Bio-based polyurethane adhesive for pavement floor tiles and use method of bio-based polyurethane adhesive

Abstract

The invention discloses a bio-based polyurethane adhesive for pavement floor tiles and a use method thereof, and the bio-based polyurethane adhesive is prepared by mixing and uniformly stirring the following raw materials in parts by mass: 90-110 parts of bio-based polyol, 15-25 parts of castor oil, 50-60 parts of polymerized MDI, a bismuth-zinc catalyst accounting for one hundred thousandth to one ten thousandth of the sum of the mass of the bio-based polyol, the castor oil and the polymerized MDI, and 1-5 parts of a defoaming agent, 1-5 parts of a drying agent, 1-4 parts of a coupling agent, 2-4 parts of fumed silica and 180-200 parts of dry silica powder. According to the bio-based polyurethane adhesive, a bio-based polyol and castor oil polyol system of a soft segment reacts with polymerized MDI of a hard segment to form a phase-separated'soft-hard segment 'microphase structure, and balance is formed; the excellent performance of the adhesive is realized through the cooperation of flexible chain segments of the bio-based polyol and the castor oil, the equilibrium reaction of the bismuth-zinc catalyst and the interface enhancement effect of the coupling agent and the inorganic filler.

Description

Technical Field

[0001] This invention relates to adhesives and methods of using them, particularly adhesives for paving bricks and methods of using them. Background Technology

[0002] Large paving stones are typically used for plazas, parking lots, and other road surfaces. These stones are usually fixed with cement mortar, which has drawbacks such as low bonding strength and poor flexibility. Under long-term use and the pressure of vehicles, the paving stones are prone to cracking, especially at the corners, as well as loosening and detachment of the adhesive. The lifespan of these paving stones is relatively short, requiring repeated replacement and maintenance. Organic adhesives are also used to fix the paving stones, but these often rely on petroleum-based raw materials, have poor environmental performance, and some contain volatile organic compounds, which can negatively impact the construction environment and human health. Summary of the Invention

[0003] Purpose of the invention: One purpose of this invention is to provide a bio-based polyurethane adhesive for road pavers, which has strong adhesion, good flexibility, and is environmentally friendly and economical; another purpose of this invention is to provide a method of using this adhesive, which, after fixing the road pavers, ensures the integrity of the pavers for a long period of time under the condition of being driven on.

[0004] Technical solution: A bio-based polyurethane adhesive for paving bricks, prepared by mixing and thoroughly stirring the following raw materials in parts by weight: 90-110 parts of bio-based polyols 15-25 parts castor oil 50-60 parts of polymeric MDI The bismuth-zinc catalyst is present in a concentration of 1 / 100,000 to 1 / 10,000 of the combined mass of bio-based polyols, castor oil, and polymeric MDI. 1-5 parts of defoamer 1-5 parts of desiccant 1-4 parts of coupling agent, 2-4 parts of fumed silica 180-200 parts of dried silica powder.

[0005] Furthermore, the bio-based polyol has a hydroxyl value of 140±10mgKOH / g, an acid value of ≤1.0mgKOH / g, a viscosity of 1000±200cps@25℃, and a moisture content of ≤0.15% (by mass).

[0006] Furthermore, the defoamer is BYK-020, the desiccant is 3A or 4A molecular sieve, and the coupling agent is KH560 or KH570.

[0007] Furthermore, the dried silica powder has a mesh size of 800–1250.

[0008] Furthermore, the ratio of bismuth to zinc in the bismuth-zinc catalyst is 1:2.

[0009] Furthermore, a bio-based polyurethane adhesive for road pavers is prepared from the following raw materials by mass: 100 parts bio-based polyol, 21 parts castor oil, 53 parts polymeric MDI, 0.004 parts bismuth zinc catalyst, 4 parts defoamer, 4 parts desiccant, 4 parts coupling agent, 2 parts fumed silica, and 200 parts dried silica powder.

[0010] A method for using the above-mentioned bio-based polyurethane adhesive for road pavers involves removing damaged pavers, cleaning the exposed road surface base, laying fiberglass mesh, uniformly applying the bio-based polyurethane adhesive onto the fiberglass mesh, and finally placing the pavers flat under their own weight. Once the bio-based polyurethane adhesive has cured, the pavers are fixed in place. The fiberglass mesh should be laid extending to the edges of the pavers.

[0011] Furthermore, at least one layer of fiberglass mesh is laid, and the bio-based polyurethane adhesive is also uniformly applied between each layer of fiberglass mesh.

[0012] Furthermore, the total thickness of the applied bio-based polyurethane adhesive is 2–5 mm.

[0013] Beneficial Effects: The bio-based polyurethane adhesive utilizes a soft-segment bio-based polyol and castor oil polyol system to react with the hard-segment polymerized MDI, forming a phase-separated "soft-hard segment" microphase structure. This equilibrium is achieved through the synergistic effect of the flexible segments of the bio-based polyol and castor oil, the balanced reaction of the bismuth-zinc catalyst, and the interfacial reinforcement effect of the coupling agent and inorganic filler. These factors combine to achieve excellent adhesive strength, flexibility, and durability, meeting the requirements for long-term service of paving bricks in complex environments. By using fiberglass mesh in conjunction with the bio-based polyurethane adhesive to fix the paving bricks, the fiberglass mesh acts as a buffer and extends the bond between the paving brick and the adhesive, achieving a minimum bond strength of 10 MPa. Attached Figure Description

[0014] Figure 1 This is a schematic diagram illustrating the method of using the present invention. Detailed Implementation

[0015] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0016] A bio-based polyurethane adhesive for paving bricks is prepared by mixing and thoroughly stirring the following raw materials in parts by weight: 90-110 parts of bio-based polyols 15-25 parts castor oil 50-60 parts of polymeric MDI The bismuth-zinc catalyst is present in a concentration of 1 / 100,000 to 1 / 10,000 of the combined mass of bio-based polyols, castor oil, and polymeric MDI. 1-5 parts of defoamer 1-5 parts of desiccant 1-4 parts of coupling agent, 2-4 parts of fumed silica 180-200 parts of dried silica powder.

[0017] The defoamer can be BYK-020, the desiccant can be 3A or 4A molecular sieve, the coupling agent can be KH560 or KH570, the dried silica powder can be 800-1250 mesh, and the ratio of bismuth to zinc in the bismuth-zinc catalyst is 1:2.

[0018] Bio-based polyol, commercially available, with a hydroxyl value of 140±10mgKOH / g, an acid value of ≤1.0mgKOH / g, a viscosity of 1000±200cps@25℃, and a moisture content of ≤0.15% (by weight).

[0019] The following describes the roles of each ingredient in a bio-based polyurethane adhesive within the adhesive system.

[0020] Bio-based polyols: These are the main soft segment components, providing bio-based flexible segments. Their molecular structure contains unsaturated fatty chain structures derived from soybean oil, combining flexibility with a certain degree of polarity. This allows them to maintain bio-based properties while improving interfacial compatibility with inorganic substrates (such as floor tiles and mortar layers). The performance parameters of bio-based polyols can effectively regulate the balance between crosslinking density and bonding strength, giving the resulting bio-based polyurethane adhesives good flexibility and resistance to thermal cycling.

[0021] Castor oil: Industrial castor oil contains natural hydroxy fatty acid esters. Its molecular chains are soft and have low polarity. On the one hand, it improves the flowability and workability of adhesives. On the other hand, it further participates in the polyurethane reaction to form chemical cross-linking points. In the adhesive system, it forms a branched structure to enhance the flexibility of the molecular chain. It complements bio-based polyols to form a flexible synergistic effect, improves the energy buffering capacity of the bonding interface, and enhances the overall toughness and bonding durability.

[0022] Polymerized MDI: As an isocyanate component, it is a source of hard segments, providing hard segment structure and reactive centers. It reacts with the soft segment polyol system (bio-based polyol + castor oil) to form a phase-separated "soft-hard segment" microphase structure of urethane bonds, which provides structural strength and heat resistance to the adhesive system and enhances the peel resistance of the bonding interface.

[0023] Bismuth-zinc catalyst (Bi∶Zn=1∶2): a low-toxicity and environmentally friendly catalyst that promotes the reaction of -NCO and -OH through synergistic catalysis. Bismuth mainly accelerates the initial reaction and promotes the hydroxyl reaction rate, while zinc improves the crosslinking balance in the later stage, balancing the reaction rate and storage stability. The two work together to ensure that the adhesive system reaction is mild and controllable, avoids the generation of bubbles, thereby improving the reaction uniformity and increasing the density and bonding strength of the cured adhesive layer.

[0024] Defoamer (BYK-020): Inhibits bubble formation during the reaction process, prevents interface defects, and ensures the continuity of the adhesive layer.

[0025] Desiccant (3A or 4A molecular sieve): Adsorbs trace amounts of moisture in the adhesive system, preventing side reactions between water and isocyanate to form urea bonds and CO2, avoiding defects such as bubbles and pores, and further improving the density and aging resistance of the cured adhesive layer. Coupling agent (KH560 or KH570): After hydrolysis on the surface of inorganic fillers, it forms silanol groups, which can react with the filler surface to form strong siloxane bonds, forming a chemical bridge. At the same time, its acryloyloxy group can form chemical or hydrogen bonds with the polyurethane system, improving the interfacial bonding force between the inorganic filler and the polyurethane matrix, thereby significantly improving the shear bond strength and durability of the adhesive system.

[0026] Fumed silica: provides thixotropy and reinforcement, improves rheological properties, prevents filler sedimentation, and forms a synergistic reinforcement network with dried silica powder, thereby improving colloidal mechanical strength and dimensional stability.

[0027] Dry silica powder: As the main inorganic filler, it endows the adhesive system with high volume stability and pressure resistance. Together with fumed silica, it forms an inorganic filler network, creating a "coarse-fine particle filler synergy". Fumed silica has a fine particle size and a large specific surface area, which can enhance the thixotropy and anti-sagging properties of the adhesive system. Dry silica powder provides skeletal support, improves the mechanical strength and dimensional stability of the colloid, and improves wear resistance and heat resistance while ensuring bonding strength. The two have a significant synergistic reinforcing effect under the ratio specified in this application.

[0028] The raw materials in the bio-based polyurethane adhesive exhibit a significant synergistic effect: the flexibility of the polyol system (bio-based polyol + castor oil) balances with the hard segments of polymerized MDI; the combination of bismuth-zinc catalyst and desiccant ensures uniform reaction and defect-free interfaces; coupling agent and inorganic filler jointly enhance interfacial bonding strength; and the overall dense network structure endows the product with excellent resistance to thermal shock and high adhesive strength. Through these combined effects, the synergistic effect of the flexible segments of bio-based polyol and castor oil, the balanced reaction of the bismuth-zinc catalyst, and the interfacial enhancement effect of the coupling agent and inorganic filler in the adhesive system collectively achieve excellent adhesive strength, flexibility, and durability, meeting the requirements for long-term service of paving bricks in complex environments.

[0029] In the preparation of bio-based polyurethane adhesives, the main reaction between the raw materials is polyurethane condensation. The reaction mechanism is an addition reaction between isocyanate (—NCO) and hydroxyl group (—OH) to form urethane bond (—NHCOO—). The reaction principle is shown in the following formula: R-NCO + R´-OH → R-NH-COOR This reaction is exothermic and is typically carried out under anhydrous conditions. During the reaction, polymeric MDI provides isocyanate groups as a source of hard segments, which react with hydroxyl groups from bio-based polyols and castor oil to form a polyurethane backbone structure. The resulting urethane bonds endow the material with good bonding strength and durability.

[0030] According to the bio-based polyurethane adhesive raw material system and synergistic mechanism of this invention, the synergistic effect between various raw materials and the influence of the main component ratio on adhesive performance can be optimized by adjusting the proportions of soft segments, hard segments, and fillers. This achieves an optimized match between flexibility, bond strength, and ease of application to meet the needs of different application scenarios. Adjustment principles: (1) Bio-based polyols and castor oil: The two together constitute a polyol system. Adjusting the ratio of the two can control the flexibility and flowability of the adhesive layer. Increasing the proportion of castor oil can improve the flexibility and workability of the adhesive layer, but the hardness will decrease slightly. Decreasing the proportion of castor oil will increase the hardness and bonding strength, but decrease the flexibility.

[0031] (2) Polymer MDI and polyol system: The ratio of hard segment to soft segment directly affects the crosslinking density and the rigid-flexible balance of the adhesive layer. Increasing polymer MDI can improve hardness and bonding strength, but may reduce toughness. Reducing MDI can increase flexibility and better absorb the stress of the floor tile.

[0032] (3) Filler and coupling agent: Dry silica powder and fumed silica form an organic-inorganic composite network under the action of coupling agent, which enhances the interfacial bonding force, shear strength and dimensional stability. Excessive filler and coupling agent ratio will affect flowability, while insufficient ratio will reduce interfacial performance.

[0033] (4) Catalyst, defoamer and desiccant: By synergistically regulating the reaction rate, bubble generation and moisture control, the adhesive layer is ensured to be uniform and dense, while ensuring the ease of construction.

[0034] Based on construction requirements, the following five bio-based polyurethane adhesive raw material formulations are listed.

[0035] Example 1 A bio-based polyurethane adhesive for road pavers is made from the following raw materials by weight: 100 parts bio-based polyol, 21 parts castor oil, 53 parts polymeric MDI, 0.004 parts bismuth zinc catalyst, 4 parts defoamer, 4 parts desiccant, 4 parts coupling agent, 2 parts fumed silica, and 200 parts dried silica powder.

[0036] This formula serves as the benchmark, achieving a balance between strength and flexibility, and is suitable for general tile replacement work.

[0037] Example 2 A bio-based polyurethane adhesive for road pavers is made from the following raw materials by weight: 105 parts bio-based polyol, 20 parts castor oil, 53 parts polymeric MDI, 0.004 parts bismuth zinc catalyst, 4 parts defoamer, 4 parts desiccant, 4 parts coupling agent, 2 parts fumed silica, and 200 parts dried silica powder.

[0038] This formula increases the proportion of soft segments in the polyol system, making the adhesive layer more flexible and suitable for scenarios requiring high application flexibility.

[0039] Example 3 A bio-based polyurethane adhesive for road pavers is made from the following raw materials by weight: 95 parts bio-based polyol, 21 parts castor oil, 56 parts polymeric MDI, 0.004 parts bismuth zinc catalyst, 4 parts defoamer, 4 parts desiccant, 4 parts coupling agent, 2 parts fumed silica, and 200 parts dried silica powder.

[0040] This formula increases the proportion of hard segments in the polyol system, improving the hardness and bonding strength of the adhesive layer, making it suitable for construction scenarios involving high-load or heavy-duty floor tiles.

[0041] Example 4 A bio-based polyurethane adhesive for road pavers is made from the following raw materials by weight: 100 parts bio-based polyol, 19 parts castor oil, 55 parts polymeric MDI, 0.004 parts bismuth zinc catalyst, 4 parts defoamer, 4 parts desiccant, 4 parts coupling agent, 2 parts fumed silica, and 210 parts dried silica powder.

[0042] This formulation increases the amount of hard segments and fillers in the polyol system, improving the interfacial bonding strength and volume stability of the adhesive layer, making it suitable for construction environments requiring high stability and durability.

[0043] Example 5 A bio-based polyurethane adhesive for road pavers is prepared from the following raw materials by weight: 105 parts bio-based polyol, 22 parts castor oil, 51 parts polymeric MDI, 0.004 parts bismuth zinc catalyst, 4 parts defoamer, 4 parts desiccant, 4 parts coupling agent, 2 parts fumed silica, and 195 parts dried silica powder.

[0044] This formula increases the soft segments of the polyol system and slightly reduces the hardness, making the adhesive layer more flexible and suitable for repairing easily cracked floor tiles.

[0045] The method of using the bio-based polyurethane adhesive for paving bricks of this invention, in conjunction with the appendix. Figure 1 As shown: Remove damaged paving stones from the road surface, and remove oil, dust, and loose materials from the road base to expose the subgrade, ensuring it is firm and dry. Then lay fiberglass mesh, the size of which depends on the area to be repaired. If the repair area is larger than a single paving stone, multiple sheets of fiberglass mesh can be laid flat, ensuring continuity at the joints. If the repair area is one or two paving stones, a single sheet of fiberglass mesh can be laid flat, but it is essential to ensure that the fiberglass mesh extends to the edge of the paving stone, and the difference in dimensions between the edges should not exceed [value missing]. Apply a 0.5cm layer of bio-based polyurethane adhesive evenly onto the fiberglass mesh. At least one layer of fiberglass mesh is needed, typically 1-3 layers. Apply bio-based polyurethane adhesive evenly between each layer of mesh. The total thickness of the applied bio-based polyurethane adhesive should be 2-5mm. Finally, place the floor tile flat and press it down with its own weight. Avoid loads and water immersion for 24 hours after replacement. Allow it to cure at room temperature for 48 hours. Once the bio-based polyurethane adhesive has cured, the floor tile is fixed, and the road surface can be driven on normally. After curing at room temperature for 48 hours, the minimum bonding strength reached was 10MPa, according to testing.

[0046] The floor tiles are fixed by combining fiberglass mesh with bio-based polyurethane adhesive. The bio-based polyurethane adhesive boasts high bonding strength, good flexibility, adaptability to temperature variations, and excellent crack resistance. The fiberglass mesh acts as a buffer and extender between the floor tiles and the adhesive, evenly distributing stress on the tiles, reducing stress concentration, and helping to maintain the integrity of the tiles and extend their service life. The bio-based polyurethane adhesive uses bio-based raw materials, exhibits stable performance in the dark environment under the tiles, and decomposes under ultraviolet light, demonstrating good environmental performance.

Claims

1. A bio-based polyurethane adhesive for paving bricks, characterized in that: It is prepared by mixing and thoroughly stirring the following raw materials in parts by weight: 90-110 parts of bio-based polyols 15-25 parts castor oil 50-60 parts of polymeric MDI The bismuth-zinc catalyst is one part to one ten-thousandth of the total mass of bio-based polyol, castor oil, and polymeric MDI; the defoamer is 1 to 5 parts. 1-5 parts of desiccant 1-4 parts of coupling agent, 2-4 parts of fumed silica 180-200 parts of dried silica powder.

2. The bio-based polyurethane adhesive for paving bricks according to claim 1, characterized in that: The bio-based polyol has a hydroxyl value of 140±10mgKOH / g, an acid value of ≤1.0mgKOH / g, a viscosity of 1000±200cps@25℃, and a moisture content of ≤0.15% (by mass).

3. The bio-based polyurethane adhesive for paving bricks according to claim 1, characterized in that: The defoamer is BYK-020, the desiccant is 3A or 4A molecular sieve, and the coupling agent is KH560 or KH570.

4. The bio-based polyurethane adhesive for paving bricks according to claim 1, characterized in that: The dried silica powder has a mesh size of 800–1250.

5. The bio-based polyurethane adhesive for paving bricks according to claim 1, characterized in that: The ratio of bismuth to zinc in the bismuth-zinc catalyst is 1:

2.

6. The bio-based polyurethane adhesive for paving bricks according to any one of claims 1 to 5, characterized in that: The product is prepared by mass fractions from the following raw materials: 100 parts bio-based polyol, 21 parts castor oil, 53 parts polymeric MDI, 0.004 parts bismuth zinc catalyst, 4 parts defoamer, 4 parts desiccant, 4 parts coupling agent, 2 parts fumed silica, and 200 parts dried silica powder.

7. A method of using the bio-based polyurethane adhesive for paving bricks according to any one of claims 1 to 6, characterized in that: Remove the damaged floor tiles, clean the exposed road surface base, then lay fiberglass mesh, and then evenly apply the bio-based polyurethane adhesive on the fiberglass mesh. Finally, lay the floor tiles flat and press them down with their own weight. After the bio-based polyurethane adhesive has cured, the floor tiles will be fixed. When laying the fiberglass mesh, it should extend to the edge of the floor tiles.

8. The method of use according to claim 7, characterized in that: At least one layer of fiberglass mesh is laid, and the bio-based polyurethane adhesive is also evenly applied between each layer of fiberglass mesh.

9. The method of use according to claim 7 or 8, characterized in that: The total thickness of the applied bio-based polyurethane adhesive is 2–5 mm.

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