CN110256840B - Preparation method of foamed nylon plate - Google Patents

Abstract

The invention discloses a preparation method of a foaming nylon plate, which comprises the steps of premixing nylon, a toughening agent, a chemical foaming agent, a nucleating agent, a lubricant and a cross-linking agent according to a formula, adding into a stretching rheological plasticizing extrusion device, performing stretching deformation to form a main flow field so as to melt and plasticize the nylon, mixing and dispersing gas generated after decomposition of the foaming agent in a polymer melt, extruding through a foaming sheet die, and then rolling by three rollers to obtain the foaming nylon plate. According to the invention, a small amount of cross-linking agent is added in an auxiliary manner, so that the melt strength of PA can be obviously improved, the nylon plate prepared by the preparation method has the advantages of uniform and fine foam pores, high foaming ratio, low opening rate, excellent performance, good processing performance, simple process flow, high production efficiency, suitability for industrial mass production and wide application prospect, and a stretching rheological plasticizing extrusion device is adopted.

Description

Preparation method of foamed nylon plate

Technical Field

The invention belongs to the technical field of high polymer materials, and particularly relates to a preparation method of a foamed nylon plate.

Background

The nylon macromolecule can form hydrogen bonds and has higher crystallinity, so the nylon macromolecule has the excellent performance of engineering plastics, and has the advantages of excellent heat resistance, oil resistance, wear resistance and the like, so the nylon macromolecule can be widely applied to a plurality of fields of automobiles, machinery, electronics and electrics, precise instruments, food packaging and the like. For the foamed nylon material, the defects of poor thermal stability and poor size stability of nylon are overcome by the uniformly distributed microporous structure of the foamed nylon material, and the function of toughening and reinforcing is achieved. The foamed nylon material has the advantages of light weight, less raw material consumption, heat insulation, buffering and the like, so that the foamed nylon material has more urgent industrial production requirements in the current times of light weight and high-speed development.

However, since nylon is a semi-crystalline polymer, its cell structure is more difficult to control than that of an amorphous polymer foam. The nylon has narrow melting range, almost does not flow below the melting point, the viscosity of the nylon is rapidly reduced above the melting point, and the melt strength is very low, so that cells collapse and break can occur during foaming of the nylon material, the mechanical property of the nylon material is greatly influenced, and meanwhile, the appearance of a product is greatly influenced by the defects of the cells, and the wide application of the foamed nylon is limited.

Therefore, the foaming process of nylon has higher requirements on the formula and equipment, and the adoption of PA (polyamide) is difficult to prepare the foam with uniform and fine cells, high foaming ratio and low open-cell ratio. At present, the research on the nylon microporous foaming material in the prior art mostly focuses on the injection molding foaming process of supercritical gas. However, the supercritical fluid has high requirements on equipment, the injection foaming method cannot realize continuous production, and the continuous extrusion method using the chemical foaming agent to prepare the microcellular foamed nylon needs to realize continuous extrusion by blending and adding a large amount of the second component resin. Chinese patent CN107163346A discloses a secondary foaming material prepared by filling a foaming agent in LDPE to prepare foaming master batches, and then blending the foaming master batches with PA by a single-screw extruder, an injection machine or a molding press. The formula and the preparation method are developed based on the existing single-screw extruder, injection machine, mould press and other equipment, and the secondary foaming preparation method of firstly filling the foaming agent in LDPE to prepare foaming master batches and then blending the foaming master batches with PA is provided in consideration of the easiness in causing the scattering loss of the foaming agent due to the direct addition of the foaming agent in the blending foaming process. However, this method still fails to achieve high-efficiency continuous production.

Disclosure of Invention

In order to relieve the defects of the prior art, the invention provides a preparation method of a foaming nylon plate, which can obviously improve the melt strength of PA by adding a small amount of cross-linking agent in an auxiliary manner.

In order to overcome the technical problems, the technical scheme adopted by the invention is as follows: a preparation method of a foaming nylon plate comprises the following steps:

adding 0.1-95 parts by weight of nylon, 1-10 parts by weight of toughening agent, 0.1-1.3 parts by weight of chemical foaming agent, 0.1-1 part by weight of nucleating agent, 0.1-0.5 part by weight of lubricant and 0.1-0.5 part by weight of cross-linking agent into a high-speed mixer for premixing;

foaming and forming: adding the premixed materials into a stretching rheological plasticizing extrusion device, forming a main flow field through stretching deformation to melt and plasticize nylon, mixing and dispersing gas generated after decomposition of a foaming agent in a polymer melt, extruding through a foaming sheet die, and then rolling by three rollers to obtain the foaming nylon plate.

As a further improvement of the scheme, the extensional rheological plastification extrusion equipment is extensional rheological plastification extrusion equipment of an eccentric rotor extrusion system.

As a further improvement of the scheme, in the foaming step, the extrusion temperature of the extensional rheology plasticizing extrusion equipment is 150-280 ℃, the die head temperature is 200-260 ℃, and the rotor speed is 20-100 r/min.

As a further improvement of the scheme, the nylon is selected from one of PA6, PA66 or PA 12.

As a further improvement of the above, the intrinsic viscosity of the nylon is greater than 2.2 dL/g.

As a further improvement of the scheme, the toughening agent is selected from one of maleic anhydride grafted and modified POE, maleic anhydride grafted ethylene propylene diene monomer copolymer, methacrylic acid dehydrated glyceride grafted POE or maleic anhydride grafted and modified SEBS.

As a further improvement of the above aspect, the chemical blowing agent is at least one selected from the group consisting of azodicarbonamide, azoisobutyronitrile, diisopropyl azodicarbonate, dinitrosopentamethylenetetramine, p-toluenesulfonyl hydrazide, p-sulfonyl diphenyl ether, p-toluenesulfonyl semicarbazide, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, zinc stearate, and zinc oxide.

As a further improvement of the scheme, the nucleating agent is at least one selected from talcum powder, calcium carbonate, nano montmorillonite, titanium dioxide and silicon dioxide.

As a further improvement of the above aspect, the lubricant is selected from one of polyethylene wax, silicone, or ethylene bis fatty acid amide.

As a further improvement of the above scheme, the crosslinking agent comprises dicumyl peroxide.

Compared with the prior art, the preparation method has the advantages that a flow field forming mode which mainly adopts stretching deformation is adopted for melt plasticizing, mixing and dispersing. The traditional screw equipment has a larger shearing action, the performance and the melt strength of the material can be reduced, and particularly for semi-crystalline polymer PA, the foaming effect is poor due to the low melt strength of the nylon material, and continuous extrusion foaming is difficult; the flow field of the extensional rheology plasticizing extrusion equipment used in the invention is mainly changed from extensional deformation, the extensional viscosity of the polymer after melting is 1-2 orders of magnitude higher than the shear viscosity, and meanwhile, the mixing and dispersing quality of gas in the melt can be improved by a plasticizing mechanism with dominant extensional rheology; in addition, the unique eccentric motion mode enables the internal unit of the extrusion system to have higher melt pressure, the melt can obtain larger pressure drop when flowing through the machine head, the gas loss in the bubble growth process can be effectively inhibited, and an ideal bubble structure with small bubble size and uniformly distributed bubbles can be formed.

The invention has the beneficial effects that: the invention provides a preparation method of a foaming nylon plate, which can obviously improve the melt strength of PA by adding a small amount of cross-linking agent, adopts a stretching rheological plasticizing extrusion device, and has the advantages of uniform and fine foam holes, high foaming ratio, low opening ratio, excellent performance, good processing performance, simple process flow and high production efficiency. The invention provides a brand-new foaming continuous preparation process for the nylon semicrystalline polymer, the production process is continuous and stable, the invention has important significance for promoting industrial development of nylon foaming in China, and the invention is suitable for industrial scale production and has wide application prospect.

Drawings

FIG. 1 is a scanning electron micrograph of the foamed nylon sheet obtained in example 1;

FIG. 2 is a scanning electron micrograph of the foamed nylon sheet obtained in comparative example 1.

Detailed Description

The present invention is specifically described below with reference to examples in order to facilitate understanding of the present invention by those skilled in the art. It should be particularly noted that the examples are given solely for the purpose of illustration and are not to be construed as limitations on the scope of the invention, as non-essential improvements and modifications to the invention may occur to those skilled in the art, which fall within the scope of the invention as defined by the appended claims. Meanwhile, the raw materials mentioned below are not specified in detail and are all commercially available products; the process steps or preparation methods not mentioned in detail are all process steps or preparation methods known to the person skilled in the art.

The manufacturers and the types of the nylon resin in the examples and the comparative examples of the present invention are as follows:

PA 6: m2500, intrinsic viscosity of about 2.5 dL/g;

PA 6: YH800, intrinsic viscosity of about 2.85 dL/g;

PA 66: amur industry, Inc., EPR27, intrinsic viscosity about 2.7 dL/g;

PA 12: switzerland EMS (china) trade ltd, L25W 40X.

Method for testing the properties of the foamed nylon sheets prepared in examples 1 to 5 and comparative example 1:

cell size: the SEM cell morphology picture is processed by a graphic analysis software (Image J5.0) and is obtained by statistical calculation.

Foaming ratio: the ratio of the average density of the unfoamed sample to the density of the foamed article.

Density: the test was carried out according to ASTM D792-2000 (i.e., drainage method), under the same conditions at least 5 specimens were selected for testing and then averaged.

Tensile strength: the foaming plate is made into a dumbbell-shaped sample bar according to the GB/T1040.1 standard, and the mechanical property is tested under the wet condition.

Example 1

Taking the following substances in percentage by weight: 92 parts by weight of PA6(M2500), 5 parts by weight of toughening agent, 1 part by weight of chemical foaming agent, 1 part by weight of nucleating agent, 0.5 part by weight of lubricant, 0.3 part by weight of crosslinking agent and the like, and sequentially adding the components into a mixer for premixing and stirring, wherein the mixing temperature is 30 ℃, the rotating speed of the mixer is 500r/min, and the mixing time is 3 minutes;

the premixed materials are put into extensional rheology plasticization extrusion equipment, the processing temperature of each section of the extensional rheology plasticization extrusion equipment is respectively set as 210 ℃ of a first section, 225 ℃ of a second section, 230 ℃ of a third section, 230 ℃ of a fourth section, 240 ℃ of a fifth section, 235 ℃ of a sixth section, 220 ℃ of a connecting section, 220 ℃ of a die head temperature 1 section, 210 ℃ of a die head temperature 2 section, 1.0mm of a die head opening, 300mm of a die opening, 22 mm of a rotor length-diameter ratio, 30r/min of a rotor speed, a nylon foaming plate extruded is formed by a three-roll device in a rolling mode, the thickness of the nylon foaming plate extruded is 2.2mm, and a foaming nylon plate finished product 1 is obtained, wherein a scanning electron microscope photo of the foaming nylon plate prepared in the embodiment 1 is shown in figure 1.

Example 2

Taking the following substances in percentage by weight: 89 parts by weight of PA6(M2500), 8 parts by weight of toughening agent, 1.5 parts by weight of chemical foaming agent, 1 part by weight of nucleating agent, 0.5 part by weight of lubricant, 0.3 part by weight of crosslinking agent and the like, and sequentially adding a mixer for premixing and stirring, wherein the mixing temperature is 30 ℃, the rotating speed of the mixer is 500r/min, and the mixing time is 3 minutes;

the premixed materials are put into extensional rheology plasticization extrusion equipment, the processing temperature of each section of the extensional rheology plasticization extrusion equipment is respectively set to 210 ℃ of the first section, 225 ℃ of the second section, 230 ℃ of the third section, 230 ℃ of the fourth section, 240 ℃ of the fifth section, 235 ℃ of the sixth section, 220 ℃ of the connection section, 220 ℃ of the die head temperature 1 section, 210 ℃ of the die head temperature 2 section, 1.0mm of the die head opening, 300mm of the mouth die width, 22 of the length-diameter ratio of the rotor and 60r/min of the rotor, the extruded nylon foaming plate is rolled and formed by a three-roll device, and the thickness of the extruded nylon foaming plate is 2.2mm, thus obtaining the finished product 2 of the foamed nylon plate.

Example 3

Taking the following substances in percentage by weight: 91 parts by weight of PA6(YH800), 6 parts by weight of toughening agent, 1 part by weight of chemical foaming agent, 1 part by weight of nucleating agent, 0.5 part by weight of lubricant, 0.3 part by weight of crosslinking agent and the like, and sequentially adding the components into a mixer for premixing and stirring, wherein the mixing temperature is 30 ℃, the rotating speed of the mixer is 500r/min, and the mixing time is 3 minutes;

the premixed materials are put into extensional rheology plasticization extrusion equipment, the processing temperature of each section of the extensional rheology plasticization extrusion equipment is respectively set to 210 ℃ of the first section, 225 ℃ of the second section, 230 ℃ of the third section, 230 ℃ of the fourth section, 240 ℃ of the fifth section, 235 ℃ of the sixth section, 220 ℃ of the connection section, 220 ℃ of the die head temperature of 1 section, 210 ℃ of the die head temperature of 2 section, 1.0mm of the die head opening, 300mm of the mouth die width, 22 mm of the length-diameter ratio of the rotor and 40r/min of the rotor, the extruded nylon foaming plate is rolled and formed by a three-roll device, and the thickness of the extruded nylon foaming plate is 2.2mm, thus obtaining the finished product 3 of the foamed nylon plate.

Example 4

Taking the following substances in percentage by weight: 90 parts by weight of PA66(EPR27), 7 parts by weight of toughening agent, 1 part by weight of chemical foaming agent, 1 part by weight of nucleating agent, 0.5 part by weight of lubricant, 0.3 part by weight of crosslinking agent and the like, and sequentially adding the components into a mixer for premixing and stirring, wherein the mixing temperature is 30 ℃, the rotating speed of the mixer is 500r/min, and the mixing time is 3 minutes;

putting the premixed material into extensional rheological plastification extrusion equipment, wherein the processing temperature of each section of the extensional rheological plastification extrusion equipment is respectively set to be 240 ℃ of the first section, 270 ℃ of the second section, 275 ℃ of the third section, 270 ℃ of the fourth section, 265 ℃ of the fifth section, 260 ℃ of the sixth section, 260 ℃ of the connecting section, 260 ℃ of the die head temperature 1 section, 250 ℃ of the die head temperature 2 section, 1.0mm of the die head opening, 300mm of the mouth die width, 22 mm of the length-diameter ratio of a rotor and 35r/min of the rotating speed of the rotor, rolling and molding the extruded nylon foaming plate by a three-roll device, and the thickness of the extruded nylon foaming plate is 2.2mm, thus obtaining the finishedproduct 4 of the foamed nylon plate.

Example 5

Taking the following substances in percentage by weight: 93 parts by weight of PA12(L25W40X), 4 parts by weight of toughening agent, 1 part by weight of chemical foaming agent, 1 part by weight of nucleating agent, 0.5 part by weight of lubricant, 0.3 part by weight of crosslinking agent and the like, and sequentially adding a mixer for premixing and stirring, wherein the mixing temperature is 30 ℃, the rotating speed of the mixer is 500r/min, and the mixing time is 3 minutes;

putting the premixed material into extensional rheological plastification extrusion equipment, wherein the processing temperature of each section of the extensional rheological plastification extrusion equipment is respectively set to be 200 ℃ of a first section, 235 ℃ of a second section, 240 ℃ of a third section, 230 ℃ of a fourth section, 220 ℃ of a fifth section, 220 ℃ of a sixth section, 220 ℃ of a connecting section, 200 ℃ of a die head temperature 1 section, 180 ℃ of the die head temperature 2 section, 1.0mm of the die head opening, 300mm of the mouth die width, 22 mm of the length-diameter ratio of a rotor and 90r/min of the rotating speed of the rotor, rolling and molding the extruded nylon foaming plate by a three-roll device, and the thickness of the extruded nylon foaming plate is 2.2mm, thus obtaining the finishedproduct 5 of the foamed nylon plate.

Comparative example 1

Taking the following substances in percentage by weight: 92 parts by weight of PA6(M2500), 5 parts by weight of toughening agent, 1 part by weight of chemical foaming agent, 1 part by weight of nucleating agent, 0.5 part by weight of lubricant, 0.3 part by weight of crosslinking agent and the like, and sequentially adding a mixer for premixing and stirring, wherein the mixing temperature is 30 ℃, the rotating speed of the mixer is 500r/min, and the mixing time is 3 minutes;

the premixed materials are put into a single screw extruder with the screw diameter of 65mm, the processing temperature of each section of the extruder is respectively set as 190 ℃ of the first section, 230 ℃ of the second section, 240 ℃ of the third section, 230 ℃ of the fourth section, 220 ℃ of the die head, 1.0mm of the die head opening, 500mm of the die head width, 32 of the length-diameter ratio, 60r/min of the rotating speed, 30r/min of the feeding machine rotating speed, the extruded nylon foaming plate is rolled and molded through a three-roller device, the thickness of the extruded nylon foaming plate is 2.2mm, and the finished foamed nylon plate 6 is prepared, wherein a scanning electron microscope photo of the foamed nylon plate prepared in the comparative example 1 is shown in figure 2.

The foamed nylon sheet products 1 to 6 obtained in the above examples 1 to 5 and comparative example 1 were respectively subjected to the performance tests of density, cell size, cell density and tensile strength (wet state), and the results are shown in the following table 1.

TABLE 1 testing of the properties of the components and corresponding finished products in the examples and comparative examples

As can be seen from table 1, the nylon plate prepared by using the extensional rheology plasticizing extrusion apparatus has uniform and fine pores, high foaming ratio, low opening ratio and more excellent performance compared with the traditional single screw.

It will be obvious to those skilled in the art that many simple derivations or substitutions can be made without inventive effort without departing from the inventive concept. Therefore, simple modifications to the present invention by those skilled in the art according to the present disclosure should be within the scope of the present invention. The above embodiments are preferred embodiments of the present invention, and all similar processes and equivalent variations to those of the present invention should fall within the scope of the present invention.

Claims (4)

1. The preparation method of the foamed nylon board is characterized by comprising the following steps:

premixing 0.1-95 parts by weight of nylon, 1-10 parts by weight of toughening agent, 0.1-1.3 parts by weight of chemical foaming agent, 0.1-1 part by weight of nucleating agent, 0.1-0.5 part by weight of lubricant and 0.1-0.5 part by weight of cross-linking agent;

foaming and forming: adding the premixed materials into a stretching rheological plasticizing extrusion device, and carrying out melt mixing, extrusion and molding to obtain a foamed nylon plate;

the cross-linking agent comprises dicumyl peroxide;

the extensional rheological plasticizing extrusion equipment is an extensional rheological plasticizing extrusion equipment of an eccentric rotor extrusion system; in the foaming step, the extrusion temperature of the extensional rheology plasticizing extrusion equipment is 150-280 ℃, the die head temperature is 200-260 ℃, and the rotor rotating speed is 20-100 r/min;

the nylon is selected from at least one of PA6, PA66 and PA 12; the inherent viscosity of the nylon is more than 2.2 dL/g;

the toughening agent is selected from at least one of maleic anhydride grafted and modified POE, maleic anhydride grafted ethylene propylene diene monomer copolymer, methacrylic acid dehydrated glyceride grafted POE or maleic anhydride grafted and modified SEBS.

2. The method according to claim 1, wherein the chemical blowing agent is at least one selected from the group consisting of azodicarbonamide, azoisobutyronitrile, diisopropyl azodicarbonate, dinitrosopentamethylenetetramine, p-toluenesulfonylhydrazide, p-sulfonylhydrazide diphenyl ether, p-toluenesulfonylsemicarbazide, sodium bicarbonate, ammonium carbonate, and ammonium bicarbonate.

3. The method according to claim 1, wherein the nucleating agent is at least one selected from the group consisting of talc, calcium carbonate, nano-montmorillonite, titanium dioxide and silica.

4. The method of claim 1, wherein the lubricant is selected from at least one of polyethylene wax, silicone, or ethylene bis fatty acid amide.

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