A high-strength, all-water-blown polyurethane foam and its preparation method

Abstract

This invention relates to a high-strength, all-water-blown polyurethane foam and its preparation method, comprising the following components by weight: a polyol blend: 100 parts polyether polyol, 2-8 parts water, 0.5-3 parts amine catalyst, 0.2-2 parts gel catalyst, 1-5 parts organosilicon surfactant, 3-8 parts composite filler, and 0-10 parts additives; wherein the composite filler is formed by coating porous nano-silica onto the surface of glass microspheres; and an isocyanate material: MDI or TDI prepolymer, wherein the isocyanate index of the MDI or TDI prepolymer is 100-120%. This invention, by in-situ coating a porous nano-silica shell onto the surface of glass microspheres, forms a unique "hard core-soft shell" gradient interface structure, aiming to improve the interfacial bonding force between the filler and the polyurethane matrix, optimize stress transmission, and endow the foam material with excellent comprehensive mechanical properties, especially compressive strength and structural stability.

Description

Technical Field

[0001] This invention belongs to the technical field of polymer materials, specifically relating to a high-strength all-water foamed polyurethane foam and its preparation method. Background Technology

[0002] Polyurethane foam (PUF) is widely used in cushioning, insulation, construction, automotive and other fields due to its excellent properties. Polyurethane foam is usually produced by reacting polyols with isocyanates and then foaming. According to its hardness, it can be divided into flexible foam and rigid foam, with flexible foam being the main type.

[0003] Traditionally, rigid polyurethane foams commonly use physical blowing agents such as chlorofluorocarbons (CFC-11), hydrochlorofluorocarbons (HCFC-141b), pentane, and HFCs to reduce density and improve thermal insulation performance. However, these blowing agents pose environmental and safety risks, such as ozone layer depletion, greenhouse effect, or flammability.

[0004] All-water foaming technology uses water as a foaming agent, reacting with isocyanates to generate carbon dioxide gas, which causes the material to foam. It does not use any volatile organic foaming agents, fundamentally eliminating ODP and GWP issues. The all-water foaming process is simple, requires no special equipment, is low-cost, environmentally friendly and non-toxic, with an ODP value of zero, making it an important alternative to foaming agents such as CFC-11 and HCFC-141b. Currently, all-water foaming has been applied in flexible polyurethane foams such as those used in furniture and mattresses.

[0005] However, all-water foaming also faces challenges: the carbon dioxide produced by all-water foaming has low solubility in polymers, resulting in larger foam pore sizes and a lower closed-cell ratio, which in turn increases the thermal conductivity and decreases the mechanical strength of the foam. At the same time, when it is necessary to reduce the foam density, a large amount of water needs to be added to produce enough carbon dioxide, but too much water will react with isocyanates to form polyurea hard segments, which will make the foam brittle, reduce its toughness and strength, and thus limit further reduction in density.

[0006] Therefore, existing all-water-blown rigid foams often have high density and low strength, making it difficult to meet the requirements of high-performance applications. How to improve the strength of foam while maintaining a low density in an all-water-blown system is a current research focus. Summary of the Invention

[0007] The purpose of this invention is to provide a high-strength, all-water-blown polyurethane foam and its preparation method, which has the characteristics of achieving all-water-blown foam while maintaining or even improving the strength of the foam.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] A high-strength, fully water-blown polyurethane foam, comprising the following components by weight:

[0010] Polyol composition: 100 parts polyether polyol, 2-8 parts water, 0.5-3 parts amine catalyst, 0.2-2 parts gel catalyst, 1-5 parts organosilicon surfactant, 3-8 parts composite filler and 0-10 parts additives; wherein, the composite filler is formed by coating porous nano-silica on the surface of glass microspheres;

[0011] Isocyanate material: MDI or TDI prepolymer, wherein the isocyanate index of the MDI or TDI prepolymer is 100-120%.

[0012] In this technical solution, polyether polyol serves as the main polyol, providing the soft segment structure. The MDI (polymethylene polyphenyl polyisocyanate) or TDI prepolymer (toluene diisocyanate) serves as the isocyanate, reacting with component A to form polyurethane and providing the hard segment and crosslinking structure. The isocyanate index is controlled between 100 and 120, ensuring a slight excess of isocyanate in the system to guarantee sufficient curing.

[0013] Preferably, the method of coating porous nano-silica onto the surface of glass microspheres is a sol-gel method; the glass microspheres are pre-treated with silane; and the mass of the glass microspheres accounts for 10-20% of the total mass of the composite reinforcing filler.

[0014] Specifically, glass microspheres, as a micron-sized component in the composite filler, can form a "micro-skeleton" structure in the foam, providing basic rigid support, helping to maintain the stability of the foam structure, and improving compressive strength and dimensional stability. Nano-silica has a high specific surface area, which can generate stronger interactions with the polyurethane matrix molecular chains, forming strong interfacial interactions, thereby improving the strength and heat resistance of the foam. In particular, the porous structure on nano-silica greatly increases the effective contact area between the filler and the polyurethane matrix. The rough porous surface provides more physical adsorption sites for the polyurethane matrix, and the polyurethane resin can penetrate into the pores, forming mechanical interlocking or a "riveting effect" after curing, significantly enhancing the physical bonding force between the interfaces.

[0015] Glass microspheres treated with silane have organic functional groups (epoxy groups) grafted onto their surface, which not only form chemical bonds with the polyurethane matrix, but also combine with blended nano-silica particles through physical adsorption or chemical action.

[0016] Preferably, the nano-silica is pretreated with silane. This improves its dispersibility in polyols.

[0017] Preferably, the nano-silica has a particle size of 10-30 nm. The glass microspheres are solid soda-lime glass microspheres with a particle size of 20-50 micrometers.

[0018] Preferably, the thickness of the nano-silica coating on the surface of the glass microspheres is 50-100 nm.

[0019] Specifically, the sol-gel method uses silanols as the silicon source and, under the action of a catalyst, hydrolyzes and condenses the silanols onto the surface of glass microspheres to form a porous shell of nano-silica, thus obtaining a core-shell structured microsphere composite. The main steps include:

[0020] A. Silica sol was prepared by using silanol salt as silicon source, ethanol as solvent, and adding appropriate amounts of water and catalyst.

[0021] B. Disperse the KH560-treated glass microspheres in a sol. Through the sol-gel reaction, nano-silica gradually forms a porous shell on the surface of the glass microspheres.

[0022] C. The coated microspheres are filtered, washed, and then dried at 80-120℃.

[0023] Furthermore, the product is heat-treated at 200-400℃ to enhance the density and stability of the shell while maintaining the porous structure.

[0024] Preferably, the polyol composition further includes 10-40 parts of polymeric polyol; the polymeric polyol is a polyester polyol or a repairable polyol containing a dynamic covalent bond structure.

[0025] Preferably, the polyether polyol or polyester polyol has a functionality of ≥3 and a hydroxyl value of 300-500 mgKOH / g.

[0026] Preferably, the polyether polyol or polyester polyol is pre-modified.

[0027] Preferably, the repairable polyol is a modified polyether polyol containing Diels-Alder adducts or disulfide bonds.

[0028] In this technical solution, the addition of modified polyether polyols containing Diels-Alder adducts or disulfide bonds may help to give the final foam material a self-healing function under heat / light stimulation.

[0029] Preferably, the mass ratio of the amine catalyst to the gel catalyst is 1-3:1.

[0030] Furthermore, the amine catalyst is a terminal amino polyether or a diethylenetriamine modified product. The tertiary amine group of the terminal amino polyether or diethylenetriamine modified product can catalyze the foaming reaction of water and isocyanate, and its amine group can react with isocyanate to participate in chain growth, thereby achieving chain extension simultaneously during the foaming process.

[0031] Furthermore, the amine catalyst is at least one of triethylenediamine, N,N-dimethylcyclohexylamine, and dimethylaminoethyl ether.

[0032] Furthermore, the gel catalyst is stannous octoate or dibutyltin dilaurate.

[0033] Preferably, the organosilicon surfactant is an organosilicon surfactant containing functional groups in its molecule that can react with isocyanates. Further, the organosilicon surfactant is a hydroxyl-terminated polysiloxane-polyether copolymer. The hydroxyl-terminated polysiloxane-polyether copolymer can reduce surface tension and stabilize bubbles during foaming, and during curing, it bonds to the polyurethane network through the reaction of its functional groups with isocyanates.

[0034] Preferably, the organosilicon surfactant is a polyether-modified silicone oil, a trisiloxane superspreading surfactant, or an ionic modified organosilicon. The ionic modified organosilicon is a phosphate ester-modified silicone oil or a quaternary ammonium salt-grafted silicone oil.

[0035] Thus, the organosilicon surfactant is used to stabilize pores, refine pore size, and chemically bond to the matrix.

[0036] Preferably, the additives include at least one of chain extenders, crosslinking agents, flame retardants, and fillers.

[0037] Preferably, the chain extender is 1,4-butanediol or ethylene glycol. The chain extender is used to adjust the molecular chain length and hardness.

[0038] Preferably, the crosslinking agent includes at least one selected from glycerol, triethanolamine, diethanolamine, and ethylenediamine. The crosslinking agent is used to increase the crosslinking density, improve foam strength, and enhance heat resistance.

[0039] Preferably, the flame retardant is an organophosphorus flame retardant, a halogenated flame retardant, or an inorganic flame retardant.

[0040] Preferably, the filler is 0.5-2 parts by weight.

[0041] Preferably, the filler comprises 1-5 parts by weight of short-cut fibers with a length of 0.5-5 mm.

[0042] Preferably, the chopped fibers are chopped glass fiber yarn, chopped carbon fiber yarn, or chopped organic synthetic fibers. In this way, the chopped fibers can form a network reinforcement effect in the foam matrix, significantly improving the tensile strength, tear strength, and impact resistance of the foam.

[0043] A method for preparing high-strength, all-water-blown polyurethane foam as described above includes the following steps:

[0044] S1. Mix the polyol mixture;

[0045] S2. Add isocyanate material, mix and carry out foaming reaction to obtain foamed polyurethane material;

[0046] S3. The polyurethane material obtained in step S2 is subjected to gradient temperature curing, that is, pre-curing at room temperature for 0.5-2 hours, and then gradually increasing the temperature to 80-120℃ and curing for 1-3 hours to obtain high-strength all-water foamed polyurethane foam.

[0047] Preferably, in step S1, the mixing speed of the polyol mixture is 500-2000 rpm, and the stirring time is 0.5-5 min.

[0048] Preferably, in step S2, the isocyanate material is added to the polyol mixture and then mixed. The mixing speed is 1000-3000 rpm and the mixing time is 10-30 seconds. After the mixture is stirred evenly, the reaction mixture is poured into a pre-prepared mold, or sprayed onto the target construction surface using a spray foaming process.

[0049] Preferably, in step S3, the heating rate of the gradual heating is 5-10℃ / min.

[0050] Traditional processes often employ one-time high-temperature curing or room-temperature natural curing. However, this solution effectively solves the problems of cell defects and insufficient curing caused by the rapid reaction and concentrated heat release of all-water foam through staged temperature control.

[0051] The beneficial effects of this invention are:

[0052] (1) This invention uses the sol-gel method to coat a layer of nano-silica porous shell on the surface of glass microspheres in situ, forming a unique "hard core-soft shell" gradient interface structure. This is intended to allow stress to be transferred more smoothly from the polyurethane matrix to the hard glass microsphere core through the porous silica shell, effectively avoiding interface stress concentration, improving the interfacial bonding force between the filler and the polyurethane matrix, optimizing stress transfer, and endowing the foam material with excellent comprehensive mechanical properties, especially compressive strength and structural stability, thereby achieving a significant improvement in the comprehensive mechanical properties of all-water foamed polyurethane foam.

[0053] (2) This invention uses water as the sole foaming agent and does not use any organic physical foaming agents, thus meeting environmental protection requirements. While ensuring environmental friendliness and non-toxicity, by introducing amine catalysts and organosilicon surfactants into the all-water foamed polyurethane system, a synergistic effect is achieved. This promotes the foaming reaction while increasing the polymer molecular weight and improving the mechanical properties of the foam. The organosilicon surfactant, as a reactive foam stabilizer, not only improves cell stability but also chemically bonds to the matrix, avoiding the aging performance degradation that may occur with traditional surfactants. The gradient temperature curing process proposed in this scheme is simple and easy to implement. While solving the problem of insufficient foam strength in all-water foamed polyurethane, it also maintains the environmental friendliness and simplicity of the process, resulting in significant economic and social benefits. Detailed Implementation

[0054] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0055] Raw material description:

[0056] Nano-silica: prepared by vapor phase method, with an average particle size of 15 nm and a specific surface area of ​​200 ± 25 m². 2 / g.

[0057] Glass microspheres: Solid sodium-calcium glass microspheres with an average particle size of 30 micrometers.

[0058] Silane coupling agent: KH560, purity ≥98%.

[0059] TEOS (Tetraethyl Orthosilicate): As a silicon source, its purity is ≥98%.

[0060] Example 1

[0061] A high-strength, fully water-blown polyurethane foam, comprising the following components by weight:

[0062]

[0063] The preparation method of the composite filler is as follows:

[0064] 20g of KH560-modified glass microspheres were weighed and dispersed in 300mL of anhydrous ethanol, and ultrasonically dispersed for 30 minutes. 20mL of LTEOS was slowly added dropwise while stirring. Then, a mixed solution of 10mL deionized water and 5mL concentrated ammonia was added dropwise to prepare a silica sol. The reaction was carried out with continuous stirring in a 40℃ water bath for 6 hours, during which nano-silica gradually formed a porous shell on the surface of the glass microspheres. After the reaction, the product was centrifuged, washed three times with anhydrous ethanol, dried in a 60℃ vacuum oven for 8 hours, and then heat-treated at 120℃ for 2 hours to stabilize the shell structure, yielding core-shell glass microspheres with a porous nano-silica shell with a surface thickness of approximately 70nm.

[0065] The preparation method of the above-mentioned high-strength all-water-blown polyurethane foam includes the following steps:

[0066] S1. Add the polyol mixture to a beaker and stir at 1500 rpm for 60 seconds until homogeneous.

[0067] S2. Add isocyanate material, stir quickly for 20 seconds and immediately pour into an open mold of 200×200×100mm; the material foams and expands rapidly, and rises within about 60 seconds to obtain foamed polyurethane material.

[0068] S3. The polyurethane material obtained in step S2 is subjected to gradient temperature curing, that is, pre-curing at room temperature for 30 minutes, then gradually increasing the temperature to 100℃ and curing for 2 hours, then demolding to obtain a fully water-foamed polyurethane foam board.

[0069] Example 2

[0070] The high-strength, fully water-blown polyurethane foam of this embodiment comprises the following components by weight:

[0071]

[0072] The preparation method of the above-mentioned high-strength all-water-blown polyurethane foam includes the following steps:

[0073] S1. Premix the polyether polyol and polyester polyol evenly, then add the remaining polyol mixture. First, stir at a low speed of 500 rpm for 30 seconds to disperse it, and then stir at a high speed of 2000 rpm for 30 seconds to form a uniform slurry.

[0074] S2. Add isocyanate material, stir quickly for 20 seconds and immediately pour into an open mold of 200×200×100mm; the material foams and expands rapidly, and rises within about 90 seconds to obtain foamed polyurethane material.

[0075] S3. The polyurethane material obtained in step S2 is subjected to gradient temperature curing, that is, pre-curing at room temperature for 30 minutes, then gradually increasing the temperature to 100℃ and curing for 2 hours, then demolding to obtain a fully water-foamed polyurethane foam board.

[0076] Example 3

[0077] The high-strength, fully water-blown polyurethane foam of this embodiment comprises the following components by weight:

[0078]

[0079] The preparation method of the above-mentioned high-strength all-water-blown polyurethane foam includes the following steps:

[0080] S1. Mix the polyol mixture except for the composite filler. First, stir at a low speed of 500 rpm for 30 seconds to disperse it. Then add the composite filler and stir at a high speed of 2000 rpm for 3 minutes to disperse the composite filler evenly.

[0081] S2. Add isocyanate material and stir rapidly at 1800 rpm for 10 seconds, then immediately pour into an open mold of 200×200×100mm; the material begins to foam and rise in about 40 seconds, and foaming is completed in about 90 seconds to obtain foamed polyurethane material.

[0082] S3. The polyurethane material obtained in step S2 is subjected to gradient temperature curing, that is, pre-curing at room temperature for 30 minutes, then gradually increasing the temperature to 100℃ and curing for 2 hours, then demolding to obtain a fully water-foamed polyurethane foam board.

[0083] Comparative Example 1

[0084] The all-water-blown polyurethane foam in this comparative example comprises the following components by weight:

[0085]

[0086] The preparation method for this comparative example is the same as that for Example 3.

[0087] Comparative Example 2

[0088] The all-water-blown polyurethane foam in this comparative example comprises the following components by weight:

[0089]

[0090] The preparation method for this comparative example is the same as that for Example 2.

[0091] Comparative Example 3

[0092] The difference between this comparative example and Example 1 is that the amount of composite filler added in this comparative example is 0, while the other components, preparation steps and parameters are the same.

[0093] The following performance tests were performed on Examples 1-3 and Comparative Examples 1-3 respectively:

[0094] (1) Foam density test

[0095] Perform the procedure according to GB / T6343-2009 standard. Cut at least five cubic samples, each with a side length of 10 mm and a volume of 100 cm³, from the center area of ​​the fully cured foam board. 3 The dimensions of the sample in the length, width, and height directions were measured using vernier calipers (accuracy not less than ±0.1 mm). Three measurements were taken in each direction, and the average value was calculated. The volume V (cm³) was then calculated. 3 Weigh the sample mass m (g) using a balance (accuracy not less than ±0.5%). Calculate the density: foam density ρ (kg / m³). 3 = (m / V) × 1000, and take the arithmetic mean of the result, accurate to 0.1 kg / m³. 3 .

[0096] (2) Foam compressive strength test

[0097] Perform the procedure according to GB / T8813-2008 standard. Cut five cubic specimens with sides of 50mm × 50mm × 50mm (±1mm) from the foam board, ensuring that at least two opposite faces are perpendicular to the foaming direction. Using a universal testing machine (equipped with a displacement sensor and a load sensor, with accuracies of no less than ±1% and ±2% respectively), place the specimens between compression plates, ensuring the compression direction is parallel to the foaming direction. Set the loading rate to 5mm / min. Record the load-displacement curve. The pressure value corresponding to when the specimen is compressed to 10% of its original thickness is the 10% deformation compressive strength (kPa) = F 10 / A, where F 10 The load (N) is the load at 10% deformation, and A is the initial bearing area of ​​the specimen (mm²). 2 ).

[0098] (3) Testing of foam tensile strength and elongation at break

[0099] Perform the test according to GB / T1040.1-2018 and GB / T1040.2-2006 standards. Prepare dumbbell-shaped specimens from foam boards using precision cutting equipment. The narrow middle section should be 25 mm long, 10 mm wide, and 4 mm thick, with clamping areas at both ends. Ensure the long axis of the specimen is parallel to the foaming direction for determining longitudinal tensile properties, or perpendicular to the foaming direction for determining transverse tensile properties. Test five valid specimens for each condition. Use a universal testing machine with a gripper featuring an anti-slip texture. Set the tensile rate to 5 mm / min and conduct the test at room temperature (23±2°C) and relative humidity 50±10%. Record the maximum load and elongation at fracture. Tensile strength (kPa) = F max / A0, where F max A0 is the maximum load (N), and A0 is the initial cross-sectional area (mm). 2 Elongation at break (%) = (L) b -L0) / L0× 100%, where L b L1 is the gauge length at the time of fracture (mm), and L2 is the initial gauge length (mm).

[0100] The test results are shown in Table 1.

[0101] Table 1

[0102]

[0103] As shown in Table 1, compared with Comparative Examples 1-3, the samples of Examples 1-3 have similar densities, but the mechanical strength of Examples 1-3 is improved to varying degrees. Comparative Examples 1 and 2 have higher strengths than Comparative Example 3, but the effect is limited, indicating that the "hard core-soft shell" gradient structure of the composite filler is effective in enhancing the interface and improving the reinforcing efficiency of the monomer filler.

[0104] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A high-strength, fully water-blown polyurethane foam, characterized in that, By weight, it includes the following components: Polyol composition: 100 parts polyether polyol, 2-8 parts water, 0.5-3 parts amine catalyst, 0.2-2 parts gel catalyst, 1-5 parts organosilicon surfactant, 3-8 parts composite filler and 0-10 parts additives; wherein, the composite filler is formed by coating porous nano-silica on the surface of glass microspheres; Isocyanate material: MDI or TDI prepolymer, wherein the isocyanate index of the MDI or TDI prepolymer is 100-120%.

2. The high-strength, all-water-blown polyurethane foam according to claim 1, characterized in that, The method for coating porous nano-silica onto the surface of glass microspheres is the sol-gel method; the glass microspheres are pre-treated with silane; the mass of the glass microspheres accounts for 10-20% of the total mass of the composite filler.

3. The high-strength, all-water-blown polyurethane foam according to claim 1, characterized in that, The polyol composition also includes 10-40 parts of polyester polyol or repairable polyol containing a dynamic covalent bond structure.

4. The high-strength, all-water-blown polyurethane foam according to claim 3, characterized in that, The polyether polyol has a functionality ≥3 and a hydroxyl value of 300-500 mgKOH / g; the polyester polyol has a functionality ≥3 and a hydroxyl value of 300-500 mgKOH / g; the repairable polyol is a polyol containing Diels-Alder adducts or a modified polyether polyol containing disulfide bonds.

5. The high-strength, all-water-blown polyurethane foam according to claim 1, characterized in that, The amine catalyst is at least one of triethylenediamine, N,N-dimethylcyclohexylamine, and dimethylaminoethyl ether; the gel catalyst is stannous octoate or dibutyltin dilaurate; the mass ratio of the amine catalyst to the gel catalyst is 1-3:

1.

6. The high-strength, all-water-blown polyurethane foam according to claim 1, characterized in that, The organosilicon surfactant is a polyether-modified silicone oil, a trisiloxane superspreading surfactant, or an ionic modified organosilicon.

7. The high-strength, all-water-blown polyurethane foam according to claim 1, characterized in that, The additives include at least one of chain extender, crosslinking agent, flame retardant, and filler, wherein the filler is 1-5 parts by weight of short-cut fibers with a length of 0.5-5 mm.

8. The high-strength, all-water-blown polyurethane foam according to claim 7, characterized in that, The chain extender is 1,4-butanediol or ethylene glycol; the crosslinking agent includes at least one of glycerol, triethanolamine, diethanolamine, and ethylenediamine; the flame retardant is an organophosphorus flame retardant, a halogenated flame retardant, or an inorganic flame retardant.

9. A method for preparing high-strength, all-water-blown polyurethane foam as described in any one of claims 1 to 8, characterized in that, The preparation method includes the following steps: S1. Mix the polyol mixture; S2. Add isocyanate material, mix and carry out foaming reaction to obtain foamed polyurethane material; S3. The polyurethane material obtained in step S2 is subjected to gradient temperature curing, that is, pre-curing at room temperature for 0.5-2 hours, and then gradually increasing the temperature to 80-120℃ and curing for 1-3 hours to obtain high-strength all-water foamed polyurethane foam.

10. The preparation method according to claim 9, characterized in that, In step S1, the mixing speed of the polyol mixture is 500-2000 rpm, and the stirring time is 0.5-5 min. In step S2, the isocyanate material is added to the polyol mixture and mixed. The mixing speed is 1000-3000 rpm and the mixing time is 10-30 seconds. After the mixture is stirred evenly, the reaction mixture is poured into a pre-prepared mold or sprayed onto the target surface using a spray foaming process. In step S3, the heating rate of the gradual heating is 5-10℃ / min.

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