KR20050057511A - Polypropylene fibres suitable for spunbonded non-woven fabrics - Google Patents

Abstract

A fibre for spunbonded fabrics comprising a propylene polymer composition (A) having an MFR (1) value from 6 to 150 g/10 min and being selected from (i) a crystalline propylene random copolymer or crystalline propylene polymer composition containing at least 0.8% by weight of ethylene and having a melting temperature of 153°C or higher, a content of fraction soluble in xylene at room temperature lower than 10% by weight, and a value of the ratio of the polymer fraction collected at the temperature range from 25° to 95°C to the xylene soluble fraction at room temperature higher than 4; and (ii) a crystalline propylene polymer composition having a melting temperature of 153°C or higher, a content of fraction soluble in xylene at room temperature lower than 10% by weight; the said composition containing at least 0.64 wt% of ethylene or a C4-C10 a-olefin recurring unit and comprising: (1) 20- 80 wt% of a crystalline propylene polymer containing up to 1.5 wt% of ethylene and/or C4-C10 a-olefin; and (II) 20-80 wt% of a crystalline propylene random copolymer selected from (IIa) a copolymer of propylene with 0.8 to 10 wt% of ethylene and/or (IIb) a copolymer of propylene with 1.5 to 18 wt% of a C4-CIO a-olefin. Said polymer composition (A) is obtainable by way of chemical degradation of a precursor polymer composition (A) having MFR values (MFR (2)) of from 0.5 to 50 g/10 min, provided that the ratio of MFR (1) to MFR (2) be from 1.5 to 60. Propylene polymer composition (ii) as described above and non- woven fabrics that are prepared with the said fibres. The said fabric is useful for coverstock and diapers.

Description

Polypropylene fiber suitable for spunbond nonwovens {POLYPROPYLENE FIBRES SUITABLE FOR SPUNBONDED NON-WOVEN FABRICS}

The present invention relates to thermally bondable fibers containing propylene polymer compositions, spunbond nonwovens obtained from such fibers and polypropylene compositions for the production of such fibers.

Definitions for fibers include spunbond fibers and / or filaments.

Fibers formed from olefin copolymers or polyolefin compositions are already known in the art. In particular, the use of random copolymers of propylene has already been observed to only improve the thermal bondability (ie bond strength) and / or calendering speed of the fibers.

Propylene random copolymer fibers are also typically used for nonwovens to improve the ductility of nonwovens and good properties are generally obtained at elevated contents of the soluble fraction. However, a disadvantage is that the elevated solvent soluble content substantially reduces the tenacity of the nonwovens.

Examples of fibers formed from olefin copolymers and polyolefin mixtures are described in EP 416 620. The polymers having a crystallinity of less than 45% can provide fibers with lower toughness and lower modulus but improved ductility than those formed from more crystalline propylene polymers and maintain fabric properties.

Another example is provided in US Pat. No. 4,211,819, which describes a hot melt adhesive fiber obtained by spinning crystalline poly (propylene-co-ethylene-co-1-butene). Since these fibers with low hot melt adhesion temperatures are used only as binder materials, mechanical properties are imparted by other materials. In fact, when the nonwoven is produced in the examples, the fibers are mixed with the rayon fibers before rolling. Applicants have now found that certain olefin copolymers and olefin copolymer compositions provide fibers with improved thermal bondability associated with a balance of good mechanical properties, and nonwovens with better balance of thermal bond properties and physical properties. Thus, at the same or even low thermal bond temperatures, the nonwovens of the present invention exhibit properties such as improved toughness and elongation compared to known spunbond nonwovens made of propylene homopolymers and copolymers having similar melt flow rates (MFR). .

Another advantage of spawnbonded nonwovens is improved softness. High ductility, along with soft touch, contributes to the final quality improvement of the nonwovens, and in particular contributes to the final quality improvement of the nonwovens for hygienic applications where highly flexible nonwoven fibers with a cloth-like appearance are appreciated on the market.

Another advantage is that by appropriately selecting some intrinsic properties of the propylene polymer material, it is possible to obtain nonwovens with good properties such as toughness even in combination with high elongation and low solvent soluble components.

Accordingly, the present invention has a MFR value (MFR (1)) of 6 to 150 g / 10 min, preferably 10 to 60, more preferably 15 to 35 and is selected from the group consisting of i) and ii) Provided are fibers for spunbond nonwovens containing polymer composition (A):

i) a crystalline propylene random copolymer or crystalline propylene polymer composition selected from a) and b):

a) a melting point of at least 155 ° C., containing at least 0.8% by weight of ethylene and optionally at least one C ₄ -C ₁₀ α-olefin, less than 5% by weight of a fraction content soluble in xylene at room temperature, to xylene soluble fraction at room temperature A copolymer or polymer composition having a value of a ratio of polymer fractions collected in a temperature rising elution fractionation (TREF) in the 25 to 95 ° C. temperature range of greater than 8; And

b) a melting point of at least 153 ° C., containing more than 2.5% by weight of ethylene and optionally at least one C ₄ -C ₁₀ α-olefin, soluble in xylene at room temperature, less than 10% by weight, preferably less than 8% by weight, and A copolymer or polymer composition having a value of a ratio of polymer fractions collected at 25 to 95 ° C. in a TREF to xylene soluble fraction at room temperature over a temperature range of 25 to 95 ° C .; And

ii) a crystalline propylene polymer composition comprising at least 0.64% by weight of ethylene and / or C ₄ -C ₁₀ α-olefin repeat units and containing (% by weight) of I) and II) below:

I) 20-80%, preferably 30- crystalline propylene homopolymer or crystalline propylene random copolymer, containing not more than 1.5% by weight, preferably not more than 0.5% by weight of ethylene and / or C ₄ -C ₁₀ α-olefins. 70%; And

     II) 20-80%, preferably 30-70%, crystalline propylene random copolymers selected from the group consisting of:

        IIa) Crystalline of propylene with 0.8 to 10% by weight of ethylene

             Copolymers; With respect to the weight of the associated (co) polymer,

             And the difference in ethylene content between the polymer (IIa) is at least 0.8% unit,

             Preferably in units of 1%, more preferably in units of 2%;

IIb) 1.5 to 18% by weight of C ₄ -C ₁₀ α-olefin and optionally ethylene

              Crystalline copolymers of propylene having; Provided that related (co) polymers

              Co-monomer between polymer (I) and polymer (IIb) by weight

              The difference in content is at least 1.5% units, preferably 2% units; And

        IIc) A mixture of copolymer (IIa) and copolymer (IIb).

 The term "copolymer" in the present invention means a polymer having two or more different repeating units, such as dipolymers and terpolymers.

Room temperature as indicated in the present invention means a temperature of about 25 ° C.

The crystalline polymer exhibits isotactic stereoregularity.

When ethylene is present as the only comonomer in component (i) (a), the comonomer exhibits an ethylene content of approximately 0.8 to 3% by weight relative to the weight of the total component.

When ethylene is present as the only comonomer in component (i) (b), the component exhibits an ethylene content of about 5% by weight or less.

When C ₄ -C ₁₀ α-olefins are also present in component (i), they are generally within 1 to 6% by weight relative to the weight of the total component (i).

Preferably the composition (ii) of the polymer composition (A) has the following characteristics:

1) melting point of 153 ° C. or higher; And

2) fraction content soluble in xylene at room temperature of less than 10% by weight, preferably less than 9% by weight.

When ethylene is also present as comonomer in the random copolymer (ii) (IIb), the ethylene content is generally within 1% by weight relative to the weight of the copolymer. In a preferred embodiment, the polymer composition (ii) contains (% by weight) of the following I) and II):

I) 20-80%, preferably 30- crystalline propylene homopolymers and / or crystalline propylene random copolymers containing not more than 1.5%, preferably not more than 0.5% of ethylene and / or C ₄ -C ₁₀ α-olefins. 70%; And

II) 20-80%, preferably 30-70%, of the crystalline random copolymer selected from:

        IIa) copolymers of propylene with 0.8-5% ethylene;

              Provided that the polymer (I) and the medium

              The difference in ethylene content between coales (IIa) is at least 0.8%;

IIb) 1.5 to 12% of C ₄ -C ₁₀ α-olefin and optionally ethylene

              Copolymers of propylene having; Provided that the weight of the (co) polymer involved

              The difference in co-monomer content between polymer (I) and polymer (IIb)

              At least 1.5% units; And

        IIc) A mixture of copolymer (IIa) and copolymer (IIb).

The composition (ii) is preferably a polymer fraction collected at temperatures ranging from 25 to 95 ° C. by TREF with a melting point of at least 155 ° C., fraction content less than 5% by weight of soluble in xylene at room temperature, and xylene for xylene soluble fraction at room temperature. The ratio of is greater than 8.

The MFR values of the two propylene polymers constituting the polymer composition (ii) can be similar or different.

Especially preferred are crystalline propylene polymer compositions (ii) wherein component (I) is a propylene homopolymer and component (II) is an ethylene-propylene random copolymer.

Particularly spunbond nonwovens having both high values of toughness and elongation at break are from fibers made of the composition (A) having an MFR (1) value of 10 to 40 g / 10 minutes, preferably 20 to 40 g / 10 minutes. Typically obtained. Preferably, the composition (A) typically exhibits a polydispersity index value of 3 to 6, more preferably 3.5 to 6. Spunbond nonwovens made from fibers containing the composition (A) typically have toughness values of 90 N / 5 cm as measured in the longitudinal direction and 60 N / 5 cm as measured in the transverse direction. Elongation at break is typically at least 90%, preferably 100%, as measured in both directions.

The fibers according to the invention are typically at a standard throughput of more than 22 cN / tex and preferably have toughness values of more than 23 cN / tex.

The elongation at break exhibited by the fibers of the invention is typically greater than 140% at standard throughput, preferably at least 150%.

Fibers according to the invention typically have a titer in the range from 0.8 to 8 dtx. Suitable fibers for spunbond fabrics are obtainable by chemical decay of the precursor polymer composition (B) having an MFR value (MFR (2)) of 0.5 to 50 g / 10 min, provided that MFR (1) for MFR (2) ) Is from 1.5 to 60, preferably from 6 to 30.

Chemical breakdown of the polymer chains of the precursor polymer (B) is carried out using suitable known techniques.

One of the techniques is based on the use of peroxides added to the polymeric material in the extruder in an amount such that a desired degree of chemical decay is obtained. This decay is achieved by bringing the polymer at a temperature at least equal to the decomposition temperature of the peroxide and in the state of mechanical shear strength.

The most conveniently used peroxides for chemical decay preferably have a decomposition temperature in the range from 150 to 250 ° C. Examples of such peroxides include di-t-butyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne, and 2,5-dimethyl-2,5-di (t -Butyl peroxy) hexane (sold under the trademark Luperox ^™ 101).

Preferably, the chemically disintegrated composition (A) has a polydispersity index value of 2 to 6, more preferably 2 to 3.

C ₄ -C ₁₀ α-olefins which may be present as comonomers in the propylene copolymer or polymer composition are formulas CH ₂ = CHR, wherein R is a linear or branched alkyl radical or aryl having 2 to 8 carbon atoms (especially Phenyl) radicals. Examples of the C ₄ -C ₁₀ α-olefins are 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene and 1-octene. Especially preferred is 1-butene.

A further embodiment of the present invention has a MFR (1) value of 6 to 150 g / 10 min, preferably 10 to 60, more preferably 15 to 35, and a chemically disintegrated propylene polymer composition (A) selected from to be:

i) a crystalline propylene random copolymer or crystalline propylene polymer composition selected from a) and b):

a) TREF as xylenes for the xylene soluble fraction at room temperature, containing at least 0.8 wt% ethylene and optionally at least one C ₄ -C ₁₀ α-olefin and a melting point of at least 155 ° C., soluble in xylene at room temperature; A copolymer or polymer composition having a value of greater than 8 by a ratio of polymer fractions collected in a temperature range of 25 to 95 ° C .; And

b) a melting point of at least 153 ° C., containing more than 2.5% by weight of ethylene and optionally at least one C ₄ -C ₁₀ α-olefin, soluble in xylene at room temperature, less than 10% by weight, preferably less than 8% by weight, and A copolymer or polymer composition having a value of a ratio of polymer fractions collected at 25 to 95 ° C. in a TREF to xylene soluble fraction at room temperature over a temperature range of 25 to 95 ° C .; And

ii) a crystalline propylene polymer composition comprising (% by weight) of 0.64% by weight or more of ethylene and / or C ₄ -C ₁₀ α-olefin repeat units and comprising the following I) and II):

I) 20-80%, preferably 30- crystalline propylene homopolymer or crystalline propylene random copolymer, containing not more than 1.5% by weight, preferably not more than 0.5% by weight of ethylene and / or C ₄ -C ₁₀ α-olefins. 70%; And

     II) 20-80%, preferably 30-70%, of crystalline propylene random copolymers selected from:

        IIa) copolymers of propylene with 0.8-5% ethylene;

              Provided that the polymer (I) and

              The difference in ethylene content between the polymers (IIa) is at least 0.8%,

              Preferably in units of 1%, more preferably in units of 2%;

IIb) 1.5 to 12% of C ₄ -C ₁₀ α-olefin and optionally ethylene

              Copolymers of propylene having; Provided that the weight of the (co) polymer involved

              The difference in co-monomer content between polymer (I) and polymer (IIb)

              At least 1.5% units, preferably 2% units; And

        IIc) A mixture of copolymer (IIa) and copolymer (IIb).

The polymer composition is obtainable by chemical breakdown of the precursor polymer composition (B) having an MFR (2) value of 0.5 to 50 g / 10 min, provided that the ratio of MFR (1) to MFR (2) is from 1.5 to 60 , Preferably it is 6-30.

 The polymer composition (A) preferably has the following characteristics:

1) melting point above 155 ℃,

2) fraction content less than 4% by weight, preferably less than 3% by weight, more preferably less than 2.5% by weight, soluble in xylene at room temperature; And

3) The value of the ratio of the polymer fractions collected in the 25 to 95 ° C. temperature range by TREF with xylene to xylene soluble fraction at room temperature is greater than 8, preferably greater than 10, more preferably greater than 12.

Preferably, the composition (A) has a polydispersity index value of 2.0 to 4.5, more preferably 2.0 to 3.0.

The propylene polymer composition (A) can be prepared by a process comprising the following steps:

1) polymerizing the monomers in one or more successive steps, each step operating in each step in the presence of the catalyst used in the previous step and the polymer formed, so that the MFR (2) value for the precursor composition is from 0.5 to 50 g / 10 min. Preparing the precursor composition (B) in advance by administering a molecular weight modifier (preferably hydrogen) in an amount such that; And

2) the precursor composition (B) obtained in step (1) so that the MFR (1) value for the final composition is from 6 to 150 g / 10 minutes, more preferably from 10 to 60 g / 10 minutes, Decay treatment at a decay ratio of 1.5 to 60, preferably 6 to 30, at a ratio of MFR (1) to MFR (2).

The precursor composition (B) is to carry out chemical breakdown of the polymer chains according to methods known in the art. For example, the decay process is carried out by means of free radical initiators such as peroxides. Examples of peroxides that can be used for this purpose are 2,5-dimethyl, 2,5-di (t-butylperoxide) hexane and dicumyl peroxide. The decay is carried out using an appropriate amount of free radical initiator and preferably takes place in an inert atmosphere such as nitrogen. Methods, apparatuses and operating conditions known in the art can be used to carry out this process. From the foregoing, it will be apparent that in the precursor composition (B), the comonomer content and relative amount are the same as in the final composition (A) (after collapse). The disintegration treatment has the effect of raising the MFR value of the composition from MFR (2) to MFR (1) such that the value of the ratio of MFR (1) to MFR (2) is 1.5 to 60, preferably 6 to 30.

The composition of the present invention may be prepared by polymerizing in one or more polymerization stages. The polymerization is carried out in the presence of stereospecific Ziegler-Natta catalyst. An essential component of the catalyst contains a titanium compound having at least one titanium-halogen bond, and an electron donor compound, both of which are solid catalyst components supported on magnesium halides in active form. Another essential component (promoter) is an organoaluminum compound, such as an aluminum alkyl compound.

External donors are optionally added.

Catalysts generally used in the process of the present invention can produce polypropylene having an isotactic index of greater than 90%, preferably greater than 95% (measured in fractions insoluble in xylene at 25 ° C. as disclosed below). have.

Catalysts having the above-mentioned features are well known in the patent literature;

Particularly advantageous are the catalysts described in US Pat. No. 4,399,054 and European Patent 45977. Other examples can be found in US Pat. No. 4,472,524.

The solid catalyst component used in the catalyst is an electron donor (internal donor), an ether, ketone, lactone, succinate, a compound containing N, P and / or S atoms, and an ester of mono- and dicarboxylic acids. It contains a compound selected from the group consisting of.

Particularly suitable electron donor compounds are non-extractable succinates; Especially preferred are succinates of formula (I):

[Wherein the radicals R ₁ and R ₂ are the same or different from each other and optionally contain a C ₁ -C ₂₀ linear or branched alkyl, alkenyl, cycloalkyl, aryl, arylalkyl or alkylaryl group; The radicals R ₃ and R ₄ are the same or different from one another and are optionally C ₁ -C ₂₀ alkyl, cycloalkyl, aryl, arylalkyl or alkylaryl groups, provided that at least one of them is branched alkyl ];

The compounds are stereoisomers of the type (S, R) or (R, S) which exist in pure form or in mixtures with respect to the two asymmetric carbon atoms identified in the structure of formula (I).

R ₁ and R ₂ are preferably C ₁ -C ₈ alkyl, cycloalkyl, aryl, arylalkyl and alkylaryl groups.

Especially preferred are compounds wherein R ₁ and R ₂ are selected from primary alkyl and are especially branched primary alkyl. Examples of suitable R ₁ and R ₂ groups are methyl, ethyl, n-propyl, n-butyl, isobutyl, neopentyl, 2-ethylhexyl. Especially preferred are ethyl, isobutyl, and neopentyl.

Especially preferred are compounds in which the R ₃ and / or R ₄ radicals are secondary alkyls such as isopropyl, sec-butyl, 2-pentyl, 3-pentyl or cycloalkyls such as cyclohexyl, cyclopentyl, cyclohexylmethyl.

Examples of the above-mentioned compounds include diethyl 2,3-bis (trimethylsilyl) succinate, diethyl 2,3-bis (2-ethylbutyl) succinate, diethyl 2,3-dibenzylsuccinate, diethyl 2 , 3-diisopropylsuccinate, diisobutyl 2,3-diisopropylsuccinate, diethyl 2,3-bis (cyclohexylmethyl) succinate, diethyl 2,3-diisobutylsuccinate, di Pure (S, R), (S, R) forms of ethyl 2,3-dynepentylsuccinate, diethyl 2,3-dicyclopentylsuccinate, diethyl 2,3-dicyclohexylsuccinate Or mixtures, optionally racemic.

Other suitable electron donor compounds are 1,3-diethers of the formula:

Where R ^I and R ^II Is the same or different and is a C ₁ -C ₁₈ alkyl, C ₃ -C ₁₈ cycloalkyl or C ₇ -C ₁₈ aryl radical; R ^III and R ^IV are the same or different and are C ₁ -C ₄ alkyl radicals; Or 5-n or 6-n ', wherein the carbon atom at the 2 position is a 5, 6, or 7 carbon atom, or an n' hetero atom selected from the group consisting of n nitrogen atoms and N, O, S and Si, respectively ( Wherein n is 1 or 2 and n 'is 1, 2, or 3) 1,3-diether belonging to a cyclic or polycyclic structure consisting of carbon atoms, said structure being 2 or 3 unsaturated (cyclopolyene Structure), optionally condensed with other cyclic structures, or substituted with one or more substituents selected from the group consisting of linear or branched alkyl radicals, cycloalkyl, aryl, aralkyl, alkaryl radicals and halogens, or Substituted with one or more of the foregoing substituents which may be condensed into other cyclic structures and also bonded to the condensed cyclic structure; One or more of the aforementioned alkyl, cycloalkyl, aryl, aralkyl, or alkaryl radicals and condensed cyclic structures optionally contain one or more heteroatoms as substituents for the carbon or hydrogen atoms, or both.

Ethers of this type are described in European Patent Applications Nos. 361493 and 728769.

Representative examples of the diether include 2-methyl-2-isopropyl-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-dimethoxypropane, 2-isopropyl-2-cyclopentyl- 1,3-dimethoxypropane, 2-isopropyl-2-isoamyl-1,3-dimethoxypropane, 9,9-bis (methoxymethyl) fluorene.

Other suitable electron donor compounds are phthalic acid esters such as diisobutyl, dioctyl, diphenyl and benzylbutyl phthalate.

The preparation of the catalyst components described above is carried out according to several methods.

For example, MgCl ₂ nROH adducts (particularly in the form of elliptical particles) where n is generally 1 to 3 and ROH is ethanol, butanol or isobutanol, react with excess TiCl ₄ containing an electron donor compound. The reaction temperature is generally 80 to 120 ° C. The solid is then isolated and reacted with TiCl ₄ once more in the presence or absence of the electron donor compound, which is then separated off and washed with an aliquot of hydrocarbon until all the chloride ions disappear. Titanium compounds represented as Ti in the solid catalyst component are generally present in amounts of 0.5 to 10% by weight. The amount of electron donor compound remaining fixed in the solid catalyst component is generally from 5 to 20 mole% relative to magnesium dihalide.

Titanium compounds that can be used for the preparation of the solid catalyst component are halides and halogen alcoholates of titanium. Titanium tetrachloride is a preferred compound.

The reaction described above results in the formation of magnesium halides in active form. Other reactions are known in the literature and this leads to the formation of magnesium halides in active form starting from magnesium compounds other than halides such as magnesium carboxylates.

The active form of magnesium halide in the solid catalyst component no longer has the maximum intensity reflection (having a surface area of less than 3 m ² / g), which appears in the spectrum of the magnesium halide deactivated in the X-ray spectrum of the catalyst component, It can be recognized by the fact that there is a shift of the maximum intensity halo with respect to the location of the maximum intensity reflection of the magnesium dihalide deactivated, or the maximum intensity reflection is at least 30% higher than the maximum intensity reflection seen in the spectrum of the deactivated magnesium halide. It can be recognized by the fact that it represents a width at a large half peak. The most active form is that the halo described above appears in the X-ray spectrum of the solid catalyst component.

Of the magnesium halides, magnesium chloride is preferred. For the most active form of magnesium chloride, the X-ray spectrum of the solid catalyst component shows halo instead of the reflection where the spectrum of inactivated chloride appears at 2.56 Hz.

Al-alkyl compounds used as promoters are linear or cyclic Al-alkyl compounds containing two or more Al atoms bonded to each other by O or N atoms or by SO ₄ or SO ₃ groups and Al-triethyl, Al-triiso Butyl, Al-trialkyl such as Al-tri-n-butyl.

Al-alkyl compounds are generally used in amounts such that the Al / Ti ratio is from 1 to 1000.

Electron donor compounds that can be used as external donors include aromatic acid esters such as alkyl benzoates, and especially silicon compounds comprising at least one Si—OR bond, wherein R is a hydrocarbon radical.

Examples of silicon compounds include (t-butyl) ₂ Si (OCH ₃ ) ₂ (cyclohexyl (methyl) Si (OCH ₃ ) ₂ (phenyl) ₂ Si (OCH ₃ ) ₂ and (cyclopentyl) ₂ Si (OCH ₃ ) _2. 1,3-diethers having the above formulas may also be advantageously used, if the internal donor is one of these diethers, the external donor may be omitted.

In particular, although many other combinations of the aforementioned catalyst components may allow to obtain polymers and polymer compositions having the features 1) and 2) described above, the random copolymer is a phthalate as an internal donor and a cyclopentyl as an external donor. Preference is given to using a catalyst containing ₂ Si (OCH ₃ ) ₂ , or the 1,3-diether as internal donor and (cyclopentyl) ₂ Si (OCH ₃ ) ₂ as external donor.

As mentioned above, the polymerization process may be performed in one or more steps. In the case of composition (ii), it may be carried out in two or more successive steps, wherein the first propylene (co) polymer and the second propylene random copolymer are subjected to the first step in the presence of the catalyst used and the polymer formed in the previous step. It is produced in separate successive steps except in each step. Obviously, when the composition (ii) contains additional (co) polymers, it is necessary to add additional polymerization steps to prepare them. The polymerization step can be carried out in a separate reactor or one or more reactors in which a gradient of monomer concentration and polymerization state occurs. The catalyst is generally added only in the first stage, but its activity is still active in all subsequent stage (s).

Control of the molecular weight is carried out using known regulators, in particular hydrogen.

By appropriately administering the concentrate of the molecular weight modifier in the relevant step, the above-mentioned MFR (2) values are obtained.

The entire polymerization process, which may be continuous or potted, is carried out in the liquid phase, in the presence or absence of an inert diluent, in the gas phase, or in a mixed liquid-gas technique by the following known techniques.

The reaction time, pressure and temperature for both stages are not critical, but are best if the temperature is 20 to 100 ° C. The pressure may be at or above atmospheric pressure. The catalyst may be precontacted with small amounts of olefins (prepolymerization).

It is also possible to use a catalytic polymerization process in the gas phase carried out in at least two interconnected polymerization zones, which supply one or more monomers to the polymerization zone in the presence of a catalyst under reaction conditions and polymer from the polymerization zone. Collecting the product, wherein the polymer particles growing in this process flow upwardly through one of the polymerization zones (rising pipes) under rapid fluidization conditions, and leave another zone of polymerization flowing downwardly under gravity action. Entering the downcomer and leaving the downcomer and reintroduced into the upcomer to establish the circulation of the polymer between the upcomer and downcomer, the method optionally characterized by:

Means are provided, in whole or in part, for preventing the gas mixture present in the riser from entering the downcomer; and

Introducing a gas and / or liquid mixture having a composition different from the gas mixture present in the riser into the downcomer.

This polymerization process is described in WO 00/02929.

According to certain advantageous embodiments of this process, the introduction of the gas and / or liquid mixture into the downcomer having a composition different from the gas mixture present in the upcoming tube is effective to prevent the gas mixture from entering the downcomer.

Propylene polymer compositions (A) used for the fibers and nonwovens of the present invention are known in the art as antioxidants, light stabilizers, heat stabilizers, antistatic agents, flame retardants, fillers, nucleophiles, pigments, antifouling agents, photosensitizers It may also contain additives commonly used.

As mentioned above, embodiments of the present invention are nonwovens. This is typically 200 g / m ² Has a weight of less than.

The fibers of the present invention can be produced by known methods for the production of spunbond nonwovens, in which the fibers are scattered to directly form and roll the fiber to obtain a nonwoven.

In a typical spunbonding process, the polymer is heated in the extruder to the melting point of the polymer or polymer composition and then the molten polymer is pumped under pressure through a spinneret containing a plurality of orifices of the desired diameter to produce a filament of the molten polymer. The filament does not carry out subsequent stretching.

The device is characterized by the fact that it includes an extruder with a die on its spinning head, a cooling tower, an air intake collection device (using Venturi tubes). Underneath this device, which uses air speed to adjust the take-up speed, the filaments are generally gathered on a conveyor belt, where they are distributed to form a landing for thermal bonding in the calender.

When using a typical spunbonding machine, it is generally convenient to apply the following process conditions:

The yield per hole is 0.1 to 2 g / min, preferably 0.2 to 1 g / min;

The molten polymer filaments supplied at the front of the spinneret are generally cooled by means of air flow and solidified as a result of the cooling;

The spinning temperature is generally from 200 to 300 ° C, preferably from 220 to 250 ° C.

The fabric may be composed of single or multilayer nonwovens.

In a preferred embodiment, the nonwoven is multilayered and at least one and at least one layer comprises fibers formed from said propylene polymer composition (A). Other layers may be obtained by spinning processes other than spunbonding and may contain other types of polymers.

Typically, spunbond nonwovens made from fibers containing the chemical disintegration composition (A) according to the invention have a toughness of at least 30 N as measured in the longitudinal direction (MD) and at least 7.7 N as measured in the transverse direction (CD). Elongation at break of at least 38% when measured in the direction and at least 58% when measured in the transverse direction.

Nonwovens of the present invention with improved tenacity, softness and enlongation at break are useful in many applications. For example, the nonwoven can be converted to coverstock and diapers.

The following examples are given for illustrative purposes and are not intended to limit the invention.

The data for the polymeric materials and fibers of the description and examples are measured in the manner of the methods recorded below.

MFR : ISO method 1133 (230 ° C, 2.16 kg)

-Melting point and crystallization temperature : by DSC with a temperature change of 20 ° C. per minute

-Ethylene content : by IR spectroscopy

Polydispersity index (PI): Determination of the molecular weight distribution of the polymer.

To measure the PI value, modulus separation at low modulus values, for example 500 Pa, is 100 rad at 0.01 rad / sec using the RMS-800 parallel plate rheometer model sold by Rheometrics (USA). It is measured at a temperature of 200 ° C. by operating at an oscillating frequency which increases to / sec. From the modulus separation, PI can be derived using the following formula:

PI = 54.6 x (modulus separation) ^-1.76

Here, modulus separation (MS) is defined as follows:

MS = (Frequency at G '= 500 Pa) / (Frequency at G "= 500 Pa)

Where G 'is a conservative modulus and G "is a low modulus.

Fraction soluble and insoluble in xylene at 25 ° C . : 2.5 g of the polymer are dissolved in 250 ml of xylene at 135 ° C. under shaking. After 20 minutes, the solution is cooled to 25 ° C., distilled under shaking and then left to stand for 30 minutes. The precipitate is filtered through filter paper, the solution is evaporated under a nitrogen stream and the residue is dried under vacuum at 80 ° C. until a constant weight is reached. In this way, the weight% of the polymer which is soluble and insoluble at room temperature is calculated.

Elution of temperature rise with xylene Fraction : Approximately 1 g of sample is dissolved in 200 ml of o-xylene and 0.1 g / l of Irganox 1010 (pentaerythryl tetrakis 3- (3,5-di-t-butyl-4-hydroxyphenyl) propanoate). The dissolution temperature is 125-135 ° C. The resulting solution is poured into a column filled with glass beads and subsequently added dropwise by slowly cooling to 25 ° C. for 16.5 hours.

The first fraction is obtained by eluting with o-xylene at room temperature. The second fraction is collected after raising the column temperature to 95 ° C. Polymer components soluble at 25 to 95 ° C. are collected as a single fraction. The successive fractions elute with o-xylene while linearly raising the temperature to 95-125 ° C. Each fraction recovered in a 200 ml solution is collected at 1 ° C. temperature increments. The polymer fraction is subsequently precipitated with acetone and filtered over a 0.5 μm PTFE filter, dried under vacuum at 70 ° C. and weighed.

Titer of filaments : Randomly select and weigh 50 fibers from 10 cm long rovings. The total weight (expressed in mg) of the 50 fibers is multiplied by 2 to obtain the titer as dtex.

Toughness and elongation at break of the filament : 100 mm long segments are cut from 500 m of spinning yarn. Randomly select a single fiber to be tested from the segment. Each single fiber to be tested is secured to the clamp of the Instron Competency System (Model 1122) and broken at a pull rate of 20 mm / min for elongation of less than 100% and 50 mm / min for elongation of greater than 100%. Tensile, the initial distance between the clamps is 20 mm. Ultimate strength (load at break) and elongation at break are measured.

Toughness is derived using the following formula.

Toughness = ultimate strength (cN) x 10 / titer (dtex).

Bonding force : When a nonwoven sample is prepared, the bond strength is measured on a 20 cm long and 5 cm wide test specimen. The 5 cm wide end is secured to the clamp of the competing system and tensioned at a clamp speed of 100 mm / min (the initial distance between the clamps is 10 cm). The maximum force measured in the longitudinal and transverse directions represents the strength of the fiber with respect to the rolling step.

Examples 1 and 2

Polymers are prepared by polymerizing propylene and ethylene under continuous conditions in a plant comprising a gas phase polymerization apparatus.

The catalyst contains a _{MgCl 2 · 2.1 C 2 H 5} OH instead of fine oval MgCl ₂ · 1.7 C ₂ are excluded, and prepared in a similar manner as in Example favor EP A 728,769 5 catalyst component only by using H ₅ OH using do.

Catalytic System and Prepolymerization Treatment

Before introducing the catalyst component into the polymerization reactor, the above-mentioned solid catalyst component was subjected to triethylaluminum (TEAL) and dicyclopentyldimethoxysilane (DCPMS) for 24 minutes at 12 ° C., and the weight ratio of TEAL to solid catalyst component was 5 minutes. And contact with an amount such that the weight ratio of TEAL to DCPMS is 4.

The catalyst system then performs prepolymerization by maintaining the suspension in liquid propylene at 20 ° C. for about 5 minutes before introducing it into the first polymerization reactor.

polymerization

The proceeding of the polymerization is carried out in a continuous manner in two series of reactors with devices for immediate delivery of the product from one reactor to one reactor next to it. Both reactors are liquid phase reactors. Polymer (I) is produced in the first reactor, while polymer (II) is produced in the second reactor.

Hydrogen is used as molecular weight regulator.

The gas phases (propylene, ethylene and hydrogen) are analyzed continuously via gas chromatography.

At the end of the reaction progress the powder is discharged and dried under nitrogen flow.

The main polymerization conditions and analytical data associated with the polymers produced in both reactors are reported in Table 1.

The polymer composition thus obtained comprises about 0.05% by weight of Luperox ^™ 101 (ie 2,5-dimethyl-2,5-di (t-butylperoxo) hexane, 0.05% by weight of calcium stearate and Ciba 0.15 weight% Irganox for sale at Specialty Chemicals B215 (ie 50 wt% pentaerythryl-tetrakis [3 (3,5-di-t-butyl-4-hydroxyphenyl] propionate and 50 wt% bis (2,4-di-t Extrusion / granulation is carried out in a twin screw extruder (L / D = 35) in the presence of -butylphenyl) phosphite) Operating conditions are: head temperature of 250 ° C., melting temperature of 239 ° C. and 21 kg / Yield of time.

The properties of the polymer composition after chemical collapse are reported in Table 1.

Comparative Examples 1 and 2 (1c and 2c)

Commercially crystalline propylene homopolymers for the spunbonding process having the characteristics reported in Table 1 are chemically disintegrated under the same reagents and conditions as used in Examples 1 and 2. The main properties of the disintegrated homopolymers are reported in Table 1.

 Example  1c  2c   One   2  First Reactor-Propylene Homopolymer  Temperature, ℃   -   -   85   85  Split, weight%   -   -   50   50  Second reactor-poly (propylene-co-ethylene)  Temperature, ℃   -   -   85   85  Split, weight%   -   -   50   50  Properties of Precursor Polymer Composition  MFR, g / 10 min  1.7  1.7  2.3  2.4  Polydispersity index  3.6  3.6  3.7  3.7  Xylene soluble fraction, weight%  4.0  4.0  2.2  2.0  Ethylene Content, Weight%   0   0  1.3  1.4  Melting point, ℃  163  163  158  158  Xylene soluble fraction at temperatures of 25-95 ° C, weight%  11.8  11.8  32.7  29.1  Properties of Polymer Composition After Chemical Collapse  MFR, g / 10 min   25   28   25   27  Xylene soluble fraction, weight%    4   4.0   2.2   2.0  Polydispersity index   2.4   2.4   2.4   2.6  Xylene-soluble fraction at 25-95 ° C., weight%  13.9    -   33.3   33.3  TREF 25-95 ° C./xylene-soluble fraction ratio   3.5    -   15.1  16.6  Note: Split = amount of polymer produced

Examples 3 and 4 and Comparative Example 3 (3c)

The polymer compositions of Examples 1 and 2 and the homopolymer of Comparative Example 1 were spun in a Leonard 25 spinning pilot line having a length / diameter ratio of 25 screws, a screw diameter of 25 mm and a compression ratio of 1: 3. This line is sold by Costruzioni Meccaniche Leonard-Sumirago (VA).

The properties and spinning properties of the filaments thus produced are reported in Table 2.

 Example     3c     3     4  Operation condition  Hole diameter, mm    0.6    0.6    0.6  Yield per hole, g / min    0.6    0.6    0.6  Die count of die     37     37     37  Die temperature, ℃    250    250    250  Melting point, ℃    258    258    258  Take-up speed, m / min   2700   2700   2700  Properties of filament  Titer, dtex   2.25   2.3   2.35  Toughness, cN / tex   21.1   26.8   24.6  Elongation at break,%   220   160   235

For the filaments of comparative example 3, the filaments according to the invention show increased toughness. The ability to produce high tensile strength filaments can be advantageously used for the manufacture of spunbond nonwovens.

Example 5 and Comparative Example 4 (4c)

The polymer composition of Example 1 and the homopolymer of Comparative Example 1 are processed in a spunbond line. This attempt is performed at full line capacity. The nonwoven fabric thus produced has a weight of 15 g / m ² .

Example 6

Example 5 is repeated except that the rolling temperature is reduced to 5 ° C.

Example 7

Example 6 is repeated except that the pressure drag air is increased to process the filaments under more stringent conditions.

The operating conditions and properties of the nonwovens obtained in Examples 5 to 7 and Comparative Example 4 are reported in Table 3.

 Example    4c     5     6    7  Operation condition  The temperature of the molten polymer in the filter, ° C.   225   225   225   225  Air jet pressure, mbar   120   120   120   135  Yield per hole, g / min   0.6   0.6   0.6   0.6  Temperature of smooth calendar, ℃   168   168   163   163  Temperature of emboss calender, ℃   170   170   165   165  Properties of Filaments and Nonwovens  Filament titer, dtex   2.9   3.0   2.9   2.8 Fabric weight, g / m ²    15    15    15    15  MD toughness, N   26.1   33.2   31.8   34.3  CD toughness, N   7.6    8.9    7.9    8.2  MD elongation at break,%    35    40    40    45  CD elongation at break,%    55    65    60    65 Ductility ¹⁾     3     4     5     5 ¹ ductile grade: 1 = bad; 2 = better than control; 3 = same as control; 4 = better than control; 5 = very good

The data indicate that the filaments of Example 3 exhibited good machinability, high consistency and no breakage under all test conditions. The nonwovens according to the invention thus produced exhibit higher ductility and higher fabric toughness than the comparative nonwovens.

Example 8 and Comparative Example 5 (5c)

The polymer composition of Example 2 and the homopolymer of Comparative Example 2 were tested in the spunbond line under the same conditions.

The main conditions for the extruder, spinning and rolling are reported in Table 4.

Example 9

The polymer composition of Example 2 is spun at higher stretching air and lower rolling temperatures than Example 8.

 Example     5c     8     9  The temperature of the molten polymer in the filter, ° C.    240    240    240  Yield per hole, g / min    0.39    0.39    0.39  Hole diameter, mm    0.45    0.45    0.45  Air jet pressure, mPa   15.19   15.19   16.17  Rolling temperature of smooth roll, ℃    139    139    134  Rolling temperature of emboss roll, ℃    139    139    134  Properties of Filaments and Nonwovens  Filament titer, dtex    1.8     1.8    1.6 Nonwoven fabric weight, g / m ²   16.3     16   16.5  MD toughness, N / 5cm   33.2     33.5   35.4  MD elongation at break,%     40     45    45  CD toughness, N / 5cm   27.3     27.9   30.1  CD elongation at break,%    35     45    45

The data in Table 4 show that the nonwoven fabric according to the present invention has an increase in fracture elongation and equal or better toughness as compared to the comparative nonwoven fabric. In particular, the nonwoven of Example 9 exhibits higher toughness in both MD and CD, while still maintaining superior elongation at break in both MD and CD than the nonwoven of Example 8.

Example 10

The polymer composition is prepared and extruded as in Example 1 except that no peroxide is added during the extrusion.

Polymerization conditions and main characteristics of the polymer are reported in Table 5.

Comparative Example 6 (6c)

A conventional propylene homopolymer for the spunbonding process having the characteristics reported in Table 5 was subjected to chemical decay as in Example 1 and the amount and form of peroxide and the additives were the same as in Example 1. The main properties of the precursors and granulated polymers are reported in Table 5.

 Example    6c    10  First Reactor-Propylene Homopolymer  Temperature, ℃    75    80  Split, weight%    50    50  Second Reactor-Propylene-Ethylene Copolymer  Temperature, ℃    75    80  Split, weight%    50    50  Properties of Precursor Polymer Composition  MFR "L", g / 10 min    1.7   36.3  Polydispersity index    3.6   3.35  Xylene soluble fraction, weight%    4.0   3.6  Ethylene Content, Weight%     0   1.2  Soluble fraction at 25-95 ° C temperature, weight%   12.3   32.8  Properties of Polymer Composition After Granulation  MFR "L", g / 10 min     32   36.4  Polydispersity index    2.6    3.3  Melting point, ℃    163  156.8  Xylene soluble fraction, weight%    4.1    3.6  Xylene-soluble fraction at 25-95 ° C., weight%   13.9   32.8  TREF 25-95 ° C./xylene-soluble fraction ratio    3.5    9.1  Note: Split = amount of polymer produced.

Example 11 and Comparative Example 7 (7c)

The polymer composition of Example 10 and the homopolymer of Comparative Example 6 are tested in the spunbond line under the same conditions.

Attempts are made at standard line capacity.

The nonwoven fabric thus produced has a weight of 35 g / m ² .

The operating conditions and properties of the nonwovens obtained in Example 11 and Comparative Example 7 are reported in Table 6.

 Example    7c    11  Operation condition  The temperature of the molten polymer in the filter, ° C.    225   225  Air jet pressure, mbar    800   800  Quenching temperature, ℃     15    15  Yield per hole, g / min    0.5    0.5  Extruder pressure, bar     80    80  Extruder screw rotation, rpm     40    40  Belt speed, m / min     45    45  Temperature of smooth calendar, ℃    139   139  Temperature of emboss calender, ℃    142   142  Properties of Filaments and Nonwovens  Filament titer, dtex    2.0   2.0 Fabric weight, g / m ²    35    35  MD toughness, N / 5cm    85.1   93.7  CD toughness, N / 5cm    56.3   64.0  MD elongation at break,%    70.9  116.1  CD elongation at break,%    68.8   117

The polymer composition of Example 10 exhibits good processability, high consistency and no breakage during testing. The nonwovens according to the invention thus produced exhibit higher elongation and toughness than the comparative nonwovens.

Example 12

The polymer composition is prepared using the same catalyst system as in Example 1.

The catalyst is sent to a gas phase polymerization apparatus comprising two cylindrical reactors, a downcomer 1 and a upcomer 2 connected to each other. The fast fluidization conditions are established in reactor 1 by recycling the gas from the gas-solid separator. The way to distinguish the gas composition in the two reactor legs is a "barrier" feed. This stream is propylene supplied to the wide top of the downcomer.

The polymer composition is then 0.030 wt% calcium stearate, 0.19 wt% Irganox Extrude as in Example 1 in the presence of B501W and 0.0730 weight% peroxide (ie Luperox 101 Akzo trademark). Irganox B501W is Irgafos (Irgafos) 168 and Irganox 1: 1 ratio of 1425 WL, Irgafos 168 is tris (2,4-di-t-butylphenyl) phosphite and Irganox 1425 WL is a 1: 1 ratio combination of polyethylene wax and calcium bis (((3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl) methyl) -ethylphosphonate, all of Ciba Commercially available from Specialty Chemicals.

The properties and polymerization conditions of the polymer composition before and after chemical collapse are reported in Table 7.

 TEAL / external donor, weight / weight      3  Temperature, ℃     75  Pressure, bar     28 _{^{C 2 - / (C 2 -}} + C 3 -) ( riser), mol / mol    0.0428  Properties of Precursor Polymer Composition  MFR, dg / min     1.3  Ethylene Content, Weight%     4.2  Xylene-soluble fraction, weight%     8.7  Xylene soluble fraction at 25-95 ° C temperature, weight%    43.1  TREF 25-95 ° C / xylene solubles ratio     4.95  Polydispersity index     3.8  Melt Enthalpy, J / g     88  Crystallization temperature, ℃     99  Properties of Polymer Composition After Chemical Collapse  MFR, dg / min     25.2  Xylene soluble fraction, weight%      8.7  Melting point, ℃     154  Xylene soluble fraction at 25-95 ° C., weight%     47.4  TREF 25-95 ° C / xylene solubles ratio     5.10  Polydispersity index     2.5 Note: C ₂ ^- = ethylene; C ₃ ^- = propylene; _{^{C 2 - / (C 2 -}} + C 3 -) = monomer feed ratio

Example 13

The polymer composition obtained in Example 12 was spun in a Leonard 25 spinning pilot line having a length / diameter ratio of 25 screws, a screw diameter of 25 mm and a compression ratio of 1: 3. This line is sold by Costrugioni Mechanic Leonard-Smilag.

The spinning test is carried out according to the following conditions: a hole diameter of 0.6 mm, yield of 0.6 g / min x hole, and mechanical values are measured for the filaments produced at a winding speed of 2700 m / min, and the spinneret is subjected to 37 holes. Have Spinning is stable without inconvenience.

Comparative Example 7 (7c)

Except that the polymer is a commercially available resin made of a propylene homopolymer with an MFR value of 25 g / 10 min, a polydispersity index of 2.6, a melting point of 161 ° C. and an amount of xylene soluble fraction of 3.2 g / ml. Example 13 is repeated. In Table 8, the properties of the filaments thus obtained are recorded in comparison with the properties of the filaments made of the commercially available homopolymer.

 Example     13    7c  Extrusion temperature, ℃    250   250  Filament titer, dtex    2.3   2.25  Toughness, cN / tex    26.0   21.1  Elongation at break,%    215   225  Binding force at 150 ° C., cN    395   130  Shrinkage,%    7.8   1.5

The high toughness of the filament having the excellent binding force of Example 13 is notable compared with the commercial product of Comparative Example 7. Shrinkage was also found to be very high. These features will improve the quality of the manufactured nonwovens.

Example 14

Example 12 is repeated except that a polymer composition, such as the polymer composition of Example 1, is prepared. The polymer composition is then extruded and granulated as in Example 1. Properties of the polymer composition and polymerization conditions are reported in Table 9.

 Example     14  TEAL / external donor, weight / weight      3  Temperature, ℃     85  Pressure, bar     28 _{^{C 2 - / (C 2 -}} + C 3 -) ( riser), mol / mol     0.1  Properties of Precursor Polymer Composition  MFR, dg / min     2.1  Ethylene Content, Weight%     1.5  Xylene-soluble fraction, weight%     2.1  Xylene soluble fraction at 25-95 ° C temperature, weight%    29.7  TREF 25-95 ° C / xylene solubles ratio    14.14  Polydispersity index    3.6  Properties of Polymer Composition After Chemical Collapse  MFR, dg / min    26.1  Xylene soluble fraction, weight%    2.4  Melting point, ℃    158  Melt Enthalpy, J / g     86  Crystallization temperature, ℃    100  Xylene soluble fraction at 25-95 ° C., weight%    34.4  TREF 25-95 ° C / xylene solubles ratio    14.33  Polydispersity index     2.5 Note: C ₂ ^- = ethylene; C ₃ ^- = propylene; _{^{C 2 - / (C 2 -}} + C 3 -) = monomer feed ratio

The polymer composition is then spun as in Example 3. The properties of the filaments thus produced are reported in Table 10.

 Properties of filament  Titer, dtex           2.3  Toughness, cN / tex          27.1  Elongation at break,%           165

Example 15

The polymer composition of Example 14 is processed in a spunbond line of full line capacity under the same conditions as in Example 7. The nonwoven fabric thus produced has a weight of 15 g / m ² .

The main properties of the nonwoven fabrics and the main spunbond line settings are summarized in Table 11 below.

 Example        15  Operation Conditions of Spunbond Line  The temperature of the molten polymer in the filter, ° C.       225  Air jet pressure, mbar       135  Yield per hole, g / min        0.6  Temperature of smooth calendar, ℃       164  Temperature of emboss calender, ℃       165  Properties of Filaments and Nonwovens  Filament titer, dtex       2.6 Fabric weight, g / m ²      15.2  MD toughness, N      33.1  CD toughness, N      10.5  MD elongation at break,%       45  CD elongation at break,%       65

The filament processed in Example 15 exhibits excellent workability, high consistency and no breakage. The nonwoven fabric thus produced shows high ductility and high toughness.

Claims (9)

Spunbonded nonwoven fabric having an MFR value (MFR (1)) of 6 to 150 g / 10 min and containing a propylene polymer composition (A) selected from i) and ii): i) Crystalline propylene random copolymer or crystalline propylene polymer composition selected from a) and b) a) with xylene for melting point of at least 155 ° C., fraction content soluble in xylene at room temperature, soluble in xylene at less than 4% by weight and at least room temperature of ethylene and optionally at least one C ₄ -C ₁₀ α-olefin; A copolymer or polymer composition having a value of a ratio of polymer fractions collected in a temperature rising elution fractionation (TREF) in the 25 to 95 ° C. temperature range of greater than 8; And b) xylene for melting point of at least 153 ° C., containing at least 2.5 weight% ethylene and optionally at least one C ₄ -C ₁₀ α-olefin, fraction content of less than 10 weight% soluble in xylene at room temperature and xylene soluble fraction at room temperature A copolymer or polymer composition having a TREF value of greater than 4 in the ratio of polymer fractions collected in a temperature range of 25 to 95 ° C .; And ii) a crystalline propylene polymer composition having a melting point of at least 153 ° C., fraction content of less than 10% by weight, soluble in xylene at room temperature; The composition comprises at least 0.64% by weight of ethylene and / or C ₄ -C ₁₀ α-olefin repeat units and containing (% by weight) of I) and II): I) 20-80% crystalline propylene homopolymer or crystalline propylene random copolymer containing not more than 1.5% by weight of ethylene and / or C ₄ -C ₁₀ α-olefins; And      II) 20-80% crystalline propylene random copolymer selected from:         IIa) copolymers of propylene having 0.8 to 10% by weight of ethylene;               Provided that the polymer (I) and the medium               The difference in ethylene content between coales (IIa) is at least 0.8%; IIb) 1.5 to 18% by weight of C ₄ -C ₁₀ α-olefin and optionally ethylene               Copolymers of propylene having; Provided that the weight of the (co) polymer involved               The difference in co-monomer content between polymer (I) and polymer (IIb)               At least 1.5% units; And         IIc) A mixture of copolymer (IIa) and copolymer (IIb). The composition (A) according to claim 1, wherein the composition (A) is collected in the temperature range of 25 to 95 ° C., fractionated by ii) a melting point of at least 155 ° C., fraction content less than 5% by weight of the fraction soluble in xylene at room temperature, and xylene for the xylene soluble fraction at room temperature. The value of the ratio of the prepared polymer fractions is greater than 8; The composition (ii) is a fiber containing (% by weight) of the following I) and II): I) 20-80% of crystalline propylene homopolymers and / or crystalline propylene random copolymers containing up to 1.5% by weight of ethylene and / or C ₄ -C ₁₀ α-olefins; And II) 20-80% of crystalline random copolymers selected from:         IIa) copolymers of propylene with 0.8 to 5% by weight of ethylene;               Provided that the polymer (I) and the medium               The difference in ethylene content between coales (IIa) is at least 0.8%; IIb) 1.5 to 12% by weight of C ₄ -C ₁₀ α-olefin and optionally ethylene               Copolymers of propylene having; Provided that the weight of the (co) polymer involved               The difference in co-monomer content between polymer (I) and polymer (IIb)               At least 1.5% units; And         IIc) Mixtures of Copolymer (IIa) and Copolymer (IIb) The composition (A) according to claim 1 or 2, wherein the composition (A) is obtainable by chemical collapse of the precursor polymer composition (B) having an MFR value (MFR (2)) of 0.5 to 50 g / 10 min, provided that MFR ( 2) A fiber having a ratio of MFR (1) to 1.5 to 60. The fiber according to any one of claims 1 to 3, wherein the difference in ethylene content between the polymer (I) and the polymer (IIa) is at least 1% by weight relative to the weight of the (co) polymer involved. The process according to any one of claims 1 to 4, characterized by melt spinning a propylene polymer composition (A) having an MFR (1) value of 6 to 150 g / 10 min and selected from i) and ii) below. Melt spinning method for the preparation of fibers according to: i) Crystalline propylene random copolymer or crystalline polymer propylene polymer composition selected from a) and b) below: a) with xylene for melting point of at least 155 ° C., fraction content soluble in xylene at room temperature, soluble in xylene at less than 4% by weight and at least room temperature of ethylene and optionally at least one C ₄ -C ₁₀ α-olefin; Copolymers or polymer compositions having a TREF value of greater than 8 in the ratio of polymer fractions collected in the temperature range from 25 to 95 ° C .; And b) a melting point of at least 153 ° C., containing more than 2.5 to 4.5% by weight of ethylene and optionally one or more C ₄ -C ₁₀ α-olefins, a fraction content of less than 10% by weight of fractions soluble in xylene at room temperature and a xylene soluble fraction at room temperature Copolymers or polymer compositions having a value of more than 4 in the ratio of polymer fractions collected in a temperature range of 25 to 95 ° C. by TREF with xylene; And ii) a crystalline propylene polymer composition having a melting point of at least 153 ° C., fraction content of less than 10% by weight, soluble in xylene at room temperature; The composition comprises at least 0.64% by weight of ethylene and / or C ₄ -C ₁₀ α-olefin repeat units and containing (% by weight) of I) and II): I) 20-80% crystalline propylene homopolymer or crystalline propylene random copolymer containing not more than 1.5% by weight of ethylene and / or C ₄ -C ₁₀ α-olefins; And      II) 20-80% crystalline propylene random copolymer selected from:         IIa) copolymers of propylene having 0.8 to 10% by weight of ethylene;               Provided that the polymer (I) and the medium               The difference in ethylene content between coales (IIa) is at least 0.8%; IIb) 1.5 to 18% by weight of C ₄ -C ₁₀ α-olefin and optionally ethylene               Copolymers of propylene having; Provided that the weight of the (co) polymer involved               The difference in co-monomer content between polymer (I) and polymer (IIb)               At least 1.5% units; And         IIc) A mixture of copolymer (IIa) and copolymer (IIb). A propylene polymer composition having an MFR value of 6 to 150 g / 10 minutes, The composition contains the following I) and II) (% by weight): I) Xylene to a melting point of at least 155 ° C., soluble in xylene at room temperature, less than 4% by weight of ethylene and / or C ₄ -C ₁₀ α-olefins, containing less than 1.5% by weight of ethylene and / or C ₄ -C ₁₀ α-olefins; 20-80% of a crystalline propylene homopolymer or crystalline propylene random copolymer having a TREF value of greater than 8 in the ratio of polymer fractions collected in the temperature range from 25 to 95 ° C .; And      II) 20-80% crystalline propylene random copolymer selected from:         IIa) copolymers of propylene having 0.8 to 10% by weight of ethylene;               Provided that the polymer (I) and the medium               The difference in ethylene content between coales (IIa) is at least 0.8%; IIb) 1.5 to 18% by weight of C ₄ -C ₁₀ α-olefin and optionally ethylene               Copolymers of propylene having; Provided that the weight of the (co) polymer involved               The difference in co-monomer content between polymer (I) and polymer (IIb)               At least 1.5% units; And         IIc) a mixture of copolymer (IIa) and copolymer (IIb); The polymer composition is obtainable by chemical breakdown of the precursor polymer composition (B) having an MFR (2) value of 0.5 to 50 g / 10 min, provided that the ratio of MFR (1) to MFR (2) is from 1.5 to 60 Propylene polymer composition. In the crystalline propylene random copolymer and the crystalline propylene polymer composition selected from: a) xylenes, containing at least 0.8% by weight of ethylene and optionally at least one C ₄ -C ₁₀ α-olefin, having a melting point of at least 155 ° C., a fraction content of less than 4% by weight of fractions soluble in xylene at room temperature and a xylene soluble fraction at room temperature Copolymer or polymer composition having a TREF value of greater than 8 in the ratio of polymer fractions collected in a temperature range of 25 to 95 ° C .; And b) TREF with xylene, containing 2.5 to 4.5% by weight of ethylene and optionally one or more C ₄ -C ₁₀ α-olefins, at a melting point of at least 153 ° C., for the xylene soluble fraction at room temperature, collected in the temperature range of 25 to 95 ° C. Copolymers or polymers having a content of more than 4 fractions; The copolymer or composition is obtainable by chemical breakdown of the precursor polymer composition (B) having an MFR (2) value of 0.5 to 50 g / 10 min, provided that the ratio of MFR (1) to MFR (2) is 1.5 Crystalline propylene random copolymer or crystalline propylene polymer composition. A process for preparing the polymer composition of claim 6 comprising the following steps: 1) polymerizing the monomers in one or more successive steps, each step operating in the presence of the catalyst used and the polymer formed in the previous step, the molecular weight in an amount such that the MFR (2) value of the precursor composition is from 0.5 to 50 g / 10 min. Administering a modulator to prepare the precursor composition (B) in advance; And 2) disintegrating the precursor composition (B) obtained in step (1) with a decay ratio of 1.5 to 60 at a ratio of MFR (1) to MFR (2). A spunbond nonwoven fabric containing the fiber of claim 1.