A method for toughening polylactic acid using waste polyurethane plastic track powder

Abstract

The present invention discloses a method for toughening polylactic acid using waste polyurethane plastic runway powder. First, the waste polyurethane plastic runway is crushed and size-screened; then the screened polyurethane powder is pretreated to be used as a toughening agent; finally, the pretreated polyurethane powder is melt-blended with polylactic acid in a certain proportion to obtain a toughened polylactic acid material. The present invention increases the compatibility and interface interaction between the waste polyurethane powder and polylactic acid by pretreating the waste polyurethane powder, and significantly improves the mechanical properties of the polylactic acid composite material, especially the elongation at break and the notched impact strength; at the same time, the waste polyurethane plastic runway powder is selected to turn waste into treasure, thereby realizing resource recycling. In addition, the preparation method of toughened polylactic acid provided by the present invention is simple, the process conditions are easy to control, and the operability is strong.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a method for toughening polylactic acid by utilizing waste polyurethane plastic track powder. Background Art

[0002] Polyurethane is widely used in the construction, automobile, coating and other industries due to its good stability, corrosion resistance and low density. At present, the annual output of polyurethane products in the world is about 30 million tons, accounting for 7.9% of the total plastic production. However, with the production and consumption of polyurethane, huge polyurethane waste is generated, and this rate is still growing at a very fast rate. At present, the transition to a circular economy is crucial for sustainable growth. In other words, better use of resources can bring not only environmental benefits but also economic benefits. Therefore, it is imperative to recycle waste polyurethane.

[0003] Polylactic acid (PLA) is a biodegradable polyester with high mechanical strength, high modulus, good biocompatibility, biodegradability and high transparency. It is also one of the most mature and widely used degradable plastics on the market. However, the inherent brittleness and poor toughness of PLA limit its application in many fields. Therefore, it is very meaningful and necessary to toughen polylactic acid.

[0004] Waste polyurethane, especially polyurethane used for plastic tracks, has a certain toughness and is the preferred material for toughening polylactic acid. Summary of the invention

[0005] In view of the problems pointed out in the above background technology, the present invention provides a method for toughening polylactic acid using waste polyurethane plastic track powder. The present invention increases the compatibility and interface interaction between waste polyurethane powder and polylactic acid by pretreating the waste polyurethane powder. After adding it to the polylactic acid matrix, the mechanical properties of the polylactic acid composite material, especially the elongation at break and the notched impact strength, are significantly improved. At the same time, waste polyurethane plastic track powder is selected to turn waste into treasure and realize resource recycling. In addition, the preparation method of toughened polylactic acid provided by the present invention is simple, the process conditions are easy to control, and the operability is strong.

[0006] The present invention discloses a method for toughening polylactic acid using waste polyurethane plastic track powder. First, the waste polyurethane plastic track is crushed and size-screened. Then, the screened polyurethane powder is pretreated to be used as a toughening agent. Finally, the pretreated polyurethane powder is melt-blended with polylactic acid in a certain ratio to obtain a toughened polylactic acid material.

[0007] The specific steps include:

[0008] S1: crush the waste polyurethane plastic track and select the size;

[0009] S2: pre-treating the screened polyurethane powder to use it as a toughening agent;

[0010] S3: melt-blending the pretreated and dried polyurethane powder and polylactic acid in a certain ratio to obtain a toughened polylactic acid material.

[0011] Preferably, in step S1, the waste polyurethane plastic track is washed with water and dried, then crushed with a high-speed crusher, and powder with a diameter of less than 0.5 mm is screened.

[0012] Preferably, in step S2, the screened powder is pretreated, including swelling and suspension polymerization processes:

[0013] The polyurethane powder is added to the acrylic ester monomer for swelling; then a proper amount of initiator is added to the acrylic ester monomer, deionized water is used as a dispersion medium, the temperature is raised and the mixture is reacted under stirring, and after the reaction is completed, the mixture is filtered, washed and dried.

[0014] Furthermore, the acrylic acid ester monomer is one of n-butyl acrylate, n-hexyl acrylate, n-octyl acrylate, n-decyl acrylate, n-dodecyl acrylate, or a combination thereof.

[0015] Furthermore, in order to enhance the interfacial bonding between the polyurethane powder and the polylactic acid matrix, allyl glycidyl ether, acrylic acid glycidyl ether, 4-hydroxybutyl acrylate glycidyl ether or methacrylate glycidyl ether is added during the swelling process.

[0016] Furthermore, in order to accelerate the swelling process, a proper amount of solvent may be added to the system, including toluene, xylene, N,N'-dimethylformamide, acetone, butanone, ethyl acetate or a mixed solvent thereof.

[0017] Furthermore, the initiator is dicumyl peroxide (DCP), azobisisobutyronitrile (AIBN) or dicumyl peroxide (BPO).

[0018] Furthermore, the reaction temperature is 60-80°C and the reaction time is 5h.

[0019] Preferably, in step S3, the amount of pretreated polyurethane powder added is 10-50 parts by mass, and the amount of polylactic acid added is 90-50 parts by mass.

[0020] Preferably, in step S3, before mixing, the polylactic acid particles are dried at a temperature of 80° C. for a drying time of 6 hours.

[0021] Preferably, in step S3, melt blending is carried out in a twin-screw extruder, the extrusion temperature is 160-190° C., and the screw speed is 50-100 rpm.

[0022] The beneficial effects of the present invention are embodied in:

[0023] The present invention utilizes waste polyurethane plastic runway powder to toughen polylactic acid, significantly improving the flexibility of polylactic acid, making it have strong flexibility and elasticity, and improving the elongation at break and notched impact strength of polylactic acid composite materials. At the same time, waste polyurethane plastic runway powder is selected to turn waste into treasure and realize resource recycling. In addition, the preparation method of toughened polylactic acid provided by the present invention is simple, and the process conditions are easy to control, which is conducive to promotion and application. DETAILED DESCRIPTION

[0024] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention, and should not be construed as limiting the scope of protection of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0025] The substances listed in the examples of the present invention are all commercially available and easily available.

[0026] Embodiment 1:

[0027] After washing and drying the waste polyurethane plastic track with water, crush it with a high-speed crusher, and screen to obtain powder with a diameter of ≤0.5mm. Take 100g of powder and place it in 200mL of n-butyl acrylate for swelling, add 2g of AIBN, and add 50mL of ethyl acetate and 50mL of allyl glycidyl ether. Place the swollen polyurethane powder in 2L of deionized water, stir evenly, ultrasonically disperse for 30min, heat to 80℃, stir at a speed of 500r / min, stir for 5h, filter, wash, and dry to obtain the treated polyurethane powder.

[0028] The preparation method of toughened polylactic acid comprises:

[0029] 1) In a drying device, place the polylactic acid particles in a vacuum drying oven at 80° C. and dry for 6 hours.

[0030] 2) Mix the pretreated polyurethane powder and polylactic acid according to the proportion, 100 parts of polylactic acid and 10 parts of the treated polyurethane powder in a twin-screw extruder, the extrusion temperature is 160-190° C., and the screw speed is 50-100 r / min.

[0031] Embodiment 2:

[0032] After washing and drying the waste polyurethane plastic track with water, crush it with a high-speed crusher, and screen to obtain powder with a size of ≤0.5mm. Take 200g of powder and place it in 400mL of n-hexyl acrylate for swelling, add 4g of AIBN, and add 100mL of ethyl acetate and 100mL of allyl glycidyl ether, place the swollen polyurethane powder in 4L of deionized water, stir evenly, ultrasonically disperse for 30min, heat to 80℃, stir at a speed of 500r / min, stir for 5h, filter, wash, and dry to obtain the treated polyurethane powder.

[0033] The preparation method of toughened polylactic acid comprises:

[0034] 1) In a drying device, place the polylactic acid particles in a vacuum drying oven at 80° C. and dry for 6 hours.

[0035] 2) Mix the pretreated polyurethane powder and polylactic acid in proportion, 100 parts of polylactic acid and 20 parts of the treated polyurethane powder in a twin-screw extruder at an extrusion temperature of 160-190° C. and a screw speed of 50-100 r / min.

[0036] Embodiment 3:

[0037] After washing and drying the waste polyurethane plastic track with water, crush it with a high-speed crusher, and screen to obtain powder with a size of ≤0.5mm. Take 300g of powder and place it in 600mL of n-octyl acrylate for swelling, add 6g of DCP, and add 150mL of ethyl acetate and 150mL of 4-hydroxybutyl acrylate glycidyl ether, place the swollen polyurethane powder in 6L of deionized water, stir evenly, ultrasonically disperse for 30min, heat to 80℃, stir at a speed of 500r / min, stir for 5h, filter, wash, and dry to obtain the treated polyurethane powder.

[0038] The preparation method of toughened polylactic acid comprises:

[0039] 1) In a drying device, place the polylactic acid particles in a vacuum drying oven at 80° C. and dry for 6 hours.

[0040] 2) Mix the pretreated polyurethane powder and polylactic acid according to the proportion, 100 parts of polylactic acid and 30 parts of the treated polyurethane powder in a twin-screw extruder, the extrusion temperature is 160-190° C., and the screw speed is 50-100 r / min.

[0041] Embodiment 4:

[0042] After washing and drying the waste polyurethane plastic track with water, crush it with a high-speed crusher, and screen to obtain powder with a size of ≤0.5mm. Take 400g of powder and place it in 800mL of n-decyl methacrylate for swelling, add 8g of AIBN, and add 200mL of toluene and 200mL of glycidyl acrylate to it, place the swollen polyurethane powder in 8L of deionized water, stir evenly, ultrasonically disperse for 30min, heat to 80℃, stir at a speed of 500r / min, stir for 5h, filter, wash, and dry to obtain the treated polyurethane powder.

[0043] The preparation method of toughened polylactic acid comprises:

[0044] 1) In a drying device, place the polylactic acid particles in a vacuum drying oven at 80° C. and dry for 6 hours.

[0045] 2) Mix the pretreated polyurethane powder and polylactic acid in proportion, 100 parts of polylactic acid and 40 parts of the treated polyurethane powder in a twin-screw extruder at an extrusion temperature of 160-190° C. and a screw speed of 50-100 r / min.

[0046] Embodiment 5:

[0047] After washing and drying the waste polyurethane plastic track with distilled water, crush it with a small high-speed crusher, and screen to obtain powder with a diameter of ≤0.5mm. Take 500g of powder and place it in 1L of n-dodecyl methacrylate for swelling, add an appropriate amount of 10g of BPO, and add 250mL of acetone and 250mL of glycidyl methacrylate to it, place the swollen polyurethane powder in 10L of deionized water, stir evenly, ultrasonically disperse for 30min, heat to 80℃, stir at a speed of 500r / min, stir for 5h, filter, wash, and dry to obtain the treated polyurethane powder.

[0048] The preparation method of toughened polylactic acid comprises:

[0049] 1) In a drying device, place the polylactic acid particles in a vacuum drying oven at 80° C. and dry for 6 hours.

[0050] 2) The pretreated polyurethane powder is mixed with polylactic acid according to a ratio of 100 parts of polylactic acid and 50 parts of the treated polyurethane powder in a twin-screw extruder at an extrusion temperature of 160-190° C. and a screw speed of 50-100 r / min.

[0051] Comparative Example 1:

[0052] Polylactic acid particles without any treatment.

[0053] Comparative Example 2:

[0054] The preparation method of toughened polylactic acid comprises:

[0055] 1) In a drying device, the polylactic acid particles and the untreated polyurethane powder are placed in a vacuum drying oven at 80° C. and dried for 6 hours.

[0056] 2) Mix untreated polyurethane powder and polylactic acid according to the proportion, 100 parts of polylactic acid and 10 parts of untreated polyurethane powder in a twin-screw extruder, the extrusion temperature is 160-190° C., and the screw speed is 50-100 rpm.

[0057] Performance test standards and methods:

[0058] The mechanical properties of the prepared polylactic acid material were measured, and the results are shown in Table 1 below.

[0059] Table 1 Properties of materials prepared in Examples 1-5 and Comparative Examples

[0060] Tensile strength / MPa Elongation at break / % <![CDATA[Notched impact strength, KJ / m 2 > Example 1 24 98 5.5 Example 2 24.8 120 9.0 Example 3 25.2 148 12.2 Example 4 25.9 162 25.9 Example 5 26.3 180 39.6 Comparative Example 1 69 10 2.5 Comparative Example 2 45 8 1.6

[0061] From the performance comparison of the materials prepared by the above-mentioned Examples 1-5 and the comparative examples, it can be seen that compared with the comparative example 1, the tensile strength of Example 1, Example 2, Example 3, Example 4, and Example 5 is reduced, but the elongation at break is significantly improved. Compared with Example 1, the elongation at break and the notched impact strength of Comparative Example 2 are improved, indicating that the pretreated polyurethane powder has increased the compatibility and interface interaction with polylactic acid. Compared with Comparative Example 1, the elongation at break of Example 5 is increased by 18 times, and the notched impact strength is increased by 15.8 times, which improves the flexibility and impact strength of the polylactic acid material, while turning waste into treasure and realizing the resource utilization of waste polyurethane.

[0062] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of specific technical features in any manner. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations. However, these simple modifications and combinations should also be regarded as the contents disclosed by the present invention, and all belong to the scope of protection of the present invention.

Claims

1. A method for toughening polylactic acid using waste polyurethane plastic track powder, characterized in that The steps include: S1: crush the waste polyurethane plastic track and select the size; S2: pre-treating the screened polyurethane powder to use it as a toughening agent; S3: melt-blending the pretreated and dried polyurethane powder and polylactic acid in a certain ratio to obtain a toughened polylactic acid material; In step S2, the screened powder is pretreated, including swelling and suspension polymerization processes: The polyurethane powder is added to the acrylic ester monomer for swelling; then an initiator is added to the acrylic ester monomer, deionized water is used as a dispersion medium, the temperature is raised and the mixture is reacted under stirring, and after the reaction is completed, the mixture is filtered, washed and dried; The acrylic acid ester monomer is one of n-butyl acrylate, n-hexyl acrylate, n-octyl acrylate, n-decyl acrylate, n-dodecyl acrylate, or a combination thereof; In order to enhance the interfacial bonding between the polyurethane powder and the polylactic acid matrix, allyl glycidyl ether, acrylic acid glycidyl ether, 4-hydroxybutyl acrylate glycidyl ether or methacrylate glycidyl ether is added during the swelling process; In step S3, the amount of pretreated polyurethane powder added is 10-50 parts by weight, and the amount of polylactic acid added is 90-50 parts by weight.

2. The method according to claim 1, characterized in that: In step S1, the waste polyurethane plastic track is washed with water and dried, then crushed with a high-speed crusher, and powder with a diameter less than 0.5 mm is screened.

3. The method according to claim 1, characterized in that: In order to accelerate the swelling process, an appropriate amount of solvent is added to the system, including toluene, xylene, N,N'-dimethylformamide, acetone, butanone, ethyl acetate or a mixed solvent thereof.

4. The method according to claim 1, characterized in that: The initiator is azobisisobutyronitrile or dicumyl peroxide.

5. The method according to claim 1, characterized in that: The reaction temperature is 60-80°C and the reaction time is 5 h.

6. The method according to claim 1, characterized in that: In step S3, melt blending is carried out in a twin-screw extruder, the extrusion temperature is 160-190° C., and the screw speed is 50-100 rpm.