EP0582904A2 - Polyester yarn with good adhesion to rubber from core-sheath filaments with two different types of polyesters - Google Patents

Abstract

Core-sheath filaments, as textile reinforcing materials in rubber articles, have a rubber adhesion of from 180 to 260 N/cm<2> if their core comprises a high-melting (co)polyester and their sheath comprises a high-melting unsaturated copolyester which has been prepared, based on the dicarboxylic acid components, with one or more unsaturated dicarboxylic acid cocomponent(s) from at least 2 mol % of alkylmaleic acid containing an alkyl group having 1 to 18 carbon atoms and/or from alkylenesuccinic acid containing an alkylene group having 1 to 18 carbon atoms, and/or polyester-forming derivatives thereof. Their core preferably comprises polyethylene glycol terephthalate and their sheath preferably comprises a copolyester containing from 95 to 98 mol % of ethylene glycol terephthalate units that has been prepared with from 2 to 5 mol % of citraconic acid and/or itaconic acid and/or polyester-forming derivatives thereof.

Description

The present invention relates to a polyester yarn with good rubber adhesion from core-sheath threads with two different types of polyesters and a process for its production.

Most rubber articles contain textile reinforcement materials as an integral part to ensure their 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 perfect functioning and a long service life of the rubber articles that contain textile reinforcement materials, for example motor vehicle tires, V-belts and conveyor belts. If the adhesive strength is insufficient, the bond between the elastomer and the thread material is released over time, which results in destruction of the textile reinforcement by scouring or, in the event of local overheating, by melting. Especially when used as filament yarn In the present polyester fibers, rubber adhesion is difficult because, due to its macromolecular structure, there are hardly any mechanical anchoring possibilities for the rubber, as is the case with cotton fiber yarns, so that special adhesives are required.

While impregnation with resorcinol-formaldehyde resins in combination with latexes (RFL dip), especially vinylpyridine latex, is sufficient for nylon yarns to improve the adhesive strength to rubber, additional special measures are necessary for polyester yarns. So-called spin-finish polyester grades have been developed to ensure adequate rubber adhesion with a conventional nylon dip (or with adhesive mixtures). For their production, specific adhesion promoters for improving the rubber adhesion, which consist of defined epoxy compounds and amine hardeners, are applied to the polyester threads at the same time as the spin finish, and the impregnation with an aqueous dispersion of resorcinol-formaldehyde resins and vinylpyridine latex takes place on cord yarn . The disadvantages of the application of epoxy compounds and one consist in the pollution of the machine parts and also in the fact that the production speeds of the polyester yarns are impaired and not inconsiderable environmental problems arise.

To avoid the application of adhesion promoters, it is known to produce bicomponent yarns whose core consists of polyethylene glycol terephthalate and whose sheath is made of a polyamide (see, for example, EP 0 398 221 A1), since polyamides naturally have better rubber adhesion than polyester. Here, however, one is faced with the problem faced that the adhesion of the polyester core with the polyamide sheath is insufficient. It is therefore necessary to reduce the core / sheath ratio of the threads in practical use for tire cords in such a way that this has the result that the good and desired polyester properties are not sufficiently effective.

The present invention was based on the object of avoiding the process step of applying the abovementioned adhesion promoters and of providing new polyester yarns with good rubber adhesion from core-sheath threads for which there is also insufficient adhesion between the core and sheath even with very large core / sheath Relationships of the threads is no longer present.

This object is achieved with the features specified in the patent claims.

The polyester yarns of core-sheath threads according to the invention are initially characterized in that the core of the core-sheath threads consists of a high-melting thread-forming polyester. In principle, all high-melting thread-forming polyesters and copolyesters, such as polyethylene glycol terephthalate, poly (ethylene-2,6-naphthalenedicarboxylate), poly (1,4-dimethylenecyclohexane terephthalate) and their mixed polyesters based on high homopolyester fractions, are suitable for this. In a preferred embodiment, the core of the core sheath threads consists at least essentially of polyethylene glycol terephthalate. These include in particular the homopolyester polyethylene glycol terephthalate, but also its copolyester, which contain at least 90 mol% of ethylene glycol terephthalate units. The remaining dicarboxylic acid and diol components this copolyester can contain the co-components customary in the production of stretched polyester structures, such as, 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 , Tetramethylene, hexamethylene and decamethylene glycol, etc.

The preferred polyesters and copolyesters for the core of the core-sheath threads should have the highest possible viscosity, i.e. have a relative solution viscosity of at least 1.8, preferably from 1.9 to 2.3, measured at 25 ° C. as a 1% strength by weight solution in the m-cresol, and have a melting point of at least 250 ° C. The desired high viscosity values can be achieved using known methods, e.g. the condensation in the melt, an additional post-condensation in the melt without or with condensation accelerator (s) or the post-condensation in the solid state.

The polyester yarns of core-sheath threads according to the invention are further characterized in that the sheath of the core-sheath threads consists of a high-melting unsaturated copolyester which, based on the dicarboxylic acid components, contains one or more unsaturated dicarboxylic acid co-component (s) at least 2 mol% of alkyl maleic acid with an alkyl group of 1 to 18 carbon atoms and / or alkylene succinic acid of 1 to 18 carbon atoms and / or their polyester-forming derivatives has been prepared. In principle, all high-melting thread-forming agents are suitable for the said polyester modification with the unsaturated dicarboxylic acid components Polyester and copolyester structures that are used for the core of the core-sheath threads, but especially those that contain at least 90 mol% of ethylene glycol terephthalate units. As unsaturated dicarboxylic acid components, citraconic acid and itaconic acid and their polyester-forming derivatives are preferred, which are used in amounts of at least 2 mol%, based on the dicarboxylic acid components.

In a particularly preferred embodiment, the sheath of the core-sheath threads consists of an unsaturated copolyester which contains 95 to 98 mol% of ethylene glycol terephthalate units and 2 to 5 mol%, preferably 3 to 4 mol%, of citraconic acid and / or itaconic acid and / or their polyester-forming derivatives has been produced. Ethylene glycol alone is preferably used as the glycol component of such unsaturated copolyesters. Preferred polyester-forming derivatives of citraconic acid and itaconic acid are, in particular, citraconic anhydride, dimethyl citraconate and dimethyl itaconic acid.

To avoid crosslinking, it may be advantageous in the preparation of the unsaturated copolyesters to carry out the transesterification and / or polycondensation in the presence of antioxidants. Sterically hindered phenols such as (5-tert-butyl-4-hydroxy-3-methyl-benzyl) -malonic acid di-n-octadecyl ester (Irganox 420), octadecyl-3- (3,5-di - tert-butyl-4-hydroxy-phenyl) propionate (Irganox 1076), 1,1-bis (5-tert-butyl-4-hydroxy-2-methyl-phenyl) butane (Irganox 414), Tetrakis [methylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] - methane (Irganox 1010), N, N'-1,6-hexamethylene-bis-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionamide (Irganox 1098), 1,3,5-tri (3,5- di-tert-butyl-4-hydroxybenzyl) -2,4,6-trimethylbenzene (Irganox 1330) and tris (2,6-dimethyl-3-hydroxy-4-tert.butylbenzyl) -s-triazine-2,4 , 6 (1H, 3H, 5H) trione (Cyanox 1790).

With the antioxidants mentioned, the above unsaturated dicarboxylic acid components can also be used in larger amounts, e.g. 8 mol%, are condensed. In general, however, 5 mol% of the unsaturated dicarboxylic acid components, based on the total of all dicarboxylic acid components, are sufficient for copolyesters which contain at least 90 mol% of ethylene glycol terephthalate units. With larger amounts of unsaturated dicarboxylic acids, this type of copolyester would result in a less advantageous melting point drop to less than 245 ° C.

Unsaturated copolyesters, which contain, for example, 96 mol% of ethylene glycol terephthalate units and 4 mol% of ethylene glycol citraconate or 4 mol% of ethylene glycol itaconate units, have a melting point of 248.9 and 246.8 ° C., respectively, so that the required dipping of cord yarns without any temperature change can be easily carried out at 240 ° C. The important freezing temperatures T _g are 79 ° C or 76 ° C in the same order, so they differ only slightly from the freezing temperature of the homopolyester polyethylene glycol terephthalate, which is 80 ° C, which is particularly advantageous for the stretchability of the bicomponent yarns. For other unsaturated types of copolyesters that are not based on essentially ethylene glycol terephthalate units, the appropriate modification amount of alkyl maleic and / or alkylene succinic acids can easily be determined by determining their melting points and freezing temperatures.

The copolyesters preferred for the sheath of the core-sheath filaments generally have a relative solution viscosity of at least 1.5, preferably 1.6 to 2.0, measured at 25 ° C. as a 1% strength by weight solution in m-cresol , and a melting point of at least 245 ° C.

In order to achieve uniformly high core / sheath ratios, the yarns according to the invention are preferably produced from core-sheath threads according to the procedure described in EP 0 398 221 A1. In this procedure, the extruded core component is fed via a first spinneret plate to a second spinneret plate in a plurality of individual streams, with each core component individual stream flowing around the extruded jacket component between the first and second spinneret plates, the two components being spun together, stretched and wound up, and the jacket component is exposed to a flow resistance at least around the area of the individual flows of the core component. A wire mesh is particularly suitable as flow resistance. Although the weight ratio of the different core / shell polymers can be varied within wide limits, the core polymer with the shell polymer is preferably melt spun in a weight ratio of 95: 5 to 80:20.

The core-shell-polymer combinations according to the invention can be spun at the same speeds as the core-shell threads intended for tire cords made of polyethylene glycol terephthalate and polyamide 66 from EP 0 398 221 A1, for example at a speed of 500 m / min or 900 m / min. In the case of the latter spinning speed, the polyester yarn is then in a first drawing stage to about 1: 3 and in one second drawing stage to a total drawing ratio of about 1: 5, while the total drawing ratio in the case of the first-mentioned spinning speed is about 1: 6.

Surprisingly, the core-sheath combinations according to the invention can also be rapidly spun with the spinning speeds of 3000-5000 m / min customary in the rapid spinning of polyester monocomponent yarns. The polyester yarns thus obtained are then drawn to about 1: 1.8 to 1: 1.2 in a first drawing stage and to a total drawing ratio of about 1: 2.4 to 1: 1.6 in a second drawing stage.

Although the tensile strength and elongation at break of the yarns can of course be varied considerably depending on the degree of stretching selected, the polyester yarns thus obtained generally have a tensile strength of 600 to 850 mN / tex, an elongation at break of 10 to 14% and a rubber adhesion of 180 to 260 N. / 2 cm on. While maintaining the usual physical data of polyester yarns intended for tire cords, the surprisingly high values for rubber adhesion make it possible to dispense with the previous use of the specific adhesion promoters described above.

The invention is illustrated by the following examples:

A. Preparation of the Unsaturated Copolyesters

48 kg of dimethyl terephthalate, 40 kg of ethylene glycol and 16.3 g of Mn (CH₃COO) ₂.4 H₂O were introduced into a stirrable 270 l steel reactor. If the dimethyl esters of alkyl-maleic acid (s) and / or alkylene-succinic acid (s) are used as modifying comonomers, these are already added to the transesterification batch, e.g. 1.58 kg dimethyl citraconate or dimethyl itaconic acid ester = 4 mol%. The transesterification was carried out at a gradually increasing temperature to 245-250 ° C. in about 2 h 15 min.

After the transesterification of the components, 17.3 g of carbethoxymethyldiethylphosphonate and 12 g of Sb₂O₃ were added. If alkyl maleic acid (s) and / or alkylene succinic acid (s) or their anhydrides or their anhydrides are used as modifying comonomers, these are also added at this time, e.g. 1.30 kg citraconic acid or itaconic acid = 4 mol% or 1.11 kg citraconic anhydride = 4 mol%. This mixture was then transferred to a stirrable 150 l autoclave. The temperature was raised to about 280 ° C and the pressure was gradually reduced to 1 mbar or lower. The polycondensation was terminated when a relative viscosity of about 1.6, measured at 25 ° C. as a 1% strength by weight solution in m-cresol, was ended. Depending on the temperature and vacuum control and the amount of modifying comonomers, the polycondensation time fluctuated between 2 and 3 hours.

As an antioxidant, 0.5% by weight of Irganox 1330 was added to the reactants at the time of addition of the modifying unsaturated comonomers.

B. Production of polyester yarns from core-sheath threads

The yarns were spun at a core to sheath ratio of 90:10 parts by weight. Its core consisted of a polyethylene glycol terephthalate with a relative viscosity of 2.04, always measured at 25 ° C as a 1% by weight solution in m-cresol. The sheath polymer consisted of the mixed polyesters produced, which are listed in the table and whose relative viscosity was about 1.6.

One extruder each served as the melting and conveying device for the core-shell polymer. The 5-zone temperatures of the extruder for the polyethylene glycol terephthalate as the core polymer were in the descending direction between 310 ° C → 297 ° C. A measuring pump ensured a throughput of about 100 g / min when spinning at a spinning speed of 900 m / min. The throughput for the core polymer was about 126 g / min for the spinning speed of 4000 m / min.

The 5-zone temperatures of the extruder for the respective mixed polyester as jacket polymer were in the descending direction between 302 ° C → 281 ° C. A measuring pump ensured a throughput of approximately 11 g / min when spinning at a spinning speed of 900 m / min. For the spinning speed of 4000 m / min, the throughput for the sheath polymer was 14 g / min.

The core-shell polymers were spun according to the procedure described in EP 0 398 221 A1. A 60 mesh stainless wire mesh was used as flow resistance. The spinneret plate contained 36 nozzles with a diameter of 500 μm, the temperature of the spin pack was kept at 297 ° C. A heating channel with a length of 40 cm and a wall temperature of 310 ° C was mounted directly under the spinneret plate.

The spun bicomponent yarns were consolidated with side air at a temperature of 20 ° C and a speed of 30 cm / min. About 1% by weight of a customary standard preparation which did not contain any adhesion promoters, such as epoxy compounds, isocyanate compounds and the like, was then applied to the polyester yarn, and the yarn was wound up at a speed of 900 m / min or 4000 m / min.

As a comparative example, core-sheath threads were produced from polyethylene glycol terephthalate at a speed of 900 m / min, the core and sheath of which consisted of the same homopolymer with a relative viscosity of 2.04.

C. Stretching the polyester yarns from core-sheath threads

Five as-spun yarn spools were assembled and drawn on a steam stretcher. The yarns to be drawn contained 180 filaments. The first stretching was carried out on heated stretching pins at a temperature of 80 ° C. The draw ratio of the yarns spun at 900 m / min or at 4000 m / min was varied slightly in the order mentioned, from approximately 1: 3 or 1: 1.4, so that the main draw point was on the fifth draw pin. The second drawing was carried out in a steam chamber with a steam temperature of 245 ° C, the residence time of the yarn in the Steam chamber was 3 seconds. In all cases, the total draw ratio of the yarns spun at 900 m / min or at 4000 m / min was 1: 5 and 1: 1.8, respectively. The following table shows the yarn properties.

D. Measurement of rubber adhesion

The yarns obtained were then twisted into a 1100 dtex X1Z435X2S435 tire cord. This cord is treated in a known manner with an aqueous dispersion based on resorcinol-formaldehyde precondensate and vinylpyridine-styrene-butadiene latex (RFL), an order of 5% by weight solids content being set on the cord. Thereafter, it was a) dried for 120 s at 150 ° C. under a tension of 20 mN / tex, b) cured for 30 s at 240 ° C. under a tension of 100 mN / tex and c) for 30 s at 240 ° C. hardened and relaxed under a tension of 20 mN / tex.

The dipped cords were vulcanized into a rubber mixture in the form of strips in accordance with ASTM D 4393-85 and the rubber adhesion was measured in N / 2 cm, ie as a release force for the 2 cm wide strips. The results are shown in the table as average values of 6 measurements each.

Claims (14)

Polyester yarn with good rubber adhesion from core-sheath threads with two different types of polyesters, characterized in that a) the core of the core-sheath threads made of a high-melting polyester or copolyester and b) the sheath of the core-sheath threads consists of a high-melting unsaturated copolyester which, based on the dicarboxylic acid components, with one or more unsaturated dicarboxylic acid co-component (s) consists of at least 2 mol% of alkyl maleic acid with an alkyl group of 1 up to 18 carbon atoms and / or from alkylene succinic acid with an alkylene group of 1 to 18 carbon atoms and / or their polyester-forming derivatives. Polyester yarn according to claim 1, characterized in that the core of the core-sheath threads at least essentially consists of polyethylene glycol terephthalate. Polyester yarn according to one or more of claims 1 to 2, characterized in that the sheath of the core-sheath threads consists of an unsaturated copolyester which contains at least 90 mol% of ethylene glycol terephthalate units and with one or more unsaturated dicarboxylic acid co-component ( n) has been prepared from at least 2 mol% of citraconic acid and / or itaconic acid and / or their polyester-forming derivatives. Polyester yarn according to one or more of claims 1 to 3, characterized in that the sheath of the core-sheath threads consists of an unsaturated copolyester which contains 95 to 98 mol% of ethylene glycol terephthalate units and with 2 to 5 mol%, preferably with 3 up to 4 mol% of citraconic acid and / or itaconic acid and / or their polyester-forming derivatives has been produced. Polyester yarn according to one or more of claims 1 to 4, characterized in that the core of the core-sheath threads, which at least essentially consists of polyethylene glycol terephthalate, has a relative solution viscosity of at least 1.8, preferably from 1.9 to 2.3, measured at 25 ° C as a 1% by weight solution in m-cresol, and has a melting point of at least 250 ° C. Polyester yarn according to one or more of claims 1 to 5, characterized in that the unsaturated copolyester in the sheath of the core-sheath threads has a relative solution viscosity of at least 1.5, preferably 1.6 to 2.0, measured at 25 ° C as a 1 wt.% solution in m-cresol, and has a melting point of at least 245 ° C. Polyester yarn according to one or more of claims 1 to 6, characterized in that the core / sheath ratio of the threads has a weight ratio of 95: 5 to 80:20. Polyester yarn according to one or more of claims 1 to 7, characterized in that it has a tensile strength of 600 to 850 mN / tex, an elongation at break of 10 to 14% and a rubber adhesion of 180 to 260 N / 2cm. Process for the production of polyester yarns with good rubber adhesion from core-sheath threads with two different types of polyesters, characterized in that a) a high-melting polyester or copolyester as the core polymer
and b) as a sheath polymer, a high-melting unsaturated copolyester is spun which, based on the dicarboxylic acid components, with one or more unsaturated dicarboxylic acid co-component (s) composed of at least 2 mol% of alkyl-maleic acid with an alkyl group of 1 to 18 carbon atoms and / or from alkylene succinic acid with an alkylene group of 1 to 18 C atoms and / or their polyester-forming derivatives has been prepared, and c) the filament yarns are further processed in a manner known per se after leaving the blowing and spinning shaft and preparation. Process according to claim 9, characterized in that a (co) polyester consisting at least essentially of polyethylene glycol terephthalate is spun as the core polymer. Method according to one or more of claims 9 to 10, characterized in that the shell polymer is spun an unsaturated copolyester which contains at least 90 mol% of ethylene glycol terephthalate units and with one or more unsaturated dicarboxylic acid co-component (s) from at least one 2 mol% citraconic acid and / or itaconic acid and / or their polyester-forming derivatives has been produced. Polyester yarn according to one or more of claims 9 to 11, characterized in that an unsaturated copolyester is spun as the sheath polymer which contains 95 to 98 mol% of ethylene glycol terephthalate units and 2 to 5 mol%, preferably 3 to 4 mol% Citraconic acid and / or itaconic acid and / or their polyester-forming derivatives has been produced. Process according to one or more of claims 9 to 12, characterized in that the core polymer is spun with the sheath polymer in a weight ratio of 95: 5 to 80:20. Method according to one or more of claims 9 to 13, characterized in that the core sheath threads are spun at a speed of 3000 to 5000 m / min.