Method for reducing melt flow rate of recovered polymer composition

Abstract

A process for reducing the melt flow rate of a recovered polymer composition comprising at least 50 wt% of a recovered polypropylene composition and at least 5 wt% of a polar polymer, the process comprising: a) providing a recovered polymer composition; b) b) adding 2 wt% to 10 wt% of a polyepoxide resin, based on the total weight of the composition, to the composition; c) melting the composition comprising components a) and b), and d) recovering the final polymer.

Description

Technical Field

[0001] The present disclosure relates to a method of reducing the melt flow rate of a polymer composition comprising at least 50 wt% of a recycled polypropylene composition and at least 5 wt% of a polar polymer such as EVOH. Background Art

[0002] It is well known in the art that in order to recycle a propylene-based composition, the composition must be melted one or more times. Melting generally deteriorates certain properties of the polymer, especially the melt flow rate (MFR) will increase. In fact, the melt flow rate (MFR) of the common recycled polypropylene on the market is measured according to the ISO 1133 method (230°C, 2.16kg), which is generally about 10g / 10min, and this value is generally used to produce injection molded articles. It is desirable to have a method that can reduce the melt flow rate (MFR) so that the recycled composition can be used for applications other than injection molding, for example, for the production of films such as cast film, blown film and biaxially oriented polypropylene (BOPP) film. The applicant has found that in a recycled polymer composition comprising at least 50wt% of a recycled polypropylene composition and at least 5wt% of a polar polymer, the melt flow rate (MFR) can be reduced by adding a third component and extruding the composition. Summary of the invention

[0003] It is therefore an object of the present disclosure to provide a method for reducing 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, the method comprising:

[0004] a) providing a recycled polymer composition comprising at least 50 wt% of a recycled polypropylene composition and at least 5 wt% of a polar polymer;

[0005] b) adding 2 wt % to 10 wt % of a polyepoxide resin to the composition based on the total weight of the composition;

[0006] c) melting the composition comprising components a) and b), and

[0007] d) recovering the final polymer;

[0008] 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

[0009] Preferably, the recycled polymer composition comprises at least 60 wt% of the recycled polypropylene composition, preferably in the range of 60 to 76 wt%, based on the total weight of the recycled polymer composition.

[0010] Preferably, the recycled polymer composition comprises at least 7 wt%, preferably at least 10 wt%, more preferably at least 15 wt% of a polar polymer. The preferred range is 5 wt% to 25 wt%. Polar polymers are defined as polymers containing polar groups such as alcohol (-OH), ether (-O-), carboxylic acid (-COOH), amine (-NH2), nitrile (-CN), thiol (-SH) groups. Examples of polar polymers include polyamides, polycarbonates, polyethyl methacrylate, acrylonitrile, butadiene, styrene terpolymers, and ethylene-vinyl alcohol copolymers (EVOH). Preferably, the polar polymer is EVOH.

[0011] The amount of polyepoxide resin added is preferably 4.0 wt% to 9.0 wt%; more preferably 6.0 wt% to 8.5 wt%. Preferably, the polyepoxide resin has a lower epoxy functionality. Epoxy functionality can be quantified as "epoxy equivalent mass". Epoxy equivalent mass represents the amount of resin containing one epoxy group, which can be calculated by dividing the number average molecular weight of the modifier by the number of epoxy groups in the molecule. The number average molecular weight of the polyepoxide disclosed herein is generally 7500 to 250000 g / mol, preferably 15000 to 150000 g / mol, more preferably 20000 to 100000 g / mol, and the polydispersity index is generally 2.5 to 7. The polyepoxide may contain less than 50, in some embodiments 5 to 45, and in some embodiments 15 to 40 epoxy groups. Accordingly, the epoxy equivalent mass may be 100 to 15,000 g / mol, preferably 200 to 10,000 g / mol, and more preferably about 500 to about 7,000 g / mol.

[0012] The polyepoxide can be a linear or branched homopolymer or copolymer (e.g., random copolymer, graft copolymer, block copolymer, etc.) containing terminal epoxy groups, backbone ethylene oxide units, and / or pendant epoxy groups. The monomers used to form the polyepoxide can be different. In a specific embodiment, for example, the polyepoxide contains at least one epoxy-functional (meth) acrylic acid monomer component. Herein, the term "(meth) acrylic acid" includes acrylic acid and methacrylic acid monomers, and salts or esters thereof, such as acrylate and methacrylate monomers. For example, suitable epoxy-functional (meth) acrylic acid monomers may include, but are not limited to, monomers containing 1,2-epoxy groups, such as glycidyl acrylate and glycidyl methacrylate. Other suitable epoxy-functional monomers include allyl glycidyl ether, glycidyl acrylate, and glycidyl itaconate.

[0013] Preferably, the polyepoxide is a terpolymer formed by an epoxy-functional (meth)acrylic monomer component, an α-olefin monomer component and a non-epoxy-functional (meth)acrylic monomer component. For example, the polyepoxide may be poly(ethylene-co-methacrylate-co-glycidyl methacrylate).

[0014] Suitable polyepoxides are available from Arkema under the trade name AX8950 or AX8900. For example, AX8950 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%. Another suitable polyepoxide is available under the trade name PTW is available from DuPont and is a terpolymer of ethylene, butyl acrylate, and glycidyl methacrylate and has a melt flow rate of 12 g / 10 min.

[0015] Preferably, the melt flow rate of the recycled polypropylene composition (starting material of the process) measured according to ISO 1133 method (230°C, 2.16kg) is in the range of 10 g / 10min to 150 g / 10min; more preferably, it is in the range of 20 g / 10min to 100 g / 10min, and further preferably, it is in the range of 25 g / 10min to 80 g / 10min.

[0016] Preferably, the recycled polypropylene composition is post-industrial resin (PIR), i.e. waste from the manufacturing process which is recycled or used again for the same material, or post-consumer resin (PCR), which is defined as, but not limited to, resin that has been used by a consumer for its intended purpose, has reached the end of its use and has been discarded into a recycling bin.

[0017] The recycled polypropylene composition preferably contains at least 50 wt% of propylene derived units; more preferably, at least 60 wt%; further preferably, at least 65 wt%. The remaining comonomers may be selected from ethylene, 1-butene, 1-hexene or 1-octene derived units, with ethylene being preferred. Examples of propylene-based polymers may be propylene homopolymers, propylene-ethylene heterophasic polymers, propylene-ethylene-1-butene terpolymers, propylene-ethylene-1-hexene terpolymers and mixtures thereof. The recycled polypropylene composition may be contaminated with other polymers, such as polyamides, polycarbonates, poly(ethyl methacrylate), acrylonitrile, butadiene, styrene terpolymers, ethylene-vinyl alcohol copolymers (EVOH).

[0018] The final polymer obtainable by the process of the present disclosure is a recycled polypropylene composition having a high melt flow rate (MFR), the MFR being determined according to ISO 1133 method (230° C., 2.16 kg). Preferably, the melt flow rate (MFR) of the recycled polypropylene composition obtainable by the process of the present disclosure, measured according to ISO 1133 method (230° C., 2.16 kg), depends on the initial melt flow rate (MFR init ). The range of MFR that can be obtained is MFR init / 1.2 to MFR init / 5.0; preferred MFR init / 1.9 to MFR init More preferably, the melt flow rate (MFR) is 1.3 g / 10 min to 8.0 g / 10 min; further preferably, it is 1.5 g / 10 min to 5.8 g / 10 min.

[0019] The final polymer obtainable by the process of the present disclosure is a recycled polypropylene composition which can be used for the preparation of films, particularly cast films, BOPP and blown films.

[0020] The following examples are used to illustrate the present invention, but are not intended to limit the present invention.

[0021] Example

[0022] Characterization methods

[0023] Melting temperature and crystallization temperature were measured by differential scanning calorimetry (DSC).

[0024] Weigh 6±1 mg of sample, heat to 220±1°C at a rate of 20°C / min, and keep at 220±1°C for 2 min in a nitrogen stream, then cool to 40±2°C at a rate of 20°C / min and keep at the temperature for 2 min to crystallize the sample. Then, melt the sample again to 220°C±1 at a heating rate of 20°C / min. Record the melting scan, obtain the thermogram, and read the melting temperature and crystallization temperature from the thermogram.

[0025] Melt flow rate: measured according to ISO 1133 method (230°C, 2.16 kg).

[0026] Xylene soluble matter at 25℃ (XS)

[0027] The xylene solubles at 25°C have been determined according to ISO 16152:2005 standard; the solution volume is 250 ml, precipitation is carried out at 25°C for 20 min, of which 10 min are carried out under stirring (magnetic stirrer), and drying is carried out at 70°C.

[0028] Intrinsic viscosity (IV)

[0029] The sample was dissolved with tetralin at 135°C and then poured into a capillary viscometer.

[0030] The viscometer tube (Ubbelohde type) is surrounded by a cylindrical glass jacket; the structure allows temperature control by circulating a thermostatic liquid.

[0031] The descent of the meniscus is timed by a photoelectric device. The passage of the meniscus in front of the upper lamp starts a counter with a quartz crystal oscillator. When the counter passes the lower lamp, the meniscus stops the counter and records the outflow time: this outflow time is converted into an intrinsic viscosity value.

[0032] Haze (based on 1mm thickness sample)

[0033] Depending on the method used, 5 x 5 cm samples are cut into 1 mm thick molded plaques and the haze values ​​are measured using a Gardner photometer unit connected to a Hazemeter model UX-10 or an equivalent instrument with a GE1209 light source with filter "C". Reference samples of known haze are used to calibrate the instrument. The plaques to be tested are prepared by the following method.

[0034] The plates with the dimensions of 75 mm × 75 mm × 1 mm were molded using a GBF Plastiniector G235190 injection molding machine at a pressure of 90 tons and according to the following processing conditions:

[0035] Screw speed: 120rpm

[0036] Back pressure: 10bar

[0037] Melting temperature: 260℃

[0038] Injection time: 5s

[0039] Switch to maintain pressure: 50bar

[0040] First stage holding pressure: 30bar

[0041] Second stage pressure: 20bar

[0042] Maintain pressure curve: first stage 5s

[0043] Second stage 10s

[0044] Cooldown: 20s

[0045] Mold water temperature: 40℃

[0046] Ethylene content in copolymer

[0047] The spectral images were acquired on a Bruker AV-600 NMR spectrometer equipped with a cryoprobe. 13 C NMR spectra. The spectrometer was operated in Fourier transform mode at 120 °C and the operating frequency was 160.91 MHz.

[0048] Using Sββ carbon at 29.9 ppm (measured by “Monomer Sequence Distribution in Ethylene-Propylene Rubber 13 C NMR.3. Use of Reaction Probability Mode "Nomenclature of CJ Carman, RA Harrington and CE Wilkes, Macromolecules, 1977, 10, 536) as an internal standard. The sample was dissolved in 1,1,2,2-tetrachloroethane-d2 at a concentration of 8% (weight / volume) at 120°C. Each spectrum was acquired using a 90° pulse, and the delay time between the pulse and cross-polarization decoupling (CPD) was 15 s to eliminate 1 H- 13 C coupling. Using a spectral window of 9000 Hz, 512 transients were stored in 32K data points.

[0049] The assignment of the spectrum, the evaluation of the triad distribution and the composition analysis were performed according to Kakugo ("Carbon-13 NMR determination of monomer sequence distribution in ethylene-propylene copolymers prepared with δ-titanium trichloride-diethyl-aluminum chloride" M. Kakugo, Y. Naito, K. Mizunuma and T. Miyatake, Macromolecules, 1982, 15, 1150) using the following equation:

[0050] PPP=100Tββ / S PPE=100Tβδ / S EPE=100Tδδ / S

[0051] PEP=100Sββ / S PEE=100Sβδ / S EEE=100(0.25Sγδ+0.5Sδδ) / S

[0052] S=Tββ+Tβδ+Tδδ+Sββ+Sβδ+0.25Sγδ+0.5Sδδ

[0053] The mole percentage of ethylene content is calculated by the following formula:

[0054] E%mol=100*[PEP+PEE+EEE] The weight percentage of ethylene content is calculated using the following formula:

[0055] 100*E%mol*MWE

[0056] E%wt.=E%mol*MWE+P%mol*MWP

[0057] Wherein P%mol is the molar percentage of propylene content, MWE and MWP are the molecular weights of ethylene and propylene, respectively.

[0058] The product of the reaction reactivity ratios r1r2 is calculated according to Carman (CJ Carman, RA Harrington and CE Wilkes, Macromolecules, 1977; 10, 536):

[0059]

[0060] The stereoregularity of the propylene sequence was determined by PPP mmT ββ (28.90-29.65ppm) and total T ββ The ratio of (29.80-28.37ppm) was calculated as the mm content.

[0061] Preparation of thin film samples

[0062] Each composition was extruded using a single screw Colin extruder (screw aspect ratio 1:25) at a film pulling speed of 7 m / min and a melt temperature of 210-250° C. to prepare a film having a thickness of 50 μm.

[0063] Per square meter (m 2 ) Determination of gel number

[0064] Per square meter (m 2 ) The determination of the number of gels was achieved by visually inspecting the number of gels of the sample film projected by a projector onto a white wall chart with an enlarged scale. At least 30 minutes after extrusion (die temperature of 250°C to 290°C, cooling roll temperature of 20°C), a film piece with a size of 130×7.5 cm was cut from the cast film. The cast film was prepared as described above.

[0065] Five different samples of the same film are counted and the final number is given by the expression No = A / S, where No is the number of particles per square meter (m 2 ), A is the number of gels counted on 5 membrane samples, and S is the total surface area of ​​the 5 membrane samples tested, in square meters (m2 ). Irregularly shaped gels are measured at the point of maximum extension.

[0066] A commercial propylene ethylene random copolymer sold as Moplen RP320M by LyondellBasell has been used to simulate a recycled polymer composition. The random copolymer has the characteristics described in Table 1.

[0067] Table 1

[0068] MFR g / 10' 8.5 Tensile modulus MPa 850 Charpy impact strength 23℃ <![CDATA[Kj / m 2 ]]> 7 Charpy impact strength 0℃ <![CDATA[Kj / m 2 ]]> 2

[0069] The random copolymer has been blended with ethylene-vinyl alcohol copolymer (EVOH), LOTADER AX8900. The melt flow rate of LOTADER AX8900 is 70 to 100 g / 10 min, the glycidyl methacrylate monomer content is 7 wt% to 11 wt%, the methyl acrylate monomer content is 13 wt% to 17 wt%, and the ethylene monomer content is 72 wt% to 80 wt%. The composition is shown in Table 2.

[0070] Table 2

[0071]

[0072] The compositions in Table 2 were extruded to form cast films, and the results of the final polymers are shown in Table 3.

[0073] Table 3

[0074] Comparative Example 1 Example 2 Comparative Example 3 Example 4 MFR g / 10min 10.08 7.75 11.50 7.76 Tm ℃ 146 147 146 145 Tc ℃ 109 110 109 101

[0075] It can be seen from Table 3 that the MFR of the examples of the present invention is relatively low.

Claims

1. A method for reducing the melt flow rate of a recycled polymer composition, the recycled polymer composition comprising at least 50 wt% of a recycled polypropylene composition and at least 5 wt% of a polar polymer, the method comprising: a) providing a recycled polymer composition comprising at least 50 wt% of a recycled polypropylene composition and at least 5 wt% of a polar polymer; b) adding 2 wt % to 10 wt % of a polyepoxide resin to the composition based on the total weight of the composition; c) melting the composition comprising components a) and b), and d) recovering the final polymer; The polar polymer is a polymer containing polar groups selected from the group consisting of alcohol (-OH), ether (-O-), carboxylic acid (-COOH), amine (-NH2), nitrile (-CN), thiol (-SH), selected from the group consisting of polyamide, polycarbonate, poly(ethyl methacrylate), acrylonitrile, butadiene, styrene terpolymer and ethylene vinyl alcohol polymer (EVOH).

2. The method according to claim 1, wherein the epoxy equivalent mass of the polyepoxide resin is 100 to 15000 g / mol.

3. The method according to any one of claims 1-2, wherein the polyepoxide resin has a melt flow rate of 70 to 100 g / 10 min, and the polyepoxide resin comprises a glycidyl methacrylate monomer content of 7 to 11 wt%, a methyl acrylate monomer content of 13 to 17 wt%, and an ethylene monomer content of 72 to 80 wt%.

4. The method according to any one of claims 1 to 3, wherein the polyepoxide resin is added in a range of 4.0 wt% to 9.0 wt%.

5. The method of any one of claims 1-5, wherein the recycled polymer composition comprises at least 60 wt% of a recycled polypropylene composition.

6. The method of any one of claims 1-6, wherein the recycled polymer composition comprises at least 7 wt% of the polar polymer.

7. The method of any one of claims 1-7, wherein the recycled polymer composition comprises at least 10 wt% of the polar polymer.

8. The method of any one of claims 1-7, wherein the recycled polymer composition comprises at least 15 wt% of the polar polymer.

9. The method of any one of claims 1-8, wherein the polar polymer is selected from the group consisting of polyamide, polycarbonate, poly(ethyl methacrylate), acrylonitrile, butadiene, styrene terpolymers and ethylene vinyl alcohol polymer (EVOH).

10. The method according to any one of claims 1 to 9, wherein the polar polymer is ethylene vinyl alcohol polymer (EVOH).

11. A film obtainable from the final polymer obtained by the process according to claims 1-12.

12. The film of claim 11 which is a cast film.

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