A polyurethane resin, polyurethane synthetic leather, its preparation method, and its application.

Abstract

This invention provides a polyurethane resin, polyurethane synthetic leather, its preparation method, and its applications. The polyurethane resin is prepared by reacting a hard segment component and a soft segment component. The raw materials for the hard segment component include diisocyanate and a small molecule chain extender, while the raw material for the soft segment component is an organosilicon diol. The polyurethane resin of this invention can solve the color development problem of synthetic leather, resulting in good overall color uniformity and excellent mechanical properties, and can be widely used in clothing and bags, etc.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and relates to a polyurethane resin, polyurethane synthetic leather, preparation method and application. Background Technology

[0002] Polyurethane synthetic leather, after years of development, is widely used in clothing, bags, shoes, and sporting goods due to its good abrasion resistance, colorability, and ease of maintenance. However, compared to genuine leather, it suffers from poor color development. Color development refers to the overall color uniformity and color difference variation of the leather surface after polyurethane resin with added dyes is used to prepare synthetic leather, thus limiting its application in high-end products. Improving the color development of polyurethane resin primarily involves enhancing the uniform dispersion of dyes within the resin. Common methods in existing technologies involve adding color-developing agents to the resin to reduce pigment viscosity, decrease dye agglomeration, and improve dye dispersion. For example, patents CN105330815A and CN103145930A disclose the addition of color-developing agents to polyurethane resins used in different types of synthetic leather to improve color development. However, the molecular weight of color-developing agents is much smaller than that of polyurethane resins, resulting in differences in compatibility. Adding too little makes it difficult to achieve the desired color development effect, while adding too much can easily lead to migration and precipitation, negatively impacting the color development. CN11303369B discloses that, based on polyurethane, adding a free agent in the later stage of the reaction significantly improves the color development effect, and no dye precipitation or color change occurs after long-term use. This patent also improves the color development effect through additives.

[0003] Therefore, in this field, solving the color development effect through additives will bring new problems. How to solve the color development problem from the perspective of polyurethane itself is the technology that this field wants to break through. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a polyurethane resin, polyurethane synthetic leather, its preparation method, and its applications. This invention addresses the color development problem of synthetic leather by designing the molecular structure of polyurethane itself, resulting in better overall color uniformity in the synthetic leather.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] On one hand, the present invention provides a polyurethane resin, which is prepared by reacting a hard segment component and a soft segment component; the raw materials of the hard segment component include diisocyanate and a small molecule chain extender, and the raw material of the soft segment component is an organosilicon diol.

[0007] In this invention, the hard segment component of the polyurethane resin includes diisocyanate and small molecule chain extender, which have a strong hydrogen bond adsorption effect on pigments. However, during the preparation of colored polyurethane synthetic leather, pigments tend to flocculate, resulting in poor color development. Existing technologies generally add additives to address this color development problem in synthetic leather. The inventors, however, designed the soft segment component of the polyurethane resin to consist solely of organosilicon segments formed from organosilicon diols. Utilizing the polarity difference between the soft and hard segment components, the organosilicon segments act as wetting, dispersing, and steric hindrance components, promoting pigment dispersion while providing a sufficiently thick barrier to prevent pigment flocculation, thus resulting in good color development in the synthetic leather.

[0008] Preferably, the raw materials for preparing the polyurethane resin, by weight percentage, include the following components:

[0009]

[0010] In the raw materials for preparing the polyurethane resin of the present invention, the content of the organosilicon diol can be 40%, 43%, 45%, 48%, 50%, 53%, 55%, 58%, 60%, 65%, 70%, 75%, 80%, 83%, or 85%; the content of diisocyanate A can be 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, or 28%; the content of diisocyanate B can be 5%, 8%, 10%, 13%, 15%, 18%, or 20%; and the content of the small molecule chain extender can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%.

[0011] Preferably, the molar ratio of the organosilicon diol to diisocyanate A is 1:1.1 to 2.5, for example, 1:1.1, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:2.3, or 1:2.5. By controlling the molar ratio of the organosilicon diol to diisocyanate A, the size of the soft and hard segments can be effectively controlled, achieving both the color development properties of synthetic leather and ensuring its mechanical properties.

[0012] Preferably, the organosilicon diol can have the following structure:

[0013]

[0014] R is selected from C1-C20 alkylene or substituted C1-C20 alkylene, wherein the substituent in the substituted C1-C20 alkylene can be C1-C10 alkyl or C6-C20 aryl, and n is an integer from 1 to 30 (e.g., 1, 3, 5, 8, 10, 13, 15, 18, 20, 23, 25, 28 or 30, etc.).

[0015] Preferably, the molecular weight of the organosilicon diol is 1000-5000 g / mol, such as 1000 g / mol, 1300 g / mol, 1500 g / mol, 1800 g / mol, 2000 g / mol, 2500 g / mol, 3000 g / mol, 3500 g / mol, 4000 g / mol, 4500 g / mol or 5000 g / mol, and more preferably 1000-3000 g / mol.

[0016] It is worth noting that this application utilizes only organosilicon with the above structure as the soft segment of polyurethane resin to obtain excellent color development properties of synthetic leather, and studies the influence of different molecular weights. The inventors found that the molecular weight of the organosilicon diol, which serves only as the soft segment, affects the color development and mechanical properties of the synthetic leather prepared from the polyurethane resin. When the molecular weight of the organosilicon diol is between 1000 and 5000 g / mol, the color development properties of the synthetic leather are generally good. However, when the molecular weight is between 4000 and 5000 g / mol, the mechanical properties of the synthetic leather decrease. The inventors analyzed that the possible reason is that although the large polarity difference between the organosilicon segments and the hard segments allows the organosilicon segments to play a role in wetting, dispersing, and steric hindrance, resulting in good color development, when the molecular weight of the organosilicon diol forming the organosilicon segments is too large, the degree of phase separation is too great, leading to a decrease in the bonding ability between the soft and hard segments of the polyurethane, thus causing a decrease in the mechanical properties of the synthetic leather, especially the tensile strength.

[0017] Preferably, the diisocyanate A and diisocyanate B are independently selected from one or a combination of at least two of 4,4'-diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), dicyclohexylmethane-4,4-diisocyanate, 4,4'-dicyclohexylmethane diisocyanate (HMDI), isophorone diisocyanate (IPDI), or polymethylene polyphenyl polyisocyanate (PAPI).

[0018] In this invention, the diisocyanate A and diisocyanate B can be the same or different.

[0019] Preferably, the small molecule chain extender is one or a combination of at least two of ethylene glycol, 1,4-butanediol, 2-methyl-1,3-propanediol, or neopentyl glycol.

[0020] Preferably, the raw materials for preparing the polyurethane resin may further include a crosslinking agent.

[0021] Preferably, the crosslinking agent in the raw materials for preparing the polyurethane resin has a weight percentage content of 0.3% to 1%, for example, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8% or 1%.

[0022] Preferably, the crosslinking agent is an alkyltriol.

[0023] Preferably, the alkyltriol is selected from any one or a combination of at least two of glycerol, trimethylolpropane, tris(hydroxymethyl)ethane, 1,2,4-butanetriol, 1,2,5-pentanetriol, 1,2,6-hexanetriol, 1,2,7-heptanetriol, 1,2,8-octanetriol, 1,2,9-nonanetriol, 1,2,10-decanetriol, or 3,7,11,15-tetramethyl-1,2,3-hexadecanetriol; more preferably, it is selected from any one or a combination of at least two of tris(hydroxymethyl)ethane, 1,2,4-butanetriol, 1,2,6-hexanetriol, 1,2,10-decanetriol, or 3,7,11,15-tetramethyl-1,2,3-hexadecanetriol.

[0024] Preferably, the alkyltriol is selected from alkyltriols with ≥6 carbon atoms (e.g., 6, 7, 8, 9, 10, 12, 16, 18, 20, 23, 25, 28, etc.).

[0025] To address the issue of decreased mechanical properties in synthetic leather made from polyurethane, the inventors added alkyltriols as crosslinking agents to enhance these properties. While using glycerol and tris(hydroxymethyl)ethane as crosslinking agents improved the mechanical properties, it reduced color development. This is likely because the use of crosslinking agents reduces the mobility of the hard segments of the polyurethane resin, thus affecting the hydrogen bonding between the hard segments and the pigments. Therefore, the inventors attempted to use crosslinking agents with longer chains. Specifically, alkyltriols with ≥6 carbon atoms effectively balanced mechanical and color development properties. The reason for this is that alkyltriols with a certain chain length can reduce the concentration of hard segments, weakening the separation between soft and hard segments and increasing the interfacial bonding between them. Simultaneously, as physical crosslinking points, they enhance the strength of the resin material itself. Furthermore, because the crosslinking points are alkyltriols with six or more carbon atoms, the mobility of the hard segment molecular chains is largely unaffected, maintaining the hydrogen bonding interaction between the hard segments and the pigments.

[0026] In a further refinement, the molar ratio of the small molecule chain extender to the crosslinking agent is controlled to be (15–40):1, such as 15:1, 18:1, 20:1, 23:1, 25:1, 28:1, 30:1, 35:1, 38:1, or 40:1. When the molar ratio of the small molecule chain extender to the crosslinking agent is too low, the mechanical properties cannot be effectively improved. When the molar ratio of the small molecule chain extender to the crosslinking agent is too high, the polyurethane resin solution is prone to gelation and loss of fluidity.

[0027] Preferably, the raw materials for preparing the polyurethane resin may further include a catalyst.

[0028] Preferably, the catalyst content in the raw materials for preparing the polyurethane resin is 0.001% to 0.01% by weight, for example, 0.001%, 0.003%, 0.005%, 0.008%, or 0.01%.

[0029] Preferably, the catalyst is an organobismuth catalyst. Preferably, the raw materials for preparing the polyurethane resin may further include a chain terminator. Preferably, the chain terminator is selected from any one or a combination of at least two of methanol, ethanol, or isopropanol.

[0030] Preferably, the weight percentage content of the chain terminator in the raw materials for preparing the polyurethane resin is 0.005% to 1%, for example, 0.005%, 0.008%, 0.01%, 0.03%, 0.05%, 0.08%, 0.1%, 0.3%, 0.5%, 0.8%, or 1%.

[0031] Preferably, the raw materials for preparing the polyurethane resin also include antioxidants.

[0032] Preferably, the antioxidant content in the raw materials for preparing the polyurethane resin is 0.01% to 1% by weight, for example, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.1%, 0.3%, 0.5%, 0.8% or 1%.

[0033] Preferably, the antioxidant is selected from any one or a combination of at least two of hindered phenolic antioxidants or phosphite antioxidants.

[0034] Preferably, the raw materials for preparing the polyurethane resin also include a solvent, and the amount of solvent is such that the mass percentage content of the other raw materials in the solvent is 30% to 50%, for example 30%, 35%, 40%, 45% or 50%.

[0035] In this invention, the content of the other preparation materials described above, excluding the solvent, is based on the total weight of the preparation materials excluding the solvent being 100%.

[0036] Preferably, the solvent is selected from dimethylformamide and / or dimethylacetamide.

[0037] On the other hand, the present invention provides a method for preparing a polyurethane resin, the method comprising the following steps:

[0038] (1) The organosilicon diol and diisocyanate A are mixed and reacted;

[0039] (2) Add a small molecule chain extender to the reaction system obtained in step (1) and carry out the reaction;

[0040] (3) Add some solvent to the reaction system obtained in step (2), and then add some diisocyanate B to react;

[0041] (4) Add the remaining diisocyanate B and the remaining solvent to the reaction system obtained in step (3) in batches, react, and obtain the polyurethane resin after the viscosity of the system stabilizes.

[0042] Preferably, the raw materials mixed in step (1) also include antioxidants.

[0043] Preferably, the reaction in step (1) is a solvent-free reaction, the reaction temperature is 60-70℃ (e.g., 60℃, 63℃, 65℃, 68℃ or 70℃), and the reaction time is 1-2 hours (e.g., 1 hour, 1.3 hours, 1.5 hours, 1.8 hours or 2 hours).

[0044] Preferably, step (2) further includes adding a crosslinking agent to the reaction system obtained in step (1).

[0045] Preferably, the reaction temperature in step (2) is 60-70°C (e.g., 60°C, 63°C, 65°C, 68°C or 70°C), and the reaction time is 0.5-2 hours (e.g., 0.5 hours, 1 hour, 1.3 hours, 1.5 hours, 1.8 hours or 2 hours).

[0046] Preferably, the reaction temperature in step (3) is 70-80°C (e.g., 70°C, 73°C, 75°C, 78°C or 80°C), and the reaction time is 1-2 hours (e.g., 1 hour, 1.3 hours, 1.5 hours, 1.8 hours or 2 hours).

[0047] Preferably, the solvent in step (3) is 20% to 50% of the total solvent, for example, 20%, 22%, 25%, 30%, 35%, 40%, 45% or 50%.

[0048] Preferably, the amount of diisocyanate B used in step (3) is 20% to 50% of the total amount of diisocyanate B, for example, 20%, 22%, 25%, 30%, 35%, 40%, 45% or 50%.

[0049] Preferably, the temperature for reacting the batch addition of diisocyanate B and solvent in step (4) is 70-80°C (e.g., 70°C, 73°C, 75°C, 78°C or 80°C), and the batch addition of diisocyanate B is generally carried out in 2 to 4 times (e.g., 2, 3 or 4 times).

[0050] Preferably, before adding the remaining diisocyanate B and the remaining solvent in batches in step (4), a catalyst is added to the reaction system obtained in step (3). Preferably, when the viscosity of the system increases to 8000-16000 mPa·s / 25℃ in step (4), a chain terminator is optionally added, and the reaction continues until the viscosity of the system stabilizes, thus obtaining the polyurethane resin.

[0051] Preferably, the reactions described in steps (1) to (4) are all carried out under stirring.

[0052] On the other hand, the present invention provides a polyurethane synthetic leather, which is prepared using the polyurethane resin described above.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] The polyurethane resin of this invention can solve the color development problem of synthetic leather, resulting in good overall color uniformity and high mechanical properties of synthetic leather, which can be widely used in clothing and bags. Detailed Implementation

[0055] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0056] Example 1

[0057] This embodiment provides a polyurethane resin, comprising the following raw material components in parts by weight:

[0058]

[0059] The addition of solvent DMF resulted in a raw material content of 35 wt% for the polyurethane resin.

[0060] The molar ratio of organosilicon diol to diisocyanate A is 1:2.

[0061] Example 2

[0062] This embodiment provides a polyurethane resin, comprising the following raw material components in parts by weight:

[0063]

[0064] The addition of solvent DMF resulted in a raw material content of 40 wt% for the polyurethane resin.

[0065] The molar ratio of organosilicon diol to diisocyanate A is 1:1.91.

[0066] Example 3

[0067] This embodiment provides a polyurethane resin, comprising the following raw material components in parts by weight:

[0068]

[0069] The addition of solvent DMF resulted in a raw material content of 45 wt% for the polyurethane resin.

[0070] The molar ratio of organosilicon diol to diisocyanate A is 1:1.6.

[0071] Example 4

[0072] The difference from Example 1 is that an equimolar amount of organosilicon diol (Shin-Etsu KF-6003, molecular weight 5000) is used to replace the organosilicon diol in Example 1, while the rest is the same as Example 1.

[0073] Specifically:

[0074] The raw material components include the following parts by weight:

[0075]

[0076] The addition of solvent DMF resulted in a raw material content of 35 wt% for the polyurethane resin.

[0077] The molar ratio of organosilicon diol to diisocyanate A is 1:2.

[0078] Example 5

[0079] The difference from Example 1 is that a crosslinking agent (trimethylolethane) was added, and the number of molar hydroxyl groups in the chain extender of Example 1 is the same as the number of molar hydroxyl groups in the chain extender and the number of molar hydroxyl groups in the crosslinking agent of Example 5. Everything else is the same as in Example 1, and the weight parts of each raw material are as follows:

[0080]

[0081] The addition of solvent DMF resulted in a raw material content of 35 wt% for the polyurethane resin.

[0082] The molar ratio of organosilicon diol to diisocyanate A is 1:2, and the molar ratio of chain extender to crosslinker is 20:1.

[0083] Example 6

[0084] The difference from Example 4 is that a crosslinking agent (trimethylolpropane) was added, and the number of molar hydroxyl groups in the chain extender of Example 4 is the same as the number of molar hydroxyl groups in the chain extender and the number of molar hydroxyl groups in the crosslinking agent of Example 6. Otherwise, it is the same as Example 4, including the following raw material components in parts by weight:

[0085]

[0086]

[0087] The addition of solvent DMF resulted in a raw material content of 35 wt% for the polyurethane resin; wherein the molar ratio of organosilicon diol to diisocyanate A was 1:2, and the molar ratio of chain extender to crosslinker was 19:1.

[0088] Example 7

[0089] The difference from Example 5 is that the crosslinking agent is replaced with an equimolar amount of trimethylolpropane.

[0090] Example 8

[0091] The difference from Example 5 is that the crosslinking agent is replaced with an equimolar amount of 1,2,8-octanetriol.

[0092] Example 9

[0093] The difference from Example 5 is that the chain extender is replaced with an equimolar amount of 1,6-hexanediol.

[0094] Example 10

[0095] The difference from Example 5 is that the molar ratio of chain extender to crosslinker is 13:1.

[0096] Comparative Example 1

[0097] The difference from Example 1 is that 20% of the molar amount of organosilicon polyol is replaced with PTMEG (molecular weight 1000), and the weight parts of each raw material are as follows:

[0098]

[0099] The addition of solvent DMF resulted in a raw material content of 35 wt% for the polyurethane resin.

[0100] The molar ratio of organosilicon diol to diisocyanate A is 1:2.

[0101] Comparative Example 2

[0102] The difference from Example 1 is that the molar ratio of organosilicon diol to diisocyanate A is 1:0.8, and the weight parts of each raw material are as follows:

[0103]

[0104] The addition of solvent DMF resulted in a raw material content of 35 wt% for the polyurethane resin; wherein the molar ratio of organosilicon diol to diisocyanate A was 1:0.8.

[0105] The preparation methods of the polyurethane resins in Examples 1-11 and Comparative Examples 1 and 2 are as follows:

[0106] 1) According to the formula, organosilicon diol and diisocyanate A are reacted under solvent-free conditions to prepare end-capped organosilicon diol. An antioxidant may be added during the preparation process. The reaction temperature is 65℃ and the time is 1 hour.

[0107] 2) Add chain extender and optional crosslinking agent to the above reaction system, and control the reaction temperature at 65℃ and the reaction time at 0.5 hours;

[0108] 3) Add a catalyst to the reaction system of step 2) and stir. During stirring, add 40% of the total amount of solvent DMF and 30% of the total amount of diisocyanate B in sequence. The reaction will thicken and the reaction temperature will be controlled at 75°C.

[0109] 4) Add the remaining diisocyanate B and the remaining solvent to the reaction system obtained in step (3) in batches, react, and when the viscosity of the reaction system reaches 12000 mPa·s / 25℃, optionally add methanol and wait for the viscosity of the system to stabilize to obtain the polyurethane resin.

[0110] The preparation methods of PU synthetic leather in Application Examples 1-11 and Comparative Application Examples 1 and 2 are as follows:

[0111] 1) Take 100 parts of the polyurethane resin prepared in Examples 1-11 and Comparative Examples 1-2, 80 parts of the solvent DMF, and 5 parts of the pigment carbon black (commonly available, particle size 50-70nm), and stir at a speed of 1500r / min to obtain a mixture.

[0112] 2) Pour the above mixture evenly onto the release paper from left to right, spread it evenly, and dry it in an oven at 130℃ to obtain PU synthetic leather;

[0113] The prepared mixture and PU synthetic leather were subjected to performance tests, and the test methods are as follows:

[0114] (1) Dispersibility of carbon black in the mixture (represented by My): The obtained mixture was subjected to a dispersibility test. Specifically, refer to DIN 55979 standard, replacing linseed oil in the standard with the mixture prepared in this example. The specific test and calculation methods are as described in DIN 55979 standard. The larger the value of My, the better the blackness, which means better dispersibility and better color development.

[0115] (2) Color development (visual observation): The obtained PU synthetic leathers were evaluated according to the following standards: Grade 5: No color difference, the blackest color, and excellent color development effect; Grade 4: No obvious color difference, and good color development effect; Grade 5: Visible color difference, and average color development effect.

[0116] The test results are shown in Table 1.

[0117] Table 1

[0118]

[0119]

[0120] The polyurethane resin described in this invention is used to prepare PU synthetic leather. Its mixed solution has normal fluidity and good color development properties. The color development property can reach level 4 or above when observed with the naked eye, indicating good color development effect. My reaches 60 or above, indicating good color development properties. The tensile strength of the synthetic leather reaches 22 MPa or above.

[0121] A comparison of Example 4 and Example 1 shows that when the molecular weight of the organosilicon diol is large, the mechanical properties of its PU synthetic leather decrease, and the color development decreases slightly.

[0122] The comparison between Example 5 and Example 1, and between Example 6 and Example 4, shows that the addition of a crosslinking agent enhances the mechanical properties of PU synthetic leather, but slightly reduces its color development.

[0123] Compared with Examples 1, 5 and 7, it can be seen that adding a crosslinking agent can improve the mechanical properties of synthetic leather. However, when the crosslinking agent is trimethylolethane, the mechanical properties of the synthetic leather are enhanced, but its color development is slightly reduced. When the crosslinking agent is trimethylolpropane, not only is the mechanical properties improved, but the color development is still good.

[0124] Compared with Example 5, Example 8 shows that when the number of carbon atoms in the crosslinking agent is greater than 6, the mechanical properties and color development properties of the synthetic leather in Example 8 are enhanced.

[0125] Compared with Example 5, Example 10 shows that when the molar ratio of small molecule chain extender to crosslinker is low, the solution state of the mixture in step (1) of the application example is abnormally fluid.

[0126] Compared with Example 1, Comparative Example 1 replaced 20% of the molar number of organosilicon polyol with PTMEG (molecular weight 1000), which reduced the amount of organosilicon polyol as the soft segment, resulting in a significant decrease in the color development of its PU synthetic leather.

[0127] Compared with Example 1, Comparative Example 2 has a molar ratio of organosilicon diol to diisocyanate A of 1:0.8, which reduces the color development of PU synthetic leather and also reduces its mechanical properties.

[0128] In summary, the synthetic leather obtained in this application embodiment has good overall color uniformity, and the synthetic leather prepared in this application embodiment has a soft and elastic feel, a dry and skin-friendly surface, a delicate and light touch, and is not greasy. It can be widely used in clothing and bags, etc.

[0129] The applicant declares that this invention illustrates the polyurethane resin, polyurethane synthetic leather, preparation method, and application of the invention through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the products of this invention, additions of auxiliary components, and selection of specific methods all fall within the protection and disclosure scope of this invention.

Claims

1. A polyurethane resin, characterized in that, The polyurethane resin is prepared by reacting a hard segment component and a soft segment component; the raw materials for the hard segment component include diisocyanate and a small molecule chain extender, and the raw material for the soft segment component is an organosilicon diol. The raw materials for preparing the polyurethane resin, by weight percentage, include: Organosilicon diols 40-85%; Diisocyanate A 8~28%; Diisocyanate B 5~20%; Small molecule chain extenders 1~10%; The molar ratio of the organosilicon diol to diisocyanate A is 1:1.1~2.5; The structure of the organosilicon diol is as follows: Wherein, R is selected from C1-C20 alkylene or substituted C1-C20 alkylene, wherein the substituent in the substituted C1-C20 alkylene is a C1-C10 alkyl or a C6-C20 aryl, and n is an integer from 1 to 30. The method for preparing the polyurethane resin includes the following steps: (1) The organosilicon diol is mixed with diisocyanate A and reacted; (2) Add a small molecule chain extender to the reaction system obtained in step (1) and carry out the reaction; (3) Add some solvent to the reaction system obtained in step (2), and then add some diisocyanate B to react; (4) Add the remaining diisocyanate B and the remaining solvent to the reaction system obtained in step (3) in batches, react, and obtain the polyurethane resin after the viscosity of the system stabilizes. When the raw materials for preparing the polyurethane resin also include a crosslinking agent, the molar ratio of the small molecule chain extender to the crosslinking agent is (15~40):

1.

2. The polyurethane resin according to claim 1, characterized in that, The molecular weight of the organosilicon diol is 1000-5000 g / mol.

3. The polyurethane resin according to claim 2, characterized in that, The molecular weight of the organosilicon diol is 1000-3000 g / mol.

4. The polyurethane resin according to claim 1, characterized in that, The diisocyanate A and diisocyanate B are independently selected from one or a combination of at least two of 4,4'-diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and isophorone diisocyanate.

5. The polyurethane resin according to claim 1, characterized in that, The small molecule chain extender is one or a combination of at least two of ethylene glycol, 1,4-butanediol, 2-methyl-1,3-propanediol, or neopentyl glycol.

6. The polyurethane resin according to claim 1, characterized in that, The raw materials for preparing the polyurethane resin also include a crosslinking agent, and the crosslinking agent has a weight percentage content of 0.3-1%.

7. The polyurethane resin according to claim 1, characterized in that, The crosslinking agent is alkyltriol.

8. The polyurethane resin according to claim 7, characterized in that, The alkyltriol is selected from any one or a combination of at least two of the following: glycerol, trimethylolpropane, tris(hydroxymethyl)ethane, 1,2,4-butanetriol, 1,2,5-pentanetriol, 1,2,6-hexanetriol, 1,2,7-heptanetriol, 1,2,8-octanetriol, 1,2,9-nonanetriol, 1,2,10-decanetriol, or 3,7,11,15-tetramethyl-1,2,3-hexadecanetriol.

9. The polyurethane resin according to claim 8, characterized in that, The alkyltriol is selected from any one or a combination of at least two of the following: tri(hydroxymethyl)ethane, 1,2,4-butanetriol, 1,2,6-hexanetriol, 1,2,10-decanetriol, or 3,7,11,15-tetramethyl-1,2,3-hexadecanetriol.

10. The polyurethane resin according to claim 9, characterized in that, Alkanetriols are selected from alkanetriols with ≥6 carbon atoms.

11. The polyurethane resin according to claim 1, characterized in that, The raw materials for preparing the polyurethane resin also include a catalyst.

12. The polyurethane resin according to claim 11, characterized in that, The catalyst in the raw materials for preparing the polyurethane resin has a weight percentage content of 0.001% to 0.01%.

13. The polyurethane resin according to claim 11, characterized in that, The catalyst is an organic bismuth catalyst.

14. The polyurethane resin according to claim 1, characterized in that, The raw materials for preparing the polyurethane resin also include a chain terminator.

15. The polyurethane resin according to claim 14, characterized in that, The chain terminator is selected from any one or a combination of at least two of methanol, ethanol, or isopropanol.

16. The polyurethane resin according to claim 14, characterized in that, The weight percentage of chain terminator in the raw materials for preparing the polyurethane resin is 0.005%~1%.

17. The polyurethane resin according to claim 1, characterized in that, The raw materials for preparing the polyurethane resin also include antioxidants.

18. The polyurethane resin according to claim 17, characterized in that, The antioxidant content in the raw materials for preparing the polyurethane resin is 0.01% to 1% by weight.

19. The polyurethane resin according to claim 17, characterized in that, The antioxidant is selected from any one or a combination of at least two of hindered phenolic antioxidants or phosphite antioxidants.

20. The polyurethane resin according to claim 1, characterized in that, The raw materials for preparing the polyurethane resin also include a solvent, and the amount of solvent used is such that the mass percentage content of the other raw materials in the solvent, excluding the solvent, is 30-50%.

21. The polyurethane resin according to claim 20, characterized in that, The solvent is selected from dimethylformamide and / or dimethylacetamide.

22. A method for preparing a polyurethane resin according to any one of claims 1-21, characterized in that, The preparation method includes the following steps: (1) The organosilicon diol is mixed with diisocyanate A and reacted; (2) Add a small molecule chain extender to the reaction system obtained in step (1) and carry out the reaction; (3) Add some solvent to the reaction system obtained in step (2), and then add some diisocyanate B to react; (4) Add the remaining diisocyanate B and the remaining solvent to the reaction system obtained in step (3) in batches, react, and obtain the polyurethane resin after the viscosity of the system stabilizes.

23. The preparation method according to claim 22, characterized in that, The raw materials mixed in step (1) also include antioxidants.

24. The preparation method according to claim 22, characterized in that, The reaction described in step (1) is a solvent-free reaction, with a reaction temperature of 60-70℃ and a reaction time of 1-2 hours.

25. The preparation method according to claim 22, characterized in that, Step (2) also includes adding a crosslinking agent to the reaction system obtained in step (1).

26. The preparation method according to claim 22, characterized in that, The reaction temperature in step (2) is 60-70℃ and the reaction time is 0.5-2 hours.

27. The preparation method according to claim 22, characterized in that, The reaction temperature in step (3) is 70-80℃, and the reaction time is 1-2 hours.

28. The preparation method according to claim 22, characterized in that, The solvent in step (3) is 20% to 50% of the total solvent.

29. The preparation method according to claim 22, characterized in that, The amount of diisocyanate B used in step (3) is 20% to 50% of the total amount of diisocyanate B.

30. The preparation method according to claim 22, characterized in that, The reaction temperature for the batch addition of diisocyanate B and solvent in step (4) is 70-80℃.

31. The preparation method according to claim 22, characterized in that, Before adding the remaining diisocyanate B and the remaining solvent in batches in step (4), a catalyst is added to the reaction system obtained in step (3).

32. The preparation method according to claim 22, characterized in that, In step (4), when the system viscosity increases to 8000~16000 mPa·s / 25℃, a chain terminator is optionally added to continue the reaction. After the system viscosity stabilizes, the polyurethane resin is obtained.

33. The preparation method according to claim 22, characterized in that, The reactions described in steps (1) to (4) are all carried out under stirring.

34. A polyurethane synthetic leather, characterized in that, The polyurethane synthetic leather is prepared using the polyurethane resin as described in any one of claims 1-21.

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