CN112851997A - Preparation method of polypropylene plate with high foaming efficiency - Google Patents
Preparation method of polypropylene plate with high foaming efficiency Download PDFInfo
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- CN112851997A CN112851997A CN202110036713.3A CN202110036713A CN112851997A CN 112851997 A CN112851997 A CN 112851997A CN 202110036713 A CN202110036713 A CN 202110036713A CN 112851997 A CN112851997 A CN 112851997A
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- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
- C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
- C08J9/122—Hydrogen, oxygen, CO2, nitrogen or noble gases
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/20—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of indefinite length
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/36—Feeding the material to be shaped
- B29C44/46—Feeding the material to be shaped into an open space or onto moving surfaces, i.e. to make articles of indefinite length
- B29C44/50—Feeding the material to be shaped into an open space or onto moving surfaces, i.e. to make articles of indefinite length using pressure difference, e.g. by extrusion or by spraying
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- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/0014—Use of organic additives
- C08J9/0023—Use of organic additives containing oxygen
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- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/0014—Use of organic additives
- C08J9/0038—Use of organic additives containing phosphorus
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- C08J2203/00—Foams characterized by the expanding agent
- C08J2203/06—CO2, N2 or noble gases
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2203/00—Foams characterized by the expanding agent
- C08J2203/08—Supercritical fluid
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
- C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
- C08J2323/10—Homopolymers or copolymers of propene
- C08J2323/12—Polypropene
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- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/04—Oxygen-containing compounds
- C08K5/13—Phenols; Phenolates
- C08K5/134—Phenols containing ester groups
- C08K5/1345—Carboxylic esters of phenolcarboxylic acids
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/49—Phosphorus-containing compounds
- C08K5/51—Phosphorus bound to oxygen
- C08K5/52—Phosphorus bound to oxygen only
- C08K5/524—Esters of phosphorous acids, e.g. of H3PO3
- C08K5/526—Esters of phosphorous acids, e.g. of H3PO3 with hydroxyaryl compounds
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Abstract
A preparation method of a polypropylene plate with high foaming efficiency is characterized by comprising the following steps: the method comprises the following steps: step 1, melting, mixing and extruding foaming-level polypropylene particles to form a pre-foamed plate, wherein the thickness of the pre-foamed plate is 20-35 mm, a plurality of through holes are formed in the direction perpendicular to the plate, and the interval between every two adjacent through holes is 3-6 mm; step 2, placing the pre-foamed sheet in a constant-temperature die cavity, filling supercritical fluid, and performing pressure-maintaining permeation and swelling on the pre-foamed sheet to form a polymer-supercritical fluid homogeneous system after the pre-foamed sheet reaches an equilibrium state; and 3, releasing pressure and foaming to obtain the polypropylene foamed sheet. The preparation method adopted by the invention has short foaming time, the foaming time of each mould is less than 30min, and the production efficiency is high; the prepared polypropylene foamed sheet can meet the requirement of temperature resistance grade of-50-120 ℃; the prepared foamed sheet is 50-80 mm in thickness, 100-200 mu m in diameter of foam holes and 20-40 times in expansion, and is an ultra-light material with excellent mechanical properties.
Description
Technical Field
The invention relates to a preparation method of a polypropylene plate, in particular to a preparation method of a polypropylene plate with high foaming efficiency.
Background
The polypropylene resin is a general polymer material, can resist the temperature of more than 120 ℃, and is widely applied to the fields of packaging, sports goods, automobiles and the like. A supercritical fluid (SCF) is a fluid above a critical temperature and above a critical pressure. Because the viscosity and the diffusion coefficient of the polymer foam material are close to those of gas, and the density and the solvation capacity of the polymer foam material are close to those of liquid, the polymer foam material can be prepared by utilizing the advantages of high diffusion rate, high solubility and the like of the supercritical fluid in the polymer. The supercritical fluid foaming technology has clean whole foaming process and can not cause pollution to the environment and foaming products, so the supercritical fluid foaming technology is more and more valued by the society.
The polypropylene foaming plate is usually prepared by a supercritical die pressing foaming process, and because the foaming temperature is low, the permeation time of the supercritical fluid is long, the foaming time is increased in stages along with the thickness of a product, and the production efficiency is low. Therefore, for the foamed sheet material with the thickness of 20-35 mm, which is demanded by the current market, the existing preparation method cannot meet the requirement on the aspect of production efficiency.
Disclosure of Invention
In order to solve the above problems, the present invention provides a method for preparing a polypropylene sheet with high foaming efficiency, which is characterized in that: the preparation method comprises the following steps:
step 1, melting, mixing and extruding foaming-level polypropylene particles to form a pre-foamed plate, wherein the thickness of the pre-foamed plate is 20-35 mm, a plurality of through holes are formed in the direction perpendicular to the plate, and the interval between every two adjacent through holes is 3-6 mm;
step 2, placing the pre-foamed sheet in a constant-temperature die cavity, filling supercritical fluid, and performing pressure-maintaining permeation and swelling on the pre-foamed sheet to form a polymer-supercritical fluid homogeneous system after the pre-foamed sheet reaches an equilibrium state;
and 3, releasing pressure and foaming to obtain the polypropylene foamed sheet.
Further, in the step 1, the polypropylene particles are foamed polypropylene resin, and the melt index MI is 2.5-7 g/10 min.
Further, in the step 1, the temperature of the melting section is controlled to be 175-195 ℃.
Further, in the step 1, 0.5% of compound antioxidant is added, wherein the compound antioxidant is one or two of antioxidant 168 and antioxidant 1010.
Further, in step 1, the diameter of the through-hole is less than 1 mm.
Further, in the step 2, the adopted supercritical fluid is one or a mixture of two of supercritical nitrogen and supercritical carbon dioxide, the pressure of the supercritical fluid is 3.5-20 MPa, and the pressure-maintaining permeation time is 15-30 min.
Further, in the step 3, pressure is relieved through a pneumatic ball valve, the pressure in the system is relieved to 0, and the pressure relief rate is 10-100 MPa/s.
After the technical scheme is adopted, the invention has the effects that:
1) the foaming time is short, the foaming time of each mould is less than 30min, and the production efficiency is high;
2) the prepared polypropylene foamed sheet can meet the requirement of temperature resistance grade of-50-120 ℃ and can meet the curing molding of common epoxy resin;
3) the prepared foamed sheet is 50-80 mm in thickness, 100-200 mu m in diameter of foam holes and 20-40 times in expansion, and is an ultra-light material with excellent mechanical properties.
Drawings
FIG. 1 is a scanning electron micrograph of a specimen slice according to example 1 of the present invention;
FIG. 2 is a scanning electron micrograph of a sample slice according to example 2 of the present invention;
FIG. 3 is a SEM image of a sample slice according to example 3 of the present invention;
FIG. 4 is a SEM image of a sample slice of example 4 of the present invention.
Detailed Description
It is specifically noted that the terms "first", "second" and "third" in the present invention are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, a feature defined as "first," "second," or "third" may explicitly or implicitly include at least one of the feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise. All directional indicators (such as up, down, left, right, front, and rear … …) in the embodiment of the present invention are only used to explain the relative positional relationship between the components, the movement, and the like in a certain posture, and if the certain posture is changed, the directional indicator is changed accordingly.
The technical solution of the present invention is further described by the following examples:
the invention provides a preparation method of a polypropylene plate with high foaming efficiency, which comprises the following steps:
step 1, melting, mixing and extruding foaming-level polypropylene particles to form a pre-foamed plate, wherein the thickness of the pre-foamed plate is 20-35 mm, a plurality of through holes are formed in the direction perpendicular to the plate, and the interval between every two adjacent through holes is 3-6 mm;
step 2, placing the pre-foamed sheet in a constant-temperature die cavity, filling supercritical fluid, and performing pressure-maintaining permeation and swelling on the pre-foamed sheet to form a polymer-supercritical fluid homogeneous system after the pre-foamed sheet reaches an equilibrium state;
and 3, releasing pressure and foaming to obtain the polypropylene foamed sheet.
The diameter of the foam hole of the polypropylene foaming plate is 100-200 μm, and the foaming ratio is 20-40 times (namely, expansion is 20-40 times). In the foaming process of the polypropylene plate, the time required for swelling and permeating to a homogeneous state is often in an exponential relation with the permeation path of the supercritical fluid, and the thicker the general plate is, the longer the swelling and permeating time is, the more 20mm thick the polypropylene plate is foamed, the permeation time is required to be more than 180min, and the efficiency is very low. According to the preparation method, the plate with the thickness of 20-35 mm is extruded and molded in the step 1, the plurality of through holes are formed in the direction perpendicular to the plate, the plate with the thickness of more than 20mm is uniformly divided into the regions with the permeation paths of 3-6 mm, the permeation is respectively carried out, the saturation is achieved within a short time of 15-30 min, and the production efficiency is improved.
Specifically, in step 1, the polypropylene particles are foamed polypropylene resin, and the melt index MI is 2.5-7 g/10min (measured by a 2.16kg weight at 230 ℃, the same applies below). Preferably, the polypropylene particles are one or more of polypropylene RS1684, polypropylene E02ES and polypropylene W331. Wherein, polypropylene RS1684, polypropylene E02ES and polypropylene W331 are olefin multipolymer such as propylene, ethylene, octene, etc., the melt flow rate is moderate, and the melt strength is high at the same time, can directly extrude and form thicker plates, and has wider foaming operation window.
Specifically, in the step 1, the temperature of the melting section is controlled to be 175-195 ℃. Tests show that poor plasticization is easily caused when the temperature of the melting section is lower than 175 ℃, and the flow of a stamping die cannot be completed; when the temperature of the melting section is higher than 195 ℃, thermal oxygen degradation is easily caused, and the performance of polypropylene is reduced.
Specifically, in the step 1, 0.5% of compound antioxidant is added, and the compound antioxidant is one or two of antioxidant 168 and antioxidant 1010. The compound antioxidant can effectively capture free oxygen free radicals during extrusion processing, reduces thermal oxidative degradation of polypropylene, further reduces yellowing and loss of molecular weight, and ensures smooth proceeding of subsequent foaming.
Specifically, in step 1, the diameter of the through-hole is less than 1 mm. The through holes mainly play a role in accelerating the permeation of polypropylene, and the through holes with the diameter smaller than 1mm can be mutually extruded to disappear after foaming is finished.
Specifically, in step 2, the supercritical fluid employed is supercritical nitrogen (N)2) And supercritical carbon dioxide (CO)2) One or two of the components are mixed, the supercritical fluid pressure is 3.5-20 MPa, and the pressure maintaining permeation time is 15-30 min. Preferably, the supercritical fluid pressure is 8 to 16 MPa. Tests show that when the supercritical fluid pressure is lower than 8MPa, the supercritical fluid is close to a non-supercritical state, and the swelling permeation efficiency is low. In addition, the supercritical fluid pressure is within the range of 16-30 MPa, the density of the supercritical fluid is not greatly changed, the solubility of the supercritical fluid in polypropylene is similar, and the gain on foaming is limited.
Specifically, in the step 3, the pressure is relieved through a pneumatic ball valve, the pressure in the system is relieved to 0, and the pressure relief rate is 10-100 MPa/s. Preferably, the pressure relief rate is 20-50 MPa/s. Tests show that when the pressure relief rate is lower than 20MPa/s, the foam cell nucleation speed is low, large foam cells are easy to form, the diameter of the foam cells is larger than 200 mu m, and the obtained foam has low mechanical property. When the pressure relief rate is higher than 50MPa/s, the nucleation speed of the foam cells is high, small foam cells are easy to form, the diameter of the foam cells is less than 100 micrometers, and the foaming ratio is lower than 20 times.
The preparation method of the invention has the following advantages:
1) the foaming time is short, the foaming time of each mould is less than 30min, and the production efficiency is high;
2) the prepared polypropylene foamed sheet can meet the requirement of temperature resistance grade of-50-120 ℃ and can meet the curing molding of common epoxy resin;
3) the prepared foamed sheet is 50-80 mm in thickness, 100-200 mu m in diameter of foam holes and 20-40 times in expansion, and is an ultra-light material with excellent mechanical properties.
Example 1
A preparation method of a polypropylene plate with high foaming efficiency selects foaming grade polypropylene resin RS1684 with a melt index of 7g/10min, and dries polypropylene particles for standby, and the preparation method comprises the following steps:
step 1, melting, mixing and extruding foaming-level polypropylene particles RS1684 for molding, adding 0.5% of compound antioxidant, wherein the compound antioxidant is antioxidant 168, the temperature of a melting section is 185 ℃, preparing a pre-foaming plate, the thickness of the pre-foaming plate is 20mm, a plurality of through holes are formed in the direction vertical to the plate, the interval between every two adjacent through holes is 3mm, the diameter of each through hole is less than 1mm, and cutting the pre-foaming plate into plates with the size of 1600 x 800 mm;
step 2, placing the pre-foamed sheet in a constant-temperature die cavity, wherein the temperature of the die cavity is 145 ℃, replacing air in the die cavity, then filling a supercritical fluid, maintaining the pressure of the supercritical fluid at 8MPa, and maintaining the pressure for permeation for 15 min;
and 3, relieving pressure through a pneumatic ball valve, wherein the pressure relief rate is 20MPa/s, quickly relieving the pressure in the die cavity from 8MPa to 0, and opening the die for foaming to obtain the polypropylene foamed plate.
The density of the polypropylene foamed sheet material is 45kg/m3The sample expands 20 times compared with the original material, the section of the sample is taken by a scanning electron microscope, the picture is shown in figure 1, and the average pore diameter is 100 mu m.
Example 2
A preparation method of a polypropylene plate with high foaming efficiency selects foaming grade polypropylene resin RS1684 with a melt index of 7g/10min, and dries polypropylene particles for standby, and the preparation method comprises the following steps:
step 1, melting, mixing and extruding foaming-grade polypropylene particles RS1684 by using a double-screw extruder, adding 0.5% of a compound antioxidant, wherein the compound antioxidant is antioxidant 168, the temperature of a melting section is 185 ℃, preparing a pre-foamed plate, the thickness of the pre-foamed plate is 35mm, a plurality of through holes are formed in the direction vertical to the plate, the interval between every two adjacent through holes is 6mm, the diameter of each through hole is less than 1mm, and cutting the pre-foamed plate into plates with the size of 1600 x 800 mm;
step 2, placing the pre-foamed sheet in a constant-temperature die cavity, wherein the temperature of the die cavity is 155 ℃, replacing air in the die cavity, filling a supercritical fluid, maintaining the pressure of the supercritical fluid at 16MPa, and maintaining the pressure for 30 min;
and 3, relieving pressure through a pneumatic ball valve, wherein the pressure relief rate is 50MPa/s, quickly relieving the pressure in the die cavity from 16MPa to 0, and opening the die for foaming to obtain the polypropylene foamed plate.
The density of the polypropylene foaming plate is 22.5kg/m3The sample expands 40 times compared with the original material, the scanning electron micrograph of the sample section is shown in figure 2, and the average pore diameter is 200 μm.
Example 3
A preparation method of a polypropylene plate with high foaming efficiency selects foaming grade polypropylene resin RS1684 with a melt index of 7g/10min, and dries polypropylene particles for standby, and the preparation method comprises the following steps:
step 1, melting, mixing and extruding foaming-grade polypropylene particles RS1684 by using a double-screw extruder, adding 0.5% of a compound antioxidant, wherein the compound antioxidant is antioxidant 168, the temperature of a melting section is 185 ℃, preparing a pre-foamed plate, the thickness of the pre-foamed plate is 30mm, a plurality of through holes are formed in the direction vertical to the plate, the interval between every two adjacent through holes is 6mm, the diameter of each through hole is less than 1mm, and cutting the pre-foamed plate into plates with the size of 1600 x 800 mm;
step 2, placing the pre-foamed sheet in a constant-temperature die cavity, wherein the temperature of the die cavity is 150 ℃, replacing air in the die cavity, then filling a supercritical fluid, maintaining the pressure of the supercritical fluid at 12MPa, and maintaining the pressure for permeation for 25 min;
and 3, relieving pressure through a pneumatic ball valve, wherein the pressure relief rate is 35MPa/s, quickly relieving the pressure in the die cavity from 12MPa to 0, and opening the die for foaming to obtain the polypropylene foamed plate.
The density of the polypropylene foaming plate is 30kg/m3The sample expands 30 times compared with the original material, the scanning electron micrograph of the sample section is shown in figure 3, and the average pore diameter is 150 mu m.
Example 4
A preparation method of a polypropylene plate with high foaming efficiency selects foaming grade polypropylene resin RS1684 with a melt index of 7g/10min, and dries polypropylene particles for standby, and the preparation method comprises the following steps:
step 1, melting, mixing and extruding foaming-grade polypropylene particles RS1684 by using a double-screw extruder, adding 0.5% of a compound antioxidant, wherein the compound antioxidant is antioxidant 168, the temperature of a melting section is 185 ℃, preparing a pre-foamed plate, the thickness of the pre-foamed plate is 32mm, a plurality of through holes are formed in the direction vertical to the plate, the interval between every two adjacent through holes is 6mm, the diameter of each through hole is less than 1mm, and cutting the pre-foamed plate into plates with the size of 1600 x 800 mm;
step 2, placing the pre-foamed sheet in a constant-temperature die cavity, wherein the temperature of the die cavity is 148 ℃, replacing air in the die cavity, then filling a supercritical fluid, maintaining the pressure of the supercritical fluid at 16MPa, and carrying out pressure-maintaining permeation for 30 min;
and 3, relieving pressure through a pneumatic ball valve, wherein the pressure relief rate is 40MPa/s, quickly relieving the pressure in the die cavity from 16MPa to 0, and opening the die for foaming to obtain the polypropylene foamed plate.
The density of the polypropylene foaming plate is 25kg/m3The sample expands 36 times compared with the original material, the scanning electron micrograph of the sample section is shown in figure 4, and the average pore diameter is 180 mu m.
Comparative example 1
A preparation method of a polypropylene plate with high foaming efficiency selects foaming grade polypropylene resin RS1684 with a melt index of 7g/10min, and dries polypropylene particles for standby, and the preparation method comprises the following steps:
step 1, melting, mixing and extruding foaming-level polypropylene particles RS1684 by a double-screw extruder for molding, adding 0.5% of compound antioxidant, wherein the compound antioxidant is antioxidant 168, the temperature of a melting section is 185 ℃, preparing a pre-foamed plate, the thickness of the pre-foamed plate is 35mm, and the pre-foamed plate is cut into plates with the size of 1600 x 800mm without through hole molding treatment;
step 2, placing the pre-foamed sheet in a constant-temperature die cavity, wherein the temperature of the die cavity is 145 ℃, replacing air in the die cavity, then filling a supercritical fluid, maintaining the pressure of the supercritical fluid at 8MPa, and maintaining the pressure for permeation for 15 min;
and 3, relieving pressure through a pneumatic ball valve, wherein the pressure relief rate is 20MPa/s, quickly relieving the pressure in the die cavity from 8MPa to 0, and opening the die for foaming to obtain the plate.
The surface of the plate is twisted, and the inside of the plate is not foamed.
Comparative example 2
A preparation method of a polypropylene plate with high foaming efficiency selects foaming grade polypropylene resin RS1684 with a melt index of 7g/10min, and dries polypropylene particles for standby, and the preparation method comprises the following steps:
step 1, melting, mixing and extruding foaming-level polypropylene particles RS1684 by a double-screw extruder for molding, adding 0.5% of compound antioxidant, wherein the compound antioxidant is antioxidant 168, the temperature of a melting section is 185 ℃, preparing a pre-foamed plate, the thickness of the pre-foamed plate is 35mm, and the pre-foamed plate is cut into plates with the size of 1600 x 800mm without through hole molding treatment;
step 2, placing the pre-foamed sheet in a constant-temperature die cavity, wherein the temperature of the die cavity is 145 ℃, replacing air in the die cavity, then filling a supercritical fluid, maintaining the pressure of the supercritical fluid at 8MPa, and carrying out pressure-maintaining permeation for 30 min;
and 3, relieving pressure through a pneumatic ball valve, wherein the pressure relief rate is 20MPa/s, quickly relieving the pressure in the die cavity from 8MPa to 0, and opening the die for foaming to obtain the plate.
The surface of the plate is twisted, the foaming layer is only 6mm, the foaming is not completed in the plate, and the foaming layer is stripped from the unfoamed part to form a cavity, so that the foamed plate cannot be prepared.
Comparative example 3
A preparation method of a polypropylene plate with high foaming efficiency selects foaming grade polypropylene resin RS1684 with a melt index of 7g/10min, and dries polypropylene particles for standby, and the preparation method comprises the following steps:
step 1, melting, mixing and extruding foaming-level polypropylene particles RS1684 by a double-screw extruder for molding, adding 0.5% of compound antioxidant, wherein the compound antioxidant is antioxidant 168, the temperature of a melting section is 185 ℃, preparing a pre-foamed plate, the thickness of the pre-foamed plate is 35mm, and the pre-foamed plate is cut into plates with the size of 1600 x 800mm without through hole molding treatment;
step 2, placing the pre-foamed sheet in a constant-temperature die cavity, wherein the temperature of the die cavity is 145 ℃, replacing air in the die cavity, filling a supercritical fluid, maintaining the pressure of the supercritical fluid at 8MPa, and maintaining the pressure and permeating for 360 min;
and 3, relieving pressure through a pneumatic ball valve, wherein the pressure relief rate is 20MPa/s, quickly relieving the pressure in the die cavity from 8MPa to 0, and opening the die for foaming to obtain the plate.
The density of the plate is 60kg/m3Compared with the original material, the material expands 15 times, the skin foam pores are fine and smooth, and the internal foam pores are thick.
The above-described embodiments are merely preferred examples of the present invention, and not intended to limit the scope of the invention, so that equivalent changes or modifications in the structure, features and principles of the invention described in the claims should be included in the claims.
Claims (7)
1. A preparation method of a polypropylene plate with high foaming efficiency is characterized by comprising the following steps: the preparation method comprises the following steps:
step 1, melting, mixing and extruding foaming-level polypropylene particles to form a pre-foamed plate, wherein the thickness of the pre-foamed plate is 20-35 mm, a plurality of through holes are formed in the direction perpendicular to the plate, and the interval between every two adjacent through holes is 3-6 mm;
step 2, placing the pre-foamed sheet in a constant-temperature die cavity, filling supercritical fluid, and performing pressure-maintaining permeation and swelling on the pre-foamed sheet to form a polymer-supercritical fluid homogeneous system after the pre-foamed sheet reaches an equilibrium state;
and 3, releasing pressure and foaming to obtain the polypropylene foamed sheet.
2. The method for preparing polypropylene plate with high foaming efficiency as claimed in claim 1, wherein the method comprises the following steps: in the step 1, the polypropylene particles are foamed polypropylene resin, and the melt index MI is 2.5-7 g/10 min.
3. The method for preparing polypropylene plate with high foaming efficiency as claimed in claim 1, wherein the method comprises the following steps: in the step 1, the temperature of the melting section is controlled to be 175-195 ℃.
4. The method for preparing polypropylene plate with high foaming efficiency as claimed in claim 1, wherein the method comprises the following steps: in the step 1, 0.5 percent of compound antioxidant is added, and the compound antioxidant is one or the mixture of antioxidant 168 and antioxidant 1010.
5. The method for preparing polypropylene plate with high foaming efficiency as claimed in claim 1, wherein the method comprises the following steps: the diameter of the through hole is less than 1 mm.
6. The method for preparing polypropylene plate with high foaming efficiency as claimed in claim 1, wherein the method comprises the following steps: in the step 2, the adopted supercritical fluid is one or a mixture of two of supercritical nitrogen and supercritical carbon dioxide, the pressure of the supercritical fluid is 3.5-20 MPa, and the pressure-maintaining permeation time is 15-30 min.
7. The method for preparing polypropylene plate with high foaming efficiency as claimed in claim 1, wherein the method comprises the following steps: and 3, relieving pressure through a pneumatic ball valve, wherein the pressure in the system is relieved to 0, and the pressure relief rate is 10-100 MPa/s.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115073854A (en) * | 2022-08-23 | 2022-09-20 | 江苏中科聚合新材料产业技术研究院有限公司 | High-temperature-resistant flame-retardant polypropylene foam material and preparation method and application thereof |
| CN115124786A (en) * | 2022-08-30 | 2022-09-30 | 江苏中科聚合新材料产业技术研究院有限公司 | Modified polypropylene master batch, heat-resistant foam material and preparation method thereof |
| CN115960383A (en) * | 2021-08-05 | 2023-04-14 | 江苏大毛牛新材料有限公司 | Environment-friendly efficient low-cost method for preparing physical foaming material |
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| CN102504323A (en) * | 2011-11-07 | 2012-06-20 | 常州天晟新材料股份有限公司 | Industrially-applicable method for preparing polymer foamed material by using supercritical fluid technology |
| CN103042647A (en) * | 2012-11-08 | 2013-04-17 | 江苏微赛新材料科技有限公司 | Method for producing polypropylene micro-porous foamed thick board |
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| CN102504323A (en) * | 2011-11-07 | 2012-06-20 | 常州天晟新材料股份有限公司 | Industrially-applicable method for preparing polymer foamed material by using supercritical fluid technology |
| CN103042647A (en) * | 2012-11-08 | 2013-04-17 | 江苏微赛新材料科技有限公司 | Method for producing polypropylene micro-porous foamed thick board |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115960383A (en) * | 2021-08-05 | 2023-04-14 | 江苏大毛牛新材料有限公司 | Environment-friendly efficient low-cost method for preparing physical foaming material |
| CN115073854A (en) * | 2022-08-23 | 2022-09-20 | 江苏中科聚合新材料产业技术研究院有限公司 | High-temperature-resistant flame-retardant polypropylene foam material and preparation method and application thereof |
| CN115124786A (en) * | 2022-08-30 | 2022-09-30 | 江苏中科聚合新材料产业技术研究院有限公司 | Modified polypropylene master batch, heat-resistant foam material and preparation method thereof |
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Application publication date: 20210528 |