High-strength all-water foaming polyurethane foam and preparation method thereof

Abstract

The invention relates to high-strength all-water-blown polyurethane foam and a preparation method thereof. The high-strength all-water-blown polyurethane foam comprises the following components in parts by weight: a polyol composite material: 100 parts of polyether polyol, 2-8 parts of water, 0.5-3 parts of an amine catalyst, 0.2-2 parts of a gel catalyst, 1-5 parts of an organosilicon surfactant, 3-8 parts of a composite filler and 0-10 parts of an auxiliary agent; wherein the composite filler is formed by coating the surfaces of glass beads with porous nano silicon dioxide; the isocyanate material is an MDI (Diphenyl Diisocyanate) or TDI (Toluene Diisocyanate) prepolymer, and the isocyanate index of the MDI or TDI prepolymer is 100 to 120 percent. The surface of the glass bead is coated with a nano silicon dioxide porous shell layer in situ to form a unique'hard core-soft shell 'gradient interface structure, so that the interface bonding force between the filler and a polyurethane matrix is improved, stress transfer is optimized, and the foam material is endowed with excellent comprehensive mechanical properties, especially compressive strength and structural stability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of high polymer materials, and particularly relates to a high-strength full-water foamed polyurethane foam and a preparation method thereof. BACKGROUND

[0002] Polyurethane foam (PUF) is widely used in cushioning, thermal insulation, construction, automobiles and other fields due to its excellent performance. Polyurethane foam is usually prepared by reacting polyol with isocyanate and foaming. According to the hardness, it can be divided into soft and hard foam, and the soft foam is the main variety.

[0003] Traditionally, polyurethane hard foam often uses physical blowing agents such as chlorofluorocarbon CFC-11, hydrochlorofluorocarbon HCFC-141b, pentane, HFC, etc. to reduce the density and improve the thermal insulation performance. However, these blowing agents have environmental and safety problems, such as ozone layer destruction, greenhouse effect or flammability, etc.

[0004] Full-water foaming technology uses water as a blowing agent to react with isocyanate to generate carbon dioxide gas to make the material foam, without using any volatile organic blowing agent, which fundamentally eliminates the ODP and GWP problems. The full-water foaming process is simple, has no special requirements for equipment, and is low in cost, environmentally friendly and non-toxic, with an ODP value of zero. It is an important alternative route to CFC-11 and HCFC-141b blowing agents. Currently, full-water foaming has been applied in soft polyurethane foam such as furniture and mattress foam.

[0005] However, full-water foaming also faces challenges: the solubility of carbon dioxide generated by full-water foaming in the polymer is low, resulting in larger foam pore size and lower closed cell rate, thereby increasing the thermal conductivity of the foam and reducing the mechanical strength. At the same time, when it is necessary to reduce the density of the foam, a large amount of water needs to be added to generate sufficient carbon dioxide, but too much water will react with isocyanate to form polyurea hard segments, which will make the foam brittle and reduce the toughness and strength, thereby limiting the further reduction of the density.

[0006] Therefore, the existing full-water foamed hard foam often has a high density and a low strength, which is difficult to meet the demand of high-performance applications. How to improve the strength of the foam while maintaining a low density in the full-water foaming system is the focus of current research. SUMMARY

[0007] The purpose of the present application is to provide a high-strength full-water foamed polyurethane foam and a preparation method thereof, which has the characteristics of realizing full-water foaming while maintaining or even improving the strength of the foam.

[0008] The purpose of the present application can be achieved by the following technical solutions: A high-strength full-water foamed polyurethane foam, by weight, comprises the following components: The polyol combination material comprises 100 parts of polyether polyol, 2-8 parts of water, 0.5-3 parts of amine catalyst, 0.2-2 parts of gel catalyst, 1-5 parts of silicone surfactant, 3-8 parts of composite filler, and 0-10 parts of auxiliary agent; wherein the composite filler is formed by coating porous nanometer silicon dioxide on the surface of glass microbeads; The isocyanate material comprises MDI or TDI prepolymer, and the isocyanate index of the MDI or TDI prepolymer is 100-120%.

[0009] In the technical solution, the polyether polyol is used as the main polyol to provide the soft segment structure. The MDI (poly methylene polyphenyl polyisocyanate) or TDI prepolymer (toluene diisocyanate) is used as the isocyanate to react with the A material to form the polyurethane and provide the hard segment and cross-linking structure. The isocyanate index is controlled between 100 and 120, so that the system has a slight excess of isocyanate to ensure sufficient curing.

[0010] Preferably, the embodiment of coating the porous nanometer silicon dioxide on the surface of the glass microbeads is the sol-gel method; the glass microbeads are pre-treated by silane modification; and the mass ratio of the glass microbeads in the total mass of the composite reinforcing filler is 10-20%.

[0011] Specifically, the glass microbeads, as the micron-level component in the composite filler, can form a "micro-skeleton" structure in the foam to provide basic rigid support and help maintain the stability of the foam structure and improve the compressive strength and dimensional stability. The nanometer silicon dioxide has a high specific surface area and can have stronger interaction with the polyurethane matrix molecular chain to form a strong interface effect, thereby improving the strength and heat resistance of the foam. The porous structure on the nanometer silicon dioxide 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 to form mechanical engagement or "rivet effect" after curing, thereby significantly enhancing the physical bonding force between the interfaces.

[0012] The glass microbeads treated by silane surface treatment have organic functional groups such as epoxy groups grafted on the surface, which can not only form chemical bonding with the polyurethane matrix, but also be combined with the blended nanometer silicon dioxide particles through physical adsorption or chemical action.

[0013] Preferably, the nanometer silicon dioxide is pre-treated by silane modification, which is beneficial to improve its dispersibility in the polyol.

[0014] Preferably, the particle size of the nanometer silicon dioxide is 10-30 nm, and the glass microbeads are solid sodium-calcium glass microbeads with a particle size of 20-50 microns.

[0015] Preferably, the thickness of the nanosilica coating on the surface of the glass microbeads is 50-100 nm.

[0016] Specifically, the sol-gel method forms a porous nanosilica shell layer on the surface of the glass microbeads by hydrolysis and polycondensation using silanol salt as the silicon source in the presence of a catalyst, thereby obtaining a microsphere composite with core-shell structure. The specific steps mainly include: A. Using silanol salt as the silicon source, ethanol as the solvent, and adding an appropriate amount of water and a catalyst to prepare a silica sol; B. Dispersing the glass microbeads treated with KH560 in the sol, and gradually forming a porous shell layer of nanosilica on the surface of the glass microbeads through sol-gel reaction; C. Filtering and washing the coated microbeads, and then drying them at 80-120℃.

[0017] Further, the product is heat-treated at 200-400℃ to enhance the compactness and stability of the shell layer while maintaining the porous structure.

[0018] Preferably, the polyol combination further includes 10-40 parts of a polymeric polyol; and the polymeric polyol is a polyester polyol or a repairable polyol containing a dynamic covalent bond structure.

[0019] Preferably, the polyether polyol or polyester polyol has a functionality ≥ 3 and a hydroxyl value of 300-500 mgKOH / g.

[0020] Preferably, the polyether polyol or polyester polyol is pre-modified.

[0021] Preferably, the repairable polyol is a modified polyether polyol containing a Diels-Alder adduct or a disulfide bond.

[0022] In the present technical solution, the addition of the modified polyether polyol containing a Diels-Alder adduct or a disulfide bond can facilitate the self-repairing function of the final foam material under thermal / light stimulation.

[0023] Preferably, the mass ratio of the amine catalyst to the gel catalyst is 1-3:1.

[0024] Further, the amine catalyst is an amino-terminated polyether or a diethylenetriamine modification. The tertiary amine groups of the amino-terminated polyether or the diethylenetriamine modification can catalyze the foaming reaction of water with isocyanate, and at the same time, the amine groups can react with isocyanate to participate in chain extension, thereby realizing chain extension simultaneously during the foaming process.

[0025] Further, the amine catalyst is at least one of triethylenediamine, N,N-dimethylcyclohexylamine, and bisdimethylaminoethyl ether.

[0026] Further, the gel catalyst is stannous octoate or dibutyltin dilaurate.

[0027] Preferably, the silicone surfactant is a silicone surfactant containing a functional group that can react with isocyanate in the molecule. Further, the silicone surfactant is a hydroxyl-terminated polysiloxane-polyether copolymer. The hydroxyl-terminated polysiloxane-polyether copolymer can reduce surface tension when foaming, stabilize bubbles, and chemically bond to the polyurethane network when solidifying by reacting with isocyanate through the functional group.

[0028] Preferably, the silicone surfactant is a polyether-modified silicone oil, a trisiloxane super-spreading surfactant, or an ionic modified silicone. The ionic modified silicone is a phosphate salt modified silicone oil or a quaternary ammonium salt grafted silicone oil.

[0029] In this way, the silicone surfactant is used to stabilize the cells, refine the pore size, and chemically bond to the matrix.

[0030] Preferably, the auxiliary agent includes at least one of a chain extender, a crosslinking agent, a flame retardant, and a filler.

[0031] Preferably, the chain extender is 1,4-butanediol or ethylene glycol. The chain extender is used to adjust the molecular chain length and hardness.

[0032] Preferably, the crosslinking agent includes at least one of glycerol, triethanolamine, diethanolamine, and ethylenediamine. The crosslinking agent is used to increase the crosslinking density, improve the foam strength and heat resistance.

[0033] Preferably, the flame retardant is an organic phosphorus-based flame retardant, a halogen-based flame retardant, or an inorganic flame retardant.

[0034] Preferably, the weight fraction of the filler is 0.5-2 parts by weight.

[0035] Preferably, the filler includes 1-5 parts by weight of short fibers with a length of 0.5-5 mm.

[0036] Preferably, the short fibers are glass fiber short yarns, carbon fiber short yarns, or organic synthetic fiber short segments. In this way, the short fibers can form a network reinforcement effect in the foam matrix, significantly improving the tensile strength, tear strength, and impact resistance of the foam.

[0037] A method for preparing the high-strength full-water foaming polyurethane foam as described above, comprising the following steps: S1, mixing a polyol composition; S2, adding an isocyanate material, mixing and performing a foaming reaction to obtain a foamed polyurethane material; S3, curing the polyurethane material obtained in step S2 by gradient temperature, i.e. pre-curing at room temperature for 0.5-2 hours, then gradually increasing the temperature to 80-120℃, and curing for 1-3 hours, to obtain high-strength full-water foamed polyurethane foam.

[0038] Preferably, in step S1, the rotation speed of the polyol combination material mixing is 500-2000 rpm, and the stirring time is 0.5-5 min.

[0039] Preferably, in step S2, after the isocyanate material is added to the polyol combination material, the mixing is carried out at a stirring speed of 1000-3000 rpm for 10-30 seconds; after uniform stirring, the reaction mixture is poured into a pre-prepared mold, or sprayed onto the target construction surface by using a spray foaming process.

[0040] Preferably, in step S3, the temperature increasing rate of the gradual temperature increase is 5-10℃ / min.

[0041] The traditional process usually uses one-time high-temperature curing or room temperature natural curing, while the present application effectively solves the problems of cell defects and insufficient curing of full-water foamed foam due to fast reaction and concentrated heat release by controlling the temperature in stages.

[0042] Advantages of the present application: (1) The present application coats a layer of nano-porous silica shell on the surface of glass microbeads in situ by sol-gel method, forming a unique "hard core-soft shell" gradient interface structure, which aims to make the stress more gently transmitted from the polyurethane matrix to the hard glass microbead core through the porous silica shell, effectively avoiding the interface stress concentration, improving the interfacial bonding force between the filler and the polyurethane matrix, optimizing the stress transmission, and endowing the foam material with excellent comprehensive mechanical properties, especially the compression strength and structural stability, thereby significantly improving the comprehensive mechanical properties of the full-water foamed polyurethane foam.

[0043] (2) The present application uses water as the only foaming agent without using any organic physical foaming agent, which meets the environmental protection requirements. Under the premise of ensuring environmental protection and non-toxicity, by introducing amine catalyst and silicone surfactant into the full-water foamed polyurethane system, a synergistic effect is formed, which promotes the foaming reaction, increases the molecular weight of the polymer, and improves the mechanical properties of the foam; the silicone surfactant as a reactive foam stabilizer not only improves the cell stability but also is chemically bonded to the matrix, avoiding the possible aging performance decline caused by traditional surfactants. The gradient temperature curing process proposed in the present application is simple and easy to implement, which not only solves the problem of insufficient strength of full-water foamed polyurethane foam, but also maintains the environmental protection and simplicity of the process, and has significant economic and social benefits. DETAILED DESCRIPTION

[0044] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined object of the present application, the following embodiments are combined to illustrate the specific embodiments, structures, features and effects of the present application in detail.

[0045] Raw material description: Nano-silica: prepared by gas phase method, average particle size 15 nm, specific surface area 200±25 m 2 / g.

[0046] Glass microbeads: solid sodium-calcium glass microbeads, average particle size 30 microns.

[0047] Silane coupling agent: KH560, purity ≥98%.

[0048] TEOS (tetraethyl orthosilicate): as a silicon source, purity ≥98%.

[0049] Example 1 A high-strength all-water foamed polyurethane foam includes the following components by weight: The preparation method of the composite filler is as follows: 20 g of glass microbeads modified by KH560 were dispersed in 300 mL of anhydrous ethanol and ultrasonically dispersed for 30 minutes. Under stirring, 20 mL of TEOS was slowly added dropwise. Then a mixed solution composed of 10 mL of deionized water and 5 mL of concentrated ammonia water was added dropwise to prepare a silica sol; the reaction was continuously stirred in a 40℃ water bath for 6 hours, and nano-silica gradually formed a porous shell layer on the surface of the glass microbeads. After the reaction was completed, the product was centrifuged, washed with anhydrous ethanol for 3 times, then dried in a vacuum oven at 60℃ for 8 hours, and finally heat-treated at 120℃ for 2 hours to stabilize the shell structure, thereby obtaining core-shell glass microbeads coated with a nano-silica porous shell layer with a thickness of about 70 nm.

[0050] The preparation method of the above high-strength all-water foamed polyurethane foam includes the following steps: S1, the polyol combination was added to a beaker and stirred at 1500 rpm for 60 seconds to uniformity.

[0051] S2, the isocyanate material was added, and after rapid stirring for 20 seconds, it was immediately poured into a 200×200×100 mm open mold; the material foamed and expanded rapidly, and the rising was completed within about 60 seconds, thereby obtaining foamed polyurethane material; S3, the polyurethane material obtained in step S2 was subjected to gradient temperature curing, i.e., pre-curing at room temperature for 30 minutes, then gradually heating to 100℃, and curing for 2 hours, demolding, thereby obtaining an all-water foamed polyurethane foam board.

[0052] Example 2 The high-strength all-water foamed polyurethane foam of the present embodiment comprises the following components by weight: The preparation method of the high-strength all-water foamed polyurethane foam comprises the following steps: S1, the polyether polyol and the polyester polyol are uniformly mixed in advance, and the remaining polyol combination is added, first stirred at a low speed of 500 rpm for 30 seconds to disperse, and then stirred at a high speed of 2000 rpm for 30 seconds to form a uniform slurry.

[0053] S2, the isocyanate material is added, and after rapid stirring for 20 seconds, it is immediately poured into a 200x200x100mm open mold; the material foams and expands rapidly, and the rising is completed in about 90 seconds to obtain foamed polyurethane material; S3, the polyurethane material obtained in step S2 is cured at a gradient temperature, i.e., pre-cured at room temperature for 30 minutes, then gradually heated to 100°C, and cured for 2 hours, demolded to obtain an all-water foamed polyurethane foam board.

[0054] Example 3 The high-strength all-water foamed polyurethane foam of the present embodiment comprises the following components by weight: The preparation method of the high-strength all-water foamed polyurethane foam comprises the following steps: S1, the polyether polyol and the polyester polyol are uniformly mixed in advance, and the remaining polyol combination is added, first stirred at a low speed of 500 rpm for 30 seconds to disperse, and then stirred at a high speed of 2000 rpm for 30 seconds to form a uniform slurry. S2, the isocyanate material is added, and after rapid stirring for 20 seconds, it is immediately poured into a 200x200x100mm open mold; the material foams and expands rapidly, and the rising is completed in about 90 seconds to obtain foamed polyurethane material; S3, the polyurethane material obtained in step S2 is cured at a gradient temperature, i.e., pre-cured at room temperature for 30 minutes, then gradually heated to 100°C, and cured for 2 hours, demolded to obtain an all-water foamed polyurethane foam board.

[0055] Comparative Example 1 The all-water foamed polyurethane foam of the present comparative example comprises the following components by weight: The preparation method of the present comparative example is the same as that of Example 3.

[0056] Comparative Example 2 The all-water foamed polyurethane foam of the present comparative example comprises the following components by weight: The preparation method of the present comparative example is the same as that of Example 2.

[0057] Comparative Example 3 The present comparative example differs from Example 1 in that the composite filler addition amount of the present comparative example is 0, and the remaining components, preparation steps and parameters are consistent.

[0058] The following performance tests were carried out on Examples 1-3 and Comparative Examples 1-3, respectively: (1) Foam density test Refer to GB / T6343-2009 standard. Cut at least 5 cubic samples with a side length of 10 mm from the center area of the completely cured foam board, and the volume is 100 cm 3 . Use a vernier caliper (accuracy not less than ±0.1 mm) to measure the length, width and height of the sample in three directions, take the average of three points in each direction, and calculate the volume V (cm 3 ). Use a balance (accuracy not less than ±0.5%) to weigh the sample mass m (g). Density calculation: Foam density p (kg / m 3 ) = (m / V) x 1000, take the arithmetic mean of the results, accurate to 0.1 kg / m 3 .

[0059] (2) Foam compression strength test Refer to GB / T8813-2008 standard. Cut 5 cubic samples with a side length of 50 mm x 50 mm x 50 mm (±1 mm) from the foam board, and ensure that at least two opposite faces are perpendicular to the foaming direction. Use a universal material testing machine (equipped with displacement sensor and load sensor, accuracy not less than ±1% and ±2% respectively), place the sample between the compression plates, and make the compression direction parallel to the foaming direction of the foam. The loading rate is set to 5 mm / min. Record the load-displacement curve, and when the sample is compressed to 10% of the original thickness, the corresponding pressure value is the 10% deformation compression strength (kPa) = F 10 / A, where F 10 is the load at 10% deformation (N), and A is the initial pressure bearing area of the sample (mm 2 ).

[0060] (3) Foam tensile strength and elongation at break test The test was performed according to GB / T 1040.1-2018 and GB / T 1040.2-2006. The dumbbell-shaped test specimens were prepared from the foam sheet using a precision cutting device, with a 25 mm long, 10 mm wide, and 4 mm thick narrow section in the middle and clamping areas at both ends. The test specimen was ensured to have its long axis parallel to the foaming direction to measure the longitudinal tensile properties or perpendicular to the foaming direction to measure the transverse tensile properties. Five valid test specimens were tested for each set of conditions. A universal material testing machine was used, with the clamps having a textured surface to prevent slipping. The tensile rate was set to 5 mm / min, and the test was performed at room temperature (23±2°C) and a relative humidity of 50±10%. The maximum load and the elongation at break were recorded. The tensile strength (kPa) = F max / A0, wherein F max is the maximum load (N), and A0 is the initial cross-sectional area (mm 2 ). The elongation at break (%) = (L b -L0) / L0x 100%, wherein L b is the gauge length at break (mm), and L0 is the initial gauge length (mm).

[0061] The test results are shown in Table 1.

[0062] Table 1 As can be seen from the test results in Table 1, the samples of Examples 1-3 have similar densities to the samples of Comparative Examples 1-3, but the mechanical strength of the samples of Examples 1-3 is improved to varying degrees. The strength of Comparative Examples 1 and 2 is higher than that of Comparative Example 3, but the effect is limited, indicating that the “hard core-soft shell” gradient structure composed of the composite filler is effective in enhancing the interface and improving the reinforcing efficiency of the monomer filler.

[0063] The above description is only a preferred embodiment of the present application and is not intended to limit the present application in any form. Although the present application has been disclosed as above with reference to the preferred embodiments, it is not intended to limit the present application, and any person skilled in the art can make some changes or modifications to the above disclosed technical content to make equivalent embodiments with equivalent changes, without departing from the technical solution of the present application. Any modification, equivalent change, and modification of the above embodiments made in accordance with the technical essence of the present application are still within the scope of the technical solution of the present application.

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 reinforcing 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 polymeric polyol; the polymeric polyol is a polyester polyol or a 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 modified polyether polyol containing Diels-Alder adducts or 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 extenders, crosslinking agents, flame retardants, and fillers.

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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