CN116199522A - PU sponge-based silicon aerogel felt and preparation method thereof - Google Patents

Abstract

The present application relates to the technical field of thermal insulation materials, in particular to a PU sponge-based silicon airgel felt and a preparation method thereof. The preparation method of the PU sponge-based silicon airgel felt provided by the application comprises the following steps: uniformly mixing siloxane, orthosilicate, water and absolute ethanol, then adding acetic acid and cetyltrimethyl bromide successively Ammonium chloride is heated and reacted to obtain a silicon source hydrolyzate; an alkali catalyst is added to the silicon source hydrolyzate, and fully stirred evenly to obtain a silica sol; the PU sponge is immersed in the silica sol for dipping treatment, and then Static aging at room temperature to obtain PU sponge/silicon airgel composites; add PU sponge/silicon airgel composites to absolute ethanol for solvent replacement; complete solvent replacement of PU sponge/silicon airgel composites After drying, the PU sponge-based silicon airgel felt is obtained. The PU sponge-based silicon airgel blanket prepared by the present application has good flexibility, resilience and excellent thermal insulation performance.

Description

A kind of PU sponge-based silicon airgel felt and preparation method thereof

technical field

The present application relates to the technical field of thermal insulation materials, in particular to a PU sponge-based silicon airgel felt and a preparation method thereof.

Background technique

Silica airgel is a solid material with interconnected nanoporous structure formed by the aggregation of nanometer-sized silica solid particles to form a three-dimensional network skeleton. The average pore size of silica aerogel is about 20nm, which is smaller than the average free path of motion of air molecules, which greatly limits heat conduction and heat convection. The equivalent thermal conductivity is very low, and it is currently the solid material with the lowest thermal conductivity in the world. Silica airgel is usually in the form of powder, granule or block, with low strength, high brittleness and poor toughness, and the powder is easy to escape and float in the air, causing serious pollution problems, thus limiting its application in construction. operability and application. In order to solve these problems, fiber mats such as ceramic fiber mats, glass fiber mats, and pre-oxidized silk fiber mats are often used as base materials to prepare fiber-reinforced silica airgel mats. This kind of fiber felt is made of short fibers with a diameter of micron through laying, needle punching and other processes. The fiber has high rigidity, poor flexibility, and stable dimension of the felt, but the short fibers are easy to fall off, and the structure difference in the thickness direction and the plane direction is large. , leading to anisotropy in the mechanical and thermal properties of the final product. In addition, the porous structure composed of short fiber aggregates has a large pore size, which has poor binding properties to airgel powder and particles, and the problem of powder falling is prominent, which in turn affects the thermal insulation performance and application of the felt. In order to improve the problem of poor tensile strength and resilience of fiber-reinforced silicon airgel felt in practical applications, patent CN111908889A discloses a composite fiber-reinforced airgel felt and its preparation method, specifically combining flexible fiber mesh tire and silicic acid The aluminum fiber mesh tires are alternately laid on the XY plane, and then connected by needle-punched flexible fibers in the Z direction to obtain a composite fiber mat. Using the composite fiber mat as a base material, a fiber-reinforced silicon airgel felt is prepared, which improves the thermal insulation performance. Stability, enhanced mechanical flexibility. However, the preparation process of the composite fiber mat is complex and time-consuming, which is not conducive to industrial mass production, and the mat is a porous fiber short fiber aggregate structure, which has an unsatisfactory binding effect on airgel; patent CN111039295B discloses a One-step method for preparing silica airgel and self-hydrophobic silica airgel insulation felt pad. During the preparation process, the silicon source hydrolysis and polycondensation reactions are carried out simultaneously, the system reaction is not complete, and the pore size of the prepared airgel is Uneven distribution, low skeleton strength and poor flexibility. Patent CN108383129A discloses a preparation method of flexible hydrophobic silica aerogels, specifically discloses the preparation of flexible hydrophobic silica aerogels using methyltrialkoxysilane and orthosilicate as silicon sources. Volatile ammonia water with a strong pungent smell is used as an alkali catalyst, which can easily cause serious environmental pollution and safety problems; and the prepared silica airgel does not contain a reinforcing substrate, and its three-dimensional porous structure will partially collapse after drying, showing A mixed system of powder, granules and irregular lumps is produced, which cannot be applied directly. Patent CN111848114A discloses a super heat-insulating airgel composite material and its preparation process. It specifically discloses the preparation of airgel composite materials by combining silica airgel and reinforced foam. During the preparation process, the wet gel composite The material is immersed in a hydrophobic reagent for hydrophobic modification. Since the PU sponge is not resistant to immersion in organic solvents, the PU sponge skeleton is dissolved and loses its mechanical properties until the structure is completely disintegrated. Based on the above analysis, it is very important to provide a method for preparing a silica airgel mat with simple process and good flexibility and mechanical properties.

Contents of the invention

The embodiment of the present application provides a preparation method of PU sponge-based silicon airgel mat to solve the problems of poor flexibility, serious powder dropping and complicated preparation process of fiber-based silicon airgel felt in the prior art. In the first aspect, the present application provides a preparation method of PU sponge-based silicon airgel felt, comprising the following steps: Step S101, mixing siloxane, orthosilicate, water and absolute ethanol uniformly, and then sequentially adding Acetic acid and cetyltrimethylammonium bromide (CTAB) are heated and reacted to obtain a silicon source hydrolyzate; step S102, adding an alkali catalyst to the silicon source hydrolyzate, and fully stirring to obtain a silica sol solution; step S103, immersing the PU sponge in the silica sol solution for dipping treatment, and then statically aging it at room temperature for 6-2 hours to obtain a PU sponge/silica airgel composite material; Step S104, PU sponge/silica airgel The composite material is added to absolute ethanol for solvent replacement to remove the moisture in the PU sponge/silicon airgel composite material; Step S105, drying the PU sponge/silicon airgel composite material to obtain the PU sponge-based silicon airgel felt. In some embodiments, the molar ratio of siloxane: orthosilicate: absolute ethanol: water is (0.4-1): (0-0.04): (3-12): (4-8). In some embodiments, the molar ratio of acetic acid:siloxane is (0.002˜0.01):1. In some embodiments, the density of the PU sponge is 20-60 kg/m3, and the thickness is 5-20 mm. In some embodiments, the molar ratio of cetyltrimethylammonium bromide:siloxane is (0.002˜0.005):1. Hexadecyltrimethylammonium bromide can promote the polycondensation reaction, which is conducive to the further polymerization of oligomers to form a long-chain silica skeleton structure that expands to three-dimensional space, making the condensation reaction more complete. In some embodiments, in step S101, the heating reaction condition is 50-60° C., and the reaction time is 10-16 hours. In some embodiments, the molar ratio of siloxane to base catalyst is 1:(0.005˜0.015). In some embodiments, in step S102, the stirring speed is 500-1500 rpm, and the stirring time is 5-15 minutes. In some embodiments, in step S103, the dipping time is 1-6 hours. In some embodiments, in step S104, the number of solvent replacements is 1 to 3 times, and the time for each replacement is 4 to 12

h. In some embodiments, in step S105, the drying method is normal pressure drying or supercritical drying. In some embodiments, the siloxane is any one or a mixture of two of dimethyldiethoxysilane, methyltriethoxysilane, and ethyltrimethoxysilane. Dimethyldiethoxysilane, methyltriethoxysilane, and ethyltrimethoxysilane have hydrophobic groups, and there is no need to modify the hydrophobicity of the composite material after dipping treatment when using these siloxanes. Sex, to avoid damage to the PU sponge. In some embodiments, the orthosilicate is any one or a mixture of methyl orthosilicate and ethyl orthosilicate. In some embodiments, the base catalyst is an aqueous solution of NaOH or KOH. Using NaOH or KOH as a catalyst has high safety, will not pollute the environment, and is easy to operate and low in cost. In the second aspect, the present application also provides the PU sponge-based silicon airgel felt prepared by the above-mentioned preparation method, the PU sponge-based silicon airgel felt is soft in texture, and the compression rebound rate in the thickness direction can reach 60-95% , less powder shedding, water contact angle of 110-140°, thermal conductivity of 0.023-0.012W/m·K. The PU sponge-based silica airgel felt prepared by this application can be applied to thermal insulation in non-high temperature scenarios (less than 120°C), such as buildings, industrial pipelines, etc., as well as thermal insulation and cold chain of refrigerators and vending machines. Transportation, medical cold preservation and other fields, at the same time, it can be used as an interlayer in clothing, outdoor products, etc., to achieve the effect of heat insulation or warmth. The preparation method provided by this application uses PU sponge with a fine and uniform open-pore structure as the base material. The PU sponge has a three-dimensional network skeleton composed of polygonal and polyhedral interweaving and stacking of polyurethane elastomer polymers and a large number of air-filled , Interpenetrating open micro pores, fine and uniform pores, small pore orientation, high porosity, good flexibility, resilience and heat insulation. In the process of preparing silica sol, the present application uses siloxane with hydrophobic groups as raw materials, without subsequent hydrophobic modification of the composite material after dipping treatment, and avoids the impact of hydrophobic modification reagents on PU sponge molecules. The destruction of the structure fully retains the characteristics of the PU sponge; using NaOH or KOH as the alkali catalyst to avoid the use of volatile gases is safe and environmentally friendly, and it is easy to operate and low in cost; after the PU sponge is dipped in silica sol, the two Silica sol is filled in the micropores of PU sponge and formed by polycondensation reaction to form silica solid microparticles with nanoscale three-dimensional porous structure. Porous structure, so as to realize the mutual embedding of multi-scale three-dimensional porous structure. After the wet PU sponge/silicon airgel composite material is replaced by ethanol and dried, the prepared PU sponge-based silicon airgel felt has good flexibility, resilience and excellent thermal insulation performance. The beneficial effects brought by the technical solution provided by this application include: 1. The preparation method provided by this application uses a PU sponge with good flexibility, resilience and uniform and dense pores as a substrate, and the PU sponge with one or more flexible groups Siloxane is the silicon source precursor. After sol, dipping, gelling, aging, replacement, and drying treatments, it not only retains the integrity of the sponge structure and good mechanical properties, but also ensures the flexibility of the silicon airgel skeleton. 2. The preparation method provided by this application combines the PU sponge with a three-dimensional porous structure with the silicon airgel with a multi-level three-dimensional porous structure, and the prepared The sponge-based silica airgel felt has a multi-scale microporous structure, and the micropores of various sizes and shapes overlap and communicate with each other, forming complex and changeable pore paths, which further restricts the movement and transmission of air molecules. 3. The preparation method provided by this application can effectively prevent the removal and escape of silicon airgel solid powder and particles, and form a better 4. The surface of the silicon airgel prepared by the preparation method provided by this application has a large number of hydrophobic groups, and no hydrophobic treatment is required, that is, the PU sponge-based silicon airgel felt is given a hydrophobic effect, It ensures the stability of the heat insulation performance of the material in actual use, and avoids the problem of the heat insulation performance of the silicon airgel felt being reduced due to humidity and water; at the same time, it simplifies the process and reduces time and economic costs; 5. Utilization The PU sponge-based silicon airgel mat prepared by the preparation method provided by the application has a self-extinguishing effect when exposed to an open flame, and has a flame-retardant effect, avoiding potential safety hazards caused by fire and flammability of conventional PU sponges during use. question.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those skilled in the art, other drawings can also be obtained based on these drawings without creative effort. Fig. 1 is a schematic flow chart of the preparation method of the PU sponge-based silicon airgel felt provided in the embodiment of the present application; Fig. 2 is a physical diagram of the PU sponge-based silicon airgel felt prepared in Example 1 of the present application; Fig. 3 is The bending diagram of the PU sponge-based silicon airgel felt prepared in Example 1 of the present application.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments It is a part of the embodiments of this application, but not all of them. Based on the embodiments in the present application, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present application. The embodiment of the present application provides a preparation method of PU sponge-based silicon airgel felt, which can solve the problems of poor flexibility, serious powder dropping and complicated preparation process in the prior art of fiber-based silicon airgel felt. Fig. 1 is the schematic flow chart of the preparation method of the PU sponge-based silicon airgel mat provided by the application, with reference to Fig. 1, the preparation method provided by the application comprises the following steps: Step S101, take siloxane, orthosilicate, water Mix with absolute ethanol evenly, then add acetic acid and cetyltrimethylammonium bromide (CTAB) in sequence, and stir in a water bath at 50-60°C for 10-16 hours to obtain a silicon source hydrolyzate; step S102, add Add an alkali catalyst to the silicon source hydrolyzate, and stir at a speed of 500-1500rpm for 5-15 minutes to obtain a silica sol solution; step S103, immerse the PU sponge in the silica sol solution for dipping treatment, and the dipping time is 1 ～6h, and static aging at room temperature for 6～24h to obtain the PU sponge/silicon airgel composite material; Step S104, placing the PU sponge/silicon airgel composite material in absolute ethanol for 1 to 3 times of solvent Replacement, the time for each replacement is 4-12h, fully remove the moisture in the PU sponge/airgel composite material; Step S105, carry out normal pressure or supercritical drying of the PU sponge/airgel composite material to obtain PU Sponge-based silicon airgel felt. The PU sponge-based silicon airgel felt provided by the present application and its preparation method are described in detail below in conjunction with the examples. Example 1: Example 1 provides a preparation method of PU sponge-based silicon airgel felt, which includes the following steps: (1) Take 10mol methyltriethoxysilane, 0.4mol methyl orthosilicate, 80mol water Mix well with 50mol absolute ethanol, then add 0.05mol acetic acid and 0.02mol cetyltrimethylammonium bromide (CTAB) in sequence, and stir for 15h in a water bath at 50°C to obtain a silicon source hydrolyzate; (2) Add 0.10 mol of sodium hydroxide to the silicon source hydrolyzate, and fully stir at 800rpm for 10 minutes to obtain a silica sol solution; Dip in the silica sol solution for 6h, and in 24

Static aging at ℃ for 12 hours to obtain the PU sponge/silicon airgel composite material; (4) Place the PU sponge/silicon airgel composite material in absolute ethanol for 2 solvent replacements, each replacement time is 8 hours , Fully remove the moisture in the PU sponge/silica airgel composite material; (5) Supercritically dry the PU sponge/silica airgel composite material to obtain the PU sponge-based silicon airgel felt. The physical picture of the PU sponge-based silicon airgel felt made in Example 1 is shown in Figure 2. The PU sponge-based silicon airgel felt has a soft texture, a compression rebound rate of 80% in the thickness direction, less powder loss, a water contact angle of 120°, and a thermal conductivity of 0.017W/m·K. The PU sponge-based silicon airgel felt prepared in Example 1 was bent, as shown in FIG. 3 , and it can be seen from FIG. 3 that the PU sponge-based silicon airgel felt showed good flexibility. The PU sponge and the PU sponge-based silicon airgel felt prepared in Example 1 are subjected to self-extinguishing tests. The specific process is as follows: use a lighter to ignite the PU sponge and the PU sponge-based silicon airgel felt respectively. The PU sponge catches fire quickly and has a large flame. , The fire spreads rapidly until the whole piece of PU sponge is completely burned; while the PU sponge-based silicon airgel felt has a slow ignition speed, a small flame, and the open flame lasts for 3 to 5 seconds and then goes out, and the fire cannot spread, which shows that the PU sponge made by this application Silica-based airgel felt has good flame retardant and self-extinguishing effect. Example 2: Example 2 provides a preparation method of PU sponge-based silicon airgel felt, including the following steps: (1) Take 6 mol of methyltriethoxysilane, 0.1 mol of ethyl orthosilicate, 100 mol of water Mix well with 40mol absolute ethanol, then add 0.03mol acetic acid and 0.03mol cetyltrimethylammonium bromide (CTAB) in sequence, and stir for 12h in a water bath at 50°C to obtain a silicon source hydrolyzate; (2) Add 0.15mol sodium hydroxide to the silicon source hydrolyzate, and stir at a speed of 1000rpm for 15 minutes to obtain a silica sol; Soak in the silica sol solution for 2 hours, and statically age at 24°C for 24 hours to obtain the PU sponge/silica airgel composite material; (4) Put the PU sponge/silica airgel composite material in absolute ethanol for 3 The second solvent replacement, each replacement time is 12h, fully remove the moisture in the PU sponge/silicon airgel composite material; (5) Supercritically dry the PU sponge/silicon airgel composite material to obtain the PU sponge base Silicone airgel felt. The PU sponge-based silicon airgel felt produced in Example 2 is soft in texture, has a compression rebound rate of 85% in the thickness direction, less powder loss, a water contact angle of 112°, and a thermal conductivity of 0.019W/m·K. Example 3: Example 3 provides a preparation method of PU sponge-based silicon airgel felt, including the following steps: (1) Take 15mol dimethyldiethoxysilane, 0.6mol methyl orthosilicate, 120mol Mix water and 100mol absolute ethanol evenly, then add 0.12mol acetic acid and 0.045mol cetyltrimethylammonium bromide (CTAB) in sequence, and stir for 12h in a water bath at 55°C to obtain a silicon source hydrolyzate; (2 ) Add 0.15mol sodium hydroxide to the silicon source hydrolyzate, and stir fully at a speed of 1000rpm for 10min to obtain a silica sol; Soak in silica sol solution for 6 hours, and statically age at 24°C for 12 hours to obtain PU sponge/silica airgel composite material; (4) Put PU sponge/silica airgel composite material in absolute ethanol for 2 times of solvent replacement, each replacement time is 10h, fully remove the moisture in the PU sponge/silicon airgel composite material; (5) Supercritically dry the PU sponge/silicon airgel composite material to obtain the PU sponge Silica-based airgel felt. The PU sponge-based silicon airgel felt obtained in Example 3 is soft in texture, has a compression rebound rate of 70% in the thickness direction, less powder shedding, a water contact angle of 132°, and a thermal conductivity of 0.015W/m·K. Example 4: Example 4 provides a preparation method of PU sponge-based silicon airgel felt, including the following steps: (1) Take 24mol ethyltrimethoxysilane, 0.6mol methyl orthosilicate, 270mol water and Mix 150mol of absolute ethanol evenly, then add 0.144mol of acetic acid and 0.072mol of cetyltrimethylammonium bromide (CTAB) in sequence, and stir for 12h in a water bath at 50°C to obtain a silicon source hydrolyzate; (2) add Add 0.24mol sodium hydroxide to the silicon source hydrolyzate, and stir at 800rpm for 10 minutes to obtain a silica sol; (3) Put a porous PU sponge felt with a density of 50kg/m3 and a thickness of 8mm on the silica Soak in the sol solution for 6 hours, and statically age at 24°C for 12 hours to obtain the PU sponge/silicon airgel composite material; (4) Put the PU sponge/silicon airgel composite material in absolute ethanol for 2 times Solvent replacement, each replacement time is 8h, fully remove the moisture in the PU sponge/silicon airgel composite material; (5) Supercritically dry the PU sponge/silicon airgel composite material to obtain PU sponge-based silicon Airgel felt. The PU sponge-based silicon airgel felt obtained in Example 4 is soft in texture, has a compression rebound rate of 83% in the thickness direction, less powder loss, a water contact angle of 135°, and a thermal conductivity of 0.014W/m·K. In the description of this specification, descriptions referring to the terms "one embodiment/mode", "some embodiments/modes", "examples", "specific examples" or "some examples" mean that the embodiments/modes or The specific features, structures, materials or features described in the examples are included in at least one embodiment/mode or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment/mode or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments/modes or examples in an appropriate manner. In addition, those skilled in the art may combine and combine different embodiments/modes or examples and features of different embodiments/modes or examples described in this specification without conflicting with each other. It should be noted that in this application, relative terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply There is no such actual relationship or order between these entities or operations. Furthermore, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus comprising a set of elements includes not only those elements, but also includes elements not expressly listed. other elements of or also include elements inherent in such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising said element. In the present application, "plurality" means at least two, such as two, three, etc., unless otherwise specified. The above description is only for the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the application. Therefore, the present application will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims (10)

1. The preparation method of the PU sponge-based silicon aerogel felt is characterized by comprising the following steps of: uniformly mixing siloxane, orthosilicate, water and absolute ethyl alcohol, and then sequentially adding acetic acid and hexadecyl trimethyl ammonium bromide for heating reaction to obtain silicon source hydrolysate; adding an alkali catalyst into the silicon source hydrolysate, and fully and uniformly stirring to obtain a silicon dioxide sol solution; immersing the PU sponge into the silicon dioxide sol solution for gum dipping treatment, and standing and aging under normal temperature conditions to obtain a PU sponge/silicon aerogel composite material; adding the PU sponge/silicon aerogel composite material into absolute ethyl alcohol to perform solvent replacement; and drying the PU sponge/silicon aerogel composite material subjected to solvent replacement to obtain the PU sponge-based silicon aerogel felt.

2. The method for preparing the PU sponge-based aerogel blanket according to claim 1, wherein the siloxane: orthosilicate: absolute ethyl alcohol: the molar ratio of water is 4-1: 0-04:3-12:4-8.

3. The method for preparing the PU sponge-based aerogel blanket according to claim 1, wherein acetic acid: the molar ratio of siloxane is 002-01: 1.

4. the method for preparing the PU sponge-based aerogel blanket according to claim 1, wherein the cetyl trimethylammonium bromide: the molar ratio of the siloxane is (002-005): 1.

5. the method for preparing the PU sponge-based silica aerogel felt according to claim 1, wherein the heating reaction condition is 50-60 ℃, and the reaction time is 10-16 h.

6. The method for preparing the PU sponge-based aerogel blanket according to claim 1, wherein the molar ratio of siloxane to base catalyst is 1:005-015.

7. The method for preparing the PU sponge-based aerogel blanket according to claim 1, wherein the siloxane is any one or a mixture of two of dimethyl diethoxy silane, methyl triethoxy silane and ethyl trimethoxy silane.

8. The method for producing a PU sponge-based aerogel blanket as claimed in claim 1, wherein the orthosilicate is any one or a mixture of two of methyl orthosilicate and ethyl orthosilicate.

9. The method for preparing the PU sponge-based aerogel blanket according to claim 1, wherein the base catalyst is sodium hydroxide or potassium hydroxide.

10. A PU sponge-based aerogel blanket, characterized in that it is produced by the production method of any one of claims 1 to 9.

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