MODIFIED CROSS-LINKED POLYETHYLENE AND PREPARATION METHOD THEREFOR, AND RECYCLED PRODUCT AND PREPARATION METHOD THEREFOR

Abstract

The present invention provides a modified cross-linked polyethylene and a preparation method therefor, and a recycled product and a preparation method therefor. The preparation method for the modified cross-linked polyethylene includes: milling waste cross-linked polyethylene by using a solid-phase force chemical reactor, and then using asphalt as a plasticizer for plasticization to obtain the modified cross-linked polyethylene. The plasticization treatment enables the decross-linked waste cross-linked polyethylene/asphalt material obtained after milling to have excellent processing fluidity, and thus, the decross-linked waste cross-linked polyethylene/asphalt material is suitable for preparing high-performance recycled products in various thermoplastic processing processes. The waste ultrafine cross-linked polyethylene powder subjected to asphalt plasticization can be formed in a compressive force field having a high pressure, and can also be suitable for thermoplastic extrusion processing of a low shear force field. The prepared recycled product has good mechanical properties.

Claims

1. A preparation method for a modified cross-linked polyethylene, comprising: obtaining a cross-linked polyethylene powder; and mixing natural liquid asphalt and the cross-linked polyethylene powder in an internal mixer.

2. The preparation method for a modified cross-linked polyethylene according to claim 1, wherein obtaining the cross-linked polyethylene powder comprises: adding the cross-linked polyethylene powder into a millstone-type solid-phase force chemical reactor for milling; and collecting the cross-linked polyethylene powder after milling.

3. The preparation method for a modified cross-linked polyethylene according to claim 2, wherein: a milling pressure of the millstone-type solid-phase force chemical reactor is 2-3 MPa; a surface temperature of a millstone of the millstone-type solid-phase force chemical reactor is controlled at 25-35? C. by introducing a circulating cooling liquid; the millstone-type solid-phase force chemical reactor mills for 13-15 cycles; and a rotation speed of the millstone is 30-50 revolutions per minute (rpm).

4. The preparation method for a modified cross-linked polyethylene according to claim 3, wherein the circulating cooling liquid is water, ethylene glycol, or glycerol.

5. The preparation method for a modified cross-linked polyethylene according to claim 1, wherein: a mixing temperature of the internal mixer is 180-200? C.; a rotation speed of the internal mixer is 30-50 revolutions per minute (rpm); a duration of the mixing is 10-30 min; and a mass ratio of the natural liquid asphalt to the cross-linked polyethylene powder is (0.1-0.3):(0.9-0.7).

6. The preparation method for a modified cross-linked polyethylene according to claim 1, wherein the natural liquid asphalt has: a penetration of 50-120 units, wherein one unit is 0.1 mm, a softening point of 42-49? C., a flash point ranging between 240? C. and 260? C., and a ductility of 120-180 cm.

7. The preparation method for a modified cross-linked polyethylene according to claim 1, wherein the natural liquid asphalt is 90# liquid asphalt.

8. The preparation method for a modified cross-linked polyethylene according to claim 2, wherein obtaining the cross-linked polyethylene powder comprises preparing a waste cross-linked polyethylene powder, comprising: pretreating a waste cross-linked polyethylene material or product with a proportion of the cross-linked polyethylene being not less than 98% by washing the waste cross-linked polyethylene material or product; and smashing the waste cross-linked polyethylene material or product to form the waste cross-linked polyethylene powder with an average particle size being not more than 1 mm.

9. The preparation method for a modified cross-linked polyethylene according to claim 8, wherein the smashing is smashing to form the waste cross-linked polyethylene powder with an average particle size being not more than 500 ?m.

10. A modified cross-linked polyethylene prepared by natural liquid asphalt and a cross-linked polyethylene powder as raw materials.

11. The modified cross-linked polyethylene according to claim 10, wherein a mass ratio of the natural liquid asphalt to the cross-linked polyethylene powder is (0.1-0.3):(0.9-0.7).

12. The modified cross-linked polyethylene according to claim 10, wherein the modified cross-linked polyethylene is prepared by a method comprising: obtaining the cross-linked polyethylene powder; and mixing the natural liquid asphalt and the cross-linked polyethylene powder in an internal mixer.

13. A preparation method for a recycled product, comprising: preparing a modified cross-linked polyethylene by the preparation method according to claim 1; smashing the modified cross-linked polyethylene to obtain a composite granular material; and performing thermoplastic processing on the composite granular material to prepare the recycled product.

14. The preparation method for a recycled product according to claim 13, wherein the modified cross-linked polyethylene is smashed to the composite granular material with an average particle size being 0.5-1 cm.

15. The preparation method for a recycled product according to claim 13, wherein the thermoplastic processing comprises extruded profile processing, injection molding processing, or calendaring.

16. The preparation method for a recycled product according to claim 13, wherein the thermoplastic processing is selected from a group consisting of: single-screw sheet extrusion processing on the composite granular material, wherein a temperature of a first zone is 150? C., a temperature of a second zone is 175? C. a temperature of a third zone is 180? C., a temperature of a hand piece is 175? C., a rotation speed is 50-100 revolutions per minute (rpm) and a die width of 10 cm; twin-screw extrusion processing on the composite granular material, wherein a die width is 30 cm, a temperature of a first zone is 150? C., a temperature of a second zone is 175? C., a temperature of a third zone is 180? C., a temperature of a hand piece is 175? C. and a rotation speed is 50-100 rpm; vulcanizing pressure plate processing on the composite granular material, wherein a temperature is 180? C. and pressure is 10 MPa, and comprising degassing for 5 times, hot pressing for 5 minutes and cold pressing to a room temperature under pressure of 10 MPa; or injection molding processing on the composite granular material, wherein temperature of a first zone is 160? C., a temperature of a second zone is 190? C., a temperature of a third zone is 190? C. and a temperature of a fourth zone is 190? C.

17. A recycled product prepared by the preparation method according to claim 13.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0057] FIG. 1 is a SEM diagram of a recycled product prepared according to example 1 of the present invention after being etched with cyclohexane. It is apparent that a waste ultrafine cross-linked polyethylene powder has good compatibility with natural liquid asphalt in a recycled product, and the asphalt can be uniformly dispersed in the waste ultrafine cross-linked polyethylene powder to play a plasticizing and lubricating role.

[0058] FIG. 2 is a picture of a recycled product prepared according to example 1 of the present invention. It is apparent that the present invention can produce a continuously extruded sheet material with a smooth surface after single-screw sheet extrusion processing in a condition of a low shear force field.

[0059] FIG. 3 is a diagram comparing torque rheology curves of recycled products prepared according to examples 1, 3 and 5 as well as comparative examples 1 and 2 of the present invention. It is apparent that compared with the comparative example 1 without adding asphalt, the technical solution of the present invention adds asphalt to toughen. The processing fluidity becomes better, and the torque decreases from 30 Nm to 6 Nm with the addition of asphalt during the mixing. In the condition that the rotation speed of the mixing is constant, the torque reflects the ease of thermoplastic processing. The lower the torque indicates that the shear force required for the mixing is lower, the powder is easier to process, and the acting force between particle flows is smaller. It fully reflects the plasticizing effect of asphalt in the material. 0%, 10%, 20%, 30%, and 40% therein refer to the added amount of the asphalt.

[0060] FIG. 4 is a diagram comparing high pressure capillary rheology of recycled products prepared according to examples 1, 3 and 5 as well as comparative examples 1 and 2 of the present invention. It is apparent that with the increase of asphalt, the apparent viscosity of the composite material gradually decreases, and the flow property increases at a shear rate, so that the thermoplastic processing can be better performed. It also indicates that the asphalt has a good toughening effect on the waste cross-linked polyethylene powder. 0%, 10%, 20%, 30% and 40% therein refer to the added amount of the asphalt.

DETAILED DESCRIPTION

[0061] The present invention will be further described by the examples in conjunction with the accompanying drawings. It should be noted that the given examples should not be construed as limiting the scope of the present invention, and that insubstantial modifications and adaptations to the present invention made by those skilled in the art according to the present invention are intended to be included within the scope of the present invention.

[0062] In the following examples, the tensile strength and breaking elongation were obtained by performing a regular tensile test on experimental samples according to the testing standard ASTM D638. Tensile strength was tested at a tensile speed of 50 mm/min.

[0063] In the following examples, 90# liquid asphalt was purchased from Liaoning Hualu Special Asphalt Co. Ltd.

[0064] The waste cross-linked polyethylene was obtained from the samples provided by TBEA Deyang Cable Co. Ltd., and the proportion of the cross-linked polyethylene was 98%.

Example 1

[0065] The method for preparing a modified cross-linked polyethylene and a recycled product using waste cross-linked polyethylene and asphalt in the present example includes the following steps. [0066] (1) A waste cross-linked polyethylene material was selected, and the material was smashed to the waste cross-linked polyethylene powder with an average particle size being not more than 1 mm after pretreatment, including washing. [0067] (2) The waste cross-linked polyethylene powder was added into a millstone-type solid-phase force chemical reactor for milling, and a waste ultrafine cross-linked polyethylene powder was collected after milling. Process parameters of the millstone-type solid-phase force chemical reactor are: milling pressure of 3 MPa: a surface temperature of a millstone controlled at 28? C. by introducing a circulating cooling liquid; milling for 15 cycles; a rotation speed of the millstone at 50 rpm; and the cooling liquid being water, ethylene glycol or glycerol. [0068] (3) Natural liquid asphalt and the waste ultrafine cross-linked polyethylene powder obtained in step (2) were added into an internal mixer for mixing to obtain the modified cross-linked polyethylene. Process parameters of the internal mixer are: a mixing temperature controlled at 180? C.: a rotation speed controlled at 50 rpm; time controlled at 10 min; and a mass ratio of the natural liquid asphalt to the waste ultrafine cross-linked polyethylene powder being 0.2:0.8. [0069] (4) The modified cross-linked polyethylene obtained after the mixing in step (3) was smashed to a composite granular material with an average particle size being 0.5-1 cm. [0070] (5) Single-screw sheet extrusion processing was performed on the composite granular material obtained in step (4) to prepare the recycled product in a form of a sheet material. Process parameters of the sheet extrusion processing are: temperatures of three zones being a first zone of 150? C., a second zone of 175? C. and a third zone of 180? C., a hand piece of 175? C., a rotation speed controlled at 100 rpm, and a die width of 10 cm.

[0071] The mechanical property test was performed on the finally prepared recycled product described above as a sample. The tensile strength was 20.3 MPa, and the breaking elongation was 610%.

Example 2

[0072] The method for preparing a modified cross-linked polyethylene and a recycled product using waste cross-linked polyethylene and asphalt in the present example includes the following steps. [0073] (1) A waste cross-linked polyethylene material was selected, and the material was smashed to the waste cross-linked polyethylene powder with an average particle size being not more than 1 mm after pretreatment, including washing. [0074] (2) The waste cross-linked polyethylene powder was added into a millstone-type solid-phase force chemical reactor for milling, and a waste ultrafine cross-linked polyethylene powder was collected after milling. Process parameters of the millstone-type solid-phase force chemical reactor are: milling pressure of 3 MPa: a surface temperature of a millstone controlled at 28? C. by introducing a circulating cooling liquid; milling for 15 cycles; and a rotation speed of the millstone at 50 rpm. [0075] (3) Natural liquid asphalt and the waste ultrafine cross-linked polyethylene powder obtained in step (2) were added into an internal mixer for mixing to obtain the modified cross-linked polyethylene. Process parameters of the internal mixer are: a mixing temperature controlled at 180? C.: a rotation speed controlled at 50 rpm; time controlled at 10 min; and a mass ratio of the natural liquid asphalt to the waste ultrafine cross-linked polyethylene powder being 0.2:0.8. [0076] (4) The modified cross-linked polyethylene obtained after the mixing in step (3) was smashed to a composite granular material with an average particle size being 0.5-1 cm. [0077] (5) Vulcanizing pressure plate processing was performed on the composite granular material obtained in step (4) to prepare the recycled product in a form of a sheet material. Process parameters are: a temperature of 180? C., pressure of 10 MPa, degassing for 5 times, hot pressing for 5 minutes, and cold pressing to a room temperature under pressure of 10 MPa.

[0078] The mechanical property test was performed on the finally prepared recycled product described above as a sample. The tensile strength was 19.2 MPa, and the breaking elongation was 560%.

Example 3

[0079] The method for preparing a modified cross-linked polyethylene and a recycled product using waste cross-linked polyethylene and asphalt in the present example includes the following steps. [0080] (1) A waste cross-linked polyethylene material was selected, and the material was smashed to the waste cross-linked polyethylene powder with an average particle size being not more than 1 mm after pretreatment, including washing. [0081] (2) The waste cross-linked polyethylene powder was added into a millstone-type solid-phase force chemical reactor for milling, and a waste ultrafine cross-linked polyethylene powder was collected after milling. Process parameters of the millstone-type solid-phase force chemical reactor are: milling pressure of 3 MPa: a surface temperature of a millstone controlled at 28? C. by introducing a circulating cooling liquid; milling for 15 cycles; and a rotation speed of the millstone at 50 rpm. [0082] (3) Natural liquid asphalt and the waste ultrafine cross-linked polyethylene powder obtained in step (2) were added into an internal mixer for mixing to obtain the modified cross-linked polyethylene. Process parameters of the internal mixer are: a mixing temperature controlled at 180? C.: a rotation speed controlled at 50 rpm; time controlled at 10 min; and a mass ratio of the natural liquid asphalt to the waste ultrafine cross-linked polyethylene powder being 0.1:0.9. [0083] (4) The modified cross-linked polyethylene obtained after the mixing in step (3) was smashed to a composite granular material with an average particle size being 0.5-1 cm. [0084] (5) Single-screw sheet extrusion processing was performed on the composite granular material obtained in step (4) to prepare the recycled product in a form of a sheet material. Process parameters of the sheet extrusion processing are: temperatures of three zones being a first zone of 150? C., a second zone of 175? C. and a third zone of 180? C., a hand piece of 175? C., a rotation speed controlled at 100 rpm, and a die width of 10 cm.

[0085] The mechanical property test was performed on the finally prepared recycled product described above as a sample. The tensile strength was 18.7 MPa, and the breaking elongation was 540%.

Example 4

[0086] The method for preparing a modified cross-linked polyethylene and a recycled product using waste cross-linked polyethylene and asphalt in the present example includes the following steps. [0087] (1) A waste cross-linked polyethylene material was selected, and the material was smashed to the waste cross-linked polyethylene powder with an average particle size being not more than 1 mm after pretreatment, including washing. [0088] (2) The waste cross-linked polyethylene powder was added into a millstone-type solid-phase force chemical reactor for milling, and a waste ultrafine cross-linked polyethylene powder was collected after milling. Process parameters of the millstone-type solid-phase force chemical reactor are: milling pressure of 3 MPa: a surface temperature of a millstone controlled at 28? C. by introducing a circulating cooling liquid; milling for 15 cycles; and a rotation speed of the millstone at 50 rpm. [0089] (3) Natural liquid asphalt and the waste ultrafine cross-linked polyethylene powder obtained in step (2) were added into an internal mixer for mixing to obtain the modified cross-linked polyethylene. Process parameters of the internal mixer are: a mixing temperature controlled at 180? C.: a rotation speed controlled at 50 rpm; time controlled at 10 min; and a mass ratio of the natural liquid asphalt to the waste ultrafine cross-linked polyethylene powder being 0.1:0.9. [0090] (4) The modified cross-linked polyethylene obtained after the mixing in step (3) was smashed to a composite granular material with an average particle size being 0.5-1 cm. [0091] (5) Vulcanizing pressure plate processing was performed on the composite granular material obtained in step (4) to prepare the recycled product in a form of a sheet material. Process parameters are: a temperature of 180? C., pressure of 10 MPa, degassing for 5 times, hot pressing for 5 minutes, and cold pressing to a room temperature under pressure of 10 MPa.

[0092] The mechanical property test was performed on the finally prepared recycled product described above as a sample. The tensile strength was 18.2 MPa, and the breaking elongation was 527%.

Example 5

[0093] The method for preparing a modified cross-linked polyethylene and a recycled product using waste cross-linked polyethylene and asphalt in the present example includes the following steps. [0094] (1) A waste cross-linked polyethylene material was selected, and the material was smashed to the waste cross-linked polyethylene powder with an average particle size being not more than 1 mm after pretreatment, including washing. [0095] (2) The waste cross-linked polyethylene powder was added into a millstone-type solid-phase force chemical reactor for milling, and a waste ultrafine cross-linked polyethylene powder was collected after milling. Process parameters of the millstone-type solid-phase force chemical reactor are: milling pressure of 3 MPa: a surface temperature of a millstone controlled at 28? C. by introducing a circulating cooling liquid; milling for 15 cycles; and a rotation speed of the millstone at 50 rpm. [0096] (3) Natural liquid asphalt and the waste ultrafine cross-linked polyethylene powder obtained in step (2) were added into an internal mixer for mixing to obtain the modified cross-linked polyethylene. Process parameters of the internal mixer are: a mixing temperature controlled at 180? C.: a rotation speed controlled at 50 rpm; time controlled at 10 min; and a mass ratio of the natural liquid asphalt to the waste ultrafine cross-linked polyethylene powder being 0.3:0.7. [0097] (4) The modified cross-linked polyethylene obtained after the mixing in step (3) was smashed to a composite granular material with an average particle size being 0.5-1 cm. [0098] (5) Single-screw sheet extrusion processing was performed on the composite granular material obtained in step (4) to prepare the recycled product in a form of a sheet material. Process parameters of the sheet extrusion processing are: temperatures of three zones being a first zone of 150? C., a second zone of 175? C. and a third zone of 180? C., a hand piece of 175? C., a rotation speed controlled at 100 rpm, and a die width of 10 cm.

[0099] The mechanical property test was performed on the finally prepared recycled product described above as a sample. The tensile strength was 17.2 MPa, and the breaking elongation was 460%.

Example 6

[0100] The method for preparing a modified cross-linked polyethylene and a recycled product using waste cross-linked polyethylene and asphalt in the present example includes the following steps. [0101] (1) A waste cross-linked polyethylene material was selected, and the material was smashed to the waste cross-linked polyethylene powder with an average particle size being not more than 1 mm after pretreatment, including washing. [0102] (2) The waste cross-linked polyethylene powder was added into a millstone-type solid-phase force chemical reactor for milling, and a waste ultrafine cross-linked polyethylene powder was collected after milling. Process parameters of the millstone-type solid-phase force chemical reactor are: milling pressure of 3 MPa: a surface temperature of a millstone controlled at 28? C. by introducing a circulating cooling liquid; milling for 15 cycles; and a rotation speed of the millstone at 50 rpm. [0103] (3) Natural liquid asphalt and the waste ultrafine cross-linked polyethylene powder obtained in step (2) were added into an internal mixer for mixing to obtain the modified cross-linked polyethylene. Process parameters of the internal mixer are: a mixing temperature controlled at 180? C.: a rotation speed controlled at 50 rpm; time controlled at 10 min; and a mass ratio of the natural liquid asphalt to the waste ultrafine cross-linked polyethylene powder being 0.3:0.7. [0104] (4) The modified cross-linked polyethylene obtained after the mixing in step (3) was smashed to a composite granular material with an average particle size being 0.5-1 cm. [0105] (5) Vulcanizing pressure plate processing was performed on the composite granular material obtained in step (4) to prepare the recycled product in a form of a sheet material. Process parameters are: a temperature of 180? C., pressure of 10 MPa, degassing for 5 times, hot pressing for 5 minutes, and cold pressing to a room temperature under pressure of 10 MPa.

[0106] The mechanical property test was performed on the finally prepared recycled product described above as a sample. The tensile strength was 17.1 MPa, and the breaking elongation was 435%.

Example 7

[0107] The method for preparing a modified cross-linked polyethylene and a recycled product using waste cross-linked polyethylene and asphalt in the present example includes the following steps. [0108] (1) A waste cross-linked polyethylene material was selected, and the material was smashed to the waste cross-linked polyethylene powder with an average particle size being not more than 1 mm after pretreatment, including washing. [0109] (2) The waste cross-linked polyethylene powder was added into a millstone-type solid-phase force chemical reactor for milling, and a waste ultrafine cross-linked polyethylene powder was collected after milling. Process parameters of the millstone-type solid-phase force chemical reactor are: milling pressure of 2 MPa: a surface temperature of a millstone controlled at 35? C. by introducing a circulating cooling liquid; milling for 13 cycles; and a rotation speed of the millstone at 50 rpm. [0110] (3) Natural liquid asphalt and the waste ultrafine cross-linked polyethylene powder obtained in step (2) were added into an internal mixer for mixing to obtain the modified cross-linked polyethylene. Process parameters of the internal mixer are: a mixing temperature controlled at 200? C.: a rotation speed controlled at 30 rpm; time controlled at 30 min; and a mass ratio of the natural liquid asphalt to the waste ultrafine cross-linked polyethylene powder being 0.2:0.8. [0111] (4) The modified cross-linked polyethylene obtained after the mixing in step (3) was smashed to a composite granular material with an average particle size being 0.5-1 cm. [0112] (5) Twin-screw extrusion processing was performed on the composite granular material obtained in step (4) to prepare the recycled product in a form of a sheet material. Process parameters of the extrusion processing are: a die width of 30 cm, a first zone of 150? C., a second zone of 175? C., a third zone of 180? C., a hand piece of 175? C., and a rotation speed controlled at 50 rpm.

Example 8

[0113] The method for preparing a modified cross-linked polyethylene and a recycled product using waste cross-linked polyethylene and asphalt in the present example includes the following steps. [0114] (1) A waste cross-linked polyethylene material was selected, and the material was smashed to the waste cross-linked polyethylene powder with an average particle size being not more than 1 mm after pretreatment, including washing. [0115] (2) The waste cross-linked polyethylene powder was added into a millstone-type solid-phase force chemical reactor for milling, and a waste ultrafine cross-linked polyethylene powder was collected after milling. Process parameters of the millstone-type solid-phase force chemical reactor are: milling pressure of 3 MPa: a surface temperature of a millstone controlled at 25? C. by introducing a circulating cooling liquid; milling for 15 cycles; and a rotation speed of the millstone at 30 rpm. [0116] (3) Natural liquid asphalt and the waste ultrafine cross-linked polyethylene powder obtained in step (2) were added into an internal mixer for mixing to obtain the modified cross-linked polyethylene. Process parameters of the internal mixer are: a mixing temperature controlled at 190? C.; a rotation speed controlled at 40 rpm; time controlled at 20 min; and a mass ratio of the natural liquid asphalt to the waste ultrafine cross-linked polyethylene powder being 0.2:0.8. [0117] (4) The modified cross-linked polyethylene obtained after the mixing in step (3) was smashed to a composite granular material with an average particle size being 0.5-1 cm. [0118] (5) Injection molding processing was performed on the composite granular material obtained in step (4) to prepare the recycled product in a form of a sheet material. Process parameters of the extrusion processing are: a temperature of a first zone of 160? C., a temperature of a second zone of 190? C., a temperature of a third zone of 190? C. and a temperature of a fourth zone of 190? C.

Comparative Example 1

[0119] The method for preparing a recycled product using waste cross-linked polyethylene in this comparative example includes the following steps. [0120] (1) A waste cross-linked polyethylene material was selected, and the material was smashed to the waste cross-linked polyethylene powder with an average particle size being not more than 1 mm after pretreatment, including washing. [0121] (2) The waste cross-linked polyethylene powder was added into a millstone-type solid-phase force chemical reactor for milling, and a waste ultrafine cross-linked polyethylene powder was collected after milling. Process parameters of the millstone-type solid-phase force chemical reactor are: milling pressure of 3 MPa: a surface temperature of a millstone controlled at 28? C. by introducing a circulating cooling liquid; milling for 15 cycles; and a rotation speed of the millstone at 50 rpm. [0122] (3) The waste ultrafine cross-linked polyethylene powder obtained in step (2) was added into an internal mixer for mixing. Process parameters of the internal mixer are: a mixing temperature controlled at 180? C.: a rotation speed controlled at 50 rpm; and time controlled at 10 min. [0123] (4) The cross-linked polyethylene material obtained after the mixing in step (3) was smashed to a cross-linked polyethylene granular material with an average particle size being 0.5-1 cm. [0124] (5) Single-screw sheet extrusion processing was performed on the cross-linked polyethylene granular material obtained in step (4) to prepare the recycled product in a form of a sheet material. Process parameters of the sheet extrusion processing are: temperatures of three zones being a first zone of 150? C., a second zone of 175? C. and a third zone of 180? C., a hand piece of 175? C., a rotation speed controlled at 100 rpm, and a die width of 10 cm.

[0125] In the preparation process, there were incomplete melting of powder, loose connection of particle flows, and unstable fluid at the die. Therefore, the extrudate was intermittent and cannot form a continuous sheet material with a smooth surface.

[0126] The mechanical property test was performed on the finally prepared recycled product described above as a sample. The tensile strength was 15.2 MPa, and the breaking elongation was 376%.

Comparative Example 2

[0127] The method for preparing a recycled product using waste cross-linked polyethylene and asphalt in this comparative example includes the following steps. [0128] (1) A waste cross-linked polyethylene material was selected, and the material was smashed to the waste cross-linked polyethylene powder with an average particle size being not more than 1 mm after pretreatment, including washing. [0129] (2) The waste cross-linked polyethylene powder was added into a millstone-type solid-phase force chemical reactor for milling, and a waste ultrafine cross-linked polyethylene powder was collected after milling. Process parameters of the millstone-type solid-phase force chemical reactor are: milling pressure of 3 MPa: a surface temperature of a millstone controlled at 28? C. by introducing a circulating cooling liquid; milling for 15 cycles; and a rotation speed of the millstone at 50 rpm. [0130] (3) Natural liquid asphalt and the waste ultrafine cross-linked polyethylene powder obtained in step (2) were added into an internal mixer for mixing. Process parameters of the internal mixer are: a mixing temperature controlled at 180? C.: a rotation speed controlled at 50 rpm; time controlled at 10 min; and a mass ratio of the natural liquid asphalt to the waste ultrafine cross-linked polyethylene powder being 0.4:0.6. [0131] (4) The modified cross-linked polyethylene obtained after the mixing in step (3) was smashed to a composite granular material with an average particle size being 0.5-1 cm. [0132] (5) Single-screw sheet extrusion processing was performed on the composite granular material obtained in step (4) to prepare the recycled product in a form of a sheet material. Process parameters of the sheet extrusion processing are: temperatures of three zones being a first zone of 150? C., a second zone of 175? C. and a third zone of 180? C., a hand piece of 175? C., a rotation speed controlled at 100 rpm, and a die width of 10 cm.

[0133] In the preparation process of sheet extrusion, the asphalt between the particle flows moved to the surface under the action of external force, and the residual asphalt on the screw can be seen obviously. In addition, the viscosity was too small, causing serious roll coating and making the processing hard.

[0134] The mechanical property test was performed on the finally prepared recycled product described above as a sample. The tensile strength was 14.5 MPa, and the breaking elongation was 350%.