CN114891264A - Expanded microsphere foaming-based double-network rigid melamine foam material and preparation method thereof - Google Patents
Expanded microsphere foaming-based double-network rigid melamine foam material and preparation method thereof Download PDFInfo
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- CN114891264A CN114891264A CN202210563160.1A CN202210563160A CN114891264A CN 114891264 A CN114891264 A CN 114891264A CN 202210563160 A CN202210563160 A CN 202210563160A CN 114891264 A CN114891264 A CN 114891264A
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- melamine
- melamine resin
- resin precursor
- foaming
- foam
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- 229920000877 Melamine resin Polymers 0.000 title claims abstract description 171
- 238000005187 foaming Methods 0.000 title claims abstract description 88
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 title claims abstract description 70
- 239000004005 microsphere Substances 0.000 title claims abstract description 49
- 238000002360 preparation method Methods 0.000 title claims abstract description 27
- 239000006261 foam material Substances 0.000 title abstract description 18
- 239000004640 Melamine resin Substances 0.000 claims abstract description 99
- 239000002243 precursor Substances 0.000 claims abstract description 77
- 239000006260 foam Substances 0.000 claims abstract description 58
- 239000004088 foaming agent Substances 0.000 claims abstract description 26
- 239000007788 liquid Substances 0.000 claims abstract description 26
- 239000008098 formaldehyde solution Substances 0.000 claims abstract description 16
- 239000000178 monomer Substances 0.000 claims abstract description 16
- 239000003054 catalyst Substances 0.000 claims abstract description 11
- 239000003999 initiator Substances 0.000 claims abstract description 11
- 239000003381 stabilizer Substances 0.000 claims abstract description 11
- 238000006116 polymerization reaction Methods 0.000 claims abstract description 10
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 claims description 36
- 238000000034 method Methods 0.000 claims description 29
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical group [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 claims description 20
- 238000006243 chemical reaction Methods 0.000 claims description 20
- 238000003756 stirring Methods 0.000 claims description 18
- BIGPRXCJEDHCLP-UHFFFAOYSA-N ammonium bisulfate Chemical compound [NH4+].OS([O-])(=O)=O BIGPRXCJEDHCLP-UHFFFAOYSA-N 0.000 claims description 11
- 229910001870 ammonium persulfate Inorganic materials 0.000 claims description 10
- HRPVXLWXLXDGHG-UHFFFAOYSA-N Acrylamide Chemical compound NC(=O)C=C HRPVXLWXLXDGHG-UHFFFAOYSA-N 0.000 claims description 9
- 230000008569 process Effects 0.000 claims description 8
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 6
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 6
- 239000002994 raw material Substances 0.000 claims description 6
- 239000000243 solution Substances 0.000 claims description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 4
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 4
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 4
- 229920001169 thermoplastic Polymers 0.000 claims description 4
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 claims description 3
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 claims description 3
- -1 acyl morpholine acrylate Chemical compound 0.000 claims description 3
- 150000001335 aliphatic alkanes Chemical class 0.000 claims description 3
- 238000007031 hydroxymethylation reaction Methods 0.000 claims description 3
- 239000011259 mixed solution Substances 0.000 claims description 3
- 229920005989 resin Polymers 0.000 claims description 3
- 239000011347 resin Substances 0.000 claims description 3
- 229920002545 silicone oil Polymers 0.000 claims description 3
- 229920001187 thermosetting polymer Polymers 0.000 claims description 3
- 229920002818 (Hydroxyethyl)methacrylate Polymers 0.000 claims description 2
- JKNCOURZONDCGV-UHFFFAOYSA-N 2-(dimethylamino)ethyl 2-methylprop-2-enoate Chemical compound CN(C)CCOC(=O)C(C)=C JKNCOURZONDCGV-UHFFFAOYSA-N 0.000 claims description 2
- OMIGHNLMNHATMP-UHFFFAOYSA-N 2-hydroxyethyl prop-2-enoate Chemical compound OCCOC(=O)C=C OMIGHNLMNHATMP-UHFFFAOYSA-N 0.000 claims description 2
- WOBHKFSMXKNTIM-UHFFFAOYSA-N Hydroxyethyl methacrylate Chemical compound CC(=C)C(=O)OCCO WOBHKFSMXKNTIM-UHFFFAOYSA-N 0.000 claims description 2
- CERQOIWHTDAKMF-UHFFFAOYSA-N Methacrylic acid Chemical compound CC(=C)C(O)=O CERQOIWHTDAKMF-UHFFFAOYSA-N 0.000 claims description 2
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 2
- 239000011258 core-shell material Substances 0.000 claims description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims description 2
- 239000002245 particle Substances 0.000 claims description 2
- 229940008099 dimethicone Drugs 0.000 claims 1
- 235000013870 dimethyl polysiloxane Nutrition 0.000 claims 1
- 239000004205 dimethyl polysiloxane Substances 0.000 claims 1
- 229920000435 poly(dimethylsiloxane) Polymers 0.000 claims 1
- 238000004132 cross linking Methods 0.000 abstract description 4
- 238000013012 foaming technology Methods 0.000 abstract description 2
- IVJISJACKSSFGE-UHFFFAOYSA-N formaldehyde;1,3,5-triazine-2,4,6-triamine Chemical compound O=C.NC1=NC(N)=NC(N)=N1 IVJISJACKSSFGE-UHFFFAOYSA-N 0.000 abstract description 2
- 229920000642 polymer Polymers 0.000 abstract description 2
- 239000002861 polymer material Substances 0.000 abstract description 2
- 238000001029 thermal curing Methods 0.000 abstract 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 19
- ZBCBWPMODOFKDW-UHFFFAOYSA-N diethanolamine Chemical compound OCCNCCO ZBCBWPMODOFKDW-UHFFFAOYSA-N 0.000 description 18
- 238000001723 curing Methods 0.000 description 14
- 239000005457 ice water Substances 0.000 description 10
- 239000007864 aqueous solution Substances 0.000 description 9
- 238000005520 cutting process Methods 0.000 description 9
- AMTWCFIAVKBGOD-UHFFFAOYSA-N dioxosilane;methoxy-dimethyl-trimethylsilyloxysilane Chemical compound O=[Si]=O.CO[Si](C)(C)O[Si](C)(C)C AMTWCFIAVKBGOD-UHFFFAOYSA-N 0.000 description 9
- 239000000203 mixture Substances 0.000 description 9
- 229940083037 simethicone Drugs 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 6
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 6
- 230000000694 effects Effects 0.000 description 3
- 239000004604 Blowing Agent Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000013007 heat curing Methods 0.000 description 2
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000012643 polycondensation polymerization Methods 0.000 description 2
- 238000006068 polycondensation reaction Methods 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 1
- 241001391944 Commicarpus scandens Species 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000004566 building material Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 125000000118 dimethyl group Chemical group [H]C([H])([H])* 0.000 description 1
- 238000007323 disproportionation reaction Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 235000019253 formic acid Nutrition 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 125000004029 hydroxymethyl group Chemical group [H]OC([H])([H])* 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000002715 modification method Methods 0.000 description 1
- QKQSRIKBWKJGHW-UHFFFAOYSA-N morpholine;prop-2-enoic acid Chemical compound OC(=O)C=C.C1COCCN1 QKQSRIKBWKJGHW-UHFFFAOYSA-N 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
- 239000003981 vehicle Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/32—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof from compositions containing microballoons, e.g. syntactic foams
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F283/00—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2203/00—Foams characterized by the expanding agent
- C08J2203/22—Expandable microspheres, e.g. Expancel®
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2351/00—Characterised by the use of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives of such polymers
- C08J2351/08—Characterised by the use of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives of such polymers grafted on to macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Phenolic Resins Or Amino Resins (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
Abstract
The invention relates to the technical field of high polymer materials, in particular to a double-network rigid melamine foam material based on expanded microsphere foaming and a preparation method thereof. The preparation method provided by the invention comprises the following steps: preparing a melamine-formaldehyde solution to obtain a melamine resin precursor; adding a foam stabilizer, a catalyst, a hydrophilic monomer, an initiator and an expanded microsphere foaming agent into a melamine resin precursor to obtain melamine resin precursor pre-polymerization liquid; the double-network rigid melamine foam based on the expansion microsphere foaming is prepared through microwave foaming and thermocuring. The invention adopts a thermal expansion microsphere foaming technology to controllably prepare the double-network double-crosslinking rigid melamine foam material with uniform structure. The advantages of different polymer networks are complemented, and the mechanical property of the rigid melamine foam material is greatly improved.
Description
Technical Field
The invention relates to the technical field of high polymer materials, in particular to a double-network rigid melamine foam material based on expanded microsphere foaming and a preparation method thereof.
Background
The rigid melamine foam is also called melamine formaldehyde rigid foam, and is a foam material prepared from melamine resin through a certain foaming process. The rigid melamine foam material has the characteristics of flame retardance, heat insulation, shock absorption, noise resistance and the like due to the unique pore structure and chemical properties, so that the rigid melamine foam material is widely applied to the fields of building materials, vehicle engineering and the like.
However, the traditional rigid melamine foam has mechanical problems of poor toughness, easy powder falling and the like due to the rigid high molecular structure. Meanwhile, rigid melamine foam materials prepared based on traditional chemical and physical foaming technologies often have cell structure defects, such as nonuniform cells, easy collapse and breakage of the structure, large opening rate and the like. These problems have greatly limited the range of applications for rigid melamine foams.
The existing research shows that the toughness of the melamine foam material can be improved by a physical modification method, a flexible chain lengthening method and a functional group end sealing method, but the methods cannot change the problems of nonuniform cells, large opening ratio and the like.
Therefore, the invention is especially provided.
Disclosure of Invention
In order to solve the problems, the invention provides a rigid melamine foam material with a novel structure and a preparation method thereof. The hard melamine foam material obtained by the invention has excellent mechanical properties of high toughness and difficult powder falling, and also has fine and uniform cell structure and higher closed cell rate.
In a first aspect, the present invention provides a method for preparing a rigid melamine foam, comprising:
s1, performing hydroxymethylation reaction on formaldehyde and melamine to obtain a melamine resin precursor;
s2, adding a foam stabilizer, a catalyst, a hydrophilic monomer, an initiator and an expanded microsphere foaming agent into the obtained melamine resin precursor, and uniformly mixing to obtain melamine resin precursor pre-polymerization liquid;
and S3, foaming and thermally curing the melamine resin precursor pre-polymerization liquid to obtain the rigid melamine foam.
According to the invention, a hydrophilic monomer polymerization reaction is introduced while the existing melamine resin polycondensation reaction is carried out, so that a double-network double-crosslinking structure is formed, and the mechanical toughness of the hard melamine resin foam material is improved; specifically, the first network is a high-density crosslinked melamine resin network formed by condensation polymerization of melamine resin oligomers and is used for bearing structural support; the second network is a high-mechanical-strength network formed by hydrophilic monomers, so that the gaps of the first network can be supplemented on the basis of keeping the original mechanical property of the melamine resin, and the toughness is improved; the advantages of the two polymer networks are complementary without losing the original characteristics, thereby greatly improving the mechanical toughness of the melamine resin and meeting the environmental protection requirement. The rigid melamine resin foam material with high toughness, fine and uniform cell structure and higher closed cell rate is obtained by improving the toughness of the melamine resin and improving the foaming method.
Meanwhile, the invention also selects the expanded microsphere foaming agent to prepare the foam material. Expanded microsphere blowing agents are thermoplastic hollow polymeric microspheres composed of a thermoplastic polymer shell and an encapsulated liquid alkane gas having an average diameter ranging from 10 μm to 50 μm, which expand when heated and stabilize against changes in volume when cooled. The foaming agent is selected for foaming a closed system, so that the foaming process is highly controllable and stable, a fine and uniform cell structure and a high closed cell rate are obtained, and the problems of cell breakage and collapse of the conventional hard melamine resin foam material are solved.
Further, the research of the invention finds that the hydroxymethyl reaction is slow and insufficient when the pH is too low, and the disproportionation reaction of formaldehyde is easy to generate formic acid and is not beneficial to the reaction when the pH is too high. Therefore, the pH of the reaction system is controlled to be between 8 and 9, and the reaction temperature is controlled to be between 80 and 90 ℃. The end point of the reaction was determined by measuring the water tolerance point with ice water. After the reaction is finished, the temperature of the system is reduced to 60 ℃, and the pH value of the system is controlled to be between 8 and 9, so that the melamine resin precursor is obtained.
In the S1, the formaldehyde is added in the form of a formaldehyde solution with a mass concentration of 37%; the mass ratio of the formaldehyde solution to the melamine is (201) -600): 270.
further, in S2, the melamine resin precursor obtained was allowed to stand at 25 ℃ for 1 to 2 days until the viscosity became 10 to 20 pas. The viscosity of the foaming agent is controlled to enable the foaming agent to have higher strength, so that the phenomena of breakage and collapse of cells in the foaming process are more effectively prevented.
In the S2, the mass ratio relationship of the raw materials is as follows: 100 parts of melamine resin precursor, 1-3 parts of foam stabilizer, 3-6 parts of catalyst, 1-3 parts of hydrophilic monomer, 0.01-0.15 part of initiator and 5-20 parts of expanded microsphere foaming agent.
In the S2, the feeding mode of each raw material is as follows: firstly, uniformly mixing a melamine resin precursor, a foam stabilizer, a catalyst, a hydrophilic monomer and an initiator to obtain a resin mixed solution; and adding an expanded microsphere foaming agent, and stirring uniformly at a high speed to obtain a melamine resin precursor prepolymer solution. Wherein the rotating speed of high-speed uniform stirring is 1000r/min, and the stirring time is 10-20 min.
In the S2, the expanded microsphere foaming agent is of a core-shell structure consisting of a thermoplastic polymer shell and liquid alkane gas, the particle size is 10-50 mu m, and the initial foaming temperature is not more than 150 ℃.
In S2, the hydrophilic monomer is selected from one or more of acrylic acid, acrylamide, hydroxyethyl acrylate, morpholine acrylate, N-dimethylacrylamide, methacrylic acid, hydroxyethyl methacrylate, dimethylaminoethyl methacrylate, and the like.
In the S2, the foam stabilizer is dimethyl silicone oil and/or hydroxyl silicone oil.
In the S2, the catalyst is one or more of acetic acid, phosphoric acid, hydrochloric acid, dilute sulfuric acid, ammonium bisulfate or citric acid.
In the S2, the initiator is ammonium persulfate.
Further, in S3, the foaming and heat curing conditions are as follows: foaming for 2-15min at 100-150 deg.C or under microwave 200-1000 w; curing at 100-120 ℃ for 2-4 h.
As one embodiment of the invention, the preparation of the rigid melamine foam comprises the following steps:
s1, performing hydroxymethylation reaction on formaldehyde and melamine, and controlling the pH of a reaction system to be between 8 and 9 and the reaction temperature to be between 85 and 90 ℃; after the reaction is finished, reducing the temperature of the system to 60 ℃, and controlling the pH of the system to be between 8.4 and 8.5 to obtain a melamine resin precursor;
the formaldehyde is added in the form of a formaldehyde solution with the mass concentration of 37%; the mass ratio of the formaldehyde solution to the melamine is (201) -600): 270;
s2, standing the obtained melamine resin precursor to enable the viscosity of the melamine resin precursor to reach 10-20 Pa.s, adding a foam stabilizer, a catalyst, a hydrophilic monomer, an initiator and an expanded microsphere foaming agent into the obtained melamine resin precursor, and uniformly mixing to obtain melamine resin precursor pre-polymerization liquid;
the feeding mode of each raw material is as follows: firstly, uniformly mixing a melamine resin precursor, a foam stabilizer, a catalyst, a hydrophilic monomer and an initiator to obtain a resin mixed solution; adding an expanded microsphere foaming agent, and stirring at a high speed to obtain a melamine resin precursor prepolymer solution; wherein the rotating speed of the high-speed uniform stirring is 1000r/min, and the stirring time is 10-20 min;
s3, foaming and thermosetting the obtained melamine resin precursor pre-polymerization liquid to obtain hard melamine foam;
in S3, the foaming and heat curing conditions are as follows: foaming for 2-15min at 100-150 deg.C or under microwave 200-1000 w; curing at 100-120 ℃ for 2-4 h.
In a second aspect, the present invention also provides a rigid melamine foam obtained by the above process.
The hard melamine foam material has a double-network double-crosslinking structure melamine foam; the dual-network dual-cross-connection structure includes: melamine resin networks formed by condensation polymerization of oligomers and networks formed by crosslinking of hydrophilic monomers.
The beneficial technical effects of the invention are embodied in the following aspects:
1. according to the invention, the foaming agent of the expanded microspheres is selected to foam a closed system, the foaming effect is achieved through expansion of the microspheres, the breakage and collapse of foam holes are avoided, and the closed-cell rate is effectively improved; simultaneously, the formed cell structure is uniform; meanwhile, the invention controls the viscosity of the melamine resin precursor for foaming to reach 10-20 Pa.s, so that the melamine resin precursor has certain strength and can also effectively prevent the breakage and the collapse of foam holes.
2. In order to solve the mechanical problem of the traditional hard melamine material, the invention utilizes two distinct high molecular networks as a dual-network interpenetrating system, wherein the first part of the dual-network is a high-density cross-linked melamine resin network formed by the polycondensation of oligomers, and the second part of the dual-network is a high-mechanical-strength network formed by functional polymerizable monomers; the melamine resin and the melamine resin have synergistic effect, so that the mechanical property of the melamine resin is greatly improved on the basis of keeping the original property.
3. In the method, foaming ways are various, the traditional heating foaming and the microwave foaming can be adopted, the dependence on equipment and instruments is reduced, and the production cost is greatly reduced.
4. The invention selects the expanded microsphere foaming agent, can ensure that the foaming process is highly controllable, and can control the foaming process through temperature, microwave power and time so as to achieve the control of the final foaming effect.
Detailed Description
The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
Example 1
The operation steps for preparing the rigid melamine foam are as follows:
(1) preparation of Melamine resin precursor
403g of formaldehyde solution is weighed and added into a reaction kettle, the temperature is raised to 60 ℃, and the mixture is stirred. 12.5g of diethanolamine is added, the pH is adjusted to 8.5, and the rotation speed is set to 180 r/min. Then adjusting the temperature to 90 ℃, adding 270g of melamine, setting the rotating speed to 200r/min, reacting for 10min after the temperature reaches 90 ℃, and measuring the water tolerance point by an ice water method. When the temperature reaches the water tolerance point, 11g of diethanolamine is added, and the temperature is reduced to 25 ℃ to obtain a melamine resin precursor.
And standing at 25 ℃ for 1 day until the viscosity of the melamine resin precursor reaches 10pa · s, and foaming.
(2) Preparation of expanded microsphere foaming-based double-network rigid melamine foam
Taking 100g of melamine resin precursor, 1g of simethicone, 6g of 50% ammonium bisulfate aqueous solution, 2g of acrylic acid, 0.02g of ammonium persulfate and 10g of expanded microsphere foaming agent (the foaming temperature is 85 ℃), and stirring for 10min at the rotating speed of 1000r/min by using a high-speed stirrer to obtain uniformly stirred melamine resin precursor prepolymer liquid.
And pouring the pre-polymerization solution of the melamine resin precursor into a mold, foaming for 10min at the temperature of 120 ℃, curing for 2h at the temperature of 120 ℃, and cutting and forming to obtain the double-network rigid melamine foam based on expansion microsphere foaming.
Example 2
The operation steps for preparing the rigid melamine foam are as follows:
(1) preparation of Melamine resin precursor
403g of formaldehyde solution is weighed and added into a reaction kettle, the temperature is raised to 60 ℃, and the mixture is stirred. 12.5g of diethanolamine was added, the pH was adjusted to 8.5 and the rotation speed was set to 180 r/min. Then adjusting the temperature to 90 ℃, adding 270g of melamine, setting the rotating speed to 200r/min, reacting for 10min after the temperature reaches 90 ℃, and measuring the water tolerance point by an ice water method. When the temperature reaches the water tolerance point, 11g of diethanolamine is added, and the temperature is reduced to 25 ℃ to obtain a melamine resin precursor.
And standing at 25 ℃ for 1 day until the viscosity of the melamine resin precursor reaches 10pa · s, and foaming.
(2) Preparation of expanded microsphere foaming-based double-network rigid melamine foam
Taking 100g of melamine resin precursor, 1g of simethicone, 6g of 50% ammonium bisulfate aqueous solution, 2g of acrylamide, 0.02g of ammonium persulfate and 10g of expanded microsphere foaming agent (the foaming temperature is 85 ℃), and stirring for 10min at the rotating speed of 1000r/min by using a high-speed stirrer to obtain the melamine resin precursor prepolymer liquid which is uniformly stirred.
And pouring the melamine resin foaming liquid into a mould, foaming for 10min at the temperature of 120 ℃, curing for 2h at the temperature of 120 ℃, and cutting and forming to obtain the double-network rigid melamine foam based on expansion microsphere foaming.
Example 3
The operation steps for preparing the rigid melamine foam are as follows:
(1) preparation of Melamine resin precursor
403g of formaldehyde solution is weighed and added into a reaction kettle, the temperature is raised to 60 ℃, and the mixture is stirred. 12.5g of diethanolamine was added, the pH was adjusted to 8.5 and the rotation speed was set to 180 r/min. Then adjusting the temperature to 90 ℃, adding 270g of melamine, setting the rotating speed to 200r/min, reacting for 10min after the temperature reaches 90 ℃, and measuring the water tolerance point by an ice water method. When the temperature reaches the water tolerance point, 11g of diethanolamine is added, and the temperature is reduced to 25 ℃ to obtain a melamine resin precursor.
And standing at 25 ℃ for 1 day until the viscosity of the melamine resin precursor reaches 10pa · s, and foaming.
(2) Preparation of expanded microsphere foaming-based double-network rigid melamine foam
Taking 100g of melamine resin precursor, 1g of simethicone, 6g of 50% ammonium bisulfate aqueous solution, 2g of acrylamide, 0.02g of ammonium persulfate and 10g of expanded microsphere foaming agent (foaming temperature of 120 ℃), and stirring for 10min at the rotating speed of 1000r/min by using a high-speed stirrer to obtain uniformly stirred melamine resin precursor prepolymer liquid.
And pouring the pre-polymerization solution of the melamine resin precursor into a mold, foaming for 10min at the temperature of 120 ℃, curing for 2h at the temperature of 120 ℃, and cutting and forming to obtain the double-network rigid melamine foam based on expansion microsphere foaming.
Example 4
The operation steps for preparing the rigid melamine foam are as follows:
(1) preparation of Melamine resin precursor
403g of formaldehyde solution is weighed and added into a reaction kettle, the temperature is raised to 60 ℃, and the mixture is stirred. 12.5g of diethanolamine was added, the pH was adjusted to 8.5 and the rotation speed was set to 180 r/min. Then adjusting the temperature to 90 ℃, adding 270g of melamine, setting the rotating speed to 200r/min, reacting for 10min after the temperature reaches 90 ℃, and measuring the water tolerance point by an ice water method. When the temperature reaches the water tolerance point, 11g of diethanolamine is added, and the temperature is reduced to 25 ℃ to obtain a melamine resin precursor.
And standing at 25 ℃ for 1 day until the viscosity of the melamine resin precursor reaches 10pa · s, and foaming.
(2) Preparation of expanded microsphere foaming-based double-network rigid melamine foam
Taking 100g of melamine resin precursor, 1g of simethicone, 6g of 50% ammonium bisulfate aqueous solution, 2g of acrylamide, 0.02g of ammonium persulfate and 10g of expanded microsphere foaming agent (the foaming temperature is 150 ℃), and stirring for 10min at the rotating speed of 1000r/min by using a high-speed stirrer to obtain the melamine resin precursor prepolymer liquid which is uniformly stirred.
And pouring the melamine resin foaming liquid into a mould, foaming for 10min at the temperature of 150 ℃, curing for 2h at the temperature of 120 ℃, and cutting and forming to obtain the double-network rigid melamine foam based on expansion microsphere foaming.
Example 5
The operation steps for preparing the rigid melamine foam are as follows:
(1) preparation of Melamine resin precursor
403g of formaldehyde solution is weighed and added into a reaction kettle, the temperature is raised to 60 ℃, and the mixture is stirred. 12.5g of diethanolamine is added, the pH is adjusted to 8.5, and the rotation speed is set to 180 r/min. Then adjusting the temperature to 90 ℃, adding 270g of melamine, setting the rotating speed to 200r/min, reacting for 10min after the temperature reaches 90 ℃, and measuring the water tolerance point by an ice water method. When the temperature reaches the water tolerance point, 11g of diethanolamine is added, and the temperature is reduced to 25 ℃ to obtain a melamine resin precursor.
And standing at 25 ℃ for 1 day until the viscosity of the melamine resin precursor reaches 10pa · s, and foaming.
(2) Preparation of expanded microsphere foaming-based double-network rigid melamine foam
Taking 100g of melamine resin precursor, 1g of simethicone, 6g of 50% ammonium bisulfate aqueous solution, 2g of acrylamide, 0.02g of ammonium persulfate and 20g of expanded microsphere foaming agent (the foaming temperature is 150 ℃), and stirring for 10min at the rotating speed of 1000r/min by using a high-speed stirrer to obtain the melamine resin precursor prepolymer liquid which is uniformly stirred.
Pouring the melamine resin foaming liquid into a mould, foaming for 2min under the condition of microwave power of 1000w, curing for 2h at 120 ℃, and cutting and forming to obtain the double-network rigid melamine foam based on expansion microsphere foaming.
Example 6
The operation steps for preparing the rigid melamine foam are as follows:
(1) preparation of Melamine resin precursor
403g of formaldehyde solution is weighed and added into a reaction kettle, the temperature is raised to 60 ℃, and the mixture is stirred. 12.5g of diethanolamine was added, the pH was adjusted to 8.5 and the rotation speed was set to 180 r/min. Then adjusting the temperature to 90 ℃, adding 270g of melamine, setting the rotating speed to 200r/min, reacting for 10min after the temperature reaches 90 ℃, and measuring the water tolerance point by an ice water method. When the temperature reaches the water tolerance point, 11g of diethanolamine is added, and the temperature is reduced to 25 ℃ to obtain a melamine resin precursor.
And standing at 25 ℃ for 1 day until the viscosity of the melamine resin precursor reaches 10pa · s, and foaming.
(2) Preparation of expanded microsphere foaming-based double-network rigid melamine foam
Taking 100g of melamine resin precursor, 1g of simethicone, 6g of 50% ammonium bisulfate aqueous solution, 2g of acrylamide, 0.02g of ammonium persulfate and 10g of expanded microsphere foaming agent (the foaming temperature is 150 ℃), and stirring for 10min at the rotating speed of 1000r/min by using a high-speed stirrer to obtain the melamine resin precursor prepolymer liquid which is uniformly stirred.
Pouring the melamine resin foaming liquid into a mould, foaming for 6min under the condition of microwave power of 200w, curing for 2h at 120 ℃, and cutting and forming to obtain the double-network rigid melamine foam based on expansion microsphere foaming.
The expanded microspheres used in examples 1-6 had highly uniform expanded volumes, thus resulting in fine and uniform cell structures; meanwhile, a double-network strategy is adopted, and the formed foam holes have higher mechanical strength, so that the foam holes are not easy to break and collapse, and the closed-cell rate is greatly improved.
Comparative example 1
The comparative example differs from example 1 in that no hydrophilic monomer is added, and the specific steps are as follows:
(1) preparation of Melamine resin precursor
403g of formaldehyde solution is weighed and added into a reaction kettle, the temperature is raised to 60 ℃, and the mixture is stirred. 12.5g of diethanolamine was added, the pH was adjusted to 8.5 and the rotation speed was set to 180 r/min. Then adjusting the temperature to 90 ℃, adding 270g of melamine, setting the rotating speed to 200r/min, reacting for 10min after the temperature reaches 90 ℃, and measuring the water tolerance point by an ice water method. When the temperature reaches the water tolerance point, 11g of diethanolamine is added, and the temperature is reduced to 25 ℃ to obtain a melamine resin precursor.
And standing at 25 ℃ for 1 day until the viscosity of the melamine resin precursor reaches 10pa · s, and foaming.
(2) Preparation of expanded microsphere foaming-based double-network rigid melamine foam
Taking 100g of melamine resin precursor, 1g of simethicone, 6g of 50% ammonium bisulfate aqueous solution and 10g of expanded microsphere foaming agent (the foaming temperature is 150 ℃), and stirring for 10min at the rotating speed of 1000r/min by using a high-speed stirrer to obtain the melamine resin precursor prepolymer liquid which is uniformly stirred.
And pouring the melamine resin foaming liquid into a mould, foaming for 6min under the condition of microwave power of 200w, curing for 2h at 120 ℃, and cutting and forming to obtain the hard melamine foam based on expansion microsphere foaming.
The results show that: because a double-network structure is not introduced, the obtained melamine foam lacks toughness and is easy to crack in the foaming process.
Comparative example 2
The comparative example differs from example 1 in that a conventional blowing agent, n-hexane, was added, with the following specific steps:
(1) preparation of Melamine resin precursor
403g of formaldehyde solution is weighed and added into a reaction kettle, the temperature is raised to 60 ℃, and the mixture is stirred. 12.5g of diethanolamine was added, the pH was adjusted to 8.5 and the rotation speed was set to 180 r/min. Then adjusting the temperature to 90 ℃, adding 270g of melamine, setting the rotating speed to 200r/min, reacting for 10min after the temperature reaches 90 ℃, and measuring the water tolerance point by an ice water method. When the temperature reaches the water tolerance point, 11g of diethanolamine is added, and the temperature is reduced to 25 ℃ to obtain a melamine resin precursor.
And standing at 25 ℃ for 1 day until the viscosity of the melamine resin precursor reaches 10pa · s, and foaming.
(2) Preparation of expanded microsphere foaming-based double-network rigid melamine foam
Taking 100g of melamine resin precursor, 1g of simethicone, 6g of 50% ammonium bisulfate aqueous solution, 2g of acrylamide, 0.02g of ammonium persulfate and 4g of foaming agent n-hexane (foaming temperature is 150 ℃), and stirring for 10min at the rotating speed of 1000r/min by using a high-speed stirrer to obtain uniformly stirred melamine resin precursor prepolymer liquid.
Pouring the melamine resin foaming liquid into a mould, foaming for 6min under the condition of microwave power of 200w, curing for 2h at 120 ℃, and cutting and forming to obtain the double-network rigid melamine foam based on expansion microsphere foaming.
The results show that: because the conventional foaming agent is adopted, the expansion volume is not uniform, the obtained melamine foam has small foaming volume, and the foaming pore diameter is relatively large and has different sizes.
Comparative example 3
The comparative example differs from example 5 in the foaming and thermosetting conditions, and comprises the following steps:
(1) preparation of Melamine resin precursor
403g of formaldehyde solution is weighed and added into a reaction kettle, the temperature is raised to 60 ℃, and the mixture is stirred. 12.5g of diethanolamine was added, the pH was adjusted to 8.5 and the rotation speed was set to 180 r/min. Then adjusting the temperature to 90 ℃, adding 270g of melamine, setting the rotating speed to 200r/min, reacting for 10min after the temperature reaches 90 ℃, and measuring the water tolerance point by an ice water method. When the temperature reaches the water tolerance point, 11g of diethanolamine is added, and the temperature is reduced to 25 ℃ to obtain a melamine resin precursor.
And standing at 25 ℃ for 1 day until the viscosity of the melamine resin precursor reaches 10pa · s, and foaming.
(2) Preparation of expanded microsphere foaming-based double-network rigid melamine foam
Taking 100g of melamine resin precursor, 1g of simethicone, 1g of 50% ammonium bisulfate aqueous solution, 2g of acrylamide, 0.02g of ammonium persulfate and 4g of n-hexane (foaming temperature is 150 ℃), and stirring for 10min at the rotating speed of 1000r/min by using a high-speed stirrer to obtain the melamine resin precursor prepolymer liquid which is uniformly stirred.
Pouring the melamine resin foaming liquid into a mould, foaming for 6min under the condition of microwave power of 200w, curing for 2h at 120 ℃, and cutting and forming to obtain the double-network rigid melamine foam based on expansion microsphere foaming.
The results show that: the content of acid is reduced, so that the foaming speed is not matched with the curing speed, and the foaming speed is higher than the curing speed, so that the melamine foam is broken, and the complete melamine foam cannot be obtained.
Although the invention has been described in detail hereinabove with respect to a general description and specific embodiments thereof, it will be apparent to those skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.
Claims (10)
1. A method for preparing a rigid melamine foam, comprising:
s1, performing hydroxymethylation reaction on formaldehyde and melamine to obtain a melamine resin precursor;
s2, adding a foam stabilizer, a catalyst, a hydrophilic monomer, an initiator and an expanded microsphere foaming agent into the obtained melamine resin precursor, and uniformly mixing to obtain melamine resin precursor pre-polymerization liquid;
and S3, foaming and thermally curing the melamine resin precursor pre-polymerization liquid to obtain the rigid melamine foam.
2. The method according to claim 1, wherein in S1, the pH of the reaction system is controlled to be between 8 and 9, and the reaction temperature is controlled to be between 80 and 90 ℃.
3. The production method according to claim 2, wherein in S1, the formaldehyde is added in the form of a formaldehyde solution having a mass concentration of 37%;
the mass ratio of the formaldehyde solution to the melamine is (201) -600): 270.
4. the method according to claim 3, wherein in S2, the melamine resin precursor is allowed to stand until the viscosity reaches 10 to 20 Pa-S, and then the raw materials are added thereto.
5. The preparation method according to claim 4, wherein in S2, the expanded microsphere foaming agent is in a core-shell structure consisting of a thermoplastic polymer shell and liquid alkane gas, the particle size is 10-50 μm, and the initial foaming temperature is not more than 150 ℃.
6. The method according to claim 5, wherein in S2, the hydrophilic monomer is selected from one or more of acrylic acid, acrylamide, hydroxyethyl acrylate, acyl morpholine acrylate, N-dimethylacrylamide, methacrylic acid, hydroxyethyl methacrylate, dimethylaminoethyl methacrylate, and the like.
7. The method according to claim 6, wherein in S2, the foam stabilizer is dimethicone and/or hydroxy silicone oil;
the catalyst is one or more of acetic acid, phosphoric acid, hydrochloric acid, dilute sulfuric acid, ammonium bisulfate or citric acid;
the initiator is ammonium persulfate.
8. The preparation method according to claim 7, wherein in the S2, the mass ratio relationship of the raw materials is as follows: 100 parts of melamine resin precursor, 1-3 parts of foam stabilizer, 3-6 parts of catalyst, 1-3 parts of hydrophilic monomer, 0.01-0.15 part of initiator and 5-20 parts of expanded microsphere foaming agent;
the feeding mode of each raw material is as follows: firstly, uniformly mixing a melamine resin precursor, a foam stabilizer, a catalyst, a hydrophilic monomer and an initiator to obtain a resin mixed solution; adding an expanded microsphere foaming agent, and stirring at a high speed to obtain a melamine resin precursor prepolymer solution; wherein the rotating speed of high-speed uniform stirring is 1000r/min, and the stirring time is 10-20 min.
9. The method according to claim 8, wherein in S3, the foaming and thermosetting conditions are as follows: foaming for 2-15min at 100-150 deg.C or under microwave 200-1000 w; curing at 100-120 ℃ for 2-4 h.
10. A rigid melamine foam obtainable by the process according to any one of claims 1 to 9.
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