Method for preparing melamine foam component with adjustable and controllable density

Abstract

The present invention belongs to the field of material processing technology, and specifically relates to a method for preparing a melamine foam component with adjustable and controllable density. The present invention foams a melamine formaldehyde resin solution in a microwave radiation field to form a lightweight melamine foam, which is then cooled and cut into rectangular plates by a cutting machine; the plates are immersed in an aqueous solution containing 0-5% silane or siloxane hydrolyzate or a slurry with a solid phase volume content of 0-25% to improve their surface properties; the foam absorbed with the aqueous solution is placed in a hot pressing mold with a large number of through-hole top covers; a hot press is used to hot press the plates, and the density and shape of the plates are adjusted by controlling the distance between the upper and lower metal hot pressing plates of the hot press; a vibration cutting machine or an engraving machine is used to perform shape processing on the hot-pressed plates to obtain the final melamine foam component with adjustable density, whose density ranges from 10 to 100 kg / m 3 , this method can effectively control the density uniformity of the product.

Description

Technical Field

[0001] The invention belongs to the technical field of material processing, and particularly relates to a method for preparing a melamine foam component with adjustable and controllable density. Background Art

[0002] Melamine foam, also known as melamine foam, is a new type of polymer material with a high open porosity (at least 98%) formed by curing and foaming melamine formaldehyde resin. The melamine foam prepared by microwave foaming technology has the characteristics of orderly internal network structure, low and uniform density, stable physical properties, and good sound absorption and noise reduction functions. In view of these advantages, melamine foam has been widely used in industry, construction, transportation, aviation and aerospace. With the continuous improvement of the performance of melamine foam and the verification of its reliability in practical applications, this material has been used for lightweight components in the aerospace field in recent years. However, although the density of high-open-cell melamine foam produced by microwave foaming technology is usually 5-8 kg / m 3 The density of melamine foam is between 100 and 200 nm, which can meet the needs of daily construction and industrial fields. However, it is insufficient for the elasticity and thermal insulation performance of higher density melamine foam required in the aviation and aerospace fields. The common method from low density to high density is hot pressing, which includes the following methods.

[0003] Single-step hot pressing: This is the simplest hot pressing method and is suitable for small products or products with a single density requirement. It completes the entire hot pressing process through a single heating and pressing process. The process is simple and easy, but it may not be able to achieve complex density requirements.

[0004] Multi-stage hot pressing: To improve the controllability of foam density and the quality of the final product, multi-stage hot pressing is increasingly being adopted. This method involves multiple steps: preheating, main heating, pressurization, and cooling. By meticulously controlling the temperature, pressure, and time of each stage, precise control of material density can be achieved.

[0005] Continuous hot pressing: Continuous hot pressing is more suitable for large-scale production and production lines that require continuous supply. This method uses continuous heating and pressurizing devices to achieve continuous flow and shaping of materials, and is suitable for producing long or continuous foam sheets.

[0006] Vacuum hot pressing: To further improve product quality and density consistency, vacuum hot pressing is widely used in high-end products. By performing hot pressing in a vacuum environment, the air content inside the material can be effectively reduced, thereby improving the product's density and physical properties.

[0007] Composite hot pressing: For plastic foam products requiring specialized properties, such as fire resistance and heat insulation, composite hot pressing is an ideal solution. This method typically incorporates other functional materials or coatings during the hot pressing process to enhance the overall performance of the foam.

[0008] The above method is usually suitable for components with a small thickness. For thick foam components, due to the foam's own thermal insulation properties, high temperature cannot be transmitted to the inside, and the density of the foam after hot pressing is uneven. Summary of the Invention

[0009] To solve the above problems, the present invention provides a method for preparing a melamine foam component with adjustable and controllable density, which can achieve precise control of the density of the melamine foam component with adjustable density and realize the requirements of fast and high-precision shape processing of melamine foam boards.

[0010] The present invention provides a method for preparing a melamine foam component with adjustable and controllable density, comprising the following steps in sequence:

[0011] a. The melamine formaldehyde resin solution is foamed in a microwave radiation field to obtain a microwave-foamed lightweight melamine foam, wherein the microwave-foamed lightweight melamine foam has a density of 5 to 10 kg / m 3 ;

[0012] b The microwave foamed lightweight melamine foam is cooled, and the cooled microwave foamed lightweight melamine foam is divided into a cuboid material, a cylindrical material or a contoured material by a cutting machine to obtain a foam material after cutting;

[0013] c. Then, the cut foam material is immersed in an aqueous solution or an aqueous slurry to obtain a foam that is fully absorbed by the aqueous solution or the aqueous slurry; the aqueous solution includes an organic silane and / or a siloxane hydrolyzate; the aqueous slurry includes a solid phase powder, silane, and a siloxane hydrolyzate; the weight content of the silane or siloxane in the aqueous solution is 0 to 5%; the solid phase powder in the aqueous slurry is nano-silicon oxide, fumed silica, aluminum oxide, or silicon carbide, and the solid content of the aqueous slurry is 0 to 25% by volume of the aqueous slurry; the weight content of the silane or siloxane in the aqueous slurry is 0 to 5%;

[0014] d. The foam filled with aqueous solution or aqueous slurry is loaded into a hot pressing mold, the top cover of the hot pressing mold has a through hole, the aperture of the through hole is The number of through holes is 100 to 10,000 per m 2 ;

[0015] e. Using a hot press to hot-press the foam filled with an aqueous solution or aqueous slurry, the density and shape of the hot-pressed sheet material are adjusted by controlling the distance between the upper and lower metal hot press plates to obtain a hot-pressed sheet material;

[0016] f using a vibration cutting machine, engraving machine for the hot-pressed sheet material is processed to obtain a density adjustable and controllable melamine foam member;

[0017] g. Measuring the density of the adjustable and controllable melamine foam member, the density of the adjustable and controllable melamine foam member is 10 to 100 kg / m 3 , measure the density of the hot pressed sheet scraps removed during the shape processing, and the difference between the maximum density and the minimum density of the hot pressed sheet scraps shall not exceed 0.2kg / m 3 .

[0018] Preferably, the hot pressing of the foam absorbed with the aqueous solution using a hot press comprises a preheating stage, a pressurizing stage and a cooling and pressure relief stage performed in sequence, wherein the temperature of the preheating stage is 110-180°C, the temperature of the pressurizing stage is 200-300°C, the cooling and pressure relief stage is naturally cooled in the air, and the pressure of the hot pressing is adjusted according to the density setting; the bottom plate, top cover and side plates of the hot press are heatable, the bottom plate and the side plates constitute a fixed mold cavity, and the top cover has holes for water replenishment and ventilation during the hot pressing process; the time of the hot pressing is regulated according to the steam escape process, and is maintained for 3-15 minutes after the steam escapes completely.

[0019] The present invention adjusts the compression rate of sheet-like melamine foam through hot pressing, thereby transforming microwave-foamed lightweight melamine foam into high-density mature foam. This effectively addresses defects such as internal stagnation, powder loss, and low tensile tear strength in microwave-foamed melamine foam, thereby achieving the elastic performance indicators of density-adjustable melamine foam components. After hot pressing, the melamine foam rebounds to a certain extent. Traditional hot pressing methods result in inconsistent rebound rates at different locations, resulting in poor product long-term shape retention. This method improves the internal and external density uniformity of the foam component, preventing uneven deformation during placement or service. DETAILED DESCRIPTION

[0020] The technical solutions of the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention, but they should not be understood as limiting the scope of protection of the present invention.

[0021] Example 1 Preparation density is 20kg / m 3 of Melamine foam components

[0022] (1) The melamine formaldehyde resin solution is foamed in a microwave radiation field to obtain microwave foamed lightweight melamine foam with a density of 5 kg / m 3 ;

[0023] (2) cooling the microwave-foamed lightweight melamine foam, and cutting the cooled microwave-foamed lightweight melamine foam into 330×330×96 mm plate materials by a cutting machine to obtain cut foam materials;

[0024] (3) soaking the cut foam material in distilled water to obtain water-saturated foam;

[0025] (4) The foam fully absorbed with water is placed in a 330×330 mm square hot pressing mold. The top cover of the mold has a through hole and the side has scales. The aperture of the through hole is The number of through holes is 900 / m 2 ;

[0026] (5) hot pressing the foam fully absorbed with water using a hot press, wherein the temperature of the preheating stage is 130° C. for 10 minutes, the temperature of the pressurizing stage is 220° C., and the hot pressing time is maintained for 5 minutes after the steam escapes completely. The density of the sheet is adjusted by controlling the distance between the upper and lower metal hot pressing plates of the hot press to 20 mm. During the hot pressing process, the water in the foam boils and turns into water vapor, which escapes through the pores of the top cover, thereby achieving foam drying, and then naturally cooling and decompressing in the air to obtain a hot pressed sheet;

[0027] (6) After the hot pressing, the hot pressed sheet was taken out and placed at room temperature for 48 hours. The thickness of the hot pressed sheet rebounded from 20 mm to 24 mm. The hot pressed sheet was layered using sand wire cutting to form two square pieces of 330 × 330 × 12 mm. The upper and lower surfaces of the square pieces were then processed using a grinder to ensure a thickness of 10 mm. The pieces were then processed into 18 pieces using a vibration cutting machine. Circular components, to obtain melamine foam components with adjustable and controllable density;

[0028] (7) Randomly select 10 circular components, weigh the mass of the circular components, and divide them by their volume to obtain the densities of 19.9 kg / m 3 , 20.1kg / m 3 , 20.1kg / m 3 , 20kg / m 3 、19.9kg / m 3 、19.9kg / m 3 , 20kg / m 3 , 20kg / m 3 , 20.1kg / m 3 and 19.9kg / m 3 The average density of the components is 20kg / m3 , the fluctuation range is ±0.1kg / m 3 .

[0029] (8) Five of the circular components were vacuum-encapsulated using an aluminum-plastic composite film to obtain five foam vacuum insulation panels with an average thermal conductivity of 0.002 W / m·K.

[0030] Example 2 Preparation density is 50kg / m 3 The hydrophobic melamine foam threaded cylindrical component has an external thread centerline diameter of 400mm, an internal thread centerline diameter of 300mm, a height of 20mm, threaded inner and outer sides, and a thread width of 4mm.

[0031] (1) The melamine formaldehyde resin solution is foamed in a microwave radiation field to obtain microwave foamed lightweight melamine foam with a density of 10 kg / m 3 ;

[0032] (2) cooling the microwave-foamed lightweight melamine foam, and processing the cooled microwave-foamed lightweight melamine foam into a cylindrical material with an outer diameter of 400 mm, an inner diameter of 300 mm, and a height of 100 mm by a cutting machine to obtain a cut foam material;

[0033] (3) soaking the cut foam material in an aqueous solution comprising an organic silane or a siloxane hydrolyzate, wherein the weight content of the silane or siloxane in the aqueous solution is 2.75%, to obtain a foam fully absorbed by the aqueous solution;

[0034] (4) The foam filled with the aqueous solution is squeezed into a hot pressing mold. Both the inner mold and the outer mold are heated. The top cover of the mold has a through hole and the side has a scale. The aperture of the through hole is 2 mm and the number of through holes is 10,000 / m 2 ;

[0035] (5) Using a top cover to squeeze the foam that has absorbed the aqueous solution, the foam is subjected to hot pressing after entering the mold. The temperature of the preheating stage is 150°C for 7 minutes, the temperature of the pressurizing stage is 240°C, and the hot pressing time is maintained for 3 minutes after the steam escapes completely. The distance between the top cover and the bottom plate of the mold is controlled to be 20 mm. During the hot pressing process, the water in the foam boils and turns into water vapor, which escapes through the pores of the top cover, achieving foam drying, preheating and heating, and then naturally cooling and decompressing in the air to obtain a hot pressed sheet.

[0036] (6) After hot pressing, the hot pressed plate is taken out and placed at room temperature for 48 hours, and then a vibration cutting machine is used to cut the bulge on the top surface of the cylindrical component caused by the exhaust hole;

[0037] (7) Weigh and measure the cylindrical components. The average density of the components is 50 kg / m 3, the hydrophobicity rate reaches 98%.

[0038] Example 3 Preparation density is 100kg / m 3 , Melamine foam fireproof insulation board with a size of 600mm×400mm×10mm

[0039] (1) The melamine formaldehyde resin solution is foamed in a microwave radiation field to obtain microwave foamed lightweight melamine foam with a density of 10 kg / m 3 ;

[0040] (2) cooling the microwave-foamed lightweight melamine foam, and cutting the cooled microwave-foamed lightweight melamine foam into 600 mm × 400 mm × 70 mm plate materials by a cutting machine to obtain cut foam materials;

[0041] (3) Then, the cut foam material is immersed in an aqueous slurry, wherein the aqueous slurry includes a solid phase powder, silane, and a siloxane hydrolyzate, wherein the solid phase powder in the aqueous slurry is fumed silica, the solid content of the aqueous slurry is 20% of the volume of the aqueous slurry, and the weight content of the siloxane in the aqueous slurry is 5%, to obtain a foam that is fully absorbed by the aqueous slurry;

[0042] (4) The foam soaked with aqueous slurry is placed in a 600mm×400mm rectangular hot pressing mold. The top cover of the mold has a through hole and the side has scales. The diameter of the through hole is 5mm and the number of through holes is 2500 / m 2 ;

[0043] (5) hot pressing the foam filled with the aqueous slurry using a hot press, wherein the temperature of the preheating stage is 160° C. for 20 minutes, the temperature of the pressurizing stage is 260° C., and the hot pressing time is maintained for 5 minutes after the steam escapes completely. The density of the sheet is adjusted by controlling the distance between the upper and lower metal hot pressing plates of the hot press to 10 mm. During the hot pressing process, the water in the foam boils and turns into water vapor, which escapes through the pores of the top cover to achieve foam drying, and then naturally cools and releases the pressure in the air to obtain a hot pressed sheet;

[0044] (6) After hot pressing, the hot pressed sheet is taken out and placed at room temperature for 48 hours and weighed. If the foam has low resilience, a vibration cutting machine is used to process the foam component.

[0045] (7) Weigh the mass of the foam component and divide it by the foam volume to obtain a density of 100 kg / m 3 , the hydrophobicity reaches 98%, the thermal conductivity is 0.026W / mK, and the fire resistance is Class A melamine insulation foam components;

[0046] (8) The foam components after hot pressing are vacuum packaged, and the packaging film material is an aluminum-plastic composite film material to obtain a foam nano-powder vacuum insulation board with an average thermal conductivity of 0.003W / mK.

[0047] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention rather than all the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a melamine foam component with adjustable and controllable density, characterized in that: The steps include the following order: a. The melamine formaldehyde resin solution is foamed in a microwave radiation field to obtain a microwave-foamed lightweight melamine foam, wherein the microwave-foamed lightweight melamine foam has a density of 5 to 10 kg / m 3 ; b The microwave foamed lightweight melamine foam is cooled, and the cooled microwave foamed lightweight melamine foam is divided into a cuboid material, a cylindrical material or a contoured material by a cutting machine to obtain a foam material after cutting; c. Then, the cut foam material is immersed in an aqueous solution or an aqueous slurry to obtain a foam that is fully absorbed by the aqueous solution or the aqueous slurry; the aqueous solution includes an organic silane and / or a siloxane hydrolyzate; the aqueous slurry includes a solid phase powder, silane, and a siloxane hydrolyzate; the weight content of the silane or siloxane in the aqueous solution is 0 to 5%; the solid phase powder in the aqueous slurry is nano-silicon oxide, fumed silica, aluminum oxide, or silicon carbide, and the solid content of the aqueous slurry is 0 to 25% by volume of the aqueous slurry; the weight content of the silane or siloxane in the aqueous slurry is 0 to 5%; d. The foam filled with aqueous solution or aqueous slurry is loaded into a hot pressing mold, the top cover of the hot pressing mold has a through hole, the aperture of the through hole is The number of through holes is 100 to 10,000 per m 2 ; e. Using a hot press to hot-press the foam filled with an aqueous solution or aqueous slurry, the density and shape of the hot-pressed sheet material are adjusted by controlling the distance between the upper and lower metal hot press plates to obtain a hot-pressed sheet material; f using a vibration cutting machine, engraving machine for the hot-pressed sheet material is processed to obtain a density adjustable and controllable melamine foam member; g. Measuring the density of the adjustable and controllable melamine foam member, the density of the adjustable and controllable melamine foam member is 10 to 100 kg / m 3 , measure the density of the hot pressed sheet scraps removed during the shape processing, and the difference between the maximum density and the minimum density of the hot pressed sheet scraps shall not exceed 0.2kg / m 3 .

2. The preparation method according to claim 1, characterized in that The hot pressing of the foam absorbed with the aqueous solution using a hot press comprises a preheating stage, a pressurizing stage and a cooling and pressure relief stage, wherein the temperature of the preheating stage is 110-180° C., the temperature of the pressurizing stage is 200-300° C., the cooling and pressure relief stage is natural cooling in the air, and the pressure of the hot pressing is adjusted according to the density setting; the bottom plate, top cover and side plates of the hot press are heatable, the bottom plate and the side plates constitute a fixed mold cavity, and the top cover has holes for water replenishment and ventilation during the hot pressing process; the hot pressing time is regulated according to the steam escape process, and is maintained for 3-15 minutes after the steam escapes completely.