Modified polyurethane foam and preparation method thereof

Abstract

The invention discloses modified polyurethane foam and a preparation method thereof, and belongs to the field of high polymer materials. The modified polyurethane foam comprises polyether polyol, a catalyst, a foaming agent, a foam stabilizer, a surface modifier, polyisocyanate and nano carbon black. The preparation method comprises the following steps: (1) preparing modified nano carbon black: dispersing nano carbon black in methylbenzene, adding a surface modifier, stirring for reaction, filtering, washing and drying; (2) preparing a nano carbon black master batch: mixing the modified nano carbon black with polyether polyol, shearing and dispersing; (3) preparing the component A: mixing polyether polyol, a catalyst, a foaming agent, a foam stabilizer and the master batch, and uniformly stirring; and (4) preparing polyurethane foam: stirring and mixing the component A and polyisocyanate, pouring into a mold for foaming, and demolding after reaction. The modified polyurethane foam provided by the invention can achieve the effects of low heat conductivity coefficient and excellent mechanical properties.

Description

Technical Field

[0001] This invention relates to polymer materials, and more particularly to a modified polyurethane foam and its preparation method. Background Technology

[0002] Polyurethane foam, as a widely used polymer material, occupies an important position in many fields such as building insulation, cold chain transportation, and aerospace due to its lightweight, high specific strength, and good thermal insulation and sound absorption properties. Currently, the thermal conductivity of ordinary polyurethane foam is typically in the range of 0.020-0.030 W / (m·K). In the field of building insulation, to achieve better energy-saving effects, the thermal conductivity of wall insulation materials needs to be below 0.025 W / (m·K); the cold chain transportation industry has even stricter requirements for insulation materials, expecting a thermal conductivity as low as below 0.020 W / (m·K). With the continuous improvement of energy-saving and performance requirements in various industries, the thermal conductivity of traditional polyurethane foam is no longer sufficient to meet increasingly stringent standards.

[0003] To reduce the thermal conductivity of polyurethane foam, existing technologies mainly explore the following directions: (1) Using low thermal conductivity blowing agents: such as hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFOs), but these blowing agents either have high global warming potential, which has a negative impact on the environment; or they are expensive, which limits their large-scale application. (2) Adding inorganic fillers: Inorganic materials such as silica aerogel and graphene can theoretically reduce the thermal conductivity, but their compatibility with the polyurethane matrix is ​​poor, which can easily lead to a significant decrease in the mechanical properties of the material in practical applications, affecting the overall performance and service life of the product. (3) Optimizing the cell structure: By controlling the foaming process, we try to reduce the cell size to reduce the thermal conductivity. However, excessive reduction in cell size will increase the diffusion resistance of gas in the cell, which may actually increase the thermal conductivity. Moreover, it requires extremely high precision in process control and is difficult to operate in practice.

[0004] Nano-carbon black, as a material with a unique nanostructure, possesses high specific surface area, high surface energy, and excellent electrical and mechanical properties, and has attracted attention in polyurethane foam modification research in recent years. Some studies have attempted to introduce nano-carbon black into polyurethane foam systems in order to improve their performance. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a modified polyurethane foam with low thermal conductivity and excellent mechanical properties.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned modified polyurethane foam.

[0007] Technical solution: The modified polyurethane foam of the present invention comprises, by weight, 100 parts polyether polyol, 0.5-3 parts catalyst, 2-5 parts foaming agent, 1-3 parts foam stabilizer, 0.5-2 parts surface modifier, 80-120 parts polyisocyanate, and 2-4 parts nano carbon black.

[0008] Preferably, the nano-carbon black has a particle size of 10-100 nm and a specific surface area of ​​50-300 m² / g. As a key modifier, nano-carbon black, with its unique nano-size effect and excellent properties, is expected to play a role in enhancing compressive strength and reducing thermal conductivity in polyurethane foam systems.

[0009] Preferably, the polyether polyol has a functionality of 2-4 and a hydroxyl value of 20-60 mgKOH / g. This type of polyether polyol possesses suitable reactivity and molecular structure, providing a stable skeletal structure for the formation of polyurethane foam.

[0010] Preferably, the NCO content of the polyisocyanate is 25-33%, and the polyisocyanate is one or more of diphenylmethane diisocyanate (MDI) and polymethylene polyphenyl polyisocyanate (PAPI). The polyisocyanate undergoes a polymerization reaction with polyether polyol to form the main structure of polyurethane.

[0011] Preferably, the surface modifier is one of silane coupling agents, titanate coupling agents, and fatty acids. The surface modifier molecule contains both groups that are compatible with the surface of carbon nanoblack (such as amino and mercapto groups) and groups that can react with the polyurethane matrix (such as alkoxy and isocyanate groups). Through chemical reaction, a chemically bonded interfacial layer is constructed on the surface of carbon nanoblack, improving the compatibility and interfacial bonding between carbon nanoblack and the polyurethane matrix.

[0012] Preferably, the catalyst is an amine catalyst or a tin catalyst. The amine catalyst is triethylenediamine (A-33) or bis(dimethylaminoethyl) ether (A-1), which can promote the reaction of isocyanate with water and initiate the foaming process; the tin catalyst is stannous octoate (T-9) or dibutyltin dilaurate (T-12). Tin catalysts mainly catalyze the polymerization reaction of isocyanate with polyols. The two catalysts work synergistically to precisely control the synthesis reaction rate and process of polyurethane foam.

[0013] Preferably, the foaming agent is water and / or a physical foaming agent, wherein the physical foaming agent is cyclopentane, isopentane, or hydrofluoroolefins (HFOs). Water is used as the main foaming agent, and physical foaming agents such as cyclopentane, isopentane, and HFOs can be added in appropriate amounts according to actual needs. Water reacts with isocyanate to produce carbon dioxide gas, forming the foam's pore structure; the physical foaming agent vaporizes and expands during heating, further increasing the pore volume, and together they determine the foam's density and pore structure.

[0014] Preferably, the foam stabilizer is a common silicone-based foam stabilizer.

[0015] The method for preparing the modified polyurethane foam of the present invention includes the following steps: (1) Preparation of modified nano carbon black: Disperse nano carbon black in toluene, add surface modifier, stir to react, filter, wash and dry; (2) Preparation of nano-carbon black masterbatch: The modified nano-carbon black is mixed with polyether polyol, sheared, and dispersed; (3) Preparation of component A: Mix polyether polyol, catalyst, foaming agent, foam stabilizer and masterbatch, and stir evenly; (4) Preparation of polyurethane foam: Mix component A with polyisocyanate, pour into mold for foaming, and demold after reaction.

[0016] Preferably, the reaction temperature in step (1) is 60-80℃ and the reaction time is 3-5 hours.

[0017] Preferably, the stirring speed in step (4) is 2000-3000 rpm, the foaming temperature is 40-60℃, and the reaction time is 25-35 min.

[0018] Invention principle: Nano carbon black typically has a particle size of less than 100 nanometers and possesses high specific surface area, excellent electrical conductivity, thermal conductivity, adsorption, and mechanical strength. It is widely used in various fields such as plastics, rubber, coatings, and inks.

[0019] This invention aims to provide a modified polyurethane foam and its preparation method. The method refines the pore structure through the nucleation effect of nano-carbon black, while simultaneously forming chemical bonds with the polyurethane matrix, significantly reducing the thermal conductivity of the polyurethane foam and enhancing its mechanical strength. By surface-modifying the nano-carbon black, its dispersion state in the polyurethane matrix is ​​optimized, and the interfacial structure between the nano-carbon black and the polyurethane matrix is ​​controlled, achieving a significant reduction in the thermal conductivity of the polyurethane foam. At the same time, the mechanical properties of the foam are maintained or even improved to meet the demands of high-performance insulation materials in various fields such as construction, cold chain, and aerospace.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The method prepares polyurethane foam by adding nano carbon black, which effectively reduces the thermal conductivity of the foam to a minimum of 0.016 W / (m・K), which is 23.8% lower than the thermal conductivity of foam with unmodified nano carbon black and 30.4% lower than the thermal conductivity of foam without nano carbon black; (2) The polyurethane foam prepared by the method has excellent compressive strength. Compared with foam without nano carbon black, its compressive strength is not only not reduced, but is even effectively improved. Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to the embodiments.

[0022] Example 1

[0023] The modified polyurethane foam of the present invention comprises, by weight, 100 parts polyether polyol, 0.5 parts triethylenediamine A-33, 0.5 parts stannous octoate T-9, 3 parts water, 2 parts DC-5043, 100 parts MDI, 3 parts nano carbon black, and 1 part KH-550.

[0024] The method for preparing modified polyurethane foam according to the present invention includes the following steps (the amount of each substance added is based on parts by weight): (1) Preparation of modified nano-carbon black: 3 parts of nano-carbon black (particle size 30 nm, specific surface area 200 m² / g) were dispersed in toluene, and 1 part of silane coupling agent (KH-550) was added. The mixture was stirred at 70℃ for 4 hours. After filtration, washing, and drying, surface-modified nano-carbon black was obtained. This method effectively improves the dispersion of nano-carbon black in polyurethane foam by adding silane coupling agent KH-550 to the nano-carbon black, thus avoiding agglomeration.

[0025] (2) Preparation of nano carbon black masterbatch: The above modified nano carbon black was mixed with 20 parts of polyether polyol (functionality 3, hydroxyl value 48 mg KOH / g), and the mixture was sheared at 15,000 rpm for 30 minutes and then ultrasonically dispersed for 1 hour to obtain nano carbon black masterbatch.

[0026] (3) Preparation of component A: Mix 80 parts of polyether polyol (functionality 3, hydroxyl value 48mgKOH / g), 1 part of catalyst (0.5 parts of triethylenediamine A-33, 0.5 parts of stannous octoate T-9), 3 parts of foaming agent (water), 2 parts of foam stabilizer (DC-5043) with the above masterbatch and stir evenly to obtain component A.

[0027] (4) Preparation of polyurethane foam: Mix component A and component B (100 parts MDI, NCO content 31.5%) under high speed stirring at 2,500 rpm, pour into mold for foaming, control mold temperature at 50℃, and demold after reaction for 30 minutes.

[0028] Example 2

[0029] The similarities between this embodiment and Embodiment 1 will not be repeated here. The differences are as follows: The polyether polyol has a functionality of 2 and a hydroxyl value of 28 mg KOH / g; component B is polymethylene polyphenyl polyisocyanate (PAPI, NCO content 31%), with an addition amount of 110 parts; the nano carbon black has a particle size of 50 nm, a specific surface area of ​​150 m² / g, and an addition amount of 2 parts; the surface modifier is titanate coupling agent (NDZ-201), with an addition amount of 0.8 parts; the catalyst is 0.3 parts bis(dimethylaminoethyl) ether (A-1) and 0.7 parts dibutyltin dilaurate (T-12); the foaming agent is 2.5 parts water and 1 part cyclopentane; the foam stabilizer is B8462; and an additional 1 part cell opener (L-5340) is added.

[0030] Example 3

[0031] The similarities between this embodiment and Embodiment 1 will not be repeated here. The differences are as follows: The amount of nano carbon black added is 4 parts.

[0032] Comparative Example 1 The similarities between this comparative example and Example 1 will not be repeated here; the differences are as follows: No nano carbon black is added. That is, steps (1)-(2) are deleted, and the amount of polyether polyol added in step (3) is 100 parts.

[0033] Comparative Example 2 The similarities between this comparative example and Example 1 will not be repeated here; the differences are as follows: Use unmodified nano-carbon black. That is, delete step (1).

[0034] Comparative Example 3 The similarities between this comparative example and Example 1 will not be repeated here; the differences are as follows: Unmodified nano-carbon black was used, and the amount of nano-carbon black added was 5 parts. That is, step (1) was deleted.

[0035] Comparative Example 4 The similarities between this comparative example and Example 1 will not be repeated here; the differences are as follows: The amount of modified nano carbon black added is 5 parts.

[0036] The performance of the samples obtained from each embodiment and comparative example was tested, including thermal conductivity, compressive strength, and closed-cell ratio. The specific test methods are as follows.

[0037] Thermal conductivity: Tested according to ASTM C518.

[0038] Compressive strength: Tested according to ASTM D1621.

[0039] Closed-cell ratio: Tested according to ASTM D6226.

[0040] The test results for each sample are shown in Table 1.

[0041] Table 1 Test results for each sample sample Thermal conductivity W / (m・K) Compressive strength (MPa) Closed-pore ratio (%) Example 1 0.016 0.35 92 Example 2 0.017 0.28 90 Example 3 0.020 0.33 91 Comparative Example 1 0.023 0.25 88 Comparative Example 2 0.021 0.27 89 Comparative Example 3 0.025 0.30 90 Comparative Example 4 0.021 0.37 91 The experimental data in the table show that adding modified nano-carbon black (Examples 1-3) to the material can effectively improve the performance of polyurethane foam, resulting in lower thermal conductivity, higher compressive strength, and higher closed-cell rate. Analysis of the data in Example 3 shows that when the amount of modified nano-carbon black added increases to 4 parts, the thermal conductivity of the material actually increases, indicating that neither more nor less modified nano-carbon black is necessarily better. When the amount of modified nano-carbon black added increases to 5 parts (Comparative Example 4), the performance of the polyurethane foam does not achieve the desired technical effect. This may be because the role of modified nano-carbon black in polyurethane depends on "uniform dispersion" and "appropriate filling." Excessive addition will disrupt this balance, leading to a comprehensive deterioration of material performance and processability through mechanisms such as agglomeration, interfacial failure, and abnormal viscosity. Therefore, controlling the amount of modified nano-carbon black added is crucial, as the result directly affects experimental data and material stability.

[0042] According to the experimental data of Comparative Examples 1-3, adding unmodified nano-carbon black to the material can also improve the performance of polyurethane foam. However, when the amount added is large, the material performance will decrease, indicating that unmodified nano-carbon black can partially improve the material performance but is still insufficient.

[0043] In summary, adding a certain proportion of modified nano-carbon black material to polyurethane materials can effectively improve material properties and reduce the thermal conductivity of polyurethane foam.

Claims

1. A modified polyurethane foam, characterized in that, By weight, it includes 100 parts polyether polyol, 0.5-3 parts catalyst, 2-5 parts foaming agent, 1-3 parts foam stabilizer, 0.5-2 parts surface modifier, 80-120 parts polyisocyanate, and 2-4 parts nano carbon black.

2. The modified polyurethane foam according to claim 1, characterized in that, The nano-carbon black has a particle size of 10-100 nm and a specific surface area of ​​50-300 m² / g.

3. The modified polyurethane foam according to claim 1, characterized in that, The polyether polyol has a functionality of 2-4 and a hydroxyl value of 20-60 mgKOH / g.

4. The modified polyurethane foam according to claim 1, characterized in that, The NCO content of the polyisocyanate is 25-33%, and the polyisocyanate is one or more of diphenylmethane diisocyanate and polymethylene polyphenyl polyisocyanate.

5. The modified polyurethane foam according to claim 1, characterized in that, The surface modifier is one of silane coupling agents, titanate coupling agents, and fatty acids.

6. The modified polyurethane foam according to claim 1, characterized in that, The catalyst is an amine catalyst or a tin catalyst. The amine catalyst is triethylenediamine or bis(dimethylaminoethyl) ether, and the tin catalyst is stannous octoate or dibutyltin dilaurate.

7. The modified polyurethane foam according to claim 1, characterized in that, The foaming agent is water and / or a physical foaming agent, wherein the physical foaming agent is cyclopentane, isopentane, or hydrofluoroolefin.

8. A method for preparing the modified polyurethane foam according to claim 1, comprising the following steps: (1) Preparation of modified nano carbon black: Disperse nano carbon black in toluene, add surface modifier, stir to react, filter, wash and dry; (2) Preparation of nano-carbon black masterbatch: The modified nano-carbon black is mixed with polyether polyol, sheared, and dispersed; (3) Preparation of component A: Mix polyether polyol, catalyst, foaming agent, foam stabilizer and masterbatch, and stir evenly; (4) Preparation of polyurethane foam: Mix component A with polyisocyanate, pour into mold for foaming, and demold after reaction.

9. The preparation method according to claim 8, characterized in that, The reaction temperature in step (1) is 60-80℃ and the reaction time is 3-5 hours.

10. The preparation method according to claim 8, characterized in that, The stirring speed in step (4) is 2000-3000 rpm, the foaming temperature is 40-60℃, and the reaction time is 25-35 min.