POLYAMIDE RECYCLING PROCESS AND POLYAMIDE OBTAINED BY RECYCLING PROCESS

Abstract

A recycling process for a polyamide waste material includes the following steps: adding a polyamide waste material into a mixed solvent to obtain a solution, heating the solution to 50° C. to a reflux temperature of the solution, conducting stirring for dissolution, and then conducting decolorization treatment and filtration to obtain a polyamide solution; and adding the polyamide solution into water, precipitating polyamide as a solid in deionized water, and conducting separation to obtain recycled polyamide. The mixed solvent includes, in parts by weight, 10-30 parts of phenol and 15-40 parts of toluene.

Claims

1. A polyamide recycling process, comprising following steps: adding a polyamide waste material into a mixed solvent to obtain a solution, heating the solution to 50° C. to a reflux temperature of the solution, conducting stirring for dissolution, and then conducting decolorization treatment and filtration to obtain a polyamide solution; and adding the polyamide solution into deionized water, precipitating polyamide in the deionized water, and conducting separation to obtain recycled polyamide; wherein the mixed solvent comprises, in parts by weight, 10-30 parts of phenol and 15-40 parts of toluene; and a weight ratio of the polyamide waste material to the mixed solvent is 1:10 to 1:2.

2. The polyamide recycling process according to claim 1, wherein after the polyamide waste material is added into the mixed solvent to obtain the solution, the solution is heated to 100° C. to the reflux temperature of the solution, and stirred for dissolution, and then the decolorization treatment and the filtration treatment are subsequently conducted.

3. The polyamide recycling process according to claim 1, wherein a decolorizing agent is added during the decolorization treatment, and a weight ratio of the decolorizing agent to the polyamide waste material is 1:8 to 1:12; and the solution is heated to 50° C. to the reflux temperature of the solution, subjected the solution to heat preservation for 0.5-2 hours, cooled the solution to a temperature of less than 50° C., and then filtered the solution to obtain the polyamide solution.

4. The polyamide recycling process according to claim 1, wherein a weight ratio of the polyamide solution to the deionized water is 1:5 to 1:50.

5. The polyamide recycling process according to claim 1, wherein the mixed solvent further comprises, in parts by weight, one or more of 0-5 parts of methanol, 0-20 parts of o-cresol, or 0-20 parts of benzyl alcohol.

6. The polyamide recycling process according to claim 1, wherein the precipitated polyamide has a temperature of 0-50° C.

7. The polyamide recycling process according to claim 3, wherein the decolorizing agent is at least one selected from activated carbon and activated clay.

8. The polyamide recycling process according to claim 1, wherein the polyamide waste material is at least one selected from an aliphatic polyamide waste material and a semi-aromatic polyamide waste material; the aliphatic polyamide waste material is at least one selected from a PA6 waste material, a PA66 waste material, a PA12 waste material, a PA1010 waste material, and a PA1012 waste material; and the semi-aromatic polyamide waste material is at least one selected from a PA6T waste material, a PA10T waste material, a PA10T10I waste material, a PA10T1010 waste material, a PA10T1012 waste material, and a PA10T6T waste material.

9. The polyamide recycling process according to claim 1, wherein further comprising a step of pulverization before the polyamide waste material is added into the mixed solvent.

10. Polyamide obtained by the polyamide recycling process according to claim 1, wherein a content of terminal carboxyl in the polyamide is in a range of 10-40 mol/t, a crystallization half-peak width is in a range of 6-12° C., and a crystallization enthalpy is in a range of -40 J/g to -60 J/g.

11. Polyamide obtained by the polyamide recycling process according to claim 2, wherein a content of terminal carboxyl in the polyamide is in a range of 10-40 mol/t, a crystallization half-peak width is in a range of 6-12° C., and a crystallization enthalpy is in a range of -40 J/g to -60 J/g.

12. Polyamide obtained by the polyamide recycling process according to claim 3, wherein a content of terminal carboxyl in the polyamide is in a range of 10-40 mol/t, a crystallization half-peak width is in a range of 6-12° C., and a crystallization enthalpy is in a range of -40 J/g to -60 J/g.

13. Polyamide obtained by the polyamide recycling process according to claim 4, wherein a content of terminal carboxyl in the polyamide is in a range of 10-40 mol/t, a crystallization half-peak width is in a range of 6-12° C., and a crystallization enthalpy is in a range of -40 J/g to -60 J/g.

14. Polyamide obtained by the polyamide recycling process according to claim 5, wherein a content of terminal carboxyl in the polyamide is in a range of 10-40 mol/t, a crystallization half-peak width is in a range of 6-12° C., and a crystallization enthalpy is in a range of -40 J/g to -60 J/g.

15. Polyamide obtained by the polyamide recycling process according to claim 6, wherein a content of terminal carboxyl in the polyamide is in a range of 10-40 mol/t, a crystallization half-peak width is in a range of 6-12° C., and a crystallization enthalpy is in a range of -40 J/g to -60 J/g.

16. Polyamide obtained by the polyamide recycling process according to claim 7, wherein a content of terminal carboxyl in the polyamide is in a range of 10-40 mol/t, a crystallization half-peak width is in a range of 6-12° C., and a crystallization enthalpy is in a range of -40 J/g to -60 J/g.

17. Polyamide obtained by the polyamide recycling process according to claim 8, wherein a content of terminal carboxyl in the polyamide is in a range of 10-40 mol/t, a crystallization half-peak width is in a range of 6-12° C., and a crystallization enthalpy is in a range of -40 J/g to -60 J/g.

18. Polyamide obtained by the polyamide recycling process according to claim 9, wherein a content of terminal carboxyl in the polyamide is in a range of 10-40 mol/t, a crystallization half-peak width is in a range of -12° C., and a crystallization enthalpy is in a range of -40 J/g to -60 J/g.

Description

DESCRIPTION OF THE EMBODIMENTS

[0022] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments are favorable for persons skilled in the art to further understand the present invention, and are not intended to limit the present invention in any manner. It should be noted that various modifications and improvements may be made by persons of ordinary skill in the art without departing from the concept of the present invention. All the modifications and improvements belong to the protection scope of the present invention.

[0023] Sources of raw materials used in the present invention are as follows.

[0024] A polyamide waste material PA12 is derived from recycled materials such as plumbing pipes and peripheral parts of automobile engines, includes a small amount of a toner, and theoretically has a PA12 content of about 95%-97%.

[0025] A polyamide waste material PA66 is derived from recycled materials of gears, bearings and other parts of mechanical equipment, includes reinforced glass fibers, and theoretically has a PA66 content of about 65%-70%.

[0026] A polyamide waste material PA10T is derived from recycled materials of peripheral parts of engines, includes reinforced glass fibers, and theoretically has a PA10T content of about 60%-70%. Phenol is industrially pure.

[0027] Toluene is industrially pure.

[0028] Methanol is industrially pure.

[0029] Benzyl alcohol is industrially pure.

[0030] O-cresol is industrially pure.

[0031] Various property test methods are as follows.

[0032] (1) Content of terminal carboxyl: The contents of terminal amino and terminal carboxyl in a polymer are measured by a potentiometric titrator. 0.45 g of a material is weighed, and 50 mL of preheated and dissolved o-cresol is added and heated for reflux until a sample is dissolved. The sample is put in a water tank at 50° C., and cooled to 50° C. 0.5 mL of a formaldehyde solution is added, and a magtron stirring solution is added to obtain a mixed solution. An electrode test part of an automatic potentiometric titrator is soaked in the mixed solution, and a calibrated KOH-ethanol solution is used to titrate the content of the terminal carboxyl at the test end.

[0033] (2) Crystallization half-peak width: With reference to the standard ASTM D3418-2003, during a test at a flow rate of 20 mL/min under the protection of nitrogen atmosphere, a sample is heated from 30° C. to 350° C. at a heating rate of 10° C./min, subjected to heat preservation at 350° C. for 5 minutes, and then cooled to 50° C. at a cooling rate of 10° C./min. At this time, the crystallization peak temperature in a crystallization curve is used as a melting point, and the crystallization half-peak width is in a temperature range of a crystallization peak at ½ of a crystallization peak height.

[0034] (3) Crystallization enthalpy: With reference to the standard ASTM D3418-2003, during a test at a flow rate of 20 mL/min under the protection of nitrogen atmosphere, a sample is heated from 30° C. to 350° C. at a heating rate of 10° C./min, subjected to heat preservation at 350° C. for 5 minutes, and then cooled to 50° C. at a cooling rate of 10° C./min. At this time, the area of a crystallization peak is used as a crystallization enthalpy value.

[0035] (4) Fusion index: With reference to the standard ASTM D1238-2010, a material is tested by a standard fusion index instrument at 190° C. under at a load pressure of 1.0 kg to obtain the mass of a molten material flowing through a standard capillary tube within 10 minutes.

[0036] (5) Hydrolysis resistance: Recycled polyamide is subjected to injection molding to obtain a standard sample strip, and the tensile strength and bending strength of the material sample strip before and after hydrolysis treatment are tested. The hydrolysis treatment is conducted under the conditions that the test sample strip is put in water at 100° C. and then boiled for 3 hours. After comparison with mechanical properties before boiling, the retention rates of the tensile strength and bending strength are calculated in percentages.

[0037] (6) Alcoholysis resistance: Recycled polyamide is subjected to injection molding to obtain a standard sample strip, and the tensile strength and bending strength of the material sample strip before and after alcoholysis treatment are tested. The alcoholysis treatment is conducted under the conditions that the test sample strip is put in ethanol at 70° C., heated, and then soaked for 3 hours. After comparison with mechanical properties before the alcoholysis treatment, the retention rates of the tensile strength and bending strength are calculated in percentages.

[0038] (7) Heat aging resistance: Recycled polyamide is subjected to injection molding to obtain a standard sample strip, and the tensile strength and bending strength of the material sample strip before and after heat aging treatment are tested. The heat aging treatment is conducted under the conditions that the test sample strip is put in an oven at 100° C. and then baked for 12 hours. After comparison with mechanical properties before baking, the retention rates of the tensile strength and bending strength are calculated in percentages.

Example 1

[0039] 100 g of a polyamide waste material PA12 was added into a mixed solvent including 100 g of phenol and 200 g of toluene, heated to 100° C., and stirred for dissolution. After 10 g of activated carbon was added, an obtained mixture was subjected to heat preservation at 100° C. under stirring for 0.5 hour, cooled to 40° C., and then filtered to obtain a polyamide solution. Then, the polyamide solution was slowly added into 3.000 g of deionized water to precipitate out polyamide. After the polyamide was dried, other properties were tested.

Example 2

[0040] Different from Example 1, 20 g of methanol was further added into the mixed solvent.

Example 3

[0041] Different from Example 1, 50 g of o-cresol was further added into the mixed solvent.

Example 4

[0042] Different from Example 1, 30 g of benzyl alcohol was further added into the mixed solvent.

Example 5

[0043] Different from Example 1, 100 g of a polyamide waste material PA12 was added into a mixed solvent including 100 g of phenol and 200 g of toluene, heated to 60° C., and stirred for dissolution.

Example 6

[0044] 100 g of a polyamide waste material PA66 was added into a mixed solvent including 80 g of phenol and 160 g of toluene, heated to 80° C., and stirred for dissolution. After 10 g of activated carbon was added, an obtained mixture was heated to 100° C., subjected to heat preservation under stirring for 0.5 hour, cooled to 30° C., and then filtered to obtain a polyamide solution. Then, the polyamide solution was slowly added into 3,000 g of deionized water to precipitate out polyamide. After the polyamide was dried, other properties were tested.

Example 7

[0045] 100 g of a polyamide waste material PA10T was added into a mixed solvent including 90 g of phenol, 160 g of toluene, and 20 g of methanol, heated to 80° C., and stirred for dissolution. After 10 g of activated carbon was added, an obtained mixture was subjected to heat preservation at 80° C. under stirring for 0.5 hour, cooled to 40° C., and then filtered to obtain a polyamide solution. Then, the polyamide solution was slowly added into 3,000 g of deionized water to precipitate out polyamide. After the polyamide was dried, other properties were tested.

Example 8

[0046] Different from Example 1, 15 g of methanol, 50 g of o-cresol, and 30 g of benzyl alcohol were further added into the mixed solvent.

Comparative Example 1

[0047] 100 g of a polyamide waste material PA12 was added into 1,500 g of a mixed solvent (including 15% of formic acid, 10% of hydrochloric acid, 35% of acetic acid, and 40% of water), stirred at 80° C. for dissolution for 4 hours, and then subjected to centrifugal separation (at a rotation speed of 4,000 R/min). An upper supernatant was added into 1,500 g of deionized water for precipitation to obtain a PA12 precipitate. After the precipitate was dried, other properties were tested.

Comparative Example 2

[0048] 100 g of a polyamide waste material PA12 was added into 200 g of phenol, heated to 100° C., and stirred for dissolution. After 10 g of activated carbon was added, an obtained mixture was subjected to heat preservation under stirring for 0.5 hour, cooled to 60° C., and then filtered to obtain a polyamide solution. Then, the polyamide solution was slowly added into 3,000 g of deionized water to precipitate out polyamide. After the polyamide was dried, other properties were tested.

Comparative Example 3

[0049] 100 g of a polyamide waste material PA12 was added into a mixed solvent including 100 g of o-cresol and 200 g of toluene, heated to 100° C., and stirred for dissolution. After 10 g of activated carbon was added, an obtained mixture was subjected to heat preservation under stirring for 0.5 hour, cooled to 40° C., and then filtered to obtain a polyamide solution. Then, the polyamide solution was slowly added into 3,000 g of deionized water to precipitate out polyamide. After the polyamide was dried, other properties were tested.

TABLE-US-00001 Various test results of examples and comparative examples Example 1 Example 2 Example 3 Example 4 Examle 5 Example 6 Example 7 Example 8 Content of terminal carboxyl, mol/t 35 36 36 35 41 31 26 36 Crystallization half-peak width, °C 10.3 10.3 10.2 10.3 10.4 8.1 6.9 10.3 Crystallization enthalpy, J/g -42 -42 -42 -42 -43 -41 -54 -42 Fusion index, g/10 min 16 19 16 16 15 9 5 19 Hydrolysis resistance, % 95 96 99 99 95 92 99 100 Heat aging resistance, % 96 96 97 98 94 94 97 98 Alcoholysis resistance, % 96 96 98 97 95 92 98 99

TABLE-US-00002 Comparative Example 1 Comparative Example 2 Comparative Example 3 Content of terminal carboxyl, mol/t 79 38 66 Crystallization half-peak width, °C 10.9 10.6 10.7 Crystallization enthalpy, J/g -45 -45 -43 Fusion index, g/10 min 19 15 16 Hydrolysis resistance, % 87 93 89 Heat aging resistance, % 80 71 85 Alcoholysis resistance, % 83 82 88

[0050] According to Example 1 and Example 2, it can be seen that when the methanol is added into the recycling solvent for synergy, not only can the fusion index of the recycled polyamide be effectively increased, but also other properties can be maintained or even improved.

[0051] According to Example 1, Example 3, and Example 4, it can be seen that when the o-cresol and the benzyl alcohol are separately added into the recycling solvent for synergy, the hydrolysis resistance, heat aging resistance, and alcoholysis resistance of the recycled polyamide can be significantly improved.

[0052] According to Example 1 and Comparative Example 1, it can be seen that when the mixed acidic solvent is used as the recycling solvent, not only is the content of the terminal carboxyl in the recycled polyamide high, crystallization properties are reduced, but also the hydrolysis resistance, heat aging resistance, and alcoholysis resistance are poor. At this time, the fusion index is high since a part of molecular chains are broken in a recycling process of the polyamide.

[0053] According to Example 1 and Comparative Example 2, it can be seen that when the single phenol is used as the recycling solvent, the crystallization properties of the recycled polyamide are also reduced to a certain extent, and the hydrolysis resistance, heat aging resistance, and alcoholysis resistance are greatly reduced.

[0054] According to Example 1 and Comparative Example 3, it can be seen that when the mixed solvent including the o-cresol and the toluene is used, the content of the terminal carboxyl in the recycled polyamide is high, and the hydrolysis resistance, heat aging resistance, and alcoholysis resistance are low.