Process for lowering the melt flow rate of a recycled polymer composition

FIELD OF THE INVENTION

[0001] The present disclosure relates to a process for lowering the melt flow rate of a polymer composition containing at least 50 wt% of a recycled polypropylene composition and at least 5 wt% of polar polymers such as EVOH.

BACKGROUND OF THE INVENTION

[0002] It is well known in the art that in order to recycle a propylene based composition the latter has to be melted one or more time. The melting usually worse some of the properties of the polymer and above all the melt flow rate (MFR) becomes higher. In fact the recycled polypropylene usually on the market has an MFR, determined according to the method ISO 1133 (230° C, 2.16 kg) of about 10 g/10 min that is a value usually used for producing injection molded articles. It would be desirable to have a process able to lower this MFR so that the recycled composition can be used for applications different from injection molding such as for producing films such as cast, blow and BOPP films. The applicant found that in a recycled polymer composition comprising at least 50 wt% of a recycled polypropylene composition and at least 5 wt% of polar polymers it is possible to lower the MFR by adding a third component and extrude the composition.

SUMMARY OF THE INVENTION

[0003] Thus an object of the present disclosure is a process for lowering the melt flow rate of a recycled polymer composition comprising at least 50 wt% of a recycled polypropylene composition, and at least 5 wt% of a polar polymer, said process comprising: a) providing recycled polymer composition comprising at least 50 wt% of a recycled polypropylene composition, and at least 5 wt% of a polar polymer; b) adding to the composition from 2 wt% to 10 wt% based on the weight of the total composition of a polyepoxides resin; c) melting the composition comprising component a) and b) and d) recover the final polymer; wherein the polar polymer is selected from the group consisting of polyamide, polycarbonate, poly(, ethyl methacrylate), Acrylonitrile, butadiene, styrene terpolymer and ethylene vinyl alcohol polymer (EVOH).

DETAILED DESCRIPTION OF THE IN VENTION

[0004] Preferably the recycled polymer composition comprises at least 60 wt% of recycled polypropylene composition, based on the total weight of the recycled polymer composition, preferred range is from 60wt% to 76 wt%.

[0005] Preferably the recycled polymer composition comprises at least 7 wt% preferably at least 10 wt%, more preferably at least 15 wt% of the polar polymer. Preferred range is from 5 wt% to 25 wt%. A polar polymer is defined as a polymer containing polar groups such as alcohol (-OH), ether (-O-), carboxylic acid (-COOH), amine (-NH2), nitrile (-CN), thiol (-SH) groups. Examples of polar polymer can be polyamide, polycarbonate, poly(, ethyl methacrylate), Acrylonitrile, butadiene, styrene terpolymer, ethylene vinyl alcohol polymer (EVOH). Preferably the polar polymer is EVOH.

[0006] The polyeproxydes resin are preferably added in a range from 4.0 wt% to 9.0wt%; more preferably from 6.0 wt% to 8.5 wt%. Preferably the polyeproxydes resin has a relatively low epoxy functionality. The epoxy functionality may be quantified as “epoxy equivalent weight.” The epoxy equivalent weight reflects the amount of resin that contains one molecule of an epoxy group, and it may be calculated by dividing the number average molecular weight of the modifier by the number of epoxy groups in the molecule. The poly epoxide of the present disclosure typically has a number average molecular weight from 7500 to 250000 grams per mole, preferably from 15000 to 150000 grams per mole, and more preferably from 20000 to 100000 grams per mole, with a poly dispersity index typically ranging from 2.5 to 7. The poly epoxide may contain less than 50, in some embodiments from 5 to 45, and in some embodiments, from 15 to 40 epoxy groups. In turn, the epoxy equivalent weight may be from 100 to 15000 grams per mole, preferably from 200 to 10000 grams per mole, and more preferably from about 500 to about 7000 grams per mole. [0007] The poly epoxide may be a linear or branched, homopolymer or copolymer (e.g., random, graft, block, etc.) containing terminal epoxy groups, skeletal oxirane units, and/or pendent epoxy groups. The monomers employed to form such polyepoxides may vary. In one particular embodiment, for example, the polyepoxide contains at least one epoxy-functional (meth)acrylic monomeric component. As used herein, the term “(meth)acrylic” includes acrylic and methacrylic monomers, as well as salts or esters thereof, such as acrylate and methacrylate monomers. For example, suitable epoxy-functional (meth)acrylic monomers may include, but are not limited to, those containing 1,2-epoxy groups, such as glycidyl acrylate and glycidyl methacrylate. Other suitable epoxy-functional monomers include allyl glycidyl ether, glycidyl ethacrylate, and glycidyl itoconate.

[0008] Preferably the polyepoxide is a terpolymer formed from an epoxy-functional (meth)acrylic monomeric component, alpha-olefin monomeric component, and non-epoxy functional (meth)acrylic monomeric component. For example, the poly epoxide may be poly(ethylene-co-methylacrylate-co-glycidyl methacrylate).

[0009] Suitable poly epoxide is commercially available from Arkema under the name

LOTADER® AX8950 or AX8900. LOTADER® AX8950, for instance, has a melt flow rate of 70 to 100 g/10 min and has a glycidyl methacrylate monomer content of 7 wt. % to 11 wt. %, a methyl acrylate monomer content of 13 wt. % to 17 wt. %, and an ethylene monomer content of 72 wt. % to 80 wt. %. Another suitable polyepoxide is commercially available from DuPont under the name ELVALOY® PTW, which is a terpolymer of ethylene, butyl acrylate, and glycidyl methacrylate and has a melt flow rate of 12 g/10 min.

[0010] .Preferably the Melt Flow Rate of the recycled polypropylene composition, starting material of the process, determined according to the method ISO 1133 (230° C, 2.16 kg), ranges from 10 g/10 min to 150 g/10 min; preferably from 20 g/10 min to 100 g/10 min, more preferably from 25 g/10 min to 80 g/10 min.

[0011] Preferably the recycled polypropylene composition is a Post-Industrial Resin (PIR), the waste generated from the manufacturing process that is reclaimed or used again in the same material or Post-Consumer Resin (PCR), defined as a resin used by the consumer for its intended purpose, that has reached its end of use, and then tossed into a recycling bin is excluded.

[0012] The recycled polypropylene composition contains preferably at least 50 wt%; more preferably at least 60 wt% ; even more preferably at least 65 wt% of derived units of propylene. The remaining comonomers can be ethylene; 1 -butene; 1 -hexene or 1 -octene derived units; ethylene being preferred. Examples of propylene based polymer can be propylene homopolymer, propylene, ethylene heterophasic polymer, propylene ethylene 1 -butene, propylene ethylene 1 -hexene terpolymers and mixtures thereof. The recycled polypropylene composition can be contaminated with other polymers such as polyamide, polycarbonate, poly(, ethyl methacrylate), Acrylonitrile, butadiene, styrene termpolymer, ethylene vynyl alcohol polymer (EVOH).

[0013] The final polymer obtainable with the process of the present disclosure is a recycled polypropylene composition having an high MFRDetermined according to the method ISO 1133 (230° C, 2.16 kg). Preferably the MFR Determined according to the method ISO 1133 (230° C, 2.16 kg) of the recycled polypropylene composition obtainable with the process of the present disclosure depends from the starting MFRinit. The MFR that can be obtained ranges from MFRinit /1.2 to MFRinit /5.0; preferably ranges from MFRinit/1.9 to MFRinit/4.0. More preferably the MFR ranges from 1.3 g/10 min to 8.0 g/lOmin; even more preferably ranges from 1.5 g/10 min to 5.8 g/10min;.

[0014] The final polymer obtainable with the process of the present disclosure that is a recycled polypropylene composition can be used for examples for obtaining films, in particular cast, BOPP and Blow films.

[0015] The following examples are given to illustrate the present invention without limiting purpose.

EXAMPLE

Characterization methods

Melting temperature and crystallization temperature: Determined by differential scanning calorimetry (DSC)

[0016] . weighting 6 ±1 mg, is heated to 220 ±1° C at a rate of 20 °C/min and kept at 220 ±1°

C for 2 minutes in nitrogen stream and it is thereafter cooled at a rate of 20° C/min to 40 ±2° C, thereby kept at this temperature for 2 min to crystallize the sample. Then, the sample is again fused at a temperature rise rate of 20° C/min up to 220° C ±1. The melting scan is recorded, a thermogram is obtained, and, from this, melting temperatures and crystallization temperatures are read.

Melt Flow Rate: Determined according to the method ISO 1133 (230° C, 2.16 kg).

Xylene-soluble fraction (XS) at 25°C

[0017] Xylene Solubles at 25°C have been determined according to ISO 16152: 2005; with solution volume of 250 ml, precipitation at 25°C for 20 minutes, 10 of which with the solution in agitation (magnetic stirrer), and drying at 70°C.

Intrinsic Viscosity (LV.) [0018] The sample is dissolved by tetrahydronaphthalene at 135 °C and then it is poured into the capillary viscometer.

[0019] The viscometer tube (Ubbelohde type) is surrounded by a cylindrical glass jacket; this setup allows temperature control with a circulating thermostated liquid.

[0020] The downward passage of the meniscus is timed by a photoelectric device. The passage of the meniscus in front of the upper lamp starts the counter which has a quartz crystal oscillator. The meniscus stops the counter as it passes the lower lamp and the efflux time is registered: this is converted into a value of intrinsic viscosity through Haze (on 1 mm plaque)

[0021] According to the method used, 5x5 cm specimens are cut molded plaques of 1 mm thick and the haze value is measured using a Gardner photometric unit connected to a Hazemeter type UX-10 or an equivalent instrument having G.E. 1209 light source with filter "C". Reference samples of known haze are used for calibrating the instrument. The plaques to be tested are produced according to the following method.

[0022] 75x75x1 mm plaques are molded with a GBF Plastiniector G235190 Injection

Molding Machine, 90 tons under the following processing conditions:

Screw rotation speed: 120 rpm

Back pressure: 10 bar

Melt temperature: 260°C

Injection time: 5 sec

Switch to hold pressure: 50 bar

First stage hold pressure: 30 bar

Second stage pressure: 20 bar

Hold pressure profile: First stage 5 sec

Second stage 10 sec

Cooling time: 20 sec

Mold water temperature: 40°C

Ethylene content in the copolymers

[0023] ¹³ C NMR spectra were acquired on a Bruker AV-600 spectrometer equipped with cry oprobe, operating at 160.91 MHz in the Fourier transform mode at 120 °C. [0024] The peak of the SPP carbon (nomenclature according to “Monomer Sequence Distribution in Ethylene-Propylene Rubber Measured by ¹³ C NMR. 3. Use of Reaction Probability Mode ” C. J. Carman, R. A. Harrington and C. E. Wilkes, Macromolecules, 1977, 10, 536) was used as an internal reference at 29.9 ppm. The samples were dissolved in 1 , 1 ,2,2-tetrachloroethane- d2 at 120 °C with a 8 % wt/v concentration. Each spectrum was acquired with a 90° pulse, and 15 seconds of delay between pulses and CPD to remove ¹ H- ¹³ C coupling. 512 transients were stored in 32K data points using a spectral window of 9000 Hz.

[0025] The assignments of the spectra, the evaluation of triad distribution and the composition were made according to Kakugo (“Carbon- 13 NMR determination of monomer sequence distribution in ethylene-propylene copolymers prepared with 5-titanium trichloride- diethylaluminum chloride” M. Kakugo, Y. Naito, K. Mizunuma and T. Miyatake, Macromolecules, 1982, 15, 1150) using the following equations:

PPP = 100 Tpp/S PPE = 1OO TP5/S EPE = 100 T55/S

PEP = 100 SPP/S PEE= 100 SP5/S EEE = 100 (0.25 SyS+0.5 S55)/S S = TPP + TP5 + T55 + SPP + SP5 + 0.25 Sy5 + 0.5 S55

[0026] The molar percentage of ethylene content was evaluated using the following equation: [0027] E% mol = 100 * [PEP+PEE+EEE]The weight percentage of ethylene content was evaluated using the following equation:

100 * E% mol * MWE

E% wt. = E% mol * MWE + P% mol * MWP

[0028] where P% mol is the molar percentage of propylene content, while MWE and MWP are the molecular weights of ethylene and propylene, respectively.

[0029] The product of reactivity ratio rlr2 was calculated according to Carman (C.J. Carman,

R.A. Harrington and C.E. Wilkes, Macromolecules, 1977; 10, 536) as: [0030] The tacticity of Propylene sequences was calculated as mm content from the ratio of the PPP mmTpp (28.90-29.65 ppm) and the whole Tpp (29.80-28.37 ppm).

Preparation of the film specimens

[0031] Films with a thickness of 50 micron are prepared by extruding each composition in a a single screw Collin extruder (length/diameter ratio of screw 1 :25) at a film drawing speed of 7 m/min and a melt temperature do 210-250 °C.

Determination of the number of gels per m ²

[0032] The determination of the number of gels per m ² is carried out by visually detecting the number of gels of a sample film projected by a projector on a white wall-chart with a magnificated scale. Film pieces of 130 x 7.5 cm are cut from a cast film at least 30 minutes after extrusion (die temperature in the range from 250° to 290°C, chill rolls temperature 20°C). The cast film is prepared as above described.

[0033] [0099] The counting is made on 5 different pieces of the same film and a final number is given by the expression No=A/S where No is the number of gels per m ² , A is the number of gels counted on 5 film pieces and S is the overall surface in m ² of the 5 films pieces examined. Gels of irregular shape are measured at the point of maximum extension.

[0034] A commercial propylene ethylene random copolymer sold by lyondellbasell as Moplen RP320M has been used to emulate the recycled polymer composition. The random copolymer has the features reported on table 1

Table 1

The random copolymer has been blended with EVOH , LOTADER AX8900. LOTADER AX8900 has a melt flow rate of 70 to 100 g/10 min a glycidyl methacrylate monomer content of 7 wt. % to 11 wt. %, a methyl acrylate monomer content of 13 wt. % to 17 wt. %, and an ethylene monomer content of 72 wt. % to 80 wt. %. The compositions are reported on table 2.

Table 2

The composition of table 2 have been extruded and cast film are produced, the results of the final polymer are reported on table 3

Table 3

From table 3 clearly results that the MFR of the examples of the invention is lower