Polymer composition for improved grade plastics from recycled materials

Abstract

The invention relates to a polymer composition comprising: (a) 60-80 wt% of recycled polypropylene (rPP); (b) 0-0.03 wt% of peroxide; (c) 3-7 wt% of heterophasic propylene ethylene copolymer; (d) 10-30 wt% of polyolefin elastomer (POE); wherein components (a) to (d) add up to 100%, and wherein the melt flow rate of component (a) has been increased by reaction with the peroxide to be in the range of 60 to 80 g / 10 min, determined according to ISO 1133 at 2.16 kg, 230°C. The invention also relates to a method of forming a polymer composition, wherein in a first step the MFR of component (a) is increased by reaction with the peroxide, and in a second step components (a) to (d) are added. The invention also relates to an article made from this new polymer composition.

Description

TECHNICAL FIELD

[0001] The present invention relates to a new and improved polymer composition comprising a high amount of recycled polypropylene (PP) and polyethylene (PE). The present invention also relates to the use of such polymer composition in the manufacture of articles, to the articles manufactured from said polymer composition and to the process for preparing such polymer composition. BACKGROUND

[0002] The popularity of plastic packaging and the importance of environmental policies have led to an increase in the importance of recycled plastic materials.

[0003] Recycling of paper, textiles, glass or metal is already carried out on a large scale, either by separate collection or by sorting the recyclates. Recycling of plastic waste and re-use of plastics is also increasing.

[0004] Substitution of virgin polymer compositions is considered the only way to solve the global plastic waste problem, stop the depletion of natural resources and promote a circular economy.

[0005] So far, recycled polymer compositions have been available in the form of flakes or granules, obtained from the collection of polyolefin packaging, containers or films available on the market, wherein the polyolefin is present in a low percentage of 5-8 wt% in the recycled polymer composition and the remaining 92-95 wt% of polyolefin is made of virgin polyolefin.

[0006] WO2020221756 describes a composition obtained from recycled polyolefins.

[0007] There is still a need to prepare products from recycled materials having a good balance of mechanical and optical properties. For example, when using virgin materials, optical properties such as tiger stripes, flow-induced surface defects during injection moulding are a problem, but when using recycled polyolefins, optical properties are increasingly increasing.

[0008] It is an object of the present invention to define a new polymer composition which can be used to prepare durable consumer goods based on 60 wt% or more of recycled polyolefins, having significantly reduced tiger stripes, excellent moulding behaviour and excellent impact strength. SUMMARY

[0009] Therefore, a polymer composition is provided, comprising:

[0010] (a) 60-80 wt% of transferred recycled polypropylene (s-rPP);

[0011] (b) 0-0.03 wt% of peroxide;

[0012] (c) 3-7 wt% of heterophasic propylene ethylene copolymer;

[0013] (d) 10-30 wt% of a polyolefin elastomer (POE);

[0014] wherein the amounts of components (a) to (d) are defined relative to the sum of (a) + (b) + (c) + (d) of the polymer composition, and wherein the melt flow rate of component (a) is in the range of 60 to 80 g / 10 min, determined according to ISO 1133 at 230 °C under 2.16 kg.

[0015] The present application also provides a process for preparing the polymer composition, polymer articles prepared therefrom, and a process for preparing said articles, in particular by injection molding.

[0016] An advantage of the polymer composition according to the present application is the unique balance of mechanical properties and flow behavior, resulting in a composition with a high content of recycled polyolefin having comparable or better properties than virgin material. DETAILED DESCRIPTION

[0017] The expression “comprises” means that components (a) to (d) must be present in the defined amounts, and that other components such as fillers, colorants and similar additives can be present in conventional amounts, for example up to 10 wt% based on the total amount of components (a) to (d). This means that the amount of components (a) + (b) + (c) + (d) preferably constitutes at least 90 wt% of the polymer composition.

[0018] Component (a): Recycled polypropylene transferred

[0019] The transferred recycled polypropylene (s-rPP) is obtained by processing recycled PP (rPP) to a higher melt flow rate and lower molecular weight with organic peroxides.

[0020] The rPP feedstock comprises plastic waste, mainly post-consumer waste (PCW) PP packaging waste, such as detergent and shampoo bottles, dairy cans and meat trays, etc. The rPP feedstock waste can be pre-sorted by a waste management company. A suitable rPP source can for example be waste collected under the DSD 324 (05-2012) and DSD 324-1 standards (03-2018).

[0021] The rPP DSD 324(05-2012) feedstock can include at least one of the following used, residue drained, rigid, system compatible articles made of polypropylene, such as bottles, cups and trays, including secondary parts such as caps, labels, etc. The rPP DSD 324(05-2012) feedstock can include a maximum total amount of 6 mass% of impurities. The impurities in the rPP DSD 324(05-2012) feedstock can include <0.5 mass% of other metal articles, <1 mass% of rigid PE articles, <0.5 mass% of expanded plastics including EPS articles, <2 mass% of plastic films, and <3 mass% of other residues. Other examples of impurities in the rPP DSD 324(05-2012) feedstock can include glass, paper, board, cardboard, composite paper / cardboard materials (e.g. liquid packaging board), aluminized plastics, other materials (e.g. rubber, stones, wood, textiles, diapers), and compostable waste (e.g. food, garden waste).

[0022] A second standard for rPP is the PP DSD 324-1 standard (03-2018). This standard is very comparable to the above mentioned PP DSD 324 standard, except that the rPP can contain more film material, up to about 10 wt%. This film material includes rPP films (such as e.g. biaxially oriented PP (BOPP)) PE films. The PP DSD 324-1 standard (03-2018) feedstock can include a maximum total amount of 4 mass% of impurities. The impurities in the PP DSD 324-1 standard (03-2018) feedstock can include <0.5 mass% of other metal articles, <1 mass% of rigid PE articles, <0.5 mass% of expanded plastics including EPS articles, <1 mass% of paper, cardboard, carton, composite paper / cardboard materials (e.g. liquid packaging cardboard), <3 mass% of other residues. Other examples of impurities in the PP DSD 324-1 standard (03-2018) feedstock can include glass, aluminized plastics, other materials (e.g. rubber, stones, wood, textiles, diapers), and compostable waste (e.g. food, garden waste).

[0023] The rPP can contain 25-75 parts by weight of packaging material (BOPP) and 75-25 pbw of rubber containing injection molded material in 100 parts. Such injection molded material can comprise rubber, such as C2-C3 rubber, thermoplastic elastomer (TPE), ethylene propylene diene rubber (EPDM) or ethylene propylene rubber (EPR).

[0024] Typically, when no rPP treatment is performed, the melt flow rate of the rPP, determined using ISO 1133-1 :2011, 2.16 kg, T = 230 °C, ranges from 10 to 20. This MFR is too low for the production of a polymer composition with a proper balance of properties.

[0025] Therefore, the use of rPP obtained directly after washing the PP from the DSD 324, without further treatment, does not result in a polymer composition according to the present application.

[0026] Preferably, the recycled PP used for the transfer of the present application has a melt flow rate in the range of 60 to 80 g / 10 min, determined using ISO 1133-1 :2011, 2.16 kg, T = 230 °C. More preferably, the MFR of component (a) is in the range of 65 to 75 g / 10 min.

[0027] It is important that the s-rPP has undergone MFR transfer by reaction of the rPP with the peroxide before the other components of the composition are added. If the other components (heterophasic propylene ethylene copolymer and polyolefin elastomer (POE)) are present during the transfer of the rPP, a composition will be obtained that does not show a proper balance of properties.

[0028] The transfer of the rPP is preferably performed with an organic peroxide, more preferably with 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (CAS 78-63-7). The transfer is preferably performed with 0.1 -0.3 wt% of the organic peroxide. Alternatively, the organic peroxide can be present as a masterbatch, wherein the peroxide is dispersed in a polymer such as polypropylene (PP). For example, 10 wt% of the organic peroxide is dispersed in 90 wt% of PP to provide a 10 wt% masterbatch. For the transfer of the rPP, 1 -3 wt% of the 10% masterbatch of the peroxide can be used. Other masterbatches can also be used and the skilled person can easily adjust the amount of masterbatch needed to transform the rPP to the desired MFR.

[0029] The transfer typically occurs in an extruder at a temperature typically between 200 °C and 270 °C.

[0030] Surprisingly it was found that changing the MFR before blending the other components and thereafter combining the s-rPP with the heterophasic propylene ethylene copolymer and the polyolefin elastomer (POE) results in a product with an improved balance of properties, including reduced tiger stripes, high cold impact, high RT impact and high tensile strength.

[0031] The s-rPP is present in 60-80 wt%, preferably 60-77.5 wt%, more preferably 62-75 wt% relative to the sum of (a) + (b) + (c) + (d) of the polymer composition; relative to the sum of (a) + (b) + (c) + (d) of the polymer composition can also be defined relative to the sum of (a) to (d) of the polymer composition.

[0032] Component (b), peroxide

[0033] Optionally, the s-rPP, the heterophasic propylene ethylene copolymer and the polyolefin elastomer (POE) are blended together with a small amount of a peroxide component (b). This component (b) is preferably present as a PP masterbatch, wherein the peroxide can be present in a weight ratio of peroxide to PP of 1 : 100 - 1 : 25, more preferably in a weight ratio of peroxide to PP of 1 : 50 - 1 : 30. The amount of the peroxide component b is between 0 and 0.03 wt% (based on wt% peroxide) with respect to the sum of components a+b+c+d.

[0034] Component (b) is not to be confused with the peroxide used for the transformation of rPP into s-rPP, which is carried out prior to blending the different components to prepare the polymer composition according to the application.

[0035] Component (b) can be used to fine-tune the flow properties of the polymer composition of the application.

[0036] Peroxides that are commonly used as crosslinking agents can be used. Preferably, organic peroxides are used. For example, the peroxide can be 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (DBPH). The latter is commercially available as 101. Alternatives include 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, dicumyl peroxide, etc.

[0037] Component (c), heterophasic propylene ethylene copolymer

[0038] Suitable heterophasic propylene ethylene copolymers are described in US2020339794 and US2020263013, which are hereby incorporated by reference. Preferably it is a copolymer satisfying the following conditions:

[0039] i) the content of ethylene derived units ranges from 6.0 wt% to 16.0 wt%;

[0040] ii) the fraction soluble in xylene at 25°C ranges from 15 wt% to 45 wt%;

[0041] iii) the intrinsic viscosity (h) of the fraction soluble in xylene at 25°C ranges from 4.0 to 9.0 dl / g; and

[0042] iv) the melt flow rate, measured according to ISO 1133 at 230°C with a load of 2.16 kg, ranges from 0.3 to 50.0 g / 10 min, more preferably from 0.5 to 5.0 g / 10 min.

[0043] Suitable examples include preferably LyondellBasell Hifax X 1956A. The amount of component (c) can be 3-7 wt%, preferably 4-6 wt% with respect to the sum of (a) to (d) of the polymer composition.

[0044] Component (d), polyolefin elastomer

[0045] Component (d) is an ethylene alpha-olefin copolymer (POE). Examples of POE are C2-C4 copolymers, C2-C6 copolymers and C2-C8 copolymers. The POE can preferably be a C2-C6 copolymer or a C2-C8 copolymer having 70-80 wt%, more preferably 73-78 wt%, most preferably 74-77 wt% of ethylene; wherein wt% is relative to the POE.

[0046] The POE used in the present application preferably comprises an ethylene (C2) octene (C8) metallocene rubber having a block structure. The density of the POE is preferably between 0.85-0.89, more preferably between 0.855-0.885, most preferably between 0.86-0.875.

[0047] The POE preferably has a MFR (190°C, 2.16 kg) of 0.3-1, more preferably 0.4-0.8, most preferably 0.45-0.7.

[0048] The POE is preferably selected from Infuse or Engage polymers, such as Infuse 9107, Infuse 9077 and Engage XLT8677. Preferably Infuse 9077 is available from DOW.

[0049] The POE is present in 10-30 wt%, preferably 15-25 wt%, more preferably about 20 wt% relative to the sum of (a) to (d) of the polymer composition.

[0050] Component e) talc

[0051] The composition preferably contains talc. The talc can for example be unmodified and preferably does not have a surface coating or surface treatment. The talc can also be referred to as talc in this application. The talc can for example be an alpha nucleating agent, such as hydrated magnesium silicate or Steamic 00SDF.

[0052] Preferably, the talc is a very finely ground talc. The inventors found that the use of a fine talc having a D50 of less than 4 microns, preferably less than 3 microns, even more preferably less than 2.5 microns in combination with recycled PP results in an increase in the impact and tensile modulus and acts as a nucleating agent for the composition, thereby increasing the mechanical properties of the composition. The D50 is measured by sedimentation graph, sedimentation analysis, Stokes law (ISO 13317-3).

[0053] The talc increases the stiffness and strength of the polymer composition and the produced articles. The talc content further influences the flow of the polymer composition during moulding, especially for thin wall applications.

[0054] Talc is preferably present in the polymer composition in an amount of 1-10 wt%, preferably 2-5 wt% or 2.5-4 wt%. The best balance of properties is achieved using a talc content of 2.5-3.5 wt% relative to the total composition. Amounts of talc lower than 1 wt% do not improve the properties of the composition, while amounts >10 wt% make the composition have a density that is too high for some applications, and the amount of tiger stripes tends to increase beyond 10 wt%.

[0055] Additional components

[0056] The composition can contain additional components, including fillers, colorants, processing aids, as well as other polymers and recycled streams.

[0057] It is important to remain within the ranges defined above, to obtain a polymer composition that can be injection molded under typical conditions, with excellent mechanical properties and aesthetic appearance. Moreover, it has been found that the order of mixing the components is relevant. In other words, component (a) must first undergo a transreaction with the peroxide, before the additional components are added.

[0058] The application is illustrated by the following examples.

[0059] Examples

[0060] A series of experiments have been performed. Experiments 1-3 and 5-7 are comparative examples, in which s-rPP is used without pre-treatment to shift to the desired MFR, and also no component c (Hifax) is added.

[0061] The formulations are provided in Table 1 below.

[0062] Experiments C1-C3 show properties with reasonable tiger stripes, but the modulus of the material is rather high, and the elongation at break and yield are too low, resulting in a very brittle material. The Charpy impact is 10 times lower than desired. The addition of Kraton rubber from C1 to C2 to C3 slightly improves the Charpy, but not enough.

[0063] In experiment C5, the amount of DOW infuse 9077 is increased relative to C1-C3, and rPE is added. As a result, the MFR is too low, the elongation at break and yield are too low, and the tiger stripes are very high.

[0064] Experiment C6 applies a different DOW Infuse 9177 in a higher amount compared to C1-C3. The properties are comparable to experiments C1-C3: the Charpy impact and elongation values are too low. This example shows a higher amount of tiger stripes.

[0065] Experiment C7 to C5 comparison: now 10 wt% Infuse 9177 is applied. Charpy impact is too low, elongation at break and elongation at yield are too low, and tiger stripes are very high.

[0066] It is very difficult to find the right balance of properties.

[0067] Surprisingly, the best balance of properties is achieved in experiment 4 (a-d). E- modulus is more than 800 N / mm 2 Elastic behavior is sufficient. Impact strength at room and low temperature is greatly improved.

[0068] Furthermore, consistently, experiment 4 (a-d) provides molded products without visible tiger stripes or other surface defects.

[0069] The results are provided in table 2 below.

[0070]

[0071] Table 1

[0072] Samples C1 C2 C3 4a 4b 4c 4d C5 C6 C7 QCP PP300U (MFR 70) grey or ivory ％ 71,0 71,0 71,0 71,0 QCP PP300t (MFR 50) grey or ivory ％ 89,8 87,8 85,8 69,8 89,8 69,8 LyondellBasell Hifax X 1956A ％ 5,0 5,0 5,0 5,0 DOW Infuse 9077 ％ 5,00 5,00 5,00 20,00 20,00 20,00 20,00 10,00 DOW Infuse 9177 10,00 10,00 QCP PE5603 grey or ivory ％ 17,00 20,00 Kraton G1657MS ％ 2,0 4,0 2,0 Steamic OOSd (talc) ％ 5,00 5,00 5,00 3,00 3,00 3,00 3,00 Masterbatch Irganox B225 30% ％ 0,20 0,20 0,20 0,50 0,50 0,50 0,50 0,75 0,20 0,20 Exxelor PE1040 ％ 0,50 DBPH 10% on PP ％ 0,50 0,50 0,50 0,50

[0073] Table 2

[0074]

[0075] Table 2, cont.

[0076]

[0077] Charpy according to NEN-ISO 179 / eA, molded bar 527 / 1A

Claims

1. A polymer composition comprising: (a) 60-80 wt% of transferred recycled polypropylene, i.e. s-rPP, wherein the transferred recycled polypropylene is obtained by processing the recycled PP to a higher melt flow rate and a lower molecular weight with an organic peroxide. (b) 0.05 wt% peroxide; (c) 3-7 wt% multiphase propylene-ethylene copolymer; (d) 10-30 wt% polyolefin elastomer, i.e., POE; The amounts of components (a) to (d) are defined relative to the sum of components (a) to (d) of the polymer composition, and the melt flow rate (MFR) of component (a) is 60 to 80 g / 10 min, determined according to ISO 1133 at 2.16 kg and 230 °C.

2. The polymer composition according to claim 1, wherein the composition further comprises (e) 1-5 wt% fine talc.

3. The polymer composition according to claim 1, wherein the MFR of component (a) is 65-75 g / 10 min, determined according to ISO 1133 at 2.16 kg and 230 °C.

4. The polymer composition of claim 1, wherein the s-rPP is obtained by transferring recycled PP with an organic peroxide, said recycled PP being obtained from PP plastic waste collected under DSD 324 (05-2012) and DSD 324-1 standards.

5. The polymer composition according to claim 1, wherein the MFR of component (a) has been increased by reaction with recycled PP and organic peroxide prior to blending components (a) to (d).

6. The polymer composition according to claim 1, wherein component (a) is present in 60-77.5 wt% relative to the sum of (a) to (d) of the polymer composition.

7. The polymer composition according to claim 6, wherein component (a) is present in 62-75 wt% relative to the sum of (a) to (d) of the polymer composition.

8. The polymer composition according to claim 1, wherein component (b) is an organic peroxide.

9. The polymer composition according to claim 8, wherein component (b) is 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, DBPH.

10. The polymer composition according to claim 1, wherein the sum of the amounts of components (a) + (b) + (c) + (d) is at least 90 wt% of the polymer composition.

11. The polymer composition according to claim 1, wherein component (c) satisfies the following condition: i) The content of ethylene-derived units, ranging from 6.0 wt% to 16.0 wt%; ii) The xylene-soluble fraction at 25°C, ranging from 15 wt% to 45 wt%; iii) The intrinsic viscosity η of the xylene-soluble fraction at 25°C, ranging from 4.0 to 9.0 dl / g; and iv) Melt flow rate, measured according to ISO 1133 at 230°C with a load of 2.16 kg, ranging from 0.3 to 50.0 g / 10 min.

12. The polymer composition of claim 11, wherein the melt flow rate, measured according to ISO 1133 at 230°C with a load of 2.16 kg, ranges from 0.5 to 5.0 g / 10 min.

13. The polymer composition according to claim 1, wherein component (c) is used in an amount of 4-6 wt% relative to the sum of (a) to (d) of the polymer composition.

14. The polymer composition according to claim 1, wherein component (d) is selected from C2-C4 copolymers, C2-C6 copolymers and C2-C8 copolymers.

15. The polymer composition according to claim 14, wherein component (d) is a C2-C6 copolymer having 70-80 wt% ethylene or a C2-C8 copolymer having 70-80 wt% ethylene, wherein wt% is relative to the POE.

16. The polymer composition of claim 15, wherein component (d) is a C2-C6 copolymer having 73-78 wt% ethylene or a C2-C8 copolymer having 73-78 wt% ethylene, wherein wt% is relative to the POE.

17. The polymer composition of claim 16, wherein component (d) is a C2-C6 copolymer having 74-77 wt% ethylene or a C2-C8 copolymer having 74-77 wt% ethylene, wherein wt% is relative to the POE.

18. The polymer composition according to claim 1, wherein component (d) is present in 15-25 wt%, wherein wt% is the sum of (a) to (d) relative to the polymer composition.

19. The polymer composition according to claim 18, wherein component (d) is present in 20 wt%, wherein wt% is the sum of (a) to (d) relative to the polymer composition.

20. A method for preparing the polymer composition according to claim 1, wherein in a first step, the MFR of component (a) is increased to the range of 60 to 80 g / 10 min by reacting recycled PP obtained from PP plastic waste collected under DSD 324 (05-2012) and DSD 324-1 standards with peroxide, as determined according to ISO 1133 at 2.16 kg and 230 °C, and in a second step components (a)-(d) are added and blended.

21. An article made from the polymer composition according to claim 1.

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