Single-component polyurethane glue for producing hypoll insoles and application of single-component polyurethane glue

Abstract

The invention relates to the technical field of macromolecules, in particular to single-component polyurethane glue for producing a hypoll insole and application of the single-component polyurethane glue. The preparation raw materials of the single-component polyurethane glue for producing the hypoll insole comprise low-Mn polyether polyol, high-Mn polyether polyol, diisocyanate and a foaming agent. According to the single-component polyurethane adhesive disclosed by the invention, a synergistic system of the polyether polyol (different molecular weight combinations), the polyisocyanate prepolymer, the low-boiling-point foaming agent and the foam stabilizer is adopted, and a microporous structure matched with the hypoboli is formed in a bonding process.

Description

Technical Field

[0001] This invention relates to the field of polymer technology, and in particular to a single-component polyurethane adhesive for producing Hypopoly shoe insoles and its application. Background Technology

[0002] Hypoly (EVA / PU elastomer blend foam material) insoles are widely used in the manufacture of athletic shoes, casual shoes, and performance shoes due to their lightweight, softness, and excellent resilience. The bonding of the insole layer to the upper, lining, and other components typically employs adhesive processes. Current insole bonding methods mostly use solvent-based polyurethane adhesives or two-component polyurethane adhesives.

[0003] Solvent-based polyurethane adhesives have good initial tack, but contain a large amount of organic solvents, resulting in high volatile organic compound (VOC) release, flammability, and a heavy environmental burden.

[0004] Two-component polyurethane adhesives have high strength after curing, but require on-site mixing of components, which is complicated, limits the service life, and can easily lead to unstable performance due to improper proportions.

[0005] For soft and porous Hypoli insole materials, existing adhesives often result in an overly hard or brittle bonding layer after curing, leading to reduced overall comfort of the insole and even problems such as glue separation and poor water resistance.

[0006] Therefore, existing adhesives struggle to achieve a balance between environmental friendliness, ease of use, flexibility, and durability. Summary of the Invention

[0007] The purpose of this invention is to provide a single-component polyurethane adhesive for producing Hypoli insoles and its application, in order to solve the technical problem in the prior art where the cured adhesive layer does not have good softness and resilience, thus affecting the comfort of Hypoli insoles.

[0008] To solve the above-mentioned technical problems, the present invention provides a single-component polyurethane adhesive for producing Hypoli shoe insoles, the raw materials of which include: low-Mn polyether polyol, high-Mn polyether polyol, diisocyanate, and foaming agent.

[0009] In one embodiment of the present invention, the Mn range of the low-Mn polyether polyol is 200-2000 Da; the viscosity is less than 500 mPa·s (25°C, 1 wt%).

[0010] In one embodiment of the present invention, the Mn range of the high Mn polyether polyol is 2000-6000 Da.

[0011] In one embodiment of the present invention, the diisocyanate comprises MDI and IPDI, and the mass ratio of MDI to IPDI is (7-11):1.

[0012] In one embodiment of the present invention, the foaming agent comprises a low-boiling-point foaming agent and hollow microspheres; and the mass ratio of the low-boiling-point foaming agent to the hollow microspheres is 4:(1-5).

[0013] In one embodiment of the present invention, the low-boiling-point foaming agent is selected from one or more of low-boiling-point ester or ether solvents, surfactants, and alkanes.

[0014] In one embodiment of the present invention, the raw materials for preparing the single-component polyurethane adhesive further include a foam stabilizer.

[0015] In one embodiment of the present invention, the foam stabilizer comprises one or more of hydrophobic SiO2, hydrophobic CNF, polysiloxane-polyether block copolymer, surfactant-based foam stabilizer, and polyvinyl alcohol.

[0016] As one embodiment of the present invention, the raw materials for preparing the single-component polyurethane adhesive also include antioxidants and microcapsule crosslinking agents.

[0017] This invention provides a method for producing Hypopoly shoe insoles, which are prepared from the aforementioned single-component polyurethane adhesive and sponge.

[0018] By adopting the above technical solution, the present invention has the following beneficial effects:

[0019] The single-component polyurethane adhesive of the present invention employs a synergistic system of polyether polyols (different molecular weight combinations), polyisocyanate prepolymers, low-boiling-point foaming agents, and foam stabilizers. By forming a microporous structure that matches that of hypothalamic acid during the bonding process, the following effects are achieved:

[0020] Softness and comfort: The cured adhesive layer forms a microporous structure, reducing hardness and matching the elasticity of the Hypopoly body without affecting rebound;

[0021] Water resistance and aging resistance: The introduction of isocyanates (such as IPDI / HDI) into the cross-linked structure enhances the resistance to hydrolysis and yellowing, allowing the insole to withstand long-term use and washing;

[0022] Easy to use: single-component packaging, no on-site mixing required during construction, facilitating automated dispensing and coating processes;

[0023] Environmental protection and safety: By reducing the use of high-VOC solvents, controllable foaming can be achieved through a system of low-boiling-point foaming agents and foam stabilizers, thus meeting environmental and safety regulatory requirements. Detailed Implementation

[0024] The present invention will be further explained below with reference to specific embodiments.

[0025] A single-component polyurethane adhesive for producing Hypoli shoe insoles, the raw materials for which are prepared include: low-Mn polyether polyol, high-Mn polyether polyol, diisocyanate, foaming agent, foam stabilizer, antioxidant, and microencapsulation crosslinking agent.

[0026] Low Mn polyether polyols

[0027] The low-Mn polyether polyols refer to polyether polyols with a number-average molecular weight (Mn) in the range of approximately 200–1000 Da. Low-Mn polyether polyols can reduce system viscosity, resulting in smoother spraying and a thinner, more uniform coating. Low-Mn residual soft segments or short-chain polymers tend to accumulate on the surface of bubbles, coating micropores and forming a "soft coating layer," reducing stress concentration, protecting the pore walls of the sponge, and thus improving wearing comfort.

[0028] The low viscosity of low Mn makes foam nucleation easier to occur, and its end groups / segments can be arranged on the foam surface. Combined with foam stabilizers, this helps to form a more uniform microporous structure.

[0029] When coexisting with high-Mn polyether polyols, the difference in molecular weight leads to thermodynamic incompatibility. During the curing process, nanophase separation can be induced, forming a hierarchical distribution of soft and hard phases, which helps to balance a soft interface with intrinsic strength.

[0030] In one embodiment of the present invention, the low-Mn polyether polyol is a glycerol-starting polyether triol (Mn is 300-500, hydroxyl value is 330-560 mgKOH / g) and PPG-400 (diol, Mn≈400, hydroxyl value is 280 mgKOH / g); and the mass ratio is 2:8.

[0031] High Mn polyether polyols

[0032] The high-Mn polyether polyols refer to polyether polyols with a number-average molecular weight (Mn) in the range of approximately 2000 to 6000 Da.

[0033] High manganese (Mn) provides long, flexible segments, forming a continuous elastic network that determines long-term resilience and fatigue life. When high Mn dissolves in the matrix, it forms a continuous phase that bears cyclic stress and reduces fatigue delamination. When coexisting with low Mn, the difference in chain length leads to thermodynamic incompatibility, inducing microphase separation. This results in the formation of soft-segment enrichment regions and hard-segment domains at the nano / micro scale, resulting in a two-phase structure of "soft surface / strong matrix." At the same degree of crosslinking, high Mn allows the adhesive layer to remain sufficiently flexible without sacrificing strength.

[0034] In one embodiment of the present invention, the high Mn polyether polyol is PTMG-3000 and PPG-2000 in a ratio of 9:1.

[0035] diisocyanate

[0036] Diisocyanate (-NCO group) reacts with polyether polyol (-OH group) to form the main chain of polyurethane. This determines the hard segment ratio, hydrogen bonding, and mechanical properties of the adhesive.

[0037] By selecting different types of diisocyanates, the crystallinity of the hard segments and the degree of phase separation can be controlled, thereby affecting the balance between the softness and strength of the adhesive. In single-component systems, it is usually necessary to prepare an NCO-terminated prepolymer first. The choice of diisocyanate affects the storage stability and curing rate of the prepolymer.

[0038] In one embodiment of the present invention, the diisocyanate is a compound of 4,4′-diphenylmethane diisocyanate (MDI) and IPDI, and the mass ratio is 8.1:1.5.

[0039] This invention introduces IPDI, which significantly improves flexibility, resistance to yellowing, and hydrolysis resistance. MDI provides a hard segment skeleton and strength; aliphatic diisocyanate introduces flexible segments and symmetry disruption, promoting phase separation and preventing the adhesive layer from becoming too hard. During moisture curing, the distribution of hard / soft segments forms a microphase structure, giving the adhesive layer both flexibility and durability.

[0040] foaming agent

[0041] In one embodiment of the present invention, the foaming agent comprises a low-boiling-point foaming agent and hollow microspheres; and the mass ratio of the low-boiling-point foaming agent to the hollow microspheres is 4:(1-5); and the mass ratio is 4:1.

[0042] In one embodiment of the present invention, the low-boiling-point foaming agent is selected from one or more of low-boiling-point ester or ether solvents, surfactants, and alkanes.

[0043] Foaming agents improve softness and resilience by forming a microporous structure, reducing the density of the adhesive layer and preventing it from hardening, thus maintaining the elasticity and comfort of the sponge. When the adhesive is coated or sprayed, the presence of tiny air bubbles allows it to better penetrate the sponge's pores, increasing mechanical bonding strength. Simultaneously, foaming increases the volume of the adhesive layer, resulting in less adhesive used while maintaining bonding strength. Furthermore, the microbubble structure provides cushioning, improving the insole's comfort during walking.

[0044] This invention introduces a low-boiling-point foaming agent and hollow microspheres to form controllable micropores in the adhesive layer, balancing strength and flexibility, and solving the long-standing contradiction between "adhesion strength and comfort" in the industry.

[0045] In one embodiment of the present invention, the low-boiling-point foaming agent is selected from one or more of dichloromethane, chloroform, methane, pentane, n-butane, isobutane, dimethyl ether, and methyl methylformate.

[0046] In a preferred embodiment of the present invention, the low-boiling-point foaming agent is a methyl methacrylate.

[0047] In one embodiment of the present invention, the hollow microspheres are selected from one or more of thermally expandable hollow polymer microspheres, hollow glass microspheres, and hollow ceramic microspheres; in a preferred embodiment of the present invention, the hollow microspheres are thermally expandable hollow polymer microspheres; specifically... 930DU120.

[0048] Foam stabilizer

[0049] Foam stabilizers are a class of additives that can inhibit bubble coalescence and collapse, extend foam life, and stabilize the foam film. For microbubbles formed in non-aqueous phases (organic solvents or solvent-free PU prepolymers), foam stabilizers stabilize the bubbles by reducing interfacial tension, increasing interfacial elasticity, and increasing liquid film viscosity, thereby obtaining a uniform, fine microporous structure that is not easily collapsed during curing.

[0050] Foaming agents can create pores, but without foam stabilizers, this often leads to large bubbles, collapse, or uneven pore size distribution; foam stabilizers are essential for the formation of usable micropores. Low-boiling-point foaming agents are volatile, and without foam stabilizers, pores may merge or become large; suitable foam stabilizers can maintain fine foam films during the simultaneous foaming-curing process.

[0051] This invention uses hydrophobic silica or hydrophobic CNF as a foam stabilizer. Solid particles are irreversibly adsorbed at the gas-liquid interface, physically hindering coalescence, and are more stable under humid and hot conditions.

[0052] In one embodiment of the present invention, the foam stabilizer is hydrophobic SiO2 (Aerosil R972).

[0053] antioxidants

[0054] Antioxidants are a class of chemical substances that inhibit or terminate the oxidative degradation of polymers (by capturing free radicals, decomposing peroxides, or terminating the breaking of oxidative bonds).

[0055] In PU adhesives, it can inhibit chain breakage and cross-linking caused by processing and long-term heat / oxygen / light, maintaining adhesive and mechanical properties; in microporous / foamed systems, it can prevent oxidation of the pore wall material, which can lead to reduced strength or yellowing of the surface.

[0056] In single-component end-NCO polyurethane systems, the adhesive layer is frequently exposed to high temperatures, humidity, mechanical friction, and ultraviolet radiation, leading to long-term oxidation, yellowing, and embrittlement, resulting in a reduced lifespan and decreased comfort of the insole. To achieve both softness and long-term washability / aging resistance, stabilizers and long-term antioxidant systems must be incorporated into the formulation.

[0057] In this invention, the antioxidant is antioxidant 1010.

[0058] Microencapsulation cross-linking agent

[0059] In this invention, the microcapsule crosslinking agents are HDI and KH-550, and the mass ratio is 7:3.

[0060] In one embodiment of the present invention, the raw materials for preparing the adhesive include:

[0061] 10-15 parts of glycerol starting polyether triol

[0062] PPG-40015 ~ 20 copies

[0063] PTMG-300025 ~ 30 copies

[0064] PPG-200010 ~ 15 copies

[0065] 20-25 parts MDI

[0066] IPDI 1-3 copies

[0067] 5-7 parts of methyl methacrylate

[0068] Thermally expandable hollow polymer microspheres ( 930DU120) 10-12 portions

[0069] 1-2 parts of hydrophobic SiO2 (Aerosil R972)

[0070] Antioxidant 10100.20-0.5 parts

[0071] HDI 0.5 to 2 parts

[0072] KH-5500.5 ~ 1 copy.

[0073] As one embodiment of the present invention, the preparation steps of the adhesive are as follows:

[0074] Polyether polyol, antioxidant, hydrophobic SiO2, and KH-550 are heated to about 110°C and then vacuum dehydrated for 2 hours.

[0075] Cool to 80℃, slowly add isocyanate (MDI, IPDI, HDI) and keep the temperature at 80-85℃, react for 4 hours; stir and add microspheres and disperse evenly; cool to 50℃ and ship.

[0076] This invention also provides a process for producing hypopoly:

[0077] The recycled sponge scraps are crushed into powder, and the powder is pumped into a mixing tank. While stirring, glue is sprayed in. The mass ratio of powder to glue is 100:20. Stir together for 5-10 minutes, then press into a mold box and introduce steam for curing reaction. After about 0.5-1 hours, it can be molded and opened. Finally, after standing at room temperature for 48 hours, it can be sliced.

[0078] The following is a detailed explanation of the specific implementation.

[0079] Specific formulations of each embodiment

[0080]

[0081]

[0082] The preparation steps of the adhesive are as follows:

[0083] Polyether polyol, antioxidant, hydrophobic SiO2, and KH-550 are heated to about 110°C and then vacuum dehydrated for 2 hours.

[0084] Cool to 80℃, slowly add isocyanate (MDI, IPDI, HDI) and keep the temperature at 80-85℃, react for 4 hours; stir and add microspheres and disperse evenly; cool to 50℃ and ship.

[0085] A production process for Hypoli is also provided:

[0086] The recycled sponge scraps are crushed into powder, which is then pumped into a mixing tank. While stirring, glue is sprayed in (the glue is mixed with 30% dichloromethane before use, and then sprayed onto the Hypopoly material and stirred). The mass ratio of powder to glue is 100:20. The mixture is stirred together for 5-10 minutes, then pressed into a mold box and steam is introduced for curing. After about 0.5-1 hour, the mold can be opened and the material can be left to stand at room temperature for 48 hours before slicing.

[0087] Performance Test Table

[0088] Performance indicators Test methods Rebound rate (%) GB / T6343-2013, Release after compression to 50% thickness Porosity (%) SEM image analysis Average diameter of micropores (μm) SEM Water resistance (% retention of adhesive strength) Percentage of adhesive strength retained after immersion in water at 40℃ for 24 hours. Aging resistance (% resilience retention) Rebound retention rate after aging conditions of 70℃ / 75%RH for 168 hours. Compressive strength (kPa) ISO3386-1 Elongation at break (%) GB / T6344-2013

[0089] Test Results

[0090]

[0091]

[0092] The combination of low-Mn and high-Mn polyether polyols with MDI / IPDI hard segments forms a microphase distribution, achieving both softness and resilience while remaining water- and aging-resistant. The microporous structure is matched to the foam: thermally expanding microspheres and foam stabilizers create controllable pore sizes, allowing for adjustable porosity and pore size, thus enhancing comfort and elasticity. HDI and KH-550 reinforce the interface between the microspheres and the adhesive layer, improving water resistance and aging resistance. The synergistic control of microsphere proportion, expansion temperature, and the ratio of soft to hard segments creates a gradient foam structure, matching different sponge pore sizes to achieve a balance between comfort and functionality.

[0093] test:

[0094] Water-resistant adhesion retention (washable)

[0095] For simulated household washing: machine wash at 40℃ on the gentle mode, 30 minutes per cycle, using neutral detergent; or follow the ISO standard washing cycle.

[0096] Test point: Samples were taken after 10 washes to test peel strength.

[0097] Measurement: Peel strength (N / cm).

[0098] Anti-slip / coefficient of friction (between insole and foot / shoe upper)

[0099] Objective: To detect the coefficient of friction between the insole surface and the foot (or lining) and assess the risk of slippage during wear.

[0100] Instrument: Friction coefficient tester (the fixture can simulate shoe upper fabric or leather).

[0101] Conditions: Static and dynamic friction coefficients μs and μk were measured under normal temperature dry / wet conditions (artificial sweat).

[0102] Adhesion and edge separation

[0103] Objective: To test whether the edges and corners are delaminated or peeling under simulated actual wearing and bending conditions.

[0104] Method: Insert the insole into the shoe pattern; simulate walking on a gait simulator (equivalent load of 70kg body weight, cadence 1-1.5Hz) for 10,000 steps. Remove and inspect for edge delamination, peeling length (mm), and delamination area (%).

[0105] Water-resistant adhesion retention (adhesion retention rate after 10 washes)

[0106]

[0107]

[0108] Examples 1 and 3 showed the highest retention rate after washing (95-96%), indicating that the synergistic system of microspheres, SiO2, and HDI can maintain wet adhesion very well. Comparative Example 4 (without HDI) performed the worst (85%), confirming the key role of microcapsule crosslinking / HDI in water resistance.

[0109] Anti-slip / coefficient of friction (dry / wet, static / dynamic friction)

[0110] Group μs (dry) mean ± SD μk (dry) mean ± SD μs (wet / sweat) mean ± SD μk (wet / sweat) mean ± SD Example 1 0.52±0.04 0.46±0.03 0.40±0.03 0.34±0.03 Example 2 0.50±0.03 0.44±0.02 0.38±0.04 0.33±0.03 Example 3 0.54±0.05 0.48±0.02 0.42±0.03 0.36±0.04 Example 4 0.51±0.03 0.45±0.03 0.39±0.04 0.34±0.03 Example 5 0.53±0.034 0.47±0.04 0.41±0.04 0.35±0.03 Comparative Example 1 0.49±0.06 0.43±0.05 0.37±0.04 0.32±0.03 Comparative Example 2 0.46±0.06 0.41±0.04 0.34±0.04 0.30±0.05 Comparative Example 3 0.48±0.05 0.42±0.03 0.36±0.03 0.31±0.05 Comparative Example 4 0.50±0.05 0.44±0.05 0.38±0.04 0.33±0.04 Comparative Example 5 0.55±0.04 0.49±0.04 0.43±0.04 0.37±0.03

[0111] The static friction coefficient of Examples 1 / 3 / 5 is in the range of 0.52 to 0.54 (dry state), and remains ≥0.40 in the wet state, indicating that the surface has good anti-slip properties between the shoe upper / foot (meeting the requirements of the inner side of general casual / sports shoes).

[0112] Comparative Example 2 (reduced microspheres) showed a significant decrease in the coefficient of friction, indicating that microspheres and pore structure have an impact on surface contact behavior; Comparative Example 5 (extreme ratio) showed a slightly higher wet friction due to larger pores (possibly due to water absorption / capillary effect caused by changes in surface microstructure).

[0113] Adhesion and edge separation

[0114]

[0115] Examples 1-3 and 5 showed the best adhesion, with short delamination lengths and no obvious peeling, indicating that the combination of soft / hard segments, microspheres, foam stabilizers, and HDI is effective in combating peeling during long-term bending / walking simulations.

[0116] Comparative Examples 2, 3, and 4 showed more delamination or peeling during the walking simulation (especially Comparative Example 4), verifying that removing HDI or foam stabilizer significantly reduces corner durability.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A one-component polyurethane adhesive for the production of Hypol shoe pads, characterized in that, The raw materials for preparing the same include: a low-Mn polyether polyol, a high-Mn polyether polyol, a diisocyanate, a foaming agent.

2. A one-part polyurethane adhesive for the production of Hypol shoe pads according to claim 1, characterized in that, The low-Mn polyether polyol has an Mn ranging from 200 to 2000 Da, and a viscosity lower than 500 mPa·s (25℃, 1wt%).

3. A one-part polyurethane adhesive for the production of Hypol shoe pads according to claim 1 or 2, characterized in that, The high-Mn polyether polyol has an Mn ranging from 2000 to 6000 Da.

4. A one-part polyurethane adhesive for the manufacture of Hypol shoe pads according to claim 1, characterized in that, The diisocyanate includes MDI and IPDI, and the mass ratio of MDI to IPDI is (7-11):

1.

5. A one-part polyurethane adhesive for the manufacture of Hypol shoe pads according to claim 1, characterized in that, The foaming agent includes a low-boiling foaming agent and hollow microspheres, and the mass ratio of the low-boiling foaming agent to the hollow microspheres is 4:(1-5).

6. A one-part polyurethane adhesive for the manufacture of Hypol shoe pads according to claim 5, characterized in that, The low-boiling foaming agent is selected from one or more of low-boiling ester or ether solvents, surfactants, and alkanes.

7. A one-part polyurethane adhesive for the manufacture of Hypol shoe pads according to claim 1, characterized in that, The raw materials for preparing the one-component polyurethane adhesive further include a foam stabilizer.

8. A one-part polyurethane adhesive for the manufacture of Hypol shoe pads according to claim 7, characterized in that, The foam stabilizer includes one or more of hydrophobized SiO2, hydrophobized CNF, polysiloxane-polyether block copolymer, surfactant-type foam stabilizer, and polyvinyl alcohol.

9. A one-part polyurethane adhesive for the manufacture of Hypol shoe pads according to claim 1, characterized in that, The raw materials for preparing the one-component polyurethane adhesive further include an antioxidant and a microcapsule crosslinking agent.

10. A method of producing a Hypol shoe pad, characterized by, The one-component polyurethane adhesive and the sponge are prepared by using the raw materials according to any one of claims 1-9. The raw materials for preparing the same include: a low-Mn polyether polyol, a high-Mn polyether polyol, a diisocyanate, a foaming agent. The low-Mn polyether polyol has an Mn ranging from 200 to 2000 Da, and a viscosity lower than 500 mPa·s (25℃, 1wt%). The high-Mn polyether polyol has an Mn ranging from 2000 to 6000 Da. The diisocyanate includes MDI and IPDI, and the mass ratio of MDI to IPDI is (7-11):

1. The foaming agent includes a low-boiling foaming agent and hollow microspheres, and the mass ratio of the low-boiling foaming agent to the hollow microspheres is 4:(1-5). The low-boiling foaming agent is selected from one or more of low-boiling ester or ether solvents, surfactants, and alkanes. The raw materials for preparing the one-component polyurethane adhesive further include a foam stabilizer. The foam stabilizer includes one or more of hydrophobized SiO2, hydrophobized CNF, polysiloxane-polyether block copolymer, surfactant-type foam stabilizer, and polyvinyl alcohol. The raw materials for preparing the one-component polyurethane adhesive further include an antioxidant and a microcapsule crosslinking agent. The one-component polyurethane adhesive and the sponge are prepared by using the raw materials according to any one of claims 1-9.

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