CN109501107B - Low-density high-foaming-rate polymer foam material and preparation method thereof - Google Patents

Low-density high-foaming-rate polymer foam material and preparation method thereof Download PDF

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CN109501107B
CN109501107B CN201811063007.2A CN201811063007A CN109501107B CN 109501107 B CN109501107 B CN 109501107B CN 201811063007 A CN201811063007 A CN 201811063007A CN 109501107 B CN109501107 B CN 109501107B
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polymer
pressure
foaming
mold
injection molding
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CN109501107A (en
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汪龙
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Hefei Huaju Weike New Material Co ltd
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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
    • B29C44/38—Feeding the material to be shaped into a closed space, i.e. to make articles of definite length
    • B29C44/42—Feeding the material to be shaped into a closed space, i.e. to make articles of definite length using pressure difference, e.g. by injection or by vacuum
    • 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
    • B29C44/02—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of definite length, i.e. discrete articles
    • B29C44/08—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of definite length, i.e. discrete articles using several expanding or moulding steps
    • 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
    • B29C44/3442—Mixing, kneading or conveying the foamable material
    • B29C44/3446—Feeding the blowing agent
    • B29C44/3449—Feeding the blowing agent through the screw
    • 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
    • B29C44/38—Feeding the material to be shaped into a closed space, i.e. to make articles of definite length
    • B29C44/42—Feeding the material to be shaped into a closed space, i.e. to make articles of definite length using pressure difference, e.g. by injection or by vacuum
    • B29C44/428—Mould constructions; Mould supporting equipment
    • 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
    • B29C44/58—Moulds
    • B29C44/586—Moulds with a cavity increasing in size during foaming
    • 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
    • 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
    • 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
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/0066—Use of inorganic compounding ingredients
    • 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
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/0066—Use of inorganic compounding ingredients
    • C08J9/0071—Nanosized fillers, i.e. having at least one dimension below 100 nanometers
    • 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
    • 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
    • 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
    • C08J2203/06—CO2, N2 or noble gases
    • 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
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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    • 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
    • C08J2323/04—Homopolymers or copolymers of ethene
    • C08J2323/06—Polyethene
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    • 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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    • C08J2325/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Derivatives of such polymers
    • C08J2325/02—Homopolymers or copolymers of hydrocarbons
    • C08J2325/04—Homopolymers or copolymers of styrene
    • C08J2325/06—Polystyrene
    • C—CHEMISTRY; METALLURGY
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    • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
    • C08J2367/04—Polyesters derived from hydroxy carboxylic acids, e.g. lactones

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  • Injection Moulding Of Plastics Or The Like (AREA)

Abstract

The invention provides a polymer foam material with low density and high foaming multiplying power and a preparation method thereof, which is prepared by a core back type micropore injection molding technology and comprises the following steps: preparing a modified polymer composite material, preparing polymer melt, filling a cavity with the polymer melt, maintaining pressure, cooling and foaming with a core retreating type. The invention adopts a high-pressure full injection mode, and polymer melt is injected into a mold cavity in the high-pressure full injection mode and completely fills the mold cavity; the polymer solution is kept in the die cavity for a period of time under a higher pressure to ensure that the prepared polymer foam material has highly controllable density and foaming ratio, namely the density is 0.1-0.5g/cm3And the foaming ratio is 2-10 times.

Description

Low-density high-foaming-rate polymer foam material and preparation method thereof
Technical Field
The invention belongs to the field of microcellular foaming of high polymer materials, and particularly relates to a low-density high-foaming-rate polymer foam material and a preparation method thereof.
Background
Microcellular foam molding technology was first proposed in the 80's of the 20 th century by Suh professor of the university of labor of Massachusetts (publication No.: US 4473665). Compared with the traditional foam plastic, the microcellular foam plastic prepared by the microcellular foaming and forming technology has the biggest characteristic that the cells are small and dense. The material can keep the advantages of common foam plastics, such as light weight, impact resistance, high specific strength, good heat insulation and sound insulation effects; meanwhile, because the size of the foam hole is smaller than the original crack in the material, the existence of the foam hole can not reduce the strength of the material, but can passivate the tip of the original crack in the material, which is beneficial to preventing the crack from expanding under the action of stress, thereby enhancing the mechanical property of the microporous foam material. In addition, unlike the conventional foaming process, the microcellular foaming technology utilizes supercritical fluid such as supercritical carbon dioxide or nitrogen as a physical foaming agent, both of which are inert gases, non-toxic and non-flammable, so that the foaming process is green and environment-friendly, has a wide development prospect in industrial application, and is called as a novel material in the 21 st century.
Subsequently, Trexel incorporated a combination of injection molding and foaming techniques, and proposed a microcellular foam injection molding process. Compared with common polymer materials, the microcellular foam injection molded product has the advantages of small density, light weight, high impact strength, high toughness, high specific strength and the like. In addition, compared with the common injection molding technology, the microcellular foaming injection molding technology has the advantages of short molding cycle, raw material saving, residual stress reduction, product surface quality improvement, mold locking force reduction and maximum injection molding pressure reduction, and meanwhile, the obtained product has high dimensional stability and can reduce warping deformation, shrinkage rate and the like. Compared with other micropore foaming technologies such as solid kettle pressure foaming and extrusion foaming, the micropore foaming injection molding technology can prepare products with three-dimensional complex precise structures, and can be widely applied to places with high precision requirements, certain requirements on mechanical properties and complex structures.
However, since the microcellular foam injection molding technology has been developed for more than 30 years, it is still difficult to fully exert its technical advantages in the actual production process, and the product performance originally designed by researchers and large-scale popularization have not been realized. The traditional microcellular foaming injection molding technology adopts a melt short shot mode to fill a mold cavity, so that the weight loss rate is low (generally 5-20%) and the foaming rate is low (generally 1.05-1.2 times); meanwhile, the polymer melt can be pre-foamed in the die stamping process, so that the size of the cells of the product is large and uneven, the sizes of the pore diameters are also uneven, and the pore diameters near the opening and at the tail end are large, which greatly limits the wide application of the microcellular foaming injection molding process in the actual production process.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a polymer foam material which can obtain uniform bubbles, low foam density and high foaming ratio and a preparation method thereof, so as to solve the problems of low foaming ratio, high product density, large cell size and the like of the traditional injection molding foaming product.
The technical scheme of the invention is as follows:
a preparation method of a polymer foam material with low density and high foaming multiplying power is prepared by a core back type micropore injection molding technology, and specifically comprises the following steps:
(1) preparation of modified polymer composite: mixing the polymer and the filler, putting the mixture into a double-screw extruder, and performing extrusion and underwater grain cutting to obtain a modified polymer composite material;
(2) preparation of a polymer melt: adding the modified polymer composite material into an automatic conveying hopper of an injection molding machine, and heating and melting the modified polymer composite material at a screw melting section; then injecting high-pressure foaming agent gas by using supercritical fluid equipment, and uniformly mixing the high-pressure foaming agent gas into the molten polymer by using a screw mixing and conveying function of an injection molding machine to obtain single homogeneous polymer/gas mixed polymer melt;
(3) filling the cavity with the polymer melt: opening a nozzle of an injection molding machine and a hot runner of a mold, injecting the polymer melt into a mold cavity by adopting a high-pressure full injection mode, and completely filling the mold cavity;
(4) pressure maintaining and cooling: after the polymer solution is filled in the cavity, the screw rod retreats; then keeping the pressure of the polymer solution in a die cavity and cooling to form a high-elasticity polymer;
(5) core back type foaming: and after the pressure maintaining is finished, opening and closing the die, expanding the cavity space of the die, foaming the high-elastic polymer, cooling and opening the die to obtain the polymer foam material with the solid skin layer and the foaming core layer.
Further, the barrel temperature of the extruder in the step (1) is 150-.
Further, the back pressure of 15-18MPa is kept in the screw of the injection molding machine in the step (2), so that the high-pressure foaming agent gas is completely dissolved into the polymer melt; the pressure of the high-pressure foaming agent gas is 24-30 MPa; the screw temperature of the injection molding machine is 180-300 ℃.
Further, the injection pressure of the polymer melt injected into the mold cavity in the step (3) is 160-.
Further, the pressure maintaining pressure of the polymer melt in the die cavity in the step (4) is 40-60MPa, and the die temperature is 40-70 ℃.
And (5) opening and closing the mold for 3-8s, at a speed of 10-30mm/s, at a distance of 1-9mm, and cooling for 30-60 s.
It is another object of the present invention to provide a polymeric foam having a density of 0.1 to 0.5g/cm3And the foaming ratio is 2-10 times.
In a further scheme, the polymer foam material is composed of 100 parts of polymer, 5-20 parts of filler and 2-8 parts of foaming agent.
In a further embodiment, the polymer is polyethylene, polylactic acid, polypropylene or polystyrene having a number average molecular weight of 20 to 60 ten thousand;
the filler is talcum powder, calcium carbonate, mica, barium sulfate, glass fiber, transparent nucleating agent sorbitol or nano clay;
the foaming agent is supercritical fluid carbon dioxide or supercritical nitrogen.
The invention adopts a high-pressure full injection mode to inject polymer melt into a mold cavity and completely fill the mold cavity; different from the conventional microcellular foaming injection molding by using a low-pressure short injection mode, a high-pressure full injection mode is adopted, the polymer melt needs to completely fill the cavity, and meanwhile, the higher injection pressure and injection speed are used for preventing gas from escaping in the filling process and foaming in advance. In addition, the polymer melt is kept at a high holding pressure for a while in the mold cavity, in order to prevent premature foaming of the polymer. In the cooling and pressure maintaining process, the viscoelastic property of the polymer is controlled, and the mold opening and closing time is regulated, so that the microcellular foaming injection molding polymer foam with low density and high foaming rate can be obtained. The polymer foam material product prepared by the invention can be applied to automobile interior and exterior decorative parts and automobile parts, and realizes the light weight of materials for the automobile parts; it can also be used in other fields such as electronics, construction, packaging, etc.
The polymer foam material prepared by the invention has highly controllable density and foaming ratio, namely the density is 0.1-0.5g/cm3And the foaming ratio is 2-10 times. Obviously superior to 5-20% weight loss and 1.05-1.2 times of foaming ratio of polymer foam materials prepared by the traditional microcellular foaming injection molding technology.
The invention has the beneficial effects that:
(1) compared with the traditional microcellular foaming injection molding process, the core back microcellular injection molding process is adopted, and the high-pressure full-injection mode is adopted to fill the mold cavity, so that the pre-foaming of the polymer melt in the flowing process can be greatly reduced.
(2) Compared with the conventional injection molding polypropylene product, the preparation method of the invention can simultaneously generate the foaming process, thereby obtaining the polymer foaming product with the same shape of the foam cells and uniform pore diameter.
(3) The invention utilizes the filler to change the melt viscoelasticity of the polymer, so that a large number of fine and dense cells can be obtained.
(4) By utilizing the core back type micropore injection molding technology, the foaming process of the polymer can be uniformly controlled, and furthermore, a large number of foam holes with small size and high density can be obtained by regulating and controlling the mold opening and closing time and speed.
(5) Compared with the traditional foaming injection molding, the preparation process provided by the invention combines a core back-off molding technology, so that the number of mold cavities can be greatly increased, and thus, an injection molding part with high foaming ratio and low density can be obtained.
Drawings
FIG. 1 is an SEM image of a low density, high expansion microcellular injection molded polymeric foam obtained in example one.
FIG. 2 is an SEM image of a low density, high expansion microcellular injection molded polymer foam from example two.
FIG. 3 is an SEM image of a low density, high expansion microcellular injection molded polymer foam obtained in example III.
FIG. 4 is an SEM image of a low density, high expansion microcellular injection molded polymer foam from example four.
FIG. 5 is an SEM image of a low density, high expansion microcellular injection molded polymer foam from example V.
FIG. 6 is an SEM image of a conventional microcellular injection molded polymeric foam material obtained in comparative example one.
Detailed Description
The following examples are only exemplary embodiments and are not intended to limit the scope of the present invention, and those skilled in the art can reasonably design the technical solutions with reference to the examples and can also obtain the results of the present invention.
The method for testing the weight reduction rate and the cell density comprises the following steps:
weight loss: firstly, respectively testing the apparent densities of the foaming material and the unfoamed material according to the GB/T6343-2009 standard, and then calculating to obtain the weight reduction rate of the final microcellular foaming material. Weight loss (%) - (1- ρ)foam/ρpolymer) X 100% where ρfoamIs the density of the foamed material, ppolymerIs the density of the unfoamed material.
The density of the polymer foam is measured by the drainage method.
Example one
A preparation method of a polymer foam material with low density and high foaming multiplying power is prepared by a core back type micropore injection molding technology, and specifically comprises the following steps:
(1) preparation of modified polymer composite: 100 parts of polylactic acid with the number average molecular weight of 20 ten thousand and 5 parts of calcium carbonate as a filler are mixed and then put into a double-screw extruder, and the modified polymer composite material is obtained through extrusion and underwater grain cutting; wherein the temperature of the extruder charging barrel is 150 ℃;
(2) preparation of a polymer melt: adding the modified polymer composite material into an automatic conveying hopper of an injection molding machine, and heating and melting the modified polymer composite material at a screw melting section; then, supercritical nitrogen 2 parts of high-pressure foaming agent gas with the injection pressure of 24MPa is injected by supercritical fluid equipment, the high-pressure foaming agent gas is uniformly mixed into the molten polymer by a screw mixing and conveying function of an injection molding machine, the temperature of a screw of the injection molding machine is 180 ℃, and the backpressure pressure of 15MPa is kept, so that the high-pressure foaming agent gas is completely dissolved into the polymer melt; obtaining a single homogeneous polymer/gas mixed polymer melt;
(3) filling the cavity with the polymer melt: opening a nozzle of an injection molding machine and a hot runner of a mold, injecting the polymer melt into a mold cavity by adopting a high-pressure full injection mode, and completely filling the mold cavity; the injection pressure is 160MPa, and the injection speed is 100 mm/s;
(4) pressure maintaining and cooling: after the polymer solution is filled in the cavity, the screw rod retreats; then keeping the pressure of the polymer solution in a die cavity at 40MPa, and cooling the polymer solution by a low-temperature die at 50 ℃ to form a high-elastic polymer;
(5) core back type foaming: after the pressure maintaining is finished, opening and closing the mold, expanding the cavity space of the mold, foaming the high-elastic polymer, cooling and opening the mold to obtain the polymer foam material with the solid skin layer and the foaming core layer; wherein the time for opening and closing the mold is 4.2s, the speed for opening and closing the mold is 10mm/s, the distance for opening and closing the mold is 1mm, and the time for cooling and opening the mold is 50 s.
The cellular morphology of the polylactic acid foam material obtained by microcellular injection molding prepared in this example is shown in FIG. 1, and the density is 0.5g/cm3The weight reduction ratio was 50% and the expansion ratio was 2 times.
Example two
A preparation method of a polymer foam material with low density and high foaming multiplying power is prepared by a core back type micropore injection molding technology, and specifically comprises the following steps:
(1) preparation of modified polymer composite: 100 parts of polyethylene with the number average molecular weight of 60 ten thousand and 15 parts of filler talcum powder are mixed and then put into a double-screw extruder, and the modified polymer composite material is obtained through extrusion and underwater grain cutting; wherein the temperature of the extruder charging barrel is 200 ℃;
(2) preparation of a polymer melt: adding the modified polymer composite material into an automatic conveying hopper of an injection molding machine, and heating and melting the modified polymer composite material at a screw melting section; then, supercritical nitrogen with the pressure of 26MPa is injected into 4 parts by supercritical fluid equipment, the supercritical nitrogen is uniformly mixed into the molten polymer by the screw mixing and conveying function of an injection molding machine, the temperature of the screw of the injection molding machine is 200 ℃, and the back pressure of 17MPa is kept, so that the high-pressure foaming agent gas is completely dissolved into the polymer melt; obtaining a single homogeneous polymer/gas mixed polymer melt;
(3) filling the cavity with the polymer melt: opening a nozzle of an injection molding machine and a hot runner of a mold, injecting the polymer melt into a mold cavity by adopting a high-pressure full injection mode, and completely filling the mold cavity; the injection pressure is 170MPa, and the injection speed is 150 mm/s;
(4) pressure maintaining and cooling: after the polymer solution is filled in the cavity, the screw rod retreats; then keeping the pressure of the polymer solution in a die cavity at 40MPa, and cooling the polymer solution by a low-temperature die at 40 ℃ to form a high-elastic polymer;
(5) core back type foaming: after the pressure maintaining is finished, opening and closing the mold, expanding the cavity space of the mold, foaming the high-elastic polymer, cooling and opening the mold to obtain the polymer foam material with the solid skin layer and the foaming core layer; wherein the time for opening and closing the mold is 3s, the speed for opening and closing the mold is 20mm/s, the distance for opening and closing the mold is 4mm, and the time for cooling and opening the mold is 50 s.
The cell morphology of the polyethylene foam material obtained by microcellular injection molding prepared in this example is shown in FIG. 2, and the density is 0.2g/cm3The weight reduction ratio was 80% and the expansion ratio was 5 times.
EXAMPLE III
A preparation method of a polymer foam material with low density and high foaming multiplying power is prepared by a core back type micropore injection molding technology, and specifically comprises the following steps:
(1) preparation of modified polymer composite: 100 parts of polypropylene with the number average molecular weight of 40 ten thousand and 8 parts of transparent sorbitol as a filler are mixed and then put into a double-screw extruder, and the modified polymer composite material is obtained through extrusion and underwater grain cutting; wherein the temperature of the extruder charging barrel is 250 ℃;
(2) preparation of a polymer melt: adding the modified polymer composite material into an automatic conveying hopper of an injection molding machine, and heating and melting the modified polymer composite material at a screw melting section; then, injecting 8 parts of high-pressure foaming agent gas supercritical carbon dioxide with the pressure of 30MPa by using supercritical fluid equipment, uniformly mixing the high-pressure foaming agent gas into the molten polymer by using a screw mixing and conveying function of an injection molding machine, wherein the temperature of a screw of the injection molding machine is 250 ℃, and the backpressure pressure of 18MPa is kept, so that the high-pressure foaming agent gas is completely dissolved into the polymer melt; obtaining a single homogeneous polymer/gas mixed polymer melt;
(3) filling the cavity with the polymer melt: opening a nozzle of an injection molding machine and a hot runner of a mold, injecting the polymer melt into a mold cavity by adopting a high-pressure full injection mode, and completely filling the mold cavity; the injection pressure is 180MPa, and the injection speed is 200 mm/s;
(4) pressure maintaining and cooling: after the polymer solution is filled in the cavity, the screw rod retreats; then keeping the pressure of the polymer solution in a die cavity at 60MPa, and cooling the polymer solution by a low-temperature die at 50 ℃ to form a high-elastic polymer;
(5) core back type foaming: after the pressure maintaining is finished, opening and closing the mold, expanding the cavity space of the mold, foaming the high-elastic polymer, cooling and opening the mold to obtain the polymer foam material with the solid skin layer and the foaming core layer; wherein the time for opening and closing the mold is 4.5s, the speed for opening and closing the mold is 30mm/s, the distance for opening and closing the mold is 9mm, and the time for cooling and opening the mold is 45 s.
The cellular morphology of the polypropylene foam material obtained by microcellular injection molding prepared in this example is shown in FIG. 3, and the density is 0.1g/cm3The weight reduction ratio was 90% and the expansion ratio was 10 times.
Example four
A preparation method of a polymer foam material with low density and high foaming multiplying power is prepared by a core back type micropore injection molding technology, and specifically comprises the following steps:
(1) preparation of modified polymer composite: 100 parts of polystyrene with the number average molecular weight of 30 ten thousand and 20 parts of mica filler are mixed and then put into a double-screw extruder, and the modified polymer composite material is obtained through extrusion and underwater grain cutting; wherein the temperature of the extruder charging barrel is 300 ℃;
(2) preparation of a polymer melt: adding the modified polymer composite material into an automatic conveying hopper of an injection molding machine, and heating and melting the modified polymer composite material at a screw melting section; then, injecting 8 parts of high-pressure foaming agent gas supercritical carbon dioxide with the pressure of 30MPa by using supercritical fluid equipment, uniformly mixing the high-pressure foaming agent gas into the molten polymer by using a screw mixing and conveying function of an injection molding machine, wherein the temperature of a screw of the injection molding machine is 300 ℃, and the backpressure pressure of 18MPa is kept, so that the high-pressure foaming agent gas is completely dissolved into the polymer melt; obtaining a single homogeneous polymer/gas mixed polymer melt;
(3) filling the cavity with the polymer melt: opening a nozzle of an injection molding machine and a hot runner of a mold, injecting the polymer melt into a mold cavity by adopting a high-pressure full injection mode, and completely filling the mold cavity; the injection pressure is 180MPa, and the injection speed is 200 mm/s;
(4) pressure maintaining and cooling: after the polymer solution is filled in the cavity, the screw rod retreats; then keeping the pressure of the polymer solution in a die cavity at 60MPa, and cooling the polymer solution by a low-temperature die at 70 ℃ to form a high-elastic polymer;
(5) core back type foaming: after the pressure maintaining is finished, opening and closing the mold, expanding the cavity space of the mold, foaming the high-elastic polymer, cooling and opening the mold to obtain the polymer foam material with the solid skin layer and the foaming core layer; wherein the time for opening and closing the mold is 6s, the speed for opening and closing the mold is 20mm/s, the distance for opening and closing the mold is 6mm, and the time for cooling and opening the mold is 60 s.
The cellular morphology of the polystyrene foam obtained by microcellular injection molding prepared in this example is shown in FIG. 4, and the density is 0.15g/cm3The weight reduction ratio was 85% and the expansion ratio was 7 times.
EXAMPLE five
A preparation method of a polymer foam material with low density and high foaming multiplying power is prepared by a core back type micropore injection molding technology, and specifically comprises the following steps:
(1) preparation of modified polymer composite: 100 parts of polypropylene with the number average molecular weight of 45 ten thousand and 10 parts of filler nano clay are mixed and then put into a double-screw extruder, and the modified polymer composite material is obtained through extrusion and underwater grain cutting; wherein the temperature of the extruder charging barrel is 300 ℃;
(2) preparation of a polymer melt: adding the modified polymer composite material into an automatic conveying hopper of an injection molding machine, and heating and melting the modified polymer composite material at a screw melting section; then, injecting 5 parts of high-pressure foaming agent gas supercritical nitrogen with the pressure of 24-30MPa by using supercritical fluid equipment, uniformly mixing the high-pressure foaming agent gas into the molten polymer by using a screw mixing and conveying function of an injection molding machine, wherein the temperature of a screw of the injection molding machine is 250 ℃, and the backpressure pressure of 18MPa is maintained, so that the high-pressure foaming agent gas is completely dissolved into the polymer melt; obtaining a single homogeneous polymer/gas mixed polymer melt;
(3) filling the cavity with the polymer melt: opening a nozzle of an injection molding machine and a hot runner of a mold, injecting the polymer melt into a mold cavity by adopting a high-pressure full injection mode, and completely filling the mold cavity; the injection pressure is 180MPa, and the injection speed is 200 mm/s;
(4) pressure maintaining and cooling: after the polymer solution is filled in the cavity, the screw rod retreats; then keeping the pressure of the polymer solution in a die cavity at 60MPa, and cooling the polymer solution by a low-temperature die at 50 ℃ to form a high-elastic polymer;
(5) core back type foaming: after the pressure maintaining is finished, opening and closing the mold, expanding the cavity space of the mold, foaming the high-elastic polymer, cooling and opening the mold to obtain the polymer foam material with the solid skin layer and the foaming core layer; wherein the time for opening and closing the mold is 4s, the speed for opening and closing the mold is 20mm/s, the distance for opening and closing the mold is 9mm, and the time for cooling and opening the mold is 50 s.
The cellular morphology of the polypropylene foam material obtained by microcellular injection molding prepared in this example is shown in FIG. 5, and the density is 0.1g/cm3The weight reduction ratio was 90% and the expansion ratio was 10 times.
Comparative example 1
(1) 100 parts of polypropylene with the number average molecular weight of 40 ten thousand and 5 parts of filler sorbitol are premixed, and then are mixed and granulated by a double-screw extruder to obtain the modified polypropylene.
(2) And putting the obtained mixture into a hopper of an injection molding machine, wherein the foaming gas is supercritical carbon dioxide, the components are 8 parts, and the gas pressure is 24 MPa. The temperature of the screw is 190-230 ℃, the back pressure is 15MPa, and the polymer and the carbon dioxide are uniformly mixed in the screw to obtain a single-phase polymer/gas solution.
(3) Injecting the polymer melt into a mold cavity and filling 80% of the volume of the mold cavity, wherein the injection speed is 100mm/s, the injection pressure is 140MPa, the mold temperature is 40 ℃, and the pressure maintaining pressure is 40 MPa.
(4) And finally, after the cooling time of the product reaches 40s, opening the die, and ejecting the polypropylene from the die to obtain the polypropylene foam material.
The cell morphology of the polypropylene foam obtained by injection molding is shown in FIG. 6, and the density is 0.8g/cm3The weight reduction ratio was 20% and the expansion ratio was 1.2 times.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. It will be understood by those skilled in the art that changes and modifications may be made to the above-described embodiments without departing from the spirit of the invention, and all such changes and modifications should be considered as within the scope of the invention.

Claims (7)

1. A preparation method of a polymer foam material with low density and high foaming ratio is characterized by comprising the following steps: the core-back type micropore injection molding technology is used for preparing the core-back type micropore injection molding material, and specifically comprises the following steps:
(1) preparation of modified polymer composite: mixing the polymer and the filler, putting the mixture into a double-screw extruder, and performing extrusion and underwater grain cutting to obtain a modified polymer composite material;
(2) preparation of a polymer melt: adding the modified polymer composite material into an automatic conveying hopper of an injection molding machine, and heating and melting the modified polymer composite material at a screw melting section; then injecting high-pressure foaming agent gas by using supercritical fluid equipment, and uniformly mixing the high-pressure foaming agent gas into the molten polymer by using a screw mixing and conveying function of an injection molding machine to obtain single homogeneous polymer/gas mixed polymer melt; wherein, the back pressure of 15-18MPa is kept in a screw of the injection molding machine, so that the high-pressure foaming agent gas is completely dissolved into the polymer melt; the pressure of the high-pressure foaming agent gas is 24-30 MPa; the temperature of a screw of the injection molding machine is 180-300 ℃;
(3) filling the cavity with the polymer melt: opening a nozzle of an injection molding machine and a hot runner of a mold, injecting the polymer melt into a mold cavity by adopting a high-pressure full injection mode, and completely filling the mold cavity; the injection pressure of the polymer melt injected into the mold cavity is 160-180MPa, and the injection speed is 100-200 mm/s;
(4) pressure maintaining and cooling: after the polymer solution is filled in the cavity, the screw rod retreats; then keeping the pressure of the polymer solution in a die cavity and cooling to form a high-elasticity polymer; wherein the pressure for maintaining the pressure is 40-60MPa, and the temperature of the die is 40-70 ℃;
(5) core back type foaming: after the pressure maintaining is finished, opening and closing the mold, expanding the cavity space of the mold, foaming the high-elastic polymer, cooling and opening the mold to obtain the polymer foam material with the solid skin layer and the foaming core layer; the density of the polymer foam material is 0.1-0.5g/cm3And the foaming ratio is 2-10 times.
2. The method of claim 1, wherein: the barrel temperature of the extruder in the step (1) is 150-300 ℃.
3. The method of claim 1, wherein: and (5) opening and closing the mold for 3-8s, at a speed of 10-30mm/s, at a distance of 1-9mm, and cooling for 30-60 s.
4. The method of claim 1, wherein: the polymer foam material consists of 100 parts of polymer, 5-20 parts of filler and 2-8 parts of foaming agent.
5. The method of claim 4, wherein: the polymer is polyethylene, polylactic acid, polypropylene or polystyrene with the number average molecular weight of 20-60 ten thousand.
6. The method of claim 4, wherein: the filler is talcum powder, calcium carbonate, mica, barium sulfate, glass fiber, transparent nucleating agent sorbitol or nano clay.
7. The method of claim 4, wherein: the foaming agent is supercritical fluid carbon dioxide or supercritical nitrogen.
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