AU2005233341B2

AU2005233341B2 - Polypropylene monofilaments with improved properties

Info

Publication number: AU2005233341B2
Application number: AU2005233341A
Authority: AU
Inventors: Claudia Fritz
Original assignee: Rhodia Chimie SAS
Current assignee: Rhodia Chimie SAS
Priority date: 2004-03-30
Filing date: 2005-03-22
Publication date: 2008-07-10
Anticipated expiration: 2025-03-22
Also published as: CA2561321A1; TW200613594A; CN1950551A; ZA200608115B; AU2005233341A1; WO2005100649A1; EP1730334A1; JP2007530813A; FR2868438B1; US20080113194A1; KR20060132985A; FR2868438A1; BRPI0508733A

Description

1 00 POLYPROPYLENE-BASED MONOFILAMENTS WITH IMPROVED PROPERTIES Field of the Invention The invention relates to polypropylene-based monofilaments having improved properties, especially an improved abrasion resistance, to a process for manufacturing these monofilaments and to their use. The invention relates more particularly to polypropylenebased monofilaments obtained from a polypropylene having a melt flow index (MFI) at 230'C/2.16 kg of less than or equal to 1.9 g/10 min.

Background of the Invention Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

Two-dimensional textile articles made of polypropylene are of great interest as chemically and mechanically resistant filtration means for filtration in the chemical, pharmaceutical and food industries.

Monofilaments made of pure polypropylene have the drawback of forming a great deal of dust as a result of the low resistance of this substance to abrasion during the weaving process. The problem of abrasion is also known in the case of other thermoplastics. Thus 784 107 mentions melt-spun, polyamide, polyester or polypropylene monofilaments that are intended for paper machine forming fabrics and for strimmer lines. According to the above patent, abrasion-resistant monofilaments are obtained using to 99% by weight of fibre-forming polymer and 1 to by weight of a maleic-anhydride-modified polyethylene/ 2 O polypropylene rubber and other additives. However, the 0 examples are limited, as regards the fibre-forming Cq polymer, to the polyamide nylon-6 and to polyethylene Sterephthalate, and also to a PA-6,6/PA-6 copolyamide.

5 The spinning rates are not mentioned.

A process for manufacturing polypropylene multifilaments intended for textile applications is also known from EP-A-1 059 370. As starting material, an isotactic polypropylene catalysed by a metallocene is used that C1 has a melt flow index greater than 19 g per 10 minutes.

SFOY (Fully Oriented Yarn) multifilaments of 10 dpf C- (denier per filament) [0.03953 mm diameter] and POY (Partially Oriented Yarn) multifilaments of 2 dpf (denier per fibre) [0.01768 mm diameter] have been described. As regards the yarns manufactured, only general indications are given. Monofilaments are not described.

Applications WO 02/086207 and WO 03/048434 describe polypropylene monofilaments, the polypropylene including additives. The polypropylene employed for manufacturing the monofilaments has a melt flow index of greater than or equal to 6 g per 10 minutes. These monofilaments have correct abrasion resistance properties.

An object of a particularly preferred form of the present invention consists in how to provide polypropylene-based monofilaments that are more abrasion resistant than the monofilaments known from the prior art. Another problem of the invention consists in how to obtain polypropylene-based monofilaments that exhibit better abrasion resistance during weaving.

An object of a particularly preferred form of the present invention consists in how to provide for the use of monofilaments possessing good abrasion resistance for the manufacture of two-dimensional high- -3 00 performance articles, especially those intended for filtration.

Unless the context clearly requires otherwise, throughout the description and the claims, the words "%comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to" (1 Although the invention will be described with reference to specific examples it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

Summary of the Invention According to a first aspect of the present invention there is provided a polypropylene-based monofilament, said monofilament consisting of a polypropylene having a melt flow index (MFI) at 230'C/2.16 kg of less than or equal to 1.9 g/10 min, and of 0.01 to 20% by weight relative to the weight of polypropylene, of a polypropylene/polyethylene copolymer having a melting point 140 0

C.

According to a second aspect of the present invention there is provided a process for manufacturing a monofilament according to any one of the preceding claims, comprising the steps of extrusion/melt-spinning of the polypropylene and the polypropylene/polyethylene copolymer, drawing and winding.

According to a third aspect of the present invention there is provided use of a monofilament according to the first aspect of the present invention, for the manufacture of two-dimensional high-performance articles.

According to a fourth aspect of the present invention there is provided a monofilament according to the first 4aspect of the present invention, when manufactured by a process according to the second aspect of the present CI invention.

5 Broadly, the invention embodies, in particular the use, for the manufacture of the monofilaments, of a polypropylene having a melt flow index (MFI) at 230°C/2.16 kg of less than or equal to 1.9 g/10 min.

The polypropylenes conventionally used in the C manufacture of monofilaments are isotactic polypropylenes.

The monofilaments of the invention advantageously have an abrasion of less than or equal to 0.014%.

The abrasion of the monofilaments is determined by gravimetric measurement of the amount of fluff produced during the manufacture of a 300 m length of woven fabric, using the method described below in the experimental part. The abrasion value corresponds to the result of the formula described below in the experimental part, calculated for a woven fabric length of 300 m.

It is particularly advantageous for the monofilaments to have an abrasion of less than 0.014%. This is because, when the abrasion is greater than 0.014%, irregularities may be produced during weaving, due to too rapid fouling of the reeds. This may shorten the time intervals between cleaning operations, thereby reducing the productivity of the loom.

The monofilaments of the invention preferably have an abrasion of less than or equal to 0.01%.

It is appropriate for the monofilaments to possess a strength of at least 50 cN/tex for an elongation corresponding to the maximum tensile stress (elongation at break) at least equal to 20%. This is because a 5 strength of less than 50 cN/tex has the drawback of increasing the number of yarn breakages during the weaving process.

5 The monofilaments of the invention advantageously have n a mechanical constant of greater than or equal to 285 cN/tex.

According to one particular embodiment of the

C

c 10 invention, the monofilaments include an additive.

CI Advantageously, the monofilaments include 0.01 to by weight of additive relative to the weight of C, polypropylene.

Advantageously, it is appropriate to use as additive a polypropylene/polyethylene copolymer having a melting point 140°C. Advantageously, this additive is present in a proportion of 1 to 20% by weight relative to the weight of polypropylene.

The invention also relates to a process for manufacturing the monofilaments of the invention, which comprises the steps of extrusion/melt-spinning, drawing and winding of the polypropylene.

The polypropylene-based monofilaments of the invention may be obtained using conventional spinning methods.

They are generally obtained by extrusion/melt-spinning, cooling in a water bath when the monofilament titre is greater than or equal to 0.05 mm, drawing and winding.

When the monofilaments of the invention include an additive, the additive is generally added to the polypropylene upstream of an extruder, before the spinning.

The monofilaments according to the invention are particularly suitable for the manufacture of twodimensional high-performance articles, and especially for the manufacture of such articles in the field of filtration. These articles, when they are intended for 6 filtration, especially in the chemical, pharmaceutical and food industries, are preferably woven fabrics.

The invention will now be described in greater detail with the aid of examples.

Polymer As polymer, a polypropylene having a melt flow index (MFI) at 230°C/2.16 kg of 1.7 g/10 min was used during the trials.

Each time 300 kg of polypropylene granules were employed, using 25 kg drums.

The polypropylene granules and the optional additive granules were fed directly into the extruder and melted.

Spinning conditions Extruder: Extruder pressure: Spinning pump: Spinning unit: Metering pump: Spinnerets: Water bath: Diameter: 40 mm; barrel length: L/D 80 bar Flow rate: 14.5 kg/h heating zones Metered volume: 10 cm 3 /revolution Electrically heated 23.19 revolutions/min.

Diameter: 0.7 mm Capillary length: 3 x D Distance between spinneret and water bath: 45 mm Temperature: 500C.

Drawinq staqes and heating channels Drawing stage 1: Drawing stage 2: 7 rolls; roll diameter: 230 mm; 1 heating channel 7 rolls; roll diameter: 230 mm; 1 heating channel 7 Drawing stage 3: 7 rolls; roll diameter: 230 mm; 2 0 heating channels rC Drawing stage 4: 4 rolls; roll diameter: 230 mm.

5 Measurement methods Melt flow index according to ASTM D1238 Determination of the titre according to SN 197 012 and SN 197 015, supplemented with DIN 53830/ 1C The mechanical constant MC is calculated using the CI following formula: MC=VDxF [cN/tex] where D denotes the elongation in and F denotes the strength in [cN/tex] Determination of the thermal shrinkage according to BISFA (Chapter 11 of the standard protocol: "Determination of the thermal shrinkage in hot air"), carried out under the following conditions: tension: 0.02 cN/dtex temperature: 120°C duration: 10 min.

Description of the abrasion tests Manufacture of sectional beams The sectional beams, of 1000 m each, were manufactured using monofilaments from 60 bobbins of the various versions.

Weaving trials The weaving trials were carried out on a ribbon loom.

Maximum possible production: 4000 revolutions/min.

The shed was formed by excentrics Working mode: no weft re-entry Density of warp yarns: 22.80 yarns/cm Reed: opening: 0.175 mm dent thickness: 0.264 mm dent width: 7.0 mm -8 00 Speed of rotation of the loom: 1000 revolutions/min.

Weaving speed: 10 rn/h Weave: Li/i (plain weave) cloth.

Evaluation of the abrasion behaviour: visual evaluation of the reeds gravimetric determination of the amount of f luf f produced.

In the visual determination, the reeds are photographed after a period of operation corresponding to a 300 m CI length of fabric, and a rating is assigned to them.

Figures 1A, lB and 1C show photographs of the reeds after a weaving trial according to the method described above. Figure 1A corresponds to Example 1, Figure lB to Example 2 and Figure 1C to the comparative example. The reeds of Figures 1A and lB show practically no fluff, whereas that of Figure 1C shows a not insignificant amount of fluff.

The evaluation of the abrasion behaviour using the gravimetric method is described below. To do this, all of the fluff formed after a period of operation corresponding to a fabric length of 300 m is collected, weighed and expressed with respect to the warp yarns using the following formula: fluff deposit mass of deposit x 100 No.of arpyars xwarp yarn length x titre 10000 The abrasion behaviour may also be evaluated using the same gravimetric method described above, but for a fabric length of 1000 m.

Figure 2 shows the results in terms of abrasion behaviour of Examples 1 and 2 and the comparative example.

9 Examples Example 1 Monofilaments were obtained from granules of polypropylene having a melt flow index (MFI) at 230 0 C/2.16 kg of 1.7 g/10 min, using a method and under the conditions described above.

Example 2 Monofilaments polypropylene polypropylene melting point were obtained from granules of and from granules consisting of and of PP/PE modified polyolefin, with a 140 0

C.

The examples are summarized in Table 1.

Table 1 Example 1 2 Additive by weight) Diameter [mm] 0.15 0.15 Strength [cN/tex] 61 56.5 Elongation corresponding 35.7 38.5 to the maximum tensile stress Mechanical constant 364 351 Thermal shrinkage 2.5 3.4 Abrasion (300 m of 0.0094 0.004 fabric) Abrasion (1000 m of 0.0206 fabric) Comparative example Monofilaments were obtained in accordance with Example 2 of Patent Application WO 03/048434. Their abrasion was 0.0156%.

10 00 The monofilaments according to the invention are suitable for the manufacture, without any abrasion, of C1 fabrics intended for filtration.

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

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".

Although the invention has been described with reference to specific examples it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

Claims

3. A monofilament according to claim 1 or claim 2, said monofilament having an abrasion value of less than or equal to 0.01%.
4. A monofilament according to any one of the preceding claims, said monofilament having a strength of at least 50 cN/tex for an elongation corresponding to the maximum tensile stress (elongation at break) at least equal to
5. A monofilament according to any one of the preceding claims, said monofilament including 1 to 20% by weight of this copolymer relative to the weight of polypropylene.
6. A process for manufacturing a monofilament according to any one of the preceding claims, comprising the steps of extrusion/melt-spinning of the polypropylene and the polypropylene/polyethylene copolymer, drawing and winding.
7. Use of a monofilament according to any one of claims 1 to 5, for the manufacture of two- dimensional high-performance articles. I 12
8. Use according to claim 7, in the field of 00 filtration.
9. Use according to claim 7 or claim 8, wherein the 5 article is a fabric for filtration. A monofilament according to any one of claims 1 to 5, when manufactured by a process according to claim 6. CI 11. A polypropylene-based monofilament, said monofilament substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples, but excluding comparative examples.
12. A process for manufacturing a monofilament substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples, but excluding comparative examples.
13. Use of a monofilament substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples, but excluding comparative examples.
14. A monofilament, when manufactured by a process substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples, but excluding comparative examples. Dated this 3 rd day of June 2008 Shelston IP Attorneys for: Rhodia Chimie