EP1838907B1 - Method for producing polyoxymethylene fibres and use of such fibres - Google Patents

Description

The present invention relates to a process for the production of polyoxymethylene fibers with high Wiederaufrichtungsvermögen, in particular monofilaments, which can be used in particular as bristles in brushes, brooms and brushes of all kinds.

Polyoxymethylene (hereinafter also referred to as "POM") is a high performance polymer with good mechanical properties and excellent chemical resistance. Moldings made of POM are characterized by high crystallinity and high moduli of elasticity.

There are already known fibers of POM, which are characterized by good mechanical properties, for example, by high strength and high moduli of elasticity, and are highly stretched after their preparation in order to fully exploit the potential of the material.

From the DE-A-1 660 287 For example, a method of making high molecular weight linear POM filaments is known. This involves preparing a spinning solution of a certain viscosity and spinning this solution by the dry or wet spinning process into POM filaments, which are then subjected to drawing on a heating stirrup. Typical draw ratios are around 1:10.

The JP-A-01 / 172.821 describes the production of POM fibers by melt spinning. The process comprises melting the raw material and spinning under defined conditions and carrying out at least a 1: 4 draw at defined input and output speeds. The process is characterized by high productivity and high-strength POM filaments are produced. EP-A-1,321,546 describes the production of high-strength and high-modulus POM split fibers. For this purpose, a film is produced using selected POM copolymers with defined viscosities. By selecting the raw material, the crystallization rate can be controlled and stable film formation and controlled stretching of the film is possible.

In EP-A-1,431,428 describes high-strength and high-modulus POM fibers. These are obtained by melt spinning using POM copolymers of selected crystallization rate. Again, by the selection of the raw material controlled stretching is possible, so that fibers are produced with very high tensile strengths.

The known developments have hitherto aimed at the production of POM fibers with the highest possible tensile strengths and moduli of elasticity. However, such fibers have low elasticity and transverse strength, resulting in low knot strength and poor recovery after bending or buckling.

Starting from this prior art, it is an object of the present invention to provide fibers with excellent resilience expressed by their Wiederaufrichtungsvermögen.

Another object of the present invention is to provide bristles which are excellent for use in paintbrushes, brooms or brushes of all kinds and whose abrasion resistance is excellent in comparison with bristles of other materials.

Another object of the present invention is to provide a process for producing these POM fibers which is characterized by high productivity.

An example of applications in which the combination of high mechanical and chemical stresses is present is the use of monofilaments or Bristles in brushes, such as scrub brushes or in particular toothbrushes. 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 chemicals.

• i) Extrudieren einer Schmelze enthaltend Polyoxymethylen-Copolymer mit einem Schmelzindex MVR (ermittelt nach ISO 1133 bei 190°C und einer Belastung von 2,16 kg) von 0,3 bis 30 ml/10 min durch eine Spinndüse,
• ii) Einbringen des gebildeten Filaments in ein Flüssigkeitsbad, das eine Temperatur von weniger als 150°C aufweist, iii) Abziehen des gebildeten Filaments,
• iv) ein- oder mehrfaches Verstrecken mit einem gesamten Verstreckverhältnis von nicht mehr als 1:6, und
• v) gegebenenfalls Erhitzen des verstreckten Filaments unter Zulassung von Schrumpf.

The present invention relates to a process for the production of fibers containing polyoxymethylene copolymers having a melt index MVR (determined according to ISO 1133 at 190 ° C and a load of 2.16 kg) of 0.3 to 30 ml / 10 min, which is a Wiederaufrichtungsvermögen , measured by the double loop method in air and / or water, of not less than 125 °, comprising the measures:

• i) extruding a melt containing polyoxymethylene copolymer having a melt index MVR (determined according to ISO 1133 at 190 ° C and a load of 2.16 kg) of 0.3 to 30 ml / 10 min through a spinneret,
• ii) introducing the formed filament into a liquid bath having a temperature of less than 150 ° C, iii) stripping the formed filament,
• iv) single or multiple stretching with a total draw ratio of no more than 1: 6, and
• v) optionally heating the drawn filament while allowing for shrinkage.

All polyoxymethylene copolymers are suitable for the production of the fibers according to the invention, provided that they have the mentioned melt indices.

Examples of suitable polyoxymethylene copolymers can be found in the EP-A-1,431,428 and in the 1,321,546 ,

In the polyoxymethylenes (POM), as used for example in the DE-A-29 47 490 In general, they are straight-chain linear polymers which generally contain at least 80%, preferably at least 90%, oxymethylene units (-CH ₂ -O-).

The term polyoxymethylene in this case comprises copolymers of formaldehyde or its cyclic oligomers, such as trioxane or tetroxane, with monomers copolymerizable therewith.

Copolymers are thus polymers derived from formaldehyde and / or its cyclic oligomers, in particular trioxane, and cyclic ethers, cyclic acetals and / or linear polyacetals. The hydroxyl end groups of these copolymers are chemically stabilized against degradation in a conventional manner, for. B. by esterification or by etherification.

Such POM copolymers are known per se to the person skilled in the art and described in the literature.

In general, these polymers have at least 50 mole percent of recurring units -CH ₂ -O- in the polymer backbone. The POM copolymers are generally prepared by copolymerization of formaldehyde or trioxane with suitable comonomers, preferably in the presence of suitable catalysts.

enthalten, wobei R¹ bis R⁴ unabhängig voneinander ein Wasserstoffatom, eine C₁-bis C₄-Alkylgruppe oder eine halogensubstituierte Alkylgruppe mit 1 bis 4 C-Atomen und R⁵ eine -CH2-, -O-CH₂-, eine C₁- bis C₄-Alkyl- oder C₁- bis C₄- Haloalkyl substituierte Methylengruppe oder eine entsprechende Oxymethylengruppe darstellen und n einen Wert im Bereich von 0 bis 3 hat.To prepare the fibers according to the invention, preference is given to POM copolymers which, in addition to the repeating units -CH ₂ -O-, also contain up to 50, preferably from 0.1 to 20 and in particular 0.5 to 10 mol% of recurring units

wherein R ¹ to R ^{4 are} independently a hydrogen atom, a C _{1 to} C ₄ alkyl group or a halogen-substituted alkyl group having 1 to 4 carbon atoms and R ^{5 is} a -CH ₂ -, -O-CH ₂ -, a C ₁ to C ₄ alkyl or C ₁ to C ₄ haloalkyl substituted methylene group or a corresponding oxymethylene group and n has a value in the range of 0 to 3.

wobei R¹ bis R⁵ und n die obengenannte Bedeutung haben.Advantageously, these groups can be introduced into the copolymers by ring opening of cyclic ethers. Preferred cyclic ethers are those of the formula

wherein R ¹ to R ⁵ and n have the abovementioned meaning.

For example, only ethylene oxide, 1,2-propylene oxide, 1,2-butylene oxide, 1,3-butylene oxide, 1,3-dioxane, 1,3-dioxolane, 1,3-dioxepane and 1,3,6-trioxacyclo-octane as cyclic ethers and linear oligo- or polyformals, such as polydioxolane or polydioxepane, called comonomers.

Copolymers of 99.5-95 mol% of trioxane and 0.5 to 5 mol% of one of the abovementioned comonomers are particularly advantageously used.

Processes for the preparation of the above-described POM copolymers are known to the person skilled in the art and described in the literature.

The POM copolymers preferably used have melting points of at least 140 ° C and molecular weights (weight average) M _w in the range of 5,000 to 200,000, preferably from 7,000 to 150,000.

End-group-stabilized POM copolymers which have C-C bonds or the methoxy end groups at the chain ends are particularly preferably used to prepare the fibers according to the invention.

The POM copolymers used to prepare the fibers according to the invention have a melt index (MVR value 190 / 2.16) of 0.3 to 30 ml / 10 min (ISO 1133), preferably an MVR value of 1 to 10 ml / 10 min and most preferably an MVR value of 1 to 3 ml / 10 min.

Preferred POM copolymers have in addition to recurring oxymethylene groups 0.5 to 10 mol%, preferably 1 to 5 mol% and in particular 1.5 to 4 mol%, of structural units derived from comonomers. The latter are usually comonomers which are only bifunctional, that is, which can not form branches or crosslinks. The POM copolymers used according to the invention are therefore in the essentially linear and are characterized by a high crystallization half-life.

Typical crystallization half-lives of the POM copolymers used according to the invention are at least 30 seconds, determined by cooling from 200 ° C to a temperature which is usually 10 ° C below the melting temperature of the respective POM copolymer, at a cooling rate of 80 ° C / minute and maintaining that temperature at that observation temperature. The determination of the time takes place from reaching the observation temperature.

Preferred POM copolymers have no or as few constituents as possible, which can accelerate the crystallization behavior. These include inorganic or organic nucleating agents, nucleating POM terpolymers or impurities resulting from the preparation of the POM copolymer. The latter can preferably be removed by reprecipitation, wherein the POM copolymer preferably in a water methanol mixture, which may contain other components such as trioxane, formaldehyde, amines, etc., under pressure, preferably between 1 bar and 50 bar, at temperatures of 100 ° C. to 250 ° C, preferably from 140 ° C, more preferably from 150 ° C to 200 ° C is dissolved. This process is also referred to as solution hydrolysis.

Particularly preferably used POM copolymers have, in addition to recurring oxymethylene groups of the formula I, 0.5 to 10 mol%, preferably 1 to 5 mol% and in particular 1.5 to 3 mol%, of oxyalkylene groups of the forms II,

- [CH ₂ -O] - (I),

- [(CH ₂ ) _m -O] _y - (II),

wherein m is an integer from 2 to 4, preferably 2, and y is 1 or 2.

The determination of the MVR value of the polyoxymethylene copolymers used according to the invention is carried out according to ISO 1133: 190 ° C / 2.16 kg

The determination of the crystallization half-life and the Wiederaufricht-ability of the fibers of the invention is carried out as described in the following examples.

Preferred polyoxymethylene copolymer fibers are derived from polyoxymethylene copolymers whose crystallization half-life is at least 100 seconds, most preferably at least 150 seconds.

Preferred polyoxymethylene copolymer fibers have a recovery capacity, measured by the double loop method in air and / or water, of at least 130 °.

The polyoxymethylene copolymer fibers typically have a tensile strength, determined according to DIN 53834-1 (tensile test on monofilaments), of up to 45 cN / tex, more preferably up to 40 cN / tex.

The polyoxymethylene copolymer fibers typically have an elongation at break, determined according to DIN 53834-1 (tensile test on monofilaments), of up to 100%, particularly preferably 25 to 100% and very particularly preferably from 30 to 100%.

For the purposes of this description, POM copolymer fibers are to be understood as meaning any POM copolymer-containing fibers.

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

Important for achieving the property profile is the use of a certain POM raw material and a not too high draw ratio.

In a preferred embodiment of the method according to the invention, the filament formed is drawn several times.

The fibers can be present in any desired form, for example as multifilaments, as staple fibers or in particular as monofilaments.

The titer of the fibers can vary widely. 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 produce the fibers, a polyoxymethylene raw material stabilized against thermal degradation is used, which may optionally contain further additives customary for POM molding compounds.

Examples of stabilizers are antioxidants, acid scavengers, formaldehyde scavengers, and / or UV stabilizers.

Examples of further additives customary for POM molding compounds are adhesion promoters, lubricants, mold release agents, fillers, such as glass beads, calcium carbonate, talc, wollastonite or silica; Reinforcing materials, such as carbon fibers, aramid fibers or glass fibers, antistatic agents or additives, which give the molding composition a desired property, such as dyes and / or pigments and / or impact modifiers and / or electrical conductivity-imparting additives, e.g. Carbon black or metal particles, as well as mixtures of these additives, but without limiting the scope of the examples mentioned.

The proportion of these stabilizers and additives in the fibers according to the invention is usually 0.2 to 30 wt.%, Preferably 0.5 to 25 wt.%, Based on the mass of the fibers.

After pressing the polymer melt through a spinneret, the hot polymer filament is cooled by introduction into a liquid bath. The liquid bath has a temperature of less than 150 ° C; the temperature of the liquid bath can vary within wide ranges, for example from -80 ° C to 150 ° C, preferably 20 ° C to 90 ° C. It can be used different cooling liquids, preferably water or a mixture of water and alcohol. Instead of a cooling bath, the filament can also be passed through different cooling baths. The cooled filament is withdrawn from the cooling bath
and optionally subsequently wound up. The removal speed is greater than the injection rate of the polymer melt.

The fiber thus produced is subsequently subjected to post-drawing, particularly preferably in several stages, in particular a two- or three-stage post-drawing, with a total draw ratio of up to 1: 6, in particular from 1: 2 to 1: 6, preferably from 1: 4 to 1 : 6, subjected. Stretching can be done on heated godets, by passing over a heated iron and / or by passing the filament through an infrared tunnel or a heating bath. The temperature during stretching is preferably 150 to 190 ° C, particularly preferably 170 to 180 ° C.

After stretching preferably followed by a heat-setting, typically temperatures of 150 to 200 ° C are used; It works at a constant length or shrinkage is allowed.

It has proved to be particularly advantageous for the production of the fibers when working at a melt temperature in the range from 180 to 230.degree.

The polyoxymethylene fibers are used in particular in the form of monofilaments or bristles in a wide variety of applications. Preferred applications include toothbrushes, hair brushes, artist and writing brushes, technical brushes, paintbrushes and painters brushes, paint rollers and ink pads, cosmetic brushes, cleaning brushes and brooms for street and household and brushes and brushes for body care.

These uses are also the subject of the present invention.

In the figure, the production process of the monofilaments according to the invention is outlined.

Plastic granules (1) are melted in an extruder (2) and pressed through a melt pump (4) through the fine opening of a nozzle plate (5). The extruded filament (8) is passed through a tempered water bath (7) and, before being wound between stretching units (10, 13, 16), drawn in heating furnaces (11, 14) in order to achieve the necessary parallel alignment of the molecules. The furnace temperatures and the stretching ratios between the individual stretching units are of crucial importance for the property profile of the monofilament produced.

Some process parameters and properties of the obtained monofilaments are shown in the table below. In the experiments, a POM copolymer was used, which was characterized by the following sizes:

Crystallization half-life: The crystallization of thin, melted at 200 ° C POM films (layer thickness 10-100 microns) was followed after rapid cooling to the respective observation temperature under the polarizing microscope with a photocell. The crystallization half-life resulted from the time between the optically detectable onset of crystallization and the achievement of half the maximum light intensity. As an observation temperature T _b at a temperature of T _b = was selected for T _m -10K POM polymers with melting points T _m. For POM types with melting points of 162 ° C, T _{b was} 152 ° C.

MVR value: determined in accordance with ISO 1133 (MVR 190 ° C / 2.16 kg)

Rebuild Capacity: Characterization was by the double loop method. For this purpose, the samples were conditioned for 24 hours in a fully air-conditioned measuring room at 23 ° C. and a relative humidity of 50% (in accordance with DIN 50014-23 / 50-1 of 07/85).

To carry out the measurement, five individual filaments having a length of 600 ± 2 mm were cut. From the individual threads, two threads of 300 mm in length were cut, these threads were knotted into two loops hanging one inside the other. A loop was hung on the hook of a tripod while the second loop was hung with the weight calculated according to the formula below. The load duration was 5 minutes. Due to the load a buckling was achieved by 180 °, wherein the radius of curvature coincided with the thread radius. After the relief, the loops were cut open 5 cm from the kink. The section of the first loop was relaxed on a glass plate in the air for five minutes. Immediately after the five minutes, the rising angle was determined with a protractor. The portion of the second loop was relaxed for five minutes at room temperature in a water bath. At the end of the five minutes The thread was removed from the water bath, placed on a glass plate and there the rising angle determined with a protractor.

G = Belastungsgewicht in Gramm
d = Faserdurchmesser in mm Tabelle Beispiel Nr. Reckwerk 1 (m/min) Ofen 1 (°C) Reckwerk 2 (m/min) Ofen 2 (°C) Verstreckung Zugspannung (N/mm²) Festigkeit (cN/tex) Dehnung (%) Wiederauf richtung in Luft (Grad) Wiederaufrichtung in Wasser (Grad) Durchmesser (mm) V1 12 180 126 190 10,96 875 62,0 26,7 95 97 0,156 V2 16 173 114 180 7,13 762 54,4 27,5 106 110 0,139 V3 16 175 110 175 6,88 733 52,4 25,9 109 113 0,142 4 27 175 150 175 5,56 569 40,6 33,2 129 131 0,139 5 20 175 110 175 5,50 466 33,3 33,3 129 132 0,142 6 18 175 100 175 5,56 326 23,2 34,7 130 133 0,139 7 16 175 90 175 5,63 222 15,9 46,0 131 132 0,137 8 18 180 96 180 5,33 230 16,4 46,7 131 133 0,145 9 18 175 100 175 5,56 353 25,2 38,5 131 134 0,148 The load was calculated according to the following formula: $$\mathrm{G}\mathrm{=}\frac{{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="imgf0001.png"\; state="\{\{state\}\}">d</figure-callout>}}^{\mathrm{2}}\mathrm{*}\mathrm{\pi }\mathrm{*}\mathrm{1280}\mathrm{*}\mathrm{2}}{\mathrm{4}}$$

G = load weight in grams
d = fiber diameter in mm table Example no. Stretching unit 1 (m / min) Oven 1 (° C) Reach 2 (m / min) Oven 2 (° C) stretching Tensile stress (N / mm ² ) Strength (cN / tex) Strain (%) Reconstruction in air (degrees) Reconstruction in water (degrees) Diameter (mm) V1 12 180 126 190 10.96 875 62.0 26.7 95 97 0.156 V2 16 173 114 180 7.13 762 54.4 27.5 106 110 0,139 V3 16 175 110 175 6.88 733 52.4 25.9 109 113 0,142 4 27 175 150 175 5.56 569 40.6 33.2 129 131 0,139 5 20 175 110 175 5.50 466 33.3 33.3 129 132 0,142 6 18 175 100 175 5.56 326 23.2 34.7 130 133 0,139 7 16 175 90 175 5.63 222 15.9 46.0 131 132 0,137 8th 18 180 96 180 5.33 230 16.4 46.7 131 133 0.145 9 18 175 100 175 5.56 353 25.2 38.5 131 134 0.148

Claims (16)

1. Method for manufacturing fibres comprising polyoxymethylene copolymers having a melt index MVR of 0.3 to 30 ml/10 min, determined according to ISO 1133 at 190°C and a load of 2.16 kg, that have a re-erecting capacity of at least 125°, measured according to the double loop method in air and/or water, comprising the measures of:

   i) extruding a melt through a spinning nozzle, the melt comprising polyoxymethylene copolymer with a melt index MVR of 0.3 to 30 ml/10 min determined according to ISO 1133 at 190°C and a load of 2.16 kg,

   ii) introducing the formed filament into a liquid bath, which has a temperature of less than 150 °C,

   iii) stripping the formed filament,

   iv) single or multiple stretching with an overall stretching ratio of not more than 1:6, and

   v) optionally, heating the stretched filament allowing shrinkage.
2. Method for manufacturing the fibres according to claim 1 comprising precipitating the polyoxymethylene copolymer under pressure at a temperature from 150°C to 200°C.
3. Method according to claim 1 or 2, characterized in that the fibres comprise polyoxymethylene copolymers, which have melting points of at least 140°C and molecular weights (weight average value) M_w in the range from 5.000 to 200.000.
4. Method according to at least any one of claims 1 to 3, characterized in that the fibres comprise polyoxymethylene copolymers, which have a melt index (MVR value of 190/2.16) from 1 to 10 ml/min.
5. Method according to at least any one of claims 1 to 4, characterized in that the fibres comprise polyoxymethylene copolymers, which besides recurring oxymehtylene groups have 0.5 to 10 mol% of structured units that are derived from comonomers.
6. Method according to at least any one of claims 1 to 5, characterized in that the fibres comprise polyoxymethylene copolymers, the crystallization half-value period thereof being at least 30 seconds, determined by cooling from 200°C to a temperature that is 10°C below the melting temperature of the respective POM-copolymer, at a cooling rate of 80°C/minute and maintaining this temperature at this observation temperature.
7. Method according to at least any one of claims 1 to 6, characterized in that the fibres do not comprise nucleating agents.
8. Method according to at least any one of claims 1 to 7, characterized in that the fibres comprise polyoxymethylene copolymers hydrolysed from solution.
9. Method according to at least any one of claims 1 to 8, characterized in that the fibres comprise polyoxymethylene copolymers, which besides recurring oxymethylene groups of the formula I have 0.5 to 10 mol% of oxyalkylene groups of the formula II
   
           -[CH₂-O]-     (I),
   
           -[(CH₂)_m-O]_y-     (II),
   
   wherein m is an integer from 2 to 4, preferably 2, and y stands for 1 or 2.
10. Method according to at least any one of claims 1 to 9, characterized in that the fibres have a re-erecting capacity of at least 130° measured according to the double loop method in air and/or water.
11. Method according to at least any one of claims 1 to 10, characterized in that the fibres have a tensile strength of up to 45cN/tex determined according to DIN 53834-1.
12. Method according to at least any one of claims 1 to 11, characterized in that the fibres have an elongation at break of up to 100% determined according to DIN 53834-1.
13. Method according to at least any one of claims 1 to 12, characterized in that the fibres are monofilaments.
14. Method according to at least any one of claims 1 to 13, characterized in that the fibres have a yarn count from 100 to 45000 dtex.
15. Use of fibres in paintbrushes and brushes, the fibres comprising polyoxymethylene copolymers with a melt index MVR of 0.3 to 30 ml/10 min (determined according to ISO 1133 at 190°C and a load of 2.16 kg) that have a re-erecting capacity of at least 125° measured according to the double loop method in air and/or water.
16. Use according to claim 15, characterized in that the fibres are used in the form of monofilaments in toothbrushes, hairbrushes, artist and writing brushes, technical brushes, painting brushes, rollers and pads, cosmetic brushes, cleaning brushes for the street and household as well as in brushes for personal hygiene.

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