Modified MDI for all-water low-density high-brightness skin polyurethane sole, preparation method and application

Abstract

The invention discloses modified MDI for improving the self-skinning integrity of all-water low-density polyurethane sole foam as well as a preparation method and application of the modified MDI. The modified MDI is prepared from the following raw materials: (1) diphenylmethane diisocyanate; (2) polyfunctional polyether polyol; the catalyst is a large-steric-hindrance organic metal catalyst such as bismuth neodecanoate, bismuth pivalate, bismuth isooctanoate and dioctyltin di-neodecanoate, when the modified MDI is used, the modified MDI is prepared into a polyurethane shoe sole stock solution B material, and the modified MDI and the polyurethane shoe sole stock solution A material are mixed and subjected to injection molding during foaming. The modified MDI is applied to the low-density all-water foaming self-bonding leather shoe sole, the density range is 0.15-0.3 g / cm < 3 >, due to the addition of the modified MDI, the skin is compact, the paint spraying and coloring glossiness is high, and the completeness of the skin is greatly improved under the low density.

Description

Technical Field

[0001] This invention belongs to the field of modified MDI technology for polyurethane, specifically relating to modified MDI for low-density polyurethane shoe soles with dense epidermis, preparation methods, and applications. Background Technology

[0002] Polyurethane (PU) soles are widely used in athletic shoes and casual shoes due to their lightweight, wear resistance, and excellent elasticity. Currently, HCFC-141B foaming agent is widely used in PU soles. However, with increasingly stringent environmental regulations, the production and use of 141B will be completely banned in China by 2026, which will have a significant impact on the PU sole industry. Water-based foaming completely replaces physical foaming agents with water. The process is simple and can be produced with existing equipment, but it results in low density (<0.3g / cm³). 3 PU shoe sole systems require the addition of more water, and the reaction of NCO with water to form foam still has many problems in application: such as fast reaction rate, decreased dimensional stability, and material properties that are too hard and brittle. In addition, the problems of many foam pores, poor gloss, and uneven coloring in the surface of all-water low-density shoe soles are particularly prominent.

[0003] Physical foaming agents liquefy at the surface to form a dense skin. However, the CO2 liquefaction conditions are harsh (31.1℃, 73.9 bar), and the skin gelation process is accompanied by gas impact, resulting in only a thin skin that is prone to problems such as dark bubbles, pinholes, and skin-core separation, leading to peeling and uneven coloring. Existing technologies, such as patents CN106188469A and CN102329409A, achieve lightweight, abrasion-resistant, and dimensionally stable foams, but their density remains at 0.3 g / cm³. 3 The above patent CN111548471B improves the rebound performance and toughness of low-density shoe soles, but does not address surface improvement. Patent CN117430782B introduces modified aromatic silanes, optimizing the amount of modified aromatic silanes and adjusting the mirror-like leveling to achieve a product with a surface finish of 395-455 kg / m². 3 It combines a non-porous skin with excellent mechanical properties at low densities; patent CN115028800A employs a triethanolamine-initiated trifunctional polyether polyol synergistic catalytic system, achieving a dynamic balance between bubble escape and skin solidification, effectively removing CO2 without pinhole residue, allowing the product to achieve a density of 310-350 kg / m³. 3 A dense, smooth skin is formed at a certain density. However, the above methods do not address densities less than 0.3 g / cm³. 3 Therefore, to improve the low-density sole surface, a new solution needs to be developed to address the surface defects that occur in existing polyurethane soles when fully water-foamed at low density. Summary of the Invention

[0004] The purpose of this invention is to provide a modified MDI for low-density all-water foamed polyurethane shoe soles with a high-gloss surface. Low-activity polyfunctional modified MDI is introduced into the polyurethane raw material B, which improves the way CO2 escapes during the foaming process and the balance between gelation and foaming, thereby filling the gap in the existing technology for improving the surface of low-density all-water foamed polyurethane.

[0005] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows:

[0006] On one hand, the present invention provides a modified MDI prepared from raw materials comprising the following components:

[0007] (1) Diphenylmethane diisocyanate;

[0008] (2) Multifunctional polyether polyols.

[0009] (3) Catalyst, wherein the catalyst is a sterically hindered organometallic catalyst, such as bismuth neodecanoate, bismuth neopentanoate, bismuth isooctanoate, dioctyltin dinedecanoate, etc.

[0010] Preferably, the diphenylmethane diisocyanate in step (1) requires a 2,4-isomer content of ≥80%, and more preferably a 2,4'-MDI isomer content of ≥90%. MDI-10;

[0011] Preferably, the polyol in step (2) has a number average molecular weight of 500-3000, and is preferably a polyether polyol obtained by copolymerizing a trifunctional initiator with low hydroxyl activity with propylene oxide, such as CHE-305. S3007 or At least one of F3056D.

[0012] On the other hand, the present invention provides a method for preparing modified MDI, comprising the following steps:

[0013] a) Weigh out diphenylmethane diisocyanate and multifunctional polyether polyol according to the isocyanate group (NCO) to hydroxyl group (OH) molar ratio of 2-2.1:1;

[0014] b) The multifunctional polyether polyol is premixed with the catalyst, and the mixture is heated and stirred under nitrogen protection to obtain the premix.

[0015] c) Add the premix from (b) dropwise to diphenylmethane diisocyanate for reaction; after terminating the reaction, a modified MDI product with a free MDI content ≤0.1% is obtained.

[0016] In step b), the temperature is raised to 50-60℃, the stirring speed is 200-400 rpm, and the stirring time is 10-20 minutes.

[0017] In step c), the reaction temperature is 50-60℃ and the reaction time is 2-3 hours.

[0018] In another aspect, the present invention provides a low-density shoe midsole material comprising the following components:

[0019] The polyurethane sole raw material A, by weight, includes: polyethylene adipate-1,4-butanediol diol (100 parts), ethylene glycol (2 parts), deionized water (1.0-2.0 parts), Dabco-LV33 (1.0-2.0 parts), HCFC-141b (0-3 parts), and silicone surfactant (0.2-0.4 parts);

[0020] The polyurethane sole raw material B comprises, by weight, prepolymer A (prepared from MDI-100, liquefied MDI and polyethylene adipate-1,4-butanediol diol in a mass ratio of 50:10-15:30-40) and modified MDI, wherein the prepolymer A and modified MDI are prepared in a mass ratio of 100:0-5.

[0021] Finally, the present invention provides a method for preparing a low-density shoe sole, comprising the following steps:

[0022] (1) Preparation of polyurethane shoe sole raw material A: Mix the components in proportion and stir at 50-60℃ for 3±0.5 hours to obtain a homogeneous composition;

[0023] (2) Preparation of polyurethane shoe sole raw material B: First, prepolymer A is prepared, and then it is mixed with modified MDI in proportion to obtain material B;

[0024] (3) Molding process: Inject materials A and B separately into a low-pressure casting machine, control the material temperature at 40-45℃, mix them at a mass ratio of A:B = 100:70-110, and then inject them into a mold at 50-60℃. Demold after 4-6 minutes to obtain a density of 0.15-0.3 g / cm³. 3 The soles of the shoes.

[0025] The beneficial effects of this invention are as follows: A novel low-activity, high-functionality modified MDI with NCO end-capped at position 4 and free NCO at position 2 was synthesized by 2,4-MDI, low-activity polyol, sterically hindered metal catalyst and low-temperature reaction. Utilizing its multifunctionality and controllable NCO activity, the gelation rate of the skin during the foaming process of all-water foam is moderately slowed down, allowing the difficult-to-liquefy CO2 to rapidly overflow in the early stage, and the foam skin to quickly form a dense structure in the later stage of foaming, significantly reducing the number of pores in the sole skin and improving gloss, color uniformity and overall mechanical strength. Detailed Implementation

[0026] To facilitate understanding of the present invention, the following description, in conjunction with embodiments, will further illustrate the invention. It should be understood that the following embodiments are merely for a better understanding of the invention and do not imply that the invention is limited to these embodiments.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The term "and / or" may be used herein to include any and all combinations of one or more of the associated listed items.

[0028] Main raw material sources

[0029] Table 1

[0030]

[0031] Main testing methods

[0032] Potentiometric titrator: METTLER TOLEOO, model: 905Titrando (for testing NCO content);

[0033] Viscometer: BROOKFIELD, Model: DV2TLVTJO (for testing system viscosity);

[0034] Foam material density: tested according to GB / T 6343-2009;

[0035] Tensile strength: Tested according to GB / T 6344-2008;

[0036] Tear strength: Tested according to GB / T 10808-2006;

[0037] Gloss: Tested according to ASTM D523 standard (60° incident angle);

[0038] Gel permeation chromatography (GPC): Agilent 1260 Infinity III, one Water HR1 column + two HR0.5 columns in series, column temperature 35℃, THF as mobile phase, flow rate 1 ml / min, RID 35℃;

[0039] Fourier Transform Infrared Spectroscopy (FTIR): Thermo Scientific TM Nicolet TM iS20 FTIR;

[0040] Carbon nuclear magnetic resonance spectroscopy (NMR) 13 C NMR): AVANCE NEO 400MHz (Bruker), CDCl3 as solvent.

[0041] Experimental Example

[0042] Weigh out MDI and hydroxyl groups according to the isocyanate group (NCO) to hydroxyl group (OH) molar ratio of 2:1. S3007. (The sentence appears to be incomplete and lacks context.) S3007 was premixed with 300ppm of bismuth neodecanoate catalyst, heated to 55°C under nitrogen protection, and stirred at 300rpm for 20 minutes for later use.

[0043] MDI was heated and stirred to 55°C under nitrogen protection, and then... S3007 was slowly added dropwise to MDI at a rate of 100 ml / min, the reaction temperature was controlled at 55℃, and the reaction was carried out at 300 rpm for 2-3 hours to obtain the modified MDI product.

[0044] Table 2. Free MDI content in MDI synthesized with different 2,4-isomers.

[0045]

[0046] Table 2 shows that when modified MDI is synthesized using MDI raw materials with different 2,4-body contents, the content of free 4,4-body is much lower than that of free 2,4-body when the 2,4-body content in the raw material is below 70%, proving that most of the two NCO groups on the 4,4-body in the raw material are fully involved in the reaction. When the 2,4-body content in the raw material is above 80%, the total amount of free MDI decreases to below 0.1%, proving that almost all of the NCO groups on the MDI in the raw material are reacted off, generating a single-terminated product. Therefore, MDI-10 is the preferred raw material.

[0047] Preparation Example 1

[0048] Weigh out 5172.4g of MDI-10 and 4827.6g of hydroxyl group (OH) according to the isocyanate group (NCO) to hydroxyl group (OH) molar ratio of 2:1. S3007. (The sentence appears to be incomplete and lacks context.) S3007 was premixed with 300ppm of bismuth neodecanoate catalyst, heated to 55°C under nitrogen protection, and stirred at 300rpm for 20 minutes for later use.

[0049] MDI-10 was heated and stirred under nitrogen protection to 55°C, and then... S3007 was slowly added dropwise to MDI-10 at a rate of 100 ml / min, the reaction temperature was controlled at 55℃, and the reaction was carried out at 300 rpm for 2-3 hours to obtain the modified MDI-1 product.

[0050] Characterization of modified MDI-1:

[0051] (1) GPC: Peak 1 (target product) retention time 17.8 min, corresponding to the peak of 1 trifunctional polyether plus 3 MDI molecules; Peak 2 (byproduct) retention time 16.3 min, corresponding to the product with higher branching degree formed by 4,4'-MDI, such as the macromolecular product formed by the NCO of one 4,4'-MDI molecule being connected to two polyol chains respectively; Peak 3 (residual MDI) retention time 24.2 min;

[0052] (2) FTIR: 2270cm -1 The absorption peak at N=C=O is significantly weakened at 3320 cm⁻¹. -1 (NH stretching), 1530cm -1 (NH bending), 1700cm -1 (C=O stretching) produces characteristic peaks of carbamates;

[0053] (3) 13 C NMR (101MHz, CDCl3): δ=153.8,139.5,137.1,135.5,130.7,129.9,129.3,127.7,127.3,1 26.4,124.3,122.1,101.4,95.2,94.9,94.8,93.2,77.2,64.7,36.4,21.5,21.2,19.8ppm.

[0054] Preparation Example 2

[0055] Weigh out 6000g of MDI-10 and 4000g of CHE-305 according to the isocyanate group (NCO) to hydroxyl group (OH) molar ratio of 2:1. Premix CHE-305 with 300 rpm of bismuth neodecanoate catalyst, heat to 55°C under nitrogen protection, and stir at 300 rpm for 20 minutes for later use.

[0056] MDI-10 was heated and stirred to 55°C under nitrogen protection, and CHE-305 was slowly added dropwise to MDI-10 at a rate of 100 ml / min. The reaction temperature was controlled at 55°C, and the reaction was carried out at 300 rpm for 2-3 hours to obtain the modified MDI-2 product.

[0057] Preparation Example 3

[0058] Weigh out 2000g of MDI-10 and 8000g of [other products] according to the isocyanate group (NCO) to hydroxyl group (OH) molar ratio of 2:1. F3056D. (The rest of the text appears to be unrelated and likely refers to a separate topic.) F3056D was premixed with 300ppm bismuth neodecanoate, heated to 55°C under nitrogen protection, and stirred at 300rpm for 20 minutes for later use.

[0059] MDI-10 was heated and stirred under nitrogen protection to 55°C, and then... S3007 was slowly added dropwise to MDI-10 at a rate of 100 ml / min, the reaction temperature was controlled at 55℃, and the reaction was carried out at 300 rpm for 2-3 hours to obtain the modified MDI-3 product.

[0060] Preparation Example 4

[0061] Weigh out 5172.4g of MDI-10 and 4827.6g of hydroxyl group (OH) according to the isocyanate group (NCO) to hydroxyl group (OH) molar ratio of 2:1. S3007. (The sentence appears to be incomplete and lacks context.) S3007 was premixed with 300ppm of catalyst dioctyltin dineodecanate, heated to 55°C under nitrogen protection, and stirred at 300rpm for 20 minutes for later use.

[0062] MDI-10 was heated and stirred under nitrogen protection to 55°C, and then... S3007 was slowly added dropwise to MDI-10 at a rate of 100 ml / min, the reaction temperature was controlled at 55℃, and the reaction was carried out at 300 rpm for 2-3 hours to obtain the modified MDI-4 product.

[0063] Preparation Example 5

[0064] Weigh out 5172.4g of MDI-10 and 4827.6g of hydroxyl group (OH) according to the isocyanate group (NCO) to hydroxyl group (OH) molar ratio of 2:1. S3007. (The sentence appears to be incomplete and lacks context.) S3007 was premixed with 300ppm of bismuth neodecanoate catalyst, heated to 60°C under nitrogen protection, and stirred at 300rpm for 20 minutes for later use.

[0065] MDI-10 was heated and stirred under nitrogen protection to 55°C, and then... S3007 was slowly added dropwise to MDI-10 at a rate of 100 ml / min, the reaction temperature was controlled at 55℃, and the reaction was carried out at 300 rpm for 2-3 hours to obtain the modified MDI-4 product.

[0066] Comparative Preparation Example 1

[0067] Weigh out 4285.7g of MDI-10 and 5714.2g of hydroxyl group (OH) according to the isocyanate group (NCO) to hydroxyl group (OH) molar ratio of 2:1. C3110A (highly reactive polyether). [The following text appears to be incomplete and requires further context: "will..."] C3110A and 300 rpm bismuth neodecanoate catalyst are premixed, heated to 55°C under nitrogen protection, and stirred at 300 rpm for 20 minutes for later use.

[0068] MDI-10 was heated and stirred under nitrogen protection to 55°C, and then... C3110A was slowly added dropwise to MDI-10 at a rate of 100 ml / min, the reaction temperature was controlled at 55℃, and the reaction was carried out at 300 rpm for 2-3 hours to obtain the modified MDI-6 product.

[0069] Comparative Preparation Example 2

[0070] Weigh out 5172.4g of MDI-10 and 4827.6g of hydroxyl group (OH) according to the isocyanate group (NCO) to hydroxyl group (OH) molar ratio of 2:1. S3007. (The sentence appears to be incomplete and lacks context.) S3007 was premixed with 300ppm of dibutyltin dilaurate catalyst, heated to 55°C under nitrogen protection, and stirred at 300rpm for 20 minutes for later use.

[0071] MDI-10 was heated and stirred under nitrogen protection to 55°C, and then... S3007 was slowly added dropwise to MDI-10 at a rate of 100 ml / min, the reaction temperature was controlled at 55℃, and the reaction was carried out at 300 rpm for 2-3 hours to obtain the modified MDI-7 product.

[0072] The following table shows the composition of the products from the preparation example:

[0073]

[0074]

[0075] The byproduct is a macromolecular product formed by NCO at both ends of a 4,4'-MDI molecule being attached to two polyol chains.

[0076] Example 1

[0077] 100 parts of polyethylene adipate-1,4-butanediol diol, 2 parts of ethylene glycol, 1.5 parts of deionized water, 1.5 parts of Dabco-LV33, and 0.3 parts of organosilicon surfactant were stirred at 60°C for 3 hours to obtain polyurethane shoe sole raw material A.

[0078] MDI-100, liquefied MDI, and polyethylene adipate-1,4-butanediol diol were mixed at a mass ratio of 50:15:35 and reacted at 75°C for 2.5 h to obtain prepolymer A (with 30 ppm phosphoric acid stabilizer added). Prepolymer A and modified MDI-1 obtained in Preparation Example 1 were mixed at 80°C for 30 min at a mass ratio of 100:5 to obtain polyurethane shoe sole raw material B.

[0079] Polyurethane shoe sole raw materials A and B are separately injected into the material tank of a low-pressure casting machine and heated to 43°C. They are then mixed at a mass ratio of A:B of 100:101, with a total mass of 81g, and injected into a 450cm³ volume. 3 The material was demolded in a copper polished shoe sole mold at 55℃ for 5 minutes, yielding a product with a density of 0.18 g / cm³. 3 Low-density sole.

[0080] Example 2

[0081] 100 parts of polyethylene adipate-1,4-butanediol diol, 2 parts of ethylene glycol, 1.5 parts of deionized water, 1.5 parts of Dabco-LV33, and 0.3 parts of organosilicon surfactant were stirred at 60°C for 3 hours to obtain polyurethane shoe sole raw material A.

[0082] MDI-100, liquefied MDI, and polyethylene adipate-1,4-butanediol diol were mixed at a mass ratio of 50:15:35 and reacted at 75°C for 2.5 h to obtain prepolymer A (with 30 ppm phosphoric acid stabilizer added). Prepolymer A and modified MDI-2 obtained in Preparation Example 2 were mixed at 80°C for 30 min at a mass ratio of 100:5 to obtain polyurethane shoe sole raw material B.

[0083] Polyurethane shoe sole raw materials A and B are separately injected into the material tank of a low-pressure casting machine and heated to 43°C. They are then mixed at a mass ratio of A:B of 100:105, with a total mass of 81g, and injected into a 450cm³ volume. 3 The material was demolded in a copper polished shoe sole mold at 55℃ for 5 minutes, yielding a product with a density of 0.18 g / cm³. 3 Low-density sole.

[0084] Example 3

[0085] 100 parts of polyethylene adipate-1,4-butanediol diol, 2 parts of ethylene glycol, 1.5 parts of deionized water, 1.5 parts of Dabco-LV33, and 0.3 parts of organosilicon surfactant were stirred at 60°C for 3 hours to obtain polyurethane shoe sole raw material A.

[0086] MDI-100, liquefied MDI, and polyethylene adipate-1,4-butanediol diol were mixed at a mass ratio of 50:15:35 and reacted at 75°C for 2.5 h to obtain prepolymer A (with 30 ppm phosphoric acid stabilizer added). Prepolymer A and modified MDI-3 obtained in Preparation Example 3 were mixed at 80°C for 30 min at a mass ratio of 100:5 to obtain polyurethane shoe sole raw material B.

[0087] Polyurethane shoe sole raw materials A and B are separately injected into the material tank of a low-pressure casting machine and heated to 43°C. They are then mixed at a mass ratio of A:B of 100:98, with a total mass of 81g, and injected into a 450cm³ volume. 3 The material was demolded in a copper polished shoe sole mold at 55℃ for 5 minutes, yielding a product with a density of 0.18 g / cm³. 3 Low-density sole.

[0088] Example 4

[0089] 100 parts of polyethylene adipate-1,4-butanediol diol, 2 parts of ethylene glycol, 1.5 parts of deionized water, 1.5 parts of Dabco-LV33, and 0.3 parts of organosilicon surfactant were stirred at 60°C for 3 hours to obtain polyurethane shoe sole raw material A.

[0090] MDI-100, liquefied MDI, and poly(ethylene adipate-1,4-butanediol) diol were mixed at a mass ratio of 50:15:35 and reacted at 75°C for 2.5 h to obtain prepolymer A (with 30 ppm phosphoric acid stabilizer added). Prepolymer A and modified MDI-4 obtained in Preparation Example 4 were mixed at 80°C for 30 min by stirring.

[0091] Polyurethane shoe sole raw materials A and B are separately injected into the material tank of a low-pressure casting machine and heated to 43°C. They are then mixed at a mass ratio of A:B of 100:101, with a total mass of 81g, and injected into a 450cm³ volume. 3 The material was demolded in a copper polished shoe sole mold at 55℃ for 5 minutes, yielding a product with a density of 0.18 g / cm³. 3 Low-density sole.

[0092] Example 5

[0093] 100 parts of polyethylene adipate-1,4-butanediol diol, 2 parts of ethylene glycol, 1.5 parts of deionized water, 1.5 parts of Dabco-LV33, and 0.3 parts of organosilicon surfactant were stirred at 60°C for 3 hours to obtain polyurethane shoe sole raw material A.

[0094] MDI-100, liquefied MDI, and polyethylene adipate-1,4-butanediol diol were mixed at a mass ratio of 50:15:35 and reacted at 75°C for 2.5 h to obtain prepolymer A (with 30 ppm phosphoric acid stabilizer added). Prepolymer A and modified MDI-5 obtained in Preparation Example 5 were mixed at 80°C for 30 min at a mass ratio of 100:5 to obtain polyurethane shoe sole raw material B.

[0095] Polyurethane shoe sole raw materials A and B are separately injected into the material tank of a low-pressure casting machine and heated to 43°C. They are then mixed at a mass ratio of A:B of 100:101, with a total mass of 81g, and injected into a 450cm³ volume. 3 The material was demolded in a copper polished shoe sole mold at 55℃ for 5 minutes, yielding a product with a density of 0.18 g / cm³. 3 Low-density sole.

[0096] Example 6

[0097] 100 parts of polyethylene adipate-1,4-butanediol diol, 2 parts of ethylene glycol, 1.5 parts of deionized water, 1.5 parts of Dabco-LV33, and 0.3 parts of organosilicon surfactant were stirred at 60°C for 3 hours to obtain polyurethane shoe sole raw material A.

[0098] MDI-100, liquefied MDI, and polyethylene adipate-1,4-butanediol diol were mixed at a mass ratio of 50:15:35 and reacted at 75°C for 2.5 h to obtain prepolymer A (with 30 ppm phosphoric acid stabilizer added). Prepolymer A and modified MDI-1 obtained in Preparation Example 1 were mixed at 80°C for 30 min at a mass ratio of 100:5 to obtain polyurethane shoe sole raw material B.

[0099] Polyurethane shoe sole raw materials A and B are separately injected into the material tank of a low-pressure casting machine and heated to 43°C. They are then mixed at a mass ratio of A:B of 100:101, with a total mass of 67g, and injected into a 450cm³ volume. 3 The shoe sole was demolded in a copper polished shoe sole mold at 55℃ for 5 minutes, yielding a product with a density of 0.15 g / cm³. 3 Low-density sole.

[0100] Example 7

[0101] 100 parts of polyethylene adipate-1,4-butanediol diol, 2 parts of ethylene glycol, 1.5 parts of deionized water, 1.5 parts of Dabco-LV33, and 0.3 parts of organosilicon surfactant were stirred at 60°C for 3 hours to obtain polyurethane shoe sole raw material A.

[0102] MDI-100, liquefied MDI, and polyethylene adipate-1,4-butanediol diol were mixed at a mass ratio of 50:15:35 and reacted at 75°C for 2.5 h to obtain prepolymer A (with 30 ppm phosphoric acid stabilizer added). Prepolymer A and modified MDI-1 obtained in Preparation Example 1 were mixed at 80°C for 30 min at a mass ratio of 100:5 to obtain polyurethane shoe sole raw material B.

[0103] Polyurethane sole raw materials A and B are separately injected into the material tank of a low-pressure casting machine and heated to 43°C. They are then mixed at a mass ratio of A:B of 100:101, with a total mass of 135g, and injected into a 450cm³ volume. 3 The material was demolded in a copper polished shoe sole mold at 55℃ for 5 minutes, yielding a product with a density of 0.3 g / cm³. 3 Low-density sole.

[0104] Comparative Example 1

[0105] 100 parts of polyethylene adipate-1,4-butanediol diol, 2 parts of ethylene glycol, 1.5 parts of deionized water, 1.5 parts of Dabco-LV33, and 0.3 parts of organosilicon surfactant were stirred at 60°C for 3 hours to obtain polyurethane shoe sole raw material A.

[0106] MDI-100, liquefied MDI, and polyethylene adipate-1,4-butanediol diol were mixed at a mass ratio of 50:15:35 and reacted at 75°C for 2.5 h to obtain prepolymer A (with 30 ppm phosphoric acid stabilizer added). Prepolymer A and modified MDI-6 obtained in Comparative Preparation Example 1 were mixed at 80°C for 30 min by stirring.

[0107] Polyurethane sole raw materials A and B are separately injected into the material tank of a low-pressure casting machine and heated to 43°C. They are then mixed at a mass ratio of A:B of 100:100, with a total mass of 81g, and injected into a 450cm³ volume. 3 The material was demolded in a copper polished shoe sole mold at 55℃ for 5 minutes, yielding a product with a density of 0.18 g / cm³. 3 Low-density sole.

[0108] Comparative Example 2

[0109] 100 parts of polyethylene adipate-1,4-butanediol diol, 2 parts of ethylene glycol, 1.5 parts of deionized water, 1.5 parts of Dabco-LV33, and 0.3 parts of organosilicon surfactant were stirred at 60°C for 3 hours to obtain polyurethane shoe sole raw material A.

[0110] MDI-100, liquefied MDI, and polyethylene adipate-1,4-butanediol diol were mixed at a mass ratio of 50:15:35 and reacted at 75°C for 2.5 h to obtain prepolymer A (with 30 ppm phosphoric acid stabilizer added). Prepolymer A and modified MDI-7 obtained in Comparative Preparation Example 2 were mixed at 80°C for 30 min by stirring.

[0111] Polyurethane shoe sole raw materials A and B are separately injected into the material tank of a low-pressure casting machine and heated to 43°C. They are then mixed at a mass ratio of A:B of 100:101, with a total mass of 81g, and injected into a 450cm³ volume. 3 The material was demolded in a copper polished shoe sole mold at 55℃ for 5 minutes, yielding a product with a density of 0.18 g / cm³. 3 Low-density sole.

[0112] Comparative Example 3

[0113] 100 parts of polyethylene adipate-1,4-butanediol diol, 2 parts of ethylene glycol, 1.5 parts of deionized water, 1.5 parts of Dabco-LV33, and 0.3 parts of organosilicon surfactant were stirred at 60°C for 3 hours to obtain polyurethane shoe sole raw material A.

[0114] MDI-100, liquefied MDI and polyethylene adipate-1,4-butanediol diol were mixed at a mass ratio of 50:15:35 and reacted at 75°C for 2.5 hours to obtain prepolymer A (with 30 ppm phosphoric acid stabilizer added), which is the polyurethane shoe sole raw material B.

[0115] Polyurethane shoe sole raw materials A and B are separately injected into the material tank of a low-pressure casting machine and heated to 43°C. They are then mixed at a mass ratio of A:B of 100:101, with a total mass of 81g, and injected into a 450cm³ volume. 3 The material was demolded in a copper polished shoe sole mold at 55℃ for 5 minutes, yielding a product with a density of 0.18 g / cm³. 3 Low-density sole.

[0116] The table below shows the mechanical property results obtained from the tests:

[0117]

[0118] Based on the results, the selected low-activity polyether needs to have high steric hindrance, be combined with a catalyst with high steric hindrance and low temperature reaction to reduce the activity of NCO2, and improve the selectivity of the catalyst for NCO4 with lower steric hindrance, so as to improve the yield of modified MDI.

[0119] During the sole preparation process, the addition of high-functionality, low-activity modified MDI enhances the overall functionality of composite material B. Simultaneously, the addition of this modified MDI has minimal impact on the milky whitening time and accelerates the post-gelation rate. During foaming, the temperature difference between the mold center and mold wall allows CO2, which cannot liquefy like physical foaming agents, to rapidly overflow in the early stages of the reaction. Furthermore, the high functionality in the later stages maintains the strength of the cell walls, preventing bubble breakage. Overall, this reduces surface pores, forming a dense structure and significantly improving surface smoothness, color uniformity, and overall mechanical strength.

[0120] It is readily understood that the above embodiments are merely illustrative examples for clear explanation and do not imply that the invention is limited thereto. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A modified MDI, prepared from raw materials comprising the following components: (1) Diphenylmethane diisocyanate; (2) Multifunctional polyether polyols; (3) Catalyst, wherein the catalyst is a sterically hindered organometallic catalyst, such as bismuth neodecanoate, bismuth neopentanoate, bismuth isooctanoate, and dioctyltin dinedecanoate.

2. The modified MDI as described in claim 1, characterized in that, The diphenylmethane diisocyanate described in step (1) requires a 2,4'-isomer content of ≥80%, preferably ≥90% of the 2,4'-MDI isomer. MDI-10.

3. The modified MDI as described in claim 1 or 2, characterized in that, The polyol mentioned in step (2) has a number average molecular weight of 500-3000, preferably a polyether polyol obtained by copolymerizing a trifunctional initiator with low hydroxyl activity and propylene oxide, such as CHE-305. S3007 or At least one of F3056D.

4. The method for preparing modified MDI according to any one of claims 1-3, characterized in that, Includes the following steps: a) Weigh out diphenylmethane diisocyanate and multifunctional polyether polyol according to the isocyanate group (NCO) to hydroxyl group (OH) molar ratio of 2-2.1:1; b) The multifunctional polyether polyol is premixed with the catalyst, and the mixture is heated and stirred under nitrogen protection to obtain the premix. c) Add the premix from (b) dropwise to diphenylmethane diisocyanate for reaction; after terminating the reaction, a modified MDI product with a free MDI content ≤0.1% is obtained.

5. The preparation method according to claim 4, characterized in that, In step b), the temperature is raised to 50-60℃, the stirring speed is 200-400 rpm, and the stirring time is 10-20 minutes; and / or, in step c), the reaction temperature is 50-60℃, and the reaction time is 2-3 hours.

6. A low-density shoe midsole material, characterized in that, It contains the following components: Polyurethane shoe sole raw material A: by weight, it includes: 100 parts of polyethylene adipate-1,4-butanediol diol, 1-2 parts of ethylene glycol, 1-2 parts of deionized water, 1-2 parts of Dabco-LV33, 0-3 parts of HCFC-141b, and 0.2-0.4 parts of silicone surfactant; Polyurethane shoe sole raw material B: by weight, it comprises: prepolymer A: prepared from MDI-100, liquefied MDI and polyethylene adipate-1,4-butanediol diol in a mass ratio of 50:10-15:30-40 and modified MDI, wherein the prepolymer A and modified MDI are prepared in a mass ratio of 100:0-5, and the modified MDI is selected from the modified MDI as described in any one of claims 1-3.

7. The method for preparing the low-density shoe midsole material as described in claim 6, characterized in that, Includes the following steps: (1) Preparation of polyurethane shoe sole raw material A: Mix the components in proportion and stir at 50-60℃ for 3±0.5 hours to obtain a homogeneous composition; (2) Preparation of polyurethane shoe sole raw material B: First, prepolymer A is prepared, and then it is mixed with modified MDI in proportion to obtain material B; (3) Molding process: Inject material A and material B separately into a low-pressure casting machine, control the material temperature at 40-45℃, mix them at a mass ratio of A:B = 100:70-110, and then pour the mixture into a mold at 50-60℃. Demold after 4-6 minutes to obtain a density of 0.15-0.3 g / cm³. 3 The soles of the shoes.

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