Hard polyamide foamed bead and molded part thereof
Through the hard polyamide foam beads with core-shell double-layer structure, the problem of difficult molding of rigid polyamide foam beads is solved, and the high welding strength foamed parts are prepared under low temperature and low pressure, which improves maturation and mechanical properties.
Patent Information
- Application Number
- CN202510662937.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-22
- Publication Date
- 2025-07-11
AI Technical Summary
The existing rigid polyamide foamed bead materials have high melting point during the molding process, the steam forming temperature and pressure exceed the limit, and the maturation degree is low, making it difficult to prepare foamed parts with high welding strength.
The hard polyamide foam beads with a core-shell double-layer structure are used. The core layer contains high melting point and high modulus polyamide, and the shell layer contains low melting point polyamide and flux agent. It is prepared by coextrusion and foaming processes to reduce the molding temperature and pressure, and improve the welding strength and maturation degree.
The high welding strength foamed parts are prepared at lower temperatures and pressures, which improves the maturity and mechanical properties of the foamed parts.
Smart Images
Figure CN120289984A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a rigid polyamide foamed bead and a molded part thereof, belonging to the field of foaming materials. Background Art
[0002] Polyamide materials, such as nylon 6, nylon 66, etc., are widely used in high-end fields such as aerospace, rail transit, automotive industry, electronic equipment, and military due to their high melting point, good heat resistance, high mechanical strength, good toughness, good wear resistance, and excellent chemical corrosion resistance. Polyamide bead foaming materials and their molded parts have excellent lightweight performance, good mechanical strength and heat resistance, and high three-dimensional shape freedom, and have attracted wide attention in the fields of lightweight automotive components and buffer parts, new energy battery buffer protection parts, photovoltaic packaging turnover parts, etc.
[0003] The main raw material of the polyamide foamed bead material disclosed in Patent CN118664818A is a long-chain polyamide elastomer, which has excellent elasticity, resilience and toughness, but has low rigidity and is mainly used in the fields of sports goods, shoe materials, etc.
[0004] Although the foamed products and their molded parts prepared from rigid polyamide (such as high-melting-point and high-modulus nylon 6, nylon 66, etc.) materials have higher rigidity, hardness and heat resistance, and are more suitable for making lightweight mechanical structure parts products, there are few patent literatures related to rigid polyamide foamed bead materials. The reason is not difficult to find that rigid polyamide foamed bead materials often have a high melting point, and the steam forming temperature and pressure of the beads are relatively high, exceeding or being within the upper limit range of the temperature and pressure of the steam forming machine (generally the pressure upper limit is 4.5 - 5 kg), and the curing degree of the foamed parts is relatively low.
[0005] Therefore, it is very important to develop a nylon foamed bead part based on rigid polyamide (such as high-melting-point and high-modulus nylon 6, nylon 66, etc.) and having a high degree of fusion. Summary of the Invention
[0006] In order to solve the problem of difficult forming of rigid polyamide (such as high-melting-point and high-modulus nylon 6, nylon 66, etc.) foamed bead materials, the present invention discloses a rigid polyamide foamed bead with high welding strength and a molded part thereof. The rigid polyamide foamed bead has a core-shell double-layer structure, the internal core layer contains a rigid high-melting-point polyamide, etc., and the external shell layer contains a low-melting-point polyamide, etc. When steam-forming this rigid polyamide foamed bead material, the forming temperature and pressure can be significantly reduced, the welding strength between the foamed beads is relatively high, the obtained molded part has a high curing degree, and the molded part as a whole has good mechanical properties.
[0007] In order to achieve the above object, the present invention adopts the following technical solutions:
[0008] A rigid polyamide foamed bead material has a core-shell structure. The core layer material includes 60-90 wt% of a high melting point and high modulus polyamide A, 1-10 wt% of a low melting point polyamide B, and 0.01-5 wt% of a nucleating agent; the shell layer material includes 90-99.9 wt% of a low melting point polyamide C. The mass ratio of the core layer material to the shell layer material is 70:30-99:1, preferably 80:20-95:5. The melting point of the polyamide C is between that of the polyamide A and the polyamide B, and is 10-30 °C lower than the melting point of the blend of the polyamide A and the polyamide B.
[0009] The melting point of the polyamide C in the shell layer is lower than that of the polyamide blend in the core layer, which is beneficial to the welding between beads during molding and increases the degree of curing of the foamed parts. It should be noted that the melting point of the polyamide C in the shell layer should be slightly lower than that of the polyamide blend in the core layer. If the melting point difference between the core and shell layers is too large, it will cause the surface of the foamed parts to be "overcooked" while the inside is "undercooked", and the overall degree of curing of the foamed parts is still not high.
[0010] The melting point of the polyamide A is 210-260 °C, the tensile modulus is 2500-3500 MPa, and the melt index is 3-20 g / 10 min. The high melting point and high modulus polyamide as the core layer structure can provide the foamed beads with high temperature resistance and mechanical strength. The polyamide A is preferably polyamide 6, polyamide 66, or a block copolymer of polyamide 6 and polyamide 66.
[0011] The melting point of the polyamide B is 130-160 °C, the tensile modulus is 2500-3000 MPa, and the melt index is 3-20 g / 10 min. The melting point of the polyamide B is very low. A small amount of addition can reduce the molding temperature and pressure of the polyamide foamed beads. At the same time, its relatively moderate tensile modulus will not cause too much sacrifice of the mechanical strength of the foamed polyamide beads. Therefore, the foamed beads can maintain a relatively high mechanical property level.
[0012] The melting point of the polyamide C is 170-200 °C, the tensile modulus is 2000-2800 MPa, and the melt index is 3-20 g / 10 min.
[0013] The core layer material further includes 1 to 20 wt% of an expansion aid, and the expansion aid is a polar group grafted elastomer, such as glycidyl acrylate grafted polyolefin elastomer, glycidyl acrylate grafted ethylene-propylene rubber, glycidyl acrylate grafted styrene-ethylene-butadiene-styrene block copolymer, maleic anhydride grafted polyolefin elastomer, maleic anhydride grafted ethylene-propylene rubber, maleic anhydride grafted styrene-ethylene-butadiene-styrene block copolymer, etc. The polar group has good compatibility with polar polyamide and serves as a "bridge" to connect the elastomer and polyamide at both ends. Under the action of hot steam during molding, the polyamide foam beads introduced with elastomers will undergo relatively large thermal expansion deformation, the welding area between adjacent foam beads increases, and the curing degree of the foam parts rises.
[0014] The core layer material and / or the shell layer material further includes 0.1 to 10 wt% of a welding aid, and the welding aid is at least one of metal powders, metal oxide powders, and nitride powders with relatively high thermal conductivity. The metal powders include aluminum powder, copper powder, iron powder, etc. The metal oxide powders include alumina powder, copper oxide powder, iron oxide powder, etc. The nitride powders include boron nitride powder, aluminum nitride powder, etc. During hot steam molding, the welding aid can absorb a large amount of external heat and quickly conduct the heat to the polyamide foam beads, prompting the temperature of the foam beads to rise instantaneously. The welding aid is preferably hexagonal boron nitride, which is in the form of flaky powder, and the powder particle length is 5 to 20 μm. The flaky structure enables heat conduction to have multidirectionality and continuity, effectively reducing the thermal conduction interface resistance between the base material and the heat-conducting material.
[0015] The core layer material further includes 0.1 to 5 wt% of a hydrolysis-resistant agent, and the hydrolysis-resistant agent is at least one of glycidyl ether, tris(2,3-epoxypropyl) isocyanate, and carbodiimide, preferably carbodiimide. The hydrolysis-resistant agent usually reacts with the terminal carboxyl groups of polyamide, effectively playing a role in end-capping and inhibiting hydrolysis.
[0016] The core layer material further includes 0.1 to 5 wt% of a chain extender, and the chain extender is a glycidyl methacrylate compound containing an epoxy functional group or a glycidyl acrylate compound containing an epoxy functional group. The chain extender can increase the molecular weight and molecular chain branching degree of polyamide, thereby improving the melt strength and facilitating foaming.
[0017] The nucleating agent is at least one of calcium carbonate, talc powder, zinc borate, sodium chloride, silicon dioxide, etc., and the particle size is 1 to 20 μm. The nucleating agent usually has a certain incompatibility with the polyamide base material, promotes the growth of pores at the interface between the nucleating agent and the base material during the foaming process of polyamide beads, and plays a role in heterogeneous nucleation. At the same time, the nucleating agent also has the functions of reducing the foaming pressure and making the pores uniform.
[0018] The polyamide foam beads can also be added with additives such as color masterbatch, lubricant, antioxidant, ultraviolet absorber, etc. according to requirements.
[0019] The preparation method of the above-mentioned rigid polyamide foam beads is as follows:
[0020] (1) After uniformly mixing the core layer material of the foam polyamide beads, put it into twin-screw extruder A, and after uniformly mixing the shell layer material of the foam polyamide beads, put it into twin-screw extruder B;
[0021] (2) Through a double-layer die head for co-extrusion, the material in extruder A is used as the core layer, and the material in extruder B is used as the shell layer;
[0022] (3) Cool the extruded filament by water, and use a pelletizer to pelletize the filament, then expandable polyamide microparticles can be prepared;
[0023] (4) Put the expandable polyamide microparticles into a high-pressure foaming kettle for foaming to obtain foamed polyamide beads.
[0024] The preparation method of the molded parts of the above-mentioned rigid polyamide foam beads is as follows:
[0025] (1) After the foamed polyamide beads are placed at normal temperature and pressure for 10 hours, put them into a sealed pressure tank, and place the pressure tank in an environment at a certain temperature. Inject compressed air into the pressure tank to keep the polyamide foam beads under pressure for several hours in an environment at a certain temperature and pressure.
[0026] (2) Inject the pre-pressed polyamide foam beads into the mold of a steam molding machine for molding to obtain a polyamide foam molded part.
[0027] The present invention has the following beneficial effects:
[0028] (1) The shell layer of the above-mentioned polyamide foam beads contains polyamide with a lower melting point, which can enable the polyamide foam beads to generate thermal expansion deformation when absorbing less steam heat during the steam molding process, increase the bonding area between the foam beads and the beads, improve the curing degree of the foamed molded part, and thus improve the mechanical properties of the foamed molded part. The low-melting-point polyamide material in the core layer also helps to further improve the welding degree between the beads and the beads, achieving the purpose of improving the curing degree of the foamed molded part.
[0029] (2) The polar groups in the elastomeric co-expanding agent have good compatibility with polar polyamide, connecting the elastomer and polyamide at both ends as a "bridge". Under the action of the molding hot steam, the polyamide foam beads introduced with the elastomer will undergo relatively large thermal expansion deformation, the welding area between adjacent foam beads increases, and the curing degree of the foamed molded part is further increased.
[0030] (3) The fusant in the foaming beads has a relatively high thermal conductivity, which can help the polyamide foaming beads better absorb heat and conduct it quickly and evenly inside the beads, making them expand more fully by being heated. Description of the Drawings
[0031] Figure 1 is the polyamide foamed molded part prepared in Example 1. Detailed Description of the Invention
[0032] The present invention will now be described in further detail with reference to the embodiments.
[0033] Example 1:
[0034] Preparation of rigid polyamide foaming beads:
[0035] (1) According to the mass ratio of Example 1 in Table 1, the high melting point and high modulus polyamide A (melting point 220°C, tensile modulus 2800 MPa, melt index 7 g / 10 min (235°C, 2.16 kg), purchased from Ube Industries, Ltd., Japan) of the core layer, the low melting point polyamide B (melting point 134°C, tensile modulus 2700 MPa, melt index 7 g / 10 min (235°C, 2.16 kg), purchased from Weifang Dongsheng Plastic Technology Co., Ltd.), the nucleating agent zinc borate (purchased from Guangdong Jinge New Materials Co., Ltd.), the hydrolysis-resistant agent carbodiimide (purchased from Shandong Yuantai New Materials Co., Ltd.), the chain extender CM2103 (purchased from Zhejiang Chuangmo New Materials Co., Ltd.), the lubricant oleic acid amide (purchased from Zhengzhou Zhuochuang Chemical Products Co., Ltd.) and the antioxidant 168 (purchased from BASF SE, Germany) were mixed evenly and then put into twin-screw extruder A. The polyamide C (melting point 180°C, tensile modulus 2500 MPa, melt index 8 g / 10 min, (235°C, 2.16 kg), purchased from Ube Industries, Ltd., Japan) of the shell layer, the lubricant oleic acid amide (purchased from Zhengzhou Zhuochuang Chemical Products Co., Ltd.) and the antioxidant 168 (purchased from BASF SE, Germany) were mixed evenly and then put into twin-screw extruder B;
[0036] (2) Co-extrusion was achieved through a double-layer die. The material in extruder A was used as the core layer, and the material in extruder B was used as the shell layer. The mass ratio of the core layer to the shell layer was 90:10;
[0037] (3) The extruded filaments were water-cooled and pelletized to obtain expandable polyamide microparticles with a particle length of 1.2 - 2.5 mm and a single weight of 0.5 - 1.8 mg
[0038] (4) Add the above-mentioned expandable polyamide particles and water into a foaming kettle, add dispersant butter and surfactant sodium dodecyl sulfate at the same time, heat the foaming kettle and introduce carbon dioxide physical foaming agent to make the foaming agent penetrate into the interior of the polyamide particles to form a homogeneous system. When the set foaming temperature of 145-160°C and the foaming pressure of 4.0-5.0Mpa are reached in the reactor, they are maintained for 15 minutes, and then the expandable polyamide particles are instantly released into a foaming pipe with an internal air pressure of less than 0.1MPa and an atmosphere temperature of 80-100°C for foaming and expansion. The expandable polyamide particles spend 4-15s in the foaming pipe to finally obtain foamed polyamide beads.
[0039] Preparation of foamed polyamide molded parts:
[0040] (1) The above-mentioned expanded polyamide beads are subjected to an air pressure of 0.5 MPa at a temperature of 70 to 90°C for 20 hours.
[0041] (2) The air-pressurized foamed polyamide beads are added to a mold of a steam molding machine for steam heating molding. The parts obtained after cooling are baked in a drying room at 80° C. to finally obtain finished foamed parts. The process parameters during the molding process and the degree of maturation of the foamed parts are shown in Table 1.
[0042] Embodiment 2-4:
[0043] Except for adding 5wt%, 10wt% and 15wt% of maleic anhydride grafted polyolefin elastomer (purchased from Coase Chemical Co., Ltd.) as a co-swelling agent in the core layer, other components and preparation methods are consistent with Example 1.
[0044] Embodiment 5-6:
[0045] Except for adding 3wt% and 6wt% of hexagonal boron nitride (purchased from Dongguan Dongchao New Material Technology Co., Ltd.) as fluxing agent in the core layer and shell layer respectively, other components and preparation methods are consistent with those in Example 1.
[0046] Embodiment 7:
[0047] Except for adding 10wt% of maleic anhydride grafted polyolefin elastomer (purchased from Coais Chemical Co., Ltd.) as a swelling agent in the core layer, and adding 3wt% of hexagonal boron nitride (purchased from Dongguan Dongchao New Materials Technology Co., Ltd.) as a flux in the core layer and the shell layer, the other components and preparation methods are consistent with Example 1.
[0048] Comparative Example 1:
[0049] Except that the expanded beads do not have a shell material, other components and preparation methods are consistent with those of Example 1.
[0050] Comparative Example 2:
[0051] Except for not adding the low melting point polyamide B in the core layer of the expanded beads, other components and preparation methods are the same as those in Example 1.
[0052] Comparative Example 3:
[0053] Except for replacing the polyamide C in the shell layer of the expanded beads with the same low melting point polyamide B as in the core layer (the melting point of which differs from the melting point of the blend of polyamide A and polyamide B in the core layer by more than 30 °C), other components and preparation methods are the same as those in Example 1.
[0054] Comparative Example 4:
[0055] Except for adding 12 wt% of the fluxing agent in the core layer of the expanded polyamide beads, other components and preparation methods are the same as those in Example 1.
[0056] Table 1
[0057]
[0058]
[0059] The degree of curing of the foamed parts in Table 1 is ranked from good to bad, and is divided into 5 (very good), 4 (better), 3 (average), 2 (worse), and 1 (very poor) in turn. 1: The number of beads with damaged pores on the fracture surface of the foamed part accounts for less than 30% of the total number of beads; 2: The number of beads with damaged pores on the fracture surface of the foamed part accounts for 30%-50% of the total number of beads; 3: The number of beads with damaged pores on the fracture surface of the foamed part accounts for 50%-70% of the total number of beads; 4: The number of beads with damaged pores on the fracture surface of the foamed part accounts for 70%-90% of the total number of beads; 5: The number of beads with damaged pores on the fracture surface of the foamed part accounts for more than 90% of the total number of beads; "+" means close to the upper limit of the interval, and "-" means close to the lower limit of the interval. For example, 4+ means that the proportion of the number of beads with damaged pores on the fracture surface of the foamed part to the total number of beads is close to 90%, and 4- means that the proportion of the number of beads with damaged pores on the fracture surface of the foamed part to the total number of beads is close to 70%.
[0060] Combining Example 1 and Comparative Example 1, it can be seen that the lower melting point polyamide C in the core-shell structure reduces the steam molding pressure, increases the bonding area between the expanded beads and the beads, and improves the degree of curing of the foamed parts.
[0061] Combining Example 1 and Comparative Example 2, it can be seen that the low melting point polyamide B in the core layer also helps to improve the welding degree between the beads and the degree of curing of the foamed parts.
[0062] It can be seen from the combination of Example 1 and Comparative Example 3 that due to the too large difference in the melting points of the core-shell materials, the surface of the foamed parts was "overcooked" while the interior was "undercooked", and the overall degree of curing of the foamed parts was not high.
[0063] It can be seen from the combination of Examples 1-4 that the addition of the expansion aid in the core layer can further improve the degree of curing of the polyamide foamed parts. The better expansibility of the elastomer can cause the polyamide foam beads to undergo a large expansion deformation when heated by the forming steam, increasing the bonding area between adjacent foam beads, and improving the degree of curing of both the surface and the interior of the foamed parts. And at the same degree of curing, the higher the elastomer content, the lower the forming pressure required for the foam beads. However, inevitably, due to the relatively low mechanical modulus of the elastomer itself, the addition of the elastomer will cause a decrease in the overall compressive strength of the material. Therefore, it is necessary to select a suitable elastomer ratio according to different requirements.
[0064] It can be seen from the combination of Examples 1, 5, and 6 that the addition of the fluxing agent boron nitride can further promote the welding of the polyamide foam beads. Compared with the polyamide resin, boron nitride has a higher thermal conductivity. During steam forming, it can quickly conduct the external heat to the polyamide foam beads, enabling them to expand and form better. Especially when both the core layer and the shell layer contain the fluxing agent, both the surface and the interior of the foamed parts have a high degree of curing, and the forming energy consumption is relatively low. Further combining with Comparative Example 4, it can be seen that when the addition amount of the fluxing agent is relatively high, exceeding 10%, even at a relatively high steam forming pressure, the degree of curing is very low. The reason is that the addition of too much inorganic matter will cause the internal cell size of the foam beads to decrease sharply, the pressure relief inside the beads is too fast, the expansibility of the beads is limited, and the degree of curing of the formed parts deteriorates.
[0065] It can be seen from the combination of Example 1 and 7 that adding the expansion aid and the fluxing agent simultaneously can better improve the degree of curing of the parts, and the forming pressure can be greatly reduced.
Claims
1. A rigid polyamide foamed bead material with a core-shell structure. The core layer material comprises 60-90 wt% of a high melting point and high modulus polyamide A, 1-10 wt% of a low melting point polyamide B, and 0.01-5 wt% of a nucleating agent. The shell layer material comprises 90-99.9 wt% of a low melting point polyamide C. The mass ratio of the core layer material to the shell layer material is 70:30-99:
1. The melting point of the polyamide C is between that of the polyamide A and the polyamide B, and is 10-30 °C lower than the melting point of the blend of the polyamide A and the polyamide B.
2. The rigid polyamide foamed bead material according to claim 1, characterized in that, The mass ratio of the core layer material to the shell layer material is 80:20-95:
5.
3. The rigid polyamide foam bead material according to claim 1, characterized in that, The melting point of the polyamide A is 210-260 °C, the tensile modulus is 2500-3500 MPa, and the melt index is 3-20 g / 10 min. The melting point of the polyamide B is 130-160 °C, the tensile modulus is 2500-3000 MPa, and the melt index is 3-20 g / 10 min. The melting point of the polyamide C is 170-200 °C, the tensile modulus is 2000-2800 MPa, and the melt index is 3-20 g / 10 min.
4. The rigid polyamide foamed bead material according to claim 1, characterized in that, The polyamide A is polyamide 6, polyamide 66, or a block copolymer of polyamide 6 and polyamide 66.
5. The rigid polyamide foam bead material according to claim 1, characterized in that, The core layer material further comprises 1-20 wt% of an auxiliary blowing agent, and the auxiliary blowing agent is a polar group grafted elastomer. The polar group grafted elastomer is at least one of glycidyl acrylate grafted polyolefin elastomer, glycidyl acrylate grafted ethylene-propylene rubber, glycidyl acrylate grafted styrene-butadiene-styrene block copolymer, maleic anhydride grafted polyolefin elastomer, maleic anhydride grafted ethylene-propylene rubber, and maleic anhydride grafted styrene-butadiene-styrene block copolymer.
6. The rigid polyamide foamed bead material according to claim 1, wherein, The core layer material and / or the shell layer material further comprises 0.1-10 wt% of a fusion aid. The fusion aid is at least one of metal powder, metal oxide powder, and nitride powder. The metal powder comprises at least one of aluminum powder, copper powder, and iron powder. The metal oxide powder comprises at least one of alumina powder, copper oxide powder, and iron oxide powder. The nitride powder comprises at least one of boron nitride powder and aluminum nitride powder.
7. The rigid polyamide foam bead material according to claim 1, characterized in that, The core layer material further comprises 0.1-5 wt% of a hydrolysis resistant agent. The hydrolysis resistant agent is at least one of glycidyl ether, tris(2,3-epoxypropyl) isocyanurate, and carbodiimide.
8. The rigid polyamide foamed bead material according to claim 1, characterized in that, The core layer material further comprises 0.1-5 wt% of a chain extender. The chain extender is a glycidyl methacrylate compound containing an epoxy functional group or a glycidyl acrylate compound containing an epoxy functional group.
9. The rigid polyamide foam bead material according to claim 1, characterized in that, The nucleating agent is at least one of calcium carbonate, talc powder, zinc borate, sodium chloride, and silicon dioxide, and the particle size is 1-20 μm.