CN109366847B - Method for improving surface quality of polymer micro-foaming injection product - Google Patents

Method for improving surface quality of polymer micro-foaming injection product Download PDF

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CN109366847B
CN109366847B CN201811387463.2A CN201811387463A CN109366847B CN 109366847 B CN109366847 B CN 109366847B CN 201811387463 A CN201811387463 A CN 201811387463A CN 109366847 B CN109366847 B CN 109366847B
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injection
foaming
solid material
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product
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CN109366847A (en
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周应国
赵旭东
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NINGHAI FIRST-RATE INJECTION MOULD Co.,Ltd.
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Jiangsu University of Science and Technology
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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

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Abstract

The invention discloses a method for improving the surface quality of a polymer micro-foaming injection product, which can prepare the polymer micro-foaming injection product with a skin-core structure, wherein the skin layer of the polymer micro-foaming injection product is completely the same as that of an unfoamed injection product, and the core layer of the polymer micro-foaming injection product is of a foaming structure. Compared with the existing foaming material, the foaming material has the advantages that the carrier gas capacity (due to the carrier gas modified master batch) of the foaming material is improved, so that the risk of large-scale permeation of gas in the foaming material to the front and rear solid materials is avoided, and the co-injection effect of the two materials (the solid material and the foaming material) is ensured; due to the existence of a large number of micropores in the product, the density of the product is reduced, the weight is reduced, corresponding raw materials are saved, and a series of corresponding advantages of a micro-foaming injection product are achieved; the front and the rear parts of the foaming material are separated by the solid material, and the foaming material is separated from the front and the rear parts after being heated in the charging barrel of the injection machine to generate gas, so that the gas decomposed from the foaming material can be utilized more efficiently, the foaming effect is more obvious, and the foam holes are more uniform.

Description

Method for improving surface quality of polymer micro-foaming injection product
Technical Field
The invention relates to a method for improving the surface quality of a polymer micro-foaming injection product, belonging to the technical field of preparation of polymer materials.
Background
In recent years, plastic injection products are widely used, and foaming can save raw materials, reduce injection pressure and shorten a molding period, so that the effects of heat insulation, shock absorption, sound insulation, improvement of impact performance and dimensional stability and the like are achieved. However, the foam injection or micro-foam injection products usually have obvious appearance defects, such as surface defects of silver lines, swirl lines, surface bubbles and gas cracks, and thus are limited to be applied to occasions requiring high product appearance.
It is believed that the occurrence of gas fracture in the flow front of the carrier gas melt upon injection into the mold cavity upon contact with the cavity surface is a major cause of poor surface quality of the foamed injection article. At present, researchers at home and abroad have proposed methods for improving the surface quality of foamed or micro-foamed injection products by improving dies and processing techniques, such as gas back pressure method, variable die temperature technique, coinjection molding and other auxiliary process parameters or nucleation rate adjusting techniques. These techniques can significantly improve the surface quality of the microfoamed injection products, but all have different limitations in application, and generally all at the expense of the microfoaming effect of the material, while the surface quality of the products obtained by said other methods, apart from the coinjection molding technique, may still be inferior to that of the conventional injection products under equivalent conditions.
The coinjection molding machine generally has two or more plasticizing injection units working simultaneously or sequentially to produce products of different layered structures, and by using the coinjection molding machine, the surface layer of the product and the surface layer of the conventional injection product can be foamed internally, so that the surface quality of the product and the surface quality of the conventional injection product can be consistent. However, to realize the coinjection molding, the investment of a coinjection molding machine and other devices is required, and meanwhile, the coinjection process involves the alternate or sequential work of two injection units, which results in the disadvantages of incoherent injection process, difference between the two injection units, and the like, and also limits the wide application of the technology. It is still very difficult to achieve the same surface quality as the co-injection molded foamed article in a conventional injection molding machine without a co-injection molding machine.
Disclosure of Invention
The purpose of the invention is as follows: the technical problem to be solved by the invention is to provide a polymer micro-foaming injection product, which has a skin-core structure, wherein the skin layer of the polymer micro-foaming injection product is completely the same as that of an unfoamed injection product, and the polymer micro-foaming injection product does not have appearance defects, has good surface quality, and has good foaming quality of a core layer.
The technical problem to be solved by the invention is to provide a method for improving the surface quality of the polymer micro-foaming injection product, which can effectively improve the surface quality of the polymer micro-foaming injection product, and the surface quality of the obtained micro-foaming injection product is completely the same as that of the unfoamed injection product.
The invention content is as follows: in order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a method for improving the surface quality of a polymer micro-foaming injection product specifically comprises the following steps:
step 1, preparing a solid material and a foamable material;
step 2, determining the total volume of the cavity of the injection mold, and determining the total mass M1 of a solid material when the cavity is filled with the solid material and the total mass M2 of a foamable material when the cavity is filled with the foamable material;
step 3, determining the weight J1 of the residual material which can be stored in the front part of the material cylinder of the injection machine and the solid material amount M1 required by each plasticizing stroke (single plasticizing stroke) when the injection machine completely adopts solid materials at the beginning stage of injection production; thereby calculating and obtaining the first adding amount of the solid material and the foamable material and the mass of the solid material and the foamable material which are required to be added in a single plasticizing process when the foamable material is added; the weight J1 of the residual material which can be stored in the front of the injection machine material barrel can be obtained by weighing the empty injection after adding different materials.
The method comprises the following steps of (1) determining the weight of a solid material, wherein the first addition amount C of the solid material is W + A1, wherein W is M1N, A1 is M1 β + M1 (0.1-0.2), N is (J1/M1) +1, J1 is the determined weight of the residual material which can be stored in the front of a charging barrel of an injection machine, M1 is the amount of the solid material required by each plasticizing process when the injection machine completely adopts the solid material, N is the number of times of air injection, and β is a material condensation layer factor of a product obtained by simulating injection and filling of the product by using commercialized software;
wherein the first addition amount of the foamable material is D (M1-A1-A2) A1/M2, A2 (M1) β;
the mass A of the solid material required to be added in a single plasticizing process when the foaming material is added is the solid material amount A1 required by the skin layer and the solid material amount A2 required by the tail end, A1 is M1 and β and M1 (0.1-0.2), A2 is M1 and β, M1 is the solid material amount M1 required by each plasticizing process when the injection machine completely adopts the solid material, and β is a material condensation layer factor when the injection and filling of the product are finished by simulating the commercialized software;
wherein, the mass B of the foaming material which is required to be added in a single plasticizing process is equal to D when the foaming material is added;
step 4, sequentially adding a first addition C of the solid material and a first addition D of the foamable material into the injection machine in sequence, and injecting the injection machine into the air for N times, wherein the times of the air injection are obtained by calculating the weight J1 of the residual material which can be stored in the front part of the injection machine material barrel and the solid material amount M1 required by each plasticizing stroke when the injection machine completely adopts the solid material, and N is (J1/M1) + 1;
step 5, adding the mass A of the solid material required by a single plasticizing stroke into the injection machine after the injection machine performs empty injection for N times, and starting primary plasticizing;
and 6, alternately adding the mass B of the foamable material required by a single plasticizing stroke and the mass A of the solid material required by the single plasticizing stroke into the same hopper of the injection machine, and circularly and alternately sequentially to prepare the polymer micro-foaming injection product with the skin-core structure.
In the step 1, the solid material is polymer resin or a blend thereof, the foamable material is formed by blending polymer resin or a blend thereof, a carrier gas modified master batch and a foaming master batch, the addition amount of the carrier gas modified master batch in the foamable material is 1-10% of the mass of the foamable material, and the addition amount of the foaming master batch is 1-5% of the mass of the foamable material.
Wherein, the polymer resin or the blend thereof in the solid material and the polymer resin or the blend thereof in the foamable material are the same or different materials.
The foaming master batch comprises the following components in parts by mass: 50-70 parts of carrier resin, 5-15 parts of foaming agent, 10% of foaming agent by mass of foaming agent, 5-20 parts of filler, 1-5% of filler by mass of coupling agent and 5-20 parts of dispersing agent.
The carrier gas modified master batch comprises the following components in parts by mass: 50-60 parts of carrier resin, 10-20 parts of compatibility regulator, 40-50 parts of melt strength modifier and 0-21 parts of polar modifier.
The carrier resin generally has good compatibility with the plastic to be processed, but is not completely compatible; the compatibility regulator is selected from the substances with good compatibility with the plastic to be processed and the carrier resin, the melt strength modifier is an elastomer matched with the plastic to be processed, and the polar modifier is a polar graft of the plastic to be processed. When the plastic to be processed is polypropylene, the polar modified material is a blend of polypropylene grafted maleic anhydride and polypropylene grafted butyl acrylate copolymer according to the mass ratio of 2: 1.
The prepared polymer microfoamed injection product with the skin-core structure has the skin layer which is completely the same as that of an unfoamed injection product, and the core layer of the polymer microfoamed injection product is of a foaming structure. The polymer micro-foaming injection product is produced by alternately adding solid material and foamable material into the same hopper in a common injection machine.
The proportion of a condensation layer at the end of injection filling of a product obtained by simulation according to commercial software is multiplied by the total volume of a melt required by the product, the product is converted into the mass of the material, the mass is determined as the minimum addition mass of the solid material in a skin layer part, A1 of the material required by an actual skin layer is the sum of the obtained minimum addition mass of the solid material (M1X β) and the widened proportion of 10-20%, and M1X (10-20%), so that A1 is M1X β + M1 (0.1-0.2).
And multiplying the proportion of a condensation layer obtained by numerical simulation according to commercial software at the end of injection filling by the total volume of the melt required by the part, amplifying by 10-20% according to the thickness of the part, and converting into the mass of the material used for the skin layer, wherein the mass of the material used for the core part is determined according to the total mass and the mass of the material used for the skin layer.
Has the advantages that: the method for processing the high-surface-quality micro-foaming product in the conventional injection machine has the following advantages: the preparation method of the invention does not need any special equipment, can realize production in a common injection molding machine, obtains products with the same surface quality as the conventional injection products and foamed inside, and has simple process and convenient operation; the foaming in the product is more beneficial to the stability of the material size and the effect of preventing the surface layer from shrinking, so that the surface quality of the prepared product reaches or even exceeds that of a common injection product; due to the existence of a large number of micropores in the product, the density of the product is reduced, the weight is reduced, corresponding raw materials are saved, the performances of the product in the aspects of sound insulation, heat insulation, shock resistance and the like are improved, and a series of corresponding advantages of a micro-foaming injection product are achieved; the front and the rear parts of the foaming material are blocked by the solid materials, and the foaming material is blocked front and rear after being heated in the charging barrel of the injection machine to generate gas, so that the gas decomposed from the foaming material can be utilized more efficiently, and the foaming effect is more obvious; compared with the existing foaming material, the foaming material has the advantages that the carrier gas capability (with the carrier gas modified master batch) of the foaming material is improved, so that the risk of large-scale permeation of gas in the foaming material to the front and rear solid materials is avoided, and the co-injection effect of the two materials (the solid material and the foaming material) is ensured; finally, a small amount of cells in the skin layer of the product obtained by conventional injection foaming have a destroying effect similar to defects, the skin-core layer of the product obtained by the invention is more definitely distributed, the cell size of the core layer is smaller, and the cell density is higher, so that the respective mechanical property advantages of the skin-core layer structure can be more favorably exerted, and the advantages are complemented.
Drawings
FIG. 1 is a schematic diagram showing the distribution of the raw materials in the barrel and the mold of the injection molding machine according to the present invention;
FIG. 2 is a comparison of the appearance of a polymer microfoamed article produced by the process of the present invention versus a conventional injection-foamed article of the prior art;
FIG. 3 shows the scanning electron microscope results of the skin-core layer structure inside the polypropylene micro-foamed product obtained by the method of the present invention;
FIG. 4 shows the scanning electron microscope results of the inner skin-core layer structure of the conventional injection polypropylene micro-foamed product in the prior art;
in fig. 1, 1 is a solid material plasticized in a charging barrel, 2 is a foamable material plasticized in the charging barrel, 3 is a screw, 4 is a fixed mold of a mold, 5 is distribution of the solid material and the foamable material filled in a cavity, and 6 is a movable mold of the mold;
in FIG. 2, a is the microfoamed injection product obtained by the method of the present invention, and b is the product obtained by conventional injection foaming.
Detailed Description
In the aspect of equipment, a common injection machine and an extruder are needed, the injection machine can be in hydraulic transmission, full-electric or electro-hydraulic combination, the injection machine does not need to be additionally provided with a self-locking nozzle, the temperature of a die is controlled by a die temperature controller heated by circulating hot oil, the extruder used for mixing raw materials can be in a single-screw or double-screw mode, and the raw materials related to the invention are all sold in the market.
Example 1
This example produced a high surface quality polypropylene microcellular foamed article in a conventional injection molding machine, as shown in fig. 1, and it can be seen from fig. 1 that the solid material and foamable material used in the present invention are alternately charged, plasticized and filled to finally form a microcellular foamed article having a solid surface and a foamed core.
Specifically, the method mainly comprises the following implementation steps:
step 1, preparing foaming master batches, namely weighing 50kg of L DPE (low density polyethylene), 5kg of AC resin (polymethyl methacrylate), 0.5kg of ZnO, 5kg of high-melting-point PE wax, 5kg of nano titanium dioxide and 0.25kg of coupling agent KH550 according to the following mass percentages, respectively drying the raw materials, uniformly mixing the raw materials in a mixing roll, and obtaining the foaming master batches by a double-screw extruder, wherein the melt temperature is 120 ℃ in the extrusion process;
step 2, preparing carrier gas modified master batch, namely weighing L DPE 50KG, EVA elastomer (ethylene-vinyl acetate copolymer) 5KG, ABS (acrylonitrile-butadiene-styrene terpolymer) 50KG, polypropylene grafted maleic anhydride 14KG and polypropylene grafted butyl acrylate copolymer 7KG, respectively drying the raw materials, uniformly mixing in a mixing roll, and preparing the carrier gas modified master batch through a double-screw extruder, wherein the melt temperature is 190 ℃ in the extrusion process;
step 3, preparing solid materials and foamable materials: wherein the solid material is polypropylene added with pigment, and the foamable material is a mixed material of polypropylene 85KG, carrier gas modified master batch 10KG and foaming master batch 5 KG;
step 4, determining the total volume of the cavity of the injection mold, and determining that the total mass M1 of the solid material when the cavity is filled with the solid material is 30G, and the total mass M2 of the foamable material when the cavity is filled with the foamable material is 26G; the total volume of the cavity of the injection mold can be calculated through the size of the cavity, and the total mass can be obtained by weighing after the cavity is filled with solid materials and foamable materials respectively to form a product;
step 5, modeling the appearance of the workpiece and a used mold thereof in numerical simulation software AUTODESKOMO L DF L OW, running simulation under corresponding process conditions to obtain that the factor of a material condensation layer is 0.1 when injection filling is finished, determining that the total mass of a solid material required by an injection skin layer is not less than 30G 0.1, and calculating 6G after widening 10% of the total mass;
step 6, determining the weight J1 of the residual material which can be stored in the front of the injection machine material barrel to be 190G, adjusting the plasticized material quantity of each plasticizing stroke of the injection machine to be M1, namely 30G, and determining the first addition quantity of the solid material to be: 210G +6G, after determining that the end material is also 10% of the total mass, the first foamable material corresponds to a mass of (30-6-3) × 26/30 ═ 18.2G;
step 7, adding 216G solid material into the injection machine, adding 18.2G foamable material, injecting the injection machine into the air for 7 times, injecting the air for 7 times, adding 9G solid material into the air, plasticizing, and performing first injection;
step 8, adding 18.2G of foaming material into the same hopper of the injection machine alternately, then adding 9G of solid material, and carrying out a normal circulation process;
and 9, obtaining a micro-foaming injection product with the surface quality completely the same as that of the unfoamed injection product and excellent internal foaming quality, wherein the appearance of the prepared polypropylene micro-foaming injection product is shown as a in figure 2. In fig. 2, a and b are respectively a microfoamed injection-molded product obtained by the method of the present invention and a conventional injection-molded product, and it can be seen from fig. 2 that the surface quality of the product obtained by the present invention is significantly better than that of the conventional injection-molded product.
In addition, the polypropylene micro-foamed product obtained in example 1 and the polypropylene product obtained by conventional injection foaming are respectively brittle and then observed under a scanning electron microscope to observe the cross-sectional morphology, and the results are shown in fig. 3 and fig. 4, it can be known by comparison that the skin-core layer distribution of the product obtained in example 1 is more definite, the cell size of the core layer is smaller, the cell density is higher, which is more favorable for exerting the respective mechanical property advantages of the skin-core layered structure, while the polypropylene product obtained by conventional injection foaming has a small number of cells (cells indicated by arrows in fig. 4) in the skin layer, and the cells in the skin layer can have the same destructive effect as the defects on the mechanical properties of the product.
Example 2
In this example, a polypropylene microfoamed injection product with high surface quality is produced in a common injection machine, and the specific implementation steps are as follows:
step 1, preparing foaming master batches, namely weighing L DPE (docosapentamine) 70kg, AC (alternating current) resin 15kg, ZnO 1.5kg, high-melting-point PE (polyethylene) wax 20kg, nano-silica 20kg and coupling agent KH550 0.2kg, respectively drying the raw materials, uniformly mixing the raw materials in a mixing roll, and preparing the foaming master batches by a double-screw extruder, wherein the melt temperature is 125 ℃ in the extrusion process;
step 2, preparing a carrier gas modified master batch, namely weighing L DPE 60KG, EVA elastomer 20KG, ABS 40KG, polypropylene grafted maleic anhydride 10KG and polypropylene grafted butyl acrylate copolymer 5KG, respectively drying the raw materials, uniformly mixing in a mixing roll, and preparing the carrier gas capability modified master batch through a double-screw extruder, wherein the melt temperature is 190 ℃ in the extrusion process;
step 3, preparing solid materials and foamable materials: wherein the solid material is polypropylene added with pigment, and the foamable material is a mixed material of polypropylene 98KG, carrier gas capability modified master batch 1KG and foaming master batch 1 KG;
step 4, determining the total volume of the cavity of the injection mold, and determining that the total mass M1 of the solid material when the cavity is filled with the solid material is 50G, and the total mass M2 of the foamable material when the cavity is filled with the foamable material is 45G;
step 5, modeling the appearance of the workpiece and a used mold thereof in numerical simulation software AUTODESKOMO L DF L OW, running simulation under corresponding process conditions to obtain that the factor of a material condensation layer at the end of injection filling is 0.12, determining that the total mass of a solid material required by an injection skin layer is not less than 50G 0.12, and after the total mass is widened by 20%, calculating the total mass to be 16G;
step 6, determining the weight J1 of the residual material which can be stored in the front of the injection machine material barrel to be 190G, adjusting the plasticized material quantity of each plasticizing stroke of the injection machine to be M1, namely 50G, and determining the first addition quantity of the solid material to be: 200G +16G, and after the terminal material is determined to be 10% of the total mass, the mass corresponding to the first foamable material is (50-16-5) × 45/50 ═ 26.1G; adding a 216G solid material, and then adding a 26.1G foamable material;
step 7, adding 216G solid material into the injection machine, adding 26.1G foamable material, injecting the injection machine into the air for 4 times, adding 21G solid material after injecting the air for 4 times, plasticizing, and performing first injection;
step 8, adding 26.1G of foaming material into the same hopper of the injection machine alternately, then adding 21G of solid material, and carrying out a normal circulation process;
and 9, obtaining the micro-foaming injection product with the surface quality completely the same as that of the unfoamed injection product and the excellent internal foaming quality.
Example 3
This example produced a high surface quality polycarbonate microfoamed injection article in a conventional injection molding machine, and the process was specifically carried out as follows:
step 1, preparing foaming master batches: weighing the following raw materials by mass: ABS: 60kg, triazinylbenzene: 10kg, barium oxide: 1kg, high melting point PE wax: 10kg, nano silica: 20kg, coupling agent KH 550: 0.2 kg; respectively drying the raw materials, uniformly mixing in a mixing roll, and obtaining a foaming master batch through a double-screw extruder, wherein the melt temperature is 190 ℃ in the extrusion process;
step 2, preparing carrier gas modified master batch: weighing the following raw materials by mass: ABS: 60kg of SEBS elastomer (hydrogenated styrene-butadiene block copolymer): 15KG, PEN (polyethylene naphthalate): 50 kg; respectively drying the raw materials, uniformly mixing in a mixing roll, and preparing a carrier gas capacity modified master batch by a double-screw extruder, wherein the melt temperature is 260 ℃ in the extrusion process;
step 3, preparing solid materials and foamable materials: wherein the solid material is polycarbonate, and the foamable material is a mixed material of 90KG polycarbonate, 5KG modified master batch with carrier gas capability and 5KG foamed master batch;
step 4, determining the total volume of the cavity of the injection mold, and determining that the total mass M1 of the solid material when the cavity is filled with the solid material is 50G, and the total mass M2 of the foamable material when the cavity is filled with the foamable material is 40G;
step 5, modeling the appearance of the workpiece and a used mold thereof in numerical simulation software AUTODESKOMO L DF L OW, running simulation under corresponding process conditions to obtain that the factor of a material condensation layer is 0.10 when injection filling is finished, determining that the total mass of the material required by an injection skin layer is not less than 50G 0.10, and after the total mass is widened to 12%, calculating the total mass to be 11G;
step 6, determining the weight J1 of the residual material which can be stored in the front of the injection machine material barrel to be 190G, adjusting the plasticized material quantity of each plasticizing stroke of the injection machine to be M1, namely 50G, and determining the first addition quantity of the solid material to be: 200G +11G, after determining that the end material is also 10% of the total mass, the first foamable material corresponds to a mass of (50-11-5) × 40/50 ═ 27.2G; adding a 211G solid material, and then adding a 27.2G foaming material;
step 7, adding a 211G solid material into the injection machine, and then adding a 27.2G foaming material; injecting the injection machine to the air for 4 times, adding the solid material 16G after injecting the injection machine to the air for 4 times, plasticizing, and injecting for the first time;
step 8, adding the foaming material 27.2G into the same hopper of the injection machine alternately, then adding the solid material 16G, and carrying out a normal circulation process;
and 9, obtaining the micro-foaming injection product with the surface quality completely the same as that of the unfoamed product and the excellent internal foaming quality.
The surface quality of the micro-foaming injection product processed by the method is completely the same as that of an unfoamed plastic product, the micro-foaming injection product has an obvious skin-core layer structure, the quality of the skin layer of the micro-foaming injection product is completely the same as that of a common injection product, and the foaming quality of the core layer is good.

Claims (7)

1. A method for improving the surface quality of a polymer micro-foaming injection product is characterized by comprising the following steps:
step 1, preparing a solid material and a foamable material;
step 2, determining the total volume of the cavity of the injection mold, and determining the total mass M1 of a solid material when the cavity is filled with the solid material and the total mass M2 of a foamable material when the cavity is filled with the foamable material;
step 3, determining the weight J1 of the residual material which can be stored in the front part of the material cylinder of the injection machine and the solid material amount M1 required by each plasticizing stroke when the injection machine completely adopts solid materials at the beginning stage of injection production; thereby calculating and obtaining the first adding amount of the solid material and the foamable material and the mass of the solid material and the foamable material which are required to be added in a single plasticizing process when the foamable material is added;
the method comprises the following steps of preparing a solid material, wherein the first addition amount of the solid material is W + A1, wherein W is M1N, A1 is M1B + M1 (0.1-0.2), N is (J1/M1) +1, J1 is the weight of the residual material which can be stored at the front part of a charging barrel of an injection machine, M1 is the amount of the solid material required by each plasticizing process when the injection machine completely adopts the solid material, N is the number of times of air injection, and β is a material condensation layer factor of the finished product when the injection and filling of the product are simulated by commercial software;
wherein the first addition amount of the foamable material is D (M1-A1-A2) A1/M2, A2 (M1) β;
the mass A of the solid material required to be added in a single plasticizing process when the foaming material is added is the solid material amount A1 required by the skin layer and the solid material amount A2 required by the tail end, A1 is M1 and β and M1 (0.1-0.2), A2 is M1 and β, M1 is the solid material amount M1 required by each plasticizing process when the injection machine completely adopts the solid material, and β is a material condensation layer factor when the injection and filling of the product are finished by simulating the commercialized software;
wherein, the mass B of the foaming material which is required to be added in a single plasticizing process is equal to D when the foaming material is added;
step 4, sequentially adding a first addition C of the solid material and a first addition D of the foaming material into the injection machine in sequence, injecting the injection machine into the air for N times, wherein the times of the air injection are obtained by calculating the weight J1 of the residual material which can be stored in the front part of the injection machine material barrel and the solid material amount M1 required by each plasticizing stroke when the injection machine completely adopts the solid material, and N is (J1/M1) + 1;
step 5, adding the mass A of the solid material required by a single plasticizing stroke into the injection machine after the injection machine performs empty injection for N times, and starting primary plasticizing;
and 6, alternately adding the mass B of the foamable material required by a single plasticizing stroke and the mass A of the solid material required by the single plasticizing stroke into the same hopper of the injection machine, and circularly and alternately sequentially to prepare the polymer micro-foaming injection product with the skin-core structure.
2. The method for improving the surface quality of a polymer microfoamed injection product according to claim 1, wherein: in the step 1, the solid material is polymer resin or a blend thereof, the foamable material is formed by blending the polymer resin or the blend thereof, a carrier gas modified master batch and a foaming master batch, wherein the addition amount of the carrier gas modified master batch is 1-10% of the mass of the foamable material, and the addition amount of the foaming master batch is 1-5% of the mass of the foamable material.
3. The method for improving the surface quality of a polymer microfoamed injection product according to claim 2, wherein: the polymer resin or the blend thereof in the solid material and the polymer resin or the blend thereof in the foamable material are the same or different materials.
4. The method for improving the surface quality of a polymer microfoamed injection product according to claim 2, wherein: the foaming master batch comprises the following components in parts by mass: 50-70 parts of carrier resin, 5-15 parts of foaming agent, 10% of foaming agent by mass of foaming agent, 5-20 parts of filler, 1-5% of filler by mass of coupling agent and 5-20 parts of dispersing agent.
5. The method for improving the surface quality of a polymer microfoamed injection product according to claim 2, wherein: the carrier gas modified master batch comprises the following components in parts by mass: 50-60 parts of carrier resin, 10-20 parts of compatibility regulator, 40-50 parts of melt strength modifier and 0-21 parts of polar modifier.
6. The method for improving the surface quality of a polymer microfoamed injection product according to claim 1, wherein: the prepared polymer microfoaming injection product with an obvious skin-core structure has the skin layer which is completely the same as that of an unfoamed injection product, and the core layer of the polymer microfoaming injection product is of a foaming structure.
7. The method for improving the surface quality of the polymer micro-foaming injection product according to claim 1, wherein in step 3, the ratio of the condensed layer at the end of the injection filling of the obtained product is simulated according to commercial software, multiplied by the total volume of the melt required by the product, and then converted into the mass of the material, and determined as the minimum added mass of the solid material in the skin layer part, and the mass A1 of the solid material required by the actual skin layer is the obtained minimum added mass of the solid material (M1 β) plus the broadened ratio of 10-20%, M1 (10-20%), so that A1 is M1 is β + M1 (0.1-0.2).
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