DE69200321T2 - EASILY PROCESSABLE AROMATIC POLYAMIDE FIBERS, THEIR PRODUCTION AND USE. - Google Patents

Description

Background of the invention Field of the invention

The invention relates to aromatic polyamide fibers with high processing quality, their production and use.

Description of the current technology

The research report of July 1980, No. 195, Description 19520, describes finishes suitable for treating industrial fibers such as polyamide and aramid fibers, the finishes containing a lubricant comprising esters consisting of an aliphatic saturated carboxylic acid and a polyhydric or aliphatic unbranched alcohol. These finishes also contain an emulsifier or emulsifier system, an antioxidant to improve the stability of the mass, polysiloxanes as a further thermostable lubricant and a sulfonated natural oil as an antistatic agent. In addition, these finishes may contain biostatics, other emulsifiers and lubricants.

However, the finishes according to the above reference are not suitable for the purposes of the invention with regard to surface friction properties, washability, protection against abrasion, fibrillation and antistatic properties of the resulting treated fibers.

High-strength, high-modulus fibers have been proposed for reinforcing elastomers and plastic materials.

EP-A-0416468, published on 13.03.91, with filing date of 01.09.90 and priority of 05.09.89, describes a coating for aramid fibers according to the general teaching of claim 1. However, the kinematic viscosity of the ester is limited to less than 70 mm²/s at 20 ºC.

Summary of the invention

Most commercial fibers exhibit high rigidity and low functional surface properties, leading to fibrillation caused mainly by excessive friction between the filaments, and low surface affinity towards most conventional elastomers, the thermoplastic and heat-setting matrices that reinforce them.

The disadvantages and defects that lead to a deterioration of physical properties such as strength and modulus have driven a strong demand for fibers with high processing quality that must be easily processable by knitting or weaving processes and do not lead to machine deposits.

According to the invention, applying a specific combination of surface treatment agents to the surface of pre-dried aramid fibers using a previously known finishing process or applying such agents to never-stretched, never-dried aramid fibers provides a new surface-treated fiber which, when used as a reinforcing element in rubber applications or as a yarn for textile weaves, exhibits excellent processing properties. The end-use behavior of finished products in which the fibers are used is therefore significantly improved.

The invention accordingly relates to aramid fibres with high Processing quality, with high modulus, improved surface friction properties, improved washability, low polymer deposition by abrasion, low fibrillation and improved long-term antistatic properties, having a coating of a lubricant, an emulsifier system, an antistatic agent and other components derived from a surface treatment agent, consisting of

(a) 30 to 70% by weight of an ester oil lubricant consisting of an ester composed of

(I) an alcohol component which is a branched primary or secondary saturated monohydric alcohol of the general formula

is,

wherein

R₁ is C₁-C₁₆ alkyl,

R₂ is H, C₁-C₁₆-alkyl if k = 1, and

R₂ is C₁-C₁₆ alkyl if k = 0,

h = 0 to 5,

k = 0 or 1,

j = 0 to 4,

m = 0 to 16

and in which the total number of carbon atoms is less than 25,

and

(II) a carboxylic acid component which is an unsaturated fatty acid of the general formula

R³-(COOH)s s = 1-6

is, in which

R³ represents C₄-C₁₇-alkenyl, C₄-C₁₇-alkadienyl, C₄-C₁₇-alkatrienyl, phenyl, naphthyl, 2-phenylethenyl or an unsaturated dicarboxylic acid of the general formula

HOOC-(CH=CH)n-COOH

is,

where n = 1 or 2,

and said ester has a solidification point of below +5 ºC, preferably below 0 ºC, a kinematic viscosity of 100 to 350 mm²/s (at 20 ºC) and an iodine number of between 30 and 140, preferably between 30 and 80,

(b) 20 to 50% by weight of an emulsifier system consisting of unsaturated ethoxylated fatty acids and/or unsaturated ethoxylated fatty alcohols and/or ethoxylated alkylamines of the general formula

R⁴-X-(EO)p(PO)q-OH

consists,

wherein

R₄ represents C₅-C₂₀-alkenyl, phenyl, naphthyl or C₈- or C₉-alkylphenyl,

X stands for -COO-, NH- or -O-,

EO stands for an ethylene oxide unit,

PO stands for a propylene oxide unit,

p = 2 to 15 and

q = 0 to 10,

(c) 5 to 15% by weight of an antistatic agent consisting of alkali salts of C₄-C₁₂-alkyl sulfonates, C₄-C₁₂-alkyl phosphates or C₄-C₂�0-alkyl carboxylic acids

(d) 0.2 to 2 wt.% of a corrosion inhibitor, and

(e) where appropriate, additives,

and wherein the amount of said coating on said fibers is 0.05 to 2.0 wt.%, preferably 0.2 to 1.0 wt.%, of the fiber.

The coating preferably consists of 50 to 60 wt.%, most preferably 55 to 60 wt.%, of the ester oil (a), 25 to 40 wt.%, most preferably 29 to 35 wt.%, of the emulsifier system (b), 5 to 10 wt.%, most preferably 5 to 7 wt.%, of the antistatic agent (c), 0.3 to 1 wt.%, most preferably 0.3 to 0.5 wt.%, of the corrosion inhibitor (d) and optionally the additives (e) if desired.

The aramid fibers according to the invention are also characterized by a specific tensile strength of 2.65 to 33.5 cN/dtex (3 to 38 g/den), a specific modulus of 8.83 to 2207 cN/dtex (10 to 2500 g/den), a dynamic friction coefficient between fiber and metal on a 1100 dtex aramid yarn of less than 0.55, preferably less than 0.50 at 200 m/min, a boundary friction coefficient between fiber and metal on a 1100 dtex aramid yarn of less than 0.10, preferably less than 0.05, at 0.016 cm/s, a deposit amount due to abrasion of less than 0.5 mg/kg of the yarn, a residual finish concentration of less than 15% by weight the original finish concentration after washing.

The fiber of the present invention provides an improved blend of properties with respect to smoke emission as measured by weight losses, fiber washability and fiber cohesion compared to fibers using other finishes.

Within the scope of the invention, "fibers" include continuous filaments as well as simple yarn or cord, staple fibers, fiber tows (e.g. by stretch breaking processes), yarns or flat textile strands, crimped staple fibers, pulps, industrial woven, twisted, knitted, braided, spirally twisted or wrapped textiles made of Aramids with a fibrous structure.

Aramids are polymers that are partially, predominantly, or exclusively composed of aromatic rings that are connected via carbamide bridges or, if necessary, additionally via other bridge structures. The structure of such aromatic polyamides can be explained by the following general formula of repeating units:

(-CO-NH-A₁-NH-CO-A₂-CO-)n

wherein A₁ and A₂ are the same or different and denote aromatic and/or polyaromatic and/or heteroaromatic rings, which may also be substituted. Typically, A₁ and A₂ independently selected from 1,4-phenylene, 1,3-phenylene, 1,2-phenylene, 4,4'-biphenylene, 2,6-naphthylene, 1,5-naphthylene, 1,4-naphthylene, phenoxyphenyl-4,4'-diylene, phenoxyphenyl-3,4'-diylene, 2,5-pyridylene and 2,6-quinolylene, which may be unsubstituted or substituted with one or more substituents which may include halogen, C₁-C₄alkyl, phenyl, carboalkoxyl, C₁-C₄alkoxyl, acyloxy, nitro, dialkylamino, thioalkyl, carboxy and sulfonyl. The -CONH- group can also be replaced by a carbonyl hydrazide group (-CONHNH-), azo or azoxy group.

Fibres derived from fully aromatic polyamides are preferred.

Examples of aramids are poly-m-phenylene isophthalamide and poly-p-phenylene terphthalamide.

Particularly suitable are poly-m-phenylene isophthalamide fibers according to US 3,287,324 and poly-p-phenylene terephthalamide fibers according to US 3,869,429 and DE 22 19 703.

Additives may be used with the aramid, and in fact it has been found that up to 10% by weight of another polymeric material may be blended with the aramid, or that copolymers may be used containing up to 10% by weight of another diamine to replace the diamine of the aramid, or up to 10% by weight of another diacid chloride to replace the diacid chloride of the aramid.

Other suitable aromatic polyamides are those with the following structure

(-NH-Ar₁-X-Ar₂-NH-CO-Ar₁-X-Ar₂-CO-)n

wherein

X stands for O, S, SO₂, NR, N₂, CR₂, CO and

R is H, C₁-C₄-alkyl and

Ar₁ and Ar₂, which may be the same or different, are selected from 1,2-phenylene, 1,3-phenylene and 1,4-phenylene and wherein at least one hydrogen atom may be substituted by halogen and/or C₁-C₄-alkyl.

The finishing formulation according to the invention comprises a lubricant, an emulsifier system, an antistatic agent and a corrosion inhibitor and, if desired, water and/or other additives.

The lubricant is an ester oil characterized as stated above. Examples of alcohol compound (I) of the ester can be 2-methyl-1-propanol, 2-butanol, 2-pentanol, 2-methyl-1-butanol, 3-methyl-3-butanol, 3-methyl-2-butanol, 2-methyl-1-pentanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, 2-pentanol, 3-heptanol, 2-octanol, 2-ethyl-1-hexanol, 3,5-dimethyl-1-hexanol, 5-nonanol, 2,6-dimethyl-4-heptanol, iso-hexadecyl alcohol or iso-tridecyl alcohol. Examples of the carboxylic acid component (II) can be lauroleic acid,

Myristoleic acid, palmitoleic acid, oleic acid, gadoleic acid, erucic acid, ricinoleic acid, tallow fatty acid, linoleic acid, linolenic acid, fumaric acid, maleic acid, cinnamic acid, naphthalenecarboxylic acid, benzoic acid, terephthalic acid, isophthalic acid, trimellitic acid or pyromellitic acid

The kinematic viscosity of the ester oil is preferably in the range of 200 to 300 mm²/s (20 ºC).

The emulsifier system according to the invention is as defined above. Examples of unsaturated fatty acids are lauroleic acid, myristoleic acid, palmitoleic acid, gadoleic acid, erucic acid or ricinoleic acid, preferably oleic acid (with 3-15 mol ethylene oxide). Examples of unsaturated fatty alcohols are elaidyl alcohol, erucyl alcohol, brassidyl alcohol, preferably oleyl alcohol and/or tallow alcohol (with 3-10 mol EO). Further examples are C8 or C9 alkylphenol ethoxylates, preferably octylphenol or nonylphenol ethoxylates (5-5 mol EO).

The antistatic compounds are alkali salts, preferably sodium salts of alkyl sulfonates (e.g. lauryl or oleyl sulfonate), alkyl phosphates, such as C4-C12 alkyl phosphates (mono/diester mixtures), and salts of fatty acids, e.g. oleic acid. The sodium chloride content should be below 0.1%. It is also possible to use alkyl sulfates, but they are not preferred because they easily hydrolyze and therefore lose their antistatic effectiveness.

Suitable corrosion inhibitors are diethanolamine salts of C₄-C₁₂-alkyl phosphate esters (mono/di) or amine salts of fatty acids or benzoic acid.

The formulation may contain water for stability reasons, even before it is diluted with water to obtain the concentration at which it is applied to the fibers.

Additives may be incorporated into the formulation if specific properties or processing conditions are required, e.g. adhesion, special cross-linking, UV protection, protection against oxidation, pigmentation or rheology adjustment. These additives may also include fungicides, bactericides and biocides.

A formulation for treating aramid fibers can be prepared by mixing all the components at an elevated temperature, preferably a temperature between 30 ºC and 40 ºC, to obtain a homogeneous and clear oil. Thus, for example, a mixture can be prepared consisting of 550 g of isobutyl oleate, 350 g of the emulsifier system consisting of 200 g of nonylphenol ethoxylate (8 EO) and 150 g of oleic acid ethoxylate (10 EO), 70 g of sodium decyl sulfonate and 5 g of diethanolamine salt of benzoic acid. If necessary, about 25 g of water is added to the mixture to remove any turbidity. The addition of water may also be necessary to obtain a stable clear oil. If necessary, the pH can be adjusted between 6 and 8, preferably to 7, by using diethanolamine or acetic acid.

The finishing formulation according to the invention is also characterized by a viscosity of 150 to 500 mm²/s, preferably 150 to 300 mm²/s (at 20 °C), a weight loss of less than 25%, preferably less than 15%, after 2 hours at 200 °C, a surface tension of a 1% emulsion of less than 35 mN/m, preferably less than 32 mN/m at 20 °C

The invention further relates to a method for producing an aromatic polyamide fiber with high processing quality which is coated on the surface with a surface treatment agent.

The coating of aramid fibers with the surface treatment agent according to the invention can be carried out in various ways, in particular, for example, according to the following methods (a) and (b).

According to method (a), the application of the surface treatment agent is carried out on a never-dried, never-stretched aramid fiber. According to method (b), the application of the surface treatment agent is carried out on a pre-dried aramid fiber, in each case using any known coating device. The finish formulation is used neat or in dilute aqueous form, which may be present in a concentration of as little as 1% by weight.

In the preferred course of process (a), the finish formulation is applied to a wet aramid fiber at a concentration of about 30% by weight in water (i.e. 30 parts by weight finish formulation + 70 parts by weight water). The emulsion-treated fiber is then dried during the stretch-drying stage of the fiber at a temperature between 150 and 190ºC, preferably at about 170ºC, for a few seconds (5 to 10 seconds) while the yarn speed is about 630 m/min (processable range 120-1200 m/min).

In the preferred course of process (b), the aramid fiber yarns and threads are passed through a dip bath of the finish formulation in a dipping device to coat them and are then dried in an air heated chamber at 80 to 190 °C, preferably at 110 to 130 °C, with a preset tension of 6 N for a 1670 dtex untwisted yarn. The most preferred temperature for this step is about 120 °C. Depending on the dip bath concentration of the finish formulation, which can be from 1 to 100 wt.% in water, the speed is from 15 to 100 m/min. A finish formulation of 100% means that the finish is undiluted.

The finish concentrations for both processes (a) and (b) are in the range of 0.05 to 2 wt.%, preferably from 0.2 to 1.0 wt.%.

If desired, processes (a) and (b) can be carried out as a multi-step process in which the fiber is alternately immersed in a surface treatment agent and dried several times. For example, the treatment agent can be applied to the never-dried wet fiber, then the fiber can be dried, and thereafter the surface treatment agent can be applied a further time or even several times with or without intermediate drying.

The fibers of the invention can be used in the reinforcement of hoses, tapes, ropes and cables, including optical cables, rubber goods and composite structures (e.g. sporting goods, medical articles, construction and acoustic materials, transport and protective equipment for civil and military uses).

Description of preferred embodiments example 1

In this example, an aramid fiber coated with the finish according to the invention in a yarn of 1100 dtex was compared with a commercially available aramid yarn of the same dtex coated with a standard finish.

The aramid fiber according to the invention shows superiority in terms of friction, in particular in terms of dynamic friction F/M (200 m/min), deposition, measured in mg/kg of yarn, and fibrillation, compared to the control aramid fiber (comparison) which is commercially available.

In the antistatic evaluation, generally good performance starts at -6 kV, thus the measured value of -2.5 kV for the fiber of the invention is excellent in terms of static electricity.

The washability (washability) is a very important factor since the residual finish concentration after a washing stage (measured in %) influences each subsequent finishing operation. The washability values mentioned in the table below were obtained on an industrial scale using fabrics made from the yarn of the invention and comparing them with control yarn which was a commercial product of the same denier treated with a standard finish. The values were confirmed in the laboratory by washing the yarns twice with soft water at 50ºC using 100 ml of water for 10 g of yarn.

The friction coefficients were determined according to the following method: a package of yarn is threaded through a tensioning device between a guide roller and two strain gauges onto a take-up roller driven by a variable speed motor. The two strain gauges record T₁ and T₂, the input and tension output, respectively. The friction coefficient is calculated according to the following formula:

T₁/T₂ = exp(a f),

where a is the angle of friction and f is the coefficient of friction (fibre against fibre, fibre against metal or fibre against ceramic, depending on whether a polished chrome or ceramic needle was used). The Rothschild friction meter R-1182 was used according to standard procedure known in the art.

The deposition due to abrasion was measured on a "Staff-Tester G 555" (Zweigle, West Germany), which determined the weight of the abraded fiber material resulting from the friction of fiber against fiber.

The fibrillation index was determined on a "G 566" apparatus (Zweigle, West Germany). Comparison of physical properties (1100 dtex fiber) Comparison according to the invention 1. Friction fiber/fiber fiber/metal 2. Deposition (mg/kg) 3. Fibrillation index 4. Washability (residual finish concentration)

Example 2

In this example, a fabric woven from the yarn of the invention and a control fabric woven from a commercially available yarn having a standard finish were tested for ballistic behavior.

The fabrics were made from 1111 dtex (1000 denier) yarns. In general, in the area of high tenacity fibers, the weaving process of ballistic fabrics results in strength losses, which are usually quantified by extracting the yarn from the fabric and measuring the Tear strength is measured according to standard methods known in the art. The following table shows that the product according to the invention offers a clear advantage since, for a heavy fabric construction (typically 20 ends per cm), the loss of strength is reduced by half (7 versus 14%). The ballistic behaviour (V₅₀: see test method) also improves by 8% at the raw material stage and by 5 to 8% at the finished product stage (which means after the final fabric treatment).

In the case of lightweight fabrics with typically 8 ends per cm, the ballistic behavior at the raw material level is further improved by 4.5%. Strength conversion and ballistic behaviour Material quality Strength loss according to the invention Strength loss comparison % improvement in ballistic behaviour V₅₀ according to the invention versus comparison HEAVY MATERIAL according to the state of the art: 1. raw 2. ballistic behaviour (raw material) 3. ballistic behaviour (finished material) LIGHT MATERIAL

Ballistic tests

The ballistic test procedure for determining V50 was conducted in accordance with the NATO standardization agreement STANAG 2920.

The V50 limiting ballistic velocity for material or armour is defined as the velocity for which the probability of penetration of the selected projectile is exactly 0.5, using the firing method with two-way approximation and calculation as described below.

Firing method for two-sided approach:

The first round should be loaded with the amount of propellant calculated to give the projectile a velocity equivalent to the estimated V50 ballistic limit of the armor. If the first round of firing results in complete penetration, the second round should be loaded with a fixed decrease in propellant calculated to give a velocity approximately 30 m/s lower than the first round. If the first round of firing results in partial penetration, the second round should be loaded with a fixed increase in propellant calculated to give a velocity approximately 30 m/s higher than the first round. After receiving the first set of penetration changes, the propellant charge should be adjusted to the fixed amount to give an increase or decrease in velocity of approximately 15 m/s. The firing is then continued according to a given procedure to obtain an estimate of V50 (BLP)[Ballistic Limit Protection].

V�5;�0 calculation:

After a number of projectiles have been fired, V50 is calculated as the average of the velocities recorded for a significant impact, where the significant impact consists of the three highest partial velocities for partial penetration and the three lowest velocities for complete penetration, provided that all six velocities are within an interval of 40 m/s.

Example 3

In this example, the evaluation of knit processability was carried out under the following conditions: ELHA circular knitting machine (model RRU), test duration 4 hours, machine speed 670 rpm, knitting speed 15 m/min, knitting structure 3 stitches/cm. End-use behaviour of different yarn types Yarn type Comparison 0 T/m Comparison 120 T/m Inventive process (a) and (b) 0 T/m Fibrillation Knitting pattern Deposition Coverage factor high Non-uniform accumulation of deposition none uniform low deposition low no deposition optimal

As can be seen from the above table, optimum productivity levels and maximum utility value can be obtained using the yarns according to the invention in comparison with the comparison yarns. The prior art product is used twisted. The results clearly show the advantage associated with the possibility of using the yarns according to the invention Yarns to avoid the twisting process.

Example 4

In this example, fatigue tests were carried out on hoses made using the yarn of the invention according to the Ford specification at pressures of 1 to 3.5 bar at 0.5 Hz according to the sharpest trapezoidal waveform.

With comparison yarn, 50,000 passes are generally achieved until failure and are sufficient to pass the test. However, for 5 hose samples containing the yarns according to the invention, 80,000 passes were obtained. This shows the clear superiority of the yarns according to the invention with regard to fatigue resistance.

Example 5

In this example, the implementation of the strength efficiency of cords made using yarns of the invention was compared with that of cords made from comparative yarns.

Compared to a commercially available aramid-based construction, up to 30% better implementation of strength efficiency was obtained for a thread construction using the yarn according to the invention. When a cord is made from several yarns, the strength of the cord should theoretically correspond to the strength of each yarn multiplied by the number of yarns, which is never the case in practice. However, the finish according to the invention helps to remedy this problem.

In a laboratory test, the strength of a parallel The final strength of a cord construction made from three commercially available 1100 dtex (1000 filament) aramid yarns with a final twist of 140 T/m (twist per meter) was determined to be 524 N. This was compared to a parallel cord construction made from three 1100 dtex yarns treated with the finish of the invention (0.8% by weight finish concentration). The final strength obtained for a yarn with a twist level of 140 T/m was 592 N, which corresponds to a 30% increase.

Example 6

In this example, several qualities of yarn according to the invention were tested and compared with the qualities exhibited by the comparison yarn.

Test conditions:

Weight loss is determined as the percentage of finish material lost after the fibers have been exposed to 230 ºC for 8 hours. The percentage of finish is determined by solvent extraction before and after heat exposure.

The percentage of residue after scouring is also determined by solvent extraction of the residual finish remaining on the fiber after scouring (scouring) according to scouring procedures known and used in the industry. The percentage is calculated in comparison to the original finish concentration determined before the scouring stage

The fiber-to-metal friction coefficient (F/M) is determined at 150 m/min using the Rothschild apparatus and the procedure described previously. Fibre Weight loss of finish when heated Residual finish after washing F/M Friction coefficient A according to the invention (non-fuming) B according to the invention C Comparison

All yarns were 1000 denier and 670 filaments and were coated in the dry state using a neat finishing formulation at a speed of 750 m/minute at a concentration of 0.8%.

The finish of A comprised a 70/30 mixture of benzenetricarboxylic acid and benzenedicarboxylic acid as the carboxylic acid component of the ester oil. The finish of B comprised a 70/30 mixture of C-18/C-16 alkenylmonocarboxylic acid as the component of the ester oil.

The control finish consisted of a C-12/C-15 mineral oil base as described in Research Report No. 195, Description 19520, July 1980.

In this example, it is noted that using the finish formulations of the invention in which a carboxylic acid component is used for the ester oil which has more than one carboxylic acid group, i.e., where n = 2-6, the finish formulation gives significantly less weight loss upon heating. Less weight loss upon heating means less smoke generation during use and operation at elevated temperatures.

Claims (16)

1. Aramid fibers with a lubricant coating, an emulsion system and an antistatic agent and other components derived from a surface treatment agent consisting of (a) 30 to 70% by weight of an ester oil lubricant, consisting of an ester composed of (I) an alcohol component which is a branched primary or secondary saturated monohydric alcohol of the general formula is, in which R₁ is C₁-C₁₆ alkyl, R₂ is H, C₁-C₁₆-alkyl if K = 1, and R₂ is C₁-C₁₆ alkyl if k = 0, h = 0 to 5, j = 0 to 4, k = 0 or 1, m = 0 to 16 and in which the total number of carbon atoms is less than 25, and (II) a carboxylic acid component which is an unsaturated fatty acid of the general formula R³-(COOH)s s = 1-6 represents, in which R³ represents C₄-C₁₇-alkenyl, C₄-C₁₇-alkadienyl, C₄-C₁₇-alkatrienyl, phenyl, naphthyl, 2-phenylethenyl or an unsaturated dicarboxylic acid of the general formula HOOC-(CH=CH)n-COOH where n = 1 or 2, and said ester has a solidification point of less than +5 ºC, a kinematic viscosity of 100 to 350 mm²/s (at 20 ºC) and an iodine number of between 30 and 140, (b) 20 to 50% by weight of an emulsifier system consisting of unsaturated ethoxylated fatty acids and/or unsaturated ethoxylated fatty alcohols and/or ethoxylated alkylamines of the general formula R⁴-X-(EO)p(PO)q-OH consists, wherein R4 is C₅-C₂₀-alkenyl, phenyl, naphthyl or C₈- or C₉-alkylphenyl, X stands for -COO-, NH- or -O-, EO stands for an ethylene oxide unit, PO stands for a propylene oxide unit, p = 2 to 15 and q = 0 to 10. (c) 5 to 15% by weight of an antistatic agent consisting of alkali salts of C4-C12 alkyl sulfonates, C4-C12 alkyl phosphates or C4-C20 alkyl carboxylic acids, (d) 0.2 to 2 wt.% of a corrosion inhibitor, and (e) optionally additives and wherein the amount of said coating on said fibers is from 0.05 to 2.0% by weight. 2. Fibers according to claim 1, characterized in that the alcohol component (I) of (a) is 2-methyl-1-propanol, 2-butanol, 2-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl-2-butanol, 2-methyl-1-pentanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, 2-pentanol, 3-heptanol, 2-octanol, 2-ethyl-1-hexanol, 3,5-dimethyl-1-hexanol, 5-nonanol, 2,6-dimethyl-4-heptanol, isohexadecyl alcohol or isotridecyl alcohol. 3. Fiber according to claim 1, characterized in that the said carboxylic acid component (II) is selected from (a) lauroleic acid, myristoleic acid, palmitoleic acid, oleic acid, gadoleic acid, erucic acid, ricinoleic acid, tallow fatty acid, linoleic acid, linolenic acid, fumaric acid, maleic acid, cinnamic acid, naphthalenecarboxylic acid, benzoic acid, terephthalic acid, isophthalic acid, trimellitic acid or pyromellitic acid. 4. Fibers according to claim 1, characterized in that the mentioned emulsifier system comprises octylphenol ethoxylates (5-15 mol EO) and/or nonylphenol ethoxylates (5-15 mol EO) and/or ethoxylated lauroleic acid, myristoleic acid, palmitoleic acid, gadoleic acid, erucic acid, rinicolic acid or oleic acid (3-15 mol EO) and/or ethoxylates of elaidyl alcohol, erucyl alcohol, brassidyl alcohol or oleyl alcohol (3-10 mol EO) and/or talc alcohol ethoxylates (3-10 mol EO). 5. Fibers according to claim 1, characterized in that the said surface treatment agent consists of 50 to 60 wt.% (a) 25 to 40 wt.% (b), 5 to 10 wt.% (c) 0.3 to 1 wt.% (d), and where appropriate, the additives (e). 6. Fibers according to claim 1, characterized in that the repeating units of the aramid have the general formula (-NH-A₁-NH-CO-A₂-CO-)n possess, in which A₁ and A₂ are the same or different and represent substituted or unsubstituted aromatic and/or polyaromatic and/or heteroaromatic rings. 7. Fibers according to claim 6, characterized in that A₁ and A₂ are independently selected from 1,4-phenylene, 1,3-phenylene, 1,2-phenylene, 4,4'-biphenylene, 2,6-naphthylene, 1,5-naphthylene, 1,4-naphthylene, phenoxyphenyl-4,4'-diyl, phenoxyphenyl- 3,4'-diyl, 2,5-pyridylene and 2,6-quinolylene, which may or may not be substituted with one or more substituents comprising halogen, C₁-C₄alkyl, phenyl, carboalkoxyl, C₁-C₄alkoxyl, acyloxy, nitro, dialkylamino, thioalkyl, carboxyl and sulfonyl, and wherein the amide group may also be replaced by a carbonyl hydrazide, azo or azoxy group. 8. Fibers according to claim 6, characterized in that the aromatic polyamide is a copolyamide in which preferably at least 80 mol% of the total amount of A₁ and A₂ represents a 1,4-phenylene and phenoxyphenyl-3,4'-diyl which may or may not be substituted and the content of phenoxyphenyl-3,4'-diylene is 10 mol% to 40 mol%. 9. Fibers according to claim 6, characterized in that the polyamide fibers consist of poly-(m-phenylene isophthalamide). 10. Fibers according to claim 6, characterized in that the polyamide fibers consist of poly-p-(phenylene terephthalamide). 11. Fibers according to claim 6, characterized in that the polyamide fibers mentioned optionally contain units derived from 3- or 4-aminobenzoic acid. 12. A process for producing aramid fibers having a coating of a surface treatment agent, comprising the steps of applying the surface treatment agent to said fiber in an aqueous system at a concentration of 1 to 100% by weight, drying the fibers at a temperature of between 150 and 190 °C, optionally repeating the application of the surface treatment agent, which is further characterized in that the surface treatment agent consists of (a) 30 to 70% by weight of an ester oil lubricant, consisting of an ester consisting of (I) an alcohol component which is a branched primary or secondary saturated monohydric alcohol of the general formula is, in which R₁ is C₁-C₁₆ alkyl, R₂ is H, C₁-C₁₆-alkyl if K = 1, and R₂ is C₁-C₁₆ alkyl if k = 0, h = 0 to 5, j = 0 to 4, k = 0 or 1, m = 0 to 16 and in which the total number of carbon atoms is less than 25, and (II) a carboxylic acid component which is an unsaturated fatty acid of the general formula R³-(COOH)s s = 1-6 represents, in which R³ represents C₄-C₁₇-alkenyl, C₄-C₁₇-alkadienyl, C₄-C₁₇-alkatrienyl, phenyl, naphthyl, 2-phenylethenyl or an unsaturated dicarboxylic acid of the general formula HOOC-(CH=CH)n-COOH represents, where n = 1 or 2 and said ester has a solidification point of less than +5 ºC, a kinematic viscosity of 100 to 350 mm²/s (at 20 ºC) and an iodine number of between 30 and 140, (b) 20 to 50% by weight of an emulsifier system consisting of unsaturated ethoxylated fatty acids and/or unsaturated ethoxylated fatty alcohols and/or ethoxylated alkylamines of the general formula R⁴-X-(EO)p(PO)q-OH consists, wherein R4 is C₅-C₂₀-alkenyl, phenyl, naphthyl or C₈- or C₉-alkylphenyl, X stands for -COO-, NH- or -O-, EO stands for an ethylene oxide unit, PO stands for a propylene oxide unit, p 2 to 15 and q = 0 to 10. (c) 5 to 15% by weight of an antistatic agent consisting of alkali salts of C4-C12 alkyl sulfonates, C4-C12 alkyl phosphates or C4-C20 alkyl carboxylic acids, (d) 0.2 to 2 wt.% of a corrosion inhibitor, and (e) where appropriate, additives. 13. Process according to claim 12, characterized in that the concentration of the surface treatment agent in water is 30% by weight. 14. Process according to claim 12, characterized in that the concentration of the surface treatment agent is 100% by weight, i.e. the surface treatment agent is pure. 15. Process according to claim 12, characterized in that the surface treatment agent is applied to never dried aramid fibers. 16. Process according to claim 12, characterized in that the surface treatment agent is applied to previously dried aramid fibers.