samples of each of the coated articles of the examples were tested in accordance with test method ARP-1536-A. This method was conducted at ambient

room temperatures and involved the application of a repetitive abrasive force to the material being tested until wear-through. More specifically, this test method requires a stainless steel mandrel

to be inserted into the coated fiberglass sleeving and involves immobilizing both the mandrel and

sleeving. The fiberglass sleeving was then subjected to repetitive stress by an abrasive element

comprising a 0.5 inch diameter precision ground drill rod having a Rockwell "C" hardness of 60-

64 and a surface finish roughness average of 16 μin. The abrasive element was oriented

perpendicular to the long axis of the sleeving and placed under a load of 2.5 pounds. The abrasive

force was applied at a rate of 200 ± 10 cycles per minute through a total stroke of 3 inches

moving longitudinally along the sleeving. The stainless steel mandrel and the abrasive element

were connected to an appropriate voltage source in series with a monitor-indicator to stop the test

when the abrasive element wore through the sleeving.

Four samples of the coated fiberglass sleeves of Examples 1 and 2 were tested for

abrasion-resistance in accordance with the test method specified above. The number of cycles to

wear-through for each of these coated fiberglass sleeves are set forth in Table 1 below. TABLE 1

Ex. 1 Sleeving A B C D

29,651 29,894 20,219 20,377

Ex. 2 Sleeving E F G H

38,627 42,812 37,062 43,478

The coatings of the coated fiberglass sleeves of Examples 1 and 2, as well as other

preferred coatings of the present invention applied to fibrous substrates, have the additional property of minimizing fray at cut ends thereof. Such coatings are further able to be used in environments having a continuous operating temperatures of up to about 180°C and for short durations in environments having temperatures of up to about 200 °C. This advantageous

combination of properties found in such coatings, together with the properties set forth above, makes such coated sleeves particularly well adapted for articles used in connection with carbon

brush leads, sensor elements, thermocouple wires and oxygen sensor assemblies in automotive

emissions monitoring systems.

COMPARATIVE EXAMPLES 1 AND 2

The following comparative examples are illustrative of coating compositions and coated

articles of the prior art. Comparative Examples 1 and 2 describe certain prior art coating

compositions applied to fiberglass sleeves and the abrasion characteristics thereof.

Two samples of fiberglass sleeving of the size used in Examples 1 and 2 were each coated

with a prior art coating composition in accordance with prior art methods. One prior art coating

composition is acrylic-based and the other is a silicone rubber composition. The abrasion- resistance of the two coated fiberglass sleeves were then tested in accordance with the test

method set forth above. The number of cycles to wear-through for each of the coated fiberglass

sleeves is set forth in Table 2 below.

TABLE 2 Ex. C-l Sleeving 2,800 Cycles (approx.)

Ex. C-2 Sleeving 2,500 Cycles (approx.)

Comparisons of the performances of coated fiberglass sleeves of the present invention, as

shown in Table 1, with the acrylic and silicone rubber coated fiberglass sleeves of the prior art, shown in Table 2, demonstrate the marked superiority in abrasion-resistance of the coated fiberglass sleeves of the present invention. Under the testing protocol described, the coated fiberglass sleeves of the present invention demonstrated from about 9 to over 16 times the

abrasion-resistance of the coated fiberglass sleeves of the prior art.

The flexibility and compressive properties of coated sleeves of the present invention and

of the prior art were also evaluated. Flexibility was tested in accordance with a protocol which involves placing a ten-inch length of coated fiberglass sleeve onto a steel mandrel. The sleeve was

then compressed axially by hand along the length of the mandrel to its limit of compressibility.

The length of the compressed sleeving was then measured to determine the percent compression.

(A sleeve which can be compressed to half its original length would have a 50% compression

whereas a product capable of being compressed to 90% of its original length would have a 10%

compression.) The compressive load was then released and the length of the sleeve was measured

after one minute to determine resilience.

Samples of the coated fiberglass sleeves of Examples 1 and 2 and Comparative Examples

1 and 2 were tested for flexibility in accordance with the test method specified above. The percent of compression and resilience for the coated fiberglass sleeves are set forth in Table 3

below.

TABLE 3

Coated Sleeving % Compression Resilience (%)

Example 1 70% 100%

Example 2 70% 100%

Example C-l 60% 80%

Example C-2 60% 100%

Comparisons of the performances of the coated fiberglass sleeves of the present invention with those coated fiberglass sleeves of prior art demonstrate the superiority in flexibility of the coated

fiberglass sleeves of the present invention. Under the testing protocol described, the coated fiberglass sleeves of the present invention were capable of about 10 percent more compression

and up to about 20 percent greater resilience.

Claims

CLAIMSWe claim:

1. A method of coating a fabric substrate comprising the steps of:

applying a relatively high solids coating composition to the fabric substrate; applying pressure to the coated fabric substrate whereby a portion of the coating

composition penetrates at least partially into the fabric substrate; and curing the coated fabric substrate.

2. The method of claim 1 wherein the fabric substrate comprises fiberglass.

3. The method of claim 1 wherein the fabric substrate is provided in a tubular form.

4. The method of claim 1 wherein the fabric substrate comprises a continuous tubular length of fiberglass.

5. The method of claim 1 wherein the coating composition is cured into a coating

capable of being axially compressed at least 50% without permanent deformation and of

withstanding at least about 10,000 cycles before failure as measured by test method ARP- 1536-A.

6. The method of claim 1 wherein the coating composition is cured into a coating

capable of being compressed at least 70% without permanent deformation or crazing and of

withstanding at least about 35,000 cycles before failure as measured by test method ARP- 1536-A.

7. The method of claim 1 wherein the application of pressure step in accomplished by means of a set of pinch rollers.

8. The method of claim 3 further comprising the step of reshaping the fabric into a

substantially tubular form after the application of pressure step.

9. The method of claim 8 wherein the reshaping step is accomplished by a die.

10. The method of claim 1 wherein the curing step comprises exposing the fabric substrate to a temperature of between about 500°F to about 1200°F for a period of about 5 to about 90 seconds.

11. The method of claim 1 wherein the curing step comprises exposing the fabric

substrate to a temperature of between about 700 °F to about 1000°F for a period of about 5 to about 30 seconds.

12. The method of claim 1 further comprising a preheating step wherein the fabric

substrate is exposed to a temperature of between about 700°F to about 1600°F for a period of

about 5 to about 60 seconds prior to the application of the coating composition.

13. The method of claim 12 wherein the preheating step comprises exposing the fabric

to a temperature of between about 1200°F to about 1400°F for a period of about 5 to about 30

seconds.

14. A method of coating a continuous tubular length of fiberglass comprising the steps of:

preheating the fiberglass for a period of about 5 to about 60 seconds by exposing the fabric substrate to a temperature of between about 700°F to about 1600°F; applying a coating composition to the fiberglass; applying pressure to the coated fiberglass whereby a portion of the coating composition

penetrates at least partially into the fiberglass; reshaping the coated fiberglass to a substantially tubular shape; and curing the coating composition onto the coated fiberglass for a period of about 5 to about

90 seconds by exposing the coated fiberglass to a temperature of between about 500 °F to about 1200°F.

15. The method of claim 14 wherein the curing step comprises exposing the coated

fiberglass to a temperature of between about 700 °F to about 1000°F for a period of about 5 to

about 30 seconds.

16. The method of claim 14 wherein the coating composition is cured into a coating

17. The method of claim 14 wherein the coating composition is cured into a coating

18. A method of coating a fabric substrate comprising the steps of: applying a heat-curable coating composition to the fabric substrate; applying pressure to the coated fabric substrate whereby a portion of the heat-curable coating composition penetrates at least partially into the fabric substrate; heat curing the coated fabric substrate; applying a UV-curable coating composition to the coated fabric substrate; and

curing the UV-curable coating composition on the coated fabric substrate by exposing the

UV-curable coating composition to UV radiation.

19. The method of claim 18 wherein the fabric substrate comprises fiberglass.

20. The method of claim 18 wherein the fabric substrate is provided in a tubular form.

21. The method of claim 18 wherein the fabric substrate comprises a continuous

tubular length of fiberglass.

22. The method of claim 18 wherein the application of pressure step in accomplished

by means of a set of pinch rollers.

23. The method of claim 20 further comprising the step of reshaping the fabric into a

substantially tubular form after the application of pressure step.

24. The method of claim 23 wherein the reshaping step is accomplished by a die.

25. The method of claim 18 wherein the heat curing step comprises exposing the fabric substrate to a temperature of between about 500°F to about 1200°F for a period of about 5 to

about 90 seconds.

26. The method of claim 18 wherein the heat curing step comprises exposing the fabric substrate to a temperature of between about 700°F to about 1000°F for a period of about 5 to

about 30 seconds.

27. The method of claim 18 wherein the UV radiation has a wavelength between about

180 and about 450 nanometers.

28. The method of claim 18 wherein the UV radiation has a wavelength between about 240 and about 380 nanometers.

29. The method of claim 18 further comprising a preheating step wherein the fabric

about 5 to about 60 seconds.

30. The method of claim 18 wherein the preheating step comprises exposing the fabric

substrate to a temperature of between about 1200°F to about 1400°F for a period of about 5 to

about 30 seconds.

31. A method of coating a continuous tubular length of fiberglass comprising the steps

of:

applying a heat-curable coating composition to the fiberglass; applying pressure to the coated fiberglass whereby a portion of the thermosetting coating

composition penetrates at least partially into the fiberglass; heat curing the coated fiberglass;

applying a UV-curable coating composition to the coated fiberglass; and curing the UV-curable coating composition on the coated fiberglass by exposing the UV-

curable coating composition to UV radiation.

32. The method of claim 31 wherein the heat curing step comprises exposing the

coated fiberglass to a temperature of between about 500°F to about 1200°F for a period of about

5 to about 90 seconds.

33. The method of claim 31 wherein the heat curing step comprises exposing the

coated fiberglass to a temperature of about 700 °F to about 1000°F for a period of about 5 to about 30 seconds.

34. The method of claim 31 wherein the UV curing step comprises exposing the UV-

curable coating composition to UV radiation having a wavelength of about 180 to about 450 nanometers.

35. The method of claim 31 wherein the UV curing step comprises exposing the UV-

curable coating composition to UV radiation having a wavelength of about 240 to about 380

nanometers.

36. The method of claim 31 further comprising the step of preheating the fiberglass prior to the application of the heat-curable coating composition.

37. The method of claim 36 wherein the preheating step comprises exposing the

fiberglass to a temperature of between about 700°F to about 1600°F for a period of about 5 to about 60 seconds.

38. The method of claim 36 wherein the preheating step comprises exposing the

fiberglass to a temperature of between about 1200°F to about 1400°F for a period of about 5 to

about 30 seconds.

39. The method of claim 31 further comprising the step of reshaping the fiberglass to a tubular form by means of a die after the pressure application step.

40. A coated article comprising:

a fabric substrate; a heat-curable coating composition applied thereto and cured thereon; and

a UV-curable coating composition applied to the coated fabric substrate and cured thereon

and thereto to form a dual-layered coating

41. The coated article of claim 40 wherein the fabric substrate comprises fiberglass.

42. The coated article of clai 40 wherein the heat-curable coating composition

comprises functionalities capable of forming bonds with a UV-curable coating composition upon

exposure to UV radiation.

43. The coated article of claim 40 wherein the UV-curable coating composition

comprises an acrylic urethane elastomer.

44. The coated article of claim 40 wherein the dual-layered coating is capable of exhibiting a minimum average dielectric breakdown of about 7,000 volts and about 3,500 volts

after a period of sixty days at 190°C