EP1637633A1 - Polyester fibres, method for their production and their use. - Google Patents

Abstract

Fiber (A) comprises aliphatic-aromatic polyester (I) and spherical particles of inorganic oxides (II) with an average diameter of less than or equal to 100 nm. Independent claims are also included for: (1) the preparation of (A); and (2) use of (II) for the preparation of (A) (preferably monofilaments) with high bending stability.

Description

The present invention relates to polyester fibers with high flexural resistance, in particular monofilaments, which can be used for example in screens or in conveyor belts.

It is known that polyester fibers, in particular monofilaments for technical applications, are in most cases subjected to high mechanical and / or thermal stresses during use. In addition, in many cases, exposure to chemical and other environmental influences to which the material must oppose sufficient resistance. For all these loads, the material must have good dimensional stability and constancy of force-elongation properties over as long as possible usage periods.

An example of technical applications where the combination of high mechanical, thermal and chemical stresses is present is the use of monofilaments in filters, screens or conveyors. This use requires a monofilament material with excellent mechanical properties, such as high initial modulus, tear strength, knot and loop strength, and high abrasion resistance coupled with high resistance to hydrolysis, to withstand the high stresses in its use and to ensure sufficient service life of the screens or conveyor belts guarantee.

Molding compositions with high chemical and physical resistance and their use for fiber production are known. Widely used Materials are polyester. It is also known to combine these polymers with other materials, for example, to set the abrasion resistance targeted.

In industrial production, such as in the manufacture or processing of papers, filters or conveyor belts are used in processes that occur at elevated temperatures and in hot humid environments. Although polyester-based manmade fibers have proven successful in such environments, when used in humid-hot environments, polyesters are prone to mechanical abrasion in addition to hydrolytic degradation.

In technical applications, abrasion can have a variety of causes. Thus, the sheet forming screen is pulled in paper machines for dewatering suction boxes with the result of increased Siebverschleißes. In the dryer section of the paper machine, screen wear occurs due to differences in speed between the paper web and the screen surface or between the screen surface and the surface of the drying drums. Tissue wear also occurs in other technical fabrics due to abrasion; e.g. in conveyor belts by grinding over fixed surfaces, in filter fabrics by mechanical cleaning and in screen printing fabrics by passing a squeegee over the screen surface.

The improvement of mechanical fiber properties by the addition of fillers is known per se.

GB-A-759,374 describes the production of synthetic fibers and films with improved mechanical properties. The claimed process is characterized by the use of very finely divided metal oxides in the form of aerosols. Particle sizes are up to 150 nm specified. As examples of polymers are called viscose, polyacrylonitrile and polyamides.

From EP-A-1,186,628 a polyester raw material containing finely dispersed silica gels is known. The individual particles have diameters of up to 60 nm and aggregates, if present, are not larger than 5 μm. The filler is said to result in polyester fibers having improved mechanical properties, improved color and improved handleability. Notes on applications for these polyester fibers are not apparent from the document.

In US-A-6,544,644 (corresponding to WO-A-01 / 02,629) monofilaments are described, which can be used inter alia in paper machines. The description mainly refers to polyamide monofilaments; In general, polyester raw materials are also mentioned. The described monofilaments are characterized by the presence of nanoscale inorganic materials. These cause an increased abrasion resistance.

EP-A-1,199,389 describes an ethylene glycol dispersion containing aggregates of ceramic nanoparticles, which are suitable for the production of high-strength and transparent polyester moldings.

JP-A-02 / 099,606 discloses a fiber having improved antimicrobial properties containing finely divided zinc oxide / silica particles.

From JP-A-02 / 210,020 a light-resistant polyester fiber is known which contains finely divided ceria.

The hitherto pursued approaches with the use of nanoscale fillers lead to fibers with improved mechanical properties. In general, however, filler additions, in addition to the desired improvement of some Properties at the same time the deterioration of other properties.

It has now surprisingly been found that selected hydrolysis-stabilized polyester raw materials comprising certain nanoscale fillers have a significantly improved abrasion resistance compared to unmodified polyester raw materials without their dynamic load capacity, expressed by the bending resistance is appreciably reduced or even increased by the filler. This property profile was found on selected polyester raw materials.

Based on this prior art, the present invention, the object of the invention to provide filled polyester fibers, which in addition to excellent abrasion resistance compared with the unfilled polyester fibers have comparable or even improved dynamic loads.

Another object of the present invention was to provide transparent fibers having high abrasion resistance and excellent dynamic loadability.

The invention relates to fibers containing aliphatic-aromatic polyester, at least one hydrolysis stabilizer and spherical particles of oxides of silicon, aluminum and / or titanium having an average diameter of less than or equal to 100 nm.

Preference is given to polyester fibers having a content of free carboxyl groups of less than or equal to 3 meq / kg.

These contain a means for occluding free carboxyl groups, for example a carbodiimide and / or an epoxide compound.

Such equipped polyester fibers are stabilized against hydrolytic degradation and are particularly suitable for use in humid-hot environments, especially in paper machines or as a filter.

The fiber-forming polyesters may be of any nature as long as they have aliphatic and aromatic groups and are melt-deformable. Within the scope of this description, aliphatic groups are also to be understood as meaning cycloaliphatic groups.

These thermoplastic polyesters are known per se. Examples of these are polybutylene terephthalate, polycyclohexanedimethyl terephthalate, polyethylene naphthalate or, in particular, polyethylene terephthalate. Building blocks of thread-forming polyesters are preferably diols and dicarboxylic acids, or appropriately constructed oxycarboxylic acids. The main acid constituent of the polyesters is terephthalic acid or cyclohexanedicarboxylic acid, but other aromatic and / or aliphatic or cycloaliphatic dicarboxylic acids may also be suitable, preferably para- or trans-aromatic compounds, e.g. 2,6-naphthalenedicarboxylic acid or 4,4'-biphenyldicarboxylic acid, and isophthalic acid. Aliphatic dicarboxylic acids, e.g. Adipic acid or sebacic acid, are preferably used in combination with aromatic dicarboxylic acids.

Typical suitable dihydric alcohols are aliphatic and / or cycloaliphatic diols, for example ethylene glycol, propanediol, 1,4-butanediol, 1,4-cyclohexanedimethanol or mixtures thereof. Preference is given to aliphatic diols having from two to four carbon atoms, in particular ethylene glycol; furthermore preferred are cycloaliphatic diols, such as 1,4-cyclohexanedimethanol.

Preference is given to using polyesters which have repeating structural units which are derived from an aromatic dicarboxylic acid and a aliphatic and / or cycloaliphatic diol.

Preferred thermoplastic polyesters are in particular selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polypropylene terephthalate, polybutylene terephthalate, polycyclohexane dimethanol terephthalate or a copolycondensate comprising polybutylene glycol, terephthalic acid and naphthalenedicarboxylic acid units.

The polyesters used according to the invention usually have solution viscosities (IV values) of at least 0.60 dl / g, preferably from 0.60 to 1.05 dl / g, particularly preferably from 0.62 to 0.93 dl / g ( measured at 25 ° C in dichloroacetic acid (DCE)).

The nanoscale spherical oxides of silicon, aluminum and / or titanium used according to the invention impart excellent abrasion resistance to the polyester fibers without adversely affecting the dynamic properties, expressed by the bending resistance.

Preferably, spherical silica is used.

The nanoscale spherical oxides of silicon, aluminum and / or titanium used according to the invention typically have average particle diameters (D ₅₀ values) of less than or equal to 50 nm, preferably less than or equal to 30 nm and particularly preferably from 10 to 25 nm.

The polyester raw materials required and filled to produce the fibers according to the invention can be produced in different ways. Thus, polyester, hydrolysis stabilizer and filler and optionally further additives can be melted with the polyester in one Mixing unit, for example in an extruder, mix and the composition is then fed directly to the spinneret or the composition is granulated and spun in a separate step. If appropriate, the resulting granules can also be spun as a masterbatch together with additional polyester. It is also possible to add the nanoscale fillers before or during the polycondensation of the polyester.

Suitable nanoscale fillers are commercially available. For example, the Nyacol® products of Nano Technologies, Inc., Ashland, MA, U.S.A. may be used.

The content of nanoscale spherical filler of the fiber according to the invention can vary within wide ranges, but is typically not more than 5 wt.%, Based on the mass of the fiber. Preferably, the content of nanoscale spherical filler in the range of 0.1 to 2.5 wt.%, In particular from 0.5 to 2.0 wt.%.

The type and amount of components a) and b) are preferably chosen so that transparent products are obtained. In contrast to polyamides, the polyesters used according to the invention are distinguished by transparency. Surprisingly, it has been found that the nanoscale spherical fillers do not adversely affect the transparency. The addition of already about 0.3 wt.% Non-nanoscale titanium dioxide (matting agent), however, causes a complete whitening of the fiber.

Furthermore, it has surprisingly been found that the abrasion resistance of the fibers according to the invention can be further increased by the addition of polycarbonate. Typically, the amount of polycarbonate is up to 5 wt.%, Preferably 0.1 to 5.0 wt.%, Particularly preferably 0.5 to 2.0 wt.%, Based on the total mass of the polymers.

In the context of this description, fibers are to be understood as meaning any fibers.

Examples are filaments or staple fibers, which consist of several individual fibers, but in particular monofilaments.

The polyester fibers according to the invention can be prepared by processes known per se.

• i) Vermischen von Polyestergranulat und kugelförmigen Teilchen aus Oxiden des Siliziums, Aluminiums und/oder Titans mit einem mittleren Durchmesser von kleiner gleich 100 nm,
• ii) Extrudieren des Gemisches enthaltend Polyester und kugelförmige Teilchen durch eine Spinndüse,
• iii) Abziehen des gebildeten Filaments, und
• iv) gegebenenfalls Verstrecken und/oder Relaxieren des gebildeten Filaments.

The invention also provides a process for producing the fibers defined above, comprising the measures:

• i) mixing polyester granules and spherical particles of oxides of silicon, aluminum and / or titanium having an average diameter of less than or equal to 100 nm,
• ii) extruding the mixture containing polyester and spherical particles through a spinneret,
• iii) stripping the formed filament, and
• iv) optionally stretching and / or relaxing the formed filament.

• v) Zuführen von Polyestergranulat, das vor oder während der Polykondensation mit Polyestergranulat mit kugelförmigen Teilchen aus Oxiden des Siliziums, Aluminiums und/oder Titans mit einem mittleren Durchmesser von kleiner gleich 100 nm vermischt worden ist, in einen Extruder,
• ii) Extrudieren des Gemisches enthaltend Polyester und kugelförmige Teilchen durch eine Spinndüse,
• iii) Abziehen des gebildeten Filaments, und
• iv) gegebenenfalls Verstrecken und/oder Relaxieren des gebildeten Filaments.

Another object of the invention is a process for the preparation of the fibers defined above comprising the measures:

• v) feeding polyester granules which have been mixed before or during the polycondensation with polyester granules with spherical particles of oxides of silicon, aluminum and / or titanium having an average diameter of less than or equal to 100 nm, into an extruder,
• ii) extruding the mixture containing polyester and spherical particles through a spinneret,
• iii) stripping the formed filament, and
• iv) optionally stretching and / or relaxing the formed filament.

The hydrolysis stabilizer may already be contained in the polyester raw material, or added before and / or after spinning.

Preferably, the polyester fibers according to the invention are drawn one or more times in the preparation.

Particularly preferably, a polyester produced by solid phase condensation is used in the production of the polyester fibers.

The polyester fibers according to the invention can be present in any desired form, for example as multifilaments, as staple fibers or in particular as monofilaments.

The titer of the polyester fibers according to the invention can likewise vary within wide limits. Examples are 100 to 45,000 dtex, in particular 400 to 7,000 dtex.

Particular preference is given to monofilaments whose cross-sectional shape is round, oval or n-shaped, where n is greater than or equal to 3.

To prepare the polyester fibers of the invention, a commercial polyester raw material can be used. This typically has levels of free carboxyl groups of 15 to 50 meq / kg of polyester. Preference is given to using polyester raw materials produced by solid phase condensation; in these, the content of free carboxyl groups is typically 5 to 20 meq / kg, preferably less than 8 meq / kg of polyester.

For producing the polyester fibers according to the invention, however, it is also possible to use a polyester raw material which already contains the nanoscale, spherical filler. During its preparation, the filler is added during the polycondensation and / or at least one of the monomers.

After pressing the polymer melt through a spinneret, the hot polymer filament is cooled, e.g. in a cooling bath, preferably in a water bath, and then wound up or peeled off. The removal speed is greater than the injection rate of the polymer melt.

The polyester fiber produced in this way is then preferably subjected to a post-drawing, more preferably in several stages, in particular a two- or three-stage post-drawing, with a total draw ratio of 1: 3 to 1: 8, preferably 1: 4 to 1: 6.

After stretching preferably followed by a heat-setting, with temperatures of 130 to 280 ° C are used; It is worked at a constant length or it is slightly re-stretched or it is allowed a shrinkage of up to 30%.

It has proven to be particularly advantageous for the preparation of the polyester fibers according to the invention, if working at a melt temperature in the range of 285 to 315 ° C and at a delay of 1: 2 to 1: 6.

The take-off speed is usually 10 - 80 m per minute.

The polyester fibers according to the invention can be used in addition to nanoscale, spherical filler still contain other auxiliaries. Examples of these are, in addition to the hydrolysis stabilizer already mentioned, processing aids, antioxidants, plasticizers, lubricants, pigments, matting agents, viscosity modifiers or crystallization accelerators.

Examples of processing aids are siloxanes, waxes or longer-chain carboxylic acids or their salts, aliphatic, aromatic esters or ethers.

Examples of antioxidants are phosphorus compounds, such as phosphoric acid esters or sterically hindered phenols.

Examples of pigments or matting agents are organic dye pigments or titanium dioxide.

Examples of viscosity modifiers are polybasic carboxylic acids and their esters or polyhydric alcohols.

The fibers of the invention can be used in all industrial fields. They are preferably used in applications in which increased wear due to mechanical stress is to be expected. Examples include the use in screens or in conveyor belts. These uses are also the subject of the present invention.

The polyester fibers according to the invention are preferably used for the production of fabrics, in particular fabrics, which are used in fabrics.

Another use of the polyester fibers in the form of monofilaments according to the invention relates to their use as conveyor belts or as components of conveyor belts.

Particularly preferred are uses of the fibers of the invention in screens, which are intended for use in the dryer section of paper machines.

These uses are also the subject of the present invention.

Another object of the present invention is the use of spherical particles of inorganic oxides having an average diameter of less than or equal to 100 nm for the production of fibers, in particular monofilaments, with high bending resistance.

The following examples illustrate the invention without limiting it.

General procedure Examples 1 V1 and V2

The components polyethylene terephthalate ("PET") and optionally hydrolysis stabilizer were mixed in the extruder, melted and spun through a 20 hole spinneret with a hole diameter of 1.0 mm at a flow rate of 488 g / min and a take-off speed of 31 m / min to monofilaments , stretched three times with degrees of stretching 1: 4,95; 1: 1.13; and 1: 0.79; and heat-set in the hot air duct at 255 ° C under heat shrinkage. The total draw was 1: 4.52. Monofilaments with a diameter of 0.40 mm were obtained.

The PET used was a type to which different amounts of nanoscale spherical silica had been added during the polycondensation. The mean diameter (D ₅₀ value) of the nanoscale filler was 50 nm.

The hydrolysis stabilizer used was a carbodiimide (Stabaxol® 1, Rheinchemie).

General Procedure Examples 3-7 and V3

Monofilaments were prepared as described in the working instructions of Examples 1, V1 and V2. Different nanoscale fillers were used and a hydrolysis stabilizer was used.

The monofilaments of Example 7 was a Ketttype with (in comparison to the monofilaments of Example 4) comparatively steep course of the force-strain diagram and comparatively low elongation at break. This property profile was adjusted by appropriately stretching and relaxing the monofilaments.

Monofilament according to Example 4: Threefold orientation with draw ratios of 1: 5.0, 1: 1.1 and 1: 0.9 (total draw ratio: 1: 4.8) and heat setting at 185 ° C. with shrinkage admission

Monofilament according to Example 7: Threefold orientation with draw ratios of 1: 4.8, 1: 1.2 and 1: 1.04 (total draw ratio: 1: 5.7) and heat setting in the third draw step at 250.degree

The fiber properties were determined as follows:

Fiber titer according to DIN EN / ISO 2060 Tensile strength according to DIN EN / ISO 2062 Elongation at break according to DIN EN / ISO 2062 Hot air shrinking according to DIN 53843

Dynamic bending test (bending strength): In a rotary head, the test specimen was bent between two metal jaws with a defined bending edge by a rotary movement (double strokes 146 / min) at an angle of 60 ° to the right and left until breakage. A fineness-related preload force of 0.675 cN / dtex was applied to the test sample. The metal baking stood in a distance corresponding to the diameter of the sample, to each other. The bending edge of the metal jaws was exactly predetermined by a fixed radius. The number of bending cycles (number of turns) to break was determined.

Knife scouring test: In a double-stroke movement (60 double strokes / min), the test sample was scrubbed over a length of 70 mm over a ceramic capillary tube. A fineness-related preload force of 0.135 cN / dtex was applied to the test sample. The number of double strokes to break was determined.

Tabelle 2 Beispiel Nr. Füllstoff Füllstoffmenge [Gew. %] Dynamischer Biegetest (Zyklen) Messerscheuertest (Zyklen) 3 kugelförmiges Siliziumdioxid 20 nm 0,4 66736 140233 4 kugelförmiges Siliziumdioxid 50 nm 0,4 114989 181223 5 kugelförmiges Siliziumdioxid 100 nm 0,4 90985 142343 6 kugelförmiges Aluminiumoxid 50 nm 0,04 16238 65822 7 kugelförmiges Siliziumdioxid 50 nm 0,4 49673 102986 V3 Nanoton (nicht spärisch) 0,1 272 19929 Tables 1 and 2 below show the composition and properties of the monofilaments.

<u> Table 2 </ u> Example no. filler Amount of filler [wt. %] Dynamic bending test (cycles) Knife scouring test (cycles) 3 spherical silica 20 nm 0.4 66736 140233 4 Spherical silica 50 nm 0.4 114989 181223 5 spherical silica 100 nm 0.4 90985 142343 6 Spherical alumina 50 nm 0.04 16238 65822 7 Spherical silica 50 nm 0.4 49673 102986 V3 Nanoton (not sparse) 0.1 272 19929

Claims (17)

Fiber containing aliphatic-aromatic polyester, at least one hydrolysis stabilizer and spherical particles of oxides of silicon, aluminum and / or titanium with an average diameter of less than or equal to 100 nm. A fiber according to claim 1, characterized in that the polyester has repeating structural units derived from an aromatic dicarboxylic acid and an aliphatic and / or cycloaliphatic diol, in particular recurring polyethylene terephthalate units, optionally in combination with other repeating structural units derived from alkylene glycols and aliphatic dicarboxylic acids. Fiber according to Claim 1, characterized in that the aliphatic-aromatic polyester has a content of free carboxyl groups of less than or equal to 3 meq / kg. A fiber according to claim 3, characterized in that the hydrolysis stabilizer is at least one carbodiimide and / or at least one epoxy compound. Fiber according to claim 1, characterized in that the spherical particles consist of silicon dioxide. Fiber according to Claim 1, characterized in that the oxide of silicon, aluminum and / or titanium has an average diameter of less than or equal to 50 nm, in particular less than or equal to 30 nm. Fiber according to claim 1, characterized in that its content of oxide of silicon, aluminum and / or titanium is 0.1 to 5 wt.%, Preferably 1 to 2 wt.%, Based on the mass of the fiber. Fiber according to Claim 1, characterized in that it contains, in addition to the aliphatic-aromatic polyester, from 0.1 to 5% by weight, preferably from 0.5 to 2% by weight, based on the total mass of the polymers, of polycarbonate. Fiber according to claim 1, characterized in that it is transparent. Fiber according to claim 1, characterized in that it is a monofilament. Process for producing the fibers according to claim 1 comprising the measures: i) mixing polyester granules with spherical particles of oxides of silicon, aluminum and / or titanium having an average diameter of less than or equal to 100 nm, ii) extruding the mixture containing polyester and spherical particles through a spinneret, iii) stripping the formed filament, and iv) optionally stretching and / or relaxing the formed filament. Process for producing the fibers according to claim 1 comprising the measures: v) feeding polyester granules, before or during the polycondensation with polyester granules with spherical particles of oxides of silicon, aluminum and / or Titans having a mean diameter of less than or equal to 100 nm is mixed in an extruder, ii) extruding the mixture containing polyester and spherical particles through a spinneret, iii) stripping the formed filament, and iv) optionally stretching and / or relaxing the formed filament. Method according to one of claims 11 or 12, characterized in that the polyester fiber is drawn one or more times. Method according to one of claims 11 or 12, characterized in that a polyester produced by solid phase condensation is used for the production of the polyester fiber. Use of fibers according to claim 1 for the production of screens or conveyor belts. Use according to claim 15, characterized in that the sieves are intended for use in the dryer section of paper machines. Use of spherical particles of oxides of silicon, aluminum and / or titanium with an average diameter of less than or equal to 100 nm for producing fibers, in particular monofilaments, with high bending resistance.