DE10232078A1 - Production of fibres containing super-absorber, e.g. for hygiene products, involves co-extruding a mixture of super-absorber and thermoplastic polymer with another thermoplastic to form bi-component filaments - Google Patents

Abstract

Fibres containing super-absorbers are produced by co-extruding a thermoplastic mixture (A) of super-absorbing polymer and synthetic thermoplastic fibre material with another thermoplastic polymer (B) to form bi-component filaments with (B) as the core and (A) as the shell. A method for the production of fibres containing super-absorbers involves making a thermoplastic mixture of super-absorbing polymer and synthetic thermoplastic fibre material (SAP fibre mixture) (A), making another thermoplastic polymer mixture (B), co-extruding the two mixtures to form bicomponent filaments with (B) as the core and (A) as the shell, and then further processing and/or chopping to the required length.

Description

The invention relates to a method for the production of fibers containing superabsorbents, using at least partial use of a fiber material which made of a thermoplastic processable mixture of superabsorbent polymer and a synthetic thermoplastic fiber material (hereinafter SAP fiber blend) is produced.

Such a method is known from the EP 0 425 269 A2 known. The known process is carried out in the following process steps: production of a mixture of a synthetic polymer and particles of a suberabsorbent and processing in the melt spinning process to form fibers which contain superabsorbents.

The fiber production after that EP 0 425 269 A2 However, known processes have proven to be extremely difficult since the filling of superabsorbents negatively changes the properties of the filament which is produced by the melt spinning process. The filament shows only a low tensile strength, which is noticeable both in the manufacture of the thread and in the finished product, ie the fibers. Because of the high brittleness, the filament cannot be stretched or processed any other way.

Because from the filaments and from them Fibers produced both woven and knitted can be as well as fleeces, led the instability and high tendency of the fibers to break into a spunbond or a twisted thread can hardly be produced.

So the task is a process for the production of fibers containing superabsorbents to indicate that leads to fibers, which in the area of nonwovens as well as for fabrics and knitted fabrics in shape of mono fibers as well as twisting (multi-filaments) can be used.

It has also been suggested ( US 6194630 B1 ) To produce fibers with superabsorbents by processing a thermoplastic polymeric material into fibers and binding the superabsorbents to this material by means of a thermal bond by heating the polymer fiber. However, this method has the disadvantage that a large part of the suberabsorbents is not liable and remains in excess and must be reintroduced into the method in each case. Here too, only small fractions of the outer surface of a fiber can be covered with appropriate absorbents. Accordingly, there is the further task of specifying a production in which a fiber is produced which, on the one hand, is easy to process and produce and, on the other hand, has a high proportion of suberabsorbents.

The above tasks will be solved by a method according to the preamble of claim 1 using the following process steps:

• - provision the SAP fiber blend,
• - provision a second thermoplastic polymer mixture,
• - coextrusion both mixtures to bicomponent filaments, in which, in thread cross-section seen, the SAP-free polymer blend the core and the SAP fiber blend the peripheral wrapping form,
• - post-processing and / or cutting the filaments to the desired fiber length.

In particular, coextrusion done so that the sheathing 10 consisting of the SAP fiber mixture up to 50% of the cross-sectional area of bicomponent filaments.

For the production of the core and the base mass of the SAP fiber mass thermoplastic polymers selected from the group polyolefins, polyamides, polyurethanes, extrudable polyvinyl alcohols, Polyether esters or other spinnable polymers.

The core of the bicomponent filaments can from a polyolefin, a mixture of polyolefins or from copolymers several polyolefins, preferably polyethylene and polypropylene and / or Polyethylenes, again preferably linear polyethylenes lower Density, exist.

something similar applies to the thermoplastic polymer of the SAP fiber blend.

The filling of the SAP fiber mix should be 5 to 50% by weight the final mixture consist of a super absorber; the latter should an average grain size of 1 up to 50 μm have.

An improvement in water absorption speed arises when the SAP fiber blend before extruding Hydrophilizing agent added becomes.

Can also improve water transfer the outer surface of the Facing layer a smooth cylinder layer can be enlarged.

The filaments obtained can in the usual way Stretched, crimped and cut. water contact must be there be avoided.

Usage examples are for the manufactured ones Non-woven fabrics absorbing bicomponent fibers, addition to fiber products not provided with SAP granules, especially airlaid fleeces made of cellulose fibers. Further uses are in the examples described.

The one to make a filament The polymers used also allow a melt spinning process which takes you from the melt to a spunbond in one step arrives.

A melt spinning system must be equipped with two extruder systems for bicomponent spinning. Who work with the extruders on one head and form a bicomponent filament. The filaments emerge from the nozzle head as a filament curtain, are captured by the cooling air and guided downwards. The filaments are cooled and drawn. The filament curtain reaches a conveyor belt via a suction roller, which holds it on the belt and continues with the belt. A pressure roller ensures easy pre-fixation of the fleece. The fleece is pulled off the belt and is finally fixed by embossing in a nip between an embossing roller and a smooth roller.

A spunbond fabric produced in this way shows good strength properties and can be in different basis weights be generated. It provides because of its high content of superabsorbents for example an important starting product for applications in the hygiene sector, in medicine, for special packaging at Transport of exuding food and for technical areas, at which depend on moisture absorption.

The manufactured by the process Fibers can both for the production of woven and knitted materials can be used where high water absorption is desired. You can used for the production of nonwovens as well as an admixture to other fiber materials not containing superabsorbents, such as cellulose fibers, the heating Melt the polymer components and create a binding effect.

Superabsorbents that are relatively brittle and therefore also to a desired one Grind grain size are, can by producing and polymerizing acrylic acid and starch in an aqueous Medium are prepared, wherein a polyfunctional monomer, such as N, N-alkylene-bis-acrylamide, is used as a networking agent. Such a procedure is in U.S. Patent 4,076,663. Superabsorbents can too be produced by inverse polymerization of acrylic acid, where here a polyfunctional component is used, such as Epichlorohydrin. Further superabsorbents are described in the U.S. Patents 4,654,039, 3,669,103 and 3,670,731. Descriptions of others superabsorbent polymer can be found in U.S. 4 076 663 and 4 340 706.

The available in the size of 5 to 40 microns superabsorbent crystals have a grain size that allows them to be in corresponding threads and Install filaments. The superabsorbents swell when they are Water or watery liquids take up. This swelling is also the case with the filaments and fibers observed, which are produced by the method. To get a better one accessibility of liquids to the absorber surfaces to allow a hydrophilizing agent is added here.

Process for the production of bicomponent fibers with the help of coextrusions are known. For example referred to U.S. Patent 5,405,682, which discloses a nonwoven is described, which is made of multi-component filaments is made from a mixture of polyolefins and elastic, thermoplastic Material.

The material can then like in the usual Melt spinning processes are produced. One thing is essential inert atmosphere, at least dry atmosphere, is used so that no water can get to the superabsorbents.

The water absorption of those later made from it Products depends from the content of superabsorbents and their consistency and swellability.

Especially when using such products on hygiene products, such as diapers, incontinence products, Sanitary pads and the like. But it is also possible that Material as a water absorbent, especially in the area to use the food technology.

The following examples show in which areas the products are manufactured and used.

Typical embodiments of the invention are described below.

example 1

A polypropylene with an MFI of 26 to 35, measured at 230 ° C and 2.16 kp load selected. The polypropylene has a molecular weight distribution that is smaller than 3.5. The density is 0.92. The following commercial products were used: Hostalen PPU 1780F, alternatively Hymont Moplen H 22 A 225 Exxon PD 3445 or hüls Vestoles TPCX 2000.

The polypropylene is added to a melt extruder with 20 to 40% by weight superabsorbent based on polyacrylate (manufactured by FAVOR ^® , manufacturer: Stockhausen GmbH and Co. KG, Krefeld), mixed and melted. The components are mixed homogeneously and intimately. The superabsorbent added to the polypropylene has a grain size of less than 50 micrometers. The grain size can be taken into account by selecting the appropriate extrusion filter.

The melt becomes a granulating device supplied avoiding any contact with water. Only air cooling is used. The granules obtained can be stored and in one process can be used to produce a bicomponent fiber.

Low density polypropylene is used as the core polymer.

The known additives necessary for spinning are added to the polymers. It are lubricants, fillers, pigments, stabilizers and the like in appropriate amounts.

The two polymers are each melted in an extruder and the corresponding extruder screws fed. The polymer stream reaches the spinnerets under pressure coextrude a bicomponent filament (see U.S. Patent 5,162,074).

A multilayer filament will after exiting the nozzle from the cooling air flow recorded and cooled specifically. On the way down, the filament is passed over godets, stretched, crimped and staple fibers of length 4 to 6 mm cut.

Make the fibers so produced a new type of superabsorbent product and can be processed into a fleece become.

Example 2

In a test double-chamber extruder a mixture of 200 g granulated and finely ground low density polyethylene with 125 g of a finely ground and sieved to a grain size smaller than 7.5 μm Superabsorbent of the brand FAVOR (Stockhausen GmbH und Co. KG, Krefeld) mixed. This mixture, hereinafter referred to as SAP fiber mixture, is called introduced into the first extruder chamber and warmed up.

For the core layer will be 300 g of granulated low density polyethylene thereof Provenance filled into the second extruder chamber as mentioned above. Both Extruder chambers and screws are brought to their required contents Extrusion temperature of the polyethylene warmed up (approx. 180 ° C). At this Temperature does not yet melt the superabsorbent granulate.

The two melts are over the Extruder screw fed to a common coextrusion die and to filaments with a concentric arrangement of core and sheath coextruded. Here, a filament with a diameter of 18 μm is produced, at where the core takes up 60% and the jacket 40% of the cross-sectional area.

The material becomes the thread of the Length 10 cm cut and heaped. Subsequently, after cooling, the cut material is combined with distilled water brought. It is able to absorb more than 80% of its weight in water.

Example 3

In a trial twin-chamber extruder like in example 1 is a mixture of 180 g of low density polyethylene mixed with 120 g of acrylate superabsorbent, as mentioned in Example 1. This SAP fiber mixture is introduced into the first extruder chamber and warmed up.

For the core layer will be 300 g of finely ground polypropylene in the second Extruder chamber filled. Both extruder chambers and screws and their contents are brought to the required extrusion temperature of polypropylene warmed up (approx. 225 ° C). At this temperature, the superabsorbent granules are not yet melting.

The two melts are over the Extruder screws are fed to a common coextrusion die and to filaments with a concentric arrangement of core and sheath coextruded. With the coextrusion die, the inside is the outside periphery contoured so that one is different from the cylinder and increased outer surface area results. It becomes a filament with a diameter of 15 mμ manufactured in which the core and 70% of the jacket take up 30% of the cross-sectional area.

The material is deposited in heap, resulting in a spunbonded arrangement. The extrudate can be done without further and without unwanted Extrude break. After cooling, it is able to do more than Absorb 80% of its weight in water.

Example 4

In a test double-chamber extruder a mixture of 250 g of a copolymer of polyethylene and ethylene vinyl acetate with 125 g of a finely ground and sieved to a grain size smaller than 7.5 μm Superabsorber made from a copolymer of 91 acrylic acid and 9% starch, cross-linked mixed with N, N'-methylene-bis-acrylamide (see US Patent 4,076,663). This mixture, hereinafter referred to as SAP fiber mixture, is in the first extruder chamber introduced and with 0.5% by weight of a nonionic hydrophilizing agent (Stantex from Cognis GmbH) mixed and heated.

For the core layer will be 300 g of granulated plasticizable polyurethane filled into the second extruder chamber. Both extruder chambers and The screws and their contents are brought to the required extrusion temperature of the polyethylene warmed up (approx. 180 ° C). At this temperature, the superabsorbent granules are not yet melting.

The two melts are over the Extruder screw fed to a common coextrusion die and to filaments with a concentric arrangement of core and sheath coextruded. A filament with a diameter of 14 μm is produced, at where the core takes up 50% and the jacket 50% of the cross-sectional area.

The material is cut into threads of length 25 cm and heaped. Then, after cooling, the cut material is brought into contact with distilled water. It is able to absorb more than 80% of its weight in water. The water absorption takes place faster than with the fibers according to the example 1 and 2.

Example 5

The material of example 2 or 3 will initially stretched, then crimped and cut to a fiber length of 4 to 6 cm. Then it will 5% by weight of cellulose fibers (pulp fibers from Nordic woods, bleached), based on the total mass, added and in an airlaid process laid and compacted by calenders with a pressure of 5 MPa. Subsequently the mixture is heated to 180 ° C. The bicomponent fibers enriched with superabsorber work both as a binder and as an absorbent.

Example 6

Filaments acc. Example 4 will be spun out as filaments, chilled on the way down, stretched and placed on an endless conveyor belt. It is known after Process a spunbond fabric made, consolidated and wound up. The Spunbond has sufficient strength for processing in Hygiene articles and also has typical superabsorbent properties.

Similarly, one can with meltblown spinning processes.

Claims (15)

Process for the production of fibers containing Superabsorbents, at least partially using a Fiber material made from a thermoplastic processable mixture superabsorbent polymer and a synthetic thermoplastic Fiber material (hereinafter referred to as SAP fiber blend) is produced, with the following process steps: - Provision of the SAP fiber mix, - provision a second thermoplastic polymer mixture, - coextrusion both mixtures to bicomponent filaments, in which, in thread cross-section seen, the SAP-free polymer blend the core and the SAP fiber blend the peripheral wrapping form - post-processing and / or cutting the filaments to the desired fiber length. A method according to claim 1, characterized in that the Coextrusion takes place in such a way that the the SAP fiber blend existing wrapping 10 up to 50% of the cross-sectional area of bicomponent filaments. A method according to claim 1 or 2, characterized in that the for the thermoplastic polymers used to manufacture the core can be selected from the group polyolefins, polyamides, polyesters, polyurethanes, Extrudable and spinnable polyalcohols, polyethers or spinnable polymers. A method according to claim 3, characterized in that the Core of the bicomponent filaments made of a polyolefin, a mixture formed from polyolefins or from copolymers of several polyolefins becomes. Method according to one of the preceding claims, characterized characterized in that the core of the bicomponent filaments made of polyethylene, preferably a linear low density polyethylene, a polypropylene or a polyethylene-polypropylene copolymer. Method according to one of the preceding claims, characterized characterized that the thermoplastic polymer of the SAP fiber blend selected is extruded from the group of polyamides, polyesters, polyurethanes Polyalcohols, polyether esters or other spinnable polymers. Method according to one of the preceding claims, characterized characterized that the thermoplastic polymer of the SAP fiber blend from a polyolefin ethylene vinyl acetate, preferably polypropylene-ethylene vinyl acetate, is formed. Method according to one of the preceding claims, characterized characterized that the thermoplastic polymer of the SAP fiber blend from a polyolefin, a mixture of polyolefins or from copolymers several polyolefins is formed. Method according to one of the preceding claims, characterized characterized that the SAP fiber blend 5 to 50% by weight of a Contains superabsorbents. Method according to one of the preceding claims, characterized characterized that the SAP fiber blend using a superabsorbent an average grain size of 1 up to 50 μm contains. Method according to one of the preceding claims, characterized characterized that the SAP fiber blend before extruding heat resistant hydrophilizing agent is attached. Method according to one of the preceding claims, characterized characterized that the Outer surface of the Facing layer a smooth cylinder layer is enlarged. Method according to one of the preceding claims, characterized in that the coex filaments are drawn. Use of according to the previous method claims produced bicomponent fibers for the production of an absorbent nonwoven. Use of according to the previous method claims bicomponent fibers produced as an additive to non-SAP granules provided fiber products, in particular airlaid nonwovens made of cellulose fibers.