Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/24—Formation of filaments, threads, or the like with a hollow structure; Spinnerette packs therefor
  • D01D5/247—Discontinuous hollow structure or microporous structure
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F1/00—General methods for the manufacture of artificial filaments or the like
  • D01F1/02—Addition of substances to the spinning solution or to the melt
  • D01F1/08—Addition of substances to the spinning solution or to the melt for forming hollow filaments
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/02—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D01F6/04—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyolefins
  • D01F6/06—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyolefins from polypropylene
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/28—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D01F6/30—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds comprising olefins as the major constituent
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F8/00—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof
  • D01F8/04—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers
  • D01F8/06—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers with at least one polyolefin as constituent

Definitions

• the present invention relates to a process for the production of foamed polypropylene fibres with reduced density.
• the present invention also relates to the foamed fibres and nonwoven made with said process. Additionally it relates to composites comprising such foamed fibres and nonwoven.
• Polypropylene is one of the most widely used polymers in fibres and nonwoven. Due to its versatility and its good mechanical and chemical properties, polypropylene is well suited to fulfill requirements in many different applications. Polypropylene fibres and nonwoven are for example used in the construction and agricultural industries, sanitary and medical articles, carpets, and textiles.
• the polypropylenes used for fibres and nonwoven have a melt flow that can range from 1 dg/min up to several thousands dg/min, depending upon the production method, final use etc.. For very strong high-tenacity fibers, the lower part of the range is preferred whereas for meltblown nonwoven, the higher part of the range is preferred.
• polypropylene used in fibre extrusion has a melt flow in the range of from 5 dg/min to about 40 dg/min.
• Polypropylene used for spunbond nonwoven typically has a melt flow index in the range of from 25 dg/min to 40 dg/min and is additionally characterised by a narrow molecular weight distribution ( Polypropylene Handbook, ed. Nello Pasquini, 2nd edition, Hanser, 2005, p. 397 ).
• Polypropylene is generally produced by the polymerisation of propylene and one or more optional comonomers in presence of a Ziegler-Natta catalyst, i.e. a transition metal coordination catalyst, specifically a titanium halide containing catalyst. These catalysts in general also contain internal electron donors, such as phthalates, diethers, or succinates. Polypropylene produced by Ziegler-Natta catalysis can be directly used without modification for the production of fibres. However, in order to improve the processability and the nonwoven properties in spunbond nonwoven the molecular weight distribution of the polypropylene needs to be narrowed, which can be done either thermally or chemically by post-reactor degradation.
• the present invention discloses a process for preparing foamed fibres or filaments that comprises the steps of:
• the present invention discloses a process for preparing foamed fibres or filaments that comprises the steps of:
• the present invention discloses a process for preparing foamed fibres or filaments that comprises the steps of:
• composition is prepared by extruding the polyolefin either with a masterbatch comprising the foaming agent or directly with the foaming agent.
• a masterbatch is used.
• blowing agents undergo chemical reactions, mostly decomposition, that liberate the blowing gas, typically N 2 , CO, CO 2 and NH 3 .
• the blowing gas is liberated either by vaporisation of a liquid having a low boiling temperature or by release of pressure in a compressed gas.
• the chemical agents that can be used in the present invention can function according to three main processes:
• the preferred polyolefin is a homo- or a co-polymer of propylene.
• the polypropylene that can be used in the present invention is either a homopolymer or a random copolymer of propylene with one or more comonomers, said comonomer being ethylene or a C 4 - C 10 alpha-olefin, such a butene-1, pentene-1, hexene-1, octene-1, 4-methyl-pentene-1.
• the preferred comonomers are ethylene and butene-
• the polypropylene that can be used in the present invention is produced by a Ziegler-Natta or by a metallocene-based catalytic system.
• a Ziegler-Natta catalyst system comprises a titanium compound having at least one titanium-halogen bond and an internal electron donor, both on a suitable support, such as for example on a magnesium halide in active form. It further comprises an organoaluminium compound, such as for example an aluminium trialkyl, and an optional external donor.
• the homo- or co-polymerisation of propylene with one or more optional comonomers can be carried out according to known techniques in one or more polymerisation reactors, for example in a slurry, bulk or gas phase process.
• a slurry process the polymerisation is carried out in a diluent, such as an inert hydrocarbon.
• a bulk process the polymerisation is carried out in liquid propylene as reactor medium.
• the molecular weight of the polymer chains, and in consequence the melt flow of the polypropylene, is regulated by the addition of hydrogen to the polymerisation medium.
• the polypropylene of the present invention is characterised by a melt flow index in the range from 1 to 2000 dg/min, as measured according to ISO 1133, condition L, at a temperature of 230°C under a load of 2.16 kg.
• a melt flow index in the range from 1 to 2000 dg/min, as measured according to ISO 1133, condition L, at a temperature of 230°C under a load of 2.16 kg.
• the melt flow of the polypropylene is in the range from 5 dg/min to 40 dg/min.
• the melt flow of the polypropylene is of at least 10 dg/min, preferably at least 12, 14, 16, 18 or 20 dg/min.
• melt flow of the polypropylene is at most 300 dg/min, preferably at most 200 dg/min, more preferably at most 150 dg/min, even more preferably at most 100 dg/min and most preferably at most 60 dg/min.
• melt flow of the metallocene polypropylene is of at least 100 dg/min, preferably at least 150 dg/min, more preferably at least 200 dg/min, even more preferably at least 250 dg/min and most preferably at least 300 dg/min.
• melt flow of the polypropylene is of at most 2000 dg/min, preferably at most 1800 dg/min, more preferably at most 1600 dg/min, and most preferably at most 1400 dg/min.
• the foamed polypropylene fibres and filaments of the present invention are produced as-spun by methods well known to the skilled person.
• the polypropylene composition comprising the chemical foaming agent is melted in an extruder, preferably passed through a melt pump to ensure a constant feeding rate and then extruded through the fine capillaries of a spinneret.
• the still molten fibres and filaments are simultaneously cooled by air, drawn to a final diameter and collected. They are for example collected on a winder or other suitable collecting means.
• An optional drawing step may be conducted after the fibres have solidified.
• the nonwovens of the present invention may be produced by any suitable method.
• the preferred methods are the spunbonding process and the melt blown process. Of these the spunbonding process is the most preferred. In the spunbonding process as well as in the melt blown process the extruded fibres and filaments are drawn in the molten state only.
• polypropylene is melted in an extruder, preferably first passed through a melt pump to ensure a constant feeding rate and then extruded from the usually circular capillaries of a spinneret, thus obtaining filaments.
• the filament formation can either be done by using one single large spinneret having a large number of holes, typically several thousands, or by using several small spinnerets each having a lower number of holes.
• the still molten filaments are quenched by an air flow.
• the diameter of the filaments is then quickly reduced by a flow of high-pressure air. Air velocities in this drawdown step can range up to several thousand metres per minute.
• the present invention also provides, , a process for the production of foamed fibres and filaments, said process comprising the steps of:
• the present invention also provides a process for the production of foamed fibres and filaments, said process comprising the steps of:
• the foamed filaments are collected on a support, for example a forming wire or a porous forming belt, thus first forming an unbonded web, which is then passed through compaction rolls and finally through a bonding step.
• Bonding of the fabric may be accomplished by thermobonding, hydroentanglement, needle punching, or chemical bonding.
• the polypropylene composition is melted in an extruder, preferably first passed through a melt pump to ensure a constant feeding rate and then through the capillaries of a special melt blowing die.
• melt blowing dies have a single line of usually circular capillaries through which the molten polymer passes.
• the still molten foamed filaments are first contacted with hot air at high speed, which rapidly draws the fibres. They are then contacted with cool air that solidifies them.
• the nonwoven is formed by depositing the foamed filaments directly onto a forming wire or a porous forming belt.
• the foamed fibres and filaments of the present invention may be multi-component foamed fibres or filaments. Preferably they are bicomponent foamed fibres or filaments. Bi- or multi-component fibres or filaments are known in many different configurations, such as for example side-by-side, sheath-core, islands-in-the-sea, pie or stripe configurations. Bi- or multi-component fibres or filaments can be formed by co-extrusion of at least two different components into one fibre or filament. This is done by feeding the different components to a corresponding number of extruders and combining the different melts into a single fibre or filament. The resulting fibre or filament has at least two different essentially continuous polymer phases.
• Such fibres or filaments their production as well as their forming a nonwoven are well known to the skilled person and are for example described in F. Fourné, Synthetician Fasern, Carl Hanser Verlag, 1995, chapter 5.2 or in B.C. Goswami et al., Textile Yarns, John Wiley & Sons, 1977, p. 371 - 376 .
• the present invention also discloses a process for the production of multi-component foamed fibres and filaments, said process comprising the steps of
• Composites may be formed from two or more nonwovens, of which at least one is made in accordance with the present invention.
• the composites comprise a spunbond nonwoven layer (S) according to the present invention or a melt blown nonwoven layer (M) according to the present invention.
• Composites in accordance with the present invention can for example be SS, SSS, SMS, SMMSS or any other combination of spunbond and melt blown nonwoven layers.
• a first nonwoven or composite, said first nonwoven or composite being in accordance with the present invention, and a film may be combined to form a laminate.
• the film preferably is a polyolefin film.
• the laminate is formed by bringing the first nonwoven or composite and the film together and laminating them to one another for example by passing them through a pair of lamination rolls.
• the laminates may further include a second nonwoven or composite, which can be, but need not be, according to the present invention, on the face of the film opposite to that of the first nonwoven or composite.
• the film of the laminate is a breathable polyolefin film, thus resulting in a laminate with breathable properties.
• the polypropylene of the present invention may also contain additives such as, by way of example, antioxidants, light stabilisers, acid scavengers, lubricants, antistatic additives, and colorants.
• additives such as, by way of example, antioxidants, light stabilisers, acid scavengers, lubricants, antistatic additives, and colorants.
• the polypropylene resin was a homopolymer of propylene prepared with a Ziegler-Natta catalyst system and sold by TOTAL Petrochemicals under the name PPH7059. It had a melt flow index of 12 dg/min.
• the chemical foaming agent was a combination of sodium carbonate and citric acid sold by Clariant under the name PEX 5035. It was available in a master batch based on polyethylene and had a decomposition temperature of from 150 to 230 °C.
• the spinnability tests were performed on a Busschaert pilot line. The conditions were as follows: the melt temperature was of 230 °C and the throughput was of 0.5 g/hole/min with a hole size of 0.5 mm. Several samples were tested: - pure polypropylene - polypropylene combined with 0.2 wt% of PEX 5035 - polypropylene combined with 0.4 wt% of PEX 5035 The spinnability results are displayed in Table I. TABLE I. PEX 5035 (wt%) Max. spin speed (m/min) 0 3000 0.2 1500 0.4 900 It can be seen that the spinnability expressed in terms of maximum spin speed is decreased drastically with increasing amount of foaming agent. This is most likely caused by the presence of bubbles in the foamed fibres.

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Citations (4)

• 2008
  • 2008-02-22 EP EP08151827A patent/EP2093313A1/fr not_active Withdrawn

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