Nano-titania enhanced all-water blown polyurethane rigid foam and methods of making and using the same

Abstract

This invention relates to the field of all-water foaming polymer materials, specifically to an all-water-blown rigid polyurethane foam reinforced with nano-titanium oxide, its preparation method, and its applications. It consists of component A and component B. Component A includes polyether polyol 1, polyether polyol 2, polyether polyol 3, a blowing agent, a silicone oil stabilizer, and an amine catalyst; component B is isocyanate. This invention uses an in-situ modified terephthalic acid nano-titanium oxide aqueous dispersion instead of pure water as the blowing agent, chemically anchoring the nano-titanium oxide to the polyurethane cross-linked network via terephthalic acid, forming rigid nano-nodes. This solves the problem of negative pressure shrinkage of the cells caused by CO2 escape in all-water foaming systems. This invention constructs a rigid skeleton synergistic system: a rigid reinforcement structure from the molecular to the network level formed by fluoroaniline polyether containing benzene rings, high-functionality sucrose polyether, and glycerol polyether, combined with chemically anchored nano-titanium oxide rigid nodes, improves the foam's compressive strength.

Description

Technical Field

[0001] This invention relates to the field of polymer all-water foaming materials technology, specifically to nano-titanium oxide reinforced all-water foamed rigid polyurethane foam, its preparation method and application. Background Technology

[0002] Rigid polyurethane foam is widely used in construction, cold chain, and pipeline insulation due to its excellent thermal insulation performance and mechanical strength. With increasingly stringent environmental regulations, traditional chlorofluorocarbon (CFC) physical blowing agents are gradually being phased out, and all-water foaming technology has become one of the mainstream alternatives. However, all-water foaming systems have significant drawbacks in practical applications: the CO2 molecules generated by the reaction of water and isocyanate have small diameters and diffuse out of the cells much faster than air enters, resulting in internal cell pressure lower than atmospheric pressure. This makes the foam prone to post-shrinkage and poor dimensional stability after molding. Furthermore, although the amount of water used in all-water foaming systems is small, the lack of dilution by physical blowing agents leads to high viscosity of the polyether composite, intense exothermic reactions, and increased foam brittleness, affecting its long-term performance. Ordinary single polyethers, such as sucrose polyether or sorbitol polyether, have limited molecular structure regularity and a single distribution of crosslinking points, resulting in a fixed ratio of rigid to flexible segments in the foam network structure, making it difficult to balance strength and shrinkage resistance. To overcome the shrinkage problem, traditional methods usually involve increasing the foam density, but this violates the principle of lightweighting and increases costs.

[0003] To improve the dimensional stability and mechanical properties of rigid polyurethane foam, existing technologies have attempted to introduce inorganic particles for reinforcement. For example, patent CN108659194A discloses a rigid polyurethane foam composite material containing inorganic particles modified with coupling agents. This material uses silane or titanate coupling agents to surface-modify inorganic particles such as silica and titanium dioxide, utilizing these particles as heterogeneous nucleating agents to refine the cell structure, while simultaneously enhancing the foam's structural rigidity and dimensional stability. However, this approach uses coupling agents to post-modify pre-formed inorganic powders, falling under the category of physical mixing and surface coating. The interaction between the inorganic particles and the polyurethane matrix is ​​primarily weak, resulting in limited interfacial bonding. Furthermore, this system still uses physical blowing agents such as cyclopentane and does not offer a specific solution to the gas diffusion and shrinkage issues inherent in all-water foaming systems.

[0004] In summary, there is currently a lack of a technical solution that can fundamentally solve the problem of late-stage shrinkage in all-water-blown polyurethane foam, while simultaneously achieving a strong chemical anchoring between the inorganic reinforcement and the polyurethane network. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a nano-titanium oxide-reinforced, all-water-blown rigid polyurethane foam. The composite polyether used is composed of high-functionality polyether, polyether containing aromatic ring structures, and low-viscosity polyether. The high-functionality component provides more reaction crosslinking points, enabling the foam to form a denser three-dimensional network. At the same time, polyethers with different molecular chain lengths can optimize the thickness distribution of the cell walls, reduce local weak areas, and thus improve compressive strength. The special polyether containing rigid benzene ring segments can significantly improve the dimensional stability of the foam, suppress volume shrinkage caused by cooling or post-curing, and especially significantly improve the shrinkage caused by the negative pressure inside the foam after CO2 escapes from the water-blown foam.

[0006] The water in the nano-aqueous dispersion obtained by in-situ modification of terephthalic acid can still react with isocyanate to generate CO2, which plays a foaming role. The terephthalic acid molecule contains two carboxyl groups, which can react with isocyanate to form amide or imide bonds. This allows TiO2 nanoparticles to be grafted onto the polyurethane network skeleton through chemical bonds, which is equivalent to introducing rigid reinforcement points locally in the foam network. This works synergistically with the rigid segments in the composite polyether to significantly improve the compressive modulus and inhibit shrinkage.

[0007] The present invention also provides a preparation method that is simple, easy to implement, and suitable for large-scale production.

[0008] The present invention also provides its application in the preparation of thermal insulation materials or structural materials.

[0009] The nano-titanium oxide reinforced all-water-blown rigid polyurethane foam of the present invention is composed of component A and component B in a mass ratio of 1:(1-1.2), wherein component A is composed of the following raw materials in parts by mass: Polyether polyol 1: 40-70 parts; Polyether polyol 2: 20-50 parts; Polyether polyol 3: 10-25 parts; Foaming agent: 1-5 parts; Silicone oil stabilizer: 1.5-3 parts; Amine catalyst: 0.5-2 parts; Component B is an isocyanate; The polyether polyol 1 is INOVOL R8336, a sucrose polyether polyol from Shandong Yinuowei New Materials Co., Ltd., which has 5 functionalities and a hydroxyl value of 360 mg KOH / g. The polyether polyol 2 is trifunctional, with a hydroxyl value of 33 mg KOH / g, and is the glycerol polyether polyol INOVOL F330N from Shandong Yinuowei New Material Co., Ltd.; The polyether polyol 3 is a polyether containing an aromatic ring structure with 4 functionalities and a hydroxyl value of 250 mg KOH / g. The synergistic blending of three polyether polyols can enhance crosslinking density and network uniformity, introduce a rigid structure, reduce shrinkage, adjust system viscosity, and improve the flowability of all-water foaming.

[0010] The foaming agent is an aqueous dispersion of titanium dioxide modified with terephthalic acid in situ. Compared with post-modification of finished inorganic powders, in-situ modification can effectively prevent the agglomeration of nanoparticles and improve their dispersion stability in polyether systems.

[0011] The polyether polyol 3 is a polyether polyol prepared by ring-opening polymerization of propylene oxide and ethylene oxide with 1-(3,5-difluorophenyl)cyclopentanamine and sucrose as initiators and dimethylacetamide (DMAC) as catalyst.

[0012] Preferably, the preparation method of the polyether polyol 3 is as follows: 16 wt% of 1-(3,5-difluorophenyl)cyclopentanamine initiator and 12 wt% of sucrose initiator are added to a reaction vessel. After pressure testing and leak detection, N2 is replaced three times. N2 is pressurized to 0.25 MPa and the temperature is raised to 90°C for 2 hours. The temperature is raised to 110°C and vacuumed to -0.1 MPa for bubbling dehydration for 1 hour. The temperature is lowered to 90°C and 1 wt% of DMAC catalyst is added. 17.8 wt% of the first-stage propylene oxide (PO) is added. After the internal pressure is lowered to -0.05 MPa, the temperature is raised to 110°C and 33.2 wt% of the second-stage PO is added. After the internal pressure is lowered to -0.05 MPa, 20 wt% of ethylene oxide (EO) is added. After the addition is complete, the internal pressure is maintained at 0.2 MPa for 1.5 hours. Vacuum is then drawn to -0.09 MPa to remove unreacted monomers, thus obtaining polyether polyol 3.

[0013] The terephthalic acid-modified aqueous dispersion of titanium dioxide is obtained by introducing terephthalic acid as a modifier during the synthesis of titanium dioxide nanoparticles and then modifying it in one step.

[0014] The preparation process of the in-situ modified titanium dioxide aqueous dispersion is as follows: tetrabutyl titanate, anhydrous ethanol, terephthalic acid, glacial acetic acid and water are added to a reaction vessel and heated to react. After filtration and washing, the modified titanium dioxide wet filter cake is obtained, which is then dispersed in water and the pH is adjusted to alkaline to obtain the in-situ modified titanium dioxide aqueous dispersion.

[0015] The dispersion into water specifically includes ultrasonic dispersion or shear dispersion.

[0016] The dispersion temperature in the water is 40-60℃.

[0017] Preferably, the preparation process of the in-situ modified titanium dioxide aqueous dispersion is as follows: 1.96g tetrabutyl titanate, 47.36g anhydrous ethanol, 0.5-2g terephthalic acid, 2.08g glacial acetic acid and 2.4g water are added to a reaction vessel and heated to 150-180℃ for 5-11h. After filtration and washing, a modified titanium dioxide wet filter cake is obtained, which is then dispersed in water and ultrasonicated at 40℃ for 20min to prepare a pre-dispersion with a solid content of 20wt%. The pH is adjusted to 8-10 with 0.1M NaOH solution to obtain the in-situ modified titanium dioxide aqueous dispersion.

[0018] The silicone oil stabilizer mentioned is AK8805 (Jinan Hongwang Chemical Co., Ltd.).

[0019] The amine catalyst mentioned is N,N-dimethylbenzylamine (BDMA).

[0020] The preparation method of nano-titanium oxide reinforced all-water-blown rigid polyurethane foam of the present invention comprises the following steps: (1) Preparation of component A Mix polyether polyol 1, polyether polyol 2, polyether polyol 3, foaming agent: in-situ modified titanium dioxide aqueous dispersion, silicone oil stabilizer and amine catalyst evenly. (2) Foaming Mix components A and B, inject into a mold, and allow to foam and mature.

[0021] Specifically, components A and B are mixed using a high-speed foaming mixer, injected into a mold, molded, and cured at room temperature for 2 hours to obtain the finished product.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention uses an aqueous dispersion of nano-titanium oxide modified with terephthalic acid in situ to replace pure water as a foaming agent, so that the nano-titanium oxide is chemically anchored in the polyurethane crosslinking network by terephthalic acid to form rigid nano nodes, which fundamentally solves the problem of negative pressure shrinkage of the foam cells caused by CO2 escape in the all-water foaming system.

[0023] (2) The present invention constructs a rigid skeleton synergistic system: a rigid reinforcement structure from the molecular level to the network level formed by fluoroaniline polyether containing benzene ring, high-functionality sucrose polyether and glycerol polyether, combined with chemically anchored nano titanium dioxide rigid nodes, which significantly improves the foam compression strength.

[0024] (3) The modified nano-titanium oxide aqueous dispersion used in this invention simultaneously acts as a foaming agent and an in-situ reinforcing agent. The water reacts with isocyanate to generate CO2, and nano-TiO2 and terephthalic acid participate in cross-linking. Foaming and reinforcement are completed simultaneously, avoiding the problems of agglomeration, poor interfacial compatibility, and complex processes caused by the traditional method of first preparing nano-powders and then physically blending them. At the same time, this integrated solution replaces the traditional physical foaming agent, avoiding the defects of high viscosity, violent exothermic reaction, and high foam brittleness in the all-water foaming system caused by insufficient dilution effect of physical foaming agents.

[0025] (4) In this invention, terephthalic acid is modified in situ during the hydrothermal growth of nano-titanium oxide, so that terephthalic acid is chemically bonded to the TiO2 surface. During the subsequent foaming process, the carboxyl groups of terephthalic acid react with isocyanate to chemically anchor the nanoparticles in the polyurethane network. This chemical bond-level bonding method has stronger interfacial bonding force compared with traditional methods such as post-modification with coupling agents and physical mixing, and effectively prevents filler agglomeration.

[0026] (5) The present invention uses a special polyether containing fluoroaniline groups. The benzene ring in its molecular structure interacts with the benzene ring in the terephthalic acid molecule. This interaction helps the nano-reinforcing units to be pre-dispersed in the polyether matrix. In conjunction with the chemical anchoring effect, it further ensures the uniform distribution of nano-titanium oxide in the foam network, thereby giving full play to the nano-reinforcing effect.

[0027] (6) The rigid polyurethane foam prepared by this invention has low density, high compressive strength, excellent dimensional stability and high surface hardness, and adopts environmentally friendly all-water foaming technology with no physical foaming agent emission. This foam material can meet the application scenarios with high requirements for material mechanical properties and dimensional stability, such as building insulation, cold chain transportation, pipeline insulation and structural load-bearing, and has broad industrialization prospects. Detailed Implementation

[0028] The present invention will be further described below with reference to the embodiments.

[0029] Unless otherwise specified, all raw materials used in the examples were commercially available. The polyether polyol 1 was INOVOL R8336, a sucrose polyether polyol with five functionalities and a hydroxyl value of 360, manufactured by Shandong Yinuowei New Materials Co., Ltd. Polyether polyol 2 is a glycerol polyether polyol INOVOL F330N with 3 functionalities and a hydroxyl value of 33, produced by Shandong Yinuowei New Material Co., Ltd. The silicone oil stabilizer is AK8805, manufactured by Jinan Hongwang Chemical Co., Ltd.

[0030] The amine catalyst is BDMA.

[0031] The commercially available nano-titanium oxide was purchased from Zhiding New Materials Co., Ltd. as ZD-TiO2-Z10.

[0032] Preparation of polyether polyol 3: 16 wt% of 1-(3,5-difluorophenyl)cyclopentylamine initiator and 12 wt% of sucrose initiator were added to the reactor. After pressure testing and leak detection, N2 was replaced three times. The reactor was pressurized to 0.25 MPa and the temperature was raised to 90 °C for 2 h. The temperature was then raised to 110 °C and the reactor was evacuated to -0.1 MPa for bubbling dehydration for 1 h. The temperature was lowered to 90 °C and 1 wt% of DMAC catalyst was added. Then, 17.8 wt% of the first-stage propylene oxide (PO) was added. After the internal pressure was lowered to -0.05 MPa, the temperature was raised to 110 °C and 33.2 wt% of the second-stage PO was added. After the internal pressure was lowered to -0.05 MPa, 20 wt% of ethylene oxide (EO) was added. After the addition was complete, the reactor was pressurized to 0.2 MPa for 1.5 h. The reactor was then evacuated to -0.09 MPa to remove unreacted monomers, thus obtaining polyether polyol 3.

[0033] Example 1 The nano-titanium oxide reinforced all-water-blown rigid polyurethane foam is composed of component A and component B in a mass ratio of 1:1.2. Component A is composed of the following raw materials in parts by mass: Polyether polyol 1:40 parts; Polyether polyol 2:35 parts; Polyether polyol 3:25 parts; Foaming agent: 1 part; Silicone oil stabilizer: 2 parts; Amine catalyst: 1.5 parts; Component B is MDI; The foaming agent is an aqueous dispersion of titanium dioxide modified with terephthalic acid in situ; The preparation process of the in-situ modified titanium dioxide aqueous dispersion is as follows: 1.96g tetrabutyl titanate, 47.36g anhydrous ethanol, 1g terephthalic acid, 2.08g glacial acetic acid and 2.4g water are added to a reaction vessel and heated to 180℃ for 9h. After filtration and washing, a modified titanium dioxide wet filter cake is obtained. The cake is then dispersed in water and ultrasonicated at 40℃ for 20min to prepare a pre-dispersion with a solid content of 20wt%. The pH is adjusted to 8 with 0.1M NaOH solution to obtain the in-situ modified titanium dioxide aqueous dispersion.

[0034] The method for preparing the nano-titanium oxide reinforced all-water-blown rigid polyurethane foam comprises the following steps: (1) Preparation of component A Polyether polyol 1, polyether polyol 2, and polyether polyol 3 were mixed to form a composite polyether. A foaming agent, titanium dioxide aqueous dispersion modified with terephthalic acid, was added. Then, silicone oil stabilizer and amine catalyst were added. The mixture was shaken evenly and then ultrasonically dispersed at 60°C for 45 minutes to obtain component A. (2) Foaming Mix components A and B, inject into a mold, and allow to foam and mature.

[0035] Specifically, components A and B are mixed in proportion using a high-speed foaming mixer, poured into a mold for foaming, and cured at room temperature for 2 hours to obtain the finished product.

[0036] Example 2 The nano-titanium oxide reinforced all-water-blown rigid polyurethane foam is composed of component A and component B in a 1:1 mass ratio. Component A consists of the following raw materials in parts by mass: Polyether polyol 1:55 parts; Polyether polyol 2:20 parts; Polyether polyol 3:25 parts; Foaming agent: 2 parts; Silicone oil stabilizer: 1.5 parts; Amine catalyst: 2 parts; Component B is MDI; The foaming agent is an aqueous dispersion of titanium dioxide modified with terephthalic acid in situ; The preparation process of the in-situ modified titanium dioxide aqueous dispersion is as follows: 1.96g tetrabutyl titanate, 47.36g anhydrous ethanol, 1g terephthalic acid, 2.08g glacial acetic acid and 2.4g water are added to a reaction vessel and heated to 180℃ for 9h. After filtration and washing, a modified titanium dioxide wet filter cake is obtained. The cake is then dispersed in water and ultrasonicated at 50℃ for 20min to prepare a pre-dispersion with a solid content of 20wt%. The pH is adjusted to 8 with 0.1M NaOH solution to obtain the in-situ modified titanium dioxide aqueous dispersion.

[0037] The method for preparing the nano-titanium oxide reinforced all-water-blown rigid polyurethane foam comprises the following steps: (1) Preparation of component A Polyether polyol 1, polyether polyol 2, and polyether polyol 3 were mixed to form a composite polyether. A foaming agent, titanium dioxide aqueous dispersion modified with terephthalic acid, was added. Then, silicone oil stabilizer and amine catalyst were added. The mixture was shaken evenly and then ultrasonically dispersed at 60°C for 45 minutes to obtain component A. (2) Foaming Mix components A and B, inject into a mold, and allow to foam and mature.

[0038] Specifically, components A and B are mixed in proportion using a high-speed foaming mixer, poured into a mold for foaming, and cured at room temperature for 2 hours to obtain the finished product.

[0039] Example 3 The nano-titanium oxide reinforced all-water-blown rigid polyurethane foam is composed of component A and component B in a mass ratio of 1:1.2. Component A is composed of the following raw materials in parts by mass: Polyether polyol 1:70 parts; Polyether polyol 2:20 parts; Polyether polyol 3:10 parts; Foaming agent: 3 parts; Silicone oil stabilizer: 3 parts; Amine catalyst: 0.5 parts; Component B is MDI; The foaming agent is an aqueous dispersion of titanium dioxide modified with terephthalic acid in situ; The preparation process of the in-situ modified titanium dioxide aqueous dispersion is as follows: 1.96g tetrabutyl titanate, 47.36g anhydrous ethanol, 1g terephthalic acid, 2.08g glacial acetic acid and 2.4g water are added to a reaction vessel and heated to 180℃ for 9h. After filtration and washing, a modified titanium dioxide wet filter cake is obtained. The cake is then dispersed in water and ultrasonicated at 60℃ for 20min to prepare a pre-dispersion with a solid content of 20wt%. The pH is adjusted to 8 with 0.1M NaOH solution to obtain the in-situ modified titanium dioxide aqueous dispersion.

[0040] The method for preparing the nano-titanium oxide reinforced all-water-blown rigid polyurethane foam comprises the following steps: (1) Preparation of component A Polyether polyol 1, polyether polyol 2, and polyether polyol 3 were mixed to form a composite polyether. A foaming agent, titanium dioxide aqueous dispersion modified with terephthalic acid, was added. Then, silicone oil stabilizer and amine catalyst were added. The mixture was shaken evenly and then ultrasonically dispersed at 60°C for 45 minutes to obtain component A. (2) Foaming Mix components A and B, inject into a mold, and allow to foam and mature.

[0041] Specifically, components A and B are mixed in proportion using a high-speed foaming mixer, poured into a mold for foaming, and cured at room temperature for 2 hours to obtain the finished product.

[0042] Example 4 The nano-titanium oxide reinforced all-water-blown rigid polyurethane foam is composed of component A and component B in a mass ratio of 1:1.1. Component A is composed of the following raw materials in parts by mass: Polyether polyol 1:40 parts; Polyether polyol 2:50 parts; Polyether polyol 3:10 parts; Foaming agent: 4 parts; Silicone oil stabilizer: 2.5 parts; Amine catalyst: 1 part; Component B is MDI; The foaming agent is an aqueous dispersion of titanium dioxide modified with terephthalic acid in situ; The preparation process of the in-situ modified titanium dioxide aqueous dispersion is as follows: 1.96g tetrabutyl titanate, 47.36g anhydrous ethanol, 0.5g terephthalic acid, 2.08g glacial acetic acid and 2.4g water are added to a reaction vessel and heated to 150℃ for 11h. After filtration and washing, a modified titanium dioxide wet filter cake is obtained. The cake is then dispersed in water and ultrasonicated at 50℃ for 20min to prepare a pre-dispersion with a solid content of 20wt%. The pH is adjusted to 10 with 0.1M NaOH solution to obtain the in-situ modified titanium dioxide aqueous dispersion.

[0043] The method for preparing the nano-titanium oxide reinforced all-water-blown rigid polyurethane foam comprises the following steps: (1) Preparation of component A Polyether polyol 1, polyether polyol 2, and polyether polyol 3 were mixed to form a composite polyether. A foaming agent, titanium dioxide aqueous dispersion modified with terephthalic acid, was added. Then, silicone oil stabilizer and amine catalyst were added. The mixture was shaken evenly and then ultrasonically dispersed at 60°C for 45 minutes to obtain component A. (2) Foaming Mix components A and B, inject into a mold, and allow to foam and mature.

[0044] Specifically, components A and B are mixed in proportion using a high-speed foaming mixer, poured into a mold for foaming, and cured at room temperature for 2 hours to obtain the finished product.

[0045] Example 5 The nano-titanium oxide reinforced all-water-blown rigid polyurethane foam is composed of component A and component B in a mass ratio of 1:1.2. Component A is composed of the following raw materials in parts by mass: Polyether polyol 1:50 parts; Polyether polyol 2:35 parts; Polyether polyol 3:15 parts; Foaming agent: 5 parts; Silicone oil stabilizer: 2.5 parts; Amine catalyst: 2 parts; Component B is MDI; The foaming agent is an aqueous dispersion of titanium dioxide modified with terephthalic acid in situ; The preparation process of the in-situ modified titanium dioxide aqueous dispersion is as follows: 1.96g tetrabutyl titanate, 47.36g anhydrous ethanol, 2g terephthalic acid, 2.08g glacial acetic acid and 2.4g water are added to a reaction vessel and heated to 160℃ for 5h. After filtration and washing, a modified titanium dioxide wet filter cake is obtained. The cake is then dispersed in water and ultrasonicated at 50℃ for 20min to prepare a pre-dispersion with a solid content of 20wt%. The pH is adjusted to 10 with 0.1M NaOH solution to obtain the in-situ modified titanium dioxide aqueous dispersion.

[0046] The method for preparing the nano-titanium oxide reinforced all-water-blown rigid polyurethane foam comprises the following steps: (1) Preparation of component A Polyether polyol 1, polyether polyol 2, and polyether polyol 3 were mixed to form a composite polyether. A foaming agent, titanium dioxide aqueous dispersion modified with terephthalic acid, was added. Then, silicone oil stabilizer and amine catalyst were added. The mixture was shaken evenly and then ultrasonically dispersed at 60°C for 45 minutes to obtain component A. (2) Foaming Mix components A and B, inject into a mold, and allow to foam and mature.

[0047] Specifically, components A and B are mixed in a certain proportion and then added to a high-speed foaming mixer for mixing. The mixture is then poured into a mold for foaming and allowed to mature at room temperature for 2 hours to obtain the finished product.

[0048] Comparative Example 1 Same as Example 1, except that the foaming agent is replaced with 0.8g of water.

[0049] Comparative Example 2 0.2g of commercially available ZD-TiO2-Z10 nano titanium dioxide was dispersed in the composite polyether, and the rest was the same as in Example 1.

[0050] Comparative Example 3 Add 0.2g of ZD-TiO2-Z10 to water and place it in a water bath at 80°C. Add 10% of the powder mass of the modifier terephthalic acid and react for 5 hours to obtain a modified dispersion that replaces the in-situ modified dispersion. The rest is the same as in Example 1.

[0051] Comparative Example 4 The polyether polyol 3 was replaced with conventional sorbitol polyether INOVOL R6205 (Shandong Yinuowei New Material Co., Ltd.), and the rest was the same as in Example 1.

[0052] Comparative Example 5 A pure nano-TiO2 aqueous dispersion without terephthalic acid modification was used as the foaming agent, i.e., no terephthalic acid was added during hydrothermal treatment, and the rest was the same as in Example 1.

[0053] Comparative Example 6 The amount of in-situ modified titanium dioxide aqueous dispersion was increased to 6 parts, and the rest was the same as in Example 1.

[0054] The finished products obtained from the examples and comparative examples were subjected to performance tests, and the test results are shown in Table 1 below: Table 1 Performance Tests:

[0055] Comparative Example 1 used pure water for foaming without introducing nano-titanium oxide. Rapid CO2 escape led to negative pressure in the bubbles, resulting in significant shrinkage and low compressive strength. Comparative Example 2 directly physical blended commercially available nano-titanium oxide, resulting in uneven particle dispersion and sedimentation, weak interfacial bonding, and poor compressive strength and dimensional stability. Comparative Example 3 used terephthalic acid to modify commercially available nano-titanium oxide, slightly improving dispersion. However, the modification was only surface adsorption, and the chemical anchoring effect was weaker than in-situ modification, resulting in performance still inferior to the examples. Comparative Example 4 replaced the aromatic ring-structured polyether polyol 3 with ordinary sorbitol polyether. Although dispersion was good, compressive strength and shrinkage resistance decreased significantly, indicating that the rigid benzene ring segments of the special polyether and the π-π interaction with terephthalic acid are crucial for synergistic enhancement. Comparative Example 5 used a pure nano-titanium oxide aqueous dispersion without terephthalic acid modification. The particle surface lacked carboxyl groups, making chemical anchoring impossible, resulting in severe aggregation and the worst performance. In Comparative Example 6, the amount of in-situ modified dispersion was increased to 6 parts. Excessive nanoparticles led to severe agglomeration, resulting in a decrease in performance, indicating that there is an optimal addition amount.

[0056] Examples 1 to 3 all used in-situ modified nano-titanium oxide dispersion and polyether polyol 3 containing aromatic ring structures, resulting in good dispersion and no precipitation. In Example 3, the foaming agent dosage was 3 parts, corresponding to 2.4 parts water and 0.6 parts nano-titanium oxide solid content. The foaming reaction was stable, with fine and uniform pores. The nanoparticles were chemically anchored to the polyurethane network through terephthalic acid, synergistically reinforcing the polyether polyol 3 with the rigid benzene ring segments, thus achieving the highest compressive strength, near-zero shrinkage, and maximum surface hardness. In Examples 4 and 5, due to the increased foaming agent dosage, slightly more nanoparticles led to agglomeration, resulting in a sequential decrease in performance. In summary, the formulation of Example 3 achieved the best balance between nano-reinforcement effect and dispersion stability, representing the optimal technical solution.

Claims

1. A nano-titanium oxide reinforced, all-water-blown rigid polyurethane foam, characterized in that, It is composed of component A and component B in a mass ratio of 1:(1-1.2), wherein component A is composed of the following raw materials in parts by mass: Polyether polyol 1: 40-70 parts; Polyether polyol 2: 20-50 parts; Polyether polyol 3: 10-25 parts; Foaming agent: 1-5 parts; Silicone oil stabilizer: 1.5-3 parts; Amine catalyst: 0.5-2 parts; Component B is an isocyanate; The polyether polyol 1 is a 5-functional sucrose polyether polyol with a hydroxyl value of 360 mg KOH / g; Polyether polyol 2 is a glycerol polyether polyol with trifunctionality and a hydroxyl value of 33 mg KOH / g; The polyether polyol 3 is a polyether containing an aromatic ring structure with 4 functionalities and a hydroxyl value of 250 mg KOH / g. The foaming agent is an aqueous dispersion of titanium dioxide modified with terephthalic acid in situ.

2. The nano-titanium oxide reinforced all-water-blown rigid polyurethane foam according to claim 1, characterized in that, The polyether polyol 3 is a polyether polyol prepared by ring-opening polymerization of propylene oxide and ethylene oxide with 1-(3,5-difluorophenyl)cyclopentanamine and sucrose as initiators and dimethylacetamide as catalyst.

3. The nano-titanium oxide reinforced all-water-blown rigid polyurethane foam according to claim 1, characterized in that, The terephthalic acid-modified aqueous dispersion of titanium dioxide is obtained by introducing terephthalic acid as a modifier during the synthesis of titanium dioxide nanoparticles and then modifying it in one step.

4. The nano-titanium oxide reinforced all-water-blown rigid polyurethane foam according to claim 3, characterized in that, The preparation process of the in-situ modified titanium dioxide aqueous dispersion is as follows: tetrabutyl titanate, anhydrous ethanol, terephthalic acid, glacial acetic acid and water are added to a reaction vessel and heated to react. After filtration and washing, the modified titanium dioxide wet filter cake is obtained, which is then dispersed in water and the pH is adjusted to alkaline to obtain the in-situ modified titanium dioxide aqueous dispersion.

5. The nano-titanium oxide reinforced all-water-blown rigid polyurethane foam according to claim 4, characterized in that, The dispersion into water is specifically achieved through ultrasonic dispersion.

6. The nano-titanium oxide reinforced all-water-blown rigid polyurethane foam according to claim 5, characterized in that, The dispersion temperature in the water is 40-60℃.

7. The nano-titanium oxide reinforced all-water-blown rigid polyurethane foam according to claim 1, characterized in that, The silicone oil stabilizer mentioned is AK8805.

8. The nano-titanium oxide reinforced all-water-blown rigid polyurethane foam according to claim 1, characterized in that, The amine catalyst is N,N-dimethylbenzylamine.

9. A method for preparing a nano-titanium oxide reinforced, all-water-blown rigid polyurethane foam according to any one of claims 1-8, characterized in that, It is prepared by the following steps: (1) Preparation of component A Mix polyether polyol 1, polyether polyol 2, polyether polyol 3, foaming agent: in-situ modified titanium dioxide aqueous dispersion, silicone oil stabilizer and amine catalyst evenly. (2) Foaming Mix components A and B, and pour the mixture into a mold to cure.

10. An application of the nano-titanium oxide reinforced all-water-blown rigid polyurethane foam according to any one of claims 1-8, characterized in that, It is used in the preparation of thermal insulation materials or structural materials.

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