Method for Recycling Waste TPO Skin Material

Abstract

The present invention discloses a method for recycling waste TPO skin materials, which relates to the technical field of material recycling and utilization. It includes sorting and cleaning the scrapped workpieces containing TPO skin materials to remove impurities, then crushing them into blocks and pouring them into a mixer, adding an aqueous solution of a swelling agent, heating and stirring for degumming and separation treatment to obtain TPO blocks; washing and drying the TPO blocks, putting them into a high-speed mixer, adding an extractant, stirring, and feeding them into a twin-screw extruder through a forced feeder for extrusion, defoaming and granulation, and then cooling, drying and pelletizing. The present invention solves the problem of resource waste caused by landfilling the scrapped workpieces containing waste TPO skin materials in the prior art. At the same time, the recycled TPO particles can be used as a toughening agent for modified PP or softer products with low bending modulus requirements such as automobile wheel covers and fender liners.

Description

Technical Field

[0001] The present invention relates to the technical field of material recycling, and particularly to a method for recycling waste TPO skin materials. Background Art

[0002] In order to adapt to the trend of lightweight and environmental protection of automotive parts and improve the recyclability and comfort of interior materials, thermoplastic polyolefin elastomer TPO has become the development direction of automotive instrument panels and door panel skins and is favored by people. Polyolefin-based thermoplastic elastomer TPO gradually replaces traditional PVC skin materials. Among them, the soft TPO skin material for automotive interiors includes, from bottom to top: 1) back coating: polyurethane-based finishing agent or polyolefin-based finishing agent; 2) foaming layer: polypropylene foam layer; 3) soft TPO surface layer; 4) water-based finishing layer: water-based polyurethane finishing agent.

[0003] However, since most automotive instrument panels and door panels use PP or ABS materials as the skeleton, and a layer of adhesive is brushed on the surface of the skeleton and then the TPO skin material is tightly adhered together by the method of vacuum thermoforming with a female mold. Therefore, the scrapped workpieces contain PP or ABS hard plastics, adhesives, TPO skins, EPP foams, surface layers and paint layers at the bottom. The separation and recycling are difficult, the cost is high, and the reuse purposes are relatively narrow. Many are not recycled but are disposed of by landfilling, failing to achieve the purpose of recycling and causing great waste of resources. Summary of the Invention

[0004] The present invention provides a method for recycling waste TPO skin materials, which can solve the problem of resource waste caused by landfilling scrapped workpieces containing waste TPO skin materials in the prior art.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] It includes the following steps:

[0007] A. Sort and clean the scrapped workpieces containing TPO skin materials to remove impurities; wherein, the impurities include resins of different types from the TPO skin materials.

[0008] B. Crush the sorted and cleaned scrapped workpieces to obtain material blocks with a diameter of 8 mm to 18 mm.

[0009] C. Pour the crushed material blocks into a mixer, add a swelling agent aqueous solution, heat and stir for degumming and separation treatment, and collect the TPO material blocks obtained after degumming and separation.

[0010] D. Wash and dry the obtained TPO pellets, put them into a high-speed mixer, add an extractant, stir, and then feed them into a twin-screw extruder through a forced feeder for extrusion, defoaming, and pelletizing. Then, cool, dry, and cut the pellets.

[0011] In the above technical solution, a more specific technical solution may further be: in step C, the swelling agent in the swelling agent aqueous solution is prepared by mixing methyl ethyl ketone and cyclohexanone in a volume ratio of methyl ethyl ketone: cyclohexanone = 1:1.

[0012] Furthermore, the concentration of the swelling agent aqueous solution is 15 wt%.

[0013] Furthermore, in step D, the extractant is octamethylcyclotetrasiloxane.

[0014] Furthermore, the addition amount of the extractant is 2 wt% of the TPO pellets.

[0015] Furthermore, in step C, the specific method for collecting the TPO pellets obtained after degumming and separation is: after the degumming and separation treatment process is completed, drain the swelling agent aqueous solution inside, then add water and stir, let it stand for sedimentation and separation, and fish out the TPO pellets floating on the water surface.

[0016] Furthermore, in step D, the twin-screw extruder is a co-rotating twin-screw extruder with double vacuum and a screw length-diameter ratio of 40:1.

[0017] Furthermore, in step D, the specific process for the twin-screw extruder to extrude, defoam, and pelletize is: the screw temperature of the twin-screw extruder is 175 °C to 215 °C, the main screw rotation speed is 300 r / min to 500 r / min, the frequency of the forced feeder is 15 Hz to 25 Hz, and the double vacuum pressure is maintained at -0.08 MPa.

[0018] Due to the adoption of the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The TPO particles recovered by the present invention can be used as a toughening agent for modified PP or softer products with low flexural modulus requirements such as automotive wheel covers and fender liners.

[0020] 2. Since TPO is only mutually soluble with PP and PE resins in the molten state and is incompatible with different types of resins such as ABS, PC, and PA resins in the molten state, if the different resins of TPO are not removed in advance when recycling waste workpieces containing TPO skin materials, it will affect the comprehensive performance of the recycled product materials, and there will also be phenomena such as delamination and decomposition during subsequent reprocessing, making it unusable. Therefore, when the present invention recycles waste workpieces containing TPO skin materials, the different resins of TPO are removed in advance.

[0021] 3. Compared with other types of swelling agents, the methyl ethyl ketone and cyclohexanone (in a 1:1 ratio) used in the present invention have a synergistic effect, which can further improve the solubility of the swelling agent and reduce the comprehensive cost. In addition, in organic solvents, methyl ethyl ketone and cyclohexanone have moderate solubility, are relatively common, have a wide source, low toxicity, and the waste liquid is easy to recycle and treat.

[0022] 4. In the present invention, by adding an aqueous solution of the swelling agent and heating and stirring, the adhesive between the TPO skin and the hard plastic (PP or ABS) swells and debonds, and then the TPO skin is debonded and separated from the hard plastic (PP or ABS).

[0023] 5. In step C of the present invention, after the debonding and separation treatment process is completed, the aqueous solution of the swelling agent inside is drained, and water is added and stirred. The TPO material block floats on the water surface and is collected by static precipitation separation using the density difference between the TPO skin and the hard plastic (PP or ABS). The aqueous solution of the swelling agent generated by this method can be recycled after filtration and precipitation separation; using the density suspension method to separate resin plastics with different densities is simple and convenient. In addition to separating the hard plastic (PP or ABS), it can also wash and remove the swelling agent remaining in the TPO crushed material; and the aqueous solution can be recycled after precipitation, without generating waste liquid, which is environmentally friendly.

[0024] 6. The present invention uses octamethylcyclotetrasiloxane as an extractant. Under the action of heat and the strong shearing force of the extruder screw, a large number of microbubbles are formed. These microbubbles are miscible with the small molecules in the TPO material block for extraction, forming a large number of bubbles. Then, under the action of the high-strength vacuum negative pressure at the rear end, these small molecules and the extractant are evacuated together. This method mainly extracts and removes volatile substances from the TPO melt through the extractant, separating and removing the residual impurities in the TPO that can be vaporized at high temperature (such as water vapor, methyl ethyl ketone, benzene, etc., which affect its performance and the small molecule gases generated by decomposition), preventing these impurities from affecting the performance of the TPO and the subsequent processing; adding the extractant for devolatilization has a better effect than simply using high-strength vacuum negative pressure for devolatilization, and can more completely separate and remove the small molecule gases that affect the performance of the TPO and are generated by decomposition.

[0025] 7. In the present invention, by adjusting the screw combination of the twin-screw extruder and increasing the screw compression ratio, that is, using a co-rotating twin-screw extruder with a double vacuum and a screw length-diameter ratio of 40:1, the screw mixing ability is enhanced, so that the TPO material block is dispersed and mixed under the action of the twin-screws of the extruder, and undergoes high-strength shearing compression, continuously squeezing and melting the pores of the TPO, compacting it, and eliminating the pores therein.

[0026] 8. The present invention limits the diameter of the crushed material blocks to be between 8 mm and 18 mm. If the diameter is too small, the output of the crusher is low, the material loss is large, it is easy to generate dust, and it increases the difficulty of subsequent processing; while if the diameter of the crushed material is too large, it is relatively difficult for the solvent to completely impregnate, and it is not easy for the contained TPO resin and hard plastic to swell and separate. It is difficult to feed the material in the subsequent processing, and the feeder is easily stuck; in addition, the size of the material block directly affects the production capacity and output rate. When the size is small, the production capacity is low and the output rate is relatively low; when the size is too large, the swelling agent cannot completely swell the adhesive, it is difficult to degum, and a long stirring time is required, which also affects the production capacity and output rate. Detailed Embodiment

[0027] The following further details the present invention in conjunction with examples;

[0028] Example 1

[0029] It includes the following steps:

[0030] A. Sort and clean the scrapped workpieces containing TPO skin materials to remove different types of resins such as ABS, PC, PA and other impurities;

[0031] B. Crush the sorted and cleaned scrapped workpieces to obtain material blocks with a diameter of 8 - 18 mm;

[0032] C. Pour the crushed material blocks into a blender, add a swelling agent aqueous solution with a concentration of 15 wt% (prepared from methyl ethyl ketone and cyclohexanone in a volume ratio of methyl ethyl ketone: cyclohexanone = 1:1), heat to 80 °C, stir for 10 min, so that the adhesive between the TPO skin and the hard plastic (PP or ABS) swells and degums, and then the TPO skin and the hard plastic (PP or ABS) are degummed and separated. Then drain the swelling agent aqueous solution, add clean water for stirring and cleaning, and then use the density difference between the TPO skin and the hard plastic (PP or ABS) to stand and precipitate for separation, and fish out the TPO material blocks floating on the water surface;

[0033] D. Dehydrate the obtained TPO material blocks, put them into a high-speed mixer, add 2 wt% of the extraction agent (i.e., octamethylcyclotetrasiloxane) of the TPO material blocks, stir for 5 min, enter a co-rotating twin-screw extruder with double vacuum and a screw length-diameter ratio of 40:1 through a forced feeder, and extrude and defoam and pelletize under the parameter conditions of a screw temperature of 175 - 215 °C, a main screw rotation speed of 500 r / min, a forced feeder frequency of 20 Hz, and a double vacuum pressure of -0.08 MPa, and then cool, dry and pelletize.

[0034] Comparative Example 1

[0035] It includes the following steps:

[0036] A. Sort and clean the scrapped workpieces containing TPO skin materials, and remove different types of resins such as ABS, PC, PA and other impurities;

[0037] B. Crush the sorted and cleaned scrapped workpieces to obtain material blocks with a diameter of 5 - 7 mm;

[0038] C. Pour the crushed material blocks into a blender, add a 15 wt% swelling agent aqueous solution (prepared from methyl ethyl ketone and cyclohexanone according to a volume ratio of methyl ethyl ketone: cyclohexanone = 1:1), heat to 80 °C, and stir for 5 min to swell and degum the adhesive between the TPO skin and the hard plastic (PP or ABS), so that the TPO skin and the hard plastic (PP or ABS) are degummed and separated. Then drain the swelling agent aqueous solution, add clean water for stirring and cleaning, and then use the density difference between the TPO skin and the hard plastic (PP or ABS) to stand and precipitate for separation, and fish out the TPO material blocks floating on the water surface;

[0039] D. Dehydrate the obtained TPO material blocks, put them into a high-speed mixer, add 2 wt% extractant (i.e., octamethylcyclotetrasiloxane) of the TPO material blocks, stir for 5 min, and enter a co-rotating twin-screw extruder with double vacuum and a screw length-diameter ratio of 40:1 through a forced feeder. Extrude, defoam and granulate under the parameter conditions of a screw temperature of 175 - 215 °C, a main screw rotation speed of 400 r / min, a forced feeder frequency of 15 Hz, and a double vacuum pressure of -0.08 MPa, and then cool, dry and pelletize.

[0040] Comparative Example 2

[0041] It includes the following steps:

[0042] A. Sort and clean the scrapped workpieces containing TPO skin materials, and remove different types of resins such as ABS, PC, PA and other impurities;

[0043] B. Crush the sorted and cleaned scrapped workpieces to obtain material blocks with a diameter of 18 - 25 mm;

[0044] C. Pour the crushed material blocks into a blender, add a 15 wt% swelling agent aqueous solution (prepared from methyl ethyl ketone and cyclohexanone according to a volume ratio of methyl ethyl ketone: cyclohexanone = 1:1), heat to 80 °C, and stir for 15 min to swell and degum the adhesive between the TPO skin and the hard plastic (PP or ABS), so that the TPO skin and the hard plastic (PP or ABS) are degummed and separated. Then drain the swelling agent aqueous solution, add clean water for stirring and cleaning, and then use the density difference between the TPO skin and the hard plastic (PP or ABS) to stand and precipitate for separation, and fish out the TPO material blocks floating on the water surface;

[0045] D. Dehydrate the obtained TPO material blocks, put them into a high-speed mixer, add 2 wt% of the extraction agent (i.e., octamethylcyclotetrasiloxane) of the TPO material blocks, stir for 5 min, and then enter a co-rotating twin-screw extruder with double vacuum and a screw length-diameter ratio of 40:1 through a forced feeder. Extrude and defoam and pelletize under the parameter conditions that the screw temperature is 175 - 215 °C, the main screw rotation speed of the host is 350 r / min, the frequency of the forced feeder is 25 Hz, and the double vacuum pressure is maintained at -0.08 MPa, and then cool, dry, and pelletize.

[0046] Comparative Example 3

[0047] It includes the following steps:

[0048] A. Sort and clean the scrapped workpieces containing TPO skin materials, and remove impurities and different types of resins, such as ABS, PC, PA, etc.;

[0049] B. Crush the sorted and cleaned scrapped workpieces to obtain material blocks with a diameter of 8 - 18 mm;

[0050] C. Pour the crushed material blocks into a mixer, add methyl ethyl ketone aqueous solution as a swelling agent, heat to 80 °C, stir for 10 min to swell and degum the adhesive between the TPO skin and the hard plastic (PP or ABS), so that the TPO skin and the hard plastic (PP or ABS) are degummed and separated. Then drain the swelling agent aqueous solution, add clean water for stirring and cleaning, and then stand and precipitate and separate using the density difference between the TPO skin and the hard plastic (PP or ABS), and fish out the TPO material blocks floating on the water surface;

[0051] D. Dehydrate the obtained TPO material blocks, put them into a high-speed mixer, add 2 wt% of the extraction agent (i.e., octamethylcyclotetrasiloxane) of the TPO material blocks, stir for 5 min, and then enter a co-rotating twin-screw extruder with double vacuum and a screw length-diameter ratio of 40:1 through a forced feeder. Extrude and defoam and pelletize under the parameter conditions that the screw temperature is 175 - 215 °C, the main screw rotation speed of the host is 450 r / min, the frequency of the forced feeder is 20 Hz, and the double vacuum pressure is maintained at -0.08 MPa, and then cool, dry, and pelletize.

[0052] Comparative Example 4

[0053] It includes the following steps:

[0054] A. Sort and clean the scrapped workpieces containing TPO skin materials, and remove impurities and different types of resins, such as ABS, PC, PA, etc.;

[0055] B. Crush the sorted and cleaned scrapped workpieces to obtain material blocks with a diameter of 8 - 18 mm;

[0056] C. Pour the crushed material blocks into a blender, add an aqueous solution of a swelling agent with a concentration of 15 wt% (prepared from methyl ethyl ketone and cyclohexanone in a volume ratio of methyl ethyl ketone: cyclohexanone = 1:1), heat to 80 °C, and stir for 10 min to swell and debond the adhesive between the TPO skin and the hard plastic (PP or ABS), so that the TPO skin and the hard plastic (PP or ABS) are debonded and separated. Then drain the aqueous solution of the swelling agent, add clean water for stirring and cleaning, and separate by static precipitation using the density difference between the TPO skin and the hard plastic (PP or ABS), and fish out the TPO material blocks floating on the water surface;

[0057] D. Dehydrate the obtained TPO material blocks, put them into a high-speed mixer, stir for 5 min, and enter a co-rotating twin-screw extruder with double vacuum and a screw length-to-diameter ratio of 40:1 through a forced feeder. Extrude and defoam and pelletize under the parameter conditions of a screw temperature of 175 - 215 °C, a main screw rotation speed of 450 r / min, a forced feeder frequency of 20 Hz, and a double vacuum pressure of -0.08 MPa, and then cool, dry, and pelletize.

[0058] Perform performance tests on the products - TPO particles prepared in Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4, and the results are shown in Table 1 below.

[0059] Table 1

[0060] 。

[0061] From the above Table 1, through Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4, it can be found that:

[0062] 1. The size of the crushed material blocks in step B directly affects the production capacity and the output rate. When the size is small, the production capacity is low and the output rate is relatively low; when the size is too large, the swelling agent cannot completely swell the adhesive, it is difficult to debond, and a long stirring time is required, which also affects the production capacity and the output rate;

[0063] 2. Using methyl ethyl ketone and cyclohexanone in a volume ratio of methyl ethyl ketone: cyclohexanone = 1:1 has significantly stronger dissolving ability than using methyl ethyl ketone alone: when using methyl ethyl ketone alone, a small part of the adhesive of the crushed material is not completely swollen, so that the TPO is not separated, affecting the production capacity and the output rate;

[0064] 3. If the TPO melt is not extracted and devolatilized in combination with an extractant, and only a strong double vacuum is used alone, small molecule impurities in the TPO material blocks cannot be completely removed, thus affecting the subsequent processing. Therefore, an extractant needs to be added during extrusion and pelletizing to obtain a product - TPO particles with good physical properties, dense and smooth.

Claims

1. A method for recycling waste TPO skin materials, characterized in that It includes the following steps: A. Sort and clean the scrapped workpieces containing TPO skin materials to remove impurities; wherein, the impurities include resins of different types from the TPO skin materials. B. Crush the sorted and cleaned scrapped workpieces to obtain material blocks with a diameter of 8 mm to 18 mm. C. Pour the crushed material blocks into a blender, add a swelling agent aqueous solution, heat and stir for degumming and separation treatment, and collect the TPO material blocks obtained after degumming and separation; wherein, the swelling agent in the swelling agent aqueous solution is prepared from methyl ethyl ketone and cyclohexanone in a volume ratio of methyl ethyl ketone:cyclohexanone = 1:

1. D. Wash and dry the obtained TPO material blocks, put them into a high-speed mixer, add an extractant, stir, and feed them into a twin-screw extruder through a forced feeder for extrusion, defoaming and granulation, and then cool, dry and pelletize; wherein, the extractant is octamethylcyclotetrasiloxane.

2. The method for recycling waste TPO skin materials according to claim 1, wherein: The concentration of the swelling agent aqueous solution is 15 wt%.

3. The method for recycling waste TPO skin materials according to claim 2, wherein: The addition amount of the extractant is 2 wt% of the TPO material blocks.

4. The method for recycling waste TPO skin materials according to claim 3, wherein: In step C, the specific method for collecting the TPO material blocks obtained after degumming and separation is: after the degumming and separation treatment process is completed, drain the swelling agent aqueous solution inside, then add water and stir, let it stand for sedimentation and separation, and fish out the TPO material blocks floating on the water surface.

5. The method for recycling waste TPO skin materials according to claim 4, wherein: In step D, the twin-screw extruder is a co-rotating twin-screw extruder with double vacuum and a screw length-diameter ratio of 40:

1.

6. The method for recycling waste TPO skin materials according to claim 1 or 2 or 3 or 4 or 5, wherein: In step D, the specific process for extrusion, defoaming and granulation by the twin-screw extruder is: the screw temperature of the twin-screw extruder is 175°C to 215°C, the main screw rotation speed is 300 r / min to 500 r / min, the frequency of the forced feeder is 15 Hz to 20 Hz, and the double vacuum pressure is maintained at -0.08 MPa.