EP0392477B1 - Coated polyamide fibre - Google Patents

Abstract

The invention concerns a polyamide fibre which has been coated with a specific reaction product of a polyfunctional epoxy component and a polyamide resin. The invention further concerns a process for coating polyamide fibres with such products.

Description

The invention relates to a polyamide fiber which is coated with a special reaction product consisting of a multifunctional epoxy component and a polyamide resin. The invention further relates to a method for coating polyamide fibers with such agents.

For the purposes of the invention, fibers are understood to mean both continuous fibers and also fiber cuts, fiber composites, yarns, cords, textile fabrics or pulps. Preferred polyamide fibers are aromatic polyamide fibers.

It is known to reinforce plastics with organic or inorganic fibers in order to obtain better material properties. The tensile strength of such composite materials or other mechanical properties increase by the amount that results from the built-in fibers. However, it has been shown that the full In many cases, the performance of the fibers cannot be exploited, since breakage occurs at the interface of the fiber with the matrix during the tearing process, and the fibers are pulled out of the matrix, so to speak. Such phenomena are observed in particular in the case of very tear-resistant fibers, for example aramid fibers.

In order to prevent this, fibers are covered in the art with surface treatment agents, for example with epoxy resin preparations or also with other resins. For example, US Pat. No. 4,652,488 proposes coating aromatic polyamide fibers with a reaction product of polyfunctional epoxides and polyfunctional amines. For this purpose, the US patent suggests starting with a special cord and coating it with a difunctional epoxide, such as, for example, the diglycidyl ether of glycerol and a difunctional amine, for example piperazine. The aim of the proposal is to obtain coatings with a relatively low residual epoxy content. Such epoxy coatings are, however, quite brittle and therefore lead to the fibers, yarns etc. being able to splice or even break during subsequent textile processing steps, such as knitting or weaving, so that deposits form in the textile machines.

In addition, fibers coated in this way show a relatively high water absorption. This is not desirable for numerous subsequent processing steps.

Canadian Patent 651,745 describes a process for the preparation of polyaminoamides by the condensation of fatty acids with alkylene polyamines. Although such polyaminoamides are known as hardeners for epoxy resins, there is no indication in the specialist literature that they can be used advantageously for the surface treatment of fibers, in particular aramid fibers.

It is therefore an object of the invention to provide a polyamide fiber, in particular an aramid fiber, which is provided with a special epoxy coating based on polyamino amides, and thereby shows more favorable processing capabilities, such as lower friction coefficients and less water absorption, but also good adhesiveness.

The invention thus relates to a polyamide fiber coated with the reaction products of a multifunctional epoxy compound and a polyamine, characterized in that a polyamide resin with amino groups, in particular amino end groups, is used as the polyamine.

Another object of the invention is the use of the above-mentioned reaction product of polyfunctional epoxides and polyamide resins as an adhesive and lubricity-imparting coating on a polyamide fiber.

In a general embodiment of the teaching according to the invention, it is therefore proposed to use a polyfunctional amine which also has amide groups as the reaction component for the polyfunctional epoxy compound. Generally suitable are polyamide resins with amino end groups. Preferred among these, however, are those polyamide resins in which one or all of the acid components are branched dicarboxylic acids and in particular dimer fatty acids, or in which at least one of the difunctional amino components is the corresponding dimer fatty acid diamine.

Dimer fatty acids are understood here to mean the dimerization products of unsaturated fatty acids. These are mixtures of substances with a high proportion of branched dicarboxylic acids of chain length C₃ die, but which also contain monofunctional fatty acids and trimers.

Among the conceivable polyamide resins with amino end groups, the reaction products of such dimer fatty acids with an excess of at least difunctional primary or secondary amines, which may also contain tertiary amino groups, are suitable. Polyamide resins based on dimer fatty acids as dicarboxylic acid and alkylenediamines, dialkylenetriamines and / or their higher homologs as amino components are particularly suitable.

Also suitable are polyaminoamide resins which are formed by reacting fatty acids and / or dimer fatty acid, but preferably unsaturated fatty acids with ethylenediamine and / or diethylenetriamine at higher temperatures and / or in the presence of catalysts, and which contain nitrogen-containing heterocycles (generally imidazoline rings) as parts of the molecule. In the case of such polyaminoamides, products are preferred in which the number of nitrogen atoms in rings is 20-90%, preferably 20-60%, based on all nitrogen atoms.

In the polyamide resins used according to the invention, the dimer fatty acids can furthermore be partially, i.e. up to about 50% by weight can be replaced by dicarboxylic acids having 3 to 20 carbon atoms. It is also possible to chain extend the polyaminoamides by reaction with e.g. Undergo lactams. Suitable lactams are caprolactam and / or lauryl lactam.

The polyaminoamides used according to the invention can also be used in admixture with other mono- or polyfunctional amines will. The amount of monofunctional amines should be limited to about 10 mol%, based on amino groups. The amount of the other multifunctional amines should not be more than 80 mol% of the total amount of amines. However, it is preferred to use such amines only in minor amounts. Suitable here are di- and trifunctional amines, as are usually used as curing agents for epoxides, for example ethylenediamine, diethylenetriamine, aliphatic or cycloaliphatic diprimary amines and the like.

When selecting suitable polyamide resins, the person skilled in the art must pay attention to the amine number. This should be more than 70, an upper limit being given by the molecular weight and being approximately 700, preferably 100.

A large number of multifunctional epoxy compounds can be combined with the polyamide resins mentioned. Attention should be paid to the functionality of the epoxy component from 2 to 4. Preference is given to semi-volatile polyfunctional epoxy compounds, especially those with ring structures, e.g. contain aromatic ring structures as a base. Preferred epoxy compounds are N-glycidyl compounds and / or O-glycidyl compounds, in particular N-glycidyl compounds with functionality 3 to 4.

A particularly suitable multifunctional epoxy compound is tetraglycidyldiaminodiphenylmethane.

When selecting the quantitative ratios, the skilled worker must ensure that the reaction products between the epoxy compound and the polyaminoamide have an excess of reactive end groups in the cured state. For polyamide resins with a functionality of at least 2 and an amine number between 80 and 90 in Combination with 4 functional epoxy compounds has proven useful to set an epoxy to amine weight ratio of 1: 5 to 1: 1, preferably 1: 3 to 1: 1.2 and in particular 2: 3.

In general, it is preferred to choose a ratio of amine hydrogens to epoxy rings between 2: 1 and 1: 2, in particular with an excess of either amine component or epoxy component. Higher amounts of amine can also be used, for example between 2 and 4 amine hydrogens per epoxy group. In this case there are amino end groups in the middle, otherwise epoxy end groups.

Another object of the invention is a method for modifying polyamide fibers with the reaction products of polyfunctional epoxides and polyamide resins, in which the polyamide resin and the polyfunctional epoxy compound are applied to the fibers simultaneously or in succession as a solution, dispersion or melt and then cured if desired at elevated temperature leaves.

It may be preferred to dissolve or disperse the epoxy compounds and the polyamide resin separately, and then to coat the fiber either in a mixture of the solutions / dispersions or in succession in the individual solutions / dispersions. Usual concentrations of the coating solutions are between 1 and 20% by weight. For example, polyfunctional epoxy component can be used in solutions with a solids content of 2 to 10% by weight and the polyamide resin component in solutions with a solids content of 10 to 20% or in dispersions and then applied. It can also be applied from the melt.

The resin solutions used according to the invention are not true physical solutions in every case. Without any disadvantage for the properties, parts of the mixed polymers can also be present in dispersed swollen or unswollen form. In such a case, discontinuation should be prevented during use. Suitable solvents are the solvents which are customary for polyamides based on dimer fatty acid. For example, mixtures of C₁ to C₁₂ alcohols, especially C₁ to C₄ alcohols, preferably in admixture with hydrocarbons. A particularly favorable solvent system consists of isopropanol and toluene, for example in a weight ratio of 9: 1.

The coating compositions of the invention may also contain other additives. For example, dyes, anti-aging agents and the like may be present. Catalysts for the reaction of amines with epoxy groups can also be used. Known catalysts for this are, for example, tertiary amines.

According to the invention, coated fibers can be made from polyamides, based on aromatic and / or aliphatic basic building blocks. Coated fibers made from aromatic polyamides are of particular importance.

Coated aromatic polyamide fibers are of particular importance in the context of the invention. Aromatic polyamide fibers are generally fibers (continuous fibers, fiber short cuts, pulps, fiber composites, yarns or textile fabrics) made of aromatic polyamides with a fibrous structure. Here Aromatic polyamides are understood to mean those polymers which partially, predominantly or exclusively consist of aromatic rings which are connected to one another by carbonamide bridges and optionally also by other bridge members. The structure of such aromatic polyamides can be illustrated in part by the following general formula: (-CO-NH A₁-NH-CO-A₂) _n , in which A₁ and A₂ represent aromatic and / or heterocyclic rings, which can also be substituted. An important class of surface-treated fibers according to the invention is derived from fully aromatic copolyamides.

Examples of such aromatic polyamides are: poly-m-phenylene-isophthalamide, trade name Nomex ^(R) (US 3,287,324); Poly-p-phenylene terephthalamide, trade name Kevlar ^(R) (DE 22 19 703). Also suitable are polyamides of this structure in which at least one of the phenyl radicals carries one or more substituents, for example lower alkyl groups, alkoxy groups or halogen atoms. Other aromatic polyamides at least partially contain building blocks which are derived from 3- or 4-amino-benzoic acid.

Also suitable for coating with the surface treatment agents according to the invention are those fully aromatic polyamide fibers which, according to DE 22 19 646, have been stretched in a nitrogen atmosphere at a temperature above 150 ° C.

Aromatic polyamides are also suitable which contain diaminodiphenylene groups, in which phenyl radicals, each carrying an amino or carboxylic acid group, have a bridge member, for example a heteroatom (O, S, SO₂, NR, N₂ or a group CR₂ (with R = H or alkyl groups) or a group CO. Finally, aromatic polyamides are also suitable, in which the aromatic rings are partly replaced by heterocycles or which also have heterocycles as substituents or chain links, and fibers according to US Pat. No. 4,075,172, which are offered under the trade name Technora ^(R) .

The surface treatment agents according to the invention can be used at various points in fiber production. For example, the surface treatment agents can be applied to moist fibers which have never been dried (on line) or they can be applied to the dried fibers (off line). It is preferred to apply the surface treatment agents after drying and, if desired, after stretching. This applies in particular to aramid fibers.

When applying to the fiber, the usual applicators can be used. These are, for example, metering application systems, roll application systems, serpentine application systems or baths.

Ultrasound treatment, electrostatic treatment or plasma treatment of the fiber or yarn can also be carried out before, during or after the application. In some cases this will be preferred to improve the penetration of the treatment agent. In any case, the devices customary here for use with solvent-containing preparations can be used. The quantity applied to the fiber is 0.01 to 12% by weight, based on fiber weights.

The fiber can be dried before or after the coating and possibly can also be coated in several layers, ie after a first coating step is dried and then coated again in a further bath. The first coating is preferably carried out with epoxy resin solutions, the second coating with the polyaminoamide solution. The drying process can be carried out using convection (for example hot air), heat conduction (for example contact drying), radiation (for example Infrared) or the like. The heat treatment of the fiber usually takes place in a range from 80 to 220 ° C., the higher temperature range can only be used with thermally stable fibers, for example with aramid fibers. The drying time can vary between a few seconds and several minutes depending on the degree of drying to be achieved and the further use of the fiber. The running speed of the fibers or yarns in the coating device can be chosen between a few meters per minute and a few hundred meters per minute depending on the desired product intake quantity. A lower limit of the drying time is about 5 seconds, an upper limit of the running speed is about 750 m / min.

The surface-coated fibers according to the invention can be used in a variety of ways. The fibers show reduced water absorption and reduced coefficients of friction, which is important during processing. For example, they show better substrate adhesion in cold adhesive processes, but can also be embedded in plastics or vulcanized in rubber, the fibers then having good binding ability to polar and non-polar types of rubber. Furthermore, the polyamide fibers coated in this way show reduced friction against one another.

Examples example 1 Coating the fibers

An epoxy resin based on tetraglycidyldiaminodiphenylmethane epoxy number 33 plus / minus 2 was dissolved in a 5% by weight solution in toluene / isopropanol (1: 1) while hot.

A polyaminoamide with an amine number between 80 and 95 based on fatty acid and diethylenetriamine analogous to Example 2 of CA 651.745 was dissolved in isopropanol while hot. The solids content of the solution was 12% by weight. The epoxy resin solution and the amine resin solution were then diluted so that the solids content epoxy to amine ratio was 2: 3. In a first step, an aromatic polyamide fiber (Kevlar ^(R) ) was first drawn through the epoxy resin solution, dried with hot air at 200 ° C and pulled through the polyamide resin solution in the second step, after which a further drying step was carried out at 200 ° C in a counter-air flow.

Example 2

The adhesive characteristics were measured before and after fatigue by pulling the yarns out of the rubber block.

To produce the test specimens, after the first drying, treated aramid yarns (Kevlar ^(R) 1670 dtex, 80 T / M) were introduced into different rubber mixtures and vulcanized at 160 ° C. for a period of 20 minutes. For this purpose, the rubber mixtures with the yarns were pressed between two plates of an electrically heated hydraulic press (18 t).

To determine the adhesiveness of the yarns, they were pulled at a speed of 125 mm / min. pulled out of the rubber blocks. The following adhesive values were measured (in each case in comparison to fibers which had been coated with a conventional epoxy resin coating):
Rubber compound ACM 173N (173N)
Rubber compound CR 169N (141N)
Rubber compound EPDM 132N (115N)

Example 3

An aramid continuous fiber of the p-phenylenediamine-terephthalamide type in the dried (off-line) state was drawn through a bath with the surface treatment agent according to the invention described above and then dried at approximately 120.degree. The yarn had a pretension of 0.6 daN. It was an untwisted 1670 dtex yarn. In a first step, a dried polyamide fiber (Kevlar ^{(R) 29) was} first drawn through the epoxy resin solution (2% by weight solid), then dried with hot air at 200 ° C and in the second step through the polyamide resin solution (3% by weight ) each in polyol / isopropanol, then dried at 200 ° C in a counter air stream.

With the yarns treated in this way, the moisture absorption was measured under standard conditions. This was 7.5% by weight for an untreated aramid yarn (Kevlar ^(R) 29), 2.4% by weight for the yarn treated according to the invention and 5% by weight for an identical yarn with a conventional epoxy coating. .

Knitting tests with treated yarns

The coefficient of friction of treated yarns compared to untreated yarns was determined in preliminary tests. The measurement was carried out in a friction measuring device (Rothschild) according to standard conditions. The coefficient of friction yarn to metal was 0.40 for the treated yarn and 0.54 for the untreated yarn. The Friction coefficient fiber to fiber was 0.055 for the treated yarn compared to 0.11 for the standard product Kevlar ^(R) 29)

Aramid yarns (Kevlar ^(R) were knitted on an ELHA ^(R) circular knitting machine (model RRU). The test lasted 4 hours. The machine speed was 670 min -1, the knitting speed 15 m / min. In contrast to untreated fibers, none The image of the knitted fabric was uniform, and there were no deposits in the knitting machine, which means that the surface treatment agents according to the invention markedly improve the knitting properties of aramid yarns.

Claims (14)

1. A polyamide fiber coated with the reaction products from a polyfunctional epoxide compound and a polyamine, characterized in that a polyamide resin containing amino groups is employed as the polyamine.
2. The polyamide fiber according to claim 1, characterized in that the polyamide resin has an amine value of from 20 to 700, and preferably from 70 to 100.
3. The polyamide fiber according to either one of claims 1 or 2, characterized in that a reaction product of a dimer fatty acid with an excess of at least difunctional primary and/or secondary amines which may also contain tertiary amino groups is employed as the polyamide resin containing amino groups.
4. The polyamide fiber according to any one of claims 1 to 3, characterized in that a reaction product of a dimer fatty acid with an excess of primary and/or secondary amines which may also contain tertiary amino groups is employed as the polyamide resin containing amino groups, which contains from 20 to 90%, and preferably from 20 to 60%, of the nitrogen atoms, based on the total number of nitrogen atoms, as ring members of imidazoline rings.
5. The polyamide fiber according to any one of the preceding claims, characterized in that a reaction product of fatty acids and/or a dimer fatty acid with alkylene diamines, dialkylene triamines and/or the higher homologues thereof is employed as the polyamide resin.
6. The polyamide fiber according to any one of the preceding claims, characterized in that the polyfunctional epoxide compound has a functionality between 2 and 4.
7. The polyamide fiber according to any one of the preceding claims, characterized in that the polyfunctional epoxide compound has 3 or 4 N-glycidyl groups and/or O-gycidyl groups.
8. The polyamide fiber according to any one of the preceding claims, characterized in that the polyfunctional epoxide compound is tetraglycidyl diaminodiphenylmethane.
9. The polyamide fiber according to any one of the preceding claims, characterized in that the cured products of the reaction of the polyfunctional epoxide resin compound with the polyamide resin on the average has terminal amino groups or terminal epoxide groups.
10. The polyamide fiber according to any one of the preceding claims, characterized in that it comprises continuous filaments, staple fibers, fiber tows, yarns, cords or flat textile fabrics at least predominantly derived from aromatic polyamides.
11. Use of the reaction product from polyfunctional epoxide compounds and polyamide resins according to the preceding claims as a coating imparting bond strength and slip on a polyamide fiber
12. A process for modifying polyamide fibers with the reaction products from polyfunctional epoxides and polyamide resins, in which process the polyamide resin comprising amino groups and the polyfunctional epoxide compound simultaneously or subsequently are applied as a solution, dispersion or melt to the fiber and then, if so desired, curing the produced coating at an elevated temperature.
13. The process according to claim 12, characterized in that the fiber is first moved through a solution or slurry of the epoxide resin component and then, optionally after an intermediate drying step, is moved through a solution or slurry of the polyamide resin comprising amino groups and thereafter is optionally dried and cured.
14. The process according to claims 12 or 13, characterized in that a reaction product is applied onto the fiber, before or after the first drying step.