Recycled polypropylene process

Abstract

The properties of recycled post-consumer and / or post-industrial polypropylene are improved by adding an ethylene copolymer (B) that contains hydrolyzable silicon-containing groups.

Description

[Technical field]

[0001] The present invention relates to a process for regenerating post-consumer and / or post-industrial polypropylene. [Background technology]

[0002] Recycling of waste materials has become an increasingly common practice in recent decades. Recycling of plastic materials is important and is widely practiced in many industries and households around the world. Many everyday items, such as bottles, bags, and product packaging, are made from plastic materials. It is important to regenerate and reuse polymers.

[0003] However, the quality of recycled plastics needs to be monitored and guaranteed. A particularly important objective in the recycling of polypropylene is to meet the processing characteristics. Polypropylene is recycled from various processes. Recycled polypropylene has been used at least once. Reclaimed polypropylene comes from post-consumer and / or post-industrial uses. Most recycled plastics are mixed into a single stream and collected and processed by material recovery facilities (MRFs). At the MRF, the materials are sorted, washed, granulated, and packaged for resale. Plastics are sorted into individual materials such as high-density polyethylene (HDPE) or poly(ethylene terephthalate) (PET), or into mixed streams of other common plastics such as polypropylene (PP), low-density polyethylene (LDPE), poly(vinyl chloride) (PVC), polystyrene (PS), polycarbonate (PC), and polyamide (PA). The single or mixed streams are then further sorted, washed, and reprocessed into pellets suitable for the selected purpose.

[0004] Although recycled plastics are largely sorted into homogenous streams and washed with aqueous and / or caustic solutions, the final reprocessed pellets remain contaminated with other plastics and various properties. For example, small amounts of polyethylene will always be present in a recycled polypropylene stream.

[0005] The usefulness of recycled polypropylene varies as the properties of the recycled stream affect it. One solution to this is to test the properties of every lot, which is difficult, expensive and impractical. To ensure consistent properties of recycled polypropylene streams, a flexible solution must be found that ensures the recycled polypropylene meets application specifications.

[0006] US Patent No. 5,999,633 discloses a process for recycling polypropylene compositions for food applications. However, there remains a desire to modify recycled polypropylene to achieve more versatile and useful polypropylene products for specific applications.

[0007] Patent Document 2 relates to a polyolefin composition comprising a virgin polyolefin base resin containing an olefin homopolymer or copolymer (A) having a hydrolyzable silicon-containing group and an inorganic mineral filler (B) containing a silanol group or a precursor thereof on the surface. Furthermore, Patent Document 2 discloses combining an ethylene copolymer (B) containing a hydrolyzable silicon-containing group with a condensation catalyst. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2012 / 117250 A1 [Patent Document 2] US Patent Application Publication No. 2011 / 0015330 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention relates to a method for producing a polypropylene composition (P) from recycled polypropylene. In particular, the present invention relates to a method for producing a polypropylene composition (P) from recycled polypropylene having a lower melt flow rate (MFR) than the recycled polypropylene used as starting material for the polypropylene composition (P). 2 The properties of the recycled post-consumer and / or post-industrial polypropylene are improved by adding an ethylene copolymer (B) comprising hydrolyzable silicon-containing groups.

[0010] When polypropylene is recycled, the MFR 2 In many applications, low MFR 2 This reduces the usefulness of recycled polypropylene because

[0011] In the industrial production of virgin polypropylene, the MFR 2 is controlled by production parameters. Therefore, the MFR of virgin polypropylene 2 There is no need to change the

[0012] The object of the present invention is to provide a method for producing a recycled polypropylene composition (P) having a MFR 2 The aim of this study is to reduce [Means for solving the problem]

[0013] Reclaimed polypropylene products are often reprocessed into pellets suitable for the chosen purpose. Process streams from single or mixed sources of polypropylene products can be used for granulation. Granulation means compounding plastics and pelletizing them. This allows the MFR of the plastic to be reduced. 2 This is generally called the deterioration of plastics. However, by introducing an ethylene copolymer (B) containing a hydrolyzable silicon-containing group, the MFR 2It has been found that the ethylene copolymer (B) used in this way is reduced. Such ethylene copolymers (B) suitably used are disclosed, for example, in EP 2582743 A1. The blending is suitably carried out in a blender in which the polymers are mixed. The blending is carried out in a suitable extruder with efficient mixing. A suitable level of mixing is required to obtain a homogeneous polymer melt and uniform polymer properties.

[0014] The recycled polypropylene of the present invention is intended for various applications, such as sheet and thermoforming, pipe, and blow molding applications. All of these applications benefit from the low MFR of the recycled polypropylene composition (P). 2 is required.

[0015] In one application, recycled polypropylene is extruded into sheets, typically with widths of 300-2000 mm. The sheets are cut and thermoformed into the desired shape. This process increases the MFR of the recycled polypropylene. 2 The melt strength of the recycled polypropylene is required to be low and controlled. 2 When polypropylene is recycled, chain scission occurs. The short chains formed by chain scission increase the MFR of the recycled polypropylene. 2 This reduces the melt strength of the recycled polypropylene.

[0016] MFR for applications such as thermoforming and pipes 2 The MFR is typically less than 5g / 10min. Recycled polypropylene can be used for other applications such as injection molding. 2 is important for the processability and mechanical strength of the final product.

[0017] In pipe applications, melt strength is important for the dimensional stability of the pipe. When the pipe is extruded, there is molten polymer inside the pipe wall. If the melt strength is low, the molten polymer will flow inside the pipe wall, resulting in a thick bottom of the pipe. A low MFR is required to meet the mechanical properties of the pipe. 2is needed.

[0018] Thus, the present invention relates to a process for regenerating a polypropylene composition (P) from a recycled polypropylene (A) and a copolymer (B), the recycled polypropylene composition (P) comprising: a) at least 50% by weight of recycled polypropylene (A); b) 0.5 to 15% by weight of an ethylene copolymer (B) containing a hydrolyzable silicon-containing group; Including, The recycled polypropylene composition (P) is blended with the recycled polypropylene composition (P) and treated with 0.5 to 15% by weight of an ethylene copolymer (B) containing a hydrolyzable silicon-containing group, and has a MFR that is at least 15% lower than that of the recycled polypropylene (A). 2 has.

[0019] The object of the present invention is to provide a method for producing a recycled polypropylene composition (P) having a MFR 2 The objective of the present invention is to control the MFR of recycled polypropylene. Recycled polypropylene (A) can be obtained by various recycling processes. Examples of such processes are recycled polypropylene obtained from post-consumer recycling or post-industrial recycling. The physical properties of recycled polypropylene vary depending on the source. Therefore, the objective of the present invention is to control the MFR of recycled polypropylene. 2 The object of the present invention is to provide efficient, simple and reliable control of the amount of ethylene copolymer (B) that contains hydrolyzable silicon-containing groups.

[0020] Compounding of polypropylene and polyethylene is a well-established technology, therefore, one advantage of the present invention is that it can be practiced with current extrusion equipment.

[0021] The present invention further relates to a recycled polypropylene composition (P), which comprises: a) at least 50% by weight of recycled polypropylene (A); b) 0.5 to 15% by weight of an ethylene copolymer (B) containing a hydrolyzable silicon-containing group; Including, The recycled polypropylene composition (P) is blended, and the polypropylene composition (P) after blending has an MFR of 1 to 5 grams / 10 minutes. 2 has.

[0022] The present invention also provides a method for producing a recycled polypropylene composition (P) having a MFR 2 The present invention also relates to the use of an ethylene copolymer (B) containing hydrolyzable silicon-containing groups as a modifier, the recycled polypropylene composition (P) comprising: a) at least 50% by weight of recycled polypropylene (A); b) 0.5 to 15% by weight of an ethylene copolymer (B) containing a hydrolyzable silicon-containing group; Includes.

[0023] As used herein, the term "recycled polymer" refers to a polymer that has been used for its former purpose and then recovered for further processing.

[0024] As used herein, the term "recycled polypropylene" refers to polypropylene that has been used for a previous purpose and then recovered for further processing. Recycled polypropylene must be sorted and aggregated into a defined stream for the recycling process.

[0025] As used herein, the term "post-consumer" refers to a source of a material that occurs after the ultimate consumer has used the material in a consumer good or product.

[0026] As used herein, the term "post-consumer recycle" (PCR) refers to materials that are produced after the end consumer has used the material and discarded the material in the waste stream.

[0027] As used herein, the term "post-industrial" refers to sources of materials that arise during the manufacture of a commodity or product.

[0028] As used herein, the term "recycled polypropylene" refers to polypropylene that is derived from recycled, post-consumer, or post-industrial polypropylene, which then becomes the raw material used to manufacture new products.

[0029] Polypropylene has at least 50% by weight propylene monomer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] In one embodiment, the amount of recycled polypropylene (A) is at least 75% by weight, preferably at least 80% by weight, most preferably at least 90% by weight.

[0031] In a preferred embodiment of the present invention, the MFR of the recycled polypropylene is 2 is at least 20% lower, more suitably at least 30% lower, compared to recycled polypropylene (A).

[0032] The polypropylene composition (P) shall total 100%. The polypropylene composition (P) may further comprise additives, pigments and other polymer fractions. The polypropylene composition (P) may comprise a pigment, suitably carbon black. This increases the density of the recycled polypropylene composition (P). The additives are suitably added by masterbatch. If further polymer fractions are added to the recycled polypropylene composition (P), suitable virgin polypropylene or polyethylene is added. Most suitably, no further polymer fractions are added.

[0033] In one embodiment, the amount of copolymer (B) containing hydrolyzable silicon-containing groups is 1 to 10% by weight, more suitably 2 to 7% by weight. The amount of copolymer (B) is adjusted according to the desired MFR of the recycled polypropylene composition (P). 2The desired MFR of the polypropylene composition (P) is determined according to the 2 is determined by the end use of the recycled polypropylene composition (P). 2 The appropriate MFR is 1 to 10 grams / 10 minutes. 2 , more appropriately 1-5 g / 10 min, and most appropriately 1-3 g / 10 min 2 The object of the present invention is to have a small amount of copolymer (B) containing hydrolyzable silicon-containing groups, which improves the compounding process. This leads to a simpler, more stable and more homogeneous composition. The amount of hydrolyzable silicon-containing groups in the polyethylene is 0.1-5% by weight, more suitably 0.5-2% by weight.

[0034] In another embodiment of the invention, the compounding temperature is 200° C. or higher. The recycled polypropylene composition (P) is compounded in at least two zones in the compounder at a temperature of at least 200° C. In a more suitable embodiment of the invention, at least two zones are 230° C. or higher, and even more suitable two zones are 240° C. or higher. The recycled polypropylene composition (P) is compounded in at least two zones in the compounder at a temperature below 270° C., more suitable below 260° C. The residence time in the compounding unit should be at least 1 minute.

[0035] The recycled polypropylene (A) is obtained by post-consumer recycling. The recycled polypropylene (A) is obtained by post-industrial recycling. In a suitable embodiment, the recycled polypropylene (A) is from post-consumer recycling. This is a more demanding process since the recycled polypropylene (A) is a mixture of various polypropylenes and is contaminated from other mixed streams of other common plastics.

[0036] In another embodiment of the present invention, the ethylene copolymer containing hydrolyzable silicon-containing groups (B) is a low-density polyethylene (LDPE). The LDPE may be recycled or virgin. Virgin means that the polymer is not used. Due to the lack of recycled ethylene copolymer containing hydrolyzable silicon-containing groups (B), it is most appropriate to use a virgin source. LDPE is produced in a high pressure process. Another reason for using virgin ethylene copolymer containing hydrolyzable silicon-containing groups (B) is that the reactivity decreases with use.

[0037] In another embodiment of the present invention, the copolymer (B) containing hydrolyzable silicon-containing groups is a grafted polyethylene, which is grafted with a silane-containing group, such as the well-known ethylene-vinylsilane.

[0038] The present invention is suitably free from peroxide and / or peroxide residues. Peroxide and / or peroxide residues may arise from various steps of reactive compounding. Peroxide may be reactively compounded into polypropylene to reduce the MFR 2 Peroxides break the polypropylene chains. As mentioned above, recycled polypropylene usually contains small amounts of polyethylene. The polyethylene may be derived from virgin polypropylene. Ethylene is generally a comonomer in polypropylene, or polyethylene has been added to polypropylene as an impact modifier, or it comes from inadequate sorting of recycled polypropylene.

[0039] In a preferred embodiment of the present invention, the entire process is free of peroxides or peroxide residues.The copolymer (B) containing hydrolyzable silicon-containing groups is suitably free of peroxides or peroxide residues.The copolymer (B) containing hydrolyzable silicon-containing groups is meant to be polyethylene, suitably LDPE produced by high pressure process.

[0040] In a preferred embodiment of the present invention, the recycled polypropylene composition (P) is free from condensation catalyst. The purpose of the condensation catalyst is to crosslink the hydrolyzable silicon-containing groups by condensation reaction. However, it is preferable to avoid condensation catalyst because it is harmful to the environment or contains strong acid.

[0041] The object of the present invention is for articles made from the recycled polypropylene composition (P) to be substantially odorless and comparable in terms of odor and mechanical properties to articles made from virgin polypropylene.

[0042] The polypropylene composition (P) after compounding suitably has an MFR of 1 to 5 grams / 10 minutes. 2 , or more appropriately, an MFR of 1 to 3 grams / 10 minutes. 2 , most appropriately an MFR of 1-2 grams / 10 minutes 2 has.

[0043] The properties of recycled polypropylene vary. The density of recycled polypropylene varies from 890 kg / m 3 ~990kg / m 3 The color can be any, but it is mostly black. The ash content is less than 2% by weight, and the recycled polypropylene composition (P) is mostly in the form of pellets or granules. The moisture content is less than 0.1% by weight. Most of the properties of the recycled polypropylene composition (P) are similar to those of recycled polypropylene.

[0044] The recycled polypropylene composition (P) is suitably used in sheet extrusion and thermoforming applications.

[0045] The present invention also relates to a process for adding recycled polypropylene composition (P). The antioxidant is added to minimize degradation during processing and oxidation during the subsequent use of the finished product. With regard to the present invention, it is important to emphasize that the presence of the antioxidant is important to minimize the degree of degradation during processing that leads to an increase in MFR. This is effective for recycled polypropylene. However, the presence of the antioxidant does not result in an increase in MFR similar to the effect discussed in this invention. In addition, it is appropriate to add antioxidants to the recycled material. This reduces the effect of chain scission that counteracts the reduction in MFR imposed by the addition of silane group-containing polyethylene. A list of suitable phenolic antioxidants is Irganox® 1010, Irganox B215, Irganox B225, Irganox E210, Songnox 1076, Songnox 1330 and Anox 20. A list of suitable phosphite antioxidants is Irgafos® 168, Songnox 1680, Songnox PQ and Alkanox 240. A preferred antioxidant is a combination of Irganox 1010 and Irgafos 168. In one embodiment, the present invention provides: a) at least 50% by weight of recycled polypropylene (A); b) 0.5 to 15% by weight of an ethylene copolymer (B) containing a hydrolyzable silicon-containing group; The MFR of the recycled polypropylene composition (P) 2 A process for controlling i) measuring the MFR2 of recycled polypropylene (A); ii) adding an ethylene copolymer (B) containing hydrolyzable silicon-containing groups; iii) compounding a recycled polypropylene composition (P); Including, The amount of ethylene copolymer (B) is adjusted to the desired MFR of the recycled polypropylene composition (P). 2 It is a process based on

[0046] Measurement method Melt flow rate (MFR 2 ) is measured according to ISO 1133 and is expressed in g / 10 min. 2 is an indicator of the flowability and therefore processability of a polymer. The higher the melt flow rate, the lower the viscosity of the polymer. MFR of polypropylene 2 is the MFR of polyethylene measured at 230°C and with a load of 2.16 kg. 2 is measured at a temperature of 190°C and a load of 2.16 kg. All examples of compositions containing at least 50% by weight of polypropylene are measured at 230°C.

[0047] material The EVS is LE-4423 available from Borealis. EVS is a low density polyethylene copolymer containing hydrolyzable silicon-containing groups. The copolymer is produced in a high pressure reactor. The density of the polymer is 923 kg / m 3 and MFR of 1.0g / 10min. 2 has.

[0048] Recycled polypropylene polymer 1 has an MFR of 2.57g / 10min 2 The polymer is obtained by collecting various plastic polypropylene articles. The polypropylene comes from post-consumer processes. Recycled polypropylene polymer 1 has a small amount of polyethylene.

[0049] Recycled polypropylene polymer 2 has an MFR of 15.0g / 10min. 2 The polymer is obtained by collecting various polypropylene articles. The polypropylene comes from post-consumer processes. Recycled polypropylene polymer 2 has a small amount of polyethylene.

[0050] Recycled Polypropylene Polymer 3 (PP-based thermoplastic olefin) has an MFR of 2.4g / 10min 2The polymer is obtained by collecting various post-industrial polypropylene articles.

[0051] The LDPE used is commercially available FA3227. FA3227 has a density of 922 kg / m 3 Density of 0.3 g / 10 min, and MFR of 0.3 g / 10 min 2 It is a low density polyethylene having the following structure.

[0052] Masterbatch of Irganox 1010 containing 10% by weight of additive.

[0053] Masterbatch of Irgafos 168 containing 10% by weight of additive.

[0054] Working Example The compositions shown in Table 1 were compounded in an 18 mm Axon 25D extruder at temperature settings of 190, 220, 230, and 230° C. Residence time was 1 minute 20 seconds.

[0055] [Table 1]

[0056] In Comparative Example 1 (Comparative Example 1), recycled polypropylene polymer 1 was blended, and the MFR after blending was 2 There is a slight increase in the tensile strength due to degradation of the polymer chains in the compounder.

[0057] In Comparative Example 2, recycled polypropylene polymer 1 is blended with LDPE having a low MFR2. The MFR of LDPE and EVS 2 Note that MFR is measured at 190°C. In inventive example 1, LDPE is replaced with EVS. Even though half the amount of EVS is added, EVS has a higher MFR than LDPE. 2 Decreased MFR despite having 2The effect of the present invention is higher. In Examples 2 and 3, EVS is further added. In Example 4, another recycled PP is used. This is because the present invention is able to reduce the starting MFR of the recycled PP. 2 This shows that they act independently.

[0058] As shown in Examples 2 and 3, the MFR 2 The decrease is greater with increasing EVS amount.

[0059] The relative difference is the MFR of the recycled polypropylene composition (P). 2 MFR of recycled polypropylene (A) 2 It is calculated as the ratio divided by minus 100%.

[0060] The examples in Table 2 were compounded on an 18mm Axon 25D extruder at different temperature settings: Setting 1 170, 180, 190, 190℃ Setting 2 190, 200, 210, 210℃ Setting 3: 210, 220, 230, 230℃ Setting 4: 230, 240, 250, 250℃ Setting 5 250, 260, 270, 270℃

[0061] [Table 2]

[0062] In Table 2, the temperature setting of the compounder is changed. When the temperature setting is increased, the MFR of the recycled polypropylene composition (P) increases. 2 In Example 9, the MFR 2 The decrease in melt temperature stops. The optimum temperature is 250° C. The temperature of the melt in the compounder is checked by an external temperature device temporarily inserted in the center of the extruder die.

[0063] Stabilizers were added in Table 3. The compositions were compounded in an 18 mm Axon 25D extruder with temperature settings of 190, 220, 230, and 230° C. The melt residence time is estimated to be 1 minute 20 seconds.

[0064] [Table 3]

[0065] As shown in Comparative Example 4, the addition of additives did not change the MFR2, but when additives were added as in Example 9, the MFR2 remained substantially the same compared to Example 2, which did not contain an antioxidant additive.

[0066] Table 4 shows examples of polypropylene compositions after industrialization.

[0067] [Table 4]

[0068] MFR 2 The change in was measured in the post-industrial recycled polypropylene composition.

Claims

1. The recycled polypropylene composition (P) is a) at least 50% by weight of recycled polypropylene (A); b) 0.5 to 15% by weight of an ethylene copolymer (B) containing hydrolyzable silicon-containing groups; Including, The recycled polypropylene composition (P) is blended. The recycled polypropylene composition (P) treated with 0.5 to 15 wt. % of an ethylene copolymer (B) containing a hydrolyzable silicon-containing group has a MFR that is at least 15% lower than that of the recycled polypropylene (A). ２ A process for regenerating a polypropylene composition (P) comprising:

2. The process of claim 1, wherein the recycled polypropylene composition (P) does not contain a condensation catalyst.

3. 2. The process according to claim 1, wherein the amount of recycled polypropylene (A) is at least 75% by weight, preferably at least 80% by weight.

4. The process according to any one of claims 1 to 3, wherein the amount of the copolymer (B) containing hydrolyzable silicon-containing groups is from 2 to 10% by weight.

5. 2. The process of claim 1, wherein the temperature of the compounding step is 230° C. or higher, preferably 240° C. or higher.

6. 2. The process of claim 1, wherein the ethylene copolymer containing hydrolyzable silicon-containing groups (B) is a LDPE.

7. 2. The process of claim 1, wherein the copolymer (B) containing hydrolyzable silicon-containing groups is a grafted polyethylene.

8. 10. The process of claim 1, wherein the process is free of peroxides and / or peroxide residuals.

9. 2. The process of claim 1, wherein the copolymer (B) containing hydrolyzable silicon-containing groups is free of peroxides or peroxide residues.

10. a) at least 50% by weight of recycled polypropylene (A); b) 0.5 to 15% by weight of an ethylene copolymer (B) containing hydrolyzable silicon-containing groups; Including, The recycled polypropylene composition (P) is blended, and the polypropylene composition (P) after blending has an MFR of 0.5 to 5 g / 10 min. ２ The recycled polypropylene composition (P) has the following structure.

11. The recycled polypropylene composition (P) according to claim 10, wherein the recycled polypropylene composition (P) does not contain a condensation catalyst.

12. The recycled polypropylene composition (P) is a) at least 50% by weight of recycled polypropylene (A); b) 0.5 to 15% by weight of an ethylene copolymer (B) containing hydrolyzable silicon-containing groups; The MFR for the recycled polypropylene composition (P) ２ Use of an ethylene copolymer (B) containing hydrolyzable silicon-containing groups as a modifier.

13. The use according to claim 12, wherein the recycled polypropylene composition (P) does not contain a condensation catalyst.