Method for preparing low-formaldehyde melamine foam material

Abstract

The invention discloses a method for preparing a low-formaldehyde melamine foam material, which comprises the following steps: firstly, adding an aldehyde compound, melamine and urea according to a certain molar ratio, uniformly mixing, heating to a certain temperature in a weak alkaline environment, and reacting to prepare expandable melamine resin; then uniformly stirring the urea formaldehyde fibers, melamine resin, a foaming agent, a curing agent and other foaming substances to obtain a foaming solution, and carrying out microwave foaming and high-temperature curing to obtain melamine foam. According to the prepared melamine foam, the strength is improved, the aldehyde content is reduced, and meanwhile the excellent flame-retardant and heat-insulating properties of the melamine foam are kept.

Description

Technical Field

[0001] The invention belongs to the technical field of flame-retardant, heat-insulating melamine foam and preparation thereof, and particularly relates to a method for preparing a low-aldehyde 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 lightweight and flame retardant, its high hardness, low strength, and easy slagging 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. Urea is added to melamine resin as an additive to reduce formaldehyde content and increase material toughness. However, there are still some problems in foam applications, such as the contradiction between the improvement of mechanical properties and the production process and raw material costs, loss of flame retardant properties, reduced heat resistance, and limited toughening.

[0004] Urea is widely used as an important modifier in melamine resins and adhesives, thereby reducing the aldehyde content of melamine, improving the quality of the resin and expanding the application field.

[0005] The present invention uses urea-formaldehyde fiber prepared by wet spinning as a reinforcing filling material to strengthen melamine foam, reduces the formaldehyde content by adding urea, and conducts a series of explorations on the performance of the prepared melamine foam. Summary of the invention

[0006] The invention provides a method for preparing a low-aldehyde melamine foam material, which has a 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, urea 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 urea-formaldehyde fiber, a foaming agent and other foaming substances to obtain a foaming liquid, foaming them with microwaves, and aging them at high temperature to obtain melamine foam.

[0008] The present invention provides a method for preparing a low-aldehyde melamine foam material, comprising the following steps: (1) Melamine, aldehyde compound, urea 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, 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) 100 parts by mass of the melamine resin obtained in step (1) are mixed with 1-5 parts by mass of urea-formaldehyde fiber, 4-15 parts by mass of a foaming agent, 1-5 parts by mass of a curing agent and 3-10 parts by mass of an emulsifier, and the mixture is stirred evenly to obtain a foaming liquid, and the foaming liquid is subjected to microwave foaming and high-temperature aging to obtain a melamine foam.

[0010] In the step (1), the molar ratio of melamine to urea is 1:(0.1-0.6), the molar ratio of melamine to aldehyde compound is 1:(2-3.5), and the mass ratio of melamine to alkaline catalyst is 1:(0.001-0.01).

[0011] In the step (1), 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 urea-formaldehyde fiber is a primary urea-formaldehyde fiber or a urea-formaldehyde fiber cured in air at 180° C. for 0.1 to 3 hours; and 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 foaming power of the microwave foaming is 2000-4000 W, and the high-temperature aging is aging at a high temperature environment of 90-130° C. for 2 hours.

[0016] The beneficial effects of the present invention are: 1. Urea-formaldehyde fiber and melamine foam are both made of aldehyde resin. By adding urea modification, the compatibility of fiber and foam is further increased. 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 urea-formaldehyde fiber in situ more excellent.

[0017] 2. Melamine foam material itself has good sound insulation and heat insulation properties. The in-situ reinforced urea-formaldehyde 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. Urea-formaldehyde 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.

[0019] 4. At the same time, the addition of urea increases the groups that react with formaldehyde and reduces the formaldehyde content in melamine foam, which makes the material more widely used in chemical industry, anti-corrosion engineering, home decoration and transportation tools. DETAILED DESCRIPTION

[0020] 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

[0021] This embodiment provides a method for preparing a low-aldehyde melamine foam material, the steps are as follows: (1) Melamine, urea and formaldehyde are mixed evenly and added to deionized water, and an alkaline catalyst sodium hydroxide is added to adjust the pH to a weak alkaline state, and the mixture is heated to 85°C. After the solution becomes clear and transparent, the mixture is reacted at a constant temperature for 20 minutes, and then the solution is 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 urea is 1:0.1, the molar ratio of melamine to aldehyde compounds is 1:2, and the mass ratio of melamine to alkaline catalyst is 1:0.001.

[0022] (2) 100 parts by mass of the obtained expandable melamine resin were mixed with 1 part of primary urea-formaldehyde fiber, 4 parts of n-pentane, 1 part of formic acid agent and 3 parts of sodium eicosyl sulfate, and then stirred at 3000 r / min for 40 seconds to prepare a foaming liquid, and 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 2 hours to obtain melamine foam.

[0023] The apparent density of the melamine foam is 4.6 kg / m 3The open porosity is 96%, the tensile strength is 1050kPa, the elongation at break is 132%, the sound absorption coefficient of 10cm melamine foam at a frequency of 110Hz-4000Hz reaches 98.5%, the formaldehyde content is 15mg / kg, the vertical burning UL-94 rating is V-0, the limiting oxygen index is 45.1%, the thermal conductivity is 0.006W / (m·K), and the foam is not easy to fall off.

[0024] Example 2 This embodiment provides a method for preparing a low-aldehyde melamine foam material, the steps are as follows: (1) Melamine, urea and acetaldehyde are mixed evenly and added to deionized water, and alkaline catalyst potassium hydroxide is added to adjust the pH to a weak alkaline state, and the mixture is heated to 110°C. After the solution becomes clear and transparent, the mixture is reacted at a constant temperature for 60 minutes, and then the solution is 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 urea is 1:0.6, the molar ratio of melamine to aldehyde compounds is 1:3.5, and the mass ratio of melamine to alkaline catalyst is 1:0.01.

[0025] (2) 100 parts by mass of the obtained expandable melamine resin were mixed with 5 parts (cured in air at 180°C for 0.1 hour) of urea-formaldehyde fiber, 15 parts of isopentane, 5 parts of acetic acid and 10 parts of sodium dodecylbenzene sulfonate, and then stirred at 3000 r / min for 100 seconds 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 hours to obtain melamine foam.

[0026] The apparent density of the melamine foam is 3.5 kg / m 3 The open porosity is 98%, the tensile strength is 945kPa, the elongation at break is 63%, the sound absorption coefficient of 10cm melamine foam at a frequency of 130Hz-4000Hz reaches 98.7%, the formaldehyde content is 15mg / kg, the vertical burning UL-94 rating is V-0, the limiting oxygen index is 44.1%, the thermal conductivity is 0.017W / (m·K), and the foam is not easy to fall off.

[0027] Example 3 This embodiment provides a method for preparing a low-aldehyde melamine foam material, the steps are as follows: (1) Melamine, urea and formaldehyde are mixed evenly and added to deionized water, and the alkaline catalyst triethanolamine is added to adjust the pH to a weak alkaline state, and the mixture is heated to 90°C. After the solution becomes clear and transparent, the mixture is reacted at a constant temperature for 50 minutes, and then the solution is 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 urea is 1:0.3, the molar ratio of melamine to aldehyde compounds is 1:3, and the mass ratio of melamine to alkaline catalyst is 1:0.008.

[0028] (2) 100 parts by mass of the obtained expandable melamine resin were mixed with 4 parts (cured at 180°C in air for 3 hours) of urea-formaldehyde fiber, 5 parts of cyclopentane, 3 parts of hydrochloric acid and 5 parts of hexadecyltrimethylammonium chloride, and then stirred at 3000 r / min for 80 seconds to prepare a foaming liquid, which was then subjected to microwave foaming at a foaming power of 3000 W and then aged at a high temperature of 110°C for 2 hours to obtain melamine foam.

[0029] The apparent density of the melamine foam is 11 kg / m 3 The 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.

[0030] Example 4 This embodiment provides a method for preparing a low-aldehyde melamine foam material, the steps are as follows: (1) Melamine, urea and acetaldehyde are mixed evenly and added to deionized water, and alkaline catalyst hexamethylenetetramine is added to adjust the pH to a weak alkaline state, and the mixture is heated to 95°C. After the solution becomes clear and transparent, the mixture is reacted at a constant temperature for 40 minutes, and then the solution is 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 urea is 1:0.2, the molar ratio of melamine to aldehyde compounds is 1:2, and the mass ratio of melamine to alkaline catalyst is 1:0.002.

[0031] (2) 100 parts by mass of the obtained expandable melamine resin were mixed with 3 parts (cured in air at 180°C for 0.3 hours) of urea-formaldehyde fiber, 5 parts of n-hexane, 2 parts of sulfuric acid and 3 parts of dodecyl polyoxyethylene ether, and then stirred at 3000 r / min for 40 seconds to prepare a foaming liquid, which was then subjected to microwave foaming at a foaming power of 2800 W and then aged at 98°C for 2 hours to obtain melamine foam.

[0032] The apparent density of the melamine foam is 9kg / m 3 The open porosity is 95%, the tensile strength is 1152kPa, the elongation at break is 84%, the sound absorption coefficient of 10cm melamine foam at a frequency of 110Hz-4000Hz reaches 98.4%, the formaldehyde content is 10mg / kg, 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.

[0033] Example 5 This embodiment provides a method for preparing a low-aldehyde melamine foam material, the steps are as follows: (1) Melamine, urea and formaldehyde are mixed evenly and added to deionized water, and an alkaline catalyst sodium hydroxide is added to adjust the pH to a weak alkaline state, and the mixture is heated to 85°C. After the solution becomes clear and transparent, the mixture is reacted at a constant temperature for 30 minutes, and then the solution is 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 urea is 1:0.5, the molar ratio of melamine to aldehyde compounds is 1:2.8, and the mass ratio of melamine to alkaline catalyst is 1:0.006.

[0034] (2) 100 parts by mass of the obtained expandable melamine resin were mixed with 4 parts (cured at 180°C in air for 2 hours) of urea-formaldehyde fiber, 12 parts of cyclohexane, 4 parts of p-toluenesulfonic acid and 6 parts of Tween-80, and then stirred at 3000 r / min for 50 seconds to prepare a foaming liquid, which was then subjected to microwave foaming at a foaming power of 2500 W and then aged at 90°C for 2 hours to obtain melamine foam.

[0035] The apparent density of the melamine foam is 10.5 kg / m 3 The open porosity is 95%, the tensile strength is 457kPa, the elongation at break is 93%, the sound absorption coefficient of 10cm melamine foam at a frequency of 130Hz-4000Hz reaches 98.5%, the formaldehyde content is 12mg / kg, the vertical burning UL-94 rating is V-0, the limiting oxygen index is 44.7%, the thermal conductivity is 0.038W / (m·K), and the foam is not easy to fall off.

[0036] Example 6 This embodiment provides a method for preparing a low-aldehyde melamine foam material, the steps are as follows: (1) Melamine, urea and formaldehyde are mixed evenly and added to deionized water, and alkaline catalyst potassium hydroxide is added to adjust the pH to weak alkalinity, and heated to 90°C. After the solution becomes clear and transparent, the reaction is continued at a constant temperature for 35 minutes, and then the solution is 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 urea is 1:0.4, the molar ratio of melamine to aldehyde compounds is 1:2.3, and the mass ratio of melamine to alkaline catalyst is 1:0.006.

[0037] (2) 100 parts by mass of the obtained expandable melamine resin were mixed with 5 parts (cured at 180°C in air for 2 hours) of urea-formaldehyde fiber, 8 parts of n-pentane, 3 parts of p-toluenesulfonic acid and 6 parts of sodium dodecylbenzenesulfonate, and then stirred at 3000 r / min for 90 seconds to prepare a foaming liquid, which was then 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.

[0038] The apparent density of the melamine foam is 4 kg / m 3 The open porosity is 96%, the tensile strength is 760kPa, the elongation at break is 33%, the sound absorption coefficient of 10cm melamine foam at a frequency of 110Hz-4000Hz reaches 98.6%, the formaldehyde content is 17mg / kg, the vertical burning UL-94 rating is V-0, the limiting oxygen index is 45.2%, the thermal conductivity is 0.037W / (m·K), and the foam is not easy to fall off.

[0039] 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 preparing a low-aldehyde melamine foam material, characterized in that Here are the steps: (1) Melamine, aldehyde compound, urea 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 foamable melamine resin; (2) 100 parts by mass of the melamine resin obtained in step (1) are mixed with 1-5 parts by mass of urea-formaldehyde fiber, 4-15 parts by mass of a foaming agent, 1-5 parts by mass of a curing agent and 3-10 parts by mass of an emulsifier, and the mixture is stirred evenly to obtain a foaming liquid, and the foaming liquid is subjected to microwave foaming and high-temperature aging to obtain a melamine foam.

2. A method for preparing a low-aldehyde melamine foam material according to claim 1, characterized in that: In the step (1), the molar ratio of melamine to urea is 1:(0.1-0.6), the molar ratio of melamine to aldehyde compound is 1:(2-3.5), and the mass ratio of melamine to alkaline catalyst is 1:(0.001-0.01).

3. A method for preparing a low-aldehyde melamine foam material according to claim 1, characterized in that: In the step (1), 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 preparing a low-aldehyde melamine foam material according to claim 1, characterized in that: In the step (2), the urea-formaldehyde fiber is a primary urea-formaldehyde fiber or a urea-formaldehyde fiber cured in air at 180° C. for 0.1-3 hours; and the foaming agent is one of n-pentane, isopentane, cyclopentane, n-hexane, and cyclohexane.

5. The method for preparing a low-aldehyde 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 preparing a low-aldehyde 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 preparing a low-aldehyde 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 foaming power of the microwave foaming is 2000-4000 W, and the high-temperature aging is aging at a high temperature environment of 90-130° C. for 2 hours.