Self-foaming polymethacrylimide foam material and preparation method thereof

Abstract

The invention provides a self-foaming polymethacrylimide foam material and a preparation method thereof, the raw materials of the self-foaming polymethacrylimide foam material comprise an acrylonitrile monomer, a methacrylic acid monomer, a copolymerizable foaming monomer, an initiator and a cross-linking agent, by introducing a copolymerizable foaming monomer to be polymerized with an acrylonitrile monomer and a methacrylic acid monomer, copolymerization of a polymethacrylimide precursor at a low temperature and self-foaming at a high temperature can be realized, so that a foaming agent does not need to be additionally added, and the foaming ratio can be accurately regulated and controlled; the finally obtained foam material can present a uniform polyhedral closed-cell structure in morphology, has a wider foaming density range and wider pore size distribution, also has excellent mechanical properties and heat resistance, can be used as a foam interlayer material, and can be used as a foam interlayer material. The method has important significance in improving the industrial production efficiency of the polymethacrylimide foam and reducing the cost.

Description

Technical Field

[0001] The invention belongs to the technical field of foaming materials, and in particular relates to a self-foaming polymethacrylimide foam material and a preparation method thereof. Background Art

[0002] Polymethacrylimide foam is a cross-linked rigid closed-cell material with the characteristics of light weight, high strength, heat insulation, sound absorption and wave absorption. It has moderate density and excellent compression performance and creep resistance. At the same density, polymethacrylimide is the foam material with the highest specific strength and specific stiffness. As a sandwich material, it is widely used in aerospace, transportation, weapons and equipment and other fields.

[0003] The foaming behavior of polymethacrylimide prepared by traditional external foaming agents is "exogenous" foaming. Once the foaming process reaches the softening temperature of the polymer, the rate of gas generation is uncertain and uncontrollable, resulting in poor uniformity of the pore structure. In addition to the external foaming agent, polymer self-foaming technology has been widely studied in recent years. Self-foaming is that the polymer precursor molecular chain contains or is grafted with thermally unstable groups, and high-temperature thermal decomposition releases small molecular gases, which has "endogenous" foaming characteristics. The self-foaming groups are evenly distributed in the system, and the foaming conditions are closely related to the softening of the polymer, which is expected to improve problems such as uneven in-mold foaming and poor cell connection.

[0004] At present, there are few reports on the production process of preparing polymethacrylimide foam by self-foaming of copolymerizable foaming monomers. For example, US8722751 and CN100390223A both disclose a polymethacrylimide foam with micropores and heat-resistant deformation, which is based on a methacrylic acid and methacrylonitrile system, with 0.01 to 15 parts by weight of tert-butyl (meth)acrylate and 0.01 to 10 parts by weight of tert-butyl alcohol as a foaming agent, the prepolymerization temperature of the system is 40 to 115°C, the foaming temperature is 150 to 250°C, and the foam density distribution is 30 to 200 kg / m 3 , but the pore size of the foam obtained by this method is small (<40μm) and the pore size distribution is narrow. For example, US5225449A, EP0532023 and JP04170408 disclose a method for preparing poly(meth)acrylimide foam by self-foaming based on (meth)acrylic acid / (meth)acrylonitrile system and tert-butyl (meth)acrylate as copolymerizable foaming monomer; wherein the molar ratio of (acrylic acid + tert-butyl acrylate) / acrylonitrile monomer is 1:0.6-1.5, the prepolymerization temperature is 50-120°C, the foaming temperature range is 180-240°C, and the foam density distribution is 10-70kg / m 3 .

[0005] At present, the existing methods use copolymerizable foaming monomers to prepare polymethacrylimide foams, which are mainly methacrylonitrile. However, the monomer reaction ratio limited by the existing methods is far from the thermal decomposition range of the foaming group, the required foaming temperature is relatively high (about 200-240°C), and the pore size of the obtained foam material is relatively small.

[0006] Therefore, developing a self-foaming polymethacrylimide foam material with a wide pore size distribution, a wide foam density range, and excellent mechanical properties is still a technical problem that needs to be solved in this field. Summary of the invention

[0007] In view of the deficiencies in the prior art, the object of the present invention is to provide a self-foaming polymethacrylimide foam material and a preparation method thereof. The self-foaming polymethacrylimide foam material does not require an external foaming agent during the foaming process, can foam by itself after being heated at a high temperature, and can precisely control the foaming ratio. At the same time, the obtained foam material can present a uniform polyhedral closed-cell structure in morphology, with a wide pore size distribution and a wide foam density range, and also has excellent mechanical properties and heat resistance, and can be used as a foam interlayer material.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a self-foaming polymethacrylimide foam material, wherein the raw materials of the self-foaming polymethacrylimide foam material are composed of the following components in parts by weight:

[0010]

[0011]

[0012] The raw materials of the self-foaming polymethacrylimide foam material provided by the present invention are composed of acrylonitrile monomer, methacrylic acid monomer, copolymerizable foaming monomer, initiator and cross-linking agent. The copolymerizable foaming monomer is introduced to polymerize with the acrylonitrile monomer and the methacrylic acid monomer, so that the obtained self-foaming polymethacrylimide foam material does not need to add an external foaming agent in the foaming process, and can foam by itself after being heated at high temperature, so that the foaming ratio can be accurately controlled. At the same time, the foam material obtained after foaming can present a uniform polyhedral closed-cell structure in morphology, can achieve a wide density range and a wide pore size distribution, and also has excellent mechanical properties and heat resistance, can be used as a foam interlayer material, and is of great significance for improving the industrial production efficiency of polymethacrylimide foam and reducing costs.

[0013] Wherein, the amount of the acrylonitrile monomer can be 40 parts by weight, 42 parts by weight, 44 parts by weight, 46 parts by weight, 48 parts by weight, 50 parts by weight, 52 parts by weight, 54 parts by weight, 56 parts by weight, 58 parts by weight or 60 parts by weight, etc.

[0014] The amount of the methacrylic acid monomer can be 10 parts by weight, 15 parts by weight, 20 parts by weight, 25 parts by weight, 30 parts by weight, 35 parts by weight, 40 parts by weight, 45 parts by weight, 50 parts by weight, 55 parts by weight or 60 parts by weight.

[0015] The amount of the copolymerizable foaming monomer can be 5 parts by weight, 10 parts by weight, 15 parts by weight, 20 parts by weight, 25 parts by weight, 30 parts by weight, 35 parts by weight, 40 parts by weight, 45 parts by weight or 50 parts by weight.

[0016] The amount of the initiator used can be 0.1 parts by weight, 0.12 parts by weight, 0.14 parts by weight, 0.16 parts by weight, 0.18 parts by weight, 0.2 parts by weight, 0.22 parts by weight, 0.24 parts by weight, 0.26 parts by weight, 0.28 parts by weight or 0.3 parts by weight, etc.

[0017] The amount of the cross-linking agent used can be 1 part by weight, 1.2 parts by weight, 1.4 parts by weight, 1.6 parts by weight, 1.8 parts by weight, 2 parts by weight, 2.2 parts by weight, 2.4 parts by weight, 2.6 parts by weight, 2.8 parts by weight or 3 parts by weight, etc.

[0018] Preferably, the self-foaming polymethacrylimide foam material comprises at least one of the compounds having the structure shown in (a) below:

[0019]

[0020] Among them, R 1 Selected from H or -CH 3 One of them, R 2 Selected from any one of the above (b);

[0021] m, n and x are each independently an integer >0 (eg, 1, 5, 10, 20, 40, 60, 80, 100, 500 or 1000, etc.).

[0022] Preferably, the density of the self-foaming polymethacrylimide foam material is 20 to 300 kg / m 3 , for example 20kg / m 3 , 50kg / m 3 , 100kg / m 3 、150kg / m 3 , 200kg / m 3 , 250kg / m 3 or 300kg / m 3 wait.

[0023] Preferably, the pore size distribution of the self-foaming polymethacrylimide foam material is 50-500 μm.

[0024] Preferably, the molar ratio of the sum of the methacrylic acid monomer and the copolymerizable foaming monomer to the acrylonitrile monomer is 1:(1.5-2.5), for example, 1:1.5, 1:1.7, 1:1.9, 1:2.1, 1:2.3 or 1:2.5.

[0025] Preferably, the copolymerizable foaming monomer includes any one of tert-butyl methacrylamide, tert-butyl acrylamide, tert-butyl methacrylate, tert-butyl acrylate, tert-butoxystyrene or tert-butyl carbonate-based styrene monomers, or a combination of at least two thereof.

[0026] Preferably, the initiator includes an azo initiator or a peroxide initiator.

[0027] Preferably, the azo initiator includes azobisisobutyronitrile and / or azobisisoheptanenitrile.

[0028] Preferably, the peroxide initiator comprises benzoyl peroxide.

[0029] Preferably, the cross-linking agent includes any one of methyl methacrylate, ethyl methacrylate, allyl methacrylate, butyl methacrylate, acrylamide or methacrylamide, or a combination of at least two thereof.

[0030] In a second aspect, the present invention provides a method for preparing the self-foaming polymethacrylimide foam material as described in the first aspect, the preparation method comprising the following steps:

[0031] (1) subjecting acrylonitrile monomer, methacrylic acid monomer, copolymerizable foaming monomer, initiator and cross-linking agent to prepolymerization to obtain a precursor;

[0032] (2) injecting the precursor obtained in step (1) into a mold, sealing the mold, and performing a copolymerization reaction to obtain a polymethacrylimide copolymer plate;

[0033] (3) subjecting the polymethacrylimide copolymer plate obtained in step (2) to dehydration treatment, foaming treatment and post-treatment to obtain the self-foaming polymethacrylimide foam material.

[0034] The preparation method of the self-foaming polymethacrylimide foam material provided by the invention has a simple experimental preparation route and does not require the addition of an additional foaming agent, which is of great significance for improving the industrial production efficiency of polymethacrylimide foam and reducing costs.

[0035] Preferably, the temperature of the prepolymerization reaction in step (1) is 40-80°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C.

[0036] Preferably, the prepolymerization reaction time in step (1) is 10 to 60 min, for example, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min.

[0037] Preferably, the prepolymerization reaction in step (1) is carried out under ultrasonic cavitation conditions.

[0038] Preferably, the temperature of the copolymerization reaction in step (2) is 40-80°C, for example, 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, 65°C, 70°C, 75°C or 80°C, etc.

[0039] Preferably, the copolymerization reaction time in step (2) is 24 to 96 h, for example, 24 h, 28 h, 32 h, 36 h, 40 h, 44 h, 48 h, 52 h, 60 h, 65 h, 70 h, 75 h, 80 h, 85 h, 90 h or 95 h.

[0040] Preferably, the temperature of the dehydration treatment in step (3) is 70-100°C, for example, 70°C, 72°C, 74°C, 76°C, 78°C, 80°C, 82°C, 84°C, 86°C, 88°C, 90°C or 100°C, etc.

[0041] Preferably, the dehydration treatment time in step (3) is 1 to 4 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours.

[0042] Preferably, the temperature of the foaming treatment in step (3) is 140-210°C, for example, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C or 210°C.

[0043] Preferably, the foaming treatment time in step (3) is 20 to 120 min, for example, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min or 120 min, etc.

[0044] Preferably, the temperature of the post-treatment in step (3) is 140-210°C, for example, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C or 210°C.

[0045] Preferably, the post-treatment time in step (3) is 2 to 8 h, for example, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h or 8 h.

[0046] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0047] (1) uniformly mixing acrylonitrile monomer, methacrylic acid monomer, copolymerizable foaming monomer, initiator and crosslinking agent, and subjecting the solution to continuous ultrasonic cavitation for 10 to 60 minutes in a constant temperature water bath at 40 to 80° C. to initiate prepolymerization of the solution to obtain a precursor;

[0048] (2) injecting the precursor obtained in step (1) into a mold assembled by a rubber ring, a clamp and a glass plate, and then immersing the sealed mold in a constant temperature water bath at 40 to 80° C. for constant temperature copolymerization for 24 to 96 hours to obtain an expandable polymethacrylimide copolymer plate;

[0049] (3) placing the expandable polymethacrylimide copolymer plate obtained in step (2) in a high temperature oven at 70-100° C. for dehydration for 1-4 hours, then foaming it at 140-210° C. for 20-60 minutes, and finally maintaining a constant temperature of 140-200° C. in the high temperature oven for 2-8 hours to obtain the self-foaming polymethacrylimide foam material.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The raw materials of the self-foaming polymethacrylimide foam material provided by the present invention are composed of acrylonitrile monomer, methacrylic acid monomer, copolymerizable foaming monomer, initiator and crosslinking agent. The copolymerizable foaming monomer is introduced to polymerize with acrylonitrile monomer and methacrylic acid monomer, so that the low-temperature copolymerization of polymethacrylimide precursor can be realized, and the polymethacrylimide foam is prepared by self-foaming at high temperature. The selected foaming temperature range and the ratio of main reaction monomer to foaming monomer can effectively improve the self-foaming polymethacrylimide with large density, small pore size and narrow distribution. The problem is that the obtained self-foaming polymethacrylimide foam material does not need to add an external foaming agent during the foaming process, and can foam by itself after being heated at high temperature, so that the foaming ratio can be accurately controlled. At the same time, the foam material obtained after foaming can present a uniform polyhedral closed-cell structure in morphology, thereby realizing the preparation of self-foaming polymethacrylimide foam materials with a wide density range and a wide pore size distribution, while ensuring its excellent mechanical properties and heat resistance, and can be used as a foam interlayer material, which is of great significance for improving the industrial production efficiency of polymethacrylimide foam and reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1A flow chart for preparing the self-foaming polymethacrylimide foam material provided in Example 1;

[0053] Figure 2 A scanning electron microscope image of the self-foaming polymethacrylimide foam material provided in Example 1;

[0054] Figure 3 This is a scanning electron microscope image of the self-foaming polymethacrylimide foam material provided in Comparative Example 3. DETAILED DESCRIPTION

[0055] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0056] Unless otherwise specified, the raw materials involved in the following specific embodiments are all conventional materials in the art and can be purchased from commercial products.

[0057] Example 1

[0058] A self-foaming polymethacrylimide foam material, the raw materials of which are composed of the following components in parts by weight:

[0059]

[0060] The preparation flow chart of the self-foaming polymethacrylimide foam material is as follows Figure 1 As shown, the preparation method thereof comprises the following steps:

[0061] (1) adding acrylonitrile monomer, methacrylic acid monomer, tert-butyl methacrylate, azobisisobutyronitrile and acrylamide into a single-necked flask, and subjecting the mixture to continuous ultrasonic cavitation treatment for 40 min in a constant temperature water bath at 45° C. to obtain a precursor;

[0062] (2) sealing the precursor obtained in step (1) in a mold assembled by a rubber ring, a clamp and a glass plate, and then immersing the sealed mold in a constant temperature water bath at 50° C. for 48 hours of constant temperature copolymerization to obtain a transparent expandable polymethacrylimide copolymer plate;

[0063] (3) placing the expandable polymethacrylimide copolymer plate obtained in step (2) in a high-temperature oven and maintaining a constant temperature of 100° C. for dehydration treatment for 2 h, then heating the temperature to 210° C. at a heating rate of 2° C. / min for foaming treatment for 20 min, and then maintaining the temperature in a high-temperature oven at 180° C. for 4 h for post-treatment to obtain the self-foaming polymethacrylimide foam material.

[0064] Example 2

[0065] A self-foaming polymethacrylimide foam material, the raw materials of which are composed of the following components in parts by weight:

[0066]

[0067] The preparation method of the self-foaming polymethacrylimide foam material comprises the following steps:

[0068] (1) adding acrylonitrile monomer, methacrylic acid monomer, tert-butyl methacrylate, azobisisobutyronitrile and acrylamide into a single-necked flask, and subjecting the mixture to continuous ultrasonic cavitation treatment for 60 min in a constant temperature water bath at 40° C. to obtain a precursor;

[0069] (2) sealing the precursor obtained in step (1) in a mold assembled by a rubber ring, a clamp and a glass plate, and then immersing the sealed mold in a constant temperature water bath at 45° C. for 96 hours of constant temperature copolymerization to obtain a transparent expandable polymethacrylimide copolymer plate;

[0070] (3) placing the expandable polymethacrylimide copolymer plate obtained in step (2) in a high-temperature oven and maintaining a constant temperature of 70° C. for dehydration treatment for 1 hour, then heating the temperature to 200° C. at a heating rate of 2° C. / min for foaming treatment for 40 minutes, and then maintaining the temperature at 180° C. for 2 hours and 160° C. for 2 hours in a high-temperature oven for post-treatment to obtain the self-foaming polymethacrylimide foam material.

[0071] Example 3

[0072] A self-foaming polymethacrylimide foam material, the raw materials of which are composed of the following components in parts by weight:

[0073]

[0074] The preparation method of the self-foaming polymethacrylimide foam material comprises the following steps:

[0075] (1) adding acrylonitrile monomer, methacrylic acid monomer, tert-butyl methacrylate, azobisisobutyronitrile and methyl methacrylate into a single-necked flask, and subjecting the mixture to continuous ultrasonic cavitation treatment for 30 min in a constant temperature water bath at 50° C. to obtain a precursor;

[0076] (2) sealing the precursor obtained in step (1) in a mold assembled by a rubber ring, a clamp and a glass plate, and then immersing the sealed mold in a constant temperature water bath at 55° C. for 48 hours of constant temperature copolymerization to obtain a transparent expandable polymethacrylimide copolymer plate;

[0077] (3) placing the expandable polymethacrylimide copolymer plate obtained in step (2) in a high-temperature oven and maintaining a constant temperature of 90° C. for dehydration treatment for 1 hour, then heating the temperature to 190° C. at a heating rate of 2° C. / min for foaming treatment for 40 minutes, and then maintaining the temperature in a high-temperature oven at 160° C. for 5 hours and 150° C. for 2 hours for post-treatment to obtain the self-foaming polymethacrylimide foam material.

[0078] Example 4

[0079] A self-foaming polymethacrylimide foam material, the raw materials of which are composed of the following components in parts by weight:

[0080]

[0081]

[0082] The preparation method of the self-foaming polymethacrylimide foam material comprises the following steps:

[0083] (1) adding acrylonitrile monomer, methacrylic acid monomer, tert-butyl methacrylate, azobisisobutyronitrile and acrylamide into a single-necked flask, and subjecting the mixture to continuous ultrasonic cavitation treatment for 20 min in a constant temperature water bath at 55° C. to obtain a precursor;

[0084] (2) sealing the precursor obtained in step (1) in a mold assembled by a rubber ring, a clamp and a glass plate, and then immersing the sealed mold in a constant temperature water bath at 60° C. for 36 hours of constant temperature copolymerization to obtain a transparent expandable polymethacrylimide copolymer plate;

[0085] (3) placing the expandable polymethacrylimide copolymer plate obtained in step (2) in a high-temperature oven and maintaining a constant temperature of 80° C. for dehydration treatment for 1 hour, then heating the temperature to 180° C. at a heating rate of 2° C. / min for foaming treatment for 60 minutes, and then maintaining the temperature in a high-temperature oven at 170° C. for 3 hours and 160° C. for 2 hours for post-treatment to obtain the self-foaming polymethacrylimide foam material.

[0086] Example 5

[0087] A self-foaming polymethacrylimide foam material, the raw materials of which are composed of the following components in parts by weight:

[0088]

[0089] The preparation method of the self-foaming polymethacrylimide foam material comprises the following steps:

[0090] (1) adding acrylonitrile monomer, methacrylic acid monomer, tert-butyl methacrylate, benzoyl peroxide and methacrylamide into a single-necked flask, and subjecting the mixture to continuous ultrasonic cavitation treatment for 10 min in a constant temperature water bath at 60° C. to obtain a precursor;

[0091] (2) sealing the precursor obtained in step (1) in a mold assembled by a rubber ring, a clamp and a glass plate, and then immersing the sealed mold in a constant temperature water bath at 60° C. for 24 hours of constant temperature copolymerization to obtain a transparent expandable polymethacrylimide copolymer plate;

[0092] (3) placing the expandable polymethacrylimide copolymer plate obtained in step (2) in a high-temperature oven and maintaining a constant temperature of 80° C. for dehydration treatment for 1 hour, then heating the temperature to 170° C. at a heating rate of 2° C. / min for foaming treatment for 80 minutes, and then maintaining the temperature in a high-temperature oven at 160° C. for 4 hours for post-treatment to obtain the self-foaming polymethacrylimide foam material.

[0093] Example 6

[0094] A self-foaming polymethacrylimide foam material is disclosed. The only difference between the self-foaming polymethacrylimide foam material and the embodiment 1 is that tert-butyl acrylamide is used to replace tert-butyl methacrylate. Other substances, dosages and preparation methods are the same as those in the embodiment 1.

[0095] Example 7

[0096] A self-foaming polymethacrylimide foam material is disclosed. The only difference between the self-foaming polymethacrylimide foam material and the embodiment 1 is that tert-butyl methacrylate is replaced by tert-butoxystyrene, and other substances, dosages and preparation methods are the same as those in the embodiment 1.

[0097] Example 8

[0098] A self-foaming polymethacrylimide foam material is different from Example 1 only in that the amount of methacrylic acid monomer used is 42 parts by weight, the amount of tert-butyl methacrylate used is 3 parts by weight, and other substances, amounts used and preparation methods are the same as those in Example 1.

[0099] Example 9

[0100] A self-foaming polymethacrylimide foam material, which is different from Example 1 only in that the amount of acrylonitrile monomer used is 40 parts by weight, the amount of methacrylic acid monomer used is 10 parts by weight, and the amount of tert-butyl methacrylate used is 50 parts by weight, and other substances, amounts and preparation methods are the same as those in Example 1.

[0101] Comparative Example 1

[0102] A polymethacrylimide foam material, the raw materials of which are composed of the following components in parts by weight:

[0103]

[0104] The preparation method of the self-foaming polymethacrylimide foam material comprises the following steps:

[0105] (1) adding acrylonitrile monomer, methacrylic acid monomer, formamide, azobisisobutyronitrile and acrylamide into a single-necked flask, and subjecting the mixture to continuous ultrasonic cavitation treatment for 20 minutes in a constant temperature water bath at 50° C. to obtain a prepolymer;

[0106] (2) sealing the prepolymer obtained in step (1) in a mold assembled by a rubber ring, a clamp and a glass plate, and then immersing the sealed mold in a constant temperature water bath at 50° C. for 48 hours of constant temperature copolymerization to obtain a transparent expandable polymethacrylimide copolymer plate;

[0107] (3) placing the expandable polymethacrylimide copolymer plate obtained in step (2) in a high-temperature oven and maintaining a constant temperature of 80° C. for dehydration treatment for 1 hour, then heating the temperature to 200° C. at a heating rate of 2° C. / min for foaming treatment for 40 minutes, and then maintaining the temperature in a high-temperature oven at 180° C. for 4 hours for post-treatment to obtain the polymethacrylimide foam material.

[0108] Comparative Example 2

[0109] A self-foaming polymethacrylimide foam material is different from Example 1 only in that the amount of methacrylic acid monomer used is 44 parts by weight, the amount of tert-butyl methacrylate used is 1 part by weight, and other substances, amounts used and preparation methods are the same as those in Example 1.

[0110] Comparative Example 3

[0111] A self-foaming polymethacrylimide foam material, which is different from Example 1 only in that the amount of acrylonitrile monomer used is 35 parts by weight, the amount of methacrylic acid monomer used is 5 parts by weight, and the amount of tert-butyl methacrylate used is 60 parts by weight. Other substances, amounts and preparation methods are the same as those in Example 1.

[0112] Structural characterization:

[0113] The polymethacrylimide foam materials provided in Example 1 and Comparative Example 3 were tested using a scanning electron microscope. The test results are as follows: Figure 2 and Figure 3 It can be seen that:

[0114] from Figure 2 and Figure 3From the comparison, it can be seen that the self-foaming polymethacrylimide foam material provided in Example 1 has a uniform polyhedral closed-cell structure, while the self-foaming polymethacrylimide foam material provided in Comparative Example 3 has an excessive amount of copolymerizable foaming monomer added, resulting in a too fast gas precipitation rate in the foaming stage, a decrease in the melt strength of the pores, and rupture of the pore walls, and cannot form a uniform closed-cell polyhedral structure.

[0115] Performance Test:

[0116] The following performance tests were performed on the polymethacrylimide foam materials provided in Examples 1 to 9 and Comparative Examples 1 to 3. The test results are shown in Table 1:

[0117] Table 1

[0118]

[0119]

[0120] Here, “ / ” means that the test cannot be performed.

[0121] From the data in Table 1, we can see that:

[0122] By comparing the data of Example 1 with that of Comparative Example 1, it can be seen that, when the densities are similar, the glass transition temperature and compressive strength of the polymethacrylimide foam material prepared by the copolymerizable foaming monomer selected in Example 1 to participate in the polymerization and foaming are higher than those of the traditional foaming method used in Comparative Example 1, indicating that the self-foaming polymethacrylimide foam material provided by the present invention has better thermal stability and compression performance.

[0123] In addition, by comparing the data of Examples 1 to 9, it can be seen that the self-foaming polymethacrylimide foam material provided by the present invention has a wider foaming range. Within the preferred range of the amount of copolymerizable foaming monomers, its density and thermal properties can be controlled by the preferred foaming temperature and foaming content, which makes the process of regulating and controlling the foam density and properties more convenient and improves the preparation efficiency.

[0124] The applicant declares that the present invention illustrates a self-foaming polymethacrylimide foam material and a preparation method thereof through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A self-foaming polymethacrylimide foam material, characterized in that: The raw materials of the self-foaming polymethacrylimide foam material are composed of the following components in parts by weight: 40-60 parts by weight of acrylonitrile monomer; 10 to 60 parts by weight of methacrylic acid monomer; 3 to 50 parts by weight of copolymerizable foaming monomer; Initiator 0.1-0.3 parts by weight; 1 to 3 parts by weight of crosslinking agent.

2. The self-foaming polymethacrylimide foam material according to claim 1, characterized in that: The foam density of the self-foaming polymethacrylimide foam material is 20 to 300 kg / m 3 ; Preferably, the pore size distribution of the self-foaming polymethacrylimide foam material is 50 to 500 μm; Preferably, the molar ratio of the sum of the methacrylic acid monomer and the copolymerizable foaming monomer to the acrylonitrile monomer is 1:(1.5-2.5).

3. The self-foaming polymethacrylimide foam material according to claim 1 or 2, characterized in that: The copolymerizable foaming monomer includes any one of tert-butyl methacrylamide, tert-butyl acrylamide, tert-butyl methacrylate, tert-butyl acrylate, tert-butoxy styrene or tert-butyl carbonate-based styrene monomers or a combination of at least two thereof.

4. The self-foaming polymethacrylimide foam material according to any one of claims 1 to 3, characterized in that: The initiator includes an azo initiator or a peroxide initiator; Preferably, the azo initiator includes azobisisobutyronitrile and / or azobisisoheptanenitrile; Preferably, the peroxide initiator comprises benzoyl peroxide.

5. The self-foaming polymethacrylimide foam material according to any one of claims 1 to 4, characterized in that: The crosslinking agent includes any one of methyl methacrylate, ethyl methacrylate, allyl methacrylate, butyl methacrylate, acrylamide or methacrylamide, or a combination of at least two thereof.

6. A method for preparing the self-foaming polymethacrylimide foam material according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: (1) subjecting acrylonitrile monomer, methacrylic acid monomer, copolymerizable foaming monomer, initiator and cross-linking agent to prepolymerization to obtain a precursor; (2) injecting the precursor obtained in step (1) into a mold, sealing the mold, and performing a copolymerization reaction to obtain a polymethacrylimide copolymer plate; (3) subjecting the polymethacrylimide copolymer plate obtained in step (2) to dehydration treatment, foaming treatment and post-treatment to obtain the self-foaming polymethacrylimide foam material.

7. The preparation method according to claim 6, characterized in that: The temperature of the prepolymerization reaction in step (1) is 40 to 80° C. and the time is 10 to 60 minutes; Preferably, the prepolymerization reaction in step (1) is carried out under ultrasonic cavitation conditions.

8. The preparation method according to claim 6 or 7, characterized in that: The copolymerization reaction temperature in step (2) is 40 to 80° C. and the reaction time is 24 to 96 hours.

9. The preparation method according to any one of claims 6 to 8, characterized in that: The temperature of the dehydration treatment in step (3) is 70-100° C. and the time is 1-4 hours.

10. The preparation method according to any one of claims 6 to 9, characterized in that: The temperature of the foaming treatment in step (3) is 140-210° C. and the time is 20-120 min; Preferably, the post-treatment in step (3) is carried out at a temperature of 140 to 210° C. and for a time of 2 to 8 hours.

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