Electric heating material with high adhesive force to foamed polyurethane as well as preparation and application of electric heating material

Abstract

The invention discloses an electric heating material with high adhesive force to foamed polyurethane and preparation and application thereof, the material is of a network polymer structure, an organic monomer molecule A and a catalyst are used as film-forming and insulating materials, and after curing is completed, the material has good adhesive force to a foamed polyurethane base material. The invention also discloses a preparation method and application of the compound. The electric heating material precursor is printed on a foaming polyurethane base material in a silk-screen printing mode, an electric heating element with high adhesive force can be obtained, and the electric heating material precursor is suitable for being used as an electric heating element of bedding articles, aerospace seats and other products.

Description

Technical Field

[0001] This invention relates to the field of new materials technology, and more specifically to an electrothermal material with high adhesion to foamed polyurethane, its preparation and application. Background Technology

[0002] With the continuous development of carbon-containing electric heating materials, their performance is becoming increasingly comprehensive, and their application scenarios are becoming more and more extensive. However, carbon-containing electric heating materials differ significantly from resistance wire heating elements or ceramic PTC heating elements: the latter two can work independently without a carrier; while carbon-containing electric heating materials are usually in liquid or powder form before molding and cannot operate independently, therefore they need to be combined with a carrier to form a complete electric heating element. Common low-temperature carriers include various film materials, such as PI film, PET film, PVC film, and PP film; high-temperature carriers are mostly mica or metal sheets with insulating surfaces. The main methods of combining with a carrier are gravure printing, screen printing, and spraying, with the first two being the most common.

[0003] Polyurethane foam is widely used in the manufacture of bedding, aerospace seats, and thermal insulation materials. Unlike the aforementioned membrane materials, mica, or metals, polyurethane foam has a porous structure and a high degree of deformation capacity. This structure presents two problems: first, the porous structure leads to high water absorption, making it difficult to control the printing thickness when printing liquid pastes, and consequently, difficult to accurately control the thickness of the heating layer; second, the high degree of deformation requires strong adhesion of the coating after curing, otherwise the coating is prone to peeling off.

[0004] Therefore, developing an electrothermal material with strong adhesion to polyurethane foam to expand the application of carbon-containing electrothermal materials in bedding and aerospace fields has become an urgent problem for those skilled in the art. Summary of the Invention

[0005] In view of this, in order to achieve high adhesion between the electrothermal material and the polyurethane foam substrate, the present invention aims to provide an electrothermal material with high adhesion to the polyurethane foam substrate, its preparation method, and its application. This material uses carbon materials as the conductive medium, small organic molecules as resin monomers, water as the reaction solvent, and small amounts of acid and photosensitizers as catalysts. An electrothermal material with high adhesion to the polyurethane foam substrate is prepared under simple reaction conditions. After mixing the above components, the mixture is screen-printed onto the polyurethane foam substrate. After heating and curing, adhesion is effectively improved, making it very suitable as an electrothermal element for bedding and aerospace products.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: An electrothermal material with high adhesion to polyurethane foam, wherein the electrothermal material has a network polymer structure and its structural formula is as follows: .

[0007] The present invention also provides a method for preparing the electrothermal material with high adhesion to foamed polyurethane, comprising the following steps: S1. At room temperature, disperse monomer A in water at a speed of 150-400 rpm and stir until homogeneous; S2. At room temperature, with the disperser speed at 600-800 rpm, add the carbon material to the dispersion system in step S1 in three batches at a mass ratio of 1:1:1. After all the material has been added, adjust the disperser speed to 850-1400 rpm and stir until the slurry surface is uniform and free of particulate matter. S3. Add catalyst and acid to the system after stirring in step S2, stir in the dark for 15 min to obtain a viscous slurry, which is the precursor of the electrothermal material with high adhesion to polyurethane foam. S4. Heat-treat the electrothermal material precursor to obtain an electrothermal material with high adhesion to foamed polyurethane. The structural formula of monomer A is as follows: .

[0008] Preferably, by weight, monomer A is 100 parts, carbon material is 44-79 parts, catalyst is 0.3-5.0 parts, acid is 6.6-10.5 parts, and water is 37-62 parts.

[0009] Preferably, the carbon material is any one or more of carbon nanotubes, graphene, carbon black, graphite, and carbon fiber, and the carbon material provides a conductive medium and certain physical support for the electrothermal material. The catalyst is one or more of thioxanthone, 2-bromothioxanthone, 2-carboxymethoxythioxanthone, or 3-carboxythioxanthone. Thioxanthone catalysts are often used in photochemical and industrial reactions. In this invention, thioxanthone is excited by natural light or lamp light to form an excited-state intermediate. This intermediate will take electrons from the isocyanate group to form a carbocation intermediate. Then, this intermediate will attack the oxygen atom on the methoxy group to undergo an esterification substitution reaction, and finally form a polymer with a network spatial structure. The acid is trifluoromethanesulfonic acid. A trace amount of trifluoromethanesulfonic acid can provide an acidic environment, increasing the solubility of monomer A in water. Simultaneously, the acid hydrolyzes the terminal methoxy group to form hydroxyl groups, which can better form hydrogen bonds with oxygen atoms on the polyurethane surface, increasing adhesion.

[0010] Preferably, the heat treatment temperature in step S4 is 60 °C and the time is 1-2.5 h.

[0011] This invention also claims protection for the application of the described electrothermal material in the fabrication of heating elements, including the following steps: An electrothermal material with high adhesion to polyurethane foam is attached to the surface of a polyurethane foam substrate, and after drying, a heating element with an electrothermal effect can be obtained.

[0012] Preferably, the thickness of the polyurethane foam is 0.2 cm to 1 cm.

[0013] Preferably, the adhesion method is as follows: the electrothermal material precursor is printed on the surface of the foamed polyurethane substrate by screen printing using a 60-mesh screen, followed by baking at 60 ℃ for 1-2.5 hours to form the substrate, and then cooling to room temperature.

[0014] Preferably, the baking time is 2 hours, and the oven needs to be preheated to 60°C before baking.

[0015] The present invention also provides a method for synthesizing the monomer A, comprising the following steps: (1) 2,4-Dimethoxybenzaldehyde and RuCl2(PPh3)3 were loaded into a stainless steel reactor. After sealing the reactor, a methanol solution of NH3 was loaded into the reactor. Then, the reactor was further pressurized with H2 to 0.5 MPa. The reactor was heated to 120 °C and reacted at a stirring rate of 800 rpm for 24 hours. After the reaction was completed, the reactor was naturally cooled to room temperature to release excess gas. Then, the mixture was extracted with ethyl acetate to obtain crude product 1. (2) Add crude product 1 and Et3N to anhydrous diethyl ether. Add the mixture slowly to the anhydrous diethyl ether solution of triphosgene under nitrogen protection at -78 °C for 1 h. Stir the mixture for 10 minutes and then slowly restore the mixture to room temperature for >1 h. Then dilute the mixture with diethyl ether, filter to remove solids, and dry the filtrate by rotary evaporation. Purify the crude product by silica gel column chromatography to obtain monomer A.

[0016] Preferably, the molar ratio of 2,4-dimethoxybenzaldehyde:RuCl2(PPh3)3 is 100:5, and the ratio of crude product 1:Et3N is 1:3; the NH3 content in the methanol solution of NH3 is 7 mol / L, and 0.2 L of the methanol solution of NH3 is added for each mol of 2,4-dimethoxybenzaldehyde; the triphosgene content in the anhydrous ether solution of triphosgene is 1 mol / L, and 0.6 L of the anhydrous ether solution of triphosgene is added for each mol of crude product 1.

[0017] Preferably, during the silica gel column chromatography purification process, the eluent volume ratio PE:EtOAc is 5:1.

[0018] As can be seen from the above technical solution, compared with the prior art, the present invention discloses an electrothermal material with high adhesion to foamed polyurethane, its preparation method and application, which has the following beneficial effects: The structures of monomer A and polymer of the present invention have the following characteristics: Monomer A has three reaction sites: a carbon atom on the isocyanate group and an oxygen atom on each of the two methoxy groups. Each monomer A can polymerize with up to three other monomer A molecules, ultimately forming an interwoven spatial structure. The polymer contains a large number of urethane structures, which are the same as those in the parent structure of polyurethane, thus allowing it to bond well to the surface. During the reaction, the methoxy groups at the polymer ends are hydrolyzed by acid into hydroxyl groups. A large number of hydroxyl groups can form hydrogen bonds with carbonyl groups, oxygen atoms on ether bonds, and other components in the polyurethane to further enhance adhesion.

[0019] The electrothermal material precursor of the present invention is screen-printed onto a polyurethane foam substrate and then cured by heating, which can effectively improve the adhesion and is very suitable as an electrothermal element for bedding and aerospace products. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0021] Figure 1 This is a photograph of the appearance of Example 1; Figure 2 This is a cross-sectional photograph of Example 1; Figure 3 For comparison, see the exterior photograph; Figure 4 This is a photo taken after the test in Comparative Example 2; Figure 5 This is a cross-sectional photograph of Comparative Example 3. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] In the following examples, each component of each raw material weighs 10 grams. The printing equipment is a TX-5080SF-P screen printing machine from Hangzhou Taoxing Printing Equipment Co., Ltd. Unless otherwise specified, the reagents, methods, instruments, and equipment used in this invention are conventional in the art. (The raw material for synthesizing monomer A is also commercially available.) The synthesis process of monomer A is as follows:

[0024] S1: Synthesis of crude product 1: 2,4-Dimethoxybenzaldehyde and RuCl2(PPh3)3 (3 mol%) were loaded into a stainless steel reactor. After sealing the reactor, a methanol solution of NH3 was loaded into the reactor (C). NH3 =7 mol / L). Then, the reactor was further pressurized with H2 to 0.5 MPa. The reactor was heated to 120 °C and reacted at a stirring rate of 800 rpm for 24 hours. After the reaction was completed, the reactor was allowed to cool naturally to room temperature, excess gas was released, and the mixture was then extracted with ethyl acetate to obtain crude product 1.

[0025] S2: Synthesis of monomer A Crude product 1 and Et3N were added to anhydrous diethyl ether (molar ratio of 2,4-dimethoxybenzylamine to Et3N was 1:3). The mixture was then slowly added (completely over 1 hour) to anhydrous triphosgene ether solution under nitrogen protection at -78 °C (triphosgene content in the anhydrous diethyl ether solution was 1 mol / L, with 0.6 L of anhydrous triphosgene ether solution added for every mol of crude product 1). The mixture was stirred for 10 minutes and then allowed to return to room temperature for at least 1 hour. The mixture was then diluted with diethyl ether, and the solids were removed by filtration. The filtrate was evaporated to dryness and purified by silica gel column chromatography (PE / EtOAc = 5:1) to obtain monomer A.

[0026] The NMR data for monomer A are as follows: 1 H NMR (CDCl3 400 MHz) δ 7.15 (d, J =7.6 Hz, 1H), 6.40-6.50 (m, 2H), 4.33 (s, 2H), 3.84 (s, 3H), 3.81 (s, 3H). 13 C NMR (CDCl3 100 MHz) δ 160.96, 158.09, 129.46, 124.56, 117.93, 103.89, 98.58, 55.38, 55.31, 42.25.

[0027] Example 1 The raw materials of each component according to the following weight ratio are: 100 parts of monomer A, 46 parts of carbon nanotubes, 1.1 parts of 3-carboxythioxanthone, 10.3 parts of trifluoromethanesulfonic acid, and 40 parts of water.

[0028] Monomer A was dispersed in water at room temperature at a speed of 210 rpm and stirred until homogeneous. Carbon nanotubes were added to the solution in batches at a mass ratio of 1:1:1 and dispersed in a disperser at a speed of 720 rpm. After all the nanotubes were added, the speed of the disperser was increased to 1060 rpm and stirred until the slurry surface was uniform and free of particulate matter. 3-Carboxythioxanthone and trifluoromethanesulfonic acid were added and stirred in the dark for 15 min. The resulting viscous slurry is a precursor for an electrothermal material with high adhesion to polyurethane foam. The application steps are as follows: Before printing, the electrothermal material precursor needs to be stirred evenly in the dark. Then, it is printed onto the polyurethane foam substrate by screen printing with a 60-mesh screen. After printing, it is baked in a forced-air oven at 60 ℃ for 2 hours. The sample is then taken out and cooled to room temperature.

[0029] Example 2 The raw materials for each component are as follows by weight: 100 parts monomer A, 75 parts graphene, 0.4 parts thioxanone, 6.6 parts trifluoromethanesulfonic acid, and 58 parts water.

[0030] Monomer A was dispersed in water at 400 rpm at room temperature and stirred until homogeneous. Graphene was added to the solution in batches at a mass ratio of 1:1:1 and dispersed in a disperser at 630 rpm. After all the graphene was added, the disperser speed was increased to 850 rpm and stirred until the slurry surface was uniform and free of particulate matter. Thioxanone and trifluoromethanesulfonic acid were added and stirred in the dark for 15 min. The resulting viscous slurry is a precursor for an electrothermal material with high adhesion to polyurethane foam. The application steps are as follows: Before printing, the electrothermal material precursor needs to be stirred evenly in the dark. Then, it is printed onto the polyurethane foam substrate by screen printing with a 60-mesh screen. After printing, it is baked in a forced-air oven at 60 ℃ for 1 hour. The sample is then taken out and cooled to room temperature.

[0031] Example 3 The raw materials for each component according to the following weight ratio are: 100 parts monomer A, 75 parts graphite, 3.6 parts 2-carboxymethoxythioxanthone, 10.4 parts trifluoromethanesulfonic acid, and 55 parts water.

[0032] Monomer A was dispersed in water at room temperature and stirred until homogeneous at 370 rpm. Graphite was added to the solution in batches at a mass ratio of 1:1:1 and dispersed in a disperser at 790 rpm. After all the graphite was added, the disperser speed was increased to 1260 rpm and stirred until the slurry surface was uniform and free of particulate matter. 2-Carboxymethoxythioxanthone and trifluoromethanesulfonic acid were added and stirred in the dark for 15 min. The resulting viscous slurry is a precursor for an electrothermal material with high adhesion to polyurethane foam. The application steps are as follows: Before printing, the electrothermal material precursor needs to be stirred evenly in the dark. Then, it is printed onto the polyurethane foam substrate by screen printing with a 60-mesh screen. After printing, it is baked in a forced-air oven at 60 ℃ for 2.3 hours. The sample is then taken out and cooled to room temperature.

[0033] Example 4 The raw materials of each component according to the following weight ratio are: 100 parts of monomer A, 59 parts of a mixture of carbon fiber and graphene in a 1:1 mass ratio, 1.7 parts of thioxanone, 8.6 parts of trifluoromethanesulfonic acid, and 55 parts of water.

[0034] Monomer A was dispersed in water at room temperature at a speed of 210 rpm and stirred until homogeneous. A mixture of carbon fiber and graphene was added to the solution in batches at a mass ratio of 1:1:1 and dispersed in a disperser at a speed of 770 rpm. After all the mixture was added, the speed of the disperser was increased to 1350 rpm and stirred until the slurry surface was uniform and free of particulate matter. Thioxanone and trifluoromethanesulfonic acid were added and stirred in the dark for 15 min. The resulting viscous slurry is a precursor for an electrothermal material with high adhesion to polyurethane foam. The application steps are as follows: Before printing, the electrothermal material precursor needs to be stirred evenly in the dark. Then, it is printed onto the polyurethane foam substrate by screen printing with a 60-mesh screen. After printing, it is baked in a forced-air oven at 60 ℃ for 2 hours. The sample is then taken out and cooled to room temperature.

[0035] Example 5 The raw materials of each component according to the following weight ratio are: 100 parts monomer A, 54 parts carbon black, 2.4 parts 2-bromothioxanone, 9.7 parts trifluoromethanesulfonic acid, and 61 parts water.

[0036] Monomer A was dispersed in water at 180 rpm at room temperature and stirred until homogeneous. Carbon black was added to the solution in batches at a mass ratio of 1:1:1 and dispersed in a disperser at 750 rpm. After all the carbon black was added, the disperser speed was increased to 1180 rpm and stirred until the slurry surface was uniform and free of particulate matter. 2-Bromothioxanone and trifluoromethanesulfonic acid were added and stirred in the dark for 15 min. The resulting viscous slurry is a precursor for electrothermal materials with high adhesion to polyurethane foam. The application steps are as follows: Before printing, the electrothermal material precursor needs to be stirred evenly in the dark, and then printed onto the polyurethane foam substrate by screen printing with a 60-mesh screen. After printing, it is baked in a forced-air oven at 60 ℃ for 1.4 hours. The sample is then taken out and cooled to room temperature.

[0037] In Examples 1-5, the chemical reaction equations for monomer A after heat treatment are as follows:

[0038] The final network polymer molecular structure obtained on the surface of the foamed polyurethane is as follows:

[0039] Comparative Example 1 The difference from Example 1 is that: 20 parts water, and the other raw materials and preparation methods are the same as in Example 1.

[0040] The application steps are as follows: Before printing, the electrothermal material precursor needs to be stirred evenly, and then printed on the polyurethane foam substrate by 60-mesh screen printing. The sample is then baked in a forced-air oven at 60 ℃ for 2 hours. The sample is then taken out and cooled to room temperature.

[0041] Comparative Example 2 The difference from Example 1 is that 10 parts of 3-carboxythioxanthone were used, while the other raw materials and preparation methods were the same as in Example 1.

[0042] The application steps are as follows: Before printing, the electrothermal material precursor needs to be stirred evenly, and then printed on the polyurethane foam substrate by 60-mesh screen printing. The sample is then baked in a forced-air oven at 60 ℃ for 2 hours. The sample is then taken out and cooled to room temperature.

[0043] Comparative Example 3 The difference from Example 1 is that trifluoromethanesulfonic acid is not added, and the other raw materials are the same as in Example 1. The preparation method is also the same, except that no acid is added during the preparation process.

[0044] The application steps are as follows: Before printing, the electrothermal material precursor needs to be stirred evenly, and then printed on the polyurethane foam substrate by 60-mesh screen printing. The sample is then baked in a forced-air oven at 60 ℃ for 2 hours. The sample is then taken out and cooled to room temperature.

[0045] Experimental Example Examples 1-5 and Comparative Examples 1-3 were tested according to the standards in Table 1, and the test results are shown in Table 2.

[0046] Table 1 Test Content

[0047] Table 2 Test Results

[0048] The results above show that Examples 1-5 meet the requirements for appearance and adhesion. In Comparative Example 1, insufficient water resulted in an excessively high viscosity of the electrothermal material precursor, making it difficult to level and preventing complete coverage of the substrate during printing. In Comparative Example 2, excessive catalyst led to over-polymerization, causing the coating to become brittle and crack after 300 kneeling pressure tests. In Comparative Example 3, the lack of acid reduced the solubility of monomer A, and insufficient acid was available to hydrolyze the methoxy groups after polymerization. This resulted in an excessively low viscosity of the electrothermal material precursor and difficulty in forming hydrogen bonds with the polyurethane surface, reducing adhesion and ultimately making it impossible to control the depth of the electrothermal material precursor's penetration into the polyurethane.

[0049] The various embodiments described in this specification are presented in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. 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 invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An electrocaloric material having high adhesion to foamed polyurethane, characterized in that The electrocaloric material is a reticular polymer structure, and its structural formula is: 。 2. A method of producing an electrocaloric material having high adhesion to foamed polyurethane according to claim 1, characterized in that The method comprises the following steps: S1. Disperse monomer A in water at room temperature under the condition of a rotating speed of 150-400 rpm, and stir until uniform; S2. In a room temperature environment, add carbon materials into the dispersion system of step S1 in three times according to the mass ratio of 1:1:1 under the condition of a rotating speed of 600-800 rpm of the disperser, adjust the rotating speed of the disperser to 850-1400 rpm after all the carbon materials are added, and stir until the surface of the slurry is uniform and no granular substances are present; S3. Add a catalyst and an acid into the system after stirring in step S2, avoid light, and stir for 15 min to obtain a viscous slurry, which is an electrocaloric material precursor with high adhesion to foamed polyurethane; S4. Heat treat the electrocaloric material precursor to obtain an electrocaloric material with high adhesion to foamed polyurethane; The structural formula of monomer A is: 。 3. The method of claim 2, wherein the electric heating material having high adhesion to the foamed polyurethane is prepared by adding the electric heating material to the foaming polyurethane composition, and foaming the foaming polyurethane composition. In terms of weight parts, monomer A is 100 parts, carbon materials are 44-79 parts, a catalyst is 0.3-5.0 parts, an acid is 6.6-10.5 parts, and water is 37-62 parts.

4. A method of producing an electrocaloric material having high adhesion to foamed polyurethane according to claim 2 or 3, characterized in that, The carbon materials are any one or several of carbon nanotubes, graphene, carbon black, graphite, and carbon fibers, the catalyst is one or several of thioxanthone, 2-bromothioxanthone, 2-carboxymethoxythioxanthone, or 3-carboxythioxanthone, and the acid is trifluoromethanesulfonic acid.

5. The method of claim 2, wherein the electric heating material having high adhesion to the foamed polyurethane is prepared by adding the electric heating material to the foaming polyurethane. The heat treatment temperature in step S4 is 60 ℃, and the time is 1-2.5 h.

6. Use of the electrocaloric material having high adhesion to foamed polyurethane according to claim 1 in the production of a heat-generating element, characterized in that, The method comprises the following steps: The electrocaloric material with high adhesion to foamed polyurethane is attached to the surface of a foamed polyurethane base material, and after drying, a heating element with an electrocaloric effect is obtained.

7. Use according to claim 6, characterized in that, The attachment method is to print the electrocaloric material precursor on the surface of the foamed polyurethane base material in a silk screen printing manner by using a 60-mesh screen plate, and then form a shape by baking at 60 ℃ for 1-2.5 h and cooling to room temperature.

8. A method of synthesizing monomer A according to claim 2, characterized in that, The method comprises the following steps: (1) Load 2,4-dimethoxybenzaldehyde and RuCl2(PPh3)3 into a stainless steel reactor, seal the reactor, then load an NH3 methanol solution into the reactor, then further pressurize the reactor to 0.5 Mpa with H2, heat the reactor to 120 ℃, and react for 24 hours under a stirring speed of 800 rpm, then naturally cool the reactor to room temperature after the reaction is completed, release the excess gas, then extract the mixture with ethyl acetate to obtain a crude product 1; (2) Add the crude product 1 and Et3N into anhydrous ether, slowly add the mixture into a triphosgene anhydrous ether solution under the condition of -78 ℃ and nitrogen protection, add completely in 1 h, stir the mixture for 10 minutes, then slowly restore the mixture to room temperature, usually >1 h, then dilute the mixture with ether, filter to remove the solid, spin dry the filtrate, and then purify the crude product by silica gel column chromatography to obtain monomer A.

9. The method of synthesis of monomer A according to claim 8, characterized in that, 2,4-dimethoxybenzaldehyde: RuCl2(PPh3)3= 100:5, crude product 1: Et3N = 1:3; NH3content in methanol solution of NH3is 7 mol / L, 0.2 L of methanol solution of NH3is added for each mol of 2,4-dimethoxybenzaldehyde; the content of triphosgene in anhydrous ethyl ether solution of triphosgene is 1 mol / L, 0.6 L of anhydrous ethyl ether solution of triphosgene is added for each mol of crude product 1.

10. The method of synthesis of monomer A according to claim 8, wherein, During the purification process by silica gel column chromatography, the volume ratio of PE:EtOAc is 5:1.

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