MEESSEN, Patric (Rue Knipp 9, La Calamine, B-4728, BE)
DULLAERT, Konraad (Tereikenlaan 2, Heverlee, B-3001, BE)
LITVINOV, Victor (Gozewijnstraat 4, WV Beek, NL-6191, NL)
SARKISSOVA-MIKHYLOVA, Marianna (Heiligenbergstraat 10, DG Bunde, NL-6141, NL)
MEESSEN, Patric (Rue Knipp 9, La Calamine, B-4728, BE)
DULLAERT, Konraad (Tereikenlaan 2, Heverlee, B-3001, BE)
LITVINOV, Victor (Gozewijnstraat 4, WV Beek, NL-6191, NL)
1. Elastic fiber comprising a polyolefin, the fiber being cross linked as a result of a reaction between acid functional groups or derivatives thereof on the polyolefin and a composition capable to form a covalent bond, characterized in that the composition comprises at least two different compounds with different functional groups, wherein the different functional groups of that composition are chosen from a group consisting of alcohol, amine, thiol, or derivatives thereof and wherein the different functional groups have a different reactivity with the acid functional groups or derivatives thereof.
2. Fiber according to claim 1 , wherein a first compound comprises primary groups and a second compound comprises secondary groups.
3. Fiber according to claim 1 , wherein the fiber further comprises a non-reactive solvent or non-reactive polymer. 4. Fiber according to claim 1 , wherein the polyolefin is a mixture of between 95 and 60 wt% of functionalized amorphous copolymer and between 5 and 40 wt% of a functionalized crystalline polymer. 5. Fiber according to claim 1 , wherein the polyolefin comprises between 1 and
4 wt% of functional groups. 6. Fiber according to claim 4, wherein the amorphous polymer is EP(D)M and the crystalline polymer is polyethylene (PE).
7. Fiber according to claim 1 , wherein the functional group is a succinic anhydride group.
8. Fabric comprising the fiber according to any of the claims 1 - 5. 9. Composite comprising the fiber according to any of the claims 1 - 5.
The invention relates to an elastic fiber comprising a polyolefin, the fiber being cross linked as a result of a reaction between acid functional groups or derivatives thereof on the polyolefin and a composition capable to form a covalent bond.
An elastic fiber comprising a polyolefin is known from e.g. FR1581819. The polyolefin in FR1581819 is carboxylated in an extruder and crosslinked in a bath containing diols or diamines. To facilitate the fiber spinning process diols or diamines were added to the extruder. This however resulted in a problem of premature crosslinking in the extruded and fibers with a relatively high level of gels.
This problem is solved by the present invention in that the composition comprises at least two different compounds with different functional groups, wherein the different functional groups of that composition are chosen from a group consisting of alcohol, amine, thiol, or derivatives thereof and wherein the different functional groups have a different reactivity with the acid functional groups or derivatives thereof. The fiber is cross-linked as a result of a reaction between acid functional groups on the polyolefin and the composition capable to form a covalent bond.
The composition capable to form a covalent bond reacts with the acid functional groups on the polyolefin as a result of which none of the compounds can migrate to the surface of the fiber.
A variety of polyolefin polymers can be used in the practice of this invention. Preferred polyolefins can be chosen from polyethylenes, ethylene-propylene copolymers, ethylene-butene copolymers, ethylene-octene copolymers, polypropylene, polyisoprenes, polybutadienes, polystyrenebutadienes, or ethylene-propylene diene terpolymers (EPDM), wherein the diene is a non-conjugated diene like e.g. 5-ethyliden- 2-norbornene (ENB), 5-vinyl-2-norbornene (VNB), dicyclopentadiene (DCPD), 1 ,4- hexadiene or mixtures thereof.
The functional groups on the polyolefin are acid groups or derivatives thereof. Acid groups or derivatives thereof on the polyolefin are understood to be of carboxylic (c) type or sulfonic (s) type bond to the polyolefin (PO). These two categories are herein after denoted by c-PO, or s-PO respectively.
Carboxylic acid functional polyolefins can be obtained by different means, amongst which the radical grafting process of the polyolefin with a suited acid monomer, the "ene"-type reaction of an unsaturated polyolefin with an acid containing olefin, the copolymerization of olefins and an acid containing co-monomer, and the selective oxidation with air, oxygen, ozone of polyolefins.
Sulfonic acid functional polyolefins can be obtained by different means, amongst which the sulfonation with oleum, the radical grafting process of the polyolefin with a suited monomer, and the copolymerization of olefins and a sulfonic acid containing co-monomer. Examples of the carboxylic acid functional groups include organic acids having a saturated or unsaturated hydrocarbon group which may be any of aliphatic, alicyclic, and aromatic hydrocarbon group. Examples of derivatives of the carboxylic acid include carboxylic acid anhydrides, thiocarboxylic acids, esters, amides, imides, and dicarboxylic acids and monoesters threreof. Exemplary carboxylic acid groups and their derivatives include radicals of the following molecules: formic acid, acetic acid, propioninc acid, butyric acid, acrylic acid, methacrylic acid, malonic acid, maleic acid, fumaric acid, succinic acid, glutaric acid, lactic acid, phthalic acid, isophthalic acid, terephthalic acid, p- phenylenediacetic acid, p-hydroxybenzoic acid, p-aminobenzoic acid, mercaptoacetic acid, and other carboxylic acids, as well as substituted carboxylic acids; succinic anhydride, maleic anhydride, phthalic anhydride, and other acid anhydrides; esters of maleic acid, esters of malonic acid, esters of succinic acid, esters of glutaric acid, ethyl acetate, and other aliphatic esters; esters of phthalic acid, esters of isophthalic acid, esters of terephthalic acid, ethyl-m-aminobenzoate, methyl-p-hydroxybenzoate, and other aromatic esters; maleamide, maleamic acid, succinicmonoamide, 5- hydroxyvaleramide, malonamide, and other amides; maleimide, succinimide, and other imides.
Among these, the functional group is preferably succinic anhydride, maleic anhydride, glutaric anhydride, phthalic anhydride, or other cyclic acid anhydride; formic acid, acetic acid, propionic acid, butyric acid or derivatives thereof.
Most preferably, in the fiber of the invention the functional group is a succinic anhydride group.
It is understood that if the acid functional groups on the polyolefin is introduced by means by a polymer modification, these functional groups can be present on the polyolefin in the form of single units as well as oligomeric units.
Examples of sulfonic groups and their derivatives include radicals of the following molecules: sulfonic acid, methylsulfonic acid, ethylsulfonic acid, benzenesulfonic acid, toluenesulfonic acid and derivatives thereof.
In the present invention, the composition capable to form a covalent bond comprises at least two compounds with functional groups, wherein the functional groups can be chosen from a group consisting of alcohol, amine, thiol, or derivatives thereof and wherein the different functional groups have a different reactivity with the acid functional groups or derivatives thereof.
Examples of the above-mentioned compounds with fuctional groups include a polyamine having two or more amino groups; a polyol having two or more hydroxy groups; and polythiol having two or more thiol groups, or a mixture of these.
Exemplary polyamine compositions include alicyclic polyamines, aliphatic polyamines, aromatic polyamines, and nitrogen-containing heterocyclic amines as described below. Exemplary alicyclic amines include 1-amino-3-aminomethyl-3,5,5- trimethylcyclohexane, bis-(4-aminocyclohexyl)methane, diaminocyclohexane, and di- (aminomethyl)cyclohexane.
Exemplary aliphatic polyamines include ethylenediamine, 1 ,3- diaminopropane, 1 ,2-diaminopropane, 1 ,4-diaminobutane, 1 ,5-diaminopentane, hexamethylene diamine, 1 ,7-diaminoheptane, 1 ,12-diaminododecane, diethylene triamine, triethylene tetramine, N.N'-dimethyl ethylenediamine, N,N'-diethyl ethylenediamine, N.N'-diisopropyl ethylenediamine, N,N'-dimethyl-1 ,3-propanediamine, N,N'-diethyl-1 ,3-propanediamine, N,N'-diisopropyl-1 ,3-propanediamine, N.N'-dimethyl- 1 ,6-hexanediamine, N,N'-diethyl-1 ,6-hexanediamine, and N,N',N"- trimethylbis(hexamethylene)thamine.
Exemplary aromatic polyamines and nitrogen-containing heterocycle amines include diaminotoluene, diaminoxylene, dimethylxylylenediamine, tris(dimethylaminomethyl)phenol, o-phenylenediamine, m-phenylenediamine, p- phenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, p-aminophenyl phenylenediamine, and 3-amino-1 ,2,4-triazole.
An advantage of a compound comprising a primary amine group is the thermally stable character of the covalent bond of such a compound formed with a cyclic anhydride group of the polyolefin. The formed imid represents an utmost temperature stable covalent bond. The primary amine containing compound will be irreversibly attached to the polymer composition. This represents a substantial
improvement of the composition since the immobilized composition will nor evaporate nor migrate to the fiber surface.
Of the polyamine composition as mentioned above, the preferred are hexamethylenediamine, N,N'-dimethyl-1 ,6-hexanediamine, and diaminodiphenylsulfone in view of their excellent effect in improving compression set, mechanical strength, and in particular, tensile strength.
The polyol is not particularly limited for its molecular weight, skeleton or the like as long as it contains two or more hydroxy groups, and exemplary polyol composition include -alcanediols, cyclic polyols, polyether polyols, polyester polyols, other polyols, and mixtures thereof as described below.
One or more of the hydroxyl functionality of the composition might be derivatized in the form of an ester, epoxide, alcoholate, full- or hemi-acetal.
Exemplary polyether polyols include polyols produced by adding at least one member selected from ethylene oxide, propylene oxide, buthylene oxide, styrene oxide, and the like to at least one member selected from polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, 1 ,1 ,1-trimethylol propane, 1 ,2,5-hexanetriol, 1 ,3-butanediol, 1 ,4-butanediol, 4, 4'-di hydroxy phenyl propane, 4,4'-dihydroxy phenyl methane, pentaerythritol, and water; polyoxytetramethylene oxide; and the like which may be used alone or in combination of two or more.
Exemplary polyester polyols include condensation polymers of one or two of ethyleneglycol, propylene glycol, butanediol, pentanediol, hexanediol, cyclohexane dimethanol, glycerin, 1 ,1 ,1-trimethylolpropane, and other low molecular weight polyols with one or two of glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, terephthalic acid, isophthalic acid, dimer acid, and other low molecular weight carboxylic acid, or one or two of oligomeric acids; and products by ring-opening polymerization of propione lactone, valerolactone or the like; which may be used alone or in combination of two or more.
Exemplary other polyols include polymer polyol, natural feedstock polyols, polycarbonate polyol; polybutadiene polyol; hydrogenated polybutadiene polyol; acrylic polyol; ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butanediol, pentanediol, hexanediol, ethyl vinylacetate copolymer, polyethylene glycol laurylamine, polypropylene glycol laurylamine and polyethylene glycol octylamine, polypropylene glycol octylamine, polyethylene glycol
stearylamine, polypropylene glycol stearylamine, and other low molecular weight polyols, which may be used alone or in combination of two or more.
The polythiol composition is not limited for its molecular weight, skeleton or the like as long as it has two ore more thiol groups. Exemplary polythiol compositions include ethanedithiol, 1 ,3-propanedithiol, 1 ,4-butanedithiol, 1 ,2- benzenedithiol, 1 ,3-benzenedithiol, 1 ,4-benzenedithiol, 1 ,10-decanedithiol, 1 ,2- ethanedithiol, 1 ,6-hexanedithiol, 1 ,9-nonanedithiol, 1 ,8-octanedithiol, 1 ,5- pentanedithiol, 1 ,3-propanedithiol, toluene-3,4-dithiol, 3,6-dichloro-1 ,2-benzenedithiol, 1 ,5-naphthalenedithiol, 1 ,2-benzenedimethanethiol, 1 ,3-benzenedimethanethiol, 1 ,4- benzenedimethanethiol, 4,4'-thiobisbenzenethiol, trimethylolpropane tris(thioglycolate), and polythiol (thiocol) or thiol-modified macromolecule (resin, rubber, etc.), which may be used alone or in combination of two or more.
Preferably at least two of the compounds comprising functional groups are compounds comprising an alcohol or a secondary amine group. A general advantage of a compound comprising an alcohol or secondary amine group is the thermally reversible character of the covalent bond that such a compound forms with the functional group of the polyolefin. The equilibrium between the alcohol or secondary amine group and e.g. a cyclic anhydride on one side and the ester acid or amid acid on the other side, lies on the anhydride side at elevated processing temperatures. Under high temperature conditions, the polymer composition according to the invention will predominantly be in the anhydride form, resulting in a low melt viscosity. Such a low melt viscosity composition is favorable to an improved fiber spinning process. After the spinning process, cooling of the fiber will shift the mentioned equilibrium towards the ester acid or amid acid. In consequence, the cooling will result in formation of covalent cross-links within the fiber composition resulting in a substantially increased strength.
The fiber according to the invention preferably comprises compounds comprising primary and secondary groups.
The at least two compounds may be mixed at a ratio adequately selected depending on the application, required physical properties, processing behavior and the like of the composition of the present invention.
The advantage of a combination of two or more compounds can be summarized in a phased reactivity of the composition capable of forming covalent bonds.
Another advantage in the combination of two compounds or more consists in the improved properties of the composition such as improved miscibility in the polymer and reduced composition melting temperature.
Examples of combinations of the compounds according to the invention are a polyol with a polyamine, a polythiol with a polyamine, a primary polyamine with a secondary polyamine or combinations of compounds with different functional groups in each compound.
Exemplary the combination of compounds are ethylene glycol with diethylene glycol, hexamethylene diamine with 1 ,6-hexanediol, 4-aminobutanol with 3- hydroxy aminobutane, m-phenylene diamine with p-phenylene diamine, phenyl ethylene diamine with diethylene glycol and ethanolamine with diethanolamine.
Alternatively, the fiber according to the invention comprises a first compound comprising primary groups and a second compound comprising secondary groups. Examples of combinations of the compounds according to the invention are a primary polyamine with a secondary polyamine, a primary polyol with a secondary polyol or a primary polyamine with a secondary polyol.
Exemplary the combination of compounds are hexamethylene diamine with N,N'-dimethyl hexamethylene diamine, diethylene glycol with cyclododecanediol, hexamethylene diamine with cyclododecanediol,
The reaction of maleated EPDM (m-EP(D)M) with Nylons that possesses terminal amino groups results in cross-linking EP(D)M, which is described e.g. in O. Okada, H. Keskkula, D.R. Paul, Polymer, 40, 2699 (1999). Due to high melting temperature of Nylons, the blends can provide high temperature stability of the fibers.
A further method to achieve an increased cross-linking speed, while avoiding premature gel formation, is an as fast as possible homogenization of the composition capable to form a covalent bond in the polyolefin melt. Dissolving the composition capable to form a covalent bond in a non-reactive solvent can attain this. Therefore, the fiber according to the invention preferably further comprises a non- reactive solvent for the composition capable to form a covalent bond. The amount of the non-reactive solvent related to the polyolefin is generally less than 20 wt%.
Alternatively, the fiber of the invention may comprise a non-reactive polymer. In one embodiment of the invention the non-reactive polymer can be used as a carrier of the composition capable to form a covalent bond. The use of a non-reactive
polymer in the composition can further improve composition characteristics by increasing or reducing crystallinity, tensile strength, elasticity and others.
To obtain a fiber with an increased initial modulus, the fiber according to the invention, preferably comprises a polyolefin, which is a mixture of between 95 and 60 wt% of functionalized amorphous copolymer and between 5 and 40 wt% of a functionalized crystalline polymer.
A major advantage of EP(D)M is its predominantly amorphous character allowing for a high elasticity. In general an ethylene content up to 60 wt% does not result in the formation of a crystalline phase. Even at higher ethylene levels of up to 80 wt% the amount of crystallinity is low compared to e.g. PE. The increase of crystallinity can provide a significant enhancement of some of the mechanical properties of the polyolefin based elastic fiber. Such property enhancement can be obtained by blending acid functional versions of a mainly amorphous polyolefin such as EPDM with a crystalline polyolefin such as PE. Lack of miscibility at ambient temperature or sole crystallinity of one polymer will result in phase separation of the two selected polymers and failure of mechanical properties due to heterogeneity of the fiber. This phase separation through immiscibility is avoided in the present invention by reactive compatibilization by using acid functional versions of the immiscible polyolefins. The reactive compatibilization can only concern a fraction of the polymers that can thus be further diluted by non- reactive miscible polymers.
A preferred embodiment of the present invention is that the amorphous polymer in the fiber is EP(D)M and the crystalline polymer is polyethylene (PE). Mechanical properties like the tensile strength and modulus strongly depend on the crosslink density. To obtain an acceptable level of crosslink density, the polyolefin in the fiber of the invention preferably comprises between 1 and 4 wt% of functional groups.
In case the composition of the fiber consists of a mixture of two or more polymers, each of the polymers will have their individual level of acid functionality. This will result after cross-linking in multimodal physical networks further improving the stress-strain properties of the fibers.
The fiber of the invention can be made by heating a functionalized polyolefin e.g. maleated or sulfonated polyolefin, or polyolefin mixture in a melting section of an extruder to a temperature of between 250 and 300 0 C and degassing the
formed melt. The composition capable to form a covalent bond is added to the melt in an amount to convert at least 50 mol% of the acid or anhydride groups of the polyolefin. The composition is dosed in its pure form, dispersed in an inert polymer or preferably dissolved in a suitable solvent. After homogenization the mixture is spun into a fiber and cooled by means of a water bath.
An excess of a non-reactant solvent e.g. added to further improve the fiber processing, can be removed by evaporation or extraction.
In view of the broad number of available parameters, optimal processing conditions will consist of an adequate combination of polyolefins type and molecular weight, functionality level and type, composition mixture and processing temperature to provide a low enough melt viscosity for a predominantly solvent free spinning process.
In a preferred embodiment of the present invention the chemical equilibrium between the cyclic anhydride functional polyolefin and the covalent bond forming composition is used to further reduce melt viscosity of the composition. By introducing the covalent bond forming composition at a relative high temperature at which the cyclic anhydride are thermodynamically more stable, cross-linking will be limited resulting in a low viscosity mixture with little shear forces and little degradation. Covalent bond formation will only occur upon cooling of the melt following the fiber spinning process.
The invention further relates to a fabric comprising the fiber of the present invention and a composite comprising the fiber of the present invention. The fibers of the present invention includes staple fibers, spunbond fibers or melt blown fibers. Staple fibers can be melt spun into the final fiber diameter directly without additional drawing, or they can be melt spun into a higher diameter and subsequently hot or cold drawn to the desired diameter using conventional fiber drawing techniques. The fiber of the present invention may also be part of a bicomponent fiber. For example, in a sheath/core bicomponent fiber (i.e., one in which the sheath concentrically surrounds the core), the functionalized and crosslinked polyolefin can be in either the sheath or the core. Typically and preferably, the polyolefin polymer is the sheath component of the bicomponent fiber. If it is the core component, then the fiber of the present invention has another advantage over the fiber known from US6709742, as the sheath component must be not such that it does not prevent the crosslinking of the core, i.e., the sheath component does not need to be transparent or translucent to UV-radiation such that sufficient UV-radiation can pass through it to substantially
crosslink the core polymer. Different polyolefin polymers can also be used independently as the sheath and the core in the same fiber, preferably where both components are elastic and especially where the sheath component has a lower melting point than the core component. The elastic fiber can be used with other fibers such as PET, nylon, cotton, Dyneema R , etc. to make elastic fabrics. As an added advantage, the heat (and moisture) resistance of certain elastic fibers can enable polyester PET fibers to be dyed at ordinary PET dyeing conditions. The other commonly used elastic fibers, especially spandex (e.g., Lycra.TM.), can only be used at less severe PET dyeing conditions to prevent degradation of properties.
Fabrics made from the elastic fibers of this invention include woven, nonwoven and knit fabrics. Nonwoven fabrics can be made various by methods, e.g., spunlaced (or hydrodynamically entangled) fabrics, carding and thermally bonding staple fibers; spunbonding continuous fibers in one continuous operation; or by melt blowing fibers into fabric and subsequently calandering or thermally bonding the resultant web. These various nonwoven fabric manufacturing techniques are well known to those skilled in the art and the disclosure is not limited to any particular method. Other structures made from such fibers are also included within the scope of the invention, including e.g., blends of these novel fibers with other fibers (e.g., poly(ethylene terephthalate) or cotton).
Fabricated articles which can be made using the elastic fibers and fabrics of this invention include elastic composite articles (e.g., diapers) that have elastic portions.
Comparative experiment A
A maleated EPM (48 wt% ethylene, 2 wt% maleic anhydride and a melt flow viscosity 4.5 dg/min at 190 0 C and 2.16 kg) was extruded in a ZSK30 extruder at 50 rpm with 10 heating zones at barrel temperatures increasing from 200 to 27O 0 C (zones 1 to 5) and a constant temperature of 250 0 C for the zones 6 to 10 through a round die with inner diameter of 2 mm and a length of 5 mm. The extruded filament was quenched using a water bath at 25 0 C. A spin-draw ratio (velocity of draw roll/velocity at spinneret orifice) of about 1.4 was used. The tensile properties of three samples of the fiber were tested on an lnstron tester.
A maleated EPM (48 wt% ethylene, 2 wt% maleic anhydride and a melt flow viscosity 4.5 dg/min at 190 0 C and 2.16 kg) was heated with m-PE (1.5 wt% maleic anhydride and a melt flow viscosity 0.5 dg/min at 190 0 C and 2.16 kg) in a ZSK30 extruder at 150 rpm with 10 heating zones at temperatures increasing from 200 to 270 °C(zones 1 to 5) and a constant temperature of 270 0 C for the zones 6 to 10. After degassing, a solution containing 1 part diethylene glycol, 2 parts cyclododecanediol in 3 parts of diethylene glycol dibutylether was added at a rate of 150 ml/h in zone 6 and the resulting mixture was extruded through a round die with inner diameter of 2 mm and a length of 5 mm. The extruded filament was quenched using a water bath at 25 0 C. A spin-draw ratio of about 1.4 was used. The tensile properties of three samples of the fiber were tested on an lnstron tester.
The properties of the Example and Comparative Experiment are given in Table 2.
With respect to the non-crosslinked fiber (A), an increase of modulus of about 8x can be obtained, without significant loss of elongation at break.
Next Patent: CORRELATING DEVICE