An open-cell foamed polypropylene material and a method of making
By preparing short-branched polypropylene with a wide molecular weight distribution, the problems of high foaming ratio and high open-cell ratio were solved, realizing the high-performance preparation of open-cell foamed polypropylene materials, which are suitable for a variety of foaming processes and fields.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SINOCHEM PETROCHEMICAL DISTRIBUTION CO LTD
- Filing Date
- 2023-08-28
- Publication Date
- 2026-07-03
Smart Images
Figure BDA0004417400380000091
Abstract
Description
Technical Field
[0001] This invention belongs to the field of polymer materials technology, specifically relating to an open-cell foamed polypropylene material and its preparation method. Background Technology
[0002] In recent years, polymer foam materials have played an increasingly important role in people's lives and production due to their excellent properties such as light weight, low thermal conductivity, and good impact resistance. Among them, open-cell materials are a special type of foam polymer with interconnected cells, where the polymer matrix material exists as continuous cell walls in the foamed product. This unique three-dimensional open-cell structure has excellent absorption and permeability properties and is widely used in sound insulation, oil and moisture absorption, and drug release.
[0003] Currently, commonly used open-cell foaming polymers include polyethylene, polypropylene, polyurethane, and polylactic acid. Among them, polypropylene, as one of the most widely used general-purpose plastics, has outstanding advantages such as corrosion resistance, excellent mechanical properties, simple processing methods, and low production costs. However, polypropylene has a linear molecular chain structure and a relatively narrow molecular weight distribution. When the processing temperature is higher than its melting point, its melt strength and melt viscosity drop sharply, making it difficult to foam during the foaming process due to the lack of strain hardening effect. In recent years, high melt strength polypropylene has been developed as a new type of polypropylene material to address the defects of linear polypropylene in foaming processing. By introducing long branches and widening the molecular weight distribution, it improves the melt strength of polypropylene and reduces strain hardening, effectively solving the defects in foaming production. However, open-cell foaming places higher demands on melt strength. Excessively high melt strength makes it difficult to induce bubble wall rupture and form through-cells; while excessively low melt strength will cause severe rupture of the bubble wall, leading to bubble merging and collapse, making it impossible to maintain the open-cell structure. However, it is often difficult to achieve both high expansion ratio and high open-cell ratio in the foaming of linear polypropylene and long-chain branched polypropylene. Therefore, there are still significant challenges in preparing polypropylene open-cell foam with high expansion ratio and high open-cell ratio. Developing low-cost, high-performance open-cell foamed polypropylene materials has important application value and significance. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide an open-cell foamed polypropylene material and a preparation method thereof, thereby obtaining an open-cell foamed polypropylene material with high foaming rate and high open-cell rate.
[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:
[0006] A method for preparing an open-cell foamed polypropylene material includes:
[0007] Low molecular weight polypropylene is obtained by reacting polypropylene with a first initiator and then extruding it.
[0008] The low molecular weight polypropylene and polypropylene are mixed in a preset ratio to obtain a mixed raw material;
[0009] A second initiator, grafting monomer, and antioxidant are added to the mixed raw materials and melt-grafted in an extruder to obtain a short-branched polypropylene with a wide molecular weight distribution.
[0010] The short-branched polypropylene is foamed to obtain an open-cell foamed polypropylene material.
[0011] Optionally, the polypropylene is a homopolymer or copolymer linear polypropylene with a melt index of 0.5-20 g / 10 min;
[0012] The first initiator is selected from at least one of benzoyl peroxide, lauroyl peroxide, dicumyl peroxide, tert-butyl peroxide, and tert-butyl hydroperoxide.
[0013] Optionally, reacting polypropylene with a first initiator and extruding it to obtain low molecular weight polypropylene includes:
[0014] By mass fractions, 100 parts of polypropylene and 0.01-0.5 parts of the first initiator are melt-mixed and reacted and extruded to obtain the low molecular weight polypropylene.
[0015] Optionally, the extrusion temperature for melt-mixed reactive extrusion is 170℃~230℃, and the extruder screw speed is 50-300rpm.
[0016] Optionally, the low molecular weight polypropylene is mixed with polypropylene in a preset ratio to obtain a mixed raw material, including: mixing 100 parts of polypropylene and 1-50 parts of low molecular weight polypropylene.
[0017] Optionally, the grafting monomer is selected from at least one of styrene, isoprene, acid anhydride, and ester;
[0018] The second initiator is selected from at least one of benzoyl peroxide, lauroyl peroxide, dicumyl peroxide, tert-butyl peroxide, and tert-butyl hydroperoxide;
[0019] The antioxidant is selected from at least one of antioxidant 1010, antioxidant 168, antioxidant 1076 and antioxidant 626.
[0020] Optionally, a second initiator, grafting monomer, and antioxidant are added to the mixed raw materials, and melt grafting is performed in an extruder to obtain a short-branched polypropylene with a wide molecular weight distribution, comprising:
[0021] 100 parts of polypropylene, 1-50 parts of low molecular weight polypropylene, 0.5-5 parts of graft monomer, 0.01-0.5 parts of second initiator, and 0.1-1 parts of antioxidant are melt-mixed and extruded in an extruder to obtain the short-branched polypropylene.
[0022] Optionally, the extrusion temperature during the melt-mixing reaction in the extruder is 160℃~250℃, and the extruder screw speed is 50-300rpm.
[0023] An open-cell foamed polypropylene material, obtained by any of the preparation methods described above.
[0024] Optionally, the melt index of the open-cell foamed polypropylene material is 5-20 g / 10 min, and the melt strength is 5-30 cN.
[0025] The above-described solution of the present invention has at least the following beneficial effects:
[0026] The wide molecular weight distribution short-branched branched polypropylene formed by this invention can improve the foaming performance of polypropylene and form an open-cell structure, resulting in an open-cell foamed polypropylene material with high foaming rate and high open-cell rate.
[0027] The obtained short-branched polypropylene achieves the adjustment of molecular chain size and molecular weight distribution through the selection of low molecular weight polypropylene molecular structure and graft monomers, so as to meet the requirements of foamed materials with different open cell ratios. Detailed Implementation
[0028] Exemplary embodiments of the present invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
[0029] An embodiment of the present invention provides a method for preparing an open-cell foamed polypropylene material, comprising: reacting polypropylene with a first initiator and extruding to obtain low molecular weight polypropylene; the low molecular weight polypropylene is a crystalline waxy or soft waxy solid with a density of 0.89; mixing the low molecular weight polypropylene with polypropylene in a preset ratio to obtain a mixed raw material; adding a second initiator, grafting monomer and antioxidant to the mixed raw material and performing melt grafting in an extruder to obtain a short-branched polypropylene with a wide molecular weight distribution; and foaming the short-branched polypropylene to obtain an open-cell foamed polypropylene material.
[0030] In this embodiment, the low molecular weight polypropylene is a crystalline waxy or soft waxy solid with a density of 0.89. Wide molecular weight distribution short-branched polypropylene refers to a product containing both relatively high (or ultra-high) molecular weight fractions and relatively low molecular weight fractions. The high molecular weight fractions have high mechanical strength and high melt strength, while the low molecular weight fractions have the advantages of low viscosity and easy processing. Therefore, wide molecular weight distribution short-branched polypropylene can simultaneously possess excellent physical and mechanical properties and processing performance.
[0031] In this embodiment, the first initiator initiates the degradation of polypropylene to form low molecular weight polypropylene. Then, the low molecular weight polypropylene is mixed with polypropylene in a certain proportion, and a second initiator, grafting monomers, antioxidants, and free radical stabilizers are added. The mixture is then melt-grafted in an extruder to obtain polypropylene with a short-branched structure. That is, by adjusting the decomposition of low molecular weight polypropylene to form polypropylene free radicals of different molecular weights, and by having these free radicals interact with the grafting monomer free radicals, the molecular chain length and molecular weight distribution of polypropylene can be controlled to meet the requirements of foamed materials with different open-cell ratios.
[0032] By utilizing the short-branched chain structure formed, the foaming performance of polypropylene material is improved while forming an open-cell structure, thus obtaining an open-cell foamed polypropylene material.
[0033] In this embodiment, the short-branched polypropylene is suitable for foaming processes such as extrusion foaming, injection molding foaming, and intermittent foaming, and can be achieved through chemical or physical foaming techniques. One optional foaming process involves placing the prepared short-branched polypropylene into a reactor and using supercritical CO2 for intermittent foaming. The immersion temperature is 140-180℃, the pressure is 10-25MPa, and after immersion for 0.5-2 hours, the pressure is rapidly released and foamed at 90-140℃ to obtain an open-cell foamed polypropylene material.
[0034] In one optional embodiment, the polypropylene is a homopolymer or copolymer linear polypropylene with a melt index of 0.5-20 g / 10 min; the first initiator is selected from at least one of benzoyl peroxide, lauroyl peroxide, dicumyl peroxide, tert-butyl peroxide, and tert-butyl hydroperoxide.
[0035] An optional embodiment involves reacting polypropylene with a first initiator and extruding to obtain low molecular weight polypropylene, comprising: melting and reacting 100 parts of polypropylene and 0.01-0.5 parts of the first initiator by mass to obtain the low molecular weight polypropylene; the extrusion temperature of the melt-mixed reaction extrusion is 170℃~230℃, and the screw speed of the extruder is 50-300 rpm.
[0036] In this embodiment, the low molecular weight polypropylene is obtained by reacting polypropylene with a first initiator and extruding. The first initiator initiates the degradation of polypropylene, thereby reducing its molecular weight during the polypropylene processing to form low molecular weight polypropylene.
[0037] One optional embodiment involves mixing the low molecular weight polypropylene with polypropylene in a preset ratio to obtain a mixed raw material, comprising: mixing 100 parts of polypropylene and 1-50 parts of low molecular weight polypropylene.
[0038] In one optional embodiment, the grafting monomer is selected from at least one of styrene, isoprene, acid anhydride, and ester; wherein the acid anhydride is selected from maleic anhydride, and the ester is selected from pentaerythritol triacrylate and glycidyl methacrylate.
[0039] The second initiator is selected from at least one of benzoyl peroxide, lauroyl peroxide, dicumyl peroxide, tert-butyl peroxide, and tert-butyl hydroperoxide; the antioxidant is selected from at least one of antioxidant 1010, antioxidant 168, antioxidant 1076, and antioxidant 626.
[0040] An optional embodiment involves adding a second initiator, grafting monomer, and antioxidant to the mixed raw materials and performing melt grafting in an extruder to obtain a short-branched polypropylene with a wide molecular weight distribution. This includes: melting and reacting 100 parts of polypropylene, 1-50 parts of low molecular weight polypropylene, 0.5-5 parts of grafting monomer, 0.01-0.5 parts of the second initiator, and 0.1-1 parts of antioxidant in an extruder to obtain the short-branched polypropylene. The extrusion temperature during the melt-mixing reaction in the extruder is 160℃~250℃, and the extruder screw speed is 50-300 rpm.
[0041] In this embodiment, the obtained short-branched polypropylene achieves adjustment of molecular chain size and molecular weight distribution through the selection of low molecular weight polypropylene molecular structure and graft monomers, so as to meet the requirements of foamed materials with different open-cell ratios.
[0042] The present invention also provides an open-cell foamed polypropylene material, which is obtained by the above preparation method.
[0043] An optional embodiment is that the open-cell foamed polypropylene material has a melt index of 5-20 g / 10 min and a melt strength of 5-30 cN; the monomer grafting rate of the open-cell foamed polypropylene material is 0.5%-10% by mass.
[0044] In this embodiment, during the foaming process of conventional polypropylene and high melt polypropylene, excessively high melt strength makes it difficult to induce the bubble wall to rupture and form through-holes; while excessively low melt strength will cause severe rupture of the bubble wall, leading to bubble cell merging and collapse, making it impossible to maintain the open-cell structure, thus making it difficult to achieve the technical problem of high foaming ratio and high open-cell ratio foamed materials.
[0045] In one optional embodiment, the open-cell foamed polypropylene material has an open-cell ratio of 50-90%.
[0046] In this embodiment, the open-cell foamed polypropylene material has an open-cell ratio of 70-90%.
[0047] Specific implementation methods of the above method:
[0048] Example 1
[0049] The open-cell foamed polypropylene material prepared in this embodiment includes the following preparation steps:
[0050] (1) Mix 100 parts of polypropylene and 0.03 parts of the first initiator evenly according to the mass ratio, and add them to a twin-screw extruder for melt reaction grafting. Set the extrusion temperature of the twin-screw extruder to 200℃ and the screw speed to 100rpm to obtain low molecular weight polypropylene.
[0051] (2) 100 parts of polypropylene, 5 parts of low molecular weight polypropylene, 0.5 parts of graft monomer, 0.1 parts of second initiator, and 0.2 parts of antioxidant were melt-mixed and grafted according to the mass fraction. The extrusion temperature of the twin-screw extruder was set to 200℃ and the screw speed was set to 100rpm to obtain short-branched polypropylene.
[0052] (3) The prepared short-branched polypropylene sample was placed in a high-pressure autoclave, the autoclave lid was sealed, and supercritical CO2 was used for intermittent foaming. The soaking temperature was 180℃ and the pressure was 15MPa. After soaking for 2 hours, the pressure was rapidly released and foamed at 140℃ to obtain open-cell foamed polypropylene material.
[0053] Example 2
[0054] The open-cell foamed polypropylene material prepared in this embodiment includes the following preparation steps:
[0055] (1) Mix 100 parts of polypropylene and 0.03 parts of the first initiator evenly according to the mass ratio, and add them to a twin-screw extruder for melt reaction grafting. Set the extrusion temperature of the twin-screw extruder to 200℃ and the screw speed to 100rpm to obtain low molecular weight polypropylene.
[0056] (2) 100 parts of polypropylene, 15 parts of low molecular weight polypropylene, 0.5 parts of graft monomer, 0.1 parts of second initiator, and 0.2 parts of antioxidant were melt-mixed and grafted according to the mass fraction. The extrusion temperature of the twin-screw extruder was set to 200℃ and the screw speed was set to 100rpm to obtain short-branched polypropylene.
[0057] (3) The prepared short-branched polypropylene sample was placed in a high-pressure autoclave, the autoclave lid was sealed, and supercritical CO2 was used for intermittent foaming. The soaking temperature was 180℃ and the pressure was 15MPa. After soaking for 2 hours, the pressure was rapidly released and foamed at 140℃ to obtain open-cell foamed polypropylene material.
[0058] Example 3
[0059] The open-cell foamed polypropylene material prepared in this embodiment includes the following preparation steps:
[0060] (1) Mix 100 parts of polypropylene and 0.03 parts of the first initiator evenly according to the mass ratio, and add them to a twin-screw extruder for melt reaction grafting. Set the extrusion temperature of the twin-screw extruder to 200℃ and the screw speed to 100rpm to obtain low molecular weight polypropylene.
[0061] (2) 100 parts of polypropylene, 30 parts of low molecular weight polypropylene, 1 part of graft monomer, 0.1 parts of second initiator, and 0.2 parts of antioxidant were melt-mixed and grafted according to the mass fraction. The extrusion temperature of the twin-screw extruder was set to 200℃ and the screw speed was set to 100rpm to obtain short-branched polypropylene.
[0062] (3) The prepared short-branched polypropylene sample was placed in a high-pressure autoclave, the autoclave lid was sealed, and supercritical CO2 was used for intermittent foaming. The soaking temperature was 180℃ and the pressure was 15MPa. After soaking for 2 hours, the pressure was rapidly released and foamed at 140℃ to obtain open-cell foamed polypropylene material.
[0063] Example 4
[0064] The open-cell foamed polypropylene material prepared in this embodiment includes the following preparation steps:
[0065] (1) Mix 100 parts of polypropylene and 0.1 parts of the first initiator evenly according to the mass ratio, and add them to a twin-screw extruder for melt reaction grafting. Set the extrusion temperature of the twin-screw extruder to 200℃ and the screw speed to 100rpm to obtain low molecular weight polypropylene.
[0066] (2) 100 parts of polypropylene, 20 parts of low molecular weight polypropylene, 0.5 parts of graft monomer, 0.1 parts of second initiator, and 0.2 parts of antioxidant were melt-mixed and grafted according to the mass fraction. The extrusion temperature of the twin-screw extruder was set to 200℃ and the screw speed was set to 100rpm to obtain short-branched polypropylene.
[0067] (3) The prepared short-branched polypropylene sample was placed in a high-pressure autoclave, the autoclave lid was sealed, and supercritical CO2 was used for intermittent foaming. The soaking temperature was 180℃ and the pressure was 15MPa. After soaking for 2 hours, the pressure was rapidly released and foamed at 140℃ to obtain open-cell foamed polypropylene material.
[0068] Example 5
[0069] The open-cell foamed polypropylene material prepared in this embodiment includes the following preparation steps:
[0070] (1) Mix 100 parts of polypropylene and 0.1 parts of the first initiator evenly according to the mass ratio, and add them to a twin-screw extruder for melt reaction grafting. Set the extrusion temperature of the twin-screw extruder to 200℃ and the screw speed to 100rpm to obtain low molecular weight polypropylene.
[0071] (2) 100 parts of polypropylene, 20 parts of low molecular weight polypropylene, 1 part of graft monomer, 0.2 parts of second initiator, and 0.2 parts of antioxidant were melt-mixed and grafted according to the mass fraction. The extrusion temperature of the twin-screw extruder was set to 200℃ and the screw speed was set to 100rpm to obtain short-branched polypropylene.
[0072] (3) The prepared short-branched polypropylene sample was placed in a high-pressure autoclave, the autoclave lid was sealed, and supercritical CO2 was used for intermittent foaming. The soaking temperature was 180℃ and the pressure was 15MPa. After soaking for 2 hours, the pressure was rapidly released and foamed at 140℃ to obtain open-cell foamed polypropylene material.
[0073] Example 6
[0074] The open-cell foamed polypropylene material prepared in this embodiment includes the following preparation steps:
[0075] (1) Mix 100 parts of polypropylene and 0.2 parts of the first initiator evenly according to the mass ratio, and add them to a twin-screw extruder for melt reaction grafting. Set the extrusion temperature of the twin-screw extruder to 200℃ and the screw speed to 100rpm to obtain low molecular weight polypropylene.
[0076] (2) 100 parts of polypropylene, 20 parts of low molecular weight polypropylene, 1 part of graft monomer, 0.2 parts of second initiator, and 0.2 parts of antioxidant were melt-mixed and grafted according to the mass fraction. The extrusion temperature of the twin-screw extruder was set to 200℃ and the screw speed was set to 100rpm to obtain short-branched polypropylene.
[0077] (3) The prepared short-branched polypropylene sample was placed in a high-pressure autoclave, the autoclave lid was sealed, and supercritical CO2 was used for intermittent foaming. The soaking temperature was 180℃ and the pressure was 15MPa. After soaking for 2 hours, the pressure was rapidly released and foamed at 140℃ to obtain open-cell foamed polypropylene material.
[0078] Comparative Example
[0079] The comparative examples differ from the embodiments in that Comparative Example 1 is conventional homopolymer polypropylene, Comparative Example 2 is the prepared low molecular weight polypropylene, and Comparative Example 3 is melt-grafted long-chain branched polypropylene, which is compared with the short-branched open-cell foamed polypropylene material of the embodiments.
[0080] Comparative Example 1
[0081] (1) Mix 100 parts of polypropylene and 0.2 parts of antioxidant evenly according to the mass ratio, and then add them to a twin-screw extruder for melt reaction extrusion. Set the extrusion temperature of the twin-screw extruder to 200℃ and the screw speed to 100rpm to obtain polypropylene material.
[0082] (2) The polypropylene sample obtained in (1) was placed in a high-pressure autoclave, the autoclave lid was sealed, and supercritical CO2 was used for intermittent foaming. The soaking temperature was 180℃ and the pressure was 15MPa. After soaking for 2 hours, the pressure was rapidly released and foamed at 140℃ to obtain open-cell foamed polypropylene material.
[0083] Comparative Example 2
[0084] (1) Mix 100 parts of polypropylene and 0.03 parts of the first initiator evenly according to the mass ratio, and add them to a twin-screw extruder for melt reaction grafting. Set the extrusion temperature of the twin-screw extruder to 200℃ and the screw speed to 100rpm to obtain low molecular weight polypropylene.
[0085] (2) The prepared short-branched polypropylene sample was placed in a high-pressure autoclave, the autoclave lid was sealed, and supercritical CO2 was used for intermittent foaming. The soaking temperature was 180℃ and the pressure was 15MPa. After soaking for 2 hours, the pressure was rapidly released and foamed at 140℃ to obtain open-cell foamed polypropylene material.
[0086] Comparative Example 3
[0087] (1) 100 parts of polypropylene, 1 part of graft monomer, 0.2 parts of second initiator, 0.2 parts of antioxidant, and 0.2 parts of free radical stabilizer were melt-mixed and grafted according to the mass fraction. The extrusion temperature of the twin-screw extruder was set to 200℃ and the screw speed was set to 100rpm to obtain short-branched polypropylene.
[0088] (2) The prepared short-branched polypropylene sample was placed in a high-pressure autoclave, the autoclave lid was sealed, and supercritical CO2 was used for intermittent foaming. The soaking temperature was 180℃ and the pressure was 15MPa. After soaking for 2 hours, the pressure was rapidly released and foamed at 140℃ to obtain open-cell foamed polypropylene material.
[0089] The tensile strength, impact strength, melt index, melt strength, foaming density, and open-cell ratio of the open-cell foamed polypropylene materials prepared in Examples 1-6 and the conventional homopolymer polypropylene, the low molecular weight polypropylene prepared in Comparative Examples 1-3, and the long-chain branched polypropylene prepared by melt grafting were tested respectively. The results are shown in Table 1.
[0090] Table 1. Test data for Examples 1-6 and Comparative Examples 1-3
[0091]
[0092] The data in the comparison table show that, compared to conventional homopolymer polypropylene raw materials, the melt index and melt strength of the polypropylene prepared by this invention are controllable within a certain range, and its foaming performance is also improved to some extent. However, compared to conventionally prepared long-chain branched polypropylene, the open-cell ratio of the polypropylene prepared by this invention is significantly increased, indicating that the polypropylene with short-chain branched structure prepared by the method of this invention can achieve the control of the molecular weight and molecular weight distribution of polypropylene by adjusting the molecular structure of low molecular weight polypropylene and the composition of grafted monomers, so as to meet the requirements of foaming materials with different open-cell ratios.
[0093] In short,
[0094] (1) The present invention can produce low molecular weight polypropylene by reacting polypropylene with a first initiator and extruding it. It utilizes the decomposition effect of polypropylene during the processing to reduce its molecular weight, and its processing technology is simple.
[0095] (2) In the second initiator reaction extrusion process, the combination of low molecular weight polypropylene free radicals and graft monomer free radicals formed by the degradation of polypropylene molecular chains under the action of the initiator are grafted onto the polypropylene molecular chains. This can effectively achieve the grafting of short-branched polypropylene while broadening its molecular weight distribution, thereby improving the foaming performance of polypropylene and forming an open-cell structure.
[0096] (3) The short-branched polypropylene obtained by the present invention achieves the adjustment of molecular chain size and molecular weight distribution by selecting the molecular structure of low molecular weight polypropylene and grafting monomers, so as to meet the requirements of foaming materials with different open pore ratios.
[0097] (4) The open-cell foamed polypropylene material of the present invention is colorless and odorless, and can well meet the production requirements of different foaming methods and foaming processes, as well as applications in various fields.
[0098] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing an open-cell foamed polypropylene material, characterized in that, include: Low molecular weight polypropylene is obtained by reacting polypropylene with a first initiator and extruding it. The low molecular weight polypropylene and polypropylene are mixed in a preset ratio to obtain a mixed raw material; A second initiator, grafting monomer, and antioxidant are added to the mixed raw materials and melt-grafted in an extruder to obtain a short-branched polypropylene with a wide molecular weight distribution. The short-branched polypropylene is foamed to obtain an open-cell foamed polypropylene material. Low molecular weight polypropylene is obtained by reacting polypropylene with a first initiator and extruding it, including: According to the mass fraction, 100 parts of polypropylene and 0.01 to 0.5 parts of the first initiator are melt-mixed and reacted and extruded to obtain the low molecular weight polypropylene; the extrusion temperature of the melt-mixed reaction extrusion is 170℃ to 230℃, and the extruder screw speed is 50 to 300 rpm; The grafting monomer is selected from at least one of styrene, isoprene, acid anhydride, and ester; A second initiator, grafting monomer, and antioxidant are added to the mixed raw materials, and melt grafting is performed in an extruder to obtain a short-branched polypropylene with a wide molecular weight distribution, comprising: 100 parts of polypropylene, 1-50 parts of low molecular weight polypropylene, 0.5-5 parts of graft monomer, 0.01-0.5 parts of second initiator, and 0.1-1 parts of antioxidant are melt-mixed and extruded in an extruder to obtain the short-branched polypropylene.
2. The method for preparing open-cell foamed polypropylene material according to claim 1, characterized in that, The polypropylene is a homopolymer or copolymer linear polypropylene with a melt index of 0.5 to 20 g / 10 min; The first initiator is selected from at least one of benzoyl peroxide, lauroyl peroxide, dicumyl peroxide, tert-butyl peroxide, and tert-butyl hydroperoxide.
3. The method for preparing open-cell foamed polypropylene material according to claim 1, characterized in that, The low molecular weight polypropylene and polypropylene are mixed in a preset ratio to obtain a mixed raw material, including: 100 parts of polypropylene and 1 to 50 parts of low molecular weight polypropylene are mixed.
4. The method for preparing open-cell foamed polypropylene material according to claim 1, characterized in that, The second initiator is selected from at least one of benzoyl peroxide, lauroyl peroxide, dicumyl peroxide, tert-butyl peroxide, and tert-butyl hydroperoxide; The antioxidant is selected from at least one of antioxidant 1010, antioxidant 168, antioxidant 1076 and antioxidant 626.
5. The method for preparing open-cell foamed polypropylene material according to claim 1, characterized in that, The extrusion temperature during the melt-mixing reaction in the extruder is 160℃~250℃, and the extruder screw speed is 50~300rpm.
6. An open-cell foamed polypropylene material, characterized in that, It is obtained by the preparation method according to any one of claims 1 to 5.
7. The open-cell foamed polypropylene material according to claim 6, characterized in that, The open-cell foamed polypropylene material has a melt index of 5-20 g / 10 min and a melt strength of 5-30 cN.