A kind of EVA foam material and preparation process thereof

Abstract

The present invention relates to the technical field of EVA foam materials, specifically to an EVA foam material and a preparation process thereof. The scheme uses EVA resin as the main material, adds polyamide elastomer, foaming agent, antioxidant, compatibilizer, calcium carbonate, coated core-shell aluminum hydroxide and calcium stearate, mixes and molds to form a sheet, and then irradiates and cross-links, and chemically foams to form an EVA foam material; under this formula of raw materials, the mechanical properties of the EVA foam material prepared by the scheme are improved. At the same time, the scheme uses coated core-shell aluminum hydroxide as a flame retardant, and can achieve relatively excellent flame retardant properties without adding a large amount of flame retardant components, and has high practicality.

Description

Technical Field

[0001] The invention relates to the technical field of EVA foam materials, in particular to an EVA foam material and a preparation process thereof. Background Art

[0002] EVA foam material is one of the more commonly used foam materials. It has good sound insulation, thermal insulation, cushioning and shock reduction, easy processing and other properties. It can be widely used in packaging, electronics, sporting goods and other fields. However, the existing EVA foam materials on the market have poor mechanical properties, low strength, poor high and low temperature resistance, and poor resilience. The above defects have greatly limited the practical application of EVA foam materials.

[0003] At the same time, the flame retardant properties of EVA foaming agents purchased on the market are poor and cannot meet consumer demand when used. Based on this, the present application discloses an EVA foaming material and a preparation process thereof to solve this technical problem. Summary of the invention

[0004] The object of the present invention is to provide an EVA foam material and a preparation process thereof to solve the problems raised in the above background technology.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A preparation process of an EVA foam material comprises the following steps:

[0007] Step (1): mixing aluminum hydroxide and anhydrous ethanol, ultrasonically dispersing for 20 to 30 minutes, adding phosphoric acid, reacting at 70 to 75° C. for 4 to 5 hours, filtering, washing, and vacuum drying to obtain coated powder; the molar ratio of aluminum hydroxide to phosphoric acid is 1:(0.3 to 0.4);

[0008] The coated powder is transferred to a mixture of anhydrous ethanol and deionized water, ethyl orthosilicate is added, stirred and reacted for 40 to 50 minutes, ammonia water is added, the reaction is continued for 30 to 40 minutes, filtered and washed, and vacuum dried to obtain core-shell aluminum hydroxide;

[0009] Step (2): mixing the core-shell aluminum hydroxide and deionized water, ultrasonically dispersing for 20 to 30 minutes, adding natural latex, stirring evenly, then adding a 2% oxalic acid aqueous solution to break the emulsion and precipitate, washing with deionized water until neutral, and vacuum drying to obtain coated core-shell aluminum hydroxide;

[0010] The amount of the core-shell aluminum hydroxide is 0.5-1wt% of the mass of the natural latex;

[0011] Step (3): drying the polyamide elastomer at 90-100° C., mixing it with EVA resin after drying, adding a foaming agent, an antioxidant, a compatibilizer, calcium carbonate, a core-shell aluminum hydroxide and calcium stearate, mixing for 10-20 minutes, kneading at 140-145° C. for 10-15 minutes, and then transferring it to a flat vulcanizer for molding for 2-3 minutes to form a sheet, cross-linking the sheet under a radiation dose of 70 KGy, and foaming it in a foaming furnace at 240° C. for 2-3 minutes to form an EVA foam material.

[0012] In a more optimized solution, in step (3), the amounts of the components are as follows: by mass fraction, 10-12wt% of polyamide elastomer, 10-15wt% of foaming agent, 1-2wt% of antioxidant, 3-4wt% of compatibilizer, 2-3wt% of calcium carbonate, 25-40wt% of core-shell aluminum hydroxide, 0.5-1wt% of calcium stearate, and the rest is EVA resin.

[0013] In a more optimized solution, in step (3), the molding temperature is 110-120° C., the molding pressure is 8-10 MPa; the foaming agent is azodicarbonamide, and the antioxidant is antioxidant 1010.

[0014] In a more optimized solution, in step (3), the preparation method of the polyamide elastomer is:

[0015] S1: Mix dodecanediamine and dodecanedioic acid and put them into a reaction kettle, add deionized water and antioxidant, replace the atmosphere with nitrogen, heat to 150-155°C, keep the temperature for reaction for 30-40 minutes, then heat to 200-205°C, release to normal pressure, discharge, and crush to obtain a prepolymer;

[0016] S2: The prepolymer and polytetrahydrofuran are mixed and put into a reaction kettle, and an antioxidant and modified aluminum hydroxide are added. The atmosphere is replaced with nitrogen, the temperature is raised to 215-220°C, and the reaction is kept at this temperature for 2-2.5 hours. The mixture is vented to normal pressure, and tetrabutyl titanate is added. The mixture is evacuated and the temperature is raised to 250-255°C. The pressure is 200-300 MPa, and the pressure is restored to normal pressure by nitrogen. The mixture is discharged to obtain a polyamide elastomer.

[0017] In a more optimized solution, in S1, the molar ratio of dodecanediamine to dodecanediacid is 1:(1.5-2); the amount of deionized water is 30wt% of the total mass of dodecanediamine and dodecanediacid, and the amount of antioxidant is 2-3wt% of the total mass of dodecanediamine and dodecanediacid.

[0018] In a more optimized solution, in S2, the molar ratio of the prepolymer and polytetrahydrofuran is 1:1, the amount of the antioxidant is 2-3wt% of the total mass of the system; the amount of tetrabutyl titanate is 2-3wt% of the total mass of the system; and the amount of modified aluminum hydroxide is 2-3wt% of the total mass of the system.

[0019] According to a more optimized scheme, the preparation steps of the modified aluminum hydroxide are as follows: mixing the core-shell aluminum hydroxide and the silane coupling agent, heating to 120-130° C., stirring for 2-3 hours, and stirring at a speed of 1000-1200 r / min to obtain the modified core-shell aluminum hydroxide; the silane coupling agent is KH-550, and the amount used is 2-3wt% of the core-shell aluminum hydroxide.

[0020] A more optimized solution is an EVA foam material prepared according to any of the preparation processes described above.

[0021] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0022] The invention discloses a preparation process of an EVA foam material, wherein the scheme uses EVA resin as the main material, adds polyamide elastomer, foaming agent, antioxidant, compatibilizer, calcium carbonate, coated core-shell aluminum hydroxide and calcium stearate, mixes and molds to form a sheet, and then irradiates and crosslinks, and chemically foams to form an EVA foam material; under the formula raw materials, the mechanical properties of the EVA foam material prepared by the scheme are improved. At the same time, the scheme uses coated core-shell aluminum hydroxide as a flame retardant, and can achieve relatively excellent flame retardant properties without adding a large amount of flame retardant components, and has high practicality.

[0023] In the present application, the scheme first uses aluminum hydroxide as the core, adds phosphoric acid to react, generates aluminum phosphate on the surface, and obtains a coated powder, and then uses the coated powder as the core and silicon dioxide as the shell to prepare core-shell aluminum hydroxide. Adding core-shell aluminum hydroxide as a flame retardant to the EVA foaming system can effectively improve the flame retardant properties of the product. At the same time, in order to avoid the problem of poor compatibility between the flame retardant and the system, the scheme also uses natural latex to coat the core-shell aluminum hydroxide to form a coated core-shell aluminum hydroxide, so as to improve the dispersibility of the flame retardant component in the system, thereby ensuring the comprehensive performance of the product.

[0024] On the other hand, the scheme utilizes dodecanediamine and dodecanedioic acid to react to generate a prepolymer, and then mixes the prepolymer with polytetrahydrofuran to react to generate a polyamide elastomer. The introduction of the polyamide elastomer can improve the mechanical properties and tensile strength of the product. The scheme also adds aminosilane coupling agent-modified core-shell aluminum hydroxide during the preparation of the polyamide elastomer, and further cooperates with the coated core-shell aluminum hydroxide to achieve flame retardancy.

[0025] The invention discloses a preparation process of an EVA foam material. The raw materials of the whole scheme are adjusted and compounded for many times, the process design is reasonable, the mechanical properties of the prepared EVA foam material are improved, and the flame retardant property is also excellent. The EVA foam material can be widely applied to multiple fields and has excellent practicality. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] In this embodiment, natural latex, industrial grade, was purchased from Shandong Fushun New Material Technology Co., Ltd.; EVA resin model is Y2022, VA=14%, purchased from Beijing Dongfang Petrochemical Co., Ltd.; compatibilizer model is C250, purchased from DuPont, USA; foaming agent is azodicarbonamide, and antioxidant is antioxidant 1010. The molecular weight of polytetrahydrofuran is 2000.

[0028] Embodiment 1: A preparation process of an EVA foam material comprises the following steps:

[0029] Step (1): 1 mol of aluminum hydroxide and 500 mL of anhydrous ethanol are mixed, ultrasonically dispersed for 20 minutes, 0.4 mol of phosphoric acid is added, the mixture is reacted at 70° C. for 5 hours, filtered, washed, and vacuum dried to obtain coated powder; 1 g of the coated powder is transferred to a mixed solution of 55 mL of anhydrous ethanol and 15 mL of deionized water, 45 mL of tetraethyl orthosilicate is added, the mixture is stirred for reaction for 40 minutes, ammonia water is added, the reaction is continued for 40 minutes, filtered, washed, and vacuum dried to obtain core-shell aluminum hydroxide.

[0030] Step (2): Mix core-shell aluminum hydroxide and deionized water, ultrasonically disperse for 20 minutes, add natural latex, stir evenly, then add 2% oxalic acid aqueous solution to break the emulsion and precipitate, wash with deionized water until neutral, and vacuum dry to obtain coated core-shell aluminum hydroxide; the amount of the core-shell aluminum hydroxide is 1wt% of the mass of the natural latex.

[0031] Step (3): drying the polyamide elastomer at 90° C., mixing it with EVA resin after drying, adding a foaming agent, an antioxidant, a compatibilizer, calcium carbonate, coated core-shell aluminum hydroxide and calcium stearate, mixing for 10 minutes, kneading at 140° C. for 15 minutes, and then transferring it to a flat vulcanizer for molding for 3 minutes, the molding temperature is 120° C., the molding pressure is 10 MPa, to form a sheet, cross-linking the sheet under a radiation dose of 70 KGy, and foaming it in a foaming furnace at 240° C. for 3 minutes to form an EVA foam material.

[0032] In step (3), the amounts of the components are as follows: by mass fraction, 10 wt% of polyamide elastomer, 15 wt% of foaming agent, 1.5 wt% of antioxidant, 3 wt% of compatibilizer, 2 wt% of calcium carbonate, 25 wt% of coated core-shell aluminum hydroxide, 0.5 wt% of calcium stearate, and the rest is EVA resin. The foaming agent is azodicarbonamide, and the antioxidant is antioxidant 1010.

[0033] The preparation method of the polyamide elastomer is as follows:

[0034] S1: dodecanediamine and dodecanedioic acid are mixed and put into a reactor, deionized water and an antioxidant are added, the atmosphere is replaced with nitrogen, the temperature is raised to 150°C, the temperature is kept for reaction for 40 minutes, the temperature is then raised to 200°C, the pressure is released to normal pressure, the material is discharged, and the prepolymer is obtained by crushing; the molar ratio of dodecanediamine and dodecanedioic acid is 1:2; the amount of deionized water is 30wt% of the total mass of dodecanediamine and dodecanedioic acid, and the amount of antioxidant is 2wt% of the total mass of dodecanediamine and dodecanedioic acid.

[0035] The preparation steps of the modified aluminum hydroxide are: mixing the core-shell aluminum hydroxide and the silane coupling agent, heating to 120° C., stirring for reaction for 3 hours, and the stirring speed is 1000 r / min to obtain the modified core-shell aluminum hydroxide; the silane coupling agent is KH-550, and the amount used is 2wt% of the core-shell aluminum hydroxide.

[0036] S2: Mix the prepolymer and polytetrahydrofuran and put them into a reactor, add antioxidant and modified aluminum hydroxide, replace the atmosphere with nitrogen, heat to 215°C, keep the temperature for reaction for 2.5 hours, release to normal pressure, add tetrabutyl titanate, evacuate and heat to 250°C, the pressure is 200MPa, fill with nitrogen to restore to normal pressure, discharge, and obtain polyamide elastomer. The molar ratio of the prepolymer and polytetrahydrofuran is 1:1, the amount of antioxidant is 2wt% of the total mass of the system; the amount of tetrabutyl titanate is 2wt% of the total mass of the system; the amount of modified aluminum hydroxide is 2wt% of the total mass of the system.

[0037] Embodiment 2: A preparation process of an EVA foam material comprises the following steps:

[0038] Step (1): 1 mol of aluminum hydroxide and 500 mL of anhydrous ethanol are mixed, ultrasonically dispersed for 25 minutes, 0.4 mol of phosphoric acid is added, the reaction is carried out at 75° C. for 4.5 hours, filtered, washed, and vacuum dried to obtain a coated powder; 1 g of the coated powder is transferred to a mixed solution of 55 mL of anhydrous ethanol and 15 mL of deionized water, 45 mL of tetraethyl orthosilicate is added, stirred for reaction for 45 minutes, ammonia water is added, the reaction is continued for 35 minutes, filtered, washed, and vacuum dried to obtain core-shell aluminum hydroxide.

[0039] Step (2): Mix core-shell aluminum hydroxide and deionized water, ultrasonically disperse for 25 minutes, add natural latex, stir evenly, then add 2% oxalic acid aqueous solution to break the emulsion and precipitate, wash with deionized water until neutral, and vacuum dry to obtain coated core-shell aluminum hydroxide; the amount of the core-shell aluminum hydroxide is 1wt% of the mass of the natural latex.

[0040] Step (3): drying the polyamide elastomer at 95° C., mixing it with EVA resin after drying, adding a foaming agent, an antioxidant, a compatibilizer, calcium carbonate, a core-shell aluminum hydroxide and calcium stearate, mixing for 15 minutes, kneading at 145° C. for 15 minutes, and then transferring it to a flat vulcanizer for molding for 3 minutes, the molding temperature is 120° C., the molding pressure is 10 MPa, to form a sheet, cross-linking the sheet under a radiation dose of 70 KGy, and foaming it in a foaming furnace at 240° C. for 3 minutes to form an EVA foam material.

[0041] In step (3), the amounts of the components are as follows: by mass fraction, 11 wt% of polyamide elastomer, 15 wt% of foaming agent, 1.5 wt% of antioxidant, 3 wt% of compatibilizer, 2 wt% of calcium carbonate, 25 wt% of core-shell aluminum hydroxide, 0.5 wt% of calcium stearate, and the rest is EVA resin. The foaming agent is azodicarbonamide, and the antioxidant is antioxidant 1010.

[0042] The preparation method of the polyamide elastomer is as follows:

[0043] S1: dodecanediamine and dodecanedioic acid are mixed and put into a reactor, deionized water and an antioxidant are added, the atmosphere is replaced with nitrogen, the temperature is raised to 155°C, the temperature is kept for reaction for 35 minutes, the temperature is then raised to 205°C, the pressure is vented to normal pressure, the material is discharged, and the prepolymer is obtained by crushing; the molar ratio of dodecanediamine and dodecanedioic acid is 1:2; the amount of deionized water is 30wt% of the total mass of dodecanediamine and dodecanedioic acid, and the amount of antioxidant is 2wt% of the total mass of dodecanediamine and dodecanedioic acid.

[0044] The preparation steps of the modified aluminum hydroxide are: mixing core-shell aluminum hydroxide and a silane coupling agent, heating to 125° C., stirring for reaction for 2.5 hours, and a stirring speed of 1000 r / min to obtain modified core-shell aluminum hydroxide; the silane coupling agent is KH-550, and the amount used is 2wt% of the core-shell aluminum hydroxide.

[0045] S2: Mix the prepolymer and polytetrahydrofuran and put them into a reactor, add antioxidant and modified aluminum hydroxide, replace the atmosphere with nitrogen, heat to 215°C, keep the temperature for reaction for 2.5 hours, release to normal pressure, add tetrabutyl titanate, evacuate and heat to 250°C, the pressure is 200MPa, fill with nitrogen to restore to normal pressure, discharge, and obtain polyamide elastomer. The molar ratio of the prepolymer and polytetrahydrofuran is 1:1, the amount of antioxidant is 2wt% of the total mass of the system; the amount of tetrabutyl titanate is 2wt% of the total mass of the system; the amount of modified aluminum hydroxide is 2wt% of the total mass of the system.

[0046] Embodiment 3: A process for preparing an EVA foam material, comprising the following steps:

[0047] Step (1): 1 mol of aluminum hydroxide and 500 mL of anhydrous ethanol are mixed, ultrasonically dispersed for 30 minutes, 0.4 mol of phosphoric acid is added, the mixture is reacted at 75° C. for 4 hours, filtered, washed, and vacuum dried to obtain coated powder; 1 g of the coated powder is transferred to a mixed solution of 55 mL of anhydrous ethanol and 15 mL of deionized water, 45 mL of tetraethyl orthosilicate is added, the mixture is stirred for reaction for 50 minutes, ammonia water is added, the reaction is continued for 40 minutes, filtered, washed, and vacuum dried to obtain core-shell aluminum hydroxide.

[0048] Step (2): Mix core-shell aluminum hydroxide and deionized water, ultrasonically disperse for 30 minutes, add natural latex, stir evenly, then add 2% oxalic acid aqueous solution to break the emulsion and precipitate, wash with deionized water until neutral, and vacuum dry to obtain coated core-shell aluminum hydroxide; the amount of the core-shell aluminum hydroxide is 1wt% of the mass of the natural latex.

[0049] Step (3): drying the polyamide elastomer at 100° C., mixing it with EVA resin after drying, adding a foaming agent, an antioxidant, a compatibilizer, calcium carbonate, a core-shell aluminum hydroxide and calcium stearate, mixing for 20 minutes, kneading at 145° C. for 10 minutes, and then transferring it to a flat vulcanizer for molding for 3 minutes, the molding temperature is 120° C., the molding pressure is 10 MPa, to form a sheet, cross-linking the sheet under a radiation dose of 70 KGy, and foaming it in a foaming furnace at 240° C. for 3 minutes to form an EVA foam material.

[0050] In step (3), the amounts of the components are as follows: by mass fraction, 12 wt% of polyamide elastomer, 15 wt% of foaming agent, 1.5 wt% of antioxidant, 3 wt% of compatibilizer, 2 wt% of calcium carbonate, 25 wt% of coated core-shell aluminum hydroxide, 0.5 wt% of calcium stearate, and the rest is EVA resin. The foaming agent is azodicarbonamide, and the antioxidant is antioxidant 1010.

[0051] The preparation method of the polyamide elastomer is as follows:

[0052] S1: dodecanediamine and dodecanedioic acid are mixed and put into a reactor, deionized water and an antioxidant are added, the atmosphere is replaced with nitrogen, the temperature is raised to 155°C, the temperature is kept for reaction for 30 minutes, the temperature is then raised to 205°C, the pressure is released to normal pressure, the material is discharged, and the prepolymer is obtained by crushing; the molar ratio of dodecanediamine and dodecanedioic acid is 1:2; the amount of deionized water is 30wt% of the total mass of dodecanediamine and dodecanedioic acid, and the amount of antioxidant is 2wt% of the total mass of dodecanediamine and dodecanedioic acid.

[0053] The preparation steps of the modified aluminum hydroxide are as follows: mixing the core-shell aluminum hydroxide and the silane coupling agent, heating to 130° C., stirring for 2 hours, and stirring at a speed of 1000 r / min to obtain the modified core-shell aluminum hydroxide; the silane coupling agent is KH-550, and the amount used is 2wt% of the core-shell aluminum hydroxide.

[0054] S2: Mix the prepolymer and polytetrahydrofuran and put them into a reactor, add antioxidant and modified aluminum hydroxide, replace the atmosphere with nitrogen, heat to 220°C, keep the temperature for 2 hours, release to normal pressure, add tetrabutyl titanate, evacuate and heat to 250°C, the pressure is 200MPa, fill with nitrogen to restore to normal pressure, discharge, and obtain polyamide elastomer. The molar ratio of the prepolymer and polytetrahydrofuran is 1:1, the amount of antioxidant is 2wt% of the total mass of the system; the amount of tetrabutyl titanate is 2wt% of the total mass of the system; the amount of modified aluminum hydroxide is 2wt% of the total mass of the system.

[0055] Comparative Example 1: Example 3 was used as the control group. In Comparative Example 1, natural latex coating was not used, and the other process steps remained unchanged.

[0056] A preparation process of an EVA foam material comprises the following steps:

[0057] Step (1): 1 mol of aluminum hydroxide and 500 mL of anhydrous ethanol are mixed, ultrasonically dispersed for 30 minutes, 0.4 mol of phosphoric acid is added, the mixture is reacted at 75° C. for 4 hours, filtered, washed, and vacuum dried to obtain coated powder; 1 g of the coated powder is transferred to a mixed solution of 55 mL of anhydrous ethanol and 15 mL of deionized water, 45 mL of tetraethyl orthosilicate is added, the mixture is stirred for reaction for 50 minutes, ammonia water is added, the reaction is continued for 40 minutes, filtered, washed, and vacuum dried to obtain core-shell aluminum hydroxide.

[0058] Step (2): drying the polyamide elastomer at 100° C., mixing it with EVA resin after drying, adding a foaming agent, an antioxidant, a compatibilizer, calcium carbonate, core-shell aluminum hydroxide and calcium stearate, mixing for 20 minutes, kneading at 145° C. for 10 minutes, and then transferring it to a flat vulcanizer for molding for 3 minutes, the molding temperature is 120° C., the molding pressure is 10 MPa, to form a sheet, cross-linking the sheet under a radiation dose of 70 KGy, and foaming in a foaming furnace at 240° C. for 3 minutes to form an EVA foam material.

[0059] In step (3), the amounts of the components are as follows: by mass fraction, 12 wt% of polyamide elastomer, 15 wt% of foaming agent, 1.5 wt% of antioxidant, 3 wt% of compatibilizer, 2 wt% of calcium carbonate, 25 wt% of core-shell aluminum hydroxide, 0.5 wt% of calcium stearate, and the rest is EVA resin. The foaming agent is azodicarbonamide, and the antioxidant is antioxidant 1010.

[0060] The preparation method of the polyamide elastomer is as follows:

[0061] S1: dodecanediamine and dodecanedioic acid are mixed and put into a reactor, deionized water and an antioxidant are added, the atmosphere is replaced with nitrogen, the temperature is raised to 155°C, the temperature is kept for reaction for 30 minutes, the temperature is then raised to 205°C, the pressure is released to normal pressure, the material is discharged, and the prepolymer is obtained by crushing; the molar ratio of dodecanediamine and dodecanedioic acid is 1:2; the amount of deionized water is 30wt% of the total mass of dodecanediamine and dodecanedioic acid, and the amount of antioxidant is 2wt% of the total mass of dodecanediamine and dodecanedioic acid.

[0062] The preparation steps of the modified aluminum hydroxide are as follows: mixing the core-shell aluminum hydroxide and the silane coupling agent, heating to 130° C., stirring for 2 hours, and stirring at a speed of 1000 r / min to obtain the modified core-shell aluminum hydroxide; the silane coupling agent is KH-550, and the amount used is 2wt% of the core-shell aluminum hydroxide.

[0063] S2: Mix the prepolymer and polytetrahydrofuran and put them into a reactor, add antioxidant and modified aluminum hydroxide, replace the atmosphere with nitrogen, heat to 220°C, keep the temperature for 2 hours, release to normal pressure, add tetrabutyl titanate, evacuate and heat to 250°C, the pressure is 200MPa, fill with nitrogen to restore to normal pressure, discharge, and obtain polyamide elastomer. The molar ratio of the prepolymer and polytetrahydrofuran is 1:1, the amount of antioxidant is 2wt% of the total mass of the system; the amount of tetrabutyl titanate is 2wt% of the total mass of the system; the amount of modified aluminum hydroxide is 2wt% of the total mass of the system.

[0064] Comparative Example 2: Example 3 was used as the control group. In Comparative Example 2, modified core-shell aluminum hydroxide was not added to the polyamide elastomer, and the other process steps remained unchanged.

[0065] A preparation process of an EVA foam material comprises the following steps:

[0066] Step (1): 1 mol of aluminum hydroxide and 500 mL of anhydrous ethanol are mixed, ultrasonically dispersed for 30 minutes, 0.4 mol of phosphoric acid is added, the mixture is reacted at 75° C. for 4 hours, filtered, washed, and vacuum dried to obtain coated powder; 1 g of the coated powder is transferred to a mixed solution of 55 mL of anhydrous ethanol and 15 mL of deionized water, 45 mL of tetraethyl orthosilicate is added, the mixture is stirred for reaction for 50 minutes, ammonia water is added, the reaction is continued for 40 minutes, filtered, washed, and vacuum dried to obtain core-shell aluminum hydroxide.

[0067] Step (2): Mix core-shell aluminum hydroxide and deionized water, ultrasonically disperse for 30 minutes, add natural latex, stir evenly, then add 2% oxalic acid aqueous solution to break the emulsion and precipitate, wash with deionized water until neutral, and vacuum dry to obtain coated core-shell aluminum hydroxide; the amount of the core-shell aluminum hydroxide is 1wt% of the mass of the natural latex.

[0068] Step (3): drying the polyamide elastomer at 100° C., mixing it with EVA resin after drying, adding a foaming agent, an antioxidant, a compatibilizer, calcium carbonate, a core-shell aluminum hydroxide and calcium stearate, mixing for 20 minutes, kneading at 145° C. for 10 minutes, and then transferring it to a flat vulcanizer for molding for 3 minutes, the molding temperature is 120° C., the molding pressure is 10 MPa, to form a sheet, cross-linking the sheet under a radiation dose of 70 KGy, and foaming it in a foaming furnace at 240° C. for 3 minutes to form an EVA foam material.

[0069] In step (3), the amounts of the components are as follows: by mass fraction, 12 wt% of polyamide elastomer, 15 wt% of foaming agent, 1.5 wt% of antioxidant, 3 wt% of compatibilizer, 2 wt% of calcium carbonate, 25 wt% of coated core-shell aluminum hydroxide, 0.5 wt% of calcium stearate, and the rest is EVA resin. The foaming agent is azodicarbonamide, and the antioxidant is antioxidant 1010.

[0070] The preparation method of the polyamide elastomer is as follows:

[0071] S1: dodecanediamine and dodecanedioic acid are mixed and put into a reactor, deionized water and an antioxidant are added, the atmosphere is replaced with nitrogen, the temperature is raised to 155°C, the temperature is kept for reaction for 30 minutes, the temperature is then raised to 205°C, the pressure is released to normal pressure, the material is discharged, and the prepolymer is obtained by crushing; the molar ratio of dodecanediamine and dodecanedioic acid is 1:2; the amount of deionized water is 30wt% of the total mass of dodecanediamine and dodecanedioic acid, and the amount of antioxidant is 2wt% of the total mass of dodecanediamine and dodecanedioic acid.

[0072] S2: Mix the prepolymer and polytetrahydrofuran and put them into a reactor, add an antioxidant, replace the atmosphere with nitrogen, heat to 220°C, keep the temperature for 2 hours, release to normal pressure, add tetrabutyl titanate, evacuate and heat to 250°C, the pressure is 200MPa, fill with nitrogen to restore to normal pressure, discharge, and obtain a polyamide elastomer. The molar ratio of the prepolymer and polytetrahydrofuran is 1:1, the amount of antioxidant is 2wt% of the total mass of the system; the amount of tetrabutyl titanate is 2wt% of the total mass of the system.

[0073] Comparative Example 3: Example 3 was used as the control group. In Comparative Example 3, only aluminum hydroxide was added as a flame retardant, and the other process steps remained unchanged.

[0074] A preparation process of an EVA foam material comprises the following steps:

[0075] Step (1): mixing aluminum hydroxide and deionized water, ultrasonically dispersing for 30 minutes, adding natural latex, stirring evenly, then adding 2% oxalic acid aqueous solution to break the emulsion and precipitate, washing with deionized water until neutral, and vacuum drying to obtain coated aluminum hydroxide; the amount of aluminum hydroxide used accounts for 1wt% of the mass of natural latex.

[0076] Step (2): drying the polyamide elastomer at 100° C., mixing it with EVA resin after drying, adding a foaming agent, an antioxidant, a compatibilizer, calcium carbonate, coated aluminum hydroxide and calcium stearate, mixing for 20 minutes, kneading at 145° C. for 10 minutes, and then transferring it to a flat vulcanizer for molding for 3 minutes, the molding temperature is 120° C., the molding pressure is 10 MPa, to form a sheet, cross-linking the sheet under a radiation dose of 70 KGy, and foaming it in a foaming furnace at 240° C. for 3 minutes to form an EVA foam material.

[0077] In step (3), the amounts of the components are as follows: by mass fraction, 12 wt% of polyamide elastomer, 15 wt% of foaming agent, 1.5 wt% of antioxidant, 3 wt% of compatibilizer, 2 wt% of calcium carbonate, 25 wt% of coated aluminum hydroxide, 0.5 wt% of calcium stearate, and the rest is EVA resin. The foaming agent is azodicarbonamide, and the antioxidant is antioxidant 1010.

[0078] The preparation method of the polyamide elastomer is as follows:

[0079] S1: dodecanediamine and dodecanedioic acid are mixed and put into a reactor, deionized water and an antioxidant are added, the atmosphere is replaced with nitrogen, the temperature is raised to 155°C, the temperature is kept for reaction for 30 minutes, the temperature is then raised to 205°C, the pressure is released to normal pressure, the material is discharged, and the prepolymer is obtained by crushing; the molar ratio of dodecanediamine and dodecanedioic acid is 1:2; the amount of deionized water is 30wt% of the total mass of dodecanediamine and dodecanedioic acid, and the amount of antioxidant is 2wt% of the total mass of dodecanediamine and dodecanedioic acid.

[0080] S2: Mix the prepolymer and polytetrahydrofuran and put them into a reactor, add antioxidant and aluminum hydroxide, replace the atmosphere with nitrogen, heat to 220°C, keep the temperature for reaction for 2h, release to normal pressure, add tetrabutyl titanate, evacuate and heat to 250°C, the pressure is 200MPa, fill with nitrogen to restore to normal pressure, discharge, and obtain polyamide elastomer. The molar ratio of the prepolymer and polytetrahydrofuran is 1:1, the amount of antioxidant is 2wt% of the total mass of the system; the amount of tetrabutyl titanate is 2wt% of the total mass of the system; the amount of aluminum hydroxide is 2wt% of the total mass of the system.

[0081] Detection experiment:

[0082] The foamed specimens prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were made into dumbbell shapes, and their tensile properties were tested with reference to GB / T6344, with a tensile speed of 500 mm / min; their resilience was tested with reference to the method of GB / T6670, with a specimen size of 100 mm×100 mm×50 mm and a steel ball drop height of 460 mm; and the limiting oxygen index of the test samples was tested.

[0083] project Tensile strength MPa Rebound rate % Limiting oxygen index Example 1 0.44 58.6 37.9 Example 2 0.46 58.9 38.4 Example 3 0.49 59.3 38.8 Comparative Example 1 0.45 58.8 37.5 Comparative Example 2 0.47 59.1 34.2 Comparative Example 3 0.41 57.2 29.8

[0084] Conclusion: The present invention discloses a preparation process of an EVA foam material. The raw materials of the whole scheme are adjusted and compounded for many times, and the process design is reasonable. The mechanical properties of the prepared EVA foam material are improved, and the flame retardant performance is also excellent. It can be widely used in multiple fields and has excellent practicality.

[0085] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation process of an EVA foam material, characterized in that: The following steps are involved: Step (1): mixing aluminum hydroxide and anhydrous ethanol, ultrasonically dispersing for 20-30 minutes, adding phosphoric acid, reacting at 70-75°C for 4-5 hours, filtering, washing, and vacuum drying to obtain coated powder; The coated powder is transferred to a mixture of anhydrous ethanol and deionized water, ethyl orthosilicate is added, stirred and reacted for 40 to 50 minutes, ammonia water is added, the reaction is continued for 30 to 40 minutes, filtered, washed, and vacuum dried to obtain core-shell aluminum hydroxide; Step (2): Mix the core-shell aluminum hydroxide and deionized water, perform ultrasonic dispersion for 20 to 30 minutes, add natural latex, stir evenly, then add oxalic acid aqueous solution to break the emulsion and precipitate, wash with deionized water until neutral, and vacuum dry to obtain coated core-shell aluminum hydroxide; Step (3): drying the polyamide elastomer at 90-100° C., mixing it with EVA resin after drying, adding a foaming agent, an antioxidant, a compatibilizer, calcium carbonate, a core-shell aluminum hydroxide and calcium stearate, mixing for 10-20 minutes, kneading at 140-145° C. for 10-15 minutes, and then transferring it to a flat vulcanizer for molding for 2-3 minutes to form a sheet, cross-linking the sheet under a radiation dose of 70 KGy, and foaming it in a foaming furnace at 240° C. for 2-3 minutes to form an EVA foam material; In step (3), the amounts of the components are as follows: by mass fraction, 10-12 wt% of polyamide elastomer, 10-15 wt% of foaming agent, 1-2 wt% of antioxidant, 3-4 wt% of compatibilizer, 2-3 wt% of calcium carbonate, 25-40 wt% of coated core-shell aluminum hydroxide, 0.5-1 wt% of calcium stearate, and the remainder is EVA resin; In step (3), the preparation method of the polyamide elastomer is: S1: Mix dodecanediamine and dodecanedioic acid and put them into a reactor, add deionized water and antioxidant, replace the atmosphere with nitrogen, heat to 150-155°C, keep the temperature for reaction for 30-40 minutes, then heat to 200-205°C, release to normal pressure, discharge, and crush to obtain a prepolymer; S2: Mix the prepolymer and polytetrahydrofuran and put them into a reactor, add an antioxidant and modified core-shell aluminum hydroxide, replace the atmosphere with nitrogen, raise the temperature to 215-220°C, keep the temperature for reaction for 2-2.5 hours, vent to normal pressure, add tetrabutyl titanate, evacuate and raise the temperature to 250-255°C, the pressure is 200-300 MPa, fill with nitrogen to return to normal pressure, discharge the material, and obtain a polyamide elastomer; The preparation steps of the modified core-shell aluminum hydroxide are as follows: mixing the core-shell aluminum hydroxide and the silane coupling agent, heating to 120-130° C., stirring for reaction for 2-3 hours, and the stirring speed is 1000-1200 r / min to obtain the modified core-shell aluminum hydroxide; the silane coupling agent is KH-550, and the amount used is 2-3wt% of the core-shell aluminum hydroxide.

2. The preparation process of an EVA foam material according to claim 1, characterized in that: In step (3), the molding temperature is 110-120° C., the molding pressure is 8-10 MPa, the foaming agent is azodicarbonamide, and the antioxidant is antioxidant 1010.

3. The preparation process of an EVA foam material according to claim 1, characterized in that: In S1, the molar ratio of dodecanediamine to dodecanediacid is 1:(1.5-2); the amount of deionized water is 30wt% of the total mass of dodecanediamine and dodecanediacid, and the amount of antioxidant is 2-3wt% of the total mass of dodecanediamine and dodecanediacid.

4. The preparation process of an EVA foam material according to claim 1, characterized in that: In S2, the molar ratio of the prepolymer and polytetrahydrofuran is 1:1, the amount of antioxidant is 2-3wt% of the total mass of the system; the amount of tetrabutyl titanate is 2-3wt% of the total mass of the system; and the amount of modified core-shell aluminum hydroxide is 2-3wt% of the total mass of the system.

5. The EVA foam material prepared according to the preparation process described in any one of claims 1 to 4.