A method for preparing melamine porous materials and its application

Abstract

This invention belongs to the field of polymer synthesis and application technology, and discloses a method for efficiently preparing melamine foam materials and their applications. This invention introduces unsaturated double bond groups into the melamine resin molecule design and employs a free radical-initiated chemical foaming technique to address the structural performance deficiencies of melamine foam materials, while simultaneously improving the overall material performance, thereby expanding its applications in high-performance adsorbent materials, wall insulation materials, and other fields. The melamine foam material efficiently prepared by the method of this invention has a brittleness mass loss rate of 2.0%, and the properties of the prepared foam material are as follows: apparent density 30-40 kg / m³. 3 The flexural strength is ≥200kPa, the compressive strength is ≥380kPa, and the volumetric water absorption rate is ≤1.0%. The brittle mass loss rate of the foam material of this invention is ≤2.0%, and it can be applied in the fields of wall insulation materials, adsorbent materials, etc.

Description

Technical Field

[0001] This invention belongs to the field of polymer synthesis and application technology, and specifically relates to a method for preparing melamine porous materials and their application. Background Technology

[0002] Melamine-formaldehyde resin, also known as melamine resin, is a high molecular polymer synthesized by the addition reaction of melamine and formaldehyde to form a prepolymer, followed by a dehydration condensation reaction. The foam material made with melamine resin as the main material has a typical three-dimensional cross-linked structure. Its foam skeleton structure is rigid but brittle, and it is prone to serious powdering and flaking at low densities.

[0003] According to patent publication CN107936282A, modified melamine resin, foaming agent, surfactant, cell opener, and curing agent are mixed in a certain proportion and placed in a mold. The mixture is then microwaved at 2450 MHz and 2 kW for 60 seconds, followed by air drying at 230–280℃ for 10–20 minutes to obtain rigid melamine foam. The foam's properties are as follows: compressive strength ≥ 0.080 MPa, flexural strength ≥ 0.375 MPa, and foam density ≥ 8.2 kg / m³. 3 The rebound rate is ≥63%. In patent publication CN110713690A, modified melamine resin, flame retardant, modifier, emulsifier, and foaming agent are mixed in a certain proportion, foamed in a microwave oven for 4 minutes at a foaming power of 2000W, and then cured in an oven at 180℃ for 1 hour to obtain modified melamine foam plastic. The product's properties are as follows: free formaldehyde content ≤0.15mg / L, tensile strength 140kPa. The calorific value is 15 MJ / Kg, and the elongation at break is about 32%. According to the patent publication text CN107501858A, toughened melamine resin, modifier, curing agent and emulsifier are mixed evenly and poured into a mold. The mixture is kept at 100-120℃ for 2-3 hours for foaming, and then allowed to stand and cool to 55-70℃ for 2-3 hours for curing to prepare melamine foam. The foam properties are as follows: compressive strength of about 0.160 MPa and elastic modulus of 2.85 MPa.

[0004] The aforementioned patent disclosures mostly involve mixing modified melamine resin with curing agents, foaming agents, and other related functional additives to form a pre-foamed liquid. Melamine foam materials are then prepared using microwave or hot air box foaming methods. During this process, the curing speed of the melamine resin must be highly synchronized with the foaming speed of the foaming agent, and the foaming agents used are often low-boiling-point organic solvents (such as n-pentane and isopentane), which easily leads to problems such as volatile organic compound (VOC) emissions. Currently, regardless of whether melamine resin is cured by acid or heat, its curing rate is slow, resulting in time-consuming and energy-intensive processes, which greatly restricts the development of melamine foam materials.

[0005] To address the aforementioned issues, it is necessary to develop an efficient method for preparing melamine porous materials. Summary of the Invention

[0006] To overcome the shortcomings and deficiencies of the prior art, the primary objective of this invention is to provide a method for preparing melamine foam materials. This invention introduces unsaturated double bond groups into the melamine resin molecule design and employs a free radical-initiated chemical foaming technique to address the aforementioned structural performance deficiencies of melamine foam materials, while simultaneously improving the overall material performance, thereby expanding its applications in high-performance adsorbent materials, wall insulation materials, and other fields.

[0007] Another object of the present invention is to provide a melamine foam material prepared by the above method.

[0008] Another objective of this invention is to provide the application of the above-mentioned melamine foam material in adsorbent materials and wall insulation materials.

[0009] The objective of this invention is achieved through the following solution:

[0010] A method for preparing melamine porous materials, comprising the following steps:

[0011] (1) Preparation of melamine resin: Weigh paraformaldehyde, mixed aldehyde solution, melamine and N-hydroxymethylacrylamide and stir evenly to obtain a mixed solution. Then adjust the pH range with alkanolamine solution, heat the mixed solution until the solution is clear, cool it down, and then add unsaturated alcohol to react. After the reaction is completed, adjust the pH range with alkanolamine solution and cool to room temperature to obtain melamine resin.

[0012] (2) Preparation of melamine foam material: Mix the melamine resin, initiator and other additives obtained in step (1) evenly, pre-react the mixture, add foaming agent after the reaction is completed, mix evenly and then foam to obtain melamine foam material.

[0013] The melamine resin in step (1) is prepared according to the following proportions by weight:

[0014] 12-15 parts of paraformaldehyde, 160-240 parts of mixed aldehyde solution, 126 parts of melamine, 15-30 parts of N-hydroxymethylacrylamide, 4-8 parts of alkanolamine solution, and 92-124 parts of unsaturated alcohols;

[0015] The mixed aldehyde solution mentioned in step (1) is a mixture of 37% formaldehyde aqueous solution and 50% glutaraldehyde aqueous solution;

[0016] The formaldehyde:glutaraldehyde molar ratio in the mixed solution described in step (1) is 1:0-1:1, and the formaldehyde content refers to the effective content after combining paraformaldehyde and the mixed aldehyde solution, preferably a molar ratio of 7:3.

[0017] The amine solution mentioned in step (1) is at least one of ethanolamine, diethanolamine, and triethanolamine, preferably diethanolamine; adjusting the pH value with the amine solution means adjusting the pH to 8-9;

[0018] The heating mentioned in step (1) refers to raising the temperature of the mixed solution to 80-95℃; the cooling refers to lowering the temperature of the mixed solution to 50-70℃.

[0019] The unsaturated alcohol mentioned in step (1) is at least one of hydroxypropyl acrylate, hydroxyethyl acrylate, and allyl glycidyl ether, preferably hydroxypropyl acrylate;

[0020] In step (1), the addition of unsaturated alcohols for reaction is preferably carried out by adding saturated alcohols dropwise over 15 minutes; the reaction time is 1-3 hours.

[0021] The pH adjustment mentioned in step (1) after the reaction is completed refers to 8-9;

[0022] The melamine foam material in step (2) is prepared according to the following proportions by weight:

[0023] Melamine resin 20-40 parts, initiator 0.2-0.5 parts, other additives 0.4-1.4 parts, foaming agent 0.4-1.6 parts;

[0024] The initiator mentioned in step (2) is at least one of azobisisobutyronitrile, sodium persulfate, potassium persulfate, ammonium persulfate, and benzoyl peroxide, preferably potassium persulfate;

[0025] The other additives mentioned in step (2) are at least one of the alkaline compounds such as sodium silicate, calcium silicate, sodium carbonate, calcium carbonate, and sodium bicarbonate; preferably, sodium silicate and sodium bicarbonate are used in combination, and the preferred mass ratio of the two is 5:2.

[0026] The pre-reaction in step (2) refers to a constant temperature of 35-75°C for 3-7 minutes, preferably 60°C for 5 minutes;

[0027] The foaming agent mentioned in step (2) is at least one of the following: 50% sulfuric acid solution, acrylic acid, methacrylic acid, etc.; preferably methacrylic acid.

[0028] The foaming conditions mentioned in step (2) refer to foaming in a 500W microwave oven for 1 to 3 minutes, preferably 2 minutes.

[0029] Unless otherwise specified, all methods described above are performed at room temperature.

[0030] A melamine foam material prepared by the above method.

[0031] The aforementioned melamine foam materials are used in fields such as adsorption materials and wall insulation materials.

[0032] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0033] (1) The melamine foam material prepared by the method of the present invention has a brittleness loss rate of 2.0%, which not only improves the brittleness and easy powdering and slagging of ordinary melamine foam materials, but also simplifies the process flow of melamine foam materials. The properties of the prepared foam material are as follows: apparent density 30-40 kg / m³ 3 The flexural strength is ≥200kPa, the compressive strength is ≥380kPa, and the volumetric water absorption rate is ≤1.0%. The brittle mass loss rate of the foam material of this invention is ≤2.0%, and it can be applied in the fields of wall insulation materials, adsorbent materials, etc.

[0034] (2) The method for preparing melamine foam material described in this invention uses readily available raw materials and achieves the actual effect of melamine foam material.

[0035] (3) The method for preparing melamine foam material described in this invention is relatively simple, and has the characteristics of flexible process, easy control and good adaptability.

[0036] (4) The present invention uses free radical initiation-chemical foaming technology to foam conventional foaming agent, initiator and modified melamine resin through conventional microwave foaming device to obtain melamine foam material. Detailed Implementation

[0037] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used, unless otherwise specified, are all commercially available products.

[0038] Unless otherwise specified, all reagents used in the examples are commercially available.

[0039] The melamine foam material prepared in the examples was tested according to the following national standard test methods:

[0040] GB / T 6343-2009 Determination of apparent density of foamed plastics and rubber;

[0041] GB / T 8813-1988 Rigid Foamed Plastics - Compression Test Method;

[0042] GB / T 8810-2005 Determination of water absorption rate of rigid foamed plastics;

[0043] GB / T 12812-2006 Determination of the fragility of rigid foamed plastics.

[0044] Example 1

[0045] (1) The preparation method of melamine resin is as follows: Weigh a certain amount of 12.6 parts of paraformaldehyde, 98.1 parts of 37% formaldehyde solution, 140 parts of 50% glutaraldehyde solution, 126 parts of melamine and 15.6 parts of N-hydroxymethylacrylamide, stir evenly at room temperature, adjust the pH value to 8-9 with 3.2 parts of 99% ethanolamine solution, heat to 85℃, and after the solution becomes clear, cool down to 60℃, add 100 parts of hydroxyethyl acrylate dropwise within 15 min, react for 2 h, adjust the pH value to 8.5 with 2.5 parts of ethanolamine solution, cool to room temperature, and set aside for use.

[0046] (2) Under stirring conditions, 30 parts of melamine resin, 0.3 parts of sodium persulfate initiator, and 0.7 parts of other additives (including 0.5 parts of sodium silicate and 0.2 parts of sodium bicarbonate) were mixed evenly. Under stirring conditions, the mixture was kept at 60°C for 5 minutes. After the pre-reaction was completed, 1.0 part of acrylic acid foaming agent was added and stirred evenly. The foaming liquid was placed in a 500W microwave oven and foamed for 2 minutes to obtain melamine foam material.

[0047] (3) The properties of the prepared melamine porous material are as follows: apparent density 36 kg / m³ 3 The flexural strength is 220 kPa, the compressive strength is 392 kPa, the volumetric water absorption rate is 0.85%, and the brittleness mass loss rate of the foam material is 1.6%.

[0048] Example 2

[0049] (1) The preparation method of melamine resin is as follows: Weigh a certain amount of 12.6 parts of paraformaldehyde, 98.1 parts of 37% formaldehyde solution, 140 parts of 50% glutaraldehyde solution, 126 parts of melamine and 20.4 parts of N-hydroxymethylacrylamide, stir evenly at room temperature, adjust the pH value to 8-9 with 4.0 parts of 99% diethanolamine solution, heat to 85℃, and after it becomes clear, cool down to 60℃, add 100 parts of hydroxyethyl acrylate dropwise within 15 min, react for 2 h, adjust the pH value to 8.7 with 3.2 parts of diethanolamine solution, cool to room temperature, and set aside for use.

[0050] (2) Under stirring conditions, 25 parts of melamine resin, 0.25 parts of potassium persulfate initiator, and 1.2 parts of other additives (including 0.85 parts of sodium silicate and 0.35 parts of sodium bicarbonate) were mixed evenly. Under stirring conditions, the mixture was kept at 50°C for 6 minutes. After the pre-reaction was completed, 0.85 parts of methacrylic acid foaming agent were added and stirred evenly. The foaming liquid was placed in a 500W microwave oven and foamed for 1.5 minutes to obtain melamine foam material.

[0051] (3) The properties of the prepared melamine porous material are as follows: apparent density 34 kg / m³ 3 The flexural strength is 210 kPa, the compressive strength is 385 kPa, the volumetric water absorption rate is 0.92%, and the brittleness mass loss rate of the foam material is 1.8%.

[0052] Example 3

[0053] (1) The preparation method of melamine resin is as follows: Weigh a certain amount of 12.8 parts of paraformaldehyde, 89.6 parts of 37% formaldehyde solution, 131 parts of 50% glutaraldehyde solution, 126 parts of melamine and 26.8 parts of N-hydroxymethylacrylamide, stir evenly at room temperature, adjust the pH value to about 8.5 with 2.8 parts of triethanolamine solution, heat to 85℃, and after the solution is clear, cool down to 65℃. Add 120 parts of hydroxypropyl acrylate dropwise within 15 min. After reacting for 1.5 h, adjust the pH value to 8.8 with 4.1 parts of triethanolamine solution, cool to room temperature and set aside for use.

[0054] (2) Under stirring conditions, 35 parts of melamine resin, 0.4 parts of ammonium persulfate initiator, and 1.4 parts of other additives (including 1.0 part of sodium silicate and 0.4 parts of sodium bicarbonate) were mixed evenly. Under stirring conditions, the mixture was kept at 75°C for 3.5 minutes. After the pre-reaction was completed, 1.2 parts of 50% sulfuric acid solution were added and stirred evenly. The foaming liquid was placed in a 500W microwave oven and foamed for 1.5 minutes to obtain melamine foam material.

[0055] (3) The properties of the prepared melamine porous material are as follows: apparent density 32 kg / m³ 3 The flexural strength is 200 kPa, the compressive strength is 380 kPa, the volumetric water absorption rate is 0.95%, and the brittleness mass loss rate of the foam material is 1.95%.

[0056] Example 4

[0057] (1) The preparation method of melamine resin is as follows: Weigh a certain amount of 12.2 parts of paraformaldehyde, 94.5 parts of 37% formaldehyde solution, 134.8 parts of 50% glutaraldehyde solution, 126 parts of melamine and 16.8 parts of N-hydroxymethylacrylamide, stir evenly at room temperature, adjust the pH value to 8-9 with 3.8 parts of diethanolamine solution, heat to 85℃, and after the solution is clear, cool down to 70℃. Add 105 parts of hydroxypropyl acrylate dropwise within 15 min. After reacting for 1.0 h, adjust the pH value to 8.8 with 4.2 parts of diethanolamine solution, cool to room temperature, and set aside for use.

[0058] (2) Under stirring conditions, 35 parts of melamine resin, 0.5 parts of azobisisobutyronitrile, and 1.0 part of other additives (including 0.7 parts of sodium silicate and 0.3 parts of sodium bicarbonate) were mixed evenly. Under stirring conditions, the mixture was kept at 45°C for 7.0 min. After the pre-reaction was completed, 0.95 parts of foaming agent acrylic acid were added and stirred evenly. The foaming liquid was placed in a 500W microwave oven and foamed for 2.5 min to obtain melamine foam material.

[0059] (3) The properties of the prepared melamine porous material are as follows: apparent density 38 kg / m³ 3 The flexural strength is 215 kPa, the compressive strength is 386 kPa, the volumetric water absorption rate is 0.75%, and the brittleness mass loss rate of the foam material is 1.55%.

[0060] Example 5

[0061] (1) The preparation method of melamine resin is as follows: Weigh a certain amount of 12.2 parts of paraformaldehyde, 94.5 parts of 37% formaldehyde solution, 134.8 parts of 50% glutaraldehyde solution, 126 parts of melamine and 29.2 parts of N-hydroxymethylacrylamide, stir evenly at room temperature, adjust the pH value to 8-9 with 2.0 parts of ethanolamine solution, heat to 85℃, and after the solution is clear, cool down to 65℃, add 100 parts of allyl glycidyl ether dropwise within 15 min, react for 3.0 h, adjust the pH value to 9.0 with 2.2 parts of ethanolamine solution, cool to room temperature, and set aside for use;

[0062] (2) Under stirring conditions, 30 parts of melamine resin, 0.3 parts of potassium persulfate initiator, and 0.6 parts of other additives (including 0.45 parts of sodium silicate and 0.15 parts of sodium bicarbonate) were mixed evenly. Under stirring conditions, the mixture was kept at 55°C for 5.5 minutes. After the pre-reaction was completed, 0.80 parts of acrylic acid foaming agent were added and stirred evenly. The foaming liquid was placed in a 500W microwave oven and foamed for 2.5 minutes to obtain melamine foam material.

[0063] (4) The properties of the prepared melamine porous material are as follows: apparent density 40 kg / m³ 3The flexural strength is 226 kPa, the compressive strength is 398 kPa, the volumetric water absorption rate is 0.50%, and the brittleness loss rate of the foam material is 1.0%.

[0064] Comparative Example 1

[0065] (1) The preparation method of melamine resin here is the same as the preparation method of melamine resin in step (1) of Example 1.

[0066] (2) Under stirring conditions, 30 parts of melamine resin and 0.7 parts of other additives (including 0.5 parts of sodium silicate and 0.2 parts of sodium bicarbonate) were mixed evenly. Under stirring conditions, the mixture was kept at 60°C for 5 minutes. After the pre-reaction was completed, 1.0 part of foaming agent acrylic acid was added and stirred evenly. The foaming liquid was placed in a 500W microwave oven and foamed for 2 minutes to obtain melamine foam material.

[0067] (3) The properties of the prepared melamine foam material are as follows: apparent density 240 kg / m³ 3 The flexural strength is 12 MPa, the compressive strength is 24 MPa, the volume water absorption rate is 0.20%, and the brittleness mass loss rate of the foam material is 0.6%.

[0068] Comparative Example 1: The apparent density of the foamed material prepared by chemical foaming is 200-300 kg / m³. 3 It is almost a spline and cannot be considered a foam material.

[0069] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A process for preparing melamine cellular material, characterized in that The preparation method comprises the following steps: (1) Preparation of melamine resin: take paraformaldehyde, mixed aldehyde solution, melamine and N-methylol acrylamide, stir them uniformly to obtain a mixed solution, then adjust the pH value of the mixed solution with an alcohol amine solution, heat the mixed solution until it is clear, cool it down, then add an unsaturated alcohol substance to react, adjust the pH value of the solution with the alcohol amine solution after the reaction is completed, and cool it to room temperature to obtain the melamine resin; (2) Preparation of melamine foam material: mix the melamine resin obtained in step (1), an initiator and other additives uniformly, pre-react the obtained mixture, add a foaming agent and mix them uniformly after the reaction is completed, and then foam to obtain the melamine foam material; The melamine resin in step (1) is prepared according to the following ratio by mass: paraformaldehyde 12-15 parts, mixed aldehyde solution 160-240 parts, melamine 126 parts, N-methylol acrylamide 15-30 parts, alcohol amine solution 4-8 parts, and unsaturated alcohol substance 92-124 parts; The mixed aldehyde solution in step (1) is a mixture of 37% formaldehyde solution and 50% glutaraldehyde solution; The alcohol amine solution in step (1) is at least one of ethanol amine, diethanol amine and triethanol amine; The heating in step (1) refers to heating the mixed solution to 80-95°C; and the cooling refers to cooling the mixed solution to 50-70°C; The initiator in step (2) is potassium persulfate; The foaming agent in step (2) is at least one of 50% sulfuric acid solution, acrylic acid and methacrylic acid; The foaming condition in step (2) refers to foaming in a 500W microwave oven, and the foaming time is 1-3min.

2. The method for preparing melamine foam material according to claim 1, wherein: The alcohol amine solution in step (1) is diethanol amine.

3. The method for preparing melamine foam material according to claim 1, wherein: The molar ratio of formaldehyde to glutaraldehyde in the mixed solution in step (1) is 7:

3.

4. The method for preparing melamine foam material according to claim 1, wherein: Adjusting the pH value of the obtained mixed solution with the alcohol amine solution in step (1) refers to adjusting the pH value to 8-9.

5. The method for preparing melamine foam material according to claim 1, wherein: The unsaturated alcohol substance in step (1) is at least one of hydroxypropyl acrylate, hydroxyethyl acrylate and allyl glycidyl ether; The time for adding the unsaturated alcohol substance to react in step (1) is 1-3h; The pH value is adjusted to 8-9 after the reaction in step (1) is completed.

6. The method for preparing melamine foam material according to claim 1, wherein: The melamine foam material in step (2) is prepared according to the following ratio by mass: Melamine resin 20-40 parts, initiator 0.2-0.5 parts, other additives 0.4-1.4 parts, and foaming agent 0.4-1.6 parts.

7. The method for preparing melamine foam material according to claim 1, wherein: The other auxiliary agent in step (2) is at least one of sodium silicate, calcium silicate, sodium carbonate, calcium carbonate, sodium bicarbonate; The pre-reaction in step (2) is constant temperature for 3-7 min at 35-75℃.

8. The method for preparing melamine cellular material according to claim 1, characterized in that: The foaming agent in step (2) is methacrylic acid; The foaming time in step (2) is 2 min.

9. A melamine cellular material prepared by the method according to any one of claims 1-8.

10. The melamine cellular material according to claim 9 in the field of adsorption materials and wall thermal insulation materials.