Spun bond nonwoven fabric

Abstract

The invention relates to a spun bond nonwoven fabric obtained by a) melt-mixing a first composition comprising a propylene-based polymer, a visbreaking agent and vitamin E under a visbreaking condition to obtain a visbroken, second composition and b) processing the visbroken, second composition by a spun bonding process to obtain the nonwoven fabric, wherein the propylene-based polymer in the first composition has a melt flow index determined according to ISO 1133-1 :2011 at 230 °C and 2.16 kg of MFI1 and the visbroken, second composition has a melt flow index determined according to ISO 1133-1 :2011 at 230 °C and 2.16 kg of MFI2 and the ratio of MFI2 to MFI1 is at least 2.0.

Description

[0001] SPUN BOND NONWOVEN FABRIC

[0002] The present invention relates to a spun bond nonwoven fabric.

[0003] Spun bond non-woven fabric has been widely used in many applications due to its excellent mechanical properties such as high tensile strength and air permeability. It also ensures the efficient production of fabric based on continuously spun fibers. Polyamide and polyester have been used for making such spun bond non-woven fabrics. Polypropylene is becoming increasingly prominent within the family of polymeric materials used for spun bond non-woven fabrics.

[0004] WO2013124219A1 discloses a spunbonded fabric comprising polypropylene fibers of a polypropylene composition that has been visbroken. In Inventive Example IE1 , a polypropylene polymer having MFR of 2 g / 10min was mixed with 400 ppm Calcium Stearate, 1000 ppm Irgafos 168 and 400 ppm Irganox 3114 and a high MFR polypropylene having an MFR of 1200 g / 10min and these mixtures were visbroken to final MFR of 34 dg / min by using a co-rotating twin-screw extruder at 200-230°C and using an appropriate amount of (tert.butylperoxy)-2,5- dimethylhexane (Trigonox 101).

[0005] It is an objective of the present invention to provide a spun bond nonwoven fabric having good mechanical properties and / or good barrier properties.

[0006] Accordingly, the present invention provides a spun bond nonwoven fabric obtained by a) melt-mixing a first composition comprising a propylene-based polymer, a visbreaking agent and vitamin E under a visbreaking condition to obtain a visbroken, second composition and b) processing the visbroken, second composition by a spun bonding process to obtain the nonwoven fabric, wherein the propylene-based polymer in the first composition has a melt flow index determined according to ISO 1133-1 :2011 at 230 °C and 2.16 kg of MFI1 and the visbroken, second composition has a melt flow index determined according to ISO 1133-1 :2011 at 230 °C and 2.16 kg of MFI2 and the ratio of MFI2 to MFI1 is at least It was surprisingly found according to the invention that the use of vitamin E provides a spun bond nonwoven fabric with good mechanical properties and / or good barrier properties. It was observed that the addition of vitamin E results in an increase in crystallization temperature, indicating that vitamin E acts as a nucleating agent. Further, the visbreaking step allows for a stable spinning process.

[0007] Step a)

[0008] The nonwoven fabric according to the invention is obtained by a process comprising melt-mixing a first composition under a visbreaking condition to obtain a visbroken, second composition. Visbreaking is per se known and conditions such as temperature and duration can be selected by the skilled person depending on the initial melt flow index and the desired melt flow index and the type of the visbreaking agent.

[0009] The visbreaking condition may be selected such that the ratio between the melt flow index determined according to ISO 1133-1 :2011 at 230 °C and 2.16 kg of the visbroken, second composition to the melt flow index determined according to ISO 1133-1 :2011 at 230 °C and 2.16 kg of the propylene-based polymer in the first composition (MFI2 / MFI1) is at least 2.0, preferably at least 5.0 or at least 10.0. Such visbreaking allows selecting starting propylene-based polymer to obtain a composition which can be spun in a stable manner. For example, the starting propylene-based polymer can be selected to obtain a visbroken composition with high MFI and narrow MWD.

[0010] Propylene-based polymer

[0011] Preferably, the propylene-based polymer in the first composition has a melt flow index MFI1 determined according to ISO 1133-1 :2011 at 230 °C and 2.16 kg of 0.1 to 10.0 dg / min.

[0012] The propylene-based polymer may be a propylene homopolymer or a propylene a- olefin random copolymer, preferably a propylene homopolymer. The random copolymer consists of at least 70.0 wt% of propylene-derived units and up to 30.0 wt% of comonomer-derived units, based on the total weight of the random copolymer. For example, the amount of the comonomer-derived units based on the total weight of the random copolymer is 1 .0 wt% to 20.0 wt%, 2.0 wt% to 10.0 wt% or 3.0 to 5.0 wt%. Preferably, the comonomer is selected from the group consisting of ethylene, 1 - butene, 1 -pentene, 4-methyl-1 -pentene, 1 -hexene, 1 -heptene and 1 -octene. Most preferably, the comonomer is ethylene.

[0013] Preferably, the amount of the propylene-based polymer is at least 90.0 wt%, preferably at least 95.0 wt%, for example 96.0 to 99.9 wt%, with respect to the total first composition.

[0014] Visbreaking agent

[0015] Preferably, the visbreaking agent comprises an organic peroxide or a hydroxylamine ester, preferably an organic peroxide. Preferably, the visbreaking agent is an organic peroxide.

[0016] Suitable organic peroxides include but are not limited to dialkyl peroxides, e.g. dicumyl peroxides, peroxyketals, peroxycarbonates, diacyl peroxides, peroxyesters and peroxydicarbonates. Specific examples of these include benzoyl peroxide, dichlorobenzoyi peroxide, dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5- di(peroxybenzoato)-3-hexene, 1 ,4-bis(tert-butylperoxyisopropyl)benzene, lauroyl peroxide, tert-butyl peracetate, a,a'-bis(tert-butylperoxy)diisopropylbenzene (Luperco® 802), 2,5- dimethyl-2,5-di(tert-butylperoxy)-3-hexene, 2,5-dimethyl-2,5-di(tert- butylperoxy)-hexane (e.g. Trigonox™ 101 manufactured by AkzoNobel), tert-butyl perbenzoate, tert-butyl perphenylacetate, tert-butyl per-sec-octoate, tert-butyl perpivalate, cumyl perpivalate, cumene hydroperoxide, diisopropyl benzene hydroperoxide, 1 ,3-bis(t-butylperoxy- isopropylbenzene, dicumyl peroxide, tertbutylperoxy isopropyl carbonate, a,a'-bis-(tert-butylperoxy)diisopropylbenzene, 2,5- dimethyl-2,5-di(tert-butylperoxy)-hexane or 3,6,9-Triethyl-3,6,9-trimethyl-1 ,4,7- triperoxonane (e.g. Trigonox™ 301 manufactured by AkzoNobel) and 3,3,5,7,7-pentamethyl-1 ,2,4-trioxepane (e.g. Trigonox™ 311 manufactured by AkzoNobel). Preferably, the organic peroxide is 2,5-dimethyl-2,5-di(tert-butylperoxy)- hexane.

[0017] Suitable hydroxylamine esters are described e.g. in W02016096690A1 , page 3, line 1 to page 5, line 14 and WO199749737, W02001090113A1 and EP1786861 referenced therein, all incorporated herein by reference. The amount of the visbreaking agent with respect to the propylene-based polymer may e.g. be 100 to 2000 ppm.

[0018] Vitamin E

[0019] Preferably, the amount of vitamin E with respect to the propylene-based polymer in the first composition is 10 to 500 ppm, preferably 30 to 100 ppm.

[0020] Antioxidants

[0021] The first composition may further comprise a primary antioxidant and / or a secondary antioxidant. As described elsewhere, the invention further relates to embodiments wherein the first composition is free of primary antioxidant and free of secondary antioxidant.

[0022] The difference between primary and secondary antioxidants is well-known in the art.

[0023] Primary antioxidants are typically organic molecules consisting of hindered phenol and amine derivatives. These primary antioxidants are radical scavengers and are usually added to polymers to protect against degradation during the service life of the finished product.

[0024] Phosphites and phophonites are examples of secondary antioxidants. Secondary antioxidants can prevent formation of additional free radicals by decomposing unstable hydroperoxides into stable alcohols and are usually added to polymers to provide processing stability during the pelletisation and extrusion and / or moulding processes. When primary antioxidants, such as hindered phenols, are utilised, polyolefins can develop a more yellow colour, decreasing the commercial value of the polyolefins.

[0025] Secondary antioxidants, such as phosphite compounds, are often utilised in polyolefins in combination with hindered phenols to increase the stability and decrease yellowing.

[0026] Primary antioxidant

[0027] The primary antioxidant may be a phenolic antioxidant comprising two or more phenolic groups per molecule. Some examples of such phenolic antioxidants include pentaerythritol tetrakis(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate), tris(3,5-di-t-butyl- 4-hydroxybenzyl)isocyanurate, and 1 ,3,5-trimethyl-2,4,6-tris(3, 5-di-t-butyl-4- hydroxybenzyl)benzene. Other examples of phenolic antioxidants include 2,2'-methylenebis(4-methyl-6-t- butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t- butylphenol), 2,2'-thiobis(4-methyl-6-t-butylphenol), 4,4'-methylenebis(2,6-di-t- butylphenol), 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol], 2,2'-ethylidenebis(2,4- di-t-butylphenol), 2,2'-butylidenebis(2-t-butyl-4-methylphenol), 1 ,1 ,3-tris(2-methyl-4- hydroxy-5-t-butylphenyl)butane, triethylene glycol-bis[3-(3-t-butyl-5-methyl-4- hydroxyphenyl)propionate], 1 ,6-hexanediol-bis[3-(3,5-di-t-butyl-4- hydroxyphenyl)propionate], 2,2-thiodiethylenebis[3-(3,5-di-t-butyl-4- hydroxyphenyl)propionate], N,N'-hexamethylenebis(3,5-di-t-butyl-4- hydroxyhydrocinnamide), 3,5-di-t-butyl-4-hydroxybenzylphosphonate-diethyl ester

[0028] 1 .3.5-tris(2,6-dimethyl-3-hydroxy-4-t-butylbenzyl)isocyanurate, 1 ,3,5-tris[(3,5-di-t-butyl- 4-hydroxyphenyl)propionyloxyethyl]isocyanurate, tris(4-t-butyl-2,6-dimethyl-3- hydroxybenzyl)isocyanurate, 2,4-bis(n-octylthio)-6-(4-hydroxy-3,5-t-butylanilino)-1 ,3,5- triazine, tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] methane, bis(3,5-di-t-butyl-4-hydroxybenzylphosphonic acid ethyl ester) calcium, bis(3,5-di-t- butyl-4-hydroxybenzylphosphonic acid ethyl ester) nickel, bis[3,3-bis(3-t-4- hydroxyphenyl)butyric acid] glycol ester, N,N'-bis[3,5-di-t-butyl-4- hydroxyphenyl)propionyl]hydrazine, 2,2'-oxaimidobis[ethyl-3-(3,5-di-t-butyl-4- hydroxyphenyl)propionate], 2,2'-methylenebis(4-methyl-6-t-butylphenol)terephthalate,

[0029] 1 .3.5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl) benzene, 3,9-bis[1 ,1-dimethyl- 2-{|3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy} ethyl]-2,4,8,10- tetraoxaspiro[5,5]-undecane, 2,2-bis[4-(2-)3,5-di-t-butyl-4- hydroxyhydrocinnamoyloxy))ethoxyphenyl] propane, and alkyl esters of [3-(3,5-di-t- butyl-4-hydroxyphenyl)propionic acid.

[0030] Many phenolic antioxidants are commercially available. Some examples include Irganox® 1010 (pentaerythritol tetrakis(3-(3,5-di-t-butyl-4- hydroxyphenyl)propionate, available from BASF), Irganox® 1098 (1 ,6-hexamethylene bis(3,5-di-t-butyl-4-hydroxyhydrocinnamate, available from BASF), ADK STAB AO-80 (3, 9-bis(2-(3-(3-t-butyl-4-hydroxy-5-methyl-phenyl)-propionyl-oxy)-1 ,1 -dimethyl)- 2,4,8, 10-tetraoxospiro[5,5]undecane, available from Adeka Palmarole), Topanol® CA (1 ,1 ,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, available from Vertellus Specialties), Irganox® 1330 (1 ,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4- hydroxybenzyl)benzene, available from BASF), Hostanox® 03 (butyric acid, 3,3-bis(3- t-butyl-4-hydroxyphenyl)ethylene ester, available from Clariant), Irganox® 3114 (1 ,3,5- tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-s-triazine-2,4,6-(1 H,3H,5H)trione, available from BASF), Cyanox® 1790 (1 ,3,5-tris(4-t-butyl-2,6-dimethyl-3-hydroxy-benzyl)-iso- cyanurate, available from Cytec), and Iragnox® 245 (triethylene-glycol-bis-3-(t-butyl-4- hydroxy-5-methyl-phenyl)propionate, available from BASF).

[0031] When present, the amount of 1 ,3,5-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-s-triazine-

[0032] 2.4.6-(1 H,3H,5H)trione in the first composition may e.g. be may e.g. be 100 to 5000 ppm. Preferably, the first composition is free of or substantially free of 1 ,3,5-tris(3',5'-di- t-butyl-4'-hydroxybenzyl)-s-triazine-2,4,6-(1 H,3H,5H)trione. Preferably, the first composition is free of 1 ,3,5-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-s-triazine-2,4,6- (1 H,3H,5H)trione or the amount of 1 ,3,5-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-s-triazine-

[0033] 2.4.6-(1 H,3H,5H)trione in the first composition is less than 100 ppm, less than 50 ppm or less than 10 ppm.

[0034] When present, the total amount of

[0035] Irganox® 1010 (pentaerythritol tetrakis(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, available from BASF),

[0036] Irganox® 1098 (1 ,6-hexamethylene bis(3,5-di-t-butyl-4-hydroxyhydrocinnamate, available from BASF),

[0037] ADK STAB AO-80 (3,9-bis(2-(3-(3-t-butyl-4-hydroxy-5-methyl-phenyl)-propionyl-oxy)- 1 ,1-dimethyl)-2,4,8,10-tetraoxospiro[5,5]undecane, available from Adeka Palmarole), Topanol® CA (1 ,1 ,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, available from Vertellus Specialties),

[0038] Irganox® 1330 (1 ,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, available from BASF),

[0039] Hostanox® 03 (butyric acid, 3,3-bis(3-t-butyl-4-hydroxyphenyl)ethylene ester, available from Clariant),

[0040] Irganox® 3114 (1 ,3,5-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-s-triazine-2,4,6- (1 H,3H,5H)trione, available from BASF),

[0041] Cyanox® 1790 (1 ,3,5-tris(4-t-butyl-2,6-dimethyl-3-hydroxy-benzyl)-iso-cyanurate, available from Cytec) and

[0042] Iragnox® 245 (triethylene-glycol-bis-3-(t-butyl-4-hydroxy-5-methyl-phenyl)propionate, available from BASF) may e.g. be 100 to 5000 ppm. Preferably, the first composition is free of these primary antioxidants or the total amount of these primary antioxidants in the first composition is less than 100 ppm, less than 50 ppm or less than 10 ppm. When present, the amount of the primary antioxidant in the first composition may e.g. be 100 to 5000 ppm. Preferably, the first composition is free of primary antioxidant or the total amount of primary antioxidant in the first composition is less than 100 ppm, less than 50 ppm or less than 10 ppm.

[0043] Secondary antioxidant

[0044] Examples of secondary antioxidants include organic phosphites and phosphonites, such as triphenyl phosphite, diphenyl alkyl phosphites, phenyl dialkylphoshites, tris(nonylphenyl)phosphite, tris(2,4-di-t-butylphenyl)phosphite, bis(2,4-di-t- butylphenyl)pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite, bis(2,4-di-t-butyl-6-methylphenyl)pentaerythritol diphosphite, bis(2,4,6-tri-t-butylphenyl)pentaerythritol diphosphite, tetrakis(2,4-di-t- butylphenyl)-4,4'-biphenylenediphosphonite, bis(2,4-di-t-butyl-6-methylphenyl)methyl phosphite, and bis(2,4-di-t-butyl-6-methylphenyl)ethyl phosphite. Some preferred secondary phenolic antioxidants are tris(2,4-di-t-butylphenyl)phosphite, bis(2,4-di-t- butyl-6-methylphenyl)ethyl phosphite, bis(2,4-di-t-butylphenyl) pentaerythritol diphosphite, and tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylenediphosphonite. The most preferred secondary phenolic antioxidant is tris(2,4-di-t-butylphenyl)phosphite.

[0045] Many of these secondary phenolic antioxidants are commercially available. Some examples include Irgafos® 168 (tris(2,4-di-t-butylphenyl)phosphite, available from BASF), and Irgafos® P-EPQ (tetrakis(2,4-di-t-butylphenyl)[1 , 1 -biphenyl]-4,4'- diylbisphosphonite, available from BASF).

[0046] When present, the amount of tris(2,4-di-t-butylphenyl)phosphite in the first composition may e.g. be may e.g. be 100 to 5000 ppm. Preferably, the first composition is free of or substantially free of tris(2,4-di-t-butylphenyl)phosphite. Preferably, the first composition is free of tris(2,4-di-t-butylphenyl)phosphite or the amount of tris(2,4-di-t- butylphenyl)phosphite in the first composition is less than 100 ppm, less than 50 ppm or less than 10 ppm.

[0047] When present, the total amount of tris(2,4-di-t-butylphenyl)phosphite and tetrakis(2,4- di-t-butylphenyl)[1 , 1 -biphenyl]-4,4'-diylbisphosphonite in the first composition may e.g. be may e.g. be 100 to 5000 ppm. Preferably, the first composition is free of or substantially free of tris(2,4-di-t-butylphenyl)phosphite and tetrakis(2,4-di-t- butylphenyl)[1 ,1-biphenyl]-4,4'-diylbisphosphonite. Preferably, the first composition is free of tris(2,4-di-t-butylphenyl)phosphite and tetrakis(2,4-di-t-butylphenyl)[1 , 1 - biphenyl]-4,4'-diylbisphosphonite or the total amount of tris(2,4-di-t- butylphenyl)phosphite and tetrakis(2,4-di-t-butylphenyl)[1 , 1 -biphenyl]-4,4'- diylbisphosphonite in the first composition is less than 100 ppm, less than 50 ppm or less than 10 ppm.

[0048] When present, the amount of the secondary antioxidant in the first composition may e.g. be 100 to 5000 ppm. Preferably, the first composition is free of secondary antioxidant or the total amount of secondary antioxidant in the first composition is less than 100 ppm, less than 50 ppm or less than 10 ppm.

[0049] Preferably, the first composition comprises calcium stearate, preferably in an amount of 100 to 1000 ppm.

[0050] Preferably, the total amount of the propylene-based polymer, the visbreaking agent, vitamin E and calcium stearate and optional primary antioxidant and optional primary antioxidant with respect to the total first composition is at least 99.5 wt%, at least 99.6 wt%, at least 99.7 wt%, at least 99.8 wt%, at least 99.9 wt%, at least 99.99 wt% or 100.00 wt%.

[0051] Preferably, the total amount of the propylene-based polymer, the visbreaking agent, vitamin E and calcium stearate with respect to the total first composition is at least 99.5 wt%, at least 99.6 wt%, at least 99.7 wt%, at least 99.8 wt%, at least 99.9 wt%, at least 99.99 wt% or 100.00 wt%.

[0052] Visbroken, second composition

[0053] Preferably, the visbroken, second composition has a melt flow index MFI2 determined according to ISO 1133-1 :2011 at 230 °C and 2.16 kg of 20 to 50 dg / min, preferably 23 to 45 dg / min, more preferably 25 to 45 dg / min, more preferably 30 to 40 dg / min.

[0054] Preferably, the visbroken, second composition has Mw of 100,000 to 200,000, more preferably 130,000 to 190,000, more preferably 150,000 to 180,000.

[0055] Preferably, the visbroken, second composition has Mn of 10,000 to 60,000, more preferably 20,000 to 50,000, more preferably 30,000 to 50,000. Preferably, the visbroken, second composition has Mw / Mn of 1.5 to 5.0, more preferably 1 .7 to 4.0, more preferably 2.0 to 3.0. Such MWD leads to a lower melt elasticity, which in turn results in a reduction of die swell and in lower resistance to fiber drawing. Thus, the stability of the spinning process as well as the maximum spinning speeds are increased. Additionally, this will allow retaining orientation and better mechanical properties of the nonwoven fabric.

[0056] Mw and Mn are determined according to ASTM D 6474-2013 under the following conditions:

[0057] Reagents

[0058] • 1 ,2,4-Trichlorobenzene (TCB), HPLC grade.

[0059] • Butylated Hydroxytoluene (BHT), as solvent stabilizer for TCB, 250mg / L(1 .0 gram 14 liters, eluant) and 250 mg / L for sample preparation.

[0060] • Narrow MWD Polystyrene standards for calibration: The polystyrene MW range of 10000 to 2,000,000 is covered in 10 individual points, sufficient to generate a reliable third order calibration. The correlation coefficient of the calibration curve must be greater than 0.997 for the acceptance criterion for calibration.

[0061] Equipment

[0062] • Waters Alliance GPC 2000 Gel Permeation Chromatograph with Differential Refractive Index Detector or

[0063] • Polymer Labs HT GPC 220 with Differential Refractive Index Detector

[0064] • or functional equivalent.

[0065] Columns

[0066] • PL Gel mixed bed Guard column (50*7,5 mm), 10 pm, P / N 1110-1120 or

[0067] • PL Gel Olexis Guard column (50 * 7.5 mm), 13 pm, P / N 1110-1400

[0068] • or functional equivalent.

[0069] Step b)

[0070] In step b), the visbroken composition is processed by a spun bonding process to obtain the nonwoven fabric. Spun bonding process is per se well-known. The major steps in the spun bonding process are web formation, web bonding, and winding into rolls. Melted polymer is first fed into an extruder and forced through a spinneret; the fibres are then stretched after cooling. The web is made by continuously placing fibres to a depth slightly larger than the final product onto a moving conveyor belt. The fibres form loose web, which may be bonded together by one of three bonding techniques: mechanical bonding, thermal bonding, or chemical bonding. The visbroken, second composition obtained by step a) as a molten composition can be directly subjected to step b). If the visbroken, second composition is solidified before b), step b) comprises melting the visbroken, second composition.

[0071] The present invention further provides an article comprising the non-woven fabric according to the invention. Preferably, the article is selected from the group consisting of upholstery, apparel, wall covering, carpet, diaper topsheet, diaper backsheet, medical fabric, surgical wrap, hospital gown, wipe, textile, and geotextile.

[0072] It is noted that the invention relates to the subject-matter defined in the independent claims alone or in combination with any possible combinations of features described herein, preferred in particular are those combinations of features that are present in the claims. It will therefore be appreciated that all combinations of features relating to the composition according to the invention; all combinations of features relating to the process according to the invention and all combinations of features relating to the composition according to the invention and features relating to the process according to the invention are described herein.

[0073] It is further noted that the term ‘comprising’ does not exclude the presence of other elements. However, it is also to be understood that a description on a product / composition comprising certain components also discloses a product / composition consisting of these components. The product / composition consisting of these components may be advantageous in that it offers a simpler, more economical process for the preparation of the product / composition. Similarly, it is also to be understood that a description on a process comprising certain steps also discloses a process consisting of these steps. The process consisting of these steps may be advantageous in that it offers a simpler, more economical process.

[0074] When values are mentioned for a lower limit and an upper limit for a parameter, ranges made by the combinations of the values of the lower limit and the values of the upper limit are also understood to be disclosed.

[0075] The invention is now elucidated by way of the following examples, without however being limited thereto. Propylene homopolymers having melt flow index (ISO1133-1 :2011 , 230 °C, 2.16 kg) shown in Table 1-1 were melt-mixed with components shown in Table 1-1 under same visbreaking conditions to obtain pellets of compositions having melt flow index (ISO1133-1 :2011 , 230 °C, 2.16 kg) shown in Table 1-1.

[0076] Properties of the obtained compositions were measured and are shown in Table 1-2.

[0077] Tc and Tm were determined by DSC according to ASTM D 3418-15

[0078] Mn and Mw were determined according to ASTM D 6474-2013 under the following conditions:

[0079] Reagents

[0080] • 1 ,2,4-Trichlorobenzene (TCB), HPLC grade.

[0081] • Butylated Hydroxytoluene (BHT), as solvent stabilizer for TCB, 250mg / L(1 .0 gram 14 liters, eluant) and 250 mg / L for sample preparation.

[0082] • Narrow MWD Polystyrene standards for calibration: The polystyrene MW range of 10000 to 2,000,000 is covered in 10 individual points, sufficient to generate a reliable third order calibration. The correlation coefficient of the calibration curve must be greater than 0.997 for the acceptance criterion for calibration.

[0083] Equipment

[0084] • Waters Alliance GPC 2000 Gel Permeation Chromatograph with Differential Refractive Index Detector or

[0085] • Polymer Labs HT GPC 220 with Differential Refractive Index Detector

[0086] • or functional equivalent.

[0087] Columns

[0088] PL Gel mixed bed Guard column (50*7,5 mm), 10 pm, P / N 1110-1120 or

[0089] PL Gel Olexis Guard column (50 * 7.5 mm), 13 pm, P / N 1110-1400 or functional equivalent.

[0090] Flexural modulus was determined according to ASTM D 790 and shown in Table 1-2. Table 1-1

[0091] Table 1-2 The results show that the use of vitamin E (Inventive example 1 , I E 1 ) results in a particularly high flexural modulus. The results also show that visbreaking of a low MFI polypropylene allows obtaining a final composition with a relatively narrow MWD.

[0092] The results further show that the use of vitamin E results in an increase in Tc, indicating that vitamin E shows nucleating behavior. This leads to an increase in mechanical properties of the composition.

[0093] It can be understood from these results that a nonwoven fabric with good mechanical properties such as good flexural modulus and / or good barrier properties such as air permeability and hydrohead can be obtained by spun bonding process of the composition of IE1.

Claims

CLAIMS1 . A spun bond nonwoven fabric obtained by a) melt-mixing a first composition comprising a propylene-based polymer, a visbreaking agent and vitamin E under a visbreaking condition to obtain a visbroken, second composition and b) processing the visbroken, second composition by a spun bonding process to obtain the nonwoven fabric, wherein the propylene-based polymer in the first composition has a melt flow index determined according to ISO 1133-1 :2011 at 230 °C and 2.16 kg of MFI1 and the visbroken, second composition has a melt flow index determined according to ISO 1133-1 :2011 at 230 °C and 2.16 kg of MFI2 and the ratio of MFI2 to MFI1 is at least 2.0.

2. The spun bond nonwoven fabric according to claim 1 , wherein the amount of vitamin E with respect to the propylene-based polymer in the first composition is 10 to 500 ppm, preferably 30 to 100 ppm.

3. The spun bond nonwoven fabric according to any one of the preceding claims, wherein the first composition is free of 1 ,3,5-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-s- triazine-2,4,6-(1 H,3H,5H)trione or the amount of 1 ,3,5-tris(3',5'-di-t-butyl-4'- hydroxybenzyl)-s-triazine-2,4,6-(1 H,3H,5H)trione with respect to the propylene- based polymer in the first composition is less than 100 ppm.

4. The spun bond nonwoven fabric according to any one of the preceding claims, wherein the first composition is free of primary antioxidant or the total amount of primary antioxidant with respect to the propylene-based polymer in the first composition is less than 100 ppm, less than 50 ppm or less than 10 ppm.

5. The spun bond nonwoven fabric according to any one of the preceding claims, wherein the first composition is free of tris(2,4-di-t-butylphenyl)phosphite or the amount of tris(2,4-di-t-butylphenyl)phosphite with respect to the propylene-based polymer in the first composition is less than 100 ppm, less than 50 ppm or less than 10 ppm.

6. The spun bond nonwoven fabric according to any one of the preceding claims, wherein the first composition is free of secondary antioxidant or the total amount of secondary antioxidant with respect to the propylene-based polymer in the first composition is less than 100 ppm, less than 50 ppm or less than 10 ppm.

7. The spun bond nonwoven fabric according to any one of the preceding claims, wherein the first composition further comprises calcium stearate, preferably in an amount of 100 to 1000 ppm with respect to the propylene-based polymer in the first composition.

8. The spun bond nonwoven fabric according to any one of the preceding claims, wherein the amount of the propylene-based polymer with respect to the total first composition is at least 90.0 wt%, preferably at least 95.0 wt%, for example 96.0 to 99.9 wt%.

9. The spun bond nonwoven fabric according to any one of the preceding claims, wherein MFI1 is 0.1 to 10.0 dg / min.

10. The spun bond nonwoven fabric according to any one of the preceding claims, wherein the first propylene-based polymer is a propylene homopolymer or a propylene random copolymer consisting of at least 70.0 wt% of propylene-derived units and up to 30.0 wt% of comonomer-derived units based on the total weight of the random copolymer, wherein the comonomer is selected from the group consisting of ethylene and a-olefins having 4-10 carbon atoms.11 . The spun bond nonwoven fabric according to any one of the preceding claims, wherein MFI2 is 20 to 50 dg / min, preferably 23 to 45 dg / min, more preferably 25 to 45 dg / min, more preferably 30 to 40 dg / min.

12. The spun bond nonwoven fabric according to any one of the preceding claims, wherein the visbroken, second composition has Mw / Mn of 1.5 to 5.0, more preferably 1 .7 to 4.0, more preferably 2.0 to 3.0 determined according to ASTM D 6474-2013.

13. The spun bond nonwoven fabric according to any one of the preceding claims, wherein the visbreaking agent comprises an organic peroxide or a hydroxylamine ester, preferably the visbreaking agent is an organic peroxide.

14. An article comprising the non-woven fabric according to any one of the preceding claims, wherein the article is selected from the group consisting of upholstery, apparel, wall covering, carpet, diaper topsheet, diaper backsheet, medical fabric, surgical wrap, hospital gown, wipe, textile, and geotextile.

15. A process for making a spun bond nonwoven fabric, comprising a) melt-mixing a first composition comprising a propylene-based polymer, a visbreaking agent and vitamin E under a visbreaking condition to obtain a visbroken, second composition and b) processing the visbroken, second composition by a spun bonding process to obtain the nonwoven fabric.

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