PROCESSING OF POLYPROPYLENE AND PRODUCTS THEREFROM

Abstract

A method for producing a low viscosity polypropylene composition may include melting a polypropylene-based composition; reducing a viscosity of the polypropylene-based composition; and optionally, repeating the melting and the reducing steps to form a low melt viscosity polypropylene-based composition; wherein the melting and viscosity decreasing steps are performed in the presence of at least one free radical generator and at least one pro-degradant stearate.

Description

BACKGROUND

Polyolefins such as polyethylene (PE) and polypropylene (PP) may be used to manufacture a varied range of articles, including films, molded products, foams, and the like. Polyolefins may have characteristics such as high processability, low production cost, flexibility, low density and recycling possibility. While plastics such as polyethylene and polypropylene have many beneficial uses, there is a need for their correct disposal after use, or even their reuse or recycling so as to minimize the environmental impact of plastic wastes.

One of the largest challenges faced by society today is to reduce greenhouse gas emissions in order to minimize the anthropogenic impact on the climate and environment. Governmental regulations may set limits on CO₂ emissions and drive the transition to a low carbon economy based on renewable energy, in addition to the development of new economic and business models. In some cases, new production techniques and material solutions may be necessary to reduce the carbon footprint of plastic manufacture.

A part of this approach is reconsidering the use of plastics in order to reduce the environmental impact of plastic waste. One option is to recycle the consumed plastic and reintroduce it in the plastic value chain. Consumed plastics, such as post-consumer resins (PCR), are available in the market, but because of the high inhomogeneity of sources and the chemical and mechanical damage that the plastic has endured (from production to waste), the properties of these resins are generally poor, and it is a challenge to reuse them in many applications that require high property standards.

In this connection, a process to reduce the viscosity of polypropylene would be particularly beneficial in the circular economy field as it would broaden the application of post-consumed or post-industrial plastics.

SUMMARY

This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

In one aspect, embodiments disclosed herein relate to a method for producing a low viscosity polypropylene-based composition that includes melting a polypropylene-based composition; reducing a viscosity of the polypropylene; and optionally, repeating the melting and the reducing steps to form a low melt viscosity polypropylene; wherein the melting and reducing steps are performed in a continuous process in the presence of at least one free radical generator and at least one pro-degradant stearate.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a frequency sweep analysis.

DETAILED DESCRIPTION

In one aspect, embodiments disclosed herein relate to methods of processing a polypropylene-based resin to provide low viscosity polypropylene-based compositions that are useful for several applications, for instance, meltblown applications, chemical recycling processes, among others.

Polypropylene-Based Compositions

The “polypropylene-based compositions” according to the present disclosure are polymer compositions comprising greater than 50 wt. % of polypropylene resin.

In one or more embodiments, the polypropylene-based composition comprises greater than 97 wt %, 98 wt. %, 99 wt. % or 100 wt. % of polypropylene based on the polymer content.

In one or more embodiments, the polypropylene-based composition is a blend of polypropylene resin and other olefin-based resins, wherein the olefin-based resin is present in an amount having a lower limit of about 0.1 wt. %, 5 wt. %, 10 wt. %, 15 wt. %, 20 wt. % or 25 wt. %, and a upper limit of 30 wt. %, 35 wt. %, 40 wt. %, 45 wt. % or 49 wt. %, wherein any lower limit may be combined with any upper limit, wherein the amounts are based on the sum of the polypropylene and olefin-based resins weights. In a preferred embodiment, the blend comprises from about 0 to 49% of polyethylene, based on the sum of polypropylene and polyethylene weight. In some embodiments, the olefin-based resins may be selected from polyethylenes, polybutylenes, ethylene-vinyl acetate copolymers, polystyrenes, and combinations thereof.

The “polypropylene resin” or “PP” according to the present disclosure are polymers comprising greater than 50 wt. % of propylene monomer. The PP may be selected from homopolymers, random copolymers, heterophasic copolymers, heterophasic random copolymers, terpolymers and mixtures thereof. In some embodiments, the copolymers may contain comonomers selected from ethylene and alpha-olefins with 4 to 10 carbon atoms.

In one or more embodiments, the polypropylene resin and olefin-based resins of the present disclosure may be selected from petroleum-based resins, biobased resins and combinations thereof.

In one or more embodiments, the polypropylene resin and olefin-based resins of the present invention may be selected from virgin resins, recycled resins and combinations thereof.

In one or more embodiments, the polypropylene-based composition may comprise combination of recycled resins, biobased resins and optionally petroleum based resins such that the resulting composition achieves low or neutral carbon emission (or even a carbon uptake).

The recycled resin may comprise one or more selected from a post-consumer resin (PCR) and a post-industrial resin (PIR), including regrind, scraps and defective articles. PCR refers to resins that are recycled after consumer use, whereas PIR refers to resins that are recycled from industrial materials and/or processes (for example, cuttings of materials used in making other articles). In one or more embodiments of the present disclosure, the recycled resin used may be a PCR that comprises one or more polyolefins. In one or more embodiments, the recycled resin is a recycled material according to ISO 14021. The recycled resin of one or more embodiments may include resins having been used in rigid applications (such as from blow molded articles, including 3D-shaped articles) as well as in flexible applications (such as from films). The recycled resin of one or more embodiments may be of any color, including, but not limited to, black, white, or grey, depending on the color used in the ultimate article. The form of the recycled resin is not particularly limited, and may be one or more of pellets, flakes, and agglomerated films.

In one or more embodiments, the polypropylene-based composition may have a viscosity of 200 to 130,000 Pa·s at 180° C. and 0.1 rad/s, measured according to ASTM: D-4440-15 (Dynamic Mechanical Properties Melt Rheology), prior to the processing method of the present invention. In one or more embodiments, polypropylene-based composition may have a viscosity having a lower limit of any of 200, 300, 500, or 1000 Pa·s at 0.1 rad/s to an upper limit of any of 15,000, 20,000, 50,000, 100,000, or 130,000 Pa·s at 0.1 rad/s.

In one or more embodiments, the polypropylene-based composition may have a melt flow rate varying from 0.1 to 35 g/10 min, as measure according to ASTM D1238 (2.16 Kg at 230° C.), prior to the processing method of the present invention.

Processing Method Description

The method for producing a low viscosity polypropylene-based according to the present disclosure comprises the following steps:

• • melting a polypropylene-based composition;
  • decreasing a viscosity of the polypropylene-based composition; and
  • optionally, repeating the melting and the viscosity decreasing steps to form a low melt viscosity polypropylene-based composition;
    wherein the melting and viscosity decreasing steps are performed in the presence of at least one free radical generator and at least one pro-degradant stearate.

In one or more embodiments, the melting and viscosity decreasing steps are performed at temperature that is equal to or less than about 350° C., preferably around 200° C. to 250° C. This temperature may be the temperature set up on the equipment (e.g. extruder).

In one or more embodiments, the melting and viscosity decreasing steps are performed in residence time less than around 2 min, preferably ranges of less than 90 s.

In one or more embodiments, the method for producing a low viscosity polypropylene-based is performed in a continuous process, such as in an extrusion. In some embodiments, the method involves melting a polypropylene-based composition in an extruder, decreasing the viscosity of the polypropylene-based composition, and extruding the melt through a die. In accordance with one or more embodiments, the melting and viscosity decreasing may be repeated.

In case an extruder is used, it may be selected from a single-, twin-, or multi-screw extruder, in particular embodiments, a twin-screw extruder is used.

The processes of one or more embodiments of the present disclosure result in the viscosity of the polypropylene-based composition decreasing in the extruder. In one or more embodiments, the process may involve multiple extrusions in series, each of which sequentially reduces the viscosity of the recycled resin. The processes of one or more embodiments may include one extrusion or more, or two extrusions or more. In embodiments where multiple extrusions are performed, each extrusion may be performed under conditions that are the same as, or different from one another. In one or more embodiments, the melting and viscosity decreasing steps are performed in a continuous loop system.

In one or more embodiments, the at least one free radical generator may comprise a peroxide. The peroxide of some embodiments may be one or more of the group consisting of 3-hydroxy-1,1-dimethylbutyl peroxyneodecanoate, a-cumyl peroxyneodecanoate, 2-hydroxy-1,1-dimethylbutyl peroxyneoheptanoate a-cumyl peroxyneoheptanoate, t-amyl peroxyneodecanoate, t-butyl peroxyneodecanoate, di(2-ethylhexyl) peroxydicarbonate, di(n-propyl) peroxydicarbonate, di(sec-butyl) peroxydicarbonate, t-butyl peroxyneoheptanoate, t-amyl peroxypivalate, t-butyl peroxypivalate, diisononanoyl peroxide, didodecanoyl peroxide, 3-hydroxy-1,1-dimethylbutylperoxy-2-ethylhexanoate, didecanoyl peroxide, 2,2′-azobis(isobutyronitrile), di(3-carboxypropionyl) peroxide, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, dibenzoyl peroxide, t-amylperoxy 2-ethylhexanoate, t-butylperoxy 2-ethylhexanoate, t-butyl peroxyisobutyrate, t-butyl peroxy-(cis-3-carboxy)propenoate, 1,1-di(t-amylperoxy)cyclohexane, 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(t-butylperoxy) cyclohexane, OO-t-amyl O-(2-ethylhexyl) monoperoxycarbonate, OO-t-butyl O-isopropyl monoperoxycarbonate, OO-t-butyl O-(2-ethylhexyl) monoperoxycarbonate, polyether tetrakis(t-butylperoxycarbonate), 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-amyl peroxyacetate, t-amyl peroxybenzoate, t-butyl peroxyisononanoate, t-butyl peroxyacetate, t-butyl peroxybenzoate, di-t-butyl diperoxyphthalate, 2,2-di(t-butylperoxy)butane, 2,2-di(t-amylperoxy)propane, n-butyl 4,4-di(t-butylperoxy)valerate, ethyl 3,3-di(t-amylperoxy)butyrate, ethyl 3,3-di(t-butylperoxy)butyrate, dicumyl peroxide, a,a′-bis(t-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5-di(t-butylperoxy) hexane, di(t-amyl) peroxide, t-butyl a-cumyl peroxide, di(t-butyl) peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne, dicetil peroxi-dicarbonato, 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane, tert-butylperoxy 2-ethylhexyl carbonate, tert-butyl-peroxide n-butyl fumarate(benzoate), dimyristoyl peroxydiicarbonate, 3,3,5,7,7-pentamethyl-1,2,4-trioxepane, tert-butyl hydroperoxide, bis(4-t-butylcyclohexyl) peroxydicarbonate, and 1,2,4,5,7,8-hexoxonane, 3,6,9-trimethyl-3,6,9-tris(ethyl and propyl derivatives).

In one or more embodiments, the at least one free radical generator may be a low-reactivity organic peroxide. The expression “low-reactivity organic peroxide” is understood to be peroxides that have a 1 hour half-life temperature greater than or equal to 165° C. Some examples include 3,3,5,7,7-Pentamethyl-1,2,4-trioxepane, terc-butyl hydroperoxide, cumyl hidroperoxide, t-amyl hidroperoxide, or mixtures thereof.

In one or more embodiments, the at least one free radical generator may be added to the polypropylene-based composition in an amount ranging from a lower limit selected from one of around 0.01, 0.1, or 0.2 wt. % to an upper limit selected from one of around 1, 1.25, or 1.5 wt. %, relative to the weight of the polypropylene-based composition, where any lower limit can be used with any upper limit.

In one or more embodiments, the polypropylene-based composition is also in the presence of a further at least one free radical generator comprising a nitroxide compound, such as 2,2,5,5-tetramethyl-1-pyrrolidinyloxy, 3-carboxy-2,2,5,5-tetramethyl-pyrrolidinyloxy, 2,2,6,6-tetramethyl-1-piperidinyloxy, 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy, 4-methoxy-2,2,6,6-tetramethyl-1-piperidinyloxy, 4-oxo-2,2,6,6-tetramethyl-1-piperidinyloxy, bis-(1-oxyl-2,2,6,6-tetramethylpiperidine-4-yl)sebacate, 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl)monophosphonate, N-tert-butyl-1-diethylphosphono-2,2-dimethyl propyl nitroxide, N-tert-butyl-1-dibenzylphosphono-2,2-dimethylpropyl nitroxide, N-tert-butyl-1-di(2,2,2-trifluoroethyl)phosphono-2,2dimethylpropyl nitroxide, N-tert-butyl-(1-diethylphosphono)-2-methyl-propyl nitroxide, N-(1-methylethyl)-1-cyclohexyl-1-(diethylphosphono) nitroxide, N-(1-phenylbenzyl)-(1-diethylphosphono)-1-methyl ethylnitroxide, N-phenyl-1-diethylphosphono-2,2-dimethyl propyl nitroxide, N-phenyl-1-diethylphosphono-1-methyl ethyl nitroxide, N-(1-phenyl 2-methyl propyl)-1-diethylphosphono-1-methyl ethyl nitroxide, N-tert-butyl-1-phenyl-2-methyl propyl nitroxide, and N-tert-butyl-1-(2-naphthyl)-2-methyl propyl nitroxide, or a mixture thereof. In such embodiments, the further at least one free radical generator comprising a nitroxide compound is added to the polypropylene-based composition in order to accelerate the beta scission reaction catalyzed by the peroxide compound.

The further at least one free radical generator may be added to the polypropylene-based composition in an amount ranging from a lower limit selected from one of 0.01, 0.1, or 0.2 wt. % to an upper limit selected from one of 1, 1.25, or 1.5 wt. %, relative to the weight of the polypropylene-based composition, where any lower limit can be used with any upper limit.

In one or more embodiments, the at least one pro-degradant stearate is selected from a group consisting of zinc stearate, tin stearate, iron (II) stearate, iron (III) stearate, cobalt stearate, manganese stearate, and any combinations thereof. Unexpectedly, in the present disclosure it was found that the beneficial effect of adding the at least one pro-degradant stearate is to decrease the amount of the free radical generator, e.g., a peroxide compound, needed in the processing method disclosed herein. Consequently, there is a lower VOC emission in the method of the present disclosure.

In one or more embodiments, the at least one pro-degradant stearate may be added to the polypropylene-based composition in an amount ranging from a lower limit selected from one of around 0.05 wt % or 0.1 wt. % to an upper limit selected from one of around 2.0 or 2.5 wt. % relative to the weight of the polypropylene-based composition, where any lower limit can be used with any upper limit.

Further possible additives include those conventionally known to a person of ordinary skill in the art. Any of the aforementioned additives may be added at any stage of a multiple extrusion process, in a sequential or simultaneous manner, independently from any order.

In case an extruder is used, the resins, free radical generators, pro-degradant stearates and other components, may be added to an extruder, either simultaneously or sequentially, into the main or secondary feeder in the form of powder, granules, or flakes. In one or more embodiments, methods may involve a single extrusion or multiple extrusions.

In one embodiment, the method of the present disclosure comprises two extrusion passes wherein the at least one free radical generator is added on the first pass and the at least one pro-degradant stearate is added on the second pass.

As mentioned above, the polypropylene-based composition may have a viscosity of about 200 to 130,000 Pa·s at 180° C. and 0.1 rad/s prior to the method of the present invention. After the one or more melting and viscosity decreasing steps of the present disclosure, the viscosity may be reduced to achieve a viscosity of less than about 300 Pa·s at 180° C. and 0.1 rad/s. Depending on the starting viscosity, desired final viscosity, and therefore extent of viscosity decreasing to achieve such final viscosity, the melting and viscosity decreasing steps may occur multiple times.

In addition, after the one or more melting and viscosity decreasing steps of the present disclosure, the melt flow rate of the low viscosity polypropylene-based obtained by the processing method is greater than about 75 g/10 min, as measure according to ASTM D1238 (2.16 Kg at 230° C.). In one or more embodiments, the melt flow rate of the achieved low viscosity polypropylene-based composition is greater than 150 g/10 min, preferably greater than 300 g/10 min, more preferably 600 g/10 min, most preferably greater than 1000 g/10 min, and most preferred greater than 1,500 g/10 min.

The process may further comprise a cleaning step. This step may be particularly useful when the polypropylene-based composition comprises recycled resins. Such a cleaning step may involve one or more of the group consisting of degassing by vacuum, the injection of supercritical CO₂, and steam stripping. This cleaning step may further include a filtering step. The filtration may remove larger components (e.g., larger than 30 microns, for example) from the molten polymer. The conditions of the filtration depend upon the identity of the components present in the melted mixture. Such a filtration process may be performed in a manner consistent with those taught by U.S. Pat. Pub. 2019/0366591, which is incorporated herein by reference.

The cleaning may be also used to remove volatile (lower molecular weight) components, such as residual peroxide and byproducts generated by the chain scission reaction. Said steps may occur during the melting and decreasing viscosity steps or in a subsequent or preliminary step. In one or more embodiments, the method includes removing at least one of low molecular weight contaminants, byproducts, volatiles, or water, from a resin by exposing it to vacuum.

In some embodiments, the resulting product is pelletized.

Applications and Uses

One or more embodiments of the present disclosure relate to low viscosity polypropylene-based compositions that are suitable for meltblowing. These compositions may be produced by the aforementioned processes. The meltblowing compositions may be meltblown, using very high velocity air flow to draw a polymer melt extruding from a die, to give meltblown polymer fibers. One or more embodiments of the present disclosure are directed to a meltblown article that comprises a plurality of fibers formed from the low viscosity polypropylene-based compositions.

In one or more embodiments, the low viscosity polypropylene-based compositions that are suitable for meltblowing may have a very low content of residual peroxides. In some embodiments, the low viscosity polymer composition may have a peroxide reside content of less than 1500 ppm.

In one or more embodiments, the low viscosity polypropylene-based compositions that are suitable for meltblowing may have a viscosity of lower than 300 Pa·s. In one embodiment, the viscosity is in a range from 10 to 300 Pa·s, such as 20 to 300 Pa·s. For example, the viscosity may have a lower limit of any of 10, 20, or 50 Pa·s, and an upper limit of any of 50, 100, 150, 200, or 300 Pa·s.

In one or more embodiments, the low viscosity polypropylene-based compositions suitable for meltblowing processing have a melt flow rate, according to ASTM D1238 (230° C., 2.16 Kg), greater than 600 g/10 min, preferably greater than 1000 g/10 min, and most preferred greater than 1,500 g/10 min.

In accordance with the present disclosure, the following procedure may be applied to measure the viscosities of both the starting material and final product. The viscosity may be measured at a temperature of 180° C. using a parallel plates geometry with 25 mm of diameter and an operational gap of 1 mm, with a defined stressor strain in the linear viscoelastic regime. A 100 Pa stress or 1% strain may be applied to oscillatory sweep from 0.1 to 625 rad/s. With this procedure, it may be possible to use a single methodology to the measure both the start polypropylene composition's viscosity as well as the low viscosity polypropylene-based compositions obtained.

In one or more embodiments, a melt blown fabric may be formed from a plurality of fibers formed from the low viscosity polypropylene-based compositions described herein. Such melt blown fabric may be nonwoven.

Further, it is also envisioned that the low viscosity polypropylene-based compositions of the present invention may also find applicability as an additive in other polymer compositions, such as when a low viscosity polymer is desired. It is envisioned for example, that the low viscosity polypropylene-based compositions described herein may be used as a viscosity modifier or as a binder or carrier in a high filled compound.

Low viscosity polypropylene-based compositions according to the present disclosure may be used as a viscosity modifier in polymer compositions to be applicable to different molding processes, including processes selected from extrusion molding, coextrusion molding, extrusion coating, injection molding, injection blow molding, inject stretch blow molding, thermoforming, cast film extrusion, blown film extrusion, foaming, extrusion blow-molding, injection stretched blow-molding, rotomolding, pultrusion, calendering, additive manufacturing, lamination, and the like, to produce manufactured articles.

Low viscosity polypropylene-based compositions according to the present disclosure may also serve as a raw material for chemical recycling processes, such as thermolysis: pyrolysis (thermal and catalytic depolymerization), hydrogenation, hydrocraking, oxycracking, gasification, hydrothermal liquefaction and other suitable known processes. In this case, it is preferred that the low viscosity polypropylene-based compositions are substantially obtained from recycled resins.

Low viscosity polypropylene-based compositions according to the present disclosure may also be used as a raw material for injection molding processes and additive manufacturing (e.g. fused filament).

EXAMPLES

Example 1

To illustrate the inventive process, polypropylene pellets were extruded in a continuous process with an organic peroxide added as a first chain scission agent. In some examples, iron stearate (FeSt) was also added, as a second chain scission agent.

The PP is a 3-melt flow homopolymer, sold commercially by Braskem with trade name FF030F2. The organic peroxide is 2,5-dimethyl di-tertbutylperoxyhexane, sold commercially by Nouryon with trade name Trigonox 101. The Iron (iii) stearate (CAS: 555-36-2) was purchased from Aldrich.

Extrusion was conducted in a 21 mm Theysson twin screw extruder with L/D=36. Polypropylene pellets were fed into the feed throat of the extruder using a first feeder operating at a constant rate of 6 kg/hour. Iron stearate was added to the extruder using a second feeder to meter an iron stearate master batch concentrate. The iron stearate master batch was produced by extruding 2 wt. percent iron stearate powder with PP FF030F3 using the extrusion conditions shown in Table 1 (FeSt MB.)

Peroxide (“T101”) was injected directly into the barrel during extrusion using a gear pump. The barrel segment upstream of the die was open to atmosphere to allow venting of volatiles.

Barrel temperatures are reported in Table 1. Nitrogen gas was fed into the feed throat of the extruder. Screw speed was set to 250 rpm. Melt pressure and melt temperature were measured near the die. The extrudate mixtures were cooled in a water bath and collected as pellets.

	TABLE 1
	Feed
	concentration,	Barrel temperatures, C.		Melt	PP feed
	wt %		Zone6	Screw	Torque,	Melt	temp,	rate,
	T101	FeSt	Zone1	Zone2	Zone3	Zone4	Zone5	(die)	speed	%	pressure	C.	kg/h
CE1	0.1	0	189	201	209	249	250	230	253	56	110	243	6
CE2	0.25	0	190	198	209	247	250	230	252	50	100	242	6
Ex1	0.1	0.1	189	198	209	243	259	239	252	69	119	243	6
Ex2	0.2	0.1	189	199	209	244	249	230	251	59	110	240	6

Melt flow index and viscosity results are reported in Table 2 for the examples described above and for a comparative control sample, which was not extruded. Melt flow was measured using ASTM procedure D1238. Viscosity was measured by a frequency sweep analysis in a shear rheometer operating at 180° C. Frequency sweep analysis (0.0628-628 rad/s), oscillatory regime, was carried out in a rotacional rheometer DHR-3—TA Instruments, using a 25 mm Parallel plate geometry, gap of 1 mm, stress of 10 Pa (determined in a previous test to be in the linear viscoelasticity regime) and a soaking time of 60 s, the results of which are shown in FIG. 1.

One can note that, when using stearate together with the peroxide compound, there is a significant decrease in the viscosity of the polymer composition.

	TABLE 2
	Feed Concentration, wt %
	T101	FeSt	Pellet MFR	Viscosity at 0.1
CE1	0.1	0	50	430
CE2	0.25	0	171	110
Ex1	0.1	0.1	84	270
Ex2	0.2	0.1	191	160

Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. § 112(f) for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.

Claims

1. A method for producing a low viscosity polypropylene-based composition, comprising:

melting a polypropylene-based composition;

decreasing a viscosity of the polypropylene-based composition; and

optionally, repeating the melting and the viscosity decreasing steps to form a low melt viscosity polypropylene-based composition;

wherein the melting and viscosity decreasing steps are performed in the presence of at least one free radical generator and at least one pro-degradant stearate.

2. The method of claim 1, wherein the melting and viscosity decreasing steps are performed at temperature that is equal to or less than 350° C.

3. The method of claim 1, wherein the melting and viscosity decreasing steps are performed at residence time of less than 2 min.

4. The method of claim 1, wherein the polypropylene-based composition is a post-consumer resin, a post-industrial resin, petroleum based virgin polyolefin, biobased polyolefin or mixtures thereof.

5. The method of claim 1, wherein the polypropylene-based composition comprises up to about 49 wt. % of an olefin-based resin.

6. The method of claim 1, wherein the polypropylene-based composition comprises up to about 49 wt. % of a polymer selected from polystyrene, ethylene-vinyl acetate polymer, other olefin-based polymers and combinations.

7. The method of claim 1, wherein the at least one free radical is added to the polypropylene-based composition in an amount ranging from about 0.01 to about 1.5 wt. %.

8. The method of claim 1, wherein the at least one free radical generator is a peroxide compound.

9. The method of claim 8, wherein the peroxide compound is one or more of the group consisting of 3-hydroxy-1,1-dimethylbutyl peroxyneodecanoate, a-cumyl peroxyneodecanoate, 2-hydroxy-1,1-dimethylbutyl peroxyneoheptanoate a-cumyl peroxyneoheptanoate, t-amyl peroxyneodecanoate, t-butyl peroxyneodecanoate, di(2-ethylhexyl) peroxydicarbonate, di(n-propyl) peroxydicarbonate, di(sec-butyl) peroxydicarbonate, t-butyl peroxyneoheptanoate, t-amyl peroxypivalate, t-butyl peroxypivalate, diisononanoyl peroxide, didodecanoyl peroxide, 3-hydroxy-1,1-dimethylbutylperoxy-2-ethylhexanoate, didecanoyl peroxide, 2,2′-azobis(isobutyronitrile), di(3-carboxypropionyl) peroxide, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, dibenzoyl peroxide, t-amylperoxy 2-ethylhexanoate, t-butylperoxy 2-ethylhexanoate, t-butyl peroxyisobutyrate, t-butyl peroxy-(cis-3-carboxy)propenoate, 1,1-di(t-amylperoxy)cyclohexane, 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(t-butylperoxy) cyclohexane, OO-t-amyl O-(2-ethylhexyl) monoperoxycarbonate, OO-t-butyl O-isopropyl monoperoxycarbonate, OO-t-butyl O-(2-ethylhexyl) monoperoxycarbonate, polyether tetrakis(t-butylperoxycarbonate), 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-amyl peroxyacetate, t-amyl peroxybenzoate, t-butyl peroxyisononanoate, t-butyl peroxyacetate, t-butyl peroxybenzoate, di-t-butyl diperoxyphthalate, 2,2-di(t-butylperoxy)butane, 2,2-di(t-amylperoxy)propane, n-butyl 4,4-di(t-butylperoxy)valerate, ethyl 3,3-di(t-amylperoxy)butyrate, ethyl 3,3-di(t-butylperoxy)butyrate, dicumyl peroxide, a,a′-bis(t-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5-di(t-butylperoxy) hexane, di(t-amyl) peroxide, t-butyl a-cumyl peroxide, di(t-butyl) peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne, dicetil peroxi-dicarbonato, 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane, tert-butylperoxy 2-ethylhexyl carbonate, tert-butyl-peroxide n-butyl fumarate(benzoate), dimyristoyl peroxydiicarbonate, 3,3,5,7,7-pentamethyl-1,2,4-trioxepane, tert-butyl hydroperoxide, bis(4-t-butylcyclohexyl) peroxydicarbonate, and 1,2,4,5,7,8-hexoxonane, 3,6,9-trimethyl-3,6,9-tris(ethyl and propyl derivatives).

10. The method of claim 8, wherein the peroxide compound is selected from a group consisting of 3,3,5,7,7-Pentamethyl-1,2,4-trioxepane, terc-butyl hydroperoxide, cumyl hidroperoxide, t-amyl hidroperoxide, or mixtures thereof.

11. The method of claim 8, wherein the polypropylene-based composition is in the presence of a further at least one free radical generator comprising a nitroxide compound selected from a group consisting of 2,2,5,5-tetramethyl-1-pyrrolidinyloxy, 3-carboxy-2,2,5,5-tetramethyl-pyrrolidinyloxy, 2,2,6,6-tetramethyl-1-piperidinyloxy, 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy, 4-methoxy-2,2,6,6-tetramethyl-1-piperidinyloxy, 4-oxo-2,2,6,6-tetramethyl-1-piperidinyloxy, bis-(1-oxyl-2,2,6,6-tetramethylpiperidine-4-yl)sebacate, 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl)monophosphonate, N-tert-butyl-1-diethylphosphono-2,2-dimethyl propyl nitroxide, N-tert-butyl-1-dibenzylphosphono-2,2-dimethylpropyl nitroxide, N-tert-butyl-1-di(2,2,2-trifluoroethyl)phosphono-2,2dimethylpropyl nitroxide, N-tert-butyl-(1-diethylphosphono)-2-methyl-propyl nitroxide, N-(1-methylethyl)-1-cyclohexyl-1-(diethylphosphono) nitroxide, N-(1-phenylbenzyl)-(1-diethylphosphono)-1-methyl ethylnitroxide, N-phenyl-1-diethylphosphono-2,2-dimethyl propyl nitroxide, N-phenyl-1-diethylphosphono-1-methyl ethyl nitroxide, N-(1-phenyl 2-methyl propyl)-1-diethylphosphono-1-methyl ethyl nitroxide, N-tert-butyl-1-phenyl-2-methyl propyl nitroxide, and N-tert-butyl-1-(2-naphthyl)-2-methyl propyl nitroxide.

12. The method of claim 1, wherein the at least one pro-degradant stearate is selected from zinc stearate, tin stearate, iron (II) stearate, iron (III) stearate, cobalt stearate, manganese stearate, and any combinations thereof.

13. The method of claim 1, wherein the at least one pro-degradant stearate is added to the polypropylene-based composition in an amount ranging from about 0.05 wt. % to 2.5 wt. %.

14. The method of claim 1, wherein the melting and viscosity decreasing steps are performed in a residence time of less than 90 s.

15. The method of claim 1, wherein the melting and viscosity reducing steps are performed in a continuous process.

16. The method of claim 1, wherein the melting and viscosity reducing steps occur in an extruder.

17. The method of claim 1, wherein the extruder is twin screw extruder.

18. The method of claim 1, wherein the melting and reducing steps are repeated at least two times.

19. The method of claim 1, wherein the repeated melting and reducing are performed in a continuous loop system.

20. The method of claim 1, wherein the method further comprises a cleaning step selected from one or more of the group consisting of degassing by vacuum, injecting supercritical CO2, steam stripping and a filtering step.

21. A low viscosity polypropylene composition prepared according to the method of claim 1.

22. A low viscosity polypropylene based-composition prepared according to claim 21 wherein the polypropylene has a viscosity of less than 300 Pa·s at 180° C. and 0.1 rad/s.

23. A melt blown fabric comprising a plurality of fibers formed from the low viscosity polypropylene composition of claim 21.

24. The melt blown fabric of claim 23, wherein the melt blown fabric is nonwoven.

25. A method for producing a melt-blown article, comprising:

melt-blowing the low viscosity polypropylene composition of claim 21.