Foamable composition, biodegradable PMI foam, and preparation method therefor

Abstract

Disclosed in the present disclosure are a foamable composition, a biodegradable PMI foam, and a preparation method therefor. The foamable composition comprises comonomers, an initiator, a foaming agent, and a crosslinking agent, wherein the comonomers comprise a first comonomer and a second comonomer, the first comonomer being one or two selected from methacrylonitrile or acrylonitrile, and the second comonomer being selected from methacrylic acid. The composition further comprises a degradation agent, and the degradation agent is one or a combination of two or more selected from polylactic acid, starch-based polyether polyol and polycaprolactone, the weight ratio of the degradation agent to the comonomers being 30-132:180. The foamable composition of the present disclosure involves scientific addition of the degradation agent and regulation on the formula and uses in-situ polymerization technology, thereby improving the biodegradation rate of the PMI foam while retaining the original high performance of the PMI foam.

Description

A foamable composition, a biodegradable PMI foam and its preparation method

[0001] Citation of relevant applications

[0002] This application claims priority to Chinese Patent Application No. 2024116798354, filed on November 22, 2024, entitled “A foamable composition, a biodegradable PMI foam and a method for preparing the same,” the entire contents of which are incorporated herein by reference for all purposes. Technical Field

[0003] This disclosure relates to the field of new foaming materials technology, and in particular to a foamable composition, a biodegradable PMI foam, and a method for preparing the same. Background Technology

[0004] Polymethacrylimide (PMI) foam is an advanced new material, typically produced by copolymerizing methacrylic acid (MAA) and methacrylonitrile (MAN) or methacrylic acid (MAA) and acrylonitrile (AN) and then foaming it. It is easy to process and has excellent strength, stiffness, thermal stability and chemical resistance. It has a wide range of applications in aerospace, rail transportation, wind power generation, consumer electronics, medical devices and other fields, and has developed rapidly in recent years.

[0005] However, with the widespread application of PMI foam, the question of how to dispose of PMI foam after disposal has become increasingly prominent and has been troubling the industry. Because PMI foam has excellent high-temperature and solvent resistance, it is difficult to degrade in the natural environment. Traditional chemical degradation methods usually require high-temperature and strongly alkaline environments, which are subject to limitations, high costs, and low efficiency; while incineration would exacerbate air pollution.

[0006] Furthermore, "white pollution" caused by waste plastics has always been a major focus of global environmental protection, and the research and development of biodegradable plastics is a global trend. For example, patent CN117777602B studied a biodegradable polypropylene plastic masterbatch, adding a mixture of ferric diethyldithiocarbamate and titanium dioxide as a degradation agent, achieving a photodegradation rate of 29% in 30 days. Patent CN112063042B studied a biodegradable polypropylene plastic, using activated carbon-coated cellulose as a degradation agent. Patent US9914824B2 studied a biodegradable polyethylene plastic, using cobalt stearate, ferric stearate, cerium stearate, manganese stearate, and vanadium stearate as biodegradable agents; the results showed that the plastic garbage bags made from it would biodegrade within 24-36 months under landfill conditions. Patent CN108264736B studied a biodegradable poly(butylene adipate-co-terephthalate), PBAT foam material, which, with the addition of 1,4-butanediol, hexanediol, or ethylene glycol as degrading agents, can achieve near-complete degradation in about 2-3 years. US11597235B2 studied a biodegradable polyurethane foam for tires, which, with the addition of dimethyl phosphonate and diethyl phosphonate as degrading agents, can degrade at temperatures above 120°C.

[0007] The widespread use of PMI foam will generate a large amount of waste, making the disposal of waste PMI foam an urgent issue. Therefore, developing environmentally friendly and biodegradable PMI foam is an important way to implement sustainable development. Summary of the Invention

[0008] Currently, PMI foam is difficult to degrade, and the disposal of waste PMI foam faces enormous economic pressure and environmental problems. Existing research has disclosed schemes for adding degrading agents to plastics such as polypropylene, polyethylene, PBAT, and polyurethane, all of which have effectively achieved the degradability of these plastics. However, the raw materials, reaction systems, product performance, and application scenarios of these plastics are very different from those of PMI foam, and the types of degrading agents are diverse and their properties vary greatly, so not all of them can be used to produce biodegradable PMI foam. The inventors of this invention have not yet found any research that can effectively achieve the degradation of PMI foam.

[0009] On the one hand, this disclosure provides a biodegradable PMI foam and its preparation method, which solves the problems of difficult waste disposal, high cost and low efficiency of traditional PMI foam.

[0010] On the other hand, this disclosure provides a method for converting existing PMI foam into biodegradable PMI foam, solving the problem of converting existing non-degradable PMI foam into biodegradable materials.

[0011] On the other hand, this disclosure provides a high-strength, high-biodegradability PMI foam.

[0012] On the other hand, this disclosure provides a degrading agent that can be used for PMI foam.

[0013] On the other hand, this disclosure provides a method for improving the biodegradability of PMI foam under composting conditions.

[0014] Specifically, this disclosure proposes the following technical solutions:

[0015] First, this disclosure provides a foamable composition comprising a comonomer, an initiator, a foaming agent, and a crosslinking agent, wherein the comonomer comprises a first comonomer and a second comonomer.

[0016] The first comonomer is selected from one or two of methacrylonitrile or acrylonitrile, and the second comonomer is selected from methacrylic acid;

[0017] The composition further includes a degradation agent selected from one or more of polylactic acid, starch-based polyether polyol, and polycaprolactone;

[0018] The mass ratio of the degrading agent to the comonomer is 30-132:180.

[0019] In some embodiments, the comonomer further includes a third comonomer selected from acrylamide monomers.

[0020] In some embodiments, the acrylamide monomer is selected from any one or a combination of two or more of acrylamide, methacrylamide, N-hydroxymethylacrylamide, and N,N-dimethylacrylamide.

[0021] In some embodiments, the initiator is selected from any one or a combination of two or more of azobisisobutyronitrile, azobisisoheptanenitrile, tert-butyl peroxide (2-ethylhexanoate), and dilauryl peroxide; the foaming agent is selected from any one or a combination of two or more of formamide, N,N-dimethylformamide, isopropanol, isobutanol, octane, and isooctane; and the crosslinking agent is any one or two of allyl methacrylate and magnesium methacrylate.

[0022] In some embodiments, the polylactic acid has a molecular weight of 30,000-150,000, the polycaprolactone has a molecular weight of 10,000-120,000, and the starch-based polyether polyol has a hydroxyl value of 300-600 mg KOH / g.

[0023] In some embodiments, the degrading agent is selected from polylactic acid.

[0024] In some embodiments, the mass ratio of the degrading agent to the comonomer is 50-110:180.

[0025] In some implementations, the mass ratio of the first comonomer to the second comonomer is 0.6-1.5:1.

[0026] In some embodiments, the foamable composition, by weight, comprises 64-120 parts of a first comonomer, 64-120 parts of a second comonomer, 1.2-3 parts of an initiator, 10-18 parts of a foaming agent, 0.8-2.4 parts of a crosslinking agent, 30-132 parts of a degrading agent, and 0-2.4 parts of a third comonomer.

[0027] In some embodiments, the foamable composition, by weight, comprises 72-110 parts of a first comonomer, 72-110 parts of a second comonomer, 1.8-2.75 parts of an initiator, 11.25-16.5 parts of a foaming agent, 0.9-2.2 parts of a crosslinking agent, 40-121 parts of a degrading agent, and 0.9-2.2 parts of a third comonomer.

[0028] In some embodiments, the foamable composition, by weight, comprises 72-88 parts of the first comonomer methacrylonitrile, 90-110 parts of the second comonomer methacrylic acid, 1.8-2.2 parts of the third comonomer methacrylamide, 2-2.75 parts of the initiator azobisisobutyronitrile, 11.25-13.75 parts of the foaming agent formamide, 1.8-2.2 parts of the crosslinking agent allyl methacrylate, and 30-99 parts of the degrading agent polylactic acid.

[0029] In some embodiments, the foamable composition, by weight, comprises 90-110 parts of acrylonitrile as a first comonomer, 72-88 parts of methacrylic acid as a second comonomer, 0.9-1.1 parts of acrylamide as a third comonomer, 1.8-2.2 parts of tert-butyl peroxide (2-ethylhexanoate) as an initiator, 13.5-16.5 parts of isopropanol as a foaming agent, 0.9-1.1 parts of magnesium methacrylate as a crosslinking agent, and 30-99 parts of polylactic acid as a degradation agent.

[0030] In some embodiments, the foamable composition comprises 70-90 parts by weight of a degrading agent.

[0031] Secondly, this disclosure also provides a biodegradable foam obtained by foaming any of the aforementioned foamable compositions.

[0032] Furthermore, this disclosure also provides a method for preparing biodegradable foam, comprising the following steps:

[0033] S1, Prepolymerization: A prepolymer is obtained by polymerizing the foamable composition of any of the preceding items;

[0034] S2. Heat treatment before foaming: The prepolymer is heat-treated to obtain the polymer;

[0035] S3. Foaming: The polymer is foamed to obtain foam.

[0036] In some implementations, in step S1, the polymerization reaction system contains a degrading agent, a comonomer, an initiator, a foaming agent, and a crosslinking agent.

[0037] In some implementations, the polymerization temperature in step S1 is 20°C-60°C.

[0038] In some implementations, the heat treatment temperature in step S2 is 60°C-120°C.

[0039] In some implementations, the foaming temperature in step S3 is 160°C-250°C.

[0040] In some implementation schemes, the following steps are also included:

[0041] S4. Heat treatment after foaming: The foam is heat-treated at 135℃-220℃ to obtain high-temperature resistant foam.

[0042] The beneficial effects of this disclosure include:

[0043] The biodegradable PMI foam disclosed herein achieves high strength and degradability by scientifically adding degrading agents and adjusting the proportion of degrading agents, while maintaining sufficient mechanical properties and effectively improving the degradation rate of PMI foam. Detailed Implementation

[0044] The technical solution of this disclosure will now be clearly and completely described. Obviously, based on the specific embodiments described in this disclosure, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this disclosure.

[0045] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this disclosure.

[0046] I. Terminology

[0047] As used herein, the term "methacrylonitrile (MAN)" is a colorless liquid organic compound with the chemical formula C4H5N, a molecular weight of 67.089, and a density of 0.8 g / cm³. 3 The molar volume is 82.8 cm³. 3 / mol. It is slightly soluble in water and chloroform, and miscible with propanol, diethyl ether, acetone, octane and toluene.

[0048] As used herein, the term "acrylonitrile (AN)" is a colorless liquid organic compound with the chemical formula C3H3N, a molecular weight of 53.063, and a density of 0.806 g / cm³. 3 The molar volume is 66.5 cm³. 3 / mol. AN is slightly soluble in water, but soluble in ethanol, ether, acetone, benzene, and carbon tetrachloride.

[0049] As used herein, the term "methacrylic acid (MAA)" is a colorless liquid organic compound with the chemical formula C4H6O2, a molecular weight of 86.089, and a density of 1.015 g / cm³. 3 The molar volume is 84.0 cm³. 3 / mol. MAA is soluble in hot water and in most organic solvents, including ethanol and diethyl ether.

[0050] When MAN / AN and MAA undergo copolymerization, a "third comonomer" is often added. As used in this article, the term "third comonomer" refers to one or more unsaturated or cyclic monomer molecules that participate in the polymerization reaction. Commonly used third comonomers include acrylamide, methacrylamide, N-hydroxymethylacrylamide, and N,N-dimethylacrylamide. Acrylamide is a white crystalline powder organic compound with the chemical formula C3H5NO, a molecular weight of 71.078, and a density of 1.322 g / cm³. 3 The molar volume is 73.9 cm³. 3 Methacrylamide is a white crystalline organic compound with the chemical formula C4H7NO, a molecular weight of 85.104, and a density of 1.115 g / cm³. It is soluble in water, ethanol, ether, and acetone, but insoluble in benzene and hexane. 3 The molar volume is 73.9 cm³. 3 / mol, characterized by being readily soluble in water, soluble in alcohol and dichloromethane, slightly soluble in ether and chloroform, and insoluble in petroleum ether and carbon tetrachloride; N-hydroxymethylacrylamide (CAS: 924-42-5) is a colorless or yellow solution organic compound with the chemical formula C4H7NO2, a molecular weight of 101.1039, and a density of 1.082 g / cm³. 3 N,N-Dimethylacrylamide (CAS: 2680-03-7) is a colorless liquid with the chemical formula C5H9NO. It has good solubility and reactivity and is widely used in the synthesis and modification of polymers.

[0051] As used herein, the term "initiator" refers to a compound with a weak bond that readily decomposes into active species and, upon heating, into free radicals. It is used to initiate free radical polymerization and copolymerization reactions of olefins and dienes, and can also be used for crosslinking and curing of unsaturated polyesters and polymer crosslinking reactions. Commonly used initiators include azobisisobutyronitrile (AIBN), azobisisoheptanenitrile (AIHHN), tert-butyl peroxide (2-ethylhexanoate), and dilauryl peroxide. Azobisisobutyronitrile (CAS: 78-67-1) is a white needle-like crystal; at lower purity, it is a white powdery crystal. It is insoluble in water but soluble in organic solvents such as methanol, ethanol, acetone, diethyl ether, petroleum ether, toluene, and aniline. It is used as an initiator in the polymerization of monomers such as vinyl chloride, vinyl acetate, and acrylonitrile. Azobisisoheptanenitrile (CAS: 4419-11-8) is a colorless or white rhombic flaky crystal; insoluble in water, soluble in organic solvents such as alcohols, ethers, and dimethylformamide; it can be used as a polymerization initiator for polymers such as polyvinyl chloride, polyvinyl alcohol, and polymethyl methacrylate. Tert-butyl peroxide (CAS: 3006-82-4), also known as TBPO (Tert-Butyl peroxy-2-ethylhexanoate), is an organic peroxide initiator, a colorless or pale yellow transparent liquid, used as a polymerization initiator for all vinyl monomers such as vinyl acetate, vinyl chloride, methacrylic acid, styrene, and ethylene; it can also be used as a thermosetting and curing catalyst for unsaturated polyester resins. Dilauroyl peroxide (CAS: 105-74-8), also known as initiator B, is a white powder, readily soluble in organic solvents such as acetone and chloroform, as well as oils, but insoluble in water; it is mainly used as a free radical polymerization initiator, often in combination with initiator A (di-tert-butyl peroxide).

[0052] As used herein, the term "foaming agent" refers to a compound that, upon heating, decomposes to release gases such as carbon dioxide and nitrogen, and forms micropores within the polymer composition. Foaming agents are used to reduce the surface tension of liquids and to surround air in a double electron layer arrangement on the liquid film surface, forming bubbles, which then combine to form foam. Commonly used foaming agents include formamide, N,N-dimethylformamide, isopropanol, isobutanol, octane, and isooctane. Formamide (CAS: 75-12-7) is a transparent, oily liquid, miscible with water and ethanol, and slightly soluble in benzene, chloroform, and diethyl ether. N,N-dimethylformamide (CAS: 68-12-2), with the chemical formula C3H7NO, is a colorless, transparent liquid. It is miscible with water and most organic solvents and has good solubility for a wide range of organic and inorganic compounds. Isopropanol (CAS: 67-63-0) is a colorless, flammable liquid with a strong odor at room temperature and pressure. It is miscible with water, alcohols, ethers, and chloroform, and its boiling point is 82°C. Isobutanol (CAS: 78-83-1) is a colorless, transparent liquid miscible with ethanol and diethyl ether, and soluble in about 20 parts of water. Its boiling point is 108°C. Octane (CAS: 111-65-9) is a colorless, transparent liquid with a boiling point of 125.67°C. Isooctane (CAS: 540-84-1) is a colorless, transparent liquid, insoluble in water, soluble in ether, and readily soluble in alcohols, acetone, benzene, chloroform, etc., with a boiling point of 98°C-99°C.

[0053] As used herein, the term "crosslinking agent" refers to a substance that generates two free radicals upon exposure, reacts with polycarbonate resins, forms bridging bonds between polymer molecular chains, and becomes a three-dimensional, insoluble substance. It is soluble in aromatic hydrocarbons, halogenated hydrocarbons, cycloalkanes, acetone, and various alcohols, slightly soluble in alkanes, and insoluble in water. Commonly used crosslinking agents include allyl methacrylate and magnesium methacrylate. Allyl methacrylate (CAS: 96-05-9) is a pale yellow liquid, readily soluble in most organic solvents, and almost insoluble in water; it is an important crosslinking agent. Magnesium methacrylate (CAS: 7095-16-1) is a white crystalline solid. It is soluble in water and some organic solvents, such as ethanol and ether, and is commonly used as a rubber additive to improve the crosslinking properties of rubber.

[0054] As used in this article, the term "degradable agent" refers to a new type of functional additive that meets environmental protection requirements. These additives are incorporated into plastics to make them easier to degrade, primarily to address the long-standing problem of white pollution. There are two methods for adding degradable agents as additives to the PMI foam reaction system: one is to add them during the polymerization stage using in-situ polymerization, and the other is to mix them in after polymerization but before foaming using a staged mixing method.

[0055] The term "in-situ polymerization" in this disclosure refers to the process in which both the degrading agent and the comonomer are added to the polymerization reaction system to carry out the polymerization reaction. In-situ polymerization allows the degrading agent to participate in the polymerization reaction and be uniformly dispersed in the prepolymer.

[0056] The term "segmented mixing" in this disclosure refers to the process of pulverizing the polymer after the comonomer has been polymerized, adding a degradation agent and resin, stirring evenly, and then further reacting it at high temperature, so that the degradation agent is bonded together with the resin and PMI foam during the foaming process.

[0057] In order to promote the degradation of PMI foam in the natural environment, the inventors added a degradation agent before foaming, making the foamed PMI foam easy to degrade, which can be used to solve the white pollution problem that has long plagued people.

[0058] To match the production system and processing application scenarios of PMI foam and to find suitable degradation agents, the inventors studied ferric diethyldithiocarbamate, titanium dioxide, ferric stearate, ethylene glycol, 1,4-butanediol, hexanediol, starch, cellulose acetate, chitosan, polyglycolic acid (PGA), poly(p-dioxanone) (PPDO), polycaprolactone (PCL), polyhydroxybutyrate (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), polylactic acid (PLA), PBAT, polybutylene succinate (PBS), and polyvinyl alcohol (PVA). After evaluating the polymerization reaction and degradation effect of PMI foam after adding degradation agents such as alcohol and PVA, it was found that starch-based polyether polyols, PLA, and PCL can be used as degradation agents in PMI foam. Starch-based polyether polyols are polyols prepared from starch as raw material and glycerol-polyethylene glycol as liquefying agent. Polylactic acid (CAS: 26100-51-6) is a polymer formed by the polymerization reaction of lactic acid molecules. It is difficult to dissolve in common organic solvents, but its dissolution can be accelerated when heated or mixed with some ester or ether solvents. Polylactic acid is a biodegradable polymer that can be degraded into harmless products by microorganisms in the natural environment, making it environmentally friendly. Polycaprolactone (CAS:24980-41-4), also known as polyε-caprolactone, is a high molecular weight organic polymer formed by ring-opening polymerization of ε-caprolactone monomers under the catalysis of a metal anion complexing catalyst. Polycaprolactone is a biodegradable polymer that is non-toxic, biodegradable in soil, has excellent miscibility, mechanical compatibility with many polymers, and good adhesion to many matrices.

[0059] II. Detailed Implementation

[0060] In one aspect, this disclosure provides a foamable composition comprising a comonomer, an initiator, a foaming agent, a crosslinking agent, and a degrading agent.

[0061] In some implementations, the preparation of PMI foam requires at least two comonomers, the first comonomer being selected from one or both of methacrylonitrile or acrylonitrile, and the second comonomer being selected from methacrylic acid.

[0062] In some embodiments, the degrading agent is selected from one or more combinations of polylactic acid, starch-based polyether polyol, and polycaprolactone.

[0063] In some embodiments, the mass ratio of the degrading agent to the comonomer is, for example, 30-132:180, such as 30:180, 35:180, 40:180, 45:180, 50:180, 55:180, 60:180, 65:180, 70:180, 75:180, 80:180, 85:180, 90:180, 95:180, 100:180, 105:180, 110:180, 115:180, 120:180, 125:180, 130:180, 132:180.

[0064] In some embodiments, the degrading agent is selected from starch-based polyether polyols.

[0065] In some embodiments, the starch-based polyether polyol has a hydroxyl value of 300-600 mg KOH / g, for example, 300 mg KOH / g, 350 mg KOH / g, 400 mg KOH / g, 450 mg KOH / g, 500 mg KOH / g, 550 mg KOH / g, and 600 mg KOH / g.

[0066] In some embodiments, the starch-based polyether polyol has a hydroxyl value of 400-500 mg KOH / g, for example, 400 mg KOH / g, 410 mg KOH / g, 420 mg KOH / g, 440 mg KOH / g, 450 mg KOH / g, 460 mg KOH / g, 470 mg KOH / g, 480 mg KOH / g, 490 mg KOH / g, and 500 mg KOH / g.

[0067] In some embodiments, the degrading agent is selected from polycaprolactone.

[0068] In some embodiments, the molecular weight of the polycaprolactone is 10,000 to 120,000, for example, 10,000, 20,000, 30,000, 40,000, 50,000, 60,000, 70,000, 80,000, 90,000, 100,000, 110,000, and 120,000.

[0069] In some embodiments, the molecular weight of the polycaprolactone is 20,000 to 110,000.

[0070] In some preferred embodiments, the molecular weight of the polycaprolactone is 30,000 to 110,000.

[0071] In some preferred embodiments, the molecular weight of the polycaprolactone is 40,000 to 100,000.

[0072] In some preferred embodiments, the molecular weight of the polycaprolactone is 50,000 to 100,000.

[0073] In some preferred embodiments, the molecular weight of the polycaprolactone is 60,000 to 90,000.

[0074] In some embodiments, the degrading agent is selected from polylactic acid, which enables the foam prepared from the foaming composition to obtain better biodegradability and mechanical properties.

[0075] In some embodiments, the polylactic acid has a molecular weight of 30,000 to 150,000, for example, 30,000, 40,000, 50,000, 60,000, 70,000, 80,000, 90,000, 100,000, 110,000, 120,000, 130,000, 140,000, and 150,000.

[0076] In some preferred embodiments, the polylactic acid has a molecular weight of 50,000 to 140,000.

[0077] In some preferred embodiments, the polylactic acid has a molecular weight of 70,000 to 120,000.

[0078] In some preferred embodiments, the polylactic acid has a molecular weight of 80,000 to 110,000.

[0079] In some embodiments, the foamable composition comprises, by weight, 64-120 parts of a first comonomer, 64-120 parts of a second comonomer, 1.2-3 parts of an initiator, 10-18 parts of a foaming agent, 0.8-2.4 parts of a crosslinking agent, 30-132 parts of a degrading agent, and 0-2.4 parts of a third comonomer.

[0080] In some embodiments, the degrading agent is in the form of 30-132 parts by weight, for example 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, 90 parts, 95 parts, 100 parts, 105 parts, 110 parts, 115 parts, 120 parts, 125 parts, 129 parts, or 132 parts.

[0081] In some embodiments, the degradation agent is 40-95 parts by weight.

[0082] In some embodiments, the degradation agent is 50-110 parts by weight.

[0083] In some preferred embodiments, the degrading agent is 50-100 parts by weight.

[0084] In some preferred embodiments, the degrading agent is 50-90 parts by weight.

[0085] In some preferred embodiments, the degradation agent is 60-90 parts by weight.

[0086] In some preferred embodiments, the degrading agent is 70-90 parts by weight.

[0087] In some preferred embodiments, the degrading agent is 75-90 parts by weight.

[0088] In some preferred embodiments, the degrading agent is 75-85 parts by weight.

[0089] In some embodiments, the foamable composition comprises, by weight, 72-110 parts of a first comonomer, 72-110 parts of a second comonomer, 1.8-2.75 parts of an initiator, 11.25-16.5 parts of a foaming agent, 0.9-2.2 parts of a crosslinking agent, 40-121 parts of a degrading agent, and 0.9-2.2 parts of a third comonomer.

[0090] In some embodiments, the degrading agent is in the form of 40-121 parts by weight, for example 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, 90 parts, 95 parts, 100 parts, 105 parts, 110 parts, 115 parts, 118 parts, or 121 parts.

[0091] In some embodiments, the degradation agent is 40-95 parts by weight.

[0092] In some embodiments, the degradation agent is 50-110 parts by weight.

[0093] In some embodiments, the degradation agent is 50-100 parts by weight.

[0094] In some preferred embodiments, the degrading agent is 50-90 parts by weight.

[0095] In some preferred embodiments, the degradation agent is 60-90 parts by weight.

[0096] In some preferred embodiments, the degrading agent is 70-90 parts by weight.

[0097] In some preferred embodiments, the degrading agent is 75-90 parts by weight.

[0098] In some preferred embodiments, the degrading agent is 75-85 parts by weight.

[0099] In some embodiments, the foamable composition comprises, by weight, 80-100 parts of a first comonomer, 80-100 parts of a second comonomer, 2-2.5 parts of an initiator, 12.5-15 parts of a foaming agent, 1-2 parts of a crosslinking agent, 30-110 parts of a degrading agent, and 1-2 parts of a third comonomer.

[0100] In some embodiments, the degrading agent is 30-110 parts by weight, for example 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, 90 parts, 95 parts, 100 parts, 105 parts, or 110 parts.

[0101] In some preferred embodiments, the degrading agent is 40-95 parts by weight.

[0102] In some preferred embodiments, the degrading agent is 50-100 parts by weight.

[0103] In some preferred embodiments, the degrading agent is 50-90 parts by weight.

[0104] In some preferred embodiments, the degradation agent is 60-90 parts by weight.

[0105] In some preferred embodiments, the degrading agent is 70-90 parts by weight.

[0106] In some preferred embodiments, the degrading agent is 75-90 parts by weight.

[0107] In some preferred embodiments, the degrading agent is 75-85 parts by weight.

[0108] In some preferred embodiments, the foamable composition comprises, by weight, 80-100 parts of a first comonomer, 80-100 parts of a second comonomer, 2-2.5 parts of an initiator, 12.5-15 parts of a foaming agent, 1-2 parts of a crosslinking agent, 70-100 parts of a degrading agent, and 1-2 parts of a third comonomer.

[0109] In some embodiments, the foamable composition comprises, by weight, 72-88 parts of the first comonomer methacrylonitrile, 90-110 parts of the second comonomer methacrylic acid, 1.8-2.2 parts of the third comonomer methacrylamide, 2-2.75 parts of the initiator azobisisobutyronitrile, 11.25-13.75 parts of the foaming agent formamide, 1.8-2.2 parts of the crosslinking agent allyl methacrylate, and 30-99 parts of the degrading agent polylactic acid.

[0110] In some embodiments, the degrading agent is 30-99 parts by weight, for example 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, 90 parts, 95 parts, and 99 parts.

[0111] In some embodiments, the degradation agent is 40-95 parts by weight.

[0112] In some preferred embodiments, the degrading agent is 50-90 parts by weight.

[0113] In some preferred embodiments, the degradation agent is 60-90 parts by weight.

[0114] In some preferred embodiments, the degrading agent is 70-90 parts by weight.

[0115] In some preferred embodiments, the degrading agent is 75-90 parts by weight.

[0116] In some preferred embodiments, the degrading agent is 75-85 parts by weight.

[0117] In some embodiments, the foamable composition comprises, by weight, 90-110 parts of acrylonitrile as a first comonomer, 72-88 parts of methacrylic acid as a second comonomer, 0.9-1.1 parts of acrylamide as a third comonomer, 1.8-2.2 parts of tert-butyl peroxide (2-ethylhexanoate) as an initiator, 13.5-16.5 parts of isopropanol as a foaming agent, 0.9-1.1 parts of magnesium methacrylate as a crosslinking agent, and 30-99 parts of polylactic acid as a degradation agent.

[0118] In some embodiments, the degrading agent is 30-99 parts by weight, for example 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, 90 parts, 95 parts, and 99 parts.

[0119] In some embodiments, the degradation agent is 40-95 parts by weight.

[0120] In some embodiments, the degradation agent is 50-90 parts by weight.

[0121] In some preferred embodiments, the degradation agent is 60-90 parts by weight.

[0122] In some preferred embodiments, the degrading agent is 70-90 parts by weight.

[0123] In some preferred embodiments, the degrading agent is 75-90 parts by weight.

[0124] In some preferred embodiments, the degrading agent is 75-85 parts by weight.

[0125] In some embodiments, the foamable composition comprises, by weight, 80 parts of the first comonomer methacrylonitrile, 100 parts of the second comonomer methacrylic acid, 2 parts of the third comonomer methacrylamide, 2.5 parts of the initiator azobisisobutyronitrile, 12.5 parts of the foaming agent formamide, 2 parts of the crosslinking agent allyl methacrylate, and 30-90 parts of the degradation agent polylactic acid.

[0126] In some embodiments, the degrading agent is 30-90 parts by weight, for example 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, or 90 parts.

[0127] In some embodiments, the degradation agent is 40-90 parts by weight.

[0128] In some embodiments, the degradation agent is 50-90 parts by weight.

[0129] In some preferred embodiments, the degradation agent is 60-90 parts by weight.

[0130] In some preferred embodiments, the degrading agent is 70-90 parts by weight.

[0131] In some preferred embodiments, the degrading agent is 75-90 parts by weight.

[0132] In some preferred embodiments, the degrading agent is 75-85 parts by weight.

[0133] In some preferred embodiments, the foamable composition comprises, by weight, 80 parts of the first comonomer methacrylonitrile, 100 parts of the second comonomer methacrylic acid, 2 parts of the third comonomer methacrylamide, 2.5 parts of the initiator azobisisobutyronitrile, 12.5 parts of the foaming agent formamide, 2 parts of the crosslinking agent allyl methacrylate, and 90 parts of the degradation agent polylactic acid.

[0134] In some embodiments, the foamable composition comprises, by weight, 100 parts of acrylonitrile as a first comonomer, 80 parts of methacrylic acid as a second comonomer, 2 parts of methacrylamide as a third comonomer, 2 parts of tert-butyl peroxide (2-ethylhexanoate) as an initiator, 15 parts of isopropanol as a foaming agent, 1 part of magnesium methacrylate as a crosslinking agent, and 30-90 parts of polylactic acid as a degradation agent.

[0135] In some embodiments, the degrading agent is 30-90 parts by weight, for example 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, or 90 parts.

[0136] In some embodiments, the degradation agent is 40-90 parts by weight.

[0137] In some embodiments, the degradation agent is 50-90 parts by weight.

[0138] In some preferred embodiments, the degradation agent is 60-90 parts by weight.

[0139] In some preferred embodiments, the degrading agent is 70-90 parts by weight.

[0140] In some preferred embodiments, the degrading agent is 75-90 parts by weight.

[0141] In some preferred embodiments, the degrading agent is 75-85 parts by weight.

[0142] In some preferred embodiments, the foamable composition comprises, by weight, 100 parts of the first comonomer acrylonitrile, 80 parts of the second comonomer methacrylic acid, 2 parts of the third comonomer methacrylamide, 2 parts of the initiator tert-butyl peroxide (2-ethylhexanoate), 15 parts of the foaming agent isopropanol, 1 part of the crosslinking agent magnesium methacrylate, and 90 parts of the degradation agent polylactic acid.

[0143] In another respect, this disclosure provides a biodegradable foam obtained by foaming any of the aforementioned foamable compositions.

[0144] On the other hand, this disclosure provides a method for preparing biodegradable foam, comprising the following steps:

[0145] S1, Prepolymerization: A prepolymer is obtained by polymerizing any of the aforementioned foamable compositions;

[0146] S2. Heat treatment before foaming: The prepolymer is heat-treated to obtain the polymer;

[0147] S3. Foaming: The polymer is foamed to obtain foam.

[0148] In some embodiments, the polymerization reaction system contains a degrading agent, a comonomer, an initiator, a foaming agent, and a crosslinking agent, such that the degrading agent and the comonomer undergo in-situ polymerization.

[0149] In some embodiments, the polymerization reaction temperature is 20°C-60°C.

[0150] In some preferred embodiments, the polymerization reaction temperature is 30°C-55°C.

[0151] In some preferred embodiments, the polymerization reaction temperature is 35°C-50°C.

[0152] In some implementations, the heat treatment temperature is 60°C-120°C.

[0153] In some preferred embodiments, the heat treatment temperature is 80°C-110°C.

[0154] In some preferred embodiments, the heat treatment temperature is 100°C-120°C.

[0155] In some preferred embodiments, the heat treatment temperature is 100°C.

[0156] In some implementations, the foaming temperature is 160°C-250°C.

[0157] In some preferred embodiments, the foaming temperature is 180°C-250°C.

[0158] In some preferred embodiments, the foaming temperature is 180°C-220°C.

[0159] In some preferred embodiments, the foaming temperature is 200°C-220°C.

[0160] In some further preferred embodiments, the foaming temperature is 200°C.

[0161] In some embodiments, the preparation method further includes the following steps:

[0162] S4. Heat treatment after foaming: The foam is heat-treated at 135℃-220℃ to obtain high-temperature resistant foam.

[0163] In some preferred embodiments, the foam is heat-treated at 150°C-220°C.

[0164] In some preferred embodiments, the foam is heat-treated at 160°C-200°C.

[0165] In some preferred embodiments, the foam is heat-treated at 180°C-220°C.

[0166] In some further preferred embodiments, the foam is heat-treated at 180°C.

[0167] In another aspect, this disclosure also provides a method for preparing biodegradable PMI foam, the preparation steps of which are as follows:

[0168] S0. Ingredients: Add 1-100 parts of methacrylonitrile or acrylonitrile, 1-100 parts of methacrylic acid, 0-10 parts of third comonomer, 0.1-10 parts of initiator, 0.1-20 parts of foaming agent, 0.1-10 parts of crosslinking agent, and 50-90 parts of degradation agent to the reaction vessel according to the stated weight, stir evenly, mix thoroughly at room temperature, and then pour into the mold;

[0169] S1. Polymerization: Place the mold in a constant temperature water bath at 20℃-60℃ for 5-15 days to allow the degradation agent and MAA / MAN / AN comonomer to undergo in-situ polymerization to obtain PMI prepolymer containing degradation agent blocks.

[0170] S2. Pretreatment: Place the PMI prepolymer board in a circulating air oven at 60℃-120℃ for 6-20 hours to obtain the PMI polymer board.

[0171] S3. Foaming: The PMI polymer board is foamed at 160℃-250℃ to obtain PMI foam;

[0172] S4. Heat treatment: PMI foam is baked at 135℃-220℃ to obtain high-temperature resistant PMI foam.

[0173] In some implementations, in step S3, the PMI polymer board is foamed at 180°C-250°C.

[0174] In some preferred embodiments, in step S3, the PMI polymer board is foamed at 180°C-220°C.

[0175] In some preferred embodiments, in step S3, the PMI polymer board is foamed at 200°C-220°C.

[0176] In some preferred embodiments, in step S3, the PMI polymer board is foamed at 200°C.

[0177] In some implementations, the PMI polymer board is foamed at the aforementioned temperature for 4 to 8 hours.

[0178] In some preferred embodiments, the PMI polymer board is foamed at the aforementioned temperature for 4 hours.

[0179] In some implementations, in step S4, the PMI foam is baked at 150°C-220°C.

[0180] In some preferred embodiments, in step S4, the PMI foam is baked at 160°C-200°C.

[0181] In some preferred embodiments, in step S4, the PMI foam is baked at 180°C-220°C.

[0182] In some preferred embodiments, in step S4, the PMI foam is baked at 180°C.

[0183] In some implementations, the PMI foam is baked at the aforementioned temperature for 20 to 48 hours.

[0184] In some preferred embodiments, the PMI foam is baked at the aforementioned temperature for 20-36 hours.

[0185] In some preferred embodiments, the PMI foam is baked at the aforementioned temperature for 24 hours.

[0186] In some embodiments, the preparation method includes the following steps (a) or (b):

[0187] (a)

[0188] S0. Ingredients: Add 80 parts of methacrylonitrile, 100 parts of methacrylic acid, 2 parts of methacrylamide, 2.5 parts of azobisisobutyronitrile, 12.5 parts of formamide, 2 parts of allyl methacrylate, and 90 parts of polylactic acid to the reaction vessel according to the stated weight, stir evenly, mix thoroughly at room temperature, and then pour into the mold.

[0189] S1. Polymerization: Place the mold in a constant temperature water bath at 35℃-50℃ for 5 days to allow the degradation agent and MAA / MAN / AN comonomer to undergo in-situ polymerization to obtain PMI prepolymer containing degradation agent blocks.

[0190] S2. Pretreatment: Place the PMI prepolymer board in a circulating air oven at 100°C for 6 hours to obtain the PMI polymer board.

[0191] S3. Foaming: The PMI polymer board is foamed at 200℃ for 4 hours to obtain PMI foam;

[0192] S4. Heat treatment: PMI foam is baked at 180℃ for 24 hours to obtain high-temperature resistant PMI foam;

[0193] or

[0194] (b)

[0195] S0. Ingredients: Add 100 parts of acrylonitrile, 80 parts of methacrylic acid, 1 part of acrylamide, 2 parts of tert-butyl peroxide (2-ethylhexanoate), 15 parts of isopropanol, 1 part of magnesium methacrylate, and 90 parts of polylactic acid to the reaction vessel according to the weight specified. Stir evenly and mix thoroughly at room temperature before pouring into the mold.

[0196] S1. Polymerization: Place the mold in a constant temperature water bath at 35℃-50℃ for 5 days to allow the degradation agent and MAA / MAN / AN comonomer to undergo in-situ polymerization to obtain PMI prepolymer containing degradation agent blocks.

[0197] S2. Pretreatment: Place the PMI prepolymer board in a circulating air oven at 100°C for 6 hours to obtain the PMI polymer board.

[0198] S3. Foaming: The PMI polymer board is foamed at 200℃ for 4 hours to obtain PMI foam;

[0199] S4. Heat treatment: PMI foam is baked at 180℃ for 24 hours to obtain high-temperature resistant PMI foam.

[0200] The following specific embodiments illustrate some implementations of biodegradable foams disclosed herein. The raw materials used in the following embodiments are all conventional commercially available products.

[0201] in,

[0202] Methacrylonitrile: Purity ≥ 99.5%

[0203] Methacrylic acid: purity ≥ 99%

[0204] Methacrylamide: Purity ≥ 98%

[0205] Acrylamide: Purity ≥ 98%

[0206] Azobisisobutyronitrile (AIB): Purity ≥ 99%

[0207] tert-butyl peroxide (2-ethylhexanoate): Purity: ≥97%

[0208] Formamide: Purity ≥ 99.5%

[0209] Isopropanol: Purity ≥ 99%

[0210] Propyl methacrylate: Purity ≥ 95%

[0211] Magnesium methacrylate: Purity ≥ 98%

[0212] Polylactic acid: Molecular weight: 70,000-120,000

[0213] Polycaprolactone: Molecular weight: 50,000-100,000

[0214] Starch-based polyether polyols: The hydroxyl value of the polyol is 400-500 mg KOH / g.

[0215] Example 1

[0216] The foamable composition comprises 80 parts of the first comonomer methacrylonitrile, 100 parts of the second comonomer methacrylic acid, 2 parts of the third comonomer methacrylamide, 2.5 parts of the initiator azobisisobutyronitrile, 12.5 parts of the foaming agent formamide, and 2 parts of the crosslinking agent allyl methacrylate.

[0217] S0. Ingredients: Add 80 parts of methacrylonitrile, 100 parts of methacrylic acid, 2 parts of methacrylamide, 2.5 parts of azobisisobutyronitrile, 12.5 parts of formamide, and 2 parts of allyl methacrylate to the reaction vessel according to the stated weight, stir evenly, and pour into the mold after fully mixing at room temperature.

[0218] S1. Prepolymerization: Place the mold in a water bath at a constant temperature of 35℃-50℃ for 5 days to obtain a transparent PMI prepolymer board.

[0219] S2. Heat treatment before foaming: Place the PMI prepolymer board in a circulating air oven and treat it at 100°C for 6 hours to obtain the PMI polymer board.

[0220] S3. Foaming: The PMI polymer board is foamed at 200℃ for 4 hours to obtain PMI foam;

[0221] S4. Heat treatment after foaming: Treat the PMI foam at 180℃ for 24 hours to obtain high-temperature resistant PMI foam.

[0222] Example 2

[0223] The foamable composition comprises 80 parts of the first comonomer methacrylonitrile, 100 parts of the second comonomer methacrylic acid, 2 parts of the third comonomer methacrylamide, 2.5 parts of the initiator azobisisobutyronitrile, 12.5 parts of the foaming agent formamide, 2 parts of the crosslinking agent allyl methacrylate, and 90 parts of the degradation agent polylactic acid.

[0224] S0. Ingredients: Add 80 parts of methacrylonitrile, 100 parts of methacrylic acid, 2 parts of methacrylamide, 2.5 parts of azobisisobutyronitrile, 12.5 parts of formamide, and 2 parts of allyl methacrylate to the reaction vessel according to the stated weight, stir evenly, and pour into the mold after fully mixing at room temperature.

[0225] S1. Prepolymerization: Place the mold in a water bath at a constant temperature of 35℃-50℃ for 5 days to obtain a transparent PMI prepolymer board.

[0226] S2. Heat treatment before foaming: Place the PMI prepolymer board in a circulating air oven and treat it at 100°C for 6 hours to obtain the PMI polymer board.

[0227] S3. Mixing: After crushing the PMI polymer board into granules, add 90 parts of polylactic acid and 8 parts of epoxy resin, and mix and stir evenly.

[0228] S4. Foaming: Place the above PMI mixture in a mold and foam at 200°C for 4 hours to obtain PMI foam;

[0229] S5. Heat treatment after foaming: Treat the PMI foam at 180℃ for 24 hours to obtain high-temperature resistant PMI foam.

[0230] Example 3

[0231] The foamable composition comprises 80 parts of the first comonomer methacrylonitrile, 100 parts of the second comonomer methacrylic acid, 2 parts of the third comonomer methacrylamide, 2.5 parts of the initiator azobisisobutyronitrile, 12.5 parts of the foaming agent formamide, 2 parts of the crosslinking agent allyl methacrylate, and 90 parts of the degradation agent polycaprolactone.

[0232] S0. Ingredients: Add 80 parts of methacrylonitrile, 100 parts of methacrylic acid, 2 parts of methacrylamide, 2.5 parts of azobisisobutyronitrile, 12.5 parts of formamide, and 2 parts of allyl methacrylate to the reaction vessel according to the stated weight, stir evenly, and pour into the mold after fully mixing at room temperature.

[0233] S1. Prepolymerization: Place the mold in a water bath at a constant temperature of 35℃-50℃ for 5 days to obtain a transparent PMI prepolymer board.

[0234] S2. Heat treatment before foaming: Place the PMI prepolymer board in a circulating air oven and treat it at 100°C for 6 hours to obtain the PMI polymer board.

[0235] S3. Mixing: After crushing the PMI polymer board into granules, add 90 parts of polycaprolactone and 8 parts of epoxy resin, and mix and stir evenly.

[0236] S4. Foaming: Place the above PMI mixture in a mold and foam at 200°C for 4 hours to obtain PMI foam;

[0237] S5. Heat treatment after foaming: Treat the PMI foam at 180℃ for 24 hours to obtain high-temperature resistant PMI foam.

[0238] Example 4

[0239] The foamable composition comprises 80 parts of the first comonomer methacrylonitrile, 100 parts of the second comonomer methacrylic acid, 2 parts of the third comonomer methacrylamide, 2.5 parts of the initiator azobisisobutyronitrile, 12.5 parts of the foaming agent formamide, 2 parts of the crosslinking agent allyl methacrylate, and 90 parts of the degradation agent starch-based polyether polyol.

[0240] S0. Ingredients: Add 80 parts of methacrylonitrile, 100 parts of methacrylic acid, 2 parts of methacrylamide, 2.5 parts of azobisisobutyronitrile, 12.5 parts of formamide, and 2 parts of allyl methacrylate to the reaction vessel according to the stated weight, stir evenly, and pour into the mold after fully mixing at room temperature.

[0241] S1. Prepolymerization: Place the mold in a water bath at a constant temperature of 35℃-50℃ for 5 days to obtain a transparent PMI prepolymer board.

[0242] S2. Heat treatment before foaming: Place the PMI prepolymer board in a circulating air oven and treat it at 100°C for 6 hours to obtain the PMI polymer board.

[0243] S3. Mixing: After crushing the PMI polymer board into granules, add 90 parts of starch-based polyether polyol and 8 parts of epoxy resin, and mix and stir evenly.

[0244] S4. Foaming: Place the above PMI mixture in a mold and foam at 200°C for 4 hours to obtain PMI foam;

[0245] S5. Heat treatment after foaming: Treat the PMI foam at 180℃ for 24 hours to obtain high-temperature resistant PMI foam.

[0246] Performance Test 1

[0247] The PMI foams obtained in Examples 1-4 were subjected to mechanical property tests, including density, compressibility, and tensile properties, as well as a 180-day biodegradation rate measurement. Density was tested according to GB / T 6343, compressibility according to GB / T 8813, tensile properties according to GB / T 1040.2, and biodegradability according to GB / T 19277.1-2011. The test results are as follows:

[0248] Test Result Table

[0249] According to GB / T 20197-2006, a biodegradability rate of 60% or higher meets the technical requirements for the degradation performance of biodegradable or compostable plastics. The test results show that in Examples 2-4, after adding the degradation agents polylactic acid, polycaprolactone, and starch-based polyether polyol, the biodegradability rate of PMI foam all exceeded 60%, meeting the technical requirements for the degradation performance of biodegradable or compostable plastics.

[0250] Generally, the mechanical properties of PMI foam increase with increasing density. The foam densities of Examples 2-4 are higher than those of Example 1, but their mechanical properties are all lower than those of the foam in Example 1.

[0251] Example 5

[0252] The foamable composition comprises 80 parts of the first comonomer methacrylonitrile, 100 parts of the second comonomer methacrylic acid, 2 parts of the third comonomer methacrylamide, 2.5 parts of the initiator azobisisobutyronitrile, 12.5 parts of the foaming agent formamide, 2 parts of the crosslinking agent allyl methacrylate, and 90 parts of the degradation agent polylactic acid.

[0253] S0. Ingredients: Add 80 parts of methacrylonitrile, 100 parts of methacrylic acid, 2 parts of methacrylamide, 2.5 parts of azobisisobutyronitrile, 12.5 parts of formamide, 2 parts of allyl methacrylate, and 90 parts of polylactic acid to the reaction vessel according to the stated weight parts, stir evenly, mix thoroughly at room temperature, and then pour into the mold.

[0254] S1. Prepolymerization: Place the mold in a constant temperature water bath at 35℃-50℃ for 5 days to allow the degradation agent and MAA / MAN comonomer to undergo in-situ polymerization to obtain PMI prepolymer containing degradation agent blocks.

[0255] S2. Heat treatment before foaming: Place the PMI prepolymer board in a circulating air oven and treat it at 100°C for 6 hours to obtain the PMI polymer board.

[0256] S3. Foaming: The PMI polymer board is foamed at 200℃ for 4 hours to obtain PMI foam;

[0257] S4. Heat treatment after foaming: Treat the PMI foam at 180℃ for 24 hours to obtain high-temperature resistant PMI foam.

[0258] Example 6

[0259] The foamable composition comprises 80 parts of the first comonomer methacrylonitrile, 100 parts of the second comonomer methacrylic acid, 2 parts of the third comonomer methacrylamide, 2.5 parts of the initiator azobisisobutyronitrile, 12.5 parts of the foaming agent formamide, 2 parts of the crosslinking agent allyl methacrylate, and 90 parts of the degradation agent polycaprolactone.

[0260] S0. Ingredients: Add 80 parts of methacrylonitrile, 100 parts of methacrylic acid, 2 parts of methacrylamide, 2.5 parts of azobisisobutyronitrile, 12.5 parts of formamide, 2 parts of allyl methacrylate, and 90 parts of polycaprolactone to the reaction vessel according to the stated weight, stir evenly, mix thoroughly at room temperature, and then pour into the mold.

[0261] S1. Polymerization: Place the mold in a constant temperature water bath at 35℃-50℃ for 5 days to allow the degradation agent and MAA / MAN comonomer to undergo in-situ polymerization to obtain PMI prepolymer containing degradation agent blocks.

[0262] S2. Heat treatment before foaming: Place the PMI prepolymer board in a circulating air oven and treat it at 100°C for 6 hours to obtain the PMI polymer board.

[0263] S3. Foaming: The PMI polymer board is foamed at 200℃ for 4 hours to obtain PMI foam;

[0264] S4. Heat treatment after foaming: Treat the PMI foam at 180℃ for 24 hours to obtain high-temperature resistant PMI foam.

[0265] Example 7

[0266] The foamable composition comprises 80 parts of the first comonomer methacrylonitrile, 100 parts of the second comonomer methacrylic acid, 2 parts of the third comonomer methacrylamide, 2.5 parts of the initiator azobisisobutyronitrile, 12.5 parts of the foaming agent formamide, 2 parts of the crosslinking agent allyl methacrylate, and 90 parts of the degradation agent starch-based polyether polyol.

[0267] S0. Ingredients: Add 80 parts of methacrylonitrile, 100 parts of methacrylic acid, 2 parts of methacrylamide, 2.5 parts of azobisisobutyronitrile, 12.5 parts of formamide, 2 parts of allyl methacrylate, and 90 parts of starch-based polyether polyol to the reaction vessel according to the stated weight, stir evenly, mix thoroughly at room temperature, and then pour into the mold.

[0268] S1. Prepolymerization: Place the mold in a constant temperature water bath at 35℃-50℃ for 5 days to allow the degradation agent and MAA / MAN comonomer to undergo in-situ polymerization to obtain PMI prepolymer containing degradation agent blocks.

[0269] S2. Heat treatment before foaming: Place the PMI prepolymer board in a circulating air oven and treat it at 100°C for 6 hours to obtain the PMI polymer board.

[0270] S3. Foaming: The PMI polymer board is foamed at 200℃ for 4 hours to obtain PMI foam;

[0271] S4. Heat treatment after foaming: Treat the PMI foam at 180℃ for 24 hours to obtain high-temperature resistant PMI foam.

[0272] Performance Test 2

[0273] Following the method described in Performance Testing 1, the mechanical properties of the PMI foam obtained in Examples 5-7, including density, compressibility, and tensile properties, as well as the final biodegradation rate after 180 days, were tested. The test results are as follows:

[0274] Test Result Table

[0275] The test results show that after adding the degradation agents polylactic acid, polycaprolactone, and starch-based polyether polyol in Examples 5-7, the biodegradability rate of PMI foam exceeded 60%, meeting the technical requirements for the degradation performance of biodegradable or compostable plastics.

[0276] Compared to the segmented mixing of Examples 2-4, where a degrading agent was added after prepolymerization, Examples 5-7 involved in-situ polymerization with a degrading agent added during the prepolymerization step. Examples 5-7 yielded PMI foams with densities essentially the same as those in Example 1, but with significantly improved mechanical properties compared to Examples 2-4. Simultaneously, the biodegradability of the PMI foams prepared in Examples 5-7 was also improved. In particular, Example 5, using polylactic acid as a degrading agent, produced PMI foams with lower densities than Examples 6 and 7, but with superior biodegradability and mechanical properties.

[0277] Example 8

[0278] The foamable composition comprises 80 parts of the first comonomer methacrylonitrile, 100 parts of the second comonomer methacrylic acid, 2 parts of the third comonomer methacrylamide, 2.5 parts of the initiator azobisisobutyronitrile, 12.5 parts of the foaming agent formamide, 2 parts of the crosslinking agent allyl methacrylate, and 30 parts of the degradation agent polylactic acid.

[0279] S0. Ingredients: Add 80 parts of methacrylonitrile, 100 parts of methacrylic acid, 2 parts of methacrylamide, 2.5 parts of azobisisobutyronitrile, 12.5 parts of formamide, 2 parts of allyl methacrylate, and 30 parts of polylactic acid to the reaction vessel according to the stated weight, stir evenly, mix thoroughly at room temperature, and then pour into the mold.

[0280] S1. Prepolymerization: Place the mold in a constant temperature water bath at 35℃-50℃ for 5 days to allow the degradation agent and MAA / MAN comonomer to undergo in-situ polymerization to obtain PMI prepolymer containing degradation agent blocks.

[0281] S2. Heat treatment before foaming: Place the PMI prepolymer board in a circulating air oven and treat it at 100°C for 6 hours to obtain the PMI polymer board.

[0282] S3. Foaming: The PMI polymer board is foamed at 200℃ for 4 hours to obtain PMI foam;

[0283] S4. Heat treatment after foaming: Treat the PMI foam at 180℃ for 24 hours to obtain high-temperature resistant PMI foam.

[0284] Example 9

[0285] The foamable composition comprises 80 parts of the first comonomer methacrylonitrile, 100 parts of the second comonomer methacrylic acid, 2 parts of the third comonomer methacrylamide, 2.5 parts of the initiator azobisisobutyronitrile, 12.5 parts of the foaming agent formamide, 2 parts of the crosslinking agent allyl methacrylate, and 40 parts of the degradation agent polylactic acid.

[0286] S0. Ingredients: Add 80 parts of methacrylonitrile, 100 parts of methacrylic acid, 2 parts of methacrylamide, 2.5 parts of azobisisobutyronitrile, 12.5 parts of formamide, 2 parts of allyl methacrylate, and 40 parts of polylactic acid to the reaction vessel according to the stated weight parts, stir evenly, and after fully mixing at room temperature, pour into the mold.

[0287] S1. Prepolymerization: Place the mold in a water bath at 35℃-50℃ for 5 days to allow the degradation agent and MAA / MAN comonomer to undergo in-situ polymerization, resulting in a transparent PMI prepolymer containing the degradation agent block.

[0288] S2. Heat treatment before foaming: Place the PMI prepolymer board in a circulating air oven and treat it at 100°C for 6 hours to obtain the PMI polymer board.

[0289] S3. Foaming: The PMI polymer board is foamed at 200℃ for 4 hours to obtain PMI foam;

[0290] S4. Heat treatment after foaming: Treat the PMI foam at 180℃ for 24 hours to obtain high-temperature resistant PMI foam.

[0291] Example 10

[0292] The foamable composition comprises 80 parts of the first comonomer methacrylonitrile, 100 parts of the second comonomer methacrylic acid, 2 parts of the third comonomer methacrylamide, 2.5 parts of the initiator azobisisobutyronitrile, 12.5 parts of the foaming agent formamide, 2 parts of the crosslinking agent allyl methacrylate, and 50 parts of the degradation agent polylactic acid.

[0293] S0. Ingredients: Add 80 parts of methacrylonitrile, 100 parts of methacrylic acid, 2 parts of methacrylamide, 2.5 parts of azobisisobutyronitrile, 12.5 parts of formamide, 2 parts of allyl methacrylate, and 50 parts of polylactic acid to the reaction vessel according to the weight specified. Stir evenly and mix thoroughly at room temperature before pouring into the mold.

[0294] S1. Prepolymerization: Place the mold in a constant temperature water bath at 35℃-50℃ for 5 days to allow the degradation agent and MAA / MAN comonomer to undergo in-situ polymerization to obtain PMI prepolymer containing degradation agent blocks.

[0295] S2. Heat treatment before foaming: Place the PMI prepolymer board in a circulating air oven and treat it at 100°C for 6 hours to obtain the PMI polymer board.

[0296] S3. Foaming: The PMI polymer board is foamed at 200℃ for 4 hours to obtain PMI foam;

[0297] S4. Heat treatment after foaming: Treat the PMI foam at 180℃ for 24 hours to obtain high-temperature resistant PMI foam.

[0298] Example 11

[0299] The foamable composition comprises 80 parts of the first comonomer methacrylonitrile, 100 parts of the second comonomer methacrylic acid, 2 parts of the third comonomer methacrylamide, 2.5 parts of the initiator azobisisobutyronitrile, 12.5 parts of the foaming agent formamide, 2 parts of the crosslinking agent allyl methacrylate, and 60 parts of the degradation agent polylactic acid.

[0300] S0. Ingredients: Add 80 parts of methacrylonitrile, 100 parts of methacrylic acid, 2 parts of methacrylamide, 2.5 parts of azobisisobutyronitrile, 12.5 parts of formamide, 2 parts of allyl methacrylate, and 60 parts of polylactic acid to the reaction vessel according to the weight specified. Stir evenly and mix thoroughly at room temperature before pouring into the mold.

[0301] S1. Prepolymerization: Place the mold in a constant temperature water bath at 35℃-50℃ for 5 days to allow the degradation agent and MAA / MAN comonomer to undergo in-situ polymerization to obtain PMI prepolymer containing degradation agent blocks.

[0302] S2. Heat treatment before foaming: Place the PMI prepolymer board in a circulating air oven and treat it at 100°C for 6 hours to obtain the PMI polymer board.

[0303] S3. Foaming: The PMI polymer board is foamed at 200℃ for 4 hours to obtain PMI foam;

[0304] S4. Heat treatment after foaming: Treat the PMI foam at 180℃ for 24 hours to obtain high-temperature resistant PMI foam.

[0305] Example 12

[0306] The foamable composition comprises 80 parts of the first comonomer methacrylonitrile, 100 parts of the second comonomer methacrylic acid, 2 parts of the third comonomer methacrylamide, 2.5 parts of the initiator azobisisobutyronitrile, 12.5 parts of the foaming agent formamide, 2 parts of the crosslinking agent allyl methacrylate, and 70 parts of the degradation agent polylactic acid.

[0307] S0. Ingredients: Add 80 parts of methacrylonitrile, 100 parts of methacrylic acid, 2 parts of methacrylamide, 2.5 parts of azobisisobutyronitrile, 12.5 parts of formamide, 2 parts of allyl methacrylate, and 70 parts of polylactic acid to the reaction vessel according to the stated weight parts, stir evenly, mix thoroughly at room temperature, and then pour into the mold.

[0308] S1. Prepolymerization: Place the mold in a constant temperature water bath at 35℃-50℃ for 5 days to allow the degradation agent and MAA / MAN comonomer to undergo in-situ polymerization to obtain PMI prepolymer containing degradation agent blocks.

[0309] S2. Heat treatment before foaming: Place the PMI prepolymer board in a circulating air oven and treat it at 100°C for 6 hours to obtain the PMI polymer board.

[0310] S3. Foaming: The PMI polymer board is foamed at 200℃ for 4 hours to obtain PMI foam;

[0311] S4. Heat treatment after foaming: Treat the PMI foam at 180℃ for 24 hours to obtain high-temperature resistant PMI foam.

[0312] Example 13

[0313] The foamable composition comprises 80 parts of the first comonomer methacrylonitrile, 100 parts of the second comonomer methacrylic acid, 2 parts of the third comonomer methacrylamide, 2.5 parts of the initiator azobisisobutyronitrile, 12.5 parts of the foaming agent formamide, 2 parts of the crosslinking agent allyl methacrylate, and 80 parts of the degradation agent polylactic acid.

[0314] S0. Ingredients: Add 80 parts of methacrylonitrile, 100 parts of methacrylic acid, 2 parts of methacrylamide, 2.5 parts of azobisisobutyronitrile, 12.5 parts of formamide, 2 parts of allyl methacrylate, and 80 parts of polylactic acid to the reaction vessel according to the stated weight parts, stir evenly, and after fully mixing at room temperature, pour into the mold.

[0315] S1. Prepolymerization: Place the mold in a constant temperature water bath at 35℃-50℃ for 5 days to allow the degradation agent and MAA / MAN comonomer to undergo in-situ polymerization to obtain PMI prepolymer containing degradation agent blocks.

[0316] S2. Heat treatment before foaming: Place the PMI prepolymer board in a circulating air oven and treat it at 100°C for 6 hours to obtain the PMI polymer board.

[0317] S3. Foaming: The PMI polymer board is foamed at 200℃ for 4 hours to obtain PMI foam;

[0318] S4. Heat treatment after foaming: Treat the PMI foam at 180℃ for 24 hours to obtain high-temperature resistant PMI foam.

[0319] Example 14

[0320] The foamable composition comprises 80 parts of the first comonomer methacrylonitrile, 100 parts of the second comonomer methacrylic acid, 2 parts of the third comonomer methacrylamide, 2.5 parts of the initiator azobisisobutyronitrile, 12.5 parts of the foaming agent formamide, 2 parts of the crosslinking agent allyl methacrylate, and 100 parts of the degradation agent polylactic acid.

[0321] S0. Ingredients: Add 80 parts of methacrylonitrile, 100 parts of methacrylic acid, 2 parts of methacrylamide, 2.5 parts of azobisisobutyronitrile, 12.5 parts of formamide, 2 parts of allyl methacrylate, and 100 parts of polylactic acid to the reaction vessel according to the stated weight parts, stir evenly, mix thoroughly at room temperature, and then pour into the mold.

[0322] S1. Prepolymerization: Place the mold in a constant temperature water bath at 35℃-50℃ for 5 days to allow the degradation agent and MAA / MAN comonomer to undergo in-situ polymerization to obtain PMI prepolymer containing degradation agent blocks.

[0323] S2. Pre-foaming treatment: Place the PMI prepolymer board in a circulating air oven and treat it at 100°C for 6 hours to obtain the PMI polymer board.

[0324] S3. Foaming: The PMI polymer board is foamed at 200℃ for 4 hours to obtain PMI foam;

[0325] S4. Heat treatment after foaming: Treat the PMI foam at 180℃ for 24 hours to obtain high-temperature resistant PMI foam.

[0326] Example 15

[0327] The foamable composition comprises 80 parts of the first comonomer methacrylonitrile, 100 parts of the second comonomer methacrylic acid, 2 parts of the third comonomer methacrylamide, 2.5 parts of the initiator azobisisobutyronitrile, 12.5 parts of the foaming agent formamide, 2 parts of the crosslinking agent allyl methacrylate, and 110 parts of the degradation agent polylactic acid.

[0328] S0. Ingredients: Add 80 parts of methacrylonitrile, 100 parts of methacrylic acid, 2 parts of methacrylamide, 2.5 parts of azobisisobutyronitrile, 12.5 parts of formamide, 2 parts of allyl methacrylate, and 110 parts of polylactic acid to the reaction vessel according to the stated weight, stir evenly, mix thoroughly at room temperature, and then pour into the mold.

[0329] S1. Prepolymerization: Place the mold in a constant temperature water bath at 35℃-50℃ for 5 days to allow the degradation agent and MAA / MAN comonomer to undergo in-situ polymerization to obtain PMI prepolymer containing degradation agent blocks.

[0330] S2. Pre-foaming treatment: Place the PMI prepolymer board in a circulating air oven and treat it at 100°C for 6 hours to obtain the PMI polymer board.

[0331] S3. Foaming: The PMI polymer board is foamed at 200℃ for 4 hours to obtain PMI foam;

[0332] S4. Heat treatment after foaming: Treat the PMI foam at 180℃ for 24 hours to obtain high-temperature resistant PMI foam.

[0333] Performance Test 3

[0334] Following the method described in Performance Testing 1, the mechanical properties of the PMI foam obtained in Examples 8-11, including density, compressibility, and tensile properties, as well as the final biodegradation rate after 180 days, were tested. The test results are as follows:

[0335] Test Result Table

[0336] The test results show that after adding 30-110 parts of polylactic acid as a degradation agent in Examples 8-15, the biodegradation rate of PMI foam exceeded 60%, meeting the technical requirements for degradation performance of biodegradable or compostable plastics.

[0337] Compared with Example 5, which added 90 parts of polylactic acid, the mechanical properties of Examples 14 and 15, which added more than 100 parts of polylactic acid, were significantly reduced.

[0338] Example 16

[0339] The foamable composition comprises 100 parts of the first comonomer acrylonitrile, 80 parts of the second comonomer methacrylic acid, 1 part of the third comonomer acrylamide, 2 parts of the initiator tert-butyl peroxide (2-ethylhexanoate), 15 parts of the foaming agent isopropanol, and 1 part of the crosslinking agent magnesium methacrylate.

[0340] S0. Ingredients: Add 100 parts of acrylonitrile, 80 parts of methacrylic acid, 1 part of acrylamide, 2 parts of tert-butyl peroxide (2-ethylhexanoate), 15 parts of isopropanol, and 1 part of magnesium methacrylate to the reaction vessel according to the stated weight parts, stir evenly, mix thoroughly at room temperature, and then pour into the mold.

[0341] S1. Prepolymerization: Place the mold in a water bath at a constant temperature of 35℃-50℃ for 5 days to obtain a transparent PMI prepolymer board.

[0342] S2. Heat treatment before foaming: Place the PMI prepolymer board in a circulating air oven and treat it at 100°C for 6 hours to obtain the PMI polymer board.

[0343] S3. Foaming: The PMI polymer board is foamed at 200℃ for 4 hours to obtain PMI foam;

[0344] S4. Heat treatment after foaming: Treat the PMI foam at 180℃ for 24 hours to obtain high-temperature resistant PMI foam.

[0345] Example 17

[0346] The foamable composition comprises 100 parts of the first comonomer acrylonitrile, 80 parts of the second comonomer methacrylic acid, 1 part of the third comonomer acrylamide, 2 parts of the initiator tert-butyl peroxide (2-ethylhexanoate), 15 parts of the foaming agent isopropanol, 1 part of the crosslinking agent magnesium methacrylate, and 90 parts of the degradation agent polylactic acid.

[0347] S0. Ingredients: Add 100 parts of acrylonitrile, 80 parts of methacrylic acid, 1 part of acrylamide, 2 parts of tert-butyl peroxide (2-ethylhexanoate), 15 parts of isopropanol, 1 part of magnesium methacrylate, and 90 parts of polylactic acid to the reaction vessel according to the weight specified. Stir evenly and mix thoroughly at room temperature before pouring into the mold.

[0348] S1. Prepolymerization: Place the mold in a constant temperature water bath at 35℃-50℃ for 5 days to allow the degradation agent and MAA / AN comonomer to undergo in-situ polymerization to obtain PMI prepolymer containing degradation agent blocks.

[0349] S2. Heat treatment before foaming: Place the PMI prepolymer board in a circulating air oven and treat it at 100°C for 6 hours to obtain the PMI polymer board.

[0350] S3. Foaming: The PMI polymer board is foamed at 200℃ for 4 hours to obtain PMI foam;

[0351] S4. Heat treatment after foaming: Treat the PMI foam at 180℃ for 24 hours to obtain high-temperature resistant PMI foam.

[0352] Performance Test 4

[0353] Following the method described in Performance Testing 1, the mechanical properties of the PMI foam obtained in Examples 16-17, including density, compressibility, and tensile properties, as well as the final biodegradation rate after 180 days, were tested. The test results are as follows:

[0354] Test Result Table

[0355] The test results show that after adding polylactic acid as a degrading agent to the basic formula 2 of this disclosure, the biodegradation rate of PMI foam exceeded 60%, meeting the technical requirements for the degradation performance of biodegradable or compostable plastics.

[0356] Compared with Example 5, Example 17 has a different basic formulation but the same degradation agent is added, resulting in a significant increase in the final tensile modulus of PMI foam.

[0357] In summary, the biodegradable PMI foam and its preparation method provided in this disclosure improve the biodegradability rate of PMI foam through the scientific addition of degradation agents and formulation adjustment. The technical solutions provided in some embodiments of this disclosure also retain the high mechanical properties of PMI foam.

[0358] Although embodiments of the present disclosure have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present disclosure, the scope of which is defined by the equivalents of the appended claims.

Claims

1. A foamable composition comprising a comonomer, an initiator, a foaming agent, and a crosslinking agent, wherein the comonomer comprises a first comonomer and a second comonomer, characterized in that: The first comonomer is selected from one or two of methacrylonitrile or acrylonitrile, and the second comonomer is selected from methacrylic acid; The composition further includes a degradation agent selected from one or more of polylactic acid, starch-based polyether polyol, and polycaprolactone; The mass ratio of the degrading agent to the comonomer is 30-132:

180.

2. The foamable composition according to claim 1, wherein, The comonomer also includes a third comonomer, which is selected from acrylamide monomers.

3. The foamable composition according to claim 2, wherein, The acrylamide monomers are selected from any one or a combination of two or more of acrylamide, methacrylamide, N-hydroxymethylacrylamide, and N,N-dimethylacrylamide.

4. The foamable composition according to any one of claims 1-3, wherein, The initiator is selected from any one or a combination of two or more of azobisisobutyronitrile, azobisisoheptanenitrile, tert-butyl peroxide (2-ethylhexanoate), and dilauryl peroxide; the foaming agent is selected from any one or a combination of two or more of formamide, N,N-dimethylformamide, isopropanol, isobutanol, octane, and isooctane; the crosslinking agent is any one or two of allyl methacrylate and magnesium methacrylate.

5. The foamable composition according to any one of claims 1-4, wherein, The molecular weight of the polylactic acid is 30,000-150,000, preferably 50,000-140,000, and more preferably 80,000-110,000; The molecular weight of the polycaprolactone is 10,000-120,000, preferably 40,000-100,000, and more preferably 60,000-90,000; The starch-based polyether polyol has a hydroxyl value of 300-600 mg KOH / g.

6. The foamable composition according to any one of claims 1-5, wherein, The degradation agent is selected from polylactic acid.

7. The foamable composition according to any one of claims 1-6, wherein, The mass ratio of the degrading agent to the comonomer is 50-110:

180.

8. The foamable composition according to any one of claims 1-7, wherein, The mass ratio of the first comonomer to the second comonomer is 0.6-1.5:

1.

9. The foamable composition according to any one of claims 1-8, wherein, By weight, it includes 64-120 parts of the first comonomer, 64-120 parts of the second comonomer, 1.2-3 parts of the initiator, 10-18 parts of the foaming agent, 0.8-2.4 parts of the crosslinking agent, 30-132 parts of the degrading agent, and 0-2.4 parts of the third comonomer.

10. The foamable composition according to claim 9, wherein, By weight, it includes 72-110 parts of the first comonomer, 72-110 parts of the second comonomer, 1.8-2.75 parts of the initiator, 11.25-16.5 parts of the foaming agent, 0.9-2.2 parts of the crosslinking agent, 40-121 parts of the degrading agent, and 0.9-2.2 parts of the third comonomer; Preferably, the foamable composition comprises, by weight, 80-100 parts of a first comonomer, 80-100 parts of a second comonomer, 2-2.5 parts of an initiator, 12.5-15 parts of a foaming agent, 1-2 parts of a crosslinking agent, 30-110 parts of a degrading agent, and 0.9-2.2 parts of a third comonomer. Preferably, the foamable composition comprises, by weight, 80-100 parts of a first comonomer, 80-100 parts of a second comonomer, 2-2.5 parts of an initiator, 12.5-15 parts of a foaming agent, 1-2 parts of a crosslinking agent, 70-100 parts of a degrading agent, and 1-2 parts of a third comonomer.

11. The foamable composition according to claim 1, wherein, By weight, it includes 72-88 parts of the first comonomer methacrylonitrile, 90-110 parts of the second comonomer methacrylic acid, 1.8-2.2 parts of the third comonomer methacrylamide, 2-2.75 parts of the initiator azobisisobutyronitrile, 11.25-13.75 parts of the foaming agent formamide, 1.8-2.2 parts of the crosslinking agent allyl methacrylate, and 30-99 parts of the degradation agent polylactic acid; Preferably, the foamable composition, by weight, comprises 80 parts of the first comonomer methacrylonitrile, 100 parts of the second comonomer methacrylic acid, 2 parts of the third comonomer methacrylamide, 2.5 parts of the initiator azobisisobutyronitrile, 12.5 parts of the foaming agent formamide, 2 parts of the crosslinking agent allyl methacrylate, and 30-90 parts of the degradation agent polylactic acid.

12. The foamable composition according to claim 1, wherein, By weight, it includes 90-110 parts of the first comonomer acrylonitrile, 72-88 parts of the second comonomer methacrylic acid, 0.9-1.1 parts of the third comonomer acrylamide, 1.8-2.2 parts of the initiator tert-butyl peroxide (2-ethylhexanoate), 13.5-16.5 parts of the foaming agent isopropanol, 0.9-1.1 parts of the crosslinking agent magnesium methacrylate, and 30-99 parts of the degradation agent polylactic acid; Preferably, the foamable composition, by weight, comprises 100 parts of the first comonomer acrylonitrile, 80 parts of the second comonomer methacrylic acid, 2 parts of the third comonomer methacrylamide, 2 parts of the initiator tert-butyl peroxide (2-ethylhexanoate), 15 parts of the foaming agent isopropanol, 1 part of the crosslinking agent magnesium methacrylate, and 30-90 parts of the degradation agent polylactic acid.

13. The foamable composition according to any one of claims 9-12, wherein, By weight, it includes 70-90 parts of the degradation agent; Preferably, the foamable composition comprises, by weight, 90 parts of a degrading agent; Preferably, the foamable composition comprises, by weight, 80 parts of the first comonomer methacrylonitrile, 100 parts of the second comonomer methacrylic acid, 2 parts of the third comonomer methacrylamide, 2.5 parts of the initiator azobisisobutyronitrile, 12.5 parts of the foaming agent formamide, 2 parts of the crosslinking agent allyl methacrylate, and 90 parts of the degradation agent polylactic acid. Preferably, the foamable composition comprises, by weight, 100 parts of the first comonomer acrylonitrile, 80 parts of the second comonomer methacrylic acid, 1 part of the third comonomer acrylamide, 2 parts of the initiator tert-butyl peroxide (2-ethylhexanoate), 15 parts of the foaming agent isopropanol, 1 part of the crosslinking agent magnesium methacrylate, and 90 parts of the degradation agent polylactic acid.

14. A biodegradable foam, characterized in that, Obtained by foaming the foamable composition according to any one of claims 1-13.

15. A method for preparing biodegradable foam, characterized in that, Includes the following steps: S1. Prepolymerization: The foamable composition according to any one of claims 1-13 is subjected to a polymerization reaction to obtain a prepolymer; S2. Heat treatment before foaming: The prepolymer is heat-treated to obtain the polymer; S3. Foaming: The polymer is foamed to obtain foam.

16. The preparation method according to claim 15, wherein, In step S1, the polymerization reaction system contains a degrading agent, a comonomer, an initiator, a foaming agent, and a crosslinking agent.

17. The preparation method according to claim 15 or 16, wherein, In step S1, the polymerization reaction temperature is 20℃-60℃, preferably 30℃-55℃, and more preferably 35℃-50℃.

18. The preparation method according to any one of claims 15-17, wherein, The heat treatment temperature in step S2 is 60℃-120℃, preferably 100℃-120℃, and more preferably 100℃.

19. The preparation method according to any one of claims 15-18, wherein, The foaming temperature in step S3 is 160℃-250℃, preferably 180℃-250℃, more preferably 200℃-220℃, and even more preferably 200℃; Preferably, the foaming time in step S3 is 4 hours to 8 hours, more preferably 4 hours.

20. The preparation method according to any one of claims 15-19, further comprising the following steps: S4. Heat treatment after foaming: The foam is heat-treated at 135℃-220℃ to obtain high-temperature resistant foam; Preferably, the foam is heat-treated at 150℃-220℃, more preferably at 180℃-220℃, and even more preferably at 180℃; Preferably, the foam heat treatment time is 20-48 hours, more preferably 24-36 hours, and even more preferably 24 hours.

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