EP1137838A2

EP1137838A2 - Method for the hydrophilic finishing of fibres based on polyolefins or polyester using sugar ester ethoxylates

Info

Publication number: EP1137838A2
Application number: EP99971875A
Authority: EP
Inventors: Paul Birnbrich; Norbert Bialas; Raymond Mathis; Petra Padurschel; Sven Wucherpfennig
Original assignee: Cognis Deutschland GmbH and Co KG
Current assignee: BASF Personal Care and Nutrition GmbH
Priority date: 1998-11-10
Filing date: 1999-10-30
Publication date: 2001-10-04
Also published as: WO2000028130A2; DE19851688A1; WO2000028130A3

Abstract

The invention relates to a method for the hydrophilic finishing of fibres which exclusively contain polyolefins or polyester. A mixture which contains (a) mostly polyolefins or polyester and (b) 0.01 to 10 wt.% in relation to the sum of polyolefin or polyester of a composition which contains at least one compound from the class of sugar ester ethoxylates is subjected to a usual forming processing method to produce fibres, atemperatures of 180° to 320 °C. According to the invention, (i) there no measured doses of transition metal compounds are added to said mixture being subjected to said forming processing, before or during the forming processing, (ii) said sugar ester ethoxylates (b) are addition products of 4 to 30 mol ethylene oxide per mol sugar esters, sugar esters being conversion products of mono- and/or oligosaccharides and/or sugar alcohols with fatty acids with 8-18 C-atoms and (iii) said sugar ester ethoxylates (b) need at least four cycles in the individual wetting test until they fail.

Description

"Process for the hydrophilic finishing of fibers

based on polyolefins or polyester

using sugar rester ethoxylates "

Field of the Invention

The invention relates to a process for the hydrophilic finishing of fibers which contain polyolefins or polyesters exclusively or entirely. Special sugar ester ethoxylates are used.

State of the art

In numerous cases, the surface of plastic products must be provided with special effects that can either not be created at all or only incompletely for technical reasons, or can only be produced disadvantageously for economic reasons. One such effect is, for example, the improvement of wettability with polar liquids such as water - technical applications are, for example, in the field of the manufacture of hygiene articles.

In the manufacture of hygiene articles, such as diapers or sanitary napkins, absorbent materials are used to absorb aqueous liquids. In order to prevent direct contact with the absorbent material during wear and to increase comfort, this material is covered with a thin, water-permeable nonwoven. Such nonwovens are usually made of synthetic fibers, such as polyolefin or polyester fibers, because these fibers are inexpensive to produce, have good mechanical properties and are thermally stable. However, untreated polyolefin or polyester fibers are not suitable for this purpose because their hydrophobic surface means that they do not have sufficient permeability to aqueous liquids.

For this purpose, the fiber surface must be made hydrophilic by an appropriate preparation. It is also desirable that the hydrophilic finish of the fiber is preserved as long as possible without the water permeability of the nonwoven being reduced. If such nonwovens are processed, for example, in diapers, they can be used several times without becoming water-impermeable. In this way, the wearing time of the diapers is increased and the waste caused by used diapers is reduced.

US-A-5,045,387 describes, for example, an agent for the hydrophilic finishing of polyolefin fibers which contains a mixture of an alkoxylated ricinoleic acid derivative, a hydrogenated ricinoleic acid derivative, a Cjg fatty acid and a polyalkoxylated polymethylsiloxane. This agent must be applied from the outside to the surface of the fibers or films.

US Pat. No. 5,654,086 describes the hydrophilic finishing of otherwise hydrophobic fibers based on thermoplastic plastics, the hydrophobic fiber being treated with a mixture of five surface-active substances (surfactants). This is to (A) polyoxyalkylene adducts of C28-50 "alcohols or alkyl amines or fatty acid amides based on C30-50 fatty acids, (B) polyoxyalkylene adducts of fatty acid amides based on C20-28" F ^_ettsäuren> ( C) fatty acid amides based on Ci6_28 fatty acids and alkanolamines, (D) polyoxyalkylene adducts Cιo-22 "alkyl phosphate salts and (E) Ci2-16 ~ alkyl sulfonate salts.

EP-A-400,622 describes a method for imparting hydrophilic properties to nonwoven materials containing hydrophobic fibers. A composition containing special polyoxyalkylated secondary or tertiary amines is introduced into a molten composition containing polyolefin before spinning.

EP-B-372 890 describes fibers based on polyolefin or polyester with a lubricant adhered to the surface. This lubricant comprises a mixture of (1) fatty acid diethanolamide, (2) a polyether-modified silicone, (3) a sorbitan fatty acid ester and (4) a metal salt of an alkyl sulfonate; Components (1) to (4) are available in special proportions. According to page 3, lines 20-26, the mixture of components (1) to (4) is applied to the surface. This technique of applying the mixture containing the four components to the surface of finished fibers is also explained in more detail on page 4, lines 6-9. There are listed as application techniques: a) the use of rollers, b) spraying and c) immersion. It is therefore a process in which a mixture of components (1) to (4) is applied to the surface of molded polyolefin parts in an additional processing step. The expression "adhered to the fiber surface" used in claim 1 of EP-B-372 890 is accordingly to be clearly understood by the person skilled in the art in such a way that it is merely a loose and temporary adhesion - for example due to relatively weak adhesive forces. by no means a permanent anchoring.

EP-B-616 622 relates to extrudable, compostable polymer compositions comprising an extrudable, thermoplastic polymer, copolymer or mixtures thereof, which comprise a degradation-promoting system comprising an autooxidative component and a Contains transition metal. The autooxidative system comprises a fatty acid, a substituted fatty acid or derivatives or mixtures thereof, the fatty acid having 10 to 22 carbon atoms and containing at least 0.1% by weight of unsaturated compounds and at least 0.1% by weight of free acid . The transition metal is contained in the composition in an amount of 5-500 ppm in the form of a salt and selected from the group cobalt, manganese, copper, cerium, vanadium and iron. The composition should be in the form of a film about 100 microns thick at 60 ° C and a relative humidity of at least 80% biodegradable within 14 days for embrittlement.

WO 98/42898 describes the use of amphiphiles for the permanent hydrophilization of the surfaces of polyolefin-based moldings, fibers and films. A mixture comprising (a) predominantly one or more polyolefins, (b) 0.01 to 10% by weight, based on the polyolefins, of one or more migratable amphiphiles and (c) 0.01 to 1000 ppm, are subjected several transition metal compounds - metal content of the transition metal compounds based on the polyolefins - at temperatures in the range from 180 to 320 ° C. in a customary manner in shaping processing such as extrusion, calendering, injection molding and the like. According to the technical teaching of WO 98/42898, it is imperative in the production of the hydrophilized polyolefin moldings that all three features (a), (b) and (c) are observed, i.e. that a transition metal compound, which is to be regarded as a catalyst, is mandatory in the production.

It is also known to improve the properties of the plastic surface in order to achieve special effects by, for example, oxidative aftertreatment methods such as corona or plasma treatment. Here, the plastic is oxidized or chemically modified in the presence of gases and discharges on the surface, which means that certain surface properties of the plastic can be modified. These methods However, in addition to high energy consumption, they always require an additional operation and lead to ozone emissions in the manufacture of plastic parts. In addition, chemical pretreatment processes, such as treatment with fluorine or chlorine gas, with chromosulfuric acid or fluorosulfonic acid, etc., have long been known.

Description of the invention

It was an object of the present invention to provide tools with which fibers based on polyolefins or polyester and materials derived therefrom, such as nonwovens, can be given a hydrophilic finish and made accessible to multiple wetting by aqueous media, for example urine.

The term “hydrophilization” - more recently “hydrophilization” is often used - is well known to the person skilled in the art. For this purpose, in the well-known standard work "Lexikon für Textilveredlung" (publisher: Hans-Karl Rouette; Volume 1; Dülmen 1995, pages 859-862) it is stated that hydrophobic fibers are made wettable by water by hydrophilization, which for example improves the washability of Synthetic fiber articles, as well as for a better wearing comfort of such articles, are examples of measuring indicators of successful hydrophilization include wetting (the surface spread of a liquid) or the height of rise (a measure of the speed with which water is transported in textile fabrics against gravity ).

In the context of the present invention, hydrophilization - synonymously for this also the term "hydrophilic finishing" is used below - is understood to mean that polyolefin or polyester surfaces which form a wetting angle of more than 90 ° with water - ie hydrophobic "interfaces - be modified by a special measure so that their critical angle is too small after this measure - values are shifted towards this. These are rather dynamic interactions of appropriately modified polymer surfaces with molecules or substrates that are not immobilized, but are in flexible contact with the polymer surface. In this regard, the effects that fall under the concept of hydrophilization are explicitly distinguished from phenomena in which molecules or substrates are in permanent fixation in contact with the polymer surface, as is the case, for example, with coatings and adhesive bonds or with dyeing and printing is.

The invention relates to a process for the hydrophilic finishing of fibers which exclusively or entirely contain polyolefins or polyesters, a mixture comprising (a) predominantly polyolefins or polyesters and (b) 0.01 to 10% by weight, based on the Sum of polyolefin and polyester - a composition which contains at least one compound from the class of the sugar ester ethoxylates, is subjected at a temperature in the range from 180 to 320 ° C. in a customary manner to shaping into fibers, where

(i) no transition metal compounds are added to the mixture which is subjected to the shaping processing before or during this shaping processing,

(ii) the sugar ester ethoxylates (b) adducts of 4 to 30 moles of ethylene oxide per mole of sugar ester, wherein sugar esters are reaction products of mono- and / or oligosaccharides and / or sugar alcohols with fatty acids with 8-18 C atoms and that

(iii) the sugar ester ethoxylates (b) need at least four cycles in the individual wetting test to fail.

The "individual wetting test" is carried out as follows: 600 g of high molecular weight polypropylene granules (commercial product "Eltex PHY 671" from Solvay) are mixed with 9.0 g (-1.5% by weight) of the substance to be tested with regard to a hydrophilic finish. This mixture is introduced into an extruder through a hopper (twin-screw extruder DSK 42/7 from Brabender OHG / Duisburg). An extruder is - as is well known to the person skilled in the art - a plastic processing machine which is suitable for the continuous mixing and plasticizing of both powder and granular thermoplastics. In addition to water cooling, which is intended to prevent premature melting of the granules or powder, there is also a counter-rotating twin screw, which is divided lengthways into three heating zones. The temperature of the heating zones and the speed of the twin screw can be controlled via a PL 2000 data processing plast corder, which is connected to the extruder via a PC interface. The heating zones I, II and III are each set to a temperature of 200 ° C., the three heating zones being air-cooled in order to keep the temperature constant. The mixture of polyopropylene granules and test substance is automatically drawn into the extruder by the twin screw running against each other and transported along the screw. The speed is set to 25 revolutions per minute to ensure thorough mixing and homogenization. This homogeneous and practically bubble-free mixture finally reaches a nozzle, which is a fourth heating zone. The temperature of this nozzle is set to 200 ° C - at this temperature the mixture leaves the extruder. The nozzle is selected so that the average diameter of the strand after it emerges from this nozzle is in the range of approximately 2-3 mm. This strand is granulated, ie cut into small pieces, with lengths of about 2-4 mm being set. The granules obtained are allowed to cool to 20 ° C. This granulate is in a melt spinning plant at a processing temperature of 280 ° C (ie you set both the melt star temperature and also the temperature of the spinneret to 280 ° C) gravimetrically (ie by gravity) converted into fibers. The fibers obtained have a fiber titer in the range from about 10 to 30 dtex (1 dtex corresponds to 1 g fiber per 10000 m fiber length). Then 500 m of this fiber are wound on a roll with a diameter of 6.4 cm. This fiber wound on the roll is withdrawn from the roll and the withdrawn circular structure is stabilized by central knotting, whereby a structure which has the shape of an "8" is obtained; this structure is referred to below as "strands".

2. A 1-1 measuring cylinder (glass cylinder with an inner diameter of 6.0 cm) is filled with distilled water at 20 ° C up to the 1000 ml mark. Now hold the strand to be tested in such a way that its longitudinal direction corresponds to the vertical of the measuring cylinder, ie that the strand appears as vertical "8". A weight consisting of Cu wire is now attached to the bottom part of this "8", the mass of the Cu wire being 0.2064 g of Cu per gram of strand. This copper wire is attached to the strand in the form of turns, the diameter of the copper wire turns being approximately 1 to 2 cm; then these copper wire turns are pressed together by lightly pressing between the thumb and forefinger. Now hold the strand with the Cu weight over the water surface of the measuring cylinder so that the lower part of the Cu weight is immersed in the water and the lowest part of the strand is about 2 mm above the water surface. Then the strand is left go and use a stopwatch to measure the time in seconds it takes for the strand to move from the 1000 ml mark to the 200 ml mark. The start and end of the measuring time are defined by the fact that the bottom end of the strand passes the 1000 ml and 200 ml mark, respectively. In the present test arrangement this means that the strand on its way between the above Marks a diving distance of 28.3 cm. This first measured value is referred to as the Cl value (“value of the first wetting cycle”).

3. The strand is removed from the measuring cylinder immediately after the Cl value has been determined, blotted with cellulose and dried for 1 hour in a forced-air drying cabinet (type UT 5042 EK from Heraeus) at 40 ° C. Then step 2 is repeated. The value now obtained in seconds of the 28.3 cm sink time is referred to as the C2 value ("value of the second wetting cycle"). Drying and determination of the 28.3 cm sink time are now repeated again, the C3 value ("value of the third wetting cycle") being obtained. Drying and determination of the 28.3 cm sink time are now repeated again, giving the C4 value ("value of the fourth wetting cycle"). Drying and determination of the 28.3 cm sink time are now repeated again, giving the C5 value ("value of the fifth wetting cycle"). If desired, the described procedure can also be repeated several times, so that if necessary, C5, C6, C7, etc. values can also be determined.

4. If 28.3 cm sink times (Cl to C5 values) are above 180 seconds, the respective cycle is ended.

5. If air bubbles get stuck on the strand, mainly in its upper part, when immersed in the water of the measuring cylinder, these are immediately removed by means of a wire or by briefly touching it with a finger.

The individual wetting test is passed if the values for Cl, C2 and C3 are each a maximum of 50 seconds or less. This is equivalent to the fact that when using a test substance suitable according to the invention, ie a sugar ester ethoxylate (b), for the hydrophilic finishing of the polypropylene, a value above 50 seconds is reached at the earliest when passing through the fourth cycle (C4 value). A sugar ester ethoxylate (b) is suitable for the purposes of the present invention if a failure, that is to say a 28.3 cm sink time value above 50 seconds, occurs at the earliest at the C4 value.

As already mentioned, the sugar ester ethoxylates (b) to be used according to the invention are addition products of 4 to 30 moles of ethylene oxide per mole of sugar ester, with reaction products of mono- and / or oligosaccharides and / or sugar alcohols with fatty acids having 8-18 C atoms among sugar esters are to be understood. These compounds can be used both individually and in combination with one another.

In a preferred embodiment, the sugar esters on which the sugar ester ethoxylates are based contain their two building blocks - the mono- or oligosaccharides or sugar alcohols on the one hand and the fatty acids on the other hand - in a molar ratio of 1: 1.

In a preferred embodiment, those sugar ester ethoxylates are used which are adducts of 4 to 20 moles of ethylene oxide per mole of sugar ester. Lauric acid is particularly preferred as the fatty acid component of the sugar ester ethoxylates.

Examples of suitable mono- or disaccharide units of the sugar ester ethoxylates are glucose, fructose, mannose, galactose, telose, gulose, allose, old rose, idose, arabinose, xylose, lyxose, libose and mixtures thereof. Examples of suitable sugar alcohol building blocks of the sugar ester ethoxylates are the polyhydroxy compounds obtainable from monosaccharides by reducing the carbonyl function, in particular pentites and hexites, for example sorbitol, mannitol, adonite, dulcitol, erythritol, xylitol and mixtures thereof.

An adduct of 20 moles of ethylene oxide with sorbitan monolaurate is a particularly preferred sugar ester ethoxylate. In a further embodiment of the invention, compounds (b) are used which require at least six cycles in the individual wetting test to fail. In the case of these compounds, all the values C1, C2, C3, C4 and C5 in the individual wetting test described above are below 50 seconds.

The compounds (b) to be used according to the invention are capable of migration. This is to be understood to mean that these compounds are able to reach the surface of the resulting polyolefin or polyester molded body in the course of the production of the fibers by, for example, extrusion processes. As a result, they accumulate on the surface or the areas close to the surface of the plastic matrix, which has been verified by the applicant by successive removal of surface layers in the order of magnitude of a few nanometers each and subsequent scanning techniques.

The polyolefin or polyester fibers which can be obtained by the process according to the invention and textile fabrics which can be produced therefrom — for example nonwovens — are distinguished by excellent wettability by aqueous media.

The technical action within the meaning of the teaching according to the invention ensures on the one hand that the desired improved and permanent surface hydrophilicity is achieved, and on the other hand that this can be achieved without impairing other material parameters.

The sugar ester ethoxylates (b) are incorporated into the plastic matrix in the course of customary shaping processing processes such as extrusion processes and the like. It may be desirable to use a pre-assembled mixture of components a) and b). Other customary auxiliaries used, which have proven themselves in general in the processing of plastics and which are known to the person skilled in the art, for example slip agents, antistatic agents, lubricants, release agents, UV stabilizers, Antioxidants, fillers, fire retardants, mold release agents, nucleating agents and antiblocking agents can be prepared accordingly in separate form and added when the finished products are finally mixed. However, it may also be desirable, for example when using the extrusion technology, to meter all or part of the components b) and / or other additives directly into the polymer melt on the extruder, so that the mixture of components a) and b) - and optionally other auxiliaries - is not already available as a ready-made product from the start, but is only present in the extruder itself. Such a technique is useful, for example, when the compounds b) to be metered into the polymer melt are in liquid form and injection of this component is easier than pre-assembly.

It may also be desirable - although not necessary to achieve the effect according to the invention - to carry out a corona or plasma treatment in the usual way after the use of components a) and b) according to the invention.

Polyolefins are preferred as component a) in the context of the invention. All known polymer and copolymer types based on ethylene or propylene are suitable here. Mixtures of pure polyolefins with copolymers are also generally suitable. Polymer types which are particularly suitable for the teaching according to the invention are listed in the following compilation:

Poly (ethylene) such as HDPE (high density polyethylene), LDPE (low density polyethylene), VLDPE (very low density polyethylene), LLDPE (linear low density polyethylene), MDPE (medium density polyethylene), UHMPE (ultra high molecular polyethylene), VPE (cross-linked polyethylene), HPPE (high pressure polyethylene); isotactic polypropylene; syndiotactic polypropylene; Metallocene catalyzed polypropylene, impact modified polypropylene, random copolymers based on ethylene and pro pylene, block copolymers based on ethylene and propylene; EPM (poly [ethylene-co-propylene]); EPDM (Poly [ethylene-co-propylene-co-conjugated diene]).

Other suitable types of polymers are: poly (styrene); Poly (methylstyrene); Poly (oxymethylene); Metallocene-catalyzed alpha-olefin or cycloolefin copolymers such as norbornene-ethylene copolymers; Copolymers containing at least 80% ethylene and / or styrene and less than 20% monomers such as vinyl acetate, acrylic acid esters, methacrylic acid esters, acrylic acid, acrylonitrile, vinyl chloride. Examples of such polymers are: poly (ethylene-co-ethyl acrylate), poly (ethylene-co-vinyl acetate), poly (ethylene-co-vinyl chloride), poly (styrene-co-acrylonitrile). Graft copolymers and polymer blends are also suitable, that is to say mixtures of polymers which contain, inter alia, the abovementioned polymers, for example polymer blends based on polyethylene and polypropylene.

In the context of the present invention, homopolymers and copolymers based on ethylene and propylene are particularly preferred. In one embodiment of the present invention, accordingly, only polyethylene is used as the polyolefin, in another embodiment only polypropylene, in another embodiment, copolymers based on ethylene and propylene.

In a very particularly preferred embodiment of the invention, component a) is polypropylene.

Another object of the invention is the use of the hydrophilized polyolefin or polyester-based fibers produced by the process described above and wettable by aqueous media for the production of textile fabrics. The textile fabrics are preferably nonwovens. In a particularly preferred embodiment, these textile fabrics are intended for use in diapers. For the latter case, the use of textile fabrics in diapers, the individual wetting test represents a suitable simulation. Diapers are usually worn over a period of 3 to 5 hours, the inside of which is wetted with urine on average up to 3 times. It must then be ensured that a hydrophilically finished fleece based on an otherwise hydrophobic plastic is sufficiently wettable so that the urine can penetrate through the fleece and be bound by the absorber material of the diaper.

Nonwovens can be produced by all methods of nonwoven production known in the prior art, as described for example in Ullmann's Encyclopedia of Industrial Chemistry, Vol. A 17, VCH Weinheim 1994, pages 572-581. Nonwovens which are produced either by the so-called "dry laid" method or by spunbonding or spunbonding are preferred. The "dry laid" method is based on staple fibers which are usually separated into individual fibers by carding and then using a aerodynamic or hydrodynamic processes are combined to form the unconsolidated nonwoven. This is then bonded, for example, to the finished nonwoven by a thermal treatment (the so-called “thermobonding”). The synthetic fibers are either heated to such an extent that their surface melts and the individual fibers are bonded to one another at the contact points, or the fibers are mixed with an additive Coated, which melts during the heat treatment and thus connects the individual fibers to one another. The connection is fixed by cooling. In addition to this method, all other methods that are used in the prior art for connecting nonwovens are of course also suitable individual filaments, which are formed by the melt spinning process from extruded polymers which are pressed under high pressure through spinnerets. The filaments emerging from the spinnerets are bundled, stretched and laid down to form a fleece, which is usually by "thermobonding" v is established. Examples

Polypropylene test specimens equipped with different test substances (B1 = example according to the invention; VI and V2 = comparative tests) were subjected to the individual wetting test described above. The test results are summarized in Table 1; the 28.3 cm sink times (in seconds) after one, two, three, four and five wetting cycles (columns C1 to C5) are indicated.

Table 1

(1) adduct of 20 moles of ethylene oxide with 1 mole of sorbitan monolaurate ("Eumulsin SML 20" from Henkel KGaA / Düsseldorf);

It is clear that the values C1, C2 and C3 of example B1 are clearly below the critical value of 50 seconds and are clearly superior to the corresponding values of comparative examples VI and V2.

Claims

Patent claims

1. A process for the hydrophilic finishing of fibers which contain all or part of polyolefins or polyesters, a mixture comprising (a) predominantly polyolefins or polyesters and (b) 0.01 to 10% by weight, based on the sum of polyolefin and polyester - a composition which contains at least one compound from the class of the sugar ester ethoxylates, at temperatures in the range from 180 to 320 ° C in a customary manner to shaping into fibers, characterized in that

2. The method according to claim 1, wherein polypropylene is used as component a).

3. The method according to claim 1 or 2, wherein the adduct of 20 moles of ethylene oxide with sorbitan monolaurate is used as component b).

4. The method according to any one of claims 1 to 3, wherein customary additional auxiliaries for processing plastics are added in the shaping processing and / or corona or plasma treatment is carried out in the usual way as an additional further processing step.

5. A method for imparting hydrophilic properties to nonwoven materials containing fibers made of polyolefin or polyester and for making them permeable to aqueous media, characterized in that the hydrophilically finished fibers based on the method prepared according to one of claims 1 to 4 of polyolefin or polyester processed in the usual way - for example to nonwovens.

6. Use of the hydrophilized polyolefin or polyester-based fibers produced by the process according to one of claims 1 to 4 and wettable by aqueous media for the production of textile fabrics.

7. Use according to claim 6, wherein the textile fabrics are nonwovens.

8. Use according to claim 6 or 7, wherein the textile fabrics are intended for use in diapers.