A benzoxazine nitrile-based resin skin foam and preparation method thereof

Abstract

The present invention relates to a benzoxazine nitrile-based resin skin foam and a preparation method thereof. The skin foam of the present invention is prepared from raw materials including a benzoxazine nitrile-based resin monomer and expandable microspheres of specific components and proportions, and is prepared by specific mixing, pre-polymerization foaming, and curing processes. The present invention overcomes the environmental pollution problems of chemical foaming agents and stabilizers in the preparation process of benzoxazine nitrile-based resin foams, as well as the interface problems and processing problems caused by physical foaming of inorganic hollow glass microspheres, and the foam obtained by the one-step method of the present invention is a skin foam, which has high mechanical strength, simple preparation process, and easy performance regulation, and has broad prospects for industrial application.

Description

Technical Field

[0001] The invention relates to the field of polymer technology, in particular to a benzoxazine nitrile-based resin skin foam and a preparation method thereof. Background Art

[0002] Polymer foam materials are widely used in the fields of construction, transportation, aerospace, etc. due to their easy processing, low cost and excellent performance. However, the mechanical properties and high temperature resistance of polymer foam materials cannot meet the needs of some high-tech fields. Polymer foam usually uses resin as the matrix, and various foams with different properties are formed by adding different foaming agents. Generally speaking, the properties of the resin matrix and the selection of the foaming agent have an important influence on the final performance of the foam.

[0003] Benzoxazine resin is a new type of phenolic resin containing N and O oxazine rings. Due to its unique structure, it has excellent mechanical properties, high temperature resistance, acid and alkali resistance, etc. At present, it has been widely used in aerospace, electronics, automobile and defense industries. In order to further improve the mechanical properties and temperature resistance of benzoxazine resins to meet the needs of more high-end fields, nitrile groups (-CN) can be introduced into benzoxazine. Resins containing phthalonitrile can usually be called nitrile-based resins, which have high operating temperatures, good flame retardant properties, good mechanical strength and corrosion resistance. As a new type of special polymer, it is also widely used in aerospace, shipbuilding and construction industries. Therefore, benzoxazine nitrile-based resin is a good high-strength, high-temperature resistant foam matrix.

[0004] There are currently two main methods for benzoxazine nitrile resin foams: chemical foaming and physical foaming. Chemical foaming usually involves adding a chemical foaming agent to a resin matrix, which is heated to react and decompose to release gas to form foam. Chemical foaming is simple to operate, but the chemical foaming agent relies on its own decomposition to foam, and the decomposed gas is mostly harmful gases such as nitric oxide, which pollutes the environment. For example, patent document CN202111315839.0 discloses a method for preparing a benzoxazine ring-containing nitrile resin sandwich structure foam using azodicarbonamide as a chemical foaming agent, Tween 80 as a foam stabilizer, and a superimposed flip foaming process. However, the decomposition of azodicarbonamide will release toxic gases such as ammonia and isocyanic acid, causing air pollution, and the foam stabilizer Tween 80 will pollute water resources, and the flip foaming process has high requirements for process equipment. In comparison, the physical foaming method has better flexibility. For example, patent document CN201310703230.X adds hollow glass microspheres to the resin matrix to reduce the pores of the foam. However, the hollow glass microspheres themselves have a low density and are easy to float in the resin melt, resulting in uneven foaming. In addition, the hollow glass microspheres are inorganic components and have poor compatibility with the organic resin itself, resulting in low interface strength, which causes a decrease in mechanical properties.

[0005] In summary, the preparation of benzoxazine nitrile-based resin foam in the above-mentioned related technologies has the defects of environmental pollution and difficulty in improving mechanical properties. Summary of the invention

[0006] The object of the present invention is to provide a benzoxazine nitrile-based resin skin foam and a preparation method thereof, which can improve the defects of environmental pollution and difficulty in improving mechanical properties in the preparation of benzoxazine nitrile-based resin foam.

[0007] In a first aspect, the present invention provides a method for preparing a benzoxazine nitrile-based resin skin foam, comprising the following preparation steps:

[0008] S1. Mixing: uniformly mixing a dispersion medium, expandable microspheres and a benzoxazine nitrile resin monomer, and then drying to remove the dispersion medium to prepare a mixed powder, wherein the drying temperature is below 100°C;

[0009] S2. Pre-polymerization foaming: The mixed powder is placed in a mold and pre-polymerized at 120 to 150 ° C for 0.5 to 1.5 h, and then a pressure of 5 to 10 MPa is applied to the mold and foamed at 180 to 200 ° C for 0.5 to 2 h to prepare a pre-polymerized foam;

[0010] S3. Curing and demoulding: curing the pre-polymerized foam at 200-340° C. for 1-18 hours, cooling and demoulding to obtain the benzoxazine nitrile-based resin skin foam.

[0011] Optionally, the mass ratio of the expandable microspheres to the benzoxazine nitrile-based resin monomer is 1-10:90-99.

[0012] Optionally, the mass ratio of the expandable microspheres to the benzoxazine nitrile-based resin monomer is 1-4:96-99.

[0013] Optionally, the benzoxazine nitrile-based resin monomer is a bisphenol A-type benzoxazine nitrile-based resin monomer.

[0014] Optionally, the expansion temperature range of the expandable microspheres is 115°C to 203°C.

[0015] Optionally, the expandable microspheres have a model of at least one of 980DU120, 920DU40, 920DU120, 920WUF40, 930DU120, 950DU80, 951DX120, 909DU80, 093DU120 or 091DU140.

[0016] Optionally, in step S3, curing is performed at one or more of the following temperatures: 200-240°C / 1-6h; 250-290°C / 1-6h; 300-340°C / 1-6h.

[0017] Optionally, in step S3, the surface of the prepared benzoxazine nitrile-based resin skin foam is dense, and a micrometer-sized pore structure is formed inside, and the diameter of the pore structure is 50 to 500 μm.

[0018] Optionally, the diameter of the pore structure is 70 to 140 μm.

[0019] In a second aspect, the present invention provides a benzoxazine nitrile-based resin skin foam, which is prepared by the aforementioned method for preparing the benzoxazine nitrile-based resin skin foam.

[0020] In summary, the present invention has at least one of the following beneficial effects:

[0021] 1. The present invention provides a benzoxazinenitrile-based resin skin foam and a preparation method thereof. The skin foam of the present invention is prepared from raw materials including a benzoxazinenitrile-based resin monomer and expandable microspheres of specific components and proportions, and is prepared by specific mixing, pre-polymerization foaming, and curing processes. The present invention overcomes the environmental pollution problems of chemical foaming agents and stabilizers in the preparation process of benzoxazinenitrile-based resin foams, as well as the interface problems and processing problems caused by physical foaming of inorganic hollow glass microspheres. The foam obtained by the one-step method of the present invention is a skin foam, which has high mechanical strength, simple preparation process, and easy performance regulation, and has broad industrial application prospects.

[0022] 2. The present invention provides a method for preparing a benzoxazine nitrile-based resin skin foam, which uses expandable microspheres as a foaming agent. The expandable microspheres are composed of a thermoplastic polymer shell and an alkane gas core, so that they have good compatibility with the benzoxazine nitrile-based resin, improve mixing uniformity and processability, and after heating, the internal air pressure increases, the shell softens and expands, and the expandable microspheres with specific components and addition ratios are used to achieve a good foaming effect. After a prepolymerization reaction at a specific temperature and a specific time, the benzoxazine nitrile-based resin monomer undergoes a prepolymerization reaction, the resin melt viscosity gradually increases, and the anchoring expandable microspheres are formed. The expandable microspheres are then foamed by applying specific pressure, temperature and time, and the expandable microspheres begin to expand. At the same time, the polymerization degree of the benzoxazine nitrile-based resin is further increased, and an internal pore structure is formed. Applying pressure helps the benzoxazine nitrile-based resin melt to flow, thereby promoting the formation of complete and uniform distribution of holes. Finally, by curing, a benzoxazine nitrile-based resin skin foam with a dense surface and a uniform and complete pore structure inside is obtained. The specific structure makes the finally prepared benzoxazine nitrile-based resin have high mechanical properties. In the subsequent embodiments, the compressive strength of the benzoxazine nitrile-based resin skin foam is measured to be above 48MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The figures are the physical pictures of the benzoxazine nitrile-based resins of Comparative Examples 4 to 8 and Examples 1 to 3.

[0024] Figure 2 The fracture scanning electron microscope images of the benzoxazine nitrile-based resins of Comparative Example 4 and Examples 1 to 3 are shown.

[0025] Figure 3 2 are compression stress-strain curves of the benzoxazine nitrile-based resins of Comparative Example 7 (left figure), Example 1 (middle figure), and Example 3 (right figure). DETAILED DESCRIPTION

[0026] The present invention provides a benzoxazine nitrile-based resin skin foam and a preparation method thereof. To make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0027] At present, benzoxazine nitrile-based resin is considered to be a good high-strength, high-temperature resistant foam matrix. There are two main methods for benzoxazine nitrile-based resin foam: chemical foaming and physical foaming. However, traditional chemical foaming usually adds a chemical foaming agent to the resin matrix, such as azodicarbonamide as a chemical foaming agent. The decomposition of azodicarbonamide will release toxic gases such as ammonia and isocyanate, causing air pollution, while traditional physical foaming is achieved by adding hollow glass microspheres. The hollow glass microspheres themselves have a low density and are easy to float in the resin melt, resulting in uneven foaming; and the hollow glass microspheres are inorganic components, have poor compatibility with the organic resin itself, and have low interface strength, resulting in decreased mechanical properties. The inventors have found in long-term experimental research that expandable microspheres are used as foaming agents. The expandable microspheres are composed of a thermoplastic polymer shell and an alkane gas core, so that they have good compatibility with benzoxazine nitrile-based resins, improve mixing uniformity and processability, and after heating, the internal air pressure increases, the shell softens and expands, and expandable microspheres with specific components and addition ratios are used to achieve a good foaming effect. Subsequently, combined with a prepolymerization reaction at a specific temperature and a specific time, the benzoxazine nitrile-based resin monomer undergoes a prepolymerization reaction, and the resin melt viscosity gradually increases, and the expandable microspheres are anchored. By applying a specific pressure, temperature and time for foaming, the expandable microspheres begin to expand, and at the same time, the polymerization degree of the benzoxazine nitrile-based resin is further increased, and an internal pore structure is formed. Applying pressure helps the benzoxazine nitrile-based resin melt flow, thereby promoting the formation of complete and uniform distribution of holes. Finally, by curing, a benzoxazine nitrile-based resin skin foam with a dense surface and a uniform and complete pore structure inside is obtained. The specific structure enables the finally prepared benzoxazine nitrile-based resin to have high mechanical properties. The present invention is obtained based on this research.

[0028] In some embodiments of the present invention, the present invention provides a method for preparing a benzoxazine nitrile-based resin skin foam, comprising the following preparation steps:

[0029] S1. Mixing: Evenly mix the dispersion medium, expandable microspheres and benzoxazine nitrile-based resin monomer, and then dry to remove the dispersion medium to prepare a mixed powder, the drying temperature is below 100°C; optionally, the drying temperature is 50-100°C. The dispersion medium is a mixed solution of anhydrous ethanol and deionized water, the mass ratio of anhydrous ethanol to deionized water is 5:1-1:5; optionally, the mass ratio of anhydrous ethanol to deionized water is 3:1-1:3. The benzoxazine nitrile-based resin monomer adopts bisphenol A type benzoxazine nitrile-based resin monomer; the expansion temperature range of the expandable microspheres adopted is 115° C. to 203° C. The model of the expandable microspheres is at least one of 980DU120, 920DU40, 920DU120, 920WUF40, 930DU120, 950DU80, 951DX120, 909DU80, 093DU120 or 091DU140; the mass fraction ratio of the expandable microspheres to the benzoxazine nitrile-based resin monomer is 1-10:90-99, which can be selected as 1-4:96-99, and can further be selected as 1-2:98-99. The mass ratio of the dispersion medium, the expandable microspheres and the benzoxazine nitrile resin monomer is 90-99: 1-10: 90-99, optionally 96-99: 1-4: 96-99, and further optionally 98-99: 1-2: 98-99. The mixing speed is 80-600 r / min, optionally 100-400 r / min; the mixing time is 1-8 hours, optionally 2-5 hours.

[0030] S2. Prepolymerization and foaming: The mixed powder is placed in a mold and prepolymerized at 120-150°C for 0.5-1.5 hours. Then, a pressure of 5-10 MPa is applied to the mold and foamed at 180-200°C for 0.5-2 hours to prepare a prepolymerized foam.

[0031] S3. Curing and demolding: The pre-polymerized foam is placed at 200-340°C for curing for 1-18 hours, and the benzoxazine nitrile-based resin skin foam is obtained after cooling and demolding. Curing is performed at one or more of 200-240°C / 1-6 hours; 250-290°C / 1-6 hours; 300-340°C / 1-6 hours. The surface of the prepared benzoxazine nitrile-based resin skin foam is dense, and a micron-scale pore structure is formed inside. The diameter of the pore structure is 50-500μm. Optionally, the diameter of the pore structure is 70-140μm.

[0032] The present invention is further described in detail below in conjunction with specific embodiments and drawings.

[0033] Example 1

[0034] The present invention provides a method for preparing a benzoxazine nitrile-based resin skin foam, comprising the following preparation steps:

[0035] S1. Mixing: The dispersion medium, expandable microspheres and benzoxazine nitrile-based resin monomer are uniformly mixed, wherein the mass ratio of the dispersion medium, expandable microspheres and benzoxazine nitrile-based resin monomer is 96 parts:4 parts:96 parts, the dispersion medium is a mixed solution of anhydrous ethanol and deionized water, the mass ratio of anhydrous ethanol to deionized water is 1:1, the model of the expandable microspheres is 950DU80, and the benzoxazine nitrile-based resin monomer is bisphenol A type benzoxazine nitrile-based resin monomer. The mixing and stirring speed is 220r / min, the time is 2h, and a viscous liquid is obtained, which is then placed in an oven at 90°C and dried for 12h to obtain a golden mixed powder.

[0036] S2. Prepolymerization and foaming: put the mixed powder prepared in step S1 into a preheated mold, and then place it in a hot press, prepolymerize it at 130°C for 1 hour, then give the mold a pressure of 10MPa, and use a 190°C / 1h program for foaming to prepare a prepolymerized foam.

[0037] S3. Curing and demolding: The pre-polymerized foam prepared in step S3 is cured at 220° C. / 1 h, and a benzoxazine nitrile resin sample is obtained after cooling and demolding.

[0038] from Figure 1 It can be seen from the physical picture that the surface of the benzoxazine nitrile-based resin prepared in Example 1 forms a dense thin wall, and the surface is smooth and the structure is complete, indicating that the prepared benzoxazine nitrile-based resin is a skin foam.

[0039] from Figure 2 It can be seen from the fracture scanning diagram that a complete and uniform micron-scale pore structure is formed inside the benzoxazine nitrile-based resin prepared in Example 1, and the diameter of the pores is 50 to 500 μm.

[0040] from Figure 3 The compressive stress-strain curve of the benzoxazine nitrile-based resin skin foam prepared in Test Example 1 can be seen in FIG. 1 , and the compressive strength of the benzoxazine nitrile-based resin skin foam in Example 1 is measured to be 68.31 MPa.

[0041] Example 2

[0042] The present invention provides a method for preparing a benzoxazine nitrile-based resin skin foam, comprising the following preparation steps:

[0043] S1. Mixing: The dispersion medium, expandable microspheres and benzoxazine nitrile-based resin monomer are uniformly mixed, wherein the mass ratio of the dispersion medium, expandable microspheres and benzoxazine nitrile-based resin monomer is 99 parts:1 part:99 parts, the dispersion medium is a mixed solution of anhydrous ethanol and deionized water, the mass ratio of anhydrous ethanol to deionized water is 1:1, the model of the expandable microspheres is 980DU120, and the benzoxazine nitrile-based resin monomer is bisphenol A type benzoxazine nitrile-based resin monomer. The mixing and stirring speed is 220r / min, the time is 2h, and a viscous liquid is obtained, which is then placed in an oven at 90°C and dried for 12h to obtain a golden mixed powder.

[0044] S2. Prepolymerization and foaming: The mixed powder prepared in step S1 is placed in a preheated mold, and then placed in a hot press, prepolymerized at 120°C for 1.5 hours, and then a pressure of 10 MPa is applied to the mold, and foaming is performed at 180°C / 2h to prepare a prepolymerized foam.

[0045] S3. Curing and demolding: The pre-polymerized foam prepared in step S3 is cured at 220° C. / 1 h, and a benzoxazine nitrile resin sample is obtained after cooling and demolding.

[0046] from Figure 1 It can be seen from the physical picture that the surface of the benzoxazine nitrile-based resin prepared in Example 2 forms a dense thin wall, and the surface is smooth and the structure is complete, indicating that the prepared benzoxazine nitrile-based resin is a skin foam.

[0047] from Figure 2 It can be seen from the fracture scanning diagram that a complete and uniform micron-scale pore structure is formed inside the benzoxazine nitrile-based resin prepared in Example 2, and the diameter of the pores is 70 to 140 μm.

[0048] Example 3

[0049] The present invention provides a method for preparing a benzoxazine nitrile-based resin skin foam, comprising the following preparation steps:

[0050] S1. Mixing: The dispersion medium, expandable microspheres and benzoxazine nitrile-based resin monomer are uniformly mixed, wherein the mass ratio of the dispersion medium, expandable microspheres and benzoxazine nitrile-based resin monomer is 90 parts:10 parts:90 parts, the dispersion medium is a mixed solution of anhydrous ethanol and deionized water, the mass ratio of anhydrous ethanol to deionized water is 1:1, the model of the expandable microspheres is 909DU80, and the benzoxazine nitrile-based resin monomer is bisphenol A type benzoxazine nitrile-based resin monomer. The mixing and stirring speed is 220r / min, the time is 2h, and a viscous liquid is obtained, which is then placed in an oven at 90°C and dried for 12h to obtain a golden mixed powder.

[0051] S2. Prepolymerization and foaming: put the mixed powder prepared in step S1 into a preheated mold, and then place it in a hot press, prepolymerize it at 150°C for 1h, then give the mold a pressure of 10MPa, and use a 200°C / 0.5h program for foaming to prepare a prepolymerized foam.

[0052] S3. Curing and demolding: The pre-polymerized foam prepared in step S3 is cured at 220°C / 1h+260°C / 1h, and a benzoxazine nitrile resin sample is obtained after cooling and demolding.

[0053] from Figure 1 It can be seen from the physical picture that the surface of the benzoxazine nitrile-based resin prepared in Example 3 forms a dense thin wall, and the surface is smooth and the structure is complete, indicating that the prepared benzoxazine nitrile-based resin is a skin foam.

[0054] from Figure 2 It can be seen from the fracture scanning diagram that a complete and uniform micron-scale pore structure is formed inside the benzoxazine nitrile-based resin prepared in Example 3, and the diameter of the pores is 50 to 100 μm.

[0055] from Figure 3 The compressive stress-strain curve of the benzoxazine nitrile-based resin skin foam prepared in Test Example 3 can be seen in FIG. 1 , and the compressive strength of the benzoxazine nitrile-based resin skin foam in Example 3 is measured to be 48 MPa.

[0056] Comparative Example 1

[0057] Patent CN105367792A synthesizes quinoxaline diamine type benzoxazine, utilizing the self-foaming behavior of the curing process. Example 1 synthesizes quinoxaline diamine type benzoxazine by curing processes at 160°C / 2h, 180°C / 3h, and 200°C / 3h without a foaming agent or a prepolymerization process, and provides actual photos of quinoxaline diamine type benzoxazine foam.

[0058] Comparative Example 2

[0059] The literature Zhang, Liying, et al. "Phthalonitrile-Based Carbon Foam with High Specific Mechanical Strength and Superior Electromagnetic Interference Shielding Performance." "ACS Applied Materials & Interfaces" (2016): 7422 reported that carbon foam was prepared using resorcinol-type nitrile resin as the matrix. Before carbonization, it was a polymer foam. Specifically, azodicarbonamide was used as the foaming agent, and there was no prepolymerization process. The foaming-curing procedure was 220℃ / 2h, 250℃ / 2h, and 280℃ / 2h to prepare resorcinol-type nitrile resin foam.

[0060] Comparative Example 3

[0061] The optimal data reported in Example 4 of patent document CN202111315839.0 specifically uses a biphenyl-type nitrile resin containing a benzoxazine ring as a matrix, Tween-80 as a stabilizer, acetone / ethanol as a dispersion medium, and azodicarbonamide as a foaming agent. The biphenyl-type nitrile resin containing a benzoxazine ring is prepared by mixing, flipping foaming and standing curing. A sandwich structure foam.

[0062] Comparative Example 4

[0063] The difference between Comparative Example 4 and Example 1 is that, in step S1, the mass ratio of the dispersion medium, expandable microspheres and benzoxazine nitrile-based resin is 96 parts: 0 parts: 96 parts, and expandable microspheres are not added; the remaining preparation steps are the same as in Example 1 to prepare benzoxazine nitrile-based resin.

[0064] from Figure 1 It can be seen from the physical picture that uneven holes are formed on the surface of the benzoxazine nitrile-based resin prepared in Comparative Example 4, indicating that the prepared benzoxazine nitrile-based resin is not a skin foam.

[0065] from Figure 2 It can be seen from the fracture scanning diagram that the benzoxazine nitrile-based resin prepared in Comparative Example 4 has no holes inside, which further indicates that Comparative Example 4 does not prepare a foam structure.

[0066] Comparative Example 5

[0067] The difference between Comparative Example 5 and Example 1 is that, in step S1, the mass ratio of the dispersion medium, expandable microspheres and benzoxazine nitrile-based resin is 0 parts: 4 parts: 96 parts, and no dispersion medium is added; the remaining preparation steps are the same as in Example 1 to prepare benzoxazine nitrile-based resin.

[0068] from Figure 1 It can be seen from the physical picture that uneven holes are formed on the surface of the benzoxazine nitrile-based resin prepared in Comparative Example 5, indicating that the prepared benzoxazine nitrile-based resin is not a skin foam.

[0069] Comparative Example 6

[0070] The difference between Comparative Example 6 and Example 1 is that the prepolymerization is omitted in step S2, and direct foaming is performed. Specifically, S2' is direct foaming: the mixed powder prepared in step S1 is placed in a preheated mold, and then placed in a hot press, a pressure of 10 MPa is applied to the mold, and foaming is performed at a temperature of 190°C / 1h to prepare a direct foam; the remaining preparation steps are the same as in Example 1, and a benzoxazine nitrile-based resin is prepared.

[0071] from Figure 1 It can be seen from the physical picture that uneven holes are formed on the surface of the benzoxazine nitrile-based resin prepared in Comparative Example 6, indicating that the prepared benzoxazine nitrile-based resin is not a skin foam.

[0072] Comparative Example 7

[0073] The difference between Comparative Example 7 and Example 1 is that, S2. Prepolymerization and foaming: the mixed powder prepared in step S1 is placed in a preheated mold, and then placed in a hot press, prepolymerized at 130°C for 1 hour, and then a pressure of 10 MPa is applied to the mold, and foaming is carried out at a rate of 210°C / 1 hour to prepare a prepolymerized foam; the remaining preparation steps are the same as in Example 1 to prepare a benzoxazine nitrile-based resin.

[0074] from Figure 1 It can be seen from the physical picture that uneven holes are formed on the surface of the benzoxazine nitrile-based resin prepared in Comparative Example 7, indicating that the prepared benzoxazine nitrile-based resin is not a skin foam.

[0075] from Figure 3 The compressive stress-strain curve of the benzoxazine nitrile-based resin skin foam prepared in Comparative Example 7 can be seen in the figure. The compressive strength of the benzoxazine nitrile-based resin skin foam in Comparative Example 7 is measured to be 28.93 MPa.

[0076] Comparative Example 8

[0077] The difference between Comparative Example 8 and Example 1 is that, S2. Prepolymerization and foaming: the mixed powder prepared in step S1 is placed in a preheated mold, and then placed in a hot press, prepolymerized at 130°C for 1h, and then foamed at 190°C / 1h to prepare a prepolymerized foam; the remaining preparation steps are the same as in Example 1 to prepare a benzoxazine nitrile-based resin.

[0078] from Figure 1 It can be seen from the physical picture that uneven holes are formed on the surface of the benzoxazine nitrile-based resin prepared in Comparative Example 8, indicating that the prepared benzoxazine nitrile-based resin is not a skin foam. Table 1 and Table 2 are the process and performance comparisons of the embodiments of the present invention and the comparative examples, respectively.

[0079] Table 1 Process comparison of each embodiment and comparative example

[0080]

[0081]

[0082] Table 2 Performance comparison of each embodiment and comparative example

[0083]

[0084] Combining Table 1 and Table 2, the benzoxazine nitrile-based resins prepared in Examples 1-3 of the present invention are formed into skin foams and have high mechanical properties, while Comparative Examples 1-8 cannot prepare skin foams and have low mechanical properties.

[0085] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to this application.

Claims

1. A method for preparing a benzoxazine nitrile-based resin skin foam, characterized in that: The method comprises the following preparation steps: S1. Mixing: uniformly mixing a dispersion medium, expandable microspheres and a benzoxazine nitrile resin monomer, and then drying to remove the dispersion medium to prepare a mixed powder, wherein the drying temperature is below 100°C; S2. Pre-polymerization foaming: The mixed powder is placed in a mold and pre-polymerized at 120 to 150 ° C for 0.5 to 1.5 h, and then a pressure of 5 to 10 MPa is applied to the mold and foamed at 180 to 200 ° C for 0.5 to 2 h to prepare a pre-polymerized foam; S3. Curing and demolding: curing the pre-polymerized foam at 200 to 340° C. for 1 to 18 hours, cooling and demolding to obtain the benzoxazine nitrile resin skin foam; The mass ratio of the expandable microspheres to the benzoxazine nitrile-based resin monomer is 1-10:90-99.

2. The method for preparing the benzoxazine nitrile-based resin skin foam according to claim 1, characterized in that: The mass ratio of the expandable microspheres to the benzoxazine nitrile-based resin monomer is 1-4:96-99.

3. The method for preparing the benzoxazine nitrile-based resin skin foam according to claim 1, characterized in that: The benzoxazine nitrile resin monomer is a bisphenol A type benzoxazine nitrile resin monomer.

4. The method for preparing the benzoxazine nitrile-based resin skin foam according to claim 1, characterized in that: The expansion temperature range of the expandable microspheres is 115°C to 203°C.

5. The method for preparing the benzoxazine nitrile-based resin skin foam according to claim 4, characterized in that: The expandable microspheres have a model number of at least one of 980DU120, 920DU40, 920DU120, 920WUF40, 930DU120, 950DU80, 951DX120, 909DU80, 093DU120 or 091DU140.

6. The method for preparing the benzoxazine nitrile-based resin skin foam according to claim 1, characterized in that: In step S3, curing is performed at one or more of the following temperatures: 200-240°C / 1-6h; 250-290°C / 1-6h; 300-340°C / 1-6h.

7. The method for preparing the benzoxazine nitrile-based resin skin foam according to claim 1, characterized in that: In step S3, the surface of the prepared benzoxazine nitrile-based resin skin foam is dense, and a micrometer-scale pore structure is formed inside, and the diameter of the pore structure is 50-500 μm.

8. The method for preparing the benzoxazine nitrile-based resin skin foam according to claim 7, characterized in that: The diameter of the pore structure is 70-140 μm.

9. A benzoxazinenitrile-based resin skin foam, prepared by the method for preparing the benzoxazinenitrile-based resin skin foam according to any one of claims 1 to 8.

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