Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
1993-08-06
2001-06-05
Dixon, Merrick (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S373000, C428S395000
Reexamination Certificate
active
06242095
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a polyester yarn with good rubber adhesion made of core-sheath fibers with two different types of polyesters and a process for making it.
BACKGROUND OF THE INVENTION
Most rubber items contain textile reinforcing materials as an integral constituent to provide for dimensional stability and to reduce the high elongation of the rubber. Good adhesion of the rubber to the textile material is an indispensable prerequisite for satisfactory function and lengthy life of rubber items that contain textile reinforcing materials, for example motor vehicle tires, V-belts, and conveyor belts. If the adhesion is inadequate, the bond between the elastomer and the fiber material is broken with time, which results in destruction of the textile reinforcement from chafing, or by melting in case of local overheating. Rubber adhesion presents difficulties, particularly with the polyester fibers present as yarn filament, since there are hardly any mechanical anchoring possibilities for the rubber because of their molecular structure, as is the case with cotton fiber yarns, so that special binders are necessary.
While impregnation with resorcinol-formaldehyde resins combined with latices (RFL dip), especially vinyl-pyridine latex, is already sufficient to improve the adhesion of nylon yarns to rubber, special additional measures are necessary for polyester yarns. For them to provide adequate rubber adhesion with a conventional nylon dip (or with adhesive mixtures), the so-called spin-finish types of polyester were developed. To make them, specific adhesion promoters are applied to the polyester fibers immediately after they are spun, simultaneously with the spinning preparation, to improve rubber adhesion; they consist of definite epoxy compounds and amine hardeners, and impregnation is carried out on the cord yarn with an aqueous dispersion of resorcinol-formaldehyde resins and vinylpyridine latex. The drawbacks to applying epoxy compounds and amines consist on the one hand of the contamination of machine parts, and also of the fact that the production rates of polyester yarns are impaired, and furthermore, substantial environmental problems occur.
To avoid the application of adhesion promoters, it is known how to produce two-component yarns whose core consists of polyethylene glycol terephthalate and whose sheath consists of a polyamide (cf., for example, EP 0 398 221 A1), since polyamides by nature show better rubber adhesion than polyesters. However, this presents the problem that the adhesion of the polyester core to the polyamide sheath is inadequate. For this reason, it is necessary to reduce the core/sheath ratio of the fibers for practical application as tire cords in a way that results in insufficient utilization of the good and desirable polyester properties.
A problem underlying this invention was to avoid the procedural step of applying the aforementioned adhesion promoters, and to make available new polyester yarns made of core-sheath fibers with good rubber adhesion, for which there is no longer inadequate adhesion between core and sheath even with very large core/sheath ratios of the fibers.
This problem is solved by the features of the invention.
SUMMARY OF THE INVENTION
Polyester yarns made of core-sheath fibers pursuant to the invention are characterized first by the fact that the core of the core-sheath fibers is comprised of a high-melting fiber-forming polyester. Fundamentally, all high-melting fiber-forming polyesters and copolyesters are suitable for this, such as polyethylene glycol terephthalate, poly(ethylene 2,6-naphthalenedicarboxylate), poly(1,4-dimethylenecyclohexane terephthalate) and their copolymers based on high proportions of homopolyester. In a preferred embodiment, the core of the core-sheath fibers consists at least substantially of polyethylene glycol terephthalate. This means particularly the homopolyester polyethylene glycol terephthalate and its copolyesters that contain at least 90 mole-% ethylene glycol terephthalate units. The remaining dicarboxylic acid and diol components of these copolyesters can be the usual coconstituents for producing extended polyester structures, for example isophthalic acid, p-hydroxybenzoic acid, p,p′-diphenyldicarboxylic acid, all possible naphthalenedicarboxylic acids, hexahydroterephthalic acid, adipic acid, sebacic acid, and glycols such as 1,4-dihydroxymethylcyclohexane, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, and decamethylene glycol, etc.
The polyesters and copolyesters preferred for the core of the core-sheath fibers should have a viscosity as high as possible, i.e., a relative solution viscosity of at least 1.8, preferably from 1.9 to 2.3, measured at 25° C. as a 1 wt. % solution in m-cresol, and a melting point of at least 250° C. The desired high viscosities can be obtained using known procedures, for example condensation in the melt, additional post-condensation in the melt with or without condensation accelerator(s), or post-condensation in the solid state.
The polyester yarns made of core-sheath fibers pursuant to the invention are also characterized by the fact that the sheath of the core-sheath fibers is comprised of a high-melting unsaturated copolyester that has been made, based on the dicarboxylic acid components, with one or more unsaturated dicarboxylic acid coconstituent(s) comprising at least 2 mole-% alkylmaleic acid with an alkyl group having from 1 to 18 carbon atoms and/or alkylenesuccinic acid with an alkylene group having from 1 to 18 carbon atoms and/or their polyester-forming derivatives. In principle, all high-melting fiber-forming polyester and copolyester structures that are used for the core of the core-sheath fibers are suitable for the polyester modification with the unsaturated dicarboxylic acid components, but especially those that contain at least 90 mole-% ethylene glycol terephthalate units. Citraconic acid and itaconic acid and their polyester-forming derivatives are preferred as unsaturated dicarboxylic acid components; they are used in amounts of at least 2 mole-% based on the dicarboxylic acid components.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In a particularly preferred embodiment, the sheath of the core-sheath fibers may consist of an unsaturated copolyester that contains 95 to 98 mole-% ethylene glycol. terephthalate units and has been made with 2 to 5 mole-%, preferably with 3 to 4 mole-% citraconic acid and/or itaconic acid and/or their polyester-forming derivatives, Ethylene glycol is preferably used alone as the glycol component of such unsaturated copolyesters. Especially preferred polyester-forming derivatives of citraconic acid and itaconic acid are citraconic anhydride, dimethyl citraconate, and dimethyl itaconate.
To avoid crosslinking, it may be advantageous when preparing the unsaturated copolyesters to carry out the transesterification and/or polycondensation in the presence of antioxidants. Especially suitable for this are sterically hindered phenols such as di-n-octadecyl (5-t-butyl-4-hydroxy-3-methylbenzyl)malonate (Irganox 420), octadecyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate (Irganox 1076), 1,1-bis(5-t-butyl-4-hydroxy-2-methylphenyl)butane (Irganox 414), tetrakis[methylene(3,5-di-t-butyl-4-hydroxyhydrocinnamate)]methane (Irganox 1010), N,N′-1,6-hexamethylenebis-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionamide (Irganox 1098), 1,3,5-tri(3,5-di-t-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene (Irganox 1330), and tris(2,6-dimethyl-3-hydroxy-4-t-butylbenzyl)-s-triazine-2,4,6(1H,3H,5H)trione (Cyanox 1790).
The above unsaturated dicarboxylic acid components can be cocondensed with the mentioned antioxidants with no problematical increase of viscosity, even in rather large quantities, for example 8 mole-%. In general, however, for polyesters that contain at least 90 mole-% ethylene glycol terephthalate units, 5 mole-% of the unsaturated dicarboxylic acid components based on the total of all dicarboxylic acid components is sufficient. With larger quantities of unsatu
Busscher Leonardus A.G.
Juijn Johannes A.
Akzo Nobel N.V.
Dixon Merrick
Oliff & Berridg,e PLC
LandOfFree
Polyester yarn with good rubber adhesion made of core-sheath... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polyester yarn with good rubber adhesion made of core-sheath..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polyester yarn with good rubber adhesion made of core-sheath... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2481880