A method for reinforcing and toughening recycled PET using waste rock wool and epoxidized natural rubber

Abstract

This invention discloses a method for reinforcing and toughening recycled PET using waste rock wool and epoxidized natural rubber, belonging to the field of functional polymers. The invention synthesizes modified rock wool by grafting epoxidized natural rubber onto the surface of waste rock wool fibers, and strengthens the phase interface between the modified rock wool and PET by utilizing the reaction of epoxy residues with recycled PET at a melting temperature, ultimately forming a multiphase, multi-layered structure of rigid rock wool fiber-flexible natural rubber-rigid PET. The resulting composite material exhibits improved impact strength and tensile strength.

Description

Technical Field

[0001] This invention belongs to the field of functional polymers, specifically relating to a method for reinforcing and toughening recycled PET using waste rock wool and epoxidized natural rubber. Background Technology

[0002] Polyethylene terephthalate (PET) is widely used in synthetic fiber clothing, beverage packaging, and new display technologies. However, this consumption also generates a huge amount of waste PET. PET has a stable molecular structure and is difficult to degrade, which can have adverse effects on the natural environment. Furthermore, its disposable nature results in significant resource waste. Recycling and reusing waste PET materials is crucial for achieving green and sustainable development.

[0003] Bamboo fiber can be reinforced and toughened by synergistic modification with low-temperature oxygen plasma and ultrasound, combined with dynamic vulcanization of natural rubber in a twin-screw extruder, supercritical CO2-assisted blending, and ester crosslinking of chain extenders with PET (CN 120718393 A). In this method, plasma and ultrasound modification are used to improve the dispersibility of bamboo fiber. The process is relatively complex and increases the production cost of composite materials based on recycled PET. Plastic flooring substrate can be made by mixing recycled PET, stone powder, chain extenders, stearic acid, oil, and elastomers (CN 119899499 A). In this method, recycled PET is used as an adhesive, but the amount used is small, resulting in a relatively small total amount of recycled PET that can be disposed of. By blending recycled PET with fresh PET, glass fiber, plasticizers, and toughening agents, the final product material has good mechanical properties and flowability (CN110330770 B). In this method, recycled PET accounts for only 10% to 30% of the total material weight, while fresh PET accounts for 20% to 40%. Summary of the Invention

[0004] This invention provides a method for reinforcing and toughening recycled PET using waste rock wool and epoxidized natural rubber. Modified rock wool is synthesized by grafting epoxidized natural rubber onto the surface of waste rock wool fibers. The phase interface between the modified rock wool and PET is strengthened by utilizing the reaction of epoxy residues with recycled PET at a melting temperature, ultimately forming a multiphase, multi-layered structure of rigid rock wool fiber-flexible natural rubber-rigid PET. The resulting composite material exhibits improved impact strength and tensile strength.

[0005] This invention relates to a method for reinforcing and toughening recycled PET using waste rock wool and epoxidized natural rubber, comprising the following steps:

[0006] Step 1: Crush the waste rock wool, wash it, and dry it;

[0007] Step 2: Add the crushed rock wool (RW) to a water / ethanol mixed solvent containing a silane coupling agent, and then dry the solution to obtain amino-modified RW;

[0008] Step 3: Mix amino-modified RW and epoxidized natural rubber (ENR) with some recycled PET in an internal mixer until homogeneous. Add a small amount of sodium glycinate during the mixing process. Finally, crush the cooled material.

[0009] Step 4: The crushed material from Step 3 is mixed with the remaining recycled PET in a suitable ratio and then extruded using an extruder to obtain the RW-ENR@PET composite material.

[0010] In step 1, the waste rock wool comes from building insulation materials or soilless cultivation substrate. The length of the crushed rock wool is 50 ~ 150 μm. It is washed with 10% sodium hydroxide solution for 30 minutes and then washed with clean water 3 times.

[0011] In step 2, the water / ethanol mixed solvent containing the dissolved silane coupling agent is composed of the silane coupling agent, water, and ethanol. After mixing, the pH is adjusted to 4-5 with acetic acid, and the mixture is alcoholyzed at room temperature for 3-4 hours. The mass ratio of water:ethanol:silane coupling agent is 8:72:20.

[0012] In step 2, the mass ratio of the crushed rock wool to the silane coupling agent is 10:1 to 10:1.5.

[0013] Furthermore, the silane coupling agent is silane coupling agent KH-550.

[0014] In step 3, the mass ratio of amino-modified RW, ENR, and sodium glycine is 1~10:1:0.1; the mass ratio of amino-modified RW to partially recycled PET is 1:1.

[0015] In step 3, the mixing temperature of the internal mixer is 260 ℃ ~ 280 ℃, and the mixing sequence is to first add some recycled PET, and after it is fully melted, add amino-modified RW, ENR and sodium glycine.

[0016] Furthermore, before mixing, 0.5% of antioxidant 1010 and 0.5% of phosphite antioxidant PEP-36 by total mass of ENR are added.

[0017] In step 4, the ratio of amino-modified RW to the total mass of recycled PET (i.e., the total amount of recycled PET added in steps 3 and 4) is 1:9 to 5:5; the extruder melt mixing temperature is 260℃ to 280℃.

[0018] The recycled PET comes from crushed beverage bottles or packaging boxes.

[0019] The beneficial effects of this invention are reflected in:

[0020] This invention improves the impact and tensile strength of recycled PET while enhancing the recycling value of waste rock wool, resulting in significant economic and environmental benefits. The invention involves reacting KH-550-modified, amino-containing rock wool fibers with epoxidized natural rubber, grafting natural rubber onto the surface of the rock wool fibers. When this RW@ENR is melt-mixed with recycled PET, the residual epoxy groups on the ENR react with the terminal hydroxyl or carboxyl groups of the PET, forming a robust phase interface and constructing a multi-phase interface structure of rock wool-natural rubber-PET matrix. The rock wool filling effectively increases the phase volume of natural rubber, achieving toughening of recycled PET with less rubber. Furthermore, the reaction of the amino group of sodium glycinate with the epoxidized natural rubber grafts sodium carboxylate onto the rubber molecular chain, thereby endowing RW@ENR with a role in promoting PET nucleation and simultaneously improving the tensile strength of the recycled PET composite material. This composite material can be used in applications requiring excellent comprehensive mechanical properties, including automotive bumpers. Attached Figure Description

[0021] Figure 1 An optical photograph of the crushed rock wool.

[0022] Figure 2 The images show polarized light microscope images of PET and PET composites after isothermal crystallization at 170 °C for 2 h. Image (a) shows PET (Comparative Example 1), image (b) shows RW@PET (Comparative Example 2), and image (c) shows RW-ENR@PET (Example 1). The scale bar in all images is 50 micrometers. Detailed Implementation

[0023] The technical solution of the present invention will be further analyzed and explained through specific embodiments below.

[0024] The PET used in the embodiments of this invention comes from defective packaging boxes produced during the production process of Anhui Lesui New Materials Co., Ltd., and the epoxidized natural rubber is a product of Shanghai Wanxiang New Materials Co., Ltd.

[0025] Example 1:

[0026] Waste rock wool was crushed into short fibers of approximately 50-150 μm in length using a shredder. The fibers were first washed with a 10% sodium hydroxide solution for 30 minutes, then washed three times with clean water, and subsequently dried at 105 °C. A mixture of 12 g water, 108 g ethanol, and 30 g silane KH-550 was prepared, and the pH was adjusted to 4-5 with acetic acid. The mixture was then alcoholyzed at room temperature for 3-4 hours. 300 g of rock wool fibers were weighed and placed in the silane solution, reacted at 80 °C for 2 hours, and then the remaining solution was dried to obtain amino-modified RW. The internal mixer was cleaned and heated to 260-280 °C. 300 g recycled PET was added, and after melting, amino-modified RW, 30 g epoxidized natural rubber, and 3 g sodium glycine were added. The mixture was stirred for 5-10 minutes at a speed of 30-60 rpm. The resulting product was then pulverized. Take 600 grams of this product and melt-extrude it with 350 grams of recycled PET using an extruder at 260-280 ℃ to obtain a PET composite material toughened with waste rock wool. The ratio of ENR, amino-modified RW to PET is approximately 0.045 : 0.45 : 1.

[0027] Example 2:

[0028] Waste rock wool was crushed into short fibers of approximately 50-150 μm in length using a shredder. The fibers were first washed with a 10% sodium hydroxide solution for 30 minutes, then washed three times with clean water, and subsequently dried at 105 °C. A mixture of 12 g water, 108 g ethanol, and 30 g silane KH-550 was prepared, and the pH was adjusted to 4-5 with acetic acid. The mixture was then alcoholyzed at room temperature for 3-4 hours. 300 g of rock wool fibers were weighed and placed in the silane solution, reacted at 80 °C for 2 hours, and then the remaining solution was dried to obtain amino-modified RW. The internal mixer was cleaned and heated to 260-280 °C. 300 g recycled PET was added, and after melting, amino-modified RW, 60 g epoxidized natural rubber, and 6 g sodium glycine were added. The mixture was stirred for 5-10 minutes at a speed of 30-60 rpm. The resulting product was then pulverized. Take 600 grams of this product and melt-extrude it with 305 grams of recycled PET using an extruder at 260-280 ℃ to obtain a PET composite material toughened with waste rock wool. The ratio of ENR, amino-modified RW to PET is approximately 0.094 : 0.47 : 1.

[0029] Example 3:

[0030] Waste rock wool was crushed into short fibers of approximately 50-150 μm in length using a shredder. The fibers were first washed with a 10% sodium hydroxide solution for 30 minutes, then washed three times with clean water, and subsequently dried at 105 °C. A mixture of 12 g water, 108 g ethanol, and 30 g silane KH-550 was prepared, and the pH was adjusted to 4-5 with acetic acid. The mixture was then alcoholyzed at room temperature for 3-4 hours. 300 g of rock wool fibers were weighed and placed in the silane solution, reacted at 80 °C for 2 hours, and then the remaining solution was dried to obtain amino-modified RW. The internal mixer was cleaned and heated to 260-280 °C. 300 g recycled PET was added, and after melting, amino-modified RW, 90 g epoxidized natural rubber, and 9 g sodium glycine were added. The mixture was stirred for 5-10 minutes at a speed of 30-60 rpm. The resulting product was then pulverized. Take 600 grams of this product and melt-extrude it with 265 grams of recycled PET using an extruder at 260-280 ℃ to obtain a PET composite material toughened with waste rock wool. The ratio of ENR, amino-modified RW to PET is approximately 0.15 : 0.49 : 1.

[0031] Example 4:

[0032] Waste rock wool was crushed into short fibers of approximately 50-150 μm in length using a shredder. The fibers were first washed with a 10% sodium hydroxide solution for 30 minutes, then washed three times with clean water, and subsequently dried at 105 °C. A mixture of 12 g water, 108 g ethanol, and 30 g silane KH-550 was prepared, and the pH was adjusted to 4-5 with acetic acid. The mixture was then alcoholyzed at room temperature for 3-4 hours. 300 g of rock wool fibers were weighed and placed in the silane solution, reacted at 80 °C for 2 hours, and then the remaining solution was dried to obtain amino-modified RW. The internal mixer was cleaned and heated to 260-280 °C. 300 g recycled PET was added, and after melting, amino-modified RW, 120 g epoxidized natural rubber, and 12 g sodium glycine were added. The mixture was stirred for 5-10 minutes at a speed of 30-60 rpm. The resulting product was then pulverized. Take 600 grams of this product and melt-extrude it with 230 grams of recycled PET using an extruder at 260-280 ℃ to obtain a PET composite material toughened with waste rock wool. The ratio of ENR, amino-modified RW to PET is approximately 0.21 : 0.52 : 1.

[0033] Example 5:

[0034] Waste rock wool was crushed into short fibers of approximately 50-150 μm in length using a shredder. The fibers were first washed with a 10% sodium hydroxide solution for 30 minutes, then washed three times with clean water, and subsequently dried at 105 °C. A mixture of 12 g water, 108 g ethanol, and 30 g silane KH-550 was prepared, and the pH was adjusted to 4-5 with acetic acid. The mixture was then alcoholyzed at room temperature for 3-4 hours. 300 g of rock wool fibers were weighed and placed in the silane solution, reacted at 80 °C for 2 hours, and then the remaining solution was dried to obtain amino-modified RW. The internal mixer was cleaned and heated to 260-280 °C. 300 g recycled PET was added, and after melting, amino-modified RW, 150 g epoxidized natural rubber, and 15 g sodium glycine were added. The mixture was stirred for 5-10 minutes at 30-60 rpm. The resulting product was then pulverized. Take 600 grams of this product and melt-extrude it with 195 grams of recycled PET using an extruder at 260-280 ℃ to obtain a PET composite material toughened with waste rock wool. The ratio of ENR, amino-modified RW to PET is approximately 0.27 : 0.55 : 1.

[0035] Comparative Example 1:

[0036] 1000 grams of recycled PET is melt-granulated.

[0037] The granulated composite material is then processed into standard samples using an injection molding process for mechanical property testing.

[0038] Comparative Example 2:

[0039] 200g of amino-modified RW prepared according to the method described in Example 1 was melt-granulated with 200g of recycled PET in an internal mixer at 260°C to 280°C. Then it was melt-granulated with 600g of recycled PET to obtain RW@PET composite material.

[0040] The granulated composite material is then processed into standard samples using an injection molding process for mechanical property testing.

[0041] The advantages of this invention will be illustrated below with specific data:

[0042] Table 1. Comparison of notched impact strength and tensile strength of PET composite materials in the examples and comparative examples.

[0043]

[0044] The impact strength in the table was determined according to national standard GB / T 1843-2008, and the tensile strength was determined according to national standard GB / T 1040.1-2025.

[0045] As shown in Table 1, the impact strength of all composite materials in Examples 1 to 5 is higher than that of the recycled PET in Comparative Example 1, and the tensile strength of all composite materials in Examples 1 to 5 is higher than that of the recycled PET in Comparative Example 1. Waste rock wool fiber and epoxidized natural rubber have a toughening and reinforcing effect on recycled PET. In Comparative Example 2, the tensile strength of the composite material was significantly improved after the KH-550 modified rock wool fiber was melt-mixed with PET, showing a significant reinforcing effect. However, since epoxidized natural rubber was not used, the impact strength of the recycled PET was not high.

[0046] from Figure 1 As can be seen, the length of the rock wool fibers after crushing is approximately 50 to 150 μm.

[0047] from Figure 2 The results show that PET has the largest crystal size, RW@PET has a relatively large crystal size, and the RW-ENR@PET composite material has the smallest crystal size. This indicates that while RW promotes PET crystallization, RW-ENR has the best nucleation effect on PET, which is clearly related to the grafting of sodium glycinate onto the epoxidized natural rubber.

Claims

1. A method for reinforcing and toughening recycled PET using waste rock wool and epoxidized natural rubber, characterized in that... Modified rock wool is synthesized by grafting epoxy natural rubber onto the fiber surface of waste rock wool. The phase interface between the modified rock wool and PET is strengthened by utilizing the reaction of epoxy residues with recycled PET at the melting temperature, ultimately forming a multiphase, multi-layered structure of rigid rock wool fiber-flexible natural rubber-rigid PET, thereby enhancing and toughening the material. The process includes the following steps: Step 1: Crush the waste rock wool, wash it, and dry it; Step 2: Add the crushed rock wool to a water / ethanol mixed solvent containing a silane coupling agent, and then dry the solution to obtain amino-modified RW; Step 3: Mix amino-modified RW and epoxidized natural rubber with some recycled PET in an internal mixer until homogeneous. Add sodium glycinate during the mixing process, and finally crush the cooled material. Step 4: The crushed material from Step 3 is melt-mixed and extruded with the remaining recycled PET using an extruder to obtain the RW-ENR@PET composite material.

2. The method according to claim 1, characterized in that: In step 1, the pulverized rock wool is 50 ~ 150 μm in length, and is washed with 10% sodium hydroxide solution and then washed with clean water.

3. The method according to claim 1, characterized in that: In step 2, the water / ethanol mixed solvent containing the silane coupling agent is composed of silane coupling agent, water and ethanol. After mixing, the pH is adjusted to 4-5 with acetic acid and alcoholyzed at room temperature for 3-4 hours.

4. The method according to claim 3, characterized in that: In the water / ethanol mixed solvent containing the dissolved silane coupling agent, the mass ratio of water:ethanol:silane coupling agent is 8:72:

20.

5. The method according to claim 1, 3, or 4, characterized in that: In step 2, the mass ratio of the crushed rock wool to the silane coupling agent is 10:1 to 10:1.

5.

6. The method according to claim 1, characterized in that: In step 3, the mass ratio of amino-modified RW, epoxidized natural rubber, and sodium glycinate is 1~10:1:0.1; the mass ratio of amino-modified RW to partially recycled PET is 1:

1.

7. The method according to claim 1, characterized in that: In step 3, the mixing temperature of the internal mixer is 260 ℃ ~ 280 ℃. The mixing sequence is to first add some recycled PET, and after it is fully melted, add amino-modified RW, ENR and sodium glycinate and mix.

8. The method according to claim 7, characterized in that: Before mixing, add 0.5% of antioxidant 1010 and 0.5% of phosphite antioxidant PEP-36 by weight of the total epoxidized natural rubber.

9. The method according to claim 1, characterized in that: In step 4, the total mass ratio of amino-modified RW to recycled PET is 1:9 to 5:5; the extruder melt mixing temperature is 260℃ to 280℃.

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