BACKGROUND OF THE INVENTION
Field Of the Invention
[0001] The present invention relates to a process for producing adhesive active polyester
yarn. More particularly, the present invention relates to a process for producing
adhesive active polyester, preferably polyethylene terephthalate, yarn wherein the
yarn is coated with an aqueous emulsion which contains an epoxy silane, and after
drawing, the yarn is exposed to ultraviolet radiation. The present invention also-relates
to the yarn produced in accordance with the process. The yarn preferably is twisted
into tire cords for the construction of pneumatic passenger tires and results in excellent
adhesion of tire cord to rubber.
DESCRIPTION OF THE PRIOR ART
[0002] Polyester tire cord requires the application of an adhesive layer to obtain bonding
to the rubber. Two types of adhesive systems, a single dip and a double dip adhesive
system, have been developed to meet this need.
[0003] In the double dip system, polyester cords are treated with a first dip which is a
dispersion of a phenol-blocked methylene bisphenylene diisocyanate, an epoxy resin,
wetting agents and water. The treated cord is cured, then treated with a second dip
of resorcinol-formaldehyde-latex and cured again.
[0004] In the single dip system, the adhesive layer is applied to the polyester yarn in
an overfinish subsequent to drawing of the yarn. The polyester yarn is plied into
cords which are treated with a resorcinol-formaldehyde latex dip and cured. The need
for the blocked diisocyanate dip in cord processing is eliminated by this system.
Low carboxyl polyester yarn treated with this system has very good ammonolytic and
hydrolytic stability, but has poor adhesion to rubber when made into tire cord. Further,
while regular carboxyl polyester yarn shows acceptable adhesion to rubber under normal
curing temperatures, a reduction of the curing temperatures has been found to adversely
affect adhesion to rubber.
[0005] The present invention significantly improves yarn to rubber adhesion of polyester
tire cords treated with the single dip system for (a) low carboxyl polyester yarn
wherein'normal curing temperatures are utilized, and (b) regular carboxyl polyeter
yarn wherein reduced curing temperatures are utilized.
[0006] The closest prior art is believed to be U.S. Patents 3,642,518 to Miki et al., 3,672,977
to Dardoufas, 3,730,892 to Marshall et al., and 4,054,634 to Marshall et al., and
British Patent Specification 1,228,173 to Jervis et al.
SUMMARY OF THE INVENTION
[0007] The present invention provides an improvement in a process for the production of
polyester yarn involving spinning and drawing steps. The present invention further
provides polyester yarn treated in accordance with the process.
[0008] The improvement comprises: exposing the yarn subsequent to the drawing step to ultraviolet
radiation; and treating the yarn with a finish composition which comprises water and
a silane having the structural formula

wherein n = 2 to 5. The step of exposing the yarn to ultraviolet radiation may occur
either prior to or subsequent to the step of treating the yarn with the finish composition.
[0009] The ultraviolet radiation preferably has wave lengths between 200 and 400 nanometers
and a peak wave length of about 253 nanometers. The time period for exposure of the
yarn to ultraviolet radiation is at least about 0.3 second, preferably about 0.3 to
7 seconds.
[0010] The finish composition may comprise about 50 to 98 weight percent of water and about
2 to 50 weight percent of the silane. When these form the major finish composition
ingredients and the finish composition is to be applied by means of a conventional
lube roll, it is preferred that a small amount, for example 0.1 weight percent, of
a nonionic wetting agent be incorporated in order to wet the lube roll; Triton X-100,
Rohm & Haas Company's tradename for polyoxyethylene 9-10 octylphenol, is satisfactory.
[0011] It is preferred that the finish composition be an overfinish composition which comprises
an oil-in-water emulsion wherein the non-aqueous portion comprises about 50 to 70
weight percent of hexadecyl stearate, about 3 to 9 weight percent of glycerol monooleate,
about 2 to 8 weight percent of decaglycerol tetraoleate, about 5 to 12 weight percent
of ethoxylated tall oil fatty acid, about 5 to 15 weight percent of sulfonated glycerol
trioleate, about 1 to 10 weight percent of ethoxylated alkyl amine, and about 2 to
45 weight percent of the silane. The preferred silane is gamma-glycidoxypropyltrimethoxysilane.
The yarn is preferably treated with a sufficient amount of the overfinish composition
that (a) about 0.4 to 1.0 weight percent based on the weight of the yarn of the non-aqueous
portion of the overfinish composition is added, and (b) about 0.05 to 0.2 weight percent
based on the weight of the yarn of the silane is added. Alternatively, the overfinish
composition can comprise about 7 to 50 weight percent of the silane, about 5 to 20
weight percent of dimethyl polysiloxane emulsion, and the balance water.
[0012] The present invention also provides, in a process for the production of polyester
yarn involving spinning and drawing steps, the improvement which comprises exposing
the yarn subsequent to the drawing step for a time period of at least about 0.3 second
to ultraviolet radiation having a wave length between about 200 and 400 nanometers;
and treating the yarn with an overfinish composition comprising about 60 to 90 weight
percent of water and about 10 to 40 weight percent of an oil portion, the oil portion
comprising about 50 to 70 weight percent of hexadecyl stearate, about 3 to 9 weight
percent of glycerol monooleate, about 2 to 8 weight percent of decaglycerol tetraoleate,
about 5 to 12 weight percent of ethoxylated tall oil fatty acid, about 5 to 15 weight
percent of sulfonated glycerol trioleate, about 1 to 10 weight percent of ethoxylated
alkyl amine, and about 2 to 45 weight percent of a silane having the structural formula

wherein n = 2 to 5.
[0013] Low carboxyl polyester yarn is defined as having about 8 to 18 carboxyl end groups
(meq./kg.). Regular carboxyl polyester yarn is defined as having about 19 to 30 carboxyl
end groups (meq./kg.).
[0014] The strip adhesion test utilized in illustrating the present invention is defined
in U.S. Patent 3,940,544 to Marshall et al'., hereby incorporated by reference.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0015] In order to demonstrate the invention, the following examples are given. They are
provided for illustrative purposes only and are not to be construed as limiting the
scope of the invention, which is defined by the appended claims. Specifically, it
is believed that the finish composition can be applied either as a spin finish during
spinning or as an overfinish subsequent to drawing of the yarn. Further, it is believed
that there are other spin finishes which would perform as satisfactorily as the one
detailed (see Table I). It is also believed that there are other compatible non-aqueous
components which would perform as satisfactorily in the overfinish composition as
the ones detailed as additional to the silane. In these examples, parts and percentages
are by weight unless specified otherwise.
[0016] The yarns of this invention can be processed by any spin draw process or spinning
and separately drawing process available to the art and the patent and technical literature,
using any suitable polyester.
[0017] The preferred polyesters are the linear terephthalate polyesters, i.e., polyesters
of a glycol containing from 2 to 20 carbon atoms and a dicarboxylic acid component
containing at least about 75 percent terephthalic acid. The remainder, if any, of
the dicarboxylic acid component may be any suitable dicarboxylic acid such as sebacic
acid, adipic acid, isophthalic acid, sulfonyl-4,4'-dibenzoic acid, or 2,8-di-benzofuran-dicarboxylic
acid. The glycol may contain more than two carbon atoms in the chain, e.g., diethylene
glycol, butylene glycol, decamethylene glycol, and bis-1,4-(hydroxymethyl)cyclohexane.
Examples of linear terephthalate polyesters which may be employed include poly(ethylene
terephthalate), poly(butylene terephthalate), poly (ethylene terephthalate/5-chloroisophthalate)
(85/15), poly(ethylene terephthalate/5-Isodium sulfo]isophthalate) (97/3), poly(cyclohexane-l,4-dimethylene
terephthalate), and poly(cyclohexane-l,4-dimethylene terephthalate/ hexahydroterephthalate)
(75/25).
EXAMPLE 1 (COMPARATIVE)
[0018] For comparative testing, a polyethylene terephthalate yarn having 11±1 carboxyl end
groups was prepared substantially in accordance with one procedure described in U.S.
Patent 3,672,977 to Dardoufas, hereby incorporated by reference, i.e., a 1000 denier
192 filament yarn was prepared comprised of polyethylene terephthalate filaments treated
with about 0.45 percent based on the weight of the yarn of a liquid spin finish identified
as spin finish A in Table I. Drawing performance of the yarn was excellent. Finish
oil on the fiber was about 0.15 to 0.25 percent.
[0019] The yarn was passed through a chamber enclosing two 4-tube layers with off-set centers
of high intensity lamps of the germicidal type having wave length of about 200 to
300 nanometers, with peak wave length at 253 nanometers. The lamps were approximately
83.8 centimeters (33 inches) in length and can be obtained from the Ultradynamics
Corporation, Santa Monica, California. The yarn made six passes through the chamber,
each pass being centered at a distance of about 1 centimeter between three of the
tubes so that high intensity ultraviolet radiation fell on all sides of the yarn.
The lamps were found to provide maximum efficiency at a temperature near 37.8°C. (.100°F.).
The yarn was exposed to the ultraviolet radiation for a total of 7 seconds.
[0020] To this yarn a secondary finish, or overfinish, identified as overfinish A of Table
II, was applied at a 3 percent total wet pickup to achieve a total oil on yarn level
of about 1,0 percent. The yarn was then twisted into 3-ply cords having 9x9 twists
per inch. Each cord was treated with a conventional non-ammoniated resorcinol-formaldehyde-latex
dip comprising vinyl pyrridine latex, resorcinol, formaldehyde, sodium hydroxide and
water, at about 4.
5 percent total solids pickup based on the weight of the cord. The cords were then
cured at treating condition 3 of Table III. The treated cords were subjected to the
strip adhesion test, results of which are presented in Table IV.
EXAMPLE 2 -(COMPARATIVE)
[0021] The procedure of Example 1 was repeated with the following changes: The yarn was
not exposed to ultraviolet radiation; and the yarn was overfinished at room temperature
with overfinish B of Table II. Results of adhesion testing are presented in Table
IV.
EXAMPLES 3-5
[0022] The procedure of Example 1 was repeated in each of Examples 3 through 5 with the
following changes: The yarn was exposed to the ultraviolet radiation for a period
of 0.3, 3 and 7 seconds, respectively, in Examples 3 through 5; and the yarn was overfinished
at room temperature with overfinish B of Table II. Results of adhesion testing are
presented in Table IV.
EXAMPLES 6 and 7
[0023] The procedure of Example 1 was repeated with the following changes: The yarn was
not exposed to ultraviolet radiation in Example 6 while in Example 7, the yarn was
exposed to ultraviolet radiation for a period of three seconds; and in both examples,
the yarn was overfinished at room temperatures with overfinish C of Table II. Results
of adhesion testing are presented in Table IV.
EXAMPLES 8-13
[0024] Polyethylene terephthalate yarn having 24
±1 carboxyl end groups was prepared in accordance with the procedure of Example 1 in
Examples 8 through 13, utilizing the spin finishes, overfinishes, ultraviolet treatment
and treating conditions specified in Table IV. Results of adhesion testing are also
presented in Table IV.
EXAMPLES 14-19
CONCLUSIONS
[0026] A comparison of Examples 1 through 7 shows the critical importance to adhesion for
low carboxyl polyethylene terephthalate yarn of both exposing the yarn to ultraviolet
radiation and treating the yarn with an aqueous finish composition containing an epoxy
silane as previously described. The adhesion ratings were especially excellent for
Example 5.
[0027] A comparison of Examples 8 through 19 shows the critical importance to adhesion for
regular carboxyl polyethylene terephthalate yarn of both exposing the yarn to ultraviolet
radiation and treating the yarn with an aqueous finish composition containing an epoxy
silane as previously described. In Examples 9, 11 and 13, the polyethylene terephthalate
yarn was exposed to ultraviolet radiation prior to treatment with an aqueous overfinish
composition containing the epoxy silane, while in Examples 15, 16, 18 and 19, the
polyethylene terephthalate yarn was treated with an aqueous overfinish composition
containing the epoxy silane prior to exposure to ultraviolet radiation. The adhesion
ratings were good in both instances. Further, it can be seen that substantially lower
curing temperatures (treating conditions of Table III) can be utilized with the regular
carboxyl yarn; this results in both energy savings and reduced plant emissions.
[0028] Alternative sources of ultraviolet radiation can be used. For example, medium wave
length (280 to 400 nanometers) fluorescent sun lamp Model FS-40 available from Westinghouse
Corporation is suitable. The intensity of ultraviolet radiation is expressed in micro-watts
per square centimeter at a given distance. The total ultraviolet energy emitted from
all sides of the ultraviolet lamp is expressed in watts. The total exposure is a product
of energy, time and area which is expressed as ultrads (microwatt seconds per square
centimeter), The same number of ultrads can be achieved with a short exposure time
at a high intensity of ultraviolet radiation, or a long exposure at a low intensity
of ultraviolet radiation. Exposures of the polyethylene terephthalate yarn to ultraviolet
radiation for a period of up to 15 minutes showed virtually no loss of yarn breaking
strength and other yarn physical properties, but did show improvement in adhesion
to rubber when treated with the overfinish system as described in this specification.
1. In a process for the production of polyester yarn involving spinning and drawing
steps, the improvement which comprises: exposing the yarn subsequent to the drawing
step to ultraviolet radiation; and treating the yarn with a finish composition which
comprises water and a silane having the structure formula

wherein n = 2 to 5.
2. A polyester yarn produced in accordance with the process of claim 1.
3. The process of claim 1 wherein the step of exposing the yarn to ultraviolet radiation
occurs prior to the step of treating the yarn with the finish composition.
4. The process of claim 1 wherein the step of exposing the yarn to ultraviolet radiation
occurs subsequent to the step of treating the yarn with the finish composition.
5. The process of claim 1 wherein the silane is gamma-glycidoxypropyltrimethoxysilane.
6. The process of claim 1 wherein the finish composition comprises about 50 to 98
weight percent of water and about 2 to 50 weight percent of the silane.
7. The process of claim 1 wherein the finish composition is an overfinish composition
which further comprises a dimethyl polysiloxane emulsion.
8. In a process for the production of polyester yarn involving spinning and drawing
steps, the improvement which comprises:
exposing the yarn subsequent to the drawing step for a time period of at least about
0.3 second to ultraviolet radiation having a wave length between 200 to 400 nanometers;
and
treating the yarn with an overfinish composition comprising about 60 to 90 weight
percent of water and about 10 to 40 weight percent of an oil portion, the oil portion
comprising about 50 to 70 weight percent of hexadecyl stearate, about 3 to 9 weight
percent of glycerol monooleate, about 2 to 8 weight percent of decaglycerol tetraoleate,
about 5 to 12 weight percent of ethoxylated tall oil fatty acid, about 5 to 15 weight
percent of sulfonated glycerol trioleate, about 1 to 10 weight percent of ethoxylated
alkylamine, and about 2 to 45 weight percent of silane having structural formula

wherein n = 2 to 5.
9. The process of claim 8 wherein the silane is gamma-glycidoxypropyltrimethoxysilane.
10. A polyester yarn produced in accordance with the process of claim 8.