Method for in-situ reinforcement of melamine foam material

Abstract

The invention discloses a method for in-situ reinforcement of a melamine foam material, which comprises the following steps: firstly, uniformly mixing melamine fibers with an aldehyde compound and melamine which are added according to a certain molar ratio, heating to a certain temperature in a weak alkaline environment, and reacting to prepare expandable melamine resin; uniformly stirring the obtained melamine resin with foaming substances such as a foaming agent and a curing agent to obtain foaming liquid, and performing microwave foaming and high-temperature curing to obtain melamine foam. According to the melamine foam prepared by the preparation method disclosed by the invention, the excellent flame retardant property of the melamine foam can be kept while the strength is ensured to be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of flame-retardant, heat-insulating and heat-insulating melamine foam and its preparation, and particularly relates to a method for in-situ reinforcing melamine foam material. Background Art

[0002] Melamine foam is a foam material with excellent performance. Compared with traditional foam materials, it has the characteristics of high open porosity, good sound absorption and moisture absorption, and aging resistance. Due to its unique three-dimensional network structure with highly cross-linked triazine rings, it has better flame retardant performance and thermal stability. Due to its special properties, it is widely used in aerospace, building materials, closed trains, battery pack insulation and fire protection and other fields.

[0003] Although melamine foam is light and flame retardant, its high hardness, low strength, easy to fall off and other characteristics greatly limit its application range. In order to broaden its application field, domestic and foreign scholars have conducted a lot of research on the enhancement of melamine foam mechanical properties from two aspects: modification of melamine foam and regulation of pore structure. Significant results have been achieved, but there are still some problems, such as the contradiction between the improvement of mechanical properties and the production process and raw material costs, the loss of flame retardant properties, the reduction of heat resistance, and the limited toughening range.

[0004] Melamine fiber is a fiber obtained by spinning with melamine formaldehyde as the main component, which has the characteristics of flame retardancy and heat insulation. The fiber surface has the same reactive groups as melamine foam. The fiber can form a good interface with the foam without surface modification, which is beneficial to the improvement of the mechanical properties of melamine foam.

[0005] The present invention uses melamine fibers prepared by wet spinning of melamine resin as reinforcing filling materials to in-situ reinforce melamine foam, which can further improve the mechanical properties of the melamine foam, and conducts a series of explorations on the properties of the prepared melamine foam. Summary of the invention

[0006] The invention provides a method for in-situ reinforcing melamine foam material, which has simple process and little pollution. The prepared melamine foam can ensure increased strength while maintaining excellent flame retardant properties of the melamine foam.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions: The invention comprises the following steps: uniformly mixing melamine fiber, melamine and aldehyde compounds, reacting them under weak alkaline conditions, heating them for reaction, cooling them down to obtain expandable melamine resin, uniformly stirring the obtained melamine resin with foaming agents and other foaming substances to obtain foaming liquid, foaming them with microwaves, and aging them at high temperature to obtain melamine foam.

[0008] The present invention provides a method for in-situ strengthening of melamine foam material, comprising the following steps: (1) Melamine fiber, melamine, aldehyde compound and alkaline catalyst are mixed and added to deionized water, the pH is adjusted to weak alkalinity, and the mixture is heated to 85-110°C. After the solution becomes clear and transparent, the reaction is continued for 20-60 minutes, and then the mixture is quickly cooled to room temperature in a cold water bath to obtain a expandable melamine resin.

[0009] (2) Mix 100 parts of the melamine resin obtained in step (1) with 4-15 parts of a foaming agent, 1-5 parts of a curing agent and 3-10 parts of an emulsifier by mass, stir the mixture evenly and prepare a foaming liquid. The foaming liquid is subjected to microwave foaming and high-temperature aging to obtain melamine foam.

[0010] In the step (1), the molar ratio of melamine to aldehyde compound is 1:(2-3.5), the mass of melamine fiber is 1-5% of the mass of melamine, and the mass ratio of melamine to alkaline catalyst is 1:(0.001-0.01).

[0011] In the step (1), the melamine fiber is a primary melamine fiber or a melamine fiber cured in air at 170° C. for 0.1-3 hours; the aldehyde compound is formaldehyde or acetaldehyde; and the alkaline catalyst is one of sodium hydroxide, potassium hydroxide, triethanolamine, and hexamethylenetetramine.

[0012] In the step (2), the foaming agent is one of n-pentane, isopentane, cyclopentane, n-hexane and cyclohexane.

[0013] In the step (2), the curing agent is one of formic acid, acetic acid, hydrochloric acid, sulfuric acid, and p-toluenesulfonic acid.

[0014] In the step (2), the emulsifier is one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, hexadecyltrimethylammonium chloride, dodecyl polyoxyethylene ether, and Tween-80.

[0015] In the step (2), the stirring process uses a high-speed mechanical stirring of 3000 r / min for 40-100 s, the microwave foaming power is 2000-4000 W, and the high-temperature aging is aging at a high temperature environment of 90-130° C. for 1-3 h.

[0016] The beneficial effects of the present invention are: 1. Melamine fiber and melamine foam are both made of melamine resin, which has better compatibility. During the reaction, the fiber and foam skeleton can be cross-linked without surface treatment of the fiber. The fiber has higher strength, which makes the mechanical properties of melamine foam reinforced by melamine fiber even better.

[0017] 2. Melamine foam material itself has good sound insulation and heat insulation properties. The in-situ reinforced melamine fiber further improves the sound absorption performance, making the material perform better in sound insulation and heat insulation applications, such as in building insulation, sound insulation panels and industrial sound insulation equipment, effectively improving energy efficiency and comfort.

[0018] 3. Melamine fiber has good chemical stability. The in-situ reinforced melamine foam material shows better corrosion resistance when it comes into contact with chemicals such as acids, alkalis and organic solvents. This makes the material more widely used in fields such as chemical industry and anti-corrosion engineering that need to resist chemical corrosion. DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention, and those skilled in the art in this field can make some non-essential improvements and adjustments based on the content of the above invention. Example 1

[0020] This embodiment provides a method for in-situ strengthening of melamine foam material, the steps are as follows: (1) Mix 1% melamine mass fraction of primary melamine fiber with melamine and formaldehyde and add them to deionized water, add alkaline catalyst sodium hydroxide to adjust the pH to weak alkalinity, heat to 100°C, and continue to react at constant temperature for 40 minutes after the solution becomes clear and transparent, then take out the solution and quickly cool it to room temperature in a cold water bath to obtain a expandable melamine resin. The molar ratio of melamine to aldehyde compound is 1:2, and the mass ratio of melamine to alkaline catalyst is 1:0.01.

[0021] (2) 100 parts by mass of the obtained expandable melamine resin were mixed with 4 parts of n-pentane, 1 part of hydrochloric acid and 3 parts of sodium dodecyl sulfate, and then stirred at 3000 r / min for 40 seconds to prepare a foaming liquid. The foaming liquid was subjected to microwave foaming at a foaming power of 2000 W, and then aged at a high temperature of 90° C. for 1 hour to obtain melamine foam.

[0022] The apparent density of the melamine foam is 3kg / m 3 The open porosity is 96%, the tensile strength is 850kPa, the elongation at break is 32%, the sound absorption coefficient of 10cm melamine foam at a frequency of 130Hz-4000Hz reaches 98.5%, the vertical burning UL-94 rating is V-0, the limiting oxygen index is 38.1%, the thermal conductivity is 0.006W / (m·K), and the foam is not easy to fall off. Example 2

[0023] This embodiment provides a method for in-situ strengthening of melamine foam material, the steps are as follows: (1) The melamine fiber, melamine and acetaldehyde were uniformly mixed in air with a melamine mass fraction of 3% and added to deionized water. The pH was adjusted to a weak alkaline state by adding an alkaline catalyst, potassium hydroxide, and heated to 110°C. After the solution became clear and transparent, the reaction was continued at a constant temperature for 60 minutes. The solution was then taken out and quickly cooled to room temperature in a cold water bath to obtain a melamine resin that could be expanded. The molar ratio of melamine to aldehyde compound was 1:3.5, and the mass ratio of melamine to alkaline catalyst was 1:0.001.

[0024] (2) 100 parts by mass of the obtained expandable melamine resin were mixed with 15 parts by mass of isopentane, 5 parts by mass of formic acid and 10 parts by mass of sodium dodecylbenzene sulfonate, and then stirred at 3000 r / min for 100 s to prepare a foaming liquid, and the foaming liquid was subjected to microwave foaming at a foaming power of 4000 W, and then aged at a high temperature of 130° C. for 2 h to obtain melamine foam.

[0025] The apparent density of the melamine foam is 3.5 kg / m 3 The open porosity is 98%, the tensile strength is 845kPa, the elongation at break is 63%, the sound absorption coefficient of 10cm melamine foam at a frequency of 130Hz-4000Hz reaches 98.5%, the vertical burning UL-94 rating is V-0, the limiting oxygen index is 42.1%, the thermal conductivity is 0.017W / (m·K), and the foam is not easy to fall off. Example 3

[0026] This embodiment provides a method for in-situ strengthening of melamine foam material, the steps are as follows: (1) Melamine fibers cured at 170°C for 3 hours in air with a melamine mass fraction of 5% were mixed with melamine and formaldehyde and added to deionized water. The pH was adjusted to a weak alkaline state by adding an alkaline catalyst, triethanolamine, and heated to 90°C. After the solution became clear and transparent, the reaction was continued at a constant temperature for 50 minutes. The solution was then taken out and quickly cooled to room temperature in a cold water bath to obtain a expandable melamine resin. The molar ratio of melamine to aldehyde compound was 1:3, and the mass ratio of melamine to alkaline catalyst was 1:0.008.

[0027] (2) 100 parts by mass of the obtained expandable melamine resin were mixed with 4 parts by mass of cyclopentane, 1 part by mass of acetic acid and 5 parts by mass of hexadecyltrimethylammonium chloride, and then stirred at 3000 r / min for 80 seconds to prepare a foaming liquid, and the foaming liquid was subjected to microwave foaming at a foaming power of 3500 W, and then aged at a high temperature of 120° C. for 2 hours to obtain melamine foam.

[0028] The apparent density of the melamine foam is 11 kg / m 3The open porosity is 96%, the tensile strength is 354kPa, the elongation at break is 31%, the sound absorption coefficient of 10cm melamine foam at a frequency of 130Hz-4000Hz reaches 98.8%, the vertical burning UL-94 rating is V-0, the limiting oxygen index is 44.5%, the thermal conductivity is 0.005W / (m·K), and the foam is not easy to fall off. Example 4

[0029] This embodiment provides a method for in-situ strengthening of melamine foam material, the steps are as follows: (1) Melamine fiber cured at 170°C for 0.3h in air with a melamine mass fraction of 1% was mixed with melamine and formaldehyde and added to deionized water. The pH was adjusted to a weak alkaline state by adding alkaline catalyst hexamethylenetetramine, and the mixture was heated to 95°C. After the solution became clear and transparent, the reaction was continued at a constant temperature for 60min. The solution was then taken out and quickly cooled to room temperature in a cold water bath to obtain a melamine resin that could be expanded. The molar ratio of melamine to aldehyde compound was 1:2, and the mass ratio of melamine to alkaline catalyst was 1:0.002.

[0030] (2) 100 parts by mass of the obtained expandable melamine resin were mixed with 5 parts by mass of n-hexane, 2 parts by mass of hydrochloric acid and 3 parts by mass of dodecyl polyoxyethylene ether, and then stirred at 3000 r / min by a high-speed machine for 40 seconds to prepare a foaming liquid, and the foaming liquid was subjected to microwave foaming at a foaming power of 2600 W, and then aged at a high temperature of 95° C. for 2.4 hours to obtain melamine foam.

[0031] The apparent density of the melamine foam is 9kg / m 3 The open porosity is 95%, the tensile strength is 952kPa, the elongation at break is 84%, the sound absorption coefficient of 10cm melamine foam at a frequency of 130Hz-4000Hz reaches 98.4%, the vertical burning UL-94 rating is V-0, the limiting oxygen index is 43.1%, the thermal conductivity is 0.016W / (m·K), and the foam is not easy to fall off. Example 5

[0032] This embodiment provides a method for in-situ strengthening of melamine foam material, the steps are as follows: (1) Melamine fiber cured at 170°C for 0.8h in air with a 4% melamine mass fraction was mixed with melamine and formaldehyde and added to deionized water. Alkaline catalyst sodium hydroxide was added to adjust the pH to weak alkalinity, and the mixture was heated to 95°C. After the solution became clear and transparent, the reaction was continued at a constant temperature for 30min. The solution was then taken out and quickly cooled to room temperature in a cold water bath to obtain a expandable melamine resin. The molar ratio of melamine to aldehyde compound was 1:2.8, and the mass ratio of melamine to alkaline catalyst was 1:0.001.

[0033] (2) 100 parts by mass of the obtained expandable melamine resin were mixed with 12 parts by mass of cyclohexane, 4 parts by mass of sulfuric acid and 6 parts by mass of Tween-80, and then stirred at 3000 r / min for 50 seconds to prepare a foaming liquid. The foaming liquid was subjected to microwave foaming at a foaming power of 2500 W, and then aged at a high temperature of 120° C. for 2 hours to obtain melamine foam.

[0034] The apparent density of the melamine foam is 10.5 kg / m 3 The open porosity is 95%, the tensile strength is 357kPa, the elongation at break is 33%, the sound absorption coefficient of 10cm melamine foam at a frequency of 130Hz-4000Hz reaches 98.3%, the vertical burning UL-94 rating is V-0, the limiting oxygen index is 34.7%, the thermal conductivity is 0.038W / (m·K), and the foam is not easy to fall off. Example 6

[0035] This embodiment provides a method for in-situ strengthening of melamine foam material, the steps are as follows: (1) Melamine fibers cured at 170°C for 3 h in air with a 3% melamine mass fraction were cut, mixed with melamine and acetaldehyde, and added to deionized water. Alkaline catalyst potassium hydroxide was added to adjust the pH to a weak alkaline state, and heated to 90°C. After the solution became clear and transparent, the reaction was continued at a constant temperature for 35 min. The solution was then taken out and quickly cooled to room temperature in a cold water bath to obtain a melamine resin that could be expanded. The molar ratio of melamine to aldehyde compounds was 1:2.3, and the mass ratio of melamine to alkaline catalyst was 1:0.006.

[0036] (2) 100 parts by mass of the obtained expandable melamine resin were mixed with 8 parts by mass of n-hexane, 3 parts by mass of formic acid and 6 parts by mass of sodium dodecylbenzene sulfonate, and then stirred at 3000 r / min by a high-speed mechanical stirrer for 90 seconds to prepare a foaming liquid, and the foaming liquid was subjected to microwave foaming at a foaming power of 3600 W, and then aged at a high temperature of 110° C. for 2 hours to obtain melamine foam.

[0037] The apparent density of the melamine foam is 4 kg / m 3 The open porosity is 96%, the tensile strength is 360kPa, the elongation at break is 33%, the sound absorption coefficient of 10cm melamine foam at a frequency of 130Hz-4000Hz reaches 98.6%, the vertical burning UL-94 rating is V-0, the limiting oxygen index is 35.2%, the thermal conductivity is 0.037W / (m·K), and the foam is not easy to fall off.

[0038] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for in-situ strengthening of melamine foam material, characterized in that Here are the steps: (1) Melamine fiber, melamine, aldehyde compound and alkaline catalyst are mixed and added into deionized water, pH is adjusted to weak alkalinity, heated to 85-110°C, and the solution is allowed to react for 20-60 minutes after it becomes clear, and then quickly cooled to room temperature in a cold water bath to obtain a expandable melamine resin; (2) Mix 100 parts of the melamine resin obtained in step (1) with 4-15 parts of a foaming agent, 1-5 parts of a curing agent and 3-10 parts of an emulsifier by mass, stir the mixture evenly and prepare a foaming liquid. The foaming liquid is subjected to microwave foaming and high-temperature aging to obtain melamine foam.

2. The method for in-situ strengthening of melamine foam material according to claim 1, characterized in that: In the step (1), the molar ratio of melamine to aldehyde compound is 1:(2-3.5), the mass of melamine fiber is 1-5% of the mass of melamine, and the mass ratio of melamine to alkaline catalyst is 1:(0.001-0.01).

3. The method for in-situ strengthening of melamine foam material according to claim 1, characterized in that: In the step (1), the melamine fiber is a primary melamine fiber or a melamine fiber cured in air at 180° C. for 0.1-3 hours; the aldehyde compound is formaldehyde or acetaldehyde; and the alkaline catalyst is one of sodium hydroxide, potassium hydroxide, triethanolamine, and hexamethylenetetramine.

4. The method for in-situ strengthening of melamine foam material according to claim 1, characterized in that: In the step (2), the foaming agent is one of n-pentane, isopentane, cyclopentane, n-hexane and cyclohexane.

5. The method for in-situ strengthening of melamine foam material according to claim 1, characterized in that: In the step (2), the curing agent is one of formic acid, acetic acid, hydrochloric acid, sulfuric acid, and p-toluenesulfonic acid.

6. The method for in-situ strengthening of melamine foam material according to claim 1, characterized in that: In the step (2), the emulsifier is one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, hexadecyltrimethylammonium chloride, dodecyl polyoxyethylene ether, and Tween-80.

7. The method for in-situ strengthening of melamine foam material according to claim 1, characterized in that: In the step (2), the stirring process uses a high-speed mechanical stirring of 3000 r / min for 40-100 s, the microwave foaming power is 2000-4000 W, and the high-temperature aging is aging at a high temperature environment of 90-130° C. for 1-3 h.