EP1453995B1 - Method for making propylene monofilaments, propylene monofilaments and their use - Google Patents

Description

The invention relates to a process for the production of polypropylene monofilaments having a melt viscosity index (MFI) 230 ° C / 2.16 kg of 2 to 16 g / 10 min, which have a diameter greater than 0.050 mm and improved abrasion resistance; it also relates to monofilaments of this polypropylene, as well as their use.

Two-dimensional polypropylene textile articles are of great interest as chemically and mechanically resistant filter media for filtration in the chemical, pharmaceutical and food industries. In this field, relatively coarse monofilaments with a diameter greater than 0.050 mm are mainly required.

Pure polypropylene monofilaments have the disadvantage of forming a lot of dust due to the low resistance of this substance to abrasion during the weaving process. The problem of abrasion is also known for other thermoplastics. This is how the EP-A2-0 784 107 mentions melt-spun monofilaments of polyamide, polyester or polypropylene for use in the fabrics of paper machines and wire edgers. According to this patent, abrasion resistant monofilaments are obtained using 70 to 99% by weight of fibrogenic polymer and 1 to 30% by weight of a polyethylene / polypropylene rubber, modified with maleic anhydride. , and other additives. However, the examples are limited, as regards the fibrogenic polymer, polyamide 6 and polyethylene terephthalate, and a copolyamide of PA66 and PA6. The spinning speeds are not specified.

Thanks to the' EP-A-1059370 there is also known a method of manufacturing polypropylene multifilament for textile applications. As the starting material, a metallocene-catalyzed isotactic polypropylene is used whose melt viscosity index must be greater than 19 g for 10 minutes in order to achieve the desired shrinkage characteristics. Indeed, to obtain a low shrinkage, high values of the MFI are necessary. Multifilaments FOY (Fully Oriented Yarns) of 10 dpf (= denier per filament) [0.03953 mm] and POY (Partially Oriented Yarns [= partially oriented yarns]) of 2 dpf (= deniers per fiber) [0.01768 mm]. As far as manufactured yarns are concerned, only general indications are given. There are no described monofilaments.

The problem of the invention is to provide an economic method of manufacturing polypropylene coarse monofilaments, resistant to abrasion. Another problem of the invention is to manufacture coarse monofilaments of polypropylene, which exhibit improved resistance to abrasion during weaving.

Still another problem is to provide the use of coarse monofilaments with good abrasion resistance, for the manufacture of two-dimensional technical articles, especially for filtration.

The problem is solved according to the invention by adding to the polypropylene 20 to 0.01% by weight of an additive upstream of the extruder, the melt is spun into a water bath, stretch it and coil it.

As polypropylene, a homopolymer having a melt viscosity index of more than 2 g / 10 min, preferably 6 to 13 g / 10 min, in particular 12 to 13 g / 10 min, is preferably used. An MFI of more than 16 g / 10 min has the disadvantage of poor mechanical characteristics and poor abrasion resistance.

It is appropriate to use an additive consisting of a combination of lubricant, filler and heat stabilizer. As a combination of lubricant, filler and heat stabilizer, 0.5 to 1.2% by weight of polyethylene waxes, calcium carbonate and sterically hindered phenols have proved to be particularly suitable.

In another variant, it is suitable to use as an additive 0.05 to 1.0% by weight, in particular 0.3 to 1.0% by weight, of a lubricant. Particularly suitable lubricants are metal salts of carboxylic acids, linear or branched hydrocarbons, fluorinated elastomers and polydimethylsiloxanes.

In yet another variant, it is appropriate to use fillers as additives. As fillers, 0.01 to 0.1 wt.% Aerosols and 0.1 to 1.0 wt.% Calcium carbonate were found to be particularly suitable.

In yet another variant, it is appropriate to use as additive 0.1 to 0.8% by weight of a thermal stabilizer. Sterically hindered phenols, phosphites and phosphonites have proved particularly suitable.

In yet another variant, it is appropriate to use as additive 1 to 20% by weight of a polypropylene / polyethylene copolymer having a melting point ≥ 140 ° C.

It is appropriate that the monofilaments have a strength of at least 50 cN / tex, for an elongation corresponding to the maximum tensile stress (elongation at break) of less than 35%, preferably less than 30%. Indeed, a strength of less than 50 cN / tex has the disadvantage of multiplying the breakages of yarn during the weaving process.

It is also important that the monofilaments have an abrasion of less than 0.05%. Indeed, when the abrasion is greater than 0.05%, irregularities occur during weaving, due to too fast fouling of the combs. This makes it necessary to shorten the intervals between cleanings, which decreases the productivity of the trade.

It is appropriate that the monofilaments are characterized by a relative breaking energy> 100% after treatment of 24 hours at 120 ° C, in particular after aging in an oven. This has the advantage of increasing the life of the filters, when subjected to a relatively high thermal load and aggressive chemicals.

The monofilaments according to the invention are particularly suitable for the manufacture of two-dimensional articles intended for filtration in the chemical, pharmaceutical and food industries.

The invention will now be described in more detail by way of examples.

Polymer

As fibrinogen polymers, five commercially available polypropylenes were used in the tests, whose melt viscosity index (MFI) 230 ° C / 2.16 kg ranged from 6.0 to 13.0 g / ml. 10 minutes. 50 kg of polypropylene granulate are mixed each time, using drums of 100 kg and an eccentric mixer. The mixing is effected, depending on the additive, according to two different methods. The different methods are explained in the examples. The granulated / additive mixture is admitted directly into the extruder and melted. Conditions of spinning Extruder: diameter: 40 mm; cylinder length: UD = 25 Extruder pressure: 80 bar flow rate: 19.76 kg / h 5 heating zones Spin pump: cubic capacity: 10 cm ³ / revolutions Spinning block: with electric heating Titration pump: 23.19 rpm Filières: diameter: 0.7 mm capillary length: 3 x D Water bath: distance between die and water bath: 45 mm temperature: 30 ° C

Drawing benches and heating channels

• Drawing bench 1: 7 slabs; diameter of the slabs: 230 mm; 1 heating channel
• Drawbench 2: 7 slabs; diameter of the slabs: 230 mm; 1 heating channel
• Drawbench 3: 7 slabs; diameter of the slabs: 230 mm; 2 heating channels
• Drawing bench 4: 4 slabs; diameter of the slabs: 230 mm

Preparation of spinning

• 5% aqueous solution

Sample preparation Examples 2, 5, 6 and 7

In the case of powdery additives, such as fillers, lubricant, heat stabilizer, etc., the granules are first rolled for half an hour in an adhesive, such as Baysilon M 100® (trademark of Bager AG), then add the rest of the additives and mix for another 1.5 hours.

Example 4

In the case of the modified polyolefins, the mixture of granules consisting of polypropylene and PP / PE modified polyolefin, melting point> 140 ° C., is mixed for one hour.

The examples have been summarized in Table 1. Table 1 Example additives Diameter [mm] Resistance [cN / tex] Elongation corresponding to the maximum tensile force [%] Specific breaking energy [cN.cm/dtex] Mechanical constant [cN / tex] Regularity of the title [U%] Relative breaking energy in the case of drying in an oven 24h / 120 ° C Abrasion [%] 1 0 0,159 55.6 18.4 0.349 238.5 2.43 77.3 .1717 2 0.15 / 0.3 / 0.3 0,160 57.7 19.3 0.373 253.5 1.66 183.6 0.0156 5 3 0 0,160 54.7 19.1 0.354 239.1 1.80 76.2 .5543 4 10 0,159 51.1 19.1 0.329 223.3 1.82 180.2 0.0254 5 0.5 0,160 54.8 17.9 0.334 231.8 2.60 69.0 0,017 6 0.15 / 0.15 0,159 55.3 18.2 0.344 235.9 2.16 68.3 0,018 7 0.15 / 0.3 / 0.3 5 0,159 55.6 18.6 0.356 239.8 2.31 71.0 8 0 0,160 54.3 19.1 0.35 237.1 1.94 139.8 0.0128 9 0 0,160 56.3 19.4 0.37 248.0 1.67 103.3 0.0386 * Breakdown energy as a percentage of the initial value
Example 1 (Reference Example 1): MFI polypropylene 13.0 g / 10 min
Example 2: Polypropylene with MFI of 6.0 g / 10 min, with a combination as an additive
Example 3 (Reference Example 2): MFI Polypropylene 12.0 g / 10 min
Example 4: MFI polypropylene 12.0 g / 10 min, with PP / PE melting point> 140 ° C as additive
Example 5: MFI polypropylene of 13.0 g / 10 min, with a lubricant as an additive
Example 6: MFI polypropylene of 13.0 g / 10 min, with a combination of heat stabilizers as additive
Example 7: MFI polypropylene of 13.0 g / 10 min, with a combination as an additive
Example 8: MFI polypropylene of 13.0 g / 10 min, with anti-gas fading stabilization
Example 9: Polypropylene with MFI of 9.0 g / 10 min, with stabilization anti-gas fading

To allow more detailed explanations, the results are represented graphically and photographically.

• la Fig. 1 montre un graphique en colonnes indiquant l'énergie de rupture spécifique, le vieillissement en étuve et l'abrasion en fonction de l'addition d'un additif selon l'exemple 2;
• -la Fig. 2 montre le comportement à l'abrasion en fonction de l'addition d'un additif selon l'exemple 4;
• la Fig. 3a montre le comportement à l'abrasion en fonction de l'addition d'un additif et du métrage fabriqué, selon l'exemple de référence (exemple 1);
• la Fig. 3b montre le comportement à l'abrasion en fonction de l'addition d'un additif et du métrage fabriqué, selon l'exemple de réalisation (exemple 8).

Right here,

• FIG. 1 shows a column chart indicating the specific breaking energy, oven aging and abrasion as a function of the addition of an additive according to Example 2;
• FIG. 2 shows the abrasion behavior as a function of the addition of an additive according to Example 4;
• FIG. 3a shows the abrasion behavior as a function of the addition of an additive and the metric produced, according to the reference example (example 1);
• FIG. 3b shows the abrasion behavior as a function of the addition of an additive and the production made, according to the embodiment example (Example 8).

In FIG. 1, the pair of columns on the left represents the specific energy of rupture, that of the medium aging in an oven and that of the right abrasion, as a function of the addition of an additive according to Example 2. The columns of left reflect the state of the art, those on the right represent the results obtained with the monofilaments according to the invention. This figure shows, with regard to abrasion, an improvement of more than 100%. However, 100% less abrasion means at least a twice as long operation time for the loom, before it needs cleaning. Similar results are obtained for the relative breaking energy. Here, the right column of the pair of middle columns also shows an improvement of more than 50%. The specific breaking energy, indicated by the right column of the pair of columns on the left, also shows an improvement over the state of the art.

Fig. 2 differs from FIG. 1 in that it indicates the abrasion as a function of the addition of an additive according to Example 4.

Fig. 3a shows photographs showing the condition of the combs of a loom after making 100 m, 200 m and 300 m of fabric using pure polypropylene monofilament [reference test (Example 1)]. The fouling by the polypropylene down after 300 m is so important that it was necessary to stop the trade.

Fig. 3b shows photographs showing the condition of the combs of a loom after making 100 m, 200 m and 300 m of fabric using the monofilament according to the invention [embodiment example (Example 8)]. Even after making 300 m of fabric, the quantity of down produced remains lower than that obtained for 100 m in the reference example.

Measurement methods:

• Indice de viscosité en fondu selon ASTM D1238
• Détermination du titre selon SN 197 012 et SN 197 015, complétées par DIN 53830
• Le calcul de la constante mécanique CM est réalisé selon la formule suivante: $$\mathrm{CM}\mathrm{=}\sqrt{\mathrm{D}}\mathrm{\cdot }\mathrm{F}\left[\mathrm{cN}\mathrm{/}\mathrm{tex}\right]$$
  

où D désigne l'allongement en [%] et F la résistance en [cN/tex].

• Melt viscosity index according to ASTM D1238
• Title determination according to SN 197 012 and SN 197 015, supplemented by DIN 53830
• The calculation of the mechanical constant CM is carried out according to the following formula: $$\mathrm{CM}\mathrm{=}\sqrt{\mathrm{D}}\mathrm{\cdot }\mathrm{F}\left[\mathrm{cN}\mathrm{/}\mathrm{tex}\right]$$
  

where D denotes the elongation in [%] and F the resistance in [cN / tex].

Description of abrasion tests Manufacture of sectional beams

The sectional beams, of 1000 m each, were made using the monofils of 80 coils of different variants.

Weaving tests

• Production maximale possible : 4000 tours/min
• La foule est formée grâce à des excentriques.
• Mode de travail : sans rentrée de trame
• Densité des fils de chaîne : 22,80 fils/cm
• Peigne : ouverture: 0,175 mm
  • épaisseur des dents : 0,264 mm
  • largeur des dents : 7,0 mm
• Vitesse de rotation du métier à tisser : 1000 tours/min
• Vitesse de tissage : 10 m/h
• Armure : toile à draps L1/1

The weaving tests are performed on a loom.

• Maximum production possible: 4000 rpm
• The crowd is formed thanks to eccentrics.
• Mode of work: without return of frame
• Density of warp yarns: 22.80 threads / cm
• Comb: opening: 0.175 mm
  • thickness of the teeth: 0,264 mm
  • teeth width: 7.0 mm
• Rotation speed of the loom: 1000 rpm
• Weaving speed: 10 m / h
• Armor: linen cloth L1 / 1

Evaluation of abrasion behavior:

• visual evaluation of the combs
• gravimetric determination of the quantity of down produced

During the visual examination, the combs are photographed after an operating time of 100 m or 200 m, preferably 300 m, and are assigned a classification.

The evaluation of the abrasion behavior according to the gravimetric method is described below. For this purpose, all the fluff is collected, after an operating time of 300 m, it is weighed and is related to the weight of the warp yarns using the following formula: $$\mathrm{deposit\; in}\%=\frac{\mathrm{mass\; of\; deposits}\cdot 100}{\mathrm{number\; of\; warp\; threads}\cdot \frac{\mathrm{length\; of\; the\; warp\; threads}\cdot \mathrm{title}}{10000}}$$

The monofilaments according to the invention, which have a diameter ≥ 0.050 mm, are suitable for the manufacture, without abrasion, of fabrics intended for filtration.

Thanks to the process according to the invention and to the monofilament according to the invention, it has been possible for the first time to weave polypropylene monofilament practically without abrasion and to considerably increase the operating time of the loom. This monofilament is particularly suitable for the manufacture of fabrics that are used for filtration in the chemical, pharmaceutical and food industries.

Claims (10)

1. Process for the fabrication of monofilaments of a polypropylene having a melt flow index (MFI) 230°C/2.16 kg of 2 to 16 g/10 min, having a diameter larger than 0.050 mm and an improved abrasion resistance, characterised in that 20 to 0.01 % by weight of an additive are added to the polypropylene upstream of the extruder, the molten material is spun in a water bath, drawn and wound up.
2. The process according to claim 1, characterised in that 0.5 to 1.2 % by weight of a combination of lubricant, filler and thermal stabilisant is used as the additive.
3. The process according to claim 1, characterised in that 0.05 to 1.0 % by weight of a lubricant is used as the additive.
4. The process according to claim 1, characterised in that 0.01 to 1.0 % by weight of fillers is used as the additive.
5. The process according to claim 1, characterised in that 0.1 to 0.8 % by weight of a thermal stabilisant is used as the additive.
6. The process according to claim 1, characterised in that 1 to 20 % by weight of a polypropylene/polyethylene copolymer with a melting point ≥ 140°C is used as the additive.
7. Monofilaments of a polypropylene with a melt flow index (MFI) 230°C/2.16 kg of 2 to 16 g/10 min, having a diameter larger than 0.050 mm and an improved abrasion resistance, characterised in that they exhibit a resistance of at least 50 cN/tex at an elongation corresponding to less than 35%, preferably less than 30% of the maximum tensile stress (elongation at rupture).
8. The monofilaments according to claim 7, characterised by an abrasion of less than 0.05%.
9. The monofilaments according to claim 7, characterised in that they have a relative tensile energy > 100 % after being treated for 24 hours at 120°C.
10. Use of the monofilaments according to claims 7 to 9 for the fabrication of two-dimensional articles intended for the filtration in the chemical, pharmaceutical and food industries.

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