CN117844092A - Non-volatile foaming material and preparation method and application thereof - Google Patents
Non-volatile foaming material and preparation method and application thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of material science and engineering, and particularly relates to a non-volatile foaming material, and a preparation method and application thereof. The raw material of the foaming material is only one thermoplastic elastomer or a combination of a plurality of thermoplastic elastomers, and a plurality of foaming cavities are arranged in the foaming material, wherein at least 95 percent of the foaming cavities have a pore diameter not smaller than 100 mu m, and at least 95 percent of the foaming cavities have a pore diameter not larger than 300 mu m. The preparation process of the foaming material utilizes high-energy electron rays to crosslink the polymer, and adopts a supercritical physical foaming method to foam and form after crosslinking, and utilizes inert gas to perform physical foaming, so that no chemical reaction occurs in the foaming process, no waste gas is discharged in the production process, no chemical residue exists in the product, and the polymer foaming material prepared by the supercritical physical foaming method has more uniform foam cells and better physical properties.
Description
Technical Field
The invention belongs to the technical field of material science and engineering, and particularly relates to a non-volatile foaming material, and a preparation method and application thereof.
Background
A foaming material is a material which forms a pore structure by controlling the distribution of gas during the manufacturing process, and the pores can reduce the density of the material and improve the elasticity and the lightness of the material to meet different requirements. Compared with the polymer body, the polymer foam material has the characteristics of reduced density, reduced heat conduction, improved energy absorption and the like caused by foaming, so that the polymer foam material is widely applied.
The foaming material is generally composed of a base material and a foaming agent, and a crosslinking mode is generally used for improving the mechanical strength of the foaming material. Wherein the base material can be polymer (such as EVA, polyurethane, polypropylene, polyethylene, polystyrene, etc.), and the foaming mode can be physical foaming agent mode or chemical foaming agent mode, and the foaming mode can be irradiation crosslinking mode, photo-crosslinking mode, chemical crosslinking mode, etc. Chemical foaming refers to a process of foaming and forming a polymer by using a chemical reaction or a chemical foaming agent, however, chemical residues, such as Azodicarbonamide (ADC), which is a common foaming agent, are often present in the chemical foaming process, and solid products of thermal decomposition at high temperature are biurea and urazole. The size of chemically foamed cells depends on the particle size and dispersion of the blowing agent, is generally coarser and increases with increasing magnification, limiting further applications of the material.
In recent years, because of the advantages of high production efficiency, no chemical residue, no pollution, no peculiar smell and the like, the supercritical foaming technology gradually attracts attention, and is a physical foaming technology, and is also a micropore foaming technology, in the injection molding, extrusion and blow molding processes, other gases such as supercritical carbon dioxide or nitrogen are firstly injected into a special plasticizing device, so that the gases and the molten raw materials are fully and uniformly mixed/diffused to form single-phase mixed sol, and then the sol is led into a mold cavity or an extrusion opening die, so that the sol generates large pressure drop, and a large amount of bubble nuclei are formed by gas precipitation; in the subsequent cooling forming process, the bubble nuclei in the sol are continuously grown and formed, and the microporous foamed plastic product is obtained. The supercritical fluid has small viscosity, density close to that of liquid, and diffusion coefficient 10-100 times that of liquid, so that it can be said that the supercritical fluid has both liquid dissolving and mass transferring capacity and high gas diffusivity. Based on these characteristics, supercritical fluids can greatly increase their solubility and diffusion coefficient in polymers, helping the blowing agent to dissolve in the polymer melt and form a homogeneous system.
In practical production, it is often necessary to improve the thermodynamic and other properties of the polymer by means of crosslinking, which can be divided into chemical crosslinking and physical crosslinking. The chemical crosslinking is to crosslink the polymer by using a chemical crosslinking agent, and similar to a foaming mode, toxic and harmful chemical substances can be remained in the material by using the chemical crosslinking agent, so that the application range of the material is limited. The physical crosslinking mode has the advantage of no toxic and harmful chemical residues, such as irradiation crosslinking technology, and is essentially a process of inducing and generating polymer chain free radicals and active groups by a pure physical method, and further generating related subsequent chemical reactions by the chain free radicals. Compared with the chemical crosslinking method, the irradiation crosslinking method can be completed at room temperature or at different temperatures, and has relatively great flexibility. In terms of production, the method has the greatest advantage that the cross-linking process and the extrusion and molding processes can be separated from each other, and long-time high-temperature vulcanization is not needed like a chemical cross-linking method, so that the energy is greatly saved; meanwhile, the introduction of a chemical cross-linking agent can be avoided, the purity of the product is improved, and simultaneously, the toxicity and pollution are reduced, so that the method is particularly suitable for the research and development of infant products and some high-performance products.
In the prior art, various methods for preparing foaming materials by combining irradiation crosslinking with a physical foaming agent are available. For example, chinese patent publication No. CN107118374B discloses a method for preparing polypropylene foaming material by irradiation crosslinking technology, comprising the following steps:
(1) Adding polypropylene into dimethylbenzene to obtain polypropylene emulsion;
(2) Dripping the radiation sensitizer into the polypropylene emulsion obtained in the step (1), filling the mixed emulsion into a radiation tube, and placing 60 The Co irradiation device irradiates to obtain irradiated polypropylene;
(3) And (3) adding the irradiated polypropylene obtained in the step (2) into a stirrer for melting and plasticizing, transferring into a charging port of a co-rotating double-screw extruder, and adding carbon dioxide into a gas injection port of the co-rotating double-screw extruder through a supercritical injection system for continuous extrusion foaming to obtain the polypropylene foaming material.
For another example, chinese patent publication No. CN115975244a discloses an ultra-light elastic foam material and a foaming process thereof, comprising the following steps:
s1, carrying out cross-linking after melting and mixing raw materials to obtain a blank;
the raw materials comprise the following components in parts by mass:
100 parts of polyolefin resin or thermoplastic elastic material, 10 parts of filler and 2-4 parts of lubricant;
s2, performing supercritical foaming and secondary foaming on the blank to obtain a foam material;
wherein, the supercritical foaming is as follows: after the carbon dioxide is inflated to 3-5 MPa, the nitrogen is inflated to 18-20 MPa. Wherein the crosslinking is crosslinking agent crosslinking or irradiation crosslinking.
For another example, chinese patent publication No. CN110343330a discloses a crosslinked polypropylene foam material and a method for preparing the same, wherein the foam material comprises a matrix resin, a gas nucleating agent, a foaming agent, an antioxidant, a cell stabilizer, and a sensitizer, and the foaming agent is supercritical carbon dioxide, supercritical nitrogen, or supercritical butane. In the preparation, (1) the matrix resin and the gas nucleating agent are added into a foaming extruder to prepare a master slice, (2) the master slice is used 60 Carrying out irradiation by a Co electron accelerator; (3) Placing the irradiated master slice into an autoclave, regulating the pressure in the autoclave to reach a set value so that the carbon dioxide reaches a supercritical state, and then cooling; (4) the collecting device collects the products.
In the prior art, although the foaming materials are prepared by combining irradiation crosslinking with a physical foaming agent, the use of chemical agents is reduced to a certain extent, the foaming materials with good performance cannot be prepared by completely performing pure physical crosslinking and using an inorganic foaming mode, and chemical additives are required to be added to form residues. However, no auxiliary agent is used for assisting irradiation crosslinking to combine with the physical foaming agent, and the obtained foaming material is often deficient in foaming effect and crosslinking degree.
In summary, there is a need for a method of preparing a foamed material by pure physical crosslinking and inorganic foaming to achieve a completely non-volatile effect and good performance of the foamed material.
Disclosure of Invention
The invention aims to provide a non-volatile foaming material, which is prepared by crosslinking a polymer by using a high-energy electron beam, then performing foam molding by using a supercritical physical foaming method, performing physical foaming by using inert gas, wherein no chemical reaction occurs in the foaming process, no waste gas is discharged in the production process, no chemical residue exists in the product, and the polymer foaming material prepared by using the supercritical physical foaming method has more uniform foam pores and better physical properties.
The invention also aims at providing a preparation method of the foaming material.
The invention also aims to provide the application field of the foaming material.
The invention adopts the technical proposal that: a non-volatile foam material, the foam material having a starting material of only one thermoplastic elastomer or a combination of thermoplastic elastomers, the foam material having a plurality of foam cavities therein, wherein at least 95% of the foam cavities have a pore size of no less than 100 μm and at least 95% of the foam cavities have a pore size of no greater than 300 μm.
The foaming material is foamed in a pure physical mode, only comprises a polymer, does not contain other volatile substances, does not release harmful gas or generate pungent smell, is very important for human health and indoor air quality, and is safer and more reliable when being used in the fields of food packaging, medical equipment, children toys and the like which are in direct contact with people. And the pure physical foaming material only contains the polymer, so that the material has higher quality stability, and does not contain other volatile substances, so that the stability and consistency of the material can be improved, and the reliability and performance of the product in the use process are ensured. The physical foaming can be a supercritical foaming technology, and the supercritical foaming forming is a physical foaming forming technology, and is also a microporous foaming forming technology, in the injection molding, extrusion and blow molding processes, other gases such as supercritical carbon dioxide or nitrogen are injected into a special plasticizing device, so that the gases and molten raw materials are fully and uniformly mixed/diffused to form single-phase mixed sol, and then the sol is guided into a mold cavity or an extrusion opening mold to cause the sol to generate large pressure drop, so that the gases are separated out to form a large number of bubble nuclei; in the subsequent cooling forming process, the bubble nuclei in the sol are continuously grown and formed, and the microporous foamed plastic product is obtained, wherein the foaming multiplying power depends on parameters such as gas type, foaming pressure, foaming time, foaming temperature and the like.
Among them, thermoplastic elastomers (Thermoplastic Elastomers, abbreviated as TPE) are a class of polymeric materials prepared from different monomer molecules by copolymerization, which have unique properties in a certain temperature range, and at high temperatures they can be shaped like plastics while at low temperatures they maintain rubbery elasticity.
In particular, the foam has a pore size of 100 to 300. Mu.m, and the material properties such as rebound resilience are not reduced compared with conventional foam having a pore size of 20 to 50. Mu.m. And because the pores occupy a larger volume, the pure physical foaming material with the same mass has larger relative volume, thus having lower density, and the low density is beneficial to lightening the weight of the product and improving the lightness and portability of the material. And the foam material has larger pore diameter and larger formed bubble interval, so that more air layers are formed, the heat insulation performance of the material is improved, the structure can effectively prevent heat conduction and reduce energy loss, and the foam material has better application prospect in the heat insulation field. In addition, the pore diameter of the foaming material is larger, more bubbles are formed, and higher rebound performance is given to the foaming material, so that the material has good energy absorption performance, and when the foaming material is impacted or extruded, the bubbles can absorb and disperse energy, so that the impact force on an object is reduced, and better buffer protection is provided. In addition, the pore diameter of the pure physical foaming material is larger, so that the material has better air permeability and permeability, which has important significance for certain application scenes, such as air filtration, liquid filtration and the like.
In particular, the pore sizes of the foaming materials are uniformly distributed, and the foaming materials have almost no pores which are particularly large or particularly small. The uniformity is beneficial to improving the stability and uniformity of the material, ensuring the uniformity of the performance of the foaming material in different areas, avoiding the performance difference caused by the pore size difference, preventing the crack which may exist from continuing to expand due to the fact that the strength is suddenly reduced due to overlarge pores at a certain place, and improving the durability of the material as a whole.
The further preferable technical scheme is as follows: the density of the foaming material is not more than 0.1g/cm 3 。
The further preferable technical scheme is as follows: the rebound rate of the foaming material is not less than 65%.
The further preferable technical scheme is as follows: the thermoplastic elastomer is an ethylene-vinyl acetate copolymer.
The further preferable technical scheme is as follows: the thermoplastic elastomer is polyethylene.
The further preferable technical scheme is as follows: the thermoplastic elastomer is a composition of an ethylene-vinyl acetate copolymer and polyethylene.
The preparation method of the non-volatile foaming material comprises the following steps:
s1, carrying out a mould pressing treatment process on the raw materials to obtain mould pressing raw materials;
s2, carrying out an irradiation treatment process on the molding raw material to obtain a cross-linking raw material;
s3, putting the crosslinking raw material into a foaming device, and introducing N 2 、CO 2 Performing supercritical mould pressing foaming process to obtain foaming raw materials;
s4, taking out the foaming raw material, and cooling to room temperature to obtain the foaming material.
Wherein the molding process is a process performed before foaming, and the raw material of the foaming material is formed into a cubic plate-like structure by applying pressure and heat. The molding process can cause the materials to be more tightly combined by applying pressure and heat, and helps to reduce the presence of uneven voids and bubbles, thereby improving the density uniformity of the materials.
The irradiation treatment is a processing process of foaming materials before foaming, and the inside of the materials is crosslinked through irradiation to form a three-dimensional netlike molecular structure. The irradiation treatment can lead the molecular interior of the foaming material to form a cross-linked structure, thereby enhancing the thermal stability of the material. The cross-linked structure can resist thermal decomposition and thermal oxidation at high temperature, so that the material has higher heat resistance and long-term stability. And the irradiation treatment can increase the molecular crosslinking degree of the foaming material, improve the strength, rigidity and durability of the material, and the crosslinking structure can increase the tensile strength, compressive strength and wear resistance of the material, so that the material is more durable and reliable in the use process. In addition, the irradiation treatment can lead the inside of the foaming material to form a cross-linking structure, thereby improving the chemical resistance of the material, reducing the interaction between the material and chemical substances, reducing the water absorption and the solubility of the material, and enhancing the corrosion resistance and the chemical medium erosion resistance of the material. In addition, the irradiation treatment enables the molecular interior of the foaming material to form a stable cross-linking structure, and the generation and activity of free radicals can be reduced, so that the oxidation resistance and ageing resistance of the material are improved, the service life of the material can be prolonged, and the performance degradation caused by ageing is reduced. In summary, irradiation crosslinking has the following advantages compared to chemical crosslinking foaming processes:
(1) The irradiation crosslinking foaming process does not use chemical crosslinking agent, so that the irradiation crosslinking foaming process does not generate harmful gas and reduces air pollution.
(2) The irradiation crosslinking foaming process is easier to control the reaction process, and the raw material selection is simpler and more convenient.
(3) The crosslinking agent of the chemical crosslinking process is decomposed in a wide temperature range by heating, resulting in defects in uniformity of the product, whereas the irradiation crosslinking process is free from such a problem because it achieves crosslinking of the product at the same temperature.
(4) The irradiation process can make the product realize the preset crosslinking under the condition of any temperature, and then foam, so that the foaming speed of the product is 1 time faster than that of the chemical crosslinking.
(5) Can produce various types of products, has convenient control of crosslinking degree, and can obtain foam materials with different pore sizes and great difference of foaming rates.
Wherein the supercritical mould pressing foaming process uses N 2 And CO 2 The formed supercritical fluid is foamed, has lower viscosity and high diffusivity, and can be rapidly diffused and permeated in the raw materials, so that the efficient foaming process is realized. The foaming mode can realize uniform bubble generation in a short time, and form a fine and uniformly distributed pore structure. The supercritical fluid has the characteristic of recycling in theory, can be recycled and reused, and reduces the waste of resources and the burden of the environment. In addition, the supercritical compression molding foaming process can realize the accurate control of the foaming process by adjusting parameters such as the pressure, the temperature and the like of the supercritical fluid, so that the pore structure, the density and the performance of the foaming material can be adjusted according to the requirements, and the requirements of different application scenes are met.
Wherein, the raw materials of the foaming material can be expanded into bubbles by heating in the foaming process, and form a required pore structure, and the cooling to the room temperature is used for solidifying and stabilizing the foaming material, so that the foaming material reaches a finished product state. Cooling to room temperature can cause the high temperature molecules in the foaming material to be recombined and solidified to form a stable molecular structure, which is helpful to enhance the stability and strength of the material and prevent the foaming material from deforming or losing shape in the subsequent use process. And cooling to room temperature can keep bubbles and pores in the foaming material in a stable form and distribution, and the diffusion and change of the bubbles can be slowed down by cooling, so that the pore structure and density required by the foaming material are maintained. In addition, after cooling to room temperature, the foaming material solidifies into the finished sheet, has certain intensity and stability, can more conveniently carry out subsequent processing and use, and the foaming material after cooling solidification can carry out processes such as cutting, forming, processing and the like, thereby meeting the requirements of different applications.
The further preferable technical scheme is as follows: in the mould pressing treatment process, the hot pressing temperature is 120-140 ℃.
The further preferable technical scheme is as follows: in the mould pressing treatment process, the pressure is 5-10MPa.
The further preferable technical scheme is as follows: in the mould pressing treatment process, the hot pressing time is 60-120s.
The further preferable technical scheme is as follows: the thickness of the raw material is 5-10mm.
The further preferable technical scheme is as follows: the irradiation dose is 6-8.5Mrad.
The further preferable technical scheme is as follows: the irradiation energy is 2-2.2Mev.
The further preferable technical scheme is as follows: in the supercritical mould pressing foaming process, N 2 、CO 2 The total pressure of (2) is 10-20MPa.
The further preferable technical scheme is as follows: in the supercritical mould pressing foaming process, the foaming temperature is 100-120 ℃.
The further preferable technical scheme is as follows: in the supercritical mould pressing foaming process, the foaming time is 60-90min.
The further preferable technical scheme is as follows: the N is 2 、CO 2 The ratio of (3-7): (3-7).
The further preferable technical scheme is as follows: the room temperature is 18-30 ℃.
The further preferable technical scheme is as follows: the supercritical mould pressing foaming process uses one of a batch foaming method, a continuous extrusion foaming method and an injection foaming method.
Among them, the batch foaming method is a physical foaming method in which a polymer is placed in an autoclave, immersed in supercritical gas, and then subjected to constant temperature and pressure until the gas is saturated, and foaming is induced by a sudden pressure reduction or sudden temperature increase. In the depressurization foaming process, the infiltration pressure of the gas and the depressurization speed are important factors influencing the cell structure; for heating, the infiltration pressure of the gas, the foaming temperature, the foaming time and the like are key to the final cell structure morphology. Firstly, placing a matrix material into a closed kettle body into which supercritical gas is introduced, soaking at constant temperature and constant pressure for a certain time to enable the gas to reach a saturated state, rapidly releasing pressure, placing a sample into a high-temperature oil bath to foam and form, and finally rapidly cooling and shaping the foamed material to a certain extent to obtain a stable cell structure. The intermittent foaming method has the advantages of simple process, easily controlled parameters, low cost and the like, and the foaming material with uniform cells and large porosity is easy to obtain.
The principle of the continuous extrusion foaming method is that a gas injection device is additionally arranged in an extruder, supercritical gas is injected into a hot-melt polymer matrix, and polymer melt and the supercritical gas are fully stirred and mixed through screw rotation, so that a polymer/supercritical gas homogeneous system is formed. And then extruding to the die opening for decompression foaming molding. The extrusion apparatus may be classified into a single screw extruder and a twin screw extruder according to the number of screws.
The injection foaming method is a supercritical gas injection foaming molding technology, is a foaming method combining supercritical gas fluid with injection molding, and has a foaming principle similar to extrusion foaming molding. And injecting supercritical gas into the machine barrel to be fully mixed with the polymer in a molten state to form a polymer/supercritical gas uniform system, then extruding at a high speed at a nozzle, filling the polymer/supercritical gas uniform system into a die, and after the die filling is completed, rapidly reducing the pressure in the die cavity to oversaturate the polymer/supercritical gas system and keeping the polymer/supercritical gas system in a thermodynamically unstable state. As the free energy of the system decreases, supercritical gas nucleation is induced. With the continuous reduction of external pressure, bubbles grow up rapidly and fill the mold to form injection foaming materials, and products obtained by injection foaming molding have the advantages of high quality, customizable shape, stable size and the like.
The foaming material is applied to the field of food packaging. The foaming material without volatile matters is prepared by a pure physical method, and chemical additives or foaming agents are not needed, so that the foaming material has high requirements on the safety and sanitation of food, and can not release harmful substances, have no adverse effect on the quality and taste of the food, and can be safely used for food packaging. The foaming material has excellent fresh-keeping performance, and the micropore structure of the foaming material can provide good heat insulation and heat preservation effects, reduce temperature change and heat conduction of food and prolong the fresh-keeping period of the food. Meanwhile, the foaming material can also prevent permeation of oxygen and moisture, reduce oxidation and deterioration speed of food, and keep freshness and quality of food. And the volatile-free foaming material generally has lower density and light weight, so that the weight of the packaging material can be reduced, and the transportation and storage cost can be reduced. Meanwhile, the foaming material can be generally recycled, so that the influence on the environment is reduced, and the environment-friendly requirement is met. On the basis, the volatile-free foaming material has good mechanical properties such as strength, rigidity, impact resistance and the like, which can provide good physical protection for food packaging and reduce the risk of damage to food during transportation and storage.
The foaming material can also be applied to the field of medical appliances. The foaming material has no volatile substances and good biocompatibility, which means that the foaming material does not generate adverse reaction or anaphylactic problem to human tissues, and can be safely used for the contact part of medical equipment. The foaming material has lower permeability and adsorptivity, can effectively prevent liquid or gas from permeating, prevents pollutants from entering the medical instrument, and protects the integrity and functions of the instrument. The foaming material has good shock absorption performance, and can effectively reduce the influence of impact and vibration on medical instruments, so that sensitive parts and fragile parts of the instruments are protected, and the service life of the instruments is prolonged. In addition, the foaming material can be customized and prepared according to the shape and the size of the medical instrument, and good adaptability and coating property are provided. Meanwhile, the foaming material can be processed through thermoforming or cutting and other processes to adapt to the requirements of different instruments.
The foaming material can also be applied to the field of children products. The foam material is free of volatile substances, which makes it very suitable for use in children's articles, such as toys, mattresses and the like, ensuring the health and safety of children. The foamed material generally has soft and elastic properties that enable it to provide a pleasant feel and protective properties in a child's article, reducing the risk of injury to the child during use. The foaming material also has good impact resistance, can effectively absorb and disperse external force, and lightens the damage of collision to articles for children and the children, thereby providing safer environment for the children in playing and activities. The foam material is free of volatile substances, uniform in internal pore size distribution and high in durability and ageing resistance, so that the children's articles can withstand long-time use and frequent operation, and the service life is prolonged.
The foaming material can also be applied to the field of sports goods. The foam material is free of volatile organic compounds, so that the foam material has lower odor, and can reduce peculiar smell and pungent odor for sports products, particularly parts with larger contact areas, such as insoles, gloves and the like, and provide more comfortable and healthy use experience. The foam material without volatile matters can reduce the injury to the athlete during the respiration, and the foam material without volatile organic matters is helpful for maintaining the health of the athlete's heart and lung. And the foam material without volatile substances does not contain additional chemical substances, and generally has higher durability and ageing resistance, so that the sports article can withstand long-time use and frequent operation, the service life is prolonged, and the replacement frequency and cost are reduced. In the field of sports goods, the material without volatile substances can reduce negative influence on environment, reduce waste generation and accord with the concept of sustainable development.
In summary, the invention has the following advantages:
1. the foaming material of the application carries out crosslinking treatment on the polymer through high-energy electron rays, is different from the traditional common chemical crosslinking method which uses a chemical crosslinking agent for crosslinking, does not add any chemical crosslinking agent into the raw materials, namely has no other side reactions in the crosslinking process and no chemical substance residues after crosslinking,
2. the foaming material does not use any chemical auxiliary agent, the crosslinking uniformity is not influenced by the dispersibility of the chemical auxiliary agent, and the distribution of the cavities in the foaming material is more uniform.
Further or more detailed benefits will be described in connection with specific embodiments.
Drawings
The invention is further described with reference to the accompanying drawings:
FIG. 1 is a schematic flow chart of a foaming material preparation process.
Fig. 2 is a scanning electron microscope image of test example one.
Fig. 3 is a scanning electron microscope image of test example two.
Fig. 4 is a scanning electron microscope image of test example three.
Fig. 5 is a scanning electron microscope image of test example four.
Fig. 6 is a scanning electron microscope image of test example five.
Fig. 7 is a scanning electron microscope image of test example six.
Detailed Description
Definition of the definition
High-voltage electron accelerator
The high-voltage electron accelerator accelerates charged particles by the action force of an electric field on charges, and accelerates the charged particles by a very high voltage, so that huge speed is obtained. The high-voltage electron accelerator mainly comprises a charged particle source, a power supply for generating an accelerating electric field, and a vacuum system for accelerating the charged particles in vacuum to avoid energy collision with gas molecules.
Supercritical mould pressing foaming device
A supercritical foaming apparatus is an apparatus that adopts supercritical fluid foaming, and can achieve foaming using various characteristics of supercritical fluid. It injects a gaseous or liquid foaming agent in the form of a supercritical fluid through a foamer into a particular foaming assembly to effect foaming. The supercritical foaming device has the advantages that the characteristics of a foaming medium in the foaming process can be controlled, and the distribution of foaming substances can be regulated to ensure the quality of products, so that a good foaming effect is obtained. For example, the supercritical foaming device can control the pressure, temperature and concentration of the medium, and the injection and distribution of the foaming medium, so as to adjust the dispersivity, quality and foaming efficiency of the foaming substance, and achieve good foaming effect. The supercritical foaming device mainly comprises a temperature control device and a foaming mold, wherein the foaming mold can be divided into an upper half mold and a lower half mold, and a foaming cavity is arranged between the upper half mold and the lower half mold.
Irradiation crosslinking
The irradiation crosslinking technique is a technique for realizing a crosslinking reaction of macromolecules by a physical method, mainly irradiation, and changing a linear polymer into a polymer with a three-dimensional space network structure.
Irradiation sensitizer
The irradiation sensitizer is a chemical auxiliary agent used in the irradiation crosslinking process, and has the functions of promoting the crosslinking of the system and expanding the surface tension of the melt, and can store the gas generated by the foaming agent generally, thereby being beneficial to forming a regular cell shape. Commonly used radiation sensitizers such as pentaerythritol triacrylate, but are not representative of the compounds described above in either the examples or comparative examples below.
Scanning Electron Microscope (SEM)
In the following examples and comparative examples, SU3500 was used as a specific model of scanning electron microscope with an operating frequency of 1.4GHz, having 800mhz fsb, using a 45nm fabrication process.
The present invention will be described in further detail with reference to the accompanying drawings.
The present embodiment is only for explanation of the present invention and is not to be construed as limiting the present invention, and modifications to the present embodiment, which may not creatively contribute to the present invention as required by those skilled in the art after reading the present specification, are all protected by patent laws within the scope of claims of the present invention.
Embodiment one:
in this embodiment, the preparation method of the non-volatile foaming material comprises the following steps:
s11, the raw material is low-density polyethylene, and the raw material is subjected to a mould pressing treatment process, wherein the mould pressing treatment process is to extrude the raw material into a 10mm plate at a speed of 20ram/min by using a single screw extruder, so as to obtain a mould pressing raw material;
s12, carrying out an irradiation treatment process on the molding raw material, wherein the process conditions of the irradiation treatment process are that a high-pressure electron accelerator is used, the energy is 2.0Mev, and the dosage is 8.5Mrad, so as to obtain a crosslinking raw material;
s13, placing the crosslinking raw material into a foaming device, wherein the device is a supercritical mould pressing foaming device, and N is used 2 ，CO 2 As foaming gas, where N 2 、CO 2 The gas volume ratio of (2) is 3:7, the total pressure of foaming gas is 14MPa, the foaming temperature is 108 ℃, the foaming time is 90min, and then the pressure is relieved until the total pressure of the foaming gas is atmospheric pressure, so that a foaming raw material is obtained;
s14, taking the foaming raw material out of the foaming device, and cooling to room temperature to obtain the foaming material.
Embodiment two:
in this embodiment, the preparation method of the non-volatile foaming material comprises the following steps:
s21, the raw material is ethylene-vinyl acetate copolymer, and the raw material is subjected to a mould pressing treatment process, wherein the mould pressing treatment process is to extrude the raw material into a 10mm plate at a speed of 20ram/min by using a single screw extruder, so as to obtain a mould pressing raw material;
s22, carrying out an irradiation treatment process on the molding raw material, wherein the process conditions of the irradiation treatment process are that a high-pressure electron accelerator is used, the energy is 2.0Mev, and the dosage is 6.0Mrad, so as to obtain a crosslinking raw material;
s23, placing the crosslinking raw material into a foaming device, wherein the device is a supercritical mould pressing foaming device, and N is used 2 ，CO 2 As foaming gas, where N 2 、CO 2 The gas volume ratio of (2) is 7:3, the total pressure of foaming gas is 13MPa, the foaming temperature is 86 ℃, the foaming time is 160min, and then the pressure is relieved until the total pressure of the foaming gas is atmospheric pressure, so as to obtain a foaming raw material;
s24, taking the foaming raw material out of the foaming device, and cooling to room temperature to obtain the foaming material.
Comparative example one
In this comparative example, the preparation method of the non-volatile foaming material is as follows:
s31, 100 parts of polypropylene and 3 parts of radiation sensitizer by weight, and carrying out mould pressing treatment on the raw materials, wherein the mould pressing treatment comprises the step of extruding the raw materials into a 10mm plate at 185ram/min by using a single screw extruder to obtain a mould pressing raw material;
s32, carrying out an irradiation treatment process on the molding raw material, wherein the process conditions of the irradiation treatment process are that a high-pressure electron accelerator is used, the energy is 2.0Mev, and the dosage is 3.5Mrad, so as to obtain a crosslinking raw material;
s33, placing the crosslinking raw material into a foaming device, wherein the device is a supercritical mould pressing foaming device and uses CO 2 As foaming gas, the total pressure of the foaming gas is 12MPa, the foaming temperature is 142 ℃, the foaming time is 120min, and then the pressure is relieved until the total pressure of the foaming gas is atmospheric pressure, so as to obtain a foaming raw material;
s34, taking the foaming raw material out of the foaming device, and cooling to room temperature to obtain the foaming material.
Test example: scanning electron microscope characterization test
The foam materials obtained in examples one, two and comparative example one were subjected to pore size testing. The test method adopts a Scanning Electron Microscope (SEM), a sample is soaked in liquid nitrogen and then is brittle broken, and then the section is sprayed with metal for shooting. The various test example parameters are shown below:
test example 1
Resolution ratio: 1280x960; pixel size: 826.8229; acceleration voltage: 5000Volt; deceleration voltage: 0Volt; the results are shown in FIG. 2.
Test example two
Resolution ratio: 1280x960; pixel size: 826.8229; acceleration voltage: 5000Volt; deceleration voltage: 0Volt; the results are shown in FIG. 3.
Test example three
Resolution ratio: 1280x960; pixel size: 1653.646; acceleration voltage: 5000Volt; deceleration voltage: 0Volt; the results are shown in FIG. 4.
Test example four
Resolution ratio: 1280x960; pixel size: 2834.822; acceleration voltage: 5000Volt; deceleration voltage: 0Volt; the results are shown in FIG. 5.
Test example five
Resolution ratio: 1280x960; pixel size: 330.7292; acceleration voltage: 5000Volt; deceleration voltage: 0Volt; the results are shown in FIG. 6.
Test example six
Resolution ratio: 1280x960; pixel size: 2834.822; acceleration voltage: 5000Volt; deceleration voltage: 0Volt; the results are shown in FIG. 7.
The results of pore size analysis of the images of test examples one, three and five are shown in the following tables, wherein tables 1 and 2 show the data of the foaming materials of examples, tables 3 and 4 show the data of the foaming materials of examples, and tables 5 and 6 show the data of the foaming materials of examples.
| Numbering device | Particle size/. Mu.m | Numbering device | Particle size/. Mu.m | Numbering device | Particle size/. Mu.m | Numbering device | Particle size/. Mu.m | Numbering device | Particle size/. Mu.m |
| 1 | 296.45 | 11 | 263.51 | 21 | 158.87 | 31 | 115.39 | 41 | 209.41 |
| 2 | 262.2 | 12 | 196.27 | 22 | 261.66 | 32 | 171.06 | 42 | 215.93 |
| 3 | 264.9 | 13 | 228.95 | 23 | 216.75 | 33 | 187.55 | 43 | 173.54 |
| 4 | 251.49 | 14 | 260.43 | 24 | 214.27 | 34 | 287.62 | 44 | 239.68 |
| 5 | 215.33 | 15 | 212.2 | 25 | 199.35 | 35 | 302.01 | 45 | 204.31 |
| 6 | 243.81 | 16 | 288.26 | 26 | 212.44 | 36 | 172.82 | 46 | 177.32 |
| 7 | 247.16 | 17 | 323.84 | 27 | 157.19 | 37 | 186.74 | 47 | 172.94 |
| 8 | 244.81 | 18 | 239.31 | 28 | 249.12 | 38 | 179.15 | 48 | 145.44 |
| 9 | 241.9 | 19 | 182.15 | 29 | 182.45 | 39 | 139.37 | 49 | 228.53 |
| 10 | 217.43 | 20 | 154.7 | 30 | 199.05 | 40 | 219.41 | 50 | 224.06 |
TABLE 1
| Range/. Mu.m | Median/. Mu.m | Quantity of | Probability of distribution |
| 115-135.9 | 125.45 | 1 | 2.00％ |
| 135.9-156.8 | 146.35 | 3 | 6.00％ |
| 156.8-177.7 | 167.25 | 7 | 14.00％ |
| 177.7-198.6 | 188.15 | 6 | 12.00％ |
| 198.6-219.5 | 209.05 | 12 | 24.00％ |
| 219.5-240.4 | 229.95 | 5 | 10.00％ |
| 240.4-261.3 | 250.85 | 7 | 14.00％ |
| 261.3-282.2 | 271.75 | 4 | 8.00％ |
| 282.2-303.1 | 292.65 | 4 | 8.00％ |
| 303.1-324 | 313.55 | 1 | 2.00％ |
TABLE 2
| Numbering device | Particle size/. Mu.m | Numbering device | Particle size/. Mu.m | Numbering device | Particle size/. Mu.m | Numbering device | Particle size/. Mu.m | Numbering device | Particle size/. Mu.m |
| 1 | 236.69 | 11 | 169.96 | 21 | 112.49 | 31 | 79.44 | 41 | 229.44 |
| 2 | 295.78 | 12 | 165.29 | 22 | 152.05 | 32 | 152.13 | 42 | 127.83 |
| 3 | 185.61 | 13 | 154.41 | 23 | 174.26 | 33 | 150.05 | 43 | 136.75 |
| 4 | 178.87 | 14 | 282.08 | 24 | 247.33 | 34 | 143.19 | 44 | 160.79 |
| 5 | 263.02 | 15 | 264.33 | 25 | 125.74 | 35 | 147.8 | 45 | 116.98 |
| 6 | 254.57 | 16 | 112.49 | 26 | 255.55 | 36 | 251.26 | 46 | 211.47 |
| 7 | 189.06 | 17 | 178.72 | 27 | 136.91 | 37 | 154.79 | 47 | 130.3 |
| 8 | 184.05 | 18 | 264.35 | 28 | 178.76 | 38 | 284.45 | 48 | 167.42 |
| 9 | 189.09 | 19 | 158.81 | 29 | 112.49 | 39 | 207.35 | 49 | 187.54 |
| 10 | 180.19 | 20 | 204.85 | 30 | 218.07 | 40 | 233.48 | 50 | 211.56 |
TABLE 3 Table 3
| Range/. Mu.m | Median/. Mu.m | Quantity of | Probability of distribution |
| 79-100.7 | 89.85 | 1 | 2.00％ |
| 100.7-122.4 | 111.55 | 4 | 8.00％ |
| 122.4-144.1 | 133.25 | 6 | 12.00％ |
| 144.1-165.8 | 154.95 | 9 | 18.00％ |
| 165.8-187.5 | 176.65 | 9 | 18.00％ |
| 187.5-209.2 | 198.35 | 5 | 10.00％ |
| 209.2-230.9 | 220.05 | 4 | 8.00％ |
| 230.9-252.6 | 241.75 | 4 | 8.00％ |
| 252.6-274.3 | 263.45 | 5 | 10.00％ |
| 274.3-296 | 285.15 | 3 | 6.00％ |
TABLE 4 Table 4
| Numbering device | Particle size/. Mu.m | Numbering device | Particle size/. Mu.m | Numbering device | Particle size/. Mu.m | Numbering device | Particle size/. Mu.m | Numbering device | Particle size/. Mu.m |
| 1 | 53.51 | 11 | 37.28 | 21 | 27.63 | 31 | 20.61 | 41 | 25.47 |
| 2 | 59.73 | 12 | 43.48 | 22 | 45.71 | 32 | 23.72 | 42 | 17.92 |
| 3 | 48.72 | 13 | 22.37 | 23 | 43.64 | 33 | 27.2 | 43 | 34.65 |
| 4 | 58.93 | 14 | 28.55 | 24 | 36.15 | 34 | 39.99 | 44 | 35 |
| 5 | 40.91 | 15 | 28.98 | 25 | 15.79 | 35 | 21.51 | 45 | 12.28 |
| 6 | 59.77 | 16 | 43.59 | 26 | 16.69 | 36 | 29 | 46 | 14.22 |
| 7 | 31.17 | 17 | 32.02 | 27 | 31.59 | 37 | 33.78 | 47 | 16.28 |
| 8 | 44 | 18 | 28.12 | 28 | 45.71 | 38 | 41.78 | 48 | 18.45 |
| 9 | 31.14 | 19 | 18.86 | 29 | 24.16 | 39 | 21.97 | 49 | 20.69 |
| 10 | 58.85 | 20 | 14.05 | 30 | 18.47 | 40 | 23.75 | 50 | 21.3 |
TABLE 5
| Range/. Mu.m | Median/. Mu.m | Quantity of | Probability of distribution |
| 12-16.8 | 14.4 | 6 | 12.00％ |
| 16.8-21.6 | 19.2 | 8 | 16.00％ |
| 21.6-26.4 | 24 | 6 | 12.00％ |
| 26.4-31.2 | 28.8 | 8 | 16.00％ |
| 31.2-36 | 33.6 | 5 | 10.00％ |
| 36-40.8 | 38.4 | 3 | 6.00％ |
| 40.8-45.6 | 43.2 | 6 | 12.00％ |
| 45.6-50.4 | 48 | 3 | 6.00％ |
| 50.4-55.2 | 52.8 | 1 | 2.00％ |
| 55.2-60 | 57.6 | 4 | 8.00％ |
TABLE 6
As can be seen from fig. 2 to 7, the foamed materials of examples one and two prepared by the pure physical method have obviously better pore diameter uniformity than the foamed material added with the irradiation sensitizer in comparative example one, and the preparation method of the present application has the advantages that the crosslinking degree is not reduced, but rather is improved to a certain extent under the condition that the irradiation sensitizer is not present, which indicates that the preparation method of the present application does not need the auxiliary effect of the irradiation sensitizer, and the irradiation sensitizer also has a certain degree of influence after the irradiation sensitizer is added while the method of the present application is used, so that the pore diameter distribution of the final foamed material is uneven.
Furthermore, referring to the data in tables 1 to 6, it is understood that the foam materials prepared in examples one and two have pore diameters ranging from 100 to 300. Mu.m, and the foam materials prepared in examples one and two have densities of 0.1g/cm 3 While the foam prepared in comparative example one is extremely uneven in pore distribution and different in size as seen in FIG. 7, although a portion having a relatively uniform pore size distribution has been selected, for example, the electron microscope image of FIG. 6 was analyzed for pore size distribution, and it was found that the pore size distribution was between 10 and 60. Mu.m, the density of the foam prepared in comparative example one was only 0.05g/cm 3 . According to common knowledge, the larger the pore size of the same material, the lower the density thereof, because most of the material is occupied by air, while the foam material prepared in comparative example one, although having a smaller pore size than that of examples one and two, has a lower density, which means that there are larger cavities in other parts of the material, and such cavities are again confirmed by fig. 7 (it is apparent that there are sharply increased cavity parts in the drawing), and such cavities greatly cause fine cracks to be generated in the material, and are further enlarged during use, thereby resulting in a reduction in the service life of the whole material.
Regarding the problem of the non-uniform cavity distribution of the foam material prepared in comparative example one, a convincing analysis was that the irradiation sensitizer added in step S31 of comparative example one was not dispersed uniformly enough, resulting in too high a degree of crosslinking where it was distributed, thereby creating more, finer pores, whereas the irradiation sensitizer was absent, and the degree of crosslinking was lower, thereby causing less crosslinking, resulting in larger pores and forming cavities, although the amount of irradiation sensitizer added was small enough (100:3), which still had a great influence. By adopting the method, the cross-linking degree of the material is almost consistent, so that the uniformity of pore distribution is very high, and the finally prepared foaming material has small anisotropism degree, namely, the material is pulled from different directions by using the same force and has considerable strength, so that the possibility of occurrence of tiny cracks can be well resisted, and the service life of the material is finally prolonged.
Test example seven
The foaming materials of the first, second and comparative example were tested for apparent density according to the national standard of the people's republic of China GB/T6343-2009 "determination of apparent density of foam and rubber", wherein the apparent density refers to the ratio of the mass of the material to the apparent volume, and the apparent volume is the real volume plus closed pore volume. Wherein the foam of example one had an apparent density of 0.1g/cm 3 The foam of example II had an apparent density of 0.1g/cm 3 The foam of comparative example one had an apparent density of 0.05g/cm 3 . It can be seen that the foam of comparative example one has relatively denser cavities than that of examples one and two, but has a smaller apparent density, which indicates that the foam of comparative example one has a larger total volume of cavities inside, in fact, for a specific reason, reference is made to fig. 7, i.e., the foam of comparative example one has more non-uniform large-pore cavities, which directly affects the overall density.
Test example eight
The rebound resilience of the foaming materials of the first and second examples was tested according to the method B described in national standard of the people's republic of China GB/T6670-2008 "determination of the rebound resilience of Soft foam Polymer Material by falling ball method", and the results show that the rebound resilience of the foaming material of the first example is 68% and the rebound resilience of the foaming material of the second example is 68%. As a comparison, the requirement for the resilience of the sponge in the national standard GB/T10802-2006 of general soft polyether polyurethane foam is more than or equal to 35%, and the requirement for the resilience of the sponge in the national standard QB/T1952.1-2012 of light industry of the people's republic of China is more than or equal to 35%, which shows that the foam materials of the first and second embodiments meet most of the standards and have wide application range.
Furthermore, wherever possible, the same or similar reference numbers are used in the drawings and the description to refer to the same or like parts or steps. The drawings are presented in simplified form and are not drawn to precise scale. For convenience and clarity only, directional terms, such as top, bottom, left, right, upward, above, below, rear and front, may be used with respect to the accompanying drawings. These and similar directional terms should not be construed to limit the scope of the disclosure in any way.
While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: many changes, modifications, substitutions and variations may be made to the embodiments without departing from the spirit and principles of the invention, the scope of which is defined by the claims and their equivalents.
Claims (23)
1. A non-volatile foam material, characterized in that the raw material of the foam material consists of one thermoplastic elastomer or a plurality of thermoplastic elastomers, and the foam material is internally provided with a plurality of foam cavities, wherein at least 95% of the foam cavities have a pore size of not less than 100 μm, and at least 95% of the foam cavities have a pore size of not more than 300 μm.
2. The non-volatile foam of claim 1, wherein the foam has a density of no greater than 0.1g/cm 3 。
3. The non-volatile foam of claim 1, wherein the foam has a rebound rate of not less than 65%.
4. The non-volatile foam material of claim 1 wherein the thermoplastic elastomer is an ethylene vinyl acetate copolymer.
5. The non-volatile foamed material of claim 1, wherein said thermoplastic elastomer is polyethylene.
6. The non-volatile foam material of claim 1 wherein the thermoplastic elastomer is a combination of ethylene vinyl acetate copolymer and polyethylene.
7. The method for producing a nonvolatile foamed material according to any one of claims 1 to 6, comprising the steps of:
s1, carrying out a mould pressing treatment process on the raw materials to obtain mould pressing raw materials;
s2, carrying out an irradiation treatment process on the molding raw material to obtain a cross-linking raw material;
s3, putting the crosslinking raw material into a foaming device, and introducing N 2 、CO 2 Performing supercritical mould pressing foaming process to obtain foaming raw materials;
s4, taking out the foaming raw material, and cooling to room temperature to obtain the foaming material.
8. The method for producing a non-volatile foam material according to claim 7, wherein the hot pressing temperature is 120 to 140 ℃ during the molding process.
9. The method for producing a non-volatile foam according to claim 7, wherein the pressure is 5 to 10MPa during the molding process.
10. The method for producing a foam material having no volatility as claimed in claim 7, wherein the hot pressing time is 60 to 120 seconds during the molding process.
11. The method for producing a non-volatile foam material according to claim 7, wherein the thickness of the raw material during the molding process is 5 to 10mm.
12. The method for preparing a non-volatile foaming material according to claim 7, wherein the irradiation dose is 6-8.5Mrad during the irradiation treatment.
13. The method for preparing a non-volatile foaming material according to claim 7, wherein the irradiation energy is 2-2.2Mev during the irradiation treatment.
14. The method for producing a non-volatile foam material according to claim 7, wherein in the supercritical molding foaming process, N 2 、CO 2 The total pressure of (2) is 10-20MPa.
15. The method for producing a non-volatile foam material according to claim 7, wherein the foaming temperature is 100 to 120 ℃ in the supercritical molding foaming process.
16. The method for preparing a non-volatile foaming material according to claim 7, wherein the foaming time is 60-90min in the supercritical compression molding foaming process.
17. The method for producing a non-volatile foam material according to claim 7, wherein the N 2 、CO 2 The ratio of (3-7): (3-7).
18. The method for producing a non-volatile foam material according to claim 7, wherein the room temperature is 18 to 30 ℃.
19. The method for producing a non-volatile foam material according to claim 7, wherein the supercritical molding foaming process uses one of a batch foaming method, a continuous extrusion foaming method, and an injection foaming method.
20. Use of the non-volatile foamed material according to any of claims 1-6, wherein the foamed material is used in the field of food packaging.
21. Use of the non-volatile foam material according to any of claims 1-6, wherein the foam material is applied in the field of medical devices.
22. Use of the non-volatile foamed material according to any of claims 1-6, wherein the foamed material is applied in the field of children's products.
23. Use of the non-volatile foamed material according to any of claims 1-6, wherein the foamed material is applied in the field of sports goods.
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|---|---|---|---|
| CN202311755157.0A CN117844092A (en) | 2023-12-20 | 2023-12-20 | Non-volatile foaming material and preparation method and application thereof |
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| CN202311755157.0A CN117844092A (en) | 2023-12-20 | 2023-12-20 | Non-volatile foaming material and preparation method and application thereof |
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